Screw for fastening and connecting different materials

Abstract

A screw (1) for fastening and connecting different materials is further improved. In a screw (1) for fastening and connecting different materials, the cross-sectional shape of a tip portion (20) has three apexes, the sides connecting the apexes each have a curved shape that protrudes outward, and ridge portions (21, 22, 23) formed by the connecting apexes in the tip portion (20) have a spiral shape that extends toward the tip in the same direction as the spiral direction of a thread groove (11) of a main screw portion (10).

Description

Technical Field

[0001] The present invention relates to a screw for fastening and connecting different materials, which can melt a thermoplastic resin serving as a base material by heat when screwed into a specified portion of the thermoplastic resin, form a thread groove in the specified portion for fixing, and can fasten and connect a raw material serving as the base material to the base material. Background Art

[0002] For example, as in the screw disclosed in Patent Document 1, the following structure is known: a pointed tip portion is provided at the front end of the screw portion, the cross-sectional shape of the pointed tip portion has three vertices, the sides connecting the respective vertices each have a curved shape protruding outward, and the pointed tip portion has a substantially triangular pyramid shape. In such a screw, by screwing in the pointed tip portion, the base material is plastically deformed by frictional heating to form a hole, and then a thread groove is formed by the screw portion to thread-connect the screw and the base material. In order to heat the base material to plastically deform it, compared with a simple conical shape of the pointed tip portion, the above-described substantially triangular pyramid shape has been desired.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2010-003901 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] For the above-described pointed tip portion, a specified length is required to generate frictional heat sufficient to plastically deform the base material. However, the pointed tip portion only exists for plastically deforming the base material, and in the state where the screw is fastened and connected to the base material, the pointed tip portion has nothing to do with the fastening and connection between the screw and the base material. In recent years, in the automotive industry and the like, the requirement for weight reduction of components has been increasing. Therefore, it has been desired to make the screw as light as possible.

[0008] Therefore, an object of the present invention is to provide a screw for fastening and connecting different materials that has been further improved.

[0009] Means for Solving the Problems

[0010] The present invention relates to a screw for fastening and connecting different materials, characterized in that it comprises a main screw part and a pointed head part. The main screw part is located in the fastening and connecting object which is the object of fastening and connecting different materials, and its outer diameter is constant, and thread grooves are formed on the outer peripheral surface. The pointed head part is continuously formed from the front end of the main screw part and tapers towards the front end. In the fastening and connecting state, the pointed head part is not located in the fastening and connecting object. Furthermore, the cross-sectional shape of the pointed head part has three vertices, and the sides connecting the vertices are respectively outwardly convex curved shapes. Moreover, the three ridge line parts continuously formed by the vertices on the outer peripheral surface of the pointed head part are made into a spiral shape that follows the same direction as the spiral direction of the thread groove of the main screw part as it goes towards the front end.

[0011] In such a structure, the ridge line parts of the pointed head part are not straight but curved in a spiral shape. Therefore, the surface area of the pointed head part is enlarged compared with the conventional structure, and the frictional heat between it and the base material becomes greater. As a result, the required length of the pointed head part can be shorter than that of the conventional structure, which helps to reduce the weight of the screw. In addition, the inclination angle of the ridge line part with respect to the axis (the inclination of the spiral) is preferably about 5° to 20°. If it is less than 5°, it is difficult to achieve the effect compared with the conventional screw, and if it exceeds 20°, there is also a risk of reduced heating efficiency due to friction.

[0012] Effects of the Invention

[0013] The screw for fastening and connecting different materials of the present invention has the following excellent effects: it can make the overall length shorter than that of the conventional structure and helps to reduce the weight. Description of the Drawings

[0014] Figure 1 It is a perspective view of the screw for fastening and connecting different materials according to an embodiment.

[0015] Figure 2 It is a side view of the screw for fastening and connecting different materials according to an embodiment.

[0016] Figure 3 (a) is a front view of the screw for fastening and connecting different materials according to an embodiment, (b) is a sectional view taken along line A-A in Figure 2 , and (c) is a sectional view taken along line B-B in Figure 2 .

[0017] Figure 4 It is an explanatory diagram showing the state of fitting the base material and the material to be fastened and connected using the screw for fastening and connecting different materials according to an embodiment.

[0018] Figure 5It is an explanatory diagram showing a fastened connection state in which a base material and a material to be fastened and connected are brought into contact with each other using different materials for fastening and connecting screws according to the relevant embodiments. Detailed Embodiments

[0019] For the implementation mode of the invention

[0020] The embodiments of the present invention will be described according to the embodiments. In addition, the present invention is not limited to the embodiments shown below, and design changes can be made appropriately. For convenience, in the embodiments, the head side of the screw for fastening and connecting different materials is defined as the rear, and the front end side of the screw for fastening and connecting different materials is defined as the front for description, but the present invention is not limited thereto.

[0021] As Figure 1 As shown, etc., the screw 1 for fastening and connecting different materials (hereinafter also simply referred to as screw 1) includes a main screw portion 10, a tapered reducing portion 15, and a pointed head portion 20. The outer diameter of the main screw portion 10 is constant and has a cylindrical shape; the tapered reducing portion 15 is continuously formed from the front (front end side) of the main screw portion 10 and has a smaller diameter than the main screw portion 10; the pointed head portion 20 is continuously formed from the front of the tapered portion 15 and is tapered toward the front end. In addition, a screw head 30 is formed at the rear of the main screw portion 10.

[0022] A thread groove 11 is formed on the outer peripheral surface of the main screw portion 10. In this embodiment, the thread direction of the thread groove 11 is a right-handed thread direction.

