Oil deterioration detection device, oil deterioration detection system, and oil deterioration detection method

Abstract

To detect deterioration of oil in more detail.SOLUTION: A oil deterioration detection device performs an analysis based on impedances of at least three first specific frequencies measured by applying AC voltages of the at least three first specific frequencies selected from a first frequency range to the opposite electrodes in a state in which the oil to be evaluated has passed between opposite electrodes; calculates an arc on the Nyquist diagram; when the calculated arc is larger than a predetermined reference arc of the oil to be evaluated, which is calculated in advance, determines that water is mixed; and calculates a water content based on the calculated shape of the arc.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an oil deterioration detection device, an oil deterioration detection system, and an oil deterioration detection method for detecting oil deterioration. [Background technology]

[0002] The performance of lubricating oil supplied to sliding parts such as bearings of equipment deteriorates as it is used. Patent Document 1 describes a device for detecting deterioration of circulating oil, which has a measuring unit that installs opposing electrodes in a container and measures the dielectric constant of the oil from the electrostatic capacitance between the electrodes, and a deterioration determining unit that performs frequency analysis of the measurement results of the measuring unit and determines whether the deterioration state of the lubricating oil is within a predetermined acceptable state.

[0003] Patent document 2 also describes a method for determining the state of a working fluid, comprising the steps of placing a pair of spaced electrodes in the fluid, applying AC signals to the electrodes over four or more frequency ranges, measuring impedance or admittance data as a function of frequency from the electrical response to the applied AC signals, measuring at least one selected from the group consisting of resistance, capacitance, omega maximum, impedance, and time constant, and comparing the measured property with a predetermined value for the property to measure an indicator of the state of the fluid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-32352 [Patent Document 2] Special Publication No. 2005-529333 Summary of the Invention [Problem to be solved by the invention]

[0005] The performance of oil can be evaluated using various criteria, as described in Patent Documents 1 and 2. However, the detection methods in Patent Documents 1 and 2 may not be able to evaluate oil deterioration depending on the cause of the oil deterioration.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide an oil deterioration detection device, an oil deterioration detection system, and an oil deterioration detection method that can detect oil deterioration in more detail. [Means for solving the problem]

[0007] To achieve the above object, the oil deterioration detection device of the present disclosure performs an analysis based on the impedance of at least three first specific frequencies measured by applying AC voltages of at least three first specific frequencies selected from a first frequency range to opposing electrodes while the oil to be evaluated passes between the opposing electrodes, calculates an arc on a Nyquist diagram, and if the calculated arc is larger than a predetermined reference arc of the oil to be evaluated, determines that moisture has been mixed in, and calculates the moisture content based on the shape of the calculated arc.

[0008] To achieve the above object, the oil deterioration detection method of the present disclosure includes the steps of applying AC voltages of at least three first specific frequencies selected from a first frequency range to opposing electrodes while the oil to be evaluated passes between the opposing electrodes to measure impedance, performing analysis based on the measured impedances of the at least three first specific frequencies and calculating an arc on a Nyquist diagram, and determining that moisture has been mixed in if the calculated arc is larger than a predetermined reference arc of the oil to be evaluated, and calculating the moisture content based on the shape of the calculated arc. [Effects of the Invention]

[0009] The present disclosure can detect oil deterioration in more detail. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a power generation unit having an oil deterioration detection system according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the general configuration of the oil deterioration detection system of this embodiment. [Figure 3] FIG. 3 is a flowchart showing an example of an oil deterioration detection method of the oil deterioration detection system of this embodiment. [Figure 4] FIG. 4 is an explanatory diagram for explaining the oil deterioration detection method. [Figure 5] FIG. 5 is an explanatory diagram for explaining the moisture content detection process. [Figure 6] FIG. 6 is an explanatory diagram for explaining the process of detecting the amount of moisture. [Figure 7] FIG. 7 is an explanatory diagram for explaining the moisture content detection process. [Figure 8] FIG. 8 is an explanatory diagram for explaining the oil deterioration detection method. [Figure 9] FIG. 9 is an explanatory diagram for explaining the base number detection process. [Figure 10] FIG. 10 is an explanatory diagram for explaining the base number detection process. [Figure 11] FIG. 11 is an explanatory diagram for explaining the oil deterioration detection method. [Figure 12] FIG. 12 is an explanatory diagram for explaining the oil deterioration detection method. [Figure 13] FIG. 13 is an explanatory diagram for explaining the soot detection process. [Figure 14] FIG. 14 is an explanatory diagram for explaining the soot detection process. [Figure 15] FIG. 15 is an explanatory diagram for explaining the soot detection process. [Figure 16] FIG. 16 is a schematic diagram showing the general configuration of the oil deterioration detection system of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations in which the respective embodiments are combined.

