Clutch assembly and types of clutch

                         Clutch Assembly

Need for Clutch:

•The clutch is located between the engine and the

  transmission.

•It provides a mechanical coupling between the engine’s

  flywheel and the transmission’s input shaft.

•All manual transmissions require the clutch to engage or

  disengage the transmission.

The clutch –

      -Allows the engine to idle while the vehicle is stopped

     -Allows for easy shifting between gears

Engages the transmission gradually (progressively) by allowing a certain amount of slippage between the transmission’s input shaft and the flywheel.

•Cover: a steel stamping or casting that houses the clutch components and attaches to the flywheel.

•Pressure plate: a cast iron plate that provides a pivot fulcrum for the diaphragm spring, a friction surface for the disc and a mounting surface for the drive straps.

•Diaphragm spring: a flat, spring-steel disc compressed between the cover and pressure plate that, when pushed by the release bearing, engages and disengages the clutch.

•Pivot ring: a steel ring attached to the clutch cover that provides a fulcrum for the diaphragm spring.

•Drive straps: flat, spring-steel strips that attach the pressure plate to the clutch cover and help lift the pressure plate away from the disc to disengage the clutch.

CLUTCH OPERATION:

                                     TYPES OF CLUTCH:

1.Friction Clutch :

•An axial clutch is one in which the mating frictional

 members are moved in a direction parallel to the shaft.

•It consist of a driving disc connected to the drive shaft and

 a driven disc connected to the driven shaft.

•A friction plate is attached to one of the members.

•Actuating spring keeps both the members in contact and

  power/motion is transmitted from one member to  the

  other.

•When the power of motion is to be interrupted the driven

  disc is moved axially creating a gap between the members

  as shown in the figure.

2.Multiple Plate Clutch :

  •Multiple plates instead single plate

  •Increases the friction surface

  •Increases the capacity clutch to transmit torque

  •Used in heavy commercial vehicles

  •If operated in an oil path – Wet clutch

3.Cone Clutch :

•Two cones covered in friction material

•When they are forced  apart, they rub against outer casing and lock them together thus engaging tow halves

•They are wedge clutch provides a positive drive when the external face of the male cone member engages with the internet face of recessed conical member.

•The facing is usually fitted to the female or recessed member in order to improve heat dissipation and durability.

•Normally cone clutch are used with epicyclic gear trains for a higher torque transmission.

•Off Road Vehicle, Racing Cars and Rallying cars 

4.Diaphragm Clutch :

• this type of diagram type springs are used instead of coil / helical

  springs.

•This type of clutch does not require any release levers as the spring

 itself acts as the series of levers.

•This type of springs do not have constant rate characteristics as in the

 case of coil springs and the pressure on the diaphragm springs

 increases until it is in flat position, thereafter decreases after passing

 this position.

•Hence the driver does not have to exert heavy pedal pressure to hold

 the clutch out of engagement compared to coil spring type.

•In coil spring type the spring pressure increases when the pedal is

 depressed to disengage the clutch and high pressure is required to

 keep the clutch in disengaged position.

5.Centrifugal Clutch:

 •Centrifugal clutch is a clutch that uses centrifugal force to connect

    two concentric shafts, with the driving shaft nested inside the driven

    shaft.

 •The input of the clutch is connected to the engine crankshaft while

    the output may drive a shaft, chain, or belt.

 •As engine revolutions per minute increase, weighted arms in the

   clutch swing outward and force the clutch to engage.

  •The most common types have friction pads or shoes radially

  mounted that engage the inside of the rim of a housing.

  •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

    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.

  •The weighted arms force these disks together and engage the clutch.