Study on ball force fluctuation of Rzeppa constant velocity joint

Rzeppa constant velocity joints are mainly used in the drive shafts of front wheel drive vehicles. This type of joint transmits driving torque through balls provided in the joint. The ball force that transmits the torque fluctuates periodically when a joint angle exists between the two transmitting axes. Although this ball force fluctuation influences joint performance aspects such as strength and durability, the reason why the ball force fluctuates is not clarified yet. To reduce ball force fluctuation, it is necessary to clarify the essential mechanisms behind the periodic fluctuation. First, this paper assumes that the ball forces are balanced with the secondary moment related to the driving torque and joint angle. A basic waveform of the ball force was constructed based on this assumption. In addition, a detailed analysis model of a Rzeppa joint was constructed, including the contact and friction forces acting on multiple parts of the joint, based on a multibody dynamics approach. This detailed joint model was validated by ball forces measured in an experiment, and converted into an ideal joint model disengaged from design and production restrictions. The basic waveform of the ball force was validated using analysis results computed using this ideal joint model. The theory that the ball forces are balanced with the secondary moment was validated. Moreover, the contribution of the design parameters of the detailed joint model to the ball force waveform was identified by conversion to the ideal model.