JPS58127142A - Detector for bearing defect - Google Patents

Abstract

PURPOSE:To promptly and reliably detect the presence of a defect irrespective of a size of a bearing, the number of revolutions, a structure and the like, by a method wherein a vibrating waveform and an envelope wavelength are extracted by passing an electric signal, converted from a mechanical vibration of a bearing, through a band filter to compute and process it. CONSTITUTION:A mechanical vibration of a bearing is detected by a vibrating sensor, an electric signal output thereof, freed of a disturbance component through an amplifier 2 and a band filter 3, is inputted to an envelope circuit 4 and an effective value computer 6. An envelope waveform from the circuit 4 is supplied to an effective value computer 5. The effective values computed by the computers 5 and 6 are supplied to an indicator 8 after a ratio of an effective value of an envelope waveform to an effective value of a vibrating waveform is found by a divider 7, and the presence of a berring defect is detected through display of an envelope index thereof irrespective of the size of the bearing, the number of revolutions, a structure and the like. The value of the divider 7 is fed to an alarm circuit 9, where necessary, and if the value of the envelope index exceeds a set value, an alarm is sounded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bearing flaw detection device, and particularly to a bearing flaw detection device.
The present invention relates to a highly versatile bearing flaw detection device that can easily detect the presence or absence of flaws in a bearing, regardless of the rotational speed of the bearing, the structure around the bearing, etc.

Conventionally, in order to diagnose abnormalities in rolling bearings built into machines, the bearings are rotated, their mechanical vibrations are converted into electrical vibrations, and the effective value, average value, and peak value of the electrical vibration waveforms are calculated. Based on the magnitude of the amplitude, it was determined whether the bearing was normal or abnormal. However, the limit values that serve as criteria for determining whether a bearing is good or bad vary greatly depending on the size of the bearing, the number of rotations, and the structure around the bearing. It was necessary to create criteria for determining the quality of the product. In other words, conventional bearings
The pot detection device has poor versatility, and its simple configuration does not allow for high-precision foot measurement.

Therefore, an object of the present invention is to have sufficient versatility regardless of the size of the bearing, the number of revolutions of the bearing, and the structure around the bearing, and to be able to immediately and reliably detect the presence or absence of scratches on the bearing. The object of the present invention is to provide a detection device.

The objects and features of the present invention will be made clearer by the following examples. The following describes an example in which the bearing flaw detection device according to the present invention is applied to a rolling bearing used in a rotating system with little external vibration such as a motor or a roller, but the present invention can of course be applied to other bearings. be.

FIG. 1 is a block system diagram showing an embodiment of the bearing flaw detection device of the present invention.

Reference numeral 1 denotes a vibration sensor, which converts mechanical vibrations of a rotating bearing such as a motor or a blower into an electrical signal. When the bearing is normal and has no scratches, the electrical signal is white noise-like, and is shown by the solid line in FIG.

Furthermore, when there is abnormality in the bearing, such as sharpening or flaking, periodic shock vibrations occur, as shown by the solid line in FIG. next,
The minute electrical signal from this sensor is amplified by an amplifier 2 and then supplied to a bandpass amplifier 3 having a pass characteristic of, for example, IKHz to several tens of KHz, which transmits the signal to a drive system or a music machine included in the signal. Remove unnecessary disturbance components such as noise generated from the system and power supply noise. The output of the bandpass filter 3 is supplied to an envelope circuit 4. This envelope circuit 4 can be constructed, for example, from a parallel circuit of a diode 10 as shown in FIG. 4, a capacitor 11 and a resistor 12 connected in series. Similarly, the time constants of the capacitor 11 and the resistor 120 are larger than the period of the vibration waveform shown in FIGS. 2 and 3, and smaller than the period of the shock waveform caused by scratches on the bearing, for example, 1 m5ec to 1
An appropriate time constant of ゜m5e4 degrees is selected. Therefore, as the output of the envelope/destruction circuit 4, waveform outputs as shown by the wave sources in FIGS. 2 and 3 are obtained. The output of the envelope circuit 4 is supplied to a first effective value calculator 5. The output of the band wave filter 3 described above is also supplied to a second effective value calculator 6. The effective value calculators 5 and 6 are for calculating the root mean square direct filling, but they may be calculators that calculate not necessarily the effective value but the average value (including the root mean square value).

