JP4701253B2 - Bolt and fastener using the same - Google Patents

Description

  The present invention has a loosening prevention function and is excellent in fatigue strength, so that various mechanical devices, iron bridges, buildings, construction machines, various transport equipment, electrical products, glasses, etc. The present invention relates to a bolt suitably used for a joint and a fastener using the bolt.

Usually, a plurality of bolts are used at the same location, and it is hardly considered that they are damaged during use unless they are loosened. In addition, the bolt has an excellent feature that the taper effect (wedge effect) of the screw enables powerful tightening even with thick members and can be easily loosened with a simple tool even when tightened. ing. On the other hand, even if it is tightened, the nut or bolt rotates backward during a long period of use, causing the phenomenon of “loosening”. Once loosening occurs, the repeated stress will continue until the part is retightened. As a result, an excessive stress is applied to the bolt, and the bolt is easily broken.
In particular, in screw fasteners (mainly bolts and nuts) used for moving parts or joints of members that receive vibration from the outside, even if they are properly tightened at the beginning, It was inevitable that the bolts were loosened by stress, and it was necessary to retighten them during the period of use.
Therefore, in order to solve these problems, various bolts having a function of preventing loosening and methods for manufacturing the same have been researched and developed in recent years.
For example, as a kind of double nuts and bolts, as in (Patent Document 1), coarse and fine screws are machined in the same place, and the coarse nuts are fitted inside and the fine nuts are fitted to the outside. Therefore, a bolt and nut fastening system that is extremely difficult to loosen has been proposed.
Further, (Patent Document 2) proposes a screw that is very difficult to loosen with only a single nut by forming the pitch of the female screw larger than the pitch of the male screw.
On the other hand, there are very few effective measures for improving the fatigue strength of bolts. For example, Patent Document 3 discloses that a male screw fitted to a female screw is shaped into a taper shape in the direction of a tensile force. A threaded joint with improved characteristics has been proposed.
Japanese Patent No. 3770320 WO2006 / 100766 Japanese Patent Publication No.56-53651

However, the above conventional technique has the following problems.
In (1) (Patent Document 1), since the double nut is used, not only the weight of the product becomes heavier, but the work man-hours required for fastening the nut increase, and it is avoided from the user. However, there was a problem that there is a case where it is limited.
In addition, such a double nut / bolt fastening system has an advantage that the screw fastening portion does not loosen when a repeated load is applied, but the bolt itself does not have any measures to improve fatigue strength. We could not expect the advantage of reducing the number of bolts or securing more safety than screw fasteners.
(2) In addition, high-strength bolts that do not cause welding distortion, are easy to work in high places, and can be disassembled are used for fixing steel structures. It had the subject that a crack generate | occur | produced. However, in the fastening system of double nuts and bolts as in (Patent Document 1), since the fatigue strength of the bolt itself is not different from the conventional one, it is desired to improve the fatigue strength of the bolt from the viewpoint of delayed fracture and stress corrosion cracking. It was.
(3) (Patent Document 2) is very easy to loosen with only a single nut and is excellent in workability, but sufficient improvement has not been made for improving fatigue strength.
That is, since the bolt (male screw) pitch is smaller than the nut (female screw) pitch, a compressive stress is generated at the bottom of the screw thread valley in a normal state. Therefore, when a tensile stress is applied from the outside, this compressive stress is applied. The tensile stress cancels out, the effect of external stress is suppressed, and fatigue strength is improved, but the bolt and nut pitches are set for the purpose of preventing loosening. There were no advantages such as reducing the number of bolts or securing more safety than the current screw fasteners.
(4) In the screw joint of (Patent Document 3), although fatigue strength can be improved, no consideration has been given to preventing loosening.
In other words, although the bolt itself is excellent in fatigue strength, since the screw fastening portion is loosened by the repeated load, the bolt is more than the current screw fastener when used in locations where repeated load (vibration) is applied. We could not expect the advantage of reducing the number or securing more safety.
(5) As described above, since the loosening of the bolt occurs at a place where a repeated load (vibration) is applied, the screw fastener originally has the function of preventing the loosening and at the same time, the fatigue strength. Although improvement is desired, in screw fasteners that have been sufficiently fastened, research on prevention of bolt breakage has been conducted because the load ratio of the external force of the bolt is only about 1/3 to 1/5. The importance of research on prevention has not been investigated for screw fasteners that have sufficient functions to prevent loosening and improve fatigue strength.
Looseness is difficult to occur, but as long as bolts with insufficient strength or bolts with sufficient strength that are susceptible to loosening are used, the number and dimensions of the bolts cannot be reduced. However, it has a problem that it lacks practicality and reliability due to lack of design freedom and man-hours for drilling and bolt tightening.

  The present invention solves the above-mentioned conventional problems, and has excellent productivity in terms of mass productivity, and has an excellent anti-loosening function and a fastening force that are difficult to loosen even when subjected to repeated loads (vibrations), and a greatly improved fatigue strength. , Providing bolts that can realize superior safety and reliability that could not be obtained with conventional screw fasteners, using bolts with a simple configuration, fewer parts, and the number of bolts and nuts used In addition to significantly reducing the size and size of the product, it is possible not only to reduce the size and weight of the product, but also to reduce the cost of the product by reducing the man-hours required for drilling and tightening bolts. It is an object of the present invention to provide a fastener having excellent practicality capable of remarkably improving flexibility and assembly workability.

