Abstract:
A flow path switching valve arranged to rotate a main valve with an auxiliary valve to switch a cooling state and a heating state, which provides a reliable operation of the main valve by simplifying the rotation movement of the auxiliary valve and the main valve and provides reduced switching time. An outdoor heat exchanger-side pressure equalizing hole and an indoor heat exchanger-side pressure equalizing hole are formed at the main valve. An occluding portion for opening and closing of the pressure equalizing holes is formed at the auxiliary valve. The main valve is rotated 90 degrees by merely operating the auxiliary valve along one direction in forward or reverse direction to switch between the cooling state and the heating state.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a flow path switching valve for switching a flow path of a cooling medium, which is used for example in a freezing cycle using a heat pump system. 
     DESCRIPTION OF THE RELATED ART 
     A conventional flow path switching valve (a four-way valve) of a type described above is disclosed for example in Japanese Patent No. 4081290 (Patent Literature 1). For the flow path switching valve of Patent Literature 1, when switching from a cooling state to a heating state, or from a heating state to a cooling state, a support shaft supporting a main valve is rotatably moved and then a closing valve support member is rotatably moved above the main valve by a drive unit, and the rotation of the closing valve support member opens or closes a connection hole or a pressure equalization hole formed at the main valve. Furthermore, the rotation of the support shaft also rotates, above a valve seat, the main valve together with the closing valve support member. In addition, in a cooling state, the pressure equalization hole is “closed” and the connection hole is “opened” by a first closing valve. Also, in a heating state, the connection hole is “closed” and the pressure equalization hole is “opened” by a second closing valve. 
     Patent Literature 1: Japanese Patent No. 4081290 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     However, for the flow path switching valve of Patent Literature 1, the main valve moves easily so the main valve is lifted above the valve seat. Thus, in order to switch from the state in which the pressure equalizing hole is “open” and the connection hole is “closed” to the state in which the pressure equalizing hole is “closed” and the connection hole is “open”, a motor is required to be inversely rotated for a predetermined angle which may cause the main valve to be move together therewith, leaving a room for an improvement. Furthermore, the closing valve which opens and closes the pressure equalizing hole and the connection hole may move freely with respect to the main valve, leaving a room for an improvement regarding to a sealing performance of the pressure equalizing hole and the connection hole. 
     Thus, an object of the present invention is to provide a simplified operation of an auxiliary valve to provide a reliable operation of the main valve during a flow path switching in which a flow path of the cooling medium between the cooling state and the heating state of the freezing cycle is switched. 
     Solution to Problem 
     The present invention according to a first aspect is a flow path switching valve for switching a direction of flow of a cooling medium for a cooling operation and a heating operation, having: a case member forming a cylindrical valve chamber; a valve seat arranged at an open end portion of the case member; a main valve arranged so as to slidably move in a direction of an axis of the valve chamber and about a valve axis; and a rotary drive unit for rotatably moving the main valve about the valve axis, wherein the valve seat includes four ports which are communicated with a discharge-side of a compressor, an intake-side of the compressor, an outdoor heat exchanger-side and an indoor heat exchanger-side, wherein the main valve includes: an outdoor heat exchanger-side communication path which selectively allows the port provided at the valve seat and communicated with the outdoor heat exchanger-side to communicate with the port communicated with the discharge-side of the compressor or with the port communicated with the intake-side of the compressor; and an indoor heat exchanger-side communication path which selectively allows the port provided at the valve seat and communicated with the indoor heat exchanger-side to communicate with the port communicated with the discharge-side of the compressor or with the port communicated with the intake-side of the compressor, wherein the flow path switching valve further includes: an outdoor heat exchanger-side pressure equalizing hole communicating the valve chamber with the outdoor heat exchanger-side communication path; and an indoor heat exchanger-side pressure equalizing hole communicating the valve chamber with the indoor heat exchanger-side communication path, wherein the main valve is provided with an auxiliary valve abutting portion at the valve chamber side of the main valve, the auxiliary valve abutting portion being arranged to receive a rotary drive of the auxiliary valve, wherein the auxiliary valve is arranged to slidably contact on the main valve and includes an occluding portion for a selectable opening and closing of the outdoor heat exchanger-side pressure equalizing hole and the indoor heat exchanger-side pressure equalizing hole, wherein the flow path switching valve further includes a main valve abutting portion for rotating the main valve, and wherein for a switching from the cooling operation to the heating operation, the main valve is rotatably moved while the outdoor heat exchanger-side pressure equalizing hole is closed and the indoor heat exchanger-side pressure equalizing hole is open, and for a switching from the heating operation to the cooling operation, the main valve is rotatably moved while the outdoor heat exchanger-side pressure equalizing hole is open and the indoor heat exchanger-side pressure equalizing hole is closed. 
