Rack bushing and steering device

Patent metadata

Field	Value
Publication number	US-11878740-B2
Application number	US-202017603898-A
Country	US
Kind code	B2
Filing date	Apr 2, 2020
Priority date	Apr 15, 2019
Publication date	Jan 23, 2024
Grant date	Jan 23, 2024

Abstract

A clearance is created between an inner circumference of a bushing main body ( 2 ) which surrounds a rack ( 5 ) across a row of rack gear teeth ( 50 ) and an outer circumference of the rack ( 5 ), and two supporting surfaces ( 21 A, 21 B) which face each other with a bushing main body axis O therebetween and a supporting surface ( 21 C) which faces a back surface of the rack ( 5 ), each extending along an x-axis direction, are formed on the inner circumference of the bushing main body ( 2 ). The rack ( 5 ) in a neutral state is supported by the two supporting surfaces ( 21 A, 21 B) so as to be displaceable along a z-axis direction, and the rack ( 5 ) in operation is stably supported by the three supporting surfaces ( 21 A- 21 C) at three places. A groove bottom position of an annular elastic member attachment groove ( 24 ), which is formed on an outer circumference of the bushing main body ( 2 ), is offset toward the support surface ( 21 B) only in an area on a support surface ( 21 B) side from the bushing main body axis O, and therefore an elastic ring ( 3 ) attached to the elastic member attachment groove ( 24 ), protrudes above an outer circumferential surface of the bushing main body ( 2 ), but only in the area on the support surface ( 21 B) side from the bushing main body axis O.

First claim

The invention claimed is:

1. A steering device configured to cause a pinion gear provided on a steering shaft to mesh with a rack gear of a steering rack with a tie rod swingably linked, thereby allowing the steering rack to reciprocate in an axial direction of the steering rack, the steering device comprising:
a rack housing having a hollow cylindrical shape, the steering rack being inserted in the rack housing in a row direction of rack gear teeth; and
a rack bushing attached to the rack housing to intervene between the steering rack and an inner circumferential surface of the rack housing, the rack bushing supporting the steering rack while allowing the steering rack to move in the row direction of the rack gear teeth, the rack bushing comprising:
a bushing main body having a hollow cylindrical shape, the steering rack being inserted into the bushing main body in the row direction of the rack gear teeth; and
an elastic member having an annular shape and arranged around an axis of the bushing main body so as to be located between the rack housing and the bushing main body;
the bushing main body comprising:
an inner circumferential surface surrounding the steering rack across a row of the rack gear teeth and supporting the steering rack, the inner circumferential surface being configured to allow the steering rack to reciprocate in the row direction of the rack gear teeth and to be displaced in a tooth depth direction of the rack gear teeth; and
an outer circumferential surface including an elastic member attachment groove formed along a circumferential direction of the bushing main body, the elastic member being attached to the elastic member attachment groove;
the inner circumferential surface comprising:
a first support surface and a second support surface each being flat and extending along the tooth depth direction of the rack gear teeth, the first support surface and the second support surface being located place opposite each other with the axis of the bushing main body therebetween and supporting the steering rack movable in the row direction of the rack gear teeth while allowing the steering rack to be displaced in the tooth depth direction of the rack gear teeth; and
a third support surface located, with respect to the circumferential direction of the bushing main body, between the first support surface and the second support surface, and facing an outer circumferential surface of the steering rack at a position on an opposite side of the axis of the bushing main body from the rack gear teeth and with a clearance in the tooth depth direction of the rack gear teeth between the outer circumferential surface of the steering rack and the third support surface; and

the elastic member attachment groove comprising:
a first groove section having a groove bottom located on and running along an arc which belongs to a first imaginary circle having a center lying on the axis of the bushing main body and which is located closer to the first support surface than the axis of the bushing main body; and
a second groove section having a groove bottom located on and running along an arc which belongs to a second imaginary circle defined as a shifted duplicate of the first imaginary circle toward the second support surface than the axis of the bushing main body,

wherein the first groove section is located closer to a place in which the steering rack is to push the rack bushing against the rack housing due to a reaction force from the tie rod when pushing the tie rod, than the axis of the bushing main body, and
wherein between the outer circumferential surface of the bushing main body and the inner circumferential surface of the rack housing, there is a space created by the elastic member embedded in the elastic member attachment groove depending on a protrusion amount of the elastic member above the outer circumferential surface of the bushing main body.

2. A steering device according to claim 1 , wherein the elastic member having the annular shape has a cross section diameter that is not more than a depth of the first groove section and not less than a minimum depth of the second groove section.

3. A steering device according to claim 1 , wherein the third support surface includes a curved surface extending in an axial direction of the bushing main body and following an external shape of the outer circumferential surface of the steering rack.

4. A steering device according to claim 2 , wherein the third support surface includes a curved surface extending in an axial direction of the bushing main body and following an external shape of the outer circumferential surface of the steering rack.

Assignees

• Mazda Motor
• Kyb Corp
• Oiles Industry Co Ltd

Inventors

• Ikeyama Gaku
• Sato Kazuya
• Kuwagaki Junya
• Fumimoto Yoshimitsu
• Takahashi Masaki
• Taniguchi Tomonori
• Ito Takuzo
• Fujikake Mitsuhiko
• Masuda Hiroki
• Kikuchi Hiroyuki
• Ouchi Jun
• Akeda Kazuhiko

Classifications

• B62D3/123 Primary

  characterised by pressure yokes · CPC title

• F16C29/02

  Sliding-contact bearings · CPC title

• F16C35/02

  in the case of sliding-contact bearings · CPC title

• B62D3/12 Primary

  of rack-and-pinion type · CPC title

• F16C29/002

  Elastic or yielding linear bearings or bearing supports · CPC title