Next, the outputs of the first and second effective value calculators 5 and 6 are sent to the divider 7, and the effective value (average value) of the envelope waveform is divided by the effective value +ii (average value) of the vibration waveform. It is normalized and the ratio of the effective value (average value) of the envelope waveform to the effective value (average (4) direct) of the vibration waveform, that is, the envelope index is determined. When there is no hot water in the bearing, the vibration waveform of any machine is close to white noise when there is little disturbance vibration, so when normalized it becomes approximately constant. On the other hand, if there is an abnormality in which the bearing is damaged, the envelope waveform is disturbed in a DC manner, and the envelope index increases from the above-mentioned substantially constant waveform. Since the degree of disturbance in the envelope waveform is correlated with the degree of deterioration of the bearing, the deterioration state of the bearing can be known from the value of the envelope index.

The output of the divider 7 is supplied to an indicator 8, which displays the value of the envelope index to visually identify the presence or absence of scratches on the bearing.The output of the divider 7 is also supplied to an alarm circuit 9, if necessary. When the supplied envelope index exceeds a preset level, a warning tone is generated and the presence or absence of damage to the bearing can be audibly identified.

Incidentally, the divider 7 is replaced by a pair of logarithmic converters 13. as shown in FIG.
14 and a differential amplifier 15, the effective iii! Take the logarithm of (average + m) and the logarithm of the effective 1st division (average uf: ) of the vibration signal and subtract it, and then
You can also find the index.

The present invention has been described above with reference to embodiments. According to the present invention, a fixed judgment can be made for various target machines with different vibration waveform amplitudes, regardless of the size of the bearing, the rotation speed of the bearing, and the structure around the bearing. Based on the standard, it is possible to immediately compare the presence or absence of bearings between the female and the actual bearings without having to accumulate data.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the bearing high detection device according to the present invention, FIG. 2 is a diagram showing the vibration signal and envelope waveform when the bearing is free of scratches, and FIG. 3 is a diagram showing the vibration signal and envelope waveform when the bearing is not damaged. FIG. 4 is a diagram showing a specific configuration of the envelope 18# circuit in FIG. 1, and FIG. FIG. [Explanation of symbols of main parts] 3...band f-wave device, 4...envelope circuit, 5
...first arithmetic unit, 6...second arithmetic unit,
(7) 7... Third arithmetic unit, 13.14... Logarithmic converter, 15... Differential amplifier. Applicant: NSK Ltd. (8) Figure 1

Claims (1)

[Claims] 1. Converting mechanical vibrations caused by rotation of a bearing into drowsy vibrations and processing electrical signals. In a bearing flaw detection device that evaluates and detects scratches on bearings, mechanical vibrations are converted into electrical vibrations, and unnecessary disturbance components caused by disturbances different from the vibrations inherent to the rotation of the bearing are detected from electrical signals. an envelope circuit for extracting an envelope waveform from the output electrical signal waveform of the band f-wave generator; and obtaining an effective value or an average value of the envelope waveform from the output of the envelope circuit. a first arithmetic unit for obtaining an effective value or an average value of an electrical signal waveform from the output of the band r-wave generator; a third arithmetic unit that calculates a ratio with the output of the arithmetic unit and gives an envelope index;
A bearing flaw detection device characterized in that the presence or absence of a defect in a bearing is identified by evaluating the envelope 1st division index. 2. In the bearing flaw detection device according to claim 1, the third arithmetic unit is constituted by a pair of logarithmic converters and a differential amplifier to which the outputs of the pair of logarithmic converters are supplied. A bearing flaw detection device characterized by: