Patent ID: 6732518
Filing Date: 2004-05-11
Classification: B60T

Abstract:
A hydraulic brake booster for use in a brake system having a housing with a first bore separated from a second bore, said first bore retaining a power piston and said second bore retaining a control valve, an input member connected to said power piston and linked to said control valve by a lever arrangement, said lever arrangement is responsive to a first input force that is communicated from the input member for moving said control valve to meter pressurized fluid to a working chamber in said housing, said pressurized fluid in said working chamber acting on said power piston to develop a hydraulic force to pressurize fluid in said first bore that is communicated to wheel brakes in a brake system to effect a corresponding brake application, said input member is characterized by a cylindrical body, a shaft having a head on a first end and axial slot located between said head and threads on a second end, a bracket located on said shaft, said bracket having a radial opening, and a spring located between said bracket and said cylindrical body and on said threads being mated with said cylindrical body said spring urges said bracket into engagement with said head; and wherein said lever arrangement is characterized by a first lever with a first end pivotally secured in said housing by a first pin and a second end located in said radial opening of said bracket, a second lever having a first end and a second end with said first pin passing through a slot in said first end, a second pin extending through said first and second levers to define a fulcrum point for said lever arrangement, and a second spring is located between said power piston and said head such that a return spring force is applied to said bracket and communicated through said fulcrum point to bring said first end of said second lever into engagement with said control valve and said second end of said first lever of said second lever into engagement with said power piston, said first input force being applied through said bracket to said second end of said second lever of said first lever causing said second end to pivot about said first pin and transmit an actuation force through said fulcrum into said second lever to move said first end and activate said control valve whereby metered pressurized fluid is communicated into said working chamber for effecting said brake application, said lever arrangement having a first length defined by a distance between said first pin and said second end on said first lever and a second length defined by a distance between said first pin and said second end of said second lever such that axial movement of said cylindrical body and said power piston is defined by a ratio of said first length to said second length and as a result said hydraulic force is proportional to said input force.