JP2021032797A - Method and system for monitoring state of rolling bearing - Google Patents

Abstract

To provide a method for monitoring the state of a rolling bearing that can detect a sign of a damage of the rolling bearing in an early stage.SOLUTION: A target bearing 2 as a monitoring target is operated so that the rate of the rotation (a first rate) of an inner wheel 6 as a rotational wheel is measured and the rate of revolution (a second rate) of the rolling body 7 is measured while the inner wheel 6 is being rotated and the rolling body 7 is being revolved. Further, the ratio of the rate of rotation of the inner wheel 6 and the rate of revolution of the rolling body 7 is compared with a predetermined threshold value so that whether there is a sign of a damage of the target bearing 2 is determined.SELECTED DRAWING: Figure 7

Description

The present invention relates to a condition monitoring method and a condition monitoring system for rolling bearings.

Rolling bearings such as ball bearings and roller bearings are incorporated in the rotary support portions of various mechanical devices. The rolling bearing includes an outer ring and an inner ring which are a pair of raceway rings arranged coaxially with each other, and a plurality of rolling elements. The outer ring has an outer ring track on the inner peripheral surface, and the inner ring has an inner ring track on the outer peripheral surface. The plurality of rolling elements are rotatably arranged between the outer ring track and the inner ring track. The inside of the rolling bearing is filled with a lubricant such as lubricating oil or grease to prevent abnormal wear and abnormal heat generation in the rolling contact portion and the sliding contact portion.

In the rolling bearing, in the state at the start of operation, an oil film having a sufficient thickness is formed on the raceway surfaces of the outer ring raceway and the inner ring raceway and the rolling surface of the rolling element, and the lubrication conditions are kept good, but the speed is high. If the product is used continuously in a relatively harsh environment such as rotation, excessive load, and high temperature, the thickness of the oil film formed on the raceway surface and the rolling surface decreases, and the lubrication conditions become strict. If the bearing is continued to be used as it is, the bearing temperature may rise, causing discoloration, softening, welding, etc. on the raceway surface and rolling surface, which may eventually lead to seizure.

Jikkai Sho 62-85721

In view of these circumstances, Japanese Patent Application Laid-Open No. 62-85721 (Patent Document 1) provides a technique for preventing seizure by measuring the temperature of the outer ring constituting the rolling bearing. Is described. According to such a conventional technique, it is possible to take measures such as urging the replacement of the rolling bearing before seizure occurs and the rolling bearing becomes non-rotatable. However, since the time from the temperature rise of the outer ring to the actual seizure is short, there is a problem that the rolling bearing must be replaced immediately. On the other hand, if the precursor of seizure can be detected earlier, not only can seizure be prevented, but also maintenance work can be performed when the equipment is not in operation. Under these circumstances, it is required to detect signs of damage such as seizure at an early stage.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a condition monitoring method and a condition monitoring system for rolling bearings, which can detect signs of damage such as seizure at an early stage. And.

As a result of diligent studies on means for solving the above-mentioned problems of the prior art, the inventors of the present invention increase the viscosity of the lubricant when the lubricant deteriorates due to the operation of the rolling bearing, and increase the revolving speed of the rolling element. We got the finding to reduce it. Further, if the operation of the rolling bearing is continued with the viscosity of the lubricant increased, an oil film having a sufficient thickness is not formed on the rolling contact surface and the sliding contact surface, and metal contact occurs on these contact surfaces. We obtained the knowledge that it will eventually lead to seizure. Further, the decrease in the revolution speed of the rolling element occurs not only in the deterioration of the lubricant but also in the case where the raceway surface and the rolling surface are peeled off, or when wear debris is caught. Therefore, we came up with the idea that if we could know the decrease in the revolution speed of the rolling elements, we could prevent not only seizure but also damage such as indentations and cracks. The present invention has been completed based on such findings. Specifically, the rolling bearing condition monitoring method and condition monitoring system of the present invention employ the following means.

The method for monitoring the state of a rolling bearing according to one aspect of the present invention is a method for monitoring the state of a rolling bearing formed by arranging a plurality of rolling elements between a rotating wheel and a stationary wheel, and is a measurement step and determination. It has a process.
In the measuring step, while rotating the rotating wheel and revolving the rolling element, the first speed, which is the rotational speed of the rotating wheel, was measured, and the revolving speed of the rolling element and the rolling element were held. This is a step of measuring a second speed, which is one of the rotation speeds of the cage.
The determination step is a step of determining the state of the rolling bearing by comparing the ratio of the first speed to the second speed with a predetermined threshold value.

In one aspect of the present invention, the measurement step can be composed of the following detection step, frequency analysis step, and ratio calculation step.
The detection step is a step of generating an eddy current by electromagnetic induction from the rotating wheel and the rolling element or the cage by using an eddy current sensor, and detecting a change in a magnetic field.
In the frequency analysis step, the rotation frequency of the rotating wheel corresponding to the first speed is obtained by FFT analysis of the output signal (output waveform) of the eddy current sensor, and the rotation frequency corresponds to the second speed. This is a step of obtaining the revolution frequency (moving frequency) of the rolling element or the rotation frequency of the cage.
The ratio calculation step is a step of calculating the ratio of the rotation frequency of the rotating wheel corresponding to the first speed to the revolution frequency of the rolling element corresponding to the second speed or the rotation frequency of the cage. Is.

In one aspect of the present invention, the revolution period ratio (=) obtained by dividing the ratio of the rotation frequency of the rotating wheel to the revolution frequency of the rolling element by the revolution frequency of the rolling element by the rotation frequency of the rotating wheel. It can be the revolution frequency of the rolling element / the rotation frequency of the rotating wheel).
In one aspect of the present invention, the rotation period ratio (=) obtained by dividing the ratio of the rotation frequency of the rotating wheel to the rotation frequency of the cage by the rotation frequency of the cage by the rotation frequency of the rotating wheel. Rotation frequency of the cage / rotation frequency of the rotating wheel).

