Expansion valve

Abstract

An expansion valve includes: a body having a second passage through which a refrigerant returning from an evaporator passes, and a mounting hole communicating with the second passage; a power element mounted on the body in such a manner as to close the mounting hole; a shaft that transmits a drive force from the power element to a valve element; and a plate that separates an open space from the second passage, has an insertion hole, through which the shaft extends, coaxially along a central axis of the plate, and limits a flow of the refrigerant from the second passage into the open space to a flow through a clearance between the shaft and the insertion hole. The insertion hole is formed such that an opening area of the clearance between the shaft and the insertion hole is 7.0 mm 2 or smaller.

What is claimed is: 
     
         1 . An expansion valve for throttling and expanding a refrigerant flowing from an upstream side and supplying the expanded refrigerant to an evaporator and for sensing a pressure and a temperature of the refrigerant returning from the evaporator to control an opening degree of a valve section, the expansion valve comprising:
 a body having a first passage through which the refrigerant flowing from the upstream side toward the evaporator passes, a second passage through which the refrigerant returning from the evaporator passes, a valve hole formed in the first passage, and a mounting hole communicating with the second passage;   a valve element that moves toward and away from the valve hole to adjust an opening degree of the valve section;   a power element having a housing mounted on the body in such a manner as to close the mounting hole, a diaphragm partitioning an inside of the housing into a closed space in which a temperature sensing medium is sealed and an open space communicating with the second passage, and a disc located in the open space in contact with the diaphragm;   a shaft extending through a partition between the first passage and the second passage, having a first end connected to the diaphragm through the disc and a second end connected to the valve element, and being configured to transmit a drive force in an axial direction to the valve element, the drive force being generated by displacement of the diaphragm; and   an inflow regulating part that separates the open space from the second passage, has an insertion hole, through which the shaft extends, coaxially along a central axis of the inflow regulating part, and limits a flow of the refrigerant from the second passage into the open space to a flow through a clearance between the shaft and the insertion hole,   wherein the insertion hole is formed such that an opening area of the clearance between the shaft and the insertion hole is 7.0 mm 2  or smaller.   
     
     
         2 . The expansion valve according to  claim 1 , wherein the inflow regulating part is constituted by a shield member located between the body and the housing and prevented from dropping off from the mounting hole. 
     
     
         3 . The expansion valve according to  claim 2 , wherein the shield member is a flat, circular plate and has the insertion hole at the center. 
     
     
         4 . The expansion valve according to  claim 2 ,
 wherein the body has a communication hole through which the mounting hole and the second passage communicate with each other, and   the shield member is supported by a stepped portion formed at a boundary of the mounting hole and the communication hole.   
     
     
         5 . The expansion valve according to  claim 3 ,
 wherein the body has a communication hole through which the mounting hole and the second passage communicate with each other, and   the shield member is supported by a stepped portion formed at a boundary of the mounting hole and the communication hole.   
     
     
         6 . The expansion valve according to  claim 5 , wherein the shield member has an outer diameter smaller than an inner diameter of the mounting hole, and the shield member is not fixed to the mounting hole in a radial direction. 
     
     
         7 . The expansion valve according to  claim 2 , wherein the shield member is held between the housing and the body. 
     
     
         8 . The expansion valve according to  claim 1 , wherein the inflow regulating part is made of a resin material having a smaller hardness than the housing. 
     
     
         9 . The expansion valve according to  claim 7 , wherein the inflow regulating part is made of a resin material having a smaller hardness than the housing. 
     
     
         10 . The expansion valve according to  claim 1 , wherein the insertion hole has a cross section of a perfect circular shape. 
     
     
         11 . The expansion valve according to  claim 3 , wherein the insertion hole has a cross section of a perfect circular shape. 
     
     
         12 . The expansion valve according to  claim 6 , wherein the insertion hole has a cross section of a perfect circular shape.