UNIT - 2 Transmission System = Clutch CHAPTER - 3 = Gear-boxs CHAPTER - 4 @ Automatic Transmission System‘axe 1294 enuarayic @aup agny anbioy («1 BAUUP SSDIYDIOH (2) adhy ‘Ayoojanqurssuog (0) adhy uoluuru) pue jeg (q) adfy ss019 (2) Ulf essen sJowanuog nbs} aynesp Ky ‘Aquiesse Yo} pus yey. x0q se8B ay9f01d3 Aiquiasse x0q sea8 ysewosypukg vaed pue picuajos xOq, veboyokods «|| yea6 yssu quersuoy Wun jasyys 524. | | 2oeuee8 usow Suis “ypinjo ojsuBewos 93/3 din wnngen, oI aynespAH, ypinjo suds pue Eq ypjnjo annisog, yon wBeiyderq ypinp reBnynuad weg {ypiny feBnyzquag reusayyy (1 feweps (1) ysinjp suo (0) " yginpp wonou requazeyig pue yeys 5 r x0q 1885 saunieno | [Tact ie | 4ainig 1 INZLSAS NOISSINSNVYL12 (tend Ba Introduction of Clutch Clutches are used whenever the ability to limit the transmission of power or motion needs to be controlled either in amount or overtime (e.g. electric screwdrivers limit how much tordue is transmitted through use of a clutch; clutches control whether automobiles transmit engine power to the wheels). In the simplest application clutches are employed in devices which have two rotating 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 to be done. In a drill for instance, one shaft is driven by a motor and the other drives a drill chuck. ‘The clutch connects the two shafts so that they may be locked together and spin at the same speed (engaged), locked together but spinning at different speeds (slipping), or unlocked and spinning at different speeds (disengaged). .s. 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. “The automotive drive train or powertrain carries power from the engine to the drive wheels. In-vehieles with a manual transitission or manual transaxle, the power flows through a clutch. Th device couples and uncouples the manual transmission or transaxle and the engine. The clutch is usually operated by'the driver's foot. Some clutches have a power-assist device to reduce diver tffort, Various électronie devices may be used so that the clutch operates automatically [4].(a) + [Er-2 —(-[Avronosie Enonmenna] axle half shaft Flywheel Clutch 5-speed manual transmission Left axle & half shaft assembly ig) 2.1! Longitudinal engine with front ‘Showing the eluteh and five-speed manual t Fig. 2.1 shows the clutch loci 2.2 shows the clutch location in affront-whcel-drive car with a transversely-mounted engine. es Right Clutch Manual half shaft transaxle Left half shaft Fig: 2:2 :/Cluteh location between the transverse engine ‘and manual transaxle in front-wheel-drive car [4],[Unrr-2) ++ (2:3) The functions of clutch are as follows [4] Ik 2 “a _Todisange the transminion/gear box grom engine by prusing the clutch down. This allows the driver to select the proper gear (Ist, IInd. IIrd, IVth, Vth, reverse or neutral) for the operating condition. White engaging (clutgh pedal moving up), the elutch slips momentarily. This provides smooth engagement and lessens the shock on gears, shafts, and other drive-train parts. As the engine develops enough torque to overcome the inertia of the vehicle. the driver wheels turn and the vehicle begins to move. = yn. All slipping has stopped. EI Requi rements of a Clutch The requirements of a clutch are as follows [3] : Torque transmission : Clutch should be able to transmit maximum torque of the engine. Gradual engagement : Clutch should engage gradually to avoid sudden jerks. Heat dissipation : It should be able to dissipate large amount of heat which is generated during the clutch operation due to friction. Dynamic balancing : It should be dynamically balanced particularly in the case of high speed engine. Vibration damping : It should have suitable mechanism to damp vibrations and to eliminate noise produced during power transmission. Size : It should be as small as possible. Free pedal play : In order to reduce effective clamping load on the carbon thrust bearing and wear, it should have free pedal play. Easy in operation : It should be easy to operate with little exertion. Lightness : The driven member of clutch should be made as light as possible so that it will not continue to rotate for any length of time