Fatigue diagnosis method of rolling machine elements and fatigue diagnosis system of rolling machine elements

Abstract

The present invention provides a method and system that can grasp the fatigue state before the bearing component is damaged and can diagnose the fatigue state without disassembling the rolling bearing. Without disassembling the rolling mechanical element, the axial and radial magnetic flux density of the structural component is measured by a magnetic sensor arranged near the structural component, and the change amount relative to the reference magnetic flux density equivalent to the magnetic flux density before the structural component is used is calculated, and the fatigue development degree of the rolling mechanical element is determined based on the change amount.

Description

Technical Field

[0001] The present invention relates to a fatigue diagnosis method and a fatigue diagnosis system for rolling mechanical elements such as rolling bearings and direct-acting devices, and more specifically, to a fatigue diagnosis method and a fatigue diagnosis system for diagnosing in a non-decomposition manner the state of a raceway surface made of a magnetic material in rolling mechanical elements such as rolling bearings having a raceway surface of rolling elements, including ball bearings such as deep groove ball bearings, cylindrical roller bearings, tapered roller bearings, spherical (self-aligning) roller bearings, or direct-acting devices having structural components having a raceway surface of rolling elements. Background Art

[0002] Rolling bearings such as ball bearings and roller bearings and direct-acting devices are assembled in the rotating support parts of various mechanical devices. For example, a rolling bearing has a pair of raceway rings, namely an outer ring and an inner ring, which are coaxially arranged with each other, and a plurality of rolling elements. The outer ring has an outer ring raceway on the inner circumference, and the inner ring has an inner ring raceway on the outer circumference. A plurality of rolling elements are arranged between the outer ring raceway and the inner ring raceway so as to roll freely. For example, a rolling bearing supports the rotating shaft rotatably on the inner side of the housing by embedding the outer ring in the housing and embedding the inner ring in the rotating shaft.

[0003] When the rolling bearing is in operation, the rolling elements repeatedly pass through the outer ring raceway and the inner ring raceway. Therefore, in the load ring, the raceway surface made of magnetic materials such as steel repeatedly bears the load from the rolling elements. Therefore, over time, the material structure (metal structure), residual stress, hardness, etc. under the surface of the raceway surface change, and rolling fatigue occurs. If such rolling fatigue worsens, cracks sometimes occur under the surface of the raceway surface, leading to peeling. If peeling occurs, not only will the abnormal noise and vibration generated during the operation of the rolling bearing increase, but cracks and ruptures may eventually occur in the raceway ring. This situation is also the case in rolling bearings that are used in a manner that applies a load to the entire circumference of the raceway ring, and direct-acting devices that have structural components with a raceway surface of rolling elements.

[0004] In view of such a situation, Japanese Patent Publication No. 2012-42338 (Patent Document 1) and the like describe a technique for detecting abnormalities in rolling bearings by monitoring vibrations caused by damage such as peeling. According to such prior art, measures such as promoting replacement can be taken before the rolling bearings become unusable due to cracks or ruptures in the raceway rings. However, since the abnormality is detected after the damage occurs, there is a possibility that the equipment must be stopped for the replacement of the rolling bearings when an abnormality is detected during the operation of a device in which a rolling bearing is assembled. On the other hand, if the development state of fatigue can be grasped before damage occurs, replacement can be performed at a time when the equipment is not in operation. In view of such a situation, it is required to grasp the development state of fatigue before damage occurs.

[0005] Japanese Patent Publication No. 63-34423 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2009-041993 (Patent Document 3) describe the following technology: using X-rays to measure the half-value width of martensite and the amount of retained austenite contained in the material structure of the bearing component constituting the rolling bearing, thereby diagnosing the fatigue development degree of the rolling bearing. According to such a diagnostic method using X-rays, the development state of fatigue can be grasped before the bearing component is damaged.

[0006] However, considering the impact of X-rays on the human body, the diagnostic method using X-rays needs to be implemented in a space shielded from the outside. The X-ray diffraction device used for diagnosis is large and is generally placed on the ground. Therefore, the diagnostic method using X-rays is difficult to perform on-site in factories and other places equipped with equipment that assembles rolling bearings that are the subject of diagnosis, and is subject to site constraints. In addition, in order to irradiate the surface of the bearing component with X-rays, the rolling bearing needs to be disassembled, so the work hours required for diagnosis increase. Furthermore, since changes in metal structure and the like occur under the surface of the bearing component, in most cases, the bearing component needs to be cut off. Therefore, there is an undesirable situation in which the rolling bearing cannot be used after diagnosis.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2012-42338

[0010] Patent Document 2: Japanese Patent Publication No. 63-34423

[0011] Patent Document 3: Japanese Patent Application Publication No. 2009-041993 Summary of the invention

[0012] Problems to be solved by the invention

[0013] The present invention is proposed to solve the above-mentioned problems, and its purpose is to provide a fatigue diagnosis method and a fatigue diagnosis system for rolling machinery elements that can grasp the development state of fatigue of the structural components of the rolling machinery elements without disassembling the rolling machinery elements and before the structural components of the rolling machinery elements are damaged.

[0014] Means for solving problems

[0015] The inventors of the present invention focused on the rolling elements repeatedly passing through the raceway surface made of magnetic materials such as steel of rolling mechanical elements such as rolling bearings and direct-acting devices, whereby the material structure (metal structure) of the raceway surface changes over time (hereinafter, this structural change is also referred to as "fatigue" in this specification). As a result, the following insights were obtained: the changes in the material structure produced under the surface of the raceway surface of the rolling mechanical element are accompanied by changes in magnetism, and different magnetic fields are generated before and after the use of the rolling mechanical element (before and after fatigue), and the magnetic flux density changes. Moreover, the insight was obtained that the amount of change in the magnetic flux density (magnetic field) is related to the degree of development of fatigue of the rolling mechanical element. Furthermore, the following insight was obtained: in the change of magnetic flux density, the amount of change in the axial and radial magnetic flux density of the rolling mechanical element is related to the development state of fatigue (the change in material structure). The present invention was completed as a result of in-depth research based on such insights.

[0016] A rolling machinery element fatigue diagnosis method according to one embodiment of the present invention is a method for diagnosing a development state of fatigue of a rolling machinery element, the fatigue diagnosis method comprising: a diagnosis step for diagnosing a fatigue state of the rolling machinery element based on changes in magnetic field information of the rolling machinery element.

[0017] As the rolling mechanical elements, there can be listed rolling bearings such as ball bearings and roller bearings having a structural component, i.e., a raceway ring, having a rolling surface made of a magnetic material such as steel that bears load from the rolling element, or direct-acting devices such as linear guides and ball screws having a structural component having a rolling surface made of a magnetic material that bears load from the rolling element.

[0018] As the magnetic field information, the magnetic field information of the structural component having the raceway surface may be used. In this case, the diagnostic process may include: a measuring process, in which a magnetic sensor (magnetic field measuring device) is arranged near the structural component to measure the magnetic field information of the structural component. For example, when the structural component is a raceway ring, the vicinity of the structural component can be set to the axial side or radial side of the raceway ring. In addition, when the structural component is a structural component of a direct-acting device, it can be set to the radial side of the structural component.

[0019] The fatigue state of the rolling bearing may be diagnosed by comparing a value of magnetic flux density corresponding to the magnetic field information measured in the measuring step with a threshold value set for the value of the magnetic flux density.

[0020] As the magnetic field information, the axial and / or radial magnetic flux density of the structural component may be used.

[0021] The diagnosis step may include a change amount calculation step of calculating a change amount of the magnetic flux density measured in the measurement step based on a reference magnetic flux density equivalent to a magnetic flux density before use of the component.

[0022] As the reference magnetic flux density, the magnetic flux density of the portion of the structural component corresponding to the non-load circle in the circumferential direction, or the magnetic flux density of the portion of the structural component corresponding to the load circle in the circumferential direction before use can be used. As the magnetic flux density measured in the measuring step, the magnetic flux density of the portion of the structural component corresponding to the load circle in the circumferential direction can be used.

[0023] The diagnostic process comprises: a determination process, using determination data to determine the fatigue development degree of the rolling mechanical element based on the change in the magnetic flux density calculated in the change calculation process, wherein the determination data represents a correlation between the fatigue development degree of the test rolling mechanical element obtained in advance by X-ray measurement using a test rolling mechanical element of the same type as the rolling mechanical element and the change in axial and / or radial magnetic flux density of a structural component of the test rolling mechanical element obtained in advance by using a test rolling mechanical element of the same type as the rolling mechanical element.

[0024] The rolling mechanism component fatigue diagnosis method according to one embodiment of the present invention may further include a preparation step for obtaining the determination data. The preparation step is a step of testing the rolling mechanism component for testing, and may include a first preparation step to a third preparation step.