In one aspect of the present invention, as the rotating wheel, a wheel that is magnetized in a part in the circumferential direction and magnetized in the part is used, or a magnet is attached to a part in the circumferential direction. Can be used.
In one aspect of the present invention, as the cage, a cage in which a part in the circumferential direction is magnetized and the portion is magnetized is used, or a magnet is attached to a part in the circumferential direction. Can be used.

In one aspect of the present invention, the eddy current sensor can be attached to a seal ring fixed to the stationary wheel.
In one aspect of the invention, the eddy current sensor can be attached to the stationary wheel.
In one aspect of the present invention, the eddy current sensor can be attached to a housing to which the stationary wheel is fixed.

The rolling bearing condition monitoring system according to one aspect of the present invention is a system for monitoring the condition of a rolling bearing in which a plurality of rolling elements are arranged between a rotating wheel and a stationary wheel, and is an eddy current. It includes a sensor, a frequency analysis unit, a ratio calculation unit, and a determination unit.
The eddy current sensor generates an eddy current by electromagnetic induction with respect to the rotating wheel and the rolling element or a cage holding the rolling element, and detects a change in a magnetic field.
The frequency analysis unit FFT analyzes the output signal of the eddy current sensor.
The ratio calculation unit calculates the ratio of the rotation frequency of the rotating wheel to the revolution frequency of the rolling element or the rotation frequency of the cage, which are analyzed by the frequency analysis unit.
The determination unit determines the state of the rolling bearing by comparing the ratio calculated by the ratio calculation unit with a predetermined threshold value.

According to the rolling bearing condition monitoring method and condition monitoring system of the present invention, signs of damage such as seizure can be detected at an early stage.

FIG. 1 is a block diagram showing a state monitoring system for rolling bearings according to the first example of the embodiment. FIG. 2 is a half cross-sectional view showing an example of a target bearing, which is a target of the condition monitoring method according to the first example of the embodiment. FIG. 3 is a graph shown to explain the principle of the condition monitoring method of the rolling bearing of this example, (A) is a graph showing a time change of the bearing temperature, and (B) is a time change of the oil film thickness. (C) is a graph showing the time change of the revolution speed of the rolling element, and (D) is a graph showing the time change of the revolution period ratio. FIG. 4 is a schematic view showing a measurement process for measuring the speeds of the rotating wheels and rolling elements constituting the target bearing by an eddy current sensor, (A) is a cross-sectional view, and (B) is (A). It is a side view seen from the right side. FIG. 5 is an example of an output signal obtained by the eddy current sensor. FIG. 6 is an example of a frequency spectrum obtained by performing FFT analysis on the output signal of the eddy current sensor. FIG. 7 is a flowchart showing a condition monitoring method according to the first example of the embodiment. FIG. 8 is a diagram corresponding to FIG. 4A showing a second example of the embodiment. FIG. 9 is a diagram corresponding to FIG. 4A showing a third example of the embodiment. FIG. 10 is a half cross-sectional view corresponding to FIG. 4A showing a fourth example of the embodiment. FIG. 11 is a diagram corresponding to FIG. 4A showing a fifth example of the embodiment. FIG. 12 is a half cross-sectional view corresponding to FIG. 4A showing a sixth example of the embodiment.

[First Example of Embodiment]
A first example of the embodiment will be described with reference to FIGS. 1 to 7.

[Overall configuration of rolling bearing condition monitoring system]
The rolling bearing condition monitoring system 1 of this example monitors whether or not a sign of damage such as seizure has occurred in the target bearing 2 to be monitored, and monitors the eddy current sensor 3 and the monitoring. The device 4 is provided.
Hereinafter, the target bearing 2 to be monitored will be described, and then the rolling bearing condition monitoring system 1 of this example will be described.

<Target bearing>
The target bearing 2 is a rolling bearing such as a ball bearing such as a deep groove type or an angular type, a tapered roller bearing, a cylindrical roller bearing, a needle bearing, or a self-aligning roller bearing, and its type (single row or double row bearing). Format) and size do not matter. As the target bearing 2, a bearing having a high need to prevent the occurrence of damage, such as a bearing incorporated in a wind power generation device, can be preferably adopted.

As shown in FIG. 2, the target bearing 2 includes an outer ring 5, an inner ring 6, a plurality of rolling elements 7, a cage 8, and a pair of seal rings 9.

The outer ring 5 is formed in an annular shape, and has an outer ring track 10 on the inner peripheral surface. The inner ring 6 is formed in an annular shape, and has an inner ring track 11 on a portion of the outer peripheral surface facing the outer ring track 10. The outer ring 5 and the inner ring 6 are arranged coaxially with each other.

The plurality of rolling elements 7 are rotatably arranged between the outer ring track 10 and the inner ring track 11. When the inner ring 6 (or outer ring 5), which is a rotating wheel, rotates, the rolling element 7 rotates around the respective central axes and revolves around the central axes of the outer ring 5 and the inner ring 6. In the illustrated example, a ball is used as the rolling element 7.

The outer ring 5, inner ring 6 and rolling element 7 are made of iron-based alloy (made of conductor) such as bearing steel represented by high carbon chromium bearing steel (SUJ2), medium carbon steel, and carburized steel, and are hardened and carburized. It is magnetic because it has been subjected to heat treatment such as quenching and carburizing, nitriding and quenching. It is desirable that the inner ring 6 and the rolling element 7 to be measured are ferromagnets such as bearing steel.

The cage 8 has pockets 12 at equal intervals in the circumferential direction, and the rolling elements 7 are rotatably held in the respective pockets 12. The cage 8 rotates at the same speed as the revolution speed of the rolling element 7. The cage 8 is made of a synthetic resin such as a polyamide resin (PA), a polyphenylene sulfide resin (PPS), or a polyacetal resin (POM), and is integrally manufactured by injection molding. In this example, the eddy current sensor 3 is used to measure the revolution speed (revolution frequency) of the rolling element 7, and the rotation speed of the cage 8 is not measured. Therefore, the cage 8 is made of synthetic resin. However, when measuring the rotation speed of the cage as in the second example of the embodiment described later, the cage is made of metal (made of a conductor), or the cage is made of a third embodiment described later. As in the example, a magnet is attached to a part of the circumferential direction.

