Hilfskraftvorrichtung,insbesondere Bremsverstaerker

摘要

1,177,686. Brake servos. ROBERT BOSCH G.m.b.H. 31 March, 1967 [1 April, 1966], No. 14703/67. Heading F2F. A servo device, e.g. a brake servo, comprises a force, member 3, Fig. 1. a follower valve 14 actuable by displacement of a control member 11, the force member, the control member and a force-transmitting member 19 each having surface portions mutually inclined to each other which define a space which can be varied by mutual displacement of the surfaces and at least one intermediate element 23 engaging all three surfaces and arranged to slide in the space so that the control member and the force member both act on the force-transmitting member. In the idle position the spring 26 loads control member 11 with its seating 12 engaging valve member 14 so that chamber 32, which is subjected to vacuum via connection 16, is connected to chamber 31 through passage 15, the valve chamber 33 and passage 24. The equalized pressure on both sides of plunger 3 causes the latter to be spring-loaded against cover 2. When brake lever 9 is depressed, the rod 10 displaces control member 11 to the left so that the connection between chambers 31, 32 is broken when valve member 14 engages shoulder 7. Further depression of brake lever 9 causes the control member 11 to lift away from valve member 14 so that atmospheric air flows via chamber 5, valve member 14 and passage 24 into chamber 31. The resulting pressure difference causes the plunger 3 to exert force on piston-rod 19, attached to a main cylinder, through balls 23. The movements of the control member 11 and plunger 3 act through tapered surfaces 22, 17 on surface 211 until a balanced position is achieved in which valve member 14 again rests with a tight seal on control member 11 and shoulder 7 to prevent further pressure rise in chamber 31. If the control force on rod 10 is removed or reduced control member 11 moves valve member 14 away from shoulder 7 so that the pressure in chamber 31 is exhausted via connections 24, 15 and chamber 32 to the vacuum source, plunger 3 moving towards its idle position. The ratio of the control and servo forces may be altered either by varying the angles of the tapered surfaces or by use of a curved surface. The tapered surfaces may be grooved to restrict the balls to radial movement. The balls 23 may be replaced by double wedges, a flexible ring of circular or triangular cross-section or a spring.