The basic function of the clutch is to engage and disengage the engine to the wheel the driver needs or when shifting gears, hence clutch is one of the vital parts of your car .If clutch stops working properly it will make the car difficult or impossible to drive. So let’s understand what makes the clutch so important.
In manual transmission car, the connection between the shaft coming from the engine and shafts which turn the wheels is controlled by clutch. The clutch connects to your engine via the engine’s flywheel. When the clutch is engaged (i.e. no pressure on the clutch pedal) the clutch disc is forced against the flywheel by powerful springs. Friction between the two parts forms a solid connection and the engine’s motion is transmitted to the transmission. Depressing the clutch pedal causes the springs holding the clutch disc against the flywheel to relax. Without being held in place, the clutch disc loses contact and stops spinning, breaking the linkage.
Components that make up Clutch System
- Pressure Plate: This is one of major component of the clutch system. This is pressure mechanism that locks the disc to the flywheel so that vehicle moves. Basically pressure plate has two important functions to perform. 1.) To hold the clutch assembly together, 2.) To release tension that allows the assembly to rotate freely.
- Clutch Disc: The clutch disc is a flat plate with friction materials on both sides and is placed between flywheel and the pressure plate. The clutch disc is locked to the flywheel when the pressure plate is engaged and disengaged when the disc is unlocked. The disc is connected to the input shaft of the transmission by the splined hub, causing the input shaft to turn when the clutch is engaged, thus causing the vehicle to move.
- Flywheel:The flywheel is an inertia device that is bolted to the engine crankshaft. It has several functions including carrying the ring gear the starter uses to crank the engine, storing energy to get the vehicle moving from a standing stop, and providing the friction surface for the clutch disc to be clamped to.
- Release Bearing: The release bearing is the actuating device that engages and disengages the pressure plate. When the clutch pedal is de-pressed, the release bearing applies pressure to the fingers of the pressure plate to disengage the drivetrain. When the clutch pedal is released, the release bearing retracts and allows the pressure plate to apply pressure to clamp the disc against the flywheel.
- Release Fork: The release fork holds the release bearing, and pivots on a ball stud as the pedal is pressed in or let out. Pushing in the pedal pivots the fork towards the pressure plate and forces the release bearing against the clutch fingers, pressing them in to disengage the clutch.
- Pilot Bushing: The pilot bushing or bearing installs in the end of the crankshaft. When the transmission is installed, the input shaft tip inserts into the pilot bushing, which supports the input in the back of the crankshaft.
Types of Clutches
These may classified as follows.
According to the method of transmitting torque
Positive clutch (Dog clutch)
In the positive clutch, grooves are cut either into the driving member or into the driven member and some extracted parts are situated into both driving and driven member. When the driver releases clutch pedal then these extracted parts insert into grooves and both driving and driven shaft revolve together. When he push the clutch pedal these extracted parts come out from grooves and the engine shaft revolve itself without revolving transmission shaft.
In this types of clutches, friction force is used to engage and disengage the clutch. A friction plate is inserted between the driving member and the driven member of clutch. When the driver releases the clutch pedal, the driven member and driving member of clutch, comes in contact with each other. A friction force works between these two parts. So when the driving member revolves, it makes revolve the driven member of clutch and the clutch is in engage position.
This type of clutch is subdivided into four types according to the design of the clutch.
- Cone clutch
It is a friction type of clutch. As the name, this type of clutch consist a cone mounted on the driven member and the shape of the sides of the flywheel is also shaped as the conical. The surfaces of contact are lined with the friction lining. The cone can be engage and disengage form flywheel by the clutch pedal.
- Single plate clutch
In the single plate clutch a flywheel is fixed to the engine shaft and a pressure plate is attached to the gear box shaft. This pressure plate is free to move on the spindle of the shaft. A friction plate is situated between the flywheel and pressure plate. Some springs are inserted into compressed position between these plates. When the clutch pedal releases then the pressure plate exerts a force on the friction plate due to spring action. So clutch is in engage position. When the driver pushes the clutch pedal it due to mechanism it serves as the disengagement of clutch.
- Multi-plate clutch
Multi-plate clutch is same as the single plate clutch but there are two or more clutch plates inserted between the flywheel and pressure plate. This clutch is compact than the single plate clutch for same transmission of torque.
