WO2019131685A1

WO2019131685A1 - Fastening nut

Info

Publication number: WO2019131685A1
Application number: PCT/JP2018/047682
Authority: WO
Inventors: 松尾　誠; 興明林田; 喜直岩本
Original assignee: 株式会社松尾工業所; 株式会社iMott
Priority date: 2017-12-25
Filing date: 2018-12-25
Publication date: 2019-07-04
Also published as: JPWO2019131685A1; JP7141622B2

Abstract

Provided is a nut in which, by moving the fastening force in bolt-nut fastening toward the open side of the nut and increasing the load sharing among the threads from the third thread on, it is possible to reduce the load on the first engaged thread, which bears the maximum load, and extend the fatigue life of the bolt with respect to crack-axis fracturing. A first embodiment of the nut is configured such that, with regard to the shape of the nut in a longitudinal sectional view, a space having a convex shape on the top is formed concentrically, centering on the thread axis, on the fastening-side nut face. The convex space is a structure in which a convex space is formed as a shape connected by straight lines, curved lines, or a combination of both. By forming said space such that, when L2 is the depth of the convex space from the nut face and L1 is the axial-direction length of the nut from the first root of a complete thread portion to the nut face, said convex space depth L2 is in the range of L1 < L2 ≤ L1 + 5 lengths of the thread pitch, more of the stress on the threads of the nut during fastening is moved to the third thread on toward the open side of the nut and load concentration on the first engaged thread of the nut and the bolt is reduced.

Description

Tightening nut

The present invention relates to a nut used in bolt and nut fastening, and for the purpose of reducing the load on the fastening meshing first peak thread.

A lot of bolts and nuts are used to fasten various structures, and many of aircraft, automobile, railway vehicles, machine tools, civil engineering machines, agricultural machines, various manufacturing devices, bridges, building structures, etc. are bolts and nuts. The conclusion is generally made. However, there are many cases in which the bolt breaks at the meshing first peak, and it is pointed out that the crack axial fracture at the bottom of the screwing mesh of the bolt in use is used as the cause. Breaking of the bolt causes the fastening itself to be broken, and the magnitude of the effect also becomes a problem.

The screw fastening part of the conventional method has the smallest cross-sectional area and the largest load sharing due to the application of repeated external load during use on the initial fastening load. The fatigue failure strength is the lowest at the part. It is known that many cracked axial fractures occur at this location.

Until now, it has been devised to make it hard to break by raising the hardness and tensile strength by material change on the bolt side and heat treatment etc. against breaking of the bolt, but such a high value with a low fracture toughness value It is also known that the bottom of a bolt thread of a strength member is sensitive to the influence of a load with an increase in notch sensitivity. However, even if such a device is used, in the case of using the conventional type nut, the load concentration state to the bottom of the screw thread of the meshing first peak does not change at all. That is, even though the improvement of the hardness and strength improvement to the bolt side so far is effective in the static fracture strength at the time of initial tightening, it is a fracture in the fatigue fracture strength under the influence of external load during use. It is often the opposite effect under the influence of toughness value.

An example is shown by the following patent documents which devised the bolt side and the nut side to this fact.

Patent Documents

1 and 3 disclose a bolt characterized in that the bolt thread to be fitted is tapered in the tensile direction of the bolt and the bolt thread is obliquely cut low, and is directed in the axial direction. The intention is to reduce the contact area between the bolt thread and the nut thread sequentially and to equalize the load from the nut thread on the bolt thread to improve the fatigue life. It is stated that this forming process may be performed on the nut, but no description or figure is shown. Patent Document 4 discloses a nut characterized in that one or both of the slope angles of the thread of the nut fitted to the bolt is smaller than the slope angle of the bolt, and It has been disclosed that the contact area of the thread of the nut is reduced to equalize the load applied to the thread and improve the fatigue life.

Patent Document 2 discloses a method of manufacturing a bolt in which a threaded portion of a bolt material is formed into a tapered shape in the direction of tensile force application, and subsequently, threading with a uniform valley diameter is performed.

In Patent Document 5, in a steel bolt in which the pitch of the bolt is smaller than the pitch of the nut, the pitch difference is in the range of 0.5 to 0.8% of the pitch tolerance specified in Japanese Industrial Standard JIS B 0205 A steel bolt is disclosed which is characterized in that it is designed to provide offsets, avoiding simultaneous contact of the screw faces, and as the fastening progresses and the screw thread is deformed by stress, the stress transfer position is sequentially A structure is disclosed that travels and receives a full load.

However, Patent Documents 1 to 5 have a problem that the screw shape is out of the standard such as JIS or ISO because they are processed on the screw threads of these bolts and nuts, and these are basically bolts The threading position is made into a dedicated part by the thickness, structure, etc. of the object to be fastened, and it is necessary to apply thread thread forming processing of the bolt to a position which becomes a specific size for each object to be fastened , These bolts are not versatile.

The prior art of these patent documents 1 to 5 does not change the load of each screw thread greatly even if the screw thread height of the bolt is lowered. And high stress will occur. In particular, in the first thread of thread engagement, there is the possibility of uneven plastic deformation on the contact surface on the nut side, and in applications where the nut is used repeatedly, there is a risk that the indentation will adversely affect fastening.

Furthermore, Patent Documents 6 to 8 propose a set of a bolt, a nut and a washer in a high strength nut for friction bonding in relation to the nut side, and Patent Document 6 in the following. A first structural example of this set is described in FIGS. 1 and 2 of the patent document. It is stated that what is important in the set of bolts, nuts and washers is to reduce the variation in torque coefficient, and therefore curved projections are formed on the outer peripheral side of the end face on the washer side of the nut to facilitate penetration into the washer. And a structure in which a receding surface and an annular groove are formed on the inner peripheral portion. It is stated that the projections formed on the seat surface and the receding surface relieve the stress concentration on the first thread of the screw at the time of fastening, and further the effect is enhanced by the annular groove. In addition, it is suggested that the use of an effective lubricant is affected as the bolt axial force is affected by the lubricating performance of the contact portion between the nut and the washer and the lubricating performance between the nut screw and the bolt screw. However, the curved projections on the nut bearing surface do not apply, and a normal planar bearing surface does not apply, and the structure as a nut, the shape of the annular groove essentially related to the stress concentration relaxation characteristics, in particular There is no description about the depth. The effect of relieving stress concentration is indicated by the magnitude of the variation in torque coefficient, but the intrinsic structure and characteristics of the combination of bolt and nut, which is the effect of lubricant, protrusion, receding surface, or groove Even though it is a relation of Inherently, the variation in torque coefficient is derived from the friction state at the screw thread or bearing surface, the material of the bolt and the hardness, and this is a factor different from the purpose of reducing the load concentration of the first tightening.

The bolt and nut structure of Patent Document 6 adopts a fastening method and a purpose that is largely different from a normal bolt and a nut fastening method in which fastening is performed while rotating the nut. In order to increase the friction of the nut bearing surface so that the nut is difficult to rotate, it is characterized in that a convex protrusion is provided on the nut bearing surface to bite into the object to be fastened. It is the part that claims to "improved the nut having the flat surface so far".

Further, a second structural example of this nut is described in FIG. 7 of Patent Document 6. A separate part is inserted into the outer periphery of the hexagonal nut, but this separate part is a kind of sleeve-like structure that is fitted to the inner hexagonal nut and can not be rotated relative to the inner hexagonal nut, and on the washer side It is characterized in that a curved projection is provided. The assumed fastening action at the time of fastening is the same as in the first structural example, and the force from the seat surface enters the curved surface-like protrusion of this chevron, and the chevron curved surface-like protrusion deforms the other seat surface Later, it enters the flange portion of the inner nut upper part. In the thin upper flange as shown in FIG. 7 of the same document 6, there is a possibility that the flange may be bent to the open side when a force for buckling the fastening side curved surface projection is entered. In this type of “non-rotating nut”, deformation of the flange is not a serious problem, but the nut seat surface projections and the flange will also be deformed, so the bolt, nut and washer set of this structure are additionally tightened There is a problem that can not be reused.

In Patent Document 7, as a shear delayed fracture preventing nut, in order to make uniform shear stress acting on a screw thread of a bolt and a nut, a rotational parachute gap at the tip of the bolt and a nut A combination of flange lip and nut has been proposed.

The longitudinal cross section of the nut of Patent Document 7 is provided with a threadless portion (11 in FIG. 1) on the upper inner diameter side, and an oblique wedge-shaped lip is at the same height as the depth without the thread. It is intruding. For this reason, the height direction dimensions of the inner corner of the recess 11 without screw and the innermost part of the wedge-shaped lip outside the screw ridge are "height of the wedge-shaped lip from the object to be fastened ねじ space without screw It is the height to the bottom of 11 ". Although patent document 7 states that "the prevention of shear delayed breakage of a bolt" is established at this time, it is necessary to put the wedge-shaped lip to the vicinity of the top of the nut when there is this purpose. Due to this lip, the rigidity of the nut is insufficient, and the rigidity of the upper part of the nut is insufficient due to the repeated external force load, and the line connecting the lip deepest part of the nut and the engraved lower part of the upper part of the bolt (dent 11) There is a high risk of breakage and there is a question of durability.

