Abstract:
The four-way selector valve relating to the invention basically comprises a motor which has a stator and a rotor, a case, and a main body including a main valve and a valve seat, both of which are arranged in a valve chest within the case. The valve seat has a suction pressure passage and a discharge pressure passage, which lead to a suction port of a compressor and a discharge port thereof, respectively, and two passage holes which lead to indoor and outdoor heat exchangers, respectively. The main valve has a connecting part which selectively leads to one of the suction pressure passage and the two passage holes, and a pressure equalization orifice which links the connecting part and the valve chest. A rotor sleeve, which comprises the rotor, is equipped with an auxiliary valve which opens or closes the pressure equalization orifice in order to transfer pressure, and an operating pin which moves the position of the main valve. The rotor of the motor rotates the auxiliary valve on the main valve and slides the main valve on the valve seat via the operating pin.

Description:
FIELD OF THE INVENTION 
     This invention relates to a four-way selector valve and more particularly to a four-way selector valve which has a main valve equipped with a relief valve for discharge pressure as an auxiliary valve. 
     DESCRIPTION OF THE RELATED ART 
     Conventionally, an air conditioner used for air-conditioning a room or for a similar purpose allows for cooling or heating depending on seasons by switching the flowing direction of refrigerant with a selector valve. 
     FIG. 8 illustrates an example of a cooling/heating cycle of an air conditioner using the selector valve. For this cycle, a compressor C, a selector valve SV, heat exchangers E 1  and E 2 , and an electronic linear control valve T are connected. As indicated with solid-line arrows, the refrigerant as used for the cooling operation flows through the compressor C, the selector valve SV, an outdoor heat exchanger E 1 , the electronic linear control valve T, and an indoor heat exchanger E 2  in this order. The refrigerant then completes the circulation by returning through the selector valve SV to the compressor C. In contrast, as indicated with dot-dash lines, the refrigerant as used for the heating flows through the compressor C, the selector valve SV, the indoor heat exchanger E 2 , the electronic linear control valve T, and the outdoor heat exchanger E 1  in this order. The refrigerant then completes the circulation by returning through the selector valve SV to the compressor C. 
     As an example of the selector valve, an art for a four-way selector valve was proposed. (See, e.g., Japanese Utility Model Registration No. 2523031). The proposed art comprises an electromagnet provided on a valve main body, a valve seat mounted at the bottom of the main body, and a rotatable valve provided in the valve main body. The valve seat has, at given angles and spacing, a discharge pressure passage which introduces the discharge pressure of the compressor, a suction pressure passage which introduces the suction pressure, a passage hole for an indoor heat exchanger and a passage hole for an outdoor heat exchanger, which lead to the respective heat exchangers. The rotatable valve is formed from plastic magnet, and has a guide hole which may alternately connect the discharge pressure passage to one of the two passage holes, and a connecting groove which may alternately connect the suction pressure passage to one of the two passage holes. The discharge pressure passage is provided with a conduit whose leading end extrudes to the end of the guide hole. The extruding part of the conduit makes contact with the end of the guide hole, thereby serving as a stopper to limit the rotation of the valve. 
     As another example of a similar four-way selector valve, an art is proposed for a four-way selector valve comprising (a) a valve seat which has a discharge pressure passage, a suction pressure passage, a passage hole for an indoor heat exchanger and a passage hole for an outdoor heat exchanger, (b) a freely sliding main valve which switches to one of the passage holes, (c) a valve chest which is formed in the main body of the valve by covering all of the passage holes with the main valve, (d) an auxiliary valve which opens/closes the suction pressure passage using magnetic force, and (e) a spring which connects the auxiliary valve and the main valve; wherein the diameter of the discharge pressure passage is smaller than that of the suction pressure passage (see, e.g., Japanese Examined Patent Publication No. 1-32389/1989). 
     Among the conventional arts, the rotatable valve or a four-way selector valve disclosed in the Japanese Utility Model Registration No. 2523031 uses switching between the flow paths for refrigerant via the discharge pressure passage, the passage hole, the suction pressure passage, and the other passage hole, which is performed inside and outside the main valve. The suction pressure occurs inside the main valve, while the discharge pressure occurs at high pressure outside the main valve. Therefore, there is a pressure difference across the main valve, which tends to cause the switching operation to become heavy. For this four-way selector valve, no particular consideration is given to make easier and quicker the switching operation between the flow paths for refrigerant. 
