JP2017156003A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner that allows refrigerator oil stagnating in an indoor machine in heating operation together with a liquid refrigerant to flow out of the indoor machine when an outdoor machine is installed at a position higher than a plurality of indoor machines.SOLUTION: A CPU 210 determines whether there is an indoor machine such that a refrigerant supercooling degree SC is equal to or larger than a liquid refrigerant stagnation-time supercooling degree SCp. On determining that there is an indoor machine such that a refrigerant supercooling degree SC is equal to or larger than a liquid refrigerant stagnation-time supercooling degree SCp, the CPU 210 starts measuring a liquid refrigerant stagnation time tlr which is a time for which the refrigerant supercooling degree SC is equal to or larger than the liquid refrigerant stagnation-time supercooling degree SCp, and determines whether the time reaches or exceeds a predetermined time tp. On determining that the liquid refrigerant stagnation time tlr reaches or exceeds the predetermined time tp, the CPU 210 calculates an average refrigerant supercooling degree SCv using refrigerant supercooling degrees Sc of respective indoor machines, and performs oil outflow control to adjust openings of respective indoor expansion valves so that the refrigerant supercooling degrees SC of the respective indoor machine reach the average refrigerant supercooling degree SCv.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an air conditioner in which a plurality of indoor units are connected to a refrigerant pipe by at least one outdoor unit.

  Conventionally, in an air conditioner in which a plurality of indoor units are connected to at least one outdoor unit by liquid pipes and gas pipes, the difference in height between the location of the outdoor unit and the location of each indoor unit, By controlling the refrigerant circuit in consideration of the height difference between the two, it has been proposed that each indoor unit can exhibit a sufficient air conditioning capability.

  For example, an air conditioner described in Patent Document 1 installs an outdoor unit including a compressor, a four-way valve, an outdoor heat exchanger, an outdoor fan, and an outdoor expansion valve on the ground, while the indoor heat exchanger and the indoor expansion valve And two indoor units equipped with indoor fans have a height difference (in Patent Document 1, one indoor unit on the first floor of the building and another indoor unit on the fourth floor, respectively) higher than the outdoor unit The refrigerant circuit is formed by connecting the two indoor units and the outdoor unit with refrigerant piping.

  When performing cooling operation with this air conditioner, the liquid refrigerant condensed in the outdoor unit and flowing into the liquid pipe from the outdoor unit flows into each indoor unit against the gravity, so the indoor unit installed at a high position The pressure of the liquid refrigerant on the upstream side (outdoor unit side) of the expansion valve is lower than the pressure of the liquid refrigerant on the upstream side of the indoor expansion valve of the indoor unit installed at a low position. For this reason, the indoor expansion of the indoor unit installed at a low position is the difference between the refrigerant pressure upstream of the indoor expansion valve of the indoor unit installed at a high position and the refrigerant pressure downstream (the indoor heat exchanger side). It becomes smaller than the pressure difference between the refrigerant pressure upstream of the valve and the refrigerant pressure downstream. The smaller the pressure difference between the upstream side and the downstream side of the indoor expansion valve, the smaller the amount of refrigerant flowing through the indoor expansion valve. Therefore, more refrigerant flows to the indoor unit installed in the lower position, while it is installed in the higher position. There is a possibility that the amount of refrigerant flowing to the indoor unit decreases and sufficient cooling capacity cannot be obtained.

  Therefore, in the air conditioner of Patent Document 1, the opening degree of the indoor expansion valve of the indoor unit installed at a low position is made smaller than the opening degree of the indoor expansion valve of the indoor unit installed at a high position by a predetermined opening degree. Thus, the refrigerant flow rate in the indoor unit installed at the low position is decreased, and the refrigerant flow rate in the indoor unit installed at the high position is increased. Thereby, while the outdoor unit is installed on the ground, even if the air conditioner is installed in a place where the two indoor units are higher than the outdoor unit with a height difference, the indoor unit installed at a high position is sufficient. Can demonstrate cooling capacity.

JP-A-4-28970

  By the way, unlike the air conditioner of Patent Document 1, when each indoor unit is installed with a height difference, and when the outdoor unit performs a heating operation with an air conditioner installed at a position higher than each indoor unit, There were the following problems.

  In the heating operation, the gas refrigerant discharged from the compressor flows into the indoor heat exchanger of each indoor unit and condenses, but the liquid refrigerant condensed in the indoor heat exchanger and flowing into the liquid pipe is installed at a high position. Since the air flows toward the outdoor unit against the gravity, the indoor unit installed at a lower position, the liquid refrigerant flowing out from the indoor unit to the liquid pipe is less likely to flow toward the outdoor unit. Thereby, the pressure of the liquid refrigerant on the downstream side (outdoor unit side) of the indoor expansion valve of the indoor unit installed at the low position is the pressure of the liquid refrigerant on the downstream side of the indoor expansion valve of the indoor unit installed at the high position. Higher than. Therefore, the indoor expansion valve of the indoor unit installed at a position where the pressure difference between the refrigerant pressure on the upstream side (indoor heat exchanger side) and the refrigerant pressure on the downstream side of the indoor expansion valve of the indoor unit installed at a low position is high. The pressure difference between the refrigerant pressure on the upstream side and the refrigerant pressure on the downstream side becomes smaller.

  The smaller the pressure difference between the refrigerant pressure upstream of the indoor expansion valve and the refrigerant pressure downstream, the smaller the amount of refrigerant flowing through the indoor expansion valve, so that more refrigerant flows to the indoor unit installed at a high position, The amount of refrigerant flowing to the indoor unit installed at a low position decreases. In particular, when the height difference between an indoor unit installed at a low position and an indoor unit installed at a high position is large, the refrigerant pressure on the upstream side of the indoor expansion valve of the indoor unit installed at a low position and the downstream side The pressure difference from the refrigerant pressure becomes almost zero, and the liquid refrigerant does not flow from the indoor unit toward the outdoor unit, that is, the liquid refrigerant stays in the indoor unit. In this case, since the refrigerating machine oil discharged from the compressor together with the refrigerant and flowing into the indoor unit installed at a low position together with the refrigerant stays with the liquid refrigerant in the indoor unit, the amount of refrigerating machine oil returning to the compressor is reduced and compressed. The machine could become poorly lubricated.

