JP2019138486A - Refrigerant circuit system and control method of defrosting operation - Google Patents

Abstract

To provide a method for preventing liquid buck from deviating in a defrosting operation of a cooling/heating free multiple refrigerant circuit.SOLUTION: A refrigerant circuit system comprises: a plurality of outdoor units; a plurality of indoor units; a high pressure gas pipe; a low pressure gas pipe; a liquid pipe; a refrigerant circuit in which the discharge side of a compressor for the outdoor unit is connected to the high pressure gas pipe, the suction side of the compressor is connected to the low pressure gas pipe, one end of outdoor heat exchanger is connected to the liquid pipe, one end of indoor heat exchanger is connected to the high pressure gas pipe and the low pressure gas pipe via a switch mechanism, and the other end of indoor heat exchanger is connected to the liquid pipe; and a control device in which in a defrosting operation of the refrigerant circuit, the operation of entire compressors is continued until defrosting of entire outdoor heat exchangers is completed.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a refrigerant circuit system and a control method for defrost operation.

  Patent Document 1 discloses a cooling / heating system including a high pressure gas pipe connected to a discharge side of a compressor of an outdoor unit, a low pressure gas pipe connected to a suction side of the compressor, and a plurality of indoor units connected to liquid pipes. A free multi-type air conditioner is described. In a cooling / heating free multi-type air conditioner, a plurality of indoor units can be individually operated for cooling and heating simultaneously. When performing a defrost operation with a cooling / heating free multi-type air conditioner, it is common to perform a cooling cycle operation in each unit and stop the operation in order from the unit in which the frost of the outdoor heat exchanger has been removed.

  Patent Document 2 discloses an expansion valve for an indoor unit so that the refrigerant amount does not cause liquid back in a defrost operation in an air conditioner in which a plurality of outdoor units and a plurality of indoor units are connected by high-pressure gas pipes and liquid pipes. A method of controlling is described.

JP 2006-177619 A JP 2014-2111251 A

  In the case of the defrost operation of the above-described cooling / heating free multi-type air conditioner, since the operation is stopped from the compressor after the defrost is completed, the circulating refrigerant is concentrated on the compressor that is performing the defrost operation until the end, The back may be biased.

  Accordingly, an object of the present invention is to provide a refrigerant circuit system and a defrost operation control method that can solve the above-described problems.

  According to one aspect of the present invention, a refrigerant circuit system includes a plurality of outdoor units, a plurality of indoor units, a high-pressure gas pipe, a low-pressure gas pipe, and a liquid pipe, and the plurality of outdoor units includes a compression. The discharge side of the machine is connected to the high-pressure gas pipe, the suction side of the compressor provided in the plurality of outdoor units is connected to the low-pressure gas pipe, and one end of the outdoor heat exchanger provided in the plurality of outdoor units is connected to the liquid pipe One end of an indoor heat exchanger connected to the plurality of indoor units is connected to the high-pressure gas pipe and the low-pressure gas pipe via a switching mechanism, and the other end of the indoor heat exchanger is connected to the liquid pipe And a control device that continues operation of all the compressors until defrosting is completed for all the outdoor heat exchangers included in the plurality of outdoor units in the defrosting operation of the refrigerant circuits. Prepare.

  According to an aspect of the present invention, the control device fully closes an expansion valve provided in the outdoor unit including the outdoor heat exchanger that has completed defrosting.

  According to an aspect of the present invention, the control device opens the expansion valve when the pressure of the outdoor heat exchanger reaches or exceeds a predetermined threshold value.

  According to an aspect of the present invention, the control device is necessary for defrosting the outdoor heat exchanger in which defrosting is not completed with respect to the refrigerant circulation amount necessary for all defrosting of the outdoor heat exchange provided in the refrigerant circuit. The number of revolutions of all the compressors is controlled in accordance with the ratio of the amount of refrigerant circulating.

  According to an aspect of the present invention, the control device is necessary for defrosting the outdoor heat exchanger in which defrosting is not completed with respect to the refrigerant circulation amount necessary for all defrosting of the outdoor heat exchange provided in the refrigerant circuit. The opening degree of the expansion valve provided in all the indoor units is reduced in accordance with the ratio of the amount of refrigerant circulating.

