JP3560830B2 - Bolt looseness judgment device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for determining bolt looseness, and more particularly to a bolt looseness determination apparatus capable of improving the reliability of determination.
[0002]
[Prior art]
As a conventional bolt looseness measuring device, there is one disclosed in, for example, JP-A-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 exciting force sensor that converts the vibration generated in the bolt into an electric signal is provided integrally, and is configured to output the exciting force waveform and the vibration waveform detected respectively to the slack meter.
[0003]
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.
[0004]
Then, the slack meter obtains a response acceleration waveform with respect to a unit excitation force by using a waveform of a maximum excitation force and a waveform of a vibration in response to the input waveform taken in the slack meter, and calculates a ratio of these. Is compared with a previously determined threshold value to quantitatively determine the degree of loosening.
[0005]
[Problems to be solved by the invention]
As described above, in the conventional bolt looseness determination device, the vibration signal generated by the impact is determined without being resolved for each frequency band. When the characteristic of the abnormality appeared at the frequency, the abnormality could not be detected accurately.
[0006]
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 determination 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.
[0007]
b. The influence of the variation of the external force applied to the object can be prevented.
c. It is possible to know that an external force outside the proper range is applied or that the input has exceeded the proper range.
d. The amplification factor of the amplifier can be easily set to an appropriate value.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the bolt looseness determining device according to the present invention, a signal detecting unit that detects a vibration generated from the bolt to which an external force is applied as a vibration signal,External force detecting means for detecting the magnitude of the external force as an external force signal,Conversion means for converting the vibration signal into a time series signal for each of a plurality of predetermined frequency bands, and extraction means for extracting the maximum value of the time series signal for each frequency band,Reference value setting means for presetting a vibration reference value for each frequency band, and correction means for 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 an external force. , Each maximum value obtained as a result of the correction is a vibration reference value, or each maximum value is a vibration reference value obtained as a result of correction, or each maximum value obtained as a result of correction is a vibration reference value obtained as a result of correction.And comparison means for comparing with.
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.
[0009]
Then, a ratio calculating means for obtaining a ratio obtained by dividing the external force signal by a preset external force reference value and a ratio determining means for determining whether the ratio is within a predetermined range are provided,The correction by the correction means for correcting at least one of the vibration signal, the time-series signal, the maximum value, and the vibration reference value is performed based on the ratio.It is characterized by the following.
The ratio calculating means determines whether 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, whether the exciting force is too small or too large, is determined. Make sure that you have applied an inappropriate external force such as
[0010]
Furthermore, 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, and the ratio calculation means is used as the amplified external force signal as the external force signal. The conversion means shall use the amplified vibration signal as the vibration signal, and a range over detection means for detecting that the peak value of at least one of the amplified external force signal and the amplified vibration signal has exceeded a predetermined value is provided. It is characterized by.
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 so that the external force signal amplification means or vibration signal amplification means is saturated. I do.
[0011]
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 operability is improved. In addition, a decrease in the S / N ratio can be prevented, and the reliability of the determination is improved.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
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 and generates a sound, and 11 is an external force that is attached to the hammer 2 and converts an exciting force applied to the bolt 1 as an external force into an electric signal. An excitation force sensor as a detecting means. Reference numeral 12 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.
[0013]
Reference numeral 14 denotes a peak hold that holds the maximum value of the DC signal output from the rectifier 13, and reference numeral 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. Reference numeral 17 denotes a trigger detector that detects a trigger from the DC signal output from the rectifier 13.
[0014]
Reference numeral 19 denotes a ratio determiner for determining whether or not the ratio obtained by the ratio calculator 15 is within a predetermined range. Reference numeral 20 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.
[0015]
Reference numeral 3 denotes a microphone which is attached to the hammer 2 and serves as a signal detecting means for converting a striking sound produced by the struck bolt 1 into an electric signal. Reference numeral 4 denotes an amplifier which amplifies 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, for example, 9 octaves from 31.25 Hz to 16 kHz so as to cover almost 20 Hz to 20 kHz, which is a human audible range, and provides a total of 28 bands to give a resolution of 1/3 octave.
[0016]
Reference numeral 6 denotes a rectifier that rectifies a signal for each frequency band obtained from the analog BPF 5 and converts 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 compensator 8 with the sound pressure reference value as the vibration reference value stored in the reference value setting device 10 by a predetermined method, 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.
[0017]
A rectifier 31 converts a signal amplified by the amplifier 4 into a direct current. Numeral 32 denotes a peak hold for holding the maximum value of the output from the rectifier 31, and numeral 33 denotes an automatic range setting device for automatically setting the amplification factor of the amplifier 4 from 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.
[0018]
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 as an operation 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 struck sound generated 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.
[0019]
This 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, after the vibration generated in the hammer 2 by the impact is converted into an electric signal by the excitation force sensor 11, the maximum value of the vibration signal is obtained by the amplifier 12, the rectifier 13, and the peak hold 14. 20 to set the gain of the amplifier 12 so as to have an appropriate measurement range.
[0020]
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 input is twice as large as the reference value. Therefore, the gain is set so that the signal level input in the reference value setting mode becomes 50% of the measurement range.
[0021]
In this way, the amplification rate 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.
[0022]
Next, the hammer 2 hits the 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 impact in the reference value setting mode. The amplified signal is converted into a direct current by the rectifier 13. The 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.
[0023]
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 object attenuates to some extent, and thereafter the output from the peak hold 14 is stored in the reference value setting unit 16 as an external force reference value.
[0024]
Similarly, the sound wave generated by the impact is converted into an electric signal by the microphone 3 and the gain set by the first impact in the reference value setting mode is given by the amplifier 4. The amplified sound pressure signal is input to a plurality of analog BPFs 5 provided so as to pass through different frequency bands, and is separated into time-series signals for each frequency band.
[0025]
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 started by a trigger signal from 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. Is
In this way, the instantaneous maximum value for each frequency band is recorded.
[0026]
After a certain period of 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 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 impact, and the reference value setting device 10 instantaneously sets the sound intensity in each frequency band. A sound pressure reference value, which is information indicating a maximum sound pressure, is stored.
[0027]
Next, an inspection mode for inspecting an object will be described. First, the bolt 1 as an object is hit with the hammer 2. 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 to DC by the rectifier 13.
[0028]
The trigger detector 17 similarly outputs a trigger from the DC signal from the rectifier 13, and the peak hold 14 records the maximum value of the DC signal for a certain time from the trigger output to the sound pressure attenuation.
In the case of the test 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.
[0029]
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 converted into a DC signal by the rectifier 6. It is converted 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.
[0030]
In the case of the inspection mode, after a certain period of time until the sound pressure decay ends, the maximum value recorded by the peak hold 7 is input to the corrector 8, and the corrector 8 calculates an appropriate correction value from the ratio obtained from the ratio calculator 15. The maximum value obtained from the calculation and the peak hold 7 is corrected and output.
[0031]
At this time, for example, assuming that the applied external force is proportional to the generated sound and the vibration level and the sound pressure are corrected in proportion, if the ratio twice as large as the reference value is obtained by calculation, the peak hold is performed. Divide the maximum value recorded in 7 by 2. In other words, 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.
[0032]
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 device 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 predetermined relationship is deviated from a predetermined relationship.
[0033]
The predetermined relationship at this time means that, for example, in a certain frequency band, when the corrected maximum value is within a range of 80% to 120% with respect to the sound pressure reference value of the frequency band, it is normal. If the value is out of the 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 assuming that, for example, a range of 70% to 110% is normal with respect to a sound pressure reference value of the frequency band, and a comparison result signal is output when the sound pressure reference value is out of the range. Are set in advance as described above.
[0034]
Further, when the sound pressure reference value is smaller than the overall sound pressure, a comparison result signal is prevented from being erroneously output in a frequency band that is not the main component by taking measures such as releasing the lower limit of the range.
[0035]
The alarm device 18 receives the comparison result signal from the comparator 9 in each frequency band, and a criterion is determined so that when the number of comparison result signals exceeds a preset number, for example, two, it is determined to be abnormal. When it is determined, an alarm is output to the outside.
[0036]
The ratio determiner 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, when there is an input less than 1/2 or more than twice, an out-of-correction-range alarm is output.
[0037]
By limiting the range of the correction by the excitation force in this way, it is possible to reliably determine even an object in which the frequency characteristic of the impact sound generated when the excitation force changes extremely is changed. An erroneous determination due to an extreme change in force can be prevented.
