Patent Publication Number: US-9404681-B2

Title: Air-conditioning apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national stage application of PCT/JP2012/001501 filed on Mar. 5, 2012, and claims priority to, and incorporates by reference, Japanese Patent Application No. 2011-048960 filed on Mar. 7, 2011. 
     TECHNICAL FIELD 
     The present invention relates to air-conditioning apparatuses, and in particular, relates to a configuration for injecting a refrigerant into a refrigerant circuit of an air-conditioning apparatus. 
     BACKGROUND ART 
     A common air-conditioning apparatus is equipped with an outdoor unit having a compressor, a four-way valve serving as flow switching means for switching the flowing direction of a refrigerant, an outdoor heat exchanger and a pressure-reducing capillary tube connected to an outlet of the outdoor heat exchanger, and an electronic expansion valve that further reduces the pressure of the refrigerant after having passed through the capillary tube; and an indoor unit having an indoor heat exchanger. The aforementioned devices contained in the outdoor unit and the indoor unit are sequentially connected by refrigerant pipes in the form of a circuit, and the refrigerant circulates through the refrigerant circuit, whereby a refrigeration cycle is formed. When the indoor heat exchanger operates as an evaporator and the outdoor heat exchanger operates as a condenser, indoor cooling is achieved. On the other hand, when the indoor heat exchanger operates as a condenser and the outdoor heat exchanger operates as an evaporator, indoor heating is achieved. The four-way valve provided at the discharge side of the compressor switches the flowing direction of the refrigerant so that the refrigerant discharged from the compressor is condensed by the indoor heat exchanger or the outdoor heat exchanger. Fans are disposed near the indoor heat exchanger and the outdoor heat exchanger and send indoor air and outdoor air thereto, respectively. 
     In recent years, outdoor units that can be used in various ways and can be connected to various types of indoor units in accordance with users&#39; demands are in demand. In this case, since the capacity of and the amount of air for the indoor heat exchanger vary depending on the type of indoor unit, the amount of refrigerant for allowing the refrigeration cycle to exhibit maximum performance would also vary. In order to properly adjust the amount of refrigerant circulating through the refrigerant circuit, an excess-refrigerant container is provided in the refrigerant circuit for retaining an excess refrigerant. A receiver serving as this excess-refrigerant container is often disposed in a suction pipe of the compressor or at a position where a liquid refrigerant exists, such as a position between an outlet of the condenser and an inlet of the evaporator. 
     In the air-conditioning apparatus having such a configuration, if a large amount of refrigerant that covers the entire refrigerant circuit is to be injected into the refrigerant circuit during production or maintenance of the air-conditioning apparatus, the refrigerant is injected from a refrigerant injection port provided in the refrigerant circuit. In particular, a configuration is disclosed in which the refrigerant is injected into the refrigerant circuit from a refrigerant injection port provided in the suction pipe of the compressor, an inlet pipe of a heat exchanger, or an outlet pipe of the heat exchanger (e.g., see Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 5-312439 (paragraph 0025, FIG. 5) 
     SUMMARY OF INVENTION 
     Technical Problem 
     Among the devices constituting the refrigerant circuit of the air-conditioning apparatus, the refrigerant is retained mainly in the compressor, the heat exchanger, and the excess-refrigerant container. Therefore, upon injection of the refrigerant into the refrigerant circuit, it is necessary to inject the refrigerant so that the refrigerant flows into the devices in which a large amount of refrigerant is to be retained. In the apparatus in the conventional art, the refrigerant is injected from a certain location of the refrigerant circuit, such as from the refrigerant injection port provided in the suction pipe of the compressor, the inlet pipe of the heat exchanger, or the outlet pipe of the heat exchanger. Even if the refrigerant is injected from the refrigerant injection port provided at any of these locations, the electronic expansion valve, the capillary tube, and the like that are provided for reducing the pressure of the refrigerant in the refrigerant circuit act as pressure-reducing members, making it impossible to reliably inject the refrigerant into the aforementioned devices, in which the refrigerant is to be mainly retained, in a well-balanced manner within a short period of time. Specifically, it takes time for the refrigerant to pass through the pressure-reducing members, thus requiring a long time for the refrigerant injection process. In addition, the pressure-reducing members act as resistance that causes the refrigerant to be injected lopsidedly to a specific device, which is a problem in that a liquid-sealed state may possibly occur. When this liquid-sealed state occurs, a liquid refrigerant expands in response to a temperature change, sometimes causing an abnormal increase in internal pressure. 
     Furthermore, with regard to a separate-type air-conditioning apparatus in which the indoor unit installed indoors and the outdoor unit installed outdoors are separated from each other, there is a problem in that, when an amount of refrigerant required in the entire refrigerant circuit is to be injected into the outdoor unit, an optimal position for a refrigerant injection port for reliably injecting the refrigerant in a well-balanced manner is not clearly defined. 
     The present invention has been made to solve the aforementioned problems and an object thereof is to provide an air-conditioning apparatus in which an amount of refrigerant required in a refrigerant circuit is reliably injected into the refrigerant circuit in a well-balanced manner within a short period of time at an outdoor-unit side so that the occurrence of a liquid-sealed state can be prevented. 
     Solution to Problem 
     An air-conditioning apparatus according to the present invention includes an outdoor unit having outdoor devices including a compressor that compresses a refrigerant, a flow switching valve that switches a flowing direction of the refrigerant, an outdoor heat exchanger that exchanges heat between the refrigerant and outdoor air, a first expansion valve that reduces pressure of the refrigerant, an excess-refrigerant container that retains an excess refrigerant of the refrigerant, and a second expansion valve that reduces the pressure of the refrigerant; and an indoor unit having an indoor heat exchanger that exchanges heat between the refrigerant and indoor air. The outdoor devices and the indoor heat exchanger are sequentially connected by refrigerant pipes so that a refrigeration cycle is formed. The air-conditioning apparatus further includes an outdoor-heat-exchanger refrigerant injection port provided in the refrigerant pipe that is directly connected to the outdoor heat exchanger, and an excess-refrigerant-container refrigerant injection port provided in the refrigerant pipe that is directly connected to the excess-refrigerant container. 
     Advantageous Effects of Invention 
