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 power steering system includes first and second valve members (40 and 42) which are movable relative to each other to port fluid to a vehicle power steering motor (31) and a pump (24) for providing fluid to the first and second valve members (40 and 42) and the power steering motor. A force transmitting member (116) is connected with the first valve member (40) and movable toward and away from the second valve member (42) for applying a force to resist relative movement between the first and second valve members. A fluid pressure chamber (138) receives fluid from the pump (24), the pressure of which acts on the force transmitting member (116). The first and second valve members (40 and 42) include passages for conducting fluid to the fluid pressure chamber (138). A fixed size bleed orifice (182) conducts fluid from the pressure chamber (138) to a reservoir (32). The orifice (182) restricts the flow of fluid from the chamber (138) to the reservoir (32).

Abstract: A electric motor, which drives a fluid pressure pump used to derive a steering assist force, is controlled in a required manner using a simplified arrangement. Specifically, a pump 11 which feeds a fluid pressure in order to produce an assist force is driven by a D.C. brushless motor 11 which is provided with means 18 for detecting a rotational position of a rotor 23 thereof. Motor control means 14, 15 drives and controls the motor to rotate at a given number of revolutions. Vehicle speed detecting means 16 detects a running speed of a vehicle. The motor control means controls the number of revolutions of the brushless motor on the basis of information representing a vehicle speed, a number of revolutions of the rotor which is determined by utilizing a signal from the rotor position detecting means, and information from means which detect a steer angle and a steering angular rate.

Abstract: A power assistance steering system for use in a vehicle comprises a restricting mechanism including a cylindrical reaction piston having a reaction surface on which said reaction pressure is applied in order to cause said reaction piston to be biased downwardly, and at least one reversed V-shaped depression formed on a bottom skirt, the cylindrical reaction piston adapted to be held on the input shaft in such a way that said reaction piston can longitudinally and slidably reciprocate with respect to the input shaft, while circumferentially locked to the input shaft, and at least one semi-spherical protrusion formed on a middle end surface of said output shaft so as to be retained within the reversed V-shaped depression.

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: To the end of ensuring a brisk maneuverability of a front and rear wheel steering vehicle without causing any unstable behavior of the vehicle, the rear wheels are steered in an opposite phase relationship to the front wheels to offset an under-steer tendency of the vehicle when a lateral acceleration acting on the vehicle is between a first prescribed value and a second prescribed value higher than the first prescribed value, and the vehicle would otherwise demonstrate an under-steer tendency, and in a same phase relationship to the front wheels to prevent an excessive slip angle from developing in the rear wheels when the detected lateral acceleration is greater than the second prescribed value, and the slip angle of the rear wheels would otherwise develop an excessive slip angle.

Abstract: A power assisted steering system, in particular, for motor vehicles, contains a servomotor (2), a servopump (3), a tank (4), a control valve (1) with a controllable feedback device (5), and a control member (46) whose choke cross section can be altered as a function of the vehicle speed. Control valve (1) is made as a four-way valve and has a supply connection (22, 23), a feedback connection (7), and two working connections (8, 10) for the lines (11, 12) that lead to the two working chambers of servomotor (2). Between feedback device (5) and supply connection (22, 23), there is arranged a device (13) for piling up the pressure medium stream and the device is made according to one practical example as a choke (50, 51). With the help of this choke (50, 51), one can achieve a hydraulic centering component in addition to a mechanical centering component.

Abstract: A hydraulic power steering system includes a pump, a flow control valve, and a bypass control valve. The flow control valve responds to a pressure drop across a metering orifice disposed in a fluid supply passage so as to control the flow rate of operating fluid by bypassing a part of the operating fluid to a reservoir. A spring chamber of the flow control valve is connected to the supply passage through a control orifice. The bypass control valve is disposed between the spring chamber and the reservoir so as to increase the amount of bypassed fluid by controlling the pressure in the spring chamber. The bypass control valve has a control spool, a load pressure introduction port connected to the upstream side of the control orifice for leading the load pressure to a first end of the control spool and a pilot port connected to the downstream side of the control orifice for leading the pressure in the spring chamber of the flow control valve to a second end of the control spool.

Abstract: In the hydraulically assisted steering system disclosed herein, a hydraulic pump for powering a steering servo is in turn driven either from the vehicle's engine, through an electrically controlled clutch, or by an electric motor which can drive the pump independently of the vehicle's engine. A signal is provided which varies as a function of vehicle's speed and disengagement of the clutch is enabled for vehicle speeds above a predetermable threshold, thereby to reduce energy consumption. The clutch is engaged, independently of vehicle speed, under high load, e.g. emergency situations.

Abstract: A power steering apparatus comprises a fluid source for supplying pressurized fluid, a power cylinder having a pair of fluid chambers, a control valve, and a drain control mechanism. The control valve is composed of first and second control portions. The first control portion has four paths connecting the fluid source and the reservoir, and each of the four paths is formed with a variable orifice of center-open type. The second control portion has two supply paths communicating the fluid source with the fluid chambers of the power cylinder, each of the supply paths being formed with a variable orifice of center-open type, and two drain paths communicating the fluid chambers with the reservoir, each of the drain paths being formed with a variable orifice of center-closed type.