How does the car clutch works?

The clutch is a mechanical element of the car that is responsible for transmitting the movement of the engine to the wheels, through the gearbox. Knowing the parts that make it up and how the clutch works is vital to avoid misuse and extend the life of the clutch. It is not a cheap breakdown, […]

The clutch is a mechanical element of the car that is responsible for transmitting the movement of the engine to the wheels, through the gearbox. Knowing the parts that make it up and how the clutch works is vital to avoid misuse and extend the life of the clutch. It is not a cheap breakdown, more than for the cost of the pieces for the amount of labour that the change of clutch entails

Located between the engine and the gearbox, the function of the clutch is to isolate the movement of the engine from the wheels while performing a gearshift (either manual or automatic, although in this article we will focus on the first). It is therefore a piece subjected to numerous efforts and that misuse can cause premature degradation.

It is not possible to assign a life of the clutch in kilometres, as in other mechanical parts. The life of the clutch depends greatly on the use of the car owner. If a car has made the majority of journeys on long motorway trips, it will hardly have been used. One that circulates a lot in the city, will not need to have travelled so many kilometres to begin to suffer wear.

As a general rule (always knowing that it can vary a lot), it is usual for the life of the clutch to be around 200,000 km. Remember that this part is not usually included in the warranty of the car, since a bad use can end it in a few days.

Remember that for a thorough inspection and correction of your car components you can visit us. Here at JB Euro Service we will help you keep your car ready for anything.

Clutch parts

Although we usually refer to it as a single element, in reality, it is a set of parts responsible for assimilating the motor movement:

  • Friction disk: it is the key and most critical part. This disc, with its two faces made of a material very similar to that of the brake pads, is coupled to the gearbox by means of an axle. Turn with the steering wheel and the pressure plate except when the pedal is pressed, which decouples to facilitate smooth gear changes. The disc springs have the function of absorbing and softening the impact when the power is transmitted to the centre and avoiding motor vibrations.
  • Thrust collar: This part, also known as a thrust bearing, separates or joins the disc every time the driver disengages or depresses the clutch pedal. When disengaging, release the pressure on the disc, create a space of sufficient size for this disk to be removed from the steering wheel and allow the driver to change speeds.
  • Flywheel: It is screwed to the end of the crankshaft, that piece that is responsible for transforming the rectilinear movement of the pistons in rotary (so that the wheels rotate). It is the support of the clutch and its mission is to accumulate inertia and regularize the movement of the propeller. When you step on the clutch, press the disc through the pressure plate. It also works as a heat sink and requires a completely flat surface to function properly.
  • Pressure plate: Known as a clutch hub as well, it includes a steel disc with the appearance of a circular crown. On one side the clutch mechanism housing is connected using the diaphragm or springs, and on the other it is connected to one of the clutch discs faces. Power reaches the driving wheels when the clutch hub presses the disc.
  • Housing or cover: It is the element that covers the clutch system, through which the flywheel is fixed using the screws. In the housing are the different diaphragms or springs that allow the clutch disc to be pressed against the pressure plate and also against the flywheel.
  • Drive mechanism: Consists of a bearing that is also known as butte. Leaning on the diaphragm, push those sheets to release or press the disc. It is mounted on a fork which is the one that moves when the clutch pedal is pressed (with a cable or by means of a hydraulic system).

How a clutch works

Broadly speaking, we can indicate that the movement of the cylinders moves to the crankshaft, to which the flywheel or flywheel is attached.

This is where the movement comes once the clutch disc is coupled to it by the main shaft. The clutch hub exerts pressure on it so that the engine power reaches the drive wheels each time the thrust bearing engages the disc. This piece, the clutch disc, is the one that suffers the most in the whole process, since it is in contact with the two elements, hence it is the one that suffers the most wear.

We can identify three positions in this process:

  • Clutch position: Disc coupled, the power is transmitted completely to the clutch, linking wheels and the engine.
  • Disengagement position: Clutch pedal is depressed, decoupling system disc. In this position, the right one to change gear, the wheels will turn free or stop, depending on the inertia.
  • Transient phase: Between both positions, the clutch must also work, softening the mechanical shocks so that the change is not made violently or that the inertia damages the engine or gearbox.

While the clutch is completely loose it does not suffer wear or strain. It is when we step on the pedal when problems can begin to happen. Especially if you step on it halfway, since the disc slides against the flywheel and the hub, accelerating the deterioration and raising the temperature a lot. For this reason, it is not recommended to take your foot on the pedal, do not use the neutral during stops or chop clutch if you want to extend your life.

Clutch types

Everything we have told you so far are general characteristics. There are different types of clutch. We can perform two different typologies. The first, the most common, leaves us with three types of clutch:

  • Mechanical friction clutch: The most common in passenger cars, formed by the flywheel on which the primary axle of the gearbox is supported. There are clutches with a single dry disk and others that carry several discs, either dry or wet.
  • Hydraulic clutches: In them, the union of the two main parts of the clutch is done by means of oil, without disc. Very common in automatic gearboxes. The energy is transmitted by a centrifugal pump that communicates with a turbine.
  • Electromagnetic clutches: They are very rare. They take advantage of the force of the electromagnetic field (electromagnetic blocking) to transmit the torque.

Other quite common difference is established by the way of pressure on the oppressor plate to couple it with the disc. There are then three different types of clutch:

  • Spring clutch: The springs on which the pressure is made are located on the periphery of the clutch disc.
  • Diaphragm clutch: This function is performed by an elastic steel diaphragm.
  • Centrifugal clutch: Both clutch and disengagement are carried out by counterweights that work by the action of the centrifugal force of the motor rotation. It is typical of the automatic exchange, since it acts automatically from a certain speed of rotation of the motor shaft.

Keep in mind that here at JB Euro Service we take pride in providing the best services for European cars in our area.