JP2000131195A - Device for judging looseness of bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device for measuring looseness of a bolt that can accurately and surely perform judgment according to a hammering sound such as the inspection of a bolt looseness. SOLUTION: Vibration force when a bolt 1 is hit by a hammer 2 is detected by a vibration force sensor 11 and the ratio with an outer force reference value is obtained by a ratio arithmetic unit 15. Also, a striking sound being generated in the bolt 1 is detected by a microphone 3 and is separated into a time series signal for each frequency band by an analog BPF 5, the time series signal is rectified at that time, and the instantaneous maximum value at each frequency band is extracted by a peak hold 7. The maximum value is corrected based on a ratio that is calculated by the ratio operation unit 15 and is compared with a preset vibration reference value by a comparator 9, a comparison result signal is outputted when the comparison result deviates from a specific relationship, and an alarm 18 gives a warning as abnormal when the number of comparison result signals is, for example, equal to or more than three. The maximum value of the time series signal for each of a plurality of frequency bands is extracted for comparison, thus improving judgment reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining a bolt looseness, and more particularly to a bolt looseness determining apparatus capable of improving reliability of determination.

[0002]

2. Description of the Related Art As a conventional bolt looseness measuring device, there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 10-82714. This is because a hammer that strikes bolts and generates vibrations is provided with a vibrating force sensor that converts the vibrating force of the hammer into an electric signal, and a knock pin that is provided at the tip of the hammer so that it can freely enter and exit in the direction of impact. An excitation force sensor that converts the vibration generated in the bolt into an electric signal is provided integrally, and is configured to output the excitation force waveform and the vibration waveform detected respectively to the slack meter.

Next, the operation will be described. First, an object bolt is hit with a hammer. The exciting force generated at this time is detected by an exciting force sensor, converted into an electric signal, and input to the slack meter as an exciting force waveform. At the same time, the vibration generated in the bolt is detected by the excitation force sensor, converted into an electric signal, and input to the slack gauge as a vibration waveform.

Then, the slack meter obtains a waveform of a response acceleration with respect to a unit vibrating force by using a waveform of a maximum vibrating force and a waveform of a vibration responsive thereto, among input waveforms taken in the slack meter, These ratios are compared with a predetermined threshold value to quantitatively determine the degree of loosening.

[0005]

As described above, the conventional bolt slackness judging device judges a vibration signal generated by an impact without decomposing the vibration signal for each frequency band. In the inspection of the hammering sound, it was not possible to detect the abnormality accurately when the characteristic of the abnormality appeared in the frequency other than the main component.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain the following bolt looseness determining device. a. The reliability of the determination can be improved by comparing the state of the vibration generated by the impact with the reference state. b. Inexpensive and high-speed processing is possible. c. It can be downsized and can flexibly respond to changes in conditions.

D. The influence of the variation of the external force applied to the object can be prevented. e. Noise from the surroundings and the effects of noise can be prevented.
Further, as further improvements, f. It is possible to know that an external force outside the proper range is applied or that the input has exceeded the proper range. g. The amplification factor of the amplifier can be easily set to an appropriate value. h. The vibration reference value can be set easily and accurately, and the reliability of the determination can be improved.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, a bolt loosening judging device according to the present invention comprises a signal detecting device for detecting a vibration generated from a bolt to which an external force is applied as a vibration signal. Means, a converting means for converting the vibration signal into a time-series signal for each of a plurality of predetermined frequency bands, an extracting means for extracting the maximum value of the time-series signal for each frequency band, and a predetermined frequency And a comparing means for comparing with a vibration reference value for each band. The vibration signal is converted into a time-series signal for each of a plurality of frequency bands, and the maximum value in each of the time-series signals is extracted. Thus, the frequency resolution of the vibration signal is improved, and the maximum value from the time-series signal is improved with high sensitivity. Can be extracted. Therefore, the characteristics of the loud sound or vibration immediately after the occurrence, which is also the characteristic of the impact, can be accurately grasped and compared.

The converting means is a plurality of band filters for passing a frequency component of a predetermined frequency band of the vibration signal. The extracting means rectifies the frequency components passing through each band filter, and converts each of the rectified frequency components. It is characterized in that the largest one of the maximum values is extracted as the maximum value. If the conversion means is a bandpass filter, the processing can be performed at a high speed, and the apparatus is simple and inexpensive. In particular,
If an analog bandpass filter is used, the processing can be speeded up.
If a digital bandpass filter is used, the size can be reduced, and the condition can be flexibly changed. Further, since the extracting means extracts the maximum value from the rectified frequency components, it is possible to detect even when the maximum value is present in the negative sign part of the vibration signal, and to accurately compare even when the vibration signal is rapidly attenuated.

Further, the conversion means is a wavelet conversion means for performing a wavelet conversion of the vibration signal, and the extraction means extracts a maximum value for each frequency band based on a result of the conversion by the wavelet conversion means. If the wavelet transform unit is used, the characteristics when separating into time-series signals for each frequency band can be improved, and the reliability of determination is improved.

The converting means is a short-time fast Fourier transform means for short-time fast Fourier transform of the vibration signal,
The extracting means extracts the maximum value for each frequency band based on the conversion result by the short-time fast Fourier transform means. The use of the short-time fast Fourier transform means improves the frequency resolution.

Further, an external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of a vibration signal, a time-series signal, a maximum value, and a vibration reference value is corrected according to the magnitude of the external force. A correction means is provided. Correction is made in accordance with the magnitude of the external force to prevent the comparison means from being affected by variations in the magnitude of the external force. Also, for example, by performing different corrections according to the external force for each frequency band, it is possible to compare with high reliability even an object with a complicated structure in which the distribution of frequency components changes according to the applied external force. it can.

In addition, an external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of a signal detecting means, a converting means, an extracting means, and a comparing means when the magnitude of the external force exceeds a predetermined value. Command means for commanding the start of operation is provided. Since the operation is not started until a command is issued, there is no possibility that noise, vibration, noise, or the like in the surroundings when no command is issued is erroneously processed as a vibration signal. Therefore, the influence of these can be prevented, and the reliability of the determination is improved.

