WO2022091680A1 - Bolt clamping-force measuring device and method - Google Patents
Bolt clamping-force measuring device and method Download PDFInfo
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- WO2022091680A1 WO2022091680A1 PCT/JP2021/035945 JP2021035945W WO2022091680A1 WO 2022091680 A1 WO2022091680 A1 WO 2022091680A1 JP 2021035945 W JP2021035945 W JP 2021035945W WO 2022091680 A1 WO2022091680 A1 WO 2022091680A1
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- bolt
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- axial force
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- 238000000034 method Methods 0.000 title claims abstract description 17
- 238000001514 detection method Methods 0.000 claims abstract description 17
- 239000013307 optical fiber Substances 0.000 claims description 15
- 238000005314 correlation function Methods 0.000 claims description 5
- 230000003287 optical effect Effects 0.000 claims description 4
- 230000001678 irradiating effect Effects 0.000 claims description 2
- 238000000691 measurement method Methods 0.000 claims 1
- 230000001902 propagating effect Effects 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000007689 inspection Methods 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 238000002679 ablation Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/50—Processing the detected response signal, e.g. electronic circuits specially adapted therefor using auto-correlation techniques or cross-correlation techniques
Definitions
- the present invention relates to a bolt axial force measuring device and a method.
- a heavy machine such as a power shovel
- a heavy machine such as a power shovel
- Large bolts are automatically tightened, and small bolts are manually tightened.
- a compressive force is generated in the member, and in response to this, an axial force (tensile force) is generated in the bolt, and the bolt is fixed by this axial force. Therefore, it is possible to inspect the bolted state by measuring the axial force of the bolt.
- Patent Document 1 discloses a bolt axial force measuring device.
- This bolt axial force measuring device includes an ultrasonic sensor mounted on the head of the bolt and a measuring device main body.
- the ultrasonic sensor vibrates by the drive pulse from the main body of the measuring device to generate ultrasonic waves.
- the ultrasonic waves are incident on the end face of the head of the bolt and propagate in the axial direction of the bolt. A part of the ultrasonic wave becomes a scattered wave by the grain boundary of the bolt, and a part of the scattered wave reaches the end face of the head of the bolt.
- the ultrasonic sensor converts the scattered wave that has reached the end face of the head of the bolt into an electric signal and outputs it to the main body of the measuring device.
- the main body of the measuring device calculates the time lag between the waveform of the scattered wave obtained from the bolt before fastening and the waveform of the scattered wave obtained from the bolt after fastening, and calculates the axial force of the bolt based on this time lag. Calculate. More specifically, the above-mentioned time lag is due to the bolt elongation and the change in sound velocity due to the axial force of the bolt, and is proportional to the axial force of the bolt. Therefore, it is possible to calculate the axial force of the bolt based on the time lag described above.
- Patent Document 1 utilizes scattered waves due to the grain boundaries of bolts as described above. As a result, unlike the case of using the reflected wave from the end face of the threaded part of the bolt, the axial force of the bolt can be measured without processing to make the end face of the head of the bolt parallel to the end face of the threaded part. It is possible.
- the degree of ultrasonic scattering by the grain boundaries of the bolt depends on the relative relationship between the size of the grain boundaries of the bolt and the wavelength of the ultrasonic wave. More specifically, when the wavelength of the ultrasonic wave is similar to the grain boundary of the bolt, the ultrasonic wave is most scattered by the grain boundary. However, when the wavelength of the ultrasonic wave is sufficiently larger than the grain boundary of the bolt, the ultrasonic wave is transmitted without being affected by the grain boundary and hardly scatters. Further, when the wavelength of the ultrasonic wave is sufficiently smaller than the grain boundary, the ultrasonic wave is reflected by the grain boundary and hardly scatters.
- the size of the grain boundaries of a bolt differs depending on the material of the bolt, and further, even if the material of the bolt is the same, it differs depending on individual differences.
- An object of the present invention is to provide a bolt axial force measuring device and a method capable of improving usability.
- the present invention is typically a bolt axial force measuring device that measures the axial force of a bolt fastened to a member by irradiating the end face of the head of the bolt with a first laser beam. 1. By detecting the laser, the second laser that irradiates the end face of the head of the bolt with the second laser beam, and the second laser light reflected by the end face of the head of the bolt.
- the present invention includes an optical detector that detects fluctuations in the end face of the head due to the multiple reflected waves, and a computer that calculates the axial force of the bolt based on the detection result of the optical detector.
- FIG. 1 is a schematic view showing the configuration of the bolt axial force measuring device in the present embodiment.
- FIG. 2 is a diagram for explaining a multiple reflected wave generated by the side surface of the threaded portion of the bolt in the present embodiment.
- the bolt 1 to be measured in this embodiment is fastened to the members 2A and 2B. More specifically, the bolt 1 is inserted into the through hole of the member 2A and the through hole of the member 2B, and the nut 3 is screwed to the tip end side thereof. As a result, the members 2A and 2B are connected.
- the bolt axial force measuring device of the present embodiment is used, for example, for inspecting the fastened state of the bolt 1.
- the laser 11 first laser
- the laser 11 involved in the generation of ultrasonic waves and the end face of the bolt 1 due to multiple reflected waves. It is provided with a laser 12 (second laser), a condenser lens 13, an optical detector 14, an A / D converter 15, a computer 16, and a display 17 for detecting fluctuations in the light.
- the computer 16 has a ROM for storing a program, a CPU for executing processing according to the program, and a RAM or a hard disk for storing the processing result.
- the laser 11 is, for example, a pulsed YAG laser, and in response to a trigger signal from the computer 16, the end face of the head 4 of the bolt 1 (specifically, for example, a position closer to the outer edge than the center of the end face as shown in the figure). ) Is irradiated with a pulsed laser beam A (specifically, for example, a laser beam having a pulse width on the order of 1 to 10 ns). As a result, the surface layer of the bolt 1 is instantaneously and locally thermally expanded to generate ultrasonic waves (thermoelastic mode).
- a longitudinal wave L propagating in the direction of about 60 degrees and a transverse wave S propagating in the direction of about 30 degrees are generated.
- Most of the longitudinal wave L is reflected by the side surface of the head portion 4 of the bolt 1 and does not reach the threaded portion 5 of the bolt 1.
- the transverse wave S propagates to the threaded portion 5 of the bolt 1 and is multiplely reflected by the side surface of the threaded portion 5 to become a multiple reflected wave.
- the transverse wave S is reflected by one screw thread and becomes a plurality of reflected waves propagating in a plurality of directions, and each reflected wave is reflected by another screw thread and becomes a plurality of reflected waves propagating in a plurality of directions. , Such reflection is repeated to form a multiple reflected wave.
