Friction clutches (friction discs). Automatic box: device

Recently, more and more often motorists prefer automatic transmission. And for that there are reasons. This box is more convenient to use, does not require frequent repairs with timely maintenance. The device AKPP assumes the presence of a number of units and mechanisms. One of these are friction discs of automatic transmission. This is an important detail in the structure of the automatic box. Well, let's look at what the AKPP clutches are for and how they work.

Characteristic

This mechanism is also called friction disks. The detail is the linkage element between the gears. At a certain moment, with the help of oil, they close and stop the necessary gear. After the transmission is switched on, they are closed again. The mechanism consists of several parts. Which ones - we will consider below.

Device

Considering the device of such a mechanism as a package of clutches of automatic transmission, it is necessary to distinguish two main components of the node:

• Metal part. It is constantly in the clutch with the body of the automatic box. The metal part of the clutches is practically stationary in the box.
• Soft. It rotates with the transmission's sun gears. Earlier, soft AKPP clutches were made of pressed cardboard. Modern boxes are equipped with mechanisms with graphite spraying. They withstand higher loads.

By the way, in the 90s the package of friction clutches was one-sided, without overlapping. The design used separately paper and metal discs. Now they have graphite sputtering, even on steel elements. Friction clutches AKPP impregnated with oil, which is protected from friction and overheating. Usually the package consists of two sets of disks. мягкий. First comes the metal, then the soft one. Both alternate with each other.

About the friction pad

This element has a cellulose basis. Disc cover impregnated with special resins. This is necessary to ensure that the disc has a good grip and does not slip when transferring the torque. Since the mechanism is subjected to constant loads, you can see a notch of a spiral shape along its perimeter. They are installed in the direction of movement of the discs. Thanks to them, the temperature of the clutches, which was caused by friction, is significantly reduced.

Note that the smaller the depth of the notch, the higher the risk of burning the disc. Oil can not pass through the grooves in the right amount. As a result, the temperature reaches 400 degrees Celsius and above. By the way, the lining can be made not only on graphite, but also on a Kevlar base. It is less prone to wear. The manufacturers themselves do not disclose the full composition of the Kevlar lining material.

Depending on the design, this element can be of different types. There are monolithic plates with split channels for oil drainage and elements consisting of separate segments. In the latter case, the segments are separated by seams up to the glue layer. Such pads are used only on expensive cars. Segment elements have a complex manufacturing technology. The patches have good heat dissipating qualities. This characteristic is achieved due to the depth of the oil drain channels.

Adhesive for friction clays

To apply this overlay to the disc surface, a special lacquer coating is used. It includes resinous compounds having a high melting point. The lining is placed on the metal surface of the disc and is glued by pressing.

Principle of operation

Friction clutches of the automatic transmission are responsible for the same function as the clutch on the mechanical box. Elements are installed on the sun gears, each of which is responsible for a certain gear. They are placed in a general construction. The number of packages of clutches can be from two (on the most simple 4-speed "automatic") to four (on modern 6-speed automatic transmissions).

So, let's look at how this mechanism works. In the "neutral" mode, the automatic transmission clutches rotate freely from each other. They are impregnated in oil, but do not work under pressure. After the driver has shifted the gearshift lever to the "drive" position, the pump pressure increases. Oil in the box goes to a special channel through the hydraulic unit.

As a result, the friction discs are pressed against each other under pressure. The correct gear of the planetary gearbox is engaged. The car starts to move. The speed of rotation of the wheels depends on the selected gear on the gear (in other words, from transmission on the box).

Requirements

Friction linings of automatic transmission must meet the following requirements:

• Wear resistance.
• High thermal conductivity (must absorb oil well).
• Heat resistance (high-quality clutches operate at temperatures up to 200 degrees Celsius without changing the properties and characteristics).
• Dynamic qualities. The disk package must transmit torque with modulating slippage.
• Static qualities (high threshold of slippage of friction clutches).

About the resource

How much can a package of clutches serve? The disk resource is large enough. Since they are constantly working in oil, they are subject to minimal wear. With the timely replacement of the transmission fluid, the resource of cliches will be 200-350 thousand kilometers. Specialists focus on the regulations for oil change in the automatic transmission. After all, if you ignore the terms, the lubricant will quickly lose its properties.

As a result, the elements of the automatic transmission (including friction ones) will operate under increased load conditions. Their resource is reduced by 3-5 times. Therefore, it is so important to change the gear oil in time. On automatic boxes, this regulation is 60 thousand kilometers (does not apply to transmissions with dry clutch). Complete or partial replacement is available. Specialists recommend using the first option. At what temperatures does the pad begin to fail? Critical values for it are 140-150 degrees. Yes, the material can withstand a load of 300 degrees, but only for a fraction of a second. Then the paper begins to crumble and burn. By the way, this affects not only the lining, but also the stubborn disks.

Repairs

Is it possible to restore such a transmission as an automatic box? Repair of clutches implies a complete replacement of the package of disks. To restore them there is no sense (the same as repairing brake pads). What is the price of the automatic transmission clutch? The cost of the new package starts from 8 thousand rubles, and this is without taking into account the works. This service, like the replacement of clutch automatic transmission, costs in Moscow from 10 thousand rubles. And they are not changing individually, but in collection, the whole package. Having learned the cost of the work, you will understand why it is so important to change the transmission fluid in time. ATP-oil, although it costs an order of magnitude more than usual, but this price does not compare with the repair of the burnt box. If the automatic machine is serviced in time, it will not be necessary to repair it for two hundred thousand kilometers.

Conclusion

So, we found out what the friction plates of the automatic transmission are. As you can see, this mechanism performs not the last function in the work of the mechanical box. And in order to protect it from wear and tear, it is recommended to follow the oil change regulations. Dirty grease is the main enemy of friction discs. Also note that from this not only the filter, but also the radiator is clogged. As a result, the box is constantly
Is subject to overheating.