Further, there is provided external force detecting means for detecting the magnitude of the applied external force as an external force signal, and a ratio calculating means for obtaining a ratio obtained by dividing the external force signal by a preset external force reference value; Correction means for correcting the relationship between the maximum value and the vibration reference value in the comparison means by correcting at least one of the vibration signal, the time-series signal, the maximum value and the vibration reference value based on the ratio; And a ratio determining means for determining whether the value is within the range. The ratio calculating means determines whether or not the ratio between the external force and the external force reference value is within a predetermined range, that is, whether the external force applied to the object, that is, the exciting force is not too small or too large. Make sure that you have applied an inappropriate external force such as If the excitation force is too small or too large, erroneous determination can be prevented, for example, when the frequency characteristics of the vibration generated by the object are different. If you know that you have applied an inappropriate external force, you can apply the external force again,
It can be operated without using much nerves, and operability is also improved.

Further, there are provided external force signal amplifying means for amplifying the external force signal and outputting it as an amplified external force signal, and vibration signal amplifying means for amplifying the vibration signal and outputting it as an amplified vibration signal. It shall be used as an external force signal, the converting means shall use the amplified vibration signal as a vibration signal, and a range over detecting means for detecting that at least one of the peak values of the amplified external force signal and the amplified vibration signal has exceeded a predetermined value. It is characterized by having been provided. In order to ensure the reliability of the measurement, it is detected that the amplified external force signal or amplified vibration signal has exceeded a predetermined value, that is, that a large signal has been input that saturates the external force signal amplification means or vibration signal amplification means. I do.

Further, the present invention is characterized in that amplification factor automatic setting means for automatically setting the amplification factor of at least one of the external force signal amplification means and the vibration signal amplification means is provided. The amplification factor can be easily set so that the amplified external force signal and the amplified vibration signal are in an appropriate output range, and the operability is improved. Further, a decrease in the S / N ratio can be prevented, and the reliability of the determination is improved.

The comparison means stores a vibration reference value set based on a vibration signal obtained when the bolt is in a predetermined tightening state.
The vibration reference value corresponding to the tightening state of the bolt can be easily stored, and the reliability of the determination increases.

Further, the comparison means stores a vibration reference value set based on a vibration signal generated from a reference value setting bolt tightened with a predetermined tightening torque. When the vibration reference value is set based on the vibration generated from the reference value setting bolt, the vibration reference value can be set easily and accurately.

The comparing means compares the bolt with a vibration reference value based on a vibration signal generated from a reference value setting bolt tightened with a plurality of tightening torques in a predetermined range including a reference torque to be tightened. It is characterized in that it is made as described above. The reference value setting bolt includes a bolt tightened with a tightening torque near the control value, and the vibration reference value and the comparison reference can be easily and accurately set based on the vibration generated from the bolt.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the configuration diagram of FIG. In the drawing, 1 is a bolt as an object, 2 is a hammer that strikes the bolt 1 to generate a hammering sound, and 11 is an external force attached to the hammer 2 and converting an exciting force as an external force applied to the bolt 1 into an electric signal. It is a vibrating force sensor as a detecting means. 1
Reference numeral 2 denotes an amplifier for amplifying the electric signal converted by the excitation force sensor 11, and reference numeral 13 denotes a rectifier for converting the signal amplified by the amplifier 12 to DC.

Reference numeral 14 denotes a peak hold that holds the maximum value of the DC signal output from the rectifier 13, and 15 denotes a ratio calculator that calculates the ratio between the output of the peak hold 14 and the external force reference value stored in the reference value setting device 16. It is. Reference numeral 17 denotes a trigger detector that detects a trigger from a DC signal output from the rectifier 13.

Reference numeral 19 denotes a ratio determiner for determining whether the ratio obtained by the ratio calculator 15 is within a predetermined range. 2
Reference numeral 0 denotes an automatic range setting device that automatically sets the amplification factor of the amplifier 12 from the maximum value output from the peak hold 14. Reference numeral 21 denotes a range over detector that detects range over from the maximum value output from the peak hold 14.

Reference numeral 3 denotes a microphone which is attached to the hammer 2 and serves as a signal detecting means for converting a hitting sound produced by the struck bolt 1 into an electric signal. Reference numeral 4 denotes an amplifier for amplifying the electric signal converted by the microphone 3. Reference numeral 5 denotes an analog BPF as conversion means for separating a signal obtained from the amplifier 4 for each frequency band. The analog BPF 5 covers nine octaves from 31.25 Hz to 16 kHz so as to cover, for example, almost 20 Hz to 20 kHz, which is a human audible range, and provides a total of 28 bands to provide a resolution of 1/3 octave.

Reference numeral 6 denotes a rectifier for rectifying a signal for each frequency band obtained from the analog BPF 5 and converting the signal into a direct current.
Reference numeral 7 denotes a peak hold as extraction means for holding the maximum value of the output from the rectifier 6, and reference numeral 8 denotes a corrector for correcting the maximum value output from the peak hold 7 based on the ratio obtained from the ratio calculator 15. Reference numeral 9 denotes a comparator for comparing the output of the corrector 8 with the sound pressure reference value as the vibration reference value stored in the reference value setting device 10 in a predetermined manner, that is, in light of a predetermined comparison reference. Reference numeral 18 denotes an alarm device as determination means for performing an overall determination based on a comparison result signal from each of the comparators 9 and outputting an alarm when it is determined to be abnormal.

A rectifier 31 converts a signal amplified by the amplifier 4 into a direct current. Reference numeral 32 denotes a peak hold that holds the maximum value of the output from the rectifier 31, and reference numeral 33 denotes an automatic range setting device that automatically sets the amplification factor of the amplifier 4 based on the maximum value output from the peak hold 32. Numeral 34 is a range over detector for detecting range over from the maximum value output from the peak hold 32.

