JP2015203638A - Axial force measuring apparatus and axial force measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial force measuring apparatus and an axial force measuring method capable of accurately measuring axial force even with a simple configuration.SOLUTION: An ultrasonic generator generates at least two kinds of burst waves which are a first burst wave and a second burst wave different from the first burst wave. A signal processing part measures propagation time T by making the first burst wave incident on a coupled long member, measures signal strength for each oscillatory frequency by making the second burst wave incident while changing the oscillatory frequency, obtains outline axial force F' in the propagation time T measured from a first master curve M1, obtains an interference frequency range fr in the outline axial force F' from a second master curve M2, obtains the maximum interference frequency Q with the maximum signal strength in the interference frequency range fr from the measured signal strength for each oscillatory frequency, and measures the axial force of the long member on the basis of the obtained maximum interference frequency Q and the second master curve M2.

Description

  The present invention relates to an axial force measuring device and an axial force measuring method. More specifically, a probe that receives ultrasonic waves from one end of the long member and receives reflected waves reflected from the other end of the long member, an ultrasonic generator that generates the ultrasonic waves, and The present invention relates to an axial force measuring device and an axial force measuring method including a signal processing unit that processes a reflected wave signal and measures the axial force of the long member.

  Conventionally, as an axial force measurement method using ultrasonic waves as described above, for example, a method shown in Patent Document 1 is known. When an axial force is applied to the bolt, the bolt is extended, and the propagation time of the ultrasonic wave is extended due to the extension of the bolt. Therefore, in the method of Patent Document 1, an ultrasonic pulse is incident from the head of the bolt and the propagation time of the ultrasonic wave reflected and returned from the bolt end is measured, and the axial force of the bolt is measured based on this propagation time. To do. However, when the length of the bolt is short, the extension of the bolt by tightening is also shortened, and the accuracy may be lowered. There is also a risk of misreading the time due to amplitude or waveform distortion.

  As another method, there is also known a method (resonance method) in which the oscillation frequency of ultrasonic waves incident from the bolt head is swept to measure the resonance frequency corresponding to the length of the bolt. In this method, in order to detect the resonance frequency corresponding to the change in the bolt length caused by the axial force, vibration energy for maintaining the resonance state must be continuously supplied.

JP-A-5-203513

  In view of such a conventional situation, an object of the present invention is to provide an axial force measuring device and an axial force measuring method capable of accurately measuring an axial force with a simple configuration.

  In order to achieve the above object, the axial force measuring device according to the present invention is characterized in that a probe that receives ultrasonic waves from one end of a long member and receives reflected waves reflected from the other end of the long member; In the configuration comprising the ultrasonic generator for generating the ultrasonic wave and the signal processing unit for processing the received reflected wave signal and measuring the axial force of the long member, the ultrasonic generator includes at least a first One burst wave and a second burst wave different from the first burst wave are generated, and the signal processing unit measures a propagation time of the first burst wave. A signal intensity measuring unit that measures the signal intensity of the second burst wave in a measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave for each oscillation frequency, and the propagation time for a known axial force Seeking first And a second master curve for obtaining a maximum interference frequency that maximizes the signal intensity with respect to the known axial force, and measuring the propagation time by causing the first burst wave to enter the fastened long member In addition, the second burst wave is incident while changing the oscillation frequency, the signal intensity is measured for each oscillation frequency, the approximate axial force at the propagation time measured from the first master curve is obtained, and the second The interference frequency range in the approximate axial force is obtained from the master curve, the maximum interference frequency that is the maximum signal strength within the interference frequency range is obtained from the measured signal intensity for each oscillation frequency, and the obtained maximum interference frequency and the second interference frequency are obtained. It is to measure the axial force of the long member by a master curve.

  According to the above configuration, the signal processing unit includes the propagation time measurement unit that measures the propagation time of the first burst wave, and the first measurement time in the measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave for each oscillation frequency. A signal strength measurement unit that measures the signal strength of two burst waves, a first master curve that determines the propagation time for a known axial force, and a second master curve that determines the maximum interference frequency that maximizes the signal strength for the known axial force With. Two different kinds of first and second burst waves are generated by one ultrasonic generator. Therefore, the apparatus configuration is simplified. For example, as shown in FIG. 9, the approximate axial force F ′ at the propagation time T of the first burst wave measured from the first master curve M1 is obtained, and the interference at the approximate axial force F ′ obtained from the second master curve M2 is obtained. The frequency range fr is obtained, and the maximum interference frequency Q that provides the maximum signal strength within the interference frequency range fr obtained from the measured signal strength for each oscillation frequency is obtained. Then, the axial force of the long member is calculated from the obtained maximum interference frequency Q and the second master curve M2. In this way, since the approximate axial force is obtained from the propagation time of the first burst wave and the interference frequency range is obtained from the approximate axial force, the maximum interference frequency of the second burst wave can be predicted, and errors due to misreading of peak values etc. Measurement can be prevented. Therefore, it is possible to measure the axial force with high accuracy with a simple configuration.

