CN111712677B

CN111712677B - Refrigeration cycle device

Info

Publication number: CN111712677B
Application number: CN201880089461.7A
Authority: CN
Inventors: 三浦贤; 今任尚希
Original assignee: Toshiba Carrier Corp
Current assignee: Toshiba Carrier Corp
Priority date: 2018-02-16
Filing date: 2018-02-16
Publication date: 2022-01-07
Anticipated expiration: 2038-02-16
Also published as: CN111712677A; WO2019159335A1; GB2583666A; JPWO2019159335A1; JP6859461B2; GB202010975D0; GB2583666B

Abstract

The invention provides a refrigeration cycle device which is excellent in reliability in that shortage of lubricating oil in each outdoor unit can be eliminated properly and quickly. When the amount of lubricating oil in any one of the compressors is less than a set value, the circulation amount of refrigerant to the outdoor unit in which the compressor is present is set to be greater than the circulation amount of refrigerant to the other outdoor units.

Description

Refrigeration cycle device

Technical Field

An embodiment of the present invention relates to a refrigeration cycle apparatus including a plurality of outdoor units.

Background

A multi-split refrigeration cycle apparatus is known which includes a plurality of outdoor units having compressors and outdoor heat exchangers, and a plurality of indoor units having indoor heat exchangers, and controls the number of operating compressors and the capacity of the compressors in each outdoor unit in accordance with the sum of the capacities required for each indoor unit.

The compressor of each outdoor unit accommodates a motor, a cylinder, and the like in a sealed casing together with a lubricating oil. The lubricating oil flows out from the sealed casing into the refrigeration cycle as the refrigerant is discharged. Therefore, the lubricating oil may be insufficient in any outdoor unit. When the lubricant is insufficient, the sliding parts such as the motor and the cylinder are in a fuel cut-off state, and a bad image is generated on the life of the compressor.

As a countermeasure, the following control is adopted: an oil separator is provided in the refrigeration cycle, and the lubricating oil retained in the oil separator is returned to each compressor as needed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-2160

Disclosure of Invention

Technical problem to be solved by the invention

Returning only the lubricating oil from the oil separator is not an adequate solution to the lack of lubricating oil.

An object of an embodiment of the present invention is to provide a refrigeration cycle apparatus having excellent reliability in which shortage of a lubricating oil in each outdoor unit can be appropriately and quickly eliminated.

Technical scheme for solving technical problem

The refrigeration cycle apparatus of claim 1 comprising: a plurality of outdoor units having compressors and outdoor heat exchangers; a plurality of indoor units having indoor heat exchangers; and a controller configured to set a circulation amount of the refrigerant to the outdoor unit in which the compressor is present to be larger than a circulation amount of the refrigerant to another outdoor unit when an amount of the lubricating oil in any one of the compressors is smaller than a set value.

Drawings

Fig. 1 is a diagram showing a configuration of embodiment 1.

Fig. 2 is a diagram showing a relationship between a circulation amount ratio of the refrigerant in each outdoor unit and a deviation ratio of the lubricating oil in each outdoor unit according to each embodiment.

Fig. 3 is a flowchart showing the control of embodiment 1.

Fig. 4 is a diagram showing the structure of embodiment 2.

Fig. 5 is a flowchart showing the control of embodiment 2.

Fig. 6 is a diagram showing the structure of embodiment 3.

Fig. 7 is a flowchart showing the control of embodiment 3.

Fig. 8 is a diagram showing the structure of embodiment 4.

Fig. 9 is a flowchart showing the control of embodiment 4.

Fig. 10 is a flow chart following fig. 9.

Fig. 11 is a diagram showing the structure of embodiment 5.

Fig. 12 is a flowchart showing the control of embodiment 5.

Detailed Description

[1] Embodiment 1

Embodiment 1 of the present invention will be described with reference to fig. 1 to 3.

As shown in fig. 1, a plurality of outdoor units a1 and a2 are connected in parallel by pipes, and a plurality of indoor units B1, B2, and … Bn are connected to the outdoor units a1 and a2 by pipes. These pipes are connected to constitute a refrigeration cycle apparatus of an air conditioner.

< Structure of outdoor unit A1 >

The outdoor unit a1 includes: a compressor 1 a; high-pressure-

side pipes

2a and 2 through which the refrigerant discharged from the compressor 1a flows; an oil separator 3 into which the gas refrigerant in the high-pressure-side pipe 2 flows; a four-way valve 4 through which the gas refrigerant passing through the oil separator 3 flows; an outdoor heat exchanger 5 into which the gas refrigerant having passed through the four-way valve 4 flows; an electric expansion valve 6 for decompressing the liquid refrigerant heading from the outdoor heat exchanger 5 to the indoor units B1, B2, and … Bn; a liquid-side filling valve 7a and a gas-side filling valve 7b for pipe connection; a receiver 8 through which the gas refrigerant having passed through the indoor units B1, B2, and … Bn flows via the four-way valve 4, and low-pressure-side pipes 9 and 9a through which the gas refrigerant flowing out of the receiver 8 is introduced into a suction port of the compressor 1 a; an outdoor fan 10 disposed in the vicinity of the outdoor heat exchanger 5; a high-pressure side temperature sensor 41 and a high-pressure side pressure sensor 42 attached to the high-pressure side pipe 2; a low-pressure-side pressure sensor 43 attached to the low-pressure-side pipe 9; a main controller 50; and an inverter 51 and the like.

The compressor 1a is a hermetic compressor in which the motor M, the cylinder Q, and the like are housed in a hermetic case together with the lubricating oil La. The oil separator 3 separates the lubricating oil L contained in the gas refrigerant flowing in from the high-pressure-side pipe 2, holds the separated lubricating oil L therein, and flows out the separated gas refrigerant to the four-way valve 4. The motor-operated expansion valve 6 is a pulse motor valve, and the opening degree thereof continuously changes according to the number of drive pulses input.

The outdoor unit a1 includes a gas return pipe 11 having one end connected to the high-pressure-side pipe 2, a gas return pipe 11a extending from the other end of the gas return pipe 11 and connected to the low-pressure-side pipe 9a, a pressure reducer, for example, a capillary tube 12, provided in the gas return pipe 11, a capillary tube 13a provided in the gas return pipe 11a, and a temperature sensor 44 attached to a downstream side of the capillary tube 12 in the gas return pipe 11. The

gas return pipes

11 and 11a return a part of the gas refrigerant in the high-pressure-side pipe 2a to the low-pressure-side pipe 9 a. The temperature sensor 44 detects a temperature T1 of the gas refrigerant that has passed through the gas return pipe 11 and has been depressurized by the capillary tube 12.

The outdoor unit a1 includes an oil return pipe 21a connected between the side of the sealed casing of the compressor 1a and the other end of the gas return pipe 11, a check valve 12a and a pressure reducer, such as a capillary tube 23a, provided in the oil return pipe 21a, and a temperature sensor 45a attached to a position downstream of the capillary tube 23a in the oil return pipe 21 a. The oil return pipe 21a is connected from the lower portion of the hermetic casing of the compressor 1a to a position at a predetermined height. This connection position is a reference for determining whether or not the amount of the lubricating oil La in the sealed housing is equal to or greater than a set value.

For example, when the oil level of the lubricant La reaches the connection position of the oil return pipe 21a, the lubricant La flows through the oil return pipe 21a, and the gas refrigerant flows through the gas return pipe 11. The temperature of the lubricating oil La flowing through the oil return pipe 21a does not drop even if the pressure is reduced by the capillary tube 23a, and the temperature of the gas refrigerant flowing through the gas return pipe 11 drops as the pressure is reduced by the capillary tube 12. In this case, since a difference is generated between the detected temperature T1 of the temperature sensor 44 and the detected temperature T2a of the temperature sensor 45a, the main controller 50 can determine that the amount of the lubricating oil La is not in a state of insufficient lubricating oil smaller than the set value.

When the oil level of the lubricating oil La does not reach the connection position of the oil equalizing pipe 21a, the gas refrigerant flows through the oil return pipe 21a and also flows through the gas return pipe 11. The gas refrigerant flowing through the oil return pipe 21a is reduced in pressure by the capillary tube 23a, and the gas refrigerant flowing through the gas return pipe 11 is reduced in pressure by the capillary tube 12, whereby the temperature is lowered. In this case, since the detected temperature T1 of the temperature sensor 44 and the detected temperature T2a of the temperature sensor 45a are almost the same, the main controller 50 can determine that the amount of the lubricating oil La is in a state of insufficient lubricating oil smaller than the set value.

The

gas return pipes

11 and 11a, the

capillary tubes

12 and 13a, the oil return pipe 21a, the check valve 22a, the capillary tube 23a, the

temperature sensors

44 and 45a, and the main controller 50 constitute oil amount detection means for detecting the amount of the lubricant La in the sealed casing of the compressor 1 a.

The outdoor unit a1 includes an oil return pipe 14 connected between the side of the oil separator 3 and the other end of the gas return pipe 11, a resistor such as a capillary tube 15 provided in the oil return pipe 14 for adjusting the amount of oil, an oil return pipe 16 connected from the bottom of the oil separator 3 to a position downstream of the capillary tube 15 in the oil return pipe 14, a resistor such as a capillary tube 17 provided in the oil return pipe 16 for adjusting the amount of oil, an electromagnetic on-off valve 18 provided at a position downstream of the capillary tube 17 in the oil return pipe 16, a main controller 50, and an inverter 51.

