JP3264480B2 - Abnormality diagnosis method for wheels with built-in bearings and low-speed rotating bearings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing an abnormality in a wheel with a built-in bearing and a low-speed rotating bearing.

[0002]

2. Description of the Related Art When a rolling bearing incorporated in a rotating machine is damaged, an impact vibration having a period proportional to the number of rotations is generated. Conventionally, there has been known a rotating bearing abnormality diagnosis method (vibration method) that measures the vibration and evaluates the vibration to detect the presence or absence of a bearing abnormality.

[0003] The vibration method is applied to a bearing diagnosis of a rotating equipment generally having a rotation speed of 100 rpm or more such as a fan, a pump, a roller, and a speed reducer. The vibration method performs a simple diagnosis and a fast Fourier transform (FFT) by trend management of a vibration signal level. Abnormality diagnosis is performed by spectrum monitoring of the characteristic frequency used. In the case of a fan or pump, since no external force acts on the bearing,
S (bearing damage) is much larger than N (equipment state), and the S / N ratio is large. On the other hand, in the case of a roller, a speed reducer, or the like, although S (bearing damage) is equal to or more than N (equipment state), an external force acts on the bearing, but since the action point is far away, the external force acts. The S / N ratio is small because it is attenuated before reaching the bearing. In such a case, when there is no material, the bearing diagnosis is performed at the time of no load idling. However, generally, in the case of a low-speed rotating bearing of 100 rpm or less, the S / N ratio is even lower, and it is difficult to diagnose the bearing by the vibration method.

For example, Japanese Patent Application Laid-Open No. Hei 5-231992 measures the vibration speed of a rotating machine in a steady state with no load and a constant rotation speed. A method is disclosed in which the presence or absence of damage is determined by comparing the initial value of the vibration speed in the above. In addition, Tokiko 62-60
No. 011 discloses that bicoherence for two arbitrarily selected frequencies is obtained from time-series data obtained by sampling vibrations at a constant period, and the bicoherence for the two frequencies arbitrarily selected is compared with a normal bicoherence for the same frequency. An arrangement for detecting the object is disclosed.

[0005] In addition to the vibration method, an AE method using an acoustic emission signal (AE signal) is known as a method for detecting a bearing abnormality. This is used, for example, for sliding bearings to detect bearing anomalies by detecting the AE signal emitted by the metal surface damage resulting from the sleeve and bush interfacing when the oil film of the sliding bearing breaks. Things.

For example, Japanese Patent Publication No. 7-26941 discloses that
An output of a predetermined range of the AE signal generated from the bearing is extracted and compared with a reference value to detect an abnormality of the bearing.

[0007]

However, the conventional vibration method has a problem that when vibration (signal S) due to bearing abnormality is low, the S / N ratio is small and diagnosis is difficult. Further, the AE method has a problem that equipment is expensive and impractical.

[0008] Further, the object to which the vibration method is applied is expanded, and the bearing-incorporated wheels 4 and 40 to 8 incorporating the bearing 2 as shown in FIG.
When trying to apply to low-speed rotating bearings of 0 rpm or less,
The conventional technology has a problem that diagnosis is difficult. For example, in the case of a wheel with a built-in bearing, the S / N ratio is small due to the influence of the tread surface and the mating material, and the vibration source made of the material is close to the bearing, so that it is easily affected by external vibration. FIG. 1 shows a state in which the wheel 4 is mounted via a pin 10 on a wheel mounting plate 8 connected to a wheel mounting housing 6.
4 is a retaining ring, and 16 is a distance collar.

In the case of a low-speed rotating bearing of 40 to 80 rpm or less, FIG. 2 shows (from the Iron and Steel Institute of Japan “Equipment Diagnosis Technology Handbook”, pp. 89-92 [Maruzen] (1986)) the rotational speed and the vibration level. As shown in the relationship, since the vibration signal level is low, special signal processing for improving the S / N ratio is required.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to improve the S / N ratio and perform a precise abnormality diagnosis even for a wheel with a built-in bearing and a low-speed rotating bearing. It is an object of the present invention to provide a method of diagnosing a built-in bearing type wheel and a low-speed rotating bearing.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a wheel with a built-in bearing and a low-speed rotating bearing, which measures the mechanical vibration of a bearing caused by the rotation of a rotating machine and uses this to determine whether or not the bearing is abnormal. In the abnormality diagnosis method, a vibration acceleration signal extracted by a low-pass filter that passes an output less than or equal to a predetermined value among the outputs from the vibration acceleration sensor is subjected to a process of raising an odd power of 3 or more, and a preset reference value is set. The above problem has been solved by determining an abnormality by comparing with the above.

Hereinafter, the process leading to the present invention will be described.