Further, when there is a space 5 at the end of the bolt 8 shown in FIG. 1 of Patent Document 7, this bolt side screw portion tip end side can also be axially extended, as shown in FIG. 4 of Patent Document 7 Exchange of power becomes smaller. For this reason, there is also a possibility that it may become a bolt and a nut which can not generate and maintain the axial force specified by JIS (ISO).

Patent Document 8 proposes a nut having a large R (a spherical surface in which the inside is recessed) in a washer and a similar R bearing surface. The washer has a larger outer diameter than the nut, and when the surface of the part to be fastened under the washer is slightly inclined, or when the surface condition is uneven or unstable, tightening the nut against the bolt The structure shows that the washer-like substrate uniformly contacts the nut bearing surface, and fastening can be performed even when the surface of the object to be fastened is unstable. However, the washer has a larger outer diameter than the nut but no mention is made of the central bore diameter. The effect and structure leading to the reduction of the load on the bottom of the bolt thread in the first engagement are not disclosed, and the purpose is different from the present invention.

JP-A-52-79163 JP-A-52-131060 U.S. Pat. No. 4,189,975 JP-A-58-160613 JP 2005-265150 A Unexamined-Japanese-Patent No. 5-288209 Japanese Patent Laid-Open No. 2002-61619 Japanese Patent Application Laid-Open No. 1-182614

In the conventional method of bolt and nut fastening, although many improvements have been made to the bolt, there is still a crack axial fracture at the bottom of the mesh engagement of the bolt, which is the reason why It has been known that excessive stress concentration on the eyes. However, it was difficult to find out the situation where stress is concentrated on the first meshing area (how the force entering the nut flows into the bolt).

FIG. 4 is a longitudinal sectional view of a general fastening of a conventional flange nut. The screw threads of the flange nut 1 are substantially uniformly formed according to JIS B 0205 (ISO 724) from the fastening side to the open side. In FIG. 4, 1 is a conventional flange nut main body, 2 is a bolt, 3 is an object to be fastened, 8 is a screw thread side of a nut thread, 8a is an end face of a screw thread side of a nut thread and a nut bearing surface, Is the open end of the nut thread, 9a is the open end face of the nut thread, 14 is the nut bearing surface, 15 is the conventional thread valley bottom, 17 is the outer periphery of the nut, and 19 is the nut thread. . The threaded portion of the bolt 2 is screwed into the threaded portion of the nut 1 to clamp the washer 23 and clamp the object 3 to be fastened.

As a result of examining the stress load sharing in the case of fastening with a conventional bolt and nut, the inventor of the present invention shares 36.5% of the first peak in the case of 7 mountains and 20.6% of the second peak. After the third peak, I found that it was decreasing gradually. More than one-third of the total load is concentrated in the first mountain, and 70% or more of the total load is shared from the first mountain to the third mountain (load sharing ratio; 100% of the total load) And when each thread share the load,%). As described above, FIG. 4 shows the conventional fastening state, and the nut 1 fastens the object 3 via the washer 23. The bolt 2 penetrates the screw hole from below and is fastened to the nut. Figure 4-1 (a) shows the Mises equivalent stress distribution of the nut (seven screw thread) same as Figure 4 (Maximum of thread valley bottom marked with * on the left side of the first ridge of bolt (No. 1) Indicates where stress is applied and crack axis fracture is likely to occur). The force entered from the nut bearing surface 14 is directed in the direction of pushing up the nearest bolt thread No. 1 and the bolt is most strongly pulling the No. 1 peak by the axial force, so the part * becomes open ing. Fig. 4-2 is a vector diagram of the Mises equivalent stress and shows what kind of force is flowing to the bolt at the maximum principal stress (tensile stress), and Fig. 4-3 also shows the minimum principal stress (compressive stress) at the vector diagram. Indicated here is the flow of force in the nut. Also in this vector diagram, it can be seen that the power is concentrated in the meshing first mountain.

With respect to the large load on the meshing first peak, it is possible to reduce the load on the meshing first peak by increasing the number of screw threads shared by the nut. On the other hand, the same analysis was conducted on the 8 and 9 peaks in addition to the 7 and 7 conventional nuts, and the load sharing was examined. As a result, when the number of peaks increases on the open side, the conventional nut is 8 nuts. In the case of meshing, the load on the first peak is about 1% down and 34.5%, and in the case of the nut 9, it is confirmed that the load on the first peak is 33.4%. The Figure 4-1 (b) shows the Mises equivalent stress distribution map of screw 8 and Figure 4-1 (c) shows the Mises equivalent stress distribution of 9 screw threads, comparing these load sharing ratios with 7 Figure 4-4 (a) (conventional nut (load distribution ratio comparison chart for 7, 8 and 9 threads) is displayed, and a comparison bar graph of these three load distribution ratios is shown in Figure 4-4 (b). In the conventional method, the load sharing ratio to mesh 1 is 36.5% at 7 mountains, 34.5% at 8 mountains, 33.4% at 9 mountains, and the number of screw threads is 7 mountains. In each case of 8 mountains and 9 mountains, excessive stress is applied to the bolt side meshing first valley thread valley bottom of ※ part in Fig. 4-1 (a), (b), (c) This result indicates that the reduction effect of the meshing first peak load is small even if the number of threads of the conventional type nut is increased.

By optimizing the structure of the nut according to the present invention with respect to the load concentration on the meshing first mesh of the conventional type nut, the bolt and the bolt are tightened by reducing the load on the first mesh meshing engagement. It is possible to provide a nut that improves the fatigue fracture life of the cracked axis fracture from the bottom of meshed first valley which is the strength weakest part.

The present invention provides the following inventions in order to solve the above-mentioned problems. That is, by increasing the load sharing after the third opening side by setting the nut structure to make the flow of the force of the load received by the nut more directed to the open side meshing thread with low load sharing, the meshing can be achieved. A nut having a structure characterized in that load concentration on a first peak is reduced.

(1) It is a nut for fastening,
A. In the shape of the longitudinal sectional view of the nut, a convex-shaped space is concentrically formed on the bearing surface on the nut fastening side around the axis of the screw, and the space is connected by a straight line, a curve or a combination thereof. It is a structure in which a space is formed as a shape, and the depth from the bearing surface of the space is L ₂ , and the axial length from the first valley bottom of the fully threaded portion of the nut to the bearing surface is L ₁ , By forming the space with the depth L ₂ of the space as L ₁ <L ₂ ≦ L ₁ + length of 5 threads of the screw thread;
B. A structure having a rectangular recess on the screw center side of the bearing surface on the fastening member side of the nut in the shape of the longitudinal sectional view of the nut, wherein the recess has an inner wall and a curve, straight line, or the like rising perpendicularly from the nut bearing surface Have a corner portion and an upper surface combined, and from the position of the upper surface the axial length of the incomplete thread portion of the nut plus the length of two pitches of the nut is La, and Assuming that the axial length from the bearing surface to the upper surface is Lb, and the radial length of the recess to the thread valley bottom of the nut and the inner wall of the recess is Lh, Lb is at least 0.001 times the La C. by forming the recess concentrically with the center of the screw in the range of 0.5 to 5 times the range of La and Lh; A nut having a two-part structure comprising a nut body having a screw shaft portion provided with a screw thread inside and a flange bearing surface portion and a pipe-like nut component having a chamfered bearing surface on at least one end face inner diameter side A shape of a longitudinal sectional view of the nut body is T-shaped, and a length in which a screw shaft portion of the nut body is introduced from the flange seat surface portion of the nut body toward the inner object of the nut component is The hollow pipe-shaped nut component is formed on the outer surface of the screw outer surface so that the incomplete screw part length s + the length of the screw pitch 0.5 or more, and the length of the incomplete screw part s + the screw pitch 5 m or less The T-shaped nut body is disposed so that the lowermost portion of the T-shaped nut body is not in contact with the object, and the uppermost portion of the nut part is in contact with the flange-like bearing surface of the T-shaped nut body The lower part of the nut part is tightened The length of the nut part is set so as to contact the object, the inner diameter surface of the nut part and the outer peripheral surface of the nut body are respectively rotatable, and the nut body and the nut part are formed concentrically with the center of the screw By doing;
By increasing the load sharing after the third mesh of meshing by setting the nut structure to make the flow of the force of the load received by the nut more directed to the open side meshing thread with low load sharing, meshing 1 mountain A nut of a structure characterized in that it is configured to reduce load concentration on the eyes.
(2) Engaging with at least a bolt on the screw thread surface of nut Threaded surface of the first screw thread or a part or all of the other screw threads with bolt side screw, or bevel on both sides of screw thread (DLC) film, BN film, WC film, CrN film, HfN film, VN film, TiN film, TiCN film, Al ₂ O ₃ film, ZnO film, SiO ₂ film, alumite, metal plating, solid lubricating layer, phosphoric acid There is provided a nut according to the above (1), which is coated with any of manganese conversion treatment, carburizing and quenching, nitriding treatment, and chromiumizing treatment, or a combination thereof.
(3) Diamond-like carbon (DLC) film, BN film, WC film, WC film, CrN film, HfN film, VN film, TiN film, TiCN film, Al ₂ O ₃ film on both or one side of the contact surface of nut body and nut part ZnO film, SiO ₂ film, alumite, metal plating, polymer resin coating, solid lubricating layer, manganese phosphate chemical conversion treatment, carburizing and quenching, nitriding treatment, chromium treatment, or any combination thereof The nut according to any one of (1) to (2).
(4) A diamond-like carbon (DLC) film, a BN film, a WC film, a CrN film, a HN film, a VN film, a TiN film, a TiCN film, an Al ₂ O ₃ film, a ZnO film, on the surface of the nut in contact with the object to be fastened. A SiO ₂ film, alumite, metal plating, polymer resin coating, solid lubricating layer, manganese phosphate conversion treatment, carburizing and quenching, nitriding treatment, chromiumizing treatment, or a combination thereof is coated (1) to Providing the nut as described in any of (3).

