On-demand transfer case with synchronized range shift and adaptive clutch control

• US 6,398,688 B2
• Filed: 06/18/2001
• Issued: 06/04/2002
• Est. Priority Date: 03/09/1999
• Status: Expired due to Fees

• Current Assignee: New Venture Gear, Incorporated (Magna International Incorporated)
• Original Assignee: New Venture Gear, Incorporated (Magna International Incorporated)
• Inventors: Mohan, Sankar K., Brown, David, Mintonye, Nancy, Eastman, Richard E.
• Primary Examiner(s): Marmor, Charles A
• Assistant Examiner(s): Parekh, Ankur
• Application Number:
  US09/883,701
• Publication Number:
  US 20010036879A1
• Time in Patent Office: 351 Days
• Field of Search: 475/199, 475/204, 475/206, 475/248, 475/252, 475/299, 180/247, 180/248, 180/249
• US Class Current: 475/204
• CPC Class Codes: B60K 17/3467 combined with a change speed gearing, e.g. range gear
• CPC Class Codes: B60K 23/0808 for varying torque distribution between driven axles, e.g. by transfer clutch

Abstract

A full-time power transfer system is disclosed to include a transfer case having a clutch assembly arranged to control speed differentiation and torque biasing across an interaxle differential, sensors for detecting and generating sensor signals indicative of various dynamic and operational characteristics of the vehicle, and a controller for controlling actuation of the clutch assembly in response to the sensor signals. Upon the occurrence of traction loss, the clutch assembly is automatically actuated for limiting interaxle slip while transferring increased drive torque to the non-slipping driveline. Under a preferred adaptive control scheme, the actuated condition of the clutch assembly is controllably modulated between its non-actuated and fully-actuated limits for automatically varying the magnitude of speed differentiation and torque biasing across the interaxle differential in response to changes in the dynamic and operational characteristics of the vehicle.

Claims

1. A transfer case comprising:

an input shaft;

first and second output shafts;

a first planetary gearset including a first sun gear fixed to said input shaft, a first ring gear, and a first pinion gear meshed with said first ring gear and said first sun gear and which is rotatably supported from a carrier;

a range sleeve fixed to said first ring gear and movable between first and second positions, said range sleeve is operable in its first position to couple said first ring gear to said first sun gear and is operable in its second position to couple said first ring gear to a stationary member;

a second planetary gearset including a second sun gear fixed to said first output shaft, a third sun gear, a second pinion gear meshed with said second sun gear and which is rotatably supported from said carrier, a third pinion gear meshed with said second pinion gear and said third sun gear and which is rotatably supported from said carrier;

a transfer mechanism connecting said third sun gear for rotation with said second output shaft;

a mode clutch including a drum fixed to said transfer mechanism, a clutch pack mounted between said drum and said carrier, and a thrust mechanism movable between first and second positions, said thrust mechanism operable in its first position to exert a minimum clutch engagement force on said clutch pack to permit relative rotation between said drum and said carrier, and said thrust mechanism is operable in its second position to exert a maximum clutch engagement force on said clutch pack to prevent relative rotation between said drum and said carrier; and

an actuator assembly for controlling coordinated movement of said range sleeve and said thrust mechanism.

2. The transfer case of claim 1 wherein said range sleeve has clutch teeth that are releasably engageable with clutch teeth on a first clutch plate fixed to said input shaft when said range sleeve is in its first position, and said range sleeve clutch teeth are releasably engageable with clutch teeth on a second clutch plate fixed to said stationary member when said range sleeve is in its second position, and further including a first synchronizer disposed between said range sleeve and said first clutch plate, and a second synchronizer disposed between said range sleeve and said second clutch plate.

3. The transfer case of claim 1 wherein said thrust mechanism includes a lever arm having a first end acting on a pressure plate for exerting said clutch engagement force on said clutch pack, and a thrust pin having a first end engaging a second end of said lever arm, and wherein said actuator assembly includes an actuator member acting on a second end of said thrust pin, and a power-operated device for moving said actuator member to cause corresponding movement of said thrust pin and said lever arm.

4. A power transfer system for use in a four-wheel drive vehicle having a power source and first and second drivelines, comprising:

a transfer case including an input shaft receiving drive torque from the power source;

a first output shaft connected to the first driveline;

a second output shaft connected to the second driveline;

a planetary gearset having a sun gear driven by said input shaft, a ring gear, a carrier coupled to said first output shaft, and pinion gears meshed with said sun gear and ring gear and which are rotatably supported from said carrier;

a range clutch fixed to said ring gear and movable between first and second positions, said range clutch is operable in its first position to couple said ring gear to said sun gear such that rotation of said input shaft causes said first output shaft to be driven at a high-range speed, and said range clutch is operable in its second position to couple said ring gear to a stationary member such that rotation of said input shaft causes said first output shaft to be driven at a low-range speed;

a transfer mechanism coupled to said second output shaft;

a mode clutch including a clutch pack operably disposed between said carrier and said transfer mechanism;

