JP3732448B2 - Spot welding tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spot joining tool used in spot joining in which a plurality of stacked metal plates are joined in a spot manner.
[0002]
[Prior art]
Conventionally, as a method of spot-joining a metal plate such as an aluminum alloy, joining by resistance spot welding and mechanical joining by rivets or screws are known. Furthermore, recently, as described in, for example, Japanese Patent Application Laid-Open No. 2001-314982, a material to be joined made of a plurality of stacked metal plates is connected to a center pin protruding along an axis and an upper side of the center pin. The main body barrel having a diameter larger than that of the central pin, and a shoulder portion extending from the outer periphery of the lower portion of the main body to the central pin. While pressing and rotating, the central pin enters and supplies heat to the joint mainly by friction between the shoulder portion and the material to be joined, and this heat causes the material to be joined near the joint to be plastically fluidized. There has been proposed a friction stir spot welding method in which materials to be joined are joined together using a spot joining tool that joins by stirring with a central pin.
[0003]
[Problems to be solved by the invention]
However, the above-described method of spot-joining a metal plate such as an aluminum alloy has the following drawbacks.
[0004]
The joining by the resistance spot welding has a problem that a large amount of electric power is required and the welding electrode is consumed rapidly, and the mechanical joining by the rivet or the screw has a problem that many joining members are required.
[0005]
In the conventional friction stir spot welding method, the spot welding tool includes a flat type or a reverse taper as the shape of the shoulder from the lower outer periphery of the main body to the small-diameter central pin. is there. In any joining tool, the center pin having the function of stirring the plastic fluidized joining material is slightly shorter than the sum of the overlapped thicknesses of the joining materials so as not to penetrate the joining materials. The length extends from the upper surface of the bonded material to the vicinity of the lower surface of the lower bonded material, and the diameter is constant. In addition, the shoulder portion, which is a heat source that causes plastic fluidization, generates frictional heat at a portion that separates the plate thickness of the bonded material on the side where the central pin enters from the bonded portion where the bonded materials contact each other, This gap in the plate thickness causes heat diffusion and reduces heating efficiency. Therefore, in order to secure the necessary heating amount, it is necessary to increase the outer diameter of the shoulder portion serving as a heat source for the purpose of increasing the friction area.
[0006]
That is, in this type of spot joint, the joint strength tends to increase as the area of the joint called nugget between the materials to be joined increases. Therefore, in order to improve the joint strength, it is necessary to increase the outer diameter of the shoulder part for the purpose of increasing the joint area, but the nugget end that is the boundary between the joint part and the non-joint part between the joined materials Since the joined parts are called crotch-like shapes at the joined part outer edge, when a load is applied from the outside, stress concentration tends to occur at this part, which may become a starting point of cracking.
[0007]
Further, when the outer diameter of the shoulder portion is increased, a dense spot interval cannot be obtained, and it is impossible to improve the overall joint strength, and the pressing force applied to the joining tool during joining may increase. In addition, the surface of the material to be bonded at the shoulder portion is scraped due to friction, and the thickness of the material to be bonded at this portion tends to be thinner than the thickness of the base material.
[0008]
When an excessive external force is applied to such a spot-joined joint, the nugget end becomes the starting point of the crack as described above, and the crack progresses toward the thin portion on the upper side, thereby causing breakage. In addition, when the thin portion is excessively thin, a crack may be generated from this portion to be broken.
[0009]
Further, these points will be described in detail with reference to FIGS. The spot welding tools 101A and 101B are movable in the vertical direction (in the direction of arrow T in FIGS. 4A and 4B) and can be rotated (indicated by arrows in FIGS. 4A and 4B) by driving means (not shown). (R direction).
