JP2014001922A - Refrigerator - Google Patents

Abstract

In a refrigeration apparatus using R32, an injection for suppressing a discharge temperature is made possible even when the operation efficiency is deteriorated by intermediate injection.
An air conditioner using an R32 refrigerant includes a compressor, an indoor heat exchanger, an outdoor expansion valve, an outdoor heat exchanger, an intermediate injection flow path, a suction injection flow path, and an injection opening / closing. Valves 66 and 68 are provided. The intermediate injection flow path 65 joins a part of the refrigerant flowing through the main refrigerant flow path 11 a to the intermediate pressure refrigerant of the compressor 20. The suction injection flow channel 67 guides a part of the refrigerant in the main refrigerant flow channel 11 a to the suction flow channel 27.
[Selection] Figure 1

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus that uses R32 as a refrigerant.

  Conventionally, a refrigerating apparatus such as an air conditioner that uses R32 as a refrigerant has been proposed. When R32 is used as a refrigerant, the discharge temperature of the compressor tends to be higher than when R410A or R22 is used as a refrigerant. An air conditioner that recognizes this problem and uses the R32 refrigerant to reduce the refrigerant discharge temperature is described in Patent Document 1 (Japanese Patent Laid-Open No. 2009-127902). In this air conditioner, a part of the liquid refrigerant exiting the gas-liquid separator arranged in the high-pressure line is bypassed to the compressor, and the bypass refrigerant is changed to a flash gas state by the internal heat exchanger. . And the bypass refrigerant | coolant used as flash gas is injected, the enthalpy of the refrigerant | coolant of the intermediate pressure state of a compressor is lowered | hung, and the refrigerant | coolant discharge temperature of a compressor is lowered | hung.

  In the air conditioner of Patent Document 1 (Japanese Patent Laid-Open No. 2009-127902), the bypass refrigerant that has become flash gas is injected into the intermediate-pressure refrigerant in the compressor, and the discharge temperature of the compressor is lowered. However, depending on the driving conditions, an increase in driving capacity due to intermediate injection may deteriorate driving efficiency. In such a case, it is conceivable to stop the intermediate injection. However, in this case, there is a case where the discharge temperature rises and it becomes difficult to continue the operation.

  An object of the present invention is to provide a refrigeration apparatus that uses R32 as a refrigerant and is capable of performing injection for suppressing discharge temperature even when the operation efficiency is deteriorated by intermediate injection.

  A refrigeration apparatus according to a first aspect of the present invention is a refrigeration apparatus that uses R32 as a refrigerant, and includes a compressor, a condenser, an expansion mechanism, an evaporator, an intermediate injection flow path, and a suction injection flow path. It has. The compressor sucks low-pressure refrigerant from the suction flow path, compresses the refrigerant, and discharges high-pressure refrigerant. The condenser condenses the high-pressure refrigerant discharged from the compressor. The expansion mechanism expands the high-pressure refrigerant that has exited the condenser. The evaporator evaporates the refrigerant expanded by the expansion mechanism. The intermediate injection flow path guides a part of the refrigerant flowing from the condenser toward the evaporator to the compressor and joins the refrigerant with the intermediate pressure of the compressor. The suction injection flow path guides a part of the refrigerant flowing from the condenser toward the evaporator to the suction flow path and joins the low-pressure refrigerant sucked into the compressor.

  In the refrigeration apparatus according to the present invention, a part of the refrigerant flowing from the condenser toward the evaporator may be merged with the intermediate pressure refrigerant of the compressor using the intermediate injection flow path, or the suction injection flow path may be used. It is also possible to join the low-pressure refrigerant sucked into the compressor in the suction flow path. For this reason, even when the operation efficiency deteriorates when the intermediate injection flow path is used, the discharge temperature of the compressor can be lowered using the suction injection flow path.

  The refrigeration apparatus according to the second aspect of the present invention is the refrigeration apparatus according to the first aspect, and further includes a switching mechanism. The switching mechanism switches between an intermediate injection state in which the refrigerant flows in the intermediate injection flow path and a suction injection state in which the refrigerant flows in the suction injection flow path.

  Here, in the intermediate injection state, part of the refrigerant flowing from the condenser toward the evaporator passes through the intermediate injection flow path and joins the intermediate pressure refrigerant of the compressor. On the other hand, in the suction injection state, part of the refrigerant flowing from the condenser toward the evaporator joins the low-pressure refrigerant sucked into the compressor through the suction injection flow path. Since the intermediate injection state and the suction injection state can be switched by the switching mechanism, even when the operation efficiency is deteriorated in the intermediate injection, the intermediate injection state is switched to the suction injection state, and the discharge temperature of the compressor is changed. Can be reduced.

  The refrigeration apparatus according to the third aspect of the present invention is the refrigeration apparatus according to the second aspect, further comprising a branch flow path, an opening degree adjusting valve, and an injection heat exchanger. The branch channel is a channel that branches from a main refrigerant channel that connects the condenser and the evaporator. The opening degree adjusting valve is provided in the branch flow path, and the opening degree can be adjusted. The heat exchanger for injection exchanges heat between the refrigerant flowing through the main refrigerant flow path and the refrigerant flowing downstream of the opening adjustment valve of the branch flow path. In this refrigeration apparatus, the refrigerant that exits the heat exchanger for injection and flows through the branch channel flows into the intermediate injection channel or the suction injection channel.

  Here, the refrigerant that flows to the compressor via the intermediate injection flow path or the suction injection flow path is decompressed by the opening degree adjustment valve provided in the branch flow path, and is heat exchanged by the heat exchanger for injection. It becomes. For this reason, by adjusting and controlling the opening of the opening adjustment valve, the refrigerant that merges with the intermediate-pressure refrigerant of the compressor or the low-pressure refrigerant sucked into the compressor is changed to superheated gas or flash gas. It is possible.

  As a result, for example, it is possible to perform injection with refrigerant gas that is usually overheated, and injection with emphasis on cooling with wet gas-liquid two-phase flash gas when the discharge temperature of the compressor becomes high. .

  The refrigeration apparatus according to the fourth aspect of the present invention is the refrigeration apparatus according to the second aspect or the third aspect, further comprising a discharge temperature sensor that detects the temperature of the refrigerant discharged from the compressor, and a control unit. ing. The control unit selectively executes intermediate injection control and inhalation injection control. The intermediate injection control is control in which the switching mechanism is set to the intermediate injection state and the refrigerant flows through the intermediate injection flow path. The suction injection control is a control in which the refrigerant is caused to flow through the suction injection flow path with the switching mechanism in the suction injection state. Further, the control unit performs suction injection control when the discharge temperature detected by the discharge temperature sensor is higher than the temperature threshold value and the rotation speed of the compressor is lower than the rotation speed threshold value.

  When the discharge temperature detected by the discharge temperature sensor becomes higher than the temperature threshold, a part of the refrigerant flowing from the condenser toward the evaporator is directly or via a suction passage so that the discharge temperature falls below the temperature threshold. It is preferable to inject. However, if the intermediate injection control is performed during a low heat load operation such as a heating operation when the outside air temperature is high, if the intermediate injection control is performed, the capacity increases and the refrigerant discharged from the compressor increases. Pressure (high pressure) goes up. Therefore, in the refrigeration apparatus according to the fourth aspect of the present invention, when the discharge temperature detected by the discharge temperature sensor is higher than the temperature threshold and the rotation speed of the compressor is lower than the rotation speed threshold, the suction injection control It is carried out. Thereby, even in the case of a low load, it is possible to reduce the discharge temperature by the suction injection control while suppressing the useless increase in capacity and ensuring the operation efficiency.

  A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to the third aspect, and includes a first temperature sensor, a second temperature sensor, and a control unit. The first temperature sensor detects the temperature of the refrigerant discharged from the compressor. The second temperature sensor detects the temperature of the refrigerant flowing out of the injection heat exchanger and flowing through the branch flow path. The control unit selectively executes intermediate injection control and inhalation injection control. The intermediate injection control is control in which the switching mechanism is set to the intermediate injection state and the refrigerant flows through the intermediate injection flow path. The suction injection control is a control in which the refrigerant is caused to flow through the suction injection flow path with the switching mechanism in the suction injection state. In the intermediate injection control, when the temperature detected by the first temperature sensor is lower than the first threshold value, the control unit adjusts the opening of the opening adjustment valve based on the temperature detected by the second temperature sensor. In addition, in the intermediate injection control, when the temperature detected by the first temperature sensor is higher than the first threshold value, the control unit adjusts the opening of the opening adjustment valve based on the temperature detected by the first temperature sensor.

  By performing intermediate injection control, it is possible to increase the capacity and efficiency, but if the discharge temperature of the compressor rises to a level where it is difficult to continue operation, the drooping will forcibly reduce the rotation speed of the compressor It becomes necessary to perform control. In order to suppress this, in the refrigeration apparatus according to the fifth aspect of the present invention, when the temperature detected by the first temperature sensor that detects the temperature of the refrigerant discharged from the compressor is higher than the first threshold value, the second temperature sensor The opening adjustment of the opening adjustment valve is performed based on the detected temperature of the first temperature sensor instead of the detected temperature. For this reason, for example, the opening degree of the opening adjustment valve is increased to increase the cooling effect by injecting wet refrigerant gas into the compressor so that the temperature detected by the first temperature sensor, which is the discharge refrigerant temperature of the compressor, is lowered. Will be able to. On the other hand, when the temperature detected by the first temperature sensor is lower than the first threshold value, the opening degree adjustment based on the detected temperature of the second temperature sensor that detects the temperature of the refrigerant that has exited the heat exchanger for injection is performed, Operation efficiency can be ensured.

