Air conditioners suitable for vehicles and methods for operating such air conditioners

Abstract

An air conditioner ( 1 ) includes an air conditioning circuit ( 2 ) in which a cooling medium circulates. An electrically powered compressor (C) is disposed within the air conditioning circuit ( 2 ) for compressing the cooling medium and discharging the cooling medium under high pressure. A refrigerant superheat feedback device ( 22 ) adjusts the superheat condition of the cooling medium that is returned to the compressor (C) for compression in order to ensure an adequate supply of lubrication oil to the compressor (C).

1 . An air conditioner comprising: 
 an air conditioning circuit comprising a circulating cooling medium and lubricating oil,    an electrically powered compressor disposed within the air conditioning circuit, the compressor being arranged and constructed to compress the cooling medium and discharge the cooling medium under high pressure, and    a refrigerant superheat feedback device arranged and constructed to adjust the superheat condition of the cooling medium that is returned to the compressor in order to ensure an adequate supply of lubrication oil to the compressor during a low load operation.    
     
     
         2 . An air conditioner as in  claim 1 , wherein the refrigerant superheat feedback device comprises an expansion valve.  
     
     
         3 . A method for compressing a cooling medium using an air conditioner that includes an electrically-driven compressor, which is arranged and constructed to compress the cooling medium and discharge the cooling medium under high pressure, comprising: 
 adjusting the superheat condition of the cooling medium that is returned to the compressor in response to a load that is applied to the air conditioner.    
     
     
         4 . A method as in  claim 3 , wherein the change of the cooling medium temperature is performed by an expansion valve.  
     
     
         5 . An air conditioner comprising: 
 an air conditioning circuit comprising a circulating cooling medium and lubricating oil,    an electrically driven compressor disposed within the air conditioning circuit, the compressor being arranged and constructed to compress the cooling medium and discharge the cooling medium under high pressure, and    a controller arranged and constructed to control the phase state of the cooling medium within the air conditioning circuit, wherein the controller causes the cooling medium supplied to an inlet of the compressor to be in dual-phase, gas-liquid state when an operating load on the air conditioner is relatively low.    
     
     
         6 . An air conditioner as in  claim 5 , further including an evaporator disposed on an upstream side of the compressor and within the air conditioning circuit, wherein the controller is further arranged and constructed to control the flow of the cooling medium at an inlet of the evaporator.  
     
     
         7 . An air conditioner as in  claim 6 , wherein the controller controls the flow of the cooling medium at the inlet of the evaporator based upon the superheat condition of the cooling medium at the outlet of the evaporator.  
     
     
         8 . An air conditioner as in  claim 6 , wherein the controller comprises a thermosensitive cylinder disposed proximal to the air conditioning circuit downstream of the evaporator and communicating with a first side of a movable diaphragm, and the air conditioning circuit communication with a second side of the movable diaphragm, the movable diaphragm being coupled an expansion valve disposed upstream of the evaporator, the thermosensitive cylinder containing a gaseous composition that is different from the cooling medium, wherein the expansion valve is arranged and constructed to control the flow of the cooling medium into the inlet of the evaporator based upon differences between the pressure of the cooling medium at the outlet of the evaporator and the pressure of the gaseous composition within the thermosensitive cylinder.  
     
     
         9 . An air conditioner as in  claim 6 , wherein the controller comprises a cross-charge expansion valve.  
     
     
         10 . An apparatus suitable for circulating cooling medium and lubrication oil to an electrically powered compressor within an air control circuit of an air conditioner, comprising: 
 a controller arranged and constructed to control the phase state of the cooling medium in the air conditioning circuit to as to supply a dual-state gas liquid cooling medium to an inlet of the compressor during operation of the air conditioner under a low load.    
     
     
         11 . An apparatus as in  claim 10 , further comprising an evaporator disposed on an upstream side of the compressor and within the air conditioning circuit, wherein the controller is arranged and constructed to control the flow of the cooling medium into an inlet of the evaporator.  
     
     
         12 . An apparatus as in  claim 11 , wherein the controller is further arranged and constructed to control the flow of the cooling medium into the inlet of the evaporator based upon the superheat condition of the cooling medium exiting an outlet of the evaporator.  
     
     
         13 . An apparatus as in  claim 12 , wherein the controller comprises a cross-charge expansion valve for controlling the flow of cooling medium into the inlet of the evaporator.  
     
     
         14 . A method for circulating a refrigerant and lubrication oil within an air conditioning circuit of an air conditioner including an electrically powered compressor, comprising: 
 supplying the lubrication oil to the compressor within a dual-state gas-liquid cooling medium when the load on the air conditioner is relatively low.    
     
     
         15 . A method as in  claim 14 , further comprising controlling the phase state of the cooling medium at an inlet of the compressor based upon the pressure at an inlet of an evaporator that is disposed on an upstream side of the compressor within the air conditioning circuit.  
     
     
         16 . An air conditioner comprising: 
 an electrically powered compressor arranged and constructed to compress a refrigerant and discharge the refrigerant under higher pressure, the refrigerant comprising lubricating oil for lubricating parts within the compressor,    a condenser receiving the refrigerant from the compressor,    an expansion valve receiving refrigerant from the condenser,    an evaporator receiving refrigerant from the expansion valve, and    means for adjusting the amount of refrigerant supplied to evaporator in order to adjust the phase state of the refrigerant that is returned to the compressor, thereby ensuring an adequate supply of lubrication oil to the compressor during a low load operation.    
     
     
         17 . An air conditioner as in  claim 16 , wherein the adjusting means contains a gas having a different composition from the refrigerant and the adjusting means is disposed proximal to an outlet port of the evaporator, wherein the gas within the adjusting means is physically isolated from the refrigerant, but assumes the same temperature as the refrigerant exiting the outlet port of the evaporator.  
     
     
         18 . An air conditioner as in  claim 17 , wherein the adjusting means further comprises a movable diaphragm coupled to the expansion valve, wherein the gas within the adjusting means communicates with a first side of the movable diaphragm and the refrigerant exiting from the outlet port of the evaporator communicates with a second side of the movable diaphragm, wherein changes in the relative pressures of the gas and refrigerant cause the movable diaphragm to move and adjust the amount of refrigerant supplied to the evaporator by the expansion valve.  
     
     
         19 . An air conditioner as in  claim 18 , wherein the adjusting means adjusts the phase state of the refrigerant returning to the compressor to be a substantially gas-liquid phase state when the compressor is operating under a relatively low load.  
     
     
         20 . A apparatus for circulating a refrigerant and lubrication oil within an air conditioning circuit of an air conditioner including an electrically powered compressor, comprising: 
 means for supplying the lubrication oil to the compressor within a dual-state gas-liquid cooling medium when the load on the air conditioner is relatively low in order to ensure reliable lubrication of the compressor.