     In the air-conditioning apparatus according to the present invention, the refrigerant is injected into the outdoor heat exchanger from the outdoor-heat-exchanger refrigerant injection port, and the refrigerant is injected into the excess-refrigerant container from the excess-refrigerant-container refrigerant injection port, so that the refrigerant is injected into the outdoor heat exchanger and the excess-refrigerant container, which have large capacities, without the refrigerant being retained lopsidedly in one device in the refrigerant circuit. Thus, an amount of refrigerant required in the refrigerant circuit can be reliably injected thereto in a well-balanced manner within a short period of time, whereby a safe air-conditioning apparatus that prevents the occurrence of a liquid-sealed state is obtained. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a refrigerant circuit of an air-conditioning apparatus according to Embodiment 1 of the present invention. 
         FIG. 2  is a pressure-versus-specific-enthalpy graph of a refrigeration cycle according to Embodiment 1 of the present invention. 
         FIG. 3  includes schematic diagrams illustrating refrigerant injection ports according to Embodiment 1 of the present invention. 
         FIG. 4  is a schematic diagram illustrating another exemplary configuration of the air-conditioning apparatus according to Embodiment 1 of the present invention. 
         FIG. 5  is a schematic diagram illustrating another exemplary configuration of the air-conditioning apparatus according to Embodiment 1 of the present invention. 
         FIG. 6  is a schematic diagram illustrating another exemplary configuration of the air-conditioning apparatus according to Embodiment 1 of the present invention. 
         FIG. 7  is a schematic diagram illustrating a refrigerant circuit of an air-conditioning apparatus according to Embodiment 2 of the present invention. 
         FIG. 8  is a schematic diagram illustrating a refrigerant circuit of an air-conditioning apparatus according to Embodiment 3 of the present invention. 
         FIG. 9  is a pressure-versus-specific-enthalpy graph of a refrigeration cycle according to Embodiment 3 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
       FIG. 1  is a schematic diagram illustrating a refrigerant circuit of an air-conditioning apparatus according to Embodiment 1 of the present invention. This air-conditioning apparatus has an outdoor unit  1  and an indoor unit  8 . The outdoor unit  1  contains outdoor devices, which include a compressor  2  that compresses a refrigerant; a four-way valve  3  serving as a flow switching valve that switches the flowing direction of the refrigerant; an outdoor heat exchanger  4  that exchanges heat between the refrigerant and outdoor air; a pressure-reducing capillary tube  5  connected to an outlet of the outdoor heat exchanger  4 ; a first expansion valve  11  and a second expansion valve  13 , in this case, a first electronic expansion valve  11  and a second electronic expansion valve  13  serving as electronic pressure-reducing means, which further reduce the pressure of the refrigerant reduced in pressure by the capillary tube  5 ; and an intermediate-pressure receiver  12  provided between the first electronic expansion valve  11  and the second electronic expansion valve  13  and serving as an excess-refrigerant container that retains an excess refrigerant. The indoor unit  8  contains an indoor heat exchanger  9  that exchanges heat between the refrigerant and indoor air. The outdoor devices (i.e., the compressor  2 , the four-way valve  3 , the outdoor heat exchanger  4 , the capillary tube  5 , the first electronic expansion valve  11 , the intermediate-pressure receiver  12 , and the second electronic expansion valve  13 ) constituting the outdoor unit  1  and the indoor heat exchanger  9  are sequentially connected by refrigerant pipes. These refrigerant pipes are filled with, for example, R410A, which is an HFC-based refrigerant, so that a refrigeration cycle is formed. Furthermore, an outdoor-heat-exchanger charge port  14  serving as an outdoor-heat-exchanger refrigerant injection port is provided between the four-way valve  3  and the outdoor heat exchanger  4 , and a receiver charge port  15  serving as an excess-refrigerant-container refrigerant injection port is provided between the intermediate-pressure receiver  12  and the second electronic expansion valve  13 . The refrigerant is injected into the refrigerant circuit via the outdoor-heat-exchanger charge port  14  and the receiver charge port  15 . Fans  7  and  10  are provided near the outdoor heat exchanger  4  and the indoor heat exchanger  9  and send outdoor air and indoor air to the outdoor heat exchanger  4  and the indoor heat exchanger  9 , respectively, so as to make the refrigerant and the air exchange heat with each other at the outdoor heat exchanger  4  and the indoor heat exchanger  9 . In the drawing, arrows denote the circulating direction of the refrigerant. Specifically, solid-line arrows correspond to the case where an indoor cooling operation is performed, whereas dotted-line arrows correspond to the case where an indoor heating operation is performed. When this air-conditioning apparatus is performing a cooling operation or a heating operation, the outdoor-heat-exchanger charge port  14  and the receiver charge port  15  are closed and are not involved with the operation of the refrigeration cycle. 
       FIG. 2  is a pressure-versus-specific-enthalpy graph of the refrigeration cycle according to Embodiment 1. The following description based on  FIGS. 1 and 2  relates to the refrigeration cycle in the case where the air-conditioning apparatus is in operation. In  FIG. 2 , the abscissa axis denotes the specific enthalpy, whereas the ordinate axis denotes the pressure. In the case where an indoor cooling operation is performed, black dots (A, B, C, D, and E) indicate the state of the refrigerant at positions denoted by black dots (A, B, C, D, and E), respectively, in  FIG. 1 . In the case where a heating operation is performed, black dots (a, b, c, d, and e) indicate the state of the refrigerant at positions denoted by black dots (a, b, c, d, and e), respectively, in  FIG. 1 . 
     The cooling operation will be described below. The indoor heat exchanger  9  contained in the indoor unit  8  operates as an evaporator, and the outdoor heat exchanger  4  contained in the outdoor unit  1  operates as a condenser. A low-temperature low-pressure refrigerant (A) is suctioned into the compressor  2  and is discharged therefrom as a high-temperature high-pressure gas refrigerant (B). Subsequently, the high-temperature high-pressure gas refrigerant (B) travels through the four-way valve  3  and transfers heat to outdoor air sent by the fan  7  by exchanging heat with the outdoor air at the outdoor heat exchanger  4  serving as a condenser, so that the temperature of the refrigerant itself decreases. Then, the refrigerant is slightly reduced in pressure (C) by the capillary tube  5  disposed at the outlet of the outdoor heat exchanger  4 , and is further reduced in pressure by the first electronic expansion valve  11 , thereby becoming an intermediate-temperature intermediate-pressure two-phase gas-liquid refrigerant (D). This intermediate-temperature intermediate-pressure refrigerant (D) flows into the intermediate-pressure receiver  12 , and a portion of the refrigerant is retained therein in accordance with the opening degree of the second electronic expansion valve  13 , whereas the remaining portion of the refrigerant flows out from the intermediate-pressure receiver  12  and is reduced in pressure by the second electronic expansion valve  13  so as to become a low-temperature low-pressure refrigerant (E), which then circulates from the outdoor unit  1  to the indoor unit  8 . In the indoor unit  8 , the refrigerant removes heat from indoor air sent by the fan  10  by exchanging heat with the indoor air at the indoor heat exchanger  9  operating as an evaporator, whereby indoor cooling is performed at this point. The refrigerant flowing out from the indoor unit  8  flows into the outdoor unit  1  again, travels through the four-way valve  3 , and is suctioned into the compressor  2  again as a low-temperature low-pressure refrigerant (A). The above-described series of cycle is repeated. 
