| 摘要 |
PURPOSE:To enable a device to hold a brake force in a fixed value, even when a brake pedal stops its step-down action halfway, by connecting a negative pressure source to a fixed pressure chamber by a pipe through a check valve and providing in the pipe the other check valve and a throttle passage which connects inlet and outlet sides of this check valve. CONSTITUTION:A negative pressure booster has a booster main unit 3, comprising a front shell 1 and a rear shell 2 and enclosing the inside, and the booster main unit partitions its inside by a power piston unit 4 into a fixed pressure chamber 5 and a pressure changing chamber 6. When the atmosphere is introduced to the pressure changing chamber 6 from a passage 24 by step-in action of a brake pedal, a pressure difference between both the chambers 5, 6 moves the above described unit 4 to the left. Here the first and second check valves 30, 37 are interposed halfway a pipe 28 connecting the fixed pressure chamber 5 to a negative pressure source. The second check valve 37 is constituted closing by a pressure difference larger than the pressure difference of the first check valve 30 while providing a valve unit 39 forming an orifice (throttle passage) 43. |
