Lubricant deterioration detection method

Abstract

To provide a method capable of easily and accurately detecting a deterioration state of a lubricant in a short time with a small amount, without requiring deterioration or cleaning of a detection device, and capable of detecting the deterioration state of the lubricant at various places without limiting the kind of a light source, with grease as the lubricant as a detection object in addition to lubricating oil.SOLUTION: A lubricant deterioration detection method includes a step of capturing an image of a lubricant alone or the lubricant diluted with a solvent together with a color sample using an imaging device, and a step of determining a deterioration state of the lubricant from image information of the captured lubricant alone or the lubricant diluted with the solvent based on image information of the captured color sample.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for detecting the deterioration state of grease and a method for detecting the deterioration state of a lubricant. [Background technology]

[0002] (First Object of the Invention) Patent Document 1 discloses a failure prediction device that predicts failure of rolling bearings by measuring the concentration of iron powder in the lubricating grease used in the rolling bearings from the disruption of the magnetic balance between the excitation coil and the detection coil. However, the technique disclosed in Patent Document 1 has a problem in that a relatively large amount of grease is required to measure the iron powder concentration. Also, the technique disclosed in Patent Document 1 cannot detect oxidative deterioration of grease.

[0003] (Second Object of the Invention) Grease is also used in various mechanical device parts, including rolling bearings and reducers. Abnormal wear is one of the causes of failure in these parts, and when abnormal wear occurs, foreign matter such as iron powder gets mixed into the grease, causing it to deteriorate. There are several factors that can cause grease to deteriorate, such as grease deterioration due to changes in composition caused by heat or grease deterioration due to oxidation.

[0004] Various methods have been studied for detecting the deterioration and other conditions of lubricating oils, which are used for similar purposes to grease. For example, Patent Document 2 discloses a color sensor that can be attached to the mechanical device itself, and this color sensor can detect the condition of the lubricating oil.

[0005] However, since grease has lower fluidity and light transmittance than lubricating oil, it is difficult to analyze the deterioration of grease.

[0006] If we limit grease deterioration to that caused by the inclusion of iron powder, for example, Patent Document 1 discloses a failure prediction device that measures the concentration of iron powder in the lubricating grease used in the part being measured from the disruption of the magnetic balance between the excitation coil and the detection coil, thereby predicting failure of the part being measured.

[0007] However, the technology disclosed in Patent Document 1 requires a relatively large amount of grease to measure the iron powder concentration. Furthermore, the sensor part of the failure prediction device needs to be installed at the desired detection location, which requires a considerable amount of time and cost from manufacturing the device to installation and prediction. Furthermore, the technology is limited to detecting deterioration due to iron powder mixed into the grease, and cannot detect deterioration due to grease oxidation or changes in composition due to heat.

[0008] (Third Object of the Invention) Lubricants used to lubricate various mechanical devices deteriorate over time due to oxidation and contamination with foreign matter during use.

[0009] As a method for detecting the deterioration state of a lubricant, for example, Patent Document 2 describes a sensor that allows lubricant to penetrate into a gap formed by a light-emitting element (white LED) and a light-receiving element (RGB sensor), and detects the deterioration state of the lubricant from the state of light transmission.

[0010] However, the method for detecting the deterioration state of a lubricant described in Patent Document 2 requires a relatively large amount of lubricant and can only measure lubricating oil, and cannot detect grease, for example. Furthermore, the sensor deteriorates when immersed in the lubricant, and the sensor must be cleaned. Furthermore, the light source is limited to a white LED, which restricts the detection location. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent No. 5188088 [Patent Document 2] Japanese Patent No. 5980591 Summary of the Invention [Problem to be solved by the invention]

[0012] With respect to the first problem of the present invention, a first object of the present invention is to provide a grease deterioration detection method that is capable of detecting grease deterioration and requires only a small amount of grease to detect the deterioration.

[0013] With respect to the second problem of the present invention, a second object of the present invention is to provide a grease deterioration detection method that can detect deterioration caused by oxidation or heat in a short time using a small amount of grease, in addition to deterioration caused by the inclusion of foreign matter such as iron powder.

[0014] With regard to the third object of the present invention, the third object of the present invention is to provide a method for detecting grease as well as lubricating oil as a lubricant, which can detect the deterioration state of a lubricant simply, quickly, and more accurately using a small amount of lubricant, without the need for deterioration or cleaning of the detection device, and which can be used in a variety of locations without being limited by the type of light source. [Means for solving the problem]

[0015] The first object of the present invention is achieved by the following configuration [1] relating to a method for detecting deterioration of grease.

[0016] [1] A method for detecting grease deterioration, comprising: a dilution step of diluting the grease with a diluent to obtain diluted grease; a measuring step of measuring the color of the diluted grease with a sensor; A grease deterioration detection method comprising:

[0017] Furthermore, preferred embodiments of the present invention relating to a grease deterioration detection method relate to the following [2] to [4].

