Equipping cars with an automatic transmission has reduced the amount of load imposed on the driver while driving. Let's talk about the device of an automatic transmission automatic transmission.
Benefits of using
The use of an automatic transmission eliminates the need for constant use of the shift lever. The speed change is performed automatically, depending on the engine load, the speed of the car and the wishes of the driver. Compared with manual box transmissions, automatic transmission has the following advantages:- increases the comfort of driving a car due to the release of the driver;
- automatically and smoothly performs switching, matching the engine load, speed, degree of pressing the gas pedal;
- protects the engine and undercarriage car overload;
- allows manual and automatic switching speeds.
There are some differences in the layout and structure of the automatic transmission of a front wheel drive vehicle and a rear wheel drive vehicle. Automatic transmission for front-wheel drive vehicles is more compact and has a compartment inside its body main gear - differential.
The principle of operation of all machines is the same. To ensure movement and performance of its functions, an automatic transmission must be equipped with the following units: a mechanism for selecting a driving mode, a torque converter, a control and monitoring unit.
What does an automatic transmission consist of?
- Torque converter (1) - corresponds to the clutch in a manual box, but does not require direct control from the driver.
- Planetary row (2) - corresponds to a block of gears in a manual transmission and serves to change the gear ratio in an automatic transmission when shifting gears.
- Brake band, front clutch, rear clutch (3) - components by means of which gear shifting is carried out.
- Control device (4). This assembly consists of an oil sump (transmission pan), a gear pump and a valve box.
It not only transmits torque, absorbs and dampens engine vibrations, but also drives the oil pump located in the gearbox housing. Oil pump fills the torque converter with transmission fluid and creates operating pressure in the control and monitoring system.
Therefore, the opinion is incorrect that a car with an automatic transmission can be started forcibly, without using a starter, but by accelerating it. The automatic transmission pump receives energy only from the engine, and if it does not work, then the pressure in the control and monitoring system is not created, no matter what position the driving mode selection lever is in. Hence, forced rotation cardan shaft does not oblige the gearbox to work and the engine to rotate.
Planetary row - unlike mechanical transmissions, which use parallel shafts and interlocking gears, planetary gears are used in the overwhelming majority of automatic transmissions.
Several planetary mechanisms are located in the gearbox housing, and they provide the necessary gear ratios. And the transfer of torque from the engine through the planetary gears to the wheels occurs using friction discs, differential and other devices. All these devices are controlled by transmission fluid through the management and control system.
Brake band - a device used to block elements of the planetary gear set.
The valve box is a channel system with positioned valves and plungers that perform monitoring and control functions. This device converts vehicle speed, engine load and accelerator pedal pressure into hydraulic signals. On the basis of these signals, due to the sequential switching on and out of the operating state of the friction blocks, the gear ratios in the gearbox are automatically changed.
Today, most drivers have no idea how they would drive a car that does not have an automatic transmission. Some newbies are horrified at the thought of having to constantly change gears manually. Many experienced drivers have also realized long ago that driving with an automatic transmission is much more convenient. Despite all this, people are tormented by the question - how to properly operate the automatic transmission? This article is about this.
Modes of operation
To understand how to operate the automatic box, you need to figure out what modes exist.
It should be noted right away that the modes "P", "R", "D" and "N" are mandatory in every box. To select one of the modes, you just need to move the gear lever to the appropriate position. In contrast of mechanical box is that the movement of the lever occurs along one line.
The mode the driver has selected will be displayed on the control panel. This makes it possible to closely monitor the road and not be distracted to look at the lever.
- "P" - parking. Used during long-term parking. It is from the parking lot that it is desirable to start the car. It is important to completely stop the car before turning on this mode.
- "R" - used to move in reverse... To turn on, you need to stop completely.
- "N" - neutral position. When the lever is in neutral, no torque is transmitted to the wheels. Should be used during minor stops.
- "D" - movement. When the selector is in this position, the car drives forward. Gear shifting is done independently. The driver only presses the gas pedal.