When the oil separator 3 retains the lubricating oil L by a predetermined amount or more, the oil return pipe 14 returns the lubricating oil L exceeding the predetermined amount to the suction side of the compressor 1 a. The oil return pipe 16 is a pipe for forcibly returning the lubricating oil L in the oil separator 3 to the suction side of the compressor 1a, and is opened by opening the electromagnetic on-off valve 18 to communicate with the oil. The main controller 50 comprehensively controls the outdoor units a1 and a2 and the indoor units B1, B2, and … Bn. The inverter 51 converts an ac voltage of the commercial ac power supply into a dc voltage, converts the dc voltage into an ac voltage having a predetermined frequency Fa (hz) and a level corresponding to the predetermined frequency Fa, and outputs the ac voltage as drive power for the motor M of the compressor 1 a. The prescribed frequency Fa is referred to as an operating frequency Fa.

< Structure of outdoor unit A2 >

The outdoor unit a2 includes a compressor 1c, a lubricant oil Lc, a high-pressure-side pipe 2c, a low-pressure-side pipe 9c, an oil return pipe 21c, a check valve 22c, a capillary tube 23c, a temperature sensor 45c, a controller 60, an inverter 61, and the like, instead of the compressor 1a, the lubricant oil La, the high-pressure-side pipe 2a, the low-pressure-side pipe 9a, the oil return pipe 21a, the check valve 22a, the capillary tube 23a, the temperature sensor 45a, the main controller 50, and the inverter 51 of the outdoor unit a 1.

The

gas return pipes

11 and 11c, the

capillary tubes

12 and 13c, the oil return pipe 21c, the check valve 22c, the capillary tube 23c, the temperature sensors 44 and 45c, and the main controller 50 constitute oil amount detection means for detecting the amount of the lubricant oil Lc in the sealed casing of the compressor 1 c.

The controller 60 notifies the main controller 50 of the detection results of the temperature sensors and the pressure sensors of the outdoor unit a2, and controls the operation of the outdoor unit a2 in accordance with an instruction from the main controller 50. The inverter 61 converts an ac voltage of the commercial ac power supply into a dc voltage, converts the dc voltage into an ac voltage having a predetermined frequency Fc (hz) and a level corresponding to the predetermined frequency Fc, and outputs the ac voltage as drive power for the motor M of the compressor 1 c. The prescribed frequency Fc is referred to as an operating frequency Fc.

The other structure is the same as that of the outdoor unit a 1. Therefore, the description thereof is omitted.

< piping Structure >

The liquid side filling valve 7a of the outdoor unit a1 and the liquid side filling valve 7a of the outdoor unit a2 are connected by a connection pipe P1, and the gas side filling valve 7b of the outdoor unit a2 and the gas side filling valve 7b of the outdoor unit a2 are connected by a connection pipe P2. Then, one end of each of the indoor heat exchangers 32 of the indoor units B1, B2, and … Bn is connected to the connection pipe P1 by a pipe via each of the motor-operated expansion valves 31 of the indoor units B1, B2, and … Bn, and the other end of each of the indoor heat exchangers 32 is connected to the connection pipe P2 by a pipe.

The heat pump type refrigeration cycle is constituted by the above pipe connections. The rated capacity of the outdoor unit a1 (the capacity of the compressor 1 a) and the rated capacity of the outdoor unit a2 (the capacity of the compressor 1 c) are the same as each other.

The indoor units B1, B2, and … Bn each have a controller 30. The controller 30 notifies the main controller 50 of a difference between the indoor temperature of the room in which each indoor unit is installed and a preset temperature as a required capacity, and controls the operation of each indoor unit in accordance with an instruction from the main controller 50.

< function of the main controller 50 >

The main controller 50 has

control units

50a, 50b, and 50c as main functions.

The controller 50a is a component of the oil amount detection means in the outdoor units a1 and a2, and detects the amounts of the lubricating oils La and Lc in the compressors 1a and 1c by the above-described detection method based on the detected temperature T1 of the temperature sensors 44 in the outdoor units a1 and a2 and the detected temperatures T2a and T2c of the temperature sensors 45a and 45c, respectively.

The control unit 50b sets the circulation amount of the refrigerant to the outdoor unit having the compressor in the shortage state to be larger than the circulation amount of the refrigerant to the other outdoor unit, when the amount of the lubricating oil La or Lc in any one of the compressors 1a and 1c detected by the control unit 50a is in the shortage state in which the amount of the lubricating oil La or Lc in the compressor is smaller than the set value. Specifically, when the amount of the lubricating oil La of the compressor 1a is in a shortage state of less than the set value, the capacity of the outdoor unit a1 in which the compressor 1a exists (the operating frequency Fa of the compressor 1 a) is increased, and the capacity of the outdoor unit a2 (the operating frequency Fc of the compressor 1 c) is decreased by the increased amount. When the amount of the lubricant oil Lc of the compressor 1c is in a shortage state of less than the set value, the capacity of the outdoor unit a2 in which the compressor 1c exists is increased, and the capacity of the outdoor unit a1 is decreased by the increased amount.

When the amounts of the lubricating oils La and Lc detected by the control unit 50a are both in a shortage state of less than the set values, the control unit 50c sets the circulation amount of the refrigerant to the outdoor unit a1 and the circulation amount of the refrigerant to the outdoor unit a2 to be the same. Specifically, the capacity of the outdoor unit a1 (the operating frequency Fc of the compressor 1 a) and the capacity of the outdoor unit a2 (the operating frequency Fc of the compressor 1 c) are set to a predetermined capacity (the operating frequency Fo) for oil recovery.

Fig. 2 shows the relationship between the circulation amount ratio of the refrigerant in the outdoor units a1 and a2 and the deviation ratio of the lubricating oil L in the outdoor units a1 and a2 for reference. In the circulation amount ratio "0.5" in which the circulation amount of the refrigerant to the outdoor unit a1 and the circulation amount of the refrigerant to the outdoor unit a2 are the same, the deviation ratio of the lubricating oil L to the outdoor unit a1 is 50%, and the deviation ratio of the lubricating oil L to the outdoor unit a2 is also 50%. In a region where the circulation amount ratio of the refrigerant to the outdoor unit a1 is greater than the circulation amount of the refrigerant to the outdoor unit a2 by more than "0.5", the deviation ratio of the lubricating oil L to the outdoor unit a1 is 50% or more, and the deviation ratio of the lubricating oil L to the outdoor unit a2 is less than 50%. In the region where the circulation amount of the refrigerant to the outdoor unit a1 is smaller than the circulation amount ratio "0.5" which is smaller than the circulation amount of the refrigerant to the outdoor unit a2, the deviation ratio of the lubricating oil L to the outdoor unit a1 is less than 50%, and the deviation ratio of the lubricating oil L to the outdoor unit a2 is 50% or more.

< control of the main controller 50 >

The control of the main controller 50 will be described with reference to the flowchart of fig. 3. Reference numerals S1 to S18 in the flowchart denote processing steps.

The main controller 50 starts a timer t1(S1), and compares the timer t1 with a predetermined time t1S, for example, 10 minutes (S2). When the timer T1 reaches the predetermined time T1S (yes in S2), the main controller 50 detects the amounts of the lubricating oils La and Lc in the compressors 1a and 1c by the above-described detection method based on the temperatures T1 and T2a detected by the

temperature sensors

44 and 45a when it is determined that the timing is the oil amount detection timing (S3). When the detected amounts of lubricating oils La, Lc are in an appropriate state of the set values or more (no in S4), main controller 50 returns to the process of S1 that was started and restarts counting t1 (S1).

When any of the detected amounts of the lubricating oils La and Lc, for example, the amount of the lubricating oil Lc is in a shortage state of being smaller than the set value (yes in S4), the main controller 50 opens the electromagnetic on-off valve 18 of the outdoor unit a2, and collects the lubricating oil L in the oil separator 3 in the outdoor unit a2 to the compressor 1c through the oil return pipe 16, the capillary tube 17, the oil return pipe 14, the

oil return pipes

11 and 11c, the capillary tube 13c, and the low-pressure-side pipe 9c (S5).

The main controller 50 starts a count t2 simultaneously with the recovery (S6), and compares the count t2 with a predetermined time t2S (S7). When the count t2 reaches the predetermined time t2S (yes in S7), the main controller 50 closes the electromagnetic opening/closing valve 18 of the outdoor unit a2, and ends the collection of the lubricating oil L to the compressor 1c (S8).

Following the completion of the recovery, the main controller 50 detects the amounts of the lubricating oils La and Lc in the compressors 1a and 1c again based on the detection temperatures T1 and T2a of the

temperature sensors

44 and 45a (S9). When the detected amounts of lubricating oils La and Lc are in an appropriate state equal to or greater than the set values (yes at S10, yes at S11), main controller 50 returns to the start of the process at S1 and restarts counting t1 (S1).

