WO2008069265A1

WO2008069265A1 - Air-conditioner

Info

Publication number: WO2008069265A1
Application number: PCT/JP2007/073566
Authority: WO
Inventors: Yoshio Ueno
Original assignee: Daikin Industries, Ltd.
Priority date: 2006-12-08
Filing date: 2007-12-06
Publication date: 2008-06-12
Also published as: JP4274236B2; JP2008145044A

Abstract

An air-conditioner having a coolant circuit constituted by use units are connected to a heat source unit and capable of performing heating operation by refrigeration cycle operation in which the high-pressure side exceeds the critical pressure of the coolant. An excessive increase of the discharge temperature of the compressor due to a coolant liquefaction phenomenon is prevented, and coolant flow noise produced in a use unit whose heating operation is at rest is suppressed. From the coolant temperature and the pressure in the use unit whose heating operation is at rest out of the use units, the amount of liquefied coolant, i.e., the amount of coolant staying in the use unit whose heating operation is at rest is computed. According to the amount of liquefied coolant, the use-side expansion mechanism of the use unit whose heating operation is at rest is controlled.

Description

Specification

Air conditioner

Technical field

The present invention relates to an air conditioner, in particular, a plurality of utilization units including a utilization side expansion mechanism and a utilization side heat exchanger are connected to a heat source unit including a compressor and a heat source side heat exchanger. It is related with the air conditioning apparatus in which the heating operation by the refrigerating cycle operation in which the high pressure side becomes the pressure exceeding the critical pressure of the refrigerant is provided.

Background art

Conventionally, a heating operation is possible having a refrigerant circuit configured by connecting a plurality of utilization units including a utilization side expansion valve and a utilization side heat exchanger to a heat source unit. There are so-called multi-type air conditioners.

In such an air conditioner, the use of a natural refrigerant such as carbon dioxide having a small influence on the environment as a refrigerant sealed in the refrigerant circuit is being studied. When natural refrigerant such as carbon dioxide having a low critical temperature is used, a refrigeration cycle operation is performed in which the refrigerant pressure on the high pressure side exceeds the critical pressure of the refrigerant (Patent Document 1). reference).

Patent Document 1: Japanese Unexamined Patent Publication No. 2003-121015

Disclosure of the invention

[0003] In the air conditioning apparatus described above, there are cases in which heating is performed with some of the plurality of usage units stopped, but in this case, the usage units in the heating stopped state are in the usage unit. Since the refrigerant flow in the refrigerant is eliminated, the refrigerant pressure at the high-pressure side of the refrigeration cycle operation is mainly the same as that of the utilization unit during heating! If the stagnation phenomenon occurs and the amount of refrigerant stagnating in the use unit when heating is stopped (hereinafter referred to as refrigerant stagnation amount) increases, the amount of refrigerant circulating in the refrigerant circuit may be insufficient. If the amount of refrigerant circulating in the refrigerant circuit is insufficient, the discharge temperature of the compressor for compressing the refrigerant excessively rises, and heating cannot be continued. On the other hand, when the upper limit value is set for the discharge temperature of the compressor and the discharge temperature of the compressor reaches the upper limit value, the opening degree of the use side expansion valve of the use unit during the heating stop is temporarily set. By increasing the control, a refrigerant flow is created in the use unit when heating is stopped, and the refrigerant in the use unit circulates through the refrigerant in the use circuit! By performing the recovery operation (hereinafter referred to as the discharge temperature upper limit control), the refrigerant stagnation phenomenon and the insufficient circulation amount are eliminated.

[0004] However, since the refrigerant recovery operation described above uses the discharge temperature of the compressor as a threshold value, control for increasing the opening of the use-side expansion valve relatively abruptly in consideration of protection of the compressor. When the upper limit control of the discharge temperature is performed, a large refrigerant flow noise is generated in the use unit that is not heating. In particular, when a refrigerant having a low critical temperature such as carbon dioxide is used, the refrigerant discharge temperature is increased because the refrigerant pressure on the high-pressure side exceeds the critical pressure of the refrigerant. Consideration for excessive rise of the refrigerant is further required, and refrigerant flow noise in the use unit during discharge temperature upper limit control is likely to occur.

An object of the present invention is to provide a refrigerant circuit configured by connecting a plurality of utilization unit forces including a utilization side expansion mechanism and a utilization side heat exchanger, and a heat source unit including a compressor and a heat source side heat exchanger. It has an air conditioner that can be heated by refrigeration cycle operation where the high pressure side exceeds the critical pressure of the refrigerant, and the discharge temperature of the compressor is excessively increased by the refrigerant stagnation phenomenon. This is to prevent the generation of refrigerant flow noise in the use unit when heating is stopped.

