JP7439591B2 - air conditioner - Google Patents

Description

The present invention relates to an air conditioner that includes an outdoor unit that includes a compressor, an outdoor heat exchanger, and an oil separator, and a plurality of indoor units that include an indoor heat exchanger.

As an air conditioner, for example, Patent Document 1 discloses a refrigerant circuit in which an outdoor unit including a compressor and an outdoor heat exchanger and a plurality of indoor units each including an indoor heat exchanger are connected by refrigerant piping. An air conditioner equipped with a control means for controlling the cooling operation or heating operation of the air-conditioned space in which each indoor unit is installed, and connected to the discharge side of the compressor to convert the discharged refrigerant into refrigerant oil and refrigerant. BACKGROUND ART An air conditioner is known that includes an oil separator to be separated, and an oil return pipe that is connected to the oil separator and the suction side of a compressor and returns the refrigerating machine oil separated by the oil separator to the suction side of the compressor. By providing the oil separator, it is possible to prevent a shortage of refrigerating machine oil in the compressor due to the refrigerating machine oil discharged from the compressor together with the refrigerant flowing to the refrigerant circuit side, flowing into the indoor heat exchanger, and staying there.

Further, in Patent Document 2, an outdoor unit and a plurality of indoor units have a refrigerant circuit connected by refrigerant piping, and a refrigerant circulates through the refrigerant circuit to cool an air-conditioned space in which each of the indoor units is installed. In an air conditioner that performs heating operation, the refrigerant charging amount in the refrigerant circuit is less than the maximum charging amount, which is the refrigerant charging amount that allows all indoor units to perform the same rated capacity according to ISO regulations etc. It is stated that when the regulated filling amount is reached, only the number of indoor units that can be covered by the regulated filling amount is to be operated.

Japanese Patent Application Publication No. 2010-230233 JP 2018-13307 Publication

As mentioned above, in the air conditioner shown in Patent Document 1, the refrigerating machine oil flows into the refrigerant circuit side together with the discharged refrigerant discharged from the compressor, and the refrigerating machine oil accumulates in the indoor heat exchanger. Although it is possible to prevent a shortage of refrigerating machine oil in the machine, on the other hand, the refrigerant discharged from the compressor always passes through an oil separator, so some of the refrigerant is returned to the compressor along with the refrigerating machine oil, causing damage to the refrigerant circuit. In some cases, the required amount of refrigerant circulation was insufficient.

Furthermore, in the air conditioner disclosed in Patent Document 2, the amount of refrigerant oil filled into the refrigerant circuit when the refrigerant is regulated is smaller than the amount of refrigerant oil that is filled into the refrigerant circuit when the refrigerant is filled at the maximum amount. be done. This is due to the following reasons.
First, it is desirable that the amount of refrigerating machine oil filled in the refrigerant circuit be as small as possible without impairing the lubrication of the compressor. If the amount of refrigerating machine oil filled in the refrigerant circuit is large, the amount of refrigerating machine oil discharged from the compressor together with the refrigerant into the refrigerant circuit will also increase, and if there is a large amount of refrigerating machine oil present on the inner wall of the refrigerant flow path in the heat exchanger, This is because heat exchange between the refrigerant and air is inhibited.

Next, the time it takes for the refrigerant oil discharged from the compressor to circulate through the refrigerant circuit and be sucked into the compressor again is determined by the number of rotations of the compressor, the displaced volume, etc., and the refrigerant circulation per unit time in the refrigerant circuit. If the amounts are the same, it can be determined by dividing the amount of refrigerant filled into the refrigerant circuit by the amount of refrigerant circulated per unit time. The smaller the amount of refrigerant filled in the refrigerant circuit, the shorter the time until refrigerating machine oil discharged from the compressor is sucked into the compressor again. The shorter the time it takes for the refrigerating machine oil discharged from the compressor to be sucked into the compressor again, the faster the refrigerating machine oil that has leaked into the refrigerant circuit is returned to the compressor, which reduces the possibility of lubrication failure due to insufficient refrigerating machine oil in the compressor. less likely to occur.

For the reasons described above, in the air conditioner shown in Patent Document 2, the amount of refrigerating machine oil that is filled into the refrigerant circuit at the time of the regulated filling amount is reduced. However, if the amount of refrigerating machine oil filled in the refrigerant circuit is reduced, if there is an indoor unit that is stopped and the refrigerating machine oil accumulated in the indoor unit does not flow out to the refrigerant circuit, the compressor will run out of refrigerating machine oil. There are cases where In such cases, it has been effective to use an oil separator to collect the refrigerating machine oil discharged from the compressor and return it to the compressor. Since a portion of the refrigerant is returned to the compressor along with the refrigerating machine oil via the oil separator, there is a greater possibility that the amount of refrigerant circulated in the refrigerant circuit will be insufficient compared to when the refrigerant charge is at the maximum amount. .

In view of the above problems, the present invention provides a refrigerant circuit in which an outdoor unit including a compressor, a four-way valve, and an outdoor heat exchanger, and a plurality of indoor units each including an indoor heat exchanger are connected by refrigerant piping. and a control means for controlling the outdoor unit and the plurality of indoor units, it is possible to solve both the shortage of refrigerant circulation required in the refrigerant circuit and the shortage of refrigerating machine oil necessary for the compressor. The present invention provides an air conditioner.

One aspect of the present invention provides a refrigerant circuit in which a compressor, a four-way valve, an outdoor unit including an outdoor heat exchanger, and a plurality of indoor units including an indoor heat exchanger are connected via refrigerant piping; An air conditioner comprising: a control means for controlling an outdoor unit and a plurality of the indoor units; and an oil return pipe that connects the suction side of the compressor and returns the refrigerating machine oil separated by the oil separator to the suction side of the compressor, and an oil return pipe that bypasses the oil separator and connects the discharge side of the compressor to the four sides. a bypass passage connecting the valve, and a switching means for switching the flow of refrigerant discharged from the compressor to either the bypass passage side or the oil separator side, and the control means controls the switching means. a normal operation in which the refrigerant discharged from the compressor is caused to flow through the bypass path by switching to the bypass path side; and, when a predetermined condition is satisfied during the normal operation, switching the switching means to the oil separator side; The oil return operation is switched to an oil return operation in which refrigerant discharged from the compressor flows into the oil separator, and even if the refrigerant flows into the oil separator, an amount sufficient to lubricate the compressor is changed. The refrigerating machine oil can be returned to the compressor, and the refrigerant can flow through the refrigerant circuit without shortage , depending on the mode of control for switching between the normal operation and the oil return operation. This is an air conditioner that operates for a short period of time.

According to the present invention, it is possible to solve both the shortage of refrigerant circulation required in the refrigerant circuit and the shortage of refrigerating machine oil required in the compressor.

It is a refrigeration circuit diagram of an indoor conditioner. It is a control block diagram which controls the switching means of an indoor harmony device.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. As an embodiment, an air conditioner will be described as an example in which ten indoor units are connected in parallel to an outdoor unit, 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.

As shown in FIG. 1, the air conditioner 1 in this embodiment includes one outdoor unit 2 and ten indoor units 5-1 connected in parallel to the outdoor unit 2 through a liquid pipe 8 and a gas pipe 9. to 5-10 (in FIG. 1, only two of these indoor units 5-1 and 5-10 are depicted). More specifically, the closing valve 25 of the outdoor unit 2 and the liquid pipe connecting portion 53 of each indoor unit 5 are connected by the liquid pipe 8. Further, the closing valve 26 of the outdoor unit 2 and the gas pipe connecting portion 54 of each indoor unit 5 are connected by a gas pipe 9. In this way, the outdoor unit 2 and the ten indoor units 5 are connected through the liquid pipe 8 and the gas pipe 9 to form the refrigerant circuit 10 of the air conditioner 1. Further, the air conditioner 1 includes a control device 80 as a control means for controlling cooling operation or heating operation of the air-conditioned space in which the indoor units 5-1 to 5-10 are installed.

<Outdoor unit configuration>
First, the outdoor unit 2 will be explained. The outdoor unit 2 is connected to a compressor 20, an oil separator 21, a check valve 49, a four-way valve 22 which is a flow path switching valve, an outdoor heat exchanger 23, an outdoor unit expansion valve 24, and a liquid pipe 8. A closing valve 25 is provided, a closing valve 26 is connected to a gas pipe 9, an accumulator 27, and an outdoor unit fan 28. Each of these devices, except for the outdoor unit fan 28, is connected to each other through refrigerant piping described in detail below to form an outdoor unit refrigerant circuit 20 that forms a part of the refrigerant circuit 10.

The compressor 20 is a variable capacity compressor whose operating capacity can be varied by being driven by a motor (not shown) whose rotational speed is controlled by an inverter. An oil level sensor 30 is provided as an oil amount detection sensor that detects the amount of machine oil. The oil level sensor 30 is arranged so as to be immersed in the refrigerating machine oil stored inside the compressor 20, and outputs a signal corresponding to the position of the stored refrigerating machine oil level. The refrigerant discharge side of the compressor 20 is connected to an oil separator 21 (described later) through a discharge pipe 40, and between the compressor 20 and the oil separator 21 in the discharge pipe 40, the flow of refrigerant in the discharge pipe 40 can be blocked. A first on-off valve 38 is provided. Further, the refrigerant suction side of the compressor 20 is connected to the refrigerant outflow side of the accumulator 27 through a suction pipe 42 .

The oil separator 21 is a centrifugal oil separator having a cylindrical sealed container. The upper surface of the airtight container of the oil separator 21 and a port a of the four-way valve 22, which will be described later, are connected through an outflow pipe 41. Further, one end of an oil return pipe 47, which will be described later, is connected to the lower surface of the airtight container of the oil separator 21. The other end of the oil return pipe 47 is connected to the suction pipe 42, and the oil return pipe 47 is provided with a capillary tube 29.

A bypass passage 48 is provided between the refrigerant discharge side of the compressor 20 and port a of the four-way valve 22 to bypass the first on-off valve 38 and the oil separator 21 and guide the refrigerant discharged from the compressor 20 to the four-way valve 22. It is being The bypass passage 48 has one end connected to the discharge pipe 40 and the other end connected to the outflow pipe 41. The bypass path 48 is provided with a second on-off valve 39 that can shut off the flow of refrigerant in the bypass path 48 . Here, the first on-off valve 38 and the second on-off valve 39 are the switching means 37 in the present invention, and by opening and closing the first on-off valve 38 and the second on-off valve 39 as appropriate, the compressor 2 It functions as a switching means for switching the refrigerant discharged from the bypass passage 48 side or the oil separator 21 side. Note that instead of using the first on-off valve 38 and the second on-off valve 39 as the switching means 37, a three-way valve is provided at the connection between the discharge pipe 40 and the bypass path 48, and discharge from the compressor 20 is performed by operating this three-way valve. The refrigerant may be switched to the bypass path 48 side or the oil separator 21 side.