[0025] The first preparation step is a step of determining the amount of change in the axial and / or radial magnetic flux density of the structural component of the test rolling machine element before and after the test. The second preparation step is a step of determining the degree of fatigue development of the test rolling machine element after the test. The third preparation step is a step of generating determination data indicating the correlation between the degree of fatigue development determined in the second preparation step and the amount of change in the magnetic flux density determined in the first preparation step.

[0026] In the second preparation step, the fatigue development degree can be obtained using the amount of reduction in the half-value width of martensite of the structural member constituting the test rolling machine element before and after the test.

[0027] In the first preparation step, the change amount of the magnetic flux density can be obtained in both the axial direction and the radial direction, and the determination data can be formed by data indicating the correlation between the fatigue development degree and the change amount of the axial magnetic flux density and the change amount of the radial magnetic flux density. In this case, the determination data can be formed by mapping the fatigue development degree on a coordinate with the change amount of the axial magnetic flux density and the change amount of the radial magnetic flux density as two axes, or by a determination map divided according to the fatigue development degree.

[0028] In the rolling machine element fatigue diagnosis method according to one aspect of the present invention, the determination data may be constituted by data indicating a correlation between the fatigue development degree and the amount of change in the magnetic flux density in either the axial direction or the radial direction.

[0029] A rolling mechanism element fatigue diagnosis method according to one embodiment of the present invention can perform diagnosis without decomposing the rolling mechanism element.

[0030] A rolling machine element fatigue diagnosis system according to one embodiment of the present invention includes a magnetic sensor, a calculation unit, a storage unit, and a determination unit.

[0031] The magnetic sensor can measure the axial and / or radial magnetic flux density of a component of a rolling machine element to be diagnosed.

[0032] The calculation unit can calculate the amount of change in the magnetic flux density measured by the magnetic sensor based on a reference magnetic flux density equivalent to the magnetic flux density before the component starts to be used.

[0033] The storage unit stores judgment data representing the correlation between the fatigue development degree of the test rolling mechanical element obtained in advance by X-ray measurement using a test rolling mechanical element of the same type as the test rolling mechanical element and the change in axial and / or radial magnetic flux density of the structural components of the test rolling mechanical element.

[0034] The determination unit determines the degree of fatigue development of the rolling mechanism element according to the amount of change in the magnetic flux density calculated by the calculation unit based on the determination data stored in the storage unit.

[0035] Effects of the Invention

[0036] The fatigue diagnosis method and fatigue diagnosis system of rolling mechanical elements of the present invention are technologies that focus on the fact that the changes in the organization accompanying the fatigue of rolling mechanical elements are accompanied by changes in the magnetic flux density (magnetic field). Magnetic lines of force are generated around the location where the magnetic field changes. Therefore, according to the fatigue diagnosis method and fatigue diagnosis system of rolling mechanical elements of the present invention, even in the non-decomposed state where the rolling mechanical elements are not decomposed, the changes in the magnetic flux density can be measured by using a magnetic sensor that can grasp the magnetic lines of force of the rolling mechanical elements. Thus, the fatigue state of the rolling mechanical elements can be diagnosed in a non-decomposed manner.

[0037] According to the fatigue diagnosis method and fatigue diagnosis system of the rolling mechanical element of the present invention, the fatigue state of the rolling mechanical element can be grasped in a non-decomposition manner before the rolling mechanical element is damaged, so that the rolling mechanical element and the device equipped with the rolling mechanical element can be operated efficiently and safely by replacing the rolling mechanical element regularly. In addition, according to the fatigue diagnosis method and fatigue diagnosis system of the rolling mechanical element of the present invention, the change of magnetic flux density can be measured only by making the magnetic sensor contact or approach the measuring surface, so it also has the effect of greatly eliminating maintenance time. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 (A) is a schematic perspective view of a fatigue diagnosis system according to a first example of an embodiment of the present invention. Figure 1 (B) in FIG. 1 is a block diagram of the fatigue diagnosis system of the first example.

[0039] Figure 2 This is a partially cutaway perspective view of an example of a roller bearing, which is a rolling machine element that is the target of the fatigue diagnosis method of the first example.

[0040] Figure 3 It is used to illustrate Figure 2 The schematic side view of one example of how the roller bearing is used is shown.

[0041] Figure 4 (A) is used to illustrate the composition of Figure 2 Schematic side view of the magnetic field lines generated by the outer ring of the roller bearing shown, Figure 4 (B) is Figure 4 XX section view of (A) in FIG.

[0042] Figure 5 This is a schematic diagram showing an example of the implementation status (measurement process) of the fatigue diagnosis method of the first example.

[0043] Figure 6 This is a schematic diagram showing another example of the implementation status (measurement process) of the fatigue diagnosis method of the first example.

[0044] Figure 7 It means that in the first example, Figure 2 FIG. 1 is a graph showing an example of test results obtained by measuring the magnetic field on the axial side surface of the raceway ring, which is a component of the roller bearing.

[0045] Figure 8 This is a block diagram of a fatigue diagnosis system according to a second example of an embodiment of the present invention.

[0046] Fig. 9 This is a flowchart showing each step of the fatigue diagnosis method according to the second example.

[0047] Fig.10 (A) is a side view showing a measuring process of measuring the magnetic flux density of a raceway ring, which is a component of a rolling machine element (roller bearing), using a magnetic sensor in the second example. Fig.10 (B) is Fig.10 YY section view of (A) in FIG.

[0048] Fig.11 This is a flowchart for explaining the execution process of the fatigue diagnosis method of the second example.

[0049] Fig.12 The scatter plot shows the calculated values ​​of the test bearings on a two-dimensional coordinate system with the fatigue development degree in the second example as the X-axis and the change in the axial magnetic flux density as the Y-axis.

[0050] Fig.13 The scatter plot shows the calculated values ​​of the test bearings plotted on a two-dimensional coordinate system with the fatigue development degree in the second example as the X-axis and the change in radial magnetic flux density as the Y-axis.

[0051] Fig.14 A scatter plot of the change in magnetic flux density as a calculated value is drawn on a two-dimensional coordinate system with the change in radial magnetic flux density in the second example as the X-axis and the change in axial magnetic flux density as the Y-axis, and a two-dimensional mapping diagram is implemented that implements a mapping corresponding to the degree of fatigue development. DETAILED DESCRIPTION

[0052] With appropriate reference to the accompanying drawings, an embodiment of the fatigue diagnosis method for rolling machinery elements of the present invention and the fatigue diagnosis system used in the fatigue diagnosis method are described. In addition, the accompanying drawings are schematic. Therefore, it should be noted that the relationship and ratio between thickness and plane dimensions are different from reality, and the drawings also contain parts with different dimensional relationships and ratios. In addition, the embodiments shown below illustrate the devices and methods for concretizing the technical ideas of the present invention, and the present invention is not limited by the materials, shapes, structures, configurations, etc. of the structural components in the embodiments shown below.

[0053] [First example of one embodiment]

[0054] use Figure 1 (A)~ Figure 7 , a first example of an implementation of the present invention is described.

[0055] [Overall structure of fatigue diagnosis system]

[0056] Figure 1 (A) and Figure 1 (B) in FIG. 1 represents a fatigue diagnosis system of the first example. The fatigue diagnosis system 1 includes a magnetic sensor (magnetic field measuring device) 3 and a diagnosis device 4 composed of an information processing device. In this example, a rolling bearing is used as a rolling mechanical element as a diagnosis object. The following describes the rolling bearing 2 that is the diagnosis object, and then describes the fatigue diagnosis system 1 of this example.

[0057] 〈Rolling machine elements (rolling bearings)〉

[0058] As rolling bearings 2, deep groove type, angular type, etc. ball bearings, tapered roller bearings, cylindrical roller bearings, needle bearings, self-aligning roller bearings and other rolling bearings can be cited, and there is no limitation on the type (bearing form) and size. The fatigue diagnosis system 1 of this example measures the magnetic field information of the rolling mechanical element that changes according to the development state of fatigue. More specifically, it measures the magnetic flux density (magnetic field) of the structural component with the raceway surface in the rolling mechanical element for diagnosis. Therefore, at least the structural component in the rolling bearing 2, that is, the raceway ring in this example, the outer ring 5 as the object of measuring the magnetic flux density needs to be made of magnetic material. As magnetic materials, steel including bearing steel, other ferromagnetic materials such as alloys including at least one of iron, cobalt, and nickel can be cited, but the present invention can be widely applied to rolling mechanical elements including structural components using paramagnetic materials or diamagnetic materials as magnetic materials.

