transmission systems

TRANSMISSION SYSTEMS

TRANSMISSION SYSTEMSRavi tandel u13me234Deep patel u13me235b. Bharath u13me236

TRANSMISSION SYSTEMFunction of transmission :-It is used to transmit engine torque to the driving wheels to drive the vehicle on the road.

Requirement of transmission systemTo provide for disconnecting the engine from the driving wheelsWhen engine is running , connect the driving wheels to engine smoothly without shockLeverage between engine and driving wheels to be variedEnable the driving wheels to rotate at different speeds.Provide relative movement between engine and riving wheelsTo provide high torque at the time of starting the engine, hill climbing and accelerating.

Transmission System - Layout

Types of transmission


They are also classified as:-

Manual transmissionFully automatic TransmissionSemi-Automatic TransmissionCombine selective Transmission


REAR WHEEL DRIVE

The transmission is usually mounted to the back of the engine.

Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels.

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FRONT WHEEL DRIVEOn a front wheel drive car, the transmission is usually combined with the final drive to form what is called a transaxle. Transaxle is a device set up in the transmission gear box, clutch, final drive, combined into a single unit. Today in cars, the front-engine, front-wheel drive, with the engine in front of the front axle, driving the front wheels is getting popular.This layout is typically chosen for its compact packaging.

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Manual Transmission Manual transmission is a type of motor vehicle transmission in which the gear ratios can be changed manually by the driver as the vehicle moves with the help of the following components.

ClutchGearboxDifferential

Automatic Transmission

Automatic transmission is a type of motor vehicle transmission that can automatically change the gear ratios as the vehicle moves, freeing the driver from having to shift gears manually.

Manual TransmissionAdvantages:-Better gas Mileage.Initial cost is less.Maintenance cost is less.

Disadvantages:-It takes longer time to learn.Difficult to drive in certain terrainHeavy clutch pedal feedback may hurt your left leg in longer run.


Driving an automatic is less distracting. No worry about shifting gears.Better to drive in trafficTo help accelerate quickly

Less fuel efficient.Takes longer to change gear between high & low options.Initial cost is high.Repair is costly.

ClutchClutch 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.

Clutch UnitFlywheel also acts as a driving memberPressure 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.

Clutch operation

Types of clutch

Single Plate Clutch

Types of clutchMulti-Plate Clutch

Types of clutchCone Clutch

Types of clutchElectromagnetic Clutch

Types of Clutch

Centrifugal Clutch

GEAR BOXGear box varies the leverage (speed ratio & hence torque ratio) between the engine & driving wheels.It is located between Clutch & Propeller shaft.Gear ratio is varied by Gear shift lever.

Explanation of gearing

Need for Gearbox

SynchronizerIf the dog teeth make contact with the gear, but the two parts are spinning at different speeds, the teeth will fail to engage and a loud grinding sound will be heard as they clatter together. For this reason, a modern dog clutch in an automobile has a synchronizer mechanism or synchromesh.Synchronizers serve to let shafts and gears (sleeves and gears in most cases) engage with each other smoothly after their speeds have been synchronized. That is, synchronization means eliminating differences in rpm between different components.

Sliding Mesh TransmissionThis is the simplest type of gear box. The figure gives a simplified view if the gear box. The power comes from the engine to the clutch shaft and hence to the clutch gear which is always in mesh with a gear on the lay shaft. All the gears on the lay shaft are fixed to it and as such they are all the time rotating when the engine is running and the clutch is engaged. Three direct and one reverse speeds are attained on suitably moving the gear on the main shaft by means of selector mechanism.

Automatic TransmissionAnautomatic transmission can automatically changegear ratiosas the vehicle moves, freeing the driver from having to shift gearsmanually.The most popular form found in automobiles is the hydraulic automatic transmission.This system uses afluid couplingin place of a frictionclutch, and accomplishes gear changes by locking and unlocking a system ofplanetary gears.

Torque Converter : A type of fluid coupling, hydraulically connecting the engine to the transmission. This takes the place of a friction clutch in a manual transmission. It transmits and decouples the engine power to the planetary gears, allowing the vehicle to come to stop with the engine still running without stalling.Planetary gears : Consisting of planetary gear sets as well as clutches and bands. These are the mechanical systems that provide the various gear ratios, altering the speed of rotation of the output shaft depending on which planetary gears are locked. To effect gear changes, one of two types of clutches or bands are used to hold a particular member of the planetary gear-set motionless, while allowing another member to rotate, thereby transmitting torque and producing gear reductions or overdrive ratios.


CVT provides infinite number of gear ratios (between a minimum & a maximum).Shifts automatically with an infinite number of ratiosSeamless power deliveryno torque interruption & power loss

Continuously Variable Transmission

Universal jointsAuniversal joint, is ajointorcouplingin a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmitrotary motion. It consists of a pair ofhingeslocated close together, oriented at 90 to each other, connected by a cross shaft. The universal joint is not aconstant-velocity joint.

Propeller shaftA drive shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement between them.

DifferentialA vehicle with two drive wheels has the problem that when it turns a corner the drive wheels must rotate at different speeds to maintain traction. The automotive differential is designed to drive a pair of wheels while allowing them to rotate at different speeds.When cornering the inner wheel travels a shorter distance than the outer wheel, so without a differential either the inner wheel rotates too fast or the outer wheel drags, which results in difficult and unpredictable handling, damage to tires and roads, and strain on (or possible failure of) the entire drivetrain.

Differential explanation, 1937

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transmission systems

Engineering