Vibration waveform inspection device

Abstract

To provide a vibration waveform inspection device for inspecting the presence or absence of abnormal vibration generated in the course of machining failure, assembly failure or the like of components.SOLUTION: A high-pass filter 7 is selectively connected according to the conditions of mechanical vibration and an abnormal vibration waveform portion in a vibration waveform signal detected by an AE sensor 3, and the attenuation factor or amplification factor of an amplifier 6 is selected. Therefore, the connection path between the AE sensor 3 and the amplifier 6 and the attenuation factor or the amplification factor of the amplifier 6 are selected in accordance with the magnitude of each of the mechanical vibration and the abnormal vibration waveform portion in the vibration waveform signal detected by the AE sensor 3 and the contrast therebetween, so that the number of quantization steps for A / D conversion of the abnormal vibration waveform portion can be maximized to ensure a sufficient number of quantization steps. It is possible to obtain a digital waveform signal that increases and decreases similarly to the increase and decrease of the vibration waveform signal, and to accurately inspect the presence or absence of abnormal vibration based on the digital waveform signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vibration waveform inspection device that inspects for abnormal high-frequency vibrations that arise from breakage of cutting tips that occurs when cutting metal parts, or from deformation or destruction that occurs in parts made of brittle materials such as ceramics when processing or assembling the parts. [Background technology]

[0002] Conventionally, during the machining or assembly of parts, high-frequency vibrations of several hundred kHz (hereinafter referred to as abnormal vibrations) occur from the early stages of when a machining tool breaks, when a part is poorly machined, or when an assembly error occurs due to a crack in a part, etc. Therefore, various vibration waveform inspection devices have been developed that can detect these abnormal vibrations and detect breakage of the machining tool, defective machining of the part, defective assembly, etc. As an example of this type of vibration waveform inspection device, an AE inspection device 51 with a structure shown in Figure 8 has been developed. In this AE inspection device 51, an acoustic emission sensor (hereinafter referred to as AE sensor) 53 that can detect the abnormal vibrations described above is attached to a machine device 52. The observable frequency of this AE sensor 53 is a wide band, from several Hz to several hundred kHz, so that not only abnormal vibrations but also mechanical vibrations with relatively low frequencies of several tens of kHz or less can be observed.

[0003] Therefore, when detecting only abnormal vibrations that occur due to breakage of a machining tool, defective part machining, defective assembly, etc., a normal vibration waveform signal that occurs when a part is machined or assembled without error is detected in advance by AE sensor 53. This normal vibration waveform signal is attenuated or amplified by amplifier 56 so that an appropriate quantization step is obtained and it falls within the observation range of A / D converter 58, and is then sent to A / D converter 58 where it is converted into a digital waveform signal. This digital waveform signal is read by control unit 60, and one waveform of a normal digital waveform signal (hereinafter referred to as a normal digital signal) is extracted from the digital waveform signal by a vibration waveform acquisition process related to one normal vibration, which is a signal processing step. This normal digital signal is then displayed on the display screen of a personal computer (hereinafter referred to as a PC), and a digital filter is created on the PC to remove mechanical vibrations in unnecessary frequency bands from the normal digital signal. When creating this digital filter, an inverse filter is created that is optimal for the normal digital signal. For example, if the normal digital signal contains vibrations of various bands, such as noise generated by peripheral devices in addition to mechanical vibrations, the filter coefficients are calculated from the amplitude of the normal digital signal using linear prediction, and the amplitude of the normal vibration waveform signal is subtracted to remove unnecessary vibrations, including mechanical vibrations. Furthermore, if there is a clear frequency difference between the normal digital signal and an abnormal digital waveform signal (hereinafter referred to as the abnormal digital signal), a digital high-pass filter is created that has a cutoff frequency that is the intermediate frequency. These digital filters are sent from the PC to the AE inspection device 51 as a filter coefficient file, and then sent to an internal memory unit (not shown) of the device 51, where they are set as digital filters that perform abnormal vibration waveform extraction processing.

[0004] Furthermore, when detecting the abnormal digital signal described above, an abnormal vibration waveform signal that occurs when a component is poorly machined or poorly assembled is detected in advance, similar to the normal digital signal. The abnormal vibration waveform signal is converted into a digital waveform signal by the A / D converter 58, similar to the normal vibration waveform signal, and the digital waveform signal is read into the control unit 60. The digital waveform signal is subjected to abnormal vibration waveform extraction processing, i.e., digital filtering by a digital filter, to extract an abnormal digital signal containing abnormal vibration. The abnormal digital signal is then subjected to full-wave rectification and smoothing processing, and then processed by a vibration waveform acquisition process related to abnormal vibration, which is one of the signal processing processes. Through this processing, an abnormal extraction signal is extracted from the abnormal digital signal, and the abnormal extraction signal is displayed on a PC, and an abnormal vibration amplitude threshold value that can be used to determine abnormal vibration from the abnormal extraction signal is set. This abnormal vibration amplitude threshold value, along with other setting values, is then sent from the PC to the AE inspection device 51 and then to an internal memory unit (not shown) of the control unit 60 of the device, where these predetermined setting values ​​are set as abnormal vibration detection conditions.

[0005] In the AE inspection device 51, vibration waveform inspection begins, and when a vibration waveform signal generated during part processing or part assembly is detected by the AE sensor 53, the vibration waveform signal is converted into a digital waveform signal. Unnecessary mechanical vibrations are removed from this digital waveform signal by the digital filter described above, and the digital waveform signal after mechanical vibration removal (hereinafter referred to as the extracted signal) is full-wave rectified and smoothed. Thereafter, the presence or absence of abnormal vibrations generated during defective part processing or part assembly is inspected by determining whether the extracted signal after full-wave rectification and smoothing is equal to or greater than the abnormal vibration amplitude threshold described above.

[0006] Furthermore, when the vibration waveform signal is detected by the above-mentioned AE sensor 53, high-frequency noise is suddenly generated due to switch operation or the like around the mechanical device 52. Since this high-frequency noise is often in the same frequency range as the abnormal vibrations that occur when parts are poorly processed or assembled, it has become necessary to eliminate its effects.

[0007] Therefore, when accurately determining whether the vibration waveform signal detected by the AE sensor 53 represents abnormal vibration, in addition to the abnormal vibration extraction signal obtained by the abnormal vibration vibration waveform acquisition process described above, an abnormal vibration determination process, which is one type of signal processing, is used to exclude sudden abnormal vibration. In this abnormal vibration determination process, the number of times the abnormal vibration extraction signal continuously exceeds the amplitude threshold for abnormal vibration, i.e., the amplitude threshold exceedance width, is set, and only the abnormal vibration extraction signal that reaches this amplitude threshold exceedance width is determined to represent abnormal vibration. By using this abnormal vibration amplitude threshold and amplitude threshold exceedance width, it is possible to exclude the influence of high-frequency noise that occurs suddenly from the vibration waveform signal detected by the AE sensor 53 and to inspect for the presence or absence of abnormal vibration that occurs in a machining tool or a part during part processing or part assembly. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Tatsuya Shikata, “Nitto Technical Report No.73”, Nitto Seiko Co., Ltd., July 1, 2013, p.23-26 Summary of the Invention [Problem to be solved by the invention]

[0009] In the AE inspection device 51, the observation range of the analog circuit associated with the AE sensor 53 is ±5 V, and the input voltage range of the A / D converter 58 is ±1 V. Therefore, when the vibration waveform signal detected by the AE sensor 53 includes both abnormal vibration and excessively large-amplitude mechanical vibration (see FIG. 9(a)), the vibration waveform signal is attenuated by the amplifier 56 so that the vibration waveform signal falls within the input voltage range (±1 V) of the A / D converter 58, thereby suppressing its amplitude (see FIG. 9(b)). In this case, if the vibration waveform signal includes excessively large-amplitude mechanical vibration, the attenuation of the signal increases. As this attenuation increases, mechanical vibrations with amplitudes excessively large relative to the abnormal vibration—in other words, weak abnormal vibrations with amplitudes smaller than the mechanical vibration—are also attenuated by the same amount. Therefore, as shown in FIG. 10, the number of quantization steps used to A / D convert the abnormal vibration waveform portion decreases, making it impossible to ensure a sufficient number of quantization steps for obtaining a digital waveform signal that approximates the vibration waveform signal detected by the AE sensor 53.

