Bolt Loosening Detection Device and Bolt Loosening Detection Method

Abstract

To provide a bolt looseness detection device and a method for detecting looseness of a bolt that can be easily set and can make it easier to check a bolt for looseness.SOLUTION: A bolt looseness detection device 10 according to an embodiment includes: a vibration detection sensor 12 for detecting vibration of a bolt fastening unit 1; a sensor support member 13 fixed to the bolt fastening unit 1, the member supporting the vibration detection sensor 12; a measuring machine connected to the vibration detection sensor 12 and located away from the bolt fastening unit 1, the measuring machine measuring the vibration detected by the vibration detection sensor 12; and a detector for detecting looseness of the bolt fastening unit 1 from the result of measurement by the measuring machine.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a bolt loosening detection device and a bolt loosening detection method for detecting loosening of a bolt fastening portion having a bolt and a nut.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2017-26134 describes a nut loosening sensor for detecting loosening of a nut tightened to a bolt of a structure or the like. The nut loosening sensor includes a nut cap with a magnet attached to the nut and a bolt cap with two output terminals attached to the bolt.

[0003] The nut loosening sensor further includes a left contact terminal and a right contact terminal attached to the magnet, and two electric wires extending from each of the two output terminals. One of the two electric wires is connected to the magnet via the left contact terminal, and the other of the two electric wires is connected to the magnet via the right contact terminal.

[0004] In the nut loosening sensor, when the nut loosens due to the influence of continuous vibration or the like during use of the bolt and a counterclockwise rotational displacement of the nut with respect to the bolt exceeds a certain value, the electric wire connected to the left contact terminal gets caught on the output terminal. Then, the electric wire cannot follow the rotational displacement of the nut and separates from the magnet, resulting in a non-conductive state between the two output terminals. By detecting this state, loosening of the nut is detected.

[0005] Japanese Patent Application Laid-Open No. 2005-69312 describes a washer for detecting bolt loosening. This washer has a rectangular shape, a through hole on one side in the longitudinal direction, and a piezoelectric element on the other side in the longitudinal direction. This washer is sandwiched between two flat washers positioned between the bolt and the nut.

[0006] A signal voltage that changes at a constant period generated by a waveform generator is input to the piezoelectric element of this washer. Along with this, the piezoelectric element vibrates in the thickness direction of the washer, and the input voltage at that time is regarded as input signal data. On the other hand, the charge generated in the piezoelectric element due to the above vibration is converted into a voltage signal to obtain output signal data.

[0007] The natural frequency of the washer is calculated from the input signal data and the output signal data. Then, after a certain period has elapsed, the natural frequency of the washer is calculated in the same way, the calculated natural frequency is compared with the natural frequency before a certain period has elapsed, and if a decrease is seen in the value of the natural frequency, it is determined that the bolt is loose.

[0008] Japanese Patent Application Laid-Open No. 2020-148504 describes a loosening detection system for an axial force member and a method for detecting loosening of an axial force member. The loosening detection system includes a keying device that applies an external force to a bolt to be inspected and a keying sound recording device in which a sound collecting device that measures the vibration of the bolt generated by the external force as sound is integrated.

[0009] The keying sound recording device is attached to the tip of an extension pole and fixed to the attachment member with a magnet or the like. The keying device incorporates a motor, a cam, and a spring, and can key with a key that moves on the circumferential surface of the head of the bolt at regular time intervals. The sound generated by this keying is collected by the sound collecting device. Then, the presence or absence of loosening of the bolt to be inspected is determined from the collected sound.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] The above-mentioned nut loosening sensor includes a nut cap and a bolt cap connected to each other via two electric wires, and detects the loosening of the nut as it rotates relative to the bolt from a non-conductive state. Therefore, since it cannot be attached without installing the nut cap on the nut and the bolt cap on the bolt, etc., there may arise a problem that the installation is complicated. Further, since this nut loosening sensor cannot detect the loosening of the nut unless the nut actually rotates and the electric wires become non-conductive, it cannot detect even a sign of loosening.

[0012] The above-mentioned washer for detecting bolt loosening has a rectangular shape with a through-hole through which the bolt passes and a piezoelectric element. This washer has a special structure and must be sandwiched between two flat washers, so there may occur a problem that the installation is complicated.