     In the case of the heating operation, the four-way valve  3  is switched so that the refrigerant flows through a circuit denoted by dotted lines in the four-way valve  3 . The refrigerant discharged from the compressor  2  travels through the four-way valve  3  so as to flow to the indoor unit  8 . The indoor heat exchanger  9  operates as a condenser, whereas the outdoor heat exchanger  4  operates as an evaporator. Specifically, the refrigerant circulates through the refrigerant circuit in a direction inverse to that in the cooling operation so that indoor heating is performed. The changes in the state of the refrigeration cycle are the same as those in the cooling operation. In the indoor heat exchanger  9 , the refrigerant transfers heat to indoor air so that the state of the refrigerant changes from (b) to (c). Subsequently, the refrigerant is reduced to intermediate pressure by the second electronic expansion valve  13 , and an intermediate-temperature intermediate-pressure refrigerant (d) is retained in the intermediate-pressure receiver  12 . The refrigerant flowing out from the intermediate-pressure receiver  12  is reduced to a low pressure (e) by the first electronic expansion valve  11  and flows into the outdoor heat exchanger  4  via the capillary tube  5 . Then, after exchanging heat with outdoor air, the refrigerant becomes a low-temperature low-pressure refrigerant (a), which is then suctioned into the compressor  2 . 
     The volume and the operational state of the indoor unit  8  vary depending on, for example, users&#39; environment. Therefore, a configuration that allows not only a predetermined indoor unit but also an indoor unit with a different volume or a different number of indoor units to be connectable to a single outdoor unit is demanded. In that case, since the capacity of and the amount of air for the indoor heat exchanger vary from indoor unit to indoor unit, the amount of refrigerant required for allowing the refrigeration cycle to exhibit maximum performance would also vary. In addition, the amount of required refrigerant differs between the heating operation and the cooling operation. In Embodiment 1, in order to properly adjust the amount of refrigerant circulating through the refrigerant circuit, the intermediate-pressure receiver  12  is provided as an excess-refrigerant container, and this intermediate-pressure receiver  12  is configured to retain an excess refrigerant in an intermediate-temperature intermediate-pressure state during operation. 
     In the refrigeration cycle, the condensing temperature and the evaporating temperature of the refrigerant will respectively be referred to as “high temperature” and “low temperature”, and the condensing pressure and the evaporating pressure of the refrigerant will respectively be referred to as “high pressure” and “low pressure”. An intermediate temperature is a temperature that is lower than the condensing temperature of the refrigerant but higher than the evaporating temperature, and an intermediate pressure is a pressure that is lower than the condensing pressure of the refrigerant but higher than the evaporating pressure. Specifically, the temperature and the pressure of the refrigerant retained in the intermediate-pressure receiver  12  vary depending on the refrigerant circulating through the refrigerant circuit. 
     The intermediate-pressure receiver  12  is provided at a position that is located between the outdoor heat exchanger  4  and the indoor unit  8  and where an intermediate-pressure liquid refrigerant exists. In detail, a refrigerant flowing out from a heat exchanger operating as a condenser is reduced in pressure in two stages by at least two pressure-reducing means, that is, the first electronic expansion valve  11  and the second electronic expansion valve  13 , and an intermediate-temperature intermediate-pressure refrigerant after being reduced in pressure by the upstream-side pressure-reducing means (i.e., the first electronic expansion valve  11  during cooling or the second electronic expansion valve  13  during heating) is retained in the intermediate-pressure receiver  12 . Specifically, by disposing the first electronic expansion valve  11  and the second electronic expansion valve  13  in front of and behind the intermediate-pressure receiver  12 , the intermediate-temperature intermediate-pressure refrigerant can be retained in the intermediate-pressure receiver  12  even if the circulating direction of the refrigerant flowing through the refrigerant pipes is reversed between the cooling operation and the heating operation. 
     With the intermediate-pressure receiver  12  provided between the first electronic expansion valve  11  and the second electronic expansion valve  13 , the electronic expansion valve located upstream of the intermediate-pressure receiver  12  in the circulating direction of the refrigerant (i.e., the first electronic expansion valve  11  during cooling or the second electronic expansion valve  13  during heating) reduces the pressure of a high-pressure refrigerant to an intermediate pressure. Furthermore, the opening degree of the electronic expansion valve located downstream of the intermediate-pressure receiver  12  in the circulating direction of the refrigerant (i.e., the second electronic expansion valve  13  during cooling or the first electronic expansion valve  11  during heating) is adjusted so that the intermediate-pressure refrigerant is reduced to a low pressure and the amount of liquid refrigerant retained in the intermediate-pressure receiver  12  is optimized. For example, when a container that retains an excess refrigerant is installed at a position where a high-temperature refrigerant may possibly flow into the container, it is desired that the container have high resistance to pressure. In Embodiment 1, since an intermediate-temperature intermediate pressure refrigerant (D or d) reduced in pressure by an electronic expansion valve provided upstream of the intermediate-pressure receiver  12  is retained in the intermediate-pressure receiver  12 , a refrigerant reduced in pressure to some extent is made to flow into the intermediate-pressure receiver  12 . This allows for improved reliability without requiring the pressure resistance as in the configuration that retains a high-pressure refrigerant. 