[0010] Furthermore, although not shown, when the mechanical vibration and abnormal vibration waveform portions in the vibration waveform signal detected by AE sensor 53 form a signal having relatively similar amplitudes, the mechanical vibration and abnormal vibration in the signal are similarly attenuated by amplifier 56 so that they both fall within the input voltage range (±1 V) of A / D converter 58. For this reason, the abnormal vibration waveform portion is attenuated by an amount corresponding to the amount of mechanical vibration included, and the number of quantization steps for A / D conversion decreases, making it impossible to ensure a sufficient number of quantization steps for obtaining a digital waveform signal that approximates the vibration waveform signal when detected by AE sensor 53.

[0011] Furthermore, although not shown, when the mechanical vibration and abnormal vibration waveform portions in the vibration waveform signal detected by the aforementioned AE sensor 53 are minute signals that fall within the input voltage range of the A / D converter 58, it is necessary to amplify the signal to the limit of the input voltage range of the A / D converter 58 so that the minute abnormal vibration waveform portion can be observed. At this time, if the vibration waveform signal contains mechanical vibration, the abnormal vibration waveform portion cannot be amplified to the extent that the mechanical vibration is amplified. As a result, the number of quantization steps for A / D converting the abnormal vibration waveform portion in the signal is reduced, and it is no longer possible to ensure a sufficient number of quantization steps to obtain a digital waveform signal that approximates the vibration waveform signal when detected by the AE sensor 53.

[0012] In either situation where the mechanical vibration and abnormal vibration waveform portions in the vibration waveform signal are compared, a sufficient number of quantization steps cannot be ensured, and therefore the digital waveform signal obtained by A / D conversion from the vibration waveform signal is a signal that does not approximate the increase and decrease in the vibration waveform signal when detected by AE sensor 53. As a result, the presence or absence of abnormal vibration is determined based on this signal, which can result in erroneous determinations of abnormal vibration as normal vibration, resulting in the problem that the waveform detection function using a digital filter cannot be fully utilized.

[0013] Furthermore, in the above-mentioned AE inspection device 51, when determining abnormal vibration, an abnormal vibration amplitude threshold and an amplitude threshold exceeding width that continuously exceeds the amplitude threshold are set, thereby eliminating the effects of high-frequency noise that occurs suddenly and making it possible to detect the presence or absence of abnormal vibration that occurs in a processing tool or a part during part processing or part assembly. However, as mentioned above, depending on the conditions of the mechanical vibration and the abnormal vibration waveform portion in the vibration waveform signal detected by AE sensor 53, the digital waveform signal obtained by A / D conversion of the vibration waveform signal may not accurately approximate the vibration waveform signal when detected by AE sensor 53.

[0014] As a result, even if the vibration waveform signal detected by AE sensor 53 has a value that reaches the amplitude threshold for determining abnormal vibration, the vibration waveform signal may not have a value that reaches the amplitude threshold due to carry-over error during A / D conversion caused by its attenuation. As a result, the extracted signal extracted by a digital filter from the digital waveform signal after A / D conversion of the vibration waveform signal may also be determined to not reach the amplitude threshold. This determination causes a discontinuity in the number of times the amplitude threshold for determining abnormal vibration is continuously exceeded, i.e., the width by which the amplitude threshold is exceeded does not reach the set width, resulting in a new problem in which the vibration waveform signal detected by AE sensor 53 contains abnormal vibration, but is instead determined to be normal vibration. [Means for solving the problem]

[0015] The present invention has been invented in view of the above problems, and is a vibration waveform inspection device comprising a detection sensor that detects vibrations occurring around or on an object to be inspected, an amplifier unit having an amplification factor that attenuates or amplifies the vibration waveform signal detected by the detection sensor, and an A / D conversion unit, wherein the vibration waveform signal attenuated or amplified by the amplifier unit is converted into a digital waveform signal by the A / D conversion unit, a digital filter is created to remove unnecessary frequencies from the digital waveform signal, and the presence or absence of abnormal vibration is inspected from the digital extracted signal extracted by the digital filter, wherein the detection sensor and the amplifier unit are selectively connected either directly or via a high-pass filter having a cutoff frequency that removes unnecessary vibrations, and the connection path between the detection sensor and the amplifier unit and the attenuation factor or amplification factor of the amplifier unit are selected according to the magnitude of the vibrations of unnecessary frequencies and the abnormal vibrations in the vibration waveform signal detected by the detection sensor and the comparison status between them.

[0016] According to the above-described configuration, depending on the magnitude of the unnecessary frequency vibration and the abnormal vibration in the vibration waveform signal detected by the detection sensor and the comparison state between them, i.e., when the mechanical vibration in the vibration waveform signal is excessively large compared to the abnormal vibration waveform portion, the detection sensor and the amplifier unit can be connected via a high-pass filter. Also, when the mechanical vibration in the vibration waveform detection signal is sufficiently small compared to the abnormal vibration portion, the detection sensor and the amplifier unit can be directly connected. Furthermore, when the mechanical vibration in the vibration waveform detection signal is not significantly different from the abnormal vibration portion, the detection sensor and the amplifier unit can be connected via a high-pass filter.

[0017] In other words, regardless of the connection path between the detection sensor and the amplifier, the attenuation rate or amplification rate of the amplifier can be selected so that the abnormal vibration waveform portion in the vibration waveform signal detected by the detection sensor falls optimally within the observation range of the A / D converter. This makes it possible to maximize the number of quantization steps for A / D converting the abnormal vibration waveform portion depending on the state of the mechanical vibration and the abnormal vibration portion in the vibration waveform signal detected by the detection sensor, ensuring a sufficient number of quantization steps to obtain a digital waveform signal that increases and decreases in approximation to the increase and decrease of the vibration waveform signal, and enabling accurate detection of the presence or absence of abnormal vibration based on the digital waveform signal.

[0018] The detection sensor of the present invention is preferably an acoustic emission sensor so that it can detect even weak abnormal vibrations when the object to be inspected is a ceramic material in which abnormal vibrations caused by cracks, etc. are particularly weak.

[0019] The connection between the detection sensor and the amplifier according to the present invention, either directly or via a high-pass filter having a cutoff frequency set to filter out unwanted vibrations, is preferably switched by a manual switch, which allows the connection between the detection sensor and the amplifier to be simply and easily switched depending on the magnitude of unwanted frequency vibrations and abnormal vibrations in the vibration waveform signal detected by the detection sensor and the comparison status between them.

[0020] The selection of whether to connect the detection sensor and amplifier unit directly or via a high-pass filter according to the present invention is preferably configured to be switched based on the maximum amplitudes of the normal vibration waveform signal and the abnormal vibration waveform signal detected in advance and their ratio. This makes it possible to automatically switch the connection in advance depending on the magnitudes of the unnecessary mechanical vibration contained in the normal vibration waveform signal and the abnormal vibration contained in the abnormal vibration waveform signal and the comparison between them, thereby automating the acquisition of the normal vibration waveform signal and the abnormal vibration waveform signal, the selection of the processing of the vibration waveform signal before A / D conversion depending on the magnitude of the mechanical vibration, and the determination of whether the vibration waveform signal is abnormal vibration.

[0021] The vibration waveform signal according to the present invention is preferably configured such that each time the signal is converted into a digital waveform signal, a determination is made as to whether the amplitude of the digitally extracted signal extracted by the digital filter reaches an amplitude threshold value for abnormal vibration, and if the determination is made that the amplitude threshold value is reached multiple times in succession, the vibration is determined to be abnormal. With this configuration, even if high-frequency noise in the same band as abnormal vibrations that occur due to faulty part processing or part assembly caused by switch operation or the like around the machinery suddenly occurs, the effects of this sudden high-frequency noise can be eliminated.

[0022] Furthermore, since the digital extraction signal related to the abnormal vibration determination described above approximates the increase or decrease of the abnormal vibration waveform portion in the vibration waveform signal detected by the detection sensor and is minimally affected by carry-over error during A / D conversion, the digital extraction signal has a waveform that accurately approximates the increase or decrease of the abnormal vibration waveform portion in the vibration waveform signal detected by the detection sensor. This makes it possible to minimize erroneous determinations, such as when a vibration waveform signal that was abnormal when detected by the detection sensor is determined to be normal vibration due to carry-over error during A / D conversion, when determining whether the amplitude threshold is reached based on the digital extraction signal.

