| 摘要 |
PURPOSE:To improve the safety of a pump during pump failure in an unit in which the brake is released by supplying pressure oil into a pressure chamber of a brake cylinder, by forcibly discharging the pressure oil in the pressure chamber wne the discharging pressure of the oil pressure pump is lowered below the prescribed value. CONSTITUTION:In a state in which a car is running without brake operation, almost all pressured oil discharged from a hydraulic pump 2 returns to an oil tank 3 passing through an ordinary brake circuit from piping 5, while the part of which reaches a port 11 of a switching valve 10 passing through piping 8 located at a upstream side of a throttled part 6, thus pushing a control piston 50 toward the right against spring force. If the pump 2 fails in its operation in this state and the pressure in the piping 5 is lowered, the said control valve 50 is pushed toward the left by the spring force. Then the switching valve 10 is switched in such a manner that the connection between an accumulator 16 and a pressure chamber 24 of a brake cylinder 21 is shut off while the pressure chamber 24 is connected to the oil tank 3. Thus a parking brake 23 is operated, informing a car driver of the pump failure. |