  The refrigeration apparatus according to the sixth aspect of the present invention is the refrigeration apparatus according to the first aspect or the second aspect, and further includes a refrigerant storage tank and a bypass flow path. The refrigerant storage tank is provided in the main refrigerant flow path connecting the condenser and the evaporator. And the gas component of the refrigerant | coolant which accumulates in the inside of a refrigerant | coolant storage tank is guide | induced to the intermediate | middle injection flow path and the suction | inhalation injection flow path.

  Here, the refrigerant that flows to the compressor via the intermediate injection flow path or the suction injection flow path becomes the gas component of the refrigerant that accumulates inside the refrigerant storage tank. That is, the refrigerant saturated gas in the refrigerant storage tank flows to the compressor. In the case of adopting such a configuration, a heat exchanger for converting the liquid refrigerant for injection into flash gas or superheated gas becomes unnecessary, and the manufacturing cost of the refrigeration apparatus can be suppressed.

  A refrigeration apparatus according to a seventh aspect of the present invention is the refrigeration apparatus according to the second aspect, wherein the switching mechanism includes a first opening / closing mechanism provided in the intermediate injection flow path and a second opening / closing mechanism provided in the suction injection flow path. Mechanism.

  Here, since the intermediate injection flow path can be closed by the first opening / closing mechanism and the suction injection flow path can be closed by the second opening / closing mechanism, the effect of switching between the intermediate injection state and the suction injection state can be ensured. Can be obtained.

  The first opening / closing mechanism and the second opening / closing mechanism may be two separate opening / closing valves, or may be one mechanism such as a three-way valve.

  A refrigeration apparatus according to an eighth aspect of the present invention is the refrigeration apparatus according to the fourth aspect, and the switching mechanism is a mechanism that switches between an intermediate injection state, an inhalation injection state, and a non-injection state. The non-injection state is a state in which the refrigerant does not flow into the intermediate injection flow path or the suction injection flow path. The control unit selectively executes intermediate injection control, inhalation injection control, and non-injection control. The non-injection control is a control in which the switching mechanism is set to a non-injection state so that the refrigerant does not flow through the intermediate injection passage and the suction injection passage. Further, the control unit selects and performs non-injection control when the discharge temperature detected by the discharge temperature sensor is lower than the temperature threshold and the rotation speed of the compressor is lower than the rotation speed threshold.

  Here, it is not necessary to reduce the temperature of the compressor by suction injection or intermediate injection because the discharge temperature is low, and when the rotation speed of the compressor is low because low capacity is required, non-injection Control is selected and executed. As a result, it is possible to suppress an increase in capacity and a decrease in operating efficiency due to suction injection or intermediate injection, and it is possible to satisfy a low capacity requirement while ensuring operating efficiency.

  The refrigeration apparatus according to the ninth aspect of the present invention is the refrigeration apparatus according to the second aspect or the seventh aspect, and the switching mechanism is a mechanism that switches between the intermediate injection state, the suction injection state, and the non-injection state. is there. The non-injection state is a state in which the refrigerant does not flow into the intermediate injection flow path or the suction injection flow path.

  Here, it is not necessary to reduce the temperature of the compressor by suction injection or intermediate injection because the discharge temperature is low, and when the rotation speed of the compressor is low because low capacity is required, non-injection It becomes possible to switch to the state. By switching in such a manner, it is possible to suppress an increase in capacity and a decrease in operating efficiency due to suction injection or intermediate injection, and it is possible to satisfy a low capacity requirement while ensuring operating efficiency.

  According to the refrigeration apparatus according to the first aspect of the present invention, the discharge temperature of the compressor can be lowered using the suction injection flow path even when the operation efficiency deteriorates when the intermediate injection flow path is used.

  According to the refrigeration apparatus according to the second aspect of the present invention, the discharge temperature of the compressor can be lowered by switching from the intermediate injection state to the suction injection state even when the operation efficiency is deteriorated in the intermediate injection.

  According to the refrigeration apparatus according to the third aspect of the present invention, the refrigerant to be merged with the intermediate pressure refrigerant of the compressor or the low pressure refrigerant sucked into the compressor by adjusting and controlling the opening of the opening adjustment valve. It is possible to use superheated gas or flash gas.

  According to the refrigeration apparatus according to the fourth aspect of the present invention, even when the load is low, the discharge that has become higher than the temperature threshold value by the suction injection control while suppressing the wasteful capacity increase and ensuring the operation efficiency. The temperature can be lowered.

  According to the refrigeration apparatus according to the fifth aspect of the present invention, when the detected temperature of the first temperature sensor that detects the temperature of the refrigerant discharged from the compressor is higher than the first threshold, the detected temperature of the second temperature sensor Instead, the opening adjustment of the opening adjustment valve is performed based on the temperature detected by the first temperature sensor. For this reason, for example, the opening degree of the opening adjustment valve is increased to increase the cooling effect by injecting wet refrigerant gas into the compressor so that the temperature detected by the first temperature sensor, which is the discharge refrigerant temperature of the compressor, is lowered. Will be able to.

  According to the refrigeration apparatus according to the sixth aspect of the present invention, in addition to the refrigerant storage tank, a heat exchanger or the like for converting the liquid refrigerant for injection into flash gas or superheated gas becomes unnecessary, and the refrigeration apparatus is manufactured. Cost can be reduced.

  According to the refrigeration apparatus according to the seventh aspect of the present invention, the intermediate injection flow path and the suction injection flow path can be reliably closed, and the effect of switching between the intermediate injection state and the suction injection state is enhanced.

  According to the refrigeration apparatus according to the eighth aspect and the ninth aspect of the present invention, if switching to a non-injection state under a predetermined condition, it is possible to suppress an increase in capacity and a decrease in operating efficiency due to suction injection or intermediate injection. Therefore, it is possible to satisfy the demand for low capacity while ensuring the operation efficiency.

The figure which shows the refrigerant | coolant piping system | strain of the air conditioning apparatus which concerns on 1st Embodiment of this invention. The control block diagram of the control part of an air conditioning apparatus. The figure which shows the control flow of injection control. The figure which shows the refrigerant | coolant piping system | strain of the air conditioning apparatus which concerns on the modification B. The figure which shows the refrigerant | coolant piping system of the air conditioning apparatus which concerns on 2nd Embodiment. The injection control flow of the air conditioning apparatus which concerns on 2nd Embodiment. The injection control flow of the air conditioning apparatus which concerns on 2nd Embodiment. The injection control flow of the air conditioning apparatus which concerns on 2nd Embodiment. The injection control flow of the air conditioning apparatus which concerns on 2nd Embodiment.

<First Embodiment>
(1) Whole structure of air conditioning apparatus FIG. 1: is a figure which shows the refrigerant | coolant piping system | strain of the air conditioning apparatus 10 which is the freezing apparatus which concerns on one Embodiment of this invention. The air conditioner 10 is a distributed type air conditioner using a refrigerant piping system, and air-conditions each room in a building by performing a vapor compression refrigeration cycle operation. The air conditioner 10 includes an outdoor unit 11 as a heat source unit, an indoor unit 12 as a large number of utilization units, a liquid refrigerant communication tube 13 as a refrigerant communication tube connecting the outdoor unit 11 and the indoor unit 12, and a gas refrigerant. And a communication pipe 14. That is, the refrigerant circuit of the air conditioner 10 shown in FIG. 1 is configured by connecting the outdoor unit 11, the indoor unit 12, and the refrigerant communication tubes 13 and 14.

  The refrigerant circuit shown in FIG. 1 is filled with refrigerant. As will be described later, the refrigerant is compressed, cooled / condensed, decompressed, heated / evaporated, and then compressed again. Cycle operation is performed. R32 is used as the refrigerant. R32 is a low GWP refrigerant with a small global warming potential, and is a kind of HFC refrigerant. Further, as the refrigerating machine oil, an ether-based synthetic oil having some compatibility with R32 is used.

(2) Detailed Configuration of Air Conditioner (2-1) Indoor Unit The indoor unit 12 is installed on the ceiling or side wall of each room, and is connected to the outdoor unit 11 via the refrigerant communication tubes 13 and 14. . The indoor unit 12 mainly includes an indoor expansion valve 42 that is a decompressor and an indoor heat exchanger 50 that is a use-side heat exchanger.

  The indoor expansion valve 42 is an expansion mechanism for decompressing the refrigerant, and is an electric valve capable of adjusting the opening degree. The indoor expansion valve 42 has one end connected to the liquid refrigerant communication tube 13 and the other end connected to the indoor heat exchanger 50.

  The indoor heat exchanger 50 is a heat exchanger that functions as a refrigerant evaporator or a condenser. The indoor heat exchanger 50 has one end connected to the indoor expansion valve 42 and the other end connected to the gas refrigerant communication pipe 14.

  The indoor unit 12 includes an indoor fan 55 for sucking indoor air into the unit and supplying it to the room again, and exchanges heat between the indoor air and the refrigerant flowing through the indoor heat exchanger 50.

