JP6540074B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner in which a plurality of indoor units are connected by refrigerant pipes to at least one outdoor unit, and more particularly to an air conditioner capable of suppressing the bias of the refrigerant in the refrigerant circuit.

  In an air conditioner having a refrigerant circuit in which an outdoor unit having a compressor, a four-way valve, an outdoor heat exchanger and an expansion valve, and an indoor unit having an indoor heat exchanger are connected by a liquid pipe and a gas pipe The refrigerant that has been discharged and flows into the heat exchanger functioning as a condenser and condenses flows into the heat exchanger functioning as an evaporator through the expansion valve, evaporates, and is sucked into the compressor again. Form a refrigeration cycle.

  In the air conditioner as described above, the refrigerant usually stays in various places of the refrigerant circuit (for example, the liquid pipe when the refrigeration cycle is operating as a heating cycle, the indoor heat exchanger of the indoor unit which is stopped) Even in the refrigerant circuit, the amount of refrigerant necessary to simultaneously exhibit the air conditioning capacity required for each indoor unit (hereinafter referred to as the air conditioning capacity except when necessary) circulates in the refrigerant circuit. The amount of refrigerant charged is determined in consideration of the amount of refrigerant remaining in the refrigerant circuit in addition to the necessary amount of refrigerant.

  However, there is a problem that the cost increases as the amount of refrigerant filled in the refrigerant circuit increases. When the refrigerant filled in the refrigerant circuit is a flammable refrigerant (for example, R32), in addition to the problem of the cost increase described above, if the refrigerant leaks into the space where the indoor unit is installed, the leakage may occur. Quantity will increase. Therefore, the refrigerant concentration in the space where the indoor unit is installed is likely to reach a concentration at which the refrigerant may be ignited.

  As a method for solving the above-mentioned problems, for example, a refrigeration cycle apparatus as described in Patent Document 1 has been proposed. The refrigeration cycle apparatus includes a compressor, a condenser for condensing a refrigerant compressed in the compressor, and a heat exchanger (hereinafter referred to as a subcooling heat exchanger) for supercooling the refrigerant flowing out of the condenser. An expansion valve for expanding the refrigerant subcooled by the subcooling heat exchanger, and an evaporator for evaporating the refrigerant expanded in the expansion valve are provided. And a refrigerating cycle device has a main circuit which connects each above-mentioned composition by refrigerant piping, a bypass pipe which bypassed an expansion valve and an evaporator, and was equipped with a bypass expansion valve, and a supercooling heat exchanger is condensed The refrigerant flowing out of the condenser and flowing through the main circuit is exchanged with the refrigerant flowing through the bypass circuit to supercool the refrigerant flowing out of the condenser.

  In the case of the refrigeration cycle apparatus described in Patent Document 1, even if the refrigerant pipe (liquid pipe) connecting the condenser and the expansion valve is long, if the supercooling heat exchanger is disposed in the vicinity of the expansion valve, the condenser The refrigerant flowing out of the refrigerant gas is brought into a gas-liquid two-phase state, and the refrigerant can be made to pass through the expansion valve as a liquid phase state by being subcooled by the subcooling heat exchanger. Therefore, the amount of liquid refrigerant in the liquid pipe can be reduced, and the amount of refrigerant charged into the refrigeration cycle apparatus can be reduced.

  The above-described method of reducing the refrigerant charge using the subcooling heat exchanger is particularly effective in a so-called multi-type air conditioner in which a plurality of indoor units are connected to one outdoor unit. In the case of the multi-type air conditioner, liquid pipes connecting the indoor units and the outdoor unit are present in the same number as the indoor units, and expansion valves corresponding to the indoor units are disposed in the outdoor unit. When the refrigerant is made to flow in the liquid phase in the liquid phase by the indoor heat exchanger of each indoor unit in order to make the refrigerant passing through each expansion valve into the liquid phase during heating operation, the amount of liquid refrigerant in each liquid pipe is It will be a huge amount. Therefore, if an outdoor unit is provided with a supercooling heat exchanger corresponding to each indoor unit and arranged on the upstream side of each expansion valve, the refrigerant flowing out from each indoor unit is brought into a gas-liquid two-phase state and flows into the outdoor unit. After that, the refrigerant may be brought into a liquid phase by each subcooling heat exchanger, and the amount of liquid refrigerant in each liquid pipe can be reduced. Therefore, the amount of refrigerant charged into the multi-type air conditioner can be greatly reduced to an amount capable of simultaneously exhibiting the air conditioning capacity required for each indoor unit.

International Publication 2009/150761

  However, in the multi-type air conditioner, the amount of liquid refrigerant in the liquid pipe is reduced by setting the refrigerant flowing out from the indoor heat exchangers of the indoor units to a gas-liquid two-phase state during heating operation. In a required indoor unit (for example, an indoor unit whose air volume is set large by the user), a liquid pipe in which a gas-liquid two-phase refrigerant whose dryness is lower than that of other indoor units is connected to the indoor unit The liquid refrigerant density in this liquid pipe becomes higher than the liquid refrigerant density in the other liquid pipes, that is, the refrigerant may be biased to this liquid pipe.

  If the refrigerant is biased to a certain liquid pipe, the amount of refrigerant circulation as a whole of the air conditioner decreases. In particular, in the case of an air conditioner that is filled with only the amount of refrigerant necessary to achieve air conditioning capacity using the above-described method, that is, the excess amount of refrigerant is filled, the amount of refrigerant circulation during heating operation There was a possibility that heating capacity might be reduced in all indoor units by

  The present invention solves the above-described problems, and can prevent a decrease in air conditioning capacity during heating operation when only the minimum amount of refrigerant necessary to exert the air conditioning capacity is filled. An object of the present invention is to provide an air conditioner.

  In order to solve the above-described problems, the air conditioner according to the present invention includes a plurality of subcooling heat exchanger units in which a compressor, an outdoor heat exchanger, an outdoor expansion valve, and a subcooling heat exchanger are connected by refrigerant piping. And a main refrigerant circuit formed by connecting the same number of indoor heat exchangers as multiple subcooling heat exchanger units, and branching from between the outdoor expansion valve of each subcooling heat exchanger unit and the subcooling heat exchanger And a bypass circuit connected to the suction side of the compressor via a single subcooling expansion valve and a plurality of subcooling heat exchangers, a compressor, flow path switching means, a plurality of outdoor expansion valves, and a subcooling expansion valve And control means for controlling And, when the main refrigerant circuit operates as a heating cycle, the control means has a plurality of subcooling heat exchange inlet temperatures, which are refrigerant temperatures on the refrigerant inlet side of the plurality of subcooling heat exchangers in the main refrigerant circuit, The supercooling heat exchange outlet temperature, which is the refrigerant temperature on the refrigerant outlet side of the subcooling heat exchanger, is detected, and the heat exchange inlet and outlet that is the temperature difference between each subcooling heat exchange inlet temperature and each subcooling heat exchange outlet temperature The temperature difference is calculated, and the refrigerant that adjusts the opening degree of the plurality of outdoor expansion valves such that the difference between the maximum value and the minimum value among the plurality of heat exchange inlet and outlet temperature differences becomes smaller than a predetermined predetermined value. Perform the bias resolution step.

  According to the air conditioning apparatus of the present invention configured as described above, even if the air conditioning apparatus is filled with only the minimum amount of refrigerant necessary to exhibit the air conditioning capacity, the air conditioning capacity resulting from the bias of the refrigerant Can be prevented.

It is explanatory drawing of the air conditioning apparatus which is embodiment of this invention, (A) is a refrigerant circuit figure, (B) is a block diagram of an outdoor unit control means and an indoor unit control means. It is a flowchart explaining the process in an outdoor unit control means in embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail based on the attached drawings. As an embodiment, a multi-type air conditioner will be described as an example in which three indoor units are connected in parallel to one outdoor unit, and cooling operation or heating operation can be performed simultaneously in all the indoor units. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the spirit of the present invention.

  As shown in FIG. 1 (A), the air conditioner 1 according to this embodiment includes one outdoor unit 2 and a first liquid pipe 8a, a second liquid pipe 8b, and a third liquid pipe 8c in the outdoor unit 2. And three indoor units 5 a to 5 c connected in parallel by a gas pipe 9.

