JP2020003363A - Abnormality diagnosis method of rolling bearing, abnormality diagnosis device, and abnormality diagnosis program - Google Patents

Abstract

To calculate a robust evaluation index by taking into consideration influences of a rotation frequency and a transfer function, and to determine the presence or absence of an abnormality with high accuracy.SOLUTION: A rotation frequency of a spindle is changed to a rotation frequency for measuring vibration in S1, and vibration acceleration is measured and stored in S2. A correction vibration value is calculated from the rotation frequency and the vibration acceleration at the vibration measurement in S3, and the correction vibration value is Fourier-transformed and an amplitude at each specific frequency is recorded in S4. When the vibration measurement at a plurality of rotation frequencies for measuring all the vibrations which are defined in a determination in S5 has been finished, an average of values of the correction vibration values at each recorded specific frequency is calculated in S6, and a value of a correction vibration value of a feature specific frequency is extracted in S7. When performing a diagnosis by using a growth rate of vibration, after repeating the vibration measurement at the rotation frequencies for measuring all the vibrations two times, an evaluation index is calculated by using a bearing-induced vibration value in S11, and it is determined whether or not the evaluation index exceeds a threshold in S12.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method, an apparatus, and a program for diagnosing an abnormality of a rolling bearing used for a machine tool or the like and supporting a rotating body such as a spindle.

When an abnormality such as damage to the inner ring occurs in the rolling bearing supporting the rotating body, vibration occurs. Since the force generated by the bearing abnormality is not a simple sinusoidal wave, the vibration of the harmonic frequency component is simultaneously observed. The frequency (characteristic frequency) of the vibration generated at this time is proportional to the rotation speed, and can be calculated from the rotation speed of the rotating body and the bearing data.
If the magnitudes of the vibrations of the two characteristic frequencies separated by the fundamental frequency are both large, the waveform of the measured vibration can be interpreted as if the amplitude fluctuates at the fundamental frequency. Therefore, there has been known a technique of performing a frequency analysis after performing an envelope process on a measured vibration waveform to quantify a degree of fluctuation of the amplitude and perform a diagnosis.
For example, in Patent Document 1, vibration or sound is measured, envelope processing and frequency analysis are performed, and the magnitude of the calculated value obtained by dividing the magnitude of the vibration of the fundamental frequency component by the overall value that is the integral value of all spectral components is measured. Indicates a method for determining the presence or absence of an abnormality.
In Patent Document 2, vibration is measured, envelope processing and frequency analysis are performed, and the value of a characteristic frequency component is individually set for each characteristic frequency in consideration of a level difference of vibration response and a rotation frequency measured in advance by a hit test. A method of making a diagnosis by comparing with a threshold is shown.

Japanese Patent No. 4120099 Japanese Patent No. 5146008

In the case of a machine such as a machine tool, in which accuracy is manually adjusted, there is machine variation within a range in which no functional problem occurs. The use environment of the machine, such as the ground of the factory and room temperature, also becomes a factor that changes the transfer function of the machine. Even when measuring vibration at the same rotation frequency where the same magnitude of excitation force is generated by the same abnormality due to the same model, it is affected by the vibration mode (transfer function) of the machine. It cannot be measured identically. In a case described later, when the magnitudes of the transfer functions of three identical models are compared, the magnitude of the magnitude of the transfer function at a certain frequency is less than about 10% of the magnitude of the largest magnitude. Investigating the distribution of the magnitude of vibration in many machines of the same model and trying to determine the threshold for distinguishing between normal and abnormal, compared to the difference in the size of the transfer function due to machine variations, In the case where the difference between the magnitude of the vibration in the normal state and the magnitude of the vibration in the abnormal state is small, it is impossible to provide a threshold for reliably discriminating between the normal state and the abnormal state in consideration of the machine variation.
When performing a diagnosis on a rotating body having a complicated vibration mode such as the main shaft of a machine tool, even if the envelope processing is performed, the rotation frequency of the rotating body is changed by 10% and the characteristic frequency is changed by 10%. Even so, the magnitude of the vibration at the characteristic frequency may change several times. This is because the magnitude of the transfer function greatly differs for each frequency. The envelope process is a process that collectively captures vibrations at a plurality of frequencies without considering that the magnitude of the transfer function differs at each frequency. Since it is a processing method in which information of a plurality of frequencies is irreversibly mixed, it is theoretically impossible to perform processing in consideration of the size of the transfer function after envelope processing.

