POWERPOWER TRANSMISSIONTRANSMISSION

The Beginning2

PedalDriver

Driver pushes on Pedal to move vehicleHe is more concern about smooth cruising i.e.. Best goutput

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Where Does the Force Come From?

Engine produces some torque, at a speed3

g p q , pPower- the rate at which work is done:

Power is Force times Velocity (linear)Power is Force times Velocity (linear)

( )( )( )( )

VelocityForcePower =

Power is Torque times Rotational Speed (rotary)

( )( )VF=q p ( y)

( )( )( )( )

=T

SpeedRotationalTorquePower( )( )ω= T

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Where Does the Force Come From?

Power is conserved:4

owe s co se ved:vehicleaxletransengine PPPP ===

POWER IS ABSOLUTE

Torque is relative (depends on gear ratio)

Ignoring Losses, of Course

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WHAT IS POWERTRAIN MATCHING ?

Selecting the right engine and gearing for a given application

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g g g g g g ppNot just performance, but giving the driver the expected response to pedal inputsTransmission shift schedules as fuel economy heavily impacted in automotive applications. Powertrain Matching makes best use of your engine potentialPowertrain Matching makes best use of your engine potential

Torque & Power shaping can give optimal performance for a given set of gearingOptimal gearing can make your car faster for no changes in engine performance

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DRIVE TRAIN7

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POWER TRAIN SYSTEM(1) Front driveshaft(1) Front driveshaft(2) Output transfer gearbox(3) Transmission(4) Upper driveshaft(5) Torque converter updrive transfer gears(6) Torque converter(6) Torque converter(7) Engine(8) Front differential(9) Front final drives(9) Front final drives(10) Centre bearing(11) Centre driveshaft(12) Rear driveshaft(12) Rear driveshaft(13) Rear differential(14) Rear final drives

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ClutchesConnects /disconnects Engine crankshaft to the transmission (gear box)Change of gears can not be

h h h i i di l smooth when the engine is directly connected with the transmission.T it th t th d Transmits the power to the road wheels smoothly

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Clutches

Friction clutches are 10

design to absorb energy during slippage.Virtually all vehicle clutches are spring-loaded friction disks loaded friction disks.

The torque transmission capacity of a clutch can be estimated as,

where, Tc is the torque capacity, f is the friction coefficient F is clamping force of

smcc nrfFT =

friction coefficient, Fc is clamping force of clutch, rm is the mean radius of the clutch, and ns is the number of friction surfaces.

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Clutch should

Consume minimum physical effort12

Be free from slipWearing surface should have long lifeBe provided a suitable mechanism for damping of vibration and elimination of noise

Main parts of clutchPressure plate:- It presses the driven plate against the p p p gflywheelDriven plate:- Is provided with annular facings and spring cushioned hub

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Types of clutchThe mostly used clutch is the friction type of following types

Cone clutch: is only used in the synchromesh units of gear boxes and sometimes in epicyclical  gear boxesp y gSingle plate clutch:‐Mostly used in cars and trucksMulti‐plate clutch:‐Mostly used in motorcycles, tractors and mostly construction equipment. This type of clutch is mostlymostly construction equipment. This type of clutch is mostly used where high torque to be transmitted and limited space availableCentrifugal clutchgFree wheel clutch or one way clutchBand type clutch Overrunning ClutchOverrunning ClutchElectrical clutchJump Clutch

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Hydrodynamics drive system

Hydrodynamic drive system includes fluid coupling or Torque

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converter. This system possesses low pressure and high velocity of hydraulic flow.

Fluid coupling:-Fluid coupling:It is a hydraulic unit that replaces clutch in a semi or fully automatic system and transmits engine torque to transmission

tsystemIt consists of driving unit called impeller and driven unit called turbine. Power flows through liquid instead of mechanical device . Maximum efficiency is unityFluid coupling always slips by about 2 to 4 % when transmitting full load u oad

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Advantages of fluid coupling

Smoothen transmission of power from engine to

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Smoothen transmission of power from engine to transmissionEli i i f l h lElimination of clutch plateDamping of the torsional vibration of the crankshaftDuring braking or down hill, the transmission shocks are absorbed by the fluid

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Torque ConvertorTorque Convertor26

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Torque ConvertorTorque Convertorqq27

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Torque converter basic operation

Coupling stage:- Turbine is rotating at 90 % of the impeller d

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speedFluid from the turbine strikes the convex side of the stator blade causing it to overrunCoupling stage will be high when acceleration is not required and the equipment is cruising At this point the torque converter is acting like a fluid clutchp q gThe impeller is rotating at engine speed, the turbine is stationary and the stator is locked against rotationAs engine speed increases impeller speed accelerates As engine speed increases impeller speed accelerates increasing vertex flowThe vertex flow strikes the turbine blades and diverted around the curvature and strikes to the concave side of the statorthe curvature and strikes to the concave side of the stator

