Audi A4

since 1994 release

Repair and operation of the car

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

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

Basic principles of functioning

The main link of all automatic transmissions are so-called planetary sets. They consist of a gear wheel round which three other gear wheels rotate. From above the ring with internal teeth is put on. Each couple 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. Switching of transfer is carried out due to keeping or release of details of a planetary set. It becomes without interruption of a stream of force. Keeping and release provide lamellar couplings and lamellar brakes with the hydraulic drive.

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

Torque hydrotransformer

Transfer of force of the engine to a transmission is carried out by means of liquid. The engine sets in motion the turbine in the torque hydrotransformer. The liquid in the hydrotransformer given to rotation by means of the directing device located between them scapular can also set in motion the turbine wheel connected to a transmission. Between the turbine rotating according to engine turns, and a turbine wheel on a transmission entrance 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 turbine of a transmission decreases more and more. But in a traditional automatic transmission still there is some "gap". In our transmissions the hydrotransformer of a torque peremykatsya in the range of the 3rd and 4th transfer and to the 4th and 5th, i.e. between the engine and an automatic transmission rigid connection dominates. It allows to cut fuel consumption.