Importance

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Abstract

The present invention is directed to a hydraulic pressure control system for controlling a hydraulic pressure in each wheel brake cylinder operatively mounted on each wheel of a vehicle, which includes a modulator disposed between a master cylinder and the wheel brake cylinder for introducing thereto and draining therefrom the brake fluid. First and second pump devices are provided for introducing the brake fluid and pressurizing it to discharge the pressurized brake fluid to the wheel brake cylinder through the modulator, respectively. The second pump device has a different suction phase from the suction phase of the first pump device. A changeover valve device is disposed between the master cylinder and the modulator, and adapted to select one of a first operating position for communicating the master cylinder with the modulator and blocking the communication between the master cylinder and the first and second pump devices, and a second operating position for communicating the master cylinder with the first and second pump devices and blocking the communication between the master cylinder and the modulator. First and second check valves are disposed between the changeover valve device and the inlets of the first and second pump devices for allowing the brake fluid to flow from the changeover valve device to the first and second pump devices and blocking the reverse flow. Preferably, the outlets of the first and second pump devices are communicated with a common volume chamber.

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First Claim