Anti-skew nut and its manufacturing method

Abstract

To provide an oblique entry prevention nut which can prevent the oblique entry of a bolt while suppressing the size enlargement of the nut as much as possible.SOLUTION: An oblique entry prevention nut of the present invention is obtained by forming a bolt guide part 13 having a circular hole 13 having an inside diameter D which is smaller than a trough diameter d1 of a female screw 12 formed at the nut, and larger than an outside diameter d2 of the bolt 20 at an end part of a nut main body 10 at a bolt insertion side. The bolt guide part 13 is formed at an inner face of an annular member 11 such as a washer and a collar, and the annular member 11 can be fixed to an end part of the nut main body 10 at the bolt insertion side. Also, the bolt guide part 13 can be formed by crushing a face of the nut main body at the bolt insertion side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a nut that prevents a bolt from being inserted at an angle into the nut, and a method for manufacturing the nut. [Background technology]

[0002] When fastening a bolt and nut, if the bolt and nut are not on the same axis and the bolt goes in at an angle to the nut as shown in Figure 12, the bolt's threads will interfere with the threads of the nut that should be in contact with them, and if the bolt is screwed in further, it will cause seizure and the bolt will not be tightened properly. This phenomenon is called slanted insertion, and once seizure (also known as galling or thread climbing) has occurred, it is not easy to restore it to its original state. This can be a serious problem, especially on automobile assembly lines that use power drivers.

[0003] To address this issue, numerous bolts with a feature to prevent cross-threading have been developed and put into practical use. A typical example is a bolt with a small-diameter incomplete thread portion or guide portion formed at the tip of the regular thread portion, as shown in Patent Document 1. However, these portions do not contribute to the fastening strength after fastening, and the inclusion of these portions increases the length of the bolt. For this reason, such cross-threading prevention bolts could not be used in locations where sufficient space for bolt fastening could not be secured. Furthermore, because the bolts have a special shape, they cannot be shared with bolts in other locations, resulting in problems such as high costs.

[0004] Meanwhile, Patent Document 2 also describes a device that provides a function to prevent slanted insertion in the nut, rather than the bolt. This involves countersinking the end of the nut on the bolt insertion side to form a circular hole larger than the maximum diameter of the nut's internal thread (internal thread root diameter), and using this circular hole to correct the insertion direction of the bolt into the nut. However, in order to correct the bolt insertion direction using this structure, it is necessary to increase the axial length of the circular hole, which poses the problem of increasing the size of the nut. In the drawings in Patent Document 2, the axial length of the circular hole is 3 to 4 times the pitch of the internal thread. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-249919 [Patent Document 2] Japanese Patent Application Publication No. 2020-133819 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to solve the above-mentioned conventional problems and provide an anti-slanted bolt nut that can prevent the bolt from being inserted at an angle while minimizing the size of the nut, and a method for manufacturing the same. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the inventors have found that in order to improve the function of preventing the bolt from being inserted at an angle while suppressing an increase in the size of the nut, it is effective to make the inner diameter of the circular hole for guiding the bolt, which is formed at the end of the nut on the bolt insertion side, as small as possible, and that it is particularly effective to make it smaller than the maximum diameter of the internal thread of the nut body (internal thread root diameter).

[0008] The present invention, based on the above findings, provides a bolt guide portion formed on the bolt insertion end of the nut body, the bolt guide portion having an inner diameter smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt. The bolt guide portion is formed on the inner surface of an annular member, which can be fixed to the bolt insertion end of the nut body, and this annular member can be a washer or a collar.