     The present invention according to a second aspect is the flow path switching valve described above, wherein the main valve extends diametrically from a shaft receiving portion at a center and includes a partition portion separating the outdoor heat exchanger-side communication path from the indoor heat exchanger-side communication path, wherein the main valve is arranged so that in a position in which the main valve is rotated for about half of a rotation range during a switching process from the cooling operation to the heating operation, the outdoor heat exchanger-side communication path and the indoor heat exchanger-side communication path are partially overlapped on the port communicated with the discharge-side of the compressor and on the port communicated with the intake-side of the compressor, respectively. 
     The present invention according to a third aspect is the flow path switching valve described in the first aspect, wherein the main valve includes an outdoor heat exchanger-side path outer wall as an outer wall of the outdoor heat exchanger-side path and an indoor heat exchanger-side path outer wall as an outer wall of the indoor heat exchanger-side path, wherein the main valve is arranged so that the switching process between the cooling operation and the heating operation, the outdoor heat exchanger-side path outer wall crosses an opening of the port communicated with the outdoor heat exchanger-side, and the indoor heat exchanger side path outer wall crosses an opening of the port communicated with the indoor heat exchanger-side. 
     The present invention according to a fourth aspect is the flow path switching valve according to any one of the first to third aspects, further including, an elastic member exerting a force on the occluding portion of the auxiliary valve towards the outdoor heat exchanger-side pressure equalizing hole and towards the indoor heat exchanger-side pressure equalizing hole. 
     The present invention according to a fifth aspect is the flow path switching valve according to any one of the first to third aspects, wherein the auxiliary valve includes two occluding portions, the one being arranged at the outdoor heat exchanger-side pressure equalizing hole side and the other one being arranged at the indoor heat exchanger-side pressure equalizing hole side, and the auxiliary valve further includes a support portion arranged to lie in the same plane as the two occluding portions. 
     The present invention according to a sixth aspect is the flow path switching valve of the fifth aspect, wherein the two occluding portions and the support portion are disposed at an equal distance from a valve axis center. 
     Advantageous Effects of the Invention 
     According to the flow path switching valve of the first aspect, for the switching from the cooling operation to the heating operation, the main valve is rotatably moved while the outdoor heat exchanger-side pressure equalizing hole is closed and the indoor heat exchanger-side pressure equalizing hole is open, and for the switching from the heating operation to the cooling operation, the main valve is rotatably moved while the outdoor heat exchanger-side pressure equalizing hole is open and the indoor heat exchanger-side pressure equalizing hole is closed. Consequently, prior to a rotation of the main valve together with the auxiliary valve, the outdoor heat exchanger-side pressure equalizing hole is closed and the indoor heat exchanger-side pressure equalizing hole is opened, or the outdoor heat exchanger-side pressure equalizing hole is opened and the indoor heat exchanger-side pressure equalizing hole is closed. Therefore, the auxiliary valve only needs to be rotated in one direction only and thus the auxiliary valve does not need to be rotated in a reverse direction at a time of switching. As a result, a reliable switching can be achieved. Furthermore, the switching operation can be simplified, reducing a switching time. 
     According to the flow path switching valve of the second aspect, at a position rotated to about a half of the rotation range during the switching process, the high-pressure cooling medium from the port communicating with the discharge-side flows into both of the outdoor heat exchanger-side path and the indoor heat exchanger-side path. Thus, there is only a small seating force involved when the main valve is seated on the valve seat, reducing a friction force between the main valve and the valve seat. Consequently, the switching can be achieved smoothly even while the compressor is operating. 
     According to the flow path switching valve of the third aspect, in addition to the advantageous effect of the second aspect, since the high-pressure cooling medium flows over the outdoor heat exchanger-side path outer wall and the indoor heat exchanger-side path outer wall and further flows into the outdoor heat exchanger-side communication path and indoor heat exchanger-side communication path, via the port communicated with the outdoor heat exchanger-side and the port communicated with the indoor heat exchanger-side, thus the switching can be achieved even more smoothly. 
     According to the flow path switching valve of the fourth aspect, in addition to the advantageous effect of the first through third aspects, since the elastic member pushes the occluding portion of the auxiliary valve towards the outdoor heat exchanger-side pressure equalizing hole and towards the indoor heat exchanger-side pressure equalizing hole, the sealing performance of the closed state of the outdoor heat exchanger-side pressure equalizing hole and the indoor heat exchanger-side pressure equalizing hole can be increased. 
