Abstract:
To provide an expansion valve which permits both the assembling cost and the cost of parts to be effectively reduced by a large margin and thus is highly economical. A high-pressure refrigerant pipe, a valve casing and a low-pressure refrigerant pipe are previously formed integrally with an evaporator. At the time of assembling, an expansion valve unit having a minimum function to serve as an expansion valve is inserted into the valve casing and fixed thereto by a clip, and a distal end portion of a temperature sensing cylinder is fixed to an outlet pipe of the evaporator, thereby constructing an expansion valve. No special joints are required to connect the expansion valve unit to the high-pressure and low-pressure refrigerant pipes, and therefore, the cost of parts can be cut down. Also, since the valve casing into which the expansion valve unit is fitted is formed integrally with the high-pressure and low-pressure refrigerant pipes and the evaporator, no pipe connection is required, thus reducing the assembling cost.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    (1) Filed of the Invention  
           [0002]    The present invention relates to an expansion valve, and more particularly, to an expansion valve which is responsive to the temperature of refrigerant delivered to a compressor from an evaporator in a refrigeration cycle to control the quantity of the refrigerant introduced into the evaporator.  
           [0003]    (2) Description of the Related Art  
           [0004]    In an air conditioning system for automobiles, a refrigeration cycle is constructed in which high-temperature high-pressure gaseous refrigerant compressed by a compressor is condensed in a condenser and the resulting high-pressure liquid refrigerant is adiabatically expanded in an expansion valve to obtain low-temperature low-pressure liquid refrigerant, which is then evaporated in an evaporator and returned to the compressor. The evaporator, to which the low-temperature refrigerant is supplied, exchanges heat with the air in the vehicle compartment, whereby the compartment is air-cooled.  
           [0005]    The expansion valve includes a temperature-sensitive chamber of which the internal pressure rises or drops in response to temperature changes of the refrigerant in a low-pressure refrigerant passage connected to the outlet of the evaporator, and a valve mechanism actuated in response to pressure rise or drop of the temperature-sensitive chamber to control the flow rate of the refrigerant supplied to the inlet of the evaporator. The valve mechanism is housed in a valve casing, whose refrigerant inlet and outlet are respectively connected by fastening members, such as nuts, to a high-pressure refrigerant pipe and a low-pressure refrigerant pipe leading to the evaporator. A temperature sensing cylinder is connected to the temperature-sensitive chamber and has a distal end portion thereof closely fixed to a refrigerant pipe connected to the outlet of the evaporator to sense the temperature of the refrigerant at the outlet of the evaporator.  
           [0006]    Originally expansion valves are designed to detect not only the temperature but the pressure of the refrigerant at the outlet of the evaporator so that the valve mechanism may be controlled also in response to variations in the pressure. There has, however, been a demand for expansion valves reduced in cost. To meet the demand, an expansion valve has been developed which senses only the temperature of the refrigerant at the outlet of the evaporator, as mentioned above, and in which a joint between the refrigerant pipe connected to the outlet of the evaporator and the refrigerant pipe leading to the compressor is omitted to cut down the cost. This arrangement is based on the fact that, when the refrigerant from the expansion valve passes through the evaporator, its pressure loss within the evaporator is almost constant and thus a pressure obtained by subtracting the pressure loss from the pressure at the outlet of the expansion valve can be regarded as the pressure of the refrigerant at the outlet of the evaporator.  
           [0007]    Even in this temperature sensing type expansion valve which requires no connection of refrigerant pipes on the outlet side of the evaporator, it is necessary that the high-pressure refrigerant pipe and the low-pressure refrigerant pipe leading to the evaporator should be connected, respectively, to the refrigerant inlet and outlet of the valve casing by fastening members when the expansion valve is assembled. Accordingly, there has been a demand for expansion valves which are further reduced in cost, inclusive of the assembling cost.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention was created in view of the above circumstances, and an object thereof is to provide an expansion valve which permits both the assembling cost and the cost of parts to be effectively reduced by a large margin and thus is highly economical.  
           [0009]    To accomplish the above object, according to the present invention, there is provided an expansion valve for sensing temperature change of a refrigerant at an outlet of an evaporator to control a flow rate of the refrigerant supplied to an inlet of the evaporator. The expansion valve comprises an expansion valve unit including a temperature-sensitive chamber whose internal pressure rises or drops in response to temperature change of the refrigerant in a low-pressure refrigerant pipe connected to the outlet of the evaporator, and a valve mechanism actuated in response to pressure rise or drop of the temperature-sensitive chamber to control the flow rate of the refrigerant supplied to the inlet of the evaporator, a valve casing having an opening into which said expansion valve unit is fitted, said valve casing being formed integrally with a high-pressure refrigerant pipe for introducing the high-pressure refrigerant, a low-pressure refrigerant pipe for letting out the refrigerant whose flow rate has been controlled, and the evaporator and fixing means for fixing said expansion valve unit fitted into said valve casing. 