In order to solve the above-described conventional problems, the bolt of the present invention and the fastener using the bolt have the following configurations.
Bolt according to claim 1 of the present invention includes a male screw portion of the pitch p _b which is formed on at least the tip portion of the bolt shank, the bolt head side or bolt a cylindrical portion of the threads of the male threaded portion A taper part in which a part of the top part is removed and a screw thread outer diameter is reduced toward the bolt head side or the bolt cylinder part side, and the bolt head side or the bolt cylinder part side from the minimum diameter part of the taper part slowly a and an incomplete thread removing unit formed by enlarged arcuately, the towards, the female screw is fastened screwed with the male screw portion and the pitch p _b of the male threaded portion The pitch _pn has a configuration in which 0.003 ≦ (p _n −p _b ) / p _b ≦ 0.05.
With this configuration, the following effects can be obtained.
(1) Taper whose outer diameter (nominal diameter) is reduced toward the bolt head side or the bolt cylindrical part side by removing a part of the top of the screw thread on the bolt head side or the bolt cylindrical part side of the male screw part. Since the height of each screw thread of the taper part screwed with the female screw gradually decreases in inverse proportion to the surface pressure to be shared, the load sharing of each screw thread of the taper part is uniform. When the female screw is screwed, it is possible to alleviate the tension and bending stress from concentrating on the bottom of the threaded portion of the taper portion near the end face of the female screw on the bolt head side or the bolt cylindrical part side (inner side). The fatigue strength can be greatly improved.
(2) Normally, stress concentration is likely to occur in the incomplete screw portion formed at the beginning of the male screw portion, but the circle gradually increases from the minimum diameter portion of the taper portion toward the bolt head side or the bolt cylindrical portion side. By forming the incomplete screw removal part by expanding the diameter in an arc shape, even if the taper part is formed, stress concentration hardly occurs in the incomplete screw removal part, and the fatigue strength improvement effect by the taper part can be maintained. it can.
(3) the pitch p _b and the pitch p _n of the female screw which is fastened screwed with the male screw portion of the male screw _{portion, 0.003 ≦ (p n -p b} ) / p b ≦ 0.05 relation by it, the pitch p _n of the female screw becomes larger than the pitch p _b of the male screw portion, a force to widen the distance between threads of the male threaded portion is screwed state, against the force Based on the force, an appropriate frictional force is generated between the male screw part and the screw thread of the nut, enabling the female screw to be screwed and tightened, and giving a large resistance in the loosening direction. Even if fluctuating stress is applied, an excellent loosening prevention function can be maintained. As a result, it is possible to reliably suppress the occurrence of loosening due to external force over a long period of use, prevent troubles associated with loosening, and have excellent reliability and maintainability.
(4) Although the tension or bending stress is not concentrated on the bottom of the thread valley near the end face on the inner side of the female screw by the action of the taper portion, even if tensile stress is applied to the bolt from the outside, the pitch p of the male screw portion _b is smaller than the pitch p _n of the female screw, in the normal (stationary) state because the compression stress occurs in the thread root of the male thread portion, sacrificed compressive stress this tensile stress phase, to ensure the effects of external stress It can be suppressed, the resistance to repeated fluctuating stress, which is the main cause of fatigue failure, can be greatly improved, and it can have an excellent anti-loosening function and fatigue strength.

Here, the bolt has a bolt head, and includes a hexagon bolt, a square bolt, an eye bolt, a square root round head bolt, a flat head bolt, a butterfly bolt, a foundation bolt, a hexagon socket head bolt, etc. Examples of parts that are formed with no bolt head include implant bolts and U bolts. The female screw to be screwed to the bolt is generally a nut, but this bolt can also be used as an embedded bolt. In this case, as the female screw, a female screw member or a joint portion embedded in the joint portion. The female screw part etc. which were formed in are used.
There is no particular restriction on the material of the bolt, and the concept can be applied to all solid materials regardless of metal or non-metal. However, particularly effective are considered to be steel materials, soft metals such as copper, aluminum, titanium and magnesium, and alloys thereof.
Examples of the cross-sectional shape of the screw thread of the male screw part include a triangular screw, a trapezoidal screw, a square screw, a saw blade screw, and a round screw.
Bolt proportion to the pitch p _b of the pitch difference p _n -p _b of the bolt and the female thread is preferably 0.3% to 5%. As this ratio becomes smaller than 0.3%, the force to increase the space between the threads of the male screw portion of the bolt by the female screw and the frictional force generated between the screw thread of the bolt and the female screw are reduced, and the loosening prevention function Tends to decrease, and as it becomes larger than 5%, it becomes easy for galling to occur between the bolt and the female screw, the tightening torque required for fastening increases, and the workability tends to deteriorate. There is a tendency and neither is preferable.

Fastener according to claim 2 of the present invention includes a bolt of claim 1, and a female screw pitch p _n at least part of which is fastened screwed with the tapered portion of the bolt, the It has the composition which is.
With this configuration, the following effects can be obtained.
(1) The bolt has a screw thread outer diameter (nominal diameter) toward the bolt head side or the bolt cylinder part side by removing a part of the top of the screw thread part on the bolt head side or the bolt cylinder part side of the male screw part. ) Has a taper portion with a reduced diameter, the height of each screw thread of the taper portion screwed with the female screw gradually decreases in inverse proportion to the surface pressure to be shared. The load sharing of the mountain is made uniform, and it is possible to alleviate the tension and bending stress from concentrating on the bottom of the threaded valley of the taper portion near the end face of the screwed female bolt head side or bolt cylindrical part side (inner side). The fatigue strength of can be greatly improved.
(2) When at least a part of the female screw is screwed and fastened with the taper portion of the bolt, the screw thread of the taper portion on the bolt head side or the bolt cylindrical portion side (inside) of the female screw is Contact is made only at the tip of the screw thread of the nut, which is easy to bend, and the contact area is reduced, so that the contact is eased and the stress at the thread valley bottom of the tapered part close to the dangerous cross section can be greatly reduced to prevent breakage. And the fatigue limit of the bolt can be improved.
(3) the pitch p _b and the pitch p _n of the male screw portion threadably engaged with a female screw to be fastened in the male screw portion of the _{bolt, 0.003 ≦ (p n -p b} ) / p b ≦ 0.05 Therefore, an appropriate frictional force is generated between the screw thread of the bolt and the female screw on the basis of the force to increase the space between the screw threads of the bolt in the screwed state and the force against the force. In addition to enabling the female screw to be screwed and tightened, a large resistance in the loosening direction can be imparted, and an excellent anti-loosening function can be maintained even when fluctuating stress is applied from the outside. As a result, it is possible to reliably suppress the occurrence of loosening due to external force over a long period of use, prevent troubles associated with loosening, and have excellent reliability and maintainability.

