JP3392350B2 - 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 wheel with a built-in bearing and a method for diagnosing abnormalities in a low speed rotary bearing.

[0002]

2. Description of the Related Art When a rolling bearing incorporated in a rotating machine is damaged, shocking vibration having a period proportional to the number of revolutions is generated. 2. Description of the Related Art Conventionally, there is known a rotary bearing abnormality diagnosis method (vibration method) in which this vibration is measured and evaluated to detect the presence or absence of abnormality in the bearing.

The vibration method is applied to bearing diagnosis of rotating equipment generally having a rotation speed of 100 rpm or more, such as a fan, a pump, a roller, and a speed reducer, and a simple diagnosis by a trend management of a vibration signal level and a fast Fourier transform (FFT). Abnormality is diagnosed by monitoring the spectrum of the used characteristic frequency. In the case of fans and pumps, since no external force acts on the bearings,
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 rollers, reduction gears, etc., S (bearing damage) is N (equipment state) or more, but external force acts on the bearing but the point of action is distant, so that the action of external force The S / N ratio is small because it is attenuated by the time it reaches the bearing. In such a case, if there is no material, the bearing is diagnosed during idling. However, generally, in the case of a low speed rotating bearing of 100 rpm or less, the S / N ratio is further lower, and bearing diagnosis by the vibration method is difficult.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 5-231992, the vibration speed of a rotating machine in a steady state with no load and a constant number of rotations is measured. It is disclosed that the presence or absence of damage is determined by comparing with the initial value of the vibration velocity in. In addition, Japanese Examined Japanese Patent Sho 62-60
In Japanese Patent No. 011 publication, bicoherence regarding two arbitrarily selected frequencies is obtained from time series data in which vibration is sampled at a constant cycle, and the bicoherence regarding the same frequency in a normal case is compared to detect abnormalities. What is made to detect is disclosed.

In addition to the vibration method, an AE method using an acoustic emission signal (AE signal) is known as a bearing abnormality detection method. When used for a plain bearing, for example, the abnormality of the plain bearing is detected by detecting the AE signal emitted by the oil film of the plain bearing being broken and the metal surface damage caused by the mutual contact between the sleeve and the bush. It is a thing.

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

However, the conventional vibration method has a problem that when the vibration (signal S) due to the bearing abnormality is low, the S / N ratio is small and the diagnosis is difficult. Further, the AE method has a problem that the equipment is expensive and not practical.

Further, the scope of application of the vibration method is expanded to include the bearing-incorporated wheels 4 and 40 to 8 in which the bearing 2 as shown in FIG. 1 is incorporated.
When trying to apply to low speed rotary bearings of 0 rpm or less,
The conventional technique 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 since the vibration source of the material is close to the bearing, it is easily affected by the external vibration. 1 shows a state in which the wheel 4 is attached to the wheel attachment plate 8 connected to the wheel attachment housing 6 via the pin 10, and 12 is an end plate of the pin 10 and 1 is an end plate.
4 is a snap ring and 16 is a distance collar.

Further, in the case of a low speed rotating bearing of 40 to 80 rpm or less, FIG. 13 (from "Equipment Diagnostic Technology Handbook" edited by the Iron and Steel Institute of Japan, pp. 89 to 92 [Maruzen] (1986)) shows the rotational speed and the vibration level. Since the vibration signal level is low, a special signal processing for improving the S / N ratio is required as shown in the relationship with.

In order to solve such a problem, the applicant has already proposed in Japanese Patent Application No. 8-317983 that the mechanical vibration of the bearing caused by the rotation of the rotating machine is measured, and this is used to detect the abnormality of the bearing. In the abnormality diagnosis method for a wheel with a built-in bearing and a low-speed rotating bearing that determines presence / absence, an odd number of 3 or more is applied to a vibration acceleration value extracted by a low-pass filter that passes an output of a predetermined value or less among outputs from the vibration acceleration sensor. It is proposed that the abnormality determination be performed by performing a multiplication process and comparing with a preset reference value.

[0011]

However, even the method proposed in Japanese Patent Application No. 8-317983 has a problem that the method of setting the reference value is not always clear.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to clarify a reference value setting method in the above method.

