Fasteners

Abstract

Reduces the screw-in resistance torque in the initial stages of screw-in. [Solution] The fastener 10 is a fastener 10 that forms an internal thread in a fastening hole formed in a screw-in member, and comprises a head 14, a shaft 12 connected to the head 14, a standard screw thread (screw thread 20) formed on the outer surface of the shaft 12, a tip screw thread (screw thread 30) positioned on the tip side of the shaft 12 from the standard screw thread and having a smaller thread angle than the standard screw thread, and a torque reduction portion (recess 32) formed on the tip screw thread that partially reduces the screw-in resistance torque caused by the tip screw thread.

Description

[Technical Field]

[0001] The present invention relates to a fastener. [Background Art]

[0002] As disclosed in the following Patent Document 1, conventionally, when a fastener such as a bolt is screwed into a fastening hole of a base material serving as a screwed member, it is known that screwing resistance torque is generated due to friction between an external thread and an internal thread even in an initial screwing stage before the head of the fastener is seated on a seating surface. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 9-291919 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, if the resistance torque in the initial screwing stage is large, screwing workability is degraded, and there is a risk that the load during internal thread forming may increase.

[0005] An object of the present invention, in consideration of the above facts, is to reduce screwing resistance torque in the initial screwing stage. [Means for Solving the Problem]

[0006] The fastener according to a first aspect is a fastener that forms an internal thread in a fastening hole formed in a screwed member, and includes a head, a shaft portion connected to the head, a standard thread formed on an outer circumferential surface of the shaft portion, a distal thread disposed on a distal end side of the shaft portion relative to the standard thread and having a thread angle smaller than that of the standard thread, and a torque reduction portion formed on the distal thread that partially reduces screwing resistance torque caused by the distal thread.

[0007] In the fastener of the first embodiment, the thread angle of the tip thread is smaller than the thread angle of the standard thread. Therefore, the thread angle that forms the female thread in the fastening hole of the screw-in member can be increased in stages from the tip thread to the standard thread. As a result, the screw-in resistance torque in the initial stage of screw-in can be reduced compared to the case with only a standard thread.

[0008] Furthermore, the tip of the screw thread has a torque reduction section formed therein, which partially reduces the screw-in resistance torque. This enhances the effect of reducing the screw-in resistance torque.

[0009] Furthermore, in the case of oblique tightening, where the shaft is inserted at an angle relative to the axial direction of the fastening hole, a moment is generated by the thrust force applied while rotating the fastener. In this case, because a torque reduction section is formed, for example, a downward force acts from a part of the screw thread to the wall of the fastening hole, and an upward force acts from the other part of the screw thread to the wall of the fastening hole. Due to these downward and upward forces, the central axis of the shaft during oblique tightening rises closer to the axial center of the fastening hole, thereby providing a corrective effect for oblique tightening.

[0010] The fastener of the second embodiment is the fastener described in the first embodiment, wherein, from a viewpoint along the axial direction of the shaft portion, the radial dimension of the tip thread is not constant, and the torque reduction portion is a portion whose radial dimension is smaller than that of the other parts.

[0011] In the fastener of the second embodiment, an internal thread is formed in the fastening hole in the portion where the diameter dimension of the tip thread is large, and the screw-in resistance torque can be reduced in the portion where the radial dimension is small.

[0012] The fastener of the third embodiment is the fastener described in the second embodiment, wherein, in view along the axial direction of the shaft portion, the tip thread is formed along a circle, and the torque reduction portion is a recess that recedes radially inward from the portion along the circle of the shaft portion.

[0013] In the fastener of the third embodiment, the tip thread has a portion that follows the curve, making it easy to form a female thread that follows the curve.

[0014] The fourth embodiment of the fastener is the fastener described in any one of the first to third embodiments, wherein the torque reduction portion is provided at multiple locations in the circumferential direction of the shaft portion.

[0015] In the fastener of the fourth embodiment, a reduction in resistive torque can be obtained at multiple locations in the circumferential direction.

[0016] The fastener of the fifth embodiment is the fastener described in any one of the first to third embodiments, wherein the height of the tip thread is greater than or equal to the height of the standard thread within a predetermined range in the circumferential direction.