after the clutch has been disengaged.Ga\- Hi35 Main Parts of a Clutch | It consist of — (a) adriving member : (b) adriven member: and {c) an operating member. Driving member has a flywheel which is mounted onthe engine crankshaft. A disc is bolted to Ay wheel which is known as pressure plate or driving dise. The driven member is a disc called clutch plate. This plate can slide freely to and from the eS a ean pes of Fri Materials Various materials have been used for the disc friction facings, including asbestos in the past. Modern clutches typically use a compound organic resin with copper wire facing or a ceramic material, There are three types of friction materials/ linings, namely : @ Woven type: Gi) Moulded type; Gil) Mill board type. ()_— Moven type : Made impregnating a cloth with certain binders or by of asbestos fiber, sometimes of brass wire. The woven sheets treated with a binding solution are baked and rolled. (ii) Moulded type : Made from o ind starch or any other suitable binding materials. Then, they heated to a certain temperature for moulding in dies under pressure. The only disadvantage of this type friction material is that each clutch facing has to be moulded separately. (ii) Mill board type : Include asbestos sheets treated with different type of impregnats. They are cheap as well as quite satisfactory in operation. ‘The most common friction materials and their coefficient of friction are as follows :| [friction . Leather 0.27 Cork’ 0.32 Fabric 0.40 le - PN? Asbestos 0.20 — Reybestos and Ferodo _| 0.20 Good clutch lini tics : ' "heen atin” od . Some types of clutches used in vehicles are given below : \Deziriationclutchay 7¢ Centrifugal clutch; (i) Tapered finger type; (ii) Crown spring type. Se 6. Hydraulic clutch; 7 Blectro-magnetic clutch; <7 9 Overrunning clutch or freewheel unit. 1. Friction clutch : It may be - (i) Single-plate clutch; oSi k \ k (2S) stag} oe se] ai Mati > Wet; ~ Dr. fe clutch; Cone clutch: ~ External; = Internal. 1 is operated in an oil batch whereas used in conjunetion with, or as part Jean and gives smoother Multi-plate clutch can be cither wet or dry, A wet elute dry clutch does not use oil. Oil immersed clutches are, however of automatic transmission. This cooling lubricating fuid keeps surfaces o 7 performance and longer life. Wet clutches, however, tend to lose some energy to the liquid. Since the surfaces of a wet clutch can be slippery, stacking multiple clutch disks can compensate from the lower coelticient of friction and so eliminate slippage under power when fully engaged. “Avin brakes a wie range of clutches ae in use-wherein they vary in their are in use thei working principle as well the method of actuation and application of normal forces. The discussion here will be limited to mechanical type friction clutches or more specifically to the plate or disc clutches also knewn as axial clutches. Frictional Contact axial or Dise Clutches: Anaxial elutch is one in which the mating frie to the shaft. Clutch consists ofa driving dise connected to t to the driven shaft. A friction plate is attached to the members in contact and power/motion is transmi sional members are moved in a direction parallel he drive shaft and a driven dise connected ‘one of the members. Actuating spring keeps both jtted from one member to the other. (Single Plate Clutch: of the engine. dl 1. When. engaged position, the clutch plate remains gripped between flywheel and pressure plate. les of clutch plate, P Due ect es, the clutch plate revolves with engine flywheel. Therefore, clutch transmits engine powerto clutch shafi. Clutch shaft is connected to transmission (or gear box) of automobile. Thus, clutch transmits power from engine to transmission system which in tum rotates wheels of engine. ‘mounted on the splines of the clutch sl When the clutch plate is to be disengaged, the clutch pedal is pressed. Because of this pressure nse mes = ea a plate is disengaged from flywheel. Thus, clutch shaft stops rotating ‘gine Ny wheel is rotating. In this positi d : peter ing. In this position, power does not reach the wheels and vehicle also Single plate clutch is shown in fig.