Fixed structure

Abstract

To provide a machine screw and a fixing structure capable of effectively suppressing warping-up of a peripheral edge portion of a screw hole.SOLUTION: In order to solve the problem, a machine screw of the present invention includes: a head portion; a shaft portion extending from the head portion to one side and having an outer peripheral surface on which a screw portion is formed; and a hole portion formed over a range from an end face at the other side of the head portion to the inside of the shaft portion, and through which a tip of a tool for rotating the machine screw around the axis of the shaft portion can be inserted from the other side. The head portion has: a reference face facing one side and extending to a radial outer side of the shaft portion; and a plurality of projecting portions projecting to one side from the reference face and formed to be arranged in a rotating direction of the shaft portion, and the plurality of projecting portions extend from the shaft portion to the radial outer side of the shaft portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention , B This relates to a fixing structure for a metal plate using a sintered body. [Background technology]

[0002] A screw for steel plates, as described in Patent Document 1, is known as a screw for fastening thin steel plates (metal plates). This screw for steel plates comprises a screw head, a parallel thread portion that extends from the screw head and has an outer peripheral surface on which a thread portion is formed, and a hole for inserting a tool. In the screw for steel plates, the hole is formed from the head to the shank, which allows the head to be made thin and prevents the head from protruding too much from the metal plate when fastened.

[0003] The screw head also has an annular protrusion formed on the outer edge of the bottom surface of the screw head, and a recess formed on the inner periphery of the protrusion.

[0004] When a steel plate screw is tightened with the steel plate abutting the convex part, the thrust of the parallel thread part causes the periphery of the screw hole in the steel plate (the part inside the convex part) to curl up (bow up), enter into the concave part and adhere tightly. As a result, the rotational resistance of the steel plate screw increases suddenly, the rotation of the steel plate screw stops, and free rotation is suppressed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-122113 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the steel plate screw described in Patent Document 1 is used to fasten a thin steel plate, the peripheral edge of the screw hole formed in the thin steel plate by the steel plate screw warps up, and this warping increases the diameter of the screw hole. As a result, the inner diameter of the screw hole becomes larger than the outer diameter of the steel plate screw, which may make it impossible to effectively prevent the steel plate screw from spinning freely relative to the thin steel plate when fastening the steel plate.

[0007] The present invention has been made in view of the above-mentioned problems, and provides a screw that can effectively suppress free rotation. Using The purpose is to provide a fixed structure. [Means for solving the problem]

[0008] In order to solve the above problems, fixed structure teeth, and two metal plates connected to each other by being penetrated in a thickness direction by the screw, wherein the screw a head; a shank extending from the head to one side and having an outer circumferential surface on which a thread is formed; and a hole formed over a range from the end face on the other side of the head to the inside of the shank, into which the tip of a tool for rotating the screw around the axis of the shank can be inserted from the other side, wherein the head has a reference surface facing one side and extending radially outward of the shank, and a plurality of protrusions protruding from the reference surface to one side and formed side by side in the rotational direction of the shank, the plurality of protrusions being The screw thread has 18 or more but less than 24 protrusions arranged in a straight line, the protrusions having a first surface formed facing the tightening direction in the rotational direction and a second surface inclined facing the opposite direction to the tightening direction in the rotational direction, the rise angle of the first surface with respect to the reference surface being larger than the rise angle of the second surface with respect to the reference surface, the shank has a tapered portion adjacent to the head and having a diameter that decreases as it goes from the reference surface to one side, and the tapered portion has a flat portion with a flat outer circumferential surface between the head and the end of the other side of the threaded portion. The shaft portion is engaged with the metal plate with the plurality of protrusions in close contact with the metal plate. .

[0009] this Used in fixed structuresWith a screw, the hole extends from the other end face of the head to the inside of the shank, so the thickness of the head can be made relatively small compared to the predetermined hole depth for inserting a tool, preventing the head from protruding too much from the metal plate when the screw is fastened to the metal plate.

[0010] Furthermore, the head has multiple protrusions that protrude from the reference surface to one side and are aligned in the direction of rotation of the shank, so when this screw is fastened to a metal plate, for example, the multiple protrusions engage with the surface of the metal plate, increasing the friction between the head and the metal plate, effectively preventing the screw from spinning freely.

[0011] Furthermore, because the multiple protrusions extend radially outward from the shank, the peripheral edge of the screw hole, which tends to warp under the force of the threaded portion, comes into contact with the multiple protrusions, thereby suppressing the warping of the peripheral edge of the screw hole. This prevents the screw hole from widening due to the warping of the peripheral edge, and increases the torque due to the increased frictional resistance, thereby suppressing the screw from spinning freely.