a thrust mechanism operable in a first position to exert a minimum clutch engagement force on said clutch pack and further operable in a second position to exert a maximum clutch engagement force on said clutch pack;

sensors for detecting an operational characteristic of the vehicle and generating sensor signals in response thereto;

a mode select mechanism permitting selection of an adaptive four-wheel high-range drive mode and a locked four-wheel low-range drive mode, said mode select mechanism generating a mode signal indicative of a particular drive mode selected; and

a control system for moving said range clutch and said thrust mechanism in response to said sensor and mode signals, said control system being operable for moving said range clutch to its first position and modulating the position of said thrust mechanism between its first and second position as a function of said sensor signals when said adaptive four-wheel high-range drive mode is selected, and said control system is operable for moving said range clutch to its second position and said thrust mechanism to its second position when said locked four-wheel low-range drive mode is selected.

5. The power transfer system of claim 4, wherein said clutch pack is mounted between said carrier and a clutch drum fixed to said transfer mechanism, and wherein said thrust mechanism includes a set of lever arms movable between said first position whereat said minimum clutch engagement force is exerted on said clutch pack and said second position whereat said maximum clutch engagement force is exerted on said clutch pack, and wherein said control system includes an actuator operable to move said lever arms between said first and second positions, and a controller for controlling actuation of said actuator.

6. The power transfer system of claim 5 wherein said thrust mechanism further includes a set of thrust pins each having a first end acting on a corresponding one of said lever arms, and a mode fork acting on a second end of said thrust pins, and wherein said actuator is operable to move said mode fork for causing corresponding movement of said thrust pins and said lever arms.

7. The power transfer system of claim 4 wherein said range clutch comprises:

a first clutch plate fixed to said input shaft;

a second clutch plate fixed to said stationary member;

a range sleeve fixed to said ring gear and having clutch teeth that are releasably engageable with clutch teeth on said first clutch plate when said range sleeve is in its first position, and said clutch teeth on said range sleeve are releasably engageable with clutch teeth on said second clutch plate when said range sleeve is in its second position;

a first synchronizer disposed between said range sleeve and said first clutch plate and which is operable to cause speed synchronization between said ring gear and said input shaft in response to movement of said range sleeve to its first position; and

a second synchronizer disposed between said range sleeve and said second clutch plate and which is operable to cause speed synchronization between said ring gear and said stationary member in response to movement of said range sleeve to its second position.

8. The power transfer system of claim 4 wherein said transfer mechanism includes a drive sprocket rotatably supported on said first output shaft, a driven sprocket fixed to said second output shaft, and a power transfer device coupling said driven sprocket to said drive sprocket, and wherein said clutch pack is interconnected between said carrier and a drum housing fixed to said drive sprocket, and wherein said thrust mechanism includes a set of lever arms movable between a first position whereat a minimum clutch engagement force is exerted on said clutch pack and a second position whereat a maximum clutch engagement force is exerted on said clutch pack, a set of thrust pins supported in throughbores formed in said drive sprocket and each having a first end engaging a corresponding one of said lever arms, and a mode piston disposed in a pressure chamber and engaging a second end of said thrust pins, whereby movement of said mode piston from a retracted position to an extended position causes corresponding movement of said lever arms from said first position to said second position.

9. The power transfer system of claim 8 wherein said control system includes a source of hydraulic fluid, a control valve for controlling the flow of fluid to said pressure chamber, and a controller operable to receive said mode and sensor signals and generate control signals for controlling actuation of said control valve, said controller operable to modulate the actuated condition of said control valve for moving said mode piston between its retracted and extended positions so as to modulate the clutch engagement force applied on said clutch pack as a function of said sensor signals when said mode signal indicates selection of said adaptive four-wheel drive mode, and said controller is further operable for controlling said control valve to move said mode piston to its extended position when said mode signal indicates selection of said locked four-wheel drive mode.

10. A transfer case comprising:

an input shaft;

first and second output shafts;

a planetary gearset including a sun gear fixed to said input shaft, a ring gear, a carrier coupled to said first output shaft, and pinion gears meshed with said ring gear and said sun gear and which are rotatably supported from said carrier;

a range clutch fixed to said ring gear and movable between first and second positions, said range clutch is operable in its first position to couple said ring gear to said sun gear and is operable in its second position to couple said ring gear to a stationary member;

a transfer mechanism coupled to said second output shaft;

a mode clutch including a drum fixed to said transfer mechanism, a clutch pack mounted between said drum and said carrier, and a thrust mechanism movable between first and second positions, said thrust mechanism operable in its first position to exert a minimum clutch engagement force on said clutch pack to permit relative rotation between said drum and said carrier, and said thrust mechanism is operable in its second position to exert a maximum clutch engagement force on said clutch pack to prevent relative rotation between said drum and said carrier; and

an actuator assembly for controlling coordinated movement of said range clutch and said thrust mechanism.

11. The transfer case of claim 10 wherein said range clutch is a range sleeve having clutch teeth that are releasably engageable with clutch teeth on a first clutch plate fixed to said input shaft when said range sleeve is in its first position, and said range sleeve clutch teeth are releasably engageable with clutch teeth on a second clutch plate fixed to said stationary member when said range sleeve is in its second position, and further comprising a first synchronizer disposed between said range sleeve and said first clutch plate, and a second synchronizer disposed between said range sleeve and said second clutch plate.

