JP2011226714A - Air conditioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioning device suppressing situations that comfort is significantly degraded and protective control is executed, by adjusting a refrigerant supply amount in an oil equalizing operation.SOLUTION: This air conditioning device 1 includes: compressors 11A, 11B connected by an oil equalizing pipe 46; accumulators 27A, 27B, recirculation piping 47 for gradually supplying liquid refrigerant stored in the accumulators 27A, 27B to the compressors 11A, 11B; and a control part 53 having an oil equalization control mode 55 for keeping amounts of lubricants to a specific level or more. In the oil equalization control mode 55, motion for rotating a part of the compressors 11A, 11B with a prescribed rotational frequency Nac to sufficiently suck the liquid refrigerant, and reducing the rotational frequency of the remaining compressor so that the refrigerant supply amount by all of the compressors keeps the refrigerant supply amount before starting the oil equalizing operation, is repeated while changing the part of the compressors so that all of the compressors are operated with the prescribed rotational frequency Nac at least once.

Description

  The present invention relates to an air conditioner.

Conventionally, an air conditioner that connects a plurality of compressors in parallel to a refrigeration cycle and supplies refrigerant to a large number of indoor units has been widely used.
In the case of this air conditioner, the air conditioning capacity, that is, the fluctuation of the refrigerant flow rate increases depending on the number of operating compressors. Since the lubricating oil of the compressor is dissolved in the refrigerant and flows in the refrigeration cycle, the distribution of the lubricating oil greatly varies with the fluctuation of the refrigerant flow rate. In addition, since it is not possible to determine to which compressor the lubricating oil circulated in the refrigeration cycle will return, there is a risk that the oil distribution will be biased when there are multiple compressors connected, leading to a lack of lubricating oil. It was.

In order to solve this problem, an oil equalizing operation that makes the amount of lubricating oil stored in a plurality of compressors substantially equal is repeatedly performed at predetermined intervals (see Patent Document 1).
In the oil leveling operation, basically, a plurality of compressors are rotated with a predetermined rotational speed difference. As a result, there is a difference in the amount of pressure loss between the gas refrigerants sucked into the compressors, resulting in a difference in the pressure inside each compressor (lubricating oil reservoir). When there is a difference in the internal pressure of each compressor, the lubricating oil moves through the oil equalizing pipe that communicates between the compressors with a pressure difference. The amount of lubricating oil in the compressor can be made substantially uniform.

  Further, in order to keep the amount of lubricating oil stored in a plurality of compressors at a certain level or more, that is, to ensure the total amount of lubricating oil, the oil leveling operation is performed with the above pressure difference. Prior to performing a recirculation operation for recirculating the lubricating oil mixed in the liquid refrigerant stored in the accumulator (gas-liquid separator) into the compressor by setting the rotational speed of each compressor to a predetermined rotational speed, generally increased. Yes.

JP-A-1-203855

  By the way, in the conventional oil leveling operation, the predetermined rotational speed which is the increased rotational speed in the reflux operation is set, and the operation with the subsequent pressure difference is increased or decreased based on the predetermined rotational speed. For this reason, since the rotation speed of a compressor becomes large compared with the time of air conditioning operation, the refrigerant | coolant amount which all the compressors supply becomes large compared with the time of air conditioning operation. As a result, a situation of overheating or overcooling occurs in the indoor unit during the oil leveling operation, which may impair comfort (air conditioning feeling) and may activate protection control.

  In view of such circumstances, an object of the present invention is to provide an air conditioner that can adjust a refrigerant supply amount during an oil leveling operation to suppress a significant decrease in comfort and a situation in which protection control is entered.

