| 摘要 |
PROBLEM TO BE SOLVED: To eliminate a complex setting in structure or a troublesome assembling work when a key is loaded in a power piston by a method wherein an input shaft is prevented from being removed off the power piston, and the rear side of a diaphragm is engaged with the rear side of a housing so as to restrict a retracting position of the power piston. SOLUTION: An inside part of a housing 3 is defined into a constant pressure chamber 6 and a variable pressure chamber 7 at its front side and rear side, respectively, in an air-tight manner. The constant pressure chamber 6 is communicated with an engine intake manifold acting as a negative pressure source through a port 20 and this is always kept at a negative pressure. An inner edge section of a movable wall 8 adjacent to the front side of a diaphragm 4 is fixed to an outer circumference section of the power piston 5. A spring 9 arranged in tension between a front shell 1 and the movable wall 8 biases the power piston 5 in a rearward direction, projections 4a integrally formed at the rear surface of the diaphragm 4 and equally spaced apart in a circumferential direction are engaged with a rear shell 2 so as to restrict a retracting position of the power piston 5. |