By the structure of the nut according to the aspects (A), (B) and (C) of the present invention, the force applied from the nut bearing surface is directed to the open side thread after the third mesh and more load is shared. The load concentration on the meshing first peak can be reduced, and this effect leads to the improvement of the fatigue fracture life of the cracked axis fracture of the bolt valley bottom of the meshing first peak.

In order to obtain this effect, it is preferable to use a nut structure in which "flow of force" is more frequently directed to the third and subsequent open side. As a method, changing the external shape and structure of the nut without changing the JIS (ISO) standard of the screw thread shape of the nut, that is, optimizing the structure to obtain the force of the nut It can be directed to the open side screw after the third peak. Alternatively, by applying a force to the meshing screw 1 peak by setting the nut as a two-piece configuration and optimizing the structure where the force passes and directing the stress entering the nut to the open side thread after the 3rd peak Reduction of concentration can be realized.

Furthermore, by adding the surface treatment to the nut shown in the above (2) to (4), the friction at the time of fastening, the slidability on the screw surface and the weatherability of the surface can be improved. It can be realized.

The above-mentioned screw meshing first ridge is, for example, a screw thread indicated by a symbol 1 shown in a bolt and a nut of the conventional method shown in FIG. The side of the first thread of the nut loads and fastens the side of the first thread of the bolt. The "first thread" of the nut is on the fastening side and the thread is the first fully threaded part having a normal thread shape. On the other hand, the above-mentioned incomplete thread portion is a portion having a length including about one pitch and a chamfer from the start of thread cutting.

The position of the first thread of the nut is the first peak of the complete thread. On the bolt side, the screw thread of the bolt engaged with the first screw thread of the nut is the first screw thread of the bolt, and the first valley bottom of the bolt is located on the fastening side of the first screw thread of the bolt.

The screw shape of the nut of the present invention preferably conforms to that defined in JIS B 0205 (ISO 724). Also, the configuration of the nut of the present invention is also applied to a nut having a thread shape which is widely used conventionally, such as an inch screw, for example, and these are also part of the present invention.

The load sharing of the fastening force by the bolt and nut works with the same sharing ratio as the initial tightening as axial force fluctuation not only at the time of initial tightening but also against external load such as vibration where external force is applied to the screw fastening portion. . In particular, it is necessary to reduce the load sharing to the first thread where the load is severe, because the fatigue fracture strength of the meshing first peak bolt thread valley bottom subjected to external force load (fluctuating axial load) combined at the same load sharing rate Is effective in improving

Although fracture of bolt and nut joints often occurs as cracked axis fracture at the bottom of meshing 1 of the bolt, there is an effect of reducing the initial joint load which is considered to be effective in improving fatigue fracture strength. Explain what it will do. The SN diagram determined from the fatigue test results for bolts shows the relationship between fatigue fracture life (repetition number Nf) and external load (stress amplitude σr), but in general, it should be shown by the following experimental formula Can.
Nf · σr ^b = C
Where Nf: The number of cycles of load until fatigue failure σr: Stress amplitude of load b: Stress index (generally 3 to 5)
C: Material constant As shown here, lowering the load on the bottom of the bolt thread bottom of the fastening meshing leads to reducing the external force load (σr) sharing, and the stress amplitude b of the lowered load (b ( In general, it leads to the effect that the number of repetitions Nf can be increased by 3 to 5).

In general, it is not possible to directly view the force transmitted in a substance, so finite element analysis is useful as a method of predicting the state of the force in the substance and the flow direction. In order to analyze each screw thread load in bolt and nut fastening of the conventional method, simulation analysis of the screw fastening part is carried out by CAE (Computer Added Engineering) method using FEM (Finite Element Method), The von Mises equivalent stress distribution of the method nut is shown in Figures 4-1 (a), (b) and (c). Further, the same analysis is performed on the aspects (A), (B) and (C) of the present invention.

In conducting this analysis, the number of screw threads of the nut is generally selected, and the number of effective threads is selected to be the same in each aspect of the present invention. The same tightening force and nut strength at the time of tightening are all adopted. The same conditions apply to the nuts having eight threads and nine threads, which are compared with those of the conventional system 7, except for the number of threads.
In the present invention mode (C), the analysis in the case of 7 threads and the analysis with 8 threads are performed, and the load sharing of the

conventional method

7 and 8 is compared respectively.

As shown in Fig. 4-1, in the conventional method, the internal stress is highest at the first meshing thread (marked by 1 in Fig. 4-1 (a)), and the second ridge (marked by 2 in Fig. 4-1). In the third peak (marked 3 in Fig. 4-1), the stress drops sharply. This situation is shown in Fig. 4-4 (a) as the load sharing ratio of all threads, and Fig. 4-4 (b) shows a comparison of the load sharing ratio in a bar graph. For the conclusion of the conventional method 7 mountain, it is shown by the bar graph of the white frame display. In this case, 35.6% of the total load is applied to the first mountain, 20.6% for the second mountain and 14.4% for the third mountain, and the load sharing up to the third mountain is actually 70% or more Reaching The load sharing ratio of each thread is only about 11 to 4% or less after the fourth peak. The bottom of the first peak of the bolt (* mark in Fig. 4-1 (a)) is highly stressed, and the crack axial fracture of the bolt that occurs when using the conventional type nut is the bolt of this first mesh. It often occurs from the bottom of the thread.

It is a longitudinal cross-sectional view which shows an example of the nut of the 1st aspect (A) of this invention. (A) Cross-sectional view of nut, (b) Top view seen from nut open side, (c) Example of top view seen from nut seat surface side. The Mises equivalent stress distribution figure of an example of the nut of 1st aspect (A) of this invention. The vector diagram of the maximum principal stress (tensile stress) of an example of the nut of the 1st aspect (A) of this invention. The vector figure of the minimum principal stress (compression stress) of an example of the nut of the 1st aspect (A) of this invention. Example of aspect (A) of this invention and the conventional system nut The load share ratio comparison of FIG. 4-1. Bar graph of an example of the embodiment (A) of the present invention and a conventional nut FIG. The modification longitudinal cross-sectional view of a 1st aspect (A) of this invention is shown. The modification longitudinal cross-sectional view of a 1st aspect (A) of this invention is shown. The longitudinal cross-sectional view which shows an example of the basic form of the nut of the 2nd aspect (B) of this invention. The longitudinal cross-sectional view of the modification of the 2nd aspect (B) of this invention. Miess corresponding stress distribution figure of the 2nd mode (B) other modifications of the present invention. 2nd aspect (B) other modification of this invention. 2nd aspect (B) other modification of this invention. The longitudinal cross-sectional view which shows an example of the nut of the 3rd aspect (C) of this invention. The Mises equivalent stress distribution figure of an example of the nut of the 3rd aspect (C) of this invention. The numerical comparison table of the load share rate of an example of the nut of the 3rd mode (C) of the present invention, and a conventional system. The bar graph of the example of the nut of the 3rd aspect (C) of this invention, and comparison with a conventional system. The Mises equivalent stress distribution figure of the modification of the nut of the 3rd aspect (C) of this invention. The numerical comparison table of the load share rate of the modification of the nut of the 3rd mode (C) of the present invention, and a conventional system. The bar graph of the modification of the nut of the 3rd aspect (C) of this invention, and comparison with a conventional system. The longitudinal cross-sectional view (a) of the flange nut of a conventional system, the top view from the top (b), and the top view from the bottom (c). Mises equivalent stress distribution map of the conventional method nut of seven screw threads. Miess equivalent stress distribution figure of the conventional type nut of eight screw threads. Mises equivalent stress distribution map of the nut of the conventional system with a screw thread number nine. The vector diagram of the maximum principal stress (tensile stress) of the conventional type nut of seven-thread number thread pile. The vector diagram of the minimum principal stress (compression stress) of the conventional type nut of seven-thread number thread pile. Conventional load share numerical value table of nut. Bar chart of conventional nut load share.