In order to solve the above problems, the present invention employs the following means.
That is, according to one aspect of the present invention, a liquid component is separated from a plurality of compressors whose rotation speed is variable and mutually connected by oil equalizing pipes, and refrigerant gas sucked into the suction side of the compressor, A gas-liquid separator that stores liquid refrigerant containing lubricating oil, and a supply pipe that gradually supplies the liquid refrigerant stored in the gas-liquid separator with the operation of the compressor to the suction side of the compressor; A control unit that controls an operation having an oil equalization control mode in which the amount of lubricating oil stored in each of the plurality of compressors is maintained at a certain level or more, the air conditioner comprising: In the control mode, a part of the plurality of compressors is rotated at a predetermined rotation speed at which the liquid refrigerant can be sufficiently sucked, and the refrigerant supply amount by all the compressors is the refrigerant supply before the oil equalizing operation is started. The operation of reducing the remaining compressor speed to maintain the quantity, Compressor Te is the air conditioning apparatus repeatedly perform the switch the part of the compressor as at least once is operated at the predetermined speed.

In the air conditioner according to this aspect, the oil equalization control mode of the control unit functions at a predetermined interval, for example. In the oil equalization control mode, some compressors among a plurality of compressors are rotated at a predetermined rotational speed capable of sufficiently sucking the liquid refrigerant stored in the gas-liquid separator, while the remaining ones are rotated. The rotation speed of the compressor is reduced so that the refrigerant supply amount by all the compressors maintains the refrigerant supply amount before the start of the oil equalizing operation.
As a result, some of the compressors are operated at an increased number of revolutions, and the remaining compressors are operated at a reduced number of revolutions, so that there is a difference in the amount of pressure loss between the gas refrigerant sucked into each compressor. Occurs and there is a difference in the pressure inside each compressor. When there is a difference in the internal pressure of each compressor, the lubricating oil moves through an oil equalizing pipe communicating between the compressors having a pressure difference. In addition, since some of the compressors are operated at a predetermined number of revolutions, the lubricating oil mixed in the liquid refrigerant stored in the gas-liquid separator can be sufficiently recirculated into the compressor.
This operation is repeated by switching some of the compressors so that all the compressors are operated at a predetermined rotational speed at least once. Therefore, each compressor returns the lubricating oil from the gas-liquid separator. A sufficient flow rate can be secured and the amount of lubricating oil in each compressor can be made substantially uniform.

At this time, the remaining compressors have their rotational speeds reduced so that the refrigerant supply amounts by all the compressors maintain the refrigerant supply amount before the start of the oil equalizing operation, so the refrigerant supply amounts supplied by all the compressors Is substantially the same as the refrigerant supply amount at the start of the oil leveling operation, in other words, the air conditioning operation. Therefore, since the amount of refrigerant supplied to the indoor unit does not change, overheating or overcooling occurs in the indoor unit during the oil leveling operation, and the comfort control (air conditioning feeling) is impaired and the protection control is activated. Can be suppressed.
Note that it is preferable to store a large amount of lubricating oil in the gas-liquid separator by performing oil return control prior to the execution of the oil equalization control mode.

  In the above aspect, in the oil equalization control mode, when the rotation speed of the remaining compressors is reduced and stopped, the stop timing is delayed by a predetermined time from the increase start timing of the partial compressors to the predetermined rotation speed. Is preferred.

The remaining compressors may be stopped depending on the state of the refrigerant supply amount in the air conditioning operation. In addition, when the remaining compressors are rotated at a very low speed, the rotational speed of some compressors is increased by the rotational speed of the remaining compressors in consideration of the durability of the compressor (from the predetermined rotational speed). May increase the number of revolutions) and stop the remaining compressors.
When the remaining compressors are stopped, the refrigerant supply amount in the remaining compressors disappears at that time. On the other hand, since the remaining compressors are switched to some compressors, and it takes time for the compressors switched to some compressors to reach the predetermined number of rotations from the stopped state, the refrigerant supply amount is gradually increased. Will increase. In other words, there is a slight time lag when the refrigerant supply amount by some compressors reaches a predetermined amount (refrigerant supply amount at the time of cooling and heating).
In this aspect, the oil equalization control mode delays the stop timing of the remaining compressors by a predetermined time from the start timing of the increase of some compressors to the predetermined rotation speed, so that the temporary refrigerant supply amount due to this time lag decreases. Can be suppressed.