[0012] Furthermore, for each of the multiple protrusions, the rise angle of the first surface facing the tightening direction relative to the reference surface is greater than the rise angle of the second surface facing the opposite direction to the tightening direction relative to the reference surface. Therefore, when tightening the screw into a metal plate, the first surface bites into the surface of the metal plate, increasing the tightening torque and preventing the screw from spinning freely. Furthermore, when loosening the screw, the sliding resistance of the second surface against the surface of the metal plate is relatively smaller than the sliding resistance against the first surface, allowing the screw to rotate smoothly.

[0013] Furthermore, the multiple protrusions are arranged at equal intervals in the rotational direction, which allows the torque generated between the head and the metal plate when the screw is tightened into the metal plate to be approximately uniform around the entire circumference of the head.

[0014] Furthermore, as the plurality of protrusions, 18 or more but less than 24 protrusions are formed aligned in the rotation direction. In this way, by appropriately setting the number of protrusions aligned in the rotation direction, This effectively increases the tightening torque of the screw against the metal plate, thereby effectively preventing the screw from spinning freely when tightening the screw into the metal plate.

[0015] The shank also has a tapered portion adjacent to the head, the diameter of which decreases from the reference plane toward one side. This allows the outer diameter of the shank on one side of the tapered portion to be smaller than the outer diameter of the end on the other side of the tapered portion, while still providing an area in the tapered portion of the shank for forming a hole with a predetermined depth. This allows the outer diameter of the shank on one side of the tapered portion to be relatively small during the initial stage of fastening the screw to a metal plate, thereby reducing the contact area between the screw and the metal plate. This reduces frictional resistance between the screw and the metal plate, thereby suppressing an increase in torque and preventing the head from protruding too far from the metal plate.

[0016] Furthermore, since the shaft engages with the metal plate with the multiple protrusions in close contact with the metal plate, a fixed structure can be provided in which the metal plates are firmly fixed together by interlocking the multiple protrusions with the metal plate, which is prevented from warping by the multiple protrusions.

[0017] In the screw, the first surface preferably forms a rising angle of 90 degrees with respect to the reference surface.

[0018] With this configuration, the first surface and the rotation direction of the screw are perpendicular to each other, so when the screw is tightened against the metal plate, the metal plate that is caught between the multiple protrusions is received from the front by the first surface, more effectively preventing the screw from spinning freely. [Effects of the Invention]

[0019] As described above, the present invention Using The fixing structure can effectively prevent the peripheral edge of the screw hole from warping upward. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a vertical cross-sectional view showing a fixing structure according to an embodiment of the present invention. [Figure 2] FIG. 4 is a side view of a screw of the fixing structure. [Figure 3] FIG. 4 is a top view showing the head of the screw. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2. [Figure 5] FIG. 4 is a side view showing a protruding portion of the screw. [Figure 6] This is an exploded oblique view showing the state in which the joist and ceiling runner are connected using the screws. [Figure 7] FIG. 10 is a cross-sectional view showing the state in which two partition studs are connected together using the screw. [Figure 8] FIG. 10 is an exploded perspective view showing the state in which the partition runner and the stud are connected using the screw. [Figure 9] FIG. 10 is an exploded perspective view showing the state in which a metal plate is fixed to a partition stud using the screw. [Figure 10] This is an exploded perspective view showing the state in which the metal plate is fixed to the joist using the screws. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are examples that embody the present invention and are not intended to limit the technical scope of the present invention.

[0022] As shown in FIG. 1, a fixing structure 1 according to an embodiment of the present invention includes a screw 10 and two metal plates 50, 50 that are connected to each other by being penetrated by the screw 10 in the thickness direction.

[0023] The screw 10 is a member for fastening two metal plates 50 together by penetrating them. Specifically, as shown in Fig. 2, the screw 10 comprises a head 20 that is disk-shaped in plan view, a shank 30 that extends from the head 20 to one side (the lower side of the paper in Fig. 2) and has an outer circumferential surface on which a threaded portion 32 is formed, and a hole 40 (see Fig. 3) into which the tip of a tool for rotating the screw 10 around the axis of the shank 30 can be inserted from the other side. The hole 40 is formed over a range from the end face of the head 20 on the other side (the upper side of the paper in Fig. 2) to the inside of the shank 30.

