METHOD OF MANUFACTURING A GEAR

摘要

The problem of the present invention involves providing a gear that has high tooth-root bending strength and for which there is no chipping of the tips of the teeth. Accordingly, the surface of the gear is carburized and the gear is strengthened by imparting residual stress, with the residual stress in the region with a surface depth of 5 μm to 20 μm being −1000 MPa or less, and the residual stress in the region with a surface depth of 50 μm to 150 μm being 1000 MPa or greater.

主权项

1. A method of manufacturing a gear including a carburized surface and strengthened by application of residual stress to the gear,
wherein the gear has:
(i) a region located at a depth of 50 μm or more but 150 μm or less from the surface and subjected to a shot peening treatment using first shot particles;(ii) a region located at a depth of 5 μm or more but 20 μm or less from the surface and subjected to a shot peening treatment using second shot particles with a smaller particle diameter and a larger hardness than the first shot particles; and(iii) a region located at a depth of 150 μm or more but 230 μm or less from the surface and subjected to a shot peening treatment using third shot particles with a larger particle diameter than the first shot particles, wherein the residual stress in the region (ii) is −1400 MPa or less, so that when a tooth of the gear is subjected to repeated stress, the repeated stress is canceled out by compressive stress to prevent surface cracks in the surface of a tooth root and improve a strengthening rate of the gear, the residual stress in the region (i) is −1000 MPa or more to prevent inner cracks and restrain tooth-tip chipping, and the residual stress in the region (iii) is −500 MPa or less so that the residual stress cancels out hertz stress caused by contact of the teeth of the gears.