AUTOMATIC TRANSMISSION # 1

INTRODUCTION

The main components that an automatic transmission include:-

•  Torque Converter
•  Planetary Gears set
•  Hydraulic unit

1. Planetary Gear Sets which are the mechanical systems that provide the various forward gear ratios as well as reverse.
2. The Hydraulic System which uses a special transmission fluid sent under pressure by an Oil Pump through the Valve.
3. Holing devices ,Body to control the Clutches and the Bands in order to control the planetary gear sets.
4. The Torque Converter which acts like a clutch to allow the vehicle to come to a stop in gear while the engine is still
   running.
5. The Governor and the Modulator or Throttle Cable that monitor speed and throttle position in order to determine when
   to shift.

   Planetary Gears set 

    
    The basic planetary gear set consists of a sun gear, a ring gear and two or more planet gears, all remaining in constant mesh. The planet gears are connected to each other through a common carrier which allows the gears to spin on shafts
   called "pinions" which are attached to the carrier.
    
   
   

   

   WORKING

   The input shaft is connected to the ring gear (Blue), The Output shaft is connected to the planet carrier (Green) which is also connected to a "Multi-disk" clutch pack. The sun gear is connected to a drum (yellow) which is also connected to the other half of the clutch pack. Surrounding the outside of the drum is a band (red) that can be tightened around the drum when required to prevent the drum with the attached sun gear from turning.

    The clutch pack is used, in this instance, to lock the planet carrier with the sun gear forcing both to turn at the same speed. If both the clutch pack and the band were released, the system would be in neutral. Turning the input shaft would turn the planet gears
   against the sun gear, but since nothing is holding the sun gear, it will just spin free and have no effect on the output shaft. To place the unit in first gear, the band is applied to hold the sun gear from moving. To shift from first to high gear, the band is released and the clutch is applied causing the output shaft to turn at the same speed as the input shaft

    Clutch Packs

   A clutch pack consists of alternating disks that fit inside a clutch drum. Half of the disks are steel and have splines that fit into groves on the inside of the drum. The other half have a friction material bonded to their surface and have splines on the inside edge that fit groves on the outer surface of the adjoining hub. There is a piston inside the drum that is activated by oil pressure at the appropriate
   time to squeeze the clutch pack together so that the two
   components become locked and turn as one.
      
   
   
   
   
   TO BE CONTINUE .. AUTOMATIC TRANSMISSION #2
   
   
   
   
   
   
   
   
   
   

AuTo inFo_ [MUST READ]

 IMPORTANT

• The aspect ratio (expressed in percentage) of the tyre is defined as the ratio of section height to section width
• If a tyre is designated as 175/65 R14 82 S, then the aspect ratio for the tyre is 65
• The piston compression rings are made of cast iron
• In order to implement gear changes in the gear unit of an automatic transmission, a hydraulic multi plate clutch is used
• When the brake pedal free play is less than the specified value, then the brake drags
• The seat belt will move out smoothly when pulled out slowly, but it will lock when pulled quickly
• The boiling point of Diesel fuel is in the range of180°C to 360 °C
• The component in the radiator of an automobile that increases the boiling point of water is pressure cap
• The temperature indicating instrument in vehicles indicates the temperature of jacket cooling water
• The process of removing the burnt gases from the engine cylinder by the fresh charge coming into the engine cylinder from the crank-case, is known as scavenging
• The process of supplying the intake air to the engine cylinder at a pressure greater than the pressure of the surrounding atmosphere is known as supercharging
•  In aluminium cylinder blocks, the cylinder liners are made of CI
• Free pedal play in car clutches is about  25 mm
• The caster is called positive when the top of the king pin is inclined to the  rear of the vehicle
• The main function of a master cylinder is to convert brake pedal force into hydraulic pressure
• The effect of vapour locking on the brake performance is that the brakes fail completely
• Clutch facings are usually attached to the plate by brass rivets
• The firing order for an opposed four cylinder l.C. engine is 1-4-3-2
• The function of positive crankcase ventilation (PCV) system is that it returns blow-by gases from the crankcase to the intake system
• The maximum torque multiplication ratio in a torque converter is about 2.5
• The sequence in which the force is transmitted through a brake system when the brake pedal is depressed is  : brake pedal - vacuum servo mechanism - master cylinder - brake lines - brake pads
• The main function of an exhaust muffler is the reduction of exhaust noise
• The purpose of transmission in an automobile is to vary the torque at the wheel
• Caster is a forward tilt of the kingpin OR backward tilt of the kingpin
• A front stabilizer bar is used to control suspension movement and body roll
•  When the front wheels of a vehicle are locked during braking, then driver loses control over the steering, and the vehicle continues moving in its current direction
• The order in which effort applied to the steering wheel is transferred to the front wheel is steering wheel - steering shaft - steering gearbox - tie rod - steering kunckle -front wheels
• The best fuels for compression ignition engines are napthalenes
• The main function of a resonator is that it reduces the intake air noise
• For the same maximum pressure and temperature Diesel cycle is more efficient than Otto cycle
• The lower cylindrical portion of the piston which improves piston cooling performance is called piston skirt
• The tyre rotation is generally done at 10000km
• The included angle is the sum of the camber and S.A.I.
• Toe can be adjusted by modifying the tie-rod attachment length 
• The main feature of MacPherson strut suspension is that non-vertical external forces are supported by the suspension arms
• The fuel pump in the programmed fuel injection (PFI) system is located in fuel tank
• The materials used for cylinder block are cast iron and aluminium alloy
• The capacity of a battery is usually expressed in terms of ampere-hours
• Vulcanizing means heating rubber under pressure
• The correct way to rectify an imbalanced wheel is to attach appropriate weights to the wheel at appropriate positions
• The crankcase dilution means dilution of lubrication oil by fuel in the crankcase
• Engine misfiring is likely to result from spark plug gap too wide
• The brake pedal during ABS operation transmits slight kickback to the driver's foot
• The gear shift lever requires two separate motions to shift gears, and the first movement selects the synchronizer 
• Two speed reverse gear arrangement is generally provided in case of tractors
• Odometer is an instrument used for measurement of distance
• Wheel base of a vehicle is the distance between the centres of the front and rear wheels
• In Diesel engines, the duration between the time of injection and the time of ignition is called delay period
• In a single dry plate clutch, torsional vibrations are absorbed by coil springs known as torsional springs
• Cushioning springs in clutch plate reduces jerky starts
• Toe-in ensures parallel rolling of the wheel thus stabilizing steering in addition to preventing both sides slipping and excessive tyre wear.
• Highest useful compression ratio (HUCR) is the highest compression ratio at which the fuel can be used in a test engine without knocking
• The function of a governor in automobiles is to limit the vehicle speed
• Bead wires are made of steel
• A maintenance free battery has lead-calcium plate grid
• The Diesel engines as compared to petrol engines require bigger flywheel
• In a forced feed lubrication system, the device used to guard against excessive oil pressure, is known as relief valve

