JP2008145044A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent excessive increase of a discharge temperature of a compressor due to a coolant liquefaction phenomenon, and to suppress coolant flow noise produced in an use unit whose heating operation is at rest, in an air conditioner having a coolant circuit constituted by connecting the plurality of use units to a heat source unit, and capable of performing the heating operation by a refrigeration cycle operation in which high-pressure side exceeds a critical pressure of the coolant. <P>SOLUTION: This air conditioner calculates the amount of liquefied coolant as the amount of coolant staying in the use unit whose heating operation is at rest on the basis of a coolant temperature and a coolant pressure in the use unit whose heating operation is at rest, among the plurality of use units, and a use-side expansion mechanism of the use unit whose heating operation is at rest, is controlled according to the amount of liquefied coolant. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is configured by connecting a plurality of utilization units including an air conditioning apparatus, in particular, a utilization side expansion mechanism and a utilization side heat exchanger, to a heat source unit including a compressor and a heat source side heat exchanger. The present invention relates to an air conditioner having a refrigerant circuit and capable of heating operation by a refrigeration cycle operation in which a high-pressure side becomes a pressure exceeding the critical pressure of the refrigerant.

  Conventionally, a so-called multi-type air conditioner capable of heating operation 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 is a device.

In such an air conditioner, the use of a natural refrigerant such as carbon dioxide having a small influence on the environment has been studied as a refrigerant enclosed in the refrigerant circuit. When a natural refrigerant having a low critical temperature such as carbon dioxide 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 (see Patent Document 1). ).
Japanese Patent Laid-Open No. 2003-121015

  In the above-described air conditioner, heating may be performed in a state in which some of the plurality of usage units are stopped. In this case, in the usage units in which heating is stopped, there is no refrigerant flow in the usage units. Therefore, the refrigerant stays in the use-side heat exchanger that is at the refrigerant pressure on the high-pressure side in the refrigeration cycle operation as in the case of the use unit during heating, so-called refrigerant stagnation occurs, and heating is stopped. If the amount of refrigerant staying in the use unit (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 will rise excessively, 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 performing control to increase the refrigerant, a refrigerant recovery operation (hereinafter referred to as discharge) is performed that creates a refrigerant flow in the usage unit when heating is stopped and returns the refrigerant that has fallen into the usage unit to the flow path portion where the refrigerant in the refrigerant circuit circulates. By performing the temperature upper limit control), the refrigerant stagnation phenomenon and the insufficient circulation amount are resolved.

  However, since the refrigerant recovery operation described above uses the discharge temperature of the compressor as a threshold value, it is necessary to perform control to increase the opening of the use side expansion valve relatively rapidly in consideration of the protection of the compressor. Yes, during the discharge temperature upper limit control, a large refrigerant flow noise is generated in the utilization unit that is stopped from heating. In particular, when a refrigerant having a low critical temperature such as carbon dioxide is used as the refrigerant, a refrigeration cycle operation is performed in which the refrigerant pressure on the high pressure side exceeds the critical pressure of the refrigerant. Consideration for excessive rise is further required, and refrigerant flow noise in the utilization unit during discharge temperature upper limit control is also likely to occur.

  An object of the present invention is to provide a refrigerant circuit configured by connecting a plurality of utilization units including a utilization side expansion mechanism and a utilization side heat exchanger to a heat source unit including a compressor and a heat source side heat exchanger. In an air conditioner that is capable of heating operation by refrigeration cycle operation in which the high pressure side exceeds the critical pressure of the refrigerant, while preventing heating from excessively increasing the discharge temperature of the compressor due to refrigerant stagnation, It is in suppressing generation | occurrence | production of the refrigerant | coolant flow noise in the utilization unit.

The air conditioner according to the first invention is configured by connecting a plurality of utilization units including a utilization side expansion mechanism and a utilization side heat exchanger to a heat source unit including a compressor and a heat source side heat exchanger. In an air conditioner having a refrigerant circuit in which a single refrigerant is sealed and capable of heating operation by a refrigeration cycle operation in which the high pressure side exceeds the critical pressure of the refrigerant, among the plurality of usage units Based on the refrigerant temperature and the refrigerant pressure in the use unit during the heating stop, the refrigerant stagnation amount that is the amount of the refrigerant staying in the use unit during the heating stop is calculated, and the use unit during the heating stop is calculated according to the refrigerant stagnation amount Control of the use side expansion mechanism.

