Important: Use custom search function to get better results from our thousands of pages

Use " " for compulsory search eg:"electronics seminar" , use -" " for filter something eg: "electronics seminar" -"/tag/" (used for exclude results from tag pages)

Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Automatic transmission system
Post: #1

Automatic transmission system

.doc  seminar report.doc (Size: 439.5 KB / Downloads: 135)

Automatic transmission system shifts the gears without assistance from the driver. They start the car moving in first and then shift into higher gears as the car speed increases and engine load decreases. The shifts are produced by hydraulic pressure acting through the transmission fluid.
The control system takes into account the engine load and in general produce changes up when the engine load is light and changes down when the engine load is heavy.


On automatic transmissions, the torque converter takes the place of the clutch found on standard shift vehicles. It is there to allow the engine to continue running when the vehicle comes to a stop.


A torque converter is a large doughnut shaped device that is mounted between the engine and the transmission. As shown in the fig.1, there are four components inside the very strong housing of the torque converter


As the speed of the turbine catches up with the pump, the fluid exit the turbine in the same direction as the pump is turning, so the stator is not needed. At these speeds, the fluid actually strikes the back sides of the stator blades, causing the stator to freewheel on its one-way clutch so it doesn't hinder the fluid moving through it. All three now elements begin to turn at approximately the same speed.


It is seen that the efficiency of the torque converter is reasonably good at only narrow range of turbine speeds. The fall-off of efficiency at low speed end of the range can be tolerated because those speeds are used for short periods. But the fall-off of efficiency at high speeds cannot be tolerated and must be circumvented. The efficiency can be increased, by substituting a direct drive for the torque converter at higher speeds.


Because the only connection between two sides of a torque converter is a fluid connection, there is always a little slippage, running from about 2-8%. To increase efficiency and mileage, most modern automatic transmissions also have something called a lockup clutch.

The compound planetary gear set looks like a simple planetary gear set but actually behaves like two planetary gear sets combined. It has one ring gear that is always the output of the transmission, but it has two sun gears and two sets of planets


The hydraulic system provides the pressurized fluid to operate an automatic transmission.Major components of the hydraulic system include the bands, clutches and oil pump. Other major components are the governor, throttle valve, modulator and the valve body.


The pump’s output pressure will increase roughly in proportion to the engine’s speed. However, the pressure necessary to actuate the various valves and to energise the clutch and band servo pistons will vary under different work conditions. Therefore the fluid pressure generated by the pump, is unlikely to suit the many operating requirements. To overcome these difficulties, a pressure regulating valve is used which automatically adjusts the pump’s output pressure to match the working requirements at any one time. The pressure regulating valve is normally a spring-loaded spool type valve.


The valve body is the brain of the automatic transmission. It contains a maze of channels and passages that direct hydraulic fluid to the numerous valves which then activate the appropriate clutch pack or band servo to smoothly shift to the appropriate gear for each driving situation. Each of the many valves in the valve body has a specific purpose and is named for that function. For example the 1-2 shift valve activates the 1st gear to 2nd gear up-shift.


The manual valve is directly connected to the gear shift handle and covers and uncovers various passages depending on what position the gear shift is placed in. If the gear shift lever is moved in the 1st gear or 2nd gear position, the up-shift and down-shift are inhibited by the manual valve.


Shift valves, as shown in fig. 8 supply hydraulic pressure to the clutches and bands to engage each gear. The valve body of the transmission contains several shift valves. The shift valve determines when to shift from one gear to the next. The shift valve is pressurized with fluid from the governor on one side, and the throttle valve on the other. The shift valve will delay a shift if the car is accelerating quickly. If the car accelerates gently, the shift will occur at a lower speed.


1. It minimizes driver fatigue, especially in heavy traffic by eliminating the need to operate the clutch pedal and gear lever for starting from rest and changing gear.
2. It contributes to safer driving because the concentration of the driver is not disturbed by the need to change gear; also, both hands can remain on the steering wheel.
3. Progress can be smoother under normal driving conditions, because gear changes will occur at the theoretically correct moment in terms of road speed and throttle opening.


1. Cars with automatic transmission are costlier than those having manual transmission.
2. Fuel economy of cars with automatic transmission is not very good.

• The automatic transmission with its torque converter and planetary gear set, can successfully replace the clutch and the manual transmission gear box.

• The planetary gear set gives the required gear ratios and the hydraulic system controls the planetary gear set.

