JP2013122361A - Air conditioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of an oil separator in an air conditioning device that can control the amount of oil in a compressor.SOLUTION: The air conditioning device 1 includes: an accumulator 20 connected to a plurality of compressors 11A and 11B at the inlet side thereof; oil separators 21A and 21B connected to the compressors 11A and 11B, respectively, at the outlet side thereof; a plurality of first oil return tubes 41A and 41B for returning lubricant oil separated by each of the oil separators 21A and 21B to the inlet side of other compressor 11B and 11A than the compressors 11A and 11B to which the oil separators 21A and 21B are connected; a bypass tube 43 branched from the first oil return tube 41A, and for introducing the lubricant oil into the accumulator 20; a second oil return tube 42 for returning the lubricant oil in the accumulator 20 to the inlet side of the compressors 11A and 11B; a second open/close valve 32 disposed on the second oil return tube 42; and a third open/close valve 33 disposed on the bypass tube 43.

Description

  The present invention relates to an air conditioner. In particular, the present invention relates to an air conditioner including a plurality of compressors in a refrigerant circuit and capable of an oil amount control operation for controlling (limiting) the amount of lubricating oil in the compressor.

  In general, an air conditioner having a refrigerant circuit in which a plurality of indoor units are connected to an outdoor unit by a refrigerant pipe in a relatively large facility such as a building or a large store. Some of these types of air conditioners have built-in multiple compressors in the outdoor unit. By controlling the operation of these multiple compressors, it is possible to operate in a wide range of air conditioning loads from low to high loads. (For example, refer to Patent Document 1).

  In the air conditioner described in Patent Document 1, oil separators are connected to the discharge sides of a plurality of compressors, and when the lubricant is discharged from each compressor along with the refrigerant, It is separated from the refrigerant and returned to the compressor via an oil return pipe. In order to suppress unevenness in the amount of lubricating oil in the plurality of compressors, the oil separators return oil to the suction side of another compressor different from the compressor to which the oil separator is connected. It is connected by an oil return pipe so that the tip does not overlap. Specifically, when the outdoor unit has two compressors, the oil separator connected to one compressor is connected to the suction side of the other compressor via an oil return pipe, The oil separator connected to the other compressor is connected to the suction side of one compressor via an oil return pipe.

JP 2011-117777 A

  If the lubricating oil discharged from the compressor circulates in the refrigerant circuit and flows into the condenser or evaporator during operation of the air conditioner, this lubricating oil may interfere with heat transfer and reduce air conditioning capacity. is there. For this reason, not only the oil separator is provided in the refrigerant circuit to suppress the circulation of the lubricating oil, but also the discharge amount of the lubricating oil from the compressor is suppressed by controlling the amount of the lubricating oil in the compressor as small as possible. Thus, there is a case where an operation (oil amount control operation) for increasing the air conditioning capability is performed. In addition, when the number of indoor units connected to the outdoor unit is small and the total pipe length is short, the amount of lubricating oil required for lubricating the compressor is also reduced, so the amount of lubricating oil in the compressor is actively reduced. By doing so, the air conditioning capacity may be increased. In order to reduce the amount of lubricating oil in the compressor in this way, it is necessary to close the oil return pipe with a valve and collect the lubricating oil separated by the oil separator in the oil separator so that it does not return to the compressor. Has been done.

  However, if the amount of lubricating oil in the compressor is reduced, the capacity of the oil separator has to be increased in order to store excess lubricating oil, which increases the size of the oil separator and increases costs. In addition, when the oil separator becomes large, it is necessary to secure a large arrangement space in the outdoor unit, and the degree of freedom in layout of the equipment in the outdoor unit is reduced, and the oil separator obstructs the air flow in the outdoor unit. There is a risk of becoming.

  The present invention relates to an air conditioner capable of reducing the size of an oil separator by preventing excess lubricant oil from accumulating in an oil separator during an oil amount control operation for controlling the amount of lubricating oil in a compressor. The purpose is to provide.

(1) An air conditioner according to a first aspect of the present invention includes a plurality of compressors connected in parallel, an accumulator connected to the suction side of these compressors, and a discharge side of each compressor. A plurality of connected oil separators and the lubricating oil separated by each oil separator are overlapped with each other to the suction side of another compressor different from the compressor to which the oil separator is connected. A plurality of first oil return pipes that return so as not to be,
A bypass pipe for branching from one first oil return pipe and flowing the lubricating oil into the accumulator;
A second oil return pipe for returning the lubricating oil in the accumulator to the suction side of the compressor;
A second on-off valve provided in the second oil return pipe;
And a third on-off valve provided in the bypass pipe.

