KR20200142183A - Spot welding device and method - Google Patents

Abstract

Disclosed is a spot welding device. According to one embodiment of the present invention, the spot welding device bonds a workpiece in which at least two steel sheets having different strength are overlapped through resistance spot welding. The spot welding device comprises a pair of electrode tips of which each is coaxially disposed in a gun frame, and one is fixated to the gun frame and another is installed to be moved forward and backward to the gun frame while having the workpiece therebetween. The electrode tips pressurize the workpiece, and each of the electrode tips can have concentric contact units of a base material having different areas by corresponding to each of steel sheets having improved and reduced strength.

Description

Spot welding device and method {SPOT WELDING DEVICE AND METHOD}

An embodiment of the present invention relates to a spot welding system, and more particularly, to a spot welding apparatus and method for spot welding steel sheets of different strength materials.

In general, electric resistance welding is an electric resistance welding method in which the base material is melted by applying an electric current to the object to be welded and the electric resistance heat generated at the contact part, and an external force is applied to it, and spot welding using an electrode tip is mainly used. Is being used.

In spot welding, when an electric current is applied while pressing both sides of an overlapped metal plate with an electrode tip, electric resistance is largely generated on the contact surface, which is a method of welding using heat generated at this time. This spot welding method is widely used when a spot welder is mounted on an industrial robot to weld panels, etc., mainly in the assembly process of vehicle body parts.

The electrode tip used for such spot welding must maintain high electrical conductivity, thermal conductivity, high strength and abrasion resistance, and as a general electrode material for spot welding, Cu-based alloys such as Cu-Cr and Cu-Zr are applied. .

On the other hand, a general vehicle body is in the form of surrounding a frame structure made of a structural reinforcement material with relatively high strength (for example, super high-tensile strength steel) with a shell plate material having relatively low strength (for example, mild steel).

Here, the higher the strength of the steel sheet, the greater the amount of alloying elements added and the higher the carbon equivalent, the greater the specific resistance, and the lower the strength of the steel sheet, the less the amount of the alloying element added, and the lower the carbon equivalent, the lower the specific resistance.

Accordingly, when spot welding is performed by overlapping a steel plate having high strength and a steel plate having low strength as described above, the heat generation and melting behavior are different due to the difference in resistivity of these steel sheets. This is because a steel sheet with high specific resistance melts first due to rapid heat generation, but a steel sheet with low specific resistance has a relatively slow melting point.

Therefore, in the case of spot welding (multi-layer welding) of steel sheets having different strengths, an asymmetric welding nugget along the axial direction of the electrode tip may be generated or non-welding may occur in the welds of the steel sheets due to the difference in resistivity between the steel sheets.

The matters described in this background are prepared to enhance an understanding of the background of the invention, and may include matters other than those of the prior art known to those of ordinary skill in the field to which this technology belongs.

Embodiments of the present invention are to provide a spot welding apparatus and method capable of preventing the generation of asymmetrical welding nuggets in a weld zone due to a difference in resistivity of steel sheets when multi-ply welding steel sheets having different strengths.

A spot welding apparatus according to an embodiment of the present invention is to join a welding object in which at least two sheets of steel plates having different strengths are overlapped by resistance spot welding, and are respectively disposed in a gun frame in a coaxial direction, and between the welding objects. One is fixed to the gun frame, the other is installed to be movable back and forth on the gun frame, and includes a pair of electrode tips for pressing the welding object, and the pair of electrode tips have strength It is possible to form concentric base metal contact portions having different areas respectively corresponding to the high steel plate and the low strength steel plate.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the base material contact portion of the electrode tip corresponding to the steel sheet having low strength may be provided with a smaller area than the base material contact portion of the electrode tip corresponding to the steel sheet having high strength. have.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the pair of electrode tips may be provided with different diameters corresponding to a steel plate having high strength and a steel plate having low strength, respectively.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode tip corresponding to the steel sheet having high strength is provided with a large diameter, and the electrode tip corresponding to the steel sheet having low strength may be provided with a small diameter. have.

In addition, the spot welding apparatus according to an embodiment of the present invention is coupled to a small-diameter electrode tip, a non-conductive material that opens a base material contact portion of the small-diameter electrode tip at the center and presses the welding object together with the base material contact portion. It may further include an electrode holder of.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode holder may form a base material support part having an outer diameter corresponding to the base material contact part of the large-diameter electrode tip on the edge side of the base material contact part of the small-diameter electrode tip. .

