Patent Publication Number: US-2022221204-A1

Title: Refrigeration cycle apparatus and four-way valve

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2020/036324, filed on Sep. 25, 2020, which claims priority under 35 U.S.C. 119(a) to Patent Application No. 2019-180596, filed in Japan on Sep. 30, 2019, all of which are hereby expressly incorporated by reference into the present application. 
    
    
     TECHNICAL FIELD 
     A refrigeration cycle apparatus including a switching mechanism that redirects a flow of refrigerant is herein disclosed. A four-way valve that redirects a flow of refrigerant is also herein disclosed. 
     BACKGROUND ART 
     Some refrigeration cycle apparatuses put into practical use are configured such that a four-way valve redirects a flow of refrigerant. For example, a technique disclosed in PTL 1 (Japanese Unexamined Patent Application Publication No. 2018-123972) concerns a rotary-type four-way switching valve (four-way valve) for redirecting a flow of refrigerant in a refrigeration cycle apparatus or, more specifically, an air conditioning apparatus. The air conditioning apparatus described in PTL 1 is configured such that the four-way valve redirects a flow of refrigerant to enable switching between cooling operation and heating operation. 
     SUMMARY 
     According to one aspect, a refrigeration cycle apparatus includes a compressor, a first heat exchanger, a second heat exchanger, and a switching mechanism. The compressor sucks in refrigerant, compresses the refrigerant, and then discharges the refrigerant. The first heat exchanger functions as a radiator in a first cycle and functions as an evaporator in a second cycle. The second heat exchanger functions as an evaporator in the first cycle and functions as a radiator in the second cycle. The switching mechanism includes a first channel and performs switching among a first connection state, a second connection state, and a third connection state. In the first connection state, the refrigeration cycle apparatus repeatedly performs the first cycle in which refrigerant flows through the compressor, the first heat exchanger, the second heat exchanger, and the compressor in that order. In the second connection state, the refrigeration cycle apparatus repeatedly performs the second cycle in which refrigerant flows through the compressor, the second heat exchanger, the first heat exchanger, and the compressor in that order. In the third connection state, a passage between the compressor and the first heat exchanger and a passage between the compressor and the second heat exchanger are closed, and the first channel in the refrigeration cycle apparatus provides interconnection between the first heat exchanger and the second heat exchanger. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a circuit diagram illustrating a first connection state of a refrigeration cycle apparatus according to a first embodiment. 
         FIG. 2  is a circuit diagram illustrating a second connection state of the refrigeration cycle apparatus according to the first embodiment. 
         FIG. 3  is a block diagram for explanation of a controller according to the first embodiment. 
         FIG. 4  is a circuit diagram illustrating a first connection state of a refrigeration cycle apparatus according to a second embodiment. 
         FIG. 5  is a circuit diagram illustrating a third connection state of a refrigeration cycle apparatus according to the second embodiment. 
         FIG. 6  is a circuit diagram illustrating a second connection state of a refrigeration cycle apparatus according to the second embodiment. 
         FIG. 7  is a block diagram for explanation of a controller according to the second embodiment. 
         FIG. 8  is a circuit diagram illustrating a first connection state of a refrigeration cycle apparatus according to a third embodiment. 
         FIG. 9  is a circuit diagram illustrating a third connection state of the refrigeration cycle apparatus according to the third embodiment. 
         FIG. 10  is a circuit diagram illustrating a second connection state of the refrigeration cycle apparatus according to the third embodiment. 
         FIG. 11  is a block diagram for explanation of a controller according to the third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     (1) Overview Referring to  FIGS. 1 and 2 , a refrigeration cycle apparatus  1  includes a compressor  10 , a first heat exchanger  20 , second heat exchangers  30 , and a switching mechanism  40 . The compressor  10  sucks in refrigerant, compresses the refrigerant, and then discharges the refrigerant. The first heat exchanger  20  functions as a radiator in a first cycle and functions as an evaporator in a second cycle. The second heat exchangers  30  each function as an evaporator in the first cycle and each function as a radiator in the second cycle.  FIG. 1  illustrates the operation of the refrigeration cycle apparatus  1  in operation in the first cycle.  FIG. 2  illustrates the operation of the refrigeration cycle apparatus  1  in operation in the second cycle. 
     The first heat exchanger  20  enables exchange of heat, for example, between outside air and refrigerant. The second heat exchangers  30  enables exchange of heat, for example, between room air and refrigerant. When the refrigeration cycle apparatus  1  operates in this operating condition, room air is cooled by the second heat exchangers  30  in the first cycle to cool a room, and room air is heated by the second heat exchangers  30  in the second cycle to heat the room. In such a case, the refrigeration cycle apparatus  1  is an air conditioner. The following describes embodiments in which the refrigeration cycle apparatus  1  is an air conditioner; however, it is not required that the refrigeration cycle apparatus  1  be an air conditioner. Refrigerant circulates through the refrigeration cycle apparatus  1 , which can repeatedly perform a vapor compression refrigeration cycle accordingly. The refrigeration cycle apparatus is applicable to, for example, heat pump water heaters, refrigerators, and coolers that provide cooling for warehouses. 
     The switching mechanism  40  performs switching among a first connection state, a second connection state, and a third connection state. In the first connection state, the refrigeration cycle apparatus  1  repeatedly performs the first cycle, in which refrigerant flows through the compressor  10 , the first heat exchanger  20 , the second heat exchangers  30 , and the compressor  10  in this order. In the second connection state, the refrigeration cycle apparatus  1  repeatedly performs the second cycle, in which refrigerant flows through the compressor  10 , the second heat exchangers  30 , the first heat exchanger  20 , and the compressor  10  in this order. In the third connection state, the refrigeration cycle apparatus  1  closes a passage between the compressor  10  and the first heat exchanger  20  and a passage between the compressor  10  and the second heat exchangers  30 . The refrigeration cycle apparatus  1  in the third connection state opens a first channel F 1  to provide interconnection between the first heat exchanger  20  and the second heat exchangers  30 . The workings of each component of the refrigeration cycle apparatus  1  in the first connection state, the second connection state, and the third connection state will be described later. 
     The switching mechanism  40  of the refrigeration cycle apparatus  1  goes through the third connection state while performing switching between the first connection state and the second connection state. In the third connection state, the first heat exchanger  20  can communicate with the second heat exchangers  30  through the first channel F 1 . Consequently, the difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  30  is reduced at the time of switching between the first connection state and the second connection state. In this way, the refrigeration cycle apparatus  1  eliminates or reduces the possibility that a large quantity of refrigerant will flow out of the first heat exchanger  20  or the second heat exchangers  30  and into a low-pressure site. 