[0013] The above-mentioned loosening detection system is attached to the tip of an extension pole and includes a keying sound recording device in which a keying device and a sound collecting device are integrated. In this loosening detection system, the loosening of the bolt cannot be detected unless one actually goes to the site where the bolt is located, keys the peripheral surface of the bolt with the keying device, and collects the sound. Therefore, since the loosening cannot be detected without going to the site deliberately, there is a problem that a great deal of labor is required for the loosening inspection work.

[0014] An object of the present disclosure is to provide a bolt loosening detection device and a bolt loosening detection method that can be easily installed and can save labor for the loosening inspection work.

Means for Solving the Problems

[0015] The bolt loosening detection device according to the present disclosure is a bolt loosening detection device that detects loosening of a bolt fastening portion having a bolt and a nut. The bolt loosening detection device includes a vibration detection sensor that detects vibration of the bolt fastening portion, a sensor support member that supports the vibration detection sensor and is fixed to the bolt fastening portion, a measuring instrument that is connected to the vibration detection sensor and is provided at a remote location away from the bolt fastening portion and measures the vibration detected by the vibration detection sensor, and a detection device that detects loosening of the bolt fastening portion from the measurement result of the measuring instrument. , The vibration detection sensor is an optical fiber cable wound around a sensor support member, and the sensor support member has a groove into which the optical fiber cable to be wound is inserted 。

[0016] In this bolt loosening detection device, a vibration detection sensor that detects vibration of the bolt fastening portion is supported by a sensor support member, and the sensor support member is fixed to the bolt fastening portion. Therefore, since the sensor support member can be fixed to the bolt fastening portion to install the vibration detection sensor, the installation of the bolt loosening detection device on the bolt fastening portion can be easily performed. The bolt loosening detection device includes a measuring instrument and a detection device provided at a remote location. The detection device is a data processing device that processes data measured by the measuring instrument. The measuring instrument is provided at a remote location away from the bolt fastening portion. Therefore, since the bolt fastening portion can be inspected without going to the site where the bolt fastening portion is located, the inspection work for loosening can be labor-saving.

[0017] The measuring instrument stores the vibration characteristics of the bolt fastening portion in a state where the bolt is not loose, and the detection device may detect that the vibration characteristics of the vibration from the vibration detection sensor have changed as loosening of the bolt fastening portion with respect to the vibration characteristics stored in the measuring instrument. In this case, the measuring instrument stores the vibration characteristics of the bolt fastening portion in a state where the bolt is not loose. The detection device detects a change in the vibration characteristics of the vibration detected by the vibration detection sensor with respect to the vibration characteristics in a state where the bolt is not loose as loosening of the bolt fastening portion. By detecting a change in the vibration characteristics as loosening of the bolt fastening portion, the loosening of the bolt fastening portion can be detected with high accuracy.

[0018] The sensor support member has a hole into which a nut or the head of a bolt fits, and may be fixed to the bolt fastening portion by fitting the nut or the head of the bolt into the hole. In this case, the nut or the head of the bolt can be fitted into the hole of the sensor support member to fix the sensor support member to the bolt fastening portion. Therefore, the installation of the bolt loosening detection device can be made even easier.

[0019] This In this case, vibrations in the bolt fastening portion can be detected with higher precision. That is, in the optical fiber cable, since changes in strain associated with vibrations can be continuously and distributively detected along the portion where the optical fiber cable contacts, loosening of the bolt fastening portion can be detected with even higher precision.

[0020] This In this case, by inserting the optical fiber cable into the groove of the sensor support member, the winding of the optical fiber cable around the sensor support member can be easily performed. Also, since the optical fiber cable is inserted into the groove, the optical fiber cable can be protected inside the groove. Therefore, the possibility of disconnection of the optical fiber cable can be further reduced.

[0021] The bolt loosening detection device includes a plurality of sensor support members, the plurality of sensor support members are connected in series to one vibration detection sensor, and the measuring instrument may be connected to an end of one vibration detection sensor. In this case, since a plurality of sensor support members are connected in series to one vibration detection sensor, vibrations of a plurality of bolt fastening portions separated from each other can be detected by one vibration detection sensor. Therefore, since the loosening of a plurality of bolt fastening portions can be inspected with a simple configuration, the inspection work for a plurality of bolt fastening portions can be made even easier without going to the site.