FIG. 3 is a graph showing an original vibration acceleration (ACC) waveform 2 hours after the start of use in the example of the bearing to which the present invention is applied, and FIG. 4 shows the result of fast Fourier transform (FFT) of this. FIG. Also, FIG.
It is a graph which shows the original vibration acceleration waveform after 11 hours of this bearing, and FIG. 6 is a grab which shows the result of having performed this with a fast Fourier transform. The vertical axis of the original waveform graph represents the signal level, and the horizontal axis is time. The vertical axis of the fast Fourier transform graph represents the level of the frequency component, and the horizontal axis represents the frequency. At both times, the bearing is in a normal state, but as shown in FIG. 5, the signal level of the original waveform after 11 hours of use has increased. These data are not subjected to the filtering process for the original waveform. In this state, the bearing may be determined to be abnormal after 11 hours of use, as shown in FIGS.

On the other hand, FIG. 7 shows that the original waveform of the vibration acceleration two hours after the start of use is 1-2 KH.
FIG. 8 is a graph showing a waveform after performing a band pass filter (BPF) process at z. FIG.
9 is a graph showing a waveform after performing a band-pass filter process of z. FIG. 9 is a graph showing a waveform after performing a bandpass filter process of 1 to 2 KHz on the original vibration acceleration waveform of the bearing 11 hours after the start of use.
Is a graph showing a waveform after a bandpass filter process of 1 to 3 KHz has been performed on the original vibration acceleration waveform of the bearing 11 hours after the start of use. These are all normal bearings. By performing the band-pass filter processing, noise components can be eliminated, and erroneous diagnosis of abnormalities while normal is eliminated. Also, as these figures show,
Bandpass filter processing is more effective at removing noise components at 1 to 2 kHz than at 1 to 3 kHz.

FIG. 11 shows an original vibration acceleration waveform of a normal bearing when the wheel mounting housing 6 shown in FIG. 1 is subjected to vibration from the outside. FIG. As shown in FIG.
FIG. 13 shows a graph obtained by performing the band-pass filter processing. Also, FIG. 14 shows a graph obtained by subjecting the original waveform of FIG. 11 to a fast Fourier transform, and FIG. 15 shows a graph obtained by subjecting the original vibration acceleration waveform of the normal bearing after use for 2 hours to band pass filter processing of 1 to 2 KHz. FIG. 16 shows a graph obtained by performing band-pass filter processing of the original vibration acceleration waveform of the normal bearing after use for 1 to 3 KHz. 11 to 1
As shown in FIG. 3, although the bearing is a normal bearing, when it is subjected to external vibration, a waveform having a level determined to be abnormal only by the band-pass filter processing is obtained. When comparing the graphs of FIGS. 12 and 13 with the graphs of FIGS. 15 and 16 showing band-pass filter processed waveforms of a normal bearing after use for 2 hours without receiving external vibration, the difference is clearly apparent. I understand.

FIG. 17 is a graph obtained by focusing on the natural frequency of the wheel mounting plate 8 shown in FIG. 1 and performing a fast Fourier transform on the measurement result. As can be seen from this graph, it is considered that the diagnosis should be performed by focusing on the signal component of 1 KHz or less.

Therefore, it is verified whether or not it is effective to perform a 1 KHz low-pass filter process on a bearing which receives vibration from the outside in order to prevent erroneous diagnosis of abnormality. As shown in the graph of the original waveform of the vibration acceleration in FIG. 11, it can be seen that the signal level increases when the bearing receives external vibration even when the bearing is in a normal state. On the other hand, as shown in FIG. 18, it is understood that the effect of the external vibration can be eliminated by performing the low-pass filter processing at 1 KHz. FIG. 19 shows a graph obtained by performing a low-pass filter process at 1 KHz in the case of an abnormal bearing. From this, the signal level is as low as about 0.1 G in the normal case, and the signal level is high in the abnormal case.
It can be seen that some of them exceed G. Therefore, this filtering process is found to be effective. However, as shown in the graph of FIG. 20, when the bearing is slightly abnormal, the signal level is low and it cannot be distinguished from normal, and it is difficult to determine the abnormality by performing low-pass filter processing at 1 KHz. Deemed necessary.

Conventionally, a crest factor has been used for abnormality diagnosis of a bearing, and a normal bearing diagnosis is remarkably shown in a peak value of a vibration acceleration. Therefore, S is the peak value and N
Is considered to be the average value, so peak value / average value = S / N
It is considered that by improving the ratio, the bearing abnormality signal becomes prominent and can be easily distinguished.

As a method therefor, in the present invention, a process of raising the signal level to an odd number of 3 or more (a cubic process or a quintic process) is performed. In the squaring processing, since a negative signal becomes positive, frequency conversion is performed, which is not preferable. Therefore, the odd power processing is desirable.

