Oil amount adjustment device, oil amount adjustment method, oil amount adjustment program, and refrigeration system

Abstract

To provide an oil amount adjustment device which supplies a refrigeration machine oil to an oil container according to a detection result, by detecting oil level height of the refrigeration machine oil in the oil container at three stages, to provide a refrigeration system, an oil amount adjustment method, and an oil amount adjustment program.SOLUTION: An oil amount adjustment device 200 is applied to a system including a plurality of compressors 11, 12, and a plurality of oil containers 13a, 13b provided corresponding to each compressor. The oil amount adjustment device 200 includes: first detection parts OLS-1a, OLS-2a provided at the oil containers 13a, 13b; second detection parts OLS-1b, OLS-2b provided below the first detection parts OLS-1a, OLS-2a; third detection parts OLS-1c, OLS-2c provided below the second detection parts OLS-1b, OLS-2b; and a control part 50 for performing oil amount adjustment of the oil containers 13a, 13b based on the detection result of each detection part.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an oil amount adjusting device, an oil amount adjusting method, an oil amount adjusting program, and a refrigeration system. [Background technology]

[0002] For example, a cooling and heating facility installed in a store or the like has, as an outdoor unit, a condensing unit in which a compressor, a condenser, and the like are mounted on the same frame to form a unit. The evaporator units (unit coolers, showcase coolers, etc.) that are combined with the condensing units vary widely in number, shape, etc. to meet individual requirements. For example, when the number of evaporator units or the length of the connecting pipes change, refrigeration oil (lubricant) may accumulate in the evaporator units or connecting pipes, causing a drop in the oil level in the compressor.In addition, there is a possibility that a malfunction of the compressor may occur due to a lack of oil.

[0003] Patent Document 1 discloses that in a compressor connected to a tank that stores oil by two pipes at different heights, two sensors are installed at different heights above the tank to detect the oil level in the tank and adjust the oil level inside the compressor. Of the two sensors, the sensor installed at the higher position detects a decrease in refrigeration oil in the tank, and the sensor installed at the lower position detects that the amount of refrigeration oil in the tank is insufficient for the amount required for normal operation of the refrigerant circuit.

[0004] Also, a technology has been proposed that increases the amount of oil by controlling the supply of oil into the tank when a low oil amount is detected. For example, Patent Document 2 discloses an oil equalization control that equalizes the uneven oil amount by changing the rotation speed of multiple compressors. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-118317 A [Patent Document 2] JP 2018-109452 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, for example, oil equalization control, which changes the compressor rotation speed to equalize the amount of oil as described in Patent Document 2, can overload the compressor if it is performed frequently, which may result in breakdowns or reduced performance.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide an oil quantity adjustment device, an oil quantity adjustment method, an oil quantity adjustment program, and a refrigeration system that reduce the load on the compressor and suppress the frequency of abnormal shutdowns of the compressor. [Means for solving the problem]

[0008] An oil amount regulating device according to a first aspect of the present disclosure is an oil amount regulating device applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to each of the compressors for supplying oil to the corresponding compressors, the oil amount regulating device including: a first detection unit provided in each of the oil containers and detecting that an oil level in the oil container is below a first oil level that is a reference for oil equalization control; a second detection unit provided in each of the oil containers below the first detection unit and detecting that the oil level in the oil container is below a second oil level that is a reference for oil return control; a third detection unit provided in each of the oil containers below the second detection unit and detecting that the oil level in the oil container is below a third oil level that is a reference for abnormality detection; and a control unit that adjusts the amount of oil in the oil containers based on detection results of the first detection unit, the second detection unit, and the third detection unit. When one of the first detection units detects that the oil level is below the first oil level and the other first detection unit does not detect that the oil level is below the first oil level, the control unit performs oil equalization control to supply oil to the oil container in which the oil level is detected to be below the first oil level, and the control unit performs the oil equalization control by changing the rotation speeds of the plurality of compressors, and does not perform the oil equalization control until a predetermined period has elapsed since the oil equalization control was performed, even if the first detection unit detects that the oil level is below the first oil level. .

[0009] An oil amount adjustment method according to a second aspect of the present disclosure is an oil amount adjustment method applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to each of the compressors for supplying oil to the corresponding compressors, the method including: a step of detecting, in each of the oil containers, that an oil level in the oil container is below a first oil level that is a reference for oil equalization control; a step of detecting, in each of the oil containers, that an oil level in the oil container is below a second oil level that is a reference for oil return control; a step of detecting, in each of the oil containers, that an oil level in the oil container is below a third oil level that is a reference for abnormality detection; and a step of adjusting the amount of oil in the oil containers based on the detection results of each of the steps. when one of the first detection units detects that the oil level is below the first oil level and the other first detection unit does not detect that the oil level is below the first oil level, an oil-equalizing control is performed to supply oil to the oil container in which the oil level is detected to be below the first oil level, and the oil-equalizing control is performed by changing the rotation speeds of the plurality of compressors, and the oil-equalizing control is not performed until a predetermined period has elapsed since the oil-equalizing control was performed, even if the first detection unit detects that the oil level is below the first oil level. .