  According to an aspect of the present invention, the control device determines that the defrosting of the outdoor heat exchanger is completed when the temperature in the vicinity of the outdoor heat exchanger becomes equal to or higher than a predetermined first threshold value.

  According to an aspect of the present invention, when the temperature in the vicinity of the outdoor heat exchanger becomes equal to or higher than a second threshold value that is lower than the first threshold value, the control device is provided in the outdoor unit that includes the outdoor heat exchanger. The opening degree of the expansion valve is reduced.

  According to one aspect of the present invention, a control method for defrost operation includes a plurality of outdoor units, a plurality of indoor units, a high-pressure gas pipe, a low-pressure gas pipe, and a liquid pipe, and the plurality of outdoor units are A discharge side of a compressor provided is connected to the high pressure gas pipe, a suction side of a compressor provided in the plurality of outdoor units is connected to the low pressure gas pipe, and one end of an outdoor heat exchanger provided in the plurality of outdoor units is the liquid. One end of an indoor heat exchanger connected to a pipe and provided in the plurality of indoor units is connected to the high-pressure gas pipe and the low-pressure gas pipe via a switching mechanism, and the other end of the indoor heat exchanger is the liquid pipe In the defrosting operation of the refrigerant circuit connected to each other, the operation of all the compressors is continued until the defrosting is completed for all of the outdoor heat exchangers included in the plurality of outdoor units.

  According to the present invention, in the refrigerant circuit of the cooling / heating free multi-type air conditioner, even when a liquid back occurs during the defrost operation, it is possible to prevent the liquid back from being biased between the compressors.

It is a figure which shows an example of the refrigerant circuit system in one Embodiment of this invention. It is a 1st figure which shows an example of the flow of the refrigerant | coolant at the time of the defrost driving | operation in one Embodiment of this invention. It is a 2nd figure which shows an example of the flow of the refrigerant | coolant at the time of the defrost driving | operation in one Embodiment of this invention. It is a flowchart which shows an example of the process in the defrost driving | operation in one Embodiment of this invention. It is a figure which shows the other example of the refrigerant circuit system in one Embodiment of this invention.

<Embodiment>
Hereinafter, a defrost operation in a cooling / heating free multi-type air conditioner according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram illustrating an example of a refrigerant circuit system according to an embodiment of the present invention.
As shown in FIG. 1, a cooling / heating-free multi-type air conditioner 100 includes a plurality of outdoor unit units (outdoor unit 1A, outdoor unit 1B) and a plurality of indoor unit units (indoor unit 2A, indoor unit 2B). A high pressure gas pipe (high pressure gas pipes 5A, 5B, 5C), a low pressure gas pipe (low pressure gas pipes 7A, 7B, 7C), a liquid pipe (liquid pipes 9A, 9B, 9C), and a control The apparatus 30 is comprised.

The outdoor unit 1A includes a compressor 10A, a four-way valve 11A, an outdoor heat exchanger 12A, and an outdoor unit expansion valve 13A. The outdoor unit 1B includes a compressor 10B, a four-way valve 11B, an outdoor heat exchanger 12B, and an outdoor unit expansion valve 13B.
The indoor unit 2A includes an indoor heat exchanger 22A and an indoor unit expansion valve 23A. The indoor unit 2B includes an indoor heat exchanger 22B and an indoor unit expansion valve 23B.
The discharge side of the compressor 10A is connected to the high pressure gas pipe 5A, and the suction side of the compressor 10A is connected to the low pressure gas pipe 7A. Similarly, the discharge side of the compressor 10B is connected to the high pressure gas pipe 5B, and the suction side of the compressor 10B is connected to the low pressure gas pipe 7B. The high pressure gas pipes 5A and 5B are connected to the high pressure gas pipe 5C, and the low pressure gas pipes 7A and 7B are connected to the low pressure gas pipe 7C. One end of the outdoor heat exchanger 12A is connected to the liquid pipe 9A, and one end of the outdoor heat exchanger 12B is connected to the liquid pipe 9B. One end of the indoor heat exchanger 22A is switchably connected to the high-pressure gas pipe 5A and the low-pressure gas pipe 7A via the branch controller 21A, and the other end is connected to the liquid pipe 9A. Similarly, one end of the indoor heat exchanger 22B is switchably connected to the high-pressure gas pipe 5B and the low-pressure gas pipe 7B via the diversion controller 21B, and the other end is connected to the liquid pipe 9B.

  First, the outdoor unit 1A will be described. The outdoor unit 1A includes a compressor 10A, a four-way valve 11A, an outdoor heat exchanger 12A, and an outdoor unit expansion valve 13A. The compressor 10A compresses the refrigerant and discharges the compressed high-pressure refrigerant. The four-way valve 11A switches the direction in which the refrigerant circulates between the heating operation and the cooling operation. The figure shows the settings for heating operation. During heating, the discharge side of the compressor is connected to the side where the capillary tube 15A is provided. The outdoor heat exchanger 12A performs heat exchange between the refrigerant and the outdoor air. The outdoor heat exchanger 12A functions as a condenser during the cooling operation and radiates heat to the outside, and functions as an evaporator during the heating operation and absorbs heat from the outside. The outdoor unit expansion valve 13A functions as an expansion valve that reduces the pressure of the high-pressure refrigerant liquid during heating operation. A temperature sensor 14A is provided in the vicinity of the outdoor heat exchanger. The same applies to the outdoor unit 1B. The outdoor unit 1A and the outdoor unit 1B operate in the same operation mode (cooling operation mode or heating operation mode), and the cooling / heating of each indoor unit is controlled by switching between diversion controllers 21A and 21B described later.

  Next, the indoor unit 2A will be described. The indoor unit 2A includes an indoor heat exchanger 22A and an indoor unit expansion valve 23A. The indoor heat exchanger 22A performs heat exchange between the refrigerant and the indoor air. The indoor heat exchanger 22 functions as an evaporator during the cooling operation and absorbs heat from the room by evaporating the refrigerant, and functions as a condenser during the heating operation and radiates heat to the room. The indoor unit expansion valve 23A functions as an expansion valve during cooling operation, and reduces the pressure of the high-pressure refrigerant liquid. A diversion controller 21A is provided between the gas pipe side of the indoor unit 2A and the gas pipe (high pressure gas pipe 5A, low pressure gas pipe 7A) side of the outdoor unit 1A. The diversion controller 21A switches the refrigerant path between the high-pressure gas pipe 5A and the low-pressure gas pipe 7A. During the cooling operation, the refrigerant path is switched to the low-pressure gas pipe 7A. During the heating operation, the high pressure gas pipe 5 is switched. The same applies to the indoor unit 2B.

  For convenience of explanation, it is assumed that the capacity of the compressor 10A included in the outdoor unit 1A and the capacity of the compressor 10B included in the outdoor unit 1B are the same. In addition, it is assumed that the specifications of the other outdoor heat exchanger 12A, the outdoor unit 1B, etc., and the corresponding devices included in the indoor unit 2A and 2B are the same. The control device 30 is a computer including a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). The control device 30 controls each device included in the outdoor unit 1A, 1B and the indoor unit 2A, 2B.

  The arrow of FIG. 1 has shown the flow of the refrigerant | coolant at the time of heating operation mode. In the case of FIG. 1, both the indoor unit 2A and 2B are performing the heating operation. The high-pressure refrigerant discharged from the compressor 10A passes through the high-pressure gas pipe 5A and is sent to the indoor unit 2A. The refrigerant dissipates heat in the indoor heat exchanger 22A, liquefies, is decompressed by the indoor unit expansion valve 23A, passes through the liquid pipe 9A, and is sent to the outdoor unit 1A. In the outdoor unit 1A, the refrigerant decompressed by the outdoor unit expansion valve 13A absorbs heat in the outdoor heat exchanger 12A and is vaporized. The vaporized refrigerant is guided to the suction side of the compressor 10A by the four-way valve 11A. The compressor 10A boosts the vaporized low-pressure refrigerant and discharges it again to the high-pressure gas pipe 5A side. The refrigerant flow between the outdoor unit 1B and the indoor unit 2B is the same.

