Vehicular drive system

• US 7,822,524 B2
• Filed: 12/23/2004
• Issued: 10/26/2010
• Est. Priority Date: 12/26/2003
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Tabata, Atsushi, Taga, Yutaka
• Primary Examiner(s): Nguyen; Cuong H
• Application Number:
  US11/019,337
• Publication Number:
  US 20050209760A1
• Time in Patent Office: 2,133 Days
• Field of Search: 475/5, 475/275, 475/127, 475/231, 475/136, 475/150, 475/1, 701/53, 701/22, 701/55, 701/51, 701/87, 701/95, 180/65.235, 180/65.25, 180/65, 180/65.28, 180/65.1, 180/65.3, 477/34
• US Class Current: 701/53
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60K 6/547 the transmission being a stepped gearing
• CPC Class Codes: B60W 10/02 including control of driveline clutches
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/10 including control of change-speed gearings
• CPC Class Codes: B60W 10/18 including control of braking systems
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/30 Control strategies involving selection of transmission gear ratio control of change speed gearings, together with other vehicle sub-units B60W10/10; HEV transmission gearing B60K6/36; gearings and control thereof F16H
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: F16H 2061/0223 Generating of new shift maps, i.e. methods for determining shift points for a schedule by taking into account driveline and vehicle conditions
• CPC Class Codes: F16H 2061/6603 characterised by changing ratio in the mechanical gearing
• CPC Class Codes: F16H 2200/0008 specially adapted for front-wheel-driven vehicles
• CPC Class Codes: F16H 2200/0034 the gear ratios comprising two forward speeds
• CPC Class Codes: F16H 2200/0039 the gear ratios comprising three forward speeds
• CPC Class Codes: F16H 2200/0043 the gear ratios comprising four forward speeds
• CPC Class Codes: F16H 2200/0047 : the gear ratios comprising five forward speeds
• CPC Class Codes: F16H 2200/0056 : the gear ratios comprising seven forward speeds
• CPC Class Codes: F16H 2200/006 : the gear ratios comprising eight forward speeds
• CPC Class Codes: F16H 2200/0086 : the gear ratios comprising two reverse speeds
• CPC Class Codes: F16H 2200/2005 : with one sets of orbital gears
• CPC Class Codes: F16H 2200/2007 : with two sets of orbital gears
• CPC Class Codes: F16H 2200/201 : with three sets of orbital gears
• CPC Class Codes: F16H 3/666 : with compound planetary gear units, e.g. two intermeshing orbital gears F16H3/663 takes precedence
• CPC Class Codes: F16H 3/728 : with means to change ratio in the mechanical gearing
• CPC Class Codes: Y02T 10/40 : Engine management systems
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y10S 903/903 : having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/904 : Component specially adapted for hev
• CPC Class Codes: Y10S 903/906 : Motor or generator
• CPC Class Codes: Y10S 903/909 : Gearing
• CPC Class Codes: Y10S 903/91 : Orbital, e.g. planetary gears

Abstract

Vehicular drive system which is small-sized and/or improved in its fuel economy.

A power distributing mechanism 16, which is provided with a differential-state switching device in the form of a switching clutch C0 and a switching brake B0, is switchable by the switching device between a differential state (continuously-variable shifting state) in which the mechanism is operable as an electrically controlled continuously variable transmission, and a fixed-speed-ratio shifting state in which the mechanism is operable as a transmission having a fixed speed ratio or ratios. The power distributing mechanism 16 is placed in the fixed-speed-ratio shifting state during a high-speed running of the vehicle or a high-speed operation of engine 8, so that the output of the engine 8 is transmitted to drive wheels 38 primarily through a mechanical power transmitting path, whereby fuel economy of the vehicle is improved owing to reduction of a loss of conversion of a mechanical energy into an electric energy. The mechanism 16 is also placed in the fixed-speed-ratio shifting state during a high-output operation of the engine 8, so that the required electric reaction of first electric motor M1 can be reduced, whereby the required size of the first electric motor M1, and the required size of the drive system 10 including the electric motor M1 can be reduced.

Claims

1. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, and a second electric motor disposed between the power transmitting member and a drive wheel of a vehicle, characterized by comprising:

a transmission mechanism that comprises a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission,

wherein said power distributing mechanism includes a first element fixed to said engine, a second element fixed to said first electric motor, and a third element fixed to said power transmitting member, and said differential-state switching device is operable to permit said first, second and third elements to be rotated relative to each other, for thereby placing the power distributing mechanism in said differential state, and to connect at least two of said first, second and third elements to each other or to hold said second element stationary, for thereby placing the power distributing mechanism in said locked state, and

wherein said power distributing mechanism is a planetary gear set,

and wherein said first element is a carrier of said planetary gear set, and said second element is a sun gear of said planetary gear set, while said third element is a ring gear of said planetary gear set,

said differential-state switching device including a clutch operable to connect selected two of said carrier, sun gear and ring gear to each other, and/or a brake operable to fix said sun gear to a stationary member.