- the multiple reflected wave reaches the end face of the head 4 of the bolt 1.
- the laser 12 is, for example, a continuous wave laser, and is a continuous wave laser on the end surface of the head 4 of the bolt 1 (specifically, for example, a position different from the irradiation position of the laser beam A from the laser 11 as shown in the figure). Irradiate light B.
- the condenser lens 13 collects the laser beam B reflected by the end face of the head portion 4 of the bolt 1.
- the photodetector 14 is, for example, a photodiode array or an interferometer, and detects the laser beam B focused by the condenser lens 13. As a result, the fluctuation of the end face of the head portion 4 of the bolt 1 due to the multiple reflected wave described above is detected, and the detection result is output as a waveform signal.
- the laser beam A of the laser 11 should have a different wavelength so as not to interfere with the laser beam B reflected by the end surface of the head portion 4 of the bolt 1.
- the A / D converter 15 converts the waveform signal (analog signal) output from the photodetector 14 into waveform data (digital signal) and outputs it to the computer 16.
- an amplifier or a low-pass filter may be provided between the photodetector 14 and the A / D converter 15 to reduce noise in the waveform signal.
- the computer 16 records the waveform data with the output timing of the trigger signal as the start time, and displays it on the display 17. Further, the computer 16 calculates the axial force of the bolt 1 based on the recorded waveform data and displays it on the display 17.
- the speed of ultrasonic waves of the bolt 1 after fastening changes due to the influence of the axial force as compared with that before fastening. Further, since the bolt 1 extends slightly in the axial direction, the propagation distance of the ultrasonic wave changes. Therefore, between the first waveform obtained as the detection result of the photodetector 14 in the unfastened state of the bolt 1 and the second waveform obtained as the detection result of the photodetector 14 in the fastened state of the bolt 1. So, there is a time lag.
- the axial force of the bolt 1 is proportional to the time lag described above. Therefore, the computer 16 calculates the time lag between the first waveform and the second waveform, and calculates the axial force of the bolt 1 based on this time lag.
- FIG. 3 is a flowchart showing the processing procedure of the computer in the present embodiment.
- step S1 the computer 16 records the first waveform 18 (see FIG. 4) obtained as the detection result of the photodetector 14 in the unfastened state of the bolt 1. Proceeding to step S2, the computer 16 reciprocates between the end face of the head 4 and the end face of the screw portion 5 when imagining the case where the ultrasonic wave propagates in the axial direction of the bolt 1 in the first waveform 18.
- a partial waveform 19 (see FIG. 5) in a time domain set to be after the time T (specifically, between the time TR1 and the time TR2) is extracted.
- step S3 the computer 16 records the second waveform 20 (see FIG. 5) obtained as the detection result of the photodetector 14 in the fastened state of the bolt 1.
- the computer 16 calculates the cross-correlation function (see FIG. 6) between the partial waveform 19 and the second waveform 20 to determine the time lag between the first waveform 18 and the second waveform 20. Calculate.
- the similarity internal product value
- the similarity between the partial waveform 19 and the second waveform 20 is calculated while shifting the time of the partial waveform 19. Then, when the similarity between the partial waveform 19 and the second waveform 20 is maximized, the time difference between the partial waveform 19 and the second waveform 20, that is, the first waveform 18 and the second waveform 20 Calculate the time lag of.
- the computer 16 calculates the axial force of the bolt 1 based on the time difference between the first waveform 18 and the second waveform 20. More specifically, the computer 16 stores a calculation table (see FIG. 7) in which the relationship between the time lag and the axial force of the bolt 1 is set, and uses this to calculate the axial force of the bolt 1.
- the axial force of the bolt 1 is measured by using the multiple reflected waves from the side surface of the screw portion 5 of the bolt 1. Therefore, unlike the case where the scattered wave due to the grain boundary of the bolt 1 is used as described in Patent Document 1, it is not necessary to change the frequency of the ultrasonic wave according to the material and individual difference of the bolt 1. That is, it is not necessary to use different devices according to the material and individual difference of the bolt 1. Therefore, usability can be improved.
- the size of the crystal grain boundary of the bolt 1 is about several ⁇ m. Therefore, in the technique described in Patent Document 1, if the incident position of the ultrasonic wave is slightly deviated, the scattered wave changes greatly. On the other hand, the size of the thread of the bolt 1 is about 0.1 to 1 mm. Therefore, in the present embodiment, the multiple reflected wave does not change significantly even if the incident position of the ultrasonic wave is slightly deviated. Therefore, the measurement of the axial force of the bolt 1 can be stabilized.
- the first waveform 18 in the first waveform 18, after the time T of reciprocating between the end face of the head 4 and the end face of the screw portion 5 when the case of propagating in the axial direction of the bolt 1 is assumed.
- the partial waveform 19 extracted in the time domain set so as to be used is used.
- the time difference between the first waveform and the second waveform is larger due to the influence of the axial force of the bolt 1 as compared with the time domain set to be before the time T. .. Therefore, the measurement accuracy of the axial force of the bolt 1 can be improved.
- the laser 11 is used to generate ultrasonic waves
- the laser 12, the condenser lens 13, and the photodetector 14 are used to detect fluctuations in the end face of the bolt 1 due to multiple reflected waves.
- the vibrator it is necessary to bring the vibrator into contact with the head 4 of the bolt 1 via a contact medium.
- the computer 16 detects the first waveform 18 obtained as the detection result of the photodetector 14 in the unfastened state of the bolt 1 and the photodetector 14 in the fastened state of the bolt 1.
- the case where the time lag with the obtained second waveform 20 is calculated and the axial force of the bolt 1 is calculated based on this time lag has been described as an example, but the present invention is not limited to this.
- the computer 16 has a first waveform obtained as a detection result of the photodetector 14 in the first fastened state of the bolt 1 and a second waveform obtained as a detection result of the photodetector 14 in the second fastened state of the bolt 1.
- the time lag with the second waveform may be calculated, and the axial force of the bolt 1 may be calculated based on this time lag.
- the laser 11 has a low irradiation energy and the surface layer of the bolt 1 is instantaneously and locally thermally expanded to generate ultrasonic waves has been described as an example. Not limited to this. For example, if it is a stage before processing the surface of the bolt 1 or if it is permissible to have an irradiation mark on the surface of the bolt 1, the laser 11 has a high irradiation energy and the bolt 1 has a high irradiation energy.
- the surface layer of the laser may be locally evaporated to generate ultrasonic waves (ablation mode).
- the propagation path of the laser beam from the laser 11 or 12 to the end face of the head portion 4 of the bolt 1 has been described by taking the case where only air intervenes, but the present invention is not limited to this.
