Analysis methods, instrumental diagnostic methods

Abstract

The present invention aims to provide an analytical method that can analyze lubricants containing magnetic powder with relatively large particle sizes with high precision, that is, by separately collecting, classifying, and evaluating the magnetic powder contained in a sample liquid, as well as to provide an instrumental diagnostic method. [Solution] The analytical method of the present invention comprises the steps of: S1 preparing a sample solution by mixing a lubricant containing magnetic powder with a dissolving solution; S2 agitating the sample solution with a magnet placed outside the container containing the sample solution, and then discarding the dissolving solution from the sample solution; S3 collecting the residue containing magnetic powder remaining inside the container and separating the magnetic powder into multiple groups according to particle size using a filter; and S4 measuring each of the magnetic powders separated into multiple groups in step S3, and analyzing the lubricant based on the obtained measurement values ​​and the particle size of the magnetic powder contained in the group.

Description

Technical Field

[0001] The present invention relates to an analysis method. More specifically, it relates to an analysis method for magnetic powder contained in lubricants and the like. The present invention also relates to an equipment diagnosis method.

Background Art

[0002] Lubricants such as lubricating oil and grease are widely used in the sliding parts of equipment. The above lubricants are used, for example, in hydraulic control devices, pumps, engines, pistons, bearings, gears, and valves.

[0003] In the sliding parts of the above equipment, since there is contact between the members constituting the equipment, wear occurs at the contact portion, and wear powder derived from the members is generated. Since the generated wear powder exists in the lubricant, the wear state of the sliding part can be estimated by analyzing the wear powder.

[0004] As the above member, a member containing iron, which is a magnetic material, is often used. As an analysis method for wear powder (magnetic powder) generated from a member containing iron, conventionally, a ferro-graphy method is known in which a sample solution containing magnetic powder is prepared, and the magnetic powder is separated by gravity and magnetic force and collected for analysis (see Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] On the other hand, in relatively large-scale equipment, the sliding parts are also larger, and the amount of magnetic powder generated by wear tends to be larger. When attempting to analyze magnetic powder with relatively large particle sizes using ferrography, it is often difficult to collect all of the magnetic powder while separating it from the lubricant. Furthermore, while filtration analysis is a method for separating magnetic powder from lubricants, in general filtration analysis, when processing large amounts of lubricant, the filter can become clogged due to the influence of non-magnetic dust, oil degradation products, thickeners, and additives present in addition to the magnetic powder, making proper separation and measurement difficult. Furthermore, from the perspective of reducing the operating costs of equipment, there is a need for a method to analyze wear particles (magnetic powder) contained in lubricants with higher precision.

[0007] Therefore, the present invention aims to provide an analytical method that can analyze lubricants containing magnetic powder with relatively large particle sizes with high precision, that is, by separately collecting and classifying the magnetic powder contained in the sample liquid. The present invention also aims to provide an instrumental diagnostic method. [Means for solving the problem]

[0008] The inventors of this invention have diligently studied and developed the present invention to solve the above problems. Specifically, they have found that the above problems can be solved by the following configuration.

[0009] [1] An analytical method comprising: step S1 of preparing a sample solution by mixing a lubricant containing magnetic powder with a dissolving solution; step S2 of agitating the sample solution with a magnet placed outside the container containing the sample solution, and then discarding the dissolving solution from the sample solution; step S3 of collecting the residue containing the magnetic powder remaining inside the container and separating the magnetic powder into multiple groups according to particle size using a filter; and step S4 of measuring the magnetic powder separated into multiple groups in step S3 for each group, and analyzing the lubricant based on the obtained measurement values ​​and the particle size of the magnetic powder contained in the group. [2] The analytical method according to [1], wherein the residue is a dispersion in which the magnetic powder is dispersed, and the magnetic powder is separated into multiple groups by wet classification. [3] The analytical method described in [1], wherein the magnetic powder is separated into multiple groups by dry classification. [4] The analytical method according to any one of [1] to [3], wherein the above dissolving solution is an organic solvent. [5] The analytical method according to [4], wherein the organic solvent is n-heptane. [6] The analytical method according to any one of [1] to [3], wherein the above-mentioned dissolving solution is a cleaning solution containing a surfactant. [7] The analytical method according to any one of [1] to [6], wherein the series of steps including step S1 and step S2 described above are performed two or more times. [8] The analytical method described in any of [1] to [7], wherein the mesh opening of the filter is 400 to 500 μm. [9] The analytical method according to any one of [1] to [8], wherein in step S3 above, the separation of the magnetic powder is performed multiple times using multiple filters with different mesh sizes.

[10] The analytical method according to any one of [1] to [9], wherein in step S4 above, at least one of the iron powder concentration value, weight, and number of magnetic powders is measured for each group.

[11] The analytical method according to any one of [1] to [9], wherein in step S4 above, at least one of the morphology, surface color, and surface shape of the magnetic powder is measured for each group.

[12] A device diagnostic method in which the above-mentioned lubricant is a lubricant taken from a sliding part of the device, and the wear condition of the sliding part is diagnosed based on the analysis results obtained by any of the analysis methods described in [1] to

[11] . [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an analytical method that can analyze lubricants containing magnetic powder with relatively large particle sizes with high precision, that is, by separately collecting, classifying, and evaluating the magnetic powder contained in the sample liquid. Furthermore, according to the present invention, an instrumental diagnostic method can also be provided. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view schematically showing an example of an embodiment of step S2 included in the analysis method of the present invention. [Figure 2] This is a cross-sectional view schematically showing another example of step S2 included in the analysis method of the present invention. [Figure 3] This is a cross-sectional view schematically showing an example of step S3 included in the analysis method of the present invention. [Figure 4] This is a graph showing the number of magnetic powder for each group of magnetic powder having different particle size ranges. [Figure 5] This is a graph showing the iron powder concentration value for each group of magnetic powder having different particle size ranges.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0013] Hereinafter, the meaning of each description in this specification is represented. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are examples, and the present invention is not limited to the embodiments described below. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0014] <Analysis Method> The analysis method of the present invention includes the following steps. Step S1: A step of preparing a sample solution by mixing a lubricant containing magnetic powder and a dissolving solution. Step S2: A step of discarding the dissolving solution from the sample solution after stirring the sample solution in a state where a magnet is arranged outside a container A containing the sample solution. Step S3: Collecting the residue containing magnetic powder remaining inside container A, and separating the magnetic powder into a plurality of groups by particle size using a filter. Step S4: Measuring the magnetic powder separated into a plurality of groups in Step S3 for each group, and analyzing the lubricant based on the obtained measurement values and the particle sizes of the magnetic powder contained in each group. Further, the analysis method of the present invention preferably includes steps described later.

[0015] In the analysis method of the present invention, in the above Step S1, it is mixed with a dissolving solution that dissolves the oil and fat component contained in the lubricant, and in the above Step S2, the lubricant and the dissolving solution are stirred and mixed in the presence of a magnetic field by a magnet to separate the magnetic powder from components such as the oil and fat component, non-magnetic dust, oil and fat degradation products, thickener, and additive, and then the components such as the oil and fat component, non-magnetic dust, oil and fat degradation products, thickener, and additive are discarded together with the dissolving solution. By performing this treatment, the separation (classification) of the magnetic powder remaining in the container by particle size in Step S3 becomes easier. Then, the magnetic powder is measured for each group by particle size, and based on the obtained measurement values and the particle sizes, a detailed analysis of the magnetic powder and the lubricant can be performed. Therefore, according to the analysis method of the present invention, for a lubricant containing magnetic powder with a relatively large particle size, which was difficult with the conventional ferrography method and filtration analysis method, an analysis with high accuracy, that is, separating, collecting, and classifying and evaluating the magnetic powder contained in the sample solution can be carried out. Hereinafter, the analysis method of the present invention will be described in detail.

[0016] [Step S1] In Step S1, a lubricant containing magnetic powder and a dissolving solution are mixed to prepare a sample solution.

[0017] The magnetic powder is not particularly limited, but it is preferable that it contains iron (Fe). The magnetic powder may also include composite particles containing, for example, a non-magnetic powder such as copper alloy powder or oil degradation products, and a magnetic material such as iron, where the composite particles as a whole are magnetic. In the composite particles, the magnetic material such as iron may be uniformly distributed throughout the composite particles, or it may be more abundantly distributed on the surface of the composite particles.

