JP5331574B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner having a refrigeration cycle formed by connecting a refrigerant suction pipe and a refrigerant discharge pipe of a plurality of compressors in parallel.

  For example, Patent Document 1 discloses an air conditioner (hereinafter referred to as a multi-unit) in which a refrigerant suction side pipe and a refrigerant discharge side pipe of each compressor provided in a plurality of outdoor units are connected in parallel to form a refrigeration cycle. Air conditioner) has been proposed. In addition, an oil separator is provided in the refrigerant discharge side piping of each compressor, and the refrigeration oil contained in the gas refrigerant discharged from the compressor is separated by the oil separator and returned to the compressor. In particular, according to this document, the amount of refrigerating machine oil returned from the oil separator to each compressor becomes non-uniform depending on the operating condition of each compressor, so that the oil separators are communicated with each other through an oil equalizing pipe and returned to each compressor. The balance of the amount of refrigerating machine oil is maintained.

  On the other hand, in Patent Document 2, as an oil separator of an air conditioner, a gas refrigerant discharged from a compressor is swirled along an inner peripheral surface of a cylindrical container, and refrigeration contained in the gas refrigerant by a centrifugal flow centrifugal force. The thing which isolates machine oil is proposed. Then, the refrigerating machine oil stored in the bottom of the cylindrical container is returned to the compressor via a return pipe connected to the bottom of the cylindrical container, and the gas refrigerant separated from the refrigerating machine oil is inserted concentrically from the top of the cylindrical container. It discharges from the opening at the lower end.

Japanese Patent Laid-Open No. 04-93561 JP 05-180539 A

  However, since Patent Document 1 maintains the balance of the refrigeration oil returned to each compressor with an oil equalizing pipe, the structure is complicated by the oil equalizing pipe, and each oil separator needs to be installed at the same height. Therefore, there is a problem that the installation work becomes complicated.

  On the other hand, the technique of Patent Document 2 is limited to a single outdoor unit, and no consideration is given to the case where a plurality of outdoor units are operated in parallel. For example, if the oil separators are connected to each other with an oil equalizing pipe as in Patent Document 1, the configuration and the installation work are complicated as described above.

  The problem to be solved by the present invention is that air having an oil separator that can simplify the configuration and installation work and can equalize the amount of refrigeration oil returned to each compressor of a plurality of outdoor units operated in parallel. It is to provide a harmony machine.

  In order to solve the above problems, an air conditioner according to the present invention includes a refrigeration cycle formed by connecting a refrigerant suction pipe and a refrigerant discharge pipe of a plurality of compressors in parallel, and inserted into the refrigerant discharge pipe of each compressor. The oil separator has a connected oil separator, and the oil separator introduces a gas refrigerant in a tangential direction of the cylindrical container, an inner cylinder inserted concentrically from the top of the cylindrical container and opened in the cylindrical container It has an inlet pipe, a gas refrigerant outlet pipe that communicates with the inside of the inner cylinder, and a return pipe that extracts the refrigeration oil stored in the cylindrical container and returns it to the compressor. The gas refrigerant inlet pipe is formed in a size smaller than the inner diameter.

  According to this, the flow rate of the gas refrigerant introduced into the cylindrical container is equal to or higher than the flow rate in the gas refrigerant inlet pipe by setting the distance between the cylindrical container and the inner cylinder to be equal to or smaller than the inner diameter of the gas refrigerant inlet pipe. The separation performance of the refrigerating machine oil can be increased. In other words, the oil separator that turns the gas refrigerant to separate the refrigerating machine oil can increase the turning force as the flow velocity increases, and can reliably improve the separation performance. Contrary to the present invention, if the interval between the cylindrical container and the inner cylinder is made larger than the inner diameter of the gas refrigerant inlet pipe, the flow rate of the gas refrigerant is reduced in the cylindrical container and the centrifugal force due to the swirling is reduced. Performance decreases.

