Abstract:
To provide an expansion valve having a low-pressure passage that is bent at right angles therein, which is reduced in untoward noise and noise of the flow of refrigerant generated when the refrigerant passes through the low-pressure passage. In an intersecting portion of a low-pressure passage, the axis of a port for introducing refrigerant returned from an evaporator, and the axis of a port for guiding out refrigerant having passed through a body block to a compressor are orthogonal to each other. A hole is formed in the body block in a direction of insertion of a shaft that transmits a driving force from a power element to a valve element, and a holder for holding the shaft. When holes coaxial with the ports, respectively, are formed by drills having the same diameter as that of the hole, the holes are formed in a manner such that the tip of one drill does not extend beyond the hole formed by the other drill, to make inner walls on an outer peripheral side along which refrigerant flows at an increased speed, smoothly continuous, without forming any recess or edge portion having a boundary portion with an angle equal to or smaller than a right angle.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY  
       [0001]     This application claims priority of Japanese Application No.2003-277971 filed on Jul. 23, 2003 and entitled “EXPANSION VALVE”.  
       BACKGROUND OF THE INVENTION  
       [0002]     (1) Field of the Invention  
         [0003]     The present invention relates to an expansion valve, and more particularly to an expansion valve that senses the temperature and pressure of refrigerant in an outlet of an evaporator in a refrigeration cycle for an automotive air conditioning system, and controls the amount of refrigerant to be supplied to the evaporator.  
         [0004]     (2) Description of the Related Art  
         [0005]     In an automotive air conditioning system, a refrigeration cycle is formed such that high-temperature, high-pressure gaseous refrigerant compressed by a compressor is condensed by a condenser; the condensed refrigerant is caused to undergo gas/liquid separation by a receiver/dryer; liquid refrigerant obtained by the gas/liquid separation is caused to undergo adiabatic expansion by an expansion valve, to be changed into low-temperature, low-pressure refrigerant, which is then evaporated by an evaporator; and the evaporated refrigerant is returned to the compressor. The evaporator to which is supplied the low-pressure refrigerant exchanges heat with the air in the compartment, to thereby cool the same.  
         [0006]     The expansion valve comprises a power element that has pressure therein increased and decreased by sensing changes in the temperature and pressure of refrigerant on the outlet side of the evaporator, and a valve portion that controls the amount of refrigerant to be supplied to the inlet side of the evaporator based on the increase and decrease in pressure within the power element.  
         [0007]     The power element includes a temperature-sensing chamber partitioned by a diaphragm made of a thin metal plate. When the power element senses changes in the temperature and pressure of refrigerant, the pressure within the temperature-sensing chamber is changed to displace the diaphragm. The displacement of the diaphragm is transmitted to a valve element of the valve portion via a shaft that extends axially, to cause the valve portion to perform opening/closing operation, whereby the flow rate of refrigerant through the valve is controlled. The valve portion has a valve seat formed in a passage extending between a port to which high-pressure refrigerant is introduced and a port from which adiabatically-expanded low-pressure refrigerant is allowed to flow. The valve element is disposed such that it can move to and away from the valve seat on an upstream side where high-pressure refrigerant is received, and the valve element is driven for opening/closing operation by the shaft extending from the power element through the valve hole thereof.  
         [0008]     The expansion valve constructed as above is disposed in an engine room, a compartment or a partition dividing them, and in the expansion valve, a pipe leading to the receiver/dryer is connected to the high-pressure inlet port of the valve portion, a pipe leading to the evaporator is connected to the low-pressure outlet port of the same, a pipe from the evaporator is connected to the low-pressure inlet port of the power element, and a pipe extending to the compressor is connected to the low-pressure outlet port of the same. In a general expansion valve, a low-pressure outlet port to which is connected a pipe extending to the compressor is provided in the same side surface where a high-pressure inlet port of a valve portion is formed, and in an opposite side surface to the side surface, there are provided a low-pressure outlet port of the valve portion and a low-pressure inlet port to which is connected a pipe from the evaporator. That is, the low-pressure outlet port though which refrigerant from the expansion valve is guided out is formed along an axis parallel to the axis of the high-pressure inlet port through which refrigerant is introduced to the expansion valve, while the low-pressure inlet and outlet ports for causing refrigerant returned from the evaporator to flow to the compressor are disposed on the same axis. This means that e.g. when the expansion valve and the evaporator are mounted in a narrow mounting space, such as an engine room, the flexibility in layout thereof is sometimes limited. For example, when the direction of a pipe of the expansion valve, connected to the evaporator, and the direction of pipes of the expansion valve, connected to the receiver/dryer and the compressor, are caused to be orthogonal to each other, the pipe connected to the compressor has to be bent halfway, which requires an extra space for bending the pipe.  
