| 摘要 |
PROBLEM TO BE SOLVED: To reliably perform sufficient assist control on brake operation on and after the second time by forming a vacuum valve and a breather valve as an electrically openable-closable solenoid valve, and driving the solenoid valve on the basis of output by detecting stepping-down of a brake pedal on the basis of a pedal stroke. SOLUTION: A different pressure chamber 1 is communicated with a vaccum chamber 2, and when an opening part of a negative pressure passage 11 is opened so as to separate from a valve element 3 as a vacuum valve, negative pressure from the vacuum chamber 2 is introduced. The different pressure chamber 1 is also communicated with an external part, and when it is opened so as to separate from a valve seat 12 in which an atmospheric pressure passage part 4 is arranged, atmospheric pressure is introduced. A control device inputs detecting information of a sensor, and outputs a control signal to drive a solenoid 5 of a vaccum booster 25. The vaccum booster 25 has a power piston 10, and a load equivalent to boosting power is transmitted to a push rod 8 and a master cylinder 26 by differential pressure generated between the vaccum chamber 2 and the different pressure chamber 1. Therefore, when vehicle speed is fast and urgency is high, control at second stepping-down time can be performed. |
