JP7375490B2 - air conditioner - Google Patents

Description

The present invention relates to an air conditioner in which a plurality of indoor units are connected to an outdoor unit through refrigerant piping.

Conventionally, air conditioners have had multiple indoor units connected to one outdoor unit through liquid and gas pipes, allowing multiple indoor units to perform cooling or heating operations at the same time. Are known. Such an air conditioner is provided with an expansion valve corresponding to each indoor unit, and by adjusting the opening degree of the expansion valve, the flow rate of refrigerant in each indoor unit can be adjusted.

When the above-described air conditioner is performing cooling operation, refrigeration oil discharged from the compressor together with refrigerant passes through an outdoor heat exchanger that functions as a condenser and flows into each indoor unit. At this time, since the expansion valve corresponding to the stopped indoor unit is fully closed, the refrigerating machine oil that has flowed into the indoor unit is blocked by the fully closed expansion valve, and the upstream side from the expansion valve is Remains in the refrigerant pipes (liquid pipes) of other vehicles and in the indoor heat exchanger of indoor units that are stopped. The stagnant refrigerating machine oil cannot flow through the refrigerant circuit and return to the compressor unless the expansion valve is opened.

If refrigerating machine oil accumulates in the liquid pipe or in the stopped indoor unit, there is a shortage of refrigerating machine oil in the compressor, resulting in poor lubrication, which may reduce the reliability of the air conditioner. Therefore, by periodically opening all expansion valves, including those corresponding to stopped indoor units, and performing an oil recovery operation that increases the rotation speed of the compressor compared to during cooling operation, the refrigerating machine oil is returned to the compressor. There is a technique (see Patent Document 1).

Patent No. 6459800

By the way, refrigeration oil is not limited to staying in liquid pipes blocked by expansion valves that are completely closed or in the indoor heat exchanger of a stopped indoor unit. Refrigerating machine oil has a low viscosity when the temperature is high or when the refrigerant is dissolved, but when the temperature is high or when the refrigerant is dissolved, the viscosity is high and it becomes difficult to flow through the refrigerant circuit. Therefore, even if the indoor unit is in operation, the temperature is low and there is little wet refrigerant (gas refrigerant containing liquid refrigerant) downstream of the indoor heat exchanger or further downstream. Refrigerating machine oil tends to accumulate in refrigerant pipes (gas pipes). Therefore, during oil recovery operation, we not only open all expansion valves, including those corresponding to stopped indoor units, but also ensure that a large amount of wet refrigerant flows into the indoor heat exchanger and gas pipe of the operating indoor unit. It is necessary to open the expansion valve to a sufficient degree.

When such an oil recovery operation is performed, the refrigerant flow rate changes compared to before the oil recovery operation is performed. During cooling operation before oil recovery operation, the refrigerant flow rate of each indoor unit is adjusted to match the required capacity of each indoor unit by the compressor and the expansion valve corresponding to each indoor unit. The oil recovery operation changes the compressor rotation speed and the opening degree of each expansion valve, and the refrigerant flow rate fluctuates, resulting in insufficient or excessive cooling capacity of the indoor unit during operation. In addition, refrigerant flows through the indoor unit when it is stopped, producing refrigerant noise. Furthermore, since a large amount of refrigerant is distributed in indoor heat exchangers, gas pipes, etc., the amount of refrigerant distributed to the expansion valve inlet side is reduced, and gas-liquid two-phase refrigerant flows into the expansion valve, which tends to increase refrigerant noise. . In particular, when the amount of refrigerant sealed is small due to refrigerant saving, the refrigerant on the expansion valve inlet side tends to be in two phases: gas-liquid, and the above situation is likely to occur.

The disclosed technology has been developed in view of these points, and is designed to reduce the user's discomfort due to insufficient or excessive cooling capacity and the generation of refrigerant noise, while suppressing the deterioration in reliability due to accumulation of refrigerating machine oil. The purpose is to provide a harmonization device.

In the disclosed aspect, an air conditioner has a refrigerant circuit in which an outdoor unit and a plurality of indoor units are connected by refrigerant piping, and a refrigerant circulates through the refrigerant circuit to cool the air-conditioned space in which each indoor unit is installed. Perform cooling operation. In the oil recovery operation in which refrigerating machine oil discharged from the compressor of the outdoor unit to the refrigerant circuit is recovered to the compressor, the air conditioner opens the expansion valve that controls the refrigerant flow rate of the indoor unit to a first predetermined opening degree. It has a control means that performs first control to perform control for opening the indoor fan and reducing the rotation speed of the indoor fan to a low rotation speed for each of the indoor units of some of the plurality of indoor units.

The disclosed air conditioner can reduce user discomfort caused by insufficient or excessive cooling capacity and generation of refrigerant noise, while suppressing deterioration in reliability due to stagnation of refrigerating machine oil.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of an air conditioner according to an embodiment of the present invention, in which (A) is a refrigerant circuit diagram and (B) is a block diagram of an outdoor unit control means and an indoor unit control means. It is a 1st flowchart which shows the flow of a process regarding oil recovery operation. It is a 2nd flowchart which shows the flow of a process regarding oil recovery operation.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. As an example, an air conditioner will be described as an example in which a plurality of indoor units are connected in parallel to one outdoor unit through refrigerant piping, and all the indoor units can perform cooling operation or heating operation at the same time. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the spirit of the present invention.