       
    
    
       [0010]    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  
       [0011]    [0011]FIG. 1 is a diagram showing a refrigeration cycle using an expansion valve according to a first embodiment of the present invention.  
         [0012]    [0012]FIG. 2 is a longitudinal sectional view showing the construction of an expansion valve unit.  
         [0013]    [0013]FIG. 3 is a longitudinal sectional view of a valve casing into which the expansion valve unit is fitted.  
         [0014]    [0014]FIG. 4(A), (B) show a clip, wherein (A) is a plan view of the clip and (B) is a sectional view taken along line a-a in (A).  
         [0015]    [0015]FIG. 5 is a side view of the expansion valve fitted with the clip.  
         [0016]    [0016]FIG. 6 is a longitudinal sectional view of the expansion valve fitted with the clip.  
         [0017]    [0017]FIG. 7 is a side view showing a state before the expansion valve is assembled.  
         [0018]    [0018]FIG. 8 is a side view showing a state after the expansion valve is assembled.  
         [0019]    [0019]FIG. 9 is a longitudinal sectional view of an expansion valve according to a second embodiment of the present invention.  
         [0020]    [0020]FIG. 10 is a longitudinal sectional view of an expansion valve according to a third embodiment of the present invention.  
         [0021]    [0021]FIG. 11 is a longitudinal sectional view of an expansion valve according to a fourth embodiment of the present invention.  
         [0022]    [0022]FIG. 12 is a side view showing an external appearance of the expansion valve according to the fourth embodiment of the present invention.  
         [0023]    [0023]FIG. 13 is a longitudinal sectional view of an expansion valve according to a fifth embodiment of the present invention.  
         [0024]    [0024]FIG. 14 is a longitudinal sectional view of an expansion valve according to a sixth embodiment of the present invention.  
         [0025]    [0025]FIG. 15 is a longitudinal sectional view of an expansion valve according to a seventh embodiment of the present invention.  
         [0026]    [0026]FIG. 16 is an exploded view showing a state before the expansion valve is assembled.  
         [0027]    [0027]FIG. 17 is a side view of an evaporator connected with the assembled expansion valve.  
         [0028]    [0028]FIG. 18 is a front view of the evaporator connected with the assembled expansion valve.  
         [0029]    [0029]FIG. 19 is a longitudinal sectional view of an expansion valve according to an eighth embodiment of the present invention.  
         [0030]    [0030]FIG. 20 is an exploded view showing a state before the expansion valve is assembled.  
         [0031]    [0031]FIG. 21 is a side view of the evaporator connected with the assembled expansion valve.  
         [0032]    [0032]FIG. 22 is a front view of the evaporator connected with the assembled expansion valve.  
         [0033]    [0033]FIG. 23 is an exploded view showing a state before an expansion valve according to a ninth embodiment of the present invention is assembled.  
         [0034]    [0034]FIG. 24 is a side view of the evaporator connected with the assembled expansion valve.  
         [0035]    [0035]FIG. 25 is a front view of the evaporator connected with the assembled expansion valve.  
         [0036]    [0036]FIG. 26 is a longitudinal sectional view of an expansion valve according to a tenth embodiment of the present invention.  
         [0037]    [0037]FIG. 27 is a sectional view taken along line b-b in FIG. 26.  
         [0038]    [0038]FIG. 28 is a bottom view showing an external appearance of a heat conducting member.  
         [0039]    [0039]FIG. 29 is a side view of the evaporator, illustrating a manner of assembling the expansion valve according to the tenth embodiment of the present invention.  
         [0040]    [0040]FIG. 30 is a front view of the evaporator, also illustrating the manner of assembling the expansion valve according to the tenth embodiment of the present invention.  
         [0041]    [0041]FIG. 31 is a side view of the evaporator connected with the assembled expansion valve.  
         [0042]    [0042]FIG. 32 is a front view of the evaporator connected with the assembled expansion valve. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]    Embodiments of the present invention will be hereinafter described in detail with reference to the drawings.  
         [0044]    [0044]FIG. 1 is a diagram illustrating a refrigeration cycle using an expansion valve according to a first embodiment of the present invention.  
         [0045]    The expansion valve  1  of the present invention comprises an expansion valve unit  2  having a minimum function to serve as an expansion valve, a valve casing  3  for receiving the expansion valve unit  2 , a clip  4  for fixing the valve casing  3  and the expansion valve unit  2  to each other, and high-pressure and low-pressure refrigerant pipes  5  and  6  welded to the valve casing  3 . The low-pressure refrigerant pipe  6  of the expansion valve  1  is connected to the high-pressure refrigerant pipe  5  through an evaporator  7 , a compressor  8 , a condenser  9  and a receiver  10 , and a temperature sensing cylinder  11  of the expansion valve unit  2  is thermally coupled to an outlet pipe  12  of the evaporator  7 , whereby a refrigeration cycle is constructed.  
