Test sequence for brake system

A method of testing a braking system for an automotive vehicle that includes a master cylinder, a brake booster, a plurality of brake assemblies, a plurality of inlet valves, each inlet valve adapted to selectively allow brake fluid to flow into one of the plurality of brake assemblies and a plurality of outlet valves, each outlet valve adapted to selectively allow brake fluid to flow from one of the brake assemblies to a brake fluid reservoir, the method includes testing a first one of the plurality of inlet valves, testing a first one of the plurality of outlet valves, and sending diagnostic information to a controller within the automotive vehicle.

INTRODUCTION

The present disclosure relates to a method of testing components within a braking system. Automotive vehicles are commonly slowed and stopped with hydraulic brake systems. These systems typically include a brake pedal, a tandem master cylinder, fluid conduits arranged in two similar but separate brake circuits, and wheel brakes in each circuit. The driver of the vehicle operates a brake pedal which is connected to the master cylinder. When the brake pedal is depressed, the master cylinder generates hydraulic forces in both brake circuits by pressurizing brake fluid. The pressurized fluid travels through the fluid conduit in both circuits to actuate brake cylinders at the wheels to slow the vehicle.

Brake systems typically use a brake booster which pressurizes the brake fluid beyond what is capable by the master cylinder. New advanced systems related to braking, such as anti-lock braking (ABS) and traction control requires precise control of the braking of each wheel independently. To accomplish this control, the hydraulic circuit that provides pressurized brake fluid from the brake booster and the master cylinder to the brakes at each of the wheels of the vehicle includes valves to selectively block or allow flow of brake fluid to and from the wheels of the vehicle.

It is important to ensure that all of the valves are operating properly. Current systems do not provide the ability to test and diagnose the operation of such valves. Thus, while current braking systems achieve their intended purpose, there is a need for a new and improved test sequence for such brake systems.

SUMMARY

According to several aspects of the present disclosure, a method of testing a braking system for an automotive vehicle that includes a master cylinder, a brake booster, a plurality of brake assemblies, a plurality of inlet valves, each inlet valve adapted to selectively allow brake fluid to flow into one of the plurality of brake assemblies and a plurality of outlet valves, each outlet valve adapted to selectively allow brake fluid to flow from one of the brake assemblies to a brake fluid reservoir, the method includes testing a first one of the plurality of inlet valves, testing a first one of the plurality of outlet valves, and sending diagnostic information to a controller within the automotive vehicle.

According to another aspect, testing a first one of the plurality of inlet valves further includes closing all of the inlet valves, actuating the brake booster and increasing the pressure of the brake fluid between the brake booster and the inlet valves to a pre-determined Boost Pressure, measuring a first plunger volume of the brake booster, opening the first one of the plurality of inlet valves, actuating the brake booster and increasing the pressure of the brake fluid between the brake booster and the inlet valves to the pre-determined Boost Pressure, measuring a second plunger volume of the brake booster, and when the difference between the first and second plunger volume exceeds an Expected Difference Threshold, sending diagnostic information that the first one of the plurality of inlet valves has not failed to the controller within the automotive vehicle.

According to another aspect, the method further includes when the difference between the first and second plunger volume does not exceed the Expected Difference Threshold, and when the first plunger volume exceeds a Fail Open Threshold, sending diagnostic information that the first one of the plurality of inlet valves has failed to an open state to the controller within the automotive vehicle.

According to another aspect, the method further includes when the difference between the first and second plunger volume does not exceed the Expected Difference Threshold, and when the first plunger volume does not exceed the Fail Open Threshold, sending diagnostic information that the first one of the plurality of inlet valves has failed to a closed state to the controller within the automotive vehicle.

According to another aspect, testing a first one of the plurality of inlet valves further includes opening the first one of the plurality of outlet valves, and when the pressure of the brake fluid between the brake booster and the inlet valves drops below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the first one of the plurality of outlet valves has not failed to the controller within the automotive vehicle.

According to another aspect, the method further includes, when the pressure of the brake fluid between the brake booster and the inlet valves does not drop below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the first one of the plurality of outlet valves has failed to a closed position to the controller within the automotive vehicle.

According to another aspect, the method further includes, testing the first one of the plurality of inlet valves and testing the first one of the plurality of outlet valves upon the occurrence of an operating event of the automotive vehicle, testing a second one of the plurality of inlet valves and testing a second one of the plurality of outlet valves upon the next occurrence of the operating event of the automotive vehicle.

According to another aspect, the method further includes, testing the first one of the plurality of inlet valves and testing the first one of the plurality of outlet valves upon the occurrence of an operating event of the automotive vehicle, and sequentially testing a different one of the plurality of inlet valves and testing a different one of the plurality of outlet valves upon each occurrence of the operating event of the automotive vehicle.