FIG. 1 is an explanatory diagram of an air conditioner according to an embodiment of the present invention, in which (A) is a refrigerant circuit diagram, and (B) is a block diagram of an outdoor unit control means and an indoor unit control means. As shown in FIG. 1, an air conditioner 1 according to the present embodiment includes one outdoor unit 2 installed outdoors in a room that is an air-conditioned space, and a liquid pipe 8 and a gas pipe installed indoors. It is equipped with 20 indoor units 5 having the same capacity and connected in parallel through pipes 9 and electric wiring 10. Specifically, one end of the liquid pipe 8 is connected to the closing valve 25 of the outdoor unit 2, and the other end of the liquid pipe 8 is branched and connected to the liquid pipe connection part 53 of each indoor unit 5. One end of the gas pipe 9 is connected to the closing valve 26 of the outdoor unit 2, and the other end of the gas pipe 9 is branched and connected to the gas pipe connecting portion 54 of each indoor unit 5. In this way, the outdoor unit 2 and the 20 indoor units 5 are connected to form the refrigerant circuit 100 of the air conditioner 1. Further, one end of the electrical wiring 10 is connected to a communication section 230 of an outdoor unit 2, which will be described later, and the other end of the electrical wiring 10 is branched and connected to a communication section 530 of each indoor unit 5, which will be described later. In addition, in FIG. 1(A), only three indoor units 5 among the 20 indoor units 5 are shown. Further, the number of indoor units 5 may be a plurality of units other than 20 units.

First, the outdoor unit 2 will be explained. 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. It includes a closing valve 26, an accumulator 28, and an outdoor fan 27. These devices except for the outdoor fan 27 are connected to each other through refrigerant piping, which will be described in detail below, to constitute an outdoor unit refrigerant circuit 20 that forms a part of the refrigerant circuit 100.

The compressor 21 is a variable capacity compressor whose operating capacity can be varied 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 port a of a four-way valve 22, which will be described later, through a discharge pipe 41, and the refrigerant suction side of the compressor 21 is connected to the refrigerant outlet side of the accumulator 28 through a suction pipe 42. has been done.

The four-way valve 22 is a valve for switching the direction in which refrigerant flows, and includes four ports a, b, c, and d. Port a is connected to the refrigerant discharge side of the compressor 21 through the discharge pipe 41, as described above. Port b is connected to one refrigerant inlet/outlet of the outdoor heat exchanger 23 through a refrigerant pipe 43 . The port c is connected to the refrigerant inflow side of the accumulator 28 through a refrigerant pipe 46 . The port d is connected to the closing valve 26 through an outdoor unit gas pipe 45.

The outdoor heat exchanger 23 exchanges heat between a refrigerant and the outside air taken into the outdoor unit 2 by rotation of an outdoor fan 27, which will be described later. One refrigerant inlet/outlet of the outdoor heat exchanger 23 is connected to the port b of the four-way valve 22 through the refrigerant pipe 43 as described above, and the other refrigerant inlet/outlet is connected to the closing valve 25 through 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 when the air conditioner 1 is performing heating operation, that is, when the outdoor heat exchanger 23 functions as an evaporator, the compressor 21 detected by the discharge temperature sensor 33 described later By adjusting the opening degree according to the discharge temperature of the valve, the discharge temperature is prevented from exceeding the upper limit of performance. Further, when the air conditioner 1 is performing cooling operation, that is, when the outdoor heat exchanger 23 functions as a condenser, its opening degree is set to be fully open.

The outdoor fan 27 is made of a resin material and is placed near the outdoor heat exchanger 23. The outdoor fan 27 is rotated by a fan motor (not shown) to draw outside air into the outdoor unit 2 from a suction port (not shown), and the outside air, which has exchanged heat with the refrigerant in the outdoor heat exchanger 23, is transferred to the outdoor unit 2 from an outlet (not shown). released to the outside.

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

In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, the discharge pipe 41 includes a discharge pressure sensor 31 that detects the pressure of the refrigerant discharged from the compressor 21, and a discharge temperature sensor 31 that detects the temperature of the refrigerant discharged from the compressor 21. A sensor 33 is provided. Near the refrigerant inlet of the accumulator 28 in the refrigerant pipe 46, there are 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. is provided.

Between the outdoor heat exchanger 23 and the outdoor expansion valve 24 in the outdoor unit liquid pipe 44, there is a sensor for detecting the temperature of the refrigerant flowing into the outdoor heat exchanger 23 or the temperature of the refrigerant flowing out from the outdoor heat exchanger 23. A heat exchanger temperature sensor 35 is provided. An outside air temperature sensor 36 is provided near a suction port (not shown) of the outdoor unit 2 to detect the temperature of outside air flowing into the interior of the outdoor unit 2, that is, the outside air temperature.

Furthermore, the outdoor unit 2 is equipped with 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. 1(B), the outdoor unit control means 200 includes a CPU 210, a storage section 220, a communication section 230, and a sensor input section 240.

The storage unit 220 includes a ROM and a RAM, and stores control programs 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 communicates with each indoor unit 5. The sensor input unit 240 takes in detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 210.

