WO2019064441A1

WO2019064441A1 - Air conditioner

Info

Publication number: WO2019064441A1
Application number: PCT/JP2017/035261
Authority: WO
Inventors: 傑鳩村
Original assignee: 三菱電機株式会社
Priority date: 2017-09-28
Filing date: 2017-09-28
Publication date: 2019-04-04
Also published as: EP3690349A4; US20210055024A1; EP3690349A1; JP6880213B2; JPWO2019064441A1; EP3690349B1; CN111133258A; CN111133258B

Abstract

In this air conditioner , an outdoor unit that has a compressor which has an injection port for introducing the refrigerant into an intake chamber, a heat source-side heat exchanger that performs heat exchange with the refrigerant, an outdoor unit-side throttle device, and an accumulator; at least one load-side throttle device; and at least one load-side heat exchanger that performs heat exchange between a load and the refrigerant are connected by piping to constitute a refrigerant circuit for circulating the refrigerant. The outdoor unit is provided with: an injection pipe which has one end connected between the heat source-side heat exchanger and the load-side throttle device in the refrigerant circuit, and the other end connected to the injection port; the outdoor unit-side throttle device that is installed in a position downstream from the one end of the injection pipe when the refrigerant flows from the load-side throttle device to the heat source-side heat exchanger; and an injection throttle device that adjusts the amount of refrigerant flowing through the injection pipe. The outdoor unit further has a control device controls the opening degree of the outdoor unit-side throttle device and the opening degree of the injection throttle device.

Description

Air conditioner

The present invention relates to an air conditioner applied to, for example, a multi-air conditioner for buildings.

An air conditioner such as a multi-air-conditioner for a building is connected, for example, between an outdoor unit (outdoor unit), which is a heat source device disposed outside the building, and an indoor unit (indoor unit) disposed in the building, through piping. Has a refrigerant circuit. The air conditioner has a refrigerant circuit that circulates a refrigerant. In the refrigerant circuit, heating or cooling of a space to be air-conditioned, which is a load, is performed by heating or cooling air using heat release or heat absorption of the refrigerant.

For example, it has an injection circuit in which a throttling device for bypass, a refrigerant heat exchanger, an open / close valve, and an injection port of a compressor are sequentially connected by an injection pipe in which liquid piping is branched between a refrigerant heat exchanger and a load side throttling device. An air conditioner has been proposed (see, for example, Patent Document 1). In this air conditioner, by injecting a refrigerant having a low degree of dryness at an intermediate pressure in the compression process of the compressor, it is possible to suppress an abnormal increase in discharge temperature while increasing the flow rate of the refrigerant. Therefore, in the heating operation in which the outside air temperature where the discharge temperature rises is low, the driving frequency of the compressor can be increased, and the heating capacity can be maintained.

JP 2008-138921 A

In an air conditioning apparatus such as a building multi air conditioner, a refrigerant is additionally sealed according to the length of connection piping between an outdoor unit and an indoor unit and the number of indoor units connected at the installation location. At this time, the amount of refrigerant may be sealed more than the specified value. If the amount of refrigerant sealed in the refrigerant circuit is excessive, the liquid level of the accumulator will be high. For this reason, liquid back (return) may occur. Excessive liquid bag may cause damage to the compressor and the like, and the reliability of the air conditioner may not be maintained.

SUMMARY OF THE INVENTION The present invention solves the problems as described above, and an object of the present invention is to provide an air conditioner that can maintain the ability to a load and ensure reliability without reducing the performance of the air conditioner.

An air conditioner according to the present invention has an injection port for introducing a refrigerant into a suction chamber, a compressor for compressing and discharging the refrigerant, a heat source side heat exchanger for heat exchange of the refrigerant, and an accumulator for accumulating the refrigerant. The outdoor unit having the above, at least one load-side expansion device for decompressing the refrigerant, and at least one load-side heat exchanger for performing heat exchange between the load and the refrigerant are connected by piping, and the refrigerant is circulated An air conditioner comprising a refrigerant circuit, wherein the outdoor unit in the refrigerant circuit has one end connected between the heat source side heat exchanger and the load side expansion device, and the other end connected to the injection port, When the refrigerant flows from the load-side throttling device to the heat-source-side heat exchanger in the injection pipe that allows part of the refrigerant flowing through the refrigerant circuit to pass toward the injection port and the refrigerant circuit And an outdoor throttling device installed downstream of the one end of the injection piping to decompress the passing refrigerant and adjust the flow rate, and an injection throttling device adjusting the amount of the refrigerant flowing through the injection piping. And a controller for controlling an opening degree of the outdoor-side throttling device and an opening degree of the injection throttling device.

According to the present invention, since the control device 60 reduces the amount of refrigerant flowing into the accumulator and prevents excess refrigerant from accumulating, the liquid level of the accumulator can be lowered, and the overflow of the accumulator can be prevented. Can. Therefore, excessive liquid back to the compressor can be prevented, damage to the compressor can be prevented, and the reliability of the air conditioner can be ensured.

It is a figure which shows an example of a structure of the air conditioning apparatus 100 which concerns on Embodiment 1 of this invention. It is a figure explaining the flow of the refrigerant in air conditioning operation mode of air harmony device 100 concerning Embodiment 1 of this invention. It is a figure explaining the flow of the refrigerant in heating operation mode of air harmony device 100 concerning Embodiment 1 of this invention. FIG. 7 is a Mollier diagram showing the state of the refrigerant when the injection is performed to the compressor 10 in the cooling operation mode in the air conditioning apparatus 100 according to Embodiment 1 of the present invention. FIG. 7 is a Mollier diagram showing the state of the refrigerant when the injection is performed to the compressor 10 in the cooling operation mode in the air conditioning apparatus 100 according to Embodiment 1 of the present invention. It is a figure which shows an example of a structure of the air conditioning apparatus 100 which concerns on Embodiment 2 of this invention. The air conditioning apparatus 100 which concerns on Embodiment 2 of this invention WHEREIN: It is a figure which shows an example of the control which the control apparatus 60 performs. It is a figure which shows an example of a structure of the air conditioning apparatus 100 which concerns on Embodiment 3 of this invention. FIG. 18 is a diagram for explaining the flow of the refrigerant in the cooling only operation mode of the air conditioning apparatus 100 according to Embodiment 3. FIG. 18 is a diagram for explaining the flow of the refrigerant in the cooling-dominated operation mode of the air conditioning apparatus 100 according to Embodiment 3. FIG. 17 is a diagram for explaining the flow of the refrigerant in the heating only operation mode of the air conditioning apparatus 100 according to Embodiment 3. FIG. 16 is a diagram for explaining the flow of the refrigerant in the heating main operation mode of the air conditioning apparatus 100 according to Embodiment 3. It is a figure which shows an example of a structure of the air conditioning apparatus 100 which concerns on Embodiment 4 of this invention. It is a figure which shows an example of a structure of the air conditioning apparatus 100 which concerns on Embodiment 5 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, in the following drawings, what attached the same code is the same or it corresponds to this, and suppose that it is common in the whole text of the embodiment described below. Further, the form of the constituent elements shown in the entire specification is merely an example, and the present invention is not limited to these descriptions. In particular, the combination of components is not limited to only the combination in each embodiment, and the components described in the other embodiments can be applied as appropriate to other embodiments. With regard to the magnitude of temperature, pressure and the like, the magnitude is not particularly determined in relation to absolute values, but is relatively determined in the state and operation of the system, the device, and the like. Also, with respect to a plurality of similar devices distinguished by subscripts, etc., the subscripts and the like may be omitted and described, in particular, when it is not necessary to distinguish or specify.

Embodiment 1
FIG. 1 is a diagram showing an example of the configuration of an air conditioning apparatus 100 according to Embodiment 1 of the present invention. As shown in FIG. 1, the air conditioning apparatus 100 of Embodiment 1 has a configuration in which an outdoor unit 1 and an indoor unit 2 are connected via, for example, two main pipes 5.

The air conditioner 100 also has a main refrigerant circuit through which the refrigerant flows and an injection flow channel. The main refrigerant circuit according to the first embodiment includes an accumulator 19, a compressor 10, a refrigerant flow switching device 11, a heat source heat exchanger 12, an outdoor throttling device 45, a load throttling device 25 and a load heat exchanger 26. Are connected in a ring shape by the main pipe 5 and the refrigerant pipe. Further, the injection flow path is from the refrigerant pipe 4 located between the outdoor expansion device 45 and the load-side expansion device 25 to the compressor suction chamber which is a chamber just before compression is started in the compressor 10. The refrigerant flows.

<Outdoor unit 1>
The outdoor unit 1 includes a compressor 10, a refrigerant flow switching device 11, a heat source side heat exchanger 12, an accumulator 19, an injection pipe 41, a heat source side fan 18, an outdoor outside expansion device 45, and an injection expansion device 42. There is. Among them, the compressor 10 constituting the main refrigerant circuit, the refrigerant flow switching device 11, the heat source side heat exchanger 12, the accumulator 19 and the outdoor expansion device 45 are connected by the refrigerant pipe 4 in the outdoor unit 1. ing.

The compressor 10 sucks and compresses the refrigerant, and discharges it in a state of high temperature and high pressure. The compressor 10 is configured of, for example, an inverter compressor or the like whose capacity can be controlled. As the compressor 10, for example, a low pressure shell structure is used. The compressor of the low pressure shell structure has a compression chamber in the closed container, and the inside of the closed container becomes a low pressure refrigerant pressure atmosphere, and sucks and compresses the low pressure refrigerant in the closed container. Moreover, the compressor 10 of Embodiment 1 is a structure which has the injection port 17 which can make a refrigerant | coolant flow in into a compression chamber from the exterior. In the first embodiment, for example, the refrigerant can be introduced from the injection port 17 into the compressor suction chamber which is a chamber just before the compression of the compressor 10 is started. By causing the refrigerant to flow from the outside into the compressor suction chamber, the discharge temperature is prevented from rising above the resistance of the compressor 10.

The refrigerant flow switching device 11 is a device that switches between the refrigerant flow in the heating operation mode and the refrigerant flow in the cooling operation mode. The refrigerant flow switching device 11 has, for example, a four-way valve. Here, the cooling operation mode is an operation mode in which the heat source side heat exchanger 12 acts as a condenser or a gas cooler. The heating operation mode is an operation mode in which the heat source side heat exchanger 12 acts as an evaporator.

The heat source side heat exchanger 12 functions as an evaporator in the heating operation mode. Further, in the cooling operation mode, it functions as a condenser or a gas cooler (in the first embodiment, a condenser). The heat source side heat exchanger 12 in the first embodiment performs heat exchange between the air supplied by the heat source side fan 18 and the refrigerant. However, it is not limited to this. Heat exchange may be performed between the refrigerant and the water. In this case, the heat source side heat exchanger 12 is a water refrigerant heat exchanger.

The accumulator 19 is provided at the suction portion of the compressor 10. The accumulator 19 stores an excess refrigerant generated due to a difference in the amount of refrigerant required between the heating operation mode and the cooling operation mode or an excess refrigerant for a transient operation change. Further, the oil return mechanism 20 is a through hole opened at the lower part of the pipe in the accumulator 19 here. The refrigeration oil and liquid refrigerant accumulated in the lower part of the accumulator 19 pass through the oil return mechanism 20 and are led to the suction side piping of the compressor 10.

The outdoor-side expansion device 45 is located in the main refrigerant circuit between the heat source side heat exchanger 12 and the load-side expansion device 25 of the indoor unit 2 and is provided in the outdoor unit 1. The outdoor side throttle device 45 is, for example, a device capable of arbitrarily controlling the opening degree (opening area) of an electronic expansion valve or the like. The outdoor throttling device 45 raises the pressure of the refrigerant between the outdoor throttling device 45 and the indoor unit 2 and decompresses the refrigerant flowing from the indoor unit 2 into the outdoor unit 1 via the main pipe 5 in the heating operation mode. And inflate. Further, the outdoor-side expansion device 45 adjusts the amount of refrigerant stored in the accumulator 19 by adjusting the opening degree.

The injection pipe 41 is a pipe that constitutes an injection flow path. In the outdoor unit 1, one end of the injection pipe 41 is connected to the refrigerant pipe 4, and the other end is connected to the injection port 17 of the compressor 10. A liquid refrigerant or a gas-liquid two-phase refrigerant is caused to flow into the compressor suction chamber of the compressor 10. At this time, the liquid refrigerant or the gas-liquid two-phase refrigerant is a high pressure or medium pressure refrigerant. The medium pressure is lower than the high pressure in the refrigeration cycle (for example, the refrigerant pressure in the condenser or the discharge pressure of the compressor 10), and the low pressure in the refrigeration cycle (for example, the refrigerant pressure in the evaporator or the suction pressure of the compressor 10) The pressure is higher than).

The injection throttle device 42 is installed in the injection pipe 41. The injection throttle device 42 adjusts the amount and pressure of the refrigerant flowing through the injection pipe 41 and flowing into the injection port 17 of the compressor 10. The injection throttling device 42 can adjust the opening degree continuously or in multiple steps based on, for example, the control of the control device 60 described later.

Further, in the outdoor unit 1, a discharge temperature sensor 43, a discharge pressure sensor 40, an outside air temperature sensor 46, and a pressure detection sensor 44 are installed. The discharge temperature sensor 43 detects the temperature of the refrigerant discharged by the compressor 10, and outputs a discharge temperature detection signal. The discharge pressure sensor 40 detects the pressure of the refrigerant discharged by the compressor 10, and outputs a discharge pressure detection signal. The outdoor temperature sensor 46 is installed at the air inflow portion of the heat source side heat exchanger 12 in the outdoor unit 1. The outside air temperature sensor 46 detects, for example, the outside air temperature that is the temperature around the outdoor unit 1 and outputs an outside air temperature detection signal. The pressure detection sensor 44 detects the pressure (intermediate pressure) of the refrigerant between the outdoor throttle device 45 and the accumulator 19 and outputs an intermediate pressure detection signal. Here, not only a pressure sensor but also a temperature sensor can be used as the pressure detection sensor 44. When a temperature sensor is used as the pressure detection sensor 44, the control device 60 described later sets the calculated saturation pressure as an intermediate pressure based on the temperature detected by the pressure detection sensor 44.

<Indoor unit 2>
The indoor unit 2 has a load-side heat exchanger 26 and a load-side throttling device 25. The load-side heat exchanger 26 functions as a condenser or a gas cooler (in the first embodiment, a condenser) in the heating operation mode. Also, in the cooling operation mode, it functions as an evaporator. The load side heat exchanger 26 performs heat exchange between the load to be heat exchanged and the refrigerant. In the first embodiment, the air in the space to be air-conditioned supplied by the load-side fan 28 is the load.

The load-side expansion device 25 is installed at a position upstream of the load-side heat exchanger 26 in the flow of the refrigerant in the cooling operation mode of the main refrigerant circuit. The load side throttle device 25 has functions as a pressure reducing valve and an expansion valve, which decompresses and expands the refrigerant. The load-side throttling device 25 can adjust the opening degree continuously or in multiple steps based on, for example, the control of the control device 60 described later. The load-side throttling device 25 is, for example, a device capable of arbitrarily controlling the opening degree of an electronic expansion valve or the like.

