Drill screw

Abstract

To provide a drill screw which can perform screw-in work by one step without the need of a plurality of steps, can prevent the occurrence of burrs, and also can suppress a screw-broken phenomenon.SOLUTION: A drill screw 10 includes: a shaft part 12 having screw parts 16, 18; cut groove parts 20, 22 traversing screw threads of the screw parts; a head part 24 having a recess 30A; a drill part 26 having a blade tip diameter larger than an outside diameter of the shaft part, and a blade tip length shorter than the outside diameter of the shaft part; a neck part 28 having its diameter gradually enlarged toward the head part side from the shaft part side; a rib part 32 arranged at an external peripheral face of the neck part; an annular protrusive edge part 34 arranged at the head part; and salient parts 44a to 44l arranged at a seat face 24A of the head part, and having step parts 46. The protrusive edge part includes: a first protrusive piece 36 protruding from a base end part 34A of the protrusive edge part; and a second protrusive piece 38 protruding toward an opposite direction. A pressing face part 40 is formed at an external peripheral face of the head part, and external peripheral side end edges 54 of the salient parts 44a to 44l are formed at a protrusive edge blade part.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a self-drilling screw, and in particular to a self-drilling screw suitable for use as a construction screw for fastening a fastened member made of a wood material or a wood substitute material to a base material made of a wood material such as various natural woods, for example, broad-leaved trees such as ulin wood, apitong, acacia, ipe, chestnut, zelkova, beech, etc., so-called hardwood (hardwood), or various artificial woods, such as synthetic wood, recycled wood, resin wood, and recycled wood-plastic composite material. [Background technology]

[0002] Traditionally, there have been places where wood has been used as a base and the fastened parts fastened to the top surface of the base have also been made of wood. For example, there are many construction sites where scaffolding such as wooden decks will be used. At construction sites where wood is used as scaffolding, it is common to use what is called artificial wood, which is made from, for example, hard pieces of natural wood, wood chips, or a mixture of wood powder and resin solidified with adhesive. When carrying out installation at such construction sites, the following steps are usually performed: pilot hole preparation (pilot hole) is made with a drill in both the base and the fastened component [Step 1], countersinking is performed in the fastened component to prevent the head of the drill screw from protruding from the base surface [Step 2], and then the drill screw is screwed in [Step 3]. However, there is a demand for a drill screw that can be installed in one go, eliminating Steps 1, 2, and 3.

[0003] However, when the base and / or fastened parts are made of hard natural hardwood such as ulin, apitong, acacia, ipe, chestnut, zelkova, beech, etc., the hardness of the natural wood varies widely, and the diameter of the pilot hole set at the design stage cannot be used to screw in the drill screw at the construction site, so the diameter of the pilot hole into which the drill screw can be screwed must be set each time at the construction site according to the hardness of the natural wood. Therefore, in the past, at construction sites, in addition to the above-mentioned labor 1 (prepared hole preparation), labor (counterboring), 2 counterboring the wood, and labor 3 (screw-in work), labor 4 (setting the pilot hole diameter) was also required depending on the hardness of the wood, which required multiple steps and was time-consuming. For this reason, there is a demand for a drill screw that can be fastened by simply screwing in the drill screw in one go, without requiring multiple steps, even when the base and the workpiece to be fastened to the base are made of hard wood (hardwood).

[0004] On the other hand, for example, Japanese Patent No. 55-34326 discloses a tapping screw in which fin-shaped blades are provided along the direction of travel at multiple points on the outer slope of the flat head of the screw, and the cross section is roughly a quarter of a circle with a shallow side in the direction of screw-in rotation and a deep side opposite, and a relief groove is drilled adjacent to each fin-shaped blade on the side in the direction of screw-in rotation that is shallow on the tapping screw portion side of the flat head and deep on the top surface side of the flat head (see, for example, Patent Document 1). This tapping screw has an escape groove drilled adjacent to the side of the fin-shaped blade in the screwing rotation direction, so that when the tapping screw is screwed into an object, chips cut off by the fin-shaped blade are smoothly introduced into the adjacent escape groove and ejected from the escape groove to the surface side of the object being screwed. Moreover, the escape groove is shallow in the screwing rotation direction and deep on the fin-shaped blade side, so that chips cut by the fin-shaped blade and entering the escape groove are pushed diagonally toward the top surface by the deep force of the fin-shaped blade side from the shallow side of the escape groove in the screwing rotation force direction on the inner wall surface of the hole of the object being screwed, and ejected smoothly from the escape groove to the top surface side. Furthermore, the escape groove is shallow on the tapping screw portion side of the countersunk head and deep on the top surface side of the countersunk head, so that chips that enter the escape groove are pushed diagonally toward the deep side of the top surface of the countersunk head by the shallow force on the tapping screw portion side on the inner wall surface of the hole of the object being screwed, and ejected smoothly in part from the escape groove.