[0009] Alternatively, instead of using such an annular member, the bolt guide portion can be formed by crushing the surface of the nut body on the bolt insertion side. Such a cross-insertion prevention nut can be manufactured by manufacturing a nut body with a large-diameter recess on the bolt insertion side, inserting a guide pin into the recess of the nut body, the guide pin having an outer diameter smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt, and plastically deforming the bearing surface of the nut body toward the guide pin to form a bolt guide portion on the bolt insertion side of the nut body, the bolt guide portion having an inner diameter smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt. Alternatively, the nut body can be provided with an annular protrusion on its bearing surface, and the protrusion can be plastically deformed toward the guide pin while the guide pin is inserted. [Effects of the Invention]

[0010] In the cross-insertion prevention nut of the present invention, the inner diameter of the bolt guide portion for preventing cross-insertion of the bolt is smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt, so that cross-insertion of the bolt can be prevented even if the axial length of the circular hole is shortened to about 1.2 to 2.0 times the pitch of the female thread. By using the cross-insertion prevention nut of the present invention, there is no need to lengthen the bolt, making it possible to fasten the bolt even in locations where there is not enough space to fasten the bolt. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a first embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram of the root diameter of the female thread and the outer diameter of the male thread. [Figure 3] FIG. [Figure 4] FIG. 10 is an explanatory diagram showing a state in which a bolt is correctly inserted. [Figure 5] FIG. 10 is an explanatory diagram showing a state in which a bolt is inserted obliquely. [Figure 6] FIG. 10 is an explanatory diagram showing a state in which a bolt is inserted obliquely. [Figure 7] FIG. 10 is an external view showing a test in which the cross-insertion prevention nut of the present invention is fixed and a bolt is screwed into it. [Figure 8] FIG. 10 is an external view showing a test in which a bolt is fixed and the cross-insertion prevention nut of the present invention is screwed into it. [Figure 9] FIG. 4 is a cross-sectional view showing a second embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing a third embodiment of the present invention. [Figure 11] FIG. 10 is a cross-sectional view showing a fourth embodiment of the present invention. [Figure 12] FIG. 10 is a cross-sectional view showing a state in which a bolt is inserted obliquely into a conventional nut. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the present invention will be described below. Fig. 1 is a cross-sectional view showing a first embodiment of the present invention, in which 10 is a nut body and 11 is an annular member attached to the end of the nut body 10 on the bolt insertion side, and in this embodiment, the annular member 11 is a washer. In this embodiment, both are made of metal. An internal thread 12 is formed in the nut body 10 as in the conventional case. A circular bolt guide portion 13 is formed on the inner surface of the annular member 11. The inner diameter D of this bolt guide portion 13 is smaller than the root diameter d1, which is the maximum diameter of the internal thread 12 formed in the nut body 10, and larger than the outer diameter d2 of the bolt 20 to be screwed into the nut body 10.

[0013] The root diameter d1 of the female thread is almost equal to the outer diameter d2 of the male thread, but if d1 and d2 were completely the same, it would be difficult to thread them together. JIS B 0101 "Screw Terminology" states that the root diameter of the female thread is A in Figure 2, and the outer diameter of the male thread is B in Figure 2. In this way, the root diameter d1 of the female thread is set slightly larger than the outer diameter d2 of the male thread, and the inner diameter D of the bolt guide portion 13 of the washer, which is the annular member 11, is set to a value between these two. In other words, d2 <D<d1となっている。

[0014] Nuts are generally manufactured by forging the outer shape and then threading the bolt. However, if threading is performed after forming the bolt guide portion 13 as described above on the nut body 10, the inner diameter D of the bolt guide portion 13 is smaller than the root diameter d1 of the female thread, and therefore threads will also be cut on the inner surface of the bolt guide portion 13. If threads are cut in this area, the function of preventing cross-insertion will be insufficient. Therefore, the cross-insertion prevention nut of the first embodiment of the present invention has a structure in which an annular member 11 equipped with the bolt guide portion 13 is separately manufactured and attached to the nut body 10, as shown in Figure 3.

[0015] For this reason, a convex portion 14 with a diameter slightly smaller than the outer diameter of the nut body 10 is formed at the end on the bolt insertion side, and a concave portion 15 with a diameter slightly smaller than this convex portion 14 is formed in the annular member 11. The convex portion 14 of the nut body 10 is press-fitted into this concave portion 15, thereby firmly attaching the annular member 11 to the nut body 10. However, the means for joining the nut body 10 and the annular member 11 is not limited to press-fitting, and welding or brazing, for example, may also be used.

