Koyo Seiko Company, Ltd.

Masanori Kobayashi

Takeo Iino

Akihiko Shiina

Tetsuya Murakami

Yoshio Ito

Tatsuo Otsuka

Osamu Sano

Kunihiro Oka

Shigetaka Kinme

Takayuki Todaka

Susumu Imagaki

Noboru Minamoto

Takashi Tsutsui

Hiroaki Murakami

Katsutoshi Nishimura

Etsuro Kitami

Tatsuhiro Yamamoto

Masashi Uota

Takashi Ohata

Hiroyuki Shigemura

Fumiyoshi Ono

Teruo Tsutsui

Ken-ichiroh Aoto

Yoshio Itou

Shoji Shibamura

Tomoyuki Takei

Takefumi Deyama

Kouji Ogushi

Yoshiyuki Saito

An electric power steering system is provided, which comprises a steering assist electric motor, and a reduction gear mechanism for reducing a rotation speed of a rotatable shaft of the electric motor. The reduction gear mechanism comprises a worm shaft driven by the rotatable shaft, and a worm wheel driven by the warm shaft. The electric power steering system further comprises a joint for coupling the rotatable shaft to the worm shaft for transmission of a driving force. Longitudinally biasing means is provided in association with the joint for longitudinally biasing the worm shaft.

Electric power steering system

A steering assist system which transmits the rotation of an electric motor to a steering shaft via a worm shaft and a worm wheel meshed with a worm of the worm shaft, where an output shaft of the electric motor and the worm shaft are interconnected via a joint. The joint includes a cylindrical first transmission member mounted on the output shaft, a cylindrical second transmission member to which the worm shaft is mounted, and a cylindrical elastic body interposed between the first and second transmission members. The joint may further include a torque limiter including a spring which is interposed between an end surface of the second transmission member and a spring seat formed at an end surface of a third transmission member in opposed relation with the end surface of the second transmission member for inhibiting relative rotation between the second and third transmission members.

Joint and a steering assist system using the same

On the outer periphery of a bearing for supporting a worm rotating interlocked with the rotation of a steering assist motor inside the housing , elastic members are provided to restrain the bearing from moving in the radial direction thereof. The force for the restraint by the elastic members is made different depending on the position in the peripheral direction thereof. A portion of the elastic member, wherein the force for restraining the movement of the bearing in the radial direction is small, energizes the worm to the meshing position of the worm and a worm wheel . Another portion, wherein the force for restraining the movement is large, restrains the worm from moving along the lead of the worm wheel . With this configuration, the elastic members can reduce the amount of the backlash at the meshing portion of the worm and the worm wheel , and can make the rotation torque applied to the meshing portion of the worm gears relatively small.

Electric power steering apparatus

An electric power steering apparatus in which a shaft of a worm interlocking with rotation of a motor for steering assistance is movable in a radial direction, a pressing body for pressing the worm toward a worm wheel is provided, and the pressing body is provided with a V-shaped contact portion to abut in two circumferential positions of the shaft and an annular elastic body for restricting movement of the pressing body in a direction crossing the radial direction.

On the outer periphery of a bearing for supporting a worm rotating interlocked with the rotation of a steering assist motor inside the housing elastic members are provided to restrain the bearing from moving in the radial direction thereof. The force for the restraint by the elastic members is made different depending on the position in the peripheral direction thereof. A portion of the elastic member, wherein the force for restraining the movement of the bearing in the radial direction is small, energizes the worm to the meshing position of the worm and a worm wheel Another portion, wherein the force for restraining the movement is large, restrains the worm from moving along the lead of the worm wheel With this configuration, the elastic members can reduce the amount of the backlash at the meshing portion of the worm and the worm wheel and can make the rotation torque applied to the meshing portion of the worm gears relatively small.

When a steering wheel is relatively quickly turned at the time of parking, before a first stopper mechanism located between an input shaft and an output shaft is operated, an elastic member attached to a movement end of a rack shaft comes into contact with a rack stopper of a rack housing , thereby absorbing the impact at the time of steering at parking. That is, the strike speed when contact portions of the first stopper mechanism are brought into contact with each other, is slowed down. Accordingly, the uncomfortable noise due to the strike sound is not given to the driver.

Power steering apparatus

A hydraulic pressure control valve includes a cylindrical valve body and a valve spool coaxially fitted therein, each having oil grooves and lands alternately provided on and along the respective peripheral inside and outside surfaces, the opposing oil grooves and lands having throttles therebetween whose throttling extent, are changeable in accordance with a relative angular displacement between the valve body and the valve spool such that the flow of a working oil is concentrated in wider throttles. Thus noise due to cavitation is reduced.

Hydraulic pressure control valve

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Nara, Japan

Masanori Kobayashi