Method for detecting deterioration of lubricating grease and method for detecting deterioration of lubricant

Abstract

This invention provides a method for detecting the deterioration of lubricating grease, which can detect the deterioration of lubricating grease, and the amount of lubricating grease required for detection is small. The lubricating grease deterioration detection method includes: a dilution step, in which the lubricating grease is diluted with a diluent to obtain diluted lubricating grease; and a measurement step, in which the color of the diluted lubricating grease is measured using a sensor.

Description

Technical Field

[0001] This invention relates to methods for detecting the deterioration state of lubricating grease and methods for detecting the deterioration state of lubricants. Background Technology

[0002] (The first aspect of this invention)

[0003] Patent Document 1 discloses a fault prediction device that determines the iron powder concentration in the grease used in rolling bearings based on the disruption of the magnetic balance in the excitation coil and the detection coil, thereby predicting the failure of the rolling bearings.

[0004] However, the technology disclosed in Patent Document 1 has the problem that the amount of grease required to determine the iron powder concentration is relatively large. Furthermore, the technology disclosed in Patent Document 1 cannot detect the oxidative deterioration of the grease.

[0005] (Second aspect of the invention)

[0006] In addition, grease is used in components of various mechanical devices, primarily rolling bearings and speed reducers. One cause of failure in these components is abnormal wear. When abnormal wear occurs, foreign matter such as iron powder mixes into the grease, leading to its deterioration. Furthermore, there are several main reasons for grease deterioration, such as deterioration caused by changes in composition due to heating, and deterioration due to oxidation.

[0007] Regarding lubricating oils used in the same applications as greases, various methods for detecting conditions such as deterioration have been studied. For example, Patent Document 2 discloses a color sensor installed on the mechanical device itself, which can detect the condition of the lubricating oil.

[0008] However, compared with lubricating oil, grease has lower fluidity and lower light transmittance, making it difficult to analyze the deterioration of grease.

[0009] If the deterioration of grease is limited to conditions caused by the incorporation of iron powder, for example, Patent Document 1 discloses a fault prediction device that measures the concentration of iron powder in the grease used in the component being measured based on the disruption of the magnetic balance in the excitation coil and the detection coil, thereby predicting the fault of the component being measured.

[0010] However, the technology disclosed in Patent Document 1 requires a relatively large amount of grease to determine the iron powder concentration. Furthermore, the sensor portion of the fault prediction device needs to be installed at the desired detection location, incurring time and cost from device manufacturing to installation and prediction. Moreover, it is limited to detecting deterioration caused by iron powder mixing into the grease, and cannot detect deterioration accompanying changes in grease composition due to oxidation or heat.

[0011] (The third aspect of this invention)

[0012] The lubricants used in the lubrication of various mechanical devices will deteriorate over time due to oxidation or the introduction of foreign matter.

[0013] As a method for detecting the deterioration state of a lubricant, Patent Document 2 describes a sensor that immerses the lubricant in 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 based on the light transmission state.

[0014] However, the method for detecting the deterioration state of lubricant described in Patent Document 2 requires a large amount of lubricant, and can only measure lubricating oil, not grease. Furthermore, there is the problem of sensor deterioration due to immersion in lubricant, and the sensor also needs to be cleaned. Moreover, the type of light source is limited to white LED, restricting the detection location.

[0015] Existing technical documents

[0016] Patent documents

[0017] Patent Document 1: Japanese Patent No. 5188088

[0018] Patent Document 2: Japanese Patent No. 5980591 Summary of the Invention

[0019] The technical problem that the invention aims to solve

[0020] Regarding the first objective of the present invention, the first objective of the present invention is to provide a method for detecting the deterioration of grease, wherein the method is capable of detecting the deterioration of grease and the amount of grease required for detecting the deterioration is small.

[0021] Regarding the second objective of the present invention, the second objective is to provide a method for detecting the deterioration of lubricating grease, which can detect deterioration caused by oxidation and heat in a short time, in addition to deterioration caused by the incorporation of foreign matter such as iron powder.

[0022] Regarding the third aspect of the present invention described above, the third objective of the present invention is to provide a method that, in addition to lubricating oil, also uses lubricating grease as a test object, can easily and quickly and more accurately detect the deterioration state of the lubricant, and can use a smaller amount of lubricant, and the detection device will not deteriorate, does not require cleaning, and is not limited by the type of light source, and can be used in a wide variety of places.

[0023] Technical means for solving problems

[0024] The first objective of the present invention is achieved by the structure described below [1] involved in the method for detecting the deterioration of grease.

[0025] [1] A method for detecting the deterioration of lubricating grease, which is a method for detecting the deterioration of lubricating grease.

[0026] The method for detecting the deterioration of the lubricating grease includes:

[0027] The dilution process involves diluting the grease with a diluent to obtain diluted grease; and

[0028] The measurement process involves using a sensor to determine the color of the diluted grease.

[0029] Furthermore, the preferred embodiments of the grease deterioration detection method of the present invention relate to the following [2] to [4].

[0030] [2] According to the grease deterioration detection method described in [1], the sensor is a color sensor.

[0031] [3] According to the deterioration detection method of the grease described in [1] or [2], the diluent is an organic solvent.

[0032] [4] According to the method for detecting the deterioration of grease described in [3], the organic solvent is at least one selected from the group consisting of n-hexane, kerosene and gasoline.

