MB motor oil with the taper of the driving wheel and the pressure plate is a disc spring compression, the input shaft and the driving wheel is connected by a key, active device consists of pressing. A group of tapered planetary friction wheel inside between the driving wheel and the pressing plate, lateral sandwiched between the taper of the fixed ring cam and speed, which consists of friction; when the compression of the active device operation, the friction wheel to do pure rolling, the fixed cam ring and the governor does not move, therefore, friction wheel in the rotation and public transport, through the planetary friction wheel central shaft and a slider driven by planetary gear bearing rotation.