Control device, compressing system, and control method

Abstract

This control device comprises: an acquiring unit for acquiring information representing a temperature and pressure of oil inside a compressor that compresses a refrigerant, and a detection result of a

Description

TITLE OF INVENTION: CONTROL DEVICE, COMPRESSING SYSTEM, AND CONTROL METHOD TECHNICAL FIELD

[0001] The present disclosure relates to a control device, a compressing system, and a control method. Priority is claimed on Japanese Patent Application No. 2022-112363, filed July 13, 2022, the content of which is incorporated herein by reference. BACKGROUND ART

[0002] The refrigeration cycle device described in Patent Document 1 has an oil extraction pipe including a capillary tube and an on-off valve connected between a sealing case and a refrigerant suction pipe of a compressor. Furthermore, a pair of temperature sensors are provided at two positions having a capillary tube located therebetween. In this constitution, if an oil surface of a lubricating oil in the sealing case reaches an appropriate oil surface position, the lubricating oil flows into an oil extraction pipe when the on-off valve is opened. On the other hand, if the oil surface of the lubricating oil in the sealing case does not reach the appropriate oil surface position, the refrigerant flows into the oil extraction pipe when the on-off valve is opened. In this constitution, it is possible to check whether the oil surface of the lubricating oil in the sealing case has reached the appropriate oil surface position on the basis of a temperature difference between the pair of temperature sensors. Citation List Patent Document

[0003] [Patent Document 1] Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2002-242833 SUMMARY OF INVENTION Technical Problem

[0004] Here, the refrigeration cycle device described in Patent Document 1 has a problem in that the refrigeration cycle device cannot detect a height of the oil surface in the compressor with high accuracy.

[0005] The present disclosure was made in order to solve the above problem, and an object of the present disclosure is to provide a control device, a compressing system, and a control method which are capable of detecting a height of an oil surface in a compressor with high accuracy.

[0006] In order to solve the above problem, a control device according to the present disclosure includes an acquiring unit which acquires information representing a temperature and a pressure of an oil inside a compressor which compresses a refrigerant and a detection result of an oil surface sensor which detects a height of an oil surface of the oil, and an adjusting unit which estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusts the detection result on the basis of the estimated degree of dilution.

[0007] A compressing system according to the present disclosure includes a compressor which compresses a refrigerant, an oil pod which has an oil inside the compressor stored therein, an oil surface sensor which is provided in the oil pod and detects a height of an oil surface of the oil, and a control device. The control device includes an acquiring unit which acquires information representing a temperature and a pressure of an oil inside the compressor and a detection result of the oil surface sensor, and an adjusting unit which estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusts the detection result on the basis of the estimated degree of dilution.

[0008] A control method according to the present disclosure includes a step of acquiring information representing a temperature and a pressure of an oil inside a compressor which compresses a refrigerant and a detection result of an oil surface sensor which detects a height of an oil surface of the oil, and a step of estimating a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusting the detection result on the basis of the estimated degree of dilution. Advantageous Effects of Invention

[0009] According to a control device, a compressing system, and a control method of the present disclosure, it is possible to detect a height of an oil surface in a compressor with high accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0010] [FIG. 1] A diagram showing an example of a constitution of a compressing system according to an embodiment in the present disclosure. [FIG. 2] A flowchart for describing an example of an operation of a control device according to an embodiment in the present disclosure. [FIG. 3] A schematic diagram for explaining an example of the operation of the control device according to the embodiment in the present disclosure and shows an example of a correspondence relationship between a pressure, a temperature, and a dilution rate. [FIG. 4] A schematic diagram for explaining an example of the characteristics of an oil surface sensor according to the embodiment in the present disclosure and shows an example of a correspondence relationship between a height of an oil surface and a capacitance. [FIG. 5] A schematic diagram for explaining an example of the characteristics of the oil surface sensor according to the embodiment in the present disclosure and shows an example of a correspondence relationship between a dilution rate and a capacitance change ratio. [FIG. 6] A schematic diagram for explaining an example of an operation of a control device according to an embodiment in the present disclosure and shows an example of a correspondence relationship between a dilution rate and a capacitance change ratio. [FIG. 7] A schematic block diagram showing a constitution of a computer relating to at least one embodiment. DESCRIPTION OF EMBODIMENTS

[0011] <First embodiment (Constitution of compressing system) A control device, a compressing system, and a control method according to an embodiment in the present disclosure will be described below with reference to FIGS. 1 to 6. FIG. 1 is a diagram showing an example of a constitution of a compressing system according to an embodiment in the present disclosure. FIG. 2 is a flowchart for describing an example of an operation of a control device according to an embodiment in the present disclosure. FIG. 3 is a schematic diagram for explaining an example of the operation of the control device according to the embodiment in the present disclosure and shows an example of a correspondence relationship between a pressure, a temperature, and a dilution rate. FIG. 4 is a schematic diagram for explaining an example of the characteristics of an oil surface sensor according to the embodiment in the present disclosure and shows an example of a correspondence relationship between a height of an oil surface and a capacitance. FIG. 5 is a schematic diagram for explaining an example of the characteristics of the oil surface sensor according to the embodiment in the present disclosure and shows an example of a correspondence relationship between a dilution rate and a capacitance change ratio. FIG. 6 is a schematic diagram for explaining an example of an operation of a control device according to an embodiment in the present disclosure and shows an example of a correspondence relationship between a dilution rate and a capacitance change ratio. In each of the drawings, the same or corresponding constituent elements are denoted by the same reference numerals and explanation thereof will be omitted as appropriate.

[0012] A compressing system 1 shown in FIG. 1 is, for example, a compressing system provided in a large capacity CO2 refrigerating machine and includes a high-stage compressor 11, a low-stage compressor 21, a control panel 3, peripheral devices thereof, and the like. In an embodiment, a refrigerant is carbon dioxide. Here, the embodiments in the present disclosure are not limited to these. The high-stage compressor 11 is a compressor which compresses a refrigerant and is connected, through a pipe 13, to an oil pod 12 having an oil (also referred to as a lubricating oil, a refrigerating machine oil, or the like) with which an inside of the high-stage compressor 11 is filled stored therein. A height of an oil surface in the oil pod 12 is the same as a height of an oil surface in the high-stage compressor 11. The height of the oil surface in the oil pod 12 is detected using an oil surface sensor 14. A refrigerant compressed using 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 a lower portion of the high-stage compressor 11. In addition, the injection circuit has a pressure sensor 16 provided on the high-stage compressor 11 side of the check valve 17. The temperature sensor 15 measures a temperature of an oil inside the high-stage compressor 11. The pressure sensor 16 measures a pressure of the oil inside the high-stage compressor 11.

[0014] The low-stage compressor 21 is a compressor which compresses a refrigerant and is connected, through a pipe 23, to an oil pod 22 having an oil with which an inside of the low-stage compressor 21 is filled stored therein. A height of an oil surface in the oil pod 22 is the same as a height of an oil surface in the low-stage compressor 21. The height of the oil surface in the oil pod 22 is measured using an oil surface sensor 24. A 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 through a check valve 27 from the injection circuit (not shown). A temperature sensor 25 is provided at a lower portion of the low-stage compressor 21. In addition, the injection circuit has a pressure sensor 26 provided on the low-stage compressor 21 side of the check valve 27. The temperature sensor 25 measures a temperature of an oil inside the low-stage compressor 21. The pressure sensor 26 measures a pressure of the oil inside the low-stage compressor 21.

[0015] Tn the embodiment, the oil surface sensor 14 and the oil surface sensor 24 are capacitance type level sensors and are also examples of a liquid surface sensor. The oil surface sensor 14 and the oil surface sensor 24 have a signal processing circuit and the like included therein, calculate a height of an oil surface on the basis of a capacitance which changes in accordance with the range of an oil in contact with the sensor, and output the calculated height of the oil surface as a detection result. At this time, the oil surface sensor 14 and the oil surface sensor 24 detect a capacitance, calculate a height of an oil surface on the basis of the detected capacitance on the assumption that a degree of dilution of the oil is a predetermined value, and output the calculated result as a detection result. Hereinafter, this predetermined value of the degree of dilution will also be referred to as a reference degree of dilution (or reference dilution rate). A dielectric constant of the oil inside the high-stage compressor 11 and the low-stage compressor 21 changes in accordance with the degree of dilution of the oil. For this reason, if the degree of dilution changes, the capacitance output by the oil surface sensor 14 and the oil surface sensor 24 changes, causing an error in the calculation result of the height of the oil surface. The oil surface sensor 14 and the oil surface sensor 24 calculate, for example, a height of the oil surface on the assumption that the degree of dilution (dilution rate) is 0%. The degree of dilution is an amount of refrigerant dissolved in the oil and is calculated using the Expression: refrigerant amount / (refrigerant amount+oil amount). The dilution rate is a value obtained by representing a degree of dilution as a percentage.

[0016] On the other hand, the control panel 3 controls each part of the compressing system 1 (or the refrigerating machine which includes the compressing system 1). The control panel 3 is a constitution example of the control device according to the present disclosure. In the embodiment, the control panel 3 includes an acquiring unit 31 and an adjusting unit 32. The acquiring unit 31 acquires information representing a temperature and a pressure of an oil inside the high-stage compressor 11 and the low-stage compressor 21 which compress a refrigerant and the detection results of the oil surface sensor 14 and the oil surface sensor 24 which detect a height of an oil surface of an oil. 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 pressure of the oil is information representing the detection results of the pressure sensor 16 and the pressure sensor 26.

[0017] The adjusting unit 32 estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusts the detection results of the oil surface sensor 14 and the oil surface sensor 24 on the basis of the estimated degree of dilution. The adjusting unit 32, for example, estimates the degree of dilution of the oil on the basis of the information representing the temperature and the pressure, calculates the capacitance detected by the oil surface sensor 14 and the oil surface sensor 24 on the basis of the detection results of the oil surface sensor 14 and the oil surface sensor 24, adjusts the calculated capacitance on the basis of the estimated degree of dilution, and calculates the height of the oil surface on the basis of the adjusted capacitance. (Example of operation of compressing system) An example of an operation of the embodiment will be described below with reference to FIGS. 2 to 6. The acquiring unit 31 and the adjusting unit 32 shown in FIG. 1 repeatedly perform the process shown in FIG. 2 over a predetermined cycle. The acquiring unit 31 and the adjusting unit 32 acquire the detection results of the oil surface sensor 14 and the detection results of the oil surface sensor 24 in parallel and perform adjustment. When the oil surface sensor 14 and the oil surface sensor 24 have the same specifications, the processing details are the same. In the following, the oil surface sensor 14 will be explained as a representative example.

[0019] In the process shown in FIG. 2, first, the acquiring unit 31 acquires a pressure, a temperature, and a height of an oil surface. The acquiring unit 31 acquires the measurement result of the pressure of the oil from the pressure sensor 16, the measurement result of the temperature of the oil from the temperature sensor 15, and the measurement result (calculation result) of the height of the oil surface from the oil surface sensor 14 (SI).

[0020] Subsequently the adjusting unit 32 calculates a dilution rate of the oil in the high-stage compressor 11 (S2). The adjusting unit 32, for example, calculates a dilution rate using a table showing a correspondence relationship between a temperature (°C), a pressure (MPa), and a dilution rate (%), as shown in FIG. 3.

[0021] Subsequently, the adjusting unit 32 calculates a capacitance at the reference dilution rate on the basis of the height of the oil surface calculated by the oil surface sensor 14 (S3). FIG. 4 shows an example of the conversion characteristics between the capacitance and the height of the oil surface in the oil surface sensor 14. As described above, the oil surface sensor 14 that is a capacitance type oil surface sensor calculates the height of the oil surface from the capacitance which changes in accordance with the height of the oil in contact with the sensor. The oil surface sensor 14 calculates the height of the oil surface assuming a dilution rate of 0%. In the case of the example shown in FIG. 4, the oil surface sensor 14 calculates the height of the oil surface using the following Expression. C is a capacitance (pF) and h is a height of an oil surface (mm).

[0022] [Math. 1]

[0023] In Step S3, the adjusting unit 32 converts a value h of the acquired height of the oil surface into a value C of a capacitance at a dilution rate of 0% using the conversion characteristics shown in FIG. 4.

[0024] Subsequently, the adjusting unit 32 adjusts the capacitance calculated in Step S3 to the capacitance at the reference dilution rate on the basis of the dilution rate calculated in Step S2 (S4). Subsequently, the adjusting unit 32 calculates the adjusted height of the oil surface on the basis of the adjusted capacitance (S5).

