Patent ID: 7992387
Filing Date: 2011-08-09
Classification: B60T

Abstract:
1. A master cylinder ( 12 ) for use in a brake system having a housing ( 22 ) with a bore ( 20 ) therein, first ( 42 ) and second ( 44 ) pistons located in said bore ( 20 ) define a rear chamber ( 64 ) and a front chamber ( 62 ) with said rear chamber ( 64 ) being connected to a reservoir ( 32 ) by way of an axial bore ( 76 ) in said second piston ( 44 ) and a radial port ( 28 ) in said housing ( 22 ) and said front chamber ( 62 ) being connected to said reservoir ( 32 ) by an axial port ( 38 ) in said housing ( 22 ) to receive fluid and maintain a fluid level in said brake system at a desired level, characterized in that said first piston ( 42 ) is separated from said second piston ( 44 ) by a first return spring ( 80 ) to define the rear chamber ( 64 ) and said second piston ( 44 ) is separated from a bottom of the bore ( 20 ) by a second return spring ( 82 ) to define the front chamber ( 62 ); said first piston ( 42 ) being defined by a first cylindrical body ( 43 ) with a closed axial bore ( 102 ) that extends from a front end toward a rear end; said second piston ( 44 ) being defined by a second cylindrical body ( 90 ) with the axial bore ( 76 ) that extends from a seat ( 52 ) on a first end to a second end, a cross bore ( 74 ) that connects said axial bore with a radial groove ( 25 ) on the peripheral surface of cylindrical body ( 90 ), and a groove ( 54 ) in the axial bore ( 76 ) adjacent the cross bore ( 74 ); a first retainer ( 100 ) retained on said first cylindrical body ( 43 ) for receiving a first end of said return spring ( 80 ) while a second retainer ( 144 ) receives a second end of said return spring ( 80 ); a rear compensation valve ( 48 ) includes a third cylindrical body ( 142 ) that is held in said second retainer ( 144 ) has a first socket ( 140 ) on a rear end and a second socket ( 141 ) on a front end and a first shaft ( 130 ) with a head ( 134 ) on a first end that is located in said first socket ( 140 ) to cage said return spring ( 80 ) between said first retainer ( 100 ) and said second retainer ( 144 ) while compressing a first actuation spring ( 150 ); a third retainer ( 181 ) is located on said second cylindrical body ( 90 ) for receiving a first end of said second return spring ( 82 ) while a second end is located on a fourth retainer ( 180 ); a front compensation valve ( 46 ) includes a fourth cylindrical body ( 143 ) that is held in the fourth retainer ( 180 ); and a second shaft ( 170 ) has a head ( 174 ) that is connected with an annular projection ( 146 ) that extends from said fourth cylindrical body ( 143 ) of the front compensation valve ( 46 ) and a second ball ( 172 ) that is retained in said second socket ( 141 ) in said third cylindrical body ( 142 ) to link the rear compensation valve ( 48 ) with the front compensation valve ( 46 ) and cage the second return spring ( 82 ) while compressing a second actuation spring ( 182 ), said fluid communication between said front chamber ( 62 ) and said rear chamber ( 64 ) and said reservoir ( 32 ) being controlled by movement of said first piston ( 42 ) in response to an input force as first actuation spring ( 150 ) closes said rear center port compensation valve ( 48 ) and said second actuation spring ( 182 ) closes said front center port compensation valve ( 46 ) to allow simultaneous pressurization of fluid in the front chamber ( 62 ) and rear chamber ( 64 ) that is supplied to the front wheel brakes ( 24 ) and rear ( 26 ) wheel brakes to effect a brake application.