[0005] Also, for example, Japanese Utility Model Application Laid-Open Publication No. 5-19618 discloses a screw characterized in that an annular protrusion is provided on the surface of the screw head facing the screw shaft, protruding in the screw axial direction along the outer periphery, and the tip of the protrusion is formed sharply (see, for example, Patent Document 2). When this screw is driven into a material up to the head, the protrusion on the outer periphery of the head bites into the material and advances into the material while cutting with the sharp tip. Therefore, the outer periphery of the head is driven in with little resistance, preventing the generation of chips due to friction, and even if chips are generated, they are cut off by the tip of the protrusion, so no biting occurs. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special No. 55-34326 [Patent Document 2] Utility Model Application Publication No. 5-19618 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the former tapping screw was insufficient in suppressing wood burrs around the screw head after the fastened member was fastened to the base, and the screw head did not sink sufficiently. Furthermore, in the latter case, if there is no pilot hole, there is a risk of the screw breaking if it is forcibly screwed in. Moreover, if the fastened member and / or base is, for example, natural wood, the natural wood repeatedly shrinks and expands due to its humidity control, and there is a risk of the screw breaking due to the warping of the natural wood itself. In other words, the screw shaft of the tapping screw is simply tapered at the tip, so it is insufficient in terms of screwability into the fastened member, and there is still room for improvement.

[0008] Therefore, a primary object of the present invention is to provide a drill screw that can be screwed in in a single step without requiring multiple steps, that can prevent the occurrence of burrs, and that can also suppress the phenomenon of screw breakage. [Means for solving the problem]

[0009] The present invention according to claim 1 is a drill screw for fastening a wood-based fastened member made of a wood material such as natural wood or a wood substitute material such as artificial wood to a wood-based base material made of a wood material such as natural wood or a wood substitute material such as artificial wood, the drill screw comprising: a shank having a thread; a kerf portion crossing the thread of the thread; a head provided at one axial end of the shank and having a recess for screwing the shank; a drill portion provided at the other axial end of the shank and having a cutting edge diameter larger than the outer diameter of the shank and a cutting edge length shorter than the outer diameter of the shank; a neck portion which gradually increases in diameter from the shank side toward the head side; a plurality of ribs provided at intervals in the circumferential direction of the outer circumferential surface of the neck, extending from the shank to the head side, the ribs having ridge portions; and a plurality of protrusions arranged adjacent to each other in the circumferential direction of the seating surface of the head and each having a step portion oriented in the rotational cutting direction of the drill portion, the protrusion portion including a first protruding piece protruding from a base end of the protruding edge portion in a direction generally parallel to the axial direction of the shank and a second protruding piece protruding from a base end of the protruding edge portion in a direction generally parallel to the axial direction of the shank and in the opposite direction to the direction of the drill screw being screwed in, the first protruding piece, the second protruding piece and the base end of the protruding edge portion form a pressing surface portion on the outer periphery of the head, and the outer periphery side edges of the plurality of protrusions are formed into a protruding edge blade portion. The present invention according to claim 2 is an invention dependent on the invention according to claim 1, and is a drill screw having a plurality of threaded portions disposed on the shank, and at least one or more of the plurality of threaded portions having at least one or more kerf portions disposed across the threads of the threaded portion. The present invention according to claim 3 is an invention dependent on the invention according to claim 1 or 2, and is a drill screw in which the multiple protrusions include a sloped surface portion extending from a lower edge portion of a step portion between adjacent protrusions to a higher edge portion between other adjacent protrusions, and an outer peripheral edge of the sloped surface portion is formed into a flange edge. Effect of the Invention

[0010] According to the present invention, there is provided a drill screw that can be screwed in in one step without requiring multiple steps, that can prevent the occurrence of burrs, and that can also suppress the phenomenon of screw breakage.

[0011] The above and other objects, features and advantages of the present invention will become more apparent from the following description of the best mode for carrying out the invention, which refers to the drawings. [Brief description of the drawings]

[0012] [Figure 1A] FIG. 1 is a diagram showing an example of an embodiment according to the present invention, in which (A) is a front view and (B) is a plan view. [Figure 1B] FIG. 2 is an enlarged view of a main part taken along the line AA in FIG. 1A(A). [Diagram 2] 2A is an enlarged view of a main portion of the embodiment shown in FIG. 1, and FIG. 2B is an enlarged end view of line BB in FIG. [Diagram 3] 1B is an enlarged detailed view of the main part of the embodiment shown in FIG. 1A, and FIG. 1B is an enlarged detailed view of the main part showing the seat side of the head of FIG. [Figure 4] 4 is an enlarged detailed view of a main part of the shaft portion of the embodiment shown in FIGS. 1A to 3. FIG. [Diagram 5] FIG. 4 is a schematic partial enlarged cross-sectional view of a main part for explaining the action and effect of the embodiment shown in FIGS. 1A to 3, and (B) is an enlarged view of part a in (A). [Figure 6] 1A to 3, and FIG. 1B is an enlarged schematic partial cross-sectional view of a portion for explaining other functions and effects of the embodiment shown in FIG. [Figure 7] 1A is a schematic partial cross-sectional view showing an enlarged view of a main part for explaining still another action and effect of the embodiment shown in FIG. 1A to FIG. 3, and FIG. [Figure 8] 5A to 5C are enlarged explanatory views showing comparative examples of the state in which a fastened member made of hard natural wood such as apitong is fastened to a base made of wood material using the drill screw according to the present invention and a conventional drill screw, where (A) shows the case of the drill screw shown in Figs. 1A to 4, and (B) shows the case of the conventional drill screw. [Figure 9] 5A to 5C are enlarged explanatory views showing comparative examples of the state in which a fastening member made of artificial wood, such as synthetic wood or a composite material of wood and recycled plastic, and a base made of wood material are fastened using the drill screw according to the present invention and a conventional drill screw, where (A) shows the case of the drill screw shown in Figs. 1A to 4, and (B) shows the case of the conventional drill screw. BEST MODE FOR CARRYING OUT THEINVENTION