     According to the flow path switching valve of the fifth aspect, in addition to the advantageous effect of the first through third aspects, since the support portion is provided so as to lie in the same plane as the two occluding portions of the auxiliary valve, the tilt of the auxiliary valve with respect to the main valve can be prevented, further increasing the sealing performance. 
     According to the flow path switching valve of the sixth aspect, in addition to the advantageous effect of the fifth aspect, since the support portion and the occluding portions are arranged at an equal distance from a valve axis center, the rotation of the auxiliary valve can be smooth also. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view of a flow path switching valve according to a first embodiment of the present invention; 
         FIG. 2  is a planar view of a valve seat of the flow path switching valve; 
         FIGS. 3A and 3B  are perspective views of a main valve of the flow path switching valve; 
         FIGS. 4A and 4B  are perspective views of an auxiliary valve of the flow path switching valve; 
         FIGS. 5A to 5C  are views showing a positional relationship of respective portions of the flow path switching valve during a cooling operation; 
         FIGS. 6A to 6C  are views showing a positional relationship of respective portions of the flow path switching valve in a switching process; 
         FIGS. 7A to 7C  are views showing a positional relationship of respective portions of the flow path switching valve during a heating operation; 
         FIG. 8  is a longitudinal sectional view of a flow path switching valve according to a second embodiment of the present invention; 
         FIG. 9  is a perspective view of a main valve of the flow path switching valve; 
         FIGS. 10A to 10C  are views showing a positional relationship of respective portions of the flow path switching valve during the cooling operation; 
         FIGS. 11A to 11C  are views showing a positional relationship of respective portions of the flow path switching valve in a switching process; 
         FIGS. 12A to 12C  are views showing a positional relationship of respective portions of the flow path switching valve during the heating operation; 
         FIGS. 13A to 13D  are views showing a flow of a cooling medium for the flow path switching valve in the switching process; 
         FIG. 14  is a view showing a structure of a main valve of a flow path switching valve according to a third embodiment and a flow of a cooling medium in a switching process; and 
         FIGS. 15A and 15B  are views showing an auxiliary valve according to another embodiment for the flow path switching valve of the respective embodiments. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes an embodiment of a flow path switching valve according to the present invention with reference to the drawings.  FIG. 1  shows a longitudinal sectional view of a flow path switching valve according to a first embodiment of the present invention,  FIG. 2  is a planar view of a valve seat of the flow path switching valve,  FIG. 3  is a perspective view of a main valve of the flow path switching valve,  FIG. 4  is a perspective view of an auxiliary valve of the flow path switching valve, and  FIGS. 5 through 7  are views explaining an operation of the flow path switching valve. It is noted that  FIG. 1  shows the main valve during which it is being switched. 
     The flow path switching valve according to the first embodiment includes a case member  1  and a valve seat member  2 . The case member  1  is provided with a valve chamber  11  cut and formed into a cylinder-like shape. Furthermore, the valve seat member  2  includes a valve seat  21  having a circular board shape and a ring  22  (refer to  FIG. 1 ) attached to a circumference of the valve seat  21 . The valve seat  21  and the ring  22  are fitted to an opening portion of the valve chamber  11 , thereby sealing the valve chamber  11 . Furthermore, a main valve  3  and an auxiliary valve  4  are received inside the valve chamber  11 , and also a drive unit  5  is mounted so as to be provided for a portion from an upper portion of the case member  1  to the inside of the valve chamber  11 . In addition, a motor not shown of the drive unit  5  is received at the upper portion of the case member  1 . 
     As shown in  FIG. 2 , the valve seat  21  is provided with a D port  21 D communicated to the valve chamber  11  and to a cooling medium discharge-side of a compressor not shown, a S port  21 S communicated to the valve chamber  11  and to a cooling medium intake-side of the compressor, a C selection port  21 C communicated to an outdoor heat exchanger-side not shown and a E selection port  21 E communicated to an indoor heat exchanger-side not shown, respectively. In addition, these ports open respectively at positions apart by 90 degrees. 
     As shown in  FIG. 3 , the main valve  3  is a member made of a resin and having a circular circumference and includes a flared portion  31  near the valve seat  21  and a cylindrical piston portion  32  which are formed in one. A piston ring  32   a  is arranged at a circumference of the piston portion  32 . With a central shaft receiving portion  33  fitted at a lower portion of a rotational shaft  51  of the drive unit  5 , the main valve  3  is arranged so as to rotatably move freely around a valve axis L. The flared portion  31  is provided with an outdoor heat exchanger-side communication path  31 A and an indoor heat exchanger-side communication path  31 B which are bored into a dome-like shape at both sides of the shaft receiving portion  33 . 
