Koyo Seiko Company, Ltd.

Takeo Iino

Masanori Kobayashi

Akihiko Shiina

Tetsuya Murakami

Shingo Maeda

Ryouhei Hayama

Naotake Kanda

Tomoyasu Kada

Kenji Higashi

Yoshio Ito

Tatsuo Otsuka

Masayuki Ueno

Takayuki Todaka

Katsutoshi Nishizaki

Osamu Sano

Masaya Segawa

Kunihiro Oka

Shirou Nakano

Masayasu Higashi

Shigetaka Kinme

Akihisa Umetani

Shuuji Kimura

Katsutoshi Nishimura

Masashi Uota

Hiroyuki Shigemura

Keiji Nomura

Ken-ichiroh Aoto

Yoshio Itou

Shoji Shibamura

Takehito Tomita

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

In a normal state, a reaction force actuator () applies an operation reaction force to an steering member () through a planetary gear mechanism (). When failure occurs in a steering actuator (), the reaction force actuator () is turned off, and a plunger () locks the rotation of one element () which is connected to the reaction force actuator (), in the planetary gear mechanism (). In turn, a manual steering mode is set up in which a rotation of the steering member () is transmitted to a pinion gear () at a transmission ratio of the carrier () holding planetary gears () and a sun gear ().

Vehicle steering device

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

In a vehicle steering apparatus, a steering actuator is controlled so that the steering angle varies in accordance with the operation of an operating member. A transmission mechanism connects an operating side rotating member that is mechanically connected to the operating member and a vehicle wheel side rotating member that is mechanically connected to the vehicle wheels so that the mutual transmission of rotation is possible. Furthermore, the rotational transmission ratio between the operating side rotating member and the vehicle wheel side rotating member can be varied.

Vehicle steering apparatus

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.

A positioning mechanism is provided for a moving member that moves linearly by the turning of a screw member driven by a stepping motor. A drive shaft driven to turn by the stepping motor is fitted, so that turning transmission is possible, into the screw member that screws into the moving member that is capable of moving linearly. A configuration prevents the moving member from turning together with the screw member when the screw member is turning. Origin positioning is performed, by using a stopper, by stopping the linear movement of moving member caused by driving the motor to turn in one direction. The moving member is positioned according to the turning steps of the motor in the other direction after the origin positioning. The drive shaft is fitted into the screw member via an elastic member interposed therebetween so that turning can be transmitted.

Positioning mechanism

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Kashiwara, Japan

Takeo Iino