Therefore, the process of dividing the magnitude of the vibration of the characteristic frequency after the envelope processing by the overall processing as in Patent Document 1 is not a method of removing the influence of the transfer function or the rotation frequency, and is calculated by the method of Patent Document 1. There is a problem in that the calculated value obtained can be used for determining the presence or absence of a flaw, but cannot be quantitatively compared.
In addition, the threshold value that takes into account the influence of the transfer function and the rotation frequency on the magnitude of the oscillation of the characteristic frequency after the envelope processing as proposed in Patent Document 2 is reasonable from the transfer function and the rotation frequency. There is a problem that it cannot be determined on a regular basis.
For this reason, in a commercially available bearing diagnosis device, the setting of a threshold value for judging an abnormality is left to the user. However, even if the rotation frequency at which the measurement is performed is slightly changed, the determination result greatly changes, and there is a problem that it is impossible to determine whether or not it is really abnormal.
On the other hand, in the case of a type of abnormality in which the magnitude of the force caused by the bearing abnormality changes depending on the rotation frequency, there is a problem that an appropriate diagnosis cannot be made unless the influence of the rotation frequency is taken into consideration.

  Accordingly, the present invention has been made in view of the above-described problem, and calculates a robust evaluation index in consideration of the influence of the rotation frequency and the transfer function, and can determine with high accuracy whether or not there is an abnormality. It is an object of the present invention to provide a method and apparatus, and an abnormality diagnosis program.

In order to achieve the above object, an invention according to claim 1 is a method for diagnosing an abnormality of a rolling bearing that supports a rotating body,
A vibration measuring step of measuring vibration of the rotating body at a plurality of rotation frequencies of the rotating body,
A frequency analysis step of dividing the vibration by a power of zero or more of a predetermined physical quantity having a proportional relationship with the rotation frequency of the rotating body at the time of vibration measurement and performing frequency analysis, and calculating a magnitude of vibration for each frequency,
A vibration average value calculating step of calculating a vibration average value in which the ratio of the frequency to the rotation frequency of the rotating body at the time of vibration measurement in the vibration measurement step is the average of the magnitude of the vibration,
Among the vibration average values, a bearing-induced vibration value extraction step of extracting a bearing-induced vibration value at a characteristic ratio frequency that is a ratio of a frequency at which vibration caused by the bearing occurs to the rotation frequency,
An evaluation index calculating step of calculating an evaluation index based on the bearing-induced vibration value,
Determining a presence or absence of an abnormality based on the evaluation index.
According to a second aspect of the present invention, in the configuration of the first aspect, in the vibration average value calculating step, any one of the rotation frequency, the reciprocal of the rotation frequency, and the logarithm of the rotation frequency becomes an equal interval. The vibration average value is calculated using the magnitude of the vibration measured in the combination of the rotation frequencies.
According to a third aspect of the present invention, in the configuration of the first or second aspect, in the vibration measuring step, the vibration measurement of the same combination of the rotation frequencies is performed a plurality of times,
In the evaluation index calculating step, the evaluation index is calculated based on a degree of change in the bearing-induced vibration value.
According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, in the vibration average value calculating step, the average is calculated using only the magnitude of the vibration whose frequency is within a predetermined range. It is characterized by taking.
In order to achieve the above object, the invention according to claim 5 is an apparatus for diagnosing an abnormality of a rolling bearing that supports a rotating body,
Vibration measuring means for measuring the vibration of the rotating body at a plurality of rotation frequencies of the rotating body,
Frequency analysis means for dividing the vibration by a power of zero or more of a predetermined physical quantity having a proportional relationship with the rotation frequency of the rotating body at the time of vibration measurement and frequency analysis, and calculating the magnitude of vibration for each frequency,
A vibration average value calculation unit that calculates a vibration average value in which a ratio of a frequency to a rotation frequency of the rotating body at the time of vibration measurement by the vibration measurement unit is averaged for the magnitude of the vibration,
Among the vibration average values, a bearing-induced vibration value extraction unit that extracts a bearing-induced vibration value at a characteristic ratio frequency that is a ratio of a frequency at which vibration caused by the bearing occurs to the rotation frequency,
Evaluation index calculating means for calculating an evaluation index based on the bearing-induced vibration value,
Determining means for determining the presence or absence of an abnormality based on the evaluation index.
In order to achieve the above object, an invention according to claim 6 is a program for diagnosing an abnormality of a rolling bearing that supports a rotating body, wherein the vibration of the rotating body measured at a plurality of rotation frequencies is measured for each rotation. A frequency analysis step, a vibration average value calculation step, a bearing-induced vibration value extraction step, and an evaluation index calculation step in the method for diagnosing abnormality of a rolling bearing according to any one of claims 1 to 4, which are input to a computer together with the frequency. And a determining step.

