US Patent 7270607 Constant velocity universal joint and method of manufacturing the same

To provide a constant velocity universal joint having a high resistance to cracking, a high dimensional stability and an excellent rolling fatigue life, the constant velocity universal joint includes an outer coupling member (5), an inner coupling member such as a tripod member (2), and a drive transmitting member such as rollers (7) operatively interposed between the outer and inner coupling members (5 and 2). At least one of the outer coupling member (5), the tripod member (2) and the rollers (7) has a carbonitrided layer and, at the same time, an austenite grain size is greater than the grade of No. 10.