Powertrain for a hybrid vehicle with all-wheel drive capability and method for controlling wheel slip

• US 20040176203A1
• Filed: 12/29/2003
• Published: 09/09/2004
• Est. Priority Date: 05/03/2001
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Motor Company
• Inventors: Kozarekar, Shailesh, Supina, Joseph
• Granted Patent: US 7,163,480 B2
• Time in Patent Office: Days
• US Class Current: 475/8
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 28/16 responsive to, or preventing, skidding of wheels brake control systems for vehicle drive stability B60T8/1755; arrangements responsive to a speed condition for adjusting wheel braking force B60T8/32; control of vehicle driving stability otherwise than by controlling the propulsion unit only B60W30/02; preventing wheel slippage by reducing power in rail vehicles B61C15/00
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/40 characterised by the assembly or relative disposition of components
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/448 Electrical distribution type
• CPC Class Codes: B60K 6/52 Driving a plurality of drive axles, e.g. four-wheel drive
• CPC Class Codes: B60K 6/54 Transmission for changing ratio
• 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 10/115 with planetary gears
• 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 2520/26 Wheel slip
• CPC Class Codes: B60W 2720/403 between front and rear axle
• CPC Class Codes: B60W 30/18027 Drive off, accelerating from standstill
• CPC Class Codes: F16H 2037/0866 Power split variators with distributing differentials, with the output of the CVT connected or connectable to the output shaft
• CPC Class Codes: F16H 2037/0873 : with switching, e.g. to change ranges
• CPC Class Codes: F16H 2200/0034 : the gear ratios comprising two forward 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 2200/2035 : with two engaging means
• CPC Class Codes: F16H 3/52 : comprising orbital spur gears
• CPC Class Codes: F16H 3/54 : one of the central gears being internally toothed and the other externally toothed
• CPC Class Codes: F16H 3/725 : with means to change ratio in the mechanical gearing
• CPC Class Codes: F16H 3/727 : with at least two dynamo electric machines for creating an electric power path inside the gearing, e.g. using generator and motor for a variable power torque path special adapted for a hybrid electric vehicle B60K6/20
• CPC Class Codes: F16H 3/728 : with means to change ratio in the mechanical gearing
• CPC Class Codes: F16H 37/046 : with an additional planetary gear train, e.g. creep gear, overdrive
• CPC Class Codes: F16H 57/04 : Features relating to lubrication or cooling or heatingin hydrokinetic gearing F16H41/30; control of lubrication or cooling in hydrostatic gearing F16H61/4165
• CPC Class Codes: F16H 57/0434 : relating to lubrication supply, e.g. pumps arrangement of pumps F16H57/0441; Pressure control grooves with pumping effect for supplying lubricant F16H57/0428; generation and variation of line pressure for transmission control F16H61/0021
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y10S 903/916 : with plurality of drive axles

Abstract

A hybrid-electric powertrain for a vehicle having forward traction wheels and rearward traction wheels in an all-wheel drive configuration. An engine and an electric motor deliver power through delivery paths to the traction wheels. The power delivery paths may have multiple ratio gearing so that more power can be delivered mechanically to improve powertrain performance and to allow the electric motor size to be reduced. The powertrain may include a controller for automatically balancing power distribution to the forward and rearward traction wheels to avoid wheel slip.

Claims

1. A powertrain for an all-wheel drive vehicle with forward and rearward sets of traction wheels, the powertrain comprising:

an engine;

an electric generator;

an electric motor;

a geared transmission having a first torque delivery element connected drivably to the engine, a second torque delivery element connected drivably to the generator and a torque output element;

the electric motor being drivably connected to the forward set of traction wheels and being electrically coupled to the generator; and

a multiple ratio gear unit drivably connecting the torque output element of the geared transmission to the rearward set of traction wheels, whereby mechanical energy is distributed to the rearward set of traction wheels and electrical energy is distributed to the forward set of traction wheels.

2. The powertrain set forth in claim 1 wherein the geared transmission comprises:

a planetary gear unit having a ring gear, a planetary carrier and a sun gear;

the engine being drivably connected to the carrier;

the generator being drivably connected to the sun gear; and

the torque output element of the geared transmission being drivably connected to the ring gear.

3. The powertrain set forth in claim 1 wherein the multiple ratio gear unit comprises:

a first element connected to the torque output element of the geared transmission;

a second element connected drivably to the rearward set of traction wheels; and

a clutch and brake friction element sub-assembly selectively connecting a third element of the multiple ratio gear unit to ground and to another one of the first and second elements of the multiple ratio gear unit, whereby multiple gear ratios for the multiple ratio gear unit are established.