         [0046]    The individual components constituting the expansion valve  1  will be now described.  
         [0047]    [0047]FIG. 2 is a longitudinal sectional view showing the construction of the expansion valve unit.  
         [0048]    The expansion valve unit  2  has an integral structure comprising a temperature-sensitive chamber  13  whose internal pressure rises or drops in response to temperature change of a refrigerant flowing through the outlet pipe  12  of the evaporator  7 , the temperature change being sensed by the temperature sensing cylinder  11 , and a valve mechanism actuated in response to the pressure rise or drop of the temperature-sensitive chamber  13  to open and close a high-pressure refrigerant passage.  
         [0049]    The temperature-sensitive chamber  13  has an internal space defined by a housing  14  made of a thick metal plate and a diaphragm  15  made of a thin flexible metal plate, and outer peripheral edges of these metal plates are caulked with a temperature-sensitive chamber mount  16  and then welded together to make the internal space airtight. The interior of the temperature-sensitive chamber is filled with a gas of saturated vapor state having identical or similar properties to the refrigerant which is a working fluid of the refrigeration cycle. The temperature sensing cylinder  11 , which comprises a capillary tube, is brazed at top of the housing  14 .  
         [0050]    The temperature-sensitive chamber mount  16  has a lower end portion thereof screwed onto an upper portion of a body  17  of the valve mechanism. The body  17  has a high-pressure refrigerant passage  18  formed almost in the middle as viewed in a longitudinal direction thereof and extending from one side to the center thereof, and a low-pressure refrigerant passage  19  axially extending through a lower end portion thereof. A hole is formed in the body  17  along the axis thereof to connect the high-pressure refrigerant passage  18  to the low-pressure refrigerant passage  19 , and an end of the hole on the same side as the low-pressure refrigerant passage  19  serves as a valve seat  20 . A spherical valve element  21  is arranged so as to face the valve seat  20  and is pressed against the valve seat  20  by a compression coil spring  22  through a valve element support  23 . The compression coil spring  22  has a base received in an adjusting screw  24 . The adjusting screw  24  is screwed in along the inner wall of the low-pressure refrigerant passage  19 , and by rotating the adjusting screw, it is possible to adjust the force of pressing the valve element  21 .  
         [0051]    A shaft  25  is axially movably inserted into the body  17  along the axis thereof, and has one end abutting against or welded to the valve element  21  and the other end abutting against the lower surface of the diaphragm  15  through a disk  26 . The shaft  25  is also held by a holder  27  in alignment with the axis of the body  17 .  
         [0052]    In the body  17  is also formed a communication passage  28  for equalizing the pressure in a space beneath the diaphragm  15  of the temperature-sensitive chamber  13  with that in the low-pressure refrigerant passage  19 . The space beneath the diaphragm  15  is sealed with an O ring  29  fitted on the shaft  25  to be isolated from the high-pressure refrigerant passage  18 . O rings  30  and  31  are fitted around the outer periphery of the body  17  at locations above and below the high-pressure refrigerant passage  18 , respectively, to seal the high-pressure refrigerant passage  18 , the temperature-sensitive chamber  13  and the low-pressure refrigerant passage  19  off from each other when the expansion valve unit  2  is fitted into the valve casing  3 . An O ring  32  is fitted around the outer periphery of the lower end portion of the temperature-sensitive chamber mount  16  to prevent the space beneath the diaphragm  15  from communicating with the atmosphere through a gap between threads by means of which the temperature-sensitive chamber mount  16  is attached to the body  17 . A backup ring  33  is also fitted around the outer periphery of the lower end portion of the temperature-sensitive chamber mount  16  to restrict displacement of the O ring  32 .  
         [0053]    In the expansion valve unit  2  constructed as described above, the refrigerant supplied to the high-pressure refrigerant pipe  5  from the receiver  10  enters the high-pressure refrigerant passage  18 , is adiabatically expanded as it passes through the gap between the valve seat  20  and the valve element  21 , and then delivered from the low-pressure refrigerant passage  19  to the evaporator  7  through the low-pressure refrigerant pipe  6 . The refrigerant output from the evaporator  7  is delivered to the compressor  8 , and the temperature of the refrigerant at the outlet of the evaporator is sensed by the temperature sensing cylinder  11 .  
         [0054]    In response to the temperature thus sensed, the pressure of the gas filled in the temperature-sensitive chamber  13  varies, that is, the pressure in the chamber  13  rises or drops. On the other hand, the refrigerant in the low-pressure refrigerant passage  19  enters the space beneath the temperature-sensitive chamber  13  through the communication passage  28 , so that the underside or lower side of the diaphragm  15  is acted upon by the refrigerant pressure in the low-pressure refrigerant passage  19 . Thus, the diaphragm  15 , the shaft  25  and the valve element  21  become stationary at a position where the refrigerant pressure, the pressure in the temperature-sensitive chamber  13  and the urging force of the compression coil spring  22  are equilibrated, thereby determining the quantity of the refrigerant delivered from the high-pressure refrigerant pipe  5  to the evaporator  7 . As the temperature of the refrigerant at the outlet of the evaporator  7  increases, the pressure in the temperature-sensitive chamber  13  rises, so that the diaphragm  15  is displaced downward. This displacement of the diaphragm pushes down the valve element  21  through the shaft  25 , increasing the valve opening and thus the flow rate of the refrigerant, whereby the temperature of the refrigerant at the outlet of the evaporator  7  is controlled in a decreasing direction. As the temperature of the refrigerant at the outlet of the evaporator  7  decreases, the individual elements operate in a manner opposite to the above, so that the temperature of the refrigerant at the outlet of the evaporator  7  is controlled in an increasing direction.  
         [0055]    [0055]FIG. 3 is a longitudinal sectional view of the valve casing to which the expansion valve unit is attached.  
         [0056]    The valve casing  3 , into which the expansion valve unit  2  is fitted, is formed into a shape matching the external form of the expansion valve unit  2 , and the expansion valve unit  2  is inserted into the valve casing from an opening shown in the upper part of the figure. A flange  34  is formed around the opening to allow the inserted expansion valve unit  2  to be fixed to the valve casing  3  by means of the clip  4 .  
         [0057]    The valve casing  3  is made of aluminum. When the evaporator  7 , which is of a stacked type, is subjected to aluminum welding in a high-temperature room, the valve casing also is subjected to aluminum welding together with the high-pressure and low-pressure refrigerant pipes  5  and  6  in the high-temperature room, to form the valve casing integrally with the high-pressure and low-pressure refrigerant pipes  5  and  6 .  
         [0058]    [0058]FIG. 4 illustrates the clip, wherein (A) is a plan view of the clip and (B) is a sectional view taken along line a-a in (A), FIG. 5 is a side view of the expansion valve fitted with the clip, and FIG. 6 is a longitudinal sectional view of the expansion valve fitted with the clip.  
         [0059]    The clip  4  is made of a hard material having elasticity, for example, stainless steel, and is a generally U-shaped member, and an elongate opening  35  is cut in a central portion of each of arms forming the sides of the clip. After the expansion valve unit  2  is fitted into the valve casing  3 , the distal ends of the arms are brought into contact with a junction where the temperature-sensitive chamber mount  16  of the expansion valve unit  2  is butted against the flange  34  of the valve casing  3  and the clip  4  is pushed sideways, whereby the peripheral edges of the temperature-sensitive chamber mount  16  and the flange  34  simultaneously fit into the elongate openings  35 . Consequently, the expansion valve unit  2  and the valve casing  3  are fixed together, as shown in FIGS. 5 and 6, so that the expansion valve is assembled.  
         [0060]    [0060]FIG. 7 is a side view showing a state before the expansion valve is assembled, and FIG. 8 is a side view showing a state after the expansion valve is assembled.  
         [0061]    The expansion valve is assembled in the manner described below. Since the evaporator  7 , the low-pressure refrigerant pipe  6 , the valve casing  3  and the high-pressure refrigerant pipe  5  are formed integrally with each other, the integral structure is first placed in an automobile, the expansion valve unit  2  is inserted into the valve casing  3 , and the clip  4  is fitted to fix the expansion valve unit  2  to the valve casing  3 . Subsequently, the distal end portion of the temperature sensing cylinder  11  of the expansion valve unit  2  is brought into close contact with the outlet pipe  12  of the evaporator  7  and fixed thereto using a band  36 .  
         [0062]    When the expansion valve is assembled, therefore, fastening members such as nuts need not be used to connect the low-pressure and high-pressure refrigerant pipes  6  and  5 , making it possible to reduce the assembling cost. Further, since the expansion valve unit  2  having a minimum function to serve as an expansion valve has only to be prepared, the cost of parts can be cut down, not to mention the fact that no fastening members are required.  
         [0063]    [0063]FIG. 9 is a longitudinal sectional view of an expansion valve according to a second embodiment of the present invention. In FIG. 9, identical reference numerals are used to denote elements identical with those appearing in FIGS. 2 and 6, and detailed description of such elements is omitted.  