[canta Vso4acy ere Cluten Flywheel Spring Clutch Pedal Fulcrum Pin Bearing y rN clutch Engine } Shaft ae Pressure Plate Clutch Plate Friction Lining Fig. 1.12 Single Plate Clutch |3].) Pressure plate Flywheel) ra foun shaft > Release > Lever plate |_| Release lever ified diagram showing the working of Siigle plate éluteh.)Advantages: ‘+The operating load is practically uniform and constant on th driven plate. Bs ‘thas a compact design, which results in smaller clutch housing. x Release lever is not required, since the diaphragm itself acts as a series of levers. It ds. (ii) Multi-plate clutch: Multi-plate clutch c tes 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 fricti ulti-plate clutch can Therefore, itis used in reavy motor vehicles which fi The eluteh altematively fitted with engine shaft and the shaft of gear box. These plate are and they assembled in a drum. One plate slides es on spines provided on pressure plate, Thus, hheel and the other on splines of pressure plate. and other has outer splines. h engine power. int each alternate plate slides in grooves on the flywt If we take two consecutive plates, then one has inner the pressure plate moves back against the force of col spring, then the elutch 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. This type of clutch has been shown in fig. 2.6.(a Clutch 3 Flywheel Pedal Pressure we Plate © a Fulcrum : iT Pin : Spring 5 <—Bearing 1 Clutch Shaft Friction Lining Clutch Plates (Fig: 2.6 2) Multicplate|Cluten [312] Flywheel Pressure plate Friction disc (Driven plate)2.10) s'c[Unrr-2 (iii) Cone Clutch: 2.8 shows the cone clutch Female Cone Bo Bearing Friction Surface Fig, 2.8: The Cone Clutch (3). h. However, instead of mating” two spinning discs, the cone clutch uses transmit torque by friction. The engine shaft consists of female cone, The male cone is mounted on the splined clutch shaft. It has the friction surfaces on the conical portion. The male cone can slide on the clutch shaft. When the clutch is engaged the friction surfaces of the male cone are in contact with that of the female cone duc to the force of spring. When the clutch pedal is pressed, the male cone slides against the spring force and the clutch is disengaged. Advantages: ‘The cone clutch e size due to the wedging action and increased surface area, Cone clutches are generally now only used in low peripheral speed applications although they were ance common in automobiles and other combustion engine transmissions. Disadvantages: © 1 , the male cone tendsto blind in the female cone gage the clutch, Py : surfaces ae considerable amount of axial, movement of the mal cult to allow. _ ‘Thoyare usually now confined to venspeaist transmissions in sacing rallying, orn extreme offrroad vehieles, although they are common in power Boats. This is beeause the clutch does not pve tobe pushed inal he way and the gears willbe changed quiker. Small eone clutches are aaa in synchronizer mectanisms in manual transmissions(Ryn 2, Centrifugal Chutet: A contritiygal eluteh i used in sone vehicles (eye: Mopeds) and also in other applications Where the speed of the engite defines the state of the clutch, for example, ina chainsaw, This clutch shoes attached to the driven shaft, rotating inside a clutch bell are held inwards by springs until centrifugal force overcomes the spring tension and the shoe(s) make contact with the bell, driving the output, In the case of a chainsaw this allows the chain to remain stationary whilst the engine is idling: once the throttle is pressed and the engine speed rises, the centrifugal clutch engages nd the cutting chain moves attached to the output shalt, The shoes Torsional damper ‘spring Adjustment nut Pressure spring Retractor sping Input splined shaft Release plate * Release bearing Release lever Eye bolt pin Eye bolt and spherical adjustment nut Knife edge link Pressure plate 2098 strust Figs 292 \Centrifugal Clutehy(22) +(e} —______———+Ter aera] Disergaged ip Fully engages oh ae phase ofr ‘Centrifugal Farce 4 i range 0 FH 1000 1500 2000 2500 2000 Engine speed, RPM ¢ output may drive th a shafi, chain, or belt. As