JP3944784B2 - Vibration detection apparatus, vibration detection method, and inspection system - Google Patents

Description

  The present invention relates to a vibration detection device, a vibration detection method, and an inspection system.

  In automobiles and home appliances, a rotating device incorporating a motor is very often used. For example, taking an automobile as an example, rotating equipment is mounted everywhere in the engine, power steering, power seat, mission and others. Household appliances include refrigerators, air conditioners, washing machines and various other products. When the rotating device is actually operated, a sound is generated with the rotation of the motor or the like.

  Some of these sounds are inevitably generated along with normal operations, and other sounds are generated due to defects. Examples of abnormal sounds associated with the failure include bearing abnormalities, internal abnormal contact, imbalance, and foreign matter contamination. More specifically, there are gear chipping, foreign object biting, spot flaws, and abnormal noise such that the rotating part and the fixed part inside the motor rub for a moment during rotation. Further, as sounds that people feel uncomfortable, for example, there are various sounds from 20 Hz to 20 kHz that humans can hear, for example, about 15 kHz. And when the sound of the predetermined frequency component is generated, it becomes an abnormal sound. Of course, abnormal sounds are not limited to this frequency.

  The sound associated with such a defect is not only unpleasant, but may cause further failure. Further, in the case of a defective product, since smooth rotation is not performed, vibration different from that of a good product may occur during operation.

  Therefore, for the purpose of quality assurance for each of these products, production factories usually perform “sensory inspection” that relies on the five senses such as hearing and tactile sensation, and determine the presence or absence of abnormal sounds. Specifically, it is done by listening with the ear or touching it with the hand to check the vibration. The sensory test is defined by the sensory test term JIS Z8144.

  By the way, the sensory test that relies on the five senses of the inspector not only requires skilled techniques, but also results in large variations in judgment results such as individual differences and changes with time. Furthermore, there is a problem that it is difficult to convert the determination results into data and numerical values and to manage them. In order to solve such problems, there is an abnormal sound inspection system for the purpose of stable inspection based on a quantitative and clear standard. This abnormal sound inspection system is an apparatus aimed at automating the “sensory inspection” process. It measures the vibration and sound of the product drive unit with a sensor, extracts various features from the obtained vibration waveform, and detects abnormalities. The presence or absence, etc. are automatically determined. In addition, although referred to as an “abnormal sound inspection system”, quality determination based on vibration is also performed.

  The inspection system includes a microphone that collects sound and a vibration pickup that collects vibration as an input device (measuring instrument). In order to accurately transmit the vibration acceleration of the object to be measured to the vibration pickup as it is, it is necessary to integrate the vibration pickup and the object to be measured, and there is a method of screwing with a bolt for the strongest integration.

  However, for example, when the final pass / fail judgment for the manufactured product is performed using the abnormal sound inspection system, a large number of objects to be measured (inspection objects) are continuously measured by one vibration pickup. In other words, each time the vibration pickup is inspected, the product to be inspected cannot be screwed with a bolt and removed at the end of the inspection.

Therefore, when the vibration of the inspection object is acquired using the vibration pickup, as shown in FIG. 1, the vibration pickup 1 is brought into contact with the surface of the object 2 and the vibration pickup 1 is measured with a predetermined force. Vibration is measured by a pressing method in which the object 2 is pressed against the contact surface. At this time, the vibration isolator 3 is disposed on the end surface opposite to the contact surface of the vibration pickup 1 and is pressed with a predetermined force through the vibration isolator 3. As a result, vibration transmitted from the object to be measured 2 to the vibration pickup 1 is absorbed and cut off by the vibration isolator 3, and the vibration isolator 3 and the pressure pickup side that presses the vibration pickup 1 to the object to be measured 2 The vibration of the object to be measured 2 is not transmitted and can be reliably detected by the vibration pickup 1. In addition, the vertical configuration of the vibration pickup is disclosed in, for example, Patent Document 1.
7-107495

  However, the conventional techniques described above have the following problems. That is, when the vibration is measured by the pressing method, the frequency characteristics change depending on the roughness, material, and shape of the contact surface between the vibration pickup 1 and the DUT 2, so that stable vibration measurement cannot be performed. This is because the contact surface between the tip portion of the vibration pickup 1 and the object 2 to be measured is locally deformed with vibration, so that it acts as a spring, and a vibration system composed of the spring and the mass of the vibration pickup 1. It can be presumed that the resonance phenomenon (contact resonance) due to.

