Bolt with sensor and method for bolting

Abstract

To provide a bolt with a sensor which can increase the strength.SOLUTION: A bolt with a sensor used to bolt a target object includes: a bolt shaft including a screw part where a screw is formed and a non-screw part where a screw is not formed; and a sensor attached to the bolt shaft, the sensor detecting a distortion of the bolt shaft. The bolt shaft includes a recessed part recessed from the outer peripheral surface of the non-screw part to store the sensor, in the outer peripheral surface of the non-screw part. The area of the cross section of the bolt shaft in the position of the recessed part is larger than the effective cross-sectional area of the bolt shaft in the screw part.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present disclosure relates to a sensor-equipped bolt and a fastening method using the sensor-equipped bolt. [Background technology]

[0002] Bolts may be used to join components. For example, Patent Document 1 discloses a system for measuring stress in a building using bolted joints. A sensor unit that detects strain occurring in a screw member having a male thread and a female thread and used in the structure of the building is provided. The sensor unit is connected to an information collection device by wire or wirelessly, and the information collection device accumulates measurement information from the sensor unit and judges abnormalities in the building based on the measurement information. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6418457 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the screw member has an axially extending storage space formed in the head and shaft of the screw member in order to place the sensor unit, so that its strength may decrease. In order to obtain the desired strength, it is necessary to increase the size of the screw member, which increases the cost. In addition, when this screw member is applied to a fastening portion of an existing object, the strength is lower than that of the existing screw, so replacing the existing screw with this screw member will result in a decrease in the fastening strength of the object. In order to maintain the fastening strength of the object, it is assumed that the screw member needs to be added while leaving the existing screw as it is, but it is usually considered difficult to add this screw member to an existing object. The present disclosure provides a sensor-equipped bolt that improves strength and a fastening method using the sensor-equipped bolt. [Means for solving the problem]

[0005] A sensor-equipped bolt according to one aspect of the present disclosure is a sensor-equipped bolt used for fastening an object, and comprises a bolt shank including a threaded portion having a thread and a non-threaded portion having no thread, and a sensor attached to the bolt shank for detecting distortion of the bolt shank, wherein the bolt shank includes a recess in the outer peripheral surface of the non-threaded portion that is recessed from the outer peripheral surface of the non-threaded portion and accommodates the sensor, and the cross-sectional area of ​​the bolt shank at the position of the recess is greater than or equal to the effective cross-sectional area of ​​the bolt shank at the threaded portion. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view showing an example of an object to be fastened by a bolt set according to an exemplary embodiment. [Figure 2A] FIG. 2A is a side view showing an example of the configuration of the first bolt in FIG. [Figure 2B] FIG. 2B is a plan view showing an example of the configuration of the first bolt in FIG. [Diagram 3] FIG. 3 is a perspective view showing an example of a case in which the first bolt in FIGS. 2A and 2B is stored when shipped from the manufacturer. [Figure 4A] 4A is a cross-sectional side view showing an example of the configuration of the second bolt of FIG. 1. FIG. [Figure 4B] 1. FIG. 4B is a plan view showing an example of the configuration of the second bolt in FIG. [Diagram 5] FIG. 5 is a side view showing an example of the configuration of the second bolt in FIG. 4A with a wireless communication device attached. [Figure 6] FIG. 6 is a flowchart showing an example of the flow of a fastening method using one bolt set. [Figure 7] FIG. 7 is a side view showing an example of a state before two members are joined together. [Figure 8] FIG. 8 is a plan view showing an example of an arrangement of the first bolt and the second bolt in the flange of FIG. [Figure 9] FIG. 9 is a flowchart showing the flow of a modified example of the fastening method using one bolt set. [Figure 10A] FIG. 10A is a side view showing an example of the configuration of a second bolt according to Modification 1. FIG. [Figure 10B] FIG. 10B is a side view showing an example of the configuration of the second bolt according to the first modification. [Figure 11] FIG. 11 is an enlarged view of the male thread of the second bolt and its surrounding area in FIG. 10B. [Figure 12] FIG. 12 is a side view showing an example of the configuration of the first bolt according to the second modification. [Figure 13] FIG. 13 is a side view showing an example of a fastening state by a first bolt according to the second modification. [Figure 14A] FIG. 14A is a side view showing an example of the configuration of a second bolt according to Modification Example 2. FIG. [Figure 14B] FIG. 14B is a side view showing an example of the configuration of the second bolt according to Modification Example 2. As shown in FIG. [Figure 15] FIG. 15 is a side view showing an example of a fastening state by a second bolt according to the second modification. [Figure 16] FIG. 16 is a flowchart showing an example of the flow of a fastening method according to Modification 3 using one bolt set. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] In the following, exemplary embodiments of the present disclosure will be described with reference to the drawings. The embodiments described below are all comprehensive or specific examples. Among the components in the following embodiments, components that are not described in an independent claim showing a top concept will be described as optional components. Each figure in the attached drawings is a schematic diagram and is not necessarily illustrated precisely. In each figure, substantially the same components are given the same reference numerals, and duplicated descriptions may be omitted or simplified. In this specification and claims, "apparatus" may mean not only one apparatus but also a system including multiple apparatuses.

[0008] FIG. 1 is a perspective view showing an example of an object T fastened by a bolt set 1 according to an exemplary embodiment. In FIG. 1, a part of the main body T1a and T2a of the members T1 and T2 is cut out so that the inside of the main body T1a and T2a of the members T1 and T2 can be seen. As shown in FIG. 1, the object T includes two members T1 and T2 to be bolted together. The object T may be any object as long as it includes a part to be bolted together. Although not limited thereto, in this embodiment, the object T is a structural body such as a column, beam, or wall of a building or structure. The members T1 and T2 are members forming the structural body. In FIG. 1, the members T1 and T2 are parts of a cylindrical column. The first member T1 includes a cylindrical main body T1a and a flange T1b at an end of the main body T1a. The second member T2 includes a cylindrical main body T2a and a flange T2b at an end of the main body T2a. Although not limited thereto, in this embodiment, the flange T1b is an inner flange extending radially inward from the main body T1a, and the flange T2b is an inner flange extending radially inward from the main body T2a. The shape and dimensions of the flange T1b are the same as those of the flange T2b.

[0009] The bolt set 1 includes a plurality of first bolts 100 and one or more second bolts 200. Although not limited thereto, in the present embodiment, the bolt set 1 includes a plurality of second bolts 200, and the number of the second bolts 200 is less than the number of the first bolts 100. In FIG. 1 , some of the plurality of first bolts 100 are omitted from illustration, and some of the plurality of second bolts 200 are also omitted from illustration.

[0010] The portion that one bolt set 1 targets for bolt fastening may be one joint portion, a part of one joint portion, one member, one structure, or the entirety of one target object T. Although not limited thereto, in this embodiment, the portion that one bolt set 1 targets for bolt fastening is one joint portion. One bolt set 1 joins flange T1b and flange T2b as the joint portions.

[0011] The annular flanges T1b and T2b are each formed with a plurality of fastening holes T1c and T2c arranged along the circular inner periphery. The number of the fastening holes T1c is the same as the number of the fastening holes T2c, and the pitch of the fastening holes T1c is the same as the pitch of the fastening holes T2c. In FIG. 1, some of the fastening holes T1c are not shown, and some of the fastening holes T2c are not shown.

[0012] The members T1 and T2 are arranged so that the flanges T1b and T2b overlap each other, and are aligned in the cylindrical axial direction of the bodies T1a and T2a so that the fastening holes T1c are aligned with the fastening holes T2c.

[0013] The first bolts 100 and the second bolts 200 are passed through pairs of fastening holes T1c and T2c, respectively, and nuts 300 are attached and tightened to fasten the flanges T1b and T2b. The first bolts 100 and the second bolts 200 are arranged such that one or more first bolts 100 are located between the second bolts 200 in a direction along the circular inner circumferential edges of the flanges T1b and T2b.

[0014] 2A and 2B are a side view and a plan view, respectively, showing an example of the configuration of the first bolt 100 of FIG. 1. In this embodiment, as shown in FIG. 2A and FIG. 2B, the first bolt 100 is a hexagonal bolt made of a magnetic metal, although this is not limited thereto. The first bolt 100 integrally includes a shaft portion 101 and a head portion 102 disposed at one end of the shaft portion 101. The first bolt 100 may include the shaft portion 101 and the head portion 102. The shaft portion 101 has a cylindrical shape and extends linearly from the head portion 102. The head portion 102 has a hexagonal column shape and is radially larger than the shaft portion 101. The axial length L of the shaft portion 101 is also referred to as the nominal length, and the diameter DA of the shaft portion 101 is also the outer diameter of the shaft portion 101 and is also referred to as the shaft diameter. The distance DB between opposite sides of the hexagonal surface 102a of the head 102 is also referred to as the two-face width, and the thickness H of the head 102 in the axial direction of the shaft 101 is also referred to as the head height. The surface 102a is the surface of the head 102 opposite the shaft 101.

[0015] The shaft portion 101 includes a male thread 101a on its outer circumferential surface. In this embodiment, the male thread 101a is formed on the outer circumferential surface over the entire axial direction of the shaft portion 101, but may be formed on the outer circumferential surface over a portion of the axial direction of the shaft portion 101. The outer diameter of the male thread 101a is also called the shaft diameter DA and is also called the nominal diameter.

[0016] Head 102 includes a marking ID indicating an identification symbol of the manufacturer of first bolt 100, and a marking indicating the mechanical properties of first bolt 100. In this embodiment, the marking indicating the mechanical properties includes, but is not limited to, a marking S indicating a strength class of first bolt 100, and a marking M indicating a material of first bolt 100. For example, marking ID, S, and M may be disposed on surface 102a of head 102.

[0017] 3 is a perspective view showing an example of a case 400 in which the first bolt 100 of FIGS. 2A and 2B is stored when it is shipped from the manufacturer. As shown in FIG. 3, the case 400 includes a mark LN indicating the lot number of the first bolt 100 on its outer surface. A plurality of first bolts 100 having the same lot number are stored in the case 400. Although not limited thereto, in this embodiment, the lot number includes a symbol PL indicating the production line, a symbol YMD indicating the production date, and a symbol ST indicating the surface treatment applied to the first bolt 100.