Next, a reference value setting mode for setting an external force reference value and a sound pressure reference value using an object serving as a reference will be described. First, the amplification factors of the amplifiers 4 and 12 are minimized. In this state, a bolt 1 tightened with a predetermined tightening torque, which is an object, is struck by a hammer 2, the generated struck sound is converted into an electric signal by a microphone 3, and the sound is converted into an analog signal by an amplifier 4, a rectifier 31, and a peak hold 32. The maximum value of the sound pressure signal that does not pass through the BPF 5 is obtained.

The maximum value is input to the automatic range setting unit 33, and the gain of the amplifier 4 is set so as to have an appropriate measurement range. Similarly, the vibration generated in the hammer 2 by the impact is converted into an electric signal by the excitation force sensor 11, and then the maximum value of the vibration signal is obtained by the amplifier 12, the rectifier 13, and the peak hold 14. 20 and sets the gain of the amplifier 12 so as to have an appropriate measurement range.

The appropriate measurement range is, for example, corrected by the difference in the excitation force as in this embodiment. If the range is 1/2 to 2 times, the maximum is 2 compared with the reference value. Since it is necessary to accept twice the input, the signal level input in this reference value setting mode is 5 times the measurement range.
The gain is set to be 0%.

In this manner, the amplification of both the vibration signal and the sound pressure signal, which are external force signals, is set by the first hit in the reference value setting mode.

Next, the hammer 2 hits a bolt 1 having no defect as a reference as an object. At this time, the vibration generated in the hammer 2 is converted into an electric signal by the excitation force sensor 11, and the amplifier 12 gives the gain set by the first hit in the reference value setting mode. This amplified signal is converted into a direct current by the rectifier 13. Trigger detector 17
Compares the DC signal from the rectifier 13 with a preset reference value, and outputs a trigger when the DC signal exceeds the reference value.

The peak hold 14 records the maximum value of the DC signal input from the rectifier 13. At this time, the operation of the peak hold 14 is started by a trigger signal from the trigger detector 17. The recording of such a maximum value is performed for a certain period of time until the sound pressure generated by the impact on the target object attenuates to some extent, and then the output from the peak hold 14 is stored in the reference value setting device 16 as an external force reference value.

Similarly, the sound wave generated by the impact is converted into an electric signal by the microphone 3, and the amplifier 4 gives the gain set by the first impact in the reference value setting mode. The amplified sound pressure signal is input to a plurality of analog BPFs 5 provided so as to pass through different frequency bands, and separated into time-series signals for each frequency band.

The time series signal separated for each frequency band by the analog BPF 5 is converted into a DC signal by the rectifier 6 and input to the peak hold 7. The maximum value recording operation of the DC signal from the rectifier 6 of the peak hold 7 is performed by the trigger detector 7.
, And is performed for a certain period of time until the sound pressure of the object is attenuated, similarly to the peak hold 14 for the vibration signal. In this way, the instantaneous maximum value for each frequency band is recorded.

After a fixed time until the sound pressure decay, the maximum value recorded by the peak hold 7 is stored in the reference setting device 10 as a sound pressure reference value. By the operation in the reference value setting mode, the reference value setting device 16 stores the external force reference value, which is information indicating the strength of the impact, and the reference value setting device 10
Stores a sound pressure reference value which is information indicating an instantaneous maximum sound pressure in each frequency band of the tapping sound.

Next, an inspection mode for inspecting an object will be described. First, a bolt 1 which is an object by a hammer 2
To blow. At this time, as in the reference value setting mode,
The vibration generated in the hammer 2 is converted into an electric signal by the excitation force sensor 11, amplified by the amplifier 12, and converted into a direct current by the rectifier 13.

The trigger detector 17 similarly outputs a trigger from the DC signal from the rectifier 13 and
Records the maximum value of the DC signal for a certain period of time from the trigger output to the sound pressure decay. In the case of the inspection mode, the maximum value recorded in the peak hold 14 is input to the ratio calculator 15 after a fixed time until the sound pressure decay, and the ratio calculator 15 sets the maximum value from the peak hold 14 and the reference value. It calculates and outputs the ratio with the external force reference value stored in the container 16.

Similarly to the reference value setting mode, the sound wave generated by the impact is converted into an electric signal by the microphone 3 and amplified by the amplifier 4, separated into a time series signal for each frequency band by the analog BPF 5, and The signal is converted into a DC signal and input to the peak hold 7. The peak hold 7 records the maximum value of the DC signal for a fixed time from the trigger output to the sound pressure decay.

In the case of the test mode, the maximum value recorded by the peak hold 7 is input to the compensator 8 after a certain period of time until the sound pressure decay, and the corrector 8 determines an appropriate value from the ratio obtained from the ratio calculator 15. The correction value is calculated, and the maximum value obtained from the peak hold 7 is corrected and output.

At this time, for example, assuming that the applied external force is proportional to the generated sound and that the correction of the vibration level and the sound pressure are performed in proportion, the ratio twice as large as the reference value is obtained by the calculation. , The maximum value recorded in the peak hold 7 is divided by two. That is, if the excitation force in the inspection mode is twice as large as the excitation force in the reference value setting mode, the maximum sound pressure obtained assuming that the sound pressure for each frequency band generated is also doubled Divide the value by 2 to convert the value to the excitation force in the reference value setting mode.

The maximum value corrected in this way is compared by the comparator 9 with the sound pressure reference value stored in the reference value setting unit 10 based on a predetermined method or a predetermined comparison reference.
In this embodiment, a comparison result signal is output to the alarm 18 when the relationship deviates from a predetermined relationship set in advance.

At this time, the predetermined relationship is, for example, that in a certain frequency band, when the corrected maximum value is within 80% to 120% of the sound pressure reference value in that frequency band, If the value is out of this range, the value is out of the range and a comparison reference is set so as to output a comparison result signal.
In another frequency band, a comparison result signal is not output when the sound pressure reference value of the frequency band is within a range of, for example, 70% to 110%, and is output when the sound pressure reference value is out of the range. Are set in advance as described above.

Further, when the sound pressure reference value is smaller than the overall sound pressure, by taking measures such as canceling the lower limit of the range, the comparison result signal is not erroneously output in the frequency band other than the main component. I do.

The alarm device 18 receives the comparison result signal from the comparator 9 in each frequency band, and determines a criterion such that when the number of comparison result signals exceeds a preset number, for example, two, it is determined to be abnormal. When an abnormality is determined, an alarm is output to the outside.

The ratio judging device 19 outputs an out-of-correction range alarm when the ratio calculated by the ratio calculator 15 exceeds a predetermined relationship. The predetermined relationship at this time is set to, for example, 1/2 to 2 times. Then, if there is an input less than や or more than twice, an out-of-correction-range alarm is output.

By thus limiting the range of the correction by the exciting force, it is possible to reliably determine the object whose frequency characteristic of the striking sound generated when the exciting force changes extremely is changed. In addition, it is possible to prevent erroneous determination due to an extreme change in the excitation force.

The correction is performed by correcting the relationship between the waveform analysis result and the sound pressure reference value, that is, the sound pressure reference value stored in the reference value setting unit 10 in the comparator 9 according to the magnitude of the vibration signal. The output of the amplifier 4 and each analog BP
Output of F5, output of rectifier 6, or reference value setting device 1
One or more of the sound pressure reference values or the like stored in 0 may be corrected.

When the magnitude of the vibration detected by the excitation force sensor 11 exceeds a predetermined value, the peak hold 1
4. Since the trigger detector 17 for instructing the start of the operation is provided to the peak hold 7 as the extracting means, the influence of noise from the surroundings can be reduced, and the reliability of the determination can be improved.

Although the trigger signal from the trigger detector 17 is given to the peak hold 7, the microphone 3, the amplifier 4, the analog BPF 5 as the converting means, the rectifier 6, the compensator 8 as the compensating means, and the comparing means The same effect can be obtained by giving the maximum value to the comparator 9 or the like to start the storage operation of the maximum value or the comparison operation.

In each of the reference value setting mode and the inspection mode, the range over detector 21 inputs the maximum value obtained from the peak hold 14 for the vibration signal, and when the maximum value exceeds a predetermined relationship, the range over is detected. Output an alarm. The range over detector 34 inputs the maximum value of the sound signal obtained from the peak hold 7, and outputs a range over alarm when the measurement signal exceeds a predetermined relationship.

The predetermined relationship at this time is set, for example, as 99% of the measurement range. In this case, when a signal exceeding 99% is input, an overrange alarm is output.

Further, by setting an appropriate measurement range in the first hit in the reference value setting mode, the trouble of manually setting the measurement range is eliminated, and the operability is improved. Further, when the range is not appropriate when setting manually, the S / N ratio is lowered and the reliability of the inspection is lowered. However, such a problem does not occur because the range is automatically set to an appropriate value. In addition, it is possible to obtain a hammering inspection apparatus with improved inspection reliability.

Further, by outputting a range over alarm immediately before the input of each signal is saturated, it is possible to prevent a false judgment due to the saturation of the amplifier and obtain a tapping sound inspection apparatus with improved inspection reliability. Becomes The inspection can be performed at high speed by using the analog BPF.

Embodiment 2 FIG. 2 is a configuration diagram of an apparatus for judging looseness of a bolt, for example, a bolt tightening a transmission tower, according to another embodiment of the present invention. In FIG. 2, the following points are different from those shown in FIG. 1, but the other configuration is the same as that shown in FIG. The maximum value of the sound pressure for each frequency band extracted by the peak hold 7 is corrected by the corrector 8 and then input to the reference setting device 10, and the reference setting device 10 determines the maximum value of the input maximum value. The difference is that an average value is obtained and used as a sound pressure reference value, a range of variation of the maximum value is determined, and a comparison reference is determined based on the range of the variation.

Each of the above-mentioned standards is set based on a sample which is actually tightened with bolts. The bolts are tightened by a torque method using, for example, a torque wrench. With reference to pages 75 to 77 of the Mechanical Engineering Handbook B1 (published on April 25, 1987, new edition), published by the Japan Society of Mechanical Engineers, B1. First, the maximum tightening stress σmax = 0.7σr (where σr is the fracture stress)... (1) is determined based on the fracture stress of the bolt material.

Assuming that the tightening coefficient Q by the torque wrench is 1.4, the minimum tightening stress σmin = σmax / 1.4 (2) is obtained. By substituting the relationship of equation (1) into equation (2), σmin = 0.5σr (3) is obtained.

The pretension to be applied to the bolt is the average stress (σmax + σmin) / 2 of the maximum and minimum fastening stress.
By multiplying 0.6σr by the effective sectional area As of the bolt, Ff = 0.6σr (As) (4)

The target value Tf of the tightening torque to be applied to obtain this pretension is: Tf = (Ff / 2) ((dp) tan (ρ1 + β) + (dw) (μw)) (5) Here, dp: effective diameter of screw dw: equivalent diameter on nut seat surface μw: friction coefficient on nut seat surface tan (ρ1) = μ / cos (α1) (μ: friction coefficient on screw surface, α1: screw thread) Flank angle in a right-angled cross section).

Here, 100 fastening portions of simulated bolts simulating the transmission tower are prepared. If the target value Tf of the tightening torque to be given is 100, σm
The tightening torque corresponding to ax and σmin is (0.7 /
0.6) × 100 = 117, (0.5 / 0.6) × 10
0 = 83, but when the management value of the target value of the tightening torque is set to plus or minus 3%, the tightening torque of the 100 simulated bolts is set to 95, 96, 97, 98, 100, 1
02, 103, 104, and 105.

First, 20 simulation bolts are tightened with a tightening torque of 100 using a torque wrench. For this, data is collected according to the procedure of the reference value setting mode described above. First, the simulation bolt is hit with the hammer 2. The vibration generated in the hammer 2 at this time is
In step 1, it is detected as an external force applied to the volt and converted into an electric signal, and the peak hold 14 extracts the maximum value. The maximum value extracted by the peak hold 14 is determined by the reference setter 16
Is stored as an external force reference value. At this time, the ratio calculator 1
5 outputs the ratio 1. These are the same as those shown in the embodiment of FIG.

