WO2015029220A1

WO2015029220A1 - Air conditioner

Info

Publication number: WO2015029220A1
Application number: PCT/JP2013/073341
Authority: WO
Inventors: 山下　浩司
Original assignee: 三菱電機株式会社
Priority date: 2013-08-30
Filing date: 2013-08-30
Publication date: 2015-03-05
Also published as: GB2533042A; GB2533042B; JP6017048B2; GB201521701D0; JPWO2015029220A1

Abstract

When a first heat exchanger, namely a heat-source-side heat exchanger (12), is acting as a condenser, this air conditioner is controlled such that, as a refrigerant flows through a first bypass pipe (4a) to an inlet-side pipe for a compressor (10) via throttling devices (14a and 14d), said refrigerant also flows through a second bypass pipe (4b) via one of the throttling devices (14b) and is introduced into a compression chamber via an injection port. When the heat-source-side heat exchanger (12) is acting as an evaporator, the air conditioner is controlled such that the refrigerant flows through the second bypass pipe (4b) via the aforementioned throttling device (14b) and is introduced into the compression chamber via the injection port and the other throttling device (14d) is either closed completely or closed down such that almost no refrigerant flows therethrough.

Description

Air conditioner

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

In an air conditioner such as a multi air conditioner for buildings, air having a refrigerant circuit for injecting a liquid refrigerant (liquid injection) from a high pressure liquid pipe to an intermediate portion of a compressor compression stroke in order to lower the discharge temperature of the compressor A harmony device exists. In this air conditioner, the discharge temperature can be controlled to the set temperature regardless of the operating state (see, for example, Patent Document 1).

There is also an air conditioner that can inject liquid refrigerant in a high-pressure state in a refrigerating cycle into piping on the suction side of a compressor in both cooling operation and heating operation (see, for example, Patent Document 2). ).

Furthermore, there is also an air conditioner that includes a supercooling heat exchanger on the refrigerant outlet side of the condenser, controls the flow rate of refrigerant flowing to the supercooling heat exchanger, and controls the discharge temperature of the compressor (for example, (See Patent Document 3).

Japanese Patent Laying-Open No. 2005-282972 (page 4, FIG. 1, etc.) JP-A-2-110255 (page 3, FIG. 1 etc.) Japanese Patent Laid-Open No. 2001-227823 (page 4, FIG. 1, etc.)

For example, in the air conditioner described in Patent Document 1 described above, only a method of injecting from a high-pressure liquid pipe to the middle of a compressor is described, and when the circulation path of the refrigeration cycle is reversed (for cooling and heating) There was a problem that it was not possible to cope with such as switching.

In the air conditioner described in Patent Document 2, a check valve is installed in parallel with both the indoor and outdoor throttle devices, and therefore, a configuration capable of sucking and injecting liquid refrigerant during cooling and heating. However, a special indoor unit is required for this purpose, and a normal indoor unit in which a check valve is not connected in parallel with the throttle device cannot be used. It was.

In the air conditioner described in Patent Document 3, the flow rate of the refrigerant flowing through the supercooling heat exchanger is controlled by the throttle device attached to the supercooling heat exchanger, and the discharge temperature is controlled. Since both the degree of supercooling at the outlet of the condenser cannot be controlled separately to the target value and the discharge temperature cannot be controlled properly while maintaining the appropriate degree of supercooling, the outdoor unit and the indoor unit If the extension pipe to be connected is long, if the discharge temperature is controlled to the target value, the degree of supercooling at the outlet of the outdoor unit cannot be controlled to the target value, and the refrigerant flowing into the indoor unit will flow in two phases due to pressure loss in the extension pipe. If the indoor unit is equipped with a throttle device, such as a multi-type air conditioner, sound may be produced or the control may become unstable if the inlet side of the throttle device becomes two-phase. There was a problem that it would end up.

The present invention has been made to solve the above-described problems, and provides an air conditioner that can stably control the discharge temperature of the compressor and the degree of supercooling of the refrigerant.

An air conditioner according to the present invention includes a compression chamber and an injection port for introducing a refrigerant into the compression chamber, a compressor that compresses and discharges the refrigerant, and a first heat exchanger that performs heat exchange of the refrigerant. , A refrigerant flow switching device for switching whether the first heat exchanger is a condenser or an evaporator, a first flow path and a second flow path, and heat exchange of the refrigerant passing through each flow path A subcooling heat exchanger that supercools the refrigerant flowing through the first flow path, a second heat exchanger that performs heat exchange of the refrigerant, and a first throttle that adjusts the pressure of the refrigerant passing through the second heat exchanger A refrigerant circuit that circulates the refrigerant by connecting a pipe to the apparatus, and the refrigerant inflow side and the excess of the pipe between the first heat exchanger and the second heat exchanger and the second flow path of the supercooling heat exchanger A first bypass pipe connecting a refrigerant outflow side of the second flow path of the cooling heat exchanger and a pipe of the refrigerant suction side of the compressor; In one bypass pipe, a second expansion device that adjusts the pressure of the refrigerant flowing from the pipe between the first heat exchanger and the second heat exchanger to the second flow path of the supercooling heat exchanger, and the first bypass pipe A third expansion device that adjusts the pressure of the refrigerant flowing from the second flow path of the supercooling heat exchanger to the refrigerant suction side pipe of the compressor, and the refrigerant outflow side of the second flow path of the supercooling heat exchanger; A second bypass pipe that connects the injection port and a fourth expansion device that adjusts the flow rate of the refrigerant flowing through the second bypass pipe, and when the first heat exchanger acts as a condenser, The refrigerant passes through the first bypass pipe through the throttle device and the third throttle device and flows through the suction side pipe of the compressor, and passes through the second bypass pipe through the fourth throttle device to pass the refrigerant into the compression chamber. The first heat exchanger is controlled to be introduced. When acting as a generator, the refrigerant is introduced into the compression chamber through the second bypass pipe through the fourth throttle device, and the opening of the third throttle device is fully closed or the refrigerant almost flows. In the cooling operation, the refrigerant is injected into the compressor chamber while greatly controlling the degree of supercooling of the refrigerant at the outlet of the supercooling heat exchanger, and discharged from the compressor. The temperature can be lowered, and the discharge temperature of the compressor can be lowered while preventing the refrigerant from being two-phased in the extension pipe, so that the operation can be safely performed and the life of the device is extended.

In the air conditioner of the present invention, the discharge temperature of the compressor is increased by allowing the refrigerant to be injected into the compression chamber of the compressor while keeping the subcooling degree of the outdoor unit outlet at an appropriate value during the cooling operation. You can make sure it ’s not too much. For this reason, damage to the compressor can be prevented and the life can be extended.

It is the schematic which shows the example of installation of the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the outline of a structure of the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the flow of the refrigerant | coolant at the time of the air_conditionaing | cooling operation mode when the discharge temperature of the air conditioning apparatus 100 which concerns on Embodiment 1 of this invention is low. FIG. 5 is a ph diagram (pressure-enthalpy diagram) during cooling operation when the discharge temperature of the air-conditioning apparatus 100 according to Embodiment 1 of the present invention is low. It is a figure which shows the flow of the refrigerant | coolant at the time of the cooling operation mode in case the discharge temperature of the air conditioning apparatus 100 which concerns on Embodiment 1 of this invention is high. FIG. 6 is a ph diagram (pressure-enthalpy diagram) during cooling operation when the discharge temperature of the air-conditioning apparatus 100 according to Embodiment 1 of the present invention is high. It is a figure which shows the flow of the refrigerant | coolant at the time of the heating operation mode of the air conditioning apparatus 100 which concerns on Embodiment 1 of this invention. FIG. 3 is a ph diagram (pressure-enthalpy diagram) during heating operation of the air-conditioning apparatus according to Embodiment 1 of the present invention.

Hereinafter, an air conditioner according to an embodiment of the invention will be described with reference to the drawings. Here, in FIG. 1 and the following drawings, the same reference numerals denote the same or corresponding parts, and are common to the whole text of the embodiments described below. And the form of the component represented by the whole specification is an illustration to the last, Comprising: It does not limit to the form described in the specification. In particular, the combination of the components is not limited to the combination in each embodiment, and the components described in the other embodiments can be applied to another embodiment. Furthermore, when there is no need to distinguish or identify a plurality of similar devices that are distinguished by subscripts, the subscripts may be omitted. In the drawings, the size relationship of each component may be different from the actual one. The level of temperature, pressure, etc. is not particularly determined in relation to absolute values, but is relatively determined in the state, operation, etc. of the system, apparatus, and the like.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram illustrating an installation example of an air-conditioning apparatus according to Embodiment 1 of the present invention. Based on FIG. 1, the installation example of the air conditioning apparatus in this Embodiment is demonstrated. The air conditioning apparatus in the present embodiment can select either the cooling mode or the heating mode as the operation mode by using the refrigeration cycle due to the phase change of the refrigerant.

In FIG. 1, the air-conditioning apparatus according to the present embodiment includes one outdoor unit 1 and a plurality of indoor units 2 that are heat source units. The outdoor unit 1 and the indoor unit 2 are connected by an extension pipe (refrigerant pipe) 5 through which the refrigerant passes.

The outdoor unit 1 is usually disposed in an outdoor space 6 that is a space outside a building 9 such as a building (for example, a rooftop). The outdoor unit 1 generates cold or warm heat and delivers it to the indoor unit 2 via the extension pipe 5. The indoor unit 2 is arranged at a position where air with adjusted temperature or the like can be supplied to the indoor space 7 which is a space (for example, a living room) inside the building 9. Cooling air or heating air is supplied to the indoor space 7.

As shown in FIG. 1, in the air conditioner according to the present embodiment, an outdoor unit 1 and each indoor unit 2 are connected to each other using two extension pipes (refrigerant pipes) 5.

Here, FIG. 1 shows an example in which the indoor unit 2 is a ceiling cassette type, but the present invention is not limited to this. For example, any type may be used as long as it can supply cooling air or heating air directly into the indoor space 7 or through a duct, such as a ceiling-embedded type or a ceiling-suspended type.

Moreover, in FIG. 1, although the case where the outdoor unit 1 is installed in the outdoor space 6 is shown as an example, it is not limited to this. For example, you may make it install the outdoor unit 1 in the enclosed space like a machine room with a ventilation opening.

Furthermore, the outdoor unit 1 may be installed in the building 9 as long as it can be exhausted outside the building 9 by an exhaust duct or the like. Further, the water-cooled outdoor unit 1 or the like may be installed inside the building 9. No matter what place the outdoor unit 1 of the present embodiment is installed, no particular problem occurs.

Also, the number of connected

outdoor units

1 and 2 is not limited to the number shown in FIG. For example, what is necessary is just to determine a number according to the building 9 in which the air conditioning apparatus which concerns on this Embodiment is installed.

FIG. 2 is a diagram showing a schematic configuration of the air-conditioning apparatus according to Embodiment 1 of the present invention. In FIG. 2 and subsequent figures, the air conditioner of the present embodiment is referred to as an air conditioner 100. Based on FIG. 2, the detailed structure of the air conditioning apparatus 100 in this Embodiment is demonstrated. As described above, the outdoor unit 1 and the indoor unit 2 are connected by the extension pipe 5 through which the refrigerant flows, and constitute a refrigerant circuit.