- the optical fiber 21 first optical fiber
- An optical fiber 22 second optical fiber
- the optical fibers 21 and 22, the condenser lens 13, and the photodetector 14 may be attached to the wrench 23 for fastening the bolt 1.
- the case where the photodetector 14 receives the laser light reflected by the end face of the head 4 of the bolt 1 via the condenser lens 13 has been described as an example. Not limited to. Although the detection intensity of the laser light is reduced, the photodetector 14 may receive the laser light reflected by the end face of the head portion 4 of the bolt 1 without passing through the condenser lens 13. That is, the condenser lens 13 may be unnecessary.
Abstract
Provided are a bolt clamping-force measuring device and method that enable improved usability. A bolt clamping-force measuring device that measures the clamping force of a bolt 1 fastened to members 2A, 2B, wherein the bolt clamping-force measuring device comprises: a laser 11 for shining a laser beam A on the end face of a head 4 of the bolt 1 to generate ultrasonic waves, whereby the ultrasonic waves propagate in the threads 5 of the bolt 1 and are multiply reflected by the flanks of the threads 5, becoming multiple-reflection waves, the multiple-reflection waves reaching the end face of the head 4; a laser 12 for shining a laser beam B on the end face of the head 4 of the bolt 1; a photodetector 14 that detects the laser beam B reflected from the end face of the head 4 of the bolt 1 and thereby detects fluctuations in the end face of the head 4 due to the multiple-reflection waves; and a computer 16 for computing the clamping force of the bolt 1 on the basis of the detection results from the light detector 14.
Description
本発明は、ボルト軸力計測装置及び方法に関する。
The present invention relates to a bolt axial force measuring device and a method.
近年、様々な工業分野において、製品の高機能化が目覚ましい。これに伴い、製品を構成する部材の構造も複雑になり、製品の信頼性をいかに担保するかが重要な課題となりつつある。そのため、製品の製造過程や出荷時あるいは供用中における検査の重要性が、これまで以上に増してきている。個々の部材の検査とともに重要視されているのが、ボルトによる部材の結合状態、すなわち、ボルトの締結状態の検査である。
In recent years, the sophistication of products has been remarkable in various industrial fields. Along with this, the structure of the members constituting the product has become complicated, and how to ensure the reliability of the product is becoming an important issue. Therefore, the importance of inspection during the manufacturing process of a product, at the time of shipment, or during operation is increasing more than ever. Along with the inspection of individual members, the inspection of the bonding state of the members by the bolts, that is, the fastening state of the bolts is emphasized.
製品の代表としてパワーショベル等の重機を例にとって説明する。重機の組み立てには、数百本から数千本のボルトが使用される。大きなボルトは自動締付け機で、小さなボルトは人力で締付けられる。このとき、部材には圧縮力が発生し、これに反発してボルトには軸力（引張力）が発生し、この軸力によってボルトが固定される。そのため、ボルトの軸力を計測することにより、ボルトの締結状態を検査することが可能である。
As a representative of the product, a heavy machine such as a power shovel will be explained as an example. Hundreds to thousands of bolts are used to assemble heavy machinery. Large bolts are automatically tightened, and small bolts are manually tightened. At this time, a compressive force is generated in the member, and in response to this, an axial force (tensile force) is generated in the bolt, and the bolt is fixed by this axial force. Therefore, it is possible to inspect the bolted state by measuring the axial force of the bolt.
特許文献１は、ボルト軸力計測装置を開示する。このボルト軸力計測装置は、ボルトの頭部に装着された超音波センサと、計測装置本体部とを備える。
Patent Document 1 discloses a bolt axial force measuring device. This bolt axial force measuring device includes an ultrasonic sensor mounted on the head of the bolt and a measuring device main body.
超音波センサは、計測装置本体部からの駆動パルスによって振動して超音波を発生する。超音波は、ボルトの頭部の端面に入射し、ボルトの軸方向に伝播する。超音波の一部は、ボルトの結晶粒界によって散乱波となり、散乱波の一部は、ボルトの頭部の端面に到達する。超音波センサは、ボルトの頭部の端面に到達した散乱波を電気信号に変換して、計測装置本体部へ出力する。
The ultrasonic sensor vibrates by the drive pulse from the main body of the measuring device to generate ultrasonic waves. The ultrasonic waves are incident on the end face of the head of the bolt and propagate in the axial direction of the bolt. A part of the ultrasonic wave becomes a scattered wave by the grain boundary of the bolt, and a part of the scattered wave reaches the end face of the head of the bolt. The ultrasonic sensor converts the scattered wave that has reached the end face of the head of the bolt into an electric signal and outputs it to the main body of the measuring device.
計測装置本体部は、締結前のボルトから得られた散乱波の波形と締結後のボルトから得られた散乱波の波形との時間ずれを演算し、この時間ずれに基づいてボルトの軸力を演算する。詳しく説明すると、前述した時間ずれは、ボルトの軸力に起因するボルトの伸び及び音速変化によるものであり、ボルトの軸力に比例する。そのため、前述した時間ずれに基づいてボルトの軸力を演算することが可能である。
The main body of the measuring device calculates the time lag between the waveform of the scattered wave obtained from the bolt before fastening and the waveform of the scattered wave obtained from the bolt after fastening, and calculates the axial force of the bolt based on this time lag. Calculate. More specifically, the above-mentioned time lag is due to the bolt elongation and the change in sound velocity due to the axial force of the bolt, and is proportional to the axial force of the bolt. Therefore, it is possible to calculate the axial force of the bolt based on the time lag described above.
特許文献１に記載の技術では、上述したようにボルトの結晶粒界による散乱波を利用する。これにより、ボルトのネジ部の端面による反射波を利用する場合とは異なり、ボルトの頭部の端面とネジ部の端面を平行にする加工を施さなくとも、ボルトの軸力を計測することが可能である。
The technique described in Patent Document 1 utilizes scattered waves due to the grain boundaries of bolts as described above. As a result, unlike the case of using the reflected wave from the end face of the threaded part of the bolt, the axial force of the bolt can be measured without processing to make the end face of the head of the bolt parallel to the end face of the threaded part. It is possible.
しかしながら、特許文献１に記載の技術には、次のような改善の余地がある。ボルトの結晶粒界による超音波の散乱の程度は、ボルトの結晶粒界の大きさと超音波の波長との相対関係に依存する。詳しく説明すると、超音波の波長がボルトの結晶粒界と同程度である場合、超音波は結晶粒界によって最も散乱する。しかし、超音波の波長がボルトの結晶粒界と比べて十分大きい場合、超音波は結晶粒界の影響を受けずに透過し、ほとんど散乱しない。また、超音波の波長が結晶粒界と比べて十分小さい場合、超音波は結晶粒界によって反射し、ほとんど散乱しない。そのため、ボルトの結晶粒界の大きさに応じて超音波の波長を変更する必要がある。すなわち、ボルトの結晶粒界の大きさに応じて、超音波センサを使い分ける必要がある。ボルトの結晶粒界の大きさは、ボルトの材質によって異なり、さらに、ボルトの材質が同じであっても個体差によって異なる。
However, the technique described in Patent Document 1 has the following room for improvement. The degree of ultrasonic scattering by the grain boundaries of the bolt depends on the relative relationship between the size of the grain boundaries of the bolt and the wavelength of the ultrasonic wave. More specifically, when the wavelength of the ultrasonic wave is similar to the grain boundary of the bolt, the ultrasonic wave is most scattered by the grain boundary. However, when the wavelength of the ultrasonic wave is sufficiently larger than the grain boundary of the bolt, the ultrasonic wave is transmitted without being affected by the grain boundary and hardly scatters. Further, when the wavelength of the ultrasonic wave is sufficiently smaller than the grain boundary, the ultrasonic wave is reflected by the grain boundary and hardly scatters. Therefore, it is necessary to change the wavelength of the ultrasonic wave according to the size of the grain boundary of the bolt. That is, it is necessary to use an ultrasonic sensor properly according to the size of the grain boundary of the bolt. The size of the grain boundaries of a bolt differs depending on the material of the bolt, and further, even if the material of the bolt is the same, it differs depending on individual differences.
本発明の目的は、使い勝手を向上することができるボルト軸力計測装置及び方法を提供することにある。
An object of the present invention is to provide a bolt axial force measuring device and a method capable of improving usability.
上記目的を達成するために、代表的な本発明は、部材に締結されたボルトの軸力を計測するボルト軸力計測装置において、前記ボルトの頭部の端面に第一のレーザ光を照射して超音波を発生させ、前記超音波が前記ボルトのネジ部に伝播し前記ネジ部の側面によって多重反射して多重反射波となり、前記多重反射波が前記頭部の端面に到達する、第一のレーザと、前記ボルトの前記頭部の端面に第二のレーザ光を照射する第二のレーザと、前記ボルトの前記頭部の端面で反射された第二のレーザ光を検出することにより、前記多重反射波による前記頭部の端面の変動を検出する光検出器と、前記光検出器の検出結果に基づいて前記ボルトの軸力を演算するコンピュータとを備える。
In order to achieve the above object, the present invention is typically a bolt axial force measuring device that measures the axial force of a bolt fastened to a member by irradiating the end face of the head of the bolt with a first laser beam. 1. By detecting the laser, the second laser that irradiates the end face of the head of the bolt with the second laser beam, and the second laser light reflected by the end face of the head of the bolt. The present invention includes an optical detector that detects fluctuations in the end face of the head due to the multiple reflected waves, and a computer that calculates the axial force of the bolt based on the detection result of the optical detector.
本発明によれば、使い勝手を向上することができる。
According to the present invention, usability can be improved.
本発明の一実施形態を、図面を参照しつつ説明する。
An embodiment of the present invention will be described with reference to the drawings.
図１は、本実施形態におけるボルト軸力計測装置の構成を表す概略図である。図２は、本実施形態におけるボルトのネジ部の側面によって生じる多重反射波を説明するための図である。
FIG. 1 is a schematic view showing the configuration of the bolt axial force measuring device in the present embodiment. FIG. 2 is a diagram for explaining a multiple reflected wave generated by the side surface of the threaded portion of the bolt in the present embodiment.
本実施形態の計測対象であるボルト１は、部材２Ａ，２Ｂに締結されている。詳しく説明すると、ボルト１は、部材２Ａの貫通孔及び部材２Ｂの貫通孔に挿入され、その先端側にナット３が螺合されている。これにより、部材２Ａ，２Ｂを結合している。
The bolt 1 to be measured in this embodiment is fastened to the members 2A and 2B. More specifically, the bolt 1 is inserted into the through hole of the member 2A and the through hole of the member 2B, and the nut 3 is screwed to the tip end side thereof. As a result, the members 2A and 2B are connected.
本実施形態のボルト軸力計測装置は、例えばボルト１の締結状態の検査に用いられるものであり、超音波の発生に係わるレーザ１１（第一のレーザ）と、多重反射波によるボルト１の端面の変動の検出に係わるレーザ１２（第二のレーザ）、集光レンズ１３、及び光検出器１４と、Ａ／Ｄコンバータ１５と、コンピュータ１６と、表示器１７とを備える。コンピュータ１６は、詳細を図示しないものの、プログラムを記憶するＲＯＭと、プログラムに従って処理を実行するＣＰＵと、処理結果を記憶するＲＡＭやハードディスクとを有する。
The bolt axial force measuring device of the present embodiment is used, for example, for inspecting the fastened state of the bolt 1. The laser 11 (first laser) involved in the generation of ultrasonic waves and the end face of the bolt 1 due to multiple reflected waves. It is provided with a laser 12 (second laser), a condenser lens 13, an optical detector 14, an A / D converter 15, a computer 16, and a display 17 for detecting fluctuations in the light. Although the details are not shown, the computer 16 has a ROM for storing a program, a CPU for executing processing according to the program, and a RAM or a hard disk for storing the processing result.
レーザ１１は、例えばパルスＹＡＧレーザであり、コンピュータ１６からのトリガ信号に応じて、ボルト１の頭部４の端面（詳細には、例えば、図示のように端面の中央よりも外縁に寄った位置）にパルスのレーザ光Ａ（詳細には、例えばパルス幅が１～１０nsのオーダであるレーザ光）を照射する。これにより、ボルト１の表面層を瞬間的かつ局所的に熱膨張させて、超音波を発生させる（熱弾性モード）。
The laser 11 is, for example, a pulsed YAG laser, and in response to a trigger signal from the computer 16, the end face of the head 4 of the bolt 1 (specifically, for example, a position closer to the outer edge than the center of the end face as shown in the figure). ) Is irradiated with a pulsed laser beam A (specifically, for example, a laser beam having a pulse width on the order of 1 to 10 ns). As a result, the surface layer of the bolt 1 is instantaneously and locally thermally expanded to generate ultrasonic waves (thermoelastic mode).
