System and method to improve engagement shift quality in automatic transmissions using engagement brake torque control

Patent metadata

Field	Value
Publication number	US-9855936-B2
Application number	US-201514924953-A
Country	US
Kind code	B2
Filing date	Oct 28, 2015
Priority date	Oct 28, 2015
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A method of controlling a vehicle includes, in response to vehicle speed being approximately zero and a driver braking torque request being greater than a park interlock threshold, commanding vehicle brakes to provide an augmented braking torque. The augmented braking torque has a magnitude that is greater than the magnitude of the braking torque request. The braking torque returns to the level of the driver braking torque request following completion of a gear shift event.

First claim

What is claimed is:

1. A method of controlling a vehicle having a braking system configured to provide braking torque to traction wheels and a transmission configured to operate according to a plurality of transmission modes, the method comprising:
in response to vehicle speed being less than a speed threshold and a driver braking request being less than a brake interlock threshold, commanding the braking system to apply a first braking torque to the traction wheels, the first braking torque being equal to the driver braking request;
in response to vehicle speed being less than the speed threshold and the driver braking request exceeding the brake interlock threshold, commanding the braking system to apply a second braking torque to the traction wheels, the second braking torque having a magnitude exceeding the driver braking request; and
in response to the transmission completing a shift from a first mode to a second mode with the second braking torque applied, commanding the braking system to adjust the magnitude of the second braking torque to a level equal to the driver braking request.

2. The method of claim 1 , wherein the second braking torque magnitude is based on the first mode of the transmission.

3. The method of claim 1 , wherein the first mode is a PARK gear and the second mode is a DRIVE gear.

4. The method of claim 1 , wherein the second braking torque magnitude is determined based on a drive shaft torque, a transmission clutch torque, and a preset torque margin.

5. The method of claim 1 , wherein commanding the braking system to apply a third braking torque includes reducing braking torque from the second braking torque to the third braking torque at a preset rate based on the second mode of the transmission.

6. A vehicle comprising:
traction wheels;
a braking system configured to provide braking torque to the traction wheels; and
a controller configured to, in response to vehicle speed being less than a speed threshold and a driver braking torque request being greater than a brake interlock threshold, command the braking system to provide an augmented braking torque to the traction wheels, the augmented braking torque being greater than the driver braking torque request.

7. The vehicle of claim 6 , further comprising a gear shifter, wherein the augmented braking torque is based on a gear shifter position when the driver braking torque request is received.

8. The vehicle of claim 6 , wherein the controller is further configured to, in response to a transmission gear shift being completed with the augmented braking torque applied, command the braking system to adjust the braking torque to a level equal to the braking torque request.

9. The vehicle of claim 8 , further comprising a gear shifter, wherein the controller is further configured to command the braking system to reduce braking torque from the augmented braking torque to the braking torque based on the braking torque request at a preset rate based on a final gear shifter position.

10. The vehicle of claim 6 , wherein the controller is further configured to, in response to a detected road grade exceeding a preset threshold, command the braking system to provide an augmented braking torque corresponding to the greater of a preset value based on a gear shifter position and a braking torque to hold the vehicle stationary at the detected road grade.

11. A method of controlling a vehicle, comprising:
in response to vehicle speed being less than a speed threshold and a driver braking torque request being greater than a brake interlock threshold, commanding vehicle brakes to provide an augmented braking torque, the augmented braking torque having a magnitude greater than the driver braking torque request.

12. The method of claim 11 , wherein the augmented braking torque magnitude is in response to a gear shifter position when the driver braking torque request is received.

13. The method of claim 11 , wherein the augmented braking torque magnitude is determined based on a drive shaft torque, a transmission clutch torque, and a preset torque margin.

14. The method of claim 11 , further comprising, in response to a transmission gear shift being completed with the augmented braking torque applied, commanding the vehicle brakes to provide a braking torque equal to the braking torque request.

15. The method of claim 14 , wherein commanding the vehicle brakes to provide a braking torque based on the braking torque request includes commanding the vehicle brakes to reduce braking torque from the augmented braking torque to the braking torque equal to the braking torque request at a calibratable rate.

16. The method of claim 15 , wherein the transmission gear shift is in response to a gear shifter being moved from an initial position to a final position, and wherein the preset rate is based on the final position.

17. The method of claim 14 , wherein the commanding the vehicle brakes to provide a braking torque equal to the braking torque request is in further response to the vehicle being stationary.

18. The method of claim 11 , wherein a detected road grade exceeds a preset threshold, and the augmented braking torque magnitude corresponds to the greater of a preset value based on a gear shifter position and a braking torque to hold the vehicle stationary at the detected road grade.

19. The method of claim 11 , further comprising in response to an acceleration request and the vehicle brakes providing the augmented braking torque, commanding the vehicle brakes to reduce braking torque at a preset rate.

Assignees

• Ford Global Tech Llc

Inventors

• Bousamra Joseph
• Suter Charles William
• Hill Thaddeus

Classifications

• B60T8/52

  Torque sensing, i.e. wherein the braking action is controlled by forces producing or tending to produce a twisting or rotating motion on a braked rotating member · CPC title

• B60T8/17 Primary

  Using electrical or electronic regulation means to control braking {(detecting or indicating faulty operation B60T8/885)} · CPC title

• B60T8/245

  Longitudinal vehicle inclination · CPC title

• B60T2201/06

  Hill holder; Start aid systems on inclined road · CPC title

• B60T8/3205

  acceleration (B60T8/34, B60T8/52, B60T8/54, B60T8/56, B60T8/58, B60T8/72, B60T8/86, B60T8/88 take precedence) · CPC title