Sensor-equipped bolt and fastening method

Abstract

A sensor-equipped bolt (200A, 200B) which is used for fastening an object comprises: a bolt shaft (211A, 211B) that includes a threaded portion (211Aa, 211Ba, 211Bb) where threading is formed and a non-threaded portion (211Ab, 211Bc) where threading is not formed; and a sensor (220A, 220B) that is attached to the bolt shaft and detects deformation of the bolt shaft. The bolt shaft includes, in the outer circumferential surface of the non-threaded portion, a recess (213Aa, 213Ba) that is recessed from the outer circumferential surface of the non-threaded portion and accommodates the sensor. The cross-sectional area of the bolt shaft at the position of the recess is equal to or greater than the effective cross-sectional area of the bolt shaft at the threaded portion.

Description

Sensor-equipped bolt and fastening method

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

[0002] Bolts are sometimes used to join components. For example, Japanese Patent No. 6418457 discloses a system for measuring stress in a building using bolted joints. A screw member having an external thread and an internal thread, which is used in the structure of the building, is provided with a sensor unit that detects strain occurring in the screw member. The sensor unit is connected to an information collection device via a wire or wirelessly, and the information collection device accumulates measurement information from the sensor unit and determines whether there is an abnormality in the building based on the measurement information.

[0003] In Japanese Patent Publication No. 6418457, the screw member has an axially extending accommodation space formed within the head and shank of the screw member to accommodate the sensor unit, which can reduce its strength. To achieve the desired strength, the screw member must be increased in size, resulting in increased costs. Furthermore, when this screw member is applied to a fastening portion of an existing object, its strength is lower than that of the existing screw, so replacing the existing screw with this screw member reduces the fastening strength of the object. To maintain the fastening strength of the object, it is expected that the existing screw will need to be left as is and the new screw member will be added. However, it is generally considered difficult to add a new screw member to an existing object.

[0004] The present disclosure provides a sensor-equipped bolt that improves strength and a fastening method using the sensor-equipped bolt. A sensor-equipped bolt according to one aspect of the present disclosure is a sensor-equipped bolt used for fastening objects, 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 that detects strain 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 that accommodates the sensor, and wherein a cross-sectional area of ​​the bolt shank at the position of the recess is equal to or greater than an effective cross-sectional area of ​​the bolt shank at the threaded portion.

[0005] FIG. 1 is a perspective view showing an example of an object fastened by a bolt set according to an exemplary embodiment. FIG. 2A is a side view showing an example of the configuration of the first bolt of FIG. 1. FIG. 2B is a plan view showing an example of the configuration of the first bolt of FIG. 1. FIG. 3 is a perspective view showing an example of a case in which the first bolts of FIGS. 2A and 2B are stored when shipped from a manufacturer. FIG. 4A is a cross-sectional side view showing an example of the configuration of the second bolt of FIG. 1. FIG. 4B is a plan view showing an example of the configuration of the second bolt of FIG. 1. FIG. 5 is a side view showing an example of the configuration of the second bolt of FIG. 4A with a wireless communication device attached. FIG. 6 is a flowchart showing an example of the flow of a fastening method using one bolt set. FIG. 7 is a side view showing an example of a state before two members are joined. FIG. 8 is a plan view showing an example of the arrangement of the first bolt and the second bolt on the flange of FIG. 7. FIG. 9 is a flowchart showing the flow of a modified example of a fastening method using one bolt set. FIG. 10A is a side view showing an example of the configuration of the second bolt according to Modification 1. FIG. 10B is a side view showing an example of the configuration of the second bolt according to Modification 1. Fig. 11 is an enlarged view of the male thread of the second bolt and its surrounding area in Fig. 10B. Fig. 12 is a side view showing an example of the configuration of a first bolt according to Modification 2. Fig. 13 is a side view showing an example of a fastening state using the first bolt according to Modification 2. Fig. 14A is a side view showing an example of the configuration of a second bolt according to Modification 2. Fig. 14B is a side view showing an example of the configuration of a second bolt according to Modification 2. Fig. 15 is a side view showing an example of a fastening state using the second bolt according to Modification 2. Fig. 16 is a flowchart showing an example of the flow of a fastening method according to Modification 3 using one bolt set.

[0006] Hereinafter, 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 recited in the independent claims showing the highest concepts will be described as optional components. Each figure in the accompanying drawings is a schematic diagram and is not necessarily an exact drawing. In each figure, substantially identical components are assigned the same reference numerals, and duplicated descriptions may be omitted or simplified. In this specification and claims, the term "device" may refer not only to one device but also to a system including multiple devices.

[0007] 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, portions of the main bodies T1a and T2a of the members T1 and T2 are cut away so that the insides of the main bodies T1a and T2a are visible. 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 portion to be bolted together. In this embodiment, the object T is a structural body such as a column, beam, or wall of a building or structure, but is not limited thereto. The members T1 and T2 are members that form the structural body. In FIG. 1, the members T1 and T2 are portions 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.

[0008] The bolt set 1 includes a plurality of first bolts 100 and one or more second bolts 200. Although not limited to this, 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 not shown, and some of the plurality of second bolts 200 are not shown.

[0009] 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. In this embodiment, the portion that one bolt set 1 targets for bolt fastening is one joint portion, although this is not limited thereto. One bolt set 1 joins flange T1b and flange T2b as the joint portion.

[0010] The annular flanges T1b and T2b each have a plurality of fastening holes T1c and T2c arranged along the inner periphery of the annular flanges T1b and T2b. The number of the fastening holes T1c and the number of the fastening holes T2c are the same, and the pitch of the fastening holes T1c and the pitch of the fastening holes T2c are the same. In FIG. 1, some of the fastening holes T1c and some of the fastening holes T2c are not shown.

[0011] The members T1 and T2 are arranged so that the flanges T1b and T2b overlap, and are aligned in the cylindrical axial direction of the main bodies T1a and T2a so that the fastening holes T1c are aligned with the fastening holes T2c.

[0012] The plurality of first bolts 100 and the plurality of 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 plurality of first bolts 100 and the plurality of second bolts 200 are arranged in a direction along the circular inner circumferential edges of the flanges T1b and T2b, such that one or more first bolts 100 are located between the second bolts 200.

[0013] 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 FIGS. 2A and 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 shank 101 and a head 102 disposed at one end of the shank 101. The first bolt 100 may be any bolt that includes the shank 101 and the head 102. The shank 101 has a cylindrical shape and extends linearly from the head 102. The head 102 has a hexagonal prism shape and is radially larger than the shank 101. The axial length L of the shank 101 is also referred to as the nominal length, and the diameter DA of the shank 101 is also the outer diameter of the shank 101 and is also referred to as the shank 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 shank 101 is also referred to as the head height. The surface 102a is the surface of the head 102 opposite to the shank 101.