[0017] In the fifth embodiment of the fastener, it is not necessary to expand the radial outer dimension of the female thread using standard threads; only the width of the female thread needs to be expanded, making it easier to form the female thread.

[0018] The fastener of the sixth embodiment is the fastener described in the fifth embodiment, wherein the tip thread is tapered toward the tip of the shaft.

[0019] In the sixth embodiment of the fastener, the female threads can be gradually formed as the shaft is screwed into the fastening hole where the female threads are not yet formed, making it easier to screw the fastener in compared to when the tip threads do not shrink in diameter.

[0020] The fastener of the seventh embodiment is the fastener described in any one of the first to third embodiments, wherein the axial length of the area in which the tip thread is formed is at least twice the pitch of the standard thread.

[0021] In the fastener of the seventh embodiment, the formation of female threads by the tip threads becomes easier compared to the case where the axial length of the area in which the tip threads are formed is less than twice the pitch in standard threads. [Effects of the Invention]

[0022] According to the present invention, the screw-in resistance torque in the initial stage of screw-in can be reduced. [Brief explanation of the drawing]

[0023] [Figure 1] It is a side view showing one embodiment of the fastener of the present disclosure. [Figure 2] It is a partially enlarged side view showing the configuration of a main part of the fastener. [Figure 3] (A) is a partially enlarged side view showing the configuration of a tip thread of the fastener, and (B) is a cross-sectional view taken along line B-B in (A). [Figure 4] It is a partially enlarged side view showing a state where the fastener is screwed into a fastening hole formed in a screwed member. [Figure 5] It is a schematic diagram showing a modified example of a tip thread. DETAILED DESCRIPTION OF EMBODIMENTS

[0024] Hereinafter, a fastener according to an embodiment of the present invention will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing mean the same components. However, unless otherwise specified in the specification, the number of each component is not limited to one, and a plurality of components may be present.

[0025] In addition, description of overlapping configurations and reference numerals in each drawing may be omitted. Note that the present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present disclosure, such as omitting configurations, replacing with different configurations, or combining a plurality of embodiments and various modified examples.

[0026] <Fastener> FIG. 1 shows a fastener 10 according to an embodiment of the present disclosure. The fastener 10 is a self-forming bolt that forms a female thread 42 in a fastening hole 40A formed in a screwed member 40 (FIG. 4).

[0027] The materials used to form the fastener 10 and the screw-in member 40 are not particularly limited, but it is preferable that the fastener 10 be made of a harder material than the screw-in member 40 so that the screw-in member 40 can be plastically deformed by the pressure from the fastener 10. For example, the fastener 10 can be made of iron and the screw-in member 40 can be made of aluminum or the like.

[0028] The fastener 10 comprises a shaft portion 12 and a head portion 14. The shaft portion 12 and the head portion 14 are connected to each other. The shaft portion 12 and the head portion 14 may be integrally molded. The head portion 14 is the part that applies rotational force (screw-in torque) to the shaft portion 12 using a tool or the like. The head portion 14 is formed in a hexagon shape when viewed from a viewpoint along the axial direction of the shaft portion 12. Regarding the shape of the head portion 14, the figure illustrates a hexagonal shape with a flange, but it is not particularly limited, and various head shapes can be applied.

[0029] Screw threads 20 and 30 are formed on the outer circumferential surface of the shaft portion 12. Screw thread 20 is a screw thread (an example of a standard screw thread in this disclosure) formed in a region 12A of a predetermined length from the head 14. In this disclosure, "standard screw thread" refers to a general machine screw thread, including a triangular screw with a thread angle of 60°. In the figure, the screw thread 20 is shown as a full thread formed along the entire length L1 of the shaft portion 12, but it is not particularly limited, and a half thread, in which the screw thread 20 is formed only on a part of the shaft portion 12, is also applicable. In the case of a half thread, effective diameter bolts or nominal diameter bolts are also applicable.

[0030] On the other hand, the screw thread 30 is a screw thread located in the region 12B on the tip side of the shaft portion 12, relative to the screw thread 20 (an example of a tip screw thread in this disclosure). The axial length L2 of region 12B (see Figure 2) is preferably 2 to 7 times the pitch of the screw thread 20.

