Control valve for a vacuum brake booster.

摘要

A brake booster (42) having a hub (78) with control valve (56) located therein. The control valve (56) has a plunger (l06) connected to an output rod (62) through a reaction disc (60) and to a brake pedal. A sleeve (ll2) which surrounds the plunger (l06) is urged toward a shoulder (ll0) on the plunger (l06) by a first resilient member (l26). An input applied to the brake pedal moves the plunger (l06) to allow air to enter into the booster (42) and create an operational pressure differential across a movable wall (50) to develop an output force. The output force is carried through the reaction disc (60) and a reaction force is carried through the plunger (l06) to balance the input force. On termination of the input force, the reaction force and first resilient means (l26) move the plunger (l06) to define a gap between an annular seat (l04) and a poppet (ll7) member to allow vacuum to evacuate air from the booster (42). When a return spring (59) moves the wall (58) to the rest position, the stop (l28) engages the booster (42) housing and holds the sleeve (ll2) stationary. The reaction force continues to sustain the gap until the operational pressure differential is eliminated. Thereafter a static pressure differential acts on the poppet member (ll7) and overcomes a reaction disc (60) resistance to move the plunger toward the annular seat to define a rest position for the plunger (l06).