The nut of the present invention is
A. In the shape of the longitudinal sectional view of the nut, a convex-shaped space is concentrically formed on the bearing surface on the nut fastening side around the axis of the screw, and the space is connected by a straight line, a curve or a combination thereof. A space is formed as a shape, the depth from the bearing surface of the space is L ₂ , and the axial length from the valley bottom of the first screw of the fully threaded portion of the nut to the bearing surface is L ₁ When forming the space, when the depth L ₂ of the space is L ₁ <L ₂ ≦ L ₁ + length of thread 5 pitches;
B. A structure having a rectangular recess on the screw center side of the bearing surface on the fastening member side of the nut in the shape of the longitudinal sectional view of the nut, wherein the recess has an inner wall and a curve, straight line, or the like rising perpendicularly from the nut bearing surface Have a corner portion and an upper surface combined, and from the position of the upper surface the axial length of the incomplete thread portion of the nut plus the length of two pitches of the nut is La, and Assuming that the axial length from the bearing surface to the upper surface is Lb, and the radial length of the recess to the thread valley bottom of the nut and the inner wall of the recess is Lh, Lb is at least 0.001 times the La C. by forming the recess concentrically with the center of the screw in the range of 0.5 to 5 times the range of La and Lh; A nut having a two-part structure comprising a nut body having a screw shaft portion provided with a screw thread inside and a flange bearing surface portion and a pipe-like nut component having a chamfered bearing surface on at least one end face inner diameter side A shape of a longitudinal sectional view of the nut body is T-shaped, and a length in which a screw shaft portion of the nut body is introduced from the flange seat surface portion of the nut body toward the inner object of the nut component is The hollow pipe-like nut component on the outer surface of the screw outer surface so that the incomplete screw thread length s + the length of the screw pitch 0.5 ridges or more and the length of the incomplete screw threads s + the screw pitch 5 ridges or less In which the bottom of the T-shaped nut body is not in contact with the object, and the top of the nut part is in contact with the flange-like bearing surface of the T-shaped nut body, Also, the bottom of the nut part The length of the nut part is set so as to contact the fastener, and the inner diameter surface of the nut part and the outer peripheral surface of the nut body are respectively rotatable so that the nut body and the nut part are concentric with the center of the screw. By forming;
By increasing the load sharing after the third peak by making the flow of the force of the load received by the nut more directed to the open side meshing thread with low load sharing, the meshing first peak The present invention is characterized in that it is configured to reduce the maximum load sharing of and reduce the load concentration on the meshing first peak. By this feature, by reducing the load on the meshing first peak, it is possible to improve the fatigue fracture life of the cracked axis fracture from the meshing first valley bottom which is the bolt fatigue strength weakest part.

The nut of the first aspect (A) and the second aspect (B) of the present invention is a one-piece structure, and a convex space is formed toward the open side on the bearing surface of the central portion on the fastening side of the nut The process of forming the concave portion is performed, and the “flow of force” is made to pass through the nut bearing surface and the outer peripheral portion of the nut body, and to be directed to the third and subsequent open side of the screw. The third aspect (C) is a two-part configuration of a nut body and a nut part, in which “flow of force” is directed to the open side of the screw on the third and subsequent sides of the screw using the nut body and the nut part It is. With such a structure, it is possible to provide a nut characterized by having a structure capable of simultaneously reducing the load sharing of both the initial tightening load and the external force load applied to the meshing first peak thread.

In the description of each aspect of the present invention, the screw thread conforms to JIS B 0205 (ISO 724).

Further, in the present invention, the length is based on one pitch of a screw, but there are a plurality of bolts and nuts having the same thickness but different in thread pitch, so in this case the thread thickness is not used. The screw pitch is adopted as one reference of the length.

In the following, the structure of the first aspect (A) is taken up as a representative, and the reduction of the load on the first engagement mesh is described.
In the first aspect (A), in the shape of a longitudinal cross-sectional view of a nut, a space of an upwardly convex shape connected to a bearing surface on a nut fastening side by a curve, a straight line, or a combination thereof centered on the screw axis. Are concentrically formed, and the depth from the bearing surface of the convex space is L ₂ , and the axial length from the bottom of the first screw of the fully threaded portion of the nut to the bearing surface is L ₁ when the depth L ₂ of the space, by forming a said space as the length range of _{_{_{L 1 <L 2 ≦ L 1}}} + screw thread 5 pitches, such the threads of the fastening when the nut stress It is characterized in that it makes more load sharing by the screw thread on the open side 3rd mountain and subsequent ones to share a lot of load in comparison with the conventional method, and reduces the concentration of load on the 1st mesh. Do. Here, the thickness of the screw shaft portion of the nut having a screw thread inside is not constant because of the structure between the space and the nut screw thread, and the shaft portion thickness connected from P ₂ side to P ₁ side is P ₂ It is also possible to make a gradual change from P ₁ to P ₁ , and the P ₂ side can be made thicker and the P ₁ side of the seat surface can be made thinner by a curve, a straight line, or a combination of them.

The longitudinal cross-sectional view of an example of the nut of a 1st aspect (A) is shown in FIG. FIG. 1 is a longitudinal sectional view of the nut (a), a plan view (b) seen from the open side of the nut, and a plan view (c) seen from the seat surface, 1 being a nut, 2 being a bolt, 3 being a fastening 4 is a space between the nut bearing surface and the lowermost end of the nut shaft, 5 is a convex space above the nut bearing surface, 7 is the screw shaft lowermost end, 8 is a nut fastening side, 9 is a release of the nut The side 9a is a nut open end, 14 is a nut bearing surface, 17 is an outer peripheral portion of the nut, 18 is a screw shaft portion provided with a screw thread inside, and 19 is a nut screw thread.

The fastening situation will be described with reference to FIG. When fastening the object 3 with the bolt 2 and the nut 1, the lowermost end 7 of the screw shaft at the central part of the bearing surface side of the nut has the air gap 4 and the force from the bearing surface It does not take place directly. Since the nut bearing surface 14 on the outer peripheral side of the space 5 is in contact with the to-be-fastened object 3, the force from the to-be-fastened object 3 at the time of fastening is exchanged at the nut bearing surface 14 in contact with the to-be-fastened object 3 . The fastening force enters the nut bearing surface 14 from the object 3 and passes through the inside of the nut to the thread 19 of the nut. At this time, the force proceeds along the inside of the nut to the curve inside on the outer periphery of the space 5, then enter the bolt through the deepest (P ₂ near) the street each thread space 5. P ₂ threads 19 nearest from the vicinity in the example of FIG. 1 is the third nut thread. The other forces are transmitted to the fourth, fifth, sixth and seventh. Thus, the force toward the open side is transmitted to the other bolt thread, and a large amount of internal stress is applied to the third and subsequent threads. The bolt remains engaged by the axial force and the 1st peak receives the maximum principal stress (tensile stress), but the load sharing of the 1st peak decreases relatively by receiving a lot of force on the open side of the nut . Further, combined with the shape effect of the nut screw shaft portion 18, the load on the first meshing engagement between the bolt and the nut is significantly reduced as compared with the structure of the conventional system. By thus directing the force to the open side thread third and later, the load on the meshing first peak can be reduced.

FIG. 1 is a view for explaining the relationship of the depth of the space 5 in the first aspect (A) of the present invention, wherein P ₁ is the bottom of the first full thread in the screw shank 18 of the nut. located in central, P ₂ is located at the deepest portion in the depth direction of the space. Let L ₁ and L ₂ be distances from the bearing surface 14 of the nut to P ₁ and P ₂ , respectively.

FIG. 1 shows an arbitrary cross section within one thread pitch through the central axis of the nut and as shown in the enlarged view of the nut screw shank 18, the screw inlet at the position of the lowermost part 7 of the screw shank 18. There is a chamfer that has been machined, and then there is an incomplete thread portion of about 1 pitch from the start of thread cutting, and a complete thread portion is connected behind it. P ₁ screw 1 rotation distance from the seating surface of the L ₁ to change position (360 degree rotation) in the affected thread pitch one peak + the chamfer length. Thus the distance L ₁ from the seat surface 14 of the P ₁ is the sum over distance dimensions and thread chamfer length and incomplete thread portion length of the gap 4.

In the above embodiments (A), as shown in FIG. 1, the point P ₁ and the space 5 in the thread root center of the first thread of the seating surface side of the nut thread that is a complete thread portion deepest relationship _{P 2} in the part is at a distance _{L 1} and _{L 2} from the seating _surface, to set the dimensions of the L 2> _{L 1} and becomes _{L 2.} L ₁ is one pitch distance when the rotation of 360 degrees because of the screw is changed, L ₂ is often a constant numerical by molding. For this reason, L ₂ is preferably at least deeper than L ₁ , but the upper limit of depth is suitably L ₁ + length of 5 pitches of screw threads. In one example of the basic form 1 it is set to P ₂ to the position of a length of about 2.4 pitch than P _1.

In the embodiment (A), changing the thickness of the screw shaft 18 toward the fastening side or changing the shape from the deepest portion (P ₂ ) of the space 5 to the shaft is the same. It is also possible to form in the vicinity of the lowermost portion 7 by the thickness. It is preferable that the shape be integrated with the shape of the space 5 and that a shape of a straight line, a curved line, or a combination thereof be adopted. It is preferable to provide a curve near the lowermost portion 7 to avoid stress concentration.

Considering the ease of processing in which the convex shape space is provided on the upper side, the space 5 having the convex shape is practically used as the space 5 having a shape connected by a smooth curve or a straight line as shown in an example or a modification of the basic form Structure. The upward convex shape may be any shape without departing from the object of the aspect (A) of the present invention, and is included in the invention of the first aspect (A). FIGS. 1-5 (a) and (b) show two modifications to FIG. 1, but mainly the shape of the space 5 and the outer shape in the seat portion are different. In either case, the force entering from the object 3 is passed through the inside of the nut 1 and directed to the open side of the three or more threads engaged with the mating bolt. Shapes having similar effects can be determined according to various conditions such as manufacturing requirements, in addition to the modification shown in FIGS.