  In order to achieve the above object, another feature of the axial force measuring apparatus according to the present invention is that a probe receives ultrasonic waves from one end of a long member and receives reflected waves reflected from the other end of the long member. In the configuration comprising a child, an ultrasonic generator that generates the ultrasonic wave, and a signal processing unit that processes the received reflected wave signal and measures the axial force of the elongated member, the ultrasonic generator includes: At least two burst waves of a first burst wave and a second burst wave different from the first burst wave are generated, and the signal processing unit is a propagation time for measuring a propagation time of the first burst wave. A measurement unit, a signal intensity measurement unit for measuring the signal intensity of the second burst wave in a measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave for each oscillation frequency, and the above-described known axial force Determine the propagation time A master curve and a second master curve for obtaining a maximum interference frequency at which the signal intensity with respect to the known axial force is maximized, and the propagation time is determined by causing the first burst wave to enter the fastened long member. Measure and make the second burst wave incident while changing the oscillation frequency, measure the signal intensity for each oscillation frequency to obtain the maximum interference frequency, and at the maximum interference frequency obtained from the second master curve Obtain an approximate axial force, obtain the propagation time range in the approximate axial force obtained from the first master curve, obtain a maximum propagation time that gives the maximum signal strength within the propagation time range from the measured propagation time, and obtain The axial force of the long member is measured by the maximum propagation time and the first master curve.

  According to the above configuration, the signal processing unit includes the propagation time measurement unit that measures the propagation time of the first burst wave, and the first measurement time in the measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave for each oscillation frequency. A signal strength measurement unit that measures the signal strength of two burst waves, a first master curve that determines the propagation time for a known axial force, and a second master curve that determines the maximum interference frequency that maximizes the signal strength for the known axial force With. Two different kinds of first and second burst waves are generated by one ultrasonic generator. Therefore, the apparatus configuration is simplified. For example, as shown in FIG. 12, the approximate axial force F ′ at the maximum interference frequency Q of the second burst wave obtained from the second master curve M2 is obtained, and the approximate axial force F ′ obtained from the first master curve M1 is obtained. The propagation time range tr is obtained, and the maximum propagation time T ′ that gives the maximum signal strength within the propagation time range tr is obtained from the measured propagation time. Then, the axial force of the long member is calculated from the obtained maximum propagation time T ′ and the first master curve M1. In this way, since the approximate axial force is obtained from the maximum interference frequency of the second burst wave and the propagation time range is obtained from the approximate axial force, the maximum propagation time of the first burst wave can be predicted, and due to misreading of the peak value etc. Incorrect measurement can be prevented. Therefore, it is possible to measure the axial force with high accuracy with a simple configuration.

  The second burst wave may be longer than the propagation time of the first reflected wave and shorter than the propagation time of the second reflected wave. If the propagation time of the first reflected wave is less than the propagation time of the first reflected wave, the interference wave does not occur, and if the propagation time of the reflected wave of the second time is exceeded, three or more waves propagating through the long member (incident wave and first wave) , The second reflected wave) makes it difficult to observe interference, and the accuracy decreases.

  The measurement time may be a time from the propagation time of the second reflected wave to the propagation time of the third reflected wave. If it is before the propagation time of the second reflected wave, it becomes interference between the transmission and the first reflected wave, but it is difficult to observe the interference because the amplitude difference is too large. On the other hand, if it is after the propagation time of the third reflected wave, the signal becomes small due to attenuation, and it is difficult to detect with high accuracy.

  The first burst wave may have a wave number of 0.5 wave or more and shorter than the arrival time of the first reflected wave. If it is smaller (shorter) than the wave number of 0.5 waves, the generation efficiency of ultrasonic waves is lowered and the accuracy is lowered. On the other hand, if the time is longer than the arrival time of the first reflected wave, a plurality of waves propagate and it is difficult to accurately measure the propagation time.

  The length of the long member is preferably 5 mm or more and 300 mm or less. If it is this length, by applying the values obtained by using the first and second burst waves to the first and second master curves, without using an oscilloscope or A / D converter with a fast sampling frequency, It is possible to measure the axial force with high accuracy using an inexpensive device.

  In order to achieve the above object, the axial force measurement method according to the present invention is characterized in that an ultrasonic wave is incident from one end of a long member and a reflected wave reflected from the other end of the long member is received and received. In the method of measuring the axial force of the long member based on a wave signal, the first burst wave is measured in advance by making the first burst wave incident from one end of the long member and the first burst wave. A second burst wave different from the above is made incident while changing the oscillation frequency, and the signal intensity of the second burst wave in the measurement time from the reflected wave propagation time to the next reflected wave propagation time is measured and known. The first master curve for obtaining the propagation time with respect to the axial force and the second master curve for obtaining the maximum interference frequency at which the signal intensity with respect to the known axial force is maximized are created and fastened. The first burst wave is made incident and the propagation time is measured, and the second burst wave is made incident while changing the oscillation frequency, and the signal intensity is measured for each oscillation frequency, from the first master curve The approximate axial force in the measured propagation time is obtained, the interference frequency range in the approximate axial force is obtained from the second master curve, and the maximum signal intensity within the interference frequency range is obtained from the measured signal intensity for each oscillation frequency. The interference frequency is obtained, and the axial force of the long member is measured by the obtained maximum interference frequency and the second master curve.

  In order to achieve the above object, another feature of the axial force measuring method according to the present invention is that an ultrasonic wave is incident from one end of a long member and a reflected wave reflected from the other end of the long member is received. In the method of measuring the axial force of the long member based on the received reflected wave signal, the first burst wave is incident from one end of the long member and the propagation time of the reflected wave is measured in advance. A second burst wave different from the first burst wave is made incident while changing the oscillation frequency, and the signal intensity of the second burst wave is measured in the measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave. Then, a first master curve for obtaining the propagation time with respect to a known axial force and a second master curve for obtaining a maximum interference frequency at which the signal intensity with respect to the known axial force is maximized are created and fastened. The first burst wave is incident on a long member to measure the propagation time, and the second burst wave is incident while changing the oscillation frequency, and the signal intensity is measured for each oscillation frequency to measure the maximum. Obtaining the interference frequency, obtaining the approximate axial force at the maximum interference frequency obtained from the second master curve, obtaining the propagation time range in the approximate axial force obtained from the first master curve, and determining the propagation time range from the measured propagation time The maximum propagation time at which the maximum signal intensity is obtained is obtained, and the axial force of the long member is measured by the obtained maximum propagation time and the first master curve.

