Abstract: Steel balls are the most important components of Rzeppa constant velocity joint, and their kinematic traits play a vital role in the function of the joint. It’s proved that the two orbits of the center of a steel ball on inner race and outer race definitely meet at a point under the constraints of these orbits, and the kinematic differential equations of the steel balls are formulated, based on which the rigorous proof of the constant velocity characteristic is presented. Relative displacements of the steel balls with respect to the inner race, the outer race and the cage are simulated with the motion of each steel ball. The obtained results demonstrate the common kinematic traits of the steel balls: all steel balls are distributed on a circle whose center is located at the center point of the line connecting the two centers of inner and outer orbits, and their in-plane orientation angular velocities are not equal to each other, but vary periodically in values around the input angular velocity; the relative displacements of the steel balls with respect to the inner race and the outer race are equal in magnitude and opposite in direction; and a steel ball can move periodically with respect to the cage slot center in both radial and tangential directions. These results are helpful in the design of Rzeppa constant velocity joint.

Key words: Characteristic of constant velocity, Kinematic simulation, Rzeppa constant velocity joint, Steel balls’ motion