[0022] The bolt loosening detection method according to the present disclosure is a bolt loosening detection method for detecting loosening of a bolt fastening portion having a bolt and a nut. The bolt loosening detection method includes a step of fixing a sensor support member that supports a vibration detection sensor for detecting vibration of the bolt fastening portion to the bolt fastening portion, and a step of measuring the vibration characteristics of the bolt fastening portion in a state where the bolt is not loosened from the vibration detected by the vibration detection sensor. A step of storing in a measuring machine provided at a remote location away from the bolt fastening portion, and a step of detecting that the vibration characteristics of the vibration from the vibration detection sensor have changed with respect to the vibration characteristics stored in the storing step as loosening of the bolt fastening portion. , The vibration detection sensor is an optical fiber cable wound around a sensor support member, and the sensor support member has a groove into which the optical fiber cable to be wound is inserted 。

[0023] In this bolt loosening detection method, a sensor support member that supports a vibration detection sensor for detecting vibration of the bolt fastening portion is fixed to the bolt fastening portion. Therefore, since the vibration detection sensor is installed by fixing the sensor support member to the bolt fastening portion, the installation of the bolt loosening detection device with respect to the bolt fastening portion can be easily performed. Further, the vibration characteristics of the vibration of the bolt fastening portion in a state where there is no loosening in the bolt fastening portion are stored by a measuring machine provided at a remote location away from the bolt fastening portion. And since it is detected that the vibration characteristics of the vibration from the vibration detection sensor have changed with respect to the stored vibration characteristics as loosening of the bolt fastening portion, the loosening of the bolt fastening portion can be detected with high accuracy. Furthermore, since the measuring machine for measuring the vibration of the bolt fastening portion is provided at a remote location away from the bolt fastening portion, the loosening of the bolt fastening portion can be measured without going to the site where the bolt fastening portion is located. Therefore, the inspection work for the loosening of the bolt fastening portion can be labor-saving.

Effects of the Invention

[0024] According to the present disclosure, the installation of the vibration detection sensor can be easily performed, and the inspection work for loosening can be labor-saving.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0026] Hereinafter, embodiments of the bolt loosening detection device and the bolt loosening detection method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. Further, the drawings may be drawn with some parts simplified or exaggerated for ease of understanding, and the dimensional ratios and the like are not limited to those described in the drawings.

[0027] FIG. 1 is a perspective view showing an exemplary bolt fastening portion 1 in which the bolt loosening detection device according to the present embodiment is installed. As an example, the bolt fastening portion 1 has a bolt 2 which is an anchor bolt for fixing the lower end portion of the lighting lamp 5, and a nut 3 fastened to the bolt 2. The lighting lamp 5 is, for example, lighting provided beside a road and illuminates the road at night or the like.

[0028] As an example, the lighting fixture 5 is made of a metal such as iron. The lighting fixture 5 includes a column portion 6 to which lighting is attached on the upper side and which extends along the vertical direction, a base plate 7 that extends horizontally from the column portion 6 at the lower end of the column portion 6, and a plurality of ribs 8. The column portion 6 is, for example, cylindrical, and the base plate 7 is square-shaped.

[0029] The base plate 7 has a plurality of through holes penetrating in the thickness direction thereof, and bolts 2 are passed through the through holes. A washer 4 is provided on the upper surface of the base plate 7, and the bolts 2 are passed through the through holes and the washer 4 from below. In plan view, the plurality of bolts 2 are arranged at positions surrounding the column portion 6. As an example, four bolts 2 are arranged so as to be square-shaped in plan view.

[0030] For example, in plan view, a plurality of ribs 8 extend radially from the column portion 6 and are fixed to the base plate 7. The ribs 8 are fixed to the side surface of the column portion 6 and the upper surface of the base plate 7. In plan view, the ribs 8 extend between a pair of bolts 2 from the column portion 6. As an example, four ribs 8 protrude from the side surface of the column portion 6.

[0031] For the lighting fixture 5, the base plate 7 is placed on the concrete C, and bolts 2 are inserted into the respective through holes of the base plate 7 from below. The base plate 7 is fixed to the concrete C by fastening nuts 3 to the portions of the bolts 2 protruding upward from the base plate 7. For example, a plurality (two as an example) of nuts 3 are fastened to the bolts 2. The bolt fastening portion 1 may include at least one of the bolts 2, the nuts 3, the washers 4, and the base plate 7.

[0032] As shown in FIGS. 1 and 2, the bolt loosening detection device 10 according to the present embodiment detects loosening of the bolt fastening portion 1. FIG. 2 is a perspective view showing the sensor unit 11 of the bolt loosening detection device 10. For example, the bolt loosening detection device 10 detects loosening of the nut 3 with respect to the bolt 2. The bolt loosening detection device 10 has a sensor unit 11 attached to the bolt fastening portion 1.

[0033] The sensor unit 11 includes a vibration detection sensor 12 that detects vibration of the bolt fastening portion 1, and a sensor support member 13 that supports the vibration detection sensor 12 and is fixed to the bolt fastening portion 1. The sensor support member 13 has a columnar shape. As an example, the sensor support member 13 has a cylindrical shape extending in the longitudinal direction D.

[0034] The sensor support member 13 has a top surface 13b located at one end in the longitudinal direction D, a bottom surface 13c facing the side opposite to the top surface 13b, and a side surface 13d located between the top surface 13b and the bottom surface 13c. The sensor support member 13 has a hole 14 that fits into the bolt fastening portion 1. For example, the hole 14 is recessed from the bottom surface 13c.

[0035] The sensor support member 13 is fixed to the bolt fastening portion 1 by fitting the nut 3 or the head of the bolt into the hole 14. The hole 14 extends along the longitudinal direction D from the bottom surface 13c of the sensor support member 13. The shape of the hole 14 when viewed along the longitudinal direction D is, for example, a shape similar to the shape of the nut 3.

[0036] When viewed along the longitudinal direction D, the area of the hole 14 is slightly smaller than the area of the nut 3. When viewed along the longitudinal direction D, the diameter of the circumscribed circle of the hole 14 is slightly smaller than the diameter of the circumscribed circle of the nut 3. Therefore, when the sensor support member 13 is fixed to the bolt fastening portion 1, the nut 3 fits while bending the edge of the hole 14, so that the sensor support member 13 can be easily and firmly coupled to the bolt fastening portion 1. Note that an adhesive may be applied to the hole 14 and the nut 3 or the head of the bolt may be fitted into the hole 14. In this case, the sensor support member 13 can be more firmly fixed to the bolt fastening portion 1.

[0037] FIG. 3 is a cross-sectional view showing a state where the sensor unit 11 (sensor support member 13) is fixed to the bolt fastening portion 1. As shown in FIGS. 2 and 3, the vibration detection sensor 12 is wound around the sensor unit 11. For example, the vibration detection sensor 12 is an optical fiber cable. In this case, the vibration detection sensor 12 is composed of an optical fiber core wire and a resin coating layer that coats the optical fiber core wire.

[0038] The sensor support member 13 has a groove 15 into which the wound vibration detection sensor 12 is inserted. The groove 15 is spiral on the side surface 13d of the sensor support member 13. The length of the groove 15 formed in the sensor support member 13 is, for example, 1 m or more. In this case, the length of the vibration detection sensor 12 wound around the sensor support member 13 is 1 m or more.

[0039] Since the length of the vibration detection sensor 12 wound around the sensor support member 13 is 1 m or more, the length of the vibration detection sensor 12 corresponding to one bolt fastening portion 1 can be sufficiently ensured, and it is possible to easily identify the location where loosening has occurred in the bolt fastening portion 1. Note that an adhesive may be applied to the groove 15, and the vibration detection sensor 12 may be inserted into the groove 15 via the adhesive. In this case, it is possible to fix the vibration detection sensor 12 more firmly to the sensor support member 13.

[0040] The diameter A of the sensor support member 13 is, for example, 3 cm or more and 10 cm or less, and is 8 cm as an example. When the sensor support member 13 is cylindrical and the diameter A is 3 cm or more, the bending radius of the vibration detection sensor 12 as an optical fiber cable can be sufficiently ensured, so that disconnection of the vibration detection sensor 12 can be more reliably suppressed. Further, when the diameter A is 10 cm or less, enlargement of the sensor support member 13 can be suppressed, and a compact sensor support member 13 can be obtained.

[0041] Vibration is detected in at least a part of the bolt fastening part 1 by the vibration detection sensor 12. The vibration detection sensor 12 is, for example, a distributed optical fiber sensor. In this case, the detailed distribution of the vibration can be grasped by the vibration detection sensor 12. Therefore, vibration detection by the sensor unit 11 can be performed with high precision.

[0042] The sensor support member 13 is made of, for example, a resin material having ultraviolet resistance. In this case, the sensor support member 13 can have ultraviolet resistance, and the weather resistance of the sensor support member 13 can be enhanced. As an example, the sensor support member 13 is made of polyvinyl chloride.

