Abstract: An apparatus (10) includes a hydraulic fluid power cylinder (116) and a steering rack (118). The rack (118) is fixed to a piston (160) in the power cylinder (116), and extends outward through an open end (172) of the power cylinder (116). An annular hydraulic fluid seal (164) is received over the rack (118) in dynamic sealing contact with the rack (118). The seal (164) defines a fixed end of a variable volume hydraulic fluid chamber (173) extending from the piston (160) to the seal (164). The apparatus (10) further includes a housing part (114) which is mounted on the power cylinder (116). The housing part (114) supports the seal (164) at a location spaced outward from the open end (172) of the power cylinder (116). In this arrangement, the housing part (114) defines an end section (191) of the fluid chamber (173) extending outward from the open end (172) of the power cylinder (116) to the seal (164).

Abstract: In the power steering apparatus, a casing comprises integrated separate sections of a valve casing in which a control valve is incorporated, a cylinder tube of a power cylinder, and a gear casing in which a steering gear is incorporated. In the cylinder tube are formed a pair of supply/discharge passages, which are parallel to the axial direction of the cylinder tube, and through which hydraulic fluid flows into/from the power cylinder. In the gear casing are formed, by casting, a pair of pipes which communicate with a pair of supply/discharge passages. In the valve casing are formed a pair of supply/discharge ports which communicate with the pair of pipes.

Abstract: A steering gear housing part (112) has a tubular portion (184) with an annular inner end surface (188). The housing part (112) is constructed with reference to a corresponding hydraulic fluid power cylinder (114) so as to be receivable in an installed position in which the tubular portion (184) extends inward through an open end (182) of the power cylinder (114) in an interference fit with the power cylinder (114). When the housing part (112) is in its installed position, the inner end surface (188) of the tubular portion (184) abuts an annular hydraulic fluid seal (162) in the power cylinder (114).

Abstract: To improve a rack and pinion steering of the generic type to reduce noise development upon opening of the pressure-relief bore as well as in steady-state operation, the invention proposes that at least one filter element forming a flow resistance be inserted between the additional bore and the pressure connection.

Abstract: A steering axle with hydrostatic two-circuit steering system for agricultural, forestry and construction vehicles. The steering axle includes a first double-acting pressure medium cylinder (1) which in the area of its center is connected with an axle bridge housing (2) and at its two ends with joint housings (4, 5) via tie bars (3) and an additional second double-acting pressure medium cylinder (6) which is mounted on one side of the axle. The second cylinder acts simultaneously together with the first pressure medium cylinder (1). In this manner a two-circuit steering system is obtained. At the same time said second double-acting pressure medium cylinder (6) is connected at one end via a ball joint (7) with a joint housing (5) and at the other end is fastened on the axle bridge housing (2).

Abstract: In a power steering system of this invention, a control valve is provided for supplying working fluid to a power cylinder by an amount proportional to a steering effort supplied to an input shaft and obstructing supply of working fluid to the power cylinder when a steering wheel is in a neutral position. A conversion mechanism which includes an operation rod (operating device) capable of operating the control valve is provided for converting the steering effort supplied to the input shaft to displacement of the operation rod. A directional control valve is provided which is disposed between the control valve and the power cylinder for switching supply of working fluid from one of cylinder chambers of the power cylinder to the other according to the direction of the steering effort on the input shaft while controlling discharge of working fluid from the cylinder chambers.

Abstract: A method is provided for controlling an electro-hydraulic power assist steering system including a variable-speed electric motor for pumping hydraulic fluid in the system. The method includes monitoring vehicle speed, vehicle steering wheel angle, and vehicle steering wheel turning rate. A parking mode or a driving mode is selected based upon the monitored vehicle speed. The speed of the variable speed electric motor is controlled based upon the monitored vehicle steering wheel turning rate if the parking mode is selected. If the driving mode is selected, the speed of the variable speed electric motor is controlled based upon the monitored vehicle speed, vehicle steering wheel angle and vehicle steering wheel angle turning rate. Accordingly, a wide range of vehicle driving conditions are accommodated and vehicle fuel efficiency is improved.