[0014] The shaft portion 101 includes a male thread 101a on its outer peripheral surface. In this embodiment, the male thread 101a is formed on the outer peripheral surface over the entire axial direction of the shaft portion 101, but may be formed on the outer peripheral surface over a portion of the axial direction of the shaft portion 101. The outer diameter of the male thread 101a is also referred to as the shaft diameter DA and nominal diameter.

[0015] The head portion 102 includes a marking ID indicating the identification symbol of the manufacturer of the first bolt 100 and a marking indicating the mechanical properties of the first bolt 100. In this embodiment, the markings indicating the mechanical properties include, but are not limited to, a marking S indicating the strength class of the first bolt 100 and a marking M indicating the material of the first bolt 100. For example, the markings ID, S, and M may be disposed on the surface 102a of the head portion 102.

[0016] 3 is a perspective view showing an example of a case 400 in which the first bolt 100 shown in FIGS. 2A and 2B is stored when shipped from the manufacturer. As shown in FIG. 3, the case 400 includes a mark LN on its outer surface indicating the lot number of the first bolt 100. The case 400 stores multiple first bolts 100 with the same lot number. 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.

[0017] Although not limited thereto, in this embodiment, the multiple first bolts 100 included in one bolt set 1 satisfy a first condition that they are identical to one another in at least one of shape and size. In this embodiment, the multiple first bolts 100 included in one bolt set 1 are identical to one another in all elements of the first condition. The shape of the first bolt 100 is a shape formed by combining the shank 101 and the head 102. The size of the first bolt 100 includes the shank diameter DA of the shank 101, the nominal length L of the shank 101, the width across flats DB of the head 102, and the head height H of the head 102. Furthermore, the multiple first bolts 100 included in one bolt set 1 satisfy a second condition that they are identical to one another in thread length, which is the axial length of the male threads 101a.

[0018] Here, in this specification and claims, "two things are the same" includes "two things that are completely identical to each other" and "two things that are substantially identical to each other and can be considered identical to 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.

[0019] The multiple first bolts 100 included in one bolt set 1 satisfy a third condition that they are identical to one another in one or more of the following: thread designation, bolt standard, thread pitch of the male thread 101a, bolt strength class, and bolt material. In this embodiment, the multiple first bolts 100 included in one bolt set 1 are identical to one another 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. Thread standards include metric threads, inch threads, and pipe threads. The metric thread standard is expressed by the symbol "M." The inch thread standard is expressed by the symbol "UNC" or "UNF." The pipe thread standard is expressed by the symbol "R," "Rc," "Rp," "G(A)," "G(B)," or "G." The nominal diameter is expressed 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 expressed as "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.

[0020] The first bolts 100 included in one bolt set 1 satisfy a fourth condition that they are the same in one or more of the following: manufacturer, model, part number, and production lot. In this embodiment, the first bolts 100 included in one bolt set 1 are the same in all elements of the fourth condition. The bolt model, bolt part number, and bolt production lot can be set by the manufacturer.

[0021] 4A and 4B are a cross-sectional side view and a plan view, respectively, showing an example of the configuration of the second bolt 200 of FIG. 1. As shown in FIGS. 4A and 4B, the second bolt 200 includes a bolt portion 210 and a sensor 220. In this embodiment, the bolt portion 210 is a hexagonal bolt made of a magnetic metal, but is not limited thereto. The sensor 220 is attached to the bolt portion 210 and detects distortion of the bolt portion 210.

[0022] The bolt portion 210 integrally includes a shank 211 and a head 212 disposed at the end of the shank 211. The shank 211 has a cylindrical shape and extends linearly from the head 212. The head 212 has a hexagonal prism shape and is radially larger than the shank 211. The shank 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 shank 211, but may also be formed on the outer circumferential surface over a portion of the axial direction of the shank 211.

[0023] The bolt portions 210 of the second bolts 200 and the first bolts 100 included in the same bolt set 1 satisfy a fifth condition that they are identical to each other in at least one of shape and size. In this embodiment, the bolt portions 210 and the first bolts 100 are identical to each other 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 identical to each other 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.

[0024] 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 bolt portions 210 and the first bolts 100 satisfy the sixth condition. The sixth condition is similar to the second condition.

[0025] Furthermore, the bolt portions 210 of the plurality of second bolts 200 and the plurality of 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 nominal size, bolt standard, thread pitch of the male thread 101a, bolt strength class, and bolt material, and in this embodiment, the plurality of bolt portions 210 and the plurality of first bolts 100 are the same in all elements of the seventh condition. The seventh condition is similar to the third condition.

[0026] 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 elements of the eighth condition. The eighth condition is similar to the fourth condition.

[0027] 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. A display ID, S, and M may be arranged on the surface 212a of the head portion 212. The surface 212a is the surface of the head portion 212 opposite to the shank 211.

[0028] 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. In this embodiment, the processing is, but is not limited to, machining. Furthermore, the bolt portion 210 includes two processed portions 213. The two processed portions 213 are arranged at positions opposite each other with respect to the axis 211b, which is the central axis of the shaft portion 211.

[0029] 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 that can accommodate 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 minimizes the effect 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 is at least large enough to accommodate the sensor element 221.

[0030] Each recess 213a extends in the axial direction of the shank 211 from the connection between the head 212 and the shank 211 toward the tip of the shank 211 on the outer circumferential surface of the shank 211 so as to accommodate the sensor element 221. Each recess 213a is recessed from the outer circumferential surface of the shank 211, specifically, recessed relative to the male thread 211a. Each recess 213a extends over a portion of the axial length of the shank 211. Each recess 213a may extend onto the surface 212b of the head 212. In this case, each recess 213a may extend radially of the shank 211 from the shank 211 to the outer edge of the surface 212b.

[0031] Each hole 213b extends in the axial direction of the shaft portion 211 and passes through the head portion 212. Each hole 213b is arranged so as to communicate with the recess 213a at the connection portion between the head portion 212 and the shaft portion 211.

[0032] For example, the recess 213a and the hole 213b of one processed portion 213 can be formed together by drilling the bolt portion 210 from the head portion 212 toward the shank 211. Thus, the bolt portion 210 can be produced by processing the first bolt 100 removed from the case 400.

[0033] The second bolt 200 includes two sensors 220. Each sensor 220 includes a sensor element 221 embedded in the outer peripheral surface of the shank 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 fits within the recess 213a and extends in the axial direction of the shank 211. The electric wire 222 is passed through the hole 213b from the shank 211 toward the surface 212a and extends out of 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.