The pair of seal rings 9 closes the openings on both sides in the axial direction of the space 13 in which the rolling element 7 is installed, which exists between the inner peripheral surface of the outer ring 5 and the outer peripheral surface of the inner ring 6. The seal ring 9 is fixed to a stationary ring (outer ring 5 in the illustrated example), and includes a core metal 14 and a sealing material 15 that covers the core metal 14. Therefore, the seal ring 9 does not rotate and is stationary together with the stationary wheel. The core metal 14 is made of a metal plate such as a stainless steel plate. The sealing material 15 is made of rubber such as acrylonitrile butadiene rubber (NBR). A part of the sealing material 15 is in contact with or close to the peripheral surface of the rotating wheel (the outer peripheral surface of the inner ring 6 in the illustrated example). The space 13 in which the rolling element 7 is installed is filled with a lubricant such as grease.

The target bearing 2 uses, for example, an inner ring rotation type in which the outer ring 5 is fitted inside the housing and the inner ring 6 is fitted outside the rotation shaft to rotatably support the rotation shaft inside the housing. It can be used in aspects. Alternatively, the target bearing 2 is an outer ring rotary type in which the outer ring 5 is fitted inside the rotating body and the inner ring 6 is fitted outside the fixed shaft to rotatably support the rotating body around the fixed shaft. It can also be used in the usage mode of. The following description describes the case where the target bearing 2 is used in the inner ring rotation type usage mode.

In this example, based on the following principle, the precursor of damage is detected at an early stage, and damage to the target bearing 2 is prevented from occurring.
The viscosity of the lubricant (grease) filled inside the target bearing 2 increases as the deterioration progresses with the use of the target bearing 2. As the viscosity increases, the lubricant becomes sticky and prevents the rolling elements 7 (and cage 8) from moving. That is, the viscous lubricant acts as a resistance and reduces the revolution speed of the rolling element 7 (rotational speed of the cage 8). Further, when the viscosity of the lubricant increases, the rolling elements 7 are likely to revolve and slip, which causes the bearing temperature to rise.

On the other hand, if the lubricant has a normal viscosity, even if it is pushed away from the raceway surface by the rolling element 7, an oil film having a sufficient thickness is required before the next rolling element 7 (adjacent in the circumferential direction) passes through. Can be reformed into the orbital plane. However, when the viscosity of the lubricant increases and it becomes sticky, it becomes impossible to reshape an oil film having a sufficient thickness on the raceway surface before the next rolling element 7 passes through. Therefore, if the use is continued in such a state, the raceway surface and the rolling surface may come into metal contact with each other, which may eventually lead to seizure.

As described above, an increase in the viscosity of the lubricant causes an increase in the temperature of the target bearing 2, a change in the oil film thickness, and a decrease in the revolution speed of the rolling element 7, respectively, but changes in these three characteristics occur. The timing is as follows. That is, as shown in (A), (B), and (C) of FIG. 3, a significant change (retracted lubricant) in the oil film thickness occurs before a significant change (rise) in the bearing temperature appears. A phenomenon in which the thickness increases without returning) appears, and at the same time, a remarkable change (decrease) in the revolution speed of the rolling element 7 appears. Therefore, if the change in the revolution speed of the rolling element 7 can be grasped, it is possible to prevent the occurrence of seizure by performing appropriate maintenance work or the like. That is, in this example, the change in the revolution speed of the rolling element 7, in which a remarkable change appears before the bearing temperature, is used as a precursor of damage such as seizure. In this example, based on such a principle, the precursor of damage is detected at an early stage, and damage to the target bearing 2 is prevented from occurring.

The rolling bearing condition monitoring system 1 of this example is based on the eddy current sensor 3 used for measuring the rotational speed of the inner ring 6 which is a rotating wheel and the revolving speed of the rolling element 7, and the output signals of the eddy current sensor 3. The target bearing 2 is provided with a monitoring device 4 for determining whether or not a sign of damage has occurred.

<Eddy current sensor>
The eddy current sensor 3 is a measuring instrument capable of detecting a change in a magnetic field generated between an object to be measured (inner ring 6 and a rolling element 7), and is connected to a monitoring device 4 via a connection cable 16. The eddy current sensor 3 and the monitoring device 4 may be connected wirelessly without being connected by the wired connection cable 16. In this example, only one eddy current sensor 3 is used.

The eddy current sensor 3 includes a detection unit and a circuit (including an oscillation circuit, a resonance circuit, a detection circuit, an amplifier circuit, and the like). The detection unit is provided at the tip (head) of the eddy current sensor 3, and has a sensor coil inside. The sensor coil generates a high-frequency magnetic field when a high-frequency current is passed from the oscillation circuit. Then, when the object to be measured exists in the high-frequency magnetic field, an eddy current is generated on the surface of the object to be measured by the electromagnetic induction phenomenon. The eddy current generated in this way creates a magnetic field that interferes with the magnetic field generated by the sensor coil. Further, when the object to be measured rotates, the mode in which the eddy current is generated changes, and the magnetic field around the sensor coil also changes. Since the change in the magnetic field changes the impedance of the sensor coil, the period and amplitude (voltage value) of the output signal are changed according to the rotation of the object to be measured. That is, the eddy current sensor 3 captures the rotation of the object to be measured as a change in the magnetic field. The eddy current sensor 3 may have a structure in which a detection unit and a circuit are integrally provided, or a structure in which a detection unit (probe) and a driver including a circuit and the like are connected by a cable.

As shown in FIG. 4, for example, the eddy current sensor 3 is attached to the outer surface of the seal ring 9 in the axial direction at one location in the circumferential direction by a fixing means such as sticking or adhesion. As a result, the detection unit of the eddy current sensor 3 is made to face the rolling element 7 (and the cage 8) via the seal ring 9. Note that, in FIG. 4B, the seal ring 9 is omitted. The detection unit of the eddy current sensor 3 may be brought into contact with the axially outer surface of the seal ring 9 or may be brought into close contact with each other. Further, the mounting position and mounting angle of the eddy current sensor 3 with respect to the seal ring 9 are regulated so that the rolling element 7 and the inner ring 6 are included in the high frequency magnetic field generated from the sensor coil. However, the mounting position of the eddy current sensor 3 is not limited to the seal ring 9, and may be mounted on other stationary members such as the outer ring 5 and the housing as long as the eddy current can be generated on the surface of the object to be measured.

