JP2009025162A - Method and device for detecting crack of component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for readily and accurately detecting a crack of a component in a short time, and a device therefor. <P>SOLUTION: This detecting device is adapted to detect a crack when one component 24 is fitted to another component 23. The detecting device includes: a sound pressure waveform fetching section 11 for generating a sound pressure waveform signal by fetching a sound waveform generated when one component 24 is fitted to another component 23, and a sound pressure level determining section 14. The sound pressure level determining section 14 judges whether a sound level of the generated sound pressure waveform signal is not smaller than or smaller than a prescribed threshold, outputs the sound waveform signal to a frequency analyzing section 15 for computing a frequency spectrum according to the sound waveform signal when the sound pressure level is not smaller than the prescribed threshold, and determines that there is not a crack on the component when the sound pressure level is smaller than the prescribed threshold. The detecting device further includes a determining section 16 that determines presence or absence of a crack on the component by using a spectrum intensity of a low frequency and a spectrum intensity of a high frequency in a frequency spectrum obtained by the frequency analyzing section 15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method and an apparatus for detecting a crack in a part, and more particularly to a method and an apparatus for detecting a crack in a part using sound generated when one part is fitted to the other part.
The present invention also relates to a method for manufacturing a stick coil, and more particularly, to a method for manufacturing a stick coil that uses the above method to determine whether or not a component of the stick coil is cracked.

  Conventionally, a fitting process for fitting one part to the other part is performed in the assembly work of the parts. By fitting the convex part of the other part into the concave part of one part, the movement in the fitting direction can be restricted for the two parts.

  Since the shape of the concave part of one part matches the shape of the convex part of the other part, when the two parts are fitted to each other, there is no gap between the fitting parts. It is formed.

  For example, a stick coil mounted in a plug hole of a gasoline engine has its components assembled and assembled.

  The stick coil is one of the components of a gasoline engine and incorporates an electronic circuit and a coil component. The stick coil is controlled by the engine control unit to supply high voltage and sufficient electrical energy to the spark plug electrodes. The stick coil controls ignition by providing controlled power to the spark plug to increase the combustion efficiency of the gasoline engine.

  An example of a front view of the stick coil 20 is shown in FIG. The stick coil 20 is vertically long and has a generally cylindrical shape. The stick coil 20 has a vertically long stick coil main body 21, a base part 23 is fixed to one end in the longitudinal direction of the stick coil main body 21, and a terminal assembly 22 is fixed to the other end. Has been formed.

  The stick coil main body 21 has a vertically long cylindrical shape, and the longitudinal direction thereof coincides with the stick coil 20. As shown in FIGS. 1 (b) and 1 (c), the stick coil body 21 includes a vertically long and cylindrical metal case part 25, and a vertically long and thin cylindrical resin part 24. The coil part 26 is formed. FIG. 1B is a partially cutaway view of the stick coil 20 shown in FIG. 1A, and the stick coil body 21 shows a cross section in which a cylindrical part 24 and a case part 25 are broken in the longitudinal direction. ing. FIG. 1C is an enlarged sectional view taken along line XX of FIG.

As shown in FIGS. 1B and 1C, the coil component 26 is inserted and arranged inside the cylindrical component 24. The cylindrical component 24 is filled with an epoxy resin (not shown), and the coil component 26 is sealed in the epoxy resin. The coil component 26 is supplied with electrical energy from the terminal assembly 22 and generates a high voltage.
The cylindrical part 24 is inserted and arranged inside the case part 25.

  As shown in FIG. 1C, the case component 25 is formed by laminating an outer layer 25a, an intermediate layer 25b, and an inner layer 25c made of metal. Each of the outer layer 25a, the intermediate layer 25b, and the inner layer 25c has a cylindrical shape in which a part thereof is cut out in the longitudinal direction, and has a C-shaped cross section. Each layer is arranged so that the lacking portions of the adjacent layers do not overlap each other. The case component 25 having such a configuration has flexibility and elasticity in the radial direction, and spreads when the stick coil 20 is assembled.

  The cylindrical part 24 has a vertically long cylindrical shape. The cylindrical part 24 is made of a thin film resin and has a predetermined extensibility. The cylindrical part 24 electrically insulates the case part 25 and the coil part 26. One end in the longitudinal direction of the cylindrical part 24 forms a fitting recess 24 a that fits into the base part 23. The fitting recess 24 a is fitted to the base part 23. In addition, one end portion in the longitudinal direction of the case component 25 is fitted to the base component 23 with a fitting recess 24 a of the cylindrical component 24 interposed therebetween.

  The terminal assembly 22 has an electronic circuit inside and has a terminal for inputting a control signal from the engine control unit. The terminal assembly 22 is controlled by the engine control unit to supply electric energy to the coil component 26.

  One end portion of the base component 23 is electrically connected to the coil component, and the other end portion is electrically connected to the spark plug. The base component 23 supplies high voltage electrical energy output from the coil component 26 to the electrode of the spark plug.

The base part 23 has a fitting convex part 23a into which the cylindrical part 24 is fitted. The fitting convex part 23a is formed with resin, and has a cylindrical shape.
The fitting convex part 23 a of the base part 23 has an outer shape fitted into the fitting concave part 24 a of the cylindrical part 24. The fitting recess 24a of the cylindrical component 24 is fitted in contact with the side surface of the fitting projection 23a as shown in FIG.

  The outer diameter of the fitting convex part 23 a of the base part 23 is slightly larger than the inner diameter of the fitting concave part 24 a of the cylindrical part 24. When fitting the fitting recess 24a to the fitting projection 23a, the cylindrical part 24 is fitted with force.

  The free end portion of the fitting convex portion 23a has a tapered shape, and when the stick coil 20 is assembled, the cylindrical part 24 can be easily fitted into the fitting convex portion 23a. The other end of the fitting convex portion 23a is joined to a collar portion 23b that restricts the movement of the fitted cylindrical part 24. The cylindrical part 24 and the case part 25 are restricted in movement in the fitting direction by the flange 23b.

  Next, a fitting process which is a main part of the method for manufacturing the stick coil 20 will be described below with reference to FIG.

  First, as shown in FIG. 2A, a cylindrical composite 27 is prepared in which a cylindrical part 24 is inserted and fixed inside a case part 25. Also, a base component composite 28 is prepared in which the coil component 26 is fixed to the free end portion of the fitting convex portion 23 a of the base component 23. The cylindrical composite body 27 and the base part composite body 28 are assembled by an assembly apparatus.

  Next, the cylindrical composite 27 is detachably fixed to the drive unit of the assembling apparatus, and the base component composite 28 is detachably fixed to the fixing part of the assembling apparatus. At this time, it is preferable that each is fixed to the assembling apparatus so that the central axis of the cylindrical composite 27 and the central axis of the base component composite 28 coincide with each other. The drive unit can be configured using a servo motor.

  Next, as shown in FIGS. 2A and 2B, the driving unit is driven to bring the cylindrical composite 27 closer to the fixed base component composite 28 while moving the cylindrical composite 27. The coil component 26 of the base component composite 28 is inserted into the cylindrical component 24. When the fitting concave portion 24a of the cylindrical part 24 abuts on the fitting convex portion 23a of the base part 23, the fitting concave portion 24a expands so as to expand outward in the diameter, and the fitting concave portion 24a. The part of the case component 25 that surrounds also expands outward in the diameter. Thus, the fitting recess 24a starts to fit into the fitting projection 23a.

  By applying force to the cylindrical part 24, the fitting convex part 23 a of the base part 23 is completely fitted into the fitting concave part 24 a of the cylindrical part 24, and the end part of the fitting concave part 24 a is the base part 23. The cylindrical composite 27 is driven toward the fixed base component composite 28 until it comes into contact with the flange 23b.

  Thereafter, as shown in FIG. 2C, the cylindrical composite 27 and the base component composite 28 are assembled. Thereafter, the cylindrical part 24 is filled with an epoxy resin, and the coil part 26 is sealed in the epoxy resin.

  In the fitting process described above, the fitting recess 24a of the cylindrical part 24 may be cracked. The reason for the occurrence of this crack is, for example, that the formation dimension of the cylindrical part 24 varies, the inner diameter of the fitting recess 24a may be smaller than the allowable range, and the cylindrical part 24 or the base part. Depending on how the composite body 28 is fixed to the assembling apparatus, the central axis of the cylindrical composite body 27 and the central axis of the base part composite body 28 may deviate beyond an allowable range. In such a case, if the thin film resin forming the cylindrical part 24 is deformed during the fitting process and exceeds the deformation limit, the fitting recess 24a is cracked.

When the cylindrical part 24 is cracked, the epoxy resin filling the cylindrical part 24 leaks from the cracked part, so that the stick coil 20 becomes a defective product.
However, since the periphery of the cylindrical part 24 is covered with the case part 25, the generated crack cannot be confirmed from the appearance of the stick coil 20.

Therefore, as a method for determining whether or not the cylindrical part 24 is cracked, for example, there is a method for detecting leakage of the cylindrical part 24.
However, inspecting the leakage of the cylindrical part 24 requires processing such as pressure injection of a leaking substance for detecting the leak into the stick coil, which takes time and labor. In addition, since a plurality of other processes for manufacturing the stick coil are included between the inspection of the leak and the fitting process, the process performed during this period is useless for defective products. There is also the problem of becoming.

  For example, Patent Document 1 and Patent Document 2 disclose a method for detecting such a crack in a component. Patent Documents 1 and 2 propose a method for detecting glass breakage using sound waves and vibration waves.

Then, the method of determining the presence or absence of a crack using the sound produced when making it fit in the said fitting process was examined as follows.
First, a sound pressure waveform signal was generated by collecting a sound generated during fitting in the fitting process, and a frequency spectrum was obtained by frequency analysis of the sound pressure waveform signal. Then, it was examined to determine the presence or absence of cracks using this frequency spectrum. The results are shown in FIGS. 3 (a) to 3 (c).

  Each of the vertical axes in FIGS. 3A to 3C indicates a frequency spectrum obtained by continuous wavelet transform of a sound pressure waveform signal that changes with time, and the horizontal axis indicates the time. Each plotted point has a darker color as the frequency spectrum intensity is higher.

  FIG. 3A shows the frequency spectrum of the cracking sound of the cylindrical part 24. On the other hand, FIG. 3B and FIG. 3C show the frequency spectrum obtained from the sound collected when the cylindrical part 24 is not cracked. That is, both figures show the frequency spectrum resulting from the assembly apparatus other than the cracking sound and the surrounding sounds.

  As a result, when a crack occurs in the cylindrical part 24, a high-intensity frequency spectrum exists around 7 kHz as shown in FIG. It was found that there was a characteristic distribution of the resulting frequency spectrum. That is, it was found that there is a possibility that the cylindrical part 24 is cracked when a frequency spectrum distribution exists in the vicinity of 7 kHz.

On the other hand, as shown in FIGS. 3 (b) and 3 (c), the frequency spectrum caused by the assembly apparatus and surrounding sounds may have a frequency spectrum distribution in the vicinity of 7 kHz although the frequency spectrum intensity is low. found. That is, it has been found that even if the cylindrical part 24 is not cracked, a frequency spectrum may exist in the vicinity of 7 kHz.
Therefore, when the frequency spectrum is used as described above, there is a risk of erroneously determining that a crack has occurred even if the cylindrical part 24 is not cracked. Therefore, it is necessary to further improve this method. I found out.

JP 2005-44180 A JP-A-6-258194

  It is an object of the present invention to provide a method and an apparatus for detecting a crack in a component that can easily and accurately detect a crack in the component in a short time. It is another object of the present invention to provide a method for manufacturing a stick coil that uses this method for detecting cracks in a component to determine whether or not a component of the stick coil is cracked.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a method for detecting a crack of a component when one component (24) is fitted to the other component (23), the one component (24) being A sound pressure waveform signal is generated by collecting sound generated when fitting (24) to the other component (23), and the sound pressure level of the generated sound pressure waveform signal is equal to or higher than a predetermined threshold value. If there is, the frequency spectrum is obtained from the sound pressure waveform signal, and the presence or absence of cracking of the component is determined using the low-frequency spectrum intensity and the high-frequency spectrum intensity in the frequency spectrum. If the sound pressure level is less than the predetermined threshold value, it is determined that there is no crack in the part.

  Thereby, the crack of components can be detected accurately in a short time.

  The invention according to claim 2 stores the generated sound pressure waveform signal, reads the stored sound pressure waveform signal, and if the sound pressure level is equal to or higher than the predetermined threshold value, the sound pressure The frequency spectrum is obtained from sound pressure waveform signals over a predetermined period before and after the time point when the level is detected to be equal to or higher than the predetermined threshold value.

  Thereby, an accurate frequency spectrum of the cracking sound can be obtained using the sound pressure waveform signal of a predetermined period in which the crack is generated.

  The invention according to claim 3 is characterized in that the presence or absence of cracking of the part is determined without contacting the one part (24) and the other part (23).