Abstract: A method of controlling a vehicle hydraulic drive system of the type including a plurality of fluid pressure actuated wheel motors (13,15) connected in a parallel circuit with a source (17) of pressure. A flow restrictor valve (65) is disposed in a downstream conduit (27) of each of the wheel motors (13,15). The method involves determining the theoretical fluid flow for each motor, the actual fluid flow through each motor, and generating an error signal (107) which is then used to bias the restrictor valve (65) toward a flow restriction position. The disclosed method can be used to achieve steering at greater than kinematic, by scrubbing the inside front wheel, or can be used to prevent wheel slip of propulsion wheels, or can be used to prevent scrubbing of a wheel during hydrostatic braking, or can even be used to achieve vehicle steering.

Abstract: Operation of a steering wheel is transmitted to a steering gear box through two cables. In this cable-type steering device, a steering torque inputted to the steering wheel is detected by a steering torque detector provided between the steering wheel and the cables. The operation of a motor for a power steering operation for driving the steering gear box is controlled on the basis of the detected steering torque. The steering torque detected by the steering torque detector includes the friction of the cables and hence, a steering torque offsetting the friction of the cables can be generated in the motor for the power steering operation, thereby providing an appropriate steering feeling. A hydraulic power steering device may be used instead of or in addition to a motor for a power steering operation.

Abstract: A steering power assist apparatus is comprised of a power cylinder whose operation is controlled by the a flow rate control valve, a first control valve and a second control valve. The flow rate control valve is connected to a discharge side of a hydraulic pump and controls the amount of the hydraulic oil to be supplied to the first and second control valves according to a load pressure. The first control valve constituted by choke valves is disposed downstream of the flow rate control valve and controls the amount of the hydraulic oil supplied to the second control valve according to a steering torque. The second control valve constituted by choke valves is disposed downstream of the flow rate control valve and controls the amount of the hydraulic oil to the power cylinder according to a steering torque. The choke valves of the second control valve are fully closed after the choke valves of the first control valve are fully closed.

Abstract: A power assisted, vacuum actuated steering system with a rotary valve and vacuum actuators. The rotary valve has two identical discs which each include grooves and channels for communicating the vacuum pressure to the vacuum actuators. The relative rotary motion of the two discs causes the vacuum pressure to pass to the vacuum actuators to assist the steering of a vehicle. A set of springs and spring arms biases the discs to a central, neutral position.

Abstract: A servo valve for a power assisted steering gear for producing an auxiliary steering force corresponding to twist between an input member and an output member which are connected to each other by a torsion bar is disclosed. There is provided a sleeve member surrounding a torsion bar and having first and second ends. The first end is prevented from being rotated with respect to the torsion bar. The second end is provided with an opening extending along the radius of the sleeve member. A plunger-containing hole extending in the radial direction is formed in an intermediate part between opposite ends of the torsion bar, and plungers are contained in the containing hole which are movable forward and backward. The plungers are urged forward by a helical compression spring interposed between the plungers. Each of the urged plungers is engaged with an edge of the opening serving as a holding arrangement, to increase the torsional rigidity of the torsion bar at the time when the valve is neutral.

Abstract: A rack-pinion type power steering apparatus includes a cylindrical stub shaft, a torsion bar, a pinion shaft, a rotor, and a sleeve. The stub shaft rotates in a steering body upon a steering operation. The torsion bar has one end fixed at one end of the stub shaft and extends through the stub shaft toward the other end of the stub shaft. The pinion shaft is pivotally connected to the other end of the torsion bar. The rotor is arranged to cover the torsion bar from the stub shaft along an extending direction of the torsion bar. The sleeve has one end integrally connected to the pinion shaft, extends from the pinion shaft along the stub shaft, and is arranged around the rotor to constitute a rotary type channel selector valve between the rotor and the sleeve. The pinion shaft is axially supported by the steering body at two end portions of the sleeve.