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Advantages of torque converter

Torque converter is the fluid clutch used in the

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Torque converter is the fluid clutch used in the automatic transmission of the construction equipmentIt multiplies the torqueIt multiplies the torqueSmoothes out the transfer of engine torque to the transmissiontransmissionActs as cushion between the engine and transmissionD ib tiDampens vibrationsVirtually wear free

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Types of Transmissionsyp

Sliding Gear35

Sliding GearConstant-MeshCo s a MesSynchromeshPowershiftH d ki iHydrokinetic

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Mechanical transmission

Th i i t itt d t th h l f

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The engine power is transmitted to the wheels of equipment through mechanical arrangements.It is achieved by gear mechanisms in manual gearboxIt is achieved by gear mechanisms in manual gearboxMostly this system is found in vehicles, trucks and light construction equipmentconstruction equipmentDepending on the no. of gear for forward speeds and reverse gear, power flows takes place in manual transmission system

T f bTypes of gear boxe1. Sliding mesh type2. Constant mesh type3. Synchromesh type

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Mechanical transmission

Sliding mesh type:- is oldest and simplest, meshing of gears 37

takes place by sliding of gears on each other. Consists of main shaft, countershaft and idler gear shaft for reverse speedConstant mesh type :- In this gearbox all the gears mesh with yp g geach other all the time. Gear changing is made easier by helical gear. The primary shaft which carries the clutch is splined and carries a gear that mesh with gears on the p g glayshaft gearSynchromesh gearbox:- Use synchromesh gear devices on the principle of engagement of two matting gears in motion and principle of engagement of two matting gears in motion and equalizes their speed with readily and smoothly and the devices used is synchronizer ring.

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Gear Design g

Spur or helical gears are meshed between parallel shafts.

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Spur or helical gears are meshed between parallel shafts.Spur gears have teeth that are parallel to the shafts, while helical gear teeth are angled with respect to the shafts. g g pHelical gears continually transfer the load from one gear to the other.Gear teeth typically have a tooth profile that is “involute” (generated by unwrapping a string from a cylinder).Constant involute profiles generate constant angular velocities.

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The Planetary Gear combinations provide 5 b i i5 basic operations

Gear ReductionP iti I S i h ld Ri i t

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Position-I Sun gear is held; Ring gear -inputPosition-II Ring gear is held; Sun gear -input

OverdriveP i i I Ri i h ld C i iPosition-I Ring gear is held; Carrier-inputPosition-II Sun gear is held; Carrier-input

ReversePosition-I Carrier is held; Ring gear-inputPosition-II Carrier is held; Sun gear-input

Direct DriveEntire planetary unit works as single unitAt a time Two units –input; one out put

NeutralWhen no unit is held

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Powershift Transmissions

Can be shifted with virtually no interruption in

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Can be shifted with virtually no interruption in power.Types of powershift transmissions: a) countershaft, Types of powershift transmissions: a) countershaft, and b) planetary.Hydraulic pressure is utilized to actuate the clutches.Hydraulic pressure is utilized to actuate the clutches.

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Fig. 12.10a Countershaft Powershift Transmission/ f(Hi/Lo Shift)

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Hi/Lo Powershift/69

When neither clutch is engaged, transmission is in neutral.When left clutch is engaged, output shaft turns slower than input.When right clutch is engaged, output shaft turns the same speed as the input.When both clutches are engaged, transmission is in ‘Park.”

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Fig. 12.10b Countershaft Powershift Transmission(Reverser)

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Reverser Powershift

Wh i h l h i d i i i

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When neither clutch is engaged, transmission is in neutral.When left clutch is engaged output shaft turns When left clutch is engaged, output shaft turns opposite direction of the input.When right clutch is engaged, output shaft When right clutch is engaged, output shaft turns the same direction as the input.When both clutches are engaged, transmission g gis in ‘Park.”

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Compound Planetary TransmissionsCompound Planetary Transmissions

Contains two set of different size planets, one

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Contains two set of different size planets, one meshing with the sun and the second meshing with the ring gear.g gMay also include two sun and/or two ring gears.

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Hydrostatic transmission system

Basic power train of hydrostatic system 73

p y y

Engine Hydraulic Control

Actuator

Engine Hydraulicpump

Controlvalve Travel

motor

Swing motorBasic power flow in hydrostatic drive systemp y yLike in hydraulic excavator

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