A discharge pipe 40 is connected to the upper part of the side surface of the airtight container of the oil separator 21 . In this way, by connecting the discharge pipe 40, the outflow pipe 41, and the oil return pipe 47 to the airtight container of the oil separator 21, the oil is discharged from the compressor 20 and enters the airtight container via the discharge pipe 40. The refrigerant containing refrigerating machine oil that has flowed in is separated into refrigerant and refrigerating machine oil inside the airtight container, the separated refrigerating machine oil returns to the compressor 20 via the oil return pipe 47, and the separated refrigerant flows through the outflow pipe 41. flows out to. Note that although refrigerant also flows into the oil return pipe 47 together with refrigerating machine oil, the amount of refrigerant flowing into the compressor 20 is regulated by the capillary tube 29 provided in the oil return pipe 47 . Further, a check valve 49 is provided in the outflow pipe 41 between the connection part of the outflow pipe 41 and the bypass path 48 and the oil separator 21, and the flow of the refrigerant from the oil separator 21 to the outflow pipe 41 is permitted. However, the flow of refrigerant from the outflow pipe 41 to the oil separator 21 is blocked.

The four-way valve 22 is a valve for switching the direction in which the refrigerant flows in the refrigerant circuit 10, and includes four ports a, b, c, and d. Port a is connected to the closed container of the oil separator 21 through the discharge pipe 40, 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 27 through a refrigerant pipe 46 . The port d is connected to the closing valve 26 through an outdoor unit pipe 45.

The outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of an outdoor unit fan 28, which will be described later. As described above, one refrigerant inlet/outlet of the outdoor heat exchanger 23 and port b of the four-way valve 22 are connected by the refrigerant pipe 43. Further, the other refrigerant inlet/outlet of the outdoor heat exchanger 23 and the closing valve 25 are connected by an outdoor unit liquid pipe 44 . The outdoor heat exchanger 23 functions as a condenser when the air conditioner 1 performs a cooling operation, and functions as an evaporator when the air conditioner 1 performs a heating operation.

The outdoor unit expansion valve 24 is provided in the outdoor unit liquid pipe 44. The outdoor unit expansion valve 24 is an electronic expansion valve driven by a pulse motor (not shown), and its opening degree is adjusted depending on the number of pulses given to the pulse motor, thereby controlling the amount of refrigerant flowing into the outdoor heat exchanger 23 or , the amount of refrigerant flowing out from the outdoor heat exchanger 23 is adjusted. The opening degree of the outdoor unit expansion valve 24 is such that when the air conditioner 1 is performing heating operation, the discharge temperature, which is the temperature of the refrigerant discharged from the compressor 21, is determined by the opening degree of the indoor units 5-1 to 5-5. The degree of opening is adjusted so that the target temperature is determined based on the heating capacity required for each. Further, the opening degree of the outdoor unit expansion valve 24 is set to be fully open when cooling operation is being performed.

As described above, the accumulator 27 has a refrigerant inflow side connected to 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 20 through the suction pipe 42. The accumulator 27 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 20 .
The outdoor unit fan 28 is made of a resin material and is arranged near the outdoor heat exchanger 23. The outdoor unit fan 28 is rotated by a fan motor (not shown) to draw outside air into the outdoor unit 2 from an inlet (not shown), and sends the outside air, which has undergone heat exchange with the refrigerant in the outdoor heat exchanger 23, to the outside from an outlet (not shown). Release to the outside of machine 2.

In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1, the discharge pipe 40 includes a discharge pressure sensor 31 that detects the discharge pressure, which is the pressure of the refrigerant discharged from the compressor 20, and a discharge pressure sensor 31 that detects the temperature of the refrigerant discharged from the compressor 20. A temperature sensor 33 is provided. Near the refrigerant inlet of the accumulator 28 in the refrigerant pipe 46, there is a suction pressure sensor 32 that detects the suction pressure, which is the pressure of the refrigerant sucked into the compressor 20, and a suction pressure sensor 32 that detects the temperature of the refrigerant sucked into the compressor 20. A suction temperature sensor 34 is provided.

Between the outdoor heat exchanger 23 and the outdoor unit expansion valve 24 in the outdoor unit liquid pipe 44, the temperature of the refrigerant flowing into the outdoor heat exchanger 23 or the temperature of the refrigerant flowing out from the outdoor heat exchanger 23 is detected. A heat exchanger temperature sensor 35 is provided for this purpose. 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.

FIG. 2 is a control block diagram of the control device 80 that controls the switching means 37 of the indoor conditioner 1. As shown in FIG. As mentioned above, the control device 80 is a control means that controls the cooling operation or heating operation of the air-conditioned space in which the indoor units 5-1 to 5-10 are installed, and includes the discharge pressure sensor 31, the discharge temperature sensor 33, An oil level sensor 30, a first on-off valve 38 and a second on-off valve 39 as switching means 37, a timer 81, and a storage section 82 are connected.

<Configuration of each indoor unit>
Next, the ten indoor units 5-1 to 5-10 will be explained. All ten indoor units 5-1 to 5-10 have the same configuration, including an indoor heat exchanger 51, an indoor unit expansion valve 52 as a refrigerant flow rate adjustment means, a liquid pipe connection part 53, and a gas It includes a pipe connection part 54 and an indoor unit fan 55. These constituent devices except for the indoor unit 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 10.

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 unit fan 55 (described later). One refrigerant inlet/outlet of the indoor heat exchanger 51 and the liquid pipe connection part 53 are connected by an indoor unit liquid pipe 71, and the other refrigerant inlet/outlet and the gas pipe connection part 54 are connected by an indoor unit gas pipe 72. The indoor heat exchanger 51 functions as an evaporator when the air conditioner 1 performs a cooling operation, and functions as a condenser when the air conditioner 1 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 unit expansion valve 52 is provided in the indoor unit liquid pipe 71. The indoor unit 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 of the indoor heat exchanger 51 ( The degree of superheating of the refrigerant at the gas pipe connecting portion 54 side is adjusted so as to reach the target degree of superheating of the refrigerant. 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 unit expansion valve 52 is determined by the refrigerant outlet (liquid pipe connection) of the indoor heat exchanger 51. The degree of subcooling of the refrigerant at the part 53 side) is adjusted so as to reach the target degree of subcooling of the refrigerant. 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 each of the indoor units 5-1 to 5-10 to exhibit sufficient cooling capacity or heating capacity. It is.

The indoor unit fan 55 is made of a resin material and is arranged near the indoor heat exchanger 51. The indoor unit 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 for the indoor air to an outlet (not shown). released 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 unit 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. 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. An indoor temperature sensor 63 that detects the temperature of indoor air flowing into the interior of the indoor unit 5 is provided near a suction port (not shown) of the indoor unit 5.

<Operation of refrigerant circuit>
Next, the flow of refrigerant and the operation of each part in the refrigerant circuit 10 during air conditioning operation of the air conditioner 1 in this embodiment will be described using FIG. 1. In the following description, first, a case in which the air conditioner 1 performs a heating operation will be described, and then a case in which the air conditioner 1 performs a cooling operation will be described. Note that solid arrows in FIG. 1 indicate the flow of refrigerant during heating operation. Moreover, the broken line arrow in FIG. 1 indicates the flow of refrigerant during cooling operation.

<Heating operation>
As shown in FIG. 1, when the air conditioner 1 performs heating operation, the four-way valve 22 is in the state shown by the solid line, that is, the port a and the port d of the four-way valve 22 are in communication with each other, and the port b and port c are switched so that they communicate with each other. Thereby, the refrigerant circuit 10 becomes a heating cycle in which each indoor heat exchanger 51 functions as a condenser and the outdoor heat exchanger 23 functions as an evaporator.

When the compressor 20 is driven while the refrigerant circuit 10 functions as a heating cycle, the refrigerant discharged from the compressor 20 flows through the discharge pipe 40 and flows into the oil separator 21, and from the oil separator 21 to the outflow pipe 41. and flows into the four-way valve 22. The refrigerant flowing out from the four-way valve 22 flows through the outdoor unit gas pipe 45 and flows into the gas pipe 9 via the closing valve 26. Note that, in the oil separator 21, the refrigerating machine oil discharged from the compressor 20 together with the refrigerant is separated from the refrigerant, and the separated refrigerating machine oil flows out from the oil separator 21 as shown by the dashed-dotted line arrow in FIG. It flows through pipe 47 and is returned to compressor 20 via suction pipe 42.

The refrigerant flowing through the gas pipe 9 is divided into the indoor units 5-1 to 5-5 via each gas pipe connection part 54. The refrigerant that has flowed into the indoor units 5-1 to 5-5 flows through each indoor unit gas pipe 72 and flows into each indoor heat exchanger 51. The refrigerant that has flowed into each indoor heat exchanger 51 exchanges heat with the indoor air taken into each indoor unit 5 by the rotation of each indoor unit fan 55, and is condensed.
In this way, each indoor heat exchanger 51 functions as a condenser, and the indoor air heated by exchanging heat with the refrigerant in each indoor heat exchanger 51 is blown into the room from the outlet (not shown). The room in which the indoor units 5-1 to 5-10 are installed is heated.

The opening degree of the refrigerant flowing into each indoor unit liquid pipe 71 from each indoor heat exchanger 51 is adjusted so that the degree of refrigerant subcooling on the refrigerant outlet side of each indoor heat exchanger 51 becomes the target degree of refrigerant subcooling. When passing through each indoor unit expansion valve 52, the pressure is reduced. Here, the target refrigerant subcooling degree is determined based on the heating capacity required of each of the indoor units 5-1 to 5-10. Further, the heating capacity is determined based on the temperature difference between the set temperature and the detected indoor temperature in each of the indoor units 5-1 to 5-10.

The refrigerant whose pressure has been reduced by each indoor unit expansion valve 52 flows out from each indoor unit liquid pipe 71 to the liquid pipe 8 via each liquid pipe connection part 53 . The refrigerant that merges in the liquid pipe 8 and flows into the outdoor unit 2 via the closing valve 25 flows through the outdoor unit liquid pipe 44, and the outdoor unit expands with the opening degree adjusted so that the discharge temperature of the compressor 20 becomes the target temperature. The pressure is further reduced when passing through the valve 24.
The refrigerant whose pressure has been reduced by the outdoor unit expansion valve 24 flows through the outdoor unit liquid pipe 44, flows into the outdoor heat exchanger 23, and is taken into the interior of the outdoor unit 5 by the rotation of the outdoor unit fan 28, which is set at the maximum rotation speed. It exchanges heat with the outside air and evaporates. The refrigerant that has flowed into the refrigerant pipe 43 from the outdoor heat exchanger 23 flows in this order through the four-way valve 22, the refrigerant pipe 46, the accumulator 27, and the suction pipe 42, and is sucked into the compressor 20 and compressed again.