  Thereby, in the process of assembling the parts by the flow operation, since the parts are not contacted when detecting the cracks, the cracks of the parts can be detected without reducing the flow speed of the parts.

  According to a fourth aspect of the present invention, a discriminant function having the high frequency spectrum intensity and the low frequency spectrum intensity as arguments is used, and when the discriminant function value is negative, it is determined that there is no part crack. It is characterized by that. According to a fourth aspect of the present invention, as described in the fifth aspect of the present invention, a number of processes for fitting the one part (24) to the other part (23) are performed, and the frequency in each process is determined. Obtaining a spectrum, creating a two-dimensional discriminant analysis diagram in which the maximum value of the low-frequency spectrum intensity in the frequency spectrum is plotted on the vertical axis and the maximum value of the high-frequency spectrum intensity is plotted on the horizontal axis; In the two-dimensional discriminant analysis diagram, an NG distribution region of a plot with a part crack and an OK distribution region of a plot without a part crack are obtained, and the discriminant function is defined as the center of the NG distribution region and the above. The method is preferably applied to a method of detecting a crack of a part that passes through an intermediate point with the center of the OK distribution region and has a straight line expression having an average inclination of the inclination of each distribution region.

  Thereby, the presence or absence of a crack of a component can be determined more accurately based on a statistical criterion.

  According to a sixth aspect of the present invention, the sound pressure waveform signal is a signal that changes with time, and the sound pressure waveform signal is wavelet transformed to obtain the frequency spectrum that changes with time.

  Thereby, the frequency spectrum of the sound pressure waveform signal can be obtained independently of time.

  The invention according to claim 7 is characterized in that the one part (24) is formed of a cylindrical thin film resin and the other part (23) is formed of a columnar resin. .

  The invention according to claim 8 is characterized in that the high-frequency spectrum intensity is caused by cracking noise of a component. Further, in the invention described in claim 8, as in the invention described in claim 9, the low-frequency spectrum intensity detects the crack of the part caused by the cracking sound of the part and the surrounding sound. It is preferably applied to the method.

  Thereby, even if it receives to the influence of a surrounding sound, the crack of components can be detected correctly.

  The invention according to claim 10 is a detection device for detecting a crack of a component when one component (24) is fitted to the other component (23), wherein the one component (24) is A sound pressure waveform input unit (11) for generating a sound pressure waveform signal by inputting a sound pressure waveform generated when fitting to the other component (23), and a sound pressure level of the generated sound pressure waveform signal is predetermined. If the sound pressure level is greater than or equal to the predetermined threshold value, and the sound pressure level is greater than or equal to the predetermined threshold value, the frequency analysis unit obtains the sound pressure waveform signal and the frequency spectrum from the sound pressure waveform signal When the sound pressure level is output to (15) and the sound pressure level is less than the predetermined threshold, the sound pressure level determination unit (14) and the frequency analysis unit (15) determine that there is no crack in the component. Low frequency spectrum intensity and high frequency By using the spectral intensity, determination unit the presence or absence of cracks in the part (16), characterized in that it comprises a.

  Thereby, the same effect as that of claim 1 can be obtained.

  The invention according to claim 11 has a cylindrical part (24) and a columnar part (23) formed of a thin film resin as constituent parts, and the cylindrical part (24) is the columnar part. A method for manufacturing a stick coil (20) formed by being fitted to a component (23), wherein the method for detecting cracks in a component according to any one of claims 1 to 9 is used. The presence or absence of a crack in the cylindrical part (24) is detected.

  Thereby, the presence or absence of the crack of a cylindrical part can be determined and a good stick coil can be manufactured.

  The reference numerals in parentheses attached to the above means are an example showing the correspondence with the specific means described in the embodiments described later.

  Hereinafter, an apparatus for detecting cracks in a component according to the present invention will be described based on a preferred embodiment with reference to the drawings.

FIG. 4 shows a functional block diagram of a device 10 (hereinafter also simply referred to as the present device 10) for detecting a crack in a component according to an embodiment of the present invention.
The apparatus 10 is provided in an assembling apparatus 30 that is one process of manufacturing the stick coil 20 described above. The apparatus 10 applies a force to the cylindrical part 24 formed of a thin film resin as one part in the fitting process, which is a main part of the manufacturing method of the stick coil 20 described with reference to FIG. When the base part 23 formed of resin as the other part is fitted, it is determined whether or not the cylindrical part 24 has been cracked. The manufacturing process of the stick coil 20 is a flow process.

  As shown in FIG. 4, the device 10 includes a sound pressure waveform input unit 11 that inputs a sound pressure waveform generated when the cylindrical part 24 is fitted to the base part 23 and generates a sound pressure waveform signal; Using the generated sound pressure waveform signal, it is determined whether or not there is a crack in the part, the storage calculation unit 12 that outputs the determination result, the output unit 17 that outputs the determination result of the storage calculation unit 12, and the storage calculation unit 12 And an equipment control unit 18 that controls the production equipment of the stick coil 20 in accordance with the determination result output from the equipment.

  The storage calculation unit 12 reads out the sound pressure waveform signal stored in the storage unit 13 that stores the generated sound pressure waveform signal, and the sound pressure level of the sound pressure waveform signal is a predetermined threshold value. If the sound pressure level is equal to or higher than the threshold value, the sound pressure waveform signal is output to the frequency analysis unit 15, and if the sound pressure level is lower than the threshold value, And a sound pressure level determination unit 14 that determines that the cylindrical part 24 is not cracked.

  In addition, the storage calculation unit 12 uses a frequency analysis unit 15 for obtaining a frequency spectrum from the input sound pressure waveform signal, a low-frequency spectrum intensity in the frequency spectrum obtained by the frequency analysis unit 15, and a high-frequency spectrum intensity. And a determination unit 16 for determining whether or not the cylindrical part 24 is cracked.

  In the present specification, the crack of the cylindrical part 24 means a crack of the thin film resin accompanied by the generation of sound and a breakage in which a part is missing.

  The apparatus 10 will be further described below.

First, the sound pressure waveform input unit 11 will be described below.
As shown in FIG. 5, the sound pressure waveform input unit 11 includes a microphone 11a, an amplifier 11b, and an analog / digital (A / D) converter 11c.

  The microphone 11a collects the sound generated by the fitting process, converts the input sound pressure waveform into a voltage, and generates a sound pressure waveform signal that changes with time. The microphone 11a outputs the generated sound pressure waveform signal to the amplifier 11b.

  From the viewpoint of collecting sound with a good S / N ratio, the microphone 11a is preferably arranged as close to the sound source as possible within a range that does not interfere with the fitting process. Specifically, in the present apparatus 10, the microphone 11 a is disposed at a position about 1 cm away from the collar portion 23 b of the base component 23.

The amplifier 11b amplifies the sound pressure waveform signal output from the microphone 11a to an appropriate voltage level as the input level of the A / D converter 11c.
The A / D converter 11c converts the input sound pressure waveform signal, which is an analog signal, into a digital signal. The sampling frequency for A / D conversion is preferably greater than twice the maximum frequency included in the cracking sound. Specifically, in this apparatus 10, the sampling frequency is 44.1 kHz.

  As the microphone 11a, for example, an electric condenser microphone is preferably used from the viewpoint of reducing cost. From the same viewpoint, it is also preferable to use a USB audio amplifier in which an amplifier 11b and an A / D converter 11c are paired.

  Since the apparatus 10 uses the microphone 11a to determine whether or not a part is cracked using only the non-contact-collected sound, the cylindrical part 24 and the base part 23 do not come into contact with each other.

Next, the storage unit 13 of the storage calculation unit 12 will be described below.
When the storage unit 13 receives a storage process start signal from the assembly device 30 of the stick coil 20, the storage unit 13 starts the storage process of the sound pressure waveform signal input from the sound pressure waveform input unit 11. In addition, when the storage unit 13 receives a storage process stop signal from the assembling apparatus 30, the storage unit 13 stops the storage process of the sound pressure waveform signal input from the sound pressure waveform input unit 11.

  Thus, the assembling apparatus 30 outputs a storage process start signal to the storage unit 13 at the start of the fitting process for fitting the cylindrical part 24 to the base part 23, and stores it at the end of the fitting process. The storage process stop signal is output to the unit 13.

  The storage unit 13 stores a sound pressure waveform signal that is a digital signal input from the sound pressure waveform input unit 11. The storage unit 13 can be configured using, for example, a semiconductor memory such as a RAM, a magnetic recording medium storage device, or an optical recording medium storage device.

Next, the sound pressure level determination unit 14 of the storage calculation unit 12 will be described below.
The sound pressure level determination unit 14 sequentially reads out the sound pressure waveform signals stored in the storage unit 13 for one fitting process from the start time of the storage. When the sound pressure level determination unit 14 detects that the sound pressure level of the sound pressure waveform signal is equal to or higher than a predetermined threshold value, the sound pressure level determination unit 14 before and after the time point when the sound pressure level is detected to be higher than the threshold value is detected. The sound pressure waveform signal over a predetermined period is read, and the read sound pressure waveform signal is output to the frequency analysis unit 15.

  The frequency analysis of the sound pressure waveform signal may be performed only on the cracking portion of the cylindrical part 24. Therefore, in the present apparatus 10, when the cylindrical part 24 is cracked, the sound pressure level is much higher than the above threshold by utilizing the fact that the sound pressure level is much higher than that without cracking sound. When this is detected, the frequency analysis of the sound pressure waveform signal is performed.

The threshold value is preferably a value that can clearly distinguish the sound pressure level when there is no cracking sound and the sound pressure level when cracking occurs. Moreover, since this threshold value changes depending on the shape of the component and the forming material or the processing conditions of the fitting process, it is preferable that the threshold value is set appropriately according to these.
As a result of examining the cracking sound of the cylindrical part 24 generated in the fitting process, in the present apparatus 10, the threshold value is set to a value that is three times the sound pressure level when there is no cracking sound.

In addition, when a crack occurs in the cylindrical part 24, the period for performing the frequency analysis is that the period from the time when the crack starts to the time when the crack ends is the target. This is preferable for frequency analysis.
In that case, since cracks may start to occur before the time point when the threshold value is detected, the time point when the frequency analysis is started is preferably a time point before the time point when the threshold value is detected. . In addition, since the time point at which the cracking ends is normally considered to be after the time point when the threshold value is detected, the time point when the frequency analysis is ended is a time point after the time point when the threshold value is detected. It is preferable.

  As a result of examining the time when the crack of the cylindrical part 24 generated in the fitting process starts to occur, the time when the crack ends, and the time when the threshold value of the sound pressure level is detected, The sound pressure waveform signal over 3 msec before and after the threshold value is detected is output to the frequency analysis unit 14 and the frequency analysis is performed to obtain the frequency spectrum. The sound pressure waveform signal for 3 msec before and after the detection of the threshold value includes a sound pressure waveform signal from the time when the cylindrical part 24 starts to crack until the time when the crack ends. become.

  On the other hand, if the sound pressure level of the read sound pressure waveform signal is less than the threshold value, the sound pressure level determination unit 14 determines that the cylindrical part 24 is not cracked. In this case, the sound pressure level determination unit 14 outputs the determination result to the output unit 17.

Next, the frequency analysis unit 15 of the storage calculation unit 12 will be described below.
As shown in FIG. 6, the frequency analysis unit 15 includes a wavelet transform calculator 15a and a corrector 15b.

  The wavelet transform computing unit 15a performs frequency analysis of the sound pressure waveform signal output from the sound pressure level determination unit 14 to obtain a frequency spectrum. The wavelet transform calculator 15 a outputs the obtained frequency spectrum to the corrector 15.

  Since the sound pressure waveform signal input to the wavelet transform computing unit 15a is a signal that changes with time, it is preferable to obtain a frequency spectrum that changes with time. Therefore, in the wavelet transform computing unit 15a of the present apparatus 10, in order to convert the sound pressure waveform signal into a frequency space independently of time, a continuous wavelet transform is used to obtain a frequency spectrum that changes with time. The upper limit of the frequency band to be obtained is set to a value half the sampling frequency described above. As the mother wavelet of the continuous wavelet transform, for example, a Gabor wavelet function can be used.

The corrector 15b can input the frequency spectrum obtained by the wavelet transform calculator 15a and correct the frequency spectrum. The corrector 15b outputs the corrected frequency spectrum to the determination unit 16.
As will be described in detail later, in the cracking discrimination process, when the spectral intensity in the low frequency region and the spectral intensity in the high frequency region are plotted in a two-dimensional discriminant analysis diagram, If they differ greatly, it is preferable to adjust the scale by correcting one or both. In such a case, the gain of the spectral intensity having a predetermined frequency bandwidth can be increased or decreased using the corrector 15b.

  The corrector 15b may correct the frequency spectrum of the microphone 11a in order to correct the frequency characteristics of the microphone 11a or to improve the discrimination accuracy of the discrimination sound analysis by the determination unit 16. In addition, if not particularly necessary, the corrector 15b may output the input frequency spectrum to the determination unit 16 without performing correction processing.