  According to the present invention, some of the plurality of compressors are rotated at a predetermined rotation speed at which the liquid refrigerant stored in the gas-liquid separator can be sufficiently sucked, and the refrigerant supply amount by all the compressors is equalized. Operation to reduce the rotation speed of the remaining compressors so as to maintain the refrigerant supply amount before the start of oil operation, switching some compressors so that all the compressors are operated at a predetermined rotation speed at least once In each compressor, the amount of lubricating oil recirculated from the gas-liquid separator can be sufficiently secured and the amount of lubricating oil in each compressor can be made substantially equal. It is possible to suppress the occurrence of overheating or overcooling in the indoor unit, impairing comfort (air conditioning feeling), and activation of protection control.

It is a block diagram which shows the refrigerating cycle of the air conditioning apparatus concerning one Embodiment of this invention. It is a time chart which shows the time change of the rotation speed of each compressor at the time of oil-equalizing operation with the air conditioning apparatus concerning one Embodiment of this invention. It is a time chart which shows the time change of the rotation speed of each compressor at the time of oil-equalizing operation by the air conditioning apparatus concerning another embodiment of one embodiment of this invention. It is a time chart which shows the time change of the rotation speed of each compressor at the time of oil-equalizing operation with the air conditioning apparatus concerning another embodiment of one Embodiment of this invention.

Hereinafter, a multi-type air conditioner 1 according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.
FIG. 1 is a block diagram showing a refrigeration cycle of an air conditioner 1 according to the present embodiment.
The air conditioner 1 includes two outdoor units 3 (3A, 3B), a plurality of indoor units 5, and a gas side pipe 7 and a liquid side pipe 9 that connect them.

Since the outdoor units 3A and 3B have substantially the same configuration, members that need to be distinguished from each other are distinguished by adding a suffix “A” or “B” after the reference numeral, and members that are less necessary. Only the reference numerals are given for explanation.
The outdoor units 3A and 3B include inverter-driven compressors 11A and 11B that compress refrigerant, an oil separator 13 that separates lubricating oil from refrigerant gas, a four-way switching valve 15 that switches a refrigerant circulation direction, and refrigerant Two outdoor heat exchangers 17 that exchange heat with the outside air, an outdoor electric expansion valve (EEVH) 19 for heating, a receiver 21 that stores liquid refrigerant, and supercooling heat exchange that provides supercooling to the liquid refrigerant The liquid component is separated from the refrigerant gas sucked into the compressor 23, the supercooled electric expansion valve (EEVSC) 25 that controls the refrigerant amount diverted to the supercooling heat exchanger 23, and the compressors 11A and 11B. Accumulators (gas-liquid separators) 27 </ b> A and 27 </ b> B for storing refrigerant, a gas side operation valve 29, and a liquid side operation valve 31 are provided.

Each of the above devices on the outdoor unit 3 side is connected in a known manner via a refrigerant pipe such as a discharge pipe 33, a gas pipe 35, a liquid pipe 37, a gas pipe 39, a suction pipe 41, and a subcooling branch pipe 43. ing. Further, between the oil separator 13 and the suction pipes 41 of the compressors 11A and 11B, the refrigerating machine oil separated from the discharged refrigerant gas in the oil separator 13 is returned to the compressors 11A and 11B by a predetermined amount. An oil return circuit 45 is provided.
Compressor 11A, 11B is comprised so that rotation speed may be adjusted with the inverter which is not shown in figure.

The gas side pipe 7 and the liquid side pipe 9 are refrigerant pipes connected to the gas side operation valve 29 and the liquid side operation valve 31 of the outdoor units 3A and 3B, and are connected to the outdoor units 3A and 3B when installed on site. The length is set according to the distance between the plurality of indoor units 5 connected thereto.
In the middle of the gas side pipe 7 and the liquid side pipe 9, it is branched appropriately so that an appropriate number of indoor units 5 are connected respectively.