The CPU 210 takes in the detection results from each sensor of the outdoor unit 2 described above via the sensor input section 240. Further, the CPU 210 receives control signals, which will be described later, transmitted from each indoor unit 5 via the communication section 230 and the electric wiring 10. The CPU 210 controls the drive of the compressor 21 and the outdoor fan 27 based on the acquired detection results and control signals. Further, the CPU 210 performs switching control of the four-way valve 22 based on the captured detection results and control signals. Furthermore, the CPU 210 adjusts the opening degree of the outdoor expansion valve 24 based on the captured detection results and control signals. Further, the CPU 210 sends a control signal to each indoor unit 5 via the electrical wiring 10 based on the captured detection results and control signals.

Next, 20 indoor units 5 will be explained. The 20 indoor units 5 are connected to an indoor heat exchanger 51, an indoor expansion valve 52, a liquid pipe connection part 53 to which the other end of the branched liquid pipe 8 is connected, and the other end of the branched gas pipe 9. A gas pipe connecting portion 54 and an indoor fan 55 are provided. These devices except for the indoor fan 55 are connected to each other through refrigerant piping, which will be described in detail below, to constitute an indoor unit refrigerant circuit 50 that forms a part of the refrigerant circuit 100.

The indoor heat exchanger 51 exchanges heat between a refrigerant and indoor air taken into the indoor unit 5 from a suction port (not shown) through the rotation of an indoor fan 55 (described later), and one refrigerant inlet/outlet is connected to a liquid pipe. 53 through an indoor unit liquid pipe 71, and the other refrigerant inlet/outlet is connected to the gas pipe connecting part 54 through an indoor unit gas pipe 72. The indoor heat exchanger 51 functions as an evaporator when the indoor unit 5 performs a cooling operation, and functions as a condenser when the indoor unit 5 performs a heating operation. In addition, the liquid pipe connection part 53 and the gas pipe connection part 54 are connected to each refrigerant pipe by welding, a flare nut, or the like.

The indoor expansion valve 52 is provided in the indoor unit liquid pipe 71. The indoor expansion valve 52 is an electronic expansion valve, and when the indoor heat exchanger 51 functions as an evaporator, that is, when the indoor unit 5 performs cooling operation, its opening degree is determined by the refrigerant outlet (gas The degree of superheating of the refrigerant at the pipe connection portion 54 side is adjusted so as to reach the target degree of refrigerant superheating. In addition, when the indoor heat exchanger 51 functions as a condenser, that is, when the indoor unit 5 performs heating operation, the opening degree of the indoor expansion valve 52 is determined at the refrigerant outlet (liquid pipe connection part) of the indoor heat exchanger 51. 53 side) is adjusted so that the degree of refrigerant subcooling becomes the target degree of refrigerant subcooling. Here, the target degree of refrigerant superheating and the target degree of refrigerant subcooling are the degree of refrigerant superheating and the degree of refrigerant subcooling necessary for the indoor unit 5 to exhibit sufficient cooling capacity or heating capacity.

The indoor fan 55 is made of a resin material and is placed near the indoor heat exchanger 51. The indoor fan 55 is rotated by a fan motor (not shown) to draw indoor air into the interior of the indoor unit 5 from an inlet (not shown), and exchanges heat with the refrigerant in the indoor heat exchanger 51 to the indoor air from an outlet (not shown). Release into the room.

In addition to the configuration described above, the indoor unit 5 is provided with various sensors. Between the indoor heat exchanger 51 and the indoor expansion valve 52 in the indoor unit liquid pipe 71, there is a liquid-side temperature sensor 61 that detects the temperature of the refrigerant flowing into or out of the indoor heat exchanger 51. It is provided. The indoor unit gas pipe 72 is provided with a gas-side temperature sensor 62 that detects the temperature of the refrigerant flowing out from or flowing into the indoor heat exchanger 51. A suction temperature sensor 63 that detects the temperature of indoor air flowing into the interior of the indoor unit 5, that is, the suction temperature, is provided near a suction port (not shown) of the indoor unit 5.

Further, the indoor unit 5 is equipped with an indoor unit control means 500. The indoor unit control means 500 is mounted on a control board stored in an electrical component box (not shown) of the indoor unit 5, and as shown in FIG. , a sensor input section 540.

The storage unit 520 is composed of a ROM and a RAM, and stores a control program for the indoor unit 5, detection values corresponding to detection signals from various sensors, setting information regarding air conditioning operation by the user, and the like. The communication unit 530 is an interface that communicates with the outdoor unit 2 and other indoor units 5. The sensor input unit 540 takes in detection results from various sensors of the indoor unit 5 and outputs them to the CPU 510.

The CPU 510 takes in the detection results from each sensor of the indoor unit 5 described above via the sensor input section 540. Further, the CPU 510 receives signals including driving information, timer operation settings, etc. set by the user by operating a remote controller (not shown) via a remote control light receiving section (not shown). Further, the CPU 510 transmits control signals including operation start/stop signals and operation information (required capacity, set temperature, indoor temperature, etc.) to the outdoor unit 2 via the communication section 530 and the electric wiring 10, and A control signal including information such as the discharge pressure detected by the outdoor unit 2 is received from the outdoor unit 2 via the communication unit 530 and the electric wiring 10 . The CPU 510 adjusts the opening of the indoor expansion valve 52 and controls the drive of the indoor fan 55 based on the acquired detection results and signals transmitted from the remote control and the outdoor unit 2.

