It has three gears to change the speed. It adopts one-grade parallel axis transmission form. The gear transmission is straight and the structure is simple and compact. 
The sliding gear is connected with the axle by the rectangle spline. The transmission and torque are reliable and the slippage is convenient.
It adopts rotating rocker. Move the ball screw to drive the shifting fork, and then push the gear slip. The gear shift operation is convenient and it has high reliability.