[0059] like Figure 2 As shown, the rolling bearing 2 includes a pair of annular raceways, namely an outer ring 5 and an inner ring 6, and a plurality of rolling elements 7. The outer ring 5 has an outer ring raceway 8 on the inner circumference, and the inner ring 6 has an inner ring raceway 9 on the outer circumference. The plurality of rolling elements 7 are arranged to roll freely between the outer ring raceway 8 and the inner ring raceway 9. The rolling elements 7 are held by a retainer 10 so as to roll freely and are arranged at equal intervals in the circumferential direction. In the example shown in the figure, tapered rollers are used as rolling elements 7. The rolling bearing 2 may also include a sealing component as required.

[0060] The outer ring 5, inner ring 6, and rolling element 7 as bearing components are made of iron alloy (steel) such as bearing steel represented by high carbon chromium bearing steel (SUJ2), medium carbon steel, carburizing steel, etc., and are subjected to heat treatment such as quenching, carburizing quenching treatment, carbonitriding quenching treatment, etc., and have magnetic properties.

[0061] The rolling bearing 2 can be used, for example, in the following inner ring rotating type usage mode, that is, the outer ring 5 is embedded in the housing, and the inner ring 6 is embedded in the rotating shaft, so that the rotating shaft is rotatably supported on the inner side of the housing. Alternatively, the rolling bearing 2 can also be used in the following outer ring rotating type usage mode, that is, by embedding the outer ring 5 in the rotating body and embedding the inner ring 6 in the fixed shaft, so that the rotating body is rotatably supported around the fixed shaft.

[0062] In this example, the fatigue state of the rolling bearing 2 is diagnosed based on the following principle. Figure 3 As shown in FIG. 1 , if the rolling bearing 2 is used in a manner in which the inner ring is rotated, and a downward radial load Fr is applied to the rotating shaft 17 on which the inner ring 6 is fitted, the lower portion (the range with the oblique checkered pattern) of the outer ring 5 constituting the rolling bearing 2 becomes the load ring, and the other portion becomes the non-load ring, as shown by the oblique checkered pattern representing the load distribution of the rolling element 7. Therefore, under the surface of the portion of the raceway surface of the outer ring raceway 8 that exists in the load ring, when the metal structure changes due to fatigue, the magnetic properties change at the same time. Specifically, the decomposition of the retained austenite as the non-magnetic layer and the relaxation of the strain of the martensite structure (the movement of the magnetic domain wall becomes easier) occur. Therefore, before and after the use of the rolling bearing 2 (before and after fatigue), the magnetic flux density (magnetic field) of the outer ring 5 changes according to the change in the magnetic properties of the outer ring 5. In addition, since the change in the magnetic flux density is related to the progress of fatigue, the fatigue state of the rolling bearing 2 can be diagnosed using the change in the magnetic flux density.

[0063] The magnetic force generated in the outer ring raceway 8 becomes higher in the load circle than in the non-load circle, so around the outer ring 5, as shown in Figure 4 (A) and Figure 4 As shown by the arrow in (B) in FIG. 1 , magnetic lines of force corresponding to the magnetic flux density are generated. Therefore, by arranging the magnetic sensor 3 near the outer ring 5 (axially to the side or radially outside), the magnetic flux density of the outer ring 5 can be measured even without disassembling the rolling bearing 2. Specifically, Figure 4 As shown in (A) in FIG. 5 , magnetic lines of force appear not only on the inner circumference side of the outer ring raceway 8 but also on the outer circumference side of the outer ring 5. Therefore, the change in magnetic flux density (magnetic field change) can be measured from the radially outer side (outer circumference side) of the outer ring 5. Figure 4 As shown in (B) in FIG. 1 , magnetic lines of force are also generated from the axial side surface (end surface) of the outer ring 5, so the change in the magnetic flux density of the outer ring 5 can also be measured from the axial side of the outer ring 5. Thus, the fatigue state of the rolling bearing 2 can be diagnosed without disassembling the rolling bearing 2.

[0064] 〈Magnetic Sensor〉

[0065] The magnetic sensor 3 is a measuring device for measuring magnetic flux density (magnetic field). Figure 1 (A) and Figure 1 As shown in (B) in FIG. 1 , it has a main body 15 and a probe 12. The main body 15 is configured in a box shape, can be carried by hand, and can display the measured value. The probe 12 is connected to the main body 15 via a signal line 16. A magnetic sensing part 11 is provided at the end of the probe 12. A Hall element that outputs a voltage proportional to the magnetic flux density is provided inside the magnetic sensing part 11. A processing part 13 that measures the magnetic flux density based on the output voltage of the Hall element is encapsulated inside the probe 12.

[0066] The probe 12 can measure the magnetic flux density based on the output voltage of the Hall element that outputs a voltage proportional to the magnetic flux density. The probe 12 is also provided with an external output unit 14. The external output unit 14 can output the measurement result of the magnetic flux density of the processing unit 13 to the main body 15 via the signal line 16. The main body 15 can output the measurement result of the magnetic flux density of the processing unit 13 to the external diagnostic device 4. The fatigue diagnosis system 1 of this example does not require a magnetic field generating unit such as a magnet as a reference, and therefore does not have such a magnetic field generating unit. In addition, a 3-axis magnetic sensor that can measure the magnetic field information in the 3-axis direction is used as the magnetic sensor 3, so that the magnetic field information combining the results of the 3-axis direction can also be obtained.

[0067] [Fatigue diagnosis method]

[0068] In the fatigue diagnosis method of this example, if Figure 5 As shown, the magnetic sensing unit 11 constituting the magnetic sensor 3 is arranged on the load ring side of the rolling bearing 2. The reason for arranging the magnetic sensing unit 11 in such a position is based on the following understanding: the rolling bearing 2 generates a magnetic field on the load ring side due to fatigue generated under the surface (including the surface and the inner part) of the raceway surface of the outer ring raceway 8, causing the magnetic field distribution to change. In addition, in this way, the intensity (magnetic flux density) of the magnetic field generated under the surface of the raceway surface of the outer ring raceway 8 is sufficiently large compared to the naturally existing external magnetic field.

[0069] The magnetic sensing unit 11 can detect the magnetic field variation under the surface of the raceway surface of the outer ring raceway 8, and detect the fatigue under the surface of the raceway surface of the outer ring raceway 8. In order to diagnose the fatigue part of the rolling bearing 2, the state of the rolling bearing 2 before use, which is the object of diagnosis, is required as a reference (standard).

[0070] The configuration position of the magnetic induction unit 11 relative to the measuring unit of the rolling bearing 2 can be adjusted according to the space around the rolling bearing 2. The magnetic induction unit 11 can be spaced from the outer ring 5 to a distance that is in contact with the measuring surface of the rolling bearing 2 or is not affected by the residual magnetic field of the rolling bearing 2. In this example, the opposing distance between the magnetic induction unit 11 and the outer ring 5 can be set to 2 mm, for example.

[0071] In addition, when detecting cracks in the steel constituting the raceway ring without performing fatigue diagnosis, it is necessary to prepare a test object (rolling bearing) that serves as a reference for no cracks, and determine whether cracks have occurred based on the measurement values ​​of the reference test object.

[0072] In contrast, in the fatigue diagnosis method of this example, since the fatigue part of the rolling bearing 2 is diagnosed, if there is a part whose quality does not change (fatigue does not occur) during the use of the rolling bearing 2, this position can be set as a reference (standard) position representing the state of the rolling bearing 2 before use. For example, in the fatigue diagnosis method of this example, by comparing the measurement results of the magnetic field information of the load ring in the outer ring raceway where the rolling element applies a load and the non-load ring in the outer ring raceway where the rolling element does not apply a load, the fatigue state of the outer ring raceway can be diagnosed. Specifically, in the use mode where the outer ring 5 of the rolling bearing 2 is fixed to a housing or the like and a radial load is applied to the outer ring 5, since the opposite side of the load ring is the non-load ring, the position of the non-load ring can be used as the reference position.

[0073] In the fatigue diagnosis method of this example, when diagnosing a rolling mechanical element, the value of the magnetic flux density obtained based on the magnetic field information obtained by the magnetic sensor can be compared with a threshold value set for the value of the magnetic flux density to diagnose the fatigue state. Figure 6 As shown, two magnetic sensors 3X ​​and 3Y having the same structure as the magnetic sensor 3 are prepared. The magnetic sensing portion 11 of each of the magnetic sensors 3X ​​and 3Y is arranged to face the axial side surface, the outer peripheral surface, or the inner peripheral surface of the outer ring 5. The surface facing the magnetic sensing portion 11 of the magnetic sensor 3X and the surface facing the magnetic sensing portion 11 of the magnetic sensor 3Y are set to be the same type of surfaces.