engine revolutions per minute increase. weighted arms in the clutch swing outward and force the clutch to engage. ion pads or 5 . On the center shaft there are an assorted number of extension springs, which connect to a clutch shoe. When the center shaft spins fast enough, the springs extend causing the clutch shoes to engage the friction face. It can be compared to a drum brake in reverse. This type can be found on most home built karts, lawn and garden equipment, fuel-powered model cars and low power chainsaws. Another type used in racing karts has friction and clutch discs stacked together like a motorcycle clutch. The weighted arms force these discs together and-engage the clutch. When the engine reaches a certain speed, the clutch activates, working somewhat like a continuously. As the load increases, the speed drops. disengaging the clutch, letting the speed rise again and reengaging the clutch, If tuned properly, the clutch will tend to keep the speed at or near the torque peak of the engine. This 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. Centrifugal clutches are often used in mopeds, under-bones, lawnmowers. go-karts, chainsaws, and mini bikes to- se Keep the internal combustion engine from stalling when the output shaft is slowed or stopped abruptly; sx Disengage loads when starting and idling. Thomas Fogarty, who also invented the balloon catheter, is credited with inventing a centrifugal clutch in the 1940s. Automobiles were being manufactured with centrifugal clutches as early as 1936.ee * (218 Advantages: % No kind of control mechanism is necessary % It is cheaper than other clutches, Ye Prevents the internal combustion engine from stalling when the output'shaft is slowed oF stopped abruptly therefore decreases the engine braking force. Disadvantages: % Since it involves friction and slipping between driver and driven parts there is loss of power. x Asit involves Slipping, therefore it is not desirable in cases where there is heavy load or in high torque requirements, 3. Semi Centrifugal Clutch: It uses centrifugal force as well as spring force for keeping it in engaged position. The. springs are designed to transmit the torque-at normal speeds, while the centrifugal force assists in Torque transmission at higher sp ds. Fig. 2.11 shows a semi-centrifugal clutch. It consists three hinged and weighted levers and three clutch springs alternately arranged at equal spaces on the pressure plate. At normal speeds, when the power transmission is low, the springs keeps the clutch engaged, the weighted levers do not have any pressure on the pressure plate. Bobweight Needle race pivot Ring gear Pivot eye Pivot bolt assembly Flywheel tolletS__ Torsional Release damper spring = Release bearing assembly Input splined Release Porked bearing lever sleeve Crankshaft Driven plate flange Pressure splined hub spring Pressure plate Cover Spigot beating plate pressing linings(254) + [Ome2 (UTOMOBILIE ENGINEERING] At high speed, when the power transmission is high, the weights fly off and the levers also exert pressure on the plate, keeping the clutch firmly engaged. When the speed decreases, the weights fall and the levers do not exert any pressure on the pressure plate. Only the spring pressure is exerted on the pressure plate which is sufficient to keep the clutch engaged. This type of clutch uses lighter pressure plate springs for a given torque carrying capacity, so that the engagement of the clutch in the lower speed range becomes possible. The centrifugal force supplements the necessary extra clamping thrust at higher speeds. Offset bob weights are attached to the release levers at their outer ends, allowing levers to be centrifugally out of balance. The centrifugal force causes the pressure plate to force against the driven plate, adding extra clamping load. Although the thrust due to the clamping springs is constant, the movement due to the centrifugal force varies as the square of the speed (fig. 2.12). Therefore, the reserve factor for the thrust spring can be reduced to 1.] compared to 1.4-1.5 for a conventional helical coil spring clutch unit. Consequently, centrifugal