JPS6161055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bearing condition determining device that can always accurately determine whether a rolling bearing is abnormal due to damage, even if the rotational speed and bearing diameter change.

In recent years, the size of plants in general industries has continued to increase in size, and along with this, rotating electric machines have also become larger and the number of installed machines has increased.

Therefore, since high reliability is required for such rotating electric machines, it is necessary to perform maintenance and inspections reliably to prevent accidents.

Rolling bearings are often used in rotating electric machines because they are easy to install and use, and their maintenance must be performed more reliably because any abnormalities in these bearings can have a large effect on other parts.

Traditionally, the means to detect abnormalities in rolling bearings mainly relied on the five senses and experience of traveling maintenance personnel, and quantitative measurement methods included measuring vibration changes and acceleration,
Examples include bearing temperature measurement and acoustic measurement using a microphone as described in Japanese Patent Publication No. 48-11920.

These devices issue an alarm or turn off the power when the detected signal exceeds or deviates from a certain level (for example, Utility Model Publication No. 47-7023), but the basics are This is based on experience and lacks generality in setting standards.

In other words, even if a high vibration value is measured for a certain bearing, various factors can be considered, such as unbalance of the rotating body, vibration from the mating machine, or influence from other nearby machines, and it is difficult to determine the general abnormality. It's hard to set a standard.

Furthermore, in a DC motor or the like where the rotational speed changes significantly, not only the bearing temperature but also the vibration value fluctuates significantly, so it is difficult to discuss the relationship between this and bearing abnormality.

Furthermore, as is well known, there has been a strong call for labor saving due to the recent rise in labor costs and labor shortages, and since maintenance and inspection are no exception, the inventor proposed a large-scale automatic maintenance centralized monitoring system using electronic computers. I thought about doing it.

In such a case, it is not possible to empirically set abnormality judgment criteria for a large number of rotating machine bearings with variously different rotational speeds and other operating conditions, and a grounded setting is required.

It is generally known that damage to a rolling bearing causes high impact acceleration. When this is detected with a vibration acceleration detector (a commercially available one is available), a vibration acceleration waveform having pulses with a constant period _T1 is obtained as shown in FIG. In this drawing, the vertical axis shows vibration acceleration, and the horizontal axis shows time. "IPV" represents the peak value of vibration acceleration due to impact (hereinafter referred to as impact value), and "M" represents the effective value of vibration acceleration. These pulses appear at equal intervals of pitch T ₁ .

Figure 2 shows the changes over time in the effective value of vibration acceleration (M) and impact value (IPV) obtained until failure occurs when a type of rolling bearing is operated at a constant load and speed. This is a kind of bearing deterioration curve. Looking at this curve, the change in the effective value (M) is small, so the deterioration is not clear, but the impact value (IPV)
Since the change is large, it is possible to clearly detect when an abnormality occurs in the bearing.

An example of a measuring instrument using this property is a circuit as shown in FIG.

In FIG. 3, 1 is a vibration acceleration detector, 2 is an electric filter, 3 is an attenuator, and 4 is an amplifier. A filter 2 extracts only appropriate frequency components from the signal from the acceleration detector 1, and after attenuating or amplifying the signal depending on the magnitude of the signal, the signal reaches a changeover switch 5. This frequency uses a component that strongly appears depending on the properties of the vibration acceleration detector 1 and scratches on the bearing.

When displaying numerical values here, the maximum measured value is displayed for a certain period of time through a maximum value holding circuit 6 which has a fast rise.

7 is for manually resetting this circuit. A meter frequency generator 8 is used to prevent the scale of the display 9 from being overscaled by the input signal. One contact of the changeover switch 5 is used to control an external protection circuit depending on the magnitude of the signal from the vibration acceleration detector 1.

In this case, the semi-fixed level setting device 1 uses the bearing dimensions and the experimentally determined judgment reference value at a constant rotation speed.
It is set to 0, and when the input signal is above this level, the comparator 11 causes the next time logic 12 to count.

When a certain condition given to the time logic 12 is satisfied, the relay 13 is activated to cause the external protection circuit 14 to issue an alarm or stop the system.