[0005] In the air conditioner according to the first invention, a plurality of utilization units including a utilization side expansion mechanism and a utilization side heat exchanger are connected to a heat source unit including a compressor and a heat source side heat exchanger. In an air conditioner capable of heating operation by refrigeration cycle operation in which the high-pressure side has a pressure exceeding the critical pressure of the refrigerant Based on the refrigerant temperature and the refrigerant pressure in the unit, the refrigerant stagnation amount, which is the amount of refrigerant that stays in the usage unit when heating is stopped, is calculated, and the usage side expansion of the usage unit when heating is stopped according to the refrigerant stagnation amount Control the mechanism. In this air conditioner, during heating, the refrigerant pressure in the user-side heat exchanger exceeds the critical pressure and is not in a gas-liquid two-phase state, so it exists in the user unit from the refrigerant temperature and refrigerant pressure in the user unit. It is possible to calculate the amount of refrigerant to be performed.

Utilizing this, the refrigerant stagnation amount of the usage unit when heating is stopped is calculated, and the use side expansion mechanism of the usage unit when heating is stopped is controlled according to the calculated refrigerant stagnation amount. Therefore, it is possible to prevent the refrigerant discharge temperature from being excessively increased due to a shortage of the refrigerant circulating in the refrigerant circuit due to the refrigerant stagnation in the use unit that is not heating.

In addition, the use side expansion mechanism is controlled more finely than when the discharge temperature upper limit control is performed, which is the refrigerant recovery operation that recovers the refrigerant that has fallen into the use unit that has stopped heating with the discharge temperature of the compressor as a threshold value. In addition, since it can be performed slowly, it is possible to suppress the generation of refrigerant flow noise in the use unit during the heating stop.

Note that “heating is stopped” here means not only when the user has intentionally instructed the unit to stop heating using a remote controller or the like, but also during the heating, This includes cases where the condition continues for a long time.

[0006] The air conditioner according to the second aspect of the invention is the air conditioner according to the first aspect of the invention. In the air conditioner according to the first aspect, the refrigerant temperature is the inlet side of the use side heat exchanger during heating, the use side during heating. It is detected by a temperature sensor provided on at least one of the outlet side of the heat exchanger and the use side heat exchanger.

In this air conditioner, temperature sensors provided on at least one of the inlet side of the use side heat exchanger during heating, the outlet side of the use side heat exchanger during heating, and the use side heat exchanger Since the refrigerant temperature detected by the above is used for calculating the refrigerant stagnation amount, the calculation accuracy of the refrigerant stagnation amount can be improved.

[0007] The air conditioner according to the third aspect of the present invention is the same as the air conditioner according to the second aspect of the present invention! When detecting the cooling medium temperature, the usage side expansion mechanism of the usage unit that is not warmed is controlled so that the refrigerant passes through the usage unit that is not heated.

This air conditioner produces a refrigerant flow in the use unit when heating is stopped. In addition, since the refrigerant temperature is detected in the heating-use unit used when calculating the refrigerant stagnation amount, the refrigerant temperature detection accuracy can be increased.

Brief Description of Drawings

FIG. 1 is a schematic configuration diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a pressure-enthalpy diagram illustrating the refrigeration cycle.

FIG. 3 is a flowchart of discharge temperature upper limit control and refrigerant stagnation control.

Explanation of symbols

[0009] 1 Air conditioner

2 Heat source unit

4, 5 Usage unit

6, 7 Refrigerant communication pipe

10 Refrigerant circuit

21 Compressor

23 Heat source side heat exchanger

41, 51 User side expansion mechanism

42, 52 User side heat exchanger

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of an air-conditioning apparatus according to the present invention will be described based on the drawings.

(1) Configuration of air conditioner

FIG. 1 is a schematic configuration diagram of an air-conditioning apparatus 1 according to an embodiment of the present invention. The air conditioner 1 is an apparatus used for indoor air conditioning by performing a vapor compression refrigeration cycle operation. In this embodiment, the air conditioner 1 is a refrigerant communication pipe that connects the heat source unit 2, a plurality of (here, two) use units 4 and 5, and the heat source unit 2 and the use units 4 and 5. The first refrigerant communication pipe 6 and the second refrigerant communication pipe 7 are provided. That is, the vapor compression refrigerant circuit 10 of the air conditioner 1 of the present embodiment is configured by connecting the heat source unit 2, the utilization units 4 and 5, and the refrigerant communication pipes 6 and 7. The Yes. Then, carbon dioxide is sealed in the refrigerant circuit 10 as a refrigerant. As will be described later, the refrigerant circuit 10 is compressed to a pressure exceeding the critical pressure of the refrigerant, cooled, depressurized, heated and evaporated, and then again. The refrigeration cycle operation of being compressed is performed.

[0011] One usage unit

The utilization units 4 and 5 are installed indoors and connected to the heat source unit 2 via the refrigerant communication pipes 6 and 7 and constitute a part of the refrigerant circuit 10.

Next, the configuration of the usage units 4 and 5 will be described. Since the usage unit 4 and the usage unit 5 have the same configuration, only the configuration of the usage unit 4 will be described here, and the configuration of the usage unit 5 indicates each part of the usage unit 4. Instead of the 40's code, the 50's code is used, and the description of each part is omitted.

The usage unit 4 mainly has a usage-side refrigerant circuit 10a (in the usage unit 5, the usage-side refrigerant circuit 10b) that constitutes a part of the refrigerant circuit 10. The use side refrigerant circuit 10a mainly includes a use side expansion mechanism 41 and a use side heat exchanger 42.

[0012] The use-side expansion mechanism 41 is a mechanism for decompressing the refrigerant. In this embodiment, the use-side expansion mechanism 41 adjusts the flow rate of the refrigerant flowing in the use-side refrigerant circuit 10a (the use-side refrigerant circuit 10b in the use unit 5). This is an electric expansion valve connected to one end of the use side heat exchanger 42 to perform the above. The use side expansion mechanism 41 has one end connected to the first refrigerant communication pipe 6 and the other end connected to the use side heat exchanger 42.

The use side heat exchanger 42 is a heat exchanger that functions as a refrigerant heater or cooler. The utilization heat exchanger 42 has one end connected to the utilization side expansion mechanism 41 and the other end connected to the second refrigerant communication pipe 7.

In the present embodiment, the usage unit 4 includes a usage-side fan 43 for sucking indoor air into the unit and supplying it to the room again. The usage unit 4 includes a refrigerant flowing through the usage-side heat exchanger 42 and the indoor air. It is possible to exchange heat. The use side fan 43 is rotationally driven by a use side fan drive motor 43a.

In addition, the utilization unit 4 is provided with various sensors. Specifically, when the use-side heat exchanger 42 is functioned as a refrigerant cooler, the first use-side heat for detecting the cooler outlet refrigerant temperature Tho is provided on the outlet side of the use-side heat exchanger 42. Exchanger temperature sensor 44 When the use side heat exchanger 42 functions as a refrigerant cooler, the use side heat exchanger 42 has a second use side heat exchanger that detects the refrigerant inlet refrigerant temperature Thi at the inlet side. A temperature sensor 45 is provided. In the present embodiment, the use side heat exchanger temperature sensors 44 and 45 are thermistors. In addition, the usage unit 4 has a usage-side control unit 46 that controls the operation of each unit constituting the usage unit 4. The use-side control unit 46 includes a microcomputer, a memory, and the like provided for controlling the use unit 4, and is connected to a remote controller (not shown) for individually operating the use unit 4. Control signals etc. can be exchanged between them, and control signals etc. can be exchanged with the heat source unit 2 via the transmission line 8a.

[0014] Heat source unit

The heat source unit 2 is installed outside and is connected to the usage units 4 and 5 through the refrigerant communication pipes 6 and 7, and the refrigerant circuit 10 is configured between the usage units 4 and 5.

Next, the configuration of the heat source unit 2 will be described. The heat source unit 2 mainly has a heat source side refrigerant circuit 10c constituting a part of the refrigerant circuit 10! /. The heat source side refrigerant circuit 10c mainly includes a compressor 21, a switching mechanism 22, a heat source side heat exchanger 23, a heat source side expansion mechanism 24, a first closing valve 25, and a second closing valve 26. have.

In the present embodiment, the compressor 21 is a hermetic compressor driven by a compressor drive motor 21a. In the present embodiment, only one compressor 21 is provided. However, the present invention is not limited to this, and two or more compressors 21 may be connected in parallel depending on the number of connected units. Good.

[0015] The switching mechanism 22 is a mechanism for switching the direction of the flow of the refrigerant in the refrigerant circuit 10. During cooling, the heat source side heat exchanger 23 is used as a refrigerant cooler compressed by the compressor 21. In addition, in order for the use side heat exchangers 42 and 52 to function as a heater for the refrigerant cooled in the heat source side heat exchanger 23, the discharge side of the compressor 21 and one end of the heat source side heat exchanger 23 are connected. As well as connecting the suction side of the compressor 21 and the second closing valve 26 (see the solid line of the switching mechanism 22 in FIG. 1), the heating-side heat exchangers 42 and 52 are connected by the compressor 21 during heating. In order to function as a cooler for the refrigerant to be compressed and the heat source side heat exchanger 23 as a heater for the refrigerant cooled in the use side heat exchangers 42, 52, the discharge of the compressor 21 It is possible to connect the suction side of the compressor 21 and one end of the heat source side heat exchanger 23 (see the broken line of the switching mechanism 22 in FIG. 1). In the present embodiment, the switching mechanism 22 is a four-way switching valve connected to the suction side of the compressor 21, the discharge side of the compressor 21, the heat source side heat exchanger 23, and the second closing valve 26. Note that the switching mechanism 22 is not limited to a four-way switching valve. For example, the switching mechanism 22 is configured to have a function of switching the flow direction of the refrigerant as described above by combining a plurality of solenoid valves. It may be.

[0016] The heat source side heat exchanger 23 is a heat exchanger that functions as a refrigerant cooler or heater.

One end of the heat source side heat exchanger 23 is connected to the switching mechanism 22, and the other end is connected to the heat source side expansion mechanism 24! /.

The heat source unit 2 has a heat source side fan 27 for sucking outdoor air into the unit and discharging it outside the room again. The heat source side fan 27 can exchange heat between the outdoor air and the refrigerant flowing through the heat source side heat exchanger 23. The heat source side fan 27 is rotationally driven by a heat source side fan drive motor 27a. Note that the heat source of the heat source side heat exchanger 23 may be another heat medium such as water, which is not limited to outdoor air.

