Vehicle Descent Control

• US 20090012690A1
• Filed: 07/05/2007
• Published: 01/08/2009
• Est. Priority Date: 07/05/2007
• Status: Active Grant

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Chrysler Group LLC (Stellantis NV)
• Inventors: Trotter, Loren M., Chiappetta, Adam C.
• Granted Patent: US 8,121,769 B2
• Time in Patent Office: Days
• US Class Current: 701/83
• CPC Class Codes: B60T 7/12 for automatic initiation; for initiation not subject to will of driver or passenger limiting speed of vehicles other than rail vehicles B60K31/00

Abstract

Vehicle descent is controlled in at least one implementation by comparing an engine braking torque to a target engine braking torque, and controlling one or more vehicle brakes to maintain the engine braking torque substantially at the target engine braking torque. The target engine braking torque may be varied as a function of one or more factors or conditions, such as accelerator position or brake application pressure.

Claims

1. A method of controlling descent of a vehicle, the method comprising the steps of:

monitoring engine braking torque;

comparing the engine braking torque to a target engine braking torque;

applying at least one brake when the engine braking torque is less than the target engine braking torque; and

releasing at least one applied brake when the engine braking torque is greater than the target engine braking torque.

2. The method of claim 1, further comprising:

receiving an indication that the vehicle is in descent.

3. The method of claim 1, further comprising:

detecting a transmission speed ratio; and

varying the target engine braking torque as a function of the detected transmission speed ratio.

4. The method of claim 3, wherein the target engine braking torque is increased as the detected transmission speed ratio increases and decreased as the detected transmission speed ratio decreases.

5. The method of claim 1, further comprising:

detecting an accelerator position; and

varying the target engine braking torque as a function of the detected accelerator position.

6. The method of claim 5, wherein the target engine braking torque is decreased as the accelerator position is advanced and increased as accelerator position is retracted.

7. The method of claim 1, further comprising:

sensing wheel speed; and

varying the target engine braking torque as a function of the sensed wheel speed.

8. The method of claim 7, further comprising:

monitoring the sensed wheel speed for at least one of wheel lock up or slippage; and

controlling the brakes to avoid wheel lock up or slippage.

9. The method of claim 7, wherein the target engine braking torque is increased as the sensed wheel speed increases and is decreased as the sensed wheel speed decreases.

10. The method of claim 1, further comprising:

sensing brake application pressure; and

varying the target engine braking torque as a function of the sensed brake application pressure.

11. The method of claim 10, wherein the target engine braking torque is decreased as the sensed brake application pressure increases and is increased as the sensed brake application pressure decreases.

12. The method of claim 1, wherein the indication of vehicle descent is received from a longitudinal accelerometer on the vehicle.

13. The method of claim 1, wherein the engine braking torque is monitored as a signal received from an engine controller.

14. The method of claim 13, wherein the engine braking torque is monitored by, and compared to the target engine braking torque using, a chassis system controller.

15. A vehicle, comprising:

a plurality of wheels;

a plurality of brakes for slowing rotation of the wheels;

a driveline coupled to at least one of the wheels;

a transmission coupled to the driveline;

an engine coupled to the transmission; and

at least one controller to control engine and brake operation, wherein the controller is configured to;

compare actual engine braking torque to a target engine braking torque;

apply at least one of the brakes when actual engine braking torque is less than the target engine braking torque; and

release at least one applied brake when actual engine braking torque is greater than the target engine braking torque.

16. The vehicle of claim 15, wherein fee controller is further configured to receive an indication that the vehicle is in descent.

17. The vehicle of claim 15, wherein the controller is further configured to:

detect a ratio of the transmission; and

vary the target engine braking torque as a function of the detected transmission speed ratio.

18. The vehicle of claim 15, wherein the vehicle further comprises an accelerator and wherein the controller is further configured to:

detect a position of the accelerator; and

vary the target engine braking torque as a function of the detected accelerator position.

19. A method of controlling descent of a vehicle automatically without a driver having to apply brakes of the vehicle, the method comprising the steps of:

comparing an engine braking torque to a target engine braking torque; and

controlling one or more of the brakes of the vehicle so as to maintain the engine braking torque substantially at the target engine braking torque;

wherein the target engine braking torque is varied as a function of at least one of accelerator position or brake application pressure.

20. The method of claim 19, wherein the target engine braking torque is decreased as the accelerator position advances and increased as the accelerator position retracts, and wherein the target engine braking torque is decreased as the brake application pressure increases and increased as the brake application pressure decreases.