A bolt includes a head, and a shank connected to the head and having a screw portion and a leading end portion. The leading end portion of the shank includes a wall portion that defines a hole. The wall portion includes: a deformation portion configured to be plastically deformed by a torque from a fastening tool to be inserted in the hole; and a space forming portion configured to form a space between the space forming portion and the fastening tool. The blot is configured such that a maximum torque applied to the deformation portion in a process, in which a part of the deformation portion is plastically deformed by the torque from the fastening tool and is accommodated in the space and the fastening tool is placed in an idle rotation state, is configured to be set to be within a predetermined range.

TECHNICAL FIELD

The present disclosure relates to a bolt that can be fastened from one side thereof.

BACKGROUND

A bolt that can be fastened from one side thereof has been proposed (for example, see Japanese Patent Application Publication No. 2000-110816).

In a bolt disclosed in Japanese Patent Application Publication No. 2000-110816, the bolt is fastened to a member to be fastened by a desired fastening torque by rotating a nut and a pintail provided on a leading end of a shank in directions opposite to each other by a wrench and by breaking the pintail.

SUMMARY

However, in the bolt in Japanese Patent Application Publication No. 2000-110816, the pintail is provided on the shank. As a result, the weight of the bolt increases and the cost increases. In addition, the pintail breaks when the bolt is fastened, and hence the pintail needs to be discarded and workability decreases when the bolt is fastened.

An object of the present disclosure is to provide a bolt of which weight and cost can be reduced.

A bolt in accordance with one or more embodiments includes a head, and a shank connected to the head and having a screw portion and a leading end portion. The leading end portion of the shank includes a wall portion that defines a hole. The wall portion includes: a deformation portion configured to be plastically deformed by a torque from a fastening tool to be inserted in the hole; and a space forming portion configured to form a space between the space forming portion and the fastening tool. The bolt is configured such that a maximum torque applied to the deformation portion in a process, in which a part of the deformation portion is plastically deformed by the torque from the fastening tool and is accommodated in the space and the fastening tool is placed in an idle rotation state, is configured to be set to be within a predetermined range.

A bolt in accordance with one or more embodiments includes a head, a shank connected to the head and having a screw portion, and a pintail provided on a leading end side of the shank and having an outer peripheral portion. The outer peripheral portion includes: a deformation portion configured to be plastically deformed by a torque from a fastening tool; and a space forming portion configured to form a space between the space forming portion and the fastening tool. The bolt is configured such that a maximum torque applied to the deformation portion in a process, in which a part of the deformation portion is plastically deformed by the torque from the fastening tool and is accommodated in the space and the fastening tool is placed in an idle rotation state, is configured to be set to be within a predetermined range.

A bolt in accordance with one or more embodiments includes a head, a shank connected to the head and having a screw portion, and a pintail provided on a leading end of the shank and having an outer peripheral surface. The outer peripheral surface is provided with a plurality of protrusion portions. The bolt is configured such that a maximum torque applied to the plurality of protrusion portions in a process, in which the plurality of protrusion portions receive a torque from a fastening tool and break from the outer peripheral surface and the fastening tool is placed in an idle rotation state, is configured to be set to be within a predetermined range.

DETAILED DESCRIPTION

A bolt according to some embodiments of the present disclosure is described with reference to the drawings.FIG. 1is a view illustrating a state in which a bolt1and a nut2are tightened to a fastened member4by a wrench3in a first embodiment.FIG. 2is a cross-sectional view of a part near a leading end portion14of the bolt1taken along a plane including an axis of the shank11.FIG. 3is a cross-sectional view of the bolt1and the inner plug3A taken along a line inFIG. 1.

The bolt1is made of steel material and includes a cylindrical shank11and a head12provided on one end of the shank11as illustrated inFIG. 1. A male screw portion13is formed on an outer periphery of the other end side of the shank11. A hole14ais formed in the leading end portion14of the shank11. The hole14ais formed so that a cross-sectional shape thereof has a certain shape along a depth direction (an axial direction of the shank11) as illustrated inFIG. 2.

As illustrated inFIG. 3, the hole14ais formed as a dodecagonal hole and an inner plug3A having a hexagonal cross section is inserted in the hole14awhen the bolt1is fastened. A wall portion15forming the hole14ain the leading end portion14has a plurality of deformation portions15A and a plurality of space forming portions15B. When the bolt1is fastened, each deformation portion15A receives a torque from a pressing portion3C of the inner plug3A and is plastically deformed. Each space forming portion15B forms a space14bbetween the space forming portion15B and the inner plug3A inserted in the hole14a. The wall portion15includes 12 deformation portions15A and12space forming portions15B and the inner plug3A includes six pressing portions3C, but only one deformation portion15A and one space forming portion15B are denoted by reference numbers inFIG. 3for simplification of illustration.

The wrench3includes the columnar inner plug3A and a cylindrical outer socket3B. The inner plug3A and the outer socket3B is made of a material having a hardness higher than the material of the bolt1.

Next, a method of tightening the bolt1according to this embodiment to the fastened member4is described.

As illustrated inFIG. 1, in a state in which the bolt1is inserted in the fastened member4and the nut2is screwed with the male screw portion13, the inner plug3A is inserted in the hole14ain the leading end portion14so that the outer socket3B surrounds the outer periphery of the nut2.

The inner plug3A and the outer socket3B are rotated in directions opposite to each other by a driving force from a driving source (not shown) of the wrench3. The inner plug3A is rotated in a rotation direction R as illustrated inFIG. 3. By this rotation, each pressing portion3C of the hexagonal inner plug3A comes into contact with the corresponding deformation portion15A and transfers a torque to the leading end portion14of the shank11. Then, the pressed deformation portion15A is plastically deformed and displaced by the torque of the inner plug3A, the plastically deformed part of each deformation portion15A is accommodated in the space14b, and the inner plug3A rotates idly.

In the bolt1, the maximum torque applied to the plurality of deformation portions15A in the process in which a part of each deformation portion15A is plastically deformed by the torque from the inner plug3A and is accommodated in the corresponding space14band the inner plug3A is placed in an idle rotation state is set within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt1can be tightened to the fastened member4by a desired fastening torque. The setting of the desired fastening torque for the bolt1can be set as appropriate by adjusting the material of the bolt1, the depth of the hole14a, the shape of the deformation portion15A, and the like.

According to the bolt1of this embodiment, the wall portion15forming the hole14ain the leading end portion14of the shank11has the plurality of deformation portions15A and the plurality of space forming portions15B that form the spaces14bbetween the plurality of space forming portions15B and the inner plug3A. A part of each deformation portion15A is plastically deformed by the torque from the inner plug3A and that displacement is accommodated in the corresponding space14b. From the abovementioned configuration, each deformation portion15A can be stably deformed and the inner plug3A can be idly rotated by applying a predetermined torque to each deformation portion15A. As a result, the fastening torque can be stabilized when the bolt1is fastened.

The bolt1of this embodiment has a structure without a pintail, and hence the weight of the bolt1can be decreased and the cost can be reduced. In the bolt1of this embodiment, no waste is generated and workability can be enhanced.

Next, modification examples (modification examples 1-1 to 1-6) of the bolt1according to the first embodiment 1 are described. The same parts as those in the bolt1according to the first embodiment 1 are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

A bolt21according to the modification example 1-1 is described.FIG. 4is a cross-sectional view of the bolt21and an inner plug3D according to the modification example 1-1 corresponding to the cross-sectional view of the bolt1and the inner plug3A taken along the line inFIG. 1.

A hole24ahaving a hexalobular shape is formed in a leading end portion24of the shank11of the bolt21. The inner plug3D has a hexalobular shape in correspondence to the hole24a.

