| 摘要 |
PURPOSE:To prevent the burning of a solenoid coil by operating an electromagnetic valve built in a brake booster device to maintain the device in a brake operating condition by alternately sending a suction current which sucks and operates a valve body and a retaining current which retains the valve body in a sucked condition. CONSTITUTION:In a brake booster device A, a shell 21 is divided into a constant pressure chamber 24 and a variable pressure chamber 25 by a diaphragm 23 and a power piston 22, and a valve mechanism 27 which changes over channels is housed in a valve body 26 formed monolithically with the power piston 22. An electromagnetic valve B is installed in a passage 28 connecting the valve mechanism 27 and the constant pressure chamber 24, and when the passage 28 is closed by the electromagnetic valve B, the brake booster device A is maintained in a brake operating condition. In this case, electric current is sent to a solenoid coil 3 of the electromagnetic valve B from a power source device which puts out alternately at a required time interval a suction current which sucks and operates a valve body 40 and a retaining current, smaller than the suction current, which maintains the valve body 40 in a sucked condition. |