  According to the features of the axial force measuring device and the axial force measuring method according to the present invention, it is possible to accurately measure the axial force with a simple configuration.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

It is a block diagram of an axial force measuring device concerning the present invention. It is a figure explaining the measurement (time difference method) of the propagation time of a 1st burst wave. It is a figure explaining the measurement (interference method) of the interference frequency of a 2nd burst wave. It is a figure explaining the relationship between the propagation of the ultrasonic wave by a time difference method, and bolt length, (a) is a figure which shows the definition of a volt | bolt and its extension, (b) is a schematic diagram of a received waveform, (c) is a high speed. A conceptual diagram of sampling, (d) is a conceptual diagram of low-speed sampling. It is a figure explaining the relationship between the propagation of the ultrasonic wave by interferometry, and bolt length, (a) is an example in which a half wavelength becomes a bolt length, (b) is an example in which one wavelength is a bolt length, (c) Is an example in which 1.5 wavelength is the volt length, and (d) is a diagram schematically showing a difference in interference frequency. It is a flowchart which shows the master curve creation procedure. (A) is a figure which shows an example of a 1st master curve, (b) is a 2nd master curve. It is a figure which shows an example of the measurement waveform in the time difference method and interference method in bolt length 160mm. It is a flowchart which shows an axial force measurement procedure. It is an example of the graph in an axial force measurement procedure, (a) is a time waveform, (b) is a 1st master curve, (c) is a 2nd master curve, (d) is an interference waveform, (e) is a 2nd master. Each curve is shown. It is a figure which shows an example of the measurement waveform in the time difference method and interference method in bolt length 30mm. It is a flowchart which shows the axial force measurement procedure which concerns on other embodiment. It is an example of the graph in the axial force measurement procedure in other embodiment, (a) is an interference waveform, (b) is a 2nd master curve, (c) is a 1st master curve, (d) is a time waveform, (e ) Indicates the first master curve.

Next, the first embodiment of the present invention will be described in more detail with reference to FIGS.
As shown in FIG. 1, the axial force measuring device 1 according to the present invention generally receives ultrasonic waves from the head 101 of a bolt 100 as a long member and reflects the reflected wave at the tip 102 of the bolt 100. Are provided, a probe 2 for receiving the ultrasonic wave, an ultrasonic generator 30 for generating an ultrasonic wave, and a signal processing unit 3 for processing the received reflected wave signal and measuring the axial force of the bolt. The signal processing unit 3 is connected to a display / input / output unit 4 configured by, for example, a personal computer (PC). As the probe 2, for example, a single-transducer type probe that is also used for transmitting and receiving ultrasonic waves is used, but a dual-element type probe may be used.

  As shown in FIG. 1, the signal processing unit 3 includes an ultrasonic generator 30, and generally includes a measurement unit 36, a master curve creation unit 37, and an axial force calculation unit 38. The ultrasonic generator 30 generates two types of burst waves 10 and 21 by the probe 2 via the power amplifier 31 in accordance with condition settings of a burst wave setting unit 41 described later. The received reflected wave signal (received waveform) is sent to the measurement unit 36 via the protection circuit 32, the frequency filter 33, the A / D converter 34, and the filter 35 and is also stored in the data storage unit 39. The measurement unit 36 measures the propagation time of the first burst wave 10 and the second burst wave 21 in the measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave for each oscillation frequency. A signal strength measuring unit 36b for measuring the signal strength of the signal. The master curve creation unit 37 creates a first master curve creation unit 37a that creates a first master curve M1 for obtaining a propagation time for a known axial force, and a first interference curve that obtains a maximum interference frequency that maximizes the signal intensity for the known axial force. A second master curve creation unit 37b for creating the second master curve M2 is provided. Then, the axial force calculation unit 38 obtains the axial force from the measurement value of the measurement unit 36 and the first and second master curves M1 and M2 created in advance.

  As shown in FIGS. 2 and 3, the ultrasonic generator 30 generates two types of burst waves, a first burst wave 10 and a second burst wave 21 that is different from the first burst wave 10. The first burst wave 10 is used for measuring the propagation time of the ultrasonic wave propagating through the bolt 100 (time difference method). The second burst wave 21 is used to measure the interference frequency of the synthesized wave generated by the interference of the ultrasonic waves propagating in the bolt 100 (interference method). That is, according to the present invention, two types of burst waves are generated by one ultrasonic generator 30 and two types of methods are used, and the axial force is accurately measured by using values obtained by these methods.

  As shown in FIG. 2A, the first burst wave 10 may have a wave number shorter than the arrival time of the first reflected wave (B1: first reflected echo) by 0.5 wave or more. When the wave number is less than 0.5 waves, the generation efficiency of burst waves (ultrasonic waves) decreases. On the other hand, if the wave number is longer than the arrival time of the first reflected wave, the first reflected echo B1 overlaps with the first burst wave 10 (incident wave), making it difficult to measure the propagation time. In this embodiment, the time difference T between the transmission echo 10 ′ (S) of the first burst wave 10 and the first reflection echo 11 ′ (B1) shown in FIG. A time waveform W1 as shown in b) is generated.

  As shown in FIG. 3A, the second burst wave 21 becomes the combined waves 20 </ b> A and 20 </ b> B by interference of incident ultrasonic waves and reflected waves propagating in the bolt 100. The second burst wave 21 is incident while changing the oscillation frequency within a predetermined range and pitch. As shown in the figure, in the second burst wave P2A having the oscillation frequency f1, the signal intensity of the synthesized wave 20A immediately after the second reflected echo B2 (portion surrounded by a broken line in the figure) is the same as the first reflected wave 22A and the second time. The reflected wave 23A interferes and becomes weak. On the other hand, in the second burst wave P2B having the oscillation frequency f2, the signal intensity of the synthesized wave 20B immediately after the second reflected echo B2 (the portion surrounded by the broken line in the figure) is the first reflected wave 22B and the second reflected wave 23B. It becomes strong by interference. Thus, if the length of the volt | bolt 100 and the length of the integral multiple of the half wavelength of the 2nd burst wave 21 correspond in a synthetic | combination wave, the wave which interferes will become the same phase and signal strength will increase. In the present embodiment, an interference frequency that is a peak of signal intensity is measured for each frequency within a predetermined range and pitch, and an interference waveform W2 as shown in FIG. 3B is generated, and the peak is maximized. Let the interference frequency be Q.

  Here, the length of the second burst wave 21 is longer than the propagation time of the first reflected wave (first reflected echo B1) and shorter than the propagation time of the second reflected wave (second reflected echo B2). There should be. If it is less than the propagation time of the first reflected wave, no interfering wave is generated and measurement is not possible. On the other hand, when the propagation time of the second reflected wave is exceeded, interference occurs in three or more waves (incident wave and first and second reflected waves) propagating in the bolt 100, and the signal intensity is discriminated by the interference. It becomes difficult.

  Furthermore, the measurement time for measuring the maximum interference frequency may be the time from the propagation time of the second reflected wave (second reflected echo B2) to the propagation time of the third reflected wave (third reflected echo B3). . For example, if the transmission signal of the second burst wave 21 is several V to several hundred V, the first reflected echo B1 is several mV to several hundred V, and the second reflected echo B2 is about half of the first reflected echo B1. . Therefore, the transmission echo becomes dominant because the amplitude difference between the transmission echo and the first reflection echo B1 is too large. Therefore, if the time from the propagation time of the first reflected wave to the propagation time of the second reflected wave is the measurement time, it is difficult to observe the interference. On the other hand, since the ultrasonic wave is attenuated every time it is repeatedly reflected, the signal intensity of the third and subsequent reflected waves (third reflected echo B3) gradually becomes weaker. Therefore, if the time from the propagation time of the reflected wave after the third time to the propagation time of the next reflected wave is the measurement time, it is difficult to observe the interference because the signal is weak. Thus, the maximum interference frequency can be detected easily and accurately by using the interference region between the first reflection echo B1 and the second reflection echo B2.

  As shown in FIG. 1, the display / input / output unit 4 generally includes a burst wave setting unit 41, a condition setting unit 42, a display unit 43, and a storage unit 44. The burst wave setting unit 41 is input and set with the oscillation frequency, wave number (length), oscillation frequency pitch, and the like of the first and second burst waves 10 and 21. The condition setting unit 42 is input and set with the length of the bolt 100, a rough axial force described later, and the like. The display unit 43 always displays the time waveform W1 and the interference waveform W2 during axial force measurement, for example, and also displays the axial force and the like of the measurement result. The storage unit 44 stores the first and second master curves M1 and M2, and the axial force calculation unit 38 refers to them.

  By the way, the length (axial length) of the bolt 100 as the long member is preferably 5 mm or more and 300 mm or less. For example, as shown in FIG. 4A, when the length of the bolt 100 before the axial force load is L and the length of the bolt 100 ′ after the axial force load is L + ΔL, the elongation (strain ε) is ΔL / L. Can be defined. Here, assuming 1000 με as a general elastic deformation range, elongation (strain ε) = 0.001. If the length of the bolt 100 is 5 mm, the length of the bolt 100 ′ is 5.005 mm.

  The propagation time t during which the ultrasonic wave having a propagation speed of 5.9 mm / μs reciprocates through the bolt 100 is t = 5 mm × 2 (reciprocal path) ÷ 5.9 mm / μs = 1.6949 ms. On the other hand, the propagation time t ′ in the bolt 100 ′ is t ′ = 5.005 mm × 2 (reciprocating path) ÷ 5.9 mm / μs = 1.6966 ms. The difference Δt is Δt = t′−t = 0.717 μs = 1.7 ns (FIG. 4B). The shorter the bolt length, the shorter the time difference Δt.

  When digital processing is performed on such a received signal (waveform), the sound pressure is converted into digital data at regular intervals (sampling frequency). As shown in FIG. 4C, the high-speed sampling A / D converter has a short sampling period and can identify a minute time difference, but the apparatus becomes expensive. On the other hand, as shown in FIG. 4 (d), the low-speed sampling A / D converter has a long sampling period and it is difficult to identify a minute time difference, but the apparatus is inexpensive. In other words, the shorter the bolt length, the shorter the sampling period is required to detect the time difference Δt. On the other hand, the time difference Δt increases as the length of the bolt increases.

  On the other hand, in the interferometry, if the general elastic deformation range is 1000 με and the length L of the bolt 100 is 300 mm, L + ΔL is 300.3 mm. Here, in the ultrasonic wave having a propagation velocity of 5.9 mm / μs, if the half wavelength is a bolt length as shown in FIG. 5A, the bolt 100 has an interference wavelength λ = 300 mm × 2 = 600 mm, an interference frequency f = 5.9 mm / μs ÷ 600 mm = 9.833 kHz. On the other hand, in the bolt 100 ′, the interference wavelength λ ′ = 300.3 mm × 2 = 600.6 mm and the interference frequency f ′ = 5.9 mm / μs ÷ 600.6 mm = 9.824 kHz. As shown in FIG. 5B, when the bolt length becomes one wavelength, the interference wavelength is reduced by half and the interference frequency is doubled. Furthermore, as shown in FIG. 5C, when the bolt length is 1.5 wavelengths, the interference wavelength is 1/3 of the half wavelength, and the interference frequency is tripled.

  Therefore, as shown in FIG. 5D, the peak of the interference intensity appears for each interference frequency. The difference in interference frequency is 9 Hz. Therefore, as the interference order (the number of half wavelengths) increases, the interference frequency increases and the difference also increases. For example, when an ultrasonic wave having an interference order of about 510 is incident on the bolt, the difference in interference frequency is 5.01 kHz, and if there is a frequency resolution of about 1 kHz, the difference in interference frequency can be detected. On the other hand, as the length of the bolt becomes longer (over 300 mm), the interference wavelength becomes longer and the interference frequency becomes smaller, so that the frequency resolution has to be improved and the apparatus becomes expensive. On the other hand, if the length of the bolt is shortened, the difference in interference frequency is also increased.

  Thus, particularly when the length of the bolt 100 is 5 mm or more and 300 mm or less, by using both the time difference method and the interferometry method, an oscilloscope, A / D converter, or high frequency resolution with a short sampling period is used. Without using a device, it is possible to measure the axial force with high accuracy using an inexpensive device.

Next, an axial force measurement procedure will be described with reference to FIGS.
As shown in FIG. 6, before the axial force measurement, first and second master curves M1 and M2 are created using test bolts having the same configuration as the target bolt. First, a test bolt is set on a tensile tester or a hydraulic jack, and a predetermined axial force is generated by pulling the test bolt. In addition, the oscillation frequency, wave number, and oscillation frequency interval of the first and second burst waves 10 and 21 incident on the burst wave setting unit 41 are input, and the length of the test bolt and the set axial force are input to the condition setting unit 42. (S1). Next, the ultrasonic generator 30 generates the first burst wave 10 in the probe 2 according to the conditions set in the burst wave setting unit 41, and receives the reflected signal (S2). When the generation of waveform data is completed in the propagation time measuring unit 36a (S3), the ultrasonic generator 30 generates the second burst wave 21 on the probe 2 according to the conditions set in the burst wave setting unit 41. Then, the reflected signal is received, and the waveform data is generated by the signal intensity measuring unit 36b (S4).

  If all measurements are not completed (S5), the axial force is changed (S7) and the above steps are repeated. If the measurement is completed with each axial force (S5), the first master curve creating unit 37a determines the propagation time of the first burst wave 10 measured by the propagation time measuring unit 36a and the set axial force as shown in FIG. A first master curve M1 is created (S6). Further, the second master curve creating unit 37b creates a second master curve M2 as shown in FIG. 7B from the maximum interference frequency of the second burst wave 21 measured by the signal intensity measuring unit 36b and the set axial force ( S6). The created first and second master curves M 1 and M 2 are stored in the storage unit 44 of the display / input / output unit 4. Then, after the first and second master curves M1 and M2 are created, axial force measurement is performed.

  Here, for example, as shown in FIG. 8, when the bolt 100 is relatively long, in the time waveform (first burst wave), it is easy to specify the propagation time from the peak signal. On the other hand, since there are a plurality of peak signals in the interference waveform (second burst wave), it is difficult to specify the frequency that is the maximum interference frequency.

  Therefore, as shown in FIG. 9, first, the oscillation frequency, the wave number, and the oscillation frequency interval of the first and second burst waves 10 and 21 incident on the burst wave setting unit 41 are input and the condition setting unit 42 as described above. Is input the length of the bolt 100 (S10). For example, an oscillation frequency of 5 MHz (for example, a variable range of 5.0 MHz to 5.1 MHz), a wave number of the first burst wave, a wave number of the second burst wave of 600, an oscillation frequency interval of 1 kHz, and a length of the bolt 100 of 160 mm are input. Next, the ultrasonic generator 30 generates the first burst wave 21 and receives the reflected signal (S2). Then, the propagation time measuring unit 36a generates the time waveform W1 and measures the peak time as the propagation time T (S12, FIG. 10 (a)).

  After measuring the propagation time T, the axial force calculation unit 38 obtains the approximate axial force F ′ at the propagation time T measured from the first master curve M1, and stores it in the condition setting unit 42. Further, the axial force calculation unit 38 obtains the interference frequency range fr in the approximate axial force F ′ from the second master curve M2 (S13, FIGS. 10B and 10C). In the present embodiment, the interference frequency range fr is set to about 10 kHz. However, the interference frequency range fr is only an example, and is set in an appropriate numerical range.

  If the approximate axial force F ′ and the interference frequency range fr can be calculated (S14), the second burst wave 21 is generated while changing the frequency at the frequency interval set within the oscillation frequency range set by the ultrasonic generator 30. The reflected signal is received (S15). Then, the signal strength measuring unit 36b generates the interference waveform W2 and obtains the maximum interference frequency Q from the interference frequency range fr obtained previously in the interference waveform W2 (S16, FIG. 10 (d)). Then, the axial force calculator 38 calculates the axial force F by substituting the obtained maximum interference frequency Q into the second master curve M2 (S17, FIG. 10 (e)). Thus, by predicting the frequency range fr where the maximum interference frequency Q of the second burst wave 21 can appear using the first burst wave 10 in advance, the maximum interference frequency Q can be accurately calculated without mistaking it. Therefore, the axial force can be measured with high accuracy by an inexpensive device without using an expensive device with high frequency resolution as described above.

Next, a second embodiment of the present invention will be described. In the following embodiments, members similar to those in the above embodiment are denoted by the same reference numerals.
In the first embodiment, the approximate axial force F ′ is calculated from the propagation time T of the first burst wave 10 first, and the interference frequency range fr is obtained from the second master curve M2 based on the approximate axial force F ′. However, the second burst wave 21 is first applied, the approximate axial force F ′ is calculated from the maximum interference frequency Q, the propagation time range tr is obtained from the first master curve M1 based on the approximate axial force F ′, and the axial force F Is also possible.

  For example, as shown in FIG. 11, when the bolt 100 is relatively short, it is easy to specify the maximum interference frequency from the peak signal in the interference waveform (second burst wave). On the other hand, since there are a plurality of peak signals in the time waveform (first burst wave), it is difficult to specify the propagation time.

  Therefore, as shown in FIG. 12, first, the oscillation frequency, the wave number, and the oscillation frequency interval of the first and second burst waves 10 and 21 incident on the burst wave setting unit 41 are input and the condition setting unit 42 as described above. The length of the bolt 100 is input to (S20). Next, the ultrasonic generator 30 generates the second burst wave 21 and receives the reflected signal (S21). Then, the signal intensity measuring unit 36b generates the interference waveform W2 and obtains the maximum interference frequency Q (S22, FIG. 13A).

  After obtaining the maximum interference frequency Q, the axial force calculation unit 38 obtains the approximate axial force F ′ at the maximum interference frequency Q obtained from the second master curve M2, and stores it in the condition setting unit 42. Moreover, the axial force calculation part 38 calculates | requires the propagation time range tr in the general axial force F 'ahead from the 1st master curve M1 (S23, FIG.13 (b) (c)).

  If the approximate axial force F 'and the propagation time range tr can be calculated (S24), the ultrasonic generator 30 generates the first burst wave 21 and receives the reflected signal (S25). Then, the propagation time measuring unit 36a generates the time waveform W1 and obtains the maximum propagation time T ′ from the propagation time range tr previously obtained in the time waveform W1 (S26, FIG. 13 (d)). In the present embodiment, the propagation time range tr is set to about 0.01 μs, but is merely an example, and is set within an appropriate numerical range.

  Then, the axial force calculation unit 38 calculates the axial force by substituting the obtained maximum propagation time T ′ into the first master curve M1 (S27, FIG. 13 (e)). Thus, by predicting the propagation time range tr in which the maximum propagation time T ′ of the first burst wave 10 can appear using the second burst wave, the maximum propagation time T ′ can be accurately detected without mistaking it. Since it can be calculated, the axial force can be measured with high accuracy by an inexpensive apparatus without using an A / D converter having a short sampling period as described above.

Finally, the possibilities of yet another embodiment of the present invention will be described.
In each of the above embodiments, the propagation time T is the time difference between the transmission echo 10 ′ (S) of the first burst wave 10 and the first reflection echo 11 ′ (B1). However, the present invention is not limited to this, and may be a time difference between the first reflected echo 11 ′ (B1) and the second reflected echo 12 ′ (B2), for example. Further, the peak time was measured as the propagation time T as shown in FIG. However, the propagation time is not limited to the peak time, and for example, the time obtained by another method such as zero cross time, threshold cross time, or cross-correlation method can be used as the propagation time. The same applies to the maximum propagation time T ′.

  In each of the embodiments described above, the amplitude value is used as the signal intensity of the second burst wave or the combined wave (reflected signal) of the second burst wave as shown in FIG. However, the signal intensity is not limited to the amplitude value, and an integral value (area) of amplitude or energy can also be used.

  In the above embodiment, the frequency, frequency pitch, wave number, etc. of each burst wave are set and input as appropriate, and are not limited to the above numerical values. Further, in each of the above embodiments, the master curve creation unit 37 is provided in the signal processing unit 3. However, it is not always necessary to provide the master curve creation unit 37 in the signal processing unit 3, and it may be configured to be able to refer to at least the first and second master curves M1 and M2 created in advance when measuring the axial force.

  In the first embodiment, the propagation time T is measured by the first burst wave 10, the interference frequency range fr is obtained through the approximate axial force F ', and the interference frequency is within the set oscillation frequency range of the second burst wave 21. The maximum interference frequency Q was determined within the range fr. However, for example, after obtaining the interference frequency range fr, the interference frequency range fr can be set as the oscillation frequency range of the second burst wave 21. Thereby, since the oscillation frequency range of the second burst wave 21 can be limited to a range where the maximum interference frequency Q will appear, the measurement time can be shortened and the axial force can be measured efficiently.

  In each of the above embodiments, axial force measurement was performed by generating two different types of burst waves from one ultrasonic generator 30. However, it is also possible to use a pulse wave and a burst wave (corresponding to the second burst wave) as shown in the following configuration in place of the first burst wave. However, since the pulse wave and the burst wave cannot be generated by one ultrasonic generator, an ultrasonic generator is required for each, and the apparatus becomes complicated and expensive. In this respect, the above embodiments are excellent. In addition, as a pulse wave, a spike pulse, a rectangular wave (square pulse), etc. can be utilized, for example, and the propagation time should just be measurable. Other points are common to the above embodiments.

  The axial force measuring device is characterized by a probe that receives ultrasonic waves from one end of a long member and receives a reflected wave reflected from the other end of the long member, and an ultrasonic generator that generates the ultrasonic waves And a signal processing unit that processes the received reflected wave signal and measures the axial force of the elongated member, wherein the ultrasonic generator includes two types of pulse waves and burst waves The signal processing unit includes a propagation time measurement unit that measures the propagation time of the pulse wave, and from the propagation time of the reflected wave to the propagation time of the next reflected wave for each oscillation frequency. A signal intensity measuring unit for measuring the signal intensity of the burst wave during the measurement time, a first master curve for obtaining the propagation time with respect to a known axial force, and a maximum with which the signal intensity with respect to the known axial force is maximized The second machine that determined the interference frequency And measuring the propagation time by allowing the pulse wave to enter a fastened long member and measuring the signal intensity at each oscillation frequency by causing the burst wave to enter while changing the oscillation frequency. The approximate axial force at the propagation time measured from the first master curve is obtained, the interference frequency range at the approximate axial force is obtained from the second master curve, and within the interference frequency range from the measured signal intensity for each oscillation frequency. The maximum interference frequency that gives the maximum signal strength is obtained, and the axial force of the long member is measured by the obtained maximum interference frequency and the second master curve.