FIG. 2 shows a transfer characteristic with respect to a frequency obtained when a vibration generator capable of generating a vibration of an arbitrary frequency is used as the DUT 2 and the frequency is swept from 0 to 20 kHz. The vibration isolator 3 was “fluororubber sponge + α gel”, and the pressing force was 3 N / cm ² . Further, the surface of the DUT 2 was ceramic, and the contact surface of the vibration pickup 1 was titanium. If resonance vibration or the like does not occur, the transfer characteristic becomes 0 dB by picking up only the vibration of the vibration generator as it is.

  As is apparent from this figure, a peak of about +20 dB is generated around 11 to 12 kHz due to contact resonance. Since the peak position generated by the contact resonance changes every time measurement is performed, if a feature amount for detecting a defect exists at a frequency at which the contact resonance occurs, the determination cannot be performed correctly. In other words, since the fluctuation of the detection output due to the fluctuation of the frequency due to the peak due to the contact resonance is large, a slight fluctuation of the vibration frequency greatly affects the output. Can no longer be used.

  Furthermore, although illustration is omitted, since the peak occurrence location based on contact resonance varies, in the frequency band where contact resonance may occur, whether it is a waveform component based on contact resonance or a frequency component generated based on failure Cannot be distinguished, and the feature quantity cannot be extracted in such a frequency band.

  An object of the present invention is to provide a vibration detection device, a vibration detection method, and an inspection system that can detect the vibration of an object to be measured using a vibration pickup by a pressing method without being affected by contact resonance. .

  The vibration detection device according to the present invention is a vibration detection device of a pressing method provided with a vibration pickup for detecting the vibration of the object to be measured, and a low rebound rubber is mounted on the vibration detection surface of the vibration pickup with respect to the object to be measured. Thus, the contact resonance generated at the contact surface between the vibration pickup and the object to be measured is reduced.

  Further, as another solution, there is a pressing type vibration detecting device provided with a vibration pickup for detecting the vibration of the object to be measured, and a low rebound rubber is mounted on the vibration detection surface of the vibration pickup with respect to the object to be measured. Configured to do.

  And in said each invention, it is good for the thickness of the said low-resilience rubber | gum to be 2 mm or less. Furthermore, it is more preferable to make it 1 mm or less. Of course, the present invention includes those thicker than 2 mm.

  The vibration detection method according to the present invention is a vibration detection method for detecting the vibration of the measurement object with the vibration pickup in a state where the vibration pickup for detecting vibration is pressed against the measurement object. Vibration was detected with a low-rebound rubber interposed between the objects to be measured.

  The low resilience rubber is preferably attached to a vibration detection surface of the vibration pickup. In addition, it is preferable that a low repulsion rubber is interposed between the vibration pickup and the object to be measured so as not to be affected by contact resonance generated at the contact surface between the vibration pickup and the object to be measured. Furthermore, the thickness of the low repulsion rubber is 2 mm or less, and the influence of contact resonance generated at the contact surface between the vibration pickup and the object to be measured and the vibration of the high frequency component generated at the object to be measured are attenuated by the low rebound rubber. It is better not to be affected.

  Further, in the inspection system according to the present invention, the feature amount is extracted from each of the vibration detection devices described above and the vibration waveform data of the measurement object detected by the vibration detection device, and the extracted feature amount and a predetermined determination rule And an inspection device that performs pass / fail determination of the object to be measured and outputs the pass / fail determination result.