The heat source side expansion mechanism 24 is a mechanism for decompressing the refrigerant. In this embodiment, the other end of the heat source side heat exchanger 23 is used to adjust the flow rate of the refrigerant flowing in the heat source side refrigerant circuit 10c. It is an electric expansion valve connected to. One end of the heat source side expansion mechanism 24 is connected to the heat source side heat exchanger 23, and the other end is connected to the first closing valve 25.

[0017] The first closing valve 25 is a valve to which a first refrigerant communication pipe 6 for exchanging refrigerant between the heat source unit 2 and the utilization units 4 and 5 is connected, and is connected to the heat source side expansion mechanism 24. Has been. The second closing valve 26 is a valve to which a second refrigerant communication pipe 7 for exchanging refrigerant between the heat source unit 2 and the utilization units 4 and 5 is connected, and is connected to the switching mechanism 22. Here, the first and second shutoff valves 25 and 26 are three-way valves provided with service ports that can communicate with the outside of the refrigerant circuit 10.

The heat source unit 2 is provided with various sensors. Specifically, on the discharge side of the compressor 21, a compressor discharge pressure sensor 28 for detecting the compressor discharge pressure Pd, and a pressure A compressor discharge temperature sensor 29 for detecting the compressor discharge temperature Td is provided. In the present embodiment, the compressor discharge temperature sensor 29 is a thermistor. Further, the heat source unit 2 includes a heat source side control unit 30 that controls the operation of each unit constituting the heat source unit 2. The heat source side control unit 30 includes a microcomputer memory provided for controlling the heat source unit 2, and the use side control units 46 and 56 of the use units 4 and 5. Control signals and the like can be exchanged via the transmission line 8a.

[0018] <Refrigerant tube>

Refrigerant communication pipes 6 and 7 are refrigerant pipes installed on site when the air conditioner 1 is installed at the installation site.

As described above, the use side refrigerant circuits 10a and 10b, the heat source side refrigerant circuit 10c, and the refrigerant communication pipes 6 and 7 are connected to constitute the refrigerant circuit 10. The air conditioner 1 according to the present embodiment includes various types of the air conditioner 1 using the use side control units 46 and 56, the heat source side control unit 30, and the transmission line 8a that connects the control units 30, 46, and 56. A control unit 8 is configured as a control means for performing operation control. The control unit 8 is connected so that it can receive the detection signals of the various sensors 29, 30, 44, 45, 54, 55, and various devices 21, 22, 24, 27, 41, 43, 51, 53 can be controlled.

[0019] (2) Operation of air conditioner

Next, the operation of the air conditioner 1 of the present embodiment will be described using FIG. 1 and FIG. Here, FIG. 2 is a pressure entry ruby diagram illustrating the refrigeration cycle in the present embodiment. The control in various operations described below is performed by the control unit 8 functioning as the operation control means. Specifically, the use side control units 46, 56, the heat source side control unit 33, and the control units 33, 46, 56 This is done by the transmission line 8a) connecting them.

Air conditioning

During cooling, the switching mechanism 22 is in the state indicated by the solid line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the heat source side heat exchanger 23, and the suction side of the compressor 21 is connected to the second closing valve 26. It has become a state. The opening degrees of the heat source side expansion mechanism 24 and the use side expansion mechanisms 41 and 51 are adjusted. Moreover, the shut-off valves 25 and 26 are opened. [0020] In the state of the refrigerant circuit 10, when the compressor 21, the heat source side fan 27, and the use side fans 43, 53 are started, low-pressure refrigerant (see point A in FIG. 2) is sucked into the compressor 21. Thus, it is compressed to a pressure exceeding the critical pressure (ie, Pep in Fig. 2) to become a high-pressure refrigerant (see point B in Fig. 2). Thereafter, the high-pressure refrigerant is sent to the heat source side heat exchanger 23 that functions as a refrigerant cooler via the switching mechanism 22 to exchange heat with the outdoor air supplied by the heat source side fan 27. (Refer to point C in Fig. 2). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 23 is sent to the utilization units 4 and 5 via the heat source side expansion mechanism 24, the first closing valve 25, and the first refrigerant communication tube 6. It is done. The refrigerant sent to each of the usage units 4 and 5 is decompressed by the usage-side expansion mechanisms 41 and 51 to become low-pressure gas-liquid two-phase refrigerant (see point D in FIG. 2), and serves as a refrigerant heater. In the functioning use-side heat exchangers 42 and 52, heat is exchanged with room air, respectively, and they are evaporated to become low-pressure refrigerant (see point A in Fig. 2). Then, the low-pressure refrigerant heated in these use side heat exchangers 42 and 52 is sent to the heat source unit 2 via the second refrigerant communication pipe 7, and the second closing valve 26 and the switching mechanism 22 are passed through. Via, it is sucked into the compressor 21 again. In this way, cooling is performed.

