Driving Power Control Apparatus for Four Wheel Drive Vehicle

• US 20090088914A1
• Filed: 05/18/2007
• Published: 04/02/2009
• Est. Priority Date: 05/24/2006
• Status: Active Grant

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Tahara, Yasuaki, Tsuchida, Michitaka, Mizutani, Ryoji, Fukushima, Tomohiro, Sakuma, Masafumi
• Granted Patent: US 8,195,348 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 17/043 Transmission unit disposed in on near the vehicle wheel, or between the differential gear unit and the wheel
• CPC Class Codes: B60K 17/356 having fluid or electric motor, for driving one or more wheels disposition of motor in, or adjacent to, traction wheel B60K7/00
• CPC Class Codes: B60K 2007/0092 the motor axle being coaxial to the wheel axle
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/52 Driving a plurality of drive axles, e.g. four-wheel drive
• CPC Class Codes: B60K 7/0007 the motor being electric
• CPC Class Codes: B60L 15/2045 for optimising the use of energy
• CPC Class Codes: B60L 2220/44 Wheel Hub motors, i.e. integrated in the wheel hub
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• 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 10/119 including control of all-wheel-driveline means, e.g. transfer gears or clutches for dividing torque between front and rear axle B60W10/14 takes precedence
• 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 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/083 Torque
• CPC Class Codes: B60W 2720/406 between left and right wheel
• CPC Class Codes: B60W 30/1882 characterised by the working point of the engine, e.g. by using engine output chart
• CPC Class Codes: Y02T 10/40 : Engine management systems
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y02T 10/84 : Data processing systems or methods, management, administration

Abstract

Front left and right wheel units (FL, FR) are driven by an engine (ENG) and a motor generator (MG2). Rear left and right wheel units (RL, RR) are independently driven by in-wheel motor type motor generators (MGR, MGL). The motor generator (MG2) and the motor generator (MGR, MGL) are configured to have different rated outputs, respectively, and be subjected to different speed reduction ratios, respectively, between the motor generators and their respectively associated drive wheel units, and thus have characteristics, respectively, in efficiency with respect to torque and vehicular speed, that exhibit high efficiency in mutually different output ranges, respectively. When a mileage oriented mode is selected as a traveling mode, an ECU (30) determines how a drive torque should be allocated between the motor generators (MG2, MGR, MGL), as based on the motors'"'"' required drive torque and vehicular speed and on each motor generator'"'"'s characteristic in efficiency, to maximize the motor generators'"'"' total efficiency.

Claims

1. A driving power control apparatus for a four wheel drive vehicle having first left and right drive wheel units and second left and right drive wheel units, comprising:

a first motor;

a first power transmission mechanism transmitting a motive power generated by said first motor to said first left and right drive wheel units coupled to a first drive shaft;

two second motors coupled to said second left and right drive wheel units, respectively, and drivable independently from each other, and having a rated output different from that of said first motor;

a second power transmission mechanism transmitting motive powers generated by said two second motors to said second left and right drive wheel units, respectively;

a first drive circuit receiving electric power from a power supply to control driving said first motor;

two second drive circuits receiving electric power from said power supply to control driving said two second motors, respectively;

a driving power allocation determination unit determining an allocation of an output between said first and second motors for a driving power that said first and second motors as a whole are required to output; and

a driving control unit controlling said first and second drive circuits to cause said first and second motors to output their respective, allocated driving powers, respectively, wherein;

at least one of said first and second power transmission mechanisms includes a speed reducer that transmits the motive power generated by an associated motor of said motors to an associated drive wheel unit of said drive wheel units such that said speed reducer reduces a rotational speed of the motive power; and

said driving power allocation determination unit includes;

storage means for previously converting a characteristic in efficiency of each of said first and second motors with respect to its torque and its rotational speed into a characteristic in efficiency of each of said first and second motors with respect to its torque and vehicular speed, and storing said characteristic in efficiency thus converted; and

first allocation determination means for determining said allocation of said output between said first and second motors, as based on a drive torque that said first and second motors as a whole are required to output and a vehicular speed, and on said characteristic in efficiency, as stored, of each of said first and second motors with respect to its torque and vehicular speed, to allow said first and second motors to output torques in total satisfying said drive torque that said first and second motors as a whole are required to output, and also to allow total efficiency of said first and second motors to be at least a predetermined threshold value.

