The principle of the automatic transmission

The gearbox is a device designed to transfer the power of the car engine to the wheels. The driver selects the appropriate gear, depending on how fast the engine rotates - this applies to the manual gearbox.

If we are talking about automatic transmission, then the driver does not need to perform manual switching, since these tasks are taken over by the automatics. Automatic gearbox allows the car to function in the most comfortable mode, while saving fuel.

The automatic transmission mechanism is packed in an aluminum casing, called a crankcase. At its center is a planetary mechanism, which consists of three sets of gears. Well, now let's take a little look at what the principle of the automatic transmission works?

So, the main gear is the first set of gears, which takes on the task of matching the engine speed with the speed of driving. His work is carried out directly. This ratio will be the same as in the manual gearbox, that is, one to one. The support of the forward clutch, that is, the part that protrudes from it, is commonly referred to as the locking stop. The locking lever is connected to the stop of the blocker by means of the drive rod.

The principle of the automatic transmission

Let's look at a few basic points.

Initial: the car is standing, but the engine is not running. In this position, the automatic transmission pump does not work, and there is no pressure in the system. The working fluid is located in a pan, a torque converter, and also in the channels of the control unit. Elements of planetary gears in this mode are also in free rotation.

Position "key to start": the engine is started, however the selector is switched to neutral position. The oil pump rotates together with the engine crankshaft and torque converter, creating a working pressure in the system, however, none of the actuators is involved, since the control unit does not generate the necessary pressure. Here it is important to note, if you are very much interested in the principle of the automatic transmission, that in the system the working pressure increases gradually. That is why many advise, before starting the movement, a few seconds to hold the selector lever in neutral position. This is very important after a long period of inactivity or in case of using an old box.

Start of movement: it is assumed that the lever is moved to the Drive position. At the same time, the pressure in the valve block is increasing, the first gear actuator is triggered, which locks the crown gear with a clutch or belt brake, but the movement does not start, because the pressure is not sufficient to completely lock the gear and activate the pressure valve.

"Acceleration" mode: assumes that the selector is in the same position as it was, while the torque converter stator is blocked, the valve block receives a signal from the centrifugal regulator at the input. After the pressure created by the centrifugal regulator exceeds the constructively incorporated one, a transition to a higher gear is made by triggering actuators that block the gears. At the same time, the overflow actuators of the previous gear are triggered, which reduces the pressure, and then turns them off. The principle of automatic transmission completely excludes the simultaneous operation of two transmissions.

At uniform movement , the speed of rotation of the torque converter pump and the turbine is equalized, and the stator starts to rotate on the rollers or balls of the overrunning clutch. Actuators have an impact on the mechanism of locking parts of the planetary series, which allows you to keep the transmission. When uniform motion is achieved, the torque converter is rigidly locked, and this increases transmission efficiency, reducing hydraulic losses.

The full principle of the automatic transmission requires a much longer description, but in this article the most important aspects of it were touched upon.