According to another aspect, a primary boost isolation valve is positioned between the brake booster and two of the plurality of inlet valves and between the master cylinder and the two of the plurality of inlet valves, the primary boost isolation valve is selectively moveable between a first position, wherein flow of brake fluid only from the master cylinder to the two of the plurality of inlet valves is open, a second position, wherein flow of brake fluid from only the brake booster to the two of the plurality of inlet valves is open, and a third position, wherein flow of brake fluid from both the master cylinder and the brake booster to the two of the plurality of inlet valves is open, and a secondary boost isolation valve is positioned between the brake booster and at the remaining of the plurality of inlet valves and between the master cylinder and the remaining of the plurality of inlet valves, the secondary boost isolation valve is selectively moveable between a first position, wherein flow of brake fluid only from the master cylinder to the remaining of the plurality of inlet valves is open, a second position, wherein flow of brake fluid from only the brake booster to the remaining of the plurality of inlet valves is open, and a third position, wherein flow of brake fluid from both the master cylinder and the brake booster to the remaining of the plurality of inlet valves is open, the method further including actuating the primary boost isolation valve to the first position, actuating the secondary boost isolation valve to the second position, actuating all of the plurality of inlet valves to the closed position, actuating the brake booster to increase the pressure of the brake fluid between the brake booster and the primary and secondary boost isolation valves to a pre-determined level, thereby causing the primary boost isolation valve to spontaneously move to the third position, wherein pressure between the brake booster and the primary and secondary boost isolation valves is substantially equal to the pressure of the brake fluid between the master cylinder and the primary and secondary boost isolation valves, de-activating the brake booster, thereby causing the primary boost isolation valve to spontaneously move back to the first position, actuating the remaining of the plurality of inlet valves to the open position, actuating the remaining of the plurality of outlet valves to the open position, actuating the secondary boost isolation valve to the first position, and when the pressure of the brake fluid between the master cylinder and the secondary boost isolation valve falls below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the secondary boost isolation valve is functioning properly.

According to another aspect, the method further includes, when the pressure of the brake fluid between the master cylinder and the secondary boost isolation valve does not fall below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the secondary boost isolation valve has failed.

According to several aspects of the present disclosure, a method of testing a braking system for an automotive vehicle that includes a brake booster, a first brake assembly associated with a first wheel of the automotive vehicle, a second brake assembly associated with a second wheel of the automotive vehicle, a third brake assembly associated with a third wheel of the motor vehicle, and a fourth brake assembly associated with a fourth wheel of the automotive vehicle, a first inlet valve adapted to selectively allow flow of brake fluid to the first brake assembly, a second inlet valve adapted to selectively allow flow of brake fluid to the second brake assembly, a third inlet valve adapted to selectively allow flow of brake fluid to the third brake assembly, and a fourth inlet valve adapted to selectively allow flow of brake fluid to the fourth brake assembly, a first outlet valve adapted to selectively allow brake fluid to flow from the first brake assembly to a brake fluid reservoir, a second outlet valve adapted to selectively allow flow of brake fluid from the second brake assembly to the brake fluid reservoir, a third outlet valve adapted to selectively allow flow of brake fluid from the third brake assembly to the brake fluid reservoir, and a fourth outlet valve adapted to selectively allow brake fluid to flow from the fourth brake assembly to the brake fluid reservoir, the method comprising sequentially and alternately testing one of the first inlet valve and the first outlet valve, the second inlet valve and the second outlet valve, the third inlet valve and the third outlet valve and the fourth inlet valve and the fourth outlet valve upon consecutive occurrences of an operational event of the automotive vehicle, and sending diagnostic information to a controller within the automotive vehicle each time one of the first inlet valve and the first outlet valve, the second inlet valve and the second outlet valve, the third inlet valve and the third outlet valve and the fourth inlet valve and the fourth outlet valve is tested.

According to another aspect, sequentially and alternately testing one of the first inlet valve and the first outlet valve, the second inlet valve and the second outlet valve, the third inlet valve and the third outlet valve and the fourth inlet valve and the fourth outlet valve upon the occurrence of an operational event of the automotive vehicle further includes closing the first, second, third and fourth inlet valves, actuating the brake booster and increasing the pressure of the brake fluid between the brake booster and the inlet valves to a pre-determined Boost Pressure, measuring a first plunger volume of the brake booster, actuating one of the first, second, third and fourth inlet valves to an open position, actuating the brake booster and increasing the pressure of the brake fluid between the brake booster and the first, second, third and fourth inlet valves to the pre-determined Boost Pressure, measuring a second plunger volume of the brake booster, and when the difference between the first and second plunger volume exceeds an Expected Difference Threshold, sending diagnostic information that the actuated one of the first, second, third and fourth inlet valves has not failed to the controller within the automotive vehicle.