A wall portion25forming the hole24ain the leading end portion24has six deformation portions25A and six space forming portions25B. When the bolt1is fastened, each deformation portion25A receives a torque from a pressing portion3E of the inner plug3D and is plastically deformed. Each space forming portion25B forms a space24bbetween the space forming portion25B and the inner plug3D inserted in the hole24a. The wall portion25forming the hole24ahas six deformation portions25A and six space forming portions25B and the inner plug3D has six pressing portions3E, but only one deformation portion25A, one space forming portion25B, and one pressing portion3E are denoted by reference numbers inFIG. 4for simplification of illustration.

The inner plug3D is rotated in the rotation direction R as illustrated inFIG. 4by the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion3E of the inner plug3D comes into contact with the corresponding deformation portion25A and transfers a torque to the leading end portion24of the shank11. Then, the pressed deformation portion25A is plastically deformed and displaced by the torque of the inner plug3D, the plastically deformed part of each deformation portion25A is accommodated in the space24b, and the inner plug3D rotates idly.

In the bolt21, the maximum torque applied to the plurality of deformation portions25A in the process in which a part of each deformation portion25A is plastically deformed by the torque from the inner plug3D and is accommodated in the corresponding space24band the inner plug3D is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt21can be tightened to the fastened member by a desired fastening torque.

Each deformation portion25A can be stably deformed and the inner plug3D can be idly rotated by applying a predetermined torque to each deformation portion25A also in the bolt21having the abovementioned configuration. As a result, the fastening torque can be stabilized when the bolt21is fastened. The bolt21of this modification example also achieves effects similar to those in the bolt1of the first embodiment.

Next, a bolt31according to the modification example 1-2 is described.FIG. 5is a cross-sectional view of the bolt31and an inner plug3F according to the modification example 1-2 corresponding to the cross-sectional view of the bolt1and the inner plug3A taken along the line inFIG. 1.

A hole34ais formed in a leading end portion34of the shank11of the bolt31. A wall portion35forming the hole34ain the leading end portion34has six inwardly projecting deformation portions35A and six space forming portions35B. Each deformation portions35A are provided on the wall portion35at regular intervals in the circumferential direction of the leading end portion34. When the bolt31is fastened, each deformation portion35A receives a torque from a pressing portion3G of the inner plug3F and is plastically deformed. Each space forming portion35B forms a space34bbetween the space forming portion35B and the inner plug3F inserted in the hole34a. The inner plug3F has six sawtooth-like pressing portions3G. The wall portion35forming the hole34ahas six deformation portions35A and six space forming portions35B and the inner plug3F has six pressing portions3G, but only one deformation portion35A, one space forming portion35B, and one pressing portion3G are denoted by reference numbers inFIG. 5for simplification of illustration.

The inner plug3F is rotated in the rotation direction R as illustrated inFIG. 5by the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion3G of the inner plug3F comes into contact with the corresponding deformation portion35A and transfers a torque to the leading end portion34of the shank11. Then, the pressed deformation portion35A is plastically deformed and displaced by the torque of the inner plug3F, the plastically deformed part of each deformation portion35A is accommodated in the space34b, and the inner plug3F rotates idly.

In the bolt31, the maximum torque applied to the plurality of deformation portions35A in the process in which a part of the deformation portion35A is plastically deformed by the torque from the inner plug3F and is accommodated in the space34band the inner plug3F is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt31can be tightened to the fastened member4by a desired fastening torque.

Each deformation portion35A can be stably deformed and the inner plug3F can be idly rotated by applying a predetermined torque to each deformation portion35A also in the bolt31having the abovementioned configuration. As a result, the fastening torque can be stabilized when the bolt31is fastened. The bolt31of this modification example also achieves effects similar to those in the bolt1of the embodiment.

Next, a bolt41according to the modification example 1-3 is described.FIG. 6is a cross-sectional view of the bolt41and an inner plug3H according to the modification example 1-3 corresponding to the cross-sectional view of the bolt1and the inner plug3A taken along the line inFIG. 1.

A hole44ais formed in a leading end portion44of the shank11of the bolt41. The hole44ahas a cross-sectional shape that is a shape formed by connecting four peak-trough shaped portions formed of a pair of a peak portion and a trough portion. The inner plug3H has a substantially equilateral quadrangle shape.

A wall portion45forming the hole44ain the leading end portion44has a deformation portion45A corresponding to the peak portion of the peak-trough shaped portion and a space forming portion45B corresponding to the trough portion of the peak-trough shaped portion. When the bolt41is fastened, each deformation portion45A receives a torque from a pressing portion31of the inner plug3H and is plastically deformed. Each space forming portion45B forms a space44bbetween the space forming portion45B and the inner plug3H inserted in the hole44a. The wall portion45forming the hole44ahas four deformation portions45A and four space forming portions45B and the inner plug3H has four pressing portions31, but only one deformation portion45A, one space forming portion45B, and one pressing portion31are denoted by reference numbers inFIG. 6for simplification of illustration.

The inner plug3H is rotated in the rotation direction R as illustrated inFIG. 6by the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, the pressing portions31of the inner plug3H comes into contact with all the deformation portions45A and transfers a torque to the leading end portion44of the shank11. Then, each deformation portion45A is plastically deformed and displaced by the torque of the inner plug3D, the plastically deformed part of each deformation portion45A is accommodated in the space44b, and the inner plug3H rotates idly.

In the bolt41, the maximum torque applied to the plurality of deformation portions45A in the process in which a part of each deformation portion45A is plastically deformed by the torque from the inner plug3H and is accommodated in the corresponding space44band the inner plug3D is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt41can be tightened to the fastened member4by a desired fastening torque.

Each deformation portion45A can be stably deformed and the inner plug3H can be idly rotated by applying a predetermined torque to each deformation portion45A also in the bolt41having the abovementioned configuration. As a result, the fastening torque can be stabilized when the bolt41is fastened. The bolt41of this modification example also achieves effects similar to those in the bolt1of the first embodiment.

Next, a bolt51according to the modification example 1-4 is described.FIG. 7Ais a cross-sectional view of a part near a leading end portion54of the bolt51according to the modification example 1-4 taken along a plane including the shaft of the shank11andFIG. 7Bis a cross-sectional view of the bolt51and an inner plug3J according to the modification example 1-4 corresponding to the cross-sectional view of the bolt1and the inner plug3A taken along the line inFIG. 1.

A hole54ais formed in the leading end portion54of the shank11of the bolt51as illustrated inFIG. 7AandFIG. 7B. A wall portion55forming the hole54ain the leading end portion54has eight inwardly projecting deformation portions55A and eight space forming portions55B. Each deformation portion55A is provided on the wall portion55at regular intervals in the circumferential direction of the leading end portion54. The deformation portions55A are provided helically along the axial direction of the shank11. That is, the axis of the deformation portion55A forming a helical shape (helical axis) and the axis of the shank11are coaxially arranged. When the bolt51is fastened, each deformation portion55A receives a torque from a pressing portion3K of the inner plug3J and is plastically deformed. Each space forming portion55B forms a space54bbetween the space forming portion55B and the inner plug3J inserted in the hole54a.

The inner plug3J has eight sawtooth-like pressing portions3K. The pressing portions3K are helically provided so as to correspond to the helical deformation portions55A. The wall portion55forming the hole54ahas six deformation portions55A and six space forming portions55B and the inner plug3J has six pressing portions3K, but only one deformation portion55A, one space forming portion55B, and one pressing portion3K are denoted by reference numbers inFIG. 7AandFIG. 7Bfor simplification of illustration.

