Abstract: A dual transmission including a fixed gear ratio planetary gear mechanism, a belt transmission mechanism capable of continuously changing speed ratio, at least one clutch, and a lock, wherein the engine power of the motorcycle is transmitted through the planetary gear mechanism to the power output shaft for a fixed gear ratio transmission, and then controlled by the clutch and the lock to be transmitted to the power output shaft in the two routes, respectively, through the planetary gear transmission mechanism and the power-split continuously variable transmission mechanism.

Abstract: The creation of the present invention is a transmission system, including an output shaft for outputting an output power; a stepped speed transmission device for steppedly speed-changing said output shaft having in a first instance a relatively lower rpm; a stepless speed transmission device for steplessly speed-changing said output shaft having in a second instance a relatively higher rpm; and a clutch device, connected to said stepped speed transmission device and said stepless speed transmission device for switching therebetween.