Torque distribution control in a motor vehicle

• US 20080234906A1
• Filed: 03/22/2007
• Published: 09/25/2008
• Est. Priority Date: 03/22/2007
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Warner, Matthew A.
• Granted Patent: US 7,832,518 B2
• Time in Patent Office: Days
• US Class Current: 701/67
• CPC Class Codes: B60K 23/0808 for varying torque distribution between driven axles, e.g. by transfer clutch
• CPC Class Codes: B60K 28/165 acting on elements of the vehicle drive train other than the propulsion unit and brakes, e.g. transmission, clutch, differential acting on brakes B60T8/17

Abstract

In a vehicle powertrain that continually transmits power to a first set of vehicle wheels and selectively transmits power through a clutch to a second set of vehicle wheels, a method for controlling the clutch includes determining that brakes for slowing the vehicle wheels are applied and that an accelerator pedal of the vehicle is depressed less than a reference magnitude, determining that the rate of change of the average front wheel speed is greater than the rate of change of the average rear wheel speed, and setting the torque capacity of the clutch to a target magnitude.

Claims

1. In a vehicle powertrain that continually transmits power to a first set of vehicle wheels and selectively transmits power through a clutch to a second set of vehicle wheels, a method for controlling the clutch, comprising the steps of:

(a) determining that brakes for slowing the vehicle wheels are applied;

(b) determining that an accelerator pedal of the vehicle is depressed less than a reference magnitude;

(c) determining that the rate of change of the average front wheel speed is greater than the rate of change of the average rear wheel speed; and

(d) setting the torque capacity of the clutch to a target magnitude.

2. The method of claim 1 wherein step (c) further comprises the steps of:

determining repetitively the speed of the front and rear vehicle wheels;

determining repetitively an average speed of the front vehicle wheels and an average speed of the rear vehicle wheels; and

using the average speed of the front and rear vehicle wheels to determine the rate of change of the average speed of the front vehicle wheels.

3. The method of claim 1 wherein step (d) further comprises the step of:

setting the duty cycle of a servo that actuates the clutch to a predetermined magnitude.

4. The method of claim 3 wherein the duty cycle is set to two percent.

5. The method of claim 1 wherein step (d) further comprises the step of:

setting the pressure in a servo that actuates the clutch to a predetermined magnitude.

6. The method of claim 1 further comprising the step of varying the torque capacity of the clutch if either the accelerator pedal of the vehicle is depressed more than a reference magnitude, or the brakes for slowing the vehicle wheels are not applied.

7. A system for controlling the transmittal of torque to first and second sets of vehicle wheels in a vehicle powertrain, comprising:

speed sensors producing signals that represent the speed of the front and rear vehicle wheels;

a first sensor producing a signal that represents the state of the engine throttle or a request to accelerate the vehicle;

a second sensor producing a signal indicating whether the wheel brakes are applied;

a clutch having a variable torque capacity for selectively transmitting torque to one of the first and second sets of vehicle wheels; and

a controller communicating with the speed sensors, the first sensor, the second sensor and the clutch, the controller being configured to determine that the wheel brakes are applied, that the engine throttle is open less than a reference magnitude, that the rate of change of the average front wheel speed is greater than the rate of change of the average rear wheel speed, and to set the torque capacity of the clutch to a target magnitude.

8. The system of claim 7, further comprising:

a servo for changing the torque capacity of the clutch; and

wherein the controller is further configured to send a command signal to the servo that causes the torque capacity of the clutch to be set to a target magnitude target in response to the command signal.

9. The system of claim 7, further comprising:

a servo for changing the torque capacity of the clutch; and

wherein the clutch is electromagnetically-actuated and the controller is further configured to send a command signal to the servo that causes the torque capacity of the clutch to be set to a target magnitude in response to a duty cycle applied to the servo.

10. The system of claim 7, further comprising:

a servo for changing the torque capacity of the clutch; and

wherein the clutch is hydraulically-actuated and the controller is further configured to send a command signal to the servo that causes the torque capacity of the clutch to be set to a target magnitude in response to a magnitude of hydraulic pressure applied to the servo.

11. The system of claim 7, further comprising;

an accelerator pedal; and

wherein the first sensor produces a signal that represents a degree to which the accelerator pedal is depressed.

12. The system of claim 7, further comprising:

a brake pedal for actuating brakes that slow the vehicle wheels; and

wherein the second sensor produces a signal in response to the position of the brake pedal indicating whether that the wheel brakes are applied.