     (2) Details on Configuration 
     (2-1) Overview of Switching Mechanism  40  of Refrigeration Cycle Apparatus  1   
     The switching mechanism  40  of the refrigeration cycle apparatus  1  includes a first port  41 , a second port  42 , a third port  43 , and a fourth port  44 . Refrigerant is compressed by the compressor  10  and then flows into the first port  41 . The second port  42  communicates with the first heat exchanger  20 . The refrigerant sucked into the compressor  10  flows out of the third port  43 . Referring to  FIGS. 1 and 2 , the refrigeration cycle apparatus  1  includes a receiver  11 , which forms a connection between the third port  43  and an inlet of the compressor  10 . The fourth port  44  communicates with the second heat exchangers  30 . 
     The switching mechanism  40  in the first connection state is as illustrated in  FIG. 1 , in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 . The switching mechanism  40  in the second connection state is as illustrated in  FIG. 2 , in which the first port  41  communicates with the fourth port  44 , and the second port  42  communicates with the third port  43 . 
     (2-2) Configuration of Switching Mechanism  40   
     Referring to  FIGS. 1 and 2 , the switching mechanism  40  includes a four-way valve  46 , a first on-off valve  51 , a second on-off valve  52 , a third on-off valve  53 , a fourth on-off valve  54 , a fifth on-off valve  55 , a sixth on-off valve  56 , a first bypass pipe P 1 , and a second bypass pipe P 2 . The four-way valve  46  is a slide-type switching valve including a valve element that slides along a straight line within the valve. The first bypass pipe P 1  and the first on-off valve  51  are included in the first channel F 1 . The second bypass pipe P 2  and the second on-off valve  52  are included in a second channel F 2 . The first bypass pipe P 1  communicates with the second port  42  and the fourth port  44 . The second bypass pipe P 2  communicates with the first port  41  and the third port  43 . 
     The first on-off valve  51  is provided to the first bypass pipe P 1 . The second on-off valve  52  is provided to the second bypass pipe P 2 . The first bypass pipe P 1  in the first connection state and the second connection state is closed by the first on-off valve  51  of the first channel F 1 . The second bypass pipe P 2  in the first connection state and the second connection state is closed by the second on-off valve  52  of the second channel F 2 . In the third connection state, the first on-off valve  51  and the second on-off valve  52  are opened, and the first bypass pipe P 1  and the second bypass pipe P 2  are opened accordingly. 
     The third on-off valve  53  is connected between an a-port  46   a  of the four-way valve  46  and a connection portion where an outlet of the compressor  10  is connected to the second bypass pipe P 2 . The fourth on-off valve  54  is connected between a b-port  46   b  of the four-way valve  46  and a connection portion where the second port  42  is connected to the first bypass pipe P 1 . The fifth on-off valve  55  is connected between a c-port  46   c  of the four-way valve  46  and a connection portion where the third port  43  is connected to the second bypass pipe P 2 . The fifth on-off valve  55  is connected between a d-port  46   d  of the four-way valve  46  and a connection portion where the fourth port  44  is connected to the first bypass pipe P 1 . 
     (2-3) Circuit Configuration of Refrigeration Cycle Apparatus  1  and Flow of Refrigerant in Circuit 
     Referring to  FIGS. 1 and 2 , the refrigeration cycle apparatus  1  includes the compressor  10 , the switching mechanism  40 , the first heat exchanger  20 , the second heat exchangers  30 , a first expansion valve  61 , a second expansion valve  62 , a third expansion valve  63 , and the receiver  11 . The refrigeration cycle apparatus  1  illustrated in  FIG. 1  includes two second heat exchangers, which are denoted by  31  and  32 , respectively. It is not required that two second heat exchangers  30  be included; that is, the refrigeration cycle apparatus  1  may include three or more second heat exchangers  30  or may include one second heat exchanger  30 . The following describes embodiments in which refrigerant in the refrigeration cycle apparatus  1  is carbon dioxide. It is not required that carbon dioxide be used as refrigerant in the refrigeration cycle apparatus  1 . The refrigerant to be used in the refrigeration cycle apparatus  1  may be a fluorocarbon refrigerant or an ammonia refrigerant. 
     When performing the first cycle, the refrigeration cycle apparatus  1  is in the first connection state. In the first connection state (i.e., the state illustrated in  FIG. 1 ), the first on-off valve  51  and the second on-off valve  52  are closed, and the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56  are opened. Refrigerant in a supercritical state is discharged from the outlet of the compressor  10  and flows into the first heat exchanger  20  by way of the first port  41  and the second port  42  of the switching mechanism  40 . In the first heat exchanger  20 , heat is exchanged between the high-temperature, high-pressure refrigerant and air such that heat is taken out of the refrigerant. The first expansion valve  61  is fully opened. A flow of refrigerant coming out of the first expansion valve  61  flows into the second expansion valve  62  and the third expansion valve  63 , where flows of refrigerant undergo decompression and expansion and then enter the second heat exchangers  31  and  32 , respectively. In a case in which one of the second heat exchangers  31  and  32  is not used, one of the second expansion valve  62  and the third expansion valve  63  is closed and the closed one corresponds to the unused one. In the second heat exchangers  31  and  32 , heat is exchanged between the low-temperature, low-pressure incoming refrigerant and air. After flowing out of the second heat exchangers  31  and  32 , the refrigerant flows into the receiver  11  by way of the fourth port  44  and the third port  43  of the switching mechanism  40 . While refrigerant in both liquid and gaseous form is retained in the receiver  11 , the compressor  10  sucks in gas refrigerant through its inlet. 
     When performing the second cycle, the refrigeration cycle apparatus  1  is in the second connection state. In the second connection state (i.e., the state illustrated in  FIG. 2 ), the first on-off valve  51  and the second on-off valve  52  are closed, and the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56  are opened. Refrigerant in a supercritical state is discharged from the outlet of the compressor  10  and flows into the second heat exchangers  31  and  32  by way of the first port  41  and the fourth port  44  of the switching mechanism  40 . In the second heat exchangers  31  and  32 , heat is exchanged between the high-temperature, high-pressure refrigerant and air such that heat is taken out of the refrigerant. The second expansion valve  62  and the third expansion valve  63  are fully opened. A flow of refrigerant coming out of the second expansion valve  62  or the third expansion valve  63  flows into the first expansion valve  61 , where the refrigerant undergoes decompression and expansion and then enters the first heat exchanger  20 . In a case in which one of the second heat exchangers  31  and  32  is not used, one of the second expansion valve  62  and the third expansion valve  63  is closed and the closed one corresponds to the unused one. In the first heat exchanger  20 , heat is exchanged between the low-temperature, low-pressure incoming refrigerant and air. After flowing out of the first heat exchanger  20 , the refrigerant flows into the receiver  11  by way of the second port  42  and the third port  43  of the switching mechanism  40 . While refrigerant in both liquid and gaseous form is retained in the receiver  11 , the compressor  10  sucks in gas refrigerant through its inlet. 