The inner plug3J is rotated in the rotation direction R as illustrated inFIG. 7Bby the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion3K of the inner plug3J comes into contact with the corresponding deformation portion55A and transfers a torque to the leading end portion54of the shank11. Then, each deformation portion55A is plastically deformed and displaced by the torque of the inner plug3J, the plastically deformed part of each deformation portion55A is accommodated in the space54b, and the inner plug3J rotates idly.

In the bolt51, the maximum torque applied to the plurality of deformation portions55A in the process in which a part of each deformation portion55A is plastically deformed by the torque from the inner plug3J and is accommodated in the space54band the inner plug3J is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt51can be tightened to the fastened member4by a desired fastening torque.

The deformation portion55A forms a helical shape and the pressing portion3K of the inner plug3J also forms a helical shape, and hence the inner plug3J can be prevented from falling out of the hole54awhen the bolt51is fastened. As a result, the depth of the hole54acan become shallower, and hence the length of bolt51can become shorter and the weight and the cost of the bolt51can be reduced. The fastening torque can be changed by changing the angle of the deformation portion55A forming a helical shape.

Each deformation portion55A can be stably deformed and the inner plug3J can be idly rotated by applying a predetermined torque to each deformation portion55A also in the bolt51having the abovementioned configuration. As a result, the fastening torque can be stabilized when the bolt51is fastened. The bolt51of this modification example also achieves effects similar to those in the bolt1of the first embodiment.

Next, a bolt61according to the modification example 1-5 is described.FIG. 8is a cross-sectional view of a part near a leading end portion64of the bolt61according to the modification example 1-5 taken along a plane including the axis of the shank11.

A hole64ais formed in the leading end portion64of the shank11of the bolt61as illustrated inFIG. 8. The hole64ais tapered in the depth direction. A wall portion forming the hole64ain the leading end portion64has the deformation portions and the space forming portions in any of the first embodiment and the modification examples 1-1 to 1-4. The leading end portion of an inner plug3L is tapered in correspondence to the shape of the hole64a.

According to the bolt61of this modification example, it is possible to easily pull out the inner plug3L from the hole64aafter the bolt61fastened. The bolt61of this modification example achieves effects similar to those in the bolts in the first embodiment 1 and the modification examples 1-1 to 1-4.

Next, a bolt71according to the modification example 1-6 is described.FIG. 9is a cross-sectional view of a part near a leading end portion74of the bolt71according to the modification example 1-6 taken along a plane including the axis of the shank11.

As illustrated inFIG. 9, the leading end portion74is provided in an end portion of the male screw portion13and the length of the leading end portion74in the direction orthogonal to the axis of the shank11is shorter than the diameter of the male screw portion13. A wall portion forming a hole74ain the leading end portion74has the deformation portions and the space forming portions in any of the first embodiment and the modification examples 1-1 to 1-4.

According to the bolt71of this modification example, the male screw portion13is short and hence the nut2can be easily fastened. The bolt71of this modification example achieves effects similar to those in the bolts in the first embodiment and the modification examples 1-1 to 1-4. The hole74ain the leading end portion74may have a linear shape (substantially cylindrical shape) along the axis of the shank11or may be tapered.

Next, a bolt81of a second embodiment of the present disclosure is described with reference toFIG. 10.

FIG. 10is a cross-sectional view of the bolt81and an inner plug3H of the second embodiment corresponding to the cross-sectional view of the bolt1and the inner plug3A taken along the line inFIG. 1. The same parts as those in the bolt41according to the modification example 1-3 of the first embodiment 1 are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

In the wall portion45, a recessed portion45cis formed on the downstream side of each deformation portion45A in the rotation direction R of the inner plug3H.

In this embodiment, the inner plug3H is rotated in the rotation direction R as illustrated inFIG. 10by rotating the inner plug3H and the outer socket3B (FIG. 1) in directions opposite to each other by the driving force from the driving source (not shown) of the wrench3(FIG. 1). By this rotation, each pressing portion31of the inner plug3H comes into contact with the corresponding deformation portion45A and transfers a torque to the leading end portion44of the shank11. Then, each deformation portion45A is plastically deformed and displaced by the torque of the inner plug3H, the plastically deformed part of each deformation portion45A is accommodated in the recessed portion45c, and the inner plug3H rotates idly.

In the bolt81, the maximum torque applied to the plurality of deformation portions45A in the process in which a part of each deformation portion45A is plastically deformed by the torque from the inner plug3H and is accommodated in the corresponding recessed portion45cand the inner plug3H is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt81can be tightened to the fastened member4by a desired fastening torque.

Each deformation portion45A can be stably deformed and the inner plug3H can be idly rotated by applying a predetermined torque to each deformation portion45A also in the bolt81having the abovementioned configuration. As a result, the fastening torque can be stabilized when the bolt81is fastened. The bolt81of this modification example achieves effects similar to those in the bolt1of the first embodiment. The hole44ain the leading end portion44may have a linear shape (substantially cylindrical shape) along the axis of the shank11or may be tapered. The leading end portion44may be provided in an end portion of the male screw portion13and the length of the leading end portion44in the direction orthogonal to the axis of the shank11may be shorter than the diameter of the male screw portion13.

Next, a bolt101of a third embodiment of the present disclosure is described with reference toFIG. 11andFIG. 12. The same parts as the bolt1, the nut2, and the wrench3described in the first embodiment are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

FIG. 11is a view illustrating a state in which the bolt101and the nut2are tightened to the fastened member4by the wrench3in the third embodiment.FIG. 12is a cross-sectional view of the bolt101and an inner socket3M taken along the XII-XII line inFIG. 11.

In the bolt101, a pintail16is provided on a leading end side of the shank11. The pintail16has a dodecagonal shape. When the bolt101is fastened, the pintail16is inserted in the cylindrical inner socket3M. An outer peripheral portion17of the pintail16has 12 deformation portions17A and12space forming portions17B. When the bolt101is fastened, each deformation portion17A receives a torque from a pressing portion3N of the inner socket3M and is plastically deformed. Each space forming portion17B forms a space16abetween the space forming portion17B and the inner socket3M. The pintail16has 12 deformation portions17A and12space forming portions17B and the inner socket3M has 12 pressing portions3N, but only one deformation portion17A, one space forming portion17B, and one pressing portion3N are denoted by reference numbers inFIG. 12for simplification of illustration.

Next, a method of tightening the bolt101according to this embodiment to the fastened member4is described.

As illustrated inFIG. 11, in a state in which the bolt101is inserted in the fastened member4and the nut2is screwed with the male screw portion13, the inner socket3M is inserted in the pintail16and the nut2is inserted in the outer socket3B.

The inner socket3M and the outer socket3B are rotated in directions opposite to each other by the driving force from the driving source (not shown) of the wrench3. The inner socket3M is rotated in the rotation direction R as illustrated inFIG. 12. By this rotation, each pressing portion3N of the inner socket3M comes into contact with the corresponding deformation portion17A and transfers a torque to the pintail16. Then, each deformation portion17A is plastically deformed and displaced by the torque of the inner socket3M, the plastically deformed part of each deformation portion17A is accommodated in the space16a, and the inner socket3M rotates idly.

In the bolt101, the maximum torque applied to the plurality of deformation portions17A in the process in which a part of each deformation portion17A is plastically deformed by the torque from the inner socket3M and is accommodated in the corresponding space16aand the inner socket3M is placed in an idle rotation state is set to be within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt101can be tightened to the fastened member4by a desired fastening torque. In the bolt101, the setting of the desired fastening torque can be set as appropriate by adjusting the material of the bolt101, the length of the pintail16, the shape of the deformation portion17A, and the like.

