Improvement of operational qualities of the modern car has led to considerable complication of its design. And equipment of cars by automatic transmission has allowed to lower sharply volume of the loading assigned to the driver during movement that also was favorably reflected in a running gear, the engine and high-speed qualities of the car. Reliability and simplicity of operation have defined the further wide use of this invention. Now automatic transmissions are applied both on automobile, and on all-wheel drive cars, and even on a truck transport.
At use of a hand-operated vehicle, for maintenance of necessary speed, it is necessary for driver to use the gear change lever often.
Application of automatic transmission excludes necessity of constant using the switching lever. Change of speed is carried out automatically, depending on loading of the engine, speed of moving of a vehicle and desires of the driver.
Therefore, in comparison with a manual transmission, automatic transmission has following conclusive advantages:
- Increases comfort of driving of the car at the expense of clearing of the driver of control functions;
- Automatically and smoothly makes switchings, co-ordinating engine loading, speed of its movement, degree of pressing a gas pedal;
- Protects the engine and a running gear of the car from overloads;
- Supposes both manual, and automatic switching of speeds.
All variety of the automatic transmissions applied today, it is conditionally possible to divide into two types. The basic distinction of these types consists in control systems and control over transmission use. For the first type that management and control functions are carried out by the special hydraulic device is characteristic. And in the second type of function of management and control carries out
The electronic device. Components and knots of automatic transmissions of both types are almost identical.
There are some distinctions in configuration and the device of automatic transmission front-wheel and заднепрйводного the car. Automatic transmission for frontприводных cars is more compact and has in the case branch of the main transfer - differential. Despite these differences, the basic functions and a principle of action of all automatic machines are identical.
To provide movement, and also for performance of other functions, automatic transmission should be equipped by following knots: the mechanism of a choice of a mode of movement, the hydrotransformer, a transmission, in management and control knot.
The mechanism of a choice of a mode of movement represents the handle placed in salon of the car and connected with a transmission by rigid or flexible draught. By means of this lever the driver chooses a car operating mode: "forward", "back", "neutral" or "parking". On the majority of cars the way of advance consists of three stages or, it is possible to tell, three modes: a mode of low speed,
Average mode and mode of normal movement. Depending on the manufacturer these modes have different designating symbols. For example, the mode of low speed is designated by symbols "L" or "I", the average mode is designated "2", "S" or "*" more often, and a mode of normal movement - "D" or "D-3", also other symbols however are applied.
The mode of low speed is used as the first transfer to a case when the big twisting moment is required at small speed of moving. For example, трогание from a place uphill, overcoming of steep slopes on small speed, driving on the road abounding with holes and ruts.
The average mode usually has only two transfers, in other words, one switching. At the pressed pedal of gas the car moves on the second transfer, and at отпускании, after several seconds, there is a braking by the engine and switching on the first transfer that gives the chance to use less often than a brake. It is the most expedient to use this mode at driving on slippery road (snow накат, ice or a glaze ice), on road with insufficiently good covering (holes, ruts), etc.
If the lever is established in position of a normal mode of movement transmission works in a three-high-speed mode. This mode is used at movement on the road having a good covering, allowing to develop high enough speed, provides unobstructed трогание from a place in small lifting etc.
Under the lever also other symbols also are put:
"Р" - Assumes a parking of the car with the idle engine;
"R" - It is used at maneuvering;
"N" - Provides free качение the car in any direction, and also its parking with working engine.
It is necessary to notice that with a view of safety automatic transmission allows to start the engine only in position "N" or "Р".
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