  The present invention solves the above-described problems, and when the outdoor unit is installed at a position higher than the plurality of indoor units, the refrigerating machine oil staying with the liquid refrigerant in the indoor unit during the heating operation is supplied to the indoor unit. An object of the present invention is to provide an air conditioner that flows out of a machine.

  In order to solve the above problems, an air conditioner according to the present invention includes an outdoor unit having a compressor and a discharge pressure detecting means for detecting a discharge pressure that is a pressure of a refrigerant discharged from the compressor, and an indoor heat exchange. A plurality of indoor units having liquid side temperature detecting means for detecting a heat exchange outlet temperature which is a temperature of a refrigerant flowing out of the indoor heat exchanger when the condenser, the indoor expansion valve and the indoor heat exchanger function as a condenser The outdoor unit is installed above the plurality of indoor units, and the installation locations of the plurality of indoor units have a height difference. And when the indoor heat exchanger is functioning as a condenser, the indoor unit in which the oil retention condition which shows that the refrigerating machine oil discharged with the refrigerant | coolant from the compressor is retaining in several indoor units is hold | maintained If there is, the refrigerant subcooling degree of each indoor unit becomes the average refrigerant subcooling degree obtained using the maximum and minimum values of the refrigerant subcooling degree, or the heat exchange outlet temperature of each indoor unit is hot. Control means for performing oil outflow control for adjusting the opening degree of each indoor expansion valve so as to obtain an average heat exchange outlet temperature obtained using the maximum value and the minimum value of the exchange outlet temperature.

  According to the air conditioner of the present invention configured as described above, when the indoor heat exchanger functions as a condenser, that is, the refrigerating machine oil staying with the liquid refrigerant in the indoor unit during the heating operation is discharged from the indoor unit. Execute oil spill control to spill. Thereby, since sufficient quantity of freezer oil can be returned to a compressor, it can prevent that a compressor becomes poor circulation.

It is explanatory drawing of the air conditioning apparatus in 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 an installation figure of an indoor unit and an outdoor unit in an embodiment of the present invention. It is a flowchart explaining the process in the outdoor unit control part in embodiment of this invention.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As an embodiment, three indoor units installed on each floor of a building are connected in parallel to one outdoor unit installed on the roof of a building, and cooling operation or heating operation can be performed simultaneously on all indoor units An air conditioning apparatus will be described as an example. The present invention is not limited to the following embodiments, and can be variously modified without departing from the gist of the present invention.

  As shown in FIG. 1 (A) and FIG. 2, an air conditioner 1 in the present embodiment is installed on one floor of a building and on each floor of the building. Three indoor units 5 a to 5 c connected in parallel by a pipe 8 and a gas pipe 9 are provided. Specifically, the liquid pipe 8 has one end connected to the closing valve 25 of the outdoor unit 2 and the other end branched to be connected to the liquid pipe connecting portions 53a to 53c of the indoor units 5a to 5c. The gas pipe 9 has one end connected to the closing valve 26 of the outdoor unit 2 and the other end branched to be connected to the gas pipe connecting portions 54a to 54c of the indoor units 5a to 5c. The refrigerant circuit 100 of the air conditioner 1 is configured as described above.

  First, the outdoor unit 2 will be described. The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, an outdoor expansion valve 24, a closing valve 25 to which one end of the liquid pipe 8 is connected, and one end of the gas pipe 9. And a close-up valve 26, an accumulator 28 as a refrigerant reservoir, and an outdoor fan 27. These devices other than the outdoor fan 27 are connected to each other through refrigerant pipes described in detail below to constitute an outdoor unit refrigerant circuit 20 that forms part of the refrigerant circuit 100.

  The compressor 21 is a variable capacity compressor that can vary its operating capacity by being driven by a motor (not shown) whose rotation 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, and the refrigerant suction side of the compressor 21 is connected to the refrigerant outflow side of the accumulator 28 by a suction pipe 42. Has been.

  The four-way valve 22 is a valve for switching the direction in which the refrigerant flows, and includes four ports a, b, c, and d. The port a is connected to the refrigerant discharge side of the compressor 21 by the discharge pipe 41 as described above. 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 inflow side of the accumulator 28 by a refrigerant pipe 46. The port d is connected to the closing valve 26 by an outdoor unit gas pipe 45.

  The outdoor heat exchanger 23 exchanges heat between the refrigerant and outside air taken into the outdoor unit 2 by rotation of an outdoor fan 27 described later. As described above, 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, and the other refrigerant inlet / outlet is connected to the closing valve 25 by the outdoor unit liquid pipe 44.

  The outdoor expansion valve 24 is provided in the outdoor unit liquid pipe 44. The outdoor expansion valve 24 is an electronic expansion valve, and the amount of refrigerant flowing into the outdoor heat exchanger 23 or the amount of refrigerant flowing out of the outdoor heat exchanger 23 is adjusted by adjusting the opening thereof. The opening degree of the outdoor expansion valve 24 is fully opened when the air conditioner 1 is performing a cooling operation. In addition, when the air conditioner 1 is performing a heating operation, the opening temperature is controlled according to the discharge temperature of the compressor 21 detected by a discharge temperature sensor 33 described later, so that the discharge temperature has a performance upper limit value. I do not exceed it.

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

  As described above, the accumulator 28 has the refrigerant inflow side connected to the port c of the four-way valve 22 via the refrigerant pipe 46 and the refrigerant outflow side connected to the refrigerant intake side of the compressor 21 via the suction pipe 42. The accumulator 28 separates the refrigerant flowing into the accumulator 28 from the refrigerant pipe 46 into a gas refrigerant and a liquid refrigerant, and causes the compressor 21 to suck only the gas refrigerant.