In cars in which a five - or four - speed gearbox is installed, the selector has several positions for moving forward: "D", "D3", "D2", "D1". These numbers show the top gear.
- "D3" - "first 3 gears". Recommended for use in cases where it is impossible to move without braking.
- "D2" - "first 2 gears". Move the lever to this position when the travel speed is less than 50 km / h. Most often used on poor quality roads.
- "D1" ("L") - "1st gear only". Used if maximum speed is 25 km / h. It is worth moving the lever to a similar position when the car is in a traffic jam.
- "ОD" - "overdrive". You should switch to this position when the speed reaches more than 75 km / h, and leave it when the speed drops below 70 km / h. The overdrive makes it possible to reduce fuel consumption when driving on motorways.
Most of the new cars with automatic transmission have several auxiliary automatic transmission modes. These include:
- "N" is the standard one used during normal driving.
- "E" - fuel saving mode. Helps the vehicle drive at a pace that significantly reduces fuel consumption.
- "S" stands for sport. When the driver switches to this mode, he can make the most of the engine power. It is not surprising that fuel consumption in this mode will be high.
- "W" for winter. It is used in those moments when you need to start driving from a slippery road surface.
Of course, there are drivers who could not get used to the automatic transmission, taking into account all its advantages. To meet the needs of these people, the Tiptronic regime was created. In essence, it assumes imitation manual control... On the box, it is implemented in the form of a groove for the selector, and is indicated by plus and minus signs. The plus makes it possible to increase the gear, and the minus - to lower, respectively.
Basic operating conditions for automatic gearbox
In order to start driving a car in which an automatic transmission is installed, you should perform the steps in the following order:
- Step on the brake pedal.
- Move the selector to the "drive" position.
- Remove from the parking brake.
- Release the brake slowly. The car will begin to move slowly.
- Step on the accelerator pedal.
- To slow down, you need to throw the gas. If you need a quick stop, then you definitely need to use the brake.
- To drive off after a minor stop, you just need to move your foot from the brake to the accelerator.
The basic rule of using automatic transmissions is to avoid sudden maneuvers. If you constantly do them, this will lead to an increase in the gap between the friction discs, and then in the differential. All this will lead to the fact that the car will jerk during each gear change.
Experienced craftsmen believe that the machine should be given a short "rest". This means that the car must be allowed to move for a few seconds. idle... It should be noted that even in a car with powerful engine, sudden movements will significantly reduce the resource of the box.
In fact, this moment is very important, because most of these boxes break in the winter. First of all, this is due to a significant drop in temperature and the fact that cars often skid on the ice. In order to maximally protect your car from damage, you should adhere to the following recommendations:
- Before the onset of cold weather, check the quality and level of the liquid in the box, and replace if necessary;
- Be sure to warm up the car before driving;
- If the car is stuck, do not step on the gas in the hope of leaving. It is worth trying to downshift (if possible) or just push;
- Use only low gears before tight bends.
What not to do
What not to do on a car with an automatic transmission:
- First of all, do not overload the box if the machine has not warmed up to required level... Even if the outside temperature is above zero, the first few kilometers, the movement should be smooth and measured.
- Automatic transmission "does not like" off-road very much. For cars with a gun, it is best to avoid roads with poor surfaces. If a " iron Horse»Stuck, sometimes it is better to use a shovel than to put pressure on the gas.
- It is not recommended to subject the automatic transmission to high loads. If there were plans to tow a trailer, then it is better to get them out of your head.
- It is strictly forbidden to start the car from the so-called pusher. Many people violate this prohibition, but it is worth remembering that this will not pass without a trace for the box.
Of course, we must not forget about the individual features of switching between modes:
- you can stay in "neutral" only if the brake is pressed;
- it is forbidden to turn off the car in "neutral";
- it is allowed to turn off the engine only in the “parking” position;
- when the car is in motion, do not move the lever to the "parking" and "backward" positions.
Summing up, it is worth noting that the automatic transmission may seem rather "finicky" and having a small resource. In fact, if you correctly exploit it, then it will delight its owner for a very long time.
Video: how to use automatic transmission correctly
Both in real life and in virtual space there is an eternal dispute between the owners of cars with automatic machines and manual gearboxes. This dispute is as endless as the one that comes first: an egg or a chicken. Without entering into it, we will simply try to fill in certain gaps in the knowledge of those novice car owners who have an automatic transmission installed.
What is it, automatic transmission?
We have heard such types of automatic transmissions as tiptronic and steptronic. A few words about these common names.
Tiptronic Is an automatic transmission that has the ability manual switching gear. In manual mode, the driver manually selects the gear by pushing the selector lever in the "+" or "-" direction.
Steptronic -Automatic transmission used in BMW. It also has the ability to manually shift gears, but the shift speed is increased, and is comparable to a manual transmission. In the steptronic, the lever moves to the positions P, R, N, and D. In addition, there is a position "M / S" (Manual / Sport), which in the "sport" mode holds the gear until reaching maximum number turns, then there is an increase in the transmission.
How does an automatic transmission work?
Automatic hydromechanical transmission in the classic version consists of planetary gearboxes, hydraulic torque converter, overrunning and friction clutches, connecting drums and shafts.
Without going into the jungle, especially with your own hands, it is strongly not recommended to do it, the principle of operation automatic transmission differs in that gear shifting occurs due to the interaction of planetary mechanisms and a hydromechanical drive using electronic actuators.
The features of automatic transmission operation have already been highlighted on the site pages. But we will repeat ourselves.
- Automatic gearbox requires careful warming up before driving, especially in winter.
- It is not recommended to move the selector lever on the fly to the P and R positions.
- There is no need to turn on neutral when going downhill, there will be no fuel economy (as it is considered), but problems with braking may arise.
- Engine braking is not performed in all modes. The manufacturer gives instructions in the Manual for more details on operation in various modes. For all our carelessness, it is advisable to adhere to these instructions. First of all, this, and secondly, not the least, is the cost of repairs or complete replacement delicate and sensitive unit - automatic transmission
Well, actually, you can start, warm up and start moving.
Good luck to you lovers of your car.
Automatic box A car's gear is designed to transfer engine power to the wheels. It selects the gear that best suits the current driving speed. The automatic transmission eliminates the need for manual gear changes. The car's computer uses sensors to determine at what moment it is necessary to switch the speed and sends a signal to in electronic format to enable or disable transmission.
The main elements of an automatic transmission
A car's automatic transmission mechanism is a system of levers and gears that transfer power to the drive wheels, allowing the engine to operate at its best.
The box is assembled in an aluminum casing called a crankcase. It houses the main components of an automatic transmission:
- A torque converter that acts as a clutch, but does not require the driver to directly control it.
- A planetary gear that changes the gear ratio when shifting.
- Rear, front clutches, brake band, directly carrying out gear shifting.
- Control device.
How does a torque converter work?
The torque converter consists of the following main elements:
- pump or impeller;
- turbine wheel;
- blocking plates;
- stator;
- overrunning clutch.
To understand how an automatic transmission works, you need to imagine its overall structure. So, the pump is mechanically connected to the engine. The turbine wheel is connected to the gearbox shaft using splines. When the impeller rotates with the engine running, an oil flow is created that rotates the turbine wheel of the torque converter.
In this case, the torque converter performs the role of a conventional fluid coupling, by means of liquid only transmitting torque from the engine to the automatic transmission shaft. When the engine speed increases, no significant increase in torque occurs.
To convert torque, the automatic transmission circuitry includes a stator. The principle of operation is that it redirects the flow of oil back to the pump impeller, causing it to rotate faster, increasing the torque. The lower the speed of rotation of the turbine wheel in relation to the pump, the more residual energy is transferred by the stator through the returned oil to the pump. Accordingly, the torque increases.
Turbine and automatic transmission pump basics
The turbine always runs slower than the pump. The maximum ratio of pump and turbine rotation speeds is achieved when the vehicle is stationary, decreasing with increasing speed vehicle (TS). The stator is connected to the torque converter through an overrunning clutch that can rotate in only one direction.
The turbine and stator blades are specially shaped so that the oil flow is redirected to back side stator blades. In this case, the stator wedges and, remaining stationary, it transfers the greatest oil energy to the pump inlet.
Due to this operating mode of the torque converter, maximum gear torque. It increases almost three times when the car starts to move.
When the vehicle accelerates, the turbine relative to the pump slips less and less until the moment when the stator wheel is picked up by the oil flow, starting to rotate in the direction freewheel overrunning clutch. At the same time, the device starts to work as a conventional fluid coupling, does not increase the torque. In this mode, the efficiency of the torque converter does not exceed 85%. This mode of operation is accompanied by the release of excess heat and an increase in fuel consumption.
Purpose of the blocking plate
This disadvantage is eliminated with the help special device - blocking plate. Despite the mechanical connection with the turbine, it is structurally designed so that it can move to the right and left. This device turns on when the vehicle reaches high speed... On command, the control device changes the oil flow so that it presses the blocking plate against the converter housing on the right.
In this case, the turbine and pump are mechanically connected to each other. To increase grip on inner side a special friction layer is applied to the converter housing. Thus, the engine is connected to the output shaft of the automatic transmission. Naturally, this blocking is immediately turned off even with slight vehicle braking.
Above, only one of the methods for blocking the torque converter was described. However, any other method has the same goal - to prevent the turbine from slipping in relation to the pump wheel. Usually the described mode of action in various sources is called Lock-Up.
It will be easier to understand the operation of a torque converter for dummies if, instead of a turbine and a pump, imagine two simple fans, one of which is powered by the network, and the other rotates due to the air flow created by the first fan. Only, instead of air, oil appears here, and the blades of the first fan (pump in the case of an automatic transmission) are set in motion not due to electricity, but due to mechanical connection with a car engine shaft.
Planetary rows
The torque converter can increase torque, but only up to a certain limit. An automatic transmission device for a more significant increase in torque, for example, when overcoming hills, as well as for reversing, provides planetary gears. Planetary gear also provides smooth gear shifting while driving without loss of engine power. Thanks to it, shifting occurs without the jolts that occur during the operation of a conventional transmission.
The planetary row includes the following elements:
- sun gear;
- satellites;
- epicycle;
- drove.
The planetary row is called due to the fact that the friction wheels rotating simultaneously around their axes and moving along with these axes are very reminiscent of the planets of the solar system. It depends on their relative position which gear is currently on.
How are gears shifted in an automatic transmission?
Gear change or change in planetary gear gear ratio carried out by blocking and unblocking the planetary gear elements by means of brake bands and clutches. IN hydraulic system automatic transmission of the car, the gear change is directly carried out by the valve. The three-speed gearbox has two such valves, one of which switches from first gear to second, the other from second to third. The four-speed box already has three valves.
Other types of automatic transmission
In addition to the hydraulic transmission considered, other types of automatic transmissions are widely used today:
- CVT automatic transmission. In this type of transmission, there is no fixed gear ratio for gears. Therefore, such an automatic transmission is called continuously variable. The principle of operation is that, unlike other "automatic machines", it uses engine power more efficiently. As a result, cars equipped with this type of transmission are more economical and comfortable.
- Robotic checkpoint. Such a box can be called automatic, since in fact it is a conventional "mechanics", where the function of the clutch pedal is entrusted to the electronic unit... Cars with which gearboxes are also quite economical, but less comfortable, as often automatic mode accompanied by jerks.
Thus, in addition to the most common hydraulic automatic transmission there are several more types of automatic boxes that differ in their design. They differ in price, efficiency, comfort of car driving. The common thing is that the driver is relieved of the need self-choice and gear shifting.
