System and Method for Controlling a Hydraulic System

• US 20040164609A1
• Filed: 06/20/2003
• Published: 08/26/2004
• Est. Priority Date: 02/26/2003
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Motor Company
• Inventors: Brewer, Michael Edward, Brown, Todd Allen
• Granted Patent: US 6,997,524 B2
• Time in Patent Office: Days
• US Class Current: 303/113.1
• CPC Class Codes: B60T 11/30 Bleed valves for hydraulic brake systems
• CPC Class Codes: B60T 17/222 by filling or bleeding of hydraulic systems
• CPC Class Codes: B60T 8/243 for roll-over protection
• CPC Class Codes: B60T 8/4809 Traction control, stability control, using both the wheel brakes and other automatic braking systems
• CPC Class Codes: B60T 8/5025 in hydraulic brake systems
• CPC Class Codes: Y10T 137/2562 Dividing and recombining

Abstract

A method for preventing a valve orifice from switching to the small size when a high build gradient is required includes briefly bleeding off a small amount of fluid at the upstream side of the valve. This momentarily reduces the pressure difference when beginning the pressure build. After the valve is opened with the large orifice, the fluid flow through the valve prevents a high pressure difference. The resulting build with the large orifice has the maximum pressure gradient.

Claims

1. A method for controlling a hydraulic system including a valve having a small orifice and a large orifice comprising:

generating a first pressure difference across the valve;

bleeding off a small amount of a fluid at an upstream side of the valve thereby generating a pressure difference less than the first pressure difference at an onset of a pressure build across the valve; and

opening the large orifice of the valve in response to said reduced pressure difference thereby preventing a high pressure difference across the valve and generating a maximum control pressure gradient.

2. A method as in claim 1 further comprising generating a deswitch pulse from a controller to activate bleeding of said fluid.

3. A method as in claim 2, wherein generating said deswitch pulse further comprises generating said deswitch pulse in response to a signal that a bleed pulse is feasible or in response to a signal that a pressure drop across the valve can be sufficiently reduced without impacting system control.

4. A method as in claim 2, wherein generating said deswitch pulse further comprises generating said deswitch pulse in response to a valve signal corresponding to the small orifice.

5. A method as in claim 4, wherein generating said deswitch pulse further comprises generating said deswitch pulse in response to a valve signal corresponding to a signal that the valve is likely switched to the small orifice.

6. A method as in claim 2, wherein generating said deswitch pulse further comprises halting said deswitch pulse in response to a signal that sufficient fluid pressure has been bled.

a method for controlling a hydraulic system including a valve having a small orifice and a large orifice comprising:

generating a first pressure difference across the valve;

controlling the valve through a controller, thereby generating a reduced pressure difference less than the first pressure difference at an onset of a pressure build across the valve; and

opening the large orifice of the valve in response to said reduced pressure difference thereby preventing a high pressure difference across the valve and generating a maximum pressure build.

7. A method as in claim 7, wherein controlling the valve through a controller further comprises overriding pressure based switching of the valve.

8. A hydraulic system comprising:

a fluid line adapted to contain a fluid;

a switchable valve coupled to said fluid line, said switchable valve comprising a small orifice and a large orifice, said switchable valve adapted to switch to said small orifice in response to a high pressure difference across said valve, said switchable valve further adapted to switch to said large orifice in response to a low pressure difference across said valve; and

a controller adapted to control said fluid line and adapted to bleed a portion of said fluid in response to an onset of a pressure build, whereby said valve opens with said large orifice, thereby generating a maximum build gradient.

9. A system as in claim 9, wherein said controller is further adapted to initiate a deswitch pulse when pressure build across said switchable valve is requested.

10. A system as in claim 9, wherein said controller is further adapted to initiate a deswitch pulse in response to a pressure build not keeping up with a pressure request.

11. A system as in claim 9, wherein said controller is further adapted to initiate a deswitch pulse in response to a signal that an orifice deswitch is feasible or a signal that said deswitch pulse has not already been performed during a current pressure lag condition or when said deswitch pulse is not currently being performed.

13. A system as in claim 9, wherein said controller includes a deswitch timer adapted to limit length of controller bleed time.

12. A system as in claim 12, wherein said controller is further adapted to reset said deswitch pulse when said pressure build no longer lags said request.

