Air Conditioning Systems For Vehicles

Abstract

An air conditioning system for a vehicle includes a compressor, a gas cooler, an expansion means, and a cooler. The system also includes an elevated pressure density detector for detecting or estimating one or more physical values having a correlation with a density of an elevated pressure refrigerant in a refrigeration cycle. An elevated pressure density controller controls the density of the elevated pressure refrigerant. This control is achieved at least in part by using at least one of the one or more physical values.

1 . An air conditioning system for a vehicle, comprising: 
 a compressor;    a gas cooler;    an expansion means;    a cooler;    an elevated pressure density detecting means for detecting or estimating one or more physical values having a correlation with a density of an elevated pressure refrigerant in a refrigeration cycle; and    an elevated pressure density control means for controlling said density of said elevated pressure refrigerant, wherein said density is controlled at least in part by using at least one of said one or more physical values.    
   
   
       2 . The air conditioning system of  claim 1 , wherein a density value of said elevated pressure refrigerant is determined from said at least one of said one or more physical values according to a predetermined characteristic, and a density target value is determined by comparing an additional physical value with a predetermined threshold value, wherein said additional physical value is either one of said one or more physical values or is detected with a second detection means.  
   
   
       3 . The air conditioning system of  claim 2 , wherein said second detection means comprises a temperature detector for detecting an outside air temperature.  
   
   
       4 . The air conditioning system of  claim 2 , wherein said elevated pressure density control means comprises means for adjusting said density value of said elevated pressure refrigerant towards said density target value.  
   
   
       5 . The air conditioning system of  claim 4 , wherein said means for adjusting said density of said elevated pressure refrigerant comprises means for controlling an opening degree of a valve or means for controlling an expansion ratio of said expansion means.  
   
   
       6 . The air conditioning system of  claim 4 , wherein said means for adjusting said density of said elevated pressure refrigerant comprises a control signal, and the magnitude of said control signal is determined from a deviation between said density target value and said density value.  
   
   
       7 . The air conditioning system of  claim 1 , wherein said expansion means comprises means for changing an opening degree of a valve or an expansion ratio of said expansion means according to a predetermined relationship between said at least one of said one or more physical values and a density target value of said density of said elevated pressure refrigerant.  
   
   
       8 . The air conditioning system of  claim 1 , wherein said expansion means comprises means for controlling an opening degree of a valve or an expansion ratio of said expansion means, so that said density of said elevated pressure-side refrigerant substantially equals a predetermined density.  
   
   
       9 . The air conditioning system of  claim 1 , wherein said elevated pressure density detecting means and said expansion means are constructed substantially integrally.  
   
   
       10 . The air conditioning system of  claim 1 , wherein said elevated pressure density detecting means comprises a temperature sensor and a pressure sensor.  
   
   
       11 . The air conditioning system of  claim 10 , wherein a density target value is controlled in response to a pressure of said elevated pressure refrigerant, and said pressure is detected by said pressure sensor.  
   
   
       12 . The air conditioning system of  claim 11 , wherein said density target value is a first value when said pressure of said elevated pressure refrigerant is greater than or equal to a predetermined value, and said density target value is a second value when said pressure of said elevated pressure refrigerant is less than said predetermined value.  
   
   
       13 . The air conditioning system of  claim 1  further comprising an outside air temperature detecting means for detecting an outside air temperature, wherein a density target value varies in response to said outside air temperature.  
   
   
       14 . The air conditioning system of  claim 13 , wherein said density target value is a first value when said outside air temperature is greater than or equal to a predetermined value, and said density target value is a second value when said outside air temperature is less than said predetermined value.  
   
   
       15 . The air conditioning system of  claim 1 , wherein said refrigerant is carbon dioxide.  
   
   
       16 . A method for controlling an air conditioning system for a vehicle during a refrigeration cycle, comprising: 
 detecting or estimating one or more physical values;    determining a density value of a density of an elevated pressure refrigerant using at least one of said one or more physical values;    determining whether a second at least one of said one or more physical values is greater than or equal to a first predetermined threshold value and generating a result;    setting a density target value based on said result;    determining a control value of a control signal using a deviation between said density value and said density target value, if said deviation is greater than or equal to a second predetermined threshold value;    controlling an expansion means with said control signal.    
   
   
       17 . The method of  claim 16 , wherein said one or more physical values comprise a temperature of said elevated pressure refrigerant, a pressure of said elevated pressure refrigerant, and an outside air temperature.  
   
   
       18 . The method of  claim 16 , further comprising controlling an opening degree of a valve or an expansion ratio of said expansion means with said control signal.  
   
   
       19 . The method of  claim 16 , wherein said step of determining said density value further comprises calculating said value according to a predetermined characteristic.  
   
   
       20 . The method of  claim 16 , wherein said step of determining said control value further comprises calculating said control value using said deviation between said density value and said density target value, if said deviation is greater than or equal to said second predetermined threshold value.