  In this air conditioner, during heating, the refrigerant pressure in the usage-side heat exchanger exceeds the critical pressure and is not in a gas-liquid two-phase state, so it exists in the usage unit from the refrigerant temperature and refrigerant pressure in the usage unit. It is possible to calculate the amount of refrigerant to be performed.

  Utilizing this, the refrigerant stagnation amount of the utilization unit during the heating stop is calculated, and by controlling the utilization side expansion mechanism of the utilization unit during the heating stop according to the calculated refrigerant stagnation amount, It is possible to prevent an excessive increase in the discharge temperature of the compressor due to a shortage of the amount of refrigerant circulating in the refrigerant circuit due to the refrigerant falling into the utilization unit that is not heating.

  In addition, compared with the case where the discharge temperature upper limit control, which is the refrigerant recovery operation for recovering the refrigerant that has fallen into the use unit during the heating stop, with the discharge temperature of the compressor as a threshold value, the control of the use side expansion mechanism is finely controlled. Moreover, since it becomes possible to carry out gently, generation | occurrence | production of the refrigerant | coolant flow noise in the utilization unit in the heating stop can be suppressed.

  In addition, the term “heating is stopped” as used herein includes not only the case where the user has intentionally instructed the heating unit to be stopped by a remote controller or the like, but also the thermo-off state and the air blowing state even during heating. This also includes cases of long duration.

  The air conditioner according to a second aspect of the invention is the air conditioner according to the first aspect of the invention, wherein the refrigerant temperature is the inlet side of the use side heat exchanger during heating, the outlet side of the use side heat exchanger during heating, And it detects with the temperature sensor provided in at least 1 of the utilization side heat exchangers.

  In this air conditioner, by a temperature sensor 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 detected refrigerant temperature is used for calculating the refrigerant stagnation amount, the calculation accuracy of the refrigerant stagnation amount can be improved.

An air conditioner according to a third aspect of the present invention is the air conditioner according to the second aspect of the present invention, for calculating the amount of refrigerant stagnation when the utilization side expansion mechanism of the utilization unit during heating stop is at the stop opening degree. When detecting the refrigerant temperature in the utilization unit that is used for heating while the heating is stopped, the utilization-side expansion mechanism of the utilization unit that is stopped for heating is controlled so that the refrigerant passes through the utilization unit that is stopped for heating.

  In this air conditioner, since the refrigerant flow in the use unit in the heating stop is generated, the refrigerant temperature in the use unit in the heating stop used for calculating the refrigerant stagnation amount is detected. The detection accuracy of the refrigerant temperature can be increased.

An air conditioner according to a fourth aspect of the present invention is the air conditioner according to any of the first to third aspects of the present invention, wherein the control of the utilization side expansion mechanism of the utilization unit during heating stop performed according to the refrigerant stagnation amount is performed. This is performed when the compressor discharge temperature has not risen to the upper limit value, and when the compressor discharge temperature has risen to the upper limit value, the use side expansion mechanism of the use unit during the heating stop regardless of the refrigerant stagnation amount Control to increase the opening of.

An air conditioner according to a fifth aspect of the present invention is the air conditioner according to any one of the first to third aspects, wherein the single refrigerant is carbon dioxide.

  As described above, according to the present invention, the following effects can be obtained.

In the first , fourth, or fifth invention, the refrigerant stagnation amount of the utilization unit during the heating stop is calculated, and the use side expansion mechanism of the utilization unit during the heating stop is controlled according to the calculated refrigerant stagnation amount. By performing the above, it is possible to prevent the amount of refrigerant circulating in the refrigerant circuit from becoming insufficient due to the refrigerant stagnation in the utilization unit that is not heating, and the discharge temperature of the compressor from being excessively increased. In addition, compared with the case where the discharge temperature upper limit control is performed, the use-side expansion mechanism can be controlled more finely and gently, so that generation of refrigerant flow noise in the use unit during the heating stop is suppressed. Can do.

  In the second invention, the calculation accuracy of the refrigerant stagnation amount can be increased.

  In 3rd invention, the detection accuracy of the refrigerant | coolant temperature in the utilization unit in the heating stop can be improved.

  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 conditioner 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 serves as a refrigerant communication tube that connects the heat source unit 2, a plurality of (here, two) use units 4 and 5, and the heat source unit 2 and use units 4 and 5. A first refrigerant communication pipe 6 and a 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 tubes 6 and 7. In the refrigerant circuit 10, carbon dioxide is sealed 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 compressed again. The refrigeration cycle operation is performed.

-Usage unit-
The utilization units 4 and 5 are installed indoors or the like and are 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 is the 40th number indicating each part of the usage unit 4. The reference numerals in the 50s are attached instead of the reference numerals, and 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 10 a mainly includes a use side expansion mechanism 41 and a use side heat exchanger 42.

  The use side expansion mechanism 41 is a mechanism for decompressing the refrigerant. In the present 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). Therefore, it is an electric expansion valve connected to one end of the use side heat exchanger 42. One end of the use side expansion mechanism 41 is connected to the first refrigerant communication pipe 6, and the other end is 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. One end of the utilization heat exchanger 42 is connected to the utilization side expansion mechanism 41, and the other end is 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, and the indoor air and the refrigerant flowing through the usage-side heat exchanger 42 are used. Heat exchange is possible. 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, the first use side heat exchanger that detects the cooler outlet refrigerant temperature Tho is provided at the outlet side of the use side heat exchanger 42 when the use side heat exchanger 42 is functioned as a refrigerant cooler. A temperature sensor 44 is provided, and the second use side heat for detecting the cooler inlet refrigerant temperature Thi is provided at the inlet side of the use side heat exchanger 42 when the use side heat exchanger 42 functions as a refrigerant cooler. An exchanger temperature sensor 45 is provided. In the present embodiment, the use side heat exchanger temperature sensors 44 and 45 are thermistors. Further, the usage unit 4 includes a usage-side control unit 46 that controls the operation of each unit constituting the usage unit 4. The usage-side control unit 46 includes a microcomputer, a memory, and the like provided for controlling the usage unit 4, and a remote controller (not shown) for operating the usage unit 4 individually. Control signals and the like can be exchanged between them, and control signals and the like can be exchanged with the heat source unit 2 via the transmission line 8a.

-Heat source unit-
The heat source unit 2 is installed outside and connected to the usage units 4 and 5 via the refrigerant communication pipes 6 and 7, and constitutes a refrigerant circuit 10 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 10 c that constitutes 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. is doing.

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

  The switching mechanism 22 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 10, and at the time of cooling, the heat source side heat exchanger 23 is used as a refrigerant cooler compressed by the compressor 21, and the use side In order for the 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 and the compressor 21. And the second closing valve 26 (see the solid line of the switching mechanism 22 in FIG. 1), and the heating side heat exchangers 42 and 52 are used as coolers for the refrigerant compressed by the compressor 21 during heating. In addition, in order to cause the heat source side heat exchanger 23 to function as a heater for the refrigerant cooled in the use side heat exchangers 42 and 52, the discharge side of the compressor 21 and the second closing valve 26 are connected and compressed. Machine 21 It is possible to connect the one end of the suction side and the heat source-side heat exchanger 23 (see dashed 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. The switching mechanism 22 is not limited to the four-way switching valve, and is configured to have a function of switching the refrigerant flow direction as described above, for example, by combining a plurality of electromagnetic valves. There may be.

  The heat source side heat exchanger 23 is a heat exchanger that functions as a refrigerant cooler or a 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 to the outside 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 is not limited to outdoor air, and may be another heat medium such as water.

  The heat source side expansion mechanism 24 is a mechanism for decompressing the refrigerant. In the present 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.

  The first closing valve 25 is a valve to which the 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. . 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 closing valves 25 and 26 are three-way valves having service ports that can communicate with the outside of the refrigerant circuit 10.

  The heat source unit 2 is provided with various sensors. Specifically, a compressor discharge pressure sensor 28 that detects the compressor discharge pressure Pd and a compressor discharge temperature sensor 29 that detects the compressor discharge temperature Td are provided on the discharge side of the compressor 21. . In the present embodiment, the compressor discharge temperature sensor 29 is a thermistor. In addition, 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, a memory, and the like provided for controlling the heat source unit 2, and is transmitted between 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 line 8a.

<Refrigerant communication pipe>
The refrigerant communication pipes 6 and 7 are refrigerant pipes that are constructed on site when the air conditioner 1 is installed at the installation location.

  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. And the air conditioning apparatus 1 of this embodiment is various operation | movement of the air conditioning apparatus 1 by the transmission line 8a which connects between utilization side control part 46,56, the heat source side control part 30, and control part 30,46,56. A control unit 8 is configured as control means for performing control. The control unit 8 is connected so that it can receive detection signals of various sensors 29, 30, 44, 45, 54, and 55, and various devices 21, 22, 24, and 27 based on these detection signals and the like. , 41, 43, 51, 53 can be controlled.

(2) Operation | movement of an air conditioning apparatus Next, operation | movement of the air conditioning apparatus 1 of this embodiment is demonstrated using FIG.1 and FIG.2. Here, FIG. 2 is a pressure-enthalpy 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 an operation control unit (more specifically, between the use side control units 46 and 56, the heat source side control unit 33, and the control units 33, 46 and 56). The transmission line 8a) connecting

-Cooling-
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 closing valves 25 and 26 are opened.

  In the state of the refrigerant circuit 10, when the compressor 21, the heat source side fan 27, and the usage side fans 43 and 53 are started, the low-pressure refrigerant (see point A in FIG. 2) is sucked into the compressor 21 and the critical pressure ( That is, it is compressed to a pressure exceeding Pcp) in FIG. 2 and becomes 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 functioning as a refrigerant cooler via the switching mechanism 22, and is cooled by exchanging heat with the outdoor air supplied by the heat source side fan 27. (See point C in FIG. 2). 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 pipe 6. 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 a low-pressure gas-liquid two-phase refrigerant (see point D in FIG. 2), and functions as a refrigerant heater. In the 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). The low-pressure refrigerant heated in the use side heat exchangers 42 and 52 is sent to the heat source unit 2 via the second refrigerant communication pipe 7 and via the second closing valve 26 and the switching mechanism 22. Then, it is sucked into the compressor 21 again. In this way, cooling is performed.

  In the above description, the case where both of the two usage units 4 and 5 perform cooling is described. However, when only one of the usage units 4 and 5 performs cooling, the usage unit 4 5, the corresponding use side expansion mechanism has a stop opening degree (for example, fully closed), so that the refrigerant does not pass through the use unit that is in the cooling stop state. Only the use unit whose mechanism is not the stop opening degree is cooled. The “cooling stopped” here means not only when the user has intentionally instructed the cooling units 4 and 5 with the remote controller or the like, but also during the cooling, The case where the air blowing state continues for a long time is also included in this because the use side expansion mechanism corresponding to the use unit in the cooling stop is at the stop opening.

-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. 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 closing valves 25 and 26 are opened.

  In the state of the refrigerant circuit 10, when the compressor 21, the heat source side fan 27, and the usage side fans 43 and 53 are started, the low-pressure refrigerant (see point A in FIG. 2) is sucked into the compressor 21 and the critical pressure ( That is, it is compressed to a pressure exceeding Pcp) in FIG. 2 and becomes a high-pressure refrigerant (see point B in FIG. 2). Thereafter, the high-pressure refrigerant is sent to the utilization 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 indoor air in the usage-side heat exchangers 42 and 52 that function as a refrigerant cooler (FIG. 2). After passing through the use side expansion mechanisms 41 and 51, they are 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 decompressed 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 functions as a refrigerant heater. It flows into the heat exchanger 23. The low-pressure gas-liquid two-phase refrigerant flowing into the heat source side heat exchanger 23 is heated by exchanging heat with the outdoor air supplied by the heat source side fan 27 and becomes 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.

  In the above description, the case where both of the two usage units 4 and 5 perform heating is described. However, when only one of the usage units 4 and 5 performs heating, the usage unit 4 5, the corresponding use-side expansion mechanism has a stop opening (for example, fully closed), so that the refrigerant does not pass through the use unit while heating is stopped. Heating is performed only for the utilization unit whose mechanism is not the stop opening degree. The “heating is stopped” here means not only when the user has intentionally instructed the heating units 4 and 5 with the remote controller or the like, but also in the thermo-off state even during heating. The case where the air blowing state continues for a long time is included in this 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 described above, in the case where only one of the two usage units 4 and 5 performs heating, the flow of the refrigerant in the usage unit while heating is stopped is eliminated. As for the refrigerant within the range from the connection portion with the refrigerant communication pipe 7 to the use side expansion mechanism, the refrigerant pressure is the same as that of the use unit during heating, that is, the refrigerant pressure on the high pressure side in the refrigeration cycle operation (that is, in FIG. And the refrigerant temperature becomes a temperature close to the ambient temperature of the place where the heating-use usage unit is installed or the ambient temperature of the usage-side heat exchanger ( If it says on FIG. 2, it will be in the state on the dotted line L which extended the line which connects the point B and the point C in the direction where a refrigerant | coolant temperature becomes low. In addition, the dashed-dotted line shown by FIG. 2 is an isotherm. Then, when the refrigerant in the usage unit that is not heating is in such a state, a refrigerant stagnation occurs in the usage-side heat exchanger. 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, when the upper limit value Tdh is set for the compressor discharge temperature Td and the compressor discharge temperature Td reaches the upper limit value Tdh, as in the prior art, in order to protect the compressor 21. In addition, by temporarily controlling the opening of the utilization side expansion mechanism of the utilization unit when heating is stopped, a refrigerant flow in the utilization unit when heating is stopped is created, and the refrigerant that has fallen into the utilization unit is removed. A refrigerant recovery operation (hereinafter referred to as discharge temperature upper limit control) for returning to the flow path portion in which the refrigerant in the refrigerant circuit 10 circulates is performed.

  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, of the two usage units 4 and 5, the usage unit 4 is heating and the usage unit 5 is in a heating stop state.

  First, in step S1, it is determined whether 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, the process proceeds to step S2, and the compression is performed. When the machine 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 degree of the use side expansion mechanism 51 of the use unit 5 during the heating stop. 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 stagnation described later). When the opening is already larger than the stop opening by the quantity control, the opening is rapidly controlled from the opening) to a relatively large first opening (for example, fully open). As a result, the refrigerant that has fallen into the utilization unit 5 while heating is stopped can be returned to the flow path portion in which the refrigerant in the refrigerant circuit 10 circulates as quickly as possible, and the compressor discharge temperature Td can be lowered.

  Next, in step S3, it is determined whether or not the compressor discharge temperature Td is lower than the upper limit value Tdh by the process in step S2. If the compressor discharge temperature Td is lower than the upper limit value Tdh, heating is stopped. Since the refrigerant stagnation phenomenon in the middle usage unit 5 is eliminated, in step S4, the usage-side expansion mechanism 51 opened to the first opening in step S2 is closed to the stop opening, and the heating of the usage unit 4 is performed. Continue. 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 the discharge temperature upper limit control, the compressor discharge temperature Td is set as a threshold value, and from the viewpoint of protecting the compressor 21. Since the opening degree of the utilization side expansion mechanism of the utilization unit during the heating stop is rapidly opened to the first opening degree, a refrigerant flow noise is generated in the utilization unit during the heating suspension.

  For this reason, excessive rise in the compressor discharge temperature Td due to the refrigerant stagnation phenomenon can be prevented, and the occurrence of refrigerant stagnation in the heating-use unit that can suppress the generation of refrigerant flow noise in the heating-use unit. It is desirable to perform the technique to do.

  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. Since the refrigerant pressure in the use side heat exchangers 42 and 52 exceeds the critical pressure Pcp and is not in a gas-liquid two-phase state, the use units 4 and 5 are determined from the refrigerant temperature and the refrigerant pressure in the use units 4 and 5. Since it is possible to calculate the amount of refrigerant present in the interior, using this fact, the refrigerant stagnation amount Ms of the utilization unit during the heating stop is calculated, and according to the calculated refrigerant stagnation amount Ms, By controlling the use side expansion mechanism of the utilization unit that is not heating, the refrigerant stagnates in the utilization unit that is not heating, so that the amount of refrigerant circulating in the refrigerant circuit 10 is insufficient, and the compressor discharge Degrees Td is decided to perform the refrigerant stagnation quantity control to prevent the excessive increase.

  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 description, it is assumed that, of the two usage units 4 and 5, the usage unit 4 is heating and the usage unit 5 is in a heating stop state.

  First, in step S6, the refrigerant temperature and the refrigerant pressure in the utilization unit 5 necessary to calculate the refrigerant stagnation amount Ms of the utilization unit 5 during the heating stop are detected. Here, for the refrigerant temperature, it is desirable to use the utilization side heat exchanger 52 having a large volume of refrigerant in the equipment constituting the utilization side refrigerant circuit 10b of the utilization unit 5 and the refrigerant temperature in the vicinity thereof. In the present embodiment, when calculating the refrigerant stagnation amount Ms, the cooler outlet refrigerant temperature Tho, the cooler inlet refrigerant temperature Thi, or the average temperature of the cooler outlet refrigerant temperature Tho and the cooler inlet refrigerant temperature Thi is calculated. Used as refrigerant temperature. Moreover, about the refrigerant | coolant pressure, since the utilization side heat exchanger 52 is connected to the discharge side of the compressor 21, in this embodiment, it compresses based on the compressor discharge pressure Pd or the compressor discharge pressure Pd. The pressure calculated in consideration of the pressure loss from the discharge side of the machine 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.

  When detecting the refrigerant temperature in the utilization unit 5 during the heating stop, the opening degree of the utilization side expansion mechanism 51 is increased to a second opening degree slightly larger than the stop opening degree in order to improve 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. Here, the second opening is smaller than the first opening in the discharge temperature upper limit control.

  Then, the refrigerant temperature and refrigerant pressure thus detected are converted into refrigerant density, and the refrigerant stagnation amount Ms is calculated based on the volume of the equipment constituting the use side refrigerant circuit 10b of the use unit 5 and the density of this refrigerant. Calculate.

  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 on the basis of the necessary refrigerant circulation amount in accordance with the total refrigerant amount enclosed in the refrigerant circuit 10 and the operating conditions of the air conditioner 1.

  When 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 use side expansion mechanism 51 of the use unit 5 during the heating stop is set to the current state. A predetermined opening increment is opened from the 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. Further, the opening increment may be a constant value, or may be a value that is variable according to a 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 that has stopped heating is returned to the flow path portion in which 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, the process of step S9 is performed. If the refrigerant stagnation amount Ms exceeds the refrigerant stagnation amount allowable value Msa, the opening of the use side expansion mechanism 51 is further opened from the current opening by a predetermined opening increment, By repeatedly performing the processes of steps S1, S6, S7, and S8, the refrigerant stagnation amount Ms becomes smaller than the refrigerant stagnation amount allowable value Msa.

  Next, in step S9, it is determined whether or not the opening degree of the use side expansion mechanism 51 of the use unit 5 during the heating stop is the stop opening degree. If the opening degree is the stop opening degree, the process directly returns to the process of step S1. When it is not the stop opening degree (that is, when the process of step S8 is performed at least once), the use side expansion mechanism 51 is closed to the stop opening degree, and the process returns to the process of step S1.

  As described above, in the present embodiment, by adopting the refrigerant stagnation amount control, the refrigerant in the refrigerant circuit 10 circulates the refrigerant stagnation in the utilization unit during the heating stop regardless of the change in the compressor discharge temperature Td. It can be gently returned to the flow channel portion. For this reason, in the present embodiment, the discharge temperature upper limit control functions only when the refrigerant circulation amount suddenly decreases to the extent that the refrigerant stagnation state in the use unit during the heating stop cannot be eliminated even by the refrigerant stagnation amount control. Therefore, the processes of steps S2 to S5 described above are hardly performed. As a result, the refrigerant stagnation amount control prevents an excessive increase in the compressor discharge temperature Td due to the refrigerant stagnation phenomenon, and the heating is stopped. It becomes possible to suppress generation | occurrence | production of the refrigerant | coolant flow noise in a utilization unit.

(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 use side heat exchangers 42 and 52 exceeds the critical pressure Pcp and is not in a gas-liquid two-phase state. Using the fact that the amount of refrigerant present in the use units 4 and 5 can be calculated from the refrigerant pressure, the refrigerant temperature and the refrigerant pressure in the use unit that is not heating among the plurality of use units 4 and 5 are calculated. On the basis of this, the refrigerant stagnation amount Ms of the utilization unit during the heating stop is calculated, and the heating stop is performed by controlling the utilization side expansion mechanism of the utilization unit during the heating stop according to the calculated refrigerant stagnation amount Ms. It is possible to prevent an excessive increase in the discharge temperature of the compressor 21 due to a shortage of the amount of refrigerant circulating in the refrigerant circuit 10 due to the refrigerant sleeping in the inside utilization unit.

  In addition, the use-side expansion mechanism is finely controlled as compared with the case where the discharge temperature upper limit control, which is the refrigerant recovery operation for recovering the refrigerant that has fallen into the use unit during the heating stop, is performed using the discharge temperature of the compressor 21 as a threshold. In addition, since it can be performed gently, it is possible to suppress the generation of refrigerant flow noise in the utilization unit during the heating stop.

(B)
In the air conditioner 1 of this embodiment, it is provided on 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, the temperature sensors 44, 45, 54, 55) is used for the calculation of the refrigerant stagnation amount Ms, the calculation accuracy of the refrigerant stagnation amount Ms can be improved.

(C)
In the air conditioning apparatus 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 use side expansion mechanism of the utilization unit while heating is stopped is controlled, the refrigerant stagnation amount Ms is calculated while causing the flow of the refrigerant in the utilization unit while heating is stopped. It becomes possible to detect the refrigerant temperature in the utilization unit during the heating stop, and the detection accuracy of the refrigerant temperature can be improved.

(4) Other Embodiments Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to these embodiments and can be changed without departing from the scope of the invention. It is.

(A)
In the above-described embodiment, the refrigerant temperatures on 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 are used for the calculation of the refrigerant stagnation amount Ms. However, when a temperature sensor is provided in the use side heat exchangers 42 and 52 themselves, the refrigerant temperature in the use side heat exchangers 42 and 52 is set to 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 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 has a configuration in which a larger number of usage units are connected to the heat source unit. May be applied. In this case, when there are a plurality of use units that are not in heating, the openings of all use-side expansion mechanisms of the use units that are in heating stop may be controlled, and the refrigerant stagnation amount Ms. You may make it control the opening degree of the utilization side expansion | swelling mechanism of a utilization unit with the largest.

  If the present invention is used, a refrigerant circuit configured by connecting a plurality of utilization units including a utilization side expansion mechanism and a utilization side heat exchanger to a heat source unit including a compressor and a heat source side heat exchanger. In an air conditioner that is capable of heating operation by refrigeration cycle operation in which the high pressure side exceeds the critical pressure of the refrigerant, and prevents an excessive increase in the discharge temperature of the compressor due to refrigerant stagnation, and heating is stopped It is possible to suppress the generation of the refrigerant flow noise in the inside usage unit.

It is a schematic block diagram of the air conditioning apparatus concerning one Embodiment of this invention. FIG. 3 is a pressure-enthalpy diagram illustrating a refrigeration cycle. It is a flowchart of discharge temperature upper limit control and refrigerant stagnation amount control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 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 Usage side expansion mechanism 42, 52 Usage side heat exchanger

Claims (3)

A plurality of utilization units (4, 5) including a utilization side expansion mechanism (41, 51) and a utilization side heat exchanger (42, 52) include a compressor (21) and a heat source side heat exchanger (23). In an air conditioner having a refrigerant circuit (10) configured by being connected to a heat source unit (2) including, and capable of heating operation by a refrigeration cycle operation in which a high-pressure side becomes a pressure exceeding the critical pressure of the refrigerant ,
Based on the refrigerant temperature and the refrigerant pressure in the utilization unit that is not in heating among the plurality of utilization units, the refrigerant stagnation amount that is the amount of refrigerant that stays in the utilization unit that is in the heating suspension is calculated, and the refrigerant stagnation amount is calculated. In response, control of the use side expansion mechanism of the use unit during the heating stop,
Air conditioner (1).   The refrigerant temperature is at least one of an entrance side of the use side heat exchanger (42, 52) during heating, an exit side of the use side heat exchanger during heating, and the use side heat exchanger. The air conditioner (1) according to claim 1, which is detected by a temperature sensor provided in the air conditioner.   The use during heating stop so that the refrigerant passes through the use unit during heating stop when detecting the refrigerant temperature in the use unit during heating stop used for calculating the refrigerant stagnation amount The air conditioner (1) according to claim 2, wherein the air conditioner (1) controls the use side expansion mechanism of the unit.

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