According to the bolt101of this embodiment, the outer peripheral portion17of the pintail16has the plurality of deformation portions17A and the plurality of space forming portions17B that form the spaces16abetween the plurality of space forming portions17B and the inner socket3M. A part of each deformation portion17A is plastically deformed by the torque from the inner socket3M and that displacement is accommodated in the corresponding space16a. From the abovementioned configuration, each deformation portion17A can be stably deformed and the inner socket3M can be idly rotated by applying a predetermined torque to each deformation portion17A. As a result, the fastening torque can be stabilized when the bolt101is fastened.

The bolt101of this embodiment has a structure in which the pintail16does not fall out, and hence no waste is generated and workability can be enhanced.

Next, modification examples (modification examples 3-1 to 3-6) of the bolt101according to the third embodiment are described. The same parts as those in the bolt101according to the third embodiment are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

A bolt111according to the modification example 3-1 is described.FIG. 13is a cross-sectional view of the bolt111and an inner socket30according to the modification example 3-1 corresponding to the cross-sectional view of the bolt101and the inner socket3M taken along the XII-XII line inFIG. 11.

A pintail26of the bolt111has a hexalobular shape. The inner socket30has a substantially hexalobular shape in correspondence to the pintail26.

An outer peripheral portion27of the pintail26has six deformation portions27A and six space forming portions27B. When the bolt111is fastened, each deformation portion27A receives a torque from a pressing portion3P of the inner socket30and is plastically deformed. Each space forming portion27B forms a space26abetween the space forming portion27B and the inner socket30. The outer peripheral portion27has six deformation portions27A and six space forming portions27B and the inner socket30has six pressing portions3P, but only one deformation portion27A, one space forming portion27B, and one pressing portion3P are denoted by reference numbers inFIG. 13for simplification of illustration.

The inner socket30is rotated in the rotation direction R as illustrated inFIG. 13by the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, the pressing portions3P of the inner socket30comes into contact with all the deformation portions27A and transfers a torque to the pintail26. Then, each deformation portion27A is plastically deformed and displaced by the torque of the inner socket30, the plastically deformed part of each deformation portion27A is accommodated in the space26a, and the inner socket30rotates idly.

In the bolt111, the maximum torque applied to the plurality of deformation portions27A in the process in which a part of each deformation portion27A is plastically deformed by the torque from the inner socket30and is accommodated in the corresponding space16aand the inner socket30is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt111can be tightened to the fastened member4by a desired fastening torque.

Each deformation portion27A can be stably deformed and the inner socket30can be idly rotated by applying a predetermined torque to each deformation portion27A also in the bolt111having the abovementioned configuration. As a result, the fastening torque can be stabilized when the bolt111is fastened. The bolt111of this modification example also achieves effects similar to those in the bolt101of the third embodiment.

Next, a bolt121according to the modification example 3-2 is described.FIG. 14is a cross-sectional view of the bolt121and an inner socket3Q according to the modification example 3-2 corresponding to the cross-sectional view of the bolt101and the inner socket3M taken along the XII-XII line inFIG. 11.

A pintail36of the bolt121has a cylindrical shape. An outer peripheral portion37of the pintail36has six outwardly projecting deformation portions37A and six space forming portions37B. The deformation portions37A are provided on the outer peripheral portion37at regular intervals in the circumferential direction thereof. When the bolt121is fastened, each deformation portion37A receives a torque from a pressing portion3R of the inner socket3Q and is plastically deformed. Each space forming portion37B forms a space36abetween the space forming portion37B and the inner socket3Q. The inner socket3Q has six pressing portions3R. The outer peripheral portion37has six deformation portions37A and six space forming portions37B and the inner socket3Q has six pressing portions3R, but only one deformation portion37A, one space forming portion37B, and one pressing portion3R are denoted by reference numbers inFIG. 14for simplification of illustration.

The inner socket3Q is rotated in the rotation direction R as illustrated inFIG. 14by the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion3R of the inner socket3Q comes into contact with the corresponding deformation portion37A and transfers a torque to the leading end portion34of the shank11. Then, each deformation portion37A is plastically deformed and displaced by the torque of the inner socket3Q, the plastically deformed part of each deformation portion37A is accommodated in the space36a, and the inner socket3Q rotates idly.

In the bolt121, the maximum torque applied to the plurality of deformation portions37A in the process in which a part of the deformation portion37A is plastically deformed by the torque from the inner socket3Q and is accommodated in the space36aand the inner socket3Q is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt121can be tightened to the fastened member by a desired fastening torque.

The deformation portion37A can be stably deformed and the inner socket3Q can be idly rotated by applying a predetermined torque to the deformation portion37A also in the bolt121having the abovementioned configuration. As a result, the fastening torque can be stabilized when the bolt121is fastened. The bolt121of this modification example also achieves other effects similar to those in the bolt101of the third embodiment.

Next, a bolt131according to the modification example 3-3 is described.FIG. 15Ais an explanatory view of a pintail46according to the bolt131of the modification example 3-3 andFIG. 15Bis a cross-sectional view of the bolt131and an inner socket3S according to the modification example 3-3 corresponding to the cross-sectional view of the bolt101and the inner socket3M taken along the XII-XII line inFIG. 11.

An outer peripheral portion47of the pintail46of the bolt131has eight outwardly projecting deformation portions47A and eight space forming portions47B as illustrated inFIG. 15AandFIG. 15B. The deformation portions47A are provided on the outer peripheral portion47at regular intervals in the circumferential direction thereof. The deformation portions47A are helically provided along the axial direction of the shank11. That is, the axis (helical axis) of the deformation portion47A forming a helical shape and the axis of the shank11are coaxially arranged. When the bolt131is fastened, the deformation portion47A receives a torque from a pressing portion3T of the inner socket3S and is plastically deformed. Each space forming portion47B forms a space46abetween the space forming portion47B the inner socket3S.

The inner socket3S has eight pressing portions3T. The pressing portions3T are helically provided so as to correspond to the helical deformation portions47A. The outer peripheral portion47has eight deformation portions47A and eight space forming portions47B and the inner socket3S has eight pressing portions3T, but only one deformation portion47A, one space forming portion47B, and one pressing portion3T are denoted by reference numbers inFIG. 15AandFIG. 15Bfor simplification of illustration.

The inner socket3S is rotated in the rotation direction R as illustrated inFIG. 15Bby the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion3T of the inner socket3S comes into contact with the corresponding deformation portion47A and transfers a torque to the leading end portion54of the shank11. Then, each deformation portion47A is plastically deformed and displaced by the torque of the inner socket3S, the plastically deformed part of each deformation portion47A is accommodated in the space46a, and the inner socket3S rotates idly.

In the bolt131, the maximum torque applied to the plurality of deformation portions47A in the process in which a part of each deformation portion47A is plastically deformed by the torque from the inner socket3S and is accommodated in the space46aand the inner socket3S is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt131can be tightened to the fastened member4by a desired fastening torque.

Each deformation portion47A forms a helical shape and each pressing portion3T of the inner socket3S also forms a helical shape, and hence the inner socket3S can be prevented from falling out of the pintail46when the bolt131is fastened. As a result, the length of the pintail46can become shorter, and hence the length of the bolt131can become shorter and the weight and the cost of the bolt131can be reduced. The fastening torque can be changed by changing the angle of the deformation portion47A forming a helical shape.

Next, a bolt141according to the modification example 3-4 is described.FIG. 16is an explanatory view of a pintail56and an inner socket3U of the bolt141according to the modification example 3-4.