Abstract: A power assist steering system is provided for use on a vehicle that has a steering implement and a steering mechanism operatively connected to a first wheel. The power assist steering system includes first and second vacuum actuators, a vacuum for providing a vacuum to the first and second vacuum actuators, an actuator for selectively activating the first and second vacuum actuators and a power assist for assisting the steering mechanism in turning the first wheel in first and second directions.

Abstract: A cable-type steering device is provided in which a sterring wheel and a gear box are connected to each other by wires, wherein a pulley to which wires are connected can be easily assembled to housings, while maintaining the enire length of the wire at a necessary minimum. A housing is divided into a first housing half and a second housing half. In assembling a pully having inner cables of Bowden wires previously wound therearound into the housing, collars mounted at ends of outer tubes of the Bowden wires are fixed in such a manner that they are sandwiched between a wire supporting groove in the first housing half and a lid portion of the second housing half.

Abstract: A power assisted steering apparatus for a vehicle has a driving source and an actuator for the vehicle's steering mechanism, to power assist the steering operation. The driving source, such as an engine, continuously drives a pump. A working passage is arranged so that working oil discharged from the pump is introduced into the actuator. A check valve is disposed in the working passage, between the actuator and the pump so that the working oil flows only one way to the actuator. An accumulator is connected to the working passage, between the check valve and the actuator to maintain a predetermined pressure in the working passage. A regulator is connected to the working passage, between the pump and the check valve to regulate flow to the actuator. When the pressure within the working passage reaches the predetermined pressure, the working fluid is dumped to a reservoir, bypassing the check valve, the accumulator, and the actuator.

Abstract: A hydraulic system for a motor vehicle includes a hydraulic pump which has a hydraulic steering device including a steering motor and a steering valve which is movable from an intermediate position in opposing directions and by which hydraulic fluid lines to and from the steering motor are controlled. A ventilator motor with the bypass line are placed in series with the steering device between the latter and the hydraulic pump. The bypass valve aids the distribution of fluid flow through the ventilator motor and the bypass line for adjustment of the fluid flow in accordance with required cooling power. The bypass valve can be adjusted to allow more hydraulic fluid to flow through the bypass line during actuation of the steering valve, thereby to lower the system pressure for reduced cost and complexity of the hydraulic pump.

Abstract: A power steering device capable of improving both operability of a vehicle and a feeling of the steering. The power steering device includes an association mechanism for mechanically associating a handle with wheels, a power cylinder for generating assisting force, and a control valve connected to the power cylinder and adapted to be changed over depending on torque inputted thereto from the handle and kept at a neutral position unless the torque is inputted thereto. The control valve functions to control the amount of fluid fed to the power cylinder when it is changed over and close a cylinder port connected to the power cylinder when it is at the neutral position.

Abstract: A power steering device capable of facilitating assembling thereof and eliminating a variation in elastic force acting on an input shaft of the power steering device. Leaf spring structures each of which includes a first leaf spring and a second leaf spring are arranged. The first leaf spring includes a spring-side support section constituted by a V- or U-shaped groove, a pair of rolling surface sections arranged so as to be contiguous to the spring-side support section and outwardly extend from both ends of the spring-side support section, a pair of support leg sections each arranged so as to be contiguous to each of the rolling surface sections and outwardly extend therefrom, and a pair of holding sections each arranged so as to be contiguous to each of the support leg sections and outwardly extend therefrom. The holding sections each are pressedly contacted with press contact surfaces or side surfaces of a spring receiving chamber, resulting in the first leaf spring being securely held.

Abstract: An apparatus (30) which controls the motion of a cab (12) of a vehicle relative to a frame of the vehicle includes a cab motion control motor (38). A pair of motor control valves (70 and 72) are provided to control fluid pressure conducted to the cab motion control motor (38). The motor control valves (70 and 72) are supplied with fluid under pressure by a power steering pump (22). The power steering pump (22) also provides fluid under pressure to a power steering motor (20) which is operable to turn steerable vehicle wheels (18).