[0033] In addition, in this specification, the inventions involved in [1] to [4] above are referred to as the "first group of inventions".

[0034] The second objective of the present invention is achieved by the structure described below [5] involved in the method for detecting the deterioration of grease.

[0035] [5] A method for detecting the deterioration of lubricating grease, which is a method for detecting the deterioration of lubricating grease.

[0036] The method for detecting the deterioration of the lubricating grease includes:

[0037] The process of clamping grease between a pair of transparent plates and spreading the grease to form a thin film; and

[0038] The process of using a camera or sensor to determine the color of the thin-film lubricating grease.

[0039] The degree of deterioration of the grease is determined by the aforementioned measurement.

[0040] Furthermore, the preferred embodiments of the grease deterioration detection method of the present invention relate to the following [6] to [7].

[0041] [6] According to the grease deterioration detection method described in [5], the sensor is a color sensor.

[0042] [7] The method for detecting the deterioration of grease according to claim [5] or [6],

[0043] The transparent material is at least one selected from the group consisting of glass, acrylic, polyethylene terephthalate, and polycarbonate.

[0044] In addition, in this specification, the inventions involved in [5] to [7] above are referred to as the "second group of inventions".

[0045] The aforementioned third objective of the present invention is achieved by the structure described below [8] involved in the lubricant deterioration detection method.

[0046] [8] A method for detecting lubricant deterioration, comprising:

[0047] The process of using a camera device to photograph the lubricant alone, or the lubricant diluted with a solvent, together with a color sample; and

[0048] The process of determining the deterioration state of the lubricant based on the image information of the captured color sample and the image information of the lubricant captured only or the lubricant diluted with the solvent.

[0049] Furthermore, the preferred embodiments of the present invention relating to the lubricant degradation detection method are as follows [9] to

[13] .

[0050] [9] According to the lubricant deterioration detection method described in [8],

[0051] Based on the white balance in the image information of the color samples, correct the white balance in the image information of the lubricant captured only, or the lubricant diluted with the solvent.

[0052] Based on the corrected image information, the deterioration state of the lubricant is determined.

[0053]

[10] According to the lubricant deterioration detection method described in [8] or [9], the camera device has a white balance correction function.

[0054]

[11] According to the lubricant deterioration detection method described in

[10] , the camera device is a digital camera or a portable terminal with a video camera.

[0055]

[12] According to the lubricant deterioration detection method described in [8] or [9], the lubricant is lubricating oil or lubricating grease.

[0056]

[13] According to the lubricant deterioration detection method described in [8] or [9], the solvent includes organic solvents, kerosene or gasoline.

[0057] It should be noted that, in this specification, the inventions involved in [8] to

[13] above are referred to as "the third group of inventions".

[0058] Invention Effects

[0059] According to the present invention described in the aforementioned "first invention group", it is possible to detect the deterioration of a lubricating grease using a small amount of grease.

[0060] According to the present invention described in the aforementioned "Second Invention Group," it is possible not only to detect the intrusion of foreign matter such as iron powder, but also to detect the deterioration of lubricating grease caused by oxidation or heat. Furthermore, since deterioration can be detected in a short time using only a small amount of lubricating grease, it is not only very useful in terms of cost and time, but also allows for the on-site determination of the degree of deterioration of the lubricating grease by collecting lubricating grease samples from any number of parts of a component.

[0061] According to the present invention described in the aforementioned "Third Invention Group," the deterioration state of lubricants caused by oxidation, foreign matter contamination, etc., can be detected easily and accurately in a short time. Furthermore, the required amount of lubricant is very small, for example, around 10mg, so the detection device does not deteriorate and does not require cleaning. In addition, it can analyze lubricants in parts that directly affect the lifespan of lubricated components, such as those near the bearing raceway, improving the accuracy of fault prediction. Moreover, in addition to lubricating oil, lubricating grease can also be used as the detection target, and there are no limitations on the light source, allowing for detection in a wide variety of environments. Attached Figure Description

[0062] Figure 1 This is a graph showing the results of analyzing the grease near the retainer of a rolling bearing using the grease deterioration detection method according to the first embodiment of the present invention.

[0063] Figure 2 This is a graph showing the results of analyzing the grease inside the seal of a rolling bearing using the grease deterioration detection method according to the first embodiment of the present invention.

[0064] Figure 3 This is a graph showing the results of analyzing the grease outside the seal of a rolling bearing using the grease deterioration detection method according to the first embodiment of the present invention.

[0065] Figure 4 This is a graph showing the relationship between brightness ΔE and maximum color difference obtained in an embodiment using the grease deterioration detection method according to the second embodiment of the present invention.

[0066] Figure 5 This is a top view showing an example of a color sample used in the third embodiment of the invention.

[0067] Figure 6 This is a graph showing the results of Test Example 1 in the third embodiment of the present invention.

[0068] Figure 7 This is a graph showing the results of test example 2 in the third embodiment of the present invention.

[0069] Symbol Explanation

[0070] 1 Color Sample

[0071] 10 backing paper

[0072] 20 color samples

[0073] 30 Identification Code

[0074] 40 Sample placement section Detailed Implementation

[0075] Hereinafter, embodiments of the present invention will be described. Furthermore, this embodiment illustrates one example of the present invention, but the present invention is not limited to this embodiment. In addition, various modifications or improvements can be made to this embodiment, and methods of making such modifications or improvements are also included in the present invention.

