Automatic transmission (automatic transmission) and its

One of the types of gearboxes in the car is an automatic transmission. It can be used without the intervention of the driver who drives the vehicle, choosing the gear ratio required for certain driving conditions. This number is caused by many factors.

Automatic transmission

This gearbox is different from the manual transmission automatic transmission. It also belongs to the planetary gearbox. It consists of several gears. They are also called satellites or planetary. They rotate around a central axis.

Purpose and operation of the automatic transmission

Many drivers more than once had to drive a car on both a manual and an automatic gearbox, and there is also a robotic box (Manual transmission), but we'll talk about it another time. There are two differences between two mechanics and an automatic machine:

  • Automatic transmission не имеет педали сцепления
  • machine does not require shifting. This happens automatically in drive mode.

The function of all transmissions is the same, but the implementation of each of the types has its own. Automatic transmission at limited speeds allows you to have a wide range of speeds. If the mechanics shift gears by blocking gears, then in the machine the same gears can provide a different gear ratio. The automatic transmission uses a planetary gear.

Automatic transmission

The design of the automatic transmission

A standard automatic transmission consists of the following basic elements:

  • hydrotransformer;
  • planetary reductor;
  • couplings (friction and overrunning);
  • drums;
  • shafts.

The design and principle of operation of the torque converter

Hydrotransformer устанавливается между коробкой передач и двигателем. Назначение этого элемента следующее – передача крутящего момента при трогании авто. При осуществлении высоких оборотов это устройство обычно блокируется, расположенными внутри муфтами. Благодаря этому меньше расходуется топливо и исчезает проскальзывание.

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The device of the torque converter is as follows: three wheels: a turbo pump, a stator, a turbine. Usually the stator is stationary and connected to the body of the automatic box. In some designs, the stator may not be attached, and its immobility will be provided by special couplings. Due to such braking a wide range of speeds is provided.


It is thanks to the use of the torque converter that there is no kinetic energy and, accordingly, the car moves smoothly, there is no load on the transmission of the car. The only disadvantage is slippage, as a result of which additional heat is generated and fuel consumption increases.

Принцип работы гидротрансформатора отличается от гидромуфты. У него моменты на турбинном и насосном колесах разные. Чтобы сэкономить топлива, в устройство стали вводить жесткое крепление между собой турбины и насоса. Такое затормаживание осуществляется при достижении более высокой скорости. При управлении Automatic transmission с помощью компьютера момент, когда необходима блокировка, выбирает программа управления.

Also, this lock allows you to have the same fuel consumption as a manual transmission. With it, you can implement engine braking and, as well as economical fuel consumption. In this mode, fuel injection stops, but only at the time of blocking the elements of the torque converter.

Planetary reductor и его работа

As part of the automatic transmission has a manual transmission. It is necessary for the implementation of the movement of the car in reverse, which is carried out with the help of a stepped change in torque. The planetary gearbox used in the design of the automatic box has compact dimensions and coaxiality of work. Usually there are several in the automatic transmission. They are connected in series with each other. Thus, their joint work is realized.

Planetary reductor

Thanks to this design, the mechanical component of the automatic transmission provides the necessary number of stages. In modern models of cars sold from 6 to 8 steps, there are also 9-speed. The planetary gearbox in the box is called the planetary gear set.

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Automatic transmission scheme

At first glance, any scheme seems complicated, but on closer examination, everything turns out to be much simpler. In the automatic box, when blocking elements of the planetary series, the necessary torque change takes place.

The gear ratio may be more or less. At a lower value, the sun gear must be stationary. With an increased value, the ring gear must be locked. The carrier that enters the planetary series, when locked, changes the direction of rotation.

Automatic transmission

Scheme of an automatic transmission

To lock in the design of the mechanism uses special couplings. Their closure occurs with the help of hydraulic cylinders. Thus, the gear shift is carried out due to the selected algorithm of the brakes and clutches.

The working fluid in the automatic transmission is distributed using a special pump. It is powered by a torque converter. The pump is the basis of the gearbox hydraulics. The principle of operation of the torque converter is a kind of torque conversion from the engine to the box. Thanks to him, a smooth transfer.