     Furthermore, as shown in  FIG. 3A , at an inside of the piston portion  32 , an auxiliary valve seat  34  is formed at an upper portion of the flared portion  31  so as to project circumferentially around the shaft receiving portion  33  distant from a shaft hole  33   a . The auxiliary valve seat  34  is provided with an outdoor heat exchanger-side pressure equalizing hole  34   a  penetrating from an outdoor heat exchanger-side communication path  31 A to the piston portion  32  and an indoor heat exchanger-side pressure equalizing hole  34   b  penetrating from an indoor heat exchanger-side communication path  31 B to the piston portion  32 . The outdoor heat exchanger-side pressure equalizing hole  34   a  and the indoor heat exchanger-side pressure equalizing hole  34   b  are disposed at 180 degrees apart around the valve axis L. 
     Furthermore, a projection portion  35  is provided at a portion of an inner circumferential face of the piston portion  32 . The projection portion  35  is formed so as to project towards the valve axis L and formed for a range of about 90 degrees. The projection portion  35  is provided with auxiliary valve abutting portions  35   a ,  35   b  arranged at both ends thereof along a circumferential direction of the valve axis L, respectively. These auxiliary valve abutting portions  35   a ,  35   b  correspond to a later-described main valve abutting portions  46   a ,  46   b  of the auxiliary valve  4 . Furthermore, a stopper  36  is formed so as to stand perpendicularly from a circumferential portion of an upper portion of the piston portion  32 . This stopper  36  is arranged within a guiding groove  13  (refer to  FIG. 5A  through  FIG. 7A ) formed circumferentially at an upper portion of the valve chamber  11  of the case member  1 , so that both end portions of the stopper  36  are arranged to contact with the end portions of the guiding groove  13  in order to regulate a rotation range of the main valve  3 . A difference between an angle between the ends of the guiding groove  13  along a length thereof as well an angle between the ends of the stopper  36  along a width thereof is 90 degrees, thus the rotation range of the main valve  3  is 90 degrees. 
     As shown in  FIG. 4 , the auxiliary valve  4  includes a disc-like shaped auxiliary valve main body portion  41  to be received within the piston portion  32  of the main valve  3  and a boss portion  42  provided at a center of the auxiliary valve main body portion  41 . A rectangular shaped rectangular hole  42   a  is formed at a center of this boss portion  42 . Furthermore, the auxiliary valve main body portion  41  is provided with a slide valve portion  43  protruding at a face of the auxiliary valve main body portion  41  towards the main valve  3  and protruding in an about 180-degree fan shape. One of both ends of this slide valve portion  43  corresponds to an occluding portion  43 A arranged at the outdoor heat exchanger-side pressure equalizing hole-side, and the other one thereof corresponds to an occluding portion  43 B arranged at the indoor heat exchanger-side pressure equalizing hole-side. Furthermore, a support portion  44  is formed at a position opposite of the slide valve portion  43  with respect to the rectangular hole  42   a . Moreover, on a circumference of a circle of the auxiliary valve  4  around the valve axis L, there are provided two pressure equalizing hole apertures  45 A,  45 B concaved with respect to the main valve  3 —side and arranged between the slide valve portion  43  and the support portion  44 . Furthermore, different-leveled portions at an outer circumference of the auxiliary valve main body portion  41  correspond to main valve abutting portions  46   a ,  46   b . Moreover, these main valve abutting portions  46   a ,  46   b  lie in the same circumference with the auxiliary valve abutting portions  35   a ,  35   b  of the main valve  3 . 
     As shown in  FIG. 1 , the drive unit  5  includes a worm wheel  52  rotatably arranged at a rotation drive shaft  51  and a worm gear  53  meshed to the worm wheel  52 , and this worm gear  53  is fixed at a drive shaft of a motor not shown. Furthermore, the worm wheel  52  is rotatably arranged at the rotation shaft  51  via a boss portion  52   a , and this boss portion  52   a  is fitted to the rectangular shaped rectangular hole  42   a  formed at the boss portion  42  of the auxiliary valve  4 . Consequently, the auxiliary valve  4  is able to slide only in a direction along the valve axis L with respect to the worm wheel  52 , while a rotation thereof about the valve axis L is regulated. Moreover, a coil spring  54  as a “force-exerting member” exerting a force on the auxiliary valve  4  towards the main valve  3  is provided between the worm wheel  52  and the auxiliary valve  4 , and this auxiliary valve  4  cooperates and rotates with the worm wheel  52 . 