[Outdoor unit 1]
In the outdoor unit 1, a compressor 10, a refrigerant flow switching device 11 such as a four-way valve, a heat source side heat exchanger 12, and an accumulator 15 are connected and connected in series with a refrigerant pipe. The main refrigerant circuit is configured together with the device 16 and the use side heat exchanger 17. Further, the outdoor unit 1 is provided with a first bypass pipe 4a, a second bypass pipe 4b, a supercooling heat exchanger 13, a throttle device 14a, a throttle device 14b, a throttle device 14c, a throttle device 14d, and a liquid separator 18. ing.

The compressor 10 sucks the refrigerant, compresses the refrigerant, and discharges it in a high temperature and high pressure state. For example, it may be configured with an inverter compressor capable of capacity control. Here, the compressor 10 of the present embodiment includes an injection port that can introduce the refrigerant into the compression chamber from the outside of the compressor 10 in the compression chamber that compresses the refrigerant inside the compressor 10. . For example, the compressor 10 has a compression chamber in a hermetically sealed container, and the inside of the hermetically sealed container has a low-pressure refrigerant pressure atmosphere, and uses a low-pressure shell structure that sucks and compresses the low-pressure refrigerant in the hermetic container. . The refrigerant flow switching device 11 switches the refrigerant flow during the heating operation and the refrigerant flow during the cooling operation. The heat source side heat exchanger 12 functions as an evaporator during heating operation, functions as a condenser or a radiator during cooling operation, and performs heat exchange between air and refrigerant supplied by a blower (not shown), The refrigerant absorbs heat to evaporate gas or dissipate heat to condense. The subcooling heat exchanger 13 is composed of, for example, a double-pipe heat exchanger or the like, has a first flow path and a second flow path, and heats between the refrigerants that exchange heat between the refrigerants passing through the flow paths. It is an exchanger. The refrigerant flowing into and out of the heat source side heat exchanger 12 passes through the first flow path. The refrigerant that has passed through the expansion device 14a flows into the second flow path, and flows out to the first bypass pipe 4a. Here, the supercooling heat exchanger 13 is not limited to a two-pipe heat exchanger, but can exchange heat between the refrigerant passing through the first flow path and the refrigerant passing through the second flow path. Any structure may be used.

In the present invention, the expansion device 14a that functions as the second expansion device adjusts the pressure and flow rate of the refrigerant that flows from the liquid separator 18 through the first bypass pipe 4a and flows into the second flow path of the supercooling heat exchanger 13. . Further, the expansion device 14b functioning as the third expansion device in the present invention passes through the first bypass pipe 4a from the second flow path of the supercooling heat exchanger 13 to the upstream side of the accumulator 15 (the suction side of the compressor 10). ) Adjust the pressure and flow rate of the refrigerant flowing in the pipe. Furthermore, the expansion device 14d that functions as the fourth expansion device in the present invention adjusts the pressure and flow rate of the refrigerant that passes through the second bypass pipe 4b. And the expansion device 14c adjusts the pressure of the refrigerant in the pipe between the expansion device 14a and the expansion device 16 in the present embodiment.

The accumulator 15 is connected to the compressor 10 via a pipe serving as a suction side flow path, and stores excess refrigerant in the refrigerant circuit. Here, the accumulator 15 may be provided as necessary. For example, when the surplus refrigerant is not generated or the surplus refrigerant is small in the refrigerant circuit, the accumulator 15 may not be provided. The liquid separator 18 is provided in the refrigerant circuit at a position on the refrigerant outflow side of the heat source side heat exchanger 12 during cooling operation (on the pipe between the heat source side heat exchanger 12 and the expansion device 16). The liquid separator 18 is provided in a pipe between the heat source side heat exchanger 12 and the use side heat exchanger 17 of each indoor unit 2 (for example, between the heat source side heat exchanger 12 and the extension pipe 5). It becomes a branching means for branching. For example, when a refrigerant in a gas-liquid two-phase state (two-phase refrigerant) passes, it is separated into a part of the liquid refrigerant (which may be all included) and the remaining refrigerant (other liquid refrigerant and gas refrigerant). A part of the liquid refrigerant flows through the first bypass pipe 4a, and the remaining refrigerant flows through the main refrigerant circuit.

For example, the first bypass pipe 4a is configured to extract the refrigerant condensed and liquefied in the heat source side heat exchanger 12 serving as a condenser during the cooling operation by using the expansion device 14a, the second flow path of the supercooling heat exchanger 13, and the expansion device. This is a pipe that bypasses the suction side flow path (upstream side of the accumulator 15) of the compressor 10 as a low-pressure superheated gas refrigerant through 14d. Here, in FIG. 2, it is connected to the upstream side of the accumulator 15, but may be connected to a pipe on the outlet side (downstream side) of the accumulator 15 because it may be a suction side flow path of the compressor 10. .

The second bypass pipe 4 b is a pipe that connects between the refrigerant outflow side of the second flow path of the supercooling heat exchanger 13 and the injection port of the compressor 10. During the cooling operation and the heating operation, the second bypass pipe 4b depressurizes the high-pressure or first medium-pressure liquid refrigerant by the action of the expansion device 14b, and the second medium-pressure is lower than the first medium-pressure. Two-phase refrigerant can be injected into the interior of the compression chamber. Here, the high pressure is the pressure of the refrigerant on the discharge side of the compressor 10. The low pressure is the pressure of the refrigerant on the suction side of the compressor 10. The intermediate pressure is lower than the high pressure and higher than the low pressure.

The outdoor unit 1 includes a discharge refrigerant temperature detection device 21, a high pressure detection device 22, a low pressure detection device 23, a liquid refrigerant temperature detection device 24, a supercooling heat exchanger inlet refrigerant temperature detection device 25, and a supercooling heat exchanger outlet. A refrigerant temperature detection device 26 and a control device 50 are provided. The discharged refrigerant temperature detection device 21 is a device that detects the temperature of the refrigerant discharged from the compressor 10. The high pressure detection device 22 is a device that detects the pressure on the discharge side of the compressor 10 on the high pressure side in the refrigerant circuit. The low-pressure detection device 23 is a device that detects the pressure on the refrigerant inflow side of the accumulator 15 on the low-pressure side in the refrigerant circuit. The liquid refrigerant temperature detection device 24 is a device that detects the temperature of the liquid refrigerant. The supercooling heat exchanger inlet refrigerant temperature detection device 25 is a device that detects the temperature of the refrigerant flowing into the second flow path of the supercooling heat exchanger 13. The supercooling heat exchanger outlet refrigerant temperature detection device 26 is a device that detects the temperature of the refrigerant flowing out from the second flow path of the supercooling heat exchanger 13. Moreover, the control apparatus 50 controls each apparatus of the outdoor unit 1 based on the detection information in various detection apparatuses, the instruction | indication contained in the signal from a remote controller, etc. For example, the frequency of the compressor 10, the rotational speed (including ON / OFF) of the blower (not shown), switching of the refrigerant flow switching device 11 and the like are controlled, and each operation mode described later is executed. In the present embodiment, for example, the expansion device 14b, the expansion device 14c, the expansion device 14d, and the like are controlled to adjust the flow rate, pressure, and the like of the refrigerant injected into the suction side of the compressor 10. For this reason, when the refrigerant | coolant which discharge temperature of the compressor 10 tends to become high temperature, such as R32 refrigerant | coolant (henceforth R32), the discharge temperature of the compressor 10 can be lowered | hung. Specific control operations performed by the control device 50 will be described in the operation description of each operation mode described later. Here, the control device 50 is configured by a microcomputer or the like.

[Indoor unit 2]
The indoor units 2 are each equipped with a throttle device 16 and a use side heat exchanger 17. The expansion device 16 and the use side heat exchanger 17 are connected to the outdoor unit 1 by the extension pipe 5. In the present invention, the expansion device 16 that functions as the first expansion device, such as an expansion valve or a flow rate adjustment device, depressurizes the refrigerant that passes therethrough. In addition, the use side heat exchanger 17 serving as the second heat exchanger in the present invention performs heat exchange between air supplied from a blower such as a fan (not shown) and the refrigerant and supplies the heat to the indoor space 7. Heating air or cooling air is generated. Although not shown in FIG. 2 and the like, each indoor unit 2 has a control device that controls the expansion device 16 and the blower.

Here, FIG. 2 shows an example in which four indoor units 2 are connected, and are illustrated as an indoor unit 2a, an indoor unit 2b, an indoor unit 2c, and an indoor unit 2d from the bottom of the page. Similarly, the diaphragm device 16 is illustrated as a diaphragm device 16a, a diaphragm device 16b, a diaphragm device 16c, and a diaphragm device 16d from the lower side of the drawing according to the indoor units 2a to 2d. The use side heat exchanger 17 is illustrated as a use side heat exchanger 17a, a use side heat exchanger 17b, a use side heat exchanger 17c, and a use side heat exchanger 17d from the lower side of the drawing. Although FIG. 2 shows four units, the number of connected indoor units 2 according to the present embodiment is not limited to four as in FIG.

Next, each operation mode executed by the air conditioner 100 will be described. The air conditioning apparatus 100 according to the present embodiment determines the operation mode of the outdoor unit 1 to be either the cooling operation mode or the heating operation mode based on an instruction from each indoor unit 2, for example.

In the air conditioner 100, all the indoor units 2 that are driven perform the same operation (cooling operation or heating operation) based on the determined operation mode to air condition the indoor space 7. Here, each indoor unit 2 can be freely operated or stopped in both the cooling operation mode and the heating operation mode.

[Cooling operation mode (when discharge temperature is low)]
FIG. 3 is a diagram showing the refrigerant flow in the cooling operation mode when the discharge temperature of the air-conditioning apparatus 100 according to Embodiment 1 of the present invention is low. For example, the discharge temperature is low when the discharge temperature is lower than 105 ° C. In FIG. 3, the cooling operation mode will be described by taking as an example a case where a cooling load is generated in all the use side heat exchangers 17. Here, in FIG. 3, a pipe indicated by a thick line indicates a pipe through which the refrigerant flows, and a direction in which the refrigerant flows is indicated by a solid line arrow.