Further, the indoor unit 2 is provided with an inlet temperature sensor 31 and an outlet temperature sensor 32. The inlet side temperature sensor 31 and the outlet side temperature sensor 32 have thermistors and the like. The inlet-side temperature sensor 31 is installed in the pipe on the refrigerant inflow side of the load-side heat exchanger 26 in the flow of the refrigerant in the cooling operation mode of the main refrigerant circuit. Then, the inlet-side temperature sensor 31 detects the temperature of the refrigerant flowing into the load-side heat exchanger 26, and outputs an inflow-side detection signal. The outlet-side temperature sensor 32 is installed in a pipe on the refrigerant outflow side of the load-side heat exchanger 26 in the flow of the refrigerant in the cooling operation mode of the main refrigerant circuit. Then, the outlet-side temperature sensor 32 detects the temperature of the refrigerant flowing out of the load-side heat exchanger 26, and outputs an outlet-side detection signal.

And the air conditioning apparatus 100 has a control device 60. The control device 60 controls the overall operation of the air conditioning device 100 based on detection signals sent from the various sensors described above and an instruction from a remote controller (not shown). For example, the control device 60 controls the drive frequency of the compressor 10, controls the number of rotations of the heat source fan 18 and the load fan 28 (including on or off), and controls the flow path switching by the refrigerant flow switching device 11. I do. Further, the control device 60 performs opening degree control of the outdoor side throttle device 45, the injection throttle device 42, and the load side throttle device 25, and the like. The control device 60 performs these controls to execute each operation mode of the air conditioner 100.

Here, the control device 60 has a microcomputer. The microcomputer has, for example, a control processing unit such as a CPU (Central Processing Unit). It also has an I / O port that manages input and output. The microcomputer also has a storage device 61. The storage device 61 is, for example, a volatile storage device (not shown) such as a random access memory (RAM) capable of temporarily storing data and a hard disk, and a nonvolatile auxiliary storage such as a flash memory capable of storing data over a long period of time. It is an apparatus (not shown). The storage device 61 has data in which the processing procedure performed by the control processing unit is a program. And a control arithmetic processing unit performs processing based on data of a program, and realizes processing of each part. However, the present invention is not limited to this, and each device may be configured by a dedicated device (hardware). Here, although the control device 60 is installed in the outdoor unit 1 in the air conditioning apparatus 100 according to the first embodiment, the present invention is not limited to this. The control device 60 may be installed in the indoor unit 2. In addition, a plurality of control devices 60 may be installed by dividing functions into the outdoor unit 1 and the indoor unit 2 or the like.

Next, each operation mode performed by the air conditioning apparatus 100 will be described. The control device 60 of the air conditioning apparatus 100 can execute a heating operation mode in which the indoor unit 2 performs cooling operation or a heating operation mode in which the indoor unit 2 performs heating operation based on an instruction from the indoor unit 2. At this time, the control device 60 can determine whether to perform injection. Each operation mode will be described together with the flow of the refrigerant.

<Cooling operation mode (without injection)>
FIG. 2 is a diagram for explaining the flow of the refrigerant in the cooling operation mode of the air conditioning apparatus 100 according to Embodiment 1 of the present invention. In FIG. 2, a case where a cooling load is generated in the load-side heat exchanger 26 will be described as an example, and the flow of the refrigerant other than the refrigerant flow in the injection in the cooling operation mode will be described. Here, in FIG. 2, the direction in which the refrigerant flows is indicated by a solid arrow.

As shown in FIG. 2, the low temperature and low pressure refrigerant is sucked and compressed by the compressor 10. Then, the high temperature and high pressure gas refrigerant is discharged from the compressor 10. The high temperature and high pressure gas refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 through the refrigerant flow switching device 11. Then, the gas refrigerant that has flowed into the heat source side heat exchanger 12 condenses while radiating to the outdoor air supplied by the heat source side fan 18, becomes high pressure liquid refrigerant, and flows out from the heat source side heat exchanger 12. The high-pressure liquid refrigerant flowing out of the heat source side heat exchanger 12 flows out of the outdoor unit 1 through the outdoor expansion device 45. Then, the high pressure liquid refrigerant flows into the indoor unit 2 through the main pipe 5.

The high-pressure refrigerant flowing into the indoor unit 2 is expanded by the load-side throttling device 25 to be a low-temperature and low-pressure gas-liquid two-phase refrigerant. The refrigerant in the gas-liquid two-phase state flows into the load side heat exchanger 26 acting as an evaporator. The gas-liquid two-phase refrigerant that has flowed into the load-side heat exchanger 26 absorbs heat from the room air to become low-temperature and low-pressure gas refrigerant while cooling the room air, and flows out from the load-side heat exchanger 26 .

Here, the degree of opening of the load-side expansion device 25 is controlled by the control device 60 so that the superheat (degree of superheat) becomes constant. Superheat is a value of a temperature difference obtained as a difference between the temperature detected by the inlet temperature sensor 31 and the temperature detected by the outlet temperature sensor 32.

The gas refrigerant flowing out of the load-side heat exchanger 26 flows out of the indoor unit 2. The refrigerant flowing out of the indoor unit 2 flows into the outdoor unit 1 again through the main pipe 5. The refrigerant flowing into the outdoor unit 1 passes through the refrigerant flow switching device 11 and the accumulator 19. At this time, the low temperature and low pressure refrigerant passes through the accumulator 19. Then, the low temperature and low pressure refrigerant is again drawn into the compressor 10.

<Heating operation mode (when not injecting)>
FIG. 3 is a view for explaining the flow of the refrigerant in the heating operation mode of the air conditioning apparatus 100 according to Embodiment 1 of the present invention. In FIG. 3, the case where the thermal load is generated in the load-side heat exchanger 26 is taken as an example, and the flow of the refrigerant other than the refrigerant flow in the injection in the heating operation mode will be described. Here, in FIG. 3, the direction in which the refrigerant flows is indicated by a solid arrow.

As shown in FIG. 3, the low temperature and low pressure refrigerant is sucked and compressed by the compressor 10. Then, the high temperature and high pressure gas refrigerant is discharged from the compressor 10. The high temperature and high pressure gas refrigerant discharged from the compressor 10 flows out of the outdoor unit 1 through the refrigerant flow switching device 11. The high temperature and high pressure gas refrigerant flowing out of the outdoor unit 1 flows into the indoor unit 2 through the main pipe 5.

The high-temperature and high-pressure gas refrigerant flowing into the indoor unit 2 flows into the load-side heat exchanger 26. The gas refrigerant that has flowed into the load-side heat exchanger 26 dissipates heat into the room air, thereby becoming room temperature liquid refrigerant while flowing through the load-side heat exchanger 26. The liquid refrigerant that has flowed out of the load-side heat exchanger 26 is expanded by the load-side throttling device 25 to become a medium-temperature and medium-pressure gas-liquid two-phase refrigerant, and flows out of the indoor unit 2. The refrigerant flowing out of the indoor unit 2 flows into the outdoor unit 1 again through the main pipe 5.

The medium-temperature and medium-pressure gas-liquid two-phase refrigerant that has flowed into the outdoor unit 1 flows into the heat source side heat exchanger 12. The gas-liquid two-phase refrigerant that has flowed into the heat source side heat exchanger 12 absorbs heat from the outdoor air to become low temperature and low pressure gas refrigerant while cooling the outdoor air, and flows out from the heat source side heat exchanger 12 . The low temperature and low pressure gas refrigerant flowing out of the heat source side heat exchanger 12 passes through the refrigerant flow switching device 11 and the accumulator 19. At this time, the low temperature and low pressure refrigerant passes through the accumulator 19. Then, the low temperature and low pressure refrigerant is again drawn into the compressor 10.

<Impact on performance without injection>
In the cooling operation mode and the heating operation mode, when injection is not performed, the control device 60 controls the injection throttle device 42 to an opening degree at which the injection throttle device 42 is fully closed. Therefore, the refrigerant does not flow in the injection pipe 41. Also, when the injection throttle device 42 is fully closed, the compressor suction chamber of the compressor 10 is at the lowest pressure in the refrigerant circuit. As described above, the compressor 10 in the first embodiment has a structure that allows the refrigerant to flow into the compressor suction chamber. Therefore, compared with the case where the intermediate compression chamber of the compressor 10 has an injection port, the injection piping between the injection throttle device 42 and the compressor suction chamber of the compressor 10 from the compressor suction chamber of the compressor 10 At 41, the refrigerant does not leak. Therefore, the efficiency of the compressor 10 is not deteriorated due to the leakage of the refrigerant. It is possible to suppress the performance degradation of the device due to the refrigerant leak.

<Cooling operation mode (flow at injection)>
(Necessity and effect outline of injection in cooling operation mode)
For example, as in R32, there is a refrigerant whose discharge temperature of the compressor 10 is higher than that of the R410A refrigerant (hereinafter referred to as R410A). In the case where the refrigerant used in the air conditioner 100 is a refrigerant whose discharge temperature is high, the discharge temperature needs to be lowered in order to prevent deterioration of refrigeration oil, burnout of the compressor 10 a and the like. Therefore, in the cooling operation mode when the refrigerant whose discharge temperature is high is used, part of the high-pressure liquid refrigerant that has flowed out from the heat source side heat exchanger 12 is transferred to the compressor 10 via the injection pipe 41. Injection is made to flow into the compressor suction chamber. When performing injection, the control device 60 controls the injection throttle device 42 and the outdoor throttle device 45 to adjust the flow rate of the refrigerant flowing through the injection pipe 41.

FIG. 4 is a Mollier chart showing the state of the refrigerant when the injection is performed to the compressor 10 in the cooling operation mode in the air conditioning apparatus 100 according to Embodiment 1 of the present invention. The horizontal axis of FIG. 4 represents specific enthalpy h [kJ / kg]. Moreover, the vertical axis | shaft of FIG. 4 represents the pressure P [MPa]. The effect of the injection in the cooling operation mode in the air conditioning apparatus 100 according to Embodiment 1 will be described using FIG. 4.

In FIG. 4, the liquid refrigerant that has flowed out of the heat source side heat exchanger 12 is in the state at point (c). The liquid refrigerant is decompressed by the outdoor throttling device 45 to be in the state of liquid or two-phase refrigerant indicated by point (d). A part of the refrigerant or the two-phase refrigerant that has been depressurized flows into the compressor suction chamber of the compressor 10 via the injection pipe 41 and the injection throttle device 42.

On the other hand, the remaining refrigerant of the decompressed liquid or the two-phase refrigerant is decompressed by the load-side throttling device 25 to be in the state of the two-phase refrigerant shown at point (g). To flow. In the load side heat exchanger 26, it becomes a low temperature and low pressure gas refrigerant indicated by point (e). The gas refrigerant flows into the compressor 10 via the main pipe 5, the refrigerant flow switching device 11 and the accumulator 19.

The gas refrigerant flowing into the compressor 10 merges with the liquid or two-phase refrigerant flowing through the injection port 17 in the compressor suction chamber. The state of the refrigerant in the compressor suction chamber is a two-phase refrigerant of high dryness and low pressure, as indicated by point (g). Then, the state of the refrigerant discharged by the compressor 10 is a high-pressure gas refrigerant indicated by point (b). The discharge temperature of the high-pressure gas refrigerant indicated by the point (b) is lower than that of the high-pressure gas refrigerant indicated by the point (b1) discharged without injection. Therefore, deterioration of the refrigeration oil and burning of the compressor 10 can be prevented.

<Control of the injection throttle device 42 in the cooling operation mode>
Control of the injection throttle device 42 by the controller 60 in the cooling operation mode will be described. The control device 60 controls the opening degree of the injection throttle device 42 based on the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43. When the opening degree of the injection throttle device 42 is increased, the flow rate of the refrigerant flowing into the compressor 10a is increased. Therefore, the discharge temperature of the refrigerant discharged from the compressor 10 is reduced. In addition, when the opening degree of the injection throttle device 42 is reduced, the flow rate of the refrigerant flowing into the compressor 10 a decreases. Therefore, the discharge temperature of the refrigerant discharged from the compressor 10 rises.

Therefore, the control device 60 determines whether the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43 is equal to or less than the discharge temperature threshold value. When the controller 60 determines that the discharge temperature is equal to or lower than the discharge temperature threshold value, the controller 60 controls the injection throttle device 42 so that the amount of refrigerant injected is reduced. Here, the discharge temperature threshold value is set in accordance with the limit value of the discharge temperature of the compressor 10.

On the other hand, when the control device 60 determines that the discharge temperature is higher than the discharge temperature threshold value, the control device 60 controls the injection throttle device 42 so that the amount of refrigerant injected increases. At this time, the control device 60 controls the injection throttle device 42 so that the discharge temperature becomes the discharge temperature threshold value. For example, control device 60 stores data indicating the relationship between the discharge temperature and the degree of opening of injection throttle device 42 in storage device 61 in the form of a table. Then, the control device 60 controls the injection throttle device 42 by determining the opening degree of the injection throttle device 42 corresponding to the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43. Here, the control device 60 may store, for example, an equation having the discharge temperature as a variable in the storage device 61 instead of the data in the form of a table. The controller 60 calculates the opening degree of the injection throttle device 42 based on the discharge temperature, and controls the injection throttle device 42.

Here, although the control device 60 performs the determination related to the control of the injection throttle device 42 based on the discharge temperature and the discharge temperature threshold value, the present invention is not limited to this. For example, based on the discharge superheat degree (discharge superheat) of the compressor 10 and the superheat degree threshold value, the determination related to the control of the injection throttle device 42 can be performed. Here, the degree of discharge superheat of the compressor 10 is the difference between the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43 and the saturation temperature calculated from the discharge pressure sensor 40.

<Operation and Effect of Injection in Cooling Operation Mode>
As described above, the injection enthalpy of the refrigerant in the compressor suction chamber of the compressor 10 can be reduced by performing the injection. Therefore, the discharge temperature of the compressor 10 can be suppressed so as not to be excessively high. For this reason, deterioration of refrigeration oil can be suppressed and breakage of the compressor 10 can be prevented. Therefore, the reliability of the entire air conditioning apparatus 100 can be secured. Further, by suppressing the rise of the discharge temperature of the compressor 10, the driving frequency of the compressor 10 can be increased. Therefore, a large amount of cooling capacity can be secured, and a large air conditioning load can be coped with. And, the user's comfort can be maintained.

<Heating operation mode (flow at injection)>
<Necessity and effect outline of injection>
In the heating operation mode, the discharge temperature of the compressor 10 is equal to or higher than the discharge temperature threshold when the driving frequency of the compressor 10 is increased, not only when the discharge temperature is high but the outside air temperature is low. It can be Therefore, in order to secure the heating capacity, injection is required when raising the drive frequency. In the heating operation mode, control for reducing the discharge temperature will be described in order to prevent deterioration of refrigeration oil caused by the discharge temperature of the compressor 10 becoming high, burnout of the compressor 10 and the like.

FIG. 5 is a Mollier chart showing the state of the refrigerant when the injection is performed to the compressor 10 in the cooling operation mode in the air conditioning apparatus 100 according to Embodiment 1 of the present invention. The horizontal axis of FIG. 5 represents specific enthalpy h [kJ / kg]. Moreover, the vertical axis | shaft of FIG. 5 represents the pressure P [MPa]. The effect of the injection in the heating operation mode in the air conditioning apparatus 100 according to Embodiment 1 will be described with reference to FIG. 5.

In FIG. 5, the liquid refrigerant that has flowed out of the load-side heat exchanger 26 is in the state at point (c). The liquid refrigerant is decompressed by the load-side throttling device 25 to be in the state of a medium pressure and medium temperature two-phase refrigerant indicated by point (d). The decompressed medium pressure and medium temperature two-phase refrigerant passes through the main pipe 5 and the refrigerant pipe 4. A part of the depressurized medium pressure and medium temperature two-phase refrigerant flows into the compressor suction chamber of the compressor 10 through the injection pipe 41 and the injection throttle device 42.

On the other hand, the remaining refrigerant of the medium pressure and medium temperature two-phase refrigerant is depressurized by the outdoor expansion device 45 to be in the state of the two-phase refrigerant indicated by point (g). To flow. In the heat source side heat exchanger 12, by absorbing heat from the outside air, it becomes a low temperature and low pressure gas refrigerant indicated by the point (e). The gas refrigerant flows into the compressor 10 via the refrigerant flow switching device 11 and the accumulator 19.

Here, although the decompressed medium-pressure and medium-temperature two-phase refrigerant as shown by the point (d) has been described as passing through the injection pipe 41, it is not limited to this. For example, a gas-liquid separator may be installed at the connection portion between the injection pipe 41 and the refrigerant pipe 4 so that the liquid refrigerant flows through the injection pipe 41. The flow of the liquid refrigerant into the injection pipe 41 makes it possible to stabilize the control of the injection throttle device 42.

The controller 60 controls the outdoor throttling device 45 and the injection throttling device 42 such that the refrigerant flows from the injection pipe 41 into the compressor suction chamber of the compressor 10. By performing the injection, the discharge temperature of the refrigerant discharged by the compressor 10 can be reduced, and the air conditioner 100 can be used safely.

<Control of Injection Throttle Device 42 in Heating Operation Mode>
The control of the injection throttle device 42 in the heating operation mode is similar to the control in the cooling operation mode. The control device 60 performs processing such as determination based on the discharge temperature and the discharge temperature threshold value, and controls the injection throttle device 42. Here, the control of the injection throttle device 42 may be performed based on the discharge superheat degree of the compressor 10 and the superheat degree threshold value.

<Control of the outdoor throttle device 45 in the heating operation mode>
In the heating operation mode, in order to flow a sufficient amount of liquid or two-phase refrigerant into the suction chamber of the compressor 10, it is necessary to increase the saturation temperature of the medium pressure and medium temperature liquid or two-phase refrigerant. Therefore, the control device 60 controls the outdoor-side throttling device 45 so that the refrigerant on the upstream side of the outdoor-side throttling device 45 becomes a medium-pressure refrigerant.

When the degree of opening of the outdoor side throttle device 45 is small, the amount of refrigerant flowing out of the outdoor side throttle device 45 decreases. On the other hand, the amount of refrigerant in the refrigerant pipe 4 between the load-side expansion device 25 and the outdoor-side expansion device 45 increases. Therefore, the pressure of the medium pressure and medium temperature liquid or two-phase refrigerant passing through the injection pipe 41 is increased.

Further, when the opening degree of the outdoor side expansion device 45 is large, the amount of refrigerant flowing out of the outdoor side expansion device 45 increases. On the other hand, the amount of refrigerant in the refrigerant pipe 4 between the load-side expansion device 25 and the outdoor-side expansion device 45 decreases. Therefore, the pressure of the medium pressure and medium temperature liquid or two-phase refrigerant passing through the injection pipe 41 is reduced.

Therefore, the control device 60 calculates the saturation temperature of the medium-temperature and medium-pressure gas-liquid two-phase refrigerant that has flowed out of the load-side throttling device 25 based on the pressure detected by the pressure detection sensor 44. Then, the opening degree of the outdoor-side throttling device 45 is adjusted so that the saturation temperature approaches a predetermined value capable of securing the flow rate necessary for injection. This predetermined value is taken as the injection temperature value. The injection temperature value is, for example, a temperature of 10 ° C. or more.

Thus, as in the cooling operation mode, the low-pressure and low-temperature gas refrigerant flowing out of the accumulator 19 and the liquid or two-phase refrigerant passing through the injection flow path are mixed in the compressor suction chamber of the compressor 10. The mixed refrigerant becomes a low-pressure two-phase refrigerant with high dryness. The compressor 10 compresses a high-dry low-pressure gas-liquid two-phase refrigerant.

<Operation and effect of injection in heating operation mode>
As described above, the injection enthalpy of the refrigerant in the compressor suction chamber of the compressor 10 can be reduced by performing the injection. Therefore, the discharge temperature of the compressor 10 can be suppressed so as not to be excessively high. For this reason, deterioration of refrigeration oil can be suppressed and breakage of the compressor 10 can be prevented. Therefore, the reliability of the entire air conditioning apparatus 100 can be secured. Further, by suppressing the rise of the discharge temperature of the compressor 10, the driving frequency of the compressor 10 can be increased. Therefore, a large amount of cooling capacity can be secured, and a large air conditioning load can be coped with. And, the user's comfort can be maintained.

<The merit of the injection structure, the opening degree of the outdoor throttling device 45>
For example, there is an air conditioner which uses a low pressure shell type compressor and injects into a pipe located on the suction side of the compressor. In such an air conditioner, when a large amount of liquid or two-phase refrigerant is injected into a pipe located on the suction side of the compressor, the liquid refrigerant stagnates in the lower part of the shell of the compressor. For this reason, the refrigeration oil is diluted by the liquid refrigerant and the concentration decreases. If the concentration of refrigeration oil decreases, the scroll in the compressor may be burnt out. Therefore, in order to suppress the amount of refrigerant to be injected, it is necessary to use a small valve in the outdoor expansion device. If a small-sized valve is used for the outdoor-side throttling device, dust etc. may be clogged in the valve and the outdoor-side throttling device may malfunction.

On the other hand, the air conditioner 100 of the first embodiment has a structure in which the compressor 10 has a low pressure shell structure and injects into a compressor suction chamber which is a chamber just before compression is started. Therefore, even if the amount of refrigerant related to the injection increases, the refrigerant injected into the scroll portion of the compressor 10 can be made to flow. Therefore, the liquid or two-phase refrigerant injected into the lower part of the shell does not stay. Therefore, refrigeration oil is not diluted and the concentration does not decrease. In addition, the amount of refrigerant related to injection can be increased. Therefore, it is not necessary to use a small-sized valve for the outdoor-side throttling device 45, and it is possible to prevent the operation failure due to the clogging of dust etc. in the valve.

<Liquid back prevention processing>
Here, for example, at the installation location of the air conditioning apparatus 100, the amount of refrigerant additionally enclosed in the refrigerant circuit may be more than a prescribed amount of refrigerant determined based on the length of the main pipe 5 or the like. is there. In such a case, when the amount of surplus refrigerant generated in the heating operation mode becomes larger than the amount of refrigerant that can be accumulated by the accumulator 19, the accumulator 19 overflows. Therefore, it is necessary to prevent a liquid back (return) in which the liquid refrigerant to the compressor 10 is excessively returned to prevent the overflow.

For example, control device 60 stores data indicating the relationship between the discharge temperature of compressor 10 and the liquid back ratio according to the liquid level of accumulator 19 in the form of a table in storage device 61 when injection is not performed. Keep it. More specifically, regarding this relationship, the discharge temperature of the compressor 10 determined by the liquid back amount at a predetermined liquid level height of the accumulator 19 and the driving frequency, suction state, discharge state, etc. of the compressor 10 Relationship with The predetermined liquid level height is, for example, a height at a refrigerant amount of 2/3 of the volume of the accumulator 19 or the like. The discharge temperature obtained in such a relationship is the liquid level adjustment threshold when injection is not performed. The liquid level adjustment threshold value is the discharge temperature of the compressor 10 which is lowered by the liquid back rate according to the liquid level height of the accumulator 19.

Further, when the injection is performed, for example, the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43 becomes a discharge temperature which is lowered by the injection including a drop in the suction enthalpy. For this reason, the liquid level adjustment threshold value is obtained by performing an operation for obtaining the discharge temperature corresponding to the suction enthalpy reduction due to the liquid bag. Therefore, the control device 60 sets a value obtained by adding the discharge temperature decrease width when the refrigerant is added by the injection to the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43 as the liquid level adjustment threshold value. Here, the liquid level adjustment threshold or the like is set based on the discharge temperature of the compressor 10, but the discharge superheat degree may be used instead of the discharge temperature. Further, the control device 60 may store, as data in the storage device 61, for example, a mathematical expression having the discharge temperature or the discharge superheat degree as a variable instead of the data in the form of a table. The control device 60 substitutes the discharge temperature or the discharge superheat degree into the equation to calculate the liquid level adjustment threshold value.

The control device 60 determines whether the discharge temperature or discharge superheat degree of the compressor 10, which is lowered by the liquid back from the accumulator 19, is equal to or less than a predetermined liquid level adjustment threshold value. The control device 60 controls the opening degree of the outdoor side throttling device 45 so as to become higher than the liquid level adjustment threshold value when determining that the discharge temperature or the discharge superheat degree is equal to or less than the liquid level adjustment threshold value. . For example, when the discharge temperature or the discharge superheat degree of the compressor 10 becomes low, the control device 60 reduces the opening degree of the outdoor side throttling device 45 to lower the liquid level of the accumulator 19.

According to the air conditioner 100 of the first embodiment, the control device 60 performs the control described above to set the fluid or the fluid in the main pipe 5 positioned between the load-side throttling device 25 and the outdoor-side throttling device 45. The phase refrigerant is allowed to stay. Then, the amount of refrigerant flowing into the accumulator 19 is reduced so that excess refrigerant does not accumulate. Therefore, the liquid level of the accumulator 19 can be lowered and overflow of the accumulator 19 can be prevented. Therefore, the dilution of the refrigerator oil due to the liquid bag in the compressor 10 can be suppressed, and damage to the compressor 10 can be prevented. And the reliability of the air conditioning apparatus 100 can be ensured.

Second Embodiment
FIG. 6 is a diagram showing an example of the configuration of an air conditioning apparatus 100 according to Embodiment 2 of the present invention. In FIG. 6, the same reference numerals as in FIG. 1 are used to perform the same operations as those described in the first embodiment. The air conditioning apparatus 100 of Embodiment 2 has a plurality of outdoor units 1 connected by piping in parallel to constitute a refrigerant circuit. In FIG. 6, two outdoor units 1 are connected in parallel.

<Outdoor unit 1a and outdoor unit 1b>
The configurations of the outdoor unit 1a and the outdoor unit 1b shown in FIG. 6 are the same as those of the outdoor unit 1 described in the first embodiment. Further, the operation in the heating operation mode and the cooling operation mode, the operation in the case of performing the injection, and the like are basically the same as the outdoor unit 1 described in the first embodiment. Therefore, when there is no need to distinguish between the outdoor unit 1a, the outdoor unit 1b, and the devices included in the outdoor unit 1a and the outdoor unit 1b, subscripts are omitted.

The outdoor unit 1a includes a compressor 10a, a refrigerant flow switching device 11a, a heat source heat exchanger 12a, an accumulator 19a, an injection pipe 41a, a heat source fan 18a, an outdoor throttling device 45a, and an injection throttling device 42a. There is. The compressor 10a, the refrigerant flow switching device 11a, the heat source side heat exchanger 12a, the accumulator 19a and the outdoor expansion device 45a are connected by the refrigerant pipe 4a in the outdoor unit 1a. Further, the injection pipe 41a and the injection throttle device 42a form an injection flow path. A discharge temperature sensor 43a, a discharge pressure sensor 40a, an outside air temperature sensor 46a, and a pressure detection sensor 44a are provided.

Further, the outdoor unit 1b includes the compressor 10b, the refrigerant flow switching device 11b, the heat source side heat exchanger 12b, the accumulator 19b, the injection pipe 41b, the heat source side fan 18b, the outdoor side expansion device 45b and the injection expansion device 42b. doing. The compressor 10b, the refrigerant flow switching device 11b, the heat source side heat exchanger 12b, the accumulator 19b, and the outdoor expansion device 45b are connected by a refrigerant pipe 4b in the outdoor unit 1b. Further, the injection pipe 41b and the injection throttle device 42b form an injection flow path. A discharge temperature sensor 43b, a discharge pressure sensor 40b, an outside air temperature sensor 46b, and a pressure detection sensor 44b are provided.

<Solution control in heating operation mode (without injection)>
The air conditioning apparatus 100 determines the amount of refrigerant sealed in the refrigerant circuit based on the cooling operation mode. In the heating operation mode, there is an operation state in which the amount of refrigerant required is smaller than that in the cooling operation mode. Therefore, the surplus refrigerant amount, which is the difference between the refrigerant amount in the refrigerant circuit and the refrigerant amount necessary in the heating operation mode, is accumulated in the accumulator 19.

Here, in the two outdoor units 1, there is the inclination of the branch of the main pipe 5 connected to each outdoor unit 1, the difference in operating capacity in each outdoor unit 1, and the like. For this reason, the amount of surplus refrigerant accumulated in the accumulator 19 of each outdoor unit 1 may not be evenly distributed, but may be accumulated unevenly. For example, in the case where the surplus refrigerant is concentrated in one of the accumulators 19, an overflow occurs when the surplus refrigerant in the accumulator 19 exceeds the capacity of the accumulator 19. When the overflow occurs, a large amount of refrigerant may be liquid-backed to the compressor 10, the refrigeration oil may be diluted, and burnout of the scroll portion of the compressor 10 may occur. Therefore, it is necessary to adjust the degree of opening of the outdoor-side expansion device 45 so that the amount of surplus refrigerant accumulated in each accumulator 19 is equal to or less than the capacity of each accumulator 19.

In addition, refrigerant oil is discharged from the compressor 10 together with the gas refrigerant, and circulates in the refrigerant circuit. Such refrigeration oil is referred to as spilled oil from the system. As described above, each accumulator 19 is provided with an oil return mechanism 20 (20a, 20b) for returning the oil outside the system to the compressor 10.

For example, when the amount of surplus refrigerant accumulated in the accumulator 19 of each outdoor unit 1 is not uniform, the accumulator 19 having a large amount of surplus refrigerant is more frozen than the other accumulator 19 via the oil return mechanism 20 from the accumulator 19 The machine oil is returned to the corresponding compressor 10. At this time, the discharge temperature of the refrigerant in the compressor 10 with a large amount of refrigeration oil is lower than the discharge temperature of the refrigerant in the compressor 10 with a small amount of refrigeration oil.

Therefore, the control device 60, which has a large amount of surplus refrigerant remaining in the accumulator 19 and returns a large amount of refrigeration oil, performs control to reduce the opening degree of the outdoor-side throttling device 45. As a result, the amount of liquid refrigerant flowing into the accumulator 19 having a large amount of surplus refrigerant is reduced.

On the other hand, the control device 60, which has a small amount of surplus refrigerant remaining in the accumulator 19 and a small amount of returned oil from the refrigerator oil, increases or does not change the opening degree of the outdoor side expansion device 45. As a result, the amount of liquid refrigerant flowing into the accumulator 19 with a smaller amount of surplus refrigerant is increased. By performing the control as described above, the refrigerant accumulated in the accumulators 19 of the two outdoor units 1 is controlled to be equal. By evenly accumulating the refrigerant in the accumulators 19 of the two outdoor units 1, overflow can be suppressed.

(Soaking control when performing injection)
Next, in the heating operation mode, control will be described to adjust so that the amount of surplus refrigerant accumulated in the accumulator 19 becomes uniform while performing injection. In such a case, the decrease in discharge temperature of the compressor 10 due to injection and the decrease in discharge temperature due to liquid back from the accumulator 19 are compared. Then, the amount of surplus refrigerant remaining in the accumulator 19 is determined.

