| 摘要 |
<p>Pneumatic motor vehicle brake servo comprising a shell (10) within which a piston (20) formed from a rear tubular part (22) supporting a skirt (14) defines, by means of an unfolding diaphragm (12), a front chamber (16) permanently connected to a vacuum source and a rear chamber (18) selectively connected to the front chamber (16) or to the atmosphere by a valve means (40) actuated by a control rod (34) capable of bearing, by means of a plunger (32), on one of the sides of a reactive disk (58) mounted on a push-rod (56). The valve means comprises a shutter co-operating by means of an active part (40) with a first valve seat (32a) formed on the plunger (32) and a second valve seat (20a) formed on the piston (20), the shutter (40) being normally urged forwards by resilient means (44). According to the invention, actuating means (60, 100, 160) are provided to urge the active part of the shutter (40) forwards while at the same time co-operating with the first (32a) and second (20a) valve seats.</p> |