[0010] An oil amount adjustment program according to a third aspect of the present disclosure is an oil amount adjustment program applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to each of the compressors for supplying oil to the corresponding compressors, the program causing a computer to execute the following processes: a process of detecting, in each of the oil containers, that an oil level in the oil container is below a first oil level that is a reference for oil equalization control; a process of detecting, in each of the oil containers, that an oil level in the oil container is below a second oil level that is a reference for oil return control; a process of detecting, in each of the oil containers, that an oil level in the oil container is below a third oil level that is a reference for abnormality detection; and a process of adjusting the amount of oil in the oil containers based on the detection results of each of the processes. When one of the first detection units detects that the oil level is below the first oil level and the other first detection unit does not detect that the oil level is below the first oil level, an oil-equalizing control is performed to supply oil to the oil container in which the oil level is detected to be below the first oil level, and the oil-equalizing control is performed by changing the rotation speeds of the plurality of compressors, and the oil-equalizing control is not performed until a predetermined period has elapsed since the oil-equalizing control was performed, even if the first detection unit detects that the oil level is below the first oil level. . Effect of the Invention

[0011] According to the present disclosure, it is possible to reduce the load on the compressor and suppress the frequency of abnormal shutdown of the compressor. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a refrigeration system according to an embodiment of the present disclosure. [Diagram 2]FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to an embodiment of the present disclosure. [Diagram 3] 1 is a schematic diagram illustrating a configuration of an oil amount adjusting device according to an embodiment of the present disclosure and its surrounding configuration; [Figure 4] 4 is a time chart showing the rotation speed and time of each compressor in oil-equalizing control according to the embodiment of the present disclosure. [Diagram 5] 5 is a flowchart showing an example of a procedure of an oil amount adjustment control process according to an embodiment of the present disclosure. [Figure 6] 5 is a flowchart showing an example of a procedure of an oil amount adjustment control process according to an embodiment of the present disclosure. [Figure 7] FIG. 13 is a diagram showing a schematic configuration of a refrigeration system including an oil equalization pipe according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an oil amount adjusting device, an oil amount adjusting method, an oil amount adjusting program, and a refrigeration system according to an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a refrigerant circuit of a refrigeration system 300 in one embodiment of the present disclosure. 1, the refrigeration system 300 mainly comprises a refrigerant circuit including compressors 11 and 12, gas coolers (condensers) 16a and 16b, an expansion valve SC-V1, a heat exchanger (evaporator) 80, etc., and a control device 100. The heat exchanger (evaporator) 80 is provided inside the showcase 2. In addition, gas-liquid separators such as an accumulator 14 and oil separators 15a and 15b are connected to the refrigerant circuit. In addition, an oil container 13a is connected to the compressor 11, and an oil container 13b is connected to the compressor 12. The above components are connected by refrigerant piping, oil piping, etc.

[0014] The compressors 11 and 12 compress a refrigerant and supply the compressed high-pressure refrigerant to a refrigerant circuit. In this embodiment, the compressor 11 is a two-stage compressor consisting of a first-stage compression section 11a at the first stage and a second-stage compression section 11b at the second stage. Similarly, the compressor 12 is a two-stage compressor consisting of a first-stage compression section 12a at the first stage and a second-stage compression section 12b at the second stage. In the refrigeration system 300, the compressors 11 and 12 are provided in parallel. As described later, the compressor 11 is connected to an oil container 13a via communication pipes CP1 and CP2, respectively, and similarly, the compressor 12 is connected to an oil container 13b via communication pipes CP3 and CP4, respectively. The refrigerant used in this embodiment is, for example, CO2. The pressure difference between high pressure and low pressure is large for the CO2 refrigerant, and a two-stage compression structure is adopted to improve compressor efficiency. In addition, to improve performance and efficiency, a gas injection mechanism is adopted to supply intermediate pressure (medium pressure) refrigerant to the second stage compression sections 11b and 12b of the compressors 11 and 12.

[0015] An upper portion of the oil container 13a is connected to the discharge side of the first-stage compression section 11a of the compressor 11 by a communication pipe CP1. In addition to the refrigeration oil flowing in from the oil return pipe RP11, during operation of the compressor 11, refrigeration oil also flows into the oil container 13a from the communication pipe CP1 that communicates with the discharge side of the first-stage compression section 11a. In addition, the bottom of the oil container 13a is connected to the bottom of the compressor 11 by a communication pipe CP2. Refrigeration oil that accumulates in the lower portion of the oil container 13a is returned to the compressor 11 through the communication pipe CP2 at the bottom.

[0016] In addition, in the oil container 13a, a first detection unit OLS-1a, a second detection unit OLS-1b, and a third detection unit OLS-1c are provided at different heights in order to detect the oil level in the oil container 13a in stages.

[0017] The first detector OLS-1a detects the oil level in the oil container 13a and detects that the oil level in the oil container 13a is lower than a first oil level that is a reference for oil equalization control, which will be described later. When the oil level in the oil container 13a is equal to or higher than the first oil level, the first detector OLS-1a outputs an ON signal, and when the oil level in the oil container 13a is lower than the first oil level, the first detector OLS-1a outputs a signal (OFF signal) indicating a drop in the oil level in the oil container 13a to the control device 100. Here, the oil equalization control is a control for adjusting the oil amounts when an imbalance occurs between the amounts of oil stored in the oil container 13a and the oil container 13b, thereby eliminating the imbalance in the oil amounts.

[0018] The second detector OLS-1b is provided below the first detector OLS-1a and detects that the oil level in the oil container 13a is below a second oil level that is a reference for oil return control, which will be described later. When the oil level in the oil container 13a is equal to or higher than the second oil level, the second detector OLS-1b outputs an ON signal, and when the oil level in the oil container 13a is below the second oil level, the second detector OLS-1b outputs a signal (OFF signal) indicating a drop in the oil level in the oil container 13a to the control device 100. Here, the oil return control refers to a control in which the refrigeration oil circulating inside the refrigeration system 300 is recovered in the accumulator 14 and the recovered refrigeration oil is returned to the compressors 11 and 12.

