Diagnostic method for oil and diagnostic system for oil

Abstract

To accurately determine a state of even oil in a very thin color or oil in a very thick color when color change of oil (to be measured) is measured by an optical sensor to detect property change of the oil.SOLUTION: The present invention relates to a diagnostic method for oil that uses an optical sensor having a white light source and an RGB sensor arranged, and the diagnostic method for oil includes setting the optical path length of light emitted from the white light source to reach the RGB sensor so that optical density at at least one of a wavelength B and a wavelength G is 0.05 to 1.5 when reflecting the light emitted from the white light source after transmitting it through oil to be measured, detecting the reflected light by the RGB sensor after transmitting the reflected light, reflected by the reflection plate, through the oil to be measured again, and evaluating properties of the oil to be measured based upon a detection signal from the RGB sensor.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an oil diagnostic technology. In particular, the present invention relates to a technology for monitoring machinery by measuring the color change of oil such as lubricating oil, insulating oil, processing oil, etc., which is used in the maintenance of large machinery that uses industrial oils, and by diagnosing the remaining life of the oil by measuring the color change of the oil that accompanies use. [Background technology]

[0002] Diagnosis of the properties of lubricants used in rotating parts such as bearings and gears is an important technique for the maintenance and preservation of large rotating machinery. Examples of large rotating machinery include wind power generator gearboxes, air compressors, ships, power generation turbines, construction machinery, agricultural machinery, cutting machines, pumps, and reduction gears for railway vehicles.

[0003] Besides lubricating oil, insulating oil is used in transformers and other devices for electrical insulation, and diagnostics of the properties of insulating oil are also important. Processing oils are also used during machining. There are various types of processing oils for various purposes, such as cutting oil, press processing oil, heat treatment oil, rust prevention oil, and cleaning oil. In this specification, industrial oils such as lubricating oil, insulating oil, and processing oil are sometimes collectively referred to as oil.

[0004] There are many different types of lubricating oils depending on their intended use. Various additives are blended into the base oil (oil used as the base material) so that each type of lubricating oil meets the required performance. Other oils may also contain additives to obtain the properties required for each type.

[0005] In recent years, machine condition monitoring has often adopted a strategy that minimizes the life cycle cost of the machine. Large machines such as power generation turbines use large amounts of lubricating oil, and changing the lubricating oil requires stopping the machine, which has negative aspects such as power generation loss and production stoppages. In addition, it requires costs for purchasing and shipping new oil, oil change work, and waste oil disposal, so it is desirable to use the lubricating oil for as long as possible. Refrigerant fluids in electric vehicles and data centers also undergo oil diagnosis, and replacement and hardware repairs are carried out. Similarly, the color of the insulating oil in transformers is monitored.

[0006] Recently, from the perspective of carbon neutrality, automobiles and other vehicles that use large amounts of petroleum-based fuels are being electrified, and fuel demand will decrease in the future. However, there are often no alternatives to industrial oil, and it is necessary to minimize usage by extending the oil change interval, etc. This is because reducing oil consumption reduces carbon dioxide emissions. However, overlooking oil deterioration and contamination can lead to machine breakdowns.

[0007] Regarding the diagnosis of lubricating oil properties, "deterioration" and "contamination" are defined and differentiated. Broadly speaking, it is necessary to diagnose two types of deterioration: (1) oxidative deterioration of lubricating oil over time, and (2) contamination by external contaminants such as water, dust, and wear powder.

[0008] (1) Oxidative deterioration of lubricating oils includes deterioration due to oxidation of the base oil and deterioration due to the consumption of additives. Oxidative deterioration of lubricating oils causes a decrease in wear resistance, changes in viscosity and viscosity index, a decrease in rust prevention properties, and a decrease in corrosion prevention properties. As a result, wear and material fatigue in gearboxes can be accelerated. While it is desirable to use oil for as long as possible, if abnormal deterioration or contamination is detected, it is necessary to change the oil promptly and inspect the equipment.

[0009] Regarding the change in transmittance in the three wavelengths of RGB (red, green, blue) of visible light, there is a method for diagnosing the timing of changing lubricating oil or signs of machine abnormalities based on the relative change from the transmittance of new oil, as described in Patent Document 1. It is described that diagnosis is made based on the change in the B value, which is the RGB value that shows the greatest change in transmittance due to oil deterioration.

[0010] There is a method for diagnosing oil deterioration using an optical sensor as described in Patent Document 2. In this sensor, the optical path length for measuring transmitted light is fixed. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2019-078718 A [Patent Document 2] WO2012 / 074109 A1 Summary of the Invention [Problem to be solved by the invention]

[0012] In the case of transmitted light measurement, as the deterioration of oil progresses, it is observed as a significant decrease in the RGB values, mainly the G and B values. In the case of oil contamination, when the oil becomes cloudy due to the ingress of water or when a large amount of soot or fine particles gets into the oil, the light from the light source is scattered regardless of wavelength, causing a decrease in all RGB values.

[0013] In the sensor that measures transmitted light, the light from the light source passes through the oil, measures the intensity of the light that reaches the RGB sensor located opposite, and outputs the result as voltage, current, etc. By evaluating the signal output of the RGB sensor, the properties of the oil can be indirectly measured.

[0014] However, when the color of the oil being measured is light, i.e., when the degree of light absorption by the oil being measured is small, the influences other than light absorption by the oil being measured become relatively large, and the measurement accuracy decreases. Specifically, the influences other than light absorption include electrical noise, fluctuations in the light source intensity, and dirt on the window material (glass, etc.).

[0015] When the oil to be measured is dark in color, that is, when the degree of light absorption by the oil to be measured is large, the oil to be measured absorbs almost all of the light, reducing the sensor signal strength and the measurement accuracy.

[0016] When trying to measure the properties of oil using conventional technology, there was a problem in that the characteristics could not be accurately measured for oils that were very light in color or very dark in color.

[0017] The objective of the present invention is to accurately determine the condition of oil (object of measurement) when detecting changes in the oil's properties by measuring color changes of the oil using an optical sensor, even when the oil is very light in color or very dark in color. [Means for solving the problem]

[0018] One aspect of the present invention is an oil diagnosis method which uses an optical sensor having a white light source and an RGB sensor, in which light emitted from the white light source is transmitted through the oil to be measured, then reflected by a reflector, and the reflected light reflected by the reflector is transmitted again through the oil to be measured, and then the reflected light is detected by the RGB sensor, and when evaluating the characteristics of the oil to be measured based on the detection signal of the RGB sensor, the optical path length from the white light source to the return to the RGB sensor is set so that the absorbance of at least one of wavelengths B and G is 0.05 or more and 1.5 or less.