[0034] The sensor element 221 detects the strain of the shank 211. The sensor element 221 detects either or both of the direction and amount of strain of the shank 211. Examples of the sensor element 221 include a strain gauge, a piezoelectric element, etc. Such a sensor element 221 can detect the expansion / contraction, torsion, or both of the shank 211. Based on the amount of expansion / contraction of the shank 211, it is possible to detect the fastening torque, which is the torque with which the bolt portion 210 is tightened, the axial force, which is the tensile force acting on the shank 211 in the axial direction, or both. Based on the amount and direction of twisting of the shank 211, it is possible to detect the axial force of the shank 211 taking into account the effect of the twisting of the shank 211 on the axial force of the shank 211. For example, it is possible to detect the axial force of the shank 211 by canceling the effect of the twisting of the shank 211. The stress generated in the shaft portion 211 can be detected based on the amount of expansion and contraction, the amount of twisting, and the direction of twisting of the shaft portion 211.

[0035] In the present embodiment, sensor element 221 is disposed in groove-shaped recess 213a extending in the axial direction of shaft portion 211, but is not limited to this. For example, recess 213a may include a portion extending in the circumferential direction of shaft portion 211 instead of or in addition to the portion extending in the axial direction of shaft portion 211. The portion extending in the circumferential direction of shaft portion 211 may have a groove-like shape. This allows sensor element 221 to extend in the circumferential direction of shaft portion 211 and effectively detect torsion of shaft portion 211 in the circumferential direction.

[0036] 5 is a side view showing an example of the configuration of the second bolt 200 of 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 sensors 220 of the second bolts 200. Although not limited thereto, in this embodiment, the bolt set 1 includes a plurality of wireless communication devices 500, the number of which is the same as the number of second bolts 200, and a wireless communication device 500 is attached to each second bolt 200.

[0037] Each wireless communication device 500 is connected via wireless communication to a processing device 2 located at a distance from the members T1 and T2. Each wireless communication device 500 receives a signal indicating the 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 smart devices 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.

[0038] 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, adhesive, sticking, 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 also include an electromagnet.

[0039] The battery 505 is housed within the housing 501 and supplies power to each component of the wireless communication device 500. The battery 505 includes a primary battery that discharges stored power, or a secondary battery that can charge and discharge power.

[0040] 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.

[0041] 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.

[0042] 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 .

[0043] The wireless communication device 500 is attached to the head 212 of the bolt portion 210 so that the attachment portion 502 is in contact with the surface 212 a of the head 212. Furthermore, the connectors 506 are connected to the connectors 222 a of the electric wires 222 of the sensors 220, thereby connecting the wireless communication device 500 to the two sensors 220.

[0044] 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 will be described in which flanges T1b and T2b of two members T1 and T2 are joined using one bolt set 1.

[0045] In step S101, as shown in Fig. 7, in order to join the members T1 and T2 to be joined, the worker positions the members T1 and T2 with the flanges T1b and T2b overlapping and the multiple fastening holes T1c and the multiple fastening holes T2c aligned. This sets the members T1 and T2 in the state they are to be joined. Fig. 7 is a side view showing an example of the state of the two members T1 and T2 before they are joined.

[0046] Next, in step S102, the worker inserts the plurality of first bolts 100 and the plurality of second bolts 200 into the aligned pairs of fastening holes T1c and T2c, respectively. At this time, the plurality of first bolts 100 and the plurality of second bolts 200 are arranged so that the plurality of 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.

[0047] In FIG. 7 , the ratio of the number of first bolts 100 to the number of second bolts 200 is 9. FIG. 8 is a plan view showing an example of the arrangement of the first bolts 100 and the second bolts 200 on the flanges T1b and T2b in FIG. 7 . For example, in FIG. 8 , the number of second bolts 200 is 6, and the number of first bolts 100 is 54. The number of 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 first bolts 100 arranged between the second bolts 200 is equal. In FIG. 7 , the number of first bolts 100 and second bolts 200, as well as the number of fastening holes T1c and T2c, are depicted as being smaller than in FIG. 8 for ease of viewing.

[0048] Next, in step S103, the worker attaches nuts 300 to the first bolt 100 and the second bolt 200, respectively, and temporarily tightens each nut 300. That is, the worker primarily tightens the first bolt 100 and the second bolt 200. In the primary tightening, each nut 300 is tightened with a torque smaller than a predetermined torque preset for the first bolt 100 and the second bolt 200. The predetermined torque is a torque used to tighten the first bolt 100 and the second bolt 200 for proper tightening. In this embodiment, the nuts 300 are tightened with the predetermined torque, but the first bolt 100 and the second bolt 200 themselves may also be tightened with the predetermined torque. In this embodiment, the first bolt 100 and the second bolt 200 have the same structure, function, strength, and characteristics, so the predetermined torque for the first bolt 100 and the second bolt 200 is the same. This maintains the state of the members T1 and T2 as they are to be joined.

[0049] 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 is the same is also due to the fact that the nuts 300 have the same strength and characteristics as the first bolt 100.

[0050] Next, in step S104, the worker attaches the wireless communication device 500 to the head 212 of the bolt portion 210 of each second bolt 200. As shown in Fig. 5, the attachment portion 502 includes a permanent magnet 502a, so the worker can install the wireless communication device 500 on the head 212 simply by placing the wireless communication device 500 on the magnetic surface 212a of the head 212. Furthermore, the worker connects the connectors 222a of the two electric wires 222 of the second bolt 200 to the two connectors 506 of the wireless communication device 500. Furthermore, the worker turns on the power of the wireless communication device 500.

[0051] 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 thereof. 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 receiving power from the processing device 2 or the transceiver 3.

[0052] 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 communicator 500 and the transceiver 3 may be any wireless communication.

[0053] For example, examples of wireless communication may include a wireless LAN (Local Area Network) such as Wi-Fi (Wireless Fidelity), a wireless WAN (Wide Area Network) using a mobile communication network, 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, 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.

[0054] Next, in step S106, the worker tightens all of the nuts 300 of the first bolt 100 and the second bolt 200 to the specified torque while checking the output result of the processing device 2. In other words, 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 strain, amount of elongation, axial force, fastening torque of the bolt portion 210 of the second bolt 200, or a combination of two or more of these.

[0055] The strain and elongation of the bolt portion 210 may be the strain and elongation of the shank 211. The axial force of the bolt portion 210 may be the tensile force acting on the shank 211. The tightening torque of the bolt portion 210 may be the torque at which the nut 300 is tightened. The tightening torque may be estimated using one or more of the strain, elongation, and axial force of the bolt portion 210. For example, by checking the tightening torque of the bolt portion 210 output by the processing device 2, an operator can confirm whether the nut 300 has been tightened to a specified torque.

[0056] 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 on 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 "tightening force of the bolt" includes the "tightening torque of the bolt," the "axial force of the bolt," or both.

[0057] The processing device 2 may have a display function using a display or the like and display the output results. Conversion of the detection results of the sensor 220 into the strain, elongation, axial force, or tightening 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 with a torque wrench or impact wrench, the tightening state, such as the tightening force, after tightening cannot be confirmed. The worker can check the tightening state of the second bolt 200 from the output results of the processing device 2.