Note that the outdoor unit control means 200 and the 20 indoor unit control means 500 described above constitute the control means of the present invention. The control means of the present invention controls oil recovery operation, which will be described later.

Next, the flow of refrigerant and the operation of each part in the refrigerant circuit 100 during air conditioning operation of the air conditioner 1 in this embodiment will be described using FIG. 1(A). In the following description, a case will be described in which the air conditioner 1 performs a cooling operation and all the indoor units 5 operate, and a detailed description of a case in which the air conditioner 1 performs a heating operation will be omitted. Further, arrows in FIG. 1(A) indicate the flow of refrigerant during cooling operation.

As shown in FIG. 1(A), when the air conditioner 1 performs cooling operation, the CPU 210 of the outdoor unit control means 200 sets the four-way valve 22 to the state shown by the solid line, that is, port a and port b of the four-way valve 22. and port c and port d are switched so that they communicate with each other. Thereby, the refrigerant circuit 100 becomes a cooling cycle in which the outdoor heat exchanger 23 functions as a condenser and each indoor heat exchanger 51 functions as an evaporator.

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 flows through the refrigerant pipe 43 and flows into the outdoor heat exchanger 23 . The refrigerant that has flowed into the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27, and is condensed. The refrigerant flowing out from the outdoor heat exchanger 23 into the outdoor unit liquid pipe 44 is depressurized by the outdoor expansion valve 24 and flows out into the liquid pipe 8 via the closing valve 25 .

The refrigerant flowing through the liquid pipes 8 flows into each indoor unit 5 via the liquid pipe connections 53. The refrigerant flowing into each indoor unit 5 flows through the indoor unit liquid pipe 71, passes through the indoor expansion valve 52, and is depressurized. The depressurized refrigerant flows into the indoor heat exchanger 51, exchanges heat with the indoor air taken into the indoor unit 5 by the rotation of the indoor fan 55, and evaporates. In this way, the indoor heat exchanger 51 functions as an evaporator, and the indoor air that has been cooled by exchanging heat with the refrigerant in the indoor heat exchanger 51 is blown indoors from the outlet (not shown). The room in which the machine 5 is installed is cooled.

The refrigerant flowing out of the indoor heat exchanger 51 flows through the indoor unit gas pipe 72 and flows out into the gas pipe 9 via the gas pipe connection part 54. The refrigerant that flows through the gas pipe 9 and flows into the outdoor unit 2 via the closing valve 26 flows in this order through the outdoor unit gas pipe 45, 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.

Note that when the air conditioner 1 performs a heating operation, the CPU 210 sets the four-way valve 22 to the state shown by the broken line, that is, so that ports a and d of the four-way valve 22 communicate with each other, and port b and port c of the four-way valve 22 communicate with each other. Switch to Thereby, the refrigerant circuit 100 becomes a heating cycle in which the outdoor heat exchanger 23 functions as an evaporator and the indoor heat exchanger 51 of each indoor unit 5 functions as a condenser.

By the way, when the air conditioner 1 performs cooling operation or heating operation, in each indoor unit 5, the CPU 510 of the indoor unit control means 500 detects the set temperature determined by the user and the suction temperature sensor 63, and outputs the detected temperature to the sensor input section. 540 , and transmits the required capacity of each indoor unit 5 based on this temperature difference to the outdoor unit 2 via the communication unit 530 .

On the other hand, the CPU 210 of the outdoor unit control means 200, which has received the required capacity of each indoor unit 5 via the communication unit 230, calculates the total required capacity which is the sum of the required capacity of each indoor unit 5, and calculates the calculated total required capacity. The rotation speed of the compressor 21 is determined to circulate the amount of refrigerant necessary to achieve the capacity through the refrigerant circuit 100. Then, the CPU 210 drives and controls the compressor 21 at the determined rotation speed.

As explained above, when the air conditioner 1 is performing the cooling operation, if there is an indoor unit 5 that is not operating, the indoor expansion valve 52 of the indoor unit 5 is fully closed. The refrigerating machine oil discharged from the compressor 21 together with the refrigerant flows into each indoor unit liquid pipe 71 via the four-way valve 22 , the outdoor heat exchanger 23 and the liquid pipe 8 . Of the machine oil, the refrigerating machine oil that has flowed into the indoor unit liquid pipe 71 provided with the fully closed indoor expansion valve 52 is dammed up by the indoor expansion valve 52 and remains in the indoor unit liquid pipe 71 . Furthermore, in the indoor unit 5 that is in operation, the gas-liquid two-phase refrigerant accompanied by refrigerating machine oil evaporates in the indoor heat exchanger 51, becomes a gas refrigerant, and flows to the indoor unit gas pipe 72 and the gas pipe 9. At this time, a part of the refrigerating machine oil does not flow together with the refrigerant and remains in the indoor heat exchanger 51, the indoor unit gas pipe 72, and the gas pipe 9.

Therefore, the air conditioner 1 performs an oil recovery operation in which the stagnant refrigerating machine oil is recovered into the compressor 21 during the cooling operation. The oil recovery operation performed by the air conditioner 1 includes a first oil recovery operation and a second oil recovery operation. Note that the first oil recovery operation is the first control of the present invention, and the second oil recovery operation is the second control of the present invention. In the first oil recovery operation, the air conditioner 1 opens the indoor expansion valve 52 to a first predetermined opening degree and rotates the indoor fan 55 for each indoor unit 5 under certain conditions. The number of revolutions is set to low. Here, the first predetermined opening degree is an opening degree sufficient to allow wet refrigerant to flow through the gas pipe 9, and is, for example, fully open. Further, the low rotational speed is a rotational speed low enough to allow wet refrigerant to flow through the gas pipe 9, and may be, for example, 0 rpm, that is, the fan may be stopped. In the second oil recovery operation, the air conditioner 1 increases the rotation speed of the compressor 21 to a predetermined rotation speed and opens the indoor expansion valve 52 to a second predetermined opening degree until a predetermined termination condition is satisfied. The operation is performed every first predetermined time T#1. Here, the predetermined termination condition is, for example, that the degree of superheat of the refrigerant sucked into the compressor becomes zero. In addition, T#1 is determined by the compressor oil discharge amount per hour, the length of the connecting piping, etc., and is the time during which it has been confirmed that the necessary oil amount can be maintained in the compressor 21 without performing oil recovery operation. be. Further, the second predetermined opening degree is an opening degree sufficient to allow wet refrigerant to flow through the gas pipe 9, and is, for example, fully open. The second predetermined opening degree may be the same as or different from the first predetermined opening degree. Note that during heating operation, the temperature of the gas pipe 9 is high and the viscosity of the oil is reduced, so that the oil tends to return to the compressor 21. Therefore, during the heating operation, the air conditioner 1 does not need to perform the oil recovery operation as described above.

In the first oil recovery operation, the air conditioner 1 opens the indoor expansion valve 52 to a first predetermined opening degree to increase the refrigerant flow rate, and lowers the rotation speed of the indoor fan 55 to reduce the rotation speed of the indoor heat exchanger. Since evaporation of the refrigerant at 51 can be suppressed, the refrigerating machine oil that was dammed up by the indoor expansion valve 52 and accumulated in the indoor unit liquid pipe 71 is flushed out, and the indoor heat exchanger 51, the indoor unit gas pipe 72, and the gas The liquid phase refrigerant flowing into the pipe 9 increases. Thereby, the refrigerating machine oil can flow together with the wet refrigerant, and the accumulation of the refrigerating machine oil can be suppressed. In addition, in the first oil recovery operation, the air conditioner 1 can suppress fluctuations in the refrigerant flow rate by recovering oil from only some of the indoor units 5, compared to a case where all indoor units 5 are recovering oil at the same time. shortages and surpluses can be suppressed. Here, some of the indoor units 5 are, for example, 5 of the 20 connected indoor units. In addition, in the first oil recovery operation, the air conditioner 1 recovers oil from only some of the indoor units 5, so that there is no shortage of refrigerant compared to a case where all indoor units 5 recover oil at the same time (the indoor expansion valve 52 Since the upstream does not become a two-phase refrigerant), the generation of refrigerant noise can be suppressed. Therefore, through the first oil recovery operation, the air conditioner 1 can reduce user discomfort while suppressing a decrease in reliability.

Further, when the indoor unit 5 stops operating, the air conditioner 1 performs the first oil recovery operation using the stopped indoor unit 5 as a part of the indoor unit 5. Here, the time when the indoor unit 5 stops operation is the period after receiving a stop instruction from a remote controller etc. until the operation of the indoor unit 5 stops, and during this period, the air conditioner 1 Start driving. When the first oil recovery operation is performed on the indoor unit 5 that is in operation, the rotation speed of the indoor fan 55 is set to a low rotation speed, thereby reducing the cooling capacity and making the user feel uncomfortable. On the other hand, by performing the first oil recovery operation on the indoor unit 5 that is stopped, the air conditioner 1 can eliminate user discomfort caused by fluctuations in cooling capacity. In addition, by performing the first oil recovery operation targeting the stopped indoor unit 5 and not targeting the stopped indoor unit 5, the air conditioner 1 can suddenly recover oil from the stopped indoor unit 5. Eliminates refrigerant noise. Therefore, the air conditioner 1 can further reduce user discomfort. Note that when performing the first oil recovery operation when the indoor unit 5 stops operating, the air conditioner 1 stops the rotation of the indoor fan 55 of the indoor unit 5 that is to be stopped.

Further, the air conditioner 1 performs the first oil recovery operation when the indoor unit 5 is stopped when the indoor unit 5 is in operation when the total operating capacity is equal to or higher than a predetermined value. The reason is that when the total operating capacity is high, many indoor units 5 are operating, so the effect on the refrigerant flow rate due to stopping the operation of the indoor units 5 is relatively small, and fluctuations in cooling capacity are reduced. This is because it can be made smaller. Conversely, if the total operating capacity is small, the effect of stopping one indoor unit 5 will be large. For example, even if three of the indoor units 5 that are in operation stop, the number of indoor units that are operating is 10 more than the case where there are five indoor units that are in operation (total operating capacity is small). (The total operating capacity is large), the fluctuation in cooling capacity is smaller. By reducing fluctuations in cooling capacity, the air conditioner 1 can further reduce user discomfort.