         [0009]     To avoid this inconvenience, an expansion valve has been proposed which is configured to be capable of having pipes connected to a body block in the form of a prism at right angles (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2001-241808 (Paragraph No. [0024], and  FIGS. 7 and 8 )) by forming ports to which are connected the pipes, in two adjacent side surfaces of the body block. This expansion valve is configured such that the axis of the high-pressure inlet port of the valve portion and the axis of the low-pressure outlet port thereof are orthogonal to each other, and the axes of the low-pressure inlet port and the low-pressure outlet port through which refrigerant returned from the evaporator passes are orthogonal to each other. Due to this construction, since the four ports are provided in the two adjacent side surfaces of the body block, it becomes possible to efficiently accommodate the expansion valve within a limited space. Now, a description will be given of the construction of a low-pressure passage through which refrigerant returned from the evaporator passes to flow to the compressor.  
         [0010]      FIG. 26  is a cross-sectional view of a low-pressure passage of a conventional expansion valve.  
         [0011]     The conventional expansion valve includes a low-pressure inlet port  101  for introducing refrigerant returned from the evaporator and a low-pressure outlet port  102  for a pipe connected to the compressor, on respective two adjacent side surfaces of a body block  100  in the form of a prism, and a low-pressure passage  103  having portions that extend from the low-pressure inlet port  101  and the low-pressure outlet port  102  along their axes and intersect at right angles within the body block  100 . The low-pressure passage  103  is formed by making holes with drills such that the respective axes of the holes are orthogonal to each other, and when forming the holes, they are drilled until the tip of one of the drills sufficiently passes through a hole made by the other of the drills, such that the holes formed by the respective drills positively communicate with each other within the body block  100 .  
         [0012]     As a result, when refrigerant introduced from the evaporator into the low-pressure inlet port  101  flows through the low-pressure passage  103 , the direction of flow thereof is changed at right angles, whereafter it flows from the low-pressure outlet port  102  to the compressor. Since the expansion valve itself contains the refrigerant passage bent at right angles, there is no need to bend pipes connected to the expansion valve, thereby making it possible to arrange the piping over the shortest length.  
         [0013]     However, when the low-pressure passage  103  is formed by drilling from the two adjacent side surfaces, drilling is continued until the tip of one drill positively passes through a portion of the cylindrical low-pressure passage  103  formed by the other drill in a direction orthogonal to the direction of drilling by the drill, and hence inner walls of the portions of the low-pressure passage  103  on the outer peripheral sides thereof, which are orthogonal to each other, are formed with recesses  104  and edge portions  105  by the tip and its vicinity of each drill. When refrigerant passes the recesses  104  and the edge portions  105  at a faster flow speed than it flows along the inner peripheral side of the low-pressure passage  103 , the flow of refrigerant is made turbulent to generate unusual noise, and the turbulent flow of the refrigerant increases noise of the flow of refrigerant.  
       SUMMARY OF THE INVENTION  
       [0014]     The present invention has been made in view of the above points, and an object thereof is to provide an expansion valve that has a low-pressure passage formed therein and bent at right angles, which is reduced in untoward noise and noise of the flow of refrigerant which are generated when the refrigerant passes through the low-pressure passage.  
         [0015]     To solve the above problem, the present invention provides an expansion valve that has ports opening in adjacent side surfaces of a prismatic body, the ports communicating with a low-pressure passage that is bent at right angles within the prismatic body, wherein the low-pressure passage is formed by drilling first and second holes in a manner such that when the first and second holes are drilled from the adjacent side surfaces along respective axes of the ports, a tip of one of the drills is stopped in the first or second hole drilled by the other of the drills.  
         [0016]     The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a front view showing the appearance of an expansion valve according to a first embodiment of the present invention.  
         [0018]      FIG. 2  is a side view showing the appearance of the expansion valve according to the first embodiment.  
         [0019]      FIG. 3  is a cross-sectional view of the expansion valve taken on line A-A of  FIG. 1 .  
         [0020]      FIG. 4  is a cross-sectional view of the expansion valve taken on line B-B of  FIG. 2 .  
         [0021]      FIG. 5  is a cross-sectional view of the expansion valve taken on line C-C of  FIG. 1 .  
         [0022]      FIG. 6  is a Cross-sectional view of the expansion valve taken on line D-D of  FIG. 2 .  
         [0023]      FIG. 7  is a longitudinal cross-sectional view showing an expansion valve according to a second embodiment of the present invention, as viewed from a plane passing through the axes of a high-pressure inlet port and a low-pressure outlet port.  
         [0024]      FIG. 8  is a longitudinal cross-sectional view showing the expansion valve according to the second embodiment, as viewed from a plane passing through the axes of a low-pressure inlet port and a low-pressure outlet port connected to an evaporator.  
         [0025]      FIG. 9  is a transverse cross-sectional view showing the expansion valve according to the second embodiment, as viewed from a plane passing through the axes of a low-pressure passage.  