The pintail56of the bolt141is tapered toward the leading end as illustrated inFIG. 16. An outer peripheral portion of the pintail56has the deformation portions and the space forming portions in any of the third embodiment and the modification examples 3-1 to 3-3. An inner peripheral surface of the inner socket3U is tapered in correspondence to the pintail56.

According to the bolt141of this modification example, it is possible to easily remove the inner socket3U from the pintail after the bolt141fastened. The bolt141of this modification example achieves effects similar to those in the bolts in the third embodiment and modification examples 3-1 to 3-3.

Next, a bolt151according to the modification example 3-5 is described.FIG. 17Ais an explanatory view of a pintail66and the inner socket3M of the bolt151according to the modification example 3-5 andFIG. 17Bis an end view of the pintail66.

As illustrated inFIG. 17AandFIG. 17B, the pintail66of the bolt151has a plurality of projection portions66D (Only one projection portion66D is denoted by a reference number inFIG. 17AandFIG. 17B.) on an end surface66C thereof in addition to the configuration in the pintail16of the bolt101of the third embodiment.

When the bolt151is fastened, the inner socket3M is rotated in the rotation direction R, the pressing portion3N of the inner socket3M comes into contact with the deformation portion17A, and a pressing projection3V provided on the inner socket3M comes into contact with each projection portion66D and transfers a torque to the pintail66. Then, the projection portion66D is plastically deformed by the torque from the inner socket3M.

According to the bolt151of this modification example, not only the outer peripheral portion17of the pintail66but also the end surface66C receives the torque of the inner socket3M, and hence the length of the pintail66can become shorter and the length of the bolt151can become shorter. As a result, the weight and the cost of the bolt151can be reduced.

The outer peripheral portion of the pintail66may be the deformation portion and the space forming portion in any of the modification examples 3-1 to 3-3 and may be tapered. The bolt151of this modification example achieves effects similar to those in the bolts in the third embodiment and the modification example 3-1 to 3-4.

Next, a bolt161according to the modification example 3-6 is described.FIG. 18Ais an explanatory view of a pintail76and the inner socket3M of the bolt161according to the modification example 3-6 andFIG. 18Bis an end view of the pintail76of the bolt161.

As illustrated inFIG. 18AandFIG. 18B, the pintail76of the bolt161has an annular recessed portion76dformed in an end surface76C thereof in addition to the configuration in the pintail16of the bolt101of the third embodiment. The pintail76has four pressed portions76E (Only one pressed portion76E is denoted by a reference number inFIG. 18AandFIG. 18B.) that narrows the width of the recessed portion76d. The width of the recessed portion76din the pressed portion76E is smaller than the diameter of a columnar projection3W provided in the inner socket30.

When the bolt161is fastened, the columnar projection3W is inserted in the recessed portion76d, the inner socket3M is rotated in the rotation direction R, each pressing portion3N comes into contact with the corresponding deformation portion17A, and each columnar projection3W comes into contact with the corresponding pressed portion76E and transfers a torque to the pintail76. Then, each pressed portion76E is plastically deformed by the torque from the inner socket3M and each cylindrical projection3W passes through the pressed portion76E.

According to the bolt161of this modification example, not only the outer peripheral portion17of the pintail76but also the end surface76C receives the torque of the inner socket3M, and hence the length of the pintail76can become shorter and the length of the bolt161can become shorter. As a result, the weight and the cost of the bolt161can be reduced.

The outer peripheral portion of the pintail76may be the deformation portion and the space forming portion in any of the modification examples 3-1 to 3-3 and may be tapered. The bolt161of this modification example achieves effects similar to those in the bolts in the third embodiment and the modification example 3-1 to 3-4.

Next, a bolt201of a fourth embodiment of the present disclosure is described with reference toFIG. 19AandFIG. 19B. The same parts as those in the bolt101described in the third embodiment are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

FIG. 19Ais an explanatory view of a pintail18and an inner socket5A of the bolt201according to the fourth embodiment andFIG. 19Bis an end view of the pintail18of the bolt201.

In the bolt201, the pintail18is provided on the leading end side of the shank11and an annular groove portion19is formed between the shank11and the pintail18. The shape of the cross section of the pintail18orthogonal to the axis of the shank11is a dodecagon (non-circular shape) and the pintail18has 12 pressed portions18A on an outer peripheral portion thereof. Eight projection portions (engagement portions)18C are provided on an end surface18B of the pintail18. The inner socket5A has 12 pressing portions5B on an inner periphery thereof and eight pressing projections5C are provided on a bottom thereof. Although 12 pressed portions18A,12projection portions18C, 12 pressing portions5B, and 12 pressing projections5C are provided, only one pressed portion18A, one projection portion18C, one pressing portion5B, and one pressing projection5C are denoted by reference numbers inFIG. 19AandFIG. 19Bfor simplification of illustration.

In this embodiment, the inner socket5A is rotated in the rotation direction R as illustrated inFIG. 19Bby rotating the inner socket5A and the outer socket3B (FIG. 1) in directions opposite to each other by the driving force from the driving source (not shown) of the wrench3(FIG. 1). By this rotation, the pressing portion5B and the pressing projection5C of the inner socket5A come into contact with all the pressed portions18A and projection portions18C and transfer a torque to the pintail18. Then, the groove portion19breaks by the torque of the inner socket5A, the pintail18is removed from the shank11, and the inner socket5A rotates idly.

In the bolt201, the maximum torque applied to the groove portion19in the process in which each pressed portion18A and each projection portion18C of the pintail18receive the torque from the inner socket5A, the groove portion19breaks, and the pintail18is placed in a state of being removed from the shank11is set to be within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt201can be tightened to the fastened member4by a desired fastening torque. The setting of the desired fastening torque in the bolt201can be set as appropriate by adjusting the material of the bolt201, the cross-sectional shape of the pintail18, the shape of the projection portion18C, and the like.

According to the bolt201having the abovementioned configuration, the torque is transferred to the pintail18by the plurality of projection portions18C of the end surface18B in addition to the plurality of pressed portions18A of the outer peripheral portion of the pintail18, and hence the length of the pintail18can become shorter. As a result, the waste and the cost can be reduced.

Next, modification examples (modification examples 4-1 to 4-2) of the bolt201according to the fourth embodiment are described. The same parts as those in the bolt201according to the fourth embodiment are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

A bolt211according to the modification example 4-1 is described.FIG. 20Ais an explanatory view of a pintail28and an inner socket5D of the bolt211according to the modification example 4-1 andFIG. 20Bis an end view of the pintail28of the bolt211.

In the bolt211, the pintail28is provided on the leading end side of the shank11and the annular groove portion19is formed between the shank11and the pintail28. The shape of the cross section of the pintail28orthogonal to the axis of the shank11is a dodecagon (non-circular shape) and the pintail28has 12 first pressed portions28A on an outer peripheral portion. A hole28c, which opens on the end surface28B and of which cross section orthogonal to the axis of the shank11is a hexagon (non-circular shape), is formed in the pintail28. The part forming each corner of the hexagonal hole28cof the pintail28serves as a second pressed portion28D. The inner socket5D has 12 first pressing portions5E on an inner periphery thereof and has a hexagonal plug5F provided in the inside thereof. The plug5F has six second pressing portions5G and is inserted in the hole28cwhen the bolt211is fastened.

The plurality of the first pressed portions28A, the plurality of second pressed portions28D, the plurality of first pressing portions5E, and the plurality of second pressing portions5G are provided, but only one first pressed portion28A, one second pressed portion28D, one first pressing portion5E, and one second pressing portion5G are denoted by reference numbers inFIG. 20AandFIG. 20Bfor simplification of illustration.