4. The powertrain set forth in claim 1 wherein the multiple ratio gear unit comprises:

a first element connected to the torque output element of the geared transmission;

a second element connected drivably to the rearward set of traction wheels;

a clutch and brake friction element sub-assembly for selectively connecting a third element of the multiple ratio gear unit to ground and to another one of the first and second elements of the multiple ratio gear unit, whereby multiple gear ratios for the multiple ratio gear unit are established; and

a slipping friction brake for providing torque reaction for the geared transmission during engine starting as the generator provides engine cranking torque.

5. The powertrain set forth in claim 1 wherein the multiple ratio gear unit includes a countershaft gear system comprising:

a first countershaft gear on a countershaft axis connected drivably to the torque output element of the geared transmission;

a second countershaft gear on the countershaft axis;

a torque output gear connected to the rearward set of traction wheels;

a first clutch selectively connecting the first and second countershaft gears; and

a second countershaft clutch selectively connecting the torque output element of the geared transmission to the rearward set of traction wheels.

6. The powertrain set forth in claim 3 wherein the multiple ratio gear unit is a planetary gear unit comprising a ring gear, a planetary carrier and a sun gear;

the ring gear being connected to the torque output element of the geared transmission, the planetary carrier being connected to the rearward traction wheels;

the clutch and brake friction element sub-assembly selectively connecting the ring gear to the sun gear to provide a high gear ratio and to selectively ground the sun gear to provide an underdrive gear ratio.

7. The powertrain set forth in claim 1 wherein geared transmission comprises:

a generator brake, the generator brake being applied to effect operation of the powertrain in a parallel mode, whereby all of the energy for powering the vehicle is transferred to the rearward set of wheels mechanically.

8. The powertrain set forth in claim 2 wherein the geared transmission comprises:

a generator brake, the generator brake being applied to effect operation of the powertrain in a parallel mode, whereby all of the energy for powering the vehicle is transferred to the rearward set of wheels mechanically.

9. The powertrain set forth in claim 1 wherein the engine develops mechanical energy and the geared transmission transfers the mechanical energy to the generator, whereby the generator converts the mechanical energy to electrical energy for the electric motor in a positive power distribution operating mode.

10. The powertrain set forth in claim 2 wherein the engine develops mechanical energy and the geared transmission transfers the mechanical energy to the generator, whereby the generator converts the mechanical energy to electrical energy for the electric motor in a positive power distribution operating mode.

11. The powertrain set forth in claim 1 wherein the electric motor functions to generate electrical energy as it is driven by the forward set of traction wheels, whereby the generator develops power opposing engine power to reduce engine speed in a negative power distribution operating mode.

12. The powertrain set forth in claim 2 wherein the electric motor functions to generate electrical energy as it is driven by the forward set of traction wheels, whereby the generator develops power opposing engine power to reduce engine speed in a negative power distribution operating mode.

13. The powertrain set forth in claim 3 wherein the clutch and brake friction element sub-assembly comprises a pressure-operated slipping friction brake grounding the third element of the multiple ratio gear unit whereby torque transfer to the rearward set of traction wheels is modified to achieve smooth vehicle start-up.

14. The powertrain set forth in claim 3 wherein the clutch and brake friction element sub-assembly comprises a pressure-operated brake defining in part powerflow paths to the rearward traction wheels, the pressure-operated brake being a slipping brake, the capacity of the slipping brake being modified during engine start-up to achieve smoothness.

15. A powertrain for an all-wheel drive vehicle with forward wheels and rearward traction wheels comprising:

an engine;

an electric generator;

an electric motor;

a geared transmission having a first torque delivery element connected drivably to the engine and a second torque delivery element connected drivably to the generator and a torque output element connected drivably to the rearward traction wheels;

a first multiple ratio gear unit drivably connecting the electric motor to the forward traction wheels, the motor being electrically coupled to the generator; and

a second multiple ratio gear unit drivably connecting the torque output element of the geared transmission to the rearward traction wheels, whereby mechanical energy is distributed to the rearward set of wheels through the second multiple ratio gear unit and electrical energy is distributed to the forward traction wheels through the first multiple ratio gear unit.

16. The powertrain set forth in claim 15 wherein the geared transmission comprises:

a planetary gear unit having a ring gear, a planetary carrier and a sun gear;

the engine being drivably connected to the carrier;

the generator being drivably connected to the sun gear; and

the torque output element of the geared transmission being drivably connected to the ring gear.

17. The powertrain set forth in claim 15 wherein the second multiple ratio gear unit comprises:

a first element connected to the torque output element of the geared transmission;

a second element connected drivably to the rearward set of traction wheels; and

a clutch and brake friction element sub-assembly selectively connecting a third element of the second multiple ratio gear unit to ground and to another of the elements of the second multiple ratio gear unit, whereby multiple gear ratios for the second multiple ratio gear unit are established.

18. The powertrain set forth in claim 15 wherein the engine develops mechanical energy and the geared transmission transfers the mechanical energy to the generator, whereby the generator converts the mechanical energy to electrical energy for the electric motor in a positive power distribution operating mode.

19. The powertrain set forth in claim 15 wherein the electric motor functions to generate electrical energy as it is driven by the forward traction wheels, whereby the generator develops power added to engine power to reduce engine speed in a negative power distribution operating mode.

20. A method for controlling power distribution to front traction wheels and to rear traction wheels in a hybrid-electric powertrain for an all-wheel drive vehicle using measured traction wheel speed information, the powertrain including an engine, a generator, an electric motor and a geared transmission, the method comprising:

transferring incrementally decreased power to a slipping traction wheel while transferring incrementally increased power to a non-slipping traction wheel, whereby the total power distributed to the traction wheels remains unchanged.

21. The method set forth in claim 20 wherein the step of transferring incrementally decreased power and incrementally increased power to the traction wheels comprises the steps of:

increasing engine torque and decreasing engine speed when the front traction wheels slip, the torque of the electric motor during front wheel slip being equal to torque at the front wheels less a computed incremental electric motor torque.

22. The method set forth in claim 20 wherein the step of transferring incrementally decreased power and incrementally increased power to the traction wheels comprises the step of:

decreasing engine torque and increasing engine speed when rear traction wheels slip, the torque of the electric motor during rear wheel slip being equal to torque at the front wheels plus a computed incremental electric motor torque.

23. A method for controlling power distribution to front traction wheels and to rear traction wheels in a hybrid-electric powertrain for an all-wheel drive vehicle, the powertrain comprising an engine, a generator, an electric motor and a geared transmission establishing power distribution to the traction wheels, the method comprising the steps of:

determining whether an all-wheel drive mode is on;

determining power demand;

conditioning the powertrain for negative power distribution when the all-wheel drive mode is off and power demand is low; and

conditioning the powertrain for positive power distribution when the all-wheel drive mode is off and power demand is high.

24. A method for controlling power distribution to front traction wheels and to rear traction wheels in a hybrid-electric powertrain for an all-wheel drive vehicle, the powertrain comprising an engine, a generator, an electric motor and a geared transmission establishing power distribution to the traction wheels, the method comprising the steps of:

determining whether an all-wheel drive mode is on; and

conditioning the powertrain for positive power distribution when the all-wheel drive mode is on, whereby the generator delivers power to the front traction wheels.

25. The method set forth in claim 24 wherein the step of conditioning the powertrain for positive power distribution when the all-wheel drive mode is on comprises the step of:

determining engine torque using a calibrated driver demand and engine speed relationship.

26. A method for managing proportional power distribution to front traction wheels and to rear traction wheels in a hybrid-electric powertrain for an all-wheel drive vehicle, the method comprising:

determining whether an all-wheel drive mode is selected;

measuring wheel speeds at the traction wheels;

obtaining one set of engine speed and torque values for the engine when the all-wheel drive mode is selected;

obtaining another set of engine speed and torque values for the engine when a two-wheel drive mode is selected;

the sets of engine speed and torque values defining operating modes for the engine characterized by selected engine performance and efficiency for all-wheel drive operation and for two-wheel drive operation;

detecting rear wheel slip; and

decreasing engine torque and increasing motor torque when the rear wheels slip, whereby total wheel torque at the rear wheels remains unchanged.

27. A method for managing proportional power distribution to front traction wheels and to rear traction wheels in a hybrid-electric powertrain for an all-wheel drive vehicle, the method comprising:

determining whether an all-wheel drive mode is selected;

measuring wheel speeds at the traction wheels;

obtaining one set of engine speed and torque values for the engine when the all-wheel drive mode is selected;

obtaining another set of engine speed and torque values for the engine when a two-wheel drive mode is selected;

the sets of engine speed and torque values defining operating modes for the engine characterized by selected engine performance and efficiency for all-wheel drive operation and for two-wheel drive operation;

detecting front wheel slip; and

increasing engine torque and decreasing motor torque when the front wheels slip, whereby total torque at the rear wheels remains unchanged.