Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Reexamination Certificate
2000-05-30
2001-09-18
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
C303S113400
Reexamination Certificate
active
06290310
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 11(1999)-149795 filed on May 28, 1999, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention is generally directed to vehicle brake systems. More particularly, the present invention pertains to a brake pressure control device for an automotive vehicle which regulates the brake pressure of a wheel brake in such a manner that while the wheel brake is isolated from a master cylinder and the master cylinder is in fluid communication with a pedal stroke simulator, hydraulic pressure outputted from another hydraulic pressure generating device other than the master cylinder is utilized.
BACKGROUND OF THE INVENTION
A known type of brake pressure control device is disclosed in, for example, Japanese Patent Laid-Open Publication No. Sho. 63-64858 published in 1978 without examination. In this known brake pressure control device, a 4-port/2-position electric changeover valve is located between the wheel brake and the master cylinder. The changeover valve is positionable in a first position and a second position. When the changeover valve is in the first position, the wheel brake is brought into fluid communication with the master cylinder such that the wheel brake is isolated from a power pressure source made up of a pump, a pressure accumulator, and other elements. When the changeover valve is in the second position, the wheel brake is brought into fluid communication with the power pressure source such that the wheel brake is isolated from the master cylinder and the master cylinder is brought into fluid communication with an absorbing device or stroke simulator.
The brake pressure control device is also equipped with a depression force sensor which detects the force applied to the brake pedal when the brake pedal is depressed. When the power pressure source is in a normal condition, if the changeover valve is switched from the first position to the second position, the hydraulic pressure outputted from the power pressure source to adjust the hydraulic pressure of the wheel brake becomes responsive to the depression amount of the brake pedal. In contrast, when the power pressure source experiences a failure, the changeover valve is switched from the second position to the first position to establish a direct application of the hydraulic pressure to the wheel brake from the master cylinder.
With the foregoing structure, although the absorbing device or stroke simulator is made up of a piston, a spring, and other elements, the absorbing device has to be provided with a seal member for preventing leakage of the brake fluid. In the event of a breakage of the seal member causing the absorbing device to fail, the changeover valve causes the master cylinder to connect to the absorbing device and disconnect from the wheel brake. Under the resulting condition, if the hydraulic pressure of the wheel brake is intended to be adjusted by using the brake pedal, the brake pedal is advanced through a distance which corresponds to the axial length of a pressure chamber of the master cylinder despite an increase in the depression force applied to the brake pedal. As a result, it becomes impossible to apply the hydraulic pressure to the wheel brake as rapidly as possible.
In light of the foregoing, a need exists for a brake pressure control device for automotive vehicles that is capable of applying brake pressure to the wheel brake as rapidly as possible upon failure of the stroke simulator.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a brake pressure control device for automotive vehicles includes a wheel brake associated with a wheel of the automotive vehicle for applying a braking force to the wheel, a master cylinder linked with a brake pedal, a power pressure source separate from the master cylinder for generating a hydraulic pressure; a hydraulic pressure control valve disposed between the power pressure source and the wheel brake to adjust the hydraulic pressure of the wheel brake by using the hydraulic pressure generated by the power pressure source; a first open/close valve which establishes and interrupts fluid communication between the master cylinder and the wheel brake, a stroke simulator connected to the master cylinder and permitting a stroke of the brake pedal when the first open/close valve is closed, a second open/close valve which establishes and interrupts fluid communication between the master cylinder and the stroke simulator, a brake operation force detector that detects the operation force of the brake pedal or the hydraulic pressure generated by the master cylinder and a stroke detector detects the stroke of the brake pedal or a stroke of the master cylinder. A control device controls the hydraulic pressure control valve in response to the detection output of the brake operation force detector by closing and opening the first open/close valve and the second open/close valve, respectively, when the power pressure source is in the normal condition. The control device closes the second open/close valve when the stroke of the brake pedal or the stroke of the master cylinder exceeds a predetermined stroke.
In addition, when the stroke of the brake pedal or the stroke of the master cylinder exceeds a predetermined stroke, the second open/close valve is closed to interrupt fluid communication between the master cylinder and the stroke simulator, thus causing the output of the brake operation force detector to increase rapidly upon failure of the stroke simulator, with the result that the wheel brake can be applied with the hydraulic pressure as rapidly as possible.
The present invention also involves configuring the control device to close the second open/close valve when the stroke of the brake pedal or the stroke of the master cylinder exceeds a predetermined stroke and the operation force of the brake pedal or the hydraulic pressure generated by the master cylinder does not exceed a predetermined value. It is thus possible to reliably detect an abnormal condition such as a failure of the stroke simulator.
Also in accordance with the present invention, the brake pressure control device is designed so that the control device closes the second open/close valve when the operation force of the brake pedal or the hydraulic pressure generated by the master cylinder relative to the stroke of the brake pedal or the stroke of the master cylinder, respectively, does not exceed a predetermined function. This also makes it possible to reliably detect an abnormal condition such as a failure of the stroke simulator.
Another aspect of the present invention involves a brake pressure control device for automotive vehicles that includes a wheel brake associated with a wheel of the automotive vehicle for applying a braking force to the wheel, a master cylinder linked with a brake pedal, a power pressure source separated from the master cylinder to generate hydraulic pressure, a hydraulic pressure control valve disposed between the power pressure source and the wheel brake to adjust hydraulic pressure of the wheel brake by using the hydraulic pressure generated by the power pressure source, a stroke simulator connected to the master cylinder, a brake operation force detection device for detecting an operation force of the brake pedal or a hydraulic pressure generated by the master cylinder, and a stroke detector for detecting the stroke of the brake pedal or the stroke of the master cylinder. The hydraulic pressure control valve is controlled in response to a detection output of the brake operation force detection device by interrupting the fluid communication between the master cylinder and the wheel brake and establishing fluid communication between the master cylinder and the stroke simulator when the power pressure source is in the normal condition. Fluid communication between the master cylinder and the stroke simulator is also interrupted when the stroke of the brake pedal or the stroke of the master cylinder
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Oberleitner Robert J.
Rodriguez Pamela J.
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