JP5471059B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner in which a plurality of outdoor units are connected in parallel.

  Conventionally, an air conditioner in which a plurality of outdoor units are connected in parallel is known. In such an air conditioner, in order to prevent the lubricating oil of the compressor (so-called refrigerating machine oil) from becoming uneven between a plurality of outdoor units and preventing any of the outdoor units from being in a state of lack of lubricating oil, The machines are connected with oil leveling pipes. However, when an oil equalizing pipe is used, the installation workability at the site is deteriorated or the cost is inevitably increased.

  Thus, for example, in the air conditioner of Patent Document 1, an oil tank or the like connected to an oil separator is provided in each of a plurality of outdoor units. During normal operation, lubricating oil from the oil separator is stored in an oil tank and supplied to the compressor through an oil supply pipe. Also, during oil leveling operation, a large amount of lubricating oil is supplied from the oil tank of the outdoor unit operating at a high frequency into the compressor of the outdoor unit and driven out of the system, and the lubricating oil is operated at a low frequency. It is collected by the compressor of the outdoor unit. In this case, a certain amount of lubricating oil is secured in the compressors of all outdoor units by sequentially switching the outdoor units that operate at a high frequency during the oil leveling operation.

JP 2007-101127 A

  By the way, in the air conditioning apparatus of patent document 1, it is necessary to provide separately the element components for eliminating the uneven state of the lubricating oil between several outdoor units. Specifically, the oil tank, the oil return pipe connecting the oil tank and the oil separator, the solenoid valve and capillary installed on the oil return pipe, the oil supply pipe connecting the oil tank and the compressor, and the oil supply pipe It is necessary to provide a solenoid valve to be installed, which necessitates an increase in the number of parts and an increase in arrangement space.

  An object of the present invention is to provide an air conditioner capable of suppressing any of a plurality of outdoor units from falling into a lack of lubricating oil while suppressing an increase in the number of parts.

  In order to solve the above problems, the invention according to claim 1 is a compressor that sucks refrigerant and compresses and discharges the sucked refrigerant, and functions as a refrigerant condenser during cooling operation and operates during heating operation. Has an outdoor unit heat exchanger that functions as a refrigerant evaporator and an oil separator that separates the lubricating oil of the compressor mixed in the refrigerant and returns the accumulated lubricating oil to the compressor, and is connected in parallel. A plurality of outdoor units, an indoor unit connected to each of the outdoor units, and having an indoor unit heat exchanger functioning as a refrigerant evaporator during cooling operation and functioning as a refrigerant condenser during heating operation, In the air conditioner including each outdoor unit and a refrigerant circuit that circulates refrigerant to the indoor unit, a detecting unit that detects an uneven state of the lubricating oil between the plurality of outdoor units, and the plurality of outdoor units Non-uniformity of the lubricant between When the state is detected, each of the corresponding compressors is arranged such that the refrigerant circulation amount of the one outdoor unit with less lubricating oil is larger than the refrigerant circulation amount of the other outdoor unit with much lubricating oil. The gist is provided with oil leveling means for driving control.

  According to this configuration, when the non-uniform state of the lubricating oil among the plurality of outdoor units is detected by the detecting unit, the refrigerant circulation amount of the one outdoor unit with a small amount of the lubricating oil by the oil leveling unit However, the corresponding compressors are driven and controlled so as to be larger than the refrigerant circulation amount of the other outdoor units with a large amount of the lubricating oil. Generally, since the lubricating oil is distributed to each of a plurality of outdoor units connected in parallel in proportion to the amount of refrigerant circulating, a larger amount of the lubrication is performed by the one outdoor unit with a small amount of lubricating oil. Oil can be distributed, and the lubricating oil among the plurality of outdoor units can be made more even. Then, any of the plurality of outdoor units can be prevented from falling into the lack of the lubricating oil.

  In addition, the equalization of the lubricating oil between the plurality of outdoor units is performed such that the refrigerant circulation amount of the one outdoor unit with less lubricating oil is larger than the refrigerant circulation amount of the other outdoor unit with more lubricating oil. Since it is realized only by driving and controlling each corresponding compressor so as to increase, for example, an element part for eliminating the uneven state of the lubricating oil (for example, securing a certain amount of lubricating oil for each outdoor unit) Therefore, it is not necessary to provide a separate oil tank or the like, and an increase in the number of parts can be suppressed.

The invention of claim 1, prior Symbol plurality of refrigerant supplied to the compressor of the outdoor unit, upstream and downstream of the confluence portion with the lubricating oil returned from the oil separator The upstream side temperature sensor and the downstream side temperature sensor that detect each temperature, and the increase in the downstream temperature with respect to the detected upstream temperature is below a predetermined temperature, so that the lubricating oil of the corresponding outdoor unit The oil leveling means determines that the amount of refrigerant circulating in the outdoor unit in which the lubricating oil is determined to be in a shortage state is equal to that of the other outdoor unit. The corresponding compressors are driven and controlled to be larger than the refrigerant circulation amount .

