| 摘要 |
PURPOSE:To prevent generation of impact noise by driving and controlling an electromagnetic valve to intermittently attract its valve body to quietly seat it on a valve seat at the time of closing the electromagnetic valve in a device that brake operating condition is maintained by closing a passage in a brake booster by means of the electromagnetic valve. CONSTITUTION:A brake booster (A), when a brake pedal is stepped on to move a valve plunger 13 forward, shuts off between a vacuum line 8 and an atomosphere line 9 by means of a valve mechanism 7 and communicates the atomosphere line 9 and an atomosphere line 10 to move a power piston 2 forward due to differential pressure between a pressure changing chamber 5 and a pressure constant chamber 4. And an electromagnetic valve 21 is closed to shut off the vacuum line for maintaining a brake under braking condition. In this case, when it is judged that operational conditions to close the electromagnetic valve 21 is effected in the operation judging unit 31 in a control unit 29, indicating voltage is output from an intermittently attracting drive unit 35 to a constant current circuit 28 to intermittently effect electricity condition applied to the solenoid coil 22 of the electromagnetic valve 21 to quietly seat a valve body on a valve seat 25. |