[0013] Fig. 1A is a diagram showing an example of an embodiment of the present invention, where (A) is a front view and (B) is a plan view. Fig. 1B is an enlarged view of a main part of Fig. 1A (A) taken along the line AA. Fig. 2 (A) is an enlarged view of a main part of the embodiment shown in Fig. 1A, and Fig. 2 (B) is an enlarged end view of line BB of Fig. 2 (A). In the embodiment shown below, a drill screw 10 is described which fastens a fastened member made of a wood material such as various natural woods, such as broad-leaved trees such as ulin wood, apitong, acacia, ipe, chestnut, zelkova, and beech, or other so-called hardwoods (hardwoods), to a base material made of the wood material or a wood substitute material such as various artificial woods, such as synthetic wood, recycled wood, resin wood, and recycled wood-plastic composite materials.

[0014] The drill screw 10 generally comprises a shank 12 having a plurality of (e.g., two-thread) threaded portions 16, 18, a head 24 connected to one axial end of the shank 12 via a shank 14, a drill portion 26 connected to the other axial end of the shank 12, a trumpet-shaped neck 28 that gradually expands in diameter from the shank 14 toward the head 24, a plurality of ribs 32 disposed at intervals in the circumferential direction of the outer periphery of the neck 28 and extending from the shank 12 toward the head 24, an annular protruding edge 34 disposed on the outer periphery of the head 24 and connected to the neck 28, and a plurality of protrusions 44a-44l disposed adjacent to each other in the circumferential direction of the seating surface of the head 24 (see, for example, FIG. 1B), and each protrusion has a step 46 oriented in the rotational cutting direction of the drill portion 26.

[0015] That is, the drill screw 10 according to this embodiment includes, for example, a cylindrical shank 12, as shown in FIG. 1A (A). On the peripheral surface of the shank 12, a large diameter threaded portion 16 as a first helical threaded portion and a small diameter threaded portion 18 as a second helical threaded portion are arranged from one end side to the other end side of the axial direction of the shank 12. The large diameter threaded portion 16 and the small diameter threaded portion 18 are arranged so as to be alternately positioned. In this case, on the outer peripheral surface of the shank 12, the thread of the large diameter threaded portion 16 and the thread of the small diameter threaded portion 18 formed to a nominal diameter smaller than the nominal diameter of the thread are arranged alternately from one end side to the other end side of the axial direction of the shank 12 as a double lead thread. In this case, the thread diameter of the large diameter threaded portion 16 is formed to be, for example, φ5.5 mm, and the thread diameter of the small diameter threaded portion 18 is formed to be, for example, φ4.5 mm.

[0016] 4, the large diameter threaded portion 16 is formed with a first kerf 20 having a V-shaped cross section that crosses the thread of the large diameter threaded portion 16, and similarly, the small diameter threaded portion 18 is formed with a second kerf 22 having a V-shaped cross section that crosses the thread of the small diameter threaded portion 18. The first kerf 20 and the second kerf 22 have a spiral kerf (diamond cut) configuration that allows cutting powder generated when fastening a fastened member 60 to a base (not shown) to escape, improving the tapping ability (screwability) of the drill screw 10. In this case, the first groove portion 20 and the second groove portion 22 are each arranged in three pieces at equal intervals (120° intervals) in the circumferential direction of the shaft portion 12. The intersection angle θ3 between the inner wall surface 20a and the inner wall surface 20b of the first groove portion 20 and the intersection angle θ4 between the inner wall surface 22a and the inner wall surface 22b of the second groove portion 22 are each preferably set in the range of 100° to 140°, and more preferably set to 120°. In addition, the first groove portion 20 and the second groove portion 22 can each be set at a predetermined inclination angle, for example, in the range of 10° to 30°, with respect to the axis (xx) of the shaft portion 12. In the drill screw according to this embodiment shown in FIG. 1A (A), the inclination angle is set to, for example, 30°.

[0017] Usually, the crossing angle θ3 and the crossing angle θ4, so-called diamond cut angle, are often 90 degrees, but in this embodiment, they are set to 120 degrees. The reason for this is that, as is the case when fastening a fastened member 60 of the same wood material as a base member (not shown) of a wood material such as hardwood, when the fastened member 60 is, for example, a deck material and the base member is a wood material, the chips of the deck material are sticky, and when drilling a pilot hole (prepared hole) with the cutting edge of the drill part 26, the chips 62a, for example, as shown in (B) of FIG. 7, tend to clog. When the chips 62a clog, the chips 62a get entangled in the large diameter screw part 16 and the small diameter screw part 18, and the valley part of the screw is filled with the chips 62a, so the screw cannot be fastened, and this adversely affects the retraction when sinking the head 24. Therefore, in order to alleviate the clogging caused by the cutting chips 62a as much as possible, the crossing angle θ3 and the crossing angle θ4 (cutting angle) are set to a wide value of 120 degrees, making it easier to discharge the cutting chips 62a (see, for example, FIG. 4).