On the other hand, the maximum value of the sound pressure signal extracted by the peak hold 7 passes through the compensator 8 as it is because the ratio output by the ratio calculator 15 is 1, and is input to the reference setting device 10 to be sounded. It is stored as a pressure reference value.

Next, the 1 tightened with a tightening torque of 100
Variations in sound pressure are obtained for the 00 simulated bolts. That is, each simulated bolt was hit with a hammer 2 on 100 samples, and each analog B of 28 bands was hit.
The maximum value of the waveform for each frequency band that has passed through the PF 5 and rectified is stored.

Then, the maximum value 1 for each of these frequency bands
The range of 00 variations, that is, the average value, the minimum value, and the maximum value (mean, min,
max) is calculated, and each frequency band A1, A2, A3,.
Data set of minimum value and maximum value in A28 DAT (at100) = ｛A1 (mean, min, max) + A2 (mean, min, max) +... + A28 (mean, min, max) Get｝.

Similarly, once the simulation bolts are completely loosened using a torque wrench, the tightening torques 95, 96,
97, 98, each data set DAT (at9
5), DAT (at96), DAT (at97), DA
T (at98) is obtained. Further, the simulation bolts are tightened to tightening torques 102, 103, 104,
T (at102), DAT (at103), DAT (a
t104), DAT (at105) is obtained.

Subsequently, from these data sets, the average value, the minimum value, and the maximum value of the maximum value when the tightening torque is changed between 97 and 103 (mean, min, max)
For each frequency band, and a data set DAT (at 97 to 103) = {A1 (mean, min, max) + A2 (mean, min, max) +... + A28 (mean, min, max)} Ask.

The tightening torque 97-
The average value of the maximum value of the sound pressure signal for each frequency band corresponding to 103 is set as the sound pressure reference value. Further, for example, if the minimum value is 60 and the maximum value is 120 in the frequency band A1 where the center frequency is the smallest, the comparison criterion in the comparator 9 is set to normal within the range of 60 to 120 and out of this range. Is set outside the range, and a comparison result signal is output to the alarm device 18.

Similarly, assuming that the minimum value is 90 and the maximum value is 110 in the frequency band A2 having the second lowest center frequency, the comparison criterion in the comparator 9 is 90 to 90.
It is set so that the comparison result signal is output when the inside of the range of 110 is normal and when the outside of the range is outside the range.
Hereinafter, the comparison reference is similarly set for all 28 bands. This reference is written in, for example, a flash memory card. If the target object is different, it is written to another flash memory card, and is replaced with the corresponding flash memory card for inspection.

A comparison method for determining a normal or abnormal state by comparing with a sound pressure reference value and outputting a comparison result signal, that is, a method of determining a comparison reference often differs for each band. So that accurate judgment can be made. It is also possible to set various reference values by hitting the actual object without using the simulated bolts. It is convenient. Further, a data set of the tightening torque which is out of the control value, for example, DAT (at95), DAT (at95)
AT (at 96), DAT (at 104), DAT (a
t105) and DAT (at98) and DAT in the control value
(At102) and the like are used for verifying the certainty of the determination.

In the case where each reference value is set from the data of the tapping sound of the actually installed bolt tightening point, for example, the following is performed. An expert selects and strikes 100 bolts with a hammer, and confirms the soundness of the location by sound. Then, a sound pressure reference value and a comparison reference are set in the same procedure as described above, based on the impact sound generated by the bolt whose soundness has been confirmed. Also, the standard deviation σ of the maximum value of the sound pressure signal
, And those out of 3σ are excluded as defective (mainly loose), and the average value and the range of variation are obtained, and are used as the sound pressure reference value and the comparison reference.

If the comparison reference is set in the comparator 9 as described above, each comparator 9 does not output a comparison result signal. The criterion is set so that the alarm device issues an alarm when more than one alarm device is sent.

In a case where the present invention is applied to tightening with a wrench or impact wrench, a reference range can be determined from a data set when tightening is performed using a torque wrench at a tightening torque near a control limit value. .

Embodiment 3 In the first embodiment, an analog BPF is used to determine the maximum value for each frequency band, but a digital BPF may be used. In this embodiment, a case where a digital BPF is used will be described with reference to the configuration diagram of FIG. In FIG. 3, reference numeral 51 denotes an A / D converter for converting an analog signal from the rectifier 13 into a digital signal, and reference numeral 52 denotes an A / D converter for converting an analog signal from the amplifier 4 into a digital signal. 53 is an A / D converter 5
1 is a maximum value computing unit that extracts the maximum value from the output of No. 1.

Reference numeral 61 denotes a digital BPF as conversion means for converting a digital signal into a time series signal for each frequency band. The digital BPF 61 is, for example, 9 to 31.25 to 16,000 Hz in order to cover almost 20 to 20,000 Hz which is a human audible range similarly to the embodiment of FIG.
For 28 octaves, a total of 28 bands are provided with a resolution of 1/3 octave. Reference numeral 62 denotes a rectifier for rectifying an AC signal from the digital BPF, and reference numeral 63 denotes a maximum value calculator as extraction means for extracting a maximum value from the rectified digital signal.

Reference numeral 64 denotes a corrector which corrects the maximum value output from the maximum value calculator 63 based on the ratio obtained from the ratio calculator 15 and outputs a correction value. A comparator 65 compares the output of the compensator 64 with the sound pressure reference value stored in the reference value setting device 66 by a predetermined method. The rectifier 62, the peak hold circuit 63, the compensator 64, the comparator 65, and the reference value setter 66 are digital BPs provided for all 28 bands.
28 are provided corresponding to F61, respectively.

A maximum value calculator 41 extracts the maximum value from the digital signal from the A / D converter 52 rectified by the rectifier 31. Other configurations are the same as those shown in FIG. 1, and the corresponding components are denoted by the same reference numerals and description thereof is omitted.

Next, the operation will be described. First, a reference value setting mode for setting each reference value using a reference target object will be described. The A / D converter 51 converts an analog DC signal from the rectifier 13 into a digital signal. At this time, the A / D converter 51 starts operation in response to the trigger signal from the trigger detector 17, and continuously performs the operation for a certain period of time until the sound pressure generated by the impact on the object attenuates to a predetermined value or less. Will be The maximum value calculator 53 extracts the maximum value of the digital signal from the output of the A / D converter 51, and this maximum value is stored in the reference value setting device 16 as an external force reference value.

Similarly, the sound wave generated by the impact is converted into an electric signal by the microphone 3, given an appropriate gain by the amplifier 4, and then converted into a digital signal by the A / D converter 52. At this time, the A / D converter 52 starts operating in response to a trigger signal from the trigger detector 17 and operates for a certain period of time until the sound pressure generated by the impact on the target object attenuates below a predetermined value. This converted digital signal is
The signals are input to 28 digital BPFs 61 set so as to pass through different frequency bands, and separated into time-series signals for each frequency band.

The time series signal separated for each frequency band by the digital BPF 61 is converted to a DC signal by the rectifier 62 and input to the maximum value calculator 63. Maximum value calculator 63
Extracts the maximum value of this DC signal,
To be stored. In this way, the instantaneous maximum value of each frequency band is extracted, and the reference value setting unit 66 is used as the sound pressure reference value.
Is stored in

By the operation of the reference value setting mode, the reference value setting device 16 stores the external force reference value, which is information indicating the strength of the hitting, and the reference value setting device 66 stores each frequency band of the striking sound. The sound pressure reference value, which is information indicating the instantaneous maximum sound pressure at the time, is stored.

Next, a judgment mode for judging an object will be described. First, a bolt 1 which is an object by a hammer 2
To blow. At this time, as in the reference value setting mode,
The vibration generated in the hammer 2 is converted into an electric signal by the excitation force sensor 11, amplified by the amplifier 12, and converted into a direct current by the rectifier 13. Similarly, the trigger detector 17 outputs a trigger signal from the DC signal from the rectifier 13 and outputs the trigger signal to the A / D converter 5.
1 converts a DC signal into a digital signal for a fixed time from the trigger output to the sound pressure decay. The maximum value calculator 53 extracts and outputs the maximum value of the digital signal.

In the judgment mode, the maximum value extracted by the maximum value calculator 53 is input to the ratio calculator 15, and the ratio calculator 15 calculates the maximum value and the external force reference value stored in the reference value setting device 16. Calculates and outputs the ratio.

Similarly to the reference value setting mode, the sound wave generated by the impact is converted into an electric signal by the microphone 3, amplified by the amplifier 4, and converted into a digital signal by the A / D converter 52. At this time, the operation of the A / D converter 52 is started by a trigger signal from the trigger detector 17, and is performed for a certain period of time until sound pressure decay. The digital signal is separated into a time series signal for each frequency band by a digital BPF 61, converted into a DC signal by a rectifier 62, and input to a maximum value calculator 63. The maximum value calculator 63 extracts and outputs the maximum value of the DC signal.

In the determination mode, the maximum value extracted by the maximum value calculator 63 is input to the corrector 64,
Reference numeral 4 calculates an appropriate correction value based on the ratio obtained from the ratio calculator 15, corrects the maximum value obtained from the maximum value calculator 63, and outputs the corrected value.

The corrected maximum value is compared with the sound pressure reference value stored in the reference value setting device 66 by the comparator 65. If the reference value deviates from a predetermined relationship set in advance, the comparison result signal is output to the alarm 18 Is output to The predetermined relationship to set is
As in the embodiment shown in FIG. 1, for example, in a certain band, when the corrected maximum value is within the range of 80% to 120% with respect to the sound pressure reference value of the band, it is normal. Off, ie less than 80% and 120
% Is set to be outside the range and a comparison result signal is output. In another band, a comparison result signal is set to be output as normal within a range of 70% to 110% with respect to the sound pressure reference value of the band and abnormal outside the range.

When the sound pressure reference value is smaller than the overall sound pressure, a comparison result signal is not erroneously output in a frequency band that is not the main component by taking measures such as canceling the comparison on the lower limit side. To When the number of input comparison result signals exceeds a preset number, for example, two, the alarm device 18 sounds a buzzer as a notification need and flashes a lamp to give an alarm.

As described above, by using the digital BPF 61 as a method for obtaining a time series signal for each frequency band, the size of the apparatus can be reduced, and since the processing is performed by software (S / W), the filter characteristic is changed or the frequency band to be diagnosed is changed. It is possible to flexibly cope with the addition of, for example.

Embodiment 4 FIG. 4 is a configuration diagram of a bolt slackness determination device showing still another embodiment of the present invention. Although the digital BPF is used to find the maximum value for each frequency band in the embodiment of FIG. 3, wavelet transform (Wavelet Transform) may be used. Hereinafter, the case where the wavelet transform is used will be described based on the configuration diagram of FIG.

In this embodiment, a wavelet transform operation unit 71 is provided to obtain a time-series signal for each frequency band.
This is the same as the embodiment. In the wavelet transform, an effective value is calculated by the analysis operation, so that it is not necessary to provide a rectifier.

In the figure, reference numeral 71 denotes a wavelet transform (WaveletTransform) as a transforming means.
An arithmetic unit that separates a digital sound pressure signal into a time series signal for each frequency band by expanding or reducing a basis function (mother wavelet). The wavelet-transformed signal is supplied to a maximum value calculator 6 provided in 28 sets.
3, input to the corrector 64 and the comparator 65.

The comparator 65 is compared with the sound pressure reference value stored in the reference value setting device 66 in the same manner as shown in FIGS. 1 and 3, and when a predetermined relationship is established, The comparison result signal is output to the alarm 18.

At this time, by selecting an appropriate basis function in accordance with the measured waveform and the phenomenon to be observed, the frequency separation characteristics can be improved, and the reliability of determination can be improved. In addition, the size of the apparatus can be reduced by using the wavelet transform operation unit.

Embodiment 5 FIG. FIG. 5 is a configuration diagram of a bolt looseness determination device showing still another embodiment of the present invention. In the embodiment of FIG. 3, the digital BPF is used to find the maximum value for each frequency band.
May be used. Hereinafter, the case where the short-time FFT is used will be described with reference to FIG. In this embodiment, a short-time FFT calculator 81 is provided to obtain a time-series signal for each frequency band.

