One of the trends in the evolution of the car - the creation of automatic transmissions. All of their diversity can be summarized in three types, each of which has its own advantages and disadvantages. |

«Hydromechanics»

Hydromechanical ACTs most widespread and used by most automakers. The first hydromechanical AKP emerged in the 30-th years XX century. The very name suggests that in their design combines hydraulic (torque) and the mechanical part (the planetary gearbox). The binding element (as well as in any other ARC) - a system of governance.

Torque transmits torque from the engine to the transmission, increasing it to 1.5 - 2.4 times, as well as perform tasks adhesion (ensures smooth starting place, and partly absorbed jerk when switching). As for the transmission of torque in the torque required is the relative slippage impeller (pump and turbine), the efficiency of transmission is reduced by 3 - 6% (for the mechanical losses are added hydraulic), which, in turn, is causing increased fuel consumption at machines with the IP. When driving in top gear in some units provide for automatic locking torque (working wheels mechanically connected).

Planetary MP, as usual, serves to further changes in the torque (receive a certain number of transfers - typically from 3 to 7). Why Planetary box? Its design allows switching stages, virtually without interrupting the transfer of torque. For this system to block any packets friction (multi-clutch), thereby altering the route of transmission of torque.

The control system will automatically include the required transmission depending on engine speed, the degree and speed of pressing the pedal «gas». Modern high-PTC with electronics as an opportunity to realize the automatic and manual gearshift. To this end, the selector is moved to an MP position, and when it is moved back, or right-left transfer sequentially switched. Some automatic control unit ensures that the inexperienced driver: if you want to include a regular transmission, but this is not done, machine includes its own. In some ACP also can include various modes ( «normal», «comfort», «Sport», «winter»). Depending on the mode switch occurs at different engine speeds.

The most «advanced» automata are able to adapt to individual driving style. Some time this MP is gathering statistics (recording the intensity of vehicle acceleration, the degree of pressing the gas pedal and a number of indicators), and then chooses the desired algorithm for automatic gearshift: the «sport» - at high speed, and the power drivers - at a lower .

Stepless transmission

A common drawback of hydraulic ACTs and robotized mechanical boxes is that because of the step change of gear, they can provide only approximate values of torque required at the given load. Unstepping (smooth) change the value of the gear ratio is achieved in transmissions using вариаторов - klinoremennyh (almost always) or toroidal (very rare).

In klinoremennyh вариаторах transfer torque belt being caught with two pairs of truncated cones for the vertices to each other. Changing the gear ratio is achieved by moving the cones to meet one another, or in the opposite direction. This changes the radius of the circle on which the belt. The ratio of the radii of the circles and determine the ratio вариатора. The first road вариаторах (DAF, «Variomatic», 1958) applied rezinokordnye belts. However, their fragility has forced to look for other materials. It proved to metal «belts», composed of trapezoidal segments and steel rings, or chain plate. Term of service is consistent with the requirements. Variator with rezinokordnymi belts now apply only to scooters and snowmobiles.

Unfortunately, one вариатора for the full transmission is not enough. For starting from the place in various designs stepless transmissions using centrifugal and electromagnetic coupling, and then began to apply torque. Back transfer provides planetary MP.

While driving with вариатором is another issue - the psychological. Driver while driving on a regular car hears the sound of changing the engine, the tone of which varies in proportion to the speed of change. But «variatornye» models are misleading: the speed of change, as the engine speed remains almost constant, as Variator supports them in the zone of maximum torque to achieve the best acceleration. Some manufacturers are adapting management systems so as to provide a few fixed transmission electron (usually 5 - 7). A driver is a choice: you can set the lever in the position of «automatic» and drive in normal mode or shift lever for manual shifting, and move it back. Klinoremennye вариаторы used in several models of Audi, Nissan, Honda, Subaru and other companies.

Another, very rare infinitely transmission design based on the use of rotating rollers, running between the two bowls, turned to each other. What is it like Bublik cored, cut in half. By changing the angle of the video, you can make the knowledge of the cup to rotate faster, slower or the same rate as the lead. As in the case of the «belt», you need to install the clutch mechanism and the reverse. Another difficulty is that for the transmission of torque should be very high pressure in the contact spot, to prevent slippage, and therefore need special class of oils. Such вариаторы until use only Nissan (Extroid CVT) and Mazda (toroidal CVT).

«Mechanics - Robot»

A number of shortcomings and successes of hydraulic PTC in the development of electronics contributed to the development of robotized gearboxes that appeared in the 80-th years XX century. In fact, it is the usual manual, in which the clutch and gear shift control the actuators receiving commands from the electronic control unit. There are different versions of these boxes. For example, can be implemented two modes of switching gears: fully automatic, where the box is the same as usual PTC, and the speed Sequential, where the driver shifts the transmission of self-oscillation lever to the right-left (back), or petals, or the buttons on the steering wheel, as in the racing bolide. Management system saves the engine from damage due to improper action by the driver (switch can be made, even without removing the leg with the pedal, automation itself will reduce the speed, turn off, turn on the clutch and transmission).

This gearbox is easier, cheaper and more efficient than conventional automatic. There is no loss of power in the torque, higher efficiency and, hence, the car consumes less fuel. Although some low-cost auto delay during gear changes, and jerk spoil the impression. Robotized «mechanics» used BMW, Citroen, Mitsubishi, Toyota and several other companies, both in the expensive business-class models, and models of A-, B-, C-Class. Different manufacturers may be called in different ways: Steptronic - a BMW, Tiptronic or Sequentiel - from Audi, MMS - a Toyota.

Now consider the advantages and disadvantages of the above transimssy

Hydromechanical PTC

"+" There is no transmission capacity constraints. Reliability and «proven» designs. Smoothly, compared to the robot MP, the gear shift.

"-" The very low efficiency, as a result - a higher fuel consumption and poorer dynamic performance. The need to periodically replace the fluid and filter. The high cost of development and production.

Robotized manual

"+" The possibility of production on the same production lines as conventional CT. Weight less than that of hydro mechanical ACTs. Cost may be higher than that of «mechanics».

"-" The lowest adaptability to changing loads. The delays and push in the switch (in the low-cost models).

Continuously drive

"+" The exact «dosing» torque. Fuel consumption is lower than with the hydro mechanical ACTs.

"-" The need for special oils (for toroidal вариаторов). Less durability due to the presence of slip (at klinoremennyh gears) or high pressure (from the toroidal transmission). Require the use of additional mechanisms for starting treatment and reverse.