JP2000131180A - Device for inspecting airtightness of can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device for detecting the airtightness of a can where the judgment of the airtight state of the can is accurately and securely made by hammering. SOLUTION: Vibration force when a can 1 is hit by a hammer 2 is detected by a vibration force sensor 11 and the ratio of the vibration force to a vibration reference value is obtained by a ratio operation unit 15. Also, a hammering sound being generated by hitting is detected by a microphone 3 and is separated into a time series signal for each frequency band by an analog BPF 5. And the time series signal is rectified 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, is compared with a vibration reference value that is preset by a comparator 9, a judgment signal is outputted when the comparison result deviates from a specific relationship, and an alarm 18 gives a warning when the number of judgment 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 a device for judging the airtightness of a can, and more particularly to an airtightness inspection device for a can which can improve the reliability of the judgment.

[0002]

2. Description of the Related Art FIG.
It is a block diagram which shows the canned-inspection apparatus of the conventional airtightness inspection apparatus of the can shown in the 2 gazette. In the figure, reference numeral 91 denotes a can which is an object, 92 denotes a hitting rod which hits the can to generate a sound, 9
Reference numeral 3 denotes a microphone for converting a tapping sound into an electric signal, and reference numeral 94 denotes an amplifier for amplifying the electric signal converted by the microphone 93. 95 is a Wide Band Pass Filte
r, hereinafter referred to as WBPF), which is related to the internal pressure of the can.
The frequency components of 00 to 2700 Hz are extracted.

Reference numeral 96 denotes a band pass filter.
Hereinafter referred to as BPF), having a band characteristic, and having a BPF of 9
6 is separated for each frequency band. 97
Is a rectifier circuit, which rectifies a signal for each frequency band obtained from the BPF 96 and converts it into a direct current. Reference numeral 98 denotes an averaging circuit for averaging the DC signal obtained from the rectifier circuit 97. It should be noted that a plurality of BPFs 96 are provided, and the ratio of the center frequencies of the respective pass bands is made constant.
Also, a plurality of rectifier circuits 97 and an averaging circuit 98 are provided corresponding to the plurality of BPFs 96.

Reference numeral 99 denotes a frequency calculation circuit, to which a signal obtained from each averaging circuit 98 is input, and calculates a frequency having a maximum peak of a sound pressure signal of a tapping sound. A frequency gauge pressure conversion circuit 100 converts the frequency obtained from the frequency calculation circuit 98 into a gauge pressure signal. A pass / fail judgment circuit 101 judges pass / fail from the gauge pressure obtained from the frequency gauge pressure conversion circuit 100.

Next, the operation will be described. First, the can 91 as an object is hit with the hitting rod 92. The tapping sound generated at this time is detected by the microphone 93 and converted into an electric signal. The electric signal obtains an appropriate gain through the amplifier 94 and has a frequency band of 900 to 2700 Hz related to the internal pressure of the can through the WBPF 95. Extracted, B
It is input to PF96.

Next, a signal for each frequency band is extracted by a plurality of BPFs 96 having band characteristics, and a temporal average level for each frequency band is obtained by DC conversion by a rectifier circuit 97 and averaging by an averaging circuit 98. . From these average levels, the frequency calculation circuit 99 calculates the frequency at which the average level becomes the maximum level, and the frequency gauge pressure conversion circuit 100
Calculates the gauge pressure inside the can 91 from the obtained frequency. The pass / fail determination circuit 101 determines whether the gauge pressure thus obtained is within a specified pressure range, and outputs an alarm if the gauge pressure is out of the specified range.

[0007]

As described above, in the hitting sound inspection device as the conventional hitting sound judging device shown in FIG. 6, the predetermined time for each frequency band in the sound pressure signal generated by the hitting. Only the frequency at which the average level in the maximum is the maximum, that is, the frequency that is the main component, is determined. Abnormality could not be detected accurately.

Further, since the average level within a predetermined time for each frequency band is evaluated, the magnitude of the instantaneous sound pressure at a plurality of frequencies generated immediately after the impact, which is a characteristic of the impact sound, cannot be evaluated. However, there is a problem that it is not possible to distinguish between a sound pressure that has been greatly generated and a sound pressure that has a long lingering sound and a low level. This is a problem that also occurs in a tap sound determination device using Fourier transform as one of the processes for level averaging.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain the following can airtightness inspection apparatus. 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. Alternatively, it can be downsized and can flexibly respond to changes in conditions. d. Operability can be improved. e. The influence of the variation of the external force applied to the object can be prevented. f. Noise from the surroundings and the effects of noise can be prevented.