[0019] The third detection unit OLS-1c is provided below the second detection unit OLS-1b and detects that the oil level in the oil container 13a is below a third oil level that is a criterion for detecting an abnormality. When the oil level in the oil container 13a is equal to or higher than the third oil level, for example, the third detection unit OLS-1c outputs an ON signal, and when the oil level in the oil container 13a is below the third oil level, the third detection unit OLS-1c outputs a signal (OFF signal) indicating a drop in the oil level in the oil container 13a to the control device 100.

[0020] Similarly, for the oil container 13b on the compressor 12 side, the upper part of the oil container 13b is connected to the discharge side of the first stage compression section 12a of the compressor 12 by a communication pipe CP3. In addition to the refrigeration oil flowing in from the oil return pipe RP12, during operation of the compressor 12, refrigeration oil also flows into the oil container 13b from the communication pipe CP3 that communicates with the discharge side of the first stage compression section 12a. In addition, the bottom of the oil container 13b is connected to the bottom of the compressor 12 by a communication pipe CP4. Refrigeration oil that has accumulated below the oil container 13b is returned to the compressor 12 through the communication pipe CP4 at the bottom. In addition, the oil container 13b is provided with a first detection unit OLS-2a, a second detection unit OLS-2b, and a third detection unit OLS-2c, similar to the first detection unit OLS-1a, the second detection unit OLS-1b, and the third detection unit OLS-1c provided in the oil container 13a.

[0021] The accumulator 14 separates the refrigerant into gas and liquid to be supplied to the compressors 11 and 12. The gas refrigerant separated in the accumulator 14 passes through a suction pipe MP14, an accumulator 21 attached to the compressor 11, and a suction pipe MP15, and is supplied to an accumulator 22 attached to the compressor 12. The gas refrigerant from which only the gas phase is further extracted in the accumulator 21 is supplied to the suction side of the first stage compression section 11a of the compressor 11. Similarly, the gas refrigerant from which only the gas phase is further extracted in the accumulator 22 is supplied to the suction side of the first stage compression section 12a of the compressor 12. In the oil equalization control and the oil return control, the refrigeration oil contained in the refrigerant recovered in the accumulator 14 is supplied to the compressor 11 via the suction pipe MP14 and to the compressor 12 via the suction pipe MP15. This makes it possible to raise the oil levels in the oil containers 13a and 13b.

[0022] The refrigerant discharged from the compressor 11 is supplied to the oil separator 15a via a discharge pipe MP01 on the discharge side. In the oil separator 15a, the refrigerant is separated from the refrigeration oil dissolved in the refrigerant, and the refrigerant flows into the gas pipe MP10 and the hot gas bypass pipe BP11.

[0023] One side of the hot gas bypass pipe BP11 is connected to the gas pipe MP10 between the oil separator 15a and the check valve CV1. The flow of the refrigerant in the hot gas bypass pipe BP11 is controlled by opening and closing the valve HG-V1. That is, when the control device 100 opens the valve HG-V1, the refrigerant discharge side of the oil separator 15a communicates with the suction side of the accumulator 14, and the refrigerant flows through the hot gas bypass pipe BP11. During operation of the refrigeration system 300, the valve HG-V1 is fully closed, so that the refrigerant flows through the gas pipe MP10 without flowing through the hot gas bypass pipe BP11.

[0024] In the oil separator 15a, the refrigerant is separated from the refrigeration oil dissolved in the refrigerant, and the refrigerant flows through the check valve CV1 to the gas pipe MP10. The bottom of the oil separator 15a and the side of the oil container 13a are connected through an oil return pipe RP11. The refrigeration oil separated in the oil separator 15a is returned to the oil container 13a through the oil return pipe RP11.

[0025] The oil return pipe RP11 is divided into two flow paths. A valve R-V1 is provided in the piping of one of the flow paths. The amount of refrigeration oil returned to the oil container 13b is adjusted by opening and closing the valve R-V1.

[0026] As with the compressor 11 side, the refrigerant discharged from the compressor 12 is supplied to the oil separator 15b via the discharge pipe MP02 on the discharge side. In the oil separator 15b, the refrigerant is separated from the refrigerant oil dissolved in the refrigerant, and the refrigerant flows into the gas pipe MP10 and the hot gas bypass pipe BP12.

[0027] One side of the hot gas bypass pipe BP12 is connected to the gas pipe MP10 between the oil separator 15b and the check valve CV2. The flow of the refrigerant in the hot gas bypass pipe BP12 is controlled by opening and closing the valve HG-V2. That is, when the control device 100 opens the valve HG-V2, the refrigerant discharge side of the oil separator 15b communicates with the suction side of the accumulator 14, and the refrigerant flows through the hot gas bypass pipe BP12. During operation of the refrigeration system 300, the valve HG-V2 is fully closed, so that the refrigerant flows through the gas pipe MP10 without flowing through the hot gas bypass pipe BP12.

[0028] As in the compressor 11 side, the oil separator 15b separates the refrigerant from the refrigeration oil dissolved in the refrigerant, and the refrigerant flows into the gas pipe MP10 via the check valve CV2. The bottom of the oil separator 15b and the side of the oil container 13b are connected by an oil return pipe RP12. The refrigeration oil separated by the oil separator 15b is returned to the oil container 13b via the oil return pipe RP12. The oil return pipe RP11 is divided into two flow paths. A valve R-V2 is provided in the piping of one of the flow paths. The amount of refrigeration oil returned to the oil container 13b is adjusted by opening and closing the valve R-V2.

[0029] The high-temperature, high-pressure refrigerant discharged from the compressors 11 and 12 is supplied to the gas coolers 16a and 16b arranged in parallel through the gas pipe MP10. The refrigerant supplied to the gas coolers 16a and 16b is condensed by heat exchange with the air sent in by the fans 17a and 17b. In the case of a CO2 refrigerant, it is cooled.