That is, the impact value (IPV) is obtained with the vibration acceleration detector 1, and if the rotation speed is below a certain level, conditions such as the rotation speed are corrected with a converter, and then the pass/fail test is determined by comparing it with the standard value. Judgment is possible. For example, Japanese Patent Application Laid-Open No. 48-29478 discloses a technique for detecting flaws in a bearing by utilizing the periodicity of vibration exceeding a reference value.

However, if the machine to be measured is under operating conditions such that the rotational speed N constantly changes over time, as shown in Figure 4B, the impact value (IPV) changes from moment to moment, as shown in Figure 4A. Therefore, it is difficult to convert it into a judgment value, and as a result, abnormality monitoring of general machinery has been severely restricted.

The present invention has been made in view of the above circumstances, and its purpose is to quantify the criteria for determining abnormalities based on damage to rolling bearings, which have traditionally been extremely difficult to quantitatively control, and to further reduce the possibility of changes in machine rotational speed from time to time. The purpose of this invention is to be able to automatically calculate successive judgment criteria even in such cases.

In order to achieve this object, the bearing condition determination device of the present invention is configured to include a tachometer, a vibration meter, a conversion means, a comparison means, a counter, and an external controller. Calculating a converted impact value or a converted standard impact value by the conversion means from the standard impact value, the rotation speed measured by the tachometer, and the impact value measured by the vibration meter,
The comparison means compares the converted impact value and the standard impact value, or the impact value and the converted standard impact value, and the counter counts the number of times the former is larger in either of the comparisons within a predetermined period of time. The external controller is activated when a predetermined number of times is exceeded.

The present invention is based on _the following principle _obtained by conducting many experiments and organizing the results using statistical methods. Obtain the impact value (IPV ₀₁ ) when there is a scratch or the impact value (IPV ₀₂ ) when there is an "abnormal" level of scratch that makes it unusable, and calculate this value for the bearing of the desired rotation speed N and diameter D. Then, calculate the impact reference value for "careful" (IPV _CAUT ) or the impact reference value for "abnormal" (IPV BAD) at the rotational speed N and diameter D, and combine these with the measured impact value (IPV _CAUT ) for the desired bearing. IPV) to determine the presence or absence of damage to the bearing.

Next, we will explain its principle. When we investigated the relationship between the circumferential speed V and the impact value (IPV) of a rolling bearing with scratches, we found that as shown in Figure 5, IPV∝V〓 ……101 However, α = a constant in the range of 1.2 to 2.0, that is, the impact value It was found that (IPV) is proportional to the circumferential speed to the α power. Further experiments revealed that the relationship between the bearing diameter D and the impact value (IPV) is IPV∝D〓 ......102 where λ = constant, that is, the impact value (IPV) is proportional to the bearing diameter to the λ power. I found out. Therefore, by combining formulas 101 and 102, if the rotational speed is represented by N, then V∝ND, so IPV∝V〓D〓=(ND)〓D〓=N〓D〓 ⁺ 〓 ∴IPV∝N〓D〓 ......103 However, β = a constant in the range of 0.5 to 0.8.Of course, α and β are values obtained through experiments, but there is no need to distinguish them depending on the type of bearing, such as ball or roller bearing.

Furthermore, it is clear that this shock value IPV is almost unaffected by the load on the bearing, and that reproducibility is very good if the detection position is in direct contact with the bearing, such as in the bearing box. Summer.

After measuring the impact value (IPV) of the following new and operating machines, taking into account the results of long-term operation tests, and organizing them using statistical methods, Equation 101 and
It was found that abnormality judgments based on damage to rolling bearings, including Type 103, can be made using the following judgment formula.

IPV ₀ = IPV (N ₀ /N) = (D ₀ /D) = ......104 However, D ₀ = Reference bearing diameter (mm) D = Bearing diameter being diagnosed (mm) N ₀ = Reference rotation speed (rpm) N = Rotation speed of the bearing being diagnosed (rpm) α, β = Constants of rotation speed and bearing dimensions (same as above) IPV = Measured vibration acceleration peak value (impact value)
(g) IPV ₀ = Impact value (g) corrected for diameter and rotation speed and converted to standard dimensions and rotation speed. In other words, the impact value (IPV) measured for any bearing is calculated when the standard rotation speed and standard diameter are used. It was found that it can be converted into an impact value (IPV ₀ ). Therefore, if you set IPV ₀₁ = "CAUTION" (CAUTION) standard impact value (g) and IPV ₀₂ = "Abnormality" (BAD) standard impact value (g) for a bearing with a standard rotation speed and standard diameter, then By comparing the set value and the measured value, if IPV ₀ < IPV ₀₁ ......105, it is "normal" IPV ₀₁ IPV ₀ < IPV ₀₂ ......106, then "care is required" IPV ₀ IPV ₀₂ ...... If it is 107, it can be determined as "abnormal".