2. A vehicular drive system according to claim 1, wherein said planetary gear set is a planetary gear set of single-pinion type.

3. A vehicular drive system according to claim 2, wherein said differential-state switching device is operable to connect said carrier and sun gear of said planetary gear set of single-pinion type, for enabling said planetary gear set to operate as a transmission having a speed ratio of 1, or to hold said sun gear stationary, for enabling the planetary gear set as a speed-increasing transmission having a speed ratio lower than 1.

4. A vehicular drive system according to claim 1, wherein said planetary gear set is a planetary gear set of double-pinion type.

5. A vehicular drive system according to claim 4, wherein said differential-state switching device is operable to connect said carrier and sun gear of said planetary gear set of double-pinion type, for enabling said planetary gear set to operate as a transmission having a speed ratio of 1, or to hold said sun gear stationary, for enabling the planetary gear set to operate as a speed-reducing transmission having a speed ratio higher than 1.

6. A vehicular drive system according to claim 1, further comprising an automatic transmission disposed between said power transmitting member and said drive wheel,

and wherein a speed ratio of said drive system is determined by a speed ratio of said automatic transmission.

7. A vehicular drive system according to claim 1, further comprising an automatic transmission disposed between said power transmitting member and said drive wheel, and wherein an overall speed ratio of said drive system is determined by a speed ratio of said power distributing mechanism and a speed ratio of said automatic transmission.

8. A vehicular drive system according to claim 6, wherein said automatic transmission is a step-variable automatic transmission.

9. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set having three elements consisting of a sun gear, a carrier and a ring gear in which said three elements are arranged as a second element, a first element and a third element, respectively, in the order of description, said first element being fixed to said engine, said second element being fixed to said first electric motor, while said third element being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to a stationary member, said power distributing mechanism being placed in a differential state by releasing said switching clutch and/or said switching brake, and in a fixed-speed-ratio shifting state in which said power distributing mechanism has a fixed speed ratio, by engaging said switching clutch and/or said switching brake; and

said step-variable automatic transmission includes a second planetary gear set, a third planetary gear set and a fourth planetary gear set, and has five rotary elements each of which is constituted by at least one of sun gears, carriers and ring gears of said second, third and fourth planetary gear sets, said five rotary elements are arranged as a fourth element, a fifth element, a sixth element, a seventh element and an eighth element, respectively, in the order of description, said fourth element being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, and said fifth element being selectively fixed through a second brake to the stationary member, while said sixth element being selectively fixed through a third brake to the stationary member, said seventh element being fixed to an output rotary member of said step-variable automatic transmission, said eighth element being selectively connected through a first clutch to said power transmitting member, said step-variable automatic transmission having a plurality of operating positions that are established by engaging actions of respective combinations of said first clutch, second clutch, first brake, second brake and third brake.

10. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set of single-pinion type having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, and said first sun gear being fixed to said first electric motor, while said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable to fix said first sun gear to a stationary member; and

said step-variable automatic transmission includes a second planetary gear set of single-pinion type, a third planetary gear set of single-pinion type and a fourth planetary gear set of single-pinion type, said second planetary gear set having a second sun gear, a second carrier and a second ring gear, and said third planetary gear set having a third sun gear, a third carrier and a third ring gear, while said fourth planetary gear set having a fourth sun gear, a fourth carrier and a fourth ring gear, said second sun gear and said third sun gear being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, and said second carrier being selectively fixed through a second brake to the stationary member, while said fourth ring gear being selectively fixed through a third brake to the stationary member, and wherein said second ring gear, said third carrier and said fourth carrier are fixed to an output rotary member of said step-variable automatic transmission, and said third ring gear and said fourth sun gear are selectively connected through a first clutch to said power transmitting member.

11. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set having three elements consisting of a sun gear, a carrier and a ring gear in which said three elements are arranged as a second element, a first element and a third element, respectively, in the order of description, said first element being fixed to said engine, said second element being fixed to said first electric motor, while said third element being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to a stationary member, said power distributing mechanism being placed in a differential state by releasing said switching clutch and/or said switching brake, and in a fixed-speed-ratio shifting state in which said power distributing mechanism has a fixed speed ratio, by engaging said switching clutch and/or said switching brake; and

said step-variable automatic transmission includes a second planetary gear set and a third planetary gear set, and has four rotary elements each of which is constituted by at least one of sun gears, carriers and ring gears of said second and third planetary gear sets, in which said four rotary elements are arranged as a fourth element, a fifth element, a sixth element and a seventh element, respectively, said fourth element being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member; and

said fifth element being selectively fixed through a second brake to the stationary member, while said sixth element being fixed to an output rotary member of said step-variable automatic transmission, said seventh element being selectively connected through a first clutch to said power transmitting member, said step-variable automatic transmission having a plurality of operating positions that are established by engaging actions of respective combinations of said first clutch, second clutch, first brake and second brake.

12. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set of single-pinion type having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, and said first sun gear being fixed to said first electric motor, while said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable to fix said first sun gear to a stationary member; and

said step-variable automatic transmission includes a second planetary gear set of single-pinion type and a third planetary gear set of single-pinion type, said second planetary gear set having a second sun gear, a second carrier and a second ring gear, and said third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, and said third carrier being selectively fixed through a second brake to the stationary member, while said second carrier and said third ring gear being fixed to an output rotary element of said step-variable automatic transmission, said second ring gear being selectively connected through a first clutch to said power transmitting member.

13. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set having three elements consisting of a sun gear, a carrier and a ring gear in which said three elements are arranged as a second element, a first element and a third element, respectively, said first element being fixed to said engine, said second element being fixed to said first electric motor, while said third element being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to a stationary member, said power distributing mechanism being placed in a differential state by releasing said switching clutch and/or said switching brake, and in a fixed-speed-ratio shifting state in which said power distributing mechanism has a fixed speed ratio, by engaging said switching clutch and/or said switching brake; and

said step-variable automatic transmission includes a second planetary gear set and a third planetary gear set, and has four rotary elements each of which is constituted by at least one of sun gears, carriers and ring gears of said second and third planetary gear sets, rotating speeds of said fourth rotary elements in which said four rotary elements are arranged as a fourth element, a fifth element, a sixth element and a seventh element, respectively, said fourth element being selectively connected through a second clutch to said power transmitting member and selectively connected through a fourth brake to said engine, and said fifth element being selectively connected through a third clutch to said engine and selectively fixed through a second brake to the stationary member, while said sixth element being fixed to an output rotary member of said step-variable automatic transmission, said seventh element being selectively connected through a first clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, said step-variable automatic transmission having a plurality of operating positions that are established by engaging actions of respective combinations of said first clutch, second clutch, third clutch and fourth clutch, first brake and second brake.

14. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set of single-pinion type having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, and said first sun gear being fixed to said first electric motor, while said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable to fix said first sun gear to a stationary member; and

said step-variable automatic transmission includes a second planetary gear set of double-pinion type and a third planetary gear set of single-pinion type, said second planetary gear set having a second sun gear, a second carrier and a second ring gear, and said third planetary gear set having a third sun gear, a third carrier and a third ring gear, said third sun gear being selectively connected through a second clutch to said power transmitting member and selectively connected through a fourth clutch to said engine, said second carrier and said third carrier being selectively connected through a third clutch to said engine and selectively fixed through a second brake to the stationary member, while said second ring gear and said third ring gear being fixed to an output rotary element of said step-variable automatic transmission, said second sun gear being selectively connected through a first clutch to said power transmitting member and selectively fixed through a first brake to the stationary member.

15. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set having three elements consisting of a sun gear, a carrier and a ring gear in which said three elements are arranged as a second element, a third element and a first element, respectively, said first element being fixed to said engine, said second element being fixed to said first electric motor, while said third element being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to a stationary member, said power distributing mechanism being placed in a differential state by releasing said switching clutch and/or said switching brake, and in a fixed-speed-ratio shifting state in which said power distributing mechanism has a fixed speed ratio, by engaging said switching clutch and/or said switching brake; and

said step-variable automatic transmission includes a second planetary gear set and a third planetary gear set, and has four rotary elements each of which is constituted by at least one of sun gears, carriers and ring gears of said second and third planetary gear sets, in which said four rotary elements are arranged as a fourth element, a fifth element, a sixth element and a seventh element, respectively, said fourth element being selectively connected through a third clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, and said fifth element being selectively connected through a second clutch to said engine and selectively fixed through a second brake to the stationary member, while said sixth element being fixed to an output rotary member of said step-variable automatic transmission, said seventh element being selectively connected through a first clutch to said power transmitting member, said step-variable automatic transmission having a plurality of operating positions that are established by engaging actions of respective combinations of said first clutch, second clutch, third clutch, first brake and second brake.

16. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set of double-pinion type having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, and said first sun gear being fixed to said first electric motor, while said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable to fix said first sun gear to a stationary member; and

said step-variable automatic transmission includes a second planetary gear set of single-pinion type and a third planetary gear set of double-pinion type, said second planetary gear set having a second sun gear, a second carrier and a second ring gear, and said third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected through a third clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, said second carrier and said third carrier being selectively connected through a second clutch to said engine and selectively fixed through a second brake to the stationary member, while said second ring gear and said third ring gear being fixed to an output rotary element of said step-variable automatic transmission, said third sun gear being selectively connected through a first clutch to said power transmitting member.

17. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set having three elements consisting of a sun gear, a carrier and a ring gear in which said three elements are arranged as a second element, a first element and a third element, respectively, said first element being fixed to said engine, said second element being fixed to said first electric motor, while said third element being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to a stationary member, said power distributing mechanism being placed in a differential state by releasing said switching clutch and/or said switching brake, and in a fixed-speed-ratio shifting state in which said power distributing mechanism has a fixed speed ratio, by engaging said switching clutch and/or said switching brake; and

said step-variable automatic transmission includes a second planetary gear set, a third planetary gear set and a fourth planetary gear set, and has five rotary elements each of which is constituted by at least one of sun gears, carriers and ring gears of said second, third and fourth planetary gear sets, in which said five rotary elements are arranged as a fourth element, a fifth element, a sixth element, a seventh element and an eighth element, respectively, said fourth element being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, and said fifth element being selectively fixed through a second brake to the stationary member, while said sixth element being selectively fixed through a third brake to the stationary member, said seventh element being fixed to an output rotary member of said step-variable automatic transmission, said eighth element being fixed to said power transmitting member, said step-variable automatic transmission having a plurality of operating positions that are established by engaging actions of respective combinations of said second clutch, first brake, second brake and third brake.

26. A vehicular drive system according to claim 17, wherein a direction of an output rotary motion of said power distributing mechanism transmitted to said automatic transmission is reversed with respect to that of an input rotary motion of said power distributing mechanism, said drive system having a rear-drive position established by engaging said third brake.

28. A vehicular drive system according to claim 17, wherein a direction of an output rotary motion of said power distributing mechanism to be transmitted to said automatic transmission is reversed with respect to that of an input rotary motion of said power distributing mechanism, said drive system having a rear-drive position established by engaging said second clutch.

18. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set of single-pinion type having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, and said first sun gear being fixed to said first electric motor, while said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable to fix said first sun gear to a stationary member; and

said step-variable automatic transmission includes a second planetary gear set of single-pinion type, a third planetary gear set of single-pinion type and a fourth planetary gear set of single-pinion type, said second planetary gear set having a second sun gear, a second carrier and a second ring gear, and said third planetary gear set having a third sun gear, a third carrier and a third ring gear, while said fourth planetary gear set having a fourth sun gear, a fourth carrier and a fourth ring gear, said second sun gear and said third sun gear being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, and said second carrier being selectively fixed through a second brake to the stationary member, while said fourth ring gear being selectively fixed through a third brake to the stationary member, and wherein said second ring gear, said third carrier and said fourth carrier are fixed to an output rotary member of said step-variable automatic transmission, and said third ring gear and said fourth sun gear are fixed to said power transmitting member.

19. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set having three elements consisting of a sun gear, a carrier and a ring gear in which said three elements are arranged as a second element, a first element and a third element, respectively, said first element being fixed to said engine, said second element being fixed to said first electric motor, while said third element being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to a stationary member, said power distributing mechanism being placed in a differential state by releasing said switching clutch and/or said switching brake, and in a fixed-speed-ratio shifting state in which said power distributing mechanism has a fixed speed ratio, by engaging said switching clutch and/or said switching brake; and

said step-variable automatic transmission includes a second planetary gear set and a third planetary gear set, and has four rotary elements each of which is constituted by at least one of sun gears, carriers and ring gears of said second and third planetary gear sets, in which said four rotary elements are arranged as a fourth element, a fifth element, a sixth element and a seventh element, respectively, said fourth element being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, and said fifth element being selectively fixed through a second brake to the stationary member, while said sixth element being fixed to an output rotary member of said step-variable automatic transmission, said seventh element being fixed to said power transmitting member, said step-variable automatic transmission having a plurality of operating positions that are established by engaging actions of respective combinations of said second clutch, first brake and second brake.

27. A vehicular drive system according to claim 19, wherein a direction of an output rotary motion of said power distributing mechanism to be transmitted to said automatic transmission is reversed with respect to that of an input rotary motion of said power distributing mechanism, said drive system having a rear-drive position established by engaging said second brake.

20. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set of single-pinion type having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, and said first sun gear being fixed to said first electric motor, while said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable to fix said first sun gear to a stationary member; and

said step-variable automatic transmission includes a second planetary gear set of single-pinion type and a third planetary gear set of single-pinion type, and said second planetary gear set having a second sun gear, a second carrier and a second ring gear, said third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively connected through a second clutch to said power transmitting member and selectively fixed through a first brake to the stationary member, said third carrier being selectively fixed through a second brake to the stationary member, while said second carrier and said third ring gear being fixed to an output rotary element of said step-variable automatic transmission, said second ring gear being fixed to said power transmitting member.

21. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, and a second electric motor disposed between the power transmitting member and a drive wheel of a vehicle, characterized by comprising:

a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission, and

an automatic transmission disposed between said power transmitting member and said drive wheel,

wherein a speed ratio of said drive system is determined by a speed ratio of said automatic transmission, and

wherein said power distributing mechanism is disposed on a first axis, and said automatic transmission is disposed on a second axis parallel to said first axis, said power transmitting member being constituted by a pair of members which are disposed on said fist and second axes, respectively, said power distributing mechanism and said automatic transmission being connected to each other through said power transmitting member, so as to transit a drive force therebetween.

22. A vehicular drive system according to claim 21, wherein said second electric motor is disposed on said first axis.

23. A vehicular drive system according to claim 21, wherein said second electric motor is disposed on said second axis.

24. A vehicular drive system according to claim 21, wherein said power transmitting member is located on one side of said power distributing mechanism which is remote from said engine.

25. A vehicular drive system according to claim 21, wherein said automatic transmission includes a differential drive gear as an output rotary member thereof, said differential drive gear being located at one end of said automatic transmission which is remote from said power transmitting member.

29. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear set having three elements consisting of a sun gear, a carrier and a ring gear in which said three elements are arranged as a second element, a first element and a third element, respectively, said first element being fixed to said engine, said second element being fixed to said first electric motor, while said third element being fixed to said power transmitting member, said power distributing mechanism further including a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to a stationary member, said power distributing mechanism being placed in a differential state by releasing said switching clutch and/or said switching brake, and in a fixed-speed-ratio shifting state in which said power distributing mechanism has a fixed speed ratio, by engaging said switching clutch and/or said switching brake; and

a direction of a rotary motion of said power transmitting member to be transmitted to said automatic transmission in a rear-drive position of the drive system is reversed by said power distributing mechanism, with respect to that in forward-drive positions of the drive system.

30. A vehicular drive system according to claim 29, wherein said step-variable automatic transmission includes a planetary gear set having a sun gear, a carrier and a ring gear which mesh with each other and constitute at least three rotary elements in which said at least three rotary elements are arranged as a fourth element, a fifth element and a sixth element, respectively, in the order of description, said fourth element being fixed to said power transmitting member such that a drive force can be transmitted to the power transmitting member, and said fifth element being fixed to an output rotary element of said automatic transmission such that the drive force can be transmitted to the output rotary element, while said sixth element is selectively fixed through a brake to a stationary member, and wherein a rear-drive position of the drive system is established by engaging said brake.

31. A vehicular drive system according to claim 29, wherein said step-variable automatic transmission includes a planetary gear set having a sun gear, a carrier and a ring gear which mesh with each other and constitute at least three rotary elements, said fourth element being fixed to said power transmitting member such that a drive force can be transmitted to the power transmitting member, and said fifth element being fixed to an output rotary element of said automatic transmission such that the drive force can be transmitted to the output rotary element, and wherein said automatic transmission further includes a clutch operable to rotate the rotary elements as a unit, and a rear-drive position of the drive system is established by engaging said clutch.

32. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear device having as three elements a sun gear, a carrier and a ring gear, said three elements consisting of a first element, a second element and a third element, said first element being fixed to said engine, said second element being fixed to said first electric motor, and said third element being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a second planetary gear set and a third planetary gear set, said second and third planetary gear sets having sun gears, carriers and ring gears selected ones of which are fixed to each other to constitute four elements consisting of a fourth element, a fifth element, a sixth element and a seventh element said fourth element being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said fifth element being selectively connected to said power transmitting member through a third clutch and selectively fixed to said stationary member through a second brake, said sixth element being fixed to an output rotary member of said automatic transmission, and said seventh element being selectively connected to said power transmitting member through a first clutch, said automatic transmission having a plurality of gear positions which are established by engaging respective combinations of said first, second and third clutches and said first and second brakes.

33. A vehicular drive system according to claim 32, wherein said differential-state switching device includes a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to said stationary member, said first planetary gear set being placed in said differential state by releasing said switching clutch and/or said switching brake, and in said locked state by engaging said switching clutch and/or said switching brake.

34. A vehicular drive system according to claim 33, wherein said plurality of gear positions includes:

a first-gear position which has a highest speed ratio and which is established by engaging said switching clutch, said first clutch and said second brake;

a second-gear position which has a speed ratio lower than that of said first-gear position and which is established by engaging said switching clutch, said first clutch and said first brake;

a third-gear position which has a speed ratio lower than that of said second-gear position and which is established by engaging said switching clutch, said first clutch and said third clutch;

a fourth-gear position which has a speed ratio lower than that of said third-gear position and which is established by engaging said switching clutch, said third clutch and said first brake; and

a fifth-gear position which has a speed ratio lower than that of said fourth-gear position and which is established by engaging said third clutch, said switching brake and said first brake.

35. A vehicular drive system according to claim 32, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear functioning as said fourth element, said second carrier and said third carrier functioning as said fifth element, said second ring gear and said third ring gear functioning as said sixth element, and said third sun gear functioning as said seventh element.

36. A vehicular drive system according to claim 32, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second carrier and said third sun gear functioning as said fourth element, said second ring gear and said third carrier functioning as said fifth element, said third ring gear functioning as said sixth element, and said third ring gear functioning as said seventh element.