[0025] FIG. 5 shows an example of a change in capacitance according to a change in dilution rate. A capacitance changes in accordance with a dilution rate of a refrigerating machine oil and CO2 and the higher the dilution rate, the lower the capacitance. Since the capacitance decreases in accordance with the dilution rate, the adjusting unit 32 divides the capacitance by the capacitance change ratio using the following Expression, adjusts it to a capacitance corresponding to a dilution rate of 0%, and then calculates a height of the oil surface.

[0026] [Math. 2] 0.178

[0027] Here, x is a dilution rate and y is an approximation function in which a capacitance change ratio having x as a variable is expressed.

[0028] FIG. 6 shows an example of the process shown in FIG. 2 when the oil surface sensor indicates 100 mm at a dilution rate of 50%. In this case, in Step S3, the capacitance is 40.8 pF based on a relationship between the capacitance at a dilution rate of 0% and the height of the oil surface.

[0029] Also, in Step S4, since the dilution rate is 50%, it is estimated that the capacitance is 0.89 times larger than that when the dilution rate is 0%. For this reason, 12 the capacitance corresponding to a dilution rate of 0% is 40.8 pF / 0.89=45.8 pF.

[0030] Furthermore, in Step S5, the height of the oil surface is calculated to be 128 mm from the capacitance of 45.8 pF which corresponds to a dilution rate of 0%.

[0031] (Actions and effects) According to the embodiment, the degree of dilution of the oil is estimated on the basis of the information representing the temperature and the pressure and the detection result of the oil surface sensor is adjusted on the basis of the estimated degree of dilution so that the height of the oil surface inside the compressor can be accurately calculated even if the degree of dilution is changed. That is to say, according to the embodiment, the height of the oil surface in the compressor can be detected with high accuracy.

[0032] (Other embodiments) Although the embodiment of the present disclosure has been described in detail above with reference to the drawings, the specific constitution is not limited to this embodiment and design modifications and the like are also included without departing from the scope of the gist of the present disclosure.

[0033] <Constitution of computer> FIG. 7 is a schematic block diagram showing a constitution of a computer according to at least one embodiment. A computer 90 includes a processor 91, a main memory 92, a storage 93, and an interface 94, The above-described control panel 3 (the acquiring unit 31 and the adjusting unit 32) is implemented in the computer 90. Furthermore, an operation of each of the above-mentioned processing units are stored in the storage 93 in the form of a program. The processor 91 reads the program from the storage 93, loads the program into the main memory 92, and performs the above processing in accordance with the program. In addition, the processor 91 has a storage region corresponding to each of the abovedescribed storage parts reserved in the main memory 92 in accordance with a program.

[0034] The program may be for realizing a part of the functions performed by the computer 90. For example, the program may perform the functions thereof in combination with other programs which have been already stored in the storage or in combination with other programs which have been installed in other devices. In other embodiments, the computer may include a custom large scale integrated circuit (LSI) such as a programmable logic device (PLD) in addition to or in place of the constitution. Examples of PLDs include programmable array logics (PALs), generic array logics (GALs), complex programmable logic device (CPLDs), and field programmable gate arrays (FPGAs). In this case, some or all of the functions realized using the processor may be realized using the integrated circuit.

[0035] Examples of the storage 93 include hard disk drives (HDDs), solid state drives (SSDs), magnetic disks, magneto-optical discs, compact disc read only memories (CD-ROMs), digital versatile disc read only memories (DVD-ROMs), and semiconductor memories. The storage 93 may be internal media directly connected to a bus of the computer 90 or may be external media connected to the computer 90 via the interface 94 or a communication circuit. Furthermore, when this program is distributed to the computer 90 via the communication circuit, the computer 90 which receives the program distributed thereto may load the program into the main memory 92 and perform the above processing. In at least one embodiment, the storage 93 is a non-transitory and tangible storage medium.

[0036] <Supplement Notes> The control device (the control panel 3) described in each of the embodiments can be ascertained, for example, as follows.

[0037] (1) A control device (a control panel 3) according to a first aspect includes an acquiring unit 31 which acquires information representing a temperature and a pressure of an oil inside a compressor (a high-stage compressor 11 and a low-stage compressor 21) which compresses a refrigerant and a detection result of an oil surface sensor (oil surface sensors 14 and 24) which detects a height of an oil surface of the oil, and an adjusting unit 32 which estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusts the detection result on the basis of the estimated degree of dilution. According to the aspect and the following aspects, it is possible to detect a height of an oil surface in a compressor with high accuracy.

