Welding bolt

Abstract

To provide a welding bolt in which shunting hardly occurs during welding. 【Solution means】A welding bolt having a head provided on one end side, a threaded portion, and a shaft portion including an intermediate portion 22 provided between the head and the threaded portion, wherein a welding protrusion 13 is provided on a seating surface that abuts against a workpiece 2 of the head, and a concave portion 14 recessed toward the shaft portion side is provided on a top surface 12 opposite to the seating surface of the head. When the welding bolt is viewed axially in a transparent manner, the top of the intermediate portion 22 is provided inside the opening edge 14a of the concave portion 14.

Description

Technical Field

[0001] The present disclosure relates to welding bolts.

Background Art

[0002] Welding bolts as shown in Patent Documents 1 and 2 are known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] A welding bolt melts a welding protrusion by passing an electric current and welds to a material to be welded. During welding, an electric current flows through the welding protrusion of the welding bolt to the material to be welded, and the welding protrusion melts. However, if the inner wall of the bolt insertion hole provided in the material to be welded comes into contact with the shaft portion of the welding bolt, an electric current may flow from the shaft portion to the material to be welded in addition to the welding protrusion, causing a shunt. If a shunt occurs, sufficient current does not flow through the welding protrusion, so there is a risk that sufficient welding strength cannot be ensured.

[0005]

[0006] ​However, in recent years, for example, high-tensile steel may be used as the material to be welded for the purpose of weight reduction or the like. High-tensile steel requires a larger current to be passed through for welding compared to conventional steel materials. For this reason, even if the countermeasures shown in the above patent document are taken, shunting is likely to occur, and there is a risk that the desired welding strength cannot be obtained or smooth operation is hindered.

[0007] Therefore, the present disclosure provides a welding bolt in which shunting is less likely to occur during welding.

Means for Solving the Problems

[0008] The welding bolt according to the present disclosure has a head provided on one end side, a threaded portion, and a shaft portion including an intermediate portion provided between the head and the threaded portion, and is a welding bolt having a welding protrusion provided on a seating surface that abuts against the material to be welded of the head, a recess recessed toward the shaft portion side is provided on a top surface of the head opposite to the seating surface, when the welding bolt is viewed axially in a perspective manner, a top portion of the intermediate portion is provided inside an opening edge of the recess.

[0009] According to the above configuration, the welding electrode contacts the top surface of the head during welding, but the recess on the top surface does not directly contact the welding electrode. That is, the welding electrode contacts only on the top surface where the recess is not open. For this reason, the welding current mainly flows in a linear route from the welding electrode through the welding protrusion to the material to be welded. On the other hand, the top portion of the intermediate portion in contact with the material to be welded is provided inside the opening edge of the recess. For this reason, even if shunting occurs, the welding current flows in a bent route that turns into the axial center direction of the welding bolt from the welding electrode and then to the material to be welded. However, since the welding current preferentially flows in a linear route and is less likely to flow in a bent route, the welding current easily flows through the welding protrusion and shunting is less likely to occur. In addition, the top of the intermediate part is in point contact with the inner wall of the bolt insertion hole when viewed from the axial direction of the welding bolt. Since the contact area of the intermediate part with the plate to be welded is small, shunting is less likely to occur during welding. For these reasons, shunting is less likely to occur during welding with the welding bolt of the present invention.

Effect of the Invention

[0010] According to the present disclosure, a welding bolt in which shunting is less likely to occur can be provided.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. In addition, the dimensions of each member shown in the drawings may be different from the actual dimensions of each member for convenience of explanation.

[0013] FIG. 1 is a perspective view of the welding bolt 1 in the present embodiment. As shown in FIG. 1, the welding bolt 1 has a head 10 and a shaft portion 20.

[0014] The head 10 is provided on one end side of the welding bolt, and includes a seating surface 11 that abuts against the material to be welded 2, and a top surface 12 (see FIG. 2) that is the surface opposite to the seating surface 11. A welding protrusion 13 is provided on the seating surface 11. The welding protrusion 13 is the portion of the seating surface 11 that directly abuts against the material to be welded 2. When sufficient current flows through the welding protrusion 13 while it is directly abutting against the material to be welded 2, the welding protrusion 13 melts. The welded bolt 1 is welded to the material to be welded 2 when the melted welding protrusion 13 solidifies again.

[0015] FIG. 2 is a top view of the welding bolt 1 in the embodiment. As shown in FIG. 2, the top surface 12 includes a recess 14. The recess 14 is recessed toward the shaft portion 20 side (see FIG. 4).

