1. Automotive Drivetrains
CLUTCHES

2. Purpose
To connect and disconnect engine power flow to the transmission at the will of the driver.

3. Clutch System
Clutch systems are used to disengage the engine from the road
When the clutch pedal is depressed, the clutch (and transmission) is disengaged from the engine

4. Clutch System
With your foot off of the pedal, the clutch is engaged to the engine.
The pressure plate holds the clutch against the flywheel, allowing power to travel through the clutch to the input shaft of the transmission ...
The engine power will transfer through the clutch to the road

5. System Components Flywheel: Transfers engine power to the clutch
Input shaft: Transfers power from clutch to the transmission
Clutch Disk (clutch): Splined to input shaft; transfers power from engine to the input shaft
Pressure Plate Assembly: Spring pressure tightly holds the clutch to the flywheel

6. Components cont:
Release Bearing (throw-out bearing): Connected through linkage or hydraulics to the clutch pedal; Provides a way for the pressure plate to release pressure on the clutch
Pilot Bearing (bushing) : Mounted in the tail of the crankshaft. Stabilizes the input shaft. Not always used for FWD.
Clutch Fork (if applicable): Slides the release bearing into and away from the pressure plate assembly

8. Components cont:
Clutch Linkage (or hydraulic plumbing): Allows the driver to operate the clutch fork
Clutch (bell-housing) Housing: Encloses the clutch assembly
May be integral with the transmission or removable

9. Clutch Components - Flywheel
Mounted on the rear of the crankshaft
Acts as balancer for engine
Adds inertia to the rotating crankshaft
Provides a surface for the clutch to contact
Usually surrounded by a ring gear for electric starter operation

10. Flywheel Construction
Usually constructed of nodular cast iron which has a high graphite content
The graphite helps lubricate engagement of the clutch
May also be constructed from cold rolled steel

11. Dual-mass Flywheel
The flywheel hub and clutch mating area are two separate components
Springs are used to dampen engine and clutch engagement oscillations

12. Dual-mass Flywheel

13. Flywheel Measurements
Run-out – measured with a dial indicator
Parallelism – straight-edge & feeler gauge
Thickness – micrometer or dial indicator

17. Clutch Components Input (clutch) shaft
Projects from the front of the transmission
Usually has a pilot which rides in a bearing or bushing in the end of the crankshaft
The clutch disc is splined to the clutch shaft

18. Clutch Components – Clutch Disc
Is squeezed between the flywheel and the pressure plate
Transmits power from the engine crankshaft to the transmission input shaft

20. Facing manufactured with frictional material (may contain asbestos)
Clutch Disc Construction
Facing manufactured with frictional material
(may contain asbestos)
Other surface materials include:
paper-based
ceramic
cotton
brass

21. Clutch Disc Types
Rigid - used primarily for industrial/racing applications.
Flexible - most common, everything from grandma’s cruiser to street/strip racing.

22. Flexible Clutch Disc
Hub flange - in direct contact with the input shaft
Friction ring - in direct contact with the flywheel/pressure plate.

23. Flexible Clutch Disc Clutch facing - friction material
marcel springs - facing dampener
Torsional springs - further dampening for clutch application
Stop pins - limits the torsional spring’s travel
Rivets -fastens the facing material to marcel (springs)

24. Pressure Plate (clutch cover)
Clutch Components
Pressure Plate (clutch cover)
Squeezes clutch disc onto flywheel
Can be engaged or disengaged
Acts like a spring-loaded clamp

25. Pressure Plate - Types
Belleville/diaphragm-type Spring: uses a cone-shaped diaphragm spring for clamping force.
Multiple-Coil Springs: DUGH!
Semi-centrifugal: clamping force increases as rotational (centrifugal) force increases

26. Belleville/diaphragm Spring:

27. Spring-type Pressure Plate

28. Benefits and Disadvantages:
Belleville/diaphragm type:
cost effective
uniform engagement
limited spring pressure
Spring:
unlimited pressure capabilities
as springs wear, pressure may become inconsistent

29. Clutch Components Release (throw-out) bearing
Operated by the clutch linkage
Presses against the pressure plate to release the clutch

31. Pilot Bearing (bushing)
Clutch Components
Pilot Bearing (bushing)
Installed (pressed) into a machined bore in the end of the crankshaft or flywheel
May be a bushing, ball-bearing or roller-bearing

33. Clutch linkage – Mechanical
Linkage-type

34. Clutch linkage – Mechanical
Cable-type

35. Clutch linkage – Hydraulic
Most Commonly used today

36. Hydraulic Clutch Master

37. Hydraulic Clutch Slave

38. Hydraulic Clutch Slave
Concentric-type

39. Dual-clutch Transmission
Essentially an “automatic” manual transmission
Delivered to the mainstream by Volkswagen – now being used/developed by most mfg.
Eliminates the “power sucking” torque-converter of an automatic transmission

40. Dual-clutch Transmission
Utilizes two input shafts – one inside of the other
Each input shaft will have a dedicated clutch or clutch pack splined to it.
A processor (computer) will engage one or the other clutches (or neither for neutral.)

41. Dual-clutch Transmission
May use a wet or dry “clutch-pack”

42. Dual-clutch Transmission
or conventional clutch disc design

43. Dual-clutch Transmission
Each of the input-shafts controls half of the transmissions gear-sets

44. Dual-clutch Transmission