Producing vehicle creep through a transmission without a torque converter

• US 8,260,513 B2
• Filed: 05/24/2010
• Issued: 09/04/2012
• Est. Priority Date: 05/24/2010
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Shelton, Matthew J., Jiang, Hong, Liu, Chunlin, Dai, Zhengyu, Fodor, Michael G.
• Primary Examiner(s): Pauls, John
• Application Number:
  US12/785,629
• Publication Number:
  US 20110288735A1
• Time in Patent Office: 834 Days
• Field of Search: 701/68, 477/71, 477/174, 180/170
• US Class Current: 701/68
• 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 10/113 with two input flow paths, e.g. double clutch transmission selection of one of the torque flow paths by the corresponding input clutch
• CPC Class Codes: B60W 2050/0012 Feedforward or open loop systems
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60W 2710/027 Clutch torque
• CPC Class Codes: B60W 2710/065 Idle condition
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 30/18063 Creeping

Abstract

A method for controlling creep in a vehicle having no transmission torque converter, includes operating an input clutch of the transmission at a desired clutch torque capacity, using a feed-forward engine torque to minimize the impact on the engine speed when additional load on the engine occurs from increasing the clutch torque capacity, producing a desired clutch slip by controlling engine idle speed, and achieving a desired vehicle speed by controlling the input clutch torque capacity.

Claims

1. A method for controlling vehicle creep using a transmission clutch, comprising:

(a) calculating a desired clutch torque that is inversely proportional to brake pressure;

(b) using a closed-loop controller to change the desired clutch torque inversely with vehicle speed;

(c) ramping clutch torque to the desired clutch torque by increasing engine torque followed by reducing engine torque to the desired clutch torque over a predetermined period;

(d) varying engine speed automatically to produce vehicle creep.

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

if a current commanded clutch torque is less than the desired clutch torque, increasing at a predetermined time rate the current commanded clutch torque to the desired clutch torque using a torque increase ramp.

3. The method of claim 1, wherein step (c) further comprises:

if a current estimate of clutch torque capacity is equal to or greater than the desired clutch torque, decreasing at a predetermined time rate the current estimate of clutch torque capacity to the desired clutch torque using a torque decrease ramp.

4. The method of claim 1, wherein step (a) further comprises calculating the desired clutch torque capacity as a function of wheel brake pressure, vehicle inclination, clutch temperature and clutch slip.

5. The method of claim 1, wherein step (b) further comprises:

using a closed loop controller, a current desired clutch torque capacity and vehicle speed and to determine the desired clutch torque capacity.

6. The method of claim 1, wherein step (c) further comprises:

if the desired clutch torque capacity is greater than a commanded clutch torque capacity, setting the increase in engine torque equal to or greater than the desired clutch torque capacity.

7. The method of claim 1, wherein step (d) further comprises:

if the desired clutch torque capacity is equal to or less than the commanded clutch torque, setting the increase in engine torque equal to or greater than a commanded clutch torque capacity.

8. The method of claim 1, wherein step (d) further comprises:

using vehicle speed and a speed ratio produced by a current gear of the transmission to determine a desired engine idle speed at which a desired slip across the clutch is produced; and

producing the desired engine idle speed.

9. A method for controlling vehicle creep using a transmission clutch, comprising:

(a) determining a desired clutch torque that is inversely proportional to brake pressure;

(b) using a closed-loop controller to change the desired clutch torque as a function of vehicle speed;

(c) ramping clutch torque to the desired clutch torque at a calibrated rate;

(d) increasing engine torque followed by reducing engine torque to the desired clutch torque over a predetermined period;

(e) varying engine speed automatically to produce vehicle creep.

10. The method of claim 9, wherein step (c) further comprises:

if the current commanded clutch torque is less than the desired clutch torque, increasing at a predetermined time rate the current commanded clutch torque to the desired clutch torque using a torque increase ramp.

11. The method of claim 9, wherein step (c) further comprises:

if a current estimate of clutch torque capacity is equal to or greater than the desired clutch torque, decreasing at a predetermined time rate the current estimate of clutch torque capacity to the desired clutch torque using a torque decrease ramp.

12. The method of claim 9, wherein step (b) further comprises:

calculating the desired clutch torque capacity as a function of wheel brake pressure, vehicle inclination, clutch temperature and clutch slip.

13. The method of claim 9, wherein step (b) further comprises:

using a closed loop controller, the desired clutch torque capacity and vehicle speed and to update the desired clutch torque capacity.

14. The method of claim 9, wherein step (c) further comprises:

if the desired clutch torque capacity is greater than a commanded clutch torque capacity, setting the increase in engine torque equal to or greater than the desired clutch torque capacity.

15. The method of claim 9, wherein step (c) further comprises:

if the desired clutch torque capacity is equal to or less than a commanded clutch torque, setting the increase in engine torque equal to or greater than the commanded clutch torque capacity.

16. The method of claim 9, wherein step (e) further comprises:

using vehicle speed and a speed ratio produced by a current gear of the transmission to determine a desired engine idle speed at which current slip across the clutch is produced; and

producing the desired engine idle speed.