[0018] [2] The grease deterioration detection method according to [1], wherein the sensor is a color sensor. [3] The grease deterioration detection method according to [1] or [2], wherein the diluting liquid is an organic solvent. [4] The grease deterioration detection method according to [3], wherein the organic solvent is at least one selected from the group consisting of n-hexane, kerosene, and gasoline.

[0019] In this specification, the inventions according to the above [1] to [4] are referred to as the "first invention group."

[0020] The second object of the present invention is achieved by the following configuration [5] relating to a method for detecting deterioration of grease.

[0021] [5] A method for detecting grease deterioration, comprising: a step of sandwiching the grease between a pair of transparent plates and spreading it to form a thin film; measuring the color of the thinned grease with a camera or sensor; A grease deterioration detection method for determining the degree of deterioration of the grease by the measurement.

[0022] Furthermore, a preferred embodiment of the present invention relating to a grease deterioration detection method relates to the following [6] or [7].

[0023] [6] The grease deterioration detection method according to [5], wherein the sensor is a color sensor. [7] The grease deterioration detection method according to [5] or [6], wherein the transparent material is at least one selected from the group consisting of glass, acrylic, polyethylene terephthalate, and polycarbonate.

[0024] In this specification, the inventions according to the above [5] to [7] are referred to as the "second invention group."

[0025] The third object of the present invention is achieved by the following configuration [8] relating to a lubricant deterioration detection method.

[0026] [8] A step of photographing the lubricant alone or the lubricant diluted with a solvent together with a color sample using an imaging device; a step of determining a deterioration state of the lubricant from image information of the lubricant alone or the lubricant diluted with the solvent, based on image information of the photographed color sample; A lubricant deterioration detection method comprising:

[0027] Furthermore, preferred embodiments of the present invention relating to a lubricant deterioration detection method relate to the following [9] to

[13] .

[0028] [9] Correcting the white balance of the image information of the photographed lubricant alone or the lubricant diluted with the solvent based on the white balance of the image information of the color sample; The lubricant deterioration detection method according to [8], wherein the deterioration state of the lubricant is determined from the corrected image information.

[10] The lubricant deterioration detection method according to [8] or [9], wherein the imaging device has a white balance correction function.

[11] The lubricant deterioration detection method according to

[10] , wherein the imaging device is a digital camera or a mobile terminal with a camera.

[12] The lubricant deterioration detection method according to [8] or [9], wherein the lubricant is lubricating oil or grease.

[13] The lubricant deterioration detection method according to [8] or [9], wherein the solvent includes an organic solvent, kerosene, or gasoline.

[0029] In this specification, the inventions according to the above items [8] to

[13] are referred to as the "third invention group." [Effects of the Invention]

[0030] According to the present invention relating to the "first invention group" described above, deterioration of grease can be detected using a small amount of grease. According to the present invention relating to the "second invention group," it is possible to detect not only the contamination of foreign matter such as iron powder, but also grease deterioration caused by oxidation and heat. Furthermore, since deterioration can be detected in a short time using a small amount of grease, it is extremely useful in terms of cost and time. In addition, by sampling grease from any number of locations on a part, it is possible to pinpoint the location of grease deterioration and determine the degree of deterioration on the spot. According to the present invention related to the "third invention group," the deterioration state of a lubricant due to oxidation degradation, foreign matter contamination, etc., can be detected simply and accurately in a short time. Furthermore, since the required amount of lubricant is very small, for example, about 10 mg, there is no deterioration of the detection device and no need for cleaning. Furthermore, it is possible to analyze the lubricant in areas that directly affect the life of the lubricated parts, such as near the raceway of a bearing, thereby improving the accuracy of failure prediction. Furthermore, grease can be detected in addition to lubricating oil, and there are no limitations on the light source, making it possible to detect in a variety of locations. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a graph showing the results of analyzing grease near the cage of a rolling bearing using a grease deterioration detection method according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a graph showing the results of analyzing grease inside a seal of a rolling bearing using the grease deterioration detection method according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a graph showing the results of analyzing grease outside the seal of a rolling bearing using the grease deterioration detection method according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the relationship between lightness ΔE and maximum color difference obtained in an example using the grease deterioration detection method according to the second embodiment of the present invention. [Figure 5] FIG. 5 is a top view showing an example of a color sample used in the third embodiment of the present invention. [Figure 6] FIG. 6 is a graph showing the results of Test Example 1 in the third embodiment of the present invention. [Figure 7] FIG. 7 is a graph showing the results of Test Example 2 in the third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the present invention will be described. Note that this embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0033] In the embodiments described below, an embodiment for explaining the present invention related to the above-mentioned "first invention group" will be referred to as the "first embodiment," an embodiment for explaining the present invention related to the above-mentioned "second invention group" will be referred to as the "second embodiment," and an embodiment for explaining the present invention related to the above-mentioned "third invention group" will be referred to as the "third embodiment."

[0034] First Embodiment First, the first embodiment will be described.

