| 摘要 |
PURPOSE:To surely operate a brake even when a hydraulic pressure source is defective, by connecting the master cylinder side of a shutoff valve and a pressure changing chamber to each other through a passage provided with a valve, which is opened when the pressure of the hydraulic pressure source drops. CONSTITUTION:When the stored pressure in an accumulator 50 and the pressure in a pressure changing chamber 33 are low due to the trouble of a hydraulic pump 49, the supply of electricity to a coil 78 is blocked by a signal from a pressure switch so that an orifice 93 is closed by a valve ball 83 on a control piston 81. When a brake pedal is then depressed, the hydraulic pressure in a master cylinder is applied to wheel cylinders and a spherical valve 40 is opened through passages 12, 34 to apply the hydraulic pressure to the pressure changing chamber 33 as well. For that reason, a plunger 28 remains stopped and a volume chamber 180 is not increased, so that the hydraulic pressure in the wheel cylinders are quickly heightened. |