  In general, the refrigerant supplied to the compressor of each outdoor unit has a temperature on the downstream side that is higher than the temperature on the upstream side of the merging portion by returning the high-temperature lubricating oil from the oil separator. . Further, the increase in the temperature on the downstream side with respect to the temperature on the upstream side of the merge portion becomes smaller as the amount of the lubricating oil returned from the oil separator is smaller, that is, as the lubricating oil in the outdoor unit becomes insufficient. . According to this configuration, the upstream side temperature sensor and the downstream side temperature sensor actually detect the temperatures on the upstream side and the downstream side of the merging portion of the plurality of outdoor units, respectively. Since the increase in the downstream temperature with respect to the upstream temperature falls below a predetermined temperature, the insufficient state determination means determines that the lubricating oil of the corresponding outdoor unit is in the insufficient state. Judgment can be made accordingly. Then, each of the compressions corresponding to each other so that the refrigerant circulation amount of the corresponding outdoor unit determined by the oil leveling means to be in a state where the lubricating oil is insufficient is larger than the refrigerant circulation amount of the other outdoor units. The machine is driven and controlled. Accordingly, a large amount of the lubricating oil can be distributed to the corresponding outdoor unit in which the lubricating oil is insufficient, and the insufficient state of the lubricating oil can be reduced. Then, any of the plurality of outdoor units can be prevented from falling into the lack of the lubricating oil.

The invention of claim 1 includes a low-side pressure sensor for detecting the pressure in the suction port of the previous SL compressor, a high-side pressure sensor for detecting the pressure of the discharge port of the compressor, is the detected who is smaller than when the pressure difference between the pressure at the discharge port of the compressor and the pressure of the inlet is large Ru and a correcting means for correcting so that the predetermined temperature decreases.

  According to this configuration, the correction means causes the predetermined temperature to be smaller when the detected pressure difference between the discharge port pressure and the suction port pressure is smaller, that is, the refrigerant circulation speed is faster. It is corrected so that it becomes smaller when it is later than when it is. Thereby, when the circulation speed of the refrigerant is fast and the influence of the temperature of the lubricating oil is small, the predetermined temperature is corrected so as to be relatively large, and the lack of the lubricating oil can be roughly determined. In addition, when the refrigerant circulation speed is slow and the heat absorption from the lubricating oil is large, the predetermined temperature is corrected to be relatively small, and the lack of the lubricating oil can be determined more strictly.

According to a second aspect of the present invention, in the air conditioning apparatus according to the first aspect, the detecting means is a refrigerant circulation amount of the plurality of outdoor units based on a rotational speed of the compressor of the plurality of outdoor units. Refrigerant circulation amount calculation means for respectively calculating refrigerant circulation amount difference calculation means for sequentially calculating the refrigerant circulation amount difference between the plurality of outdoor units, and refrigerant circulation amount for integrating the sequentially calculated refrigerant circulation amount difference Difference integrating means, and unequal state determining means for determining that the lubricating oil between the corresponding outdoor units is in an unequal state when the accumulated refrigerant circulation amount difference exceeds a predetermined threshold value. The gist.
According to this configuration, the detection means calculates the refrigerant circulation amount of each outdoor unit based on the rotation speed of the compressor of the plurality of outdoor units by the refrigerant circulation amount calculation unit, and the refrigerant circulation amount The difference calculation means sequentially calculates the refrigerant circulation amount difference between the plurality of outdoor units, the refrigerant circulation amount difference integration means integrates the sequentially calculated refrigerant circulation amount difference, and the accumulated refrigerant circulation amount difference Exceeds a predetermined threshold value, it can be determined by the non-uniform state determination means that the lubricating oil between the corresponding outdoor units is in an uneven state. For this reason, if the rotational speed of the compressor of the plurality of outdoor units can be detected, it is possible to detect an uneven state of the lubricating oil between the plurality of outdoor units in a calculation without providing a special sensor. And increase in the number of parts can be suppressed.
According to a third aspect of the present invention, in the air conditioner according to the first or second aspect , when it is determined that the lubricating oil of the corresponding outdoor unit is in a shortage state even after processing by the oil equalizing means. The gist of the present invention is that it includes an indoor unit oil return means for performing indoor unit oil return control.

