| 摘要 |
PURPOSE:To obtain a necessary brake action even when the pressure of a liquid pressure source is lowered by cutting off the communication between a pressure chamber and a liquid pressure release source when the pressure of the liquid pressure source is lowered. CONSTITUTION:When a pump 51 fails before a coil 64 is energized, an operating liquid is not stored in an accumulator 52, and the stored pressure is lowered as the operating liquid is fed to a pressure chamber 31. Thereby, the piston 84 of a valve means 94 is moved to the left, a ball valve 83 is pressed to a valve seat 82, and the communication between the pressure chamber 31 and a reservoir 54 is cut off. Accordingly, even if the pressure of a master cylinder is applied to the left end surface of a plunger 25, the plunger 25 is not moved to the right because the chamber 31 is closed. Therefore, the brake power is not reduced. Moreover, even if the pump 51 fails while the coil 64 is being energized, the pressure of the accumulator 52 is fed to the pressure chamber 31 as the coil 64 is de-energized, the pressure storage quantity of the accumulator 52 is decreased, and the valve 94 is closed. Thus, likewise the brake power is not reduced.
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