[0023] Another aspect of the present invention is characterized by a configuration including a detection sensor that detects vibrations occurring around or on an object to be inspected, a high-pass filter having a cutoff frequency set to remove unnecessary vibrations from a vibration waveform signal detected by the detection sensor, an amplifier that attenuates or amplifies the vibration waveform signal that passes through the high-pass filter, and an A / D converter, wherein the vibration waveform signal amplified by the amplifier is converted into a digital waveform signal by the A / D converter, a digital filter is created to remove unnecessary frequencies from the digital waveform signal, and the presence or absence of abnormal vibration is inspected from the digital extracted signal extracted by the digital filter.

[0024] According to the above configuration, the vibration waveform signal detected by the detection sensor is filtered by the high-pass filter to remove unnecessary mechanical vibrations in a frequency band below the cutoff frequency, and is then attenuated or amplified to fit within the observation range of the A / D converter, which then converts the signal into a digital waveform signal. Therefore, particularly when the signal is attenuated to fit within the observation range of the A / D converter, the attenuation rate can be significantly smaller than when mechanical vibrations are included. This minimizes the effect of carryover errors during A / D conversion, and the digital extraction signal extracted from the digital waveform signal is a signal that approximates the increase or decrease in the abnormal vibration waveform portion of the vibration waveform signal detected by the detection sensor. Therefore, the presence or absence of abnormal vibration can be accurately detected based on the digital extraction signal.

[0025] Furthermore, with the above configuration, unnecessary mechanical vibrations can first be removed by the high-pass filter 7 from the vibration waveform signal detected by the detection sensor, and then high-frequency noise in a band lower than the band of abnormal vibrations that cannot be completely removed by the high-pass filter 7 can be removed by the digital filter. Therefore, it is possible to reduce the amount of high-frequency noise that is superimposed on abnormal vibrations that occur when parts are poorly processed or assembled and is subjected to A / D conversion, and it is possible to inspect for abnormal vibrations while eliminating the effects of high-frequency noise as much as possible. [Effects of the Invention]

[0026] According to the present invention as described above, a high-pass filter is selectively connected and the attenuation rate or amplification rate of the amplifier is selected depending on the state of mechanical vibration and abnormal vibration waveform portions in the vibration waveform signal detected by the detection sensor. Therefore, regardless of the state of unnecessary mechanical vibration and abnormal vibration waveform portions in the vibration waveform signal detected by the detection sensor, the A / D converted digital waveform signal becomes a signal that approximates the increase or decrease in the vibration waveform signal detected by the detection sensor, and the presence or absence of abnormal vibration can be checked based on the digital waveform signal. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a block diagram showing the configuration of an AE inspection device which is an example of a vibration waveform inspection device according to an embodiment of the present invention. [Figure 2] 4 is a flowchart illustrating an outline of signal processing by a control unit arranged in an AE inspection device that is an example of a vibration waveform inspection device according to an embodiment of the present invention. [Figure 3] 4 is a main flowchart illustrating a vibration waveform inspection program (for both normal and abnormal vibration waveform acquisition) incorporated into a control unit of an AE inspection device that is an example of a vibration waveform inspection device according to an embodiment of the present invention. [Figure 4] 4 is a sub-flowchart illustrating a vibration waveform inspection (for both normal and abnormal vibration waveform acquisition) program incorporated in a control unit of an AE inspection device that is an example of a vibration waveform inspection device according to an embodiment of the present invention. [Figure 5] 2 is a waveform diagram showing a vibration waveform signal at point A in FIG. 1 when the mechanical vibration is excessive relative to the abnormal vibration waveform portion, with the abnormal vibration partially enlarged. [Figure 6(a)] FIG. 2 is an explanatory diagram showing the number of quantization steps when the abnormal vibration waveform portion is AD converted, of the vibration waveform signal at point B in FIG. 1 when the mechanical vibration is excessive compared to the abnormal vibration waveform portion and the AE sensor and amplifier are connected via a high-pass filter. [Figure 6(b)]6(b) is a partially cutaway explanatory diagram showing a digitally extracted signal at point C in FIG. 2 of a digital waveform signal that is A / D converted from the vibration waveform signal in FIG. 6(a) and the quantization step during the conversion. [Figure 7] FIG. 2 is an explanatory diagram illustrating a process for determining an abnormal vibration waveform portion in an AE inspection device that is an example of a vibration waveform inspection device according to an embodiment of the present invention. [Figure 8] FIG. 1 is a block diagram showing the configuration of a conventional vibration waveform inspection device. [Figure 9(a)] 9 is a waveform diagram showing a vibration waveform signal at point A in FIG. 8 when the mechanical vibration is excessive relative to the abnormal vibration waveform portion, with the abnormal vibration being partially enlarged. [Figure 9(b)] FIG. 9 is a waveform diagram of a vibration waveform signal at point B in FIG. 8 . [Figure 10] 9 is a partially cutaway explanatory diagram of the vibration waveform signal at point B in FIG. 8, showing the number of quantization steps when the abnormal waveform portion is AD converted by the AD conversion section. DETAILED DESCRIPTION OF THE INVENTION

[0028] (First embodiment) As an example of a vibration waveform inspection device according to a first embodiment of the present invention, an AE inspection device that detects the presence or absence of weak high-frequency vibrations resulting from breakage of a machining tool or deformation or fracture of a component, particularly a component made of a fragile material such as ceramic, during component processing or assembly will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an AE inspection device (hereinafter referred to as the AE device), which includes a detection sensor attached to a machine 2 that processes or assembles components. This detection sensor detects vibrations occurring around an object to be inspected or due to deformation or fracture of the object to be inspected. For example, an acoustic emission sensor (hereinafter referred to as the AE sensor) 3 is used, which is optimal for detecting high-frequency vibrations of several hundred kHz (hereinafter referred to as abnormal vibrations) that occur from the early stages of breakage of a machining tool, defective component processing, or defective assembly due to cracks or the like. The AE sensor 3 can observe a wide frequency range, from several Hz to several hundred kHz, making it possible to observe not only abnormal vibrations but also relatively low-frequency mechanical vibrations of several tens of kHz or less. A plurality of AE sensors 3 may be attached to the machine 2, in which case a plurality of digital filters configured in the control unit 10 (described later) can be provided, and these digital filters can be combined as desired.

[0029] The AE sensor 3 is selectively connected to an amplifier 6 either directly or via a high-pass filter 7 via a manual switch 5, which is an example of a changeover switch, so that a vibration waveform signal detected by the AE sensor 3 is sent to the amplifier 6 via either connection path. The amplifier 6 is connected to an A / D converter 8 and is configured to perform A / D conversion on the vibration waveform signal. The high-pass filter 7 is set to have a cutoff frequency that filters out unnecessary mechanical vibrations, and is configured to send a vibration waveform signal from which mechanical vibrations have been filtered out to the amplifier 6.

[0030] The connection path between the AE sensor 3 and the amplifier 6 and the attenuation rate or amplification rate of the amplifier 6 are selected according to the magnitude of the unnecessary mechanical vibration and the abnormal vibration in the vibration waveform signal detected by the AE sensor 3 and the comparison state between them. For example, when the unnecessary mechanical vibration in the vibration waveform signal is excessively large compared to the abnormal vibration waveform portion (see FIG. 5 ) or is equal to the abnormal vibration waveform portion, the connection between the AE sensor 3 and the amplifier 6 via the high-pass filter 7 is selected in order to exclude the mechanical vibration and perform A / D conversion on the abnormal vibration waveform portion. At this time, when the abnormal vibration waveform portion in the vibration waveform signal is outside the input voltage range of the A / D converter 8, the amplifier 6 is set to an attenuation rate that brings the abnormal vibration waveform portion within the input voltage range of the A / D converter 8. Furthermore, when the abnormal vibration waveform portion is within the input voltage range of the A / D converter 8, the amplifier 6 is set to an amplification rate that obtains the optimal number of quantization steps when A / D converting the abnormal vibration waveform portion.

[0031] To give a further example of the situation of mechanical vibration and abnormal vibration in the vibration waveform signal mentioned above, when the mechanical vibration is small compared to the abnormal vibration waveform portion, the effect of the mechanical vibration is small when A / D converting the abnormal vibration waveform portion, so the AE sensor 3 and the amplifier unit 6 are directly connected. At this time, when the abnormal vibration waveform portion is outside the input voltage range of the A / D converter 6, an attenuation rate that causes the abnormal vibration waveform portion to fall within the input voltage range of the A / D converter 6 is set in the amplifier unit 6. Furthermore, when the abnormal vibration waveform portion is within the input voltage range of the A / D converter 6, an amplification rate that obtains the optimal number of quantization steps when A / D converting the abnormal vibration waveform portion is set in the amplifier unit 6.