In this example, a high-frequency magnetic field is generated from the sensor coil of the eddy current sensor 3 while rotating the inner ring 6 and revolving the rolling element 7. As a result, eddy currents due to electromagnetic induction are generated on the surfaces of the inner ring 6 and the rolling element 7 which are the objects to be measured. As a result, the impedance of the sensor coil changes, and an output signal as shown in FIG. 5 is obtained. The output signal thus obtained is the rotation long period of a signal that changes at a cycle corresponding to the speed (sine wave) S _I of the inner ring 6, the short period that varies in a cycle correlated with the revolution speed of the rolling elements 7 signal S _R becomes one synthesized in. Hereinafter, the reason why such an output signal can be obtained by the eddy current sensor 3 will be described.

First, the reason why the signal S _I that changes at a cycle corresponding to the rotation speed of the inner ring 6 can be obtained.
The magnetic characteristics of the inner ring 6 have some variations in the circumferential direction, for example, due to the fact that the heat treatment is not uniformly applied in the circumferential direction. Therefore, when an eddy current is generated on the surface of the inner ring 6 by electromagnetic induction while rotating the inner ring 6, the magnetic field around the sensor coil changes according to the change in the magnetic characteristics of the inner ring 6, so that the eddy current sensor 3 from the signal S _I that changes at a cycle corresponding to the rotation speed of the inner ring 6 can be obtained.

Next, the reason why the signal S _R which varies in a cycle correlated with the revolution speed of the rolling elements 7 are obtained.
When the detection unit of the eddy current sensor 3 faces the rolling element 7 and the rolling element 7 revolves, the detecting unit of the eddy current sensor 3 determines whether the rolling element 7 faces the rolling element 7 or not. It repeats alternately at a cycle that correlates with the revolution speed of. Therefore, while the rolling revolve elements 7, when the eddy currents are generated on the surface of the rolling element 7 by electromagnetic induction, the signal S _R is obtained which varies in a cycle correlated with the revolution speed of the rolling elements 7.

Therefore, the eddy current sensor 3, if eddy currents are generated by electromagnetic induction for each rolling element 7 to the inner ring 6 and the revolution of rotating, the signal S _I that changes at a cycle corresponding to the rotation speed of the inner ring 6, rolling output signal signal S _R are synthesized to vary in a cycle correlated with the revolution speed of the moving object 7 can be obtained.

<Monitoring device>
The monitoring device 4 has a function of determining whether or not a sign of damage has occurred in the target bearing 2. The monitoring device 4 includes an input unit 17 for inputting data, a storage unit 18 for storing data, a frequency analysis unit 19 for performing FFT analysis, and a ratio calculation unit 20 for calculating the periodic ratio. A determination unit 21 for determining the presence or absence of a sign of damage, and an output unit 22 for outputting the determination result are provided.

The output signal of the eddy current sensor 3 is input to the input unit 17 of the monitoring device 4 via the connection cable 16. Specifically, an output signal as shown in FIG. 5 is input to the input unit 17 and stored in the storage unit 18. Further, a predetermined threshold value obtained in advance is input to the input unit 17 of the monitoring device 4 and stored in the storage unit 18.

The frequency analysis unit 19 performs FFT (Fast Fourier Transform) analysis on the output signal (output waveform) of the eddy current sensor 3. As a result, from the output signal of the eddy current sensor 3, a frequency component ( _fw ) representing the rotation speed of the inner ring 6 which is the first speed and a frequency component (wh) representing the revolution speed of the rolling element 7 which is the second speed ( It is taken out separately from _fr). Specifically, when the output signal of the eddy current sensor 3 is subjected to FFT analysis, a frequency spectrum (FFT waveform) as shown in FIG. 6 can be obtained. Thus, obtained from the peak frequency of the frequency spectrum, a frequency component representing the rotational speed of the inner ring 6 (f _w), the frequency component representing the revolution speed of the rolling elements 7 and (f _r). Specifically, a plurality of peak frequencies (not only the primary component but also the higher-order component) appear on the frequency spectrum, and the frequency component ( _fw ) representing the rotation speed of the inner ring 6 and the frequency component (fw) representing the rotation speed of the inner ring 6 are as follows. It is possible to discriminate from the _{frequency component (fr} ) representing the revolution speed of the rolling element 7. That is, the frequency component (f _w ) of the inner ring 6 can be obtained by the rotation speed (rpm) / time (60 min) of the inner ring 6, and the frequency component that is _{an integral multiple of the frequency component (f w} ) of the inner ring 6 is the inner ring. It can be obtained at a rotation speed (rpm) / time (60 min) × n (n = 2, 3, ...) Of 6. Therefore, among the plurality of peak frequencies appearing on the frequency spectrum, the peak frequencies appearing at regular intervals can be determined to be the peak frequencies relating to the inner ring 6. Of the plurality of peak frequencies related to the inner ring 6, the lowest peak frequency with a black circle symbol in FIG. 6 is the frequency component ( _fw ) of the inner ring 6, and the remaining peak frequency with a white circle symbol is , It can be determined that it corresponds to an integral multiple of the frequency component ( _{fw) of the inner ring 6.} On the other hand, the frequency component (f _r) of the rolling elements 7, can be obtained by the revolution speeds of the rolling number of elements × rolling elements, to become a value obtained by considering the number of rolling elements, the frequency components of the inner race 6 (f _w ) Is higher than the peak frequency. Therefore, it can be determined that the peak frequency with the triangle symbol in FIG. 6 is the frequency component ( _{fr) of the rolling element 7.}

Ratio calculating section 20 calculates the ratio of the rotational frequency _{(f w)} and the rolling elements 7 of the revolution frequency of the inner ring 6 _{(f r).} The reason for this is that the revolution speed of the rolling element 7 used as a precursor of damage is affected not only by the viscosity of the lubricant but also by the rotation speed of the inner ring 6 which is a rotating wheel. That is, when the rotation speed of the inner ring 6 increases, the revolution speed of the rolling element 7 increases, and when the rotation speed of the inner ring 6 decreases, the revolution speed of the rolling element 7 also decreases. Therefore, by obtaining the ratio of the rotation speed of the inner ring 6 to the revolution speed of the rolling element 7, the influence of the rotation speed of the inner ring 6 is eliminated. In particular, in this example, the revolution frequency ( _fr ) of the rolling element 7 is divided by the rotation frequency (f _w ) of the inner ring 6 to calculate the revolution period ratio (R = _fr / f _w). Then, the obtained revolution period ratio (R) is stored in the storage unit 18.

The determination unit 21 compares the revolution period ratio (R) calculated by the ratio calculation unit 20 with a predetermined threshold value (T) stored in advance in the storage unit 18, and compares the state of the revolution speed of the rolling element 7. To judge. For example, as shown in FIG. 3D, the threshold value (T) is slightly smaller (T <R _{0 ) than the orbital period ratio (R 0) when no abnormality occurs in the target bearing 2.} ) Is adopted, when the orbital period ratio (R) is larger than the threshold value (T), it is determined that there is no sign of damage, and when the orbital period ratio (R) is smaller than the threshold value (T), it is determined that there is no sign of damage. It can be determined that there is a sign of damage. Further, if necessary, the difference (TR) between the revolution period ratio (R) and the threshold value (T) can be obtained, and the degree of damage progress (progress) can be determined based on this difference. Further, by setting a plurality of threshold values, the progress of damage can be determined.

The output unit 22 visually displays the result of the determination by the determination unit 21 as a numerical value on a display, or audibly outputs the result by a speaker or the like. In addition, when the degree of damage progress is obtained, the result can also be displayed (output).

The monitoring device 4 can be configured by, for example, a personal computer, and executes each of the above-mentioned functions by executing a program.

[Rolling bearing condition monitoring method]
Next, a method of monitoring the state of the target bearing 2 will be described using the rolling bearing state monitoring system 1 of this example described above. The monitoring of the target bearing 2 is performed at a site such as a factory equipped with equipment in which the target bearing 2 is incorporated. For example, when the target bearing 2 is a bearing for a wind power generation device, the eddy current sensor 3 is arranged in the nacelle of the wind power generation device, and the monitoring device 4 is arranged in a monitoring facility or the like for remote monitoring. Can be done. Further, the monitoring of the target bearing 2 can be continuously performed from the initial state in which the target bearing 2 is incorporated in the equipment, or can be performed intermittently after a predetermined time. In the state monitoring method of this example, as shown in FIG. 7, a measurement step (S1) and a determination step (S2) are performed.

<Measurement process>
When performing the measurement step (S1), for example, as shown in FIG. 4, the eddy current sensor 3 is attached in advance to one location in the circumferential direction of the axial side surface of the seal ring 9. Then, by operating the equipment in which the target bearing 2 is incorporated, the first speed, which is the rotational speed of the inner ring 6, is measured while rotating the inner ring 6 and revolving the rolling element 7, and the rolling element 7 The second speed, which is the revolution speed, is measured. In this example, the measurement step (S1) is divided into _a detection step (S1 a), a frequency analysis step (S1 _b ), and a ratio calculation step (S1 _C).

<< Detection process >>
In the detection step (S1 _a ), the rotation frequency of the inner ring 6 and the revolution frequency of the rolling element 7 are measured by the eddy current sensor 3. Specifically, a high-frequency magnetic field is generated from the sensor coil of the eddy current sensor 3 while rotating the inner ring 6 and revolving the rolling element 7. As a result, eddy currents due to electromagnetic induction are generated on the surfaces of the inner ring 6 and the rolling element 7. Then, the magnetic field around the sensor coil is changed to change the impedance of the sensor coil. Here, since the magnetic characteristics of the inner ring 6 have some variations in the circumferential direction, the magnetic field around the sensor coil changes according to the change in the magnetic characteristics of the inner ring 6, and the rotation speed of the inner ring 6 is increased. signal S _I is obtained which varies in accordance period. Further, since the detection unit of the eddy current sensor 3 alternately repeats the state of facing the rolling element 7 and the state of not facing the rolling body 7 based on the revolution of the rolling element 7 at a cycle correlated with the revolution speed of the rolling element 7. rolling signal S _R is obtained which varies in a cycle correlated with the revolution speed of the moving object 7. That is, as shown in FIG. 5, the signal S _I that changes at a cycle corresponding to the rotation speed of the inner ring 6, and the signal S _R which varies in a cycle correlated with the revolution speed of the rolling elements 7 are synthesized output A signal is obtained. The output signal of the eddy current sensor 3 is input to the input unit 17 of the monitoring device 4 by the connection cable 16 or wirelessly.

<< Frequency analysis process >>
In the frequency analysis step (S1 _b), the frequency analysis unit 19 of the monitoring device 4 performs FFT analysis on the output signal of the eddy current sensor 3 (output waveform), frequency components representing the rotation speed of the inner ring 6 (f _{w ) And the frequency component (fr} ) representing the revolution speed of the rolling element 7 are separately taken out.

<< Ratio calculation process >>
In ratio calculating step (S1 _C), by the ratio calculation unit 20 of the monitoring device 4, which is the ratio between the rotation frequency _{(f w)} and the rolling elements 7 of the revolution frequency of the inner ring 6 _{(f r),} orbital period ratio (R ) Is calculated.

<Judgment process>
In the determination step (S2), the determination unit 21 of the monitoring device 4 compares the revolution period ratio (R) with a predetermined threshold value (T) stored in advance in the storage unit 18, and revolves the rolling element 7. Determine the speed status. Specifically, it is determined whether or not the revolution speed of the rolling element 7 has decreased to the extent that it can be said to be a precursor of damage such as seizure. Then, when it is determined that there is no sign of damage, for example, after a lapse of a predetermined time, the process returns to the measurement step (S1) and monitoring is started again. On the other hand, when it is determined that there is a sign of damage, the output unit 22 of the monitoring device 4 visually displays the determination result on a display, or audibly outputs the determination result by a speaker or the like. In addition, the progress of damage is also displayed if necessary.

According to the rolling bearing condition monitoring system 1 and the condition monitoring method of this example as described above, it is possible to detect a sign of damage such as seizure at an early stage.
That is, in this example, the change in the revolution speed of the rolling element 7 in which a remarkable change appears before the bearing temperature is used as a precursor of damage such as seizure. Therefore, the precursor of seizure can be detected earlier than the case where the temperature change is used as in the conventional technique described in Japanese Patent Application Laid-Open No. 62-85721 (Patent Document 1). Therefore, not only can seizure be prevented from occurring, but also maintenance work such as replenishment or replacement of lubricant can be performed when the equipment is not in operation. In addition, when measuring the temperature of the outer ring, it is difficult to determine whether the temperature is changing based on the external temperature change or the temperature is changing as a precursor of damage, and the precursor of damage is accurately detected. However, in this example, since the change in the revolution speed of the rolling element 7 that is not affected by the external temperature change is used, it is possible to accurately catch the precursor of damage. Further, deterioration of the lubricant is also caused by a temperature rise inside the bearing, and is therefore particularly effective for monitoring the target bearing 2 used in a high temperature environment. Further, in both cases of the bearing for high-speed rotation and the bearing for low-speed rotation, the revolving speed of the rolling element 7 decreases as a precursor of damage. Therefore, according to this example, it is used at any rotation speed. Bearings to be monitored can also be monitored.

_{Further, since the eddy current sensor 3 can measure the rotation speed of the inner ring 6 (rotation frequency f w} ) and the revolution speed of the rolling element 7 (revolution frequency _fr ) in a non-contact manner only by attaching the eddy current sensor 3 to the seal ring 9. In order to attach the eddy current sensor 3, the target bearing 2 does not need to be specially processed. Further, since the rotation speed of the inner ring 6 and the revolution speed of the rolling element 7 can be measured at the same time by one eddy current sensor 3, the system can be miniaturized and the cost can be reduced. Further, when a rotation sensor is used to measure the rotation speed of the inner ring 6 and the revolving speed of the rolling element 7, it is necessary to attach an encoder to the inner ring 6 and the rolling element 7, respectively. In this example, this is performed. No need for such an encoder. Therefore, the degree of freedom in selecting the target bearing 2 can be increased.

[Second Example of Embodiment]
A second example of the embodiment will be described with reference to FIG.
In this example, the property that the rotation speed of the cage 8a holding the rolling element 7 becomes the same as the revolving speed of the rolling element 7 is utilized. That is, the rolling bearing state monitoring system 1 measures the rotation speed (rotation frequency) of the cage 8a instead of the revolving speed of the rolling element 7, and monitors the state of the target bearing 2a.

Therefore, in this example, the cage 8a is made of metal (made of a conductor). Specifically, when the cage 8a is a press cage (corrugated cage), for example, a cold-rolled steel plate or a hot-rolled steel plate can be used as a material, and the cage 8a holds by punching. In the case of a vessel, for example, carbon steel for machine structure (S25C to S45C) or the like can be used as a material.

Then, as in the first example of the embodiment, the eddy current sensor 3 is attached to the axial outer surface of the seal ring 9 while rotating the inner ring 6 and revolving the rolling element 7. A high-frequency magnetic field is generated from the sensor coil. As a result, eddy currents due to electromagnetic induction are generated on the surfaces of the inner ring 6 and the cage 8a. Then, the magnetic field around the sensor coil is changed to change the impedance of the sensor coil. Here, when the cage 8a is a press cage as shown in FIG. 8, for example, the side surface of the cage 8a has a rotational speed of the cage 8a with respect to the detection unit of the eddy current sensor 3. Since it approaches and moves away in a correlated cycle, a signal that changes in a cycle that correlates with the rotation speed of the cage 8a can be obtained.

In this example, since the change in the rotation speed of the cage 8a rotating at the same speed as the revolution speed of the rolling element 7 is used as a sign of damage such as seizure, the sign of damage can be detected at an early stage. Further, a bearing using a ceramic rolling element, which cannot measure the revolution speed of the rolling element by the eddy current sensor 3, can be monitored.
Other configurations and effects are the same as in the first example of the embodiment.

[Third example of the embodiment]
A third example of the embodiment will be described with reference to FIG.
In this example, in order to measure the rotation speed (rotation frequency) of the inner ring 6 which is a rotating wheel more accurately, the side surface or the outer peripheral surface of the inner ring 6 is fixed to one place in the circumferential direction by a fixing means such as sticking or bonding. , The magnet 23 is attached. The shape and size of the magnet 23 and its mounting position are not particularly limited as long as the rotation of the inner ring 6 is not hindered (the rotation balance is not significantly disturbed).

Then, as in the case of the first example of the embodiment, the inner ring 6 is rotated and the rolling element 7 is revolved by the eddy current sensor 3 attached to the axial outer surface of the seal ring 9 constituting the target bearing 2b. While doing so, a high-frequency magnetic field is generated from the sensor coil of the eddy current sensor 3. As a result, eddy currents due to electromagnetic induction are generated on the surfaces of the inner ring 6 and the rolling element 7. Then, the magnetic field around the sensor coil is changed to change the impedance of the sensor coil. At this time, since the magnet 23 generates a magnetic field separately from the magnetic field caused by the eddy current, a signal that changes at a cycle corresponding to the rotation speed of the inner ring 6 can be obtained.

In this example as described above, the rotation speed (rotation frequency) of the inner ring 6 can be measured more accurately. Further, a bearing using a ceramic inner ring, which cannot measure the rotation speed of the inner ring by the eddy current sensor 3, can be monitored. Instead of the structure of this example, it is also possible to adopt a configuration in which a part of the inner ring in the circumferential direction is magnetized to magnetize the part. When such a configuration is adopted, almost the same effect as when a magnet is attached can be obtained without disturbing the rotational balance of the inner ring.
Other configurations and effects are the same as in the first example of the embodiment.

[Fourth Example of Embodiment]
A fourth example of the embodiment will be described with reference to FIG.
In this example, the double-row rolling bearing is the target bearing 2c, and the mounting position of the eddy current sensor 3 is changed from the structure of the first example of the embodiment.

The target bearing 2c includes an outer ring 5a, an inner ring 6a, rolling elements 7a arranged in multiple rows, and a cage 8b. The target bearing 2c of this example is an open type bearing in which the openings on both sides in the axial direction of the space 13a in which the rolling element 7a is installed are not blocked by the seal ring. Further, in the illustrated example, a roller is used as the rolling element 7a.

The outer ring 5a has a double row of outer ring tracks 10a and 10b on the inner peripheral surface. Further, the outer ring 5a is provided with oil holes 24 penetrating the outer ring 5a in the radial direction at a plurality of locations in the circumferential direction at an axial intermediate portion located between the outer ring tracks 10a and 10b in a double row. .. The inner ring 6a has a double-row inner ring track 11a and 11b on the outer peripheral surface. The rolling elements 7a rotatably held by the cage 8b are arranged between the double-row outer ring raceways 10a and 10b and the double-row inner ring raceways 11a and 11b. Lubricating oil (oil) is supplied to the space 13a in which the rolling element 7a is installed through the oil hole 24 in which the eddy current sensor 3 is not inserted.

In this example, the eddy current sensor 3 is attached to the outer ring 5a by using one oil hole 24 among the plurality of oil holes 24. Specifically, the eddy current sensor 3 is inserted into the oil hole 24 from the outside in the radial direction so that the detecting portion thereof faces the outer peripheral surface of the inner ring 6a. Further, with the eddy current sensor 3 attached to the outer ring 5a in this way, the inner ring 6a and the rolling elements 7a in at least one row are included in the high-frequency magnetic field generated from the sensor coil.

Also in the case of this example, a high-frequency magnetic field is generated from the sensor coil of the eddy current sensor 3 while rotating the inner ring 6a and revolving the rolling element 7a. As a result, eddy currents due to electromagnetic induction are generated on the surfaces of the inner ring 6a and the rolling element 7a. Then, the magnetic field around the sensor coil is changed to change the impedance of the sensor coil. As a result, an output signal obtained by synthesizing a signal that changes in a cycle corresponding to the rotation speed of the inner ring 6a and a signal that changes in a cycle that correlates with the revolution speed of the rolling element 7a is obtained.

In this example as described above, a bearing without a seal ring can be monitored. Further, since the eddy current sensor 3 can be attached to the outer ring 5a by using the existing oil hole 24, it is not necessary to perform special processing on the target bearing 2c including the outer ring 5a.
Other configurations and effects are the same as in the first example of the embodiment.

[Fifth Example of Embodiment]
A fifth example of the embodiment will be described with reference to FIG.
In this example, from the structure of the first example of the embodiment, only the mounting position of the eddy current sensor 3 is changed without changing the structure of the target bearing 2. That is, in this example, the eddy current sensor 3 is attached to the axial side surface of the outer ring 5. The means for fixing the eddy current sensor 3 to the outer ring 5 is not particularly limited, and for example, sticking, adhesion, bolt fixing, or the like can be adopted.

In this example as described above, the posture of the eddy current sensor 3 can be stabilized as compared with the structure in which the eddy current sensor 3 is attached to the seal ring. Therefore, the measurement accuracy can be improved. In addition, bearings such as a structure in which the ceiling is fixed to the rotating wheel can be monitored.
Other configurations and effects are the same as in the first example of the embodiment.

[6th Example of Embodiment]
A sixth example of the embodiment will be described with reference to FIG.
In this example, the hub unit bearing for wheel support is the target bearing 2d. The target bearing 2d includes an outer ring 5b that does not rotate in the used state, a hub 25 corresponding to the inner ring that rotates together with a rotating body for braking such as wheels, discs, and drums in the used state, and rolling elements 7b arranged in multiple rows. It includes a 7c, a pair of cages 8c and 8d, and a pair of sealing members 26a and 26b.
Regarding the target bearing 2d, the outer side in the axial direction is the left side in FIG. 12 which is the outer side in the width direction of the vehicle when assembled to the vehicle, and the inner side in the axial direction is the center side in the width direction of the vehicle when assembled to the vehicle. It is the right side of FIG. Further, the axial direction, the radial direction, and the circumferential direction refer to each direction of the hub 25 unless otherwise specified.

The outer ring 5b is made of medium carbon steel such as S53C and has a substantially cylindrical shape. An axially intermediate portion of the outer peripheral surface of the outer ring 5b has a stationary flange 27 that is coupled to the knuckle of the suspension device. The inner peripheral surface of the outer ring 5b has a double row of outer ring tracks 10c and 10d. The outer ring 5b has a sensor mounting hole 28 penetrating the outer ring 5b in the radial direction in a portion between the outer ring tracks 10c and 10d in a double row at the intermediate portion in the axial direction. The sensor mounting hole 28 is formed in, for example, a portion of the outer ring 5b located on the upper side in the vertical direction in a state where the outer ring 5b is fixed to the suspension device.

The hub 25 is arranged coaxially with the outer ring 5b on the inner diameter side of the outer ring 5b, and is configured by combining a hub ring 29 made of medium carbon steel such as S53C and an inner ring element 30 made of high carbon chrome steel such as SUJ2. Has been done. On the outer peripheral surface of the hub 25, double-row inner ring raceways 11c and 11d are provided at portions facing the double-row outer ring raceways 10c and 10d.

The hub ring 29 is a shaft member that fits and holds the inner ring element 30 on the outside, and has a rotary flange 31 extending radially outward on the axially outer portion of the outer peripheral surface. A fixing member 32 such as a stud is used to fix the wheel constituting the wheel and the rotating body for braking to the rotating flange 31. Since the target bearing 2d of this example is for a driven wheel, the hub wheel 29 is configured in a solid state. However, it can also be applied to hub unit bearings for drive wheels. When applied to a hub unit bearing for a drive wheel, a hub wheel having a spline hole in the radial center for spline engaging the spline shaft constituting the drive shaft member can be used. ..

The rolling element 7b rotatably held by the cage 8c is arranged between the outer ring track 10c and the inner ring track 11c in the outer row in the axial direction, and is rotatably held by the cage 8d. Reference numeral 7c is arranged between the outer ring track 10d and the inner ring track 11d in the inner row in the axial direction. Further, grease (not shown) is sealed in an annular space 13b that exists between the inner peripheral surface of the outer ring 5b and the outer peripheral surface of the hub 25 and in which a plurality of rolling elements 7b are installed. Then, in order to prevent the grease sealed in the space 13b from leaking to the outside and to prevent foreign matter such as muddy water from entering the space 13b, the axial outer opening of the space 13b is closed by the sealing member 26a. Moreover, the axially inner opening of the space 13b is closed by the sealing member 26b. The sealing members 26a and 26b are a seal ring alone or a combination seal ring formed by combining a seal ring and a slinger.

In this example, the eddy current sensor 3 is inserted into the sensor mounting hole 28 from the outside in the radial direction so that the detection portion thereof faces the outer peripheral surface of the hub wheel 29. Further, with the eddy current sensor 3 attached to the outer ring 5b in this way, the hub ring 29 and the rolling elements 7b (or 7c) in either row are included in the high-frequency magnetic field generated from the sensor coil. ing. Further, in this example, the monitoring device 4 (see FIG. 1) can be incorporated in the engine control unit (ECU) mounted on the vehicle body.

Also in the case of this example, a high-frequency magnetic field is generated from the sensor coil of the eddy current sensor 3 while rotating the hub 25 corresponding to the inner ring and revolving the rolling elements 7b and 7c. As a result, eddy currents due to electromagnetic induction are generated on the surfaces of the hub wheel 29 and the rolling element 7b (or 7c). Then, the magnetic field around the sensor coil is changed to change the impedance of the sensor coil. As a result, the output is a combination of a signal that changes in a cycle corresponding to the rotation speed of the hub wheel 29 and a signal that changes in a cycle that correlates with the revolution speed of the rolling elements 7b (or 7c) in either row. Get a signal.

In this example as described above, the hub unit bearing for wheel support can be monitored. In such an example, it is possible to notify the driver or the like by turning on a warning light arranged around the driver's seat that a sign of damage has occurred in the target bearing 2d.
Other configurations and effects are the same as in the first example of the embodiment.

The structures and methods of the examples of the above-described embodiments can be appropriately combined and implemented as long as there is no contradiction.

The method for monitoring the state of rolling bearings of the present invention is not limited to single-row rolling bearings, but double-row rolling bearings can be targeted as target bearings. Further, not only the rolling bearing of the inner ring rotation type but also the rolling bearing on the outer ring rotation side can be targeted. In this case, the rotation speed of the outer ring, which is a rotating wheel, and the revolution speed of the rolling element or the rotation speed of the cage are measured. Further, not only radial bearings but also thrust bearings can be targeted. Further, as the lubricant to be filled inside the rolling bearing, not only grease but also lubricating oil (oil) can be used.

1 Rolling bearing fatigue diagnosis system 2, 2a, 2b, 2c, 2d Target bearing 3 Eddy current sensor 4 Monitoring device 5, 5a, 5b Outer ring 6, 6a Inner ring 7, 7a, 7b, 7c Rolling element 8, 8a, 8b, 8c, 8d cage 9 Seal ring 10, 10a, 10b, 10c, 10d Outer ring track 11, 11a, 11b, 11c, 11d Inner ring track 12 Pocket 13, 13a, 13b Space 14 Core metal 15 Seal material 16 Connection cable 17 Input section 18 Storage unit 19 Frequency analysis unit 20 Calculation unit 21 Judgment unit 22 Output unit 23 Magnet 24 Oil hole 25 Hub 26a, 26b Sealing member 27 Static flange 28 Sensor mounting hole 29 Hub wheel 30 Inner ring element 31 Rotating flange 32 Fixing member

Claims (3)

It is a method of monitoring the state of a rolling bearing for monitoring the state of a rolling bearing formed by arranging a plurality of rolling elements between a rotating wheel and a stationary wheel.
While rotating the rotating wheel and revolving the rolling element, the first speed, which is the rotating speed of the rotating wheel, is measured, and the revolving speed of the rolling element and the rotating speed of the cage holding the rolling element are measured. The measurement process, which measures the second velocity, which is one of
A determination step of determining the state of the rolling bearing by comparing the ratio of the first speed to the second speed and a predetermined threshold value.
A method for monitoring the condition of rolling bearings. The measurement step includes a detection step, a frequency analysis step, and a ratio calculation step.
In the detection step, an eddy current sensor is used to generate an eddy current by electromagnetic induction from the rotating wheel and the rolling element or the cage, and detect a change in the magnetic field.
In the frequency analysis step, the output signal of the eddy current sensor is FFT analyzed to obtain the rotation frequency of the rotating wheel corresponding to the first speed, and the rolling element corresponding to the second speed. Find the revolution frequency or the rotation frequency of the cage,
In the ratio calculation step, the ratio of the rotation frequency of the rotating wheel corresponding to the first speed to the revolution frequency of the rolling element corresponding to the second speed or the rotation frequency of the cage is calculated.
The method for monitoring the state of a rolling bearing according to claim 1. A rolling bearing condition monitoring system for monitoring the condition of rolling bearings in which a plurality of rolling elements are arranged between a rotating wheel and a stationary wheel.
An eddy current sensor that generates an eddy current by electromagnetic induction from the rotating wheel and the rolling element or a cage holding the rolling element and detects a change in a magnetic field.
A frequency analysis unit that analyzes the output signal of the eddy current sensor by FFT,
A ratio calculation unit that calculates the ratio of the rotation frequency of the rotating wheel to the revolution frequency of the rolling element or the rotation frequency of the cage, which are analyzed by the frequency analysis unit, respectively.
A determination unit that determines the state of the rolling bearing by comparing the ratio calculated by the ratio calculation unit with a predetermined threshold value.
Rolling bearing condition monitoring system.

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