Daimler Chrysler Ag

Thomas Finkenberger

Wolfgang Straub

Jan Gaertner

Juergen Wertenbach

J&uuml;rgen Wertenbach

Roland Caesar

Florian Kauf

A refrigerant circuit for a motor vehicle air-conditioning system has a refrigerant compressor, a cooler connected downstream of the refrigerant compressor, a restrictor for expanding the refrigerant, and an evaporator for transferring heat to the refrigerant. Pressure in the refrigerant circuit is measured firstly on the high-pressure side and secondly on the low-pressure side. An air-conditioning system can be driven directly or indirectly by the motor vehicle driving engine. The refrigerant in the refrigerant circuit is almost completely liquefied upstream of the restrictor, so that it is easy to determine the refrigerant mass flow. As a result, it becomes possible to determine the compressor torque which is consumed by the refrigerant circuit and to control the motor vehicle driving engine accordingly.

Method for operating a refrigerant circuit, method for operating a motor vehicle driving engine, and refrigerant circuit

The invention relates to a method for operating a subcritically and transcritically operated vehicle air conditioner having a vapor compression circuit in which in which a compressor, a gas cooler, an expansion valve and an evaporator are connected in series and form an integral closed cycle. On the high-pressure side of the vapor compression circuit, for the purpose of offering refrigerating capacity, a pressure is produced which is supercritical with reference to the critical pressure of the refrigerant circulating in the circuit, and a subcritical pressure is reached simultaneously on the low-pressure side of the circuit. Thermal energy is fed via the evaporator to the refrigerant cooled down on the low-pressure side with the refrigerant mass flow being regulated by the compressor and the desired high pressure being set by means of an expansion valve. During the starting operation of the vehicle air conditioner the refrigerant mass flow is set directly to a required value and the refrigerant pressure is set in accordance with at least one prescribed parameter, and the air conditioner is regulated upon the overshooting of safety pressure limits P1-P4, the regulation depending upon which safety pressure limits are overshot.

Method for operating a subcritically and transcritically operated vehicle air conditioner

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Kernen-Stetten, Germany

Thomas Finkenberger