clutch can be used for heavy duty applications requiring transmission of greater torque loads. Centrifugal fe OD thrust 83 140] T ‘of 25, 120 fs a2 % 5 100 ie 8 = @& 80) 8 SE 60 5 28 5 SE 40 8 gs Ex 20) 0 0 1000 2000 3000 4000 Engine speed, RPM ntritugal clutch characte 4. Electro-Magnetic Clutch: Blectro-magnetic clutches operate electrically, but transmit torque mechanically. This is why they used to be referred to as electro-mechanical clutches. Over the years, EM became known as mn method versus physical electromagnetic versus electro mechanical, referring more about their actua hes started becoming popular over 60 years ago, the variety of applications operation. Since the clu and clutch designs has increased dramatically, but the basic operation remains the same. Single-face clutches make up approximately 90% of all electromagnetic clutch sales.Engagement: When the clutch is Tequired to actuate, current flows through the electromagnet, which produces a magnetic fi of the clutch becomes magnetized and sets up a mature is pulled against the rotor and a frictional ly short time, the load is accelerated to match the thereby engaging the armature and the output hub of the clutch, In most instances, the rotor is constantly rotating with the input all the time, eld. The rotor portion magnetic loop that attracts the armature. The at force is generated at contact. Within a relative speed of the rotor, Disengagement: When current is removed from the clutch, the armat most designs, springs hold the armature away creating a small air gap. Mure is free to tum with the shaft. In from the rotor surface when power is released, Cycling: Cycling is achieved by interrupting the current through the electromagnet, Slippage normally occurs only during acceleration, Whensthe clutch is fully engaged, there is no relative slip, assuming the clutch is sized properly, and thus torque transfer is 100% efficient. Advantages and disadvantages: The electromagnetic clutch is most suitable for remote operation since no linkages are Fequired to control its engagement. It has fast, smooth operation. However, dissipates as heat in the electromagnetic actuator every time the clutch is eng; risk of overheating. Consequently the maximum operating temperature of the by the temperature rating of the insulation of the electromagnet, Another disadvantage is higher initial cost. because energy aged, there is a clutch is limited This is a major limitation.| (26) s+ (Umr-2) ‘Avrowomme Exemaeamna This type of clutch is used in some Renault cars. 5. Vacuum Clutch : The vacuum clutch is operated by the vacuum existing in the engine manifold. Fi the vacuum clutch mechanism. It consists ofa vacuum cylinder with piston, solenoid operated value, reservoir and a non-return value. ‘The reservoir is connected to the engine manifold through a non-return valve. Vacuum cylinder is connected to the reservoir through solenoid operated valve. The solenoid is operated from the battery and the circuit incorporates a switch which is placed in the gear lever. The switch is operated when the driver holds the lever to change gears. When the throttle in wide opened, the pressure in the inlet manifold increases, due to which the non-return valve closes, isolating the reservoir from the manifold. Thus, a vacuum exists in the reservoir all the time. In the normal operation, the switch in the gear lever remains open and the solenoid operated valve remains in its bottom position. In this position atmospheric pressure acts on both the side of the position of the vacuum cylinder, because the vacuum cylinder is open to the atmosphere through a vent, When the driver hold the lever to change the gear, the switch is closed, energizing the solenoid which pulls the valve up. This connects one side of vacuum cylinder to the reservoir. Due to the difference of pressure on the vacuum cylinder position, it moves. ‘This movement of the position is transmitted by a linkage to the clutch, causing it to disengage. When the driver is not operating the gear lever, the switch is open and the clutch remains engaged due to the force of springs. ‘Switch