- Diaphragm clutch
This clutch is similar to the single plate clutch except diaphragm spring is used instead of coil springs for exert pressure on the pressure plate. In the coil springs, one big problem occurs that these springs do not distribute the spring force uniformly. To eliminate this problem, diaphragm springs are used into clutches. This clutch is known as diaphragm clutch.
This clutch uses hydraulic fluid to transmit the torque. According to their design, this clutch is subdivided into two types.
- Fluid coupling
It is a hydraulic unit that replaces a clutch in a semi or fully automatic clutch. In this type of clutch there is no mechanical connection between driving member and driven member. A pump impeller is blotted on a driving member and a turbine runner is bolted on the driven member. Both the above units are enclosed into single housing filled with a liquid. This liquid serve as the torque transmitter from the impeller to the turbine. When the driving member starts rotating then the impeller also rotates outward through the liquid by centrifugal action. This liquid then enters the turbine runner and exerts a force on the runner blade. This make the runner as well as the driven member rotate. The liquid from the runner then flows back into the pump impeller, thus completing the circuit. It is not possible to disconnect to the driving member to the driven member when the engine is running. So the fluid coupling is not suitable for ordinary gear box. It is used with automatic or semi-automatic gear box.
- Hydraulic torque converter
Hydraulic torque converter is same as the electric transformer. The main purpose of the torque converter is to engage the driving member to driven member and increase the torque of driven member. In the torque converter, an impeller is bolted on the driving member, a turbine is bolted on the driven member and a stationary guide vanes are placed between these two members. This all parts are enclosed into single housing which filled with hydraulic liquid. The impeller rotates with the driven member and it through the liquid outward by centrifugal action. This liquid flowing from the impeller to turbine runner exerts a torque on the stationary guide vanes which change the direction of liquid, thereby making possible the transformation of torque and speed. The difference of torque between impeller and turbine depends upon these stationary guide vanes. The hydraulic torque converter is serve the function of clutch as well as the automatic gear box.
According to the method of engaging force:
- Spring types clutch
In this types of clutches, helical or diaphragm springs are used to exert a pressure force on the pressure plate to engage the clutch. These springs are situated between pressure plate and the cover. These springs are inserted into compact position into the clutch. So when it is free to move between these two members, it tends to expand. So it exert a pressure force on the pressure plate thus it brings the clutch in engage position.
- Centrifugal clutch
As the name in the centrifugal clutch, centrifugal force is used to engage the clutch. This type of clutch does not require any clutch pedal for operating the clutch. The clutch is operated automatically depending upon engine speed. It consist a weight pivoted on the fix member of clutch. When the engine speed increases, it increases the weight of flywheel due to the centrifugal force, operating the bell crank lever, which presses the pressure plate. This makes the clutch engage.
- Semi-centrifugal clutch
One big problem occur in centrifugal clutch is that they work sufficient enough at higher speeds but at lower speed they don’t do their work sufficiently. So the need of another type of clutch occurs, which can work at higher speed as well as at lower speed. This type of clutch is known as semi-centrifugal clutch. This type of clutch uses centrifugal force as well as spring force for keeping it in engaged position. The springs are designed to transmit the torque at normal speed, while the centrifugal force assists in torque transmission at higher speeds.
- Electro-magnetic clutch
In the electromagnetic clutch electro-magnet is used to exert a pressure force on pressure plate to make the clutch engage. In this type of clutch, the driving plate or the driven plate is attached to the electric coil. When the electricity is provide into these coils then the plate work as the magnate and it attract another plate. So both plates join when the electricity provides and the clutch is in engage position. When the driver cut the electricity, this attraction force disappear, and the clutch is in disengage position.
According to the method of control:
- Manual clutch
In this type, clutch is operated manually by the driver when he needs or when shifting the gear. This type of clutch uses some mechanical, hydraulically or electrical mechanism to operate the clutch. All friction clutches are included in this category.
- Automatic clutch
This type of clutch used in modern vehicles. This clutch has self-operated mechanism which control the clutch when the vehicle need. Centrifugal clutch, hydraulic torque converter and fluid coupling includes in it. These types of clutches are always used with the automatic transmission box.
These are the main types of clutches used in automobile industries to transmit power. So if you are looking for buying the clutch for your car click here: www.spareshub.com