If the amount of lubricant oil La is in an appropriate state of being equal to or greater than the set value (yes in S10) and the amount of lubricant oil Lc is still in a state of being insufficient (no in S11) among the amounts of lubricant oil La and Lc detected in the above-described process of S9, the main controller 50 increases the operating frequency Fc of the compressor 1c by the predetermined value Δ F (S12), thereby increasing the capacity of the outdoor unit a 2. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a1 by the capacity increasing portion of the outdoor unit a2, and reduce the operating frequency Fa of the compressor 1a by a predetermined value. By this decrease, the total capacity of the outdoor units a1 and a2 can be maintained at a value corresponding to the sum of the required capacities of the indoor units B1, B2, and … Bn, regardless of the increase in the capacity of the outdoor unit a 2.

When the capacity of the outdoor unit a2 increases, the amount of refrigerant returned from the indoor units B1, B2, and … Bn to the outdoor unit a2 through the connecting pipe P2 increases. As the circulation amount of the refrigerant to the outdoor unit a2 increases, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases, and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases. As a result, the amount of the lubricant oil Lc in the compressor 1c increases, and the lubricant shortage of the compressor 1c is eliminated.

When the operation frequency Fc increases, the main controller 50 starts counting t3(S16), and compares the count t3 with a predetermined time t3S (S17). When the timer t3 reaches the predetermined time t3S (yes in S17), the main controller 50 cancels the increase in the capacity of the outdoor unit a2 due to the increase in the operation frequency Fc and the decrease in the capacity of the outdoor unit a1 due to the decrease in the operation frequency Fa (S18). Subsequently, the main controller 50 returns to the process of S9 to detect the amounts of the lubricating oils La and Lc again (S9). When the detected amounts of lubricating oils La, Lc are in an appropriate state of being equal to or greater than the set values (yes at S10, yes at S11), main controller 50 returns to the started process at S1 and starts counting t1 again (S1).

When the amount of lubricating oil La is in a shortage state of being smaller than the set value (no in S10) and the amount of lubricating oil Lc is in an appropriate state of being equal to or larger than the set value (yes in S13) among the detected amounts of lubricating oil La and Lc, the main controller 50 increases the operating frequency Fa of the compressor 1a by the predetermined value Δ F (S14), thereby increasing the capacity of the outdoor unit a 1. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a2 by the capacity increasing portion of the outdoor unit a2, and reduce the operating frequency Fa of the compressor 1a by a predetermined value. By this decrease, the total capacity of the outdoor units a1 and a2 can be maintained at a value corresponding to the sum of the required capacities of the indoor units B1, B2, and … Bn, regardless of the increase in the capacity of the outdoor unit a 1.

When the capacity of the outdoor unit a1 increases, the amount of refrigerant returning from the indoor units B1, B2, … Bn to the outdoor unit a1 increases. As the circulation amount of the refrigerant to the outdoor unit a1 increases, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases, and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases. As a result, the amount of the lubricant La in the compressor 1a increases, and the shortage of the lubricant La in the compressor 1a is eliminated.

When the operation frequency Fa rises, the main controller 50 starts counting t3(S16), and compares the count t3 with a predetermined time t3S (S17). When the timer t3 reaches the predetermined time t3S (yes in S17), the main controller 50 cancels the increase in the capacity of the outdoor unit a1 due to the increase in the operation frequency Fa and the decrease in the capacity of the outdoor unit a2 due to the decrease in the operation frequency Fc (S18). With the release, the main controller 50 returns to the process of S9, and detects the amounts of the lubricating oils La and Lc in the compressors 1a and 1c again based on the detected temperatures T1 and T2a of the

temperature sensors

44 and 45a (S9). When the detected amounts of lubricating oils La, Lc are in an appropriate state of being equal to or greater than the set values (yes at S10, yes at S11), main controller 50 returns to the started process at S1 and starts counting t1 again (S1).

If both the amounts of lubricating oils La and Lc detected in the process of S9 are in a shortage state of less than the set values (no in S10 and no in S13), the main controller 50 sets the operating frequency Fa of the compressor 1a and the operating frequency Fc of the compressor 1c to the operating frequency Fo for oil recovery in common (S15). The operation frequency Fo is a value that is variably set by the main controller 50 in accordance with the sum of the required capacities of the indoor units B1, B2, and … Bn on the assumption that the total capacity of the outdoor units a1 and a2 based on the operation frequencies Fa and Fc is maintained at a value corresponding to the sum of the required capacities.

In this way, by commonly setting the operating frequencies Fa and Fc to the operating frequency Fo for oil recovery, the capacity of the outdoor unit a1 and the capacity of the outdoor unit a2 are set to predetermined capacities corresponding to the operating frequency Fo. As a result, the circulation amount of the refrigerant to the outdoor unit a1 and the circulation amount of the refrigerant to the outdoor unit a2 become the same (circulation amount ratio "0.5"), and as a result, the deviation ratio of the lubricating oil L to the outdoor unit a1 and the deviation ratio of the lubricating oil L to the outdoor unit a2 are equalized to 50%. Thus, the lubricant L flowing out of the refrigeration cycle returns to both the compressors 1a and 1c uniformly and efficiently, and the shortage of the lubricant in the compressors 1a and 1c is eliminated.

When the operating frequency Fo is set, the main controller 50 starts counting t3(S16), and compares the count t3 with a predetermined time t3S (S17). When the count t3 reaches the prescribed time t3S (yes at S17), the main controller 50 releases the setting of the operating frequency Fo (S18). With the release, the main controller 50 returns to the process of S9 to detect the amounts of the lubricating oils La and Lc again (S9).

As described above, when the lubricant oil La of the compressor 1a is in a shortage state, the capacity of the outdoor unit a1 in which the compressor 1a is present is increased and the circulation amount of the refrigerant to the outdoor unit a1 is increased, when the lubricant oil Lc of the compressor 1c is in a shortage state, the capacity of the outdoor unit a2 in which the compressor 1c is present is increased and the circulation amount of the refrigerant to the outdoor unit a2 is increased, and when the lubricant oils La and Lc of the compressors 1a and 1c are both in a shortage state, the capacities of the outdoor units a1 and a2 are set to the predetermined capacity for oil recovery and the circulation amounts of the refrigerant to the outdoor units a1 and a2 are set to the same state, whereby the shortage of the lubricant oil in the outdoor units a1 and a2 can be appropriately and quickly eliminated.

[2] Embodiment 2

Embodiment 2 of the present invention will be described with reference to fig. 4 and 5. The configurations of the outdoor units a1 and a2 will be described only with respect to the differences from embodiment 1.

As shown in fig. 4, the outdoor unit a1 includes: two compressors 1a, 1 b; high-pressure-

side pipes

2a and 2b through which the refrigerant discharged from the compressors 1a and 1b flows; a high-pressure-side pipe 2 in which the refrigerants in the high-pressure-

side pipes

2a and 2b merge; low-pressure-side pipes 9a and 9b for introducing the gas refrigerant in the low-pressure-side pipe 9 into suction ports of the compressors 1a and 1 b; gas return pipes 11a and 11b for introducing the gas refrigerant in the gas return pipe 11 into the low-pressure-side pipes 9a and 9 b;

oil return pipes

21a and 21b connected between the side portions of the respective hermetic cases of the compressors 1a and 1b and the other end of the gas return pipe 11; check valves 12a and 12b and pressure reducers such as capillary tubes 23a and 23b provided in the

oil return pipes

21a and 21 b; temperature sensors 45a and 45b attached to positions on the lower side of the capillaries 23a and 23b in the oil return pipes 21a and 12 b; and inverters 51, 52, etc. The inverter 52 converts an ac voltage of the commercial ac power supply into a dc voltage, converts the dc voltage into an ac voltage having a predetermined frequency Fb (hz) and a level corresponding to the predetermined frequency Fb, and outputs the ac voltage as driving power for the motor M of the compressor 1 b. The predetermined frequency Fb is referred to as an operating frequency Fb.

The

gas return pipes

11 and 11a, the

capillary tubes

temperature sensors

44 and 45a, and the main controller 50 constitute oil amount detection means for detecting the amount of the lubricant La in the sealed casing of the compressor 1 a. The gas return pipes 11 and 11b, the

capillary tubes

12 and 13b, the oil return pipe 21b, the check valve 22b, the capillary tube 23b, the temperature sensors 44 and 45b, and the main controller 50 constitute oil amount detection means for detecting the amount of the lubricating oil Lb in the sealed casing of the compressor 1 b.

On the other hand, the outdoor unit a2 includes: two compressors 1c, 1 d; high-pressure-

side pipes

2c and 2d through which the refrigerant discharged from the compressors 1c and 1d flows; a high-pressure-side pipe 2 in which the refrigerants in the high-pressure-

side pipes

2c and 2d merge; low-pressure-side pipes 9c and 9d for introducing the gas refrigerant in the low-pressure-side pipe 9 into suction ports of the compressors 1c and 1 d;

gas return pipes

11c and 11d for introducing the gas refrigerant in the gas return pipe 11 into the low-pressure-side pipes 9c and 9 d; oil return pipes 21c and 21d connected between the side portions of the respective hermetic cases of the compressors 1c and 1d and the other end of the gas return pipe 11; check valves 12c and 12d and pressure reducers such as capillary tubes 23c and 23d provided in the oil return pipes 21c and 21 d; temperature sensors 45c and 45d attached to positions on the lower side of the capillary tubes 23c and 23d in the oil return tubes 21c and 12 d; and inverters 61, 62, etc. The inverter 62 converts an ac voltage of the commercial ac power supply into a dc voltage, converts the dc voltage into an ac voltage having a predetermined frequency Fd (hz) and a level corresponding to the predetermined frequency Fd, and outputs the ac voltage as drive power for the motor M of the compressor 1 d. The predetermined frequency Fd is referred to as an operating frequency Fd.

