How does a car's automatic transmission work?
Most modern automatic transmissions use a set of gears called a planetary or epicyclic unit.
The planetary gear unit consists of a central (sun) gear, an outer gear with internal teeth (an epicyclic gear), and two or three planetary gears that rotate between the sun gear and the outer gear.
The power train is connected to a mechanism known as a converter, which acts as a hydraulic drive between the engine and transmission.
If the sun gear is stationary, the planets move around it due to the planetary gear carrier, and the increase in speed is achieved through the rotation of the epicyclic gear.
If the outer wheel is stationary, the sun gear rotates, the gear ratio increases and the speed decreases.
If the planets are stationary and power is applied to the sun gear, the outer gear moves in the opposite direction.
To engage direct transmission without changing speed or direction of movement, the entire unit must rotate as a single unit.
Converter
Sectional view of the converter, inside there is a blade wheel, turbine and reactor.
How the converter works
At high speeds the reactor begins to rotate. If the turbine, impeller and reactor rotate at the same speed, the oil flow will not be diverted.
At low speeds, the reactor stands still and oil flows onto the impeller, increasing turbine torque.
The converter is a hydraulic transmission that operates like a clutch, but under fluid pressure.
The converter consists of three main parts - a paddle wheel attached to the flywheel, a turbine connected to the gearbox via a drive shaft, and a reactor with a one-way freewheel located between the paddle wheel and the turbine.
As engine speed increases, the centrifugal force exerted on the fluid by the impeller imparts torque (or turning force) to the turbine.
The reactor converts this force by redirecting fluid flow back to the impeller to increase torque at low speeds.
After the engine warms up and begins to produce more energy, the reactor will rotate freely, because there will be no need for transformation. In this case, the converter will work like a hydrodynamic clutch, connecting the engine to the gearbox.
The large diagram shows the main components of the converter - impeller, reactor and turbine.
The smaller diagram shows the direction of fluid movement under the influence of centrifugal force.
A similar effect is achieved by blocking the planetary gears and the planetary gear carrier.
Many three-speed automatic transmissions contain two sets of epicyclic gears.
Locking of the elements is achieved through hydraulic pressure, which acts on the brake band or multi-plate clutch.
Tape wrapped around the outer wheel prevents it from spinning, and the clutch discs block the sun gear and planets.
The increase or decrease in pressure depends on the operation of a complex system of hydraulic valves and sensors that determine the engine load level, driving speed and throttle position.
The so-called throttle is connected to the throttle. kick-down mechanics, i.e. fast acceleration. When the driver presses the gas pedal sharply, the lower gear is engaged almost instantly.
Many automatic transmissions use a braking system that allows you to hold a low gear for as long as necessary.
Simplified diagram of an epicyclic gear unit
When the central (sun) gear is stationary, the planets rotate around it along with the carrier and outer gear.
When the sun and outer gears are locked, the planets cannot rotate on their own, so the entire unit rotates.
When the carrier is locked, the sun gear rotates the planets, and the outer gear rotates in the opposite direction.
First gear
Front-wheel drive is engaged and the engine rotates the first outer wheel.
The planets rotate the common sun gear in the opposite direction.
The carrier of the second planetary set is held by the brake band, the planets of the second set rotate their outer wheel and output shaft, providing a double reduction in speed.
Second gear
Second gear allows the car to move at medium speed. Front-wheel drive is engaged and the engine rotates the first outer wheel.
The sun gear is locked and the planets are moving around it. The carrier moves in the same direction.
The carrier shaft is a secondary shaft, so the speed is reduced once. The second set of planets and their carriers rotate freely.
Top gear
Front-wheel drive is engaged and the engine rotates the first outer wheel.
In addition, a reverse clutch operates, which simultaneously locks the sun and outer gears, causing them to rotate at the same speed.
The planets cannot move, and the carrier rotates at the speed of the engine. The final impact is exerted by the carrier shaft, which also rotates at engine speed (direct drive).
Reverse
On the gear lever, reverse is usually indicated by the letter R. Front wheel drive is disengaged and the first outer wheel rotates freely.