[0024] The shank 30 has a threaded portion 32 formed so that the screw 10 can be tightened against the metal plate 50 by rotating the screw 10 clockwise, and can be loosened against the metal plate 50 by rotating the screw 10 counterclockwise. Hereinafter, the clockwise direction of rotation of the screw 10 will be referred to as the tightening direction A, and the counterclockwise direction will be referred to as the loosening direction B. Note that the screw 10 may have a threaded portion 32 in which the tightening direction A and loosening direction B are opposite to those described above.

[0025] The head 20 has a configuration for preventing the screw 10 from spinning freely relative to the metal plate 50 when the screw 10 is rotated in the fastening direction A while the screw 10 is fastened to the metal plate 50. Specifically, as shown in Figures 4 and 5, the head 20 has a reference surface 22 that faces one side and extends radially outward from the shank 30, and a plurality of protrusions 24 that protrude from the reference surface 22 to one side and are aligned in the rotational direction of the shank 30.

[0026] In this embodiment, the thickness of the head 20 is set in the range of 0.55 mm to 0.70 mm to prevent the head 20 from protruding too much from the metal plate 50 when the screw 10 is fastened to the metal plate 50.

[0027] The multiple protrusions 24 are portions that suppress freewheeling of the screw 10 by generating torque between the screw 10 and the metal plate 50 when the screw 10 is tightened against the metal plate 50. The multiple protrusions 24 are arranged at equal intervals in the rotational direction so that the resistance generated between the head 20 and the metal plate 50 when the screw 10 is tightened against the metal plate 50 is approximately uniform around the entire circumference of the head 20.

[0028] Table 1 shows the results of three measurements of the maximum loads (kgf) α to γ ​​generated between each screw and the metal plate 50 when screws with 0, 18, and 24 protrusions 24 are fastened to the metal plate 50, and the average values. Specifically, α to γ ​​represent the maximum loads generated when the head 20 is in contact with the metal plate 50. Note that α is the maximum load generated between the metal plate 50 and a screw with 0 protrusions 24, β is the maximum load generated between the metal plate 50 and a screw with 18 protrusions 24, and γ is the maximum load generated between the metal plate 50 and a screw with 24 protrusions 24, and the numbers in parentheses represent the number of protrusions 24 in each case.

[0029] [Table 1]

[0030] As shown in Table 1 above, the inventors have confirmed that the maximum tightening torque of the screw 10 (the maximum of the average values ​​in Table 1) exists within a range where the number of protrusions aligned in a row in the rotational direction is 1 to 24. Furthermore, the inventors have confirmed that the average value of the maximum value of the load generated between the screw 10 and the metal plate 50 is larger and the tightening torque increases when the number of protrusions aligned in a row in the rotational direction is 18 compared to when the number is 24.

[0031] For this reason, it is preferable that the plurality of protrusions 24 be formed in a number of less than 24 and aligned in a line in the rotational direction, and it is more preferable that the plurality of protrusions 24 be formed in a number of 18 and aligned in a line in the rotational direction as shown in Fig. 4. In addition, it is preferable that the height of the plurality of protrusions 24 be set in the range of 14.3% to 36.4% of the thickness of the head 20.

[0032] As shown in Fig. 4, the multiple protrusions 24 extend radially outward from the shaft portion 30. As shown in Fig. 5, the multiple protrusions 24 have a first surface 24a facing the tightening direction A of the rotational direction, and a second surface 24b facing the opposite direction to the tightening direction (loosening direction B) of the rotational direction. The second surface 24b is inclined so as to approach the reference surface 22 as it moves from the first surface 24a toward the loosening direction B.

[0033] The multiple protrusions 24 have a shape that is set so that the resistance between the first surface 24a and the metal plate 50 when the screw 10 is rotated in the tightening direction A is greater than the resistance between the second surface 24b and the metal plate 50 when the screw 10 is rotated in the loosening direction B. Specifically, the rise angle of the first surface 24a with respect to the reference surface 22 is greater than the rise angle of the second surface 24b with respect to the reference surface 22, as shown in Fig. 5. In this embodiment, the rise angle of the first surface 24a with respect to the reference surface 22 is set to 90 degrees, and the rise angle of the second surface 24b with respect to the reference surface 22 is set to less than 90 degrees.

[0034] In this embodiment, the multiple protrusions 24 are provided adjacent to each other in the rotational direction. Specifically, the other edge (the edge in the loosening direction) of the second surface 24b is connected to the edge of the first surface 24a of another adjacent protrusion 24 in the tightening direction A.

