1. Accelerating and decelerating are commonly referred to as transmission gearbox
2. Change the transmission direction. For example, we can use two sector gears to vertically transmit the force to another rotating shaft
3. Change the rotating torque. Under the same power condition, the faster the gear rotates, the smaller the torque the shaft receives, and vice versa
4. Clutch function: we can separate the engine from the load by separating two originally engaged gears, such as the brake clutch
5. Distribute power For example, we can use one engine to drive multiple slave shafts through the main shaft of the gearbox, thus realizing the function of one engine driving multiple loads