12. The transfer case of claim 10 wherein said thrust mechanism includes a lever arm having a first end acting on a pressure plate for exerting said clutch engagement force on said clutch pack, and a thrust pin having a first end engaging a second end of said lever arm, and wherein said actuator assembly includes an actuator member acting on a second end of said thrust pin, and a power-operated device for moving said actuator member to cause corresponding movement of said thrust pin and said lever arm.

13. A transfer case comprising:

an input shaft;

first and second output shafts;

a transfer mechanism coupled to said second output shaft and including a drive sprocket rotatably supported on said first output shaft;

an interaxle differential having an input member coupled to said input shaft, a first output member coupled to said first output shaft, and a second output member coupled to said drive sprocket;

a mode clutch including a drum fixed to said drive sprocket and a clutch pack mounted between said input member and said drum;

a clutch actuation mechanism including a lever arm having a first end acting on said clutch pack, a thrust pin supported in a throughbore formed in said drive sprocket and having a first end acting on a second end of said lever arm, and an actuation member acting on a second end of said thrust pin, said actuation member being movable between first and second positions for causing corresponding pivotal movement of said lever arm between a first position and a second position, said lever arm operable in its first position to exert a minimum clutch engagement force on said clutch pack and is operable in its second position to exert a maximum clutch engagement force on said clutch pack; and

a power-operated actuator for controlling movement of said actuation member between its first and second positions.

14. The transfer case of claim 13 wherein said mode clutch further includes an end plate connecting said drum to said drive sprocket, said end plate supporting said lever arm for movement between its first and second position, and said clutch actuation mechanism further comprising a return spring for urging said lever arm toward its first position.

15. The transfer case of claim 14 wherein said input member of said interaxle differential is a ring gear fixed to said input shaft, said first output member is a sun gear fixed to said first output shaft, and said second output member is a carrier fixed to said drive sprocket, said carrier rotatably supporting a gearset which is meshed with said sun gear and said ring gear.

16. The transfer case of claim 14 wherein said input member of said interaxle differential is a carrier, said first output member is a first sun gear fixed to said first output shaft, and said second output member is a second sun gear fixed to said drive sprocket, and wherein said carrier supports a gearset that is meshed with said first and second sun gears.

17. The transfer case of claim 13 wherein said actuation member is a mode fork, and wherein said power-operated actuator includes a motor having a drive member operably connected to said mode fork for controlling axial movement thereof.

18. The transfer case of claim 13 wherein said actuation member is a mode piston disposed in a pressure chamber, and wherein said power operated actuator includes a source of hydraulic fluid, a control valve for controlling the flow of fluid to said pressure chamber, and a controller for controlling actuation of said control valve, said controller operable to modulate the actuated condition of said control valve for moving said mode piston between its first and second positions in said pressure chamber for modulating the clutch engagement force applied on said clutch pack as a function of sensor signals.

19. A transfer case comprising:

an input shaft;

first and second output shafts;

a planetary gearset including a sun gear fixed to said input shaft, a ring gear, and a set of pinion gears meshed with said ring gear and said sun gear and which are rotatably supported from a carrier;

a range sleeve fixed to said ring gear and moveable between first and second positions, said range sleeve is operable in its first position to couple said ring gear to said sun gear and is operable in its second position to couple said ring gear to a stationary member;

an interaxle differential driven by said carrier and having a first output operably fixed for rotation to said first output shaft, a second output operably fixed for rotation with said second output shaft, and a gearset for transferring drive torque from said carrier to said first and second outputs while permitting speed differentiation therebetween;

a mode clutch for controlling speed differentiation and torque biasing between said first and second outputs of said interaxle differential; and

an actuator assembly for controlling movement of said range sleeve.

20. The transfer case of claim 19 wherein said range sleeve has clutch teeth that are releasably engageable with clutch teeth on a first clutch plate fixed to said input shaft when said range sleeve is in its first position, and said range sleeve clutch teeth are releasably engageable with clutch teeth on a second clutch plate fixed to said stationary member when said range sleeve is in its second position, and further including a first synchronizer disposed between said range sleeve and said first clutch plate, and a second synchronizer disposed between said range sleeve and said second clutch plate.

21. The transfer case of claim 19 wherein said mode clutch includes a clutch pack disposed between said carrier and one of said first and second outputs of said interaxle differential, and a thrust mechanism operable for exerting a clutch engagement force on said clutch pack.

22. The transfer case of claim 21 wherein said actuator assembly is further operable to control movement of said thrust mechanism.

23. The transfer case of claim 22 wherein said thrust mechanism includes a lever arm having a first end acting on a pressure plate for exerting said clutch engagement force on said clutch pack, and wherein said actuator assembly includes an actuator member acting on a second end of said lever arm, and a power-operated device for moving said actuator member to cause corresponding movement of said lever arm.