  Low-rebound rubber refers to rubber having a low rebound coefficient and rebound resilience compared to normal rubber, and is sometimes referred to as non-rebound rubber or vibration-damping rubber. Since the low-repulsion rubber absorbs the influence such as the roughness of the contact surface between the vibration pickup and the object to be measured, the low-repulsion rubber suppresses the occurrence of contact resonance or absorbs it even if it occurs. There will be no impact. In other words, a rubber that is not affected by such contact resonance can be said to be a low-resilience rubber.

Thereby, vibration generated from the object to be measured can be reliably detected even in a frequency band where contact resonance has occurred. As a result, in the inspection system, the frequency component in the frequency band can be used as the feature amount, and the quality determination can be performed with high accuracy.
The vibration pickup is also referred to as an acceleration pickup, a vibration sensor, an accelerometer, a vibration detector, an acceleration sensor, or the like, and may be any device that can detect vibration.

  In the present invention, since the low elastic rubber is interposed between the object to be measured and the vibration pickup, the vibration of the object to be measured is accurately detected by using the vibration pickup without being affected by the contact resonance. be able to.

  FIG. 3 shows an embodiment of an inspection system according to the present invention. In this example, a signal from a vibration detection sensor 11 and a microphone (not shown) that is placed in contact with or close to the object 10 to be inspected (workpiece) and the vibration detection sensor 11 are amplified by an amplifier 12 and then converted into digital data by an AD converter 13. After the change, the inspection apparatus 15 is provided. Also, the operation timing and other data are obtained from the PLC 16. Then, the inspection device 15 acquires sound data collected by the microphone and waveform data based on the vibration data collected by the vibration detection sensor 11, extracts the feature amount, and performs pass / fail determination. This result is given to the PLC 16, for example, and written in a predetermined memory area. Then, the determination result is output to the programmable display (PT) 17 connected to the PLC 16. For convenience of illustration, the PLC that provides the operation timing is the same as the PLC that manages the PT 17 that displays the pass / fail judgment result, but may be configured as a separate device.

  The inspection device 15 can be realized by, for example, a personal computer, and an application program mounted on the personal computer can be realized by configuring functional blocks as shown in FIG. That is, it comprises a preprocessing unit 15a, a calculation unit 15b, and a determination unit 15c. In the present embodiment, the AD converter 13 is provided and digital data is supplied to the inspection device 15. However, analog data may be supplied without using the AD converter 13. In that case, an AD conversion processing unit is provided in the inspection apparatus 15.

  In the pre-processing unit 15a, the feature amount can be easily extracted from the calculation target data hit by the AD converter 13 (the data recorded by the diameter data detected by the vibration detection sensor 11 or the like). Pre-processing is performed. As an example, a signal component in a predetermined frequency band is extracted by a band pass filter, a signal component in a frequency band generated in the case of a defective product or the like by high frequency component amplification processing or low frequency component amplification processing, or FFT May be analyzed. Of course, the type of preprocessing is not limited to the above, and various modifications can be made.

  The feature amount calculation unit 15b extracts a desired feature amount from the preprocessed data. The feature quantity to be extracted includes RMS (Route Mean Square Value) indicating the magnitude of the vibration level, XP indicating the average value of the data up to the nth highest vibration level of the data in one frame, In addition to AMXa indicating the average value up to the n-th highest data change amount, various types can be used. Such a feature amount is obtained for each workpiece to be inspected (measurement object 10).

  The determination unit 15c inputs the feature value extracted by the feature calculation unit 15b to the fuzzy engine, obtains an inference value indicating the degree of badness, and determines “OK”, “GRAY”, “NG” based on the inference value. Final decision and output the result.

