Screw shaft and method for manufacturing same, and electric position adjusting device for steering wheel and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-12043302-B2
Application number	US-201917267266-A
Country	US
Kind code	B2
Filing date	Jul 17, 2019
Priority date	Aug 10, 2018
Publication date	Jul 23, 2024
Grant date	Jul 23, 2024

Abstract

A screw shaft includes a large-diameter shaft portion having a male-side screw portion over the entire length of the outer circumferential surface thereof; a first small-diameter shaft portion arranged adjacent to one side in the axial direction of the large-diameter shaft portion, and having an outer diameter that is smaller than the outer diameter of the large-diameter shaft portion, and having a helical first rolling mark on the outer circumferential surface thereof; and a second small-diameter shaft portion arranged adjacent to the other side in the axial direction of the large-diameter shaft portion, and having an outer diameter that is smaller than the outer diameter of the large-diameter shaft portion, and having a helical first rolling mark on the outer circumferential surface thereof.

First claim

The invention claimed is:

1. A screw shaft, comprising:
a large-diameter shaft portion, and a small-diameter shaft portion;
the large-diameter shaft portion having a male-side screw portion over an entire length of an outer circumferential surface thereof; and
the small-diameter shaft portion being arranged adjacent in an axial direction to the large-diameter shaft portion, having an outer diameter that is smaller than an outer diameter of the large-diameter shaft portion, and having a helical rolling mark on an outer circumferential surface thereof that is in phase with an extension line of a spiral curve that is a root circle line of the male-side screw portion, wherein
the male-side screw portion comprises a completely threaded portion having a specified thread height, and incompletely threaded portions not reaching the specified thread height arranged at edge portions on both ends in the axial direction of the male-side screw portion, and
the entire male-side screw portion functions as a normal threaded portion and only the rolling mark corresponds to a non-threaded portion that does not function as the normal threaded portion.

2. The screw shaft according to claim 1 , wherein
the outer diameter of the small-diameter shaft portion is no less than 0.9 times and no more than 1.1 times the root circle diameter of the male-side screw portion.

3. The screw shaft according to claim 1 , comprising
an adjacent shaft portion that is arranged adjacent to the small-diameter shaft portion on a side in the axial direction opposite to the large-diameter shaft portion, and that has an outer diameter larger than the outer diameter of the small-diameter shaft portion.

4. The screw shaft according to claim 1 , wherein
the small-diameter shaft portion comprises: a first small-diameter shaft portion arranged on one side in the axial direction of the large-diameter shaft portion; and a second small-diameter shaft portion arranged on the other side in the axial direction of the large-diameter shaft portion.

5. The screw shaft according to claim 4 , wherein
both an outer diameter of the first small-diameter shaft portion and an outer diameter of the second small-diameter shaft portion are no less than 0.9 times and no more than 1.1 times the root circle diameter of the male-side screw portion.

6. The screw shaft according to claim 5 , wherein
the screw shaft may be incorporated in an electric position adjusting device for a steering wheel.

7. The screw shaft according to claim 4 , wherein
the screw shaft may be incorporated in an electric position adjusting device for a steering wheel.

8. A method for manufacturing a screw shaft, comprising:
a step of performing a rolling process on a work comprising a large-diameter shaft portion for rolling, and a small-diameter shaft portion for rolling arranged adjacent in an axial direction to the large-diameter shaft portion for rolling, and having an outer diameter that is smaller than an outer diameter of the large-diameter shaft portion for rolling; wherein the rolling process generates walking of the work using a plurality of rolling dies in order to form a male-side screw portion over an entire length in the axial direction of an outer circumferential surface of the large-diameter shaft portion for rolling; and
in the process of performing the rolling process on the work, a helical rolling mark is formed on an outer circumferential surface of the small-diameter shaft portion for rolling using the rolling dies, while at the same time performing the rolling process for forming the male-side screw portion on the outer circumferential surface of the large-diameter shaft portion for rolling, wherein
the male-side screw portion comprises a completely threaded portion having a specified thread height, and incompletely threaded portions not reaching the specified thread height arranged at edge portions on both ends in the axial direction of the male-side screw portion, and
the entire male-side screw portion functions as a normal threaded portion and only the rolling mark corresponds to a non-threaded portion that does not function as the normal threaded portion.

9. The method for manufacturing a screw shaft according to claim 8 , wherein
an outer diameter of the small-diameter shaft portion for rolling is no less than 0.9 times and no more than 1.1 times a root circle diameter of a male-side screw portion to be formed on an outer circumferential surface of the large-diameter shaft portion for rolling.

10. The method for manufacturing a screw shaft according to claim 8 , wherein
the work comprises an adjacent shaft portion that is arranged adjacent to the small-diameter shaft portion for rolling on the opposite side in the axial direction to the large-diameter shaft portion for rolling, and that has an outer diameter larger than an outer diameter of the small-diameter shaft portion for rolling.

11. The method for manufacturing a screw shaft according to claim 8 , wherein
the work is configured such that the small-diameter shaft portion for rolling of which comprises a first small-diameter shaft portion for rolling arranged on one side in the axial direction of the large-diameter shaft portion for rolling, and a second small-diameter shaft portion for rolling arranged on the other side in the axial direction of the large-diameter shaft portion for rolling.

12. The method for manufacturing a screw shaft according to claim 11 , wherein
both an outer diameter of the first small-diameter shaft portion and an outer diameter of the second small-diameter shaft portion are no less than 0.9 times and no more than 1.1 times the root circle diameter of the male-side screw portion.

13. The method for manufacturing a screw shaft according to claim 11 , wherein
a screw shaft incorporated in an electric position adjusting device for a steering wheel is applied as the screw shaft.

14. A feed screw mechanism comprising:
a screw shaft, having:
a large-diameter shaft portion, and
a small-diameter shaft portion;
the large-diameter shaft portion having a male-side screw portion over an entire length of an outer circumferential surface thereof; and
the small-diameter shaft portion being arranged adjacent in an axial direction to the large-diameter shaft portion, having an outer diameter that is smaller than an outer diameter of the large-diameter shaft portion, and having a helical rolling mark on an outer circumferential surface thereof that is in phase with an extension line of a spiral curve that is a root circle line of the male-side screw portion; and

a nut having a female-side screw portion on an inner circumferential surface that engages with the male-side screw portion, and
a part in the axial direction of the female-side screw portion capable of being arranged at a position in the axial direction deviated from the male-side screw portion, wherein
the rolling mark does not engage with the female-side screw portion of the nut.

15. An electric position adjusting device for a steering wheel comprising:
an electric motor, a feed screw mechanism and a steering component; wherein
the feed screw mechanism includes a screw shaft having a male-side screw portion on an outer circumferential surface thereof and a nut having a female-side screw portion on an inner circumferential surface that engages with the male-side screw portion; and is configured so that the screw shaft and the nut are able to move relative to each other in an axial direction based on relative rotation of the screw shaft and the nut due to a rotation force transmitted from the electric motor;
the steering comp

Assignees

• Nsk Ltd

Inventors

• Saito Takeshi

Classifications

• B21H3/04

  Making by means of profiled-rolls {or die rolls} · CPC title

• F16H25/24

  Elements essential to such mechanisms, e.g. screws, nuts (F16H25/22 takes precedence) · CPC title

• B21H3/046

  working radially · CPC title

• F16H2025/2075

  Coaxial drive motors · CPC title

• B62D1/181 Primary

  with power actuated adjustment, e.g. with position memory · CPC title