Audi A4

Since 1994 of release

Repair and car operation

In Audi A4 two various models of an automatic transmission are used for installation: first, developed VW a transmission AG-4 for the four-cylinder engine without a turbo-supercharging, secondly, designed ZF a transmission 5 HP 18 for the six-cylinder engine. As it is already clear on a designation, it is a question in one case of a four-speed transmission, in other case – about five-step.

Both transmissions cope in the elektronno-hydraulic way, and this management works depending on various entrance parametres (number of turns of the engine, speed of movement, loading and so forth) when the following transfer joins. Besides, management distinguishes a manner of driving of the driver and establishes points of a gear change from "sports" to "economic", thus it is not necessary to put in action any switch. All the system as a whole is called DSP – Dynamische Schalt-Programm (the dynamic program of a gear change). Besides, at a transfer choice the lay of land is considered – i.e. Automatics chooses a mode of the gear change different from movement on mountain road on equal road.

Main principles of functioning

The basic link of all automatic transmissions are so-called planetary complete sets. They consist of a gear wheel round which three other gear wheels rotate. From above the ring with an internal teeth is put on. Each pair from these elements is connected in a set of gear gear wheels and forms an own small two-speed transmission. In these transmissions the way of their switching is ingenious. Transfer switching is carried out at the expense of keeping or liberation of details of the planetary complete set. It becomes without interruption of a stream of force. Keeping and liberation provide lamellar couplings and lamellar brakes with a hydraulic drive.

For reception of a multistage transmission two planetary complete sets are consistently connected. At a correct arrangement of transfers it is formed four- or a five-speed transmission with backing transfer. Coordination of work of complete sets of gear wheels is provided with transmission management.

The twisting moment hydrotransformer

Transfer of force of the engine to a transmission is carried out by means of a liquid. The engine actuates the turbine in the twisting moment hydrotransformer. The liquid in the hydrotransformer, resulted in rotation, by means of located between them лопаточного the directing device can actuate also the wheel of the turbine connected to a transmission. Between the turbine rotating according to turns of the engine, and a turbine wheel on a transmission input always there is a distinction among turns. In a start of motion it the biggest, in process of increase in speed the difference in number of turns between the turbine of the pump and the transmission turbine decreases more and more. But in a traditional automatic transmission still there is some "backlash". In our transmissions the twisting moment hydrotransformer перемыкается in a range of 3rd and 4th transfer and to 4th and 5th, i.e. Between the engine and an automatic transmission rigid connection dominates. It allows to lower the fuel expense.