The inner socket5D is rotated in the rotation direction R as illustrated inFIG. 20Bby the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each first pressing portion5E and each second pressing portion5G of the inner socket5D come into contact with the corresponding first pressed portion28A and the corresponding second pressed portion28D and transfer a torque to the pintail28. Then, the groove portion19breaks by the torque of the inner socket5D, the pintail28is removed from the shank11, and the inner socket5D rotates idly.

In the bolt211, the maximum torque applied to the groove portion19in the process in which each first pressed portion28A and each second pressed portion28D of the pintail28receive the torque from the inner socket5D, the groove portion19breaks, and the pintail28is placed in a state of being removed from the shank11is set to be within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt211can be tightened to the fastened member4by a desired fastening torque.

According to the bolt211having the abovementioned configuration, the torque is transferred to the pintail28by the plurality of second pressed portions28D in addition to the plurality of first pressed portions28A of the outer peripheral portion of the pintail28and hence the length of the pintail28can become shorter. As a result, the waste and the cost can be reduced.

A bolt221according to the modification example 4-2 is described.FIG. 21Ais an explanatory view of a pintail38and an inner socket5H of the bolt221according to the modification example 4-2 andFIG. 21Bis an end view of the pintail38of the bolt221.

In the bolt221, the pintail38is provided on the leading end side of the shank11and the annular groove portion19is formed between the shank11and the pintail38. The shape of the cross section of the pintail38orthogonal to the axis of the shank11is a dodecagon (non-circular shape) and the pintail38has 12 first pressed portions38A on an outer peripheral portion. A hole38c, which opens on an end surface38B and of which cross section orthogonal to the axis of the shank11is a hexagon (non-circular shape), is formed in the pintail38. The portion forming each corner of the hexagonal hole38cof the pintail38serves as a second pressed portion38D. Eight projection portions (engagement portions)38E are provided on the end surface38B of the pintail38.

The inner socket5H has 12 first pressing portions51on an inner periphery thereof and has a hexagonal plug5J and eight pressing projections5K provided in the inside thereof. The plug5J has six second pressing portions5L and is inserted in the hole38cwhen the bolt221is fastened.

The plurality of the first pressed portions38A, the plurality of second pressed portions38D, the plurality of projection portions38E, the plurality of first pressing portions5E, the plurality of second pressing portions5L, and the plurality of pressing projections5K are provided, but only one first pressed portion38A, one second pressed portion38D, one projection portion38E, one first pressing portion5E, one second pressing portion5L, and one pressing projection5K are denoted by reference numbers inFIG. 21AandFIG. 21Bfor simplification of illustration.

The inner socket5H is rotated in the rotation direction R as illustrated inFIG. 21Bby the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each first pressing portion5E, each second pressing portion5L, and each pressing projection5K of the inner socket5H come into contact with the corresponding first pressed portion38A, the corresponding second pressed portion38D, and the corresponding projection portion38E and transfer a torque to the pintail38. Then, the groove portion19breaks by the torque of the inner socket5H, the pintail38is removed from the shank11, and the inner socket5H rotates idly.

In the bolt221, the maximum torque applied to the groove portion19in the process in which each first pressed portion38A, each second pressed portion38D, and each projection portion38E of the pintail38receive the torque from the inner socket5H, the groove portion19breaks, and the pintail38is placed in a state of being removed from the shank11is set to be within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt221can be tightened to the fastened member4by a desired fastening torque.

According to the bolt221having the abovementioned configuration, the torque is transferred to the pintail38by the plurality of second pressed portions38D and the plurality of projection portions38E of the end surface38B in addition to the plurality of first pressed portions38A of an outer peripheral portion of the pintail38, and hence the length of the pintail38can become shorter. As a result, the waste and the cost can be reduced.

In the fourth embodiment and the modification examples thereof, the shapes of the cross sections of the pintails18,28, and38orthogonal to the axis of the shank11have dodecagonal shapes, but may have a hexagonal or a hexalobular shape. In the same manner, the shapes of the cross sections of the holes28cand38cformed in the pintails28and38orthogonal to the axis of the shank11are hexagons, but may be dodecagonal hole shapes or hexalobular shapes.

Next, a bolt301of a fifth embodiment of the present disclosure is described with reference toFIG. 22AandFIG. 22B. The same parts as those described in the bolt1of the first embodiment 1 are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

FIG. 22Ais a cross-sectional view of a part near a leading end portion of the bolt301according to the fifth embodiment taken along a plane including the axis of the shank11andFIG. 22Bis a cross-sectional view of the bolt301and an inner plug6A according to the fifth embodiment corresponding to the cross-sectional view of the bolt1and the inner socket3A taken along the line inFIG. 1.

A hole22ais formed in a leading end portion22of the shank11of the bolt301. Eight inwardly projecting protrusion portions22C are provided on a wall surface22bof the hole22a. The protrusion portions22C are provided on the wall surface22bat regular intervals in the circumferential direction of the leading end portion22. When the bolt301is fastened, each protrusion portion22C receives a torque from a pressing portion6B of the inner plug6A and breaks from the wall surface22b. Eight protrusion portions22C are provided on the wall surface22bof the hole22aand the inner plug6A has eight pressing portions6B, but only one protrusion portion22C and one pressing portion6B are denoted by reference numbers inFIG. 22AandFIG. 22Bfor simplification of illustration.

In this embodiment, the inner plug6A is rotated in the rotation direction R as illustrated inFIG. 22Bby rotating the inner plug6A and the outer socket3B (FIG. 1) in directions opposite to each other by the driving force from the driving source (not shown) of the wrench3(FIG. 1). By this rotation, each pressing portion6B of the inner plug6A comes into contact with the corresponding protrusion portion22C and transfers a torque to the leading end portion34of the shank11. Then, each protrusion portion22C breaks from the wall surface22bby the torque of the inner plug6A and the inner plug6A rotates idly.

In the bolt301, the maximum torque applied to the plurality of protrusion portions22C in the process in which the plurality of protrusion portions22C receives a torque from the inner plug6A and breaks from the wall surface22band the inner plug6A is placed in an idle rotation state is set to be within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt301can be tightened to the fastened member4by a desired fastening torque. The setting of the desired fastening torque can be set as appropriate by adjusting the material of the bolt301, the size of the protrusion portion22C, and the like.

According to the bolt301of this embodiment, the amount of waste can be smaller than that in the case in which the desired fastening torque is acquired by breaking the pintail. Thus, risks caused by falling wastes can be reduced when the bolt301is used at a high place. The bolt301has a structure without a pintail, and hence the weight of the bolt301can be decreased and the cost can be reduced.

Next, modification examples (modification examples 5-1 to 5-3) of the bolt301according to the fifth embodiment are described. The same parts as those in the bolt301according to the fifth embodiment are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

A bolt311according to the modification example 5-1 is described.FIG. 23Ais a cross-sectional view of a part near a leading end portion32of the bolt311according to the modification example 5-1 taken along a plane including the shaft of the shank11andFIG. 23Bis a cross-sectional view of the bolt311and an inner plug6C according to the modification example 5-1 corresponding to the cross-sectional view of the bolt1and the inner socket3A taken along the line inFIG. 1.

A hole32ais formed in the leading end portion32of the shank11of the bolt311. Eight inwardly projecting protrusion portions32C are provided on a wall surface32bof the hole32a. The protrusion portions32C are provided on the wall surface32bat regular intervals in the circumferential direction of the leading end portion32. The protrusion portions32C are helically provided along the axial direction of the shank11. That is, the axis (helical axis) of the protrusion portion32C forming a helical shape and the axis of the shank11are coaxially arranged. When the bolt311is fastened, each protrusion portion32C receives a torque from a pressing portion6D of the inner plug6C and breaks from the wall surface32b.

The inner plug6C has eight pressing portions6D. The pressing portions6D are helically provided so as to correspond to the helical protrusion portions32C. Eight protrusion portions32C are provided on the wall surface32bof the hole32aand the inner plug6C has eight pressing portions6D, but only one protrusion portion32C and one pressing portion6B are denoted by reference numbers inFIG. 23AandFIG. 23Bfor simplification of illustration.

The inner plug6C is rotated in the rotation direction R as illustrated inFIG. 23Bby the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion6D of the inner plug6C comes into contact with the corresponding protrusion portion32C and transfers a torque to the leading end portion32of the shank11. Then, each protrusion portion32C breaks from the wall surface32bby the torque of the inner plug6C and the inner plug6C rotates idly.

The maximum torque applied to the plurality of protrusion portions32C in the process in which each protrusion portion32C receives a torque from the inner plug6C and breaks from the wall surface32band the inner plug6C is placed in an idle rotation state is set to be within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt311can be tightened to the fastened member4by a desired fastening torque.

Each protrusion portion32C forms a helical shape and each pressing portion6D of the inner plug6C also forms a helical shape, and hence the inner plug6C can be prevented from falling out of the hole32awhen the bolt311is fastened. As a result, the depth of the hole32acan be reduced, and hence the length of the bolt311can become shorter and the weight and the cost of the bolt311can be reduced. The fastening torque can be changed by changing the angle forming the helical shape of each protrusion portion32C. The bolt311having the abovementioned configuration achieves effects similar to those in the bolt301of the fifth embodiment.

A bolt321according to the modification example 5-2 is described.FIG. 24Ais an explanatory view of a pintail42of the bolt321according to the modification example 5-2 andFIG. 24Bis a cross-sectional view of the bolt321and an inner socket6E according to the modification example 5-2 corresponding to the cross-sectional view of the bolt101and the inner socket3M taken along the XII-XII line inFIG. 11.

In the bolt321, the pintail42is provided on the leading end side of the shank11. The pintail42is inserted in the cylindrical inner socket6E when the bolt321is fastened. On an outer peripheral surface42A of the pintail42,12outwardly projecting protrusion portions42B are provided. The protrusion portions42B are provided on the outer peripheral surface42A of the pintail42at regular intervals in the circumferential direction of the pintail42. When the bolt321is fastened, each protrusion portion42B receives a torque from each pressing portion6F of the inner socket6E and breaks from the outer peripheral surface42A. The pintail42has 12 protrusion portions42B and the inner socket6E has 12 pressing portions6F, but only one protrusion portion42B and one pressing portion6F are denoted by reference numbers inFIG. 24AandFIG. 24Bfor simplification of illustration.

The inner socket6E is rotated in the rotation direction R as illustrated inFIG. 24Bby the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion6F of the inner socket6E comes into contact with the corresponding protrusion portion42B and transfers a torque to the pintail42. Then, each protrusion portion42B breaks from the outer peripheral surface42A by the torque of the inner socket6E and the inner socket6E rotates idly.

In the bolt321, the maximum torque applied to the plurality of protrusion portions42B in the process in which each protrusion portion42B receives a torque from the inner socket6E and breaks from the outer peripheral surface42A and the inner socket6E is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt321can be tightened to the fastened member4by a desired fastening torque.

The bolt321of this modification example achieves effects similar to those in the bolt301according to the fifth embodiment.

Next, a bolt331according to the modification example 5-3 is described.FIG. 25Ais an explanatory view of a pintail52of the bolt331according to the modification example 5-3 andFIG. 25Bis a cross-sectional view of the bolt331and an inner socket6G according to the modification example 5-3 corresponding to the cross-sectional view of the bolt101and the inner socket3M taken along the XII-XII line inFIG. 11.

Eight outwardly projecting protrusion portions52B are provided on an outer peripheral surface52A of the pintail52of the bolt331as illustrated inFIG. 25AandFIG. 25B. The protrusion portions52B are provided on the outer peripheral surface52A at regular intervals in the circumferential direction thereof. The protrusion portions52B are helically provided along the axial direction of the shank11. That is, the axis (helical axis) forming a helical shape of the protrusion portion52B and the axis of the shank11are coaxially arranged. When the bolt331is fastened, each protrusion portion52B receives a torque from a pressing portion6H of the inner socket6G and breaks from the outer peripheral surface52A.

The inner socket6G has eight pressing portions6H. The pressing portions6H are helically provided so as to correspond to the helical protrusion portions52B. Eight protrusion portions52B are provided on the outer peripheral surface52A and the inner socket6G has eight pressing portions6H, but only one protrusion portion52B and one pressing portion6H are denoted by reference numbers inFIG. 25AandFIG. 25Bfor simplification of illustration.

The inner socket6G is rotated in the rotation direction R as illustrated inFIG. 25Bby the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion6H of the inner socket6G comes into contact with the corresponding protrusion portion52B and transfers a torque to the pintail52. Then, each protrusion portion52B breaks from the outer peripheral surface52A by the torque of the inner socket6G and the inner socket6G rotates idly.

In the bolt331, the maximum torque applied to the plurality of protrusion portions52B in the process in which each protrusion portion52B receives a torque from the inner socket6G and breaks from the outer peripheral surface52A and the inner socket6G is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt331can be tightened to the fastened member4by a desired fastening torque.

Each protrusion portion52B forms a helical shape and each pressing portion6H of the inner socket6G also forms a helical shape, and hence the inner socket6G can be prevented from falling out of the pintail52when the bolt331is fastened. As a result, the length of the pintail52can become shorter, and hence the length of the bolt331can become shorter and the weight and the cost of the bolt331can be reduced. The fastening torque can be changed by changing the angle forming a helical shape of the protrusion portion52B.

The bolt331having the abovementioned configuration achieves effects similar to those in the bolt301of the fifth embodiment. In the fifth embodiment and the modification example 5-1, the shapes of the holes22aand32ain the leading end portions22and32are linear shapes (substantially cylindrical shapes) along the axis of the shank11, but may be tapered shapes. In the same manner, in the modification examples 5-2 and 5-3, the shapes of the pintails42and52are linear shapes (substantially cylindrical shapes) along the axis of the shank11, but may be tapered shapes. In the fifth embodiment and the modification example 5-1, each length of the leading end portions22and32in the direction orthogonal to the axis of the shank11may be shorter than the diameter of the male screw portion13in the same manner as the bolt71according to the modification example 1-6. As illustrated inFIG. 26, a plurality of end surface protrusion portions42D may be provided on an end surface42C of the pintail42of the bolt321and the plurality of end surface protrusion portions42D may be broken in addition to the plurality of protrusion portions42B when the bolt321fastened. As a result, the pintail42can become shorter.

Next, a bolt401of a sixth embodiment of the present disclosure is described with reference toFIG. 27AandFIG. 27B. The same parts as those in the bolt1described in the first embodiment are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

FIG. 27Ais a cross-sectional view of a part near a leading end portion23of the bolt401according to the sixth embodiment taken along a plane including the shaft of the shank11andFIG. 27Bis a cross-sectional view of the bolt401and an inner plug7A according to the sixth embodiment corresponding to the cross-sectional view of the bolt1and the inner socket3A taken along the line inFIG. 1.

A hexalobular hole23ais formed in the leading end portion23of the shank11of the bolt401. The inner plug7A has a hexalobular shape in correspondence to the hole23a.

A wall portion23B forming the hole23ain the leading end portion23has six pressed portions23C and six extension portions23D. When the bolt401is fastened, each pressed portion23C receives a torque from a pressing portion7B of the inner plug7A and is pushed outward. Each extension portion23D is plastically deformed and extended by the torque from the inner plug7A. The wall portion23B forming the hole23ahas six pressed portions23C and six extension portions23D and the inner plug7A has six pressing portions7B, but only one pressed portion23C, one extension portion23D, and one pressing portion7B are denoted by reference numbers inFIG. 27AandFIG. 27Bfor simplification of illustration.

In this embodiment, the inner plug7A and the outer socket3B (FIG. 1) are rotated in directions opposite to each other by the driving force from the driving source (not shown) of the wrench3(FIG. 1). The inner plug7A is rotated in the rotation direction R as illustrated inFIG. 27B. By this rotation, each pressing portion7B of the inner plug7A comes into contact with the corresponding pressed portion23C and transfers a torque to the leading end portion23of the shank11. Then, each pressed portion23C is pressed by the corresponding pressing portion7B. Consequently, each extension portion23D is plastically deformed and extended, each pressed portion23C is extruded outward, the entire leading end portion23is deformed so as to expand, and the inner plug7A rotates idly. As a result, the shape of the leading end portion23of the bolt401expands as illustrated inFIG. 28.

In the bolt401, the maximum torque applied to the pressed portion23C in the process in which each pressed portion23C receives a torque from the inner plug7A and is extruded outward, the entire shape of the leading end portion23expands in the direction orthogonal to the axis of the shank11, and the inner plug7A is placed in an idle rotation state is set to be within a predetermined range. The predetermined range corresponds to a desired fastening torque range. As a result, the bolt401can be tightened to the fastened member4by a desired fastening torque. The setting of the desired fastening torque in the bolt401can be set as appropriate by adjusting the material of the bolt401, the depth of the hole23a, the shapes of each pressed portion23C and each extension portion23D, and the like.

The maximum length of the leading end portion23in the direction orthogonal to the axis of the shank11after the expansion of the shape of the leading end portion23is longer than the inner diameter of the nut2. Thus, according to the bolt401of this embodiment, loosening and falling of the nut2can be prevented after the bolt401is fastened. The bolt401of this embodiment has a structure without a pintail, and hence the weight of the bolt401can be decreased and the cost can be reduced. In the bolt401of this embodiment, no waste is generated and workability can be enhanced.

Next, modification examples (modification examples 6-1 to 6-3) of the bolt401according to the sixth embodiment are described. The same parts as those in the bolt401according to the sixth embodiment are denoted by the same reference numbers and description thereof is omitted. Only the different parts are described.

A bolt411according to the modification example 6-1 is described.FIG. 29is a cross-sectional view of the bolt411and an inner plug7C according to the modification example 6-1 corresponding to the cross-sectional view of the bolt1and the inner socket3A taken along the line inFIG. 1.

A hole33ais formed in a leading end portion33of the shank11of the bolt411. A wall portion33B forming the hole33ain the leading end portion33has two inwardly projecting pressed portions33C and two extension portions33D. Each pressed portion33C receives a torque from a pressing portion7D of the inner plug7C and is pushed outward when the bolt411is fastened. Each extension portion33D is plastically deformed and extended by the torque from the inner plug7C.

The inner plug7C is rotated in the rotation direction R as illustrated inFIG. 29by the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion7D of the inner plug7C comes into contact with the corresponding pressed portion33C and transfers a torque to the leading end portion33of the shank11. Then, each pressed portion33C is pressed by each pressing portion7D. Consequently, each extension portion33D is plastically deformed and extended, each pressed portion33C is extruded outward, the entire leading end portion33is deformed so as to expand, and the inner plug7C rotates idly. As a result, a part of the shape of the leading end portion33of the bolt411expands.

In the bolt411, the maximum torque applied to the pressed portion33C in the process in which each pressed portion33C receives a torque from the inner plug7C and is extruded outward, a part of the shape of the leading end portion33expands in the direction orthogonal to the axis of the shank11, and the inner plug7C is placed in an idle rotation state is set to be within a predetermined range. As a result, the bolt411can be tightened to the fastened member4by a desired fastening torque.

The bolt411of this modification example also achieves effects similar to those in the bolt401of the sixth embodiment.

Next, a bolt421according to the modification example 6-2 is described.FIG. 30is a cross-sectional view of the bolt421and an inner plug7E according to the modification example 6-2 corresponding to the cross-sectional view of the bolt1and the inner socket3A taken along the line inFIG. 1.

A hexagonal hole43ais formed in a leading end portion43of the shank11of the bolt421. A wall portion43B forming the hole43aof the leading end portion43has six pressed portions43C. Each pressed portion43C is located on the downstream side of each corner portion of the hexagonal hole43ain the rotation direction R of the inner plug7E. The inner plug7E has a hexagonal cross section and a pressing portion7F that presses each pressed portion43C. A groove43eextending from an end surface of the leading end portion43toward the head12side is formed in an outer peripheral surface43D of the leading end portion43at a location corresponding to each corner portion of the hole43a. The leading end portion43has six pressed portions43C and six grooves43eand the inner plug7E has six pressing portions7E, but only one pressed portion43C, one groove43e, and one pressing portion7F are denoted by reference numbers inFIG. 30for simplification of illustration.

The inner plug7E is rotated in the rotation direction R as illustrated inFIG. 29by the driving force from the driving source (not shown) of the wrench3(FIG. 1) also in this modification example. By this rotation, each pressing portion7F of the inner plug7E comes into contact with the corresponding pressed portion43C and transfers a torque to the leading end portion43of the shank11. Then, each pressed portion43C is pressed by the corresponding pressing portion7F. Consequently, the leading end portion43breaks along each groove43e, each pressed portion43C is extruded outward, the entire leading end portion43is deformed so as to expand, and the inner plug7C rotates idly. As a result, the shape of the leading end portion43of the bolt421expands.

The bolt421of this modification example also achieves effects similar to those in the bolt401of the sixth embodiment.

Next, a bolt431according to the modification example 6-3 is described.FIG. 31Ais a view illustrating a leading end portion53of the bolt431according to the modification example 6-3 in a state before fastening andFIG. 31Bis a view illustrating the leading end portion53of the bolt431according to the modification example 6-3 in a state after fastening.

A hole53ais formed in the leading end portion53of the shank11of the bolt431. The screw portion13is not formed on the outer periphery of the leading end portion53. The maximum length of the leading end portion53in the direction orthogonal to the axis of the shank11after the expansion of the shape of the leading end portion53is shorter than the inner diameter of the nut2as illustrated inFIG. 31B. As a result, it is possible to easily remove the nut2according to the bolt431according to this modification example.

The above-mentioned embodiments of the present disclosure is merely exemplified for description of the present disclosure and is not intended to limit the scope of the present disclosure to only those described in the embodiments. A person skilled in the art could embody the present disclosure in other various modes without departing from the gist of the present disclosure.

For example, in the bolt1of the first embodiment, an outer peripheral surface14B of the leading end portion14may have a dodecagonal shape and may serve as a torque transfer portion that receives a torque from a removal tool when the bolt1is removed as illustrated inFIG. 32. As a result, the shape of the head12can be simplified.

An additional pintail86serving as a torque transfer portion that receives a torque from the removal tool when the bolt101is removed may be provided on the leading end of the pintail16of the bolt101of the third embodiment as illustrated inFIG. 33. As a result, the shape of the head12can be simplified. When the bolt101is fastened, the pintail86may be used as a torque transfer portion when the bolt101is removed and the pintail16may be used as a torque transfer portion that receives a torque from the removal tool.