     Among the conventional arts, the four-way selector valve according to Japanese Examined Patent Publication No. 1-32389/1989 uses switching between flow paths for refrigerant by the main valve after eliminating the pressure difference across the main body of the valve. Since the main valve is rotated by the elongation and compression of elastic members, no special consideration is given to make quicker the switching operation between the flow paths for refrigerant, nor to the reliability of the four-way selector valve. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a four-way selector valve which provides easier and quicker switching between flow paths for refrigerant, assures higher reliability, and allows itself to be configured more simply to decrease product cost. In order to accomplish the object, the four-way selector valve of the present invention basically comprises a motor which has a stator and a rotor, a case, and a main body. The main body includes a main valve and a valve seat, both of which are arranged in a valve chest within the case. The valve seat has a suction pressure passage led to a suction port of a compressor, and a discharge pressure passage led to a discharge port of the compressor. The valve seat further has two passage holes led to indoor and outdoor heat exchangers, respectively. The main valve has a connecting part which selectively connects the suction pressure passage to one of the two passage holes, and a pressure equalization orifice which links the connecting part and the valve chest. The rotor comprises a rotor sleeve having the auxiliary valve which opens or closes the pressure equalization orifice in order to transfer pressure. The operating pin moves the position of the main valve. The rotor of the motor rotates the auxiliary valve on the main valve and slides the main valve on the valve seat via the operating pin. 
     The four-way selector valve of the invention, which is configured as described above, may have, on the main valve, an auxiliary valve which moves pressure inside and outside the main valve. The rotation of the rotor may turn the auxiliary valve to rotate on the main valve, thereby to open or close the pressure equalization orifice so that pressure may move between the connecting part and the valve chest. In addition, the main valve slides on the valve seat in the valve chest. Therefore, the number of operating parts may be reduced, the configuration of the selector valve may be made simpler, the reliability of the inverter valve can be improved, and the switching operation between flow paths for refrigerant can be performed easily and quickly by the main valve. 
     Another embodiment of the four-way selector valve according to this invention is that the auxiliary valve may be a relief valve, located between the rotor and the main valve, retained to the rotor sleeve, and mounted on the main valve so that it may slide thereon. Alternatively, the rotor sleeve may be equipped with a supporting shaft concentric to the rotational center of the main valve, and the operating pin may be retained to the rotor sleeve and turns the main valve while rotating together with the rotor. 
     Yet another embodiment of the four-way selector valve according to the invention is that the supporting shafts at the top and bottom of the rotor sleeve may be provided with elastic members which energize or press the auxiliary valve and the main valve toward the valve seat. Alternatively, the valve seat may be provided with a main valve stopper which limits the rotation range of the main valve and that the main valve has a stopper contactor which makes contacts with the main valve stopper. The position of switching by the main valve between the flow paths for refrigerant can securely be regulated, and the production cost for the main valve can be reduced if a same material is used for the stopper contactor and the main valve. 
     Still another embodiment of the four-way selector valve according to the invention is that either the main valve stopper or the stopper contactor comprises a magnet and that the other consists of a magnetic substance. The switching position for the flow paths for refrigerant can be more securely retained by the magnetic force of the main valve stopper or the stopper contactor, and the vibration resistance of the four-way selector valve can be further improved. 
     Another embodiments of the four-way selector valve according to the invention is that at least one of the main valve, the auxiliary valve, and the valve seat may be coated with lubricative anodized aluminum film, which improves the lubricative property in sliding the main valve or the auxiliary valve. As a result, the sliding friction may become so low that the stable operation can be performed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective illustration for appearance of the four-way selector valve in the first embodiment of the invention. 
     FIG. 2 is an exploded perspective illustration for the four-way selector valve as shown in FIG.  1 . 
     FIG. 3 is a vertical sectional view of the four-way selector valve as shown in FIG.  1 . 
     FIG. 4A is a sectional view of the four-way selector valve, taken along the line  4 A— 4 A of FIG.  3 . 
     FIG. 4B is a sectional view of the four-way selector valve, taken along the line  4 B— 4 B of FIG.  3 . 
     FIGS. 5A through 5D are top views illustrating the operation of the four-way selector valve as shown in FIG.  1 . 
     FIGS. 6A through 6D are vertical sectional views of the four-way selector valve as shown in FIG.  1 . 
     FIG. 7 is a vertical sectional view of the four-way selector valve in another embodiment of the invention. 
