22 February 2016

What is Clutche?

The clutch is a mechanical device, which is used to connect and disconnect the source of power from remaining parts of the power transmission system.

Clutch engaged
Clutch disengaged

                                Clutch Disengaged                                                                                     Clutch Engaged   

Clutch transmits engine power to the gearbox and allows the transmission to be interrupted while a gear is selected to move off from a stationary position or when gears are changed while the car is moving.

one of the shafts is typically driven by a motor or pulley, and the other shaft drives another device. one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so that they can either be locked together and spin at the same speed or be decoupled and spin at different speeds.

In a car, a clutch is necessary because the engine spins all the time, but the car wheels don't. In order for a car to stop without killing the engine, the wheels need to be disconnected from the engine somehow. The clutch allows us to smoothly engage a spinning engine to a non-spinning transmission by controlling the slippage between them.

Clutch disc

The clutch has these three parts sandwiched together creating friction and syncing the engine and the wheels(through gearbox).
To represent the engine we have the flywheel which is attached to the crank and it moves with the engine.
  • The clutch disc
Between the flywheel and the pressure plate is the clutch disc. 
The clutch disc has friction surfaces similar to a brake pad on both sides that make or break contact with the metal flywheel and pressure plate surfaces, allowing for smooth engagement and disengagement.
  • The Pressure Plate
When the clutch pedal is depressed, the pressure plate releases, allowing itself and the flywheel to spin independently of the disc, which prevents torque from being transmitted from the engine to the gearbox. Generally made of cast iron or steel, the pressure plate uses a diaphragm-type spring to apply force against the disc once engaged, which is fastened to the assembly by a series of straps.
  • Throwout Bearings
The throwout bearing sits against the pressure plate in either a push-style or pull-style arrangement that compresses the diaphragm and releases the disc when the clutch pedal is depressed. Once force is applied, the diaphragm releases tension, allowing the disc to spin independently of the assembly.
Simply adding additional clutch plates will make the system engage much faster and more efficiently the problem is that the outer pads will wear out fast.

Mainly clutches are divided into 2 parts:

  1. Friction clutches and
  2. Fluid flywheel

Friction clutches:

These clutches works on the principle of friction exist in between two rotating shafts when they come in contact with each other.

Fluid flywheel:

Fluid flywheel clutches works on transfer of energy from one rotor to the other by means of some fluid.

Types of friction clutches:

  1. Cone clutch
  2. Single plate clutch
  3. Multi-plate clutch
  4. Semi-centrifugal clutch
  5. Centrifugal clutch
  6. Hydraulic  clutches
  7. Electromagnetic clutches
1. Cone clutch: Cone clutches are nothing, but frictional clutches with conical surfaces. The area of contact differs from normal frictional surfaces. 

The conical surface provides a taper, which means that while a given amount of actuating force brings the surfaces of the clutch into contact really slowly, the pressure on the mating surfaces increases rapidly.  

2. Single plate clutch: These clutches are having a single frictional surface to transmit the power between two shafts. These clutches are larger in size when compared to multi-plate clutches of the same transmission capacity.

3. Multi-plate clutches: These clutches are used in the applications where you don't have enough space to install large single-plate clutches. They provide a better coefficient of friction, as the surface area is increased due to the presence of multiple plates.

4. Centrifugal clutches: Centrifugal and semi-centrifugal clutches Works on the principle of centrifugal force and transmits the power between the shafts when a certain speed is attained by the shafts.

5. Hydraulic clutches: As the name itself suggests, operated by hydraulic pressure.

6. Electromagnetic clutches: These clutches engage the theory of magnetism on to the clutch mechanisms. The ends of the driven and driving pieces are kept separate and they act as the pole pieces of a magnet. When a DC current is passed through the clutch system, the electromagnet activates and the clutch is engaged.