Patent ID: 6021876
Filing Date: 2000-02-08
Classification: B60K,F15B,Y10T

Abstract:
A two stage pressure control valve, comprising:an electric first stage pilot consisting of a single coil operated servomotor, said first stage pilot further having a pilot supply port, a pilot tank port and a single outlet port, Pressurized hydraulic fluid being provided to said pilot supply port, said first stage pilot further including means for regulating the flow of hydraulic fluid from said outlet port to said pilot tank port to thereby provide a variable pressurized hydraulic fluid to said outlet port and at a pressure that is proportional to an electric input signal applied to said single coil and which is variable between first and second values;a second stage hydraulic valve having a valve body with a bore extending therein and a spool reciprocally movable in said bore, a first end of said bore being coupled to said outlet port of said electric first stage pilot;a spring abutment in said bore only at a second end remote from said first end, a spring oriented between and abutting said spring abutment and an end of said spool remote from said outlet port on said first stage pilot and urging said spool to oppose said pressurized hydraulic fluid at said first stage outlet port;said second stage further including a pair of supply ports on and spaced along said valve body and supplying a continuous high pressure hydraulic fluid to said supply ports; andfirst and second operative valve means interposed between said supply ports and said spool for separately controlling a magnitude of a pressure of the supply of pressurized hydraulic fluid to opposite axially facing first and second control surfaces on said spool, said first and second operative valve means being configured to supply pressurized hydraulic fluid to only one of said first and second control surfaces at a time so that said pressurized hydraulic fluid adds to or subtracts from a force of said spring abutting said end of said spool remote from said outlet port to facilitate a balancing of said spool against an equivalent pressurized hydraulic fluid at said first stage outlet port in every position of said spool.