According to the first, fifth, and sixth aspects of the present invention, the average is calculated after removing the influence of the rotation frequency from the measured vibration value. Obtainable. The evaluation index calculated from the bearing-induced vibration value is also less affected by the machine variation, so that it is easy to set a threshold value for determining an abnormality. That is, it is possible to calculate a robust evaluation index in consideration of the influence of the rotation frequency and the transfer function, and determine the presence or absence of abnormality with high accuracy.
According to the second aspect of the present invention, in addition to the above effects, the effect of reducing variations in the size of the transfer function and the variation in the size of the transfer function for each specific frequency is improved.
According to the third aspect of the present invention, in addition to the above-described effects, the value of the evaluation index is a value that does not depend on the value of the magnitude of the transfer function. Diagnosis using the same threshold value is possible even when measuring at the sensor position.
According to the fourth aspect of the invention, in addition to the above-described effects, the effect of reducing the variation of the transfer function in the machine and the variation of the transfer function in each specific frequency is further improved.

FIG. 2 is a functional block diagram of a rolling bearing abnormality diagnosis device. 5 is a graph showing a relationship between an exciting force due to a bearing abnormality and an angular velocity. 9 is a graph showing a variation in the magnitude of a transfer function in the same model. 9 is a graph showing the average dispersion of the magnitude of the transfer function in the same model. It is a flowchart of an abnormality diagnosis method. FIG. 11 is an explanatory diagram of a diagnosis result display when a growth rate of vibration is used as an evaluation index. It is explanatory drawing of a diagnosis result display at the time of using the maximum value of a bearing origin vibration value as an evaluation parameter | index.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a functional block diagram showing a configuration in a case where an abnormality diagnosis device for a rolling bearing is applied to a main shaft of a machine tool, and will be specifically described based on this diagram.
The main shaft 1 is rotatably attached to the main shaft housing 2 via a bearing 7 which is a rolling bearing, and a tool 3 for performing processing is fixed. The motor 4 drives the main shaft 1. The motor 4 is provided with a speed detector 5, and the measured rotation frequency of the motor 4 is input to the control device 6. At the time of machining, the control device 6 controls the current supplied to the motor 4 so that the rotation frequency of the motor 4 measured by the speed detector 5 is maintained at the command rotation frequency.

  A vibration sensor 8 as vibration measuring means is attached to the main shaft housing 2. Vibration acceleration measured by the vibration sensor 8 is converted into a digital value by an A / D converter 9 and stored together with a rotation frequency at the time of vibration measurement. Stored in the unit 10. The storage unit 10 also stores a preset threshold value. The arithmetic unit 11 which is a computer calculates the characteristic ratio frequency of the bearing abnormality from the bearing data stored in the storage unit 10 according to the abnormality diagnosis program stored in the storage unit 10, and calculates the vibration stored in the storage unit 10. From the rotational frequency and the vibration acceleration at the time of measurement, multiplication, Fourier transformation, calculation of an absolute value, and interpolation are performed to calculate a corrected vibration value, which will be described later, for the specific frequency, and calculate the magnitude of vibration for each frequency. . In addition, the calculation unit 11 calculates a vibration average value obtained by averaging vibration magnitudes having the same frequency ratio with respect to the rotation frequency of the main shaft 1 at the time of vibration measurement, and vibration due to the bearing of the vibration average value occurs. A bearing-induced vibration value at a characteristic ratio frequency, which is a ratio of the frequency to the rotation frequency, is extracted. Further, the calculation unit 11 calculates the degree of abnormality, which is an evaluation index, based on the bearing-induced vibration value, and determines whether the bearing 7 is normal. That is, the calculation unit 11 functions as a frequency analysis unit, a vibration average value calculation unit, a bearing-induced vibration value extraction unit, an evaluation index calculation unit, and a determination unit. The diagnosis result by the calculation unit 11 is displayed on the display unit 12.

When the inner ring wound is locally present in the bearing 7, the inner ring wound rotates with the rotation of the main shaft 1 and the direction of vibration generated when the rolling element passes through the position of the wound changes. for frequencies body passes, the vibration of only high frequency rotational frequency f _ROT only low frequency rotation frequency f _ROT is observed. The calculation of the characteristic frequency can be performed as in the following Expressions 1 and 2. Here, f _{I, N−} is the characteristic frequency on the lower side next to the inner ring wound N order, f _{I, N +} is the characteristic frequency on the higher side next to the inner ring wound N order, Z is the number of rolling elements of the bearing 7, and D is the bearing 7 , D is the diameter of the rolling element of the bearing 7, and α is the contact angle of the bearing 7.

