Patent ID: 8152475

Claim:
A method for controlling the operation of a compressor, in which the compressor is switched off by a control unit to avoid thermal damage if a compressor temperature value (Ts(Tc)) calculated by said unit exceeds an upper threshold value (T max ), or remains switched on or is switched on if there is a compression requirement and if a lower threshold value (T min ) is not reached, comprising the steps of: storing a mathematical-physical model in memory of the control unit wherein the mathematical-physical model characterizes cooling and heating properties of the compressor; and calculating a temperature value (Ts(Tc)) of the compressor indirectly and cyclically by means of the mathematical-physical model by determining physical-technical influencing variables (U), which influence the estimated temperature (Ts(Tc)) in a changing manner, determining, with the aid of the influencing variables (U), at least one relative temperature (Tc 1 ; Tc 2 ), which describes the thermal state of the compressor, adding or subtracting, for this purpose, the currently applicable influencing variables (U) from the cyclically prior value of the relative temperature (Tc 1 , Tc 2 ), so that a currently applicable relative temperature (Tc 1 ; Tc 2 ) is obtained as the result of this calculation, determining a currently applicable estimated temperature (Ts(Tc)), taking into account the heating and cooling behavior of the compressor, from this currently applicable relative temperature (Tc 1 ; Tc 2 ) and the ambient temperature (T∞) of the compressor, and then using this cyclically calculated temperature (Ts(Tc)) for carrying out a limit value comparison with a lower temperature threshold value (T min ) and an upper temperature threshold value (T max ), on the basis of which the operation of the compressor is controlled, wherein the influencing variables (U) are entered in a heating function (B(U)), which describes the heating behavior of a specific compressor.