The

gas return pipes

11 and 11c, the

capillary tubes

12 and 13c, the oil return pipe 21c, the check valve 22c, the capillary tube 23c, the temperature sensors 44 and 45c, and the main controller 50 constitute oil amount detection means for detecting the amount of the lubricant oil Lc in the sealed casing of the compressor 1 c. The

gas return pipes

11 and 11d, the

capillary tubes

12 and 13d, the oil return pipe 21d, the check valve 22d, the capillary tube 23d, the

temperature sensors

44 and 45d, and the main controller 50 constitute oil amount detection means for detecting the amount of the lubricating oil Ld in the sealed casing of the compressor 1 d.

The controller 60 notifies the main controller 50 of the detection results of the temperature sensors and the pressure sensors of the outdoor unit a2, and controls the operation of the outdoor unit a2 in accordance with an instruction from the main controller 50.

The controller 50a of the main controller 50 is a component of each oil amount detection means in the outdoor units a1, a2, and detects the amounts of the lubricating oils La, Lb, Lc, Ld in the compressors 1a, 1b, 1c, 1d based on the detected temperature T1 of each temperature sensor 44 in the outdoor units a1, a2 and the detected temperatures T2a, T2b, T2c, T2d of the

temperature sensors

45a, 45b, 45c, 45d, respectively.

The control unit 50b sets the refrigerant circulation amount to the outdoor unit of the compressor in the shortage state to be larger than the refrigerant circulation amount to the other outdoor units, when the amount of the lubricating oil La, Lb, Lc, Ld in any of the compressors 1a, 1b, 1c, 1d detected by the control unit 50a is in the shortage state in which the amount of the lubricating oil in any of the compressors is smaller than the set value. Specifically, when only the amount of the lubricating oil La of the compressor 1a is smaller than the set value, the capacity of the outdoor unit a1 in which the compressor 1a exists (the total operating frequency F1 of the operating frequency Fa and the operating frequency Fb) is increased, and the capacity of the outdoor unit a2 (the total operating frequency F2 of the operating frequency Fc and the operating frequency Fd) is decreased by the increased amount. When the amount of the lubricant oil Lc of only the compressor 1c is smaller than the set value, the capacity of the outdoor unit a2 in which the compressor 1c exists (the total operating frequency F2) is increased, and the capacity of the outdoor unit a1 (the total operating frequency F1) is decreased by the increased amount.

When all of the amounts of the lubricating oils La, Lb, Lc, and Ld in the compressors 1a, 1b, 1c, and 1d detected by the control unit 50a are in a shortage state of being smaller than the set value, the control unit 50c sets the circulation amount of the refrigerant to the outdoor unit a1 and the circulation amount of the refrigerant to the outdoor unit a2 to be the same state. Specifically, when all of the amounts of lubricating oils La, Lb, Lc, and Ld are in a shortage state smaller than the set value, the capacity of the outdoor unit a1 (the total operating frequency F1) and the capacity of the outdoor unit a2 (the total operating frequency F2) are set to the predetermined capacity for oil recovery (the operating frequency Fo) on the condition that the number of compressors 1a and 1b in the outdoor unit a1 operated at the current time is the same as the number of compressors 1c and 1d in the outdoor unit a2 operated at the current time.

However, when all of the amounts of lubricating oils La, Lb, Lc, and Ld are in the insufficient state smaller than the set value, if the number of compressors 1a and 1b in the outdoor unit a1 operating at the current time is larger than the number of compressors 1c and 1d in the outdoor unit a2 operating at the current time, the controller 50c preferentially increases the capacity of the outdoor unit a1 (the total operating frequency F1) and decreases the capacity of the outdoor unit a2 (the total operating frequency F2) by the increased amount as the supplementary control. When the amounts of lubricating oils La, Lb, Lc, and Ld are all in a shortage state smaller than the set values, if the number of compressors 1c and 1d in the outdoor unit a2 operating at the current time is larger than the number of compressors 1a and 1b in the outdoor unit a1 operating at the current time, the capacity of the outdoor unit a2 (the total operating frequency F2) is preferentially increased, and the capacity of the outdoor unit a1 (the total operating frequency F1) is decreased by the increased amount.

The other structure is the same as embodiment 1. Therefore, the description thereof is omitted.

The control executed by the main controller 50 will be described below with reference to the flowchart of fig. 5. The description of the same control as that of embodiment 1 is omitted, and only the control different from that of embodiment 1 will be described.

When the count t1 reaches the predetermined time t1S (yes in S2), the main controller 50 detects the amounts of the lubricating oils La, Lb, Lc, and Ld in the compressors 1a, 1b, 1c, and 1d when determining that the oil amount detection timing is reached (S3). When the detected amounts of the lubricating oils La, Lb, Lc, and Ld are in an appropriate state of being equal to or greater than the set values (no in S4), the main controller 50 returns to the started process of S1 and restarts the count t1 (S1).

If the detected amounts of the lubricating oils La, Lb, Lc, and Ld are in a shortage state where the amount of the lubricating oil Lc is smaller than the set value, for example (yes in S4), the main controller 50 opens the electromagnetic opening/closing valve 18 of the outdoor unit a2, and recovers the lubricating oil L in the oil separator 3 in the outdoor unit a2 to the compressors 1c and 1d through the oil return pipe 16, the capillary tube 17, the oil return pipe 14, the

oil return pipes

11, 11c, and 11d, the

capillary tubes

13c and 13d, and the low-pressure side pipes 9c and 9d (S5).

After the recovery is completed, the main controller 50 detects the amounts of the lubricating oils La, Lb, Lc, and Ld again (S9).

When the detected amounts of lubricating oils La, Lb, Lc, and Ld are in an appropriate state of being equal to or greater than the set values (yes at S10, yes at S11), the main controller 50 returns to the started process at S1 and restarts the count t1 (S1).

However, when it is detected that the amount of lubricating oil Lc is still in a shortage state of less than the set value (yes in S10, no in S11), the main controller 50 increases the total operating frequency F2 of the operating frequency Fc of the compressor 1c and the operating frequency Fd of the compressor 1d by the predetermined value Δ F (S12), thereby increasing the capacity of the outdoor unit a 2. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a1 by the capacity increasing portion of the outdoor unit a2, and reduce the total operating frequency F1 of the operating frequency Fa of the compressor 1a and the operating frequency Fb of the compressor 1b by a predetermined value.

When the capacity of the outdoor unit a2 increases, the amount of refrigerant returned from the indoor units B1, B2, and … Bn to the outdoor unit a2 through the connecting pipe P2 increases. As the circulation amount of the refrigerant to the outdoor unit a2 increases, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases, and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases. As a result, the amounts of the lubricating oils Lc and Ld in the compressors 1c and 1d increase, and the shortage of the lubricating oil in the compressor 1c is eliminated.

If the amount of lubricating oil La is insufficient (no in S10, yes in S13), for example, among the amounts of lubricating oil La, Lb, Lc, and Ld detected in the process of S9, the main controller 50 increases the total operating frequency F1 by the predetermined value Δ F (S14), thereby increasing the capacity of the outdoor unit a 1. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a2 by the capacity increasing portion of the outdoor unit a1 and lower the total operating frequency F2 by a predetermined value.

When the capacity of the outdoor unit a1 increases, the amount of refrigerant returning from the indoor units B1, B2, … Bn to the outdoor unit a1 increases. As the circulation amount of the refrigerant to the outdoor unit a1 increases, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases, and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases. As a result, the amount of the lubricating oil La, Lb in the compressors 1a, 1b increases, and the shortage of the lubricating oil in the compressor 1a is eliminated.

When all of the amounts of the lubricating oils La, Lb, Lc, and Ld detected in the process of S9 are in the insufficient state (no in S10 and no in S13), the main controller 50 determines the magnitude relationship between the number of operating compressors 1a and 1b in the outdoor unit a1 and the number of operating compressors 1c and 1d in the outdoor unit a2 (S21 and S23).

When the number of compressors 1a and 1b in the outdoor unit a1 is equal to the number of compressors 1c and 1d in the outdoor unit a2 (no in S21 and no in S23), the main controller 50 sets the total operating frequencies F1 and F2 to the operating frequency Fo for oil recovery in common (S15).

In this way, by commonly setting the total operating frequencies F1 and F2 to the operating frequency Fo for oil recovery, the capacity of the outdoor unit a1 and the capacity of the outdoor unit a2 become predetermined capacities corresponding to the operating frequency Fo. Thus, the circulation amount of the refrigerant to the outdoor unit a1 and the circulation amount of the refrigerant to the outdoor unit a2 become the same, and as a result, the deviation ratio of the lubricating oil L to the outdoor unit a1 and the deviation ratio of the lubricating oil L to the outdoor unit a2 are both equalized to 50%. Thus, the lubricant oil L flowing out of the refrigeration cycle is returned to both of the outdoor units a1 and a2 uniformly and efficiently, and the shortage of the lubricant oil in the compressors 1a, 1b, 1c, and 1d is eliminated.