[0058] Next, in step S107, after completing the tightening of all nuts 300 of the first bolts 100 and second bolts 200, the worker checks the tightening force of all second bolts 200 based on the output results of the processing device 2. If there are any second bolts 200 whose tightening force is smaller than the preset target tightening force (Yes in step S107), the process proceeds to step S108. If there are no second bolts 200 whose tightening force is smaller than the target tightening force (No in step S107), the worker ends the joining operation of the flanges T1b and T2b. The target tightening force is a tightening force that is preset for the second bolts 200 and is required for target tightening, such as proper tightening. The target tightening force includes a target axial force, a target tightening torque, or both. The target tightening torque may be the same as or different from the specified torque.

[0059] In step S108, the worker retightens at least some of the nuts 300 of the first bolt 100 and the second bolt 200 to the 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 some of the first bolt 100 and the second bolt 200, the targets of retightening may include the second bolt 200 whose tightening force is smaller than the target tightening force and the first bolt 100 surrounding the second bolt 200.

[0060] Next, the worker returns to step S107, checks the fastening forces of all second bolts 200 based on the output results of the processing device 2, and repeats step S107 and subsequent steps.

[0061] Through 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 all of the first bolt 100 and the second bolt 200 are tightened with a tightening force within a specified range. Furthermore, because 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 a uniform 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.

[0062] 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 nuts 300 of the second bolt 200 whose fastening force exceeds the upper limit of the target range and the nuts 300 of the first bolt 100 surrounding the second bolt 200. Furthermore, the worker may retighten at least the loosened nuts 300, the nuts 300 of the second bolt 200 whose fastening force is below the lower limit of the target range, and the nuts 300 of the first bolt 100 surrounding the second bolt 200, to a specified torque. Alternatively, the worker may retighten all the nuts 300 of the first bolt 100 and the second bolt 200 to a specified torque. This allows the fastening forces of the first bolt 100 and the second bolt 200 to be equalized. The lower limit of the target range may be the target fastening force.

[0063] 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 will be described in which flanges T1b and T2b of two members T1 and T2 are joined using one bolt set 1.

[0064] Steps S201 to S206 are the same as steps S101 to S106 in FIG. 6, respectively.

[0065] In step S207, after completing the tightening of all nuts 300 of the first bolts 100 and second bolts 200, the worker checks the fastening forces of all second bolts 200 based on the output results of the processing device 2. If there are any second bolts 200 whose fastening force is smaller than the target fastening force (Yes in step S207), the process proceeds to step S208, and if there are no second bolts 200 whose fastening force is smaller than the target fastening force (No in step S207), the worker ends the joining work of flanges T1b and T2b.

[0066] In step S208, the worker inputs a command to the processing device 2 to set the retightening torque of the first bolt 100 and the second bolt 200. The retightening torque is the torque at which the first bolt 100 and the second bolt 200 are tightened again. The processing device 2 determines the retightening torque using the tightening force of the second bolt 200 that is equal to or greater than the target tightening force. To determine the retightening torque, the processing device 2 uses statistical values ​​of the tightening forces of the second bolt 200 that are equal to or greater than the target tightening force. Examples of statistical values ​​may include the mean, maximum, median, and mode of the tightening forces of the second bolt 200 that are equal to or greater than the target tightening force. The processing device 2 calculates the torque required to tighten the nut 300 to achieve the calculated statistical value, and determines the calculated torque as the retightening torque. For example, the average value of the 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.

[0067] For example, among the fastening forces of the second bolts 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 in accordance with a command input to the processing device 2 by an operator, a control program of the processing device 2, or both.

[0068] 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 some of the first bolt 100 and the second bolt 200, the targets of retightening may be the second bolt 200 whose tightening force is smaller than the target tightening force, and the first bolts 100 surrounding the second bolt 200.

[0069] Next, the worker returns to step S207, checks the fastening forces of all second bolts 200 based on the output results of the processing device 2, and repeats step S207 and subsequent steps.

[0070] Through steps S201 to S209, the first bolt 100 and the second bolt 200 are retightened with a retightening torque corresponding to the fastening state of the second bolt 200 that satisfies the target fastening force, so that all of the first bolt 100 and the second bolt 200 are fastened with a fastening force within the specified range. Furthermore, because 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 fastened with a uniform force.

[0071] In step S207, it may be determined whether the tightening force is within a preset target range. If the tightening force is outside the target range (Yes in step S207), in step S209, the worker may loosen the nuts 300 of the second bolt 200 whose tightening force exceeds the upper limit of the target range and the nuts 300 of the first bolt 100 surrounding the second bolt 200. The worker may retighten at least the loosened nuts 300, the nuts 300 of the second bolt 200 whose tightening force is below the lower limit of the target range, and the nuts 300 of the first bolt 100 surrounding the second bolt 200, with a retightening torque. Alternatively, the worker may retighten all the nuts 300 of the first bolt 100 and the second bolt 200 with a retightening torque. This allows the tightening forces of the first bolt 100 and the second bolt 200 to be equalized. The lower limit of the target range may be the target tightening force.

[0072] [Modification 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. Like the second bolt 200 according to the embodiment, the second bolt 200A is obtained by processing the first bolt 100, but differs from the second bolt 200 according to the embodiment in the structure of the processed portion and the structure of the sensor. Below, the second bolt 200A according to this modification will be described, focusing on the differences from the embodiment, and a description of the similarities with the embodiment will be omitted as appropriate.

[0073] 10A and 10B are side views showing an example of the configuration of a second bolt 200A according to Modification 1. FIG. 10B is a view of the second bolt 200A viewed from a direction rotated 90° about the central axis 211Ad of the shank 211A of the bolt portion 210A relative to FIG. 10A . FIG. 11 is an enlarged view of the male thread 211Aa and its surrounding area of ​​the second bolt 200A in FIG. 10B . As shown in FIGS. 10A , 10B , and 11 , the second bolt 200A includes a 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 shank 211A and a head 212A. The shank 211A extends linearly from the head 212A.

[0074] The shank 211A includes a non-threaded portion 211Ab and a male thread 211Aa located distally of the non-threaded portion 211Ab. In other words, the bolt portion 210A is a partially threaded bolt including the male thread 211Aa on a portion of the outer circumferential surface of the shank 211A. In this modification, the male thread 211Aa is formed by threading the outer circumferential surface of the shank 211A. Therefore, the thread diameter D2 of the male thread 211Aa is the same as or slightly smaller than the diameter D1 of the non-threaded portion 211Ab, i.e., they are equivalent. 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 the intermediate diameter between the diameters D2 and D3, i.e., the average diameter of the diameters D2 and D3.

[0075] 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 partially 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 shank 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 shank 211A.

[0076] The first recess 213Aa extends circumferentially on the outer peripheral 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 further than the outer peripheral 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.

[0077] The first recess 213Aa has a width B1 in the axial direction of the shaft portion 211A, which is sufficient to accommodate the sensor elements 221Aa and 221Ab of the sensor 220A. The width B1 is the width in the axial direction of the shaft portion 211A. Therefore, the first recess 213Aa has a cylindrical shape with an axial length 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. Therefore, the first recess 213Aa is a cylindrical groove.

[0078] The cross-sectional area of ​​the shank 211A at the first recess 213Aa is equal to or greater than the area of ​​a circle with an effective diameter D4. This cross-sectional area of ​​the shank 211A is the area of ​​a cross section of the shank 211A perpendicular to the axis 211Ad of the shank 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 shank 211A at the male thread 211Aa, and is also referred to as the effective cross-sectional area. Therefore, the strength of the shank 211A at the first recess 213Aa may be equal to or greater than the strength of the shank 211A at the male thread 211Aa. Examples of the strength may include tensile strength, shear strength, bending strength, torsional strength, etc. Although not limited thereto, in this modified example, the cross-sectional area of ​​the shaft portion 211A at the first recess 213Aa in the axial direction of the shaft portion 211A is equal to or larger than the area of ​​a circle with an effective diameter D4 throughout the first recess 213Aa in the axial direction of the shaft portion 211A.

[0079] Although not limited thereto, in this modification, the depth d1 of the first recess 213Aa is equal to or less than the difference (D1-D4) between the diameter D1 of the non-threaded portion 211Ab and the effective diameter D4, and preferably equal to or less than half of the difference (D1-D4). For example, the diameter D1a of the shank 211A at the bottom of the first recess 213Aa is equal to or greater than the effective diameter D4. For example, the diameter D1a may be a diameter whose radius is the smallest distance between the axis 211Ad and the bottom of the first recess 213Aa. Therefore, the shank 211A at the first recess 213Aa can have cross-sectional characteristics that are superior to those of the shank 211A at the male thread 211Aa, with respect to forces, impacts, 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 throughout 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 throughout the entire first recess 213Aa in the axial direction of the shaft portion 211A.

[0080] The second recess 213Ab extends on the outer peripheral surface 211Aba of the non-threaded portion 211Ab from the first recess 213Aa to the connection portion between the head 212A and the shank 211A. Although not limited thereto, in this modification, the second recess 213Ab extends in the axial direction of the shank 211A and is aligned with the hole 213Ac in the axial direction of the shank 211A.

[0081] The second recess 213Ab has a width B2 that is significantly smaller than its axial length. The width B2 is the circumferential width centered on the axial center 211Ad of the shaft portion 211A and is significantly smaller than the axial width B1 and 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 or smaller than the depth d1. The depth d2 is the radial depth of the shaft portion 211A from the outer peripheral surface 211Aba of the non-threaded portion 211Ab. The second recess 213Ab only needs to have a width B2 and a depth d2 that can accommodate the electric wire 222A (described later) extending along the second recess 213Ab. For example, the second recess 213Ab is a narrow groove.

[0082] The cross-sectional area of ​​the shank 211A at the position of the second recess 213Ab is equal to or greater than the area of ​​a circle with the effective diameter D4. This cross-sectional area of ​​the shank 211A is the area of ​​a cross section of the shank 211A perpendicular to the axial center 211Ad of the shank 211A and crossing the second recess 213Ab. Therefore, the strength of the shank 211A at the portion where the second recess 213Ab is formed can be equal to or greater than the strength of the shank 211A at the male thread 211Aa. Note that, although not limited thereto, in this modification, the cross-sectional area of ​​the shank 211A at the position of the second recess 213Ab is equal to or greater than the area of ​​a circle with the effective diameter D4 throughout the entire second recess 213Ab in the axial direction of the shank 211A.

[0083] Furthermore, in this modification, because the depth d2 of the second recess 213Ab is the same as the depth d1 of the first recess 213Aa, the diameter of the shank 211A at the bottom of the second recess 213Ab is equal to or greater than the effective diameter D4. For example, this diameter may be a diameter defined by the minimum distance between the axis 211Ad of the shank 211A and the bottom of the second recess 213Ab. Therefore, the shank 211A at the position of the second recess 213Ab may have cross-sectional characteristics that are superior to those of the shank 211A at the male thread 211Aa in terms of resistance to force, impact, etc. Although not limited thereto, in this modification, the diameter of the shank 211A at the bottom of the second recess 213Ab is equal to or greater than the effective diameter D4 throughout the entire circumferential direction of the bottom of the second recess 213Ab around 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 throughout the entire second recess 213Ab in the axial direction of the shaft portion 211A.

[0084] 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 properties as the first bolt 100. Note that the strength and cross-sectional properties of the first bolt 100 depend on the strength and cross-sectional properties of the male thread portion of the first bolt 100.

[0085] The sensor 220A includes sensor elements 221Aa and 221Ab, an electric wire 222A, a relay terminal 223A, and a coating 224A. In this modification, the sensor elements 221Aa and 221Ab include a sheet-like strain gauge and a terminal, and the relay terminal 223A is a sheet-like foil terminal. The relay terminal 223A electrically connects the terminals of the sensor elements 221Aa and 221Ab to the electric wire 222A.

[0086] The sensor elements 221Aa and 221Ab and the relay terminal 223A are disposed within 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. Because the sensor elements 221Aa and 221Ab and the relay terminal 223A have a thickness smaller than the depth d1, they fit within the first recess 213Aa and do not protrude radially. The relay terminal 223A is disposed closer to the second recess 213Ab than the sensor elements 221Aa and 221Ab, for example, aligned with the second recess 213Ab in the axial direction of the shaft portion 211A. The sensor elements 221Aa and 221Ab are disposed on opposite sides of the axis 211Ad of the shaft portion 211A, for example, rotated 180° from each other around the axis 211Ad. The sensor elements 221Aa and 221Ab are arranged at positions facing each other across the axis 211Ad. Lead wires extending from the terminals of the sensor elements 221Aa and 221Ab are connected to the relay terminal 223A.

[0087] The electric wire 222A is connected at one end to the relay terminal 223A and is housed within the second recess 213Ab along the second recess 213Ab. The electric wire 222A then passes through the hole 213Ac and extends out of the head 212A. A connector 222a is attached to the other end of the electric wire 222A.

[0088] The coating 224A is applied to the recesses 213Aa and 213Ab to cover the sensor elements 221Aa and 221Ab, the electric wire 222A, and the relay terminal 223A. The coating 224A is formed of an electrically insulating material. The coating 224A is preferably formed of a material that can be in a flexible state and a hardened state, such as a resin material. Examples of the resin material include a thermosetting resin such as an epoxy resin.