     According to the structure described above, the auxiliary valve  4  is driven by the drive unit  5  and rotated. The main valve  3  rotates together with the auxiliary valve  4  while the main valve abutting portion  46   a  is abutted on the auxiliary valve abutting portion  35   a  or while the main valve abutting portion  46   b  is abutted on the auxiliary valve abutting portion  35   b . Furthermore, the stopper  36  of the main valve  3  abuts on the end portion of the guiding groove  13  and the rotation of the main valve  3  stops. In addition, a cooling mode corresponds to abutting on the one end portion of the guiding groove  13  and a heating mode corresponds to abutting on the other end portion thereof. Furthermore, in the cooling mode, the outdoor heat exchanger-side pressure equalizing hole  34   a  is opened by the pressure equalizing hole aperture  45 A of the auxiliary valve  4  and the indoor heat exchanger-side pressure equalizing hole  34   b  is closed by the occluding portion  43 B of the slide valve portion  43 . In the heating mode, the indoor heat exchanger-side pressure equalizing hole  34   b  is opened by the pressure equalizing hole aperture  45 B of the auxiliary valve  4  and the indoor heat exchanger-side pressure equalizing hole  34   a  is closed by the occluding portion  43 A of the slide valve portion  43 . 
     The auxiliary valve  4  is pushed towards the main valve  3  by the coil spring  54  (elastic member), and thus the slide valve portion  43  (occluding portion) is pushed against the outdoor heat exchanger-side pressure equalizing hole  34   a  or the indoor heat exchanger-side pressure equalizing hole  34   b , increasing the sealing performance in a closed state of the outdoor heat exchanger-side pressure equalizing hole  34   a  or the indoor heat exchanger-side pressure equalizing hole  34   b . Furthermore, the support portion  44  is arranged to lie in the same plane with the two occluding portions  43 A,  43 B of the auxiliary valve  4  (a plane of the slide valve portion  43 ). Therefore, a tilt of the auxiliary valve  4  with respect to the main valve  3  can be prevented, further increasing the sealing performance. Moreover, since the support portion  44  and the occluding portion  43 A,  43 B are disposed at an equal distance from a center of the valve axis L, the rotation of the auxiliary valve  4  can be smooth. 
     Next, a switching operation of a cooling operation state and a heating operation state is explained in reference with  FIG. 5  through  FIG. 7 .  FIG. 5  through  FIG. 7  show a positional relationship of the respective portions viewing from the valve seat  21  towards the drive unit  5 . Solid lines, dotted lines, diagonal lines and such are not intended to show the antero-posterior position nor the structure.  FIG. 5A ,  FIG. 6A  and  FIG. 7A  show a positional relationship of the guiding groove  13  and the stopper  36  of the main valve, and  FIG. 5B ,  FIG. 6B  and  FIG. 7B  show a positional relationship of the inside of the piston portion  32  and the auxiliary valve  4 , and  FIG. 5C ,  FIG. 6C  and  FIG. 7C  show a positional relationship of the main valve  3  and the valve seat  21 . Furthermore,  FIG. 5  corresponds to the cooling operation state,  FIG. 6  corresponds to the switching process of the operation state and  FIG. 7  corresponds to the heating operation state. 
     Firstly, during the cooling operation of  FIG. 5 , as shown in  FIG. 5C , the D port  21 D is communicated with the C switching port  21 C by the outdoor heat exchanger-side communication path  31 A, and the S port  21 S is communicated with the E switching port  21 E by the indoor heat exchanger-side communication path  31 B. In addition, the support portion  44  of the auxiliary valve  4  is slidably contacted on the auxiliary valve seat  34 . Due to the high-pressure cooling medium introduced from the D port  21 D, a pressure of a space outside the main valve  3  becomes high and a pressure of the indoor heat exchanger-side communication path  31 B becomes low. Therefore, the differential pressure acting on the main valve  3  causes the main valve  3  to be seated on the valve seat  21  in a closely contacted manner. 