     The following description relates to a case where a refrigerant is injected into the refrigerant circuit of the air-conditioning apparatus during production thereof. In view of the volumes (capacities) of the devices constituting the air-conditioning apparatus, the outdoor heat exchanger  4  normally has the largest volume, the intermediate-pressure receiver  12  has the second largest volume, and then the indoor heat exchanger  9  and the compressor  2  and so on. For example, the outdoor heat exchanger  4  has a volume of about 5000 cc, the intermediate-pressure receiver  12  has a volume of about 3000 cc, the indoor heat exchanger  9  has a volume of about 500 to 1000 cc, and the compressor  2  has a volume of about 500 cc. In particular, in a separate-type air-conditioning apparatus in which the indoor unit  8  and the outdoor unit  1  are separated from each other, a refrigerant is injected into the outdoor unit  1  in advance at a factory, etc. At an installation location, operation is performed after connecting the indoor unit  8  to the refrigerant pipes of the outdoor unit  1 . This allows for a safe and easy process in view of assembly and installation. Therefore, upon injection of a refrigerant into the outdoor unit  1 , a large amount of refrigerant that can cover the entire refrigerant circuit is injected, meaning that a sufficient amount of refrigerant that at least fills the outdoor heat exchanger  4  and the intermediate-pressure receiver  12  having large capacities needs to be reliably injected. In addition, the refrigerant needs to be injected in a well-balanced manner in accordance with the capacities of the outdoor heat exchanger  4  and the intermediate-pressure receiver  12 . 
       FIG. 3  includes schematic diagrams illustrating an example of the outdoor-heat-exchanger charge port  14  serving as an outdoor-heat-exchanger refrigerant injection port and the receiver charge port  15  serving as an intermediate-receiver refrigerant injection port, which are used for injecting a refrigerant into the refrigerant circuit.  FIG. 3( a )  illustrates the outdoor-heat-exchanger charge port  14  provided in a refrigerant pipe  16   a  that is directly connected to the outdoor heat exchanger  4 . To the refrigerant pipe  16   a  is connected a branch pipe  17  whose one end is connected to a valve  18  having an opening-and-closing function. The valve  18  is opened and is attached to, for example, a refrigerant pipe  19  or a refrigerant hose (denoted by a dotted line) connected to a refrigerant container (not shown) so that the refrigerant in the refrigerant container is injected into the outdoor heat exchanger  4  from the refrigerant pipe  16   a  via the refrigerant pipe  19 , the valve  18 , and the branch pipe  17 . After injecting the refrigerant, the valve  18  is closed. 
     The refrigerant pipe directly connected to the outdoor heat exchanger  4  is a refrigerant pipe that is connected to a pipe in the outdoor heat exchanger  4  without any intervening devices that are constituent of e the refrigerant circuit, for example, pressure-reducing members such as the capillary tube  5  and the electronic expansion valves  11  and  13 . The outdoor-heat-exchanger charge port  14  is connected to the outdoor heat exchanger  4  only via the refrigerant pipe. 
     The receiver charge port  15  provided in a refrigerant pipe  16   b  that is directly connected to the intermediate-pressure receiver  12  has a similar configuration. In  FIG. 3( b ) , a branch pipe  17  whose one end is connected to a valve  18  having an opening-and-closing function is connected to the refrigerant pipe  16   b  directly connected to the intermediate-pressure receiver  12 . This valve  18  is opened and, for example, a refrigerant pipe  19  (denoted by a dotted line) connected to a refrigerant container (not shown) is attached to the valve  18  so that the refrigerant in the refrigerant container is injected into the intermediate-pressure receiver  12  from the refrigerant pipe  16   b  via the refrigerant pipe  19 , the valve  18 , and the branch pipe  17 . After injection of the refrigerant, the valve  18  is closed. 
     Similar to the above, the refrigerant pipe directly connected to the intermediate-pressure receiver  12  is a refrigerant pipe that is connected to a pipe in the intermediate-pressure receiver  12  without any intervening devices that are the constituents of the refrigerant circuit, for example, pressure-reducing members such as the capillary tube  5  and the electronic expansion valves  11  and  13 . The receiver charge port  15  is connected to the intermediate-pressure receiver  12  only via the refrigerant pipe. 
     In a configuration provided with a single charge port in the entire refrigerant circuit, as in the apparatus in the conventional art, for example, if the refrigerant is to be injected into the refrigerant circuit from the charge port  14  provided near the outdoor heat exchanger  4 , the existence of the capillary tube  5  and the first electronic expansion valve  11  serving as pressure-reducing members creates resistance that makes it difficult for the refrigerant to move and flow into the intermediate-pressure receiver  12 , causing most of the refrigerant to be retained in the outdoor heat exchanger  4 . Because the upstream side and the downstream side of the intermediate-pressure receiver  12  are respectively connected to the electronic expansion valves  11  and  13 , it is difficult to inject the refrigerant into the intermediate-pressure receiver  12  if the charge port is provided near the outdoor heat exchanger  4 , or it is difficult to inject the refrigerant into the outdoor heat exchanger  4  if the charge port is provided near the intermediate-pressure receiver  12 . Although the refrigerant may gradually flow into the intermediate-pressure receiver  12  or the outdoor heat exchanger  4  by passing through the pressure-reducing members, the injection time is too long. 
     In contrast, in Embodiment 1, the refrigerant is reliably injected into the outdoor heat exchanger  4  from the outdoor-heat-exchanger charge port  14 . Furthermore, since there are no pressure-reducing members between the outdoor-heat-exchanger charge port  14  and the outdoor heat exchanger  4 , the refrigerant is injected smoothly within a short period of time. Likewise, the refrigerant is reliably injected into the intermediate-pressure receiver  12  from the receiver charge port  15 , and since there are no pressure-reducing members between the receiver charge port  15  and the intermediate-pressure receiver  12 , the refrigerant is injected smoothly within a short period of time. Accordingly, since an amount of refrigerant required in the refrigerant circuit is distributively injected into the outdoor heat exchanger  4  and the intermediate-pressure receiver  12 , the occurrence of a liquid-sealed state caused by the refrigerant being injected lopsidedly to a specific device in the refrigerant circuit is prevented, whereby the refrigerant is safely injected. 
     Furthermore, a required amount of refrigerant can be injected from the outdoor-heat-exchanger charge port  14  in accordance with the capacity of the outdoor heat exchanger  4 . Likewise, a required amount of refrigerant can be injected from the receiver charge port  15  in accordance with the capacity of the intermediate-pressure receiver  12 . Therefore, an amount of refrigerant required in the refrigerant circuit can be distributively injected into the outdoor heat exchanger  4  and the intermediate-pressure receiver  12  in a well-balanced manner. Accordingly, a required amount of refrigerant can be injected in accordance with the different capacities of the outdoor heat exchanger  4  and the intermediate-pressure receiver  12  constituting the refrigerant circuit. 
