Automatic Transmission Construction

Automatic transmission

The invention of the automatic transmission is an impressive step to improving the car’s transmission. Using of automatic transmissions in passenger cars greatly facilitated driving, and the driver stopped paying attention to gear shifting.

You can read useful information about automatic transmission construction below. In addition, you will know how an automatic transmission work and main differences between mechanical and automatic transmissions.

Advantages of Automatic Transmission

The advantage of automatic transmission is the driver does not need to constantly monitor gear changes. The required speed is switched on automatically depending on the engine load and the driving speed.

List of automatic transmission advantages

  • Increased driving comfort due to the release of the driver;
  • Automatic gear shifting depending on engine load, driving speed;
  • Overload protection of the engine and car chassis;
  • Choice between manual and automatic gear shifting.

Types of Automatic Transmission

Automatic transmissions are divided into two types depending on the transmission control and monitoring system.

Types of Automatic Transmission
  1. Automatic transmission with a hydraulic device;
  2. Automatic transmission with electronic control device.

Automatic transmissions can differ in design features depending on the drive of the car: front or rear.

Automatic transmission of front-wheel drive vehicles is equipped with a main gear compartment – differential.

The principle of operation of automatic transmissions is almost the same, and to perform its functions, the automatic transmission is equipped with a torque converter, a mechanism for selecting a driving mode, a control and monitoring unit.

Diagram of an Automatic Transmission

Diagram of the device of an automatic transmission

The torque converter is a clutch in a manual transmission, but does not require direct control by the driver, and performs all operations automatically.

Planetary gear – a block of gears, which serves to change the gear ratio when changing gears.

The brake band, front and rear clutches are auxiliary elements, thanks to which gear changes are carried out.

The automatic transmission control device is a unit responsible for control and consists of an automatic transmission pan, a gear pump and a valve box.


Torque converter for transferring engine torque to an automatic transmission element, smoothing engine vibration, driving an oil pump. The oil pump generates the operating pressure of the transmission fluid in the torque converter and control and monitoring system. Installed in the housing between the engine and the gearbox and operates the clutch function. The torque converter is subjected to high loads during operation, so its parts did not wear out, it is filled with transmission fluid.

Planetary Gear – Automatic transmissions use planetary gears. In the automatic transmission case, there are several planetary mechanisms that provide the required gear ratios. The transfer of torque from the engine to the wheels occurs with the help of friction discs through planetary gears, differential and other devices. The devices are controlled by the control and monitoring system through the use of transmission fluid.

Brake band – a device designed to block elements of the planetary gear set.

Valve box – a system of channels with valves and plungers, the function of which is control and management. The main function of the valve body is to sense and convert the travel speed, engine load and gas pedal pressure into hydraulic signals. Thanks to these signals, the friction blocks come into operation sequentially turning on and out of the operating state, thereby changing the gear ratio in the automatic transmission of the automatic transmission.

Author: delfi

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