     FIG. 8 is a diagram of cyclic flow for air-conditioning. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, the embodiments of the four-way selector valve according to the invention are described below. FIGS. 1 through 4A and  4 B illustrate an embodiment of the four-way selector valve according to the invention. FIG. 1 is a perspective view of appearance of the four-way selector valve according to the embodiment. FIG. 2 is a perspective view of the four-way selector valve. FIG. 3 is a vertical sectional view of the four-way selector valve. FIGS. 4A and 4B consist of sectional views of the four-way selector valve as illustrated in FIG.  3 . 
     The four-way selector valve  100  in the illustrated embodiment comprises a motor  10  equipped with a stepping motor, and a main body  50  equipped with a main valve  70 . For this four-way selector valve  100 , a main valve  70  rotates on a seat valve  80  when the stepping motor is turned on, so that the flow path for refrigerant is switched. 
     The motor  10  comprises a stator  20  and a rotor  40 . The stator  20  is provided with a stator coil  21  and a yoke  22  which are vertically housed therein. A cable  23  consisting of bundled lead wires and a connector  24  provided on the outer surface of the stator  20  are connected to the stator coil  21 . 
     A mount  25  of given height is provided on the top of the stator  20 . A snapper  26  made of a metal sheet is retained to the mount with a screw  27 . A relatively thin, spherical part  26   a  of the snapper  26  engages into one of four dimples  32  which are provided at given angles (90 degrees each) and spacing on the circumferential surface of a upper cylindrical part  31  of a case  30  which will be described later. This prevents the stator  20  from rotating and slipping off the upper cylindrical part  31 . When the spherical part  26   a  engages with one of the dimples  32 , they fit to each other on the same surface. 
     The rotor  40  comprises a rotor sleeve  41 , an upper supporting shaft  42  which is inserted into the center of the top of the rotor sleeve  41 , and a lower supporting shaft  43  which is inserted into the center of the bottom of the rotor sleeve  41 . The rotor sleeve  41  is equipped with a magnet  48  on its circumferential surface. 
     The upper end of the upper supporting shaft  42  makes point-contact with the peak of the inner spherical surface of the upper cylindrical part  31 . The upper supporting shaft  42  is provided with an upper coil spring  44  which is an elastic member to energize or press a rotor sleeve  41  and an auxiliary valve  61 , which is a relief valve and will be described later, toward a main valve  70  via a spring holder  45 , which is an integral part of the upper supporting shaft  42 , and others. On the other hand, the lower supporting shaft  43  is provided with a lower coil spring  46  which is an elastic member to energize or press the main valve  70  toward a valve seat  80  (i.e., to energize or press the rotor sleeve  41  upward) via a spring holder  47  and others. The energizing force of the upper coil spring is larger than that of the lower coil spring. Thus, the auxiliary valve  61  is energized toward the main valve  70 , and the main valve  70  is energized toward the valve seat  80 . 
     The main body  50  comprises a case  30 , which is a can, the main valve, the valve seat  80 , and a group of conduits  90 . The case  30  according to this embodiment consists of an upper cylindrical part  31  with a spherical top, a lower cylindrical part  33  having larger diameter than that of the upper cylindrical part  31 . The lower cylindrical part extends from the bottom of the upper cylindrical part  31  and forms a single unit therewith, and a flange  35  which outwardly extends from the bottom of the lower cylindrical part  33 . The upper cylindrically part  31  is covered with the rotor  40 , and the rotor  40  is covered with the upper cylindrical part  31 . The lower cylindrical part  33  covers the valve seat  80  which has a flange  89  at its bottom. The flange  35  and the flange  89  are coupled with bolts  69  so that the case  30  and the valve seat  80  are retained as a single unit. The main valve  70  is accommodated within the lower cylindrical part  33  of the case  30 , and placed on the top of the valve seat  80  so as to allow the main valve  70  to slide thereon. The internal part of the lower cylindrical part  33  is formed as a valve chest  73 . 
     The auxiliary valve  61  and a relatively cylindrical operating pin  64  are provided on the top of the main valve  70 . The auxiliary valve  61  opens/closes a pressure equalization orifice  77  in the main valve  70 , thereby making connection/disconnection with the valve chest  73  in the case  30  so that pressure can be moved. The operating pin  64  rotates together with the rotor  40 , thereby sliding the main valve  70 . The auxiliary valve  61  and the operating pin  64  are retained to respective positions appropriately separated from a straight line passing through the axial center of the lower supporting shaft  43  of the rotor  40 . A stator coil  21  is excited through a cable  23  and a connector  24 . Thus, the main valve  70  is rotated on the valve seat  80  by the operating pin  64  via the rotor  40 . Accordingly, switching between the flow paths for refrigerant, which will be described later, is performed. Along with this switching, the auxiliary valve  61  rotates on the main valve  70  via the rotor  40 , thereby opening/closing the pressure equalization orifice. 
