Brake booster apparatus

Abstract

In a vacuum type brake booster apparatus, the response in an initial stage of operating brakes is made sluggish so as to improve the brake feeling in a normal operation area, while the response is improved at the time of panic braking when the brake pedal is largely depressed to thereby reduce a stopping distance at the time of braking. A throttling mechanism is constituted by a position variable piston fixed to an operating rod of a brake booster of a vacuum type and a circumferential wall portion surrounding the position variable piston with a certain gap being formed therebetween. The gap thus formed constitutes an atmospheric pressure inlet passage into a variable pressure chamber, and the size of the gap is constructed so as to be varied when the position of the position variable piston is changed relative to the circumferential wall portion through an axial actuation of the operating rod, whereby the incoming volume per unit time of the atmospheric pressure into the variable pressure chamber is constructed to be varied in response to the brake pedal depression stroke in such a manner that the incoming volume remains small in the initial stage of operating the barke pedal, while it increases as the brake pedal depression stroke increases.

Dependencies are inferred from the claim text.