[0010]
When spot joining is performed using the spot joining tools 101A and 101B, for example, the joining tools 101A and 101B are rotated to a predetermined joining position (joining point) between two superposed materials 2 and 3 to be joined. (Here, the materials 2 and 3 to be joined may be aluminum plates, copper plates, or iron plates). When the center pins 12 ′ and 12 ″ of the joining tools 101A and 101B are lowered, first, the center pins 12 ′ and 12 ″ abut on the upper surface of the material to be joined 2 placed on the upper side, and then the shoulder portions 13 ′ and 13 ″ abuts. Friction heat is generated at the contact surface between the shoulder portions 13 ′ and 13 ″ and the material 2 to be joined, and heat is supplied to the vicinity of the joint portions 4 ′ and 4 ″, thereby the shoulder portions 13 ′ and 13 ′. Since the materials 2 and 3 in the vicinity of “and the joints 4 ′ and 4 ″ are plastically fluidized, the joints 4 ′ and 4 ″ are formed by stirring them with the central pins 12 ′ and 12 ″. When the joining tools 101A and 101B are removed and the joining portions 4 ′ and 4 ″ are cooled and hardened, the joining is completed.
[0011]
In the conventional spot welding tools 101A and 101B, the center pins 12 'and 12 "having a function of stirring the plastic fluidized workpieces 2 and 3 do not penetrate the lower workpiece 3. Is slightly shorter than the overlap thickness of the materials 2 and 3 to be joined, but extends from the upper surface of the upper material 2 to the vicinity of the lower surface of the lower material 3 and their diameters d and d ′. On the other hand, the shoulder portions 13 ′ and 13 ″ serving as heat sources for causing plastic fluidization are the upper sides from which the joining tools 101A and 101B enter from the joining portions 4 ′ and 4 ″ where the materials 2 and 3 are in contact with each other. Friction heat is generated at the portion of the material to be bonded 2 separated by the plate thickness L0. Since the central pins 12 ′ and 12 ″ have the lengths as described above, the friction heat generation portion and the joint are joined. The portions 4 ′ and 4 ″ correspond to the plate thickness L0 of the material 2 to be joined. Therefore, in order to secure the necessary amount of heating, as described above, the shoulder is intended to increase the friction area. It is necessary to increase the outer diameters D and D ′ of the portions 13 ′ and 13 ″.
[0012]
However, the shoulder portions 13 ′ and 13 ″ have a substantially horizontal plane shape shown in FIG. 4 (a) or a reverse tapered surface shape shown in FIG. 4 (b), respectively, and when the spot welding tools 101A and 101B are pushed in. The fluidized material to be joined is pushed away by the center pins 12 ′, 12 ″ and the shoulder portions 13 ′, 13 ″. After the spot welding tools 101A, 101B are pulled out, the fluidized material to be joined is cured. Then, the shape of the upper surface of the bonded portion of the material to be bonded 2 placed on the upper portion is a depression, and the wall thickness is a portion formed thinly in the vicinity of the outer edge of the bonded portions 4 ′ and 4 ″. ing. As described above, the plate thicknesses L2 and L2 ′ of the upper bonded material 2 at the tips (nugget ends) of the diameters C2 and C2 ′ indicating the sizes of the joints 4 ′ and 4 ″ are thinner than the original plate thickness L0. Therefore, when an external force is applied to separate the materials to be joined 2 and 3 from each other, cracks K and K ′ are generated from the outer edge (nugget end) of the joints 4 ′ and 4 ″ toward the thin part or from the thin part. As a result, the joints 4 ′ and 4 ″ are isolated and do not play the role of joining the materials 2 and 3 to be joined, resulting in a reduction in joining force.