     Either of the refrigerant injection processes may precede the other. For example, the refrigerant may be injected into the intermediate-pressure receiver  12  from the receiver charge port  15  after the injection of the refrigerant into the outdoor heat exchanger  4  from the outdoor-heat-exchanger charge port  14 . Alternatively, the refrigerant may be injected into the outdoor heat exchanger  4  from the outdoor-heat-exchanger charge port  14  after the injection of the refrigerant into the intermediate-pressure receiver  12  from the receiver charge port  15 . Furthermore, injecting the refrigerant simultaneously into the intermediate-pressure receiver  12  and the outdoor heat exchanger  4  shortens the time required for the refrigerant injection process. 
     The configurations of the outdoor-heat-exchanger charge port  14  and the receiver charge port  15  are not limited to those described above, and alternative configurations are permissible. For example, if the refrigerant is to be preliminarily injected into the refrigerant circuit during the manufacturing process, the branch pipes may simply be connected to the refrigerant pipes and be closed by, for example, brazing after the refrigerant is injected through these branch pipes. In this case, if an injection is necessary again, the injection process can be performed again by cutting the brazed sections. 
     Accordingly, the outdoor-heat-exchanger charge port  14  is provided in the refrigerant pipe that is directly connected to the large-capacity outdoor heat exchanger  4  constituting the refrigerant circuit, and the receiver charge port  15  is provided in the refrigerant pipe that is directly connected to the intermediate-pressure receiver  12 , so that the refrigerant can be reliably injected into the outdoor heat exchanger  4  and the intermediate-pressure receiver  12 , thereby allowing for improved reliability of the refrigerant injection process and also achieving a shorter injection time. In particular, an amount of refrigerant required in the refrigerant circuit can be injected thereto at the outdoor-unit side. Although the refrigerant injection process performed during the manufacturing process is described above, the present invention is not limited to this. For example, even if there is a need to additionally inject the refrigerant into the refrigerant circuit after installation, an amount of refrigerant required in the refrigerant circuit can be injected from the outdoor-heat-exchanger charge port  14  and the receiver charge port  15 , whereby the refrigerant can be injected reliably in a well-balanced manner within a short period of time, advantageously. 
     According to Embodiment 1, the air-conditioning apparatus includes the outdoor unit  1  having outdoor devices, which include the compressor  2  that compresses the refrigerant, the flow switching valve  3  that switches the flowing direction of the refrigerant, the outdoor heat exchanger  4  that exchanges heat between the refrigerant and outdoor air, the first expansion valve  11  that reduces the pressure of the refrigerant, the excess-refrigerant container  12  that retains an excess refrigerant of the refrigerant, and the second expansion valve  13  that reduces the pressure of the refrigerant; and the indoor unit  8  having the indoor heat exchanger  9  that exchanges heat between the refrigerant and indoor air. The outdoor devices and the indoor heat exchanger  9  are sequentially connected by the refrigerant pipes so that a refrigeration cycle is formed. The air-conditioning apparatus further includes the outdoor-heat-exchanger refrigerant injection port  14  provided in the refrigerant pipe  16   a  that is directly connected to the outdoor heat exchanger  4 , and the excess-refrigerant-container refrigerant injection port  15  provided in the refrigerant pipe  16   b  that is directly connected to the excess-refrigerant container  12 . Thus, the refrigerant can also be injected into the large-capacity excess-refrigerant container  12  in a well-balanced manner without a large amount of refrigerant being lopsidedly injected only into the outdoor heat exchanger  4 . Consequently, an air-conditioning apparatus is provided in which an amount of refrigerant required in the refrigerant circuit can be reliably and safely injected thereto within a short period of time, advantageously. 
       FIG. 4  is a schematic diagram illustrating another exemplary configuration of the air-conditioning apparatus according to the present invention. With regard to the position of the outdoor-heat-exchanger charge port, in the configuration in  FIG. 1 , the outdoor-heat-exchanger charge port  14  is provided in the refrigerant pipe  16   a  that serves as a refrigerant pipe directly connected to the outdoor heat exchanger  4  and that extends between the four-way valve  3  and the outdoor heat exchanger  4 . In the exemplary configuration shown in  FIG. 4 , a capillary tube is not provided between the outdoor heat exchanger  4  and the first electronic expansion valve  11 , and an outdoor-heat-exchanger charge port  20  is provided in a refrigerant pipe  16   d  extending between the outdoor heat exchanger  4  and the first electronic expansion valve  11 . 
     This configuration is similar to that in  FIG. 1  in that the refrigerant can be injected into the outdoor heat exchanger  4  from the outdoor-heat-exchanger charge port  20  and in that the refrigerant can be injected into the intermediate-pressure receiver  12  from the receiver charge port  15 . A required amount of refrigerant can be reliably injected in a well-balanced manner without the refrigerant being lopsided to one of the outdoor heat exchanger  4  and the intermediate-pressure receiver  12 , which are large-capacity devices among the devices constituting the outdoor unit  1 , thereby allowing for improved reliability of the refrigerant injection process and also achieving a shorter injection time. 
       FIG. 5  is a schematic diagram illustrating another exemplary configuration of the air-conditioning apparatus according to the present invention. With regard to the position of the receiver charge port, in the configurations in  FIG. 1  and  FIG. 4 , the receiver charge port  15  is provided in the refrigerant pipe  16   b  that serves as a refrigerant pipe directly connected to the intermediate-pressure receiver  12  and that extends between the intermediate-pressure receiver  12  and the second electronic expansion valve  13 . In the exemplary configuration shown in  FIG. 5 , a receiver charge port  21  is provided in a refrigerant pipe  16   c  extending between the first electronic expansion valve  11  and the intermediate-pressure receiver  12 . 
     This configuration is similar to that in  FIG. 1  in that the refrigerant can be injected into the outdoor heat exchanger  4  from the outdoor-heat-exchanger charge port  14  and in that the refrigerant can be injected into the intermediate-pressure receiver  12  from the receiver charge port  21 . A required amount of refrigerant can be reliably injected in a well-balanced manner without the refrigerant being lopsided to one of the outdoor heat exchanger  4  and the intermediate-pressure receiver  12 , which are large-capacity devices among the devices constituting the outdoor unit  1 , thereby allowing for improved reliability of the refrigerant injection process and also achieving a shorter injection time. 
     By providing the receiver charge port  21  in the refrigerant pipe  16   c  extending between the first electronic expansion valve  11  and the intermediate-pressure receiver  12  in the configuration in  FIG. 4 , a similar advantage can be achieved. 
