A fixed type constant velocity universal joint includes an outer joint member, an inner joint member, eight balls, and a cage. The fixed type constant velocity universal joint has a ball retaining mechanism. A ratio of an axial length from a joint center to an opening-side end surface of the outer joint member to a diameter of each of the balls is within a range of 0.35 to 0.52. A ratio of a width of the cage to the diameter of each of the balls is within a range of 1.63 to 1.80. The ball retaining mechanism includes a cylindrical shaft portion at an end portion of a shaft and an angle restriction stopper surface of the outer joint member.

Provided is a gripping method including: a phase matching step of matching tool relief grooves of a contact metal member and track grooves of a constant velocity universal joint component with each other in phase; a measuring step of measuring phase differences between the track grooves of the constant velocity universal joint component and a female spline of the constant velocity universal joint component; a matching step of matching, based on a result of the measuring step, a stopper with a recessed portion of the female spline having the smallest phase difference and gripping the constant velocity universal joint component by a collet chuck. Under a state in which the constant velocity universal joint component is gripped by the collet chuck, the contact metal member holds the constant velocity universal joint component.

A constant velocity joint includes an outer part having a connecting portion and an opening portion and a plurality of axial grooves forming outer raceways, and an inner part having a plurality of axial grooves forming inner raceways. Each outer raceway and inner raceway form a raceway pair, a ball being disposed in each raceway pair. Each raceway pair defines a region in axial cross-section with respect to a groove longitudinal axis conceptually divided into four quadrants. The outer raceway is in the first and second quadrants and the inner raceway is in the third and fourth quadrants. With torque transmission in a first direction, the ball has two contact points in the first quadrant and/or two contact points in the third quadrant, and with torque transmission in a second direction, the ball has two contact points in the second quadrant and/or two contact points in the fourth quadrant.

A constant-velocity universal joint including a generally cup-shaped outer joint member and an inner joint member that define first and second groove portions. A pinch angle by which a ball is pinched in the first groove portion is open toward an opening of the outer joint member. A pinch angle by which the ball is pinched in the second groove is open toward a bottom of the outer joint member. An absolute value of the pinch angle in a larger-pinch-angle groove portion that is one of the first and second groove portions, is larger than an absolute value of the pinch angle in a smaller-pinch-angle groove portion that is the other of the first and second groove portions in a reference state. A radial clearance in the smaller-pinch-angle groove portion is larger than a radial clearance in the larger-pinch-angle groove portion when torque is not transmitted in the reference state.

A power transmission shaft includes: a bearing including a cylindrical portion, an internal spline portion, and an internal spline side annular groove including a bottom surface, and a first side wall and a second side wall, the first side wall which includes a first inclination surface inclined with respect to the rotation axis of the shaft portion, and on which the circlip is abutted in a state where a radius of the circlip is decreased within the internal spline side annular groove, and the second side wall on which the circlip is abutted in the state where the radius of the circlip is decreased within the internal spline side annular groove.

A constant velocity joint is provided with at least a pair of tracks whose geometry is defined based on ball path that follows a parametric equation and the parametric function is in the form of a polynomial displacement function of a fourth order or larger.

A constant-velocity rotary joint includes an outer joint portion with outer ball tracks, an inner joint portion with inner ball tracks, balls guided in a track pair formed by one outer ball track and one inner ball track, and a cage with windows to accommodate and retain the balls. Each outer ball track has an outer ball track center line. Each inner ball track has an inner ball track center line. When the constant-velocity rotary joint is straight, the inner ball track center line and the outer ball track center line of the track pair intersect in an intersection point and are not mirror-symmetrical with respect to a mirror plane through the intersection point, and the inner portion of the inner ball track center line widens more, with respect to a longitudinal axis of the outer joint portion, than the outer portion of the outer ball track center line.

A speed-reducing or -increasing apparatus, with first and second crown gears facing one another, with a cam unit that causes the first crown gear to incline with respect to the second crown gear so that the first crown gear meshes with the second crown gear, that causes the first crown gear to precess in such a manner as to move the meshing position, and couples to an input or output shaft. A rolling element is between the cam unit and the first crown gear, and the cam unit includes a first member that couples to the input or output shaft and a second member made of steel and including a rolling element rolling portion where the rolling element rolls, the second member configured to be incapable of rotating relatively to the first member, and at least part of the first member having a lower specific gravity than the second member.

A forging apparatus includes an ironing mechanism and a phase alignment mechanism. The ironing mechanism includes: a punch set, which is fitted into a cylindrical portion of a pre-processing material to be formed into the outer joint member, and is radially expandable and contractible, the cylindrical portion having grooves formed in an inner peripheral surface thereof; and a die having a hole into which the cylindrical portion is press-fitted. The phase alignment mechanism is configured to align phases of the grooves in the inner peripheral surface of the pre-processing material and phases of track groove portion forming surfaces of the punch set with each other before the pre-processing material is fitted to the punch set.

A drive axle assembly includes a wheel bearing mounted to an axle housing, a shaft assembly including a first shaft on an inboard side thereof to which a driving force of a power train is transmitted, and a second shaft on an outboard side thereof which is shaft-connected to the inside of the axle housing by a constant-velocity joint and is separably assembled to the first shaft, and a boot assembly including a first end portion fixed to an external ring of the wheel bearing and a second end portion assembled to the shaft assembly to be rotatable relative to the shaft assembly, and configured to restrict rotation of the boot and prevent foreign substances from being introduced therein.