Rear wheel drive is engaged and the engine rotates the first sun gear.
The second carrier is locked, the second sun gear rotates its planets and the outer gear in the opposite direction, providing reverse drive.
Source: http://17koles.ru/how/kak-rabotaet-avtomaticheskaya-korobka-peredach-avtomobilya
Automatic transmission: design and principle of operation
Nowadays, a large number of car enthusiasts use an automatic transmission (automatic transmission), and every year there are more and more of them.
Automatic transmission not only reduces the driver's workload when driving a car compared to a manual gearbox (MT) during a trip, but also helps the driver reduce fuel consumption by shifting gears at optimal engine speeds, depending on the selected driving mode.
The automatic transmission was invented in America, from where it became widespread. Currently, in the USA and many European countries, the popularity of manual transmissions is not very high; they are used by approximately 5% of drivers. However, the demand for cars with automatic transmission in Russia is constantly growing and today half of the foreign cars sold in Russia are equipped with automatic transmission.
Hydraulic gearbox
All automatic transmissions can be divided into several main types:
- CVTs;
- Hydraulic automatic transmissions;
- Robotic mechanics.
Hydraulic automatic transmission
The automatic transmission, based on the operation of a torque converter, has been seriously modified at the request of Europeans and currently has several operating modes (winter, sport, economical), corresponding to each driving style.
Also in classic automatic machines the number of gears increases. In the 90s there were only 4-speed automatic transmissions, but now they can be 8-speed.
Sectional view of a classic automatic transmission
Components of the automatic transmission:
- torque converter;
- Manual Transmission;
- working fluid pump;
- cooling and control system;
- brake band;
- planetary gear set (planetary gearbox)
The main automatic transmission units are: a torque converter and a mechanical planetary gearbox.
Torque converter device
The torque converter changes and transmits torque from the engine to the manual transmission. Located between the engine and gearbox. The torque converter contains two blade machines: a centripetal turbine and a centrifugal pump.
Among other things, the torque converter contains a reactor wheel, a freewheel (overrunning clutch), and a locking clutch. The pump wheel provides connection to the engine crankshaft, and the turbine wheel provides connection to the manual transmission. A fixed reactor wheel is fixed between these two wheels.
All wheels of the torque converter have blades of a certain shape with channels that allow the passage of the working fluid, because the operation of the torque converter is based on the continuous circulation of the working fluid, which transfers energy from the engine to the transmission.
The fluid flow from the pump wheel is transferred to the turbine wheel, then to the reactor wheel. Due to the fact that the reactor blades have a unique structure, the fluid flow increases, increasing the speed of the pump wheel. The fluid flow changes its direction after the angular velocities of the pump and turbine wheels are equalized.
The overrunning clutch is engaged and the reactor wheel begins to rotate. The torque converter begins to transmit only torque.
The lock-up clutch is designed to lock the torque converter, and the freewheel (overrunning clutch) ensures reverse rotation of the reactor wheel.
The design of a manual gearbox is much simpler, allowing you to change the torque in steps and move in reverse.
Often consisting of two planetary gearboxes connected in series, modern automatic transmissions can be either six-speed or eight-speed.
The advantage of an automatic transmission is that the planetary gearboxes used in them are more compact and have coaxial operation.
Electronic control system
The electronic control system processes signals coming from various sensors, and, having processed them, sends control signals to the distribution module.
Planetary series
The main advantage of a planetary gear is its compactness, the use of one central shaft. The planetary gear allows you to change speeds without jerks, jolts or loss of power. The transmission automatically changes gears; for this, the driver only needs to manipulate the gas pedal, pressing or releasing it.
Components of the planetary gear set:
- sun gear;
- satellite;
- ring gear;
- drove
Planetary gear in a semi-disassembled state
Rotation is transmitted under the condition that one or two elements of the planetary gearbox are blocked. Friction clutches and brakes lock these elements.
To hold certain elements, a brake is used, and to lock the elements together, a clutch is activated, providing torque transmission.
Hydraulic cylinders, controlled by a distribution module, operate the brakes and clutches.
CVT automatic transmission
A CVT is a continuously variable automatic transmission in which the gears do not have a fixed gear ratio.
