The car’s clutch makes it possible to start off smoothly and shift into the next gear. In vehicles with combustion engines, the clutch ensures the reliable and at the same time releasable connection between the engine and the transmission. When changing gear, a step on the clutch pedal is enough to interrupt the power from the engine to the gearbox. Find out now everything about the structure and function of the clutch in the car.

Structure and function of the clutch in the car

In a car, the clutch provides the connection between the engine and the gearbox. When the clutch is closed, the power is transmitted from the engine to the gearbox. From here, the power is transferred to the wheels of the vehicle. However, it is often necessary to disconnect the connection between the engine and the gearbox, for example if the wheels of the vehicle are to stand still. In addition, the clutch compensates for differences in speed that occur when changing gears and dampens vibrations.

Coupling separates engine and gearbox

The clutch interrupts the connection between the engine and the gearbox when needed. Without this function of the clutch, it would not be possible to stop the car with the engine running. It is also only possible to start the car smoothly by carefully engaging the clutch. In addition, the clutch enables problem-free gear changes in vehicles with manual transmission. Without the interruption of the power transmission between the engine and the gearbox, this would not be possible.

This is how the clutch in the car is designed

The clutch in a car essentially consists of three parts. These are the engine flywheel, the clutch disc and the clutch pressure plate. In addition, there is a release system that is responsible for opening and closing the clutch. Depending on the vehicle, the clutch is operated via a clutch cable, a hydraulic system or by means of electrical assistance.

The engine flywheel is firmly connected to the output journal of the crankshaft. The pressure plate in turn is bolted to the flywheel. The flywheel and pressure plate always rotate with the engine speed. Between the pressure plate and the engine flywheel is the clutch disc. This is not connected to the crankshaft, but to the gear shaft.

When the clutch is closed, the clutch disc is pressed firmly against the engine flywheel by the pressure plate. Since clutch discs are equipped with friction linings, a frictional connection is created between the flywheel and the clutch disc. If the clutch is open, however, the pressure plate no longer exerts pressure on the clutch disc. The clutch disc no longer transmits the engine torque from the flywheel to the gearbox.

Automatic transmission clutch

The clutch principle is not only used in manual transmissions, but also in automatic transmissions. While many automatic transmissions are designed with a torque converter or as a continuously variable automatic, the clutch component is present twice in dual-clutch transmissions. With this type of clutch, one clutch is responsible for even and one for odd gears. The change to the next gear is automatic; there is no clutch pedal with this type of transmission.

This is what happens when you step on the clutch pedal

In contrast to a vehicle with an automatic transmission, the driver of a manual transmission must engage the clutch and shift gears himself. For this purpose, every manually shifted car is equipped with a clutch pedal. When the driver steps on the pedal, the clutch opens. This is done via a mechanism with a clutch fork or via a central release bearing. The power flow between the engine and the gearbox is interrupted at this moment.

Many modern cars have a hydraulically operated clutch. In such a hydraulic clutch, a clutch master cylinder is coupled to the clutch pedal. When the clutch pedal is depressed, pressure is built up via the cylinder and transmitted to the clutch via the clutch line. Here, a so-called clutch slave cylinder actuates the clutch, or a hydraulic release bearing is used.

Wear on the clutch

The clutch in a car is a classic wearing part. The component is stressed every time the vehicle is driven off. This is because the clutch has to absorb a lot of force. Every time another gear is engaged, the clutch is also used. This causes the linings on the clutch disc in particular to wear out over time. Other components of the clutch can break or wear out.

The service life of a clutch depends on many factors. In addition to the manufacturer and vehicle model, these include the mileage and use of the vehicle. Only rarely does a clutch need to be replaced before the vehicle has reached a mileage of 100,000 kilometres. In some cases, clutches can last 200,000 kilometres or more. Frequent starts or high loads in particular cause the clutch to wear out more quickly.

Influence the service life of the coupling

Among car drivers, there are some tips for extending the service life of clutches. It is not uncommon for the service life of the clutch to depend on factors that each driver can influence himself. These include the individual driving behaviour with the car. For example, drivers should avoid engaging the clutch at high speeds in order to protect the clutch disc.

Only partially depressing the pedal can also lead to increased wear and a shorter service life of the clutch. In this case, the clutch grinds and is not fully open. Also, when stopping at red lights, the pedal should not be held down instead of taking the car out of gear. In this case, the mechanism for operating the clutch may wear out more quickly.

If the clutch is defective

If the clutch is defective, the use of the car is restricted or no longer possible. A defect in the clutch often manifests itself in unusual behaviour of the car when starting or during gearshifts. For example, if the clutch is defective, symptoms such as a jerky start or worsened acceleration will occur.

Drivers often notice a defect when the clutch slips when shifting up. Unusual noises when changing gears or a clutch pedal that is difficult to operate can also indicate a defect. In extreme cases, gears can no longer be engaged if the car’s clutch is defective.

Replacing a defective clutch is quite complex and sometimes associated with higher costs. As a rule, the engine and the gearbox must be separated from each other in order to be able to replace the clutch. Depending on the vehicle model, the effort and material costs vary, so that the offer for the repair can be different in each case.

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