US 2002/0170769 A1Published application

Power steering device

AssigneeUnisia Jecs Corporation

InventorsToshimitsu Sakaki, Chiharu Nakazawa, Tadaharu Yokota, Masakazu Kurata

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Abstract

A first fluid passage extends from a first outlet/inlet port of a hydraulic pump to a first work chamber of a power cylinder, and a second fluid passage extends from a second outlet/inlet port of the pump to a second work chamber of the power cylinder. A switch system switches the role of the first and second outlet/inlet ports in accordance with a turning direction of a steering wheel. Flow control mechanisms are respectively incorporated with the first and second fluid passages, so that a controlled flow of hydraulic fluid from the hydraulic pump to the first or second work chamber and vice versa are appropriately carried out thereby providing the driver with a comfortable steering feeling. A bypass arrangement may be provided between the first and second fluid passages to deal with a residual pressure that would be remained in the first or second work chamber when the hydraulic pump is under inoperative condition.

Claims16

Dependent claims

A power steering device for a motor vehicle, comprising:

a steering mechanism including a steering wheel;
a hydraulic power mechanism for assisting operation of said steering mechanism in accordance with movement of said steering wheel, said hydraulic power mechanism including a power cylinder, a piston slidably disposed in said power cylinder to divide the interior of said power cylinder into first and second work chambers and a transmission mechanism for transmitting movement of said piston to said steering mechanism to assist the same;
a reversible hydraulic pump having a first outlet/inlet port and a second outlet/inlet port;
a first fluid passage extending from said first outlet/inlet port to said first work chamber;
a second fluid passage extending from said second outlet/inlet port to said second work chamber;
a switch system for switching the role of said first and second outlet/inlet ports in accordance with a turning direction of said steering wheel;
a first valve arranged in each of said first and second fluid passages, said first valve being constructed to permit a fluid flow from said hydraulic power source toward said power cylinder when a hydraulic pressure produced by said hydraulic pump is larger than that in the corresponding work chamber by a given pressure;
and
a second valve arranged in each of said first and second fluid passages in parallel with said first valve, said second valve being constructed to permit only a fluid flow from the work chamber toward said hydraulic pump.

6 more elements

A power steering device for a motor vehicle, comprising:

a steering mechanism including a steering wheel;
a hydraulic power mechanism for assisting operation of said steering mechanism in accordance with movement of said steering wheel, said hydraulic power mechanism including a power cylinder, a piston slidably disposed in said power cylinder to divide the interior of said power cylinder into first and second work chambers and a transmission mechanism for transmitting movement of said piston to said steering mechanism to assist the same;
a reversible hydraulic pump having a first outlet/inlet port and a second outlet/inlet port;
a first fluid passage extending from said first outlet/inlet port to said first work chamber;
a second fluid passage extending from said second outlet/inlet port to said second work chamber;
a switch system for switching the role of said first and second outlet/inlet ports in accordance with a turning direction of said steering wheel;
a first flow control arrangement arranged between said first and second fluid passages, said first flow control arrangement selectively connecting and disconnecting said first and second fluid passages in accordance with a magnitude of a hydraulic pressure produced by said hydraulic pump, and said first flow control arrangement connecting said first and second fluid passages when said hydraulic pump is under inoperative condition;
and
a second flow control arrangement arranged between said first and second fluid passages, said second flow control arrangement permitting a flow of residual pressure in one of said first and second work chambers toward the other of said first and second work chambers when said hydraulic pump is under inoperative condition.

6 more elements

Dependencies are inferred from the claim text.