  In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, a discharge pressure sensor 31 that is a discharge pressure detecting unit that detects a discharge pressure that is a pressure of a refrigerant discharged from the compressor 21 and a discharge pressure sensor 31 that discharges from the compressor 21 A discharge temperature sensor 33 for detecting the temperature of the refrigerant to be discharged is provided. Near the refrigerant inlet of the accumulator 28 in the refrigerant pipe 46, a suction pressure sensor 32 that detects the pressure of the refrigerant sucked into the compressor 21 and a suction temperature sensor 34 that detects the temperature of the refrigerant sucked into the compressor 21. And are provided.

  Between the outdoor heat exchanger 23 and the outdoor expansion valve 24 in the outdoor unit liquid pipe 44, the temperature of the refrigerant flowing into the outdoor heat exchanger 23 or the temperature of the refrigerant flowing out of the outdoor heat exchanger 23 is detected. A heat exchanger temperature sensor 35 is provided. An outdoor air temperature sensor 36 that detects the temperature of the outside air that flows into the outdoor unit 2, that is, the outside air temperature, is provided near the suction port (not shown) of the outdoor unit 2.

  The outdoor unit 2 includes an outdoor unit control means 200. The outdoor unit control means 200 is mounted on a control board stored in an electrical component box (not shown) of the outdoor unit 2. As shown in FIG. 1B, the outdoor unit control means 200 includes a CPU 210, a storage unit 220, a communication unit 230, and a sensor input unit 240.

  The storage unit 220 includes a ROM and a RAM, and stores a control program for the outdoor unit 2, detection values corresponding to detection signals from various sensors, control states of the compressor 21 and the outdoor fan 27, and the like. The communication unit 230 is an interface that performs communication with the indoor units 5a to 5c. The sensor input unit 240 captures detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 210.

  CPU210 takes in the detection result in each sensor of outdoor unit 2 mentioned above via sensor input part 240. FIG. In addition, the CPU 210 takes in control signals transmitted from the indoor units 5 a to 5 c via the communication unit 230. The CPU 210 performs drive control of the compressor 21 and the outdoor fan 27 based on the detection results and control signals taken in. In addition, the CPU 210 performs switching control of the four-way valve 22 based on the detection results and control signals taken in. Furthermore, the CPU 210 adjusts the opening degree of the outdoor expansion valve 24 based on the acquired detection result and control signal.

  Next, the three indoor units 5a to 5c will be described. The three indoor units 5a to 5c are branched into indoor heat exchangers 51a to 51c, indoor expansion valves 52a to 52c, and liquid pipe connection portions 53a to 53c to which the other ends of the branched liquid pipes 8 are connected. Gas pipe connection parts 54a to 54c to which the other end of the gas pipe 9 is connected and indoor fans 55a to 55c are provided. And these each apparatus except indoor fan 55a-55c is mutually connected by each refrigerant | coolant piping explained in full detail below, and comprises the indoor unit refrigerant circuit 50a-50c which makes a part of refrigerant circuit 100. FIG. The three indoor units 5a to 5c all have the same capacity, and if the refrigerant supercooling degree on the refrigerant outlet side of the indoor heat exchangers 51a to 51c during the heating operation can be set to a predetermined value (for example, 10 deg) or less, The indoor unit can demonstrate sufficient heating capacity.

  In addition, since the structure of all the indoor units 5a-5c is the same, in the following description, only the structure of the indoor unit 5a is demonstrated and description is abbreviate | omitted about the other indoor units 5b and 5c. Moreover, in FIG. 1, what changed the end of the number provided to the component apparatus of the indoor unit 5a from a to b and c becomes the component apparatus of the indoor units 5b and 5c corresponding to the component apparatus of the outdoor unit 5a. .

The indoor heat exchanger 51a exchanges heat between indoor air taken into the indoor unit 5a from a suction port (not shown) by rotation of a refrigerant and an indoor fan 55a described later. 53a is connected by the indoor unit liquid pipe 71a, and the other refrigerant inlet / outlet and the gas pipe connecting part 54a are connected 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.
Note that the refrigerant pipes of the liquid pipe connecting part 53a and the gas pipe connecting part 54a are connected by welding, flare nuts, or the like.

  The indoor expansion valve 52a is provided in the indoor unit liquid pipe 71a. The indoor expansion valve 52a is an electronic expansion valve, and when the indoor heat exchanger 51a functions as an evaporator, that is, when the indoor unit 5a performs a cooling operation, the opening degree of the indoor expansion valve 52a depends on the refrigerant outlet (gas gas) of the indoor heat exchanger 51a. The refrigerant superheat degree at the pipe connecting portion 54a side) is adjusted to be the target refrigerant superheat degree. Here, the target refrigerant superheat degree is a refrigerant superheat degree for exhibiting sufficient cooling capacity in the indoor unit 5a. Further, when the indoor heat exchanger 51a functions as a condenser, that is, when the indoor unit 5a performs a heating operation, the opening of the indoor expansion valve 52a is the refrigerant outlet (liquid pipe connection portion) of the indoor heat exchanger 51a. 53a side) is adjusted so that the refrigerant subcooling degree on the refrigerant side becomes an average refrigerant subcooling degree described later.

  The indoor fan 55a is formed of a resin material and is disposed in the vicinity of the indoor heat exchanger 51a. The indoor fan 55a is rotated by a fan motor (not shown) to take indoor air from the suction port (not shown) into the indoor unit 5a, and the indoor air exchanged with the refrigerant in the indoor heat exchanger 51a from the blower outlet (not shown). Supply indoors.

