Clutch, Mt, Amt

K Ganesh Babu

The Automotive Research Association of India, Pune

Introduction

Transmission Types

Manual

Automated Manual

Automatic

Continuously variable

Dual Clutch

Propeller Shaft

Universal joints

Final drive

Differential

Transmission Trends



It is used to transmit engine torque to the driving wheels to drive the vehicle on the road.



To provide for disconnecting the engine from the driving wheels

When engine is running , connect the driving wheels to engine smoothly without shock

Leverage between engine and driving wheels to be varied

Turn the drive to 900

Enable the driving wheels to rotate at different speeds.

Provide relative movement between engine and driving wheels






Manual Transmission (MT) – Conventional Definition

Moving away from rest – dry plate clutch

Achieving ratio change – external cylindrical gears

Power interruption

Mechanism for ratio change

▪ Positively engaged shifting dogs, synchronised (passenger cars and commercial vehicles)

▪ Positively engaged non-synchronised (motorcycles)

Control of ratio change – manual

When a driver wants to change from one gear to another in a standard stick-shift car, he first presses down the clutch pedal

This operates a single clutch, which disconnects the engine from the gearbox and interrupts power flow to the transmission

Then the driver uses the stick shift to select a new gear, a process that involves moving a toothed collar from one gear wheel to another gear wheel of a different size

Devices called synchronizers match the gears before they are engaged to prevent grinding

Once the new gear is engaged, the driver releases the clutch pedal, which re-connects the engine to the gearbox and transmits power to the wheels.



Clutch is used to disengage and engage the engine with rest of the transmission systems.

To disengage while starting the engine and while changing gear ratio.

To engage after starting of the engine and gear shift operation.


Transmit maximum torque of the engine.

Engage gradually to avoid sudden jerks.

Dissipate maximum amount of heat.

Dynamically balanced.

Damp the vibrations and noise.

As small as possible.

Easy to operate.



Cone clutch

Flat Plate clutch Dry or Wet type clutch No. of friction plates

(Single or Multiple) Actuation mode (Cable or

Hydraulic) Actuation spring (Helical or

Diaphragm) Centrifugal clutch


Flywheel

Clutch Cover Assembly

Clutch Disc Assembly

Flywheel also acts as a driving member

Pressure plate is connected to clutch cover assembly.

Clutch Cover assembly is bolted to the flywheel.

Clutch springs placed between Pressure plate & Cover plate, press the Pressure plate against the clutch plate.

Thus Clutch plate is squeezed between Flywheel & Pressure plate.



Components:

1. Flywheel2. Friction Facing3. Cover Stamping4. Pressure Plate5. Cushion Plate Rivets with Clutch

Plate6. Diaphragm Spring7. Damper8. Transmission Shaft9. Actuation Lever10. Splined Shaft11. Pilot bearing rest12. Ring fulcrum (for Diaphragm Spring)13. Drive Strap/Clip/Lock14. Clutch Cover Assembly Bolted with

flywheel


Location: b/w Flywheel &Clutch Cover Assembly.

Mounting: over splinedtransmission shaft.

Friction facings riveted tocushioning plates

Cushion plates riveted toclutch plate and retainingplate

Torsion springs mountedon splined hub

It is mounted over cushion plate.

It helps in generating friction force

Grooves are created on the surface offacing in order to eradicate the problemof friction disk sticking to flywheel.

Graphite Particles (they are inexpensive,increase wear rate, increase heatresistance)

Sintered/Ceramic Metals (high powertransmission and good heat resistance)

Fibrous Reinforcements: Fiberglass,Acrylics, Rayons, Aramids, Mineral Fiber& Cotton Fiber.


Cushion is a wave shapedcomponent of the sheet of 0.5mm thickness.

It is riveted to friction facing andclutch plate (disc plate) as well.

Allowable compression is 1 to 2mm


DiscPlate / Clutch Plate Riveted with cushions. It faces the flywheel

side. Disc Plate and Retainer Plate are riveted

together using stop pins.

RetainerPlate It faces the transmission shaft side. Disc plate and retainer plates have voids to

accommodate dampers.


Hub is splined and is attached to Hub plate.

Hub is mounted on a splined transmissionshaft and slides over the same at the timeof engagement and disengagement.

Hub plate is placed between disc (clutch)plate and retainer plate

Hub Plate had voids to accommodatedampers (like retainer and disc plate)

Hub plate possesses relative motion (w.r.t.retainer & disc plate) during damping thevibrations. Hence transmits less vibrationsto transmission shaft. So a smooth drive


Damper is strategically placed in b/wdisc plate, retainer plate and hub plate,in such a manner that one face remainsin contact with hub plate and anotherwith retainer & disc (clutch) plate.

Jerks from flywheel are absorbed bythese dampers and less jerks aretransmitted to transmission shaft.

Oil Hardened and Tempered Steel Wire


Clutch Cover Assemblycomprises of pressureplate, diaphragm springclutch cover, fulcrumrings and strap platesetc..

Mounting: It is boltedwith the flywheel andprovides extra frictionalsurface for the Clutchdisc to transmit power.


Flattened on one face to provide frictionsurface for clutch disc. And on other face,fulcrum is made for actuation spring.

Its is held with clutch cover using drivestraps and clips and is actuated by eitherDiaphragm spring or Helical spring.

Pressure plate also rotates as engine’sspeed.

CI is used for better heat dissipationcapacity and wear resistance.

The minimum travel of the pressure plateshould be the compression length ofcushion plate


Actuation spring holds the pressure

plate with Clutch disc in normal

condition.