[0013]
An object of the present invention is to prevent a decrease in the strength of a joint joint while suppressing an increase in the diameter of a shoulder portion and an accompanying increase in pressing force when performing friction stir spot welding of a plurality of metal workpieces. It is to provide a joining tool.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a central pin protruding along the axis, a main body trunk connected to an upper side of the central pin and having a diameter larger than that of the central pin, A shoulder portion that extends from the outer periphery of the lower portion to the central pin, and enters the central pin while pressing and rotating to a joint point of a plurality of stacked metal members to be joined, and is mainly joined to the shoulder portion. A spot welding tool for supplying heat to the joint portion by friction with the material, plasticizing the material to be joined in the vicinity of the joint portion by this heat, and joining it by stirring it with the central pin, The center pin has a length slightly longer than a length corresponding to the sum of the thicknesses of the remaining materials to be bonded, excluding the lowermost material to be bonded, and the shoulder portion has the center On the pin It is characterized by a diameter upwards of the central pin from the position a shape gradually increasing. Here, “the central pin has a length slightly longer than the length corresponding to the sum of the thicknesses of the remaining materials to be bonded, excluding the lowermost material to be bonded,” In the case of two materials, the center pin penetrates only the upper material to be joined, which means that the length is slightly longer than the length corresponding to the thickness of the upper material to be joined. In the case of three pieces, the central pin penetrates only two of the three pieces located on the upper side, so that it has a length slightly longer than the length corresponding to the thickness of the upper two pieces to be joined. Meaning. That is, it means that the length is slightly longer than the length corresponding to the sum of the thicknesses of the remaining bonded materials excluding the lowermost bonded material regardless of the number of bonded materials. “Slightly longer length” means that the center pin is the lower material to be joined when the number of materials to be joined is two, and the lowest (three from the top) when there are three materials to be joined. This means that it is sufficient that the member to be welded has a length that allows the member to be joined to the extent that stirring of the plastic fluidized member is not impaired.
[0015]
According to the invention according to claim 1 having the above-described configuration, the center pin is slightly longer than the length corresponding to the sum of the thicknesses of the remaining materials to be bonded excluding the lowermost material to be bonded. Since it is only what has long length, the shoulder part which generate | occur | produces frictional heat can be made to approach the junction part to which to-be-joined materials are joined rather than the conventional to-be-joined material upper surface. Therefore, the heating efficiency is improved, the plastic flow region is increased, and the outer edge diameter (nugget diameter) of the joint portion can be increased. This contributes to an increase in joint strength. And if the joint strength similar to the conventional one is ensured, the area of the shoulder portion and the pressing force applied to the welding tool can be reduced.
[0016]
In addition, since the shoulder portion has a shape in which the diameter gradually increases from the upper end position of the central pin toward the upper side of the central pin, the plastic fluid material is easily flown in the plate thickness direction guided by the shoulder portion, From this point, it is easy to increase the joint strength.
[0017]
According to a second aspect of the present invention, the shoulder portion is formed with a pocket portion for accommodating the plastic fluidized material to be joined, and the pocket portion has a diameter larger than an outer edge diameter (nugget diameter) of the joint portion. And when the said center pin approachs to a to-be-joined material, it has a volume more than the capacity | capacitance of the to-be-joined material which plastically fluidizes and pushes away, and reaches from the said joining part outer edge to the to-be-joined material upper surface by the center pin entrance side. It is desirable that the distance is equal to or greater than the thickness of the material to be joined on the central pin entry side .
[0018]
According to the invention which concerns on Claim 2 which has said structure, it becomes possible to store and store the to-be-joined material which is plastic-fluidized and pushed away using a pocket part, and the surface of the to-be-joined material in a shoulder part can be stored. Reduction of wall thickness due to friction is prevented. Therefore, the thickness of the material to be bonded after curing is prevented from being reduced, and the strength is improved as compared with the conventional bonded joint.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a spot welding tool according to the present invention will be described with reference to FIGS.
[0020]
1 and 2 are sectional views of a spot joining tool according to the present invention and a spot joining portion to which the spot joining tool is applied. The spot bonding referred to in the present invention means that the materials 2 and 3 which are metal plates are superposed and placed on, for example, the pedestal 5 and bonded while rotating the spot welding tool 1 at a high speed. It is applied to the joining points of the materials 2 and 3 for spot joining.
[0021]
A spot welding tool 1 used for this spot welding is, for example, as shown in FIG. 1A, a central pin 12 protruding along an axis, and a diameter larger than the central pin 12 connected to the upper side of the central pin 12. The main body trunk portion 11 and a shoulder portion 13 extending from the lower outer periphery of the main body trunk portion 11 to the center pin 12 are provided. Then, heat (friction heat) is supplied to the joint portion 4 mainly by friction between the shoulder portion 13 and the materials 2 and 3 to be joined. With this heat, the materials 2 and 3 to be joined in the vicinity of the joint portion 4 are plastically fluidized and agitated and mixed by the center pin 12, and then the joining tool 1 is pulled out and cured to be joined. Thus, the joint part 4 is formed after the spot joining tool 1 is pulled out and cured. The to-be-joined material 2 and the to-be-joined material 3 become a structure joined intermittently by the junction part 4 formed with the predetermined pitch.
[0022]
The center pin 12 has a length substantially equal to the thickness of the material to be joined 2 on the side where the center pin 12 enters. In addition, in this example, since the to-be-joined materials 2 and 3 are two pieces, it has a length a little longer than the length corresponded to the thickness of the 1 or several to-be-joined material which the said center pin 12 penetrates and approachs. Thus, in order to bring the shoulder portion 13 close to the joint portion 4, the shoulder portion 13 has a length substantially equal to the thickness of the material to be joined 2 on the side on which the central pin 12 enters.
[0023]
The shoulder portion 13 serving as a generation source of the frictional heat is formed so that the diameter gradually increases from the upper end position of the center pin 12 toward the upper side of the center pin 12. By forming such a shoulder portion 13, the shoulder portion 13 can be brought close to the joint portion 4 where the materials to be joined 2 and 3 are joined, and heating efficiency is improved. Therefore, when securing the joint strength similar to the conventional one, it is possible to reduce the area (outer edge diameter) of the shoulder portion 13 and the pressing force applied to the welding tool 1.
[0024]
The amount by which the spot welding tool 1 is pushed into the materials to be joined 2 and 3 is below the overlapping portion between the members 2 and 3 to be joined to the position where the material to be joined 3 set on the lower side does not penetrate. Therefore, the surface (bottom surface) 3a of the lower material 3 to be joined is a clean surface that can be used as the outer surface of the product.
[0025]
If it is necessary to increase the friction area, the shoulder portion 13A can be extended horizontally (the horizontal portion 13a) where it comes into contact with the main body trunk portion 11A as in the joining tool 1A shown in FIG. Good. Further, as shown in FIGS. 1A and 1B, the shoulder portions 13 and 13A do not need to have a conical shape whose diameter increases linearly upward, as shown in FIG. As in the joining tools 1B and 1D shown in (d), the shoulder portions 13B and 13D can be formed into a cross-sectional curved shape whose diameter gradually increases upward.
[0026]
Moreover, the pocket part 10 which accommodates the to-be-joined materials 2 and 3 plastically fluidized can be formed in the shoulder part 13C like the joining tool 1C shown in FIG. The diameter B of the pocket portion 10 is larger than the outer edge diameter (nugget diameter) C1 of the joint portion 4, and the distance from the outer edge of the joint portion 4 to the upper surface of the material to be joined 2 on the central pin entry side formed by the pocket portion 10 (Shortest distance) C3 is set to be equal to or greater than the plate thickness L0 of the material to be joined 2 (base material). If it does in this way, as shown in FIG.1 (b), when it is necessary to make it a shoulder part extended in a horizontal direction where it connects with the main body trunk | drum 11, and increasing a friction area, it expands in the said horizontal direction, for example. The plastic fluidized material to be joined easily flows into the thickness-reduced portion due to friction on the surface of the material to be joined at the shoulder portion 13C, so that it contributes particularly to the plate thickness and can prevent the thickness from being reduced. Effective in improving joint strength.
[0027]
The volume of the pocket portion 10 formed in the shoulder portion 13C needs to be formed to be equal to or larger than the capacity of the material to be joined that is plastically fluidized and pushed away when the central pin 12 enters the material 2 to be joined.
[0028]
If the pocket portion 10 is provided in this way, it is possible to reliably store and store the material to be joined that is plastically fluidized and displaced with respect to the thickness-reduced portion due to friction on the surface of the material 2 to be joined in the shoulder portion 13C. Since it can do, the thickness reduction of the to-be-joined material after hardening can be prevented.