[0018] Although not limited thereto, in this embodiment, the first bolts 100 included in one bolt set 1 satisfy a first condition that they are the same in at least one of shape and size. In this embodiment, they are the same in all elements of the first condition. The shape of the first bolt 100 is a shape formed by combining a shank 101 and a head 102. The size of the first bolt 100 includes a shaft diameter DA of the shank 101, a nominal length L of the shank 101, a width across flats DB of the head 102, and a head height H of the head 102. Furthermore, the first bolts 100 included in one bolt set 1 satisfy a second condition that they are the same in thread length, which is the axial length of the male thread 101a.

[0019] Here, in this specification and claims, "two things are the same as each other" includes "two things are completely identical to each other" and "two things are substantially the same as each other and can be considered to be the same as each other." For example, two things are the same if the difference between them is due to tolerance or manufacturing error. For example, two things are the same if they fall within the same category or range.

[0020] The first bolts 100 included in one bolt set 1 satisfy a third condition that they are the same in at least one of the following: thread designation, bolt standard, thread pitch of the male thread 101a, bolt strength category, and bolt material. In this embodiment, the first bolts 100 included in one bolt set 1 are the same in all elements of the third condition. The thread designation is expressed by combining a symbol representing the thread standard with a number following the symbol representing the nominal diameter. The thread standards include metric threads, inch threads, and pipe threads. The metric thread standard is represented by the symbol "M". The inch thread standard is represented by the symbol "UNC" or "UNF". The pipe thread standard is represented by the symbol "R", "Rc", "Rp", "G(A)", "G(B)", or "G". The nominal diameter is represented in units such as millimeters in the metric system, or inches in the imperial system. For example, the designation of a metric thread with a nominal diameter of 32 mm is represented by "M32". Examples of bolt standards may include national standards such as JIS standards, standards set by organizations or associations related to bolts, and standards set by bolt manufacturers.

[0021] The multiple first bolts 100 included in one bolt set 1 satisfy a fourth condition that they are the same in one or more of the manufacturer, model, part number, and production lot. In this embodiment, the multiple first bolts 100 included in one bolt set 1 are the same in all of the elements of the fourth condition. The bolt model, bolt part number, and bolt production lot can be set by the manufacturer.

[0022] 4A and 4B are a cross-sectional side view and a plan view, respectively, showing an example of the configuration of second bolt 200 in FIG. 1. As shown in FIGS. 4A and 4B, second bolt 200 includes bolt portion 210 and sensor 220. Although not limited to this embodiment, bolt portion 210 is a hexagonal bolt made of a magnetic metal. Sensor 220 is attached to bolt portion 210 and detects distortion of bolt portion 210.

[0023] The bolt portion 210 integrally includes a shaft portion 211 and a head portion 212 disposed at an end of the shaft portion 211. The shaft portion 211 has a cylindrical shape and extends linearly from the head portion 212. The head portion 212 has a hexagonal prism shape and is radially larger than the shaft portion 211. The shaft portion 211 includes a male thread 211a on its outer circumferential surface. In this embodiment, the male thread 211a is formed on the outer circumferential surface over the entire axial direction of the shaft portion 211, but may be formed on the outer circumferential surface over a portion of the axial direction of the shaft portion 211.

[0024] The bolt portions 210 of the second bolts 200 and the first bolts 100 included in the same bolt set 1 satisfy the fifth condition that they are the same in at least one of shape and size. In this embodiment, they are the same in all elements of the fifth condition. The fifth condition is similar to the first condition. In other words, the bolt portions 210 of the second bolts 200 and the first bolts 100 included in the same bolt set 1 are the same in the shape formed by combining the shank and the head, the shank diameter DA of the shank, the nominal length L of the shank, the width across flats DB of the head, and the head height H of the head.

[0025] Furthermore, the bolt portions 210 of the second bolts 200 and the first bolts 100 included in the same bolt set 1 may satisfy a sixth condition that the male thread lengths of the bolt portions 210 and the first bolts 100 are the same, and in this embodiment, the sixth condition is satisfied. The sixth condition is similar to the second condition.

[0026] Furthermore, the bolt portions 210 of the second bolts 200 and the first bolts 100 included in the same bolt set 1 may satisfy a seventh condition that they are the same in one or more of the thread designation, the bolt standard, the thread pitch of the male thread 101a, the strength class of the bolt, and the material of the bolt, and in this embodiment, they are the same in all the elements of the seventh condition. The seventh condition is similar to the third condition.

[0027] The bolt portions 210 of the second bolts 200 and the first bolts 100 included in the same bolt set 1 may satisfy an eighth condition that they are the same in one or more of the manufacturer, model, part number, and production lot, and in this embodiment, they are the same in all of the elements of the eighth condition. The eighth condition is similar to the fourth condition.

[0028] Therefore, in this embodiment, the bolt portion 210 is the first bolt 100 taken out from the case 400 that stores the first bolt 100 included in the same bolt set 1 as the bolt portion 210. Therefore, the bolt portion 210 has the same structure, function, strength and characteristics as the first bolt 100. The display ID, S and M may be arranged on the surface 212a of the head 212. The surface 212a is the surface of the head 212 opposite the shaft portion 211.

[0029] The bolt portion 210 includes one or more processed portions 213 that have been processed to attach the sensor 220 to the bolt portion 210. Although not limited thereto, in this embodiment, the processing is machining. Furthermore, the bolt portion 210 includes two processed portions 213. The two processed portions 213 are disposed at positions opposite to each other with respect to the axis 211b that is the central axis of the shaft portion 211.

[0030] Each processed portion 213 includes a recess 213a formed in the shaft portion 211 and a hole 213b formed in the head portion 212. The recess 213a has a shape capable of accommodating the sensor element 221 included in the sensor 220, and in this embodiment, has a groove-like shape. The processed portion 213 has a shape that suppresses the influence on the strength of the bolt portion 210. The recess 213a has a size that prevents the sensor element 221 from protruding radially outward from the shaft portion 211, and has a size that can at least accommodate the sensor element 221.

[0031] Each recess 213a extends in the axial direction of the shaft portion 211 on the outer circumferential surface of the shaft portion 211 from a connection portion between the head portion 212 and the shaft portion 211 toward the tip of the shaft portion 211 so as to accommodate the sensor element 221. Each recess 213a is recessed from the outer circumferential surface of the shaft portion 211, specifically, recessed into the male thread 211a. Each recess 213a extends over a portion of the axial length of the shaft portion 211. Each recess 213a may extend onto the surface 212b of the head portion 212. In this case, each recess 213a may extend in the radial direction of the shaft portion 211 from the shaft portion 211 to the outer edge of the surface 212b.

[0032] Each hole 213b extends in the axial direction of shaft portion 211 and passes through head portion 212. Each hole 213b is disposed so as to communicate with recess 213a at the connection portion between head portion 212 and shaft portion 211.

[0033] For example, the recess 213a and the hole 213b of one processed portion 213 can be formed together by performing cutting processing on the bolt portion 210 from the head portion 212 toward the shaft portion 211 with a drill. Thus, the bolt portion 210 can be generated by processing the first bolt 100 taken out of the case 400.

[0034] The second bolt 200 includes two sensors 220. Each sensor 220 includes a sensor element 221 embedded in the outer circumferential surface of the shaft portion 211 of the bolt portion 210, and an electric wire 222 extending from the sensor element 221. A connector 222a is attached to the tip of the electric wire 222. The sensor element 221 is disposed in the recess 213a. The sensor element 221 is contained in the recess 213a and extends in the axial direction of the shaft portion 211. The electric wire 222 is passed through the hole 213b from the shaft portion 211 toward the surface 212a, and extends outside the hole 213b at the surface 212a. The sensor element 221 outputs a signal indicating the detection result to a device connected to the electric wire 222.

[0035] The sensor element 221 detects the distortion of the shaft portion 211. The sensor element 221 detects either or both of the direction and amount of distortion of the shaft portion 211. Examples of the sensor element 221 may include a strain gauge, a piezoelectric element, and the like. Such a sensor element 221 can detect the expansion / contraction, twisting, or both of the shaft portion 211. Based on the amount of expansion / contraction of the shaft portion 211, it is possible to detect the fastening torque, which is the torque with which the bolt portion 210 is fastened, the axial force, which is the tensile force acting on the shaft portion 211 in the axial direction, or both of the above. Based on the amount and direction of twisting of the shaft portion 211, it is possible to detect the axial force of the shaft portion 211 taking into account the effect of the twisting of the shaft portion 211 on the axial force of the shaft portion 211. For example, it is possible to detect the axial force of the shaft portion 211 with the effect of the twisting of the shaft portion 211 canceled. Based on the amount of expansion and contraction, amount of twisting, and direction of twisting of shaft portion 211, it is possible to detect the stress generated in shaft portion 211.

[0036] In this embodiment, the sensor element 221 is disposed in a groove-shaped recess 213a extending in the axial direction of the shaft portion 211, but is not limited thereto. For example, the recess 213a may include a portion extending in the circumferential direction of the shaft portion 211 instead of or in addition to the portion extending in the axial direction of the shaft portion 211. The portion extending in the circumferential direction of the shaft portion 211 may have a groove-like shape. This allows the sensor element 221 to extend in the circumferential direction of the shaft portion 211, and to effectively detect the torsion of the shaft portion 211 in the circumferential direction.

[0037] Fig. 5 is a side view showing an example of the configuration of the second bolt 200 in Fig. 4A with a wireless communication device 500 attached. As shown in Figs. 1 and 5, the bolt set 1 further includes one or more wireless communication devices 500. The one or more wireless communication devices 500 are detachably attached to one or more of the second bolts 200 and connected to the sensor 220 of the second bolt 200. Although not limited thereto, in this embodiment, the bolt set 1 includes a plurality of wireless communication devices 500, the same number as the number of second bolts 200, and a wireless communication device 500 is attached to each second bolt 200.

[0038] Each wireless communication device 500 is connected via wireless communication to a processing device 2 disposed at a position away from the members T1 and T2. Each wireless communication device 500 receives a signal indicating a detection result from the sensor 220 and transmits the signal indicating the detection result to the processing device 2. Examples of the processing device 2 may include an electronic circuit board, an electronic control unit, a microcomputer, a notebook personal computer, a desktop personal computer, a workstation, a smart device, other electronic devices, and other terminal devices. Examples of the smart device may include a smartphone, a smart watch, a tablet terminal, and the like. The processing device 2 includes a processing circuit. The processing circuit may include a computer system including a processor and a memory.

[0039] The wireless communication device 500 includes a housing 501, an attachment portion 502, an antenna 503, a circuit 504, a battery 505, and a connector 506. The attachment portion 502 attaches the housing 501 to the bolt portion 210. The attachment portion 502 may have a structure for attachment using one or more combinations of magnetic force, adhesion, pasting, suction, and clamping. Although not limited thereto, in this embodiment, the attachment portion 502 has a structure for attachment using magnetic force and includes a permanent magnet 502a. The attachment portion 502 may include an electromagnet.

[0040] Battery 505 is housed within housing 501 and supplies power to each component of wireless communication device 500. Battery 505 includes a primary battery that discharges stored power, or a secondary battery that is capable of charging and discharging power.

[0041] Two connectors 506 are arranged, and the two connectors 506 are connected to the connectors 222a of the electric wires 222 of the two sensors 220. Each connector 506 is connected to the connector 222a of the electric wire 222 to establish a connection between the sensor 220 and the wireless communication device 500. One or three or more connectors 506 may be arranged to be connected to one or three or more connectors 222a of the sensor 220.

[0042] The circuit 504 receives signals indicating the detection results from the two sensors 220, and transmits a signal based on the received detection results to the outside via the antenna 503. The circuit 504 may include one or more of a circuit for amplifying the received signal, a circuit for converting the received signal, and a communication circuit for wireless communication.

[0043] The antenna 503 transmits and receives signals to and from devices with which a wireless communication connection has been established with the wireless communication device 500 .

[0044] The wireless communication device 500 is attached to the head 212 of the bolt portion 210 such that the attachment portion 502 is in contact with the surface 212a of the head 212. Furthermore, the wireless communication device 500 is connected to the two sensors 220 by connecting each connector 506 to the connector 222a of each electric wire 222 of the sensor 220.

[0045] An example of a fastening method using one bolt set 1 will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of the flow of the fastening method using one bolt set 1. Below, an example of joining flanges T1b and T2b of two members T1 and T2 using one bolt set 1 will be described.

[0046] In step S101, as shown in Fig. 7, in order to join the components T1 and T2 to be joined, the worker places the components T1 and T2 in a state in which the flanges T1b and T2b are overlapped and the multiple fastening holes T1c and the multiple fastening holes T2c are aligned. This sets the state of the components T1 and T2 to a state in which they should be joined. Fig. 7 is a side view showing an example of the state before the two components T1 and T2 are joined.

[0047] Next, in step S102, the worker inserts the multiple first bolts 100 and the multiple second bolts 200 into the aligned pair of fastening holes T1c and T2c, respectively. At this time, the multiple first bolts 100 and the multiple second bolts 200 are arranged such that the multiple first bolts 100 are positioned between the second bolts 200 in a direction along the circular inner circumferential edges of the flanges T1b and T2b.

[0048] In FIG. 7, the ratio of the number of the first bolts 100 to the number of the second bolts 200 is 9. FIG. 8 is a plan view showing an example of the arrangement state of the first bolts 100 and the second bolts 200 in the flanges T1b and T2b in FIG. 7. For example, in FIG. 8, the number of the second bolts 200 is 6, and the number of the first bolts 100 is 54. The number of the first bolts 100 arranged between the second bolts 200 in the direction along the circular inner peripheral edge of the flange T1b is 9. As in this example, it is preferable to arrange the second bolts 200 so that the number of the first bolts 100 arranged between the second bolts 200 is uniform. In FIG. 7, the number of the first bolts 100 and the second bolts 200 and the number of the fastening holes T1c and T2c are drawn smaller than those in FIG. 8 in order to make the drawing easier to see.

[0049] Next, in step S103, the worker attaches the nuts 300 to the first bolt 100 and the second bolt 200, respectively, and provisionally fastens each nut 300. That is, the worker primarily fastens the first bolt 100 and the second bolt 200. In the primary fastening, each nut 300 is fastened with a torque smaller than a specified torque preset for the first bolt 100 and the second bolt 200. The specified torque is a torque for fastening the first bolt 100 and the second bolt 200 for proper fastening. In this embodiment, the nut 300 is fastened with a specified torque, but the first bolt 100 and the second bolt 200 themselves may be fastened with a specified torque. In this embodiment, the first bolt 100 and the second bolt 200 have the same structure, function, strength, and characteristics, so the specified torques of the first bolt 100 and the second bolt 200 are the same. As a result, the state of the members T1 and T2 is maintained in a state in which they should be joined.

[0050] Although not limited thereto, in this embodiment, all of the nuts 300 used for the first bolt 100 and the second bolt 200 satisfy the same conditions as the first to fourth conditions of the first bolt 100, and are the same in all elements included in each condition. The fact that the specified torque of the first bolt 100 and the second bolt 200 are the same is also due to the fact that the nuts 300 have the same strength and characteristics as the first bolt 100.

[0051] Next, in step S104, the worker attaches wireless communication device 500 to head 212 of bolt portion 210 of each second bolt 200. As shown in Fig. 5, because attachment portion 502 includes permanent magnet 502a, the worker can install wireless communication device 500 in head 212 simply by placing wireless communication device 500 on surface 212a of head 212, which has magnetism. Furthermore, the worker connects connectors 222a of two electric wires 222 of second bolt 200 to two connectors 506 of wireless communication device 500. Furthermore, the worker turns on the power of wireless communication device 500.

[0052] Next, in step S105, the worker operates the processing device 2 to establish a wireless communication connection between the processing device 2 and each wireless communication device 500. As shown in FIG. 7, in this embodiment, the processing device 2 is connected to the transceiver 3 via wired communication, wireless communication, or a combination of these. The processing device 2 establishes a wireless communication connection between the transceiver 3 and each wireless communication device 500. The transceiver 3 is a communication device and may further have a wireless power transmission function. In the example of FIG. 7, the transceiver 3 is disposed inside the main body T1a of the member T1 or inside the main body T2a of the member T2, and is connected to the processing device 2 via wired communication. Each wireless communication device 500 may be capable of transmitting and receiving information to and from the processing device 2, and may be capable of receiving power from the processing device 2 or the transceiver 3.

[0053] The communication between the processing device 2 and the transceiver 3 may be any wired or wireless communication, or any combination of wired and wireless communication. The wireless communication between the wireless communication device 500 and the transceiver 3 may be any wireless communication.

[0054] For example, examples of wireless communication include wireless LAN (local area network) such as WiFi (Wireless Fidelity). The communication may include a wireless WAN (Wide Area Network) using a local area network, a mobile communication network, or the like, satellite communication, short-range wireless communication such as Bluetooth (registered trademark) and ZigBee (registered trademark), or a combination of two or more of these. The mobile communication network may use a fourth generation mobile communication system or a fifth generation mobile communication system, or the like. In this embodiment, the wireless communication between the wireless communication device 500 and the transceiver 3 is short-range wireless communication.

[0055] Next, in step S106, the worker tightens all of the nuts 300 of the first bolt 100 and the second bolt 200 with a specified torque while checking the output result of the processing device 2. That is, the worker performs the second tightening of the first bolt 100 and the second bolt 200. The processing device 2 outputs fastening state information representing the fastening state of each second bolt 200, using the signals received from each sensor 220. Examples of the fastening state information of the second bolt 200 include the amount of distortion, the amount of elongation, the axial force, the fastening torque of the bolt portion 210 of the second bolt 200, or a combination of two or more of these.

[0056] The strain amount and elongation amount of the bolt portion 210 may be the strain amount and elongation amount of the shank 211. The axial force of the bolt portion 210 may be a tensile force acting on the shank 211. The fastening torque of the bolt portion 210 may be a torque at which the nut 300 is fastened. The fastening torque may be estimated using one or more of the strain amount, elongation amount, and axial force of the bolt portion 210. For example, an operator can check whether the nut 300 is fastened to a specified torque by checking the fastening torque of the bolt portion 210 output by the processing device 2.

[0057] In this embodiment, the processing device 2 outputs at least the fastening force of the second bolt 200 as the fastening state information. The fastening force of the second bolt 200 is the force with which the second bolt 200 presses down the flanges T1b and T2b, which are the objects to be fastened, and represents the force with which the second bolt 200, together with the nut 300, clamps the flanges T1b and T2b. The fastening force of the second bolt 200 includes one or both of the axial force and fastening torque of the bolt portion 210. In this specification and claims, the "fastening force of the bolt" includes the "fastening torque of the bolt", the "axial force of the bolt", or both of these.

[0058] The processing device 2 may have a display function using a display or the like and display the output result. Conversion of the detection result of the sensor 220 into the amount of strain, elongation, axial force, or fastening torque of the bolt portion 210 may be performed by either the circuit 504 of the wireless communication device 500 or the processing device 2. For example, even if the nut 300 is tightened to a specified torque by a torque wrench or impact wrench, the fastening state such as the fastening force after tightening cannot be confirmed. The worker can check the fastening state of the second bolt 200 from the output result of the processing device 2.

[0059] Next, in step S107, after completing the tightening of all the nuts 300 of the first bolt 100 and the second bolt 200, the worker checks the fastening force of all the second bolts 200 based on the output result of the processing device 2. If there is any second bolt 200 whose fastening force is smaller than the preset target fastening force (Yes in step S107), the process proceeds to step S108, and if there is any second bolt 200 whose fastening force is smaller than the target fastening force (No in step S107), the worker ends the joining operation of the flanges T1b and T2b. The target fastening force is a fastening force that is preset for the second bolt 200 and is required for target fastening such as proper fastening. The target fastening force includes a target axial force, a target fastening torque, or both. The target fastening torque may be the same as the specified torque, or may be different.

[0060] In step S108, the worker retightens at least some of the nuts 300 of the first bolt 100 and the second bolt 200 to a specified torque while checking the output result of the processing device 2. In this embodiment, the targets of retightening are all of the first bolt 100 and the second bolt 200. For example, when retightening a portion of the first bolt 100 and the second bolt 200, the targets of retightening may include the second bolt 200 whose fastening force is smaller than the target fastening force, and the first bolt 100 around the second bolt 200.

[0061] Next, the worker returns to step S107, checks the fastening forces of all second bolts 200 based on the output results from processing device 2, and repeats step S107 and subsequent steps.

[0062] In steps S101 to S108, the worker tightens the first bolt 100 and the second bolt 200 while checking that the tightening force of the second bolt 200 satisfies the target tightening force, so that the first bolt 100 and the second bolt 200 are all tightened with a tightening force within a specified range. Furthermore, since the bolt portions 210 of the first bolt 100 and the second bolt 200 are the same in one or more of structure, function, strength, and characteristics, the entire flanges T1b and T2b can be tightened with an equal tightening force. The order of steps S103 and S104 is not limited to the above example, and for example, step S103 may be performed after step S104.

[0063] In step S107, it may be determined whether the fastening force is within a preset target range. If the fastening force is outside the target range (Yes in step S107), in step S108, the worker may loosen the nut 300 of the second bolt 200 whose fastening force exceeds the upper limit of the target range and the nut 300 of the first bolt 100 around the second bolt 200. Furthermore, the worker may re-tighten at least the loosened nut 300, the nut 300 of the second bolt 200 whose fastening force is below the lower limit of the target range, and the nut 300 of the first bolt 100 around the second bolt 200 with a specified torque. Alternatively, the worker may re-tighten all the nuts 300 of the first bolt 100 and the second bolt 200 with a specified torque. This makes it possible to equalize the fastening forces of the first bolt 100 and the second bolt 200. The lower limit of the target range may be the target fastening force.

[0064] A modified example of the fastening method using one bolt set 1 will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the flow of the modified example of the fastening method using one bolt set 1. Below, an example in which flanges T1b and T2b of two members T1 and T2 are joined using one bolt set 1 will be described.

[0065] Steps S201 to S206 are the same as steps S101 to S106 in FIG.

[0066] In step S207, after completing the tightening of all nuts 300 of the first bolt 100 and the second bolt 200, the worker checks the fastening force of all second bolts 200 based on the output result of the processing device 2. If there is any second bolt 200 whose fastening force is smaller than the target fastening force (Yes in step S207), the process proceeds to step S208, and if there is no second bolt 200 whose fastening force is smaller than the target fastening force (No in step S207), the worker ends the joining operation of the flanges T1b and T2b.

[0067] In step S208, the worker inputs a command to set the re-tightening torque of the first bolt 100 and the second bolt 200 to the processing device 2. The re-tightening torque is a torque for tightening the first bolt 100 and the second bolt 200 when the first bolt 100 and the second bolt 200 are tightened again. The processing device 2 determines the re-tightening torque using the fastening force of the second bolt 200 whose fastening force is equal to or greater than the target fastening force. The processing device 2 uses a statistical value of the fastening force of the second bolt 200 whose fastening force is equal to or greater than the target fastening force in order to determine the re-tightening torque. Examples of the statistical value may include the average value, maximum value, median value, and mode value of the fastening force of the second bolt 200 whose fastening force is equal to or greater than the target fastening force. The processing device 2 calculates the torque required to tighten the nut 300 to realize the calculated statistical value, and determines the calculated torque as the re-tightening torque. For example, the average fastening force may be the average value of all the fastening forces of the second bolts 200 that are greater than or equal to the target fastening force, or it may be the average value of a portion extracted from the fastening forces of the second bolts 200 that are greater than or equal to the target fastening force.

[0068] For example, among the fastening forces of the second bolt 200 that are equal to or greater than the target fastening force, fastening forces that exceed a preset upper limit of the fastening force may be excluded from the calculation of the statistical value. The processing device 2 may determine the fastening forces to be excluded according to a command input to the processing device 2 by an operator, a control program of the processing device 2, or both.

[0069] Next, in step S209, the worker retightens at least some of the nuts 300 of the first bolt 100 and the second bolt 200 with a retightening torque while checking the output result of the processing device 2. In this embodiment, the targets of retightening are all of the first bolt 100 and the second bolt 200. For example, when retightening a portion of the first bolt 100 and the second bolt 200, the targets of retightening may be the second bolt 200 whose fastening force is smaller than the target fastening force, and the first bolts 100 around the second bolt 200.

[0070] Next, the worker returns to step S207, checks the fastening forces of all second bolts 200 based on the output results from processing device 2, and repeats step S207 and subsequent steps.

[0071] By steps S201 to S209, the first bolt 100 and the second bolt 200 are re-tightened with a re-tightening torque corresponding to a fastening state of the second bolt 200 that satisfies the target fastening force, so that the first bolt 100 and the second bolt 200 are all fastened with a fastening force within a specified range. Furthermore, the bolt portions 210 of the first bolt 100 and the second bolt 200 are the same in one or more of structure, function, strength, and characteristics, so that the entire flanges T1b and T2b can be fastened with an even force.

[0072] In step S207, it may be determined whether the fastening force is within a preset target range. If the fastening force is outside the target range (Yes in step S207), in step S209, the worker may loosen the nut 300 of the second bolt 200 whose fastening force exceeds the upper limit of the target range and the nut 300 of the first bolt 100 around the second bolt 200. The worker may re-tighten at least the loosened nut 300, the nut 300 of the second bolt 200 whose fastening force is below the lower limit of the target range, and the nut 300 of the first bolt 100 around the second bolt 200 with a re-tightening torque. Alternatively, the worker may re-tighten all the nuts 300 of the first bolt 100 and the second bolt 200 with a re-tightening torque. This makes it possible to equalize the fastening forces of the first bolt 100 and the second bolt 200. The lower limit of the target range may be the target fastening force.

[0073] [Variation 1] The bolt set 1 of the present disclosure can also be applied to the first bolt 100 and the second bolt 200A according to Modification 1. The second bolt 200A is obtained by machining the first bolt 100, like the second bolt 200 according to the embodiment, but differs from the second bolt 200 according to the embodiment in the structure of the machined portion and the structure of the sensor. Below, the second bolt 200A according to this modification will be described, focusing on the points that differ from the embodiment, and the description of the points that are the same as the embodiment will be omitted as appropriate.

[0074] 10A and 10B are side views showing an example of the configuration of the second bolt 200A according to the first modification. FIG. 10B is a view of the second bolt 200A viewed from a direction rotated 90° around the central axis 211Ad of the shaft portion 211A of the bolt portion 210A with respect to FIG. 10A. FIG. 11 is an enlarged view of the male thread 211Aa and its surroundings of the second bolt 200A in FIG. 10B. As shown in FIGS. 10A, 10B, and 11, the second bolt 200A includes the bolt portion 210A and a sensor 220A. The bolt portion 210A is a hexagonal bolt as in the embodiment. The bolt portion 210A includes a shaft portion 211A and a head portion 212A. The shaft portion 211A extends linearly from the head portion 212A.

[0075] The shaft portion 211A includes a non-threaded portion 211Ab that is not threaded, and a male thread 211Aa that is located on the tip side of the non-threaded portion 211Ab. In other words, the bolt portion 210A is a half-threaded bolt that includes a male thread 211Aa on a part of the outer circumferential surface of the shaft portion 211A. In this modification, the male thread 211Aa is formed by threading the outer circumferential surface of the shaft portion 211A. Therefore, the diameter D2 of the thread of the male thread 211Aa is the same as or slightly smaller than the diameter D1 of the non-threaded portion 211Ab, that is, they are equal. The root diameter D3 of the male thread 211Aa and the effective diameter D4 of the male thread 211Aa are smaller than the diameter D1 of the non-threaded portion 211Ab. The effective diameter D4 is an intermediate diameter between the diameters D2 and D3, that is, the average diameter of the diameters D2 and D3.

[0076] The bolt portion 210A includes a processed portion 213A for attaching the sensor 220A to the bolt portion 210A. The bolt portion 210A has the same structure, shape, and dimensions as the first bolt 100, except for the processed portion 213A. In this modification, the first bolt 100 is also a half-threaded bolt including a non-threaded portion and a male thread. The processed portion 213A includes recesses 213Aa and 213Ab formed in the non-threaded portion 211Ab, and a hole 213Ac formed in the head portion 212A. The hole 213Ac extends in the axial direction of the shaft portion 211A and penetrates the head portion 212A. The hole 213Ac communicates with the second recess 213Ab at the connection portion between the head portion 212A and the shaft portion 211A.

[0077] The first recess 213Aa extends in the circumferential direction on the outer circumferential surface 211Aba of the non-threaded portion 211Ab, centered on the axis 211Ad, which is the central axis of the shaft portion 211A. The first recess 213Aa is recessed from the outer circumferential surface 211Aba of the non-threaded portion 211Ab. Although not limited thereto, in this modified example, the first recess 213Aa is a cylindrical recess that is continuous in the circumferential direction. Note that the first recess 213Aa may be interrupted in the circumferential direction.

[0078] The first recess 213Aa has a width B1 in the axial direction of the shaft portion 211A so that the sensor elements 221Aa and 221Ab of the sensor 220A can be accommodated therein. The width B1 is the width in the axial direction of the shaft portion 211A. Thus, the first recess 213Aa has a cylindrical shape with an axial length of B1. Although not limited thereto, in this modified example, the width B1 and depth d1 of the first recess 213Aa are constant in the circumferential direction. The depth d1 is the depth from the outer peripheral surface 211Aba of the non-threaded portion 211Ab in the radial direction of the shaft portion 211A. Thus, the first recess 213Aa is a cylindrical groove.

[0079] The cross-sectional area of ​​the shaft portion 211A at the first recess 213Aa is equal to or larger than the area of ​​a circle with an effective diameter D4. The cross-sectional area of ​​the shaft portion 211A is the area of ​​a cross section of the shaft portion 211A perpendicular to the axis 211Ad of the shaft portion 211A and crossing the first recess 213Aa. The area of ​​the circle with the effective diameter D4 is the substantial cross-sectional area of ​​the shaft portion 211A at the male thread 211Aa, and is also called the effective cross-sectional area. Therefore, the strength of the shaft portion 211A at the first recess 213Aa may be equal to or larger than the strength of the shaft portion 211A at the male thread 211Aa. Examples of the strength may include tensile strength, shear strength, bending strength, torsional strength, and the like. Although not limited thereto, in this modification, the cross-sectional area of ​​shaft portion 211A at first recess 213Aa in the axial direction of shaft portion 211A is equal to or larger than the area of ​​a circle with effective diameter D4 over the entire first recess 213Aa in the axial direction of shaft portion 211A.

[0080] Although not limited thereto, in this modified example, the depth d1 of the first recess 213Aa is equal to or smaller than the difference (D1-D4) between the diameter D1 of the non-threaded portion 211Ab and the effective diameter D4, and is preferably equal to or smaller than 1 / 2 of the difference (D1-D4). For example, the diameter D1a of the shaft portion 211A at the bottom of the first recess 213Aa is equal to or larger than the effective diameter D4. For example, the diameter D1a may be a diameter having a radius equal to the minimum distance between the axis 211Ad and the bottom of the first recess 213Aa. Therefore, the shaft portion 211A at the first recess 213Aa may have cross-sectional characteristics superior to those of the shaft portion 211A at the male thread 211Aa against force, impact, and the like. The cross-sectional characteristics are also referred to as cross-sectional performance. Examples of the cross-sectional characteristics may include the moment of inertia, moment of inertia, section modulus, and radius of inertia. Although not limited thereto, in this modified example, the diameter D1a of the shaft portion 211A is equal to or larger than the effective diameter D4 over the entire cross section of the shaft portion 211A at the first recess 213Aa. Although not limited thereto, in this modified example, the diameter D1a of the shaft portion 211A is equal to or larger than the effective diameter D4 over the entire first recess 213Aa in the axial direction of the shaft portion 211A.

[0081] The second recess 213Ab extends on the outer circumferential surface 211Aba of the non-threaded portion 211Ab from the first recess 213Aa to a connection portion between the head 212A and the shaft portion 211A. Although not limited thereto, in this modified example, the second recess 213Ab extends in the axial direction of the shaft portion 211A and is aligned with the hole 213Ac in the axial direction of the shaft portion 211A.

[0082] The second recess 213Ab has a width B2 that is significantly smaller than the axial length of the second recess 213Ab. The width B2 is a circumferential width centered on the axis 211Ad of the shaft portion 211A, and is significantly smaller than the axial width B1 and the circumferential width of the first recess 213Aa. In this modification, the depth d2 of the second recess 213Ab is the same as the depth d1 of the first recess 213Aa, but may be greater than the depth d1 or may be smaller than the depth d1. The depth d2 is a depth from the outer peripheral surface 211Aba of the non-threaded portion 211Ab in the radial direction of the shaft portion 211A. The second recess 213Ab may have a width B2 and a depth d2 that can accommodate the electric wire 222A described later that extends along the second recess 213Ab. For example, the second recess 213Ab is a narrow groove.

[0083] The cross-sectional area of ​​the shaft portion 211A at the position of the second recess 213Ab is equal to or larger than the area of ​​a circle with the effective diameter D4. The cross-sectional area of ​​the shaft portion 211A is the area of ​​a cross section of the shaft portion 211A perpendicular to the axis 211Ad of the shaft portion 211A and crossing the second recess 213Ab. Therefore, the strength of the shaft portion 211A at the portion where the second recess 213Ab is formed can be equal to or larger than the strength of the shaft portion 211A at the male thread 211Aa. Although not limited thereto, in this modification, the cross-sectional area of ​​the shaft portion 211A at the position of the second recess 213Ab is equal to or larger than the area of ​​a circle with the effective diameter D4 throughout the entire second recess 213Ab in the axial direction of the shaft portion 211A.

[0084] Furthermore, in this modification, since the depth d2 of the second recess 213Ab is the same as the depth d1 of the first recess 213Aa, the diameter of the shaft portion 211A at the bottom of the second recess 213Ab is equal to or larger than the effective diameter D4. For example, the above diameter may be a diameter having a radius of the minimum distance between the axis 211Ad of the shaft portion 211A and the bottom of the second recess 213Ab. Therefore, the shaft portion 211A at the position of the second recess 213Ab may have cross-sectional characteristics superior to those of the shaft portion 211A at the male thread 211Aa against force, impact, and the like. Although not limited thereto, in this modification, the diameter of the shaft portion 211A at the bottom of the second recess 213Ab is equal to or larger than the effective diameter D4 over the entire bottom of the second recess 213Ab in the circumferential direction centered on the axis 211Ad. Although not limited thereto, in this modification, the diameter of the shaft portion 211A at the bottom of the second recess 213Ab is equal to or larger than the effective diameter D4 over the entire second recess 213Ab in the axial direction of the shaft portion 211A.

[0085] Although the bolt portion 210A described above includes the processed portion 213A, it can have the same strength as the first bolt 100 and can also have the same cross-sectional characteristics as the first bolt 100. The strength and cross-sectional characteristics of the first bolt 100 depend on the strength and cross-sectional characteristics of the male thread portion of the first bolt 100.

[0086] The sensor 220A includes sensor elements 221Aa and 221Ab, an electric wire 222A, a relay terminal 223A, and a coating 224A. Although not limited thereto, in this modification, the sensor elements 221Aa and 221Ab include a sheet-shaped strain gauge and a terminal, and the relay terminal 223A is a sheet-shaped foil terminal. The relay terminal 223A electrically connects the terminals of the sensor elements 221Aa and 221Ab to the electric wire 222A.

[0087] The sensor elements 221Aa and 221Ab and the relay terminal 223A are disposed in the first recess 213Aa. For example, the sensor elements 221Aa and 221Ab and the relay terminal 223A are attached to the bottom of the first recess 213Aa. The sensor elements 221Aa and 221Ab and the relay terminal 223A have a thickness smaller than the depth d1, so that they are accommodated in the first recess 213Aa and do not protrude in the radial direction. The relay terminal 223A is disposed at a position closer to the second recess 213Ab than the sensor elements 221Aa and 221Ab, and is disposed, for example, so as to be aligned with the second recess 213Ab in the axial direction of the shaft portion 211A. The sensor elements 221Aa and 221Ab are disposed at positions on the opposite sides with respect to the axis 211Ad of the shaft portion 211A, and are disposed, for example, at positions rotated 180° from each other around the axis 211Ad. The sensor elements 221Aa and 221Ab are disposed at positions facing each other across the axis 211Ad. Lead wires extending from terminals of the sensor elements 221Aa and 221Ab are connected to the relay terminal 223A.

[0088] The electric wire 222A is connected to the relay terminal 223A at one end and is accommodated in the second recess 213Ab along the second recess 213Ab. The electric wire 222A further extends to the outside of the head 212A through the hole 213Ac. A connector 222a is attached to the other end of the electric wire 222A.

[0089] The coating 224A is applied to the recesses 213Aa and 213Ab, and covers the sensor elements 221Aa and 221Ab, the electric wire 222A, and the relay terminal 223A. The coating 224A is made of an electrically insulating material. The coating 224A is preferably made of a material that can be in a flexible state and a hardened state, such as a resin material. Examples of the resin material may include a thermosetting resin such as an epoxy resin.

[0090] The connector 222a is connected to a wireless communication device 500 as shown in Fig. 5 attached to the bolt portion 210A. The wireless communication device 500 applies a voltage to the sensor elements 221Aa and 221Ab to measure the change in electrical resistance value due to the expansion and contraction of the sensor elements 221Aa and 221Ab, and transmits the measurement result to the processing device 2. The processing device 2 calculates the expansion and contraction direction and amount of each of the sensor elements 221Aa and 221Ab based on the received measurement result, and calculates the strain direction and amount of strain of the shaft portion 211A and the direction and magnitude of the force acting on the shaft portion 211A based on the difference between the expansion and contraction direction and amount of the sensor elements 221Aa and 221Ab. This makes it possible to detect the axial force and shear force acting on the shaft portion 211A, as well as the twist direction and amount of twist of the shaft portion 211.

[0091] As a method for checking the strength of the bolt portion 210A, a predetermined tensile force is applied along the axial direction of the bolt portion 210A by a strength measurement device to the bolt portion 210A in a state in which the wireless communication device 500 shown in Fig. 5 is connected, and it is possible to determine whether the predetermined strength is satisfied. That is, in a state in which a predetermined tensile force is applied in the axial direction of the bolt portion 210A, the processing device 2 shown in Fig. 5 calculates the amount of expansion and contraction (the amount of extension in this state) of the shaft portion 211A based on the change in the electrical resistance values ​​of the sensor elements 221Aa and 221Ab. The processing device 2 further determines that the calculated amount of expansion and contraction is within a predetermined range that is stored in advance in correspondence with the required strength, thereby determining that the strength of the shaft portion 211A against the tensile force in the axial direction satisfies the same strength as the first bolt 100.

[0092] [Variation 2] The first bolt 100B according to the modified example 2 and the second bolt 200B according to the modified example 2 can also be applied to the bolt set 1 of the present disclosure. The first bolt 100B is a double-threaded bolt that does not have a head and includes male threads on both ends of the shaft. The second bolt 200B is obtained by machining the first bolt 100B. The second bolt 200B differs from the second bolt 200A according to the modified example 1 in terms of the structure of the machined portion. Below, the first bolt 100B and the second bolt 200B according to this modified example will be described, focusing on the points that are different from the embodiment and the modified example 1, and the description of the points that are the same as the embodiment or the modified example 1 will be omitted as appropriate.

[0093] FIG. 12 is a side view showing an example of the configuration of the first bolt 100B according to the second modification. As shown in FIG. 12, the first bolt 100B includes a shank 101B extending linearly. The shank 101B includes male threads 101Ba and 101Bb at both ends on the outer circumferential surface, and a non-threaded portion 101Bc between the male threads 101Ba and 101Bb. In this modification, the axial length of the male thread 101Ba is shorter than the axial length of the male thread 101Bb, and the male threads 101Ba and 101Bb are formed by threading the outer circumferential surface of the shank 101B. The diameter of the threads of the male threads 101Ba and 101Bb is equal to the diameter of the non-threaded portion 101Bc. The root diameters of the male threads 101Ba and 101Bb and the effective diameters of the male threads 101Ba and 101Bb are smaller than the diameter of the non-threaded portion 101Bc.

[0094] FIG. 13 is a side view showing an example of a fastening state by the first bolt 100B according to the second modification. As shown in FIG. 13, when the flanges T1b and T2b are fastened by the first bolt 100B, the first bolt 100B is passed through the fastening hole T1c of the flange T1b and the fastening hole T2c of the flange T2b. Furthermore, a washer 310 and a nut 300 are attached to the male threads 101Ba and 101Bb at both ends, respectively, and the nut 300 is tightened. Although not limited thereto, in this modification, on the male thread 101Ba side, the nut 300 is tightened up to the root of the male thread 101Ba. The washer 310 has a circular plate shape, and the first bolt 100B is passed through a hole in the center of the washer 310. The washer 310 is disposed between the nut 300 and the flange T1b and between the nut 300 and the flange T2b.

[0095] 14A and 14B are side views showing an example of the configuration of a second bolt 200B according to Modification 2. FIG. 14B is a view of the second bolt 200B viewed from a direction rotated 90° about the central axis 211Bd of the shaft portion 211B of the bolt portion 210B with respect to FIG. 14A. As shown in FIGS. 14A and 14B, the second bolt 200B includes a bolt portion 210B and a sensor 220B. The bolt portion 210B includes a processed portion 213B for attaching the sensor 220B to the bolt portion 210B. The bolt portion 210B has the same structure, shape, and dimensions as the first bolt 100B, except for the processed portion 213B.

[0096] The bolt portion 210B includes a shaft portion 211B extending linearly. The shaft portion 211B includes male threads 211Ba and 211Bb at both ends on the outer circumferential surface, and a non-threaded portion 211Bc between the male threads 211Ba and 211Bb. The axial length of the male thread 211Ba is shorter than the axial length of the male thread 211Bb. The diameter of the threads of the male threads 211Ba and 211Bb is equal to the diameter of the non-threaded portion 211Bc. The root diameter of the male threads 211Ba and 211Bb and the effective diameter of the male threads 211Ba and 211Bb are smaller than the diameter of the non-threaded portion 211Bc.

[0097] The processed portion 213B includes a first recess 213Ba formed in the non-threaded portion 211Bc, and a second recess 213Bb extending from the first recess 213Ba toward the male thread 211Ba.

[0098] The first recess 213Ba has a structure similar to that of the first recess 213Aa of Modification 1. The first recess 213Ba extends in a circumferential direction centered on the axis 211Bd of the shaft portion 211B on the outer circumferential surface 211Bca of the non-threaded portion 211Bc. The first recess 213Ba has a cylindrical shape.

[0099] The cross-sectional area of ​​the shaft portion 211B at the first recess 213Ba is equal to or larger than the area of ​​a circle with an effective diameter of the male threads 211Ba and 211Bb. Therefore, the strength of the shaft portion 211B at the first recess 213Ba can be equal to or larger than the strength of the shaft portion 211A at each of the male threads 211Ba and 211Bb. Although not limited thereto, in this modification, the cross-sectional area of ​​the shaft portion 211B at the first recess 213Ba is equal to or larger than the area of ​​a circle with an effective diameter of the male threads 211Ba and 211Bb throughout the entire first recess 213Ba in the axial direction of the shaft portion 211B.

[0100] The diameter of the shaft portion 211B at the bottom of the first recess 213Ba is equal to or larger than the effective diameter of the male threads 211Ba and 211Bb. Therefore, the shaft portion 211B at the first recess 213Ba can have cross-sectional characteristics superior to those of the shaft portion 211B at the male threads 211Ba and 211Bb, respectively. Although not limited thereto, in this modification, the diameter of the shaft portion 211B at the bottom of the first recess 213Ba is equal to or larger than the effective diameter of the male threads 211Ba and 211Bb throughout the entire cross section of the shaft portion 211B at the first recess 213Ba. Although not limited thereto, in this modification, the diameter of the shaft portion 211B at the bottom of the first recess 213Ba is equal to or larger than the effective diameter of the male threads 211Ba and 211Bb throughout the entire first recess 213Ba in the axial direction of the shaft portion 211B.

[0101] The second recess 213Bb extends in the axial direction of the shaft portion 211B from the first recess 213Ba toward the male thread 211Ba. Although not limited thereto, in this modification, the second recess 213Bb is formed only in the non-threaded portion 211Bc and does not reach the male thread 211Ba. Therefore, the second recess 213Bb has a structure similar to that of the second recess 213Ab of the first modification.

[0102] The second recess 213Bb has a width that is significantly smaller than the axial length of the second recess 213Bb. The width of the second recess 213Bb is a circumferential width centered on the axis 211Bd, and is significantly smaller than the axial length and circumferential width of the first recess 213Ba. In this modification, the depth of the second recess 213Bb is equal to or smaller than the depth of the first recess 213Ba. The depths of the recesses 213Ba and 213Bb are depths from the outer peripheral surface 211Bca of the non-threaded portion 211Bc in the radial direction of the shaft portion 211B. The second recess 213Bb may have a width and depth that can accommodate the electric wire 222A extending along the second recess 213Bb. For example, the second recess 213Bb is a narrow groove.

[0103] The cross-sectional area of ​​the shaft portion 211B at the position of the second recess 213Bb is equal to or larger than the area of ​​a circle of the effective diameter of the male threads 211Ba and 211Bb. The cross-sectional area of ​​the shaft portion 211B is the area of ​​a cross section of the shaft portion 211B perpendicular to the axis 211Bd of the shaft portion 211B and crossing the second recess 213Bb. Therefore, the strength of the shaft portion 211B at the portion where the second recess 213Bb is formed may be equal to or larger than the strength of the shaft portion 211B at each of the male threads 211Ba and 211Bb. Although not limited thereto, in this modified example, the cross-sectional area of ​​the shaft portion 211B at the position of the second recess 213Bb is equal to or larger than the area of ​​a circle of the effective diameter of the male threads 211Ba and 211Bb throughout the second recess 213Bb in the axial direction of the shaft portion 211B.

[0104] The diameter of the shaft portion 211B at the bottom of the second recess 213Bb is equal to or larger than the effective diameter of the male threads 211Ba and 211Bb. Therefore, the shaft portion 211B at the second recess 213Bb can have cross-sectional characteristics superior to those of the shaft portion 211B at the male threads 211Ba and 211Bb. Although not limited thereto, in this modified example, the diameter of the shaft portion 211B at the bottom of the second recess 213Bb is equal to or larger than the effective diameter of the male threads 211Ba and 211Bb over the entire bottom of the second recess 213Bb in the circumferential direction centered on the axis 211Bd. Although not limited thereto, in this modified example, the diameter of the shaft portion 211B at the bottom of the second recess 213Bb is equal to or larger than the effective diameter of the male threads 211Ba and 211Bb over the entire second recess 213Bb in the axial direction of the shaft portion 211B.

[0105] The bolt portion 210B as described above can have the same strength as the first bolt 100B, despite including the processed portion 213B.

[0106] The sensor 220B includes the sensor elements 221Aa and 221Ab, the electric wire 222A, the relay terminal 223A, and the coating 224A, similar to the sensor 220A of the first modification. The sensor elements 221Aa and 221Ab and the relay terminal 223A are disposed in the first recess 213Ba. The relay terminal 223A is disposed at a position closer to the second recess 213Bb than the sensor elements 221Aa and 221Ab, and is disposed, for example, so as to be aligned with the second recess 213Bb in the axial direction of the shaft portion 211B. The sensor elements 221Aa and 221Ab are disposed at positions on the opposite sides with respect to the axis 211Bd of the shaft portion 211B, and are disposed, for example, at positions rotated 180° from each other around the axis 211Bd. The sensor elements 221Aa and 221Ab are disposed at positions facing each other across the axis 211Bd.

[0107] The electric wire 222A is connected at one end to the relay terminal 223A and is housed in the second recess 213Bb along the second recess 213Bb. The coating 224A is applied to the recesses 213Ba and 213Bb, and covers the sensor elements 221Aa and 221Ab, the electric wire 222A, and the relay terminal 223A.

[0108] FIG. 15 is a side view showing an example of a fastening state by the second bolt 200B according to the second modification. As shown in FIG. 15, when the flanges T1b and T2b are fastened by the second bolt 200B, the bolt portion 210B is passed through the fastening hole T1c of the flange T1b and the fastening hole T2c of the flange T2b. Furthermore, a washer 310B and a nut 300 are attached to the male thread 211Ba, and a washer 310 and a nut 300 are attached to the male thread 211Bb, and the nut 300 is tightened. Although not limited thereto, in this modification, on the male thread 211Ba side, the nut 300 is tightened up to the root of the male thread 211Ba. The washer 310B is disposed between the nut 300 and the flange T1b, and the washer 310 is disposed between the nut 300 and the flange T2b.

[0109] The washer 310B disposed on the male thread 211Ba includes a recess 310Bb extending from a hole 310Ba in the center to an outer periphery. The recess 310Bb may be formed on either a surface 310Bc of the washer 310B facing the flange T1b or a surface 310Bd of the washer 310B facing the nut 300. Although not limited thereto, in this modified example, when the nut 300 is fastened to the base of the male thread 211Ba, the second recess 213Bb can extend in the axial direction of the shaft portion 211B to the position of the recess 310Bb and communicate with the recess 310Bb.

[0110] The recess 310Bb extends in the radial direction of the washer 310B. The recess 310Bb has a width and depth capable of accommodating the electric wire 222A extending along the recess 310Bb. For example, the recess 310Bb may have a depth equal to or greater than that of the recess 213Ba or 213Bb, and may have a width equal to or greater than that of the second recess 213Bb. For example, the recess 310Bb is a narrow groove.

[0111] The washer 310B is arranged so that the position of the recess 310Bb and the position of the second recess 213Bb match in the circumferential direction centered on the axis 211Bd. When the washer 310B is attached to the shaft portion 211B, the electric wire 222A of the sensor 220B extending from the second recess 213Bb is passed through the recess 310Bb of the washer 310B and drawn outward in the radial direction from the washer 310B. This prevents the electric wire 222A from being affected by deformation or damage caused by the tightening of the nut 300. Although not limited thereto, in this modified example, the recess 310Bb is located on the surface 310Bc facing the flange T1b.

[0112] Forming recess 310Bb in washer 310B makes it possible to provide second bolt 200B with a structure for drawing out electric wire 222A without affecting the strength of bolt portion 210B and nut 300, the cross-sectional characteristics of bolt portion 210B, or the retention of fastening by bolt portion 210B and nut 300. Drawing out electric wire 222A through recess 310Bb can prevent damage to electric wire 222A due to contact with an object more effectively than when electric wire 222A is drawn out at a position closer to the tip of shaft portion 211B than nut 300.

[0113] It should be noted that washer 310B may be used for second bolt 200 of the embodiment and second bolt 200A of Modification 1. In this case, holes 213b and 213Ac formed in heads 212 and 211A may be omitted.

[0114] [Variation 3] A modification of the fastening method using a bolt set including a first bolt and a second bolt according to any of the embodiment and modification 1-2 will be described. Fig. 16 is a flowchart showing an example of the flow of the fastening method according to modification 3 using one bolt set 1.

[0115] In step S301, a strength test is performed on the second bolt 200, 200A or 200B before the bolt set is used to fasten an object. In this modification, a strength test is performed in the elastic region of the bolt. As a result, the second bolt does not undergo plastic deformation due to the test, and the cross-sectional characteristics and strength of the second bolt can be maintained unchanged before and after the test. Examples of the strength test may include a tensile test, a shear test, an axial force-torque test of the bolt, and a torque coefficient test. For example, equipment such as a tension-compression tester is used for the strength test. The tension-compression tester can obtain a relationship between the tensile force and the elongation amount of the second bolt in the elastic region. Furthermore, during the strength test, a detection result may be obtained from the sensor 220, 220A or 220B. As a result, a relationship between the test result of the tension-compression tester and the detection result of the sensor can be obtained. Such a relationship can be used to monitor the fastening force of the second bolt after the fastening is completed, which will be described later. For example, the result of converting the detection result of the sensor into the test result of the tension-compression tester can be used. Furthermore, it can be determined whether the detection result of the sensor is normal or not.

[0116] As a result of the above-mentioned test, the relationship between the force acting on the second bolt and the elastic deformation of the second bolt, such as the relationship between the tensile force, elongation, and strain of the second bolt, can be obtained. From the relationship obtained in this way, it is possible to calculate the tightening torque for realizing a desired axial force in the fastened first and second bolts. Furthermore, it is possible to determine whether the second bolt has a strength equivalent to that of the first bolt.

[0117] In step S301, the first bolt 100 or 100B may be subjected to the same strength test as that performed on the second bolt 200, 200A or 200B.

[0118] Steps S302 and S303 are similar to steps S101 and S102 shown in FIG. 6 of the embodiment, respectively.

[0119] Next, in step S304, the worker attaches nuts to the first bolt and the second bolt, and tightens each nut to a predetermined torque. The predetermined torque is a specified torque, but if the tightening torque calculated in step S301 is greater than the specified torque, the tightening torque may be the specified torque.

[0120] Next, steps S305 and S306 are respectively similar to steps S104 and S105 shown in FIG. 6 of the embodiment.

[0121] Next, in step S307, the worker monitors the fastening force of the second bolt after the fastening is completed by referring to the output result of the processing device 2. For example, the axial force of the second bolt may be monitored as the fastening force.

[0122] If there is a second bolt whose fastening force is smaller than the target fastening force (Yes in step S308), the worker proceeds to step S309, and if there is no second bolt whose fastening force is smaller than the target fastening force (No in step S308), the worker returns to step S307.

[0123] In step S309, the worker tightens at least some of the nuts of the first bolt and the second bolt with a predetermined torque. In this modified example, the tightening target is all of the first bolt and the second bolt. For example, the tightening target may be some of the bolts including the second bolt whose tightening force is smaller than the target tightening force and the first bolts around the second bolt. The second bolt whose tightening force is smaller than the target tightening force may be replaced with a new second bolt that has not been used for tightening. All of the first bolt and the second bolt may be replaced with new first bolt and second bolt that have not been used for tightening. After executing step S309, the process returns to step S308, and the tightening force is determined. After executing step S309, the process may return to step S307.

[0124] According to the third modification, fastening and post-fastening management can be performed using actually detected data regarding the strength, characteristics, etc. of at least the second bolt 200, 200A or 200B.

[0125] [Other embodiments] Although exemplary embodiments and modifications of the present disclosure have been described above, the present disclosure is not limited to the above-mentioned embodiments and modifications. In other words, various modifications and improvements are possible within the scope of the present disclosure. For example, the present disclosure also includes embodiments in which various modifications have been made to the embodiments or modifications, and embodiments in which components in different embodiments and modifications are combined.

[0126] For example, in the embodiment and the modified example, the first bolt 100 and the bolt portion 210, 210A of the second bolt 200, 200A are hexagonal bolts, but are not limited thereto. The first bolt 100 and the bolt portion 210, 210A may include a shaft portion including a threaded portion. For example, the head of the first bolt 100 and the bolt portion 210, 210A may have any shape in plan view other than a hexagon, such as a circle, and may include a hole into which a Phillips screwdriver or a flathead screwdriver or the like engages. For example, the first bolt 100 and the bolt portion 210, 210A may be a double-threaded bolt that does not include a head and includes threaded portions at both ends, or a fully threaded bolt.

[0127] In the embodiment, the sensor element 221 of the sensor 220 is disposed in the recess 213a of the shaft portion 211 of the bolt portion 210 of the second bolt 200, but is not limited to this. For example, the sensor element 221 may be disposed on the outer circumferential surface of the shaft portion 211, or may be disposed inside the shaft portion 211. The electric wire 222 of the sensor 220 is disposed in the hole 213b penetrating the head portion 212 of the bolt portion 210, but is not limited to this. For example, the electric wire 222 may be disposed through the recess 213a extending to the surface 212b of the head portion 212, or may be disposed through the inside of the shaft portion 211.

[0128] In the first and second modified examples, the sensors 220A and 220B include two sensor elements 221Aa and 221Ab, but are not limited thereto. The sensors 220A and 220B may include three or more sensor elements. In this case, two or more of the three or more sensor elements may be arranged side by side in the circumferential direction of the shaft portions 211A and 211B, or may be arranged side by side in the axial direction of the shaft portions 211A and 211B.

[0129] In the embodiment, the number of first bolts 100 disposed in each gap between the second bolts 200 in the circumferential direction of the flanges T1b and T2b is the same, but is not limited to this. The number of first bolts 100 in one or more of the multiple gaps between the second bolts 200 may be different from the number of first bolts 100 in the other gaps. The gaps between the multiple first bolts 100 and the multiple second bolts may also be uniform or unequal.

[0130] Examples of each aspect of the technology of the present disclosure are as follows: A sensor-equipped bolt according to a first aspect of the present disclosure is a sensor-equipped bolt used for fastening an object, and includes a bolt shank including a threaded portion where a thread is formed and a non-threaded portion where a thread is not formed, and a sensor attached to the bolt shank for detecting distortion of the bolt shank, the bolt shank includes a recess in the outer circumferential surface of the non-threaded portion that is recessed from the outer circumferential surface of the non-threaded portion and that accommodates the sensor, and the cross-sectional area of ​​the bolt shank at the position of the recess is equal to or larger than the effective cross-sectional area of ​​the bolt shank at the threaded portion.

[0131] According to the above aspect, since the cross-sectional area of ​​the bolt shank at the recess is equal to or larger than the effective cross-sectional area of ​​the bolt shank at the threaded portion, the strength of the bolt shank at the recess is equal to or larger than the strength of the bolt shank at the threaded portion. The bolt shank can have the same strength as when no recess is formed on the bolt shank. Therefore, the strength of the sensor-equipped bolt can be improved.

[0132] In the first aspect above, in the sensor-equipped bolt according to the second aspect of the present disclosure, the diameter of the bolt shank at the position of the recess may be greater than or equal to the effective diameter of the bolt shank at the threaded portion.

[0133] According to the above embodiment, since the diameter of the bolt shank at the recess is equal to or larger than the effective diameter of the bolt shank at the threaded portion, the cross section of the bolt shank at the recess can have cross-sectional properties superior to the effective cross section of the bolt shank at the threaded portion in terms of strength and impact resistance, etc., thereby making it possible to further improve the strength of the sensor-equipped bolt.

[0134] In the above second aspect, in the sensor-equipped bolt according to the third aspect of the present disclosure, the diameter of the bolt shank at the position of the recess may be a diameter whose radius is the minimum distance between the bottom of the recess and the central axis of the bolt shank.

[0135] According to the above aspect, the minimum circular cross section of the bolt shank at the recess is equal to or larger than the effective cross section of the bolt shank at the threaded portion, and therefore the bolt shank at the recess has better cross-sectional properties than the bolt shank at the threaded portion.

[0136] In any of the first to third aspects above, in a sensor-equipped bolt according to a fourth aspect of the present disclosure, the recess may be a cylindrical groove extending circumferentially around the central axis of the bolt shaft.

[0137] According to the above aspect, the bolt shank can be easily machined to form the recessed portion. Furthermore, the bolt shank can have uniform strength in the circumferential direction at the recessed portion.

[0138] In any of the first to fourth aspects above, in a sensor-equipped bolt according to a fifth aspect of the present disclosure, the sensor includes a sheet-shaped terminal, two or more sheet-shaped strain gauges connected to the terminal, and an electric wire connected to the terminal, and the bolt shank includes a first recess as the recess that accommodates the terminal and the two or more strain gauges, and a second recess that extends from the first recess in the axial direction of the bolt shank and accommodates the electric wire, and the cross-sectional area of ​​the bolt shank at the position of the second recess may be greater than or equal to an effective cross-sectional area of ​​the bolt shank at the threaded portion.

[0139] According to the above aspect, since the sensor is compact, the strain gauge and the terminal can be accommodated in the first recess without making the first recess excessively large. Furthermore, since the sensor detects strain in the bolt shaft at two or more positions, various behaviors of the bolt shaft can be detected. Furthermore, since the electric wire is accommodated in the second recess, damage to the electric wire can be prevented. Furthermore, since the cross-sectional area of ​​the bolt shaft at the position of the second recess is equal to or larger than the effective cross-sectional area of ​​the bolt shaft at the threaded portion, the bolt shaft can have the same strength as when the second recess is not formed in the bolt shaft.

[0140] In the above fifth aspect, in the sensor-equipped bolt according to the sixth aspect of the present disclosure, the diameter of the bolt shank at the position of the second recess may be greater than or equal to the effective diameter of the bolt shank at the threaded portion.

[0141] According to the above embodiment, the diameter of the bolt shank at the position of the second recess is greater than or equal to the effective diameter of the bolt shank at the threaded portion, so that the cross-section of the bolt shank at the position of the second recess can have superior cross-sectional characteristics to the effective cross-section of the bolt shank at the threaded portion.

