| 摘要 |
Known brake actuating devices include a pressure source and a valve arrangement operated by a brake pedal with the pressure fluid being fed by the valve arrangement to a control chamber which has as one of its boundaries a pressure piston acting on a master cylinder piston. The pressure piston of the known device is operated mechanically by the brake pedal upon failure of the pressure fluid supply. However, the brake pedal travel is increased in so doing. According to the present invention the control chamber has a second piston forming a boundary thereof opposite the pressure piston which keeps a pressure fluid channel open between the control chamber and the valve arrangement in the normal operating condition and closes the pressure fluid channel during failure of the pressure fluid supply so that the pressure piston is operated by the second piston without any appreciable increase in brake pedal travel. |
