Electro-hydraulic transmission control

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The electrohydraulic transmission control (EGS) ( English : Electronic gearbox system ) is a control system for automatic transmissions in the passenger and truck sector.

Automatic selector lever of a Ford Five Hundred

With it, the hydraulic transmission control is linked with an electronic transmission control. In the case of more modern generations, the electronic transmission control unit is connected to the other electronic control units , such as the engine control unit or the ESP control unit , via the CAN bus .

advantages

The advantages of this type of control are:

  • High shift comfort
  • shared use of sensors, which means cost reduction
  • Noise reduction
  • Consumption reduction
  • Reduction of exhaust gases
  • Shift characteristic selection possible, for example Economic (economical), Winter, Sport and so on
  • Adjustment to driver type possible, for example through AGS = adaptive transmission control

With the help of the electro-hydraulic transmission control, it is also possible to operate converter clutches with slip control ; this avoids vibrations in the drive train with improved converter efficiency .

Some special functions

In vehicles with EGS, adaptive transmission control systems and special safety precautions, for example in interlock and shift lock, are implemented.

Interlock

The key can only be removed from the ignition lock when the selector lever is in position "P" (park). This is done mechanically, for example, using a cable. This prevents the vehicle from rolling away after the ignition key has been removed.

Shift lock

After starting, the selector lever can only be moved from position "P" (park) or "N" (idle) if the foot brake is pressed at the same time. This prevents the vehicle from starting unintentionally.

Adaptive transmission control

Based on various criteria, it selects a suitable gearshift program from several different gearshift programs, for example fuel-efficient or sporty. The resulting gear actuation is corrected by other influencing factors, such as the driving situation.

Switching program selection

It is essentially dependent on the driver type assessment, environmental recognition and driving situation recognition.

Driver type recognition

Kick-Fast Rating

How quickly is the throttle valve opened by the driver, i.e. how quickly the accelerator pedal is depressed. If you step down quickly, a sporty program is selected; the transmission usually shifts down one gear.

Kick-down evaluation

If the accelerator pedal is depressed as far as it will go (full throttle) and the kick-down switch is pressed, the performance-optimized program is selected. The fuel consumption is highest in this program because the transmission usually shifts several gears down. Depending on the position of the accelerator pedal, upshifts only take place when the maximum speed is reached.

Driving operation detection

When driving at constant speed, a consumption-optimized shift program is selected; this initiates an earlier upshift of the gears or, in some models, in conjunction with the engine management system, a cylinder bank deactivation .

Further special functions are the environmental identification (for example winter) or the driving situation identification (for example driving uphill or cornering).

swell

  • Europe teaching material: specialist knowledge of automotive engineering . Edition 2001. Page 412, ISBN 3-8085-2067-1 .
  • Bosch: Automotive paperback . 22nd edition. Page 306.