Method For Controlling The Operation Of An Air-Conditioning Loop In A Vehicle

Abstract

The present invention relates to a method for controlling the outlet temperature (TRCPO) of a compressor (CP) built into the air-conditioning loop of a vehicle in which a subcritical refrigerant fluid flows and including a condenser (CD), an expansion valve (EXV), and an evaporator (EV). The monitoring method comprises the steps of calculating a limit temperature at the compressor inlet (TRCPI_L), estimating a temperature at the compressor inlet (TRCPI_E), and modifying a control signal of the compressor (PWM CP ) or a setpoint value of the evaporation temperature (SP_T EV ).

1 . A method for controlling the outlet temperature (TRCPO) of a compressor (CP) built into an air-conditioning loop of a vehicle in which flows a subcritical refrigerant fluid and comprising at least a condenser (CD), an expansion valve (EXV), and an evaporator (EV), the control method comprising:
 a step of calculating a limit temperature at the inlet of the compressor (TRCPI_L),   step of estimating a temperature at the inlet of the compressor (TRCPI_E), and   a step of modifying a control signal of the compressor (PWM CP ) or a setpoint value of the evaporation temperature (SP_T EV ).   
     
     
         2 . A control method according to  claim 1 , wherein the air-conditioning loop comprises an internal exchanger (IHX) for carrying out heat transfers between the fluid flowing between the condenser (CD) and the expansion valve (EXV) and the fluid flowing between the evaporator (EV) and the compressor (CP). 
     
     
         3 . A control method according to  claim 1 , further comprising:
 a step of acquiring a speed of the vehicle (V V ), an external temperature (T E ), and a pressure measured at the outlet of the condenser (PRCDO_M).   
     
     
         4 . A control method according to  claim 1 , further comprising:
 a step of acquiring a pressure at the outlet of the condenser (PRCDO_M), a pressure estimated at the inlet of the compressor (PRCPI_E), a speed of the compressor (N CP     —   M) and a predetermined limit temperature at the inlet of the condenser (TRCDI_L).   
     
     
         5 . A control method according to  claim 4 , characterized in that further comprising:
 a step of acquiring an amperage for controlling the control valve of the compressor (I V— M),   and wherein the step of estimating the pressure at the inlet of the compressor (PRCPI_E) is carried out as a function of an amperage for controlling the control valve of the compressor (I v— M).   
     
     
         6 . A control method according to  claim 4 , wherein the step of calculating the limit temperature at the inlet of the compressor (TRCPI_L) is carried out as a function of the estimated pressure at the inlet of the compressor (PRCPI_E), of the speed of the compressor (N CP     —   M), and of the predetermined limit temperature at the inlet of the condenser (TRCDI_L). 
     
     
         7 . A control method according to  claim 6 , further comprising:
 a step of determining an efficiency parameter (EF_IHX) of the internal exchanger (IHX).   
     
     
         8 . A control method according to  claim 7 , wherein the step of determining the efficiency parameter (EF_IHX) is carried out as a function of a mass flow (MF) of the refrigerant fluid. 
     
     
         9 . A control method according to  claim 8 , further comprising:
 a step of determining the mass flow (MF) carried out as a function of the speed of the vehicle (V V ), of the external temperature (T E ), and of the pressure measured at the outlet of the condenser (PRCDO_M).   
     
     
         10 . A control method according to  claim 8 , further comprising:
 a step of determining a pressure estimated at the outlet of the evaporator (PREVO_E) from the estimated pressure at the inlet of the compressor (PRCPI_E) and of the mass flow (MF) of the refrigerant fluid.   
     
     
         11 . A control method according to  claim 7 , further comprising:
 a step of estimating a pressure drop (ΔP EV     —     CP ) between the outlet of the evaporator (EV) and the inlet of the compressor (CP) from the mass flow (MF) of the refrigerant fluid.   
     
     
         12 . A control method according to  claim 11 , wherein the step of estimating the pressure at the outlet of the evaporator (PREVO_E) is carried out as a function of the pressure drop (ΔP EV     —     CP ) and of the estimated pressure at the inlet of the compressor (PRCPI_E). 
     
     
         13 . A control method according to  claim 10 , further comprising:
 a step of determining characteristics of overheating (SH_E) as a function of the estimated pressure at the outlet of the evaporator (PREVO_E).   
     
     
         14 . A control method according to  claim 13 , further comprising:
 a step of estimating the temperature at the outlet of the evaporator (TREVO_E) from characteristics of overheating (SH_E) and from the estimated pressure at the outlet of the evaporator (PREVO_E).   
     
     
         15 . A control method according to  claim 20 , comprising:
 a step of calculating a limit temperature at the outlet of the evaporator (TREVO_L) from the efficiency parameter of the exchanger (EF_IHX), from the limit temperature at the compressor inlet (TRCPI_L) and from the pressure saturation temperature at the condenser inlet (Tsat(PRCDI_M)),   a step of calculating a limit pressure at the evaporator outlet (PREVO_L) from the limit temperature at the evaporator outlet (TREVO_L) and from characteristics of overheating (SH_E),   a step of calculating a limit pressure at the compressor inlet (PRCPI_L) from the limit pressure at the evaporator outlet (PREVO_L), and from the estimated pressure drop (ΔP EV     —     CP ), and   a step of calculating a limit value of the amperage for controlling the control valve of the compressor (I V     —   L) as a function of the limit pressure at the compressor inlet (PRCPI_L).   
     
     
         16 . A control method according to  claim 13 , further comprising:
 a step of calculating the temperature at the evaporator outlet (TREVO_E) from an estimated pressure saturation temperature at the outlet of the evaporator (Tsat(PREVI_E)) and from characteristics of the overheating (SH_E),   a step of estimating a limit temperature at the condenser outlet (TRCDO_L) from the efficiency parameter (EF_IHX), from the estimated temperature at the evaporator outlet (TREVO_E) and from the limit temperature at the compressor inlet (TRCPI_L), and   a step of estimating a limit pressure at the condenser outlet (PRCDO_L) from the limit temperature at the condenser outlet (TRCDO_L).   
     
     
         17 . A control method according to  claim 1 , wherein the modification step is such that the control signal of the compressor (PWM CP ) or the setpoint value of the evaporation temperature (SP_T EV ) is modified when the estimated temperature at the inlet of the compressor (TRCPI_E) is greater than or equal to the calculated limit temperature at the compressor inlet (TRCPI_L). 
     
     
         18 . A control method according to  claim 15 , wherein the modification step is such that the control signal for the control valve of the compressor is modified for the amperage for controlling the control valve of the compressor (I V     —   M) to always be less than the limit value of the amperage for controlling the control valve of the compressor (I V     —   L). 
     
     
         19 . A control method according to  claim 16 , wherein the modification step is such that the control signal of the compressor (PWM CP ) or the setpoint value of the evaporation temperature (SP_T EV ) is modified when the pressure at the condenser outlet (PRCDO_M) is greater than or equal to the limit pressure at the condenser outlet (PRCDO_L). 
     
     
         20 . A control method according to  claim 12 , further comprising:
 a step of determining characteristics of overheating (SH_E) as a function of the estimated pressure at the outlet of the evaporator (PREVO_E).