[0018] In this drill screw 10, the thread portion is a double lead thread with multiple (for example, two-thread) thread portions 16 and 18, but the thread portions may be single-thread or may have three or more threads. Also, while three first kerf portions 20 and three second kerf portions 22 are provided as the kerf portions, it is sufficient that at least one kerf portion is provided, and if multiple thread portions are provided, it is preferable to provide them in the thread portion with the larger thread diameter.

[0019] In the self-drilling screw 10 according to this embodiment, a head 24, which is, for example, a circular dish-shaped head in plan view and has a diameter larger than the maximum diameter of the neck 22, is disposed on one axial end side of the shaft 12, via the shank 14 and the neck 22. A drive unit 30 capable of engaging with a tightening tool such as an electric screwdriver or electric wrench is disposed in the center of the surface of the head 24. The drive unit 30 is, for example, dish-shaped, and has a recess 30a in its center. The recess 30a is, for example, formed in a hole groove portion having a rectangular shape in plan view. Regarding the setting of the outer diameter of the head 24 (approximate to the outer diameter of the bearing surface 24A), considering that when the drill screw 10 is used to connect a base material and a fastened member, the outer diameter of the head 24 creates resistance when sinking the head 24, causing the head to skip, if the cutting edge diameter of the head 24 is made large in order to prevent the head 24 from skipping, the female thread of the base material made of wood material such as hardwood may break, causing the head 24 to not sink. It is possible to make the head 24 as small as possible to make it easier to sink, but the outer diameter of the head 24 cannot be made too small in order to prevent the fastened member 60 from expanding, and it was considered that φ9.0 mm is appropriate for the outer diameter D1 of the head 24.

[0020] In the drill screw 10 according to this embodiment, as shown in FIG. 1A(A) and FIG. 2(A) and (B), the neck portion 28 has a taper angle θ1. A plurality of (e.g., eight) ribs 32 are arranged on the outer peripheral surface of the neck portion 28 at intervals in the circumferential direction of the neck portion 28, extending from the shank portion 14 side to the head portion 24 side. The plurality of ribs 32 have ridge portions 32A in which two oblique sides forming the ribs 32 are inclined at equal angles with respect to a direction perpendicular to the axis (xx) of the shank portion 12 and intersect at an intersection angle θ5 of approximately 90°. The intersection angle θ5 of the ridge portions 32A may be formed in a range of, for example, 60° to 90°. The two oblique sides forming the ribs 32 may be formed so as to be asymmetrically inclined with respect to a direction perpendicular to the axis of the shank portion 12.

[0021] On the other hand, as shown in Figures 1A (A), 2 (A), and 5 (B), head 24 is provided with a flattened annular protruding edge portion 34 that is connected to neck portion 24 and has a predetermined length and thickness from its outer peripheral edge radially inward of head 24. 5B, the protruding edge 34 includes a first protruding piece 36 and a second protruding piece 38 each having a right-angled triangular cross section and a wedge shape. The first protruding piece 36 protrudes from the base end 34A of the protruding edge 34 substantially parallel to the axial direction (xx) of the head 24 and in the screwing direction of the drill screw 10. The second protruding piece 38 protrudes from the base end 34A of the protruding edge 34 substantially parallel to the axial direction (xx) of the head 24 and in the opposite direction to the screwing direction of the drill screw 10.

[0022] In the protruding edge portion 34, when the lower end surface of the base end portion 34A is the base portion 36a of the first protruding piece 36, the side (line segment) extending vertically downward from the base portion 36a is the vertical side portion 36b of the first protruding piece 36, and the side opposite to the right angle portion 36d of the first protruding piece 36 where the base portion 36a and the vertical side portion 36b intersect is the oblique side portion 36c of the first protruding piece 36, the area surrounded by the base portion 36a, the vertical side portion 36b, and the oblique side portion 36c constitutes the first protruding piece 36 having, for example, a right-angled triangular cross section and a wedge-shaped aspect. In this case, the first protruding piece 36 has an apex portion 36e at the intersection of the vertical side portion 36a and the oblique side portion 36c.

[0023] On the other hand, when the upper end surface of the base end portion 34A is the bottom side 38a of the second protruding piece 38, the side (line segment) extending vertically downward from this bottom side 38a is the vertical side 38b of the second protruding piece 38, and the side opposite to the right angle 38d of the second protruding piece 38 where the bottom side 38a and the vertical side 38b intersect is the oblique side 38c of the second protruding piece 38, the area surrounded by this bottom side 38a, vertical side 38b, and oblique side 38c constitutes the second protruding piece 38 having, for example, a right-angled triangular cross section and a wedge-shaped aspect. In this case, the second protruding piece 38 has an apex part 38e at the intersection of the vertical side part 38b and the oblique side part 38c.