<Cooling operation>
When the air conditioner 1 performs cooling operation, as shown in FIG. and port d are switched so that they communicate with each other. Thereby, the refrigerant circuit 10 becomes a cooling cycle in which each indoor heat exchanger 51 functions as an evaporator and the outdoor heat exchanger 23 functions as a condenser.

When the compressor 20 is driven while the refrigerant circuit 10 functions as a cooling cycle, the refrigerant discharged from the compressor 20 flows through the discharge pipe 40 and flows into the oil separator 21, and from the oil separator 21 to the outflow pipe 41. and flows into the four-way valve 22. Then, the refrigerant flowing out 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 unit fan 28, and is condensed. The refrigerant flowing out from the outdoor heat exchanger 23 to the outdoor unit liquid pipe 44 passes through the outdoor unit expansion valve 24 which is fully open, and flows out into the liquid pipe 8 via the closing valve 25. Note that, in the oil separator 21, the refrigerating machine oil discharged from the compressor 20 together with the refrigerant is separated from the refrigerant, and the separated refrigerating machine oil flows out from the oil separator 21 as shown by the dashed-dotted line arrow in FIG. It flows through pipe 47 and is returned to compressor 20 via suction pipe 42.

The refrigerant flowing through the liquid pipe 8 flows into the indoor units 5-1 to 5-10 via each liquid pipe connection part 53. The refrigerant flowing into the indoor units 5-1 to 5-10 flows through each indoor unit liquid pipe 71, and the opening degree is adjusted so that the degree of refrigerant superheating at each refrigerant outlet of each indoor heat exchanger 51 becomes the target degree of refrigerant superheating. When passing through each adjusted indoor unit expansion valve 52, the pressure is reduced. Here, the target refrigerant superheat degree is determined based on the cooling capacity required of each of the indoor units 5-1 to 5-5. Further, the cooling capacity is determined based on the temperature difference between the set temperature and the detected indoor temperature in each of the indoor units 5-1 to 5-10.

The refrigerant flowing into each indoor heat exchanger 51 from each indoor unit liquid pipe 71 exchanges heat with the indoor air taken into the indoor units 5-1 to 5-10 by the rotation of each indoor unit fan 55. Evaporate. In this way, each indoor heat exchanger 51 functions as an evaporator, and the indoor air cooled by exchanging heat with the refrigerant in each indoor heat exchanger 51 is blown into the room from the outlet (not shown). The room in which the indoor units 5-1 to 5-10 are installed is cooled.
The refrigerant that has flowed out from each indoor heat exchanger 51 into each indoor unit gas pipe 72 flows out into gas pipe 9 via each gas pipe connection portion 54 . The refrigerant that merges in 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 27, and the suction pipe 42, and is sucked into the compressor 20. and compressed again.

Next, the first on-off valve 38 and the second on-off valve 39 as the switching means 37 of this embodiment are controlled to control the normal operation in which the refrigerant discharged from the compressor 20 flows to the bypass path 48 side, and the compression The operation of the oil return operation in which the refrigerant discharged from the machine 20 flows to the oil separator 21 side will be explained.
<Normal operation>
The normal operation is an operation in which the control device 80 controls the first on-off valve 38 and the second on-off valve 39 to flow the refrigerant discharged from the compressor 20 to the bypass path 48 side. When the air conditioner 1 starts operating, the control device 80 closes the first on-off valve 38 and opens the second on-off valve 39. As a result, the refrigerant discharged from the compressor 20 flows through the bypass passage 48 without flowing into the oil separator 21, and flows through the four-way valve 22 to the indoor units 5-1 to 5-10 during heating operation. During cooling operation, the heat flows to the outdoor heat exchanger 23. In normal operation, the refrigerating machine oil discharged from the compressor 20 together with the refrigerant flows to the indoor units 5-1 to 5-10 or the outdoor heat exchanger 23, but some of the discharged refrigerant flows through the oil separator 27. It is possible to prevent the air from being returned to the compressor 20 through the air.

<Oil return operation>
The oil return operation is an operation in which the control device 80 controls the first on-off valve 38 and the second on-off valve 39 to flow the refrigerant discharged from the compressor 20 to the oil separator 21 side. The control device 80 opens the first on-off valve 38 and closes the second on-off valve 39 when a predetermined condition is met during normal operation. When the first on-off valve 38 opens and the second on-off valve 39 closes, the refrigerant discharged from the compressor 20 does not flow into the bypass path 48 but flows into the oil separator 21 . Refrigerating machine oil that has flowed into the oil separator 21 together with the refrigerant is separated from the refrigerant and flows to the suction side of the compressor 20 via the oil return pipe 47 . On the other hand, the refrigerant separated from the refrigerating machine oil by the oil separator 21 flows through the outflow pipe 41 and the four-way valve 22 to the indoor units 5-1 to 5-10 during heating operation, and to the outside during cooling operation. It flows into the heat exchanger 23. As described above, in the oil return operation, part of the refrigerant oil and refrigerant separated by the oil separator 27 is returned to the compressor 20 via the oil return pipe 47, so that the refrigerant oil discharged from the compressor 20 is There is no stagnation in the refrigerant circuit, especially in the outdoor heat exchanger or indoor heat exchanger. Therefore, it is possible to prevent the compressor 20 from running out of refrigerating machine oil.

Next, the control device 80 operates the switching means 37 to direct the refrigerant and refrigeration oil discharged from the compressor 20 to the bypass passage 48, and operates the switching means 37 to direct the refrigerant and refrigeration oil discharged from the compressor 20 to the bypass path 48. Regarding the oil return operation that guides the refrigerant and refrigeration machine oil to the oil separator 21, a control mode for switching from normal operation to oil return operation and a control mode for switching from oil return operation to normal operation will be described.

A first mode of control for switching between normal operation and oil return operation is a mode for switching between normal operation and oil return operation based on the passage of time. When the normal operation is started, the timer 81 is started, and when the timing result of the timer 81 has elapsed for a first predetermined time (an example of the predetermined conditions of the present invention), for example, 4 hours, the control device 80 stops the oil from normal operation. Switch to return operation. Then, when a second predetermined time, for example, 10 minutes has elapsed after switching to the oil return operation, the control device 80 switches from the oil return operation to the normal operation (hereinafter, the second predetermined time refers to the oil return operation (This refers to the time it takes to switch to normal operation.) As a result, the refrigerating machine oil that flows out from the compressor 20 to the refrigerant circuit side together with the refrigerant during normal operation can be returned to the compressor 20 via the oil separator 27, so the compressor 20 is lubricated. The required amount of refrigerating machine oil can be secured. Also, during the oil return operation, a part of the refrigerant discharged from the compressor 20 does not flow to the refrigerant circuit 10 side and returns to the compressor 20 together with the refrigerating machine oil. In the embodiment, by setting the time period to 10 minutes), a shortage of refrigerant on the refrigerant circuit 10 side can be suppressed.

The first predetermined time of four hours illustrated above is a time determined in advance by conducting tests, etc., and if normal operation continues beyond this time, the amount of refrigerating machine oil remaining in the refrigerant circuit 10 will increase, causing the compressor 20 to overflow. This is the time determined as the time during which there is a possibility that the required amount of refrigerating machine oil may not be secured. Further, the second predetermined time of 10 minutes for the oil return operation similarly illustrated is also a time determined in advance through tests, etc., and if the oil return operation is continued for this period, it will be sufficient to lubricate the compressor 20. This is the time determined as the time during which the amount of refrigeration oil can be returned to the compressor. The predetermined time for performing the normal operation and the time for performing the oil return operation may be determined as appropriate through experiments or the like.

The second mode of control for switching between normal operation and oil return operation is a mode for switching between normal operation and oil return operation based on the amount of oil inside the compressor 20. When normal operation is started and the value detected by oil level sensor 30 provided in compressor 20 becomes less than a predetermined value (an example of the predetermined condition of the present invention), control device 80 switches from normal operation to oil return operation. Then, when the value detected by the oil level sensor 30 provided in the compressor 20 becomes a predetermined value or more during the oil return operation, the control device 80 switches from the oil return operation to the normal operation. As a result, the refrigerating machine oil that flows out from the compressor 20 to the refrigerant circuit side together with the refrigerant during normal operation can be returned to the compressor 20 via the oil separator 27, so the compressor 20 is lubricated. The required amount of refrigerating machine oil can be secured. Also, during the oil return operation, a part of the refrigerant discharged from the compressor 20 does not flow to the refrigerant circuit 10 side and returns to the compressor 20 together with the refrigerating machine oil. In the embodiment, by setting the time period to 10 minutes), a shortage of refrigerant on the refrigerant circuit 10 side can be suppressed.

The third mode of control for switching between normal operation and oil return operation is a mode for switching between normal operation and oil return operation based on the degree of discharge superheat. In the refrigerant circuit 10 of the air conditioner 1, when the degree of suction superheat of the refrigerant sucked into the compressor 10 decreases, the discharge superheat degree of the refrigerant discharged from the compressor 10 also decreases. Furthermore, as the suction superheat degree of the suction refrigerant decreases, the proportion of the suction refrigerant in a wet state increases, and when the wet refrigerant is sucked into the compressor 10, the refrigerating machine oil dissolves in the wet refrigerant. The proportion of refrigerating machine oil mixed into the discharged refrigerant increases. Therefore, by measuring the discharge superheat degree of the discharged refrigerant, it is possible to estimate whether the amount of refrigerating machine oil discharged together with the refrigerant discharged from the compressor 10 is large or small (an example of the predetermined conditions of the present invention). Therefore, the third mode of control for switching between normal operation and oil return operation is to switch between normal operation and oil return operation based on the degree of discharge superheat.

When normal operation is started, the control device 80 calculates the degree of discharge superheat from the information of the discharge pressure sensor 31 and the discharge temperature sensor 33, and determines whether the calculated degree of discharge superheat continues to be less than a predetermined value. For example, the control device 80 determines that there is a shortage of refrigerating machine oil in the compressor 20 and switches from normal operation to oil return operation. Then, when the degree of discharge superheat calculated during the oil return operation becomes equal to or higher than a predetermined value, the control device 80 switches from the oil return operation to the normal operation. Note that the fact that the discharge superheat degree is less than a predetermined value indicates that refrigerant oil is mixed with the refrigerant sucked into the compressor and the refrigerant is in a wet state. As a result, the refrigerating machine oil that flows out from the compressor 20 to the refrigerant circuit side together with the refrigerant during normal operation can be returned to the compressor 20 via the oil separator 27, so the compressor 20 is lubricated. The required amount of refrigerating machine oil can be secured. Also, during the oil return operation, a part of the refrigerant discharged from the compressor 20 does not flow to the refrigerant circuit 10 side and returns to the compressor 20 together with the refrigerating machine oil. In the embodiment, by setting the time period to 10 minutes), a shortage of refrigerant on the refrigerant circuit 10 side can be suppressed.
The discharge superheat degree can be determined by calculating the condensation temperature from the discharge pressure detected by the discharge pressure sensor 3, and subtracting the condensation temperature calculated from the discharge temperature detected by the discharge temperature sensor 33. can.