       FIG. 6  is a schematic diagram illustrating another exemplary configuration of the air-conditioning apparatus according to the present invention. In this exemplary configuration, three charge ports  14 ,  15 , and  21  are provided. Specifically, the outdoor-heat-exchanger charge port  14  is provided in the refrigerant pipe  16   a  directly connected to the outdoor heat exchanger  4 , the receiver charge port  15  is provided in one refrigerant pipe  16   b  directly connected to the intermediate-pressure receiver  12 , and the receiver charge port  21  is provided in the other refrigerant pipe  16   c  directly connected to the intermediate-pressure receiver  12 . The refrigerant is injected into the outdoor heat exchanger  4  from the outdoor-heat-exchanger charge port  14 , and the refrigerant is injected into the intermediate-pressure receiver  12  from the two receiver charge ports  15  and  21 . In this exemplary configuration, because the refrigerant can be injected into the intermediate-pressure receiver  12  simultaneously from the two receiver charge ports  15  and  21 , the time required for the process of filling the intermediate-pressure receiver  12  with the refrigerant can be shortened, whereby a sufficient amount of refrigerant can be reliably injected into the refrigerant circuit. 
     Furthermore, in the case where the outdoor heat exchanger  4  and the first electronic expansion valve  11  are connected by the refrigerant pipe  16   d  as in  FIG. 4 , two outdoor-heat-exchanger charge ports  14  and  20  may be provided. By injection of the refrigerant into the outdoor heat exchanger  4  from the two outdoor-heat-exchanger charge ports  14  and  20 , the time required for the process of filling the outdoor heat exchanger  4  with the refrigerant can be shortened, whereby a sufficient amount of refrigerant can be reliably injected into the refrigerant circuit. 
     According to Embodiment 1, the excess-refrigerant-container refrigerant injection port  15  or  21  is provided for both or at least either one of the refrigerant pipe  16   c , extending between the first expansion valve  11  and the excess-refrigerant container  12 , and the refrigerant pipe  16   b , extending between the second expansion valve  13  and the excess-refrigerant container  12 , whereby an air-conditioning apparatus is obtained in which a required amount of refrigerant can be reliably injected into the intermediate-pressure receiver  12  within a short period of time, advantageously. 
     Furthermore, the outdoor-heat-exchanger refrigerant injection port  14  or  20  is provided for at least one of or each of the refrigerant pipe  16   a  extending between the flow switching valve  3  and the outdoor heat exchanger  4  and the refrigerant pipe  16   d  extending between the first expansion valve  11  and the outdoor heat exchanger  4 , whereby an air-conditioning apparatus is obtained in which a required amount of refrigerant can be reliably injected into the outdoor heat exchanger  4  within a short period of time, advantageously. 
     Embodiment 2 
       FIG. 7  is a schematic diagram illustrating a refrigerant circuit of an air-conditioning apparatus according to Embodiment 2 of the present invention. In the drawing, reference numerals or characters that are the same as those in  FIG. 1  denote the same or equivalent components. The configuration of Embodiment 2 is one to which a plurality of, that is, n (which is an integer greater than 1) number of indoor units  8 - 1  to  8 - n  are connectable. In the configuration, branch sections  22   a  and  22   b  of the refrigerant circuit are provided in the outdoor unit  1 , and n number of second electronic expansion valves  13 - 1  to  13 - n  that respectively correspond to the indoor units  8 - 1  to  8 - n  are provided. In this case, the outdoor-heat-exchanger charge port  14  is provided in the refrigerant pipe  16   a  that is directly connected to the outdoor heat exchanger  4 , and the receiver charge port  15  is provided in the refrigerant pipe  16   b  that is directly connected to the intermediate-pressure receiver  12 . In the drawing, solid-line arrows denote the circulating direction of the refrigerant when a cooling operation is performed by the indoor units  8 , and dotted-line arrows denote the circulating direction of the refrigerant when a heating operation is performed by the indoor units  8 . 
     In the case where the plurality of indoor units  8 - 1  to  8 - n  are provided, indoor heat exchangers  9 - 1  to  9 - n  provided therein are connected in parallel to the outdoor heat exchanger  4 , and the refrigerant pipes are ramified into n number of refrigerant pipes at the branch sections  22   a  and  22   b . The amount of refrigerant flowing through the indoor heat exchangers  9 - 1  to  9 - n  is adjusted by the second electronic expansion valves  13 - 1  to  13 - n  provided in the respective refrigerant pipes. 
     Because the configuration according to Embodiment 2 is provided with the plurality of indoor units  8 - 1  to  8 - n , a larger amount of refrigerant is required in the refrigerant circuit that achieves this configuration, as compared with that in Embodiment 1. For example, if all of the indoor units  8 - 1  to  8 - n  operate at the same time, the outdoor unit  1  would be constituted of an outdoor heat exchanger  4  with a large capacity in correspondence with the plurality of indoor heat exchangers  9 - 1  to  9 - n  in operation. Therefore, the amount of refrigerant required in the refrigerant circuit is larger than that in the configuration provided with a single indoor unit  8 , meaning that a large amount of refrigerant is injected into the refrigerant circuit. However, there is also a case where only one of the indoor units  8 - 1  to  8 - n  operates. In this case, the amount of refrigerant circulating through the refrigerant circuit is small, resulting in a large amount of excess refrigerant. For this reason, a large amount of excess refrigerant becomes retained in the intermediate-pressure receiver  12 , making it necessary for the intermediate-pressure receiver  12  to have a large capacity. Specifically, in the air-conditioning apparatus equipped with the plurality of indoor units  8 - 1  to  8 - n , the outdoor heat exchanger  4  and the intermediate-pressure receiver  12  provided have larger capacities than those in the configuration in  FIG. 1 . 
     In the air-conditioning apparatus equipped with the outdoor heat exchanger  4  and the intermediate-pressure receiver  12  that have large capacities, the refrigerant is injected into the outdoor heat exchanger  4  from the outdoor-heat-exchanger charge port  14  provided in the refrigerant pipe  16   a  directly connected to the outdoor heat exchanger  4 , and the refrigerant is injected into the intermediate-pressure receiver  12  from the receiver charge port  15  provided in the refrigerant pipe  16   b  directly connected to the intermediate-pressure receiver  12 . By injecting the refrigerant into the outdoor heat exchanger  4  and the intermediate-pressure receiver  12  constituting the outdoor unit  1  in this manner, an amount of refrigerant required in the refrigerant circuit can be reliably injected thereto in a well-balanced manner in accordance with the capacities of the outdoor heat exchanger  4  and the intermediate-pressure receiver  12 . Therefore, because of absence of a liquid-sealed state being caused, the safety of the refrigerant injection process can be ensured, the reliability thereof can be improved, and a shorter refrigerant injection time can be achieved. Furthermore, by injecting the refrigerant simultaneously into the intermediate-pressure receiver  12  and the outdoor heat exchanger  4 , the refrigerant injection time can be further shortened. 