According to another aspect, the method further includes, when the difference between the first and second plunger volume does not exceed the Expected Difference Threshold, and when the first plunger volume exceeds a Fail Open Threshold, sending diagnostic information that the actuated one of the first, second, third and fourth inlet valves has failed to an open state to the controller within the automotive vehicle.

According to another aspect, the method further includes, when the difference between the first and second plunger volume does not exceed the Expected Difference Threshold, and when the first plunger volume does not exceed the Fail Open Threshold, sending diagnostic information that the actuated one of the first, second, third and fourth inlet valves has failed to a closed state to the controller within the automotive vehicle.

According to another aspect, sequentially and alternately testing one of the first inlet valve and the first outlet valve, the second inlet valve and the second outlet valve, the third inlet valve and the third outlet valve and the fourth inlet valve and the fourth outlet valve upon the occurrence of an operational event of the automotive vehicle further includes actuating one of the first, second, third and fourth outlet valves corresponding to the actuated one of the first, second, third and fourth inlet valves to an open position, and when the pressure of the brake fluid between the brake booster and the first, second, third and fourth inlet valves drops below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the actuated one of the first, second, third and fourth outlet valves has not failed to the controller within the automotive vehicle.

According to another aspect, the method further includes, when the pressure of the brake fluid between the brake booster and the first, second, third and fourth inlet valves does not drop below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the actuated one of the first, second, third and fourth outlet valves has failed to a closed position to the controller within the automotive vehicle.

According to another aspect, a primary boost isolation valve is positioned between the brake booster and the first and second inlet valves and between the master cylinder and the first and second inlet valves, the primary boost isolation valve is selectively moveable between a first position, wherein flow of brake fluid only from the master cylinder to the first and second inlet valves is open, a second position, wherein flow of brake fluid from only the brake booster to the first and second inlet valves is open, and a third position, wherein flow of brake fluid from both the master cylinder and the brake booster to the first and second inlet valves is open, a secondary boost isolation valve is positioned between the brake booster and at the third and fourth inlet valves and between the master cylinder and the third and fourth inlet valves, the secondary boost isolation valve is selectively moveable between a first position, wherein flow of brake fluid only from the master cylinder to the third and fourth inlet valves is open, a second position, wherein flow of brake fluid from only the brake booster to the third and fourth inlet valves is open, and a third position, wherein flow of brake fluid from both the master cylinder and the brake booster to the third and fourth inlet valves is open, the method including, actuating the primary boost isolation valve to the first position, actuating the secondary boost isolation valve to the second position, actuating the first, second third and fourth inlet valves to the closed position, actuating the brake booster to increase the pressure of the brake fluid between the brake booster and the primary and secondary boost isolation valves to a pre-determined level, thereby causing the primary boost isolation valve to spontaneously move to the third position, wherein pressure between the brake booster and the primary and secondary boost isolation valves is substantially equal to the pressure of the brake fluid between the master cylinder and the primary and secondary boost isolation valves, de-activating the brake booster, thereby causing the primary boost isolation valve to spontaneously move back to the first position, actuating the third and fourth inlet valves to the open position, actuating the third and fourth outlet valves to the open position, actuating the secondary boost isolation valve to the first position, and when the pressure of the brake fluid between the master cylinder and the secondary boost isolation valve falls below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the secondary boost isolation valve is functioning properly, and when the pressure of the brake fluid between the master cylinder and the secondary boost isolation valve does not fall below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the secondary boost isolation valve has failed.

According to several aspects of the present disclosure, a method of testing a braking system for an automotive vehicle includes, upon consecutive occurrences of an operational event of the automotive vehicle sequentially and alternately testing one of a first inlet valve and a first outlet valve that are associated with a first wheel and first brake assembly, a second inlet valve and a second outlet valve that are associated with a second wheel and a second brake assembly, a third inlet valve and a third outlet valve that are associated with a third wheel and a third brake assembly, and a fourth inlet valve and a fourth outlet valve that are associated with a fourth wheel and a fourth brake, wherein testing one of the first inlet valve and the first outlet valve, the second inlet valve and the second outlet valve, the third inlet valve and the third outlet valve and the fourth inlet valve and the fourth outlet valve further includes closing the first, second, third and fourth inlet valves, actuating a brake booster and increasing the pressure of brake fluid between the brake booster and the first, second, third and fourth inlet valves to a pre-determined Boost Pressure, measuring a first plunger volume of the brake booster, actuating one of the first, second, third and fourth inlet valves to an open position, actuating the brake booster and increasing the pressure of brake fluid between the brake booster and the first, second, third and fourth inlet valves to the pre-determined Boost Pressure, measuring a second plunger volume of the brake booster, and when the difference between the first and second plunger volume exceeds an Expected Difference Threshold, sending diagnostic information that the actuated one of the first, second, third and fourth inlet valves has not failed to the controller within the automotive vehicle, and when the difference between the first and second plunger volume does not exceed the Expected Difference Threshold, and when the first plunger volume exceeds a Fail Open Threshold, sending diagnostic information that the actuated one of the first, second, third and fourth inlet valves has failed to an open state to the controller within the automotive vehicle, and when the difference between the first and second plunger volume does not exceed the Expected Difference Threshold, and when the first plunger volume does not exceed the Fail Open Threshold, sending diagnostic information that the actuated one of the first, second, third and fourth inlet valves has failed to a closed state to the controller within the automotive vehicle.

According to another aspect, testing one of the first inlet valve and the first outlet valve, the second inlet valve and the second outlet valve, the third inlet valve and the third outlet valve and the fourth inlet valve and the fourth outlet valve further includes actuating one of the first, second, third and fourth outlet valves corresponding to the actuated one of the first, second, third and fourth inlet valves to an open position, and when the pressure of the brake fluid between the brake booster and the first, second, third and fourth inlet valves drops below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the actuated one of the first, second, third and fourth outlet valves has not failed to the controller within the automotive vehicle, and when the pressure of the brake fluid between the brake booster and the first, second, third and fourth inlet valves does not drop below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the actuated one of the first, second, third and fourth outlet valves has failed to a closed position to the controller within the automotive vehicle.

According to another aspect, the method further includes, actuating a primary boost isolation valve to a first position, wherein the primary boost isolation valve is positioned between the brake booster and the first and second inlet valves and between a master cylinder and the first and second inlet valves and is selectively moveable between a first position, wherein flow of brake fluid only from the master cylinder to the first and second inlet valves is open, a second position, wherein flow of brake fluid from only the brake booster to the first and second inlet valves is open, and a third position, wherein flow of brake fluid from both the master cylinder and the brake booster to the first and second inlet valves is open, actuating a secondary boost isolation valve to a second position, wherein the secondary boost isolation valve is positioned between the brake booster and at the third and fourth inlet valves and between the master cylinder and the third and fourth inlet valves, the secondary boost isolation valve is selectively moveable between a first position, wherein flow of brake fluid only from the master cylinder to the third and fourth inlet valves is open, a second position, wherein flow of brake fluid from only the brake booster to the third and fourth inlet valves is open, and a third position, wherein flow of brake fluid from both the master cylinder and the brake booster to the third and fourth inlet valves is open, actuating the first, second third and fourth inlet valves to the closed position, actuating the brake booster to increase the pressure of the brake fluid between the brake booster and the primary and secondary boost isolation valves to a pre-determined level, thereby causing the primary boost isolation valve to spontaneously move to the third position, wherein pressure between the brake booster and the primary and secondary boost isolation valves is substantially equal to the pressure of the brake fluid between the master cylinder and the primary and secondary boost isolation valves, de-activating the brake booster, thereby causing the primary boost isolation valve to spontaneously move back to the first position, actuating the third and fourth inlet valves to the open position, actuating the third and fourth outlet valves to the open position, actuating the secondary boost isolation valve to the first position, and when the pressure of the brake fluid between the master cylinder and the secondary boost isolation valve falls below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the secondary boost isolation valve is functioning properly, and when the pressure of the brake fluid between the master cylinder and the secondary boost isolation valve does not fall below a pre-determined threshold within a pre-determined amount of time, sending diagnostic information that the secondary boost isolation valve has failed.

DETAILED DESCRIPTION

Referring toFIG.1, a hydraulic brake system10is adapted to provide pressurized brake fluid to a plurality of brake assemblies12A,12B,12C,12D in an automotive vehicle. In the exemplary embodiment shown inFIG.1, the automotive vehicle includes a first wheel14A, a second wheel14B, a third wheel14C, and a fourth wheel14D. A first brake assembly12A is associated with the first wheel14A and is adapted to provide braking of the first wheel14A. A second brake assembly12B is associated with the second wheel14B and is adapted to provide braking of the second wheel14B. A third brake assembly12C is associated with the third wheel14C and is adapted to provide braking of the third wheel14C. A fourth brake assembly12D is associated with the fourth wheel14D and is adapted to provide braking of the fourth wheel14D.

