JP2011031267A - Resistance welding apparatus, resistance welding method, and electrode used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably perform joining without causing any crack even with a high-hardness material by reliably bringing the outer electrode of a coaxial electrode into contact with a workpiece. <P>SOLUTION: The tip end 11 of an outer electrode 10 is made to be bitten in the workpiece W by gradually reducing the wall thickness of the tip end 11 of the outer electrode 10 toward the tip end side. Thus, a space to be formed between the workpiece W and the outer electrode 10 is absorbed, and the tip end 11 of the outer electrode 10 can be reliably brought into contact with the workpiece. Further, since the area of the tip end 11 of the outer electrode 10 is reduced, the contact pressure in the contact part of the outer electrode 10 with the workpiece W can be increased, and thus, force for pressing the electrode against the workpiece W can be reduced, and deformation of the workpiece W can be prevented. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a resistance welding apparatus, a resistance welding method, and an electrode used for these.

  As a resistance welding method, for example, as shown in FIG. 15 (a), so-called one-side spot welding is performed in which two electrodes 101 and 102 are brought into contact with one surface of a workpiece W on which two metal plates are stacked and energized. Are known. In this case, a current flows between the electrodes 101 and 102 along a path indicated by a dotted line in FIG. 15B, and therefore, the current density of the counterpart electrode side portion of the contact portion between each electrode 101 and 102 and the workpiece W. Becomes higher and the temperature becomes higher (the high temperature portion is indicated by S1), and the current density on the opposite side becomes lower and the temperature becomes lower (the low temperature portion is indicated by S2). If the temperature of the workpiece becomes too high, the workpiece surface may partially melt and cracks may occur on the workpiece surface. If the workpiece temperature is too low, the workpiece may not be sufficiently softened and bonded. . For this reason, it is necessary to set the value of the current flowing through the electrodes so that cracks do not occur in the high temperature portion S1 of the contact portion and the workpiece is sufficiently joined in the low temperature portion S2 of the contact portion.

  However, when welding a material having a high melting point such as high-tensile steel (high-tensile steel), it is necessary to increase the temperature to at least 1000 ° C. or higher. For this reason, when the current value is increased so that the low temperature portion S2 of the contact portion is 1000 ° C. or higher, cracking occurs in the high temperature portion S1, and if the current value is suppressed so that cracking does not occur in the high temperature portion S1, There was a dilemma that the workpieces were not joined at the part S2, and it was extremely difficult to set the current value appropriately.

  For example, in Patent Document 1, as shown in FIG. 16A, an inner electrode 203 is disposed on an inner periphery of a cylindrical outer electrode 201 (second portion 9) via an insulator 202 (electrical insulator 8). A welding apparatus having an electrode (hereinafter referred to as a coaxial electrode) in which the (first central cylindrical portion 7) is provided coaxially is shown. According to such a coaxial electrode, the current density between the outer electrode 201 and the inner electrode 203 can be evenly distributed in the circumferential direction as shown in FIG. In the contact portion, a temperature difference is not formed unlike the high temperature portion S1 and the low temperature portion S2, and the temperature can be made uniform. Therefore, even when welding materials such as high-strength steel, it is possible to set the current value that does not cause cracks in the workpiece and that can reliably join the workpiece relatively easily. It becomes.

JP-A-4-284980 JP 51-142453 A

  In the configuration of Patent Document 1 above, in order to make the current density uniform between the inner electrode 203 and the outer electrode 201 in the circumferential direction, it is necessary to ensure that the tip portions of the inner electrode 203 and the outer electrode 201 are in contact with the workpiece. There is. However, if the tips of the inner electrode 203 and the outer electrode 201 are displaced, for example, the inner electrode 203 floats from the workpiece W as shown in FIG. 17, or the outer electrode 201 floats from the workpiece W as shown in FIG. There is a risk that. Further, as shown in FIG. 19, when the work W has a minute recess P or a minute recess is formed at the tip of the outer electrode 201 (not shown), a part of the tip of the outer electrode 201 becomes part of the workpiece. There is a risk of not touching.

  Further, when welding is performed using the coaxial electrode, it is necessary to press the coaxial electrode against the workpiece with a predetermined pressure. However, since the outer electrode has a larger diameter than a normal electrode (see FIG. 15), a predetermined diameter is required. It is necessary to press against the work with a strong force in order to ensure the surface pressure. When the electrode is strongly pressed against the workpiece in this way, the workpiece is bent, and there is a possibility that a part of the tip portion of the electrode is not in contact with the workpiece.

  As described above, when the contact state between each electrode and the workpiece deteriorates, the current density between the electrodes becomes non-uniform, and the merit of using the coaxial electrode is lost.

  For example, the welding apparatus shown in Patent Document 2 shows a configuration in which the outer electrode is slidable with respect to the inner electrode and can be moved up and down separately. According to this welding apparatus, in the case shown in FIGS. 17 and 18, each electrode can be brought into contact with the workpiece by relatively moving the inner electrode and the outer electrode up and down. However, as shown in FIG. 19, it is not possible to cope with a case where a part of the tip of the outer electrode does not contact the workpiece.