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode holder has an open end that opens a base material contact portion of the small-diameter electrode tip, and is connected to the open end so that the small-diameter electrode tip can be inserted. It may include an insertion hole.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the insertion hole includes a first inner diameter surface having a cross-sectional diameter gradually increasing as the distance from the open end increases so as to support the side of the base metal contact portion of the small diameter electrode tip. And a second inner diameter surface having the same cross-sectional diameter along the axial direction of the small diameter electrode tip to support the rest of the small diameter electrode tip.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode holder is provided in a ring type, and the insertion hole may form an inner diameter surface having the same cross-sectional diameter along the axial direction of the small-diameter electrode tip. have.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode tip corresponding to the high strength steel plate is provided with a large diameter, and the electrode tip corresponding to the low strength steel plate corresponds to the large diameter electrode tip. It may be composed of a first portion having an outer diameter and a second portion integrally connected to the first portion as a small diameter having an outer diameter smaller than that of the first portion.

In addition, in the spot welding apparatus according to an embodiment of the present invention, a non-conductive electrode holder that opens the base material contact part at the center and presses the welding object together with the base material contact part may be coupled to the second part. .

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode holder forms a base material support part having an outer diameter corresponding to the base material contact part of the large-diameter electrode tip on the edge side of the base material contact part of the second part, and the second To form an open end to open the base material contact portion of the part, the second part is connected to the open end to be insertable, and an insertion hole having an inner diameter surface of the same cross-sectional diameter along the axial direction of the second part is formed. I can.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode holder is provided in a ring type, and may be fixed to the first part through an adhesive.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode tip corresponding to the steel plate having high strength is provided with a large diameter, and the electrode tip corresponding to the steel plate having low strength has a cross-section as the distance from the contact portion of the base metal increases. The diameter may be provided in a tapered shape gradually increasing.

In addition, in the spot welding apparatus according to an embodiment of the present invention, a non-conductive electrode holder that opens the base material contact part at the center and presses the welding object together with the base material contact part is coupled to the tapered electrode tip. I can.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the electrode holder forms a base material support portion having an outer diameter corresponding to the base material contact portion of the large-diameter electrode tip on the edge of the base material contact portion of the tapered electrode tip, and the tapered An inner diameter surface that forms an open end to open the base material contact part of the shaped electrode tip, is connected to the open end so that the tapered electrode tip can be inserted, and the cross-sectional diameter gradually increases as the distance from the base material contact part of the tapered electrode tip increases. Insertion holes can be formed.

In addition, in the spot welding apparatus according to an embodiment of the present invention, the pair of electrode tips may be provided with the same diameter corresponding to a steel plate having high strength and a steel plate having low strength, respectively.

In addition, in the spot welding apparatus according to an embodiment of the present invention, a non-conductive coating layer as a base material support part may be formed on the electrode tip corresponding to the steel sheet having low strength on the edge side of the base material contact part.

In addition, the spot welding method according to an embodiment of the present invention includes (a) providing a welding object in which at least two steel plates having different strengths are stacked, and (b) a first corresponding to a low strength steel plate. The welding object is placed between the electrode tip and the second electrode tip corresponding to the high-strength steel plate, and the welding object is pressed through the base metal contact portions of the first and second electrode tips, and the first and second electrode tips A process of applying a set welding current, and in the (b) process, a base material contact part having an area smaller than that of the base material contact part of the second electrode tip is provided to the first electrode tip, and the edge of the base material contact part of the second electrode tip A non-conductive base material support part corresponding to an outer diameter of the base material contact part of the first electrode tip may be provided on the side.

In addition, in the spot welding method according to an embodiment of the present invention, in the step (b), a non-conductive electrode holder having the base material support and mounted on the first electrode tip may be provided.

In addition, in the spot welding method according to an embodiment of the present invention, in the step (b), a non-conductive coating layer having the base material support portion and formed on the edge of the base material contact portion of the first electrode tip may be provided. .

The embodiment of the present invention can prevent the generation of an asymmetric nugget while changing the current density between the steel plates through the difference in the contact area of the electrode tips with the steel plates of the different strength base material and the uniformity of pressing the electrode tips through the electrode holder. have.

In addition, effects obtained or predicted by the embodiments of the present invention will be disclosed directly or implicitly in the detailed description of the embodiments of the present invention. That is, various effects predicted according to an embodiment of the present invention will be disclosed within a detailed description to be described later.