Here, as for the material of the female screw, the same material as that of the bolt is preferably used. However, when a part of hard metal is used, if both the bolt and the female screw are the same hard, they are bitten during fitting. In this case, it is desirable to make the material of the female screw that is difficult to break somewhat soft. Specifically, the relationship between Vickers hardness Hv _n Vickers hardness Hv _b and the female screw of the bolt are preferably used those _{0.5Hv b ≦ Hv n <Hv b} . _If the pitch difference between the bolt pitch p _b and the female screw pitch pn is small, the difference in hardness can be reduced. Therefore, depending on the pitch difference, the respective hardnesses Hv _b , Hv can be reduced from the aforementioned ranges. You can choose.

A third aspect of the present invention is the fastener according to the second aspect, wherein the female screw is screwed with the tapered portion of the bolt within a range of 50% to 80% of the total length of the female screw. It has the composition which is.
With this configuration, in addition to the operation obtained in the second aspect, the following operation can be obtained.
(1) When the female screw is screwed with the taper portion of the bolt in the range of 50% to 80% of the total length of the nut, at the screw valley bottom of the taper portion of the bolt on the inner end face side of the female screw, which is a dangerous section. Therefore, the load sharing can be made uniform and the stress concentration of tension and bending can be alleviated and the contact per piece can be alleviated reliably and efficiently, and the fatigue strength is highly reliable.

Here, the female screw is preferably screwed with the taper portion of the bolt within a range of 50% to 80% of the total length of the female screw. As the taper portion included in the fitting portion between the female screw and the male screw portion becomes less than 50% of the total length of the female screw, the effect of improving the fatigue strength by the taper portion tends to decrease, and as the taper portion exceeds 80%, the taper portion increases. There is a tendency that the effect of improving the fatigue strength by the portion decreases, and the catch between the female screw and the male screw portion decreases, and the tightening force tends to decrease, both of which are not preferable.
In addition, in order to make the position of the female screw an optimum position, the length of the bolt shaft portion of the bolt is selected according to the thickness of the body to be fastened, but if necessary, by using a washer, A good fastening state can be obtained by adjusting the position, and an excellent fatigue strength and a loosening prevention function can be realized.

Invention of Claim 4 is a fastener of Claim 2 or 3, Comprising: Of the said volt | bolt fitted to the screw thread of the said bolt head side of the said female screw, or the edge part of the said bolt cylindrical part side. The height of the thread of the taper portion is 10% to 75% of the height of the thread of the female thread.
With this configuration, in addition to the operation obtained in the second or third aspect, the following operation can be obtained.
(1) The height of the thread of the tapered portion that fits the thread on the end of the female screw on the bolt head side or the bolt cylindrical portion side is 10% to 75% higher than the height of the female screw. As a result, a sufficient tightening force can be secured, and a reduction in safety can be prevented.

  Here, the height of the thread of the taper portion that fits with the thread on the bolt head side or the end of the bolt cylindrical portion of the female screw is 10% to 75% higher than the height of the female screw. Preferably. Fatigue strength decreases as the height of the thread of the taper portion that engages with the thread of the female thread on the inner end face side of the female thread, which is a critical section, becomes lower than 10% of the height of the thread of the female thread. However, the hooking of each screw thread in the taper portion is reduced, the load of the remaining screw thread is increased, the stress concentration tends to occur, and the fastening stability tends to decrease. As it becomes higher than 75%, there is a tendency that the effect of improving the fatigue strength by the taper portion becomes difficult to obtain.

As described above, according to the bolt of the present invention and the fastener using the bolt, the following advantageous effects can be obtained.
According to the first aspect of the invention, the following advantageous effects can be obtained.
(1) By uniformly decreasing the height of each screw thread of the taper portion screwed with the female screw so as to be inversely proportional to the surface pressure to be shared, the load sharing of each screw thread of the taper portion is made uniform. It is possible to provide a bolt with excellent safety and reliability that can alleviate the concentration of tension and bending stress on the bottom of the thread valley of the tapered portion near the inner end face of the female screw, and can greatly improve the fatigue strength.
(2) With the incomplete screw removal part formed by gradually expanding the diameter from the minimum diameter part of the taper part toward the bolt head side or the bolt cylindrical part side, the occurrence of stress concentration can be prevented, The fatigue strength improvement effect by the taper portion can be maintained and the occurrence rate of delayed fracture, stress corrosion cracking, etc. can be reduced, and a bolt excellent in long life and fastening stability can be provided.