Comparison using equations 105 to 107 would be acceptable, but in the present invention, the theory is advanced as follows in order to further simplify the apparatus.

That is, by further transforming equation 104, IPV=IPV ₀ /N ₀ 〓D ₀ 〓・N〓D〓, so if K=IPV ₀ /N ₀ 〓D ₀ 〓, then IPV=KN〓D〓... ...It becomes 108. Also, if K ₁ = IPV ₀₁ /N ₀ 〓D ₀ 〓 K ₂ = IPV ₀₂ /N ₀ 〓D ₀ 〓, the reference value for comparison is IPV _CAUT = K ₁ N〓D〓 ......109 IPV _BAD =K ₂ N〓D〓 ......110, and the level of the reference value is varied to match the rotational speed and diameter of the bearing to be measured.

Therefore, by using formulas 109 and 110, the measurement results under operating conditions different from the standard state can be reduced to N.
It is possible to make a comparison by correcting it by and D, and it is possible to determine whether the bearing is "normal", "needs attention", or "abnormal".

In other words, if IPV＜IPV _CAUT ……111, it is “normal” IPV _CAUT IPV＜IPV _BAD ……112, it is “need to be careful” If IPVIPV _BAD ……113, it can be determined to be “abnormal” .

However, in reality, the impact value (IPV) can become large due to external impacts other than scratches on the bearing, so when the values of formulas 112 and 113 above are reached, a pulse is generated. It is preferable to count this number and only when it exceeds a certain number, determine that it is "necessary to be careful" or "abnormal".

An embodiment of the rolling bearing condition determining device according to the present invention will be described below with reference to FIGS. 6 and 7.

FIG. 6 is a block diagram showing one embodiment of the present invention. FIG. 7 schematically shows an example of signal waveforms at key points of each block in FIG.

Now, in FIG. 6, reference numeral 1 denotes a piezoelectric element type vibration acceleration detector mounted directly on a rolling bearing, and its output is passed through an amplifier 4 and a high-pass filter 15, which allows only high frequency components to pass.

In a damaged bearing, the waveform a is a combination of low-frequency waviness associated with rotation and a sharp impact pulse, or impact value (IPV), when a rolling element passes through a flaw, as shown in Figure 7a. Since only this impulse value (IPV) is extracted after passing through the high-pass filter 15, the waveform becomes as shown in FIG. 7b. The high-pass filter 15 is for improving the signal/noise ratio and is not absolutely necessary.

The calibration 51 is a calibration/operation signal oscillator for calibrating and checking the operation since the output per unit acceleration of the detection element 1 is different from one another, and 52 is a connection switch.

If the pulse waveform thus obtained is given a fast rise and a long time constant by the meter function generator 8a, the level corresponding to approximately the peak value will be displayed on the display via the contact of the switch 5, as shown in FIG. 7C. 9, and this alone can provide effective information.

In addition to the vibration acceleration detector 1, a rotation detector 16 such as a photoelectric type or a proximity switch is attached to the rotating machine to be measured.

17 is this amplifier, 18 is an F/V converter that converts the voltage into a DC voltage e ₀₁ proportional to the number of rotations, and the signal waveform thereof is as shown in FIG. 7d.

The rotation speed detector 16 is mainly necessary when the object to be measured is a device whose rotation speed changes from time to time, such as the DC motor of the present invention. In such a case, a generator 19 such as a DC voltage proportional to the rotational speed may be provided, the output of which may be set in relation to the rotational speed of the device, and the voltage e' ₀₁ may be extracted. This relationship is shown in FIG. 7e.

Reference numeral 20 denotes a switch for selecting two types of rotation signals: variable/fixed. 21 is the voltage e ₀₁ or
This is a converter that converts e _{′ 01 into} the voltage e ₁ ∝N〓 that will be the input for the judgment calculation _described in the principle section above. Figure 7g
It is replaced by a certain functional relationship as shown in .
This output is directed to multiplier 22.