[0021] It should be noted that, in the above description, the force S described when both of the two usage units 4 and 5 perform cooling is used when only one of the usage units 4 and 5 performs cooling. In any one of the usage units ₄ and 5, the corresponding usage-side expansion mechanism has a stop opening degree (for example, fully closed), so that the refrigerant does not pass through the usage unit when the cooling is stopped! Thus, the use-side expansion mechanism is not at the stop position! /, And only the use unit is cooled. Note that “cooling stopped” here means not only when the user has intentionally issued a cooling stop command to the use units 4 and 5 by a remote controller or the like, but also when the thermostat is off. Even when the air condition and the air blowing state continue for a long time, the usage side expansion mechanism corresponding to the usage unit that is in the cooling stop state is at the stop opening, so this is included.

Heating

During heating, the switching mechanism 22 is in the state indicated by the broken line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the second closing valve 26, and the suction side of the compressor 21 is connected to the heat source side heat exchanger 23. Connected. The opening degrees of the heat source side expansion mechanism 24 and the use side expansion mechanisms 41 and 51 are adjusted. Moreover, the shut-off valves 25 and 26 are opened.

[0022] In this state of the refrigerant circuit 10, when the compressor 21, the heat source side fan 27, and the use side fans 43, 53 are started, low-pressure refrigerant (see point A in FIG. 2) is sucked into the compressor 21. Thus, it is compressed to a pressure exceeding the critical pressure (ie, Pep in Fig. 2) to become a high-pressure refrigerant (see point B in Fig. 2). Thereafter, the high-pressure refrigerant is sent to the use units 4 and 5 via the switching mechanism 22, the second closing valve 26 and the second refrigerant communication pipe 7. The high-pressure refrigerant sent to each of the usage units 4 and 5 is cooled by exchanging heat with room air in the usage-side heat exchangers 42 and 52 that function as a refrigerant cooler (Fig. After passing through the use side expansion mechanism 41, 51, it is sent to the heat source unit 2 via the first refrigerant communication pipe 6. The high-pressure refrigerant sent to the heat source unit 2 is reduced in pressure by the heat source side expansion mechanism 24 to become a low-pressure gas-liquid two-phase refrigerant (see point D in FIG. 2), and serves as a refrigerant heater. It flows into the side heat exchanger 23. Then, the low-pressure gas-liquid two-phase refrigerant flowing into the heat source side heat exchanger 23 evaporates by heat exchange with the outdoor air supplied by the heat source side fan 27 to become a low pressure refrigerant. (Refer to point A in FIG. 2), the air is again sucked into the compressor 21 via the switching mechanism 22. In this way, heating is performed.

[0023] It should be noted that in the above description, when only one of the power usage units 4 and 5 is heating when the two usage units 4 and 5 are both heating, For the other of the usage units ₄ and 5, the corresponding usage side expansion mechanism is at the stop opening (for example, fully closed), so that the refrigerant does not pass through the usage unit when heating is stopped! /, Thus, the use side expansion mechanism is not at the stop position! /, And only the use unit is heated. Note that “heating is stopped” as used herein includes not only the case where the user has intentionally instructed the heating units 4 and 5 to be stopped by the remote controller or the like, but also the thermo-off even during heating. Even if the state or the air blowing state continues for a long time, it is included because the use side expansion mechanism corresponding to the use unit in the heating stop is at the stop opening.

Discharge temperature upper limit control and refrigerant stagnation control

As mentioned above, when only one of the two usage units 4, 5 is heating Therefore, the flow of refrigerant in the usage unit when heating is stopped is eliminated, so the refrigerant in the range from the connection with the second refrigerant communication pipe 7 of the usage unit when heating is stopped to the usage side expansion mechanism is The refrigerant pressure becomes the refrigerant pressure on the high-pressure side of the refrigeration cycle operation (that is, the pressure almost the same as the refrigerant pressure at points B and C in Fig. 2), and the refrigerant temperature The temperature is close to the ambient temperature of the place where the use unit is stopped and the ambient temperature of the use side heat exchanger (in Fig. 2, the refrigerant temperature is the line connecting point B and point C. (It will be on the dotted line L extended in the direction of decreasing). Incidentally, the alternate long and short dash line shown in FIG. 2 is an isotherm. When the refrigerant in the use unit during the heating stop is in such a state, the refrigerant mainly stays in the use-side heat exchanger, that is, a so-called refrigerant stagnation phenomenon occurs. The amount of refrigerant that stays (hereinafter referred to as refrigerant stagnation amount Ms) increases, and the amount of refrigerant circulating in the refrigerant circuit 10 may be insufficient. If the amount of refrigerant circulating in the refrigerant circuit 10 is insufficient, the discharge temperature of the compressor 21 for compressing the refrigerant (that is, the compressor discharge temperature Td) rises excessively, and heating cannot be continued. End up.

Therefore, in the present embodiment, in order to protect the compressor 21, the upper limit value Tdh is set for the compressor discharge temperature Td as in the conventional case, and the compressor discharge temperature Td is set to the upper limit value Tdh. When the temperature reaches the value, the control unit temporarily increases the opening of the usage-side expansion mechanism of the user unit that is not in heating, thereby creating a refrigerant flow in the user unit that is not heating. A refrigerant recovery operation (hereinafter referred to as discharge temperature upper limit control) is performed in which the refrigerant that has fallen into the unit is returned to the flow path portion where the refrigerant in the refrigerant circuit 10 circulates.