[0076] Furthermore, in the embodiments shown below, the embodiments of the present invention described in the "first group of inventions" are referred to as "first embodiments", the embodiments of the present invention described in the "second group of inventions" are referred to as "second embodiments", and the embodiments of the present invention described in the "third group of inventions" are referred to as "third embodiments".

[0077] <First Implementation>

[0078] First, the first embodiment will be described.

[0079] The method for detecting the deterioration of lubricating grease according to this embodiment includes: a dilution step of diluting the lubricating grease with a diluent to obtain diluted lubricating grease; and a measurement step of measuring the color of the diluted lubricating grease with a sensor.

[0080] According to the grease deterioration detection method described in this embodiment, grease deterioration can be detected by measuring the color of diluted grease using a sensor. That is, if the grease deteriorates, its color changes; therefore, by using a sensor to measure the color of the grease, it is possible to determine whether the grease has deteriorated due to use or storage.

[0081] Specific examples of detectable grease deterioration include grease oxidation and the introduction of foreign matter into the grease. Specific examples of sensors used for measurement include color sensors.

[0082] Furthermore, according to the grease deterioration detection method of this embodiment described above, the deterioration state and degree of grease can be determined by measuring the color of diluted grease using a sensor. That is, since the degree of color change increases as grease deterioration intensifies, the degree of grease deterioration caused by use or storage can be determined by measuring the color of the grease using a sensor.

[0083] For example, by comparing the color of the grease whose deterioration level needs to be determined with the color of a reference grease, the state and degree of grease deterioration can be determined. In detail, undeteriorated greases such as unused grease or freshly manufactured grease are used as reference greases. The reference grease is diluted with a diluent to obtain diluted reference grease, and the color of the diluted reference grease is measured using a sensor (reference grease measurement process).

[0084] Next, the grease used as the sample to be determined for its degree of deterioration is diluted with a diluent to obtain diluted grease (dilution step), and the color of the diluted grease is measured using a sensor (measurement step). Then, the degree of deterioration of the grease is 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 should be noted that for both the reference grease and the grease used as the sample, it is preferable that the type of diluent and the color measurement conditions are the same.

[0085] Therefore, by using the grease deterioration detection method according to this embodiment, the degree of deterioration of grease used in, for example, rolling bearings can be determined. Knowing the degree of grease deterioration allows for the appropriate determination of when to perform maintenance such as replenishing unused grease to the rolling bearing or replacing the rolling bearing.

[0086] Furthermore, in the grease deterioration detection method according to this embodiment, since the color of the diluted grease (made by diluting the grease with a diluent) is measured, a small amount of grease (e.g., 10 mg) is sufficient for deterioration detection. Even with a small amount of grease, both oxidation deterioration and foreign matter contamination can be detected in a short time.

[0087] Furthermore, in the grease deterioration detection method according to this embodiment, since the amount of grease required for deterioration detection is small, it is possible to analyze the grease present near the track that directly affects the life of the rolling bearing. Therefore, it is possible to determine the degree of deterioration of the grease used in rolling bearings and predict rolling bearing failures with high precision.

[0088] There are no particular restrictions on the conditions for diluting grease with a thinner. The temperature can be room temperature, as long as the thinner does not evaporate. Heating is also acceptable. Furthermore, dilution can be done by stirring or not.

[0089] In addition, there is no particular limitation on the dilution ratio when diluting the grease with a diluent. In order to measure the color with high accuracy, it is preferable to dilute with 1 or more but less than 10,000 parts by weight of diluent relative to 1 part by weight of grease, more preferably with 10 or more but less than 10,000 parts by weight of diluent, and even more preferably with 10 or more but less than 1,000 parts by weight of diluent.

[0090] Furthermore, there are no particular limitations on the type of diluent, as long as it is easily miscible with the grease and has colorlessness and transparency to the extent that it does not cause obstruction when measuring the color of the diluted grease using a sensor; organic solvents are preferred. One type of diluent may be used alone, or two or more may be used in combination.

[0091] Specific examples of organic solvents include petroleum products such as kerosene, light oil, 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.

[0092] <Examples related to the first implementation>

[0093] An example of monitoring the deterioration of grease used in rolling bearings is provided. The rolling bearing used is a deep groove ball bearing, nominal number 6530VV, with an inner diameter of 25 mm, an outer diameter of 62 mm, and a width of 17 mm. The grease used has lithium soap as a thickener and a mixture of poly-α-olefin and diester oil as the base oil (kinematic viscosity at 40°C is 15.9 mm). 2 / s), with a consistency of No. 2.

[0094] The grease was filled into the interior of the rolling bearing, and a radial load of 98 N and an axial load of 1470 N were applied while the bearing was rotated at a speed of 10000 min. -1Rotate the inner ring. Set the outer ring temperature to 140°C. Set the rotation time to 100 hours, 200 hours, 300 hours, and 417 hours. After each of these rotation times, collect grease from the rolling bearing. The grease collection points are: the area near the retainer of the rolling bearing, the area near the seal and its inner side, and the area near the seal and its outer side. It should be noted that the 417-hour rotation time is the time required for rotation to stop when the outer ring temperature reaches 170°C.