[0016] In the thus configured anti-angled insertion nut of the present invention, the inner diameter D of the bolt guide portion 13 formed on the annular member 11 is larger than the outer diameter d2 of the bolt 20, so that when the bolt 20 is inserted without being tilted relative to the nut body 10 as shown in Figure 4, fastening can be performed without any problems. Note that Figures 4 to 6 exaggerate the difference in the radial direction.

[0017] However, if the bolt 20 is inserted at an angle into the nut body 10 as shown in Figure 5, the threads of the external thread of the bolt 20 come into contact with the inner surface of the bolt guide portion 13, and the bolt 20 cannot be screwed in as is. With the angle of inclination as shown in Figure 5, the bolt 20 cannot advance any further, and will spin freely, so no seizure will occur.

[0018] 6, if the inclination angle of the bolt 20 becomes even larger, the tip of the bolt 20 hits the end face of the washer, which is the annular member 11, and the bolt 20 cannot be screwed in as is, so the bolt 20 spins freely. As a result, no seizure occurs.

[0019] Experimental results confirmed that, to achieve the aforementioned effect of preventing oblique bolt insertion, it is desirable for the axial length of the bolt guide portion 13 of the annular member 11 to be at least 1.2 times the pitch of the internal thread 12. Because the bolt guide portion 13 is the portion that prevents oblique bolt insertion, if its axial length is shorter than this, it will not be able to reliably prevent oblique bolt insertion. However, increasing the thickness of the annular member 11 improves the oblique bolt insertion prevention function, but it results in an increase in the size and cost of the oblique bolt insertion prevention nut. For this reason, the axial length of the bolt guide portion 13 is preferably 1.2 to 2.0 times the pitch of the internal thread 12. More preferably, it is 1.2 to 1.5 times the pitch of the internal thread 12. Thus, in the present invention, by making the inner diameter D of the bolt guide portion 13 smaller than the root diameter of the internal thread 12, the axial length of the bolt guide portion 13 can be reduced to less than half of that of a conventional bolt guide portion.

[0020] To confirm the effectiveness of the present invention, tests were conducted as shown in Figures 7 and 8. The bolts and nuts used in the tests were M10 size with a 1.25 mm pitch. As shown in Figure 7, the anti-skew nut of the first embodiment was fixed to a vise 30, and the bolt 20 was attached to an impact wrench 40 and tightened from an oblique direction. The impact wrench 40 was rotated in the state shown in Figure 7, with the tilt angle set to approximately 15 degrees, but the bolt 20 simply spun freely without seizing. After that, the tilt angle was reduced while the impact wrench 40 was still rotating, and the bolt 20 could be threaded in when the anti-skew nut and the bolt 20 were coaxial.

[0021] Next, as shown in Figure 8, a similar test was conducted with the bolt 20 fixed in the vise 30 and the anti-cross-insertion nut of the present invention attached to the impact wrench 40. In this case, the impact wrench 40 was rotated with the tilt angle set to approximately 15 degrees as shown in Figure 8, but the nut simply spun freely without seizing. After that, the tilt angle was reduced while the impact wrench 40 was still rotating, and the nut 20 could be threaded in when the anti-cross-insertion nut and bolt 20 were coaxial. This confirmed that no seizure occurred when tightening the bolt or the nut.

[0022] In the first embodiment described above, the annular member 11 is a thin-walled washer that is press-fitted onto the outside of the nut body 10. However, in the second embodiment shown in Fig. 9, the annular member 11 is a collar that is press-fitted into the interior of a recess 16 formed in the seating surface of the nut body 10. The inner diameter of this collar is smaller than the root diameter of the female thread formed in the nut body 10 and larger than the outer diameter of the bolt. Note that, as shown in Fig. 9, if the collar is press-fitted into the recess 16 after threading the inner surface of the flange nut, no threads will be formed in the bolt guide portion 13 of the collar.

[0023] In the first and second embodiments, a two-component structure was adopted in which an annular member 11 was attached to the nut body 10, but in the third embodiment shown in Figure 10, the bolt guide 13 is formed by crushing the surface on the bolt insertion side of the nut body 10. As shown in the upper diagram of Figure 10, after threading the inner surface of the flange nut, a recess 17 slightly larger in diameter than the root diameter of the female thread is formed, and then the bearing surface of the nut body 10 is crushed to reduce the inner diameter of the recess 17 as shown in the lower diagram of Figure 10, forming a bolt guide 13 that is smaller than the root diameter of the female thread and larger than the outer diameter of the bolt. In this third embodiment, the anti-cross-insertion nut can be made into a one-component structure.

[0024] As shown in Figure 10, it is desirable to insert a guide pin 50 into the nut body 10 before crushing the bearing surface of the nut body 10. This guide pin 50 has a small-diameter portion 52 that is inserted into the female thread portion of the nut body 10 and a large-diameter portion 53 that is located in the recess 17 of the nut body 10. The outer diameter of the large-diameter portion 53 is smaller than the root diameter of the female thread and larger than the outer diameter of the bolt. As a result, as shown in the lower diagram of Figure 10, a bolt guide portion 13 with an inner diameter smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt can be formed at the end of the nut body 10 on the bolt insertion side. The guide pin 50 allows for accurate dimensions, which has the advantage of improving the dimensional accuracy of the bolt guide portion 13.

[0025] In the fourth embodiment shown in FIG. 11 , a nut body 10 is first manufactured, with a large-diameter recess 17 formed on the bolt insertion side and an annular protrusion 51 formed on the seating surface. Next, a guide pin 50 similar to that of the third embodiment is inserted into the nut body 10. With the guide pin 50 inserted as shown in the upper diagram of FIG. 11 , the annular protrusion 51 on the seating surface of the nut body 10 is plastically deformed toward the guide pin 50. As shown in the lower diagram of FIG. 11 , a bolt guide portion 13 having an inner diameter smaller than the root diameter of the internal thread formed in the nut and larger than the outer diameter of the bolt can be formed at the end of the nut body 10 on the bolt insertion side. The use of the guide pin 50 in the bolt guide portion 13 of this fourth embodiment also has the advantage of improving the dimensional accuracy of the bolt guide portion 13.

[0026] As described above, the cross-insertion prevention nut of the present invention can prevent the bolt from being inserted cross-wise while minimizing the increase in size of the nut. [Explanation of symbols]

[0027] 10 Nut body 11 Annular member 12 Female thread 13 Bolt guide part 14 Convex part 15 recess 16 Recess 17 Recess 20 volts 30 Vice 40 Impact wrench 50 guide pin 51 protrusion 52 Small diameter section 53 Large diameter section

Claims

1. This nut is characterized by having a bolt guide portion formed at the end of the nut body on the bolt insertion side, the bolt guide portion having an inner diameter smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt.

2. 2. The bolt guide portion is formed on the inner surface of an annular member, and the annular member is fixed to the end of the nut body on the bolt insertion side.

3. 3. The cross-insertion prevention nut according to claim 2, wherein the annular member is a washer or a collar.

4. 2. The nut according to claim 1, wherein the bolt guide portion is formed by crushing the surface of the nut body on the bolt insertion side.

5. A method for manufacturing a nut that prevents cross-insertion, characterized by: manufacturing a nut body with a large-diameter recess formed on the bolt insertion side; inserting a guide pin into the recess of the nut body, the guide pin having an outer diameter smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt; and plastically deforming the seating surface of the nut body toward the guide pin, thereby forming a bolt guide portion at the end of the nut body on the bolt insertion side, the bolt guide portion having an inner diameter smaller than the root diameter of the female thread formed in the nut and larger than the outer diameter of the bolt.

6. The method for manufacturing a nut that prevents cross-insertion as described in claim 5, characterized in that the nut body has an annular protrusion on its seating surface, and the protrusion is plastically deformed toward the guide pin with the guide pin inserted.

Images