FIG. 2 shows the results of measuring the vibration acceleration at a plurality of rotation frequencies for the main shaft 1 supported by the bearing 7 having the inner ring wound, calculating the vibration amplitude of the characteristic ratio frequency, and performing the operation based on the bearing abnormality corresponding to each characteristic ratio frequency. The vibration force F due to the bearing abnormality calculated by dividing the vibration force by the transfer function to the vibration at the position of the vibration sensor 8 is plotted on the horizontal axis of the angular velocity.
However, the transfer function used here is not a transfer function from the excitation force due to the bearing abnormality to the vibration at the position of the vibration sensor 8, but the vibration at the position of the vibration sensor 8 when the vicinity of the bearing is excited. Is substituted for the transfer function obtained in. Here, the vicinity of the bearing is defined as a position in the frequency range in which the position and the direction / magnitude of the vibration caused by the vibration of the bearing when the vibration is applied to the position of the vibration sensor 8 are determined by finite element analysis or the like. , Which indicates the same position. According to the reciprocity theorem, which is the same even when the input and output of the transfer function are interchanged, the transfer function obtained by exciting the vicinity of the bearing in a certain frequency range is changed from the exciting force due to the bearing abnormality to the vibration at the position of the vibration sensor 8. Can be substituted for the transfer function of

  From FIG. 2, it can be seen that the exciting force due to the bearing abnormality tends to increase with the increase in the angular velocity. Generally, the exciting force due to the bearing abnormality is proportional to the square of the angular velocity. If there is an inner ring wound, it is considered that the main shaft 1 is displaced and deformed in the direction of the wound when the rolling element passes. At this time, the locus (displacement) of the center of gravity of the main shaft 1 is constant regardless of the rotation frequency. Therefore, the force generated as a reaction for displacing the center of gravity of the spindle 1 is proportional to the second derivative of the displacement of the center of gravity. Since the frequency of the vibration displacement of the center of gravity is a characteristic frequency proportional to the rotation frequency and the angular velocity, this force is proportional to the square of the rotation frequency when the vibration is measured. From these experimental results and hypotheses, it is estimated that the excitation force due to the inner ring wound is approximated in proportion to the square of the rotation frequency.

In this way, when the relationship between the excitation force due to the bearing abnormality and the rotation frequency becomes clear, it becomes possible to calculate a value (corrected vibration value) excluding the influence of the rotation frequency from the measured vibration value. By performing vibration measurement at a plurality of rotation frequencies, it is possible to realize processing for reducing the influence of the magnitude of the transfer function.
When measurement is performed at a plurality of rotation frequencies, it is difficult to discuss the characteristic frequency that changes according to the rotation frequency. Therefore, the measurement is performed using a value obtained by dividing the characteristic frequency by the rotation frequency (feature ratio frequency). The characteristic ratio frequency k _{I, N−} on the N-th lower side of the inner ring wound and the characteristic ratio frequency k _{I, N +} on the higher N-th side of the inner ring wound can be obtained as shown in the following Expressions 3 and 4. it can.

On the other hand, when the rotation frequency is f _ROT , the magnitude F (k, f _ROT ) of the excitation force due to the bearing abnormality at the characteristic ratio frequency k is a constant F ^* that depends on the degree of damage to the bearing 7 and does not depend on the rotation frequency. And can be expressed as in the following Equation 5.

Assuming that the magnitude of the transfer function from the excitation force due to the bearing abnormality to the vibration at the position of the vibration sensor 8 is G (k, f _ROT ), the characteristic ratio when the rotation frequency measured by the vibration sensor 8 is f _ROT The magnitude A (k, f _ROT ) of the vibration at the frequency k can be expressed as in the following Expression 6. The magnitude G (k, f _ROT ) of the transfer function takes another value when the rotation frequency is different even if the specific frequency is the same.

Therefore, the magnitude A (k, f _ROT ) of the vibration measured by the vibration sensor 8 and the constant F ^* which depends on the degree of damage to the bearing 7 and does not depend on the rotation frequency have the following equation ⁽ 7).

In order to remove the influence of the change in the magnitude of the excitation force due to the bearing abnormality due to the rotation frequency from the measured vibration, the magnitude of the vibration A (k, f _ROT ) at the characteristic ratio frequency k is calculated by calculating the angular velocity 2πf _ROT The corrected vibration value A ^* (k, f _ROT ) may be obtained by the following equation 8 by dividing by the power.

FIG. 3 shows the magnitude of the transfer function of each of the three same models and the minimum ratio of the magnitude of the transfer function to the maximum of the three. Since the magnitude of the transfer function greatly varies due to a slight difference in the rotation frequency, it is apparent that if the characteristic frequency is changed by changing the measured rotation frequency, the magnitude of the measured vibration is greatly changed. Further, at a certain frequency, the machine with the smallest transfer function is about 10% or less of the largest machine. As described above, the transfer function G (k, f _ROT ) has a machine variation even for machines having the same structure, and the vibrations are completely different depending on the combination of the machine and the rotation frequency even if the degree of abnormality is the same. Therefore, it is difficult to set a threshold value that is determined to be abnormal because it is likely to be measured. Further, the magnitude of the transfer function changes depending on the use environment and use condition of the machine.
Therefore, when the magnitude A (k, f _ROT ) of the vibration at the characteristic ratio frequency k in _{Equation 7} is replaced with the corrected vibration value A ^* (k, f _ROT ) using _{Equation 8} , the following _Equation 9 is obtained.