[0031] Figure 2 shows a magnified view of the area enclosed by the dashed line in Figure 1. As shown in this figure, the thread angle θ2 of thread 30 (the angle formed by the two sides of the thread) is smaller than the thread angle θ1 of thread 20. The thread angles θ1 and θ2 are not particularly limited, but as an example, θ1 can be 60° and θ2 can be 30° or more and 45° or less. Also, θ2 can be an acute angle and can be an angle smaller than θ1.

[0032] Furthermore, the height of the thread 30 is higher than the height of the standard thread 20 within a predetermined range in the circumferential direction. Specifically, the thread 30 is Δt higher than the thread 20. The height Δt is set within a range that allows the female thread, which is paired with the male thread of the thread 20, to pass through. Note that the height of the thread 30 may be the same as the height of the thread 20. In other words, the height of the thread 30 only needs to be greater than or equal to the height of the thread 20.

[0033] Furthermore, the "predetermined range in the circumferential direction" may be the entire area of ​​the formed threads 30A, 30B, and 30C described later, or just a part of it. For example, it may be a range of one full turn (360°) in the circumferential direction from the part connected to the screw thread 20, or it may be a range of 1 / 3 of a turn (120°), 1 / 2 of a turn (180°), 2 / 3 of a turn (270°), etc. Alternatively, it may be a range larger than one full turn in the circumferential direction (for example, 450°, 540°, etc.). This range can be appropriately changed depending on the height of the screw threads 20 and 30, the screw thread angle, the pitch, the material of the fastener 10 and the screw-in member 40, etc.

[0034] Furthermore, the screw threads 30 decrease in diameter towards the tip of the shaft portion 12. In other words, the height of the screw threads 30 is lower towards the tip of the shaft portion 12 than a predetermined range in the circumferential direction.

[0035] (torque reduction section) The screw thread 30 has a recess 32 formed therein, which serves as a torque reduction portion that partially (partially in the circumferential direction of the screw thread 30) reduces the screwing resistance torque caused by the screw thread 30.

[0036] As shown in Figure 3B, in a view along the axial direction of the shaft portion 12, the thread 30 is formed along the circle CI, but the radial dimension of the thread 30 is not constant. The recess 32 is a part of the thread 30 whose radial dimension is smaller than that of other parts. In other words, the recess 32 is a part of the thread 30 that is recessed radially inward from the part along the circle CI of the shaft portion 12. Note that the circle CI is a virtual circle along the top of the thread when the shaft portion 12 is viewed in cross-section.

[0037] As shown in Figures 3A and 3B, the recesses 32 are provided at multiple locations in the circumferential direction of the shaft portion 12. Specifically, the recesses 32 are provided, for example, at 120° intervals in the circumferential direction.

[0038] In the screw thread 30, if the three portions demarcated by the recess 32 are designated as formed threads 30A, 30B, and 30C from the tip side of the shaft portion 12, then formed threads 30A, 30B, and 30C are portions that follow a circle.

[0039] Furthermore, the circumferential length C of the molded peak 30A and one of the recesses 32 is 1 / 3 of the total circumferential length. The same applies to the circumferential length of the molded peak 30B and one of the recesses 32, and the circumferential length of the molded peak 30C and one of the recesses 32.

[0040] <Mechanism and Effects> In this embodiment, the fastener 10 is formed when the shaft portion 12 is screwed into the fastening hole 40A of the screw-in member 40, causing the hole wall of the fastening hole 40A to plastically deform due to the threads 30 and 20, thereby forming the female thread 42. In other words, this embodiment employs a two-stage forming structure in which the female thread is roughly formed by the threads 30 at the tip, and then finished by the threads 20.

[0041] Furthermore, in the fastener 10, the thread angle of the screw thread 30 (e.g., 30°, 45°) is smaller than the thread angle of the screw thread 20 (e.g., 60°). Therefore, the angle of the screw threads that form the female thread 42 in the fastening hole 40A of the screw-in member 40 shown in Figure 4 can be increased in stages from the screw thread 30 to the screw thread 20. As a result, the screw-in resistance torque in the initial stage of screw-in can be reduced compared to the case where only the screw thread 20 is present.

[0042] In other words, because the thread angle of thread 30 is smaller than that of thread 20, the radial pressing component against the inner wall of the fastening hole 40A is reduced. Therefore, compared to the case where only thread 20 is present, frictional resistance in the initial stage of screwing is reduced, and the screwing resistance torque can be reduced.