• Automatic transmission system shifts the gears automatically, depending upon both, speed of vehicle and load on the engine.
Post: #2

Automatic transmission system

.doc  Automatic transmission system .doc (Size: 77.5 KB / Downloads: 45)


In USA, the first automatic transmission with a torque converter an epicyclic gearing was introduced in mid 1930 and in Europe in 1950
Simple automatic system is refined by many advance features. So that the sophistication control of system is possible and also comfort to driver. Safety for passanger is increased. All automatic transmission systems are controlled with reference to vehicle speed and engine load. Due to electronic control used in transmission of power from engine to road wheel though the torque converter and its system on additional features may introduced.
e.g. 1) Indication of engine temperature and ambient temperature.
2) Skid prevention on icy road.
3) Rate of change of acceleration
In earlier systems these data are obtained by mechanical, electrical and pneumatic sensors. But now a days these data can be obtained from electronic sensors.
In automatic transmission system, the driver only needs to manually select the forward set of gears (D-range) or the reverse gear(R-range). The automation changing gear ratio relieve the driver of the responsibility of selecting the best possible ratio for each condition and make driving easier and more comfortable.


Automatic transmission system consists of following parts.


It increases the torque from engine in a about 2:1 to 3:1.Thus, it serves as some purpose as that of gearbox. Hence variable torque obtained at output shaft. It contains three members i.e. impeller or driving member connected to engine turbine or driven member connected to o/p shaft and stator which is fixed to frame through freewheel clutch. Fig 1. shows hydraulic torque converter.(5)


Epicyclic gears are used for multiplying the twisting force or torque from engine. This system is necessary during sudden acceleration or during climbing where more torque require than the capacity of torque converter. The epicyclic gear set can increase speed and reduce torque, reduce speed and increase torque, reverse the direction of rotation, acts as a solid shaft, and disconnect the driving and driven shaft. Typical epicyclic gear train is shown in fig.2
The operation of epicyclic gearbox is listed in following table no. 1.

Speed Driving member Driven member Stationary member
Forward fast Planet carrier Ring gear Sun gear
Forward very fast Planet carrier Sun gear Ring gear
Forward slow Ring gear Planet carrier Sun gear
Forward very slow Sun gear Planet carrier Ring gear
Reverse slow Sun gear Ring gear Planet carrier
Reverse fast Ring gear Sun gear Planet carrier


The band brakes are used to temporally lock the epicyclic gear to the transmission case. Due to its self servo effect, it is suitable for securing the epicyclic gears member to the transmission case. When the band brake is released the brake tries to moves back due to the self servo effect. This directional holding capacity minimises and softens gear change shocks.(4)
Fig 3. shows band brake.


In automatic transmission system multiplate clutch is used. Because in car less space is available and as number of plates increases then torque transmission capacity is also increases. The clutch pack has hydraulically operated piston. When oil pressure operates then clutch is engaged position, and when oil pressure is released then return spring push the piston towards its original position and thus clutch is in disengaged position.(3)

Marked Categories : automatic gear box project, seminar on automatic transmission, project about automatic transmission, electronic automatic gear transmission system seminar, automatic transmission, automatic transmission seminarprojects, engineering project on transmission system, automatic transmision system last year project, mechanical engineering transmission system design project report, automatic transmission system, transmission project ideas automobile, automatic gear system using torque converter, transmission system, seminar on automatic transmission system, automatic transmission project report, auto transmission and ignition syseom project report, one way clutch,

Quick Reply
Type your reply to this message here.

Image Verification
Image Verification
(case insensitive)
Please enter the text within the image on the left in to the text box below. This process is used to prevent automated posts.

Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  research paper of automatic sprocket side stand system pdf Guest 1 0 26-10-2017 10:24 AM
Last Post: jaseela123
  Industrial Conveyor System Using Magnetic Levitation system seminar code 2 251 25-10-2017 12:03 PM
Last Post: jaseela123
  literature review on 3 phase automatic changeover switch pdf Guest 1 0 25-10-2017 11:41 AM
Last Post: jaseela123
  ppt on loss less transmission through gas insulated transmissiom system Guest 2 1,181 24-10-2017 10:55 AM
Last Post: kunalpawar11
  automatic vehicle smoke analyser ppt Guest 1 145 14-10-2017 02:40 PM
Last Post: jaseela123
  paper presentation on recent trends in power generation and transmission Guest 1 447 14-10-2017 11:08 AM
Last Post: jaseela123
  rain sensing automatic car wiper project using 8051 microcontroller Guest 1 0 13-10-2017 02:21 PM
Last Post: jaseela123
  pdf fabrication of automatic vehicle over speed controller system for school zone Guest 1 190 13-10-2017 01:17 PM
Last Post: jaseela123
  advantages and disadvantages of ehv ac transmission Guest 1 520 12-10-2017 02:25 PM
Last Post: jaseela123
Last Post: jaseela123
This Page May Contain What is Automatic transmission system And Latest Information/News About Automatic transmission system ,If Not ...Use Search to get more info about Automatic transmission system Or Ask Here