  Even after the treatment by the oil leveling means, when it is determined that the lubricating oil of the corresponding outdoor unit is in a shortage state, the lubricating oil is used as the indoor unit (indoor unit heat exchanger) or the indoor unit and each outdoor unit. It is thought that it is attached to the wall surface of the refrigerant pipe connecting the machine and is sleeping. According to this configuration, when it is determined that the lubricating oil of the corresponding outdoor unit is in a shortage state even after processing by the oil leveling means, the indoor unit oil return control (that is, the outdoor unit) is performed by the indoor unit oil return unit. The refrigerant condensed in the heat exchanger is passed through the indoor unit in the liquid state, and the lubricating oil in the outdoor unit is removed by pushing the lubricating oil together with the refrigerant. The state can be reduced.

  According to the present invention, it is possible to provide an air conditioner capable of suppressing any of the plurality of outdoor units from falling into a lubricating oil shortage state while suppressing an increase in the number of components.

The circuit diagram which shows the refrigerant | coolant system | strain of one Embodiment of this invention. The graph which shows the relationship between the rotational speed of a compressor, and a refrigerant | coolant flow rate. The graph which shows the relationship between a refrigerant | coolant flow volume and oil separation efficiency. The flowchart which shows the control aspect of the embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a refrigerant system of the air-conditioning apparatus according to the present embodiment. As shown in the figure, the air conditioner includes a plurality of (in the present embodiment, two) outdoor units 10A and 10B and an indoor unit 30. The outdoor units 10A and 10B have the same configuration, and the configuration of one outdoor unit 10A will be described below as a representative. Moreover, when distinguishing the members of both outdoor units 10A and 10B, description will be made by adding A and B to the reference numerals of the corresponding members for convenience.

  The outdoor unit 10A is provided with a compressor 12 as a compressor that is rotationally driven by a driving source (not shown) (for example, a gas engine or an electric motor). The compressor 12 sucks the refrigerant from the suction port 12a, compresses the sucked refrigerant, and sends the refrigerant to the four-way valve 14 connected to the discharge port 12b via the refrigerant pipe 13a. The refrigerant pipe 13a is provided with an oil separator 26 as an oil separator. The oil separator 26 separates the lubricating oil of the compressor 12 mixed in the refrigerant and stores the lubricating oil.

  The four-way valve 14 is connected to the outdoor unit heat exchanger 15 through the refrigerant pipe 13b, is connected to the sub heat exchanger 16 through the refrigerant pipe 13c, and is further connected to the on-off valve 17 through the refrigerant pipe 13d. Has been. The on-off valve 17 is connected to a distribution pipe 18 through a refrigerant pipe 13e. The four-way valve 14 is connected to an accumulator 19 through a refrigerant pipe 13f, and the accumulator 19 is connected to the suction port 12a of the compressor 12 through a refrigerant pipe 13g. The oil separator 26 is connected to the junction 20 with the refrigerant pipe 13g through the refrigerant pipe 13h. An oil return valve 21 is provided in the refrigerant pipe 13h. The lubricating oil accumulated in the oil separator 26 is returned to the compressor 12 when the oil return valve 21 is opened.

  The outdoor unit heat exchanger 15 functions as a refrigerant condenser during the cooling operation and functions as a refrigerant evaporator during the heating operation, and is connected to the supercooling heat exchanger 22 via the refrigerant pipe 13i. Has been. In addition, a check valve 23 that allows the refrigerant to flow to the supercooling heat exchanger 22 side is disposed in the refrigerant pipe 13i, and a flow rate adjustment valve 24a is disposed in parallel with the check valve 23. . The sub heat exchanger 16 functions as a refrigerant evaporator during heating operation, and is connected to the supercooling heat exchanger 22 via a refrigerant pipe 13j. And the flow control valve 24b is arrange | positioned at the refrigerant | coolant piping 13j. The supercooling heat exchanger 22 is connected to the on-off valve 27 through the refrigerant pipe 13k, and the on-off valve 27 is connected to the distribution pipe 25 through the refrigerant pipe 13l.

  As described above, the outdoor unit 10B also has the same configuration as the outdoor unit 10A. In these outdoor units 10A and 10B, each on-off valve 17 is connected to the distribution pipe 18 via the refrigerant pipes 13eA and 13eB, and each on-off valve 27 is connected to the distribution pipe 25 via the refrigerant pipes 13lA and 13lB. Being connected in parallel.

  An indoor unit heat exchanger 31 installed in the indoor unit 30 is connected to the distribution pipe 18 via a refrigerant pipe 32a and to the distribution pipe 25 via a refrigerant pipe 32b. An expansion valve 33 is disposed in the refrigerant pipe 32b. The indoor unit heat exchanger 31 functions as a refrigerant evaporator during the cooling operation and functions as a refrigerant condenser during the heating operation.

  The refrigerant pipes 13a to 13l of the outdoor units 10A and 10B and the refrigerant pipes 32a and 32b of the indoor unit 30 constitute a refrigerant circuit L that circulates refrigerant to the outdoor units 10A and 10B and the indoor unit 30.