[0024] In this drill screw 10, by forming the first protruding piece 36 and the second protruding piece 38 on the protruding edge portion 34, in particular, as shown in Fig. 5(B), for example, a single pressing surface portion 40 having a trapezoidal cross section is formed on the outer periphery of the protruding edge portion 34 by the base end portion 34A of the protruding edge portion 34, the first protruding piece 36, and the second protruding piece 38. In this case, the pressing surface portion 40 is formed by the vertical side portion 36b of the first protruding piece 36, the outer periphery end surface 34E (the outer periphery end surface of the head portion 24) of the base end portion 34A of the protruding edge portion 34, and the vertical side portion 38b of the second protruding piece 38. 1A(B), the first protruding piece 36 and the second protruding piece 38 are formed continuously around the entire outer periphery of the head 24. That is, the pressing surface portion 40 is formed in an annular shape in a plan view around the entire outer periphery of the protruding edge portion 34.

[0025] In this embodiment, the angle of the apex corner 36e of the first protruding piece 36 and the angle of the apex corner 38e of the second protruding piece 38 are each formed to, for example, 30°. In this case, it is particularly preferable that the angle of the apex corner 36e of the first protruding piece 36 is formed to, for example, 10° to 40°, more preferably, for example, 10° to 30°, and even more preferably, for example, 10° to 25°.

[0026] In the drill screw 10 according to this embodiment, in particular, twelve protrusions 44a to 44l are arranged on the bearing surface 24A of the head 24 as serrations having the function of saw-tooth cutting blades for cutting the outer peripheral edge of the countersunk hole 62 and for finish cutting the inner peripheral surface 62A of the countersunk hole 62. Next, the structure of the protrusions 44a to 44l will be described in detail below with reference to, for example, Figs. 1A(A), 1B, 2(A), and 3(A) and 3(B). That is, on the seat surface of the head 24, for example, twelve protrusions 44a, 44b, 44c, 44d, 44e, 44f, 44g, 44h, 44i, 44j, 44k, 44l are arranged adjacent to each other in the circumferential direction of the seat surface 24. Each of these protrusions 44a to 44l is formed with a step portion 46 oriented in the rotary cutting direction of the drill portion 26, and thus in the rotation direction of the head 24. Each step portion 46 includes a high end edge portion 48 and a low end edge portion 50. As shown in FIG. 1B and FIG. 3B, each of these protrusions 44a to 44l is provided with an inclined surface portion 52 extending from each low end edge portion 50 of the step portion 46 between adjacent protrusions 44a to 44l to each high end edge portion 48 between other adjacent protrusions 44a to 44l. In this case, the outer peripheral edge 54 of each inclined portion 52 functions as a “flange blade” that cuts the outer peripheral edge of the countersink hole 62 and also finishes cutting the inner peripheral surface 62A of the countersink hole 62.

[0027] In particular, in the drill screw 10 according to this embodiment, the drill portion 26 is formed with a cutting edge diameter D5 (φ5.0 mm) larger than the outer diameter D6 (φ3.6 mm) of the shank 12 and a cutting edge length L2 (3.0 mm) shorter than the outer diameter D6 (φ3.6 mm) of the shank 12. The cutting edge angle θ2 of the drill portion 26 is set to, for example, 100 degrees in order to be specialized for fastening wood materials such as oak by making it sharper than usual. According to the development history of the "drill screw 10" by the inventor of the present invention, the reason for setting the dimensions of the cutting edge diameter D5 (φ5.0 mm) and short cutting edge length L2 (3.0 mm) of the drill portion 26 is that the initial prototype of the "drill screw 10" had a cutting edge diameter of 4.1 mm and a cutting edge length of 5.0 mm, but resistance was high when screwing in, and the threads broke before the head 24 was sunk. In this case, it is believed that the resistance during tapping was high because the base (not shown) and the fastened member 60 were made of hard wood and the cutting edge diameter was small.

[0028] The next prototype was made with a cutting edge diameter (outer diameter) of 4.5 mm and a cutting edge length of 5.0 mm. Although there was no problem with the threads breaking off when screwing in, there was a large resistance when sinking the head 24, causing the head to fly off. As a method to solve the problem of head skipping, we tried to make a larger pilot hole (prepared hole) by increasing the diameter of the cutting edge, and reduce the resistance when sinking the head 24. In this case, we made a pilot hole with a wood drill and verified the screwing in of the drill screw.

[0029] Further trials were made with a tip diameter of 5.0 mm and a tip length of 5.0 mm; this significantly reduced the resistance to screwing in, but when several screws were hammered in, several of them went in at an angle while being screwed in, and when the screws were removed, the tip broke. This is thought to be because the speed at which the screw lead advances and the speed at which the cutting edge of the drill portion 26 cuts the fastened workpiece 60 did not match, causing the cutting edge to penetrate into the base wood material and be twisted off. The cause of this problem in the current prototype is thought to be that the cutting edge diameter was large at 5.0 mm and the length was set to a long 5.0 mm, making the drill portion 26 more susceptible to twisting forces when the cutting edge of the drill portion 26 penetrated the material.

[0030] As a countermeasure to this problem, the cutting edge diameter was set to 5.0 mm, the cutting edge length to 3.0 mm, and the cutting edge angle to 100°, which solved the problem of thread breakage. By combining the form of the drill portion 26 with the form of the head 24, we arrived at the dimensional setting of the cutting edge diameter and cutting edge length of the drill portion 26 in the "drill screw" of the present invention.