37. A vehicular drive system according to claim 32, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear functioning as said fourth element, said second ring gear functioning as said fifth element, said third carrier functioning as said sixth element, and said second carrier and said third ring gear functioning as said seventh element.

38. A vehicular drive system according to claim 32, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear functioning as said fourth element, said second ring gear and said third ring gear functioning as said fifth element, said third carrier functioning as said sixth element, and said second carrier and said third sun gear functioning as said seventh element.

39. A vehicular drive system according to claim 32, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said third sun gear functioning as said fourth element, said second ring gear functioning as said fifth element, said second carrier and said third ring gear functioning as said sixth element, and said second sun gear and said third carrier functioning as said seventh element.

40. A vehicular drive system according to claim 32, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear functioning as said fourth element, said second carrier and third ring gear functioning as said fifth element, said second ring gear and said third carrier functioning as said sixth element, and said third sun gear functioning as said seventh element.

41. A vehicular drive system according to claim 32, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said third sun gear functioning as said fourth element, said second ring gear functioning as said fifth element, said second carrier and said third carrier functioning as said sixth element, and said second sun gear and said third ring gear functioning as said seventh element.

42. A vehicular drive system according to claim 32, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear functioning as said fourth element, said third carrier functioning as said fifth element, said second carrier and said third ring gear functioning as said sixth element, and said second ring gear functioning as said seventh element.

52. A vehicular drive system according to claim 32,

said automatic transmission includes a plurality of input clutches selectively connected to an output shaft of said power distributing mechanism;

and

said automatic transmission has a plurality of gear positions which are established by selectively engaging and releasing said plurality of input clutches.

43. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said second carrier and said third carrier being selectively connected to said power transmitting member through a third clutch and selectively fixed to said stationary member through a second brake, said second ring gear and said third ring gear being fixed to an output rotary member of said automatic transmission, and said third sun gear being selectively connected to said power transmitting member through a first clutch.

51. A vehicular drive system according to claim 43, wherein said shifting-state switching device includes a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable fix said first sun gear to said stationary member.

44. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a first clutch, said second carrier and said third sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said second ring gear and said third carrier being selectively connected to said power transmitting member through a third clutch and selectively fixed to said stationary member through a second brake, and said third ring gear being fixed an output rotary member of said automatic transmission.

45. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said second carrier and said third ring gear being selectively connected to said power transmitting member through a first clutch, said second ring gear being selectively connected to said power transmitting member through a third clutch and selectively fixed to said stationary member through a second brake, and said third carrier being fixed to an output rotary member of said automatic transmission.

46. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said second carrier and said third sun gear being selectively connected to said power transmitting member through a first clutch, said second ring gear and said third ring gear being selectively connected to said power transmitting member through a third clutch and selectively fixed to said stationary member through a second brake, and said third carrier being fixed to an output rotary member of said automatic transmission.

47. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third carrier being selectively connected to said power transmitting member through a second clutch, said second carrier and said third ring gear being integrally fixed to each other for rotation as a unit and fixed to an output rotary member of said automatic transmission, said second ring gear being selectively connected to said power transmitting member through a third clutch and selectively fixed to a stationary member through a second brake, and said third sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a first brake.

48. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said second carrier and said third ring gear being selectively connected to said power transmitting member through a third clutch and selectively fixed to a stationary member through a second brake, said second ring gear and said third carrier being fixed to an output rotary member of said automatic transmission, and said third sun gear being selectively connected to said power transmitting member through a first clutch.

49. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third ring gear being selectively connected to said power transmitting member through a second clutch, said second carrier and said third carrier being fixed to an output rotary member of said automatic transmission, said second ring gear being selectively connected to said power transmitting member through a third clutch and selectively fixed to a stationary member through a second brake, and said third sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a first brake.

50. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively fixed to a stationary member through a first brake, said second carrier and said third ring gear being fixed to an output rotary member of said automatic transmission, said second ring gear being selectively connected to said power transmitting member through a first clutch, and said third carrier being selectively connected to said power transmitting member through a third clutch and selectively fixed to said stationary member through a second brake.

53. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, an automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said automatic transmission includes a plurality of input clutches selectively connected to an output shaft of said power distributing mechanism; and

said automatic transmission has a plurality of gear positions which are established by selectively engaging and releasing said plurality of input clutches,

wherein said power distributing mechanism includes a first planetary gear set having as three elements a sun gear, a carrier and a ring gear, said three elements consisting of a first element, a second element and a third element in a direction from one of opposite ends of a collinear chart toward the other end, said collinear chart having straight lines indicating rotating speeds of said three elements, said first element being fixed to said engine, said second element being fixed to said first electric motor, and said third element being fixed to said power transmitting member,

and wherein said power distributing mechanism further includes a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission.

54. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, an automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said automatic transmission includes a plurality of input clutches selectively connected to an output shaft of said power distributing mechanism; and

said automatic transmission has a plurality of gear positions which are established by selectively engaging and releasing said plurality of input clutches,

wherein said power distributing mechanism includes a first planetary gear set having as three elements a sun gear, a carrier and a ring gear, said three elements consisting of a first element, a second element and a third element in a direction from one of opposite ends of a collinear chart toward the other end, said collinear chart having straight lines indicating rotating speeds of said three elements, said first element being fixed to said engine, said second element being fixed to said first electric motor, and said third element being fixed to said power transmitting member.

86. A vehicular drive system according to claim 54, wherein said automatic transmission is a step-variable automatic transmission.

55. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a first planetary gear device having as three elements a sun gear, a carrier and a ring gear, said three elements consisting of a first element, a second element and a third element said first element being fixed to said engine, said second element being fixed to said first electric motor, and said third element being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a second planetary gear set and a third planetary gear set, said second and third planetary gear sets having sun gears, carriers and ring gears selected ones of which are fixed to each other to constitute four elements consisting of a fourth element, a fifth element, a sixth element and a seventh element, said fourth element being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said fifth element being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said sixth element being fixed to an output rotary member of said automatic transmission, and said seventh element being selectively fixed to said stationary member through a first brake, said automatic transmission having a plurality of gear positions which are established by engaging respective combinations of said first and second clutches and said first, second and third brakes.

56. A vehicular drive system according to claim 55, wherein said differential-state switching device includes a switching clutch operable to connect said second element to said first element, and/or a switching brake operable to fix said second element to said stationary member, said first planetary gear set being placed in said differential state by releasing said switching clutch and/or said switching brake, and in said locked state by engaging said switching clutch and/or said switching brake.

57. A vehicular drive system according to claim 56, wherein said plurality of gear positions includes:

a first-gear position which has a highest speed ratio and which is established by engaging said switching clutch, said first clutch and said first brake;

a second-gear position which has a speed ratio lower than that of said first-gear position and which is established by engaging said switching clutch, said second clutch and said first brake;

a third-gear position which has a speed ratio lower than that of said second-gear position and which is established by engaging said switching clutch, said first clutch and said second clutch;

a fourth-gear position which has a speed ratio lower than that of said third-gear position and which is established by engaging said switching clutch, said second clutch and said second brake; and

a fifth-gear position which has a speed ratio lower than that of said fourth-gear position and which is established by engaging said second clutch, said switching brake and said second brake.

58. A vehicular drive system according to claim 55, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second carrier and said third sun gear functioning as said fourth element, said second ring gear functioning as said fifth element, said third carrier functioning as said sixth element, and said second sun gear and said third ring gear functioning as said seventh element.

59. A vehicular drive system according to claim 55, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second carrier and said third sun gear functioning as said fourth element, said second ring gear and said third carrier functioning as said fifth element, said third ring gear functioning as said sixth element, and said second sun gear functioning as said seventh element.

60. A vehicular drive system according to claim 55, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear functioning as said fourth element, said second ring gear and said third carrier functioning as said fifth element, said third ring gear functioning as said sixth element, and said second carrier functioning as said seventh element.

61. A vehicular drive system according to claim 55, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear functioning as said fourth element, said second ring gear functioning as said fifth element, said third carrier functioning as said sixth element, and said second carrier and said third ring gear functioning as said seventh element.

62. A vehicular drive system according to claim 55, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said third sun gear functioning as said fourth element, said second carrier functioning as said fifth element, said second ring gear and said third carrier functioning as said sixth element, and said second sun gear and said third ring gear functioning as said seventh element.

63. A vehicular drive system according to claim 55, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear functioning as said fourth element, said second carrier functioning as said fifth element, said second ring gear and said third ring gear functioning as said sixth element, and said third carrier functioning as said seventh element.

64. A vehicular drive system according to claim 55, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear functioning as said fourth element, said second carrier and said third carrier functioning as said fifth element, said second ring gear and said third ring gear functioning as said sixth element, and said third sun gear functioning as said seventh element.

65. A vehicular drive system according to claim 55, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear functioning as said fourth element, said second ring gear and said third ring gear functioning as said fifth element, said third carrier functioning as said sixth element, and said second carrier and said third sun gear functioning as said seventh element.

66. A vehicular drive system according to claim 55, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second carrier functioning as said fourth element, said second ring gear and said third ring gear functioning as said fifth element, said third carrier functioning as said sixth element, and said second sun gear and said third sun gear functioning as said seventh element.

67. A vehicular drive system according to claim 55, wherein said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear functioning as said fourth element, said third ring gear and said third ring gear functioning as said fifth element, said second ring gear and said third carrier functioning as said sixth element, and said second carrier and said third sun gear functioning as said seventh element.

68. A vehicular drive system according to claim 55, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear functioning as said fourth element, said second carrier functioning as said fifth element, said second ring gear and said third carrier functioning as said sixth element, and said third ring gear functioning as said seventh element.

69. A vehicular drive system according to claim 55, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear functioning as said fourth element, said second carrier and said third ring gear functioning as said fifth element, said second ring gear and said third carrier functioning as said sixth element, and said third sun gear functioning as said seventh element.

70. A vehicular drive system according to claim 55, wherein said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said third sun gear functioning as said fourth element, said second ring gear functioning as said fifth element, said second carrier and said third carrier functioning as said sixth element, and said second sun gear and said third ring gear functioning as said seventh element.

71. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third ring gear being selectively fixed to a stationary member through a first brake, said second carrier and said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to said stationary member through a second brake, said second ring gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said third carrier being fixed to an output rotary member of said automatic transmission.

84. A vehicular drive system according to claim 71, wherein said shifting-state switching device includes a switching clutch operable to connect said first carrier and said first sun gear to each other, and/or a switching brake operable fix said first sun gear to said stationary member.

72. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a first clutch, said second carrier and said third sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said second sun gear being selectively fixed to a stationary member through a first brake, said second carrier and said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to said stationary member through a second brake, said second ring gear and said third carrier being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, and said third ring gear being fixed an output rotary member of said automatic transmission.

73. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to a stationary member through a first brake, said second sun gear and said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier being selectively fixed to said stationary member through a first brake, said second ring gear and said third carrier being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, and said third ring gear being fixed to an output rotary member of said automatic transmission.

74. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said second ring gear and said third ring gear being fixed to an output rotary member of said automatic transmission, and said third carrier being selectively fixed to said stationary member through a first brake.

75. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third ring gear being selectively fixed to a stationary member through a first brake, said second carrier being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said second ring gear and said third carrier being fixed to an output rotary member of said automatic transmission, said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to said stationary member through a second brake.

76. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary.gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said second ring gear and said third ring gear being fixed to an output rotary member of said automatic transmission, and said. third carrier selectively fixed to said stationary member through a first brake.

77. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a double-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier and said third carrier being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said second ring gear and said third ring gear being fixed to an output rotary member of said automatic transmission, said third sun gear being selectively fixed to said stationary member through a first brake.

78. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier and said third sun gear being selectively fixed to said stationary member through a first brake, said second ring gear and said third ring gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said third carrier being fixed an output rotary member of said automatic transmission.

79. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively fixed to a stationary member through a first brake, said second carrier being selectively connected to said power transmitting member through a first clutch and selectively fixed to said stationary member through a second brake, said second ring gear and said third ring being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said third carrier being fixed an output rotary member of said automatic transmission.

80. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a double-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier and said third sun gear being selectively fixed to said stationary member through a first brake, said second ring gear and said third carrier being fixed to an output rotary member of said automatic transmission, and said third ring gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake.

81. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said second ring gear and said third carrier being fixed to an output rotary member of said automatic transmission, and said third ring gear being selectively fixed to said stationary member through a first brake.

82. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to a stationary member through a second brake, said second carrier and said third ring gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, said second ring gear and said third carrier being fixed to an output rotary member of said automatic transmission, and said third sun gear being selectively fixed to said stationary member through a first brake.

83. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, a step-variable automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a single-pinion type first planetary gear device having a first sun gear, a first carrier and a first ring gear, said first carrier being fixed to said engine, said first sun being fixed to said first electric motor, and said first ring gear being fixed to said power transmitting member, said power distributing mechanism further including a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission; and

said automatic transmission includes a single-pinion type second planetary gear set having a second sun gear, a second carrier and a second ring gear, and a single-pinion type third planetary gear set having a third sun gear, a third carrier and a third ring gear, said second sun gear and said third ring gear being selectively fixed to a stationary member through a first brake, said second carrier and said third carrier being fixed to an output rotary member of said automatic transmission, and said second ring gear being selectively connected to said power transmitting member through a second clutch and selectively fixed to said stationary member through a third brake, and said third sun gear being selectively connected to said power transmitting member through a first clutch and selectively fixed to said stationary member through a second brake.

85. A vehicular drive system including a power distributing mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, an automatic transmission disposed between said power transmitting member and a drive wheel of a vehicle, and a second electric motor disposed between said power transmitting member and said drive wheel, characterized in that:

said power distributing mechanism includes a planetary gear device having as three elements a sun gear, a carrier and a ring gear, said three elements consisting of a first element, a second element and a third element which are arranged in the order of said second element, said first element and said third element, said first element being fixed to said engine, said second element being fixed to said first electric motor, and said third element being fixed to said power transmitting member; and

said automatic transmission is arranged to increase a rotating speed of said power transmitting member

wherein said power distributing mechanism further includes a differential-state switching device operable to place said power distributing mechanism selectively in a differential state in which the power distributing mechanism is operable as an electrically controlled continuously variable transmission, and a locked state in which the power distributing mechanism is not operable as the electrically controlled continuously variable transmission.