Clutches

Chapter: 7

Clutches

Learning Objectives

While reading and after studying this chapter, you will be able to:

• Understand the functions of a clutch and list the various types of clutch. 

• Explain the working of a single plate clutch and derive an expression for the torque transmitted by the single plate clutch.

• Describe how the number of plates are calculated in the multiplate clutch.

• Dérive an expression for the frictional torque of a cone clutch based on uniform wear and uniform pressure theory.

• Explain the working of a centrifugal clutch

SYLLABUS

Friction clutches- Types - Single plate and multiplate clutches Cone clutch - Centrifugal clutch

INTRODUCTION

• A clutch is a mechanical device used to connect or disconnect the driven shaft from the driving shaft at the will of the operator while power is transmitted from driving to driven shaft.

• Clutches are widely used in automobiles. In an automobile clutch is a transmission device which is used to engage and disengage the power from the engine to the rest of the system. 

• For the above said reason, the clutch is located in between the engine and the transmission system. When the clutch is engaged to the engine, power is transmitted to the wheels. If it is disengaged the power is not transmitted to the rest of the system even though engine is running and hence the vehicle stops. Therefore for coupling the engine smoothly to the power transmission during starting from rest and gear shifting, clutch is used.

1. Principles of Operation of the Clutch

The clutch works on the principle of friction. When two friction surfaces are brought in contact with each other and pressed, they are united due to the friction between them. The friction between the two surfaces depends upon the area of the surfaces, pressure applied upon them and coefficient of friction of the surface materials. The principle of friction clutch is understood with the help of Fig.7.1.

The two surfaces can be separated and brought into contact when required. Ope surface is considered as driving member and the other as driven member. The driving member is kept rotating. When the driven member is brought in contact to the driving member, it also starts rotating. When the driven member is separated from the driving member it does not revolve. This is the principle behind the operation of the clutch.

2. Types of Friction Clutches

From the subject point of view, friction clutches are classified as shown in Fig.7.2,