  The correction process performed by the corrector 15b can be determined by appropriately setting a correction coefficient in the corrector 15b.

  The determination unit 16 determines whether or not the cylindrical part 24 is cracked using the frequency spectrum output from the frequency analysis unit 15. The determination unit 16 outputs the determination result to the output unit and the equipment control unit 18 as necessary.

Specifically, the determination unit 16 determines whether or not the cylindrical part 24 is cracked using the low-frequency spectrum intensity and the high-frequency spectrum intensity in the frequency spectrum.
Next, the reason why the determination unit 16 uses the low-frequency frequency spectrum intensity and the high-frequency frequency spectrum intensity will be described below.

  First, using this apparatus 10, the sound pressure waveform signal of the cracking sound of the cylindrical part 24 and the sound pressure waveform signal when no cracking occurs in the cylindrical part 24 are collected, and the respective frequency spectra are obtained. And compared. The results are shown in FIGS.

7 and 8 show the sound pressure waveform signal and its frequency spectrum when the cylindrical part 24 is cracked.
FIG. 7A shows the sound pressure over a total of 6 msec, 3 msec before and after the time when the sound pressure level determination unit 14 detects that the sound pressure level of the sound pressure waveform signal is equal to or higher than the threshold value. A waveform signal is shown. FIG. 7B shows a frequency spectrum obtained by performing continuous wavelet transform on the sound pressure waveform signal of FIG. Each plotted point has a darker color as the frequency spectrum intensity is higher. FIG. 8A and FIG. 8B are similar views.

On the other hand, FIGS. 9 and 10 show the sound pressure waveform signal and its frequency spectrum when the cylindrical part 24 is not cracked. That is, FIG. 9 and FIG. 10 show the sound pressure waveform signal and its frequency spectrum resulting from the assembly device 30 and the surrounding sounds.
FIG. 9A shows a sound pressure waveform signal over 6 msec including the time when the cylindrical part 24 is fitted to the base part 23. FIG. 9B shows a frequency spectrum obtained by performing continuous wavelet transform on the sound pressure waveform signal of FIG. Each plotted point has a darker color as the frequency spectrum intensity is higher. FIG. 10A and FIG. 10B are similar views.

  Next, the frequency spectrum of FIG. 7B and FIG. 8B is compared with the frequency spectrum of FIG. 9B and FIG. It turned out.

  First, as a common point, the frequency spectrum distribution exists in the low frequency region of less than 10 kHz both when there is a cracking sound and when there is no cracking, as described with reference to FIG. That is, the low-frequency spectrum intensity is caused by the cracking sound of the parts and the sound of the assembling apparatus 30 and its surroundings.

  Next, as a difference, the frequency spectrum of FIG. 7 (b) and FIG. 8 (b) caused by cracking sound has a frequency spectrum of high frequency caused by cracking sound in the vicinity of 10 kHz to 20 kHz. It exists with strength. On the other hand, there is almost no frequency spectrum in the vicinity of 10 kHz to 20 kHz of the frequency spectrum of FIG. 9B and FIG. That is, the high-frequency spectrum intensity is mainly due to the cracking sound of parts.

  Therefore, in the present apparatus 10, when the cylindrical part 24 is cracked, it exists in the frequency spectrum, but when the cylindrical part 24 is not cracked, it hardly exists in the frequency spectrum, and the assembling apparatus. The frequency spectrum of the high frequency, which is a characteristic of cracking sound, which hardly originates from the sound of 30 and its surroundings, is used to determine whether or not the cylindrical part 24 is cracked.

  Further, as a characteristic of cracking sound, a frequency spectrum having a low frequency of less than 10 kHz is also used for determining whether or not the cylindrical part 24 is cracked. For example, a device that generates high-frequency sound may be used around the assembling device 30. When the microphone 11 a of the sound pressure waveform input unit 11 inputs such high-frequency sound, the frequency spectrum thereof is used. This is because there is a possibility that a high frequency spectrum around 10 kHz to 20 kHz exists. Therefore, the determination of the presence or absence of cracks in the frequency spectrum of a low frequency of less than 10 kHz as well as the frequency spectrum of a high frequency in the vicinity of 10 kHz to 20 kHz was made to prevent erroneous determination.

  More specifically, the determination unit 16 uses a discriminant function having the high-frequency spectrum intensity and the low-frequency spectrum intensity as arguments. If the discriminant function value is negative, the determination unit 16 determines that there is no part crack.

  Next, an example of how to obtain the discriminant function will be described below. In this example, the discriminant function is obtained according to the so-called discriminant analysis method.

  First, a large number of the above fitting processes for applying a force to the cylindrical part 24 and fitting it to the base part 23 are performed to obtain a frequency spectrum in each process, and the maximum value of the low-frequency spectrum intensity in the frequency spectrum is plotted on the vertical axis. A two-dimensional discriminant analysis diagram is created by plotting the maximum value of the high-frequency spectrum intensity as the value on the horizontal axis.

Here, in order to create a two-dimensional discriminant analysis diagram, from the viewpoint of improving statistical reliability, the number of plots with and without cracks in the cylindrical part 24 is 30 or more. It is preferable to use it.
The maximum value of the low-frequency spectrum intensity was selected from the frequency region where the frequency was less than 10 kHz in each frequency spectrum. Moreover, the maximum value of the spectrum intensity of the high frequency in the frequency spectrum was selected from the frequency range of 10 kHz to 22.1 kHz in each frequency spectrum.

  Next, in the two-dimensional discriminant analysis diagram, the NG distribution region P of the plot with the crack of the cylindrical part 24 and the OK distribution region Q of the plot with no crack of the cylindrical part 24 are obtained.

Here, assuming that each of the NG distribution region P and the OK distribution region Q is a Gaussian distribution, the two-dimensional discriminant analysis chart is statistically processed to obtain the center of each distribution.
FIG. 11 shows an example of the two-dimensional discriminant analysis diagram created in this way. In the example shown in FIG. 11, the plots indicating the peripheries of the NG distribution region P and the OK distribution region Q represent positions that are separated from the center of the distribution by a value that is three times the standard deviation.

  The distribution width of the NG distribution region P in the vertical axis direction and the horizontal axis direction is larger than that of the OK distribution region Q. In addition, the maximum value of the high-frequency spectrum intensity in the OK distribution region Q is very small compared to the NG distribution region P.

  In the example shown in FIG. 11, the average value of the frequency that gives the maximum value of the frequency spectrum intensity of the high frequency in the NG distribution region P is about 20 kHz. Moreover, the average value of the frequency giving the maximum value of the frequency spectrum intensity of the low frequency in the NG distribution region P was about 7 kHz.