Since these drawings are for reference only to explain the embodiments of the present invention, the technical idea of the present invention should not be limited to the accompanying drawings.
1 is a view schematically showing a spot welding apparatus according to an embodiment of the present invention.
2 is a view showing a base material contact portion of an electrode tip applied to a spot welding apparatus according to an embodiment of the present invention.
3 is a view showing an electrode holder applied to the spot welding apparatus according to an embodiment of the present invention.
4 is a view for explaining a spot welding method using the spot welding apparatus according to an embodiment of the present invention.
5 to 8 are diagrams showing modified examples of the spot welding apparatus according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various forms and is not limited to the embodiments described herein.

In order to clearly describe the present invention, parts irrelevant to the description have been omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

Such drawings are for reference only to specifically and clearly describe a preferred embodiment of the present invention and a technical idea or feature, and it should be noted in advance that it may differ from actual product specifications.

In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, so the present invention is not necessarily limited to those shown in the drawings, and the thickness is enlarged to clearly express various parts and regions. Done.

In the following detailed description, the names of the components are divided into first, second, etc. to distinguish them because the names of the components are the same, and are not necessarily limited to the order in the following description.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

In addition, terms such as "...unit", "...means", "...part", "...member" described in the specification refer to a unit of a comprehensive constitution that performs at least one function or operation. it means.

1 is a view schematically showing a spot welding apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the spot welding apparatus 100 according to an embodiment of the present invention may be applied to a vehicle body assembly line that assembles a structure to be welded to a vehicle body, such as a predetermined vehicle body component, for example, a vehicle body panel and a vehicle body frame. .

For example, the spot welding apparatus 100 according to an embodiment of the present invention is used to assemble the vehicle body by spot welding, by spot welding, to a skeleton structure of a structural reinforcing material having relatively high strength and a skeleton structure of a structural reinforcing material having a relatively high strength. Can be applied to the process.

Here, the structural reinforcing material having high strength may include a (ultra) high-tensile steel plate, and the outer plate materials having low strength may include a mild steel plate. Further, the (ultra) high-tensile steel sheet may include a 120K grade steel sheet, and the mild steel sheet may include a steel sheet of relatively lower strength than the (ultra) high-tensile steel sheet.

The spot welding apparatus 100 according to an exemplary embodiment of the present invention may join a welding object P as a base material in which at least two steel plates having different strengths are overlapped, as described above, by resistance spot welding.

In the above, the welding object P is a stack of steel plates having different strengths. Hereinafter, for convenience, a steel plate having relatively high strength is referred to as a first steel plate 1, and a steel plate having relatively low strength is referred to as a second steel plate (2). ).

The spot welding apparatus 100 may spot-weld the steel plates 1 and 2 of the welding object P as electric resistance heat while applying a set pressure to the welding object P and passing a set welding current. Furthermore, the spot welding apparatus 100 is mounted on an arm of a welding robot, and can be moved along a set teaching path of the welding robot.

In the above, an example of spot welding a vehicle body part as a welding object P is described, but the present invention is not necessarily to be understood as being limited thereto, and if a welding object applied to a structure of various types and uses is spot welding The technical idea of the present invention can be applied.

Hereinafter, as shown in the drawing, based on the state in which the apparatus 100 is placed in the vertical direction and the welding object P is stacked in the vertical direction, the welding object P is spotted through the apparatus 100. An example of welding will be described.

That is, the following describes an example of spot welding a multi-ply welding object P in which a plurality of second steel plates 2 are stacked on the lower side of the first steel plate 1 with the first steel plate 1 on the upper side. , A portion facing the upper side may be defined as an upper, upper, upper, and upper surface, and a portion facing the lower side may be defined as a lower, lower, lower and lower surface.

However, the definition of the direction as described above is a relative meaning, and the direction may vary depending on the reference position of the object P and the bonding direction of the device 100, so that the above direction must be the reference direction of the present embodiment. It is not limited.

Further, the "end (one end, the other end, one end, the other end, etc.)" in the following may be defined as either end, and a certain portion including the end (one end, the other end, one end, etc.) , The other end, etc.).

The spot welding apparatus 100 according to an embodiment of the present invention has a structure capable of preventing generation of an asymmetrical welding nugget in the welding portion due to a difference in resistivity of the steel sheets when multi-layer welding of steel sheets having different strengths.