Calculating a value obtained by averaging the rotation frequencies under N conditions within a predetermined range for Expression 9, the following Expression 10 is obtained. The left side of Equation 10 is the average of the corrected vibration values (vibration average value), and is also the bearing-induced vibration value at the characteristic ratio frequency k. The right side of Equation 10 is a product of the average of the magnitude of the transfer function of the characteristic ratio frequency k corresponding to each of the plurality of rotation frequencies and a constant F ^* that depends on the degree of damage to the bearing and does not depend on the rotation frequency.

FIG. 4 shows an average of transfer function magnitudes (average of magnitudes of vibration) for each of the specific frequencies corresponding to each of the plurality of rotation frequencies for the three same models. It can be seen that the average of the magnitude of the transfer function hardly changes even if the specific frequency differs in a specific specific frequency range. In addition, the average of the transfer function sizes has small machine-to-machine variation, and even if the machine has the smallest average of the transfer function, there is about 70% of the size of the largest machine.
The constant F ^* that depends on the degree of damage to the bearing and does not depend on the rotation frequency is the same regardless of Equations 9 and 10, and is proportional to the constant F ^* that depends on the degree of damage to the bearing and does not depend on the rotation frequency. Since the machine variation of the coefficient is small, it is higher to calculate the evaluation index by the average of the corrected vibration values (the value of the left side of Formula 10) than to calculate the evaluation index by the value on the left side of Formula 9 (corrected vibration value). Diagnostic accuracy. Compared to the average machine variation in the magnitude of the transfer function, the difference in the magnitude of the vibration between the normal and abnormal cases is sufficiently large. Therefore, by collecting a sufficient number of data of the same model, the average of the corrected vibration value (Equation 10) Setting of the threshold value for the evaluation index calculated from the value on the left side) is easy.

Further, the magnitude of the corrected vibration value measured under the same conditions after the bearing has rotated M times is A ^* '(k, f _ROT ), and the transfer function at that time is G' (k, f _ROT ). Assuming that a constant that depends and does not depend on the rotation frequency is F ^* ′, the following Expression 11 is similarly established. Since the average of the magnitudes of the transfer functions is less affected by the use environment and use situation of the machine, the following approximation 12 is established.

  The vibration growth rate R is defined as the ratio of the increment of the constant that depends on the degree of damage of the bearing per rotation of the bearing and does not depend on the rotation frequency to the average of the constant that depends on the degree of damage of the bearing and does not depend on the rotation frequency. Equation 13 is set. Since Expression 13 does not include the magnitude of the transfer function, it is a value that can be compared between different models.

Although F ^* and F ^* ′ included in Equation 13 cannot be directly measured, Equation 13 is rewritten as Equation 14 below using Equations 8, 9, 9, 10, and 12. Can be

The right side of Expression 14 includes only measurable or calculable variables, and it is easy to estimate the growth rate R of vibration. When it is difficult to collect a sufficient number of data of the same model, an abnormality can be detected by obtaining the distribution of the growth rate R of the vibration that does not include the variable depending on the model and setting a threshold value.
Here, the case where the growth rate R of the vibration is calculated as the ratio of the increase amount of the vibration to the average of the vibration per one rotation of the bearing is shown. However, the ratio of the average value of the vibration in two measurements, the number of rotations of the bearing, M, it is also possible to use a different definition formulas such as the following equation 15 using the rotation number M ₀ of the bearing of the reference.

FIG. 5 shows a flowchart of a method for diagnosing an abnormality of the bearing 7, and a specific description will be given based on this flowchart.
First, in S1, the rotation frequency of the main shaft 1 is changed to the rotation frequency for measuring vibration, and in S2, the vibration acceleration is measured and stored by the vibration sensor 8 (S1, S2: vibration measurement step).
Next, in S3, a corrected vibration value is calculated from the rotation frequency and the vibration acceleration at the time of vibration measurement, and in S4, a Fourier transform of the corrected vibration value is performed. Is recorded (S3, S4: frequency analysis step).
Then, in S5, it is determined whether or not the vibration measurement at a plurality of rotation frequencies for measuring all the predetermined vibrations has been completed. If the vibration measurement has been completed, the process proceeds to S6, and if not completed, Returning to S1, the processing up to S4 is repeated.
Here, it is desirable that the plurality of rotation frequencies at which vibration is measured be a combination of rotation frequencies such that any one of the rotation frequency, the reciprocal of the rotation frequency, and the logarithm of the rotation frequency is equally spaced. If the vibration average value is calculated using the magnitude of the vibration measured by such a combination of the rotation frequencies, the variation in the size of the transfer function and the variation in the magnitude of the transfer function for each specific frequency are calculated. The reduction effect is improved.

