Abstract: 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.

Abstract: A main servo valve 4 is switched in response to a relative angular displacement between an input and an output shaft for supplying an operating oil discharged from a pump to or displacing such operating oil from a power cylinder 6. An auxiliary servo valve 10 is disposed between the input and the output shaft and is connected in parallel relationship with the main servo valve 4 so as to be operated jointly therewith. A vehicle speed responsive valve 16 which opens or closes a flow path in accordance with the vehicle speed is disposed upstream of the auxiliary servo valve 10. The pump comprises a pair of pumps 2, 12 of smaller size. At low speeds, the speed responsive valve 16 is closed, and the oil discharged from the pair of pumps 2, 12 are merged to be introduced into the main servo valve 4. As the vehicle speed increases, the speed responsive valve 16 is gradually opened, and at a vehicle speed above a given value, one of the pumps, 12, ceases to operate.

Abstract: 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.

Abstract: 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.

Abstract: In each of both ends of a land portion provided between channels which are formed in a slidable contact surface of a rotor assembled in a sleeve so as to be rotationally displaceable relative to the sleeve and thus control connection and disconnection of fluid paths, a chamfer is formed from an edge to a throttling action end portion of the land portion of the rotor so as to have at least one flat acting surface and a curved acting surface continuously connected to the flat acting surface. The curved acting surface of the chamfer is formed to have a smooth, continuously curved surface with a radius of curvature which decreases gradually from a connection portion with respect to the flat acting surface to a point at which it is connected to an outer diameter portion of the rotor.

Abstract: A hydraulic pressure acting in a hydraulic reaction chamber of a power steering system is controlled. A spool valve is formed with portions having a greater and a smaller diameter, which portions are partly situated in an annular groove formed in a valve opening and communicating with the hydraulic reaction chamber. A spring is disposed to one side of the spool valve nearer the portion of a greater diameter to urge it toward the portion of a smaller diameter. Toward the portion of a smaller diameter, the spool valve abuts against a rod of a solenoid. The hydraulic pressure from a pump is introduced into the annular groove through a variable throttle formed in the portion of a greater diameter while the hydraulic pressure in the annular groove is returned to a tank through a variable throttle formed in the portion of a smaller diameter.

Abstract: A subpump has its discharge flow rate increased in response to an increase in a vehicle speed. A variable throttle is disposed in a discharge passage from the subpump, and an oil pressure taken from the upstream side of the variable throttle is introduced into a hydraulic reaction chamber to produce a steering action. A main pump has its flow rate increased or decreased in accordance with a number of revolutions thereof, and feeds a pressure oil to a power steering control valve through a passage in which a fixed restriction is disposed. An oil pressure which prevails upstream of the fixed restriction acts upon the variable throttle to change its area of opening, thereby controlling the steering force.

Abstract: A steering force control apparatus for a power steering system includes a valve. The valve includes a valve hole, a spool, and a spring. A main pump oil supply path branched from a main hydraulic path extending from a pump to a power cylinder, a reaction path connected to a hydraulic reaction chamber, and a discharge path connected to a tank are open to the valve hole to be spaced apart from each other by predetermined distances along an axis of the valve. The spool is slidably arranged in the valve hole and has land portions so as to change connecting states of the main pump oil supply path, the reaction path, and the discharge path. The spring always biases the spool in one direction. A subpump oil supply path for supplying a fluid from a subpump whose delivery pressure is changed is connected to an end of the spool which is biased by the spring, thereby controlling an operation of the spool by the subpump in correspondence with a vehicle speed.

Abstract: A reaction pressure control mechanism of power steering apparatus includes a power cylinder, to which a pressure oil discharged from an oil pump is supplied through a control valve, and oil discharged from the oil pump is branched to be introduced into a hydraulic reaction chamber, which produces steering reaction. A pair of variable restrictions are formed in a supply and discharge passage to and from the hydraulic reaction chamber, and a single spool which is operated by a solenoid is effective to increase the opening of one of the variable restrictions while reducing the opening of the other restriction. A plunger is disposed in opposing relationship with a rod associated with the solenoid and on which the spool is fixedly mounted so that when the oil pressure in the reaction chamber exceeds a given value, such oil pressure is introduced to the backside of the plunger to cause the spool to be driven back, thus reducing the opening of the variable restriction associated with the supply passage.

Abstract: A hydraulic reaction device of a power steering apparatus includes a vehicle-speed responsive pump, a reaction plunger, a hydraulic reaction chamber, a path, and a variable control unit. The vehicle-speed responsive pump has a pressure oil discharge flow rate which changes in accordance with a vehicle speed. The reaction plunger selectively constraining relative pivotal displacement between input and output shafts constituting a rotary flow path switching valve of the power steering apparatus. The hydraulic reaction chamber receives the pressure oil from the pump to apply a reaction oil pressure to the reaction plunger. The path is arranged to connect the hydraulic reaction chamber to a tank. The variable control unit (a variable throttle portion 37 of a reaction oil pressure control valve 11) for variably controlling a flow rate of the pressure oil flowing through the path.

Abstract: A fluid control valve device includes a sleeve, a rotor, and a first recess groove. The sleeve has an inner circumferential surface in which two types of axial channel grooves communicating with an input port and a return port are formed in the circumferential direction, and left and right output ports are open in land portions between the channel grooves. The rotor is inserted in the inner circumferential surface of the sleeve so as to be rotatably held relative to the sleeve and has an outer circumferential surface in which channel grooves communicating with the axial channel grooves of the sleeve are formed in the circumferential direction at positions opposite to the land portions in which the output ports of the sleeve are open, and first and second land portions are formed at positions opposite to the channel grooves of the sleeve.

Abstract: A rotary valve for power steering apparatus includes an input shaft, an output shaft disposed in axial alignment with the input shaft and connected thereto by a torsion bar, a valve rotor formed on the input shaft, and a valve sleeve connected to the output shaft and fitted over the valve rotor. A return oil path in the input shaft is formed inside a step defined in the internal surface of the valve sleeve while a return oil path in the valve sleeve is formed in a cylindrical portion of an increased internal diameter and extends therefrom along the step to define a return flow groove.

Abstract: A control apparatus of a power steering device having a steering force control device for changing a steering force in accordance with a vehicle speed includes a detecting unit for detecting a road surface resistance. The steering force control device controls the power steering device such that the steering force is reduced as the road surface resistance obtained from the detecting unit is reduced.

Abstract: 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.

Abstract: 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.

Abstract: A hydraulic reaction force apparatus for a power steering system includes input and output shafts, guide holes, balls, a reaction force reception portion, a hydraulic reaction force chamber, and a reaction force piston. The output shaft is coaxial with the input shaft, the output shaft and the input shaft being rotatable relative to each other. The guide holes axially extend through a flange formed on one of the input and output shafts. The balls are axially slidable in the guide holes, respectively. The reaction force reception portion is formed on the other one of the input and output shafts so as to oppose one major surface of the flange. The reaction force reception portion is adapted to receive the balls. The hydraulic reaction force chamber is formed on the other major surface of the flange which opposes its one major surface. The reaction force piston is slidably coaxial with the input and output shafts in the hydraulic reaction force chamber.

Abstract: 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.