Brake fluid within the hydraulic brake system10is pressurized by a master cylinder16and a brake booster18. The master cylinder16and the brake booster18pull brake fluid from a brake fluid reservoir20and feed pressurized brake fluid to the hydraulic brake system10. A plurality of inlet valves22A,22B,22C,22D are adapted to selectively allow brake fluid to flow into the brake assemblies12A,12B,12C,12D. A first inlet valve22A is adapted to selectively allow brake fluid to flow into the first brake assembly12A. A second inlet valve22B is adapted to selectively allow brake fluid to flow into the second brake assembly12B. A third inlet valve22C is adapted to selectively allow brake fluid to flow into the third brake assembly12C. A fourth inlet valve22D is adapted to selectively allow brake fluid to flow into the fourth brake assembly12D.

A plurality of outlet valves24A,24B,24C,24D are adapted to selectively allow brake fluid to flow out of the brake assemblies12A,12B,12C,12D. A first outlet valve24A is adapted to selectively allow brake fluid to flow out of the first brake assembly12A. A second outlet valve24B is adapted to selectively allow brake fluid to flow out of the second brake assembly12B. A third outlet valve24C is adapted to selectively allow brake fluid to flow out of the third brake assembly12C. A fourth outlet valve24D is adapted to selectively allow brake fluid to flow out of the fourth brake assembly12D.

A primary boost isolation valve26is positioned between the brake booster18and a portion of the plurality of inlet valves22A,22B,22C,22D and between the master cylinder16and the portion of the plurality of inlet valves22A,22B,22C,22D. The primary boost isolation valve26is fed by both the master cylinder16through a primary master cylinder circuit28, and by the brake booster18through a brake booster circuit30.

As shown in the exemplary embodiment ofFIG.1, the primary boost isolation valve26feeds brake fluid to the first and second inlet valves22A,22B. The primary boost isolation valve26is selectively moveable between a first position, a second position and a third position. When the primary boost isolation valve26is in the first position, the primary boost isolation valve26only allows brake fluid from the master cylinder16to flow to the first and second inlet valves22A,22B. When the primary boost isolation valve26is in the second position, the primary boost isolation valve26only allows brake fluid from the brake booster18to flow to the first and second inlet valves22A,22B. When the primary boost isolation valve26is in the third position, the primary boost isolation valve26allows brake fluid from both the master cylinder16and the brake booster18to flow to the first and second inlet valves22A,22B.

A secondary boost isolation valve32is positioned between the brake booster18and the remaining of the plurality of inlet valves22A,22B,22C,22D and between the master cylinder16and the remaining of the plurality of inlet valves22A,22B,22C,22D. The secondary boost isolation valve32is fed by both the master cylinder16through a secondary master cylinder circuit34, and by the brake booster18through the brake booster circuit30. As shown in the exemplary embodiment ofFIG.1, The secondary boost isolation valve32feeds brake fluid to the third and fourth inlet valves22C,22D. The secondary boost isolation valve32is selectively moveable between a first position, a second position and a third position. When the secondary boost isolation valve32is in the first position, the secondary boost isolation valve32only allows brake fluid from the master cylinder16to flow to the third and fourth inlet valves22C,22D. When the secondary boost isolation valve32is in the second position, the secondary boost isolation valve32only allows brake fluid from the brake booster18to flow to the third and fourth inlet valves22C,22D. When the secondary boost isolation valve32is in the third position, the secondary boost isolation valve32allows brake fluid from both the master cylinder16and the brake booster18to flow to the third and fourth inlet valves22C,22D.

A method of testing the hydraulic brake system10according to the present disclosure includes testing a first one of the plurality of inlet valves22A,22B,22C,22D, testing a first one of the plurality of outlet valves24A,24B,24C,24D, and sending diagnostic information to a controller within the automotive vehicle. In an exemplary embodiment, the first inlet valve22A and the first outlet valve24A, the second inlet valve22B and the second outlet valve24B, the third inlet valve22C and the third outlet valve24C and the fourth inlet valve22D and the fourth outlet valve24D are sequentially and alternately tested upon consecutive occurrences of an operational event of the automotive vehicle.

For example, when the ignition switch of the automotive vehicle is turned off, the first inlet valve22A and the first outlet valve24A are tested. The next time the automotive vehicle is used, and when the ignition switch is again turned off, the second inlet valve22B and the second outlet valve24B are tested. The process is repeated so each time the ignition switch is turned off, one of the first inlet valve22A and the first outlet valve24A, the second inlet valve22B and the second outlet valve24B, the third inlet valve22C and the third outlet valve24C and the fourth inlet valve22D and the fourth outlet valve24D are tested in sequence. This reduces the testing time as compared to testing all of the first inlet valve22A and the first outlet valve24A, the second inlet valve22B and the second outlet valve24B, the third inlet valve22C and the third outlet valve24C and the fourth inlet valve22D and the fourth outlet valve24D each time the ignition switch is turned off.