[0089] Connector 222a is connected to a wireless communication device 500, as shown in FIG. 5 , attached to bolt portion 210A. By applying a voltage to sensor elements 221Aa and 221Ab, wireless communication device 500 measures changes in electrical resistance due to expansion and contraction of sensor elements 221Aa and 221Ab and transmits the measurement results to processing device 2. Based on the received measurement results, processing device 2 calculates the expansion and contraction direction and amount of each of sensor elements 221Aa and 221Ab, and calculates the direction and amount of strain of shank 211A and the direction and magnitude of force acting on shank 211A based on the difference between the expansion and contraction direction and amount of sensor elements 221Aa and 221Ab. This makes it possible to detect the axial force and shear force acting on shank 211A, as well as the torsional direction and amount of torsion of shank 211A.

[0090] As a method for confirming the strength of the bolt portion 210A, a predetermined tensile force is applied along the axial direction of the bolt portion 210A using strength measurement equipment while the wireless communication device 500 shown in FIG. 5 is connected, thereby determining whether the predetermined strength is satisfied. That is, when 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 elongation amount in this state) of the shank 211A based on changes in the electrical resistance values ​​of the sensor elements 221Aa and 221Ab. The processing device 2 further determines whether the calculated amount of expansion and contraction is within a predetermined range stored in advance in association with the required strength, thereby determining that the bolt portion 210A has a strength equivalent to that of the first bolt 100 in terms of strength against the axial tensile force of the shank 211A.

[0091] [Modification 2] The bolt set 1 of the present disclosure can also be applied to a first bolt 100B according to Modification 2 and a second bolt 200B according to Modification 2. The first bolt 100B is a double-threaded bolt that does not have a head and includes male threads on both ends of the shank. The second bolt 200B is obtained by machining the first bolt 100B. The second bolt 200B differs from the second bolt 200A according to Modification 1 in the structure of the machined portion. Below, the first bolt 100B and the second bolt 200B according to this modification will be described, focusing on the differences from the embodiment and Modification 1, and descriptions of the similarities to the embodiment or Modification 1 will be omitted as appropriate.

[0092] FIG. 12 is a side view showing an example of the configuration of a first bolt 100B according to Modification 2. 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 of its 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.

[0093] FIG. 13 is a side view showing an example of a fastening state using a first bolt 100B according to Modification 2. As shown in FIG. 13 , when fastening the flanges T1b and T2b using the first bolt 100B, the first bolt 100B is passed through the fastening hole T1c in the flange T1b and the fastening hole T2c in 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, the nut 300 is tightened on the male thread 101Ba side all the way to the base of the male thread 101Ba. The washer 310 has an annular plate shape, and the first bolt 100B is passed through a central hole in 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.

[0094] 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 shank 211B of the bolt portion 210B relative 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.

[0095] The bolt portion 210B includes a linearly extending shaft portion 211B. 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 diameters of the threads of the male threads 211Ba and 211Bb are equal to the diameter of the non-threaded portion 211Bc. The root diameters of the male threads 211Ba and 211Bb and the effective diameters of the male threads 211Ba and 211Bb are smaller than the diameter of the non-threaded portion 211Bc.

[0096] 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.

[0097] The first recess 213Ba has a structure similar to that of the first recess 213Aa of Modification 1. The first recess 213Ba extends circumferentially on the outer peripheral surface 211Bca of the non-threaded portion 211Bc, centered on the axis 211Bd of the shaft portion 211B. The first recess 213Ba has a cylindrical shape.

[0098] The cross-sectional area of ​​the shank 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 shank 211B at the first recess 213Ba can be equal to or larger than the strength of the shank 211B at each of the male threads 211Ba and 211Bb. Note that, although not limited to, in this modification, the cross-sectional area of ​​the shank 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 shank 211B.

[0099] The diameter of the shank 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 shank 211B at the first recess 213Ba can have cross-sectional characteristics that are equal to or superior to those of the shank 211B at the male threads 211Ba and 211Bb. Note that, although not limited thereto, in this modification, the diameter of the shank 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 shank 211B at the first recess 213Ba. Although not limited thereto, in this modification, the diameter of the shank 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 shank 211B.

[0100] 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 in the first modification.

[0101] The second recess 213Bb has a width significantly smaller than its axial length. The width of the second recess 213Bb is the 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 less than the depth of the first recess 213Ba. The depths of the recesses 213Ba and 213Bb are the 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 only needs to have a width and depth sufficient to accommodate the electric wire 222A extending along the second recess 213Bb. For example, the second recess 213Bb is a narrow groove.

[0102] The cross-sectional area of ​​the shank 211B at the position of the second recess 213Bb is equal to or greater than the area of ​​a circle with an effective diameter of the male threads 211Ba and 211Bb. This cross-sectional area of ​​the shank 211B is the area of ​​a cross section of the shank 211B perpendicular to the axial center 211Bd of the shank 211B and crossing the second recess 213Bb. Therefore, the strength of the shank 211B at the portion where the second recess 213Bb is formed may be equal to or greater than the strength of the shank 211B at each of the male threads 211Ba and 211Bb. Note that, although not limited thereto, in this modification, the cross-sectional area of ​​the shank 211B at the position of the second recess 213Bb is equal to or greater than the area of ​​a circle with an effective diameter of the male threads 211Ba and 211Bb throughout the entire second recess 213Bb in the axial direction of the shank 211B.

[0103] 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 that are equal to or superior to those of the shaft portion 211B at the male threads 211Ba and 211Bb. Note that, although not limited thereto, in this modification, 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 throughout 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 in the axial direction of the shaft portion 211B is equal to or larger than 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 bolt portion 210B as described above can have the same strength as the first bolt 100B, despite including the processed portion 213B.

[0105] Similar to the sensor 220A of Modification 1, the sensor 220B includes sensor elements 221Aa and 221Ab, an electric wire 222A, a relay terminal 223A, and a coating 224A. The sensor elements 221Aa and 221Ab and the relay terminal 223A are disposed within the first recess 213Ba. The relay terminal 223A is disposed closer to the second recess 213Bb than the sensor elements 221Aa and 221Ab, for example, aligned with the second recess 213Bb in the axial direction of the shaft portion 211B. The sensor elements 221Aa and 221Ab are disposed on opposite sides of the shaft center 211Bd of the shaft portion 211B, for example, rotated 180° from each other about the shaft center 211Bd. The sensor elements 221Aa and 221Ab are disposed opposite each other across the shaft center 211Bd.

[0106] The electric wire 222A is connected at one end to the relay terminal 223A and is housed within 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.

[0107] FIG. 15 is a side view showing an example of a fastening state by the second bolt 200B according to Modification 2. As shown in FIG. 15 , when the flanges T1b and T2b are fastened with 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 all the way to the base 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.

[0108] The washer 310B disposed on the male thread 211Ba includes a recess 310Bb extending from a central hole 310Ba to the 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 modification, when the nut 300 is tightened all the way to the base of the male thread 211Ba, the second recess 213Bb extends in the axial direction of the shank 211B up to the position of the recess 310Bb and can communicate with the recess 310Bb.

[0109] The recess 310Bb extends in the radial direction of the washer 310B. The recess 310Bb has a width and depth that can accommodate 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.

[0110] The washer 310B is arranged so that the recess 310Bb and the second recess 213Bb are aligned in the circumferential direction about 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 out radially outward from the washer 310B. This prevents the electric wire 222A from being affected by deformation or damage caused by tightening the nut 300. Although not limited thereto, in this modification, the recess 310Bb is located on the surface 310Bc facing the flange T1b.

[0111] 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 electric wire 222A from being damaged by contact with an object more effectively than when electric wire 222A is drawn out at a position closer to the tip of shank 211B than nut 300.

[0112] The washer 310B may be used for the second bolt 200 of the embodiment and the second bolt 200A of Modification 1. In this case, the holes 213b and 213Ac formed in the heads 212 and 211A may be omitted.

[0113] [Modification 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 Modifications 1 and 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.

[0114] 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 bolt's elastic range. This prevents the second bolt from undergoing plastic deformation during the test, allowing the second bolt to maintain its cross-sectional characteristics and strength unchanged before and after the test. Examples of strength tests include tensile tests, shear tests, bolt axial force-torque tests, and torque coefficient tests. For example, equipment such as a tension-compression testing machine is used for the strength test. The tension-compression testing machine can obtain the relationship between the tensile force and elongation of the second bolt in the elastic range. Furthermore, detection results may be obtained from the sensor 220, 220A, or 220B during the strength test. This allows the relationship between the test results of the tension-compression testing machine and the sensor detection results to be obtained. This relationship can be used to monitor the fastening force of the second bolt after fastening is complete, as described below. For example, the sensor detection results can be converted into test results from the tension-compression testing machine. Furthermore, it can be determined whether the sensor detection results are normal.

[0115] As a result of the above-described 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 required to achieve a desired axial force in the fastened first and second bolts. Furthermore, it is possible to determine whether the second bolt has the same strength as the first bolt.

[0116] In step S301, the same strength test as that for the second bolt 200, 200A, or 200B may be performed on the first bolt 100 or 100B.

[0117] Steps S302 and S303 are respectively similar to steps S101 and S102 shown in FIG. 6 of the embodiment.

[0118] 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.

[0119] Next, steps S305 and S306 are respectively similar to steps S104 and S105 shown in FIG. 6 of the embodiment.

[0120] 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.

[0121] 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.

[0122] In step S309, the worker tightens at least some of the nuts of the first bolt and the second bolt to a predetermined torque. In this modified example, the tightening targets are all of the first bolts and the second bolts. For example, the tightening targets may be some of the bolts, including the second bolts whose tightening force is smaller than the target tightening force and the first bolts surrounding the second bolts. Note that the second bolts whose tightening force is smaller than the target tightening force may be replaced with new second bolts that have not been used in tightening. Note that all of the first bolts and the second bolts may be replaced with new first bolts and second bolts that have not been used in tightening. After executing step S309, the process returns to step S308, where the tightening force is determined. Note that after executing step S309, the process may return to step S307.

[0123] According to the third modification, it becomes possible to perform fastening and post-fastening management using actually detected data on the strength, characteristics, etc. of at least the second bolt 200, 200A or 200B.

[0124] [Other Embodiments] Illustrative embodiments and modifications of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and modifications. That is, various modifications and improvements are possible within the scope of the present disclosure. For example, embodiments in which various modifications have been made to the embodiments or modifications, and embodiments constructed by combining components of different embodiments and modifications, are also included within the scope of the present disclosure.

[0125] For example, in the embodiment and modified examples, the bolt portions 210, 210A of the first bolt 100 and the second bolts 200, 200A are hexagonal bolts, but are not limited to this. The first bolt 100 and the bolt portions 210, 210A may include a shank including a threaded portion. For example, the heads of the first bolt 100 and the bolt portions 210, 210A may have any shape in plan view other than a hexagon, such as a circle, and may include a hole for engaging a Phillips screwdriver or a flathead screwdriver. For example, the first bolt 100 and the bolt portions 210, 210A may be double-threaded bolts that do not include a head but include threaded portions on both ends, or fully threaded bolts.

[0126] In the embodiment, the sensor element 221 of the sensor 220 is disposed in the recess 213a of the shank 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 shank 211, or may be disposed inside the shank 211. The electric wire 222 of the sensor 220 is disposed in the hole 213b that penetrates the head 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 that extends to the surface 212b of the head 212, or may be disposed through the inside of the shank 211.

[0127] In Modifications 1 and 2, sensors 220A and 220B include, but are not limited to, two sensor elements 221Aa and 221Ab. 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 shaft portions 211A and 211B, or may be arranged side by side in the axial direction of shaft portions 211A and 211B.

[0128] In the embodiment, the number of first bolts 100 arranged 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 other gaps. The gaps between the multiple first bolts 100 and the multiple second bolts may also be uniform or unequal.

[0129] Examples of aspects 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 objects, and comprises a bolt shank including a threaded portion on which a thread is formed and a non-threaded portion on which no thread is formed, and a sensor attached to the bolt shank for detecting distortion of the bolt shank, the bolt shank including a recess on the outer peripheral surface of the non-threaded portion that is recessed from the outer peripheral surface of the non-threaded portion and that houses the sensor, and the cross-sectional area of ​​the bolt shank at the position of the recess is equal to or greater than the effective cross-sectional area of ​​the bolt shank at the threaded portion.

[0130] According to the above-described embodiment, the cross-sectional area of ​​the bolt shank at the recess is equal to or greater than the effective cross-sectional area of ​​the bolt shank at the threaded portion, so the strength of the bolt shank at the recess is equal to or greater than the strength of the bolt shank at the threaded portion. This allows the bolt shank to have the same strength as if no recess were formed on the bolt shank. This improves the strength of the sensor-equipped bolt.

[0131] In the first aspect described 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 equal to or greater than the effective diameter of the bolt shank at the threaded portion.

[0132] According to the above-described embodiment, 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, so that the cross section of the bolt shank at the recess can have cross-sectional characteristics superior to the effective cross section of the bolt shank at the threaded portion in terms of strength and impact resistance, etc. This makes it possible to further improve the strength of the sensor-equipped bolt.

[0133] In the second aspect described above, 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 smallest distance between the bottom of the recess and the central axis of the bolt shank.

[0134] 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 recessed portion has better cross-sectional properties than the bolt shank at the threaded portion.

[0135] In any of the first to third aspects described above, in the 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.

[0136] 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.