[0012] 1 is a block diagram showing the schematic configuration of a power generation unit having an oil deterioration detection system according to this embodiment. In this embodiment, the oil deterioration detection system is described as being used to measure the deterioration (state) of lubricating oil in the power generation unit, but is not limited to this. The oil deterioration detection system can be used to detect the state (deterioration state) of various lubricating oils and hydraulic oils.

[0013] The power generation unit 10 of this embodiment has an engine body 12, a turbocharger 14, a generator 16, and a lubricating oil supply unit 18. The engine body 12 is a gas engine, diesel engine, or the like that burns fuel and rotates a rotating shaft. The turbocharger 14 has a turbine that rotates using energy discharged from the engine body 12, and a compressor that rotates integrally with the turbine compresses air and supplies it to the engine body 12. The generator 16 is connected to the engine body 12 and is rotated by the engine body 12 to generate electricity.

[0014] The lubricating oil supply unit 18 supplies lubricating oil to the engine body 12, the turbocharger 14, and the generator 16, and collects lubricating oil discharged from the engine body 12, the turbocharger 14, and the generator 16. The lubricating oil supply unit 18 has a lubricating oil tank 20, a lubricating oil line 22, a pump 24, a cooler 26, a filter 28, a backwash strainer 30, a bypass pipe 32, a three-way valve 34, a first sensor unit 50, a second sensor unit 52, and a third sensor unit 54. Note that in this embodiment, three sensor units are shown to illustrate the positions of the units, but deterioration of the lubricating oil can be detected with just one sensor unit.

[0015] The lubricating oil tank 20 stores lubricating oil discharged from the engine body 12, the turbocharger 14, and the generator 16. A lubricating oil line 22 connects the lubricating oil tank 20 to the engine body 12, the turbocharger 14, and the generator 16, supplies oil from the lubricating oil tank 20 to the engine body 12, the turbocharger 14, and the generator 16, and discharges lubricating oil from the engine body 12, the turbocharger 14, and the generator 16 into the lubricating oil tank 20. A pump 24 is disposed on the lubricating oil line 22 and supplies lubricating oil from the lubricating oil tank 20 to the engine body 12, the turbocharger 14, and the generator 16. The lubricating oil supply unit 18 supplies lubricating oil to the engine body 12, the turbocharger 14, and the generator 16 by cooling the lubricating oil in a cooler 26, removing foreign matter with a filter 28, and sending it with the pump 24.

[0016] The cooler 26 is disposed downstream of the pump 24 in the lubricating oil line 22. The cooler 26 cools the lubricating oil flowing through the lubricating oil line 22. The filter (main strainer) 28 is disposed downstream of the cooler 26 in the lubricating oil line 22. The filter 28 removes foreign matter contained in the lubricating oil flowing through the lubricating oil line 22. The lubricating oil that has passed through the filter 28 is supplied to the engine body 12, the turbocharger 14, and the generator 16. The filter 28 removes the removed foreign matter by backwashing. The backwash strainer 30 is supplied with the lubricating oil that is discharged when the filter 28 is backwashed. The backwash strainer 30 removes foreign matter from the lubricating oil that is discharged when the filter 28 is backwashed, and discharges the lubricating oil from which the foreign matter has been removed into the lubricating oil tank 20.

[0017] The bypass pipe 32 is a pipe that bypasses the cooler 26. The three-way valve 34 is a valve that connects the line passing through the cooler 26, the bypass pipe 32, and the filter 28. The three-way valve 34 switches between a state in which the line passing through the cooler 26 is connected to the filter 28 and a state in which the bypass pipe 32 is connected to the filter 28, thereby controlling the temperature of the lubricating oil. Furthermore, the three-way valve 34 can adjust the ratio between the flow rate of the lubricating oil passing through the cooler 26 and the flow rate of the lubricating oil passing through the bypass pipe 32 by connecting both the line passing through the cooler 26 and the bypass pipe 32 to the filter 28 and adjusting the opening degree of each. The three-way valve 34 controls the temperature of the lubricating oil by adjusting the ratio between the flow rate of the lubricating oil passing through the cooler 26 and the bypass pipe 32.

[0018] The first sensor unit 50 detects the deterioration state of the lubricant flowing through the lubricant line 22. The first sensor unit 50 includes an oil deterioration detection system 60, a sensor line 62, and a valve 64. The oil deterioration detection system 60 detects the deterioration state of the lubricant. The oil deterioration detection system 60 will be described later. One end of the sensor line 62 is connected to a position downstream of the filter 28 in the circulation line 22, and the other end is connected to the backwash strainer 30. A portion of the lubricant that has passed through the filter 28 flows into the sensor line 62, passes through the oil deterioration detection system 60, and then discharges it to the backwash strainer 30. The valve 64 is disposed on the sensor line 62, and by switching between opening and closing, switches whether or not lubricant is supplied to the oil deterioration detection system 60. The valve 64 also functions as a flow control valve that adjusts the flow rate of lubricant supplied to the oil deterioration detection system 60 by adjusting its opening degree.

