HYDRAULIC HYBRID VEHICLE METHOD OF SAFE OPERATION

• US 20120123661A1
• Filed: 01/23/2012
• Published: 05/17/2012
• Est. Priority Date: 10/18/2006
• Status: Active Grant

• Current Assignee: United States Department Of Health And Human Services (Government of the United States of America)
• Original Assignee: United States Department Of Health And Human Services (Government of the United States of America)
• Inventors: Gray, Charles L. Jr.
• Granted Patent: US 8,646,565 B2
• Time in Patent Office: Days
• US Class Current: 701/99
• CPC Class Codes: B60K 2006/126 the hydraulic accumulator starts the engine
• CPC Class Codes: B60K 6/12 by means of a chargeable fluidic accumulator
• CPC Class Codes: B60L 2240/486 Operating parameters
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60W 2540/16 Ratio selector position
• CPC Class Codes: B60W 30/18027 Drive off, accelerating from standstill
• CPC Class Codes: B60W 30/18054 at stand still, e.g. engine in idling state hill holding B60W30/18118
• CPC Class Codes: F16H 2312/20 Start-up or shut-down
• CPC Class Codes: F16H 61/4096 with pressure accumulators
• CPC Class Codes: F16H 61/4192 Detecting malfunction or potential malfunction, e.g. fail safe
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A hydraulic hybrid vehicle includes elements such as a hydraulic pump driven by an internal combustion engine and arranged to draw in low pressure fluid and pump the fluid at high pressure to an accumulator. A hydraulic motor is powered by the pressurized fluid. Safety processes are provided for detecting and addressing a number of conditions that may arise in the operation of the hydraulic hybrid vehicle, including an initialization procedure for start-up of the vehicle, a shut-down procedure, and procedures for detecting and responding to failure of the pump or motor, internal and external fluid leaks, and non-responsive actuation and mode control systems.

Claims

1. A method of operating a hydraulic hybrid vehicle system, comprising:

measuring a fluid flow at a high-pressure fluid source;

calculating a fluid flow through a hydraulic machine;

comparing a reference value with an absolute value of a difference between the measured flow and the calculated flow; and

repeating the measuring, calculating, and comparing steps if the absolute value does not exceed the reference value.

2. The method of claim 1 wherein the measuring step comprises:

obtaining a first fluid pressure value at a first point in a fluid transmission path;

obtaining a second fluid pressure value at a second point in the fluid transmission path; and

deriving the measured fluid flow from the first and second fluid pressure values and predetermined pressure drop characteristics of the fluid transmission path between the first and second points.

3. The method of claim 1 wherein the calculating step comprises multiplying a displacement setting of the machine by an rpm setting of the machine.

4. The method of claim 1, comprising shutting down the system if the absolute value exceeds the reference value.

5. The method of claim 4 wherein the shutting down step comprises:

commanding the hydraulic machine to a zero displacement;

commanding a mode valve to a neutral position;

shutting down an internal combustion engine;

closing a high-pressure fluid supply valve; and

closing a low-pressure fluid supply valve after the commanding steps and after the shutting down step.

6. A method of operating a hydraulic hybrid vehicle system, comprising:

detecting displacement of a hydraulic motor;

comparing detected displacement of the motor with a commanded displacement;

repeating the detecting and comparing steps if an absolute value of a difference between the detected displacement and the commanded displacement does not exceed a first reference value;

signaling a non-critical system fault and repeating the detecting and comparing steps if the absolute value of the difference between the detected displacement and the commanded displacement exceeds the first reference value but not a second reference value; and

removing the motor from system operation if the absolute value of the difference between the detected displacement and the commanded displacement exceeds the second reference value.

7. The method of claim 6, comprising sending a plurality of high-pressure pulses to an actuator control valve.

8. The method of claim 6, comprising commanding the motor to a displacement of zero if the absolute value of the difference between the detected displacement and the commanded displacement exceeds the second reference value, then repeating the detecting and comparing steps prior to performing the removing step.

9. The method of claim 8, comprising:

deactivating a first actuator control valve if the absolute value of the difference between the detected displacement and the commanded displacement exceeds the second reference value;

activating a second actuator control valve after performing the deactivating step;

commanding the motor to a displacement of zero after performing the activating step;

repeating the detecting and comparing steps after performing the commanding step and prior to performing the removing step.

10. The method of claim 6 wherein the removing step comprises shutting down the system.

11. The method of claim 10, comprising signaling a critical system fault after performing the shutting down step.

12. The method of claim 6 wherein the removing step comprises:

commanding a mode valve to a neutral position;

confirming a position of the mode valve;

signaling a non-critical system fault if, after performing the commanding step, the mode valve is in the neutral position; and

shutting down the system if, after performing the commanding step, the mode valve is not in the neutral position.

13. The method of claim 6 wherein the removing step comprises:

closing an isolation valve; and

signaling a non-critical system fault.