  In addition to the configuration described above, the indoor unit 5a is provided with various sensors. Between the indoor heat exchanger 51a and the indoor expansion valve 52a in the indoor unit liquid pipe 71a, liquid side temperature detecting means for detecting the temperature of the refrigerant flowing into or out of the indoor heat exchanger 51a. A certain liquid side temperature sensor 61a is provided. The indoor unit gas pipe 72a is provided with a gas side temperature sensor 62a that detects the temperature of the refrigerant flowing out of the indoor heat exchanger 51a or flowing into the indoor heat exchanger 51a. Near the suction port (not shown) of the indoor unit 5a, there is provided a suction temperature sensor 63a which is a suction temperature detecting means for detecting the temperature of the indoor air flowing into the indoor unit 5a, that is, the suction temperature. In the vicinity of a blow-out opening (not shown) of the indoor unit 5a, blow-out temperature detecting means for detecting the temperature of the air discharged from the indoor unit 5a into the room by exchanging heat with the refrigerant in the indoor heat exchanger 51a, that is, the blow-out temperature. The blowout temperature sensor 64a is provided.

  The indoor unit 5a includes an indoor unit control means 500a. The indoor unit control means 500a is mounted on a control board stored in an electrical component box (not shown) of the indoor unit 5a. As shown in FIG. 1B, a CPU 510a, a storage unit 520a, a communication unit 530a, And a sensor input unit 540a.

  The storage unit 520a includes a ROM and a RAM, and stores a control program for the indoor unit 5a, detection values corresponding to detection signals from various sensors, setting information regarding 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 sensor input unit 540a captures detection results from various sensors of the indoor unit 5a and outputs them to the CPU 510a.

The CPU 510a takes in the detection result of each sensor of the indoor unit 5a described above via the sensor input unit 540a. Further, the CPU 510a takes in a signal including operation information set by operating a remote controller (not shown), a timer operation setting, and the like via a remote control light receiving unit (not shown). Further, the CPU 510a transmits a control signal including an operation start / stop signal and operation information (set temperature, indoor temperature, etc.) to the outdoor unit 2 via the communication unit 530a, and discharge pressure detected by the outdoor unit 2. A control signal including such information is received from the outdoor unit 2 via the communication unit 530a. The CPU 510a performs the opening degree adjustment of the indoor expansion valve 52a and the drive control of the indoor fan 55a based on the acquired detection result and the signal transmitted from the remote controller and the outdoor unit 2.
The outdoor unit control unit 200 and the indoor unit control units 500a to 500c described above constitute the control unit of the present invention.

  The air conditioning apparatus 1 described above is installed in a building 600 shown in FIG. Specifically, the outdoor unit 2 is arranged on the roof (RF), the indoor unit 5a is on the third floor (3F), the indoor unit 5b is on the second floor (2F), and the indoor unit 5c is on the first floor (1F), Each is installed. And the outdoor unit 2 and the indoor units 5a-5c are mutually connected by the liquid pipe 8 and the gas pipe 9 which were mentioned above, and these liquid pipe 8 and the gas pipe 9 are in the wall surface of the building 600 which is not shown in figure. Or buried in the ceiling. In FIG. 2, the height difference between the indoor unit 5a installed on the third floor, which is the top floor, and the indoor unit 5c installed on the first floor, which is the bottom floor, is represented by H.

  Next, the flow of the refrigerant and the operation of each part in the refrigerant circuit 100 during the air conditioning operation of the air-conditioning apparatus 1 in the present embodiment will be described with reference to FIG. In the following description, the case where the indoor units 5a to 5c perform the heating operation will be described, and the detailed description will be omitted when the cooling / defrosting operation is performed. Moreover, the arrow in FIG. 1 (A) has shown the flow of the refrigerant | coolant at the time of heating operation.

  As shown in FIG. 1A, when the indoor units 5a to 5c perform the heating operation, the CPU 210 of the outdoor unit control means 200 is in a state where the four-way valve 22 is indicated by a solid line, that is, the port a and the port of the four-way valve 22 Switching is performed so that d communicates and port b and port c communicate. Thereby, the refrigerant circuit 100 becomes a heating cycle in which the outdoor heat exchanger 23 functions as an evaporator and the indoor heat exchangers 51a to 51c function as condensers.

  The high-pressure refrigerant discharged from the compressor 21 flows through the discharge pipe 41 and flows into the four-way valve 22, and from the four-way valve 22 to the outdoor unit gas pipe 45, the closing valve 26, the gas pipe 9, and the gas pipe connection portions 54 a to 54 c. In this order and flow into the indoor units 5a to 5c. The refrigerant that has flowed into the indoor units 5a to 5c flows through the indoor unit gas pipes 72a to 72c, flows into the indoor heat exchangers 51a to 51c, and is taken into the indoor units 5a to 5c by the rotation of the indoor fans 55a to 55c. Heat exchanges with room air and condenses. In this way, the indoor heat exchangers 51a to 51c function as condensers, and the indoor air heated by exchanging heat with the refrigerant in the indoor heat exchangers 51a to 51c is blown into the room from a blower outlet (not shown). Thus, the room where the indoor units 5a to 5c are installed is heated.

  The refrigerant flowing out of the indoor heat exchangers 51a to 51c flows through the indoor unit liquid pipes 71a to 71c, passes through the indoor expansion valves 52a to 52c, and is decompressed. The decompressed refrigerant flows through the indoor unit liquid pipes 71a to 71c and flows into the liquid pipe 8 through the liquid pipe connection portions 53a to 53c.

  The refrigerant flowing through the liquid pipe 8 flows into the outdoor unit 2 through the closing valve 25. The refrigerant flowing into the outdoor unit 2 flows through the outdoor unit liquid pipe 44 and is further reduced in pressure when passing through the outdoor expansion valve 24 having an opening degree corresponding to the discharge temperature of the compressor 21 detected by the discharge temperature sensor 33. The The refrigerant flowing into the outdoor heat exchanger 23 from the outdoor unit liquid pipe 44 evaporates by exchanging heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27. The refrigerant flowing out of the outdoor heat exchanger 23 flows in the order of the refrigerant pipe 43, the four-way valve 22, the refrigerant pipe 46, the accumulator 28, and the suction pipe 42, and is sucked into the compressor 21 and compressed again.

  When the indoor units 5a to 5c perform the cooling / defrosting operation, the CPU 210 indicates that the four-way valve 22 is indicated by a broken line, that is, the port a and the port b of the four-way valve 22 communicate with each other. And so that port d communicates. Thereby, the refrigerant circuit 100 becomes a cooling cycle in which the outdoor heat exchanger 23 functions as a condenser and the indoor heat exchangers 51a to 51c function as evaporators.

  Next, with reference to FIGS. 1 to 3, the operation, action, and effect of the refrigerant circuit according to the present invention in the air-conditioning apparatus 1 of the present embodiment will be described. In addition, the liquid side temperature sensors 61a-61c when the indoor heat exchanger 51a functions as a condenser serve as the heat exchange outlet temperature sensor of the present invention.

  As shown in FIG. 2, in the air conditioning apparatus 1 of this embodiment, the outdoor unit 2 is installed on the rooftop of the building 600, and the indoor units 5a to 5c are installed on each floor. That is, the outdoor unit 2 is installed at a position higher than the indoor units 5a to 5c, and the installation location of the indoor unit 5a and the indoor unit 5c has a height difference H. In this case, when the air conditioning apparatus 1 performs a heating operation, there are the following problems.

  In the heating operation, the gas refrigerant discharged from the compressor 21 flows through the outdoor unit gas pipe 45 from the discharge pipe 41 through the four-way valve 22, flows out of the outdoor unit 2, and the indoor heat exchangers of the indoor units 5a to 5c. It flows into 51a-51c and condenses. At this time, since the outdoor unit 2 is installed at a position higher than the indoor units 5a to 5c, the liquid refrigerant condensed in the indoor heat exchangers 51a to 51c and flowing out to the liquid pipe 8 is against the gravity against the outdoor unit 2 Will flow through the liquid pipe 8.

  Accordingly, the lower the installation position of the indoor units 5 a to 5 c with respect to the installation position of the outdoor unit 2, the more difficult the liquid refrigerant flowing out to the liquid pipe 8 flows toward the outdoor unit 2. Therefore, the pressure of the liquid refrigerant on the downstream side (outdoor unit 2 side) of the indoor expansion valve 52c of the indoor unit 5c installed on the first floor is the indoor expansion of the indoor units 5a and 5b installed on the other floors. It becomes higher than the pressure of the liquid refrigerant on the downstream side of the valves 52a and 52b. As a result, the pressure difference between the refrigerant pressure on the upstream side (indoor heat exchanger 51c side) of the indoor expansion valve 52c of the indoor unit 5c and the refrigerant pressure on the downstream side is upstream of the indoor expansion valves 52a and 52b of the indoor units 5a and 5b. It becomes smaller than the pressure difference between the refrigerant pressure on the side and the refrigerant pressure on the downstream side.

  In the state of the refrigerant circuit 100 as described above, the smaller the pressure difference between the refrigerant pressure upstream of the indoor expansion valves 52a to 52c and the refrigerant pressure downstream, the smaller the amount of refrigerant flowing through the indoor expansion valves 52a to 52c. Accordingly, the amount of refrigerant flowing through the indoor unit 5c installed on the first floor is smaller than the amount of refrigerant flowing through the other indoor units 5a and 5b. This becomes more significant as the height difference H between the indoor unit 5c installed on the first floor (lowest position) and the indoor unit 5a installed on the third floor (highest position) increases. Increases (for example, 50 m), the pressure difference between the upstream side and the downstream side of the indoor expansion valve 52c of the indoor unit 5c becomes almost zero, and the liquid refrigerant does not flow from the indoor unit 5c toward the outdoor unit 2, that is, The liquid refrigerant stays in the indoor unit 5c. In this case, the refrigeration oil discharged from the compressor 21 together with the refrigerant to the refrigerant circuit 100, flowing through the refrigerant circuit 100 together with the refrigerant, and flowing into the indoor unit 5c also stays with the liquid refrigerant in the indoor unit 5c. For this reason, the amount of refrigeration oil returning to the compressor 21 may decrease, and the compressor 21 may be poorly lubricated.

  Therefore, in the present invention, when the air conditioner 1 is performing the heating operation, among the indoor units 5a to 5c, there is an indoor unit that satisfies the oil retention condition indicating that the refrigerating machine oil is retained. When doing so, oil outflow control is performed so that the refrigeration oil flows out from the indoor unit to the refrigerant circuit 100. Here, the oil retention condition is that the refrigerant supercooling degree on the refrigerant outlet side (outdoor expansion valves 52a to 52c side) of the indoor expansion valves 52a to 52c is equal to or higher than a predetermined supercooling degree (for example, 20 deg) when the liquid refrigerant stays. If there is an indoor unit 5a to 5c in which the liquid refrigerant residence time, which is the time during which the state has been continued, continues for a predetermined time (for example, 10 minutes), the indoor unit may interfere with lubrication of the compressor 21. It shows that it comes.

  Note that the degree of supercooling at the time of liquid refrigerant retention is obtained by performing a test or the like in advance and stored in the storage unit 220 of the outdoor unit control means 200, and the liquid refrigerant accumulates in the indoor units 5a to 5c. This corresponds to the degree of refrigerant supercooling when the liquid refrigerant temperature on the refrigerant outlet side (outdoor expansion valves 52a to 52c side) of the expansion valves 52a to 52c becomes a low temperature that is familiar with the room temperature. That is, in the indoor units 5a to 5c in which the degree of refrigerant supercooling is equal to or higher than the degree of supercooling during liquid refrigerant retention, the liquid refrigerant stays in the indoor unit.

  Further, the predetermined time of the oil retention condition is also obtained in advance by performing a test or the like and stored in the storage unit 220 of the outdoor unit control means 200. In the indoor units 5a to 5c, the above-described refrigerant supercooling degree is equal to or higher than the liquid refrigerant retention supercooling degree, that is, the time in which the liquid refrigerant is staying in the indoor units 5a to 5c. If a certain liquid refrigerant residence time is equal to or longer than a predetermined time, the compressor 21 is troubled with lubrication because the refrigeration oil flows out of the indoor units 5a to 5c and does not return to the outdoor unit 2 during the predetermined time. Indicates that there is a fear.