[0016] Returning to FIG. 1, the shaft portion 20 includes a threaded portion 21 and an intermediate portion 22 provided between the head 10 and the threaded portion 21. A male thread with a thread 21a is formed on the threaded portion 21. FIG. 3 is a view of the state where the welding bolt 1 is inserted into the material to be welded 2 as seen from the direction of the shaft portion 20. As shown in FIG. 3, the intermediate portion 22 has a top portion 22a. In this embodiment, the intermediate portion 22 is hexagonal, and the top portion 22a forms the apex of the hexagon. Also, as shown in FIG. 2, when the intermediate portion 22 is seen through from the top surface 12, the top portion 22a of the intermediate portion 22 is provided inside the opening edge 14a of the recess 14 of the top surface 12.

[0017] Note that, as shown in FIG. 3, the diameter of the bolt insertion hole 2a provided for inserting the welding bolt 1 into the material to be welded 2 is generally about 1 mm larger than the nominal diameter of the thread. This is to provide a clearance to facilitate the insertion of the welding bolt 1.

[0018] Incidentally, it is ideal that the welding bolt 1 is installed at the center of the bolt insertion hole 2a and only the material to be welded 2 is in contact with the welding protrusion 13. However, in reality, when the welding bolt 1 is inserted into the bolt insertion hole 2a, it may be disposed off-center. At this time, as shown in FIG. 3, the welding bolt 1 inserted into the bolt insertion hole 2a generates an intermediate contact point P where not only the welding protrusion 13 and the material to be welded 2 but also the top 22a of the intermediate portion 22 and the material to be welded 2 are in contact.

[0019] As described above, if the inner wall of the bolt insertion hole provided in the material to be welded comes into contact with the shaft portion of the welding bolt, there is a risk that the welding current will cause a shunt current to flow from the shaft portion to the material to be welded in addition to the welding protrusion. If a shunt occurs, sufficient current may not flow through the welding protrusion, so there is a risk that sufficient welding strength cannot be ensured.

[0020] Next, with reference to FIG. 4, the reason why the welding bolt 1 in the present embodiment can reduce the shunt will be described. FIG. 4 is a cross-sectional view taken along the line I-I of FIG. 3. As shown in FIG. 4, the welding bolt 1 is inserted into the insertion hole 2a of the welding member 2. The material to be welded 2 and the head 10 of the welding bolt 1 are sandwiched between the upper electrode 3 and the lower electrode 4. Further, the welding bolt 1 and the material to be welded 2 are in contact not only at the welding protrusion 13 but also at the top 22a of the intermediate portion 22. Hereinafter, it is referred to as an intermediate contact point P between the material to be welded 2 and the top 22a of the intermediate portion 22.

[0021] During welding, current flows from the upper electrode 3 to the lower electrode 4 through the welding bolt 1 and the material to be welded 2. At this time, the region where the top surface 12 is in contact with the upper electrode 3 is only the region outside the opening edge 14a of the recess 14, and a gap S is provided between the region where the recess 14 is provided and the upper electrode 3. That is, on the top surface 12, current does not flow in from the portion with the gap S, and current flows in from the region without the gap S. For this reason, the welding current mainly follows a linear route R A from the upper electrode 3 through the welding protrusion 13 to the material to be welded 2.

[0022] On the other hand, the top 22a of the intermediate portion 22 in contact with the work piece 2 is provided inside the opening edge 14a of the recess 14. That is, the intermediate portion contact point P also exists inside the opening edge 14a of the recess 14. Therefore, if shunting occurs, this welding current flows through a bent route R that turns from the upper electrode 3 in the axial center direction of the welding bolt 1 and then reaches the work piece 2 B and flows through it.

[0023] Generally, the current preferentially flows through a straight route R A and is less likely to flow through the bent route R B . Therefore, in the welding bolt 1 of this embodiment, the current easily flows through the welding protrusion 13, and shunting is less likely to occur. Also, according to the above configuration, the top 22a of the intermediate portion 22 is in point contact with the inner wall of the bolt insertion hole 2a when viewed from the axial direction of the welding bolt 1. Since the contact area of the intermediate portion 22 with the work piece is small, the occurrence of shunting is further reduced.

[0024] Returning to FIG. 2, in the welding bolt 1 in this embodiment, when viewed through from the top surface 12, the welding protrusion 13 is provided outside the opening edge 14a of the recess 14 on the top surface 12. Therefore, since the welding current flows more linearly from the upper electrode 3 through the welding protrusion 13 to the work piece 2, the occurrence of shunting is further reduced.