  In the example shown in FIG. 11, each of the NG distribution region P and the OK distribution region Q has a different distribution slope. The NG distribution region P has an inclination with respect to the vertical axis and the horizontal axis, whereas the OK distribution region Q has an inclination substantially along the vertical axis.

Thereafter, the discriminant function is obtained as an equation of a straight line passing through an intermediate point between the center of the NG distribution region P and the center of the OK distribution region Q and having an average inclination of the inclinations of the respective distribution regions. The formula of this straight line is shown by a chain line in FIG.
An example of this discriminant function is f (x, y) = ax + by + c. Here, x is the maximum value of the frequency spectrum intensity at the high frequency, y is the maximum value of the frequency spectrum intensity at the low frequency, and a, b, and c are constants.

  This discriminant function is preferably translated by a predetermined amount toward the center of the OK distribution region Q because the cylindrical part 24 having a crack is not determined to have no crack due to a statistical error.

The discriminant function obtained in this way is set in the determination unit 16.
And the determination part 16 determines the presence or absence of the crack of the cylindrical component 24 using the said discriminant function as follows.

  First, the determination unit 16 selects the maximum value of the low-frequency spectrum intensity and the maximum value of the high-frequency spectrum intensity from the frequency spectrum output by the frequency analysis unit 15.

  Here, the determination unit 16 may select the maximum value of the high-frequency spectrum intensity and the maximum value of the low-frequency spectrum intensity for each input frequency spectrum. In order to achieve this, the maximum value of the high frequency spectrum intensity is set to the average value of the frequency giving the maximum value of the high frequency frequency spectrum intensity of the NG distribution region P, that is, the frequency spectrum intensity of 20 kHz. Similarly, the maximum value of the low-frequency spectrum intensity is set to the average value of the frequency that gives the maximum value of the low-frequency frequency spectrum intensity in the NG distribution region P, that is, the frequency spectrum intensity of 7 kHz. Alternatively, the maximum value of the frequency spectrum intensity may be selected from a predetermined range centered on the average value of each frequency, for example, ± 3 kHz.

  Next, the determination unit 16 calculates the maximum value of the selected high-frequency spectrum intensity and the maximum value of the low-frequency spectrum intensity, calculates the value of the discriminant function using these as arguments, and if the value is negative, It is determined that there is no crack in the cylindrical part 24, and when it is 0 or more, it is determined that the cylindrical part 24 has a crack.

  If it demonstrates in the example shown in FIG. 11, if the determination part 16 is located in the area | region below the formula of the straight line shown with a dashed line, the spectral value of a low frequency will be that there is no crack of the cylindrical component 24. judge. On the other hand, if the maximum value of the low-frequency spectral intensity is located in the upper region including the straight line expression indicated by the chain line, it is determined that the cylindrical part 24 is cracked. Note that FIG. 11 does not show the portion where the value of the vertical axis is equal to or less than zero in the above linear equation.

  Then, the determination unit 16 outputs the determination result to the output unit 17. If the determination unit 16 determines that the cylindrical part 24 is cracked, the determination unit 16 also outputs the determination result to the equipment control unit 18.

Next, the output unit 17 will be described below.
The output unit 17 includes an output device such as a monitor or a printer. The output unit 17 outputs the determination result input from the determination unit 16 using the output device.

Next, the facility control unit 18 will be described below.
When the equipment control unit 18 inputs a determination result indicating that the cylindrical part 24 is cracked from the determination unit 16, an alarm is issued by the alarm device, and the cylindrical part 24 is moved from the flow process of manufacturing the stick coil 20. The work-in-process of the stick coil 20 having a crack is quickly and automatically removed from the manufacturing process.

  The storage calculation unit 12 of the apparatus 10 described above can be realized using, for example, an industrial computer or a personal computer equipped with an input / output interface. That is, the hardware configuration of the storage operation unit 12 includes, for example, a central processing unit (CPU), a numerical operation processor, a semiconductor memory such as ROM or RAM, a magnetic recording medium storage device or an optical recording medium storage device, an input / output interface, and the like. can do. The storage processing or determination processing performed by the apparatus 10 is realized by a central processing unit (CPU) or a numerical arithmetic processor executing a predetermined program recorded on the magnetic recording medium or the optical recording medium.

  According to the apparatus 10 described above, it is possible to easily determine the presence or absence of the cylindrical part 24 after assembly by the fitting process, and to detect the cylindrical part 24 having a crack in a short time. Therefore, in the manufacturing process of the stick coil 20 provided with the present apparatus 10, when the processing in the assembling apparatus 30 is finished, the work-in-process product of the stick coil 20 having a crack in the cylindrical part 24 is moved to the next process. It can be removed from the manufacturing process before.

  Further, in the present apparatus 10, by using the low-frequency spectrum intensity and the high-frequency spectrum intensity in the frequency spectrum, the cylindrical part 24 can be cracked even under the influence of the assembly apparatus 30 and surrounding sounds. It can be detected accurately.

  Further, since the apparatus 10 does not come into contact with the component when detecting the crack of the cylindrical component 24, the cylindrical component can be obtained without reducing the flow rate of the component in the flow process for manufacturing the stick coil 20. The presence or absence of 24 cracks can be detected.

  Moreover, in this apparatus 10, since the said discriminant function is defined based on a statistical judgment standard, the presence or absence of the crack of the cylindrical component 24 can be determined more correctly.

  As described above, the cylindrical part 24 formed of a thin film resin and the base part 23 that is a columnar part are included as constituent parts, and the cylindrical part 24 is formed by being fitted to the base part 23. In the manufacturing process of the stick coil 20, a non-defective stick coil can be manufactured by detecting the presence or absence of cracks in the cylindrical part 24 using the apparatus 10. 2A to 2C, the main part of the method for manufacturing the stick coil 20 has been described, but the other parts of the stick coil 20 can be manufactured in accordance with a conventional method.

  Next, referring to FIG. 12 and FIG. 13, based on a preferred embodiment using the apparatus 10 for detecting cracks of the embodiment shown in FIG. However, it will be described below.

  The present embodiment is a method for detecting a crack in a part when a force is applied to a cylindrical part 24 which is one part and the base part 23 which is the other part is fitted. A sound pressure waveform signal is generated by sampling a sound generated when the base component 23 is fitted, and if the sound pressure level of the generated sound pressure waveform signal is equal to or higher than a predetermined threshold, the frequency is calculated from the sound pressure waveform signal. The spectrum is obtained, and the presence or absence of cracking of the component is determined using the low-frequency spectrum intensity and the high-frequency spectrum intensity in the frequency spectrum, and the sound pressure level of the sound pressure waveform signal is less than the predetermined threshold value. If so, it is determined that there is no crack in the part.