         [0026]      FIG. 10  is a longitudinal cross-sectional view showing an expansion valve according to a third embodiment of the present invention, as viewed from a plane passing through the axes of a high-pressure inlet port and a low-pressure outlet port.  
         [0027]      FIG. 11  is a longitudinal cross-sectional view showing the expansion valve according to the third embodiment, as viewed from a plane passing through the axes of a low-pressure inlet port and a low-pressure outlet port connected to an evaporator.  
         [0028]      FIG. 12  is a transverse cross-sectional view showing the expansion valve according to the third embodiment, as viewed from a plane passing through the axes of a low-pressure passage.  
         [0029]      FIG. 13  is a transverse cross-sectional view showing an expansion valve according to a fourth embodiment of the present invention, as viewed from a plane passing through the axes of a low-pressure passage.  
         [0030]      FIG. 14  is a transverse cross-sectional view showing an expansion valve according to a fifth embodiment of the present invention, as viewed from a plane passing through the axes of a low-pressure passage.  
         [0031]      FIG. 15  is a transverse cross-sectional view showing an expansion valve according to a sixth embodiment of the present invention, as viewed from a plane passing through the axes of a low-pressure passage.  
         [0032]      FIG. 16  is a front view showing the appearance of an expansion valve according to a seventh embodiment of the present invention.  
         [0033]      FIG. 17  is a side view showing the appearance of the expansion valve according to the seventh embodiment.  
         [0034]      FIG. 18  is a cross-sectional view of the expansion valve taken on line A-A of  FIG. 16 .  
         [0035]      FIG. 19  is a cross-sectional view of the expansion valve taken on line B-B of  FIG. 17 .  
         [0036]      FIG. 20  is a cross-sectional view of the expansion valve taken on line C-C of  FIG. 16 .  
         [0037]      FIG. 21  is a front view showing the appearance of an expansion valve according to an eighth embodiment of the present invention.  
         [0038]      FIG. 22  is a side view showing the appearance of the expansion valve according to the eighth embodiment.  
         [0039]      FIG. 23  is a cross-sectional view of the expansion valve taken on line A-A of  FIG. 21 .  
         [0040]      FIG. 24  is a cross-sectional view of the expansion valve taken on line B-B of  FIG. 22 .  
         [0041]      FIG. 25  is a cross-sectional view of the expansion valve taken on line C-C of  FIG. 21 .  
         [0042]      FIG. 26  is a cross-sectional view of a low-pressure passage of a conventional expansion valve. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.  
         [0044]      FIG. 1  is a front view showing the appearance of an expansion valve according to a first embodiment of the present invention.  FIG. 2  is a side view showing the appearance of the expansion valve according to the first embodiment.  FIG. 3  is a cross-sectional view of the expansion valve taken on line A-A of  FIG. 1 .  FIG. 4  is a cross-sectional view of the expansion valve taken on line B-B of  FIG. 2 .  FIG. 5  is a cross-sectional view of the expansion valve taken on line C-C of  FIG. 1 .  FIG. 6  is a cross-sectional view of the expansion valve taken on line D-D of  FIG. 2 .  
         [0045]     Referring first to  FIG. 1 , the expansion valve  1  according to the first embodiment includes a body block  2  having a front surface formed with a high-pressure inlet port T 1  to which is connected a high-pressure refrigerant pipe for receiving high-temperature, high-pressure refrigerant from a condenser, and a low-pressure outlet port T 4  connected to a refrigerant pipe leading to a compressor. As shown in  FIG. 2 , the body block  2  has a left side surface thereof formed with a low-pressure outlet port T 2  to which is connected a low-pressure refrigerant pipe for supplying low-temperature, low-pressure refrigerant expanded and reduced in pressure by the expansion valve  1  to an evaporator, and a low-pressure inlet port  3  connected to a refrigerant pipe extending from the outlet of the evaporator.  
         [0046]     As shown in  FIG. 3  and  FIG. 4 , within the body block  2 , there is formed a fluid passage communicating between the port T 1  and the port T 2 , in which a valve seat  3  is integrally formed with the body block  2 , and a ball-shaped valve element  4  is disposed on the upstream side of the valve seat  3  in a manner opposed to the valve seat  3 . As a result, a gap between the valve seat  3  and the valve element  4  forms a variable orifice for restricting high-pressure refrigerant, and the refrigerant undergoes adiabatic expansion when it flows through the variable orifice.  
         [0047]     Further, in a portion of the fluid passage toward the high-pressure inlet port T 1 , there are disposed a valve element receiver  5  for receiving the valve element  4 , and a compression coil spring  6  urging the valve element  4  via the valve element receiver  5  in the direction of seating the valve element  4  on the valve seat  3 . The compression coil spring  6  is received by a spring receiver  7  and an adjustment screw  8  screwed into the body block  2  for adjustment of load of the compression coil spring  6 .  
         [0048]     At the upper end of the body block  2 , there is provided a power element  9  which comprises an upper housing  10  and a lower housing  11 , made of thick metal, a diaphragm  12  made of a thin metal plate having flexibility and disposed in a manner dividing the space enclosed by the housings, and a disk  13  disposed below the diaphragm  12 . The space enclosed by the upper housing  10  and the diaphragm  12  forms a temperature-sensing chamber which is filled with refrigerant gas and the like, and is sealed with a metal ball  14  joined to the upper housing  10  by resistance-welding. The disk  13  has an upper part formed with an increased diameter such that the part radially protrudes outward, and the underside of the increased diameter portion is configured to be brought into abutment with the inner wall surface of the lower housing  11  opposed thereto such that the underside functions as a stopper limiting the downward motion of the diaphragm  12 , thereby defining the maximum valve lift of the expansion valve  1 .  
         [0049]     Below the disk  13 , a shaft  15  is disposed for transmitting displacement of the diaphragm  12  to the valve element  4 . The shaft  15  is inserted through a through hole  16  formed in the center of the body block  2 .  
         [0050]     The through hole  16  has an expanded upper portion thereof, and an O ring  17  is disposed at a stepped portion thereof. The O ring  17  seals a gap between the shaft  15  and the through hole  16 , thereby preventing refrigerant from leaking into a low-pressure passage between the ports T 3  and T 4 .  
         [0051]     Further, the upper end of the shaft  15  is held by a holder  18  which has a hollow cylindrical portion extending downward across the low-pressure passage between the ports T 3  and T 4 . The lower end of the holder  18  is fitted in the expanded portion of the through hole  16  and the lower end face restricts the motion of the O ring  17  toward the upper open end of the through hole  16 .  
         [0052]     At the upper end of the holder  18 , the disk  13  is movably held in the direction of displacement of the diaphragm  12 , and further a spring  19  is disposed for urging the shaft  15  from a radial direction. This configuration of applying lateral load to the shaft  15  with the spring  19  prevents the axial motion of the shaft  15  from sensitively reacting to changes in pressure of the high-pressure refrigerant introduced into the high-pressure inlet port T 1 , to thereby form a vibration suppressing mechanism for suppressing generation of untoward vibration noise caused by vibrations of the shaft  15  in the axial direction. Further, the top of the holder  18  has a pressure equalizing passage formed therethrough for causing the low-pressure passage communicating between the ports T 3  and T 4  to communicate with the space below the diaphragm  12 , such that the refrigerant returned from the evaporator can enter the space below the diaphragm  12 .  
         [0053]     As shown in FIGS.  3  to  5 , the low-pressure passage communicating between the ports T 3  and T 4  is formed by boring a cylindrical hole  20  from the upper surface of the body block  2  using a tool, such as an end mill, further, making a hole  21  coaxial with the port T 4  from the front side surface of the body block  2  using a drill such that the hole  21  communicates with the hole  20 , and making a hole  22  coaxial with the port T 3  from the left side surface of the body block  2  using a drill such that the hole  22  communicates with the hole  20 . At this time, the holes  20 ,  21 , and  22  are formed to have the same diameter, with central axes thereof being orthogonal to each other, whereby the outer peripheral portion of an intersecting portion of the low-pressure passage has a radiused shape. Therefore, when the refrigerant flows through the low-pressure passage, the radiused shape of the intersecting portion along which the refrigerant flows at an increased speed makes the flow of refrigerant non-turbulent to cause the refrigerant to flow smoothly, whereby it is possible to reduce generation of untoward noise caused by turbulence of the flow of the refrigerant and noise of the flow of refrigerant.  
         [0054]     Further, as shown in  FIG. 2  and  FIG. 3 , the body block  2  is formed with through holes  23  for having bolts passed therethrough for mounting the expansion valve, and, as shown in  FIG. 1  and  FIG. 3 , a screw hole  24  for having a stud bolt implanted therein for mounting the expansion valve. As shown in  FIG. 6 , the through holes  23  for having the bolts passed therethrough each have one open end thereof formed with a countersunk hole  25  coaxial therewith. Due to this configuration, by passing the mounting bolts through the through holes  23  such that the heads of the bolts are positioned in the countersunk holes  25 , it is possible to prevent the heads of the bolts from protruding from the body block  2 , thereby making it possible to further reduce installation space for the expansion valve  1 . The power element  9  on the top of the body block  2  is covered with a heat-resistant cap  26 . The heat-resistant cap  26  is used particularly in the case where the expansion valve  1  is disposed within an engine room. This is because the temperature of the atmosphere within the engine room becomes very high, and therefore with a view to improvement in the temperature characteristics of the expansion valve  1 , the power element  9  is prevented from being adversely affected by the high temperature of the atmosphere within the engine room.  