Referring toFIG.2, a flow chart36illustrates the method of testing one of the inlet valves22A,22B,22C,22D. Starting at block38, the ignition switch is turned off and the test sequence begins. It should be understood that other suitable events may trigger the testing.

At block40, all of the inlet valves22A,22B,22C,22D are closed, all of the outlet valves24A,24B,24C,24D are closed and the primary and secondary boost isolation valves26,32are moved to the second position.

Moving to block42, the brake booster18is actuated. The brake booster18includes a plunger44that when actuated moves forward, as indicated by arrow46, to push brake fluid from the brake booster18through the brake booster circuit30to the primary and secondary boost isolation valves26,32. The primary and secondary boost isolation valves26,32, now in the second position, allow brake fluid to flow to the inlet valves22A,22B,22C,22D. Because the inlet valves22A,22B,22C,22D are closed, pressure of the brake fluid between the inlet valves22A,22B,22C,22D and the brake booster18will increase as the plunger44within the brake booster18moves forward. The brake booster18is actuated until the pressure of the brake fluid between the brake booster18and the inlet valves22A,22B,22C,22D increases to a pre-determined Boost Pressure. The pressure of the brake fluid between the brake booster18and the inlet valves22A,22B,22C,22D is measured by a brake booster circuit pressure sensor66that is located within the brake booster circuit30.

Referring toFIG.4andFIG.5,FIG.4is a chart wherein the x-axis50denotes time, and the y-axis52denotes the position of the plunger44within the brake booster18.FIG.5is a chart wherein the x-axis54denotes time and the y-axis56denotes the pressure of the brake fluid between the brake booster18and the inlet valves22A,22B,22C,22D (within the brake booster circuit30), as measured by the brake booster pressure sensor66. As the plunger44within the brake booster18moves forward, as indicated by58inFIG.4, the pressure of the brake fluid between the brake booster18and the inlet valves22A,22B,22C,22D increases, as indicated at60inFIG.5. Once the pressure of the brake fluid between the brake booster and the inlet valves reaches the pre-determined Boost Pressure62, the brake booster18is deactivated and the plunger44within the brake booster18is retracted, causing the pressure within the brake booster circuit30to drop, as indicated at70.

Moving on to block64, a first plunger volume is calculated using the position of the plunger44within the brake booster18. A position sensor48within the brake booster18determines the position of the plunger44within the brake booster18.

Moving on to block68, one of the first, second, third and fourth inlet valves22A,22B,22C,22D is opened, connecting the brake booster circuit30to one of the first, second, third and fourth brake assemblies12A,12B,12C.12D at one of the first, second, third and fourth wheels14A.14B,14C,14D.

Moving to block72, the brake booster18is again actuated, moving the plunger44within the brake booster18forward. All of the outlet valves24A,24B,24C,24D are closed, as the plunger44moves forward, brake fluid will be pressurized between the brake booster18and the three of the inlet valves22A,22B,22C,22D that are still closed and the closed one of the outlet valves24A,24B,24C,24D that is associated with the opened one of the inlet valves22A,22B,22C,22D. For example, if the first inlet valve22A is being tested, as the plunger44within the brake booster18moves forward, brake fluid will be pushed through the opened first inlet valve22A and into the first brake assembly12A. As the plunger44within the brake booster18continues to move forward, as indicated by74inFIG.4, the pressure of the brake fluid between the brake booster18and the closed second, third and fourth inlet valves22B,22C,22D and the closed first outlet valve24A will increase, as indicated by76inFIG.5. Once the pressure of the brake fluid between the brake booster18and the closed second, third and fourth inlet valves22B,22C,22D and the closed first outlet valve24A increases back to the pre-determined Boost Pressure62, the brake booster18is de-activated and the plunger44within the brake booster18is held in place.

Moving on to block78, a second plunger volume is calculated using the position of the plunger44within the brake booster18. If the opened one of the inlet valves22A,22B,22C,22D failed to open, then there will not be a dramatic reduction in the pressure of the brake fluid in the brake booster circuit30. Thus, when the brake booster18is re-activated at block72, the plunger44within the brake booster18will only need to move slightly or not at all to bring the pressure within the brake booster circuit30back up to the pre-determined Boost Pressure62, and the difference between the first and second plunger volume will be minimal or even zero. Thus, when the brake booster18is re-activated at block72, the plunger44within the brake booster18will need to move significantly to bring the pressure within the brake booster circuit30back up to the pre-determined Boost Pressure62, and the difference between the first and second plunger volume will be significant.