Here, the flow of the refrigerant will be described. In FIG. 1, the refrigerant flow during the cooling operation and the heating operation is represented by solid arrows and broken arrows.
During the cooling operation, the refrigerant that has exited the compressor 12 (12A) of the outdoor unit 10A passes through the oil separator 26 and the four-way valve 14, and is then guided to the outdoor unit heat exchanger 15. Here, the refrigerant is deprived of heat by the outside air and condensed and liquefied, and is further brought into a supercooled state by the supercooling heat exchanger 22. Then, the refrigerant is guided to the distribution pipe 25. Similarly, the refrigerant that has exited the compressor 12 (12B) of the outdoor unit 10B is guided to the distribution pipe 25 according to the above.

  Refrigerant from both outdoor units 10A and 10B joined at the distribution pipe 25 passes through the refrigerant pipe 32b and is depressurized by the expansion valve 33 of the indoor unit 30, and takes heat from the room by the indoor unit heat exchanger 31 and vaporizes. Thereafter, the refrigerant is guided to the distribution pipe 18 through the refrigerant pipe 32a and distributed to the outdoor units 10A and 10B. At this time, the refrigerant is distributed to each of the outdoor units 10A and 10B in proportion to each refrigerant flow rate (or a ratio thereof). Then, the refrigerant distributed to the outdoor unit 10A returns to the compressor 12 (12A) through the four-way valve 14 and the accumulator 19. Similarly, the refrigerant distributed to the outdoor unit 10B returns to the compressor 12 (12B) according to the above. Through the above process, the room is cooled.

  On the other hand, during the heating operation, the refrigerant that has exited the compressor 12 (12A) of the outdoor unit 10A passes through the oil separator 26 and the four-way valve 14, and is then guided to the distribution pipe 18. Similarly, the refrigerant that has exited the compressor 12 (12B) of the outdoor unit 10B is guided to the distribution pipe 18 according to the above.

  Refrigerant from both outdoor units 10A and 10B joined at the distribution pipe 18 passes through the refrigerant pipe 32a and is guided to the indoor unit heat exchanger 31 (indoor unit 30). Here, the refrigerant releases heat into the room and condenses and liquefies. Thereafter, the refrigerant decompressed by the expansion valve 33 of the indoor unit 30 is guided to the distribution pipe 25 through the refrigerant pipe 32b and distributed to the outdoor units 10A and 10B. At this time, similarly to the cooling operation, the refrigerant is distributed to each of the outdoor units 10A and 10B in proportion to the refrigerant flow rate (or the ratio). The refrigerant distributed to the outdoor unit 10A is depressurized by the flow rate adjusting valves 24a and 24b, and the refrigerant passing through the flow rate adjusting valve 24a is sent to the outdoor unit heat exchanger 15 and the refrigerant passing through the flow rate adjusting valve 24b is changed. Each is led to the sub heat exchanger 16. The refrigerant absorbs and vaporizes heat from the outside air in the outdoor unit heat exchanger 15, and absorbs and vaporizes heat from an appropriate medium (for example, coolant) in the sub heat exchanger 16. Thereafter, the refrigerant that has passed through the outdoor unit heat exchanger 15 and passed through the four-way valve 14 and the refrigerant that has passed through the sub heat exchanger 16 join together, and return to the compressor 12 (12A) via the accumulator 19. Similarly, the refrigerant distributed to the outdoor unit 10B returns to the compressor 12 (12B) according to the above. Through the above process, the room is heated.

  Next, the electrical configuration of the present embodiment will be described. As shown in FIG. 1, each outdoor unit 10A, 10B is provided with a control device 40 mainly composed of, for example, a microcomputer. The control devices 40A and 40B of both outdoor units 10A and 10B are electrically connected to each other so as to share information. Each control device 40 is electrically connected to an upstream temperature sensor 41 that detects the outlet temperature of the accumulator 19 (the temperature on the upstream side of the merging portion 20) T1, and the intake temperature of the compressor 12 (the merging portion). The downstream temperature sensor 42 for detecting the temperature 20) of the downstream side 20) is electrically connected. Each control device 40 is electrically connected to a low-side pressure sensor 43 that detects the pressure PL of the suction port 12a of the compressor 12, and also detects a pressure PH of the discharge port 12b of the compressor 12. The sensor 44 is electrically connected. Furthermore, a rotation sensor 45 that detects the rotation speed N of the compressor 12 is electrically connected to each control device 40. The control device 40A (40B) drives and controls the compressor 12A (12B) and the like based on the information of the other control device 40B (40A) and the detection results of the sensors 41 to 45 of the corresponding outdoor unit 10A (10B). .

