Instabilities Occurring in an Automotive A/C Loop Equipped with an Externally Controlled Compressor and a Thermal Expansion Valve

The new compressor generation, called externally controlled compressors, is able to be electronically driven from zero to its maximum displacement. The cooling power can be adjusted to the exact need and this way the fuel consumption of the automotive A/C loop can be reduced. Unfortunately, for the mean and low thermal loads on the evaporator, this new opportunity is limited by A/C loop operation instabilities.

Thanks to an automatic approach of the coupling TxV - Evaporator, we can explain the origin of these instabilities and we can show the involvement of this new compressor generation.

Then we propose different improvements such as:

• a better account of the automatic parameters of the TxV and the evaporator (gains, time constants).
• a TxV setting modification.
• a new generation of TxV with a leakage.

These solutions are discussed according to their interest.