     The main valve forms a roughly fan-shaped part with a central part  72  which is connected to the lower supporting shaft  43 , and a top surface  75  extending outward from the central part  72 . At the central part  72 , a connecting hole  71  is provided so that the lower supporting shaft can be inserted thereinto. 
     The main valve  70  has pin contactors  78 A and  79 A provided symmetrically on its right and left surfaces. In addition, stopper contactors  78   a  and  79   a , which make contact with main valve stopper  86  provided on the valve seat  80 , are located on the lower parts of the pin contactors  78 A and  79 A. The stopper contactors  78   a  and  79   a  are shaped so as to provide the optimal control curve, control line, or the like, which assures that the main valve  70  is rotated in accordance with the rotational angle per unit pulse of the stepping motor via the operating pin  64  and that the motion of the main valve  70  is regulated by making contact with the main valve stopper  86 . 
     Apart from the above configuration, the main valve  70  and the valve seat  80  in this embodiment may be configured to use magnets such as a ferrite magnet for the stopper contactors  78   a  and  79   a  thereof, and using a magnetic substance of iron or the like for the main valve stopper  86 . In this case, the contact between the stopper contactors  78   a  or  79   a  and the main valve stopper  86  is maintained with magnetic force. This ensures that the position of switching between the flow paths by the main valve is more securely held with magnetic force  70 , and enables further improvement of the vibration resistance of the four-way selector valve  100 . Of course, the intensity of the magnetic force is set, as appropriate, to a smaller value than the rotational force  10  of the motor  10 . 
     If the central part  72  of the main valve  70  and the top surface  75  thereof are made of resin, the stopper contactors  78   a  and  79   a  are molded by insert molding. If the central part  72  and the top surface  75  are made of metal such as aluminum, the stopper contactors  78   a  and  79   a  may be bonded. The stopper contactors  78   a  and  79   b  may be magnetic bodies, and the main valve stopper  86  may be made of a magnet. 
     The main valve  70  internally provides a connecting part  74  which connects to one of a suction pressure passage  82  in the valve seat  80 , a passage hole  84  for the outdoor heat exchanger, and a passage hole  85  for the indoor heat exchanger, and a pressure equalization orifice  77  which connects the connecting part  74  and the valve chest  73 . 
     The auxiliary valve  61  comprises a rotor press-fitting part  62  and a blocking part  63  for the pressure equalization orifice. The rotor press-fitting part  62  is press-fit and retained to the bottom of the rotor  40 . The blocking part  63  for the pressure equalization orifice makes contact with the top of the main valve  70 . Both the pressure of refrigerant in the valve chest  73  and that for refrigerant in the connecting part  74  are given to the top and bottom of the main valve  70 . 
     The top of the valve seat  80  is flat, making contact with the bottom of the main valve  70 . A bolt  69  is inserted into a bolt hole  87  in a flange  89  from the bottom of the valve seat and a bolt hole  34  in a flange  35  of the case  30 , and then tightened. As illustrated in FIGS. 4A and 4B, the central part has a press-fitting hole  81  in which the lower supporting shaft  43  is press-fit and retained. In given positions radially separated from the center of the lower supporting shaft  43 , there are a suction pressure passage  82  which introduces the suction pressure of the compressor, a discharge pressure passage  83  which introduces the discharge pressure, a passage hole  84  for the outdoor heat exchanger, and a passage hole  85  for the indoor heat exchanger. In addition, a main valve stopper  86 , which is shaped like a cylinder and used to regulate the rotational position of the main valve  70 , is secured. The case  30  and the valve seat  80  are coupled and retained with an O-ring, making the valve chest  73  airtight. 
     As illustrated in FIG. 4, the suction pressure passage  82  and the discharge pressure passage are symmetrically provided with respect to the lower supporting shaft  43 . In addition, the passage hole  84  for the outdoor heat exchanger and the passage hole  85  for the in door heat exchanger are symmetrically provided with respect to the lower supporting shaft  43  at given angles from the suction pressure passage  82  and the discharge pressure passage  83 . The main valve stopper  86  is provided in an appropriate position along the straight line between the suction pressure passage  82  and the discharge pressure passage  83 , and located between the lower supporting shaft  43  and the discharge pressure passage  83 . The group of conduits  90  consists of four conduits, namely, a suction pressure conduit  92  which is connected to the suction pressure passage  82 , a discharge pressure conduit  93  which is connected to the discharge pressure passage  83 , a conduit  94  for the outdoor heat exchanger, which is connected to the passage hole  84  for the outdoor heat exchanger, and a conduit  95  for the indoor heat exchanger, which is connected to the passage hole  85  for the indoor heat exchanger. Each of the conduits is connected and retained to the bottom of the valve seat  80 . 