This article continues the series on electrical protection devices - automatic switches, RCDs, difavtomats, in which we will analyze in detail the purpose, design and principle of their operation, as well as consider their main characteristics and analyze in detail the calculation and selection of electrical protection devices. Will conclude this series of articles step by step algorithm, in which briefly, schematically and in a logical sequence will be considered complete algorithm calculation and selection of circuit breakers and RCDs.
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Well, in this article we will figure out what a circuit breaker is, what it is intended for, how it works, and consider how it works.
Circuit breaker (or usually just "automatic") is a contact switching device that is designed to turn on and off (ie, to switch) an electrical circuit, protect cables, wires and consumers (electrical devices) from overload currents and short-circuit currents.
Those. the circuit breaker has three main functions:
1) circuit switching (allows you to turn on and off a specific section of the electrical circuit);
2) provides protection against overload currents, disconnecting the protected circuit when a current that exceeds the permissible flows in it (for example, when a powerful device or devices are connected to the line);
3) disconnects the protected circuit from the supply network when large short-circuit currents appear in it.
Thus, the automata simultaneously perform the functions protection and functions management.
By design there are three main types of circuit breakers available:
— air circuit breakers (used in industry in circuits with high currents of thousands of amperes);
— molded case circuit breakers (designed for a wide range of operating currents from 16 to 1000 Amperes);
— modular circuit breakers , the most known to us, to which we are accustomed. They are widely used in everyday life, in our homes and apartments.
They are called modular because their width is standardized and, depending on the number of poles, is a multiple of 17.5 mm; this issue will be discussed in more detail in a separate article.
We, on the pages of the site, will consider modular circuit breakers and residual current devices.
The device and principle of operation of the circuit breaker.
The thermal release does not work immediately, but after some time, allowing the overload current to return to its normal value. If during this time the current does not decrease, the thermal release is triggered, protecting the consumer circuit from overheating, melting of the insulation and possible fire of the wiring.
An overload can be caused by connecting powerful devices to the line that exceed the rated power of the protected circuit. For example, when a very powerful heater or an electric stove with an oven (with a power exceeding the rated power of the line) is connected to the line, or at the same time several powerful consumers (electric stove, air conditioner, washer, boiler, electric kettle, etc.), or a large number of simultaneously switched on appliances.
Short circuit the current in the circuit instantly increases, the magnetic field induced in the coil according to the law of electromagnetic induction moves the solenoid core, which activates the release mechanism and opens the power contacts of the circuit breaker (i.e. movable and fixed contacts). The line is opened, allowing you to remove power from the emergency circuit and protect the machine itself, the electrical wiring and the shorted electrical appliance from fire and destruction.
The electromagnetic release operates almost instantly (about 0.02 s), unlike thermal, but at significantly higher currents (from 3 or more values \u200b\u200bof the rated current), so the wiring does not have time to heat up to the melting temperature of the insulation.
When the contacts of the circuit are opened, when it passes electricity, an electric arc arises, and the greater the current in the circuit, the more powerful the arc. An electric arc causes erosion and destruction of contacts. To protect the contacts of the circuit breaker from its destructive action, the arc arising at the moment of opening of the contacts is directed to arc chute (consisting of parallel plates), where it crushes, decays, cools and disappears. When the arc burns, gases are formed, they are discharged out of the machine body through a special hole.
It is not recommended to use the circuit breaker as a conventional circuit breaker, especially if it is turned off when a powerful load is connected (i.e. when high currents in the chain), as this will accelerate the destruction and erosion of the contacts.
So let's recap:
- the circuit breaker allows you to switch the circuit (moving the control lever up - the machine is connected to the circuit; moving the lever down - the machine disconnects the supply line from the load circuit);
- has a built-in thermal release that protects the load line from overload currents, it is inertial and trips after a while;
- has a built-in electromagnetic release that protects the load line from high short-circuit currents and trips almost instantly;
- contains an arc-extinguishing chamber that protects power contacts from the destructive action of an electromagnetic arc.
We have analyzed the design, purpose and principle of operation.
In the next article, we will look at the main characteristics of a circuit breaker that you need to know when choosing one.
Look The design and principle of operation of the circuit breaker in video format:
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