What is the Principle of a Clutch?
3 Answers
The principle of a clutch is: The clutch consists of friction plates, spring plates, a pressure plate, and a power output shaft. It is located between the engine and the transmission, used to transfer the torque stored on the engine flywheel to the transmission, ensuring that the vehicle delivers appropriate driving force and torque to the driving wheels under different driving conditions. It belongs to the category of the powertrain. Operating states: The clutch has three operating states: disengaged when the clutch pedal is pressed, fully engaged when the clutch pedal is not pressed, and partially engaged (semi-engaged) when the clutch pedal is partially pressed. When the vehicle starts, the driver presses the clutch pedal, and the movement of the clutch pedal pulls the pressure plate backward, separating the pressure plate from the friction plates. When the vehicle is driving normally, the pressure plate tightly presses against the friction plates on the flywheel, at which point the friction between the pressure plate and the friction plates is at its maximum, maintaining relative static friction between the input and output shafts, with both rotating at the same speed. The last state is the semi-engaged state of the clutch, where the friction between the pressure plate and the friction plates is less than in the fully engaged state. In this state, there is sliding friction between the clutch pressure plate and the friction plates on the flywheel, with the flywheel rotating faster than the output shaft, transferring part of the power from the flywheel to the transmission. Precautions: Generally, the clutch plays a role when the vehicle starts or shifts gears. At this time, there is a speed difference between the first and second shafts of the transmission. The engine's power must be disconnected from the first shaft before the synchronizer can effectively synchronize the speed of the first shaft with that of the second shaft. After the gear is engaged, the clutch then connects the first shaft to the engine's power, allowing the power to continue transmitting. In the clutch, there is also an indispensable damping device. It consists of two disks similar to flywheels placed together, with rectangular grooves on the disks where springs are arranged. When encountering intense impacts, the springs between the two disks interact elastically, damping external stimuli and effectively protecting the engine and the clutch.
After driving for so many years, I feel that the clutch is like a translator between the person and the car. The engine wants to keep spinning, while the wheels need to stop and go as required. When you press the clutch pedal, the pressure plate and flywheel separate, like two people letting go of a tight handshake, cutting off the power. This allows for smooth gear shifting. As you slowly release the pedal, the friction disc is pressed back against the flywheel by the spring, like palms gradually coming together, reconnecting the power. The most important part of driving a manual transmission is finding the half-engagement point—it feels like the car is taking a deep breath: the engine sound deepens, and the front of the car lifts slightly. Clutch lifespan depends on habits; drivers who frequently ride the clutch might need new discs in a year, while my uncle’s taxi only had two replacements in 500,000 kilometers.
Having disassembled hundreds of clutches in repair shops, the basic principle is best demonstrated with a wrench. The engine is connected to a large iron disc called the flywheel at the rear. Inside the clutch housing lies a sandwich structure: the outermost part is the pressure plate with spring fingers, the middle holds the friction disc, and the splines of the friction disc grip the transmission shaft. When the pedal is pressed, the release bearing pushes open the pressure plate springs, causing the friction disc to lose pressure and stop rotating. When the pedal is released, the springs compress the sandwich tightly, and the friction disc, adhering to the flywheel, starts rotating to transmit power. A common issue is slipping—either due to oil contamination in older cars or worn-out discs that can't be pressed tightly. When modifying for racing, reinforced spring discs were replaced, resulting in more aggressive engagement but a pedal feel as heavy as stepping on a brick.