Abstract: A steering valve (30) directs hydraulic fluid from a hydraulic fluid source to a hydraulic cylinder of a steering system in a vehicle. The steering valve includes a rotatable first shaft (32) having a first face valve member (36) on an end portion of the first shaft and a rotatable second shaft (34) having a second face valve member (50) on an end portion of the second shaft. The first face valve member (36) includes a plurality of channels (40, 42) fluidly connected with the hydraulic cylinder and the second face valve member (50) includes a plurality of passages (54, 56) fluidly connected with the hydraulic fluid source. A rotatable intermediate disk (70) is located between the first and second face valve members (36, 50). The intermediate disk (70) includes a plurality of axially extending bores (80a-80d) for fluidly connecting the plurality of channels (40, 42) with the plurality of passages (54, 56).

Abstract: A hydraulic power steering system for a vehicle comprising a hydraulic fluid displacement pump, operated by a thermal engine of the vehicle and provided with a suction port and a delivery port, a reservoir for collecting said fluid, connected to suction port, a double-acting hydraulic cylinder, capable of controlling direction of front wheels of the vehicle, and a distribution unit fitted with an inlet port, connected to delivery port, a vent port, connected to reservoir and two service ports, connected to respective chambers of hydraulic cylinder; distribution unit comprising a first and a second distributor, respectively controlled by hydraulic cylinder and by a steering wheel of the vehicle and movable with respect to each other; pump being of the variable displacement type and system further comprising a flow request sensor from and to chambers of cylinder and a device for adjusting displacement of pump, controlled by sensor.

Abstract: In the power steering device adapted to transmit a steering force to the front wheels via the pair of cables subjected to a tensile force, there is an apprehension that the cables might be unacceptably slacked to deteriorate the steering performance. To avoid such apprehension, at least one of two casings separately housing a drum on the side of the steering wheel and a drum on the side of the power cylinder is provided with a novel tensioner functioning to tension the inner cables by pressing the rollers against the respective inner cables under the biasing effect of the spring.

Abstract: A power assisted steering apparatus for a vehicle having a driving source, such as an engine, has an actuator, a hydraulic pump, a working oil pressure passage, and a drive switch. The actuator, which is in the vehicle steering mechanism, receives a supply or exhaust of a working oil to assist the steering operation. The pump is selectively driven by an engine via a clutch mechanism. The working oil discharged from the pump is introduced into the actuator via the passage. The check valve is interposed within the passage to enable flow in one direction away from the pump. The drive switch structure is disposed within the passage, downstream from the check valve. With this arrangement, the drive switch structure can be activated by pressure in the passage downstream of the check valve to control the clutch mechanism.

Abstract: In a toothed-rack power-assisted steering, which is provided for motor vehicles in particular, a pinion (2) seated in a steering housing (1) is in engagement with a toothed rack (6). A servo motor (8) is disposed as a power assist, whose piston rod (10) is drivingly connected with the toothed rack (6). The two work chambers (12, 13) of the servo motor (8) are connected with a control device (18) via work lines (12, 13), which are connected with a cylinder (11) of the servo motor (8) and with the control device (18) via two connecting elements (24, 25). Each work line (14, 15) has a collar (32). Each line is held on the connecting element (24, 25) by a fastening clasp (34) which projects over the collar (32). The fastening clasp (34) has an essentially rectangular and flat base (35). An elongated slit (36), open toward one side, is located in the base (35), through which the fastening clasp (34) can be pushed from the side over the line (14, 15) and the connecting element (24, 25).

Abstract: A power steering system for a motor vehicle, comprising a steering wheel actuated by the driver of the vehicle, at least one steered wheel, an actuator motor that is activated to assist the steering movement initiated by the driver and a locking device for locking the steering wheel in at least one predetermined position. The steering wheel is moved to the predetermined position by activation of the actuator motor upon detection of a predetermined preset operating condition. Using the actuator motor to move the steering wheel to the predetermined position frees the driver from having to manually turn the steering wheel to the locking position upon shutdown of the vehicle. This has the advantage of increasing the comfort of such a steering system since the driver is freed from having to turn the steering wheel after shutdown of the vehicle and of increasing protection against theft since the driver does not have to remember to engage the steering lock upon shutdown of the vehicle.