Next, the control mode of this embodiment will be described.
As shown in FIG. 2, it has been confirmed that the flow rate of the refrigerant circulating through each of the outdoor units 10A and 10B increases as the rotational speed of the corresponding compressors 12A and 12B increases. Therefore, a difference in the refrigerant flow rate circulating between the outdoor units 10A and 10B (refrigerant circulation amount difference) is generated by setting the rotational speed difference between the compressors 12A and 12B. Such a difference in rotational speed between the compressors 12A and 12B is, for example, in order to avoid deterioration in performance when the pressure (PH) at the discharge port 12b of any of the compressors 12A and 12B becomes excessive. This is caused by forcibly stopping the rotation of the motor (so-called high pressure avoidance). It has also been confirmed that the lubricating oil mixed in the refrigerant is distributed to each of the outdoor units 10A and 10B substantially in proportion to the flow rate of the refrigerant circulating through each of the outdoor units 10A and 10B. Therefore, the lubricating oils of the outdoor units 10A and 10B are distributed unevenly every time the above-described refrigerant circulation amount difference occurs, and the oil amounts of the lubricants become non-uniform according to the integration.

  Further, in this embodiment, a swirl type oil separator 26 is employed, and as shown in FIG. 3, the oil separation efficiency correlated with the amount of oil recovered by the oil separator 26 has a large refrigerant circulation amount. It has been confirmed that it grows. Therefore, when there is a refrigerant flow rate difference between the outdoor units 10A and 10B, the amount of oil collected by the corresponding oil separators 26 becomes uneven according to the refrigerant circulation amount difference.

In the present embodiment, using such characteristics, the non-uniform state of the lubricating oil between the outdoor units 10A and 10B is detected based on the refrigerant circulation amount of both the outdoor units 10A and 10B (detection means).
More specifically, as described above, the flow rate of the refrigerant circulating through each of the outdoor units 10A and 10B increases as the rotational speed of the corresponding compressors 12A and 12B increases. Accordingly, the control devices 40A and 40B of the outdoor units 10A and 10B are circulated with the refrigerant circulation amount VA of the outdoor units 10A and 10B based on the rotational speeds NA and NB of the compressors 12A and 12B detected by the corresponding rotation sensors 45A and 45B. , VB are respectively calculated (refrigerant circulation amount calculating means). Each of the control devices 40A and 40B sequentially calculates a refrigerant circulation amount difference DV that is a difference between the refrigerant circulation amounts VA and VB between the outdoor units 10A and 10B (refrigerant circulation amount difference calculating means). Furthermore, each of the control devices 40A and 40B integrates the refrigerant circulation amount difference DV sequentially calculated (refrigerant circulation amount difference integration means), and the accumulated refrigerant circulation amount difference (hereinafter also referred to as an integrated value SDV) is predetermined. By exceeding the threshold value Vth, it is determined that the lubricating oil between the corresponding outdoor units 10A and 10B is in an uneven state (uneven state determining means). At this time, a relative shortage state (hereinafter also referred to as “system low OCR (Oil Circulation Ratio) state”) of the lubricating oil of any of the outdoor units 10A and 10B is determined. Hereinafter, the determination of the lack of lubricating oil in the outdoor units 10A and 10B is also referred to as system low OCR determination.

  When there is a system low OCR determination, the control devices 40A and 40B allow the refrigerant circulation amount of one outdoor unit 10A and 10B with less lubricating oil to be larger than the refrigerant circulation amount of the other outdoor units 10A and 10B with much lubricating oil. Thus, the corresponding compressors 12A and 12B are driven and controlled (equalizing means). At this time, the total refrigerant circulation amount of both outdoor units 10A and 10B is preferably the refrigerant circulation amount corresponding to the overall air conditioning requirement (air conditioning load). At this time, the lubricating oil returned from the indoor unit 30 is distributed in proportion to the refrigerant circulation amount of each of the outdoor units 10A and 10B in the connection portions (distribution pipes 18 and 25) of both the outdoor units 10A and 10B. It is recovered by the corresponding oil separator 26 according to the refrigerant circulation amount of each outdoor unit 10A, 10B. Accordingly, a large amount of lubricating oil returns to the corresponding outdoor units 10A and 10B that are in a shortage state of the lubricating oil, thereby reducing the shortage state of the lubricating oil. Hereinafter, such drive control of the compressors 12A and 12B is also referred to as oil equalization control.

  Incidentally, the amount of oil that can be held in each oil separator 26 is determined by the relationship between the position of the outlet pipe of the oil separator 26 and the oil level of the stored lubricating oil. The lubricating oil that has returned too much to the units 10A and 10B flows out to the refrigerant circuit outside the outdoor units 10A and 10B. Accordingly, when the refrigerant circulation amount difference is set between the outdoor units 10A and 10B during the oil leveling control, the lubricating oil easily returns to the outdoor units 10A and 10B having a large refrigerant circulation amount, and flows out to the refrigerant circuit outside the lubricating oil again. And repeat the cycle. When the oil equalization control is completed and the setting of the refrigerant circulation amount difference is eliminated, the lubricating oil circulating in the refrigerant circuit outside the outdoor units 10A and 10B returns to the outdoor units 10A and 10B evenly and returns to the lubricating oil. Is eliminated.