[0095] Each collected 10 mg sample of lubricating grease was dissolved in 1 mL of n-hexane to obtain diluted lubricating grease. Then, the hue of each diluted lubricating grease was measured using a T-ODS-301 oil diagnostic instrument manufactured by MKT Taisei Co., Ltd. Hue was represented by three colors: red (R), green (G), and blue (B), and each color was represented by 256 gray levels from 0 to 255. The brightness ΔE of each diluted lubricating grease was calculated by substituting the RGB values ​​obtained from the color sensor into the following formula.

[0096] ΔE=(R 2 +G 2 +B 2 ) 0.5

[0097] In addition, the difference between the maximum and minimum values ​​of the RGB values ​​obtained from the color sensor is calculated and used as the maximum color difference of each diluted grease.

[0098] exist Figure 1-3 The graph shows the brightness ΔE and maximum color difference plotted for each sampling point of the grease. Figure 1 The data collection area for the chart is the area near the holder. Figure 2 The data collection point for the chart is the inner part of the seal. Figure 3 The data collection point for the chart is the outer part of the seal. Additionally, the numbers recorded near the plotted points in the chart represent the rotation time of the rolling bearing. A rotation time of 0 hours represents unused grease; this unused grease is used as the baseline grease, and its color is measured in the same manner as the grease at each rotation time.

[0099] As the rolling bearing rotates for a longer period, the grease deteriorates more. With increased deterioration, the grease's hue changes, the maximum color difference increases, and the brightness ΔE decreases. That is, the grease's color changes from colorless (white) to black. Then, if the brightness ΔE is plotted against the maximum color difference, a curve like the one shown in the graph is drawn using arrows that are curved into approximately semicircles.

[0100] Additionally, the brightness ΔE of unused grease is approximately 442 (R=255, G=255, B=255), but as the grease deteriorates, the brightness ΔE approaches 0. This may indicate that solid particles such as wear dust are mixed into the grease as foreign matter.

[0101] right Figures 1-3 The diagram illustrates this. Unused grease is almost colorless and has a large brightness ΔE, but as the rotation time increases, the grease turns brownish-brown, thus decreasing the brightness ΔE and reducing the blue hue, resulting in a larger maximum color difference. Furthermore, if the rotation time is extended further, as the grease approaches sintering near the rolling bearing, its color becomes close to black (R=0, G=0, B=0), further decreasing the brightness ΔE and resulting in a smaller maximum color difference.

[0102] Thus, if the brightness ΔE and the maximum color difference are plotted, a curve as shown in the graph is drawn using arrows that are bent into a roughly semi-circular shape. Therefore, by observing where the curve plotting the brightness ΔE and the maximum color difference of the diluted grease is located on the aforementioned curve, the degree of grease deterioration can be determined.

[0103] <Second Implementation>

[0104] Next, the second embodiment will be described.

[0105] The method for detecting grease deterioration according to this embodiment includes: a step of holding the grease between a pair of transparent plates and spreading it into a thin film; and a step of measuring the color of the thin-filmed grease using a camera or sensor. The degree of grease deterioration is determined through the above measurement steps.

[0106] In addition, other steps besides those described above may be included without compromising the effectiveness of the present invention.

[0107] (Thin film processing)

[0108] If grease deteriorates, its color will change. However, grease has lower fluidity and higher viscosity than lubricating oil. Therefore, even in situations with low light transmittance, where there is a significant color difference between an initial state with no deterioration and a state of severe deterioration, it is difficult to discern subtle differences in deterioration.

[0109] In this embodiment, a step is included to spread the grease into a thin film by sandwiching it between a pair of transparent plates. This increases the light transmittance of the grease, allowing subtle differences in deterioration to be clearly identified as variations in hue.

[0110] Furthermore, a small amount of grease is sufficient to spread it into a thin film. Therefore, by analyzing the grease at specific points that directly affect the lifespan of components with grease, the accuracy of fault prediction increases. Specifically, in the case of a rolling bearing, analysis of the grease present near the track allows for high-precision determination of the degree of grease degradation used in rolling bearings and the prediction of bearing failures.

[0111] A pair of transparent materials can be used to sandwich and spread the grease, thereby enabling the grease to be film-formed. In addition, there are no particular limitations as long as it does not affect the observation of the grease's color.

[0112] For example, it is preferably selected from at least one of glass, acrylic, polyethylene terephthalate and polycarbonate, among which the same transparent material can be used as a pair of transparent materials, or two different materials can be used as a pair of transparent materials.

[0113] The transparent material plate only needs to have a flat surface to hold the grease; its size and thickness are not particularly limited. The preferred range for plate size and thickness varies depending on the transparent material used, the spreading method, and the amount of grease. For example, when using two pieces of sliding glass as a pair of transparent materials, and applying force to spread the grease from the sliding glass, the glass only needs to have sufficient strength and thickness to prevent it from breaking under that force. Furthermore, the transparent material only needs to be large enough to prevent the thin film of grease from flying out during spreading. Also, the size and thickness of the pair of transparent material plates do not need to be identical.