In the case of the cooling operation mode shown in FIG. 3, in the outdoor unit 1, the control device 50 switches the refrigerant flow switching device 11 to the flow channel through which the refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12. To instruct. Then, the compressor 10 compresses the low-temperature and low-pressure refrigerant and discharges the 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 through the refrigerant flow switching device 11. Then, the heat source side heat exchanger 12 condenses and liquefies while radiating heat to the outdoor air, and becomes a high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the heat source side heat exchanger 12 passes through the first flow path of the expansion device 14c and the supercooling heat exchanger 13 that are fully opened. The refrigerant that has passed through the first flow path of the supercooling heat exchanger 13 is branched into two flow paths. One flows out of the outdoor unit 1 through the liquid separator 18. The other flows into the first bypass pipe 4a. The high-temperature and high-pressure liquid refrigerant flowing into the first bypass pipe 4a is decompressed by the expansion device 14a to become a low-temperature and low-pressure two-phase refrigerant, and the second flow path of the supercooling heat exchanger 13 and the fully-open expansion device 14d are connected. Pass through and flow into the upstream flow path of the accumulator 15. At this time, in the supercooling heat exchanger 13, heat exchange is performed between the high-temperature and high-pressure liquid refrigerant passing through the first flow path and the low-temperature and low-pressure two-phase refrigerant passing through the second flow path. Therefore, the refrigerant passing through the first flow path is cooled by the refrigerant passing through the second flow path, and the refrigerant passing through the second flow path is heated by the refrigerant passing through the first flow path.

The flow rate of the refrigerant passing through the second flow path (first bypass pipe 4a) of the supercooling heat exchanger 13 is adjusted by the opening degree (opening area) of the expansion device 14a because the expansion device 14d is fully open. become. The control device 50 detects the excess of the refrigerant on the downstream side of the first flow path of the supercooling heat exchanger 13 that is the temperature difference between the saturation temperature of the detection pressure of the high pressure detection device 22 and the detection temperature of the liquid refrigerant temperature detection device 24. The opening degree (opening area) of the expansion device 14a is controlled so that the degree of cooling approaches the target value. Here, the second flow path of the supercooling heat exchanger 13 is a temperature difference between the detected temperature of the supercooling heat exchanger outlet refrigerant temperature detection device 26 and the detection temperature of the supercooling heat exchanger inlet refrigerant temperature detection device 25. The degree of opening of the expansion device 14a may be controlled so that the temperature difference (degree of superheat) of the refrigerant approaches the target value. Further, the liquid refrigerant temperature detection device 24 may be provided at the other end of the first flow path of the supercooling heat exchanger 13.

The high-temperature and high-pressure liquid refrigerant flowing out of the outdoor unit 1 passes through the extension pipe 5 and flows into each of the indoor units 2 (2a to 2d). The high-temperature and high-pressure liquid refrigerant that has flowed into the indoor unit 2 (2a to 2d) is expanded by the expansion device 16 (16a to 16d) to become a low-temperature and low-pressure two-phase refrigerant and serves as an evaporator. 17 (17a to 17d) and absorbs heat from the air flowing around the use side heat exchanger 17 to become a low-temperature and low-pressure gas refrigerant. Then, the low-temperature and low-pressure gas refrigerant flows out of the indoor unit 2 (2a to 2d), flows into the outdoor unit 1 again through the extension pipe 5, passes through the refrigerant flow switching device 11, and passes through the first bypass pipe 4a. The refrigerant flows through and merges with the refrigerant bypassed to the upstream side of the accumulator 15, then flows into the accumulator 15, and is then sucked into the compressor 10 again.

At this time, the opening degree (opening area) of the expansion devices 16a to 16d is the temperature difference between the detection temperature of the use side heat exchanger gas refrigerant temperature detection device 28 and the detection temperature of the use side heat exchanger liquid refrigerant temperature detection device 27. (Superheat degree) is controlled so as to approach the target value.

Here, in the present embodiment, the supercooling heat exchanger 13 is used in order to reliably supercool the refrigerant even when the extension pipe 5 is long (for example, 100 m). Provided. When the extension pipe 5 is long, the pressure loss in the extension pipe 5 increases. For this reason, if the degree of supercooling of the refrigerant is small, the refrigerant may become a two-phase refrigerant before reaching the indoor unit 2. When the two-phase refrigerant flows into the indoor unit 2, the two-phase refrigerant flows into the expansion device 16. A throttling device such as an expansion valve or a flow rate adjusting device has a property of generating a sound around when a two-phase refrigerant flows. Since the expansion device 16 of the present embodiment is disposed in the indoor unit 2 that sends temperature-adjusted air to the indoor space 7, if the generated sound leaks into the indoor space 7, it makes the resident feel uncomfortable. Sometimes. Further, when the two-phase refrigerant flows into the expansion device 16, the pressure is not stabilized, and the operation of the expansion device 16 becomes unstable. Therefore, it is necessary to flow into the expansion device 16 a liquid refrigerant that is reliably supercooled. From the above, the supercooling heat exchanger 13 is provided. The first bypass pipe 4a is provided with a throttle device 14a, and the flow rate of the low-temperature and low-pressure two-phase refrigerant flowing in the second flow path of the supercooling heat exchanger 13 is increased by increasing the opening degree (opening area) of the throttle device 14a. If it increases, the supercooling degree of the refrigerant | coolant which flows out out of the 1st flow path of the supercooling heat exchanger 13 will increase. Conversely, when the flow rate of the low-temperature and low-pressure two-phase refrigerant flowing in the second flow path of the supercooling heat exchanger 13 is reduced by reducing the opening (opening area) of the expansion device 14a, the first of the supercooling heat exchanger 13 is reduced. The degree of supercooling of the refrigerant flowing out of the flow path is reduced. Thus, by adjusting the opening degree (opening area) of the expansion device 14a, the degree of supercooling of the outlet refrigerant in the first flow path of the supercooling heat exchanger 13 can be controlled to an appropriate value. However, from the viewpoint of reliability, it is not preferable that the compressor 10 sucks a low dryness refrigerant mixed with a large amount of liquid refrigerant in a normal operation. Therefore, in the present embodiment, the first bypass pipe 4 a is connected to the refrigerant inflow side (upstream side) pipe of the accumulator 15. The accumulator 15 is for storing surplus refrigerant. Most of the refrigerant bypassed to the refrigerant inflow side of the accumulator 15 by the first bypass pipe 4a is stored inside the accumulator 15, and a large amount is stored in the compressor 10. It is possible to prevent the liquid refrigerant from returning.

The above is the operation of each device and the refrigerant flow in the refrigerant circuit when the discharge temperature of the compressor 10 is low in the cooling operation mode. The case where the discharge temperature of the compressor 10 is high will be described later. Since the discharge temperature of the compressor 10 is low, the second bypass pipe 4b is fully closed or has a small opening so that the refrigerant does not flow, so that the refrigerant does not flow into the second bypass pipe 4b. Here, in the cooling operation mode, the discharge temperature does not increase unless the temperature around the heat source side heat exchanger 12 is very high.

FIG. 4 is a ph diagram (pressure-enthalpy diagram) during cooling operation when the discharge temperature of the air-conditioning apparatus 100 according to Embodiment 1 of the present invention is low. In the cooling operation mode, the refrigerant compressed and discharged by the compressor 10 (point G in FIG. 4) is condensed and liquefied by the heat source side heat exchanger 12 to become a high-pressure liquid refrigerant (point J in FIG. 4). . Further, the supercooling heat exchanger 13 is cooled by the refrigerant branched to the first bypass pipe 4a to increase the degree of supercooling (point L in FIG. 4) and flows into the liquid separator 18. A part of the liquid refrigerant branched into the second flow path of the supercooling heat exchanger 13 by the liquid separator 18 is decompressed by the expansion device 14a, and then heated by the supercooling heat exchanger 13 to be evaporated and gasified. The refrigerant passes through the first bypass pipe 4a and the fully-open throttle device 14d, and flows into the refrigerant inflow side of the accumulator 15. On the other hand, the high-pressure two-phase refrigerant that has passed through the liquid separator 18 flows out of the outdoor unit 1, passes through the extension pipe 5, flows into the indoor unit 2, and is expanded by the expansion device 16 (16 a to 16 d) of the indoor unit 2. The pressure is reduced (point K in FIG. 4). Further, after evaporating in the use side heat exchanger 17 (17a to 17d), it flows out of the indoor unit 2, passes through the extension pipe 5, and flows into the outdoor unit 1. Then, after passing through the refrigerant flow switching device 11 and flowing through the first bypass pipe 4a and joining with the refrigerant bypassed to the upstream side of the accumulator 15, the refrigerant flows into the accumulator 15 (point F in FIG. 4).

Here, it is desirable that the expansion device 14a can change the opening area, such as an electronic expansion valve. If the electronic expansion valve is used, the flow rate of the refrigerant passing through the second flow path of the supercooling heat exchanger 13 can be arbitrarily adjusted, and the supercooling degree of the refrigerant flowing out of the outdoor unit 1 can be finely controlled. Can do. However, the aperture device 14a is not limited to this. For example, an opening / closing valve such as a small electromagnetic valve may be combined so that the opening degree can be selected and controlled in a plurality of stages. In addition, the capillary tube may be configured to perform supercooling according to the refrigerant pressure loss. Although the controllability is slightly worse than in the case of an electronic expansion valve or the like, the degree of supercooling can be brought close to the target. On the other hand, the expansion device 14b may be any device that can close the flow path. In the cooling operation mode when the discharge temperature of the compressor 10 is low, the expansion device 14d is fully open, and any device may be used as long as no large pressure loss occurs. For example, an electromagnetic valve or the like that opens and closes a flow path, an electronic expansion valve or the like that can change the opening area may be used. Here, the fully open state does not mean a state where no pressure loss occurs, but means a state where the pressure loss is not so large.

When the cooling operation mode is executed, the operation is stopped because there is no need to flow the refrigerant to the use side heat exchanger 17 (including the thermo-off) without the heat load. At this time, the expansion device 16 corresponding to the stopped indoor unit 2 is fully closed or set to a small opening at which the refrigerant does not flow.

[Cooling operation mode (when discharge temperature is high)]
FIG. 5 is a diagram showing the refrigerant flow in the cooling operation mode when the discharge temperature of the air-conditioning apparatus 100 according to Embodiment 1 of the present invention is high. A high discharge temperature is, for example, a case where the discharge temperature is 105 ° C. or higher without injection. In FIG. 5, the cooling operation mode will be described by taking as an example a case where a cooling load is generated in all the use side heat exchangers 17. Here, the pipes indicated by bold lines in FIG. 5 indicate the pipes through which the refrigerant flows, and the directions in which the refrigerant flows are indicated by solid arrows.

In the case of the cooling operation mode shown in FIG. 5, in the outdoor unit 1, the control device 50 switches the refrigerant flow switching device 11 to the flow channel through which the refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12. To instruct. Then, the compressor 10 compresses the low-temperature and low-pressure refrigerant and discharges the 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 through the refrigerant flow switching device 11. Then, the heat source side heat exchanger 12 condenses and liquefies while radiating heat to the outdoor air, and becomes a high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the heat source side heat exchanger 12 passes through the first flow path of the expansion device 14c and the supercooling heat exchanger 13 that are fully opened. The refrigerant that has passed through the first flow path of the supercooling heat exchanger 13 is branched into two flow paths. One flows out of the outdoor unit 1 through the liquid separator 18. The other flows into the first bypass pipe 4a. The compressor 10 compresses the low-temperature and low-pressure refrigerant and discharges the 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 through the refrigerant flow switching device 11. Then, the heat source side heat exchanger 12 condenses and liquefies while radiating heat to the outdoor air, and becomes a high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the heat source side heat exchanger 12 passes through the first flow path of the expansion device 14c and the supercooling heat exchanger 13 that are fully opened. The refrigerant that has passed through the first flow path of the supercooling heat exchanger 13 is branched into two flow paths, one of which flows out of the outdoor unit 1 through the liquid separator 18, and the other reaches the expansion device 14a. It flows into the flow path. The high-temperature and high-pressure liquid refrigerant flowing into the first bypass pipe 4a is reduced in pressure by the expansion device 14a to become a first medium-pressure two-phase refrigerant, and passes through the second flow path of the supercooling heat exchanger 13 and the expansion device 14d. Then, it flows into the flow path on the upstream side of the accumulator 15. At this time, in the supercooling heat exchanger 13, heat exchange is performed between the high-temperature and high-pressure liquid refrigerant passing through the first flow path and the first medium-pressure two-phase refrigerant passing through the second flow path. Therefore, the refrigerant passing through the first flow path is cooled by the refrigerant passing through the second flow path, and the refrigerant passing through the second flow path is heated by the refrigerant passing through the first flow path.

The flow rate of the refrigerant passing through the second flow path of the supercooling heat exchanger 13 is adjusted by the opening degree (opening area) of the expansion device 14a. The control device 50 detects the excess of the refrigerant on the downstream side of the first flow path of the supercooling heat exchanger 13 that is the temperature difference between the saturation temperature of the detection pressure of the high pressure detection device 22 and the detection temperature of the liquid refrigerant temperature detection device 24. The opening degree (opening area) of the expansion device 14a is controlled so that the degree of cooling approaches the target value.

As described above, in the present embodiment, the supercooling heat exchanger 13 is provided in order to reliably supercool the refrigerant even when the extension pipe 5 is long. And the supercooling degree of the exit refrigerant | coolant of the 1st flow path of the supercooling heat exchanger 13 can be controlled to an appropriate value by adjusting the opening degree (opening area) of the expansion device 14a.

Here, when a refrigerant such as R32, which tends to have a higher discharge temperature of the compressor 10 than R410A, is used as the refrigerant, it is necessary to lower the discharge temperature in order to prevent deterioration of the refrigerating machine oil, burning of the compressor 10, and the like. There is. Therefore, a part of the refrigerant that has passed through the second flow path of the supercooling heat exchanger 13 is branched to pass through the second bypass pipe 4b and the expansion device 14b, and through an injection port provided in the compressor 10. Then, it flows into the compression chamber of the compressor 10. By allowing the refrigerant to flow in from the injection port, the temperature of the refrigerant discharged from the compressor 10 can be lowered, and it can be used safely.

Here, the second bypass pipe 4b is connected to an injection port provided in the compression chamber of the compressor 10. In order to protect the compressor 10, it is necessary to prevent the discharge temperature of the compressor 10 from becoming too high. For example, even if the refrigerant is bypassed to the refrigerant inlet side (upstream side) of the accumulator 15, most of the refrigerant is stored in the accumulator 15, and only a part of the refrigerant flows into the compressor 10. Therefore, the two-phase refrigerant having a high dryness can be directly injected into the compression chamber via the second bypass pipe 4b and the injection port of the compressor 10.

The flow rate of the refrigerant passing through the second bypass pipe 4b is adjusted by the opening degree (opening area) of the expansion device 14b. When the opening degree (opening area) of the expansion device 14b is increased and the flow rate of the refrigerant flowing through the second bypass pipe 4b is increased, the discharge temperature of the compressor 10 decreases. Conversely, when the opening degree (opening area) of the expansion device 14b is reduced and the flow rate of the refrigerant flowing through the second bypass pipe 4b is reduced, the discharge temperature of the compressor 10 increases. Therefore, by adjusting the opening degree (opening area) of the expansion device 14b, it is possible to control the discharge temperature of the compressor 10, which is the detection value of the discharge refrigerant temperature detection device 21, to approach the target value.

Further, in the cooling operation mode, when the temperature around the heat source side heat exchanger 12 is high, for example, in the case of high outside air cooling, the discharge temperature of the compressor 10 becomes high, and the injection through the second bypass pipe 4b is necessary. It becomes.

FIG. 6 is a ph diagram (pressure-enthalpy diagram) during cooling operation when the discharge temperature of the air-conditioning apparatus 100 according to Embodiment 1 of the present invention is high. Based on FIG. 6, the detail of the operation | movement which concerns on injection is demonstrated. In the cooling operation mode, the refrigerant (point I in FIG. 6) compressed and discharged by the compressor 10 is condensed and liquefied by the heat source side heat exchanger 12 to become a high-pressure liquid refrigerant (point J in FIG. 6). . Further, the supercooling heat exchanger 13 is cooled by the refrigerant branched to the first bypass pipe 4a to increase the degree of supercooling (point L in FIG. 6), and flows into the liquid separator 18.

Part of the liquid refrigerant branched by the liquid separator 18 and flowing to the first bypass pipe 4a side is decompressed by the expansion device 14a and becomes the first intermediate pressure (point M in FIG. 6). And it is divided into the refrigerant | coolant which flows through the 1st bypass piping 4a as it is, and the refrigerant | coolant which branches to the 2nd bypass piping 4b. Among these, the refrigerant flowing through the second bypass pipe 4b is reduced to the second intermediate pressure through the expansion device 14b, and is injected into the compression chamber from the injection port provided in the compression chamber of the compressor 10. Then, it merges with the refrigerant sucked into the compressor 10 and compressed to the second intermediate pressure. In addition, the refrigerant flowing through the first bypass pipe 4 a is decompressed to a low pressure via the expansion device 14 d and flows into the upstream flow path of the accumulator 15.

On the other hand, the high-pressure two-phase refrigerant that has passed through the liquid separator 18 flows out of the outdoor unit 1, passes through the extension pipe 5, flows into the indoor unit 2, and is expanded by the expansion device 16 (16 a to 16 d) of the indoor unit 2. The pressure is reduced (point K in FIG. 6). Further, after evaporating in the use side heat exchanger 17 (17a to 17d), it flows out of the indoor unit 2, passes through the extension pipe 5, and flows into the outdoor unit 1. Then, the refrigerant flows through the refrigerant flow switching device 11, flows through the first bypass pipe 4 a, joins the refrigerant bypassed to the upstream side of the accumulator 15, and then flows into the accumulator 15. Further, the refrigerant that has flowed out of the accumulator 15 passes through the suction side flow path and is sucked into the compressor 10.

Here, the compressor 10 of the present embodiment is a low-pressure shell type compressor. The sucked refrigerant and oil flow into the lower part of the compressor 10. In addition, a motor is disposed in the intermediate portion. In the upper part, the high-temperature and high-pressure refrigerant compressed in the compression chamber is discharged from the compressor 10 after being discharged into the discharge chamber in the sealed container. Therefore, the metal sealed container of the compressor 10 has a portion exposed to the high-temperature and high-pressure refrigerant and a portion exposed to the low-temperature and low-pressure refrigerant. For this reason, the temperature of the sealed container becomes an intermediate temperature. Further, since current flows through the motor, it generates heat. Therefore, the low-temperature and low-pressure gas refrigerant sucked into the compressor 10 is heated by the sealed container and the motor of the compressor 10 and the temperature rises (point F in FIG. 6). Then, it is sucked into the compression chamber and compressed to the second intermediate pressure in the compression chamber (point N in FIG. 6). When the refrigerant is injected into the compression chamber of the compressor 10 via the second bypass pipe 4b, the temperature of the refrigerant in the merged portion of the refrigerant sucked from the suction side flow path and the refrigerant related to the injection in the compression chamber. (Point H in FIG. 6). Then, the compression is further continued in the compression chamber, whereby a high-pressure gas refrigerant is discharged from the compressor 10. For this reason, when the refrigerant is caused to flow in via the second bypass pipe 4b, the temperature of the refrigerant is reduced at the merged portion, and therefore, the discharge temperature with respect to the discharge temperature of the compressor 10 when not flowing (point G in FIG. 6). Decreases (point I in FIG. 6). For example, even when using a refrigerant whose discharge temperature of the compressor 10 is higher than R410A, such as R32, the discharge temperature of the compressor 10 can be lowered and can be used safely. it can. In addition, reliability is increased.

Now, in the cooling operation mode in which the discharge temperature is high, it is necessary to control so that both the degree of supercooling of the first flow path of the supercooling heat exchanger 13 and the discharge temperature of the compressor 10 are close to the target. For example, the control device 50 performs the following control. First, the opening degree (opening area) of the expansion device 14a is changed so that the degree of supercooling of the refrigerant that has passed through the first flow path of the supercooling heat exchanger 13 approaches the target value. The refrigerant flow rate flowing through the second flow path is controlled. And the opening degree (opening area) of the expansion device 14b is changed so that the discharge temperature of the compressor 10 approaches the target value, and the refrigerant flow rate flowing into the injection port of the compressor 10 via the second bypass pipe 4b is changed. Control.

At this time, the refrigerant flowing through the second flow path of the supercooling heat exchanger 13 is branched into the first bypass pipe 4a in which the expansion device 14d is installed and the second bypass pipe 4b in which the expansion device 14b is installed. . When the discharge temperature of the compressor 10 is low, the expansion device 14b is set to a fully closed position or a small opening at which the refrigerant does not flow, and the expansion device 14d is set to a full open state. And when discharge temperature becomes high, even if it changes the opening degree of the expansion device 14b, setting the expansion device 14d to full open, the flow inside the expansion device 14d installed in the 1st bypass piping 4a Since the resistance is small, most of the refrigerant flows through the first bypass pipe 4a. For this reason, the discharge temperature of the compressor 10 cannot be controlled by adjusting the flow rate of the refrigerant flowing through the injection port of the compressor 10 via the second bypass pipe 4b.

Therefore, in order to change the flow rate of the refrigerant flowing through the second bypass pipe 4b by controlling the opening of the expansion device 14b, the opening of the expansion device 14d is adjusted in accordance with the change in the opening (opening area) of the expansion device 14b. It is necessary to change the degree (opening area). For example, when the discharge temperature of the compressor 10 is low, the expansion device 14d is fully opened, the expansion device 14b is fully closed, or the opening degree is small so that the refrigerant does not flow. From this state, even when the discharge temperature of the compressor 10 becomes high, the discharge temperature of the compressor 10 becomes high while keeping the flow rate of the refrigerant flowing through the second flow path of the supercooling heat exchanger 13 from changing greatly. Control not to be too much. For this reason, the control of the diaphragm device 14b and the control of the diaphragm device 14d are interlocked (substantially simultaneously) so that the sum of the aperture area of the diaphragm device 14b and the aperture area of the diaphragm device 14d does not change significantly. For example, a value obtained by subtracting the opening area of the expansion device 14b that controls the discharge temperature as a target from the opening area when the expansion device 14d is fully open may be used as the opening area of the new expansion device 14d.

