Automotive Drivetrains

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Automotive Drivetrains

• CLUTCHES

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

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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

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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

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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

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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

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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

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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

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Dual-mass Flywheel

• The flywheel hub and clutch mating area are two
  separate components
• Springs are used to dampen engine and clutch
  engagement oscillations

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Dual-mass Flywheel
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Flywheel Measurements

• Run-out measured with a dial indicator
• Parallelism straight-edge feeler gauge
• Thickness micrometer or dial indicator

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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

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Clutch Components Clutch Disc

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

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Clutch Disc Construction

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

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Clutch Disc Types

• Rigid - used primarily for industrial/racing
  applications.
• Flexible - most common, everything from grandmas
  cruiser to street/strip racing.

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Flexible Clutch Disc

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

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Flexible Clutch Disc

• Clutch facing - friction material
• marcel springs - facing dampener

• Torsional springs - further dampening for clutch
  application
• Stop pins - limits the torsional springs travel
• Rivets -fastens the facing material to marcel
  (springs)

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Clutch Components Pressure Plate (clutch cover)

• Squeezes clutch disc onto flywheel
• Can be engaged or disengaged
• Acts like a spring-loaded clamp

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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
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Belleville/diaphragm Spring
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Spring-type Pressure Plate
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Benefits and Disadvantages

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

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Clutch Components Release (throw-out) bearing

• Operated by the clutch linkage
• Presses against the pressure plate to release the
  clutch

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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

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Clutch linkage Mechanical Linkage-type
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Clutch linkage Mechanical Cable-type
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Clutch linkage Hydraulic Most Commonly used
today
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Hydraulic Clutch Master
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Hydraulic Clutch Slave
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Hydraulic Clutch Slave Concentric-type
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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

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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.)

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Dual-clutch Transmission

• May use a wet or dry clutch-pack

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Dual-clutch Transmission

• or conventional clutch disc design

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Dual-clutch Transmission

• Each of the input-shafts controls half of the
  transmissions gear-sets

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Dual-clutch Transmission