Importance

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Abstract

A steel gear 1 includes a generally cylindrical outer peripheral ring portion 2, on an outer peripheral surface 20a of which a toothed shape 10 is formed, and a flange portion 3 provided to extend radially inward from an inner peripheral surface 20b of the outer peripheral ring portion 2. The outer peripheral ring portion 2 includes a first projecting portion 21 that projects toward one side in the axial direction with respect to a coupling position at which the first projecting portion 21 is coupled to the flange portion 3, and a second projecting portion 22 that projects toward the other side in the axial direction with respect to a coupling position at which the second projecting portion 22 is coupled to the flange portion 3. The axial length of the first projecting portion 21 is longer than the axial length of the second projecting portion 22. The outer peripheral ring portion 2 includes a carburized layer 4 formed in a surface layer of the toothed shape 10, and a thermal history layer 5 formed in a region including the carburized layer 4 and at a depth, in the inward direction from the outer peripheral surface 20a, larger than the depth of the carburized layer 4, the thermal history layer 5 having a history of being heated through high-frequency induction heating until becoming austenite. The depth T of the thermal history layer 5 in the inward direction from a tooth bottom 104 of the toothed shape 10 is larger at the second projecting portion 22 than at the first projecting portion 21.

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First Claim