[0038]
Note that the correction may be 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, the output of each analog BPF 5, the output of the rectifier 6, or one or more of the sound pressure reference values stored in the reference value setting device 10.
[0039]
Further, when the magnitude of vibration detected by the excitation force sensor 11 exceeds a predetermined value, a trigger detector 17 is provided for instructing the peak hold 14 and the peak hold 7 as extraction means to start operation. Therefore, the influence of noise and the like from the surroundings can be reduced, and the reliability of determination can be improved.
[0040]
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 conversion means, the rectifier 6, the corrector 8 as the correction means, and the comparison as the comparison means The same effect can be obtained by giving the signal to the device 9 or the like to start the storage operation of the maximum value or to start the comparison operation.
[0041]
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 outputs a range over alarm when the maximum value exceeds a predetermined relationship. I do. The range over detector 34 inputs the maximum value obtained from the peak hold 7 for the sound signal, and outputs a range over alarm when the measurement signal exceeds a predetermined relationship.
[0042]
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, a range over alarm is output.
[0043]
In addition, 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.
Furthermore, when the range is not appropriate when setting manually, the S / N ratio decreases and the reliability of the inspection decreases, but such a problem occurs because the appropriate range is set automatically. In addition, it is possible to obtain a tapping sound inspection apparatus with improved inspection reliability.
[0044]
In addition, by outputting the range over alarm immediately before the input of each signal is saturated, it is possible to prevent the erroneous determination due to the saturation of the amplifier, and to obtain a tapping sound inspection apparatus with improved inspection reliability.
The inspection can be performed at high speed by using the analog BPF.
[0045]
Embodiment 2 FIG.
FIG. 2 is a configuration diagram of an apparatus for judging looseness of a bolt, for example, a bolt tightening a power 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 other configurations are the same as those 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.
[0046]
Each of the above-mentioned standards is set based on a sample which is actually tightened with bolts. The bolt is to be tightened by a torque method using, for example, a torque wrench. With reference to pages 75-77 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 based on the fracture stress of the bolt material
σmax = 0.7σr (where σr is the breaking stress) (1)
Is determined.
[0047]
Minimum tightening stress with a tightening factor Q of 1.4 using a torque wrench
σmin = σmax / 1.4 (2)
Ask for.
By substituting the relationship of equation (1) into equation (2),
σmin = 0.5σr (3)
Get.
[0048]
The pretension to be applied to the bolt is obtained by multiplying the average stress (σmax + σmin) /2=0.6σr of the maximum and minimum tightening stresses by the effective sectional area As of the bolt.
Ff = 0.6σr (As) (4)
It becomes.
[0049]
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)
Where, dp: effective diameter of screw
dw: equivalent diameter on nut seat
μw: friction coefficient on nut seat
tan (ρ1) = μ / cos (α1)
(Μ: coefficient of friction on the thread surface, α1: flank angle in a section perpendicular to the thread)
It is.
[0050]
Here, 100 tightening portions of simulated bolts simulating the tower of the transmission line are prepared. If the target value Tf of the tightening torque to be given is 100, the tightening torque corresponding to σmax and σmin is (0.7 / 0.6) × 100 = 117, (0.5 / 0.6 ) × 100 = 83, but when the management value of the target value of the tightening torque is set to ± 3%, the tightening torque of the 100 simulated bolts is set to 95, 96, 97, 98, 100, 102. , 103, 104, 105.
[0051]
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. At this time, the vibration generated in the hammer 2 is detected as an external force applied to the bolt by the excitation force sensor 11, converted into an electric signal, and the maximum value is extracted by the peak hold 14. The maximum value extracted by the peak hold 14 is stored in the reference setting device 16 as an external force reference value. At this time, the ratio calculator 15 outputs the ratio 1. These are the same as those shown in the embodiment of FIG.
[0052]
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 obtain the sound pressure reference value. Is stored as
[0053]
Next, a variation in sound pressure is calculated for the 100 simulated bolts tightened with a tightening torque of 100. In other words, each simulated bolt is hit with the hammer 2 for 100 samples, and the maximum value of the rectified waveform in each frequency band that has passed through each analog BPF 5 of 28 bands and is rectified is stored.
[0054]
Then, the range of 100 maximum values for each frequency band, that is, the average value, the minimum value, and the maximum value (mean, min, max) of the maximum value for each frequency band are obtained, and each frequency band A1, Data set of minimum and maximum values in A2, A3,.
