Friction in Clutch

Friction in Clutch

1. Mechanics of Machines UME 306 Friction in Clutch

2. Conical Pivot Bearing Trapezoidal or Truncated Conical Pivot Bearing Flat Collar Bearing Conical Collar Bearing Previous lecture

3. Friction Clutches Disc Clutches Cone Clutches Centrifugal Clutches Today’s lecture

4. 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. Clutch

5. WHAT IS CLUTCHES ? A  clutch  is a mechanical device that engages and disengages the power transmission , especially from driving shaft to driven shaft. 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 an engine or other power unit (the driving member) while the other shaft (the driven member) provides output power for work.

6. MAIN PARTS OF A 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.

7. TYPES OF CLUTCHES 1) Positive contact clutches jaw clutches toothed clutches 2 ) Friction clutches Disc clutches Cone clutches centrifugal clutches

8. 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 .

9. TYPES OF CLUTCHES Mechanical clutches 1)Positive contact clutches jaw clutches toothed clutches 2)Friction clutches Disc clutches Cone clutches centrifugal clutches

10. TYPES OF CLUTCHES Mechanical clutches 1)Positive contact clutches jaw clutches toothed clutches 2)Friction clutches Disc clutches Cone clutches centrifugal clutches

11. TYPES OF CLUTCHES Mechanical clutches 1)Positive contact clutches jaw clutches toothed clutches 2)Friction clutches Disc clutches Cone clutches centrifugal clutches

12. System Components Flywheel : Transfers engine power to the clutch Input shaft : Transfers power from clutch to the transmission Clutch Disk (clutch ) : Splined to input shaft; transfers power from engine to the input shaft Pressure Plate Assembly : Spring pressure tightly holds the clutch to the flywheel

13. Clutch Disc Types Rigid Flexible

14. Clutch linkage – Mechanical Linkage-type

15. 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.

16. 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. Transmission 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 inturn 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. Single plate clutch is show n fig.

17. Design of clutch plate

18. Single Plate Clutch W =total axial load R1 =External radius of clutch plate R2 =internal radius of the clutch plate P =intensity of pressure between contacting surfaces. µ =coefficient of friction between contacting surfaces

19. Single Plate Clutch Consider a elemental ring of radius ‘r’ and thickness δr on the contacting surface. therefore, Area of the ring on contacting surface is, Axial load on the ring is, δW = pressure×Area of the ring

20. Single Plate Clutch Frictional resistance offered by ring is, Frictional torque acting on the ring is,

21. Single Plate Clutch Torque transmitted by single plate clutch is obtained by considering following two assumptions (a)uniform pressure theory (b)uniform wear theory

22. Single Plate Clutch (a)uniform pressure theory: Assuming that the intensity of pressure over the entire contacting surface area is constant, Total torque transmitted by single plate clutch can be obtain by integrating Equation Then, p=constant

23. Single Plate Clutch (1)within limit R2 to R1 we [∵p=Constant] R 1 R 2

24. …….(A) Equation ( A ) gives the torque transmitted by single plate clutch due to friction considering uniform pressure theory.

25. Single Plate Clutch (b) Uniform Wear Theory In this theory, we are considering that wear which take place is uniform over the entire contacting surface i.e. P.r =constant P.r =C P=C/r …...(3)

26. Single Plate Clutch Axial load acting on the ring is δW =p 2π r δr δW =2 π C δ r …(4) Integrating above Equation(4) within limit we get, δW = (C/r) 2 π r δr

27. Single Plate Clutch We know that frictional torque acting on ring is,

28. Single Plate Clutch Torque transmitted by single plate clutch can be obtain by integrating the Equation (4 ) within the limit R2 to R1 we get, R 1 R 2 R 1 R 2

29. Single Plate Clutch This is the torque transmitted by single plate due to friction considering uniform wear theory.

30. Single Plate Clutch Power transmitted by single plate clutch is given by,

31. 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.

32. 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, hence 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. This type of clutch has been shown in Figure.

33. For multiplate clutch For uniform pressure theory, For uniform wear theory,

34. Multi plate Clutch Notes: In case of new clutch ,the intensity of pressure is uniform along the surface of clutch but in case of old clutch uniform theory is more correct. For single plate clutch normally both sides of the plate are effective .there for single plate clutch has two pairs of contacting surface i.e. n=2. In actual practice, usually the theory of uniform wear is used in analysis of clutch.

35. Intensity of pressure is maximum at the inner radius R2 of the friction or contact surface, Intensity of pressure is minimum at the inner radius R1 of the friction or contact surface,

36. In mutilate disc clutch no of disc on driving shaft no of disc on driven shaft So no. of pairs in contact,

37. Clutch plate

38. DIFFERENCE BETWEEN SINGLE AND MULTI-PLATE CLUTCHES :- The number of pairs of contacting surfaces in the single plate clutch is one or at the most, two. These are more number of contacting surfaces in the multi-disk clutch. As the number of contacting surfaces is increased, the torque transmitting capacity is also increased, other conditions being equal. In other words, for a given torque capacity, the size of the multi-plate clutch is smaller than that of the single plate clutch, resulting in compact construction.

39. The work done by friction force during engagement is converted into heat. More heat is generated in the multi-plate clutch due to increased number of contacting surface. Heat dissipation is a serious problem in the multi-plate clutch. Therefore, multi-plate clutches are wet clutches, while single plate clutches are dry. The coefficient of friction decreases due to cooling oil, thereby reducing the torque transmitting capacity of the multi-plate clutch. The coefficient of friction is high in dry single plate clutches. Single plate clutches are used in applications where large radial space is a available, such as trucks and cars. Multi-disk clutches are used in applications where compact construction is desirable, e.g., scooter and motorcycle.

40. Cone clutch α = semi-apex angle of the cone Only one pair of driving surfaces is possible, n =1 The maximum torque transmitted = T = μ Wr m cosec α

41. Advantages: It may be made in smaller size or require less actuating force compared with plate clutch Disadvantages: For small cone angle and exposure to dust and dirt tends to bind the two cones and it becomes difficult to disengage them.

42. Centrifugal clutch Centrifugal clutch Driving shaft Driven shaft Friction lining Total friction torque , T = n µ R (F-P) F=mrω 2 ω ω

43. Next Balancing Balancing of rotating masses Balancing of reciprocating masses

44. for you kind attention Contact details: Rohit Kumar Singla Email ID: [email protected]