If we compare the CVT with other automatic transmissions, its advantage lies in the efficient use of engine power, because the crankshaft speed is optimally matched to the load on your car, which ensures fairly high fuel economy. Also, when driving a car with a CVT automatic transmission, a high level of comfort is achieved due to the continuous change in torque, as well as the absence of jerks.
CVT gearbox
CVT automatic transmission device
General structure of a CVT automatic transmission:
- sliding pulleys;
- differential;
- V-belt;
- torque converter;
- planetary reverse gear mechanism;
- hydraulic pump;
- electrical control unit
Sliding pulleys look like two wedge-shaped “cheeks” located on the same shaft. A hydraulic cylinder compresses the discs depending on the speed and puts them into action.
CVT automatic transmission cross-section
The torque converter has the same functions as in a classic automatic transmission, i.e. transmits and changes torque.
The device that distributes torque to the drive wheels is called a differential.
The planetary reverse gear mechanism causes the output shaft to rotate in the opposite direction.
In order to create pressure of the working fluid, the torque converter starts the hydraulic pump.
The control unit is used to control the actuators of the variator, depending on the signals supplied from the sensors (crankshaft location, fuel consumption control, ABS, ESP, etc.).
At the moment, the CVT cannot be combined with powerful engines, and therefore the CVT cannot become a competitor to the classic automatic.
Robotic mechanics
Robotic mechanics is a manual transmission in which there is no clutch pedal, and its functions are performed by an electronic unit.
Robotic mechanics
The robotic transmission combines the comfort of an automatic transmission with the reliability and fuel efficiency of a manual transmission. In most cases, a “robot” is cheaper than a classic automatic transmission. Currently, all leading automakers are trying to equip their cars with robotic gearboxes. However, it is worth noting that the so-called “robots” fail faster than other automatic transmissions.
Robotic automatic transmission device
General structure of the robotic gearbox:
- clutch;
- Manual Transmission;
- clutch and gear drive;
- control system
A friction type clutch, a separate disc or a package of friction discs is used. Progression consists of a double clutch that transmits torque without interrupting the power flow. A robotic automatic transmission can have either an electric clutch and gear drive, or a hydraulic one.
Let's look at the advantages and disadvantages, as well as how each of them works. The electric motor and mechanical transmission in the electric drive are the executive bodies. This drive is characterized by low gear shift speeds, about 0.3 to 0.5 seconds, its advantage is low power consumption.
Gear shifting in a hydraulic drive is performed by hydraulic cylinders controlled by solenoid valves, using more energy and having a faster gear shift speed (0.05 - 0.06 seconds on some sports cars).
The main disadvantage of a robotic gearbox is the rather long time it takes to change one gear, which leads to jerks and dips in the car's dynamics, and also reduces the comfort of driving the vehicle.
This problem was solved by introducing an automatic transmission with two clutches (preselective gearbox), gears can be changed without loss of power. Having a double clutch, you can select the next gear when the gear is engaged and engage it at the right time without interrupting the operation of the box.
There are two operating modes: automatic and semi-automatic. In automatic mode, the electronic control unit implements a specific transmission control algorithm using actuators.
Semi-automatic operation allows sequential shifting from lower to higher gears (and vice versa), with the selector lever and/or steering wheel paddles assisting in gear changes.
Video - automatic transmission
At the moment, there are many different gearboxes in the world, differing in their pros and cons. Some are characterized by economical fuel consumption, others - quick gear changes, etc. Therefore, each driver will be able to choose a gearbox that meets all his criteria for himself and his driving style.
Source: http://AvtoMotoSpec.ru/poleznoe/ustrojstvo-avtomaticheskoj-korobkoj-peredach.html
We study the principle of operation of automatic transmission
Today, automatic transmission is becoming increasingly popular among car enthusiasts. Despite the complex design and relatively high price, a considerable part of modern cars are equipped with an automatic transmission.
The automatic transmission function is completely similar to the mechanics. The automatic transmission receives the rotational indicator, changes it and transmits it to the actuators.