[0035] The grease deterioration detection method according to this embodiment is a method for detecting grease deterioration, and includes a dilution process for diluting grease with a diluent to obtain diluted grease, and a measurement process for measuring the color of the diluted grease with a sensor. According to the grease deterioration detection method of the present embodiment, the deterioration of the grease can be detected by measuring the color of the diluted grease with a sensor. That is, since the color of the grease changes as it deteriorates, by measuring the color of the grease with a sensor, it is possible to determine whether the grease has deteriorated due to use or storage. Specific examples of grease deterioration that can be detected include oxidation of the grease and the inclusion of foreign matter in the grease. A specific example of a sensor used for measurement is a color sensor.

[0036] Furthermore, according to the grease deterioration detection method of the present embodiment, the state and degree of deterioration of the grease can be determined by measuring the color of the diluted grease with a sensor. That is, the degree of color change increases as the grease deterioration progresses, so by measuring the color of the grease with a sensor, the degree of grease deterioration due to use or storage can be determined.

[0037] For example, the state and degree of deterioration of the grease can be determined by comparing the color of the grease whose degree of deterioration is to be determined with the color of a reference grease. More specifically, an undegraded grease such as unused grease or grease immediately after production is used as the reference grease, and this reference grease is diluted with a diluent to obtain a diluted reference grease, and the color of the diluted reference grease is measured with a sensor (reference grease measurement step).

[0038] Next, the grease serving as the sample for which the degree of deterioration is to be determined is diluted with a diluent to obtain diluted grease (dilution step), and the color of the diluted grease is measured with a sensor (measurement step).The degree of deterioration of the grease is then determined by comparing the color of the diluted reference grease obtained in the reference grease measurement step with the color of the diluted grease obtained in the measurement step (comparison step).It is preferable that the type of diluent and the color measurement conditions be the same for the reference grease and the sample grease.

[0039] Therefore, by using the grease deterioration detection method according to this embodiment, it is possible to determine the degree of deterioration of grease used in, for example, rolling bearings, etc. If the degree of grease deterioration is known, it is possible to appropriately determine the timing for performing maintenance such as replenishing the rolling bearing with unused grease or replacing the rolling bearing.

[0040] Furthermore, in the grease deterioration detection method according to this embodiment, the color of diluted grease obtained by diluting grease with a diluent is measured, so only a small amount of grease (e.g., 10 mg) is required for deterioration detection. Even with a small amount of grease, both oxidative deterioration and deterioration due to foreign matter contamination can be detected in a short period of time.

[0041] Furthermore, in the grease deterioration detection method according to this embodiment, only a small amount of grease is required to detect deterioration, so it is possible to analyze grease present near the raceway, which directly affects the lifespan of the rolling bearing. This makes it possible to determine the degree of deterioration of the grease used in the rolling bearing and to predict rolling bearing failures with high accuracy.

[0042] The conditions for diluting the grease with the diluent are not particularly limited, and the temperature may be room temperature or may be heated to a level that does not cause the diluent to volatilize. Furthermore, stirring may or may not be performed during dilution. Furthermore, the dilution ratio when diluting the grease with a diluent is not particularly limited, but in order to measure color with high precision, it is preferable to dilute the grease by mixing 1 part by mass of diluent to 10,000 parts by mass, more preferably 10 parts by mass to 10,000 parts by mass, and even more preferably 10 parts by mass to 1,000 parts by mass.

[0043] Furthermore, the type of diluent is not particularly limited as long as it is easily mixed with the grease and is colorless and transparent to such an extent that it does not interfere with the color measurement of the diluted grease with a sensor, but an organic solvent is preferred. One type of diluent may be used alone, or two or more types may be mixed and used.

[0044] Specific examples of organic solvents include petroleum such as kerosene, diesel, and gasoline, alcohols such as methanol and ethanol, ketone-based solvents such as acetone and methyl ethyl ketone, aliphatic hydrocarbons such as n-hexane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as chloroform and monochlorobenzene, ester-based solvents such as ethyl acetate, and ether-based solvents such as tetrahydrofuran.

[0045] <Examples according to the first embodiment> This section describes an example of monitoring the degree of deterioration of lubricating grease used in rolling bearings. The rolling bearing used was a deep groove ball bearing with a bearing number of 6305VV, with an inner diameter of 25 mm, an outer diameter of 62 mm, and a width of 17 mm. The thickener used in the grease was lithium soap, and the base oil was a mixture of poly-α-olefin and diester oil (kinematic viscosity at 40°C was 15.9 mm). 2 / s.) and the consistency is No. 2.

[0046] This grease was loaded inside the rolling bearing and subjected to a radial load of 98N and an axial load of 1470N at a rotational speed of 10,000 min ‐1 The inner ring was rotated at 140°C. The outer ring temperature was 140°C. The rotation times were 100, 200, 300, and 417 hours, and grease was sampled from the rolling bearing after each of these rotation times. Grease was sampled from three locations: near the cage of the rolling bearing, the inner part near the seal, and the outer part near the seal. Note that rotation was stopped after 417 hours because the outer ring temperature had risen to 170°C.