[0010]

In the airtightness inspection apparatus for a can according to the present invention, signal detection means for detecting a vibration generated from an object to which an external force is applied as a vibration signal, and a plurality of predetermined signals for detecting the vibration signal. A conversion unit for converting the time series signal into a time series signal for each frequency band; an extraction unit for extracting the maximum value of the time series signal for each frequency band; and comparing each maximum value with a preset vibration reference value for each frequency band. And a comparing means.

[0011] Since the vibration signal is converted into a time series signal for each of a plurality of frequency bands and the maximum value of each of the time series signals is extracted, the frequency resolution of the vibration signal is improved, and the sensitivity from the time series signal is improved. The maximum value can be extracted well. Therefore, it is possible to accurately grasp the characteristics of the loud sound or vibration immediately after the occurrence, which is also the characteristic of the striking sound, and make a comparison.

The converting means is a plurality of band filters for passing frequency components of a predetermined frequency band of the vibration signal, and the extracting means rectifies the frequency components passing through each band filter, and converts the rectified frequency components. The maximum value among the peak values is extracted as the maximum value.

If the conversion means is a bandpass filter, the processing can be performed at 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. In addition, since the extraction means extracts the maximum value from the rectified frequency components, it can be detected even if the maximum value is present in the negative sign portion of the vibration signal, and can be accurately compared even in the case of an object where the vibration signal rapidly attenuates. .

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 means is used, the characteristics at the time of separating the signal into time-series signals for each frequency can be improved, and the reliability of determination can be improved.

[0015] 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 a maximum value for each frequency band based on a conversion result by the short-time fast Fourier transform means. The use of the short-time Fourier 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.

Further, 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 surrounding noise, vibration, noise and the like when there is no command are erroneously processed as a vibration signal. Therefore, the influence of these can be prevented, and the reliability of comparison 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 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 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. It is made clear that an inappropriate external force that is out of this range is applied. 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 it is known that an inappropriate external force has been applied, the external force may be applied again, so that the operation can be performed without using much nerves, and the operability is 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, the fact that the amplified external force signal or the amplified vibration signal exceeds a predetermined value, that is, that a large signal that saturates the external force signal amplifying means or the vibration signal amplifying means is input. To detect.

Further, the present invention is characterized in that 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.

The amplification factor can be easily set so that the amplified external force signal and the amplified vibration signal have an appropriate output range.
Operability is improved. Further, a decrease in the S / N ratio can be prevented, and the reliability of the determination is improved.

Further, a hitting means for applying an external force to the can is rotatably supported at an intermediate portion, and has an arm having a ball formed of an elastic body at one end, and an intermediate portion between the arm supporting portion and the ball. A stopper that stops rotation at the position is provided, a spring that pulls in the direction in which the arm abuts the stopper is mounted, and a drive mechanism that pushes down the other end of the arm and opens it is provided. . By using this impact device, the external force applied to the can is stabilized, and the variation in the determination of the airtight state of the can is reduced.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. 1 is a can of an object, 2 is a hammer which strikes the can 1 and generates a sound, 11
Is a vibrating force sensor attached to the hammer 2 for converting a vibrating force into an electric signal, 12 is an amplifier for amplifying the electric signal converted by the vibrating force sensor 11, and 13 is a signal for converting the signal amplified by the amplifier 12 to DC. A rectifier to convert.

Numeral 14 is a peak hold for holding the maximum peak value of the DC signal output from the rectifier, and 15 is a ratio calculator for calculating the ratio between the output of the peak hold 14 and the external force reference value stored in the reference value setting device 16. , 17 is a rectifier 13
Is a trigger detector that detects a trigger from the DC signal output from the trigger signal.

Reference numeral 19 denotes a ratio judging unit for judging the ratio obtained by the ratio calculator 15, and 20 denotes a range automatic unit for automatically setting the amplification factor of the amplifier 12 from the peak value output from the peak hold 7 or the peak hold 14. It is a setting device. Reference numeral 21 denotes a range over detector which detects an over range from the peak value output from the peak hold 14.

Reference numeral 3 denotes a microphone which is attached to the hammer 2 and converts the hitting sound of the blown can into an electric signal. 4 denotes an amplifier which amplifies the electric signal converted by the microphone 3.
Is an analog bandpass filter (hereinafter referred to as an analog BPF) as a converting means for separating a signal obtained from the amplifier 4 for each frequency band. This analog BPF 5
For example, in order to cover almost 20 Hz to 20 kHz, which is a human audible range, nine octaves from 31.25 Hz to 16 kHz are targeted, and a total of 28 bands are provided 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 to DC. Reference numeral 7 denotes a peak hold for holding the maximum peak value of the output from the rectifier 6; A corrector for correcting the peak value output by the peak hold 7 from the obtained ratio;
Reference numeral 9 denotes a comparator for comparing the output of the compensator 8 with the value stored in the reference value setting unit 10, and reference numeral 18 denotes an overall judgment based on the comparison result from each comparator 9 to determine that an abnormality has occurred. Is an alarm that outputs an alarm to

31 is a rectifier that does not pass through the analog BPF,
32 is a peak hold for holding the maximum peak value of the output from the rectifier 31; 33 is an automatic range setting device for automatically setting the amplification factor of the amplifier 4 from the peak value output from the peak hold 32; Is an over-range detector that detects over-range from the peak value output from.

Next, a reference value setting mode for setting each 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, the can 1 as an object is hit by the hammer 2, the generated hitting sound is converted into an electric signal by the microphone 3, and the maximum value of the hitting sound signal is obtained by the rectifier 31 and the peak hold 32 that do not pass through the analog NBPF. .

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 due to 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. To set 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 the first embodiment. If the range is 1/2 to 2 times, the range is at most 2 compared to 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 way, the amplification rate of both the vibration and the sound pressure is set by the first hit in the reference value setting mode.

Next, the can 1 as a reference object is hit with the hammer 2. At this time, the vibration generated in the hammer 2 is converted into an electric signal by the excitation force sensor 11 and
At 2, the gain set by the first hit in the reference value setting mode is given. This amplified signal is converted to a rectifier 1
In step 3, it is converted to DC. The trigger detector 17 is a rectifier 13
Is compared with a preset reference value, and when the DC signal exceeds this reference value, a trigger output is performed.

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 carried out 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.

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. A plurality of amplified sound pressure signals are provided, input to an analog BPF 5 set to pass 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 started by a trigger signal from the trigger detector 17 and is performed for a certain period of time until the sound pressure of the target is attenuated similarly to the vibration peak hold 14. In this way, the instantaneous maximum value for each frequency band is recorded. 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.

By the operation in the reference value setting mode, the reference value setting device 16 stores the information indicating the strength of the impact, and the reference value setting device 10 stores the instantaneous maximum in each frequency band of the hitting sound. Information indicating the sound pressure is stored.

Next, an inspection mode for inspecting an object will be described. First, a can 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 the peak hold 14 records the maximum value of the DC signal for a certain period of time from the trigger output to the sound pressure attenuation.

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 certain period of time until the sound pressure decay, and the ratio calculator 15 determines the maximum value from the peak hold 14 as the maximum value. The ratio with respect to the reference value stored in the reference value setting device 16 is calculated and output.

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 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 fixed 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, corrected to the maximum value obtained from the peak hold 7, and output.

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

The maximum value corrected in this manner is compared with the reference value stored in the reference value setting device 10 by the comparator 9 and, when the predetermined value exceeds a predetermined relationship, an alarm 18 is issued as an alarm. Is output to

The predetermined relationship at this time is such that, for example, in a band, a corrected maximum value is set as normal within a range of 80% to 120% with respect to a vibration reference value of the band, and abnormal outside the range. Keep it. Further, in another certain band, for example, 70 to 1 with respect to the vibration reference value of the band.
It is set so that the determination is made as normal within the range of 10% and abnormal outside the range.

Further, when the vibration reference value is smaller than the overall sound pressure, the judgment signal is prevented from being erroneously output in a frequency band other than the main component by taking measures such as canceling the comparison on the lower limit side.