[0019] Another aspect of the present invention is an oil diagnostic system comprising: an optical sensor, in which a white light source and an RGB sensor are arranged on the same plane and a distance between the white light source and the RGB sensor is fixed; a holding section that holds the oil to be measured isolated from the optical sensor; a wall constituting at least a part of the holding section and isolating the oil to be measured and the optical sensor; a first transparent section provided on the wall for transmitting light emitted from the white light source into the oil to be measured; a reflecting section provided on the wall for reflecting the light transmitted through the oil to be measured; and a second transparent section provided on the wall for receiving the light reflected by the reflecting section by the RGB sensor, wherein the optical path length of the light emitted from the white light source passing through the first transparent section, the oil to be measured, the reflecting section, the oil to be measured, and the second transparent section in this order to reach the RGB sensor is set so that the absorbance of at least one of wavelengths B and G is 0.05 or more and 1.5 or less. Effect of the Invention

[0020] According to the present invention, when an optical sensor is used to measure the color change of oil (object of measurement) and detect changes in the properties of the oil, the condition of the oil can be accurately determined even for oils that are very light in color or very dark in color.

[0021] Problems, configurations, effects, and the like other than those mentioned above will become apparent from the description of the embodiments below. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a graph showing the relationship between transmittance and absorbance. [Diagram 2] FIG. 2 is a graph showing the color change of engine oil with use. [Diagram 3] 1 is a graph showing the spectral sensitivity characteristics of an RGB color sensor. [Figure 4] FIG. 2 is a graph showing the color change of engine oil with use. [Diagram 5] FIG. 2 is a graph showing the color change of engine oil with use. [Figure 6] FIG. 2 is a graph showing the color change of engine oil with use. [Figure 7] FIG. 2 is a graph showing the color change of engine oil with use. [Figure 8] FIG. 1 is a conceptual diagram showing a configuration of an oil diagnosis system. [Figure 9] FIG. 11 is a table showing the relationship between the optical path length and the absorbance of oil. [Figure 10] FIG. 2 is a graph showing the relationship between absorbance and viscosity of oil. [Figure 11] FIG. 2 is a graph showing the relationship between absorbance and viscosity of oil. [Figure 12] FIG. 4 is a graph showing changes in various indicators accompanying deterioration of oil. [Figure 13] FIG. 4 is a graph showing changes in various indicators accompanying deterioration of oil. [Figure 14] FIG. 1 is a schematic diagram of a lubricant oil monitoring system for a wind turbine generator. [Figure 15] FIG. 1 is a conceptual diagram of a rotating part equipped with an optical sensor for lubricant. [Figure 16] FIG. 4 is a flow chart showing a lubricant diagnosis process. [Figure 17] FIG. 2 is a graph showing the concept of the results of acquiring lubricant color data (B / R value) stored in chronological order. [Figure 18] FIG. 11 is a graph showing the relationship between viscosity and elapsed time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The embodiments will be described in detail with reference to the drawings. However, the present invention should not be interpreted as being limited to the description of the embodiments shown below. It will be easily understood by those skilled in the art that the specific configuration can be changed without departing from the concept or purpose of the present invention.

[0024] In the configurations of the embodiments described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and duplicated explanations may be omitted.

[0025] When there are multiple elements having the same or similar functions, they may be described by using the same reference numeral with different subscripts. However, when there is no need to distinguish between multiple elements, the subscripts may be omitted.

[0026] The designations "first," "second," "third," and the like in this specification are used to identify components and do not necessarily limit the number, order, or content. Furthermore, numbers for identifying components are used in each context, and a number used in one context does not necessarily indicate the same configuration in another context. Furthermore, a component identified by a certain number does not prevent the component from also having the function of a component identified by another number.

[0027] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings, etc. may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings, etc.

[0028] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

[0029] In this specification elements expressed in the singular are intended to include the plural unless the context clearly indicates otherwise.

[0030] In the case of a sensor or device with a fixed optical path length, it is not possible to accurately measure the color of very light-colored oil or the color of very dark-colored oil. In the embodiment described below, when an optical sensor is used to measure the color change of the oil (measurement target) and detect changes in the oil's properties, the optimal optical path length is selected, or, among the RGB values, the G value or B value is selected according to the color intensity, and combined with the R value to accurately determine the state of the oil. This makes it possible to accurately evaluate the characteristics of oils that are very light-colored or very dark-colored using a non-contact optical sensor.

[0031] <Monitoring using oil color change> The method for monitoring machines using the color change of oil such as lubricating oil according to the embodiment is characterized in that, in diagnosing oil deterioration and contamination using an optical sensor in the visible range, the ratio of values ​​indicating transmittance at any two different wavelengths is used as an index to realize correct observation of oil deterioration. Note that, assuming that in principle (transmittance = 1 - absorptance), in the embodiment, transmittance and absorptance have the same meaning.

[0032] There are various types of lubricating oil, including engine oil, turbine oil, hydraulic oil, bearing oil, sliding surface oil, gear oil, compressor oil, and cutting oil. Lubricating oil is composed of base oil and additives. Additives include antioxidants, rust inhibitors, antifoaming agents, viscosity index improvers, oiliness improvers, extreme pressure additives, detergent dispersants, pour point depressants, and emulsifiers. Oils used for purposes other than lubrication include transformer oil, cleaning oil, and cutting oil. For many oils, color changes due to use can be used to determine when to change the oil or to indicate abnormalities in the machine.

[0033] Lubricating oils are composed of base oils and additives. Base oils include mineral oils made from petroleum, high-performance synthetic oils, and bio-oils made from plants. Synthetic oils are highly pure, very chemically stable, and do not easily deteriorate. Therefore, color changes in lubricating oils that use synthetic oils are often caused by the consumption of additives. On the other hand, mineral oils and bio-oils have low purity and contain ester structures that are somewhat chemically unstable, so the base oils can become discolored with use. Coloring can also occur due to the consumption of additives.

[0034] As a specific example of changes in oil color, new oil is colorless or pale yellow, and as the days of use pass, it turns from yellow, orange, reddish brown, and then dark brown. Depending on the type of oil, new oil may be dark in color, and the color may turn even darker with use. Also, new oil may be colorless or pale yellow, and the color may change only slightly even after long periods of use.

[0035] <Absorbance conditions> When determining the color coordinates of the oil to be measured by measuring transmitted light, it is necessary to select the optical path length according to the absorbance of the oil to be measured. Note that in this specification, the optical path length refers to the physical length of the optical path (physical dimension).