  And in the air conditioning apparatus 1 of this invention, when the indoor unit 5a-5c with which the said oil retention condition is satisfied exists during the heating operation, the oil outflow control demonstrated below is performed. In the oil spill control, the refrigerant supercooling degree on the refrigerant outlet side of the indoor expansion valves 52a to 52c is calculated periodically (for example, every 30 seconds), and the maximum value and the minimum value are extracted from the calculated refrigerant subcooling degree. Then, an average refrigerant supercooling degree that is an average value of these is obtained. Next, the opening degree of the indoor expansion valves 52a to 52c of the indoor units 5a to 5c is adjusted so that the refrigerant subcooling degree on the refrigerant outlet side of the indoor heat exchangers 51a to 51c becomes the average refrigerant subcooling degree.

  For example, when the air conditioner 1 is performing a heating operation, the refrigerant supercooling degree of the indoor unit 5a is 6 deg and the refrigerant subcooling degree of the indoor unit 5b is 10 deg, while liquid refrigerant is accumulated in the indoor unit 5c. It is assumed that the refrigerant supercooling degree is 26 deg., Which is larger than 20 deg. If the state in which the refrigerant supercooling degree is equal to or higher than the supercooling degree during liquid refrigerant retention in the indoor unit 5c continues for a predetermined time: 10 minutes or more, that is, if the oil retention condition is satisfied in the indoor unit 5c, Oil outflow control is executed to cause the refrigeration oil staying in the unit 5c to flow out from the indoor unit 5c.

  In the oil spill control, first, the average refrigerant supercooling degree of the refrigerant supercooling degree of the indoor units 5a to 5c (in the case of the above example, the maximum value: 26 deg and the minimum value: 13 deg which is an average value of 6 deg) is obtained and obtained. In the indoor units 5a and 5b having a refrigerant subcooling degree smaller than the average refrigerant subcooling degree, the opening degree of the indoor expansion valves 52a and 52b is reduced to increase the refrigerant subcooling degree to the average refrigerant subcooling degree. The refrigerant pressure on the downstream side of the expansion valves 52a and 52b decreases.

  On the other hand, in the indoor unit 5c having a refrigerant subcooling degree larger than the average refrigerant subcooling degree, the refrigerant pressure on the downstream side of the indoor expansion valves 52c also decreases as the refrigerant pressure on the downstream side of the indoor expansion valves 52a and 52b decreases. In addition, the pressure difference between the upstream side and the downstream side of the indoor expansion valve 52c increases. Thereby, even if the opening degree of the indoor expansion valve 52c is increased to reduce the refrigerant subcooling degree of the indoor unit 5c to the average refrigerant subcooling degree and the opening degree is fully opened, the indoor heat exchange of the indoor unit 5c is performed. The liquid refrigerant staying in the vessel 51 c flows out to the liquid pipe 8. At this time, from the indoor unit 5c, the refrigeration oil staying in the indoor unit 5c together with the liquid refrigerant flows out to the liquid pipe 8, flows through the liquid pipe 8 together with the liquid refrigerant, and flows into the outdoor unit 2. Therefore, the compressor 21 A sufficient amount of refrigeration oil is returned to prevent the compressor 21 from being poorly lubricated.

  Next, control at the time of heating operation in the air-conditioning apparatus 1 of the present embodiment will be described with reference to FIG. FIG. 3 shows a flow of processing related to control performed by the CPU 210 of the outdoor unit control unit 200 when the air-conditioning apparatus 1 performs heating operation. In FIG. 3, ST represents a step, and the number following this represents a step number. Note that FIG. 3 mainly illustrates the processing related to the present invention, and other processing, for example, control of the refrigerant circuit 100 corresponding to the operating conditions such as the set temperature and the air volume instructed by the user. Description of general processing related to the harmony device 1 is omitted. Moreover, in the following description, the case where all the indoor units 5a to 5c are performing the heating operation will be described as an example.

  In the following description, the discharge pressure of the compressor 21 detected by the discharge pressure sensor 31 of the outdoor unit 2 is Ph, the high-pressure saturation temperature obtained using the discharge pressure Ph is Ths, and the liquid side temperature sensors of the indoor units 5a to 5c. The heat exchange outlet temperature detected by 61a-61c is obtained by subtracting the heat exchange outlet temperature To from the high-pressure saturation temperature Ths (To, if it is necessary to refer to each indoor unit individually, it is described as Toa-Toc). The refrigerant supercooling degree on the refrigerant outlet side of the indoor heat exchangers 51a to 51c is SC (indicated as SCa to SCc when it is necessary to refer to each indoor unit individually), and the refrigerant supercooling in each indoor unit The average refrigerant supercooling degree obtained using the maximum value and the minimum value of the degree SC is SCv, the liquid refrigerant residence supercooling degree is SCp, the liquid refrigerant residence time is tlr, and the predetermined time is tp.

  First, CPU 210 determines whether or not the user's operation instruction is a heating operation instruction (ST1). If it is not a heating operation instruction (ST1-No), the CPU 210 executes a cooling / dehumidifying operation start process that is a start process of a cooling operation or a dehumidifying operation (ST17). Here, the cooling / dehumidifying operation start process is a process performed when the CPU 210 operates the four-way valve 22 to set the refrigerant circuit 100 to the cooling cycle, and when the cooling operation or the dehumidifying operation is first performed. Then, the CPU 210 activates the compressor 21 and the outdoor fan 27 at a predetermined rotational speed, and controls the driving of the indoor fans 55a to 55c and the indoor expansion valves 52a to 52c with respect to the indoor units 5a to 5c via the communication unit 230. Is instructed to adjust the opening degree of the air and starts control of the cooling operation or the dehumidifying operation (ST18), and the process proceeds to ST13.