Here, for example, a compressor 10a mounted on the outdoor unit 1a will be described as an example. First, when the controller 60a determines that the discharge temperature or the discharge superheat degree of the compressor 10a is higher than the target discharge temperature threshold value or the superheat degree threshold value, the controller 60a increases the opening degree of the injection throttle device 42a. Take control. By increasing the opening degree of the injection throttle device 42a, the discharge temperature of the compressor is lowered.

At this time, it is possible to predict the flow rate of the refrigerant by injection and the enthalpy of the refrigerant to be injected based on the opening degree of the injection throttle device 42a and the pressure before and after. Further, the discharge temperature of the compressor 10a when injection is not performed is determined from the discharge pressure and the efficiency of the compressor 10a, such as the drive frequency of the compressor 10a, the pressure and temperature of the suction side of the compressor 10 when injection is not performed, etc. It can be predicted.

Then, when the injection is performed, the flow rate and enthalpy of the refrigerant by the injection, and the flow rate and the enthalpy of the refrigerant sucked into the compressor 10a when the injection is not performed are synthesized. By the synthesis, the enthalpy of the refrigerant in the compressor suction chamber can be calculated.

Here, the refrigerant in the compressor suction chamber has a lower enthalpy than in the case where injection is not performed, and is in a two-phase state of high dryness. Then, from the difference between the discharge temperature calculated from the state of the enthalpy of the refrigerant in the compressor suction chamber and the discharge temperature when injection is not performed, the width of the decrease in discharge temperature when the refrigerant is added by injection is predicted. be able to.

Further, when the surplus refrigerant amount of the accumulator 19a increases, the liquid level rises, and the liquid head, which is the pressure of the liquid, increases. For this reason, the liquid back rate from the oil return mechanism 20 is higher than when the liquid level is low. Therefore, the discharge temperature of the compressor 10a is reduced. As described above, when the liquid level of the accumulator 19a rises when the refrigerant is added by the injection, the liquid level adjustment threshold value described above decreases due to the liquid back rate according to the liquid level of the accumulator 19a. It becomes the discharge temperature of the compressor 10a. Then, the control device 60 adjusts the outdoor-side throttling device 45a according to the predicted liquid level. Then, when it is determined that the discharge temperature or the discharge superheat degree of the compressor 10a is smaller than the liquid level adjustment threshold value, the control device 60 performs control to make the outdoor-side expansion device 45a smaller. The flow rate of the refrigerant flowing into the accumulator 19a is reduced, and the amount of surplus refrigerant accumulated in the accumulator 19a is reduced to lower the liquid level.

Further, as described above, when the injection is not performed, the liquid level adjustment threshold value becomes the value of the discharge temperature of the compressor 10 which is lowered by the liquid back rate according to the liquid level height of the accumulator 19 . When injection is performed, the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43 is a value obtained by adding the discharge temperature decrease width when the refrigerant is added by the injection.

The control device 60 causes the discharge temperature of the compressor 10 to be higher than the liquid level adjustment threshold value, and the outdoor-side throttling so that the liquid level of the accumulator 19a becomes equal to or less than the target liquid level. The opening degree of the device 45 is controlled.

Further, in order to simplify the control in each control device 60, in each outdoor unit 1, each injection throttle device 42 in each outdoor unit 1 is opened when injection is performed to lower the discharge temperature of the compressor 10. The difference of degrees may be calculated. Based on the difference in the degree of opening of the injection throttle device 42, the difference in the amount of surplus refrigerant of the accumulator 19 mounted on each outdoor unit 1 is predicted, and the degree of opening of the outdoor side throttle device 45 is adjusted.

For example, it is assumed that the discharge temperatures of the respective compressors 10 are substantially equal (for example, ± 1 ° C.), and the temperatures detected by the respective pressure detection sensors 44 are also substantially equal. At this time, for example, when the opening degree of the injection throttle device 42a is larger than the opening degree of the injection throttle device 42b, the liquid back amount from the accumulator 19b is larger than the liquid back amount from the accumulator 19a. It will be a lot. Therefore, it can be determined that the liquid level of the accumulator 19b is high. At this time, when the discharge temperature of the compressor 10b is smaller than the liquid level adjustment threshold, the liquid level of the accumulator 19b can be lowered by closing the opening degree of the outdoor throttling device 45b.

In such a case, for example, if the opening degree of the injection throttling device 42 can be made larger by, for example, making it an opening degree of 1⁄5 or more of the full opening degree, erroneous detection due to variations in the opening degree is prevented. be able to. Therefore, the controller 60 can predict the liquid level difference between the accumulators 19 more accurately.

The compressor 10 in the second embodiment has a low pressure shell structure. Moreover, it is the structure which makes injection flow in into a compressor suction chamber. Therefore, even if the injection amount is increased, the refrigerant injected into the scroll portion of the compressor 10 can be made to flow. Therefore, the liquid or the two-phase refrigerant injected into the lower part of the shell does not stay. Therefore, the refrigeration oil is not diluted by the liquid refrigerant. In addition, since the injection amount can be increased, the degree of opening of the outdoor expansion device 45a can be increased.

(Control flowchart)
FIG. 7 is a diagram showing an example of control performed by the control device 60 in the air-conditioning apparatus 100 according to Embodiment 2 of the present invention. FIG. 7 shows an example of a flowchart relating to the liquid equalization control of each accumulator 19 while performing injection. The processing operation of the control device 60 at the time of injection will be described with reference to FIG. Here, it is assumed that each control device 60 of each outdoor unit 1 performs the processing of steps CT1 to CT7. Then, with regard to the process of step CT100, it is assumed that one of the control devices 60 of the control devices 60 of each outdoor unit 1 performs the process based on the data sent from the other control devices 60. In addition, although processing such as determination is performed based on the discharge temperature of the compressor 10 here, the processing may be performed by calculating the discharge superheat degree instead of the discharge temperature.

(Step CT1)
The control device 60 starts the operation of the air conditioner 100 when there is an operation request such as the cooling operation or the heating operation from the indoor unit 2. Thereafter, the process proceeds to step CT2.

(Step CT2)
The control device 60 acquires the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43. Then, the discharge temperature of the compressor 10 is compared with the discharge temperature threshold value. The discharge temperature threshold is, for example, 110 ° C. If it is determined by comparison that the discharge temperature of the compressor 10 is equal to or lower than the discharge temperature threshold, the process proceeds to step CT4. Here, if it is a temperature within a temperature range (for example, 110 ° C. ± 1 ° C.) including the discharge temperature threshold, it is assumed to be the same as the discharge temperature threshold. If it is determined that the discharge temperature of the compressor 10 is higher than the discharge temperature threshold value, the process proceeds to step CT3.

(Step CT3, Step CT4)
The control device 60 controls the opening degree of the injection throttle device 42 so that the discharge temperature of the compressor 10 detected by the discharge temperature sensor 43 approaches the discharge temperature threshold value. For example, when the control device 60 determines that the discharge temperature of the compressor 10 is higher than the discharge temperature threshold value, the controller 60 increases the opening degree of the injection throttle device 42 (step CT3). Further, when it is determined that the discharge temperature of the compressor 10 is lower than the discharge temperature threshold value, the control device 60 reduces the opening degree of the injection throttle device 42. Then, when determining that the discharge temperature of the compressor 10 is the same as the discharge temperature threshold value, the control device 60 maintains the opening degree of the injection throttle device 42 (step CT4). When the control of the opening of the injection throttle device 42 is performed, the control device 60 proceeds to the process of step CT5.

(Step CT5)
The controller 60 acquires an intermediate pressure that is the pressure of the refrigerant passing through the injection pipe 41 detected by the pressure detection sensor 44. Then, the intermediate pressure is compared with the intermediate pressure threshold. The intermediate pressure threshold is, for example, 1.1 MPa when the refrigerant is R410A. Further, it is determined whether or not control to increase the opening degree of the outdoor-side expansion device 45 is performed by the process of step CT100 described later. If it is determined that the control is not performed to make the control equal to or lower than the intermediate pressure threshold or to increase the opening degree of the outdoor throttling device 45, the process proceeds to step CT7. Here, if it is a pressure within the pressure range (1.1 MPa ± 0.05 MPa) including the intermediate pressure threshold, it is assumed to be the same as the intermediate pressure threshold. If it is determined that the intermediate pressure is higher than the intermediate pressure threshold and the control for increasing the opening degree of the outdoor throttling device 45 is performed, the process proceeds to step CT6.

(Step CT6, Step CT7)
The controller 60 controls the opening degree of the outdoor-side throttling device 45 such that the intermediate pressure detected by the pressure detection sensor 44 approaches the intermediate pressure threshold. For example, when the control device 60 determines that the intermediate pressure is higher than the intermediate pressure threshold and the control to increase the opening degree of the outdoor expansion device 45 is performed, the control device 60 increases the opening degree of the outdoor expansion device 45 (Step CT6). In addition, when the control device 60 determines that the intermediate pressure is lower than the intermediate pressure threshold value, the control device 60 reduces the opening degree of the outdoor-side throttling device 45. Then, the control device 60 has the discharge temperature of the compressor 10 equal to the discharge temperature threshold, or the intermediate pressure is higher than the intermediate pressure threshold, and the opening degree of the outdoor-side throttling device 45 is increased. If it is not determined, the opening degree of the injection throttle device 42 is maintained (step CT7). When the control of the opening of the injection throttle device 42 is performed, the control device 60 proceeds to the process of step CT100.

<Step CT100: Liquid equalization control of accumulator 19 of each outdoor unit 1>
Step CT100 is a step which performs liquid equalization control so that the amount of surplus refrigerant which accumulator 19 which each outdoor unit 1 mounts becomes below in amount set up beforehand. Here, the surplus refrigerant amount of the amount set in advance is, for example, an amount that is equal to or less than the liquid level height of 2/3 of the volume for each accumulator 19.

(Step CT101)
The control device 60 acquires the discharge temperatures of the compressor 10a and the compressor 10b detected by the discharge temperature sensor 43a and the discharge temperature sensor 43b. Then, it is determined whether the discharge temperature of the compressor 10a is smaller than the liquid level adjustment threshold described above, and whether the discharge temperature of the compressor 10b is equal to or higher than the liquid level adjustment threshold. If it is determined that the discharge temperature of the compressor 10a is smaller than the liquid level adjustment threshold and the discharge temperature of the compressor 10b is equal to or higher than the liquid level adjustment threshold, the process proceeds to step CT102. Otherwise, the process proceeds to step CT103.

(Step CT102)
The controller 60 controls the outdoor-side throttle device 45a and the outdoor-side throttle so that the discharge temperatures of the compressor 10a and the compressor 10b detected by the discharge temperature sensor 43a and the discharge temperature sensor 43b approach the liquid level adjustment threshold. The opening degree of the device 45b is controlled. Since the discharge temperature of the compressor 10a is less than the liquid level adjustment threshold value, the control device 60a performs control to reduce the opening degree of the outdoor side expansion device 45a. Further, since the discharge temperature of the compressor 10b is equal to or higher than the liquid level adjustment threshold value, the control device 60b performs control to increase the opening degree of the outdoor side expansion device 45b. However, if the discharge temperature of the compressor 10b is a temperature within a temperature range (for example, 100 ° C. ± 1 ° C.) including the liquid level adjustment threshold, control is performed assuming that it is the same as the liquid level adjustment threshold The device 60b performs control to maintain the opening degree of the outdoor-side throttle device 45b. Then, the process proceeds to step CT2.

(Step CT103)
The controller 60 determines whether the discharge temperature of the compressor 10a is equal to or higher than the above-described liquid level adjustment threshold with respect to the discharge temperature of each compressor 10 detected by each discharge temperature sensor 43, and the compressor 10b. It is determined whether the discharge temperature of the fluid is smaller than the liquid level adjustment threshold. If it is determined that the discharge temperature of the compressor 10a is equal to or higher than the liquid level adjustment threshold and the discharge temperature of the compressor 10b is smaller than the liquid level adjustment threshold, the process proceeds to step CT104. Otherwise, the process proceeds to step CT105.

(Step CT104)
Since the discharge temperature of the compressor 10a is equal to or higher than the liquid level adjustment threshold value, the control device 60a performs control to increase the opening degree of the outdoor side expansion device 45a. However, if the discharge temperature of the compressor 10a is a temperature within a temperature range (for example, 100 ° C. ± 1 ° C.) including the liquid level adjustment threshold, control is performed assuming that it is the same as the liquid level adjustment threshold The device 60a performs control to maintain the opening degree of the outdoor-side throttle device 45a. Further, since the discharge temperature of the compressor 10b is smaller than the liquid level adjustment threshold value, the control device 60b performs control to reduce the opening degree of the outdoor side expansion device 45b. Then, the process proceeds to step CT2.

(Step CT105)
The control device 60 controls the discharge temperature of the compressor 10a and the compressor 10b for the discharge temperature of the compressor 10a and the compressor 10b detected by the discharge temperature sensor 43a and the discharge temperature sensor 43b to be the liquid level adjustment threshold described above. Determine if it is less. If it is determined that the discharge temperature of the compressor 10a and the compressor 10b is smaller than the liquid level adjustment threshold value, the process proceeds to step CT106. Otherwise, the process proceeds to step CT107.

(Step CT106)
The

control devices

60a and 60b perform control to reduce the opening degree of the outdoor side throttle device 45a and the outdoor side throttle device 45b because the discharge temperatures of the compressor 10a and the compressor 10b are smaller than the liquid level adjustment threshold. . Then, the process proceeds to step CT2.

(Step CT107)
Since the

control devices

60a and 60b have discharge temperatures of the compressor 10a and the compressor 10b equal to or higher than the liquid level adjustment threshold value, control to increase the opening degree of the outdoor expansion device 45a and the outdoor expansion device 45b is performed. Do. However, if the discharge temperature of compressor 10a or compressor 10b is a temperature within a temperature range (for example, 100 ° C. ± 1 ° C.) including the liquid level adjustment threshold, it is the same as the liquid level adjustment threshold It shall be. Then, the control device 60a or the control device 60b performs control to maintain the opening degree of the outdoor side throttle device 45a or the outdoor side throttle device 45b. Then, the process proceeds to step CT2.

Here, the discharge temperature threshold value and the liquid level adjustment threshold value have been described as being fixed values set in advance, but are not limited thereto. For example, the setting may be changed to a value corresponding to the compression ratio, which is a value obtained by dividing the discharge pressure by the suction pressure, the drive frequency of the compressor 10, and the like, based on data of a formula and a table format. By changing the threshold value, the detection accuracy of the liquid back from the accumulator 19 according to the operating state of the compressor 10 can be increased.

In step CT100 described above, the discharge temperature of the compressor 10a, the discharge temperature of the compressor 10b, and the magnitude relationship between the liquid level adjustment threshold value are divided into four patterns, and the outdoor-side throttling device 45a and the outdoor-side throttling The opening control of the device 45b was performed. Although the discharge temperature of each compressor 10 satisfies the liquid level adjustment threshold in the opening degree control of each outdoor side expansion device 45 by a combination like step CT100, the amount of liquid refrigerant is stored in each accumulator 19 Even when there is a bias, the refrigerant can be dispersed to make the liquid uniform. For this reason, the risk of refrigerant overflow from the accumulator 19 can be reduced. However, it is not limited to this. For example, the opening degree control of the outdoor throttling device 45a is performed based on the comparison between the discharge temperature of the compressor 10a and the liquid level adjustment threshold, and the discharge temperature of the compressor 10b is compared based on the liquid level adjustment threshold. The opening control of the outdoor-side throttling device 45b may be performed to perform independent control.