[0036] According to Lambert's law, absorbance is proportional to the optical path length, and according to Beer's law, absorbance is proportional to the concentration. The absorbance of a measured object such as a lubricant is A, the incident intensity of the light from the transmitted light measurement light source to the measured object is I0, and the intensity when the light passes through the measured object and is detected by the RGB sensor is I. x Then, the absorbance A is expressed by the following equation according to Beer-Lambert's law.

[0037] A = -log 10 (I x / I0) …(1) A = k*c*L …(2) Here, k is a proportionality constant, c is the concentration, and L is the optical path length.

[0038] When the color of the oil to be measured is light (for example, absorbance less than 0.05), the influence of factors other than light absorption by the oil to be measured becomes relatively large, and the measurement accuracy decreases. Specifically, influences other than light absorption include electrical noise, fluctuations in light source intensity, and dirt on the window material (glass, etc.). For example, when the absorbance A of the oil to be measured is 0.022 (transmittance 95%), if dirt that reduces the transmittance by 1% adheres to the flow path wall, the absorbance will become 0.027, a change of 23%. The absorption by dirt has a large effect on the absorption by the oil to be measured, and the accuracy of the color measurement decreases.

[0039] If the oil to be measured is dark in color (for example, absorbance over 1.5), the oil to be measured absorbs almost all of the light, reducing the measurement accuracy. In addition, the effect of dirt adhesion becomes greater. For example, when the absorbance of the oil to be measured is 1.500 (transmittance 3.16%), if dirt that reduces the transmittance by 1% adheres to the flow path wall, the absorbance will become 1.666, a change in absorbance of 12%, and the absorption by the dirt will have a large effect and reduce the accuracy of the color measurement. Therefore, for example, an absorbance of 1.5 is set as the allowable limit.

[0040] Considering the measurement accuracy, it is desirable to optically measure the oil to be measured in the range where the absorbance A is 0.02 or more and 2.00 or less. More preferably, it is desirable to optically measure the oil to be measured in the range where the absorbance A is 0.05 or more and 1.50 or less.

[0041] <Absorbance and Transmittance> Figure 1 is a graph showing the relationship between absorbance and transmittance. According to the formula (1) of the above Lambert-Beer's law, absorbance and transmittance are mutually convertible and have the relationship as shown in Figure 1. The output of the optical sensor is proportional to the transmittance.

[0042] <RGB Color Diagnosis> Measure the absorbance or transmittance at RGB three wavelengths, for example, 460 nm, 540 nm, and 620 nm with an optical sensor to diagnose the degree of deterioration of the lubricating oil. Most of the oils to be measured show absorption for light in the range of wavelengths from 400 nm to 800 nm. The wavelengths of RGB to be measured also vary depending on the characteristics of the sensor, but an error of about plus or minus 10% is generally allowed. The RGB sensor measures the light of the light source that has passed through the lubricating oil and outputs it as a voltage value or a current value. This output value corresponds to the value of the transmittance of light for each wavelength.

[0043] <Ratio and ΔE> The diagnosis of the deterioration of the lubricating oil by RGB values is to normalize the RGB values when measuring the new oil to (255, 255, 255) or (100, 100, 100), ΔE = √(R 2 + G 2 + B 2 ) MCD = (the difference between the maximum value and the minimum value among RGB) There is a diagnostic method using these two indicators.

[0044] In addition, there is a diagnostic method based on the change in RGB values. Also, for example, there is a diagnostic method using the ratio of two values selected from RGB, such as B / R and G / R.

[0045] These estimate the characteristic changes of the oil to be measured based on the color change of the oil to be measured. According to a typical diagnostic method, for a sample equivalent to the oil to be measured in advance, data reflecting the color change over time and data on characteristic changes are acquired, a calibration curve is obtained from the correlation between the color change and the characteristic change, and a threshold value indicating the boundary of the preferable characteristics is set, enabling the diagnosis of the oil to be measured.

[0046] <Switching between B and G> Preferable conditions for absorbance to obtain good quantitativeness are, for example, 0.05 or more and 1.5 or less. It is advisable to create a calibration curve for diagnosing the deterioration of lubricating oil in advance. For example, when setting a threshold value for viscosity and monitoring, the RGB values when the viscosity reaches the threshold value are measured in advance using deteriorated oil. From the absorbance transition of the lubricating oil from new oil to reaching the threshold value, the optical path length and which value of B and G to use for monitoring can be determined.

[0047] In many cases, among RGB, the change in R is the smallest, the change in B is the largest, and G often shows a value between R and B. When performing diagnosis based on the ratio of two values selected from RGB, since R is positioned like a baseline, the absorbance of R may be less than 0.05, and for G and B, it is desirable that they are 0.05 or more and 1.5 or less.

[0048] <Color change due to deterioration> Figure 2 is a diagram showing the color change (absorbance) accompanying the use of engine oil. The absorbance of the oil with respect to the wavelength shown on the horizontal axis is shown on the vertical axis. A is new oil, B is oil used for 2 months, C is oil used for 6 months, and D is the absorbance in the visible range of oil used for 1 year.

[0049] The apparent color of new oil A was light brown, B was brown, C was slightly dark brown, and D was dark brown. Similar color changes occur in gear oil, turbine oil, hydraulic operating oil, bearing oil, sliding surface oil, compressor oil, cutting oil, rolling oil, and insulating oil. It can be seen that the degree of change in absorbance accompanying the use of the oil differs at each wavelength of RGB.

[0050] Figure 3 shows the spectral sensitivity characteristics of an RGB color sensor composed of a Si photodiode array. It uses 3-channel (RGB) photodiodes with sensitivity to blue (wavelength 460 nm), green (wavelength 540 nm), and red (wavelength 620 nm). This color sensor has spectral sensitivity characteristics close to human eye sensitivity, and can be used to express the color of oil as a color coordinate.

[0051] Absorbance and transmittance are defined as follows: When light passes through a sample of a certain optical path length, Absorbance = -log(I i / I0) Transmittance (%)= (I0 / I i ) x 100 Here, I i is the incident light intensity, and I0 is the transmitted light intensity. As is clear from the formula, absorbance and transmittance can be converted into each other.

[0052] Figure 2 shows the color change (absorbance) of engine oil measured with an RGB color sensor with the characteristics shown in Figure 3. The R (Red) value has a small change, the B (Blue) value has a larger change than R and G, and the G (Green) value has a change between R and B.