  In addition, the indoor unit 12 includes an indoor control unit 92 that controls various sensors and the operation of each unit constituting the indoor unit 12. The indoor control unit 92 includes a microcomputer, a memory, and the like provided for controlling the indoor unit 12, and controls with a remote controller (not shown) for individually operating the indoor unit 12. Exchange of a signal etc. is performed, and exchange of a control signal etc. is performed via the transmission line 93 with the outdoor control part 91 of the outdoor unit 11 mentioned later.

(2-2) Outdoor unit The outdoor unit 11 is installed outside the building where the room where the indoor unit 12 is located or in the basement of the building, and is connected to the indoor unit 12 via the refrigerant communication pipes 13 and 14. Has been. The outdoor unit 11 mainly includes a compressor 20, a four-way switching valve 15, an outdoor heat exchanger 30, an outdoor expansion valve 41, a bridge circuit 70, a high-pressure receiver 80, an injection motor operated valve 63, and an injection. The heat exchanger 64 includes an intermediate injection on / off valve 66, a suction injection on / off valve 68, a liquid side closing valve 17, and a gas side closing valve 18.

  The compressor 20 is a hermetic compressor driven by a compressor motor. The number of the compressors 20 is only one in the present embodiment, but is not limited to this, and two or more compressors may be connected in parallel according to the number of indoor units 12 connected. The compressor 20 sucks the gas refrigerant from the suction passage 27 via the compressor accessory container 28. A discharge pressure sensor for detecting the discharge refrigerant pressure and a discharge temperature sensor 95 for detecting the discharge refrigerant temperature are attached to the refrigerant pipe 29 on the discharge side of the compressor 20. In addition, a suction temperature sensor that detects the temperature of the refrigerant sucked into the compressor 20 is attached to the suction flow path 27. The compressor 20 includes an intermediate injection port 23. The intermediate injection port 23 will be described later.

  The four-way switching valve 15 is a mechanism for switching the direction of refrigerant flow. During the cooling operation, the outdoor heat exchanger 30 functions as a refrigerant condenser compressed by the compressor 20 and the indoor heat exchanger 50 functions as a refrigerant evaporator cooled in the outdoor heat exchanger 30. In addition, the four-way switching valve 15 connects the refrigerant pipe 29 on the discharge side of the compressor 20 and one end of the outdoor heat exchanger 30, and the suction flow path 27 (the compressor attached container 28 on the suction side of the compressor 20). And the gas-side shut-off valve 18 (see the solid line of the four-way switching valve 15 in FIG. 1). Further, during the heating operation, the indoor heat exchanger 50 functions as a refrigerant condenser compressed by the compressor 20, and the outdoor heat exchanger 30 functions as a refrigerant evaporator cooled in the indoor heat exchanger 50. For this purpose, the four-way switching valve 15 connects the refrigerant pipe 29 on the discharge side of the compressor 20 and the gas-side shut-off valve 18 and connects the suction flow path 27 and one end of the outdoor heat exchanger 30 ( (Refer to the broken line of the four-way switching valve 15 in FIG. 1). In the present embodiment, the four-way switching valve 15 is a four-way valve connected to the suction flow path 27, the refrigerant pipe 29 on the discharge side of the compressor 20, the outdoor heat exchanger 30, and the gas side shut-off valve 18.

  The outdoor heat exchanger 30 is a heat exchanger that functions as a refrigerant condenser or evaporator. One end of the outdoor heat exchanger 30 is connected to the four-way switching valve 15, and the other end is connected to the outdoor expansion valve 41.

  The outdoor unit 11 has an outdoor fan 35 for sucking outdoor air into the unit and discharging it to the outdoor again. The outdoor fan 35 exchanges heat between the outdoor air and the refrigerant flowing through the outdoor heat exchanger 30, and is driven to rotate by an outdoor fan motor. The heat source of the outdoor heat exchanger 30 is not limited to outdoor air, and may be another heat medium such as water.

  The outdoor expansion valve 41 is an expansion mechanism for decompressing the refrigerant, and is an electric valve capable of adjusting the opening degree. One end of the outdoor expansion valve 41 is connected to the outdoor heat exchanger 30, and the other end is connected to the bridge circuit 70.

  The bridge circuit 70 has four check valves 71, 72, 73 and 74. The inlet check valve 71 is a check valve that allows only the flow of refrigerant from the outdoor heat exchanger 30 toward the high-pressure receiver 80. The outlet check valve 72 is a check valve that allows only the flow of refrigerant from the high-pressure receiver 80 toward the indoor heat exchanger 50. The inlet check valve 73 is a check valve that allows only the flow of refrigerant from the indoor heat exchanger 50 toward the high-pressure receiver 80. The outlet check valve 74 is a check valve that allows only a refrigerant flow from the high-pressure receiver 80 to the outdoor heat exchanger 30 via the outdoor expansion valve 41. In other words, the inlet check valves 71 and 73 function to flow a refrigerant from one of the outdoor heat exchanger 30 and the indoor heat exchanger 50 to the high-pressure receiver 80, and the outlet check valves 72 and 74 are connected to the outdoor from the high-pressure receiver 80. It fulfills the function of flowing the refrigerant to the other of the heat exchanger 30 and the indoor heat exchanger 50.

  The high-pressure receiver 80 is a container that functions as a refrigerant storage tank, and is provided between the outdoor expansion valve 41 and the liquid-side closing valve 17. The high-pressure receiver 80 into which high-pressure refrigerant flows during both the cooling operation and the heating operation keeps the temperature of the surplus refrigerant stored therein relatively high. Therefore, the surplus refrigerant including the refrigerating machine oil is separated into two layers and the refrigerating machine oil is placed on the upper part. There is no problem of gathering.

  An injection heat exchanger 64 is provided between the outlet of the high pressure receiver 80 and the outlet check valves 72 and 74 of the bridge circuit 70. A branch pipe 62 is branched from a part of the main refrigerant flow path 11a that connects the outlet of the high-pressure receiver 80 and the heat exchanger 64 for injection. The main refrigerant flow path 11 a is a main flow path for liquid refrigerant that connects the outdoor heat exchanger 30 and the indoor heat exchanger 50. The high-pressure receiver 80 is provided between the outdoor expansion valve 41 and the liquid side shut-off valve 17 in the main refrigerant flow path 11a.

  The branch pipe 62 is provided with an injection motor operated valve 63 whose opening degree can be adjusted. The branch pipe 62 is connected to the second flow path 64 b of the injection heat exchanger 64. That is, when the injection motor-operated valve 63 is open, the refrigerant branched from the main refrigerant channel 11 a to the branch pipe 62 is decompressed by the injection motor-operated valve 63 and the second channel 64 b of the injection heat exchanger 64. Flowing into. Note that the second flow path 64 b of the heat exchanger for injection 64 constitutes a part of the branch pipe 62.

  The refrigerant that has been decompressed by the injection motor-operated valve 63 and flows into the second flow path 64 b of the injection heat exchanger 64 exchanges heat with the refrigerant that flows through the first flow path 64 a of the injection heat exchanger 64. The first flow path 64a of the heat exchanger for injection 64 constitutes a part of the main refrigerant flow path 11a. After the heat exchange in the injection heat exchanger 64, the refrigerant flowing through the branch pipe 62 flows into an intermediate injection flow path 65 or a suction injection flow path 67 described later. Further, an injection temperature sensor 96 that detects the temperature of the refrigerant after heat exchange in the injection heat exchanger 64 is attached to the downstream side of the injection heat exchanger 64 of the branch pipe 62.

  The heat exchanger for injection 64 is an internal heat exchanger adopting a double tube structure, and as described above, from the refrigerant flowing through the main refrigerant channel 11a that is the main channel, and the main refrigerant channel 11a for injection. Heat exchange is performed with the refrigerant for injection flowing through the branched branch pipe 62. One end of the first flow path 64 a of the injection heat exchanger 64 is connected to the outlet of the high-pressure receiver 80, and the other end is connected to the outlet check valves 72 and 74 of the bridge circuit 70.

  The liquid side closing valve 17 is a valve to which a liquid refrigerant communication tube 13 for exchanging refrigerant between the outdoor unit 11 and the indoor unit 12 is connected. The gas-side closing valve 18 is a valve to which a gas refrigerant communication pipe 14 for exchanging refrigerant between the outdoor unit 11 and the indoor unit 12 is connected, and is connected to the four-way switching valve 15. Here, the liquid side closing valve 17 and the gas side closing valve 18 are three-way valves provided with service ports.

  The compressor accessory container 28 is disposed in the suction flow path 27 between the four-way switching valve 15 and the compressor 20, and when the refrigerant containing a large amount of liquid components transiently flows into the compressor 20. It plays a role in preventing liquid refrigerant from being inhaled. Although the compressor attached container 28 is provided here, in addition to this, an accumulator for preventing liquid back to the compressor 20 may be disposed in the suction flow path 27.

  A suction injection flow path 67 is connected to a pipe connecting the compressor accessory container 28 and the compressor 20 in the suction flow path 27. The suction injection flow path 67 is a pipe connecting the suction flow path 27 and the downstream portion of the branch pipe 62 on the injection heat exchanger 64. The suction injection flow path 67 is provided with a suction injection open / close valve 68. The suction injection on-off valve 68 is an electromagnetic valve that switches between an open state and a closed state.