FIG. 21 shows a signal obtained by multiplying the signal shown in FIG. As shown in the upper graph of FIG. 21, the signal level and the noise component are each increased by a factor of 10 when the amplification is increased by a factor of 10. On the other hand, in the case of the cubic processing as shown in the lower graph of FIG. 21, a low level signal such as a noise component is kept low, and the difference from a higher signal such as a bearing abnormality signal is large. Become.

Therefore, the cubic processing increases the difference (crest factor) between the abnormal signal level and the average signal level, and is more effective for diagnosing a bearing abnormality.

FIG. 22 shows a case where the waveform of the normal bearing subjected to the 1 kHz low-pass filter processing is multiplied by 10 and a case where the waveform is subjected to the cube processing. As shown in this graph, the influence of external vibration is eliminated by the low-pass filter. Therefore, even if the cube processing is performed, the influence of external vibration is not exerted. There is no risk of diagnosis.

As described above, according to the present invention, since the vibration acceleration signal extracted by the low-pass filter is subjected to a process of raising the vibration acceleration signal to an odd power of 3 or more, the S / N ratio is improved and the diagnosis of the bearing abnormality is performed. It has become possible to perform normally.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 23 is a schematic configuration diagram of a system for performing a bearing abnormality diagnosis according to the present invention. In FIG. 23, 1
Numeral 0 denotes a vibration acceleration sensor for detecting a vibration acceleration signal of the bearing, and 12 receives and amplifies the vibration acceleration signal, and 1
It is a vibrometer that performs low-pass filter processing at KHz. The signal from the vibrometer 12 is sampled by the local station 14 where the local station 14
The cubic processing is performed, and abnormality diagnosis is performed. The result of the diagnosis is sent to the central station 16 and displayed.

The operation of the present embodiment will be described below.
First, a detection signal that picks up a vibration acceleration as shown in FIG. 24 is detected by the vibration acceleration sensor 10 and sent to the vibrometer 12. In the vibration meter 12, this detection signal is
Amplified as shown in FIG. 25 and 1KH as shown in FIG.
The low-pass filter processing of z is performed to cut off signals in frequency ranges unnecessary for diagnosis. This is because the vibration acceleration signal generated at the time of bearing abnormality cannot be selected with the original signal, and the vibration signal level at the time of abnormality is low and the S / N ratio is small in the low-speed rotating bearing. When external vibration is applied, S
/ N ratio decreases. The reason is that the vibration acceleration signal at the time of bearing abnormality is 1 KHz or less. This low-pass filter processing eliminates noise components to prevent erroneous diagnosis.

At the local station 14, the vibrometer 1
In response to the 1 KHz low-pass filter processing waveform output from the second sampler, data is sampled for 5 seconds per data as shown in FIG. 27, and A / D converted at a sampling pitch of 50 μsec as shown in FIG. Collect. At this time, sampling can be performed while switching the input of 16 channels.

Thereafter, at the local station 14,
The cube processing is performed on all sampling points of the final data. In this case, the sampling point is 5 sec ÷ 50 μsec = 1
00000 points. This makes it possible to determine an abnormality when it is difficult to make a determination using only the filter. The reason for raising to the third power is that, in the case of a low-speed rotating bearing such as a wheel with a built-in bearing, as described above, the signal level difference from the noise component is small and it is difficult to discriminate the signal to a slightly abnormal degree. This is because the S / N ratio can be improved and the level difference between the abnormal signal and the noise component can be remarkable. If the power is a square, a negative value is also converted to a positive value. However, if the power is an odd number such as a power of three, the positive / negative state of the signal does not change. Therefore, the power may be an odd number power such as the fifth power regardless of the third power. FIG.
Shows a cubic processing waveform.

Next, abnormality determination is performed by comparing the data after the cubing process with a preset reference value for abnormality determination.
From the time when the peak value exceeds the reference value to the time when the peak value falls below the reference value, that is, when the number of appearances of the peak that exceeds the reference value exceeds a predetermined reference number of times, it is determined that there is an abnormality. For example, in the case of the waveform shown in FIG. 29, if the reference number of determinations is 2, the number of peaks exceeding the reference value is three or more, and it is determined that there is an abnormality.

If the determination result is abnormal, alarm information is output to the central station 16. In the central station 16, the local station 14
(Alarm information, maximum value of cubic operation value, reference value for abnormality determination, etc.) are displayed on the CRT screen. At the same time, the cube processing waveform of the latest final data is displayed on the CRT screen.

As a offline display, a cube processing waveform of data collected and stored in the past is displayed on a CRT screen.

In this embodiment, it is effective to perform a cubic processing of the signal obtained by the low-pass filter processing of 1 KHz. However, depending on the size of the target bearing and the rigidity of the wheel fixing material, the region higher than 1 KHz ( For example, 3KH
z may be more effective in some cases.
Therefore, the low-pass filter is not limited to 1 KHz, but may be several KHz.