[0032] The A / D conversion unit 8 is connected to a control unit 10, and is configured so that the vibration waveform signal passing through the amplification unit 6 is converted into a digital waveform signal at a sample rate sent from the control unit 10, and the digital waveform signal is sent to the control unit 10. Also connected to the control unit 10 are a display unit 11, an internal memory unit 12 that stores various information, an external memory unit 13, and an I / O for connecting to an external terminal (hereinafter referred to as external I / O) 14.

[0033] The display unit 11 is provided with operation buttons 11a, such as a power button, the manual switch 5 mentioned above, an inspection start button for sending an inspection start command to the control unit 10, and an inspection end button for sending an inspection end command to the control unit 10, as well as lamps 11b, such as an abnormality determination indicator lamp that displays an abnormality determination in response to an abnormality determination display code described below during vibration waveform inspection. The external I / O 14 is also connected to the mechanical device 2 mentioned above, and is further connected to a personal computer (hereinafter referred to as PC), an example of a computer, when setting various setting values ​​for the AE device 1. The PC is configured to be able to communicate serially with the AE device 1 via a COM port, and is configured to create operation commands including various setting values ​​and send them to the AE device 1, as well as receive various vibration waveform signals sent from the AE device 1 and reset various setting values ​​based on these.

[0034] The operation commands include a normal vibration waveform acquisition start command (hereinafter referred to as a normal vibration acquisition command) for acquiring a normal vibration waveform signal that occurs when a part is processed or assembled properly, an abnormal vibration waveform acquisition start command (hereinafter referred to as an abnormal vibration acquisition command) for acquiring an abnormal vibration waveform signal that includes abnormal vibration that occurs when a part is processed improperly or when a part is assembled improperly, a command to stop acquisition of these, a detection condition setting command, a command to end the setting, and a setting value save command.

[0035] The normal vibration acquisition command has, as setting values, the attenuation rate or amplification rate of the amplifier unit 6, the sample rate of the A / D converter 8, and a normal vibration amplitude threshold. The normal vibration acquisition command is created to cause the AE device 1 to transmit a normal digital waveform signal, which is A / D converted from a normal vibration waveform signal, to a PC when creating a digital filter for removing mechanical vibrations containing unnecessary frequencies when detecting abnormal vibrations from a vibration waveform signal. When the PC receives the normal digital waveform signal (described below), an optimal digital filter is created in accordance with the normal digital waveform signal. For example, if the normal digital waveform signal contains vibrations due to high-frequency noise or the like that constantly occurs in the same band as abnormal vibrations, an inverse filter is created having filter coefficients calculated from the amplitude of the normal digital waveform signal using linear prediction, and which can subtract the amplitude of the normal vibration waveform signal to remove the mechanical vibrations.

[0036] Furthermore, if there is a clear difference in frequency between the normal digital waveform signal described above and the abnormal digital waveform signal described below, a digital high-pass filter with an intermediate frequency as its cutoff frequency is created as the digital filter. Any of the digital filters described above is sent as a filter coefficient file from the PC to the AE device 1, and is stored in the internal storage unit 12 described above as a setting value for the vibration waveform inspection program described below together with its type (inverse filter, digital high-pass filter) as a digital filter that performs abnormal vibration waveform extraction processing.

[0037] The abnormal vibration acquisition command has as its setting values ​​the aforementioned attenuation rate or amplification rate, the sample rate, as well as the abnormal vibration amplitude threshold and the type of digital filter. The abnormal vibration acquisition command is created to transmit an abnormality extraction signal (described later) from the AE device 1 to the PC when setting the abnormal vibration amplitude threshold, setting the number of times the abnormal vibration continues to exceed the amplitude threshold (i.e., setting the width of the amplitude threshold exceedance), creating a digital filter, etc.

[0038] The detection condition setting command has the aforementioned attenuation rate or amplification rate, sample rate, abnormal vibration amplitude threshold, and digital filter type as setting values, and is created to transmit the abnormal digital waveform signal, which is A / D converted from the abnormal vibration waveform signal when the abnormal vibration amplitude threshold exceeding width is set, from the AE device 1 to the PC. The setting value save command also has setting values ​​obtained from the various vibration waveform signals acquired by the aforementioned operation commands. These setting values ​​include the sample rate of the A / D converter 8, the attenuation rate or amplification rate of the amplifier 6, the digital filter type, the abnormal vibration amplitude threshold, and the abnormal vibration amplitude threshold exceeding width.

[0039] The information stored in the internal storage unit 12 includes various setting values ​​included in the operation commands described above, inspection results for the presence or absence of abnormal vibration, etc. The setting values ​​are stored in the internal storage unit 12 as described above, and at the same time, are set as setting values ​​for the vibration waveform inspection program. The external storage unit 13 is configured to store up to two types of waveform files, each of which has a file name assigned to each waveform, of vibration waveform signals acquired in response to each of the operation commands described above, and also to store filter coefficient files and the like transmitted from a PC.

[0040] As shown in FIG. 2, the control unit 10 described above is configured to perform both digital filtering and full-wave rectification and smoothing, or only full-wave rectification and smoothing, each time receiving a digital waveform signal from the A / D conversion unit 8, and to perform any one of signal processing on the full-wave rectified and smoothed signal: vibration waveform acquisition processing relating to normal vibration or abnormal vibration, vibration waveform acquisition processing relating to abnormal vibration, and abnormal vibration determination processing.

