PURPOSE: To obtain a good operation feeling at the initial operation of a main driving piston by communicating the system of a first reaction chamber or an accumulating chamber with a liquid tank via a normally-open type jumping valve which closes when the pressure in a boost chamber exceeds a prescribed pressure.
CONSTITUTION: When a main driving piston 19 is moved forward by the input from a brake pedal 2 to introduce a fluid pressure into a boost chamber 132, by receiving the fluid pressure, a booster piston 17 is moved forward to contract the volume of a first reaction chamber 221. However, in such a stage that the fluid pressure in a boost chamber 131 is less than a prescribed value, a jumping valve 80 is opened, and the system of the chamber 221 or a stroke accumulator 65 is opened to a fluid tank 52, therefore a reaction force is not produced in the chamber 221. In other words, a reaction force is not given to the main driving piston 19. When the fluid pressure inside the chamber 131 exceeds a prescribed value, the valve 80 is closed and thereafter a pressure is accumulated in an accumulating chamber 68 from the chamber 221 as the piston 17 moves forward, and the pressure is transmitted to the chambers 221, 222 to provide a reaction force to the piston 19.
SHIMIZU MUTSUMI
MIYAGAWA YUKITAKA
SAKURAI KAZUYA
HONDA MOTOR CO LTD
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