Control value for motor vehicle fluid power circuit

Claim 2

In a motor vehicle fluid power circuit having a fluid pump, a steering gear, a brake booster, and an accumulator, a control valve; said control valve including a housing having an inlet port for receiving fluid from said fluid pump, a first outlet port for supplying fluid to said steering gear, a second outlet port for supplying fluid to said accumulator, a first passage hydraulically connecting said inlet port to said outlet port, a second passage hydraulically connecting said inlet port to said second outlet port, a first spool movable between an open position for opening said first passage and a closed position for closing said first passage, a spring biasing said first spool to said closed position, a second spool slidably disposed in a bore, said second spool including a first portion exposed to fluid inlet port pressue and a second portion of greater lateral crosssectional area than said first portion exposed to accumulator pressure, and said second spool being movable in said bore by application to said first and second portions of a predetermined pressure in said inlet port and said accumulator to engage said first spool and move said first spool against the bias of said spring from said closed position to said open position.

Claim 3

A control valve in accordance with claim 1 wherein said first spool includes a portion exposed to atmospheric pressure under all conditions.

Claim 4

A control valve in accordance with claim 2 wherein said first spool includes another portion exposed to inlet port pressure when said first spool is in said closed position.

Claim 5

A control valve in accordance with claim 3 wherein the lateral cross-sectional area of said other portion of said first spool is less than the lateral cross-sectional area of said first portion of said second spool, whereby a decrease in said inlet port pressure decreases the net force opposing movement of said first spool from said closed position to said open position.

Claim 6

A control valve in accordance with claim 4 wherein the preload of said spring is equal to the product of said predetermined pressure multiplied times the sum of said lateral cross-sectional area of said other portion of said first spool and said lateral cross-sectional area of said second portion of said second spool minus the product of said predetermined pressure multiplied times the lateral cross-sectional area of said first portion of said second spool.

Claim 7

A control valve in accordance with claim 1 including a one-way check valve in said second passage for blocking fluid flow in a direction from said second outlet port to said inlet port.

Claim 8

A control valve in accordance with claim 1 including a bleed passage between said inlet port and said first outlet port for maintaining a small flow of fluid from said inlet port to said first outlet port under all conditions.

Claim 9

A control valve in accordance with claim 7 including a priority piston, said priority piston being movable between a first position and a second position, said priority piston closing said second passage when said priority piston is in said second position, and said priority piston including a lateral cross-sectional area exposed to the fluid pressure of said first outlet port, whereby the force of said first outlet fluid pressure acting against said priority piston area moves said priority piston from said first position to said second position.

Claim 10

A control valve in accordance with claim 8 wherein said priority piston includes another lateral cross-sectional area exposed to atmospheric pressure.

Claim 11

A control valve in accordance with claim 9 including a one-way check valve in said second passage, said one-way check valve being movable between an open position and a closed position for preventing the flow of fluid in a direction from said accumulator to said inlet port, and said priority piston retaining said one-way cHeck valve in said closed position when said priority piston is in said second position.

Claim 12

A control valve in accordance with claim 9 wherein said priority piston includes means to open a bypass passage around said poppet from said inlet port to said first outlet port when said priority piston is in said second position.

Claim 13

In a motor vehicle fluid power circuit having a fluid pump, a steering gear, a brake booster, and an accumulator, a control valve; said control valve including a housing having an inlet port for receiving fluid from said fluid pump, a first outlet port for supplying fluid to said steering gear, a second outlet port for supplying fluid to said accumulator, a first passage hydraulically connecting said inlet port to said first outlet port, a second passage hydraulically connecting said inlet port to said second outlet port, a valve seat in said first passage intermediate said inlet port and said first outlet port, a poppet axially movable between an open position axially spaced from said valve seat and a closed position axially engaging said valve seat for closing said first passage, a spring biasing said poppet to said closed position, a differential area piston slidably disposed in a bore, said differential area piston including a first end exposed to fluid inlet port pressure and a second end of greater lateral cross-sectional area than said first end exposed to accumulator pressure, and said differential area piston being movable in said bore by application to said first and second ends of a predetermined pressure in said inlet port and said accumulator to engage said poppet and move said poppet against the bias of said spring from said closed position to said open position.

Claim 14

In a motor vehicle fluid power circuit having a fluid pump, a steering gear, a brake booster, and an accumulator, a control valve; said control valve including a housing having an inlet port for receiving fluid from said fluid pump, a first outlet port for supplying fluid to said steering gear, a second outlet port for supplying fluid to said accumulator, a first passage hydraulically connecting said inlet port to said first outlet port, a second passage hydraulically connecting said inlet port to said second outlet port, a valve seat in said first passage intermediate said inlet port and said first outlet port, a poppet axially movable between an open position axially spaced from said valve seat and a closed position axially engaging said valve seat for closing said first passage, a spring biasing said poppet to said closed position, a differential area piston slidably disposed in a bore, said differential area piston including a first end exposed to fluid inlet port pressure and a second end of greater lateral cross-sectional area than said first end exposed to accumulator pressure, and said differential area piston being movable in said bore by application to said first and second ends of a predetermined pressure in said inlet port and said accumulator to engage said poppet and move said poppet against the bias of said spring from said closed position to said open position.

Claim 15

A control valve in accordance with claim 12 wherein said poppet includes an end portion exposed to fluid inlet port pressure, and said poppet end portion is of smaller lateral cross-sectional area than said first end of said differential area piston whereby a decrease in fluid inlet port pressure decreases the net force urging said poppet to said closed position.

Claim 16

In a motor vehicle fluid power circuit having a fluid pump, a steering gear, a brake booster, and an accumulator, a control valve; said control valve including a housing having an inlet port for receiving fluid from said fluid pump, a first outlet port for supplying fluid to said steering gear, a second outlet port for supplying fluid to said accumulator, a bore extending through said housing and hydraulically connecting said inlet port to said first outlet port, a passage hydraulically connecting said inlet port to said second outlet port, a valve seat in said bore intermediate said inlet port and said first outlet port, a poppet slidably disposed in one end of said bore for axial movement between an open position axially spaced from said valve seat and a closed position axially engaging said valve seat, said poppet including a first end exposed to atmospheric pressure and a second end exposed to fluid inlet port pressure, a spring biasing said poppet to said closed position, a differential area piston slidably disposed in the other end of said bore in axially aligned relationship with said poppet, said differential area piston including a first end exposed to fluid inlet port pressure and a second end of greater lateral cross-sectional area than said first end exposed to accumulator pressure and a differential area exposed to atmospheric pressure, said differential area piston being movable in said bore by application of a predetermined pressure in said inlet port and said accumulator to said first and second differential area piston ends to axially engage said poppet and move said poppet against the bias of said spring from said closed position to said open position, and said second end of said poppet being of smaller lateral cross-sectional area than said first end of said differential area piston whereby a decrease in fluid inlet port pressure decreases the net force urging said poppet to said clOsed position.

Claim 17

In a motor vehicle fluid power circuit having a fluid pump, a steering gear, a brake booster, and an accumulator, a control valve; said control valve including a housing having an inlet port for receiving fluid from said fluid pump, a first outlet port for supplying fluid to said steering gear, a second outlet port for supplying fluid to said accumulator, a bore extending through said housing and hydraulically connecting said inlet port to said first outlet port, a passage hydraulically connecting said inlet port to said second outlet port, a valve seat in said bore intermediate said inlet port and said first outlet port, a poppet slidably disposed in one end of said bore for axial movement between an open position axially spaced from said valve seat and a closed position axially engaging said valve seat, said poppet including a first end exposed to atmospheric pressure and a second end exposed to fluid inlet port pressure, a spring biasing said poppet to said closed position, a differential area piston slidably disposed in the other end of said bore in axially aligned relationship with said poppet, said differential area piston including a first end exposed to fluid inlet port pressure and a second end of greater lateral cross-sectional area than said first end exposed to accumulator pressure and a differential area exposed to atmospheric pressure, said differential area piston being movable in said bore by application of a predetermined pressure in said inlet port and said accumulator to said first and second differential area piston ends to axially engage said poppet and move said poppet against the bias of said spring from said closed position to said open position, and said second end of said poppet being of smaller lateral cross-sectional area than said first end of said differential area piston whereby a decrease in fluid inlet port pressure decreases the net force urging said poppet to said clOsed position.