14. The method of claim 6 wherein the detecting step comprises:

obtaining a first displacement value from a first displacement position sensor;

obtaining a second displacement value from a second displacement position sensor;

comparing the first and second displacement values;

providing the first displacement value as the detected displacement if the first and second displacement values are substantially equal; and

providing, as the detected displacement, the one of the first and second displacement values that is closest in value to the commanded displacement if the first and second displacement values are not substantially equal.

15. The method of claim 14 wherein the detecting step comprises signaling a non-critical system fault after performing the providing-the-one step.

16. A method of operating a hydraulic hybrid vehicle system, comprising:

controlling, while a shift selector of the vehicle is in a position other than park or neutral, a displacement of a hydraulic motor, at least in part, in accordance with a position of an accelerator pedal; and

commanding the displacement of the motor to zero while the shift selector is in the park or neutral position.

17. The method of claim 16, comprising:

starting, if an internal combustion engine is not already running, the internal combustion engine when the shift selector is moved to the park position; and

running the internal combustion engine while the shift selector is in the park position and operation of the vehicle is enabled.

18. The method of claim 16, comprising:

controlling, while the shift selector is in the park position, a throttle position of the internal combustion engine, at least in part, in accordance with the position of the accelerator pedal; and

controlling, while the shift selector is in a position other than the park or neutral positions, the throttle position of the internal combustion engine in accordance with factors other than the position of the accelerator pedal.

19. The method of claim 16, comprising:

providing a signal if a driver of the vehicle leaves the vehicle driver'"'"'s seat while operation of the vehicle is enabled.

20. The method of claim 16, comprising:

providing a signal if a driver of the vehicle leaves the vehicle driver'"'"'s seat while the shift selector is in a position other than park.

21. The method of claim 16, comprising:

preventing removal of a key from the vehicle while the shift selector is in a position other than park.

22. the method of claim 16, comprising:

setting a displacement of the hydraulic motor to a value sufficient to cause the vehicle to creep in a direction indicated by the shift selector, while the shift selector is in a position other than park or neutral, an accelerator pedal is not depressed, and the vehicle is traveling at less than a threshold speed; and

setting the displacement of the hydraulic motor to zero while the accelerator pedal is not depressed and the vehicle is traveling at more than the threshold speed.

23. The method of claim 22 wherein the threshold speed is less than about five miles per hour.

24. The method of claim 16, comprising:

signaling a shut-down of the vehicle system;

disabling operation of the vehicle;

commanding the hydraulic motor to a zero displacement;

commanding a mode valve to a neutral position;

shutting down an internal combustion engine;

closing a high-pressure fluid supply valve after performing the commanding steps and the shutting down step; and

closing a low-pressure fluid supply valve after performing the commanding steps.

25. The method of claim 24, comprising:

checking, immediately following the signaling step and before performing any other step, a position of a shift selector; and

canceling the remaining steps if the shift selector is not in the park position.

26. The method of claim 24, comprising venting fluid pressure from a high-pressure portion of the system to a low-pressure portion of the system after performing closing the high-pressure fluid supply valve.

27. The method of claim 16, comprising:

controlling, while the shift selector is in a position other than park or neutral, a mode and displacement of the hydraulic motor, at least in part, in accordance with a position of a brake pedal, such that when the brake pedal is applied, a torque opposing a direction of travel of the vehicle is applied; and

reducing the displacement of the hydraulic motor toward a displacement of zero as a speed of the vehicle approaches zero, regardless of the pressure applied to the brake pedal.

28. The method of claim 27 wherein the reducing step comprises reducing the displacement of the hydraulic motor toward a displacement of zero as the speed of the vehicle approaches zero, such that the displacement of the motor is at zero while the vehicle is traveling below a threshold speed.

29. The method of claim 16, comprising:

momentarily reducing displacement of the motor, regardless of the position of the accelerator pedal or of a brake pedal if, while the vehicle is moving, a rotation speed of one of two drive wheels is significantly greater than a rotation speed of the other of the two drive wheels.

30. A method of operating a hydraulic hybrid vehicle system, comprising:

measuring a fluid pressure within a casing of a hydraulic motor of the system;

comparing the measured fluid pressure with a first reference value;

closing a high-pressure fluid supply valve if the measured fluid pressure exceeds the first reference value.

31. The method of claim 30, comprising signaling a critical system fault after performing the closing step.

32. The method of claim 30, comprising signaling a non-critical system fault if the measured fluid pressure exceeds a second reference value but not the first reference value.

33. The method of claim 30, comprising disabling operation of the system after performing the closing step.

34. The method of claim 30, comprising moving an actuator control valve to a position, if power to the actuator control valve is removed, such that fluid pressure is applied to an actuator controlled by the actuator control valve to move a displacement of a hydraulic motor of the system to a displacement of zero.

35. The method of claim 34 wherein the moving step includes applying a spring bias to a component of the actuator control valve.

36. The method of claim 30, comprising:

moving a mode control valve to a position, if power to the mode control valve is removed, such that the motor is decoupled from a high-pressure fluid supply.

37. The method of claim 36 wherein the moving step includes placing a first fluid port of the motor in fluid communication with a second fluid port of the motor.