Rock shaft and steering system

Patent metadata

Field	Value
Publication number	US-10138990-B2
Application number	US-201615067534-A
Country	US
Kind code	B2
Filing date	Mar 11, 2016
Priority date	Mar 17, 2015
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A rack shaft of the present invention includes: an effective rack tooth row formed by plastic deformation of a shaft member and having a plurality of rack teeth that mesh with a pinion; a ball screw portion having no rack tooth; an ineffective rack tooth that is formed between the effective rack tooth row and the ball screw portion and that does not mesh with the pinion; and a padding portion that extends from an end of the ball screw portion toward the ineffective rack tooth and that covers at least a part of the ineffective rack tooth.

First claim

What is claimed is:

1. A rack shaft, comprising:
a rack tooth portion including a plurality of rack teeth, the rack tooth portion being formed by plastic deformation of a shaft member;
a non-rack tooth portion having no rack tooth and being at an end of the rack tooth portion, wherein a closest one of the plurality of rack teeth to the non-rack tooth portion is an ineffective rack tooth that is configured to not mesh with a pinion, and remaining ones of the plurality of rack teeth form an effective rack tooth row that is configured to mesh with a pinion; and
a padding portion that extends in an axial direction of the rack shaft from an end of the non-rack tooth portion toward the ineffective rack tooth and that extends beyond the ineffective rack tooth in the axial direction, wherein
the ineffective rack tooth includes portions extending from opposite sides of the padding portion in opposite directions that are transverse to the axial direction, and
the padding portion is formed to extend to a side face of a first effective rack tooth, the first effective rack tooth being a first one of the effective rack tooth row that is adjacent to the ineffective rack tooth.

2. The rack shaft according to claim 1 , wherein
the padding portion is provided on both sides in an axial direction of the effective rack tooth row.

3. The rack shaft according to claim 1 , wherein
the shaft member is a solid member.

4. The rack shaft according to claim 1 , wherein
the padding portion has a tapered shape from the non-rack tooth portion toward the effective rack tooth row as viewed in a direction perpendicular to an axis of the shaft member and a tooth trace of the effective rack tooth row, and the padding portion has a symmetrical shape with respect to a straight line passing through a midpoint of the tooth trace of the effective rack tooth row and parallel to the axis of the shaft member,
wherein the tooth trace is defined by an intersection of a side face and a top surface of one of the plurality of rack teeth that form the effective rack tooth row.

5. The rack shaft according to claim 4 , wherein
the ineffective rack tooth is formed on both sides of the straight line passing through the midpoint of the tooth trace of the effective rack tooth row and parallel to the axis of the shaft member as viewed in the direction perpendicular to the axis of the shaft member and the tooth trace of the effective rack tooth row.

6. A steering system, comprising:
a housing;
the rack shaft according to claim 1 , which is supported by the housing so as to be movable in the axial direction, and is coupled to a wheel of a vehicle; and
a pinion shaft that is supported by the housing so as to be rotatable about an axis thereof, that meshes with the effective rack tooth row of the rack shaft, and is coupled to a steering system of the vehicle.

7. The rack shaft according to claim 1 , wherein
the padding portion has a furthest point in the axial direction at a side face of the first effective rack tooth of the effective rack tooth row that is adjacent to the ineffective rack tooth.

8. The rack shaft according to claim 7 , wherein
the ineffective rack tooth has opposite side faces extending to a peak height in a direction perpendicular to the axial direction, and
the padding portion intersects a portion of the ineffective tooth in the axial direction at a height that is lower than the peak height in the direction perpendicular to the axial direction.

9. The rack shaft according to claim 7 , wherein
the ineffective rack tooth has opposite side faces extending to a peak height in a direction perpendicular to the axial direction, and
the padding portion intersects a portion of the ineffective tooth in the axial direction at a height that is higher than the peak height in the direction perpendicular to the axial direction.

10. The rack shaft according to claim 1 , wherein
the padding portion has a furthest point in the axial direction at a bottom surface of the rack tooth portion between a side face of the ineffective rack tooth and a side face of a first effective rack tooth of the effective rack tooth row that is adjacent to the ineffective rack tooth.

11. The rack shaft according to claim 1 , wherein
each of the plurality of rack teeth has opposite side faces extending from a bottom of the rack tooth portion to a peak, one of the opposite side faces intersecting with the peak to define a tooth trace of the effective rack tooth row that extends in a direction transverse to the axial direction, and
the padding portion has a tapered shape from the non-rack tooth portion toward the effective rack tooth row as viewed in a direction perpendicular to the axial direction of the shaft member and perpendicular to the tooth trace of the effective rack tooth row.

12. The rack shaft according to claim 11 , wherein
the padding portion has a symmetrical shape with respect to a straight line extending in the axial direction of the shaft member and passing through a midpoint of the tooth trace of the effective rack tooth row.

Assignees

• Jtekt Corp

Inventors

• Mitsui Kuniaki
• Inagaki Ryota

Classifications

• B62D3/126 Primary

  characterised by the rack · CPC title

• F16H55/26 Primary

  Racks · CPC title