[0035] In order for the plurality of protrusions 24 to efficiently bite into the metal plate 50, the angle formed between the first surface 24a and the second surface 24b is an acute angle, as shown in Fig. 5. In this embodiment, the height (length in the axial direction) of the plurality of protrusions 24 is set within a range of 0.10 mm to 0.20 mm.

[0036] The shank 30 has a tapered section 34 adjacent to the head 20 and having a diameter that decreases from the reference plane 22 to one side, a trunk section 35 connected to the tapered section 34 and having a constant diameter along the axial direction, a tip section 36 connected to the trunk section 35 and having a diameter that decreases to one side, and a threaded section 32 provided on the outer circumferential surfaces of the tapered section 34, trunk section 35, and tip section 36. The shank 30 engages with the metal plate 50 with the multiple protrusions 24 in close contact with the metal plate 50.

[0037] In this embodiment, the hole 40 is formed in a cross shape as shown in Fig. 3. The hole 40 is formed over the range from the other end face of the head 20 to the inside of the tapered portion 34 of the shaft 30.

[0038] The depth of hole 40 is predetermined by standards, so if hole 40 is formed only in head 20, it is necessary to ensure the thickness of head 20. In this embodiment, hole 40 is formed over the range from the other end face of head 20 to the inside of tapered portion 34 of shank 30, which allows the thickness of head 20 to be relatively small.

[0039] 2, the tapered portion 34 has a flat portion 38 for suppressing warping of the peripheral edges of the screw holes of the two metal plates 50, 50. The flat portion 38 is formed at the other end of the tapered portion 34, and its radially outer peripheral surface is flat. In other words, the threaded portion 32 is provided in an area of ​​the shaft portion 30 on one side of the flat portion 38.

[0040] The axial length of the flat portion 38 is set to be approximately the same as the total thickness of the two metal plates 50, 50, specifically, approximately 1.0 mm. Furthermore, a thin steel plate having a thickness of approximately 0.4 mm to 0.5 mm is used as the metal plate 50 in this embodiment. As a result, the metal plates 50, 50 are disposed in the gap between the head 20 of the screw 10 and the other end of the threaded portion 32.

[0041] An embodiment to which such a fixing structure 1 is applied will be described below.

[0042] (1) Example 1 As shown in Figure 6, the fixing structure of Example 1 has a ceiling runner 102 extending in a predetermined direction, a tubular joist 104 extending in a direction perpendicular to the predetermined direction and connected to the ceiling runner 102, and screws 10 that fix the ceiling runner 102 and the joist 104 together.

[0043] The ceiling runner 102 has a mounting plate portion on which the end of the joist 104 rests. The mounting plate portion of the ceiling runner 102 and the side walls of the joist 104 that rest on the mounting surface of the mounting plate portion correspond to the metal plates 50, 50, respectively. By tightening the screws 10 to the mounting plate portion of the ceiling runner 102 and the side walls of the joist 104, the side walls of the joist 104 are fixed to the mounting plate portion of the ceiling runner 102.

[0044] (2) Example 2 As shown in Figure 7, the fixing structure of Example 2 has two first studs 202, 202 arranged side by side in a predetermined direction, a second stud 204 connecting these two first studs 202, 202, and a screw 10 fixing these first studs 202, 202 and the second stud 204 together.

[0045] The first studs 202, 202 and the second stud 204 are each formed from a C-shaped steel. Specifically, the first studs 202, 202 and the second stud 204 each have a web, a pair of flanges rising from both ends of the web, and a lip rising from the edge of the flange opposite the edge to which the web is connected.

[0046] In this embodiment, the web of the second stud 204 is arranged so as to straddle the flanges of the two first studs 202. The flanges of the first studs 202 and the web of the second stud 204 correspond to the metal plates 50, respectively. By tightening the screws 10 into the webs of the first studs 202 and the second stud 204, the web of the second stud 204 is fixed to the flanges of the first studs 202.

[0047] (3) Example 3 As shown in Figure 8, the fixing structure of Example 3 comprises a partition runner 304 extending in a predetermined direction and having a groove that opens upward and is perpendicular to the predetermined direction, a tubular partition stud 302 that is rectangular in cross section and extends in the vertical direction, with its lower end inserted into the groove of the partition runner 304, and a screw 10 that fixes the partition runner 304 and the partition stud 302.

[0048] The partition runner 304 has a placement portion on which the partition stud 302 is placed, and a pair of clamping portions that rise from both ends of the placement portion in the width direction and clamp the partition stud 302 therebetween.

