Patent ID: 6425312
Filing Date: 2002-07-30
Classification: B60T

Abstract:
A brake booster comprising:a housing; a power piston dividing the interior of the housing into a constant pressure chamber and a variable pressure chamber; a valve body supported by the power piston; a plunger provided in the valve body for axial movement; an input rod interconnecting a brake pedal and the plunger so that an operation of the brake pedal is transmitted to the plunger to cause its axial movement; a valve mechanism provided in the valve body for controlling supply of operating fluid to the variable pressure chamber in response to the axial movement of the plunger so that a thrust output force is generated by pressure difference created between the variable pressure chamber and the constant pressure chamber based on the operation of the valve mechanism; an electromagnetic biasing means including a movable member for operating the valve mechanism independently from the operation of the input rod, the movable member slidably provided in the valve body; and a reaction force mechanism acting a reaction force on the movable member according to pressure difference between the variable pressure chamber and the constant pressure chamber, wherein, the reaction force mechanism acts the reaction force on the movable member so that an increasing rate of the thrust output force is in accord with an increasing rate of the reaction force.