Screw hole structure

Abstract

To provide a screw hole structure that allows for easy tightening of the screw shaft and is easy to manufacture. [Solution] A screw hole structure in which a screw hole 20 is formed in a thin plate, wherein the screw hole 20 is constructed by providing a plurality of protrusions 22 on the inner circumferential surface of a through hole 21 that screw into the screw groove of a screw shaft, and the plurality of protrusions 22 are spaced apart along a helical curve on the inner circumferential surface so that they do not overlap each other in a plan view. The plurality of protrusions 22 can also be arranged along a plurality of helical curves on the inner circumferential surface. In conventional screw hole structures, when a screw shaft is screwed into the screw hole, the opening edge along the plane elastically deforms in a helical shape to form a screw thread, so there was a risk that the restoring force of the opening edge acting on the screw shaft during tightening would make the tightening work difficult.

Description

Technical Field

[0001] The present invention relates to a screw hole structure.

Background Art

[0002] As a screw hole structure in which a screw hole is formed in a thin plate portion, for example, the configuration disclosed in Patent Document 1 is known. In this screw hole structure, a deformation promoting portion formed of a notch is formed in a part of an opening edge of the screw hole provided in the thin-walled portion, and a thread is formed by deforming the opening edge with the deformation promoting portion.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the above-described conventional screw hole structure, when a screw shaft is screwed into the screw hole, the planar opening edge is elastically deformed into a spiral shape to form a thread. Therefore, the restoring force of the opening edge acts on the screw shaft during tightening of the screw shaft, which may make the tightening operation difficult.

[0005] Therefore, an object of the present invention is to provide a screw hole structure that allows easy tightening of a screw shaft and is easy to manufacture.

Means for Solving the Problem

[0006] The above object of the present invention is achieved by a screw hole structure in which a screw hole is formed in a thin plate, wherein the screw hole is configured by providing a plurality of projections that screw into thread grooves of a screw shaft on an inner circumferential surface of a through hole, and the plurality of projections are arranged at intervals along a helical curve on the inner circumferential surface so as not to overlap each other in a plan view.

[0007] In the screw hole structure of the present invention, the multiple protrusions can be arranged along multiple helical curves on the inner circumferential surface.

[0008] Furthermore, the screw hole structure of the present invention can be configured such that multiple thin plates are connected by screwing a screw shaft into the screw hole while the multiple thin plates are stacked together. [Effects of the Invention]

[0009] According to this invention, it is possible to provide a screw hole structure that allows for easy tightening of the screw shaft and is easy to manufacture. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing a screw hole structure according to one embodiment of the present invention. [Figure 2] This is an enlarged view of the main part of Figure 1. [Figure 3] Figure 1 is a plan view of the screw hole structure. [Figure 4] This is an enlarged view of the main part of Figure 3. [Figure 5] This is an enlarged view of the main part of section AA in Figure 3. [Figure 6] This figure illustrates one step in the manufacturing process of the screw hole structure shown in Figure 1. [Figure 7] This figure illustrates other steps in the manufacturing process for the screw hole structure shown in Figure 1. [Figure 8] This is a plan view showing a screw hole structure according to another embodiment of the present invention. [Figure 9] Figure 8 is an enlarged view of the main part of the BB cross section. [Figure 10] This is a perspective view showing a screw hole structure according to yet another embodiment of the present invention. [Figure 11] Figure 10 is a plan view of the screw hole structure. [Figure 12] Figure 11 is a cross-sectional view of CC. [Figure 13] Figure 10 is a bottom view of the screw hole structure. [Figure 14] It is an enlarged view of a principal part of the D-D cross-section of FIG. 13 MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing a screw hole structure according to an embodiment of the present invention. As shown in FIG. 1, the screw hole structure of the present embodiment is configured by forming a screw hole 20 in a thin plate 10.

[0012] The thin plate 10 is, for example, a flat plate-shaped member made of a steel plate such as SPCC or SUS, or a resin plate formed by injection molding or the like. The thickness of the thin plate 10 is, for example, about 0.8 to 3.0 mm.

[0013] The screw hole 20 is configured by providing a plurality of protrusions 22 on a smooth inner circumferential surface of a through hole 21 penetrating the thin plate 10 in the thickness direction. A screw shaft such as a screw or a bolt can be inserted into the screw hole 20, and the plurality of protrusions 22 are screwed into thread grooves of the screw shaft. The size of the screw hole 20 is not particularly limited, and for example, it can correspond to a screw shaft of M3 to M8.

[0014] FIG. 3 is a plan view of the screw hole structure shown in FIG. 1, and FIG. 4 is an enlarged view of a principal part of FIG. 3. As shown in FIGS. 3 and 4, in the present embodiment, three protrusions 22 are provided so as to protrude inward from the inner circumferential surface of the through hole 21. Each protrusion 22 is formed in an arc shape in plan view along the inner circumference of the through hole 21, and is arranged so as not to overlap each other in plan view.

[0015] Further, FIG. 5 is an enlarged view of a principal part of the A-A cross-section of FIG. 3. As shown in FIG. 5, the protrusion 22 has a trapezoidal cross-section, and is provided along one helical curve S which is an imaginary line on the inner circumferential surface of the through hole 21, thereby forming a single-start thread.