  As described above, the compressor 20 is provided with the intermediate injection port 23. The intermediate injection port 23 is a refrigerant introduction port for flowing a refrigerant from the outside into an intermediate pressure refrigerant in the middle of compression in the compressor 20. An intermediate injection flow path 65 is connected to the intermediate injection port 23. The intermediate injection flow path 65 is a pipe that connects the downstream portion of the branch pipe 62 with respect to the injection heat exchanger 64 and the intermediate injection port 23. The intermediate injection flow path 65 is provided with an intermediate injection on / off valve 66. The intermediate injection on-off valve 66 is an electromagnetic valve that switches between an open state and a closed state. Instead of the compressor 20 having two compressors arranged in series, an intermediate injection flow path 65 is provided in the refrigerant pipe connecting the discharge port of the low stage compressor and the suction port of the high stage compressor. It is also possible to adopt a connection configuration.

  As shown in FIG. 1, the tip of the branch pipe 62 extending to the compressor 20 through the injection heat exchanger 64 is connected to the intermediate injection flow path 65 and the suction injection flow path 67 through the bifurcated pipe. Yes. When the intermediate injection on / off valve 66 is in the open state, the refrigerant flowing through the branch pipe 62 through the injection heat exchanger 64 is injected from the intermediate injection flow path 65 into the intermediate injection port 23, and the suction injection on / off valve 68 is opened. In the state, the refrigerant flowing through the branch pipe 62 is injected from the suction injection flow channel 67 into the suction flow channel 27 and is sucked into the compressor 20.

  The outdoor unit 11 includes various sensors and an outdoor control unit 91. The outdoor control unit 91 includes a microcomputer, a memory, and the like provided to control the outdoor unit 11, and controls signals and the like via a transmission line 93 with the indoor control unit 92 of the indoor unit 12. Exchange. As the various sensors, the above-described discharge pressure sensor, discharge temperature sensor 95, suction temperature sensor, injection temperature sensor 96, and the like are provided.

(2-3) Refrigerant communication pipes The refrigerant communication pipes 13 and 14 are refrigerant pipes that are constructed on site when the outdoor unit 11 and the indoor unit 12 are installed at the installation location.

(2-4) Control Unit A control unit 90 as a control unit that performs various operation controls of the air conditioning apparatus 10 is performed by an outdoor control unit 91 and an indoor control unit 92 that are connected via a transmission line 93 as illustrated in FIG. It is configured. As shown in FIG. 2, the control unit 90 receives detection signals from the various sensors 95, 96,..., And based on these detection signals, the various devices 20, 35, 41, 55, 63, 66. , 68,... Are controlled.

  The control unit 90 includes a cooling operation control unit 90a for performing a cooling operation using the indoor heat exchanger 50 as an evaporator, and a heating operation control for performing a heating operation using the indoor heat exchanger 50 as a condenser. The unit 90b includes an injection control unit 90c for performing injection control in the cooling operation and the heating operation.

(3) Operation | movement of an air conditioning apparatus Next, operation | movement of the air conditioning apparatus 10 which concerns on this embodiment is demonstrated. In addition, control in various operations described below is performed by the control unit 90 that functions as an operation control unit.

(3-1) Basic operation of cooling operation At the time of cooling operation, the four-way switching valve 15 is in the state indicated by the solid line in FIG. 1, that is, the discharged gas refrigerant from the compressor 20 flows to the outdoor heat exchanger 30, and Then, the suction flow path 27 is connected to the gas side closing valve 18. The outdoor expansion valve 41 is fully opened, and the opening degree of the indoor expansion valve 42 is adjusted. The closing valves 17 and 18 are in an open state.

  In this state of the refrigerant circuit, the high-pressure gas refrigerant discharged from the compressor 20 is sent to the outdoor heat exchanger 30 that functions as a refrigerant condenser via the four-way switching valve 15, and is sent by the outdoor fan 35. It is cooled by exchanging heat with the supplied outdoor air. The high-pressure refrigerant that has been cooled and liquefied in the outdoor heat exchanger 30 becomes supercooled by the injection heat exchanger 64 and is sent to each indoor unit 12 via the liquid refrigerant communication tube 13. The refrigerant sent to each indoor unit 12 is reduced in pressure by the indoor expansion valve 42 to become a low-pressure gas-liquid two-phase refrigerant, and exchanges heat with indoor air in the indoor heat exchanger 50 functioning as an evaporator of the refrigerant. Then, it evaporates and becomes a low-pressure gas refrigerant. Then, the low-pressure gas refrigerant heated in the indoor heat exchanger 50 is sent to the outdoor unit 11 via the gas refrigerant communication pipe 14 and is sucked into the compressor 20 again via the four-way switching valve 15. . In this way, the room is cooled.

  When only some of the indoor units 12 are in operation, the indoor expansion valve 42 of the stopped indoor units 12 is set to a stop opening (for example, fully closed). In this case, the refrigerant hardly passes through the indoor unit 12 that is not operating, and only the indoor unit 12 that is operating is cooled.

(3-2) Basic Operation of Heating Operation During the heating operation, the four-way switching valve 15 is in the state indicated by the broken line in FIG. 1, that is, the refrigerant pipe 29 on the discharge side of the compressor 20 is connected to the gas side shut-off valve 18. In addition, the suction flow path 27 is connected to the outdoor heat exchanger 30. The opening degree of the outdoor expansion valve 41 and the indoor expansion valve 42 is adjusted. The closing valves 17 and 18 are in an open state.

  In the state of this refrigerant circuit, the high-pressure gas refrigerant discharged from the compressor 20 is sent to each indoor unit 12 via the four-way switching valve 15 and the gas refrigerant communication pipe 14. The high-pressure gas refrigerant sent to each indoor unit 12 passes through the indoor expansion valve 42 after being cooled by exchanging heat with indoor air in the indoor heat exchanger 50 functioning as a refrigerant condenser. Then, it is sent to the outdoor unit 11 via the liquid refrigerant communication tube 13. When the refrigerant is cooled by exchanging heat with room air, the room air is heated. The high-pressure refrigerant sent to the outdoor unit 11 becomes a supercooled state in the injection heat exchanger 64 and is decompressed by the outdoor expansion valve 41 to become a low-pressure gas-liquid two-phase state refrigerant as a refrigerant evaporator. It flows into the functioning outdoor heat exchanger 30. The low-pressure gas-liquid two-phase refrigerant flowing into the outdoor heat exchanger 30 is heated by exchanging heat with the outdoor air supplied by the outdoor fan 35 and evaporated to become a low-pressure refrigerant. The low-pressure gas refrigerant exiting the outdoor heat exchanger 30 is again sucked into the compressor 20 via the four-way switching valve 15. In this way, the room is heated.

(3-3) Injection control in each operation The injection control unit 90c, which is one of the functional units of the control unit 90, improves the operating capacity and lowers the discharge temperature of the compressor 20 during cooling operation and heating operation. In principle, intermediate injection or inhalation injection is performed. Intermediate injection means that a part of the refrigerant flowing in the main refrigerant flow path 11a is branched from the condenser toward the evaporator, and refrigerant gas is injected into the intermediate injection port 23 of the compressor 20 through the intermediate injection flow path 65. is there. In the suction injection, a part of the refrigerant flowing in the main refrigerant flow path 11a from the condenser toward the evaporator is branched, and the refrigerant gas is injected into the intake flow path 27 through the intake injection flow path 67 and sucked into the compressor 20. It is to let you. Both the intermediate injection and the suction injection have the effect of lowering the discharge temperature of the compressor 20. Further, the intermediate injection further has an effect of increasing the driving ability. The injection control unit 90c performs intermediate injection according to the rotation speed (or frequency) of the compressor 20 controlled by the inverter and the refrigerant discharge temperature Tdi discharged from the compressor 20 and detected by the discharge temperature sensor 95. Intermediate injection control to be performed or suction injection control to perform suction injection is executed. However, when any injection control is not necessary, these injection controls are stopped. That is, the injection control unit 90c selectively performs intermediate injection control, inhalation injection control, and non-injection control that does not perform injection at all.

  FIG. 3 shows a flow of injection control by the injection control unit 90c. First, in step S1, it is determined whether the rotation speed of the compressor 20 is larger or smaller than a predetermined threshold value. The predetermined threshold value is set to a value that is, for example, a considerably small number of revolutions that cannot be set to a smaller number of revolutions, or a value that reduces the efficiency of the compressor motor when the number of revolutions is lowered. Is done.

  When it is determined in step S1 that the rotation speed of the compressor 20 is equal to or greater than the threshold value, intermediate injection control is performed. In the intermediate injection control, the intermediate injection on / off valve 66 is opened and the suction injection on / off valve 68 is closed. In the intermediate injection control, in step S2, it is determined whether or not the discharge temperature Tdi of the refrigerant discharged from the compressor 20 detected by the discharge temperature sensor 95 is higher than the first upper limit value. For example, the first upper limit value is set to 95 ° C. When the discharge temperature Tdi is lower than the first upper limit value, in step S3, based on the temperature Tsh of the injection refrigerant downstream of the injection heat exchanger 64 detected by the injection temperature sensor 96, The opening degree of the injection motor-operated valve 63 is adjusted. The injection control unit 90c is configured to control the injection motor-operated valve 63 so that the intermediately injected gas refrigerant becomes a superheated gas, that is, the gas refrigerant having a superheat degree of several degrees C. flows into the intermediate injection flow path 65. Control the opening. Thereby, appropriate capability improvement is achieved. On the other hand, if it is determined in step S2 that the discharge temperature Tdi is higher than the first upper limit value, in step S4, the opening degree of the injection motor operated valve 63 is determined based on the discharge temperature Tdi of the refrigerant discharged from the compressor 20. Is controlled. Here, the wetness control for moistening the gas refrigerant to be subjected to the intermediate injection is performed so that the discharge temperature Tdi is lower than the first upper limit value. That is, the injection control unit 90c controls the opening degree of the injection motor-operated valve 63 so that the intermediately injected gas refrigerant becomes a gas-liquid two-phase flash gas in order to enhance the cooling effect of the intermediate injection.