     Accordingly, with the plurality of indoor units  8 - 1  to  8 - n  provided in Embodiment 2, an outdoor unit  1  is obtained that can comply with various configurations, so that an air-conditioning apparatus in which an amount of refrigerant required in the refrigerant circuit can be reliably and safely injected thereto within a short period of time at the outdoor-unit side, advantageously. 
     Embodiment 3 
       FIG. 8  is a schematic diagram illustrating a refrigerant circuit of an air-conditioning apparatus according to Embodiment 3 of the present invention. In the drawing, reference numerals or characters that are the same as those in  FIG. 1  denote the same or equivalent components. In Embodiment 3, a heat exchanging unit  24  where the refrigerant flowing through a refrigerant pipe  23  (this refrigerant pipe  23  will be referred to as “suction pipe”) connected to the suction side of the compressor  2  exchanges heat with the refrigerant retained in the intermediate-pressure receiver  12  serving as an excess-refrigerant container is provided. The heat exchanging unit  24  is configured such that the suction pipe  23  extends through the liquid refrigerant retained in the intermediate-pressure receiver  12 . Although the refrigerant pipe in the heat exchanging unit  24  is indicated by a thick line in the drawing to provide an easier understanding of the heat exchanging unit  24 , the refrigerant pipe may have a same or similar thickness or diameter as the other refrigerant pipes in an actual configuration. 
     A low-temperature low-pressure refrigerant in the suction pipe  23  is made to exchange heat with the excess refrigerant retained in the intermediate-pressure receiver  12  by the heat exchanging unit  24  so as to receive heat from the intermediate-temperature intermediate-pressure excess refrigerant retained in the intermediate-pressure receiver  12 . Subsequently, the refrigerant is suctioned into the compressor  2 . By receiving heat from the intermediate-temperature intermediate-pressure excess refrigerant, the refrigerant at the suction side of the compressor  2  can be reliably turned into a gas state as indicated by AA shown in a pressure-versus-specific-enthalpy diagram in  FIG. 9 . In other words, superheat (S) at the right side of a saturated vapor line can be ensured for the refrigerant to be suctioned into the compressor  2 . If a refrigerant in a liquid state is suctioned into the compressor  2 , the compressor  2  may possibly result in a failure, or the efficiency thereof may decrease. In the configuration according to Embodiment 3, since superheat (S) can be ensured so that the refrigerant can be reliably suctioned into the compressor  2  in a gas state, the reliability of the compressor  2  can be improved, and the load on the compressor  2  can be reduced, thereby improving the efficiency. The pressure-versus-specific-enthalpy diagram shown in  FIG. 9  is a graph in which the abscissa axis denotes the specific enthalpy and the ordinate axis denotes the pressure. In the graph, D-DD and A-AA denote sections where the refrigerant retained in the intermediate-pressure receiver  12  and the refrigerant flowing through the suction pipe  23  exchange heat with each other at the heat exchanging unit  24  of the intermediate-pressure receiver  12 . 
     In the refrigerant circuit having the intermediate-pressure receiver  12  and also having the heat exchanging unit  24  that exchanges heat between the refrigerant flowing through the suction pipe  23  and the excess refrigerant, as in this configuration, the outdoor-heat-exchanger charge port  14  and the receiver charge port  15  are provided so that the refrigerant can be injected into the outdoor heat exchanger  4  and the intermediate-pressure receiver  12 . Thus, the refrigerant can be injected in a well-balanced manner into the outdoor heat exchanger  4  and the intermediate-pressure receiver  12  that have large capacities among the devices contained in and constituting the outdoor unit  1 , whereby an air-conditioning apparatus is obtained in which an amount of refrigerant required in the refrigerant circuit can be reliably and safely injected thereto within a short period of time. 
     In particular, in this configuration, the heat of the excess refrigerant in the intermediate-pressure receiver  12  can be effectively utilized. 
     According to Embodiment 3, the heat exchanging unit  24  that exchanges heat between the refrigerant flowing through the refrigerant pipe  23  connected to the suction side of the compressor  2  and the refrigerant retained in the excess-refrigerant container  12  is provided, so that the refrigerant to be suctioned into the compressor  2  is suctioned into the compressor  2  after exchanging heat with the refrigerant retained in the excess-refrigerant container  12  at the heat exchanging unit  24 . Thus, the heat in the excess-refrigerant container  12  is effectively utilized so that a circuit configuration with improved reliability of the compressor  2  is achieved. In this circuit configuration, the outdoor-heat-exchanger refrigerant injection port  14  and the excess-refrigerant-container refrigerant injection port  15  are provided so that the refrigerant can be injected into the outdoor heat exchanger  4  and the excess-refrigerant container  12 . Consequently, the refrigerant can be injected in a well-balanced manner into the outdoor heat exchanger  4  and the excess-refrigerant container  12  that have large capacities among the devices contained in and constituting the outdoor unit  1 , whereby an air-conditioning apparatus is obtained in which an amount of refrigerant required in the refrigerant circuit can be reliably and safely injected thereto within a short period of time. 
     Although the heat exchanging unit  24  is configured such that the suction pipe  23  extends through the refrigerant retained in the intermediate-pressure receiver  12  in  FIG. 8 , the configuration thereof is not limited to this. For example, the suction pipe  23  may be wound in close contact with the inner wall or the outer wall of the intermediate-pressure receiver  12 . Any configuration is permissible so long as the refrigerant to be suctioned into the compressor  2  is suctioned into the compressor  2  after exchanging heat with the excess refrigerant retained in the intermediate-pressure receiver  12 . 
     Similar to Embodiment 1, in Embodiment 2 and Embodiment 3, the charge port  15  may be replaced with a charge port that is provided in the refrigerant pipe  16   c  directly connected to the intermediate-pressure receiver  12 , or a charge port may be provided in each of the two refrigerant pipes  16   b  and  16   c  such that the refrigerant is injected into the intermediate-pressure receiver  12  from both charge ports. 
     Furthermore, the charge port  14  may be replaced with a charge port that is provided in the refrigerant pipe  16   d  (see  FIG. 4 ) directly connected to the outdoor heat exchanger  4 , or a charge port may be provided in each of the two refrigerant pipes  16   a  and  16   d  such that the refrigerant is injected into the outdoor heat exchanger  4  from both charge ports. By injection of the refrigerant from a plurality of charge ports, the refrigerant injection time can be further shortened. 
     REFERENCE SIGNS LIST 
       1  outdoor unit  2  compressor  3 flow switching valve  4  outdoor heat exchanger  5  capillary tube  7  outdoor fan  8 ,  8 - 1 ,  8 - 2 ,  8 -n indoor unit  9 ,  9 - 1 ,  9 - 2 ,  9 -n indoor heat exchanger  10  indoor 
     