[0053] Here, the color of new engine oil is measured by an RGB color sensor, and the color coordinates of the new oil are (255, 255, 255). The color coordinates of the new oil can be, for example, (100, 100, 100), or may be values ​​such as (100, 97, 80). The colors of used oil and deteriorated oil can be measured using the same measurement method as that of new oil. There is also a method of selecting two values ​​from the three RGB values ​​and evaluating them as a ratio of the two values, for example, B / R, G / R, R / B, and R / G. In this case, the color coordinates of the new oil may be normalized to (255, 255, 255) or (100, 100, 100) and then the ratio may be obtained, or the voltage output value or current output value of the sensor may be used. For example, the maximum voltage output value of the RGB sensor may be set to 100, and the other two values ​​may be relative values ​​when the maximum value is set to 100.

[0054] <Optical path length> The results shown in Figure 2 are for an optical path length (2d in this case) of 10 mm. Assume that light emitted from a light source is reflected by a reflecting surface located at a distance d (5 mm in this case), and the light that returns after a round trip optical path of 10 mm is detected. Since the absorbance at wavelength B (460 nm) is greater than 0.05 and does not exceed 1.5, the absorbance at B and R (620 nm) can be used to diagnose engine oil deterioration. Since the absorbance at wavelength G (540 nm) is also greater than 0.05 and less than 1.5, the value of wavelength G can be used to diagnose engine oil deterioration. Since the absorption change in the measured oil is greater for wavelength B than for wavelength G, it can be said that the sensitivity to aging is good.

[0055] FIG. 4 is a graph showing the color change (absorbance) of engine oil measured with an RGB color sensor having the characteristics shown in FIG. 3 with an optical path length of 40 mm.

[0056] FIG. 5 is a graph showing the color change (absorbance) of engine oil measured with an RGB color sensor having the characteristics shown in FIG. 3 with an optical path length of 20 mm.

[0057] FIG. 6 is a graph showing the color change (absorbance) of engine oil measured with an RGB color sensor having the characteristics shown in FIG. 3 with an optical path length of 2.0 mm.

[0058] FIG. 7 is a graph showing the color change (absorbance) of engine oil measured with an RGB color sensor having the characteristics shown in FIG. 3 with an optical path length of 1.0 mm.

[0059] Since absorbance is proportional to the optical path length, for example, when the optical path length is 40 mm, it will look like Figure 4. If engine oil deterioration is diagnosed using absorbance at wavelengths B (460 nm) and R (620 nm), new oil A has an absorbance at wavelength B of 1.5 or less, but samples B, C, and D have absorbances that far exceed 1.5, so it is not appropriate to use wavelength B. On the other hand, the absorbance at wavelength G (540 nm) does not exceed 1.5 for any of the samples, so it is better to use the values ​​of G and R.

[0060] The absorbance of engine oils A, B, C, and D when the optical path length was 20 mm was as shown in Figure 5. In this case, the absorbance of sample D was too high to use wavelength B for diagnosing engine oil deterioration, so it is better to use wavelength G.

[0061] Thus, for diagnosing oil deterioration, it is advisable to select a wavelength between wavelengths B and G whose absorbance is between 0.05 and 1.5.

[0062] Figure 6 shows the absorbance when the optical path length is 2 mm. This shows that the optical path length is insufficient to accurately diagnose the deterioration of this oil. Similarly, Figure 7 shows the absorbance when the optical path length is 1 mm, which is insufficient to diagnose the deterioration of this oil.

[0063] In this way, by changing the optical path length depending on the color depth of the oil, it is possible to perform accurate deterioration diagnosis.

[0064] <Diagnostic system type> 8 is a cross-sectional view showing an example of a system configuration for measuring oil color. An oil diagnosis system 800 includes an oil flow path 810, an optical sensor 820, and an information processing device 830. The characteristics of a measurement target oil 812 flowing through the flow path 810, for example from left to right in the figure, are measured by the optical sensor 820, and the measured data is processed by the information processing device 830. This system makes it possible to select the wavelengths (B and G) used in oil deterioration diagnosis and to set at least one of the optical path length.

[0065] The information processing device 830 includes an input device 831, an output device 832, a processing device 833, and a storage device 834. The information processing device 830 may be, for example, a general server or a personal computer. The storage device 834 stores calibration curve data 8341, which will be described later. In addition, diagnostic software 8342 is stored. Measurement data from the optical sensor 820 is input to the input device 831 and processed by the processing device 833. The processing result is output by the output device 832. The processing for diagnosis is performed by the processing device 833 reading out the diagnostic software 8342 and executing it.

[0066] In the optical sensor 820, a white light source 821 and an RGB sensor 822 are mounted on a housing 823. The white light source 821 and the RGB sensor 822 are fixed to the housing 823, and the interval (2×d2) is fixed. By integrating the white light source 821 and the RGB sensor 822, it becomes easy to mount them in the oil diagnosis system 800.

[0067] Of the wall surfaces constituting the flow channel 810, the wall surface close to the optical sensor 820 is a transparent flow channel wall 811, which has a sufficient transmittance, for example, 90% or more, to the light from the white light source 821 and the light incident on the RGB sensor 822. Of the wall surfaces constituting the flow channel 810, the wall surface farther from the optical sensor 820 is a visible light reflector 813, which has a sufficient reflectance, for example, 90% or more, to the light from the white light source 821. The cross-sectional shape of the flow channel 810 may be circular or rectangular, and is arbitrary.

[0068] The white light source 821 and the RGB sensor 822 arranged on the same plane are in contact with the transparent flow path wall 811. The light emitted from the white light source 821 is transmitted through the transparent flow path wall 811 and the measured oil 812, and then enters the visible light reflector 813 at an incident angle θ. The reflected light reflected by the visible light reflector 813 at a reflection angle θ is detected by the RGB sensor 822. By arranging the white light source 821 and the RGB sensor 822 via the transparent flow path wall 811 in this way, the measured oil 812, the white light source 821, and the RGB sensor 822 can be isolated, making it easier to maintain and manage the system. Note that instead of making the entire transparent flow path wall 811 transparent, the parts in contact with the white light source 821 and the RGB sensor 822 may be transparent windows.

[0069] When the flow path width of the flow path 810 filled with the oil to be measured 812 is d1, the optical path length passing through the oil to be measured 812 is 2L, and the distance between the white light source 821 and the RGB sensor 822 is twice d2, the following relationship holds: L=d1 / cosθ L = √((d1) 2 + (d2) 2 )

[0070] At this time, in order to accurately measure the color coordinates of the oil to be measured, it is preferable that the optical path length 2L is adjusted so that the absorbance of wavelength G or B is 0.05 or more and 1.5 or less. In a system using an RGB sensor 822 in which the positional relationship between the white light source 821 and the RGB sensor 822 is fixed as described above (i.e., a system in which d2 is invariable), it is preferable to adjust the flow path width as follows to obtain a preferable optical path length 2L, or alternatively or in addition, to have the diagnostic software 8342 select a wavelength that provides a preferable absorbance.