In S6, a vibration average value is calculated for the recorded corrected vibration value for each specific frequency (vibration average value calculation step), and in S7, the corrected vibration value (bearing-induced vibration value) at the characteristic ratio frequency is extracted. (Bearing-induced vibration value extraction step).
Next, in S8, it is determined whether or not to make a diagnosis based on the growth rate of vibration (the degree of change in the bearing-induced vibration value) selected and set in advance by the person responsible for the diagnosis. If the diagnosis is made based on the growth rate of the vibration, the process proceeds to S9. If the diagnosis is not made based on the growth rate of the vibration, the process proceeds to S11.
When the diagnosis is performed based on the growth rate of the vibration, in S9, it is determined whether or not the vibration measurement at the rotation frequency for measuring all the vibrations has been repeated twice. If the vibration measurement is repeated twice, the process proceeds to S11. On the other hand, if the vibration measurement has not been repeated twice, the process proceeds to S10, a running-in operation is performed until the bearing 7 rotates for a preset time or number of times, and the process proceeds to S1.

  Then, in S11, an evaluation index is calculated from the bearing-induced vibration value (evaluation index calculation step), and in S12, it is determined whether the evaluation index has exceeded a threshold value (determination step). Here, when the evaluation index exceeds the threshold value, it is determined that the evaluation index is abnormal in S13, and when the evaluation index does not exceed the threshold value, it is determined that the evaluation index is normal in S14. Display such a diagnostic result. FIG. 6 is a diagnosis result screen when the growth rate of vibration is used as the evaluation index, and FIG. 7 is a diagnosis result screen when the maximum value of the bearing-induced vibration value is used as the evaluation index.

  As described above, according to the abnormality diagnosis method, the abnormality diagnosis device, and the abnormality diagnosis program for the rolling bearing according to the above-described embodiment, the vibration measurement step of measuring the vibration of the main shaft 1 at a plurality of rotation frequencies of the main shaft 1 and the vibration measurement step Frequency analysis step of calculating the magnitude of vibration for each frequency by dividing by the square of the angular velocity that is proportional to the rotation frequency of the main shaft 1 and calculating the magnitude of vibration for each frequency. A vibration average value calculating step of calculating a vibration average value obtained by averaging the magnitude of vibration having the same frequency with respect to the rotation frequency; and a ratio of the frequency at which the vibration caused by the bearing 7 of the vibration average value occurs to the rotation frequency. A bearing-induced vibration value extraction step for extracting a bearing-induced vibration value at a characteristic ratio frequency, and an evaluation index calculation for calculating an evaluation index based on the bearing-induced vibration value By executing the step and the determining step of determining the presence or absence of an abnormality based on the evaluation index, the average is calculated after removing the influence of the rotation frequency from the measured vibration value. , And a bearing-induced vibration value can be obtained. The evaluation index calculated from the bearing-induced vibration value is also less affected by the machine variation, so that it is easy to set a threshold value for determining an abnormality. That is, it is possible to calculate a robust evaluation index in consideration of the influence of the rotation frequency and the transfer function, and determine the presence or absence of abnormality with high accuracy.

Particularly, in this case, in the vibration measurement step, vibration measurement of the same combination of rotation frequencies is performed a plurality of times at intervals of rotation of the bearing for a predetermined time or predetermined rotation so that the growth of vibration can be clearly grasped with respect to measurement variations. In the evaluation index calculation step, the evaluation index is calculated based on the degree of change of the bearing-induced vibration value (vibration growth rate), so that the value of the evaluation index depends on the value of the magnitude of the transfer function. Therefore, even when the main shaft 1 having a different structure is diagnosed or when the measurement is performed at different positions of the vibration sensor 8, the same threshold value can be used for the diagnosis.
Further, in the vibration average value calculating step, the average is obtained by using only the magnitude of the vibration in which the frequency of the vibration is within a predetermined range. The effect of reducing the variation of the magnitude of each of the specific frequencies is further improved.