Furthermore, the air conditioner 1 performs the first oil recovery operation when stopping the indoor unit 5 due to the rotation operation, which is when the indoor unit 5 is stopped when the total operating capacity is equal to or greater than a predetermined value. Here, rotation operation means that some of the indoor units 5 are stopped when the total required capacity exceeds the threshold required capacity, and the indoor units 5 that are stopped are periodically changed in order to avoid an operation where there is a shortage of refrigerant. This is a driving style. In the rotation operation, since the plurality of indoor units 5 are sequentially stopped, oil can be recovered from the plurality of indoor units 5 and the gas pipe 9 downstream thereof, and stagnation of refrigerating machine oil can be suppressed. Further, in the rotation operation, since an indoor unit 5 having the same capacity as the indoor unit 5 that is stopped starts operating, fluctuations in the overall refrigerant flow rate can be reduced, and fluctuations in cooling capacity can be reduced. Therefore, by performing the first oil recovery operation when the indoor unit 5 is stopped due to the rotation operation, the air conditioner 1 can further reduce the user's discomfort while further suppressing a decrease in reliability.

In addition, the air conditioner 1 performs the first oil recovery operation when stopping the indoor unit 5 due to the rotation operation, and after the end condition of the first oil recovery operation is satisfied, the air conditioner 1 performs the first oil recovery operation in a new operation room where the rotation operation starts a new operation. Open the indoor expansion valve 52 of the machine 5. The air conditioner 1 starts the indoor expansion valve of the newly operated indoor unit 5 in the rotation operation at the end of the first oil recovery operation (that is, at the timing of closing the indoor expansion valve 52 of the indoor unit 5 to be stopped), not at the start of the first oil recovery operation. 52 is opened, it is possible to reduce fluctuations in the overall refrigerant flow rate and in cooling capacity. Therefore, the air conditioner 1 can further reduce user discomfort.

In addition, the air conditioner 1 performs the first oil recovery operation when stopping the indoor unit 5 due to the rotation operation, and after the completion condition of the first oil recovery operation is satisfied, the indoor unit 5 performs the first oil recovery operation. The indoor expansion valve 52 is closed. At this time, the air conditioner 1 begins to close the indoor expansion valve 52 of the indoor unit 5 that has performed the first oil recovery operation, and at the same time begins to open the indoor expansion valve 52 of the newly operated indoor unit 5 that has performed the rotation operation. At the same time as the indoor expansion valve 52 of the indoor unit 5 that performed the first oil recovery operation begins to close, the indoor expansion valve 52 of the newly operated indoor unit 5 in the rotation operation begins to open. At the same time as the refrigerant flow rate of the unit 5 decreases, the refrigerant flow rate of the newly operated indoor unit 5 increases. Therefore, the air conditioner 1 can further reduce fluctuations in the overall refrigerant flow rate, and can further reduce fluctuations in cooling capacity. Therefore, the air conditioner 1 can further reduce user discomfort.

Moreover, when the air conditioner 1 performs the first oil recovery operation, it lengthens the interval until the next second oil recovery operation. That is, when the air conditioner 1 performs the first oil recovery operation, the air conditioner 1 sets the second predetermined time T#2, which is larger than the first predetermined time T#1, as the interval until the next second oil recovery operation. When the first oil recovery operation is performed, a portion of the refrigerating machine oil remaining in the indoor unit 5 and the gas pipe 9 where the first oil recovery operation was performed can be recovered into the compressor 21. Therefore, the air conditioner 1 can lengthen the interval until the next second oil recovery operation, reduce the frequency of the second oil recovery operation, and reduce the fluctuations in cooling capacity caused by the second oil recovery operation. Reduce the frequency of sounds. Therefore, the air conditioner 1 can further reduce user discomfort.

Furthermore, the air conditioner 1 sets the condition for ending the first oil recovery operation to be that the degree of superheat of the refrigerant sucked into the compressor becomes 0, or that a predetermined oil recovery time T#3 elapses. When the degree of superheat of the compressor suction refrigerant becomes 0 and the first oil recovery operation is ended, the air conditioner 1 resets the time count from the previous end of the second oil recovery operation. When the degree of superheating of the compressor suction refrigerant becomes 0, it means that the wet refrigerant has passed through the entire path from the indoor unit 5 where the first oil recovery operation was performed to the suction of the compressor 21, and this path This means that the stagnant refrigerating machine oil was able to be recovered into the compressor 21. Therefore, the air conditioner 1 can secure a certain amount of refrigerating machine oil in the compressor 21 without performing the second oil recovery operation that collects the refrigerating machine oil from all the indoor units 5 and gas pipes 9. . Therefore, the air conditioner 1 can reset the time count from the end of the previous second oil recovery operation, treating it as the same as the execution of the second oil recovery operation, and reduce the frequency of the second oil recovery operation. This reduces the frequency of cooling capacity fluctuations and refrigerant noise caused by the second oil recovery operation. Therefore, the air conditioner 1 can further reduce user discomfort.

Next, the flow of processing related to oil recovery operation will be explained. FIGS. 2A and 2B are flowcharts showing the flow of processing related to oil recovery operation. Note that in FIGS. 2A and 2B, a case will be described in which the first oil recovery operation is performed while the rotation operation is being performed. As shown in FIG. 2A, the air conditioner 1 starts counting the timer #1 and turns off the flag #1 (step S1). Here, timer #1 is a count value processed by the CPU 210, and counts the time since the end of the previous second oil recovery operation. Further, flag #1 is a flag indicating whether or not the first oil recovery operation has been performed since the previous second oil recovery operation.

Then, the air conditioner 1 determines whether or not the cooling operation is in progress (step S2), and if the cooling operation is not in progress (step S2-No), the process ends. On the other hand, if the cooling operation is in progress (step S2-Yes), the air conditioner 1 determines whether flag #1 is OFF (step S3), and if flag #1 is OFF, (Step S3-Yes), it is determined whether timer #1 is greater than T#1 (Step S4).

If timer #1 is greater than T#1 (step S4-Yes), air conditioner 1 performs the second oil recovery operation. That is, the air conditioner 1 increases the compressor rotation speed to a predetermined rotation speed and opens the indoor expansion valve 52 to a second predetermined opening degree (step S6). Then, the air conditioner 1 determines whether a predetermined termination condition is satisfied (step S7), and if the predetermined termination condition is not satisfied (step S7-No), the determination in step S7 is made. repeat. Then, when the predetermined termination condition is satisfied (step S7-Yes), the air conditioner 1 resets the timer #1, turns off the flag #1, and changes the compressor rotation speed and the opening degree of the indoor expansion valve 52. is returned to the state before the start of the second oil recovery operation (step S8). Then, the air conditioner 1 returns to step S2.

On the other hand, if flag #1 is not OFF in step S3 (step S3-No), the air conditioner 1 determines whether timer #1 is greater than T#2 (step S5). If timer #1 is greater than T#2 (step S5-Yes), the air conditioner 1 proceeds to step S6.

Further, if timer #1 is not greater than T#1 in step S4 (step S4-No), or if timer #1 is not greater than T#2 in step S5 (step S5-No), the air conditioner The device 1 determines whether to change the indoor unit that is stopped due to rotation operation (step S9). Note that the condition for the determination is, for example, whether a predetermined time has elapsed since the indoor unit to be stopped was changed last time. If the indoor unit to be stopped is not changed (step S9-No), the air conditioner 1 returns to step S2.

On the other hand, when changing the indoor unit to be stopped (step S9-Yes), the air conditioner 1 performs the first oil recovery operation. That is, the air conditioner 1 stops the rotation of the indoor fan 55 and opens the indoor expansion valve 52 to the first predetermined opening degree for the indoor unit 5 that is newly stopped due to the rotation operation (step S10). Then, the air conditioner 1 starts counting the timer #2 (step S11). Here, timer #2 is a count value processed by the CPU 210, and counts the time from the start of the first oil recovery operation.

Then, the air conditioner 1 determines whether the degree of superheat of the compressor suction refrigerant is 0 (step S12), and if it is 0 (step S12-Yes), resets timer #1 ( Step S13). Then, the air conditioner 1 opens the indoor expansion valve 52 of the newly operated indoor unit 5 in the rotation operation, and closes the indoor expansion valve 52 of the indoor unit 5 that has performed the first oil recovery operation (step S15). Then, the air conditioner 1 resets the timer #2, stops counting the timer #2, turns on the flag #1 (step S16), and returns to step S2.

On the other hand, if the degree of superheat of the compressor suction refrigerant is not 0 (step S12-No), the air conditioner 1 determines whether timer #2 is greater than T#3 (step S14), and T# If it is not greater than 3 (step S14-No), the process returns to step S12. On the other hand, if timer #2 is greater than T#3 (step S14-Yes), the air conditioner 1 moves to step S15.

As described above, the air conditioner 1 of the present embodiment operates in a part of the room by opening the indoor expansion valve 52 to the first predetermined opening degree and reducing the rotation speed of the indoor fan 55 to a low rotation speed. The first oil recovery operation is carried out for each machine 5. The air conditioner 1 increases the refrigerant flow rate by opening the indoor expansion valve 52 to a first predetermined opening degree, and lowers the rotation speed of the indoor fan 55 to reduce the refrigerant in the indoor heat exchanger 51. Since the evaporation of the refrigerating machine oil is suppressed, the refrigerating machine oil that has been dammed up by the indoor expansion valve 52 and accumulated in the indoor unit liquid pipe 71 is flushed out, and also flows to the indoor heat exchanger 51, the indoor unit gas pipe 72, and the gas pipe 9. Increase the liquid phase refrigerant and flow the refrigerating machine oil together with the wet refrigerant to suppress the accumulation of the refrigerating machine oil. Furthermore, since the air conditioner 1 collects oil for each of the indoor units 5, it suppresses insufficient or excessive cooling capacity and generation of refrigerant noise, compared to a case where oil is collected from all indoor units 5 at the same time. Therefore, the air conditioner 1 can reduce user discomfort while suppressing a decrease in reliability.

Furthermore, when the indoor unit 5 stops, the air conditioner 1 performs the first oil recovery operation on the stopped indoor unit 5, so that fluctuations in the cooling capacity are suppressed and the indoor unit 5 that has stopped is Prevents refrigerant noise that occurs when recovering oil from Thereby, the air conditioner 1 can further reduce user discomfort.

In addition, when the air conditioner 1 stops the indoor units 5 that are in operation when the total operating capacity is greater than or equal to a predetermined value, the air conditioner 1 performs the first oil recovery operation for the indoor units 5 to be stopped. Fluctuations can be reduced. Thereby, the air conditioner 1 can further reduce user discomfort.