An automatic transmission, like its mechanical counterpart, is divided according to the number of operating modes and the method of their activation. Depending on the type of gearbox, different clutch methods may be used.
The most common and reliable type of gearbox is the principle of an automatic transmission with a hydraulic drive and three stages of modes.
Let's consider the main components of an automatic transmission, as well as the principle of their operation.
- Hydraulic transformer.
This device changes the torque and its subsequent transmission, thanks to the working fluid.
As a rule, a ready-made composition for automatic transmissions is used as a working mixture.
The use of analogues is highly undesirable for the correct operation of all components of the mechanisms and preserving the service life of the box.
It is a set of working elements in the form of gears. The gearbox is the most important mechanism of an automatic transmission and requires some attention when operating a vehicle.
- Control set. The entire operation of the machine is controlled using a special system included in the machine.
The combination of these elements ensures automatic gear shifting. Let us consider in more detail the main features of the constituent elements and their role in the operation of the system.
Hydraulic transformer
Automatic transmission
This device simultaneously performs several essential functions for the operation of the gear shift system. The transformer is a clutch element and at the same time transmits rotation to the gearbox. The gearbox contains an automatic transmission, the pump disk is tightly coupled to the flywheel.
The turbine element, in turn, interacts with the gearbox shaft. Between these combinations there is a working mixture. Thus, two bundles of automatic transmission components interact with each other using a special composition.
When the car's engine is active, the action of the flywheel is transmitted to the pump disk, which in turn sends the mixture to the turbine elements. In this regard, the components of the turbine part of the car begin to move under a certain influence.
The liquid is not repelled from the working parts and does not interfere with the proper operation of the pump, thanks to a certain rule laid down in the creation of the automatic box. The transmission contains an element with a special bend of the wings. It is located in the middle of the aggregates discussed above.
Thus, the function of the automatic transmission is accompanied by the following actions: after reacting to the movement of the turbine disk, the working fluid acts on the pump and changes the rotation rates to the required ones. At this time, two forces act simultaneously as part of the system: the working mixture and the car engine.
When the pump starts, the intermediate mechanism does not perform any action. Otherwise, the movement of the blades would interfere with the functioning of the mixture. Therefore, the intermediate wings rotate at the required speed under the influence of fluid pressure.
When the pump reaches a speed corresponding to the rotation speed of the turbine, the engine power is transferred to the gearbox thanks to the fluid. Thus, the transformer performs the function of a hydraulic clutch.
But for further transmission of torque, the action of a mechanism interacting with the active shaft is required.
Gearbox.
The automatic transmission gearbox includes several components: a clutch mechanism and brake elements. Thus, the gearbox is a unit in which: around the central gear, there are satellites that interact with the drive.
This set is surrounded by a gear. During movement, the drive transmits rotation to the gear. The clutch element combines several discs that interact with each other. As the central shaft rotates, the coupling discs also come into action.
In the case of three modes in the gearbox, there are two rows of sequential clutches. The first gear is connected to gear number two, then the second interacts with the next one.
To actuate the clutch, the system includes a special piston, which receives movement due to a certain pressure.
The brake is a grip mechanism that stops the action of one of the gearbox elements. If the central gear stops, the speed of all side elements decreases accordingly.
Correct interaction of components is only possible if the speed of the component mechanisms is the same. Thus, by completely stopping or partially slowing down one of the system mechanisms, we achieve a complete reduction in speed.
This automatic transmission design is most often used on cars with rear-wheel drive and the engine located in the front of the car. In this case, we considered the location of all box modes on one axis.
Thus, the dimensions of the automatic transmission are significantly reduced. To control the processes described above, the system includes a hydraulic control unit.
Control system
The control system includes a pump, controller, lubricating fluid conductors and a set of actuators.
An important role in the process of controlling the components of an automatic transmission is played by the speed of the engine and the load on the drive wheels of the vehicle. When the engine starts, the pump creates optimal pressure to reduce the output rotation speed. Thus, the first gear of the gearbox is engaged.
According to the increase in engine speed, the pump changes the pressure parameters and controls subsequent switching of transmission modes. As the load on the car's wheels increases, the controller monitors the pressure and repeats the work processes in direct or reverse order.