  The vibration detection sensor 11 according to the present embodiment is mounted on the above-described inspection system. FIG. 5 shows a schematic configuration thereof, and FIG. 6 shows a specific configuration. As shown in the figure, in the present embodiment, a low rebound rubber 21 is provided at the tip 20 a of the vibration pickup 20. The low resilience rubber 21 is also referred to as non-resilience rubber or vibration damping rubber, and is a rubber having a small resilience elasticity (%) (2 to 13 in this embodiment). A vibration isolator 23 is attached to the other end of the vibration pickup 20. For example, as shown in FIG. 6, the vibration isolator 23 can have a two-layer structure of a fluororubber sponge 23a and an insulator 23b.

  When actually measuring the vibration, the low-rebound rubber 21 provided at the tip 20 a of the vibration pickup 20 is brought into contact with the object to be measured 10. Thereby, the low repulsion rubber 21 is interposed between the vibration pickup 20 and the DUT 10, so that the influence of contact resonance can be reduced. This can be presumed that the low-rebound rubber absorbs influences such as the roughness of the contact surface, so that stable measurement can be performed.

  Since the vibration detection sensor 11 is not affected by contact resonance even if vibration is detected by the pressing method, for example, even when the quality of a product such as an engine is determined using the inspection system shown in FIG. The vibration of the product can be detected with high accuracy by pressing the vibration detection sensor 11 against the product to be measured 10. That is, there is no need to fix with a bolt, and for example, vibration can be detected by simply pressing the vibration detection sensor 11 against a product flowing on the line. That is, in-line inspection is possible.

FIG. 7 and subsequent figures show the results of experiments conducted to verify the effects of the present invention. First, similarly to the experimental apparatus for obtaining the result of FIG. 2, the material of the DUT 10 is ceramic, and the surface of the tip 20a of the vibration pickup 20 is titanium. And the low resilience rubber | gum 21 used AP50 (thickness is 1 mm) of the honey night (trademark) by Inner and Outer Rubber Co., Ltd. The rebound resilience of this AP50 is 6%. The pressing force was 3 N / cm ² . Except for using the predetermined low-resilience rubber 21 as described above, the transfer characteristics with respect to frequency were measured in the same manner as in the experiment of the conventional product. As a result, an experimental result as shown in FIG. 7 was obtained. As is apparent from FIG. 7, the contact resonance with the peak occurring in the vicinity of 11 to 12 kHz is eliminated, and a flat characteristic with a transmission characteristic of approximately 0 dB is obtained from 10 kHz to 20 kHz. Of course, it is 0 dB even in a frequency band of 10 kHz or less that can be measured conventionally. As a result, it can be seen that the peak disappears and a broadband measurement is possible.

  Next, the same experiment was conducted by changing the material and thickness of the low-rebound rubber to be used. In addition, since all the low resilience rubber used for this experiment used the thing made by Inner and Outer Rubber Co., Ltd., only the model number is shown and specified below. FIG. 8 shows the results when GP35L is used as the low-rebound rubber 21 and the thickness is changed to 1, 2, and 3 mm. This GP35L has a very small impact resilience of 2%. The configuration and the experimental method other than the low resilience rubber are the same as in the case of FIG.

  Then, as is apparent from FIG. 8, when the thickness is 1 mm, it becomes flat at almost 0 dB until reaching 20 kHz. Further, as the thickness increases to 2 mm and 3 mm, the signal level of the output decreases from 10 kHz to 20 kHz. However, when the thickness is 2 mm, it is about -10 dB at 20 kHz, so that there is no practical problem. When the thickness is 3 mm, the signal level is about -20 dB at 20 kHz and the signal level is small, and there is a problem with S / N. However, if it is allowed up to -10 dB, it can be measured up to about 13 kHz, and contact resonance Unlike the above case, this experimental result is reproducible, and the obtained transfer characteristic does not change greatly every time the experiment is performed, so that it is possible to extract the feature amount in the case of a defect or the like.