[0114] The amount of grease sandwiched between a pair of transparent material 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. However, from the viewpoint of making the thickness and area of ​​the grease easily detectable when spread out, 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 analyzing the grease in portions that directly affect the lifespan of the component using a needle point, it is preferably 10 mg or less, more preferably 5 mg or less, and even more preferably 2 mg or less.

[0115] From the viewpoint of ease of visual recognition during inspection, the size of the spread grease is preferably 1.5 mm or more in diameter, more preferably 3 mm or more, and even more preferably 5 mm or more. Furthermore, from the viewpoint of ease of operation, the size of the spread grease is preferably 30 mm or less in diameter, more preferably 15 mm or less. It should be noted that the above sizes do not mean that the spread grease is a perfect circle. That is, the area of ​​the spread grease only needs to be approximately the same as the area of ​​a circle with the aforementioned diameter.

[0116] From the viewpoint of improving the accuracy of hue analysis, the thickness of the spread grease is preferably 10 μm or more, more preferably 20 μm or more. Furthermore, from the viewpoint of preventing excessively low light transmittance, the thickness of the spread grease is preferably 0.5 mm or less, more preferably 0.1 mm or less. However, when foreign matter such as iron powder is added to the grease, the thickness can be changed depending on the size of the iron powder.

[0117] The thickness of the spread grease can be calculated based on the amount, specific gravity, and area of ​​the grease used. Alternatively, it can be directly measured using a dielectric constant test.

[0118] There are no particular limitations on the method of collecting grease from components. For example, methods such as directly collecting grease from bearings using a scraper or collecting grease discharged from a grease outlet can be used.

[0119] While a thin film of grease is not specifically required, its use is not excluded.

[0120] For example, if the grease is severely degraded and has hardened, making it difficult to form a thin film even when spread between two transparent plates, a thinner can be used to reduce the viscosity of the grease, thus enabling film formation. Additionally, if the grease is severely degraded and its color is too dark to determine the extent of deterioration, a thinner can be used to lighten its color, making it easier to assess.

[0121] There is no particular limit to the dilution ratio when diluting grease with a diluent; it can be determined appropriately based on the condition of the grease.

[0122] The diluent is not particularly limited as long as it is easily miscible with the grease and has a degree of colorlessness and transparency that does not obstruct the measurement of the grease's color using a camera or sensor; organic solvents are preferred. One type of diluent may be used alone, or two or more may be used in combination.

[0123] Specific examples of organic solvents include petroleum products such as kerosene, light oil, 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.

[0124] (Measurement Procedure)

[0125] Next, a process is performed to measure the color of the grease after it has been thinned using a camera or sensor. This measurement is used to determine the degree of grease deterioration.

[0126] Specific examples of grease deterioration that can be detected include grease oxidation, changes in grease composition due to heat, and the introduction of foreign matter such as iron powder into the grease.

[0127] Among the sensors used for measurement, color sensors are preferred because they can directly distinguish the color of grease.

[0128] The more severe the deterioration of a grease, the greater the change in its color. Therefore, by using sensors such as color sensors to measure the color of a grease, the degree of deterioration of the grease can be determined.

[0129] The grease deterioration detection method described in this embodiment improves the light transmittance of the grease by thinning it into a film, allowing for the precise identification of subtle differences in deterioration as variations in hue. Therefore, the degree of grease deterioration can be detected in detail.

[0130] In one embodiment, the degree of grease deterioration is determined by comparing the color of the thin-film grease with the color of a reference grease. Specifically, undeteriorated grease, such as unused grease or freshly manufactured grease, is used as a "reference grease." This reference grease is sandwiched between a pair of transparent plates and spread into a thin film. Preferably, the amount, spread area, and thickness of the reference grease are the same as those of the grease being tested for deterioration. The color of this reference grease is measured using a sensor and used as a reference for subsequent measurements.

[0131] Next, as described above, the color of the grease, which is the object of the degradation test, is measured using a sensor after it has been sandwiched between a pair of transparent materials and spread into a thin film. Then, the degree of degradation of the grease is determined by comparing its color with that of a reference grease.

[0132] When using a camera instead of a sensor to measure the color of the grease, the color is compared with that of a reference grease to determine the degree of grease deterioration, just as described above.

[0133] With white grease placed against a background, the grease, which is the object to be tested for the degree of degradation, is held between a pair of transparent materials and spread out to form a thin film. The grease is then photographed, for example, along with a color sample. The color sample is used for color standardization, thereby allowing for correction of white balance and other parameters in the photographed image. Regardless of the brightness or other conditions of the shooting location, the degree of degradation can be determined.

[0134] For a reference grease that is sandwiched between a pair of transparent materials and spread out to form a thin film, it can be photographed and corrected together with the grease to be tested for deterioration while white grease is placed in the background, or it can be photographed in advance with a color sample to achieve a state after white balance and other corrections, and then compared with the color of the actual photographed and corrected grease to be tested for deterioration.

[0135] The degree of deterioration is judged by the brightness of the color of the thin-film grease, as measured by a camera or sensor.

[0136] The hue is represented by three colors: red (R), green (G), and blue (B), each represented by 256 gray levels ranging from 0 to 255. The brightness ΔE of the grease is calculated by substituting the RGB values ​​obtained from the sensor or the RGB values ​​extracted from the hue information of an image captured by a camera and corrected into the following formula.

[0137] ΔE=(R 2 +G 2 +B 2 ) 0.5

[0138] In addition, the difference between the maximum and minimum values ​​of the RGB values ​​obtained by measurement through a camera or sensor is set as the maximum color difference for each grease.

[0139] For the reference grease and the grease used to test the degree of deterioration, the brightness ΔE and maximum color difference are calculated respectively. The brightness ΔE is plotted on the X-axis and the maximum color difference is plotted on the Y-axis, thereby determining the degree of deterioration of the grease.

[0140] Thus, by using the grease deterioration detection method described in this embodiment, the degree of deterioration of grease used in applications such as rolling bearings can be determined at specific locations. Knowing the degree of deterioration at each location where grease is applied allows for the appropriate determination of when to replenish unused grease to rolling bearings, replace rolling bearings, and perform other maintenance, as well as taking measures to adjust the maintenance schedule for each location.

[0141] Furthermore, in the grease deterioration detection method described in this embodiment, only a small amount of grease is needed to detect deterioration, and the detection can be performed in a short time. Therefore, the degree of deterioration of grease collected from components such as rolling bearings can be determined very easily and accurately on-site.

[0142] Furthermore, it can detect not only degradation caused by the intrusion of foreign matter, but also degradation caused by oxidation and degradation caused by changes in composition due to heat, making it extremely useful.

[0143] <Examples related to the second implementation>

[0144] [Examples 1-7]

[0145] Monitor the degree of deterioration of the grease used in rolling bearings.

[0146] The rolling bearing uses an inner diameter of 25mm, an outer diameter of 62mm, and a width of 17mm. Grease is filled inside the rolling bearing, which is then continuously rotated under conditions of 2000 r / min, bearing outer ring temperature of 120℃, radial load of 98N, and axial load of 1470N. Commercially available grease is used, with lithium soap as the thickener, a consistency of No. 2, and mineral oil as the base oil.

[0147] The test times are as shown in Table 1, ranging from 0 to 600 hours. After each rotation period, grease was collected from the outside of the seals in the rolling bearing using a scraper. It should be noted that in the embodiment with a rotation time of 600 hours, rotation stopped after the time elapsed, but could not be restarted due to the increased bearing torque.

[0148] One mg of the collected grease was sandwiched between a pair of sliding glass plates and spread out under pressure, forming a thin film with a diameter of 6 mm and a thickness of approximately 40 μm. Next, the grease film was photographed, and tonal information was extracted from the image data. White balance correction was performed by photographing the grease along with color samples. The tones are represented by three colors: red (R), green (G), and blue (B), each represented by 256 gray levels from 0 to 255. The brightness ΔE of each grease was calculated by substituting the RGB values ​​into the following formula. Additionally, the difference between the maximum and minimum RGB values, i.e., the maximum color difference, was also calculated.

[0149] ΔE=(R 2 +G 2 +B 2 ) 0.5

[0150] The results are shown in Table 1 and Figure 4 In addition, Figure 4 The numbers recorded near the plotting points indicate the rotation time.

[0151] [Table 1]

[0152] Table 1

[0153]

[0154] As a result, the grease in Example 1, referred to as the reference grease, was almost colorless and had a high brightness ΔE. In contrast, the grease deteriorated and turned brownish-red over time. Specifically, the brightness ΔE decreased, the blue (B) value in the hue decreased, and thus a continuous change with a larger maximum color difference was observed.

[0155] Based on the brightness ΔE and the location of the maximum color difference Figure 4 The approximate semi-circular position shown indicates the degree of grease deterioration.

[0156] As the grease deteriorates, its color changes from colorless (white) to brown. That is, the grease's brightness ΔE decreases, and the blue (B) value decreases with brown color, thus increasing the maximum color difference. Furthermore, as the rotation time increases further, and the rolling bearing nears burnout, the deterioration intensifies, and the grease's color changes from brown to black (R=0, G=0, B=0). Therefore, the brightness ΔE decreases further, and the maximum color difference also decreases.

[0157] Such changes are represented by curves plotted with roughly semi-circular, curved arrows, as shown in the graph. Furthermore, in regions where the brightness ΔE is close to 0, it may indicate not only deterioration due to grease oxidation, but also the presence of solid particles such as wear dust as foreign matter mixed into the grease.

[0158] In Examples 1 to 7, since the grease outside the seal in the rolling bearing is used as the object of deterioration detection, the color change is smaller compared with the grease applied to the part that actually helps lubrication. However, as a threshold, when the brightness ΔE of the new grease with a rotation time of 0, which serves as the reference grease, reaches about half of the brightness ΔE, it is preferable to reapply the grease or replace the rolling bearing.

[0159] In the actual use of the grease deterioration detection method described in this embodiment, such as Figure 4 By plotting the brightness ΔE and the maximum color difference, and observing where the curve, which is roughly a semi-circular arrow, is located, the degree of grease deterioration can be determined at a glance, thus making it the preferred option.

[0160] <Third Implementation Method>

[0161] First, the third implementation method will be described.

[0162] As the lubricant degradation detection method of the present invention (hereinafter referred to as the "degradation detection method"), firstly, the device or equipment using lubricating oil or grease (hereinafter collectively referred to as "lubricant") is stopped, such as a rolling bearing or ball screw device. The lubricant is collected and placed in a container, and photographed together with a color sample. Various camera devices can be used for the photographing, and there are no particular limitations on their type; for example, portable terminals with built-in cameras such as digital cameras, smartphones, and tablets can be used. Furthermore, there are no particular limitations on the type of light source used during the photographing, allowing for detection in various locations.