The alarm device 18 receives the judgment signal from the frequency band comparator 9 and outputs an alarm to the outside as an abnormality when the judgment signal exceeds a predetermined number, for example, two.

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 correction by the exciting force, it is possible to reliably inspect even an object whose frequency characteristic of a striking sound generated when the exciting force changes extremely is changed. It becomes possible.

Further, there is provided command means for commanding the start of at least one of signal detection means, conversion means, extraction means and comparison means when the magnitude of vibration exceeds a predetermined value by the trigger detector 17. Therefore, the influence of noise or the like from the surroundings can be reduced, and the reliability of determination can be improved.

Further, by starting the operation of the can airtightness inspection apparatus in response to a trigger signal from the trigger detector 17, it is possible to prevent noise from surroundings and the influence of noise, thereby improving the reliability of determination. The trigger detector 1
Although the trigger signal of 7 is given to the peak hold 14 and 7, the trigger signal is given to the vibration detector 11, the amplifier 12, the analog BPF 5, the rectifier 6, the compensator 8, the comparator 9 and the like to start the operation of storing the maximum value. Alternatively, the same effect is obtained even when the comparison operation is started.

In each of the reference value setting mode and the inspection mode, the range over detector 21 inputs the peak value obtained from the peak hold 14 for the vibration signal,
An overrange alarm is output when the peak value exceeds a predetermined relationship. The range over detector 34 inputs the peak value obtained from the peak hold 7 for the sound signal,
An overrange alarm is output 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 at 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 an airtight inspection device for cans with improved inspection reliability.

Further, by outputting a range over alarm immediately before the input of each signal is saturated, an erroneous determination due to the saturation of the amplifier is prevented, and an airtightness inspection apparatus for a can with improved inspection reliability can be obtained. It becomes possible. The inspection can be performed at high speed by using the analog BPF.

Embodiment 2 In the first embodiment, the analog BPF is used to find the maximum value for each frequency.
A digital BPF may be used. In the second embodiment, a case where a digital BPF is used will be described with reference to FIG. In FIG. 2, 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.
It is a D converter. Numeral 53 denotes a maximum value calculator as an extracting means for extracting the maximum value from the digital signal from the A / D converter 51.

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 peak value output from the maximum value calculator 63 based on the ratio obtained from the ratio calculator 15 and outputs a corrected value. Reference numeral 65 denotes a comparator as a comparing means, which outputs the output of the compensator 64 and the reference value setting device 66
Is compared with the reference value stored in. The rectifier 62,
The peak hold circuit 63, the compensator 64, the comparator 65, and the reference value setting unit 66 are digital B provided for all 28 bands.
28 are provided corresponding to the PFs 61, 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 and stores it in the reference value setting device 16 as a peak 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. The converted digital signal is input to 28 digital BPFs 61 set to pass different frequency bands, and is 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 into a DC signal by the rectifier 62,
It is input to the maximum value calculator 63. The maximum value calculator 63 is
The maximum value of the DC signal is extracted and stored in the reference value setting device 66. In this way, the instantaneous maximum value for each frequency band is extracted and stored in the reference value setting unit 66. By the operation in the reference value setting mode, the reference value setting device 16 stores the information indicating the strength of the impact, and the reference value setting device 66
Stores information indicating the instantaneous maximum sound pressure in each frequency band of the tapping sound.

Next, a judgment mode for judging an object will be described. First, the can 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 period from the trigger output to the sound pressure attenuation. The maximum value calculator 21 extracts and outputs the maximum value of the digital signal.

In the judgment mode, the maximum value extracted by the maximum value calculator 21 is input to the ratio calculator 15, and the ratio calculator 15 calculates the maximum value and the peak reference value stored in the reference value setter 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,
3 is input. The maximum value calculator 63 extracts and outputs the maximum value of the DC signal.

In the judgment 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 reference value stored in the reference value setting device 66 by the comparator 65, and is output to the alarm device 18 as an alarm when the value exceeds a predetermined relationship set in advance. The predetermined relationship to be set is, for example, 80 to 1 with respect to the reference value as in the embodiment shown in FIG.
It is set so that a judgment signal is output with a normal value within a range of 20% and an abnormal value when the value falls outside this range.
Further, in another certain band, a determination signal is output as a normal state within a range of 70 to 110% with respect to a vibration reference value of the band and an abnormal state outside the range. Alarm device 18
When the number of input determination signals exceeds a preset number, for example, two, a buzzer sounds as a notification and a lamp flashes to give an alarm.