Other operations are the same as those of the embodiment shown in FIG. In the short-time FFT, an effective value is calculated by the analysis operation, so that it is not necessary to provide a rectifier. In FIG. 5, reference numeral 81 denotes a short-time FF as a conversion unit.
T (SFFT: Short-Time Fast Fo)
uri-Transform) computing unit, which obtains a time-series signal for each frequency band.

As described above, the short-time F which is a Fourier transformer
By providing the FT calculator 81 and obtaining a time-series signal for each frequency band, the frequency resolution can be improved.

Therefore, the reliability of diagnosis can be improved in the case where a characteristic appears in a change in frequency due to the configuration of the wall portion by utilizing the excellent resolution of the short-time FFT. Further, the size of the apparatus can be reduced by using the short-time FFT operation unit.

In each of the above-described embodiments, a method in which an external force is applied by a hammer has been described. However, a method in which an external force is applied by other means, or a method in which an exciting force is applied by an electromagnetic wave, a cylinder, or the like, can also be used. .

In each of the above embodiments, the external force is detected by the excitation force sensor 11 and the striking sound is detected by the microphone 3, but the striking sound is detected by using a vibration detector instead of the microphone. Is also good. In the above embodiment, the audible frequency is referred to as a sound, and the frequency range wider than the audible frequency is referred to as a vibration. However, in the present invention, the determination device is not limited to the sound, and the sound and the vibration may be referred to. Without distinction, it includes those due to vibration.

Although the alarm device 18 is used to give an alarm, each signal in this determination and the calculated value, for example, each sound pressure reference value stored in the setting device 10 in the embodiment of FIG. And a range serving as a reference for determining whether or not to output a comparison result signal set in the comparator 9, a correction value calculated by the ratio calculator 15, a corrected maximum value from each corrector 8 in determination, and the like. Those that are displayed on the CRT in a band shape and are out of the range are color-coded with red or the like, so that they can be easily confirmed, and the operability can be improved.

The maximum value corrected by the corrector 8 can be superimposed on the normal range and shown so as to be visually grasped. At this time, if it is determined that the result is out of the predetermined range, the maximum value detected at that time may be displayed in red or the like.

Instead of the sound pressure reference value and the comparison reference shown in the third to fifth embodiments, the sound pressure reference value and the comparison reference obtained in the same manner as in the second embodiment are used. You can also.

[0100]

Since the present invention is configured as described above, it has the following effects.

Signal detecting means for detecting a vibration generated from a bolt to which an external force is applied as a vibration signal; converting means for converting the vibration signal into a time series signal for each of a plurality of predetermined frequency bands; Since extraction means for extracting a value for each frequency band and comparison means for comparing each maximum value with a preset vibration reference value for each frequency band are provided,
It is possible to accurately grasp the frequency distribution of the large sound pressure immediately after the occurrence, which is also a characteristic of the tapping sound, and improve the reliability of comparison.

The converting means is a plurality of band filters for passing frequency components of a predetermined frequency band of the vibration signal. The extracting means rectifies the frequency components passing through each band filter, and converts each of the rectified frequency components. Since the maximum value among the maximum values is extracted as the maximum value, if the conversion means is a band filter, the processing can be performed at a high speed, and the apparatus is simple and inexpensive. Further, since the extracting means extracts the maximum value from the rectified frequency components, it is possible to detect even when the maximum value is present in the negative sign part of the vibration signal, and to accurately compare even when the vibration signal is rapidly attenuated.

Further, the transforming means is a wavelet transforming means for wavelet transforming the vibration signal, and the extracting means extracts the maximum value for each frequency band based on the result of the conversion by the wavelet transforming means. It is possible to improve characteristics at the time of separating into time series signals for each frequency band, and it is possible to improve reliability of comparison and determination.

Since the converting means is a short-time fast Fourier transforming means and the extracting means extracts the maximum value for each frequency band based on the result of the conversion by the short-time fast Fourier transforming means, the frequency resolution is improved. be able to.

Further, an external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of a vibration signal, a time-series signal, a maximum value, and a vibration reference value is corrected according to the magnitude of the external force. Since it is characterized by the provision of a correction means, by correcting according to the magnitude of the external force,
In the comparison by the comparison means, the influence of the variation in the magnitude of the external force can be prevented, and the reliability of the comparison is improved.

An external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of a signal detecting means, a converting means, an extracting means, and a comparing means when the magnitude of the external force exceeds a predetermined value. A command means for commanding the start of operation is provided. Since the operation is not started until a command is issued, the surrounding noise, vibration, noise, etc. when there is no command may be erroneously processed as a vibration signal. There is no. Therefore, the influence of these can be prevented, and the reliability of the determination is improved.

Further, there is provided external force detecting means for detecting the magnitude of the applied external force as an external force signal, and a ratio calculating means for calculating a ratio obtained by dividing the external force signal by a preset external force reference value; Correction means for correcting the relationship between the maximum value and the vibration reference value in the comparison means by correcting at least one of the vibration signal, the time-series signal, the maximum value and the vibration reference value based on the ratio; It is characterized in that it is provided with a ratio determining means for determining whether or not it is within the range. it can.

Further, external force signal amplifying means for amplifying the external force signal and outputting it as an amplified external force signal and vibration signal amplifying means for amplifying the vibration signal and outputting it as an amplified vibration signal are provided. It shall be used as an external force signal, the converting means shall use the amplified vibration signal as a vibration signal, and a range over detecting means for detecting that at least one of the peak values of the amplified external force signal and the amplified vibration signal has exceeded a predetermined value. Since it is characterized in that it has been provided, it is detected that the amplified external force signal or the amplified vibration signal exceeds a predetermined value, that is, it is detected that a large signal is input such that the external force signal amplifying means or the vibration signal amplifying means is saturated. As a result, the reliability of the measurement can be ensured.