     (2-4) Switching Between First Cycle and Second Cycle of Refrigeration Cycle Apparatus  1   
     In the first embodiment, switching between the first connection state and the second connection state is performed to enable switching between the first cycle and the second cycle. The switching mechanism  40  goes through the third connection state while making a transition from the first connection state to the second connection state or while making a transition from the second connection state to the first connection state. In the third connection state, the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56  are closed, and the first on-off valve  51  and the second on-off valve  52  are then opened. 
     In the first connection state prior to a transition from the first connection state to the second connection state, the refrigerant is at high pressure when flowing through the first heat exchanger  20 , and the refrigerant is at low pressure when flowing through the second heat exchangers  31  and  32  (the second heat exchangers  30 ). In this case, the refrigerant is at high pressure when flowing through regions located downstream of the outlet of the compressor  10 , and the refrigerant is at low pressure when flowing through regions located upstream of the inlet of the compressor  10 . In the second connection state prior to a transition from the second connection state to the first connection state, the refrigerant is at low pressure when flowing through the first heat exchanger  20 , and the refrigerant is at high pressure when flowing through the second heat exchangers  31  and  32  (the second heat exchangers  30 ). In this case, the refrigerant is at high pressure when flowing through regions located downstream of the outlet of the compressor  10 , and the refrigerant is at low pressure when flowing through regions located upstream of the inlet of the compressor  10 . 
     The switching mechanism  40  goes through the third connection state while making a transition from the first connection state to the second connection state. When the switching mechanism  40  is in the third connection state, the refrigerant flows through the first channel F 1  (the first bypass pipe P 1  and the first on-off valve  51 ) and then flows into the first heat exchanger  20  and toward the second heat exchangers  31  and  32  (the second heat exchangers  30 ). The difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  31  and  32  (the second heat exchangers  30 ) is reduced or eliminated due to the flow of refrigerant from the first heat exchanger  20  to the second heat exchangers  31  and  32  (the second heat exchangers  30 ). 
     The switching mechanism  40  goes through the third connection state while making a transition from the second connection state to the first connection state. When the switching mechanism  40  is in the third connection state, the refrigerant flows through the first channel F 1  (the first bypass pipe P 1  and the first on-off valve  51 ) and then flows into the second heat exchangers  31  and  32  (the second heat exchangers  30 ) and toward the first heat exchanger  20 . The difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  31  and  32  (the second heat exchangers  30 ) is reduced or eliminated due to the flow of refrigerant from the second heat exchangers  31  and  32  (the second heat exchangers  30 ) to the first heat exchanger  20 . 
     When the switching mechanism  40  is in the third connection state, the refrigerant flows through regions located downstream of the outlet of the compressor  10  to the receiver  11  located upstream of the inlet of the compressor  10  by way of the second channel F 2  (the second bypass pipe P 2  and the second on-off valve  52 ). The difference between the pressure of refrigerant flowing through regions located downstream of the outlet of the compressor  10  and the pressure of refrigerant flowing through regions located upstream of the inlet of the compressor  10  is reduced or eliminated due to the flow of refrigerant from the compressor  10  to the receiver  11 . 
     (2-5) Control of Refrigeration Cycle Apparatus  1   
     The refrigeration cycle apparatus  1  according to the first embodiment includes a controller  90  (see  FIG. 3 ) to cause internal devices to implement the operation described above. The controller  90  is, for example, a computer. The computer includes, for example, a control arithmetic unit and a storage unit. The control arithmetic unit may be a processor. Referring to  FIG. 3 , the controller  90  includes a CPU  91 , which is a processor. For example, the control arithmetic unit reads a program stored in the storage unit and executes the program to perform predetermined processing, such as image processing, arithmetic processing, or sequential processing. The control arithmetic unit can also execute programs to record results of arithmetic operations onto the storage unit and to read information stored in the storage unit. The storage unit may be used as a database. Memory  92  is included as the storage unit in the controller  90 . 
     The controller  90  controls the compressor  10 , the first expansion valve  61 , the second expansion valve  62 , the third expansion valve  63 , and the switching mechanism  40 . The controller  90  controls the four-way valve  46  and six valves (the first on-off valve  51 , the second on-off valve  52 , the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) such that switching of the switching mechanism  40  is controlled. The six valves (the first on-off valve  51 , the second on-off valve  52 , the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) may each be an electromagnetic valve that is capable of switching between the opened state and the closed state in accordance with a signal from the controller  90 . 
     In the first connection state, the controller  90  sets the four-way valve  46  into the state illustrated in  FIG. 1 , in which the a-port  46   a  communicates with the b-port  46   b,  and the c-port  46   c  communicates with the d-port  46   d.  In the first connection state, the controller  90  sets the on-off valves into the state in which the first on-off valve  51  and the second on-off valve  52  are closed, and the other on-off valves (the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) are opened. When a transition from the first connection state to the third connection state takes place, the controller  90  causes the four on-off valves (the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) to close, with the four-way valve  46  remaining in the first connection state. The controller  90  then causes the first on-off valve  51  and the second on-off valve  52  to open. When a transition from the third connection state to the second connection state takes place, the controller  90  causes the first on-off valve  51  and the second on-off valve  52  to close. The controller  90  then sets the four-way valve  46  into the state illustrated in  FIG. 2 , in which the a-port  46   a  communicates with the d-port  46   d,  and the c-port  46   c  communicates with the b-port  46   b.  In this state, the controller  90  causes the four on-off valves (the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) to open. 
     In the second connection state, the controller  90  sets the four-way valve  46  into the state illustrated in  FIG. 2 . In the second connection state, the controller  90  sets the on-off valves into the state in which the first on-off valve  51  and the second on-off valve  52  are closed, and the other on-off valves (the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) are opened. When a transition from the second connection state to the third connection state takes place, the controller  90  causes the four on-off valves (the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) to close, with the four-way valve  46  remaining in the second connection state. The controller  90  then causes the first on-off valve  51  and the second on-off valve  52  to open. When a transition from the third connection state to the second connection state takes place, the controller  90  causes the first on-off valve  51  and the second on-off valve  52  to close. The controller  90  then sets the four-way valve  46  into the state illustrated in  FIG. 1  and causes the four on-off valves (the third on-off valve  53 , the fourth on-off valve  54 , the fifth on-off valve  55 , and the sixth on-off valve  56 ) to open. 
