Hybrid Transmission Housing refers to the hybrid power system. The Transmission system that can couple the engine and the power of the driving motor together in a certain way and achieve speed change and torque change is the hybrid transmission. Hybrid transmission can be divided into special hybrid transmission and improved hybrid transmission based on traditional transmission integrated hybrid unit (drive motor and corresponding control system). It can be manufactured by CNC engraving, Sand Casting, transparent acrylic(PMMA/PC) 3D Printing.

The core of Toyota THS hybrid is a set of planetary gear structure, the structure of planetary gear is divided into: sun wheel, outer gear ring and planetary gear and planetary frame to form the whole. The feature of the complete set of gears is that as long as one of the structures is rotated, the other two structures can be rotated, and the power shunt is realized. And as long as the speed or torque of two of the structures is determined, the speed or torque of another structure can be obtained.

So far, Toyota's THS hybrid power system has been developed for four generations, namely THS- I, THS- II, THS- III, THS- IV, which are used in different periods of the model. As the first Prius car series to be put into use, a total of four generations have used four generations of hybrid powertrains.
Advantages:
 The gear ring is connected with the big motor and output to the wheel end. The speed of the gear ring and the output torque can be realized through the combination of different torque and speed of the engine and the motor.
 It is similar to the E-CVT when selecting the best operating point of the engine speed is continuously changed.
 At the same time, the structure is much simpler, occupies much less space and weight, and the cost is low.