         [0064]    In the expansion valve of the second embodiment, the temperature-sensitive chamber mount  16  of the temperature-sensitive chamber  13  is screwed onto the body  17  with a sealant applied to threads  37  by means of which the elements  16  and  17  are fixed together. This prevents the space beneath the diaphragm  15  from communicating with the atmosphere through a gap between the threads  37 . It is therefore unnecessary to use the O ring  32  and the backup ring  33  which are required in the expansion valve of the first embodiment.  
         [0065]    The expansion valve is assembled by inserting the expansion valve unit  2  into the valve casing  3  and then fitting the clip  4 , as in the expansion valve of the first embodiment.  
         [0066]    [0066]FIG. 10 is a longitudinal sectional view of an expansion valve according to a third embodiment of the present invention. In FIG. 10, identical reference numerals are used to denote elements identical with those appearing in FIGS. 2 and 6, and detailed description of such elements is omitted.  
         [0067]    In the expansion valve of the third embodiment, the low-pressure refrigerant pipe  6  has its end portion enlarged in diameter to serve as a valve casing  3   a , and the high-pressure refrigerant pipe  5  is joined integrally to the valve casing by aluminum welding.  
         [0068]    [0068]FIG. 11 is a longitudinal sectional view of an expansion valve according to a fourth embodiment of the present invention, and FIG. 12 is a side view showing an external appearance of the expansion valve of the fourth embodiment. In FIGS. 11 and 12, identical reference numerals are used to denote elements identical with those appearing in FIGS. 2 and 6, and detailed description of such elements is omitted.  
         [0069]    In the expansion valve of the fourth embodiment, the valve casing  3  and the expansion valve unit  2  are fixed together by caulking upper and lower ends of a coupling  38 . Specifically, after the expansion valve unit  2  is inserted into the valve casing  3 , the coupling  38  is fitted and the upper and lower ends thereof are caulked.  
         [0070]    Alternatively, the upper end of the coupling  38  may be narrowed in advance, and after the coupling  38  is fitted on the expansion valve unit  2  inserted into the valve casing  3 , the lower end of the coupling  38  may be caulked to fix the elements  2  and  3  together.  
         [0071]    [0071]FIG. 13 is a longitudinal sectional view of an expansion valve according to a fifth embodiment of the present invention. In FIG. 13, identical reference numerals are used to denote elements identical with those appearing in FIGS. 2 and 6, and detailed description of such elements is omitted.  
         [0072]    In the expansion valve of the fifth embodiment, a valve casing  3   b  has an extended end portion at the opening thereof, and after the expansion valve unit  2  is inserted into the valve casing  3   b , the open end of the valve casing  3   b  is caulked to fix the expansion valve unit  2  to the valve casing  3   b.    
         [0073]    Also, the expansion valve unit  2  has a groove  39  formed on the outer peripheral surface of the body  17 . Thus, when the expansion valve unit  2  is inserted into the valve casing  3   b , a space is defined between the expansion valve unit and the valve casing  3   b , and this space ensures smooth flow of the refrigerant.  
         [0074]    [0074]FIG. 14 is a longitudinal sectional view of an expansion valve according to a sixth embodiment of the present invention. In FIG. 14, identical reference numerals are used to denote elements identical with those appearing in FIGS. 2 and 6, and detailed description of such elements is omitted.  
         [0075]    In the expansion valve of the sixth embodiment, the groove  39  is formed on the outer peripheral surface of the body  17  of the expansion valve unit  2 , and after the expansion valve unit  2  is inserted into the valve casing  3 , a portion of the valve casing  3  corresponding in position to the groove  39  is caulked to be pressed into the groove  39  so that the expansion valve unit  2  may not be detached from the valve casing  3 . The valve casing may be caulked over a circumferential region except for the joint where the high-pressure refrigerant pipe  5  is joined, or at one or more spots.  
         [0076]    [0076]FIG. 15 is a longitudinal sectional view of an expansion valve according to a seventh embodiment of the present invention. In FIG. 15, identical reference numerals are used to denote elements identical with those appearing in FIG. 6, and detailed description of such elements is omitted.  
         [0077]    In the expansion valve of the seventh embodiment, the temperature of the refrigerant in the outlet pipe  12  of the evaporator  7  is detected not by the temperature sensing cylinder  11 , but through the agency of heat conduction by a heat conducting member  41 .  
         [0078]    The heat conducting member  41  is made of an alloy having elasticity, such as a copper alloy or a beryllium alloy, and has an engaging portion  42  at one end thereof for engagement with the clip  4  and a pipe receiving portion  43  at the other end thereof, the pipe receiving portion being arcuately curved in conformity with the external form of the outlet pipe  12  of the evaporator  7 . The heat conducting member  41  is configured such that when the clip  4  is attached, the area of contact between the heat conducting member and the temperature-sensitive chamber  13  of the expansion valve unit  2  is large.  