[0019] The second sensor unit 52 detects the deterioration state of the lubricant flowing through the lubricant line 22. The second sensor unit 52 includes an oil deterioration detection system 70, a sensor line 72, and a valve 76. The oil deterioration detection system 70 detects the deterioration state of the lubricant in the same manner as the oil deterioration detection system 60. One end of the sensor line 72 is connected to the filter 28, and the other end is connected to the backwash strainer 30. The sensor line 72 receives the lubricant from the filter 28, passes it through the oil deterioration detection system 70, and then discharges it to the backwash strainer 30. The valve 76 is disposed on the sensor line 72, and by switching between opening and closing, switches whether or not lubricant is supplied to the oil deterioration detection system 70. The valve 76 also functions as a flow control valve that adjusts the flow rate of lubricant supplied to the oil deterioration detection system 70 by adjusting its opening degree.

[0020] The third sensor unit 54 detects the deterioration state of the lubricant flowing through the lubricant line 22. The third sensor unit 54 includes an oil deterioration detection system 80, a sensor line 82, and a valve 84. The oil deterioration detection system 80 detects the deterioration state of the lubricant. The oil deterioration detection system 80 will be described later. One end of the sensor line 82 is connected to a position on the circulation line 22 between the lubricant tank 20 and the pump 24, and the other end is connected to the backwash strainer 30. A portion of the lubricant stored in the lubricant tank 20 flows into the sensor line 82, passes through the oil deterioration detection system 80, and then discharges the lubricant into the backwash strainer 30. The valve 84 is disposed on the sensor line 82 and switches between opening and closing to supply or not supply lubricant to the oil deterioration detection system 80. The valve 84 also functions as a flow control valve that adjusts the flow rate of the lubricant supplied to the oil deterioration detection system 80 by adjusting its opening degree.

[0021] The first sensor unit 50, the second sensor unit 52, and the third sensor unit 54 allow the lubricating oil to flow from the filter 28 toward the backwash strainer 30 due to the pressure difference of the lubricating oil, and the lubricating oil can be supplied to the oil deterioration detection system 60 without providing a driving force such as a pump. Also, as described above, in this embodiment, the first sensor unit 50, the second sensor unit 52, and the third sensor unit 54 are arranged, but the deterioration state of the lubricating oil can be measured with any one of the sensor units. Also, the arrangement positions of the sensor units are not limited to this.

[0022] Next, the oil deterioration detection systems 60, 70, and 80 will be described using Figure 2. The oil deterioration detection systems 60, 70, and 80 have the same basic configuration except for their locations, so the oil deterioration detection system 60 will be described below as a representative.

[0023] FIG. 2 is a schematic diagram showing the overall configuration of the oil deterioration detection system of this embodiment. The oil deterioration detection system 60 measures the deterioration state of lubricating oil flowing into a sensor line 62. The oil deterioration detection system 60 includes a measuring device 100, an arithmetic processing device (oil deterioration detection device) 101, and a temperature detection unit 103. In the oil deterioration detection system 60 of this embodiment, the measuring device 100, the temperature detection unit 103, and the arithmetic processing device (oil deterioration detection device) 101 are arranged in close proximity and connected by wires to transmit and receive data via the wiring, but this is not limited to this. The arithmetic processing device (oil deterioration detection device) 101 may communicate with the measuring device 100 and the temperature detection unit 103 wirelessly. Furthermore, the arithmetic processing device (oil deterioration detection device) 101 may transmit and receive data with the measuring device 100 and the temperature detection unit 103 via a public communication network.

[0024] The measuring device 100 applies an AC voltage to the lubricant flowing through the sensor line 62 and detects fluctuations in the impedance of the lubricant relative to the AC voltage. The measuring device 100 can switch the frequency of the AC voltage between multiple values ​​and detects the impedance of the lubricant relative to AC voltages of multiple frequencies.

[0025] The measurement device 100 includes a measurement unit 102, a substrate unit 104, and a power supply 106. The power supply 106 supplies power to the substrate unit 104. The measurement unit 102 includes a flow path 110, a counter electrode 112, and a working electrode 114. The flow path 110 is connected to the sensor line 62 and is a path through which the hydraulic oil flowing through the sensor line 62 flows. The counter electrode 112 and the working electrode 114 are two flat electrodes facing each other across the flow path 110. The counter electrode 112 and the working electrode 114 form part of the wall surface of the flow path 110. In other words, the counter electrode 112 and the working electrode 114 come into contact with the hydraulic oil flowing through the flow path 110.

[0026] The substrate unit 104 generates an AC voltage to be applied to the counter electrode 112 and the working electrode 114 of the measurement unit 102, supplies the voltage to the counter electrode 112 and the working electrode 114, and measures the impedance of the lubricant to which the AC voltage is applied. The substrate unit 104 includes a power supply circuit 120, a frequency control unit 121, a selector 122, an impedance measurement circuit 124, a calculation unit 126, and a communication unit 128.

