JP2024010832A - Control device, compression system, and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device, a compression system, and a control method which can accurately detect a height of an oil level within a compressor.

SOLUTION: A control device includes: an acquisition part which acquires information indicating a temperature and a pressure of oil within a compressor for compressing refrigerant, and a detection result of an oil level sensor for detecting a height of an oil level; and a correction part which infers a dilution degree of the oil on the basis of the information indicating the temperature and the pressure, and corrects the detection result on the basis of the inferred dilution degree.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates to a control device, a compression system, and a control method.

In the refrigeration cycle device described in Patent Document 1, an oil extraction pipe provided with a capillary tube and an on-off valve is connected between a closed case of a compressor and a refrigerant suction pipe. Furthermore, a pair of temperature sensors are provided at two positions sandwiching the capillary tube. With this configuration, if the oil level of the lubricating oil in the sealed case has reached an appropriate oil level position, the lubricating oil will flow into the oil outlet pipe when the on-off valve is opened. On the other hand, if the lubricating oil level in the sealed case has not reached the appropriate oil level position, the refrigerant will flow into the oil outlet pipe when the on-off valve is opened. With this configuration, based on the temperature difference between the pair of temperature sensors, it is possible to confirm whether the oil level of the lubricating oil in the sealed case has reached an appropriate oil level position.

Japanese Patent Application Publication No. 2002-242833

However, the refrigeration cycle device described in Patent Document 1 has a problem in that the height of the oil level in the compressor cannot be detected with high accuracy.

The present disclosure has been made to solve the above problems, and aims to provide a control device, a compression system, and a control method that can accurately detect the height of the oil level in a compressor. .

In order to solve the above problems, a control device according to the present disclosure provides information representing the temperature and pressure of oil inside a compressor that compresses refrigerant, and detection results of an oil level sensor that detects the height of the oil level of the oil. and a correction unit that estimates the degree of dilution of the oil based on information representing the temperature and the pressure, and corrects the detection result based on the estimated degree of dilution.

A compression system according to the present disclosure includes a compressor that compresses a refrigerant, an oil pod that stores oil inside the compressor, and an oil level sensor that is provided in the oil pod and that detects the height of the oil level. and a control device, wherein the control device obtains information representing the temperature and pressure of oil inside the compressor and a detection result of the oil level sensor, and information representing the temperature and the pressure. and a correction unit that estimates the dilution of the oil based on the dilution and corrects the detection result based on the estimated dilution.

A control method according to the present disclosure includes the steps of acquiring information representing the temperature and pressure of oil inside a compressor that compresses refrigerant and a detection result of an oil level sensor that detects the height of the oil level; The method includes a step of estimating a degree of dilution of the oil based on information representing the temperature and the pressure, and correcting the detection result based on the estimated degree of dilution.

According to the control device, compression system, and control method of the present disclosure, the height of the oil level in the compressor can be detected with high accuracy.

1 is a diagram illustrating an example configuration of a compression system according to an embodiment of the present disclosure. 3 is a flowchart illustrating an example of the operation of the control device according to the embodiment of the present disclosure. FIG. 3 is a schematic diagram for explaining an example of the operation of the control device according to the embodiment of the present disclosure, and shows an example of the correspondence between pressure, temperature, and dilution rate. FIG. 3 is a schematic diagram for explaining an example of the characteristics of the oil level sensor according to the embodiment of the present disclosure, and shows an example of the correspondence between oil level height and capacitance. FIG. 2 is a schematic diagram for explaining an example of the characteristics of the oil level sensor according to the embodiment of the present disclosure, and shows an example of the correspondence between the dilution rate and the capacitance change ratio. FIG. 3 is a schematic diagram for explaining an example of the operation of the control device according to the embodiment of the present disclosure, and shows an example of the correspondence between the dilution rate and the capacitance change ratio. FIG. 1 is a schematic block diagram showing the configuration of a computer according to at least one embodiment.