The low-pressure gas that has been gas-liquid separated by the accumulators 27A and 27B is supplied to the suction side of the compressors 11A and 11B through the suction pipe 41 constituting the refrigerant pipe.
The refrigerant passing through the supercooled electric expansion valve 25 is supplied to the accumulators 27A and 27B via the branch pipe 43 and the suction pipe 41.
The liquid refrigerant separated into gas and liquid by the accumulators 27A and 27B is supplied to the suction pipe 41 through a reflux pipe (supply pipe) 47 having a capillary tube.

  An oil equalizing pipe 46 is provided for communicating the inside of the compressor 11A (lubricating oil reservoir) and the inside of the compressor 11B (lubricating oil reservoir). The oil equalizing pipe 46 is provided with an opening / closing valve 48 on the compressor 11A, 11B side.

A plurality of indoor units 5 are provided, and the configuration of each indoor unit 5 is the same.
The indoor unit 5 is provided with an indoor heat exchanger 49 for exchanging heat between the refrigerant and room air for indoor air conditioning, and an indoor expansion valve (EEVC) 51 for cooling.

  The air conditioner 1 is provided with a control unit 53 that controls its operation. The control unit 53 is provided with an oil leveling control mode 55 for controlling an oil leveling operation in which the amount of lubricating oil stored in the compressors 11A and 11B of the air conditioner 1 is maintained at a certain level or more.

The air conditioning operation operation of the air-conditioning apparatus 1 according to the present embodiment configured as described above will be described.
The cooling operation is performed as follows.
The high-temperature and high-pressure refrigerant gas compressed by the compressors 11A and 11B is discharged from the compressors 11A and 11B, and the oil separator 13 separates the refrigerating machine oil contained in the refrigerant.
Thereafter, the refrigerant gas is condensed and liquefied through the four-way switching valve 15 and heat exchange with the outside air in the outdoor heat exchanger 17. This liquid refrigerant passes through the outdoor expansion valve 19 and is temporarily stored in the receiver 21.

The liquid refrigerant whose circulation amount is adjusted by the receiver 21 is partly divided into the branch pipe 43 in the process of flowing through the supercooling heat exchanger 23 and is adiabatically expanded by the supercooling expansion valve (EEVSC) 25. Heat exchange with the refrigerant provides a degree of supercooling.
The liquid refrigerant is led out from the outdoor units 3A and 3B to the liquid side pipe 9 through the liquid side operation valve 31. The liquid refrigerant led out to the liquid side pipe 9 is diverted to each indoor unit 5.

The liquid refrigerant flowing into each indoor unit 5 is adiabatically expanded by the indoor expansion valve (EEVC) 51 and flows into the indoor heat exchanger 49 as a gas-liquid two-phase flow.
In the indoor heat exchanger 49, heat is exchanged between the circulated indoor air and the refrigerant, and the indoor air is cooled and provided for indoor cooling.
On the other hand, the refrigerant is gasified and returns to the outdoor units 3A and 3B through the gas side pipe 7 again.

The refrigerant gas passing through the gas pipe 39 returned to the outdoor units 3A and 3B is introduced into the accumulators 27A and 27B through the four-way switching valve 15 and the suction pipe 41.
In the accumulators 27A and 27B, the liquid component contained in the refrigerant gas is separated, and only the gas component is sucked into the compressors 11A and 11B through the suction pipe 41. This refrigerant is compressed again in the compressors 11A and 11B, and the cooling operation is performed by repeating the above cycle.