  By the way, the above-described determination of the lack of lubricating oil in the outdoor units 10A and 10B (system low OCR determination) is indirect using the rotational speeds of the compressors 12A and 12B. Therefore, each control device 40 uses the temperatures T1 and T2 actually detected by the upstream temperature sensor 41 and the downstream temperature sensor 42 to make a shortage of lubricating oil in the outdoor units 10A and 10B (hereinafter, “ The determination of “actual operation low OCR state” is also performed (insufficient state determination means).

  More specifically, high temperature lubricating oil is returned to the refrigerant supplied to the compressor 12 (suction port 12a) of each outdoor unit 10A, 10B from the oil separator 26 through the refrigerant pipe 13h, so that the outlet temperature T1 of the accumulator 19 is reached. In contrast, the suction temperature T2 of the compressor 12 increases. The increase ΔT (= T2−T1) of the suction temperature T2 with respect to the outlet temperature T1 is such that the smaller the amount of lubricating oil returned from the oil separator 26, that is, the less lubricating oil in the outdoor units 10A and 10B becomes. The degree of superheat due to oil decreases and decreases. Each control device 40 determines the lack of lubricating oil in the corresponding outdoor units 10A and 10B when the increase ΔT is lower than the predetermined temperature Tth. Hereinafter, the determination of the lack of lubricating oil in the outdoor units 10A and 10B described above is also referred to as actual operation low OCR determination.

  In addition, each control device 40 has a predetermined temperature Tth when the pressure difference ΔP (= PH−PL) between the pressures PH and PL is smaller than when the pressure difference is large, that is, when the refrigerant circulation speed is slower than when the refrigerant is fast. Correction is made so as to decrease (correction means). Thus, when the refrigerant circulation speed is fast and the influence of the lubricating oil temperature is small, the predetermined temperature Tth is corrected so as to be relatively large, and the insufficient condition of the lubricating oil is more roughly determined. However, when the heat absorption from the lubricating oil is slow, the predetermined temperature Tth is corrected to be relatively small, and the lack of lubricating oil is determined more strictly.

  Specifically, when the pressure difference ΔP is small (for example, 0.35 ≦ ΔP ≦ 1 [MPa]), each control device 40 sets a relatively small predetermined temperature Tth1 (for example, 1 ° C.) as the predetermined temperature Tth. Set. And each control apparatus 40 performs actual operation low OCR determination of the said outdoor unit 10A, 10B because the state in which "(DELTA) T <Tth1" is materialized continues for predetermined time (for example, 2 minutes). On the other hand, when the pressure difference ΔP is large (for example, ΔP ≧ 1 [MPa]), each control device 40 sets a relatively large predetermined temperature Tth2 (for example, 3 ° C.) as the predetermined temperature Tth. And each control apparatus 40 performs actual operation low OCR determination of the said outdoor unit 10A, 10B because the state in which "(DELTA) T <Tth2" is materialized continues for predetermined time (for example, 2 minutes).

Even when the actual operation low OCR determination is made, the control devices 40A and 40B perform the oil equalization control. Thereby, the shortage state of the lubricating oil is reduced in the above-described manner.
Further, if the low OCR state (actual operation low OCR state) is still not solved by the oil leveling control, the lubricating oil is used as the indoor unit 30 (indoor unit heat exchanger 31) or the indoor unit 30 and each outdoor unit. Since it is thought that it has adhered to the wall surface of the refrigerant | coolant piping which connects 10A and 10B, and is sleeping, each control apparatus 40 performs indoor unit oil return control (indoor unit oil return means).

  Specifically, at the time of cooling operation, by opening the expansion valve 33 of the indoor unit 30 for a predetermined time, the refrigerant condensed in each of the outdoor units 10A and 10B is allowed to pass through the indoor unit 30 while being in a liquid state. Lubricating oil adhering to the indoor unit 30 or the refrigerant pipe connecting the indoor unit 30 and each outdoor unit 10A, 10B is pushed away together with the refrigerant. Thereby, lubricating oil is collect | recovered in outdoor unit 10A, 10B.

  Alternatively, during the heating period (winter season, etc.), by switching the four-way valve 14, the refrigerant flow path is changed so that a so-called defrosting operation is performed, so that the lubricating oil in the outdoor units 10 </ b> A and 10 </ b> B is changed according to the cooling operation. Is recovered.

  Note that if the low OCR state (actual operation low OCR state) cannot be resolved even by the above oil leveling control and indoor unit oil return control, it is estimated that there is an abnormality such as a pipe breakage. The notification means (warning lamp, buzzer, etc.) is driven to notify the user.