<First embodiment>
(Compression system configuration)
Hereinafter, a control device, a compression system, and a control method according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 6. FIG. 1 is a diagram illustrating a configuration example of a compression system according to an embodiment of the present disclosure. FIG. 2 is a flowchart illustrating an example of the operation of the control device according to the embodiment of the present disclosure. FIG. 3 is a schematic diagram for explaining an example of the operation of the control device according to the embodiment of the present disclosure, and shows an example of the correspondence between pressure, temperature, and dilution rate. FIG. 4 is a schematic diagram for explaining an example of the characteristics of the oil level sensor according to the embodiment of the present disclosure, and shows an example of the correspondence between oil level height and capacitance. FIG. 5 is a schematic diagram for explaining an example of the characteristics of the oil level sensor according to the embodiment of the present disclosure, and shows an example of the correspondence between the dilution rate and the capacitance change ratio. FIG. 6 is a schematic diagram for explaining an example of the operation of the control device according to the embodiment of the present disclosure. In addition, in each figure, the same reference numerals are used for the same or corresponding components, and the description thereof will be omitted as appropriate.

The compression system 1 shown in FIG. 1 is, for example, a compression system installed in a large-capacity CO2 refrigerator, and includes a high-stage compressor 11, a low-stage compressor 21, a control panel 3, and their peripheral devices. . In this embodiment, the refrigerant is carbon dioxide. However, embodiments of the present disclosure are not limited thereto.

The high-stage compressor 11 is a compressor that compresses refrigerant, and an oil pod 12 that stores oil (also referred to as lubricating oil, refrigerating machine oil, etc.) filled inside the high-stage compressor 11 is connected by a pipe 13. There is. The oil level height in the oil pod 12 matches the oil level height in the high stage compressor 11. The oil level height within the oil pod 12 is detected by an oil level sensor 14. The refrigerant compressed by the low-stage compressor 21 is introduced into the high-stage compressor 11 via an intercooler 41, an accumulator 42, a capillary 43, a strainer 44, and the like. Furthermore, a cooling refrigerant is supplied to the high-stage compressor 11 from an injection circuit (not shown) via a check valve 17 . A temperature sensor 15 is provided at the bottom of the high-stage compressor 11. Further, in the injection circuit, a pressure sensor 16 is provided on the high-stage compressor 11 side of the check valve 17. The temperature sensor 15 measures the temperature of oil inside the high-stage compressor 11. The pressure sensor 16 measures the oil pressure inside the high-stage compressor 11.

The low-stage compressor 21 is a compressor that compresses refrigerant, and is connected to an oil pod 22 through a pipe 23 that stores oil to be filled inside the low-stage compressor 21 . The oil level height in the oil pod 22 matches the oil level height in the low stage compressor 21. The oil level height within the oil pod 22 is measured by an oil level sensor 24. Refrigerant is introduced into the low stage compressor 21 via an accumulator (not shown) or the like. Furthermore, a cooling refrigerant is supplied to the low-stage compressor 21 from an injection circuit (not shown) via a check valve 27 . A temperature sensor 25 is provided at the bottom of the low stage compressor 21. Further, in the injection circuit, a pressure sensor 26 is provided on the low stage compressor 21 side of the check valve 27. The temperature sensor 25 measures the temperature of the oil inside the low stage compressor 21. The pressure sensor 26 measures the oil pressure inside the low stage compressor 21.

In this embodiment, the oil level sensor 14 and the oil level sensor 24 are capacitance type level sensors, and are an example of a liquid level sensor. The oil level sensor 14 and the oil level sensor 24 are equipped with internal signal processing circuits, etc., and calculate the height of the oil level based on the capacitance that changes depending on the range of oil in contact with the sensor. The results are output as detection results. At this time, the oil level sensor 14 and the oil level sensor 24 detect the capacitance, and based on the detected capacitance, calculate the height of the oil level on the assumption that the dilution level of the oil is a predetermined value. Then, the calculated result is output as the detection result. In addition, below, the dilution degree of this predetermined value is also called a standard dilution degree (or standard dilution rate). The dielectric constant of the oil inside the high-stage compressor 11 and the low-stage compressor 21 changes depending on the degree of dilution of the oil. Therefore, when the degree of dilution changes, the capacitance output by the oil level sensor 14 and the oil level sensor 24 changes, causing an error in the calculation result of the oil level height. The oil level sensor 14 and the oil level sensor 24 calculate the height of the oil level on the assumption that the degree of dilution (dilution rate) is 0%, for example. Note that the degree of dilution is the degree of the amount of refrigerant that dissolves in oil, and is determined by the amount of refrigerant/(amount of refrigerant + amount of oil). The dilution rate is a value expressed as a percentage.