On the other hand, the heating operation is performed as follows.
The high-temperature and high-pressure refrigerant gas compressed by the compressors 11A and 11B is discharged from the compressors 11A and 11B, and after the refrigerating machine oil contained in the refrigerant is separated by the oil separator 13, the four-way switching valve 15 It is supplied to the gas side pipe 7 side.
This refrigerant is led out from the outdoor units 3A and 3B via the gas side operation valve 29 and the gas side pipe 7, and further branched and introduced into each indoor unit 5.

The high-temperature and high-pressure refrigerant gas introduced into the indoor unit 5 is heat-exchanged with the indoor air circulated in the indoor heat exchanger 49, and the indoor air is heated and used for indoor heating.
On the other hand, the refrigerant is condensed and returned to the outdoor units 3A and 3B through the indoor expansion valve (EEVC) 51 and the liquid side pipe 9.

The refrigerant passing through the liquid pipe 9 returned to the outdoor unit 3 reaches the supercooling heat exchanger 23 via the liquid side operation valve 31, and unlike the case of cooling, the supercooling expansion valve 25 is not always operated. In some cases, supercooling may not be applied. Then, the amount of circulation is adjusted by flowing into the receiver 21 and once stored.
The liquid refrigerant is adiabatically expanded by the outdoor expansion valve (EEVH) 19 and then flows into the outdoor heat exchanger 17.

In the outdoor heat exchanger 17, heat is exchanged between the blown outside air and the refrigerant, and the refrigerant absorbs heat from the outside air and is evaporated and gasified.
This refrigerant is introduced from the outdoor heat exchanger 17 through the four-way switching valve 15 and through the suction pipe 41 to the accumulators 27A and 27B.
In the accumulators 27A and 27B, the liquid component contained in the refrigerant gas is separated, and only the gas component is sucked into the compressors 11A and 11B through the suction pipe 41. This refrigerant is compressed again in the compressors 11A and 11B. The heating operation is performed by repeating the above cycle.

Next, the oil leveling operation in the oil leveling control mode 55 will be described with reference to FIG. The compressor 11A is operated at the operating speed Na, and the compressor 11B is operated at the operating speed Nb.
In the oil equalization control mode 55, a predetermined rotational speed Nac at which the liquid refrigerant stored in the accumulators 27A and 27B can be sufficiently sucked is set.

  In the oil equalization control mode 55, when one (partial) compressor, for example, the compressor 11A is operated at a predetermined rotational speed Nac, the other (remaining) compressor 11B is operated at what rotational speed. For example, it is calculated whether the refrigerant amount supplied by the operating compressors 11A and 11B can be secured. When the required number of rotations of the compressor 11B is very small, when the compressor 11B is operated at that number of rotations, if it is determined that the compressor B is defective, the compressor B is stopped. In this case, the compressor 11A is operated at a rotational speed N slightly larger than the predetermined rotational speed Nac in order to add the refrigerant supply amount to be supplied by the compressor 11B.

If the required number of rotations of the compressor 11B is a certain level, the number of rotations N of the compressor 11A is set to a predetermined number of rotations Nac, and the compressor 11B is also operated.
Further, when the necessary rotation speed of the compressor 11B is 0, the rotation speed N of the compressor 11A is set to a predetermined rotation speed Nac, and the compressor 11B stops operation.

  The oil leveling control mode 55 starts the oil leveling operation at time point X. The oil leveling control mode 55 increases the rotational speed of the compressor 11A from the rotational speed Na during operation toward the rotational speed N. The oil leveling control mode 55 stops the compressor 11B after a time (predetermined time) T0 from the time point X. This is because there is a time lag in the capacity increase of the compressor 11A, and thus the temporary refrigerant supply amount due to the time lag is suppressed from decreasing.

Since the compressor 11A is operated at the increased rotation speed N and the compressor 11B is stopped, a difference in pressure loss occurs between the gas refrigerant sucked into the compressors 11A and 11B, and the compressors 11A and 11B There is a difference in internal pressure. When there is a difference between the internal pressures of the compressors 11A and 11B, the lubricating oil moves through the oil equalizing pipe 46 communicating between the compressors 11A and 11B having a pressure difference.
Further, since the compressor 11A is operated at a rotational speed N greater than the predetermined rotational speed Nac, the lubricating oil mixed in the liquid refrigerant stored in the accumulator 27A can be sufficiently recirculated into the compressor 11A. .