[0038] (2) The control device (the control panel 3) according to a second aspect is the control device (the control panel 3) in (1), in which the pressure is a measurement result of a pressure sensor (pressure sensors 16 and 26) provided in an injection circuit which cools an inside of the compressor.

[0039] (3) The control device (the control panel 3) according to a third aspect is the control device (the control panel 3) in (1) or (2), in which the oil surface sensor is a capacitance type level sensor.

[0040] (4) The control device (the control panel 3) according to a fourth aspect is the control device (the control panel 3) in (3), in which the oil surface sensor detects a capacitance and outputs a result of calculating, as the detection result, a height of the oil surface on the basis of the detected capacitance on the assumption that the degree of dilution of the oil is a predetermined value, and the adjusting unit estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure, calculates the capacitance detected by the oil surface sensor on the basis of the detection result, adjusts the calculated capacitance on the basis of the estimated degree of dilution, and calculates a height of the oil surface on the basis of the adjusted capacitance.

[0041] (5) A compressing system 1 according to a fifth aspect includes a compressor (a high-stage compressor 11 and a low-stage compressor 21) which compresses a refrigerant, oil pods 12 and 22 which have an oil inside the compressor stored therein, oil surface sensors 14 and 24 which are provided in the oil pods and detect a height of an oil surface of the oil, and a control device (a control panel 3), in which the control device includes an acquiring unit 31 which acquires information representing a temperature and a pressure of the oil inside the compressor and a detection result of the oil surface sensor, and an adjusting unit 32 which estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusts the detection result on the basis of the estimated degree of dilution.

[0042] (6) A control method according to a sixth aspect includes a step (SI) of acquiring information representing a temperature and a pressure of an oil inside a compressor which compresses a refrigerant and a detection result of an oil surface sensor which detects a height of an oil surface of the oil and steps (S2 to S5) of estimating a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusting the detection result on the basis of the estimated degree of dilution. INDUSTRIAL APPLICABILITY

[0043] According to a control device, a compressing system, and a control method of the present disclosure, it is possible to detect a height of an oil surface in a compressor with high accuracy. REFERENCE SIGNS LIST

[0044] 1 Compressing system 11 High-stage compressor 12 Oil pod 21 Low-stage compressor 22 Oil pod 14, 24 Oil surface sensor 15, 25 Temperature sensor 16, 26 Pressure sensor 3 Control panel 32 Adjusting unit

Claims

1. A control device, comprising:an acquiring unit which acquires information representing a temperature and a pressure of an oil inside a compressor which compresses a refrigerant and a detection result of an oil surface sensor which detects a height of an oil surface of the oil; andan adjusting unit which estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusts the detection result on the basis of the estimated degree of dilution.

2. The control device according to claim 1, wherein the pressure is a measurement result of a pressure sensor which is provided in an injection circuit which cools an inside of the compressor.

3. The control device according to claim 1 or 2, wherein the oil surface sensor is a capacitance type level sensor.

4. The control device according to claim 3, wherein the oil surface sensor detects a capacitance and outputs a result of calculating, as the detection result, a height of the oil surface on the basis of the detected capacitance on the assumption that a degree of dilution of the oil is a predetermined value, andthe adjusting unit estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure, calculates the capacitance detected by the oil surface sensor on the basis of the detection result, adjusts the calculated capacitance on the basis of the estimated degree of dilution, and calculates a height of the oil surface on the basis of the adjusted capacitance.

5. A compressing system, comprising:a compressor which compresses a refrigerant;an oil pod which has an oil inside the compressor stored therein;an oil surface sensor which is provided in the oil pod and detects a height of an oil surface of the oil; anda control device,wherein the control device includes5 an acquiring unit which acquires information representing a temperature and apressure of an oil inside the compressor and a detection result of the oil surface sensor, andan adjusting unit which estimates a degree of dilution of the oil on the basis of the information representing the temperature and the pressure and adjusts the detection10 result on the basis of the estimated degree of dilution.

6. A control method, comprising:a step of acquiring information representing a temperature and a pressure of an oil inside a compressor which compresses a refrigerant and a detection result of an oil surface sensor which detects a height of an oil surface of the oil; and15 a step of estimating a degree of dilution of the oil on the basis of the informationrepresenting the temperature and the pressure and adjusting the detection result on the basis of the estimated degree of dilution.

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