Automotive Drivetrains

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. 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 - indirect 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. 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. 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