[0027] The power supply circuit 120 is connected to the power supply 106 and supplies the power supplied from the power supply 106 to each unit, specifically, the frequency control unit 121, the impedance measurement circuit 124, the calculation unit 126, and the communication unit 128. The power supply circuit 120 boosts or lowers the power supplied from the power supply 106 and supplies the required current and voltage to each unit. The power supply circuit 120 may also have a function of converting AC to DC, or a function of converting AC to DC.

[0028] The frequency control unit 121 converts the frequency of the voltage supplied from the power supply circuit. The frequency control unit 121 includes oscillation circuits 130, 132, 134, 136, and 138. The oscillation circuits 130, 132, 134, 136, and 138 generate AC voltages at different frequencies that are set individually. The oscillation circuits 130, 132, and 134 generate AC voltages at a first specific frequency selected from a first frequency range. The oscillation circuits 136 and 138 generate AC voltages at a second specific frequency selected from a second frequency range.

[0029] Here, the first frequency range is a frequency range in which the calculation processing device 101 can process and determine the water content and base number contained in the lubricating oil. The first frequency range is preferably 50 mHz to 7 MHz. One of the first specific frequencies is 50 mHz to 10 Hz, one of the first specific frequencies is 10 Hz to 500 Hz, and one of the first specific frequencies is 500 Hz to 7 MHz. For example, the oscillator circuit 130 generates an AC voltage with a specific frequency of 1 kHz, the oscillator circuit 130 generates an AC voltage with a specific frequency of 100 Hz, and the oscillator circuit 130 generates an AC voltage with a specific frequency of 1 Hz.

[0030] Here, the second frequency range is a frequency range in which the calculation processing device 101 can process and determine the soot contained in the lubricant, and is a frequency range lower than the first frequency range. The second frequency range is preferably 0.25 mHz to 50 mHz. One of the second specific frequencies is 10 mHz to 50 mHz, and another of the second specific frequencies is 0.25 mHz to 10 mHz. For example, the oscillator circuit 136 generates an AC voltage with a specific frequency of 8 mHz, and the oscillator circuit 138 generates an AC voltage with a specific frequency of 1 mHz. Note that the first specific frequency and the second specific frequency are merely examples and are not limited thereto.

[0031] The selector 122 is disposed between the frequency control unit 121 and the counter electrode 112 and working electrode 114, and selects one of the oscillation circuits 130, 132, 134, 136, and 138, and applies the AC voltage generated by the selected circuit to the counter electrode 112 and working electrode 114.

[0032] The impedance measurement circuit 124 measures the impedance of the lubricating oil flowing through the flow path 110 by detecting the timing of application of the AC voltage and the amplitude of the current value from the counter electrode 112 and the working electrode 114 to which the AC voltage is applied. The impedance measurement circuit 124 sends the detected impedance value to the arithmetic processing device 101.

[0033] The calculation unit 126 generates signals that cause the substrate unit 104 to execute various processes. The calculation unit 126 has a CPU 140 and a memory 142. The CPU (Central Processing Unit) 140 executes various calculations. The memory 142 serves as a work area for the calculations of the CPU 140, and stores the calculation results of the CPU 140. The memory 142 also stores programs for the calculations executed by the CPU 140. The communication unit 128 communicates with the calculation processing device 101, and outputs the measurement results of the impedance.

[0034] The arithmetic processing device 101 analyzes the results measured by the measuring device 100, converts the impedance of the lubricant into an RC equivalent circuit, and creates a Nyquist diagram based on the converted results. The arithmetic processing device 101 stores information on the characteristics of the lubricant on a reference Nyquist diagram, compares the analysis results with the reference values, and calculates the deterioration state of the lubricant, specifically, the moisture value, base number, and soot amount, based on the comparison results. The analysis method will be described later. The arithmetic processing device 101 is a so-called personal computer, tablet, or the like, and includes a calculation unit such as a CPU, storage devices such as ROM and RAM, an input unit through which an operator inputs operations, a display unit, etc. In addition to the program for performing the arithmetic processing, the arithmetic processing device 101 also pre-calculates and stores information on parameters that serve as the evaluation criteria, analysis results for the reference lubricant, calculation criteria for the moisture value, base number, and soot amount based on deviations from the reference values, and information on temperature-dependent fluctuations.

[0035] The temperature detection unit 103 detects the temperature of the lubricating oil flowing through the sensor line 62. The temperature detection unit 103 sends the detection result to the arithmetic processing unit 101.

[0036] Next, an example of an oil deterioration detection method of the oil deterioration detection system will be described with reference to Figs. 3 to 15. Fig. 3 is a flowchart showing an example of an oil deterioration detection method of the oil deterioration detection system of this embodiment. Fig. 4 is an explanatory diagram for explaining the oil deterioration detection method. Figs. 5 to 7 are explanatory diagrams for explaining the water content detection process, respectively. Figs. 9 and 10 are explanatory diagrams for explaining the base number detection process. Figs. 11 and 12 are explanatory diagrams for explaining the oil deterioration detection method. Figs. 13 to 15 are explanatory diagrams for explaining the soot detection process, respectively.