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

Embodiment 3 FIG. 3 is a configuration diagram of an airtightness inspection device for a can according to the third embodiment. In the second embodiment, the digital BPF is used to obtain the maximum value for each frequency, but wavelet transform (Wavelet Transform) may be used. In the third embodiment, a case where a wavelet transform is used will be described with reference to FIG.

In the third embodiment, a wavelet transform calculator 71 is provided to obtain a time-series signal for each frequency band, and the other operations are the same as those in the second embodiment. The wavelet transform is
Since the effective value is calculated by the analysis operation, there is no need to provide a rectifier.

In the drawing, reference numeral 71 denotes a wavelet transform (Wavelet Transform) calculator as a conversion means, which converts a digital sound pressure signal into a time-series signal for each frequency band by expanding or reducing a basis function (mother wavelet). To separate. The wavelet-transformed signal is
28 sets of maximum value calculator 63, corrector 64, and comparator 65 are input. The comparator 65 is compared with the reference value stored in the reference value setting device 66 in the same manner as that shown in FIGS. 1 and 12, and outputs a determination signal when a predetermined relationship is established. 18 is output.

At this time, by selecting an appropriate basis function in accordance with a measured waveform or a phenomenon to be observed, the frequency separation characteristics can be improved, and the reliability of determination can be improved. Further, the size of the device can be reduced by using the wavelet transform.

Embodiment 4 FIG. 4 is a configuration diagram of an airtightness inspection device for a can according to the fourth embodiment. In the second embodiment, the digital BPF is used to find the maximum value for each frequency band, but a short-time FFT may be used. In the fourth embodiment, a case where short-time FFT is used will be described with reference to FIG. In the fourth 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 in the second embodiment. In the FFT 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 81 denotes a short-time FFT (STF
T: Short-Time Fourier-Transform) computing unit for obtaining 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, by utilizing the excellent resolution of the short-time FFT, the reliability of diagnosis can be improved in the case where a change in frequency appears due to the structure of the test object. Further, the size of the device can be reduced by using the short-time FFT transform.

Embodiment 5 FIG. Embodiment 5 is an embodiment of a hitting means for hitting a can. In the first to fourth embodiments, the inspector hits the can with a hammer. However, the magnitude of the impact varies depending on the individual and may vary depending on the degree of fatigue of the inspector as well as the mood. It is expected to be. In the fifth embodiment, an inspection is performed by a hitting device as described below so that the hitting is always constant.

FIG. 5 shows the structure of the striking device. In the figure, 110 is an arm made of an elastic body, 111 is a ball made of an elastic body, 112 is a rotating shaft that rotatably supports the arm 110, 113 is a stopper that regulates the rotating position of the arm 110, 114 is a spring for applying a rotational force to the arm, 115 is a drive mechanism for pushing down and opening the other end of the arm, and 116 is a gantry.

The ball 111 is made of an elastic material so that no noise is produced in the sound of the ball hitting the can.
Reference numeral 0 denotes a state in which the ball 111 is attached to one end, and is formed to have appropriate elasticity. Drive mechanism 11
5 is rotated once by a miniature motor, for example, to push down and open the other end 110a of the arm 110,
When the arm 110 is released, it is returned by the pulling force of the spring 114, and the ball 11 hits the can at the moment when the arm comes into contact with the stopper 113.

By using a drive mechanism 115 as a motor, remote control is possible, and a constant impact can be automatically applied to the can. By driving the can airtightness inspection device using this impact device, the accuracy of determination of airtightness of the can can be increased.

Further, in each of the above-described embodiments, the example in which an external force is applied by a hammer is shown. However, a method in which an external force is applied by other means, or a method in which an external force is applied by an electromagnetic wave or a cylinder may be used.

[0083]

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

Signal detecting means for detecting a vibration generated from a can to which an external force is applied as a vibration signal; converting means for converting the vibration signal into time-series signals for a plurality of predetermined frequency bands; Extraction means for extracting the 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. The frequency distribution of the pressure can be accurately grasped, and the reliability of comparison can be improved.