According to the second aspect of the invention, the following advantageous effects can be obtained.
(1) By screwing and fastening at least a part of the female screw with the taper part of the bolt, the screw thread of the taper part on the inner end face of the female screw is brought into contact only at the tip side of the screw thread of the female screw that is easily bent. The contact area can be reduced, the contact per piece can be relaxed, the stress at the bottom of the threaded valley of the taper portion close to the dangerous cross section can be greatly reduced, and the bolt can be prevented from being broken. It is possible to provide a fastener with excellent safety and reliability that can be greatly improved.
(2) the pitch p _b and the pitch p _n of the male screw portion threadably engaged with a female screw to be fastened in the male screw portion of the _{bolt, 0.003 ≦ (p n -p b} ) / p b ≦ 0.05 Therefore, an appropriate frictional force is generated between the screw thread of the bolt and the female screw on the basis of the force to increase the space between the screw screw threads by the female screw and the force against the force. Can be screwed and tightened, and can be given a large resistance in the loosening direction. Even if it is used for a long period of time, it is difficult to loosen due to external fluctuating stress. A fastener with excellent properties can be provided.
(3) Combined with a reliable loosening prevention function and greatly improved fatigue strength, the number and dimensions of bolts and female screws can be greatly reduced, and the product can be made smaller and lighter. In addition, the number of man-hours required for drilling and tightening bolts can be reduced to reduce the cost of products, and the flexibility of product design, assembly workability, and mass productivity can be significantly improved. It is possible to provide a fastener that can be used and has excellent utility and resource saving.

According to the invention described in claim 3, in addition to the effect described in claim 2, the following advantageous effects can be obtained.
(1) The screw thread bottom of the taper portion of the bolt on the inner end face side of the female screw, which is a dangerous section, by screwing the female screw with the taper portion of the bolt within a range of 50% to 80% of the total length of the female screw. In addition, in addition to ensuring uniform and efficient load sharing, reducing stress concentration during tension and bending, and reducing the impact per piece, it is strong at the threaded portion with the male screw portion excluding the taper portion. Fastening force can be obtained, and it is possible to provide a fastener that is excellent in reliability and reliability of a loosening prevention function as well as reliability in fatigue strength.

According to the invention described in claim 4, in addition to the effect described in claim 2 or 3, the following advantageous effect can be obtained.
(1) Tightening is sufficient by setting the height of the thread of the taper part to be fitted to the thread of the inner end of the female thread to be 10% to 75% of the height of the thread of the female thread. It is possible to provide a fastener that can secure a force and prevent a reduction in safety, and can be used repeatedly and has excellent durability and resource saving.

Hereinafter, bolts and fasteners using the bolts according to embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a side view of the main part of the bolt according to the first embodiment, and FIG. 2 is an enlarged schematic side view of part A of FIG.
In FIG. 1, 1 is the bolt of the first embodiment, 2 is the bolt shaft portion of the bolt 1, 3 is the bolt head of the bolt 1 formed by cold forging or the like, 4 is the bolt shaft portion 2 by cutting or rolling. It is the external thread part of the volt | bolt 1 formed from the front-end | tip part to the predetermined part.
Next, details of the male screw portion of the bolt will be described.
In FIG. 2, 4 a is the top of the screw thread of the male screw part 4, 4 b is the valley bottom of the male screw part 4, 4 c is the flank of the male screw part 4, and 5 is the screw thread on the bolt head 3 side of the male screw part 4. The taper portion of the bolt 1 with a part of the top portion removed and the outer diameter (nominal diameter) of the screw thread being reduced toward the bolt head 3 side, is gradually from the smallest diameter portion of the taper portion 5 toward the bolt head 3 side. This is an incomplete screw removing portion of the bolt 1 formed by expanding the outer diameter (nominal diameter) of the screw thread in a circular arc shape.

FIG. 3 is a cross-sectional schematic side view of the relevant part showing a usage state of the fastener using the bolt of the first embodiment.
In FIG. 3, reference numeral 10 _denotes a female screw having a pitch pn in a fastener using the bolt according to the first embodiment in which a part on the bolt head 3 side is screwed and fastened to the taper portion 5 of the bolt 1 having a pitch p _b. nut as, 20 the fastener which is fastened by fastener with bolts of the first embodiment, h _n is thread height of the nut 10, h _t the end of the bolt head 3 side of the nut 10 The center height of the thread of the taper portion 5 of the bolt 1 to be fitted to the screw thread (referred to as the minimum screw thread height of the taper portion 5 fitted to the nut 10), l _n is the total length of the nut 10, and l _t is This is the length of the portion of the taper portion 5 of the bolt 1 that is screwed with the nut 10.

3, the pitch p _b of the bolt 1, the relationship between the pitch p _n of the nut 10, was set to be _{0.003 ≦ (p n -p b)} / p b ≦ 0.05. As the proportion of the pitch difference p _n -p _b of the bolt 1 and the nut 10 to the pitch p _b of the bolt 1 in the screwing range of the bolt 1 and the nut 10 is less than 0.3%, threads of the bolt 1 by a nut 10 And the frictional force generated between the bolt 1 and the screw thread of the nut 10 tends to be reduced, and the locking function tends to be lowered, and as it becomes larger than 5%, the bolt 1 and the nut 10 This is because it has been found that galling is likely to occur in between, the tightening torque required for fastening increases, and the workability tends to deteriorate.
When 0.003 ≦ (p _n −p _b ) / p _b ≦ 0.05, resistance is generated when the bolt 1 and the nut 10 are screwed together, but the pitch difference between the two is small, and the screw thread Since it is in a range that can be absorbed by elastic deformation, it can be easily fastened only with a commonly used tool.
There are no particular restrictions on the material of the bolts 1 and nuts 10, which may be metal or non-metal, but from the standpoint of effectiveness, steel materials and soft metals such as copper, aluminum, titanium, and magnesium and those These alloys are preferred. If some of the hard metals are used, if both the bolt 1 and the nut 10 are similarly hard, there is a risk of biting at the time of fitting. In this case, the nut 10 that is hard to break is used. It is desirable to make the material of the material somewhat soft. Specifically, the relationship between Vickers hardness Hv _n Vickers hardness Hv _b and the nut 10 of the bolt 1 are preferably used those _{0.5Hv b ≦ Hv n <Hv b} . If the pitch difference of the pitch p _n of the pitch p _b and the nut 10 of the bolt 1 is small, it is possible to smaller difference in hardness, in response to the pitch difference, each of the hardness Hv _b, range Hv described above You can choose from.