The oil equalization control mode 55 reverses the roles of the compressor 11A and the compressor 11B when a preset time elapses between the operation at the rotational speed N of the compressor 11A and the stop state of the compressor 11B. That is, the oil equalization control mode 55 stops the compressor 11A and operates the compressor 11B at the rotation speed N.
If it does in this way, lubricating oil will move through the oil equalization pipe | tube 46 between compressor 11A, 11B. Since the compressor 11B is operated at a rotational speed N greater than the predetermined rotational speed Nac, the lubricating oil mixed in the liquid refrigerant stored in the accumulator 27B can be sufficiently recirculated into the compressor 11B.

  As described above, since all the compressors 11A and 11B are operated at least once at the rotational speed N higher than the predetermined rotational speed Nac, the compressors 11A and 11B are supplied with the recirculation amount of the lubricating oil from the accumulators 27A and 27B. Can be secured sufficiently, and the amount of lubricating oil in the compressors 11A and 11B can be made substantially equal.

When the compressor to be stopped is switched from the compressor 11B to the compressor 11A, the timing for starting the compressor 11B from the stopped state and the timing for stopping the compressor 11A are the time (predetermined time) T1 than the former. Delayed.
Since it takes time for the compressor 11B to reach the rotational speed N from the stopped state, the refrigerant supply amount gradually increases. In other words, there is a slight time lag before the refrigerant supply amount by the compressor 11B reaches a predetermined amount (refrigerant supply amount at the time of cooling and heating).
In the oil equalization control mode 55, the stop timing of the compressor 11A is delayed by the time T1 from the increase start timing to the rotation speed N of the compressor 11B, so that the temporary refrigerant supply amount due to this time lag is reduced. Can be suppressed.

The time T1 is set to be larger than the time T0 because the rotation speed difference is large and the time lag time is large.
The time T0 and the time T1 are set as necessary. For example, the time T0 and the time T1 are about half of the time required to increase the rotational speed.
In addition, when the compressor 11 to be stopped is operated at a low rotational speed, the refrigerant supply of the compressor 11 gradually decreases, so that the timing of the decrease coincides with the timing of increasing the other rotational speed. Alternatively, it may be delayed by a time smaller than the time T1.

In the present embodiment, there are two outdoor units 3A and 3B, but the present invention can be similarly applied to three outdoor units 3. The third outdoor unit 3 is connected in parallel by a gas side pipe 7 and a liquid side pipe 9 as shown by a one-dot chain line in FIG. The third compressor 11C is connected in parallel with the compressors 11A and 11B by an oil equalizing pipe 46.
Here, a case where the oil leveling operation is performed in a state where the compressors 11A and 11B are operated and the compressor 11C is stopped will be described.
Even in this case, the oil equalization control mode 55 is similar to the above-described two compressors 11A and 11B, and when the compressor 11A, for example, the compressor 11A is operated at the predetermined rotation speed Nac, the remaining compressor 11B. , 11C is calculated at what rotational speed to ensure the amount of refrigerant supplied by the compressors 11A, 11B during operation. Then, the rotational speed N of the compressor 11 operating at the predetermined rotational speed Nac is determined in the same manner as described above.

Here, a description will be given by operating one compressor 11 at the rotation speed N and stopping the other two compressors 11.
The oil leveling control mode 55 starts the oil leveling operation at time point X. The oil leveling control mode 55 increases the rotational speed of the compressor 11A from the rotational speed Na during operation toward the rotational speed N. The oil leveling control mode 55 stops the compressor 11B after a time (predetermined time) T0 from the time point X. That is, the compressors 11B and 11C are stopped. This is because there is a time lag in the capacity increase of the compressor 11A, and thus the temporary refrigerant supply amount due to the time lag is suppressed from decreasing.

