In this article, we are going to study the Types of Clutches in brief with their Advantages and Disadvantages.
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Introduction of Clutch:
The clutch is a mechanical device that works is to engage and disengages power transmission especially from driving to driven shaft. It is used in the automobile sector.
Now moving to different types of clutches,
Types of Clutches:
Here are following different types of Clutches:
- Positive and Spline Clutch
- Friction clutch
- Single Plate Clutch
- Multi-plate Clutch
- Cone Clutch
- Centrifugal Clutch
- Hydraulic clutch
- Electromagnetic Clutch
- Hysteresis-powered Clutch
- Semi-Centrifugal Clutch
- Diaphragm Clutch
- Vacuum Clutch
- Freewheel Clutch
Positive or Spline or Dog clutch:
In the positive clutch, grooves are cut either into the driving member or into the driven member, and specially designed parts are situated into both driving and the driven member.
The driver release clutch pedal then these special parts will insert into grooves and driving and driven shaft starts revolving together when he pushes the clutch pedal these parts come out from grooves and the engine shaft revolve without driven shaft.
The friction clutch is a device used to transmit the rotary motion of one shaft to another when desired. The axes of the two shafts are coincident.
The surfaces can be pressed firmly against one against when engaged and the clutch tends to rotate as a single unit.
Single Plate clutch:
A disc clutch consists of a Clutch plate attached to a hub that has splines cut on it and which is free to slide a on splines cut on the driven shaft in the axial direction means parallel to the shaft.
The clutch plate is made of metal generally of steel and has a ring of friction lining on each side which has large coefficient friction. The engine shaft supports a Flywheel.
A spring-loaded pressure plate presses the clutch plate firmly against the Flywheel when the clutch is Engaged. the disengaged position, the springs press the cover attached to the Flywheel.
Thus both the Flywheel and the pressure plate rotate with the driving shaft. The movement of the clutch pedal is the movement of the pressure plate through a thrust bearing.
The pressure plate pull by the release levers and the friction linings on the clutch plate is in no contact with the pressure plate or the Flywheel. The Flywheel rotates without driving the clutch plate and thus, the driven shaft.
When we pressed off the foot from the pedal, the pressure on the thrust bearing is released. As a result, the springs become free to move the pressure plate to bring in contact with the clutch plate.
The clutch plate slides on the splined hub and is gripped between the pressure plate and the Flywheel. The friction between the linings on the clutch plate and the Flywheel on one side and the pressure plate on the other cause the clutch and hence the driven shaft to rotate.
In case if the resisting torque on the driver shaft more than the torque at the clutch, a clutch slip will occur.
In the multi-plate clutch, the number of frictional linings and the metal plates is increased which increases the capacity of the clutch to transmit torque.
Friction rings have splined on outer boundary and Engage with corresponding splines on the Flywheel. They are free to slide axially. The friction material thus rotates with the Flywheel and the engine shaft. The number of friction rings depends upon the torque to be transmitted.
The driven shaft also supports disc on the splines and them which rotate with the driven shaft and can slide in the axial direction If the adding force on the pedal is removed. If n is the total number of plates both on the driving and the driven members, the number of active surfaces will be n-1 because 1 surface will be common.
In a cone clutch the contact surfaces in the form of cones. In the Engaged position, the friction surfaces of the two cones are in complete contact due to spring pressure which will make in touch all the time. When the clutch is engaged.
If F is the axial Force, Fn the normal force and £ the semi–cone angle of the clutch then for a conical collar with uniform wear theory.
The main disadvantage of the Cone clutch is If the angle of the cone is made smaller than 200 the male cone tends to adhere in the female cone and it becomes difficult to disengage the clutch.
Cone clutch is used in low-speed applications. Cone clutch is commonly used in ix engines and automobiles.
It is also used in very specialist transmissions in racing, rallying, or in extreme off-road vehicles. Cone clutches are used in powerboats.
Centrifugal Clutches are being increasingly used in automobiles and machines.
A Centrifugal clutch has a driving member consisting of four slipping blocks and blocks kept by position means of flat springs for this purpose. As the speed of the shaft increases, the Centrifugal force on the shoes increases.
The condition when centrifugal force more than the resisting force of springs, then the shoes will move forward and press against the inside of the rim and thus the torque is transmitted to the rim.
The only clutch is Engaged when the motor gets sufficient speed to take up the load inefficient manner. The outer surfaces of the shoes are lined with some friction material.
On the input shaft, there are large extension springs, which connect to a clutch shoe. When driving spins fast enough, the springs extend causing the clutch shoes to engage the friction face.