     Second Embodiment 
     (3) Overview 
     As with the refrigeration cycle apparatus  1  according to the first embodiment (see  FIGS. 1 and 2 ), a refrigeration cycle apparatus  1  according to a second embodiment (see  FIGS. 4, 5, and 6 ) includes a compressor  10 , a first heat exchanger  20 , second heat exchangers  30 , and a switching mechanism  40 . The overview of the refrigeration cycle apparatus  1  according to the first embodiment has been described above under the heading “(1) Overview”, which also holds true for the refrigeration cycle apparatus  1  according to the second embodiment and will not be further elaborated here. 
     (4) Details on Configuration 
     (4-1) Overview of Switching Mechanism  40  of Refrigeration Cycle Apparatus  1   
     Referring to  FIGS. 4 to 6 , the switching mechanism  40  of the refrigeration cycle apparatus  1  includes a first port  41 , a second port  42 , a third port  43 , and a fourth port  44 . Refrigerant is compressed by the compressor  10  and then flows into the first port  41 . The second port  42  communicates with the first heat exchanger  20 . The refrigerant flows through the third port  43  and is then sucked into the compressor  10 . Referring to  FIGS. 4 and 6 , the refrigeration cycle apparatus  1  includes a receiver  11 , which forms a connection between the third port  43  and an inlet of the compressor  10 . The fourth port  44  communicates with the second heat exchangers  30 . 
     The switching mechanism  40  in the first connection state is as illustrated in  FIG. 4 , in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 . The switching mechanism  40  in the third connection state is as illustrated in  FIG. 5 , in which the second port  42  communicates with the fourth port  44 , and the first port  41  communicates with the third port  43 . The switching mechanism  40  in the second connection state is as illustrated in  FIG. 6 , in which the first port  41  communicates with the fourth port  44 , and the second port  42  communicates with the third port  43 . 
     (4-2) Configuration of Switching Mechanism  40   
     Referring to  FIGS. 4 and 6 , the switching mechanism  40  includes a four-way valve  47 , a first on-off valve  51 , a second on-off valve  52 , a first bypass pipe P 1 , and a second bypass pipe P 2 . The four-way valve  47  is a rotary-type switching valve including a valve element  47   v  that rotates within the valve. That is, the four-way valve  47  is a rotary valve. The valve element  47   v  includes a first inner flow path  47   a  and a second inner flow path  47   b.  The valve element  47   v  is powered by a motor  47   m  (see  FIG. 7 ) to rotate. The valve element  47   v  of the four-way valve  47  rotates 90 degrees to enable switching between the first connection state and the second connection state. The valve element  47   v  of the four-way valve  47  can rotate 90 degrees to effect a transition from one state (in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 ) to another state (in which the first port  41  communicates with the fourth port  44 , and the second port  42  communicates with the third port  43 ). The valve element  47   v  of the four-way valve  47  can rotate 45 degrees to effect a transition from the first connection state to the third connection state or a transition from the second connection state to the third connection state. Although an embodiment will be described in which the valve element  47   v  rotates 90 degrees or 45 degrees, the angle of rotation required for switching of the four-way valve  47  is not limited to these degrees. In some embodiments, the switching of the four-way valve  47  is effected by rotation to a desired angle. 
     The first bypass pipe P 1  and the first on-off valve  51  are included in a first channel F 1 . The second bypass pipe P 2  and the second on-off valve  52  are included in a second channel F 2 . The first bypass pipe P 1  communicates with the second port  42  and the fourth port  44 . The second bypass pipe P 2  communicates with the first port  41  and the third port  43 . 
     The first on-off valve  51  is provided to the first bypass pipe P 1 . The second on-off valve  52  is provided to the second bypass pipe P 2 . The first bypass pipe P 1  in the first connection state and the second connection state is closed by the first on-off valve  51  of the first channel F 1 . The second bypass pipe P 2  in the first connection state and the second connection state is closed by the second on-off valve  52  of the second channel F 2 . In the third connection state, the first on-off valve  51  and the second on-off valve  52  are opened, and the first bypass pipe P 1  and the second bypass pipe P 2  are opened accordingly. 
     (4-3) Circuit Configuration of Refrigeration Cycle Apparatus  1  and Flow of Refrigerant in Circuit 
     The difference between the circuit configuration of the refrigeration cycle apparatus  1  according to the first embodiment and the circuit configuration of the refrigeration cycle apparatus  1  according to the second embodiment is in the internal configuration of the switching mechanism  40 , and the circuit configuration in the second embodiment is otherwise identical to the circuit configuration in the first embodiment. Thus, the circuit configuration of the refrigeration cycle apparatus  1  according to the second embodiment and the flow of refrigeration cycle apparatus in the circuit will not be further elaborated here. 
     (4-4) Switching between First Cycle and Second Cycle of Refrigeration Cycle Apparatus  1   
     In the first embodiment, switching between the first connection state and the second connection state is performed to enable switching between the first cycle and the second cycle. The same holds true for the second embodiment. The switching mechanism  40  goes through the third connection state while making a transition from the first connection state to the second connection state or while making a transition from the second connection state to the first connection state. The valve element  47   v  rotates 45 degrees to effect a transition from the first connection state to the third connection state or a transition from the second connection state to the third connection state. Once the valve element  47   v  completes a 45-degree turn, the first inner flow path  47   a  and the second inner flow path  47   b  are connected to none of the four ports (the first port  41 , the second port  42 , the third port  43 , and the fourth port  44 ). In other words, the valve element  47   v  does not provide interconnection between the four ports (the first port  41 , the second port  42 , the third port  43 , and the fourth port  44 ). When a transition from the first connection state to the third connection state or a transition from the second connection state to the third connection state takes place, the switching mechanism  40  opens the first on-off valve  51  and the second on-off valve  52  after the rotation of the valve element  47   v.    
     When the switching mechanism  40  in the second embodiment goes through the third connection state, the difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  31  and  32  (the second heat exchangers  30 ) is reduced or eliminated, as has been described above in relation to the first embodiment. When the switching mechanism  40  in the second embodiment goes through the third connection state, the difference between the pressure of refrigerant flowing through regions located downstream of the outlet of the compressor  10  and the pressure of refrigerant flowing through regions located upstream of the inlet of the compressor  10  is reduced or eliminated, as has been described above in relation to the first embodiment. 