     Next, at a time of switching from the cooling operation state to the heating operation state, when the compressor is stopped and the drive unit portion  5  is activated, only the auxiliary valve  4  rotates from a state shown in  FIG. 5B  in a clockwise direction. At this time, the support portion  44  of the auxiliary valve  4  slidably moves on the auxiliary valve seat  34 . Then, the main valve abutting portion  46   b  of the auxiliary valve  4  abuts on the auxiliary valve abutting portion  35   b  of the main valve  3  as shown in  FIG. 6B , and the indoor heat exchanger-side equalizing pressure hole  34   b  of the main valve  3  is opened by the equalizing pressure hole aperture  45 B of the auxiliary valve  4 , while the outdoor heat exchanger-side pressure equalizing hole  34   a  closed by the occluding portion  43 A of the slide valve portion  43  of the auxiliary valve  4 . Consequently, a pressure of the valve chamber  11  above the piston ring  32   a  provided at the piston portion  32  of the main valve  3  gradually becomes low, and the main valve  3  is lifted against the pushing force of the coil spring  54 . Therefore, the differential pressure acting on the main valve  3  decreases, and thus the pushing force by the coil spring  54  becomes larger than the lifting force of the main valve  3 , thereby the main valve  3  is seated on the valve seat  21 . 
     In addition, at this time, since the main valve abutting portion  46   b  of the auxiliary valve  4  is abutted on the auxiliary valve abutting portion  35   b  of the main valve  3 , the auxiliary valve  4  rotates together with the main valve  3 . Then, the stopper  36  of the main valve  3  abuts on the one end of the guiding groove  13  as shown in  FIG. 7A , and the rotation of the auxiliary valve  4  and the main valve  3  is stopped. Then, the compressor is activated to produce the heating operation state. In addition, when the stopper  36  is abutted on the one end of the guiding groove  13 , a motor and a drive circuit of the drive unit  5  are overloaded, which can be detected to stop the motor. 
     In this heating operation state, as shown in  FIG. 7C , the D port  21 D is communicated with the E switching port  21 E by the indoor heat exchanger-side communication path  31 B, and the S port  21 S is communicated with the C switching port  21 C by the outdoor heat exchanger-side communication path  31 A. Also, the indoor heat exchanger-side pressure equalizing hole  34   b  is opened and the outdoor heat exchanger-side pressure equalizing hole  34   a  is closed. Due to the high-pressure cooling medium introduced from the D port  21 D, a pressure of a space outside the main valve  3  becomes high and a pressure of the outdoor heat exchanger-side communication path  31 A becomes low. Therefore, the differential pressure acting on the main valve  3  causes the main valve  3  to be seated onto the valve seat  21  in a closely contacted manner. When switching from the heating operation state to the cooling operation state can be achieved by the operation reverse of the above-described operation. 
     As described above, when switching from the cooling operation to the heating operation, the auxiliary valve  4  is required to be rotated only in one direction. Consequently, the inverse rotation of the auxiliary valve (refer to the afore-mentioned Patent Literature 1) is not needed, preventing the displacement of the main valve  3 . 
       FIG. 8  is a longitudinal sectional view of a flow path switching valve according to a second embodiment of the present invention,  FIG. 9  is a perspective view of a main valve of the above-described flow path switching valve,  FIG. 10  through  FIG. 12  are views explaining the above-described flow path switching valve, in which the components and elements similar to those of the first embodiment are indicated by the same reference sign used in the first embodiment to eliminate the detailed explanation.  FIG. 11  is a view showing the main valve in while being switched. 
     The difference between the flow path switching valve according to the second embodiment and the flow path switching valve according to the first embodiment is the shape of the main valve  3 ′. As shown in  FIG. 9 , the main valve  3 ′, similar to that of the first embodiment, is a member made of resin and has a circular circumference, and is constituted of a flared portion  37  near a valve seat  21  and a cylindrical piston portion  32  which are formed in one. The piston portion  32  includes a shaft receiving portion  33 , an auxiliary valve seat  34 , a projection portion  35  and a stopper  36  having the same structure similar to those in the first embodiment. 
     The flared portion  37  is provided with an outdoor heat exchanger-side communication path  37 A and an indoor heat exchanger-side communication path  37 B bored into a dome-like shape at both sides of the shaft receiving portion  33 . There is also provided a partition portion  371  extending diametrically from the shaft receiving portion  33 , and the outdoor heat exchanger-side communication path  37 A is separated from the indoor heat exchanger-side communication path  37 B by this partition portion  371 . Furthermore, there are provided an outdoor heat exchanger-side communication path outer wall  372 A and an indoor heat exchanger-side communication path outer wall  372 B extending from an end portion of the partition portion  371  and arranged parallel to the partition portion  371 . The outdoor heat exchanger-side communication path outer wall  372 A corresponds to an outer wall of the outdoor heat exchanger-side communication path  37 A, and the indoor heat exchanger-side communication path outer wall  372 B corresponds to an outer wall of the indoor heat exchanger-side communication path  37 B. 
