Hitachi, Ltd.

Unisia Jecs Corporation

Hitachi Unisia Automotive, Ltd.

Michiya Hiramoto

Tadaharu Yokota

Masakazu Kurata

Yukio Sudo

Chiharu Nakazawa

Yukio Uchida

Jun Soeda

Issei Kanari

Hiroshi Hoya

Norikatsu Hoshina

Susumu Shinozaki

Kohtaro Shiino

Hiroyuki Simizu

A variable displacement vane pump that assuredly suppresses seizing of mutually contacting surfaces of a pressure plate and a rotor where the pressure plate is formed, at one side surface thereof that slidably contacts the rotor, with an annular lubricating groove. The lubricating groove is on a seal surface of the side surface at a position between arcuate back pressure grooves formed on the seal surface and a through opening which is formed in a center part of the pressure plate to receive the drive shaft. A radial width of the lubricating groove is set to a range from 10% to 25% of a radial width of the seal surface, and a distance from a center of the radial width of the lubricating groove to an inner cylindrical surface of the through opening is set to a range from 24% to 70% of the radial width of the seal surface.

Variable displacement vane pump

A power steering system for a vehicle. The system includes a hydraulic power cylinder, first and second hydraulic lines, a bypass passage through which the first and second hydraulic lines are connected with each other, and a flow passage change-over device adapted to close the bypass passage during steering assisting. A supply passage and a return passage are disposed in parallel with each other to form part of each of the first and second hydraulic lines. The flow passage change-over device is disposed in each of the first and second hydraulic lines. A differential pressure regulating valve is disposed in each of the return passages and adapted to allow hydraulic fluid to flow toward the hydraulic pressure source in a condition where pressure on side of the hydraulic power cylinder becomes higher than a set pressure or higher than pressure on side of the hydraulic pressure source.

Power steering system

A power steering system includes: a first drain passage for draining an oil pressure from a first oil passage, a second drain passage for draining the oil pressure from a second oil passage, and a pair of a first and second switch valves. When one of the first oil passage and the second oil passage is so pressurized by an operation of a reversible oil pump as to have an increased internal pressure, the pair of the first switch valve and the second switch valve allow the following: i) closing one of the first drain passage and the second drain passage which one is connected to the oil passage having the thus increased internal pressure, while ii) opening the other of the first drain passage and the second drain passage which other is connected to the oil passage that is so depressurized as to have a decreased internal pressure.

A power steering system for a vehicle, comprises a steering shaft connected to a steering mechanism. A hydraulic power cylinder is provided for assisting a steering effort of the steering mechanism. A reversible pump is provided having first and second discharge ports which are respectively connected through first and second hydraulic lines with two hydraulic pressure chambers of the hydraulic power cylinder so that the two hydraulic pressure chambers are respectively provided with hydraulic pressures. A driving device is provided for driving the reversible pump to rightly and reversely rotate. A differential pressure regulating valve is disposed in the hydraulic circuit to maintain pressure at least in the first and second hydraulic lines at a level of atmospheric pressure or higher in an inoperative condition of the reversible pump.

An oil seal or fluid seal for providing a seal between a cylinder and a piston rod is provided. The oil seal has an annular seal lip which has on a conical inner circumferential surface thereof a plurality of annular projections which are arranged axially of the seal lip. One of the annular projections which is located more axially outside of the cylinder is larger in the height above the inner circumferential surface than one of the annular projections which is located more axially inside of the cylinder. By this, under a condition where the annular projections which are located more axially inside of the cylinder are subjected to a high pressure within the cylinder, the annular projections which are located more axially inside of the cylinder and the annular projections which are located more axially outside of the cylinder are nearly equal in the contact pressure against the piston rod, thus causing all of the annular projections to deform nearly equally. The annular projections are all brought into contact with the piston rod at nearly equal contact areas.

Oil seal

A damping force characteristic variable type shock absorber which takes a mode of operation into a first mode, a second mode, a third mode, and a fourth mode is connected to a damping force characteristic basic mode switching block and a damping force characteristic special mode switching block. This first mode is such that when the vehicular vertical direction determined by the vehicular vertical behavior determinator is upward, an extension phase provides a relatively high damping force characteristic and a compression phase provides a relatively low damping force characteristic. The second mode is such that when the vehicular vertical direction determined by the vehicular vertical behavior determinator is downward, the extension phase provides a relatively low damping force characteristic and the compression phase provides a relatively highly damping force characteristic. The third mode is such that when the vehicular vertical behavior determinator is neither upward nor downward, both of extension and compression phases provide the relatively low damping force characteristics. The fourth mode is such that when a predetermined condition of a vehicular motion is satisfied, the damping force characteristics in both extension and compression phases are relatively high.

Apparatus and method for controlling damping force characteristic of

A method of driving a stepping motor comprises providing a chopping signal to a drive current of the stepping motor when a chopping condition is on, and synchronizing output of the chopping signal with output of a drive signal for driving stepwise the stepping motor.

Method and apparatus of driving stepping motor

A fixing bracket for a pressurized fluid buffer device such as a shock absorber or the like is formed as a single piece U-shaped bracket having a circular body portion for surrounding an outer cylinder of the shock absorber and opposed mounting flange portions for attachment to a vehicular chassis. At a location axially outward of the location of bolt holes for attaching the fixing bracket, opposes pairs of projected tooth portions are provided oriented toward each other to contact an exposed portion of the outer cylinder. According to this structure, during vehicle bouncing, for examples the tooth portions are urged to wedge, or bite into the outer cylinder for counteracting forces in a separation direction of the flange portions. Thus, strength is improved while installation processing is reduced. Further, according to this arrangement both manufacturing and installation costs may be significantly reduced while structural features and design flexibility are improved.

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Yokohama, Japan

Michiya Hiramoto