     (4-5) Control of Refrigeration Cycle Apparatus  1   
     The refrigeration cycle apparatus  1  according to the second embodiment includes a controller  90  (see  FIG. 7 ) to cause internal devices to implement the operation described above. A CPU 91  and memory  92  are included as a processor and a storage unit, respectively, in the controller  90  according to the second embodiment, as in the controller  90  according to the first embodiment. 
     The difference between the controller  90  according to the first embodiment and the controller  90  according to the second embodiment is in the control of the switching mechanism  40 . The following describes the way the controller  90  controls the switching mechanism  40 . The controller  90  according to the second embodiment controls the four-way valve  47 , the first on-off valve  51 , and the second on-off valve  52  such that switching of the switching mechanism  40  is controlled. The first on-off valve  51  and the second on-off valve  52  may each be an electromagnetic valve that is capable of switching between the opened state and the closed state in accordance with a signal from the controller  90 . The motor  47   m  provided to the four-way valve  47  may be a stepping motor capable of adjusting the angle of rotation in accordance with a signal from the controller  90 . 
     In the first connection state, the controller  90  sets the four-way valve  47  into the state illustrated in  FIG. 4 , in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 . Under the control of the controller  90 , the first on-off valve  51  and the second on-off valve  52  in the first connection state are kept in the closed state. When a transition from the first connection state to the third connection state takes place, the controller  90  controls the motor  47   m  in such a manner that the valve element  47   v  of the four-way valve  47  rotates 45 degrees (see  FIG. 5 ). The controller  90  then causes the first on-off valve  51  and the second on-off valve  52  to open. When a transition from the third connection state to the second connection state takes place, the controller  90  causes the first on-off valve  51  and the second on-off valve  52  to close. The controller  90  then causes the valve element  47   v  of the four-way valve  47  to rotate 45 degrees, where a 90-degree turn relative to the valve element  47   v  in the first connection state is made. The switching mechanism  40  is thus brought into the state illustrated in  FIG. 6 , in which the first port  41  communicates with the fourth port  44 , and the third port  43  communicates with the second port  42 . 
     In the second connection state, the controller  90  may, for example, set the four-way valve  47  into the state illustrated in  FIG. 6 . Under the control of the controller  90 , the first on-off valve  51  and the second on-off valve  52  in the second connection state are kept in the closed state. When a transition from the second connection state to the third connection state takes place, the controller  90  controls the motor  47   m  in such a manner that the valve element  47   v  of the four-way valve  47  rotates 45 degrees (see  FIG. 5 ). The controller  90  then causes the first on-off valve  51  and the second on-off valve  52  to open. When a transition from the third connection state to the first connection state takes place, the controller  90  causes the first on-off valve  51  and the second on-off valve  52  to close. The controller  90  then causes the valve element  47   v  of the four-way valve  47  to rotate 45 degrees, where a 90-degree turn relative to the valve element  47   v  in the second connection state is made. The switching mechanism  40  is thus brought into the state illustrated in  FIG. 4 , in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 . 
     The valve element  47   v  described above rotates counterclockwise to effect a transition from the first connection state to the second connection state and rotates clockwise to effect a transition from the second connection state to the first connection state. It is not required that the rotation of the valve element  47   v  be controlled in the manner mentioned above. In some embodiments, the valve element  47   v  under the control of the controller  90  rotates clockwise to effect a transition from the first connection state to the second connection state and rotates clockwise to effect a transition from the second connection state to the first connection state. 
     Third Embodiment 
     (5) Overview 
     As with the refrigeration cycle apparatus  1  according to the first embodiment (see  FIGS. 1 and 2 ), a refrigeration cycle apparatus  1  according to a third embodiment (see  FIGS. 8, 9, and 10 ) includes a compressor  10 , a first heat exchanger  20 , second heat exchangers  30 , and a switching mechanism  40 . The overview of the refrigeration cycle apparatus  1  according to the first embodiment has been described above under the heading “(1) Overview”, which also holds true for the refrigeration cycle apparatus  1  according to the third embodiment and will not be further elaborated here. 
     (6) Details on Configuration 
     (6-1) Overview of Switching Mechanism  40  of Refrigeration Cycle Apparatus  1   
     Referring to  FIGS. 8 to 10 , the switching mechanism  40  of the refrigeration cycle apparatus  1  includes a first port  41 , a second port  42 , a third port  43 , and a fourth port  44 . Refrigerant is compressed by the compressor  10  and then flows into the first port  41 . The second port  42  communicates with the first heat exchanger  20 . The refrigerant flows through the third port  43  and is then sucked into the compressor  10 . Referring to  FIGS. 8 and 10 , the refrigeration cycle apparatus  1  includes a receiver  11 , which forms a connection between the third port  43  and an inlet of the compressor  10 . The fourth port  44  communicates with the second heat exchangers  30 . 
     The switching mechanism  40  in the first connection state is as illustrated in  FIG. 8 , in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 . The switching mechanism  40  in the third connection state is as illustrated in  FIG. 9 , in which the second port  42  communicates with the fourth port  44 , and the first port  41  communicates with the third port  43 . The switching mechanism  40  in the second connection state is as illustrated in  FIG. 10 , in which the first port  41  communicates with the fourth port  44 , and the second port  42  communicates with the third port  43 . 
     (6-2) Configuration of Switching Mechanism  40   
     Referring to  FIGS. 8 and 10 , the switching mechanism  40  includes a four-way valve  48 . The first port  41 , the second port  42 , the third port  43 , and the fourth port  44  of the switching mechanism  40  are also regarded as a first port  41 , a second port  42 , a third port  43 , and a fourth port  44  of the four-way valve  48 . The four-way valve  48  is a rotary-type switching valve including a valve element  48   v  that rotates within the valve. That is, the four-way valve  48  is a rotary valve. The valve element  48   v  includes a first inner flow path  48   a,  a second inner flow path  48   b,  a first bypass channel  48   c,  and a second bypass channel  48   d.  The first inner flow path  48   a,  the second inner flow path  48   b,  the first bypass channel  48   c,  and the second bypass channel  48   d  are channels provided in the valve element  48   v,  which is rotatable. The four-way valve  48  is designed such that the first bypass channel  48   c  and each of the first inner flow path  48   a,  the second inner flow path  48   b,  and the second bypass channel  48   d  cross at different levels. Thus, the first inner flow path  48   a,  the second inner flow path  48   b,  the first bypass channel  48   c,  and the second bypass channel  48   d  do not communicate with each other within the valve element  48   v.  The Cv value of the first bypass channel  48   c  is greater than the Cv value of the second bypass channel  48   d.  More specifically, the valve element  48   v  is designed such that the flow path cross-sectional area of the first bypass channel  48   c  is greater than the flow path cross-sectional area of the second bypass channel  48   d.    
