| 摘要 |
The invention relates to a power assisted brake for motor vehicles, comprising an assistance-device housing (1) whose inner space is divided by a movable wall (2) into a vacuum chamber (4) and a working chamber (3), as well as a control valve (12) which controls a pressure difference acting on the movable wall (2) and is positioned in a control casing (5) supporting the movable wall (2). The control valve (12) consists of at least two sealing seats (15, 16) which are arranged concentrically in relation to each other and a valve body (10) which in the control casing (5) delimits a pneumatic space (17) which can be subjected to the pneumatic pressure prevailing in the working chamber (3). The essence of the invention lies in the fact that the valve body (10) is provided with at least two sealing lips (50, 51) having different diameters which delimit the pneumatic space (17) in the control casing (5) and in that the active pneumatic surface of the space (17) influenced by the difference in diameter substantially coincides with the pneumatic surface delimited between the two sealing seats (15, 16).
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