During actuation it disengages the

pressure plate with friction disc,

hence cuts off the power flow.

Types: Diaphragm Spring / Helical

Spring.


Diaphragm spring loaded assembly occupies less axial space, even the

cooling fins can be mounted with the use of diaphragm spring.

During initial stage of clutch facing wear, clamp load increases.

Continued wear eventually results in fall of clamp load, once the clamp load

gets over to the hump.

Heat treatment Process:50CrV4 Quenching at 880˚C Tempering at 12 stages


Drive Straps used to hold pressure plate with

the clutch cover

Cover Stamping It contacts the diaphragm

spring at a specified fulcrumdiameter. Fulcrum elementsmay be the wire rings up andbelow the diaphragm springand riveted to the coverstamping.



avi

Clutch2.exe

Clutch is always is in engaged state.

It can be disengaged by pressing of Clutch pedal.

Disengagement is effected by non – contact of Clutch plate both with Flywheel face & Pressure plate face.

Frictional heat is dissipated by openings present in Clutch housing & Cover




Gear box varies the leverage (speed ratio & hence torque ratio) between the engine & driving wheels.

It is located between Clutch & Propeller shaft.

It is provided with either 4 speed or 5 speed ratios or more depending on design.

Gear ratio is varied by Gear shift lever.



Constant mesh

Sliding mesh

Synchro mesh


gearbox

Driveline_gear.exe



5-speed Single layshaft 5-speed, intermediate shaft off input shaft



Implications of 6-speed Transmissions

Packaging constraints

▪ Gearbox length

▪ Distance from input shaft to final drive shaft

The trend began among versions with the highest performance, or premium brand

High Performance Diesel require high ratio spread

The trend is spreading rapidly:

Virtually every European and Japanese OEM now offers a 6-speed manual gearbox in at least some of its models

VW has announced that it will fit only 6-speed gearboxes across its range in the near future for all their European cars

6-speed, twin-layshaft 6-speed, intermediate shaft off layshaft


56123/4

4

FD

R

33 4 R

5 6 1 2

FD

1


Manual Transmission (MT) – Discussion of different layouts

Single layshaft design cheapest and simplest

Move from 5 to 6-speed inevitable, hence increased axial packaging constraints

Some single layshaft 6-speed transmissions made, but difficult to package, leads to narrow face widths, poor axial contact ratio etc.

options on reducing axial packaging identified

▪ Intermediate shaft off input shaft

▪ Twin layshaft, twin final drive pinion

Collars are moved by forks.

Forks are controlled by three shift rods, engaged by shift lever.

Movement of the shift lever causes the movement of collars towards required gear for engagement with main shaft

Sequential shifting for two wheelers


A device used to bring two adjacent members to the same speed before allowing the sleeve to engage them

The two elements are friction clutch and toothed clutch.

Lock the positive engagement until speeds are synchronized

Establish the positive engagement and power flow.


Synchronizer is splined on the shaft

Gear is running freely with NRB on shaft

Cone on the gear (blue) fits into cone-shaped area in the collar.

Friction between the cone and collar synchronize the collar & gear.

The outer portion of the collar (sleeve) then slides so that the dogteeth engage the gear.


Synchronizer cone with selector teeth

Blocker ring

SleeveBlocker ring

Strut

HubSpring

Spring







Transmission cost to weight ratio


Source: Lechner


Prospects for commercial success

▪ Cheap to make

▪ Durable, efficient

▪ Easy to install

▪ Established in marketplace and with manufacturing infrastructure

▪ Gives control to the driver

▪ But driver comfort an issue with increasing traffic density

▪ Hence automation must be considered


Automation of Clutch and Gear shifting operations

Elimination of Clutch Pedal

Modification of Gear Shifting lever

Minimum modifications in manual transmission


Clutch Actuator

Selection and Shifting Actuator

Automation of Clutch operation and Gear shifting.

Clutch slip control during starting

Hill start aid system which will assist the driver in hold and move the vehicle in hill slope

Necessary fail safe systems such as sudden shifting from higher gear to lowest gear and vice versa


Reduced driver effort

Improved Clutch life

Utilization of existing manufacturing facilities for manual transmission

Lower production cost than automatic transmissions

Higher efficiency than automatic transmissions



Gear Shift Actuator AMTClutch ActuatorSource: Luk

Engine Torque

Clutch Pedal Force


H - Gate


Driver

ECUVehicle Speed

Clutch Actuator

Transmission Actuator

Vehicle Transmission Clutch

Selector lever Traffic Conditions

Signal

Signal

Intention

Drive TorqueActuation


Pulse Signal Conditioner

Analog Signal Conditioner

Contact Point

Signal input

circuit

ECU

Power Unit

Multiplexer

Motor Drive Circuit

Indicator Drive Circuit

Starter Inhibitor

Vehicle Speed

Input Shaft RPM

Clutch Stroke

Selector lever

Gear Position

Transmission Actuator

Clutch Actuator

Indicator

Starter

Engine Start

Starter should be operated only when the gear is in neutral position

When engine is not running and in power on, ECU will disengage clutch

When engine speed exceeds a specified rpm, ECU engages clutch gradually


Vehicle Start

On pressing the accelerator pedal, ECU controls the clutch actuator travel and clutch engagement

Gear Change

While engaging the clutch after gear shift, the ECU determines clutch actuator travel based on shifted gear position and accelerator pedal stroke


Clutch disengagement

While gear shifting and when accelerator pedal is released, if the vehicle speed is lower than a set speed for select gear position, the ECU disengages clutch


Clutch, Mt, Amt

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