In addition, when the air conditioner 1 stops the indoor unit 5 by rotation operation, it performs the first oil recovery operation for the indoor unit 5 to be stopped and the gas pipe 9 downstream thereof, thereby suppressing the accumulation of refrigerating machine oil. At the same time, fluctuations in cooling capacity can be reduced. Thereby, the air conditioner 1 can further reduce user discomfort while further suppressing a decrease in reliability.

Furthermore, when performing the first oil recovery operation for the indoor unit 5 that is stopped due to the rotation operation, the air conditioner 1 performs the first oil recovery operation on the newly operated indoor unit 5 in the rotation operation after the end condition of the first oil recovery operation is satisfied. Since the indoor expansion valve 52 is opened, fluctuations in cooling capacity can be reduced. Thereby, the air conditioner 1 can further reduce user discomfort.

In addition, the air conditioner 1 starts to close the indoor expansion valve 52 of the indoor unit 5 that has performed the first oil recovery operation, and at the same time starts to open the indoor expansion valve 52 of the newly operated indoor unit 5 that is in the rotation operation. Fluctuations in ability can be made smaller. Thereby, the air conditioner 1 can further reduce user discomfort.

In addition, when the air conditioner 1 performs the first oil recovery operation, the interval until the next second oil recovery operation is lengthened, so the frequency of the second oil recovery operation is reduced, and the second oil recovery operation is performed. Reduces fluctuations in cooling capacity and frequency of refrigerant noise caused by Thereby, the air conditioner 1 can further reduce user discomfort.

Moreover, when the degree of superheat of the compressor suction refrigerant becomes 0 and the first oil recovery operation is ended, the air conditioner 1 resets the time count from the previous end of the second oil recovery operation. Thereby, the air conditioner 1 can reduce the frequency of the second oil recovery operation and further reduce user discomfort.

In this embodiment, a case has been described in which the indoor unit 5 is provided with the indoor expansion valve 52. However, the air conditioner is equipped with an expansion valve that controls the refrigerant flow rate of the indoor unit, for example, in a liquid pipe, for each indoor unit. It may be provided in association with each indoor unit immediately after branching so as to be distributed.

1 Air conditioner 2 Outdoor unit 5 Indoor unit 8 Liquid pipe 9 Gas pipe 10 Electric wiring 21 Compressor 31 Discharge pressure sensor 33 Discharge temperature sensor 52 Indoor expansion valve 55 Indoor fan 71 Indoor unit liquid pipe 72 Indoor unit gas pipe 100 Refrigerant circuit 200 Outdoor unit control means 210 CPU
220 Storage unit 230 Communication unit 240 Sensor input unit 500 Indoor unit control means 510 CPU
530 Communication Department

Claims (7)

An air conditioner having a refrigerant circuit in which an outdoor unit and a plurality of indoor units are connected by refrigerant piping, and in which a refrigerant circulates through the refrigerant circuit to perform cooling operation of an air-conditioned space in which each indoor unit is installed. ,
In an oil recovery operation in which refrigerating machine oil discharged from a compressor of the outdoor unit to the refrigerant circuit is recovered to the compressor, an expansion valve that controls the refrigerant flow rate of the indoor unit is opened to a first predetermined opening degree, and the indoor fan comprising a control means for performing first control for controlling the rotation speed to a low rotation speed for each of some of the indoor units of the plurality of indoor units;
The control means controls the compressor to a predetermined rotation speed and controls the opening degree of all the expansion valves for controlling the refrigerant flow rate of the indoor unit to a second predetermined opening degree at first predetermined time intervals. and if the first control is performed before the first predetermined time elapses from the previous second control, the time until the next second control is longer than the first predetermined time. 2 Change to the specified time,
Air conditioner. When stopping operation of the indoor units, the control means performs the first control using the indoor units to be stopped as part of the indoor units .
The air conditioner according to claim 1. The control means performs the first control when stopping the operation of the indoor units in operation when the total operating capacity of the plurality of indoor units is greater than or equal to a predetermined value .
The air conditioner according to claim 2. The control means stops the indoor units to be stopped when the total required capacity exceeds the threshold required capacity, performs a rotation operation that is an operation in which the indoor units to be stopped are periodically changed, and performs a rotation operation in which the indoor units to be stopped are periodically changed. performing the first control when stopping the operation of the machine ;
The air conditioner according to claim 3. The control means opens an expansion valve that controls the refrigerant flow rate of the newly operated indoor unit in the rotation operation after the termination condition of the first control is satisfied .
The air conditioner according to claim 4. The control means controls the refrigerant flow rate of the newly operated indoor unit at the same time as starting to close an expansion valve that controls the refrigerant flow rate of the indoor unit that has performed the first control after the termination condition of the first control is satisfied. Start opening the expansion valve ,
The air conditioner according to claim 5. Suction pressure detection means for detecting suction pressure that is the pressure of refrigerant sucked into the compressor;
Suction temperature detection means for detecting a suction temperature that is the temperature of the refrigerant sucked into the compressor ;
It further has
The control means terminates the first control when the degree of superheat of the refrigerant sucked into the compressor becomes 0 or a predetermined oil recovery time elapses, and resumes the first control when the degree of superheat becomes 0. If completed, reset the time count from the previous second control until the first predetermined time elapses ;
The air conditioner according to claim 1 .

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