[0071] 8, if d2 is constant, in order to adjust the optical path length 2L, it is necessary to adjust at least one of the optical path length between the white light source 821 and the visible light reflector 813 and the optical path length between the RGB sensor 822 and the visible light reflector 813. In a typical example, by appropriately adjusting the flow path width d1, it is possible to adjust the optical path length 2L and appropriately adjust the absorbance. A specific example of the flow path width d1 is the diameter of the pipe that constitutes the oil flow path 810.

[0072] 8, the white light source 821 and the RGB sensor 822 are in contact with the transparent flow path wall 811, but for example, a structure can be used in which the light of the white light source 821 is reflected by a mirror and then incident on the oil to be measured 812, or the light is reflected by a mirror just before the RGB sensor 822 and then received by the RGB sensor 822. Furthermore, a structure in which a prism or lens is interposed can also be used. By employing these configurations, the optical path length from the white light source 821 to the RGB sensor 822 can be adjusted.

[0073] <Sensor installation> The optical sensor 820 can measure the color of the oil without directly contacting the oil 812 to be measured. The sensor can be installed in a place similar to a level gauge for checking the oil level. Alternatively, the optical sensor 820, oil flow path 810, and visible light reflector 813 may be installed in an oil tank, bypass line, or the like. However, the oil to be measured does not need to be flowing, and may be measured in a stagnant area such as a tank.

[0074] <Scope of application> The types of oil that can be diagnosed by color measurement using the optical sensor 820 include engine oil, turbine oil, hydraulic oil, bearing oil, sliding surface oil, gear oil, compressor oil, cutting oil, insulating oil, cutting processing oil, press processing oil, heat treatment oil, rust prevention oil, cleaning oil, etc. There are no particular limitations on the devices that use the oil. EXAMPLES

[0075] Here is an example of gear oil diagnosis. New oil (sample 1) and gear oils with different degrees of deterioration, one month old (sample 2), three months old (sample 3), and six months old (sample 4), were collected. The viscosity threshold value (200 cP) was used to determine whether this oil needed to be changed. The viscosity of new oil was 160 cP, but the viscosity increased with use, and sample 4's viscosity was 200 cP, so it was decided to change it.

[0076] FIG. 9 is a table showing the results of measuring these four samples (ASTM1 to ASTM4) using the oil diagnostic system 800 of FIG. 8. In the system of FIG. 8, the light from the white light source 821 is incident at θ=60°. The absorbance at the three RGB wavelengths was measured by filling a flow path with a gear oil sample and setting it to four different optical path lengths (d1=2 mm, 5 mm, 6.8 mm, 10 mm). The output value of the optical sensor 820 was converted into absorbance.

[0077] The table in Figure 9 shows the absorbance at wavelengths B (460 nm), G (540 nm), and R (620 nm) for each optical path length. As this gear oil deteriorates, among RGB, the absorbance at wavelength B increases the most, and the absorbance at wavelength R changes the least, so it is desirable to make a diagnosis using the ratio of B to R.

[0078] FIG. 10 shows the relationship between the absorbance and viscosity of B when the flow path width d1 is 2 mm in FIG. 8. In this embodiment, by using the calibration curve showing the relationship between the color information obtained by the optical sensor and the characteristics of the oil to be measured, it is possible to estimate the characteristics of the oil to be measured without contact. The data of the calibration curve as shown in FIG. 10 is stored in the storage device 834 shown in FIG. 8 as the calibration curve data 8341, and the color information obtained by the optical sensor 820 is input from the input device 831. The processing device 833 uses the diagnostic software 8342 to compare the calibration curve with the color information and perform necessary calculations, and the estimated characteristics of the oil to be measured are output from the output device 832. At this time, the diagnostic software 8342 determines the wavelength to be used for diagnosis based on the data shown in FIG. 9 in advance, for example, as follows.

[0079] Figure 11 shows the relationship between B / R and viscosity when the flow path width d1 is 2 mm in Figure 8. Here, when calculating B / R, the sensor output value corresponding to the transmittance was used.

[0080] The optical path length suitable for each sample was determined based on the condition that the absorbance was between 0.05 and 1.5.

[0081] Referring to FIG. 9, when the flow path width d1 = 2 mm, the absorbance at wavelength B (460 nm) was 0.06 to 1.50, which roughly met the conditions, and therefore diagnosis could be performed using the ratio of B to R.

[0082] Referring to Figure 9, when the flow path width d1 = 5 mm, the absorbance at wavelength B exceeded 1.5 for samples 3 and 4. On the other hand, the absorbance at wavelength G (540 nm) of new oil was 0.041, which was below 0.05, but exceeded 0.05 soon after use began, so a diagnosis was made using the value of wavelength G.

[0083] Referring to FIG. 9, when the flow path width d1=6.8 mm, the absorbance at wavelength G was between 0.05 and 1.5, so the value of wavelength G was used for diagnosis.

[0084] Referring to FIG. 9, when the flow path width d1=10 mm, the absorbance exceeded 1.5 for both wavelengths B and G before reaching the viscosity threshold value.

[0085] When the flow path width d1 was set to 1 mm, the flow path width was too narrow for the oil to flow, and no measurement was performed.

[0086] As a result of these studies, it became clear that the flow path width d1 should be set between 2 mm and 6.8 mm. EXAMPLES

[0087] Here is an example of a diagnosis of hydraulic oil (hereinafter referred to as hydraulic oil) for a large ship. It was measured using the oil diagnosis system 800 in Figure 8. d2 = 6 mm, θ = 72°. This hydraulic oil was supposed to be replaced when the total acid number reached 2.

[0088] The optical path length was set to d1 = 3 mm because the absorbance of wavelength B was set to be within the range of 0.05 to 1.5 from the new oil until the total acid number threshold was reached.

[0089] Figure 12 shows the changes in viscosity, total acid number, antioxidant concentration, contamination level, and B / R value measured by an optical sensor that accompany the use of hydraulic oil. The color coordinates (R, G, B) of new oil were set to (255, 255, 255) using the output of the optical sensor.

[0090] Here, the contamination level is a value determined by the mass method as specified in the JIS B 9931 standard. An increase in contamination level means that the amount of organic insoluble matter increases due to oxidation of the hydraulic oil. There is a correlation between the contamination level and the B / R value, and by creating a calibration curve in advance, it is possible to monitor the increase in contamination level by measuring the B / R value. In the example of Figure 12, the timing of contamination level 5 can be detected when the B / R value becomes approximately 1.2 or less.