     The valve element  48   v  is powered by a motor  48   m  (see  FIG. 11 ) to rotate. The valve element  48   v  of the four-way valve  48  rotates 90 degrees to enable switching between the first connection state and the second connection state. The valve element  48   v  of the four-way valve  48  can rotate 90 degrees to effect a transition from one state (in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 ) to another state (in which the first port  41  communicates with the fourth port  44 , and the second port  42  communicates with the third port  43 ). The valve element  48   v  of the four-way valve  48  can rotate 45 degrees to effect a transition from the first connection state to the third connection state or a transition from the second connection state to the third connection state. Although an embodiment will be described in which the valve element  48   v  rotates 90 degrees or 45 degrees, the angle of rotation required for switching of the four-way valve  48  is not limited to these degrees. In some embodiments, the switching of the four-way valve  48  is effected by rotation to a desired angle. 
     The second port  42  communicates with the fourth port  44  through the first bypass channel  48   c  when the valve element  48   v  is in the state illustrated in  FIG. 9  (the third connection state). The first port  41  communicates with the third port  43  through the second bypass channel  48   d  when the valve element  48   v  is in the state illustrated in  FIG. 9  (the third connection state). In the first connection state (see  FIG. 8 ) and the second connection state (see  FIG. 10 ), neither the first bypass channel  48   c  nor the second bypass channel  48   d  is connected to the outside of the valve element  48   v;  that is, the first bypass channel  48   c  and the second bypass channel  48   d  are blocked. The first bypass channel  48   c  and the second bypass channel  48   d  in the third embodiment are thus analogous to the first channel F 1  and the second channel F 2 , respectively. 
     (6-3) Circuit Configuration of Refrigeration Cycle Apparatus  1  and Flow of Refrigerant in Circuit 
     The difference between the circuit configuration of the refrigeration cycle apparatus  1  according to the first embodiment and the circuit configuration of the refrigeration cycle apparatus  1  according to the third embodiment is in the internal configuration of the switching mechanism  40 , and the circuit configuration in the third embodiment is otherwise identical to the circuit configuration in the first embodiment. Thus, the circuit configuration of the refrigeration cycle apparatus  1  according to the third embodiment and the flow of refrigeration cycle apparatus in the circuit will not be further elaborated here. 
     (6-4) Switching between First Cycle and Second Cycle of Refrigeration Cycle Apparatus  1   
     In the first embodiment, switching between the first connection state and the second connection state is performed to enable switching between the first cycle and the second cycle. The same holds true for the third embodiment. The switching mechanism  40  goes through the third connection state while making a transition from the first connection state to the second connection state or while making a transition from the second connection state to the first connection state. The valve element  48   v  rotates 45 degrees to effect a transition from the first connection state to the third connection state or a transition from the second connection state to the third connection state. Once the valve element  48   v  completes a 45-degree turn, the first inner flow path  48   a  and the second inner flow path  48   b  are connected to none of the four ports (the first port  41 , the second port  42 , the third port  43 , and the fourth port  44 ). In other words, the four ports (the first port  41 , the second port  42 , the third port  43 , and the fourth port  44 ) do not communicate with each other through either the first inner flow path  48   a  or the second inner flow path  48   b.  The switching mechanism  40  in the third connection state allows the second port  42  to communicate with the fourth port  44  through the first bypass channel  48   c.  The switching mechanism  40  in the third connection state also allows the first port  41  to communicate with the third port  43  through the second bypass channel  48   d.    
     When the switching mechanism  40  in the third embodiment goes through the third connection state, the difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  31  and  32  (the second heat exchangers  30 ) is reduced or eliminated, as has been described above in relation to the first embodiment. When the switching mechanism  40  in the third embodiment goes through the third connection state, the difference between the pressure of refrigerant flowing through regions located downstream the outlet of the compressor  10  and the pressure of refrigerant flowing through regions located upstream of the inlet of the compressor  10  is reduced or eliminated, as has been described above in relation to the first embodiment. 
     (6-5) Control of Refrigeration Cycle Apparatus  1   
     The refrigeration cycle apparatus  1  according to the third embodiment includes a controller  90  (see  FIG. 11 ) to cause internal devices to implement the operation described above. A CPU 91  and memory  92  are included as a processor and a storage unit, respectively, in the controller  90  according to the third embodiment, as in the controller  90  according to the first embodiment. 
     The difference between the controller  90  according to the first embodiment and the controller  90  according to the third embodiment is in the control of the switching mechanism  40 . The following describes the way the controller  90  controls the switching mechanism  40 . The controller  90  according to the third embodiment controls the four-way valve  48  such that switching of the switching mechanism  40  is controlled. The motor  48   m  provided to the four-way valve  48  may be a stepping motor capable of adjusting the angle of rotation in accordance with a signal from the controller  90 . Signals of different frequencies may be used such that the rotational speed of the stepping motor provided as the motor  48   m  may be changed in accordance with the frequency of the signal input to the motor  48   m.  A different approach may be adopted to change the rotational speed of the motor  48   m.  For example, gears for transmitting rotation of the motor  48   m  may be disposed, in which case the rotational speed can be changed in accordance with the gear ratio. 
     For example, the refrigeration cycle apparatus  1  is configured such that the rotational speed decreases when there is a significant difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  30 . This feature of the refrigeration cycle apparatus  1  offers the following advantage: the lower the rotational speed is, the longer the duration of the third connection state is. Conversely, the refrigeration cycle apparatus  1  is configured such that the rotational speed increases when there is a little difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  30 . This feature of the refrigeration cycle apparatus  1  offers the following advantage: the higher the rotational speed is, the shorter the time it takes to enable switching between the first connection state and the second connection state is. 
     In the first connection state, the controller  90  sets the four-way valve  48  into the state illustrated in  FIG. 8 , in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 . When a transition from the first connection state to the third connection state takes place, the controller  90  controls the motor  48   m  in such a manner that the valve element  48   v  of the four-way valve  48  rotates 45 degrees (see  FIG. 9 ). When a transition from the third connection state to the second connection state takes place, the controller  90  causes the valve element  48   v  of the four-way valve  48  to rotate 45 degrees, where a 90-degree turn relative to the valve element  48   v  in the first connection state is made. The switching mechanism  40  is thus brought into the state illustrated in  FIG. 10 , in which the first port  41  communicates with the fourth port  44 , and the third port  43  communicates with the second port  42 . 
