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CLUTCHPRESENTATIONBY ONKAR NATH1215040037

WHY DO WE NEED CLUTCHClutches are useful in devices with two rotating shafts. In these devices, one of the shafts is typically driven by a motor or pulley, and the other shaft is driving another device. In a drill, for instance, one shaft is driven by a motor and the other is driving a drill chuck. The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds.

• In a car, you need a clutch because the engine spins all the time and the car wheels don't. In order for a car to stop without killing the engine, the wheels need to be disconnected from the engine somehow. The clutch allows us to smoothly engage a spinning engine to a non-spinning transmission by controlling the slippage between them. To understand how a clutch works, it helps to know a little bit about friction.

CLUTCH INTRODUCTION• A clutch is a mechanical device that provides for

the transmission of power (and therefore usually motion) from one component (the driving member) to another (the driven member) when engaged, but can be disengaged.

• Clutches are used whenever the transmission of power or motion must be controlled either in amount or over time (e.g., electric screwdrivers limit how much torque is transmitted through use of a clutch; clutches control whether automobiles transmit engine power to the wheels).

• In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). In these devices, one shaft is typically attached to a motor or other power unit (the driving member) while the other shaft (the driven member) provides output power for work. While typically the motions involved are rotary, linear clutches are also possible

• Clutch is used to engage or disengage the engine to the transmission or gear box.

• When the clutch is in engaged position, the engine power or rotary motion of engine crankshaft is transmitted to gear box and then to wheels.When clutch is disengaged, the engine power does not reach to gear box (and to wheels) although engine is running. Clutch is also used to allow shifting or changing of gears when vehicle is running. For shifting gears, clutch is first disengaged then gear is shifted and then clutch is engaged. Clutch has to be disengaged to stop the vehicle and also at the time of idling.

PRINCIPLE OF CLUTCH• It operates on the principle of friction. When two

surfaces are brought in contact and are held against each other due to friction between them, they can be used to transmit power. If one is rotated, then other also rotates. One surface is connected to engine and other to the transmission system of automobile. Thus, clutch is nothing but a combination of two friction surfaces.

MAIN PARTS OF CLUTCH• It consists of • (a) a driving member, • (b) a driven member, and • (c) an operating member.

• Driving member has a flywheel which is mounted on the engine crankshaft. A disc is bolted to flywheel which is known as pressure plate or driving disc.

• The driven member is a disc called clutch plate. This plate can slide freely to and fro on the clutch shaft.

• The operating member consists of a pedal or lever which can be pressed to disengaged the driving and driven plate.

TYPES OF CLUTCHSome types of clutches used in vehicles are given below : • (a) Friction Clutch : It may be (i) single plate clutch, (ii)

multi-plate clutch, or (iii) cone clutch. Multi-plate clutch can be either wet or dry. A wet clutch is operated in an oil batch whereas a dry clutch does not use oil.

(b) Centrifugal clutch. (c) Semi-centrifugal clutch. (d) Hydraulic clutch. (e) Positive clutch. (f) Vacuum clutch. (g) Electromagnetic clutch.

FRICTION CLUTCH • The vast majority of clutches ultimately

rely on frictional forces for their operation. The purpose of friction clutches is to connect a moving member to another that is moving at a different speed or stationary, often to synchronize the speeds, and/or to transmit power. Usually, as little slippage (difference in speeds) as possible between the two members is desired.

TYPES OF FRICTION CLUTCH

I. single plate clutch

II. multi-plate clutch or (iii) cone clutch. Multi-plate clutch can be either wet or dry. A wet clutch is operated in an oil batch whereas a dry clutch does not use oil.

SINGLE PLATE CLUTCH• A single plate is commonly used in cars

and light vehicles. It has only one clutch plate which is mounted on the splines of the clutch shaft. A flywheel is mounted on the crankshaft of the engine. A pressure plate is connected to the flywheel through the bolts and clutch springs. It is free to slide on the clutch shaft with the movement of clutch pedal. When clutch is in engaged position, the clutch plate remains gripped between flywheel and pressure plate. Friction linings are provided on both the sides of clutch plate. On one side clutch plate is in touch with flywheel and on other side with pressure

• plate. Due to friction on both sides, the clutch plate revolves with engine flywheel. Therefore, clutch transmits engine power to clutch shaft. Clutch shaft is connected to transmission (or gear box) of automobile. Thus, clutch transmits power from engine to transmission system which intern rotates wheels of engine.

• When the clutch plate is to be disengaged, the clutch pedal is pressed. Because of this pressure plate moves back and clutch plate is disengaged from flywheel. Thus, clutch shaft stops rotating even if engine flywheel is rotating. In this position, power does not reach the wheels and vehicle also stops running.

