Atsugi Motor Parts Company, Limited

Unisia Jecs Corporation

Atsugi Unisia Corp.

Koichi Komatsu

Seiji Uemura

Tadaharu Yokota

Shinich Komatsu

Tatsuyoshi Maruyama

Norihiro Saita

Toshinori Aihara

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.

Power assisted steering apparatus for automotive vehicle

A pressure control valve unit includes a valve housing formed with a valve bore. The valve housing is also formed with an inlet port, a drain port and a control port. A valve spool is disposed in the valve bore for selectively establishing fluid communication between the control port and the inlet port, and between the control port and the drain port. The drain port is connected to a first drain path which selectively establishes and blocks fluid communication between the drain port and a working fluid source and to a second drain path which normally connect the drain port to the working fluid source. A flow restricting orifice is provided in the second drain path for constantly permitting limited flow rate of the working fluid from the drain port and the working fluid source. The flow restricting orifice generates damping force for damping surge pressure.

Pressure control valve unit

A power-assist device for an automotive steering system employs an easy-to-assemble hydraulic pressure control valve to compensate for differential forces on opposite sides of an actuating piston in an unbalanced hydraulic cylinder. The piston divides the cylinder into first and second working chambers which are each connected to a hydraulic pump and a return reservoir via first and second spool valves, respectively. The spool valves are actuated axially by a torsion bar connected to the stub shaft of the steering column, so that they reciprocate axially within bores through the valve body as the steering wheel is turned back and forth. Lands on the spool valves oppose slightly larger lands the bores to define orifices which control the rates of hydraulic supply and drain to and from the working chambers of the cylinder. The cross-sections of the orifices change as the spool valves reciprocate and the first-chamber supply and second-chamber drain orifices are larger than the others due to the increased internal diameters of the corresponding bore lands. This boosts the hydraulic pressure in the first working chamber in order to compensate for its reduced effective piston area, which is due to the effect of a piston rod connecting the piston to wheel-orientation control mechanisms. The first and second spool valves are identical; the bores are contoured differentially to provide the necessary dimensional differences among the control orifices.

Power assist device for automotive steering system

A steering control system for a vehicle is provided. This system includes a front power cylinder which provides steering assistance for front wheels and a rear power cylinder which provides steering assistance for rear wheels. The system further includes a single hydraulic pump which provides a pressurized hydraulic fluid to the front and rear power cylinders and a flow dividing valve which controls a supply rate of the pressurized hydraulic fluid to the front and rear power cylinders based on vehicle speed to steer the front and rear wheels with a preselected steering angle relationship.

Steering control system for vehicle

A power-assist device for an automotive steering system employs spool valves with different external diameters to control the fluid pressure in smaller and larger area chambers of a pressure control valve which controls pressure in an unbalanced cylinder device. The different size of spool valves are disposed within different sizes of bores formed through a housing of the pressure control valve for defining wider fluid path area for introducing larger amount of working fluid into the smaller area chamber in comparison with that for the larger area chamber and narrower fluid path for draining the working fluid in the smaller area chamber for lower drainage rate in comparison with that for the larger area chamber.

Power steering valve with two spools of different size to compensate

A rack-and-pinion steering gear structure for a vehicle including a rack housed within a cylinder and driven by means of a pinion shaft, comprises an annular piston received with suitable axial clearance in an annular groove defined by three surfaces, namely the end face of one end of the rack, a seating surface of a head of a bolt screwed into a boss projecting from the end of the rack, and the outer periphery of the boss itself. An elastic annular seal member is interposed between the inner periphery of the piston and the outer periphery of the boss.

Rack-and-pinion steering gear structure for a vehicle

A rack-and-pinion steering gear structure for a vehicle including a rack housed within a cylinder driven by means of a pinion shaft, comprising: a bolt having a threaded portion screwed in a threaded hole formed in one end face of the rack and a shoulder linked integrally with the threaded portion and smaller in diameter than the rack but greater in diameter than the threaded portion; and a piston housed within a groove formed by the shoulder of the bolt, the seating surface of the bolt head, and the end face of the rack, with clearances with respect to the groove in the axial and radial directions.

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Atsugi, Japan

Koichi Komatsu