  When the rotational speed of the compressor 20 is lower than the threshold value in step S1, the process proceeds to step S5, and it is determined whether or not the discharge temperature Tdi of the refrigerant discharged from the compressor 20 is higher than the first upper limit value. Here, when the discharge temperature Tdi is lower than the first upper limit value, it is not necessary to cool the compressor 20 and there is no merit of further reducing the rotation speed of the compressor 20, so that the intermediate injection is also sucked. No injection is performed (the description is omitted in the flow of FIG. 3). That is, the intermediate injection on / off valve 66 and the suction injection on / off valve 68 are also closed. If it is determined in step S5 that the discharge temperature Tdi is higher than the first upper limit value, suction injection control is performed. In the suction injection control, the intermediate injection on / off valve 66 is closed and the suction injection on / off valve 68 is opened. Further, in the suction injection control in step S6, the opening degree of the injection motor operated valve 63 is controlled based on the discharge temperature Tdi of the refrigerant discharged from the compressor 20. Here, wetness control is performed to wet the gas refrigerant to be sucked and injected so that the discharge temperature Tdi is lower than the first upper limit value. That is, the injection control unit 90c controls the opening degree of the injection motor operated valve 63 so that the gas refrigerant sucked and injected becomes a gas-liquid two-phase flash gas in order to enhance the cooling effect of the suction injection.

  When the discharge temperature Tdi of the refrigerant discharged from the compressor 20 detected by the discharge temperature sensor 95 exceeds a second upper limit value that is higher than the first upper limit value, the drooping control of the compressor 20 starts and the rotation speed is forced. When the detected temperature Tdi exceeds the third upper limit value that is higher than the second upper limit value, the control unit 90 issues a stop command for the compressor 20.

(4) Features of the air conditioner (4-1)
In the air conditioner 10 according to the present embodiment, the intermediate injection flow path 65 and the suction injection flow path 67 are provided, and the intermediate injection open / close valve 66 and the suction injection open / close valve are used as a switching mechanism for switching between which the injection is performed. 68. The intermediate injection is performed in the intermediate injection state (the intermediate injection on / off valve 66 is open and the suction injection on / off valve 68 is closed), and the suction injection state (the intermediate injection on / off valve 66 is closed and the suction injection is performed). Suction injection is performed when the on-off valve 68 is open. And when the injection control part 90c of the control part 90 is suppressing the rotation speed of a compressor by low load, such as heating operation when external temperature is high, it is operation efficiency if intermediate injection control was performed. 3 is performed, the suction injection control as in step S6 shown in FIG. 3 is performed, and the discharge temperature of the compressor 20 is lowered.

  As described above, in the air conditioner 10, since the intermediate injection control and the suction injection control are properly used, it is possible to secure the operation efficiency while continuing the operation by reducing the discharge temperature of the compressor 20.

(4-2)
In the air conditioning apparatus 10 according to the present embodiment, the injection refrigerant provided in the branch pipe 62 is an injection refrigerant that flows to the compressor 20 via the intermediate injection flow path 65 or the suction injection flow path 67. The refrigerant is depressurized by the valve 63 and heat-exchanged by the injection heat exchanger 64. Therefore, by adjusting and controlling the opening degree of the injection motor operated valve 63, the refrigerant for injection to be merged with the intermediate pressure refrigerant of the compressor 20 or the low pressure refrigerant sucked into the compressor 20 as shown in step S3. It is possible to use a superheated gas or a flash gas as in step S4 or step S6.

  As a result, the intermediate injection is normally performed with the superheated refrigerant gas as in step S3, and the intermediate injection emphasizing cooling is performed with the wet gas-liquid two-phase flash gas when the discharge temperature of the compressor 20 becomes high. It is possible to perform (step S4).

(4-3)
In the air conditioning apparatus 10 according to the present embodiment, when the discharge temperature Tdi detected by the discharge temperature sensor 95 is higher than a first upper limit value that is a threshold value, the branch pipe 62 is set so that the discharge temperature Tdi falls below the first upper limit value. It is preferable to lower the temperature of the compressor 20 with an injection refrigerant flowing through the refrigerant.

  However, if the intermediate injection is performed during an operation in which the heat load is small and the rotation speed of the compressor 20 is reduced, such as a heating operation when the outside air temperature is high, the capacity is increased and the compressor 20 discharges. The refrigerant pressure (high pressure) increases.

  In view of this, in the air conditioner 10 according to the present embodiment, the rotation speed of the compressor 20 is lower than the threshold (No in step S1), and the discharge temperature Tdi detected by the discharge temperature sensor 95 is the first upper limit value. If it is higher (Yes in step S5), even if the intermediate injection control has been performed so far, the control is switched to the suction injection control (step S6). Thereby, even in the case of a low load, the discharge temperature Tdi can be lowered by the suction injection control while suppressing the unnecessary increase in capacity and ensuring the operation efficiency.

  The reason why the intermediate injection control is not performed when the rotational speed of the compressor 20 is lower than the threshold is, for example, that the rotational speed of the compressor 20 can be reduced by performing the intermediate injection, but the rotational speed is already low. This is because if the number is further reduced, the efficiency of the compressor motor will deteriorate. Even in such a case, if the discharge temperature Tdi of the compressor 20 rises above the first upper limit value, it will fall into a situation of drooping control or stop of the compressor 20, so suction injection is performed. Is going. The suction injection has the effect of lowering the discharge temperature of the compressor 20 as in the case of the intermediate injection. On the other hand, the suction injection has almost no effect of increasing the capacity as in the case of the intermediate injection. Operation efficiency can be ensured. In particular, in the air conditioning apparatus 10 according to the present embodiment, R32 is used as a refrigerant, and the enthalpy difference between the high pressure and the low pressure increases as the high / low differential pressure increases. Control is effective.

(4-4)
In the air conditioner 10 according to the present embodiment, the intermediate injection control is performed to increase the capacity and the efficiency. However, when the discharge temperature Tdi of the compressor 20 increases to a level where it is difficult to continue the operation. Therefore, it becomes necessary to perform drooping control for forcibly reducing the rotational speed of the compressor 20 or to stop the compressor 20.

  In order to suppress this, in the air conditioner 10, when the detected temperature (discharge temperature Tdi) of the discharge temperature sensor 95 is higher than the first upper limit value, instead of the detection temperature of the injection temperature sensor 96, the discharge temperature sensor 95 The opening degree of the injection motor operated valve 63 is adjusted based on the detected temperature (step S4). In step S4, the cooling effect is enhanced by intermediately injecting the wet refrigerant gas into the compressor 20 so that the discharge temperature of the compressor 20 is lowered. On the other hand, when the detected temperature (discharge temperature Tdi) of the discharge temperature sensor 95 is lower than the first upper limit value, the injection motor-operated valve 63 based on the detection temperature of the injection temperature sensor 96 downstream of the injection heat exchanger 64. Is adjusted (step S3) to ensure operating efficiency.

(5) Modification (5-1) Modification A
In the air conditioning apparatus 10 of the above embodiment, two electromagnetic valves, the intermediate injection on / off valve 66 and the suction injection on / off valve 68, are employed as a switching mechanism for switching between the intermediate injection and the suction injection. A three-way valve may be arranged at a place where three pipes of the branch pipe 62, the intermediate injection flow path 65, and the suction injection flow path 67 intersect.

(5-2) Modification B
In the air conditioner 10 of the above-described embodiment, the refrigerant for injection is supplied from the branch pipe 62 branched from the main refrigerant channel 11a to the intermediate injection channel 65 and the suction injection channel 67. Instead, as shown in FIG. 4, the gas component of the refrigerant accumulated in the high-pressure receiver 180 provided in the main refrigerant flow path 111a is taken out by the bypass flow path 182 and the intermediate injection flow path 65 or A configuration in which a refrigerant for injection is supplied to the suction injection flow path 67 can also be adopted.

  The air conditioner 110 according to Modification B is obtained by replacing the outdoor unit 11 of the air conditioner 10 of the above embodiment with an outdoor unit 111. The outdoor unit 111 removes the bridge circuit 70, the high-pressure receiver 80, the branch pipe 62, the injection motor-operated valve 63, and the injection heat exchanger 64 from the outdoor unit 11, and instead, the high-pressure receiver 180 and the bypass channel 182. And an injection bypass electric valve 184. In the outdoor unit 111, the devices having the same reference numerals as those of the outdoor unit 11 are the same as the devices of the above-described embodiment, and thus the description thereof is omitted.