[0163] like Figure 5 As shown, color sample 1 is a list of multiple color samples 20 arranged in different shades and intensities from white (top left in the figure) to black (bottom right in the figure) on the surface of the backing paper 10. Furthermore, the image information of color sample 1 is printed on the backing paper 10 as an identification code 30. The identification code 30 may be a barcode, an illustrated QR code (registered trademark), or the like.

[0164] Then, the collected lubricant is placed in a petri dish or a transparent bottle (not shown), and placed on the sample placement part 40 indicated by circles in the figure. It is then photographed using various imaging devices along with color sample 1. Here, a lubricant collection amount of approximately 10 mg is sufficient, representing a very small amount. Furthermore, the lubricant may or may not require solvent dilution. As for the solvent, there are no particular limitations as long as it is easily miscible with the lubricant and has colorlessness and transparency to the extent that it does not obstruct the photographing of the lubricant's color. Specifically, organic solvents, kerosene-based solvents, and gasoline-based solvents are preferred. Furthermore, by diluting the lubricant with a solvent, it is possible to more finely differentiate lubricants that have turned dark, especially black.

[0165] The image information of the captured lubricant is compared with the image information of color sample 1. At this time, it is preferable to correct the white balance in the captured image information of the lubricant. By correcting the white balance, the captured image information of the lubricant can be made appropriate based on the image information of color sample 1, regardless of the environment of the shooting location, i.e., the testing location, which may be affected by factors such as brightness.

[0166] Furthermore, if the camera device used has a white balance correction function, the aforementioned white balance correction can be performed using that function. Alternatively, the image information obtained by the camera device can be sent to an external processing device such as a server, where the white balance correction can be performed using that processing device's white balance correction function. Additionally, the comparison between the image information of the lubricant described later and the image information of color sample 1 can be performed either within the camera device or in an external processing device.

[0167] Next, the hue of the lubricant image after white balance correction (hereinafter referred to as the "corrected image") is determined. The hue is represented by three colors: red (R), green (G), and blue (B). Based on the RGB values ​​of the corrected image, the luminance (ΔE) is calculated according to the following formula (1).

[0168] Brightness (ΔE) = (R) 2 +G 2 +B 2 ) 0·5 (1)

[0169] In addition, the difference between the maximum and minimum values ​​in the RGB values ​​is used as a lubricant to correct the maximum color difference in the image.

[0170] Furthermore, as shown in the experimental examples described later, lubricant samples were collected at predetermined usage intervals, and the aforementioned brightness (ΔE) and maximum color difference were calculated. A graph was plotted with brightness (ΔE) as the X-axis and maximum color difference as the Y-axis to observe the correlation. Based on this graph, the degree of deterioration (deterioration state) of the collected lubricant could be determined. This degree of deterioration could then be reflected in the appropriate lubricant replacement period.

[0171] In addition, the correction corresponding to the dilution rate enables camera devices and servers to have correction functions, which can be performed through pre-made correction tables, etc.

[0172] <Example of the Third Embodiment>

[0173] The following examples, as Test Example 1, illustrate the monitoring of the deterioration state of the grease in rolling bearings, and as Test Example 2, illustrate the monitoring of the deterioration state of the lubricating oil in rolling bearings.

[0174] (Example 1: An example of monitoring the deterioration state of grease in rolling bearings)

[0175] A rolling bearing with an inner diameter of 25 mm, an outer diameter of 62 mm, and a width of 17 mm was used for continuous rotation under the following conditions: inner ring rotation, grease lubrication, speed of 2000 r / min, bearing outer ring temperature of 120°C, radial load of 98 N, and axial load of 1470 N. A commercially available grease with a mineral oil base, lithium soap as the thickener, and a consistency of No. 2 was used as the lubricant.

[0176] Then, grease was collected from the rolling bearings after 100, 200, 300, 400, 500, and 600 hours of operation. It should be noted that for the rolling bearings that had been running for 600 hours, after stopping operation and collecting grease, an attempt was made to restart operation, but due to the increased bearing torque, it was impossible to restart.

[0177] The amount of grease collected was 10 mg, which was dissolved in 1 mL of hexane.

[0178] The collected greases were placed in petri dishes and then placed on the sample placement area of ​​the color samples. Each grease and color sample was photographed together using a digital camera with white balance correction. The RGB values ​​were calculated from the corrected images. Furthermore, the luminance (ΔE) and maximum color difference were calculated based on the calculated RGB values, and the results are shown in Table 2 below.

[0179] [Table 2]

[0180] Table 2

[0181]

[0182] in addition, Figure 6 The results are shown by plotting brightness (ΔE) on the X-axis and maximum color difference on the Y-axis. The numbers in the graph represent the respective operating times (hr). As a result, the new product has almost no color and high brightness. However, as the operating time increases, the grease deteriorates and turns brown, thus decreasing the brightness, gradually reducing the blue tint, and increasing the maximum color difference, observed as a continuous change along curve A, indicated by the roughly semi-circular arrow in the graph.

[0183] Therefore, the collected grease was photographed together with color samples, and the brightness (ΔE) and maximum color difference of the corrected image were calculated. This was based on the location... Figure 6 The location of curve A indicates the degree of deterioration of the collected grease.

[0184] (Example 2: An example of monitoring the deterioration state of lubricating oil in rolling bearings)

[0185] The thrust cylindrical roller bearing, with an inner diameter of 60 mm, an outer diameter of 95 mm, and a nominal height of 26 mm, is used for continuous rotation under the following conditions: inner ring rotation, oil lubrication, speed of 500 r / min, bearing temperature of 100 °C, and axial load of 60 kN. A VG32 equivalent lubricant is used at a supply rate of 0.1 L / min.

[0186] Then, after the thrust cylindrical roller bearing was run for 515 hours, 800 hours, and 1136 hours, lubricating oil was collected from the oil recovery tank.

[0187] The lubricating oil was collected in 1 mL volume and placed in a petri dish without dilution. This dish was then placed on the sample placement area of ​​the color sample. Each lubricating oil sample and the color sample were photographed together using a digital camera with white balance correction. The RGB values ​​were then calculated from the corrected images. Furthermore, the luminance (ΔE) and maximum color difference were calculated based on the RGB values, and the results are shown in Table 3 below.

[0188] [Table 3]

[0189] Table 3

[0190]

[0191] in addition, Figure 7 The results are shown by plotting brightness (ΔE) on the X-axis and maximum color difference on the Y-axis. The numbers in the graph represent the respective operating times (hr). As a result, the new product has almost no color and high brightness. However, as the operating time increases, the grease deteriorates and turns brown, thus decreasing the brightness, gradually reducing the blue tint, and increasing the maximum color difference. A continuous change is observed along curve B, indicated by the roughly semi-circular arrow in the graph.

[0192] Therefore, the collected lubricating oil and color samples were photographed together, and the brightness (ΔE) and maximum color difference of the corrected image were calculated. Based on the location... Figure 7 The location of curve B indicates the degree of deterioration of the collected lubricating oil.

[0193] Various embodiments have been described above with reference to the accompanying drawings; however, the present invention is not limited to the examples described above. Various modifications and variations will be conceived by those skilled in the art within the scope of the appended claims, but it should be understood that they will naturally fall within the technical scope of the present invention. Furthermore, the structural elements of the above embodiments can be combined arbitrarily without departing from the spirit of the present invention.

[0194] Furthermore, the contents of Japanese patent applications filed on June 3, 2021 (Japanese Patent Application No. 2021-093548), February 21, 2022 (Japanese Patent Application No. 2022-025090), March 4, 2022 (Japanese Patent Application No. 2022-004481), and May 27, 2022 (Japanese Patent Application No. 2022-086825) are incorporated herein by reference.

Claims

1. A method for detecting the deterioration of lubricating grease, characterized in that, The method for detecting the deterioration of the lubricating grease includes: The dilution process involves diluting the grease with a diluent to obtain diluted grease; and In the testing process, a sensor is used to measure the color of the diluted grease. The degree of deterioration of the grease is determined by comparing the color of the diluted grease with the color of the reference grease.

2. The method for detecting the deterioration of lubricating grease according to claim 1, characterized in that, The sensor is a color sensor.

3. The method for detecting the deterioration of lubricating grease according to claim 1 or 2, characterized in that, The diluent is an organic solvent.

4. The method for detecting the deterioration of lubricating grease according to claim 3, characterized in that, The organic solvent is at least one selected from the group consisting of n-hexane, kerosene, and gasoline.

5. A method for detecting the deterioration of lubricating grease, characterized in that, The method for detecting the deterioration of the lubricating grease includes: The process of diluting the grease with a diluent to obtain diluted grease; The process of clamping diluted grease between a pair of transparent plates and spreading the diluted grease to form a thin film; and The process of using a camera or sensor to determine the color of the thinned, diluted grease. The degree of deterioration of the grease is determined by the aforementioned measurement.

6. The method for detecting the deterioration of lubricating grease according to claim 5, characterized in that, The sensor is a color sensor.

7. The method for detecting the deterioration of lubricating grease according to claim 5 or 6, characterized in that, The transparent material is at least one selected from the group consisting of glass, acrylic, polyethylene terephthalate and polycarbonate.

8. A grease deterioration detection method characterized by, have: The process of preparing backing paper with color samples, wherein the image information of the color samples is printed on the backing paper as an identification code; The process of placing the grease diluted with solvent into a container and placing the container on the sample placement part of the backing paper; The process of using a camera device to photograph the solvent-diluted grease together with a color sample; and The process of comparing the image information of the grease diluted with solvent with the image information of the color sample to determine the deterioration state of the grease.

9. The method for detecting grease deterioration according to claim 8, characterized in that, Based on the white balance in the image information of the color samples, the white balance in the captured image information of the grease diluted with solvent is corrected. The deterioration state of the grease is determined based on the corrected image information.

10. The method for detecting grease deterioration according to claim 8 or 9, characterized in that, The camera device has a white balance correction function.

11. The method for detecting grease deterioration according to claim 10, characterized in that, The camera device is a digital camera or a portable terminal with a video camera.

12. The method for detecting grease deterioration according to claim 8 or 9, characterized in that, The solvents include organic solvents, kerosene, or gasoline.

Images