| 摘要 |
PROBLEM TO BE SOLVED: To adjust a booster output in a wide range according to the operation of a solenoid mechanism without sacrificing the responsiveness by a simple constitution. SOLUTION: This brake booster drives a needle 34 to a rear side by an electromagnetic force of a solenoid 31, transmits the movement to a valve seat member 21 via a pin 50 to open a breather valve 27, and introduces atmospheric air to a variable pressure chamber to provide a booster output by the pressure difference from a constant pressure chamber. The pressure in the constant pressure chamber is introduced into a chamber 54 in one end side of the needle 34 via a passage 56 while the atmospheric air is introduced into a chamber 55 in the other end side via a passage 57 respectively and a drive reaction according to the pressure difference between the constant pressure chamber and the variable pressure chamber is allowed to act on the needle 34 so that the booster output proportional to the solenoid current is provided. The area of the passage 57 is appropriately set to control the atmosphere quantity introduced into the chamber 54 in one side of the needle and the drive reaction acting on the needle 34 is suppressed to small till the booster output increases sufficiently so as to prevent the deterioration of the responsiveness.
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