  Furthermore, the present inventors have found that in the oil separator of the present invention, the distance between the liquid level of the refrigerating machine oil and the lower end of the inner cylinder affects the separation performance. That is, when the amount of refrigerating machine oil storage increases and the distance between the refrigerating machine oil level and the lower end of the inner cylinder decreases, the swirling time of the gas refrigerant decreases and the refrigerating machine oil wound up by the discharged gas refrigerant is gas. Since it is introduced into the refrigerant outlet pipe, an oil separator with a large amount of refrigerating machine oil has poor separation performance. In particular, it has been found that when the liquid level of the refrigerating machine oil rises and the distance from the lower end of the inner cylinder falls below a certain value, the refrigerating machine oil separation efficiency is remarkably lowered. Therefore, by adjusting the initial filling amount of the refrigerating machine oil, the dimensions of the oil separator, etc., and making the liquid level of the refrigerating machine oil (distance from the lower end of the inner cylinder) below the set height, It was found that the amount of refrigeration oil returned to the compressor can be made uniform.

  Also, if the load on each compressor is different, the amount of refrigerating machine oil separated and stored by each oil separator may change, and the liquid level may exceed the set height. However, oil separators with a large amount of refrigerating machine oil have reduced refrigerating machine oil separation performance, and refrigerating machine oil that has not been separated is introduced from the gas refrigerant outlet pipe through the outdoor heat exchanger or directly into the indoor units connected in parallel. Is done. The content of the refrigeration oil in the liquid refrigerant or gas refrigerant introduced from each oil separator into the indoor unit is made uniform by mixing, returns to each compressor, and is introduced again into each oil separator. And since the oil separator with little storage amount of refrigerating machine oil has high separation performance, more refrigerating machine oil will be separated. In this way, the amount of refrigerating machine oil stored in each oil separator becomes uniform while the operation is maintained. According to this, since the amount of refrigerating machine oil returned to each compressor can be made uniform with only an oil separator without using an oil equalizing pipe, the configuration and installation of an air conditioner having a plurality of outdoor units operated in parallel Work can be simplified.

  The maximum amount of oil that can be stored in each oil separator is determined in advance based on the amount of refrigerating machine oil that the entire refrigeration cycle holds, and the size of each oil separator and the set liquid level height of the refrigerating machine oil (with the lower end of the inner cylinder and The distance). This set liquid level (set oil level) height is determined so that the separation efficiency of the refrigerating machine oil in the oil separator is, for example, 85% or more and less than 100%. In this case, the separation efficiency is up to 85%. Designed as the maximum amount of oil that can be stored up to the liquid level when it drops. The set liquid level can be obtained by experimentation so that the separation level of the refrigerating machine oil in the oil separator becomes a liquid level that significantly decreases.

  It is also possible to make all the oil separators have the same shape. When the oil separator has the same shape, the manufacturing design of the oil separator is facilitated, and the cost of the oil separator can be reduced.

  According to the present invention, there is provided an air conditioner including an oil separator that can simplify the configuration and installation work, and can equalize the amount of refrigerating machine oil returned to each compressor of a plurality of outdoor units operated in parallel. it can.

It is a block diagram of the oil separator of one Embodiment of this invention. It is a systematic diagram of the refrigerating cycle of one embodiment of the present invention. It is a horizontal sectional view of the position of the gas refrigerant inlet pipe of FIG. It is a figure which shows the isolation | separation performance of the oil separator with respect to the liquid level height of refrigerator oil, and the distance to an inner cylinder lower end. It is a figure which shows the flow of refrigerating machine oil when the refrigerating machine oil in an oil separator is biased.

  Hereinafter, the present invention will be described based on embodiments. FIG. 1 shows a configuration diagram of an oil separator provided in an air conditioner according to an embodiment of the present invention, and FIG. 2 shows a system diagram of a refrigeration cycle of the air conditioner according to an embodiment of the present invention. As shown in the figure, the air conditioner of the present embodiment is a multi air conditioner composed of a plurality of (for example, two in the figure) outdoor units and a plurality of (for example, three in the figure) indoor units, The refrigerant suction pipe 2 and the refrigerant discharge pipe 3 of each compressor 1 are connected in parallel to form a refrigeration cycle.

  A compressor 1, an accumulator 7, an oil separator 9, a four-way valve 11, an outdoor heat exchanger 13, and an outdoor expansion valve 15 are provided in the casing of each outdoor unit surrounded by a broken line in FIG. The compressor 1 is, for example, a variable capacity compressor 1, and the capacity of the compression chamber can be increased or decreased according to the required air conditioning capacity. A refrigerant suction pipe 2, a refrigerant discharge pipe 3, and a pipe 17 are connected to the compressor 1. The other end of the pipe 17 is connected to the refrigerant discharge pipe 3, and when the refrigeration oil in the compressor 1 exceeds the set range, the refrigeration oil in the compressor 1 is discharged to the refrigerant discharge pipe 3. . When the accumulator 7 is inserted and connected to the refrigerant suction pipe 2 and the liquid refrigerant is contained in the gas refrigerant, the liquid refrigerant is separated from the gas refrigerant so that the liquid refrigerant does not easily enter the compressor 1. Yes. An oil separator 9 is inserted and connected to the refrigerant discharge pipe 3 of the compressor 1 so that the refrigeration oil contained in the gas refrigerant is separated and stored, and the stored refrigeration oil is returned to the compressor 1. A four-way valve 11 is provided on the downstream side of the oil separator 9. The four-way valve 11 changes the refrigerant flow path during cooling operation and heating operation. The position of the four-way valve 11 in FIG. 2 indicates the flow path during the heating operation, but during the cooling operation, the four-way valve 11 is adjusted to a position rotated 90 ° clockwise.

  The outdoor heat exchanger 13 is provided with a heat transfer tube through which the refrigerant flows, and the outside air is blown toward the heat transfer tube by a fan (not shown) to exchange heat between the refrigerant and the outside air. The outdoor heat exchanger 13 is provided with an outdoor expansion valve 15 that depressurizes the refrigerant introduced into the outdoor heat exchanger 13, and the outdoor expansion valve 15 is controlled to a set opening by an opening control means (not shown). It has become.

  On the other hand, an indoor heat exchanger 19 and an indoor expansion valve 21 are provided in the casing of each indoor unit surrounded by a broken line in FIG. The indoor heat exchanger 19 is provided with a heat transfer tube through which the refrigerant flows, and the indoor air is sucked through a heat transfer tube by a fan (not shown) to exchange heat between the refrigerant and the indoor air. Yes. The indoor heat exchanger 19 is provided with an indoor expansion valve 21 that depressurizes the refrigerant introduced into the indoor heat exchanger 19, and the indoor expansion valve 21 is controlled to a set opening by an opening control means (not shown). It has become.

  Next, the characteristic configuration of the present embodiment will be described. Each oil separator 9 provided in each outdoor unit includes a cylindrical container 22 and an inner cylinder 23 that is inserted concentrically from the top of the cylindrical container 22 and opened into the cylindrical container 22. A gas refrigerant inlet pipe 27 that introduces a gas refrigerant into the cylindrical container 22 is connected to the cylindrical container 22. One end of the gas refrigerant inlet pipe 27 is connected from the tangential direction of the cylindrical container 22, and the other end communicates with the refrigerant discharge pipe 3. A return pipe 29 for extracting the refrigerating machine oil stored in the cylindrical container 22 and returning it to the compressor 1 is connected to the bottom of the cylindrical container 22. The other end of the return pipe 29 is connected to the suction side of the compressor 1. The return pipe 29 is provided with a solenoid valve 31 and a capillary tube 33 so that the refrigeration oil is returned to the compressor 1 in accordance with the operation status. The opening and closing of the electromagnetic valve 31 is controlled by a control means (not shown) so that, for example, the air conditioner is opened during operation and closed during operation. A gas refrigerant outlet pipe 35 having a smaller diameter than the inner cylinder 23 is connected to the upper end of the inner cylinder 23. The gas refrigerant outlet pipe 35 communicates with the inside of the inner cylinder 23. The interval between the cylindrical container 22 and the inner cylinder 23 is formed such that the interval b is equal to or smaller than the inner diameter a of the gas refrigerant inlet pipe 27 as shown in FIG. The length d of the inner cylinder 23 can be appropriately selected according to the separation performance and the like, and can be larger than the distance e from the upper end of the cylindrical container 22 to the center of the gas refrigerant inlet pipe 27, for example.