  Here, for example, it is assumed that the control device 30 starts the defrost operation based on the fact that the operation time in the heating operation mode has reached a predetermined time or the measured values of the temperature sensors 14A and 14B. The control device 30 switches the connection between the ports of the four-way valves 11A and 11B and the diversion controllers 21A and 21B from the state of FIG. 1 to FIG. FIG. 2 is a first diagram illustrating an example of a refrigerant flow during a defrost operation according to an embodiment of the present invention. Then, the refrigerant circulates in the direction indicated by the arrow in FIG. Specifically, the high-pressure refrigerant discharged from the compressor 10A is guided to the outdoor heat exchanger 12A side by the four-way valve 11A. The refrigerant dissipates heat in the outdoor heat exchanger 12A, condenses and liquefies, is decompressed by the outdoor unit expansion valve 13A, passes through the liquid pipe 9A, and is sent to the indoor unit 2A. In the indoor unit 2A, the low-pressure refrigerant decompressed by the indoor unit expansion valve 23A absorbs heat in the indoor heat exchanger 22A and is vaporized. The vaporized refrigerant is guided to the low pressure gas pipe 7 by the diversion controller 21A. The vaporized refrigerant passes through the low-pressure gas pipe 7 and is sent to the outdoor unit 1A, and is guided to the suction side of the compressor 10A. The compressor 10A pressurizes and discharges the vaporized low-pressure refrigerant. The refrigerant circulates in the same path, and the high-pressure and high-temperature refrigerant removes frost attached to the outdoor heat exchanger 12A. The refrigerant flow in FIG. 2 is the same flow as in the cooling operation mode.

  When the defrost operation is performed, the frost of the outdoor heat exchangers 12A and 12B is melted, and the temperature measured by the temperature sensors 14A and 14B is increased by the passage of the high-pressure refrigerant. The control device 30 determines that the defrosting of the outdoor heat exchanger 12A has been completed when the temperature measured by the temperature sensor 14A reaches a predetermined threshold value. Here, the capacities of the compressors 10A, 10B are all the same, but the difference in the capacities of the compressors 10A, 10B, the individual differences of the outdoor heat exchangers 12A, 12B, the daily Depending on various conditions such as temperature differences, the completion timing of defrosting of the outdoor heat exchanger 12A and the outdoor heat exchanger 12B may be different.

  In the conventional control, for example, when it is determined that the defrosting of the outdoor heat exchanger 12A is completed, the control device 30 stops the compressor 10A. Then, depending on the operating conditions and operating environment, liquid back may occur during the defrost operation, but the liquid back concentrates on the compressor 10 </ b> B that continues operation, and the liquid back is biased. For example, if the defrosting of the outdoor heat exchanger 12A is always completed early due to the influence of the installation location or the difference in the capacity of the compressors 10A and 10B, which trouble that only the compressor 10B in which the liquid back is concentrated breaks down. there is a possibility. Therefore, in the present embodiment, the following control is performed to prevent the unevenness of the liquid back and reduce the liquid back amount. Defrosting will be described with an example in which the outdoor heat exchanger 12A is completed first.

(1) When the defrost operation of the outdoor heat exchanger 12A is completed, the control device 30 does not stop the operation of the compressor 10A and continues the operation.
(2) Since it is not necessary to supply a higher temperature refrigerant to the outdoor heat exchanger 12A any more, the outdoor unit expansion valve 13A is fully closed.
Even after the defrost operation on the outdoor heat exchanger 12A side is completed, it is possible to prevent the liquid back from being biased by operating the compressors 10A and 10B. The flow of the refrigerant after performing the controls (1) and (2) will be described later with reference to FIG.

(3) The rotational speed of the compressors 10A and 10B is decreased in accordance with the circulating refrigerant amount. For example, assuming that the compressors 10A and 10B have the same capacity and the number of revolutions when the defrost operation is performed for two outdoor heat exchangers 12A and 12B is 100, the defrost operation of the outdoor heat exchanger 12A is After completion, since only the outdoor heat exchanger 12B is targeted, the circulation amount of the refrigerant may be halved. Therefore, the rotational speeds of the compressors 10A and 10B are both reduced to 50. When the capacities of the compressors 10A and 10B are different, the control device 30 causes the overall refrigerant circulation amount to be 1/2 and the rotation speeds of the compressors 10A and 10B so that the discharge amounts of the compressors 10A and 10B are equal. To control.

(4) Further, the opening degree of the indoor unit expansion valves 23A and 23B of the indoor unit 2A and 2B is reduced in accordance with a decrease in the circulation amount of the refrigerant. For example, the control device 30 controls the indoor unit expansion valves 23A and 23B so that the refrigerant flow rate passing through the indoor unit expansion valves 23A and 23B becomes 1/2 as the refrigerant circulation amount becomes 1/2. Each opening degree is controlled based on the valve characteristics.
By reducing the opening of the indoor unit expansion valves 23A and 23B on the indoor unit units 2A and 2B side, the refrigerant circulation amount can be reduced and the liquid back amount can be reduced.

(5) When the temperature measured by the temperature sensor 14B is equal to or higher than the predetermined temperature, the control device 30 determines that the defrost of the outdoor heat exchanger 12B is completed, and ends the defrost operation. Control device 30 resumes the heating cycle operation.

  FIG. 3 is a second diagram illustrating an example of the refrigerant flow during the defrost operation in the embodiment of the present invention. FIG. 2 shows the flow of the refrigerant after the controls (1) and (2) are performed. The arrows in FIG. 2 indicate the flow of the refrigerant after the defrosting on the outdoor unit 1A side is completed. The control device 30 continues the operation without stopping the compressor 10A. Further, the control device 30 fully closes the outdoor unit expansion valve 13A. Then, the refrigerant discharged from the compressor 10A does not flow into the outdoor heat exchanger 12A, passes through the high pressure gas pipes 5A and 5C, and reaches the high pressure gas pipe 5B. The high-pressure refrigerant that has reached the high-pressure gas pipe 5B merges with the high-pressure refrigerant discharged from the compressor 10B, and is guided to the outdoor heat exchanger 12B by the four-way valve 11B. The high-pressure refrigerant supplied to the outdoor heat exchanger 12B dissipates heat in the outdoor heat exchanger 12B and melts frost in the outdoor heat exchanger 12B. A part of the refrigerant condensed in the outdoor heat exchanger 12B is decompressed by the indoor unit expansion valve 23B, passes through the liquid pipe 9B, and is sent to the outdoor unit 1B. In the outdoor unit 1B, the refrigerant decompressed by the outdoor unit expansion valve 13B is vaporized by the indoor heat exchanger 22B. The vaporized refrigerant is guided to the low-pressure gas pipe 7B by the diversion controller 21B, passes through the low-pressure gas pipe 7B, and reaches the suction side of the compressor 10B. The compressor 10B boosts and discharges the low-pressure refrigerant. Thereafter, the above route is circulated.

  On the other hand, the remaining part of the refrigerant passes through the liquid pipe 9C, reaches the liquid pipe 9A, and is sent to the outdoor unit 1A. In the outdoor unit 1A, the refrigerant decompressed by the outdoor unit expansion valve 13A is vaporized by the indoor heat exchanger 22A. The vaporized refrigerant is guided to the low pressure gas pipe 7A by the diversion controller 21A, passes through the low pressure gas pipe 7A, and reaches the suction side of the compressor 10A. The compressor 10A boosts the low-pressure refrigerant and discharges it to the high-pressure gas pipe 5A side. Thereafter, the above route is circulated.

  Thus, even after the defrosting of some of the outdoor heat exchangers 12A is finished, the operation of the compressor 10A is continued, so that the damp refrigerant is not sucked only by the compressor 10B, and the liquid back is discharged. The bias can be reduced. In particular, by controlling the rotational speed so that the amount of refrigerant discharged from the compressors 10A and 10B is equal (the same rotational speed if the capacity of the compressors 10A and 10B is the same), the liquid back amount is equally distributed. be able to. Moreover, since only the defrost of the remaining outdoor heat exchangers 12B needs to be performed after the defrost of some of the outdoor heat exchangers 12A is completed, the amount of refrigerant circulation can be reduced. Therefore, the refrigerant circulation amount may be reduced by reducing the rotation speed of the compressors 10A and 10B and reducing the opening degree of the indoor unit expansion valves 23A and 23B. Alternatively, the rotation speed of the compressors 10A and 10B may be maintained, and a large amount of refrigerant may be supplied to the remaining outdoor heat exchanger 12B so that the defrosting is completed quickly.

  Further, for example, the indoor unit expansion valve 23A may be fully closed so that no refrigerant is supplied to the indoor unit 2A side. Thereby, the effect which makes the start-up of the heating operation in the indoor unit 2A side after the completion of the defrost operation quick can be expected. The indoor unit expansion valve 23B may be fully closed.

  Further, for example, although the outdoor unit expansion valve 13A is fully closed, for example, when the pressure balance of the outdoor unit 1A, 1B is lost or the pressure of the outdoor heat exchanger 12A is increased, the refrigerant circulation In order to stabilize the pressure or eliminate the risk of pressure increase, the control device 30 may open the outdoor unit expansion valve 13A at a predetermined opening degree. Thereby, the refrigerant circulates also in the outdoor heat exchanger 12A, the outdoor unit expansion valve 13A, and the liquid pipe 9A, and an increase in pressure on the outdoor heat exchanger 12A side can be avoided. Note that the opening degree of the outdoor unit expansion valve 13A may be an opening degree (slightly open) that does not reduce the efficiency of the defrost operation.

Next, an example of the processing flow of the defrost operation of this embodiment will be described with reference to FIG.
FIG. 4 is a flowchart illustrating an example of a process during the defrost operation according to the embodiment of the present invention.
It is assumed that the defrost operation start condition is satisfied during the heating operation. The control device 30 switches the four-way valves 11A and 11B and switches the branch flow controllers 21A and 21B to start the defrost operation (step S11). Specifically, the operation described with reference to FIG. 2 is started. The control device 30 monitors the temperatures measured by the temperature sensors 14A and 14B, and determines whether or not the defrosting is completed in the outdoor unit 1A or 1B (step S12). When the defrost is not completed (step S12; Yes), the defrost operation is measured.

Here, it is assumed that the temperature measured by the temperature sensor 14A is equal to or higher than a predetermined threshold. The control device 30 determines that the defrost is completed in the outdoor unit 1A (step S12; Yes). Then, the control device 30 fully closes the outdoor unit expansion valve 13A on the defrost completion side while operating the compressor 10A (step S13). Moreover, the control apparatus 30 controls the rotation speed of a compressor according to the circulation amount of a required refrigerant | coolant (step S14). For example, when the number of outdoor heat exchangers is two as a whole as in the refrigerant circuits shown in FIGS. 1 to 3, when one defrost is completed, the circulation amount of the refrigerant is reduced to half. For example, when there are four outdoor heat exchanger machines and one defrost is completed, the circulation amount of the refrigerant is reduced to 3/4. That is, the circulation rate is reduced in accordance with the ratio of the refrigerant circulation amount necessary for the defrosting of the outdoor heat exchanger 12B or the like that has not been defrosted with respect to the refrigerant circulation amount necessary for the defrosting of all the outdoor heat exchangers 12A or the like. . The control device 30 calculates the number of rotations of the compressor corresponding to the capacity of each compressor and the total refrigerant circulation amount so that the refrigerant discharge amount of each compressor becomes equal, and controls each compressor.
Further, the control device 30 throttles the indoor unit expansion valve in accordance with the circulation amount of the refrigerant (step S15). For example, when the refrigerant circulation amount is halved, the opening degree is adjusted so that the refrigerant flow rate is also halved.

  Next, the control device 30 monitors the pressure of the outdoor heat exchanger 12A on the side where the outdoor unit expansion valve is fully closed, and determines whether the pressure has increased to a predetermined threshold value. For example, a pressure sensor is provided in the vicinity of the entrance / exit of the outdoor heat exchangers 12A and 12B, and the control device 30 monitors the measurement value of the pressure sensor to make a determination. When the pressure rises, the control device 30 opens the outdoor unit expansion valve 13A at a predetermined opening (step S16). The control device 30 may open the outdoor unit expansion valve 13A for a predetermined time and return it to the fully closed state, or may continue the operation while keeping it slightly open. The control device 30 continues to monitor the pressure on the defrost end side, and controls the opening degree of the outdoor unit expansion valve 13A as necessary.

  When defrost is completed in all the outdoor heat exchangers (step S17; Yes), the control device 30 ends the defrost operation (step S18) and restarts the heating operation. In addition, when defrosting is simultaneously completed in all the outdoor unit 1A, 1B by step S12, defrost operation is complete | finished and it returns to heating operation. When defrosting is not completed in all the outdoor heat exchangers (step S17; No), the processing from step S12 is repeated.

