Patent ID: 6161463
Filing Date: 2000-12-19
Classification: B60T

Abstract:
In a negative pressure booster equipped with an electromagnetic auxiliary control means comprising:a booster shell accommodating booster pistons which partition an inside of the booster shell into front negative pressure chambers communicating with a negative pressure source and rear operation chambers;a valve cylinder slidably supported on the rear wall of the booster shell and connected to the booster pistons;an input member movable to-and-fro, a control valve for switching communication of the operation chambers with the negative pressure chambers and with air, and an electromagnetic auxiliary control means for increasing an operation quantity of the control valve when it is excited while the input member advances within the valve cylinder;said control valve having a single valve element which is supported for to and fro movement within a prescribed stroke to the input member and spring-biased to a side of a retraction limit thereof, and when the single valve element advances toward the valve cylinder, the control valve interrupts communication between the operation chambers and the negative pressure chambers to increase the communication opening degree between the operation chambers and air in accordance with a degree of advancement, and when the single valve element retreats from the valve cylinder, the control valve interrupts communication between the operation chambers and air to increase the communication opening degree between the operation chambers and negative pressure chambers in accordance with a degree of retraction;the electromagnetic auxiliary control means including a fixed core fixed to the valve cylinder, a solenoid mounted on the fixed core, and a movable core coupled with the valve element to be opposite to the fixed core, such that when the solenoid is excited while the input member advances, the electromagnetic auxiliary control means operates the movable core so that the advancement quantity of the valve element for the valve cylinder exceeds that of the valve element by the input member; anda gap between the fixed core and the movable core such that when the solenoid is excited and the input member remains non-excited, the valve element remains in a closed position.