[0043] Furthermore, the screw thread 30 has a recess 32 formed therein, which serves as a torque reduction section that partially reduces the screwing resistance torque. This enhances the effect of reducing the screwing resistance torque.

[0044] In other words, in the screw thread 30, the larger diameter formed threads 30A, 30B, and 30C form the female thread 42 into the fastening hole 40A, and the smaller radial recess 32 reduces the screwing resistance torque. Also, since the formed threads 30A, 30B, and 30C follow the curve, it is easy to form the female thread 42 that follows the curve.

[0045] Furthermore, since the recesses 32 are provided at multiple locations in the circumferential direction of the shaft portion 12, a reduction in resistive torque can be obtained at multiple locations in the circumferential direction.

[0046] Furthermore, when the shaft portion 12 is inserted at an angle with respect to the axial direction LH of the fastening hole 40A during oblique fastening, a moment M is generated by the thrust F that presses the fastener 10 while rotating it. At this time, because the recess 32 is formed, for example, a downward force F1 acts from the formed ridge 30B to the hole wall of the fastening hole 40A, and an upward force F2 acts from the formed ridge 30A to the hole wall of the fastening hole 40A. Due to forces F1 and F2, the central axis CL of the shaft portion 12 during oblique fastening rises up so that it approaches the axial center LH of the fastening hole 40A, thereby providing a corrective effect for oblique fastening.

[0047] Furthermore, the threads 30 are higher than the threads 20 in a predetermined range in the circumferential direction (for example, a range of 360° in the circumferential direction). As a result, the threads 20 do not need to expand the radial outer dimension of the female thread 42, and only the width of the female thread 42 needs to be expanded, making it easier to form the female thread 42.

[0048] Furthermore, the screw threads 30 decrease in diameter towards the tip of the shaft portion 12. This allows the female threads 42 to be gradually formed as the shaft portion 12 is screwed into the fastening hole 40A, which does not yet have female threads, making it easier to screw in the fastener 10 compared to when the screw threads 30 do not decrease in diameter.

[0049] Furthermore, the range in which the thread 30 is formed (length L2 of region 12B) is between 2 and 7 times the pitch of the thread 20. This makes it easier to apply a greater fastening force with the thread 20 compared to the case where length L2 is greater than 7 times the pitch of the thread 20. Also, it makes it easier to form the female thread 42 with the thread 30 compared to the case where length L2 is less than 2 times the pitch of the thread 20. In other words, by setting it within this range, the balance between the torque reduction effect of the thread 30 and the axial force that can ultimately be applied by the thread 20 is optimized.

[0050] Furthermore, a female thread 42 corresponding to the diameter and pitch of the screw thread 20 is formed in the fastening hole 40A of the screw-in member 40 formed using the fastener 10. As a result, the female thread 42 formed in the fastening hole 40A has a shape corresponding to the screw thread 20, thus ensuring compatibility with general bolts that do not have screw threads 30. In other words, a general bolt can be screwed into the screw-in member 40 after the female thread 42 has been formed by the fastener 10.

[0051] <Other Embodiments> In the above embodiment, as shown in Figure 3B, the threads 30 are formed along the circle CI in the formed threads 30A, 30B, and 30C in a view along the axial direction of the shaft portion 12, but the embodiments of this disclosure are not limited thereto.

[0052] For example, as shown in Figure 5, the thread 30 does not necessarily have to have a portion that follows the circle CI. In this figure, the thread 30 is formed in a five-lobed shape and is inscribed in the circle CI at five points (formed threads 30A, 30B, 30C, 30D, and 30E). A recess 32 is formed that is recessed radially inward relative to these five points in the shaft portion 12. The thread 30 is not limited to a five-lobed shape, but may also be three-lobed or four-lobed, etc.

[0053] In other words, in this disclosure, the radial dimension of the screw thread 30 is not constant when viewed from a perspective along the axial direction of the shaft portion 12, and the torque reduction portion can be formed as a portion whose radial dimension is smaller than that of other parts.

