Negative pressure type booster for motor vehicle, has its output changed by adjusting driving force of actuator, to enable to change braking force

摘要

When a brake pedal is operated, an air valve seat moves forward along with an input element (28) which transmits power to an output rod (49). A reaction disk (48) makes the input element to retreat during driving of an actuator (41), so that the air valve seat engages with an air sealing portion. The output of the output rod is varied based on driving force of actuator. The booster has a housing enclosing movable walls which divide a pressure space into front chambers (23,25) and back chambers (24,26). A power piston (22) is connected to the movable wall. The input element is arranged in the power piston and moves by the operation of the brake pedal. A negative pressure valve seat is formed in the power piston. The piston also has the air sealing portion and a negative pressure sealing portion. The front chamber is connected with air when the air valve seat separates from the air sealing portion and the front chamber is connected with negative pressure source when the negative pressure valve seat separates from the negative pressure sealing portion. The same is applicable for the back chamber when the power piston moves, the movable wall and the output rod are moved forward. The power from the input element is transmitted to the output rod. The reaction disk makes the input element to retreat according to the magnitude of the reaction force which corresponds to the output of the output element.