     Similar to the first embodiment, during the cooling operation as shown in  FIG. 10 , the D port  21 D is communicated with the C switching port  21 C by the outdoor heat exchanger-side communication path  37 A, and the S-port  21 S is communicated with the E switching port  21 E by the indoor heat exchanger-side communication path  37 B. Also, the outdoor heat exchanger-side pressure equalizing hole  34   a  is opened and the indoor heat exchanger-side pressure equalizing hole  34   b  is closed. Due to the high-pressure cooling medium introduced from the D port  21 D, a pressure of a space outside the main valve  3 ′ becomes high and a pressure of the indoor heat exchanger-side communication path  37 B becomes low. Therefore, the differential pressure acting on the main valve  3 ′ causes the main valve  3 ′ to be seated on the valve seat  21  in a closely contacted manner. 
     At a time of switching from the cooling operation state to the heating operation state, although in the first embodiment the compressor is at a stop, in the second embodiment the switching can be performed without stopping the compressor. First, when the drive unit portion  5  is activated, the auxiliary valve  4  rotates from a state shown in  FIG. 10B  in a clockwise direction, and the main valve abutting portion  46   b  of the auxiliary valve  4  abuts on the auxiliary valve abutting portion  35   b  of the main valve  3 ′ as shown in  FIG. 11B . Also, the indoor heat exchanger-side equalizing pressure hole  34   b  opens and the outdoor heat exchanger-side pressure equalizing hole  34   a  closes. Consequently, a pressure of the valve chamber  11  above the piston ring  32   a  provided at the piston portion  32  of the main valve  3 ′ gradually becomes low, and a pressure of a space outside the main valve  3 ′ below the piston ring  32   a  and a space inside the outdoor heat exchanger-side communication path  37 A increase, producing a lifting force by which the main valve  3 ′ is lifted against the pushing force of the coil spring  54 . Therefore, the differential pressure acting on the main valve  3 ′ decreases, and thus the pushing force by the coil spring  54  becomes larger than the lifting force of the main valve  3 ′, thereby the main valve  3 ′ is seated on the valve seat  21 . It is noted that even in this condition, as explained in reference with  FIG. 13 , a seating force of the main valve  3 ′ on the valve seat  21  is small. 
     At this time, since the main valve abutting portion  46   b  of the auxiliary valve  4  is abutted on the auxiliary valve abutting portion  35   b  of the main valve  3 ′, the auxiliary valve  4  rotates together with the main valve  3 ′. Then, the stopper  36  of the main valve  3 ′ abuts on the one end of the guiding groove  13  as shown in  FIG. 12A , and the rotation of the auxiliary valve  4  and the main valve  3 ′ are stopped to produce the heating operation state. In this heating operation state, as shown in  FIG. 12C , the D port  21 D is communicated with the E switching port  21 E by the indoor heat exchanger-side communication path  37 B, and the S-port  21 S is communicated with the C switching port  21 C by the outdoor heat exchanger-side communication path  37 A. Also, the indoor heat exchanger-side pressure equalizing hole  34   b  is opened and the outdoor heat exchanger-side pressure equalizing hole  34   a  is closed. The high-pressure cooling medium introduced from the D port  21 D causes a pressure of a space outside the main valve  3 ′ to be high as well as a pressure of the outdoor heat exchanger-side communication path  37 A to be low, and thus the main valve  3 ′ is seated onto the valve seat  21  in a closely contacted manner. When switching from the heating operation state to the cooling operation state can be achieved by the operation reverse of the above-described operation. 
     As described above, also in the second embodiment, the auxiliary valve  4  is required to be rotated only in one direction when switching from the cooling operation to the heating operation. Consequently, the inverse rotation of the auxiliary valve (refer to the afore-mentioned Patent Literature 1) is not in need, preventing the displacement of the main valve  3 ′. 
       FIG. 13  is a view explaining in detail a flow of the cooling medium in a switching process according to the second embodiment and shows the switching process from the cooling operation state to the heating operation state. As described above, the rotation of the auxiliary valve  4  causes the main valve  3 ′ to rotate in order according to  FIG. 13A  through  FIG. 13D .  FIG. 13B  shows a position rotated to half of the rotation range of the switching process, in which the outdoor heat exchanger-side communication path  37 A and the indoor heat exchanger-side communication path  37 B are partially overlapped with the D port  21 D and the S port  21 S, respectively. In addition, the outdoor heat exchanger-side communication path outer wall  372 A is arranged to cross over an opening of the C port  21 C communicated with the outdoor heat exchanger-side, and the indoor heat exchanger-side communication path outer wall  372 B is arranged to cross over an opening of the E port  21 E communicated with the indoor heat exchanger-side. 