  The operation of the present embodiment configured as described above will be described by taking heating operation as an example. The gas refrigerant compressed by each compressor 1 is introduced into each oil separator 9 through the refrigerant discharge pipe 3, and the refrigerating machine oil contained in the gas refrigerant is separated. The gas refrigerant from which the refrigerating machine oil is separated is discharged from the oil separator 9, passes through the valve 37 by the four-way valve 11, and is directly guided to the indoor heat exchanger 19. The gas refrigerant introduced into the indoor heat exchanger 19 condenses and releases latent heat to the indoor air to become a liquid refrigerant. The liquid refrigerant discharged from the indoor heat exchanger 19 passes through the valve 39, is decompressed by the outdoor expansion valve 15 that is throttled to the set opening degree, and is introduced into the outdoor heat exchanger 13. The liquid refrigerant introduced into the outdoor heat exchanger 13 evaporates by exchanging heat with the outside air to become a gas refrigerant, and is introduced into the accumulator 7 via the four-way valve 11. The gas refrigerant introduced into the accumulator 7 is introduced into the compressor 1 through the refrigerant suction pipe 2 and compressed after the unevaporated liquid refrigerant is removed. When the air conditioner is stopped, the valves 37 and 39 are closed to prevent the refrigerant from flowing between the outdoor unit and the indoor unit.

  Next, the characteristic operation of this embodiment will be described. The gas refrigerant discharged from the compressor 1 is introduced into the cylindrical container 22 from the tangential direction of the cylindrical container 22 through the gas refrigerant inlet pipe 27. At this time, since the distance between the cylindrical container 22 and the inner cylinder is equal to or smaller than the inner diameter of the gas refrigerant inlet pipe 27, the flow rate of the gas refrigerant introduced into the cylindrical container 22 is equal to or equal to the flow rate in the gas refrigerant inlet pipe 27. This can be done. The gas refrigerant introduced into the cylindrical container 22 turns along the interval between the cylindrical container 22 and the inner cylinder 23. The refrigerating machine oil in the gas refrigerant is separated by the swirling centrifugal force, adheres to the inner peripheral surface of the cylindrical container 22, flows down, and is stored at the bottom of the cylindrical container 22. The gas refrigerant from which the refrigerating machine oil has been separated is discharged from the gas refrigerant outlet pipe 35 and led to the indoor heat exchanger 19. The refrigerating machine oil stored at the bottom of the cylindrical container 22 is returned to the compressor 1 through the return pipe 29 by opening the electromagnetic valve 31 as appropriate. Normally, the electromagnetic valve 31 is open during operation of the compressor and closed during stoppage. In addition, the initial filling amount of the refrigerating machine oil, the dimensions of the oil separator 9 and the like may be adjusted so that the amount of the refrigerating machine oil stored in each oil separator 9 falls within a certain range. The refrigerating machine oil separated by the differential pressure in the suction side of the compressor 1 and the oil separator 9 is returned to the compressor 1. The amount of refrigerating machine oil returned is determined by the magnitude of the resistance in the capillary tube 33. Since the resistance of the capillary tube 33 changes in correlation with the size (passage area) and the length thereof, it is determined in consideration of the differential pressure. The capillary tube 33 is designed so that the state in which the refrigerating machine oil is always stored in the oil separator 9 is maintained.