On the other hand, the control panel 3 controls each part of the compression system 1 (or the refrigerator including the compression system 1). The control panel 3 is an example of a configuration of a control device according to the present disclosure. In this embodiment, the control panel 3 includes an acquisition section 31 and a correction section 32. The acquisition unit 31 includes information representing the temperature and pressure of oil inside the high-stage compressor 11 and the low-stage compressor 21 that compress refrigerant, and an oil level sensor 14 and an oil level sensor 24 that detect the height of the oil level. Obtain the detection results. The information representing the temperature of the oil is information representing the detection results of the temperature sensor 15 and the temperature sensor 25. The information representing the oil pressure is information representing the detection results of the pressure sensor 16 and the pressure sensor 26.

The correction unit 32 estimates the degree of dilution of oil based on information representing temperature and pressure, and corrects the detection results of the oil level sensor 14 and the oil level sensor 24 based on the estimated degree of dilution. For example, the correction unit 32 estimates the degree of dilution of the oil based on information representing temperature and pressure, and calculates the static level detected by the oil level sensor 14 and the oil level sensor 24 based on the detection results of the oil level sensor 14 and the oil level sensor 24. The capacitance is calculated, the calculated capacitance is corrected based on the estimated dilution, and the height of the oil level is calculated based on the corrected capacitance.

(Example of compression system operation)
Next, an example of the operation of this embodiment will be described with reference to FIGS. 2 to 6. The acquisition unit 31 and correction unit 32 shown in FIG. 1 repeatedly execute the process shown in FIG. 2 at a predetermined period. Note that the acquisition unit 31 and the correction unit 32 acquire and correct the detection results of the oil level sensor 14 and the oil level sensor 24 in parallel. When the oil level sensor 14 and the oil level sensor 24 have the same specifications, the contents of the processing are the same. Below, the oil level sensor 14 will be explained as a representative.

In the process shown in FIG. 2, first, the acquisition unit 31 acquires pressure, temperature, and oil level height. The acquisition unit 31 acquires the measurement results of the oil pressure from the pressure sensor 16, the measurement results of the oil temperature from the temperature sensor 15, and the measurement results (calculation results) of the oil level height from the oil level sensor 14 ( S1).

Next, the correction unit 32 calculates the dilution rate of oil in the high-stage compressor 11 (S2). The correction unit 32 calculates the dilution rate using, for example, a table as shown in FIG. 3 that shows the correspondence between temperature (° C.), pressure (MPa), and dilution rate (%).

Next, the correction unit 32 calculates the capacitance at the standard dilution rate based on the oil level height calculated by the oil level sensor 14 (S3). FIG. 4 shows an example of conversion characteristics between capacitance and oil level height in the oil level sensor 14. As described above, the oil level sensor 14, which is a capacitive oil level sensor, calculates the oil level height from the capacitance that changes depending on the height of the oil in contact with the sensor. Note that the oil level sensor 14 calculates the oil level height assuming a dilution rate of 0%. In the example shown in FIG. 4, the oil level sensor 14 calculates the oil level height using the following formula. C is the capacitance (pF), and h is the oil level height (mm).

In step S3, the correction unit 32 uses the conversion characteristics shown in FIG. 4 to convert the obtained oil level height value h into a capacitance value C at a dilution rate of 0%.