     In the second connection state, the controller  90  sets the four-way valve  48  into the state illustrated in  FIG. 10 . When a transition from the second connection state to the third connection state takes place, the controller  90  controls the motor  48   m  in such a manner that the valve element  48   v  of the four-way valve  48  rotates 45 degrees (see  FIG. 9 ). When a transition from the third connection state to the first connection state takes place, the controller  90  causes the valve element  48   v  of the four-way valve  48  to rotate 45 degrees, where a 90-degree turn relative to the valve element  48   v  in the second connection state is made. The switching mechanism  40  is thus brought into the state illustrated in  FIG. 8 , in which the first port  41  communicates with the second port  42 , and the third port  43  communicates with the fourth port  44 . 
     The valve element  48   v  described above rotates counterclockwise to effect a transition from the first connection state to the second connection state and rotates clockwise to effect a transition from the second connection state to the first connection state. It is not required that the rotation of the valve element  48   v  be controlled in the manner mentioned above. In some embodiments, the valve element  48   v  under the control of the controller  90  rotates clockwise to effect a transition from the first connection state to the second connection state and rotates clockwise to effect a transition from the second connection state to the first connection state. 
     (7) Modifications 
     (7-1) Modifications  1 A,  2 A, and  3 A 
     The refrigeration cycle apparatus  1  according to each of the first, second, and third embodiments described above uses carbon dioxide as refrigerant and is configured such that refrigerant in a supercritical state is discharged from the compressor  10 . It is not required that refrigerant brought into a supercritical state in the refrigeration cycle apparatus  1  be carbon dioxide. The refrigerant to be used in the refrigeration cycle apparatus  1  may be a fluorocarbon refrigerant. The refrigeration cycle apparatus  1  may use R23 as refrigerant and may be configured such that refrigerant in a supercritical state is discharged from the compressor  10 . 
     (7-2) Modifications  1 B,  2 B, and  3 B 
     The refrigeration cycle apparatus  1  according to each of the first, second, and third embodiments described above is configured such that refrigerant in a supercritical state is discharged from the compressor  10 . It is not required that refrigerant in a supercritical state be discharged from the compressor  10 , and the refrigeration cycle apparatus  1  may be configured such that refrigerant in gaseous form is discharged from the compressor  10 . 
     (8) Features 
     (8-1) 
     As described above, the refrigeration cycle apparatus  1  goes through the third connection state while the switching mechanism  40  of the refrigeration cycle apparatus  1  performs switching between the first connection state and the second connection state of the refrigeration cycle apparatus  1 . In the third connection state, the first channel F 1  provides intercommunication between the first heat exchanger  20  and the second heat exchangers  30 . The refrigeration cycle apparatus  1  is configured such that the difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  30  is reduced at the time of switching between the first connection state and the second connection state. This eliminates or reduces the possibility that refrigerant under high pressure in the first heat exchanger  20  or the second heat exchangers  30  will flow out in large quantity into a low-pressure site such as the receiver  11  or the intake side (located upstream of the inlet) of the compressor  10  at the time of switching of the switching mechanism  40 . 
     (8-2) 
     The switching mechanism  40  of the refrigeration cycle apparatus  1  changes the intercommunication between four ports (the first port  41 , the second port  42 , the third port  43 , and the fourth port  44 ) to enable switching among the first connection state, the second connection state, and the third connection state. In the third connection state, refrigerant is allowed to flow through the second port  42  and the fourth port  44  such that the refrigerant can flow into and out of the first heat exchanger  20  and the second heat exchangers  30 . The refrigerant in the first heat exchanger  20  or the refrigerant in the second heat exchangers  30  is decompressed due to a transition to the third connection state. This eliminates or reduces the possibility that refrigerant in the first heat exchanger  20  or the second heat exchangers  30  will flow out in large quantity into a low-pressure site. 
     (8-3) 
     When the refrigeration cycle apparatus  1  according to the first embodiment or the second embodiment is in the third connection state, refrigerant is allowed to flow through the first bypass pipe P 1  and the first on-off valve  51 , that is, through the first channel F 1  such that the refrigerant can flow into and out of the first heat exchanger  20  and the second heat exchangers  30 . The high-pressure refrigerant in the first heat exchanger  20  and the high-pressure refrigerant in the second heat exchangers  30  are decompressed accordingly. This eliminates or reduces the possibility that a large quantity of refrigerant will flow out of the first heat exchanger  20  and into a low-pressure site such as the receiver  11  or the intake side of the compressor  10  when a transition to the second connection state is completed. This also eliminates or reduces the possibility that a large quantity of refrigerant will flow out of the second heat exchangers  30  and into the receiver  11  or the intake side of the compressor  10  when a transition to the first connection state is completed. The first embodiment and the second embodiment each adopt such a simple configuration or, more specifically, the first bypass pipe P 1  and the first on-off valve  51  to eliminate or reduce the possibility that a large quantity of refrigerant will flow into the receiver  11  or the intake side of the compressor  10  at the time of switching between the first connection state and the second connection state. 
     (8-4) 
     While the switching mechanism  40  performs switching between the first connection state and the second connection state, the refrigeration cycle apparatus  1  according the first embodiment or the second embodiment is brought into the third connection state, in which the second channel F 2  provides interconnection between the intake side (located upstream of the inlet) of the compressor  10  and the discharge side (located downstream of the outlet) of the compressor  10 . Consequently, refrigerant on the discharge side of the compressor  10  is decompressed. In this way, the refrigeration cycle apparatus  1  addresses problems associated with a flow of refrigerant from the discharge side of the compressor  10  to a low-pressure site at the time of switching between the first connection state and the second connection state. The effect of reducing noise (impulsive sound) is an advantage of reducing the flow of refrigerant from the discharge side of the compressor  10  to a low-pressure. 
     (8-5) 
     When the refrigeration cycle apparatus  1  according to the first embodiment or the second embodiment is in the third connection state, refrigerant is allowed to flow through the second bypass pipe P 2  and the second on-off valve  52 , that is, through the second channel F 2  such that the refrigerant can flow from the discharge side of the compressor  10  and into the intake side of the compressor  10 . The pressure on the discharge side of the compressor  10  is reduced accordingly. This eliminates or reduces the possibility that an upsurge in the flow of refrigerant from the discharge side of the compressor  10  to a low-pressure site will occur when a transition to the first connection state or to the second connection state is completed. The first embodiment and the second embodiment each adopt such a simple configuration or, more specifically, the second bypass pipe P 2  and the second on-off valve  52  to reduce the flow of refrigerant from the discharge side of the compressor  10  when a switching between the first connection state and the second connection state is performed. 