  Another feature of the axial force measuring device is that a probe that receives ultrasonic waves from one end of a long member and receives a reflected wave reflected from the other end of the long member, and an ultrasonic wave that generates the ultrasonic waves An axial force measuring device including a generator and a signal processing unit that processes a received reflected wave signal and measures an axial force of the elongated member, wherein the ultrasonic generator generates a pulse wave and a burst wave. Two types of ultrasonic waves are generated, and the signal processing unit includes a propagation time measurement unit that measures the propagation time of the pulse wave, and the propagation of the next reflected wave from the propagation time of the reflected wave for each oscillation frequency. A signal intensity measuring unit for measuring the signal intensity of the burst wave in a measurement time up to time, a first master curve for obtaining the propagation time with respect to a known axial force, and the signal intensity with respect to the known axial force being maximum. The maximum interference frequency A master curve, and measuring the propagation time by making the pulse wave incident on a fastened long member and making the burst wave incident while changing the oscillation frequency to increase the signal intensity for each oscillation frequency. Measured to determine the maximum interference frequency, to determine the approximate axial force at the maximum interference frequency determined from the second master curve, to determine and measure the propagation time range in the approximate axial force determined from the first master curve The maximum propagation time that is the maximum signal intensity within the propagation time range is obtained from the propagation time, and the axial force of the long member is measured by the obtained maximum propagation time and the first master curve.

  The axial force measurement method is characterized in that an ultrasonic wave is incident from one end of the long member and a reflected wave reflected from the other end of the long member is received, and the long member is An axial force measurement method for measuring an axial force, in which a pulse wave is incident from one end of the long member to measure a propagation time of a reflected wave, and a burst wave different from the pulse wave is changed in oscillation frequency. The first master curve obtained by measuring the signal intensity of the burst wave in the measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave and obtaining the propagation time with respect to a known axial force. And creating a second master curve for obtaining the maximum interference frequency at which the signal intensity with respect to the known axial force is maximized, and measuring the propagation time by making the pulse wave incident on the fastened long member. In addition, the burst wave is incident while changing the oscillation frequency, and the signal intensity is measured for each oscillation frequency, the approximate axial force in the propagation time measured from the first master curve is obtained, and the second master curve Determine the interference frequency range in the approximate axial force, determine the maximum interference frequency that is the maximum signal strength within the interference frequency range from the measured signal intensity for each oscillation frequency, and by the determined maximum interference frequency and the second master curve The purpose is to measure the axial force of the long member.

  Another feature of the axial force measuring method is that an ultrasonic wave is incident from one end of the long member, a reflected wave reflected from the other end of the long member is received, and the long length is based on the received reflected wave signal. A method of measuring an axial force of a member, wherein a pulse wave is incident from one end of the long member to measure a propagation time of a reflected wave and a burst wave different from the pulse wave is oscillated in frequency. First, the propagation time with respect to a known axial force was determined by measuring the signal intensity of the burst wave during the measurement time from the propagation time of the reflected wave to the propagation time of the next reflected wave. A second master curve for obtaining a master curve and a maximum interference frequency that maximizes the signal intensity with respect to the known axial force is created, and the pulse wave is incident on the fastened long member to determine the propagation time. Measurement In addition, the burst wave is made incident while changing the oscillation frequency, the signal intensity is measured for each oscillation frequency to obtain the maximum interference frequency, and the approximate axial force at the maximum interference frequency obtained from the second master curve. Obtaining the propagation time range in the approximate axial force obtained from the first master curve, obtaining the maximum propagation time that gives the maximum signal intensity within the propagation time range from the measured propagation time, and obtaining the obtained maximum propagation. The axial force of the long member is measured by time and the first master curve.

  INDUSTRIAL APPLICABILITY The present invention can be used as an axial force measuring device and measuring method for a fastening object such as a bolt or a screw as a long member used in, for example, automobile parts, mechanical devices, other industrial devices, equipment, plants, and the like. . It can also be used as an axial force measuring device and measuring method for other long members such as medical bolts.

1: axial force measuring device, 2: probe, 3: signal processing unit (device main body), 4: display / input / output unit (PC), 10: first burst wave, 11, 11 ′: first reflected wave (B1), 12, 12 ′: Second reflected wave (B2), 20A, 20B: Composite wave, 21: Second burst wave, 22: First reflected wave (B1), 23: Second reflected wave ( B2), 30: ultrasonic generator, 31: power amplifier, 32: protection circuit, 33: frequency filter, 34: A / D converter, 35: filter, 36: measurement unit, 36a: propagation time measurement unit, 36b : Signal intensity measurement unit, 37: master curve creation unit, 37a: first master curve creation unit, 37b: second master curve creation unit, 38: axial force calculation unit, 39: data storage unit, 41: burst wave setting unit 42: condition setting unit, 43: display unit, 44: storage unit, 00: bolt, 101: head (one end), 102: tip (other end), F: axial force, F ′: approximate axial force, fr: interference frequency range, Q: maximum interference frequency, T: propagation time, T ′: maximum propagation time, tr: propagation time range, W1: time waveform, W2: interference waveform