Since the compressor 11A is operated at the increased rotation speed N and the compressors 11B and 11C are stopped, a difference in pressure loss occurs in the gas refrigerant sucked into the compressors 11A, 11B, and 11C, and the compression is performed. There is a difference in the pressure inside the machines 11A, 11B, 11C. When there is a difference in the internal pressure of the compressors 11A, 11B, and 11C, the lubricating oil moves through the oil equalizing pipe 46 that communicates between the compressors 11A, 11B, and 11C having a pressure difference.
Further, since the compressor 11A is operated at a rotational speed N greater than the predetermined rotational speed Nac, the lubricating oil mixed in the liquid refrigerant stored in the accumulator 27A can be sufficiently recirculated into the compressor 11A. .

The oil leveling control mode 55 reverses the roles of the compressor 11A and the compressor 11B when a preset time elapses when the compressor 11A is operated at the rotational speed N and the compressors 11B and 11C are stopped. That is, the oil equalization control mode 55 stops the compressor 11A and operates the compressor 11B at the rotation speed N.
If it does in this way, lubricating oil will move through the oil equalization pipe | tube 46 between compressor 11A, 11B, 11C. Since the compressor 11B is operated at a rotational speed N greater than the predetermined rotational speed Nac, the lubricating oil mixed in the liquid refrigerant stored in the accumulator 27B can be sufficiently recirculated into the compressor 11B.

  The oil equalization control mode 55 reverses the roles of the compressor 11B and the compressor 11C when a preset time elapses when the compressor 11B is operated at the rotational speed N and the compressors 11A and 11C are stopped. That is, the oil equalization control mode 55 stops the compressor 11B and operates the compressor 11C at the rotation speed N. Thereby, the lubricant oil of the compressors 11A, 11B, and 11C is moved, and the lubricant oil can be sufficiently recirculated from the accumulator 29 to the compressor 11C.

  Thus, since all the compressors 11A, 11B, and 11C are operated at least once at the rotational speed N greater than the predetermined rotational speed Nac, the compressors 11A, 11B, and 11C are connected to the accumulators 27A, 27B, and 27C. In addition, a sufficient amount of lubricating oil can be secured and the amount of lubricating oil in the compressors 11A, 11B, and 11C can be made substantially equal.

  The timing of stopping is delayed by time T1 from the timing of starting from the stopped state, respectively, and the temporary refrigerant supply amount is suppressed from decreasing.

Further, the present invention can be similarly applied to four outdoor units 3 connected in parallel.
Here, the case where the oil leveling operation is performed in a state where all the compressors 11A, 11B, 11C, and 11D are operating as illustrated in FIG. 4 will be described.
Even in this case, the oil leveling control mode 55 is similar to the above-described two compressors 11A and 11B. When some compressors, for example, the compressors 11A and 11C are operated at the predetermined rotation speed Nac, the remaining compression is performed. It is calculated at what rotational speed the machines 11B and 11D are operated to ensure the amount of refrigerant supplied by the operating compressors 11A, 11B, 11C, and 11D. Then, the rotational speed N of the compressor 11 operating at the predetermined rotational speed Nac is determined in the same manner as described above.

Here, the description will be made by operating the two compressors 11 at the rotation speed N and stopping the other two compressors 11.
The oil leveling control mode 55 starts the oil leveling operation at time point X. The oil equalization control mode 55 increases the rotational speeds of the compressors 11A and 11C from the rotational speeds Na and Nc during operation toward the rotational speed N. The oil leveling control mode 55 stops the compressors 11B and 11D after a time (predetermined time) T0 from the time point X. This is because there is a time lag in increasing the capacities of the compressors 11A and 11C, so that the temporary refrigerant supply amount due to the time lag is prevented from being lowered.