  Here, the principle that the amount of refrigerating machine oil returned to each compressor 1 can be made uniform (equalized oil) only by each oil separator 9 will be described with reference to FIG. The vertical axis of FIG. 4 shows the separation performance (separation efficiency) of the oil separator 9, and the horizontal axis shows the distance between the liquid level of the refrigerator oil and the lower end of the inner cylinder 23. In other words, the separation performance is the amount of refrigerating machine oil that is not separated by the oil separator 9. For example, high separation performance means that a large amount of refrigerating machine oil is separated by the oil separator 9, and the separation performance is low. Means that the oil separator 9 hardly separates the refrigerating machine oil. As illustrated, the separation performance correlates with the distance c between the liquid level of the refrigerating machine oil stored in the cylindrical container 22 and the lower end of the inner cylinder 23. That is, when the amount of refrigerating machine oil stored in the cylindrical container 22 increases and the distance between the refrigerating machine oil level and the lower end of the inner cylinder 23 decreases, the separation performance decreases. Further, when the distance between the liquid level of the refrigerating machine oil and the lower end of the inner cylinder 23 becomes a certain value or less, the separation performance is rapidly lowered. That is, when the distance c between the liquid level of the refrigerating machine oil and the lower end of the inner cylinder 23 becomes a certain value or less (separation limit), the area where the refrigerating machine oil can hardly be separated from the area where the refrigerating machine oil can be separated (separation area) (non-separable area). )become. Utilizing this characteristic, the initial filling amount of the refrigerating machine oil, the size of the oil separator, etc. so that the separation limit is reached when the distance c between the liquid level of the refrigerating machine oil of each oil separator 9 and the lower end of the inner cylinder 22 becomes a certain value or less. Adjust. Thereby, the separation performance of the refrigerating machine oil in each oil separator 9 is in a certain range (for example, the separation performance of the oil separator 9 in which the refrigerating machine oil is not stored is 100%, a range of 85% or more and less than 100%). The amount of refrigerating machine oil stored in each oil separator 9 can be made substantially uniform. In addition, the design point of each oil separator 9 does not need to be the same, For example, you may set suitably in the range whose separation performance is 85% or more and less than 100%. For example, when the separation performance falls below 85%, the separation performance of the oil separator 9 suddenly drops, and the separation limit is set so that the refrigeration oil is discharged from the oil separator 9 to the refrigeration cycle via the gas refrigerant outlet pipe 35. can do.

  Further, when the load on the compressor 1 varies depending on the operating condition of the air conditioner, the amount of refrigerating machine oil stored in each oil separator 9 may change. For example, as shown in FIG. 5, the liquid level of the oil separator 9a of the outdoor unit 40a may exceed the separation limit. However, in the oil separator 9a, since the liquid level height of the refrigerating machine oil exceeds the separation limit, the refrigerating machine oil wound up and stored in the refrigerating machine oil or the gas refrigerant that has not been separated is introduced into the gas refrigerant outlet pipe 35. The Then, the gas refrigerant containing a large amount of refrigerating machine oil is mixed with the gas refrigerant discharged from the outdoor units 40b and 40c to be uniform, and the amount of refrigerating machine oil contained in the gas refrigerant increases. This gas refrigerant passes through each indoor unit and is introduced into each oil separator 9a, b, c of each outdoor unit 40a, b, c. Refrigerating machine oil is hardly separated by the oil separator 9a having a low separation performance, and a large amount of refrigerating machine oil is separated by the oil separators 9b and 9c having a high separation performance. In this way, the amount of refrigerating machine oil stored between the oil separators 9a, 9b, 9c is made uniform while the operation is maintained.