[0018] Examples of lubricants containing magnetic powder include lubricants for sliding parts of operating machinery, specifically lubricants for hydraulic control devices, pumps, engines, pistons, bearings, gears, and valves. While not particularly limited, bearing or gear lubricants are preferred as lubricants containing magnetic powder for use in the analytical method of the present invention. Lubricants may be lubricating oils whose main component is oil, or lubricating greases whose main component is grease. Hereinafter, the oils and greases that are the main components contained in lubricants will be collectively referred to as "oils and fats." The lubricant can be collected from the sliding parts mentioned above. The amount collected can be adjusted as needed, but for example, 3 to 500 mL is preferred.

[0019] The above sample solution is prepared by mixing a lubricant containing magnetic powder with a dissolving solution. The dissolving solution is not particularly limited, but it is preferably a component that dissolves components other than the magnetic powder contained in the lubricant, and more preferably a component that is miscible with the oil and fat components contained in the lubricant.

[0020] Examples of dissolving solutions include cleaning solutions containing surfactants, such as liquid soap, liquid compound soap, and liquid synthetic detergent. The cleaning solution may also be a diluted solution obtained by diluting liquid soap, liquid compound soap, or liquid synthetic detergent with water. The surfactant contained in such a cleaning solution dissolves the oil and fat in the dissolving solution, promoting the separation of the magnetic powder from the oil and fat. Furthermore, since the above cleaning solutions are mainly composed of detergent and water, the health risks to the human body are extremely low. Specific examples of suitable commercially available cleaning solutions include, but are not limited to, "Lucky Boy Eco Surf Ace" and "Lucky Boy Seven Next" manufactured by Asahi Kasei Advance Corporation. When diluting a commercially available cleaning solution concentrate with water, it is preferable to dilute it so that the mass of the concentrate relative to the mass of water is in a predetermined ratio. The ratio of the mass of the concentrate relative to the mass of water is preferably 30 to 60% by mass, more preferably 40 to 55% by mass, and even more preferably 45 to 50% by mass.

[0021] Organic solvents may be used as the dissolving agent. Examples of organic solvents include hydrocarbon solvents, alcohol solvents, ether solvents, ester solvents, and ketone solvents. Examples of hydrocarbon solvents include n-pentane, n-hexane, cyclohexane, benzene, n-heptane, toluene, n-octane, xylene, n-nonane, n-decane, n-undecane, diesel fuel, and kerosene. Examples of alcohol-based solvents include methanol, ethanol, propanol, isopropyl alcohol, heptanol, hexanol, and octanol. Examples of ether-based solvents include dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, and furan. Examples of ester solvents include methyl acetate, ethyl acetate, γ-butyrolactone, propyl acetate, butyl acetate, ethyl butyrate, and pentyl acetate. Examples of ketone solvents include acetone, methyl ethyl ketone, diethyl ketone, and cyclohexanone. The dissolving solution may be a mixture of two or more organic solvents. As organic solvents, hydrocarbon solvents are preferred because they are commonly used as cleaning solutions in penetrant testing, a type of non-destructive testing, and because they have low toxicity and a high flash point, making them superior in terms of safety and ease of storage and management. N-heptane, kerosene, or light oil are more preferred.

[0022] The method for mixing the lubricant and the solvent to prepare the sample solution is not particularly limited and may be carried out by known methods. The mixing of the lubricant and the solvent may be performed in container A used in step S2, or the sample solution may be prepared in a container other than container A and then placed in container A. In step S1, the mixture containing the lubricant and the solvent may be stirred. Stirring can be carried out by known methods, such as by convection of the mixture using a stirring rod, spatula or a stirrer, by oscillating the container holding the mixture, or by applying shear force to the mixture with a rotating blade. Ultrasonic waves may also be irradiated onto the mixture.

[0023] The lubricant content in the sample solution prepared by step S1 can be adjusted as appropriate, but it is preferably 10 to 60% by mass, more preferably 40 to 55% by mass, and even more preferably 45 to 50% by mass, based on the total mass of the sample solution. The sample solution may be prepared by diluting it so that the mass of the lubricant is in a predetermined ratio to the mass of the dissolving solution. The ratio of the mass of the lubricant to the mass of the dissolving solution is preferably 5 to 35% by mass, more preferably 20 to 35% by mass, and even more preferably 25 to 30% by mass.

[0024] Furthermore, it is preferable to pre-measure the amount of magnetic powder contained in the lubricant and dilute it with a solvent to achieve a predetermined content. The magnetic powder content in a lubricant can be measured by known methods. For example, a predetermined amount of lubricant can be measured, diluted to a predetermined concentration to create a measurement solution, and quantitative ferrography can be performed using this solution. The magnetic powder content may also be measured using a particle counter or the like with respect to the measurement solution. The amount of magnetic powder contained in the lubricant can also be measured using a grease iron powder concentration meter or an oil iron powder concentration meter, as this allows for the measurement of magnetic powder within a wider particle size range. Furthermore, when measuring magnetic powders with an even wider particle size range, it is preferable to reduce the amount of lubricant, perform multiple iron powder concentration measurements within the measurable range of the grease iron powder concentration meter, and use the average of the obtained measurements as the iron powder concentration value.

[0025] [Process S2] In step S2, a magnet is placed outside container A containing the sample solution, the sample solution is stirred, and then the dissolving solution is discarded from the sample solution. The dissolution solution discarded in step S2 contains, for example, oil and grease components from the lubricant, as well as non-magnetic dust, oil and grease degradation products, thickeners, and additives. Hereinafter, these non-magnetic dust, oil and grease degradation products, thickeners, and additives will be collectively referred to as "non-magnetic components."

[0026] Process S2 will be explained in more detail using diagrams. Figure 1 is a schematic cross-sectional view showing an example of an embodiment of process S2. Figure 1 shows a state in which a magnet 2 is placed outside container 1 (container A), a sample liquid 4 is contained in container 1, and a stirrer 3 is inserted into the sample liquid 4. A magnet 2, which is an annular shape in plan view, is positioned in the center of the outer bottom of container 1. The stirrer 3 is an electric blender and is used to stir the sample liquid 4. The sample liquid 4 contains a mixture of a lubricant containing magnetic powder and a dissolving solution.

[0027] When the sample liquid 4 is stirred using the stirrer 3 with the magnet 2 positioned outside the container 1, the magnetic powder contained in the lubricant, regardless of particle size, is attracted to the magnet 2 and accumulates inside the bottom of the container 1. On the other hand, the oil and non-magnetic components contained in the lubricant are separated from the magnetic powder by the action of the dissolving solution contained in the sample liquid 4 and transferred to the dissolving solution of the sample liquid 4. After stirring, when the dissolving solution is collected and discarded, the oil and non-magnetic components are discarded along with the dissolving solution, but the magnetic powder is not included in the discarded dissolving solution and remains accumulated inside the bottom of the container 1 by the magnet 2. By performing the process using a magnet in step S2, oil and non-magnetic components can be reliably separated from the magnetic powder contained in the lubricant in a short time, and the influence of oil and grease in subsequent classification and measurement can be largely eliminated, thereby improving the accuracy of the analysis.

[0028] Figure 2 is a schematic cross-sectional view showing another example of an embodiment of process S2. Figure 2 shows a state in which a magnet 2 is placed outside container 5 (container A), a sample liquid 6 is contained in container 5, and two spatulas 7 for stirring are inserted into the sample liquid 6. In the example shown in Figure 2, by stirring the sample liquid 6 with the two spatulas 7 while the magnet 2 is placed outside container 5, the magnetic powder contained in the lubricant accumulates inside the bottom surface of container 5, and any trace amounts of oil remaining on the surface of the magnetic powder are transferred to the dissolving solution of the sample liquid 6. After stirring, the dissolving solution is discarded, thereby discarding the oil and leaving the magnetic powder on the inside bottom surface of container 5.

[0029] In step S2, the container A for containing the sample solution is not particularly limited, and a known container can be selected. It is preferable to select a material for container A that is non-magnetic, does not dissolve in the dissolving solution, and has high hardness. Examples of materials for container A include non-magnetic stainless steel (SUS), inorganic glass, oil-resistant resins such as polyethylene terephthalate and polycarbonate, and oil-resistant coated paper. Container A is preferably made of a material that is resistant to both deformation and grinding, and has high hardness, as this facilitates high-speed stirring. The shape of container A is not particularly limited, but a cylindrical container with a flat bottom is preferred as it facilitates the stirring process. The volume of container A is not particularly limited, but 450 to 3000 mL is preferred, and 2000 to 3000 mL is more preferred. Specifically, a stainless steel ball can be used as container A.