[0041] Furthermore, the control unit 10 has a vibration waveform inspection program for specifically carrying out the above-mentioned processing. This vibration waveform inspection program is composed of the following steps shown in FIGS. P1) Wait for the reception of an inspection start command or data from the PC. P2) It is determined whether or not an inspection start command has been received, and if an inspection start command has been received, the process jumps to P18). P3) Creates operation commands (gain, sample rate, attenuation rate or amplification rate, amplitude threshold for normal and abnormal vibration, normal and abnormal vibration acquisition with set values ​​according to each command, detection condition setting, setting value saving) and stop commands (stop normal and abnormal vibration acquisition, stop detection condition setting, etc.) according to the data received from the PC. P4) When the received data is a normal vibration acquisition command, the various setting values ​​of the normal vibration acquisition command (sample rate, attenuation rate or amplification rate, and normal vibration amplitude threshold) are called up and stored in the internal memory unit 12 (thereby setting the sample rate in the A / D conversion unit 8, the attenuation rate or amplification rate in the amplifier unit 6, and the normal vibration amplitude threshold as the criteria for determining normal vibration). P5) The digital waveform signal that is A / D converted at the sample rate is read in each time it is converted, and the normal digital waveform signal that reaches the normal vibration amplitude threshold is extracted from that signal until it is one waveform, and each waveform is temporarily saved in memory. Note that this memory can save a predetermined number of signals, that is, up to one waveform, and up to two types of signals at each processing stage can be selected and saved, and these types are set in advance. P6) Determine whether the number of normal digital waveform signals stored in memory for each waveform has reached a predetermined number, and if this number has not reached the predetermined number, return to P5. P7) The normal digital waveform signal in the memory is transferred to the buffer (and immediately transferred from the buffer to the PC), the memory is cleared, and the process returns to P1. P8) When the received data is a command to stop acquiring normal vibration, reset the attenuation rate or amplification rate of the amplifier 6 in the internal memory 12, the sample rate of the A / D converter 8, and the amplitude threshold value of normal vibration, and return to P1. P9) When the received data is an abnormal vibration acquisition command, the various setting values ​​of the abnormal vibration acquisition command (sample rate, attenuation rate or amplification rate, type of digital filter, and abnormal vibration amplitude threshold) are called up and stored in the internal storage unit 12 (thereby setting the sample rate in the A / D conversion unit 8, the attenuation rate or amplification rate in the amplifier unit 6, the type of digital filter as a digital filter processing condition, and the abnormal vibration amplitude threshold as an abnormal vibration determination processing condition). P10) The digital waveform signal that has been A / D converted at the sample rate is read in each time it is converted, and the signal is digitally filtered using a digital filter. The extracted signal after this processing is then full-wave rectified and smoothed, and from the extracted signal after this processing, extracted signals that reach the amplitude threshold for abnormal vibration and are determined to be abnormal vibration (hereinafter referred to as abnormal extracted signals) are extracted until one waveform is reached, and each waveform is temporarily saved in memory. P11) Determine whether the number of abnormality extracted signals stored in memory for each waveform has reached a predetermined number, and if this number has not reached the predetermined number, return to P10. P12) Transfer all abnormality extracted signals in memory to the buffer (and immediately transfer them from the buffer to the PC), clear the memory, and return to P1. P13) If the received data is an abnormal vibration acquisition stop command, the attenuation rate or amplification rate of the amplifier 6, the sample rate of the A / D converter 8, the type of digital filter, and the amplitude threshold of abnormal vibration in the internal memory 12 are reset, and the process returns to P1. P14) When the received data is a detection condition setting command, steps P9 and P10, which are operated by the abnormal vibration acquisition command, are executed, one waveform of the abnormality extraction signal is extracted, and it is temporarily saved in memory. P15) Transfer one waveform of the abnormality extracted signal from the memory to the buffer (immediately transfer from the buffer to the PC), clear the memory, and return to P1. P16) If the received data is a detection condition setting stop command, reset the attenuation rate or amplification rate of the amplifier 6, the sample rate of the A / D converter 8, the type of digital filter, and the amplitude threshold value of abnormal vibration in the internal memory 12, and return to P1. P17) If the received data is a setting value save command, the various setting values ​​of the command (sample rate, attenuation rate or amplification rate, type of digital filter, amplitude threshold for abnormal vibration, and amplitude threshold exceedance range) are called up and stored in the internal memory 12 (these setting values ​​are thereby set as the various settings of the vibration waveform inspection program), and the process returns to P1. P18) The digital waveform signal converted at the sample rate is read each time it is converted and digitally filtered using a digital filter. P19) The digital extracted signal (hereinafter referred to as extracted signal) extracted through digital filtering is subjected to full-wave rectification and smoothing. P20) Temporarily saves the extracted signal after full-wave rectification and smoothing in memory (memory can store up to one waveform) P21) It is determined whether the test results up to this point have been judged to be abnormal, and if they are, jump to P28. P22) It is determined whether the extracted signal after full-wave rectification and smoothing processing reaches the amplitude threshold of abnormal vibration, and if it reaches the threshold, it jumps to P25. P23) Clears the extracted signal after full-wave rectification and smoothing in the memory. P24) Clear the number of times the amplitude threshold is exceeded, i.e., the amplitude threshold exceedance width and the test results, and jump to P32. P25) Gradually increase the number of times the amplitude threshold is exceeded, i.e., the amplitude threshold exceedance. P26) It is determined whether the amplitude threshold exceeding width has reached the set width, and if it has not reached the set width, the process jumps to P32. P27) Save the test results as abnormality judgments. P28) Determine whether the extracted signal in memory after full-wave rectification and smoothing has reached the specified number for one waveform, and if it has not reached the specified number, jump to P32. P29) A predetermined number (for one waveform) of extracted signals in memory after full-wave rectification and smoothing processing, which are determined to be abnormal vibrations, i.e., abnormality extracted signals, are transferred to a buffer, and from the buffer to the PC and external storage unit 13, and the memory and amplitude threshold exceedance width are cleared. P30) Save any abnormality detected in the test results for notification purposes and clear the test results. P31) An abnormality determination display code is output to the display unit 11 and to the machine device 2 via the external I / O 14. P32) It is determined whether or not an inspection end command has been received, and if not, the process returns to P18. P33) Clear the memory, the number of times the amplitude threshold is exceeded, that is, the amplitude threshold exceeding width and the test result. P34) End.

[0042] In the AE device 1, various setting values ​​required for vibration waveform inspection are created on the display screen of a PC while observing the vibration waveform signal detected by the AE sensor 3. When creating these setting values, the vibration waveform signal generated when a part is processed to a good product or assembled to a good product, i.e., the normal vibration waveform signal, and the vibration waveform signal generated when a part is processed improperly or assembled improperly, i.e., the abnormal vibration waveform signal, are detected in advance.

[0043] When detecting a normal vibration waveform signal that occurs during non-defective processing or assembly of a part, a normal vibration acquisition command having the setting values ​​(sample rate, attenuation rate or amplification rate, normal vibration amplitude threshold) required to detect a normal vibration waveform signal, created on the PC, is sent from the PC to the AE device 1. At this time, when the AE sensor 3 is directly connected to the amplifier 6 by the aforementioned manual switch 5, the attenuation rate of the amplifier 6 is initially set to the ratio between the observation range (±5 V) of the analog circuit associated with the AE sensor 3 and the input voltage range (±1 V) of the A / D converter. When the AE sensor 3 is connected to the amplifier 6 via the aforementioned high-pass filter 7 by the aforementioned manual switch 5, the amplification rate of the amplifier 6 is initially set to 1.

[0044] In addition, when detecting a vibration waveform signal that occurs when a part is poorly processed or poorly assembled, i.e., an abnormal vibration waveform signal, an abnormal vibration acquisition command having the setting values ​​(sample rate, attenuation rate or amplification rate, abnormal vibration amplitude threshold) required to detect the abnormal vibration waveform signal created on the PC in the same way as for a normal vibration waveform signal is sent from the PC to the AE device 1.

[0045] When the AE device 1 receives a normal vibration acquisition command, the command calls up the set values ​​of the sample rate, attenuation rate or amplification rate, and normal vibration amplitude threshold, and the sample rate is set in the A / D conversion unit 8, the attenuation rate or amplification rate is set in the amplifier unit 6, and the normal vibration amplitude threshold is set as the criteria for determining normal vibration, and these are stored in the internal memory unit 12.

[0046] The AE device 1 then processes or assembles the component into a non-defective product, and the vibration waveform signal obtained at this time is detected by the AE sensor 3 as a normal vibration waveform signal. This normal vibration waveform signal is sent to the amplifier 6, either directly or via a high-pass filter 7, where it is attenuated or amplified. It is then A / D converted to a digital waveform signal at the sample rate by the A / D converter 8. Each time this A / D conversion is performed, the digital waveform signal is read by the controller 10 and compared with a normal vibration amplitude threshold. Once the digital waveform signal reaches the amplitude threshold, a normal digital waveform signal (hereinafter referred to as a normal digital signal) consisting of a predetermined number of digital waveform signals is temporarily stored in memory. Once a predetermined number of normal digital signals for this waveform have been acquired, these signals are sent to the PC. An optimal normal digital signal representing the mechanical vibration is obtained from these normal digital signals. If an optimal normal digital signal cannot be acquired, the settings in the normal vibration acquisition command are changed until a normal vibration acquisition stop command is received. The above-mentioned operation is then repeated to obtain a normal digital signal that is optimal for the mechanical vibration. The sample rate and the attenuation or amplification factor of the amplifier 6 at this time are stored in the PC.

[0047] Furthermore, when the AE device 1 receives an abnormal vibration acquisition command, the command retrieves the set values ​​of the sample rate, attenuation rate or amplification rate, digital filter type, and abnormal vibration amplitude threshold (initial value is the minimum value). The sample rate is set in the A / D converter 8, the attenuation rate or amplification rate in the amplifier 6, the digital filter type as a processing condition of the signal processor, and the abnormal vibration amplitude threshold as a judgment condition for abnormal vibration, and these are stored in the internal memory 12. Subsequently, the AE device 1 detects a component processing defect or component assembly defect, and the vibration waveform signal generated at this time is detected by the AE sensor 3 as an abnormal vibration waveform signal. This abnormal vibration waveform signal is converted into an abnormal digital waveform signal (hereinafter referred to as an abnormal digital signal), and each time an abnormal digital signal is processed by a digital filter. The extracted signal after the digital filter processing is full-wave rectified and smoothed. The extracted signal after the full-wave rectified and smoothed processing is extracted until it reaches the abnormal vibration amplitude threshold (hereinafter referred to as an abnormal extracted signal), and each waveform is temporarily stored in memory. When a predetermined number of abnormality extraction signals for one waveform have been acquired, these signals are sent to the PC. Thereafter, as with the normal vibration acquisition command, an abnormality extraction signal optimal for the settings of the abnormal vibration amplitude threshold and the width over the threshold is acquired from these abnormality extraction signals. In addition, the type of digital filter, the abnormal vibration amplitude threshold, and the width over the amplitude threshold at this time are stored on the PC.