[0047] 10 mg of each sampled grease was dissolved in 1 mL of n-hexane to obtain diluted grease. The hue of each diluted grease was then measured using an oil diagnostic meter, T-ODS-301, manufactured by MKT Taisei Co., Ltd. Hue is expressed in three colors: red (R), green (G), and blue (B), each of which is expressed in 256 gradations from 0 to 255. The RGB values ​​obtained by the color sensor were substituted into the following formula to calculate the lightness ΔE of each diluted grease. ΔE=(R 2 +G 2 +B 2 ) 0.5 In addition, the difference between the maximum and minimum values ​​of the RGB values ​​obtained by the color sensor was calculated and used as the maximum color difference for each diluted grease.

[0048] Figures 1 to 3 show graphs plotting the lightness ΔE and maximum color difference for each sampled location of the grease. The sampled location for the graph in Figure 1 is the area near the cage, the sampled location for the graph in Figure 2 is the inner part of the seal, and the sampled location for the graph in Figure 3 is the outer part of the seal. The numerical values ​​written near the plots in the graphs are the rotation time of the rolling bearing. The 0-hour rotation time represents unused grease, and with unused grease as the reference grease, the hue was measured in the same way as for the grease at each rotation time.

[0049] As the rotation time of a rolling bearing increases, the degree of grease deterioration increases, and as the degree of grease deterioration increases, the hue of the grease changes, the maximum color difference increases, and the lightness ΔE decreases. In other words, the color of the grease changes from colorless (white) to black. When lightness ΔE and maximum color difference are plotted, a curve is drawn as shown on the graph with an arrow that curves in a roughly semicircular shape.

[0050] Furthermore, the brightness ΔE of unused grease is approximately 442 (R=255, G=255, B=255), but as the degree of grease deterioration increases, the brightness ΔE approaches 0. This may indicate that solid particles such as wear debris have become mixed into the grease as foreign matter.

[0051] Let us now explain the graphs in Figures 1 to 3. Unused grease is almost colorless and has a high lightness ΔE, but as the rotation time increases, the color of the grease becomes brownish, so the lightness ΔE decreases, and as the blue color decreases, the maximum color difference increases. Then, as the rotation time increases further, the color of the grease approaches black (R=0, G=0, B=0) as the rolling bearing approaches seizure, so the lightness ΔE decreases even further and the maximum color difference also decreases.

[0052] In this way, when the lightness ΔE and maximum color difference are plotted, a curve is drawn as shown on the graph with an arrow that is curved in an approximately semicircular shape. Therefore, the degree of deterioration of the grease can be determined by seeing where the plot of the lightness ΔE and maximum color difference of the diluted grease is located on the above curve.

[0053] Second Embodiment Next, a second embodiment will be described.

[0054] The grease deterioration detection method according to this embodiment includes a step of sandwiching the grease between a pair of transparent plates and spreading it to form a thin film, and a step of measuring the color of the thin film of grease with a camera or a sensor. The degree of deterioration of the grease is determined by the measuring step. Furthermore, steps other than the above steps may be included within the scope that does not impair the effects of the present invention.

[0055] (Thinning process) Grease changes color as it deteriorates. However, compared to lubricating oil, grease has low fluidity and high viscosity. As a result, it has low light transmittance, and while it is possible to distinguish large differences in hue, such as between an initial state with no deterioration and a state with significant deterioration, it is difficult to distinguish subtle differences in deterioration.

[0056] In contrast, this embodiment includes a process of sandwiching the grease between a pair of transparent plates and spreading it to form a thin film, which increases the light transmittance of the grease and makes it possible to clearly distinguish subtle differences in deterioration as differences in hue. Furthermore, a small amount of grease is sufficient to spread the grease and form a thin film. This allows for pinpoint analysis of the grease in areas that directly affect the lifespan of the part to which it is attached, improving the accuracy of failure prediction. Specifically, if the part in question is a rolling bearing, the grease present near the raceway can be analyzed to determine the degree of deterioration of the grease used in the rolling bearing and predict rolling bearing failure with high accuracy.

[0057] The pair of transparent materials is not particularly limited as long as it can sandwich the grease between them and spread it to form a thin film of the grease, and does not affect the observation of the hue of the grease. For example, at least one selected from the group consisting of glass, acrylic, polyethylene terephthalate, and polycarbonate is preferred, and among these, the pair of transparent materials may be the same or two different types may be used as the pair of transparent materials.

[0058] The size and thickness of the transparent material plates are not particularly limited as long as the surfaces that sandwich the grease are flat. The preferred ranges for the size and thickness of the plates vary depending on the transparent material used, the spreading method, the amount of grease, etc. For example, when two glass slides are used as a pair of transparent materials and the grease is spread by applying human force from above the glass slides, the strength and thickness of the glass need only be sufficient to prevent the grease from breaking due to that force. Furthermore, the transparent material need only be large enough to prevent the thin film of grease from spilling out when the grease is spread. Furthermore, the size and thickness of the pair of transparent material plates do not necessarily need to be the same.