Hereinafter, the discharge temperature upper limit control will be described with reference to FIG. Here, FIG. 3 is a flowchart of the discharge temperature upper limit control and the refrigerant stagnation amount control in the present embodiment. In the following description, it is assumed that, out of the two usage units 4 and 5, the usage unit 4 is heating and the usage unit 5 is not heating.

[0025] First, in step S1, it is determined whether or not the compressor discharge temperature Td has risen to the upper limit value Tdh. If the compressor discharge temperature Td has risen to the upper limit value Tdh, step S2 When the compressor discharge temperature Td has not risen to the upper limit value Tdh, the process proceeds to steps S6 to S10 (that is, refrigerant stagnation amount control described later). Next, in step S2, control is performed to increase the opening of the use-side expansion mechanism 51 of the use unit 5 while heating is stopped. More specifically, when the compressor discharge temperature Td rises to the upper limit value Tdh, the opening degree of the use side expansion mechanism 51 is changed to the current opening degree (for example, the stop opening degree or the refrigerant described later). If the opening amount is already larger than the stop opening amount due to the stagnation amount control, the opening amount is rapidly controlled from the opening amount to a relatively large first opening amount (for example, fully open). As a result, the refrigerant that has fallen in the use unit 5 while heating is stopped is returned to the flow path portion where the refrigerant in the refrigerant circuit 10 circulates as fast as possible, and the compressor discharge temperature Td is reduced. it can.

Next, in step S3, the force at which the compressor discharge temperature Td is lower than the upper limit value Tdh is determined by the process of step S2, and the compressor discharge temperature Td is lower than the upper limit value Tdh. In this case, since the refrigerant stagnation phenomenon in the use unit 5 while heating is stopped has been eliminated, in step S4, the use side expansion mechanism 51 opened to the first opening in step S2 is closed to the stop opening. Continue to heat unit 4 in use. On the other hand, when the compressor discharge temperature Td does not fall below the upper limit value Tdh, for example, a process of stopping the compressor 21 is performed from the viewpoint of protecting the compressor 21 as in step S5.

In this way, by performing the discharge temperature upper limit control, it is possible to eliminate the stagnation of the refrigerant in the utilization unit 5 during the heating stop mainly for the purpose of protecting the compressor 21. However, in the method of eliminating the stagnation of the refrigerant in the use unit during the heating stop by such discharge temperature upper limit control, the compressor discharge temperature Td is used as a threshold value, and the viewpoint of protecting the compressor 21 Therefore, the opening degree of the utilization side expansion mechanism of the utilization unit while heating is stopped is rapidly opened to the first opening degree, so that a refrigerant flow noise is generated in the utilization unit when heating is stopped.

[0027] Therefore, it is possible to prevent an excessive increase in the compressor discharge temperature Td due to the refrigerant stagnation phenomenon, and to suppress the generation of refrigerant flow noise in the heating unit while heating is stopped. It is desirable to use a technique to eliminate stagnation. Therefore, the inventor of the present application, as in the present embodiment, in the refrigerant circuit 10 capable of performing the heating operation by the refrigeration cycle operation in which the high pressure side exceeds the critical pressure of the refrigerant, as shown in FIG. , The refrigerant pressure in the use side heat exchanger 42, 52 is critical pressure P Since it exceeds cp and is not in a gas-liquid two-phase state, it becomes possible to calculate the amount of refrigerant present in the usage units 4 and 5 from the refrigerant temperature and refrigerant pressure in the usage units 4 and 5. Using this fact, the refrigerant stagnation amount Ms of the utilization unit while heating is stopped is calculated, and the utilization side expansion mechanism of the utilization unit when heating is stopped is controlled according to the calculated refrigerant stagnation amount Ms. Therefore, the refrigerant stagnation amount control is performed to prevent the refrigerant amount circulating in the refrigerant circuit 10 from being insufficient and the compressor discharge temperature Td from excessively rising due to the stagnation of the refrigerant in the use unit when heating is stopped. I have to.

Hereinafter, the refrigerant stagnation amount control will be described with reference to FIG. As described above, the refrigerant stagnation amount control is a control performed when the compressor discharge temperature Td has not risen to the upper limit value Tdh in step S1. In the following, out of the two usage units 4 and 5, usage unit 4 is heating and usage unit 5 is not heating.