ボルト１の頭部４の端面の法線方向を０度とした場合に、例えば、約６０度の方向に伝播する縦波Ｌと、約３０度の方向に伝播する横波Ｓが発生する。縦波Ｌの大部分は、ボルト１の頭部４の側面などで反射し、ボルト１のネジ部５に到達しない。横波Ｓは、ボルト１のネジ部５に伝播し、ネジ部５の側面によって多重反射して多重反射波となる。詳しく説明すると、横波Ｓが１つのネジ山で反射されて複数の方向に伝播する複数の反射波となり、各反射波が別のネジ山で反射されて複数の方向に伝播する複数の反射波となり、このような反射が繰り返されて多重反射波となる。多重反射波は、ボルト１の頭部４の端面に到達する。
When the normal direction of the end face of the head 4 of the bolt 1 is set to 0 degrees, for example, a longitudinal wave L propagating in the direction of about 60 degrees and a transverse wave S propagating in the direction of about 30 degrees are generated. Most of the longitudinal wave L is reflected by the side surface of the head portion 4 of the bolt 1 and does not reach the threaded portion 5 of the bolt 1. The transverse wave S propagates to the threaded portion 5 of the bolt 1 and is multiplely reflected by the side surface of the threaded portion 5 to become a multiple reflected wave. More specifically, the transverse wave S is reflected by one screw thread and becomes a plurality of reflected waves propagating in a plurality of directions, and each reflected wave is reflected by another screw thread and becomes a plurality of reflected waves propagating in a plurality of directions. , Such reflection is repeated to form a multiple reflected wave. The multiple reflected wave reaches the end face of the head 4 of the bolt 1.
レーザ１２は、例えば連続波レーザであり、ボルト１の頭部４の端面（詳細には、例えば、図示のようにレーザ１１からのレーザ光Ａの照射位置とは異なる位置）に連続波のレーザ光Ｂを照射する。集光レンズ１３は、ボルト１の頭部４の端面で反射されたレーザ光Ｂを集光する。光検出器１４は、例えばフォトダイオードアレイ又は干渉計であり、集光レンズ１３で集光されたレーザ光Ｂを検出する。これにより、上述した多重反射波によるボルト１の頭部４の端面の変動を検出し、その検出結果を波形信号として出力する。なお、レーザ１１のレーザ光Ａは、ボルト１の頭部４の端面で反射されたレーザ光Ｂと干渉しないように、波長を異ならせるほうがよい。
The laser 12 is, for example, a continuous wave laser, and is a continuous wave laser on the end surface of the head 4 of the bolt 1 (specifically, for example, a position different from the irradiation position of the laser beam A from the laser 11 as shown in the figure). Irradiate light B. The condenser lens 13 collects the laser beam B reflected by the end face of the head portion 4 of the bolt 1. The photodetector 14 is, for example, a photodiode array or an interferometer, and detects the laser beam B focused by the condenser lens 13. As a result, the fluctuation of the end face of the head portion 4 of the bolt 1 due to the multiple reflected wave described above is detected, and the detection result is output as a waveform signal. The laser beam A of the laser 11 should have a different wavelength so as not to interfere with the laser beam B reflected by the end surface of the head portion 4 of the bolt 1.
Ａ／Ｄコンバータ１５は、光検出器１４から出力された波形信号（アナログ信号）を波形データ（デジタル信号）に変換して、コンピュータ１６へ出力する。なお、図示しないものの、光検出器１４とＡ／Ｄコンバータ１５の間に増幅器やローパスフィルタを設け、波形信号のノイズを低減してもよい。
The A / D converter 15 converts the waveform signal (analog signal) output from the photodetector 14 into waveform data (digital signal) and outputs it to the computer 16. Although not shown, an amplifier or a low-pass filter may be provided between the photodetector 14 and the A / D converter 15 to reduce noise in the waveform signal.
コンピュータ１６は、例えばトリガ信号の出力タイミングを開始時間として波形データを収録すると共に、表示器１７に表示させる。また、コンピュータ１６は、収録した波形データに基づいてボルト１の軸力を演算すると共に、表示器１７に表示させる。
The computer 16 records the waveform data with the output timing of the trigger signal as the start time, and displays it on the display 17. Further, the computer 16 calculates the axial force of the bolt 1 based on the recorded waveform data and displays it on the display 17.
ここで、ボルト１の軸力の演算方法の原理について説明する。締結後のボルト１は、締結前と比べ、軸力の影響で超音波の速度が変化する。また、ボルト１が軸方向に若干伸びるので超音波の伝播距離が変化する。そのため、ボルト１の未締結状態における光検出器１４の検出結果として得られた第一の波形と、ボルト１の締結状態における光検出器１４の検出結果として得られた第二の波形との間で、時間ずれが生じる。ボルト１の軸力は、前述した時間ずれに比例する。そのため、コンピュータ１６は、第一の波形と第二の波形との時間ずれを演算し、この時間ずれに基づいてボルト１の軸力を演算する。
Here, the principle of the calculation method of the axial force of the bolt 1 will be explained. The speed of ultrasonic waves of the bolt 1 after fastening changes due to the influence of the axial force as compared with that before fastening. Further, since the bolt 1 extends slightly in the axial direction, the propagation distance of the ultrasonic wave changes. Therefore, between the first waveform obtained as the detection result of the photodetector 14 in the unfastened state of the bolt 1 and the second waveform obtained as the detection result of the photodetector 14 in the fastened state of the bolt 1. So, there is a time lag. The axial force of the bolt 1 is proportional to the time lag described above. Therefore, the computer 16 calculates the time lag between the first waveform and the second waveform, and calculates the axial force of the bolt 1 based on this time lag.
次に、本実施形態のコンピュータの処理手順を説明する。図３は、本実施形態におけるコンピュータの処理手順を表すフローチャートである。
Next, the processing procedure of the computer of this embodiment will be described. FIG. 3 is a flowchart showing the processing procedure of the computer in the present embodiment.
まず、ステップＳ１にて、コンピュータ１６は、ボルト１の未締結状態における光検出器１４の検出結果として得られた第一の波形１８（図４参照）を収録する。ステップＳ２に進み、コンピュータ１６は、第一の波形１８のうち、超音波がボルト１の軸方向に伝播した場合を仮想したときの頭部４の端面とネジ部５の端面の間を往復する時間Ｔより後となるように設定された時間領域（詳細には、時間ＴＲ１と時間ＴＲ２の間）における部分波形１９（図５参照）を抽出する。
First, in step S1, the computer 16 records the first waveform 18 (see FIG. 4) obtained as the detection result of the photodetector 14 in the unfastened state of the bolt 1. Proceeding to step S2, the computer 16 reciprocates between the end face of the head 4 and the end face of the screw portion 5 when imagining the case where the ultrasonic wave propagates in the axial direction of the bolt 1 in the first waveform 18. A partial waveform 19 (see FIG. 5) in a time domain set to be after the time T (specifically, between the time TR1 and the time TR2) is extracted.