As mentioned earlier, in order to determine whether a bearing is abnormal, the obtained shock value is corrected using the rotational speed and the bearing diameter D.
e ₀₂ is required and 23 is its setter.

FIG. 7f shows an example of the output characteristics of this setting device. Furthermore, 24 converts this into a voltage e ₂ proportional to the β power of the diameter D, that is, e ₂ ∝D〓, as shown in Fig. 7h, according to the "shaft diameter" term of the criterion equation 108 for determination. Setter 23 and converter 2 for explanation
Although 4 has been described separately, it goes without saying that one is sufficient as long as there is a variable resistor that has a fixed functional relationship.

This converted shaft diameter signal is sent to the multiplier 22 described above.
be led to.

An important point of the present invention is to perform determination calculations using the vibration signal, rotation signal, and shaft diameter signal simultaneously.

The multiplier 22 calculates e ₁ = (rotation speed) and e ₂ =
(bearing diameter) are multiplied by each other, and then multiplied by a constant K ₁ that creates a judgment criterion that requires attention to obtain a new value of voltage E ₁ =
Calculate K ₁ ×e ₁ ×e ₂ . This corresponds to expression 109 of the caution judgment criterion described in the principle section.

The level of voltage _E1 obtained in this way that changes according to the rotational speed in Fig. 7 1 gives the classification limits between the "normal" and "need caution" regions of the bearing, and is applied via the CAUT contact of the switch 33. The pulses enter the comparator 25, and in the comparator 25, only pulses having an impulse value (IPV) of this level _E1 or higher among the signals from the vibration acceleration detector 1 can reach the next waveform shaper 26. The output waveform of the comparator 25 in FIG. 7j explains this situation.

The waveform shaper 26 shapes pulses of a certain level or higher into rectangular pulses so that they can be easily counted by the counter 27 thereafter, and the output signal is as shown in FIG. 7k.

At this stage, the presence or absence of pulses above a certain level and the number of pulses are important, and the individual magnitudes are no longer an issue. The counter 27 and time logic 28 are connected in a closed loop, and determine how many counts the counter has made within a certain period of time (for example, one second). ), for example, the "Caution Required" 31 on the display 29 lights up to notify maintenance personnel. At this time, if a predetermined time elapses before the value in the time logic 28 reaches 0 or a certain number, the value in the counter 27 is automatically cleared. At this time, "normal" 32 is lit on the display 29. This relationship is schematically shown in Figure 7l. These operations are to prevent malfunctions due to accidental shock pulses.

At the same time, when the time logic 28 detects "Caution required" 31, an internal relay (not shown) is activated and the changeover switch 33 is shifted to the "BAD" side.

Then, the output of the multiplier 22 is sent to a new multiplier 34.
A higher level voltage E ₂ is set by E ₂ =K ₂ /K ₁ E ₁ =K ₂ ×e ₁ ×e ₂ . This corresponds to abnormality determination criterion formula 110 described in the principle section.

That is, this becomes the comparison value of the input shock waveform in FIG.
30 lights up, and at the same time, "Caution required" 31, which had been lit until now, goes out, clearly indicating that the bearing has already reached its usable limit. These contacts and power supply circuits are things that anyone can easily devise, so they are not specified in this paper.

Further, if external protection or alarm is required depending on the degree of damage, it is triggered by the control signal 35.

If desired, in order to quantitatively understand the damage state,
The output _E1 of the multiplier and level setter 22 is bypassed, and the impact value IPV that has passed through the bypass filter 15 is divided by the divider 36, and after correction for the rotation speed and bearing diameter, the meter After passing through the function generator 8b and the changeover switch 5,
The display 9 is caused to display values corresponding to "normal", "needs attention", and "abnormal".

According to the above configuration, the shock values (IPV ₀₁ ) and (IPV ₀₂ ) of the limits of "care required" and "abnormal" at the reference rotation speed N ₀ are tested for one bearing with the diameter D ₀ to be used as the reference. If the impact value (IPV) at a given diameter D and a given number of revolutions N is determined by
The level voltages _E1 and _E2 corresponding to the critical impact value (IPV _CAUT ) and (IPV _BAD ) are automatically calculated, and the number of pulses passing through these levels is counted to identify the presence or absence of scratches. It is possible to determine whether the damage is a serious injury requiring caution or an abnormality that cannot be used.