     At least one of the main valve  70 , the auxiliary valve  61 , and the valve seat  80  according to this embodiment may be coated with lubricative anodized aluminum film. For the lubricative anodized aluminum film, e.g., “KASHIMA COAT” (product name: Miyaki Co., Ltd.) is used as follows: The main valve  70  is made of aluminum. This aluminum is anodized to create a hard alumina layer. Molybdenum disulfide is electrolytically deposited. Coating this lubricative anodized aluminum film improves the lubricative property of the main valve  70 . 
     Not only the main valve  70 , but also a blocking portion of the pressure equalization orifice  63  on the auxiliary valve  61  and the valve seat  80  are made of aluminum. The lubricative anodized aluminum film is coated over them, enabling further improvement of the lubricative property between the auxiliary valve  61  and the main valve  70  and that between the main valve  70  and the valve seat  80 . 
     For the lubricative anodized aluminum film, not only the “KASHIMA COAT,” but also “UNIMITE” (product name: Ueda Anodized Aluminum Film Industries Co., Ltd.) or “TOUGHMITE” (product name: Ueda Anodized Aluminum Film Industries Co., Ltd.) may similarly be used for at least one of the main valve, the auxiliary valve, and the valve seat. 
     Coating the lubricative anodized aluminum film decreases the sliding friction between the auxiliary valve and the main valve and that between the main valve and the valve seat, thereby making the operation stable. The improved lubricative property enables the operation of the four-way selector valve at low torque. Thus, the motor can be downsized. 
     The operation of the four-way selector valve  100  is described below. FIGS. 5A through 5D and FIGS. 6A through 6D illustrate the operation of the four-way selector valve  100  according to its internal structure. FIGS. 5A through 5D illustrate the same operation condition as shown in FIGS. 6A through 6D respectively. 
     FIGS. 5A and 6A illustrates the setup for the cooling operation, wherein the suction pressure conduit  92  and the conduit  95  for the indoor heat exchanger are connected via the connecting part  74  of the main valve  70 , and wherein the discharge pressure conduit  93  and the conduit  94  for the outdoor heat exchanger are connected to the outside of the main valve  70 , i.e., to the valve chest  73 . In this state, there is a great difference between the pressure in the valve chest  73  and that in the connecting part  74 . The main valve  74  is pressed against the valve seat  80  with this pressure difference and does not move easily. Therefore, the four-way selector valve  100  according to this embodiment uses the auxiliary valve  61 , which is a relief valve, to switch the flow path for refrigerant from this state. This is intended to balance the pressure in the valve chest  73  with that in the connecting part, and to rotate the main valve  70  after eliminating the force which press the main valve  70 . 
     In the state of FIGS. 5A and 6A, the operating pin  64  and the auxiliary valve  61 , which are rotated via the rotor  40  by pulse input to the stepping motor, are rotated clockwise as shown in FIGS. 5B and 6B. This releases the pressure equalization orifice  77  in the main valve  70 , which has been closed by the blocking part  63  for the pressure equalization orifice on the auxiliary valve  61 . Thus, the refrigerant in the valve chest  73  is sent to the connecting part  74  via the pressure equalization orifice  77 , and then the pressure in the valve chest  74  is balanced with that in the connecting part  74 . 
     As in the state of FIGS. 5B and 6B, after the balance has been acquired between the pressure in the valve chest  73  and that in the connecting part  74 , the operating pin  64 , which makes contact with the pin contactor  79 A on the main valve  70 , presses the main valve  70 , thereby rotating and sliding the main valve  70  clockwise on the valve seat  80 . The rotation continues until the stopper contactor  79   a  separates from the main valve stopper  86  and the other stopper contactors  78   a  make contact with the main valve stopper as shown in FIGS. 5C and 6C. This operation switches the connection between-the suction pressure conduit  92  and the conduit  95  for the indoor heat exchanger by the main valve  70  to that between the suction pressure conduit  92  and the conduit  95  for the indoor heat exchanger  95 . If the stopper contactor  78   a  and the main valve stopper  86  maintain the contacting state by their own magnetic force, the main valve  70  is more securely retained to its position. 