作業者がボルト１を締結した後、ステップＳ３に進む。ステップＳ３にて、コンピュータ１６は、ボルト１の締結状態における光検出器１４の検出結果として得られた第二の波形２０（図５参照）を収録する。
After the worker fastens the bolt 1, the process proceeds to step S3. In step S3, the computer 16 records the second waveform 20 (see FIG. 5) obtained as the detection result of the photodetector 14 in the fastened state of the bolt 1.
ステップＳ４に進み、コンピュータ１６は、部分波形１９と第二の波形２０との相互相関関数（図６参照）を演算することにより、第一の波形１８と第二の波形２０との時間ずれを演算する。相互相関関数では、部分波形１９の時間をずらしながら、部分波形１９と第二の波形２０との類似度（内積値）を演算する。そして、部分波形１９と第二の波形２０との類似度が最大になるときの、部分波形１９と第二の波形２０との時間ずれ、すなわち、第一の波形１８と第二の波形２０との時間ずれを演算する。
Proceeding to step S4, the computer 16 calculates the cross-correlation function (see FIG. 6) between the partial waveform 19 and the second waveform 20 to determine the time lag between the first waveform 18 and the second waveform 20. Calculate. In the cross-correlation function, the similarity (internal product value) between the partial waveform 19 and the second waveform 20 is calculated while shifting the time of the partial waveform 19. Then, when the similarity between the partial waveform 19 and the second waveform 20 is maximized, the time difference between the partial waveform 19 and the second waveform 20, that is, the first waveform 18 and the second waveform 20 Calculate the time lag of.
ステップＳ５に進み、コンピュータ１６は、第一の波形１８と第二の波形２０との時間ずれに基づいてボルト１の軸力を演算する。詳しく説明すると、コンピュータ１６は、前述した時間ずれとボルト１の軸力の関係が設定された演算テーブル（図７参照）を記憶しており、これを用いてボルト１の軸力を演算する。
Proceeding to step S5, the computer 16 calculates the axial force of the bolt 1 based on the time difference between the first waveform 18 and the second waveform 20. More specifically, the computer 16 stores a calculation table (see FIG. 7) in which the relationship between the time lag and the axial force of the bolt 1 is set, and uses this to calculate the axial force of the bolt 1.
以上のように本実施形態では、ボルト１のネジ部５の側面による多重反射波を利用して、ボルト１の軸力を計測する。そのため、特許文献１に記載のようにボルト１の結晶粒界による散乱波を利用する場合とは異なり、ボルト１の材質や個体差に応じて超音波の周波数を変更する必要がない。すなわち、ボルト１の材質や個体差に応じて機器を使い分ける必要がない。したがって、使い勝手を向上することができる。
As described above, in the present embodiment, the axial force of the bolt 1 is measured by using the multiple reflected waves from the side surface of the screw portion 5 of the bolt 1. Therefore, unlike the case where the scattered wave due to the grain boundary of the bolt 1 is used as described in Patent Document 1, it is not necessary to change the frequency of the ultrasonic wave according to the material and individual difference of the bolt 1. That is, it is not necessary to use different devices according to the material and individual difference of the bolt 1. Therefore, usability can be improved.
また、ボルト１の結晶粒界の大きさは、数μｍ程度である。そのため、特許文献１に記載の技術では、超音波の入射位置が若干ずれると、散乱波が大きく変化する。これに対し、ボルト１のネジ山の大きさは、０．１～１ｍｍ程度である。そのため、本実施形態では、超音波の入射位置が若干ずれても、多重反射波が大きく変化しない。したがって、ボルト１の軸力の計測を安定させることができる。
Further, the size of the crystal grain boundary of the bolt 1 is about several μm. Therefore, in the technique described in Patent Document 1, if the incident position of the ultrasonic wave is slightly deviated, the scattered wave changes greatly. On the other hand, the size of the thread of the bolt 1 is about 0.1 to 1 mm. Therefore, in the present embodiment, the multiple reflected wave does not change significantly even if the incident position of the ultrasonic wave is slightly deviated. Therefore, the measurement of the axial force of the bolt 1 can be stabilized.
また、本実施形態では、第一の波形１８のうち、ボルト１の軸方向に伝播した場合を仮想したときの頭部４の端面とネジ部５の端面の間を往復する時間Ｔより後となるように設定された時間領域で抽出された部分波形１９を用いる。前述した時間領域では、時間Ｔより前となるように設定された時間領域と比べ、ボルト１の軸力の影響を受けて第一の波形と第二の波形との時間ずれが大きくなっている。そのため、ボルト１の軸力の計測精度を高めることができる。
Further, in the present embodiment, in the first waveform 18, after the time T of reciprocating between the end face of the head 4 and the end face of the screw portion 5 when the case of propagating in the axial direction of the bolt 1 is assumed. The partial waveform 19 extracted in the time domain set so as to be used is used. In the above-mentioned time domain, the time difference between the first waveform and the second waveform is larger due to the influence of the axial force of the bolt 1 as compared with the time domain set to be before the time T. .. Therefore, the measurement accuracy of the axial force of the bolt 1 can be improved.
また、本実施形態では、レーザ１１を用いて超音波を発生させると共に、レーザ１２、集光レンズ１３、及び光検出器１４を用いて多重反射波によるボルト１の端面の変動を検出する。例えば振動子を用いて超音波を発生させると共に反射波を検出する場合には、接触媒質を介し振動子をボルト１の頭部４に接触させる必要がある。しかし、本実施形態では、レーザ１１，１２等をボルト１の頭部４に接触させる必要がなく、接触媒質も必要としない。そのため、作業者の負担を軽減することができる。
Further, in the present embodiment, the laser 11 is used to generate ultrasonic waves, and the laser 12, the condenser lens 13, and the photodetector 14 are used to detect fluctuations in the end face of the bolt 1 due to multiple reflected waves. For example, in the case of generating ultrasonic waves and detecting reflected waves using a vibrator, it is necessary to bring the vibrator into contact with the head 4 of the bolt 1 via a contact medium. However, in the present embodiment, it is not necessary to bring the lasers 11, 12, etc. into contact with the head 4 of the bolt 1, and no contact medium is required. Therefore, the burden on the worker can be reduced.
なお、上記一実施形態において、コンピュータ１６は、ボルト１の未締結状態における光検出器１４の検出結果として得られた第一の波形１８とボルト１の締結状態における光検出器１４の検出結果として得られた第二の波形２０との時間ずれを演算し、この時間ずれに基づいてボルト１の軸力を演算する場合を例にとって説明したが、これに限られない。コンピュータ１６は、ボルト１の第一の締結状態における光検出器１４の検出結果として得られた第一の波形とボルト１の第二の締結状態における光検出器１４の検出結果として得られた第二の波形との時間ずれを演算し、この時間ずれに基づいてボルト１の軸力を演算してもよい。
In the above embodiment, the computer 16 detects the first waveform 18 obtained as the detection result of the photodetector 14 in the unfastened state of the bolt 1 and the photodetector 14 in the fastened state of the bolt 1. The case where the time lag with the obtained second waveform 20 is calculated and the axial force of the bolt 1 is calculated based on this time lag has been described as an example, but the present invention is not limited to this. The computer 16 has a first waveform obtained as a detection result of the photodetector 14 in the first fastened state of the bolt 1 and a second waveform obtained as a detection result of the photodetector 14 in the second fastened state of the bolt 1. The time lag with the second waveform may be calculated, and the axial force of the bolt 1 may be calculated based on this time lag.
また、上記一実施形態において、レーザ１１は、照射エネルギーが低いものであって、ボルト１の表面層を瞬間的かつ局所的に熱膨張させて超音波を発生させる場合を例にとって説明したが、これに限られない。例えば、ボルト１の表面の加工処理を行う前段階であるか、若しくは、ボルト１の表面に照射痕がついても許されるのであれば、レーザ１１は、照射エネルギーが高いものであって、ボルト１の表面層を局所的に蒸発させて超音波を発生させてもよい（アブレーションモード）。
Further, in the above embodiment, the case where the laser 11 has a low irradiation energy and the surface layer of the bolt 1 is instantaneously and locally thermally expanded to generate ultrasonic waves has been described as an example. Not limited to this. For example, if it is a stage before processing the surface of the bolt 1 or if it is permissible to have an irradiation mark on the surface of the bolt 1, the laser 11 has a high irradiation energy and the bolt 1 has a high irradiation energy. The surface layer of the laser may be locally evaporated to generate ultrasonic waves (ablation mode).
また、上記一実施形態において、レーザ１１又は１２からボルト１の頭部４の端面までのレーザ光の伝播経路は、空気のみが介在する場合を例にとって説明したが、これに限られない。例えば図８で示す変形例のように、レーザ１１に接続され、ボルト１の頭部４の端面に向けてレーザ光Ａを伝送する光ファイバ２１（第一の光ファイバ）と、レーザ１２に接続され、ボルト１の頭部４の端面に向けてレーザ光Ｂを伝送する光ファイバ２２（第二の光ファイバ）とを設けてもよい。更に、光ファイバ２１，２２、集光レンズ１３、及び光検出器１４を、ボルト１を締結するためのレンチ２３に付設してもよい。
Further, in the above embodiment, the propagation path of the laser beam from the laser 11 or 12 to the end face of the head portion 4 of the bolt 1 has been described by taking the case where only air intervenes, but the present invention is not limited to this. For example, as in the modification shown in FIG. 8, the optical fiber 21 (first optical fiber) connected to the laser 11 and transmitting the laser beam A toward the end surface of the head portion 4 of the bolt 1 is connected to the laser 12. An optical fiber 22 (second optical fiber) that transmits the laser beam B toward the end surface of the head portion 4 of the bolt 1 may be provided. Further, the optical fibers 21 and 22, the condenser lens 13, and the photodetector 14 may be attached to the wrench 23 for fastening the bolt 1.
また、上記一実施形態及び変形例において、光検出器１４は、集光レンズ１３を介し、ボルト１の頭部４の端面で反射されたレーザ光を受光する場合を例にとって説明したが、これに限られない。レーザ光の検出強度が低下するものの、光検出器１４は、集光レンズ１３を介さず、ボルト１の頭部４の端面で反射されたレーザ光を受光してもよい。すなわち、集光レンズ１３を不要としてもよい。
Further, in the above embodiment and the modified example, the case where the photodetector 14 receives the laser light reflected by the end face of the head 4 of the bolt 1 via the condenser lens 13 has been described as an example. Not limited to. Although the detection intensity of the laser light is reduced, the photodetector 14 may receive the laser light reflected by the end face of the head portion 4 of the bolt 1 without passing through the condenser lens 13. That is, the condenser lens 13 may be unnecessary.
１ ボルト
２Ａ，２Ｂ 部材
４ 頭部
５ ネジ部
１１ レーザ（第一のレーザ）
１２ レーザ（第二のレーザ）
１４ 光検出器
１６ コンピュータ
２１ 光ファイバ（第一の光ファイバ）
２２ 光ファイバ（第二の光ファイバ）
２３ レンチ 1 Volt 2A, 2B member 4 Head 5 Thread 11 Laser (first laser)
12 laser (second laser)
14Photodetector 16 Computer 21 Optical fiber (first optical fiber)
22 Optical fiber (second optical fiber)
23 wrench
２Ａ，２Ｂ 部材
４ 頭部
５ ネジ部
１１ レーザ（第一のレーザ）
１２ レーザ（第二のレーザ）
１４ 光検出器
１６ コンピュータ
２１ 光ファイバ（第一の光ファイバ）
２２ 光ファイバ（第二の光ファイバ）
２３ レンチ 1
12 laser (second laser)
14
22 Optical fiber (second optical fiber)
23 wrench
Claims (8)
- 部材に締結されたボルトの軸力を計測するボルト軸力計測装置において、
前記ボルトの頭部の端面に第一のレーザ光を照射して超音波を発生させ、前記超音波が前記ボルトのネジ部に伝播し前記ネジ部の側面によって多重反射して多重反射波となり、前記多重反射波が前記頭部の端面に到達する、第一のレーザと、
前記ボルトの前記頭部の端面に第二のレーザ光を照射する第二のレーザと、
前記ボルトの前記頭部の端面で反射された第二のレーザ光を検出することにより、前記多重反射波による前記頭部の端面の変動を検出する光検出器と、
前記光検出器の検出結果に基づいて前記ボルトの軸力を演算するコンピュータとを備えたことを特徴とするボルト軸力計測装置。 In a bolt axial force measuring device that measures the axial force of a bolt fastened to a member,
The end face of the head of the bolt is irradiated with the first laser beam to generate ultrasonic waves, and the ultrasonic waves propagate to the threaded portion of the bolt and are multiplely reflected by the side surface of the threaded portion to form a multiple reflected wave. The first laser, at which the multiple reflected waves reach the end face of the head,
A second laser that irradiates the end face of the head of the bolt with a second laser beam,
A photodetector that detects fluctuations in the end face of the head due to the multiple reflected waves by detecting a second laser beam reflected by the end face of the head of the bolt.