Next, another embodiment shown in FIG. 8 will be described.

Although FIG. 6 of the first embodiment of the present invention has been presented as having the best correspondence with theory, this proposal does not include any measure of improving circuit stability or signal/noise ratio from electrical signal processing technology. Not limited.

FIG. 8 shows a modified example in this sense.

The principle is as follows.

In other words, taking the judgment of "normal" and "needs caution" as an example, by comparing the measured impact value (IPV) and the standard impact value (IPV _CAUT ) for "needs caution", the range of "normal" is determined.
From formula 111, it can be determined by IPV/IPV _CAUT 1......114. And since the critical impact value (IPV _CAUT ) for “need caution” is formula 109, the following
Type 115 can be induced.

IPV/IPV _CAUT = (1/K ₁ N〓) x (IPV
/D〓) =1/E ₃ ×e ₃ ......115 However, K ₁ N〓=E ₃ IPV/D〓=e ₃ .

Therefore, the comparison between IPV and IPV _CAUT is (1/K ₁ N〓)
It is conceivable to multiply the term by a value obtained by dividing IPV by D〓 in advance. By processing in this way, the measured impact value (IPV), which has a wide range of values depending on the bearing diameter D, can be kept within a fairly constant numerical range, which is advantageous because the amplification factor does not become excessive in signal processing. This improves the signal/noise ratio and increases the reliability of measurements.

A modified embodiment based on this principle will be described below with reference to FIG. First, as in the case of Figure 6, 23
24 is a bearing diameter signal setting device, and 24 is a converter, which together create e ₂ ∝D〓.

The signal impulse value (IPV) that has passed through the vibration acceleration detector 1, amplifier 4, and high-pass filter 15 is sent to the divider 38.
is divided by the aforementioned axis correction signal e ₂ to obtain the calibration voltage e ₃ =IPV/e ₂ .

The signal from the rotation speed detector 16 is sent to an amplifier 17,
After selecting either the signal from the F/V converter 18 or the signal from the setting device 19 with the switch 20, the function setting device 39 creates a value of the level voltage E ₃ such that E ₃ =K ₁ N〓. This voltage E ₃ is necessary for determining whether it is "normal" or "needs caution", and it goes without saying that the multiplier 40 changes it to another reference value E ₄ for "needs caution" or "abnormal".

33 is a selection switch for E ₃ and E ₄ which is automatically turned on by a time logic (not shown).

Here, as in equation 115, the shock value e ₃ corrected by the bearing diameter earlier is divided by the level voltage E ₃ by the divider 41, and this value is sent to the comparator 42.
114, and if it is larger than 1, a pulse signal as shown in FIG. 7j is sent to the waveform shaper 26.

Hereinafter, the counter 27, time logic 28, etc. are constructed in the same manner as in FIG. 6, and determine whether "normal", "needs caution", or "abnormal", so illustrations and explanations thereof will be omitted.

Further, since the intermediate circuits to the display device 9 and the like do not particularly affect the explanation of this modification, illustrations and explanations thereof have been omitted to avoid complication.

In this way, as described in the principle section, the reliability of the measured values is improved.

Next, a further different embodiment will be described with reference to FIG.

FIG. 9 shows an embodiment of the present invention in which an electronic computer is introduced to centrally manage the bearings of a large number of rotating machines.

As mentioned above, the determination of whether a rolling bearing is "normal", "needs attention", or "abnormal" is made by measuring the vibration impact value (IPV), operating speed N, and bearing diameter D, and calculating the standard condition. The method is to correct the impact value and compare the impact value (IPV) with the judgment standard value.

As shown in FIG. 9, the outputs of the vibration acceleration detector 1 and the rotation speed detector 16 attached to each rotary machine 44 are sent to selectors 45 and 4 via amplifiers 4 and 17, respectively.
Connect to 6. The output of the tachometer from the selector 46 is passed through an analog/digital (A/D) converter 47 and is input to the computer 48 for calculating the determination level. The impact value (IPV) that has passed through the selector 45 is input to the comparator 25 via the high-pass filter 15 .