[0013]

SUMMARY OF THE INVENTION The present invention measures the mechanical vibration of a bearing caused by the rotation of a rotating machine and uses the measured mechanical vibration to determine whether or not the bearing has an abnormality. of the abnormality diagnosis method, it performs a process of the third power of the vibration acceleration value retrieved by the filter for passing the output of a predetermined value of the output from the vibration acceleration sensor, the 3
The multiplied number is the vibration acceleration of the bearing under normal conditions per unit time.
As twice to 3 squared value threshold, it was possible to determine more abnormal traversal Ru number <br/>, it is obtained by solving the above problems.

[0014] Further, one in which the cubed value was made to the abnormality determination using an approximate curve indicating the times <br/> number and bearing rotational speed relationship exceeds the threshold.

The number of times the cubed value exceeds the threshold value
The abnormality determination is made by using a damage determination diagram showing the relationship between the number and the rotational speed of the bearing .

As a result of the inventors' analysis of vibration waveforms with different rotational speeds and load conditions using an experimental machine, as shown in FIG. 2, the value obtained by cubed the vibration acceleration of the abnormal bearing is normal per unit time. The maximum peak value of the cube of the vibration acceleration of the bearing is 2
Take times to 3 squared number of times exceeding the values in one axis, while
It was discovered that the plot of the data has a characteristic approximated by a quadratic curve when the axis of is the bearing rotation speed. The present invention is
It was made by utilizing this characteristic.

[0017]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

In this embodiment, the rotation speed is 5, 10, 1
The vibration acceleration values of the normal bearing and the abnormal bearing were cubed, and the values were compared with each other by varying the vibration acceleration value in four stages of 5 and 20 rpm.

Specifically, first, as shown in FIG. 3, the peak value of the value obtained by raising the vibration acceleration value of a normal bearing to the cube is 2 ³ = 8.
Set the threshold to double.

Next, as shown in FIG. 4, the number of times that the value of the vibration acceleration value of the abnormal bearing cubed to the third power exceeds the threshold value set per unit time (for example, 1 minute) is counted.

Further, as shown in FIG. 5, the vertical axis represents the count number and the horizontal axis represents the rotational speed.

The plotted points are 2 as shown in FIG.
It can be approximated to the following curve, and the abnormality determination can be performed by setting the upper part of the approximate curve to the dangerous range, the lower limit of the variation of the data to the replacement required range, and the lower limit of the variation to the caution region.

FIG. 6 is a schematic configuration diagram of a system for diagnosing a bearing abnormality according to the present invention. In FIG. 6, 20 is a vibration acceleration sensor that detects a vibration acceleration signal of the bearing, and 22 is a vibration acceleration signal, which is amplified by 1K.
It is a vibrometer that performs a low-pass filter (LPF) process that passes Hz or less. The signal from the vibrometer 22 is sampled by the local station 24, and the local station 24 performs a cube process to perform abnormality diagnosis. The result of the diagnosis is sent to the central station 26 and displayed.

The operation of this system will be described below.
First, the vibration acceleration sensor 20 detects a detection signal picking up the vibration acceleration as shown in FIG. 7, and sends it to the vibrometer 22. The vibrometer 22 amplifies this detection signal as shown in FIG. 8 and performs low-pass filter processing of 1 KHz as shown in FIG. 9 to cut off signals in a frequency range unnecessary for diagnosis. This is because the vibration acceleration signal generated when the bearing is abnormal cannot be selected with the original signal as it is, 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. Further, the S / N ratio becomes small when the vibration from the outside is received. In addition, the vibration acceleration signal when the bearing is abnormal is 1KH.
This is because z or less. This low-pass filter process eliminates noise components to prevent erroneous diagnosis.

At the local station 24, the vibrometer 2
The low-pass filtered waveform of 1kHz which is the output of 2 is received, data is sampled for 5 seconds per data as shown in FIG. 10, and the data is A / D converted at a sampling pitch of 50 μsec as shown in FIG. Collect. At this time, it is possible to sample while switching the input of 16 channels.

Thereafter, at the local station 24,
The cube processing is performed on all sampling points of the final data. In this case, the sampling point is 5 sec ÷ 50 μsec = 10
It is 0000 points. As a result, it is possible to make an abnormality determination when it is difficult to make a determination using only the filter. It should be noted that the reason for raising the cube 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 difficult to discriminate when the abnormality is a little abnormal. This is because the S / N ratio can be improved and the level difference between the abnormal signal and the noise component can be made noticeable. Also, if the value is squared, the negative value is also converted to positive, but if it is an odd power such as cubed, the positive / negative state of the signal does not change . Figure 12
Shows the cube processing waveform.

Next, an abnormality determination is performed using the damage determination diagram as shown in FIG.

If the determination result is abnormal, alarm information is output to the central station 26. In the central station 26, the local station 24
Warning information (warning information, maximum value of cubed calculation value, reference value for abnormality determination, etc.) is displayed on the CRT screen. At the same time, the cubed waveform of the latest final data is displayed on the CRT screen.

Further, as an offline display, a cubed waveform of the data collected and stored in the past is displayed on the CRT screen.

In this system, it has been effective to cube the signal by the low-pass filter processing of 1 KHz, but depending on the size of the target bearing and the rigidity of the wheel mounting material, a region higher than 1 KHz (for example, 3KH
In some cases, a low pass filter of z) is more effective.
Therefore, the low-pass filter is not limited to 1 KHz and may be several KHz.

The curve of the damage determination diagram is not fixed to that shown in FIG. 2, but changes depending on the measuring instrument or the like.

[0032]

As described above, according to the present invention, the criterion for abnormality determination is clarified, and accurate abnormality determination can be performed.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of a damage determination diagram used in the present invention.

FIG. 3 is a diagram showing an example of a cube processing waveform of a normal bearing according to the embodiment of the present invention.

[Fig. 4] Similarly, a diagram showing an example of a cube processing waveform of an abnormal bearing.

FIG. 5 is a diagram showing an example in which the number of times that the cube value of the vibration acceleration of the abnormal bearing exceeds a threshold value within a unit time is plotted on the vertical axis with the horizontal axis of the bearing rotation speed.

FIG. 6 is a configuration diagram showing a schematic configuration of a system to which a bearing abnormality diagnosis method of the present invention is applied.

FIG. 7 is a graph showing a detected vibration acceleration signal.

8 is a graph showing a waveform obtained by amplifying the detection signal of FIG.

9 is a graph showing a waveform obtained by subjecting the waveform of FIG. 8 to low-pass filter processing of 1 KHz.

FIG. 10 is a graph showing how data is sampled from a low-pass filtered waveform.

FIG. 11 is a graph showing how data is sampled from a waveform that has been similarly low-pass filtered.

FIG. 12 is a graph showing a waveform that has been cubed.

FIG. 13 is a diagram showing a relationship between a rotation speed and a vibration level in a low speed rotary bearing, which is described in the prior art document.

[Explanation of symbols]

2 ... Bearing 4 ... wheels 20 ... Vibration acceleration sensor 22 ... Vibration meter 24 ... Local station 26 ... Central Station

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kyo Yamamura, Inventor, 1st Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture (no address), Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Kenji Yamamoto, Kawashima-dori Kawashima, Okayama Prefecture Chome (no address) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Noriaki Inoue 3-48 Takahata-cho, Nishinomiya-shi, Hyogo Kawatetsu Advantech Co., Ltd. (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G01M 13/04 G01H 17/00

Claims (3)

(57) [Claims] 1. A method for diagnosing an abnormality in a wheel with a built-in bearing and a low-speed rotary bearing, which comprises measuring mechanical vibration of a bearing caused by rotation of a rotating machine and using the measured mechanical vibration to determine whether or not there is an abnormality in the bearing. performs a process of the third power of the vibration acceleration value retrieved by the filter for passing the output of a predetermined value of the output from the sensor, the number was the third power is twice the vibration acceleration of bearings in the normal per unit time 3 squared value as threshold, bearing built-in wheels and abnormality diagnosis method for low speed bearing and judging more abnormal <br/> number of Ru exceeds this by. 2. The method for diagnosing an abnormality in a wheel with a built-in bearing and a low-speed rotating bearing according to claim 1, wherein the value raised to the third power is the front.
An abnormality diagnosis method for a wheel with a built-in bearing and a low-speed rotating bearing, which is characterized by making an abnormality determination using an approximate curve showing the relationship between the number of times the threshold value is exceeded and the number of rotations of the bearing. 3. The method for diagnosing an abnormality in a wheel with a built-in bearing and a low-speed rotary bearing according to claim 2, wherein the value raised to the third power is the front.
An abnormality diagnosis method for a wheel with a built-in bearing and a low-speed rotating bearing, characterized by making an abnormality determination using a damage determination diagram showing the relationship between the number of times the threshold value is exceeded and the number of rotations of the bearing.