  If it is a heating operation instruction in ST1 (ST1-Yes), the CPU 210 executes a heating operation start process (ST2). Here, the heating operation start process is a state in which the CPU 210 operates the four-way valve 22 to bring the refrigerant circuit 100 into the state shown in FIG. 1A, that is, the refrigerant circuit 100 is set to the heating cycle. It is a process performed when performing.

  Next, the CPU 210 performs a heating operation start process (ST3). In the heating operation start process, the CPU 210 activates the compressor 21 and the outdoor fan 27 at a rotational speed corresponding to the required capacity from the indoor units 5a to 5c. The CPU 210 takes in the discharge temperature of the compressor 21 detected by the discharge temperature sensor 33 via the sensor input unit 240 and adjusts the opening degree of the outdoor expansion valve 24 according to the taken-in discharge temperature. Furthermore, CPU210 transmits the driving | operation start signal to the effect of starting heating operation via the communication part 230 with respect to indoor unit 5a-5c.

  The CPUs 510a to 510c of the indoor unit control means 500a to 500c of the indoor units 5a to 5c that have received the operation start signals via the communication units 530a to 530c turn the indoor fans 55a to 55c at the number of rotations according to the air volume instruction of the user. The interior of the indoor heat exchangers 51a to 51c is turned on so that the refrigerant subcooling degree at the refrigerant outlets (liquid pipe connection parts 53a to 53c side) becomes the target refrigerant subcooling degree (for example, 6 deg) during the heating operation. The opening degree of the expansion valves 52a to 52c is adjusted. Here, the target refrigerant supercooling degree is a value obtained by performing a test or the like in advance and stored in the storage units 530a to 530c, and it is confirmed that the heating capacity is sufficiently exhibited in each of the indoor units 5a to 5c. It is the value that has been made. During the heating operation, the CPUs 510a to 510c adjust the opening degrees of the indoor expansion valves 52a to 52c so that the above-described target refrigerant subcooling degree is obtained except when the oil retention condition is established and the oil outflow control is executed.

  Next, the CPU 210 takes in the discharge pressure Ph detected by the discharge pressure sensor 31 via the sensor input unit 240, and sends the heat exchange outlet temperature To (Toa to Toc) from each of the indoor units 5 a to 5 c via the communication unit 230. (ST4). The heat exchange outlet temperature To is the value detected by the liquid side temperature sensors 61a to 61c in the indoor units 5a to 5c by the CPUs 510a to 510c and transmitted to the outdoor unit 2 via the communication units 530a to 530c. It is. Each detection value mentioned above is taken into each CPU every predetermined time (for example, every 30 seconds), and is memorized in each storage part.

  Next, the CPU 210 obtains the high-pressure saturation temperature Ths using the discharge pressure Ph taken in in ST4 (ST5), and uses the obtained high-pressure saturation temperature Ths and the heat exchange outlet temperature To taken in in ST4 to each indoor unit 5a. The refrigerant supercooling degree SC (SCa to SCc) of ˜5c is obtained (ST6).

  Next, the CPU 210 determines whether or not there is an indoor unit in which the refrigerant supercooling degree SC obtained in ST6 is equal to or higher than the liquid refrigerant retention supercooling degree SCp among the indoor units 5a to 5c (ST7). . If there is no indoor unit in which the refrigerant supercooling degree SC is equal to or higher than the liquid refrigerant retention supercooling degree SCp (ST7-No), the CPU 210 stores a flag F, which will be described later, as 0 in the storage unit 220 and retains the liquid refrigerant. The time tlr is reset (ST16). The process proceeds to ST13.

  If there is an indoor unit in which the refrigerant supercooling degree SC is equal to or higher than the liquid refrigerant retention supercooling degree SCp (ST7-Yes), the CPU 210 reads the flag F stored in the storage unit 220 and reads the read flag F Is determined to be 0 (ST8).

  This flag F is for determining whether or not the measurement of the liquid refrigerant residence time tlr has already started. If the flag F is 0 in ST8, the refrigerant is supercooled in the indoor units 5a to 5c. This indicates that an indoor unit having a degree SC of the supercooling degree SCp at the time of liquid refrigerant retention needs to be started and measurement of the liquid refrigerant residence time tlr needs to be started. If the flag F is 1, it indicates that the liquid refrigerant residence time tlr has already been measured. Although not shown, the flag F is set to 0 when the air conditioner 1 is started.

  If flag F is not 0 in ST8 (ST8-No), CPU 210 advances the process to ST10. If the flag F is 0 (ST8-Yes), the CPU 210 starts measuring the liquid refrigerant residence time tlr using its own timer function, and stores the flag F as 1 (ST9) in the storage unit 220. , The process proceeds to ST10. The processes from ST7 to ST10 described above are processes for determining whether or not the oil retention condition is satisfied.

  In ST10, the CPU 210 determines whether or not the liquid refrigerant residence time tlr started to be measured in ST9 is equal to or longer than the predetermined time tp. If the liquid refrigerant residence time tlr is not equal to or longer than the predetermined time tp (ST10-No), the CPU 210 advances the process to ST13. If the liquid refrigerant residence time tlr is equal to or longer than the predetermined time tp (ST10-Yes), the CPU 210 calculates the average refrigerant subcooling degree SCv using the refrigerant subcooling degree SC of the indoor units 5a to 5c obtained in ST6. (ST11). Specifically, the CPU 210 extracts the maximum value and the minimum value from the refrigerant supercooling degrees SCa to SCc of the indoor units 5a to 5c, obtains the average value thereof, and sets this as the average refrigerant subcooling degree SCv. .