  The above components are connected as follows. One end of the first liquid pipe 8a is connected to the first liquid side closing valve 28a of the outdoor unit 2 and the other end is connected to the closing valve 53a of the indoor unit 5a, and one end of the second liquid pipe 8b is the second of the outdoor unit 2 The other end is connected to the liquid side shutoff valve 28b and the other end is connected to the shutoff valve 53b of the indoor unit 5b, one end of the third liquid pipe 8c is connected to the third liquid side shutoff valve 28c of the outdoor unit 2, and the other end is connected to the indoor unit 5c. Each is connected to the closing valve 53c. Further, one end of the gas pipe 9 is connected to the gas side closing valve 29 of the outdoor unit 2 and the other end is branched to be connected to the closing valves 54a to 54c of the indoor units 5a to 5c. Thus, the outdoor unit 2 and the indoor units 5a to 5c are connected by the first liquid pipe 8a, the second liquid pipe 8b, the third liquid pipe 8c, and the gas pipe 9, and the refrigerant circuit of the air conditioner 1 10 are configured. The portion of the refrigerant circuit 10 excluding a bypass circuit described later is the main refrigerant circuit in the present invention.

  First, the outdoor unit 2 will be described with reference to FIG. The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, a first subcooling heat exchanger unit 30a, a second subcooling heat exchanger unit 30b, and a third subcooling heat exchange. Unit 30c, the subcooling expansion valve 26, the outdoor fan 27, a first closing valve 28a having one end connected to the first liquid pipe 8a, and a second closing valve having one end connected to the second liquid pipe 8b. 28 b, a third closing valve 28 c whose one end is connected to the third liquid pipe 8 c, a gas side closing valve 29 whose one end is connected to a gas pipe, and an outdoor unit control means 200. Then, the respective units other than the outdoor fan 27 and the outdoor unit control means 200 are mutually connected by respective refrigerant pipes which will be described in detail below, and constitute an outdoor unit refrigerant circuit 20 which forms a part of the refrigerant circuit 10 .

  The compressor 21 is a variable capacity compressor that can change its operating capacity by being driven by a motor (not shown) whose rotational speed is controlled by an inverter. The refrigerant discharge side of the compressor 21 is connected to a port a of a four-way valve 22 described later by a discharge pipe 41. The refrigerant suction side of the compressor 21 is connected to a port c of a four-way valve 22 described later by a suction pipe 42.

  The four-way valve 22 is a valve for switching the flow direction of the refrigerant, and has four ports a, b, c, d. The port a is connected to the refrigerant discharge side of the compressor 21 by a discharge pipe 41. The port b is connected to one refrigerant inlet / outlet of the outdoor heat exchanger 23 by a refrigerant pipe 43. The port c is connected to the refrigerant suction side of the compressor 21 by a suction pipe 42. The port d is connected to the gas-side shutoff valve 29 by the outdoor unit gas pipe 44.

  The outdoor heat exchanger 23 exchanges heat between the outside air taken into the interior of the outdoor unit 2 from the suction port (not shown) by rotation of the outdoor fan 27 described later and the refrigerant. One refrigerant inlet / outlet of the outdoor heat exchanger 23 is connected to the port b of the four-way valve 22 by the refrigerant pipe 43 as described above, and one end of the outdoor unit liquid pipe 45 is connected to the other refrigerant inlet / outlet. The outdoor heat exchanger 23 functions as a condenser when the refrigerant circuit 10 is in the cooling cycle, and functions as an evaporator when the refrigerant circuit 10 is in the heating cycle.

  The other end of the outdoor unit liquid pipe 45 is connected to one end of a first liquid dividing pipe 46a, one end of a second liquid dividing pipe 46b, and one end of a third liquid dividing pipe 46c. The other end of the first liquid dividing pipe 46a is connected to the first liquid side closing valve 28a, and the other end of the second liquid dividing pipe 46b is connected to the second liquid side closing valve 28b, and the other end of the third liquid dividing pipe 46c Is connected to the third liquid side closing valve 28c.

  In the first liquid distribution pipe 46a, a first outdoor expansion valve 24a and a first supercooling heat exchanger 25a are provided in order from the outdoor heat exchanger 23 toward the first liquid side closing valve 28a. A first subcooling heat exchanger unit 30a is configured by the first liquid dividing pipe 46a, the first outdoor expansion valve 24a, and the first subcooling heat exchanger 25a. Further, a second outdoor expansion valve 24b and a second subcooling heat exchanger 25b are provided in order from the outdoor heat exchanger 23 to the second liquid side shut-off valve 28b in the second liquid distribution pipe 46b. A second subcooling heat exchanger unit 30b is configured by the second liquid dividing pipe 46b, the second outdoor expansion valve 24b, and the second subcooling heat exchanger 25b. Furthermore, a third outdoor expansion valve 24c and a third subcooling heat exchanger 25c are provided in order from the outdoor heat exchanger 23 to the third liquid side closing valve 28c in the third liquid distribution pipe 46c. A third subcooling heat exchanger unit 30c is configured by the third liquid dividing pipe 46c, the third outdoor expansion valve 24c, and the third subcooling heat exchanger 25c.

  One end of a first bypass pipe 47a is connected between the first outdoor expansion valve 24a and the first subcooling heat exchanger 25a in the first liquid distribution pipe 46a. One end of a second bypass pipe 47b is connected between the second outdoor expansion valve 24b and the second subcooling heat exchanger 25b in the second liquid branch pipe 46b. One end of a third bypass pipe 47c is connected between the third outdoor expansion valve 24c and the third subcooling heat exchanger 25c in the third liquid branch pipe 46c. The other end of the first bypass pipe 47a, the other end of the second bypass pipe 47b, and the other end of the third bypass pipe 47c are connected to one end of the inflow pipe 48 provided with the subcooling expansion valve 26. There is.

  The first bypass pipe 47 a is provided with a first check valve 11 a that allows the refrigerant to flow only in the direction toward the subcooling expansion valve 26. The second bypass pipe 47 b is provided with a second check valve 11 b that allows the refrigerant to flow only in the direction toward the subcooling expansion valve 26. The third bypass pipe 47 c is provided with a third check valve 11 c that allows the refrigerant to flow only in the direction toward the subcooling expansion valve 26.

  Each of the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchanger 25c is a micro formed by laminating metal foils having flow paths formed by etching. It is a flow path heat exchanger. In general, the microchannel heat exchanger can be miniaturized because it has a high heat transfer performance compared to a plate-type heat exchanger or a double-pipe heat exchanger, and a plurality of subcoolings as in the present embodiment. If it employ | adopts to the outdoor unit 2 which needs to provide a heat exchanger, the enlargement of the outdoor unit 2 can be prevented.

  In the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchanger 25c, two refrigerant channels are arranged in parallel, and flow through these two refrigerant channels. The refrigerants exchange heat with each other. One flow path of each of the subcooling heat exchangers 25a to 25c constitutes a part of the first liquid dividing pipe 46a, the second liquid dividing pipe 46b, and the third liquid dividing pipe 46c. Further, one end of each of the other flow paths of the subcooling heat exchangers 25 a to 25 c is connected to the inflow pipe 48, and the other end of each is connected to the outflow pipe 49. The other end of the outflow pipe 49 is connected to the suction pipe 42.

  The first outdoor expansion valve 24a, the second outdoor expansion valve 24b, the third outdoor expansion valve 24c, and the subcooling expansion valve 26 are each an electronic expansion valve. By adjusting the opening degree of the first outdoor expansion valve 24a, the amount of refrigerant flowing through the indoor heat exchanger 51a of the indoor unit 5a described later and the amount of refrigerant flowing through the first subcooling heat exchanger 25a are adjusted. By adjusting the opening degree of the second outdoor expansion valve 24b, the amount of refrigerant flowing through the indoor heat exchanger 51b of the indoor unit 5b described later and the amount of refrigerant flowing through the second subcooling heat exchanger 25b are adjusted. By adjusting the opening degree of the third outdoor expansion valve 24c, the amount of refrigerant flowing through the indoor heat exchanger 51c of the indoor unit 5c described later and the amount of refrigerant flowing through the third subcooling heat exchanger 25c are adjusted.