[0037] The oil deterioration detection system 60 measures the temperature of the lubricating oil with the temperature detection unit 103 (step S12).

[0038] The oil deterioration detection system 60 selects a first specific frequency (step S14). Specifically, the selector 122 selects an oscillator circuit that generates an AC voltage to be applied to the measurement unit 102. In the present embodiment, one oscillator circuit is selected from the oscillator circuits 130, 132, and 134. The oil deterioration detection system 60 applies an AC voltage from the selected oscillator circuit to the measurement unit 102, and measures the impedance with the impedance measurement circuit 124 (step S16).

[0039] After measuring the impedance, the oil deterioration detection system 60 determines whether all impedances at the first specific frequency have been measured (step S18). In this embodiment, the oil deterioration detection system 60 uses the oscillator circuits 130, 132, and 134 to determine whether impedance measurements at three different first specific frequencies have been completed. If the oil deterioration detection system 60 determines that measurements have not been completed (No in step S18), it returns to step S14, selects an oscillator circuit that has not been measured, and measures the impedance.

[0040] If the oil deterioration detection system 60 determines that the measurement is complete (Yes in step S18), it performs equivalent circuit analysis based on the measurement results at the first specific frequency (step S20). FIG. 4 is an explanatory diagram for explaining an oil deterioration detection method. As shown in FIG. 4, the oil deterioration detection system 60 identifies three points on a Nyquist diagram based on the impedance values ​​detected at each of the three AC voltages of the first specific frequency, and creates a first arc 202 that passes through the three points. The arc 204 shown in FIG. 4 is a reference arc calculated based on the impedance measured with the lubricating oil in a reference state. In this embodiment, the arc 204 is an RC parallel circuit with a peak frequency of 100 Hz.

[0041] The oil deterioration detection system 60 executes a water contamination amount calculation process based on the results of the equivalent circuit analysis (step S22). The oil deterioration detection system 60 performs fitting between the calculated first arc 202 and the reference arc 204. If the oil deterioration detection system 60 determines that the first arc 202 matches the reference arc 204, it determines that water has not been mixed into the lubricating oil. Note that the determination criterion may be that the arc 204 is used as a reference and that a difference between the first arc 202 and the reference arc 204 is within a predetermined range to determine that they match. If the first arc 202 does not match the reference arc 204, the oil deterioration detection system 60 calculates the water content based on the arc size of the first arc 202 and the difference in size from the reference arc 204.

[0042] Figures 5 to 7 are explanatory diagrams illustrating the moisture content detection process. Figures 5 to 7 show the results of equivalent circuit analysis of measurement results when the moisture content of the same lubricant is changed. Figure 5 shows the relationship between frequency and resistance. Figure 6 shows the relationship between frequency and capacitance. Figure 7 is a Nyquist diagram created by analyzing the measurement results. As shown in Figures 5 to 7, the impedance of a lubricant changes when it contains moisture. Specifically, as shown in Figure 7, the arc of the Nyquist diagram becomes larger as the moisture content increases. Also, as shown in Figure 5, the relationship between frequency and resistance changes depending on the moisture content. On the other hand, as shown in Figure 6, the capacitance, which is the C component of the transmission circuit, does not change even when the moisture content changes.

[0043] Using the above relationship, the oil deterioration detection system 60 calculates the amount of water contained in the lubricant from the first arc of the Nyquist line, which is created based on the impedances calculated at the three first specific frequencies. FIG. 8 is an explanatory diagram for explaining the oil deterioration detection method. FIG. 8 is a graph showing the relationship between frequency and resistance for lubricant oils under various conditions. As shown in FIG. 8, by performing measurements at three first specific frequencies, 1 kHz, 100 Hz, and 1 Hz, it is possible to obtain impedances that show different characteristics of each lubricant oil.

[0044] The oil deterioration detection system 60 executes a base number calculation process based on the results of the equivalent circuit analysis (step S26). FIGS. 9 and 10 are explanatory diagrams for explaining the base number detection process. FIG. 9 is a graph showing the relationship between base number and resistance in the equivalent circuit analysis results. FIG. 10 is a graph showing the relationship between base number and capacitance in the equivalent circuit analysis results. As shown in FIGS. 9 and 10, the values ​​of the resistance and capacitance components of the equivalent circuit change depending on the base number of the lubricating oil. The resistance increases as the base number decreases. The capacitance fluctuates little until the base number reaches a predetermined value, and increases rapidly when the base number falls below the predetermined value. The oil deterioration detection system 60 calculates the base number from the capacitance and resistance value at the maximum value of the calculated vertex of the arc. In this embodiment, the result when the first specific frequency is 100 Hz is close to the maximum value of the vertex of the arc. Therefore, the base number can be calculated by using the capacitance and resistance value calculated using the impedance resulting from the first specific frequency being 100 Hz and the relationship shown in FIGS. 9 and 10. Here, when the base number of a lubricating oil falls below a certain level, it can be considered that the performance of the lubricating oil has deteriorated.

[0045] Next, the oil deterioration detection system 60 selects a second specific frequency (step S28). Specifically, the selector 122 selects an oscillator circuit that generates an AC voltage to be applied to the measurement unit 102. In the present embodiment, one oscillator circuit is selected from the oscillator circuits 136 and 138. The oil deterioration detection system 60 applies an AC voltage from the selected oscillator circuit to the measurement unit 102, and measures the impedance using the impedance measurement circuit 124 (step S30).

[0046] After measuring the impedance, the oil deterioration detection system 60 determines whether all impedances at the second specific frequencies have been measured (step S32). In this embodiment, the oil deterioration detection system 60 uses the oscillator circuits 136 and 138 to determine whether impedance measurements at two different second specific frequencies have been completed. If the oil deterioration detection system 60 determines that measurements have not been completed (No in step S32), it returns to step S28, selects an oscillator circuit that has not been measured, and measures the impedance.

[0047] When the oil deterioration detection system 60 determines that the measurement is complete (Yes in step S32), it performs equivalent circuit analysis based on the measurement results at the second specific frequency (step S34). FIGS. 11 and 12 are explanatory diagrams for explaining an oil deterioration detection method. As shown in FIGS. 11 and 12, the oil deterioration detection system 60 identifies three points on the Nyquist diagram based on the impedance values ​​detected using AC voltages of the two second specific frequencies and the maximum value on the real axis of arc 202 (the point where the imaginary number is 0), and creates second arcs 210 and 212 that pass through the three points. FIG. 11 shows the second arc 210 calculated based on a lubricating oil containing impurities. FIG. 12 shows the second arc 212 calculated based on a lubricating oil containing no impurities. In this embodiment, the foreign matter is soot. As shown in FIGS. 11 and 12, when no tin is mixed in, the diameter of the second circular arc 212 becomes large, and on the scale showing the first circular arc 202, it becomes large enough to be approximated as a straight line.

[0048] The oil degradation detection system 60 executes a foreign matter amount calculation process based on the results of the equivalent circuit analysis (step S36). The oil degradation detection system 60 performs fitting between the calculated second arc and a reference second arc. If the oil degradation detection system 60 determines that the second arc matches the reference second arc, it determines that soot is present in the lubricating oil. The determination criterion may be that the calculated second arc matches the reference second arc if the difference between the calculated second arc and the reference second arc is within a predetermined range. If the calculated second arc matches the reference second arc, the oil degradation detection system 60 calculates the amount of soot based on the size of the second arc and the slope of a linear approximation of the real axis of the second arc up to a predetermined value. The oil degradation detection system 60 may also determine that soot is not present if the second arc diverges or is larger than a predetermined value.

[0049] 13 to 15 are explanatory diagrams illustrating the soot detection process. FIGS. 13 to 15 show the results of equivalent circuit analysis of measurement results when the impurity content of the same lubricating oil is changed. FIG. 13 shows the relationship between frequency and resistance. FIG. 14 shows the relationship between frequency and capacitance. FIG. 15 is a Nyquist diagram created by analyzing the measurement results. As shown in FIGS. 13 to 15, the impedance of the lubricating oil at each frequency changes as the impurity content changes. As shown in FIG. 15, when soot is not present, the diameter of the second arc becomes larger and essentially diverges. When soot is present, an approximate arc of approximately the same height as the first arc can be formed. The oil degradation detection system 60 of this embodiment calculates the amount of soot based on the impedance at an AC voltage of 0.008 Hz.

[0050] The oil degradation detection system 60 of the present disclosure can detect lubricating oil degradation due to moisture, base number (acid), and foreign matter (soot) by detecting the impedance of the lubricating oil at a first specific frequency and a second specific frequency and performing equivalent circuit analysis. Specifically, moisture and base number can be evaluated by detecting the impedance at three or more first specific frequencies in a first frequency range and evaluating the impedance using a Nyquist diagram. Furthermore, soot can be evaluated by detecting the impedance at two or more second specific frequencies in a second frequency range and evaluating the impedance using a Nyquist diagram. This makes it possible to effectively detect moisture, foreign matter, and corrosive components (base number) that may adversely affect sliding parts when lubricating oil is supplied to the sliding parts.