In the calculator 48, the bearing diameter D of each rotary machine 44 is separately stored. The comparator 25 includes the calculator 4
First, the value for determining whether it is “normal” or “needs attention” within 8.
A voltage E ₁ corresponding to IPV _CAUT is calculated from the rotational speed N and the bearing diameter D to create a determination level, and a digital/analog (D/A) converter 49 provides a comparison signal.

As a result, if there is a pulse that has passed through the comparator 25, it is converted into a rectangular wave by the waveform shaper 26 and sent to the computer 4.
8 is input.

In the calculator 48, one time logic is constructed, and when the pulse count number within a certain time is less than a certain number, it is "normal", and when it reaches a certain number, it is "needs attention" or "abnormal", and the judgment reference value is determined. again
Reset the voltage to E ₂ , which corresponds to IPV _BAD , and compare again. As a result, if the number of pulse counts within a certain period of time does not reach a certain value, it indicates "need to be careful", and when it reaches a certain number, it indicates "abnormal".

Therefore, one bearing is marked as ``normal'' or ``needs attention''.
After the determination of "abnormality" is completed, maintenance processing such as recording the necessary information and issuing a warning is performed, and then the diagnosis is transferred to another bearing, the selectors 45 and 46 are switched, and the determination is made in the same manner. Repeat.

By doing so, maintenance and monitoring can be carried out automatically and intensively in a factory operating a large number of rotating machines with different bearing diameters D and rotational speeds N.

As described above, in the present invention, a converted impact value or a converted standard impact value is calculated for the bearing diameter and rotation speed of a rotating machine, and these are compared with the standard impact value or impact value.
It is possible to obtain a bearing condition determination device that can make determinations of "normal", "needs attention", and "abnormal" without any trouble even under operating conditions where the rotational speed constantly fluctuates, such as with a DC motor, which was previously impossible. Furthermore, since the determination level is a quantitative value depending on the rotational speed N of the shaft and the bearing diameter D, reliability is high.

Furthermore, in the present invention, an electronic computer is used for a large number of bearings, at least the bearing diameter is memorized, judgment criteria are calculated, and the condition of each bearing is selectively judged. This makes it possible to automatically and centrally perform maintenance and monitoring of machine bearings.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can of course be implemented with various modifications without changing the gist thereof.

[Brief explanation of the drawing]

Figure 1 is a diagram of the shock waveform observed in a damaged bearing, Figure 2 is a graph of the effective value of vibration acceleration and impact value obtained during operation at a constant speed until failure occurs versus time, and Figure 3 is a diagram of the impact value versus time. A block diagram of an example of a conventional bearing condition determination device. Figures 4A and B are shock waveform diagrams and rotational speed curve diagrams when the rotational speed of a damaged bearing changes. Figure 5 is a diagram showing the peripheral speed of the bearing and the impact. A curve diagram showing the relationship between values, FIG. 6 is a block diagram of an embodiment of the bearing condition determination device of the present invention, FIG. 7 is a signal waveform diagram corresponding to each part of FIG. 6, and FIG. 8 is a different embodiment. FIG. 9 is a block diagram of a further different embodiment. 1... Vibration acceleration detector, 16... Rotation speed detector, 23... Bearing diameter setter, 22, 34... Multiplier, 25... Comparator, 27... Counter.

Claims (1)

[Claims] 1. A tachometer that measures the rotation speed of a rotating machine, a vibration meter that detects an impact value of a bearing of the rotating machine, and a vibration meter that uses the bearing diameter and the rotation speed of the rotating machine to calculate the impact value to a predetermined reference bearing. A converted shock value is calculated by converting the value between the bearing diameter and a predetermined reference rotational speed, or a predetermined reference impact value is converted into the case of a predetermined reference bearing diameter and a predetermined reference rotational speed by converting the bearing diameter of the rotating machine into the rotational speed. a conversion means for calculating a converted standard impact value by converting into a number, a comparing means for comparing the converted impact value with the standard impact value or comparing the impact value with the converted standard impact value, and a predetermined time period. a counter for counting the number of times the converted impact value is larger than the reference impact value or the number of times the impact value is larger than the converted reference impact value; and an external controller that operates in response to a signal from the counter. A bearing condition determination device comprising: