What Is A Clutch? Its Functions, Parts and Diagram

In a car engine, there is a mechanical device that allows the engine to work at a stationary position We refer to it as a clutch. The component engages and disengages power transmission, especially from the driving shaft to the driven shaft.

In other words, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). In this reading, we’ll explore what a clutch is, its diagram, function, parts, types, and how it works.

Let’s begin!

What Is A Car Clutch?

A clutch is a mechanical device that disconnects an output shaft from a rotating input shaft, acting as a linkage between the engine and transmission in motor vehicles. It allows the engine speed to be determined by the speed of the driven wheels, reducing the need for a clutch.

In other words, a clutch is a mechanical device that engages and disengages the power transmission from the driving shaft to the driven shaft.

The device features two shafts; one is connected to the engine or power unit (the driving member), while the other shaft provides the power output that does the work.

Simply put, a clutch separates the engine’s power from the transmission and engages it when necessary. Pressing down the clutch pedal disengages the connection, and releasing it allows the power to flow to the transmission and the wheels.

The clutch is a crucial component in directing power from the engine to the gearbox, ensuring smooth operation of the vehicle’s wheels.

In electric drills, the clutch’s input shaft is driven by a motor, and the output shaft is connected to the drill bit. The clutch allows the drill bit to spin at the same speed as the motor, spin at a lower speed, or remain stationary while the motor is spinning.

Functions Of Clutch

The clutch helps the engine run in a stationary position.
You can use it to lower engine speed.
It enables easy gear changes.
Smooth vehicle control is achieved.

Parts Of A Clutch

A car clutch has several key components that work together to perform this task. Below are the main parts of a car clutch:

Flywheel

This clutch part is mounted on the crankshaft; it keeps running as long as the engine is working. A friction disc is mounted on the outer side of the flywheel.

Friction Disc

The friction disc could be a single or multiple discs, depending on its application. It is made of material with a high coefficient of friction. The friction disc is mounted on a drive shaft.

Pressure Plate

The pressure plate features another friction disc on it. The splined hub mounts this pressure plate.

Spring and Release Levers

The function of the springs is to move the friction disc back and forth. Clutches use diaphragm springs, and levers help to retract the spring.

Diagram Of A Car Clutch

Types of Clutches In A Car

Car clutches come in different types, each suited for specific vehicle types, driving styles, and transmission systems. Below are the common types of car clutches:

Friction Clutch

In this clutch, surfaces attached to the driven and driving shafts create friction that transfers the drive. These surfaces are lined with cork, asbestos, or other fibrous material.

Cars with friction clutches need to have the linings replaced periodically. The friction clutch is of two different types: a single-plate clutch and a multiple-plate clutch.

Single clutch plate: the single clutch is the most common and used clutch found on modern light vehicles. It helps transmit torque and power from the engine to the transmission input shaft. It is just on the plate, as the name indicates.

A multiple clutch plate, as its name suggests, employs numerous clutches to establish frictional contact with the engine’s flywheel. This transmits power between the engine shaft and the transmission shaft of the vehicle. The number of friction surfaces determines the capacity of the clutch to transmit torque.

Centrifugal Clutch

Centrifugal types of clutches use a centrifugal force to engage the clutch, unlike others that work with spring force. The benefit of this clutch is that the driver can easily stop the vehicle in any gear without stalling the engine.

The vehicle can be easily started in any gear by pressing the accelerator pedal.

The working of a centrifugal clutch is quite different, as it consists of weights A pivoted at B. The weights fly off due to the centrifugal force when the engine speed increases. The centrifugal force applied operates the bell crank levers, which press plate C.

Plate C’s movement presses the spring E, which in turn intensely presses the clutch plate D on the flywheel against the spring G. This action engages the clutch.

The spring G helps disengage the clutch at low speeds of about 500 rpm, and the stop H limits the movement of the weights.

Semi-Centrifugal Clutch

The semi-centrifugal clutch also uses centrifugal force along with a spring force, which helps it in the engaged position. The clutch consists of levers, clutch springs, a pressure plate, friction lining, a flywheel, and a clutch plate.

The working of a semi-centrifugal clutch also occurs at normal engine speeds; when the power transmission is low, the springs keep the clutch engaged. The weighted levers do not put any pressure on the pressure plate.

And at high engine speeds, when the power transmission is high, the weights fly, which allows the levers to exert pressure on the plate. This keeps the clutch firmly engaged.

The springs in these types of clutches consist of less stiff springs, which allows the driver not to experience any strain while operating the clutch.

Hydraulic Clutch

In the working principle of a hydraulic clutch, the oil reservoir pumps oil into the accumulator with the aid of a pump. The engine and this pump collaborate, and the control valve connects the accumulation to the cylinder.

The switch mounted on the gear lever is responsible for operating the control valve. The linkage mechanism is what connects the piston to the clutch.

The switch opens the control valve when the driver holds the gear lever to change the gears, which allows the oil under pressure to enter the cylinder.

The oil pressure moves the piston forward and backward, which causes the clutch to get disengaged. When the driver releases the gear lever, the switch opens, closing the control valve and engaging the clutch.

Cone Clutch

In a cone clutch, the friction surfaces are in a conical shape with two surfaces to transmit torque. The engine shaft consists of a female cone and a male cone. The splined clutch shaft mounts the male cone and slides on it. This conical portion has a friction surface.

When the clutch engages, the force of the spring contacts the friction surfaces of the male and female cones. However, when the clutch pedal is pressed, the male cone slides toward the spring force, which disengages the clutch.

One of the great benefits of a cone clutch is that the normal force acting on the friction surface is greater than the axial force. The cone clutch has some limitations, such as the tendency of the male cone to bind with the female cone, which makes disengagement difficult.

Diaphragm Clutch

The diaphragm clutch contains a diaphragm on a conical spring, which produces pressure on the pressure plate for engaging the clutch. The spring used is either a crown or finger type, which is attached to the pressure plate.

In this type of clutch, the engine power is transmitted from the crankshaft to the flywheel, which contains a friction lining. The pressure plate is located behind the clutch plate because it applies pressure to it.

In diaphragm clutch working, the diaphragm is a conical shape of the spring that allows the outside bearing to move towards the flywheel when pressed. The diaphragm spring, when pressed by the flywheel, pushes the pressure plate backward.

This allows the pressure on a plate to be restricted, and the clutch will be disengaged. If the clutch pedal is released, the pressure plate and diaphragm spring will come back to their normal positions, and the clutch will get engaged.

The advantage of the clutch is that there are no release levers because the spring takes the position. Drivers do not need to apply such heavy pedal pressure to hold the clutch disengaged.

This occurs when you depress the pedal to disengage the clutch, increasing the coil spring pressure.

Electromagnetic Clutch

The electromagnetic clutch operates electrically, but it transmits its power mechanically. This clutch has no mechanical linkage to control its engagement, which is why fast and smooth operation occurs.

It uses a remote for its operation, allowing the clutch to be operated from a distance.

The battery supplies the electrical power, and the clutch flywheel has a winding. The winding facilitates the passage of electricity, generates an electromagnetic field, and engages the pressure plate. Cutting off its power supply causes it to disengage.

In an electromagnetic clutch, there is a clutch release switch in the gear level, which allows the driver to operate the gear lever when changing gears. This switch is operated by cutting off the current supply to the winding, which causes the disengagement.

Dog and Spline Clutch

We use the dog and spline types of clutches to connect the gear and shaft, or lock and shaft, together. The major parts of the clutch are the dog clutch, which contains the external teeth, and the sliding sleeve, which has the internal teeth.

The design of the shafts ensures they rotate at the same speed and never slip. Connecting the two shafts engages the clutch.

When the sliding sleeve moves back on the splined shaft and loses contact with the driving shaft, these types of clutches disengage. They primarily assist in locking different gears in manual transmission vehicles.

Vacuum Clutch

This clutch uses the existing vacuum in the engine manifold to work. The vacuum clutch consists of a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.

The reservoir is connected to the inlet manifold through a non-return valve. A solenoid-operated valve connects a vacuum cylinder to a reservoir.

The battery powers this solenoid, and the gear lever in the circuit houses a switch. The switch is operated when the driver changes the gear by holding the gear lever.

The solenoid energizes and pulls the valve up, which connects one side of the vacuum cylinder to the reservoir. This mechanism opens the passage between the vacuum and the reservoir.

Different levels of pressure allow the vacuum cylinder piston to move forward and backward. A linkage transmits the movement of the piston to the clutch, which causes it to disengage.

If the gear lever is not operated, the switch is open, and the clutch remains engaged because of the force of the springs.

Freewheel Unit

The freewheel unit clutch is also known as a spring clutch, one-way clutch, or overrunning clutch. Its transmission power is in one direction, just as in bicycle transmission. The freewheel is located behind the gearbox.

The main shaft transmits the power from the main shaft to the output shaft, which drives the output shaft when the planetary gears are in overdrive.

There is a hub and an outer race contained on the flywheel unit. This hub has internal splines to connect it to the transmission main shaft. The outer surface of the hub has 12 cams designed to hold 12 rollers in a cage between them and the outer race.

The outer race is splined to the overdrive outer shaft.