[0030] The magnet used in step S2 may be a permanent magnet or an electromagnet. Examples of permanent magnets include alloy magnets and rare earth magnets, with rare earth magnets being more preferred and neodymium magnets being even more preferred in that they generate a strong magnetic field. The number of magnets used in step S2 can be appropriately selected depending on the size of container A, the amount of sample liquid, and the size of the magnets, but one or more is sufficient, 1 to 5 is preferred, and 2 to 4 is more preferred. The size of the magnet can be adjusted as needed, but for example, in the case of a ring-shaped magnet, it may be 2-10 mm thick, 20-50 mm outer diameter, and 10-40 mm inner diameter (diameter of the hole). The position of the magnets outside container A can be selected as appropriate, but it is preferable to perform the stirring process with the magnets positioned mainly outside the bottom surface of container A, as shown in Figure 1. The type, number, size, and arrangement of the magnets described above are appropriately selected so that a magnetic field of sufficient strength is generated in the sample liquid, attracting the magnetic powder and accumulating inside container A.

[0031] In step S2, with a magnet placed on the outside of container A (see Figure 1), the sample liquid contained in container A is stirred. As for the stirring method, the known methods mentioned in the description of step S1 can be applied. In particular, it is preferable to use an electric blender or a miniature electric stirring device to rapidly convection the sample liquid, as this provides better separation efficiency between the magnetic powder and the oil and non-magnetic components. The stirring time can be adjusted as appropriate, but is preferably 5 to 20 minutes, and more preferably 10 to 15 minutes. The stirring process may be carried out continuously or intermittently in multiple sessions. When the stirring process is carried out in multiple sessions, the preferred stirring time mentioned above is the total time of the multiple stirring sessions. In step S2, it is preferable to perform the stirring of the sample liquid without placing a magnet on the outside of container A, as this further promotes the separation of the magnetic powder from the oil and non-magnetic components.

[0032] In step S2, after stirring the sample solution, the dissolving solution is discarded from the sample solution. The above-mentioned dissolution solution is disposed of with a magnet placed outside container A. This allows the oil and non-magnetic components contained in the lubricant to be disposed of together with the dissolution solution, without having to discard the magnetic powder that has been attracted to the magnet and accumulated inside container A. As a result, the magnetic powder separates from the oil and non-magnetic components contained in the lubricant and remains inside container A. The method for disposing of (discharging) the dissolving solution containing oils and non-magnetic components is not particularly limited as long as it is a method of removing the liquid phase of the sample solution contained in container A. Examples include tilting container A to drain off the supernatant of the sample solution (decantation), and using a suction device such as a dropper to collect and dispose of the dissolving solution.

[0033] (Repeat process) Steps S1 and S2 may be repeated. By repeating the process, the separation of oil and grease from the magnetic powder can be further promoted, and the analytical accuracy can be further improved. Repetitive processing means performing a series of steps, including steps S1 and S2, two or more times. There is no particular upper limit on the number of times repetitive processing can be performed, but it is usually five times or less.

[0034] In the iterative process, the conditions for steps S1 and S2, which are performed two or more times, may be independent, identical, or different. For example, when performing a repetitive process, the dissolving solution used in step S1 may be the same or different.

[0035] When performing repeated processing, it is preferable to use two or more different dissolving solutions. This is because using different types of dissolving solutions further promotes the removal of oily and non-magnetic components from the magnetic powder. The combination of two or more different dissolving solutions is not particularly limited, but it is preferable to use the cleaning solution containing the surfactant mentioned above first (for example, the first time) and then use the organic solvent later (for example, the second time). In this case, it is even more preferable to perform the drying treatment described later on the residue remaining in container A between the series of processes using the cleaning solution and the series of processes using the organic solvent.

[0036] When performing repeated processing, the container A used in the first process may be used again in subsequent processes, or a different container A may be used in subsequent processes. When using a different container A for the second and subsequent uses, the volume of container A is not particularly limited, but 30 to 180 mL is preferred, and 45 to 60 mL is more preferred. Furthermore, the material and shape of container A used in this case, including preferred embodiments, are as described above. For container A used from the second time onward, a stainless steel cup can be used.

[0037] (Drying treatment) After discarding the dissolving solution from container A in step S2, a drying treatment may be performed to dry the residue containing magnetic powder remaining in container A. By performing the drying treatment, liquid components (e.g., washing solution, water, and organic solvents, etc.) adhering to the residue can be volatilized and removed. In particular, when steps S1 and S2 are carried out using a first dissolving solution, and then steps S1 and S2 are carried out again using a second dissolving solution of a different type than the first dissolving solution, it is preferable to perform a drying treatment before carrying out step S1 using the second dissolving solution in order to avoid mixing of the different dissolving solutions. The drying method is not particularly limited and may be dried at room temperature and atmospheric pressure, by heating, or by reducing pressure. For heating, a method using a heat dryer to blow hot air onto the residue is preferred. Furthermore, when drying, it is preferable to carry out the process with magnets placed on the outside of container A.

[0038] [Process S3] In step S3, the residue containing magnetic powder remaining inside container A is collected, and the magnetic powder is separated into multiple groups according to particle size using a filter. Hereinafter, the operation of separating the magnetic powder into multiple groups according to particle size will also be simply referred to as "classification." In step S3, the number of classification steps is selected as appropriate depending on the purpose of the analysis. Classification may be performed only once using one filter, or it may be performed multiple times using multiple filters. When classification is performed multiple times, it is preferable that the mesh sizes of the filters used are different from each other. The classification method is not particularly limited; it may be dry classification or wet classification.

[0039] A known sieving method can be applied as a dry classification method using a filter. For example, after step S2, the residue remaining inside container A is transferred to the upper surface of the filter material, and the magnetic powder is classified by vibrating the filter and the residue as needed. It is preferable to subject the residue to the above drying treatment before subjecting it to dry classification. Dry classification may be either a single-stage system using one filter or a multi-stage system using multiple filters.

[0040] As a wet classification method using a filter, known filtration methods can be applied. For example, after step S2, a dispersion medium is added to container A to prepare a dispersion in which magnetic powder is dispersed, and then the residual dispersion is transferred to the upper surface of the filter material, thereby classifying the magnetic powder. As the dispersion medium, the dissolving solution used in steps S1 and S2 can be used, with organic solvents being preferred, hydrocarbon solvents more preferred, and n-heptane, kerosene, or light oil being even more preferred. The method for preparing the dispersion is not particularly limited and can be prepared in accordance with the method of mixing the lubricant and dissolving solution described in step S1. Wet classification may be either a single-stage system using one filter or a multi-stage system using multiple filters.

[0041] Process S3 will be explained in more detail using diagrams. Figure 3 is a schematic cross-sectional view showing an example of an embodiment of process S3. In Figure 3, filters F3, F2, and F1 are arranged on the container 10 (container C) in this order from the side closest to the container 10. The mesh opening of filter F1 is larger than that of filter F2, and the mesh opening of filter F2 is larger than that of filter F3. With multiple filters arranged on top of the container 10 in this manner, the residue containing the magnetic powder obtained by step S2 is placed on the upper surface of the uppermost filter F1. Due to gravity and vibrations applied as needed, some of the magnetic powder remains on the filter, while some passes through the filter. As a result, the magnetic powder obtained by step S2 is separated according to its particle size into groups: a group that remains on filter F1, a group that remains on filter F2, a group that remains on filter F3, and a group that is contained in the container 10 (11 in Figure 3). The separated magnetic powder is then subjected to step S4, which will be described later, for each group.

[0042] In the embodiment shown in Figure 3, an example is shown in which classification is performed using three filters with different mesh sizes. However, the number of classifications performed in step S3 (equal to the number of filters through which the residue passes) may be one or multiple times. When performing classification multiple times, a single-stage classification using one filter may be performed multiple times while changing the filter, a multi-stage classification using multiple filters may be performed only once, or, as shown in the second embodiment described later, a multi-stage classification using multiple filters may be performed multiple times while changing the filter.

[0043] The filters used in step S3 (filters F1, F2, and F3 in Figure 3) are not particularly limited, and known filters having a mesh structure used in dry classification and / or wet classification can be used. Examples of materials for the filter media include non-magnetic stainless steel (SUS), glass, chemical fibers, nylon, plastics, and carbon fibers. The mesh size of the filter is appropriately selected depending on the purpose of analysis and measurement, the number of classification steps (number of groups generated by separation), the size of the equipment used to collect the lubricant, etc. In step S3, for example, a filter with a mesh size of 10 to 5000 μm can be used, and it is preferable to use a filter with a mesh size of 50 to 2500 μm. The shape of the filter media is not particularly limited and can be circular, square, or elliptical, for example.

[0044] In step S3, when classification is performed only once to separate the magnetic powder into two groups, the mesh size of the filter used is, for example, 250 to 550 μm, with 400 to 500 μm being preferred. More specifically, a SUS wire mesh with a mesh size of 460 μm can be used. Furthermore, when classifying magnetic powder into multiple groups by performing classification multiple times, it is preferable to use filters with different mesh sizes in each classification. When performing classification multiple times, the difference in mesh sizes between the two filters with the closest mesh sizes among the multiple filters used may be, for example, 50 to 500 μm, and is preferably 150 to 300 μm.

[0045] An example of a suitable filter combination used in process S3 is a combination of SUS wire mesh with mesh openings of 150 μm, 460 μm, 680 μm, 960 μm, 1200 μm, 1500 μm, 1780 μm, and 2000 μm, respectively. When carrying out step S3 using the above combination of SUS wire mesh, it is preferable to pass the residue through filters with mesh openings of 2000 μm, 1780 μm, 1500 μm, 1200 μm, 960 μm, 680 μm, 460 μm, and 150 μm, respectively, in that order.

[0046] The container that receives the residue that has passed through the filter in step S3 (hereinafter also referred to as "container C") is not particularly limited, and a known container used in dry classification or wet classification can be selected. The material of container C may be the same as the material of container A, including preferred embodiments. The shape of container C is not particularly limited, but a cylindrical container with a flat bottom is preferred because it facilitates the installation of the filter. The volume of container C is not particularly limited, but 50 to 200 mL is preferred, and 80 to 100 mL is more preferred. Furthermore, the volume of container C is preferably about 2 to 2.5 times the amount of residue supplied to the top surface of the filter. Specifically, a stainless steel petri dish can be used as container C.

[0047] In step S3, the method for transferring the residue from the inside of container A to the top surface of the filter is not particularly limited and can be appropriately selected depending on the residue. In the case of wet classification, which classifies a dispersion of magnetic powder, for example, one method is to draw the dispersion contained in container A with a dropper and drop it onto the upper surface of the filter from above. When dropping the magnetic powder onto the upper surface of the filter from above, it is preferable to divide the dropping into several portions, changing the area to which the dropping is performed each time, in order to drop the dispersion over a wider area.

[0048] When performing dry classification, one method for transferring the residue contained in container A to the top surface of the filter is to attach a magnet to one end of a plate-shaped silicon steel or low-carbon steel, make the opposite end magnetic, attract the residue, and then remove the magnet on the top surface of the filter, thereby causing the residue to fall onto the top surface of the filter. The size of the above-mentioned plate-shaped silicon steel and low-carbon steel is preferably 0.5 to 1.5 mm in thickness, 5 to 10 mm in width, and 50 to 100 mm in length. There are no particular restrictions on the magnets used, but for rectangular magnets, a size of approximately 1.0 to 2.0 mm in thickness, 5 to 10 mm in width, and 10 to 20 mm in length is preferred, and for round magnets, a size of approximately 1.0 to 2.0 mm in thickness and 5 to 10 mm in outer diameter is preferred.

[0049] [Process S4] In step S4, the magnetic powder separated into multiple groups in step S3 is measured for each group, and the lubricant is analyzed based on the obtained measurements and the particle size of the magnetic powder contained in the group.

[0050] In step S4, for example, for each of the multiple groups separated by particle size, elements such as the iron powder concentration, mass, and number of magnetic powder particles are measured. The iron powder concentration value of the magnetic powder contained in each group can be measured using known iron powder concentration measuring instruments, such as grease iron powder concentration measuring instruments and oil iron powder concentration measuring instruments. The mass of the magnetic powder contained in each group can be measured by known mass measurement methods. The measurement unit of the measuring instrument used should preferably be 1 / 100g or larger.

[0051] The number of magnetic powder particles in each group may be measured using a known particle counter, or by observation using an optical microscope. If the number of magnetic powder particles is large, the number of magnetic powder particles may be calculated based on the measured iron powder concentration value. Specifically, after measuring the iron powder concentration value for the entire group, the iron powder concentration value of some countable magnetic powder particles is measured, and then the number of magnetic powder particles is measured separately for some of the magnetic powder particles. From the obtained measured values, the total number of magnetic powder particles for the group can be calculated using the following formula. (Total number of magnetic powder particles in the group) = (Number of magnetic powder particles in a portion of the group) × (Total iron powder concentration in the group) / (Iron powder concentration in a portion of the magnetic powder particles) The number of magnetic powder particles can also be calculated based on the measured mass of each particle using the same method as described above. As the particle size of magnetic powder increases, the iron powder concentration or mass of each magnetic powder particle also increases. Therefore, when comparing the relative distribution of magnetic powder generation by particle size due to wear, that is, the content of magnetic powder by particle size in the lubricant, it is preferable to measure the number of magnetic powder particles and analyze them in the process described later. On the other hand, if the distribution of magnetic powder can be clearly recognized by visual inspection, another method is to spread the magnetic powder evenly on a magnetic sheet according to its classification, photograph the resulting image, and examine the particle size distribution of the magnetic powder.

[0052] The method for transferring the magnetic powder classified in step S3 and remaining on the top surface of the filter or contained in container C to each measuring device is not particularly limited, but the method for transferring the residue to the top surface of the filter as described in step S3 can be applied. If step S3 is a wet classification and container C contains a dispersion containing magnetic powder, it is preferable to discard the dispersion medium from the dispersion, dry it if necessary, and then use the magnetic powder remaining inside container C for each measurement. As a disposal method for the dispersion medium, for example, the method of discarding the dissolving agent from the sample liquid as described in step S2 can be applied. As a drying method, for example, the drying treatment described in step S2 can be applied.

[0053] In addition, as a measurement in step S4, the shape, surface color, and surface form of the magnetic powder contained in each group may be observed. Based on the above observations, it is possible to infer the causes of magnetic powder (wear particles) generation in the sliding parts of the equipment, such as severe peeling wear accompanied by sliding, fatigue peeling wear accompanied by rolling, and steady-state wear. In the case of magnetic powder caused by severe peeling wear accompanied by sliding, for example, discoloration or seizure due to frictional heat, streaks due to brittle fracture, cutting marks, and wrinkles may be observed. In the case of magnetic powder caused by fatigue peeling wear accompanied by rolling, for example, the periphery of the magnetic powder becomes rolled due to fatigue fracture caused by repeated pressing, and further, cracks and a smooth surface state may be observed. The above observations are performed, for example, using an optical microscope. The observation magnification can be set as appropriate, but examples include 100 to 2000 times.

[0054] Next, the lubricant is analyzed based on the measured values ​​for each group obtained by the above method (iron powder concentration, mass, number, shape, surface color, and surface condition of the magnetic powder, etc.) and the particle size of the magnetic powder included in each group.

[0055] Typically, ferrography can only collect magnetic powder particles that are small in size (e.g., less than 150 μm). Therefore, if the magnetic powder particles in the lubricant are relatively large (e.g., 150 μm or larger), measurement and analysis using ferrography becomes difficult. For example, in rolling bearings with an inner ring diameter of Φ400 mm or more, when the bearing reaches the end of its lifespan, magnetic powder particles with a size of 150 μm or larger tend to be discharged from the flaking area. Furthermore, if the inner ring of the rolling bearing becomes even larger, the amount of magnetic powder discharged also increases, reaching 2000 to 5000 μm. On the other hand, in general filtration analysis methods, if the amount of lubricant processed is large, the filter may become clogged with non-magnetic components such as non-magnetic dust, oil degradation products, thickeners, and additives present in addition to the magnetic powder, making proper separation and measurement difficult. In contrast, the analytical method of the present invention is not limited by the particle size of the magnetic powder contained in the lubricant or the oil content, and it is possible to measure and analyze the characteristics of each particle size of the magnetic powder contained in the lubricant, and it is possible to analyze lubricants containing magnetic powder with relatively large particle sizes with higher accuracy. As mentioned above, the larger the scale of the equipment, the larger the sliding parts become, and the larger the magnetic powder generated by wear becomes. Therefore, the analytical method of the present invention is a more suitable analytical method for lubricants used in the sliding parts of relatively large equipment.