Referring toFIG.6, a chart is shown wherein the x-axis80denotes calculated plunger volume and the y-axis82denotes the pressure of the brake fluid within the brake booster circuit30. The pressure increase that occurs when the brake booster18is activated with all inlet valves22A,22B,22C,22D closed is indicated at84. The pressure increase that occurs when the brake booster18is re-activated after one of the first, second, third and fourth inlet valves22A,22B,22C,22D is closed is indicated at86.

Moving to block88, the difference between the first and second plunger volume is compared to an Expected Difference Threshold90at a pre-determined boost pressure level. Moving on to block92, if the difference between the first and second plunger volume exceeds the Expected Difference Threshold90, diagnostic information is sent indicating that the opened one of the first, second, third and fourth inlet valves22A,22B,22C,22D has not failed to the controller within the automotive vehicle. As shown inFIG.6, the actual plunger volume difference94required to bring the pressure of the brake fluid within the brake booster circuit30exceeds the Expected Difference90, and thus is an indication that the opened one of the first, second, third and fourth inlet valves22A,22B,22C,22D is functioning properly. The Expected Difference Threshold90is a measure that is calculated to account for the additional volume needed to be filled and pressurized by brake fluid when one of the inlet valves22A,22B,22C,22D has been opened.

Moving to block96, if the difference between the first and second plunger volume does not exceed the Expected Difference Threshold90, the first plunger volume is compared to an Fail Open Threshold. Moving to block98, if the first plunger volume exceeds a Fail Open Threshold, diagnostic information is sent that the first one of the plurality of inlet valves22A,22B,22C,22D has failed to an open state to the controller within the automotive vehicle. When the brake booster18initially actuates, and all of the inlet valves22A,22B,22C,22D are actuated to a closed position, if the inlet valve that is being tested has failed to an open state, it will take longer for the brake booster18to build pressure within the brake booster circuit30. The Fail Open Threshold is a plunger volume that is calculated to be beyond what would be expected when the inlet valves22A,22B,22C,22D are all closed.

Moving to block100, if the difference between the first and second plunger volume does not exceed the Expected Difference Threshold, and if the first plunger volume does not exceed the Fail Open Threshold, diagnostic information is sent indicating that the one of the plurality of inlet valves22A,22B,22C,22D that is being tested has failed to a closed state to the controller within the automotive vehicle.

Moving to block102, if the difference between the first and second plunger volume exceeds the Expected Difference Threshold90, and it is determined that the tested one of the inlet valves22A,22B,22C,22D has not failed, the boost plunger44position is held constant, as shown inFIG.4, and the one of the outlet valves24A,24B,24C,24D corresponding to the tested one of the inlet valves22A,22B,22C,22D is tested by opening the one of the outlet valves24A,24B,24C,24D corresponding to the tested one of the inlet valves22A,22B,22C,22D.

Moving to block104, after the one of the outlet valves24A,24B,24C,24D corresponding to the tested one of the inlet valves22A,22B,22C,22D is opened, the pressure drop within the brake booster circuit30is monitored to determine how quickly the pressure within the brake booster circuit drops.

Moving to block106, if the pressure of the brake fluid in the brake booster circuit30drops below a pre-determined threshold108within a pre-determined amount of time110, diagnostic information is sent that the tested outlet valve has not failed to the controller within the automotive vehicle.

Referring toFIG.5, when the tested outlet valve is opened at the time indicated by114, if the tested one of the outlet valves24A,24B,24C,24D is functioning properly and opens, the pressurized brake fluid will flow through the tested one of the outlet valves24A,24B,24C,24D causing the pressure to drop in the brake booster circuit30, as indicated at116. If this is the case, the pressure will fall off below the pre-determined threshold108within the pre-determined amount of time, as indicated inFIG.5.

If the pressure of the brake fluid between the brake booster18and the inlet valves22A,22B,22C,22D does not drop below the pre-determined threshold108within the pre-determined amount of time110, moving to block118, diagnostic information that the tested one of the outlet valves24A,24B,24C,24D has failed to a closed position is sent to the controller within the automotive vehicle.

Moving to block112, the system resets itself and prepares to cycle at the next occurrence of a specified operating event of the vehicle, such as by way of non-limiting example, whenever the ignition of the automotive vehicle is shut off.

Referring toFIG.3, in an exemplary embodiment of the present disclosure the method includes testing the secondary boost isolation valve32, at block120. Moving to block122, the primary boost isolation valve26is actuated to the first position, the secondary boost isolation valve32is actuated to the second position and all of the inlet valves22A,22B,22C,22D are actuated to the closed position.