However, when the number of compressors 1a and 1b in the outdoor unit a1 is larger than the number of compressors 1c and 1d in the outdoor unit a2 (yes in S21), the main controller 50 increases the total operating frequency F1 by the predetermined value Δ F (S22), thereby increasing the capacity of the outdoor unit a 1. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a2 by the capacity increasing portion of the outdoor unit a1 and lower the total operating frequency F2 by a predetermined value.

In this way, the capacity of the outdoor unit a1 that operates a large number of outdoor units increases, and it is preferable to increase the amount of refrigerant circulating to the outdoor unit a1, thereby increasing the deviation ratio of the lubricating oil L to the outdoor unit a 1. As a result, the amounts of the lubricating oils La and Lb in the compressors 1a and 1b increase, and at least the shortage of the lubricating oil on the outdoor unit a1 side is eliminated.

When the number of compressors 1c, 1d in the outdoor unit a2 is larger than the number of compressors 1a, 1b in the outdoor unit a1 (no in S21, yes in S23), the main controller 50 increases the total operating frequency F2 by the predetermined value Δ F (S24), thereby increasing the capacity of the outdoor unit a 2. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a1 by the capacity increasing portion of the outdoor unit a2 and lower the total operating frequency F1 by a predetermined value.

In this way, the capacity of the outdoor unit a2 that operates a large number of outdoor units increases, and it is preferable to increase the amount of refrigerant circulating to the outdoor unit a2, thereby increasing the deviation ratio of the lubricating oil L to the outdoor unit a 2. As a result, the amounts of the lubricating oils Lc and Ld in the compressors 1c and 1d increase, and at least the shortage of the lubricating oil on the outdoor unit a2 side is eliminated.

As described above, when the lubricating oil shortage exists on the outdoor unit a1 side, the capacity of the outdoor unit a1 is increased and the circulation amount of the refrigerant to the outdoor unit a1 is increased, and when the lubricating oil shortage exists on the outdoor unit a2 side, the capacity of the outdoor unit a2 is increased and the circulation amount of the refrigerant to the outdoor unit a2 is increased, so that the lubricating oil shortage in the outdoor units a1 and a2 can be appropriately and quickly eliminated.

When all of the lubricating oils La, Lb, Lc, and Ld are in a shortage state and the number of compressors in the outdoor units a1 and a2 is the same, the capacity of the outdoor units a1 and a2 is set to a predetermined capacity for oil recovery, and the circulation amounts of the refrigerants to the outdoor units a1 and a2 are equalized, whereby the shortage of the lubricating oils in the outdoor units a1 and a2 can be appropriately and quickly resolved. Further, when the lubricating oils La, Lb, Lc, and Ld are all in a shortage state and the number of compressors in the outdoor units a1 and a2 is different, the capacity of the outdoor unit on the side where the number of compressors is large is increased and the circulation amount of the refrigerant to the same outdoor unit is preferentially increased, whereby the shortage of the refrigerant amount in at least one outdoor unit can be appropriately and quickly resolved.

[3] Embodiment 3

Embodiment 3 of the present invention will be described with reference to fig. 6 and 7. The configurations of the outdoor units a1 and a2 will be described only with respect to the differences from embodiment 1.

As shown in fig. 6, the outdoor unit a1 includes one compressor 1a, a bypass pipe 71 that bypasses the refrigerant in the high-pressure-side pipe 2a to the accumulator 8 leading to the low-pressure-side pipe 9, and an electromagnetic on-off valve 72 provided in the bypass pipe 71. The outdoor unit a2 includes one compressor 1c, a bypass pipe 71 that bypasses the refrigerant in the high-pressure-side pipe 2c to the accumulator 8 leading to the low-pressure-side pipe 9, and an electromagnetic on-off valve 72 provided in the bypass pipe 71.

The controller 50a of the main controller 50 is a component of the oil amount detection means in the outdoor units a1 and a2, and detects the amounts of the lubricating oils La and Lc in the compressors 1a and 1c based on the detected temperature T1 of the temperature sensors 44 in the outdoor units a1 and a2 and the detected temperatures T2a and T2c of the temperature sensors 45a and 45c, respectively.

The control unit 50b determines whether or not the capacity of the outdoor unit of the compressor in which the shortage exists can be increased when the amount of the lubricant oil La or Lc in any one of the compressors 1a and 1c detected by the control unit 50a is in the shortage state of less than the set value, increases the capacity of the same outdoor unit and reduces the capacity of the other outdoor unit by the increased portion when the capacity can be increased, and opens the electromagnetic on-off valve 72 in the other outdoor unit to bypass the gas refrigerant on the high pressure side to the low pressure side when the capacity can not be increased. Specifically, when only the amount of the lubricating oil La of the compressor 1a is in a shortage state of less than the set value, it is determined whether or not the capacity of the outdoor unit a1 in which the compressor 1a is present can be increased (increase in the operation frequency Fa) at the present time, and when the capacity can be increased, the capacity of the outdoor unit a1 is increased and the capacity of the outdoor unit a2 (the operation frequency Fc) is decreased by the increased portion, and when the capacity can be increased, the electromagnetic on-off valve 72 of the outdoor unit a2 is opened to bypass the gas refrigerant on the high pressure side in the outdoor unit a2 to the low pressure side. Further, in the case where only the amount of the lubricant oil Lc of the compressor 1c is in the insufficient state of being smaller than the set value, it is determined whether or not the capacity (increase of the operation frequency Fc) of the outdoor unit a2 in which the compressor 1c is present can be increased at the present time, and in the case where the capacity can be increased, the capacity of the outdoor unit a2 is increased and the capacity (operation frequency Fa) of the outdoor unit a1 is decreased by the increased portion, and in the case where the capacity can be increased, the electromagnetic on-off valve 72 of the outdoor unit a1 is opened to bypass the gas refrigerant on the high pressure side in the outdoor unit a1 to the low pressure side.

When the amounts of the lubricating oils La and Lc detected by the control unit 50a are both in a shortage state of less than the set values, the control unit 50c sets the circulation amount of the refrigerant to the outdoor unit a1 and the circulation amount of the refrigerant to the outdoor unit a2 to be the same. Specifically, the capacity (operating frequency Fc) of the outdoor unit a1 and the capacity (operating frequency Fc) of the outdoor unit a2 are set to be the same as the predetermined capacity (operating frequency Fo) for oil recovery.

The control executed by the main controller 50 will be described with reference to the flowchart of fig. 7. The description of the same control as that of embodiment 1 is omitted, and only the control different from that of embodiment 1 will be described.

If the amount of lubricant oil La is in an appropriate state of being equal to or greater than the set value (yes in S10) and the amount of lubricant oil Lc is in a shortage state of being smaller than the set value (no in S11) among the amounts of lubricant oil La and Lc detected in the process of S9, the main controller 50 determines whether or not the capacity (increase in the operating frequency Fc) of the outdoor unit a2 having the compressor 1c can be increased at the present time (S12 a). For example, when the cooling load is not large and the operation frequency Fc has a sufficient liftable width with respect to the upper limit value in control, the main controller 50 determines that the capacity of the outdoor unit a2 can be increased (yes in S12 a). When the cooling load increases due to an increase in the outside air temperature or the like and the operating frequency Fc has reached the upper limit value of the control or the vicinity thereof, the main controller 50 determines that the capacity of the outdoor unit a2 can be increased (no in S12 a).

If the capacity of the outdoor unit a2 can be increased (yes in S12a), the main controller 50 increases the operation frequency Fc by the predetermined value Δ F (S12b), thereby increasing the capacity of the outdoor unit a 2. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a1 by the capacity increasing portion of the outdoor unit a2 and decrease the operating frequency Fa by a predetermined value.

When the capacity of the outdoor unit a2 increases, the circulation amount of the refrigerant to the outdoor unit a2 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases, and as a result, the amount of the lubricating oil Lc in the compressor 1c increases. The shortage of the lubricant oil of the compressor 1c is eliminated.

If the capacity of the outdoor unit a2 cannot be increased (no in S12a), the main controller 50 opens the electromagnetic on-off valve 72 of the outdoor unit a1 to bypass the high-pressure gas refrigerant in the outdoor unit a1 to the low-pressure side. By this bypass, the so-called high pressure relief, the capacity of compressor a1 is reduced. When the capacity of the outdoor unit a1 decreases, the capacity of the outdoor unit a2 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a2 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases, and as a result, the amount of the lubricating oil Lc in the compressor 1c increases. The shortage of the lubricant oil of the compressor 1c is eliminated.

If the amount of lubricant oil Lc is in the appropriate state of being equal to or greater than the set value (no in S10) and the amount of lubricant oil La is in the insufficient state of being smaller than the set value (yes in S13) among the amounts of lubricant oil La and Lc detected in the process of S9, the main controller 50 determines whether or not the capacity of the outdoor unit a1 in which the compressor 1a is present can be increased (increase in the operating frequency Fa) at the present time point (S14 a). For example, in the case where the cooling load is not so large and the operating frequency Fa of the compressor 1a has a sufficient liftable width with respect to the upper limit value in control, the main controller 50 determines that it is in a condition in which the capacity of the outdoor unit a1 can be increased (yes in S14 a). When the cooling load increases due to an increase in the outside air temperature or the like and the operating frequency Fa of the compressor 1a has reached the upper limit value in control or its vicinity, the main controller 50 determines that the capacity of the outdoor unit a1 can be increased (no in S14 a).

