| 摘要 |
<p>In a negative pressure booster (1) of the present invention, at the time of performing a usual braking operation in a low deceleration region, a force attributed to the pressure difference between pressures applied to a variable pressure chamber and a constant pressure chamber is equal to or smaller than a sum of a set spring load of a spring (31) and a spring load of a valve spring (18). Accordingly, a vacuum valve seat member (27) is not moved and the usual braking operation is performed at a small servo ratio. Further, during the usual braking operation in an intermediate deceleration region, the force attributed to the pressure difference is larger than the sum of the above-mentioned spring loads and hence, the vacuum valve seat member (27) moves rearwardly while pushing a valve element (12). Accordingly, a valve opening quantity of an atmospheric valve (16) is increased while shortening a pedal stroke and hence, a braking operation for intermediate deceleration is performed at a larger servo ratio, whereby brake manipulation feeling can be enhanced.</p> |