  The high-pressure receiver 180 is a container provided in a part of the main refrigerant flow path 111 a that connects the outdoor expansion valve 41 and the liquid side closing valve 17. The main refrigerant flow path 111 a is a main flow path for liquid refrigerant that connects the outdoor heat exchanger 30 and the indoor heat exchanger 50. The high-pressure receiver 180 into which high-pressure refrigerant flows during both the cooling operation and the heating operation keeps the temperature of the excess refrigerant stored therein relatively high. Therefore, the excess refrigerant containing the refrigeration oil is separated into two layers and the refrigeration oil is placed on the upper part. There is no problem of gathering. In the internal space of the high-pressure receiver 180, liquid refrigerant is normally present in the lower portion and gas refrigerant is present in the upper portion, and a bypass flow path 182 extends from the upper portion of the internal space toward the compressor 20. The bypass flow path 182 is a pipe that plays a role of guiding the gas component of the refrigerant accumulated in the high-pressure receiver 180 to the compressor 20. The bypass passage 182 is provided with an injection bypass electric valve 184 whose opening degree can be adjusted. By opening the injection bypass electric valve 184, intermediate injection is performed in the intermediate injection state (the intermediate injection on / off valve 66 is open and the suction injection on / off valve 68 is closed), and the suction injection state (intermediate injection) Suction injection is performed when the on-off valve 66 is closed and the suction injection on-off valve 68 is open.

  In the air conditioner 110 according to Modification B, the refrigerant that flows to the compressor 20 via the intermediate injection flow path 65 or the suction injection flow path 67 becomes the gas component of the refrigerant that accumulates inside the high-pressure receiver 180. . That is, the saturated gas of the refrigerant in the high-pressure receiver 180 flows to the compressor 20. In the air conditioner 110, in the same way as the air conditioner 10 of the above embodiment, the intermediate injection control and the suction injection control can be selectively used, and the injection heat exchanger 64 of the above embodiment is not necessary. The manufacturing cost of the harmony device 110 can be kept small. On the other hand, since the wet gas cannot be injected and is basically injected with a saturated gas, it is not possible to perform the control for increasing the cooling effect of the injection (the control as in step S4 in the above embodiment).

Second Embodiment
In the air conditioner 10 of the first embodiment, the refrigerant for injection is supplied from the branch pipe 62 branched from the main refrigerant channel 11a to the intermediate injection channel 65 and the suction injection channel 67. Yes. Further, in the air conditioner 110 of Modification B of the first embodiment, the refrigerant gas component accumulated in the high-pressure receiver 180 provided in the main refrigerant flow path 111a is taken out by the bypass flow path 182 and intermediate from the bypass flow path 182. A configuration is adopted in which an injection refrigerant is supplied to the injection flow path 65 and the suction injection flow path 67. Instead of these configurations, the air conditioner can be configured so that both the injection by the branch pipe 262 and the injection by the bypass channel 282 extending from the receiver 280 can be selected.

(1) Configuration of Air Conditioner In the air conditioner according to the second embodiment, the outdoor unit 11 of the air conditioner 10 of the first embodiment using R32 as a refrigerant is replaced with the outdoor unit 211 shown in FIG. Is. Hereinafter, the outdoor unit 211 will be described in such a manner that parts that overlap with the outdoor unit 11 of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The outdoor unit 211 mainly includes a compressor 20, a four-way switching valve 15, an outdoor heat exchanger 30, an outdoor expansion valve 41, a bridge circuit 70, a high-pressure receiver 280, and a first injection motor-operated valve 263. , An injection heat exchanger 264, a second injection motor operated valve 284, an intermediate injection on / off valve 266, a suction injection on / off valve 268, a liquid side shut-off valve 17, and a gas side shut-off valve 18. .

  Compressor 20, compressor accessory container 28, suction flow path 27, refrigerant pipe 29 on the discharge side of compressor 20, discharge temperature sensor 95, intermediate injection port 23, four-way switching valve 15, liquid side closing valve 17, gas side Since the closing valve 18, the outdoor heat exchanger 30, the outdoor expansion valve 41, the outdoor fan 35, and the bridge circuit 70 are the same as those in the first embodiment, the description thereof is omitted.

  The high-pressure receiver 280 is a container that functions as a refrigerant storage tank, and is provided between the outdoor expansion valve 41 and the liquid-side closing valve 17. The high-pressure receiver 280 into which high-pressure refrigerant flows during both the cooling operation and the heating operation keeps the temperature of the excess refrigerant stored therein relatively high. There is no problem of gathering. A receiver outlet pressure sensor 292 is provided in a receiver outlet pipe extending from the lower part of the high-pressure receiver 280 to the heat exchanger 264 for injection. The receiver outlet pipe is a part of a main refrigerant channel 211a described later. The receiver outlet pressure sensor 292 is a sensor that detects the pressure value (high pressure value) of the high-pressure liquid refrigerant.

  In the internal space of the high-pressure receiver 280, liquid refrigerant is normally present in the lower part and gas refrigerant is present in the upper part, but a bypass channel 282 extends from the upper part of the internal space toward the compressor 20. The bypass channel 282 is a pipe that plays a role of guiding the gas component of the refrigerant accumulated in the high-pressure receiver 280 to the compressor 20. The bypass passage 282 is provided with a second injection bypass electric valve 284 whose opening degree can be adjusted. When the second injection bypass electric valve 284 is opened, a gas refrigerant flows into an intermediate injection flow path 265 or a suction injection flow path 267 described later via the injection common pipe 202.

  An injection heat exchanger 264 is provided between the outlet of the high pressure receiver 280 and the outlet check valves 72 and 74 of the bridge circuit 70. A branch pipe 262 is branched from a part of the main refrigerant flow path 211a that connects the outlet of the high-pressure receiver 280 and the heat exchanger for injection 264. The main refrigerant flow path 211a is a main flow path for liquid refrigerant that connects the outdoor heat exchanger 30 and the indoor heat exchanger 50.

  The branch pipe 262 is provided with a first injection motor-operated valve 263 whose opening degree can be adjusted. The branch pipe 262 is connected to the second flow path 264b of the heat exchanger for injection 264. That is, when the electric injection valve 263 is open, the refrigerant branched from the main refrigerant flow path 211a to the branch pipe 262 is decompressed by the first injection electric valve 263, and the second flow of the injection heat exchanger 264 is performed. It flows to the path 264b.

  The refrigerant having been depressurized by the first injection motor-operated valve 263 and having flowed into the second flow path 264b of the injection heat exchanger 264 exchanges heat with the refrigerant flowing through the first flow path 264a of the injection heat exchanger 264. After the heat exchange in the injection heat exchanger 264, the refrigerant flowing through the branch pipe 262 flows into the intermediate injection flow path 265 or the suction injection flow path 267, which will be described later, through the injection common pipe 202. An injection temperature sensor 296 that detects the temperature of the refrigerant after heat exchange in the injection heat exchanger 264 is attached to the branch pipe 262 downstream of the injection heat exchanger 264.

  The heat exchanger for injection 264 is an internal heat exchanger having a double tube structure, and one end of the first flow path 264a is connected to the outlet of the high-pressure receiver 280, and the other end of the first flow path 264a is Connected to outlet check valves 72 and 74 of the bridge circuit 70.

  The injection common pipe 202 includes a bypass flow path 282 extending from the high-pressure receiver 280 and each end of the branch pipe 262 extending from the main refrigerant flow path 211a through the injection heat exchanger 264, an intermediate injection on-off valve 266, and a suction injection on-off valve 268. It is a pipe connecting When at least one of the first injection motor-operated valve 263 and the second injection bypass motor-operated valve 284 is opened, and the intermediate injection on-off valve 266 or the suction injection on-off valve 268 is opened, the refrigerant flows into the injection common pipe 202, and the intermediate injection Alternatively, inhalation injection is performed.

  The intermediate injection flow path 265 extends from the intermediate injection on-off valve 266 connected to the injection common pipe 202 to the compressor 20. Specifically, one end of the intermediate injection flow path 265 is connected to the intermediate injection on / off valve 266, and the other end of the intermediate injection flow path 265 is connected to the intermediate injection port 23 of the compressor 20.

  The suction injection flow path 267 extends from the suction injection on / off valve 268 connected to the injection common pipe 202 to the suction flow path 27. Specifically, one end of the suction injection flow path 267 is connected to the suction injection on-off valve 268, and the other end of the suction injection flow path 267 connects the compressor accessory container 28 and the compressor 20 in the suction flow path 27. Connected to piping.

  The intermediate injection on / off valve 266 and the suction injection on / off valve 268 are electromagnetic valves that switch between an open state and a closed state.

(2) Operation of Air Conditioner Next, the operation of the air conditioner according to the second embodiment will be described. The control in various operations described below is performed by the control unit of the outdoor unit 211 that functions as an operation control unit.

(2-1) Basic operation of cooling operation At the time of cooling operation, the four-way switching valve 15 is in the state indicated by the solid line in FIG. 5, that is, the discharged gas refrigerant from the compressor 20 flows to the outdoor heat exchanger 30, and Then, the suction flow path 27 is connected to the gas side closing valve 18. The outdoor expansion valve 41 is fully opened, and the opening degree of the indoor expansion valve 42 is adjusted. The closing valves 17 and 18 are in an open state.