Next, a mode for eliminating the above-described low OCR state by each control device 40 will be collectively described with reference to a flowchart of FIG.
In a state where two outdoor units 10A and 10B are operated (S (step) 1), the system low OCR determination is performed (S2). If it is not determined that the system low OCR determination is “present”, an actual operation low OCR determination is further performed (S3). Here, if it is determined that the actual operation low OCR determination is “present”, or if it is determined that the system low OCR determination is “present” in S2, oil equalization control is performed (S4).

  After performing the oil equalization control, it is determined whether or not the actual operation low OCR state has been resolved after a predetermined time (for example, 5 minutes) has elapsed (S5). When it is determined that the actual operation low OCR state is not resolved, indoor unit oil return control is performed (S6).

Again, it is determined whether or not the actual operation low OCR state has been resolved (S7). If it is determined that the actual operation low OCR state is still not resolved, a notification process is performed (S8).
On the other hand, if it is not determined in S3 that the actual operation low OCR determination is “present”, or if it is determined in S5 and S7 that the actual operation low OCR state has been resolved, normal operation is performed or started (S9).

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) In this embodiment, when an uneven state of the lubricating oil between the outdoor units 10A and 10B is detected, the refrigerant circulation amount of the one outdoor unit 10A and 10B with a small amount of lubricating oil is different from that with a large amount of lubricating oil. Each of the corresponding compressors 12A and 12B is driven and controlled so as to be larger than the refrigerant circulation amount of the outdoor units 10A and 10B, whereby a large amount of lubricating oil is distributed to the one outdoor unit 10A and 10B with less lubricating oil. The lubricating oil between the outdoor units 10A and 10B can be made more even. And it can suppress that either outdoor unit 10A, 10B falls into the lack of lubricating oil. Further, since the equalization of the lubricating oil between the outdoor units 10A and 10B is realized only by driving and controlling the corresponding compressors 12A and 12B in the above-described manner, for example, for eliminating the uneven state of the lubricating oil There is no need to separately provide component parts (such as an oil tank), and an increase in the number of parts and an increase in arrangement space can be suppressed.

  (2) In this embodiment, based on the rotational speeds NA and NB of the compressors 12A and 12B of the outdoor units 10A and 10B, the refrigerant circulation amounts VA and VB of the outdoor units 10A and 10B are calculated, and the outdoor units 10A and 10B are calculated. The refrigerant circulation amount difference DV is sequentially calculated, the refrigerant circulation amount difference DV is integrated, and the accumulated refrigerant circulation amount difference (SDV) exceeds a predetermined threshold value Vth, so that the lubricating oil between the outdoor units 10A and 10B is increased. It can be determined that there is an unequal state. For this reason, if the rotational speeds NA and NB of the compressors 12A and 12B of the outdoor units 10A and 10B can be detected, the non-uniform state of the lubricating oil between the outdoor units 10A and 10B can be detected in calculation without providing a special sensor. And the increase in the number of parts can be suppressed.

  In addition, the detection timing of the unequal state of the lubricating oil, that is, the degree of the unequal state at the time of detection, can be easily adjusted by selecting and setting the predetermined threshold value Vth. For example, the predetermined threshold value Vth is set to be relatively small. Therefore, it is possible to detect the unequal state of the lubricating oil in advance.

  (3) In this embodiment, the upstream side temperature sensor 41 and the downstream side temperature sensor 42 actually detect the outlet temperature T1 and the suction temperature T2 in the outdoor units 10A and 10B, respectively, and the suction temperature T2 relative to the outlet temperature T1. When the increase ΔT is lower than the predetermined temperature Tth, it is possible to determine the lack of lubricating oil in the outdoor unit according to the actual situation. And when it is judged that the lubricating oil of any outdoor unit 10A, 10B is in a shortage state, the shortage of the lubricating oil in the outdoor unit 10A, 10B can be reduced by performing oil equalization control. it can.

  (4) In this embodiment, when the pressure difference ΔP between the pressure PH of the discharge port 12b of the compressor 12 and the pressure PL of the suction port 12a detected by the low-side pressure sensor 43 and the high-side pressure sensor 44 is smaller than when it is large. Is corrected so that the predetermined temperature Tth becomes smaller. As a result, when the circulation speed of the refrigerant is fast and the influence of the temperature of the lubricating oil is small, the predetermined temperature Tth is corrected so as to be relatively large, and the lack of lubricating oil can be roughly determined. When the circulation speed of the oil is slow and the heat absorption from the lubricating oil is large, the predetermined temperature Tth is corrected to be relatively small, and the lack of lubricating oil can be judged more strictly.