Moreover, the structure of the air conditioning apparatus 100 which connected two outdoor units 1 in parallel was demonstrated to the example here. However, the same effect can be obtained even if the number of connected outdoor units 1 is three or more.

As described above, according to the second embodiment, the control device 60 can adjust the liquid level of the accumulator 19 mounted on the plurality of outdoor units 1 while performing injection to ensure high performance. Therefore, by preventing the overflow of the accumulator 19 while maintaining the comfort of the user, it is possible to perform the liquid equalization control of the accumulator 19 and to prevent the liquid back to the compressor 10. Therefore, breakage or the like of the compressor 10 can be prevented, and the reliability of the entire air conditioning apparatus 100 can be secured.

Third Embodiment
FIG. 8 is a diagram showing an example of the configuration of the air conditioning apparatus 100 according to Embodiment 3 of the present invention. Next, an air conditioner according to Embodiment 3 of the present invention will be described. Here, the same reference numerals are given to devices having the same functions and operations as the first embodiment and the second embodiment.

As shown in FIG. 8, the air conditioning apparatus 100 includes two outdoor units 1 (1a, 1b) that are heat source units, a plurality of indoor units 2 (2a, 2b, 2c, 2d), and the outdoor unit 1 And the indoor units 2a to 2d, and has a relay device 3 provided with an opening / closing device. The outdoor unit 1 and the relay device 3 are connected by a plurality of main pipes 5 through which the refrigerant flows. The relay device 3 and each of the indoor units 2a to 2d are connected by a plurality of branch pipes 8 through which the refrigerant flows. Cold heat or heat generated by the outdoor unit 1 is supplied to the indoor units 2a to 2d via the relay device 3.

In the third embodiment, the outdoor unit 1 and the relay device 3 are connected using two main pipes 5, and the relay device 3 and the indoor units 2a to 2d each use two branch pipes 8. It is connected. Thus, installation of the air conditioner 100 is achieved by connecting the outdoor unit 1 and the relay device 3 and between the relay device 3 and the indoor units 2a to 2d using two pipes. It can be done easily.

<Outdoor unit 1>
The outdoor unit 1 includes the compressor 10, the refrigerant flow switching device 11, the heat source side heat exchanger 12, the heat source side fan 18, and the accumulator 19, as in the first embodiment and the like. Further, it has an outdoor-side throttle device 45, an injection throttle device 42, an outdoor-side throttle device 45, an injection pipe 41 and the like.

The outdoor unit 1 according to the third embodiment is further provided with a first connection pipe 6, a second connection pipe 7, and first backflow prevention devices 13, 14, 15 and 16. Here, check valves are used as the first backflow prevention devices 13-16. The first backflow prevention device 13 prevents the high temperature and high pressure gas refrigerant from flowing back from the first connection pipe 6 to the heat source side heat exchanger 12 in the heating only operation mode and the heating main operation mode. is there. The first backflow prevention device 14 prevents the high pressure liquid or the gas-liquid two-phase refrigerant from backflowing from the first connection pipe 6 to the accumulator 19 in the cooling only operation mode and the cooling main operation mode It is a thing. The first backflow prevention device 15 prevents the high pressure liquid or the gas-liquid two-phase refrigerant from backflowing from the second connection pipe 7 to the accumulator 19 in the cooling only operation mode and the cooling main operation mode It is a thing. The first backflow prevention device 16 prevents the high temperature and high pressure gas refrigerant from flowing back from the flow path on the discharge side of the compressor 10 to the second connection pipe 7 in the heating only operation mode and heating only operation mode It is

As described above, by providing the first connection piping 6, the second connection piping 7, and the first backflow prevention devices 13 to 16, the flow of the refrigerant to be made to flow into the relay device 3 can be obtained regardless of the operation requested by the indoor unit 2. It can be in a fixed direction. Although check valves are used as the first backflow prevention devices 13 to 16 here, the configuration of the first backflow prevention devices 13 to 16 is not limited thereto as long as it can prevent the backflow of the refrigerant. . For example, as the first backflow prevention devices 13 to 16, it is also possible to use an opening / closing device or a throttling device having a fully closed function.

Here, in the air conditioning apparatus 100 of the third embodiment, the refrigerant can pass through the injection throttle device 42 and the outdoor throttle device 45 when in the heating only operation mode and the heating main operation mode. Therefore, injection and the like are not performed in the cooling only operation mode and the cooling main operation mode.

<Indoor unit 2a to 2d>
The plurality of indoor units 2a to 2d have, for example, the same configuration. The indoor units 2a to 2d respectively include load

side heat exchangers

26a, 26b, 26c, 26d and load

side expansion devices

25a, 25b, 25c, 25d. Each of the load side heat exchangers 26a to 26d is connected to the outdoor unit 1 via the branch pipe 8, the relay device 3 and the main pipe 5. In each of the load side heat exchangers 26a to 26d, heating air or cooling air to be supplied to the indoor space is generated by heat exchange between the air supplied by the load side fan (not shown) and the refrigerant. Ru. The load-side throttling devices 25a to 25d are, for example, capable of variably adjusting the opening degree continuously or in multiple steps. As the load side throttle devices 25a to 25d, for example, electronic expansion valves or the like are used. The load-side throttling devices 25a to 25d have functions as pressure reducing valves and expansion valves, and decompress and expand the refrigerant. The load-side expansion devices 25a to 25d are provided upstream of the load-side heat exchangers 26a to 26d in the refrigerant flow in the cooling operation mode (for example, the all-cooling operation mode).

The indoor unit 2 also has inlet side temperature sensors 31a to 31d for detecting the temperature of the refrigerant flowing into the load side heat exchangers 26a to 26d. Further, it has outlet side temperature sensors 32a to 32d for detecting the temperature of the refrigerant flowing out of the load side heat exchangers 26a to 26d. The inlet temperature sensors 31a to 31d and the outlet temperature sensors 32a to 32d are, for example, thermistors or the like. Each of the inlet temperature sensors 31a to 31d and the outlet temperature sensors 32a to 32d outputs a detection signal to the control device 60.

Although four indoor units 2a to 2d are illustrated in FIG. 8, the number of indoor units connected may be two, three, or five or more.

<Relaying device 3>
The relay device 3 includes a gas-liquid separator 29, a first relay throttling device 30, and a second relay throttling device 27. The plurality of first opening / closing devices 23a to 23d, the plurality of second opening / closing devices 24a to 24d, the second backflow prevention devices 21a to 21d (for example, check valves), the third backflow prevention devices 22a to 22d (for example, reverse) Stop valve).

The gas-liquid separator 29 separates the high-pressure gas-liquid two-phase refrigerant generated by the outdoor unit 1 into liquid refrigerant and gas refrigerant in the cooling-heating mixed operation mode in which the cooling load is large. The gas-liquid separator 29 allows the separated liquid refrigerant to flow into the lower pipe in the drawing, and supplies cold heat to some of the indoor units 2 and causes the separated gas refrigerant to flow into the upper pipe in the drawing. , Supply heat to some other indoor units 2. The gas-liquid separator 29 is provided at the inlet of the relay device 3 in the flow of the refrigerant.

The first relay throttle device 30 has functions as a pressure reducing valve and an on-off valve. The first relay expansion device 30 decompresses the liquid refrigerant to adjust it to a predetermined pressure, and opens and closes a flow path of the liquid refrigerant. The first relay throttle device 30 is, for example, capable of variably adjusting the opening degree continuously or in multiple steps. As the first relay device throttle device 30, for example, an electronic expansion valve or the like is used. The first relay expansion device 30 is provided on a pipe from which the liquid refrigerant flows out from the gas-liquid separator 29.

The second relay throttle device 27 has functions as a pressure reducing valve and an on-off valve. The second relay expansion device 27 opens and closes the refrigerant flow path in the heating only operation mode, and adjusts the bypass liquid flow rate in accordance with the indoor load in the heating main operation mode. The second relay throttling device 27 is, for example, capable of variably adjusting the opening degree continuously or in multiple steps. As the second relay throttle device 27, for example, an electronic expansion valve or the like is used.

The plurality of first opening / closing devices 23a to 23d are provided for each of the plurality of indoor units 2a to 2d (in this case, four in total). The first opening and closing devices 23a to 23d open and close the flow paths of the high-temperature and high-pressure gas refrigerant supplied to the indoor units 2a to 2d, respectively. The first opening and closing devices 23a to 23d are configured by, for example, solenoid valves or the like. The first opening and closing devices 23a to 23d are connected to the gas side piping of the gas-liquid separator 29, respectively. The first opening and closing devices 23a to 23d may be an expansion device having a fully closing function as long as they can open and close the flow path.

The plurality of second opening / closing devices 24a to 24d are provided for each of the plurality of indoor units 2a to 2d (in this case, four in total). The second open / close devices 24a to 24d open and close the flow paths of the low-pressure and low-temperature gas refrigerant flowing out of the indoor units 2a to 2d, respectively. The second opening and closing devices 24a to 24d are configured by, for example, solenoid valves or the like. The second opening and closing devices 24a to 24d are connected to low pressure pipes which conduct to the outlet side of the relay device 3, respectively. The second opening / closing devices 24a to 24d may be an expansion device having a fully closing function as long as they can open and close the flow path.

A plurality of second backflow prevention devices 21a to 21d are provided for each of the plurality of indoor units 2a to 2d (four in total in the third embodiment). The second backflow prevention devices 21a to 21d allow high pressure liquid refrigerant to flow into the indoor unit 2 performing the cooling operation, and are connected to the piping on the outlet side of the first relay device expansion device 30. In the cooling main operation mode and the heating main operation mode, the medium-temperature and medium-pressure liquid or gas-liquid two-phase refrigerant whose degree of supercooling can not be sufficiently ensured from the load-side expansion device 25 of the heating indoor unit 2 However, it can be prevented from flowing into the load-side expansion device 25 of the indoor unit 2 being cooled. In the third embodiment, check valves are used as the second backflow prevention devices 21a to 21d, but the configuration of the second backflow prevention devices 21a to 21d is limited to this as long as the backflow of the refrigerant can be prevented. Absent. For example, as the second backflow prevention devices 21a to 21d, it is also possible to use an open / close device or a throttling device having a fully closed function.

The plurality of third backflow prevention devices 22a to 22d are provided for each of the plurality of indoor units 2a to 2d (in this case, four in total). The third backflow prevention devices 22a to 22d allow the high pressure liquid refrigerant to flow into the indoor unit 2 performing the cooling operation, and are connected to the piping on the outlet side of the first relay device expansion device 30. In the cooling-dominated operation mode and the heating-dominated operation mode, the third relay device 22a to 22d receives a medium-temperature and medium-pressure liquid or a two-phase refrigerant from the first relay device expansion device 30 that does not have a sufficient degree of subcooling. It prevents the flow to the load-side expansion device 25 of the indoor unit 2 being cooled. In the third embodiment, the check valves are used as the third backflow prevention devices 22a to 22d, but the configuration of the third backflow prevention devices 22a to 22d is limited to this as long as the backflow of the refrigerant can be prevented. Absent. For example, as the third backflow prevention devices 22a to 22d, it is also possible to use an open / close device or a throttling device having a fully closed function.

Further, at the inlet side of the first relay throttling device 30 in the relay device 3, a throttling device inlet side pressure sensor 33 is provided. The throttling device inlet side pressure sensor 33 detects the pressure of the high pressure refrigerant. A throttle device outlet side pressure sensor 34 is provided on the outlet side of the first relay throttle device 30. The expansion device outlet side pressure sensor 34 detects the intermediate pressure of the liquid refrigerant on the outlet side of the first relay expansion device 30 in the cooling main operation mode.

Also in the air conditioning apparatus 100 shown in FIG. 8, the control device 60 (60a, 60b) controls the overall operation of the air conditioning apparatus 100 based on detection signals from various sensors and an instruction from the remote controller. For example, the control device 60 performs control of the drive frequency of the compressor 10 and rotation number control (including on and off control) of the heat source fan 18 and the load fan. Further, the control device 60 performs flow path switching of the refrigerant flow switching device 11, opening degree control of the injection throttle device 42, opening degree control or opening / closing control of the outdoor side throttle device 45. The control device 60 controls the opening degree of the load side expansion device 25, the opening and closing control of the first opening and closing devices 23a to 23d, the opening and closing control of the second opening and closing devices 24a to 24d, the opening and closing control of the first relay device opening device 30; The opening and closing control and the like of the second relay throttle device 27 are performed. By these controls, control device 60 executes each operation mode. Here, although the control device 60 is provided in the outdoor unit 1, the control device 60 may be provided in the indoor units 2 a to 2 d or may be provided in the relay device 3. Further, the control device 60 may be provided for each unit (for example, each of the outdoor unit 1, the indoor units 2a to 2d and the relay device 3). Then, the plurality of control devices 60 may combine the respective functions to perform the process related to the liquid back prevention and the like.

Each operation mode performed by the air conditioning apparatus 100 will be described. The control device 60 of the air conditioning apparatus 100 can perform the cooling operation or the heating operation independently in each of the indoor units 2a to 2d based on an instruction from each of the indoor units 2a to 2d. That is, the air conditioning apparatus 100 can perform the same operation (cooling operation or heating operation) in all the indoor units 2a to 2d, and can also perform different operations in each of the indoor units 2a to 2d.

The operation modes executed by the air conditioner 100 can be roughly classified into a cooling operation mode and a heating operation mode. The cooling operation mode includes a cooling only operation mode and a cooling main operation mode. The cooling only operation mode is an operation mode in which all the indoor units 2a to 2d not in the stopped state perform the cooling operation. That is, in the cooling only operation mode, all the load side heat exchangers 26a to 26d not in the stop state function as the evaporator. In the cooling main operation mode, a part of the indoor units 2a to 2d performs the cooling operation, and the other part of the indoor units 2a to 2d performs the heating operation, and the cooling load is higher than the heating load. Is also a large operating mode. That is, in the cooling main operation mode, a part of the load side heat exchangers 26a to 26d functions as an evaporator, and another part of the load side heat exchangers 26a to 26d functions as a condenser.

The heating operation mode includes an all heating operation mode and a heating main operation mode. The all heating operation mode is an operation mode in which all the indoor units 2a to 2d not in the stop state perform the heating operation. That is, in the heating only operation mode, all the load side heat exchangers 26a to 26d which are not in the stopped state function as the condenser. The heating main operation mode is a cooling / heating mixed operation mode in which a part of the indoor units 2a to 2d performs the cooling operation and another part of the indoor units 2a to 2d performs the heating operation. Is also a large operating mode. Each operation mode will be described below.

<Full cooling operation mode>
FIG. 9 is a diagram for explaining the flow of the refrigerant in the cooling only operation mode of the air conditioning apparatus 100 according to the third embodiment. In FIG. 9, the flow direction of the refrigerant is indicated by a solid arrow. Here, it is assumed that a cold load is generated only in the load side heat exchanger 26a and the load side heat exchanger 26b. In the case of the cooling only operation mode, the control device 60 switches the refrigerant flow switching device 11 of the outdoor unit 1 so that the refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12.

First, low-temperature and low-pressure refrigerant is compressed by the compressor 10 and discharged as high-temperature and high-pressure gas refrigerant. The high temperature and high pressure gas refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 via the refrigerant flow switching device 11. Then, the heat is released to the outdoor air by the heat source side heat exchanger 12 and becomes a high pressure liquid refrigerant. The high-pressure liquid refrigerant flowing out of the heat source side heat exchanger 12 flows out of the outdoor unit 1 through the first backflow prevention device 13 and flows into the relay device 3 through the main pipe 5.