DAT (at100) = {A1 (mean, min, max) + A2 (mean, min, max) +... + A28 (mean, min, max)}
Get.
[0055]
Similarly, after temporarily loosening the simulation bolts completely using a torque wrench, the bolts are tightened to tightening torques 95, 96, 97, 98, and the data sets DAT (at95), DAT (at96), DAT (at97), DAT (at98) is obtained. Further, the simulation bolts are tightened to the tightening torques 102, 103, 104, and 105 to obtain DAT (at 102), DAT (at 103), DAT (at 104), and DAT (at 105).
[0056]
Subsequently, the average value, the minimum value, the maximum value, and (mean, min, max) of the maximum value when the tightening torque is changed from 97 to 103 are extracted from each data set for each frequency band. ,data set
DAT (at 97 to 103) = {A1 (mean, min, max) + A2 (mean, min, max) +... + A28 (mean, min, max)}
Ask for.
[0057]
The average value of the maximum value of the sound pressure signal for each frequency band corresponding to the tightening torques 97 to 103 obtained as described above 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.
[0058]
Similarly, assuming that the minimum value is 90 and the maximum value is 110 in the frequency band A2 whose center frequency is the second smallest, the comparison standard in the comparator 9 is set to normal within the range of 90 to 110, It is set so that the comparison result signal is output when the value becomes out of 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.
[0059]
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 is often different for each band. Make a decision. In addition, it is 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 outside the control value, for example, DAT (at95), DAT (at96), DAT (at104), DAT (at105), and DAT (at98) and DAT (at102) within the control value are Used to verify the certainty of the judgment.
[0060]
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. In addition, the standard deviation σ of the maximum value of the sound pressure signal is obtained, and those that deviate from 3σ are excluded as defective (mainly loose), and the average value and the range of variation are obtained.
[0061]
If the comparison reference is set in the comparator 9 as described above, each comparator 9 will not output a comparison result signal. The criterion is set so that the alarm device issues an alarm when sent to the device 18.
[0062]
In the case where the present invention is applied to tightening with a wrench or impact wrench, the reference range can be similarly determined from a data set when tightening is performed using a torque wrench with a tightening torque near the control limit value.
[0063]
Embodiment 3 FIG.
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. Reference numeral 53 denotes a maximum value calculator for extracting the maximum value from the output of the A / D converter 51.
[0064]
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 targets nine octaves from 31.25 to 16,000 Hz to substantially cover the human audible range of 20 to 20,000 Hz, as in the embodiment of FIG. A total of 28 bands are provided to give each resolution. 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.
[0065]
Numeral 64 denotes a corrector, which corrects the maximum value output by 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. It should be noted that 28 rectifiers 62, peak hold circuits 63, correctors 64, comparators 65, and reference value setting devices 66 are provided corresponding to the digital BPFs 61 provided for all 28 bands.
[0066]
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.
[0067]
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 a trigger signal from the trigger detector 17, and continuously operates for a certain period of time until the sound pressure generated by the impact on the target object attenuates below a predetermined value. Is 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.
[0068]
Similarly, the sound wave generated by the impact is converted to an electric signal by the microphone 3, given an appropriate gain by the amplifier 4, and then converted to 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 to a predetermined value or less. The converted digital signal is 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.
[0069]
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. The maximum value calculator 63 extracts the maximum value of the DC signal and stores it in the reference value setting device 66. In this way, the instantaneous maximum value of each frequency band is extracted and stored in the reference value setting unit 66 as a sound pressure reference value.
[0070]
By such an 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 66 instantaneously outputs the impact sound in each frequency band. A sound pressure reference value, which is information indicating a maximum sound pressure, is stored.
[0071]
Next, a determination mode for determining an object will be described. First, the bolt 1 as an object is hit with the hammer 2. 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 to DC by the rectifier 13. Similarly, the trigger detector 17 outputs a trigger signal from the DC signal from the rectifier 13, and the A / D converter 51 converts the DC signal into a digital signal for a certain time from the trigger output to the sound pressure attenuation. The maximum value calculator 53 extracts and outputs the maximum value of the digital signal.
[0072]
In the case of the determination 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 ratio between the maximum value and the external force reference value stored in the reference value setter 16. Is calculated and output.