[0025] FIG. 5 is a cross-sectional view for explaining the tapered portion 23 of the welding bolt 1 in the embodiment. As shown in FIG. 5, in the welding bolt 1 in this embodiment, a round shaft portion 24 having a smaller diameter than the intermediate portion 22 is provided between the intermediate portion 22 and the threaded portion 21. Further, the intermediate portion 22 and the round shaft portion 24 are connected by a tapered portion 23. Since the round shaft portion 24 has a smaller diameter than the intermediate portion 22, in the tapered portion 23, the shaft portion 20 is reduced in diameter from the seating surface 11 toward the threaded portion 21

[0026] When there is no tapered portion connecting the intermediate portion and the round shaft portion as in Patent Document 2, a discontinuous step is formed between the intermediate portion and the round shaft portion. At this time, when the bolt is dropped into the bolt insertion hole, this step may ride up on the work piece to be welded, and there is a risk that the bolt will not enter the depth of the bolt insertion hole. In this case, the operator needs to manually correct the position of the bolt in order to insert the bolt to the depth of the bolt insertion hole, which may hinder smooth operation.

[0027] In the welding bolt 1 of the present embodiment, the tapered portion 23 connects the round shaft portion 24 and the intermediate portion 22. That is, there is no discontinuous step between the round shaft portion 24 and the intermediate portion 22. Therefore, when the welding bolt 1 is dropped into the bolt insertion hole 2a, the tapered portion 23 is less likely to ride up on the work piece to be welded 2, and the welding bolt 1 is easily inserted to the depth of the bolt insertion hole 2a by its own weight. That is, the operator does not need to correct the position of the welding bolt 1 after dropping it in, so that the welding bolt 1 that can be welded with a simpler and smoother operation can be provided.

[0028] Also, in the welding bolt 1 of the present embodiment, the diameter of the circumscribed circle of the top 22a of the intermediate portion 22 is equal to the nominal diameter of the thread.

[0029] ISO965-2 (1998) stipulates the range of values that the nominal diameter of the thread and the diameter of the thread crest of the male thread corresponding thereto can take. According to ISO965-2 (1998), when the nominal diameter of the thread is 1.6 to 20 (tolerance class is 6g), the diameter of the thread crest with respect to the nominal diameter of the thread is about 93.5% to 99.8%. That is, since the diameter of the circumscribed circle of the top 22a of the intermediate portion 22 is equal to the nominal diameter of the thread, the diameter of the circumscribed circle of the top 22a of the intermediate portion 22 is about 0.2% to 6.5% larger than the diameter of the thread crest.

[0030] In Patent Document 1, similar to the present embodiment, an insertion hole 1 mm larger than the nominal diameter of the thread is provided in the work piece to be welded 2. However, in order to accurately position the welding bolt, the guide portion of Patent Document 1 is configured to be inscribed in the insertion hole provided in the work piece to be welded 2. For example, in Patent Document 1, a guide portion inscribed in a circle with a diameter of 9 mm is provided for an M8 screw. At this time, the diameter of the guide portion is 12.5% or more larger than the diameter of the thread crest. At this time, when the welding bolt is dropped into the bolt insertion hole, there is a risk that the guide portion will ride up on the workpiece 2 to be welded. In this case, the operator needs to manually correct the position of the bolt in order to insert the bolt to the bottom of the bolt insertion hole, which may hinder smooth operation.

[0031] Therefore, in the welding bolt 1 of the present embodiment, when the nominal diameter of the screw is 1.6 to 20 (tolerance class is 6g), the diameter of the intermediate portion 22 is 0.2% to 6.5% larger than the diameter of the thread crest 21a. That is, compared with Patent Document 1, the intermediate portion 22 is only slightly larger than the diameter of the thread crest 21a. Further, a tapered portion 23 is provided between this slightly protruding portion and the round shaft portion 24. Thereby, when the welding bolt 1 is dropped into the bolt insertion hole 2a, the intermediate portion 22 does not ride up on the workpiece to be welded, so the welding bolt 1 is inserted to the bottom of the bolt insertion hole 2a by its own weight. That is, the operator does not need to correct the position of the welding bolt 1 after dropping it in, so it is possible to provide a welding bolt 1 that can be welded with a simpler and smoother operation.