[0051] In the above embodiment, the water content, base number, and soot were detected as the deterioration state of the lubricating oil. However, it is also possible to detect only the water content and base number, or only the water content. FIG. 16 is a schematic diagram showing the overall configuration of the oil deterioration detection system of this embodiment. In the oil deterioration detection system 60a shown in FIG. 16, the frequency control unit 121a includes oscillator circuits 130, 132, and 134, but does not include oscillator circuits 136 and 138. The oil deterioration detection system 60a only includes an oscillator circuit that generates an AC voltage in the first frequency range, and does not include an oscillator circuit that generates an AC voltage in the second frequency range. As a result, the oil deterioration detection system 60a can detect the deterioration state of the lubricating oil with fewer oscillator circuits, although the information on the deterioration state that can be detected is reduced.

[0052] In addition, in this embodiment, the number of first specific frequencies in the first frequency range is three, but it may be three or more, and it may be four or five or more. In this embodiment, the number of second specific frequencies in the second frequency range is two, but it may be two or more, and it may be three or four or more.

[0053] The oil deterioration detection systems 60, 70, 80 of the present disclosure include a measuring device 100 that applies AC voltages of at least three first specific frequencies selected from a first frequency range to the opposing electrodes while the oil to be evaluated passes between them to measure impedance, and a calculation processing device 101 that performs analysis based on the impedances of the at least three first specific frequencies measured by the measuring device, calculates an arc on a Nyquist diagram, and determines that moisture is present if the calculated arc is larger than a predetermined reference arc for the oil to be evaluated, and calculates the amount of moisture based on the shape of the calculated arc. In addition, the calculation processing device (oil deterioration detection device) 101 performs analysis based on the impedance of at least three first specific frequencies measured by applying AC voltages of at least three first specific frequencies selected from a first frequency range to the opposing electrodes while the oil to be evaluated passes between the opposing electrodes, calculates an arc on the Nyquist diagram, and if the calculated arc is larger than a predetermined reference arc of the oil to be evaluated that is calculated in advance, determines that moisture has been mixed in, and calculates the moisture content based on the shape of the calculated arc.

[0054] This makes it possible to detect the amount of moisture that causes deterioration of oil by detecting impedance.

[0055] The first frequency range is preferably 50 mHz to 7 MHz, inclusive. By setting the first frequency range within this range, the water content and base number can be suitably detected.

[0056] Preferably, one of the first specific frequencies is 50 mHz to 10 Hz, one of the first specific frequencies is 10 Hz to 500 Hz, and one of the first specific frequencies is 500 Hz to 7 MHz. By including three first specific frequencies that satisfy the above ranges, the arc can be calculated with high accuracy using the Nyquist diagram.

[0057] The measurement device preferably includes a plurality of oscillator circuits each of which emits the first specific frequency, and a selector for switching between the oscillator circuits. This allows for frequency switching with a simple configuration. Note that the measurement device may also use a separate mechanism to switch or change the frequency of the AC voltage.

[0058] The calculation processing device preferably calculates the resistance value by assuming the calculated capacitance of the arc to be the same as that of the reference arc, thereby calculating the moisture content. This makes it possible to suitably calculate the moisture content.

[0059] The calculation processing device preferably calculates the base number from the calculated maximum capacitance of the vertex of the arc and the resistance value, thereby making it possible to suitably detect the base number.

[0060] Preferably, the measurement device applies AC voltages of at least two second specific frequencies selected from a second frequency range lower than the first frequency range to the opposing electrodes to measure the impedance, and the calculation processing device performs analysis based on the maximum value of the real axis of the first arc, which is an arc based on the first specific frequency, and the impedances of the at least two second specific frequencies measured by the measurement device, calculates a second arc on the Nyquist diagram, and compares the second arc with a reference circle of the oil to be evaluated that has been calculated in advance to determine whether impurities are present. This allows for efficient detection of foreign matter.

[0061] The second frequency range is preferably 0.25 mHz to 50 mHz, inclusive, so that foreign matter can be suitably detected.

[0062] The impurity is preferably soot, and soot contamination can be suitably detected.

[0063] The oil deterioration detection method of the present disclosure includes the steps of applying AC voltages of at least three first specific frequencies selected from a first frequency range to the counter electrodes while the oil to be evaluated passes between the counter electrodes and measuring the impedance, performing an analysis based on the impedances of the at least three first specific frequencies measured by the measurement device and calculating an arc on a Nyquist diagram, and determining that moisture is present if the calculated arc is larger than a predetermined reference arc for the oil to be evaluated and calculating the moisture content based on the shape of the calculated arc. This allows the oil deterioration detection system 60 to detect the moisture content that causes oil deterioration by detecting the impedance.

[0064] It is preferable to further include a step of calculating the base number from the capacitance of the maximum value at the apex of the calculated arc and the resistance value. This enables the oil deterioration detection system 60 to detect the base number, which is the cause of oil deterioration, by detecting the impedance.