[0091] The degree of contamination based on this mass method has a strong correlation with the formation of sludge and varnish in lubricating oil, and the formation of sludge and varnish can be predicted by monitoring the degree of contamination.

[0092] The above example shows the monitoring of the degree of contamination, but the viscosity, total acid number, antioxidant concentration, and water contamination can also be monitored using the B / R value in the same way. EXAMPLES

[0093] An example of gas engine oil diagnosis is shown in Figure 13. Figure 13 shows the changes in viscosity, total acid number, antioxidant concentration, and B / R that occur with the use of engine oil that uses mineral oil as the base oil.

[0094] Measurements were made using the oil diagnostic system 800 in Figure 8. d2 = 5 mm, d1 = 7 mm, and θ = 66°. This gas engine oil used synthetic oil as the base oil, and was a type of oil that did not darken in color even with use. The RGB output values ​​were not standardized with the values ​​for new oil, and the output values ​​were used as is to make the diagnosis.

[0095] The viscosity is the kinematic viscosity (unit: cP) at 40°C, and the antioxidant concentration is the relative concentration (antioxidant concentration of new oil is set to 1) determined by FT-IR (Fourier transform infrared spectroscopy). The viscosity of this engine oil increases with use, and the viscosity could be monitored using a calibration curve created from the correlation between viscosity and B / R value.

[0096] The total acid number and antioxidant concentration can also be monitored using the B / R value. EXAMPLES

[0097] In this embodiment, the above-mentioned monitoring method is applied to a system and method for monitoring lubricating oil for a wind power generator. This embodiment is a monitoring system for lubricating oil supplied to a mechanical drive unit of a wind power generator. This system includes an input device, a processing device, a storage device, and an output device. The storage device stores additive concentration data that stores the concentration of additives in the lubricating oil in chronological order, and the processing device estimates the time at which the additive concentration in the lubricating oil, which is determined from the chromaticity characteristics of the lubricating oil, will reach a predetermined threshold value, based on optical sensor data that measures the chromaticity of the lubricating oil, which can quantify the additive concentration in the lubricating oil.

[0098] This embodiment is a method for monitoring the lubricant of a wind power generator using an optical lubricant sensor, using a server equipped with a processing device, a storage device, an input device, and an output device. This method executes a first step of acquiring chromaticity data of the lubricant of the wind power generator, a second step of measuring the concentration of additives contained in the sample, a third step of storing the measured additive concentrations in a chronological order in the storage device to obtain additive concentration data, and a fourth step of estimating the time at which the additive concentration will reach a predetermined threshold value by the processing device processing the additive concentration data.

[0099] (1. Overall system configuration) A schematic diagram of a lubricant monitoring system for a wind power generator having a lubricant supply system is shown in Figure 14. Inside the nacelle 3 of the wind power generator 1, there are a main shaft 31, a gearbox 33, a generator 34, and bearings such as yaw and pitch bearings (not shown), which are supplied with lubricant from an oil tank 37. In addition, the wind power generator also has the general components such as a hub 4, a nacelle bulkhead 30, a shrink disk 32, a main frame 35, a radiator 36, and a coupling 38.

[0100] 14, multiple wind turbines 1 are usually installed on the same site, and are collectively referred to as a farm 200a, etc. Each wind turbine 1 is equipped with various sensors (not shown) in the lubricating oil supply system, and sensor signals reflecting the state of the lubricating oil are collected in a server 210 in the nacelle 3.

[0101] Furthermore, the sensor signals obtained from the server 210 of each wind turbine 1 are sent to an aggregation server 220 arranged for each farm. Data from the aggregation server 220 is sent to the central server 240 via the network 230. Data from other farms 200b and 200c is also sent to the central server 240. Furthermore, the central server 240 can send instructions to each wind turbine 1 via the aggregation server 220 and server 210. In this way, the system of the embodiment enables remote monitoring of oil.

[0102] (2. Sensor placement) 15 is a conceptual diagram of a rotating part equipped with a lubricant sensor. Lubricant is supplied to a rotating part 302 from a lubricant supply device 301 such as a pump. The lubricant supply device 301 is connected to an oil tank 37 and receives the supply of lubricant. The rotating part 302 is, for example, a gearbox 33 or other general part where mechanical contact occurs, and is not particularly limited.

[0103] The optical sensor 304 is disposed in the flow path of the lubricant to detect the state of the lubricant. In this embodiment, a transparent measuring unit 303 is provided in a flow path (near the end of the lubricant path) branched from the lubricant flow path connected to the lubricant drain port of the rotating part 302, and a part of the lubricant is introduced into this measuring unit 303. The optical sensor 304 is then installed in the measuring unit 303. That is, the oil diagnosis system 800 of FIG. 8 is disposed at the position of the measuring unit 303. The reason why the measuring unit 303 is not provided in the main flow path of the lubricant is to adjust the flow rate of the lubricant in the measuring unit 303 to a flow rate suitable for detecting the state of the lubricant. The lubricant discharged from the rotating part 302 returns to the oil tank 37 via the filter 305. Note that the filter 305 is not essential. The optical sensor 304 measures the color coordinate of the lubricant. The state of the lubricant can be evaluated based on the change in the color coordinate of the lubricant over time.

[0104] In this embodiment, the optical sensor 304 includes an optical sensor equipped with a visible light source and a light receiving element. The optical sensor acquires chromaticity information (R, G, B values) of the lubricating oil. The optical sensor 304 acquires chromaticity data by transmitting visible light from a visible light source into the oil and detecting the visible light transmitted through the oil with light receiving elements having sensitivity to R, G, and B, respectively. The acquired chromaticity data reflects the oil's absorption rate or transmittance for light of each wavelength. The ratio of the two wavelengths is calculated from the acquired chromaticity data, and the amount of remaining additive in the lubricating oil is calculated using a calibration curve previously calculated from the correlation between the ratio of the two wavelengths and the amount of remaining additive, and deterioration diagnosis and remaining life diagnosis are performed.

[0105] The quality of lubricating oil deteriorates with use and it no longer performs its initial function. For this reason, maintenance such as replacement is required depending on the deterioration of the quality. In order to know the timing of such maintenance, it is useful for the efficiency of maintenance management to be able to monitor data that can be collected by optical sensors 304 installed on-site at a remote location. The data collected by the optical sensors 304 is collected, for example, in a server 210 in the nacelle 3, and then sent to a central server 240 that collects data from multiple farms via an aggregation server 220 that aggregates data within the farm 200.

[0106] However, for analyses that require equipment for measurement, such as LC (liquid chromatography), FT-IR, and NMR (nuclear magnetic resonance), samples of the lubricating oil must be collected as appropriate and analyzed using separately provided equipment. It is desirable to store the results of these LC, FT-IR, and NMR measurements as data separately in the central server 240, consolidate the data, and take these data into consideration when understanding the properties of the lubricating oil.

[0107] The data to be collected may include not only data related to the lubricant but also data showing the operating status of the wind turbine. For example, the wind turbine output value (the higher the output value, the faster the lubricant deteriorates), the actual operating time (the longer the operation time, the faster the lubricant deteriorates), the machine temperature (the higher the temperature, the faster the lubricant deteriorates), the shaft rotation speed (the faster the speed, the faster the lubricant deteriorates), etc. These can be collected from sensors of known configurations installed at various points on the wind turbine or from the control signals of the device.

[0108] (3. Lubricant diagnosis flow) FIG. 16 is a flow diagram showing the lubricant diagnosis process according to this embodiment. The process shown in FIG. 16 is performed under the control of any of the server 210, the aggregation server 220, and the central server 240 in FIG. 14. An example of the configuration of the server 210, the aggregation server 220, and the central server 240 is shown in FIG. 8 as the information processing device 830. In the following example, it is assumed that the central server 240 performs the functions of calculation and control. The software stored in the storage device of the server is executed by the processor, and the predetermined processing is realized in cooperation with other hardware. Note that functions equivalent to those configured by software can also be realized by hardware such as FPGA (Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit).

[0109] When the central server 240 performs control, since it has multiple wind power generators 1 under its control, the following processing is performed for each wind power generator. This processing is basically a repetitive process, and the start timing is set by a timer or the like, for example, starting the processing at midnight every day (S601). Also, the central server 240 can perform the processing at any timing according to the operator's instructions.

[0110] In step S602, the central server 240 checks when the lubricant should be changed. The initial value of the change time can be calculated physically, for example, by using the Arrhenius reaction rate, assuming that the lubricant is operating at the design temperature, and the remaining life can be initially set. This change time can be updated later in step S610 based on actual measurement data.

[0111] If it is time to change the lubricant, the lubricant is changed in step S603. Since changing the lubricant is usually done by a worker, the central server 240 displays and notifies the worker when and what to change.

[0112] If it is not time to change the lubricant, in step S604, the central server 240 performs diagnosis using the sensor data. In addition to the lubricant color information obtained by the optical sensor, the sensor data may include temperature, oil pressure, and the concentration of particles contained in the lubricant. The data collected by the optical sensor 304 is sent to the central server 240, which evaluates the characteristics of the lubricant, for example, by comparing the parameters obtained from the sensor with predetermined thresholds.

[0113] If the diagnosis result in step S605 is abnormal, the lubricating oil is changed in step S603. If no abnormality is found, step S606 is performed. In step S605, for example, if the B / R value based on the R, G, and B values ​​of the optical sensor changes from a decrease to an increase, it is determined that there is a contamination abnormality. In process S605, the judgment may be made using the G / R value, B value, G value, and ΔE value.

[0114] In S605, using the correlation between viscosity and B / R, if the viscosity calculated from the B / R value measured by the optical sensor exceeds a predetermined threshold, it is determined that there is an abnormality in the viscosity. It is also possible to determine that there is an abnormality in the viscosity when the B / R is smaller than a predetermined threshold without calculating the viscosity from the B / R value.

[0115] In process S606, the chromaticity measurement data and the like are input to the central server 240, and the data is stored in chronological order.

[0116] From the standpoint of preventive and planned maintenance of wind turbine generators, it is desirable to perform predictive diagnosis of deterioration of the lubricating oil based on changes in the concentration of additives contained in the lubricating oil before it is determined that there is an abnormality.

[0117] FIG. 17 is a graph diagram showing the concept of the results of acquiring chromaticity data (B / R value) of lubricating oil stored in chronological order. The horizontal axis indicates time (months), and the vertical axis indicates B / R. For example, B / R is observed at fixed points, and chromaticity data up to 60 months is plotted. A significant relationship is observed between the elapsed time and B / R, and for example, B / R decreases linearly with time. Note that the (R, G, B) values ​​may be stored as data and the B / R value may be calculated, or the calculated B / R value may be digitized.

[0118] In this example, in process S607, the viscosity threshold is set to 200, and the time to replace is estimated to be the point when the viscosity estimated from the additive concentration measurement results stored in chronological order reaches 200. As an estimation method, various known methods may be adopted. If actual measured values ​​are obtained, a known method of extrapolating data can be used on the assumption that the viscosity increases monotonically. Furthermore, if the viscosity changes in a more complex manner, a known method such as function fitting (curve fitting) can be used.

[0119] In this embodiment, the time-series chromaticity data measured by the optical sensor, namely B / R, is stored and the degree of deterioration of the lubricating oil is estimated based on this.

[0120] The replacement timing estimation result obtained by step S607 can be displayed as a lubricant diagnosis result (step S608).

[0121] 18 shows an example of the display of the results of process S610. Since the viscosity is predicted to reach 200 in 50 months, the new replacement time can be set to a time before that (for example, half a month before). Process S610 completes one cycle of processing, and in process S602 of the next cycle, a determination process is performed according to the new replacement time.

[0122] For example, after S608, the chromaticity data measured by the optical sensor can be converted to color and displayed on the display screen of the lubricant diagnosis results. By displaying the deterioration state of the lubricant in color on the display screen in this way, the worker can visually recognize the deterioration state of the lubricant. This allows, for example, workers to visually check the condition of the lubricant at the site and detect the deterioration of the lubricant. This helps to get a rough understanding of the chemical state.

[0123] As described above, according to this embodiment, by using the correlation between the ratio of two values ​​of the RGB measurement values ​​obtained by the optical sensor and the viscosity obtained in advance, the life of the lubricant can be detected early without being affected by the performance fluctuation of the optical sensor. Therefore, by performing maintenance such as appropriate lubricant replacement, it is possible to prevent abnormalities in the wind turbine generator. It is also possible to optimize the replacement period of the lubricant. Moreover, the viscosity can be measured by a simple method, and by installing the optical sensor in the nacelle, it is possible to remotely monitor the deterioration of the lubricant online.

[0124] In this embodiment, a method and system for monitoring by installing an optical sensor in the lubricating oil of a rotating part is described. The lubricating oil inside the rotating parts is sampled during inspection, and the oil is optically measured outside the rotating parts. Similar diagnoses can also be performed using sensor measurements.

[0125] As described in the examples, in a diagnostic method for oil containing additives that absorbs light in the wavelength range of 400 nm to 800 nm, the intensity of light transmitted through the oil is measured with an RGB sensor, and the condition of the oil is determined by measuring the optical path length at which the absorbance at wavelength G or wavelength B is between 0.05 and 1.5.

[0126] Alternatively, the system configuration uses an optical sensor equipped with a light source and a light receiving element sensitive to the wavelengths RGB, with the light source and light receiving element arranged on the same plane, and the light source and RGB sensor are in contact with the flow path wall that is transparent to visible light.The light emitted from the white light source passes through the transparent flow path wall and the oil to be measured, and is reflected by a reflector.The reflected light is detected by the RGB sensor to obtain chromaticity information corresponding to the wavelengths RGB, and the condition of the oil is diagnosed based on the ratio of the two chromaticity information items, R and G or B, selected from the RGB.

[0127] In this way, when the optical sensor measures the color change of the oil (object to be measured) to detect changes in the oil's properties, the condition of the oil can be accurately determined even for oils that are very light in color or very dark in color.

[0128] According to the above embodiment, efficient oil maintenance management can be realized, which reduces energy consumption, reduces carbon emissions, prevents global warming, and contributes to the realization of a sustainable society. [Explanation of symbols]

[0129] Oil diagnostic system 800, flow path 810, transparent flow path wall 811, measured oil 812, visible light reflector 813, optical sensor 820, white light source 821, RGB sensor 822, housing 823

Claims

1. Using an optical sensor with a white light source and RGB sensors, The light emitted from the white light source is transmitted through the oil to be measured, and then reflected by a reflector. The light reflected by the reflector is transmitted again through the oil to be measured, and then the reflected light is detected by the RGB sensor. When evaluating the characteristics of the oil to be measured based on the detection signal of the RGB sensor, an optical path length from the white light source to the RGB sensor is set so that the absorbance of at least one of the wavelengths B and G is 0.05 or more and 1.5 or less; How to diagnose oil.

2. The wavelength used for evaluating the characteristics of the oil to be measured is selected from wavelength B and wavelength G, the wavelength having an absorbance of 0.05 or more and 1.5 or less. The method for diagnosing oil according to claim 1.

3. The optical sensor has the white light source and the RGB sensor disposed on the same plane, and the distance between the white light source and the RGB sensor is fixed. The method for diagnosing oil according to claim 1.

4. The optical sensor is arranged such that the white light source and the RGB sensor face a transparent wall and are isolated from the oil to be measured, The light emitted from the white light source is incident on the oil to be measured through the transparent wall, The reflected light is incident on the RGB sensor through the transparent wall. The method for diagnosing oil according to claim 3.

5. Among the walls constituting the flow path or container of the oil to be measured, at least a part facing the optical sensor is the transparent wall, and at least a part of the wall facing the transparent wall is the reflector, The dimensions of the flow path or the container are set so that the light path length from the white light source to the return to the RGB sensor has an absorbance of at least one of the wavelengths B and G of 0.05 or more and 1.5 or less. The method for diagnosing oil according to claim 4.

6. When the absorbance at wavelength B is 0.05 or more and 1.5 or less, the characteristics of the oil to be measured are evaluated based on the ratio of the output values ​​of the RGB sensor at wavelengths B and R. When the absorbance at wavelength B is 1.5 or less, the characteristics of the oil to be measured are evaluated based on the ratio of the output values ​​of the RGB sensor at wavelengths G and R. The method for diagnosing oil according to claim 1.

7. The optical path length from the white light source to the RGB sensor is 2 mm or more. The method for diagnosing oil according to claim 1.

8. Using an information processing device having an input device, an output device, a processing device, and a storage device, determining a calibration curve and a threshold value based on a correlation between a change in at least one of the viscosity, total acid number, moisture, and additive concentration of the oil to be measured, which have been previously measured, and an output value of the RGB sensor, and storing the calibration curve and a threshold value in the storage device; Evaluating the characteristics of the oil to be measured based on the output values ​​of the RGB sensor input from the input device and the calibration curve, and diagnosing the oil to be measured based on the threshold value. The method for diagnosing oil according to claim 1.

9. The oil to be measured absorbs light in the wavelength range of 400 nm to 800 nm. The method for diagnosing oil according to claim 1.

10. When evaluating the characteristics of the oil to be measured based on the detection signal of the RGB sensor, For all of the oils to be evaluated, a wavelength at which the absorbance is 0.05 or more and 1.5 or less is used. The method for diagnosing oil according to claim 1.

11. an optical sensor in which a white light source and an RGB sensor are arranged on the same plane, and a distance between the white light source and the RGB sensor is fixed; a holding portion for holding the oil to be measured in a state separated from the optical sensor; a wall constituting at least a part of the holding portion and isolating the oil to be measured from the optical sensor; a first transparent portion provided on the wall for transmitting light emitted from the white light source to the oil to be measured; a reflecting portion provided on the wall for reflecting light transmitted through the oil to be measured; a second transparent portion provided on the wall for receiving the light reflected by the reflecting portion by the RGB sensor; Equipped with The optical path length of the light emitted from the white light source passing through the first transparent portion, the oil to be measured, the reflecting portion, the oil to be measured, and the second transparent portion in this order until it reaches the RGB sensor is set so that the absorbance of at least one of the wavelengths B and G is 0.05 or more and 1.5 or less. Oil diagnostic system.

12. The holding portion is a flow path through which the oil to be measured flows. The oil diagnostic system of claim 11.

13. an information processing device having an input device, an output device, a processing device, and a storage device; storing a calibration curve showing the relationship between the characteristics of the oil to be measured and color information in the storage device; The input device receives color information of the oil to be measured obtained by the RGB sensor, When the processing device estimates the characteristics of the oil to be measured using the color information and the calibration curve, the color information is selected from the wavelengths B and G whose absorbance is 0.05 or more and 1.5 or less. The oil diagnostic system of claim 11.

14. The processing device includes: When the absorbance at wavelength B is 0.05 or more and 1.5 or less, the characteristics of the oil to be measured are evaluated based on the ratio of the output values ​​of the RGB sensor at wavelengths B and R. When the absorbance at wavelength B exceeds 1.5, the characteristics of the oil to be measured are evaluated based on the ratio of the output values ​​of the RGB sensor at wavelengths G and R.

14. The oil diagnostic system of claim 13.

15. The optical path length from the white light source to the RGB sensor is 2 mm or more. The oil diagnostic system of claim 11.

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