[0049] The side surface of the stud 302 and the clamping portion of the partition runner 304 correspond to the metal plates 50, 50, respectively. By tightening the screws 10 into the side surface of the stud 302 and the clamping portion of the partition runner 304, the clamping portion of the partition runner 304 is fixed to the side surface of the stud 302.

[0050] (4) Example 4 9, the fixing structure of Example 4 comprises a plurality of first studs 202 arranged in a row, a partition wall supported by the first studs 202, 202 between two adjacent first studs 202, 202, connecting members 404 connecting the first studs 202 to the partition wall, and screws 10 fixing the first studs 202 to the connecting members 404. The first studs 202 used in this example are the same as the first studs 202 of Example 2.

[0051] The connecting member 404 has a plate-like portion that is fixed in close contact with the flange of the first stud 202. The flange of the first stud 202 and the plate-like portion of the connecting member 404 correspond to the metal plates 50, 50, respectively. By tightening the screws 10 into the flange of the first stud 202 and the plate-like portion of the connecting member 404, the connecting member 404 is fixed to the flange of the first stud 202.

[0052] (5) Example 5 10, the fixing structure of the fifth embodiment includes two adjacent sills 104, 104, a connecting member 504 that connects the two sills 104, 104, and a screw 10 that fixes the sills 104, 104 and the connecting member 504. The sills 104 of this embodiment are the same as the sills 104 of the first embodiment.

[0053] The connecting member 504 has a plate-like portion that is fixed in close contact with the two sills 104, 104. The sills 104 and the plate-like portion of the connecting member 504 correspond to the metal plates 50, 50, respectively. The connecting member 504 is fixed to the sills 104 by tightening the screws 10 into the sills 104 and the plate-like portions of the connecting member 504.

[0054] (Action and effect) With the screw 10 of this embodiment, the hole 40 is formed over the range from the other end face of the head 20 to the inside of the shank 30, so the thickness of the head 20 can be made relatively small compared to the depth of the hole 40, which is predetermined as a dimension that allows a tool to be inserted. This makes it possible to prevent the head 20 from protruding too much from the metal plate 50 when the screw 10 is fastened to the metal plate 50.

[0055] Furthermore, the head 20 has multiple protrusions 24 that protrude from the reference plane to one side and are aligned in the rotational direction of the shank 30, so when the screw 10 is fastened into a metal plate 50, the multiple protrusions 24 engage with the surface of the metal plate 50, increasing the frictional force between the head 20 and the metal plate 50. This effectively prevents the screw 10 from spinning freely.

[0056] Furthermore, because the multiple protrusions 24 extend radially outward from the shank 30, the peripheral edge of the screw hole, which tends to warp due to the force from the threaded portion, can be prevented from warping by abutting against the multiple protrusions 24. This increases the area where the multiple protrusions 24 and the surface of the metal plate 50 interlock, increasing frictional resistance and increasing torque, thereby preventing the screw 10 from spinning freely.

[0057] Furthermore, the rise angle of the first surface 24a relative to the reference surface 22 is larger than the rise angle of the second surface 24b relative to the reference surface 22. Therefore, when the screw 10 is fastened to the metal plate 50, the first surface 24a bites into the surface of the metal plate 50, increasing the fastening torque and preventing the screw 10 from spinning freely. Furthermore, when the screw 10 is loosened, the sliding resistance of the second surface 24b relative to the surface of the metal plate 50 is relatively smaller than the sliding resistance relative to the first surface 24a, allowing the screw 10 to rotate smoothly.

[0058] Furthermore, the rise angle of the first surface 24a relative to the reference surface 22 is 90 degrees, and the first surface 24a and the rotation direction of the screw 10 are perpendicular to each other. Therefore, when the screw 10 is tightened against the metal plate 50, the metal plate 50 that is caught between the multiple protrusions 24 is received from the front by the first surface 24a, thereby more effectively preventing the screw 10 from spinning freely.

[0059] Furthermore, since the multiple protrusions 24 are formed in a line at equal intervals in the rotational direction, the torque generated between the head 20 and the metal plate 50 when the screw 10 is tightened into the metal plate 50 can be made approximately uniform around the entire circumference of the head 20.

[0060] Furthermore, since 18 protrusions 24 are formed in a row in the rotational direction, the number of protrusions 24 aligned in a row in the rotational direction is appropriately set, which effectively increases the tightening torque of the screw 10 against the metal plate 50. This effectively prevents the screw 10 from spinning freely when tightening the screw 10 against the metal plate 50.