What is important in the present embodiment (A) is the formation of an upwardly convex space 5 formed on the bearing surface side of the nut. In particular, it is a selection of the depth, and L ₂ is set such that L ₁ <L ₂ ≦ L ₁ + length of 5 pitches of screw thread is satisfied, and the force passing near P ₂ and the force pulled from the bolt By realizing a nut shape of a structure having a corresponding strength, it is possible to direct a large flow of force to the third and subsequent threads on the open side, and the load on the meshing first peak can be reduced.

In general, when a force is applied to a certain point from the outside of a flat plate, the force spreads in proportion to the size from the location to the inside, the force travels the shortest path, and the force does not bend at a steep angle even when it bends. It is known that power passes through easily accessible places and that power does not pass through space. The characteristics of how this force is transmitted can be clearly read also in the Mises equivalent stress distribution and the vector diagram.

Based on how this force is transmitted, the von Mises equivalent stress distribution diagram of Fig. 1-1 corresponding to the aspect (A), the vector diagram of the maximum principal stress (tensile stress) where the flow of force can be seen in Fig. 1-2, The flow of force can be confirmed by the vector diagram of the minimum principal stress (compression stress) in Fig. 1-3. Especially in the vector diagram, small arrows are closely arranged, the direction shows the direction of force, the length shows the magnitude of force, and the density of the arrangement is the situation where a lot of force flows in each direction at that place Is shown.

The von Mises equivalent stress distribution diagram of FIG. 1-1 visualizes the above vector diagram as an overall stress distribution, and is color-coded in black and white four gradations. Focusing on where the direction of the arrow points in the vector diagrams (Fig. 1-2, Fig. 1-3), the points where many forces are facing go to the threads in the nut, but where many are pointing It is No. 3 and No. 4 of the nut thread. It can also be seen that there are also many toward the

open side

5, 6 and 7 thread. As for the nut screw thread fastening side, it is transmitted while bending in the direction of No. 2 and then No. 1 so as to wind a vortex from the vicinity of P ₂ . In Fig. 1-2, the bolt thread and the bolt shaft are subjected to an axial force that pulls them toward the fastening side, so from the diagonal thread surface of the nut to the diagonal thread surface of the bolt I can see how I was concentrating and putting power. Since the bolt axial force is directed to the fastening side, the No. 1 thread is subjected to the largest tensile stress, but No. 1 and No. 2 of the nut are bent from around P ₂ around the screw shaft 18 It receives more of the small force and the tensile force from the bolt, and it is in a situation where it is pulled to the fastening side in order of strength, such as the nut screws No. 3, No. 2 and No. 1. For this reason, in the case of the No. 1 nut screw, a black color appears to indicate that the internal stress is low. The shape effect of the screw shaft is added here.

In the analysis diagram of the modified example shown in FIG. 1-1, FIG. 1-2, and FIG. 1-3, the force from the nut flows in the direction of the thread ridge after the third peak, and the fastening meshing first peak Reduce the load on The load sharing after the third peak has increased compared to the conventional method, and the power reaches to the seventh peak. In particular, the stress large area (white display area) in Fig. 1-1 is narrow and small for the 1st, 2nd, and 3rd thread threads, and dark gray (stress is slightly small for 4th, 5th, 6th and 7th). ) Appear in a wide area.

As seen in the same figure 4-1 in the conventional method, the vector diagram 4-2 of the maximum principal stress, and the figure 4-3 in the minimum principal stress, in the conventional manner, the situation where it is controlled by the force passing through the innermost diameter side of the nut In contrast to this, the stress distribution map of FIG. 1-1 of the present invention has a completely different stress distribution, and the aspect (A) of the present invention is such that the flow direction of force is tightened toward the third mesh and thereafter. It is clearly shown to reduce the load on the mesh 1st peak.

As a result of these, the load sharing ratio of the meshing first peak in one example of the aspect (A) is 26.3% (conventional method: 35.6%). A comparison chart of this result with that of the conventional method 7 mountain based on the load sharing ratio of each mountain is shown in FIG. 1-4 (a), and a comparison bar graph of this numerical value is shown in FIG. 1-4 (b). From this comparison, it can be read that the load sharing after the third peak is increased and the load sharing of the meshing first peak is reduced in the example of the nut of the mode (A) as compared with the conventional method.

Regarding each corner of the convex space structure nut in the first aspect (A), the processing of each corner is preferably as follows. It is preferred to use corner shapes which are made with optimal stress concentration relaxation curves for each part location. The stress concentration relaxation curve has, for example, a quadratic curve (simple R, composite R, ellipse, etc.), and a straight line such as an oblique C-cut can also be used.

In the first aspect (A), with regard to the surface roughness of the nut, the screw surface conforms to the JIS standard, and the sliding surface has a fine-class finish, and the other surface has an intermediate-class finish or a required surface roughness. However, it is desirable that the surface roughness be consistent with the surface treatment described later.

Next, the nut of the second aspect (B) of the present invention will be described.
The nut (B) of the present invention has a rectangular recess on the screw center side of the bearing surface on the fastening member side of the nut in the shape of the longitudinal sectional view of the nut, and the recess rises vertically from the bearing surface It has an inner length and a curve, a straight line, or a corner and an upper surface that combines them, and the axial length from the position of the upper surface is the axial length of the incomplete thread of the nut plus the two pitch lengths of the nut When the axial length of the recess from the bearing surface to the upper surface is Lb, and the radial length of the recess to the bottom of the screw thread of the nut and the inner wall of the recess is Lh, Lb is at least 0.001 times La A recess having a length of 1 time or less and Lh of 0.5 to 5 times the length of La is formed concentrically with the center of the screw.

By forming the recess in the bearing surface portion of the nut in this manner, the flow of force entering the nut upon fastening enters from the entire surface of the nut bearing surface in contact with the object, and flows along the wall of the nut recess, It passes near the corner, goes to the vicinity of the central part of the nut, after the third mountain on the open side, and flows widely dispersed in all the screw threads. Although the tensile stress that enters the nut from the bolt is the largest at the first mesh, the stress applied to the screw thread of the nut during fastening can be shared more by the screw thread side at the open end, It is possible to reduce the load on the first engagement between the nut and the bolt.

The present invention mode (B) will be described with reference to the drawings. FIG. 2 is a longitudinal sectional view showing an example of the nut of the second aspect (B) of the present invention, and the nut 1 has a structure having a recess 10 in the lower portion of the inner diameter of the nut. In the recess 10, a wall 11 standing vertically from a nut bearing surface 14 in contact with the object 3 to be fastened, and a corner portion 12 having a straight line sandwiched by curves connected thereon (a straight line on this corner 12 is from the fastening side of the nut It is preferable to face the screw valley bottom of the second and subsequent peaks. Fig. 2 shows an example facing the second valley bottom), and there is the upper surface 13 connected from the corner 12 and the innermost screw side of the upper surface 13 Is an open space composed of a line leading to the thread 19 having a chamfered portion and an incomplete thread portion sequentially on the open side. The recess 10 has an axial length La, which is the sum of the chamfered dimension of the threaded portion of the nut 1 + the axial length s of the incompletely threaded portion and the two pitches of the nut. Lb is 0.001 times or more of La as Lb is the axial length from Lb to the upper surface 13 and Lh is the radial length of the recess 10 from the thread valley bottom 15 of the nut 1 to the inner wall 11 of the recess 10 The recess 10 is formed concentrically with the center of the screw, with a length not more than double and Lh being a length not less than 0.5 times and not more than 5 times La.

Various modifications can be made to the second aspect (B) of the present invention. Fig. 2-1 shows a first modification, in which the corner portion 12 of the recess 10 has one stress concentration relaxation curve structure, and the corner portion 12 is connected to the upper surface 13 so as to sequentially chamfer and incompletely screw , Through the thread root 15 to the thread 19. The dimension in the recess is such that the axial length of the incomplete thread portion of the nut 1 + the axial length s of the chamfer plus the length of 2 pitches of the nut is La, and from the bearing surface 14 to the upper surface 13 of the recess 10 Lb is 0.001 times or more and 1 times or less of La when the axial length of L is Lb, and the radial length of the recess 10 to the thread valley bottom 15 of the nut 1 and the inner wall 11 of the recess 10 is Lh. The recess 10 is formed concentrically with the center of the screw with a length Lh of 0.5 to 5 times the length of La. In the modification of FIG. 2-1, Lh is about 1.1 times La. By adopting this structure, the force flow can be made to flow much from the nut bearing surface 14 through the outer peripheral portion of the nut and to the third and subsequent peaks on the open side. In addition, the nut has a simple shape for processing, and has the advantage of easy manufacture including shape confirmation.