In the above description, control is performed to fully close the outdoor unit expansion valve on the defrost completion side after completion of one of the plurality of outdoor heat exchangers 12A and 12B. For example, defrosting is completed. When approaching, the outdoor unit expansion valve on the side that is predicted to be completed may be controlled not to fully close but to reduce the opening degree without waiting for completion. Thereby, circulation of the refrigerant | coolant to the outdoor heat exchanger near completion of defrost can be reduced, and the part can be sent to another outdoor heat exchanger. At this time, the control device 30 may reduce the refrigerant circulation amount by performing control to reduce the compressor rotation speed and the opening of the indoor unit expansion valve.
For example, in the case of the outdoor heat exchanger 12A, the determination that the defrost is approaching completion may be that the temperature measured by the temperature sensor 14A is a predetermined temperature lower than the completion of the defrost operation.

  In addition, the refrigerant circuit illustrated in FIG. 1 etc. is an example, and is not limited to this. The refrigerant circuit system and the control method of the present embodiment can be applied to an apparatus including a refrigerant circuit that can perform a so-called three-tube cooling and heating simultaneous operation. For example, three or more indoor unit units and outdoor unit units may be provided. Another example of the refrigerant circuit is shown in FIG.

FIG. 5 is a diagram illustrating another example of the refrigerant circuit system according to the embodiment of the present invention.
As shown in FIG. 5, the air conditioner 100A includes a plurality of outdoor unit units 1A, 1B, and 1C, a plurality of indoor unit units 2A, 2B, 2C, and 2D, a high-pressure gas pipe 5 that connects them, and a low-pressure gas pipe. 7, the liquid pipes 9, 9 </ b> A, 9 </ b> B, 9 </ b> C and the control device 30.
The discharge side of the compressor 10A is connected to the high pressure gas pipe 5A, and the suction side of the compressor 10A is connected to the low pressure gas pipe 7A. Similarly, the discharge side of the compressor 10B is connected to the high pressure gas pipe 5B, and the suction side is connected to the low pressure gas pipe 7B. The discharge side of the compressor 10C is connected to the high pressure gas pipe 5C, and the suction side is connected to the low pressure gas pipe 7C. One end of the outdoor heat exchanger 12A is connected to the liquid pipe 9A, one end of the outdoor heat exchanger 12B is connected to the liquid pipe 9B, and one end of the outdoor heat exchanger 12A is connected to the liquid pipe 9C. One end of the indoor heat exchanger 22A is switchably connected to the high-pressure gas pipe 5 and the low-pressure gas pipe 7 via the branch controller 21A, and the other end is connected to the liquid pipe 9. Similarly, one end of the indoor heat exchanger 22B is switchably connected to the high-pressure gas pipe 5 and the low-pressure gas pipe 7 via the branch flow controller 21B, and the other end is connected to the liquid pipe 9. One end of the indoor heat exchanger 22C is switchably connected to the high-pressure gas pipe 5 and the low-pressure gas pipe 7 via the branch controller 21C, and the other end is connected to the liquid pipe 9. One end of the indoor heat exchanger 22D is switchably connected to the high-pressure gas pipe 5 and the low-pressure gas pipe 7 via the branch controller 21D, and the other end is connected to the liquid pipe 9.

  Even in the case of the refrigerant circuit illustrated in FIG. 5, when starting the defrost operation, the control device 30 operates the compressors 10A, 10B, and 10C until the defrost of all the outdoor heat exchangers 12A, 12B, and 12C is completed. continue. Thereby, the unevenness | liquidity of a liquid back can be prevented. Further, for example, when the defrost of the outdoor heat exchanger 12A is completed first, the control device 30 is configured so that the outdoor unit expansion valve 13A is fully closed and the refrigerant circulation amount is 2/3. Control to reduce the rotational speed of 10C and control to throttle the opening of the indoor unit expansion valves 23A, 23B, 23C, 23D are performed. As a result, the amount of liquid back can be reduced. Also, response to pressure increase during defrost operation by controlling the opening and closing of the outdoor unit expansion valve provided on the downstream side of the heat exchanger where defrost has been completed (downstream of the refrigerant flow during defrost operation) I do.

  According to this embodiment, the unevenness | liquidity of a liquid back can be reduced by aligning the stop of several compressor 10A, 10B, 10C at the time of a defrost operation. Further, the liquid back amount can be reduced by adjusting the refrigerant circulation amount. Further, when the outdoor unit expansion valve 13A is fully closed (slightly opened), an abnormally high pressure increase during defrost operation is achieved by opening the outdoor unit expansion valve 13A with respect to the pressure increase of the outdoor heat exchanger 12A. Risk can be reduced.

