| 摘要 |
PURPOSE:To obtain a sure brake keeping action by providing an electromagnetic closing valves on each of a passage for connecting the front and rear pressure chambers of a negative-pressure brake booster via the valve mechanism of the toggle joint and a passage for connecting the rear pressure chamber to a negative pressure source and controlling these valves in accordance with an operating condition. CONSTITUTION:A brake booster has a shell 1 which is partitioned into front and rear pressure chambers 4, 5 by means of a diaphragm 3 having a piston 2, and a valve mechanism 7 for switching over a passage between both pressure chambers 4, 5 and a passage for connecting the rear pressure chamber 5 to a negative pressure source is provided on a valve body 6 integrally provided on the shaft portion of the piston 2. In this case, first and second electromagnetic closing valves MGV1, MGV2 for opening/closing the passage 15 connecting both pressure chambers 4, 5 and the passage 29 for connecting the rear pressure chamber 5 to the negative pressure source respectively are provided. During the operation of brakes, for example, if the OFF condition of an accelerator signal and the stopping condition of a vehicle continue for a defined time, control is performed so as to close the first electromagnetic closing valve MGV1 to keep a braking action. |
