What are the functions of the clutch?

1. Ensure the smooth start of the car
Before starting, the car is stationary. If the engine and the gearbox are rigidly connected, once the gear is engaged, the car will suddenly rush forward due to the sudden power connection, which will not only cause damage to the machine parts, but also the driving force will not be enough to overcome the huge inertia generated by the car's forward rush, causing the engine speed to drop sharply and stall. If the clutch is used to temporarily separate the engine and the gearbox at the start, and then the clutch is gradually engaged, due to the slippage between the active part and the driven part of the clutch, the torque transmitted by the clutch can be gradually increased from zero, and the driving force of the car will also gradually increase, so that the car can start smoothly.
2. Easy to shift gears
During the driving process of the car, different gearbox gears are often used to adapt to the changing driving conditions. If there is no clutch to temporarily separate the engine and the gearbox, the meshing force transmission gear in the gearbox will be difficult to separate because the load is not unloaded and the pressure between the meshing tooth surfaces is very large. The other gear to be meshed will be difficult to mesh because the circumferential speeds of the two are not equal. Even if it is forced into meshing, it will produce a large impact on the tooth end, which is easy to damage the machine parts. The clutch is used to temporarily separate the engine and the gearbox and then shift gears. The original meshing pair of gears is unloaded due to the load, and the pressure between the meshing surfaces is greatly reduced, so it is easy to separate. As for the other pair of gears to be meshed, since the rotational inertia of the driving gear is very small after being separated from the engine, the circumferential speed of the gears to be meshed can be equal or nearly equal by using appropriate shifting actions, thereby avoiding or reducing the impact between the gears.
3. Preventing overload of the transmission system
When the car is braked in an emergency, the wheels suddenly slow down sharply, and the transmission system connected to the engine still maintains the original speed due to the inertia of rotation, which often produces an inertia moment far greater than the engine torque in the transmission system, making the parts of the transmission system easy to damage. Since the clutch transmits torque by friction, when the load in the transmission system exceeds the torque that can be transmitted by friction, the master and slave parts of the clutch will automatically slip, thus preventing the transmission system from overloading.
4. Reduce torsional vibration shock
The working principle of the automobile engine determines the instability of its output torque. During the power stroke, the combustion chamber gas explosion produces a huge impact torque, while during other strokes, the engine is dragged back by inertia. Although the inertia of the engine's own rotating system can reduce torsional vibration, the remaining impact force still has an adverse effect on the subsequent gearbox and transmission shaft. The damping spring (tangential distribution) in the clutch can significantly reduce the torsional vibration impact caused by the engine and extend the life of the transmission gear.