[0048] After acquiring the normal vibration waveform signal and the abnormal vibration waveform signal, the PC sends a detection condition setting command to the AE device 1 to set the abnormal vibration detection conditions. When the AE device 1 receives the detection condition setting command, the command calls up the set values ​​of the sample rate, attenuation rate or amplification rate, type of digital filter, and abnormal vibration amplitude threshold (initial value is the minimum value), just as with the abnormal vibration acquisition command. The sample rate is set in the A / D conversion unit 8, the attenuation rate or amplification rate in the amplifier unit 6, and the type of digital filter and abnormal vibration amplitude threshold as the processing conditions and abnormal vibration judgment conditions of the signal processing unit, respectively, and are stored in the internal storage unit 12. After that, an abnormality extraction signal for one waveform is extracted, this abnormality extraction signal is temporarily stored in memory, and the abnormality extraction signal is sent to the PC.

[0049] The abnormality extraction signal is displayed on the display screen of a PC, and the PC acquires the optimal number of times the abnormal vibration amplitude threshold is exceeded, i.e., the amplitude threshold exceedance width, which can eliminate the effects of sudden high-frequency noise, from the abnormality extraction signal. If the optimal amplitude threshold exceedance width cannot be acquired, the abnormal vibration amplitude threshold in the detection condition setting command is changed until a detection condition setting stop command is received. The above operation is then repeated until the optimal threshold exceedance width, which can eliminate the effects of sudden high-frequency noise, is acquired. The type of digital filter, the abnormal vibration amplitude threshold, and the amplitude threshold exceedance width at this time are stored on the PC.

[0050] Furthermore, once creation of the various setting values ​​described above has been completed, a setting value save command containing the setting values ​​(sample rate, attenuation rate or amplification rate, type of digital filter, amplitude threshold for abnormal vibration, and width over amplitude threshold) stored on the PC is sent to the AE device 1. When the AE device 1 receives the setting value save command, the various setting values ​​contained in the command are set as setting values ​​required for detecting abnormal vibration, i.e., the sample rate is set in the A / D conversion unit 8, the attenuation rate or amplification rate is set in the amplifier unit 6, the type of digital filter is set as processing conditions for the signal processing unit, and the amplitude threshold for abnormal vibration and width over amplitude threshold are set as conditions for determining abnormal vibration, and these are stored in the internal storage unit 12.

[0051] After completing the setting of the settings required for detecting abnormal vibrations as described above, when an inspection start command is sent from the inspection start button on the display unit 11, the vibration waveform signal detected by the AE sensor 3 is sent to the A / D converter 8 via a route selected by the manual switch 5, i.e., either directly or via a high-pass filter 7, and is A / D converted to a digital waveform signal at the sample rate. This digital waveform signal is read by the control unit 10 each time A / D conversion is performed, and is digitally filtered by the digital filter. The processed signal, i.e., the extracted signal extracted by the digital filter, is full-wave rectified and smoothed, and the extracted signal after full-wave rectification and smoothing is temporarily stored in memory.

[0052] At this time, if the vibration waveform signal described above is a signal sent directly to amplifier 6, the mechanical vibration in the signal is sufficiently small compared to the abnormal vibration waveform portion, so the attenuation rate of amplifier 6 may be small when keeping the signal within the input voltage observation range (within ±1 V) of A / D converter 8. As a result, the vibration waveform signal, the digital waveform signal obtained from the signal, and the extracted signal after full-wave rectification and smoothing of the digital waveform signal become signals that increase and decrease in a manner that roughly approximates the abnormal vibration waveform portion in the vibration waveform signal detected by AE sensor 3.

[0053] Furthermore, when the vibration waveform signal described above is a signal sent to the amplifier 6 via the high-pass filter 7, the signal may contain mechanical vibrations of excessive amplitude or may be insignificant compared to the abnormal vibration waveform portion, resulting in a signal from which mechanical vibrations in the band below the cutoff frequency have been removed by the high-pass filter 7. As a result, the vibration waveform signal sent to the amplifier 6 contains roughly only abnormal vibrations and sudden high-frequency noise, so that the attenuation rate of the amplifier 6 can be small when the signal is kept within the input voltage observation range (within ±1 V) of the A / D converter 8. Therefore, the vibration waveform signal, the digital waveform signal obtained from the signal, and the extracted signal after full-wave rectification and smoothing of the digital waveform signal are signals that increase and decrease in a manner that roughly approximates the abnormal vibration waveform portion in the vibration waveform signal detected by the AE sensor 3.

[0054] In the case where the vibration waveform signal described above is a signal sent to amplifier 6 via high-pass filter 7, and the abnormal vibration waveform portion is smaller than the input voltage within the observation range of A / D converter 8 described above and cannot be observed, the signal is amplified by an amplification factor that amplifies the signal to the limit of the observation range of A / D converter 8. As a result, the vibration waveform signal, the digital waveform signal obtained from the signal, and the extracted signal after full-wave rectification and smoothing of the digital waveform signal become signals that increase or decrease in a manner that roughly approximates the abnormal vibration waveform portion in the vibration waveform signal detected by AE sensor 3.

[0055] In other words, when the vibration waveform signal of any of the connection paths described above is A / D converted, an attenuation rate or amplification rate is selected so that the signal increases or decreases in a manner that roughly approximates the abnormal vibration waveform portion detected by the AE sensor 3, depending on the magnitude of each of the unnecessary mechanical vibrations and abnormal vibrations, i.e., the abnormal vibration waveform portion in the signal, and the comparison between these, and therefore a sufficient number of quantization steps is ensured to obtain a digital waveform signal (when connected via high-pass filter 7, see Figure 6(a)). As a result, the digital waveform signal obtained by A / D conversion of the vibration waveform signal becomes a signal that accurately approximates the increase and decrease in the vibration waveform signal, and the aforementioned extracted signal extracted from the digital waveform signal also has a waveform that accurately approximates the increase and decrease in the abnormal vibration waveform portion extracted from the vibration waveform signal by high-pass filter 7 (see Figure 6(b)).

[0056] When the extracted signal after full-wave rectification and smoothing described above is temporarily saved, it is determined whether the inspection results of the vibration waveform up to that point have been judged to be abnormal, and if this is judged to be abnormal, it means that the extracted signal after full-wave rectification and smoothing up to that point has been judged to be an abnormal waveform, so it is determined whether the extracted signals after full-wave rectification and smoothing in memory have reached a predetermined number for one waveform. In this judgment, if the extracted signals described above have not reached the predetermined number and an inspection end command has not been received from display unit 11, a new digital waveform signal is read, and all subsequent extracted signals after full-wave rectification and smoothing are temporarily saved in memory until they reach the predetermined number, that is, the equivalent of one waveform.

[0057] When determining whether the inspection results of the vibration waveforms up to this point have been judged to be abnormal, if they have not been judged to be abnormal, a determination is made as to whether the extracted signal after full-wave rectification and smoothing has reached the amplitude threshold for abnormal vibration. If the judgment shows that the extracted signal after full-wave rectification and smoothing has not reached the amplitude threshold, the extracted signal after full-wave rectification and smoothing, the amplitude threshold excess width, and the inspection result stored in memory are cleared, and a determination is made as to whether an inspection end command has been received from display unit 11. If the inspection end command has not been received at this time, a new digital waveform signal is read, and the above-mentioned processing is repeated.

[0058] Furthermore, when determining whether the extracted signal after the above-mentioned full-wave rectification and smoothing process reaches the amplitude threshold, if the extracted signal reaches the amplitude threshold, the width by which the amplitude exceeds the threshold is gradually increased. Next, it is determined whether the width by which the amplitude exceeds the threshold reaches a set width, and if it does, it is determined that the extracted signal has reached the amplitude threshold for abnormal amplitude multiple times in succession and is not sudden high-frequency noise. As a result, the extracted signal after full-wave rectification and smoothing process, which is temporarily stored in memory, is determined to be abnormal vibration, and the inspection result is saved as an abnormality determination.