[0029]
【The invention's effect】
According to the first aspect of the present invention, the central pin has a length slightly longer than the length corresponding to the sum of the thicknesses of the remaining materials to be bonded, excluding the material to be bonded located on the lowermost side. Since it was set as a thing, a shoulder part can be brought close to the junction part to which to-be-joined materials are joined, heating efficiency can be improved, and a plastic flow area | region can be increased. Thereby, the outer edge diameter (nugget diameter) of the said junction part can be increased, and it can contribute to the increase in joint strength. In addition, since the shoulder portion has a shape in which the diameter gradually increases from the upper end position of the central pin toward the upper side of the central pin, the plastic fluid material is guided by the shoulder portion and easily flows in the plate thickness direction. This is also advantageous in increasing the joint strength.
[0030]
According to the invention of claim 2, when the shoulder portion has a larger diameter than the pocket portion (outer edge diameter (nugget diameter) of the joint portion), and the central pin enters the material to be joined, The thickness from the outer edge of the joint portion to the upper surface of the material to be joined on the central pin entry side is the plate thickness of the material to be joined on the central pin entry side. As described above, it becomes possible to store and store the material to be bonded that is plastically fluidized and pushed away, and the thickness of the material to be bonded is reduced due to the friction of the surface of the material to be bonded at the shoulder portion. Thickness) can be prevented, and the strength can be improved as compared with a conventional joint.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a spot welding tool to which a spot welding tool according to the present invention is applied and a joint portion, (a) is a cone-shaped spot joint in which a shoulder portion linearly increases in diameter upward. An example of a tool is shown, (b) shows an example of a spot joining tool in which a horizontal part is provided on the outer edge part of the shoulder part, and (c) and (d) show a diameter of the shoulder part increasing in a curved line upward. An example of a spot welding tool is shown.
FIG. 2 is a cross-sectional view of a spot joining tool to which a spot joining tool according to the present invention is applied and a pocket part is formed in a part of a shoulder part and the joining part.
FIGS. 3A and 3B are cross-sectional views of a conventional spot welding tool and a joining portion, in which FIG. 3A shows an example of a spot joining tool with a flat shoulder portion, and FIG. 3B shows a spot joining tool with a shoulder portion having a reverse taper shape; An example is shown.
[Explanation of symbols]
1, 1A to 1D Spot joining tool 2 Joined material 3 Joined material 4 Joined portion 10 Pocket portion 11 Body trunk portion 12 Central pin 13, 13A to 13D Shoulder portion B Pocket portion outer diameter C1, C2 Diameter of joined portion ( Nugget diameter)
C3 Distance from the outer edge (nugget end) of the joint part to the upper surface of the material to be joined on the central pin entry side formed by the pocket part D Diameter of the shoulder part (outer diameter)
d Diameter of center pin

Claims (2)

A central pin projecting along the axis, a main body barrel connected to the upper side of the central pin and having a diameter larger than the central pin, and a shoulder portion extending from a lower outer periphery of the main body portion to the central pin, The center pin enters the joining point of the overlapped metal workpiece to be joined while pressing and rotating, and heat is supplied to the joint mainly by friction between the shoulder portion and the workpiece. The material to be joined in the vicinity of the joint is plastically fluidized, and is a spot joining tool for joining by stirring with the center pin,
The center pin has a length slightly longer than the length corresponding to the sum of the thicknesses of the remaining materials to be bonded excluding the material to be bonded located on the lowermost side ,
The spot joining tool, wherein the shoulder portion has a shape in which a diameter gradually increases from an upper end position of the center pin toward an upper side of the center pin. Forming a pocket portion for accommodating the material to be plastically fluidized in the shoulder portion;
The pocket portion has a diameter larger than an outer edge diameter (nugget diameter) of the joint portion, and when the center pin enters the material to be joined, the pocket portion has a capacity greater than a capacity of the material to be joined that is plastically fluidized and displaced. Having a volume of
The spot joining tool according to claim 1, wherein a distance from the outer edge of the joining portion to the upper surface of the material to be joined on the central pin entry side is equal to or greater than a plate thickness of the material to be joined on the central pin entry side .

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