  Hereinafter, this embodiment will be further described. FIG. 12 is a flowchart showing an example of an operation procedure of the device 10 for detecting a crack in a component according to the present invention. FIG. 13 is a flowchart for explaining the processing in step S13 in FIG.

  The apparatus 10 is provided in an assembling apparatus 30 that is a process of manufacturing the stick coil 20. In the assembling apparatus 30, the parts that flow through the manufacturing process of the stick coil 20 are sequentially assembled.

  First, in step S 10, the apparatus 10 uses the sound pressure waveform input unit 11 to collect sound generated when a force is applied to the cylindrical part 24 to fit the base part 23, and a sound pressure waveform signal is obtained. Is generated. The sound pressure waveform input unit 11 outputs the generated sound pressure waveform signal to the storage unit 13 of the calculation storage unit 12.

  Next, in step S <b> 11, the storage unit 13 determines whether a storage process start signal is input from the assembling apparatus 30. If the start signal is input, the storage unit 13 proceeds to step S12. On the other hand, if the memory | storage part 13 has not input the start signal, it will return before S11.

  Next, in step S <b> 12, the storage unit 13 stores the sound pressure waveform signal until a storage process stop signal is input from the assembling apparatus 30.

  Next, in step S <b> 13, the storage calculation unit 12 performs a determination process for the sound pressure waveform signal stored in the storage unit 13. Details of the process of S13 will be described later.

  Next, in step S <b> 14, the apparatus 10 outputs a determination result using the output unit 18. In this manner, after the detection processing for the presence or absence of cracking of the cylindrical part 24 is completed for one fitting process, the cylindrical part 24 is returned to the previous fitting process and the next fitting process. Continue detection processing for cracks.

  Next, the process of S13 will be described in detail below with reference to FIG.

  First, in step S <b> 20, the sound pressure level determination unit 14 reads the sound pressure waveform signal stored in the storage unit 13.

  Next, in step S21, the sound pressure level determination unit 14 determines whether the sound pressure level of the read sound pressure waveform signal is equal to or higher than the threshold value. If the sound pressure level is equal to or higher than the threshold value, the process proceeds to step S22. On the other hand, if the sound pressure level of the read sound pressure waveform signal is less than the threshold value, the process proceeds to step S28.

  Next, in step S22, the sound pressure level determination unit 14 reads out the sound pressure waveform signal over 6 msec before and after the point in time when it is detected that the sound pressure level is equal to or higher than the threshold value. The waveform signal is output to the frequency analysis unit 15.

  Next, in step S <b> 23, the frequency analysis unit 15 obtains a frequency spectrum by performing continuous wavelet transform on the read sound pressure waveform signal, and outputs the frequency spectrum to the determination unit 16.

  Next, in step S24, the determination unit 16 selects the maximum value of the low-frequency spectrum intensity and the maximum value of the high-frequency spectrum intensity from the input frequency spectrum, and uses the above discriminant function as an argument. Find the value.

  Next, in step S25, the determination unit 16 determines whether the value of the discriminant function is positive or negative. If the value of the discriminant function is negative, the process returns to S20. On the other hand, if the value of the discriminant function is 0 or more, the process proceeds to step S26.

  If the process proceeds from S25 to S20, the process from S20 is repeated. That is, when the sound pressure waveform signal stored in a certain fitting process has a plurality of points indicating the sound pressure level equal to or higher than the threshold value, for each point indicating the threshold value, , S22 to S25 are performed.

  On the other hand, when the process proceeds from S25 to step S26, in S26, the determination unit 16 determines that the cylindrical part 24 has a crack.

  Next, in step S27, the determination unit 16 outputs a determination result that the equipment control unit 18 has a crack in the cylindrical part 24 to the equipment control unit 18, and proceeds to step S30. The equipment control unit 18 that has input the determination result issues an alarm with an alarm device and removes the work-in-process product of the stick coil 20 that the cylindrical part 24 is cracked from the manufacturing process of the stick coil 20.

  On the other hand, when the process proceeds to step S28 in S21, in S28, the sound pressure level determination unit 14 determines whether or not all the sound pressure waveform signals have been read. If all the sound pressure waveform signals have been read, the process proceeds to step S29. On the other hand, if all the stored sound pressure waveform signals have not been read, the process returns to before S20 and repeats the processes of S20 and S21.

  Next, in step S29, the sound pressure level determination unit 14 determines that there is no crack in the cylindrical part 24, and proceeds to step S30. That is, when the sound pressure waveform signal stored in a certain fitting process does not have any point indicating the sound pressure level equal to or higher than the threshold value, the present embodiment does not perform frequency analysis. It is determined that the cylindrical part 24 is not cracked.

  Next, in step S30, the apparatus 10 ends the sound pressure waveform signal discrimination processing, returns to the processing in FIG. 12, and proceeds to S14.

  According to the above-described embodiment, when the sound pressure waveform signal stored in a certain fitting process has a plurality of points indicating sound pressure levels equal to or higher than the threshold value, the respective threshold values are used. Since the presence or absence of a crack is determined using the frequency spectrum for each point indicating a value, the crack of the cylindrical part 24 can be reliably detected.

  If the sound pressure waveform signal stored in a certain fitting process does not have any point indicating the sound pressure level equal to or higher than the threshold value, the cylindrical part 24 is not subjected to frequency analysis. Since it can be determined that there are no cracks, unnecessary frequency analysis is not performed, and the time required for detection is short.

  The method and apparatus for detecting cracks and the method for manufacturing a stick coil according to the present invention are not limited to the above-described embodiments or embodiments, and can be appropriately changed without departing from the spirit of the present invention.

  For example, in the above-described embodiments and implementations, the high frequency spectrum intensity is mainly caused by the cracking sound of the component, and the low frequency spectrum intensity is generated by the cracking sound of the component, the assembly device, and the surrounding sound. However, the low-frequency spectral intensity is mainly due to the cracking noise of the parts, and the high-frequency spectral intensity is due to the cracking noise of the parts and the assembly equipment and the surrounding sounds. You may do it.

  In the embodiment and the embodiment described above, the low-frequency spectrum intensity is obtained from around 7 kHz, and the high-frequency spectrum intensity is obtained from around 20 kHz. Since it varies depending on the shape and forming material of the component or the processing conditions of the fitting process, it is preferable to appropriately select two frequency values resulting from cracking of the component in accordance with these conditions.