  Further, although not shown, when an experiment was performed using a low-rebound rubber (GP35L) having a thickness of 0.5 mm, it was confirmed that it was constant in the vicinity of 0 dB, which was almost the same as in the case of 1 mm. In addition, since the above-mentioned four kinds of products are sold as commercial products, it was performed using the products. However, if a low-rebound rubber can be produced even with a thickness of less than 0.5 mm, sufficient effects can be exhibited. Can be estimated. That is, when the frequency exceeds 10 kHz, the amplitude of vibration becomes very small, and therefore the thickness of the low-resilience rubber is sufficiently thick even if it is 0.1 mm, for example. Therefore, when it is desired to obtain a substantially flat characteristic up to 20 kHz, the thickness of the low-rebound rubber is preferably 1 mm or less, and stable measurement is possible over a wide range even at 2 mm or less. Further, conventionally, 10 kHz or more cannot be extracted from the feature amount, and considering the variation in the frequency of occurrence of contact resonance, even if it is 5 kHz or more, it is not preferable because it causes a determination error. A sufficient effect is obtained.

  Further, GP60L was used as the low resilience rubber, and the thickness was changed to 1 m, 2 m, and 3 m, except that the experiment was performed under the same conditions as described above. As a result, the transmission characteristics shown in FIG. 9 (thickness 1 mm), FIG. 10 (thickness 2 mm), and FIG. 11 (thickness 3 mm) were obtained. Similar to GP35L, GP60L has a low rebound resilience of 2% and is different in other characteristics. As is apparent from the figure, when the thickness is 1 mm, it is almost flat up to 20 kHz, and the signal level decreases in the frequency band of 10 kHz or more as the thickness increases. Although this material was also tested several times, almost the same results were obtained and there was little variation.

  Next, AP30 (rebound resilience is 8%) having a thickness of 0.5 mm was used as the low resilience rubber, except that the experiment was performed under the same conditions as described above. As a result, as shown in FIG. 12, a substantially flat characteristic was obtained at 20 kHz or less.

  Next, an experiment was performed by changing the material of the object to be measured. Specifically, an acrylic plate (thickness 1 mm) was attached to the surface of the vibration generator used in the above experiment, and the other conditions were the same as above. The low resilience rubber used was AP50, and the thicknesses of 1 mm, 2 mm, and 3 mm were examined. As a result, transfer characteristics as shown in FIG. 13 were obtained. On the other hand, as a comparative example, an experiment was performed using a sensor having a conventional configuration in which a low resilience rubber was not provided on the surface of the vibration generator attached to the surface of the vibration generator as in the above example. As a result, the result shown in FIG. Obtained.

  As is clear from FIG. 13, the signal level drops even at a thickness of 1 mm in the vicinity of 20 kHz. However, as described above, the degree of signal level attenuation and the state of occurrence are constant at each thickness. Compared with the comparative example without the low elastic rubber shown in FIG. 14, it can be said that the low elastic rubber of any thickness exhibits a sufficiently effective effect.

  Further, although not specifically shown, when an experiment was conducted using a low-rebound rubber having a rebound resilience of 12% and a thickness of 1 mm, an experimental result of a low-rebound rubber having a rebound resilience of 6% and a thickness of 1 mm (FIG. 7, It was found that substantially the same characteristics as in FIG. 13) were obtained, and the influence of contact resonance could be reduced. Also, when the resilience is 12% and the thickness is 2 mm, the characteristics are almost the same as the experimental results (FIG. 13) of the low resilience rubbers each having the resilience of 6% and the thickness of 2 mm and 3 mm even when the thickness is 3 mm. was gotten.

  Furthermore, low-rebound rubber having a rebound resilience of 13% is also commercially available, and when the same experiment was attempted at 1 mm, 2 mm, and 3 mm, the rebound resilience was the same as that of 12%, and the same experimental results were obtained. Obtained (results almost the same as those in FIGS. 7 and 13).

  Furthermore, as for the thickness of the low resilience rubber, experimental results of 1 mm, 2 mm, and 3 mm were shown, but in addition, five types of low resilience rubbers of 5 mm, 10 mm, 15 mm, 20 mm, and 30 mm were commercially available. Yes. It was confirmed from the experimental results that these five types of low-resilience rubbers with different thicknesses can reduce the influence of contact resonance occurring on the contact surface between the vibration pickup and the object to be measured. (However, on the other hand, it was also found that the vibration of the high frequency component generated in the object to be measured is attenuated by the low rebound rubber).