[0016] The screw hole structure of this embodiment, having the above configuration, can be manufactured, for example, using a pair of molded pins 110 and 120 shown in Figure 6. The molded pins 110 and 120 shown in Figure 6 have a tip portion having a diameter slightly larger than the diameter of the through hole 21, and a plurality of notches 111 and 121 are formed on the outer edge of the tip portion. When the tips of the pair of molded pins 110 and 120 are inserted from above and below into the through hole 21 formed as a pilot hole in the thin plate 10, as shown in Figure 7, the tip surfaces of the molded pins 110 and 120 come into contact, and the notches 111 and 121 become one, thereby forming a plurality of accommodating spaces inside the through hole 21. These accommodating spaces serve as relief for the plastic deformation of the thin plate 10 caused by the insertion of the molded pins 110 and 120, and as the material of the thin plate 10 moves into each accommodating space by plastic flow, a plurality of protrusions 22 of the screw hole 20 are formed.

[0017] This method for manufacturing a screw hole structure is applicable whether the thin plate 10 is a metal plate or a resin plate. It allows for the easy formation of uniformly shaped protrusions 22 without material stagnation or plastic collapse, resulting in a screw hole structure that facilitates tightening of the screw shaft. Furthermore, it can improve the pull-out strength of the screw shaft and the crush resistance of the protrusions 22, as well as stabilize the surface dispersion effect described later.

[0018] Furthermore, since burring, a process frequently used to form screw holes in thin plates, is eliminated, the shape of the thin plate 10 can be kept flat, resulting in practical benefits such as reduced risk of interference with other components, relaxation of design constraints, reduction of processes and cycle time, and elimination of post-processing due to zero cutting burrs.

[0019] Figure 8 is a plan view showing a screw hole structure according to another embodiment of the present invention, and Figure 9 is an enlarged view of the main part of the BB cross section in Figure 8. As shown in Figure 8, in the screw hole structure of this embodiment, the four protrusions 22a, 22b are arranged along the inner circumference of the through hole 21 so as not to overlap each other in a plan view.

[0020] In the screw hole structures shown in Figures 1 to 5, multiple protrusions 22 are arranged along a single helical curve S on the inner circumferential surface of the through hole 21, whereas in the screw hole structures shown in Figures 8 and 9, multiple protrusions 22a and 22b are arranged along two helical curves S1 and S2 on the inner circumferential surface of the through hole 21. Specifically, two protrusions 22a facing each other in the plan view of Figure 8 are spaced apart from each other along the helical curve S1 shown in Figure 9, and two protrusions 22b facing each other in the plan view of Figure 8 are spaced apart from each other along the helical curve S2 shown in Figure 9. These four protrusions 22a and 22b constitute a double-start screw. Thus, the screw hole structure of this invention can accommodate not only single-start screws but also double-start screws.

[0021] The screw hole structures shown in Figures 8 and 9 can also be manufactured using the same manufacturing method as described above, by forming multiple notches 111 and 121 of the pair of molded pins 110 and 120 shown in Figure 6 so as to create two independent plastic flow paths.

[0022] Figure 10 is a perspective view showing a screw hole structure according to yet another embodiment of the present invention. The screw hole structure shown in Figure 10 is constructed by connecting two thin plates 10a and 10b, which have the same shape as the thin plate 10 having a screw hole 20 shown in Figure 1, by screwing a screw shaft (not shown) into the respective screw holes 20a and 20b. In Figure 10, the two thin plates 10a and 10b are stacked at different sizes, but thin plates of the same size and shape may be stacked, or three or more thin plates may be stacked. The connection of each thin plate 10a and 10b may be made using only screws, or bolts and nuts may be used.

[0023] Figure 11 is a plan view of the screw hole structure shown in Figure 10, and Figure 12 is a cross-sectional view of the CC of Figure 11. As shown in Figure 12, two thin plates 10a and 10b are stacked so that the screw holes 20a and 20b are in communication with each other, and a screw shaft 30 is screwed into the screw holes 20a and 20b.

[0024] Figure 13 is a bottom view of the screw hole structure shown in Figure 10, and Figure 14 is an enlarged view of the main part of the DD cross section of Figure 13. As shown in Figures 13 and 14, one thin plate 10a is provided with an engaging projection 11a that protrudes toward the contact surface with the other thin plate 10b. This engaging projection 11a engages with an engaging portion 12b formed to penetrate both the front and back surfaces of the other thin plate 10b, thereby preventing misalignment and rotational misalignment between the two thin plates 10a and 10b.

[0025] The screw hole structure shown in Figures 10 to 14 allows the tightening force of the screw shaft 30 to be distributed over a wide area of ​​the thin plates 10a and 10b, as shown by the hatching in Figure 11. This surface distribution effect significantly reduces the local stress acting on the base of the protrusion 22 due to the tightening of the screw shaft 30, and even if the thickness of the thin plates 10a and 10b is reduced, plastic collapse can be reliably prevented and the protrusion 22 can be formed stably.

[0026] The uses of this invention are not particularly limited, but for example, it can be used to sandwich a sheet material such as a poster between two thin plates, or to attach a thin plate-shaped member to a gypsum board surface that does not have pre-drilled holes. [Explanation of symbols]

[0027] 10 thin plate 20 screw holes 21 Through hole 22 Protrusion 30 Screw shaft S spiral curve

Claims

1. A screw hole structure in which screw holes are formed in a thin plate, The aforementioned screw hole is constructed by providing a plurality of protrusions on the inner circumferential surface of the through hole that engage with the screw groove of the screw shaft. The screw hole structure is arranged such that the multiple protrusions do not overlap with each other in a plan view, and are spaced apart along the spiral curve on the inner circumferential surface.

2. The screw hole structure according to claim 1, wherein the plurality of protrusions are arranged along a plurality of helical curves on the inner circumferential surface.

3. The screw hole structure according to claim 1, wherein a plurality of the thin plates are connected by screwing a screw shaft into the screw hole while the plurality of thin plates are stacked.

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