  By adjusting the opening degree of the supercooling expansion valve 26, the first bypass pipe 47a and the first check valve 11a are branched from each of the first liquid dividing pipe 46a, the second liquid dividing pipe 46b and the third liquid dividing pipe 46c. It flows to the inflow pipe 48 via the second bypass pipe 47b and the second check valve 11b, the third bypass pipe 47c and the third check valve 11c, respectively, and from the inflow pipe 48 to the first supercooling heat exchanger 25a, the second The amount of refrigerant flowing out to the outflow pipe 49 after heat exchange with the refrigerant flowing in each liquid dividing pipe in each of the subcooling heat exchangers after flowing into the subcooling heat exchanger 25b and the third subcooling heat exchanger 25c Adjust. The first bypass pipe 47a, the second bypass pipe 47b, the third bypass pipe 47c, the first check valve 11a, the second check valve 11b, the third check valve 11c, and the inflow described above The bypass circuit of the present invention is constituted by the pipe 48, the outflow pipe 49, the subcooling expansion valve 26, and the refrigerant flow paths of the respective subcooling heat exchangers connected to the inflow pipe 48 and the outflow pipe 49. .

  The outdoor fan 27 is formed of a resin material and disposed in the vicinity of the outdoor heat exchanger 23. The outdoor fan 27 is rotated by a fan motor (not shown) to take in the outside air from the suction port (not shown) into the interior of the outdoor unit 2 and exchange the heat with the refrigerant in the outdoor heat exchanger 23 from the outlet (not shown) Release to the outside of 2.

  In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, the discharge pipe 41 has a high pressure sensor 31 for detecting a discharge pressure which is a pressure of the refrigerant discharged from the compressor 21 and a temperature of the refrigerant discharged from the compressor 21. A discharge temperature sensor 33 for detecting the discharge temperature is provided. The suction pipe 42 has a low pressure sensor 32 for detecting a suction pressure which is a pressure of the refrigerant sucked into the compressor 21, and a suction temperature sensor 34 for detecting a suction temperature which is a temperature of the refrigerant sucked into the compressor 21. Is provided.

  The outdoor heat exchanger 23 is provided with an outdoor heat exchange temperature sensor 35 that detects the temperature of the outdoor heat exchanger 23. The outdoor unit liquid pipe 45 is provided with a heat exchange fluid side sensor 36 for detecting the temperature of the refrigerant flowing into the outdoor heat exchanger 23 or flowing out of the outdoor heat exchanger 23.

  A first refrigerant temperature sensor 37a for detecting the temperature of the refrigerant flowing through the first liquid dividing pipe 46a between the first subcooling heat exchanger 25a and the first liquid side closing valve 28a in the first liquid dividing pipe 46a Is provided. A second refrigerant temperature sensor 37b that detects the temperature of the refrigerant flowing through the second liquid dividing pipe 46b between the second subcooling heat exchanger 25b and the second liquid side shut-off valve 28b in the second liquid dividing pipe 46b. Is provided. A third refrigerant temperature sensor 37c that detects the temperature of the refrigerant flowing through the third liquid dividing pipe 46c between the third subcooling heat exchanger 25c and the third liquid side shut-off valve 28c in the third liquid dividing pipe 46c. Is provided.

  Between the first outdoor expansion valve 24a and the first subcooling heat exchanger 25a in the first liquid branch pipe 46a, there is a first liquid temperature sensor 38a for detecting the temperature of the refrigerant flowing through the first liquid branch pipe 46a. It is provided. Between the second outdoor expansion valve 24b and the second subcooling heat exchanger 25b in the second liquid branch pipe 46b, there is a second liquid temperature sensor 38b that detects the temperature of the refrigerant flowing through the second liquid branch pipe 46b. It is provided. Between the third outdoor expansion valve 24c and the third subcooling heat exchanger 25c, there is provided a third liquid temperature sensor 38c that detects the temperature of the refrigerant flowing through the third liquid dividing pipe 46c.

  The inflow pipe 48 is provided with an inflow temperature sensor 39 for detecting a subcooling heat AC input temperature which is a temperature of the refrigerant flowing into the first subcooling heat exchanger 25a. Further, the outflow pipe 49 is provided with an outflow temperature sensor 40 for detecting a temperature of the subcooling heat AC which is the temperature of the refrigerant flowing out of the first subcooling heat exchanger 25a. Further, an outside air temperature sensor 100 for detecting the temperature of outside air flowing into the outdoor unit 2, that is, the outside air temperature, is provided in the vicinity of a suction port (not shown) of the outdoor unit 2.

  In addition, the outdoor unit 2 is provided with an outdoor unit control means 200. The outdoor unit control means 200 is mounted on a control board stored in an electrical equipment box (not shown) of the outdoor unit 2, and as shown in FIG. 1B, the CPU 210, the storage unit 220, the communication unit 230 and Is equipped.

  The storage unit 220 is composed of a ROM and a RAM, and detects detected values corresponding to control programs of the outdoor unit 2 and detection signals from various sensors, control states of the compressor 21 and the outdoor fan 27, various tables to be described later Remember. The communication unit 230 is an interface that communicates with the indoor units 5a to 5c.

  The CPU 210 takes in detection values from various sensors, and also transmits an operation information signal including operation start / stop signals and operation information (set temperature, indoor temperature, etc.) transmitted from the indoor units 5a to 5c via the communication unit 230. Input. The CPU 210 controls the opening degree of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, the third outdoor expansion valve 24c, and the supercooling expansion valve 26 based on the various detected values taken in and the input various information. Also, drive control of the compressor 21 and the outdoor fan 27 and switching control of the four-way valve 22 are performed.

  Next, the three indoor units 5a to 5c will be described. The three indoor units 5a to 5c are connected to the indoor heat exchangers 51a to 51c, the first liquid pipe 8a, the second liquid pipe 8b, and the third liquid pipe 8c, and the liquid side shut-off valves 53a to 53c and a branch The gas side shut-off valves 54a-54c to which the other end of the gas pipe 9 was each connected, indoor fans 55a-55c, and indoor unit control means 500a-500c are provided. Then, the indoor unit refrigerant circuit 50a to a part of the refrigerant circuit 10 are connected to one another by respective refrigerant pipes described below in detail, except for the indoor fans 55a to 55c and the indoor unit control means 500a to 500c. It constitutes 50c.

  Since all the configurations of the indoor units 5a to 5c are the same, in the following description, only the configuration of the indoor unit 5a will be described, and the descriptions of the other indoor units 5b and 5c will be omitted. Further, in FIG. 1 (A), the constructions of the indoor units 5b and 5c corresponding to the constituent units of the outdoor unit 5a are obtained by changing the end of the numbers given to the constituent units of the indoor unit 5a from a to b and c, respectively. It becomes an apparatus.

  The indoor heat exchanger 51a exchanges heat with indoor air taken into the interior of the indoor unit 5a from a suction port (not shown) provided in the indoor unit 5a by rotation of the refrigerant and an indoor fan 55a described later. The refrigerant inlet / outlet is connected to the liquid side shut-off valve 53a by the indoor unit liquid pipe 71a, and the other refrigerant inlet / outlet is connected to the gas side shut-off valve 54a by the indoor unit gas pipe 72a. The indoor heat exchanger 51a functions as an evaporator when the indoor unit 5a performs a cooling operation, and functions as a condenser when the indoor unit 5a performs a heating operation.

  The indoor fan 55a is a cross flow fan formed of a resin material disposed in the vicinity of the indoor heat exchanger 51a, and is rotated by a fan motor (not shown) to allow the indoor unit 5a to receive The air is taken in, and the indoor air heat-exchanged with the refrigerant in the indoor heat exchanger 51a is supplied to the room from a not-shown outlet provided in the indoor unit 5a.

  In addition to the configuration described above, the indoor unit 5a is provided with various sensors. The indoor heat exchanger 51a is provided with an indoor heat exchange temperature sensor 61a that detects the temperature of the indoor heat exchanger 51a. Further, an indoor temperature sensor 62a for detecting the temperature of the indoor air flowing into the indoor unit 5a, that is, the indoor temperature, is provided in the vicinity of a suction port (not shown) of the indoor unit 5a.

  Further, the indoor unit 5a is provided with an indoor unit control means 500a. The control means 500a is mounted on a control board stored in a not-shown electrical component box of the indoor unit 5a, and includes a CPU 510a, a storage unit 520a, and a communication unit 530a, as shown in FIG. 1 (B). ing.

  The storage unit 520a is configured by a ROM and a RAM, and stores detection values corresponding to detection programs from the control program of the indoor unit 5a and various sensors, setting information on air conditioning operation by the user, and the like. The communication unit 530a is an interface that communicates with the outdoor unit 2 and the other indoor units 5b and 5c.