[0043] Note that the sensor support member 13 may be made of a material other than a resin material, and a covering member for covering the sensor support member 13 may be further provided. In this case, if the covering member is made of a weather-resistant material, the weather resistance of the sensor unit 11 can be enhanced.

[0044] FIG. 4 is a diagram schematically showing the configuration of the bolt loosening detection device 10. As shown in FIGS. 3 and 4, for example, one end and the other end of the vibration detection sensor 12 extend from the sensor support member 13. For example, the bolt loosening detection device 10 includes at least one vibration detection sensor 12, a plurality of sensor support members 13 around which the vibration detection sensor 12 is wound, a measuring instrument 16 connected to one end of the vibration detection sensor 12, and a detection device 17.

[0045] The plurality of sensor support members 13 are connected in series to one vibration detection sensor 12. Each of the plurality of sensor support members 13 may be attached to each of the plurality of bolt fastening parts 1 of the lighting lamp 5, for example, or may be attached to the bolt fastening part 1 of a structure X other than the lighting lamp 5.

[0046] The bolt fastening portion 1 of the structure X may be, for example, a high-strength bolt used for a lighting fixture of a type different from the lighting fixture 5, a sign post such as a portal sign, a support of a bridge, a fall prevention device, an electrification pole of a railway, a fixing anchor for an outdoor unit, or a friction joint of steel materials. Thus, the plurality of sensor support members 13 around which the vibration detection sensor 12 according to the present embodiment is wound can be attached to various structures X including the lighting fixture 5, and the loosening of bolts of various structures X including the lighting fixture 5 can be detected with high precision.

[0047] The measuring instrument 16 may detect vibration, for example, via the vibration detection sensor 12 which is an optical fiber cable by distributed acoustic sensing (DAS).

[0048] By the way, the vibration characteristics of the bolt fastening portion 1 in a state where the bolt 2 is loose are different from the vibration characteristics of the bolt fastening portion 1 in a state where the bolt 2 is not loose. Specifically, for example, when the bolt 2 becomes loose due to corrosion of the bolt 2 or the like, the bolt 2 or the nut 3 rattles, and the vibration characteristics due to an input such as traffic vibration change.

[0049] That is, when the bolt 2 becomes loose, the frequency distribution of the vibration of the bolt fastening portion 1 including the bolt 2 and the nut 3 changes. FIG. 5(a) is a graph schematically showing the vibration characteristics of the bolt fastening portion 1 in a sound state (a state where the bolt 2 is not loose). FIG. 5(b) is a graph schematically showing the vibration characteristics of the bolt fastening portion 1 in a state where the bolt 2 is loose. As shown in FIGS. 5(a) and 5(b), as an example, when the bolt 2 becomes loose, it is considered that the vibration frequency of the bolt fastening portion 1 decreases and the vibration frequency of the peak of the frequency distribution of the vibration decreases.

[0050] In this embodiment, a vibration detection sensor 12, which is an optical fiber cable, is connected to the measuring instrument 16, and the vibration characteristics of the bolt fastening part 1 in a sound state are stored in the measuring instrument 16. The detection device 17 detects signs of abnormalities such as corrosion and loosening in the bolt fastening part 1 based on whether there is a change in the vibration characteristics from the vibration characteristics in the sound state stored in the measuring instrument 16. The detection device 17 detects loosening of the bolt fastening part 1 from the measurement results of the measuring instrument 16.

[0051] As shown in FIG. 4, the measuring instrument 16 and the detection device 17 are provided, for example, in a remote location separated from the lighting fixture 5 having the bolt fastening part 1 or the structure X. As an example, the measuring instrument 16 and the detection device 17 are provided in a management office Y that manages a plurality of structures. In the above bolt loosening detection device 10, it is first necessary to install the sensor unit 11 on the bolt fastening part 1 of the lighting fixture 5 or the structure X. However, after installing the sensor unit 11, if the measuring instrument 16 and the detection device 17 are connected to the management office Y or the like, the vibrations of a plurality of bolt fastening parts 1 can be measured at once. Therefore, significant labor savings in the inspection of the bolt fastening part 1 can be achieved.

[0052] Next, the bolt loosening detection method according to this embodiment will be described. As an example, hereinafter, as shown in FIG. 1, a method for detecting loosening of the bolt fastening part 1 having the bolt 2 and the nut 3 will be described.

[0053] First, as shown in FIG. 2, a sensor unit 11 including a vibration detection sensor 12 and a sensor support member 13 is prepared (step of preparing the sensor unit). For example, the vibration detection sensor 12 is wound around the sensor support member 13 while inserting an intermediate portion of the vibration detection sensor 12 into the groove 15 of the sensor support member 13 to produce the sensor unit 11.

[0054] Next, as shown in FIG. 3, the sensor support member 13 is fixed to the bolt fastening portion 1 (step of fixing the sensor support member). Specifically, a nut 3 is fitted into the hole 14 of the sensor support member 13, and the sensor support member 13 is press-fitted into the nut 3. Alternatively, the head of a bolt different from the nut 3 may be fitted into the hole 14 of the sensor support member 13, and the sensor support member 13 may be press-fitted into the head of the bolt.

[0055] Then, as shown in FIG. 4, while serially connecting a plurality of sensor support members 13 to one vibration detection sensor 12 (step of serially connecting a plurality of sensor support members), the plurality of sensor support members 13 are fixed to a plurality of bolt fastening portions 1 (step of fixing a plurality of sensor support members to a plurality of bolt fastening portions).

[0056] Then, a measuring instrument 16 and a detection device 17 are connected to one end of the vibration detection sensor 12 (step of connecting the measuring instrument). At this time, the measuring instrument 16 and the detection device 17 are connected at a remote location away from the bolt fastening portion 1. Further, terminal processing is performed on the other end of the vibration detection sensor 12. Thereafter, the vibration detection sensor 12 detects the vibration of each of the plurality of bolt fastening portions 1.

[0057] For example, when measurement light is input from the measuring instrument 16 to the vibration detection sensor 12, backscattered light is generated from each of the plurality of bolt fastening portions 1. The measuring instrument 16 detects the vibration of each of the plurality of bolt fastening portions 1, for example, by acquiring the spectrum of the backscattered light for each bolt fastening portion 1. First, the measuring instrument 16 stores the vibration characteristics of the bolt fastening portion 1 in a state where the bolt 2 is not loose from the vibration detected by the vibration detection sensor 12 (step of storing the vibration characteristics).

[0058] For example, the above steps are performed at the time of initial installation of the bolt loosening detection device 10. The loosening of the plurality of bolt fastening portions 1 is measured, for example, after a certain period has elapsed since the initial installation (for example, several years or several months later). At this time, the measuring instrument 16 and the detection device 17 are connected to one end of the vibration detection sensor 12, and the detection device 17 detects the presence or absence of loosening of the bolt fastening portion 1 with respect to the plurality of bolt fastening portions 1.

[0059] The detection device 17 compares the vibration characteristics of the bolt fastening part 1 in a state where the bolt 2 stored in the measuring machine 16 is not loose with the vibration characteristics of the vibration of the bolt fastening part 1 detected by the vibration detection sensor 12 after a certain period of time has elapsed. Then, when the detection device 17 detects that the vibration characteristics of the vibration from the vibration detection sensor 12 have changed with respect to the vibration characteristics of the bolt fastening part 1 in a state where the bolt 2 is not loose, the detection device 17 detects the loosening of the bolt fastening part 1 (the step of detecting as loosening of the bolt fastening part). The detection device 17 performs the above detection for each of the plurality of bolt fastening parts 1, and identifies the bolt fastening part 1 whose vibration characteristics have changed as the bolt fastening part 1 in which loosening has occurred. Through the above steps, a series of steps of the bolt loosening detection method are completed.

[0060] Next, the effects obtained from the bolt loosening detection device 10 and the bolt loosening detection method according to the present embodiment will be described in detail. In the bolt loosening detection device 10 and the bolt loosening detection method according to the present embodiment, the vibration detection sensor 12 that detects the vibration of the bolt fastening part 1 is supported by the sensor support member 13, and the sensor support member 13 is fixed to the bolt fastening part 1.

[0061] Therefore, since the sensor support member 13 can be fixed to the bolt fastening part 1 to install the vibration detection sensor 12, the installation of the bolt loosening detection device 10 with respect to the bolt fastening part 1 can be easily performed. That is, the bolt loosening detection device 10 can be easily attached to the existing bolt fastening part 1.

[0062] The bolt loosening detection device 10 includes a measuring instrument 16 and a detection device 17 provided at a remote location away from the bolt fastening portion 1. The measuring instrument 16 stores the vibration characteristics of the bolt fastening portion 1 in a state where the bolt 2 is not loose. The detection device 17 detects a change in the vibration characteristics of the vibration detected by the vibration detection sensor 12 with respect to the vibration characteristics in a state where the bolt 2 is not loose as loosening of the bolt fastening portion 1. By detecting a change in the vibration characteristics as loosening of the bolt fastening portion 1, loosening of the bolt fastening portion 1 can be detected with high accuracy. Further, the measuring instrument 16 is provided at a remote location away from the bolt fastening portion 1. Therefore, the bolt fastening portion 1 can be inspected without going to the site where the bolt fastening portion 1 is located, so that the inspection work for loosening can be labor-saving.

[0063] In the present embodiment, the sensor support member 13 has a hole 14 into which the nut 3 or the head of the bolt fits, and is fixed to the bolt fastening portion 1 by fitting the nut 3 or the head of the bolt into the hole 14. In this case, the nut or the head of the bolt can be fitted into the hole 14 of the sensor support member 13 to fix the sensor support member 13 to the bolt fastening portion 1. Therefore, the installation of the bolt loosening detection device 10 can be made easier.

[0064] In the present embodiment, the vibration detection sensor 12 is an optical fiber cable wound around the sensor support member 13. Therefore, vibration in the bolt fastening portion 1 can be detected with higher accuracy. That is, in the optical fiber cable, vibration can be continuously and distributively detected along the portion where the optical fiber cable contacts, so that loosening of the bolt fastening portion 1 can be detected with even higher accuracy.

[0065] In the present embodiment, the sensor support member 13 has a groove 15 into which the vibration detection sensor 12, which is an optical fiber cable to be wound, is inserted. Therefore, by inserting the vibration detection sensor 12 into the groove 15 of the sensor support member 13, the vibration detection sensor 12 can be easily wound around the sensor support member 13. Further, by inserting the vibration detection sensor 12 into the groove 15, the vibration detection sensor 12 can be protected inside the groove 15. Therefore, the possibility of disconnection of the vibration detection sensor 12 can be further reduced.

[0066] In the present embodiment, the bolt loosening detection device 10 includes a plurality of sensor support members 13, and the plurality of sensor support members 13 are connected in series to one vibration detection sensor 12, and the measuring instrument 16 is connected to an end of one vibration detection sensor 12. Therefore, since a plurality of sensor support members 13 are connected in series to one vibration detection sensor 12, the vibrations of a plurality of bolt fastening portions 1 that are separated from each other can be detected by one vibration detection sensor 12. Therefore, since the loosening of the bolt fastening portions 1 at a plurality of locations can be inspected with a simple configuration, the inspection work for the plurality of bolt fastening portions 1 can be performed more easily without going to the site.

[0067] As described above, embodiments of the bolt loosening detection device and the bolt loosening detection method according to the present disclosure have been described. However, the present disclosure is not limited to the contents of the above-described embodiments, and can be appropriately changed within the scope of the gist described in the claims. That is, the configuration, shape, size, number, material, and arrangement mode of each part of the bolt loosening detection device, and the content and order of the steps of the bolt loosening detection method can be appropriately changed within the scope of the above gist.

[0068] For example, in the foregoing embodiment, the vibration detection sensor 12 is an optical fiber cable, and the sensor support member 13 having the groove 15 into which the vibration detection sensor 12 is inserted has been described. However, the sensor support member may not have a groove into which the vibration detection sensor is inserted. For example, the vibration detection sensor 12 may be wound around the side surface 13d of the sensor support member 13. For example, the sensor support member 13 may be in a columnar shape (e.g., a cylindrical shape) that is split in half along the longitudinal direction D. As a result, due to the vibration transmitted from the bolt fastening portion 1, a slight opening occurs at the interface of the columnar sensor support member 13 that is split in half, and local strain occurs in the optical fiber cable wound across the interface, thereby enhancing the sensitivity of vibration detection.

[0069] Also, instead of the vibration detection sensor 12, a vibration detection sensor that is not an optical fiber cable may be provided. As shown in FIG. 6, instead of the vibration detection sensor 12, an acceleration sensor 22 and a cable 23 extending from the acceleration sensor 22 may be used. In this case, for example, instead of the groove 15 of the sensor support member 13, a sensor support member 26 having a recess 25 in which the acceleration sensor 22 is disposed can be used. The end of the cable 23 extending from the acceleration sensor 22 is connected to the measuring instrument. Also in this case, when the sensor support member 26 is fixed to the bolt fastening portion 1, the same operational effects as those of the foregoing embodiment can be obtained.

[0070] For example, in the foregoing embodiment, the sensor support member 13 fixed to the bolt fastening portion 1 by fitting the nut 3 into the hole 14 has been described. This sensor support member 13 may be diverted to another bolt fastening portion 1 after a certain period of time from the installation time. Also, in the foregoing embodiment, an example in which the sensor support member 13 is in a cylindrical shape has been described. However, the sensor support member may be in an elliptical columnar shape or an oblong columnar shape, and the shape of the sensor support member can be changed as appropriate.

[0071] In the foregoing embodiments, the sensor support member 13 having the nut 3 or the hole 14 that fits into the head of the bolt has been described. However, instead of the sensor support member 13, for example, a bolt loosening detection device provided with a sensor support member fixed to the washer 4 by adhesion or the like may be used. In the case of the sensor support member fixed to the washer 4, since the washer 4 is a part where the movement allowance during loosening is large, the sensitivity of loosening detection can be enhanced. Also, a bolt loosening detection device provided with a sensor support member fixed to the base plate 7 by adhesion or the like may be used. Thus, the location where the sensor support member is attached can be changed as appropriate.

Explanation of Signs

[0072] 1... Bolt fastening part, 2... Bolt, 3... Nut, 4... Washer, 5... Lighting lamp, 6... Column part, 7... Base plate, 8... Rib, 10... Bolt loosening detection device, 11... Sensor unit, 12... Vibration detection sensor, 13... Sensor support member, 13b... Top surface, 13c... Bottom surface, 13d... Side surface, 14... Hole, 15... Groove, 16... Measuring instrument, 17... Detection device, 22... Acceleration sensor, 23... Cable, 25... Recess, 26... Sensor support member, A... Diameter, C... Concrete, D... Longitudinal direction, X... Structure, Y... Management office.

Claims

1. A bolt loosening detection device for detecting loosening of a bolt fastening portion having a bolt and a nut, comprising: a vibration detection sensor for detecting vibration of the bolt fastening portion; a sensor support member that supports the vibration detection sensor and is fixed to the bolt fastening portion; a measuring instrument that is connected to the vibration detection sensor and is provided at a remote location away from the bolt fastening portion, and measures the vibration detected by the vibration detection sensor; a detection device that detects loosening of the bolt fastening portion from the measurement result of the measuring instrument; and wherein: the vibration detection sensor is an optical fiber cable wound around the sensor support member; the sensor support member has a groove into which the wound optical fiber cable is inserted; a bolt loosening detection device.

2. The measuring instrument stores vibration characteristics of the bolt fastening portion in a state where the bolt is not loose; the detection device detects that the vibration characteristics of the vibration from the vibration detection sensor have changed with respect to the vibration characteristics stored in the measuring instrument as loosening of the bolt fastening portion. The bolt loosening detection device according to claim 1.

3. The sensor support member has a hole into which the nut or the head of the bolt fits, and is fixed to the bolt fastening portion by fitting the nut or the head of the bolt into the hole. The bolt loosening detection device according to claim 1 or 2.

4. Comprising a plurality of the sensor support members; the plurality of sensor support members are connected in series to one vibration detection sensor; the measuring instrument is connected to an end of one vibration detection sensor. The bolt loosening detection device according to any one of claims 1 to 3.

5. A bolt loosening detection method for detecting loosening of a bolt fastening portion having a bolt and a nut, comprising: a step of fixing a sensor support member that supports a vibration detection sensor for detecting vibration of the bolt fastening portion to the bolt fastening portion; a step of storing, by a measuring instrument provided at a remote location away from the bolt fastening portion, vibration characteristics of vibration of the bolt fastening portion in a state where the bolt is not loose from the vibration detected by the vibration detection sensor; a step of detecting that the vibration characteristics of the vibration from the vibration detection sensor have changed with respect to the vibration characteristics stored in the storing step as loosening of the bolt fastening portion. and wherein: the vibration detection sensor is an optical fiber cable wound around the sensor support member; The sensor support member has a groove into which the optical fiber cable to be wound is inserted. Bolt loosening detection method.

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