  Since the air conditioner of the present invention includes a bypass pipe branched from one first oil return pipe and a third on-off valve provided on the bypass pipe, by opening the third on-off valve, Lubricating oil can be allowed to flow from the first first oil return pipe into the accumulator through the bypass pipe. Further, each first oil return pipe is configured so that the oil return destinations of the lubricating oil separated by each oil separator do not overlap each other to the suction side of another compressor different from the compressor to which the oil separator is connected. Therefore, any lubricating oil flowing in another first oil return pipe different from the one first oil return pipe may be allowed to flow into the accumulator via the first oil return pipe and the bypass pipe. it can. The air conditioner includes a second oil return pipe that returns the lubricating oil in the accumulator to the compressor, and a second on-off valve provided on the second oil return pipe. By closing the, the lubricating oil flowing into the accumulator can be stored in the accumulator. As described above, the oil amount control operation for controlling (limiting) the amount of lubricating oil in the compressor can be performed, and the surplus lubricating oil can be stored not in the oil separator but in a larger capacity accumulator. . Therefore, each oil separator can be reduced in size, the cost can be reduced, the degree of freedom of the layout of the equipment in the outdoor unit of the air conditioner is increased, and the flow of air in the outdoor unit is hardly hindered. Become.

(2) It is preferable that the air conditioner includes a first on-off valve on the downstream side of the branch portion of the bypass pipe in the first oil return pipe.
According to this configuration, when performing the oil amount control operation, the entire amount of the lubricating oil flowing through the first oil return pipe can be sent to the bypass pipe by closing the first on-off valve. Lubricating oil can be reduced quickly.

(3) The air conditioner described in (1) above opens the third on-off valve and closes the second on-off valve when performing an oil amount control operation for controlling the amount of lubricating oil in the compressor. It is preferable that an opening / closing control unit that controls opening / closing by interlocking each valve is provided.
With such a configuration, the oil amount control operation can be executed smoothly.

(4) The air conditioner described in (2) above opens the third on-off valve and performs the first and second on-off valves when performing an oil amount control operation for controlling the amount of lubricating oil in the compressor. It is preferable to provide an open / close control unit that controls opening and closing of each valve in conjunction with each other.
With such a configuration, the oil amount control operation can be executed smoothly.

(5) The air conditioner further includes a detection unit that detects the amount of lubricating oil in the compressor. When the oil amount control operation is performed, the detection unit causes the lubricating oil in the compressor to be detected. When it is detected that the amount has decreased to a predetermined amount, the opening / closing control unit preferably performs control to reverse the opening / closing state of each valve.
According to this configuration, when the lubricating oil in the compressor is reduced to a predetermined amount, for example, a minimum amount capable of proper operation, the lubricating oil is transferred from the accumulator to the compressor via the second oil return pipe. The oil amount control operation can be continuously performed while maintaining the amount of lubricating oil in the compressor appropriately.

(6) A flow rate adjusting unit may be provided on the upstream side of the branch portion of the bypass pipe in the first oil return pipe.
With such a configuration, the flow rate of the lubricating oil flowing through one first oil return pipe and the lubricating oil flowing through the bypass pipe can be adjusted by one flow rate adjusting unit.

(7) The air conditioner according to the second aspect of the present invention includes a plurality of compressors connected in parallel, an accumulator connected to the suction side of these compressors, and a discharge side of each compressor. A plurality of connected oil separators and the lubricating oil separated by each oil separator are overlapped with each other to the suction side of another compressor different from the compressor to which the oil separator is connected. A plurality of first oil return pipes that return so as not to be,
A bypass pipe for branching from one first oil return pipe and flowing the lubricating oil into the accumulator;
A second oil return pipe for returning the lubricating oil in the accumulator to the suction side of the compressor;
The operation of causing the lubricating oil separated in each oil separator to flow into the accumulator via the first oil return pipe and the bypass pipe and storing the lubricating oil, and the lubricating oil stored in the accumulator to be returned to the second oil return An oil amount control mechanism for controlling the amount of lubricating oil in the compressor by performing an operation of returning to the compressor via a pipe.

