| 摘要 |
Disclosed is a brake booster device wherein the construction of a valve mechanism and in particular, of a negative pressure valve seat are simplified, so that the circumferential length of the negative pressure valve seat and the area through which the pressure difference between a constant pressure chamber and a variable pressure chamber acts on a negative pressure valve can be easily set or designed to meet the valve characteristic. The brake booster device is of the type that when the stepping force exerted on a brake pedal causes a plunger and an output piston to move relative to each other, switching is carried out to make a variable pressure chamber communicate with either of the atmosphere and a constant pressure chamber and that the pressure difference between the variable pressure chamber and the constant pressure chamber is thus caused to move a partition member and an output piston forward, whereby an output rod is pushed to generate pressurized brake fluid in a master cylinder. In the brake booster device of the aforementioned type, closed, elongate negative pressure valve seats are protruded from a rear end flat surface portion of the output piston to encircle passages communicating with the constant pressure chamber, while an annular valve seat is formed at the rear surface of the plunger to encircle an atmosphere leading passage. Negative pressure valves and an atmosphere valve respectively contactable with the negative pressure valve seats and the atmosphere valve seat are formed on a valve member at respective positions spaced in the axial direction. Communication passages are provided at the outer surface of the valve member between the negative pressure valves and the atmosphere valve to make the interior of the valve member with the variable pressure chamber.
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