First, in step S6, the refrigerant temperature and the refrigerant pressure in the usage unit 5 necessary for calculating the refrigerant stagnation amount Ms of the usage unit 5 during the heating stop are detected. Here, as the refrigerant temperature, it is desirable to use the use side heat exchanger 52 having a large volume of refrigerant in the equipment constituting the use side refrigerant circuit 10b of the use unit 5 and the refrigerant temperature in the vicinity thereof. In this embodiment, when calculating the refrigerant stagnation amount Ms, the refrigerant outlet refrigerant temperature Tho, the condenser inlet refrigerant temperature Thi, or the average temperature of the condenser outlet refrigerant temperature Tho and the condenser inlet refrigerant temperature Thi. It is used as the refrigerant temperature. Regarding the refrigerant pressure, since the use side heat exchanger 52 communicates with the discharge side of the compressor 21, in this embodiment, the refrigerant pressure is based on the compressor discharge pressure Pd or the compressor discharge pressure Pd. Thus, the pressure calculated in consideration of the pressure loss from the discharge side of the compressor 21 to the branch portion of the second refrigerant communication pipe 7 is used as the refrigerant pressure when calculating the refrigerant stagnation amount Ms.

[0029] It should be noted that when detecting the refrigerant temperature in the use unit 5 while heating is stopped, the opening degree of the use-side expansion mechanism 51 is set to a second value slightly larger than the stop opening degree in order to increase the detection accuracy of the refrigerant temperature. It is desirable to allow the refrigerant to pass through the use unit 5 when heating is stopped by opening it to the opening. Here, the second opening is smaller than the first opening in the discharge temperature upper limit control. Then, the refrigerant temperature and refrigerant pressure detected in this way are converted into refrigerant density, and the refrigerant stagnation is based on the volume of the equipment constituting the usage side refrigerant circuit 10b of the usage unit 5 and the density of this refrigerant. Calculate the quantity Ms.

Next, in step S7, it is determined whether or not the refrigerant stagnation amount Ms obtained by the calculation exceeds the allowable value Msa of the refrigerant stagnation amount. Here, the allowable value Msa of the refrigerant stagnation amount is a value determined based on the total refrigerant amount enclosed in the refrigerant circuit 10 and the necessary refrigerant circulation amount according to the operating conditions of the air conditioner 1.

[0030] If the refrigerant stagnation amount Ms exceeds the allowable value Msa of the refrigerant stagnation amount, the process proceeds to step S8, and the opening degree of the utilization side expansion mechanism 51 of the utilization unit 5 during the heating stop. Is opened by a predetermined opening increment from the current opening (for example, the stop opening or the opening when the refrigerant stagnation amount control is already larger than the stop opening). . Here, the opening increment of the use side expansion mechanism 51 is smaller than the opening increment when opening to the first opening in the discharge temperature upper limit control. The opening increment may be a constant value or a value that can be varied according to the deviation between the refrigerant stagnation amount Ms and the allowable value Msa. As a result, the refrigerant that has stagnated in the use unit 5 while heating is stopped is returned to the flow path portion where the refrigerant in the refrigerant circuit 10 circulates, and the refrigerant stagnation amount Ms is reduced regardless of the change in the compressor discharge temperature Td. Control can be performed. Then, after the process of step S8, the processes of steps S1, S6, and S7 are performed again, and if the refrigerant stagnation amount Ms becomes smaller than the refrigerant stagnation amount allowable value Msa, step S9 is performed. If the refrigerant stagnation amount Ms exceeds the refrigerant stagnation amount allowable value Msa, the opening degree of the use-side expansion mechanism 51 is further increased from the current opening degree by a predetermined opening degree increment. The process of steps Sl, S6, S7, and S8 is repeated so as to be opened, so that the refrigerant stagnation amount Ms becomes smaller than the allowable value Msa of the refrigerant stagnation amount.

[0031] Next, in step S9, it is determined whether or not the opening degree of the utilization side expansion mechanism 51 of the utilization unit 5 during the heating stop is the stop opening force. Returning to the process, if it is not the stop opening (that is, if the process of step S8 has been performed at least once), the use-side expansion mechanism 51 is closed to the stop opening and the process of step S1 is performed. Return. As described above, in the present embodiment, by adopting the refrigerant stagnation amount control, the refrigerant in the refrigerant circuit 10 converts the refrigerant stagnation into the use unit during the heating stop regardless of the change in the compressor discharge temperature Td. It can be gently returned to the circulating flow path portion. For this reason, in the present embodiment, the discharge temperature upper limit control functions only when the refrigerant circulation amount decreases so rapidly that the refrigerant stagnation state in the use unit during the heating stop cannot be eliminated even by the refrigerant stagnation amount control. As a result, the processes in steps S2 to S5 described above are hardly performed.As a result, the refrigerant stagnation amount control prevents excessive rise in the compressor discharge temperature Td due to the refrigerant stagnation phenomenon, and the heating is stopped. It is possible to suppress the generation of refrigerant flow noise in other units.

[0032] (3) Features of the air conditioner

The air conditioner 1 of the present embodiment has the following features.

(A)

In the air conditioner 1 of the present embodiment, the refrigerant pressure in the usage-side heat exchangers 42 and 52 exceeds the critical pressure Pep and is not in a gas-liquid two-phase state. Using the fact that it is possible to calculate the amount of refrigerant present in the usage units 4 and 5 from the refrigerant pressure, the refrigerant temperature and the refrigerant pressure in the usage unit that is not heating among the usage units 4 and 5 are calculated. Based on this, the refrigerant stagnation amount Ms of the usage unit while heating is stopped is calculated, and the use side expansion mechanism of the usage unit when heating is stopped is controlled according to the calculated refrigerant stagnation amount Ms. As a result, it is possible to prevent the amount of refrigerant circulating in the refrigerant circuit 10 from being deficient when the refrigerant stagnates in the use unit when heating is stopped, and the discharge temperature of the compressor 21 from being excessively increased. Yes.