  In the above-described embodiment and implementation, the frequency analysis unit 15 uses continuous wavelet transform, but may perform frequency transform using short-time Fourier transform.

1A shows a front view of the stick coil, FIG. 1B is a partially broken front view of the stick coil shown in FIG. 1A, and FIG. The XX expanded sectional view of 1 (a) is shown. FIG. 2A to FIG. 2C are diagrams for explaining a main part of the method of manufacturing the stick coil. FIG. 3A shows the frequency spectrum of the cracking sound of the cylindrical part, and FIG. 3B and FIG. 3C show the frequency spectrum of the assembling apparatus and surrounding sounds. FIG. 4 is a functional block diagram of an apparatus for detecting a crack in a component according to an embodiment of the present invention. FIG. 5 is a diagram for explaining the sound pressure waveform input unit of FIG. FIG. 6 is a diagram illustrating the frequency analysis unit of FIG. FIG. 7 (a) shows the sound pressure waveform signal when the cylindrical part is cracked, and FIG. 7 (b) shows the frequency spectrum of the sound pressure waveform signal of FIG. 7 (a). Yes. 8A shows another sound pressure waveform signal when a cylindrical part is cracked, and FIG. 8B shows the frequency spectrum of the sound pressure waveform signal of FIG. 8A. Show. FIG. 9A shows the sound pressure waveform signal when the cylindrical part is not cracked, and FIG. 9B shows the frequency spectrum of the sound pressure waveform signal of FIG. 9A. ing. FIG. 10 (a) shows another sound pressure waveform signal when the cylindrical part is not cracked, and FIG. 10 (b) shows the frequency spectrum of the sound pressure waveform signal of FIG. 10 (a). Is shown. FIG. 11 shows a two-dimensional discriminant analysis diagram used by the apparatus of FIG. FIG. 12 is a flowchart showing a procedure of a method for detecting a crack in a component according to the present invention. FIG. 13 is a flowchart for explaining the process of S13 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Detection apparatus which detects crack of part 11 Sound pressure waveform input part 11a Microphone 11b Amplifier 11c A / D converter 12 Memory | storage calculation part 13 Memory | storage part 14 Sound pressure level determination part 15 Frequency analysis part 15a Wavelet conversion calculator 15b Corrector DESCRIPTION OF SYMBOLS 16 Judgment part 17 Output part 18 Equipment control part 20 Stick coil 21 Stick coil main body 22 Terminal assembly 23 Base part 23a Fitting convex part 23b Collar part 24 Cylindrical part 24a Fitting recessed part 25 Case part 25a Outer layer 25b Middle layer 25c Inner side Layer 26 Coil parts 30 Assembly device

Claims (11)

A method of detecting a crack in a component when fitting one component (24) to the other component (23),
A sound pressure waveform signal is generated by collecting a sound generated when the one component (24) is fitted to the other component (23);
If the sound pressure level of the generated sound pressure waveform signal is equal to or higher than a predetermined threshold, a frequency spectrum is obtained from the sound pressure waveform signal, and a low-frequency spectrum intensity and a high-frequency spectrum intensity in the frequency spectrum are obtained. To determine if there is a crack in the part,
If the sound pressure level of the sound pressure waveform signal is less than the predetermined threshold value, it is determined that there is no crack in the part.
A method for detecting cracks in a part characterized by the above. The generated sound pressure waveform signal is stored, the stored sound pressure waveform signal is read, and if the sound pressure level is equal to or higher than the predetermined threshold value,
2. The component according to claim 1, wherein the frequency spectrum is obtained from a sound pressure waveform signal over a predetermined period before and after detecting that a sound pressure level is equal to or higher than the predetermined threshold. How to detect cracks.   The method for detecting cracks in a component according to claim 1 or 2, wherein the presence or absence of a crack in the component is determined without contacting the one component (24) and the other component (23).   The discriminant function having the high frequency spectrum intensity and the low frequency spectrum intensity as arguments is used, and when the discriminant function value is negative, it is determined that there is no crack in the part. 4. A method for detecting a crack in a component according to any one of 3 above. A number of processes for fitting the one part (24) to the other part (23) are performed to obtain the frequency spectrum in each process, and the maximum value of the spectrum intensity of the low frequency in the frequency spectrum is plotted on the vertical axis. A two-dimensional discriminant analysis diagram in which the maximum value of the high-frequency spectrum intensity is plotted as the value on the horizontal axis,
In the two-dimensional discriminant analysis diagram, an NG distribution area of a plot with a crack of a part and an OK distribution area of a plot with no crack of the part are obtained,
The discriminant function is
5. The straight line equation passing through an intermediate point between the center of the NG distribution region and the center of the OK distribution region and having an average inclination of the inclinations of the respective distribution regions. To detect cracks in parts.   6. The sound pressure waveform signal is a signal that changes with time, and the frequency spectrum that changes with time is obtained by wavelet transforming the sound pressure waveform signal. A method for detecting cracks in the described part.   The one part (24) is made of a cylindrical thin film resin, and the other part (23) is made of a columnar resin. The method of detecting the crack of the component as described in a term.   The method for detecting cracks in a component according to any one of claims 1 to 7, wherein the high-frequency spectrum intensity is caused by a cracking sound of the component.   The method of detecting cracks in a component according to any one of claims 1 to 8, wherein the low-frequency spectrum intensity is caused by a crack sound of the component and an ambient sound. A detection device for detecting a crack in a component when fitting one component (24) to the other component (23),
A sound pressure waveform input unit (11) for generating a sound pressure waveform signal by inputting a sound pressure waveform generated when the one component (24) is fitted to the other component (23);
It is determined whether the sound pressure level of the generated sound pressure waveform signal is equal to or higher than a predetermined threshold, and if the sound pressure level is equal to or higher than the predetermined threshold, the sound pressure waveform signal is A sound pressure level determination unit (15) that outputs a frequency spectrum from the sound pressure waveform signal to a frequency analysis unit (15) and determines that there is no cracking of the component if the sound pressure level is less than the predetermined threshold value. 14)
A determination unit (16) for determining the presence or absence of cracks in the component using the low-frequency spectrum intensity and the high-frequency spectrum intensity in the frequency spectrum obtained by the frequency analysis unit (15);
A detection device for detecting cracks in a component, comprising: A cylindrical part (24) and a columnar part (23) formed of a thin film resin are included as constituent parts, and the cylindrical part (24) is fitted to the columnar part (23). A method of manufacturing a formed stick coil (20), comprising:
A method of manufacturing a stick coil, wherein the presence or absence of cracks in the cylindrical part (24) is detected using the method for detecting cracks in a part according to any one of claims 1 to 9.