A constant velocity universal joint includes an outer joint member and an inner joint member between which torque is transferred through intermediation of balls while allowing angular displacement. A power transmission shaft is coupled to the inner joint member to allow torque transmission therebetween. A mounting and dismounting mechanism configured to mount and dismount the power transmission shaft to and from the inner joint member is provided between the inner joint member and the power transmission shaft. The mounting and dismounting mechanism includes a tubular member, a snap ring mounted inside the tubular member, a pushing member arranged on a radially outer side of the snap ring to be movable in a radial direction, and an annular member arranged on an outer peripheral surface of the tubular member to be movable in an axial direction.

Provided is a spline structure with which contact surface area between an outer-side member and balls can be ensured, and contact surface area between an inner-side member and the balls can be ensured. This spline structure is provided with an outer-side member having a first track groove on the inner surface, an inner-side member having a second track groove on the outer surface, and balls disposed between the first track groove and the second track groove so as to allow the inner-side member to be inclined relative to the outer-side member. A bottom part extending along the length direction of the first track groove has a linear shape. A bottom part extending along the length direction of the second track groove has a concave curved shape.

Provided is a spline structure with which contact surface area between an outer-side member and balls can be ensured, and contact surface area between an inner-side member and the balls can be ensured. This spline structure is provided with an outer-side member having a first track groove on the inner surface, an inner-side member having a second track groove on the outer surface, and balls disposed between the first track groove and the second track groove so as to allow the inner-side member to be inclined relative to the outer-side member. A bottom part extending along the length direction of the first track groove has a linear shape. A bottom part extending along the length direction of the second track groove has a concave curved shape.

A fixed type constant velocity universal joint has an operation mode in which, when a maximum operating angle is taken, in a column portion that is one of column portions on both sides of a pocket of a cage receiving a torque transmission ball at a phase angle and is located on a side corresponding to a phase angle larger than the phase angle, a projection end portion obtained by projecting an end portion of a spherical inner peripheral surface of the outer joint member on the opening side in a perpendicular direction toward the spherical outer peripheral surface of the cage and a projection end portion obtained by projecting an end portion of the spherical outer peripheral surface of the inner joint member on the back side in the perpendicular direction toward the spherical inner peripheral surface of the cage overlap in the axial direction of the cage.

Track grooves of an outer joint member include first and second track groove portions. An end portion of the ball raceway center line of each of the first track groove portions is located on the opening side with respect to a joint center and a ball raceway center line of each of the second track groove portions is connected to the end portion. A ball raceway center line of each of the track grooves of the inner joint member is formed to be mirror-image symmetrical with a ball raceway center line of a corresponding one of the paired track grooves of the outer joint member with respect to a plane that includes the joint center at an operating angle of 0 and is orthogonal to a joint axial line.

Track grooves of an outer joint member include first and second track groove portions. An end portion of the ball raceway center line of each of the first track groove portions is located on the opening side with respect to a joint center and a ball raceway center line of each of the second track groove portions is connected to the end portion. A ball raceway center line of each of the track grooves of the inner joint member is formed to be mirror-image symmetrical with a ball raceway center line of a corresponding one of the paired track grooves of the outer joint member with respect to a plane that includes the joint center at an operating angle of 0 and is orthogonal to a joint axial line.

A transfer device is provided, which includes an input shaft configured to receive a driving force generated by a drive source, an output shaft configured to output a portion of the driving force to part-time drive wheels of a vehicle, a transfer case accommodating the input and output shafts, at least two output bearings rotatably supporting the output shaft, and a constant-velocity (CV) joint connected to the output shaft and provided on a first side of the part-time drive wheels with respect to the output shaft. The output shaft is formed with a recessed opening portion opening toward the first side and receiving at least a part of the CV joint therein. The transfer case has an annular intruding part extending from the first side of the output shaft into the recessed opening portion. A first output bearing is located inside the recessed opening portion.

In a fixed type constant velocity universal joint according to the present invention, six torque transmitting ball tracks (20) are defined as a first track, a second track, a third track, a fourth track, a fifth track, and a sixth track along a circumferential direction. Further, in the fixed type constant velocity universal joint according to the present invention, an axial offset amount of a curvature center of each of track grooves (12) of an outer joint member (13) and an axial offset amount of a curvature center of each of track grooves (15) of an inner joint member (16) are set to 0. Further, in the fixed type constant velocity universal joint according to the present invention, the track grooves (12) of the outer joint member (13) and the track grooves (15) of the inner joint member (16) are each inclined with respect to an axis line.

In a fixed type constant velocity universal joint according to the present invention, six torque transmitting ball tracks (20) are defined as a first track, a second track, a third track, a fourth track, a fifth track, and a sixth track along a circumferential direction. Further, in the fixed type constant velocity universal joint according to the present invention, an axial offset amount of a curvature center of each of track grooves (12) of an outer joint member (13) and an axial offset amount of a curvature center of each of track grooves (15) of an inner joint member (16) are set to 0. Further, in the fixed type constant velocity universal joint according to the present invention, the track grooves (12) of the outer joint member (13) and the track grooves (15) of the inner joint member (16) are each inclined with respect to an axis line.

A constant velocity universal joint is provided which includes an inner ring and an outer ring. A cage is disposed between an outer spherical surface of the inner ring and an inner spherical surface of the outer ring, and has windows in which respective balls are received. The cage has ball contact surface areas with which the balls come into contact, and includes soft portions that are lower in hardness than the ball contact surface areas. The soft portions are formed by local heat treatment at portions of the windows that are kept out of contact with the balls or surface portions around the windows.