  The CPU 510a takes in detection values of various sensors, and inputs a signal including an operating condition set by operating the remote controller (not shown) by the user, a timer operation setting and the like via the remote controller light receiving unit (not shown). The CPU 510a performs drive control of the indoor fan 55a based on the various detected values taken in and the various information input. In addition, the CPU 510a transmits an operation information signal including an operation start / stop signal and operation information (such as a set temperature and an indoor temperature) to the outdoor unit 2 via the communication unit 530a.

  Next, the flow of the refrigerant and the operation of each part in the refrigerant circuit 10 at the time of the air conditioning operation of the air conditioning apparatus 1 in the present embodiment will be described using FIG. In the following description, the indoor units 5a to 5c perform the heating operation, and the detailed description of the cooling operation / defrosting operation is omitted. Moreover, the arrow in FIG. 1 (A) has shown the flow of the refrigerant | coolant at the time of heating operation.

  As shown to FIG. 1 (A), when indoor units 5a-5c perform heating operation, ie, when the refrigerant circuit 10 becomes a heating cycle, in the outdoor unit 2, the four-way valve 22 shows the state shown by a solid line, ie, , The port a and the port d of the four-way valve 22 communicate with each other, and the ports b and c communicate with each other. Thus, the outdoor heat exchanger 23 functions as an evaporator, and the indoor heat exchangers 51a to 51c function as a condenser.

  The high-pressure refrigerant discharged from the compressor 21 flows into the outdoor unit gas pipe 44 from the discharge pipe 41 through the four-way valve 22 and flows into the gas pipe 9 from the outdoor unit gas pipe 44 through the gas side shut-off valve 29. Do. The refrigerant flowing into the gas pipe 9 branches and flows into the indoor units 5a to 5c via the gas side closing valves 54a to 54c.

  The refrigerant flowing into the indoor units 5a to 5c flows through the indoor unit gas pipes 72a to 72c and flows into the indoor heat exchangers 51a to 51c. The refrigerant flowing into the indoor heat exchangers 51a to 51c exchanges heat with indoor air taken into the interior of the indoor units 5a to 5c from the suction ports (not shown) by the rotation of the indoor fans 55a to 55c and condenses. As described above, the indoor heat exchangers 51a to 51c function as a condenser, and the indoor air that has exchanged heat with the refrigerant in the indoor heat exchangers 51a to 51c is installed from the outlets (not shown) to the indoor units 5a to 5c. Each room is heated by blowing out into the room where it is located.

  The refrigerant flowing out of the indoor heat exchangers 51a to 51c flows through the indoor unit liquid pipes 71a to 71c, and the first liquid pipe 8a, the second liquid pipe 8b, and the third liquid pipe 8c flow through the liquid side shut-off valves 53a to 53c. Flow into From the first liquid pipe 8a, the second liquid pipe 8b, and the third liquid pipe 8c to the outdoor unit 2 through the first liquid side closing valve 28a, the second liquid side closing valve 28b, and the third liquid side closing valve 28c The inflowing refrigerant flows through the first liquid dividing pipe 46a, the second liquid dividing pipe 46b, and the third liquid dividing pipe 46c, and the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat It flows into the exchanger 25 c and is cooled by heat exchange with the refrigerant flowing from the inflow pipe 48 through the subcooling expansion valve 26. The refrigerant that has exchanged heat in each subcooling heat exchanger and has flowed out to the outflow pipe 49 flows through the outflow pipe 49 and flows into the suction pipe 42.

  Part of the refrigerant cooled by the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchanger 25c is a first bypass pipe 47a, a second bypass pipe 47b, and The remaining gas flows through the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c and is decompressed, and then flows into the outdoor unit liquid pipe 45. The control of the degree of opening of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, the third outdoor expansion valve 24c, and the supercooling expansion valve 26 will be described later.

  The refrigerant flowing from the outdoor unit liquid pipe 45 into the outdoor heat exchanger 23 exchanges heat with the outside air taken into the interior of the outdoor unit 2 by the rotation of the outdoor fan 27 and evaporates. The refrigerant flowing out of the outdoor heat exchanger 23 flows through the refrigerant pipe 43, flows into the four-way valve 22, flows from the four-way valve 22 to the suction pipe 42, is sucked into the compressor 21, and is compressed again.

  When the indoor units 5a to 5c perform the cooling operation or the defrosting operation, that is, when the refrigerant circuit 10 has a cooling cycle, in the outdoor unit 2, the four-way valve 22 is indicated by a broken line, that is, the four-way valve 22. Are switched so that port a and port b communicate with each other and port c and port d communicate with each other. Thus, the outdoor heat exchanger 23 functions as a condenser, and the indoor heat exchangers 51a to 51c function as an evaporator.

  Next, using FIG. 1 and FIG. 2, the first outdoor expansion valve 24 a, the second outdoor expansion valve 24 b, and the third outdoor expansion valve 24 c when the air conditioner 1 of the present embodiment is performing the heating operation. The control of the degree of opening of the subcooling degree expansion valve 26 will be described in detail.

  In the following description, the discharge pressure of the compressor 21 detected by the high pressure sensor 31 is calculated using Pd and the discharge pressure Pd, and the condensation temperature in the indoor heat exchangers 51a to 51c is Tc, and the outdoor heat exchange temperature sensor 35 The evaporation temperature in the outdoor heat exchanger 23 to be detected is Te, the discharge temperature of the compressor 21 detected by the discharge temperature sensor 33 is Td, the target discharge temperature is Tdtg, and the difference between the discharge temperature Td and the target discharge temperature Tdtg (Td The discharge temperature difference which is −Tdtg) is taken as ΔTd. The target discharge temperature Tdtg is a temperature that can prevent liquid back to the compressor 21 and can suppress an increase in the discharge temperature Td, and in the present embodiment, the condensation temperature Tc and the evaporation temperature Te Calculate using.

  In addition, the subcooling heat exchange inlet temperatures detected by the first refrigerant temperature sensor 37a / the second refrigerant temperature sensor 37b / the third refrigerant temperature sensor 37c are Tv1 / Tv2 / Tv3, the condensation temperature Tc, and the respective subcooling heat exchange inlet temperatures The difference between Tv1 / Tv2 / Tv3 (Tc-Tv1, Tc-Tv2, Tc-Tv3) is taken as the degree of supercooling SCf1 / SCf2 / SCf3, respectively.

  In addition, the subcooling heat exchange outlet temperature detected by the first liquid temperature sensor 38a / the second liquid temperature sensor 38b / the third liquid temperature sensor 38c is Tl1 / Tl2 / Tl3, and the subcooling heat exchange inlet temperature Tv1 / Tv2 / Tv3. The temperature difference (Tv1-Tl1, Tv2-Tl2, Tv3-Tl3) between and the subcooling heat exchange outlet temperature Tl1 / Tl2 / Tl3 is respectively set as the heat exchange inlet temperature difference? Tc1 /? Tc2 /? Tc3. The heat exchange inlet temperature difference ΔTc1 / ΔTc2 / ΔTc3 has the largest value as the heat exchange inlet temperature difference maximum value ΔTcmax, the smallest value as the heat exchange inlet temperature difference minimum value ΔTcmin, the heat exchange inlet temperature The average value of the differences ΔTc1 / ΔTc2 / ΔTc3 is taken as ΔTca.

  Furthermore, the subcooling heat AC input temperature detected by the inflow temperature sensor 39 is Tsi, the subcooling heat AC output temperature detected by the outflow temperature sensor 40 is Tso, and the subcooling heat AC output temperature Tso and the subcooling heat AC input temperature Tsi And the bypass superheat degree which is the difference (Tso-Tsi) from the

  If the state of the refrigerant passing through the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c is a gas-liquid two-phase state when the air conditioner 1 is performing the heating operation, When the refrigerant passes through these outdoor expansion valves, there is a possibility that the flow noise of the refrigerant may be generated, and if the refrigerant having a nonuniform ratio between the liquid phase and the gas phase passes through the outdoor expansion valves, The pressure difference between the refrigerant pressure on the refrigerant inflow side (each subcooling heat exchanger side) of each outdoor expansion valve and the refrigerant pressure on the refrigerant outflow side (the outdoor heat exchanger 23 side) becomes unstable and the heating cycle is not stable There is a risk.

  Accordingly, the state of the refrigerant passing through the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c should be a liquid phase state in which the flow noise and pressure difference of the refrigerant described above are hard to occur. Is preferred. However, when the degree of supercooling is controlled to increase at the refrigerant outlet side of each of the indoor heat exchangers 51a to 51c in order to bring the refrigerant passing through each outdoor expansion valve into a liquid phase state, each room in the refrigerant circuit 10 Between the refrigerant outlet side of the heat exchangers 51a to 51c to the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c, that is, the indoor unit liquid pipes 71a to 71c, and the first The liquid pipe 8a and the second liquid pipe 8b and the third liquid pipe 8c, and the first closing valve 28a in the first liquid dividing pipe 46a to the first outdoor expansion valve 24a, and the second closing valve 28b in the second liquid dividing pipe 46b The amount of liquid refrigerant may increase between the second outdoor expansion valve 24b and between the third closing valve 28c and the third outdoor expansion valve 24c in the third liquid distribution pipe 46c.

  And, from the refrigerant outlet side of each of the indoor heat exchangers 51a to 51c to each of the outdoor expansion valves, the amount of refrigerant necessary to exhibit the air conditioning capacity (cooling capacity and heating capacity) required by the air conditioner 1 If the refrigerant circuit 10 is filled with refrigerant in consideration of the amount of liquid refrigerant in between, the amount of refrigerant to be filled increases and the cost increases, and if the refrigerant to be filled is a flammable refrigerant, each indoor unit 5a If a refrigerant leak occurs in the space where 5c to 5c are installed, the amount of leakage may be equivalent to the concentration at which the refrigerant may be ignited.

  Therefore, when the air conditioning apparatus 1 is performing the heating operation, the degree of supercooling SCf on the refrigerant outlet side of each of the indoor heat exchangers 51a to 51c becomes a predetermined value (0 ° C. in this embodiment), By adjusting the degree of opening of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c, the first subcooling heat exchanger from the refrigerant outlet side of each of the indoor heat exchangers 51a to 51c. The state of the refrigerant between the refrigerant inlet side of each of the second subcooling heat exchanger 25b and the third subcooling heat exchanger 25c is set as a gas-liquid two-phase state (supercooling degree adjustment step described later), By adjusting the opening degree of the cooling expansion valve 26, the gas-liquid two-phase state which has flowed into each of the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchanger 25c. Of the refrigerant is cooled to a liquid state (temperature Section step).

  As described above, by adjusting the opening degree of each of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, the third outdoor expansion valve 24c, and the supercooling expansion valve 26, each indoor heat in the refrigerant circuit 10 described above Since the amount of liquid refrigerant from the refrigerant outlet side of the exchangers 51a to 51c to the refrigerant inlet side of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c decreases, each indoor It is sufficient to fill the air conditioner 1 with only the amount of refrigerant necessary to achieve the air conditioning capacity required at the same time in the units 5a to 5c, that is, without filling the air conditioner 1 with an excessive amount of refrigerant. It will be good too.

  However, when the refrigerant flowing into each liquid pipe is brought into a gas-liquid two-phase state by adjusting the opening degree of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c described above, each liquid The dryness of the refrigerant flowing through the tube can not be determined. Therefore, when a large heating capacity is required in a certain indoor unit, for example, in the case where the air volume is set large by the user in the indoor unit 5a (that is, the number of rotations of the indoor fan 55a increases), the other indoor units Since the gas-liquid two-phase refrigerant whose dryness is lower than 5b and 5c flows out from the indoor unit 5a to the first liquid pipe 8a, the liquid refrigerant density in the first liquid pipe 8a is the second liquid pipe 8 and the third liquid It becomes higher than the liquid refrigerant density in the pipe 8c. Thereby, the amount of liquid refrigerant in the first liquid pipe 8a becomes larger than the amount of liquid refrigerant in the second liquid pipe 8 and the third liquid pipe 8c, that is, the refrigerant is biased to the first liquid pipe 8a.

  As described above, when the refrigerant is biased to a certain liquid pipe, the refrigerant circulation amount in the refrigerant circuit 10 of the air conditioner 1 is reduced. In particular, only the amount of refrigerant necessary to achieve the air conditioning capacity simultaneously required by the indoor units 5a to 5c by using the above-described method is filled in the air conditioner 1 and not filled with an excessive amount of refrigerant. In this case, there is a risk that the heating capacity of all the indoor units may be reduced due to the reduction of the refrigerant circulation amount in the refrigerant circuit 10.

  Therefore, in the present invention, after performing the subcooling degree adjustment step, the respective subcooling heat exchange inlets of the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchanger 25c. The heat exchange inlet temperature difference ΔTc1 / ΔTc2 / ΔTc3, which is the temperature difference between the temperatures Tv1 / Tv2 / Tv3 and the respective subcooling heat exchange outlet temperatures Tl1 / Tl2 / Tl3, is determined, and among these, the maximum value ΔTcmax and the minimum value ΔTcmin By adjusting the opening degree of the first outdoor expansion valve 24 a to the third outdoor expansion valve 24 c so that the difference becomes a predetermined value (less than 1 ° C. in the present embodiment), the refrigerant is biased to any liquid pipe Execute the refrigerant bias cancellation step to cancel the operating condition.

  Then, after performing the refrigerant bias elimination step, the refrigerant in the gas-liquid two-phase state that has flowed into the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchanger 25c is cooled The average value ΔTca of the heat exchange inlet temperature differences ΔTc1 / ΔTc2 / ΔTc3 is determined to obtain a liquid phase state, and the average value ΔTca is in a predetermined range (in the embodiment, 2.5 ° C. or more and 3.5 ° C. The temperature difference adjustment step of adjusting the opening degree of the subcooling expansion valve 26 so as to be the following) is performed.

  Next, processing performed by the CPU 210 of the outdoor unit control means 200 when the air conditioning apparatus 1 performs the heating operation will be described using FIG. 2. At the time of heating operation, the CPU 210 performs five steps of (1) heating operation preparation step, (2) discharge temperature adjustment step, (3) supercooling degree adjustment step, (4) refrigerant bias cancellation step, and (5) temperature difference adjustment step. Perform one process.

  Hereafter, the process in connection with each step of said (1)-(5) is demonstrated in detail using FIG. In the flowchart shown in FIG. 2, ST represents a processing step, and the numbers following this represent a step number. Moreover, in FIG. 2, it demonstrates centering on the process in connection with each step of said (1)-(5), The process when the air conditioning apparatus 1 performs a cooling operation and a defrost operation, and a user's instruction | indication The description of the general processing such as control of the refrigerant circuit 10 corresponding to the operating conditions such as the set temperature and the air flow is omitted.

(1) Heating operation preparation step When the air conditioner 1 starts the heating operation, the CPU 210 switches the four-way valve 22 so that ports a and d communicate with ports b and c. The first outdoor expansion valve 24a, the second outdoor expansion valve 24b, the third outdoor expansion valve 24c, and the supercooling expansion valve 26 are set to predetermined initial opening degrees (ST1). Here, the initial opening degree of each expansion valve is obtained in advance by a test or the like and stored in the storage unit 22, and is an opening degree that can prevent the liquid back to the compressor 21. Then, the CPU 210 starts the compressor 21 and the outdoor fan 27, and transmits an operation start signal to the indoor units 5a to 5c via the communication unit 230. The CPUs 510a to 510c of the outdoor unit control means 500a to 500c that receive this signal via the communication units 530a to 530c activate the indoor fans 55a to 55c.
As described above, the outdoor unit 2 and the indoor units 5a to 5c start the operation, and the refrigerant circulates in the refrigerant circuit 1 to start the heating operation.

  The CPU 210 that has finished the processing of ST1 starts timer measurement (ST2), and proceeds to ST3.

(2) Discharge Temperature Adjustment Step Next, the CPU 210 takes in the discharge pressure Pd detected by the high pressure sensor 31 and the evaporation temperature Te detected by the outdoor heat exchange temperature sensor 35, and uses the taken discharge pressure Pd to condense temperature Tc is calculated (ST3). The CPU 210 periodically fetches the discharge pressure Pd and the evaporation temperature Te (for example, once every 30 seconds) and stores it in the storage unit 220, and stores the calculated condensation temperature Tc in the storage unit 220. ing.

  Next, the CPU 210 calculates the target discharge temperature Tdtg using the calculated condensation temperature Tc and the taken evaporation temperature Te (ST4), takes in the discharge temperature Td detected by the discharge temperature sensor 33, and calculates the discharge temperature difference ΔTd. = Td-Tdtg is calculated (ST5). The CPU 210 periodically fetches the discharge temperature Td and stores the discharge temperature Td in the storage unit 220, and also stores the calculated discharge temperature difference and ΔTd in the storage unit 220.

  Next, the CPU 210 determines whether the calculated discharge temperature difference ΔTd is -1 ° C. or more and 1 ° C. or less (ST6). If the discharge temperature difference ΔTd is −1 ° C. or more and 1 ° C. or less (ST6-Yes), the CPU 210 proceeds to ST10. If the discharge temperature difference ΔTd is not more than −1 ° C. and not more than 1 ° C. (ST6-No), the CPU 210 determines whether the discharge temperature difference ΔTd is less than −1 ° C. (ST7).

If the discharge temperature difference ΔTd is less than -1 ° C. (ST7-Yes), the CPU 210 sets the opening degree of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c to a predetermined opening degree. Decrease (ST8). If the discharge temperature difference ΔTd is not less than -1 ° C. (ST7-No), the CPU 210 sets the opening degree of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c to a predetermined opening degree. Increase (ST9). Here, reducing or increasing the predetermined opening means reducing or adding the number of pulses given to a stepping motor (not shown) provided in each outdoor expansion valve. For example, the number of pulses is determined each time the determination in ST7 is performed. 1 subtract or add As described above, the discharge temperature Td is brought close to the target discharge temperature Tdtg by adjusting the opening degree of each of the outdoor expansion valves 24a to 24c.
The CPU 210 having finished the processing of ST8 or ST9 advances the processing to ST10.

(3) Subcooling Degree Adjustment Step In ST10, the CPU 210 takes in the subcooling heat exchange inlet temperature Tv1 detected by the first refrigerant temperature sensor 37a, and subtracts the subcooling heat exchange inlet temperature Tv1 from the condensation temperature Tc calculated in ST3. The degree SC21 of subcooling at the refrigerant inlet side of the first subcooling heat exchanger 25a is calculated. Further, the CPU 210 takes in the subcooling heat exchange inlet temperature Tv2 detected by the second refrigerant temperature sensor 37b, subtracts the subcooling heat exchange inlet temperature Tv2 from the condensation temperature Tc calculated in ST3, and reduces the second subcooling heat exchanger 25b. The degree of subcooling SCf2 at the refrigerant inlet side of the Furthermore, the CPU 210 takes in the subcooling heat exchange inlet temperature Tv3 detected by the third refrigerant temperature sensor 37c and subtracts the subcooling heat exchange inlet temperature Tv3 from the condensation temperature Tc calculated in ST3 to obtain a third subcooling heat exchanger The degree of subcooling SCf3 at the refrigerant inlet side of 25c is calculated. The CPU 210 stores the calculated subcooling degrees SCf1 to SCf3 in the storage unit 220.

Next, the CPU 210 determines whether all the calculated subcooling degrees SCf1 to SCf3 are 0 ° C. (ST11). If all the subcooling degrees SCf are 0 ° C. (ST11-Yes), the CPU 210 proceeds to ST13. If any one or two of the subcooling degree SCf is not 0 ° C. (ST11-No), the CPU 210 determines that the first subcooling heat exchanger 25a does not have a subcooling degree SCf of 0 ° C., and the second subcooling The opening degrees of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c respectively corresponding to the heat exchanger 25b and the third subcooling heat exchanger 25c are respectively increased by a predetermined opening degree (ST12). Here, to increase the predetermined opening means to add the number of pulses given to the stepping motor (not shown) provided in each outdoor expansion valve as in ST9, for example, every time the determination in ST11 is performed once Add one. By adjusting the opening degree of each of the outdoor expansion valves 24a to 24c in this manner, the refrigerant flowing out of each of the indoor units 5a to 5c to each of the liquid pipes 8a to 8c is regarded as a gas-liquid two-phase refrigerant.
The CPU 210 that has finished the processing of ST12 advances the processing to ST13.

(4) Refrigerant bias elimination step In step ST13, the CPU 210 takes in the subcooling heat exchange inlet temperature Tv1 detected by the first refrigerant temperature sensor 37a and the subcooling heat exchange outlet temperature Tl1 detected by the first liquid temperature sensor 38a. The subcooling heat exchange outlet temperature Tl1 is subtracted from the cooling heat exchange inlet temperature Tv1 to calculate the heat exchange inlet / outlet temperature difference ΔTc1 in the first subcooling heat exchanger 25a. Further, the CPU 210 takes in the subcooling heat exchange inlet temperature Tv2 detected by the second refrigerant temperature sensor 37b and the subcooling heat exchange outlet temperature Tl2 detected by the second liquid temperature sensor 38b. The heat exchange inlet / outlet temperature difference ΔTc2 in the second subcooling heat exchanger 25b is calculated by subtracting the cooling heat exchange outlet temperature Tl2. Furthermore, the CPU 210 takes in the subcooling heat exchange inlet temperature Tv3 detected by the third refrigerant temperature sensor 37c and the subcooling heat exchange outlet temperature Tl3 detected by the third liquid temperature sensor 38c, from the subcooling heat exchange inlet temperature Tv3. The subcooling heat exchange outlet temperature Tl3 is reduced to calculate the heat exchange inlet / outlet temperature difference ΔTc3 in the third subcooling heat exchanger 25c.

  Next, the CPU 210 calculates the maximum value of the heat exchange inlet temperature difference among the calculated heat exchange inlet temperature differences ΔTc1 to ΔTc3 as the maximum value ΔTcmax of the heat exchange inlet temperature difference, and the minimum value of the heat exchange inlet temperature difference as the minimum value ΔTcmin of the heat exchange inlet temperature difference. While assuming it, average value (DELTA) Tca of heat exchange entrance temperature difference (DELTA) Tc1- (DELTA) Tc3 is calculated (ST14). The CPU 210 stores the maximum value ΔTcmax, the minimum value ΔTcmin, and the calculated average value ΔTca in the storage unit 220.

  Next, the CPU 210 determines whether the difference (ΔTcmax−ΔTcmin) between the maximum value ΔTcmax and the minimum value ΔTcmin is less than 1 ° C. (ST15). This condition (.DELTA.Tcmax-.DELTA.Tcmin <1.degree. C.) is obtained by conducting a test in advance and stored in the storage unit 220. The refrigerant is stored in any of the first liquid pipe 8a to the third liquid pipe 8c. It is a condition that can be judged not to be biased.

If the difference between the maximum value ΔTcmax and the minimum value ΔTcmin is less than 1 ° C. (ST15-Yes), the CPU 210 proceeds to ST18. If the difference between the maximum value ΔTcmax and the minimum value ΔTcmin is not less than 1 ° C. (ST15-No), the CPU 210 controls the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchange. Among the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c corresponding to the subcooling heat exchanger in which the heat exchange inlet / outlet temperature difference .DELTA.Tc is the maximum value .DELTA.Tcmax. The degree of opening of the outdoor expansion valve is increased by a predetermined degree (ST16). In addition, among the first subcooling heat exchanger 25a, the second subcooling heat exchanger 25b, and the third subcooling heat exchanger 25c, the subcooling heat exchanger in which the heat exchange inlet / outlet temperature difference ΔTc is the minimum value ΔTcmin. The degree of opening of any one of the corresponding first outdoor expansion valve 24a, second outdoor expansion valve 24b, and third outdoor expansion valve 24c is reduced by a predetermined degree (ST17). Here, increasing or decreasing the predetermined opening means adding or reducing the number of pulses given to a stepping motor (not shown) provided in each outdoor expansion valve as in ST8 and ST9, for example, the determination of ST15 is performed once. Add 1 pulse number for each run. By adjusting the opening degree of each of the outdoor expansion valves 24a to 24c in this manner, when the refrigerant is biased to any one of the first liquid pipe 8a to the third liquid pipe 8c, the bias is eliminated.
The CPU 210 that has finished the processing of ST17 advances the processing to ST18.

  Next, the CPU 210 determines whether or not a predetermined time has elapsed since the start of the timer operation in ST2, that is, the start of the heating operation (ST18). If the predetermined time has not elapsed (ST18-No), the CPU 210 returns the processing to ST3, and if the predetermined time has elapsed (ST18-Yes), the CPU 210 resets the timer (ST19) and returns to ST20. Proceed with the process.

  Here, the reason for determining whether to proceed to the next step or return the process to ST3 is as follows depending on whether or not a predetermined time has elapsed since the heating operation was started. In the temperature difference adjustment step of (5) performed after ST20, the opening degree adjustment of the subcooling expansion valve 26 is performed. At this time, if the opening degree of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c is large, even if the opening degree adjustment of the subcooling expansion valve 26 is performed, the second subcooling degree SCs1 to SCs1 It is difficult for SCs3 to be a value within a predetermined range. Therefore, there is a possibility that the opening degree of the subcooling expansion valve 26 may be increased more than necessary in order to set the second subcooling degrees SCs1 to SCs3 to values within the predetermined range. When the opening degree of the subcooling expansion valve 26 is made larger than necessary, there is a possibility that the second subcooling degree SCs1 to SCs3 may exceed the upper limit value of the predetermined range.

  On the other hand, since the discharge temperature difference ΔTd is less than −1 ° C. immediately after starting the heating operation, the discharge temperature difference ΔTd is −1 ° C. or more and 1 ° C. or less in the discharge temperature adjustment step of (2). The opening degree of each outdoor expansion valve is reduced until it becomes (see ST6 to ST8 described above).

  Therefore, the predetermined time until the opening degree of the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c does not affect the opening degree adjustment of the subcooling expansion valve 26 For example, 10 minutes, determined beforehand by a test or the like and stored in the storage unit 220), by repeating the processes of ST3 to ST18, the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor The opening degree of the expansion valve 24c is reduced, and the opening degree of the subcooling expansion valve 26 is adjusted, so that the second degree of subcooling SCs1 to SCs3 tends to become a value within a predetermined range.

(5) Temperature difference adjustment step In ST20, the CPU 210 determines whether the average value ΔTca of the heat exchange inlet temperature difference ΔTc calculated in ST14 is 2.5 ° C. or more and 3.5 ° C. or less. This condition (2.5.degree. C..ltoreq..DELTA.Tca.ltoreq.3.5.degree. C.) is obtained in advance by performing tests and the like and stored in the storage unit 220, and the maximum of the refrigerant bias cancellation step of (3) is obtained. In the state where the difference between the value ΔTcmax and the minimum value ΔTcmin is less than 1 ° C., the condition is that it is determined that the state of the refrigerant passing through each of the outdoor expansion valves 24a to 24c is surely in the liquid phase.

  If the average value ΔTca of the heat exchange inlet temperature difference ΔTc is 2.5 ° C. or more and 3.5 ° C. or less (ST20-Yes), the CPU 210 proceeds to ST26. If the average value ΔTca of the heat exchange inlet temperature difference ΔTc is not more than 2.5 ° C. and not more than 3.5 ° C. (ST20-No), the CPU 210 determines that the average value ΔTca of the heat exchange inlet temperature difference ΔTc is less than 2.5 ° C. It is determined whether there is any (ST21).

  If the average value ΔTca of the heat exchange inlet temperature difference ΔTc is less than 2.5 ° C. (ST21-Yes), the CPU 210 detects the supercooling heat AC input temperature Tsi detected by the inflow temperature sensor 39 and the outflow temperature sensor 40 The subcooling heat AC output temperature Tso is taken in, and the subcooling heat AC input temperature Tsi is subtracted from the subcooling heat AC output temperature Tso to calculate the bypass superheat degree SHb (ST22). The CPU 210 periodically fetches the subcooling heat AC inlet temperature Tsi and the subcooling heat AC output temperature Tso and stores it in the storage unit 220, and stores the calculated bypass superheat degree SHb in the storage unit 220. ing.

  Next, the CPU 210 determines whether the calculated bypass superheat degree SHb is less than 2 ° C. (ST23). If the bypass superheat degree SHb is less than 2 ° C. (ST23-Yes), the CPU 210 advances the processing to ST26 without adjusting the opening degree of the subcooling expansion valve 26. If the bypass superheat degree SHb is not less than 2 ° C. (ST23-No), the CPU 210 increases the opening degree of the subcooling expansion valve 26 by a predetermined opening degree (ST24). The term "increase the predetermined opening degree" means adding the number of pulses given to the stepping motor (not shown) provided in the supercooling expansion valve 26. For example, one pulse number is added each time the determination in ST23 is performed.

  The reason for determining whether the opening degree of the subcooling expansion valve 26 is to be increased based on the value of the bypass superheat degree SHb in the above-described temperature difference adjustment step is as follows. In the first subcooling heat exchanger 25a to the third subcooling heat exchanger 25c, if the opening degree of the subcooling expansion valve 26 is increased to increase the amount of refrigerant flowing through the bypass circuit, the first subcooling heat exchanger 25a to 25c In the third subcooling heat exchanger 25c, the amount of heat exchange with the refrigerant flowing in the first liquid distribution pipe 46a to the third liquid distribution pipe 46c is increased. However, if the bypass superheat degree SHb is less than a predetermined value (2 ° C. in the present embodiment), the heat exchange amount is increased even if the degree of opening of the subcooling expansion valve 26 is further increased to increase the amount of refrigerant flowing through the bypass circuit. It will not increase. In addition, if the amount of refrigerant flowing through the bypass circuit is increased and the degree of bypass superheat SHb becomes less than 2 ° C., the refrigerant having a low degree of dryness may be sucked into the compressor 21 and liquid compression may occur in the compressor 21.

  In consideration of the above problems, as described above, when the bypass superheat degree SHb is less than 2 ° C. when the average value SCsa of the second degree of subcooling is not 2.5 ° C. or more and 3.5 ° C. or less, Supercooling only when the degree of opening of the subcooling expansion valve 26 is not increased and the bypass superheat degree SHb is not less than 2 ° C when the average value SCsa of the second degree of supercooling is not 2.5 ° C or more and 3.5 ° C or less The opening degree of the expansion valve 26 is increased to adjust the average value SCsa of the second degree of subcooling to be 2.5 ° C. or more and 3.5 ° C. or less.

In ST21, if the average value ΔTca of the heat exchange inlet temperature difference ΔTc is not less than 2.5 ° C. (ST21-Yes), the CPU 210 reduces the opening degree of the subcooling expansion valve 26 by a predetermined opening degree (ST25). Proceed with the process. The term “reducing the predetermined opening” means reducing the number of pulses given to a stepping motor (not shown) provided in the supercooling expansion valve 26. For example, the number of pulses is reduced by one each time the determination in ST23 is made. In this manner, the opening degree of the subcooling expansion valve 26 is adjusted, and the average value SCsa of the second degree of subcooling is set to a value of 2.5 ° C. or more and 3.5 ° C. or less to pass through each outdoor expansion valve 24 a to 24 c. The state of the refrigerant to be
The CPU 210 that has finished the processing of ST20, ST23, ST24, and ST25 advances the processing to ST26.

In ST26, the CPU 210 determines whether or not there is an operation stop instruction to the air conditioning apparatus 1. Here, the operation stop is a case where the operation stop is instructed by the user in all the indoor units 5a to 5c. If the operation stop is instructed (ST26-Yes), the CPU 210 stops the compressor 21 and the outdoor fan 27, and the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, the third outdoor expansion valve 24c, The outdoor unit 2 is stopped with the subcooling expansion valve 26 fully closed. Further, the CPU 210 transmits an operation stop signal to the indoor units 5a to 5c via the communication unit 230. The CPUs 510a to 510c of the outdoor unit control means 500a to 500c that receive this signal via the communication units 530a to 530c stop the indoor fans 55a to 55c.
If the operation stop has not been instructed (ST26-No), the CPU 210 returns the process to ST3.

  In the embodiment described above, in the processing of ST11 to ST12, the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c are set such that all the subcooling degrees SCf become 0 ° C. The degree of opening is adjusted, but the degree of supercooling SCf such that the state of the refrigerant becomes a gas-liquid two-phase state in each liquid pipe due to the pressure loss in the first liquid pipe 8a, the second liquid pipe 8b, and the third liquid pipe 8c. If so, the first outdoor expansion valve 24a, the second outdoor expansion valve 24b, and the third outdoor expansion valve 24c such that all the subcooling degree SCf becomes a value higher than 0 ° C., for example, 1 ° C. or 2 ° C. You may adjust the opening degree of.

  Although the case where the microchannel heat exchanger in which two refrigerant channels are arranged in parallel is used as the first to third subcooling heat exchangers has been described, the two refrigerant channels are orthogonal to each other. The refrigerant may be branched and flowed from the inflow pipe 48 to the respective subcooling heat exchangers. Further, although the effects of the present invention can be obtained by using a plate type heat exchanger or a double pipe heat exchanger instead of the microchannel heat exchanger, these can be obtained from the microchannel heat exchanger and the like. The outdoor unit 2 is larger than in the case where the microchannel heat exchanger is used for the subcooling heat exchanger because the size is larger than that of the outdoor unit 2.

  Further, in the present embodiment, the degree of opening adjustment of the subcooling expansion valve 26 is adjusted so that the average value ΔTca of the heat exchange inlet temperature difference ΔTc becomes a value within a predetermined range (2.5 ° C. or more and 3.5 ° C. or less). Although the case has been described, the present invention is not limited thereto, and each heat exchange inlet temperature difference ΔTc may be either the maximum value ΔTcmax or the minimum value ΔTcmin of the heat exchange inlet temperature difference ΔTc extracted in ST14 of FIG. The opening degree adjustment of the subcooling expansion valve 26 may be performed, and the opening degree adjustment of the subcooling expansion valve 26 is adjusted so that each heat exchange inlet / outlet temperature difference ΔTc becomes a predetermined value (for example, 3 ° C.). You may go. However, when adopting a method other than the above embodiment, if the heat exchange inlet / outlet temperature difference ΔTc is set to the maximum value ΔTcmax or the minimum value ΔTcmin or a predetermined value or more, the state of the refrigerant passing through the outdoor expansion valves 24a to 24c. The condition is that it is known to be in the liquid phase state.

  Furthermore, the effects of the present invention can be obtained by using various refrigerants such as CFC refrigerant, HCFC refrigerant, fluorocarbon refrigerant such as HFC refrigerant, mixed refrigerant, etc. As the refrigerant, it is preferable to use a refrigerant having a large enthalpy difference (corresponding to the refrigeration capacity) in the condensation process. As described in the embodiment, in the present invention, the refrigerant in the gas-liquid two-phase state is made to flow out from the indoor unit so that the degree of subcooling is not taken by the indoor heat exchanger during heating operation. The difference in enthalpy decreases, and the heating capacity decreases compared to when the degree of subcooling is taken. However, if a refrigerant having a large enthalpy difference in the condensation process from the beginning is used, it becomes easy to satisfy the heating capacity required in the space where the indoor unit is installed, and the heating capacity can be secured while obtaining the effects of the present invention.

DESCRIPTION OF SYMBOLS 1 air conditioner 2 outdoor unit 5a-5c indoor unit 8a-8c 1st-3rd liquid pipe 23 outdoor heat exchanger 24a 1st outdoor expansion valve 24b 2nd outdoor expansion valve 24c 3rd outdoor expansion valve 25a 1st supercooling Heat exchanger 25b Second subcooling heat exchanger 25c Third subcooling heat exchanger 26 Subcooling expansion valve 31 High pressure sensor 32 Low pressure sensor 33 Discharge temperature sensor 34 Intake temperature sensor 35 Outdoor heat exchange temperature sensor 37a First refrigerant temperature sensor 37b second refrigerant temperature sensor 37c third refrigerant temperature sensor 38a first liquid temperature sensor 38b second liquid temperature sensor 38c third liquid temperature sensor 39 inflow temperature sensor 40 outflow temperature sensor 45 outdoor unit liquid pipe 46a first liquid dividing pipe 46b first 2 liquid distribution pipe 46c third liquid distribution pipe 47a first bypass pipe 47b second bypass pipe 47c third bypass pipe 48 inflow pipe 49 Extraction pipe 51a~51c indoor heat exchanger 61a~61c indoor heat exchange temperature sensor 71a~71c indoor liquid pipe 200 outdoor unit controller 210 CPU
220 storage unit 230 communication unit 500a to 500c indoor unit control means 510a to 510c CPU
520a to 520c storage unit 530a to 530c communication unit SCf1 to SCf3 degree of supercooling SHb bypass superheat degree Pd discharge pressure Te evaporation temperature Tc condensation temperature Td discharge temperature Tdtg target discharge temperature ΔTd discharge temperature difference Tl1 to Tl3 supercooling heat exchange outlet temperature Tv1 ~ Tv3 Supercooling heat exchange inlet temperature Tsi Supercooling heat AC input temperature Tso Supercooling heat AC output temperature ΔTc1 to ΔTc3 Heat exchange inlet temperature difference ΔTcmax Heat exchange inlet temperature difference maximum value ΔTcmin Heat exchange inlet temperature difference minimum value ΔTca Average value of crossing inlet temperature difference

Claims (8)

A plurality of subcooling heat exchanger units in which a compressor, an outdoor heat exchanger, an outdoor expansion valve and a subcooling heat exchanger are connected by refrigerant piping, and the same number of indoors as the plurality of subcooling heat exchanger units A main refrigerant circuit formed by connecting a heat exchanger,
The compressor is branched from between the outdoor expansion valve and the subcooling heat exchanger of each of the subcooling heat exchanger units, and the compressor is connected via a single subcooling expansion valve and the plurality of subcooling heat exchangers. A bypass circuit connected to the suction side of the
The compressor, before Symbol plurality of the outdoor expansion valve, and a control means for controlling the subcooling expansion valve,
An air conditioner having
When the main refrigerant circuit operates as a heating cycle, the control means operates as follows:
Subcooling heat exchange inlet temperature, which is the refrigerant temperature on the refrigerant inlet side of the plurality of subcooling heat exchangers in the main refrigerant circuit, and refrigerant temperature on the refrigerant outlet side of the plurality of subcooling heat exchangers in the main refrigerant circuit And detecting the temperature difference between the heat transfer inlet and the outlet, which is a temperature difference between the temperature of each of the supercooling heat exchanger and the temperature of the outlet of the supercooling heat exchanger, Performing a refrigerant bias elimination step of adjusting the opening degree of the plurality of outdoor expansion valves such that the difference between the maximum value and the minimum value of the inlet / outlet temperature difference is smaller than a predetermined value determined in advance;
An air conditioner characterized by The control means is configured to set the opening degree of the subcooling expansion valve such that the heat exchange inlet / outlet temperature difference becomes a heat exchange inlet / outlet temperature difference indicating that the refrigerant flowing through the plurality of outdoor expansion valves is in a liquid phase. Further perform a temperature difference adjustment step to adjust the
The air conditioning apparatus according to claim 1, wherein the air conditioning apparatus comprises: In the temperature difference adjustment step,
Adjusting the opening degree of the subcooling expansion valve such that an average value of the plurality of heat exchange inlet / outlet temperature differences becomes a value within a predetermined predetermined range;
Air conditioner according to 請 Motomeko 2 you wherein a. In the temperature difference adjustment step,
The plurality of heat exchange inlet / outlet temperature differences become the maximum value or the minimum value among the plurality of heat exchange inlet / outlet temperature differences after the average value becomes a value within a predetermined predetermined range. Adjust the opening degree of the subcooling expansion valve,
The air conditioner according to claim 3 , wherein In the temperature difference adjustment step,
Adjusting the opening degree of the subcooling expansion valve such that the plurality of heat exchange inlet / outlet temperature differences become predetermined predetermined values;
Air conditioner according to 請 Motomeko 2 you wherein a. The plurality of subcooling heat exchanger units are adjusted by adjusting the degree of opening of the plurality of outdoor expansion valves and setting the degree of refrigerant supercooling on the refrigerant outlet side of the plurality of indoor heat exchangers to a predetermined value. Performing a degree of supercooling adjustment step of bringing a refrigerant flowing in a refrigerant pipe connecting the plurality of indoor heat exchangers into a gas-liquid two-phase state;
The air conditioning apparatus according to any one of claims 1 to 5, wherein The plurality of subcooling heat exchangers are configured of microchannel heat exchangers,
The air conditioning apparatus according to any one of claims 1 to 6, wherein     The air conditioner according to any one of claims 1 to 7, wherein R32 is used as the refrigerant flowing through the main refrigerant circuit and the bypass circuit.

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