[0031] In the self-drilling screw 10 according to the present invention, the cutting edge diameter D5 (outer diameter) of the drill portion 26 is set to be relatively large because hardwood is often used as the fastened member 60 and base material (not shown), which creates resistance when sinking the head 24. In order to reduce this resistance, the cutting edge diameter is made large, which results in a large hole being drilled, and the aim is to reduce the amount of compression of the head 24 against the fastened member 60, making it easier to sink.

[0032] The reason for setting the cutting edge length L2 (axial length) of the drill portion 26 relatively short is that when a screw is applied to the fastened member 60 and the base material, the drill portion 26 advances with the lead, but because the fastened member 60 and the base material are hardwood (hardwood), the cutting edge of the drill portion 26 penetrates the fastened member 60 and the base material, causing a problem of the shaft portion 12 of the drill portion 26 or the cutting edge of the drill portion 26 being twisted off. To solve this problem, the cutting edge length L2 is shortened so that the cutting edge of the drill portion 26 is not twisted off when it penetrates the fastened member 60, for example. In addition, the cutting edge angle of the drill portion 26 is set to 100 degrees, and the cutting edge angle is sharper than usual, so that the drill portion 26 is specialized for wood such as oak.

[0033] In the drill screw 10 of this embodiment, as shown in, for example, FIGS. 7(A) and 7(B), when a fastened workpiece 60 is fastened to a base material (not shown), it is possible to form a pocket portion 66 on the back side of the head 24 in a portion surrounded by the seat surface (back side) 24A of the head 24, the inner circumferential surface of the first protruding piece 36, i.e., the oblique side portion 36c of the first protruding piece 36, and the outer circumferential surface of the neck portion 24.

[0034] Next, in the self-drilling screw 10 according to the present embodiment described above, the dimensions of the following members shown in, for example, FIGS. 1A, 1B, 2, 3, 4, and 7 will be illustrated. That is, the outer diameter (outer diameter of the seat) D1 of the head 24 is formed to φ9.0 mm, the inner diameter D2 of the seat 24A is formed to φ6.8 mm, the outer diameter D3 of the drive portion 30 is formed to φ8.5 mm, the inner diameter D4 of the drive portion 30 is formed to φ7.5 mm, the outer diameter D5 of the drill portion 26 is formed to φ5.0 mm, the outer diameter D6 of the shaft portion 12 (in this case, the diameter is approximately the same as the root diameter of the large diameter thread portion 16 and the small diameter thread portion 18) is formed to φ3.6 mm, and the outer diameter D7 of the shank portion 14 is formed to φ4.05 mm. , the taper angle θ1 of the neck portion 28 is formed at 56 degrees, the cutting edge angle θ2 of the drill portion 26 is formed at 100 degrees, the opening angle (diamond cut angle) θ3 of the first kerf portion 20 is formed at 120 degrees, the opening angle (diamond cut angle) θ4 of the second kerf portion 22 is formed at 120 degrees, the intersection angle (vertex angle) θ5 of the ridge portion 32A of the rib portion 32 is formed at 90 degrees, the height H1 of the rib portion 32 is formed at 0.4 mm, and the height (thickness) H2 of the protruding edge portion 34 is formed at 1.0 mm, The height H3 of the drive portion 30 is formed to be 0.6 mm, the length L1 of the shaft portion 12 is formed to be 55 mm, the (axial) length L2 of the drill portion 26 is formed to be 3.0 mm, the total (axial) length L3 of the drill screw 10 is formed to be 71 mm, the length L4 from the cutting edge of the drill portion 26 to the lower end of the second protruding piece 38 of the protruding edge portion 34 is formed to be 70 mm, and the width W1 of the rib portion 32 is formed to be 0.8 mm.

[0035] The drill screw 10 according to this embodiment shown in Figs. 1A to 4 and the like has the above-mentioned configuration, and therefore provides the following functions and effects. That is, when this drill screw 10 is used to fasten a fastened member 60 made of hard natural wood such as apitong (wood called oak or hardwood) to a base material (not shown) made of the same hard wood, the first protruding piece 36 is screwed into the fastened member 60 while rotating, as shown in Figures 5 and 6, for example, thereby preventing the fastened member 60 from expanding due to compression.

[0036] In this case, when the drill screw 10 is screwed into the fastened member 60, as shown in Fig. 5B and Fig. 6B, the apex corner 36e at the tip of the wedge-shaped first protruding piece 36 functions as a cutting blade against the fastened member 60. Therefore, a countersunk hole 62 is formed in the fastened member 60 around the protruding edge 34, as shown in Fig. 6, for example. Therefore, the apex corner 36e at the tip of the first protruding piece 36 can be more effectively screwed into the fastened member 60. In other words, the head 24 of the drill screw 10 can be sufficiently sunk into the surface side of the fastened member 60.

