Dual actuation master cylinder

Abstract

A master cylinder ( ) for use in a brake system ( ). The master cylinder ( ) has a housing ( ) with a first ( ) and second ( ) pistons located in a bore ( ) by first ( ) and second ( ) resilient members to define first ( ) and second ( ) chambers therein. The first ( ) and second ( ) chambers are respectively connected to a reservoir ( ) to receive fluid and maintain a desired fluid level in the brake system ( ) and to front ( ′) and rear ( ′) wheel brakes to supply pressurized fluid to effect a brake application. Fluid received from the reservoir ( ) by [to] the second chamber ( ) is controlled by a center port compensation valve ( ). The center port compensation valve ( ) has a head ( ′) connected to a linkage member ( ′) that joins a first retainer ( ′) with a second retainer ( ′) to cage the second resilient member ( ). An actuation arrangement has a first input member ( ) that responds' to an operator input to initially move the first piston ( ) and the second ( ) piston to compress the second ( ) resilient means and allow head ( ′) to engage a seat ( ′) to terminate communication between reservoir ( ) and the second chamber ( ). Thereafter movement of the second piston ( ) pressurizes fluid in the second ( ) chamber to effect a first brake application. The actuation arrangement is characterized by a second input member ( ) that responds to an electronic signal to develop a force that acts on a plunger to compress the second resilient member ( ) and move the head ( ′) into engagement with seat ( ′) to terminate communication from the reservoir ( ) to the second- chamber ( ) and thereafter moves to pressurize fluid in the second chamber ( ) and effect a second brake application.