Next, as a fourth mode of control for switching between normal operation and oil return operation, a mode for performing rotation operation, which will be described later, will be described. In an air conditioner, the refrigerant charging amount in the refrigerant circuit 10 is the maximum charging amount that allows all indoor units 5-1 to 5-10 to exhibit their rated capacity according to regulations such as ISO. Control for switching between normal operation and oil return operation in the air conditioner 100 with a smaller regulated filling amount will be described. Note that the air conditioner 100 is the same as the air conditioner 1 except for the amount of refrigerant charged in the refrigerant circuit.

First, control of air conditioning operation in the air conditioner 100 will be explained. In the air conditioner 100, the amount of refrigerant charged in the refrigerant circuit 10 is such that all the indoor units 5-1 to 5-10 can achieve their maximum capacity according to regulations such as ISO. Since the regulated charging amount is smaller than the maximum refrigerant charging amount, the air conditioning capacity required from each indoor unit 5-1 to 5-10 is in accordance with the regulated charging amount to be filled into the refrigerant circuit 10. If only the air conditioning capacity can be demonstrated, for example, even if all the indoor units are required to have the rated capacity, all the indoor units 5-1 to 5-10 will not be able to achieve the rated capacity.

Therefore, in the air conditioner 100, by stopping some of the indoor units 5-1 to 5-10, the operating indoor units are allowed to perform at their rated capacity. At this time, if the indoor unit to be stopped is fixed, the air-conditioned environment of the indoor space handled by the indoor unit to be stopped may deteriorate, causing discomfort to users present in the indoor space. Therefore, some of the indoor units 5-1 to 5-10 are stopped according to the difference between the maximum filling amount and the regulated filling amount, and the indoor units to be stopped are changed at a predetermined timing, for example, every hour. Performs rotation control. In this embodiment, since the air conditioning capacity of one indoor unit corresponds to the shortage of the regulated filling amount with respect to the maximum filling amount, the rotation operation is performed when one of the indoor units 5-1 to 5-10 is used. Stop the indoor unit of the stand.

In the air conditioner 100 of the present embodiment, when the total value of the air conditioning capacity required by each indoor unit exceeds the threshold required capacity that is predetermined according to the regulated filling amount and stored in the storage unit 82, Among the indoor units, nine indoor units corresponding to the threshold required capacity are operated, and the remaining one indoor unit is stopped. Rotation control is then performed to periodically change the indoor units to be stopped.

In this embodiment, the number of indoor units corresponding to the threshold required capacity is nine, and the number of indoor units to be stopped is one, so the control device 80 receives requests from each of the indoor units 5-1 to 5-10. When the total capacity exceeds the threshold required capacity stored in the storage unit 82, first, the indoor unit 5-1 is stopped for a predetermined period of time (for example, one hour). When one hour has elapsed, the control device 80 starts the indoor unit 5-1 and stops the indoor unit 5-2 for one hour. After that, indoor unit 5-3, indoor unit 5-4, indoor unit 5-5 are stopped in order for 1 hour each up to indoor unit 5-10, and after indoor unit 5-10 is stopped for 1 hour, indoor unit is turned on again. Machine 5-1 will be stopped for one hour. Note that the above-mentioned predetermined time of 1 hour is determined in advance by conducting tests, etc., and even if the indoor unit stops during this time, the air conditioning environment in the air-conditioned space that the indoor unit is in charge of will deteriorate extremely (for example, if the setting This is the time when it has been confirmed that the temperature difference between the room temperature and the room temperature will not be 6 degrees Celsius or more.

The mode of control for switching between normal operation and oil return operation when performing rotation control as described above is as follows. By rotation control, the control device 80 switches from normal operation to oil return operation at the timing of stopping indoor unit 5-1, which has already been stopped, and indoor unit 5-2, which is to be stopped next.
The switching from normal operation to oil return operation in rotation control is the timing at which indoor unit 5-2 is stopped next to indoor unit 5-1 (an example of the predetermined conditions of the present invention). For example, the oil return operation is started a second predetermined time (for example, 10 minutes) before the indoor unit 5 to be stopped is switched from the indoor unit 5-1 to the indoor unit 5-2, and the indoor unit to be stopped is switched from the indoor unit 5-2 to the indoor unit 5-2. At the time of switching from indoor unit 5-1 to indoor unit 5-2, oil return operation is switched to normal operation.

When rotation control is performed, refrigerant does not flow in the indoor unit 5 that is stopped during cooling operation because the indoor expansion valve 52 of the indoor unit 5 is closed. Furthermore, in the indoor unit 5 that is stopped during the heating operation, only a small amount of refrigerant flows because the indoor expansion valve 52 of the indoor unit 5 is slightly opened. Therefore, in a stopped indoor unit, refrigerating machine oil tends to stay in the indoor heat exchanger 51, and as the stop time passes, the amount of refrigerating machine oil staying in the indoor heat exchanger 51 increases. For example, at the time of switching the indoor unit to be stopped from indoor unit 5-1 to indoor unit 5-2, a large amount of refrigerating machine oil remains in the indoor unit 5-1, and a lot of refrigerating machine oil remains in the indoor unit 5-2. At this point, most of the refrigerating machine oil remains in the refrigerant circuit 10 except for the compressor 20. Considering the above, control is performed to start the oil return operation a second predetermined time before switching the indoor unit 5 to be stopped, and to switch from the oil return operation to normal operation at the time of switching the indoor unit 5 to be stopped. By doing so, retention of refrigerating machine oil in the refrigerant circuit 10 can be effectively suppressed.