In Gear Balte Inlet iN Lever Marys Solenoid Vent Non-Return E Vacuum Valve c Cylinder | To Clutch = Ve Reservoir > feraulic Cluteh Hydraulic clutch has some ir ly fas some working pr insteat iS roce: 7 ves SS instead a ts of a cylinder with piston. * Baz] g.2.15 show : of vacuum, oil is us S the mechanism of a hydraulic elute. It eon Iaewir nates rontrol valve, pump, ac " con Pump, accumulator and oil reservoir, ‘The piston is connected to the clutch by @ ; clutch by @ linkag The pump is operat y ine it 1 perated by the engine itself. The oil from the reservoir is pumped into the tank. The tank is connected to the cyli 7 cylinder through F electrically controlled by a switch in the gear ae the control valve. The control valve is When the dri ee ee holds the gear lever to change the gears, the switch is operated to ofsn the ae ree the oil under pressure to the cylinder. Due to oil pressure, the piston moves causing the clutch to be disengaged. As soon as the driver leaves the gear lever. the switch js open which closes the control valve and the clutch is en: Accumulator reservoir — SF To clutch Control valve Cylinder Fig, 1.15: Mechanism ofa hydraulic clutch. Prouble-Diagnosis of Clutch Trouble-diagnosis of clutch is given below (2): S.No. “Complaint Possible Cause Check or Correction 1. | Clutchslips (ie, when | (i) Oilon the lining () Replace the fining and | the cluich is engaged, there is a lack of firm contact between the flywheel pressure plate ‘and driven plate. because of leaks in engine seal or gear box. (ji) Too small a clearance of clutch. (iii) Worn out facing. (iv) Weak clutch springs. correct leaks. (ii) Adjust the clearance to the required back- lash of pedal. (ii) Install a new friction plate. (iv) Install a new set of |__ springs. | xERIE hub of the friction plate binds on the clutch shaft.) 2. | Chuch fails to (Excessive clutch disengage clearance. Gi) Friction plate not ' Do ane = fros they mene Eesy. | se : | Gi) Replace The Seep on Friction plate. inated REICH ; - foes |G) Fase the sw iuich grabs (e., the | (i) Scored comtact suriaces @) Face “3 50 of flywheel or pressure plate warped. (ii) Warped friction plete. (iii) Release levers not | evenly placed. Below is given the comparative clutch data of some Indien au: Comparative Clutch Data of some Indian Automobiles | a “S.No. Vehicle make “Type of clutch ‘ 1, | Ambassador | Single dry plate i 2._| Fiat 1100 Single dry plate i 3.__| Prensier Padmini Single dry plate 4. Fiat Uno | Single dry plate = 4 5. | Maruti 800 | Dry single disc type = q 6. | Jeep CI, C34 WD | Single dry plate (Mahindra & Mahindra) 7. | Tata Mobile — 201 pick and | Single dry plate . friction Tata 608 8._| Ashok Leyland Comet Diaphragm type 9. | Dodge (passenger) Single dry plate Forgo Model 10. | Swaraj Mazda | Single dry plate (hydraulically operated) 11. | Ford F516 C Truck Single dry plate | (hydraulically operated) |[_ 12. | Royal Enfield, Bullet Multiplate 13, | Yamaha RX-100 Wet multiple disc type [ 14. | Rajdoot 175 c.c. Wet multiple dise type 15. [LML Vespa. Wet multiplate 16. | Luna ‘Automatic centrifugal eluteh toteQL What isa clutch ? Q.2 What are the functions of a clutch ? Q.3 Explain briefly the principle of operation of a clutch. Q.4 Why is clutch placed between the flywheel and transmission ? Q.5 State the purpose of the followit @ Driven plate i) Pressure plate : (iil) Torsional springs (iv) Coil spring (v) Clutch disc. Q.6 Describe briefly the various types of friction materials linings used in clutches. Q.7 What are the properties of a good clutch lining ?_ Q.8 How are clutches classified ? Q.9 Explain the working of a cone clutch. Q.10 Describe briefly with a neat sketch the construction and working oi a single plate clutch. . Q.11 Differentiate between () Single and multiplate clutches , and (i) Dry and wet clutch. Q.12 Give the working of a diaphargm spring type single plate clutch, Q.13 What are the advantages of a diaphragm spring type single plate clutch, Q.14 Wit the help of a neat sketch explain the construction and worki ing of a multiplate clutch. a amp Q.15 Describe briefly the parts of a plate clutch. ooo