Further, the relationship between the total length l _n of the nut 10 and the length l _t of the portion of the taper portion 5 of the male screw portion 4 of the bolt 1 to be screwed together is 0.5 l _n ≦ l _t ≦ 0. .8 l _n . As the taper portion 5 included in the fitting portion of the nut 10 and the male screw portion 4 of the bolt 1 becomes less than 50% of the total length l _n of the nut 10, the fatigue strength improving action by the taper portion 5 tends to decrease, As the ratio exceeds 80%, the fatigue strength improving action by the taper portion 5 decreases, and the catch between the nut 10 and the male screw portion 4 tends to decrease, and the tightening force by the nut 10 tends to decrease. This is because.
The height h _t of the threads of the tapered portion 5 which threads mate with the end portion of the bolt head 3 side of the nut 10, the relationship between the height h _n of the threads of the nut 10, 0.1 h _n ≦ h _t ≦ 0.75 h _n . As the thread height h _{t of} the taper portion 5 fitted to the thread of the nut 10 on the inner end face side of the nut 10, which is a dangerous section, becomes lower than 10% of the height h _n of the thread 10 of the nut 10. The fatigue strength is reduced, the hooking of each screw thread in the taper portion 5 is reduced, the burden of the remaining screw thread is increased, the stress concentration is likely to occur, and the dimensional accuracy is increased. Fluctuation is likely to occur, and fluctuations in fatigue strength are likely to occur due to the influence thereof, and the fastening stability tends to be lowered. As it becomes higher than 75%, the effect of improving the fatigue strength by the tapered portion 5 tends to become difficult to obtain. It is because I understood.

3, in the state where the tightening is completed at a predetermined position, when viewed from the nut 10 side, the force to tend to bring said pitch p _b of the screw thread of the male screw portion 4 bolt 1 to the pitch p _n of the nut 10, i.e. The force to push the screw thread of the male screw part 4 in the left-right direction works as shown by the arrow.
On the other hand, when viewed from the bolt 1 side, a force that resists the force of pushing the screw thread of the male screw part 4 is generated, and an appropriate frictional force is generated between the screw thread of the bolt 1 and the nut 10 so that it is difficult to loosen. It has become.
In FIG. 3, the direction of the force for expanding the screw thread of the male screw part 4 indicated by the arrow is divided into right and left at the position of ½ of the total length of the nut 10. If the position changes, the fitting state of each screw thread of the bolt 1 and the nut 10 changes periodically, and accordingly, the direction in which the force acts also changes periodically.

In a normal combination of bolts and nuts having the same pitch, tensile stress is generated at the bottom of the screw valley of the bolt in use, and compressive stress is generated at the nut side. Since the diameter of the screw valley bottom is larger on the nut side than on the bolt side, in general, breakage easily occurs from the bolt side. When the bolt breaks down due to fatigue, the breakage generally occurs from the inner end face side of the nut to be screwed in due to tensile stress.
In this embodiment, the pitch p _b of the bolt 1 is smaller than the pitch p _n of the nut 10, in the normal (stationary) state, the compression stress in the screw root of the bolt 1 of the inner end face of the nut 10 has occurred It is possible to cancel out the tensile stress applied to the bolt 1 from the outside, to reliably suppress the influence of the external stress, and to greatly improve the resistance against the fluctuating stress.
Further, by gradually reducing the height of each screw thread of the taper portion 5 screwed with the nut 10 so as to be inversely proportional to the surface pressure shared by the screw thread, the load of each screw thread of the taper portion 5 is reduced. The load is made uniform, and the tension and bending stress are concentrated on the bottom of the thread valley of the taper portion 5 near the inner end face of the nut 10, and a part of the nut 10 is screwed with the taper portion 5 of the bolt 1. By fastening, it can be brought into contact with the screw thread of the taper portion 5 on the inner end face of the nut 10 only at the tip end side of the screw thread of the nut 10 which is easily bent, the contact area can be reduced, The stress at the thread valley bottom of the taper portion 5 close to the dangerous section is greatly reduced.
Due to these synergistic effects, the fatigue strength of the bolt 1 can be dramatically improved in addition to the loosening prevention function.

To manufacture the bolt 1 of the first embodiment, first, the incomplete screw removing portion 6 and the taper portion 5 are formed in the bolt material in the drawing process.
Next, the male screw part 4 is formed by a rolling process or a cutting process. In this case, the pitch p _n of the pitch p _b and the nut 10 of the bolt 1, so that a relationship of _{0.003 ≦ (p n -p b)} / p b ≦ 0.05.
Incidentally, to produce a bolt 1 so as to conform to dimensional specifications, such as ISO or JIS, may pitch than p _b of the bolt 1 so as to further satisfy the above formula to produce a nut 10 of the larger pitch p _n but on the basis of the nut 10 that is constructed to the dimensional specifications, such as ISO or JIS, such that pitch than p _n of the nut 10 so as to satisfy the above equation to produce a bolt 1 small pitch p _b If it makes it, the existing nut 10 can be used as it is, and it is excellent in versatility and usability.
In the present embodiment, the case where the nut 10 is used as the female screw to be screwed into the bolt 1 has been described. However, when the bolt 1 is used as an embedded bolt, the female screw is embedded in the joint portion. It is possible to use a female screw member formed, a female screw portion formed in the joint portion, or the like.