Each of the above experiments was performed with a pressing force of 3 N / cm ² , but it was confirmed that the same effect can be obtained even if the pressing force is changed. As an example, experimental results when the pressing force is 10 N / cm ² are shown. The thickness of the low-rebound rubber used at this time was 1 mm, and the rebound resilience was 2%, which was measured 10 times. As shown in FIG. 15, in the conventional configuration in which the low resilience rubber is not mounted, a large peak occurs in the transmission characteristic within the range of 10 to 20 kHz due to the influence of contact resonance, and the occurrence position varies, but the low resilience In the case of the product of the present invention mounted with rubber, it was confirmed that the influence of contact resonance was suppressed as shown in FIG.

It is a figure which shows a prior art example. It is a graph which shows the conventional measurement. It is a figure showing one suitable embodiment of an inspection system concerning the present invention. It is a figure which shows the internal structure of a test | inspection apparatus. It is a figure which shows suitable one Embodiment of the vibration detection apparatus (vibration detection sensor) which concerns on this invention. It is a figure which shows suitable one Embodiment of the vibration detection apparatus (vibration detection sensor) which concerns on this invention. It is an experimental result for demonstrating the effect of this invention. It is an experimental result for demonstrating the effect of this invention. It is an experimental result for demonstrating the effect of this invention. It is an experimental result for demonstrating the effect of this invention. It is an experimental result for demonstrating the effect of this invention. It is an experimental result for demonstrating the effect of this invention. It is an experimental result for demonstrating the effect of this invention. It is an experimental result (comparative example) for demonstrating the effect of this invention. It is an experimental result (comparative example) for demonstrating the effect of this invention. It is an experimental result for demonstrating the effect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Measured object 11 Vibration detection sensor 12 Amplifier 13 AD converter 15 Inspection apparatus 16 PLC
17 Programmable Display 20 Vibration Pickup 21 Low Rebound Rubber 23 Vibration Isolator 23a Fluoro Rubber Sponge 23b Insulator

Claims (7)

A vibration detection device of a pressing type equipped with a vibration pickup for detecting the vibration of an object to be measured,
A vibration detecting apparatus, wherein a low-rebound rubber is attached to a vibration detection surface of the vibration pickup with respect to an object to be measured to reduce contact resonance occurring on the contact surface between the vibration pickup and the object to be measured. A vibration detection device of a pressing type equipped with a vibration pickup for detecting the vibration of an object to be measured,
A vibration detection apparatus comprising a low-rebound rubber mounted on a vibration detection surface of the vibration pickup with respect to an object to be measured. A vibration detection method for detecting vibration of a measurement object with the vibration pickup in a state where a vibration pickup for detecting vibration is pressed against the measurement object,
A vibration detection method, wherein vibration is detected in a state where a low repulsion rubber is interposed between the vibration pickup and the object to be measured.   The vibration detection method according to claim 3, wherein the low resilience rubber is attached to a vibration detection surface of the vibration pickup.   4. A low repulsion rubber is interposed between the vibration pickup and the object to be measured, so that it is not affected by contact resonance generated at the contact surface between the vibration pickup and the object to be measured. The vibration detection method described in 1.   The thickness of the low rebound rubber is 2 mm or less, the influence of contact resonance that occurs at the contact surface between the vibration pickup and the object to be measured, and the influence that the vibration of the high frequency component that occurs at the object to be measured is attenuated by the low rebound rubber. The vibration detection method according to claim 5, wherein the vibration detection method is not received. The vibration detection device according to claim 1 or 2,
A feature value is extracted from the vibration waveform data of the measurement object detected by the vibration detection device, and the quality of the measurement object is determined based on the extracted feature value and a predetermined determination rule. An inspection system comprising: an inspection device that outputs

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