US 5,505,275 AGranted

Power steering system

AssigneeTecho Corporation

InventorEdward H. Phillips

Life of this patent

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Abstract

A power steering system (10) for a motor vehicle having a power cylinder with the piston mounted in the power cylinder which divides the power cylinder into first (30) and second (32) chambers. The steering system includes a valve assembly having a rotary input member (40) and a valve sleeve 42 and first and second pairs of open center input valves (18), each which has an inlet and an outlet. The inlets of the input valves are fluidly connected to pump output. The valve assembly further includes a pair of closed center input valves (4b) and a normally closed by-pass valve (50). A hydraulic pump (12) is controlled so as to maintain a constant pressure drop between the inlets and outlets of the closed center valve (4b) and normally closed by-pass valves (50) whereby initial fluid flow through the control valve is proportional to the area of a variable orifice comprised within the normally closed by-pass valve (50). When sufficient torque is applied to the rotary input member (40) one of the closed center valves (46) begins to open whereby total flow through the control valve is proportional to the combined area of orifices comprised within both the opening of closed center valve (4b) and the normally closed by-pass valve (50).

Claims8

Dependent claims

A power steering system for a motor vehicle of the type having a power cylinder, a piston mounted in the power cylinder and dividing the power cylinder into a first and second chamber, said power steering system comprising:

a source of pressurized fluid having an input and an output,
means for maintaining a fluid pressure between said input and said output,
a valve assembly comprising
a rotary input member,
a pair of input open center valves, each having an inlet and an outlet, said inlets of said input valves being fluidly connected to said pressurized fluid source output,
a pair of output open center valves each having an inlet and an outlet, said inlet of one output valve being fluidly connected to said outlet of one input valve and the inlet of the other output valve being fluidly connected to said outlet of the other input valve,
a closed center valve connected in series with said pairs of said open center valves and said source of pressurized fluid,
means for fluidly connecting said outlet of one input valve to the first chamber of the power cylinder and for fluidly connecting said outlet of the other input valve to the second chamber of the power cylinder,
wherein said open center valves variably close and said closed center valve variably open progressively with torque applied to said rotary input member to create a differential pressure between said chambers of said power cylinder,
means for sensing speed of the vehicle,
bypass valve means connected in parallel with said closed center valve, and
means responsive to said speed sensing means for actuating said bypass valve means from an open to a closed position in an amount related to vehicle speed.

9 more elements

a source of pressurized fluid having an input and an output,
means for maintaining a fluid pressure between said input and said output,
a valve assembly comprising
a rotary input member,
a pair of input open center valves, each having an inlet and an outlet, said inlets of said input valves being fluidly connected to said pressurized fluid source output,
a pair of output open center valves each having an inlet and an outlet, said inlet of one output valve being fluidly connected to said outlet of one input valve and the inlet of the other output valve being fluidly connected to said outlet of the other input valve,
a closed center valve connected in series with said pairs of said open center valves and said source of pressurized fluid,
means for fluidly connecting said outlet of one input valve to the first chamber of the power cylinder and for fluidly connecting said outlet of the other input valve to the second chamber of the power cylinder,
wherein said open center valves variably close and said closed center valve variably open progressively with torque applied to said rotary input member to create a differential pressure between said chambers of said power cylinder,
first one way valve means connected between said outlet of said closed center valve and said first chamber of the power cylinder to enable fluid flow between said outlet of said closed center valve and said first chamber when the fluid pressure in said first chamber falls below a preset value, and
second one way valve means connected between said outlet of said closed center valve and said second chamber of the power cylinder to enable fluid flow between said outlet of said closed center vane and said second chamber when the fluid pressure in said second chamber falls below a preset value.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/322,448Filed 5 Oct 1994 · continuation in part
Priority: 9 Sep 1993
Granted: 9 Apr 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification14 codes

B62D 5/062
Fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle: details, component parts
B62D 5/06
Power-assisted or power-driven steering: fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
B62D 5/065
Fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle: characterised by specially adapted means for…
B62D 5/083
Characterised by type of steering valve used: rotary valves