[0065] The oil deterioration detection method preferably includes the steps of applying AC voltages of at least two second specific frequencies selected from a second frequency range lower than the first frequency range to the opposing electrodes and measuring the impedance, calculating a second arc on a Nyquist diagram by performing an analysis based on the maximum value of the real axis of a first arc based on the first specific frequency and the measured impedances of the at least two second specific frequencies, and comparing the second arc with a reference circle of the oil to be evaluated that has been calculated in advance to determine whether impurities have been mixed in. This allows the oil deterioration detection system 60 to detect the presence of foreign matter that may cause oil deterioration by detecting the impedance. [Explanation of symbols]

[0066] 10 Power Generation System 12 Engine body 14 Supercharger 16. Generator 18 Lubricating oil supply unit 20 Lubricating Oil Tank 22 Lubricant Line 24 Pump 26 Cooler 28 filters 30 Backwash strainer 32 Bypass piping 34 Three-way valve 50 First sensor unit 52 Second sensor unit 54 Third sensor unit 60, 70, 80 Oil Deterioration Detection System 62, 72, 82 sensor lines 64, 76, 84 valves 100 Measuring Equipment 101 Processing device (lubricant deterioration detection device) 102 Measurement section 104 Circuit Board 106 Power supply 110 Distribution path 112 Opposite 114 Working electrode 120 Power supply circuit 121 Frequency Control Unit 122 Selector 124 Impedance measurement circuit 126 Arithmetic section 128 Communications Department 130, 132, 134 Oscillator circuits 140 CPU 142 memory

Claims

1. While the oil to be evaluated passes between the opposing electrodes, AC voltages of at least three first specific frequencies selected from a first frequency range are applied to the opposing electrodes, and an analysis is performed based on the impedances of at least three first specific frequencies measured, and an arc on a Nyquist diagram is calculated. If the calculated arc is larger than a predetermined reference arc of the oil to be evaluated, the oil is determined to contain moisture, and the amount of moisture is calculated based on the shape of the calculated arc. applying AC voltages of at least two second specific frequencies selected from a second frequency range lower than the first frequency range to the opposing electrodes to measure impedance, and performing analysis based on the maximum value of the real axis of a first arc based on the first specific frequencies and the measured impedances of the at least two second specific frequencies; calculating a second arc on a Nyquist diagram; and comparing the second arc with a reference circle of the oil to be evaluated that has been calculated in advance to determine whether impurities are present; An oil deterioration detection device that determines that no impurities are mixed in if the second arc is larger than the reference circle by a predetermined amount or more, or if the second arc diverges.

2. The oil deterioration detecting device according to claim 1 , wherein the first frequency range is from 50 mHz to 7 MHz.

3. one of the first specific frequencies is equal to or greater than 50 mHz and less than 10 Hz; one of the first specific frequencies is equal to or greater than 10 Hz and less than 500 Hz; 3. The oil deterioration detecting device according to claim 1, wherein one of the first specific frequencies is equal to or greater than 500 Hz and equal to or less than 7 MHz.

4. 4. The oil deterioration detection device according to claim 1, wherein the resistance value is calculated by assuming that the capacitance of the calculated arc is the same as the value of the reference arc, and the amount of moisture is calculated.

5. 5. The oil deterioration detecting device according to claim 1, wherein the base number is calculated from the calculated maximum capacitance of the vertex of the arc and the resistance value.

6. The oil deterioration detection device according to any one of claims 1 to 5, wherein the second frequency range is 0.25 mHz to 50 mHz.

7. The oil deterioration detecting device according to any one of claims 1 to 6, wherein the impurities are soot.

8. a measuring device that applies AC voltages of at least three first specific frequencies selected from a first frequency range to the counter electrodes while the oil to be evaluated passes between the counter electrodes, and measures impedance; The oil deterioration detection device according to any one of claims 1 to 7, The measuring device includes: a plurality of oscillation circuits each configured to emit the first specific frequency; and a selector for switching the oscillation circuit.

9. a step of applying AC voltages of at least three first specific frequencies selected from a first frequency range to the counter electrodes while the oil to be evaluated passes between the counter electrodes, and measuring impedance; performing an analysis based on the measured impedances of at least three first specific frequencies to calculate arcs on a Nyquist diagram; a step of determining that water is mixed in when the calculated arc is larger than a predetermined reference arc of the oil to be evaluated, and calculating the amount of water based on the shape of the calculated arc; applying AC voltages of at least two second specific frequencies selected from a second frequency range lower than the first frequency range to the counter electrode and measuring impedance; a step of calculating a second arc on a Nyquist diagram by performing an analysis based on a maximum value of a real axis of a first arc, which is an arc based on the first specific frequency, and the impedances of at least two second specific frequencies measured; and a step of comparing the second arc with a reference circle of the oil to be evaluated that is calculated in advance to determine whether impurities are present. An oil deterioration detection method that determines that no impurities are mixed in if the second arc is larger than the reference circle by a predetermined amount or more, or if it diverges.

10. The oil deterioration detection method according to claim 9, further comprising a step of calculating a base number from the calculated maximum capacitance of the vertex of the arc and the resistance value.

Images