Hybrid Electric Vehicle Hold Function

• US 20110136625A1
• Filed: 11/18/2010
• Published: 06/09/2011
• Est. Priority Date: 12/09/2009
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: McGee, Ryan, Boesch, Mathew, Yu, Hai
• Granted Patent: US 8,579,765 B2
• Time in Patent Office: Days
• US Class Current: 477/185
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 10/188 hydraulic brakes
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60W 30/18027 Drive off, accelerating from standstill
• CPC Class Codes: B60W 30/18118 Hill holding

Abstract

A vehicle powertrain with engine start-stop characteristics is capable of maintaining a vehicle stationary on a roadway with a gradient when wheel brakes are applied to stop the vehicle as the engine is shut down. Vehicle creep and vehicle launch is achieved as the engine is re-started following detection of a brake release signal based on engine speed.

Claims

1. A method for controlling a vehicle having a powertrain with an engine, and vehicle wheel brakes;

the method comprising;

stopping the engine in response to application of the wheel brakes as the vehicle approaches a stopped state on a roadway with a gradient;

maintaining the brakes applied during an engine re-start time interval whereby vehicle motion is avoided during an engine cranking mode;

detecting engine speed during an engine cranking mode; and

releasing the brakes during the engine cranking mode in response to detection of a peak engine speed during a transition from the cranking mode to an engine idle mode.

2. The method set forth in claim 1 wherein the brakes are fluid pressure actuated and wherein a brake release decision is made after the engine is commanded to start.

3. The method set forth in claim 2 wherein a brake hold function is used to maintain the vehicle on the gradient after a brake release is detected.

4. The method set forth in claim 3 wherein actuating pressure from an active pressure source for the brake hold function is applied to the brakes at a pressure level that is higher than a driver input brake pressure level if the driver brake input pressure level is insufficient to hold the vehicle on a gradient.

5. The method set forth in claim 4 wherein the active pressure source is an electric fluid pump.

6. A method for controlling a vehicle having a powertrain with an engine and wheel brakes;

the method comprising;

stopping the engine in response to application of the wheel brakes as the vehicle approaches a stopped state on a roadway with a gradient;

maintaining the brakes applied during an engine re-start time interval whereby vehicle motion is avoided during an engine cranking mode;

detecting engine speed during the engine cranking mode; and

releasing the brakes during the engine cranking mode in response to detection of a rate of increase in engine speed that exceeds a pre-calibrated value during a transition from the cranking mode to a vehicle launch mode.

7. The method set forth in claim 6 wherein the brakes are fluid pressure actuated and wherein a brake release decision is made as the engine is commanded to start

8. The method set forth in claim 7 wherein a brake hold function is used to maintain the vehicle on the gradient after a brake release is detected.

9. The method set forth in claim 8 wherein actuating pressure from an active pressure source is applied to the brakes at a pressure level that is higher than a driver brake pressure level if the driver brake pressure level is insufficient to hold the vehicle on a gradient.

10. The method set forth in claim 9 wherein the active pressure source is an electric fluid pump.

11. A method for controlling motion of a vehicle on a road gradient, the vehicle having an engine, vehicle wheel brakes, and an active fluid pressure source for establishing a brake hold function;

the method comprising;

stopping the engine in response to application of the wheel brakes;

maintaining the brakes applied using the brake hold function during an engine re-start time interval as a starter motor is cranking the engine;

detecting engine speed characteristics including a peak engine speed during cranking of the engine; and

releasing the brakes at the end of the engine re-start time interval in response to detection of a predetermined engine speed characteristic as the vehicle enters a vehicle creep mode.

12. The method set forth in claim 11 wherein the step of releasing the brakes is made following a brake release decision that is dependent upon an occurrence of at least one of multiple release conditions including:

(i) a driver brake re-apply is detected;

(ii) an advancing engine throttle motion is detected; and

(iii) a calibrated time expires following brake application during engine cranking.

15. The method set forth in claim 11 wherein detection of engine speed characteristics during a transition from an engine cranking mode to an engine idle mode includes detection of an instant when a calibrated engine speed threshold has been passed for a calibrated amount of time;

and

releasing the brakes at that instant.

19. The method set forth in claim 11 wherein the detected speed at the engine speed peak is followed by low pass filtering and high pass filtering to obtain a smooth engine speed signal.

20. The method set forth in claim 11 wherein the detected speed at the engine speed peak is followed by low pass filtering and high pass filtering to obtain a smooth derivative of an engine speed signal.

21. The method set forth in claim 11 wherein the engine speed characteristics include rate of increase of engine speed during an engine cranking mode;

and

releasing the brakes when the rate of increase of engine speed exceeds a pre-calibrated value.

22. The method set forth in claim 11 wherein the brake hold function, using actuating pressure from the active pressure source, maintains the vehicle on a gradient larger than a predetermined value until powertrain torque is greater than a gradient induced torque.

23. The method set forth in claim 11 wherein the brake hold function, using actuating pressure from an active pressure source, maintains the vehicle on a gradient larger than a predetermined value until an engine throttle advancement is detected.

24. The method set forth in claim 11 wherein the brake hold function, using actuating pressure from the active pressure source, maintains the vehicle on a gradient larger than a predetermined value until a driver releases the brakes after an engine start up.

13. A method for controlling motion of a vehicle on a road gradient, the vehicle having an engine, and vehicle wheel brakes;

the method comprising;

stopping the engine in response to application of the wheel brakes;

maintaining the brakes applied during an engine re-start time interval as the engine is cranking;

detecting an increase in engine speed at a pre-calibrated rate during engine cranking; and

releasing the brakes at the end of the engine re-start time interval in response to detection of an increase in engine speed at a pre-calibrated rate as the vehicle enters a vehicle launch mode.

14. The method set forth in claim 13 wherein the step of releasing the brakes is made following a brake release decision that is dependent upon an occurrence of at least one of multiple release conditions including:

(i) a driver brake re-apply is detected;

(ii) an advancing engine throttle motion is detected;

(iii) a calibrated time expires following brake application during engine cranking.

16. A method for controlling motion of a vehicle on a road gradient, the vehicle having an engine, and wheel brakes;

the method comprising;

stopping the engine in response to application of the wheel brakes;

maintaining the brakes applied during an engine re-start time interval as the engine is cranking;

detecting an instant during the engine re-start time interval when engine speed exceeds a pre-calibrated engine speed threshold for a pre-calibrated amount of time; and

releasing the brakes to prepare for a vehicle launch.

17. The method set forth in claim 16 wherein the instant that the brakes are released is at the start of a vehicle creep mode.

18. The method set forth in claim 16 wherein the instant that the brakes are released is at the start of a vehicle launch mode.