[0137] In any of the above first to fourth aspects, in a sensor-equipped bolt according to a fifth aspect of the present disclosure, the sensor includes a sheet-like terminal, two or more sheet-like strain gauges connected to the terminal, and an electric wire 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 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 equal to or greater than the effective cross-sectional area of ​​the bolt shank at the threaded portion.

[0138] According to the above aspect, the sensor is compact, so the strain gauge and terminal can be accommodated within the first recess without making the first recess excessively large. Furthermore, the sensor detects strain on the bolt shank at two or more positions, making it possible to detect various behaviors of the bolt shank. Furthermore, the electric wire is accommodated within the second recess, preventing damage to the electric wire. Furthermore, the cross-sectional area of ​​the bolt shank at the position of the second recess is equal to or greater than the effective cross-sectional area of ​​the bolt shank at the threaded portion, allowing the bolt shank to have the same strength as if the second recess were not formed on the bolt shank.

[0139] 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 equal to or greater than the effective diameter of the bolt shank at the threaded portion.

[0140] According to the above aspect, since 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 cross section of the bolt shank at the position of the second recess can have cross-sectional characteristics superior to the effective cross section of the bolt shank at the threaded portion.

[0141] In the above fifth or sixth aspect, in the sensor-equipped bolt according to the seventh aspect of the present disclosure, the first recess may extend in a circumferential direction centered on the 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.

[0142] According to the above aspect, the second recess is compact, so that the effect that the formation of the second recess has on the strength of the bolt shank can be reduced.

[0143] In any of the above first to seventh aspects, the sensor-equipped bolt according to an eighth aspect of the present disclosure may further include 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 passing through the bolt head in the axial direction of the bolt shank, and an electric wire included in the sensor may be drawn to the outside through the hole.

[0144] According to the above aspect, the electric wire can be drawn out from the sensor-equipped bolt without interfering with the nut that threads onto the bolt shank or the object to be fastened, thereby enabling stable measurement of the bolt shank by the sensor.

[0145] 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, interposed between a nut that screws onto the threaded portion and the object, wherein the washer includes 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.

[0146] According to the above-described embodiment, the electric wire can be pulled out from the sensor-equipped bolt without interfering with the nut that threads onto the bolt shank or the object to be fastened. By forming the third recess in the washer, the amount of processing of the bolt shank required to pull out the electric wire can be reduced. This prevents a decrease in the strength of the bolt shank.

[0147] 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 results of the sensor to a device wirelessly connected to the wireless communication device.

[0148] 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 connecting the sensor to the device to which the sensor outputs is eliminated. This reduces the risk of the sensor's detection results being affected by damage to the wires, etc. This allows for stable output of the sensor's detection results.

[0149] 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 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 in 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 results of the sensors; and monitoring the fastening force of the one or more second bolts after fastening via the processing device.

[0150] According to the above aspect, the second bolt with the sensor can have the same strength as the first bolt without the processed portion and sensor. Therefore, the first and second bolts after tightening can exhibit similar behavior with respect to distortion, etc. By monitoring the tightening force of the second bolt via a processing device, an operator can check the overall tightening condition of the object. Furthermore, by conducting a strength test in the elastic range on the second bolt before use in tightening, the relationship between the elastic deformation of the second bolt and the force acting on the second bolt can be obtained. Using this relationship, the tightening torque of the first and second bolts can be determined. Furthermore, a criterion for determining whether or not there is an abnormality in the tightening force during monitoring via a processing device can be determined.

[0151] In the above-mentioned eleventh aspect, in the fastening method according to the twelfth aspect of the present disclosure, conducting the strength test may include determining whether 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 the second bolt into the multiple fastening holes of the object may include using the second bolt that has a strength equivalent to that of the first bolt.

[0152] According to the above aspect, in the strength test in the elastic range, the sensor detection results are 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 sensor detection results are normal. Furthermore, the relationship between the amount of elastic deformation of the second bolt and the force acting on the second bolt can be obtained based on the sensor detection results. This relationship can be used to determine whether the fastening force of the second bolt after fastening is abnormal. Furthermore, because the second bolt determined to have a strength equivalent to that of the first bolt based on the sensor detection results is used for fastening, the sensor detection results of the second bolt after fastening can indicate the fastening state of the second bolt with high accuracy.

[0153] All numbers such as ordinal numbers and quantities used in this specification are provided as examples to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the illustrated numbers. The connection relationships between components are provided as examples 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.

[0154] Because the present disclosure may be embodied 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 intended to be illustrative and not limiting. All modifications within the scope of the claims and their equivalents are intended to be embraced by the claims.

Claims

1. A sensor-equipped bolt used for fastening objects, comprising: a bolt shank including a threaded portion where a thread is formed and a non-threaded portion where no thread is formed; 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 that accommodates the sensor, and a 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.

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

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

4. A sensor-equipped bolt as claimed in any one of claims 1 to 3, wherein the recess is a cylindrical groove extending in the circumferential direction around the central axis of the bolt shaft.

5. A sensor-equipped bolt as claimed in any one of claims 1 to 4, wherein the sensor includes a sheet-like terminal, two or more sheet-like strain gauges connected to the terminal, and an electric wire 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 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 is equal to or greater than the effective cross-sectional area of ​​the bolt shank at the threaded portion.

6. The sensor-equipped bolt according to claim 5, wherein 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.

7. A sensor-equipped bolt as described in claim 5 or 6, wherein the first recess extends in a circumferential direction centered on the central axis of the bolt shank, and the width of the second recess in the circumferential direction is smaller than the width and length of the first recess in the circumferential direction and in the axial direction of the bolt shank.

8. A sensor-equipped bolt as claimed in any one of claims 1 to 7, further comprising 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 passing through the bolt head in the axial direction of the bolt shank, and an electric wire contained in the sensor is pulled out to the outside through the hole.

9. A sensor-equipped bolt as claimed in any one of claims 1 to 8, further comprising a washer disposed on the bolt shank between a nut that screws 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 is pulled out to the outside through the third recess.

10. A bolt with a sensor as described in any one of claims 1 to 9, further comprising a wireless communication device connected to the sensor, the wireless communication device including: a battery that applies voltage to the sensor; and an antenna that outputs the detection result of the sensor to a device wirelessly connected to the wireless communication device.

11. A fastening method for fastening an object using the sensor-equipped bolt according to claim 10, comprising: conducting a strength test in an elastic range on one or more second bolts, each of which is the sensor-equipped bolt and which includes a processed portion for attaching the sensor including the formation of the recess; setting a plurality of first bolts, which do not include the processed portion and the sensor and which 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 results of the sensor; and monitoring the fastening force of the one or more second bolts after fastening via the processing device.

12. The fastening method described in claim 11, wherein 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 the multiple fastening holes of the object includes using the second bolt which has a strength equivalent to that of the first bolt.

Images