         [0079]    Specifically, the heat conducting member  41  is formed like a plate, while the housing  14  constituting the temperature-sensitive chamber  13  of the expansion valve unit  2  has a flat top face. The housing  14  has a hole formed in the center of the top face thereof to permit gas to be introduced therein, and the hole is sealed with a ball in a gaseous atmosphere by resistance welding.  
         [0080]    [0080]FIG. 16 is an exploded view showing a state before the expansion valve is assembled, FIG. 17 is a side view of the evaporator connected with the assembled expansion valve, and FIG. 18 is a front view of the evaporator connected with the assembled expansion valve.  
         [0081]    The manner of assembling the expansion valve of the seventh embodiment will be now described. The evaporator  7  is formed integrally with the valve casing  3 , the high-pressure and low-pressure refrigerant pipes  5  and  6 , and the outlet pipe  12 . The valve casing  3  is located remoter from the front face of the evaporator  7  than the outlet pipe  12  extending parallel to the front face.  
         [0082]    To assemble the expansion valve, first, the expansion valve unit  2  is inserted into the valve casing  3 , as indicated by arrow  44 , then the heat conducting member  41  is engaged with the clip  4 , as indicated by arrow  45 , and finally the clip  4  is pushed in, as indicated by arrow  46 , to fasten together the temperature-sensitive chamber mount  16  of the inserted expansion valve unit  2  and the flange  34  of the valve casing  3  in a manner such that the distal end portion of the heat conducting member  41  is in contact with the underside of the outlet pipe  12 . Thus, when the temperature-sensitive chamber mount  16  of the expansion valve unit  2  and the flange  34  of the valve casing  3  are fixed together by the clip  4 , the pipe receiving portion  43  of the heat conducting member  41  receives the outlet pipe  12 , as best shown in FIG. 17. Since, in this case, the pipe receiving portion  43  of the heat conducting member  41  is pushed down, as viewed in the figure, the heat conducting member  41  is pressed against the top face of the expansion valve unit  2 , whereby the temperature of the refrigerant flowing through the outlet pipe  12  is transmitted effectively to the temperature-sensitive chamber  13  via the pipe receiving portion  43 .  
         [0083]    [0083]FIG. 19 is a longitudinal sectional view of an expansion valve according to an eighth embodiment of the present invention. In FIG. 19, identical reference numerals are used to denote elements identical with those appearing in FIG. 6, and detailed description of such elements is omitted.  
         [0084]    In the expansion valve of the eighth embodiment, the temperature of the refrigerant in the outlet pipe  12  of the evaporator  7  is detected not by the temperature sensing cylinder  11  or the heat conducting member  41 , but by means of heat conducted directly from the outlet pipe  12 .  
         [0085]    The temperature-sensitive chamber  13  of the expansion valve unit  2  has a pipe receiving portion  47  formed in the top face thereof as a recess matching the external form of the outlet pipe  12  of the evaporator  7 . The outlet pipe  12  is located directly on the pipe receiving portion  47  such that the outlet pipe  12  and the temperature-sensitive chamber  13  directly contact with each other, whereby the temperature-sensitive chamber  13  can directly detect the temperature of the refrigerant flowing through the outlet pipe  12 .  
         [0086]    [0086]FIG. 20 is an exploded view showing a state before the expansion valve is assembled, FIG. 21 is a side view of the evaporator connected with the assembled expansion valve, and FIG. 22 is a front view of the evaporator connected with the assembled expansion valve.  
         [0087]    The manner of assembling the expansion valve of the eighth embodiment will be now described. The evaporator  7  is formed integrally with the valve casing  3 , the high-pressure and low-pressure refrigerant pipes  5  and  6 , and the outlet pipe  12 . Portions of the low-pressure refrigerant pipe  6  and the outlet pipe  12  extending parallel to the front face of the evaporator  7  are located at an equal distance from the front face, while a portion of the low-pressure refrigerant pipe  6  joined integrally with the valve casing  3  in alignment therewith is tilted outward in a direction away from the front face of the evaporator  7 .  
         [0088]    To assemble the expansion valve, first, the expansion valve unit  2  is inserted into the valve casing  3 , as indicated by arrow  48 . In this case, the expansion valve unit  2  is inserted into the valve casing  3  in a manner such that the high-pressure refrigerant passage  18  in the body  17  is aligned with the high-pressure refrigerant pipe  5  and that the pipe receiving portion  47  of the temperature-sensitive chamber  13  is orientated in the same direction as the outlet pipe  12 . Subsequently, the clip  4  is attached, as indicated by arrow  49 , to fasten together the temperature-sensitive chamber mount  16  of the inserted expansion valve unit  2  and the flange  34  of the valve casing  3 , and finally the tilted portion of the low-pressure refrigerant pipe  6  is raised to an upright position, as indicated by arrow  50 , so as to be parallel with the front face of the evaporator  7 . At this time, the outlet pipe  12  passes over the inclined surface of the housing  14  of the temperature-sensitive chamber  13  and fits in the recessed pipe receiving portion  47 .  
         [0089]    Consequently, the temperature-sensitive chamber  13  receives a load on contact with the outlet pipe  12  and thus is held in urging contact therewith, so that the temperature of the refrigerant flowing through the outlet pipe  12  is transmitted directly to the temperature-sensitive chamber  13 .  
         [0090]    [0090]FIG. 23 is an exploded view showing a state before an expansion valve according to a ninth embodiment of the present invention is assembled, FIG. 24 is a side view of the evaporator connected with the assembled expansion valve, and FIG. 25 is a front view of the evaporator connected with the assembled expansion valve. In these figures, identical reference numerals are used to denote elements identical with those appearing in FIGS.  20  to  22 , and detailed description of such elements is omitted.  
         [0091]    The manner of assembling the expansion valve of the ninth embodiment will be now described. Like the expansion valve of the eighth embodiment, the evaporator  7  is formed integrally with the valve casing  3 , the high-pressure and low-pressure refrigerant pipes  5  and  6 , and the outlet pipe  12 . Portions of the low-pressure refrigerant pipe  6  and the outlet pipe  12  extending parallel to the front face of the evaporator  7  are located at an equal distance from the front face, while a portion of the low-pressure refrigerant pipe  6  joined integrally with the valve casing  3  in alignment therewith is tilted outward in a direction away from the front face of the evaporator  7 .  
         [0092]    To assemble the expansion valve, first, the expansion valve unit  2  is inserted into the valve casing  3 , as indicated by arrow  51 . In this case, the expansion valve unit  2  is inserted into the valve casing  3  in a manner such that the high-pressure refrigerant passage  18  in the body  17  is aligned with the high-pressure refrigerant pipe  5  and that the pipe receiving portion  47  of the temperature-sensitive chamber  13  is orientated in the same direction as the outlet pipe  12 . Subsequently, the tilted portion of the low-pressure refrigerant pipe  6  is raised to an upright position, as indicated by arrow  52 , so as to be parallel with the front face of the evaporator  7 . At this time, the outlet pipe  12  passes over the inclined surface of the housing  14  of the temperature-sensitive chamber  13  and fits in the recessed pipe receiving portion  47 .  
         [0093]    Consequently, the expansion valve unit  2  receives a load on contact with the outlet pipe  12  and thus is prevented from being detached from the valve casing  3 , and also since the temperature-sensitive chamber  13  is held in urging contact with the outlet pipe  12 , the temperature of the refrigerant flowing through the outlet pipe  12  is transmitted directly to the temperature-sensitive chamber  13 .  
         [0094]    [0094]FIG. 26 is a longitudinal sectional view of an expansion valve according to a tenth embodiment of the present invention, FIG. 27 is a sectional view taken along line b-b in FIG. 26, and FIG. 28 is a bottom view showing an external appearance of a heat conducting member. In these figures, identical reference numerals are used to denote elements identical with those appearing in FIGS. 1 and 10, and detailed description of such elements is omitted.  
         [0095]    In the expansion valve of the tenth embodiment, a heat conducting member  53  is placed on the housing  14  of the temperature-sensitive chamber  13  and has one end disposed in contact with the outlet pipe  12  of the evaporator  7 .  
         [0096]    The heat conducting member  53  is made of a material having high heat conductivity, such as copper or copper alloy. As shown in FIG. 28, the heat conducting member comprises a flat temperature-sensitive chamber contact portion  54  disposed in contact with the entire flat top face of the housing  14  of the temperature-sensitive chamber  13 , to ensure sufficient contact with the housing  14 , and a semicylindrical pipe contact portion  55  raised at one end of the temperature-sensitive chamber contact portion  54  and having an end face with a curvature equal to that of the outer periphery of the outlet pipe  12  of the evaporator  7 .  
         [0097]    Also, the heat conducting member  53  has an upper surface covered with a heat insulating cover  56 . The heat insulating cover  56  is made of a resin having low heat conductivity and is preferably formed integrally with the heat conducting member  53  by insert molding. The heat insulating cover  56  prevents heat from being radiated from the heat conducting member  53  and also prevents the heat conducting member from being influenced by the ambient temperature. Also, the heat insulating cover  56  has engaging portions  57  disposed at two side edges of the semicylindrical pipe contact portion  55  and having inner side faces with a curvature equal to that of the pipe contact portion  55 . The engaging portions  57  serve to keep the pipe contact portion  55  of the heat conducting member  53  in contact with the outlet pipe  12 , and also to fix the pipe contact portion  55  to the outlet pipe  12 .  
         [0098]    Further, the heat conducting member  53  placed on the housing  14  of the temperature-sensitive chamber  13  is pressed by a presser lever  58  so that the temperature-sensitive chamber contact portion  54  may be held in urging contact with the top face of the housing  14  of the temperature-sensitive chamber  13 . The presser lever  58  is made of a hard material having elasticity, and has one end portion engaged with the clip  4  and the other end portion disposed to press the heat conducting member  53  from above the heat insulating cover  56  against the housing  14  by means of its elasticity.  
         [0099]    [0099]FIG. 29 is a side view of the evaporator, illustrating the manner of assembling the expansion valve according to the tenth embodiment of the present invention, FIG. 30 is a front view of the evaporator, also illustrating the manner of assembling the expansion valve of the tenth embodiment, FIG. 31 is a side view of the evaporator connected with the assembled expansion valve, and FIG. 32 is a front view of the evaporator connected with the assembled expansion valve.  
         [0100]    The manner of assembling the expansion valve of the tenth embodiment will be now described. Like the expansion valve of the ninth embodiment, the evaporator  7  is formed integrally with the valve casing  3   a , the high-pressure and low-pressure refrigerant pipes  5  and  6 , and the outlet pipe  12 .  
         [0101]    To assemble the expansion valve, first, the expansion valve unit  2  is inserted into the valve casing  3   a , as indicated by arrow  59  in FIG. 30. Subsequently, the heat conducting member  53  is attached to the outlet pipe  12  of the evaporator  7 . Specifically, with the engaging portions  57  of the heat insulating cover  56  held in contact with the outlet pipe  12  of the evaporator  7 , the heat insulating cover is pushed toward the outlet pipe  12 , as indicated by arrow  60  in FIG. 29. As a result, the engaging portions  57  are elastically deformed outward as they are pushed beyond the thickest portion of the outlet pipe  12 , whereupon the pipe contact portion  55  of the heat conducting member  53  comes into contact with the peripheral surface of the outlet pipe  12  and the engaging portions  57  hold the outlet pipe  12  therebetween, so that the heat conducting member  53  is attached to the outlet pipe  12 .  
         [0102]    Subsequently, the heat conducting member  53  and the heat insulating cover  56  are turned, as indicated by arrow  61 , such that the temperature-sensitive chamber contact portion  54  of the heat conducting member  53  faces the housing  14  of the temperature-sensitive chamber  13 . Then, as indicated by arrow  62 , the heat conducting member  53  and the heat insulating cover  56  are moved along the outlet pipe  12  to be fitted on the housing  14  of the temperature-sensitive chamber  13 .  
         [0103]    Finally, with the presser lever  58  engaged with the clip  4 , as indicated by arrow  63 , the clip  4  is pushed in, as indicated by arrow  64 , to fasten together the temperature-sensitive chamber mount  16  of the inserted expansion valve unit  2  and the flange  34  of the valve casing  3   a . Thus, the temperature-sensitive chamber mount  16  of the expansion valve unit  2  and the flange  34  of the valve casing  3   a  are fixed together by the clip  4 , as best shown in FIGS. 31 and 32, so that the expansion valve unit  2  is prevented from being detached from the valve casing  3   a . Also, since the presser lever  58  presses the heat conducting member  53  and the heat insulating cover  56  against the housing  14  of the temperature-sensitive chamber  13 , the temperature of the refrigerant flowing through the outlet pipe  12  is effectively transmitted to the temperature-sensitive chamber  13  via the heat conducting member  53 . In this case, the heat insulating cover  56  prevents heat from being radiated from the heat conducting member  53  and also prevents the heat conducting member from being influenced by the ambient temperature.  
         [0104]    As described above, the expansion valve of the present invention comprises an expansion valve unit having a minimum function to serve as an expansion valve, a valve casing formed integrally with the high-pressure and low-pressure refrigerant pipes and the evaporator, and capable of receiving the expansion valve unit therein, and fixing means for fixing the expansion valve unit fitted into the valve casing, wherein the expansion valve is assembled by inserting the expansion valve unit into the valve casing and then fixing the two together by the fixing means. This makes it unnecessary to use fastening members such as nuts for connecting the low-pressure and high-pressure refrigerant pipes to the valve casing. Also, since the expansion valve unit having a minimum function to serve as an expansion valve has only to be prepared, the cost of parts can be cut down. Further, the expansion valve can be assembled simply by fitting the expansion valve unit into the valve casing and fixing the two by the fixing members, so that the assembling cost can also be reduced.  
         [0105]    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.