In general, the expansion device is often designed so that the opening degree and the opening area correspond to each other in a shape that is almost a straight line. In such a case, a value obtained by subtracting the opening of the expansion device 14b that controls the discharge temperature from the opening when the expansion device 14d is fully open may be set as the opening of the new expansion device 14d. For example, it is assumed that the expansion device 14b and the expansion device 14d have the same capacity (the opening area at the time of the fully open position is substantially the same) and are the same type of expansion device. More specifically, the opening degree of full opening is 1500 pulses, and the refrigerant stops flowing at an opening degree of 100 pulses or less. Further, it is assumed that the expansion device 14b and the expansion device 14d are designed so that the opening degree and the opening area correspond to each other in a form that is almost a straight line.

In such an assumption, when the discharge temperature is low, the expansion device 14d is set to 1500 pulses, and the expansion device 14b is set to 100 pulses. At this time, the sum of the opening of the expansion device 14d and the opening of the expansion device 14b is 1600 pulses. Here, it is assumed that the discharge temperature of the compressor 10 is increased, and the opening degree of the expansion device 14b is controlled with the discharge temperature as a target value, resulting in 600 pulses. At this time, the opening degree of the expansion device 14d is controlled almost simultaneously with the control of the expansion device 14b. The opening of the expansion device 14d is set to 1000 pulses obtained by subtracting 600 pulses, which is the opening of the expansion device 14b, from 1600 pulses, which is the total opening of the two expansion devices. In this case, the flow resistance inside the expansion device 14d installed in the first bypass pipe 4a is increased, and the flow resistance inside the expansion device 14b installed in the second bypass pipe 4b is reduced. It becomes possible to flow the refrigerant through the bypass pipe 4b. Each time the opening degree of the expansion device 14b is controlled, the discharge temperature of the compressor 10 can be appropriately controlled by also controlling the opening degree of the expansion device 14d.

Here, it has been described that the diaphragm device 14b and the diaphragm device 14d are controlled almost simultaneously. However, in actuality, the diaphragm devices are not simultaneously controlled but are sequentially controlled at each control timing. Therefore, “substantially simultaneous” in the present embodiment means that the aperture devices are controlled at the same control timing (for example, every 30 seconds). Even at the same control timing, in actuality, the respective throttle devices are not simultaneously controlled. For example, the aperture of the aperture device 14b is controlled, and then the aperture of the aperture device 14d is controlled in many cases. In this way, either sequential control or simultaneous control may be used. In the case of sequential control, the opening of the expansion device 14d may be controlled first, and then the opening of the expansion device 14b may be controlled. Further, even if the control timing of the expansion device 14b and the expansion device 14d is slightly shifted (for example, from about 30 seconds to about 1 minute), no major problem occurs, and the degree of supercooling of the supercooling heat exchanger 13 and the compressor 10 Both discharge temperatures can be controlled to a target. However, it is better to control each expansion device at the same control timing, and the discharge temperature reaches the target value earlier. In addition, the control of the discharge temperature is better when the expansion device 14b and the expansion device 14d are controlled simultaneously rather than sequentially.

As described above, when the expansion device 14b and the expansion device 14d have the same capacity (the opening area at the fully open position is almost the same), the total opening area of the two expansion devices is controlled to be substantially the same. Is desirable. Here, the total opening area of the two aperture devices being substantially the same means that, for example, the total opening area of both is within a range of about ± 1%. For example, as in the example described above, when the total opening is 1600, the total opening only needs to be within 1600 ± 16 pulses. For example, when the opening degree of the expansion device 14b is 600 pulses, the opening degree of the expansion device 14d may be set to a pulse between 984 pulses and 1016 pulses.

In addition, the controllability is slightly worse than when the total opening area is within a range of about ± 1%, but if the total opening area of the two aperture devices is within a range of about ± 10%, the compression is reduced. The discharge temperature of the machine 10 can be normally controlled to the target value. For example, as in the example described above, when the total opening is 1600, the total opening may be within 1600 ± 160 pulses. For example, when the opening degree of the expansion device 14b is 600 pulses, the opening degree of the expansion device 14d may be set to a pulse between 840 pulses and 1160 pulses. Further, the controllability is further deteriorated, but if the total opening area of both is within a range of about ± 20%, the control responsiveness is slightly deteriorated, but there is no problem in control, and the discharge temperature is reduced. The target value can be controlled. For example, as in the example described above, when the total opening is 1600, the total opening may be within 1600 ± 320 pulses. For example, when the opening degree of the expansion device 14b is 600 pulses, the opening degree of the expansion device 14d may be set to a pulse between 680 pulses and 1320 pulses.

Here, a case has been described where the expansion device 14b and the expansion device 14d have the same capacity (the opening areas at the fully opened position are almost the same). However, the present invention is not limited to this, and different types and different capacities. It does not matter. When the types and the like are different, both aperture devices may be controlled so that the total aperture area of the aperture portion of the aperture device 14b and the aperture area of the aperture device 14d is substantially the same.

Further, even if the total opening area of the expansion device 14b and the total opening area of the expansion device 14d are slightly different, the opening amount (opening area) of the expansion device 14d corresponding to the change in the opening amount (opening area) of the expansion device 14b. ) May be changed in the opposite direction. Thereby, the degree of opening (opening area) of the expansion device 14a is adjusted to control the degree of supercooling of the first flow path of the supercooling heat exchanger 13, and the expansion device 14b installed in the second bypass pipe 4b is opened. The discharge temperature of the compressor 10 can be controlled by adjusting the degree (opening area). Here, changing in the reverse direction means, for example, that if the opening degree (opening area) of the expansion device 14b increases, the opening degree (opening area) of the expansion device 14d decreases, and the opening degree (opening area) of the expansion device 14b. ) Is reduced, the aperture (opening area) of the expansion device 14d is changed to be increased. For example, it is assumed that the opening area at the maximum opening of the expansion device 14b is 1.5 times the opening area at the maximum opening of the expansion device 14d, and the opening and the opening area have a linear relationship. As for the expansion device 14b, it is assumed that the fully opened opening is 2000 pulses and the minimum opening at which the refrigerant does not flow is 200 pulses. And about the expansion | swelling apparatus 14d, fully open opening degree shall be 1000 pulses and the minimum opening degree from which a refrigerant | coolant does not flow shall be 100 pulses. Under such conditions, when the discharge temperature is low, the expansion device 14d is set to 1000 pulses at the maximum opening, and the expansion device 14b is set to 200 pulses at the minimum opening. When the opening temperature of the expansion device 14b is controlled so that the discharge temperature of the compressor 10 becomes high and the discharge temperature of the compressor 10 becomes the target value, the control device 50 has an appropriate opening amount of 800 pulses for the expansion device 14b. Is calculated. At this time, the opening of the expansion device 14b is controlled from the minimum 200 pulses to the new 800 opening, and the expansion of the expansion device 14d is changed from the fully open 1000 pulses. Control to close. Then, the opening degree of the expansion device 14d is determined based on, for example, Expression (1). This is to close the expansion device 14d at the same rate as the opening rate of the expansion device 14b.

When substituting a specific value based on the condition into equation (1), equation (2) is obtained. When the equation (2) is calculated, 400 pulses are obtained.

Therefore, the control device 50 controls the opening of the expansion device 14b to 400 pulses at the control timing for controlling the opening of the expansion device 14d to 800 pulses. At this time, the amount of change in the opening of each expansion device is (800−200) = 600 pulses for the expansion device 14d, and (400−100) = 300 pulses for the expansion device 14b. In each of the throttle devices, the change is about 33% with respect to the difference between the maximum opening and the minimum opening of the respective throttle devices.

Thus, even if there is a difference in the capacity (opening area at the maximum opening) between the expansion device 14b and the expansion device 14d, the amount of change in the opening amount of the expansion device 14d corresponding to the change in the opening amount of the expansion device 14b. And the discharge temperature of the compressor 10 can be controlled to the target value by controlling the direction of change of the opening of the expansion device 14b and the direction of change of the opening of the expansion device 14d in opposite directions. However, in this case, the total area of the aperture area of the aperture device 14b and the aperture area of the aperture device 14d is different before and after the control. Therefore, it is necessary to control the opening degree of the expansion device 14a and keep the degree of supercooling of the first flow path of the supercooling heat exchanger 13 at a target.

For example, when the expansion device 14b and the expansion device 14d have different capacities, the relationship between the opening degree and the opening area is better when the relationship is a linear relationship, but is not limited thereto. Regardless of the form of correspondence, the same control can be performed as long as the opening increases and the opening area increases.

As described above, in the cooling operation mode in which the discharge temperature of the compressor 10 is high, the expansion device 14a is controlled so that the degree of supercooling of the first flow path of the supercooling heat exchanger 13 approaches the target, The flow rate of the refrigerant flowing through the second flow path of the supercooling heat exchanger 13 is adjusted. Further, the flow rate of the refrigerant flowing through the second bypass pipe 4b connected to the injection port of the compressor 10 is adjusted by controlling the opening degree of the expansion device 14b so that the discharge temperature of the compressor 10 approaches the target. At this time, the diaphragm device 14d is controlled in conjunction with the diaphragm device 14b, and is calculated based on the opening (opening area) of the throttle device 14b after the control to set the opening (opening area) of the diaphragm device 14d. By doing so, it is possible to appropriately control both the degree of supercooling of the supercooling heat exchanger 13 and the discharge temperature of the compressor 10.

Here, the opening change direction of the expansion device 14b and the opening change direction of the expansion device 14d are opposite to each other. For example, when controlling the opening area of the expansion device 14b to be large, the control device 50 controls the opening area of the expansion device 14d to be small. Further, when controlling the aperture area of the aperture device 14b to be small, the aperture area of the aperture device 14d is controlled to be large.

Here, the angle at which the injection port of the compressor 10 opens into the compression chamber is usually immediately after the suction port of the compression chamber is closed. In this case, the pressure in the compression chamber where the injection port is located is a value close to a low pressure (pressure on the suction side). At this time, the expansion device 14b and the expansion device 14d are of the same capacity (the opening area at the fully opened position is substantially the same). However, the flow rate through the throttle device is proportional to the square root of the pressure difference across the throttle device. For example, if the injection port of the compressor 10 opens into the compression chamber after the suction angle of the compression chamber is closed and the rotation angle becomes considerably large, the pressure in the compression chamber is sufficiently higher than the low pressure. Therefore, the pressure difference before and after the expansion device 14b becomes smaller than the pressure difference before and after the expansion device 14d. For this reason, the controllability is improved by increasing the capacity of the expansion device 14b (opening area at the fully open position) relative to the capacity of the expansion device 14d (opening area at the fully open position). Even in this case, there is no change in linking the control of the expansion device 14b and the control of the expansion device 14d. Based on the amount of change in the opening or opening of the expansion device 14b or the amount of change in the opening area or opening area, the control device 50 changes the amount of opening or opening of the expansion device 14d or changes in the opening area or opening area. What is necessary is just to calculate the quantity.

Here, as the expansion device 14a, it is desirable to change the opening area, such as an electronic expansion valve, but it is not limited to this. For example, it may be configured by combining on-off valves such as small solenoid valves, or may be configured by a capillary tube.