  In this state of the refrigerant circuit, the high-pressure gas refrigerant discharged from the compressor 20 is sent to the outdoor heat exchanger 30 that functions as a refrigerant condenser via the four-way switching valve 15, and is sent by the outdoor fan 35. It is cooled by exchanging heat with the supplied outdoor air. The high-pressure refrigerant that has been cooled and liquefied in the outdoor heat exchanger 30 is supercooled by the injection heat exchanger 264 and sent to each indoor unit 12. The operation in each indoor unit 12 is the same as that in the first embodiment. The low-pressure gas refrigerant returning from each indoor unit 12 to the outdoor unit 11 is again sucked into the compressor 20 via the four-way switching valve 15. Basically, indoor cooling is performed in this way.

(2-2) Basic operation of heating operation At the time of heating operation, the four-way switching valve 15 is in the state indicated by the broken line in FIG. 5, that is, the refrigerant pipe 29 on the discharge side of the compressor 20 is connected to the gas-side closing valve 18. In addition, the suction flow path 27 is connected to the outdoor heat exchanger 30. The opening degree of the outdoor expansion valve 41 and the indoor expansion valve 42 is adjusted. The closing valves 17 and 18 are in an open state.

  In the state of this refrigerant circuit, the high-pressure gas refrigerant discharged from the compressor 20 is sent to each indoor unit 12 via the four-way switching valve 15 and the gas refrigerant communication pipe 14. The operation in each indoor unit 12 is the same as that in the first embodiment. The high-pressure refrigerant that has returned to the outdoor unit 11 again passes through the high-pressure receiver 280, becomes supercooled by the injection heat exchanger 264, and flows to the outdoor expansion valve 41. The refrigerant that has been decompressed by the outdoor expansion valve 41 and is in a low-pressure gas-liquid two-phase state flows into the outdoor heat exchanger 30 that functions as an evaporator. The low-pressure gas-liquid two-phase refrigerant flowing into the outdoor heat exchanger 30 is heated by exchanging heat with the outdoor air supplied by the outdoor fan 35 and evaporated to become a low-pressure refrigerant. The low-pressure gas refrigerant exiting the outdoor heat exchanger 30 is again sucked into the compressor 20 via the four-way switching valve 15. Basically, indoor heating is performed in this way.

(2-3) Injection control in each operation In principle, the control unit performs intermediate injection or suction injection for the purpose of improving the operation capacity and lowering the discharge temperature of the compressor 20 during cooling operation or heating operation. The intermediate injection is to inject the refrigerant that has flowed from the injection heat exchanger 264 and / or the high-pressure receiver 280 to the injection common pipe 202 into the intermediate injection port 23 of the compressor 20 through the intermediate injection flow path 265. In the suction injection, the refrigerant flowing from the heat exchanger for injection 264 and / or the high-pressure receiver 280 to the injection common pipe 202 is injected into the suction flow path 27 through the suction injection flow path 267 and is sucked into the compressor 20. It is. Both the intermediate injection and the suction injection have the effect of lowering the discharge temperature of the compressor 20. Further, the intermediate injection further has an effect of increasing the driving ability.

  The controller controls the rotation speed (or frequency) of the compressor 20 that is controlled by the inverter, the refrigerant discharge temperature Tdi that is discharged from the compressor 20 and detected by the discharge temperature sensor 95, and the downstream side of the heat exchanger 264 for injection. Injection control is performed based on the injection refrigerant temperature detected by the injection temperature sensor 296. Specifically, intermediate injection control for performing intermediate injection or inhalation injection control for performing inhalation injection is executed. Further, the control unit operates in a non-injection state in which neither injection is performed when conditions for which neither intermediate injection nor inhalation injection should be performed. In other words, the control unit selectively performs intermediate injection control, inhalation injection control, and non-injection control that does not perform injection at all.

  Next, the flow of injection control by the control unit will be described with reference to FIGS. 6A to 6D.

  First, in step S21, it is determined whether the rotation speed of the compressor 20 is larger or smaller than a predetermined threshold value. The predetermined threshold value is set to a value that is, for example, a considerably small number of revolutions that cannot be set to a smaller number of revolutions, or a value that reduces the efficiency of the compressor motor when the number of revolutions is lowered. Is done.

(2-3-1) Intermediate injection control When it is determined in step S21 that the rotation speed of the compressor 20 is equal to or greater than the threshold value, the process proceeds to step S22 to determine whether the cooling operation or the heating operation is being performed. Here, during the heating operation, intermediate injection is mainly performed in which the gas refrigerant taken out from the high-pressure receiver 280 is passed through the intermediate injection flow path 265.

(2-3-1-1) Intermediate injection control during heating When it is determined in step S22 that the heating operation is being performed, the flow proceeds to step S23, and the discharge of the discharge refrigerant of the compressor 20 detected by the discharge temperature sensor 95 is performed. It is determined whether the temperature Tdi is higher than the first upper limit value. For example, the first upper limit value is set to 95 ° C. If the result is NO, the process proceeds to step S24, where the intermediate injection on / off valve 266 is opened and the suction injection on / off valve 268 is closed. When they are already in that state, they are maintained. In step S24, the opening degree of each of the first injection motor-operated valve 263 and the second injection bypass motor-operated valve 284 is adjusted. Since the discharge temperature Tdi is in the normal range, the first injection motor-operated valve 263 has a predetermined degree of supercooling in the liquid refrigerant flowing out of the high-pressure receiver 280 and flowing through the main refrigerant channel 211a in accordance with basic heating operation control. The opening is adjusted so that it is turned on. Moreover, the opening degree of the second injection bypass electric valve 284 is adjusted so that the gas refrigerant of the high-pressure receiver 280 flows into the intermediate injection flow path 265. On the other hand, if it is determined in step S23 that the discharge temperature Tdi is higher than the first upper limit value, the process proceeds to step S25. Here, since it is necessary to lower the discharge temperature Tdi, the opening degree of each of the first injection motor-operated valve 263 and the second injection motor-operated valve 284 is adjusted based on the discharge temperature Tdi. Specifically, in step S25, wetness control for moistening the gas refrigerant to be subjected to intermediate injection is performed so that the discharge temperature Tdi quickly falls below the first upper limit value. That is, in order to enhance the cooling effect of the intermediate injection, the opening degree of the first injection motor-operated valve 263 and the like is adjusted so that the intermediately injected gas refrigerant becomes a gas-liquid two-phase flash gas.

(2-3-1-2) Intermediate injection control during cooling When it is determined in step S22 that the cooling operation is being performed, the process proceeds to step S26, in which it is determined whether or not the discharge temperature Tdi is higher than the first upper limit value. The Here, if the discharge temperature Tdi is higher than the first upper limit value, the process proceeds to step S27, and mainly from the injection heat exchanger 264 to the intermediate injection flow path 265 in order to perform wetness control to wet the gas refrigerant to be subjected to the intermediate injection. And let the refrigerant flow. Specifically, in step S27, the intermediate injection on / off valve 266 is opened, the suction injection on / off valve 268 is closed, and the opening of the first injection motor-operated valve 263 is based on the discharge temperature Tdi. Be controlled. In step S27, the second injection bypass electric valve 284 is opened as necessary. In this step S27, since the gas-liquid two-phase wet gas refrigerant is intermediately injected into the compressor 20 from the heat exchanger for injection 264, it can be expected that the discharge temperature Tdi that is increasing rapidly decreases.

  If it is determined in step S26 that the discharge temperature Tdi is lower than the first upper limit value and it is not necessary to lower the discharge temperature Tdi, both the refrigerant from the high pressure receiver 280 and the refrigerant from the heat exchanger for injection 264 are used. Intermediate injection. Specifically, the process proceeds to step S30 through step S28 and step S29, the intermediate injection on-off valve 266 is opened, the suction injection on-off valve 268 is closed, and further, the first injection motor operated valve 263 is turned on. The opening degree and the opening degree of the second injection bypass electric valve 284 are adjusted. In step S28, it is determined whether or not the high pressure value of the liquid refrigerant detected by the receiver outlet pressure sensor 292 at the outlet of the high pressure receiver 280 is lower than a threshold value. This threshold is a value that is initially set based on the height difference (the difference in height of the installation location) between the outdoor unit 211 and the indoor unit 12 of the air conditioner. The refrigerant is set in a flash gas state before passing through the indoor expansion valve 42 of the unit 12, and the passing sound is increased. If it is determined in step S28 that the high pressure value is lower than the threshold value, it is necessary to increase the high pressure value. Therefore, the degree of decompression at the outdoor expansion valve 41 is increased by increasing the opening degree of the outdoor expansion valve 41 in a slightly throttled state. loosen. As a result, the refrigerant gas component of the high-pressure receiver 280 decreases, the amount of gas refrigerant from the high-pressure receiver 280 occupying the entire injection refrigerant amount decreases, and the injection ratio from the high-pressure receiver 280 decreases. On the other hand, if the high pressure value exceeds the threshold value in step S28, the process proceeds to step S30 with the same injection ratio. In step S30, the intermediate injection on-off valve 266 is opened as described above, and both the refrigerant flowing from the high pressure receiver 280 and the refrigerant flowing from the injection heat exchanger 264 are transferred from the intermediate injection flow path 265 to the compressor 20. Flows to the intermediate injection port 23. In step S30, the opening degree of the injection motor operated valve 263 is adjusted based on the temperature Tsh of the refrigerant for injection downstream of the injection heat exchanger 264, and the outdoor expansion is performed based on the injection ratio. In conjunction with the opening degree of the valve 41, the opening degree of the second injection bypass electric valve 284 is adjusted.