[0023] The outer diameter of the tapered reducing portion 15 is set to be approximately equal to the diameter of the bottom of the thread groove 11 of the main screw portion 10. First, the inner peripheral surface of the hole of the base material W1 perforated by the pointed head portion 20 is adjusted by the tapered reducing portion 15, and a thread shape is formed on the inner peripheral surface of the hole by the thread groove 11 of the main screw portion 10, and the screw 1 is threadedly connected.

[0024] The cross-sectional shape of the pointed head portion 20, as Figure 3 shown in (b) of, has three vertices 21a, 22a, 23a, and the sides connecting the vertices 21a, 22a, 23a each have a curved shape convex outward. In addition, each of the vertices 21a, 22a, 23a is the point farthest from the axis L along the radial direction, and is not a sharp shape with a corner, but is curved roundly so as to protrude outward at the front end as shown in (b) of Figure 3 of.

[0025] Moreover, the ridge lines 21, 22, 23 connecting the vertices 21a, 22a, 23a in the pointed head portion 20 become spiral shapes that incline in the right-handed thread direction as they go toward the front end. This is the same direction as the spiral direction of the thread groove 11. That is, if Figure 3of (b) and showing the cross-sectional shape at approximately the middle part of the tip portion 20 Figure 3 If (c) is compared, the positions of the vertices 21a, 22a, and 23a are offset about the axis of the screw 1.

[0026] As Figure 2 shown, the offset angle α of the ridge lines 21, 22, and 23 from the axis is 10° in this embodiment.

[0027] In addition, in the figure, for easy understanding, the ridge lines 21, 22, and 23 are depicted by double-dot dash lines. However, as described above, in order for the outer peripheral surface near the vertices 21a, 22a, and 23a to be circular, the outer shapes of the ridge lines 21, 22, and 23 also become curved lines that bulge outward.

[0028] Such a screw 1, as Figure 4 shown, is used when the material to be fastened and connected W2 is bonded to the base material W1 made of a thermoplastic resin. Since the base material W1 is a thermoplastic resin, it is melted by the frictional heat generated between it and the tip portion 20 as the screw 1 rotates about its axis, and the screw 1 bites in.

[0029] At a point where the screw 1 has bitten into the base material W1 to a certain extent, corresponding thread grooves are formed in the base material W1 by the thread grooves 11 of the main screw portion 10 of the screw 1, and the screw 1 is threadedly connected to the base material W1.

[0030] At this time, as Figure 5 shown, in the fastened and connected state X where the screw 1 is threadedly connected to the base material W1, on the inner surface of the base material W1 on the opposite side of the screw 1 inserted therethrough, a bulging portion 50 is formed around the screw 1 by melting the base material W1. Thread grooves are also formed on the inner peripheral surface of the bulging portion 50, and the strength of the threaded connection between the base material W1 and the screw 1 is further increased.

[0031] In addition, in Figure 5 the shown fastened and connected state X, the fastened and connected base material W1 and the material to be fastened and connected W2 are located at the main screw portion 10 of the screw 1, and the tip portion 20 is located in the inner side direction penetrating from the base material W1. That is, the tip portion 20 has nothing to do with the fixed connection between the base material W1 and the material to be fastened and connected W2 in the fastened and connected state X.

[0032] In this way, the ridge line portions 21, 22, and 23 of the tip portion 20 form a spiral structure that is offset from the axis. Compared with the conventional screw in which the ridge line portion is along the axis, the outer surface area of the tip portion 20 is enlarged, the contact area with the base material W1 is increased, and more frictional heat is generated. Since the more frictional heat is generated, the easier it is for the base material W1 to undergo plastic deformation due to heat, the overall length of the tip portion 20 can be made shorter compared to the conventional structure. The tip portion 20 becomes an unnecessary part after the fastening connection of the base material, and the shorter the overall length of the tip portion 20, the more it can contribute to the weight reduction of the screw 1.

[0033] In the above embodiment, the dimensions and shapes of each part can be appropriately and freely selected.

[0034] In order to eliminate the defective condition in which the screw is improperly screwed due to the base material W1 bulging 1 also toward the surface side, for example, the following structure may also be adopted: a concave portion is formed at the boundary between the main screw portion 10 and the screw head portion 30 to absorb the bulge of the base material W1 toward the surface side.

[0035]

Explanation of symbols

[0036] 1: Screw for fastening connection of different materials

[0037] 10: Main screw portion

[0038] 11: Thread groove

[0039] 15: Introduction portion

[0040] 20: Tip portion

[0041] 21, 22, 23: Ridge line portions

[0042] 21a, 22a, 23a: Vertices

[0043] 30: Screw head portion

[0044] 50: Bulging portion

[0045] W1: Base material (object of fastening connection)

[0046] W2: Material to be fastened and connected (object of fastening connection)

[0047] X: Fastening connection state

[0048] α: Offset angle.

Claims

1. A screw for fastening and connecting different materials, characterized in that, It has a main screw part and a pointed part, The main screw part is located in the fastening connection object which is a fastening connection object of mutually different materials in the fastening connection state, its outer diameter is constant, and thread grooves are formed on the outer peripheral surface; The pointed part is continuously formed from the front end of the main screw part and is reduced in diameter toward the front end, In the fastening connection state, the pointed part is not located in the fastening connection object, Furthermore, the cross-sectional shape of the pointed part has three vertices, and the sides connecting the vertices are respectively outwardly convex curved shapes, Moreover, the three ridge line parts continuously formed by the vertices in the outer peripheral surface of the pointed part are made into a spiral shape that goes in the same direction as the spiral direction of the thread groove of the main screw part as it goes toward the front end.

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