A Mises equivalent stress distribution chart of one example of FIG. 2 which is a basic example of the present mode (B) is shown in FIG. If the Mises equivalent stress distribution in FIG. 2-2 is carefully examined, the force entering from the nut bearing surface 14 often flows toward the 45 ° diagonal thread in the nut bearing surface. From the point close to the center of the bearing surface 14 toward the screw thread side 45 degrees diagonally parallel to the corner 12 straight line part, the force flowing from the nut thread No. 3 to No. 4 and 45 degrees from the stepped outer periphery of the nut It is seen that the screw heads 5 and 6 head to the screw thread side while leaning to the screw thread side. The force flowing around the corner 12 and flowing horizontally to the first mountain on the fastening side parallel to the upper surface 13 is small. A small black stress appears in the rear of the No. 1 thread of the nut (inside the nut). Such a black portion is not found in the conventional nut (FIG. 4-1), and it is considered that the force passing through the corner 12 is flowing on the slightly open side of the black portion. The force spread in the nut will receive the force drawn from the bolt thread when it reaches the thread, but the load on the first meshing tooth as a result of the force being distributed to many threads is conventionally Compared to the scheme is reduced.

In the basic example of this mode (B) shown in FIG. 2, the ability to direct the force entering from the nut bearing surface 14 to the open side of the nut can be easily controlled as compared with the modification of FIG. For example, the length of the upper surface of the reference numeral 13 in the figure is increased, and the Lh length in the bearing surface is increased to about 2.0 times La, or the inclination of the straight portion of the corner 12 is inclined by more than 45 degrees. And a structure in which the length of the wall 11 is slightly shortened. Thus, the direction of the force can be controlled by optimally combining the elements of the recess, and the load sharing to the meshing first peak can be reduced. Although not shown, even in the case of the other modified example of the aspect (B), the load sharing ratio of the meshing first peak shows a numerical value less than 30%.

A bar graph comparing the load sharing rates of the example of FIG. 2 of the mode (B) and the conventional method is shown in FIG. 2-3 (a) and FIG. The black frame display in the bar graph shows a modification of the aspect (B). By the way, the load sharing ratio is reduced to 29.6% in the modification of the mode (B) as compared with 35.6% in the conventional method in the meshing first peak. The aspect (B) increases after the third peak.

In addition, the shape of the open side of the nut of the present embodiment (B) may be a shape that can use a conventional fastening tool, such as a hexagon or a square.

With regard to surface roughness of wall surface 11, corner 12 and top surface 13 of nut bearing surface 14 or recess 10, the screw has a fine-class finish according to JIS standard, the nut seat surface has a fine-class finish, and the other surface has a rough finish Alternatively, although it is preferred to have a co-finish, it is more preferred to have a surface that is compatible with the surface treatment.

With regard to the corners on the recess 10, the nut bearing surface 14 and other surfaces, all corners preferably have a shape having a stress concentration relaxation curve such as a circular arc, a quadratic curve such as a part of an ellipse, etc. Is desirable.

Next, the third aspect (C) of the present invention will be described.
C. A nut having a two-part structure comprising a nut body having a screw shaft portion provided with a screw thread inside and a flange bearing surface portion and a pipe-like nut component having a chamfered bearing surface on at least one end face inner diameter side A shape of a longitudinal sectional view of the nut body is T-shaped, and a length in which a screw shaft portion of the nut body is introduced from the flange seat surface portion of the nut body toward the inner object of the nut component is The hollow pipe-shaped nut component is formed on the outer surface of the screw outer surface so that the incomplete screw part length s + the length of the screw pitch 0.5 or more, and the length of the incomplete screw part s + the screw pitch 5 m or less The T-shaped nut body is disposed so that the lowermost portion of the T-shaped nut body is not in contact with the object, and the uppermost portion of the nut part is in contact with the flange-like bearing surface of the T-shaped nut body The lower part of the nut part is tightened The length of the nut part is set so as to contact the object, the inner diameter surface of the nut part and the outer peripheral surface of the nut body are respectively rotatable, and the nut body and the nut part are formed concentrically with the center of the screw By doing;
It is characterized in that the stress applied to the screw thread of the nut at the time of fastening is more directed to the screw thread on the open side and after the third thread on the open side to reduce the load concentration on the first engagement between the nut and the bolt. Do.

A longitudinal sectional view of a nut according to a third aspect (C) of the present invention is exemplarily shown in FIG. The shape of the longitudinal sectional view of the nut body 1 is substantially T-shaped, and the nut body 1 is integrated with the screw shaft portion provided with a screw thread inside, and at least on the side surface of the flange lower surface portion screw shaft portion 18 of the nut body 1 It has a structure in which a pipe-shaped nut part 6 having a chamfering structure for preventing interference with the shaft part 18 is disposed on one inner diameter side of one side, and the nut main body shaft part 18 is rotatable in the nut part 6 The body 1 is screwed with a bolt 2 inside, and contacts and rotates with the nut part 6 at the sliding surface 16. The length from the top surface 22 of the nut part 6 to the bearing surface 14 is from the flange seating surface of the nut body 1 to the top of the screw shaft so that the screw shaft lowermost part 7 of the nut body 1 does not contact the object 3 to be fastened. The structure in which the nut part 6 is in contact with the object 3 is shown longer than the length to the lower part 7. The upper open side outer shape of the nut body 1 can be shaped according to the fastening tool. The thickness of the screw shaft portion 18 in which a screw thread is provided in the axial direction of the nut main body 1 may be constant, or the open side is thick and the object side is narrowed, and further, the length of the shaft portion is halfway It can also be made thinner. Further, as shown in FIG. 3, the bearing surface 20 of the nut part 6 can be enlarged to reduce the contact pressure at the time of fastening of the nut part 6 and the object 3 to be fastened.

When fastening the to-be-fastened object 3 by the bolt 2 and the nut body 1 and the nut part 6, the fastening side lowermost surface 7 of the nut body 1 is not in direct contact with the to-be-fastened Since it is in contact with the object 3, the flow of force at the time of fastening is directed to the open side of the nut body 1 via the contact surface 16 between the nut component 6 and the nut body 1 and further directed to each thread. At this time, the force enters the nut body 1 from the nut part 6, but the position thereof is much from the vicinity of the innermost diameter portion of the contact surface 16 where the nut part 6 and the nut body 1 are in contact. Go to the second and subsequent threads and reach the open thread while expanding.

As shown in FIG. 3, the curved portion transitioning from the flange portion of the nut body to the screw shaft portion 18 and the inner diameter side shoulder portion of the nut part 6 desirably have each other even if their shape and size may change. A stress concentration relaxation curve capable of maintaining a non-interfering structure is provided to prevent stress concentration on both the nut body and the nut component. The load sharing situation of the thread changes from the relative relationship of the position of the thread at the axial height of the screw in the screw shank 18 which corresponds to the contact face 16 of the nut part 6 and the nut body 1.

In this aspect (C), it is possible to direct the force to the nut thread close to the open side of the nut body 1, and how to share the load is the strength of the nut 1, the material, and the strength of the nut part 6. , It can be decided from the material and their shape. L ₂ at the height of the surface 16 where the nut part 6 and the nut body 1 contact is in the range of L ₁ + length of 0.5 thread pitch ≦ L ₂ ≦ L ₁ + length of 5 threads pitch The inside is desirable.

Here, as shown in FIG. 3, L ₁ indicates the distance from the point P _{1 at the} bottom of the fully threaded No. 1 screw valley on the screw thread side of the screw thread 18 of the nut to the nut bearing surface 14. , P ₁ and the bearing surface of the nut, there is a gap 4 and a total length s of the chamfer and the screw imperfection. A structure in which the lowermost end 7 of the screw shaft portion 18 of the nut main body 1 does not touch the object 3 by adjusting the axial length of the nut part 6, the length of the air gap 4 and the projection amount of the screw shaft portion 18 It can be done.

In FIG. 3, the number of screw threads of the nut is eight, as an example. This is due to the purpose of improving the rigidity of the nut itself due to the balance of force due to the flow of a large amount of stress on the open side of the nut due to the influence of the screw shaft. As an example, a step or a taper or a combination of these is provided on the outer periphery of the screw shaft portion 18 of the nut body 1. Moreover, in FIG. 3, it is the structure which increased the contact area which the bearing surface 20 of the nut component 6 contacts the to-be-fastened object 3, and the effect of reducing the fastening surface pressure of the bearing surface 20 which the nut component 6 and the to-be-fastened object 3 contact is there.

There are many variations of the present aspect (C), but there is one relating to a method of use (not shown). There is a modified (use implementation) example in which the nut part 6 is replaced with the object 3 to be fastened, the nut body 1 is directly screwed on the bolt 2 coming out of the object 3 and the object 3 can be fastened. . In this modification, the screw shaft portion 18 of the nut body 1 is rotatably inserted into the screw hole of the object 3 to be fastened, and the hole inlet provided on the object 3 is a nut part 6 as shown in FIG. The nut main body 1 can be fastened directly to the fastened object 3 via the bolt 2 by setting it as a structure having a large stress concentration relaxation curve or an equivalent effect thereof. The nut body 1 and the to-be-fastened object 3 make contact at the surface 16 of the flange bearing surface of the nut body 1. In such a case, as shown in FIG. 3, the bolt 2 is directed in the direction in which the screw thread comes out from the side of the object to be fastened, and is set to be screwed with the nut body 1. Also in such a modification, a large amount of force can be flowed after the third thread on the open side thread of the nut main body, and the load reduction in the first mesh can be implemented. Such usage and chamfering shapes are also part of the present invention. The advantages in this case include, in addition to the effects of the aspect (C), reduction in the number of parts, weight reduction, reduction in the amount of projection of the nut, and the like.