Moving to block124, the brake booster18is actuated and the plunger44within the brake actuator18moves forward pressurizing the brake fluid between the brake booster18and the primary and secondary boost isolation valves26,32(the brake booster circuit30) to a pre-determined level. By way of non-limiting example, the brake fluid within the brake booster circuit30is pressurized to approximately 30 Bar. The brake fluid in the primary master cylinder circuit28is not pressurized, and the pressure difference between the brake booster circuit30and the primary master cylinder circuit28causes the primary boost isolation valve26to spontaneously move to the third position. At this point, the pressure of the brake fluid within the brake booster circuit30and the primary and secondary master cylinder circuits28,34equalizes, wherein pressure between the brake booster18and the primary and secondary boost isolation valves26,32is substantially equal to the pressure of the brake fluid between the master cylinder16and the primary and secondary boost isolation valves26,32.

Moving to block126, the brake booster18is de-activated and the plunger44within the brake booster18moves back to de-pressurize the brake fluid in the brake booster circuit30. Now the pressure in the primary and secondary master cylinder circuits28,34is higher than the pressure in the brake booster circuit30, causing the primary boost isolation valve26to spontaneously move back to the first position, the brake booster circuit30is de-pressurized, and the primary and secondary master cylinder circuits28,34remain pressurized.

Moving to block128, the third and fourth inlet valves22C,22D are actuated to an open position. Moving to block130, the third and fourth outlet valves24C,24D are actuated to an open position. Moving to block132, the secondary boost isolation valve32is actuated to the first position. Opening the third and fourth inlet valves22C,22D and the third and fourth outlet valves24C,24D provides a clear path for brake fluid to flow from the secondary boost isolation valve32through the third and fourth inlet valves22C,22D, through the third and fourth outlet valves24C,24D, and back to the brake fluid reservoir20. When the secondary boost isolation valve32is actuated to the first position, brake fluid from the secondary master cylinder circuit34flows through the secondary boost isolation valve32causing the pressure of the brake fluid within the secondary master cylinder circuit34to fall off.

Referring toFIG.7, a chart is illustrated wherein the x-axis134denotes time and the y-axis136denotes pressure of the brake fluid within the brake booster circuit30. Referring again to block124, the brake booster is actuated and the plunger within the brake actuator moves forward pressurizing the brake fluid between the brake booster and the primary and secondary boost isolation valves26,32(the brake booster circuit30) to a pre-determined level, as indicated at138inFIG.7. Referring again to block126, the brake booster is de-activated, as indicated at140inFIG.7, and the plunger44within the brake booster18moves back to de-pressurize the brake fluid in the brake booster circuit30, as indicated by142inFIG.7.

Referring toFIG.8, a chart illustrates wherein the x-axis144denotes time and the y-axis146denotes the pressure of brake fluid in the primary and secondary master cylinder circuits28,34. Referring again to block126, the brake booster18is de-activated and the plunger44within the brake booster18moves back to de-pressurize the brake fluid in the brake booster circuit, as indicated at142inFIG.7, and the primary and secondary master cylinder circuits28,34remain pressurized, as indicated by148and150inFIG.8.

Referring again to block128, the third and fourth inlet valves are actuated to an open position. Referring again to block130, the third and fourth outlet valves are actuated to an open position. Referring again to block132, the secondary boost isolation valve is actuated to the first position. When the secondary boost isolation valve32is actuated to the first position, brake fluid from the secondary master cylinder circuit34flows through the secondary boost isolation valve32causing the pressure of the brake fluid within the secondary master cylinder circuit34to fall off, as indicated by152inFIG.8.

If the secondary boost isolation valve32is functioning properly, the pressure of the brake fluid within the secondary master cylinder circuit34will fall off, as indicated by the line152. Correspondingly, the pressure within the primary master cylinder circuit28will fall off slightly slower than the secondary master cylinder circuit34, as indicated by the line154inFIG.8.

Moving to block156, the pressure of the brake fluid between the master cylinder16and the secondary boost isolation valve32is monitored to determine how quickly the pressure falls off. Moving to block158, if the pressure of the brake fluid between the master cylinder16and the secondary boost isolation valve32does not fall below a pre-determined threshold160within a pre-determined amount of time162, diagnostic information is sent that the secondary boost isolation valve has failed.

If the pressure of the brake fluid between the master cylinder16and the secondary boost isolation valve32(secondary master cylinder circuit34) falls below the pre-determined threshold160within the pre-determined amount of time162, as shown inFIG.8, moving to block162, diagnostic information is sent that the secondary boost isolation valve32is functioning properly.

Similarly to the first inlet valve22A and the first outlet valve24A, the second inlet valve22B and the second outlet valve24B, the third inlet valve22C and the third outlet valve24C and the fourth inlet valve22D and the fourth outlet valve24D, the secondary boost isolation valve32may be tested upon the occurrence of an operational event of the automotive vehicle.