  (5) In the present embodiment, the indoor unit oil return control is performed when it is determined that the lubricating oil of the corresponding outdoor units 10A and 10B is in a shortage state even after the oil leveling control is performed. 30 or the lubricating oil adhering to the wall surface of the refrigerant pipe connecting the indoor unit 30 and each outdoor unit 10A, 10B can be recovered, and the lack of lubricating oil in the corresponding outdoor unit can be reduced. .

In addition, you may change said embodiment as follows.
When it is determined that the system low OCR determination is “Yes” in S2, the oil equalization control execution (S4) may be repeated as it is until the determination is not made.

  In the embodiment, the refrigerant flow rate is calculated based on the rotational speed N of the compressor 12, but instead, the refrigerant flow rate is calculated based on the rotational speed of the drive source (gas engine, electric motor, etc.) of the compressor 12. You may calculate.

-The compressor 12 installed in each outdoor unit 10A, 10B may be plural.
-Multiple indoor units 30 may be provided.
-Three or more outdoor units may be provided in parallel connection.

  -You may control all the outdoor units (10A, 10B) in multiple numbers by one common control apparatus.

  L ... Refrigerant circuit, 10A, 10B ... Outdoor unit, 12, 12A, 12B ... Compressor (compressor) 15 ... Outdoor unit heat exchanger, 20 ... Merger, 26 ... Oil separator, 30 ... Indoor unit, 31 ... Indoor Machine heat exchanger, 40... Control device (detection means, oil leveling means, refrigerant circulation amount calculation means, refrigerant circulation amount difference calculation means, refrigerant circulation amount difference integration means, non-uniform state determination means, deficient state determination means, correction means , Indoor unit oil return means), 41 ... upstream temperature sensor, 42 ... downstream temperature sensor, 43 ... low pressure sensor, 44 ... high pressure sensor, 45 ... rotation sensor.

Claims (3)

A compressor that sucks in the refrigerant and compresses and discharges the sucked refrigerant. The compressor functions as a refrigerant condenser during cooling operation and functions as a refrigerant evaporator during heating operation. An oil separator that separates the lubricating oil of the compressor and returns the accumulated lubricating oil to the compressor, and a plurality of outdoor units connected in parallel;
An indoor unit having an indoor unit heat exchanger connected to each of the outdoor units, functioning as a refrigerant evaporator during cooling operation and functioning as a refrigerant condenser during heating operation;
In the air conditioner provided with each outdoor unit and a refrigerant circuit for circulating a refrigerant in the indoor unit,
Detecting means for detecting an uneven state of the lubricating oil between the plurality of outdoor units;
When an uneven state of the lubricating oil among the plurality of outdoor units is detected, the refrigerant circulation amount of the one outdoor unit with a small amount of the lubricating oil is the refrigerant circulation of the other outdoor unit with a large amount of the lubricating oil. Oil leveling means for driving and controlling each of the corresponding compressors to be greater than the amount ;
An upstream temperature sensor for detecting temperatures of a refrigerant supplied to the compressors of the plurality of outdoor units on an upstream side and a downstream side of a joining portion with the lubricating oil returned from the oil separator, and A downstream temperature sensor;
A shortage state determining means for determining that the lubricating oil of the corresponding outdoor unit is in a shortage state because an increase in downstream temperature with respect to the detected upstream temperature is below a predetermined temperature ;
The oil leveling means adjusts the corresponding compressors so that the refrigerant circulation amount of the corresponding outdoor unit determined to be in a state where the lubricating oil is insufficient is larger than the refrigerant circulation amount of the other outdoor units. Drive control,
Furthermore, a low-side pressure sensor that detects the pressure of the suction port of the compressor;
A high-side pressure sensor for detecting the pressure at the discharge port of the compressor;
And correction means for correcting the predetermined temperature to be smaller when the pressure difference between the detected pressure at the discharge port of the compressor and the pressure at the suction port is smaller than when the pressure difference is large. Air conditioner. In the air conditioning apparatus according to claim 1,
The detection means includes
Refrigerant circulation amount calculating means for calculating the refrigerant circulation amount of each of the plurality of outdoor units based on the rotation speed of the compressor of the plurality of outdoor units;
Refrigerant circulation amount difference calculating means for sequentially calculating a refrigerant circulation amount difference between the plurality of outdoor units;
Refrigerant circulation amount difference integration means for integrating the sequentially calculated refrigerant circulation amount difference;
Air conditioning, comprising: an unequal state determining means for determining that the lubricating oil between the corresponding outdoor units is in an unequal state when the accumulated refrigerant circulation amount difference exceeds a predetermined threshold value apparatus. In the air conditioning apparatus according to claim 1 or 2 ,
An air conditioner including an indoor unit oil return unit that performs indoor unit oil return control when it is determined that the lubricating oil of the corresponding outdoor unit is in a shortage state even after processing by the oil leveling unit.

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