Electric power steering system
AssigneeJtekt Corporation
InventorsToshihiro Asakura, Takuya Nakayama, Tetsuya Kaneko
Life of this patent
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Abstract
Assist force that assists an operation of a steering system of a vehicle is applied to a rack shaft by transmitting driving force of a motor to the rack shaft via a motor shaft and a ball screw nut. A step is formed on the outer periphery of the ball screw nut. An end portion of a third housing is arranged to face a bearing such that the distance that the ball screw nut is able to move relative to the motor shaft in axial direction and the relative movable length is longer than a predetermined length.
Claims6
An electric power steering system that applies assist force that assists an operation of a steering system of a vehicle to a rack shaft by transmitting driving force of a motor to the rack shaft, the system comprising:
- a cylindrical motor shaft through which the rack shaft of the vehicle is passed, and that is rotated by driving of the motor;
- a motion conversion mechanism that has an engaging portion engaged with the motor shaft, and that converts a rotational motion of the motor shaft into an axial linear motion of the rack shaft:
- a bearing that is arranged on an outer periphery of the motion conversion mechanism;
- and
- a restricting member that restricts a distance, to a predetermined distance, that the motion conversion mechanism is able to move relative to the motor shaft, wherein
- the motion conversion mechanism moves in a same direction in which the engaging portion becomes disengaged;
- the bearing is provided so as to be movable together with the motion conversion mechanism in the same direction in which the engaging portion becomes disengaged;
- the restricting member is formed of a member that is arranged to face the bearing with a predetermined clearance left between the restricting member and the bearing;
- and
- a length of the engaging portion is set longer than the predetermined distance.
Dependencies are inferred from the claim text.