JPH0249384Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an abnormality detector that can immediately detect an abnormality or the degree of abnormality in a rolling bearing.

Conventionally, when measuring the vibration of a rolling bearing to detect an abnormality, the abnormality of the bearing has been evaluated based on the effective value, peak value, average value, etc. of the vibration of the rolling bearing. However, the vibration values of bearings vary greatly depending on the size of the bearing, the number of rotations, and the structure around the bearing, so in order to accurately determine the quality of the bearing, it is necessary to accumulate data for each target machine. It was necessary to create criteria for determining pass/fail.

For this reason, Japanese Patent Application Laid-Open No. 47-9446 and Utility Model Application No. 53-
In order to overcome the above drawbacks, Publication No. 72951 includes
Not the absolute value of vibration (effective value, average value, peak value, etc.), but the ratio of the peak value and effective value of vibration (crest factor)
An apparatus for detecting anomalies based on is shown.
A method for detecting an abnormality in a rolling bearing using this crest factor (peak value/effective value) is as follows.

Generally, the vibration of a rolling bearing under normal conditions is
The vibration value varies depending on the bearing size and usage conditions, and the vibration waveform has a random shape that resembles white noise, as shown in the first image. For this reason, even if the absolute value of vibration differs from bearing to bearing, the crest factor of vibration is a substantially constant value (approximately 3 to 5) for all bearings as long as the bearing is normal. On the other hand, if scratches or flaking occur on the raceway surface or rolling surface of a bearing component, the parts of the bearing that engage with this defect will collide (for example, if there is a scratch on the raceway surface of the outer ring, (The rolling elements collide with the scratches), so the vibration waveform of the bearing becomes a superimposition of impact vibrations due to the collision on a white noise waveform, as shown in FIG. The vibration value of the bearing at this time is such that, since the individual impact vibrations occur for a short time, the effective value of the vibration, which is time-averaged, does not increase much, but the peak value increases significantly. Therefore, when the crest factor is determined, it is usually much larger than the normal value.

The manner in which the crest factor increases due to bearing abnormality is not easily affected by the size of the bearing, the number of revolutions, and the surroundings of the bearing, so it is possible to judge whether the bearing is good or bad for any mechanical device based on a fixed criterion. This provides the advantage that bearing abnormalities can be diagnosed immediately without having to accumulate past vibration data.

The inventions and ideas described in the above-mentioned publications are all bearing abnormality detection devices that utilize the relationship between the crest factor of bearing vibration and abnormalities, but when actually manufacturing the device, the following is required. There are some problems.

In order to calculate the crest factor, that is, the peak value/effective value, it is necessary to perform division, but this requires a high-precision analog divider circuit, which requires delicate circuit adjustment and expensive parts. was essential.

The purpose of this invention is to eliminate the above-mentioned drawbacks and provide a highly practical abnormality detector that can detect abnormalities in rolling bearings and the degree of abnormality. The effective value of vibration is amplified to a predetermined multiplication factor, this amplified effective value is compared with the instantaneous value of vibration, and if the instantaneous value of vibration exceeds the level of the amplified effective value, A pulse signal with a time width equal to the time of This is a rolling bearing abnormality detector equipped with an alarm circuit configured to issue an alarm.

Next, an embodiment of this invention will be described with reference to the drawings. The detector shown in FIG. 3 detects the presence or absence of an abnormality in the rolling bearing B to be detected. 1 is a vibration sensor that detects mechanical vibration of the rolling bearing B and converts it into an electrical signal; 2 3 is an amplifier for amplifying the minute electric signal from the vibration sensor 1, and 3 is a bandpass filter for removing unnecessary disturbance components generated from the drive system of the bearing and other mechanical systems from the amplified signal. , for example 1KHz, several 10KHz
It is a band wave transmitter with a pass characteristic of . 4 is an effective value circuit for determining the effective value from the output of the band wave generator 3, and 5 is an effective value circuit for multiplying the output from the effective value circuit 4 by a predetermined factor, that is, K times (usually about 10 times). The DC amplifier 6 is a Schmitt trigger circuit that outputs a pulse signal having a time width equal to the time during which the output from the bandpass amplifier 3 exceeds the level of the effective value multiplied by K. 7
is a monostable multivibrator that outputs another pulse at a fixed time interval T (T = selected from several tens of milliseconds to several hundred milliseconds) each time the pulse signal is output, and this monostable multivibrator 7
The alarm circuit 8 is configured to issue an alarm in response to the output pulse of the alarm circuit 8. The alarm circuit 8 may include components such as a light emitting diode or a buzzer for displaying an alarm, either alone or in combination as appropriate.

If there is a harmful scratch on a bearing, even if the impact vibration caused by the scratch is relatively mild, it will reduce the effective value by 10%.
It will more than double. Therefore, by setting a threshold value to about 10 times the effective value and counting pulses for vibrations that exceed this threshold value, it is possible to obtain a nearly constant value for any type of bearing, that is, for any type of mechanical device, as long as the disturbance vibration is small. The quality of the bearing can be determined based on the criteria.

The above-mentioned magnification K varies somewhat depending on the type of bearing, but it is usually about 10 times, and is a value that is appropriately selected depending on the degree of abnormality of the rolling bearing to be tolerated.

In the above inspection device, when the rolling bearing B is normal, the instantaneous value of the detected vibration does not exceed the effective value multiplied by K, so no signal is output from the Schmitt trigger circuit 6. Therefore, there is no output from the subsequent circuits, so no alarm is issued, but if an abnormality occurs in the rolling bearing B, the instantaneous value of vibration will exceed the effective value multiplied by K as shown in Figure 4. When this occurs, a pulse signal is output from the Schmitt trigger circuit 6 as shown in Fig. 5, and this output signal enters the monostable multivibrator 7, which outputs a pulse signal as shown in Fig. 6. A pulse signal at regular intervals is outputted, and this signal is input to the alarm circuit 8, an alarm is issued, and an abnormality in the rolling bearing B can be known.

As the abnormality of the rolling bearing progresses, the number of scratches on the raceway surfaces of the bearing components increases, and the frequency of impact vibrations caused by collisions shown in FIG. 2 also increases. Therefore, the number of pulses generated by the Schmitt trigger circuit 6 increases, and as a result, the frequency of pulse signals output from the monostable multivibrator 7 also increases. From this, it can be said that the frequency of output pulses of the monostable multivibrator 7 represents the degree of deterioration of the bearing. Therefore, by changing the alarm output level (for example, the light intensity of a light emitting diode or the volume of a buzzer) according to the frequency of this output pulse, it is possible to know not only whether there is an abnormality in the bearing, but also the extent of the abnormality. .

In the above embodiment, the effective value of the signal based on vibration was used, but instead of this effective value, the waveform factor (in the case of bearing vibration, approximately
1.2) can be used as a substitute, and in this case, an average value circuit can be used instead of an effective value circuit.

The detector of this invention uses a Schmitt trigger circuit without using the analog divider used in the detection devices described in Japanese Patent Application Laid-open No. 47-9446 and Japanese Utility Model Application No. 53-72951. Because it uses a simple electrical circuit like a monostable multivibrator,
It is a compact and inexpensive detector that does not require delicate adjustments or expensive parts like a divider.Furthermore, this detector can detect scratches on a rolling bearing as a frequency of output pulses of a monostable multivibrator. Since it is detected, the output pulses increase according to the number of flaws, and this has a useful feature in that it is possible to know the degree of abnormality in the rolling bearing.

[Brief explanation of the drawing]

Fig. 1 is a vibration waveform diagram of a normal rolling bearing, Fig. 2 is a vibration waveform diagram of an abnormal rolling bearing, Fig. 3 is a block diagram of a detector showing an embodiment of this invention, and Fig. 4 is a diagram of a shock absorber. FIG. 5 is a diagram of the input waveform to the Schmidt trigger circuit, FIG. 5 is a diagram of the output waveform of the Schmitt trigger circuit, and FIG. 6 is a diagram of the output waveform of the monostable multivibrator. Explanation of symbols, 1 is a vibration sensor, 2 is an amplifier, 3
is a band reactor, 4 is an effective value circuit, 5 is a DC amplifier, 6 is a Schmitt trigger circuit, 7 is a monostable multivibrator, and 8 is an alarm circuit.

Claims (1)

[Scope of utility model registration request] An amplifier for amplifying minute signals from the vibration sensor in a device that detects mechanical vibration in a rolling bearing by converting it into an electrical signal using a vibration sensor, and detects an abnormality in the rolling bearing based on the detected signal. , a bandpass filter for removing unnecessary signals, an effective value circuit that calculates the effective value from the output of the bandpass filter, and the output of the effective value detection circuit as K.
Compare the DC amplifier that amplifies the current by two times, the effective value amplified by K times, and the output from the bandpass filter, and if the output of the bandpass filter exceeds the effective value of K times, the time exceeds. A Schmitt trigger circuit that outputs pulse signals with equal time widths, a monostable multivibrator activated by the pulse signals, and an alarm that can adjust the output level to vary according to the frequency of the output signal from the monostable multivibrator. Anomaly detector for rolling bearings equipped with a circuit.