According to the bolt of the first embodiment of the present invention as described above, the following operation is obtained.
(1) A part of the top of the screw thread on the bolt head 3 side of the male screw part 4 is removed and the taper part 5 having a screw thread outer diameter reduced toward the bolt head 3 side is provided. Since the height of each screw thread of the taper portion 5 to be combined gradually decreases in inverse proportion to the surface pressure to be shared, the load sharing of each screw thread of the taper portion 5 becomes uniform, and the nut 10 (female screw). When the screw is screwed, it is possible to alleviate the concentration of tension and bending stress on the thread valley bottom of the taper portion 5 near the end face on the bolt head 3 side (inner side) of the nut 10, and greatly improve the fatigue strength of the bolt 1. can do.
(2) Usually, stress concentration is likely to occur in the incomplete screw portion formed at the beginning of the male screw portion 4, but gradually becomes an arc shape from the minimum diameter portion of the taper portion 5 toward the bolt head 3 side. By expanding the diameter and forming the incomplete screw removing portion 6, even if the tapered portion 5 is formed, stress concentration hardly occurs in the incomplete screw removing portion 6 and the effect of improving the fatigue strength by the tapered portion 5 is maintained. be able to.
(3) the pitch p _n of the pitch p _b and the male screw portion 4 and screwed a nut 10 which is fastened to the male screw portion 4 (female screw) _{is, 0.003 ≦ (p n -p b} ) / p b by a relationship ≦ 0.05, the pitch p _n of the nut is greater than the pitch p _b of the male screw portion 4, and Grow the spacing of the male screw portion 4 of the threads in threaded engagement state force Based on the force against the force, an appropriate frictional force is generated between the male screw portion 4 and the screw thread of the nut 10 to enable the nut 10 to be screwed and tightened and to have a large resistance in the loosening direction. And an excellent anti-loosening function can be maintained even when fluctuating stress is applied from the outside. As a result, it is possible to reliably suppress the occurrence of loosening due to external force over a long period of use, prevent troubles associated with loosening, and have excellent reliability and maintainability.
(4) The action of the taper portion 5 does not cause tension or bending stress to concentrate on the bottom of the screw valley near the end face inside the nut 10, but even if a tensile stress is applied to the bolt 1 from the outside, the male screw portion 4. the pitch p _b is smaller than the pitch p _n of the nut 10, in the normal (stationary) state because the compression stress occurs in the thread root of the male screw portion 4, sacrificed compressive stress this tensile stress phase, the external stress The influence can be surely suppressed, the resistance to repeated fluctuating stress, which is the primary cause of fatigue failure, can be greatly improved, and both an excellent loosening prevention function and fatigue strength can be provided.

According to the fastener using the bolt of Embodiment 1 of the present invention as described above, the following operation is obtained.
(1) The bolt 1 has a taper portion 5 in which a part of the top of a part of a screw thread on the bolt head 3 side of the male screw part 4 is removed and a screw thread outer diameter is reduced toward the bolt head 3 side. As a result, the height of each screw thread of the taper portion 5 screwed with the nut 10 gradually decreases in inverse proportion to the surface pressure to be shared, so that the load sharing of each screw thread of the taper portion 5 is made uniform. It is possible to alleviate the concentration of tension and bending stress on the thread valley bottom of the taper portion 5 near the end face of the bolt head 3 side (inner side) of the screwed nut 10, and to greatly improve the fatigue strength of the bolt 1. Can do.
(2) When at least a part of the nut 10 is screwed and fastened with the taper portion 5 of the bolt 1, the nut 10 is bent with respect to the thread of the taper portion 5 on the end face of the bolt head 3 side (inner side). Easy contact with the tip of the screw thread of the nut 10 and the contact area is reduced, so that the contact is eased, and the stress at the bottom of the threaded valley of the taper portion 5 close to the dangerous section is greatly reduced to prevent breakage. The fatigue limit of the bolt 1 can be improved.
(3) the pitch p _n of the nut 10 (a female screw) fastened screwed with pitch p _b and the male screw portion 4 of the male screw portion 4 of the bolt 1, 0.003 ≦ (p _n -p _b) / P _b ≦ 0.05 so that the screw of the bolt 1 and the nut 10 is based on the force to increase the distance between the screw threads of the bolt 1 in the screwed state and the force against the force. Appropriate frictional force is generated between the mountains, and the nut 10 can be screwed and tightened, and a large resistance in the loosening direction can be imparted, providing an excellent anti-loosening function even when fluctuating stress is applied from the outside. Can be maintained. As a result, it is possible to reliably suppress the occurrence of loosening due to external force over a long period of use, prevent troubles associated with loosening, and have excellent reliability and maintainability.
(4) When the nut 10 is screwed with the taper portion 5 of the bolt 1 in the range of 50% to 80% of the total length l _n of the nut 10, the bolt 1 on the inner end face side of the nut 10 which is a dangerous cross section At the bottom of the threaded valley of the taper portion 5, the load sharing can be made uniform, the stress concentration of tension and bending can be alleviated, and the stress per piece can be alleviated, and the fatigue strength is highly reliable. According to the thickness of the body 20 to be fastened, the length of the bolt shaft 2 of the bolt 1 is selected, and if necessary, the position of the nut 10 is adjusted to an optimum position by using a washer. A state can be obtained, and excellent fatigue strength and a loosening prevention function can be realized.
(5) The thread height h _{t of} the taper portion 5 fitted to the thread on the bolt head 3 side end of the nut 10 is 10% to 75% of the thread height h _n of the nut 10. Due to the height, a sufficient tightening force can be secured, and a reduction in safety can be prevented.

以上のようにして、振動バーレルに締結した締結具に、ＮＡＳ式高速緩み試験機（米国航空機規格ＮＡＳ３３５０に準じる）を用いて、ボルトの軸方向と直交する方向に振動を繰り返し与える振動試験を１７分間（３００００回）行った。振動数は１７８０ｒｐｍｍ、加振ストロークは１１ｍｍ、インパクトストロークは１９ｍｍとした。
評価の結果、比較例１では、試験後にナットに緩みが発生したが、実施例１〜３については、試験後にナットに緩みが発生しているものはなかった。 Hereinafter, the present invention will be specifically described by way of examples. The present invention is not limited to these examples.
(Evaluation of pitch difference by Examples 1 to 3 and Comparative Examples 1 and 2)
First, based on the M16 coarse nut as defined in JIS B 0205-1997, by the manufacturing method described in Embodiment 1, to produce a bolt pitch p _b is different.
The proportion of the pitch difference p _n -p _b of the bolt and the nut with respect to the pitch p _b of bolts were prepared (%) shown in Table 1.
Since the bolt of Comparative Example 2 was galling with the nut, the bolts of Examples 1 to 3 and Comparative Example 1 were inserted into the vibration barrel, and M16 defined in JIS B 0205-1997 was inserted into the male screw portion of the bolt. Were tightened with the same tightening torque (145 N · m).
In order to obtain sufficient fatigue strength, the ratio of the minimum screw thread height of the taper part fitted to the nut (= (h _t / h _n ) × 100 (%)) is 10%, and the taper part length with respect to the entire length of the nut Table 1 shows the results of evaluation with the ratio of (= (l _t / l _n ) × 100 (%)) being 80%.

As described above, using a NAS type high-speed looseness tester (according to US aircraft standard NAS3350) to the fastener fastened to the vibration barrel, a vibration test in which vibration is repeatedly applied in a direction orthogonal to the axial direction of the bolt is performed. For 3 minutes (30000 times). The frequency was 1780 rpm, the excitation stroke was 11 mm, and the impact stroke was 19 mm.
As a result of evaluation, in Comparative Example 1, the nut was loosened after the test, but in Examples 1 to 3, none of the nut was loosened after the test.

Next, fatigue strength tests were performed on the bolts of Examples 1 to 3 and Comparative Example 1.
The bolts of Examples 1 to 3 and Comparative Example 1 are inserted into the jig, and the nut M16 defined in JIS B 0205-1997 is screwed into the male screw portion of the bolt, and the same tightening torque (145 N · m ) The position of the nut is as shown in Table 1.
Using a servo type fatigue tester (± 392 kN), the bolt head and nut were repeatedly pulled in the axial direction of the bolt, and the number of repetitions (time) until failure occurred was counted. The tensile average stress was constant at 176.4 MPa, and the repetition rate was 500 times / minute.
Evaluation was made into a relative value when the fatigue strength of a conventional fastener in which a coarse bolt of M16 and a coarse nut were screwed together was taken as 100%.
As shown in Table 1, in Examples 1 to 3 the proportion of the pitch difference p _n -p _b of the bolt and the nut with respect to the pitch p _b of the bolt satisfies the range of 0.3% to 5%, conventional 2 times It was found to have excellent fatigue strength.
Bolt the small Comparative Example 1 ratio of pitch difference p _n -p _b of the bolt and nut than 0.3% of the pitch p _b of the fastener equivalent fatigue screwed conventional coarse bolt and coarse nut It was found that there was only strength and the effect of improving fatigue strength could not be obtained.

尚、実施例４〜１２、比較例３〜１０のボルトに螺合したナットに嵌合するテーパ部の最小螺子山高さの割合（＝（ｈ_t／ｈ_n）×１００（％））及びナット全長に対するナットが螺着されたテーパ部長さの割合（＝（ｌ_t／ｌ_n）×１００（％））は、それぞれ表２に示した通りである。
振動バーレルに締結した締結具に、ＮＡＳ式高速緩み試験機（米国航空機規格ＮＡＳ３３５０に準じる）を用いて、ボルトの軸方向と直交する方向に振動を繰り返し与える振動試験を１７分間（３００００回）行った。振動数は１７８０ｒｐｍｍ、加振ストロークは１１ｍｍ、インパクトストロークは１９ｍｍとした。
評価の結果、試験後又は試験中にナットに緩みが発生するものはなく、実施例４〜１２、比較例３〜１０の全てが合格となった。 (Evaluation of nut screwing position according to Examples 4 to 12 and Comparative Examples 3 to 10)
Examples 1-3, in the evaluation of pitch difference by Comparative Examples 1 and 2, the pitch p _b of the bolt, 0.003 ≦ a relationship pitch p _n of the nut _{(p n -p b) / p} b ≦ 0. with 05 excellent since loosening prevention function is found to result, the bolt and the pitch p _b of the relationship of the pitch p _n of nut _{(p n -p b) / p} b = 0.02 Table 2 shows the results of evaluating the occurrence of looseness and fatigue strength while keeping the position constant (corresponding to Example 2) and changing the position of the nut.