The von Mises equivalent stress distribution of this embodiment (C) is shown in FIG. Here, a nut body having a structure with eight threads is used for FEM analysis of the aspect (C) nut. This is because the rigidity of the nut itself is improved by the flow of a large amount of stress on the open side of the nut under the influence of the screw shaft. According to this, the conventional nut of the comparison standard uses the value of the thread 8 thread.

In the Mises equivalent stress distribution chart in Figure 3-1, the magnitude of the stress is color-coded in the four-step color, white indicates high stress, black indicates low stress, middle light gray indicates stress somewhat large, dark gray It represents a little small.

As an outline of FIG. 3-1, the force entered from the bearing surface 20 of the nut part 6 is black at the lowermost part, and obliquely upward from dark gray to light gray toward the nut main body 1, the nut main body 1 and nut The surface 16 with which the component 6 contacts is white with high compressive stress at the top and bottom, which is the maximum stress, but in this part, the 7 to 8 thread ridges of the nut main body 1 have a white or gray band of high stress facing You can see what you are doing. Further, immediately after entering the nut body 1, white and light gray are seen toward the nut shaft portion 18, but this portion is under tensile stress. A white color is visible through this portion to the bottom of the thread between nut threads # 4 and # 3 and # 3 and # 2. In addition, it seems that the vicinity of No. 3 thread is passing the most power. Furthermore, at the nut side No. 1, black color appears inside, which indicates that the first ridge portion has small stress. Looking again at the whole, the

screw threads

1, 2 and 3 of the nut 1 at the screw shaft portion receive a force that can be pulled from the bolt. The force transmitted from the nut to the bolt is large at No. 3 of the screw thread, is applied to the fourth, fifth, sixth, seventh, and eighth, and a dark gray is also visible at the seventh and eighth. Looking at the bolt side, white is small in the first to third areas near the screw thread, but light gray appears in the fourth and fifth. In addition, the dark gray is spread over the entire length up to the bolt thread No. 8. It can be seen that stress is widely spread inside the bolt in this manner. I can see how the force spreads in the direction of the nut.

A comparison of FIG. 3-1 of this embodiment (C) with FIG. 4-1 by the conventional method reveals that the von Mises equivalent stress distribution map has a completely different appearance. In Fig. 4-1 of the conventional method, the force is immediately applied to the fastening side No. 1 and most of the forces are transferred by No. 1 and then gradually become smaller as the second and third. It can be seen that they are only sharing.

Comparison of an example of the aspect (C) and the conventional method is shown in FIG. 3 (a) a load sharing ratio, and (b) a bar graph, for performance comparison of the aspect (C) of the present invention and the conventional method. Here, the load sharing ratio of the meshing first peak of this mode (C) is 22.9%, which is far from 34.5% of the conventional system. In the third and subsequent figures, the load carrying rate in the mode (C) is higher. This comparison is made with both nut threads of eight.

The analysis of the modification in the 7th mountain of the aspect (C) of the present invention is shown in the stress distribution map of Miess in FIG. 3-3, and the comparison with the 7th mountain of the conventional method is shown in FIG. Comparative bar graphs are shown in -4 (b). The load sharing ratio of the meshing first peak in this modified example is 24.0%, which is significantly different from 35.6% of the conventional system. Here, both are compared with seven threads.

Thus, the aspect (C) is found to be correlated between the axial position of the flange bearing surface of the nut body 1 and the position of the screw thread of the nut body (screw shaft portion projection amount), and the amount of force flow to the open side It is suggested that it affects the load sharing of the mesh 1st mountain. By the way, in Fig. 3-1 and Fig. 3-3, the protrusion amount of the nut body shaft 18 is changed, and Fig. 3-1 is different from about 3.5 mountain in Fig. 3-3 and Fig. 3-3 is about 4.3 mountain. There is.

In order to avoid stress concentration, the corners of the parts of the third aspect (C) of the present invention (C) and other parts in contact with the corners 20 and the nut body of the nut part 6 are stress concentration relieved It is desirable to provide a curve. Also, the size and shape of these stress concentration relaxation curves can be determined arbitrarily.

The surface roughness of the bearing surface 20 of the nut part 6 is fine-finishing, or both the surface 16 where the nut body 1 and the nut part 6 contact are fine-finishing, the surface of the screw is a surface roughness according to JIS, other surface roughness In order to have consistency with the surface treatment to be described later, such as rough finish or co-finishing, it is preferable to set an optimal surface roughness depending on the place.

The T-shaped nut structure does not necessarily have to be a strict T-shaped structure, and may have a modified structure without departing from the scope of the invention. For example, it may be a cross structure. Moreover, it is also possible for the nut body upper part to have a shape that can use a fastening tool such as a normal hexagon, which is more preferable.

In the present invention, even if the aspect is different from (A), (B) and (C), the flow of the load force received by the nut as described above is achieved by the open side meshing thread with low load sharing. By increasing the load sharing after the third peak as a nut structure that is directed more, it is possible to provide a nut configured to reduce the maximum load sharing of the meshing first peak. Thereby, by reducing the load on the meshing first peak, it is possible to achieve the purpose of extending the fatigue fracture life that causes the crack axial fracture from the meshing first bottom of the bolt meshing.

The nuts according to the first to third aspects of the present invention can utilize materials conventionally used. As materials, alloy steels such as mild steel, carbon steel, nickel chromium steel, chromium steel, nickel chromium molybdenum steel, non-ferrous metals such as stainless alloy steel, aluminum alloy, nickel alloy, titanium alloy, resin, ceramic (oxide, nitrided Materials, materials such as objects, carbides, etc. are suitably used.

The screw can be formed by the same method as the conventional method, for example, screw forming with a tap, NC (numerical control) lathe, machining center (MC), combined processing machine (combined processing machine of lathe and milling cutter), EDM, or any combination thereof, press plastic working, cold / hot / warm press, forging, casting, injection molding, precision casting, 3D printer processing, molding, MIMS, or for roughing material production It can do by combining them. With respect to the thread size and strength, shapes and the like defined in industrial standards of each country (in Japan, JIS B 0205: 2001, JIS B 0 216: 1987, JIS B 1051: 2000, etc.) can be adopted.

The formation of the nut of the first aspect (A) by an NC lathe will be described as an example. The external part is manufactured by cold, warm, hot forging / pressing, cutting, nut former, Swiss type automatic lathe, etc. The space part on the seat side of the nut or concave rectangular rectangular shape is NC lathe, automatic disc, Etc. Then, the nut of the present invention is manufactured by forming a screw thread of a nut using cutting, grinding, cutting tap, and rolling tap in the same manner as forming a conventional screw thread. be able to. Alternatively, after changing the manufacturing order and forming a screw thread with a similar device using a tap, a space or a substantially rectangular recess may be formed on the bearing surface side of the nut, and then the outer peripheral shape may be formed.

Although the manufacturing method of the nut of another mode becomes substantially the same, if an example is given, a member can be divided roughly into a member which becomes a nut body and a member which becomes a nut part. The outer shape of the nut and the preparation of the screw lower hole adopt hot press / cold / warm press, forging, cutting, casting, etc., and produce a one-part type nut or a substantially T-shaped shape. The top is formed so that a fastening tool such as a hexagon can be used to facilitate fastening with a normal tool, and a tap is passed through a pilot hole made by cutting, cold / hot forging, casting, etc. Form a mountain / valley. The threaded portion may be formed by turning or grinding. The nut part can be manufactured by cutting a pipe, cold / warm / hot forging, casting, continuous automatic cutting from a round bar with a CNC lathe, etc., or a combination of these. It may be formed by a 3D printer. When it is made of resin or ceramic, a combination of methods such as injection molding, sintering and the like, and cutting and grinding may be performed. The surface roughness of the contact surface of the nut and the nut part can be selected and adopted to reduce the sliding resistance. It can be processed by selecting or combining from a mirror polished surface, a polished surface, a precision cutting surface, a pressing surface with a precision die, micro shot peening, glass bead shot and the like. Also, in the combination of the nut body and the nut part, the nut body rotates while rotating around the screw central axis, so that the fastening object surface and the nut screw central axis are kept perpendicular. It is desirable to make

For example, when the material is metal, the surface before the nut and the bolt start to be tightened has a surface roughness such as shaving and polishing, the coefficient of friction μ is also dry μ μ 0.5, and wet μ μ 0 It is known to be .1. However, after the start of fastening, when the gap disappears and the base material is strongly pressure-bonded, the lubricant flows out, the oxide film on the metal surface peels off, and a metal surface appears. At this time, particularly in a dry environment, a strong pressure contact state where metal bonding occurs on the metal surface is achieved. In this case, it is difficult to assume that the friction coefficient of the screw thread is the same as it is, and it is possible that the friction coefficient rises non-linearly and reaches a size where both threads adhere.

A segment-like diamond-like carbon (S-DLC) film having a diamond-like carbon film which has a function of being divided into grooves not having a film and having a film provided on a sliding surface divided. When the film is formed between the substrates that are in contact with each other while receiving, as long as the film is present, it is possible to maintain the substrates rubbing together without changing the coefficient of friction (μ ≒ 0.15). The adhesion durability is shown in many experiments by the present inventors. In the case where there is an S-DLC film on the screw thread on the fastening side of the nut, the effect of the increase in the coefficient of friction is small when at least the S-DLC film on the screw engaging first thread is present.