How A Clutch Works In A Car

The clutch consists of two different plates; one is mounted to the flywheel, and the other moves over the crankshaft. The amount of torque applied determines the amount of axial load that is applied to the friction disc.

This is to say, the more the axial load, the more the power transmission, and the less the axial load, the lesser the power transmission.

The movable disc, which is splined on the crankshaft, moves back and forth with the aid of the clutch pedal. The pressure plate applies the load, connecting to multiple helical springs or a single diaphragm spring.

If the clutch pedal is completely pressed, the moveable friction disc moves back from the shaft, which disengages from the flywheel.

There is no power or torque transmission because the pressure plate is not applying any axial load. This is why the engine can run without moving. If the clutch pedal is completely released, the moveable friction disc slides forward on the shaft to the flywheel.

This is the engaged condition when the disc touches the flywheel. The amount of clutch pedal actuation also affects the working pressure applied. This means the amount of axial load applied by the pressure plate will reflect on the power transmitted.

What is a Slipping Clutch and Its Causes

When a clutch improperly engages or disengages the transmission, the car may slip out of gear or struggle to stay in gear when accelerating, known as clutch slipping.

Poor adjustment, wear and tear, or a lack of lubrication can cause this. A slipping clutch means it has lost the ability to hold the same amount of torque, causing intermittent sliding when engine torque exceeds its maximum capacity.

Third or fourth gear is where you’ll notice this issue the most, and it will only get worse until you replace the clutch.

In rare cases, a worn clutch may leave the car unable to transmit engine power to the ground, causing it to lose torque while accelerating and becoming difficult to control.

Causes of a slipping clutch

Common causes of clutch slipping include the age of the vehicle, lack of routine maintenance, infrequent servicing, and aggressive driving. Over time and with high mileage, clutch wear and tear can lead to power loss in the clutch plate.

Factors such as driving in stop-and-go traffic and low fluid levels in the clutch system can also contribute to this issue.

If the clutch plate is worn out, it may need to be replaced, and the same goes for a worn clutch release bearing or a broken cable. These problems typically require the expertise of a mechanic familiar with clutch and gearbox operations.

Symptoms of a Bad and Slipping Clutch

You will experience the following if your car clutch is slipping: a grinding sound, difficulty changing gears, unusually high RPM, intense vibration, a harsh burning smell from the engine, a clutch that feels soft or spongy when pressed, and a stuck clutch pedal.

From the gearbox, grinding sounds are coming.
There is difficulty changing gears when applying or releasing the clutch.
When traveling forward or changing gear, the vehicle suddenly judders, jerks, or stutters.
When the gear slips out during acceleration, the RPMs are unusually high.
If you place your hand on the gear stick, you should feel intense vibrations from the gearbox.
Coming from the gearbox was a strong, burning smell.
The clutch pedal should resist when pressed, but it feels soft and spongy.
When you start going, the clutch pedal may stick or refuse to return to its original position.

If you have seen any of the aforementioned symptoms, you should know this is what a slipping clutch feels like, and you should take your vehicle to a reputable neighborhood garage right away or get in touch with a mobile technician.

How to fix a slipping clutch

Most slipping clutches are not repairable, but changing driving habits may help. Consulting a mechanic is the best course of action to diagnose and resolve the problem.

While clutch repair or replacement may seem costly, it’s better than getting stuck on the road. If you notice your clutch slipping, it’s not a wise idea to keep driving, as it could fail at any time.

To avoid problems, drive carefully and have your clutch checked every 60,000 miles.

FAQs

What is a clutch on a car?

At its core, a car clutch is essentially a mechanical device that connects and disconnects the engine’s power from the transmission, allowing you to change gears smoothly.

It’s an essential component of manual transmissions, serving as the intermediary between the engine and the wheels.

How do I know if my pressure plate is worn out?

greater RPM. inability to shift or engage gears. The clutch pedal has reduced resistance. There is a burning odor emanating from the clutch.

What are the first signs of clutch failure?

The clutch pedal vibrates, sticks, or is spongy when you press it.
The clutch pedal makes a squeaking or moaning sound when it is depressed.
Even while you can crank the engine, you can’t seem to accelerate.
You’re experiencing difficulty switching gears.

How do I know if my shift fork is bent?

All the gears shift smoothly and nicely as it moves up and down.
When riding a bike in gear with the clutch pulled in after it has warmed up to operational temperature (170+), there is a “clunk” and “clank” sound.

What connects to the clutch fork?

The clutch thrust bearing is pressed up against by the clutch fork. The clutch fork, a straightforward but crucial part, is connected to either a cable or a slave cylinder depending on how it operates.

The clutch fork pivots from the end mounting point when the clutch pedal is depressed.

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What Is A Clutch? Its Functions, Parts and How it Works