In addition, the ratio (= (h _t / h _n ) × 100 (%)) of the minimum screw thread height of the taper portion fitted to the nut screwed to the bolts of Examples 4 to 12 and Comparative Examples 3 to 10 and the nut The ratio of the length of the taper portion in which the nut is screwed to the total length (= (l _t / l _n ) × 100 (%)) is as shown in Table 2, respectively.
Using a NAS type high-speed looseness tester (according to the US aircraft standard NAS3350) to the fasteners fastened to the vibration barrel, a vibration test is repeatedly applied for 17 minutes (30000 times) in a direction perpendicular to the axial direction of the bolt. It was. The frequency was 1780 rpm, the excitation stroke was 11 mm, and the impact stroke was 19 mm.
As a result of the evaluation, there was no loosening of the nut after the test or during the test, and all of Examples 4 to 12 and Comparative Examples 3 to 10 passed.

Next, fatigue strength tests were performed on the bolts of Examples 4 to 12 and Comparative Examples 3 to 10.
Evaluation was performed in the same manner as in Examples 1 to 3 and Comparative Example 1 except that the position of the nut was different.
As shown in Table 2, the minimum thread height h _t of the tapered portion to be fitted to the nut, with 10% to 75% of the height of the height h _n of the threads of the nut, the nut is, the total length of the nut l It was found that Examples 4 to 12 screwed with the taper portion of the bolt in the range of 50% to 80% of _n had excellent fatigue strength.
In Comparative Example 4, 6 and 8 were the smallest thread height h _t of the tapered portion to be fitted to the nut 80% of the height h _n of the threads of the nut, the conventional coarse bolt and coarse nut It was found that there was only a fatigue strength equivalent to that of the screwed fastener, and an effect of improving fatigue strength could not be obtained.
Furthermore, it was found that the effect of improving the fatigue strength sharply decreased in Comparative Example 9 in which the nut was screwed with the taper portion of the bolt at 40% of the total length l _n of the nut as compared with 50% of Example 4. . Further, in Comparative Example 10 in which the nut is screwed with the taper portion of the bolt at 90% of the total length l _n of the nut, it has been found that 1.5 times the fatigue strength of the conventional nut can be obtained. _Since most of _n is screwed at the tapered portion, there is a possibility that it may be completely pulled out by an external force or the like, and it is not preferable because it is not reliable in fastening.
In Comparative Example 3, 5, 7 to the minimum thread height h _t of the tapered portion was 5% of the height h _n of the threads of the nut to be fitted to the nut, the minimum thread taper portion to be fitted to the nut While the crest height h _t is 50 percent to embodiment 5, 8, 11 almost as fatigue strength of the height h _n of the threads of the nut, the minimum thread height of the tapered portion to be fitted to the nut the h _t as peak example 4, 7, 10, which was 10% of the height h _n of the threads of the nut, has decreased rapidly fatigue strength, of 5% to 10% range, little position It can be said that this is an unstable region where the fatigue strength is likely to vary due to the difference. Further, since there is little catching of each screw thread in the taper portion, the burden on the remaining screw thread that is fitted increases, stress concentration is likely to occur, and this is not preferable because it is not practical. Further, if the height of the screw thread is lowered, it is not preferable because it is easily affected by variations in dimensional accuracy, lacks in production stability, tends to cause variations in fatigue strength, and lacks fastening stability.
In this embodiment, a bolt formed in a typical M16 size that is generally used is used, but the same tendency as in Tables 1 and 2 is observed regardless of the bolt size.
* Check the fatigue strength test (in red) for any problems.

  The present invention can be obtained with a conventional screw fastener by combining the excellent anti-loosening function and fastening force which are excellent in mass production and difficult to loosen even when subjected to repeated load (vibration), and a greatly improved fatigue strength. Providing bolts that can realize superior safety and reliability that were not present, and using the bolts, the configuration is simple, the number of parts is small, the number of bolts and nuts used, and the dimensions are greatly reduced. In addition to reducing the size and weight of the product, it is possible to reduce the cost of the product by reducing the man-hours required for drilling and tightening bolts, significantly improving product design flexibility and assembly workability. It is possible to provide fasteners with excellent practicality that can be made, from various mechanical devices, iron bridges, buildings, construction machines, various transport equipment, electrical products, movable parts such as glasses, or from the outside Can increase the reliability of the joint portion of the member which receives the motion, it is possible to reduce the incidence of delayed fracture and stress corrosion cracking.

Side view of main part of bolt of embodiment 1 Enlarged schematic side view of part A in FIG. Sectional schematic cross-sectional side view of the relevant part showing the use state of the fastener using the bolt of the first embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bolt 2 Bolt axial part 3 Bolt head 4 Male screw part 4a Top part 4b Valley bottom part 4c Frank 5 Taper part 6 Incomplete screw removal part 10 Nut 20 Fastened object

Claims (4)

A part of the male screw part of pitch p _b formed on at least the tip part side of the bolt shaft part and the top of the screw head on the bolt head side or the bolt cylindrical part side of the male screw part is removed. A taper portion having a reduced screw thread outer diameter toward the bolt cylindrical portion side, and a diameter gradually increasing from the smallest diameter portion of the taper portion toward the bolt head side or the bolt cylindrical portion side in an arc shape. It has been formed and an incomplete thread removing unit, the pitch p _n of the female screw which is fastened screwed with the male screw portion and the pitch p _b of the male screw portion, 0.003 ≦ (p _n -P _b ) / p _b ≦ 0.05. The bolt of claim 1, a fastener and having a female thread pitch p _n at least part of which is fastened screwed with the tapered portion of the bolt, the. The fastener according to claim 2, wherein the female screw is screwed with the tapered portion of the bolt within a range of 50% to 80% of the total length of the female screw. The height of the thread of the taper portion of the bolt that fits with the thread of the end of the female screw on the bolt head side or the bolt cylindrical portion side is 10 times the height of the screw thread of the female screw. The fastener according to claim 2 or 3, wherein the height is from% to 75%.

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