(2-3-2) Control for maintaining low capacity The above-described steps S22 to S30 are controls when it is determined in step S21 that the rotation speed of the compressor 20 is equal to or greater than a threshold value. Since there is still room for further reduction in the rotational speed of the compressor 20, the operating capacity is basically improved by injection. Therefore, intermediate injection is selected instead of inhalation injection.

  However, if it is determined in step S21 that the rotation speed of the compressor 20 is smaller than the threshold value, this means that the compressor 20 has already been lowered to a low capacity, and the operating capacity is increased. Is contrary to the user request, so that the compressor 20 in the low-capacity state is controlled to maintain the same capacity.

(2-3-2-1) Suction Injection Control If it is determined in step S21 that the rotation speed of the compressor 20 is smaller than the threshold value, the process proceeds to step S31, and whether the discharge temperature Tdi is higher than the first upper limit value. It is determined whether or not. Here, if the discharge temperature Tdi is higher than the first upper limit value, it is necessary to lower the discharge temperature Tdi. Therefore, the process proceeds to step S33 or step S34, and suction injection is performed.

(2-3-2-1-1) Suction injection control during heating When it is determined in step S31 that the discharge temperature Tdi is higher than the first upper limit value, and further in step S32, it is determined that the heating operation is being performed. Suction injection is mainly performed in which the refrigerant from the high-pressure receiver 280 flows from the suction injection flow path 267 to the suction flow path 27. Specifically, in step S33, the intermediate injection on / off valve 266 is closed, and the suction injection on / off valve 268 is opened. Based on the discharge temperature Tdi, the opening degree of the second injection bypass electric valve 284 is adjusted so that a large amount of gas refrigerant accumulates in the high-pressure receiver 280 in the heating operation and flows into the suction injection flow path 267, and the heat for injection The opening degree of the first injection motor-operated valve 263 is adjusted so that the refrigerant flowing from the exchanger 264 to the suction injection flow path 267 becomes flash gas.

(2-3-2-1-2) Suction injection control during cooling When it is determined in step S31 that the discharge temperature Tdi is higher than the first upper limit value, and further in step S32, it is determined that the cooling operation is being performed. Suction injection is mainly performed in which the refrigerant from the heat exchanger for injection 264 flows through the suction injection flow path 267. Specifically, in step S34, the intermediate injection on / off valve 266 is closed, and the suction injection on / off valve 268 is opened. Based on the discharge temperature Tdi, the opening degree of the first injection motor-operated valve 263 is adjusted so that the refrigerant flowing from the injection heat exchanger 264 to the suction injection flow path 267 becomes flash gas. In step S34, the second injection bypass electric valve 284 is opened as necessary.

(2-3-2-2) Non-injection control If it is determined in step S31 that the discharge temperature Tdi is lower than the first upper limit value and there is no need to lower the discharge temperature Tdi, the non-injection state is selected. Is done. That is, neither suction injection nor intermediate injection for lowering the discharge temperature Tdi nor intermediate injection for improving the driving ability is required, and it is desirable to stop the injection, and therefore, a non-injection state is adopted. In step S35, the control unit closes the intermediate injection on / off valve 266 and the suction injection on / off valve 268, and opens the opening of the first injection motor-operated valve 263 and the opening of the second injection bypass motor-operated valve 284 to the minimum. To the degree. When the minimum opening is zero, the opening of the first injection motor-operated valve 263 and the second injection bypass motor-operated valve 284 are fully closed.

  Thus, in the air conditioning apparatus according to the second embodiment, since the discharge temperature Tdi is low, there is no need to lower the temperature of the compressor 20 by suction injection or intermediate injection, and compression is performed because low capacity is required. The non-injection control is selected and executed when the rotational speed of the machine 20 is small. As a result, it is possible to suppress an increase in capacity and a decrease in operation efficiency due to suction injection or intermediate injection, and the air conditioner according to the second embodiment can satisfy a low capacity requirement while ensuring operation efficiency. ing.

10,110 Air conditioning equipment (refrigeration equipment)
11a, 111a Main refrigerant flow path 20 Compressor 27 Suction flow path 30 Outdoor heat exchanger (condenser, evaporator)
41 Outdoor expansion valve (expansion mechanism)
42 Indoor expansion valve (expansion mechanism)
50 Indoor heat exchanger (evaporator, condenser)
62,262 Branch pipe (branch flow path)
63,263 Electric valve for injection (opening adjustment valve)
64,264 Heat exchanger for injection 65,265 Intermediate injection flow path 66,266 Intermediate injection on / off valve (switching mechanism)
67,267 Suction injection flow path 68,268 Suction injection on / off valve (switching mechanism)
90 Control unit 95 Discharge temperature sensor (first temperature sensor)
96 Temperature sensor for injection (second temperature sensor)
180,280 High pressure receiver (refrigerant storage tank)
182, 282 Bypass flow path

JP 2009-127902 A

Claims (9)

In a refrigeration system using R32 as a refrigerant,
A compressor (20) for sucking low-pressure refrigerant from the suction flow path (27), compressing the refrigerant, and discharging high-pressure refrigerant;
A condenser (30, 50) for condensing the high-pressure refrigerant discharged from the compressor;
An expansion mechanism (42, 41) for expanding the high-pressure refrigerant exiting the condenser;
An evaporator (50, 30) for evaporating the refrigerant expanded by the expansion mechanism;
An intermediate injection flow path (65, 265) for guiding a part of the refrigerant flowing from the condenser toward the evaporator to the compressor and joining the refrigerant with an intermediate pressure of the compressor;
A suction injection flow path (67, 267) for guiding a part of the refrigerant flowing from the condenser toward the evaporator to the suction flow path and joining the low pressure refrigerant sucked into the compressor;
A refrigeration apparatus (10, 110). A switching mechanism (66, 68, 266, 268) for switching between an intermediate injection state in which the refrigerant flows in the intermediate injection flow path and a suction injection state in which the refrigerant flows in the suction injection flow path;
The refrigeration apparatus according to claim 1, further comprising: Branch passages (62, 262) branched from a main refrigerant passage (11a) connecting the condenser and the evaporator;
An opening adjustment valve (63, 263) provided in the branch flow path and capable of adjusting the opening;
An injection heat exchanger (64, 264) for exchanging heat between the refrigerant flowing through the main refrigerant flow path and the refrigerant flowing downstream of the opening adjustment valve of the branch flow path;
Further comprising
The refrigerant flowing out of the injection heat exchanger and flowing through the branch flow path flows into the intermediate injection flow path or the suction injection flow path.
The refrigeration apparatus according to claim 2. A discharge temperature sensor (95) for detecting the temperature of the refrigerant discharged from the compressor;
An intermediate injection control in which the switching mechanism is in the intermediate injection state and a refrigerant flows through the intermediate injection flow path, and an intake injection control in which the switching mechanism is in the suction injection state and a refrigerant flows in the suction injection flow path are selectively A control unit (90) to execute;
Further comprising
The controller performs the suction injection control when a discharge temperature detected by the discharge temperature sensor is higher than a temperature threshold and a rotation speed of the compressor is lower than a rotation speed threshold;
The refrigeration apparatus according to claim 2 or 3. A first temperature sensor (95) for detecting the temperature of the refrigerant discharged from the compressor;
A second temperature sensor (96) for detecting the temperature of the refrigerant flowing out of the heat exchanger for injection and flowing through the branch flow path;
An intermediate injection control in which the switching mechanism is in the intermediate injection state and a refrigerant flows through the intermediate injection flow path, and an intake injection control in which the switching mechanism is in the suction injection state and a refrigerant flows in the suction injection flow path are selectively A control unit (90) to execute;
Further comprising
In the intermediate injection control, the control unit,
When the temperature detected by the first temperature sensor is lower than the first threshold, the opening adjustment valve is adjusted based on the detected temperature of the second temperature sensor,
When the temperature detected by the first temperature sensor is higher than a first threshold, the opening adjustment of the opening adjustment valve is performed based on the detected temperature of the first temperature sensor.
The refrigeration apparatus according to claim 3. A refrigerant storage tank (180) provided in a main refrigerant flow path (111a) connecting the condenser and the evaporator;
A bypass flow path (182) for guiding a gas component of the refrigerant accumulated in the refrigerant storage tank to the intermediate injection flow path (65) and the suction injection flow path (67);
The refrigeration apparatus according to claim 1, further comprising: The switching mechanism includes a first opening / closing mechanism (66, 266) provided in the intermediate injection flow path and a second opening / closing mechanism (68, 268) provided in the suction injection flow path.
The refrigeration apparatus according to claim 2. The switching mechanism (66, 68, 266, 268) includes the intermediate injection state, the suction injection state, and a non-injection state in which no refrigerant flows through the intermediate injection passage and the suction injection passage. Switching mechanism,
The controller is
The intermediate injection control, the suction injection control, and the non-injection control in which the switching mechanism is set to the non-injection state so that no refrigerant flows through the intermediate injection flow path and the suction injection flow path are selectively executed. Is,
The non-injection control is performed when the discharge temperature detected by the discharge temperature sensor is lower than the temperature threshold and the rotation speed of the compressor is lower than the rotation speed threshold.
The refrigeration apparatus according to claim 4. The switching mechanism (66, 68, 266, 268) includes the intermediate injection state, the suction injection state, and a non-injection state in which no refrigerant flows through the intermediate injection passage and the suction injection passage. A mechanism to switch,
The refrigeration apparatus according to claim 2 or 7.

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