When the engine shaft reaches a certain RPM (Revolutions Per Minute), the clutch activates, working almost as it will gradually increase As the load increases the R.P.M. drops thereby disengaging the clutch and letting the RPM rise again and reengaging the clutch.
These results in a fair bit of waste heat, but over a broad range of speeds, it is much more useful than a direct drive in many applications like mopeds and go-karts, etc. Weaker spring or heavier shoes will cause the clutch to engage at a lower R.P.M. while a stronger spring or lighter shoes will cause the clutch to engage at a higher R.P.M.
- Centrifugal Clutch has less maintenance.
- It is not expensive.
- It does not need clutch pedal because it’s automatic.
- It helps to prevent the engine from stop running.
- Due to slipping and friction, there is a loss of power.
- It will transfer a high amount of power.
- It causes overheating problems.
- Its engagement and disengagements depend upon the speed of the driving shaft.
This type of clutch use fluid means the use of hydraulics to transmit the torque. According to their design, this clutch is subdivided into two types:-
It is a hydraulic unit that can be clutch in a semi or fully automatic mode.in this type of clutch, there is no mechanical connection between the driving member and the driven member.
A pump impeller is blotted on a driving member and engine a turbine runner is bolted on the driven member. (Gearbox).both the above unit is enclosed into single housing filled with a liquid. This liquid will act as the torque transmitted from the impeller to the turbine.driving member will starts rotating then the impeller rotates and then by the liquid by centrifugal action in the outward direction.
This liquid then enters the turbine runner and exerts a force on the runner then flows back into the pump impeller, thus complete the circuit.
So the fluid coupling is not suitable for normal gearboxes which are used nowadays and it will be used with automatic and semi-automatic gearboxes.
Hydraulic torque converter:
A hydraulic torque converter has the same principle as that of the electric transformer.
The main purpose of the torque converter is to engage the driving member to driven members and increase the torque of the driven members. These 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.
The difference of torque between impeller and turbine depends and upon these stationary guide vanes. the hydraulic torque converter serves the function of the clutch as well as the automatic gearbox.
In the electromagnetic clutch electromagnetism is used to exert a pressure force one pressure plate to make the clutch engage. In this type of clutch, the driving plate is attached to the electric coils.
When the electricity is provided into these coils then the plate work as the magnet and it attracts another plate. So both plates join when the electricity provides and the clutch is in engage position. When the driver cuts the electricity, this attraction force disappears, and the clutch is in the disengaged position.
They should not be used for high speeds that have speeds over 50 rpm otherwise damage to the clutch teeth occurs when trying to engage the clutch.
How it’s work: When current flows through the clutch coil, the coil becomes an electromagnet and produces a magnetic line of flux. This flux is then transferred through the small gap between the field and the rotor.
The rotor portion of the clutch becomes magnetized and sets up a magnetic loop, which attracts the armature teeth to the rotor teeth.
When current is removed from the clutch field, the armature is free to turn with the shaft spring hold the armature away from the rotor surface when power is released creating a small air gap and providing complete disengagement from input to output
Electrical hysteresis units have an extremely high torque range. Since these units can be controlled, they are ideal for testing applications where varying torque is required. Torque which is drag one is minimal that offers available torque range of any Electromagnetic applications.
Since all torque is transmitted magnetically there is no contact so no wear occurs to any of the torque transfer components providing for extremely long life.
When the current is applied it creates magnetic flux this passes into the rotor portion of the field.
The hysteresis disk physically passes through the rotor without touching it. These disks have the ability to become magnetized depending upon the strength of the flux this means as the rotor rotates, magnetic drag between the rotor and the hysteresis disk takes place causing rotation.
When current is removed from the clutch, the armature is free to turn and no relative force is transmitted between either member. Therefore the only torque sees the input and the output is bearing drag.
Here how the clutch works, when a DC voltage is applied to the Electromagnet coil a magnetic field is created.
The magnetic circuit passes through the clutch rotor and armature. The force is large enough to deflect the flat spring and the armature is pulled across a small air gap into the rotor face.
The friction between the rotor. When electrical power is removed from the coil the flat spring returns.
It is used in racing car engines, high powered engines where clutch disengagements require appreciable and tiresome drivers effort.
The power transmitted partly by clutch springs and remaining by the centrifugal action of an extra weight provided in the system.
In this type, springs are used instead of coil / helical springs. This type of clutch does not require any release levers as the spring itself acts as the series of levers.
Vacuum clutch linkage operated by engine Vacuum created during suction stroke. The vacuum clutch consists of a vacuum reservoir tank that is connected to the engine inlet manifold through a non-return valve.
The reservoir connected to a solenoid valve which is operated by battery and switch in the gear lever and Control valve attached to the vacuum cylinder consist of piston and plunger which further connected to release fork and release bearing.
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