Abstract: In a hydraulic power steering for a motor vehicle with a hydraulic servomotor and a servovalve arrangement in communication with opposite servomotor actuating chambers by way of separate communication conduits through which the actuating chambers can be pressurized or depressurized for the operation of the servomotor depending on a force applied by an operator to a steering means, the communication conduits include valve arrangements permitting, when they are open, the release of hydraulic fluid from the actuating chambers but blocking the release of hydraulic fluid when they are closed thereby hydraulically locking the power steering.

Abstract: A torsion element (1) for a steering valve is provided. The torsion element (1) comprises a torsionally elastic rod member (2) having axially opposite first and second end areas (3, 4) which are rotatable relative to one another. The rod member (2) has a circumferentially spaced plurality of radially and axially extending indentations (10) adjacent the second end area. A generally tubular, torsionally stiff sleeve member (6) encircles the rod member (2) and is fixedly attached to the first end area (4) of the rod member. The sleeve member (6) includes a circumferentially spaced plurality of radially and axially extending grooves (9) which align with and radially overlie the plurality of indentations (10) in a neutral steering condition. The sleeve member (6) further includes a circumferentially spaced plurality of radial slots (7).

Abstract: In a power steering apparatus comprising a pump, a reservior, a power cylinder having two opposite chambers, and a rotary control vale, the rotary control valve consists of a first control portion which communicates between the pump and the reservior, and a second control portion which communicates not only between the pump and the reservior but also with the power cylinder. In the first control portion, each of four underlapping variable orifices is so provided as to take the form of underlap in itself. In the second control portion, two underlapping variable orifices are provided on the side of the pump, and besides each of two overlapping variable orifices is so provided as to take the form of overlap in itself on the side of the reservior. In this manner, while a steering wheel is operated within a predetermined angle, an opening area of the overlapping variable orifice changes little.

Abstract: A power steering gear for a motor vehicle including a pinion head and a spool shaft rotatable relative to each other, a torsion bar between the spool shaft and the pinion head, a valve spool formed integrally on the spool shaft, a valve body closely received on the spool shaft around the valve spool and rotatable relative to the spool shaft, and a tripod joint coupling the valve body to the pinion head for unitary rotation and consisting of three equally angularly spaced slots in an end of the valve body and three equally angularly spaced radial pins on the pinion head each having a spherical lobe closely received in a corresponding one of the slots in the valve body. An inboard end of the spool shaft adjacent the pinion head is unsupported laterally on the pinion head except through the valve body and the tripod joint and, consequently, floats with the valve body in the event of lateral runout between the pinion head and the spool shaft to minimize valve hysteresis attributable to such lateral runout.

Abstract: A fluid power vehicle steering gear (10) comprises a tubular housing (22), a fluid (34) disposed within the tubular housing, and a member (20) movable relative to the housing in response to a change in the fluid pressure in the housing. The fluid comprises a mixture of a base oil and a grease. The weight of the grease in the mixture is about 0.1% to about 5% of the weight of the base oil in the mixture.

Abstract: A controllable slide car for controllably simulating oversteer and understeer conditions in a moving automobile. The controllable slide car comprises a rear steering linkage assembly that attaches to the rear wheel mounting assemblies of an automobile and a controller for controllably steering the rear steering linkage assembly. The controller is powered by the battery of the automobile and manually controlled by a control unit to steer the rear wheel mounting assemblies.

Abstract: In order to improve a method for controlling the speed of an electromotor-driven pump of a hydraulic power steering device of a motor vehicle as a function of the steering speed, so that the overall efficiency of the system is optimized in a simple manner; it is proposed that the required volume flow of hydraulic fluid, calculated according to a determined steering speed, is increased up to a maximum by an additional correction factor that takes into account the overall efficiency of the system, in order to use the result to calculate and to adjust the set speed of the pump.

Abstract: A hydraulic feedback control for hydraulic power steering systems having first and second shaft sections rotatable relative to one another within limits, and whose relative rotation controls a servo valve system. At least one compressor working chamber is provided in the form of a piston working chamber. A piston is arranged in the piston working chamber, and is displaceable therein and separate from the first shaft section. The piston is tensioned by a pressure in a piston working chamber against a spring engaged with the first shaft section. A maximum possible displacement travel of the piston relative to the second shaft section is limited by a stop mounted thereon. The feedback control is designed so that with limited frictional losses, controllable torques can be produced which counteract the relative rotation between the shaft sections.

Abstract: A hydraulic power steering gear assembly includes an assembly body defining a piston chamber having opposed chamber ends with plunger passages formed in the ends, a reciprocating piston and a chamber having opposed ends and a passage extending between the piston ends, a check valve at each end of the piston passage, and a plunger assembly in each plunger passage with each assembly including a spring frictionally holding assembly in the passage and a poppet extending into the chamber to unseat a ball valve as the piston is moved toward one end of the chamber.

Abstract: A fluid control system (10) for a vehicle power steering mechanism having a manually driven steering member and a fluid driven driving member (16) operatively connected to steering means of the vehicle by which steerage of the vehicle is achieved, the control system (10) including a first valve (12) for metering pressurised fluid flow to the fluid operated driving member (16) in response to the force required to move the steering means when operating the manually driven steering member, the first valve (12) including at least two independent metering valve means (170, 171) each of which are simultaneously operated by the steering member to meter fluid flow to and/or from the fluid operated driving member (16) at a predefined rate, at least one of the metering valve means (170, 171) communicating independently to a drain via a second valve (14), the second valve (14) being arranged to selectively connect and disconnect said at least one of said valve means (170, 171) to the drain in response to vehicle speed.

Abstract: A screw member is screwed into a spool which is axially movably inserted into a housing. The opening of the throttling portion of a variable throttle valve is varied according to the axial shifting of the spool according to the rotation of the screw member. The centerline of the screw member is eccentric to the centerline of the spool. The eccentricity prevents the spool from rotating together with the screw member.

Abstract: A steering system and method of a mowing vehicle comprise Left and right rear wheels rotating about a king pin for steering the vehicle, an Ackermann steering mechanism for steering these left and right rear wheels and a rear axle housing swingably connected with the vehicle about a yawing axis in a horizontal plane by use of a hydraulic cylinder. When the vehicle makes a U-turn for example to the right during the mowing work, the rear axle housing is fully swung to the left in the horizontal plane by a specified angle and fixed therein while the left and right rear wheels are held at the neutral position. After the rear axle housing is fixed at that angle, the left and right rear wheels are rotated about the king pin to the left and then the vehicle makes a U-turn to the right.

Abstract: A power steering apparatus comprising structure for smoothing a load detection signal obtained by detecting the load of a hydraulic pump and structure for controlling the rotational speed of an electric motor for driving the hydraulic pump, wherein the control valve controls a working oil pressure by a hydraulic pump on the basis of manipulation of steering wheel, whereby the steering operation is assisted.

Abstract: A lightweight housing (12) for a hydraulic power steering gear (10) includes a tubular structure (34 or 68) with a longitudinal central axis (21 or 23). The tubular structure (34 or 68) has layers extending circumferentially around the axis (21 or 23), including an inner layer (100), an outer layer (102), and an intermediate layer (104) between the inner and outer layers (100 and 102). The inner layer (100) is formed of plastic material. An inner surface (118 or 120) of the inner layer (100) defines an outer boundary of a space (36,38 or 88) containing hydraulic fluid under pressure. The outer layer (102) is formed of metal material. The intermediate layer (104) is formed of elastomeric material, and is compressively loaded radially between the inner and outer layers (100 and 102).

Abstract: A rotary slide valve for power-assisted steering mechanisms of motor vehicles has two valve elements (1, 2) which are arranged to be coaxially movable within each other and are connected with each other via a torsion rod (7) and a backlash coupling (8) in such a way that they are rotatable around each other by maximally the pivot path of the backlash coupling. The inner valve element (1) is connected with a valve inlet member (3) and the outer valve element (2) with a valve outlet member (4), fixed against relative rotation. The one part of the backlash coupling (8) is formed on the radially inner valve element (1) by claws (10) which project in relation to its front face in the axial direction. The other part of the backlash coupling (8) is constituted by two pins (11) which are disposed parallel with each other in the radially outer valve element (2), whose axes (12) are located in a plane (13) extending perpendicularly in respect to the axis (14) of the rotary slide valve.

Abstract: In a device for controlling the pressure to be supplied to a hydrostatic steering unit (1) by means of a control signal (s), there is a rotary slide valve arrangement, one slide valve element of which is rotatable by means of a steering means (5) and the other side valve element of which is corrected by means of a measuring motor (16). Together with a series throttle (AV), a control throttle (AS) forms a series circuit independent of the intake path of the steering motor (4), which circuit is connected between a pressure source (CF) and the tank (6). The control throttle (AS) has a closing characteristic that extends substantially across the entire working range of the angle of rotation of the slide valve elements. The control signal (s) is tapped between the series throttle (AV) and the control throttle (AS). This provides a pressure control that is independent of load.

Abstract: A fluid supply system provides hydraulic fluid to a series combination of an automotive fan motor and a power steering unit. There is a bypass line around the fan motor for prioritizing the operation of the power steering unit. A normally closed pressure sequencing valve opens the bypass line when the pressure across the overall series combination exceeds a predetermined limit. Optional second and third bypass lines are disclosed for respectively bypassing either the power steering unit or the fan motor in case of abnormal conditions therein.

Abstract: A power steering apparatus is composed a fluid source for discharging pressurized fluid, a power cylinder, a control valve responsive to operation of a steering wheel for supplying the power cylinder with pressurized fluid from the fluid source, and a reservoir. The control valve has a first control portion for controlling the flow of pressurized fluid from the fluid source to the reservoir, and a second control portion for controlling the flow of pressurized fluid to the power cylinder. The first control portion has four paths communicating with the fluid source and the reservoir, and each of the four paths is formed with a center-open variable orifice which opens when the control valve is in a neutral state.

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 device for automobile type vehicles having a hydraulic power cylinder for assisting in steering front end wheels of the vehicle. The hydraulic power cylinder has a piston and piston rod fixed thereto reciprocable in two opposite directions of travel. The opposite ends of the piston rod are linked to respective front wheels of the vehicle for turning the individual steering wheels in a direction in which the piston rod travels. The piston rod has a rack with which a pinion is engaged and rotated by a shaft rotated by a drum coupled to the shaft for effecting manual steering. Another drum is provided and is rotated by the steering wheel by the vehicle driver. The drums are operationally coupled by a pair of flexible cables for rotating the drums by the steering wheel to move the piston rod rack in the desired steering direction. A direction control valve having a rotatable rotor is coupled to the drum which drives the rack pinion.

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: A centering device for steering valves which includes a rotary rod (1) that is firmly connected at an endpiece (1A) with a drive shaft (3) and at another endpiece (1B) with a power takeoff shaft (4). Fine-centering is provided because rotary rod (1) cannot establish any exact mid-way centering between a rotary slide (3A) and a valve bushing (6). The fine-centering device consists of a tube-shaped endpiece (7) that is attached to the drive shaft and that bears a metal bellows (8) and a centering piece (10) that is connected with the bellows. Centering piece (10) is axially prestressed by metal bellows (8) and, via roller bodies (12) presses against another centering piece (14). Centering piece (14) is part of a bearing race (15) of a needle bearing (16) that is pressed upon the endpiece (1B) of rotary rod (2), the endpiece (1B) being connected to the power takeoff shaft (3).

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 centering device for steering valves contains a torsion bar (1) that is clamped between a drive part (2) and a power take-off part (3). Because torsion bar (1) does not permit any exact central positioning, a radial borehole (6) of a valve bushing (3A) connected with the power take-off part (3) is provided. A pin (7) which includes a ball-shaped end engages an oblique surface groove (8) and the pin (7) is loaded by a ring-shaped spring (11). Spring (11) sits in a ring groove (10) and includes a flattened section (12). In the area of the flattened section (12), pin (7) engages a recess (13) of spring (11). The mutually rotatable structural parts can be set exactly in the neutral position by this centering device.