Note that the switching from normal operation to oil return operation in the rotation control is not at the second predetermined time before the time point at which the indoor unit 5 to be stopped is switched, but from the normal operation to the oil return operation at the time point at which the indoor unit 5 to be stopped is switched. , the oil return operation may be switched to normal operation after a second predetermined period of time has elapsed from the time when the indoor unit 5 to be stopped is switched, or the normal operation may be switched to normal operation after a certain period of time has elapsed from the time when the indoor unit 5 to be stopped is switched. The oil return operation may be switched from the oil return operation to the normal operation after a second predetermined period of time has elapsed from the time when the normal operation was switched to the oil return operation. That is, switching from normal operation to oil return operation in rotation control may be performed at the timing of switching the indoor unit 5 to be stopped.

Furthermore, for switching from oil return operation to normal operation in rotation control, the conditions for switching from oil return operation to normal operation as explained in any of the first to third aspects described above are adopted. I don't mind.
Although the embodiments have been described above with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art.

1... Air conditioner, 2... Outdoor unit, 5-1 to 5-10... Indoor unit, 10... Refrigerant circuit, 20... Compressor, 21... Oil separator, 23... Outdoor heat exchanger, 30... Oil level sensor, 37...Switching means, 38...First on-off valve, 39...Second on-off valve, 51...Indoor heat exchanger, 47...Oil return pipe, 48...Bypass path, 80...Control device, 81...Timer, 82...Storage unit

Claims (6)

A refrigerant circuit in which a compressor, a four-way valve, an outdoor unit equipped with an outdoor heat exchanger, and a plurality of indoor units equipped with an indoor heat exchanger are connected by refrigerant piping; In an air conditioner equipped with a control means for controlling the machine,
an oil separator connected to the discharge side of the compressor to separate the discharged refrigerant into refrigeration oil and refrigerant;
an oil return pipe that connects the oil separator and the suction side of the compressor and returns the refrigerating machine oil separated by the oil separator to the suction side of the compressor;
a bypass passage that bypasses the oil separator and connects the discharge side of the compressor and the four-way valve;
a switching means for switching the flow of refrigerant discharged from the compressor to either the bypass path side or the oil separator side,
The control means switches the switching means to the bypass path side to cause the refrigerant discharged from the compressor to flow into the bypass path during normal operation, and when a predetermined condition is satisfied during the normal operation, the switching means is switched to the oil separator side, and an oil return operation is performed in which the refrigerant discharged from the compressor is caused to flow into the oil separator. Switching between the normal operation and the oil return operation is performed to such an extent that a sufficient amount of the refrigerating machine oil to lubricate the compressor can be returned to the compressor, and the refrigerant can flow through the refrigerant circuit without shortage. An air conditioner characterized by operating for a short period of time set depending on a control mode . The air conditioner according to claim 1, wherein the control means performs the oil return operation at regular intervals as the predetermined condition. The compressor includes an oil amount detection sensor that detects the amount of refrigerating machine oil in the compressor,
The control means performs the oil return operation when it is determined that the refrigerating machine oil amount in the compressor is insufficient based on the detection by the oil amount detection sensor as the predetermined condition. 1. The air conditioner according to 1. The refrigerant circuit includes a discharge pressure sensor and a discharge temperature sensor,
The control means calculates a discharge superheat degree using each detection value of the discharge pressure sensor and the discharge temperature sensor as the predetermined condition, and if the calculated discharge superheat degree is less than a predetermined value, the oil The air conditioner according to claim 1, wherein the air conditioner performs a return operation. A refrigerant circuit in which a compressor, a four-way valve, an outdoor unit equipped with an outdoor heat exchanger, and a plurality of indoor units equipped with an indoor heat exchanger are connected by refrigerant piping; In an air conditioner equipped with a control means for controlling the machine,
an oil separator connected to the discharge side of the compressor to separate the discharged refrigerant into refrigeration oil and refrigerant;
an oil return pipe that connects the oil separator and the suction side of the compressor and returns the refrigerating machine oil separated by the oil separator to the suction side of the compressor;
a bypass passage that bypasses the oil separator and connects the discharge side of the compressor and the four-way valve;
a switching means for switching the flow of refrigerant discharged from the compressor to either the bypass path side or the oil separator side,
The refrigerant circuit is filled with a regulated charging amount that is a smaller amount of refrigerant than the maximum charging amount that is the amount of refrigerant necessary for all of the indoor units to exhibit their rated capacities,
The control means switches the switching means to the bypass path side to cause the refrigerant discharged from the compressor to flow into the bypass path during normal operation, and when a predetermined condition is satisfied during the normal operation, the switching means is switched to the oil separator side, and an oil return operation is performed in which the refrigerant discharged from the compressor flows into the oil separator,
As the predetermined condition, rotation control is executed to stop the operation of the indoor unit and change the stopped indoor unit at a predetermined timing according to the difference between the maximum filling amount and the regulated filling amount,
An air conditioner characterized in that the oil return operation is performed when changing the stopped indoor unit to be stopped at a predetermined timing. The switching means includes a first on-off valve disposed in the bypass path and a second on-off valve disposed between the oil separator and the compressor,
The control means opens the first on-off valve and closes the second on-off valve in the case of the normal operation, and closes the first on-off valve and opens the second on-off valve in the case of the oil return operation. The air conditioner according to any one of claims 1 to 5.

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