Method for determining the power of an electric motor of a hybrid compressor

Abstract

The invention relates to a method for determining the power (W elec ) of an electric motor ( 20 ) for driving a hybrid compressor ( 10; 10′ ) of an air-conditioning circuit of a motor vehicle having a heat engine during phases in which the drive of the hybrid compressor by the heat engine is interrupted. According to the invention, said method includes steps that consist of: defining a maximum temperature (T max ) measured at a point ( 13 ) of said air-conditioning circuit; setting a reference duration (t ref ) for the phases during which the drive of the hybrid compressor ( 10; 10′ ) by the heat engine is interrupted; determining the power (W elec ) of the electric motor ( 20 ) such that, at the end of said reference duration (t ref ), the temperature measured at said point ( 13 ) of the air-conditioning circuit is at most equal to said maximum temperature (T max ). The invention can be used for air-conditioning motor vehicles having a heat engine and provided with an automatic stopping and restarting system.

1 . A method for determining the power of an electric motor intended to drive a hybrid compressor of an air-conditioning circuit of an engine motor vehicle during phases of interruption of driving of the hybrid compressor by the engine, the method comprising:
 defining a maximum temperature measured at a point of said air-conditioning circuit;   fixing a reference duration for the phases of interruption of driving of the hybrid compressor by the engine; and   determining the power of the electric motor so that on completion of said reference duration, the temperature measured at said point of the air-conditioning circuit is at most equal to said maximum temperature.   
     
     
         2 . The method as claimed in  claim 1 , wherein said maximum temperature is measured at the evaporator of the air-conditioning circuit. 
     
     
         3 . The method as claimed in  claim 2 , wherein said maximum temperature is the air-conditioning discomfort threshold. 
     
     
         4 . The method as claimed in  claim 1 , wherein the ratio of a power of the electric motor to a power necessary for the electric motor to maintain the temperature at said point of the air-conditioning circuit equal to said temperature at commencement of a phase of interruption of driving by the engine lies between 0.2 and 0.8. 
     
     
         5 . The method as claimed in  claim 4 , wherein said ratio lies between 0.3 and 0.55. 
     
     
         6 . The method as claimed in  claim 1 , said hybrid compressor comprises a first compression chamber able to be driven by said engine and a second compression chamber able to be driven by said electric motor during the phases of interruption of driving of the hybrid compressor by the engine. 
     
     
         7 . The method as claimed  claim 1 , wherein said hybrid compressor comprises a variable-capacity compression chamber, able to be driven by the engine in a higher interval of capacities and by the electric motor in a lower interval of capacities during the phases of interruption of driving of the hybrid compressor by the engine. 
     
     
         8 . The method as claimed in  claim 1 , wherein said interruption of driving is a stopping of the engine. 
     
     
         9 . The method as claimed in  claim 8 , wherein said stopping of the engine is an automatic stopping determined by a function for automatic stopping and restarting of the engine of the vehicle (“Stop and Start”). 
     
     
         10 . The method as claimed in  claim 1 , wherein said interruption of driving is a decoupling of the engine from the hybrid compressor determined by a vehicle acceleration request.