     Therefore, the high-pressure cooling medium flowing from the D port  21 D flows into the outdoor heat exchanger-side communication path  37 A and the indoor heat exchanger-side communication path  37 B via the D port  21 D. Also, the high-pressure cooling medium flowing from the D port  21 D flows around the circumference of the main valve  3 ′ and flows into the S-port  21 S and flows into the outdoor heat exchanger-side communication path  37 A via the C-port  21 C, and flows into the indoor heat exchanger-side communication path  37 B via the E-port  21 E. This cooling medium flows into the outdoor heat exchanger-side communication path  37 A and the indoor heat exchanger-side communication path  37 B together flow into the S-port  21 S. Furthermore, as shown by arrows in  FIGS. 13A ,  13 C and  13 D, the condition in which the high-pressure cooling medium flows into the outdoor heat exchanger-side communication path  37 A and the indoor heat exchanger-side communication path  37 B, and further flows into the S-port  21 S, is almost the same for the positions before and after with respect to the half of rotation range. 
     As described above, since during the switching process the high-pressure cooling medium flows into both of the outdoor heat exchanger-side communication path  37 A and the indoor heat exchanger-side communication path  37 B, there is only a small force involved when the main valve  3 ′ is seated on the valve seat  21 , reducing a friction force between the main valve  3 ′ and the valve seat  21 . Consequently, even in a condition in which the compressor is operating, the switching can be achieved smoothly. 
     In the second embodiment described above, in a position of half of the rotation range of the main valve  3 ′ in the switching process and also in a process before and after that, the outdoor heat exchanger-side communication path outer wall  372 A and the indoor heat exchanger-side communication path outer wall  372 B are arranged so as to cross over the C-port  21 C and the E-port  21 E, thus the switching can be achieved even more smoothly. However, as shown in  FIG. 14 , the shape of the outdoor heat exchanger-side communication path outer wall  372 A′ and the indoor heat exchanger-side communication path outer wall  372 B′ may be similar to that of the first embodiment. In this case also, the outdoor heat exchanger-side communication path  37 A and the indoor heat exchanger-side communication path  37 B are partially overlapped on the D port  21 D and the S-port  21 S, respectively. Consequently, the high-pressure cooling medium flows from the D port  21 D into the outdoor heat exchanger-side communication path  37 A and the indoor heat exchanger-side communication path  37 B, thus the switching can be achieved smoothly even in a condition in which the compressor is operating. 
       FIG. 15  shows another embodiment of the auxiliary valve  4 , in which the auxiliary valve  4  and the main valve  3  (or the main valve  3 ′) are seen from the drive unit  5 . Although the occluding portion  43 A,  43 B is formed by the single slide valve portion  43  in the embodiment described above, the occluding portion  43 A and the occluding portion  43 B may be formed individually as shown in  FIG. 15A . Furthermore, as shown in  FIG. 15B , the two occluding portions  43 A,  43 B may be formed in 180 degrees apart, and two support portions  441 ,  442  may be formed therebetween. In this case, the position of the outdoor heat exchanger-side pressure equalizing hole  34   a  and the indoor heat exchanger-side pressure equalizing hole  34   b  may also be changed according to the rotation range of the auxiliary valve  4  and the position of the occluding portions  43 A,  43 B. 
     REFERENCE SIGNS LIST 
       1  case member 
       3 ,  3 ′ main valve 
       4  auxiliary valve 
       5  drive unit 
       11  valve chamber 
       21  valve seat 
       21 D D port 
       21 S S port 
       21 C C switching port 
       21 E E switching port 
       31 A outdoor heat exchanger-side communication path 
       31 B indoor heat exchanger-side communication path 
       34   a  outdoor heat exchanger-side pressure equalizing hole 
       34   b  indoor heat exchanger-side pressure equalizing hole 
       37 A outdoor heat exchanger-side communication path 
       37 B indoor heat exchanger-side communication path 
       371  partition portion 
       372 A outdoor heat exchanger-side communication path outer wall 
       372 B indoor heat exchanger-side communication path outer wall 
       43 A outdoor heat exchanger-side occluding portion 
       43 B indoor heat exchanger-side occluding portion 
       44  support portion