Claims (8)

A probe that receives ultrasonic waves from one end of a long member and receives reflected waves reflected from the other end of the long member, an ultrasonic generator that generates the ultrasonic waves, and a signal of the received reflected waves An axial force measuring device comprising a signal processing unit that processes the axial force of the elongated member,
The ultrasonic generator generates at least two burst waves of a first burst wave and a second burst wave different from the first burst wave,
The signal processing unit is a propagation time measurement unit that measures the propagation time of the first burst wave;
A signal intensity measuring unit that measures the signal intensity of the second burst wave in the measurement time from the reflected wave propagation time to the next reflected wave propagation time for each oscillation frequency;
A first master curve for determining the propagation time for a known axial force;
A second master curve for obtaining a maximum interference frequency at which the signal intensity with respect to the known axial force is maximized,
The first burst wave is incident on a fastened long member to measure the propagation time, and the second burst wave is incident while changing the oscillation frequency, and the signal intensity is measured for each oscillation frequency. ,
Obtain the approximate axial force at the propagation time measured from the first master curve,
Obtain the interference frequency range in the approximate axial force from the second master curve,
From the measured signal strength for each oscillation frequency, find the maximum interference frequency that is the maximum signal strength within the interference frequency range,
An axial force measuring device that measures the axial force of the long member based on the obtained maximum interference frequency and the second master curve. A probe that receives ultrasonic waves from one end of a long member and receives reflected waves reflected from the other end of the long member, an ultrasonic generator that generates the ultrasonic waves, and a signal of the received reflected waves An axial force measuring device comprising a signal processing unit that processes the axial force of the elongated member,
The ultrasonic generator generates at least two burst waves of a first burst wave and a second burst wave different from the first burst wave,
The signal processing unit is a propagation time measurement unit that measures the propagation time of the first burst wave;
A signal intensity measuring unit that measures the signal intensity of the second burst wave in the measurement time from the reflected wave propagation time to the next reflected wave propagation time for each oscillation frequency;
A first master curve for determining the propagation time for a known axial force;
A second master curve for obtaining a maximum interference frequency at which the signal intensity with respect to the known axial force is maximized,
The first burst wave is incident on a fastened long member to measure the propagation time, and the second burst wave is incident while changing the oscillation frequency, and the signal intensity is measured for each oscillation frequency. To obtain the maximum interference frequency,
Obtain the approximate axial force at the maximum interference frequency obtained from the second master curve,
Obtain the propagation time range in the approximate axial force obtained from the first master curve,
From the measured propagation time, find the maximum propagation time that is the maximum signal strength within the propagation time range,
An axial force measuring device that measures the axial force of the long member based on the obtained maximum propagation time and the first master curve. 3. The axial force measuring device according to claim 1, wherein the second burst wave has a length equal to or longer than a propagation time of the first reflected wave and less than a propagation time of the second reflected wave. The axial force measuring device according to claim 1, wherein the measurement time is a time from a propagation time of the second reflected wave to a propagation time of the third reflected wave. The axial force measuring device according to any one of claims 1 to 4, wherein the first burst wave has a wave number of 0.5 wave or more and shorter than an arrival time of the first reflected wave. The axial force measuring device according to any one of claims 1 to 5, wherein a length of the long member is 5 mm or more and 300 mm or less. Axial force measurement that receives an ultrasonic wave from one end of the long member and receives a reflected wave reflected from the other end of the long member and measures the axial force of the long member based on the received reflected wave signal A method,
First, a first burst wave is incident from one end of the elongated member to measure the propagation time of the reflected wave, and a second burst wave different from the first burst wave is incident while changing the oscillation frequency to reflect the reflected wave. A first master curve for determining the propagation time with respect to a known axial force by measuring the signal intensity of the second burst wave in the measurement time from the propagation time of the wave to the propagation time of the next reflected wave, and the known axial force Create a second master curve to find the maximum interference frequency that maximizes the signal intensity for
Measuring the signal intensity for each oscillation frequency by making the first burst wave incident on the elongated member fastened and measuring the propagation time and making the second burst wave incident while changing the oscillation frequency,
Obtain the approximate axial force at the propagation time measured from the first master curve,
Obtain the interference frequency range in the approximate axial force from the second master curve,
From the measured signal strength for each oscillation frequency, find the maximum interference frequency that is the maximum signal strength within the interference frequency range,
An axial force measurement method for measuring an axial force of the long member by using the obtained maximum interference frequency and the second master curve. Axial force measurement that receives an ultrasonic wave from one end of the long member and receives a reflected wave reflected from the other end of the long member and measures the axial force of the long member based on the received reflected wave signal A method,
First, a first burst wave is incident from one end of the elongated member to measure the propagation time of the reflected wave, and a second burst wave different from the first burst wave is incident while changing the oscillation frequency to reflect the reflected wave. A first master curve for determining the propagation time with respect to a known axial force by measuring the signal intensity of the second burst wave in the measurement time from the propagation time of the wave to the propagation time of the next reflected wave, and the known axial force Create a second master curve to find the maximum interference frequency that maximizes the signal intensity for
Measure the propagation time by making the first burst wave incident on the fastened long member, and measure the signal intensity for each oscillation frequency by making the second burst wave incident while changing the oscillation frequency. Determining the maximum interference frequency;
Obtain the approximate axial force at the maximum interference frequency obtained from the second master curve,
Obtain the propagation time range in the approximate axial force obtained from the first master curve,
From the measured propagation time, find the maximum propagation time that is the maximum signal strength within the propagation time range,
An axial force measuring method for measuring an axial force of the long member based on the obtained maximum propagation time and the first master curve.

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