  The air conditioner having the above configuration does not store the lubricating oil discharged from the compressor in the oil separator when the oil amount control operation for controlling the lubricating oil amount in the compressor is performed, but rather than the oil separator. Store in a large capacity accumulator. Therefore, the oil separator can be reduced in size, the cost can be reduced, the degree of freedom in the layout of the equipment in the outdoor unit of the air conditioner can be increased, and the resistance to the air flow in the outdoor unit can be reduced. it can. Also, the lubricating oil separated by each oil separator is not overlapped with the oil return destination to the suction side of another compressor different from the compressor to which the oil separator is connected by the first oil return pipe. Therefore, only one bypass pipe branched from one first oil return pipe is provided, and the lubricating oil flowing through the other first oil return pipes is accumulated from any one first oil return pipe via the bypass pipe. It flows into and is stored. Therefore, not only the oil separator connected to the first oil return pipe but also other oil separators can be reduced in size.

  According to the present invention, when the oil amount control operation for controlling the amount of lubricating oil in the compressor is performed, surplus lubricating oil can be stored not in the oil separator but in a larger capacity accumulator. Can be miniaturized.

It is a schematic diagram which shows the refrigerant circuit of the air conditioning apparatus which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the refrigerant circuit of the air conditioning apparatus which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the refrigerant circuit of the air conditioning apparatus which concerns on the 3rd Embodiment of this invention.

[First Embodiment]
FIG. 1 is a schematic diagram showing a refrigerant circuit of the air-conditioning apparatus according to the first embodiment of the present invention. The air conditioner 1 is a multi-type air conditioner for buildings, for example, and is a refrigerant circuit so that one or a plurality of indoor units 3 are connected to one or a plurality of outdoor units 2 so that a refrigerant can circulate. 10 is formed.
The outdoor unit 2 is provided with compressors 11A and 11B, a four-way switching valve 12, an outdoor heat exchanger 13, an outdoor expansion valve 14, an accumulator 20, oil separators (oil separators) 21A and 21B, and the like. Connected by piping. The outdoor unit 2 is provided with a blower fan 23.

  The indoor unit 3 is provided with an indoor expansion valve 15, an indoor heat exchanger 16, and the like. The four-way switching valve 12 and the indoor heat exchanger 16 are connected by a gas side refrigerant communication pipe 17a, and the outdoor expansion valve 14 and the indoor expansion valve 15 are connected by a liquid side refrigerant communication pipe 17b. A gas side shut-off valve 18 and a liquid side shut-off valve 19 are provided at a terminal portion of the internal refrigerant circuit of the outdoor unit 2. The gas side closing valve 18 is arranged on the four-way switching valve 12 side, and the liquid side closing valve 19 is arranged on the outdoor expansion valve 14 side. A gas side refrigerant communication pipe 17 a is connected to the gas side shutoff valve 18, and a liquid side refrigerant communication pipe 17 b is connected to the liquid side shutoff valve 19.

The outdoor heat exchanger 13 is a cross fin tube type heat exchanger, for example, and is used to exchange heat with the outside air. The outdoor unit 2 is configured to take outside air into the inside by the blower fan 23, perform heat exchange with the outdoor heat exchanger 13, and then blow out to the outside.
The indoor heat exchanger 16 is also a cross fin tube type heat exchanger, for example, and is used to exchange heat with indoor air. The indoor unit 3 is configured so that indoor air is taken into the indoor unit 3 by a fan (not shown), heat exchange is performed with the indoor heat exchanger 16, and then blown into the room. In FIG. 1, only one indoor unit 3 is illustrated, but two or more indoor units 3 may be connected in parallel.

  The outdoor unit 2 of the present embodiment is provided with two compressors 11A and 11B, and these two compressors 11A and 11B are connected in parallel. Each of the compressors 11A and 11B is a variable capacity type (variable capacity type) compressor, and the operation speed of the motor is adjusted stepwise or continuously by inverter control of the built-in motor. Is possible. In the following description, the compressor 11A disposed on the right side of FIG. 1 may be referred to as a first compressor, and the compressor 11B disposed on the left side may be referred to as a second compressor. And the air conditioning apparatus 1 of this Embodiment is comprised so that it may drive the 1st compressor 11A preferentially, when operating only one compressor with a small air-conditioning load.