In the above embodiment, the vibration value (corrected vibration value) in consideration of the rotation frequency is divided by the square of the angular velocity. However, any physical quantity such as the rotation frequency itself that is proportional to the rotation frequency is equivalent. May be replaced because the effect of (1) is obtained. Although the case where the value of the exponent of the exponent is 2 is shown, it can be replaced with another numerical value (the value of the exponent is 0 or more) that can achieve the purpose of reducing the effect of changing the exciting force depending on the rotation frequency. It is possible.
In addition, since the calculation of dividing by the square of the angular velocity is a process of merely dividing by a constant scalar amount, the frequency analysis step in the above embodiment is an example in which a corrected vibration value is calculated before frequency analysis. Since it does not affect the calculation result as long as the vibration average value calculation step is not started, any timing such as, for example, calculating the acceleration in the frequency domain by performing Fourier transform and dividing by the square of the angular velocity, etc. Good.
On the other hand, when calculating the evaluation index from the bearing-induced vibration value, the average value of the bearing-induced vibration values at each characteristic ratio frequency may be employed, or the maximum growth rate of the vibration at each characteristic ratio frequency may be obtained. It may be a value or an average value. Further, the value of the vibration average value other than the bearing-induced vibration value may be determined by a complicated function or the like that refers to the value.

In addition, in the above embodiment, the bearing abnormality due to the inner ring wound has been described as an example. However, the present invention may be applied to a different bearing abnormality such as damage to a rolling element.
Further, the present invention is applicable to a rolling bearing used for a machine other than a machine tool.
Furthermore, as an abnormality diagnosis device, in addition to the form incorporated in the machine tool, at least the storage unit, the arithmetic unit, and the display unit can be communicated with the machine tool by wire or wireless as a separate device from the machine tool, and the The abnormality diagnosis method may be executed based on an abnormality diagnosis program while measuring and acquiring data. In this way, centralized management can be performed for a plurality of machine tools.

  1. Spindle, 2. Spindle housing, 3. Tool, 4. Motor, 5. Speed detector, 6. Control device, 7. Bearing, 8. Vibration sensor, 9. A / D converter, 10 storage unit, 11 operation unit, 12 display unit.

In order to achieve the above object, an invention according to claim 1 is a method for diagnosing an abnormality of a rolling bearing that supports a rotating body,
A vibration measuring step of measuring vibration of the rotating body at a plurality of rotation frequencies of the rotating body,
A frequency analysis step of dividing the vibration by a power of an exponent larger than zero of a predetermined physical quantity that is proportional to the rotation frequency of the rotating body at the time of vibration measurement and frequency analysis to calculate the magnitude of vibration for each frequency When,
A vibration average value calculating step of calculating a vibration average value in which the ratio of the frequency to the rotation frequency of the rotating body at the time of vibration measurement in the vibration measurement step is the average of the magnitude of the vibration,
Among the vibration average values, a bearing-induced vibration value extraction step of extracting a bearing-induced vibration value at a characteristic ratio frequency that is a ratio of a frequency at which vibration caused by the bearing occurs to the rotation frequency,
An evaluation index calculating step of calculating an evaluation index based on the bearing-induced vibration value,
Determining a presence or absence of an abnormality based on the evaluation index.
According to a second aspect of the present invention, in the configuration of the first aspect, in the vibration average value calculating step, any one of the rotation frequency, the reciprocal of the rotation frequency, and the logarithm of the rotation frequency becomes an equal interval. The vibration average value is calculated using the magnitude of the vibration measured in the combination of the rotation frequencies.
According to a third aspect of the present invention, in the configuration of the first or second aspect, in the vibration measuring step, the vibration measurement of the same combination of the rotation frequencies is performed a plurality of times,
In the evaluation index calculating step, the evaluation index is calculated based on a degree of change in the bearing-induced vibration value.
According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, in the vibration average value calculating step, the average is calculated using only the magnitude of the vibration whose frequency is within a predetermined range. It is characterized by taking.
In order to achieve the above object, the invention according to claim 5 is an apparatus for diagnosing an abnormality of a rolling bearing that supports a rotating body,
Vibration measuring means for measuring the vibration of the rotating body at a plurality of rotation frequencies of the rotating body,
Frequency analysis means for dividing the vibration by a power of an exponent larger than zero of a predetermined physical quantity which is proportional to the rotation frequency of the rotating body at the time of vibration measurement and frequency analysis to calculate the magnitude of vibration for each frequency When,
A vibration average value calculation unit that calculates a vibration average value in which a ratio of a frequency to a rotation frequency of the rotating body at the time of vibration measurement by the vibration measurement unit is averaged for the magnitude of the vibration,
Among the vibration average values, a bearing-induced vibration value extraction unit that extracts a bearing-induced vibration value at a characteristic ratio frequency that is a ratio of a frequency at which vibration caused by the bearing occurs to the rotation frequency,
Evaluation index calculating means for calculating an evaluation index based on the bearing-induced vibration value,
Determining means for determining the presence or absence of an abnormality based on the evaluation index.
In order to achieve the above object, an invention according to claim 6 is a program for diagnosing an abnormality of a rolling bearing that supports a rotating body, wherein the vibration of the rotating body measured at a plurality of rotation frequencies is measured for each rotation. A frequency analysis step, a vibration average value calculation step, a bearing-induced vibration value extraction step, and an evaluation index calculation step in the method for diagnosing abnormality of a rolling bearing according to any one of claims 1 to 4, which are input to a computer together with the frequency. And a determining step.