[0059] The amount of grease sandwiched between a pair of transparent plates, i.e., the amount of grease required for the grease deterioration detection method according to this embodiment, varies depending on the size of the transparent material used and the hardness of the grease, but from the viewpoint of making the thickness and area of ​​the grease easily detectable when spread apart, it is preferably 0.1 mg or more, more preferably 0.2 mg or more, and even more preferably 0.5 mg or more. Furthermore, from the viewpoint of pinpointing and analyzing the grease in areas that directly affect the lifespan of a part, it is preferably 10 mg or less, more preferably 5 mg or less, and even more preferably 2 mg or less.

[0060] From the viewpoint of ease of visual recognition during detection, the size of the grease after being spread out is preferably 1.5 mm or more in diameter, more preferably 3 mm or more, and even more preferably 5 mm or more. From the viewpoint of ease of handling, the size of the grease after being spread out is preferably 30 mm or less in diameter, more preferably 15 mm or less in diameter. Note that the above size does not mean that the grease after being spread out is an exact circle. In other words, it is sufficient if the area of ​​the grease after being spread out is approximately the same as the area of ​​a circle with the above diameter.

[0061] The thickness of the grease after spreading is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of improving the accuracy of the hue analysis. Furthermore, from the viewpoint of preventing excessively low light transmittance, the thickness of the grease after spreading is preferably 0.5 mm or less, more preferably 0.1 mm or less. However, if foreign matter such as iron powder is present in the grease, the thickness may vary depending on the size of the iron powder. The thickness of the grease after spreading can be calculated from the amount of grease used, its specific gravity, and the area, or can be measured directly using a dielectric constant measurement.

[0062] There are no particular limitations on the method for collecting grease from parts, but examples include a method of collecting grease directly from bearings etc. using a spatula, and a method of collecting grease coming out from a grease outlet.

[0063] Although a diluent is not particularly necessary for thinning the grease, the use of a diluent is not excluded. For example, if the grease has solidified due to severe degradation and is difficult to spread by sandwiching it between a pair of transparent plates, the viscosity of the grease may be reduced using a diluent before thinning. Also, if the grease has deteriorated so much that its color is too dark to determine the degree of deterioration, the color of the grease may be lightened using a diluent to make it easier to determine. The dilution ratio when diluting the grease with a diluent is not particularly limited and is determined appropriately depending on the state of the grease.

[0064] The diluent is not particularly limited as long as it is easily mixed with the grease and is colorless and transparent enough to not interfere with measuring the color of the grease with a camera or a sensor, but an organic solvent is preferred. One diluent may be used alone, or two or more diluents may be mixed and used.

[0065] Specific examples of organic solvents include petroleum solvents such as kerosene, diesel, and gasoline; alcohols such as methanol and ethanol; ketone solvents such as acetone and methyl ethyl ketone; aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as chloroform and monochlorobenzene; ester solvents such as ethyl acetate; and ether solvents such as tetrahydrofuran.

[0066] (Measuring process) Next, a process is performed in which the color of the thin film of grease is measured using a camera or a sensor, and the degree of deterioration of the grease is determined based on this measurement. Specific examples of grease deterioration that can be detected include oxidation of the grease, changes in the grease's components due to heat, and the inclusion of foreign matter such as iron powder in the grease.

[0067] The sensor used for the measurement is preferably a color sensor, since it can directly determine the color of the grease. The more the grease deteriorates, the greater the change in color. Therefore, the degree of deterioration of the grease can be determined by measuring the color of the grease with a sensor such as a color sensor. In particular, the grease deterioration detection method according to this embodiment makes the grease thin, thereby increasing the light transmittance of the grease and enabling subtle differences in deterioration to be clearly distinguished as differences in hue, thereby enabling the degree of grease deterioration to be detected in detail.

[0068] In one embodiment, the degree of grease deterioration is determined by comparing the color of the thin film of grease with the color of a reference grease. Specifically, undegraded grease, such as unused grease or grease immediately after production, is used as the "reference grease," and this reference grease is sandwiched between a pair of transparent plates and spread to form a thin film. The amount of the reference grease and the area and thickness after spreading are preferably the same as the amount of the grease whose deterioration is to be detected and the area and thickness after spreading. The color of this reference grease is measured with a sensor and used as the standard for subsequent measurements.

[0069] Next, the grease to be detected for deterioration is sandwiched between a pair of transparent materials and spread out to form a thin film, and the color of the thin film is measured with a sensor.The color of the thin film is then compared with the color of a reference grease to determine the degree of deterioration of the grease.

[0070] When the color of the grease is measured using a camera instead of a sensor, the degree of deterioration of the grease is determined by comparing the color with the color of the reference grease in the same manner as above.