         [0055]     In the expansion valve  1  configured as above, before an air conditioner is started, the power element  9  detects a sufficiently higher temperature than when the air conditioner is in operation, so that the pressure in the temperature-sensing chamber of the power element  9  is high, causing the diaphragm  12  to be displaced downward, as viewed in the figures, and the disk  13  is brought into abutment with the lower housing  11 . The displacement of the diaphragm  12  is transmitted to the valve element  4  of a valve portion via the shaft  15 , whereby the expansion valve  1  is fully opened. Therefore, at the start of the air conditioner, the expansion valve  1  supplies refrigerant to the evaporator at a maximum flow rate.  
         [0056]     As the temperature of the refrigerant returned from the evaporator is lowered, the temperature in the temperature-sensing chamber of the power element  9  is lowered, whereby the refrigerant gas in the temperature-sensing chamber is condensed on the inner surface of the diaphragm  12 . This causes the pressure in the temperature-sensing chamber to be reduced to displace the diaphragm  12  upward, so that the shaft  15  is pushed by the compression coil spring  6 , to move upward. As a result, the valve element  4  is moved toward the valve seat  3 , whereby the passage area of the variable orifice is reduced to decrease the flow rate of refrigerant sent into the evaporator. Thus, the valve lift of the expansion valve  1  is set to a value corresponding to a flow rate dependent on the cooling load.  
         [0057]      FIG. 7  is a longitudinal cross-sectional view showing an expansion valve according to a second embodiment of the present invention, as viewed from a plane passing through the axes of a high-pressure inlet port and a low-pressure outlet port.  FIG. 8  is a longitudinal cross-sectional view showing the expansion valve according to the second embodiment, as viewed from a plane passing through the axes of a low-pressure inlet port and a low-pressure outlet port connected to an evaporator.  FIG. 9  is a transverse cross-sectional view showing the expansion valve according to the second embodiment, as viewed from a plane passing through the axes of a low-pressure passage. It should be noted that the expansion valve according to the second embodiment has the same general view as that of the expansion valve according to the first embodiment, and hence figures showing the appearance thereof are omitted. Further, in FIGS.  7  to  9 , component elements identical or equivalent to those shown in FIGS.  1  to  6  are designated by the same reference numerals, and detailed description thereof is omitted.  
         [0058]     In the expansion valve according to the second embodiment, an intersecting portion of the low-pressure passage communicating between ports T 3  and T 4  is formed to be larger than the intersecting portion of the low-pressure passage of the expansion valve according to the first embodiment. More specifically, as shown in FIGS.  7  to  9 , the intersecting portion of the low-pressure passage is formed by making a hole from the upper surface of the body block  2  using a tool, such as an end mill, then boring the hole using a tool, such as a boring tool, to thereby form a cylindrical hole  20 , further drilling a hole  21  coaxial with a port T 4  from the front side surface of the body block  2  such that the hole  21  communicates with the hole  20 , and drilling a hole  22  coaxial with the port T 3  from the left side surface of the body block  2  such that the hole  22  communicates with the hole  20 . This makes it possible to cause the outer peripheral portion of the intersecting portion of the low-pressure passage to have a radiused shape, and the intersecting portion provides a wider passage. Therefore, when the refrigerant flows through the low-pressure passage, the radiused shape of the intersecting portion along which the refrigerant flows at an increased speed makes the flow of refrigerant non-turbulent to cause the refrigerant to flow smoothly, whereby it is possible to reduce generation of untoward noise caused by turbulence of the flow of refrigerant and noise of the flow of refrigerant.  
         [0059]      FIG. 10  is a longitudinal cross-sectional view showing an expansion valve according to a third embodiment of the present invention, as viewed from a plane passing through the axes of a high-pressure inlet port and a low-pressure outlet port.  FIG. 11  is a longitudinal cross-sectional view showing the expansion valve according to the third embodiment, as viewed from a plane passing through the axes of a low-pressure inlet port and a low-pressure outlet port connected to an evaporator.  FIG. 12  is a transverse cross-sectional view showing the expansion valve according to the third embodiment, as viewed from a plane passing through the axes of a low-pressure passage. It should be noted that the expansion valve according to the third embodiment also has the same general view as that of the expansion valve according to the first embodiment, and hence figures showing the appearance thereof are omitted. Further, in FIGS.  10  to  12 , component elements identical or equivalent to those shown in FIGS.  1  to  6  are designated by the same reference numerals, and detailed description thereof is omitted.  