In the above embodiment, the vibration value (corrected vibration value) in consideration of the rotation frequency is divided by the square of the angular velocity. However, any physical quantity such as the rotation frequency itself that is proportional to the rotation frequency is equivalent. May be replaced because the effect of (1) is obtained. Although the case where the value of the exponent of the exponent is 2 is shown, replace it with another value (the value of the exponent is greater than 0) that can achieve the purpose of reducing the effect of the excitation force changing with the rotation frequency. Is possible.
In addition, since the calculation of dividing by the square of the angular velocity is a process of merely dividing by a constant scalar amount, the frequency analysis step in the above embodiment is an example in which a corrected vibration value is calculated before frequency analysis. Since it does not affect the calculation result as long as the vibration average value calculation step is not started, any timing such as, for example, calculating the acceleration in the frequency domain by performing Fourier transform and dividing by the square of the angular velocity, etc. Good.
On the other hand, when calculating the evaluation index from the bearing-induced vibration value, the average value of the bearing-induced vibration values at each characteristic ratio frequency may be employed, or the maximum growth rate of the vibration at each characteristic ratio frequency may be obtained. It may be a value or an average value. Further, the value of the vibration average value other than the bearing-induced vibration value may be determined by a complicated function or the like that refers to the value.

Claims (6)

A method for diagnosing an abnormality of a rolling bearing that supports a rotating body,
A vibration measuring step of measuring vibration of the rotating body at a plurality of rotation frequencies of the rotating body,
A frequency analysis step of dividing the vibration by a power of zero or more of a predetermined physical quantity having a proportional relationship with the rotation frequency of the rotating body at the time of vibration measurement and performing frequency analysis, and calculating a magnitude of vibration for each frequency,
A vibration average value calculating step of calculating a vibration average value in which the ratio of the frequency to the rotation frequency of the rotating body at the time of vibration measurement in the vibration measurement step is the average of the magnitude of the vibration,
Among the vibration average values, a bearing-induced vibration value extraction step of extracting a bearing-induced vibration value at a characteristic ratio frequency that is a ratio of a frequency at which vibration caused by the bearing occurs to a rotation frequency,
An evaluation index calculating step of calculating an evaluation index based on the bearing-induced vibration value,
Determining a presence or absence of an abnormality based on the evaluation index.   In the vibration average value calculation step, using the magnitude of the vibration measured in the combination of the rotation frequency, the reciprocal of the rotation frequency, the logarithm of the rotation frequency is such that any one of the logarithm of the rotation frequency is at equal intervals The method for diagnosing abnormality of a rolling bearing according to claim 1, wherein the vibration average value is calculated by using the method. In the vibration measurement step, the rotation frequency performs the vibration measurement of the same combination a plurality of times,
The method according to claim 1, wherein in the evaluation index calculation step, the evaluation index is calculated based on a degree of a change in the bearing-induced vibration value.   The abnormality diagnosis of the rolling bearing according to any one of claims 1 to 3, wherein in the vibration average value calculating step, an average is obtained by using only the magnitude of the vibration whose vibration frequency is within a predetermined range. Method. An apparatus for diagnosing an abnormality of a rolling bearing that supports a rotating body,
Vibration measuring means for measuring the vibration of the rotating body at a plurality of rotation frequencies of the rotating body,
Frequency analysis means for dividing the vibration by a power of zero or more of a predetermined physical quantity having a proportional relationship with the rotation frequency of the rotating body at the time of vibration measurement and frequency analysis, and calculating the magnitude of vibration for each frequency,
A vibration average value calculation unit that calculates a vibration average value in which a ratio of a frequency to a rotation frequency of the rotating body at the time of vibration measurement by the vibration measurement unit is averaged for the magnitude of the vibration,
Of the vibration average value, bearing-induced vibration value extraction means for extracting a bearing-induced vibration value at a characteristic ratio frequency that is a ratio of a frequency at which vibration caused by the bearing occurs to a rotation frequency,
Evaluation index calculating means for calculating an evaluation index based on the bearing-induced vibration value,
An abnormality diagnosis device for a rolling bearing, comprising: determination means for determining the presence or absence of an abnormality based on the evaluation index.   5. A frequency analysis step in the method for diagnosing abnormality of a rolling bearing according to claim 1, wherein the vibration of the rotating body measured at a plurality of rotation frequencies is input together with each of the rotation frequencies. An abnormality diagnosis program for a rolling bearing, which executes a value calculation step, a bearing-induced vibration value extraction step, an evaluation index calculation step, and a determination step.

Images