[0074] exist Figure 6 In the example shown, in order to measure the magnetic flux density of the load ring of the outer ring 5, the magnetic sensing portion 11 of the first magnetic sensor 3X is arranged to be opposite to the position corresponding to the load ring in the circumferential direction on the outer circumferential surface of the outer ring 5. In contrast, in order to measure the magnetic flux density of the non-load ring, the magnetic sensing portion 11 of the second magnetic sensor 3Y is arranged to be opposite to the position corresponding to the non-load ring in the circumferential direction on the outer circumferential surface of the outer ring 5. In this way, the magnetic sensing portion 11 is also arranged on the non-load ring side, so that the non-load ring side is set as the reference position. That is, the magnetic field information of the magnetic sensor arranged on the non-load ring can be used as a reference magnetic flux density (equivalent to the magnetic flux density of the rolling bearing 2 before use).

[0075] Thus, for example, by comparing the difference between the value of the magnetic flux density obtained based on the magnetic field information obtained by the magnetic sensor 3X and the value of the magnetic flux density obtained based on the magnetic field information obtained by the magnetic sensor 3Y (reference value) with a threshold value related to the difference that is manually set in advance, the fatigue state of the rolling bearing 2 can be diagnosed.

[0076] On the other hand, in the case of a usage method in which a load is applied to the entire circumference of the raceway of the rolling bearing 2 (for example, when the outer ring rotates), the entire circumference of the raceway is fatigued, so it is impossible to set a reference position for diagnosing the fatigue state of the rolling bearing that is the object of diagnosis. In the case of such a usage method, a place that exists in the surroundings of the rolling bearing 2 and does not cause a change in the magnetic field even if the rolling bearing 2 is used can be set as a reference position. Alternatively, in the case where there is no magnetic body that causes a change in the magnetic field in the air (space) around the rolling bearing 2, the space can also be used as a reference. That is, the value of the magnetic flux density obtained by configuring the magnetic field information measured by arranging the magnetic sensing part of the magnetic sensor toward the air can be used as a reference value. In this way, in the usage method in which the entire circumference of the structural component of the direct-acting device having a raceway surface that receives a load from the raceway of the rolling bearing or the rolling element becomes a load circle, the rolling bearing or the part other than the structural component that is not affected by the magnetic field change can be used as a reference. In this case, it is necessary to reset the state of the magnetic field of the rolling mechanical element before use to 0.

[0077] In the fatigue diagnosis method of rolling machinery elements in this example, in order to properly grasp the state of the magnetic field of the rolling machinery elements themselves, such as rolling bearings and direct-acting devices, which are the objects of diagnosis, it is preferred not to perform demagnetization, magnetization, etc. before the measurement (diagnosis) performed by the magnetic sensor. This is because, for example, the magnetic sensor measures the magnetic flux density of the raceway or structural component itself that changes due to the load on the raceway or the structural component having a raceway surface. Therefore, if the magnetic field state changes due to demagnetization or magnetization, an accurate diagnosis cannot be performed. In addition, when performing fatigue diagnosis, it is not necessary to fix the magnetic sensor. The operator can also hold the magnetic sensor and measure the entire circumference along the raceway of the rolling bearing or the structural component of the direct-acting device. However, in the case where higher diagnostic accuracy is required, it is preferred to fix the magnetic sensor to a predetermined value for diagnosis.

[0078] [Example 1]

[0079] An example of a fatigue diagnosis method for a rolling bearing 2 using the magnetic sensor 3 according to the first example of the embodiment will be described.

[0080] In this embodiment, a deep groove ball bearing that has completed functional evaluation is used as the rolling bearing 2 as the diagnostic object. The deep groove ball bearing is not disassembled into the inner ring, outer ring, rolling element and retainer, and is used for diagnosis (measurement) as a whole deep groove ball bearing. During diagnosis, a test shaft (not shown) is inserted into the inner ring 6 of the rolling bearing 2 that has completed functional evaluation. In addition, the outer ring 5 of the rolling bearing 2 is fixed to the test housing (not shown), and the bearing cover (not shown) is set on the test housing from the axial side of the rolling bearing 2.

[0081] The probe 12 constituting the magnetic sensor 3 is brought into contact with or close to the axial side surface of the outer ring 5 fixed to the test housing to measure the magnetic flux density of the axial side surface of the outer ring 5. In addition, in order to measure the magnetic field characteristics after the test, the rolling bearing 2 is not demagnetized or magnetized before the measurement.

[0082] The probe 12 of the magnetic sensor 3 is set on the bearing cover so that the magnetic sensing part 11 is opposite to the axial side of the outer ring 5. In this state, the magnetic flux density of the outer ring 5 with the load ring and the non-load ring is measured by the magnetic sensor 3. In this embodiment, the magnetic flux density (the direction and intensity of the magnetic pole) is measured at four positions (0°, 90°, 180°, and 270°) spaced every 90 degrees in the circumferential direction of the bearing cover. Specifically, the center of the load ring is set to the position of 180°, and the opposite side located on the opposite side in the diameter direction relative to the center of the load ring is set to the position of 0° as a reference. The position shifted 90° to one side in the circumferential direction from the 0° position is set to the position of 90°, and the position shifted 90° to the other side in the circumferential direction from the 0° position is set to the position of 270°.

[0083] Figure 7 The measurement results of this embodiment are shown. Specifically, for the outer ring 5, the magnetic flux density in the depth direction relative to the measurement surface is measured at each of the positions of 0°, 90°, 180° and 270° arranged in four equal parts, and the difference values ​​of each of these measurement results are calculated based on the magnetic flux density at the 0° position. Figure 7 The results are shown in Figure 7 As can be seen from the measurement results shown, the magnetic flux density in the load circle corresponding to the position of 180° changes the most compared with the magnetic flux density (reference magnetic flux density) in the non-load circle corresponding to the position of 0°.

[0084] Similarly, when a rolling bearing with wear and discoloration on the outer ring raceway was used as a diagnostic object, the magnetic flux density was measured from the axial side of the outer ring. As a result, a larger change in the magnetic field was confirmed compared to the result of pure fatigue. The reason for this is believed to be that the contact between metals that causes wear and discoloration on the raceway surface will produce a larger magnetic field change than the material change caused by fatigue, which is reflected in the measured value of the magnetic flux density.

[0085] From the insights based on such experiments, it can be seen that by applying the fatigue diagnosis method of this example and measuring the magnetic flux density from the axial side or circumferential surface of the raceway ring, it is possible to not only understand the fatigue state of the rolling mechanical element in a non-decomposed manner, but also understand the presence or absence of damage to the structural components of the rolling mechanical element and the degree of damage, or the cause of the damage (for example, whether it is a deviation that causes wear or discoloration).

[0086] As described above, according to the fatigue diagnosis method of the rolling machine element of this example, the magnetic field information of the outer ring 5 of the rolling bearing 2 can be measured from the axial side surface or the peripheral surface of the outer ring 5 of the rolling bearing 2 by the magnetic sensor 3, and the fatigue state of the outer ring 5 of the rolling bearing 2 can be diagnosed based on the change of the magnetic field information of the outer ring 5 obtained by the magnetic sensor 3. Therefore, it is of course possible to set the rolling bearing 2 to be non-destructive, and it is also possible to diagnose the fatigue state of the rolling bearing 2 in a state where the rolling bearing 2 is not disassembled. In addition, by grasping the magnetic field information, the fatigue part of the rolling bearing 2 can be detected. In addition, not only the fatigue part of the rolling bearing 2 can be detected, but also the damaged part such as wear can be detected.

[0087] In addition, according to the fatigue diagnosis method of the rolling machine element of this example, the fatigue state of the outer ring 5 constituting the rolling bearing 2 can be grasped before the rolling bearing 2 is damaged. Therefore, for example, a threshold value can be pre-set for the value of the magnetic flux density corresponding to the magnetic field information, and the threshold value can be compared with the value of the magnetic flux density obtained based on the magnetic field information of the outer ring 5 to diagnose the fatigue state of the rolling bearing 2. As a result, the period of regular replacement of the rolling bearing 2 can be more appropriately determined, and the rolling bearing 2 and the device having the rolling bearing 2 can be operated more efficiently and safely. In this regard, the same is true when the fatigue diagnosis method of the rolling machine element of this example is applied to a direct-acting device having a structural component with a raceway surface.

[0088] [Second example of one embodiment]

[0089] use Figure 8 to Figure 14 , a second example of an implementation of the present invention is described.

[0090] [Overall structure of fatigue diagnosis system]

[0091] The fatigue diagnosis system 1a of this example diagnoses the fatigue development state of the rolling bearing 2 that is the object of diagnosis, and is equipped with a magnetic sensor 3a and a diagnostic device 4a. The fatigue diagnosis system 1a is configured to be sufficiently small compared to the X-ray diffraction device and can be carried. The structure of the rolling bearing 2 that is the object of diagnosis is the same as that of the first example, so the description related to the rolling bearing 2 is omitted. In this example, the case where the present invention is applied to a rolling bearing as a rolling mechanical element is described. Specifically, in the outer ring and the inner ring that are structural components of the rolling bearing 2, bearing steel represented by high carbon chromium bearing steel (SUJ2) is used as a magnetic material. However, the fatigue diagnosis system and fatigue diagnosis method of this example can also be widely applied to rolling bearings that use other magnetic materials as structural components, direct-acting devices with structural components having raceway surfaces, and the like.

[0092] In this example, the fatigue state of the rolling bearing 2 is diagnosed based on the following principle. As described in the first example, Figure 3 As shown in FIG. 1 , if the rolling bearing 2 is used in a manner in which the inner ring is rotated, and a downward radial load Fr is applied to the rotating shaft 17 on which the inner ring 6 is externally fitted, the magnetic flux density (magnetic field) of the outer ring 5 changes before and after the use of the rolling bearing 2 (before and after fatigue). The change in magnetic flux density is caused by the change in the material structure of the magnetic material present in the load ring portion, so there is a correlation between the change in magnetic flux density before and after the use of the rolling bearing 2 and the degree of change in the material structure. Since the state of the material structure can be grasped by X-ray measurement, the correlation between the change in magnetic flux density before and after the use of the rolling bearing 2 and the fatigue development degree (degree of change in material structure) obtained by the diagnostic method using X-rays is obtained in advance. As a result, the fatigue development degree obtained when the diagnostic method using X-rays is implemented can be estimated based on the change in magnetic flux density before and after the use of the rolling bearing 2. In this example, the fatigue state of the rolling bearing 2 is determined based on such a principle.

[0093] like Figure 8 As shown, the fatigue diagnosis system 1a of this example includes a magnetic sensor 3a and a diagnosis device 4a.

[0094] 〈Magnetic Sensor〉

[0095] The magnetic sensor 3a is a measuring device capable of measuring magnetic flux density (magnetic field) in one direction or multiple directions, and is connected to the diagnostic device 4a via a connection cable 18. In this example, only one magnetic sensor 3a is provided, but a plurality of magnetic sensors may be provided.

[0096] The magnetic sensor 3a is composed of a detection unit, a circuit (including a driving circuit, a processing circuit, etc.), and a substrate on which the detection unit and the circuit are mounted. The detection unit is composed of magnetic detection elements such as MI elements, Hall elements, Hall ICs, MR elements, GMR elements, AMR elements, and TMR elements. In this example, as the detection unit, an MI element is used, and the magnetic sensor 3a is set as an MI sensor capable of measuring the magnetic flux density in three directions. The MI sensor is a magnetic sensor that utilizes the magnetoresistance effect of an amorphous wire. In such an MI sensor, a high-frequency pulse current is excited to the detection unit (amorphous wire) by a driving circuit, and the induced electromotive force generated in the detection unit is detected by a detection circuit.

[0097] The magnetic sensor 3a is arranged near the outer ring 5 or the inner ring 6, which is a raceway ring, and the magnetic flux density (direction and strength of the magnetic field) of the outer ring 5 or the inner ring 6 is measured. The arrangement of the magnetic sensor 3a near the outer ring 5 or the inner ring 6 is determined according to the use of the rolling bearing 2. For example, in the raceway ring where the load ring and the non-load ring are generated, since fatigue is easy to develop in the load ring, it is preferable to arrange the magnetic sensor 3a near the portion of the raceway ring corresponding to the load ring in the circumferential direction (preferably the maximum load position at the circumferential center of the load ring).

[0098] In this example, an MI sensor capable of measuring magnetic flux density in three directions is used as the magnetic sensor 3a, so that the magnetic flux density in the axial, radial, and circumferential directions of the rolling bearing 2 can be simultaneously measured with high accuracy by the magnetic sensor 3a. However, in fatigue diagnosis, it is sufficient to use the magnetic flux density in at least one of the axial and radial directions of the rolling bearing 2, among the measured values ​​in the three directions, for which a correlation with the fatigue development degree has been confirmed.

[0099] The magnetic sensor 3a is used in the execution process to measure the magnetic flux density (M1) of the rolling bearing 2 after use (after fatigue, current state), and is also used to measure the reference magnetic flux density (M0) equivalent to the magnetic flux density before the start of use (before fatigue, new state) of the rolling bearing 2. In addition, in the preparation process, it is also preferred to use the magnetic sensor 3a or a sensor of the same type as the magnetic sensor 3a.

[0100] 〈Diagnostic device〉

[0101] The diagnostic device 4a has a function of determining the degree of fatigue development of the rolling bearing 2. The diagnostic device 4a includes: an input unit 19 for inputting data; a storage unit 20 for storing data; a calculation unit 21 for calculating the amount of change in magnetic flux density; a determination unit 22 for determining the degree of fatigue development of the rolling bearing 2; and an output unit 23 for outputting the determination result.

[0102] The output signal of the magnetic sensor 3a is input to the input unit 19 of the diagnostic device 4a via the connection cable 18. Specifically, two types of magnetic flux densities (M0, M1) before and after use of the rolling bearing 2 are input to the diagnostic device 4a. The signal input from the magnetic sensor 3a is converted into processable data (for example, from analog data to digital data) as required, classified according to its type and stored in the storage unit 20. In addition, the judgment data indicating the correlation between the change amount of magnetic flux density and the fatigue development degree obtained in advance in the preparation process is input to the input unit 19 of the diagnostic device 4a and stored in the storage unit 20.

[0103] The calculation unit 21 has the following function: by obtaining the difference (M1-M0) between the reference magnetic flux density (M0) corresponding to the magnetic flux density before the start of use of the rolling bearing 2 and the magnetic flux density (M1) after the use of the rolling bearing 2, the change amount (C) of the rolling bearing 2 before and after use is calculated, and the calculated change amount (C) of the magnetic flux density is stored in the storage unit 20.

[0104] The determination unit 22 determines (estimates) the fatigue development degree of the rolling bearing 2 after use based on the determination data stored in the storage unit 20 and the change (C) of the magnetic flux density of the rolling bearing 2 calculated by the calculation unit 21. For example, when the determination data is represented by a function, the fatigue development degree is obtained by substituting the change (C) of the magnetic flux density into the variable in the function. In addition, when the determination data is represented by a determination map divided according to the fatigue development degree, the fatigue development degree is obtained by determining in which area of ​​the determination map the change (C) of the magnetic flux density is depicted. And, when the determination data is represented by a threshold value (numerical value), the fatigue development degree is obtained by comparing (determining) the relationship between the displacement of the magnetic flux density and the threshold value.

[0105] The output unit 23 displays the degree of fatigue development of the rolling bearing 2 obtained by the determination unit 22 on a display visually, for example, using a numerical value, or outputs it auditorily through a speaker, etc. In addition, it is also possible to display (output) determination results such as "can continue to be used", "replacement preparation (inventory confirmation)", and "need to be replaced" according to the degree of fatigue development.

[0106] The diagnostic device 4a can be constituted by, for example, a personal computer (information processing device), and can execute the above functions by executing a program. The diagnostic device 4a can also have a function of obtaining determination data indicating the correlation between the change amount of magnetic flux density and the degree of fatigue development.

[0107] [Fatigue diagnosis method]

[0108] A method for performing fatigue diagnosis of a rolling bearing 2 using the fatigue diagnosis system 1a of this example will be described. Fig. 9As shown, the preparation step and the execution step are performed when performing fatigue diagnosis of the rolling bearing 2. In the fatigue diagnosis method of this example, the execution step corresponding to the diagnosis step in the fatigue diagnosis method of the present invention is a necessary step, while the preparation step is optional.

[0109] 〈Preparation process〉

[0110] The preparation process in this example is a process for obtaining judgment data using multiple test bearings of the same type as the rolling bearing 2. Usually, it is not performed on-site in a factory or other facility equipped with equipment for assembling the rolling bearing 2, but in other facilities equipped with an X-ray diffraction device. Such a preparation process does not need to be performed every time when fatigue diagnosis of the rolling bearing 2 is performed, and only needs to be performed once. In this example, the preparation process includes the following first preparation process (S p 1) The second preparation step (S p 2) and the third preparation step (S p 3) In addition, before the preparation process, the test bearings are demagnetized.