     As in the state shown in FIGS. 5C and 6C, the suction pressure conduit  92  and the conduit  94  for the outdoor heat exchanger reversibly rotate the stepping motor after they has been connected in the connecting part  74 . This continues to rotate the operating pin  64  and the auxiliary valve  61  counterclockwise as shown in FIGS. 5D and 6D until the blocking part  63  for the pressure equalization orifice on the auxiliary valve  61  closes the pressure equalization orifice  77  in the main valve  70 . This operation results in the setup for the heating operation, wherein the suction pressure conduit  92  and the conduit  94  for the outdoor heat exchanger are connected via the connecting part  74  of the main valve  70  and wherein the discharge pressure conduit  93  and the conduit  95  for the indoor heat exchanger are connected via the valve chest  73 . 
     To switch the state shown in FIGS. 5D and 6D to the setup for the cooling operation in the state shown in FIGS.  5 A and  6 A, e.g., the pressure equalization orifice  77  closed by the blocking part  63  for the pressure equalization orifice on the auxiliary valve should be released, and then the main valve  70  should be rotated until the operating pin  64  makes contact with the contactor  78 A and the stopper contactor  79   a  makes contact with the main valve stopper  86 . 
     As stated above, the embodiment according to the invention provides the following function using the above configuration: 
     For the four-way selector valve  100  according to the embodiment, after the auxiliary valve  61  has been rotated on the main valve  70  with input pulse of the motor  10 , the main valve is rotated on the valve seat  80 . Therefore, after the pressure balance between the valve chest  73  and the connecting part  74  has been acquired, the refrigerant flow can be switched. This means that the flow paths for refrigerant can be switched more easily and quickly than in the case where the main valve is rotated using elastic members. In addition, the reliability of the four-way selector valve can be improved. 
     The auxiliary valve  61  is positioned between the rotor  40  and the main valve  70 , mounted on the main valve  70 , and pressed by the upper coil spring  44  toward the main valve  70 . It rotates together with the rotor  40  and functions as a relief valve which eliminates a pressure difference between the connecting part  74  and the valve chest  73 . Therefore, the flow path for refrigerant can be switched promptly, and product cost for the four-way selector valve can be reduced by decreasing the number of movable parts. 
     If the stopper contactors  78   a  and  79   a , and the main valve stopper  86  maintain the contact state by their own magnetic force, the switching position of the main valve  70  with respect to the valve seat  80  can securely be held against vibrations. Thus, the reliability of the four-way selector valve  100  can be further improved. 
     One embodiment according to the invention has been described above in detail. However, the invention is not limited to this embodiment, nor limited to any air conditioner, but can be applied for every product that switches a flow path. 
     FIG. 7 is a sectional view illustrating another embodiment according to the invention. 
     The four-way selector valve as generally represented by code  200  has the same configuration as that of the previously described four-way selector valve. Therefore, the same parts are assigned the same code and the description thereof is omitted. 
     For the four-way selector valve  200 , a supporting shaft  140  which supports a rotor  140  comprises a single shaft. The supporting shaft  140  is press-fit into a press-fitting hole  81  in a valve seat  80  and then retained. A bearing  148  is located in two places, the top and bottom of a rotor sleeve  41 , between the supporting shaft  140  and the rotor sleeve  41 . 
     A snap ring  141  and a coil spring  142  are fit to the end of the supporting shaft  140  opposite to the side of the valve seat  80 . The coil spring  142  energizes a rotor  140  toward the valve seat  80  via a spring holder ring  143 . A snap ring  145  and a coil spring  146  are fit between the rotor sleeve  41  of the supporting shaft  140  and the main valve  70 . The coil spring  146  energizes the main valve  70  toward the valve seat  80  via a spring holder ring  147 . 
     The four-way selector valve  200  further decreases the number of parts, requires no shaft alignment as opposed to the case where two supporting shafts are used, and has a simpler structure. In addition, the rotational accuracy of the rotor is improved. 
     As can be understood from the above description, the four-way selector valve according this invention has the auxiliary valve provided on the top of the main valve. After the pressure balance between the valve chest and the connecting part of the main valve has been acquired, the positional switching of the main valve is performed. Therefore, the switching operation between the flow paths for refrigerant can be improved so that it becomes easier and quicker. At the same time, the product cost for the selector valve can be reduced. 
     Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciated that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention. 
     The disclosure of Japanese Patent Application No. 2000-330377 filed Oct. 30, 2000, including specification, drawings and claims are herein incorporated by reference in its entirety.