Steering device

Patent metadata

Field	Value
Publication number	US-9969422-B2
Application number	US-201615361175-A
Country	US
Kind code	B2
Filing date	Nov 25, 2016
Priority date	Dec 4, 2015
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

Two flat surface portions are provided on portions of a rack shaft away from rack teeth and a back surface in the circumferential direction. The two flat surface portions are parallel to each other. A rotation stopping member has a case and a low-friction member. The hollow portion provided inside the case includes two flat surface portions that face each other in a direction Y and extend in parallel with each other, and two flat surface portions that face each other in a direction Z and extend orthogonally to the flat surface portions. A slight clearance is provided between the outer surface of the rack shaft and the inner surface of the rotation stopping member (low-friction member). The rotation stopping member is disposed on the outer periphery of the rack shaft. The outer periphery of the rotation stopping member is fixed to the inner periphery of a rack housing.

First claim

What is claimed is:

1. A steering device comprising:
a steering shaft that includes a pinion shaft that has pinion teeth;
a steered shaft that is reciprocally movable in an axial direction and that has a portion in which a screw groove is provided in an outer periphery, the steered shaft being provided with a first abutment portion located at a position that is away from the screw groove in the axial direction of the steered shaft;
a ball screw mechanism that has a cylindrical nut threadably engaged with the screw groove via a plurality of balls, the ball screw mechanism being configured to apply a force in the axial direction to the steered shaft on a basis of rotation of the nut;
a motor that applies rotational torque to the nut;
a rack housing that has an insertion portion through which the steered shaft is inserted;
a rack end mounted to each of both end portions of the steered shaft and coupled to a steered wheel; and
a rotation stopping member provided between an outer peripheral surface of the steered shaft and an inner peripheral surface of the insertion portion and between an end surface of the rack housing against which the rack end abuts and the ball screw mechanism in the axial direction of the steered shaft, the rotation stopping member having a second abutment portion that faces the first abutment portion via a clearance and that abuts against the first abutment portion when the steered shaft is rotated in the circumferential direction.

2. A steering device according to claim 1 ,
wherein the steered shaft has a portion provided with rack teeth meshed with the pinion teeth at different position from the screw groove in the axial direction, the steered shaft being provided with the first abutment portion located at a position that is away from the rack teeth and a back surface of the steered shaft in a circumferential direction about a center axis of the steered shaft, and is away from the screw groove in the axial direction of the steered shaft;
the rack teeth and the pinion teeth constitute a rack-and-pinion mechanism that converts rotation of the steering shaft into reciprocal linear motion of the steered shaft through meshing between the pinion teeth and the rack teeth;
the rotation stopping member is provided between an outer peripheral surface of the steered shaft and an inner peripheral surface of the insertion portion and between an end surface of the rack housing against which the rack end abuts and the rack-and-pinion mechanism in the axial direction of the steered shaft.

3. The steering device according to claim 1 , wherein:
the first abutment portion includes two flat surface portions that extend in parallel with each other; and
the second abutment portion includes two flat surface portions that extend in parallel with each other.

4. The steering device according to claim 3 , wherein:
the back surface of the steered shaft is a cylindrical surface;
the two flat surface portions provided on the steered shaft are provided on an inner side with respect to an extended curved surface of the cylindrical surface as the back surface of the steered shaft as seen in the axial direction; and
a distance between the two flat surface portions provided on the rotation stopping member is set to be larger than a distance between the two flat surface portions provided on the steered shaft, and smaller than an outside diameter of the extended curved surface of the cylindrical surface as the back surface of the steered shaft as seen in the axial direction.

5. The steering device according to claim 2 , wherein:
the rotation stopping member restricts a rotational angle of the steered shaft in the circumferential direction to an allowable rotational angle or less; and
the clearance between the first abutment portion of the steered shaft and the second abutment portion of the rotation stopping member is set such that the allowable rotational angle is smaller than a rotational angle of the steered shaft in the circumferential direction at which the rack teeth of the steered shaft and the pinion teeth of the pinion shaft are deformed.

6. The steering device according to claim 2 , wherein
the first abutment portion provided on the steered shaft is provided at a position at which the first abutment portion is orthogonal to the rack teeth in the circumferential direction of the steered shaft.

7. The steering device according to claim 2 , wherein
the rotation stopping member is provided between an end surface of the rack housing in the axial direction that is close to the rack-and-pinion mechanism and the rack-and-pinion mechanism, and in a vicinity of the rack-and-pinion mechanism.

8. The steering device according to claim 1 , wherein
a low-friction member made of a material that is lower in frictional resistance than the rack housing is disposed on an inner peripheral surface of the rotation stopping member.

9. The steering device according to claim 1 , wherein
the rotation stopping member and the rack housing have approximately the same thermal expansion rate.

10. The steering device according to claim 2 , wherein;
the insertion portion is provided with a housing hole that penetrates to an outside of the rack housing;
a center line of the housing hole is provided so as to be orthogonal to a center line of the insertion portion;
the steering device has a rack guide that includes a plug attached to an inner wall portion of the housing hole and an end portion of the housing hole close to the outside, a support yoke that is provided so as to be movable back and forth with respect to the plug and that supports the steered shaft so that the steered shaft is slidable in the axial direction, and an urging member disposed between the support yoke and the plug to urge the support yoke toward the steered shaft;
the rotation stopping member restricts a rotational angle of the steered shaft in the circumferential direction to an allowable rotational angle or less; and
the allowable rotational angle of the steered shaft, which is decided in accordance with the clearance between the first abutment portion and the second abutment portion, is set to be smaller than a maximum accompanying rotation angle, which is decided in accordance with a first factor which is a clearance in the axial direction between the support yoke and the plug and a clearance in a radial direction between the support yoke and the housing hole, a second factor which is a backlash in the axial direction of the pinion shaft with respect to the rack housing, a third factor which is a backlash in the radial direction of the pinion shaft with respect to the rack housing, and a fourth factor which is a clearance between meshed portions of the pinion shaft and the steered shaft, the maximum accompanying rotation angle being an angle to which the steered shaft has been rotated in the circumferential direction until the clearances and the backlashes are eliminated.

11. The steering device according to claim 10 , wherein
the second factor and the third factor are decided in accordance with a backlash of a bearing itself, the bearing being configured to support the pinion shaft so that the pinion shaft is rotatable with respect to the rack housing, a clearance between the pinion shaft and the bearing, and a clearance between the bearing and the rack housing.

Assignees

• Jtekt Corp

Inventors

• Yamamoto Yasuharu

Classifications

• F16H2025/2096

  using endless flexible members · CPC title

• F16H2025/2081

  Parallel arrangement of drive motor to screw axis · CPC title

• B62D3/123 Primary

  characterised by pressure yokes · CPC title

• B62D5/0448

  Ball nuts · CPC title

• F16C2202/22

  Coefficient of expansion · CPC title