Further, the expansion device 14d only needs to change the flow resistance in accordance with the change in the opening degree of the expansion device 14b. For this reason, although it is desirable to comprise the electronic expansion valve etc. which can change an opening area, it is not restricted to this. For example, a plurality of solenoid valves may be combined in parallel so that the opening area can be changed in a plurality of stages in accordance with the change in the opening degree of the expansion device 14b. In this case, since the opening area cannot be continuously changed, the control accuracy of the discharge temperature is slightly deteriorated, but there is no problem because the discharge temperature can be controlled so as not to exceed the limit value.

Further, as described above, since it is not necessary to flow the refrigerant to the use side heat exchanger 17 (including the thermo-off) without the heat load, the operation is stopped. At this time, the expansion device 16 corresponding to the stopped indoor unit 2 is fully closed or set to a small opening at which the refrigerant does not flow.

As described above, two bypass pipes are provided on the downstream side of the second flow path of the supercooling heat exchanger 13, and the first bypass pipe 4a is connected to the upstream side of the accumulator 15 (compressor) via the expansion device 14d. The refrigerant is allowed to flow in the flow path on the suction side 10), and the refrigerant can be injected into the compression chamber of the compressor 10 through the expansion device 14 b in the second bypass pipe 4 b. At this time, by controlling the expansion device 14b and the expansion device 14d in an interlocked manner, even when the extension pipe 5 is long, the refrigerant flowing into the indoor unit 2 can be reliably in a state of being supercooled, and In the condition where the discharge temperature of the compressor 10 becomes high, the discharge temperature of the compressor 10 can be reliably controlled so as not to exceed the upper limit.

Here, the refrigerant that has passed through the second flow path of the supercooling heat exchanger 13 is a low-temperature two-phase refrigerant or gas refrigerant. For example, when the discharge temperature of the compressor 10 is slightly higher than the limit temperature, a low-temperature gas refrigerant may be flowed into the compression chamber of the compressor 10 via the second bypass pipe 4b. On the other hand, when the discharge temperature is considerably higher than the limit temperature, it is necessary to flow a low-temperature two-phase refrigerant into the compression chamber of the compressor 10. When the refrigerant that has passed through the second flow path of the supercooling heat exchanger 13 is in a two-phase state, the refrigerant in the two-phase state is branched into the first bypass pipe 4a and the second bypass pipe 4b. In this case, the refrigerant flowing into the branch portion between the first bypass pipe 4a and the second bypass pipe 4b is configured to flow from bottom to top in the direction of gravity (height direction), for example. Then, the branched flow path is configured so that the branched refrigerant flows at substantially the same height in the height direction. If comprised in this way, a liquid refrigerant can branch the refrigerant | coolant of a two-phase state neatly (evenly), without biasing to one flow path. In this case, a T-type joint or a Y-type joint is used for the branch portion. Further, even if the branching portion is slightly inclined, there is no problem as long as it is slightly inclined, and the two-phase refrigerant is neatly distributed. This allowable inclination angle is within about 15 degrees, and if it is less than this, the two-phase refrigerant can be distributed without any problem. However, the branching portion between the first bypass pipe 4a and the second bypass pipe 4b is not limited to this, as long as the refrigerant in the two-phase state can branch cleanly without biasing the refrigerant liquid to one side, Any structure may be used.

[Heating operation mode]
FIG. 7 is a diagram showing a refrigerant flow when the air-conditioning apparatus 100 according to Embodiment 1 of the present invention is in the heating operation mode. In FIG. 7, the heating operation mode will be described by taking as an example a case where a thermal load is generated in all the use side heat exchangers 17. Here, the pipes indicated by bold lines in FIG. 5 indicate the pipes through which the refrigerant flows, and the directions in which the refrigerant flows are indicated by solid arrows.

In the case of the heating operation mode shown in FIG. 7, in the outdoor unit 1, the control device 50 controls the refrigerant flow switching device 11 so that the refrigerant discharged from the compressor 10 does not pass through the heat source side heat exchanger 12. 1 is instructed to switch to the flow path that flows out into the indoor unit 2. Then, the compressor 10 compresses the low-temperature and low-pressure refrigerant and discharges the high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 passes through the refrigerant flow switching device 11 and flows out of the outdoor unit 1. The high-temperature and high-pressure gas refrigerant that has flowed out of the outdoor unit 1 passes through the extension pipe 5 and flows into each of the indoor units 2 (2a to 2d). The high-temperature and high-pressure gas refrigerant flowing into the indoor unit 2 (2a to 2d) flows into each of the use side heat exchangers 17 (17a to 17d) and circulates around the use side heat exchangers 17 (17a to 17d). It liquefies while radiating heat to the air, and becomes a high-temperature and high-pressure liquid refrigerant. The liquid refrigerant flowing out from the use side heat exchanger 17 (17a to 17d) is expanded by the expansion device 16 (16a to 16d) to become a first medium pressure two-phase refrigerant, and the indoor unit 2 (2a to 2d). Spill from. The first medium-pressure two-phase refrigerant flowing out of the indoor unit 2 flows into the outdoor unit 1 again through the extension pipe 5.

At this time, the opening degree (opening area) of the expansion devices 16a to 16d is the temperature difference (supercooling) between the condensation temperature in the use side heat exchangers 17a to 17d and the detection temperature of the use side heat exchanger liquid refrigerant temperature detection device 27. Is controlled so as to approach the target value. For example, the control device 50 of the outdoor unit 1 determines a value of the condensation temperature in the use side heat exchangers 17a to 17d, and sends a signal to the control device (not shown) of each indoor unit 2 by communication.

The first medium-pressure two-phase refrigerant that has flowed into the outdoor unit 1 flows into the liquid separator 18. A part of the liquid refrigerant that has flowed into the liquid separator 18 flows out from the outlet provided on the lower side in the direction of gravity of the liquid separator 18, flows through the first bypass pipe 4a, and passes through the expansion device 14a. The liquid refrigerant having the first intermediate pressure is decompressed by the expansion device 14a, becomes a two-phase refrigerant having the second intermediate pressure, and passes through the second flow path of the supercooling heat exchanger 13. By passing through the second flow path of the supercooling heat exchanger 13, it becomes a two-phase refrigerant or gas refrigerant that is heated by the refrigerant that has passed through the first flow path of the supercooling heat exchanger 13 and has increased in dryness. . And it flows in into a compression chamber from the injection port provided in the compressor 10 through the 2nd bypass piping 4b and the expansion device 14b of a full open state.

The remaining two-phase refrigerant that has flowed into the liquid separator 18 flows out from an outlet provided near or above the center of the liquid separator 18 in the direction of gravity, and flows into the first flow path of the supercooling heat exchanger 13. To do. The first medium pressure two-phase refrigerant that has flowed into the first flow path of the supercooling heat exchanger 13 is slightly cooled by the second medium pressure refrigerant flowing through the second flow path of the supercooling heat exchanger 13, and the dryness Spills out a little smaller. Then, the pressure is reduced through the expansion device 14 c to become a low-temperature and low-pressure two-phase refrigerant and flows into the heat source side heat exchanger 12. The low-temperature and low-pressure two-phase refrigerant absorbs heat from the air flowing around the heat source side heat exchanger 12 in the heat source side heat exchanger 12, evaporates and flows out as a low temperature and low pressure gas refrigerant. Then, the refrigerant is again sucked into the compressor 10 through the refrigerant flow switching device 11 and the accumulator 15.

As described above, in the cooling operation mode, the refrigerant flows through the second flow path of the supercooling heat exchanger 13, the refrigerant flowing through the first flow path of the supercooling heat exchanger 13 is supercooled, and is sent to the extension pipe 5. It was. Here, in the heating operation mode, it is not necessary to supercool the refrigerant flowing through the extension pipe 5. The first purpose of flowing the refrigerant through the second flow path of the supercooling heat exchanger 13 is to lower the discharge temperature when the discharge temperature of the compressor 10 becomes too high. The second purpose is to improve the heating capacity. Both are necessary when the outside air temperature is low. For this reason, when the outside air temperature is relatively high (for example, when the discharge temperature is 105 ° C. or less without injection), the discharge temperature of the compressor 10 is not so high, and it is not necessary to improve the heating capacity. In this case, the control device 50 controls the throttle device 14b to be fully closed or to a small opening at which the refrigerant does not flow so that the refrigerant does not flow into the second bypass pipe 4b. In the heating operation mode, the expansion device 14d is normally set to a fully closed position or a small opening at which the refrigerant does not flow, so that the refrigerant does not flow into the first bypass pipe 4a.

Here, when a refrigerant such as R32, in which the discharge temperature of the compressor 10 is higher than that of R410A, is used as the refrigerant, the discharge temperature is higher than when R410A is used at a slightly higher outside temperature. For example, it is necessary to lower the discharge temperature in order to prevent deterioration of refrigeration oil, burnout of the compressor 10, and the like.

As described above, a two-phase refrigerant having a high degree of dryness can be directly injected into the compressor 10 through the second bypass pipe 4 b connected to the injection port of the compressor 10.

The flow rate of the refrigerant passing through the second bypass pipe 4b is adjusted by the opening degree (opening area) of the expansion device 14b. When the opening degree (opening area) of the expansion device 14b is increased and the flow rate of the refrigerant flowing through the second bypass pipe 4b is increased, the discharge temperature of the compressor 10 decreases. Conversely, when the opening degree (opening area) of the expansion device 14b is reduced and the flow rate of the refrigerant flowing through the second bypass pipe 4b is reduced, the discharge temperature of the compressor 10 increases. Therefore, the discharge temperature of the compressor 10 can be controlled by adjusting the opening degree (opening area) of the expansion device 14b. For example, in the heating operation mode, a two-phase refrigerant having a high degree of dryness is injected into the compression chamber of the compressor 10. At this time, the degree of discharge superheat is calculated from the discharge temperature detected by the discharge refrigerant temperature detection device 21 and the saturation temperature of the pressure detected by the high pressure detection device 22, and control is performed so that the discharge superheat degree falls within the target range. If it does in this way, the quantity of the refrigerant | coolant which can be injected will increase and a heating capability can be improved.

For example, as described above, when R32 is used as the refrigerant, the discharge temperature tends to be high, so that the compressor 10 is injected. In such a case, basically, it is not necessary to improve the heating capacity. Therefore, the control device 50 may control the amount of refrigerant to be injected with the discharge temperature as a target. Of course, even when R32 is used, the injection amount may be controlled with the discharge superheat degree as a target in order to improve the heating capacity.

Further, the expansion device 14c controls the refrigerant pressure between the expansion device 16 and the expansion device 14a (liquid separator 18) to be the first intermediate pressure. As described above, the first intermediate pressure is lower than the high pressure on the discharge side of the compressor 10 and is the pressure on the downstream side of the second bypass pipe 4b. And it is a pressure higher than the 2nd intermediate pressure which is the pressure of the injection port of the compression chamber of the compressor 10. By maintaining the refrigerant pressure between the expansion device 16 and the expansion device 14c at the first intermediate pressure, the differential pressure across the expansion device 14a can be secured, and the refrigerant can be reliably injected into the compressor 10. it can. Here, the opening degree (opening area) of the expansion device 14c is controlled so that the intermediate pressure obtained by converting the detected temperature of the liquid refrigerant temperature detection device 24 into the saturation pressure approaches the target value.