If the capacity of the outdoor unit a1 can be increased (yes in S14a), the main controller 50 increases the operation frequency Fa by the predetermined value Δ F (S14b), thereby increasing the capacity of the outdoor unit a 1. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a2 by the capacity increasing portion of the outdoor unit a1 and lower the operating frequency Fc by a predetermined value.

When the capacity of the outdoor unit a1 increases, the circulation amount of the refrigerant to the outdoor unit a1 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases, and as a result, the amount of the lubricating oil La in the compressor 1a increases. The shortage of the lubricant oil of the compressor 1a is eliminated.

If the outdoor unit a2 is not in a condition where the capacity can be increased (no in S14a), the main controller 50 opens the electromagnetic on-off valve 72 of the outdoor unit a2 to bypass the high-pressure gas refrigerant in the outdoor unit a2 to the low-pressure side. By this bypass, the so-called high pressure relief, the capacity of compressor a2 is reduced. When the capacity of the outdoor unit a2 decreases, the capacity of the outdoor unit a1 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a1 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases, and as a result, the amount of the lubricating oil La in the compressor 1a increases. The shortage of the lubricant oil of the compressor 1a is eliminated.

[4] Embodiment 4

Embodiment 4 of the present invention will be described with reference to fig. 8 to 10. The configurations of the outdoor units a1 and a2 will be described only with respect to the differences from embodiment 1.

As shown in fig. 8, the outdoor unit a1 includes two compressors 1a and 1b, a bypass pipe 71 that bypasses the refrigerant in the high-pressure side pipe 2a to the accumulator 8 that leads to the low-pressure side pipe 9, and an electromagnetic on-off valve 72 provided in the bypass pipe 71. The outdoor unit a2 includes two compressors 1c and 1b, a bypass pipe 71 that bypasses the refrigerant in the high-pressure-side pipe 2c to the accumulator 8 leading to the low-pressure-side pipe 9, and an electromagnetic on-off valve 72 provided in the bypass pipe 71.

temperature sensors

45a, 45b, 45c, 45d, respectively.

The control unit 50b determines whether or not the capacity of the outdoor unit in which the compressor in the shortage state is present can be increased in a case where the amount of the lubricating oil La, Lb, Lc, Ld in any of the compressors 1a, 1b, 1c, 1d detected by the control unit 50a is in the shortage state in which the amount of the lubricating oil La, Lb, Lc, Ld in the compressor is smaller than the set value, increases the capacity of the same outdoor unit and decreases the capacity of the other outdoor unit by the increasing portion in a case where the capacity can be increased, and opens the electromagnetic on-off valve 72 in the other outdoor unit to bypass the gas refrigerant on the high pressure side to the low pressure side in a case where the capacity can be increased. Specifically, when only the amount of the lubricating oil La of the compressor 1a is in a shortage state of being smaller than the set value, it is determined whether or not the capacity of the outdoor unit a1 in which the compressor 1a is present can be increased (increase of the total operating frequency F1) at the present time point, and when the capacity can be increased, the capacity of the outdoor unit a1 is increased and the capacity of the outdoor unit a2 (the total operating frequency F2) is decreased by the increased portion, and when the capacity can not be increased, the electromagnetic on-off valve 72 of the outdoor unit a2 is opened so that the gas refrigerant on the high-pressure side in the outdoor unit a2 is bypassed to the low-pressure side. Further, when only the amount of the lubricant oil Lc of the compressor 1c is in the insufficient state of being smaller than the set value, it is determined whether or not the capacity of the outdoor unit a2 in which the compressor 1c is present can be increased (increase of the total operating frequency F2) at the present time point, and when the capacity can be increased, the capacity of the outdoor unit a2 is increased and the capacity of the outdoor unit a1 (the total operating frequency F1) is decreased by the increased portion, and when the capacity can not be increased, the electromagnetic on-off valve 72 of the outdoor unit a1 is opened so that the gas refrigerant on the high pressure side in the outdoor unit a1 is bypassed to the low pressure side.

When all of the amounts of the lubricating oils La, Lb, Lc, and Ld detected by the control unit 50a are in a shortage state smaller than the set value, the control unit 50c sets the circulation amount of the refrigerant to the outdoor unit a1 and the circulation amount of the refrigerant to the outdoor unit a2 to be the same. Specifically, when all of the amounts of lubricating oils La, Lb, Lc, and Ld are in a shortage state smaller than the set value, the capacity of the outdoor unit a1 (the total operating frequency F1) and the capacity of the outdoor unit a2 (the total operating frequency F2) are set to the predetermined capacity for oil recovery (the operating frequency Fo) on the condition that the number of compressors 1a and 1b in the outdoor unit a1 operated at the current time is the same as the number of compressors 1c and 1d in the outdoor unit a2 operated at the current time.

However, when all of the amounts of the lubricating oils La, Lb, Lc, and Ld are in the insufficient state smaller than the set value, when the number of the compressors 1a and 1b operated at the current time is larger than the number of the compressors 1c and 1d operated at the current time, the controller 50c determines as the supplementary control whether or not the capacity of the outdoor unit a1 can be increased at the current time (increase of the total operating frequency F1), and when the capacity can be increased, preferentially increases the capacity of the outdoor unit a1 (the total operating frequency F1) and decreases the capacity of the outdoor unit a2 (the total operating frequency F2) by the increased portion, and when the capacity can not be increased, opens the electromagnetic on-off valve 72 of the outdoor unit a2 to bypass the high-pressure side gas refrigerant in the outdoor unit a2 to the low-pressure side. When the number of compressors 1c and 1d operating at the current time is larger than the number of compressors 1a and 1b operating at the current time, it is determined whether or not the capacity of the outdoor unit a2 in which the compressors 1c and 1d are present can be increased (increase of the total operating frequency F2) at the current time, when the capacity can be increased, the capacity of the outdoor unit a2 (the total operating frequency F2) is preferentially increased and the capacity of the outdoor unit a1 (the total operating frequency F1) is decreased by the increased amount, and when the capacity can be increased, the electromagnetic on-off valve 72 of the outdoor unit a1 is opened to bypass the gas refrigerant on the high pressure side in the outdoor unit a1 to the low pressure side.

The control executed by the main controller 50 will be described with reference to the flowchart of fig. 9 and the flowchart of fig. 10 following the flowchart of fig. 9. The description of the same control as that of embodiment 2 is omitted, and only the control different from that of embodiment 2 will be described.

If only the amount of the lubricant oil Lc is in a shortage state of less than the set value among the amounts of the lubricant oils La, Lb, Lc, and Ld detected in the process of S9 (yes in S10 and no in S11), the main controller 50 determines whether or not the capacity of the outdoor unit a2 in which the compressor 1c is present can be increased (increase in the total operating frequency F2) at the current time point (S12 x). For example, when the cooling load is not so large and the total operating frequency F2 has a sufficient liftable width with respect to the upper limit value in control, the main controller 50 determines that the capacity of the outdoor unit a2 can be increased (yes in S12 x). When the cooling load increases due to an increase in the outside air temperature or the like and the total operating frequency F2 has reached the upper limit value for control or its vicinity, the main controller 50 determines that the capacity of the outdoor unit a2 can be increased (no in S12 x).

If the capacity of the outdoor unit a2 can be increased (yes in S12x), the main controller 50 increases the total operating frequency F2 by the predetermined value Δ F (S12y), thereby increasing the capacity of the outdoor unit a 2. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a1 by the capacity increasing portion of the outdoor unit a2 and lower the total operating frequency F1 by a predetermined value.

When the capacity of the outdoor unit a2 increases, the circulation amount of the refrigerant to the outdoor unit a2 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases, and as a result, the amounts of the lubricating oils Lc and Ld in the compressors 1c and 1d increase. The shortage of the lubricant oil of the compressor 1c is eliminated.

If the capacity of the outdoor unit a2 cannot be increased (no in S12x), the main controller 50 opens the electromagnetic on-off valve 72 of the outdoor unit a1 to bypass the high-pressure gas refrigerant in the outdoor unit a1 to the low-pressure side. By this bypass, the so-called high pressure relief, the capacity of compressor a1 is reduced. When the capacity of the outdoor unit a1 decreases, the capacity of the outdoor unit a2 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a2 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases, and as a result, the amounts of the lubricating oils Lc and Ld in the compressors 1c and 1d increase. The shortage of the lubricant oil of the compressor 1c is eliminated.

If only the amount of the lubricating oil La is in a shortage state of being smaller than the set value among the amounts of the lubricating oils La, Lb, Lc, and Ld detected in the process of S9 (no in S10 and yes in S13), the main controller 50 determines whether or not the capacity of the outdoor unit a1 in which the compressor 1a is present can be increased (increase in the total operating frequency F1) at the present time point (S14 x). For example, when the cooling load is not so large and the total operating frequency F1 has a sufficient liftable width with respect to the upper limit value in control, the main controller 50 determines that 1 is in a condition in which the capacity of the outdoor unit a1 can be increased (yes in S14 x). When the cooling load increases due to an increase in the outside air temperature or the like and the total operating frequency F1 has reached the upper limit value of the control or its vicinity, the main controller 50 determines that the capacity of the outdoor unit a1 can be increased (no in S14 x).

If the capacity of the outdoor unit a1 can be increased (yes in S14x), the main controller 50 increases the total operating frequency F1 by the predetermined value Δ F (S14y), thereby increasing the capacity of the outdoor unit a 1. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a2 by the capacity increasing portion of the outdoor unit a1 and lower the total operating frequency F2 by a predetermined value.

When the capacity of the outdoor unit a1 increases, the circulation amount of the refrigerant to the outdoor unit a1 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases, and as a result, the amounts of the lubricating oils La and Lb in the compressors 1a and 1b increase. The shortage of the lubricant oil of the compressor 1a is eliminated.

If the outdoor unit a2 is not in a condition where the capacity can be increased (no in S14S), the main controller 50 opens the electromagnetic on-off valve 72 of the outdoor unit a2 to bypass the high-pressure gas refrigerant in the outdoor unit a2 to the low-pressure side. By this bypass, the so-called high pressure relief, the capacity of compressor a2 is reduced. When the capacity of the outdoor unit a2 decreases, the capacity of the outdoor unit a1 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a1 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases, and as a result, the amounts of the lubricating oils La and Lb in the compressors 1a and 1b increase. The shortage of the lubricant oil of the compressor 1a is eliminated.

If all of the amounts of the lubricating oils La, Lb, Lc, and Ld detected in the above-described process of S9 are in a shortage state of less than the set values (no in S10 and no in S13), the main controller 50 determines the magnitude relationship between the number of compressors 1a and 1b in the outdoor unit a1 operating at the current time and the number of compressors 1c and 1d in the outdoor unit a2 operating at the current time (S21 and S23).

When the number of operating compressors 1a, 1b at the current time is the same as the number of operating compressors 1c, 1d at the current time (no in S21, no in S23), the main controller 50 sets the total operating frequency F1 and the total operating frequency F2 to the operating frequency Fo for oil recovery in common (S15).

However, when the number of the compressors 1a, 1b operating at the current time is larger than the number of the compressors 1c, 1d operating at the current time (yes at S21), it is determined whether or not the total operating frequency F1 of the compressors 1a, 1b can be increased (S22 x). If the total operating frequency F1 can be increased (yes in S22x), the main controller 50 increases the total operating frequency F1 by the predetermined value Δ F (S22y), thereby preferentially increasing the capacity of the outdoor unit a 1. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a2 by the capacity increasing portion of the outdoor unit a1 and lower the total operating frequency F2 by a predetermined value.

When the capacity of the outdoor unit a1 increases, the circulation amount of the refrigerant to the outdoor unit a1 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases, and as a result, the amounts of the lubricating oils La and Lb in the compressors 1a and 1b increase. At least the shortage of the lubricating oil on the outdoor unit A1 side is eliminated.

If the outdoor unit a1 is not in a condition where the capacity can be increased (no in S22x), the main controller 50 opens the electromagnetic on-off valve 72 of the outdoor unit a2 to bypass the high-pressure gas refrigerant in the outdoor unit a2 to the low-pressure side. By this bypass, the so-called high pressure relief, the capacity of compressor a2 is reduced. When the capacity of the outdoor unit a2 decreases, the capacity of the outdoor unit a1 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a1 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a1 increases and the deviation ratio of the lubricating oil L to the outdoor unit a2 decreases, and as a result, the amounts of the lubricating oils La and Lb in the compressors 1a and 1b increase. At least the shortage of the lubricating oil on the outdoor unit A1 side is eliminated.

When the number of compressors 1c and 1d operating at the current time is larger than the number of compressors 1a and 1b operating at the current time (no in S21, yes in S23), it is determined whether or not the total operating frequency F2 of the compressors 1c and 1d can be increased (S24 x). If the total operating frequency F2 can be increased (yes in S24x), the main controller 50 increases the total operating frequency F2 by the predetermined value Δ F (S24y), thereby preferentially increasing the capacity of the outdoor unit a 2. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a1 by the capacity increasing portion of the outdoor unit a2 and lower the total operating frequency F1 by a predetermined value.

When the capacity of the outdoor unit a2 increases, the circulation amount of the refrigerant to the outdoor unit a2 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases, and as a result, the amounts of the lubricating oils Lc and Ld in the compressors 1c and 1d increase. At least the shortage of the lubricating oil on the outdoor unit A2 side is eliminated.

If the total operating frequency F2 is not satisfied and can be increased (no in S24x), the main controller 50 opens the electromagnetic on-off valve 72 of the outdoor unit a1 to bypass the high-pressure gas refrigerant in the outdoor unit a1 to the low-pressure side. By this bypass of the gaseous refrigerant, so-called high pressure relief, the capacity of the compressor a1 is reduced. When the capacity of the outdoor unit a1 decreases, the capacity of the outdoor unit a2 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a2 increases. Accordingly, the deviation ratio of the lubricating oil L to the outdoor unit a2 increases and the deviation ratio of the lubricating oil L to the outdoor unit a1 decreases, and as a result, the amounts of the lubricating oils Lc and Ld in the compressors 1c and 1d increase. At least the shortage of the lubricating oil on the outdoor unit A2 side is eliminated.

[5] Embodiment 5

Embodiment 5 of the present invention will be described with reference to fig. 11 and 12. The configurations of the outdoor units a1 and a2 will be described only with respect to the differences from embodiment 1.

As shown in fig. 11, the outdoor unit a1 includes one compressor 1a, a heat exchanger 81, a bypass pipe 82, and a motor-operated expansion valve 83. The bypass pipe 82 is connected from the liquid-side pipe between the outdoor heat exchanger 5 and the indoor units B1, B2, and … Bn to the low-pressure-side pipe between the four-way valve 4 and the accumulator 8. The motor-operated expansion valve 83 is a pulse monitoring valve with a variable opening degree and is provided in the bypass pipe 82. The heat exchanger 81 includes a1 st flow path 81a disposed in the liquid-side piping between the outdoor heat exchanger 5 and the indoor units B1, B2, and … Bn, and a2 nd flow path 81B disposed downstream of the motor-operated expansion valve 83 in the bypass pipe 82, and heat exchange between the refrigerant in the 1 st flow path 81a and the refrigerant in the 2 nd flow path 81B is performed.

When the motor-operated expansion valve 83 is opened, the liquid refrigerant in the liquid-side pipe flows into the flow passage 81b of the heat exchanger 81. The refrigerant flowing in absorbs heat from the liquid refrigerant in the flow path 81a and evaporates, becoming a gas refrigerant. The gas refrigerant passes through the bypass pipe 82 and flows to the low-pressure-side pipe between the four-way valve 4 and the accumulator 8.

The outdoor unit a2 includes one compressor 1c, and also includes the same heat exchanger 81, bypass pipe 82, and motor-operated expansion valve 83 as the outdoor unit a 1.

The control unit 50b determines whether or not the capacity of the outdoor unit in which the compressor in the shortage state is present can be increased, when the capacity of the outdoor unit can be increased, the capacity of the same outdoor unit is increased and the capacity of the other outdoor unit is decreased by the increased portion, in a case where the capacity of the outdoor unit can be increased, and opens the motor-operated expansion valve 83 in the other outdoor unit at a predetermined opening degree to bypass the refrigerant in the liquid-side pipe to the low-pressure side, in a case where the capacity of the outdoor unit in the shortage state is not increased, of the amounts of the lubricating oils La and Lc in the compressors 1a and 1c detected by the control unit 50 a. Specifically, when only the amount of the lubricating oil La of the compressor 1a is in a shortage state of less than the set value, it is determined whether or not the capacity of the outdoor unit a1 in which the compressor 1a is present can be increased (increase in the operation frequency Fa) at the present time point, the capacity of the outdoor unit a1 is increased and the capacity of the outdoor unit a2 (operation frequency Fc) is decreased by the increased portion when the capacity can be increased, and the opening degree of the electric expansion valve 83 of the outdoor unit a2 is opened at a predetermined opening degree and the opening degree of the electric expansion valve 83 which bypasses the liquid refrigerant in the liquid-side piping in the outdoor unit a2 to the low-pressure side is increased stepwise by the predetermined opening degree when the capacity can be increased. Further, when only the amount of the lubricating oil Lc of the compressor 1c is in the insufficient state of being smaller than the set value, it is determined whether or not the capacity (increase of the operation frequency Fc) of the outdoor unit a2 in which the compressor 1c is present can be increased at the present time, when the capacity can be increased, the capacity of the outdoor unit a2 is increased and the capacity (operation frequency Fa) of the outdoor unit a1 is decreased by the increased portion, and when the capacity can be increased, the electromagnetic on-off valve 83 of the outdoor unit a1 is opened at a predetermined opening degree to bypass the liquid refrigerant in the liquid-side piping in the outdoor unit a1 to the low-pressure side, and the opening degree of the electric expansion valve 83 is increased step by the predetermined amount.

The control executed by the main controller 50 will be described with reference to the flowchart of fig. 12. The description of the same control as that of embodiment 1 is omitted, and only the control different from that of embodiment 1 will be described.

If only the amount of the lubricant oil Lc is in a shortage state of being smaller than the set value among the amounts of the lubricant oils La and Lc detected in the process of S9 (yes in S10 and no in S11), the main controller 50 determines whether or not the capacity (increase in the operating frequency Fc) of the outdoor unit a2 in which the compressor 1c is present can be increased at the present time (S12 a).