         [0060]     In the expansion valve according to the third embodiment, the low-pressure passage communicating between ports T 3  and T 4  is formed using a tool with a rounded tip. More specifically, a hole  21  coaxial with the port T 4  is drilled from the front side surface of the body block  2  using a drill with a rounded tip, and then a hole  22  coaxial with the port T 3  is drilled from the left side surface of the body block  2  using a drill with a rounded tip, whereby an intersecting portion of the low-pressure passage is formed. At this time, when one of the holes  21  and  22  is drilled, the drill for making the one hole is caused to stop at a position where the tip of the drill coincides with the inner wall of the other of the holes  21  and  22 . As a result, the intersecting portion of the low-pressure passage has an outer peripheral portion thereof formed on an inner wall  27  which is radiused-shaped, following the contour of the tip of the drill. Therefore, since refrigerant introduced into the port T 3  is caused to flow along the radiused-shaped inner wall  27  of the low-pressure passage, it is possible to reduce generation of untoward noise caused by turbulence of the flow of refrigerant and noise of the flow of refrigerant.  
         [0061]      FIG. 13  is a transverse cross-sectional view showing an expansion valve according to a fourth embodiment of the present invention, as viewed from a plane passing through the axes of a low-pressure passage. It should be noted that the expansion valve according to the fourth embodiment has the same general view and longitudinal cross-sectional configuration as those of the expansion valve according to the third embodiment, and hence figures showing the appearance and longitudinal cross-sectional views thereof are omitted. Further, in  FIG. 13 , component elements identical or equivalent to those shown in  FIG. 12  are designated by the same reference numerals, and detailed description thereof is omitted.  
         [0062]     In the expansion valve according to the fourth embodiment, an intersecting portion of the low-pressure passage communicating between ports T 3  and T 4  is configured such that an edge line  28 , which is a juncture of machined portions formed by drilling, is cut off therefrom, to thereby eliminate an edge portion from the inner peripheral side of the intersecting portion. The edge line  28  is cut off with a tool, such as a machining tool or an end mill, inserted into each of the ports T 3  and T 4 . As a result, the inner wall surface of the intersecting portion is chamfered to form cut faces  29 , and the edge portion of the expansion valve according to the third embodiment, having an angle of 90 degrees, is caused to have a larger angle. This makes it possible to cause refrigerant to smoothly flow along the inner peripheral side of the intersecting portion, thereby making it possible to further reduce generation of untoward noise and noise of the flow of refrigerant.  
         [0063]      FIG. 14  is a transverse cross-sectional view showing an expansion valve according to a fifth embodiment of the present invention, as viewed from a plane passing through the axes of a low-pressure passage. It should be noted that the expansion valve according to the fifth embodiment has the same general view and longitudinal cross-sectional configuration as those of the expansion valve according to the third embodiment, and hence figures showing the appearance and longitudinal cross-sectional views thereof are omitted. Further, in  FIG. 14 , component elements identical or equivalent to those shown in  FIG. 12  are designated by the same reference numerals, and detailed description thereof is omitted.  
         [0064]     In the expansion valve according to the fifth embodiment, the low-pressure passage communicating between ports T 3  and T 4  is formed using a tool having a tip angle (cutting edge angle) of 120 degrees. More specifically, a hole  21  coaxial with the port T 4  is drilled from the front side surface of the body block  2  using a drill having a tip angle of 120 degrees, and then a hole  22  coaxial with the port T 3  is drilled from the left side surface of the body block  2  using a drill having a tip angle of 120 degrees, whereby an intersecting portion of the low-pressure passage is formed. When the holes  21  are  22  drilled, the drills are caused to stop at respective locations before the respective tips of the drills reach the inner walls of the holes  21  and  22 . As a result, the intersecting portion of the low-pressure passage has an outer peripheral portion thereof formed on an inner wall  27  formed by a combination of shapes following the contours of the tips of the drills. At this time, although an edge portion, which is a juncture of machined portions, is formed by drilling using the tips of the drills, no significant turbulence of the flow of refrigerant is caused by the edge portion since the edge portion has an obtuse angle of 150 degrees. Therefore, when refrigerant introduced into the port T 3  flows in an outer peripheral portion of the low-pressure passage, it flows substantially along the inner wall  27 , so that it is possible to reduce generation of untoward noise caused by turbulence of the flow of refrigerant and noise of the flow of refrigerant.  
         [0065]      FIG. 15  is a transverse cross-sectional view showing an expansion valve according to a sixth embodiment, as viewed from a plane passing through the axes of a low-pressure passage. It should be noted that the expansion valve according to the sixth embodiment has the same general view and longitudinal cross-sectional configuration as those of the expansion valve according to the third embodiment, and hence figures showing the appearance and longitudinal cross-sectional views thereof are omitted. Further, in  FIG. 15 , component elements identical or equivalent to those shown in  FIG. 14  are designated by the same reference numerals, and detailed description thereof is omitted.  
         [0066]     In the expansion valve according to the sixth embodiment, the low-pressure passage communicating between ports T 3  and T 4  is formed using a tool having a tip angle (cutting edge angle) of 90 degrees. More specifically, a hole  21  coaxial with the port T 4  is drilled from the front side surface of the body block  2  using a drill having a tip angle of 90 degrees, and then a hole  22  coaxial with the port T 3  is drilled from the left side surface of the body block  2  using a drill having a tip angle of 90 degrees, whereby an intersecting portion of the low-pressure passage is formed. When one of the holes  21  and  22  is made by drilling, the drill is caused to stop at a position where the tip of the drill coincides with the inner wall of the other of the holes  21  and  22 . As a result, the intersecting portion of the low-pressure passage has an outer peripheral portion thereof formed on an inner wall  27  having a shape following the shape of the tip of the drill. Therefore, refrigerant introduced into the port T 3  flows along the inner wall  27  of the low-pressure passage, so that it is possible to reduce generation of untoward noise caused by turbulence of the flow of refrigerant and noise of the flow of refrigerant.  
         [0067]      FIG. 16  is a front view showing the appearance of an expansion valve according to a seventh embodiment of the present invention.  FIG. 17  is a side view showing the appearance of the expansion valve according to the seventh embodiment.  FIG. 18  is a cross-sectional view of the expansion valve taken on line A-A of  FIG. 16 .  FIG. 19  is a cross-sectional view of the expansion valve taken on line B-B of  FIG. 17 .  FIG. 20  is a cross-sectional view of the expansion valve taken on line C-C of  FIG. 16 . In FIGS.  16  to  20 , component elements identical or equivalent to, those shown in FIGS.  1  to  5  are designated by the same reference numerals, and detailed description thereof is omitted.  
         [0068]     In contrast to the expansion valves  1  according to the first to sixth embodiments, which are of a so-called block type, the expansion valve  1  according to the seventh embodiment is called a plug type expansion valve. This expansion valve  1  includes a plug having a valve portion and a power element  9  and functioning as an expansion valve, and a valve casing  30 , and is assembled by inserting and rigidly fixing the plug in the valve casing  30 . As shown in  FIGS. 16 and 17 , the valve casing  30  has ports T 1  and T 4  and ports T 2  and T 3  formed in two adjacent side surfaces thereof.  
         [0069]     Referring to  FIG. 20 , a low-pressure passage communicating between the ports T 3  and T 4  is formed by boring a cylindrical hole  20  from the upper surface of the valve casing  30  using a tool, such as an end mill, further drilling a hole  21  coaxial with the port T 4  from the front side surface of the valve casing  30  using a drill such that the hole  21  communicates with the hole  20 , and drilling a hole  22  coaxial with the port T 3  from the left side surface of the valve casing  30  using a drill such that the hole  22  communicates with the hole  20 . The plug disposed across the low-pressure passage has a diameter larger than the outer diameter of the holder  18  of the expansion valve  1  according to each of the first to sixth embodiments, and therefore the hole  20  is configured to have a larger diameter than those of the holes  21  and  22 . This eliminates edge portions having an acute angle from an inner wall of the low-pressure passage on an outer peripheral side thereof, so that when refrigerant flows through the low-pressure passage, it smoothly flows through the intersecting portion, which makes it possible to reduce generation of untoward noise and noise of the flow of refrigerant.  
         [0070]     As shown in  FIGS. 18 and 19 , the power element  9  of the plug comprises an upper housing  10 , a lower housing  11 , a diaphragm  12 , and a disk  13 . As shown in  FIG. 19 , the disk  13  has a central portion thereof integrally formed with an inclined surface portion inclined with respect to a plane in abutment with the diaphragm  12 , and a sliding portion extended from the inclined surface portion in a manner hanging downward such that it is brought into contact with an inner wall surface of the lower housing  11 .  
         [0071]     The lower housing  11  has a holder  18  welded to a lower open end thereof. Part of the outer peripheral portion of the holder  18  welded to the lower housing  11  is formed with a pressure equalizing hole  31  that makes open a space below the diaphragm  12  within which the disk  13  is disposed.  
         [0072]     The valve portion of the plug has a body  32  an upper end of which is screwed into the holder  18 , and the body  32  has a shaft  15  axially movably held therein. The shaft  15  has an upper end extending through the holder  18  into the space below the diaphragm  12 , for being brought into abutment with the inclined surface in the center of the disk  13 . The shaft  15  has a ball-shaped valve element  4  spot-welded to the lower end face thereof. Therefore, the valve element  4  can move to and away from a valve seat  3  integrally formed with the body  32  according to the upward and downward movements of the shaft  15 .  
         [0073]     Further, the shaft  15  has a groove circumferentially formed in an upper portion thereof, in which is fitted a stopper  33 . A spring  34  is disposed via a washer between the stopper  33  and a stepped portion formed in the body  32  in a manner surrounding the shaft  15 . This configuration causes the spring  34  to always urge the shaft  15  against the inclined surface of the disk  13 , with respect to the body  32 , to thereby cause lateral load to be applied to the shaft  15 , and at the same time urge the valve element  4  rigidly fixed on the shaft  15  in the valve-closing direction. Further, the spring  34  acts to cause a reaction force to the lateral load, which is applied to the shaft  15 , to urge the sliding portion of the disk  13  against the inner wall surface of the lower housing  11 . This imparts sliding resistance to the axial motion of the shaft  15 , thereby suppressing undesired vibrations of the shaft  15  in the axial direction.  
         [0074]     The body  32  screwed into the holder  18  can change the load of the spring  19  by having its amount of screwing into the holder  18  adjusted. This contributes to adjustment of the set point of the expansion valve  1 .  
         [0075]     The expansion valve  1  is assembled by mounting the plug configured as above in the valve casing  30 . The plug is mounted in the valve casing  30  by inserting the plug into the valve casing  30  from above, and screwing the power element  9  into the valve casing  30  by a screw formed on the outer peripheral surface of the hanging portion of the lower housing  11 . It should be noted that the operation of the expansion valve  1  configured as above is the same as the operations of the expansion valves  1  according to the first to sixth embodiments, and hence detailed description thereof is omitted.  
         [0076]      FIG. 21  is a front view showing the appearance of an expansion valve according to an eighth embodiment of the present invention.  FIG. 22  is a side view showing the appearance of the expansion valve according to the eighth embodiment.  FIG. 23  is a cross-sectional view of the expansion valve taken on line A-A of  FIG. 21 .  FIG. 24  is a cross-sectional view of the expansion valve taken on line B-B of  FIG. 22 .  FIG. 25  is a cross-sectional view of the expansion valve taken on line C-C of  FIG. 21 . In FIGS.  21  to  25 , component elements identical or equivalent to those shown in  FIG. 16  to  FIG. 20  are designated by the same reference numerals, and detailed description thereof is omitted.  
         [0077]     The expansion valve  1  according to the eighth embodiment is called a capsule type expansion valve. The expansion valve  1  includes a capsule that has a valve portion and a power element  9  and functions as an expansion valve, and a valve casing  30 , and is assembled by mounting the capsule into the valve casing  30 . As shown in  FIG. 21  and  FIG. 22 , the valve casing  30  has ports T 1  and T 4 , and ports T 2  and T 3  formed in two adjacent side surfaces thereof.  
         [0078]     As shown in  FIG. 25 , a low-pressure passage communicating between the ports T 3  and T 4  is formed by boring a cylindrical hole  20  from the upper surface of the valve casing  30  using a tool, such as an end mill, further making a hole  21  coaxial with the port T 4  from the front side surface of the valve casing  30  using a drill such that the hole  21  communicates with the hole  20 , and making a hole  22  coaxial with the port T 3  from the left side surface of the valve casing  30  using a drill such that the hole  22  communicates with the hole  20 . The low-pressure passage has the power element  9  of the capsule disposed therein, such that refrigerant flows through a space above the power element  9 . Since the intersecting portion of the low-pressure passage has no edge portion having an acute angle on an inner wall on an outer peripheral side thereof, refrigerant can smoothly flow through the intersecting portion, whereby it is possible to reduce generation of untoward noise and noise of the flow of refrigerant.  
         [0079]     As shown in  FIGS. 23 and 24 , the power element  9  of the capsule comprises an upper housing  10 , a lower housing  11 , a diaphragm  12 , a partition  35 , and a disk  13 . Activated carbon  36  for adjusting the temperature characteristics of the expansion valve  1  is placed in a chamber enclosed by the upper housing  10  and the partition  35 .  
         [0080]     The valve portion of the capsule has a body  32  an upper end of which is screwed into the lower housing  11 , and the body  32  has a shaft  15  axially movably held therein. The upper end of the shaft  15  is supported by the holder  18  disposed on the upper end of the body  32 . The holder  18  is urged by a spring  37  such that it is brought into abutment with the disk  13 . A ball-shaped valve element  4  urged by a compression coil spring  6  via a valve element receiver  5  is brought into abutment with the lower end face of the shaft  15 . Load of the compression coil spring  6  is adjusted by an adjustment screw  8  screwed into the valve casing  30 , whereby the set point of the expansion valve  1  is adjusted.  
         [0081]     The expansion valve  1  is assembled by mounting the capsule configured as above into the valve casing  30 . The capsule is mounted in the valve casing  30  by inserting the capsule into the valve casing  30  from above, and closing the upper opening of the valve casing  30  with a lid  38 , and fixing the lid  38  by a stop ring  39 , such as a C ring. It should be noted that the operation of the expansion valve  1  configured as above is the same as the operations of the expansion valves  1  according to the first to seventh embodiments, and hence detailed description thereof is omitted.  
         [0082]     The expansion valve according to the present invention can reduce untoward noise and noise of the flow of refrigerant, and therefore provides advantageous effects in that it does not cause occupant discomfort.  
         [0083]     The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.