Studies on Contact Geometry and Limiting Resistant Torque Characteristics of the Variable Torque Slipping Clutch with Skewed Rollers

A slipping clutch capable of delivering a constant resistant torque is described in this paper. Its principle is based on the resistance to slipping offered by the askew disposed cylindrical rollers rolling and slipping between the two specially shaped races. There are three types of this slipping clutch, namely the Right, Left and Cross Skewing respectively, which are distinguished by the directions of the roller askew arrangement and the rotation of the driving race. As a newly developed engineering surface, the surface of the races is in the spatial line contact with the skewed cylindrical rollers. After the equations of the race surface is established, the contact geometry of the tangency between the roller and races is investigated. This is essential for understanding the clutch properties and furthering the contact stress and EHL analyses. In addition, the analyzing procedure used here is also helpful for the study of other sophisticated line contact problems. Based on the assumptions of the maximum static friction force and the uniform distribution of the applied axial force along the contact line, the limiting torque characteristics are discussed in detail. The analysis of the maximum resistant torque clarifies the existence of self-locking problems under certain design parameters. On the other hand, the analysis of the minimum resistant torque shows how the resistant torque approaches the minimum values with changes of the geometrical parameters. These analyses provide the design principals for this slipping clutch in order to optimize the torque characteristics. The preliminary experiments are conducted with two types out of the three and the results prove those concluded from the theoretical analyses very well.