[0056] The measured values ​​for each group may be summarized in a table along with the particle size for each group. Summarizing the data in a table makes it easier to identify the characteristics of the magnetic powder according to its particle size, thus facilitating the analysis in this process and the diagnosis of the wear condition of the sliding parts.

[0057] Alternatively, a graph may be created using the measured values ​​for each group, with the particle size of each group as the variable. In particular, it is preferable to create a graph showing the number of magnetic powder particles and their particle size. This is because the particle size of the magnetic powder mainly discharged from the sliding part can be easily evaluated from the peak of the measured values ​​in the created graph, and the degree of wear progression of the sliding part can be more concretely estimated. Furthermore, by accumulating data such as measured values ​​for each group, the table and graphs mentioned above, and understanding their trends, it becomes possible to manage the trend of wear progression in the sliding parts.

[0058] <Equipment diagnostic method> The equipment may be diagnosed based on the analysis results obtained using the above analysis method. In particular, it is preferable to analyze the lubricant collected from the sliding part using the analytical method of the present invention and diagnose the wear state of the sliding part based on the obtained analytical results. This is because the wear state of the equipment can be easily estimated by classifying the particle size of the magnetic powder generated by wear and performing analyses such as graphing the measured characteristic values ​​and particle size. Furthermore, understanding the wear and tear of such equipment contributes to proper maintenance and replacement of equipment components, and can be used for equipment maintenance management and repair planning, enabling stable equipment operation.

[0059] The present invention's equipment diagnostic method allows for the diagnosis of the wear condition of parts of equipment where lubricant is used, based on the above analysis results and, if necessary, by referring to diagnostic criteria. Diagnostic criteria should be created in advance, before the diagnosis is performed. For example, diagnostic criteria can be created by repeatedly performing the above analysis, measuring and analyzing the characteristic values ​​of magnetic powder for each particle size, and confirming the wear condition of the parts where the lubricant is actually used.

[0060] The following are specific examples of diagnostic criteria in equipment-based diagnostic methods. The first diagnostic criterion involves classifying the magnetic powder using a filter with a mesh size of 460 μm in process S3, and using the ratio of magnetic powder remaining on the filter to magnetic powder that passed through the filter as the diagnostic criterion.

[0061] The inventors have confirmed that as the amount of magnetic powder remaining on a 460 μm mesh filter increases, wear and damage to equipment such as bearings become more pronounced. Therefore, an increase in magnetic powder remaining on a 460 μm mesh filter can be set as a level requiring attention regarding wear and damage. For example, if the number of magnetic particles that have passed through the filter is greater than the number of magnetic particles remaining on the filter, the wear state of the sliding part from which the lubricant was collected can be presumed to be steady-state wear. On the other hand, if the number of magnetic particles remaining on the filter is greater than the number of magnetic particles that have passed through the filter, the wear state of the sliding part from which the lubricant was collected exceeds steady-state wear, and it can be presumed that wear is progressing.

[0062] It is preferable to perform the above-mentioned equipment diagnostics periodically at predetermined intervals. By performing periodic diagnostics of the equipment using the first diagnostic criteria described above, the degree of wear can be grasped numerically, making it easier to manage wear trends. For example, by periodically measuring the iron powder concentration in a lubricant containing magnetic powder, the bearing wear trend can be numerically assessed. If the iron powder concentration shows a gradual increase or no increase at all, it can be diagnosed that there is little to no damage to the bearing. On the other hand, if the increase is rapid, bearing damage should be suspected. A rapid increase in iron powder concentration is always due to an increase in the particle size of the magnetic powder and an increase in the amount of magnetic powder generated. There are no particular restrictions on the interval between periodic checkups, and they can be selected as appropriate depending on the equipment, but for example, they may be every 1 to 12 months, and preferably every 1 to 3 months.

[0063] The second diagnostic criterion involves classifying the magnetic powder using multiple filters in process S3, measuring and analyzing the magnetic powder remaining on each filter, and using the relative particle size distribution of the measured characteristic values ​​as the diagnostic criterion. The more the measurement results are biased towards larger particle sizes, the more advanced the wear is, suggesting that the wear state of the sliding part is close to its limit (lifespan) and that the remaining life is short. For example, when selecting multiple filters, it is preferable to choose filters with mesh openings ranging from 50 to 2500 μm such that the difference in mesh openings is between 50 and 500 μm (more preferably between 150 and 300 μm).

[0064] The following explains how wear caused by contact between components is eliminated, using bearings as an example. First, regarding the contact state of the outer ring, inner ring, rolling elements, and cage in a bearing, we will describe the case of a radial ball bearing where the rotation axis is used horizontally and the outer ring is fixed as an example. In a bearing, the rolling elements rotate while contacting the outer and inner rings. Furthermore, as the rolling elements rotate, the inner ring rotates, causing the rolling elements to revolve around the raceway surface of the outer ring. Note that the above series of operations can occur even without a cage. In other words, a new bearing can rotate even without a cage. This section describes in detail the contact conditions of the outer ring, inner ring, rolling elements, and cage during use. For example, when a radial bearing is loaded from above to below, the load on the outer ring is localized to a point below the bearing's rotational axis, causing significant wear on its contact surface. The inner ring, being in rotation, experiences wear across its entire circumferential surface. Similarly, the rolling elements also experience wear across their entire circumferential surface. The cage, however, experiences very little load and is therefore less prone to wear. Based on the interrelationships of the parts described above, the part of the bearing that is most susceptible to wear is the contact surface of the outer ring.

[0065] Next, we will discuss contact wear of the outer ring, inner ring, rolling elements, and cage of the bearing, as well as magnetic powder. The following example is for a self-aligning roller bearing subjected to heavy loads. For example, in a new bearing, the outer ring, inner ring, and rolling elements primarily make rolling contact. However, strictly speaking, this is rolling contact accompanied by a small amount of slippage. Therefore, even with lubrication, metal-on-metal friction causes wear. In this case, the wear particles discharged from the bearing are fine magnetic particles. In the case of bearings, this is often evaluated as steady-state wear. Next, as wear progresses, the rolling contact between the outer ring, inner ring, and rolling elements becomes sliding contact. Furthermore, repeated stress is continuously applied to the contact surfaces, and the wear particles discharged from the bearing in this case are magnetic particles resulting from fatigue peeling wear. Because the magnetic particles are rolled over a long period during discharge, their surface is smooth, and cracks form around them due to the rolling effect. In cases of extreme rolling, a pinpoint light brown discoloration may appear on the surface. Additionally, repeated stress is continuously applied locally to the contact surface of the outer ring, leading to concentrated fatigue peeling wear. While a bearing in this state is not considered to have reached the end of its lifespan, poor lubrication and high-load use can shorten its lifespan.

[0066] Next, as wear and fatigue peeling wear progress, sliding contact becomes stronger than rolling contact in the outer ring, inner ring, and rolling elements. In this case, the wear particles discharged from the bearing are mainly magnetic particles of severe peeling wear. During discharge, the particles are rolled while sliding for a short period of time, causing fine wrinkles to form on the surface of the magnetic particles, and long cracks to form around the magnetic particles due to the rolling effect. Furthermore, due to the significant sliding and rolling effect, dark brown discoloration appears on the surface everywhere. On the other hand, at this point, the cage and rolling elements begin to slide against each other, and severe wear occurs. If the cage is made of a copper alloy, this can be observed as weak magnetic powder of the copper alloy. A bearing in this state is considered to have reached the end of its lifespan.

[0067] Next, as wear and fatigue delamination progress, the sliding contact between the outer ring, inner ring, rolling elements, and cage becomes stronger than the rolling contact. In extreme cases, the rolling elements revolve while sliding rather than rolling. In this case, the wear particles discharged from the bearing are mainly magnetic particles of severe delamination wear. Because the magnetic particles are rolled with significant sliding over a short period of time during discharge, the surface of the magnetic particles develops severely uneven wrinkles, and long cracks form around the magnetic particles due to the rolling effect. Furthermore, due to the significant sliding and rolling effect, a dark brown discoloration accompanied by streaks appears on the entire surface of the magnetic particles. In addition, black fine particles can be seen remaining on the surface of the magnetic particles. If the cage material is a copper alloy, a large amount of weak magnetic particles of the copper alloy can be observed. A bearing in this state is considered to have passed the point at which it has reached the end of its lifespan and is no longer fulfilling its role as a bearing.