14. A system as in claim 14, wherein said controller is further adapted to reset said deswitch timer when said pressure build no longer lags an RSC request.

15. A control system for a vehicle comprising:

a first brake bleed mechanism adapted to bleed a portion of a fluid in response to a deswitch signal;

a second brake bleed mechanism;

a fluid line coupled to said first brake bleed mechanism and said second brake bleed mechanism and adapted to contain said fluid;

a switchable valve coupled to said fluid line and comprising a small orifice and a large orifice, said switchable valve adapted to switch to said small orifice in response to a high pressure difference across said valve, said switchable valve further adapted to switch to said large orifice in response to a low pressure difference across said valve; and

a controller adapted to generate said deswitch signal at a beginning of a pressure build thereby relieving pressure on an upstream side of said switchable valve through said first brake bleed mechanism, whereby said switchable valve switches to said large orifice thereby allowing maximum fluid flow through said switchable valve.

16. A system as recited in claim 16 further comprising:

a first caliper; and

a second caliper, wherein said first brake bleed mechanism is coupled to said first caliper and said second brake bleed mechanism is coupled to said second caliper.

17. A system as recited in claim 16, wherein said controller is adapted to generate said deswitch signal, wherein said pressure on said upstream side of said switchable valve is relieved by requesting a brief pressure build for said first bleed mechanism.

18. A system as recited in claim 16, wherein said first bleed mechanism and said second bleed mechanism are on a single brake circuit.

19. A system as recited in claim 16 further comprising a driver pedal, wherein said controller halts said deswitch signal in response to driver braking or a significant pressure build from a driver pedal.

20. A system as recited in claim 16, further comprising a braking device,

wherein said controller generates said deswitch signal in response to a pressure lag condition, wherein said pressure lag condition is determined when a pressure estimate for said first brake bleed mechanism is lower than a pressure requested by said braking device for said first bleed mechanism.

21. A system as recited in claim 21, wherein said controller further comprises a deswitch timer and is further adapted to reset said deswitch signal when said pressure build no longer lags said pressure requested for said first bleed mechanism.

22. A system as recited in claim 22, wherein said deswitch timer limits said deswitch signal to thereby relieve pressure from the upstream side of the valve while preventing a significant decrease in pressure on a downstream side of said switchable valve.

23. A dynamic control system comprising:

a plurality of sensors generating a dynamic control signal;

a brake system comprising a fluid line coupled to a brake bleed mechanism and adapted to contain brake fluid, said brake system further comprising a switchable valve coupled to said fluid line and comprising a small orifice and a large orifice, said switchable valve adapted to switch to said small orifice in response to a high pressure difference across said valve, said switchable valve further adapted to switch to said large orifice in response to a low pressure difference across said valve; and

a controller controlling said brake system in response to said dynamic control signal, said controller generating a pressure build and a pressure bleed at a beginning of said pressure build thereby relieving pressure on an upstream side of said switchable valve through said first brake bleed mechanism, whereby said switchable valve switches to said large orifice thereby allowing maximum fluid flow through said switchable valve.

24. The system of claim 24, wherein the dynamic control system is a rollover control system, and the dynamic control signal is a rollover control signal.

25. A method for controlling a hydraulic system including a plurality of sensors and a valve, the valve having a small orifice and a large orifice comprising:

generating a rollover signal from one of the sensors;

generating a first pressure difference across the valve;

bleeding off a small amount of a fluid at an upstream side of the valve thereby generating a pressure difference less than the first pressure difference at an onset of a pressure build across the valve;

opening the large orifice of the valve in response to said reduced pressure difference thereby preventing a high pressure difference across the valve and generating a maximum pressure gradient; and

controlling a braking mechanism in response to fluid received through the large orifice.

26. A dynamic control system comprising:

a plurality of sensors generating a dynamic control signal;

a brake system comprising a fluid line coupled to a brake bleed mechanism and adapted to contain brake fluid, said brake system further comprising a switchable valve coupled to said fluid line and comprising a small orifice and a large orifice, wherein a valve control signal determines which of said large orifice and said small orifice is used for fluid flow; and

a controller controlling said brake system in response to said dynamic control signal, said controller generating a pressure build and further generating said valve control signal at a beginning of said pressure build, whereby said switchable valve switches to said large orifice thereby allowing maximum fluid flow through said switchable valve.