[0059] When determining whether the extracted signal after the above-mentioned full-wave rectification and smoothing process reaches the amplitude threshold, the extracted signal is a signal that increases or decreases in a manner that is roughly similar to the abnormal vibration waveform portion in the vibration waveform signal detected by the AE sensor 3, regardless of whether the extracted signal is a signal from a direct connection path between the AE sensor 3 and the amplifier unit 6 or via the high-pass filter 7, and the presence or absence of abnormal vibration can be accurately detected based on the extracted signal.

[0060] Furthermore, when determining whether the extracted signal after the above-mentioned full-wave rectification and smoothing process reaches the amplitude threshold, the extracted signal is a signal that increases and decreases in approximation to the abnormal vibration waveform portion of the vibration waveform signal detected by the AE sensor 3, and is therefore a signal that is not affected by carry-over errors during A / D conversion. Therefore, when determining whether the extracted signal reaches the amplitude threshold and whether the width by which the amplitude threshold is exceeded reaches a set width, i.e., when determining whether the extracted signal reaches the amplitude threshold multiple times in succession, carry-over errors during A / D conversion do not cause the extracted signal near the amplitude threshold to fail to reach the amplitude threshold for abnormal vibration (see Figure 7). As a result, the extracted signal's continuous exceedance of the threshold is not interrupted, preventing the width by which the amplitude threshold is exceeded from reaching the set width, eliminating the erroneous determination that a vibration waveform signal that indicates abnormal vibration when detected by the AE sensor 3 is normal vibration.

[0061] When determining whether the amplitude threshold exceeding width has reached the set width as described above, if it is determined that the amplitude threshold exceeding width has not reached the set width, it is determined whether an inspection end command has been received from display unit 11. If this command has not been received, a new digital waveform signal is read and the above-described processing is repeated.

[0062] When determining whether the width by which the amplitude exceeds the threshold has reached the set width, if it is determined that the width by which the amplitude exceeds the threshold has reached the set width, the test result is set as an abnormality, and then it is determined whether the number of extracted signals after full-wave rectification and smoothing processing in the memory has reached a predetermined number (for one waveform).

[0063] Furthermore, the system determines whether the number of extracted signals after full-wave rectification and smoothing in the memory has reached a predetermined number (for one waveform). If the number has reached the predetermined number, the extracted signal after full-wave rectification and smoothing for one waveform in the memory is transferred to a buffer as an extracted signal for abnormality, and then from the buffer to a PC and external storage unit 13 (after transfer, the memory and amplitude threshold overrange are cleared). The inspection results are saved in internal storage unit 12 for notification, and then an abnormality determination display code is sent to display unit 11, after which the inspection results are cleared. As a result, abnormal vibration is displayed on display unit 11 using the abnormality determination display lamp, and at the same time, the abnormal vibration inspection results are sent to machine device 2 via external I / O 14. The system then determines whether an inspection end command has been received from display unit 11, and the above-mentioned operation is repeated until the inspection end command is received. Regardless of the reception of any of the inspection end commands described above, the extracted signal after full-wave rectification and smoothing, the amplitude threshold overrange, and the inspection results in memory are cleared.

[0064] (Second embodiment) An AE device according to a second embodiment of the present invention (hereinafter referred to as the second AE device) will be described. Although not shown, the second AE device is a modified version of the AE device (hereinafter referred to as the first AE device) 1 of the first embodiment. Therefore, the other components of the second AE device are identical to those of the first AE device 1, and therefore a description of the specific configuration and effects of those components will be omitted. Furthermore, in describing the second AE device, components identical to those of the first AE device 1 will be assigned the same reference numerals. As described above, the second AE device of this embodiment is a modified version of the first AE device 1, with the manual switch 5 disposed in the first AE device 1 removed and the AE sensor 3 and amplifier unit 6 connected via a high-pass filter 7.

[0065] With this configuration, the vibration waveform signal sent to the A / D converter 8 always has mechanical vibrations in the band below its cutoff frequency filtered out by the high-pass filter 7, resulting in a signal that contains only abnormal vibrations and sudden high-frequency noise. Therefore, when the signal is kept within the input voltage observation range of the A / D converter 8 (within ±1 V), the attenuation rate of the amplifier 6 can be small. This allows the attenuation rate of the amplifier 6 to be small when the vibration waveform signal contains mechanical vibrations of excessive amplitude or when the mechanical vibrations in the signal are not significantly different from the abnormal vibration portion. Therefore, the number of quantization steps used to A / D convert the vibration waveform signal is not significantly reduced, ensuring a sufficient number of quantization steps. As a result, the digital waveform signal obtained from the signal and the extracted signal obtained after full-wave rectification and smoothing of the digital waveform signal increase and decrease in a manner that roughly approximates the abnormal vibration waveform portion of the vibration waveform signal detected by the AE sensor 3. The presence or absence of abnormal vibration can be accurately detected from these digital signals, i.e., the extracted signal.

[0066] Furthermore, with this configuration, mechanical vibrations can first be removed by the high-pass filter 7 from the vibration waveform signal detected by the AE sensor 3, and then unnecessary vibrations in the high-frequency band of the mechanical vibrations that cannot be completely removed by the high-pass filter 7 can be removed by the digital filter. Therefore, since it is possible to extract only abnormal vibrations that occur when parts are poorly machined or assembled, it is possible to inspect for abnormal vibrations while eliminating the effects of mechanical vibrations as much as possible.

[0067] The second AE device described above uses an AE sensor 3, just like the first AE device 1, but in environments with small mechanical vibrations, other vibration detection sensors such as piezoelectric sensors may be used, and the object to be inspected may also be made of ceramic material.

[0068] Furthermore, in the second AE device described above, similarly to the first AE device 1, when determining whether or not the vibration waveform signal detected by the AE sensor 3 is abnormal vibration, each time the vibration waveform signal is converted into a digital waveform signal, it is determined whether or not the amplitude of the digital extracted signal after passing through a digital filter reaches an amplitude threshold value for abnormal vibration, and if the threshold value is reached multiple times in succession, it may be configured to determine that abnormal vibration exists. In this case, too, the same effects as those of the first AE device 1 can be obtained.

[0069] As described above, the present invention is a vibration waveform inspection device that includes an AE sensor 3 that detects vibrations occurring in or around an object under inspection, an amplifier unit 6 having an amplification factor that attenuates or amplifies the vibration waveform signal detected by the AE sensor 3, and an A / D conversion unit 8, and converts the vibration waveform signal attenuated or amplified by the amplifier unit 6 into a digital waveform signal using the A / D conversion unit 8, creates a digital filter that removes unnecessary frequencies from the digital waveform signal, and inspects the digital extracted signal extracted by the digital filter for the presence or absence of abnormal vibration.The AE sensor 3 and the amplifier unit 6 are selectively connected either directly or via a high-pass filter 7 that has a cutoff frequency that removes unnecessary mechanical vibrations, and the connection path between the AE sensor 3 and the amplifier unit 6 and the attenuation factor or amplification factor of the amplifier unit 6 are selected depending on the magnitude of the vibrations of unnecessary frequencies and the abnormal vibrations in the vibration waveform signal detected by the AE sensor 3 and the comparison status between them.

[0070] With this configuration, depending on the magnitude of the unnecessary frequency vibrations and abnormal vibrations in the vibration waveform signal detected by the AE sensor 3 and the comparison status between them, i.e., when the unnecessary mechanical vibrations in the vibration waveform signal are excessively large compared to the abnormal vibration waveform portion, the AE sensor 3 and amplifier unit 6 can be connected via the high-pass filter 7. Also, when the unnecessary mechanical vibrations in the vibration waveform detection signal are sufficiently small compared to the abnormal vibration portion, the AE sensor 3 and amplifier unit 6 can be directly connected. Furthermore, when the mechanical vibrations in the vibration waveform detection signal are not significantly different from the abnormal vibration portion, the AE sensor 3 and amplifier unit 6 can be connected via the high-pass filter 7.

[0071] In other words, regardless of the connection path between the AE sensor 3 and amplifier 6 described above, the attenuation rate or amplification rate of amplifier 6 can be selected so that the abnormal vibration waveform portion in the vibration waveform signal detected by AE sensor 3 falls within the observation range of A / D converter 8. This makes it possible to maximize the number of quantization steps for A / D conversion of the abnormal vibration waveform portion depending on the state of unnecessary mechanical vibration and the abnormal vibration waveform portion in the vibration waveform signal detected by AE sensor 3, ensuring a sufficient number of quantization steps to obtain a digital waveform signal that increases and decreases in approximation to the increase and decrease of the vibration waveform signal described above, and enabling accurate detection of the presence or absence of abnormal vibration based on this digital waveform signal.