[0111] exist Fig. 9 The first preparation step (S p 1), the magnetic sensor 3a is used to measure the axial and / or radial magnetic flux density of the test bearing before and after the test, and the change amount thereof is calculated. The test is carried out in the following manner: the test bearing is assembled in the test device, and the test bearing is operated for a predetermined time or until the bearing is damaged in the same manner of use and under the same conditions (load conditions, lubrication conditions, number of revolutions, etc.) as the rolling bearing 2. Before and after such a test, the test bearing is not disassembled, and the magnetic flux density at the same position of the raceway ring is measured by the magnetic sensor 3a. Specifically, the magnetic flux density of the portion of the raceway ring corresponding to the load ring in the circumferential direction (preferably the circumferential center position of the load ring) is measured. Therefore, the magnetic sensor 3a is arranged near the portion of the raceway ring corresponding to the load ring in the circumferential direction, so that the detection portion of the magnetic sensor 3a is in contact with or close to the axial side surface or circumferential surface of the raceway ring. In addition, for the test bearing after the test, no demagnetization treatment is performed before measuring the magnetic flux density.

[0112] The magnetic flux density value of the test bearing before the test may be replaced by, for example, a value obtained by measuring the portion of the raceway ring corresponding to the non-load ring in the circumferential direction with the magnetic sensor 3a after the test. In this case, the preparation step in this example can be omitted.

[0113] In the first preparation step (S pIn 1), for each test bearing, the magnetic flux density before and after the test is obtained, and the change (difference) in the magnetic flux density before and after the test is obtained.

[0114] Second preparation step (S p 2) and the first preparation step (S p 1) Implemented in parallel, by X-ray measurement using an X-ray diffraction device, the fatigue development degree of the test bearing after the test is obtained. Specifically, before and after the test, X-rays are irradiated to the same position (the portion corresponding to the load circle) in the raceway ring constituting the test bearing where the magnetic flux density is measured using the magnetic sensor 3a, and an X-ray diffraction spectrum is obtained, thereby understanding the state of the metal structure (material structure) of the raceway surface. At this time, in the measurement after the test, if there is a situation where the X-ray irradiation does not reach the measurement surface, the raceway ring is cut off as needed for measurement. Then, the reduction in the half-value width of martensite before and after the test is obtained based on the X-ray diffraction spectrum.

[0115] In the X-ray measurement, not only the reduction in the half width of martensite but also the reduction in the amount of retained austenite and the value of residual stress can be measured. Therefore, the fatigue development degree (%) is calculated using the following formula (1).

[0116] Fatigue development degree (%) = k × (reduction in half-value width of martensite + a × reduction in retained austenite) (1)

[0117] In the above formula (1), k is a coefficient determined by the environment in which the bearing is used, and a is a coefficient determined by the metal material.

[0118] Different from the above-mentioned formula (1), the fatigue development degree may be obtained using the following formula (2).

[0119] Fatigue development degree (%) = 60 × reduction in half-value width of martensite (2)

[0120] The larger the value of the fatigue development degree (%) obtained by the above formula (1) and the above formula (2), the more advanced the fatigue is. In addition, the above formula (2) is a calculation formula that takes into account the reduction amount of retained austenite and can be used when calculating the fatigue development degree. However, when it is necessary to calculate the fatigue development degree with higher accuracy, it is preferable to use the above formula (1).

[0121] In the third preparation step (S p 3), find the value indicating that in the second preparation step (S p 2) and the fatigue development degree obtained in the first preparation step (S p Specifically, in the first preparation step (S p1), in the case where the changes in the axial and radial magnetic flux density of the test bearing are obtained, determination data (database) such as mappings, tables, relational expressions, thresholds, etc., which represent the correlation between the fatigue development degree and the changes in the axial magnetic flux density and the changes in the radial magnetic flux density are obtained. When the determination data is set as a mapping, it can be set as a two-dimensional determination map in which the fatigue development degree is mapped on coordinates with the changes in the axial magnetic flux density and the changes in the radial magnetic flux density as two axes. In order to generate a determination map, first, as Fig.14 As shown, a coordinate is generated with the change in radial magnetic flux density as the X-axis and the change in axial magnetic flux density as the Y-axis, and the change in magnetic flux density as the calculated value is plotted on the coordinate. Next, by making the shape, color, size, etc. of the plot different (grouped) according to the degree of fatigue development, each plot on the coordinate is associated with the degree of fatigue development (established an association). Based on this, focusing on the deviation of the plot position of each group on the coordinate, the coordinate is divided according to the degree of fatigue development, and the judgment range of the degree of fatigue development is determined. That is, a judgment area corresponding to the degree of fatigue development is set on the coordinate. Specifically, an area with a fatigue development degree of less than 80%, an area with a fatigue development degree of more than 80% and less than 100%, an area with a fatigue development degree of more than 100%, etc. are set on the coordinate.

[0122] In contrast, in the first preparation step, when only the change in magnetic flux density in either the axial or radial direction of the test bearing is calculated, judgment data such as a mapping, a relational expression, a table, a threshold value, etc. representing the correlation between the degree of fatigue development and the change in magnetic flux density in either direction are calculated.

[0123] The above-mentioned determination data (mapping, table, relational expression, etc.) differs according to the type, size, material, use conditions, etc. of the rolling bearing 2, so the determination data is prepared in advance according to the rolling bearing 2 to be diagnosed. In other words, when the rolling bearing 2 of the same specification is diagnosed multiple times, the determination data does not need to be generated every time the diagnosis is performed, and it only needs to be generated once at the beginning.

[0124] 〈Execution process〉

[0125] The execution process is a process (diagnosis process) for performing fatigue diagnosis on the rolling bearing 2. Unlike the preparation process, it is performed on site such as a factory equipped with equipment for assembling the rolling bearing 2. In this example, the execution process includes the following measurement process (S a 1) Change calculation process (S a 2) and the determination process (S a 3).

[0126] In the measurement process (S a1), the rolling bearing 2 is removed from the device, and the rolling bearing 2 is not disassembled, and the axial and / or radial magnetic flux density of the rolling bearing 2 is measured by the magnetic sensor 3a arranged near the raceway ring. Specifically, Fig.10 As shown, the magnetic sensor 3a is arranged near the portion of the raceway of the rolling bearing 2 corresponding to the load ring in the circumferential direction (preferably the circumferential center of the load ring), so that the detection portion of the magnetic sensor 3a is in contact with or close to the axial side or circumferential surface of the raceway. In the example shown in the figure, the rolling bearing 2 is not disassembled and the magnetic sensor 3a is arranged near the circumferential center of the load ring of the outer ring 5, so that the detection portion of the magnetic sensor 3a is close to the axial side of the outer ring 5. Then, the axial and / or radial magnetic flux density (M1) of the rolling bearing 2 is obtained. The output signal of the magnetic sensor 3a is input to the diagnostic device 4a via the connecting cable 18.

[0127] In the variation calculation step (S a 2), the calculation unit 21 of the diagnostic device 4a calculates the time from the reference magnetic flux density (M0) corresponding to the magnetic flux density before the use of the rolling bearing 2 to the measurement step (S a 1) The change (C) of the magnetic flux density (M1) measured in

[0128] The reference magnetic flux density (M0) can be measured by any of the following methods (A) to (D) according to the use mode of the rolling bearing 2 (the range of load ring generation) and the like, and stored in the storage unit 20 .

[0129] (A) In the raceway of the rolling bearing 2 in a new state, the magnetic sensor 3 is arranged at a position corresponding to the measurement step (S a The same position (position serving as the load zone) as the measurement position of the magnetic flux density (M1) in 1) is measured in advance before the rolling bearing 2 is used.

[0130] (B) The magnetic sensor 3a is arranged at a portion of the raceway of the used rolling bearing 2 corresponding to the non-loaded ring in the circumferential direction (for example, on the opposite side of the maximum load position in the diametrical direction), and in the measuring step (S a 1) before and after, or with the measurement process (S a 1) Perform the measurements simultaneously.

[0131] (C) The magnetic sensor 3 a is disposed near the raceway of a reference bearing (standard bearing) of the same type as the rolling bearing 2 to perform measurement.

[0132] (D) The magnetic sensor 3a is disposed at a peripheral position (for example, space) away from the rolling bearing 2 and not subject to changes in the magnetic field, and measurement is performed.

[0133] In addition, when the reference magnetic flux density (M0) is measured simultaneously with the measurement process (magnetic flux density (M1)), as shown in FIG. Figure 6 As shown in the example, two magnetic sensors 3a can be used to measure two magnetic flux densities at the same time. In addition, when the method (B) is adopted, for example, by fixing the magnetic sensor 3a and rotating the raceway ring (rotating one circle), the magnetic flux density of the raceway ring for one circle can be measured, and two magnetic flux densities (M0, M1) can be obtained therefrom. Conversely, the raceway ring can be fixed, and the magnetic sensor 3a can be rotated along the raceway ring for one circle while measuring the magnetic flux density, but from the perspective of ensuring the measurement accuracy, it is preferred to fix the magnetic sensor 3a for measurement.