[0033] In addition, the use side expansion mechanism is compared with the case where the discharge temperature upper limit control is performed which is the refrigerant recovery operation in which the refrigerant that has stagnation in the use unit that is not heating is recovered using the discharge temperature of the compressor 21 as a threshold value. This makes it possible to finely control the air flow and to perform it slowly, so that it is possible to suppress the generation of the refrigerant flow noise in the utilization unit when the heating is stopped.

(B)

In the air conditioner 1 of the present embodiment, at least one of the inlet side of the use side heat exchangers 42 and 52 during heating and the outlet side of the use side heat exchangers 42 and 52 during heating. Since the refrigerant temperature detected by the temperature sensor (here, temperature sensors 44, 45, 54, 55) provided for the two is used for calculating the refrigerant stagnation amount Ms, the calculation accuracy of the refrigerant stagnation amount Ms is improved. Can be increased.

[0034] (C)

In the air conditioner 1 of the present embodiment, when detecting the refrigerant temperature in the heating-use usage unit used for calculating the refrigerant stagnation amount Ms, the refrigerant passes through the heating-use usage unit. In addition, since the control of the use side expansion mechanism of the usage unit when heating is stopped is performed, it is used when calculating the refrigerant stagnation amount Ms while causing the flow of refrigerant in the usage unit when heating is stopped. It becomes possible to detect the refrigerant temperature in the utilization unit when heating is stopped, and the accuracy of refrigerant temperature detection can be improved.

(4) Other embodiments

As described above, the specific configurations of the embodiments of the present invention based on the drawings can be changed without departing from the gist of the invention which is not limited to these embodiments.

[0035] (A)

In the above-described embodiment, the refrigerant temperatures on the inlet side of the usage-side heat exchangers 42 and 52 during heating and the outlet side of the usage-side heat exchangers 42 and 52 during heating are used for calculating the refrigerant stagnation amount Ms. However, if the use side heat exchangers 42 and 52 themselves are provided with temperature sensors, the refrigerant temperature in the use side heat exchangers 42 and 52 is determined as the inlet of the use side heat exchangers 42 and 52 during heating. The refrigerant stagnation amount Ms may be used instead of the refrigerant temperature at the outlet side of the use-side heat exchangers 42 and 52 during heating or in combination with these refrigerant temperatures.

(B)

In the above-described embodiment, the example in which the present invention is applied to the configuration in which the two usage units 4 and 5 are connected to the heat source unit 2 has been described. However, the present invention is applied to a configuration in which a larger number of usage units are connected to the heat source unit. The invention may be applied. In this case, if there are multiple use units that are not in heating, all use sides of the use units that are in heating stop are You may make it control the opening degree of an expansion mechanism, and you may make it control the opening degree of the utilization side expansion mechanism of a utilization unit with the largest refrigerant | coolant stagnation amount Ms. Industrial applicability

If the present invention is used, a plurality of utilization units including a utilization side expansion mechanism and a utilization side heat exchanger are connected to a heat source unit including a compressor and a heat source side heat exchanger. It has an air conditioner that has a refrigerant circuit and can be heated by refrigeration cycle operation where the high-pressure side exceeds the critical pressure of the refrigerant, and the excessive discharge temperature of the compressor due to refrigerant stagnation. In addition to preventing the rise, it is possible to suppress the generation of refrigerant flow noise in the use unit when heating is stopped.

Claims

The scope of the claims

[1] A plurality of utilization units (4, 5) including a utilization side expansion mechanism (41, 51) and utilization side heat exchangers (42, 52) are connected to a compressor (21) and a heat source side heat exchanger ( 23) and a refrigerant circuit (10) configured by being connected to a heat source unit (2), which can be heated by a refrigeration cycle operation in which the high pressure side becomes a pressure exceeding the critical pressure of the refrigerant. In the air conditioner,

Based on the refrigerant temperature and the refrigerant pressure in the use unit that is not in heating among the plurality of use units, the refrigerant stagnation amount that is the amount of refrigerant that stays in the use unit in the heating stop is calculated. Depending on the amount of refrigerant stagnation, control of the use side expansion mechanism of the use unit during the heating stop,

Air conditioner (1).

[2] The refrigerant temperature is selected from among an inlet side of the use side heat exchanger (42, 52) during heating, an outlet side of the use side heat exchanger during heating, and the use side heat exchanger. The air conditioner (1) according to claim 1, wherein the air conditioner (1) is detected by at least one temperature sensor.

[3] When detecting the refrigerant temperature in the heating-use usage unit used to calculate the refrigerant stagnation amount, the refrigerant passes through the heating-use usage unit. The air conditioner (1) according to claim 2, which controls the use side expansion mechanism of the use unit while heating is stopped.