Patent ID: 7334943

Claim:
A structure supporting a differential rotatably, comprising: an inner ring arranged at said differential; an outer ring arranged at an external peripheral portion formed to surround said differential; and a rolling element rolling between said inner ring and said outer ring, wherein at least one of said inner ring, said outer ring and said rolling element has a carbo-nitrided layer and has an austenite grain size number falling within a range exceeding 10, wherein steel is carbo-nitrided at a temperature higher than an A 1 transformation point and then cooled to a temperature lower than said A 1 transformation point, and the steel is subsequently reheated to a range of temperature of no less than said A 1 transformation point and less than said temperature applied to carbo-nitride the steel and the steel is then quenched to produce at least any one of said inner ring, said outer ring and said rolling element, and wherein at least one of the inner ring, the outer ring and the rolling element contains carbon in an amount of 0.95%-1.10%, silicon in an amount of 0.15%-0.35%, manganese in an amount of at most 0.5%, phosphorus in an amount of at most 0.025%, sulfur in an amount of at most 0.025%, chromium in an amount of 1.30%-1.60%, and molybdenum in an amount of less than 0.08%, with the remainder formed of Fe and an unavoidable impurity.