Next, the correction unit 32 corrects the capacitance calculated in step S3 to the capacitance at the reference dilution rate based on the dilution rate calculated in step S2 (S4). Next, the correction unit 32 calculates the corrected oil level height based on the corrected capacitance (S5).

FIG. 5 shows an example of a change in capacitance in response to a change in dilution rate. The capacitance changes depending on the dilution rate of refrigerating machine oil and CO2, and the higher the dilution rate, the lower the capacitance. Since the capacitance decreases depending on the dilution rate, the correction unit 32 divides the capacitance by the capacitance change ratio and corrects it to a capacitance equivalent to a dilution rate of 0%, and then calculates the oil level height using the following formula. do.

Here, x is the dilution rate. y is an approximate function representing the capacitance change ratio with x as a variable.

FIG. 6 shows an example of the process shown in FIG. 2 when the oil level sensor indicates 100 mm at a dilution rate of 50%. In this case, in step S3, the capacitance is 40.8 pF based on the relationship between the capacitance and the oil level height at a dilution rate of 0%.

Furthermore, in step S4, since the dilution rate is 50%, it is estimated that the capacitance is 0.89 times as large as the capacitance when the dilution rate is 0%. Therefore, the capacitance corresponding to a dilution rate of 0% is 40.8 pF/0.89=45.8 pF.

Further, in step S5, the oil level height is determined from the capacitance of 45.8 pF corresponding to a dilution rate of 0%, and is found to be 128 mm.

(action/effect)
According to this embodiment, the degree of dilution of oil is estimated based on information representing temperature and pressure, and the detection result of the oil level sensor is corrected based on the estimated degree of dilution, so even if the degree of dilution changes, the compressor The height of the internal oil level can be calculated accurately. That is, according to this embodiment, the height of the oil level in the compressor can be detected with high accuracy.

(Other embodiments)
Although the embodiment of the present disclosure has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes within the scope of the gist of the present disclosure. .

<Computer configuration>
FIG. 7 is a schematic block diagram showing the configuration of a computer according to at least one embodiment.
Computer 90 includes a processor 91, main memory 92, storage 93, and interface 94.
The above-described control panel 3 (the acquisition unit 31 and the correction unit 32) is installed in the computer 90. The operations of each processing section described above are stored in the storage 93 in the form of a program. The processor 91 reads the program from the storage 93, expands it into the main memory 92, and executes the above processing according to the program. Further, the processor 91 reserves storage areas corresponding to each of the above-mentioned storage units in the main memory 92 according to the program.

The program may be for realizing a part of the functions to be performed by the computer 90. For example, the program may function in combination with other programs already stored in storage or in combination with other programs installed in other devices. Note that in other embodiments, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or in place of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor may be implemented by the integrated circuit.

Examples of the storage 93 include HDD (Hard Disk Drive), SSD (Solid State Drive), magnetic disk, magneto-optical disk, CD-ROM (Compact Disc Read Only Memory), and DVD-ROM (Digital Versatile Disc Read Only Memory). , semiconductor memory, etc. Storage 93 may be an internal medium connected directly to the bus of computer 90, or may be an external medium connected to computer 90 via an interface 94 or a communication line. Furthermore, when this program is distributed to the computer 90 via a communication line, the computer 90 that received the distribution may develop the program in the main memory 92 and execute the above processing. In at least one embodiment, storage 93 is a non-transitory, tangible storage medium.

<Additional notes>
The control device (control panel 3) described in each embodiment can be understood, for example, as follows.

(1) The control device (control panel 3) according to the first aspect includes information indicating the temperature and pressure of oil inside the compressors (high-stage compressor 11 and low-stage compressor 21) that compress refrigerant, and an acquisition unit 31 that acquires the detection results of oil level sensors (oil level sensors 14 and 24) that detect the height of the oil level; and an acquisition unit 31 that estimates the degree of dilution of the oil based on information representing the temperature and the pressure. , a correction unit 32 that corrects the detection result based on the estimated dilution. According to this aspect and each of the following aspects, the height of the oil level in the compressor can be detected with high accuracy.