FIG. 8 is a ph diagram (pressure-enthalpy diagram) during heating operation of the air-conditioning apparatus according to Embodiment 1 of the present invention. In the heating operation mode, the refrigerant (point I in FIG. 8) compressed and discharged by the compressor 10 flows out of the outdoor unit 1 through the refrigerant flow switching device 11 and passes through the extension pipe 5 to the indoor unit. Flows into 2. Then, after being condensed in the use side heat exchanger 17 of the indoor unit 2, it passes through the expansion device 16 and returns to the outdoor unit 1 via the extension pipe 5. Furthermore, it flows to the expansion device 14 c via the first flow path of the liquid separator 18 and the supercooling heat exchanger 13. By adjusting the opening degree of the expansion device 14c, the pressure of the refrigerant (refrigerant upstream of the expansion device 14c) flowing between the expansion device 16 and the expansion device 14c is controlled to be the first intermediate pressure ( Point J in FIG. Part of the liquid refrigerant of the first medium-pressure refrigerant flowing between the expansion device 16 and the expansion device 14c is branched by the liquid separator 18 (point J _{1 in} FIG. 8). A part of the branched liquid refrigerant passes through the first bypass pipe 4a, is decompressed by the expansion device 14a, and becomes a second medium-pressure refrigerant (point M in FIG. 8). Furthermore, by passing through the second flow path of the supercooling heat exchanger 13, heat is exchanged with the refrigerant flowing through the first flow path of the supercooling heat exchanger 13, and the second intermediate pressure having a high dryness is heated. (A point M _{1 in} FIG. 8). And it injects into the compression chamber from the injection port which the compressor 10 has via the 2nd bypass piping 4b and the expansion device 14b of a full open state.

On the other hand, when a part of the liquid refrigerant branches off in the liquid separator 18, the remaining refrigerant slightly increases in dryness (point J _{2 in} FIG. 8). The remaining refrigerant passes through the first flow path of the supercooling heat exchanger 13 and is cooled by exchanging heat with the refrigerant flowing through the second flow path of the supercooling heat exchanger 13 (FIG. 8). point _J 3 of). Further, the pressure is reduced by the expansion device 14c to become a low-pressure two-phase refrigerant (point K in FIG. 8). The low-pressure two-phase refrigerant evaporates in the heat source side heat exchanger 12 and then flows into the accumulator 15 through the refrigerant flow switching device 11. Further, the refrigerant that has flowed out of the accumulator 15 passes through the suction side flow path and is sucked into the compressor 10.

Here, the compressor 10 of the present embodiment is a low-pressure shell type compressor. The sucked refrigerant and oil flow into the lower part of the compressor 10. In addition, a motor is disposed in the intermediate portion. In the upper part, the high-temperature and high-pressure refrigerant compressed in the compression chamber is discharged from the compressor 10 after being discharged into the discharge chamber in the sealed container. Therefore, the metal sealed container of the compressor 10 has a portion exposed to the high-temperature and high-pressure refrigerant and a portion exposed to the low-temperature and low-pressure refrigerant. For this reason, the temperature of the sealed container becomes an intermediate temperature. Further, since current flows through the motor, it generates heat. Therefore, the low-temperature and low-pressure gas refrigerant sucked into the compressor 10 is heated by the sealed container and the motor of the compressor 10 and the temperature rises (point F in FIG. 8). Then, it is sucked into the compression chamber and compressed to the second intermediate pressure in the compression chamber (point N in FIG. 8). When the refrigerant is injected into the compression chamber of the compressor 10 via the second bypass pipe 4b, the temperature of the refrigerant in the merged portion of the refrigerant sucked from the suction side flow path and the refrigerant related to the injection in the compression chamber. (Point H in FIG. 8). Then, the compression is further continued in the compression chamber, whereby a high-pressure gas refrigerant is discharged from the compressor 10. For this reason, when the refrigerant is introduced through the second bypass pipe 4b, the temperature of the refrigerant is reduced at the merged portion, and therefore, the discharge temperature with respect to the discharge temperature of the compressor 10 when the refrigerant is not introduced (point G in FIG. 8). Decreases (point I in FIG. 8). For example, even when using a refrigerant whose discharge temperature of the compressor 10 is higher than R410A, such as R32, the discharge temperature of the compressor 10 can be lowered and can be used safely. it can. In addition, reliability is increased.

Here, it is desirable that the expansion device 14c can change the opening area, such as an electronic expansion valve. If an electronic expansion valve is used, the first intermediate pressure, which is the pressure of the refrigerant upstream of the expansion device 14c, can be adjusted to an arbitrary pressure, and the discharge temperature can be finely controlled. However, the aperture device 14c is not limited to this. For example, an opening / closing valve such as a small electromagnetic valve may be combined so that the opening degree can be selected and controlled in a plurality of stages. In addition, the capillary tube may be configured to perform supercooling according to the refrigerant pressure loss. Although the controllability is slightly worse than that of the electronic expansion valve, the discharge temperature can be brought close to the target.

Further, the method for obtaining the detected temperature of the liquid refrigerant temperature detecting device 24 by converting to the saturated pressure when obtaining the first intermediate pressure has been described. By adopting this method, the system can be configured at low cost. However, it is not limited to this. For example, a pressure sensor may be provided, and the first intermediate pressure may be obtained using the directly detected pressure. The expansion device 14a is composed of an electronic expansion valve or the like whose opening area can be changed. Then, the control device 50 sets the discharge superheat degree calculated by the temperature difference between the discharge temperature of the compressor 10 detected by the discharge refrigerant temperature detection device 21 and the high pressure saturation temperature detected by the high pressure detection device 22 to the target range. The opening area of the expansion device 14a is controlled so as to enter the inside. Further, when it is determined that the discharge temperature has exceeded a certain value (for example, 110 ° C., etc.), the discharge temperature may be controlled to be opened by a certain degree of opening, for example, 10 pulses. Alternatively, the target temperature may be set in a range instead of a constant value, and the discharge temperature may be controlled so as to fall within the target temperature range (for example, between 100 ° C. and 110 ° C.). In the heating operation mode, normally, the expansion device 14b is fully opened, and the expansion device 14d is fully closed. When starting up, the expansion device 14b may be fully closed.

Here, when the heating operation mode is executed, it is not necessary to flow the refrigerant to the use side heat exchanger 17 (including the thermo-off) without the heat load (heating load). However, in the heating operation mode, if the expansion device 16 corresponding to the use-side heat exchanger 17 without a heating load is fully closed or has an opening that is small enough to prevent the refrigerant from flowing, the use-side heat of the stopped indoor unit 2 In the exchanger 17, the refrigerant is cooled by the ambient air, condensed and collected, and the refrigerant circuit as a whole may be short of refrigerant. Therefore, in the present embodiment, during heating operation, the opening (opening area) of the expansion device 16 corresponding to the use-side heat exchanger 17 having no heat load is set to a large opening such as full opening so that the refrigerant can pass therethrough. To. For this reason, accumulation of the refrigerant can be prevented.

The opening degree (opening area) of the expansion device 14a is controlled so that the discharge superheat degree approaches a target value (for example, 40 ° C.) or is controlled so as to fall within a target range (for example, 30 ° C. to 40 ° C.). . The target value of the discharge superheat degree is set to a different value based on the outside air temperature, the degree of improvement in the heating capacity exhibited by the indoor unit 2 is as large as possible at each outside air temperature, and the discharge temperature does not exceed the limit temperature. Set to value.

Further, the opening degree (opening area) of the expansion device 14a may be controlled so that the discharge temperature of the compressor 10 approaches the target value. The target value of the discharge temperature is set lower than the limit value of the discharge temperature. However, since the heating capability which the indoor unit 2 exhibits can be increased at a higher temperature, it is desirable to set the temperature as high as possible. For example, when the discharge temperature limit of the compressor 10 is 120 ° C., the frequency of the compressor 10 is decelerated when it exceeds 110 ° C. so that the discharge temperature does not exceed 120 ° C. Therefore, when injection is performed to lower the discharge temperature of the compressor 10, a temperature between 100 ° C. and 110 ° C. (eg, 105 ° C.), which is a little lower than 110 ° C., which is the temperature at which the frequency of the compressor 10 decelerates. Etc.) may be set to a target value for the discharge temperature. Here, when the frequency is not decelerated by 110 ° C., the target value of the discharge temperature may be a temperature between 100 ° C. and 120 ° C. (for example, 115 ° C.).

Embodiment 2. FIG.
Although not particularly shown in the above-described first embodiment, a four-way valve is generally used as the second refrigerant flow switching device 19. However, the present invention is not limited to this, and a plurality of two-way flow switching valves, three-way flow switching valves, and the like may be used so that the flow switching similar to the four-way valve can be performed.

Further, although the case where four indoor units 2 are connected has been described as an example, the same thing as in the first embodiment can be established regardless of how many indoor units 2 are connected.

Here, the details of the configuration of the liquid separator 18 are not particularly described in the first embodiment. For example, it has one inlet-side channel and two outlet-side channels, separates the liquid refrigerant from the refrigerant flowing in from the inlet-side channel, and flows out from one outlet-side channel to the first bypass pipe 4a. Anything that can do. Further, even if some gas refrigerant is mixed in the refrigerant flowing out to the first bypass pipe 4a, if the degree of mixing of the gas refrigerant does not greatly affect the control of the expansion device, the liquid separator 18 The liquid refrigerant separation efficiency may not be 100%.

In the above-described embodiment, the case where there is one outdoor unit 1 has been described, but a plurality of units may be connected. At this time, a diversion portion or a merging portion of the refrigerant flowing into and out of the plurality of outdoor units 1 may be located outside each outdoor unit 1.

Further, although the compressor 10 has been described by way of example using a low-pressure shell type compressor, for example, the same effect can be obtained even when a high-pressure shell type compressor is used.

In Embodiment 1 described above, no refrigerant other than R32 is mentioned. For example, the effect of the present invention is particularly great when a refrigerant, such as R32, that tends to increase the discharge temperature is used. However, it is not limited to R32. For example, in addition to R32 is a R32, a tetrafluoropropene base refrigerant small formula global warming potential is represented by _CF 3 _CF = CH ₂ HFO1234yf, refrigerant mixed with HFO1234ze such (non-azeotropic mixed refrigerant) May be used. For example, when R32 is used as the refrigerant, the discharge temperature rises by about 20 ° C. in the same operation state as compared with the case where R410A is used. For this reason, it is necessary to lower the discharge temperature, and the effect of the injection according to the present invention is great. In the mixed refrigerant of R32 and HFO1234yf, when the mass ratio of R32 is 62% (62 wt%) or more, the discharge temperature is 3 ° C. or more higher than when the R410A refrigerant is used. For this reason, the injection according to the present invention has a great effect of lowering the discharge temperature. 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 injection according to the present invention has a great effect of lowering the discharge temperature. In addition, the refrigerant type in the mixed refrigerant is not limited to this, and even a mixed refrigerant containing a small amount of other refrigerant components has no significant effect on the discharge temperature and has the same effect. Further, for example, any refrigerant that can be used in a mixed refrigerant containing a small amount of R32, HFO1234yf, and other refrigerants, and whose discharge temperature is higher than R410A, needs to lower the discharge temperature. Have the same effect.