To this end, the spot welding apparatus 100 according to an embodiment of the present invention basically includes a gun frame F, a first electrode tip 10, a second electrode tip 20, and an electrode holder 30. And, it will be described for each configuration as follows.

In the above, the gun frame F is for installing various components to be described below, and may be provided as, for example, a "C" type welding gun. Furthermore, the gun frame F may be mounted on the tip of the multi-articulated arm of a welding robot (not shown in the drawings).

The gun frame F may include various accessory elements such as brackets, bars, rods, plates, blocks, rails, collars, etc. for supporting respective components to be described below.

These various accessory elements are for installing each of the constituent elements to be described below to the gun frame F, and in the embodiment of the present invention, except for exceptional cases, the aforementioned various accessory elements are collectively referred to as the gun frame F. do.

The first electrode tip 10 is also referred to as a fixed electrode tip and a lower electrode tip, and is fixedly installed at one end (lower end in the drawing) of the gun frame F. The first electrode tip 10 supports the second steel plate 2 of the object P to be welded, and may apply a welding current set to the second steel plate 2.

The second electrode tip 20 is also referred to as a movable electrode tip and an upper electrode tip, and corresponds to the first electrode tip 10 at the other end (upper end in the drawing) of the gun frame F in a vertical direction. It is installed to be able to move backwards and forwards. The second electrode tip 20 may press the first steel plate 1 of the object P to be welded, and apply a welding current set to the first steel plate 1.

Here, the second electrode tip 20 is the second steel plate 2 of the object P to be welded through the first electrode tip 10 by placing the object P to be welded between the first electrode tip 10 and the first electrode tip 10. ) Is moved in a downward direction through the driving source D and can pressurize the first steel plate 1.

The drive source D may include a known technology moving device that converts rotational motion of a servo motor into a linear motion or a known technology operating cylinder device that performs linear motion by pneumatic pressure.

In an embodiment of the present invention, the first and second electrode tips 10 and 20 are disposed in the vertical coaxial direction on the gun frame F, respectively, and correspond to the first and second steel plates 1 and 2, respectively. Thus, it can be provided with different apertures (cross-sectional diameters).

For example, the second electrode tip 20 corresponding to the first steel plate 1 is provided with a large diameter, and the first electrode tip 10 corresponding to the second steel plate 2 is a second electrode tip ( 20) It is provided with a smaller diameter with a relatively smaller cross-sectional diameter.

The meaning of the large-diameter and the small-diameter as described above is a relative meaning that the cross-sectional diameter of each electrode tip is large and small, and the numerical values of the large-diameter and small-diameter are not limited to any specific values in the present embodiment.

Furthermore, in an embodiment of the present invention, the first and second electrode tips 10 and 20 have different areas as shown in FIG. 2 corresponding to the first and second steel plates 1 and 2. It forms the first and second base metal contact portions 11 and 21 of the retained concentric circles, respectively.

The first base material contact part 11 is a part that contacts the second steel plate 2 of the object P and presses the second steel plate 2, and has a diameter set at the top of the first electrode tip 10. It is formed flat.

The second base material contact part 21 is a part that contacts the first steel plate 1 of the object P and presses the first steel plate 1, and has a diameter set at the lower end of the second electrode tip 20. It is formed flat.

Here, the first base material contact part 11 is provided with a smaller area than the second base material contact part 21. This will be natural as the first electrode tip 10 is provided with a small diameter and the second electrode tip 20 is provided with a large diameter.

In an embodiment of the present invention, the electrode holder 30 presses the second steel plate 2 of the object P together with the first base material contact portion 11 of the first electrode tip 10, and the first It is coupled to the electrode tip 10.

The electrode holder 30 is a non-conductor made of a non-conductive material, which opens the first base material contact part 11 at the top center and supports and presses the second steel plate 2 together with the first base material contact part 11. I can. The electrode holder 30 may be coupled to the first electrode tip 10 in a male and female manner.

As shown in FIG. 3, the electrode holder 30 has a base material support part 31 having an outer diameter corresponding to the second base material contact part 21 of the second electrode tip 20 on the upper surface. The base material support part 31 forms the same surface as the first base material contact part 11, and is located at the edge of the first base material contact part 11 with the first base material contact part 11 in the center.

Further, the electrode holder 30 has an open end 33 and an insertion hole 35. The open end 33 opens the first base material contact portion 11 of the first electrode tip 10. That is, the open end 33 is located at the center side of the base material support part 31.