[0054] Furthermore, in the above embodiment, the recesses 32 are provided at three locations (at 120° intervals in the circumferential direction) of the shaft portion 12, but the embodiments of this disclosure are not limited to this. For example, the recesses 32 may be provided at one, two, or four or more locations in the circumferential direction of the shaft portion 12. By adjusting the number of recesses 32, a desired reduction in resistance torque can be obtained.

[0055] Furthermore, in the above embodiment, the screw threads 30 are made to decrease in diameter towards the tip of the shaft portion 12, but the embodiments of this disclosure are not limited to this. For example, the diameter of the screw threads 30 may be constant. By adjusting the diameter of the fastening hole 40A, the shaft portion 12 can be screwed in without reducing the diameter of the screw threads 30.

[0056] In each of these embodiments, the screw-in resistance torque in the initial stage of screw-in can be reduced. Furthermore, this fastener 10 can be screwed onto any member with a pre-formed female thread (such as a nut) rather than the screw-in member 40. In this case, the fastener 10 functions as a normal bolt. Thus, this disclosure can be implemented in various forms.

[0057] <Note> (1) A fastener that forms an internal thread into a fastening hole formed in a screw-in member, The head and The shaft portion connected to the head portion, The standard threads formed on the outer surface of the shaft portion, In the aforementioned shaft portion, a tip thread is positioned closer to the tip than the standard thread, and the thread angle is smaller than that of the standard thread. A torque reduction portion is formed on the tip thread, which partially reduces the screw-in resistance torque caused by the tip thread, A fastener equipped with [a specific feature].

[0058] (2) In a view along the axial direction of the shaft portion, the radial dimension of the tip thread is not constant, and the torque reduction portion is a portion whose radial dimension is smaller than that of other parts. (1) The fastener described above.

[0059] (3) In a view along the axial direction of the shaft portion, the tip thread is formed along a circle, and the torque reduction portion is a recess that extends radially inward from the portion along the circle of the shaft portion. (2) The fastener described above.

[0060] (4) The torque reduction section is provided at multiple locations in the circumferential direction of the shaft. A fastener described in any one of (1) to (3).

[0061] (5) The height of the tip thread is greater than or equal to the height of the standard thread within a predetermined range in the circumferential direction. A fastener described in any one of (1) to (4).

[0062] (6) The aforementioned tip threads are tapered in diameter towards the tip of the shaft portion. (5) The fastener described above.

[0063] (7) The axial length of the area where the tip thread is formed is at least twice the pitch of the standard thread. A fastener described in any one of (1) to (6). [Explanation of Symbols]

[0064] 10 Fasteners 12 Shaft section 14 Head 20 threads (standard threads) 30 threads (threads at the tip) 32 Recess (torque reduction section) 40 Screw-in member 40A Fastening hole 42 Female thread

Claims

1. A fastener that forms an internal thread into a fastening hole formed in a screw-in member, The head and The shaft portion connected to the head portion, The standard threads formed on the outer surface of the shaft portion, In the aforementioned shaft portion, a tip thread is positioned closer to the tip than the standard thread, and the thread angle is smaller than that of the standard thread. A torque reduction portion is formed on the tip thread, which partially reduces the screw-in resistance torque caused by the tip thread, Equipped with, The axial length of the area where the tip thread is formed is between 2 and 7 times the pitch of the standard thread. Fasteners.

2. In a view along the axial direction of the shaft portion, the radial dimension of the tip thread is not constant, and the torque reduction portion is a portion whose radial dimension is smaller than that of other parts. The fastener according to claim 1.

3. In a view along the axial direction of the shaft portion, the tip thread is formed along a circle, and the torque reduction portion is a recess that extends radially inward from the portion along the circle of the shaft portion. The fastener according to claim 2.

4. The torque reduction section is provided at multiple locations in the circumferential direction of the shaft. A fastener according to any one of claims 1 to 3.

5. The height of the tip thread is greater than or equal to the height of the standard thread within a predetermined range in the circumferential direction. A fastener according to any one of claims 1 to 3.

6. The aforementioned tip threads are tapered in diameter towards the tip of the shaft portion. The fastener according to claim 5.

7. The height of the tip thread is higher than the height of the standard thread in a predetermined range in the circumferential direction, and is lower towards the tip of the shaft portion than the predetermined range. The fastener according to claim 6.

Images