       
         
           
               
             
               
                   
               
               
                 Reference Signs List 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 1 
                 outdoor unit 
                 2 
                 compressor 
                 3 
                 flow switching valve 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 4 
                 outdoor heat exchanger 
                 5 
                 capillary tube 
                 7 
                 outdoor fan 8, 
               
            
           
           
               
               
               
               
               
               
            
               
                 8-1, 8-2, 8-n 
                 indoor unit 
                 9, 9-1, 9-2, 9-n 
                 indoor heat exchanger 
                 10 
                 indoor 
               
            
           
           
               
               
               
               
               
               
            
               
                 fan 
                 11 
                 first expansion valve 
                 12 
                 excess-refrigerant container 
                 13, 13-1, 
               
            
           
           
               
               
               
               
            
               
                 13-2, 13-n 
                 second expansion valve 
                 14 
                 outdoor-heat-exchanger refrigerant 
               
            
           
           
               
               
               
            
               
                 injection port 
                 15 
                 excess-refrigerant-container refrigerant injection port 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 16a, 16b, 16c, 16d 
                 refrigerant pipe 
                 17 
                 branch pipe 
                 18 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 on-off valve 
                 19 
                 refrigerant pipe 
                 20 
                 outdoor-heat-exchanger 
               
            
           
           
               
               
               
            
               
                 refrigerant injection port 
                 21 
                 excess-refrigerant-container refrigerant injection port 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 22a, 22b 
                 branch section 
                 23 
                 suction pipe 
                 24 
                 heat 
               
            
           
           
               
            
               
                 exchanging unit