[0072] The vibration waveform signal according to the present invention may be configured to be detected by an acoustic emission sensor so that even weak abnormal vibrations can be detected when the object to be inspected is a material such as a ceramic material in which abnormal vibrations caused by cracks or the like are particularly weak.

[0073] Furthermore, the connection between the AE sensor 3 and the amplifier 6 according to the present invention, either directly or via a high-pass filter 7, may be configured to be switchable by a manual switch 5, so that the unnecessary mechanical vibration and the abnormal vibration waveform portion in the vibration waveform signal detected by the detection sensor can be simply and easily switched regardless of the situation.

[0074] Furthermore, the vibration waveform signal of the present invention may be configured such that each time it is converted into a digital waveform signal, a determination is made as to whether the amplitude of the digitally extracted signal extracted by the digital filter reaches an amplitude threshold value for abnormal vibration, and if the determination results in the amplitude reaching the threshold value multiple times in succession, it is determined to be abnormal vibration. With this configuration, even if high-frequency noise in the same band as abnormal vibration that occurs due to defective part processing or defective part assembly caused by switch operation or the like around the machine 2 suddenly occurs, the effects of this sudden high-frequency noise can be eliminated.

[0075] Furthermore, the digital extraction signal related to the abnormal vibration determination described above approximates the increase and decrease of the abnormal vibration waveform portion in the vibration waveform signal detected by the AE sensor 3, and is also minimally affected by carry-over errors during A / D conversion, so the digital extraction signal has a waveform that accurately approximates the increase and decrease of the abnormal vibration waveform portion in the vibration waveform signal detected by the AE sensor 3. This makes it possible to minimize erroneous determinations, such as when a vibration waveform signal that was abnormal when detected by the AE sensor 3 is determined to be normal vibration due to carry-over errors during A / D conversion, when determining whether the amplitude threshold is reached based on the digital extraction signal.

[0076] Another aspect of the present invention is characterized by a configuration comprising an AE sensor 3 that detects vibrations occurring around or on an object to be inspected, a high-pass filter 7 in which a cutoff frequency is set to remove unnecessary mechanical vibrations from the vibration waveform signal detected by the AE sensor 3, an amplifier 6 having an amplification factor that amplifies the vibration waveform signal that passes through the high-pass filter 7, and an A / D converter 8, in which the vibration waveform signal amplified by the amplifier 6 is converted into a digital waveform signal by the A / D converter 8, a digital filter is created to remove unnecessary frequencies from the digital waveform signal, and the presence or absence of abnormal vibration is inspected from the digital extracted signal extracted by the digital filter.

[0077] With this configuration, the vibration waveform signal detected by the AE sensor 3 is filtered by the high-pass filter 7 to remove unnecessary mechanical vibrations in a frequency band below the cutoff frequency. The signal is then attenuated or amplified to fit within the observation range of the A / D converter 8, and is then A / D converted into a digital waveform signal by the A / D converter 8. Therefore, particularly when the signal is attenuated to fit within the observation range of the A / D converter 8, the attenuation rate can be significantly smaller than when mechanical vibrations are included. This minimizes the effects of carryover errors during A / D conversion, and the digital extraction signal extracted from the digital waveform signal approximates the increase or decrease in the abnormal vibration waveform portion of the vibration waveform signal detected by the detection sensor. Therefore, the presence or absence of abnormal vibration can be accurately detected based on the digital extraction signal. Furthermore, if the vibration waveform signal that has passed through the high-pass filter 7 is too small to be observed, it is amplified to the limit of the observation range of the A / D converter 8. As a result, as in the case described above, the A / D converted digital waveform signal is affected by carryover errors during A / D conversion. In this case, when checking for abnormal vibration based on the digital extracted signal extracted from the signal, only vibration waveform signals that are not abnormal at the time of detection by the AE sensor 3 are judged to be abnormal vibrations. Therefore, abnormal vibrations will not be overlooked during the inspection.

[0078] Furthermore, with the above configuration, unnecessary mechanical vibrations can first be removed by the high-pass filter 7 from the vibration waveform signal detected by the detection sensor, and then high-frequency noise in a band lower than the band of abnormal vibrations that cannot be completely removed by the high-pass filter 7 can be removed by the digital filter. Therefore, it is possible to reduce the amount of high-frequency noise that is superimposed on abnormal vibrations that occur when parts are poorly processed or assembled and is subjected to A / D conversion, and it is possible to inspect for abnormal vibrations while eliminating the effects of high-frequency noise as much as possible.

[0079] In the first AE device 1 described in the first embodiment of the present invention, the connection between the AE sensor 3 and the amplifier unit 6 is configured to be switched by a manual switch 5. However, it may also be configured to be automatically switched based on the maximum amplitudes of the normal vibration waveform signal and the abnormal vibration waveform signal detected in advance and their ratio. This configuration enables the aforementioned connection to be automatically switched in advance based on the magnitudes of the unnecessary mechanical vibration contained in the normal vibration waveform signal and the abnormal vibration contained in the abnormal vibration waveform signal and the comparison between them. This enables the acquisition of the normal vibration waveform signal and the abnormal vibration waveform signal, the selection of processing for the vibration waveform signal before A / D conversion based on the magnitude of the mechanical vibration, and the determination of whether the vibration waveform signal represents abnormal vibration to be automated. Furthermore, the specific configurations of the various components of the present invention are not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the present invention. [Explanation of symbols]

[0080] 1...AE inspection equipment, 2...machine equipment, 3...Acoustic emission sensor, 5...Manual switch, 6...amplification section, 7...high-pass filter, 8...A / D conversion section, 10...control unit, 11...display unit, 11a...operation buttons, 11b... Lamps, 12... Internal memory unit, 13... External memory unit, 14...I / O for connecting external terminals PC...personal computer

Claims

1. A vibration waveform inspection device comprising a detection sensor that detects vibrations occurring around or on an object to be inspected, an amplifier unit having an amplification factor that attenuates or amplifies the vibration waveform signal detected by the detection sensor, and an A / D conversion unit, wherein the vibration waveform signal attenuated or amplified by the amplifier unit is converted into a digital waveform signal by the A / D conversion unit, a digital filter is created to remove unnecessary frequencies from the digital waveform signal, and the presence or absence of abnormal vibration is inspected from the digital extracted signal extracted by the digital filter, wherein the detection sensor and the amplifier unit are selectively connected either directly or via a high-pass filter having a cutoff frequency that removes unnecessary vibration, and the vibration waveform inspection device is configured to select the connection path between the detection sensor and the amplifier unit and the attenuation factor or amplification factor of the amplifier unit depending on the magnitude of the vibrations of unnecessary frequencies and the abnormal vibrations in the vibration waveform signal detected by the detection sensor and the comparison status between them.

2. 2. The vibration waveform inspection device according to claim 1, wherein the detection sensor is an acoustic emission sensor.

3. 3. The vibration waveform inspection device according to claim 1, wherein the connection between the detection sensor and the amplifier unit is switched by a manual switch either directly or via a high-pass filter having a cutoff frequency set to filter out unnecessary vibrations.

4. 3. The vibration waveform inspection device according to claim 1, wherein the selection of whether to connect the detection sensor to the amplifier unit directly or via a high-pass filter is made based on the maximum amplitudes of the normal vibration waveform signal and the abnormal vibration waveform signal detected in advance and the ratio between them.

5. 3. The vibration waveform inspection device according to claim 1, wherein each time the vibration waveform signal is converted into a digital waveform signal, a determination is made as to whether the amplitude of the digital extracted signal extracted by the digital filter reaches an amplitude threshold value for abnormal vibration, and if the amplitude threshold value is reached multiple times in succession, the vibration is determined to be abnormal.

6. a high-pass filter having a cutoff frequency set to remove unnecessary vibrations from the vibration waveform signal detected by the detection sensor; an amplifier unit that attenuates or amplifies the vibration waveform signal that passes through the high-pass filter; and an A / D converter unit, wherein the vibration waveform signal amplified by the amplifier unit is converted into a digital waveform signal by the A / D converter unit, a digital filter is created to remove unnecessary frequencies from the digital waveform signal, and the presence or absence of abnormal vibrations is inspected from the digital extracted signal extracted by the digital filter.

Images