Next, the CPU 210 transmits the average refrigerant supercooling degree SCv obtained in ST11 and the high-pressure saturation temperature Ths obtained in ST5 to the indoor units 5a to 5c via the communication unit 230 (ST12). The CPUs 510a to 510c of the indoor units 5a to 5c that have received the average refrigerant supercooling degree SCv and the high pressure saturation temperature Ths via the communication units 530a to 530c, respectively, use the liquid side temperature sensors 61a to 61 from the high pressure saturation temperature Ths received from the outdoor unit 2. The heat exchanger outlet temperatures Toa to Toc detected in 61c are subtracted to obtain the refrigerant subcooling degrees SCa to SCc, and the obtained refrigerant subcooling degrees SCa to SCc become the average refrigerant subcooling degree SCv received from the outdoor unit 2. Next, the opening degree of the indoor expansion valves 52a to 52c is adjusted.
The processes from ST4 to ST12 described above are processes related to the oil spill control of the present invention.

  CPU210 which finished the process of ST12 judges whether there exists the operation mode switching instruction | indication by a user (ST13). Here, the operation mode switching instruction is an instruction to switch from the current operation (here, heating operation) to another operation (cooling operation or dehumidifying operation). When there is an operation mode switching instruction (ST13-Yes), the CPU 210 returns the process to ST1. When there is no operation mode switching instruction (ST13-No), the CPU 210 determines whether or not there is an operation stop instruction by the user (ST14). The operation stop instruction indicates that all the indoor units 5a to 5c stop the operation.

  If there is an operation stop instruction (ST14-Yes), the CPU 210 executes an operation stop process (ST15) and ends the process. In the operation stop process, the CPU 210 stops the compressor 21 and the outdoor fan 27 and fully closes the outdoor expansion valve 24. Moreover, CPU210 transmits the driving | operation stop signal to the effect of stopping a driving | operation via the communication part 230 with respect to indoor unit 5a-5c. The CPUs 510a to 510c of the indoor units 5a to 5c that have received the operation stop signals via the communication units 530a to 530c stop the indoor fans 55a to 55c and fully close the indoor expansion valves 52a to 52c.

  If there is no operation stop instruction in ST14 (ST14-No), CPU 210 determines whether or not the current operation is a heating operation (ST19). If the current operation is the heating operation (ST19-Yes), the CPU 210 returns the process to ST3. If the current operation is not the heating operation (ST19-No), that is, if the current operation is the cooling operation or the dehumidifying operation, the CPU 210 returns the process to ST18.

  In each of the embodiments described above, the case where oil outflow control is executed using the refrigerant supercooling degree of each indoor unit has been described. However, instead of the refrigerant supercooling degree, liquid side temperature detecting means (liquid side temperature sensor) is used. Oil outflow control may be executed using the heat exchange outlet temperature of the indoor heat exchanger of each indoor unit detected in 61a to 61c). When oil spill control is performed using the heat exchanger outlet temperature, the heat exchanger outlet temperature of each indoor unit is the average heat exchanger outlet temperature obtained using the maximum value and the minimum value of these heat exchanger outlet temperatures. Thus, the opening degree of each indoor expansion valve is adjusted.

  In addition, as the oil retention condition, a case has been described in which it is determined whether or not the liquid refrigerant residence time that is equal to or higher than the supercooling degree during liquid refrigerant residence of the refrigerant supercooling degree of each indoor unit continues for a predetermined time or more. However, instead of this, the heat at the time of liquid refrigerant retention is the heat exchange outlet temperature when the heat exchange outlet temperature of the indoor heat exchanger of each indoor unit is accustomed to room temperature by the liquid refrigerant remaining in the indoor unit. The time during which the temperature is equal to or lower than the outlet temperature may be set as the refrigerant residence time, and it may be determined whether or not the refrigerant residence time continues for a predetermined time or more.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2 Outdoor unit 5a-5c Indoor unit 31 Discharge pressure sensor 51a-51c Indoor heat exchanger 52a-52c Indoor expansion valve 61a-61c Liquid side temperature sensor 63a-63c Suction temperature sensor 64a-64c Outlet temperature sensor 100 Refrigerant Circuit 200 Outdoor unit control unit 210 CPU
500a to 500c Indoor unit controller 510a to 510c CPU
Ph Discharge pressure SC Refrigerant supercooling degree SCv Average refrigerant supercooling degree SCp Liquid refrigerant residence supercooling degree Ths High pressure saturation temperature To Heat exchange outlet temperature tlr Liquid refrigerant residence time tp Predetermined time

Claims (2)

An outdoor unit having a compressor and a discharge pressure detecting means for detecting a discharge pressure that is a pressure of a refrigerant discharged from the compressor;
Liquid side temperature detection for detecting the heat exchange outlet temperature, which is the temperature of the refrigerant flowing out of the indoor heat exchanger when the indoor heat exchanger functions as a condenser. Having a plurality of indoor units having means,
The outdoor unit is installed above the plurality of indoor units, and is an air conditioner having a height difference in an installation place of the plurality of indoor units,
When the indoor heat exchanger functions as a condenser,
When there is an indoor unit in which the oil retention condition indicating that the refrigerating machine oil discharged together with the refrigerant from the compressor is retained in the plurality of indoor units,
The refrigerant subcooling degree of each indoor unit becomes the average refrigerant subcooling degree obtained using the maximum value and the minimum value of the refrigerant subcooling degree, or the heat exchange outlet temperature of each indoor unit is the same Control means for performing oil outflow control for adjusting the opening of each of the indoor expansion valves so as to obtain an average heat exchange outlet temperature determined using the maximum value and the minimum value of the outlet temperature,
An air conditioner characterized by that. The state in which the oil retention condition is equal to or higher than the degree of supercooling at the time of liquid refrigerant retention, which is the degree of refrigerant supercooling when the liquid refrigerant is retained in each indoor unit among the degree of refrigerant supercooling of each indoor unit Alternatively, the state where the heat exchange outlet temperature of each indoor unit is equal to or lower than the heat exchange outlet temperature during liquid refrigerant retention, which is the heat exchange outlet temperature when liquid refrigerant is retained in each indoor unit, continues. Stipulated by whether or not the refrigerant residence time, which is the time to be, is equal to or longer than a predetermined time,
The air conditioner according to claim 1.

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