[0071] The grease to be detected for deterioration is sandwiched between a pair of transparent materials and spread out to form a thin film, which is then photographed against a white background, for example, with a color sample. The color sample is used to standardize colors, and this makes it possible to correct the white balance of the image after shooting, allowing the degree of deterioration to be determined regardless of conditions such as the brightness of the location where the image is taken.

[0072] The reference grease may be sandwiched between a pair of transparent materials and spread to form a thin film, and then photographed and corrected together with the grease to be detected for deterioration, with a white background placed against it. Alternatively, the grease may be photographed in advance with a color sample, with the white balance and other settings corrected, and this may be compared with the color of the grease to be detected for deterioration that has actually been photographed and corrected.

[0073] The color of the thin film of grease measured by a camera or sensor is used to determine the degree of deterioration based on its brightness. Hue is expressed using three colors: red (R), green (G), and blue (B), each of which is expressed in 256 levels from 0 to 255. The RGB values ​​obtained by the sensor, or the RGB values ​​extracted from the hue information in an image captured and corrected by a camera, are substituted into the following formula to calculate the lightness ΔE of the grease. ΔE=(R 2 +G 2 +B 2 ) 0.5 The difference between the maximum and minimum values ​​of the RGB values ​​obtained by measurement with a camera or sensor is defined as the maximum color difference for each grease.

[0074] The above-mentioned lightness ΔE and maximum color difference are calculated for the reference grease and the grease to be detected for degradation, and the lightness ΔE is plotted on the X-axis and the maximum color difference on the Y-axis, thereby making it possible to determine the degree of degradation of the grease.

[0075] In this way, by using the grease deterioration detection method according to this embodiment, it is possible to narrow down the locations and determine the degree of deterioration of grease used in, for example, rolling bearings, etc. If the degree of deterioration for each location where grease is applied is known, it is possible to appropriately determine the timing for maintenance such as refilling the rolling bearing with unused grease or replacing the rolling bearing, and also to take measures such as changing the maintenance timing for each location.

[0076] Furthermore, the grease deterioration detection method according to this embodiment requires only a small amount of grease for deterioration detection, and can detect deterioration in a short time, so the degree of deterioration of grease collected from parts such as rolling bearings can be determined on the spot very easily and accurately. Furthermore, this is extremely useful because it can detect not only deterioration due to the inclusion of foreign matter, but also deterioration due to oxidation and changes in components caused by heat.

[0077] <Examples according to the second embodiment> [Examples 1 to 7] The deterioration of lubricating grease used in rolling bearings was monitored. The rolling bearings used had an inner diameter of 25 mm, an outer diameter of 62 mm, and a width of 17 mm, and the grease was loaded inside the rolling bearings, which were then rotated continuously at a rotational speed of 2000 r / min, a bearing outer ring temperature of 120°C, a radial load of 98 N, and an axial load of 1470 N. The thickener used in the grease was lithium soap, and the commercially available grease used had a consistency of No. 2 and a mineral oil base oil. The test time was varied from 0 to 600 hours as shown in Table 1, and after each rotation time, grease was collected from the outside of the seal in the rolling bearing using a spatula. Note that in the example with a rotation time of 600 hours, rotation was stopped after the time elapsed, but could not be restarted thereafter due to an increase in bearing torque.

[0078] 1 mg of the collected grease was sandwiched between a pair of glass slides and spread with force to form a thin film with a diameter of 6 mm and a thickness of approximately 40 μm. The thin film of grease was then photographed with a camera, and hue information was extracted from the image data. At this time, white balance correction was performed by photographing the grease together with a color sample. Hue is expressed in three colors: red (R), green (G), and blue (B), and each color is expressed in 256 gradations from 0 to 255. The RGB values ​​of each grease were substituted into the following formula to calculate the lightness ΔE of each grease. The maximum color difference, which is the difference between the maximum and minimum RGB values, was also calculated. ΔE=(R 2 +G 2 +B 2 ) 0.5 The results are shown in Table 1 and Figure 4. The numbers written near the plots in Figure 4 indicate the rotation times.

[0079] [Table 1]

[0080] As a result, Example 1, which can be called the reference grease, had almost no color and a high lightness ΔE, but as the rotation time passed, the grease deteriorated and turned brown. Specifically, a continuous change was observed in which the lightness ΔE decreased and the blue (B) value of the hue decreased, resulting in an increase in the maximum color difference.

[0081] The degree of grease deterioration can be determined by where on the semicircular shape shown in Figure 4 the brightness ΔE and maximum color difference are located. As the degree of grease deterioration increases, the color of the grease changes from colorless (white) toward brown. In other words, the lightness ΔE of the grease decreases, and as it turns brown, the blue (B) value decreases, so the maximum color difference increases. Then, as the rotation time increases and the rolling bearing approaches seizure, the degree of deterioration increases, and the color of the grease changes from brown toward black (R=0, G=0, B=0). Therefore, the lightness ΔE decreases further, and the maximum color difference also decreases. Such changes will form a curve as shown on the graph with an arrow that curves in a roughly semicircular shape. Note that when the brightness ΔE is in the range close to 0, it may indicate not only deterioration due to oxidation of the grease, but also the presence of solid particles such as wear powder mixed into the grease as foreign matter.