2. The driving power control apparatus for a four wheel drive vehicle according to claim 1, further comprising:

a driving power detection unit detecting a driving power that said first and second motors as a whole are required to output; and

a vehicular speed detection unit detecting said vehicular speed, wherein said first allocation determination means includes storage means for previously setting and storing therein an allocation of said output between said first and second motors that maximizes said total efficiency of said first and second motors, as based on said characteristic in efficiency of each of said first and second motors with respect to its torque and vehicular speed, for each combination of said drive torque that said first and second motors as a whole are required to output and said vehicular speed, and said first allocation determination means extracts from said storage means an allocation of said output between said first and second motors that corresponds to said drive torque, as detected, that said first and second motors as a whole are required to output, and to said vehicular speed as detected.

3. The driving power control apparatus for a four wheel drive vehicle according to claim 2, further comprising a steering angle detection unit detecting a steering angle of said vehicle, wherein said first allocation determination means corrects, as based on said steering angle of said vehicle as detected, said allocation of said output between said first and second motors as determined.

4. The driving power control apparatus for a four wheel drive vehicle according to claim 2, further comprising a wheel unit slip detection unit detecting that said first and second left and right drive wheel units slip, wherein when said wheel unit slip detection unit detects that either ones of said first and second left and right drive wheel units slip, said first allocation determination means corrects said allocation of said output between said first and second motors as determined.

5. The driving power control apparatus for a four wheel drive vehicle according to claim 1, wherein said driving power allocation determination unit further includes:

means for obtaining an evaluation value indicating a level of stability in behavior of said vehicle for each combination of said drive torque that said first and second motors as a whole are required to output and said vehicular speed, as based on said allocation of said output between said first and second motors and on a condition that said vehicle assumes in traveling;

second allocation determination means for selecting any allocation(s) of said output between said first and second motors, as based on said drive torque that said first and second motors as a whole are required to output and said vehicular speed and on said characteristic in efficiency, as converted, of each of said first and second motors with respect to its torque and vehicular speed, such that a total sum of said torques output from said first and second motors satisfies said drive torque that said first and second motors as a whole are required to output and said total efficiency of said first and second motors is also at least said predetermined threshold value, and for determining as said allocation of said output between said first and second motors an allocation of said any allocation(s) selected that maximizes said evaluation value in accordance with said condition that said vehicle assumes in traveling; and

select means externally operable for selecting one of said first and second allocation determination means in accordance with how said select means is operated.

6. The driving power control apparatus for a four wheel drive vehicle according to claim 1, further comprising:

a voltage conversion circuit converting voltage between said power supply and said first drive circuit;

a first switch circuit closed to be capable of supplying said second drive circuits with a voltage from said power supply directly; and

a second switch circuit closed to be capable of supplying said second drive circuits with a voltage output from said voltage conversion circuit, wherein said driving power allocation determination unit further includes;

calculation means for calculating a target value for said voltage input to said second drive circuits, as based on said driving power allocated to said second motors;

first opening/closing control means operative in response to said target value, as calculated, being at most said voltage received from said power supply, for closing said first switch circuit and also opening said second switch circuit; and

second opening/closing control means operative in response to said target value, as calculated, being higher than said voltage received from said power supply, for opening said first switch circuit and also closing said second switch circuit.

7. The driving power control apparatus for a four wheel drive vehicle according to claim 1, wherein said first left and right drive wheel units configure front wheel units of said vehicle and said second left and right drive wheel units configure rear wheel units of said vehicle.

8. The driving power control apparatus for a four wheel drive vehicle according to claim 1, wherein said first left and right drive wheel units configure rear wheel units of said vehicle and said second left and right drive wheel units configure front wheel units of said vehicle.

9. The driving power control apparatus for a four wheel drive vehicle according to claim 1, wherein said two second motors are each an in-wheel motor.

10. The driving power control apparatus for a four wheel drive vehicle according to claim 1, wherein:

said vehicle is a hybrid vehicle;

said first power transmission mechanism provides a composition of a motive power generated by an internal combustion engine and the motive power generated by said first motor and transmits said composition to said first left and right drive wheel units coupled to said first drive shaft; and

said driving power allocation determination unit determines an allocation of an output between said internal combustion engine and all of said first and second motors for a driving power that said vehicle is required to output, and said driving power allocation determination unit also determines an allocation of said output between said first and second motors for a driving power, as determined, that said first and second motors as a whole are required to output.

11. The driving power control apparatus for a four wheel drive vehicle according to claim 1, wherein said speed reducer is configured to apply different speed reduction ratios to the motive power generated by said first motor and transmitted to said first left and right drive wheel units and those generated by said second motors and transmitted to said second left and right drive wheel units, respectively.