  In addition, it is possible to appropriately replace the components in the above-described embodiments with known components without departing from the spirit of the present invention. The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. The air conditioner 100 is an example of a refrigerant circuit system. The diversion controllers 21A to 21D are examples of a switching mechanism.

1A, 1B, 1C ... outdoor unit 2A, 2B, 2C ... indoor unit 5A, 5B, 5C ... high pressure gas pipe 7A, 7B, 7C ... low pressure gas pipe 9A, 9B, 9C ..Liquid pipes 10A, 10B, 10C ... Compressors 11A, 11B, 11C ... Four-way valves 12A, 12B, 12C ... Outdoor heat exchangers 13A, 13B, 13C ... Outdoor unit expansion valves 14A, 14B, 14C ... temperature sensors 21A, 21B, 21C, 21D ... shunt controllers 22A, 22B, 22C, 22D ... indoor heat exchangers 23A, 23B, 23C, 23D ... indoor unit expansion valves 30. ..Control device 100, 100A ... Air conditioner

Claims (8)

A plurality of outdoor units, a plurality of indoor units, a high pressure gas pipe, a low pressure gas pipe, and a liquid pipe,
A discharge side of a compressor included in the plurality of outdoor units is connected to the high pressure gas pipe,
A plurality of the outdoor units equipped with a compressor, the suction side is connected to the low-pressure gas pipe,
One end of an outdoor heat exchanger provided in the plurality of outdoor units is connected to the liquid pipe,
One end of an indoor heat exchanger included in the plurality of indoor units is connected to the high pressure gas pipe and the low pressure gas pipe via a switching mechanism, and the other end of the indoor heat exchanger is connected to the liquid pipe. Circuit,
In the defrost operation of the refrigerant circuit, a control device that continues the operation of all the compressors until the defrost is completed for all the outdoor heat exchangers included in the plurality of outdoor units,
A refrigerant circuit system comprising:   The refrigerant circuit system according to claim 1, wherein the control device fully closes an expansion valve provided in the outdoor unit including the outdoor heat exchanger that has been defrosted. The control device opens the expansion valve when the pressure of the outdoor heat exchanger is equal to or higher than a predetermined threshold;
The refrigerant circuit system according to claim 2. The control device according to a ratio of a refrigerant circulation amount necessary for defrosting of the outdoor heat exchanger that has not been defrosted to a refrigerant circulation amount necessary for defrosting of all the outdoor heat exchangers included in the refrigerant circuit. To control the rotational speed of all the compressors,
The refrigerant circuit system according to any one of claims 1 to 3. The control device according to a ratio of a refrigerant circulation amount necessary for defrosting of the outdoor heat exchanger that has not been defrosted to a refrigerant circulation amount necessary for defrosting of all the outdoor heat exchangers included in the refrigerant circuit. Reducing the opening degree of the expansion valve provided in all the indoor units,
The refrigerant circuit system according to any one of claims 1 to 4. When the temperature in the vicinity of the outdoor heat exchanger is equal to or higher than a predetermined first threshold, the control device determines that the defrost of the outdoor heat exchanger is completed.
The refrigerant circuit system according to any one of claims 1 to 5. When the temperature in the vicinity of the outdoor heat exchanger becomes equal to or higher than a second threshold value that is lower than the first threshold value, the control device decreases the opening degree of the expansion valve provided in the outdoor unit including the outdoor heat exchanger. Let
The refrigerant circuit system according to claim 6. A plurality of outdoor units, a plurality of indoor units, a high pressure gas pipe, a low pressure gas pipe, and a liquid pipe,
A discharge side of a compressor included in the plurality of outdoor units is connected to the high pressure gas pipe,
A plurality of the outdoor units equipped with a compressor, the suction side is connected to the low-pressure gas pipe,
One end of an outdoor heat exchanger provided in the plurality of outdoor units is connected to the liquid pipe,
One end of an indoor heat exchanger included in the plurality of indoor units is connected to the high pressure gas pipe and the low pressure gas pipe via a switching mechanism, and the other end of the indoor heat exchanger is connected to the liquid pipe. In the defrosting operation of the circuit, the operation of all the compressors is continued until the defrosting is completed for all of the outdoor heat exchangers included in the plurality of outdoor units.
Control method for defrost operation.

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