Thanks to the considered actions, we obtain automatic engagement of the optimal gear while the vehicle is moving.
Of course, the operating principle of an automatic transmission is much more complex than that of its mechanical counterpart, yet the automatic transmission has earned its appreciation among motorists. The automatic principle makes driving a car simpler and more comfortable.
automatic transmission diagram
Automatic transmission is often chosen by ladies or novice drivers. Because the ease of use of an automatic transmission allows you to fully master your driving style without being distracted by changing gears. In addition, an automatic transmission will reduce fuel consumption in urban environments with constant traffic jams.
Despite a number of worthy advantages, automatic transmission has its disadvantages, including:
- Higher consumption of the fuel mixture compared to a manual transmission (under the same operating conditions.
- The car takes longer to accelerate.
- Inability to use the full power of the matorator.
- Difficult operation in extreme weather conditions.
- Picky about weather and road conditions.
- Lack of engine braking.
Of course, many fans of mechanics are dissatisfied with the lack of control over the car when equipped with this type of transmission. Therefore, it is impossible to say obviously which box is better to use.
In this case, everything completely depends on the preferences of the car enthusiast and his driving style. It is important to understand that the principle of an automatic transmission is more complex and if malfunctions occur, it is difficult to diagnose and restore the transmission yourself.
After studying the material provided, you can independently understand the causes of the problem and save some money on the services of car workshops. Otherwise, the cost of the automatic transmission is fully justified by its convenience, especially in a cramped city.
Check and maintain the automatic transmission in a timely manner, this way you will extend its service life and avoid the cost of car repairs.
Good luck studying the structure and operating principle of automatic transmission!
Source: http://carmend.ru/engine/izuchaem-princip-raboty-akpp.html
How to use an automatic transmission - what is it, does it work, on the car, reasons, gears, should
Are you planning to buy a car with an automatic transmission? Then it won’t hurt to understand the rules for its use. After all, if you don’t know how to use the automatic transmission, you can cause it to break down.
A car with an automatic transmission is a convenient vehicle. But the automatic transmission is not suitable for those who want to feel the dynamics of the movement.
If you are a supporter of a car with this type of gearbox, the following information on how an automatic transmission should work will be very useful to you.
What you need to know
Let's look at the features of the design and operation of an automatic transmission so that you can make the right choice for yourself.
After all, if the automatic transmission is used incorrectly, a breakdown may occur, the repair and replacement of which will cost a pretty penny.
Definitions
So, automatic transmission robot - what is it? An automatic transmission is a type of vehicle transmission that provides automatic selection of gear ratios that correspond to driving conditions, taking into account a number of factors.
Automatic transmissions are considered to be the planetary part of the units, with the help of which gears are changed.
With torque converters (and without them, the automatic transmission cannot work normally), it forms an automatic transmission.
Using an automatic transmission involves changing gears without driver intervention.
Basic functions of the lever
Using this type of gearbox is much easier than others. The automatic transmission has several functions and modes:
| R–Park | Used when parking. If you enable this mode, the internal blocker is activated. This function requires the parking brakes to operate. The car does not move |
| R–Reverse | This function is responsible for moving the machine backwards |
| N-Neutral | It is a neutral gear that is used before the driver chooses the direction of travel. Allows you to tow a vehicle. But this mode cannot be used often |
| D-Drive | In this mode, forward movement is possible. When switching to this mode, be sure to use the brake pedal (but not at high speed). Locking possible |
| 4-3-2-L | Special modes that are used on various roads. If you want to drive in mountainous areas, use L mode. This way the car will drive at the same speed |
| D3(S) mode | In this gear, the vehicle is controlled on uneven surfaces, especially when climbing and descending. This mode provides better brake response. |
| D2 | It is a low gear for overcoming descent and ascent. Relevant for use on sand and icy conditions |
| Steptronic, tiptronic | Allows you to change gears manually. This increases control over vehicle movement on a dangerous road section. Not every system has such modes |
| Sport or Kick down | Allows motors to spin more to generate lower speed. In this mode, the car can accelerate sharply (when overtaking, advancing). Engine performance is maximum. Not advisable to use every day |
| Shift | Function for calling a service. In the case when the power is turned off, it becomes possible to disable the locking of the automatic transmission levers. Very rarely used |
There are also a number of additional functions.
How does an automatic transmission work?
Let us outline the basic rules that owners of cars with automatic transmission should not forget.
Operating principle
The principle of operation of the automatic transmission for different types of gearboxes is only one due to the fact that in all cases there is one device.
Comprises:
| Fluid couplings (torque converter) | What is located between the gearbox housing and the engine. It transmits torque when the car starts moving |
| Planetary gearbox | Indirect torque transmission |
| Friction clutches | With the help of which gear shifts occur when automatic transmission elements communicate or disconnect |
| Overrunning clutch | With the help of which shocks are reduced when changing gears |
| Connecting shafts and drums | — |
Instructions for use
The spool valves present in the automatic transmission can direct the flow of oil to the pistons of the brake band and friction clutch.
Adjust the position using the handle or using automatic commands. There are 2 types of automation:
| Electronic | The movement of the spools is carried out by solenoids, the cable of which has an outlet to the control unit of the box |
| Hydraulic | Oil pressure is applied, including when the driver presses the gas. The automatic transmission will receive information about what position the pedal is in. As a result, the spools switch |
Let us briefly list the basic rules for using an automatic transmission. The main thing is not to use slip, especially in winter.
Otherwise, you can overload the box and system. It’s great if there is traction control, with the help of which you can normally drive onto a flat road.
This function cannot be completely disabled, but it is possible to minimize its functionality.
Otherwise, problems with the operation of the automatic transmission may occur. A gearbox of this type should be regularly diagnosed and the transmission replaced in a timely manner.
Don't forget these points:
| Don't push start your car | So as not to break the system |
| Switching between opposite modes is not allowed | When the car is moving |
| You can park or use reverse then | When the vehicle comes to a complete stop |
| To ensure normal operation of the blocker | Use the parking brake when stopping on slopes |
| Don't use neutral mode | When you are in a traffic jam |
| Don't mix oils | With additional additive |
| Stick to maintenance schedules | — |
| Cannot exceed | Set speeds in each range |
| If you forcefully change speed | Select a mode for which the speed data is not a limit |
| Some cars allow the use of 4th overdrive gear | When you press the OD button. When it is disabled, the indicator will notify you of this |
Recommendations for use in winter conditions
Difficulties may arise in winter. To prevent breakdowns, you must remember the following features:
| When turning on slippery roads, use only low gear | This way, maneuvering will be correct and smooth, and the risk of an accident will be minimal. |
| Warm up the system before driving | So that the oil in the automatic transmission can warm up. If you're in a hurry and can't wait, then drive slowly for at least a while so the car can warm up. |
| When the car warms up | Place the gear shift levers in several positions without releasing the brakes. Stay in each position for a few seconds |
| Take care of your car | Use gentle modes for a couple of kilometers after you start driving. |
Remember - under heavy loads, more heat is generated in the torque converters. Consider installing additional radiators to cool the box.
Source: http://jurist-protect.ru/kak-polzovatsja-korobkoj-avtomat/
Design and maintenance of an automatic transmission
The main difference between a car’s automatic transmission and a manual transmission is that it allows you to free your right hand from unnecessary movements. The automatic transmission provides the appropriate choice of gear ratio without driver intervention. There are differences in the design features. The automatic transmission operates due to a hydromechanical drive and planetary mechanisms.
In cars with automatic transmission there is no clutch pedal , since there is no need for it. In such cars, you don’t need to change gears yourself - just put the gearbox mode selection lever on Drive. While performing the same functions, manual and automatic transmissions operate completely differently. Let's take a closer look at the features of the latter's device.
Example of an automatic transmission
Thanks to the automatic transmission, the car's engine is able to operate in a limited speed range. At the same time, it provides him with a wide range of speeds. Thanks to this unit, driving the car has become much easier for the driver.
Among the main elements of a classic automatic transmission:
- torque converter;
- clutches (friction, overrunning);
- planetary reductions;
- connecting shafts;
- drums.
