Automotive Drivetrains CLUTCHES Purpose To connect and disconnect

Automotive Drivetrains CLUTCHES

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

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

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

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

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

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

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

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

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

Dual-mass Flywheel

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

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

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

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

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

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

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)

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

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

Belleville/diaphragm Spring:

Spring-type Pressure Plate

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

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

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

Clutch linkage – Mechanical Linkage-type

Clutch linkage – Mechanical Cable-type

Clutch linkage – Hydraulic Most Commonly used today

Hydraulic Clutch Master

Hydraulic Clutch Slave

Hydraulic Clutch Slave Concentric-type

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

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

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

Dual-clutch Transmission n or conventional clutch disc design

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

Dual-clutch Transmission