Master cylinder and brake booster for a brake system

Abstract

A brake system for ( ) a vehicle having a brake booster ( ) with an output put rod ( ) for providing a primary piston ( ) in a master cylinder ( ) with an input force to pressurize fluid which is supplied to wheel brakes ( ) of a vehicle to effect a brake application in response to an operator input force. The master cylinder ( ) has a first housing ( ) with a bore ( ) therein for retaining the primary piston ( ) in a first pressure chamber ( ). The bore ( ) has a first compensation passage ( ) connected to a fluid supply ( ) and an outlet port ( ) connected to the wheel brakes ( ). The primary piston ( ) has a first position of rest whereby the first pressure chamber ( ) is connected to a fluid supply ( ) through the first compensation passage ( ). The brake booster ( ) has a second housing ( ) with an interior separated by a movable wall ( ) into a front chamber ( ) and a rear chamber ( ). A first return spring ( ) urges the movable wall ( ) to a second position of rest whereby the front chamber ( ) and rear ( ) chamber are connected to a first source of fluid pressure. A control valve ( ) responsive to the operator input force connects the rear chamber ( ) with a second fluid pressure to create a pressure differential across the movable wall ( ). The pressure differential acts on the movable wall ( ) to develop an operational force which overcomes the first return spring ( ) and provides the primary piston ( ) with an input force to move the primary piston ( ) past the compensation passage ( ) and thereafter pressurize fluid in the first chamber ( ) to effect a brake application. The brake system ( ) is characterized by fixing the primary piston ( ) to the output push rod ( ) such that the primary piston ( ) is moved to the first position of rest by the first return spring ( ) returning the movable wall ( ) to the second position of rest in an absence of an operator input being applied to the control valve ( ).