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How does the machine work?

This article is devoted to the automatic transmission device - an automatic gearbox in a car. You will learn how the machine works, what are the main parts and the functions that these parts perform. Well, we begin with the basic elements of an automatic transmission.

How the automatic transmission works: the main nodes

I must say that the modern automatic transmission is perhaps the most difficult device in the car, which contains thousands of electronic, hydraulic and mechanical components. However, all these components are included in certain nodes of the automatic transmission, with which we will now introduce you.

  • The torque converter (in abbreviated form, it is often referred to as GT) - performs the same function as the clutch in a mechanical transmission, but does not require direct control;
  • Planetary number - this node is used to change the gear ratio in the automatic transmission when shifting gears. It corresponds to the gear unit in the manual transmission - a mechanical gearbox;
  • Brake band, as well as front friction and rear friction - with the help of these components, in fact, shifting gears in the automatic transmission;
  • Control device - controls the gear shift in the transmission, has a built-in electronic control system.

The general principle of the automatic transmission

Many people know that the automatic transmission, as they also call the automatic transmission, shifts gears on its own, and the gear shift directly depends on the speed of the car. This provides the driver with comfortable and pleasant enough conditions for driving. The driver only needs to choose the direction of the car, that is, go forward or backward. Of course, for more accurate and economical driving experienced drivers still use the manual transmission, but the automatic transmission greatly simplifies the task for those who do not want to pay attention to the acquisition of driving skills. But how does the automatic box work if you look at this design from the inside? In a nutshell, this can not be said, so get ready for a detailed description. As we said earlier, the automatic transmission consists of 3 main parts: electronics, hydraulics and mechanics.With the help of electronics, various modes of transmission are controlled, as well as its connections with other automotive systems. Hydraulics transmits torque and power to the wheels - the main executive unit of the machine, and the mechanical part performs the actual gear shift.

Torque, power and automatic transmission

The work of the automatic transmission is based primarily on the work of the engine of the car, and the torque (as well as the power characteristics) can vary, depending on the speed. For a better understanding of how the machine works, you need to understand how the engine works: the lower the engine speed, the less torque and power will be, and in order to set the machine in motion, you need to apply all its power. Further, during acceleration: the faster the car moves, the less torque and power are needed, but the frequency indicators remain maximum. And here that small period of time, when the moment and power differ by constancy (at least relative) at high frequency, is compensated by the transmission, which transmits the modified gear ratio to the motor.Automatic transmission itself changes the power performance and torque in order to ensure optimal operating conditions of the engine and, consequently, the movement of the car. In addition, the work of the automatic transmission also ensures smooth shifting (naturally, automatic, that is, without driver participation) without loss of efficiency, thus avoiding jolts and jerks during the transition from one gear to another. This is done by automatic transmission forces planetary gears and GT - hydraulic transformer. Well, now let's talk about how each program works in a multi-stage automatic transmission. If you are not familiar with such a term as a planetary gear, then it is advisable to read the introductory. The fact is that without an understanding of this it is impossible to understand the very principle of the automatic transmission. In addition, you will find in this article descriptions of the most important parts of the planetary gear, which we will discuss in the following chapters.

First gear

In the standard transmission, the automatic transmission has 4 forward gears and 1 reverse gear. In 1st gear, a torque converter drives a small sun gear clockwise (it has 30 teeth).A clockwise rotation provides a unidirectional clutch. As for the crown transmission (has 72 teeth), it rotates in the direction of input rotation. In this case, the input rotation of the shaft should be opposite to the output one, since the direction of rotation is negative, but in fact they are the same, since the dual planetary gear is working here - the 1st set of satellites rotates the 2nd gear, and the gear rotates which changes the direction of rotation.

Second gear

Here, two planetary gears are connected to a common carrier of satellites. At the 1st stage, the satellite carrier uses the sun (this time - large sun) gear as the crown gear. Thus, the 1st part consists of a small sun gear - a small sun, a carrier of satellites and a crown - a large solar transmission. The input torque passes through the small sun, and the crown gear (large sun) is held by the brake band, but the output becomes the carrier of the satellites. At the 2nd stage, the satellite carrier is the entrance to the 2nd planetary gear, and the large sun gear, which is at rest, no longer serves as a crown, but as the sun, the ring gear is the exit.

Third gear

Most automatic transmissions here have a ratio of 1: 1, for which you just need to block two of the three parts of the planetary gear. However, this can be achieved and easier - you just need to slow down both sun gears with the help of a torque converter. If both "suns" rotate in one direction, then the satellites, of course, are blocked, since they can only rotate in opposite directions. As a result, the ring gear is blocked together with the satellites, which leads to the rotation of the whole mechanism as a whole, and, thus, that gear ratio is 1: 1.


You can also find such a name as "overdrive." In this case, the output shaft rotates 1 turn in 2/3 of the input shaft rotation. It will be clearer if we express it in torque figures. When the engine is running at 2000 rpm (input speed), the output speed will in this case be 3000 rpm. This will allow your car to fly on the highway, while the engine itself will work slowly and calmly.

Reverse gear

It is very reminiscent of the 1st gear,however, instead of a small sun gear, a large sun is driven by a GT turbine, and the small gear also rotates freely, but in the opposite direction. Brake tape reversing keeps drove satellites. It turns out that the reverse gear ratio is slightly less than the number of the 1st gear.


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