[0068] The analytical method and instrumental diagnostic method of the present invention allow for the classification of magnetic powder by particle size, and enables easy and detailed quantitative evaluation and analysis of magnetic powder by particle size. This allows for the rapid acquisition of the technology, enabling even those without specialized knowledge to estimate the wear state of sliding parts and appropriately diagnose equipment.

[0069] <First Embodiment> An example of a specific embodiment of a method for analyzing lubricants is shown. The analysis method according to the first embodiment includes the following steps A1 to A9. Step A3 corresponds to step S1, step A4 corresponds to step S2, step A5 corresponds to step S3, and steps A6 to A9 correspond to step S4. Step A1: A step to prepare 0.5 to 1.5 mL of lubricant containing magnetic powder, a dissolving solution, container A, container C, and an iron powder concentration meter. If the lubricant is grease, the amount of lubricant is preferably about 1.0 mL. If the lubricant is an oil such as lubricating oil or hydraulic fluid, the amount of lubricant is preferably about 1.5 mL. The amount of dissolving solution is preferably about 5.0 to 10.0 mL. Process A2: A process to measure the iron powder concentration value of the lubricant using an iron powder concentration meter. Step A3: A step in which the entire amount of lubricant is transferred into container A, the dissolving solution is injected, and the lubricant and dissolving solution are mixed to prepare the sample solution. Step A4: With a magnet positioned facing the outside of the bottom of container A, the sample liquid contained in container A is stirred, and then the dissolving solution is discarded. Step A5: The dissolving solution is poured back into container A, the magnet is removed from a position facing the outside of the bottom of container A, and the sample liquid contained in container A is drawn up with a dropper. Then, the sample liquid is dropped onto the upper surface of a filter with a mesh size of 460 μm placed on top of container C. Step A6: A step to collect the magnetic powder remaining on the filter and measure the iron powder concentration, weight, or number of particles of the classified magnetic powder. Step A7: With a magnet placed facing the outside of the bottom of container C, the process of discarding the dissolving solution from the sample liquid contained in container C after passing through the filter. Step A8: A step to collect the magnetic powder remaining in container C and measure the iron powder concentration, weight, or number of particles of the classified magnetic powder. Step A9: A step to create a numerical comparison graph using the iron powder concentration value, weight, or number obtained in steps A6 and A8, and the particle size range of each classified group (whether it remained on or passed through a filter with a mesh size of 460 μm). The analysis of the first embodiment is preferably performed as part of the periodic inspection of the above-mentioned equipment.

[0070] <Second Embodiment> Other examples of specific embodiments of the method for analyzing lubricants are shown. The analysis method according to the second embodiment includes the following steps B1 to B13. Steps B2 and B5 correspond to step S1, steps B3 to B4 and B6 to B7 correspond to step S2, steps BB8 to B10 correspond to step S3, and steps B11 to B13 correspond to step S4.

[0071] Step B1: A step of preparing a first dissolving solution obtained by diluting a lubricant containing magnetic powder and a cleaning solution containing a surfactant with water, a second dissolving solution which is a hydrocarbon solvent, containers A1 and A2 which are container A, and containers C1, C2 and C3 which are container C. Step B2: A step in which the lubricant and the first dissolving solution are mixed and the sample solution A is placed in container A1. Step B3: With a magnet positioned facing the outside of the bottom of container A1, the sample liquid A contained in container A1 is stirred, and the first dissolving solution is discharged (discarded) from container A1. The stirring time can be adjusted as appropriate, but for example, it is 1 to 5 minutes, and preferably 2 to 3 minutes. Through this step, the oil and non-magnetic components contained in the lubricant are separated from the magnetic powder and discarded together with the first dissolving solution. Step B4: A step to dry the residue remaining in container A1, which includes magnetic powder and a small amount of the first dissolving solution. This step primarily removes the water contained in the first dissolving solution.

[0072] Step B5: This step involves injecting the second dissolving solution into container A1 to prepare sample solution B containing magnetic powder and the second dissolving solution, and then transferring sample solution B to container A2. The amount of second dissolving solution to be injected is appropriately selected according to the amount of residual magnetic powder, but 2 to 5 mL is preferred. To ensure smooth operation in the next step, an additional 1 to 3 mL of second dissolving solution may be injected. Step B6: With a magnet positioned facing the outside of the bottom of container A2, the sample liquid B contained in container A2 is stirred, and then the second dissolving solution is discarded. Step B7: With the magnet removed from the position facing the outside of the bottom of container A2, the second dissolving solution is poured back into container A2.

[0073] Step B8: This step involves stacking 2-3 filters on top of container C1 and pouring sample liquid B from container A2 onto the top surface of the uppermost filter. In this step, the filters used have different mesh sizes, and are arranged so that the mesh size increases as the filter is positioned higher up. For example, starting from the filter closest to container C1, filters with a mesh size of 1500 μm, 1780 μm, and 2000 μm are arranged. Container C1 contains sample liquid C1, which includes the magnetic powder and second dissolving solution that have passed through all the filters. Step B9: This step involves stacking 2-3 filters on top of container C2 and pouring sample liquid C1 from container C1 onto the top surface of the uppermost filter. The mesh sizes of the filters used in this step are all smaller than those used in step B8 and larger than those used in step B10, which will be described later. Furthermore, the mesh sizes of the filters used are all different, and the filters are arranged so that the mesh size increases as they are positioned higher up. For example, filters with a mesh size of 680 μm, 940 μm, and 1200 μm are arranged in order from the side closest to container C2. Container C2 contains sample liquid C2, which includes the magnetic powder and the second dissolving solution that have passed through all the filters. Step B10: This step involves stacking 2-3 filters on top of container C3 and pouring the sample liquid C2 from container C2 onto the top surface of the uppermost filter. In this step, the filters used have different mesh sizes, and are arranged so that the mesh size increases as the filter is positioned higher up. For example, a filter with a mesh size of 150 μm and a filter with a mesh size of 460 μm are placed in order from the side closest to container C3. Container C3 contains the sample liquid C3, which includes the magnetic powder and the second dissolving solution that have passed through all the filters.

[0074] Step B11: A step in which the magnetic powder remaining in each filter in steps B8, B9, and B10 is collected, and the iron powder concentration value, weight, or number of particles of the magnetic powder is measured for each group. Step B12: A step to create a numerical comparison graph using the iron powder concentration value, weight, or number obtained in Step B11, and the particle size range of each classified group. Step B13: For each group of magnetic powders, observe the morphology, surface color, and surface irregularities of the magnetic powder to diagnose any abnormal magnetic powders.

[0075] By performing the analysis according to the second embodiment, measurement values ​​and analysis results of magnetic powder can be obtained for each particle size range, making it possible to predict, for example, the wear state of the sliding part with greater accuracy. For example, if there is a large number of larger-particle magnetic powder particles (or a high iron powder concentration or weight), it suggests that wear is occurring in the sliding parts and that the time for replacing the parts is approaching. In particular, if there is a large number of magnetic powder particles remaining in a filter with a mesh size of 2000 μm or more, the time for replacing the parts becomes clear. Furthermore, the surface condition and color of larger-particle magnetic powder are easier to observe, and this observation allows for the determination of usage conditions such as excessive load or seizing. On the other hand, when there are many magnetic powder particles with smaller particle sizes, the wear on the components used in the sliding parts is relatively small, suggesting that the time for component replacement is not yet approaching. In particular, when there are many magnetic powder particles with particle sizes in the range of 150 to 460 μm, it becomes clear that there is still plenty of time before the components need to be replaced. Thus, in the second embodiment, a more detailed analysis of the lubricant containing magnetic powder can be performed, allowing for a more accurate diagnosis of the wear condition of the sliding parts. [Examples]

[0076] The present invention will be described in more detail below based on examples. The materials, quantities, proportions, processing details, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0077] [Example 1] <Analysis Procedure> The following containers were prepared. • Container A1: Stainless steel bowl, inner diameter 200mm, height 140mm, volume 3800mL. Container A2: Stainless steel cup, inner diameter 57mm, height 50mm, volume 100mL. • Containers C1, C2, C3, and C4: Stainless steel petri dishes, 88mm in diameter, 20mm in height, 125mL in volume. In addition, eight types of stainless steel mesh screens were prepared, each with a mesh opening of 2000 μm, 1780 μm, 1500 μm, 1200 μm, 940 μm, 680 μm, 460 μm, or 150 μm (hereinafter also referred to as "filters F1 to F8" in order of increasing mesh opening).

[0078] Lubricant for analysis was collected from the lubricating grease of a thrust roller bearing (inner diameter approximately 6000 mm) used for rotation in a continuous casting facility (hereinafter simply referred to as "bearing"). The collected lubricant contained magnetic powder. As shown in Figure 1, three annular magnets M1 (neodymium magnets, 5 mm thick, 15 mm inner diameter, 31 mm outer diameter) were placed on the outside of the bottom surface of container A1. 87.56 g of the above-mentioned lubricant, a first solution consisting of a mixture of 100 mL of liquid compound soap (manufactured by Asahi Kasei Advance Corporation, "Lucky Boy® Eco Surf® Ace") and 400 mL of purified water were added to container A1. The resulting mixture was stirred for 30 seconds using an electric blender (for cooking, 100V) to obtain sample solution A.

[0079] After stirring, the first dissolving solution contained in sample liquid A was discarded by tilting container A1 while the annular magnet M1 was still placed on the outside of the bottom surface of container A1. It was confirmed that the discarded first dissolving solution contained oil and grease components from the lubricant, as well as non-magnetic dust, oil degradation products, thickeners, and additives. It was also confirmed that residue containing magnetic powder had accumulated on the inside of the bottom of container A1. A small amount of residue was collected, and the amount of lubricant contained in the residue was measured using a digital microscope (Keyence Corporation, VHX-7000 (lens: VHX-E100 - magnification 100~400x, and VHX-E500 - magnification 500~2500x)) at an observation magnification of 300x, and a small amount of lubricant was found to be present. To separate the lubricant, a first solution consisting of a mixture of 50 mL of the above-mentioned compound soap and 200 mL of purified water was added to container A1, and the mixture was stirred again for 30 seconds using an electric blender to obtain sample solution A. After stirring, the first solution contained in sample solution A was discarded while the annular magnet M1 was still placed outside the bottom of container A1. The amount of lubricant contained in the residue accumulated on the inside of the bottom of container A1 was measured in the same manner as above, and it was confirmed that there was almost no lubricant present.

[0080] After removing the annular magnet M1 from the outside of the bottom of container A1, the residue accumulated inside the bottom of container A1 was dried by blowing hot air from a hair dryer (household hair dryer, 100V) for about 90 seconds. This drying process evaporated the water contained in the residue.

[0081] After drying, 3 mL of n-heptane was poured into container A1 as the second dissolving solution, and the residue and n-heptane were stirred with a silicone rubber spatula to obtain sample solution B. After stirring, all of sample solution B was transferred from container A1 to container A2 to facilitate the next step. At that time, it was confirmed that no magnetic powder remained on the silicone rubber spatula or in container A1.

[0082] The sample liquid B, transferred to container A2, was stirred for approximately 1 minute using two stainless steel spatulas (spatula 7) without placing the annular magnet M1 outside the bottom surface of container A2. This degreasing of the magnetic powder was achieved by dissolving the small amount of oil contained in the residue. After stirring, the annular magnet M1 was placed outside the bottom surface of container A2 and held in this state for 30 seconds, after which the n-heptane was discarded from the sample liquid B. Furthermore, the residue accumulated inside the bottom of container A2 was dried for 60 seconds using the aforementioned dryer, evaporating the n-heptane adhering to the residue.

[0083] Similar to the example shown in Figure 3, filters F3 (SUS wire mesh with a mesh opening of 1500 μm), F2 (SUS wire mesh with a mesh opening of 1780 μm), and F1 (SUS wire mesh with a mesh opening of 2000 μm) were placed on top of container C1 in this order.

[0084] The residue accumulated on the inside of the bottom of container A2 was transferred to the top surface of filter F1. The magnetic material was moved using the following procedure: A silicon steel plate was magnetized with a disc-shaped magnet M2 (neodymium magnet, 2 mm thick, 10 mm outer diameter). The residue containing magnetic material powder that had accumulated on the inside of the bottom of container A2 was attracted to the edge of the magnetized silicon steel plate. Next, the disc-shaped magnet M2 was removed from the silicon steel plate on top of filter F1, thereby transferring the residue that had been attracted to the silicon steel plate onto the top surface of filter F1.

[0085] Next, the nylon brush was positioned so that a dense area of ​​residue was located between the entire bristles of the nylon brush and the filter. The dense area of ​​residue was then struck with the entire bristles of the nylon brush, using just enough force to cause the nylon brush to bounce back due to the elasticity of the bristles. This vibrated the residue, separating it by particle size. In addition, since the entire filter vibrates simultaneously with striking the dense area of ​​residue with the nylon brush, the sieving of the residue is further promoted. After confirming that the amount of residue passing through filter F1 did not increase even when the residue was vibrated, filter F1 was removed. This series of operations was also performed on filters F2 and F3. This separated the residue into two groups: the group remaining on filters F1, F2, and F3 (referred to as "Group 1," "Group 2," and "Group 3," respectively) and the group that passed through filters F1, F2, and F3 and fell into container C1.

[0086] Filters F6 (SUS wire mesh with a mesh opening of 680 μm), F5 (SUS wire mesh with a mesh opening of 940 μm), and F4 (SUS wire mesh with a mesh opening of 1200 μm) were placed on top of container C2 in this order.

[0087] Next, the group of residue that had passed through filters F1-F3 and fallen into container C1 was transferred to the top surface of filter F4 in the same manner as described above. Subsequently, in the same manner as described above, By using the entire tip of a nylon brush to strike the densely packed areas of residue, the residue was vibrated and separated by particle size. This series of operations was also performed on filters F5 and F6. As a result, the residue was separated into two groups: the group remaining on filters F4, F5, and F6 (referred to as "Group 4," "Group 5," and "Group 6," respectively) and the group that passed through filters F4, F5, and F6 and fell into container C2.

[0088] Filter F8 (a stainless steel wire mesh with a mesh size of 150 μm) and filter F7 (a stainless steel wire mesh with a mesh size of 460 μm) were placed on top of container C3 in that order.

[0089] Next, the group of residue that had passed through filters F1 to F6 and fallen into container C2 was transferred to the top surface of filter F7 in the same manner as described above. Subsequently, the residue was vibrated by tapping the densely packed areas of the residue with the entire tip of a nylon brush, similar to the method described above, thereby separating the residue by particle size. This same procedure was also performed on filter F8. This separated the residue into groups that remained on filters F7 and F8, which have different mesh sizes (referred to as "group 7" and "group 8," respectively), and groups that passed through filters F7 and F8 and fell into container C3.

[0090] Next, the groups of residues remaining on each filter, categorized by particle size, were quantitatively evaluated. Specifically, the number of magnetic powder particles in each group was measured. For groups 1-4 with a small number of particles, the number of magnetic powder particles in each group was directly measured. For groups 5-8 with a large number of particles, the number of magnetic powder particles was calculated using the following method based on the measurement of iron powder concentration values. Taking group 5 as an example, first, the total iron powder concentration value for group 5 was measured. Next, some countable magnetic powder particles were collected from group 5, and the iron powder concentration value and count of the collected magnetic powder particles were measured. From the obtained total iron powder concentration value for group 5, as well as the iron powder concentration value and number of particles of the collected magnetic powder particles, the number of magnetic powder particles in group 5 was calculated using the following formula. (Total number of magnetic powder particles in the group) = (Number of magnetic powder particles collected from a portion of the group) × (Total iron powder concentration value in the group) / (Iron powder concentration value of the collected portion of the magnetic powder)

[0091] Each iron powder concentration value was measured using a grease iron powder concentration meter (manufactured by Shin-Cosmos Electric Co., Ltd., product name "SDM-72").

[0092] Table 1 summarizes the filter numbers and mesh sizes used in Example 1, as well as the calculated number of magnetic powder particles in each group.

[0093] [Table 1]

[0094] Figure 4 is a graph showing the number of magnetic particles in each group of magnetic particles with different particle sizes. From Table 1 and the graph in Figure 4, it was found that the number of magnetic particles in the sampled lubricating grease peaked in group 8, which remained on filter F8 with a mesh size of 150 μm. Analysis of these results confirmed that the bearing from which the lubricating grease was collected was only slightly damaged (steady-state wear).

[0095] <Surface observation results of magnetic powder> The magnetic powders included in groups 1-8, obtained by the method described above, were subjected to surface observation using an optical microscope. For the optical microscope, a digital microscope (manufactured by Keyence Corporation, VHX-7000 (lenses: VHX-E100 - magnification 100~400x, and VHX-E500 - magnification 500~2500x)) was used, with observation magnifications of 300x and 1500x.

[0096] Observations of the magnetic powders in groups 1-8 all showed similar results, including deep streaks and fine wrinkles, dark brown discoloration, cracks where the magnetic powder was torn, and severe peeling wear such as cutting marks across the entire surface of the magnetic powder.

[0097] Based on the observations described above, the following analysis results were obtained regarding the bearing's operating condition. It was hypothesized that when the pressure of a heavy thrust load was applied to the raceway surface of the outer ring via the inner ring and rolling elements, fine wrinkles and cracks occurred across the entire surface of the magnetic powder. Furthermore, since the rotation of the rolling elements is linear, it was hypothesized that when the rolling elements rotated while sliding in order to rotate (revolve), deep streaks, fine wrinkles, and dark brown discoloration occurred across the entire surface of the magnetic powder.

[0098] Based on the analysis results of the above bearing usage conditions, the following analysis results were obtained regarding the bearing wear state. Severe peeling wear was suspected to be occurring on the outer ring, inner ring, and rolling element raceway surfaces of the bearing, as well as on the metal contact surfaces of the cage. However, the peak in the number of magnetic particles was in group 8 with a mesh size of 150 μm, which was relatively small compared to the size of the bearing (inner diameter of approximately 6000 mm). It is known that when such large-diameter bearings wear out and reach the end of their lifespan, the main component of magnetic particles mixed into the lubricating grease is magnetic particles with a particle size of approximately 2000 μm, and if the wear progresses further, magnetic particles with a particle size of 5000 μm or larger become the main component. Therefore, it was inferred that the wear condition of the bearing from which lubricating grease was collected as an analytical lubricant in Example 1 indicated that there was still a sufficient period remaining until the end of its lifespan.

[0099] [Example 2] Similar to Example 1, a lubricant sample for analysis was taken from the bearing lubricant grease. The sampled lubricant contained magnetic powder. 0.8 mL was measured from the lubricant, and the iron powder concentration was measured using the above measuring instrument. The result showed that the iron powder concentration of 0.8 mL of lubricant was 1.530%.

[0100] 0.8 mL of lubricant was placed in container A2. Next, 3 mL of n-heptane was added to container A2 as a dissolving agent, and the mixture was stirred for approximately 3 minutes using two stainless steel spatulas to obtain sample solution A. After stirring, an annular magnet M1 was placed on the outside of the bottom of container A2, and this state was held for 2 seconds, after which the n-heptane was discarded from sample solution A. After discarding the n-heptane, the residue accumulated on the inside of the bottom of container A2 was dried for approximately 2 minutes using the aforementioned dryer, evaporating any trace amounts of n-heptane remaining on the inside of the bottom of container A2. By mixing the lubricant with n-heptane, the oily components in the lubricant dissolved into the n-heptane and were discarded along with the n-heptane. Furthermore, the non-magnetic dust, oily degradation products, thickeners, and additives in the lubricant were not attracted to the magnet and were therefore discarded along with the n-heptane. In other words, the degreased magnetic powder from the above process remained as residue on the inside of the bottom of container A2.

[0101] Filter F7 (a stainless steel wire mesh with a mesh size of 460 μm) was placed on top of container C1 in this order. The residue accumulated on the inside of the bottom of container A2 was transferred to the top surface of filter F7 in the same manner as in Example 1, where the residue was transferred to the top surface of filter F1. Next, the filter F7 was lightly tapped with a nylon brush to vibrate the residue, and the residue was then separated by particle size. It was confirmed that the amount of residue passing through the filter F7 did not increase even when the residue was vibrated. This separated the residue into two groups: Group A, which remained on filter F7, and Group B, which passed through filter F7 and fell into container C1.

[0102] The iron powder concentration values ​​for the obtained groups A and B were measured using the above measuring instrument. The results showed that the iron powder concentration value for group A was 1.200%, and the iron powder concentration value for group B was 0.650%.

[0103] Figure 5 is a graph showing the iron powder concentration values ​​for Group A and Group B, which are magnetic powders with different particle size ranges. As is clear from the graph in Figure 5, the iron powder concentration value of Group B that passed through the 460 μm mesh filter F7 was approximately twice the iron powder concentration value of Group A that remained on the filter F7. Furthermore, the particle size of the wear particles generated by the initial wear of the bearing was less than 460 μm, and as bearing wear progressed, the amount of wear particles with a particle size of 460 μm or more tended to increase. Based on the measurement results of the iron powder concentration values ​​for each group in Example 2 and the above trend, it was inferred that in the bearings from which the lubricating grease used in Example 2 was collected, the amount of iron powder concentration in Group A tended to increase, indicating a tendency for wear to progress slightly.

[0104] The following preliminary tests confirmed that the wear tendency of bearings can be determined by periodically measuring the iron powder concentration in a fixed amount (0.8 mL) of lubricant containing magnetic powder. Lubricant with an iron powder concentration of 9.000% was collected from lubricating grease used in actual bearings. The obtained lubricant was diluted with oil to prepare samples of lubricant with iron powder concentrations of 1.000%, 2.000%, 3.000%, 4.000%, 5.000%, 6.000%, 7.000%, and 8.000%. For each sample, the magnetic powder was separated by particle size using a filter F7 with a mesh size of 460 μm, as described above, and the iron powder concentration values ​​of the magnetic powder remaining on the filter F7 and the magnetic powder that passed through the filter F7 were measured. As a result, it was confirmed that in all samples, the iron powder concentration value of the magnetic powder remaining on the filter F7 was higher than the iron powder concentration value of the magnetic powder that passed through the filter F7. This confirmed that, in the analysis of a fixed amount (0.8 mL) of lubricant, the total amount of iron powder concentration in the magnetic powder had little effect on the relative relationship of iron powder concentration values ​​for each particle size. Furthermore, by separating the magnetic powder using a 460 μm mesh filter and comparing the iron powder concentration values ​​of each, it was possible to analyze the condition of bearing damage.

[0105] In the above embodiment, the magnetic powder in the lubricating grease of the thrust roller bearing was analyzed using the method of the present invention to infer the wear state of the thrust roller bearing. However, the magnetic powder analysis and wear state analysis of the other sliding parts described above can be performed in the same manner. [Explanation of Symbols]

[0106] 1,5 Container (Container A) 2 Magnets 3 Stirrer 4,6 Sample solution 7 Spatula 10 Container (Container C) 11 Magnetic powder F1, F2, F3 filters

Claims

1. Step S1 involves mixing a lubricant containing magnetic powder with a dissolving solution to prepare a sample solution, Step S2 involves placing a magnet outside the container holding the sample solution, stirring the sample solution, and then discarding the dissolving solution from the sample solution. Step S3 involves collecting the residue containing the magnetic powder remaining inside the container and separating the magnetic powder into multiple groups according to particle size using a filter. An analytical method comprising: step S4, which involves measuring the magnetic powder separated into multiple groups in step S3 for each group, and analyzing the lubricant based on the obtained measurement values ​​and the particle size of the magnetic powder contained in the group.

2. The analytical method according to claim 1, wherein the residue is a dispersion liquid in which the magnetic powder is dispersed, and the magnetic powder is separated into multiple groups by wet classification.

3. The analytical method according to claim 1, wherein the magnetic powder is separated into multiple groups by dry classification.

4. The analytical method according to any one of claims 1 to 3, wherein the dissolving solution is an organic solvent.

5. The analytical method according to claim 4, wherein the organic solvent is n-heptane.

6. The analytical method according to any one of claims 1 to 3, wherein the dissolving solution is a cleaning solution containing a surfactant.

7. The analytical method according to any one of claims 1 to 3, wherein a series of steps including step S1 and step S2 are performed two or more times.

8. The analytical method according to any one of claims 1 to 3, wherein the mesh opening of the filter is 400 to 500 μm.

9. The analytical method according to any one of claims 1 to 3, wherein in step S3, the separation of the magnetic powder is performed multiple times using a plurality of filters with different mesh sizes.

10. The analytical method according to any one of claims 1 to 3, wherein in step S4, at least one of the iron powder concentration value, weight, and number of magnetic powder particles is measured for each group.

11. The analytical method according to any one of claims 1 to 3, wherein in step S4, at least one of the morphology, surface color, and surface shape of the magnetic powder is measured for each group.

12. The lubricant is a lubricant taken from a sliding part of the equipment. A diagnostic instrument method for diagnosing the wear state of the sliding part based on the analysis results obtained by the analysis method described in any one of claims 1 to 3.

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