(2) The control device (control panel 3) according to the second aspect is the control device (control panel 3) according to (1), in which the pressure is provided in an injection circuit that cools the inside of the compressor. These are measurement results of pressure sensors (pressure sensors 16 and 26).

(3) A control device (control panel 3) according to a third aspect is the control device (control panel 3) according to (1) or (2), in which the oil level sensor is a capacitive level sensor. be.

(4) The control device (control panel 3) according to a fourth aspect is the control device (control panel 3) of (3), in which the oil level sensor detects capacitance and the detected static The height of the oil level is calculated based on the capacitance on the premise that the dilution level of the oil is a predetermined value, and the result is output as the detection result, and the correction unit calculates the height of the oil level based on the temperature and the Estimating the dilution of the oil based on information representing pressure, calculating the capacitance detected by the oil level sensor based on the detection result, and correcting the capacitance calculated based on the estimated dilution. Then, the height of the oil level is calculated based on the corrected capacitance.

(5) The compression system 1 according to the fifth aspect includes a compressor (high stage compressor 11 and low stage compressor 21) that compresses refrigerant, and oil pods 12 and 22 that store oil inside the compressor. , oil level sensors 14 and 24 provided in the oil pod to detect the height of the oil level, and a control device (control panel 3), the control device controlling the level of oil inside the compressor. an acquisition unit 31 that acquires information representing temperature and pressure and a detection result of the oil level sensor; and an acquisition unit 31 that estimates the degree of dilution of the oil based on the information representing the temperature and the pressure, and based on the estimated degree of dilution. A correction section 32 that corrects the detection result is provided.

(6) The control method according to the sixth aspect acquires information representing the temperature and pressure of oil inside a compressor that compresses refrigerant and the detection result of an oil level sensor that detects the height of the oil level. estimating the degree of dilution of the oil based on information representing the temperature and the pressure, and correcting the detection result based on the estimated degree of dilution (S2 to S5).

1...Compression system 11...High stage compressor 12...Oil pod 21...Low stage compressor 22...Oil pods 14, 24...Oil level sensors 15, 25...Temperature sensors 16, 26...Pressure sensor 3...Control panel 31...Acquisition Section 32...Correction section

Claims (6)

an acquisition unit that acquires information representing the temperature and pressure of oil inside a compressor that compresses refrigerant and a detection result of an oil level sensor that detects the height of the oil level;
A control device comprising: a correction unit that estimates a degree of dilution of the oil based on information representing the temperature and the pressure, and corrects the detection result based on the estimated degree of dilution. The control device according to claim 1, wherein the pressure is a measurement result of a pressure sensor provided in an injection circuit that cools the inside of the compressor. The control device according to claim 1 or 2, wherein the oil level sensor is a capacitance type level sensor. The oil level sensor detects a capacitance, and based on the detected capacitance, the height of the oil level is calculated based on the premise that the dilution level of the oil is a predetermined value. This is the output as a result,
The correction unit estimates the dilution of the oil based on information representing the temperature and the pressure, calculates the capacitance detected by the oil level sensor based on the detection result, and adjusts the capacitance detected by the oil level sensor to the estimated dilution. The control device according to claim 3, wherein the capacitance calculated based on the calculated capacitance is corrected, and the height of the oil level is calculated based on the corrected capacitance. a compressor that compresses refrigerant;
an oil pod that stores oil inside the compressor;
an oil level sensor that is provided in the oil pod and detects the height of the oil level;
and a control device;
The control device,
an acquisition unit that acquires information representing the temperature and pressure of oil inside the compressor and a detection result of the oil level sensor;
A compression system comprising: a correction unit that estimates a degree of dilution of the oil based on information representing the temperature and the pressure, and corrects the detection result based on the estimated degree of dilution. acquiring information representing the temperature and pressure of oil inside a compressor that compresses refrigerant and a detection result of an oil level sensor that detects the height of the oil level;
A control method comprising: estimating a dilution of the oil based on information representing the temperature and the pressure, and correcting the detection result based on the estimated dilution.

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