Patent ID: 6543332
Filing Date: 2003-04-08
Classification: B60T

Abstract:
A hydraulic booster device chiefly comprising a housing including a cylinder bore, an inlet port connected to a pump and an outlet port for discharging a working fluid in said cylinder bore; a servo piston movably fitted into said cylinder bore and for defining a servo chamber communicating with said inlet port within said cylinder bore; a valve bore formed in said servo piston and for communicating said inlet port with said outlet port; and a spool movably inserted into said valve bore; and valve means comprising, as a main component, the spool movably inserted into said valve bore, and forming a clearance between a land portion on an outer periphery of said spool and an inner peripheral wall of said valve bore in response to an input made by a driver, thereby throttling a flow of a working fluid flowing towards said outlet port from said inlet port so that a working fluid pressure occurs within said servo chamber,wherein said valve means includes, sequentially in the axial direction of the servo chamber from the inlet port to the outlet port, a first land portion on the spool, a first stepped portion on the inner peripheral wall of said valve bore, a second land portion on the spool, and a second stepped portion on the inner peripheral wall of the valve bore; the first land portion and the first stepped portion forming a first valve, and the second land portion and the second stepped portion forming a second valve; and a throttling area made by said second valve is larger than a throttle area made by said first valve.