In some cases, the automatic transmission design includes a brake band, which performs the function of braking one of the drums. The exception is automatic transmissions manufactured by Honda. They do not use planetary gearboxes, but special shafts with gears (they are also used in manual transmissions).
Video about the design of an automatic transmission:
http://www.youtube.com/watch?v=7avIrCPOpm4
The main function of the torque converter is to transmit the slipping torque when starting the car. When the engine reaches high speeds, the friction clutch locks the torque converter. This makes slipping impossible.
The planetary gearbox, in turn, indirectly transmits torque.
The “package” (as friction clutches are called) performs the function of direct gear shifting due to the separation and communication of automatic transmission elements.
Unlike its manual sister, an automatic transmission engages and disengages the same set of gears. This is what makes planetary gearing possible.
Planetary gear model
Automatic transmission operating modes
The automatic transmission can operate in several modes. Since the second half of the last century, almost all automatic transmissions have been equipped with a standard set of modes, which are indicated on the lever in Latin symbols:
- N (neutral gear) - used when towing or short parking;
- D (forward movement) - used if all stages are engaged, excluding overdrive gears;
- R (reverse) - turns on only when the car has completely stopped moving;
- L (low gear) - used for so-called quiet running;
- P (parking mode) - locks the drive wheels, has nothing to do with the parking brake.
There is a strict sequence of automatic transmission modes - P⇒R⇒N⇒D⇒L .
Standard letter designations for automatic transmission modes
It is worth noting that modern cars can be equipped with automatic transmissions with additional operating modes:
- O/D (overdrive) - allows you to automatically switch to overdrive gears; ensures uniform movement on the highway;
- D3 (for city driving) - provides for the use of only first/second/third gears or disabling overdrives;
- S or 2 (“winter” mode) - includes lower gears;
- L or 1 - Uses first gear only.
Features of operating a car with automatic transmission
Driving a car with an automatic transmission has its own nuances. Before you start driving such a car, you should first start the engine and warm it up well. “Mechanics” are undemanding in this matter, but for an automatic transmission, warming up is important, since this affects its ability to shift to higher gears. You only need to start the car in park mode (P) .
Within a few minutes of engine operation, the transmission fluid can flare up to the required operating temperature, after which you can not be afraid to start driving.
Press the brake pedal, move the lever to drive mode (D) and release the pedal to move the vehicle.
It should be noted that there is no need to release the brake smoothly, since the torque converter provides smooth starting. This process does not require driver intervention.
Video about warming up the automatic transmission:
Automatic transmission care
The automatic transmission is one of the most complex elements of a car, so it needs proper care. Experts note that the most dangerous thing for an automatic transmission is overheating, as a result of which its resource sharply decreases, various deformations form in the seals, and oil begins to leak from the crankcase. In this regard, you should not overload such a car.
The key to automatic transmission maintenance is to regularly check the oil level. If it starts to leak, the automatic transmission signals you about the need for its prevention.
In this case, the oil must be replaced in a timely manner.
If a manual transmission does not require frequent oil changes, then an automatic transmission needs this procedure after every thirty to forty thousand kilometers of driving.
So, there are several rules for automatic transmission care and prevention that must be followed. The most important thing is checking the fluid level in the gearbox . If there is not enough oil in the unit, this can lead to the torque converter slipping and overheating. If there is too much transmission fluid, it will foam.
In any case, the automatic transmission may fail. Therefore, constantly monitor the oil and add exactly the amount required according to the level. To check the fluid level, you need to warm up the box and drive the car for about 10 kilometers. Having parked the car on a level surface, you should take out the dipstick, wipe it, insert it back and remove it.
You will see a corresponding trace of oil, which will allow you to determine the amount of oil.
The process of replacing automatic transmission fluid
Note that you can learn a lot from the appearance of the transmission fluid. Its color and smell play an important role:
- A reddish transparent tint, the absence of a pronounced odor and any small particles indicate the serviceability of the automatic transmission.
- A brownish color indicates that the oil needs to be changed urgently.
