1. The variable angle power transmission mechanism is used to change the position of the transmission axis, which is the "joint" component of the universal transmission device of the automobile drive system. Cross-shaft rigid universal joint is widely used in automobiles. The maximum angle of intersection between adjacent two axles is 15~20. The cross shaft is one of the key parts of the cross shaft rigid universal joint.

2. The main failure of universal joint of transmission shaft is the wear and tear of journal and bearing and the bending deformation of each journal, resulting in the center line of each shaft of the cross shaft is not in the same plane, or the adjacent two axis center line is not vertical. Because the wear clearance of the cross journal and bearing of the universal joint is too large, the cross shaft sways during operation, which makes the center line of the drive shaft deviate from its rotation center line, and causes the vibration phenomenon of the drive shaft and the abnormal noise phenomenon of the drive shaft in operation. Wear is mainly caused by lack of lubrication.