If the capacity of the outdoor unit a2 cannot be increased (no in S12a), the main controller 50 opens the motor-operated expansion valve 83 of the outdoor unit a1 at a predetermined opening degree (initial opening degree) to bypass the liquid refrigerant in the liquid-side piping in the outdoor unit a1 to the low-pressure side (S12 c). By this bypass, the capacity of compressor a1 is reduced. When the capacity of the outdoor unit a1 decreases, the capacity of the outdoor unit a2 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a2 increases. Accordingly, the deviation ratio of the lubricant oil L to the outdoor unit a2 increases and the deviation ratio of the lubricant oil L to the outdoor unit a1 decreases.

In this bypass, the main controller 50 increases the count value N by "1" (S31). Then, the main controller 50 starts counting t3(S16), and compares the count t3 with a predetermined time t3S (S17). When the count t3 reaches the predetermined time t3S (yes in S17), the main controller 50 releases the bypass by opening the electric expansion valve 83 (S18). Subsequently, the main controller 50 returns to the process of S9, and again detects the amounts of the lubricating oils La and Lc (S9). When the detected amounts of lubricating oils La, Lc are in an appropriate state of being equal to or greater than the set values (yes at S10, yes at S11), main controller 50 clears count value N (S30), returns to the started process at S1, and restarts count t1 (S1).

If the amount of the lubricating oil Lc detected here is still in an insufficient state (yes in S10, no in S11) smaller than the set value and the capacity of the outdoor unit a2 cannot be increased (increase in the operating frequency Fc) (no in S12a), the main controller 50 opens the motor-operated expansion valve 83 of the outdoor unit a1 again to bypass the liquid refrigerant in the liquid-side piping of the compressor a1 to the low-pressure side (S12 c). At this time, the main controller 50 sets the opening degree of the motor-operated expansion valve 83 to an opening degree that is larger than the first predetermined opening degree (initial opening degree) by a predetermined amount in proportion to the count value N (═ 1). In this way, the opening degree of the motor-operated expansion valve 83 is increased in stages to increase the bypass amount of the refrigerant, thereby accelerating the capacity reduction of the outdoor unit a 1. Thereby, the amount of the lubricant oil Lc in the compressor 1c is reliably increased, and the shortage of the lubricant oil in the compressor 1c is promptly eliminated.

Further, if only the amount of the lubricant oil La is in a shortage state of less than the set value among the amounts of the lubricant oils La and Lc detected in the process of S9 (no in S10 and yes in S13), the main controller 50 determines whether or not the capacity of the outdoor unit a1 in which the compressor 1a is present can be increased (increase in the operation frequency Fa) at the present time (S14 a).

If the capacity of the outdoor unit a1 can be increased (yes in S14a), the main controller 50 increases the operation frequency Fa by the predetermined value Δ F (S14b), thereby increasing the capacity of the outdoor unit a 2. Simultaneously, the main controller 50 should reduce the capacity of the outdoor unit a2 by the capacity increasing portion of the outdoor unit a1 and lower the operating frequency Fc by a predetermined value.

If the capacity of the outdoor unit a1 cannot be increased (no in S14a), the main controller 50 opens the motor-operated expansion valve 83 of the outdoor unit a2 at a predetermined opening degree to bypass the liquid refrigerant in the liquid-side piping in the outdoor unit a2 to the low-pressure side (S14 c). By this bypass, the capacity of compressor a2 is reduced. When the capacity of the outdoor unit a2 decreases, the capacity of the outdoor unit a1 relatively increases, and the circulation amount of the refrigerant to the outdoor unit a1 increases. Accordingly, the deviation ratio of the lubricant oil L to the outdoor unit a1 increases and the deviation ratio of the lubricant oil L to the outdoor unit a2 decreases.

If the amount of the lubricating oil La detected here is still in an insufficient state (no in S10, yes in S13) smaller than the set value and the capacity of the outdoor unit a1 cannot be increased (increase in the operation frequency Fa) (no in S14a), the main controller 50 opens the motor-operated expansion valve 83 of the outdoor unit a2 again to bypass the liquid refrigerant in the liquid-side piping of the compressor a2 to the low-pressure side (S14 c). At this time, the main controller 50 sets the opening degree of the motor-operated expansion valve 83 to an opening degree that is larger than the first predetermined opening degree (initial opening degree) by a predetermined amount in proportion to the count value N (═ 1). In this way, the opening degree of the motor-operated expansion valve 83 is increased in stages to increase the bypass amount of the refrigerant, thereby accelerating the capacity reduction of the outdoor unit a 2. Thereby, the amount of the lubricant La in the compressor 1a is reliably increased, and the shortage of the lubricant La in the compressor 1a is promptly eliminated.

In addition, although the description has been given of the case where the outdoor units a1 and a2 each have one compressor in the 5 th embodiment, the same description may be applied to the case where the outdoor units a1 and a2 each have two compressors as in the 4 th embodiment.

[6] Modification example

In the above embodiments, the following configurations are adopted: the recovery of the lubricating oil L from the oil separator 3 is performed when the shortage of lubricating oil occurs, and the circulation amount of the refrigerant to the outdoor unit is controlled regardless of the fact that the shortage of lubricating oil cannot be eliminated, but the following configuration may be adopted: when the lubricating oil is insufficient, the circulation amount of the refrigerant to the outdoor unit is immediately controlled.

In the above embodiments, the case where the amount of the lubricating oil is detected based on the refrigerant temperature and the oil temperature has been described as an example, but various detection methods such as detecting the amount of the lubricating oil using a float floating on the oil surface in the compressor, or detecting the amount of the lubricating oil based on the dielectric constant may be employed.

The above embodiments and modifications are merely examples, and are not intended to limit the scope of the present invention. The new embodiments and modifications can be implemented in other various forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. The above embodiments and modifications are included in the scope and gist of the invention, and are also included in the invention described in the scope of claims and equivalents thereof.

Description of the reference symbols

Outdoor units of A1 and A2 …, indoor units of B1 to Bn …, compressors of 1a to 1d …, high-pressure side pipes of 2, 2a and 2B …, 3 … oil separators, 4 … four-way valves, outdoor heat exchangers of 5 …, electric expansion valves of 6 …, oil return pipes of 11, 11a and 11B …, temperature sensors of 30 … controllers, 44 and 45a to 45d …, main controllers of 50 …, controllers of … 60 …, inverters of 51, 52, 61 and 62 …, bypass pipes of 71 …, electromagnetic opening and closing valves of 72 …, heat exchangers of 81 …, bypass pipes of 82 … and electric expansion valves of 83 ….

Claims

1. A refrigeration cycle apparatus, comprising:

a plurality of outdoor units having a compressor and an outdoor heat exchanger;

a plurality of indoor units having indoor heat exchangers; and

a controller configured to set a circulation amount of the refrigerant to the outdoor unit in which the compressor is present to be larger than a circulation amount of the refrigerant to another outdoor unit when an amount of the lubricating oil in any one of the compressors is smaller than a set value,

each outdoor unit includes a high-pressure-side pipe through which refrigerant discharged from each compressor flows, a low-pressure-side pipe through which refrigerant sucked into each compressor flows, a bypass pipe connected between the high-pressure-side pipe and the low-pressure-side pipe, and an on-off valve provided in the bypass pipe,

the controller determines whether or not the capacity of the outdoor unit in which the compressor is present can be increased when the amount of the lubricating oil in any one of the compressors is smaller than the set value, increases the capacity of the same outdoor unit and decreases the capacity of the other outdoor unit by the increased amount when the capacity of the outdoor unit can be increased, and opens the on-off valves in the other outdoor units when the capacity of the outdoor unit can not be increased.

2. The refrigeration cycle apparatus according to claim 1,

the controller sets the circulation amounts of the refrigerant to the outdoor units to be in the same state when the amounts of the lubricating oil in the compressors are all smaller than the set value.

3. A refrigeration cycle apparatus, comprising:

a plurality of outdoor units having a compressor and an outdoor heat exchanger;

a plurality of indoor units having indoor heat exchangers; and

each outdoor unit includes a liquid-side pipe between each outdoor heat exchanger and each indoor unit, a low-pressure-side pipe through which refrigerant sucked into each compressor flows, a bypass pipe connected between the liquid-side pipe and the low-pressure-side pipe, and an electric expansion valve provided in the bypass pipe,

the controller determines whether or not the capacity of the outdoor unit in which the compressor is present can be increased when the amount of the lubricating oil in any one of the compressors is smaller than the set value, increases the capacity of the same outdoor unit and decreases the capacity of the other outdoor unit by the increased amount when the capacity of the outdoor unit can be increased, and opens the motor-operated expansion valve in the other outdoor unit at a predetermined opening degree when the capacity of the outdoor unit cannot be increased.

4. The refrigeration cycle apparatus according to claim 3,

each outdoor unit includes:

and a heat exchanger including a1 st flow path disposed in the liquid-side pipe and a2 nd flow path disposed downstream of the motor-operated expansion valve in the bypass pipe, wherein heat exchange of the refrigerant is performed between the 1 st flow path and the 2 nd flow path.

5. The refrigeration cycle apparatus according to claim 3,

the controller opens the motor-operated expansion valve in the other outdoor unit at a predetermined opening degree and increases the opening degree of the motor-operated expansion valve by a predetermined amount in a stepwise manner if the state in which the expansion is possible is not satisfied.