[0073]
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 attenuation. 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.
[0074]
In the case of the determination mode, the maximum value extracted by the maximum value calculator 63 is input to the corrector 64, and the corrector 64 calculates an appropriate correction value based on the ratio obtained from the ratio calculator 15, and calculates the maximum value. The maximum value obtained from is corrected and output.
[0075]
The corrected maximum value is compared with the sound pressure reference value stored in the reference value setting device 66 by the comparator 65, and if the reference value deviates from a predetermined relationship set in advance, a comparison result signal is output to the alarm device 18. You. The predetermined relationship to be set is, for example, in a certain band, the corrected maximum value is within a range of 80% to 120% with respect to the sound pressure reference value of the band, as in the embodiment shown in FIG. It is set so that a comparison result signal is output when a certain value is out of the range, that is, when the value is out of the range, that is, less than 80% and more than 120% are out of the range. In another band, the comparison result signal is set such that the range within the range of 70% to 110% of the sound pressure reference value of the band is normal, and the range outside the range is abnormal, and the comparison result signal is output.
[0076]
If the sound pressure reference value is smaller than the overall sound pressure, a comparison result signal is prevented from being 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.
When the number of input comparison result signals exceeds a preset number, for example, two, the alarm device 18 sounds a buzzer and flashes a lamp to warn the user as a notification.
[0077]
As described above, the use of the digital BPF 61 as a method of obtaining a time-series signal for each frequency band makes it possible to reduce the size of the device, and to change the filter characteristics and add a frequency band to be diagnosed because the processing is performed by software (S / W). Can be flexibly dealt with.
[0078]
Embodiment 4 FIG.
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 obtain 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.
[0079]
In this embodiment, a wavelet transform calculator 71 is provided to obtain a time-series signal for each frequency band, and other operations are the same as those in the embodiment of FIG. In the wavelet transform, an effective value is calculated by the analysis operation, so that there is no need to provide a rectifier.
[0080]
In the drawing, reference numeral 71 denotes a wavelet transform (Wavelet Transform) calculator as a conversion means, which 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 signals are input to a maximum value calculator 63, a compensator 64, and a comparator 65 provided in 28 sets.
[0081]
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 set, a comparison result signal is output. Is output to the alarm 18.
[0082]
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 are improved, and the reliability of the determination can be improved. Further, the size of the apparatus can be reduced by using the wavelet transform operation unit.
[0083]
Embodiment 5 FIG.
FIG. 5 is a configuration diagram of a bolt looseness determination device showing still another embodiment of the present invention. Although the digital BPF is used to determine the maximum value for each frequency band in the embodiment of FIG. 3, a short-time FFT 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.
[0084]
Other operations are the same as those of the embodiment shown in FIG. In the short-time FFT, the 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 fast Fourier-transform (SFFT) calculator as a conversion means, which obtains a time-series signal for each frequency band.
[0085]
Thus, by providing the short-time FFT calculator 81 as a Fourier transformer and obtaining the time-series signal for each frequency band, the frequency resolution can be improved.
[0086]
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.
[0087]
Further, in each of the above-described embodiments, the example in which an external force is applied by a hammer is shown, but the present invention can also be applied to 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.
[0088]
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 a vibration detector may be used instead of the microphone for the striking sound. In the above embodiment, the audible frequency is referred to as sound, and the frequency range wider than this is referred to as vibration. However, in the present invention, the determination device is not limited to sound, and the sound and vibration are not limited to sound. Without distinction, it includes those due to vibration.
[0089]
Although the alarm device 18 is shown to warn, each signal and the calculated value in such determination, for example, each sound pressure reference value stored in the setting device 10 and the comparator in the embodiment of FIG. 9, a reference range for determining whether or not to output a comparison result signal, a correction value calculated by the ratio calculator 15, a corrected maximum value from each of the correctors 8 in the determination, and the like, in the form of a dot or a band. In addition, items that are displayed outside the range and are out of the range can be easily checked by, for example, being colored in red or the like, so that operability can be improved.
[0090]
The maximum value corrected by the corrector 8 may be superimposed on a 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.
[0091]
Further, instead of the sound pressure reference value and the comparison reference described in the third to fifth embodiments, a sound pressure reference value and a comparison reference obtained by the same definition method as that described in the second embodiment can be used. .
[0092]
【The invention's effect】
Since the present invention is configured as described above, it has the following effects.
[0093]
Signal detection means for detecting vibration generated from a bolt to which an external force is applied as a vibration signal,External force detecting means for detecting the magnitude of the external force as an external force signal,Conversion means for converting the vibration signal into a time series signal for each of a plurality of predetermined frequency bands, and extraction means for extracting the maximum value of the time series signal for each frequency band,Reference value setting means for presetting a vibration reference value for each frequency band, and correction means for 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 an external force. , Each maximum value obtained as a result of the correction is a vibration reference value, or each maximum value is a vibration reference value obtained as a result of correction, or each maximum value obtained as a result of correction is a vibration reference value obtained as a result of correction.Since the comparison means is provided for comparison, it is possible to prevent the influence of the variation in the magnitude of the external force in the comparison in the comparison means by correcting according to the magnitude of the external force. Is improved.
[0094]
Then, a ratio calculating means for obtaining a ratio obtained by dividing the external force signal by a preset external force reference value and a ratio determining means for determining whether the ratio is within a predetermined range are provided,The correction by the correction means for correcting at least one of the vibration signal, the time-series signal, the maximum value, and the vibration reference value is performed based on the ratio.Therefore, it can be understood that an inappropriate external force that is out of the predetermined range is applied, and the reliability of comparison can be improved.
[0095]
Furthermore, 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, and the ratio calculation means is used as the amplified external force signal as the external force signal. The conversion means shall use the amplified vibration signal as the vibration signal, and a range over detection means for detecting that the peak value of at least one of the amplified external force signal and the amplified vibration signal has exceeded a predetermined value is provided. Since the amplified external force signal and the amplified vibration signal exceed a predetermined value, that is, a large signal that saturates the external force signal amplifying means and the vibration signal amplifying means is detected and measured. Reliability can be ensured.
[0096]
In addition, an automatic gain setting means for automatically setting the gain of at least one of the external force signal amplifying means and the vibration signal amplifying means is provided, so that the amplified external force signal and the amplified vibration signal can be appropriately output. The amplification factor can be easily set to be within the range, and the operability is improved. In addition, a decrease in the S / N ratio can be prevented, and the reliability of the determination is 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 corrector, 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 device, 19 ratio judgment device, 20 range automatic setting device,
21 range over detector, 31 rectifier, 32 peak hold,
33 automatic range 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 corrector, 65 comparator,
66 Reference value setting unit, 71 Wavelet transform operation unit, 81 Short-time FFT operation unit.

Claims (4)

Signal detection means for detecting vibration generated from a bolt to which an external force is applied as a vibration signal, external force detection means for detecting the magnitude of the external force as an external force signal, and detecting the vibration signal for each of a plurality of predetermined frequency bands. Converting means for converting to a series signal; extracting means for extracting the maximum value of the time series signal for each of the frequency bands; reference value setting means for presetting a vibration reference value for each of the frequency bands; and a magnitude of the external force. Correction means for correcting at least one of the vibration signal, the time-series signal, the maximum value, and the vibration reference value in accordance with the vibration signal, the maximum value obtained as a result of the correction, A comparison means for comparing the value and each of the maximum values with the vibration reference value obtained as a result of the correction, or each of the maximum values obtained as a result of the correction with the vibration reference value obtained as a result of the correction ; To For example was the bolt of the slack determination device. Ratio calculation means and the ratio determining the ratio obtained by dividing by an external force signal preset external force reference value provided and determining ratio judging means whether it is within the predetermined range, the vibration signal and the time-series by the correction means 2. The bolt looseness judging device according to claim 1, wherein the correction for correcting at least one of the signal, the maximum value, and the vibration reference value is performed based on the ratio . 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 the vibration signal and outputting it as an amplified vibration signal, wherein the ratio calculating means uses the amplified external force signal as the external force signal The conversion means uses the amplified vibration signal as a vibration signal, and a range over detection means for detecting that at least one of the peak values of the amplified external force signal and the amplified vibration signal exceeds a predetermined value is provided. The looseness determination device for a bolt according to claim 2, wherein: 4. The bolt looseness judging device according to claim 3, further comprising automatic gain setting means for automatically setting at least one of the external force signal amplifying means and the vibration signal amplifying means .

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