Single plate and Multi-plate clutch

Single plate clutch

An axial clutch is one in which the mating frictional members are moved in a direction parallel to the shaft. 

Single Plate and Multi-plate clutch come under the axial clutches. The flywheel is mounted on the driving Shaft by means of key and friction plate is mounted to driven shaft by means of splines. The splines are made on the driven shaft to provide axial movement for engagement and disengagement. Actuating spring keeps friction plate and flywheel are in contact and power/motion is transmitted from driver shaft to driven shaft. When the power of motion is to be interrupted the driven disc is moved axially creating a gap between the members by means of the fork is inserted into the collar on the driven shaft.

Figure 1 Schematic of single plate clutch 

A single disc or plate clutch, as shown in Fig 1 consists of a clutch plate whose both sides are faced with a frictional material. It is mounted on the hub which is free to move axially along the splines of the driven shaft. The pressure plate is mounted inside the clutch body which is bolted to the flywheel. Both the pressure plate and the flywheel rotate with the engine crankshaft or the driving shaft. The pressure plate pushes the clutch plate towards the flywheel by a set of strong springs which are arranged radially inside the body. The three levers (also known as release levers or fingers) are carried on pivots suspended from the case of the body. These are arranged in such a manner so that the pressure plate moves away from the flywheel by the inward movement of a thrust bearing. The bearing is mounted upon a forked shaft and moves forward when the clutch pedal is pressed.

When the clutch pedal is pressed down, its linkage forces the thrust release bearing to move in towards the flywheel and pressing the longer ends of the levers inward. The levers are forced to turn on their suspended pivot and the pressure plate moves away from the flywheel by the knife edges, thereby compressing the clutch springs. This action removes the pressure from the clutch plate and thus moves back from the flywheel and the driven shaft becomes stationary. On the other hand, when the foot is taken off from the clutch pedal, the thrust bearing moves back by the levers. This allows the springs to extend and thus the pressure plate pushes the clutch plate back towards the flywheel.

Figure 2 Exploded view of Single plate clutch

The axial pressure exerted by the spring provides a frictional force in the circumferential direction

when the relative motion between the driving and driven members tends to take place. If the torque

due to this frictional force exceeds the torque to be transmitted, then no slipping takes place and the

power is transmitted from the driving shaft to the driven shaft.

Multi-plate Clutch

A multi-plate clutch, as shown in figure 3, consists of two sets of plates A and B. plates of set A are usually made of hardened steel, while those of set B are made of bronze. Plates of set A  are connected to driven shaft by means of splines. There are through bolts are passed through the holes in the plates of set B which is bolted to the drum keyed to the driving shaft. A clearance fit between the bolt and the holes in the plates allow disks of set B to move in axial direction. the axial force p, which is required to hold the plates together, is provided by means of springs. 

when the driving shaft rotates, the drum, along with bolts and plates of set B, also rotate. Power is transmitted from the plates of set B to those of set A by means of friction.   

 Figure 3 Multi-plate clutch

METHOD OF ANALYSIS

 Uniform Pressure

The torque that can be transmitted by a clutch is a function of its geometry and the magnitude of the actuating force applied as well the condition of contact prevailing between the members. The applied force can keep the members together with a uniform pressure all over its contact area and the consequent analysis is based on uniform pressure condition

Uniform wear

However as the time progresses some wear takes place between the contacting members and this may alter or vary the contact pressure appropriately and uniform pressure condition may no longer prevail. Hence the analysis here is based on uniform wear condition

Design of Clutch --  https://learnmachinedesign.blogspot.com/2018/12/design-of-clutch.html