[0032] Next, with reference to FIG. 6, a modified example of the intermediate portion 22 and the welding protrusion 13 will be described. FIG. 6 is a diagram for explaining a modified example of the welding bolt 1 in the embodiment. The welding bolt 1A in the modified example is different in the shape of the intermediate portion compared with the welding bolt 1 in the present embodiment. The intermediate portion 22 of the welding bolt 1 in the present embodiment is hexagonal when viewed from the axial direction, but the intermediate portion 22A of the welding bolt 1A in the modified example is dodecagonal, and half of its angles are larger than two right angles. At this time, six angles that are smaller than two right angles are the top portions 22aA. Further, all of the top portions 22aA are subjected to R chamfering.

[0033] Even in the case of the welding bolt 1A in the modified example, the recess 14 is provided on the top surface 12, and the top 22aA of the intermediate portion 22A is provided inside the opening edge 14a of the recess 14. Therefore, the same operational effects as those of the welding bolt 1 in the present embodiment can be obtained.

[0034] Also, the welding protrusion 13 of the welding bolt 1 in the present embodiment was in the shape of a substantially hemisphere, but the shape of the welding protrusion 13 is not limited to the example of the present embodiment. The welding protrusion 13A of the welding bolt 1A in the modified example is provided with a mountain-shaped welding protrusion 13A along a part of the circumference of the seating surface 11. Even with such a welding protrusion 13A, the same effects as those of the present embodiment can be obtained.

[0035] As described above, the present invention has been described based on the embodiments. The present embodiment is an example of the present disclosure and is not limited to the above-described embodiment, and can be freely modified, improved, etc. Additionally, the material, shape, dimensions, numerical values, form, number, arrangement location, etc. of each component in the above-described embodiment are arbitrary as long as the present invention can be disclosed, and are not limited.

[0036] For example, the welding bolt in the present disclosure is assumed to be manufactured particularly using high-tensile steel. However, even when the material is not high-tensile steel, shunting is a phenomenon that can occur, and it is clear from the above description that the actions and effects of the welding bolt in the present embodiment are effective not only when the material is high-tensile steel. Therefore, it should be understood that the material of the welding bolt in the present disclosure is not limited to high-tensile steel.

[0037] The recess provided on the top surface of the welding bolt in the present embodiment is an inverted conical shape, but the shape of the recess is not limited to the example of the present embodiment. For example, even if the recess is cylindrical, the same effects as those of the present embodiment can be obtained.

[0038] In the present embodiment, an example with six tops has been described, but the welding bolt of the present disclosure is not limited to the example of the present embodiment. As long as the same actions and effects as those of the present embodiment can be obtained, the number of tops is not limited. Similarly, although three protrusions for welding were provided in this embodiment, the number of protrusions for welding of the welding bolt in the present disclosure is not limited.

[0039] In this embodiment, an example in which current flows from the upper electrode to the lower electrode has been described, but the present disclosure is not limited to this example. It is obvious that the same effects as those of this embodiment can be obtained even when current flows from the lower electrode to the upper electrode.

Explanation of Reference Numerals

[0040] 1 Welding bolt 2 Welded material 2a Bolt insertion hole 3 Upper electrode 4 Lower electrode 10 Head 11 Seating surface 12 Top surface 13, 13A Protrusions for welding 14 Recess 14a Opening edge 20 Shaft portion 21 Threaded portion 21a Thread 22, 22A Intermediate portion 22a, 22aA Top 23 Tapered portion 24 Round shaft portion P Intermediate portion contact point R A Linear route R B Bent route S Gap

Claims

1. a head provided on one end side, a threaded portion, and a shaft portion including an intermediate portion provided between the head and the threaded portion, which is a welding bolt, a welding protrusion is provided on a seating surface that abuts against a material to be welded of the head, a recess recessed toward the shaft portion side is provided on a top surface of the head opposite to the seating surface, when the welding bolt is viewed axially in a perspective manner, a top portion of the intermediate portion is provided inside an opening edge of the recess, welding bolt.

2. when the welding bolt is viewed axially in a perspective manner, the welding protrusion is provided outside an opening edge of the recess, the welding bolt according to Claim 1.

3. a round shaft portion having a smaller diameter than the intermediate portion is provided between the intermediate portion and the threaded portion, and the intermediate portion and the round shaft portion are connected by a tapered portion, the welding bolt according to Claim 1 or 2.

4. a diameter of an outer circumscribed circle of the intermediate portion is equal to a nominal diameter of a screw, the welding bolt according to Claim 3.

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