Patent ID: 6499577
Filing Date: 2002-12-31
Classification: B60T,F16D,Y10T

Abstract:
A valve apparatus for controlling hydraulic pressure for a clutch or brake, said valve apparatus comprising:a pressure control valve having an output port, said pressure control valve also having a clutch or brake cylinder inner pressure feedback chamber at one end thereof and a pilot pressure receiving chamber at another end thereof, said pressure control valve being adapted to introduce clutch or brake engagement pressure hydraulic fluid, which is to flow into a clutch or brake cylinder hydraulic chamber, into said clutch or brake cylinder inner pressure feedback chamber, and being operable to increase a hydraulic fluid pressure of the clutch or brake engagement pressure hydraulic fluid to balance with a magnitude of pilot pressure generated in said pilot pressure receiving chamber such that said pressure control valve controls a clutch or brake cylinder pressure; a pilot fluid passage having a throttle, said pilot fluid passage adapted to allow the clutch or brake engagement pressure hydraulic fluid to flow as pilot fluid to said pilot pressure receiving chamber of said pressure control valve; a pressure proportional valve having a valve element, said pressure proportional valve being operable to control a pressure of the pilot fluid that flows into said pilot pressure receiving chamber by positioning said valve element at one of a drain interruption position, a throttle position, and a drain release position; a proportional solenoid being operable to change a position of said valve element of said pressure proportional valve against the flow of the pilot fluid, and control a magnitude of the pressure of the pilot fluid; and a pressure switch communicating with said output port of said pressure control valve, said pressure switch being operable to detect a clutch or brake initial engagement hydraulic fluid pressure when the clutch or brake cylinder hydraulic chamber is being filled with the clutch or brake engagement pressure hydraulic fluid.