Clutch mechanism unit 2

Automobile Unit-2, Basic principle of Clutch and Fundamentals related clutch mechanism

1. INTRODUCTION WHAT..? / WHY …?? / How ….???

2. Clutch & its Necessity Is an intermediate mechanism which is placed in b/w the flywheel and the gearbox. It enables the rotary motion of the shafts by friction mechanism to solve the following purposes Clutch remains in the engaged position and Allows flow of power from engine to the gearbox. Make possible to change the gears in the gearbox by engaging and disengaging the gearbox from the flywheel (Crank shaft). Disengagement of the clutch is required when the gear position is to be changed or when the vehicle needs to be kept in neutral position.

3. Requirements of efficient/good clutch Gradual engagement. Effortless operation. Better heat dissipation. Better vibration damping. Free from slipping. Should be capable of transmitted full or maximum torque/power. Should be in exact dynamic balancing at high speed. Should be smallest possible in size.

4. Clutch Parts and Operation Clutch parts Flywheel Friction disc / Clutch disc Pressure plate Pressure Springs Release mechanism Clutch disc pushed against flywheel with enough force Due to Friction, Disc will rotate with flywheel.

5. Clutch Disc It is also known as friction plate and possesses clutch facing on its both sides.

6. Facings are made of high friction materials such as Asbestos, Leather, Cork or Cotton fabric. The two facings are riveted on a steel plate. The clutch plate is mounted on an internally splined hub. The clutch plate houses 4 to 8 torsion springs to resist torsional shocks and vibrations.

7. Pressure Plate Pressure plate is round, cast iron plate with same diameter as the clutch disc. Its one side is machined smooth. This side presses the clutch disc facing area against the flywheel. Its another side is shaped to facilitate attachment of pressure springs and clutch release mechanisms.

8. Types of Clutches Positive clutches. Gradual engagement clutches. Frictional clutches Fluid flywheel / Fluid Coupling

9. Friction Clutches Transmission of power is through two rotating friction disc. Friction clutches are further divided into following two types;- Depending upon medium Dry clutch Wet clutch Depending upon type of friction plate Single plate Helical spring type Diaphragm spring type Multi plate Cone clutch Semi centrifugal clutch Centrifugal clutch Electromagnetic clutch

10. Working Principle of Friction Clutch

11. factors affect its torque transmitting ability Coefficient of Friction (µ) Axial Pressure, W The maximum value of W is limited about 100-120 N n allowable pressure is 130- 200kPa. Effective Mean Radius of contact surfaces, R The value of R can’t be increased beyond a certain max. value, which depends upon the space available.

12. Cone Clutch Contact surface are in the form of Cones. In the engaged position, the male cone is fully inside to the female cone. Spring is used to engage or disengage the male cone.

13. Cone Clutch Advantages The only advantage is that the normal force acting on the contact surface is large than the axial force as compare to plate clutch. Disadvantages If the angle of cone is smaller than about 20 o , the male cone tend to bind or join the female cone and it becomes difficult to disengage the clutch Slipping of male cone.

14. Single Plate Clutch - Helical Spring Type

15. Diaphragm Clutch Diaphragm spring replaces release levers and coil springs Diaphragm pivots off pivot rings when clutch pedal is depressed Advantages Requires less effort and takes up less space Spring pressure becomes greater as disc wears Well balanced

16. IMPORTANT QUESTIONS..?? Describe the function/purpose of following components (a). Clutch Disc (b). Pressure plate (c). Torsional Springs (d). Pressure Springs. Why is a clutch installed b/w the engine flywheel and transmission? List the various functions of the clutch. Discuss the design principles of a friction plate clutch. Which factors affect its torque transmitting ability? What type of clutch is used in case of motorcycles? Explain its construction and working in details. With a suitable sketch describe the working of a multiplate clutch. Differentiate b/w a dry clutch and a wet clutch.