CVT [ AUTOMATIC TRANSMISSION -INFINITIVE GEAR RATIOS]

 There are various configuration of CVT  one is below

History of the CVT

Leonardo DaVinci sketched the first CVT in 1490. Dutch automaker DAF first started using CVTs in their cars in the late 1950s; however technology limitations made CVTs unsuitable for engines with more than around 100 horsepower. In the late 80s and early 90s, Subaru offered a CVT in their Justy mini-car, while Honda used one in the high-mileage Honda Civic HX of the late 90s.
Improved CVTs capable of handling more powerful engines were developed in the late 90s and2000s, and CVTs can now be found in cars from Nissan, Audi, Honda, Ford, GM, and other automakers.

COMPONENTS OF CVT

1.PRIMARY PULLEY
2.SECONDARY PULLEY
3. BELT

PRIMARY PULLEY

The main components of the primary pulley are fixed and movable sheaves, a set of two flyweights, and a compression spring. As the engine speed increases, the flyweights tend to swing open and push the movable sheave inward toward the fixed sheave. However, this movement is not possible until the force created by the flyweights is able to overcome the force caused by the primary spring. Once this is occurs, the flyweights must also overcome the resisting force caused by friction between the belt and
the sheaves as well as the spring forces in both the primary and secondary pulleys.

SECONDARY PULLEY 

The secondary pulley includes fixed and moveable sheaves and a spring loaded in compression. As the primary begins to shift, its two sheaves move closer together. This,in turn, narrows the width of the v-slot driving the belt to a larger diameter. The normal force caused by the wedging of the belt between the sheaves forces the secondary sheaves apart, which allows the belt to move to a smaller diameter on the secondary. This is the process that shifts the system to a higher gear ratio. In an ideal case, such a combination is capable of producing an overdrive gear a ratio of 0.75:1 in the CVT. The initial reduction provided by the CVT is 3.5:1 

To have better understanding follow the above x-section of  cvt

The stratified charge engine_

The principle of the stratified charge engine is to deliver a
mixture that is sufficiently rich for combustion in the immediate
vicinity of the spark plug and in the remainder of the cylinder,
a very lean mixture that is so low in fuel that it could not
be used in a traditional engine. On an engine with stratified
charge, the delivered power is no longer controlled by the
quantity of admitted air, but by the quantity of petrol injected,
as with a diesel engine.

 HOW DOES IT WORK?

One approach consists in dividing the combustion chamber

so as to create a pre-combustion chamber where the spark

plug is located. The head of the piston is also modified. It contains

a spheroid cavity that imparts a swirling movement to

the air contained by the cylinder during compression. As a

result, during injection, the fuel is only sprayed in the vicinity

of the spark plug.

But other strategies are possible. For example, it is also possible

to exploit the shape of the admission circuit and use

artifices, like “swirl” or “tumble” stages that create turbulent

flows at their level.

All the subtlety of engine operation in stratified mode

occurs at level of injection. This comprises two principal

modes: a lean mode, which corresponds to operation at very

low engine load, therefore when there is less call on it, and a

“normal” mode, when it runs at full charge and delivers maximum

power.

In the first mode, injection takes place at the end of the compression

stroke. Because of the swirl effect that the piston

cavity creates, the fuel sprayed by the injector is confined

near the spark plug. As there is very high pressure in the

cylinder at this moment, the injector spray is also quite concentrated.

The “directivity” of the spray encourages even

greater concentration of the mixture. A very small quantity of

fuel is thus enough to obtain optimum mixture richness in the

zone close to the spark plug, whereas the remainder of the

cylinder contains only very lean mixture. The stratification of

air in the cylinder means that even with partial charge it is

also possible to obtain a core of mixture surrounded by layers

of air and residual gases which limit the transfer of heat to the

cylinder walls.This drop in temperature causes the quantity

of air in the cylinder to increase by reducing its dilation, delivering

the engine additional power. When idling, this process

makes it possible to reduce consumption by almost 40% compared

to a traditional engine. And this is not the only gain.

Functioning with stratified charge also makes it possible to

lower the temperature at which the fuel is sprayed. All this

leads to a reduction in fuel consumption which is of course

reflected by a reduction of engine exhaust emissions.