The high-pressure liquid refrigerant flowing into the relay device 3 passes through the gas-liquid separator 29 and the first relay device throttling device 30, and most passes through the second

backflow prevention devices

21a and 21b and the branch pipe 8, and the load side throttling It is expanded by the device 25 to become a low temperature and low pressure gas-liquid two-phase refrigerant. The remaining part of the high-pressure refrigerant is expanded by the second relay throttling device 27 to become a low-temperature and low-pressure gas refrigerant or a refrigerant in a gas-liquid two-phase state. Then, it flows into the low pressure pipe on the outlet side of the relay device 3. At this time, the opening degree of the second relay expansion device 27 is controlled such that the subcool (degree of subcooling) of the refrigerant becomes constant.

The refrigerant in the gas-liquid two-phase state expanded by the load-

side throttling devices

25a and 25b respectively flows into the load-

side heat exchangers

26a and 26b acting as an evaporator, and absorbs room air by absorbing heat from room air. While cooling, it becomes a low temperature and low pressure gas refrigerant. At this time, the load-side expansion device 25a is opened so that the superheat (degree of superheat) obtained as the difference between the temperature detected by the inlet temperature sensor 31a and the temperature detected by the outlet temperature sensor 32a becomes constant. The degree is controlled. Similarly, the degree of opening of the load-side expansion device 25b is controlled such that the superheat obtained as the difference between the temperature detected by the inlet temperature sensor 31b and the temperature detected by the outlet temperature sensor 32b is constant. Ru.

The gas refrigerant that has flowed out of the load

side heat exchangers

26a and 26b flows out of the relay device 3 via the branch pipe 8 and the second opening /

closing devices

24a and 24b. The refrigerant flowing out of the relay device 3 flows into the outdoor unit 1 again through the main pipe 5. The refrigerant that has flowed into the outdoor unit 1 passes through the first backflow prevention device 16 and is again drawn into the compressor 10 via the refrigerant flow switching device 11 and the accumulator 19.

In the load side heat exchanger 26c and the load side heat exchanger 26d having no heat load, it is not necessary to flow the refrigerant, and the corresponding load

side expansion devices

25c and 25d are closed. ing. Then, when a cold load is generated in the load side heat exchanger 26c or the load side heat exchanger 26d, the load side expansion device 25c or the load side expansion device 25d is opened to circulate the refrigerant. At this time, the degree of opening of the load-side expansion device 25c or the load-side expansion device 25d is controlled in the same manner as the load-

side expansion device

25a or 25b. At this time, the superheat (degree of superheat) obtained as a difference between the temperature detected by the

inlet temperature sensor

31c or 31d and the temperature detected by the

outlet temperature sensor

32c or 32d is made constant.

<Cooling-based operation mode>
FIG. 10 is a diagram for explaining the flow of the refrigerant in the cooling main operation mode of the air-conditioning apparatus 100 according to Embodiment 3. In FIG. 10, the flow direction of the refrigerant is indicated by a solid arrow. Here, it is assumed that a cold load is generated only in the load side heat exchanger 26a, and a thermal load is generated only in the load side heat exchanger 26b. In the cooling main operation mode, the control device 60 switches the refrigerant flow switching device 11 so that the refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12.

First, low-temperature and low-pressure refrigerant is compressed by the compressor 10 and discharged as high-temperature and high-pressure gas refrigerant. The high temperature and high pressure gas refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 via the refrigerant flow switching device 11. Then, the heat source side heat exchanger 12 releases the heat to the outdoor air and becomes a refrigerant in a gas-liquid two-phase state. The refrigerant flowing out of the heat source side heat exchanger 12 flows into the relay device 3 through the first backflow prevention device 13 and the main pipe 5.

The refrigerant in the gas-liquid two-phase state that has flowed into the relay device 3 is separated into a high pressure gas refrigerant and a high pressure liquid refrigerant in the gas / liquid separator 29. The high-pressure gas refrigerant flows into the load-side heat exchanger 26b acting as a condenser after passing through the first opening / closing device 23b and the branch pipe 8. The high-pressure gas refrigerant releases the heat to the indoor air, thereby becoming a liquid refrigerant while heating the indoor air. At this time, the load side expansion device 25b is a subcool obtained as a difference between a value obtained by converting the pressure detected by the expansion device inlet side pressure sensor 33 into a saturation temperature and the temperature detected by the inlet side temperature sensor 31b. The opening degree is controlled so that the cooling degree) becomes constant. The liquid refrigerant that has flowed out of the load-side heat exchanger 26b is expanded by the load-side throttling device 25b, and flows through the branch pipe 8 and the third backflow prevention device 22b.

After that, the medium pressure liquid refrigerant that has been separated by the gas-liquid separator 29 and expanded to the intermediate pressure in the first relay device expansion device 30 merges with the liquid refrigerant that has passed through the third backflow prevention device 22b. At this time, in the first relay throttle device 30, the pressure difference between the pressure detected by the throttle device inlet side pressure sensor 33 and the pressure detected by the throttle device outlet side pressure sensor 34 is a predetermined pressure difference (for example, The opening degree is controlled to be 0.3 MPa.

Most of the combined liquid refrigerant is expanded by the load-side throttling device 25a via the second backflow prevention device 21a and the branch pipe 8, and becomes a low-temperature and low-pressure gas-liquid two-phase refrigerant. The remaining part of the liquid refrigerant is expanded by the second relay throttling device 27 to become a low temperature and low pressure gas refrigerant or a refrigerant in a gas-liquid two-phase state. At this time, the degree of opening of the second relay expansion device 27 is controlled such that the subcool (degree of subcooling) of the refrigerant becomes constant. Then, it flows into the low pressure pipe on the outlet side of the relay device 3.

On the other hand, the high-pressure liquid refrigerant separated in the gas-liquid separator 29 flows into the indoor unit 2a via the second backflow prevention device 21a. The refrigerant in the gas-liquid two-phase state expanded by the load-side expansion device 25a of the indoor unit 2a flows into the load-side heat exchanger 26a acting as an evaporator, and cools room air by absorbing heat from room air. While becoming a low temperature and low pressure gas refrigerant. At this time, the load-side expansion device 25a is opened so that the superheat (degree of superheat) obtained as the difference between the temperature detected by the inlet temperature sensor 31a and the temperature detected by the outlet temperature sensor 32b becomes constant. The degree is controlled. The gas refrigerant that has flowed out of the load-side heat exchanger 26a flows out of the relay device 3 via the branch pipe 8 and the second opening / closing device 24a. The refrigerant flowing out of the relay device 3 flows into the outdoor unit 1 again through the main pipe 5. The refrigerant that has flowed into the outdoor unit 1 passes through the first backflow prevention device 16 and is again drawn into the compressor 10 via the refrigerant flow switching device 11 and the accumulator 19.

side expansion devices

25c and 25d are closed. There is. Then, when a cold load is generated in the load side heat exchanger 26c or the load side heat exchanger 26d, the load side expansion device 25c or the load side expansion device 25d is opened to circulate the refrigerant. At this time, the opening degree of the load-side expansion device 25c or the load-side expansion device 25d is controlled. At this time, the degree of opening of the load-side throttling device 25c or the load-side throttling device 25d is controlled so that the superheat (degree of superheat) becomes constant, similarly to the load-

side throttling device

25a or 25b. The superheat is the difference between the temperatures detected by the

inlet temperature sensors

31c and 31d and the temperatures detected by the

outlet temperature sensors

32c and 32d.

In the cooling main operation mode of the air conditioning apparatus 100 of the third embodiment, for example, the heat source side heat exchanger 12 in one of the outdoor units 1 may become an evaporator. In the outdoor unit 1 described above, the operation of the device in the case of performing the injection and the liquid back prevention and the liquid leveling control is the same as that described in the first embodiment and the second embodiment.

<All heating operation mode>
FIG. 11 is a diagram for explaining the flow of the refrigerant in the heating only operation mode of the air conditioning apparatus 100 according to the third embodiment. In FIG. 11, the flow direction of the refrigerant is indicated by a solid arrow. Here, it is assumed that thermal load is generated only in the load side heat exchanger 26a and the load side heat exchanger 26b. In the case of the heating only operation mode, the control device 60 controls the refrigerant flow switching device 11 so that the heat source side refrigerant discharged from the compressor 10 flows into the relay device 3 without passing through the heat source side heat exchanger 12. Switch.

First, low-temperature and low-pressure refrigerant is compressed by the compressor 10 and discharged as high-temperature and high-pressure gas refrigerant. The high temperature and high pressure gas refrigerant discharged from the compressor 10 flows out of the outdoor unit 1 through the refrigerant flow switching device 11 and the first backflow prevention device 14. The high-temperature and high-pressure gas refrigerant flowing out of the outdoor unit 1 flows into the relay device 3 through the main pipe 5.

The high-temperature and high-pressure gas refrigerant flowing into the relay device 3 passes through the gas-liquid separator 29, the first opening /

closing devices

23a and 23b, and the branch pipe 8, and then the load side heat exchanger 26a acting as a condenser and the load side. It flows into each of the heat exchangers 26b. The refrigerant flowing into the load-side heat exchanger 26a and the load-side heat exchanger 26b dissipates heat into the room air, and thereby becomes a liquid refrigerant while heating the room air. The liquid refrigerant that has flowed out from the load side heat exchanger 26a and the load side heat exchanger 26b is expanded by the load

side expansion devices

25a and 25b, respectively. Then, it flows into the outdoor unit 1 again through the branch pipe 8, the second relay throttling device 27 controlled to the open state of the third

backflow prevention devices

22 a, 22 b, and the main pipe 5. At this time, the load-side expansion device 25a is a subcool obtained as a difference between a value obtained by converting the pressure detected by the expansion device inlet-side pressure sensor 33 into a saturation temperature and the temperature detected by the inlet-side temperature sensor 31a. The opening degree is controlled so that the cooling degree) becomes constant. Similarly, the load-side expansion device 25b is a subcool obtained as a difference between a value obtained by converting the pressure detected by the expansion device inlet-side pressure sensor 33 into saturation temperature and the temperature detected by the inlet-side temperature sensor 31b. The opening degree is controlled so that the cooling degree) becomes constant.

The refrigerant that has flowed into the outdoor unit 1 passes through the first backflow prevention device 15 and becomes a low temperature and low pressure gas refrigerant while absorbing heat from the outdoor air in the heat source side heat exchanger 12, and the refrigerant flow switching device 11 and the accumulator It is again drawn into the compressor 10 via 19.

side expansion devices

25c and 25d are closed. There is. Then, when a cold load is generated in the load side heat exchanger 26c or the load side heat exchanger 26d, the load side expansion device 25c or the load side expansion device 25d is opened to circulate the refrigerant. At this time, the degree of opening of the load-side expansion device 25c or the load-side expansion device 25d is controlled so that the superheat (degree of superheat) becomes constant, similarly to the load-

side expansion device

25a or 25b described above. Ru. The superheat is obtained as a difference between the temperature detected by the

inlet temperature sensors

31c and 31d and the temperature detected by the

outlet temperature sensors

32c and 32d.

In the air conditioning apparatus 100 of the third embodiment, the injection in the heating only operation mode, and the operation of the device in the case of performing the liquid back prevention and the liquid equalization control and the control of the control device 60 are the first embodiment and the embodiment. It is the same as that described in 2.

<Heating main operation mode>
FIG. 12 is a diagram for explaining the flow of the refrigerant in the heating main operation mode of the air conditioning apparatus 100 according to the third embodiment. In FIG. 12, the flow direction of the refrigerant is indicated by a solid arrow. Here, it is assumed that a cold load is generated only in the load side heat exchanger 26a, and a thermal load is generated only in the load side heat exchanger 26b. In the case of the heating main operation mode, the control device 60 controls the refrigerant flow switching device 11 so that the heat source side refrigerant discharged from the compressor 10 flows into the relay device 3 without passing through the heat source side heat exchanger 12. Switch.

Low temperature and low pressure refrigerant is compressed by the compressor 10 and discharged as high temperature and high pressure gas refrigerant. The high temperature and high pressure gas refrigerant discharged from the compressor 10 flows out of the outdoor unit 1 through the refrigerant flow switching device 11 and the first backflow prevention device 14. The high-temperature and high-pressure gas refrigerant flowing out of the outdoor unit 1 flows into the relay device 3 through the main pipe 5.

The high temperature and high pressure gas refrigerant flowing into the relay device 3 flows through the gas-liquid separator 29, the first opening / closing device 23b and the branch pipe 8 and then flows into the load side heat exchanger 26b acting as a condenser. The refrigerant that has flowed into the load-side heat exchanger 26b becomes a liquid refrigerant while heating room air by radiating heat to the room air. The liquid refrigerant flowing out of the load-side heat exchanger 26b is expanded by the load-side throttling device 25b and passes through the branch pipe 8 and the third backflow prevention device 22b. The liquid refrigerant is then expanded by the load-side throttling device 25a after passing mostly through the second backflow prevention device 21a and the branch pipe 8, and becomes a low temperature and low pressure gas-liquid two-phase refrigerant. The remaining part of the liquid refrigerant is expanded by the second relay throttling device 27, which is also used as a bypass, to become a medium-temperature and medium-pressure liquid or a gas-liquid two-phase refrigerant. The refrigerant in the liquid or gas-liquid two-phase state flows into the low pressure pipe on the outlet side of the relay device 3.

The refrigerant in the gas-liquid two-phase state expanded by the load-side expansion device 25a flows into the load-side heat exchanger 26a acting as an evaporator, absorbs heat from room air, and cools the room air, thereby reducing the temperature. And a medium-pressure gas-liquid two-phase refrigerant. The refrigerant in the gas-liquid two-phase state which has flowed out of the load-side heat exchanger 26a flows out of the relay device 3 via the branch pipe 8 and the second opening / closing device 24a. The refrigerant flowing out of the relay device 3 flows into the outdoor unit 1 again through the main pipe 5. The refrigerant flowing into the outdoor unit 1 passes through the first backflow prevention device 15 and becomes a low temperature and low pressure gas refrigerant while absorbing heat from the outdoor air in the heat source side heat exchanger 12. The gas refrigerant is again drawn into the compressor 10 through the refrigerant flow switching device 11 and the accumulator 19.

At this time, the load-side expansion device 25b is a subcool obtained as a difference between a value obtained by converting the pressure detected by the expansion device inlet-side pressure sensor 33 into a saturation temperature and the temperature detected by the inlet-side temperature sensor 31b. The opening degree is controlled so that the cooling degree) becomes constant. On the other hand, the load-side expansion device 25a has an opening degree such that the superheat (degree of superheat) obtained as a difference between the temperature detected by the inlet temperature sensor 31a and the temperature detected by the outlet temperature sensor 32b becomes constant. Is controlled.

At this time, the opening degree of the second relay expansion device 27 is controlled such that the subcool (degree of subcooling) of the refrigerant becomes constant. For example, in the second relay throttling device 27, the pressure difference between the pressure detected by the throttling device inlet side pressure sensor 33 and the pressure detected by the throttling device outlet side pressure sensor 34 is a predetermined pressure difference (for example, 0. The opening degree is controlled to be 3 MPa).

side expansion devices

25c and 25d are closed. ing. When a heat load is generated in the load heat exchanger 26c or the load heat exchanger 26d, the load throttling device 25c or the load throttling device 25d is opened to circulate the refrigerant.

In the air conditioner 100 of the third embodiment, the operation in the case of performing the injection in the heating main operation mode and the liquid back prevention and the liquid equalization control and the control of the control device 60 are the first embodiment and the embodiment. It is the same as that described in 2.

As described above, Embodiment 1 and the embodiment are also applied to the air conditioner 100 of Embodiment 3 that can perform simultaneous heating and cooling by connecting a plurality of outdoor units 1 (1a and 1b) in parallel. Similar to 2, excessive liquid back can be prevented by injection and liquid equalization control.

Fourth Embodiment
FIG. 13 is a diagram showing an example of the configuration of an air conditioning apparatus 100 according to Embodiment 4 of the present invention. The air conditioner 100 shown in FIG. 13 is a main pipe in which the refrigerant flows through the load-side heat exchanger 26a and the load-side heat exchanger 26b in which the outdoor unit 1 and the relay unit 3 are provided in the relay unit 3. Connected by 5 Further, the relay device 3 and the indoor unit 2 are also connected by a heat medium pipe 70 in which a heat medium such as water or brine flows through the load heat exchanger 26a and the load heat exchanger 26b. Here, in FIG. 13, the same reference numerals as in FIGS. 1, 6 and 8 carry out the same operations as described in the first to third embodiments.

Also in the air conditioning apparatus 100 of the fourth embodiment, the refrigerant can pass through the injection throttle device 42 and the outdoor throttle device 45 in the all heating operation mode and the heating main operation mode. Therefore, injection and the like are not performed in the cooling only operation mode and the cooling main operation mode.

<Relaying device 3>
The relay device 3 includes two load side heat exchangers 26, two load side throttle devices 25, two opening / closing devices 50, and two relay unit refrigerant flow switching devices 51. In addition, the relay device 3 includes two pumps 71, four first heat medium flow path switching devices 72, four second heat medium flow path switching devices 73, and four heat medium flow rate adjustment devices 75. It is mounted.

The two load side heat exchangers 26 (load side heat exchanger 26a, load side heat exchanger 26b) in the fourth embodiment function as a condenser (radiator) or an evaporator. The load-side heat exchanger 26 performs heat exchange between the heat source side refrigerant and the heat medium, and transfers cold heat or heat generated by the outdoor unit 1 and stored in the heat source side refrigerant to the heat medium. The load-side heat exchanger 26a is provided between the load-side expansion device 25a and the relay refrigerant flow switching device 51a in the refrigerant circuit, and serves to heat the heat medium in the cooling / heating mixed operation mode. . Further, the load-side heat exchanger 26b is provided between the load-side expansion device 25b and the relay refrigerant flow switching device 51b in the refrigerant circuit, and serves to cool the heat medium in the cooling / heating mixed operation mode. It is.

The two load side throttling devices 25 (load side throttling device 25a, load side throttling device 25b) have functions as pressure reducing valves and expansion valves, and decompress and expand the heat source side refrigerant. The load side expansion device 25a is provided on the upstream side of the load side heat exchanger 26a in the flow of the heat source side refrigerant during the cooling operation. The load-side expansion device 25b is provided upstream of the load-side heat exchanger 26b in the flow of the heat source-side refrigerant during the cooling operation. The two load side throttling devices 25 may be configured by devices whose opening degree can be variably controlled, for example, an electronic expansion valve or the like.

The two opening and closing devices 50 (opening and

closing devices

50a and 50b) are configured by two-way valves and the like, and open and close the refrigerant pipe 4. The opening and closing device 50a is provided in the refrigerant pipe 4 on the inlet side of the heat source side refrigerant. The opening and closing device 50b is provided in a pipe connecting the refrigerant pipe 4 on the inlet side and the outlet side of the heat source side refrigerant. The two relay unit refrigerant flow switching devices 51 (relay unit refrigerant flow switching unit 51a, relay unit refrigerant flow switching unit 51b) are configured by a four-way valve or the like, and switch the flow of the heat source side refrigerant according to the operation mode It is a thing. The relay unit refrigerant flow switching device 51a is provided on the downstream side of the load side heat exchanger 26a in the flow of the heat source side refrigerant during the cooling operation. The relay unit refrigerant flow switching device 51b is provided on the downstream side of the load side heat exchanger 26b in the flow of the heat source side refrigerant during the cooling only operation.

The two pumps 71 (pumps 71 a and 71 b) pressurize and circulate the heat medium flowing through the heat medium pipe 70. The pump 71 a is provided in the heat medium pipe 70 between the load-side heat exchanger 26 a and the second heat medium channel switching device 73. The pump 71 b is provided in the heat medium pipe 70 between the load-side heat exchanger 26 b and the second heat medium channel switching device 73. The two pumps 71 may be configured by, for example, pumps whose displacement can be controlled.

The four first heat medium flow path switching devices 72 (the first heat medium flow path switching device 72a to the first heat medium flow path switching device 72d) are configured by a three-way valve or the like, and switch the heat medium flow paths. It is a thing. The first heat medium channel switching device 72 is provided in a number (here, four) according to the number of installed indoor units 2. In the first heat medium flow switching device 72, one of the three sides is the load side heat exchanger 26a, one of the three sides is the load side heat exchanger 26b, and one of the three sides is the heat medium flow control device 75 are respectively connected, and are provided on the outlet side of the heat medium channel of the use side heat exchanger 76. The first heat medium flow switching device 72a, the first heat medium flow switching device 72b, the first heat medium flow switching device 72c, and the first heat medium flow passage are arranged from the lower side of the drawing in correspondence to the indoor unit 2. It is illustrated as the switching device 72d.

The four second heat medium flow path switching devices 73 (the second heat medium flow path switching devices 73a to 73d) are constituted by a three-way valve or the like, and switch the heat medium flow paths. It is a thing. The second heat medium flow path switching device 73 is provided in a number (four in this case) according to the number of installed indoor units 2. In the second heat medium channel switching device 73, one of the three sides is the load side heat exchanger 26a, one of the three sides is the load side heat exchanger 26b, and one of the three sides is the use side heat exchanger 76 are respectively connected and provided on the inlet side of the heat medium channel of the use side heat exchanger 76. The second heat medium flow switching device 73a, the second heat medium flow switching device 73b, the second heat medium flow switching device 73c, and the second heat medium flow passage from the lower side of the drawing in correspondence with the indoor unit 2. It is illustrated as the switching device 73d.

The four heat medium flow rate adjusting devices 75 (heat medium flow rate adjusting devices 75a to 75d) are constituted by a two-way valve or the like which can control the opening area, and control the flow rate flowing to the heat medium piping 70. It is a thing. The number of the heat medium flow control devices 75 is four (here, four) according to the number of installed indoor units 2. One of the heat medium flow control devices 75 is connected to the use side heat exchanger 76, and the other is connected to the first heat medium flow path switching device 72, and the heat medium flow path outlet side of the use side heat exchanger 76 is provided. It is provided. The heat medium flow control device 75a, the heat medium flow control device 75b, the heat medium flow control device 75c, and the heat medium flow control device 75d are illustrated from the lower side of the drawing in correspondence with the indoor unit 2. Further, the heat medium flow control device 75 may be provided on the inlet side of the heat medium channel of the use side heat exchanger 76.

In addition, various sensors are installed in the relay device 3. A signal related to detection of the sensor is sent to, for example, the control device 60.

The two first heat medium temperature sensors 37 (first heat medium temperature sensor 37 a, first heat medium temperature sensor 37 b) are the heat medium flowing out of the load side heat exchanger 26, that is, at the outlet of the load side heat exchanger 26. The temperature of the heat medium is detected. The first heat medium temperature sensor 37 is installed in the heat medium pipe 70 at the inlet side of each pump 71.

Four second heat medium temperature sensors 38 (second heat medium temperature sensors 38 a to second heat medium temperature sensors 38 d) are provided between the first heat medium flow path switching device 72 and the heat medium flow rate adjustment device 75. The temperature of the heat medium flowing out of the use side heat exchanger 76 is detected. The number (in this case, four) of the second heat medium temperature sensors 38 is provided according to the number of installed indoor units 2.

Four heat exchanger temperature sensors 35 (heat exchanger temperature sensor 35 a to heat exchanger temperature sensor 35 d) are provided on the inlet side or the outlet side of the heat source side refrigerant of the load side heat exchanger 26. It becomes the inlet side temperature sensor 31 or the outlet side temperature sensor 32 in the first embodiment and the second embodiment.

The pressure sensor 36 (pressure sensor 36a and pressure sensor 36b) detects the pressure of the heat source side refrigerant flowing between the load side heat exchanger 26b and the load side expansion device 25b.

The operation mode of the air conditioner 100 is the same as that of the air conditioner 100 described in the third embodiment, that is, the all-cooling operation mode in which all the indoor units 2 being driven execute the cooling operation, and the indoors being driven. There is an all heating operation mode in which all of the units 2 perform the heating operation. Further, there are a cooling main operation mode to be executed when the cooling load is larger and a heating main operation mode to be executed when the heating load is larger.

<Full cooling operation mode>
In the case of the cooling only operation mode, the high temperature / high pressure gas refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 via the refrigerant flow switching device 11, dissipates heat to the surrounding air, and condenses and condenses As a high pressure liquid refrigerant, it flows out of the outdoor unit 1 through the first backflow prevention device 13. Then, it flows into the relay device 3 through the main pipe 5. The refrigerant flowing into the relay device 3 passes through the opening / closing device 50a, and is expanded by the load side expansion device 25a and the load side expansion device 25b to become a low temperature and low pressure two-phase refrigerant. The two-phase refrigerant flows into each of the load side heat exchanger 26a and the load side heat exchanger 26b acting as an evaporator, absorbs heat from the heat medium circulating in the heat medium circulation circuit, and becomes a low temperature low pressure gas refrigerant. The gas refrigerant flows out of the relay device 3 via the relay refrigerant flow switching device 51a and the relay refrigerant flow switching device 51b. Then, it flows into the outdoor unit 1 again through the main pipe 5. The refrigerant flowing into the outdoor unit 1 passes through the first backflow prevention device 16 and is again drawn into the compressor 10 via the refrigerant flow switching device 11 and the accumulator 19.

In the heat medium circulation circuit, the heat medium is cooled by the refrigerant in both the load side heat exchanger 26a and the load side heat exchanger 26b. The cooled heat medium flows in the heat medium pipe 70 by the pump 71a and the pump 71b. The heat medium that has flowed into the use side heat exchangers 76a to 76d via the second heat medium flow path switching devices 73a to 73d absorbs heat from indoor air. The indoor air is cooled to cool the air-conditioned space. The refrigerant that has flowed out of the use side heat exchangers 76a to 76d flows into the heat medium flow rate adjustment devices 75a to 75d. Then, the refrigerant flows into the load side heat exchanger 26a and the load side heat exchanger 26b through the first heat medium flow path switching devices 72a to 72d, is cooled, and is sucked into the pump 71a and the pump 71b again. The heat medium flow control devices 75a to 75d corresponding to the use side heat exchangers 76a to 76d having no heat load are fully closed. Further, the heat medium flow control devices 75a to 75d corresponding to the use side heat exchangers 76a to 76d having the heat load adjust the opening degree, and adjust the heat load on the use side heat exchangers 76a to 76d.

<Cooling-based operation mode>
In the cooling main operation mode, the high temperature / high pressure gas refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 through the refrigerant flow switching device 11, dissipates heat to surrounding air, and condenses, It becomes a two-phase refrigerant and flows out of the outdoor unit 1 through the first backflow prevention device 13. Then, it flows into the relay device 3 through the main pipe 5. The refrigerant that has flowed into the relay device 3 flows into the load-side heat exchanger 26b that functions as a condenser through the relay-machine refrigerant flow switching device 51b, and dissipates heat to the heat medium circulating in the heat medium circulation circuit. It becomes a liquid refrigerant. The high-pressure liquid refrigerant is expanded by the load-side throttling device 25 b to become a low-temperature low-pressure two-phase refrigerant. The two-phase refrigerant flows into the load-side heat exchanger 26a acting as an evaporator via the load-side throttling device 25a, absorbs heat from the heat medium circulating in the heat medium circulation circuit, and becomes a low pressure gas refrigerant. It flows out of the relay device 3 via the flow path switching device 51a. Then, it flows into the outdoor unit 1 again through the main pipe 5. The refrigerant flowing into the outdoor unit 1 passes through the first backflow prevention device 16 and is again drawn into the compressor 10 via the refrigerant flow switching device 11 and the accumulator 19.

In the heat medium circulation circuit, the heat of the refrigerant is transferred to the heat medium by the load-side heat exchanger 26b. Then, the heated heat medium flows in the heat medium pipe 70 by the pump 71 b. The heat medium flowing into the use side heat exchangers 76a to 76d having a heating request by operating the first heat medium channel switching devices 72a to 72d and the second heat medium channel switching devices 73a to 73d dissipates heat into the indoor air Do. The indoor air is heated to heat the air-conditioned space. On the other hand, the cold heat of the refrigerant is transferred to the heat medium by the load side heat exchanger 26a. Then, the cooled heat medium flows in the heat medium pipe 70 by the pump 71 a. The heat medium flowing into the use side heat exchangers 76a to 76d having a cooling request by operating the first heat medium channel switching devices 72a to 72d and the second heat medium channel switching devices 73a to 73d absorbs heat from indoor air Do. The indoor air is cooled to cool the air-conditioned space. The heat medium flow control devices 75a to 75d corresponding to the use side heat exchangers 76a to 76d having no heat load are fully closed. Further, the heat medium flow control devices 75a to 75d corresponding to the use side heat exchangers 76a to 76d having the heat load adjust the opening degree, and adjust the heat load on the use side heat exchangers 76a to 76d.

In the cooling main operation mode of the air conditioning apparatus 100 of the fourth embodiment, for example, the heat source side heat exchanger 12 in one of the outdoor units 1 may become an evaporator. In the outdoor unit 1 described above, the operation of the device in the case of performing the injection and the liquid back prevention and the liquid leveling control is the same as that described in the first embodiment and the second embodiment.

<All heating operation mode>
In the case of the heating only operation mode, the high temperature / high pressure gas refrigerant discharged from the compressor 10 flows out of the outdoor unit 1 through the first connection pipe 6 and the first backflow prevention device 14 through the refrigerant flow switching device 11 Do. Then, it flows into the relay device 3 through the main pipe 5. The refrigerant that has flowed into the relay device 3 flows into the load-side heat exchanger 26a and the load-side heat exchanger 26b through the relay refrigerant flow switching device 51a and the relay refrigerant flow switching device 51b, and is thermally The heat is released to the heat medium circulating in the medium circulation circuit, and becomes a high pressure liquid refrigerant. The high-pressure liquid refrigerant is expanded by the load-side throttling device 25a and the load-side throttling device 25b to become a low-temperature, low-pressure two-phase refrigerant, and flows out of the relay device 3 through the opening / closing device 50b. Then, it flows into the outdoor unit 1 again through the main pipe 5. The refrigerant having flowed into the outdoor unit 1 passes through the second connection pipe 7 and the first backflow prevention device 15, flows into the heat source side heat exchanger 12 acting as an evaporator, absorbs heat from the surrounding air, It becomes a gas refrigerant. The gas refrigerant is again drawn into the compressor 10 via the refrigerant flow switching device 11 and the accumulator 19. The operation of the heat medium in the heat medium circulation circuit is the same as that in the cooling only operation mode. In the all heating operation mode, the heat medium is heated by the refrigerant in the load side heat exchanger 26a and the load side heat exchanger 26b, and dissipated to room air by the use side heat exchanger 76a and the use side heat exchanger 76b, Heating the air conditioning target space.

In the air conditioning apparatus 100 of the fourth embodiment, the injection in the heating only operation mode, and the operation of the device in the case of performing the liquid back prevention and the liquid equalization control and the control of the control device 60 are the first embodiment and the embodiment. It is the same as that described in 2.

<Heating main operation mode>
In the heating main operation mode, the high-temperature, high-pressure gas refrigerant discharged from the compressor 10 passes through the first connection pipe 6 and the first backflow prevention device 14 via the refrigerant flow switching device 11, and the outdoor unit 1 Flow out of Then, it flows into the relay device 3 through the main pipe 5. The refrigerant that has flowed into the relay device 3 flows into the load-side heat exchanger 26b that functions as a condenser through the relay-machine refrigerant flow switching device 51b, and dissipates heat to the heat medium circulating in the heat medium circulation circuit. It becomes a liquid refrigerant. The high-pressure liquid refrigerant is expanded by the load-side throttling device 25 b to become a low-temperature low-pressure two-phase refrigerant. The two-phase refrigerant flows into the load side heat exchanger 26a acting as an evaporator via the load side expansion device 25a, absorbs heat from the heat medium circulating in the heat medium circulation circuit, and the relay machine refrigerant flow switching device 51a It flows out from the relay device 3 via Then, it flows into the outdoor unit 1 again through the main pipe 5. The refrigerant flowing into the outdoor unit 1 flows through the second connection pipe 7 and the first backflow prevention device 15 into the heat source side heat exchanger 12 acting as an evaporator, and absorbs heat from the surrounding air, so that the low temperature low pressure It becomes a gas refrigerant of The gas refrigerant is again drawn into the compressor 10 via the refrigerant flow switching device 11 and the accumulator 19. The operation of the heat medium in the heat medium circulation circuit, the first heat medium flow path switching devices 72a to 72d, the second heat medium flow path switching devices 73a to 73d, the heat medium flow control devices 75a to 75d, and the use side heat The operations of the exchangers 76a to 76d are the same as in the cooling main operation mode.

In the air-conditioning apparatus 100 of Embodiment 4, the operation in the case of performing injection in the heating main operation mode, and liquid back prevention and liquid equalization control, and control of the control device 60 are described in Embodiment 1 and Embodiment. It is the same as that described in 2.

<Main pipe 5 and heat medium piping 70>
In each operation mode in the fourth embodiment, the refrigerant flows through the main pipe 5 connecting the outdoor unit 1 and the relay device 3, and the heat medium pipe 70 connecting the relay device 3 and the indoor unit 2 is water, antifreeze, etc. The heat transfer medium is flowing.

When the heating load and the cooling load are mixedly generated in the use side heat exchanger 76, the first heat medium flow path switching device 72 corresponding to the use side heat exchanger 76 performing the heating operation and The second heat medium channel switching device 73 is switched to the channel connected to the load side heat exchanger 26b for heating. Further, the first heat medium channel switching device 72 and the second heat medium channel switching device 73 corresponding to the use side heat exchanger 76 performing the cooling operation are connected to the load side heat exchanger 26a for cooling. Switch to the flow path. Therefore, the heating operation and the cooling operation can be freely performed in each indoor unit 2.

As described above, the air according to the fourth embodiment can perform simultaneous heating and cooling operation by connecting in parallel a plurality of outdoor units 1 having the heat medium circulation circuit and the refrigerant circuit and having the devices that constitute the refrigerant circuit. Also in the conditioning apparatus 100, as in the first and second embodiments, excessive liquid back can be prevented by injection and liquid equalization control.

Embodiment 5
The air conditioner 100 according to the present invention is not limited to the first to fourth embodiments, and various modifications are possible. For example, in the embodiment described above, although the case where the discharge temperature threshold is 110 ° C. in the cooling operation mode and the heating operation mode is illustrated, the discharge temperature threshold is the discharge temperature of the compressor 10. It may be set according to the limit value. For example, when the limit value of the discharge temperature of the compressor 10 is 120 ° C., the controller 60 controls the operation of the compressor 10 so that the discharge temperature does not exceed 120 ° C. Specifically, when the discharge temperature exceeds 110 ° C., the control device 60 performs control to lower the frequency of the compressor 10 to decelerate.

Therefore, when the above-described injection is performed to lower the discharge temperature of the compressor 10, the temperature slightly lower than 110 ° C., which is the temperature (discharge temperature threshold) for lowering the frequency of the compressor 10, is 90 ° C. to 105 ° C. The target discharge temperature (liquid level adjustment threshold) may be set in advance to a temperature (e.g., 100 ° C., etc.) between the above. For example, if the drive frequency of the compressor 10 is not lowered when the discharge temperature exceeds 110 ° C., the discharge temperature threshold is set to 90 ° C. or more and 120 ° C. or less (for example, 110 ° C.) do it.

In Embodiments 1 to 4, the use of a refrigerant such as the R410A refrigerant or the R32 refrigerant has been described as an example, but other refrigerants may be used. For example, using a mixed refrigerant (non-azeotropic mixed refrigerant) of an R32 refrigerant and a tetrafluoropropene-based refrigerant (HFO1234yf, HFO1234ze, etc.) represented by the chemical formula CF ₃ CF = CH ₂ with a small global warming potential It is also good. In particular, when R32 is used as the refrigerant, the discharge temperature rises by about 20 ° C. in the same operating state as compared with the case where R410A is used. Therefore, it is necessary to lower the discharge temperature when using the R32 refrigerant. Therefore, the effect of performing the injection described in the first embodiment and the like is large. Thus, the effect is particularly enhanced when using a refrigerant whose discharge temperature is high.

In the mixed refrigerant of R32 refrigerant and HFO 1234yf, when the mass ratio of R32 is 62% (62 wt%) or more, the discharge temperature is higher by 3 ° C. or more than when R410A refrigerant is used. For this reason, the effect obtained by lowering the discharge temperature by the above-described injection is large. Further, in the mixed refrigerant of R32 and HFO1234ze, when the mass ratio of R32 is 43% (43 wt%) or more, the discharge temperature is 3 ° C. or more higher than when the R410A refrigerant is used. For this reason, the effect obtained by lowering the discharge temperature by the above-described injection is large. Further, the type of refrigerant in the mixed refrigerant is not limited to this. Even when a mixed refrigerant containing a small amount of other refrigerant components is used, the discharge temperature is not greatly affected, and the same effect as described above is obtained. Further, for example, even in the case of using a mixed refrigerant containing a small amount of R32, HFO 1234yf and other refrigerants, the same effect as described above is obtained.

Furthermore, as the refrigerant of the embodiment described above, a refrigerant such as CO ₂ (R744) which operates in a supercritical state on the high pressure side can also be used. Also in this case, since the discharge temperature needs to be reduced, the discharge temperature can be reduced by setting the air conditioner 100 to the refrigerant circuit configuration of the above-described embodiment.

For example, in the air conditioners capable of simultaneous operation in heating and heating in the third embodiment and the fourth embodiment, the configuration in which the outdoor unit 1 and the relay device 3 are connected using the two main pipes 5 is illustrated. However, not only this but various well-known methods can be used. For example, the present invention can be applied to an air conditioner in which the outdoor unit 1 and the relay device 3 are connected using three main pipes 5 and can perform simultaneous heating and cooling operation. Also in such an air conditioning apparatus, it is possible to suppress an excessive rise in the temperature of the high-pressure and high-temperature gas refrigerant discharged from the compressor 10 as in the above-described embodiment.

In the first embodiment and the like, although the compressor 10 has been described as a low pressure shell type compressor, for example, a high pressure shell type compressor can also be used. Although low pressure shell type compressors are effective for injection into the compressor suction chamber, the same effects as described above can be obtained even when high pressure shell type compressors are used.

Further, in the above-described Embodiment 1 and the like, the outdoor unit 1 has the heat source side fan 18, and the indoor unit 2 has the load side fan 28. However, it is not limited to this. For example, the load side fan 28 can be configured not to be mounted by using a load such as a panel heater using radiation as the load side heat exchanger 26.

FIG. 14 is a diagram showing an example of the configuration of the air conditioning apparatus 100 according to Embodiment 5 of the present invention. As the heat source side heat exchanger 12, it is possible to use a water refrigerant heat exchanger that performs heat exchange between the refrigerant that has passed through the water pipe 80 and a liquid such as antifreeze liquid. The heat source side heat exchanger 12 and the load side heat exchanger 26 do not limit the heat exchange object as long as they can release or absorb heat of the refrigerant.

Further, in the embodiment described above, in the case of the air conditioner dedicated to cooling or heating only, the refrigerant flow switching device 11 can be omitted.

1, 1a, 1b outdoor unit, 2, 2a, 2b, 2c, 2d indoor unit, 3 relay device, 4, 4a, 4b refrigerant piping, 5 main pipes, 6 first connection piping, 7 second connection piping, 8 branch pipes 10, 10a, 10b Compressor, 11, 11a, 11b Refrigerant flow switching device, 12, 12a, 12b Heat source side heat exchanger, 13, 14, 15, 16 First backflow prevention device, 17, 17a, 17b Injection Port, 18, 18a, 18b Heat source fan, 19, 19a, 19b Accumulator, 20, 20a, 20b Oil return mechanism, 21a, 21b, 21c, 21d Second backflow prevention device, 22a, 22b, 22c, 22d Third Backflow prevention device, 23a, 23b, 23c, 23d first switching device, 24a, 24b, 24c, 24d second switching device, 25, 25a 25b, 25c, 25d Load-side throttling device 26, 26, 26a, 26b, 26c, 26d Load-side heat exchanger, 27 second relay throttling device 28, 28 load-side fan, 29 gas-liquid separator, 30 first relay throttling Devices 31, 31a, 31b, 31c, 31d Inlet temperature sensors 32, 32, 32a, 32b, 32c, 32d Outlet temperature sensors, 33 throttle device inlet pressure sensors, 34 throttle device outlet pressure sensors, 35, 35a, 35b, 35c, 35d heat exchanger temperature sensor, 36, 36a, 36b pressure sensor, 37, 37a, 37b first heat medium temperature sensor, 38, 38a, 38b second heat medium temperature sensor, 40, 40a, 40b discharge pressure Sensor, 41, 41a, 41b Injection piping, 42, 42a, 42b a Jection throttle device, 43, 43a, 43b Discharge temperature sensor, 44, 44a, 44b Pressure detection sensor, 45, 45a, 45b Room outside throttle device, 46, 46a, 46b Outside air temperature sensor, 50, 50a, 50b Switchgear , 51, 51a, 51b relay machine refrigerant flow path switching device, 60, 60a, 60b control device, 61, 61a, 61b storage device, 70 heat medium piping, 71, 71a, 71b pump, 72, 72a, 72b, 72c, 72d first heat medium flow path switching device, 73, 73a, 73b, 73c, 73d second heat medium flow path switching device, 75, 75a, 75b, 75c, 75d heat medium flow rate adjusting device, 76, 76a, 76b, 76c , 76d Use side heat exchanger, 80 water piping, 100 air conditioner.

Claims

An outdoor unit having an injection port for introducing a refrigerant into a suction chamber, a compressor for compressing and discharging the refrigerant, a heat source side heat exchanger for exchanging heat of the refrigerant, and an accumulator for storing the refrigerant;
At least one load-side throttle device for decompressing the refrigerant;
An air conditioner comprising a refrigerant circuit in which a load and at least one load-side heat exchanger for performing heat exchange with the refrigerant are connected by a pipe to circulate the refrigerant.
The outdoor unit is
In the refrigerant circuit, one end is connected between the heat source side heat exchanger and the load side expansion device, the other end is connected to the injection port, and a part of the refrigerant flowing in the refrigerant circuit is Injection piping that passes through to the injection port,
In the refrigerant circuit, when the refrigerant flows from the load-side expansion device to the heat source-side heat exchanger, the refrigerant circuit is installed at a position downstream of the one end of the injection pipe to decompress the refrigerant passing therethrough. An outdoor throttling device to adjust the flow rate,
And an injection throttle device for adjusting the amount of the refrigerant flowing through the injection pipe,
An air conditioning apparatus further comprising a control device that controls the opening degree of the outdoor side throttle device and the opening degree of the injection throttle device.
The air conditioning apparatus according to claim 1, wherein a plurality of the outdoor units are connected in parallel by piping to configure the refrigerant circuit.
The controller is
When it is determined that the discharge temperature of the refrigerant discharged by the compressor is equal to or higher than a predetermined discharge temperature threshold, the injection throttle is set such that the discharge temperature is lower than the discharge temperature threshold. The air conditioning apparatus according to claim 1, wherein the opening degree of the apparatus is controlled.
The controller is
The air conditioning apparatus according to claim 1 or 2, wherein the discharge temperature of the refrigerant discharged by the compressor controls the opening degree of the injection throttle device with a discharge temperature threshold value determined in advance as a target.
The controller is
The discharge temperature of the compressor, which is lowered due to the liquid return from the accumulator, is higher than the liquid level adjustment threshold when it is determined that the discharge temperature is lower than a predetermined liquid level adjustment threshold. The air conditioner according to any one of claims 1 to 3, wherein an opening degree of the outdoor side throttle device is controlled.
When the opening degree of the injection throttle device is open, the liquid level adjustment threshold is lowered by the opening degree of the injection throttle device to the discharge temperature which is lowered by the liquid return from the accumulator. The air conditioner according to claim 5, wherein a temperature value of a minute is added.
The said control apparatus calculates the discharge superheat degree of the said refrigerant | coolant which the said compressor discharges, replaces with the said discharge temperature, and performs the process based on the said discharge superheat degree in any one of Claims 3-6. The air conditioner of description.
The outdoor unit further includes a refrigerant flow switching device that switches the flow of the refrigerant between the cooling operation mode and the heating operation mode,
The air conditioner according to any one of claims 1 to 7, wherein the control device controls an opening degree of the injection throttle device in a heating operation mode.
In the heating operation mode, a plurality of heating operations are all heating operation modes in which all of the plurality of load-side heat exchangers not in the stop state function as a condenser, and a plurality of load-side heat exchangers not in the stop state The air conditioner according to claim 8, further comprising: a heating main operation mode in which some of the load-side heat exchangers function as a condenser and the other load-side heat exchangers function as an evaporator.
A plurality of indoor units on which the load-side throttling device and the load-side heat exchanger are respectively mounted;
A relay device for relaying between the outdoor unit and the indoor units;
The refrigerant circuit is connected by piping such that the refrigerant circulates between the device of the outdoor unit and the devices of the plurality of indoor units via the relay device. The air conditioner according to any one of the preceding claims.
The refrigerant circuit having the load-side heat exchanger that performs heat exchange between the refrigerant and the heat medium using the heat medium different from the refrigerant as the load;
A pump for pressurizing the heat medium, the load side heat exchanger, a use side heat exchanger for exchanging heat with air to be air conditioned, and a heat medium for adjusting the flow rate of the heat medium flowing in and out of the use side heat exchanger The air conditioning apparatus according to any one of claims 1 to 9, further comprising: a heat medium circulation circuit that connects the flow control device to a pipe and circulates the heat medium.
The air conditioner according to any one of claims 1 to 11, wherein the heat source side heat exchanger is a water refrigerant heat exchanger that performs heat exchange between water and the refrigerant.