     (8-6) 
     When the refrigeration cycle apparatus  1  according to the third embodiment is in the third connection state, refrigerant is allowed to flow through the first bypass channel  48   c,  that is, the first channel F 1  such that the refrigerant can flow into and out of the first heat exchanger  20  and the second heat exchangers  30 . The high-pressure refrigerant in the first heat exchanger  20  and the high-pressure refrigerant in the second heat exchangers  30  are decompressed accordingly. This eliminates or reduces the possibility that a large quantity of refrigerant will flow out of the first heat exchanger  20  and into a low-pressure site such as the receiver  11  or the intake side of the compressor  10  when a transition to the second connection state is completed. This also eliminates or reduces the possibility that a large quantity of refrigerant will flow out of the second heat exchangers  30  and into the receiver  11  or the intake side of the compressor  10  when a transition to the first connection state is completed. The third embodiment adopts such a simple configuration or, more specifically, the first bypass channel  48   c  to eliminate or reduce the possibility that a large quantity of refrigerant will flow into the receiver  11  or the intake side of the compressor  10  at the time of switching between the first connection state and the second connection state. 
     (8-7) 
     When the refrigeration cycle apparatus  1  according to the third embodiment is in the third connection state, refrigerant is allowed to flow through the second bypass channel  48   d,  that is, the second channel F 2  such that the refrigerant can flow from the discharge side of the compressor  10  and into the intake side of the compressor  10 . The pressure on the discharge side of the compressor  10  is reduced accordingly. This eliminates or reduces the possibility that an upsurge in the flow of refrigerant from the discharge side of the compressor  10  to a low-pressure site will occur when a transition to the first connection state or to the second connection state is completed. The third embodiment adopts such a simple configuration or, more specifically, the second bypass channel  48   d  to reduce the flow of refrigerant from the discharge side of the compressor  10  when a switching between the first connection state and the second connection state is performed. 
     (8-8) 
     The refrigeration cycle apparatus  1  according to the third embodiment is configured such that the Cv value of the first bypass channel  48   c  is greater than the Cv value of the second bypass channel  48   d.  It is thus ensured that the time it takes to reduce the difference in the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  30  will not be much longer than the time it takes to reduce the pressure difference between the discharge side and the intake side of the compressor  10 . In other words, it is ensured that the time required to eliminate or reduce the pressure difference through the use of the first bypass channel  48   c  will not be much longer than the time required to eliminate or reduce the pressure difference through the use of the second bypass channel  48   d.  The duration of the third connection state will be shorter than if the Cv value of the first bypass channel  48   c  is equal to the Cv value of the second bypass channel  48   d.    
     The refrigeration cycle apparatus  1  according to the first embodiment and the refrigeration cycle apparatus  1  according to the second embodiment may be configured such that the Cv value of the first channel F 1  is greater than the Cv value of the second channel F 2 . Effects equivalent to those produced by the refrigeration cycle apparatus  1  according to the third embodiment may be achieved accordingly. 
     (8-9) 
     The switching mechanism  40  of the refrigeration cycle apparatus  1  according to the third embodiment may be a rotary valve designed such that the rotational speed of the valve element  48   v  is changeable. For example, the refrigeration cycle apparatus  1  is configured such that the rotational speed decreases when there is a significant difference between the pressure of refrigerant in the first heat exchanger  20  and the pressure of refrigerant in the second heat exchangers  30 . The lower the rotational speed is, the longer the duration of the third connection state is. When being configured such that the rotational speed is changed in accordance with the pressure difference, the refrigeration cycle apparatus  1  can operate in a manner so as to eliminate or reduce the pressure difference to a satisfactory degree no matter how large the pressure difference is. A pressure sensor may be disposed on the discharge side of the compressor  10  to measure the pressure of refrigerant in the first heat exchanger  20  or the pressure of refrigerant in each second heat exchanger  30 , whichever is higher. The controller  90  may be configured to acquire the measurements such that the rotational speed of the switching mechanism  40  is able to be changed in accordance with the pressure of refrigerant in the first heat exchanger  20  or the pressure of refrigerant in each second heat exchanger  30 , whichever is higher. 
     (8-10) 
     When the four-way valve  48  according to the third embodiment in the third connection state illustrated in  FIG. 9 , the second port  42  communicates with the fourth port  44  through the first bypass channel  48   c.  This enables a reduction in the difference between the pressure of refrigerant in a portion being part of the refrigerant circuit and connected to the second port  42  and the pressure of refrigerant in a portion being part of the refrigerant circuit and connected to the fourth port  44 . Such a simple configuration or, more specifically, the first bypass channel  48   c  of the four-way valve  48  is conducive to reducing the flow of refrigerant from the relevant portion of the refrigerant circuit (the portion connected to the second port  42  or the portion connected to the fourth port  44 ) to a low-pressure site. 
     (8-11) 
     When the four-way valve  48  according to the third embodiment in the third connection state illustrated in  FIG. 9 , the first port  41  communicates with the third port  43  through the second bypass channel  48   d.  This enables a reduction in the difference between the pressure of refrigerant in a portion being part of the refrigerant circuit and connected to the first port  41  and the pressure of refrigerant in a portion being part of the refrigerant circuit and connected to the third port  43 . Such a simple configuration or, more specifically, the second bypass channel  48   c  of the four-way valve  48  is conducive to reducing the flow of refrigerant from the relevant portion of the refrigerant circuit (the portion connected to the first port  41  or the portion connected to the third port  43 ) to a low-pressure site. 
     (8-12) 
     The four-way valve  48  according to the third embodiment is configured such that the Cv value of the first bypass channel  48   c  is greater than the Cv value of the second bypass channel  48   d.  It can be prevent that the time required to eliminate or reduce the pressure difference through the use of the first bypass channel  48   c  will not be much longer than the time required to eliminate or reduce the pressure difference through the use of the second bypass channel  48   d.  Consequently, the duration of the third connection state will be shorter than if the Cv value of the first bypass channel  48   c  is equal to the Cv value of the second bypass channel  48   d.    
     While the embodiments of the present disclosure have been described herein above, it is to be appreciated that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure presently or hereafter claimed. 
     EXPLANATION OF REFERENCES 
       1  refrigeration cycle apparatus 
       10  compressor 
       20  first heat exchanger 
       30  second heat exchanger 
       40  switching mechanism 
       41  first port 
       42  second port 
       43  third port 
       44  fourth port 
       48  four-way valve 
       48   c  first bypass channel 
       48   d  second bypass channel 
       51  first on-off valve 
       52  second on-off valve 
     F 1  first channel 
     F 2  second channel 
     P 1  first bypass pipe 
     P 2  second bypass pipe 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Unexamined Patent Application Publication No. 2018-123972