[0142] In the above fifth or sixth aspect, in a sensor-equipped bolt according to a seventh aspect of the present disclosure, the first recess extends in a circumferential direction centered on a central axis of the bolt shank, and the width of the second recess in the circumferential direction may be smaller than the width and length of the first recess in the circumferential direction and in the axial direction of the bolt shank.

[0143] According to the above embodiment, the second recess is compact, and therefore the effect of the formation of the second recess on the strength of the bolt shank can be reduced.

[0144] In any of the above first to seventh aspects, the sensor-equipped bolt according to an eighth aspect of the present disclosure further comprises a bolt head connected to an end of the bolt shank and adjacent to the non-threaded portion, the bolt head including a hole communicating with the recess and penetrating the bolt head in the axial direction of the bolt shank, and an electric wire included in the sensor may be pulled out to the outside through the hole.

[0145] According to the above aspect, the electric wire can be drawn out from the sensor-equipped bolt to the outside without interfering with the nut that screws onto the bolt shank or with an object to be fastened. This enables stable measurement of the bolt shank by the sensor.

[0146] In any of the above first to eighth aspects, the sensor-equipped bolt according to a ninth aspect of the present disclosure may further include a washer disposed on the bolt shank between a nut screwed onto the threaded portion and the object, the washer including a third recess extending from the bolt shank to the periphery of the washer on a surface facing the nut or the object, and an electric wire included in the sensor may be pulled out to the outside through the third recess.

[0147] According to the above embodiment, the electric wire can be drawn out from the sensor-equipped bolt without interfering with the nut screwed onto the bolt shank or with the object of fastening. By forming the third recess in the washer, the amount of processing of the bolt shank required to draw out the electric wire can be reduced. This prevents the strength of the bolt shank from decreasing.

[0148] In any of the above first to ninth aspects, the sensor-equipped bolt according to a tenth aspect of the present disclosure may further include a wireless communication device connected to the sensor, and the wireless communication device may include a battery that applies voltage to the sensor and an antenna that outputs the detection result of the sensor to an apparatus wirelessly connected to the wireless communication device.

[0149] According to the above aspect, the sensor can operate stably by receiving power from the wireless communication device. By providing the wireless communication device, the need for wires to connect the sensor to the device to which the sensor outputs is eliminated. This reduces the possibility of the output of the sensor detection results being hindered by damage to the wires, etc. This allows the sensor to output stably the detection results.

[0150] A fastening method according to an eleventh aspect of the present disclosure is a fastening method for fastening an object using the sensor-equipped bolt according to the tenth aspect above, comprising: conducting a strength test in an elastic range on one or more second bolts, each of which is the sensor-equipped bolt and each of which includes a processed portion that has been processed to attach the sensor including the formation of the recess; setting a plurality of first bolts that do not include the processed portion and the sensor and have the same structure, shape and size as the second bolt excluding the processed portion, and the one or more second bolts, into a plurality of fastening holes of the object; tightening the plurality of first bolts and the one or more second bolts with a predetermined torque; attaching one or more wireless communication devices to the one or more second bolts after fastening; establishing a wireless communication connection between the one or more wireless communication devices and a processing device that outputs the detection result of the sensor; and monitoring the fastening force of the one or more second bolts after fastening via the processing device.

[0151] According to the above embodiment, the second bolt with the sensor can have a strength equivalent to that of the first bolt not including the processed portion and the sensor. Therefore, the first bolt and the second bolt after fastening can show similar behavior with respect to distortion, etc. An operator can check the overall fastening state of an object by monitoring the fastening force of the second bolt via a processing device. Furthermore, by performing a strength test in the elastic range on the second bolt before it is used for fastening, a relationship between the elastic deformation amount of the second bolt and the force acting on the second bolt can be obtained. By using such a relationship, the tightening torque of the first bolt and the second bolt can be determined. Furthermore, a criterion for determining whether or not there is an abnormality in the fastening force during monitoring via a processing device can be determined.

[0152] In the above eleventh aspect, in a fastening method according to a twelfth aspect of the present disclosure, conducting the strength test includes determining whether or not the second bolt has a strength equivalent to that of the first bolt with respect to at least strength against axial tensile force based on an amount of expansion and contraction obtained from the sensor when a predetermined tensile force along the axial direction is applied to the second bolt, and setting into a plurality of fastening holes of the object may include using the second bolt having a strength equivalent to that of the first bolt.

[0153] According to the above embodiment, in the strength test of the elastic region, the detection result of the sensor is used to determine whether the second bolt has a strength equivalent to that of the first bolt. This makes it possible to determine whether the detection result of the sensor is normal. Furthermore, a relationship between the elastic deformation amount of the second bolt and the force acting on the second bolt based on the detection result of the sensor can be obtained. Such a relationship can be used to determine whether the fastening force of the second bolt after fastening is abnormal. Furthermore, since the second bolt determined to have a strength equivalent to that of the first bolt based on the detection result of the sensor is used for fastening, the detection result of the sensor of the second bolt after fastening can indicate the fastening state of the second bolt with high accuracy.

[0154] All numbers such as ordinal numbers and quantities used in this specification are exemplified to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the exemplified numbers. The connection relationships between components are exemplified to specifically explain the technology of the present disclosure, and the connection relationships that realize the functions of the present disclosure are not limited to these.

[0155] Since the present disclosure may be implemented in various forms without departing from the scope of its essential characteristics, the scope of the present disclosure is defined by the appended claims rather than the description in the specification, and therefore the exemplary embodiments and modifications are illustrative and not limiting. All modifications within the scope of the claims and their equivalents are intended to be embraced by the claims. [Explanation of symbols]

[0156] 1 bolt set 2 Processing equipment 100, 100B First bolt 200, 200a‐200f, 200A, 200B 2nd bolt 210, 210A, 210B Bolt part 211, 211A, 211B Shaft (bolt shaft) 211a, 211Aa, 211Ba, 211Bb Male thread (threaded part) 211Ab, 211Bc Non-threaded part (non-threaded part) 212, 212A Head (Bolt Head) 213, 213A, 213B processing part 213a Recess 213Aa, 213Ba First recess 213Ab, 213Bb Second recess 213b, 213Ac holes 220, 220A, 220B Sensors 221, 221Aa, 221Ab sensor elements 222, 222A wire 300 Nut 310, 310B Washer 310Bb Recess (third recess) 500 Wireless Communication Device T object T1, T2 parts

Claims

1. A sensor-equipped bolt used for fastening an object, a bolt shank including a threaded portion on which threads are formed and a non-threaded portion on which threads are not formed; a sensor attached to the bolt shaft and detecting a distortion of the bolt shaft; the bolt shank includes a recess in an outer peripheral surface of the non-threaded portion that is recessed from the outer peripheral surface of the non-threaded portion and that accommodates the sensor; The cross-sectional area of ​​the bolt shank at the recess is equal to or larger than the effective cross-sectional area of ​​the bolt shank at the threaded portion. Bolt with sensor.

2. The diameter of the bolt shank at the recess is equal to or larger than the effective diameter of the bolt shank at the threaded portion. The sensor-equipped bolt according to claim 1.

3. The diameter of the bolt shank at the position of the recess is a diameter having a radius equal to the minimum distance between the bottom of the recess and the central axis of the bolt shank. The sensor-equipped bolt according to claim 2.

4. The recess is a cylindrical groove extending in a circumferential direction about the central axis of the bolt shaft. The sensor-equipped bolt according to claim 1.

5. The sensor includes a sheet-like terminal, two or more sheet-like strain gauges connected to the terminal, and electric wires connected to the terminal; the bolt shank includes a first recess as the recess that accommodates the terminal and the two or more strain gauges, and a second recess that extends from the first recess in an axial direction of the bolt shank and accommodates the electric wire, The cross-sectional area of ​​the bolt shank at the position of the second recess is equal to or larger than the effective cross-sectional area of ​​the bolt shank at the threaded portion. A sensor-equipped bolt according to any one of claims 1 to 4.

6. The diameter of the bolt shank at the position of the second recess is equal to or larger than the effective diameter of the bolt shank at the threaded portion. The sensor-equipped bolt according to claim 5.

7. The first recess extends in a circumferential direction about a central axis of the bolt shaft, A width of the second recess in the circumferential direction is smaller than a width and a length of the first recess in the circumferential direction and in the axial direction of the bolt shaft. The sensor-equipped bolt according to claim 5.

8. a bolt head connected to an end of the bolt shank and adjacent to the non-threaded portion; The bolt head includes a hole that communicates with the recess and passes through the bolt head in an axial direction of the bolt shaft, The electric wires contained in the sensor are led out through the hole. The sensor-equipped bolt according to claim 1.

9. The bolt further includes a washer disposed on the bolt shaft between a nut that is screwed onto the threaded portion and the object, the washer includes a third recess extending from the bolt shank to a periphery of the washer on a surface facing the nut or the object; The electric wire included in the sensor is led out to the outside through the third recess. The sensor-equipped bolt according to claim 1.

10. Further comprising a wireless communication device connected to the sensor, The wireless communication device includes: a battery for applying a voltage to the sensor; and an antenna for outputting the detection result of the sensor to a device wirelessly connected to the wireless communication device. The sensor-equipped bolt according to claim 1.

11. A fastening method for fastening an object using the sensor-equipped bolt according to claim 10, comprising the steps of: performing a strength test in an elastic region on one or more second bolts, each of which is a bolt with a sensor, and each of which includes a processed portion for mounting the sensor, including the formation of the recess; Setting a plurality of first bolts, each of which does not include the processed portion and the sensor and has the same structure, shape and size as the second bolt except for the processed portion, and the one or more second bolts into a plurality of fastening holes of the object; tightening the plurality of first bolts and the one or more second bolts to a predetermined torque; Attaching one or more of the wireless communication devices to the one or more second bolts after fastening; and establishing a wireless communication connection between the one or more wireless communicators and a processing device that outputs the detection results of the sensor; and monitoring the fastening force of the one or more second bolts after fastening via the processing device. Fastening method.

12. conducting the strength test includes determining whether or not the second bolt has a strength equivalent to that of the first bolt with respect to at least a strength against a tensile force in an axial direction, based on an amount of expansion and contraction obtained from the sensor when a predetermined tensile force along an axial direction is applied to the second bolt; The step of setting the second bolt into the plurality of fastening holes of the object includes using the second bolt having a strength equivalent to that of the first bolt. The fastening method according to claim 11.

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