WORKING OF SINGLE PLATE CLUTCH• Working: The diagram shows the pressure plate pulled back by the release levers against the compression springs; so that the friction lining on the clutch plate are free of wheel rotates without driving the clutch plate and hence the shaft.• When the pressure of the thrust race is released the compression springs are free to move the pressure plate to the left bringing it in contact with the clutch plate.

• The pressure plate moves to the left, sliding the clutch

plate on its splined hub, along the driven shaft until the friction touches the flywheel .

• The compression springs now cause the lining to be gripped between the pressure plate and the flywheel

and pressure plate causes the clutch plate to revolve, tuning the driven shaft.

What is multiplane clutch• A multiple plate clutch is a type of

clutch system where multiple driven and drive plates are used in order to make up for torque loss due to slippage. This slippage is usually caused by a fluid that the plates are immersed in for cooling, cleaning and lubrication. This type of clutch system is commonly referred to as a wet clutch system. The type of arrangement is what is found in the automatic transmission in your car. This clutch system allows gears to be shifted up and/or down, without interrupting the power flow through the transmission, by lifting the accelerator.

Multi Plate Clutch• A multi-plate clutch has more than one driven plate.

Although this type of clutch has been widely used on cars up to about 1930, the several advantages of the single-plate clutch, specifically its ability to completely disengage the drive has caused a very rare use of a multi-plate unit as a main transmission clutch installed between the engine and gear box. However, a multi-plate type of clutch finds a use in automatic gearboxes. In these gearboxes, a number of clutches hold the various gear elements, and as the clutch diameter in these units is limited, a multi-plate clutch is suitable.

MULTIPLATE CLUTCH• Multi-plate clutch consists of more than

one clutch plates contrary to single plate clutch which consists of only one plate. Friction surfaces are made in case of multi-plate clutch. Due to increased number of friction surfaces, a multi-plate clutch can transmit large torque. Therefore, it is used in racing cars and heavy motor vehicles witch have high engine power. The clutch plates are alternatively fitted with engine shaft and the shaft of gear box. He plates are firmly held by the force of coil springs and they assembled in a drum.

• One plate slides in the grooves on the flywheel and the next plate slides on spines provided on pressure plate. Thus, each alternate plate slides in grooves on the flywheel and the other on splines of pressure plate. If we take two consecutive plates, then one has inner and other has outer splines.

• When the clutch pedal is pressed, the pressure plate moves back against the force of coil spring, hen the clutch plates are disengaged and engine flywheel and gear box are decoupled. However, when clutch pedal is not pressed the clutch remain in engaged position and the power can be transmitted from engine flywheel to the gear box.

ADVANTAGE• The main purpose for a wet multi-plate clutch is

increased power transmission capability in a compact size. As a side effect, multi-plate wet clutches generally have very good progressive engagement “feel”. This is why they are used as crane hoist clutches, tracked vehicle steering clutches, and heavy machine tool drives, apart from motorcycles.

• Wet clutches are designed for moderate slipping, partly due to the cooling effect of the oil, and partly due to the hydrodynamic effects present preventing shoe contact. Properly maintained, a wet clutch should last many times longer than a dry single-plate clutch under similar service conditions

Multi-plate Spring type clutch• Illustrates the layout of a multi-plate

spring type clutch, fitted on early motor cars. A cover, bolted to the flywheel, engages by means of slots with a series of lugs on the outer plates. These steel plates may be plain or fitted with cork or friction material inserts and act on inner plates, splined to a hub. Thrust springs push the plates together to form a drive.

• For the clutch disengagement, the end plate is withdrawn to compress the springs and release the other plates. In this arrangement it is difficult to ensure the disengagement of all plates. To overcome this problem the plates are either dished or fitted with small springs to push the plates apart.Generally wet type clutch is used in automatic gearboxes, and is operated by a piston governed by hydraulic pressure. Sintered bronze plates of partially fusing powdered bronze or compressed paper are used in many designs. The porous surface of this plate traps the oil, to provide long life and smooth operation.

Multi-Plate Diaphragm Type Clutch• These clutches basically have drive and

driven plates. The drive plates are not allowed to rotate independently by using interlocking lugs and slots, which do not permit relative rotational spin, but axial movement. The driven plates are mounted on the internally splined hubs, which splines on the gearbox spigot shaft (Fig. 24.17).A dished annular disc forms the diaphragm spring, the inner portion of which is radially slotted and the outer ends are enlarged with a circular hole to prevent stress concentration during disengagement. These radial slots divide the disc into number of release levers

• During operation, due to engagement and disengagement of the clutch, the diaphragm cone angle changes continuously as wear occurs. In order to accommodate the change, the diaphragm pivots and rolls about the fulcrum rings. During engagement of the clutch the diaphragm bears against the outer ring, and during disengagement the reaction load is taken by the inner ring. As the friction linings wear, the spring diaphragm becomes more dished so that a larger axial clamping load is applied initially. As the linings wear increases, the distance between the cover pressing and pressure plate become excessive, so that the axial thrust begins to decline.