[0033]

As described above, according to the present invention, the signal taken out by the low-pass filter is raised to an odd power of 3 or more, so that the S / N ratio is improved and the accuracy of the bearing abnormality determination is determined. Can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a wheel with a built-in bearing to which a vibration method is applied.

FIG. 2 is a diagram showing a relationship between a rotational speed and a vibration level in a bearing of 40 to 80 rpm or less.

FIG. 3 is a graph showing an original vibration acceleration waveform after two hours of use when the bearing is normal.

FIG. 4 is a graph showing a waveform obtained by performing a fast Fourier transform on the waveform of FIG. 3;

FIG. 5 is a graph showing an original vibration acceleration waveform after 11 hours of use when the bearing is normal.

FIG. 6 is a graph showing a waveform obtained by performing a fast Fourier transform on the waveform of FIG. 5;

FIG. 7 shows the original waveforms 1 to 2 after use for 2 hours when the bearing is normal.
Graph showing a waveform subjected to bandpass filter processing at 2 kHz

FIG. 8 is a graph showing waveforms that have also been subjected to bandpass filter processing of 1 to 3 KHz.

FIG. 9 shows an original waveform after 11 hours of use when the bearing is normal.
Graph showing waveforms subjected to bandpass filter processing of up to 2 KHz

FIG. 10 is a graph showing waveforms that have also been subjected to bandpass filter processing of 1 to 3 KHz.

FIG. 11 is a graph showing an original waveform of vibration acceleration of a normal bearing.

12 is a graph showing a waveform obtained by subjecting the waveform of FIG. 11 to bandpass filter processing at 1 to 2 kHz.

FIG. 13 is a graph showing waveforms that have also been subjected to bandpass filter processing of 1 to 3 KHz.

14 is a graph showing a waveform obtained by performing a fast Fourier transform on the waveform of FIG. 11;

FIG. 15 shows the original waveform of a normal bearing after use for 2 hours is 1 to 2K.
Is a graph showing a waveform subjected to a band-pass filter processing of Hz.

FIG. 16 shows the original waveform of a normal bearing after use for 2 hours is 1 to 3K.
Is a graph showing a waveform subjected to a band-pass filter processing of Hz.

FIG. 17 is a graph showing a waveform obtained by performing a fast Fourier transform on a waveform obtained by measuring the frequency of the wheel mounting plate.

FIG. 18 is a graph showing a waveform obtained by subjecting an original waveform when a normal bearing receives external vibration to a low-pass filter process of 1 kHz.

FIG. 19 is a graph showing a waveform subjected to 1 KHz low-pass filtering when a bearing is abnormal;

FIG. 20 is a graph showing a waveform subjected to a 1 KHz low-pass filter process when the bearing is slightly abnormal;

FIG. 21 is a graph showing a waveform obtained by amplifying the waveform of FIG.

FIG. 22 is a graph showing a case where a normal bearing is subjected to external vibration and a case where the normal bearing is amplified by a factor of 10 and a case where the normal bearing is subjected to cubic processing;

FIG. 23 is a configuration diagram schematically showing the configuration of a system to which the bearing abnormality diagnosis method of the present invention is applied;

FIG. 24 is a graph showing a detected vibration acceleration signal.

FIG. 25 is a graph showing a waveform obtained by amplifying the detection signal of FIG. 24;

26 is a graph showing a waveform obtained by subjecting the waveform of FIG. 25 to a low-pass filter process at 1 KHz.

FIG. 27 is a graph showing a state in which data is collected from a waveform subjected to a low-pass filter processing.

FIG. 28 is a graph showing a state in which data is collected from a waveform that has also been subjected to low-pass filtering.

FIG. 29 is a graph showing a state in which an abnormality is determined using a waveform subjected to cubic processing;

[Explanation of symbols]

 10 Vibration acceleration sensor 12 Vibrometer 14 Local station 16 Central station

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Okamoto 3-48 Takahata-machi, Nishinomiya-shi, Hyogo Kawatetsu Advantech Co., Ltd. (56) References JP-A-7-270228 (JP, A) JP-A-1 -152335 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01M 13/04

Claims (1)

(57) [Claims] An abnormality diagnosis method for a wheel with a built-in bearing and a low-speed rotating bearing, which measures mechanical vibration of a bearing caused by rotation of a rotating machine and determines whether or not the bearing is abnormal by using the measured vibration. The vibration acceleration signal extracted by a low-pass filter that passes an output that is equal to or less than a predetermined value among the outputs from the sensor is subjected to a process of raising an odd number of 3 or more, and is compared with a preset reference value to determine abnormality. An abnormality diagnosis method for a wheel with a built-in bearing and a low-speed rotating bearing.