Expansion device

Abstract

An expansion device which is capable of reducing generation of untoward noise due to vibration of a valve element and suppressing a valve element suction phenomenon which occurs when high-pressure refrigerant flows through a variable orifice formed between a valve seat and the valve element. A damper chamber is formed by a cylinder formed in a housing formed with a valve seat, a piston integrally formed with a valve element, and an adjustment screw. When the valve element undergoes a sudden change in pressure of introduced refrigerant, the volume of the damper chamber changes to accommodate sudden motion of the valve element, whereby vibration of the valve element is suppressed, to reduce generation of untoward noise. The ratio (b/a) of the valve element diameter (b) of the valve element to the port diameter (a) of a valve hole is set to a value not larger than 1.5 so as to suppress a valve element suction phenomenon and pass refrigerant at a flow rate corresponding to a differential pressure between a primary pressure and a secondary pressure.

1 . An expansion device having a valve element disposed at a location downstream of a valve seat in a state urged in a valve-closing direction by a spring, the expansion device being capable of passing refrigerant at a flow rate corresponding to a differential pressure between a primary pressure in a refrigerant inlet port and a secondary pressure in a refrigerant outlet port, comprising: 
 damper means provided in the valve element, for accommodating motion of the valve element in an opening or closing direction when the valve element undergoes a sudden change in pressure.    
   
   
       2 . The expansion device according to  claim 1 , wherein the damper means comprises a cylinder formed in a housing formed with the valve seat such that the cylinder extends in the same axial direction as the valve element, a piston disposed in the cylinder and integrally formed with the valve element, and a damper chamber whose volume can be changed by the piston.  
   
   
       3 . The expansion device according to  claim 2 , wherein the damper chamber is closed by an adjustment member screwed or press-fitted in an open end of the cylinder, and the spring is interposed between the piston and the adjustment member.  
   
   
       4 . The expansion device according to  claim 3 , wherein the adjustment member is formed with a fixed orifice in communication with the damper chamber.  
   
   
       5 . The expansion device according to  claim 3 , comprising a stopper screwed or press-fitted in the adjustment member in a manner movable back and forth along an axis of the adjustment member, for restricting a stroke of the piston in a valve-opening direction.  
   
   
       6 . The expansion device according to  claim 5 , wherein the stopper is formed with a fixed orifice communicating with the damper chamber.  
   
   
       7 . The expansion device according to  claim 1 , wherein a ratio (b/a) of a valve element diameter (b) of the valve element to a port diameter (a) of the valve hole is not larger than 1.5.  
   
   
       8 . The expansion device according to  claim 1 , applied to a refrigeration cycle using carbon dioxide as the refrigerant.