[0030] The refrigerant cooled or condensed in the gas coolers 16a and 16b is sent to a heat exchanger 80 provided in the showcase 2 via a gas-liquid two-phase pipe MP11 and a liquid pipe MP12. At this time, the refrigerant is depressurized by a valve SC-V1 provided in the liquid pipe MP12, and then sent to the heat exchanger 80. In the heat exchanger 80, heat is exchanged between the refrigerant and a target medium (e.g., air, water), and the refrigerant that has been heated is output to a pipe IP10.

[0031] The pipe IP10 branches into a pipe IP11 and a pipe IP12, and the refrigerant is sent to the compressor 11 through the pipe IP11 and is sent to the compressor 12 through the pipe IP12. In addition, the liquid phase refrigerant in the heat exchanger 80 is supplied to the accumulator 14 through a return pipe MP13.

[0032] The control device 100 controls the refrigeration system 300 according to the present disclosure. Specifically, it controls the compressors 11 and 12, the gas coolers 16a and 16b, the fans 17a and 17b, and each valve. The control device 100 also includes an oil amount adjustment control unit 50. The oil amount adjustment control unit 50 adjusts the amount of oil in the oil containers 13a and 13b based on the detection results (ON signal, OFF signal) input from the first detection units OLS-1a and OLS-2a, the second detection units OLS-1b and OLS-2b, and the third detection units OLS-1c and OLS-2c.

[0033] FIG. 2 is a diagram illustrating an example of a hardware configuration of the control device 100 according to an embodiment of the present disclosure. 2, the control device 100 is a computer system, and includes, for example, a CPU 51, a ROM (Read Only Memory) 52 for storing programs executed by the CPU 51, a RAM (Random Access Memory) 53 that functions as a work area when each program is executed, a hard disk drive (HDD) 54 as a large-capacity storage device, and a communication unit 55 for connecting to a network or the like. Note that other storage devices such as a solid-state drive (SSD) may be used as the large-capacity storage device. These units are connected via a bus 58.

[0034] The control device 100 may also include an input unit including a keyboard, a mouse, and the like, and a display unit including a liquid crystal display device or the like for displaying data.

[0035] Next, the oil amount adjusting device 200 according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a schematic diagram of the configuration of the oil amount adjusting device 200 and its peripheral configuration. As shown in Fig. 3, the oil amount adjusting device 200 according to this embodiment includes first detection units OLS-1a and OLS-2a, second detection units OLS-1b and OLS-2b, third detection units OLS-1c and OLS-2c, and an oil amount adjustment control unit 50, which are provided in the oil containers 13a and 13b. A series of processing steps realized by the oil amount adjustment control unit 50 described below is recorded in the form of a program (e.g., an oil amount adjustment program) in the hard disk drive 54 or the like provided in the control device 100, and the CPU 51 reads this program into the RAM 53 or the like and executes information processing and arithmetic processing to realize various functions described below. The program may be installed in the ROM 52 or other storage medium in advance, may be provided in a state stored in a computer-readable storage medium, or may be distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories. In this embodiment, the oil amount adjustment control unit 50 is incorporated in the control device 100, but the present invention is not limited to this example. For example, the oil amount adjustment control unit 50 may be provided separately from the control device 100, and information may be exchanged between the control device 100 and the oil amount adjustment control unit 50.

[0036] Various controls performed by the oil amount adjustment control unit 50 will be described below.

[0037] [Oil equalization control operation] The oil amount adjustment control unit 50 executes the oil equalization control, for example, when the detection results of the first detection unit OLS-1a of the oil container 13a and the first detection unit OLS-2a of the oil container 13b detect that at least one of the oil levels of the oil containers 13a and 13b is below the first oil level that is the reference for the oil equalization control. For example, as illustrated in FIG. 3, when the first detection unit OLS-1a detects that the oil level is below the first oil level and the first detection unit OLS-2a does not detect that the oil level is below the first oil level, the oil amount adjustment control unit 50 increases the rotation speed of the compressor 11 and decreases the rotation speed of the compressor 12. As a result, the pressure of the compressor 11 decreases, and the amount of oil that the compressor 11 draws from the accumulator 14 becomes larger than during normal operation. Conversely, the pressure of the compressor 12 increases, and the amount of oil that the compressor 12 draws from the accumulator 14 becomes smaller than during normal operation. In this way, by changing the rotation speeds of the compressors 11 and 12 and continuing the oil equalization control for a predetermined time, the difference in the oil levels between the oil container 13a and the oil container 13b decreases. Then, the oil amount adjustment control unit 50 ends the oil equalization control after the predetermined time has elapsed. Note that the oil amount adjustment control unit 50 may end the oil equalization control when the first detection units OLS-1a and OLS-2a detect that the oil levels in the oil containers 13a and 13b are higher than the first oil level, respectively. Furthermore, when the first detection unit OLS-2a detects that the oil levels are below the first oil level, but the first detection unit OLS-1a does not detect that the oil levels are below the first oil level, the oil amount adjustment control unit 50 increases the rotation speed of the compressor 12 and decreases the rotation speed of the compressor 11. Furthermore, in this embodiment, after the oil-equalizing control is performed, the next oil-equalizing control is not performed until a predetermined time has elapsed.

[0038] [Time chart of compressor speed change under oil equalization control] Fig. 4 is a time chart showing the rotation speeds and time of the compressors 11 and 12 in oil-equalizing control. Fig. 4 is a diagram showing an example of control of the rotation speeds of the compressors 11 and 12 when the oil level in the oil container 13a is below the first oil level and the oil level in the oil container 13b is equal to or higher than the first oil level as shown in Fig. 3.

[0039] (time t0~t1) First, when oil equalization control is not performed, the oil amount adjustment control unit 50 drives the compressors 11 and 12 at a rotation speed according to the load.

[0040] (time t1) Next, at time t1, if the first detection unit OLS-1a or OLS-2a detects that the oil level in the oil container 13a or the oil level in the oil container 13b is below the first oil level, the oil amount adjustment control unit 50 executes oil equalization control.

[0041] (time t2~t5) Next, between times t2 and t5, the oil amount adjustment control unit 50 changes the rotation speeds of the compressors 11 and 12 stepwise every predetermined time from oil-equalizing control step 1 to oil-equalizing control step 3. Specifically, the rotation speed of the compressor 11 is increased stepwise, and the rotation speed of the compressor 12 is decreased stepwise.

[0042] (After time t5) Then, when the oil equalization control step 3 is performed for a predetermined period, it is assumed that the oil amounts are equalized, and the oil equalization control is terminated and normal control is resumed. Note that the present invention is not limited to this example, and for example, the oil equalization control may be terminated when the first detection units OLS-1a and OLS-2a detect that the oil levels in the oil containers 13a and 13b are higher than the first oil level during the oil equalization control.

[0043] [Oil return control operation] In addition, when the second detection unit OLS-1b or OLS-2b detects that the oil level in the oil container 13a or the oil level in the oil container 13b is below the second oil level, the oil return control is executed by the oil amount adjustment control unit 50. In the oil return control, for example, when the second detection unit OLS-1b or OLS-2b detects that the oil level is below the second oil level, the oil amount adjustment control unit 50 increases the rotation speed of the compressors 11 and 12. This reduces the pressure of each of the compressors 11 and 12, and the amount of oil that the compressors 11 and 12 draw from the accumulator 14 becomes greater than during normal operation. In this way, by increasing the rotation speed of the compressors 11 and 12 and continuing operation for a predetermined time, the amount of oil in the oil containers 13a and 13b increases. Then, when the oil return control has been performed continuously for a predetermined time, it is determined that the refrigeration oil has sufficiently returned to the oil containers 13a and 13b, and the oil return control is terminated. In addition, the oil return control may be terminated, for example, when the second detection units OLS-1b and OLS-2b detect that the oil levels in the oil containers 13a and 13b are equal to or higher than the second oil level during the oil return control. In addition, the rotation speed control of the compressors 11 and 12 in the oil return control may be changed stepwise, similar to the oil equalization control.

[0044] [Abnormal stop operation] In addition, when the third detection unit OLS-1c or OLS-2c detects that the oil level in the oil container 13a or the oil level in the oil container 13b falls below the third oil level, the oil amount adjustment control unit 50 performs an abnormal stop due to lack of oil.

[0045] 〔flowchart〕 Next, an example of the oil amount adjustment control process for the oil containers 13a and 13b executed by the oil amount adjustment control unit 50 will be described. Figures 5 and 6 are flowcharts showing an example of the procedure of the oil amount adjustment control process according to this embodiment. The following oil amount adjustment control process is started, for example, when the refrigeration system 300 is started.

[0046] First, when the refrigeration system 300 is started (S101), it is determined whether the compressors 11 and 12 are operating (S102). As a result, if both the compressors 11 and 12 are not operating (S103: NO), the process of step S102 is repeated until the compressors 11 and 12 start operating.

[0047] Furthermore, when at least one of the compressors 11 and 12 is operating (S102: YES), the subsequent control is performed on the operating compressor. Note that in the following explanation, a case where both compressors 11 and 12 are operating is exemplified, but when either one of the compressors is stopped, the following processing is performed on the operating compressor. First, it is determined whether or not either of the first detection units OLS-1a and OLS-2a is off, that is, whether or not the oil level in either of the oil containers 13a and 13b is below the first oil level (S103). As a result, if neither of the first detection units OLS-1a and OLS-2a is off (S103: NO), that is, if the oil levels in both of the oil containers 13a and 13b are above the first oil level, the process returns to step S102 and the subsequent processes are performed.

[0048] Also, if the oil container 13a or 13b is off (S103: YES), it is determined whether or not any of the second detection units OLS-1b and OLS-2b is off (S104). As a result, if none of the second detection units is off, that is, if the oil level in either of the oil containers 13a and 13b is below the second oil level (S104: NO), it is determined whether the elapsed time since the previous oil equalization control was performed is equal to or longer than a predetermined time (S105). As a result, if the elapsed time since the previous oil equalization control was performed is equal to or longer than the predetermined time (S105: YES), the oil equalization control is performed (S106). As a result, the rotation speeds of the compressors 11 and 12 are changed based on the detection results of the first detection units OLS-1a and OLS-2a, and the imbalance of the oil levels in the oil containers 13a and 13b is reduced.

[0049] Next, it is determined whether a predetermined period of time has elapsed since the oil equalization control was executed (S107). As a result, if the predetermined time has not elapsed (S107: NO), the oil equalization control is continued until the predetermined period of time has elapsed. Then, if the oil equalization control has been executed for the predetermined period of time (S107: YES), the process returns to step S102 and the subsequent process is executed.

[0050] On the other hand, if it is determined in step S104 that any of the second detection units is off (S104: YES), or if the time elapsed since the previous oil equalization control was executed is less than the predetermined time in step S105 (S105: NO), it is determined whether the third detection units OLS-1c and OLS-2c are off (S108 in FIG. 6). As a result, if none of the third detection units is off, that is, if the oil level in neither of the oil containers 13a and 13b is below the third oil level (S108: NO), the oil return control is executed (S109). As a result, the rotation speeds of the compressors 11 and 12 are changed based on the detection results of the second detection units OLS-1b and OLS-2b, and the amount of oil in the oil containers 13a and 13b is increased.

[0051] Next, it is determined whether a predetermined period of time has elapsed since the oil return control was executed. If the predetermined period of time has not elapsed, the oil return control is continued until the predetermined period of time has elapsed. Then, when the oil return control has been executed for the predetermined period of time (S110: YES), the process returns to step S102 in FIG. 5 and the subsequent process is executed.

[0052] On the other hand, if it is determined in step S108 that any of the third detection units is off (S108: YES), the refrigeration system 300 is temporarily stopped (S111). This control is realized, for example, by outputting an oil amount abnormality detection signal (a signal for stopping the refrigeration system) from the oil amount adjustment control unit 50 to a control unit (not shown) in the control device 100 that controls the start and stop of the system.

[0053] Next, it is determined whether the number of times that the third detection unit has been determined to be off is the first time. As a result, if the third detection unit has been determined to be off for the first time (S112: YES), an inching operation is performed for a predetermined time (S113) to drive the fans and valves to increase the amount of oil in the oil containers 13a and 13b, and then the process returns to step S101 in FIG. 5 to restart the refrigeration system 300 and performs the subsequent processes.

[0054] On the other hand, if the third detection unit has not been turned off for the first time (S112: NO), it is determined that an abnormality has occurred in the refrigeration system 300, and the refrigeration system 300 is allowed to continue in a stopped state while a notification is sent to the administrator urging the administrator to resolve the abnormality (S114).

[0055] Next, it is determined whether the abnormality that occurred in the refrigeration system 300 has been resolved (S115). If the abnormality has not been resolved (S115: NO), the abnormality stop state is continued until it is determined that the abnormality has been resolved.

[0056] On the other hand, if the abnormality has been resolved (S115: YES), the process returns to step S101 in FIG. 5, and the subsequent processes are repeated.

[0057] As described above, according to the oil amount adjusting device, oil amount adjusting method, oil amount adjusting program, and refrigeration system of this embodiment, the oil level heights in the oil containers 13a and 13b are detected in stages by the first detectors OLS-1a and OLS-2a, the second detectors OLS-1b and OLS-2b, and the third detectors OLS-1c and OLS-2c, respectively, and the amount of oil in each of the oil containers 13a and 13b is adjusted based on these detection results by the oil amount adjustment control unit 50. This makes it possible to maintain the amount of oil in each of the oil containers 13a and 13b at an appropriate level.

[0058] Although the present disclosure has been described above using the embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various modifications or improvements can be made to the above embodiments without departing from the gist of the invention, and the forms in which such modifications or improvements are made are also included in the technical scope of the present disclosure. In addition, the above embodiments may be appropriately combined. Furthermore, the process flow described in the above embodiment is also an example, and unnecessary steps may be deleted, new steps may be added, or the process order may be rearranged, without departing from the spirit of the present disclosure.

[0059] For example, in the above embodiment, the case where oil is supplied from the accumulator 14 to each of the compressors 11 and 12 has been described, but the present invention is not limited to this example. For example, as shown in Fig. 7, the oil container 13a and the oil container 13b may be connected by an oil equalizing pipe OEP1, and the oil equalizing control and the oil return control may be performed by controlling the opening and closing of a valve OE-V1 provided on the oil equalizing pipe OEP1.

[0060] The following describes the oil amount adjustment control when oil is supplied through such an oil equalization pipe OEP1. For convenience, the following description will be given by taking as an example a case where the oil level in the oil container 13a is below the first oil level and the oil level in the oil container 13b is above the first oil level. That is, the example shows a state where the amount of oil in the oil container 13a is less than the amount of oil in the oil container 13b. When oil equalization control is performed in this state, the oil amount adjustment control unit 50 opens the valve OE-V1 and further increases the rotation speed of the compressor 11 to reduce the pressure inside the compressor 11. This causes refrigeration oil to move from the compressor 12 to the compressor 11 via the oil equalization pipe OEP1, eliminating the imbalance of refrigeration oil between the compressors 11 and 12. Furthermore, after a predetermined time has elapsed since starting the oil equalization operation, the oil amount adjustment control unit 50 returns the rotation speed of that compressor to its original value and ends the oil equalization control.

[0061] In the present embodiment, the oil equalization control and the oil return control are terminated when each control is continuously performed for a predetermined period of time, but the present invention is not limited to this example. For example, each control may be stopped when the detection result of each detection unit satisfies a specific condition.

[0062] In addition, in the present embodiment, the oil containers 13a, 13b are connected to the compressors 11 and 12 by the communication pipes CP1 to CP4, but the installation positions of the oil containers 13a, 13b are not limited to this. For example, the oil containers 13a, 13b may be provided inside the compressors 11, 12. The oil containers 13a, 13b are not limited to a specific configuration such as an oil pod or an oil pack, and may be anything that stores refrigeration oil.

[0063] Furthermore, the oil amount adjustment procedure shown in Figs. 5 and 6 is an example, and for example, unnecessary steps may be deleted, new steps may be added, or the processing order may be changed.

[0064] The oil amount adjusting device and refrigeration system, the oil amount adjusting method, and the oil amount adjusting program according to the present disclosure described above can be understood as follows, for example. The oil amount regulating device (200) according to the present disclosure is an oil amount regulating device applied to a system (300) including a plurality of compressors (11, 12) and a plurality of oil containers (13a, 13b) provided corresponding to the respective compressors and for supplying oil to the corresponding compressors, the oil amount regulating device including a first detection unit (OLS-1a, OLS-2a) provided in each oil container and detecting that the oil level in the oil container is below a first oil level that is a reference for oil equalization control, and a second detection unit (OLS-2a, OLS-3a) provided in each oil container and detecting that the oil level in the oil container is below a first oil level that is a reference for oil equalization control. and a second detection unit (OLS-1b, OLS-2b) that is provided in each oil container and detects whether the oil level in the oil container is below a second oil level that is a criterion for oil return control, a third detection unit (OLS-1c, OLS-2c) that is provided in each oil container below the second detection unit and detects whether the oil level in the oil container is below a third oil level that is a criterion for abnormality detection, and a control unit (50) that adjusts the amount of oil in the oil container based on the detection results of the first detection unit, the second detection unit, and the third detection unit.

[0065] According to the oil amount adjusting device of the present disclosure, the amount of oil in each oil container is adjusted based on the detection results of the first, second, and third detection units. In this way, the oil level in the oil container is detected stepwise by the first to third detection units, and the amount of oil in the oil container is adjusted by the control unit based on these detection results, so that it is possible to maintain an appropriate amount of oil in the oil container. In particular, since the second detection unit is provided between the first and third detection units, even if the amount of oil in the oil container decreases rapidly after detection by the first detection unit, the second detection unit detects the decrease in oil in the oil container before the third detection unit detects an abnormality. This makes it possible to reduce the frequency with which the oil level falls below the third oil level, which is the criterion for abnormality detection.

[0066] In the oil amount adjusting device according to the present disclosure, the control unit is On the other hand The first detector detects that the oil level is below the first oil level. The other first detection unit does not detect that the oil level is below the first oil level. In this case, oil equalization control is performed to supply oil to the oil container in which it has been detected that the oil level is lower than the first oil level.

[0067] According to the oil amount adjusting device of the present disclosure, On the other hand The first detector detects that the oil level is below the first oil level. The other first detection unit does not detect that the oil level is below the first oil level. When the oil level of the oil container is detected to be lower than the first oil level, oil is supplied to the oil container in which the oil level is detected to be lower than the first oil level. This eliminates unevenness in the amount of oil between the oil containers.

[0068] In the oil amount regulating device of the present disclosure, the control unit performs oil equalization control by changing the rotation speeds of the multiple compressors, and does not perform oil equalization control until a predetermined period has elapsed since performing the oil equalization control, even if the first detection unit detects that the oil level is below the first oil level.

[0069] According to the oil amount adjusting device of the present disclosure, it is possible to limit the frequency of performing oil equalization control, thereby limiting the frequency at which the rotation speed of the compressor is forcibly increased or decreased due to the amount of oil, and thus making it possible to suppress breakdowns or performance degradation of the compressor due to the oil equalization control.

[0070] In the oil quantity regulating device of the present disclosure, when the second detection unit detects that the oil level in the oil container is below the second oil level, the control unit performs oil return control to supply oil to the oil container whose oil level is detected to be below the second oil level.

[0071] According to the oil amount adjusting device of the present disclosure, when the second detection unit detects that the oil level is lower than the second oil level, oil is supplied to the oil container whose oil level is detected to be lower than the second oil level. For example, when the oil equalization control based on the detection of the first detection unit is performed at a predetermined interval, the amount of oil in the oil container may rapidly decrease during the interval. Even in such a case, when the second detection unit detects a decrease in the oil level in the oil container, the oil return control is performed. This makes it possible to perform the oil return control based on the detection result of the second detection unit before the third detection unit detects an abnormality. As a result, it is possible to prevent an abnormal stop before it occurs, and to suppress the frequency of abnormal stop.

[0072] In the oil amount adjusting device according to the present disclosure, the control unit stops operation of the system when the third detection unit detects that the oil level in the oil container is below the third oil level.

[0073] According to the oil amount adjusting device of the present disclosure, when the third detector detects that the oil level is below the third oil level, the operation of the system is stopped. In this way, the system will not be operated with an insufficient amount of oil in the oil container, so that it is possible to prevent performance degradation and failure of the equipment.

[0074] In the oil quantity regulating device of the present disclosure, the control unit performs oil supply control to supply oil to the oil container when the system is restarted after being stopped, and stops operation of the system if the third detection unit detects that the oil level in the oil container is below the third oil level after the oil supply control.

[0075] According to the oil amount adjusting device of the present disclosure, when the third detector detects that the oil level is below the third oil level, the operation of the system is stopped. In this way, the system will not be operated with an insufficient amount of oil in the oil container, so that it is possible to prevent performance degradation and failure of the equipment.

[0076] In the oil amount regulating device according to the present disclosure, each oil container is disposed inside the corresponding compressor.

[0077] According to the oil amount adjusting device of the present disclosure, the oil container is disposed inside the compressor, so that the system configuration can be simplified.

[0078] The refrigeration system according to the present disclosure includes a plurality of compressors that compress a refrigerant, a plurality of oil containers corresponding to each compressor for supplying oil to the corresponding compressor, an evaporator that evaporates the refrigerant by heat exchange, a condenser that condenses the refrigerant by heat exchange, and the oil amount adjustment device described above.

[0079] The oil quantity adjustment method disclosed herein is an oil quantity adjustment method applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to each compressor for supplying oil to the corresponding compressors, and includes the steps of: detecting, in each oil container, that the oil level in the oil container is below a first oil level which is a criterion for oil equalization control; detecting, in each oil container, that the oil level in the oil container is below a second oil level which is a criterion for oil return control; detecting, in each oil container, that the oil level in the oil container is below a third oil level which is a criterion for abnormality detection; and adjusting the oil quantity in the oil container based on the detection results of each step.

[0080] The oil amount adjustment program of the present disclosure is an oil amount adjustment program applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to each compressor for supplying oil to the corresponding compressors, and causes a computer to execute the following processes: a process of detecting, in each oil container, that the oil level in the oil container is below a first oil level that is a criterion for oil equalization control; a process of detecting, in each oil container, that the oil level in the oil container is below a second oil level that is a criterion for oil return control; a process of detecting, in each oil container, that the oil level in the oil container is below a third oil level that is a criterion for abnormality detection; and a process of adjusting the oil amount in the oil container based on the detection results of each process. [Explanation of symbols]

[0081] 2: Showcase 11, 12: Compressor 11a, 12a: first stage compression section 11b, 12b: second stage compression section 13a, 13b: Oil container 14, 21, 22: Accumulator 15a, 15b: Oil separator 16a, 16b: Gas cooler 17a, 17b: Fan 50: Oil amount adjustment control section 51: CPU 52 :ROM 53: RAM 54: Hard disk drive 55: Communications Department 58: Bus 80: Heat exchanger 100: Control device 200: Oil amount adjustment device 300: Refrigeration system OLS-1a,OLS-2a: 1st detection part OLS-1b, OLS-2b: Second detector OLS-1c, OLS-2c: Third detector MP01,MP02:Discharge pipe MP10: Gas Pipe MP11: Gas-liquid two-phase pipe MP12: Liquid tube MP13: Return pipe MP14,MP15: Suction pipe BP11, BP12: Hot gas bypass pipe CP1,CP2,CP3,CP4:Communication pipe RP11, RP12: Oil return pipe IP10, IP11, IP12: Piping OEP1: Oil equalizing pipe SC-V1,HG-V1,HG-V2,R-V1,R-V2,OE-V1:Valve CV1, CV2: Check valve

Claims

1. An oil amount regulating device applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to each of the compressors for supplying oil to the corresponding compressors, a first detection unit provided in each of the oil containers and configured to detect whether an oil level in the oil container is lower than a first oil level that is a reference for oil equalization control; In each of the oil containers, a second detection unit is provided below the first detection unit and detects whether the oil level in the oil container is below a second oil level that is a reference for oil return control; a third detection unit provided in each of the oil containers below the second detection unit and configured to detect when the oil level in the oil container is below a third oil level that is a criterion for detecting an abnormality; A control unit that adjusts the amount of oil in the oil container based on detection results of the first detection unit, the second detection unit, and the third detection unit; Equipped with the control unit performs oil equalization control to supply oil to the oil container in which the oil level is detected to be below the first oil level when one of the first detection units detects that the oil level is below the first oil level and the other first detection unit does not detect that the oil level is below the first oil level, The control unit performs the oil equalization control by changing the rotation speeds of the multiple compressors, and does not perform the oil equalization control until a predetermined period of time has elapsed since the oil equalization control was performed, even if the first detection unit detects that the oil level is lower than the first oil level.

2. The oil quantity regulating device according to claim 1, wherein the control unit performs oil return control to supply oil to the oil container whose oil level is detected to be below the second oil level when the second detection unit detects that the oil level in the oil container is below the second oil level.

3. 3. The oil quantity regulating device according to claim 1, wherein the control unit stops operation of the system when the third detection unit detects that the oil level in the oil container is lower than the third oil level.

4. The oil quantity regulating device of claim 3, wherein the control unit performs oil supply control to supply oil to the oil container when the system is restarted after being stopped, and stops operation of the system if the third detection unit detects that the oil level in the oil container is lower than the third oil level after the oil supply control.

5. The oil amount regulating device according to claim 1 , wherein each of the oil containers is disposed inside the corresponding one of the compressors.

6. A plurality of compressors for compressing a refrigerant; a plurality of oil containers provided corresponding to the compressors, each of the oil containers being configured to supply oil to the corresponding compressor; an evaporator that evaporates the refrigerant by heat exchange; a condenser that condenses the refrigerant by heat exchange; An oil amount adjusting device according to any one of claims 1 to 5, A refrigeration system equipped with

7. An oil amount adjustment method applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to the respective compressors for supplying oil to the corresponding compressors, comprising: detecting, in each of the oil containers, that the oil level in the oil container is below a first oil level that is a reference for oil equalization control; detecting whether the oil level in each of the oil containers is below a second oil level that is a reference for oil return control; detecting, in each of the oil containers, that the oil level in the oil container is below a third oil level that is a criterion for detecting an abnormality; adjusting the amount of oil in the oil container based on the detection results of each of the steps; having When one of the first detection units detects that the oil level is lower than the first oil level, and the other first detection unit does not detect that the oil level is lower than the first oil level, an oil equalization control is performed to supply oil to the oil container in which the oil level is detected to be lower than the first oil level, The oil amount adjustment method performs the oil equalization control by changing the rotation speeds of the plurality of compressors, and does not perform the oil equalization control until a predetermined period of time has elapsed since the oil equalization control was performed, even if the first detection unit detects that the oil level is lower than the first oil level.

8. An oil amount adjustment program applied to a system including a plurality of compressors and a plurality of oil containers provided corresponding to each of the compressors for supplying oil to the corresponding compressors, a process for detecting whether an oil level in each of the oil containers is lower than a first oil level that is a reference for oil equalization control; a process for detecting whether an oil level in each of the oil containers is lower than a second oil level that is a reference for oil return control; a process of detecting whether an oil level in each of the oil containers is below a third oil level that is a criterion for detecting an abnormality; A process of adjusting the amount of oil in the oil container based on the detection results of each of the processes. When one of the first detection units detects that the oil level is below the first oil level, and the other first detection unit does not detect that the oil level is below the first oil level, an oil equalization control process is performed to supply oil to the oil container in which the oil level is detected to be below the first oil level; performing the oil-equalizing control by changing the rotation speeds of the plurality of compressors, and not performing the oil-equalizing control until a predetermined period of time has elapsed since the oil-equalizing control was performed, even if the first detection unit detects that the oil level is lower than the first oil level; An oil amount adjustment program that causes a computer to execute the above.

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