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 peak values is extracted as the maximum value, if the converting means is a band-pass filter, the processing can be performed at 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 the reliability of comparison and determination.

Since the converting means is a short-time fast Fourier transform 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 transform 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.

Further, 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 is 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 such that the external force signal amplifying means or the vibration signal amplifying means is saturated is input. As a result, the reliability of the measurement can be ensured.

[0092] 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 obtained. 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.

Further, a striking means for applying an external force to the can is rotatably supported at an intermediate portion, and has an arm having a ball formed of an elastic body at one end, and an intermediate portion between the arm supporting portion and the ball. A stopper that stops rotation at a position is provided, a spring that pulls in a direction in which the arm comes into contact with the stopper is mounted, and a driving mechanism that pushes the other end of the arm downward to open is provided. I do.
By using this impact device, the external force applied to the can is stabilized, and the variation in the determination of the airtight state of the can is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an airtightness inspection device for a can according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram of an airtightness inspection device for a can according to Embodiment 2 of the present invention.

FIG. 3 is a configuration diagram of an airtightness inspection device for a can according to Embodiment 3 of the present invention.

FIG. 4 is a configuration diagram of an airtightness inspection device for a can according to Embodiment 4 of the present invention.

FIG. 5 is a configuration diagram of a hitting device of the can airtightness inspection device.

FIG. 6 is a configuration diagram of a conventional can airtightness inspection device.

[Explanation of symbols]

1 Object (can), 2 hammer, 3 microphone, 4
Amplifier, 5 analog BPF, 6 rectifier, 7 peak hold, 8 corrector, 9 comparator, 10 reference value setter, 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, 1
9 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 ,
61 digital BPF, 62 rectifier, 53, 63 maximum value calculator, 64 corrector, 65 comparator, 66 reference value setter, 71 wavelet transform calculator, 81 short-time FFT calculator, 110 arm, 111 ball,
112 rotating shaft, 113 stopper, 114 spring, 1
15 drive mechanism, 116 mount.

Claims (10)

[Claims] 1. A signal detecting means for detecting a vibration generated from a can 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; An airtightness inspection apparatus for a can, comprising: extraction means for extracting a maximum value of a series signal for each of the frequency bands; and comparison 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 passing through the band-pass filters, and extracts a maximum value among peak values of the rectified frequency components as maximum values. An airtightness inspection device for the can described. 3. The method according to claim 1, wherein the transforming means is a wavelet transforming means for transforming the detection signal into a wavelet, 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 7. An airtightness inspection device for a can according to Item 1. 4. A short-time fast Fourier transform means for performing a short-time fast Fourier transform of a detection 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 airtightness inspection apparatus for a can according to claim 1, wherein: 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 airtightness inspection apparatus for a can according to claim 1, further comprising a correction 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 can airtightness inspection apparatus according to claim 1, further comprising a command unit for commanding the start of the 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; The vibration signal, a time-series signal, a maximum value, and a correction means for correcting at least one of the vibration reference values based on the correction means for changing a relationship between the maximum value and the vibration reference value in the comparison means. 2. The airtightness inspection device for a can according to claim 1, further comprising a ratio determination unit configured to determine whether the ratio is within a predetermined range. 8. An external force signal amplifying means for amplifying an external force signal and outputting the amplified external force signal, and a vibration signal amplifying means for amplifying the vibration signal and outputting the amplified vibration signal as an amplified vibration signal, wherein the ratio calculating means includes the amplified external force signal. Is used as an external force signal, the converting means uses the amplified external force 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. 8. The airtightness inspection apparatus for a can according to claim 7, further comprising an over-detection unit. 9. An airtightness inspection apparatus for a can according to claim 7, further comprising automatic amplification factor setting means for automatically setting the amplification factor of at least one of the external force signal amplification device and the vibration signal amplification device. . 10. A striking means for applying an external force to a can is rotatably supported at an intermediate portion, and has an arm to which a ball formed of an elastic body is attached at one end, and a supporting portion of the arm and the ball. A stopper for stopping rotation at an intermediate position of the arm is provided, a spring for pulling the arm in a direction in which the arm comes into contact with the stopper is mounted, and a drive mechanism for pushing down the other end of the arm to open it is provided. An airtightness inspection device for a can according to any one of claims 1 to 9, wherein: