Jidosha Kiki Co., Ltd.

Ikuo Nomura

Yasuyoshi Emori

Hiroshi Ohsaki

Tetsuya Koike

Yukimitsu Minamibata

A vehicle speed responsive power steering apparatus enables a pressure which acts upon a power cylinder to be variably controlled in accordance with a vehicle speed or the like, thus allowing an assisting force to be controlled in a variable manner. A control valve CV selectively connects a pump P and a tank T to left and right chambers CL, CR of a power cylinder. The control valve comprises a first and a second fluid pressure bridge circuit 10, 20. The first fluid pressure bridge circuit includes a left and a right path 12, 13, in which a first and a second pair of variable throttles 1R, 1L and 2L, 2R are disposed which are opened or closed in response to a steering operation. The left and the right chamber of the cylinder are connected to the respective paths at the junctions between the variable throttles. A pair of paths 21, 22 branch from a supply path 11 extending from the pump, and a second fluid pressure bridge circuit is defined between the paths 21, 22, in parallel relationship with the first fluid pressure bridge circuit. The second fluid pressure bridge circuit includes variable throttles 3L, 3R, 4R, 4L which are opened and closed in response to a steering operation, and a vehicle speed responsive variable throttle valve 6 which is controlled to be opened or closed in accordance with a vehicle speed.

Power steering apparatus

A power steering apparatus includes a main hydraulic path, a reactive oil pressure supply path, and a hydraulic reaction mechanism. The main hydraulic path supplies an oil pressure from a pump to a flow path switching valve connected to a power cylinder. The reactive oil pressure supply path branches from a portion of the main hydraulic path. The hydraulic reaction mechanism introduces part of the oil pressure, caused to diverge by the reactive oil pressure supply path, into a hydraulic reaction chamber for generating a steering reaction through a hydraulic reaction control valve mechanism controlled in accordance with the traveling conditions of a vehicle. A restriction smaller in diameter than the main hydraulic path is arranged between a branch portion branching from the main hydraulic path and the hydraulic reaction control valve mechanism, midway along the reactive oil pressure supply path.

Power steering apparatus having hydraulic reaction mechanism

A hydraulic reaction-type steering force control apparatus is provided to improve the sealing performance of a seal ring for preventing liquid leakage from a hydraulic reaction chamber by improving throttling actions in oil passages of chambers before and after the seal ring to prevent the reversal in pressure between the chambers before and after the seal ring. This eliminates a discontinuity phenomenon occurring due to a temporary deficiency of reaction oil pressure during steering operation caused by leakage from the hydraulic reaction chamber. The hydraulic reaction chamber constitutes a hydraulic reaction mechanism supplied with a reaction oil pressure from a hydraulic reaction force control valve mechanism, which is controlled in accordance with vehicle running conditions. A reaction piston has seal members on its slide surfaces and selectively constrains a relative rotational displacement between input and output shafts of a power steering system. First and second low-pressure chambers are allowed to communicate with a tank through their respective throttles. Also, a low-pressure chamber in the hydraulic reaction force control valve mechanism is connected on the upstream side of the throttle at position midway along a connection passage between the first low-pressure chamber and the tank. With this arrangement, the pressure in the hydraulic reaction chamber can be set substantially equal to or higher than the internal pressure in the first low-pressure chamber at any instant limiting the directions of the pressures acting on the seal members of the reaction piston to a predetermined direction constantly.

Steering force control apparatus for power steering system

A steering force controller for power steering apparatus is disclosed, which controls an oil pressure supplied to an oil pressure reaction chamber in accordance with a position of a spool valve which is caused to be displaced fore and aft in accordance with a vehicle speed. The spool valve is slidably fitted into a sleeve which is in turn disposed within a bore formed in a housing. The oil pressure supplied to the oil pressure reaction chamber can be controlled in accordance with the displaced position of the spool valve with respect to the sleeve. A regulating member is provided for causing an axial displacement of the sleeve, thus facilitating a regulation of a relative position between the spool valve and the sleeve.

Steering force controller for power steering apparatus

A hydraulic reaction force apparatus for a power steering system includes input and output shafts, a flange, balls, a reaction force receiving portion, a hydraulic reaction force chamber, and an annular reaction force piston. The input and output shafts are accommodated in a body. The flange is formed on one of the input and output shafts and has axial through guide holes. The balls are movably fitted in the guide holes, respectively. The reaction force receiving portion is formed on the other one of the input and output shafts to axially receive the balls. The hydraulic reaction force chamber is formed at a position opposite to the reaction force receiving force receiving portion with respect to the flange. The reaction force piston is movably and coaxially fitted on the output shaft with a clearance to urge the balls against the reaction force receiving portion so as to generate a restriction force corresponding to a reaction force oil pressure. The restriction force acts between the input and output shafts. Seal rings are disposed between the reaction force piston and the body and between the reaction force piston and the one of the input and ouput shafts.

Hydraulic reaction force apparatus for power steering system

A rack-and-pinion steering apparatus of center-takeoff type is disclosed in which track rods are connected to an intermediate portion of a rack shaft. A stop member is secured to the rack shaft for limiting the axial movement of the rack shaft by abutment against a housing. A resilient member is mounted on a part of these contacting surfaces so that the resilient member initially contacts either component to absorb impact before a contact occurs between metals, thus assuring the stroke limiting function while reducing the generation of percussion sounds.

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Saitama, Japan

Ikuo Nomura