In the nut according to any one of the first to third aspects (A) to (C) of the present invention, a bolt side thread engaged with at least a bolt on the thread surface of the first thread or part or all of more threads. Diamond-like carbon (DLC) film, BN film, WC film, WN film, CrN film, HfN film, VN film, TiN film, TiCN film, Al ₂ O ₃ film, ZnO film on the surface in contact with the surface or slopes on both sides of the screw thread SiO ₂ film, alumite, metal plating, solid lubricant, manganese phosphate conversion treatment, carburizing and quenching, nitriding treatment, nitriding treatment, any combination of these, or a combination of these to form a protective film, It is further suitable for achieving smooth fastening operation and stable fastening. The screw thread surface preferably includes at least a meshing first screw thread surface, and it is preferable that the DLC film is also formed on the more open side screw. By forming the DLC protective film, roughening and peeling of the metal surface can be suppressed, the coefficient of friction can be stabilized, and more stable fastening can be achieved. Preferably, the DLC film is in the form of segments which are divided, for example, in a grid by grooves (S-DLC film).

Further, in the first and second aspects (A) and (B) of the present invention, in the nut according to the third aspect (C), the nut body and the nut component Covering the sliding surface 16 or the surface 14 of the nut part in contact with the object to be fastened with a diamond-like carbon (DLC) film to form a protective film realizes smooth fastening operation and stable fastening. Are further preferred. By forming the DLC protective film on the sliding surface, roughening and peeling of the metal surface can be suppressed, the coefficient of friction can be stabilized, and more stable fastening can be achieved. Preferably, the DLC film is in the shape of, for example, a grid divided into segments by a groove without a film (S-DLC film). In the case of the S-DLC film, the groove portion without the film becomes an oil groove, and when the oil is supplied, the seat surface friction coefficient is stabilized, which contributes to the stability of fastening.

In order to deposit the DLC film on the surface on which the nut body and the nut component slide, the bearing surface of the nut, and the inner surface of the screw, vapor deposition (CVD or PVD) is preferred. Examples thereof include plasma CVD using a high frequency power as a power source or sputtering such as magnetron sputtering or ion beam sputtering. The film thickness of the DLC film depends on the shape of the nut, the part of the nut, the usage, etc., but is usually 0.01 to 10 μm, and more preferably 0.5 to 3 μm.

Although the effect of forming a diamond-like carbon film on the screw thread surface, the nut, the nut part, or the part where washers contact each other or on the surface (seating surface) in contact with the object to be fastened has been described Other materials can be selected for the purpose of reducing the frictional resistance or reducing the change in the frictional resistance. For example, BN film, WC film, CrN film, HfN film, VN film, TiN film, TiCN film, Al ₂ O ₃ film, ZnO film, SiO ₂ film, alumite, metal plating, solid lubricating layer, manganese phosphate conversion treatment It is possible to select any of carburizing and quenching, nitriding, chromizing, polymer resin coating, or a combination thereof. These membranes are effective in realizing smooth fastening operation and stable fastening.

As types of surface film formation or surface treatment, metal plating, polymer resin coating, alumite treatment, vacuum deposition, ion plating, plasma treatment such as PVD, CVD and the like can be suitably applied.

In addition, surface treatment can be applied to the outer surface of the nut or nut part, and weather resistance improvement, appearance improvement, identification indication provision, decoration, etc. can be appropriately performed.

According to the present invention, it is possible to reduce the load on the meshing first peak that shares the maximum load in bolt and nut fastening, and to improve the fatigue strength of the crack axial fracture from the meshing first root of the bolt mesh. Can provide a nut having a feature that can be

DESCRIPTION OF SYMBOLS 1 Nut, nut main body 2 bolt 3 to-be-fastened object 4 Air gap between lowermost part 20 of nut bearing surface 14 or nut part 6 and lower end 7 of screw shaft 5 convex space (including back curve of screw shaft etc. )
6 Nut parts 7 Screw shaft lower end 8 Nut fastening side direction 8a Nut fastening seat surface 9 Nut opening side direction 9a Nut open end 10 Recess in nut 11 Wall inside recess (wall of recess)
12 Corner portion in recess of nut 13 Upper surface of nut recess 14 Bearing surface of nut 15 Nut screw valley bottom 16 Surface where nut body and nut parts contact (sliding surface)
17 outer periphery of nut body 18 screw shaft of nut body 19 screw thread of nut body 20 lowermost portion of nut part 6 outer periphery of nut body 1 22 top of nut part 23 washer 24 located on screw shaft of nut body The shortest length that P ₁ enters the nut part (s + 0.5 pitch length)
25 The maximum length (Pt of s + 5 pitch) that P ₁ on the screw shaft of the nut body enters the nut part
P ₁ distance L ₂ nuts from point L ₁ nut bearing surface 14 located at the innermost part of the convex space point P ₂ nuts located valley of the complete thread portion of the fastening-side one peak th nut screw to P ₁ thread pitch two-peak fraction and an incomplete thread portion of the distance P nut screw one peak pitch La nuts from the seating surface 14 to P ₂ (including the chamfered) nut bearing surface from the total length Lb nut bearing surface 14 of length s Length to inner top surface 13 Lh Length between wall surface 11 and thread root 15 in nut bearing surface s Total length of chamfer length and thread imperfection length

Claims

It is a nut for fastening,
A. In the shape of the longitudinal sectional view of the nut, a convex-shaped space is concentrically formed on the bearing surface on the nut fastening side around the axis of the screw, and the space is connected by a straight line, a curve or a combination thereof. A space is formed as a shape, the depth from the bearing surface of the space is L 2 , and the axial length from the valley bottom of the first screw of the fully threaded portion of the nut to the bearing surface is L 1 When forming the space, when the depth L 2 of the space is L 1 <L 2 ≦ L 1 + length of thread 5 pitches;
B. A structure having a rectangular recess on the screw center side of the bearing surface on the fastening member side of the nut in the shape of the longitudinal sectional view of the nut, wherein the recess has an inner wall and a curve, straight line, or the like rising perpendicularly from the nut bearing surface Have a corner portion and an upper surface combined, and from the position of the upper surface the axial length of the incomplete thread portion of the nut plus the length of two pitches of the nut is La, and Assuming that the axial length from the bearing surface to the upper surface is Lb, and the radial length of the recess to the thread valley bottom of the nut and the inner wall of the recess is Lh, Lb is at least 0.001 times the La C. by forming the recess concentrically with the center of the screw in the range of 0.5 to 5 times the range of La and Lh; A nut having a two-part structure comprising a nut body having a screw shaft portion provided with a screw thread inside and a flange bearing surface portion and a pipe-like nut component having a chamfered bearing surface on at least one end face inner diameter side A shape of a longitudinal sectional view of the nut body is T-shaped, and a length in which a screw shaft portion of the nut body is introduced from the flange seat surface portion of the nut body toward the inner object of the nut component is The hollow pipe-shaped nut component is formed on the outer surface of the screw outer surface so that the incomplete screw part length s + the length of the screw pitch 0.5 or more, and the length of the incomplete screw part s + the screw pitch 5 m or less The T-shaped nut body is disposed so that the lowermost portion of the T-shaped nut body is not in contact with the object, and the uppermost portion of the nut part is in contact with the flange-like bearing surface of the T-shaped nut body The lower part of the nut part is tightened The length of the nut part is set so as to contact the object, the inner diameter surface of the nut part and the outer peripheral surface of the nut body are respectively rotatable, and the nut body and the nut part are formed concentrically with the center of the screw By doing;
The maximum load sharing of the meshing 1st peak is reduced by setting it as the nut structure which makes the flow of the load force received by the nut face more toward the open side meshing thread with low load sharing, meshing 3rd mesh A nut characterized in that the load concentration on the meshing first peak is reduced by increasing the subsequent load sharing.
Diamond-like carbon (DLC) on the surface of the screw thread surface of the nut that engages with at least the bolt and the surface that contacts the bolt side screw of the first screw thread or other threads or some or all of the screw threads Film, BN film, WC film, CrN film, HfN film, VN film, TiN film, TiCN film, Al 2 O 3 film, ZnO film, SiO 2 film, alumite, metal plating, solid lubricating layer, manganese phosphate conversion treatment The nut according to claim 1, wherein the nut is formed by coating any of a carburizing and quenching treatment, a nitriding treatment, and a chromiumizing treatment, or a combination thereof.
Diamond-like carbon (DLC) film, BN film, WC film, CrN film, HfN film, VN film, TiN film, TiCN film, Al 2 O 3 film, ZnO film, SiO 2 on contact sliding surfaces of nuts and nut parts A film, alumite, metal plating, solid lubricating layer, manganese phosphate conversion treatment, carburizing and quenching, nitriding treatment, chromization treatment, polymer resin coating, or a combination of these films is coated. Nuts described in.
A diamond-like carbon (DLC) film, a BN film, a WC film, a CrN film, a HN film, a VN film, a TiN film, a TiCN film, an Al 2 O film on a bearing surface of a nut part or on a bearing surface of a nut 3 film, ZnO film, SiO 2 film, alumite, metal plating, polymer resin coating, solid lubricating layer, manganese phosphate conversion treatment, carburizing and quenching, nitriding treatment, chromium treatment or any combination of these films The nut according to any one of claims 1 to 3, wherein