  The accumulator 20 is connected to the suction sides of the two compressors 11A and 11B. The accumulator 20 can store surplus refrigerant generated in the refrigerant circuit in accordance with fluctuations in the air conditioning load on the indoor unit 3 side. The accumulator 20 includes an intake pipe 20a that takes in the gaseous refrigerant from the four-way switching valve 12, a delivery pipe 20b that sends the gaseous refrigerant to the compressors 11A and 11B, and refrigerant and lubricating oil accumulated in the accumulator 20 to the compressor. A returning liquid return pipe (second oil return pipe) 42 is connected. The liquid return pipe 42 is provided between the bottom of the accumulator 20 and the middle part of the delivery pipe 20b. The liquid return pipe 42 is provided with a second electromagnetic valve (second on-off valve) 32.

  First and second oil separators 21A and 21B are connected to the discharge sides of the first and second compressors 11A and 11B, respectively. The first and second oil separators 21A and 21B separate the lubricating oil from the refrigerant when the lubricating oil is discharged together with the refrigerant from the first and second compressors 11A and 11B. The separated refrigerant is sent to the four-way switching valve 12, and the separated lubricating oil is returned to the compressors 11B and 11A via oil return pipes (first oil return pipes) 41A and 41B.

  The oil return pipes 41A and 41B of the oil separators 21A and 21B return oil to the suction sides of the other compressors 11B and 11A different from the compressors 11A and 11B to which the oil separators 21A and 21B are connected. The destination is connected so as not to overlap. Specifically, the oil return pipe 41A that returns the lubricating oil from the first oil separator 21A connected to the first compressor 11A is connected to the suction side of the second compressor 11B. Conversely, the oil return pipe 41B that returns the lubricating oil from the second oil separator 21B connected to the second compressor 11B is connected to the suction side of the first compressor 11A. Therefore, the lubricating oil discharged from the compressors 11A and 11B is sucked by the other compressors 11B and 11A, respectively, thereby eliminating the unevenness of the lubricating oil between the compressors 11A and 11B. It is like that.

  Both the oil return pipes 41A and 41B are provided with capillary tubes 36A and 36B constituting a flow rate adjusting unit. The capillary tubes 36A and 36B adjust the flow rate of the lubricating oil that returns to the compressors 11A and 11B and suppress the refrigerant mixed with the lubricating oil from being sucked into the compressors 11A and 11B from the oil return pipes 41A and 41B. doing. Further, the oil return pipe 41A connected to the first oil separator 21A is provided with a first electromagnetic valve (first on-off valve) 31 on the downstream side of the capillary tube 36A.

  Check valves 35A and 35B are provided between the first and second oil separators 21A and 21B and the four-way switching valve 12, respectively. The check valves 35A and 35B can prevent the reverse flow of the refrigerant from the four-way switching valve 12 side to the first and second oil separators 21A and 21B, and only the first compressor 11A operates. When the second compressor 11B is stopped, the refrigerant discharged from the first compressor 11A can be prevented from flowing back to the second oil separator 21B side.

The four-way switching valve 12 reverses the flow of the refrigerant, switches the refrigerant discharged from the first and second compressors 11A and 11B to the outdoor heat exchanger 13 and the indoor heat exchanger 16, and supplies the cooling operation. And heating operation can be switched.
Specifically, during the cooling operation, the four-way switching valve 12 is switched as indicated by a solid line. Thereby, the refrigerant discharged from the compressors 11 </ b> A and 11 </ b> B is supplied to the outdoor heat exchanger 13, and then is decompressed by the indoor expansion valve 15 and supplied to the indoor heat exchanger 16. At this time, the outdoor heat exchanger 13 functions as a condenser to condense and liquefy the high-temperature and high-pressure gaseous refrigerant compressed by the compressors 11A and 11B, the indoor heat exchanger 16 functions as an evaporator, and an expansion valve The low-temperature and low-pressure liquid refrigerant decompressed by 15 is evaporated and vaporized.

  During the heating operation, the four-way selector valve 12 is switched as indicated by the dotted line, and the refrigerant flow is reversed. As a result, the outdoor heat exchanger 13 functions as an evaporator to evaporate and vaporize the low-temperature and low-pressure liquid refrigerant decompressed by the outdoor expansion valve 14, and the indoor heat exchanger 16 functions as a condenser. The high-temperature and high-pressure gaseous refrigerant compressed by the two compressors 11A and 11B is condensed and liquefied.

  The expansion valves 14 and 15, the four-way switching valve 12, the first and second compressors 11 </ b> A and 11 </ b> B, etc., are turned on / off according to the operation switch of the air conditioner 1 and sensor outputs such as a temperature sensor and a pressure sensor. The operation is controlled by the controller. In particular, the first and second compressors 11 </ b> A and 11 </ b> B are operated and controlled so as to satisfy the required capacity according to the air conditioning load on the indoor unit 3 side.

(About oil quantity control operation)
When the first and second compressors 11A and 11B are operated, the lubricating oil is discharged together with the refrigerant, and the lubricating oil is separated from the refrigerant by the first and second oil separators 21A and 21B, but not completely separated. Lubricating oil may circulate through the refrigerant piping together with the refrigerant. When the lubricating oil flows into the outdoor heat exchanger 13 or the indoor heat exchanger 16, heat transfer between the refrigerant and air (outside air or indoor air) is hindered, which may cause a decrease in air conditioning capability. is there. Therefore, it can be said that suppressing the circulation of the lubricating oil in the refrigerant circuit is desirable for enhancing the air conditioning capability.

  In general, the compressors 11A and 11B are more likely to discharge lubricating oil as the amount of lubricating oil inside increases. Therefore, limiting the amount of lubricating oil in the compressors 11 </ b> A and 11 </ b> B to be small is effective for suppressing the circulation of the lubricating oil to the refrigerant circuit 10. Therefore, the air conditioner 1 of the present embodiment can perform an oil amount control operation for performing control to reduce the amount of lubricating oil stored in the first and second compressors 11A and 11B to be less than normal. It is possible. And the air conditioning apparatus 1 of this Embodiment controls the amount of lubricating oil in the 1st, 2nd compressor 11A, 11B to predetermined | prescribed simultaneously, and it is not the oil separator 21A, 21B for the excess lubricating oil. The accumulator 20 is configured to accumulate. Therefore, the air conditioning apparatus 1 includes a bypass pipe 43 for sending the lubricating oil to the accumulator 20, and an oil amount control mechanism 50 for sending the lubricating oil to the accumulator 20 through the bypass pipe 43 and storing the lubricating oil. It has.

The bypass pipe 43 branches from the downstream side of the capillary tube 36A upstream of the first solenoid valve 31 in the oil return pipe 41A connected to the first oil separator 21A, and is upstream of the accumulator 20 (the refrigerant inflow side). ) Of the intake pipe 20a. The bypass pipe 43 is provided with a third electromagnetic valve (third on-off valve) 33.
On the other hand, the oil amount control mechanism 50 includes a first electromagnetic valve 31 provided in the oil return pipe 41A, a second electromagnetic valve 32 provided in the liquid return pipe (second oil return pipe) 42 of the accumulator 20, and a bypass. A third electromagnetic valve 33 provided in the pipe 43, an open / close control unit 51 for controlling the open / close operation of these electromagnetic valves 31, 32, 33, and a detection unit 52 for detecting the amount of lubricating oil in the compressors 11A, 11B. And.

  Next, the operation of the air conditioner 1 will be described. First, when performing a normal operation (steady operation) that is not an oil amount control operation, the open / close control unit 51 opens the first and second electromagnetic valves 31 and 32 and closes the third electromagnetic valve 33. ~ 33 are controlled. As a result, the lubricating oil discharged together with the refrigerant from the first and second compressors 11A and 11B is separated from the refrigerant by the first and second oil separators 21A and 21B, and secondly from the oil return pipes 41A and 41B. , Are returned to the first compressors 11B and 11A. Further, the lubricating oil that has not been completely separated by the first and second oil separators 21A and 21B and circulated through the refrigerant circuit 10 passes through the accumulator 20 to the first and second compressors 11A and 11B from the liquid return pipe 42. Returned. Further, the opening / closing control unit 51 closes the second electromagnetic valve 32 when the first and second compressors 11A and 11B are in a wet operation state, and the liquid refrigerant accumulated in the accumulator 20 is compressed by the compressor. It is prevented from being taken into 11A and 11B.

  When switching from the steady operation to the oil amount control operation, the opening / closing control unit 51 controls the valves 31 to 33 so as to close the first and second electromagnetic valves 31 and 32 and open the third electromagnetic valve 33. The lubricating oil discharged together with the refrigerant from the first and second compressors 11A and 11B is separated from the refrigerant by the first and second oil separators 21A and 21B and flows to the oil return pipes 41A and 41B. 1 Since the solenoid valve 31 is in a closed state, the lubricating oil flowing through the oil return pipe 41A on the first oil separator 21A side is not returned to the second compressor 11B, but is returned from the bypass pipe 43 to the accumulator 20. Inflow. Further, the lubricating oil flowing through the oil return pipe 41B on the second oil separator 21B side is sucked into the first compressor 11A as it is and discharged again from the first compressor 11A, and then the first oil separator 21 and It flows into the accumulator 20 from the bypass pipe 43 through the first oil return pipe 41A. And since the 2nd solenoid valve 32 is made into the closed state, the lubricating oil which flowed into the accumulator 20 is stored in the accumulator 20 without returning to the 1st, 2nd compressor 11A, 11B.

  By continuing the above operation, the amount of lubricating oil stored in the accumulator 20 gradually increases, and conversely, the amount of lubricating oil in the first and second compressors 11A and 11B decreases. As the amount of lubricating oil in the first and second compressors 11A and 11B decreases, the lubricating oil discharged from the first and second compressors 11A and 11B also decreases, and the lubricating oil circulating in the refrigerant circuit 10 is reduced. Can be reduced. Therefore, the heat exchange in the outdoor heat exchanger 13 and the indoor heat exchanger 16 is not hindered by the lubricating oil, and the air conditioning capacity can be suitably increased.

  If the above operation is continued, the amount of lubricating oil in the compressors 11A and 11B continues to decrease, but it is necessary to secure the minimum amount of lubricating oil necessary for the operation of the compressors 11A and 11B. For this reason, the air conditioning apparatus 1 of this Embodiment is provided with the detection part 52 which detects the amount of lubricating oil in compressor 11A, 11B. The amount of lubricating oil in the compressors 11A and 11B can be obtained by calculation from the operation time, the operation speed, and the like. Therefore, the detection unit 52 of the present embodiment measures the elapsed time after the start of the oil amount control operation, and when the predetermined time has elapsed, the amount of lubricating oil in the compressors 11A and 11B is set to a predetermined appropriate lower limit amount (appropriate lower limit amount) It is determined that the oil amount has been reduced to a lower limit amount that enables a correct oil amount control operation. When the detection unit 52 determines that the lubricating oil amount of the compressors 11A and 11B has decreased to the appropriate lower limit amount, the opening / closing control unit 51 changes the opening / closing states of the first to third electromagnetic valves 31 to 33. Control to reverse. That is, the opening / closing control unit 51 performs control to open the first and second electromagnetic valves 31 and 32 and close the third electromagnetic valve 33.

  By performing such control, the air conditioner 1 is in an operation state substantially similar to the steady operation, and the lubricating oil stored in the accumulator 20 is returned from the liquid return pipe 42 to the compressors 11A and 11B. The lubricating oil discharged from the compressors 11A and 11B is returned to the compressors 11B and 11A without flowing through the bypass pipe 43 via the oil return pipes 41A and 41B.

When the operation of returning the lubricating oil to the compressors 11A and 11B is executed for a predetermined time, the detection unit 52 determines that the amount of lubricating oil in the compressors 11A and 11B is an appropriate upper limit amount (an upper limit amount that allows an appropriate oil amount control operation). ). Then, the open / close control unit 51 performs control to reverse the open / close states of the first to third electromagnetic valves 31 to 33 again based on the determination by the detection unit 52. That is, the open / close control unit 51 performs control to close the first and second electromagnetic valves 31 and 32 and open the third electromagnetic valve 33. As a result, surplus lubricating oil can be stored in the accumulator 20 again.
By repeating the above operation, the oil amount control operation can be continued.

  As described above, in the present embodiment, when the oil amount control operation is performed, the lubricating oil is not stored in the oil separators 21A and 21B, but is stored in the accumulator 20 having a relatively large capacity. doing. Therefore, the oil separators 21A and 21B can be reduced in size, and the cost can be reduced. Moreover, the freedom degree of the layout of the apparatus in the outdoor unit 2 can be raised by downsizing the oil separators 21A and 21B. In addition, it is possible to prevent the oil separators 21A and 21B from obstructing the air flow in the outdoor unit 2.

In the present embodiment, the lubricating oil separated in all the oil separators 21A and 21B can be sent to the accumulator 20 only by providing the bypass pipe 43 in one oil return pipe 41A. Therefore, all the oil separators 21A and 21B can be downsized.
Further, since the bypass pipe 43 is branched from the downstream side of the capillary tube 36A in the oil return pipe 41A, the flow rate of the lubricating oil flowing through the oil return pipe 41A and the bypass pipe 43 is adjusted by one capillary tube 36A. Can do.

[Second Embodiment]
FIG. 2 is a schematic diagram showing a refrigerant circuit of an air-conditioning apparatus according to the second embodiment of the present invention.
The air conditioning apparatus 1 according to the present embodiment includes first to third compressors 11A to 11C. In the present embodiment, the first compressor 11A is a compressor that is operated with priority over the other compressors 11B and 11C.

  The first to third oil separators 21A to 21C are connected to the discharge sides of the first to third compressors 11A to 11C, respectively. The oil return pipes 41A to 41C of the first to third oil separators 21A to 21C are different from the compressors 11A to 11C connected to the oil separators 21A to 21C, as in the first embodiment. The compressors 11A to 11C are connected to the suction side so that the oil return destinations do not overlap each other.

  Specifically, in the example shown in FIG. 2, the oil return pipe 41A connected to the first oil separator 21A is connected to the suction side of the second compressor 11B and connected to the second oil separator 21B. The oil return pipe 41B is connected to the suction side of the third compressor 11C, and the oil return pipe 41C connected to the third oil separator 21C is connected to the suction side of the first compressor 11A. Therefore, also in the present embodiment, it is possible to suitably eliminate the unevenness of the lubricating oil amount between the compressors 11A to 11C.

The oil return pipes 41A to 41C are provided with capillary tubes 36A to 36C, respectively. Further, check valves 35A to 35C are provided between the oil separators 21A to 21C and the four-way switching valve 12.
The bypass pipe 43 branches off from the oil return pipe 41A connected to the first oil separator 21A and is connected to the intake pipe 20a of the accumulator 20. The bypass pipe 43 is provided with a third electromagnetic valve 33.
The operations of the open / close control unit 51 and the detection unit 52 are the same as those in the first embodiment. Therefore, the present embodiment has the same operational effects as the first embodiment.

[Third Embodiment]
FIG. 3 is a schematic diagram showing a refrigerant circuit of an air-conditioning apparatus according to the third embodiment of the present invention.
In the present embodiment, the oil return pipe 41A connected to the first oil separator 21A is not provided with the first electromagnetic valve 31, and the first capillary tube 36A is a bypass pipe 43 in the oil return pipe 41A. This is different from the first embodiment in that it is provided on the downstream side.

  When performing the oil amount control operation in the air conditioning apparatus 1 of the present embodiment, the opening / closing control unit 51 performs control to close the second electromagnetic valve 32 and open the third electromagnetic valve 33. Therefore, part of the lubricating oil separated by the first oil separator 21A flows from the oil return pipe 41A to the bypass pipe 43, and the rest is sucked by the second compressor 11B. However, since the oil return pipe 41A is provided with the capillary tube 36A on the downstream side of the bypass pipe 43, the flow resistance of the bypass pipe 43 is relatively smaller than that of the oil return pipe 41A, and lubrication to the bypass pipe 43 is performed. More oil flow can be achieved. As described above, the lubricating oil is stored in the accumulator 20 as in the first embodiment, and the amount of lubricating oil in the compressors 11A and 11B can be controlled.

  In the present embodiment, since the number of electromagnetic valves can be reduced, it can be configured at a lower cost than in the first embodiment. On the other hand, in the present embodiment, since a part of the lubricating oil flowing through the oil return pipe 41A is returned to the compressor 11B, it takes time to reduce the amount of lubricating oil in the compressors 11A and 11B. Therefore, the first embodiment is more advantageous in that the lubricating oil in the compressors 11A and 11B can be rapidly reduced.

The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the invention described in the claims.
For example, the detection unit of the oil amount control mechanism may be configured to directly detect the amount of lubricating oil in the compressor using a sensor.
Moreover, this invention is applicable also to the air conditioning apparatus provided with four or more compressors. The plurality of compressors may be a combination of a variable capacity compressor and a constant capacity compressor. In this case, it is preferable that the first compressor that is activated preferentially is a variable capacity type. The plurality of compressors may be a combination of constant capacity compressors.
The air conditioner may perform only one of the cooling operation and the heating operation. In this case, the four-way switching valve can be omitted.

11A, 11B, 11C Compressor 20 Accumulator 21A, 21B, 21C Oil separator 31 First on-off valve 32 Second on-off valve 33 Third on-off valve 36A Flow rate adjusting unit 41A, 41B, 41C Oil return pipe (first oil return pipe) )
42 Liquid return pipe (second oil return pipe)
43 Bypass pipe 50 Oil control mechanism 51 Open / close control unit 52 Detection unit

Claims (7)

A plurality of compressors (11A, 11B, 11C) connected in parallel, an accumulator (20) connected to the suction side of these compressors (11A, 11B, 11C), and each compressor (11A, 11B, 11C) and a plurality of oil separators (21A, 21B, 21C) respectively connected to the discharge side, and the lubricating oil separated by each oil separator (21A, 21B, 21C) 21B, 21C) are connected to the suction side of another compressor (11A, 11B, 11C) different from the compressor (11A, 11B, 11C) to which the plurality of first oil return destinations are returned so as not to overlap each other. An oil return pipe (41A, 41B, 41C), and an air conditioner comprising:
A bypass pipe (43) for branching from one first oil return pipe (41A) and allowing the lubricating oil to flow into the accumulator (20);
A second oil return pipe (42) for returning the lubricating oil in the accumulator (20) to the suction side of the compressor (11A, 11B, 11C);
A second on-off valve (32) provided in the second oil return pipe (42);
An air conditioner comprising: a third on-off valve (33) provided in the bypass pipe (43).   The air conditioner according to claim 1, further comprising a first on-off valve on a downstream side of the branch portion of the bypass pipe in the one first oil return pipe.   When performing an oil amount control operation for controlling the amount of lubricating oil in the compressor (11A, 11B, 11C), the third on-off valve (33) is opened and the second on-off valve (32) is closed. Furthermore, the air conditioning apparatus of Claim 1 provided with the opening-and-closing control part (51) which controls opening and closing each valve (32, 33) interlockingly.   When performing an oil amount control operation for controlling the amount of lubricating oil in the compressor (11A, 11B, 11C), the third on-off valve (33) is opened, and the first and second on-off valves (31, 31) The air conditioner according to claim 2, further comprising an open / close control unit (51) for controlling the opening and closing of each valve (31, 32, 33) in an interlocked manner so as to close the valve 32). A detector (52) for detecting the amount of lubricating oil in the compressor (11A, 11B, 11C);
When the detection unit (52) detects that the lubricating oil in the compressor (11A, 11B, 11C) has decreased to a predetermined amount during the oil amount control operation, the opening / closing control unit The air conditioner according to claim 3 or 4, wherein (51) performs control to reverse the open / close state of each valve (31, 32, 33).   The flow rate adjustment part (36A) is provided in the upstream of the branch part of the bypass pipe (43) in the one first oil return pipe (41A). The air conditioning apparatus described in 1. A plurality of compressors (11A, 11B, 11C) connected in parallel, an accumulator (20) connected to the suction side of these compressors (11A, 11B, 11C), and each compressor (11A, 11B, 11C) and a plurality of oil separators (21A, 21B, 21C) respectively connected to the discharge side, and the lubricating oil separated by each oil separator (21A, 21B, 21C) 21B, 21C) are connected to the suction side of another compressor (11A, 11B, 11C) different from the compressor (11A, 11B, 11C) to which the plurality of first oil return destinations are returned so as not to overlap each other. An oil return pipe (41A, 41B, 41C), and an air conditioner comprising:
A bypass pipe (43) for branching from one first oil return pipe (41A) and allowing the lubricating oil to flow into the accumulator (20);
A second oil return pipe (42) for returning the lubricating oil in the accumulator (20) to the suction side of the compressor (11A, 11B, 11C);
Lubricating oil separated in each oil separator (21A, 21B, 21C) flows into the accumulator (20) via each first oil return pipe (41A, 41B, 41C) and the bypass pipe (43). By performing the operation of storing and the operation of returning the lubricating oil stored in the accumulator (20) to the compressor (11A, 11B, 11C) via the second oil return pipe (42). And an oil amount control mechanism (50) for controlling the amount of lubricating oil in the compressor (11A, 11B, 11C).

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