| 摘要 |
PROBLEM TO BE SOLVED: To provide a single air pressure type booster device that is smoothly applicable to stroke increase by reducing ineffective thrust when a brake pedal is operated. SOLUTION: The diameter of an axial hole in the valve body 5 of a power piston is increased and the diameter of the atmospheric valve seat part 8 of a plunger 7 placed in the axial hole is increased. The atmospheric valve seat part 8 is placed adjacent to a negative pressure valve seat part 9 provided on the inner surface of the valve body 5 and conical surfaces 37, 38 increasing flow passage areas according to the movement of the plunger 7 are provided on the respective backs of the valve seat parts 8, 9. By increasing the diameter of the atmospheric valve seat part 8 of the plunger 7, a retracting force working on the plunger 7 when the device is not actuated is increased to reduce a difference between returning forces produced by a valve spring 12 and a return spring 13, to reduce ineffective thrust working on an input shaft 6 operating in conjunction with a brake pedal. Clearance formed by the conical surfaces 37, 38 on the backs of the valve seat parts 8, 9 secures the desired flow passage areas to prevent delay of actuation. |