- The dark shade of the liquid, combined with the smell of burnt metal and the presence of small grains, warns that the gearbox will soon fail because its rubbing parts are burning.
Prevention of automatic transmission malfunctions
We have already mentioned that the automatic transmission is complex and therefore needs more careful treatment than a manual transmission. The latter is almost impossible to break, but the automatic transmission is not so reliable. Take into account some features during its operation to prevent possible breakdowns:
- Do not switch the selector to modes R and P while driving. If your automatic transmission is reliable enough, then the car will simply stall. However, in most of these situations, the transmission simply breaks down. Therefore, be careful - turn on the mentioned modes only after the vehicle has completely stopped moving.
- Do not overuse the kick-down function. A car with an automatic transmission can be accelerated sharply by shifting to the lowest gear. The engine speed increases sharply, due to which acceleration occurs. This switching is carried out by sharply pressing the gas pedal. But you should not use this technique often - it will significantly reduce the transmission life, and fuel consumption will increase.
- Do not overload the vehicle. You should not tow other vehicles or trailers that are heavier than yours.
- Do not drive on mud or weak road surfaces. If you skid, the automatic transmission will overheat and break down. If this happens, then do not get out onto a dry area by rocking the car back and forth. This will damage the gearbox. It's better to ask other motorists for help.
A manual transmission is less demanding than an automatic
Operating an automatic transmission in winter
Most automatic transmissions break down in winter. There are two reasons for this:
- low air temperature has a detrimental effect on the resources of the automatic transmission;
- Wheel slip on ice when starting to move damages the transmission.
In this regard, it is necessary to prepare the car for winter in advance. Be sure to change the hydraulic fluid and automatic transmission filter before the onset of cold weather. Also follow some guidelines for warming up the engine. Start the car in the cold, warm up the engine and gearbox.
Apply the brake and select L, R or D mode on the lever. Please note - if the engine stalls, let it warm up some more. The colder it is outside, the longer you need to keep your foot on the brake pedal.
If the air temperature is 20 degrees below zero, warm up the automatic transmission for about five to eight minutes.
When starting to drive, put the selector in L mode and drive 100 meters. Then move the lever to positions 2, 3 and D.
During this period of time, the transmission fluid will have time to go through several passes through the box and get into the clutches.
Since the speed will be low, as will the engine speed, the process of turning on the friction elements will take place in an optimal, gentle mode. This will prevent them from wearing out.
Cross-section of a Lexus car automatic transmission
What oil to use for automatic transmission refueling
The hydraulic fluid in an automatic transmission serves not only as a lubricant, but also as a working fluid that is subjected to high power loads and temperature changes. In such conditions, only special oils can effectively perform the necessary functions. Automatic transmission fluid is usually designated as ATF ( Automatic TransmissionFluid ).
The oil must meet certain characteristics. First of all, this is high fluidity, which the box especially needs in the cold season.
However, in order to prevent the liquid from leaking during the heating process, a special thickener is added to it, which is effective only at high temperatures.
Moreover, friction modifiers and various additives are introduced into the oil to prevent friction, wear, and oxidation of parts.
If it occurs to you to pour any other fluid into the gearbox instead of ATF, this will lead to immediate failure. At the same time, oil for automatic transmissions is perfect for mechanical units.
Also, you should not buy a fluid that is of a lower rank than that recommended by the automatic transmission manufacturer. However, in a desperate situation, filling with such oil is acceptable.
As soon as you buy a suitable transmission fluid, it must be urgently changed in the box to avoid malfunctions.
Video about changing automatic transmission oil:
Remember that the service life of an automatic transmission is much shorter than that of a manual transmission. It can range from 150 to 300 thousand kilometers. Deviation from these figures depends on the driver’s driving style and on the timeliness of automatic transmission maintenance.
Constant intensive acceleration, incorrect selector switching, and avoidance of replacing the fluid and filter greatly influence the reduction in the service life of the box.
By following our simple recommendations for operating an automatic transmission and driving quietly, you can significantly increase its service life before the need for major repairs arises.
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Source: http://365cars.ru/soveti/kak-ustroena-avtomaticheskaya-transmissiya-avtomobilya.html
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