[0061] Furthermore, the shank 30 has a tapered portion 34 adjacent to the head 20, the diameter of which decreases from the reference plane 22 toward one side. This allows the outer diameter of the shank 30 on one side of the tapered portion 34 to be smaller than the outer diameter of the end of the tapered portion 34 on the other side, while still ensuring an area in the tapered portion of the shank 30 for forming a hole 40 with a predetermined depth. As a result, in the initial state of fastening the screw 10 to the metal plate 50, the outer diameter of the portion of the shank 30 on one side of the tapered portion 34 (tip portion 36) is relatively small, thereby reducing the contact area between the screw 10 and the metal plate 50. This reduces the frictional resistance between the screw 10 and the metal plate 50, thereby preventing the head 20 from protruding from the metal plate 50 from becoming too large while suppressing an increase in torque.

[0062] Furthermore, the shaft portion 30 engages with the metal plate 50 with the multiple protrusions 24 in close contact with the metal plate 50, and by engaging the multiple protrusions 24 with the metal plate 50, which is prevented from warping by the multiple protrusions 24, a fixing structure 1 can be provided in which the metal plates 50, 50 are firmly fixed together.

[0063] (Variation) The above-described embodiments are merely examples of preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.

[0064] In the above embodiment, the hole 40 is formed in a cross shape, but the shape of the hole 40 is not limited to a cross shape and may be formed in, for example, a minus shape or the like.

[0065] In the above embodiment, a thin steel plate is used as the metal plate 50, but the plate that can be used as the metal plate 50 is not limited to a thin steel plate, and a plate made of other metals such as an aluminum plate may also be used.

[0066] In the above embodiment, the rising angle of the first surface 24a with respect to the reference surface 22 is set to 90 degrees. However, the rising angle of the first surface 24a with respect to the reference surface 22 does not have to be set to 90 degrees.

[0067] In the above embodiment, the multiple protrusions 24 were formed in a row in the rotational direction, but the positions at which the multiple protrusions 24 are formed are not limited to this, and for example, they may be formed at positions spaced apart from each other radially on the shaft portion 30.

[0068] In the above embodiment, the axial length of the flat portion 38 is set to be approximately equal to the total thickness of the two metal plates 50, 50, but it does not necessarily have to be approximately equal to the total thickness. For example, the axial length of the flat portion 38 may be set to be smaller than the total thickness of the two metal plates 50, 50. This allows the force pushed up by the threaded portion 32 to be used as a force for engaging the multiple protrusions 24. As a result, the metal plates 50, 50 are pushed upward by the threaded portion 32, making it possible to strengthen the anti-rotation function.

[0069] It goes without saying that various other design modifications are possible within the scope of the claims of the present invention. [Explanation of symbols]

[0070] 1 Fixed structure 10 bis 20 heads 22 Reference plane 24 Protrusion 24a First Side 24b Second Side 30 Shaft 32 Threaded part 34 Tapered section 35 Torso 36 Tip 38 Flat area 40 Hole 50 metal plate A Tightening direction B Loosening direction

Claims

1. A screw and two metal plates connected to each other by being penetrated in the thickness direction by the screws; The screw is The head and a shaft portion extending from the head portion to one side and having an outer circumferential surface on which a thread portion is formed; a hole formed over a range from the end surface on the other side of the head to the inside of the shank, into which a tip of a tool for rotating the screw around the axis of the shank can be inserted from the other side; The head portion has a reference surface facing one side and extending radially outward of the shaft portion, and a plurality of protrusions protruding from the reference surface to one side and formed side by side in a rotational direction of the shaft portion, As the plurality of protrusions, 18 or more but less than 24 protrusions are formed which extend from the shaft portion radially outward of the shaft portion and are arranged at equal intervals in the rotational direction, The plurality of protrusions have a first surface formed facing a tightening direction in the rotation direction, and a second surface inclined facing a direction opposite to the tightening direction in the rotation direction, a rising angle of the first surface with respect to the reference surface is larger than a rising angle of the second surface with respect to the reference surface; the shaft portion has a tapered portion adjacent to the head portion and having a diameter that decreases toward one side from the reference plane; the tapered portion has a flat portion with a flat outer circumferential surface between the head and the other end of the threaded portion, A fixed structure in which the shaft portion is engaged with the metal plate with the multiple protrusions in close contact with the metal plate.

2. The fixing structure according to claim 1, A fixed structure, wherein the first surface has a rising angle of 90 degrees relative to the reference surface.

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