Further, since amplification factor automatic setting means for automatically setting the amplification factor of at least one of the external force signal amplifying means and the vibration signal amplifying means is provided, the amplified external force signal and the amplified vibration signal can be adjusted. The amplification factor can be easily set so as to be in an appropriate output range, and operability is improved.
Further, a decrease in the S / N ratio can be prevented, and the reliability of the determination is improved.

Since the comparison means stores a vibration reference value set based on a vibration signal obtained when the bolt tightening state is a predetermined state, the bolt tightening is performed. The vibration reference value according to the state can be easily stored, and the reliability of the determination can be improved.

Further, the comparison means is characterized in that it stores a vibration reference value set based on a vibration signal generated from a reference value setting bolt tightened with a predetermined tightening torque. The vibration reference value can be set based on the vibration generated from the value setting bolt, the vibration reference value can be set easily and accurately, and the reliability of comparison is improved.

The comparison means compares the bolt with a vibration reference value based on a vibration signal generated from a reference value setting bolt tightened with a plurality of tightening torques in a predetermined range including a reference torque to be tightened. The bolts for setting the reference value include those tightened with a tightening torque near the control value, and the vibration reference is easily and accurately based on the vibration generated from this bolt. Values and comparison criteria can be set, and the operation is easy and the reliability of comparison can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a bolt looseness determination device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a bolt looseness determination device according to another embodiment of the present invention.

FIG. 3 is a configuration diagram of a bolt looseness determination device according to another embodiment of the present invention.

FIG. 4 is a configuration diagram of a bolt looseness determination device according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a bolt looseness determination device according to another embodiment of the present invention.

[Explanation of symbols]

1 object (volt), 2 hammer, 3 microphone, 4 amplifier, 5 analog BPF, 6 rectifier, 7
Peak hold circuit, 8 compensator, 9 comparator, 10
Reference value setting device, 11 Excitation force sensor, 12 Amplifier,
13 rectifier, 14 peak hold, 15 ratio calculator, 16 reference value setting device, 17 trigger detector, 18
Alarm, 19 ratio judgment device, 20 range automatic setting device,
21 range over detector, 31 rectifier, 32 peak hold, 33 range automatic setting device, 34 range over detector, 41 maximum value calculator, 51, 52 A / D
Converter, 53 maximum value calculator, 61 digital BPF,
62 rectifier, 63 maximum value calculator, 64 compensator, 6
5 Comparator, 66 Reference value setting unit, 71 Wavelet transform operation unit, 81 Short-time FFT operation unit.

Claims (12)

[Claims] 1. A signal detecting means for detecting a vibration generated from a bolt to which an external force is applied as a vibration signal; a converting means for converting the vibration signal into a time series signal for each of a plurality of predetermined frequency bands; A bolt looseness judging device comprising: extracting means for extracting the maximum value of a series signal for each of the frequency bands; and comparing means for comparing each of the maximum values with a preset vibration reference value for each of the frequency bands. 2. The converting means is a plurality of bandpass filters for passing a frequency component of a predetermined frequency band of the vibration signal,
2. The method according to claim 1, wherein the extracting means rectifies the frequency components passed through the band-pass filters, and extracts the largest one of the maximum values of the rectified frequency components as the maximum value. A bolt looseness determination device as described in the above. 3. The method according to claim 1, wherein the transforming means is a wavelet transforming means for performing a wavelet transform on the vibration signal, and the extracting means extracts a maximum value for each frequency band based on a result of the transformation by the wavelet transforming means. Item 1. The bolt looseness determination device according to Item 1. 4. The short-time fast Fourier transform means for short-time fast Fourier transform of the vibration signal, and the extracting means extracts a maximum value for each frequency band based on a result of the conversion by the short-time fast Fourier transform means. 2. The bolt looseness judging device according to claim 1, wherein the bolt is loose. 5. An external force detecting means for detecting the magnitude of the applied external force, and correcting at least one of a vibration signal, a time-series signal, a maximum value, and a vibration reference value according to the magnitude of the external force. The bolt looseness judging device according to claim 1, further comprising a correcting means. 6. An external force detecting means for detecting the magnitude of the applied external force, and at least one of a signal detecting means, a converting means, an extracting means, and a comparing means when the magnitude of the external force exceeds a predetermined value. 2. The bolt looseness judging device according to claim 1, further comprising command means for commanding start of operation. 7. An external force detecting means for detecting the magnitude of the applied external force as an external force signal, and a ratio calculating means for calculating a ratio obtained by dividing the external force signal by a preset external force reference value; Correcting means for correcting at least one of the vibration signal, the time-series signal, the maximum value, and the vibration reference value based on the relationship to change the relationship between the maximum value and the vibration reference value in the comparing means; 2. The bolt looseness determining device according to claim 1, further comprising a ratio determining unit configured to determine whether the bolt is within the range. 8. An external force signal amplifying means for amplifying an external force signal and outputting it as an amplified external force signal, and a vibration signal amplifying means for amplifying a vibration signal and outputting the amplified vibration signal as an amplified vibration signal, wherein the ratio calculating means comprises the amplified external force signal. Is used as an external force signal, the converting means uses the amplified vibration signal as a vibration signal, and a range for detecting that the peak value of at least one of the amplified external force signal and the amplified vibration signal exceeds a predetermined value. The bolt looseness judging device according to claim 7, further comprising an over-detection means. 9. A bolt looseness judging device according to claim 8, further comprising amplification factor automatic setting means for automatically setting the amplification factor of at least one of the external force signal amplifying means and the vibration signal amplifying means. apparatus. 10. The apparatus according to claim 1, wherein the comparing means stores a vibration reference value set based on a vibration signal obtained when the bolt is in a predetermined tightening state. Item 10. The bolt slackness determining device according to any one of Items 9. 11. The comparison means for storing a vibration reference value set based on a vibration signal generated from a reference value setting bolt tightened with a predetermined tightening torque. The bolt looseness determination device according to claim 10. 12. The comparison means compares the bolt with a vibration reference value based on a vibration signal generated from a reference value setting bolt tightened with a plurality of tightening torques in a predetermined range including a reference torque to tighten the bolt. 12. The bolt looseness judging device according to claim 11, wherein the bolt loosening is determined.