Since the compressors 11A and 11C are operated at the increased rotation speed N and the compressors 11B and 11D are stopped, a difference in the amount of pressure loss occurs in the gas refrigerant sucked into the compressors 11A, 11B, and 11C. The pressures in the compressors 11A, 11B, 11C, and 11D are different. When there is a difference in the internal pressures of the compressors 11A, 11B, 11C, and 11D, the lubricating oil moves through the oil equalizing pipe 46 that communicates between the compressors 11A, 11B, 11C, and 11D having a pressure difference.
Further, since the compressors 11A and 11C are operated at a rotational speed N greater than the predetermined rotational speed Nac, the lubricating oil mixed in the liquid refrigerant stored in the accumulators 27A and 27C is sufficiently contained in the compressors 11A and 11C. Can be refluxed.

The oil equalization control mode 55 stops the compressors 11A and 11C when the operation at the rotational speed N of the compressors 11A and 11C and the stop state of the compressors 11B and 11D have elapsed in advance. 11D is operated at the rotation speed N.
Subsequently, the oil leveling control mode 55 stops the compressors 11C and 11D when the preset time has elapsed after the operation of the compressors 11B and 11D at the rotational speed N and the stop state of the compressors 11A and 11C have elapsed. 11A and 11B are operated at a rotational speed N.
Next, the oil leveling control mode 55 stops the compressors 11A and 11B when the operation at the rotational speed N of the compressors 11A and 11B and the stop state of the compressors 11C and 11D have elapsed in advance. 11C and 11D are operated at the rotation speed N.
Since the operation in these states is the same as described above, a duplicate description is omitted here.

  In this way, the four compressors 11A, 11B, 11C, and 11D are operated for two periods each at a rotational speed N greater than the predetermined rotational speed Nac by changing the combination of the two compressors. The lubricating oil mixed in the stored liquid refrigerant can be sufficiently recirculated, and the amount of lubricating oil through the oil equalizing pipe 46 can be made uniform.

  Also in this case, the timing at which the compressor 11 is stopped is delayed by the time T1 from the timing at which the compressor 11 is started from the stopped state, thereby suppressing the temporary refrigerant supply amount from decreasing.

The present invention is not limited to the embodiments described above, and various modifications may be made without departing from the spirit of the present invention.
For example, in the present embodiment, a plurality of outdoor units 3 having one compressor 11 are provided, but one or a plurality of outdoor units 3 having a plurality of compressors 11 are provided. The same can be applied to things.

1 Air Conditioner 11, 11A, 11B, 11C, 11D Compressor 27A, 27B Accumulator 46 Oil Leveling Pipe 47 Recirculation Pipe 53 Control Unit 55 Oil Leveling Control Mode T0, T1 Time

Claims (2)

A plurality of compressors whose rotation speed is variable and connected to each other by oil equalizing pipes;
A gas-liquid separator that separates a liquid component from refrigerant gas sucked into the suction side of the compressor and stores liquid refrigerant containing lubricating oil;
A supply pipe for gradually supplying the liquid refrigerant stored in the gas-liquid separator with the operation of the compressor to the suction side of the compressor;
A control unit that controls an operation having an oil equalization control mode in which the amount of lubricating oil stored in the plurality of compressors is held at a certain level or more, respectively,
In the oil equalization control mode, a part of the plurality of compressors is rotated at a predetermined rotation speed at which the liquid refrigerant can be sufficiently sucked, and the refrigerant supply amount by all the compressors is before the oil equalization operation is started. The operation of reducing the rotation speed of the remaining compressors so as to maintain the refrigerant supply amount is repeated by switching the some compressors so that all the compressors are operated at the predetermined rotation speed at least once. An air conditioner characterized by performing. In the oil equalization control mode, when the remaining compressors are stopped by reducing the number of rotations, the stop timing is delayed by a predetermined time from the increase start timing of the partial compressors to the predetermined number of rotations. The air conditioning apparatus according to claim 1.

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