Brake pressure control apparatus and method

A brake pressure control of the type particularly suitable for automotive vehicles having a wheel brake operated by a wheel cylinder, a brake pedal, a master cylinder connected to said wheel cylinder and operated by said brake pedal to generate fluid pressure to operate said wheel cylinder, with an anti-locking and traction slip control system, and operating on fluid pressure, said anti-locking control system consisting of at least one inlet valve and at least one outlet valve for modulation of pressure in said wheel cylinder, at least one pump for generating fluid pressure, said pump having an intake having a fluid connection to said master cylinder and an output having a fluid connection to said wheel cylinder, a controller, pressure fluid circuit means for pressure modulation of said wheel cylinder to establish controlled pressure increase and decrease phases in said wheel cylinder, said inlet valve disposed upstream of said wheel cylinder interposed between said pump output and said wheel cylinder, said outlet valve connected downstream of said wheel cylinder and opened by said controller during a pressure decrease phase, and pressure fluid accumulator means including an accumulator chamber connected to said wheel cylinder via said outlet valve, said accumulator pressure chamber thereby upon commencement of said pressure decrease phase receiving fluid flow from said wheel cylinder to act as a pressure relief, a fluid connection connecting said pump intake to said master cylinder, further including accumulator operated valve means interposed between said master cylinder and said intake of said pump, means operating said valve means by said accumulator means to normally provide unrestricted flow between said maser cylinder and said pump intake but restricting said fluid connection between said pump intake and said master cylinder only after said accumulator chamber has received fluid flow from said wheel cylinder after commencement of said pressure decrease phase.

A method of controlling brake pressure in an anti-locking control system for a vehicle wheel cylinder operated brake, which wheel cylinder is operated by pressure generated in a master cylinder, said control system including a controller, a pump having an intake and output sides, said control system further including an inlet valve connected between said wheel cylinder and pump output side and said master cylinder, a blocking valve disposed between said master cylinder and said inlet valve, an outlet valve between the wheel cylinder and said intake side of said pump, said inlet valve and said outlet valve controlled by said controller such that pressure decrease, constant pressure and pressure re-increase phases are established in said wheel cylinder, an accumulator including a cylinder, a piston movable in said cylinder against the force of a spring acting on one end of said piston, and an accumulator chamber, defined in part by the other end of said piston opposite said end acted on by said spring and in communication with said wheel cylinder, a fluid connection between said pump intake side and said master cylinder and also between said accumulator chamber and said pump intake side, said method comprising the step of controlling communication between said pump intake and said master cylinder and accumulator chamber respectively by movement of said accumulator piston, said controlling step including the further steps of closing off said fluid connection between said master cylinder and said pump intake side by movement of said accumulator piston caused by pressurizing of said accumulator chamber and opening said fluid connection between said accumulator chamber and said pump intake side by said piston movement caused by pressurization of said accumulator chamber.