Method of manufacturing a flexible externally toothed gear for strain wave gearing

Patent metadata

Field	Value
Publication number	US-9874273-B2
Application number	US-201514611304-A
Country	US
Kind code	B2
Filing date	Feb 2, 2015
Priority date	Feb 26, 2014
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

A method for manufacturing a flexible externally toothed gear includes: a first step (ST 1 ) for producing a primary molded article by performing near-net-shape plastic working on a material comprising a nickel-free low-alloy steel having a silicon content of 1.45-1.5 wt %; a second step (ST 2 ) for martempering the primary molded article; a third step (ST 3 ) for producing a secondary molded article from the primary molded article; and a fourth step (ST 4 ) for shot-peening the secondary molded article to change the surface portions of the tooth part and other parts to martensite. A flexible externally toothed gear can be obtained in which the surface hardness is kept within a prescribed range and the fatigue strength and abrasion resistance are high.

First claim

The invention claimed is:

1. A method for manufacturing a flexible externally toothed gear for a strain wave gearing, the method comprising:
a first step for producing a cup-shaped or top-hat-shaped primary molded article approximating a shape of the flexible externally toothed gear for the strain wave gearing by performing near-net-shape plastic working on a material comprising nickel-free low-alloy steel having a silicon content of 1.45-1.5 wt % and a carbon content of 0.18-0.23 wt %;
a second step for martempering the primary molded article so that a hardness thereof is set to HRC 30 to 50;
a third step for producing a secondary molded article by performing turning and gear-cutting on the martempered primary molded article, the secondary molded article having a diaphragm part and a tooth part formed thereon; and
a fourth step for shot-peening the secondary molded article to change a metal structure of a surface layer portion of the tooth part and the diaphragm part to martensite.

2. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 1 , wherein
the martempering temperature in the second step is set to a value within a range from 290° C. to 400° C.

3. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 1 , wherein
the martempering temperature in the second step is set to a value within a range from the martensite start temperature Ms to a temperature 117° C. lower than the temperature Ms.

4. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 1 , wherein
the shot-peening in the fourth step is multistage shot-peening in which at least two stages of shot-peening are performed.

5. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 1 , wherein
the near-net-shape plastic working in the first step is forging or drawing.

6. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 2 , wherein
the near-net-shape plastic working in the first step is forging or drawing, and
the shot-peening in the fourth step is multistage shot-peening in which at least two stages of shot-peening are performed.

7. A method for manufacturing a flexible externally toothed gear for a strain wave gearing, comprising:
a first step for producing a cylindrical primary molded article approximating a shape of the flexible externally toothed gear for the strain wave gearing by performing near-net-shape plastic working on a material comprising nickel-free low-alloy steel having a silicon content of 1.45-1.5 wt % and a carbon content of 0.18-0.23 wt %;
a second step for martempering the primary molded article so that a hardness thereof is set to HRC 30 to 50;
a third step for producing a secondary molded article by performing turning and gear-cutting on the martempered primary molded article, the secondary molded article having a tooth part formed thereon; and
a fourth step for shot-peening the secondary molded article to change a metal structure of a surface layer portion of the tooth part to martensite.

8. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 7 , wherein
the martempering temperature in the second step is set to a value within a range from 290° C. to 400° C.

9. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 7 , wherein
the martempering temperature in the second step is set to a value within a range from the martensite start temperature Ms to a temperature 117° C. lower than the temperature Ms.

10. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 8 , wherein
the shot-peening in the fourth step is multistage shot-peening in which at least two stages of shot-peening are performed.

11. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 7 , wherein
the near-net-shape plastic working in the first step is forging or drawing.

12. The method for manufacturing a flexible externally toothed gear for a strain wave gearing according to claim 8 , wherein
the near-net-shape plastic working in the first step is forging or drawing, and
the shot-peening in the fourth step is multistage shot-peening in which at least two stages of shot-peening are performed.

Assignees

• Harmonic Drive Systems

Inventors

• Kobayashi Masaru
• ORII Daisuke

Classifications

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/04

  containing manganese · CPC title

• C21D6/002

  containing Cr (C21D6/004 takes precedence) · CPC title

• C21D9/32

  for gear wheels, worm wheels, or the like · CPC title

• C21D6/005

  containing Mn · CPC title