[0037] Furthermore, by forming the pressing surface portion 40 of the protruding edge portion 34 on the outer periphery of the head 24, when the drill screw 10 is screwed into the fastened member 60 and sinks therein, the contact area y between the pressing surface portion 40 and a portion of the surface of the fastened member 60 that has been shaved off (the inner periphery 62A of the countersunk hole 62) is increased, as shown in FIG. 6(B), and the pressing surface portion 40 is tightly attached to the inner periphery 62A of the countersunk hole 62 over a wider area. Therefore, it is possible to prevent the material of the fastened portion 60 that has been scraped off by the drill portion 26 and the first protruding piece 36 of the self-drilling screw 10 from escaping upward on the outer periphery side of the head 24.

[0038] Furthermore, by increasing the contact area y with the inner surface 62A of the countersunk hole 62, the pressing surface portion 40 can press the inner surface 62A of the countersunk hole 62 radially outwardly of the head 24 with the pressing surface portion 40 to fix the fastened member 60 in response to deformation of the fastened member 60 caused by temperature changes due to climate changes, infiltration of rainwater, humidity changes due to drying, etc., thereby minimizing deformation of the fastened member 60.

[0039] After the drill screw 10 is fastened, the pressure surface portion 40 closes the gap between the outer peripheral edge of the head of the drill screw 10 and the fastened member 60, preventing, for example, rainwater, etc. from entering the gap, thereby preventing deformation of the inner peripheral surface 64A of the pilot hole (prepared hole) 64 by the drill screw 10.

[0040] Furthermore, in the drill screw 10 according to this embodiment, as shown in Fig. 7A and 7B, a pocket portion 66 (a portion called an undercut) is formed on the back side of the head 24. Therefore, when a part of the fastened member 60 is compressed by the head 24 of the drill screw 10, the pocket portion 66 is compressed by the head 24 of the drill screw 10, and the shavings of the fastened member 60 shaved off by the drill portion 26 and the first protruding piece 36 can be stored in the pocket portion 66. Therefore, it is possible to prevent the material of the fastened member 60 shaved off by the drill portion 26 and the first protruding piece 36 of the drill screw 10 from escaping to the upper outer periphery side of the head 24. In an embodiment of the present invention, the taper angle of the neck 28 is 56 degrees and the inner diameter D2 of the seat 24A is φ6.8 mm, thereby forming a pocket portion 66 between the seat 24A and the fastened member 60, with the aim of suppressing the bulging of the fastened member 60 when the head 24 is lowered.

[0041] In the drill screw 10 according to this embodiment, the above-mentioned first protruding piece 36 and second protruding piece 38 are continuously disposed all around the outer periphery of the head 24. This makes it possible to more effectively exert the action and effect of the pressing surface 40 of the protruding edge 34 as compared to, for example, a case in which the first protruding piece 36 and the second protruding piece 38 are formed discontinuously at intervals on the outer periphery of the head 24.

[0042] Furthermore, in the drill screw 10 according to this embodiment, the outer circumferential surface 28a of the neck portion 28 is tapered so that the diameter gradually increases toward the head 24, thereby making it possible to increase the size of the pocket portion 66 (undercut). In this case, when a part of the fastened member 60 is compressed by the head 24 of the drill screw 10, the pocket portion 66 is compressed by the head 24 of the drill screw 10, and is also able to accumulate and store a larger amount of shavings 62a of the fastened member shaved off by the drill portion 26 and the first protruding piece 36.

[0043] In addition, the neck portion 28 has a taper angle θ1 of 56 degrees, the seat surface 24A has an inner diameter D2 of φ6.8 mm, and a plurality of rib portions 32 are formed on the outer circumferential surface of the neck portion 28, thereby providing an effective grinding effect on the fastened member 60. In other words, when the drill screw 10 is screwed into the workpiece 60, the rib portion 32 scrapes away the workpiece 60 around the neck portion 28, thereby making it easier for the head 24 to sink from the surface of the workpiece 60.

[0044] Furthermore, in the drill screw 10 according to this embodiment, in particular, twelve protrusions 44a to 44l are arranged on the bearing surface 24A of the head 24 as serrations having the function of saw-tooth cutting blades that cut the outer peripheral edge of the countersunk hole 62 and finish cut the inner peripheral surface 62A of the countersunk hole 62. Therefore, the function of these protrusions 44a to 44l as cutting blades improves the scraping effect on the fastened member 60, making it easier to sink the head 24. That is, the outer peripheral edge 54 of each of the inclined surfaces 52 of the protrusions 44a to 44l functions as a "flange blade" that cuts the outer peripheral edge of the countersunk hole 62 and finish cuts the inner peripheral surface 62A of the countersunk hole 62 as a saw-tooth cutting blade.

[0045] Furthermore, in the self-drilling screw 10 according to this embodiment, in particular, the drill portion 26 shown in FIG. 1(A) forms a pilot hole 64 in the fastened workpiece 60, thereby preventing the fastened workpiece 60 from lifting up. Furthermore, the tip hole (pilot hole) 64 can prevent excessive interference between the neck 24 of the drill screw 10 and the fastened member 60. In this case, resistance when the head 24 of the drill screw 10 sinks is also reduced, making it relatively easy for the head 24 to sink, and preventing the drill screw 10 from spinning freely.