In general, the heat source side heat exchanger 12 and the use side heat exchangers 17a to 17d are often equipped with a blower that promotes condensation or evaporation of the refrigerant by blowing air. Absent. For example, as the use side heat exchangers 17a to 17d, a panel heater using radiation can be used. Further, as the heat source side heat exchanger 12, a water-cooled type heat exchanger that exchanges heat with a liquid such as water or antifreeze can be used. Any material can be used as long as it can dissipate or absorb heat from the refrigerant.

In addition, here, the direct expansion type air conditioner in which the refrigerant is circulated by connecting the pipe between the outdoor unit 1 and the indoor unit 2 has been described as an example, but the present invention is not limited thereto. For example, a repeater is provided between the outdoor unit 1 and the indoor unit 2. Then, the refrigerant is circulated between the outdoor unit and the relay unit, and a heat medium such as water and brine is circulated between the relay unit and the indoor unit, and the relay unit performs heat exchange between the refrigerant and the heat medium. The present invention can also be applied to an air conditioner that performs air conditioning, and has the same effect. In such an air conditioner, installation of the liquid separator 18 becomes unnecessary.

1 outdoor unit, 2, 2a, 2b, 2c, 2d indoor unit, 4a first bypass piping, 4b second bypass piping, 5 extension piping, 6 outdoor space, 7 indoor space, 9 building, 10 compressor, 11 refrigerant flow Path switching device, 12 heat source side heat exchanger, 13 supercooling heat exchanger, 14a, 14b, 14c, 14d expansion device, 15 accumulator, 16, 16a, 16b, 16c, 16d expansion device, 17, 17a, 17b, 17c , 17d use side heat exchanger, 18 liquid separator, 19 second refrigerant flow switching device, 21 discharge refrigerant temperature detection device, 22 high pressure detection device, 23 low pressure detection device, 24 liquid refrigerant temperature detection device, 25 supercooling heat Exchanger inlet refrigerant temperature detection device, 26 Supercooling heat exchanger outlet refrigerant temperature detection device, 27 Usage side heat exchanger liquid refrigerant temperature detection device, 28 Use-side heat exchanger gas refrigerant temperature detecting unit, 50 control unit, 100 air conditioner.

Claims

A compressor having a compression chamber and an injection port for introducing the refrigerant into the compression chamber, and compressing and discharging the refrigerant;
A first heat exchanger that performs heat exchange of the refrigerant;
A refrigerant flow switching device for switching whether the first heat exchanger is a condenser or an evaporator;
A supercooling heat exchanger that has a first flow path and a second flow path, heat-exchanges the refrigerant that passes through each flow path, and supercools the refrigerant that flows through the first flow path;
A second heat exchanger for exchanging heat of the refrigerant;
A refrigerant circuit for circulating the refrigerant by connecting a pipe to the first expansion device that adjusts the pressure of the refrigerant passing through the second heat exchanger;
The piping between the first heat exchanger and the second heat exchanger, the refrigerant inflow side of the second flow path of the supercooling heat exchanger, and the refrigerant of the second flow path of the supercooling heat exchanger A first bypass pipe connecting the outflow side and the refrigerant suction side pipe of the compressor;
In the first bypass pipe, a second throttle for adjusting the pressure of the refrigerant flowing from the pipe between the first heat exchanger and the second heat exchanger to the second flow path of the supercooling heat exchanger. Equipment,
A third expansion device that adjusts the pressure of the refrigerant flowing from the second flow path of the supercooling heat exchanger to the refrigerant suction side pipe of the compressor in the first bypass pipe;
A second bypass pipe connecting the refrigerant outflow side of the second flow path of the supercooling heat exchanger and the injection port;
A fourth expansion device that adjusts the flow rate of the refrigerant flowing through the second bypass pipe,
When the first heat exchanger acts as a condenser, the first bypass pipe is passed through the second throttling device and the third throttling device to supply the refrigerant to the suction side pipe of the compressor. While flowing, controlling the refrigerant to be introduced into the compression chamber through the second bypass pipe through the fourth expansion device, and when the first heat exchanger acts as an evaporator, The refrigerant is introduced into the compression chamber through the second bypass pipe through the fourth expansion device, and the opening of the third expansion device is controlled to be fully closed or the amount of refrigerant hardly flows. Air conditioner.
A refrigerant whose discharge temperature, which is the temperature of the refrigerant on the refrigerant discharge side of the compressor, is higher than R410A under the same conditions, is used as the refrigerant.
The opening degree of the second expansion device is controlled so that the degree of supercooling of the refrigerant on the refrigerant outflow side of the first flow path of the supercooling heat exchanger is close to the target value, and the discharge temperature is made close to the target value. The air conditioning apparatus according to claim 1, further comprising a control device that controls an opening degree of the fourth throttle device.
A discharge temperature detecting means for detecting a discharge temperature of the compressor;
High pressure detecting means for detecting the pressure of the refrigerant on the refrigerant discharge side of the compressor;
Liquid refrigerant temperature detection means for detecting the temperature of the refrigerant on the refrigerant outflow side of the first flow path of the supercooling heat exchanger,
The control device is configured to adjust the degree of supercooling, which is a temperature difference between the saturation temperature of the pressure related to detection by the high pressure detection means and the temperature related to detection by the liquid refrigerant temperature detection device, to a target value. The air conditioning apparatus according to claim 2, wherein the opening degree of the fourth throttle device is controlled so that the discharge temperature related to detection by the discharge temperature detecting means approaches a target value.
A discharge temperature detecting means for detecting a discharge temperature of the compressor;
High pressure detecting means for detecting the pressure of the refrigerant on the refrigerant discharge side of the compressor;
Liquid refrigerant temperature detection means for detecting the temperature of the refrigerant on the refrigerant outflow side of the first flow path of the supercooling heat exchanger,
The control device is configured to adjust the degree of supercooling, which is a temperature difference between the saturation temperature of the pressure related to detection by the high pressure detection means and the temperature related to detection by the liquid refrigerant temperature detection device, to a target value. When the first heat exchanger is acting as a condenser, the opening of the fourth expansion device is adjusted so that the discharge temperature related to detection by the discharge temperature detecting means approaches the target value. When the first heat exchanger functions as an evaporator, the discharge superheat degree, which is the difference between the discharge temperature and the saturation temperature of the pressure detected by the high pressure detection means, is brought close to the target value. The air conditioner according to claim 2, wherein the opening degree of the fourth throttle device is controlled as described above.
The control device controls the third diaphragm device in conjunction with the fourth diaphragm device, and adjusts the opening degree, the change amount of the opening degree, or the opening area or the change amount of the opening area after the control of the fourth diaphragm device. 5. The air conditioner according to claim 3, wherein the air conditioner calculates an opening degree, a change amount of the opening degree, an opening area, or a change amount of the opening area based on the third expansion device.
When the control device performs control to increase the aperture area of the fourth diaphragm device, the control device performs control to reduce the aperture area of the third diaphragm device, and performs control to reduce the aperture area of the fourth diaphragm device. The air conditioner according to claim 5, wherein when performing, control is performed to increase an opening area of the third expansion device.
In the control device, the sum of the aperture area of the third aperture device and the aperture area of the fourth aperture device is a value obtained by adding the aperture area of the third aperture device and the aperture area of the fourth aperture device. The opening of the third throttling device is set so as to be within a range of ± 20%, or the sum of the opening of the third throttling device and the fourth opening is the opening of the third throttling device. 7. The air conditioner according to claim 6, wherein the opening degree of the third throttling device is set to fall within a range of ± 20% of a value obtained by adding the degree and the opening degree of the fourth throttling device. apparatus.
In the control device, the sum of the aperture area of the third aperture device and the aperture area of the fourth aperture device is a value obtained by adding the aperture area of the third aperture device and the aperture area of the fourth aperture device. The opening of the third throttling device is set so as to be within a range of ± 10%, or the sum of the opening of the third throttling device and the fourth opening is the opening of the third throttling device. 8. The air conditioner according to claim 7, wherein the opening degree of the third throttling device is set so as to be within a range of ± 10% of a value obtained by adding the degree and the opening degree of the fourth throttling device. apparatus.
In the control device, the sum of the aperture area of the third aperture device and the aperture area of the fourth aperture device is a value obtained by adding the aperture area of the third aperture device and the aperture area of the fourth aperture device. The opening of the third throttling device is set so as to be within a range of ± 1%, or the sum of the opening of the third throttling device and the fourth opening is the opening of the third throttling device. 9. The air conditioner according to claim 8, wherein the opening degree of the third throttling device is set to be within a range of ± 1% of a value obtained by adding the degree and the opening degree of the fourth throttling device. apparatus.
The air conditioner according to any one of claims 1 to 9, wherein a mixed refrigerant containing R32 or 62% or more of R32 in mass ratio is used.
The control device sets the target value of the discharge temperature to a value between 100 ° C. and 120 ° C., and adjusts the opening of the fourth expansion device based on the target value of the discharge temperature. The air conditioning apparatus according to any one of claims 10 to 10.
The control device sets the target value of the discharge temperature to a value between 100 ° C. and 110 ° C., and adjusts the opening of the fourth throttle device based on the target value of the discharge temperature. The air conditioning apparatus described in 1.
The refrigerant circuit further includes an accumulator that is connected to the suction side of the compressor and stores excess refrigerant, the first bypass pipe is connected to a refrigerant inflow side of the accumulator,
The compressor, the accumulator, the supercooling heat exchanger, the second expansion device, the third expansion device, the fourth expansion device, the first heat exchanger, the first bypass pipe, and the second bypass pipe The air conditioning apparatus according to any one of claims 1 to 12, wherein the air conditioner is accommodated in an outdoor unit.
A liquid separator capable of separating the liquid refrigerant from the refrigerant passing through the flow path between the first heat exchanger and the second heat exchanger;
The air conditioning apparatus according to any one of claims 1 to 13, wherein a part of the liquid refrigerant separated by the liquid separator is passed through the first bypass pipe.
From the refrigerant | coolant outflow side of the 2nd flow path of the said supercooling heat exchanger, the two-phase refrigerant | coolant branch part which distributes a two-phase refrigerant | coolant equally to a said 1st bypass piping and a said 2nd bypass piping is further provided. The air conditioning apparatus according to claim 14.
The two-phase refrigerant branch is a T-type or Y-type joint, and is installed in such a direction that the refrigerant flows from the lower side to the upper side in the direction of gravity and is distributed at substantially the same height in the direction of gravity. The air conditioning apparatus according to claim 15.