[0134] In the determination process (S a 3), the determination unit 22 determines (estimates) the fatigue development degree of the rolling bearing 2 based on the determination data stored in the storage unit 20 and the change (C) in the magnetic flux density calculated by the calculation unit 21. Specifically, by comparing the change (C) in the magnetic flux density with the determination data, the value of the fatigue development degree obtained when the diagnostic method using X-rays is implemented is estimated based on the change (C) in the magnetic flux density before and after the use of the rolling bearing 2. At this time, the determination data for comparison uses data obtained based on the change in the magnetic flux density in the same direction (axial or / and radial) as the direction of the magnetic flux density measured in the measuring process. For example, in the measuring process, when only the axial (or radial) magnetic flux density is obtained, the determination data uses data indicating the correlation between the axial (or radial) magnetic flux density and the fatigue development degree. When the determination data is Fig.14 In the case of a judgment map as shown, which is divided into an area with a fatigue development degree of less than 80%, an area with a fatigue development degree of more than 80% and less than 100%, and an area with a fatigue development degree of more than 100%, by determining in which area of ​​the judgment map the change in magnetic flux density (C) before and after the use of the rolling bearing 2 is drawn, it is estimated that the fatigue development degree of the area is the fatigue development degree of the rolling bearing 2.

[0135] If the value of the fatigue development degree of the rolling bearing 2 is estimated as described above, the fatigue development degree of the rolling bearing 2 obtained by the determination unit 22 is displayed on a display, for example, visually, or outputted auditorily through a speaker, etc., through the output unit 23 of the diagnostic device 4a. In addition, it is also possible to display the determination results such as "can continue to be used", "replacement preparation (inventory confirmation)", and "replacement required" according to the determined fatigue development degree.

[0136] According to the fatigue diagnosis system 1a and fatigue diagnosis method of this example, the development state of fatigue can be grasped before the bearing parts are damaged, and fatigue diagnosis can be performed without disassembling the rolling bearing 2. That is, in this example, by finding the change in the magnetic flux density before and after the use of the rolling bearing 2, the fatigue development degree obtained when the diagnostic method using X-rays is implemented can be estimated. Therefore, before the bearing parts constituting the rolling bearing 2 are damaged such as peeling, the development state of fatigue of the rolling bearing 2 can be grasped. Therefore, the rolling bearing 2 can be replaced at a time when the equipment is not in operation, or the rolling bearing 2 can be replaced regularly, etc., so that the equipment can be operated efficiently and safely. In addition, the fatigue diagnosis of the rolling bearing 2 can be performed on site such as a factory equipped with equipment assembled with the rolling bearing 2. Since the judgment result can be known on site, early response corresponding to the fatigue state of the rolling bearing 2 can be performed.

[0137] In this example, there is no need to disassemble the rolling bearing 2 in order to understand the development state of fatigue of the rolling bearing 2, so the man-hours required for diagnosis (maintenance) can be reduced compared to the case of performing the diagnosis method using X-rays. In addition, there is no need to cut the bearing parts as in the diagnosis method using X-rays, and the diagnosis can be performed in a non-destructive manner, so the rolling bearing 2 after diagnosis can be reassembled in the equipment and used.

[0138] The magnetic sensor 3a only measures the magnetic flux density that changes due to changes in the metal structure caused by fatigue, and when diagnosing fatigue, there is no need to apply voltage to the rolling bearing 2 from the outside. In addition, since the value of the axial or / and radial magnetic flux density used to generate the judgment data can be obtained as the output value of the magnetic sensor 3a without signal processing, the calculation processing required to generate the judgment data is simple.

[0139] [Example 2]

[0140] In this example, an example of the preparation process for generating judgment data is described. In this example, 72 tapered roller bearings (model: HR32017XJ) are prepared as test bearings. Then, the 72 test bearings are used as the object, and the rotating shaft (inner ring) is driven at 1500 min. while lubricating each part by forced lubrication and oil supply in the use mode of inner ring rotation. -1 The rotating shaft was rotated and the following test was conducted on the rotating shaft: as the test load, a radial load Fr of 61740N (6300kgf) was applied, and an axial load Fa of 18620N (1900kgf) was applied. In addition, the outer diameter of the test bearing (HR32017XJ) was 130mm and the inner diameter was 85mm, and the bearing components (outer ring, inner ring and tapered roller) were all made of high carbon chromium bearing steel.

[0141] For 32 of the 72 test bearings, the test bearings were removed from the test apparatus after 1 hour, 24 hours, 48 ​​hours, 96 hours, 250 hours, and 1000 hours from the start of the test, and the magnetic flux density values ​​were measured without disassembling the test bearings.

[0142] In contrast, for 40 test bearings, before the test, iron powder (hardness 870Hv, size 150μm or less, mass 0.3g) was mixed into the lubricating oil (ISO-VG10), and the bearings were operated for 1 minute under the same conditions as the above test to form an indentation on the raceway surface, and then the above test was carried out. In the above test after the indentation was formed, the bearings were operated without mixing iron powder into the lubricating oil until the bearings were damaged. Then, the test bearings were removed from the test device, and the value of the magnetic flux density was measured without disassembling the test bearings.

[0143] The magnetic flux density was measured using a magnetic sensor manufactured by Tokyo Rigaku K.K. (model BE90A1E). Fig.10 Similarly, the measurement position of the magnetic sensor is set to the circumferential center of the load ring where fatigue is most likely to develop, and the detection part is closely opposed to the axial side of the outer ring for measurement. The measurement timing is before the test starts and after the test ends, and the magnetic flux density is measured at the same measurement position. In addition, the change in magnetic flux density before and after the test is calculated by subtracting the value of magnetic flux density before the test starts from the value of magnetic flux density after the test ends.

[0144] The fatigue development degree of the test bearing before and after the test was determined by X-ray measurement using an X-ray diffraction device (manufactured by Rigaku Co., Ltd.). Specifically, before and after the test, X-rays were irradiated to the same position as the measurement position of the magnetic sensor in the raceway surface of the outer ring raceway to obtain an X-ray diffraction spectrum. Then, based on the X-ray diffraction spectrum, the reduction in the half-value width of martensite before and after the test was determined using the formula (2). There is a tendency that the longer the test time, the greater the fatigue development degree. In addition, the sample with an indentation on the raceway surface becomes a larger value regardless of the test time.

[0145] Fig.12 The calculated values ​​for each test bearing are plotted on a scatter plot with the fatigue development degree as the X-axis and the change in axial magnetic flux density before and after the test as the Y-axis. Fig.12 It can be confirmed that the greater the degree of fatigue development, the greater the change in axial magnetic flux density. Therefore, if a relational expression (approximate straight line, approximate curve, etc.) representing the correlation between the degree of fatigue development and the change in axial magnetic flux density is obtained, the relational expression can be used as judgment data.

[0146] In addition, Fig.12 In the example, the shape of the plot is displayed differently according to the fatigue development degree. Specifically, the fatigue development degree is divided into three groups, and the plot of the group with a fatigue development degree of less than 80% is represented by a circle, the plot of the group with a fatigue development degree of 80% or more and less than 100% is represented by a triangle, and the plot of the group with a fatigue development degree of 100% or more is represented by a quadrilateral. Here, if we focus on the deviation of the plot position of each group on the coordinate, we can Fig.12 Find (obtain) the threshold value for determining the degree of fatigue development. Fig.12 Generally speaking, if the change in the axial magnetic flux density is larger than Mx, the fatigue development degree is 80% or more, and if the change in the axial magnetic flux density is smaller than Mx, the fatigue development degree is less than 80%. Therefore, by using Mx as a threshold value, when the change in the axial magnetic flux density is larger than Mx, it can be determined that the fatigue development degree is 80% or more, and when the change in the axial magnetic flux density is smaller than Mx, it can be determined that the fatigue development degree is less than 80%.

[0147] Fig.13 The calculated values ​​for each test bearing are plotted on a scatter plot with the fatigue development degree as the X-axis and the change in radial magnetic flux density before and after the test as the Y-axis. Fig.13 It can be confirmed that the greater the degree of fatigue development, the greater the change in radial magnetic flux density. Therefore, if a relational expression (approximate straight line, approximate curve, etc.) representing the correlation between the degree of fatigue development and the change in radial magnetic flux density is obtained, the relational expression can be used as determination data.

[0148] and Fig.12 Likewise, Fig.13 The shape of the plot is also displayed differently according to the fatigue development degree (in three groups). Here, if we focus on the deviation of the plot position of each group on the coordinate, Fig.13 It is also possible to find (obtain) a threshold value for determining the degree of fatigue development. Fig.13 In general, if the change amount of the radial magnetic flux density is larger than My, the fatigue development degree is 100% or more, and if the change amount of the radial magnetic flux density is smaller than My, the fatigue development degree is less than 100%. Therefore, by using My as the threshold value, when the change amount of the radial magnetic flux density is larger than My, the fatigue development degree can be determined to be 100% or more, and when the change amount of the radial magnetic flux density is smaller than My, the fatigue development degree can be determined to be less than 100%.

[0149] Fig.14 The scatter plot shows the calculated value of the change in magnetic flux density for each test bearing, with the change in radial magnetic flux density as the X-axis and the change in axial magnetic flux density as the Y-axis. Fig.12as well as Fig.13 Likewise, Fig.14 The shape of the plot is also displayed differently according to the fatigue development degree (in three groups). Fig.14 , it can be found that the plotting of the group with a fatigue development degree of more than 100% is concentrated in the first quadrant, the plotting of the group with a fatigue development degree of more than 80% and less than 100% is concentrated in the second quadrant, and the plotting of the group with a fatigue development degree of less than 80% is concentrated in the third quadrant. Therefore, by mapping the fatigue development degree on the coordinates, it is used as a two-dimensional judgment mapping. That is, the first quadrant can be set as an area with a fatigue development degree of more than 100%, the second quadrant can be set as an area with a fatigue development degree of more than 80% and less than 100%, and the third quadrant can be set as an area with a fatigue development degree of less than 80%. In addition, it is also possible to obtain a relational expression (approximate straight line, approximate curve, etc.) that represents the correlation between the fatigue development degree and the change in the axial magnetic flux density and the change in the radial magnetic flux density, and use the relational expression as judgment data.

[0150] As described above, in this embodiment, three kinds of judgment data can be obtained, namely, judgment data indicating the correlation between the degree of fatigue development and the amount of change in the axial magnetic flux density, judgment data indicating the correlation between the degree of fatigue development and the amount of change in the radial magnetic flux density, and judgment data indicating the correlation between the degree of fatigue development and the amount of change in the axial magnetic flux density and the amount of change in the radial magnetic flux density. Therefore, such judgment data are pre-stored in the storage unit 20 of the diagnostic device 4a for on-site diagnosis of the rolling bearing 2. It is possible to decide which judgment data to use based on the required diagnostic accuracy (diagnostic information). Specifically, when higher diagnostic accuracy is required, use Fig.14 The judgment data (two-dimensional judgment map) showing the correlation between the fatigue development degree and the change in the axial magnetic flux density and the change in the radial magnetic flux density are shown. In addition, no matter which judgment data is used, it is possible to estimate the fatigue development degree obtained when the diagnostic method using X-rays is implemented without actually performing X-ray-based measurements.

[0151] The above-mentioned examples of the embodiments of the present invention can be implemented in combination as appropriate unless any contradiction occurs.

[0152] The fatigue diagnosis method of the rolling machine element of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made as long as it does not deviate from the main purpose of the present invention. For example, in the fatigue diagnosis method of the first example, since it is a relative comparison between the load circle and other parts, it is not necessary to make the raceway circle go around once, for example, it is also possible to compare only the load circle and the non-load circle opposite to it. In addition, as long as the method can capture the changes in the load circle, the object of comparison may not be the non-load circle.

[0153] In each example of the embodiment of the present invention, a fatigue diagnosis method using rolling bearings as the diagnosis object is described, but the fatigue diagnosis method of the rolling mechanical element of the present invention is not limited to this. According to the mechanism of action of the diagnosis, based on the change of the magnetic field information of the rolling mechanical element itself such as the rolling bearing or the direct-acting device, the fatigue state of the rolling mechanical element and the presence or absence of damage to the structural components of the rolling mechanical element, the degree of damage, and the cause of damage can be diagnosed. Specifically, the diagnostic system and the diagnostic method of the present invention can be applied to direct-acting devices such as linear guides and ball screws. In addition, the diagnostic system and the diagnostic method of the present invention can be applied not only when the structural components of the rolling mechanical element are made of ferromagnetic materials, but also when they are made of paramagnetic materials or diamagnetic materials, as long as the change of the magnetic field information can be obtained by the magnetic sensor.

[0154] When a rolling bearing is used as a diagnosis object, it is not limited to a single-row rolling bearing, and a multi-row rolling bearing can be used as an object. In addition, it is not limited to a radial bearing, and a thrust bearing can also be used as an object.

[0155] Description of Reference Numerals

[0156] 1.1a Fatigue diagnosis system

[0157] 2 Rolling bearings

[0158] 3, 3a, 3X, 3Y Magnetic Sensors

[0159] 4.4a Diagnostic device

[0160] 5 Outer ring

[0161] 6 Inner circle

[0162] 7 Rolling elements

[0163] 8 Outer ring raceway

[0164] 9 Inner ring raceway

[0165] 10 Retainer

[0166] 11 Magnetic induction unit

[0167] 12 Probe

[0168] 13 Processing Department

[0169] 14 External output

[0170] 15 Main body

[0171] 16 Signal lines

[0172] 17 Rotation axis

[0173] 18 Connecting cables

[0174] 19 Input section

[0175] 20 Storage

[0176] 21 Computing Department

[0177] 22 Judgment Department

[0178] 23 Output section.

Claims

1. A fatigue diagnosis method for a rolling machine element, wherein the fatigue diagnosis method diagnoses the development state of fatigue of the rolling machine element, characterized in that: The rolling mechanical element is a rolling bearing or a linear motion device having a structural component having a raceway surface made of a magnetic material. The fatigue diagnosis method comprises: a diagnosis step of diagnosing a fatigue state of the rolling mechanical element based on a change in magnetic field information of the rolling mechanical element; The diagnostic step includes: a measuring step of measuring magnetic field information of the structural component by a magnetic sensor disposed near the structural component; The magnetic field information is the axial and radial magnetic flux density of the structural component, The diagnostic step comprises: a change amount calculation step of calculating the change amount from a reference magnetic flux density corresponding to the magnetic flux density before the use of the structural component to the magnetic flux density measured in the measuring step; The diagnostic process comprises: a determination process, using determination data to determine the fatigue development degree of the rolling mechanical element based on the change in the magnetic flux density calculated in the change calculation process, wherein the determination data represents a correlation between the fatigue development degree of the test rolling mechanical element obtained in advance by X-ray measurement using a test rolling mechanical element of the same type as the rolling mechanical element and the change in axial and radial magnetic flux density of a structural component of the test rolling mechanical element obtained in advance by using a test rolling mechanical element of the same type as the rolling mechanical element.

2. The fatigue diagnosis method of rolling machine elements according to claim 1, characterized in that: The reference magnetic flux density is the magnetic flux density of a portion of the structural component corresponding to the non-loaded circle in the circumferential direction, or the magnetic flux density of a portion of the structural component corresponding to the loaded circle in the circumferential direction before use. Furthermore, the magnetic flux density measured in the measuring step is the magnetic flux density of a portion of the structural component corresponding to the load circle in the circumferential direction.

3. The fatigue diagnosis method of rolling machine elements according to claim 1, characterized in that: The fatigue diagnosis method further comprises a preparation step for obtaining the determination data. The preparation process comprises: A first preparation step is to obtain the amount of change in the axial and radial magnetic flux density of the structural component of the test rolling machine element before and after the test; a second preparation step of obtaining a fatigue development degree of the test rolling machine element after the test; The third preparation step is to generate the determination data indicating the correlation between the fatigue development degree obtained in the second preparation step and the amount of change in the magnetic flux density obtained in the first preparation step.

4. The fatigue diagnosis method of rolling machine elements according to claim 1, characterized in that: The determination data is formed by a determination map obtained by mapping the degree of fatigue development on coordinates having the amount of change in the axial magnetic flux density and the amount of change in the radial magnetic flux density as two axes.

5. The fatigue diagnosis method of rolling machine elements according to claim 1, characterized in that: The rolling mechanism element is not disassembled for diagnosis.

6. A fatigue diagnosis system for rolling machine elements, characterized in that: The fatigue diagnosis system comprises: A magnetic sensor capable of measuring the axial and radial magnetic flux density of a component of a rolling machine element to be diagnosed; a calculation unit capable of calculating a change amount from a reference magnetic flux density corresponding to the magnetic flux density before the use of the structural component to the magnetic flux density measured by the magnetic sensor; a storage unit storing determination data indicating a correlation between a fatigue development degree of the test rolling mechanical element obtained in advance by X-ray measurement using a test rolling mechanical element of the same type as the rolling mechanical element and a change amount of axial and radial magnetic flux density of a structural component of the test rolling mechanical element obtained in advance using a test rolling mechanical element of the same type as the rolling mechanical element; A determination unit determines a degree of fatigue development of the rolling machine element based on the determination data stored in the storage unit and according to the amount of change in the magnetic flux density calculated by the calculation unit.

Images