[0046] An application experiment conducted by the inventor of the present invention using the self-drilling screw 10 according to this embodiment is shown in FIGS. FIG. 8 is an enlarged explanatory diagram of a main portion showing a comparative example of the state in which a fastened member made of hard natural wood such as apitong and a base made of wood material are fastened using the drill screw of the present invention and a conventional drill screw, (A) shows the case of the drill screw shown in FIGS. 1 to 4, and (B) shows the case of the conventional drill screw. FIG. 9 is an enlarged explanatory diagram showing a comparative example of the state in which the drill screw according to the present invention and a conventional drill screw are used to fasten a fastened member made of artificial wood such as synthetic wood or a composite material of wood and recycled plastic to a base made of wood material, where (A) shows the case of the drill screw shown in FIGS. 1 to 4, and (B) shows the case of the conventional drill screw. As shown in Figs. 8 and 9, it was found that the drill screw 10 according to this embodiment can clearly sink the head 24 and prevent the occurrence of burrs, compared to the conventional drill screws. [Explanation of symbols]

[0047] 10 Drill Screw 12 Shaft 14 Shank 16 Large diameter screw portion (first screw portion) 18 Small diameter threaded section (second threaded section) 20 First groove 20a, 20b Inner wall surface of the first screw portion 22 Second groove 22a, 22b Inner wall surface of the second screw portion 24 Head 24A Seat 26 Drill Section 28 Neck 28a Outer periphery of neck 30 Drive unit 30A Drive recess 32 Rib section 32A Rib ridge 34 Edge 34A Base end of flange 34E Outer periphery of base end of flange 36 First protruding piece 36a: Base of the first protruding piece 36b Vertical piece of the first protruding piece 36c: Oblique side of the first protruding piece 36d Right angle of the first protruding piece 36e Apex of the first protruding piece 38 Second protruding piece 38a: Base of the second protruding piece 38b Vertical piece of the second protruding piece 38c: the hypotenuse of the second protruding piece 38d Right angle of second protruding piece 38e Apex of the second protruding piece 40 Pressing surface 42 Serration 44a,44b,44c,44d,44e,44f,44g,44h,44i,44j,44k,44l Projection 46 Step 48 High edge of step 50 Lower edge of step 52 Slope 54 Outer peripheral edge of the inclined surface (flange blade portion) 56 Inner edge of the slope 60 Parts to be fastened 62a Chips from the fastened parts cut off by drill screws 62 Counterbore 62A Inner surface of counterbore 64 Tip hole (pre-drilled hole) 64A Inner surface of tip hole 66 Pocket section D1 Head outer diameter (bearing surface outer diameter) D2 Inner diameter of seat D3 Outside diameter of drive D4 Inner diameter of drive D5 Outside diameter of drill part D6 Shaft outer diameter D7 Shank outer diameter θ1 Neck taper angle θ2 Drill tip angle θ3 Opening angle of the groove of the first thread θ4 Opening angle of the groove of the second thread θ5 Intersection angle of ridge of rib H1 Rib height H2 Height of flange H3 Height of drive unit L1 Shaft length L2 Drill length L3 Total length of drill screw L4: The length from the tip of the drill to the bottom of the second protruding piece of the flange W1 Rib width xx Axis of shaft

Claims

1. A self-drilling screw for fastening a wood-based fastened member made of a wood material such as natural wood or a wood substitute material such as artificial wood to a wood-based base material made of a wood material such as natural wood or a wood substitute material such as artificial wood, A shaft portion having a threaded portion; a kerf section across the threads of the threaded portion; a head portion provided on one axial end side of the shaft portion and having a recess into which the shaft portion is screwed; a drill portion disposed on the other axial end side of the shank portion, the drill portion having a cutting edge diameter larger than an outer diameter of the shank portion and a cutting edge length shorter than the outer diameter of the shank portion; A neck portion whose diameter gradually increases from the shaft portion side toward the head portion side, a plurality of ribs extending from the shaft portion toward the head portion at intervals in a circumferential direction on an outer circumferential surface of the neck portion, the ribs having ridges; a ring-shaped protruding edge portion having a predetermined length and thickness and disposed radially inward from an outer peripheral edge of the head portion and connected to the neck portion; a plurality of protrusions arranged adjacent to each other in a circumferential direction of the bearing surface of the head and having a step portion oriented in a rotary cutting direction of the drill portion; The protruding edge portion is a first protruding piece protruding from a base end of the protruding edge portion in a direction substantially parallel to the axial direction of the shaft portion and in a direction in which the drill screw is screwed in; and A second protruding piece protruding from a base end of the protruding edge portion in a direction substantially parallel to the axial direction of the shaft portion and opposite to the screwing direction of the drill screw, a pressing surface portion is formed on an outer periphery of the head portion by the first protruding piece, the second protruding piece, and the base end portion of the protruding edge portion, A self-drilling screw, wherein outer peripheral edges of the plurality of protrusions are formed into flange cutting edges.

2. 2. The drill screw according to claim 1, wherein the shank has a plurality of threads disposed thereon, and one or more of the plurality of threads has at least one or more kerfs disposed thereon transversely to the threads of the threads.

3. The plurality of protrusions include an inclined surface portion extending from a lower edge portion of a step portion between adjacent protrusions to a higher edge portion between other adjacent protrusions, The self-drilling screw according to claim 1 , wherein an outer peripheral edge of the beveled portion is formed into a flange edge.

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