A study on the loading cam of the parallel shaft traction drive transmission

Abstract

This paper describes a design method of the loading cam of the parallel shaft traction drive transmission which achieves high transmission efficiency. The geometrical profile of the cam which provides loading force in proportion to the transmitting force was determined with considering elastic deformation of components of the transmission. The loading force and transitional motion of the cam equipped on the prototype transmissions were measured and they agreed well calculations that shows the design method is proper. The required power of the ratio change actuator for the multi steps mechanism using the crank shaft was calculated. It was very small compering with transmitting power of the transmission that means effect on whole energy loss is small. Analysis on kinetic motion of the cam was executed by calculations and measurements have confirmed this system has potential which occurs self-excited vibration. Hydraulic circuit consisting of pistons and orifice is effective to avoid the vibration that was confirmed by calculations and measurements. Traction coefficient of the presented multi steps transmission decreases greatly at ratio change with large slip so that the transmission cannot execute power transmission. The shut off valve adding on the hydraulic circuit to fix transitional motion of the cam can transmit power to provide loading force with large slip at ratio change. Test result conducted the 2-speed transmission equipped with this mechanism achieves smooth and quick ratio change. This study shows the presented cam and its design method solve the most vital issue for traction drives which is how to provide suitable loading force.