  According to this, since the flow rate of the gas refrigerant introduced into the cylindrical container 22 can be made equal to or higher than the flow rate in the gas refrigerant inlet pipe 27, the centrifugal force due to the swirling can be increased, and the oil separator 9 The separation performance can be improved with certainty.

  Further, in the oil separator 9 of the present embodiment, the initial filling amount of the refrigerating machine oil, the dimensions of the oil separator 9 and the like are adjusted, and the liquid level of the refrigerating machine oil (distance c from the lower end of the inner cylinder 23) is set to the set height. By making it below, the amount of refrigerating machine oil returned to each compressor can be made uniform only by the oil separator 9. As a result, since it is not necessary to use an oil equalizing pipe, the configuration and installation work of an air conditioner including a plurality of outdoor units operated in parallel can be simplified. Furthermore, since the amount of refrigeration oil returned to each compressor 1 can be made uniform, it is possible to suppress the occurrence of a shortage of refrigeration oil in the compressor 1, so that the air conditioner can be stably operated.

  Moreover, since the refrigeration oil can be made uniform without changing the frequency of the compressor, an air conditioner in which power consumption does not increase excessively can be obtained. Further, since the refrigeration oil is stored on the discharge side of the high-pressure compressor 1 so as not to be affected by the pressure reduction on the refrigerant suction pipe 2 side due to the high-speed start-up of the compressor 1, oil forming due to reduced-pressure boiling is suppressed. it can. Further, the control constant (time from command to operation) for determining the opening degree of the expansion valve is determined by the solubility of the refrigerant and the refrigerating machine oil. Since the solubility of the refrigerant and the refrigerating machine oil changes as the pressure decreases, it is necessary to change the control constant by disposing the oil separator 9 on the discharge side of the high-pressure compressor 1 and storing the refrigerating machine oil. And the reliability of the air conditioner can be improved.

  In addition, although this embodiment demonstrated as an example of heating operation, it cannot be overemphasized that cooling operation can be performed by switching the four-way valve 11 and making the flow direction of a refrigerant | coolant reverse with heating operation.

  Further, each oil separator 9 may be any oil separator whose liquid level height and the distance between the lower end of the inner cylinder 23 and the separation performance can be correlated. In particular, by using an oil separator having the same shape, the oil separator The manufacturing design can be facilitated, and the cost of the oil separator can be reduced. Further, by making the outer diameter of each oil separator 9 the same and changing only the overall length according to the capacity of the compressor 1 or the outdoor unit, the amount of refrigerating machine oil returned to each compressor 1 can be made substantially uniform.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Refrigerant suction pipe 3 Refrigerant discharge pipe 9 Oil separator 22 Cylindrical container 23 Inner cylinder 27 Gas refrigerant inlet pipe 29 Return pipe 35 Gas refrigerant outlet pipe

Claims (1)

A refrigerating cycle formed by connecting a refrigerant suction pipe and a refrigerant discharge pipe of a plurality of compressors in parallel; and an oil separator inserted and connected to the refrigerant discharge pipe of each of the compressors. A container, an inner cylinder inserted concentrically from the top of the cylindrical container and opened in the cylindrical container, a gas refrigerant inlet pipe for introducing a gas refrigerant in a tangential direction of the cylindrical container, and an inner side of the inner cylinder The gas refrigerant outlet pipe communicated, and a return pipe for extracting the refrigerating machine oil stored in the cylindrical container and returning it to the compressor, the interval between the cylindrical container and the inner cylinder being the gas refrigerant A liquid level that is formed in a size that is equal to or smaller than the inner diameter of the inlet pipe and that reaches a separation limit where the distance from the lower end of the inner cylinder to the liquid level of the refrigerating machine oil stored in the bottom of the cylindrical container becomes small and the refrigerating machine oil cannot be separated The entire refrigeration cycle There air conditioner comprising determining the size of the oil separator as the liquid level of the maximum oil quantity of each oil separator, which has been calculated based on the amount of the refrigeration oil held.

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