Structure And Type According to the shape classification: there are straight gear,front wheel drive engine and transmission the teeth are parallel to the axis of the gear, the structure is simple, easy to manufacture, but the contact degree is small when meshing, the transmission smoothness is poor, the noise is large, often used in some low-speed and light-load transmission with low precision and noise requirements; Helical gear, the tooth direction and the axis have a certain Angle, the contact degree is large, the bearing capacity is high, the transmission is stable and the noise is low, but the axial force will be generated, and the corresponding bearing needs to be added to withstand the axial force, which is widely used in various transmissions; Double helical gear, equivalent to two helical Angle opposite helical gear combination, the axial force cancels each other, the carrying capacity is higher, often used in large, heavy equipment transmission. Classified by function: including input gear, connected with the engine crankshaft, receive the power from the engine and input to the gearbox; The output gear is connected with the drive shaft to transmit the power in the gearbox after the transmission to drive the wheels and other components of the vehicle; Intermediate gear, located between the input gear and the output gear, plays the role of transition transmission, change the transmission direction and adjust the transmission ratio. Working Principle Power transmission: the engine operation drives the input gear on the input shaft to rotate, the input gear engages with other gears, and relies on the interaction between teeth and teeth to transfer the power to the intermediate gear (if any) and the output gear, and finally transfers the power to the driving wheel and other components through the output shaft to make the vehicle or equipment move. Variable speed principle: Change the transmission ratio by meshing gears with different numbers of teeth. For example, when the big gear drives the small gear, the speed of the small gear will be faster than the big gear, but the output torque will be smaller, to achieve growth and torque reduction; On the contrary, when the pinion drives the big gear, the speed of the big gear slows down, the torque increases, and the torque increases. In this way, transmission gears enable the vehicle or equipment to obtain the right speed and torque under different working conditions