A bolt axial force measuring device including a computer that calculates the axial force of the bolt based on the detection result of the photodetector. - 請求項１に記載のボルト軸力計測装置において、
前記コンピュータは、
前記ボルトの未締結状態又は第一の締結状態における前記光検出器の検出結果として得られた第一の波形と前記ボルトの第二の締結状態における前記光検出器の検出結果として得られた第二の波形との時間ずれを演算し、
前記時間ずれに基づいて前記ボルトの軸力を演算することを特徴とするボルト軸力計測装置。 In the bolt axial force measuring device according to claim 1,
The computer
The first waveform obtained as the detection result of the photodetector in the unfastened state or the first fastened state of the bolt and the second waveform obtained as the detection result of the photodetector in the second fastened state of the bolt. Calculate the time lag with the second waveform,
A bolt axial force measuring device, characterized in that the axial force of the bolt is calculated based on the time lag. - 請求項２に記載のボルト軸力計測装置において、
前記コンピュータは、
前記第一の波形のうち、超音波が前記ボルトの軸方向に伝播した場合を仮想したときの前記頭部の端面と前記ネジ部の端面の間を往復する時間より後となるように設定された時間領域における部分波形を抽出し、
前記部分波形と前記第二の波形との相互相関関数を演算することにより、前記第一の波形と前記第二の波形との時間ずれを演算することを特徴とするボルト軸力計測装置。 In the bolt axial force measuring device according to claim 2,
The computer
Of the first waveform, it is set to be after the time to reciprocate between the end face of the head and the end face of the threaded portion when imagining the case where the ultrasonic wave propagates in the axial direction of the bolt. Extract the partial waveform in the time domain
A bolt axial force measuring device, characterized in that a time lag between the first waveform and the second waveform is calculated by calculating a cross-correlation function between the partial waveform and the second waveform. - 請求項１に記載のボルト軸力計測装置において、
前記第一のレーザに接続され、前記ボルトの前記頭部の端面に向けて前記第一のレーザ光を伝送する第一の光ファイバと、
前記第二のレーザに接続され、前記ボルトの前記頭部の端面に向けて前記第二のレーザ光を伝送する第二の光ファイバとを備え
前記第一の光ファイバ、前記第二の光ファイバ、及び前記光検出器は、レンチに付設されたことを特徴とするボルト軸力計測装置。 In the bolt axial force measuring device according to claim 1,
A first optical fiber connected to the first laser and transmitting the first laser beam toward the end face of the head of the bolt.
The first optical fiber, the second optical fiber, comprising a second optical fiber connected to the second laser and transmitting the second laser beam toward the end face of the head of the bolt. , And the optical detector is a bolt axial force measuring device, which is attached to a wrench. - 部材に締結されたボルトの軸力を計測するボルト軸力計測方法において、
第一のレーザから前記ボルトの頭部の端面に第一のレーザ光を照射して超音波を発生させ、前記超音波が前記ボルトのネジ部に伝播し前記ネジ部の側面によって多重反射して多重反射波となり、前記多重反射波が前記頭部の端面に到達し、
第二のレーザから前記ボルトの前記頭部の端面に第二のレーザ光を照射し、前記頭部の端面で反射された第二のレーザ光を光検出器で検出することにより、前記多重反射波による前記頭部の端面の変動を検出し、
前記光検出器の検出結果に基づいて前記ボルトの軸力を演算することを特徴とするボルト軸力計測方法。 In the bolt axial force measuring method for measuring the axial force of a bolt fastened to a member,
The end face of the head of the bolt is irradiated with the first laser beam from the first laser to generate ultrasonic waves, and the ultrasonic waves propagate to the threaded portion of the bolt and are repeatedly reflected by the side surface of the threaded portion. It becomes a multiple reflected wave, and the multiple reflected wave reaches the end face of the head, and becomes a multiple reflected wave.
The multiple reflection is performed by irradiating the end face of the head of the bolt with the second laser beam from the second laser and detecting the second laser light reflected by the end face of the head with a photodetector. Detects fluctuations in the end face of the head due to waves,
A method for measuring a bolt axial force, which comprises calculating the axial force of the bolt based on the detection result of the photodetector. - 請求項５に記載のボルト軸力計測方法において、
前記ボルトの未締結状態又は第一の締結状態における前記光検出器の検出結果として得られた第一の波形と前記ボルトの第二の締結状態における前記光検出器の検出結果として得られた第二の波形との時間ずれを演算し、
前記時間ずれに基づいて前記ボルトの軸力を演算することを特徴とするボルト軸力計測方法。 In the bolt axial force measuring method according to claim 5,
The first waveform obtained as the detection result of the photodetector in the unfastened state or the first fastened state of the bolt and the second waveform obtained as the detection result of the photodetector in the second fastened state of the bolt. Calculate the time lag with the second waveform,
A bolt axial force measuring method, characterized in that the axial force of the bolt is calculated based on the time lag. - 請求項６に記載のボルト軸力計測方法において、
前記第一の波形のうち、超音波が前記ボルトの軸方向に伝播した場合を仮想したときの前記頭部の端面と前記ネジ部の端面の間を往復する時間より後となるように設定された時間領域における部分波形を抽出し、
前記部分波形と前記第二の波形との相互相関関数を演算することにより、前記第一の波形と前記第二の波形との時間ずれを演算することを特徴とするボルト軸力計測方法。 In the bolt axial force measuring method according to claim 6,
Of the first waveform, it is set to be after the time to reciprocate between the end face of the head and the end face of the threaded portion when imagining the case where the ultrasonic wave propagates in the axial direction of the bolt. Extract the partial waveform in the time domain
A method for measuring a bolt axial force, which comprises calculating a time lag between the first waveform and the second waveform by calculating a cross-correlation function between the partial waveform and the second waveform. - 請求項５に記載のボルト軸力計測方法において、
前記第一のレーザに接続され且つレンチに付設された第一の光ファイバを用いて、前記ボルトの前記頭部の端面に向けて前記第一のレーザ光を伝送し、
前記第二のレーザに接続され且つ前記レンチに付設された第二の光ファイバを用いて、前記ボルトの前記頭部の端面に向けて前記第二のレーザ光を伝送し、
前記レンチに付設された前記光検出器で、前記ボルトの前記頭部の端面で反射された第二のレーザ光を検出することにより、前記多重反射波による前記頭部の端面の変動を検出することを特徴とするボルト軸力計測方法。 In the bolt axial force measuring method according to claim 5,
Using the first optical fiber connected to the first laser and attached to the wrench, the first laser beam is transmitted toward the end face of the head of the bolt.
Using a second optical fiber connected to the second laser and attached to the wrench, the second laser beam is transmitted toward the end face of the head of the bolt.
The photodetector attached to the wrench detects the fluctuation of the end face of the head due to the multiple reflected waves by detecting the second laser beam reflected by the end face of the head of the bolt. Bolt axial force measurement method characterized by this.
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