Expansion device

Abstract

To provide an expansion device which shortens cool down time when an automotive air conditioner is started under a high-load condition. An expansion device having a differential pressure control valve is configured such that a temperature-sensing actuator (shape-memory alloy spring) is disposed at an refrigerant outlet of the expansion device, and when an air conditioner is started under a high-load condition in which the temperature of refrigerant at the refrigerant outlet is high, the shape-memory alloy spring senses the high temperature, to urge a spring determining a valve-opening point of the differential pressure control valve, whereby the differential pressure control valve is opened in advance or placed in a state capable of opening in response to a very low differential pressure, thereby making it possible to cause refrigerant to flow at a large flow rate until the temperature of refrigerant at the refrigerant outlet is lowered to a temperature assumed when the air conditioner functions.

1 . An expansion device for expanding refrigerant circulating through a refrigeration cycle, comprising: 
 a differential pressure control valve that is responsive to differential pressure between pressure at a refrigerant inlet and pressure at a refrigerant outlet, to open; and    an actuator that sets valve-opening differential pressure at which said differential pressure control valve opens, to a lower value, when refrigerant at the refrigerant outlet is higher in temperature than a temperature at which the refrigeration cycle is operating in a steady state or higher in pressure than pressure corresponding to the temperature.    
   
   
       2 . The expansion device according to  claim 1 , wherein said actuator is a shape-memory alloy spring which senses a temperature of the refrigerant at the refrigerant outlet, and is operable when the temperature of the refrigerant becomes higher than the temperature at which the refrigeration cycle is operating in the steady state, to increases a rate of increase in load thereof to thereby set the valve-opening differential pressure at which said differential pressure control valve opens, to a lower value, or thereby open said differential pressure control valve.  
   
   
       3 . The expansion device according to  claim 1 , wherein said actuator senses pressure of the refrigerant at the refrigerant outlet to thereby convert the pressure to a stroke in a direction of opening or closing said differential pressure control valve, and is operable when the sensed pressure becomes equal to pressure corresponding to a temperature higher than the temperature at which the refrigeration cycle is operating in the steady state, to increase the stroke to thereby set the valve-opening differential pressure at which said differential pressure control valve opens to zero or a very low differential pressure.  
   
   
       4 . The expansion device according to  claim 3 , wherein said actuator includes a stopper for inhibiting the valve-opening differential pressure from being changed for said differential pressure control valve, when said actuator senses the pressure of the refrigerant at the refrigerant outlet corresponding to the temperature at which the refrigeration cycle is operating in the steady state.  
   
   
       5 . The expansion device according to  claim 3 , wherein said actuator is a power element that hermetically holds a diaphragm between a first housing having a center projected outward and a second housing having an opening in a center thereof, and has a snap plate or a disc spring provided within said first housing, for supporting said diaphragm as said diaphragm is displaced inward by receiving the pressure of the refrigerant at the refrigerant outlet, and for being largely displaced inward when the pressure becomes equal to the pressure corresponding to the temperature higher than the temperature at which the refrigeration cycle is operating in the steady state.  
   
   
       6 . The expansion device according to  claim 5 , wherein said second housing of said power element includes a diaphragm-receiving portion which has an annular shape and has a portion opposed to said diaphragm radially inwardly extended, and wherein a space formed by said first housing and said diaphragm is filled with gas.  
   
   
       7 . The expansion device according to  claim 5 , comprising pressure-sensing follow-up means for axially moving said differential pressure control valve back and forth by following displacement of said diaphragm, and wherein said differential pressure control valve is maintained in an open state when said diaphragm senses pressure even higher than pressure which sets the valve-opening differential pressure to 0.  
   
   
       8 . An expansion device for expanding refrigerant circulating through a refrigeration cycle, comprising: 
 a first differential pressure control valve that is responsive to differential pressure between pressure at a refrigerant inlet and pressure at a refrigerant outlet, to open;    a second differential pressure control valve that has a valve hole formed between the refrigerant inlet and the refrigerant outlet, and has a diameter larger than that of said first differential pressure control valve; and    an actuator that sets valve-opening differential pressure at which said second differential pressure control valve opens, to a lower value, when refrigerant at the refrigerant outlet is higher in temperature than a temperature at which the refrigeration cycle is operating in a steady state or higher in pressure than pressure corresponding to the temperature.    
   
   
       9 . The expansion device according to  claim 8 , wherein said actuator is a shape-memory alloy spring which senses a temperature of the refrigerant at the refrigerant outlet, and is operable when the temperature of the refrigerant becomes higher than the temperature at which the refrigeration cycle is operating in the steady state, to increases a rate of increase in load thereof to thereby set the valve-opening differential pressure at which said second differential pressure control valve opens, to a lower value, or thereby open said second differential pressure control valve.  
   
   
       10 . The expansion device according to  claim 8 , wherein said actuator senses pressure of the refrigerant at the refrigerant outlet to thereby convert the pressure to a stroke in a direction of opening or closing said second differential pressure control valve, and is operable when the sensed pressure becomes equal to pressure corresponding to a temperature higher than the temperature at which the refrigeration cycle is operating in the steady state, to increase the stroke to thereby set the valve-opening differential pressure at which said second differential pressure control valve opens to zero or a very low differential pressure.  
   
   
       11 . The expansion device according to  claim 10 , comprising pressure-sensing follow-up means for axially moving said second differential pressure control valve back and forth by following a change in the stroke, and wherein said second differential pressure control valve is maintained in an open state when the sensed pressure becomes even higher than pressure which sets the valve-opening differential pressure at which said second differential pressure control valve opens to 0.