| 摘要 |
PURPOSE:To increase the hydraulic pressure of a rear wheel cylinder when one system falls into failure by supplying the hydraulic pressure to the rear wheel cylinder by means of a hydraulic pressure control valve, determined by a stepped piston ratio. CONSTITUTION:While two systems of a master cylinder 2 are normal, the stepped piston 23 is pressed to a left direction and stays still as being pressed. On the other hand, at the time of the failure of the hydraulic pressure of the front side system, the stepped piston 23 moves toward a right direction as resisting a compression spring 37, and closes the liquid path 35A. Then, the liquid in a third hydraulic pressure chamber 33 is supplied to the liquid path 35B of the rear wheel cylinder up to the hydraulic pressure PRII, determined by a sectional area ratio between the small diameter part 23a and the large diameter part 23b of the stepped piston 23, and the hydraulic pressure PRII is increased higher than the hydraulic pressure PMR of the master cylinder. Thus, at the time that the system of one side falls into the failure, the hydraulic pressure of the rear wheel cylinder can be elevated higher than the hydraulic pressure of the master cylinder.
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