The insertion hole 35 is a portion into which the first electrode tip 10 is inserted and is connected to the open end 33. The insertion hole 35 is a first inner diameter surface 37 having a cross-sectional diameter gradually increasing as it moves downward from the open end 33 to support the first base material contact portion 11 side of the first electrode tip 10 Is forming.

In addition, the insertion hole 35 forms a second inner diameter surface 39 having the same cross-sectional diameter along the axial direction of the first electrode tip 10 to support the rest of the first electrode tip 10. Here, the first inner diameter surface 37 and the second inner diameter surface 39 are interconnected.

Hereinafter, the operation of the spot welding apparatus 100 according to an embodiment of the present invention configured as described above and a spot welding method using the spot welding apparatus 100 will be described in detail with reference to the accompanying drawings.

4 is a view for explaining a spot welding method using the spot welding apparatus according to an embodiment of the present invention.

Referring to FIG. 4, first, in the embodiment of the present invention, a first steel plate having a relatively high strength (1: for example, a vehicle body skeleton structure as an ultra-high tensile steel) has a relatively low strength compared to the first steel plate 1 Steel plates (2: for example, an outer plate material as mild steel) are set, and the first and second steel plates 1 and 2 are clamped through a clamper or the like.

In this state, in the embodiment of the present invention, the first and second electrode tips 10 and 20 are positioned on the upper and lower sides of the welding object P interposed with the drawing as a reference (see FIG. 1 ). ).

Here, the fixed position of the first and second electrode tips 10 and 20 with respect to the welding object P moves the gun frame F toward the welding object P through a welding robot (not shown in the drawing). And can be done. In addition, the first electrode tip 10 is positioned on the second steel plate 2 side of the object P to be welded, and the second electrode tip 20 is positioned on the first steel plate 1 side. 2 The electrode tips 10 and 20 are positioned along the coaxial direction facing each other.

Next, in an embodiment of the present invention, the gun frame F is moved upward through the welding robot, and the second electrode tip 20 is moved downward by the forward operation of the driving source D.

Then, the first electrode tip 10 presses the pressure set on the second steel plate 2 of the object P through the first base material contact portion 11, and the second electrode tip 20 is the second base material. The first steel plate 1 is pressed at a set pressure through the contact portion 21.

Here, in the embodiment of the present invention, since the non-conductive electrode holder 30 is coupled to the first electrode tip 10 having a small diameter, the second base material contact portion of the second electrode tip 20 having a large diameter The second steel plate 2 of the object P to be welded is pressed together with the first base material contact portion 11 of the first electrode tip 10 through the base material support portion 31 having an outer diameter corresponding to (21).

Therefore, in the embodiment of the present invention, the uneven pressing of the first and second steel plates 1 and 2 by the small-diameter first electrode tip 10 and the large-diameter second electrode tip 20 is prevented by the electrode holder ( 30) through the base material support portion 31, it is possible to maintain the symmetry (uniformity) of the electrode pressing force for the first and second steel plates (1, 2).

Accordingly, in the embodiment of the present invention, a second electrode tip having a large diameter due to uneven pressure between the first and second electrode tips 10 and 20 to the welding portion of the first and second steel sheets 1 and 2 It is possible to prevent the occurrence of high contact resistance in 20) through the base material support 31 of the electrode holder 30.

Then, in the embodiment of the present invention, a welding current is applied to the first and second electrode tips 10 and 20. Then, the first and second electrode tips 10 and 20 energize the first and second steel plates 1 and 2 of the object P to be welded through the first and second base material contact portions 11 and 21. .

Accordingly, in an embodiment of the present invention, pressure is applied to the set welds of the first and second steel plates 1 and 2 through the first and second electrode tips 10 and 20, and welding heat is performed by electric resistance due to energization. The weld can be spot-welded while generating.

In this process, in the embodiment of the present invention, since the first base material contact part 11 of the first electrode tip 10 has a smaller area than the second base material contact part 21 of the second electrode tip 20, the first 2 In the side of the first steel plate (1) having high strength in contact with the base material contact portion 21, the current density can be kept low, and the strength of the first steel plate contacting portion 11 of the first electrode tip 10 is low. 2 On the side of the steel plate 2, the current density can be kept relatively high.

To further explain, in the embodiment of the present invention, the pressure unevenness of the first and second steel plates 1 and 2 due to the difference in diameter (differential cross-sectional diameter) of the first and second electrode tips 10 and 20 is prevented by the electrode holder. The current applied to the first and second electrode tips 10 and 20 due to the difference in the area between the first and second base metal contact parts 11 and 21 while solving through the base metal support 31 of 30 It is possible to cause a large change in the current density at the side of the first and second steel plates 1 and 2 without affecting.

That is, in the embodiment of the present invention, a path through which current flows toward the second steel sheet 2 having a small specific resistance is formed narrowly, and a path through which current flows toward the first steel sheet 1 having a large specific resistance is formed wide, and the first and A large change can be made in the current density at the side of the second steel plate (1, 2).

Therefore, in the embodiment of the present invention, the difference in contact area between the first and second electrode tips 10 and 20 with respect to the first and second steel plates 1 and 2 and the first and second electrode holders 30 By making a large change in the current density between the steel plates 1 and 2 through the uniformity of pressure of the electrode tips 10 and 20, it is possible to prevent the generation of asymmetric nugget that occurs during welding between the different strength base materials.

Accordingly, in the embodiment of the present invention, as the current density at the side of the first steel plate 1 having high strength is kept low and the current density at the side of the second steel plate 2 having low strength is kept high, the first and second It is possible to balance the calorific value at the interface of the steel plates 1 and 2, and contribute to the generation of the symmetrical nugget (N) and the enlargement of the nugget diameter, thereby further improving the weldability and welding quality of the welding object (P).

Furthermore, in an embodiment of the present invention, by coupling the electrode holder 30 to the first electrode tip 10 of the small diameter corresponding to the second electrode tip 20 of the large diameter, the first and second steel plates 1 Since the symmetry of the electrode pressing force with respect to, 2) can be maintained, it is possible to suppress the occurrence of indentation in the second steel plate 2 with relatively low strength, and thereby further improve the welding appearance quality of the welding object P. have.

5 to 8 are diagrams showing modified examples of the spot welding apparatus according to an embodiment of the present invention.

Referring to FIG. 5, in the first modified example, the first electrode tip 10 is provided with a small diameter, and the second electrode tip 20 is provided with a large diameter, and is provided in a ring type. It may include an electrode holder 130 of.

The electrode holder 130 is coupled to the first electrode tip 10, opening the first base material contact part 11 of the first electrode tip 10 at the center, and welding together with the first base material contact part 11 The object can be pressurized.

The electrode holder 130 includes a base material support part 131 having an outer diameter corresponding to the second base material contact part 21 of the second electrode tip 20 at the edge of the first base material contact part 11 of the first electrode tip 10. The open end 133 is formed in the same plane and opens the first base material contact portion 11 in the center.

In addition, the electrode holder 130 has an insertion hole 135 connected to the open end 133 so that the first electrode tip 10 can be inserted. In the above, the insertion hole 135 forms an inner diameter surface 137 having the same cross-sectional diameter along the axial direction of the first electrode tip 10.

Since the remaining configurations and effects according to the first modified example are as described above, a more detailed description will be omitted.

Referring to FIG. 6, in the second modified example, the second electrode tip 20 has a large diameter. In addition, the first electrode tip 210 is a first portion 251 having an outer diameter corresponding to the second electrode tip 20 and a small diameter having an outer diameter smaller than that of the first portion 251 and the first portion 251 ) Consists of a second portion 252 integrally connected to. In the above, the first base material contact part 211 is formed on the upper surface of the second part 252.

Furthermore, in this modified example, the first base material contact part 211 is opened in the center at the second part 252 of the first electrode tip 210, and presses the welding object together with the first base material contact part 211. The non-conductive electrode holder 230 is coupled.

Since the electrode holder 230 is provided in a ring type, a base material support part 231 having an outer diameter corresponding to the second base material contact part 21 of the second electrode tip 20 is attached to the first electrode tip 210. It is formed in the same plane on the edge side of the base material contact part 211.

In addition, the electrode holder 230 has an open end 233 in the center that opens the first base material contact portion 211 of the second portion 252. In addition, the electrode holder 230 is connected to the open end 233 so that the second part 252 can be inserted, and is inserted with an inner diameter surface 237 having the same cross-sectional diameter along the axial direction of the second part 252 A hole 235 is formed.

Here, the electrode holder 230 as described above may be fixed to the first portion 251 of the first electrode tip 210 through the structural adhesive 250. The electrode holder 230 may be fitted into the second part 252 through the insertion hole 235 and bonded to the upper surface of the first part 251 through an adhesive 250.

The remaining configurations and effects according to the second modified example are the same as described above, and a more detailed description will be omitted.

Referring to FIG. 7, in the third modified example, the second electrode tip 20 has a large diameter. In addition, the first electrode tip 310 forms a first base material contact portion 311 on an upper end, and is provided in a tapered shape whose cross-sectional diameter gradually increases as the distance from the first base material contact portion 311 increases.

In addition, a non-conductive electrode holder 330 that opens the first base material contact part 311 at the center and presses the welding object together with the first base material contact part 311 is fastened to the first electrode tip 310.

The electrode holder 330 includes a base material support part 331 having an outer diameter corresponding to the second base material contact part 21 of the second electrode tip 20 at the edge side of the first base material contact part 311 of the first electrode tip 310. Are formed in the same plane. The electrode holder 330 has an open end 333 for opening the first base material contact portion 311 of the first electrode tip 310 in the center.

In addition, the electrode holder 330 has an insertion hole 335 connected to the open end 333 so that the first electrode tip 310 can be inserted. The insertion hole 335 forms an inner diameter surface 337 whose cross-sectional diameter gradually increases as the distance from the first base material contact portion 311 of the first electrode tip 310 increases.

Since the remaining configurations and effects according to the third modified example are as described above, a more detailed description will be omitted.

Referring to FIG. 8, in the fourth modified example, the first and second electrode tips 410 and 20 are each provided with the same diameter. In addition, a first base material contact portion 411 is formed in the center of the upper surface of the first electrode tip 410, and a non-conductive coating layer (in the upper surface of the first electrode tip 410) on the edge side of the first base material contact part 411 ( 450) is formed.

The coating layer 450 has a base material support part having an outer diameter corresponding to the second base material contact part 21 of the second electrode tip 20 with the first base material contact part 411 in the center on the upper surface of the first electrode tip 410 ( 431 is formed in the same plane on the edge side of the first base material contact portion 411. The coating layer 450 opens the first base material contact part 411 on the same plane as the base material support part 431 on the upper surface of the first electrode tip 410.

The remaining configurations and effects according to the fourth modified example are the same as described above, so a more detailed description will be omitted.

Although the embodiments of the present invention have been described above, the technical idea of the present invention is not limited to the embodiments presented in the present specification, and those skilled in the art who understand the technical idea of the present invention within the scope of the same technical idea, components It will be possible to easily propose another embodiment by adding, changing, deleting, adding, etc., but it will be said that this is also within the scope of the present invention.

1: 1st steel plate 2: 2nd steel plate
10, 210, 310, 410: first electrode tip
11, 211, 311, 411: first base material contact portion
20: second electrode tip 21: second base material contact portion
30, 130, 230, 330: electrode holder
31, 131, 231, 331, 431: base material support
33, 133, 233, 333: open end
35, 135, 235, 335: insertion hole
37, 39, 137, 237, 337: inner diameter surface
250: adhesive 251: first part
252: second part 450: coating layer
D: Drive source F: Gun frame
N: Nugget P: Welding object
100: spot welding device.

Claims (20)

As a spot welding apparatus for joining a welding object in which at least two sheets of steel plates having different strengths are overlapped by resistance spot welding,
A pair of each disposed in the gun frame in a coaxial direction, one of which is fixed to the gun frame with the object to be welded therebetween, the other is installed to be movable back and forth on the gun frame, and pressurizes the object to be welded Including the electrode tip of,
The pair of electrode tips are spot welding apparatus, characterized in that, respectively, corresponding to the high strength steel plate and the low strength steel plate to form concentric contact portions of the base metal having different areas. The method of claim 1,
Spot welding apparatus, characterized in that the base metal contact portion of the electrode tip corresponding to the low strength steel sheet is provided with a smaller area than the base metal contact portion of the electrode tip corresponding to the high strength steel sheet. The method of claim 2,
The pair of electrode tips,
Spot welding apparatus, characterized in that provided with different diameters corresponding to each of the high strength steel plate and the low strength steel plate. The method of claim 3,
The electrode tip corresponding to the high strength steel plate is provided with a large diameter,
Spot welding apparatus, characterized in that the electrode tip corresponding to the low strength steel sheet is provided with a small diameter. The method of claim 3,
A non-conductive electrode holder coupled to the small-diameter electrode tip, opening the base material contact part of the small-diameter electrode tip in the center and pressing the welding object together with the base material contact part
Spot welding device, characterized in that it further comprises. The method of claim 5,
The electrode holder,
A spot welding apparatus, characterized in that a base material support portion having an outer diameter corresponding to the base material contact portion of the large-diameter electrode tip is formed on an edge side of the base material contact portion of the small-diameter electrode tip. The method of claim 6,
The electrode holder,
An open end for opening the base material contact portion of the small-diameter electrode tip,
Insertion hole connected to the open end so that the small diameter electrode tip can be inserted
Spot welding device comprising a. The method of claim 7,
The insertion hole,
A first inner diameter surface having a cross-sectional diameter gradually increasing as it moves away from the open end to support the side of the base metal contact portion of the small-diameter electrode tip;
A second inner diameter surface having the same cross-sectional diameter along the axial direction of the small-diameter electrode tip to support the rest of the small-diameter electrode tip
Spot welding device comprising a. The method of claim 7,
The electrode holder is provided in a ring type,
The insertion hole spot welding apparatus, characterized in that to form an inner diameter surface having the same cross-sectional diameter along the axial direction of the small-diameter electrode tip. The method of claim 2,
The electrode tip corresponding to the high strength steel plate is provided with a large diameter,
The electrode tip corresponding to the low-strength steel plate includes a first portion having an outer diameter corresponding to a large-diameter electrode tip, and a second portion integrally connected to the first portion as a small diameter having an outer diameter smaller than the first portion. Spot welding device, characterized in that consisting of. The method of claim 10,
In the second part,
A spot welding apparatus, characterized in that the base material contact portion is opened at a center and a non-conductive electrode holder for pressing the welding object is coupled together with the base material contact portion. The method of claim 11,
The electrode holder,
Forming a base material support portion of an outer diameter corresponding to the base material contact portion of the large-diameter electrode tip on the edge side of the base material contact portion of the second portion,
Forming an open end to open the base material contact portion of the second portion,
The spot welding apparatus, characterized in that the second portion is connected to the open end so as to be insertable, and forming an insertion hole having an inner diameter surface of the same cross-sectional diameter along the axial direction of the second portion. The method of claim 12,
The electrode holder,
Spot welding apparatus, characterized in that provided in a ring type and fixed to the first portion through an adhesive. The method of claim 2,
The electrode tip corresponding to the high strength steel plate is provided with a large diameter,
The electrode tip corresponding to the low-strength steel plate is a spot welding apparatus, characterized in that provided in a tapered shape in which the cross-sectional diameter gradually increases as the distance from the base material contact portion increases. The method of claim 14,
In the tapered electrode tip,
A spot welding apparatus, characterized in that the base material contact portion is opened at a center and a non-conductive electrode holder for pressing the welding object is coupled together with the base material contact portion. The method of claim 15,
The electrode holder,
A base material support having an outer diameter corresponding to the base material contact part of the large-diameter electrode tip is formed on the edge of the base material contact part of the tapered electrode tip,
Forming an open end for opening the base material contact portion of the tapered electrode tip,
A spot welding apparatus comprising: an insertion hole having an inner diameter surface that is connected to the open end so that the tapered electrode tip can be inserted, and whose cross-sectional diameter gradually increases as the distance from the base material contact portion of the tapered electrode tip increases. The method of claim 2,
The pair of electrode tips are provided with the same diameter corresponding to each of a high strength steel plate and a low strength steel plate,
Spot welding apparatus, characterized in that a non-conductive coating layer as a base material support part is formed on the edge side of the base material contact part on the electrode tip corresponding to the low strength steel sheet. (a) providing a welding object in which at least two steel plates having different strengths are stacked; And
(b) placing the welding object between the first electrode tip corresponding to the low-strength steel plate and the second electrode tip corresponding to the high-strength steel plate, and passing the welding object through the base metal contact portions of the first and second electrode tips. Pressurizing and applying a set welding current to the first and second electrode tips; includes,
In the step (b), a base material contact part having an area smaller than that of the base material contact part of the second electrode tip is provided to the first electrode tip, and the outer diameter of the base material contact part of the first electrode tip at the edge of the base material contact part of the second electrode tip Spot welding method, characterized in that it provides a non-conductive base material support corresponding to. The method of claim 18,
In the process (b),
A spot welding method comprising the base material support and providing a non-conductive electrode holder mounted on the first electrode tip. The method of claim 18,
In the process (b),
A spot welding method comprising providing a non-conductive coating layer having the base material support and formed on the edge of the base material contact part of the first electrode tip.

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