[0082] In Examples 1 to 7, the grease outside the seal in the rolling bearing was the target for degradation detection, and so the change in hue was smaller compared to the grease applied to the parts that actually contribute to lubrication. However, when the brightness ΔE reaches a range that is about half the brightness ΔE of new grease with a rotation time of 0, which serves as the reference grease threshold, it is preferable to reapply grease or replace the rolling bearing itself.

[0083] When actually using the grease deterioration detection method according to this embodiment, it is preferable to plot the lightness ΔE and maximum color difference as shown in Figure 4 and see where it is located on the curve that resembles an arrow that curves in a roughly semicircular shape, because this allows the degree of grease deterioration to be determined at a glance.

[0084] <Third embodiment> First, the third embodiment will be described.

[0085] In the lubricant deterioration detection method of the present invention (hereinafter referred to as the "deterioration detection method"), first, a device or equipment that uses lubricating oil or grease (hereinafter collectively referred to as "lubricant"), such as a rolling bearing or ball screw device, is stopped, and the lubricant is collected and placed in a container, and photographed together with a color sample. Various imaging devices can be used for the photography, and there are no particular restrictions on the type, but the photography can be carried out using, for example, a digital camera or a mobile device with a camera such as a smartphone or tablet. There are also no particular restrictions on the type of light source used when photographing, making detection possible in a variety of locations.

[0086] As shown in Fig. 5, the color sample 1 is a list of multiple color samples 20 with different hues and shades, ranging from white (upper left in the figure) to black (lower right in the figure), arranged on the surface of a mount 10. In addition, image information of the color sample 1 is printed as an identification code 30 on the mount 10. The identification code 30 may be a barcode or a QR code (registered trademark) as shown in the figure.

[0087] The collected lubricant is then placed in a container (not shown), such as a petri dish or a transparent bottle, and placed on the sample placement section 40 indicated by a circle in the figure. The sample is then photographed together with the color sample 1 using various imaging devices. A very small amount of lubricant, approximately 10 mg, is sufficient. The lubricant may be used alone or diluted with a solvent. The solvent is not particularly limited as long as it is easily mixed with the lubricant and is colorless and transparent enough to not interfere with photographing the color of the lubricant. Specifically, organic solvents, kerosene, and gasoline are preferred. Diluting the lubricant with a solvent allows for more precise separation of lubricants that have turned dark, particularly black.

[0088] The captured image information of the lubricant is compared with the image information of the color sample 1. At this time, it is preferable to correct the white balance of the captured image information of the lubricant. By correcting the white balance, the captured image information of the lubricant can be made to more appropriately conform to the image information of the color sample 1 regardless of the environment of the capture location, i.e., the detection location, where brightness and the like may be affected.

[0089] If the imaging device used has a white balance correction function, the white balance correction can be performed by that function, but the image information obtained by the imaging device can also be sent to an external processing device such as a server and corrected by the white balance correction function of that processing device. Furthermore, the comparison between the image information of the lubricant and the image information of the color sample 1, which will be described later, can also be performed within the imaging device or by an external processing device.

[0090] Next, the hue of the image of the lubricant whose white balance has been corrected (hereinafter referred to as the "corrected image") is calculated. The hue is expressed using three colors: red (R), green (G), and blue (B), and the brightness (ΔE) is calculated using the following formula (1) based on the RGB values ​​of the corrected image. Brightness (ΔE)=(R 2 +G 2 +B 2 ) 0.5 ···(1)

[0091] The difference between the maximum and minimum values ​​in the RGB values ​​is set as the maximum color difference of the lubricant-corrected image.

[0092] As shown in the test example described later, the lubricant was sampled at predetermined intervals of use, and the lightness (ΔE) and maximum color difference were determined. A correlation was observed by plotting the lightness (ΔE) on the X axis and the maximum color difference on the Y axis to create a graph, and the deterioration level (deterioration state) of the sampled lubricant could be determined based on this graph. This deterioration level can be reflected in determining when to replace the lubricant, etc. The correction according to the dilution rate can be performed by providing the imaging device or server with a correction function and using a correction table prepared in advance.

[0093] <Example of the Third Embodiment> Below, Test Example 1 shows an example in which the deterioration state of grease in a rolling bearing was monitored, and Test Example 2 shows an example in which the deterioration state of lubricating oil in a rolling bearing was monitored.

[0094] (Test example 1: Monitoring the deterioration state of grease in rolling bearings) A rolling bearing with an inner diameter of 25 mm, an outer diameter of 62 mm, and a width of 17 mm was used, and it was continuously rotated under the following conditions: inner ring rotation, lubrication with grease, rotation speed: 2000 r / min, bearing outer ring temperature: 120°C, radial load: 98 N, axial load: 1470 N. The grease used was a commercially available grease with a consistency of No. 2, which uses mineral oil as the base oil and lithium soap as the thickener.

[0095] Grease was then sampled from the rolling bearings after they had been operated for 100, 200, 300, 400, 500 and 600 hours. For the rolling bearing that had been operated for 600 hours, operation was stopped and the grease sampled, and then an attempt was made to restart the operation, but this was not possible due to an increase in bearing torque.

[0096] The amount of grease collected was 10 mg, and it was dissolved in 1 mL of hexane.

[0097] Each sampled grease was placed in a petri dish and placed on the sample holder of the color sample. Each grease and the color sample were photographed together with a digital camera equipped with a white balance correction function, and the RGB values ​​were calculated from the corrected image. The lightness (ΔE) and maximum color difference were calculated from the obtained RGB values, and the results are shown in Table 2 below.

[0098] [Table 2]

[0099] Figure 6 shows the results of plotting the lightness (ΔE) on the X axis and the maximum color difference on the Y axis. The numbers in the figure indicate the operating time (hr) for each item. As a result, new items had almost no color and high lightness. However, as operating time passed, the grease deteriorated and turned brown, causing the lightness to decrease, the color to become less blue, and the maximum color difference to increase, with a continuous change observed along curve A, indicated by the approximately semicircular arrow in the figure.

[0100] Therefore, the degree of deterioration of the sampled grease can be determined by photographing the sampled grease together with a color sample, calculating the brightness (ΔE) and maximum color difference of the corrected image, and determining where it is located on curve A shown in Figure 6.

[0101] (Test example 2: Monitoring the deterioration of lubricating oil in rolling bearings) A cylindrical thrust roller bearing with an inner diameter of 60 mm, an outer diameter of 95 mm, and a nominal height of 26 mm was used, and it was continuously rotated under the following conditions: inner ring rotation, lubrication with lubricant, rotation speed: 500 r / min, bearing temperature: 100°C, axial load: 60 kN. The lubricant used was equivalent to VG32, and was supplied at a rate of 0.1 L / min.

[0102] Then, after the thrust cylindrical roller bearing was operated for 515 hours, 800 hours and 1136 hours, the lubricating oil was collected from the oil recovery tank.

[0103] The lubricant was collected in an amount of 1 mL, placed in a petri dish without dilution, and placed on the sample holder of the color sample. Each lubricant and the color sample were photographed together with a digital camera equipped with a white balance correction function, and the RGB values ​​were calculated from the corrected image. The lightness (ΔE) and maximum color difference were calculated from the obtained RGB values, and the results are shown in Table 3 below.

[0104] [Table 3]

[0105] Figure 7 shows the results of plotting the lightness (ΔE) on the X axis and the maximum color difference on the Y axis. The numbers in the figure indicate the operating time (hr) for each item. As a result, new items had almost no color and high lightness. However, as operating time passed, the grease deteriorated and turned brown, causing the lightness to decrease, the color to become less blue, and the maximum color difference to increase, with a continuous change observed along curve B, indicated by the roughly semicircular arrow in the figure.

[0106] Therefore, the degree of deterioration of the sampled lubricant can be determined by photographing the sampled lubricant together with a color sample, calculating the brightness (ΔE) and maximum color difference of the corrected image, and determining where it is located on curve B shown in Figure 7.

[0107] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0108] This application is based on a Japanese patent application filed on June 3, 2021 (Patent Application No. 2021-093548), a Japanese patent application filed on February 21, 2022 (Patent Application No. 2022-025090), a Japanese design registration application filed on March 4, 2022 (Patent Application No. 2022-004481), and a Japanese patent application filed on May 27, 2022 (Patent Application No. 2022-086825), the contents of which are incorporated by reference into this application. [Explanation of symbols]

[0109] 1 color swatch 10 Mount 20 color samples 30 Identification Code 40 Sample placement section

Claims

1. A step of photographing the lubricant alone or the lubricant diluted with a solvent together with a color sample using an imaging device; a step of determining a deterioration state of the lubricant from image information of the lubricant alone or the lubricant diluted with the solvent, based on image information of the photographed color sample; A lubricant deterioration detection method comprising:

2. correcting the white balance of the photographed image information of the lubricant alone or the lubricant diluted with the solvent based on the white balance of the image information of the color sample; The lubricant deterioration detection method according to claim 1 , further comprising: determining a deterioration state of the lubricant from the corrected image information.

3. The lubricant deterioration detection method according to claim 1 or 2, wherein the imaging device has a white balance correction function.

4. The lubricant deterioration detection method according to claim 3 , wherein the imaging device is a digital camera or a mobile terminal with a camera.

5. 3. The lubricant deterioration detection method according to claim 1, wherein the lubricant is lubricating oil or grease.

6. The lubricant deterioration detection method according to claim 1 or 2, wherein the solvent includes an organic solvent, kerosene, or gasoline.

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