Types of clutch Assemblies

Diaphragm Spring

Clutch Cover

  • Three types of clutch pressure plate assemblies.

    • Includes : a diaphragm spring, coil spring, and semi-centrifugal spring type.

  • Also called pressure plate cover

  • holds all components together, covers the springs, levers, and pressure plate.

Pressure plate

  • smooth surface, made up of cast iron

  • strong / dissipates heat well

  • pressing and releasing the clutch pedal moves the pressure plate back and fourth.

  • moves the pressure plate away from the clutch disc

Leaf Spring

  • strip of spring steel, riveted to the pressure plate & clutch cover, connecting them together.

  • flexes the leaf spring to allow the spring to move back and forth.

Diaphragm Spring

  • is cone-shaped until pushed on by release bearing pushes on it.

  • flattens out when pushed & pulls back on the pressure plate.

  • when released, it goes back to cone-shape allowing it to reengage the plate.

Pivot (spacer bolt)

  • attaches to the diaphragm spring to the pressure plate.

  • the diaphragm spring moves & flattens, it pulls back on the pivot.

Coil Spring - Clutch cover

  • perform the same function as the ‘diaphragm spring’

  • holds components such as, springs, pivots, and release levers all together in one.

  • found usually in heavy duty trucks / heavy duty vehicles

Coil Spring - Pressure plate

  • similar to the diaphragm plate version.

  • flat, made of iron to wear and dissipate heat.

  • moves back and forth against the clutch disc as it engages and disengages from the transmission.

Coil Spring - Release Lever

  • pulls back on the pressure plate when release bearing pushes on it.

  • can be weighted at the release-bearing end to multiply the holding force used to clamp against the clutch disc. (added for leverage)

Coil spring

  • maintain pressure on the clutch disc.

  • spring pushes on the clutch cover and the pressure plate

  • The release lever must overcome the spring pressure to pull back the pressure plate.

  • different springs change the spring pressure placed on the pressure plate

Coil spring - Pivot pin ( Fulcrum pin )

  • allows the release lever to move the pressure plate back and forth.

  • this disengages the clutch by pulling the pressure plate forward, away from the clutch cover towards the clutch disc.

  • the pivot, along with the tension of the coil springs, determine how much pedal pressure is needed

Semi-centrifugal Spring - Variation of coil spring

  • variation of the coil spring pressure plate

  • speed determines the holding pressure of the clutch disc

Weighted Release Lever

  • uses a weighted release lever to increase the holding force on clutch disc.

  • The faster the engine spins, the more weighted the release lever pushes on the pressure plate.

  • the weighted release lever allows the use of a lighter-strength spring to push on pressure plate

    • Less clutch pedal effort is needed to disengage the clutch

-Characteristics of a diaphragm spring

  • component is cone-shaped until pressed on by released bearing

  • many fingers act to pull back on the pressure plate

-Characteristics of coil spring

  • release lever must overcome spring pressure to pull back the pressure plate

  • components uses weighted release levers

Mechanical Clutch linkage

  • engage and release the clutch :     

    • Pedal

    • release fork

    • mechanical linkage

    • clutch cable

    • adjuster

Clutch Pedal

  • clutch foot pedal is apart of the lever, attaches to a pivot.

    • pivot is part of the dash frame & typically cannot be removed without removing other dash components

  • molded rubber cover that goes over the foot pedal for grip

Adjustment Rod

  • attaches to the adjustment rod & clutch cable

  • adjustment rod and clutch cable transfers the clutch pedal movement to the clutch 

Over-center Spring

  • Uses a return spring ( over-center spring )

  • to return the clutch pedal back to the up position so that it is back to operational again

  • spring is attached to the clutch pedal and the dash frame

Clutch Release Fork

    Clutch release fork : 

  • moves the release bearing 

  • operates the clutch 

Clutch release forks connect to the : 

  • release bearing

  • clutch release system 

Mechanical Linkage : 

  • uses adjustment rod that connects between the clutch pedal and relay lever 

  • moves in and out to adjust free play in the linkage

  • relay lever ( equalizer rod )

  • transfers the clutch pedal movement from the adjustment rod to the clutch release lever

  • could use a retracting spring to ensure the clutch release lever stays in contact with the release rod

Cable and cable ends

  • clutch cable connects into a groove or snaps on stud on the clutch pedal 

  • cable pulls through the outer shell, the other end connects the cables outer shell secures to a stationary bracket on the transmission 

  • moves the release lever

Outer Shell

  • made up of flexible plastic material, protects the cable from water, dirt, other contaminants.

  • also uses guides that are steel shell, preventing bindings and touching of other components 

Cable boot

  • flexible rubber covers attached to the end of the outer shell and the end and the end of the cable

  • protects from elements and other possible damage

Manual Adjustment 

  • can be made of a cable or lever system.

  • threaded rod moves in or out to shorten or lengthen the cable

Automatic adjuster 

  • is used on a cable system 

  • tension pawl lifts when the clutch is released. 

  • completes when free play is automatically reduced by the pawl and gear mechanism