  The problem to be solved by the present invention is that, in resistance welding using a coaxial electrode, the tip of each electrode (especially the outer electrode) is reliably brought into contact with the workpiece, thereby causing cracks even in a high-hardness material. It is to join without fail.

  In order to solve the above-described problems, the present invention provides an outer electrode formed in a cylindrical shape, an inner electrode that is coaxially arranged on the inner periphery of the outer electrode, and is relatively movable in the central axis direction with respect to the outer electrode. A resistance welding apparatus that welds the work by bringing the inner electrode and outer electrode tip portions into contact with the workpiece and energizing the workpiece, and gradually reducing the thickness of the outer electrode tip portion toward the tip side. It is characterized by that.

  In this way, by gradually reducing the thickness of the tip portion of the outer electrode toward the tip side, the area of the tip portion of the outer electrode is reduced, so that the surface pressure at the contact portion with the workpiece can be increased. This makes it possible to bite the tip of the outer electrode into the workpiece. As a result, even when a minute recess is formed on the surface of the workpiece or the tip of the outer electrode, the recess is absorbed by biting the outer electrode into the workpiece, and the tip of the outer electrode is securely in contact with the workpiece. Can be made. Moreover, since the surface pressure in the contact part of an outer electrode and a workpiece | work can be raised because the area of the front-end | tip part of an outer electrode becomes small, the force which presses an electrode to a workpiece | work can be made small. Accordingly, it is possible to avoid a situation in which a part of the tip of the electrode is not in contact with the work due to the work being deformed by the pressing force of the electrode.

  That is, the present invention is a resistance welding apparatus having an outer electrode formed in a cylindrical shape and an inner electrode that is coaxially arranged on the inner periphery of the outer electrode and is relatively movable in the central axis direction with respect to the outer electrode. In this method, welding is performed by bringing the tip of the outer electrode into contact with the work and causing the tip of the inner electrode to come into contact with the work. In this state, electricity is passed between the inner electrode and the outer electrode. Thus, it can be characterized as a welding method for performing welding.

  In the resistance welding apparatus, if the non-contact portion that does not contact the workpiece is positively provided at the tip of the cylindrical outer electrode, the contact area between the outer electrode and the workpiece can be further reduced. The outer electrode can be further easily bite into the workpiece. At this time, by providing a contact portion where the outer electrode and the workpiece are in contact with each other and a non-contact portion where they are not in contact with each other at equal intervals in the circumferential direction, the current density between the inner electrode and the outer electrode is equalized in the circumferential direction Can be distributed.

  As described above, according to the present invention, since the entire surface of the outer electrode can be reliably brought into contact with the workpiece, even a high-hardness material can be reliably welded without causing cracks. it can.

It is sectional drawing of a welding apparatus. It is sectional drawing of a coaxial electrode. It is a front view of a coaxial electrode. It is a bottom view of a coaxial electrode. It is sectional drawing of the front-end | tip part of an inner side electrode. It is sectional drawing which shows the procedure which makes a coaxial electrode contact | abut to a workpiece | work. It is sectional drawing which shows the procedure which makes a coaxial electrode contact | abut to a workpiece | work. It is sectional drawing which expands and shows the contact part of an outer side electrode and a workpiece | work. It is sectional drawing which shows the state which made the outer side electrode dig into a workpiece | work. It is sectional drawing which shows the procedure which contact | abuts the coaxial electrode of the welding apparatus which concerns on 2nd Embodiment to a workpiece | work. It is sectional drawing which shows the procedure which contact | abuts the coaxial electrode of the welding apparatus which concerns on 2nd Embodiment to a workpiece | work. It is sectional drawing which shows the procedure which contact | abuts the coaxial electrode of the welding apparatus which concerns on 3rd Embodiment to a workpiece | work. It is sectional drawing which shows the procedure which contact | abuts the coaxial electrode of the welding apparatus which concerns on 3rd Embodiment to a workpiece | work. It is sectional drawing which shows the procedure which contact | abuts the coaxial electrode of the welding apparatus which concerns on 3rd Embodiment to a workpiece | work. (A) is sectional drawing which shows the mode of the resistance welding by the conventional electrode, (b) is a top view which shows distribution of the current density in the workpiece | work surface. (A) is sectional drawing which shows the mode of the resistance welding by the conventional coaxial electrode, (b) is a top view which shows distribution of the current density in the workpiece | work surface. It is sectional drawing which shows the state which made the conventional coaxial electrode contact | abutted to the workpiece | work. It is sectional drawing which shows the state which made the conventional coaxial electrode contact | abutted to the workpiece | work. It is sectional drawing which shows the state which made the conventional coaxial electrode contact | abutted to the workpiece | work.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the resistance welding apparatus according to the first embodiment of the present invention is coaxial with a cylindrical outer electrode 10 and a coaxial electrode 30 having an inner electrode 20 disposed on the inner periphery of the outer electrode 10. A support portion 40 that supports the electrode 30, an outer electrode moving means (a spring 50 in this embodiment) for moving the outer electrode 10 in the axial direction with respect to the support portion 40, and an inner electrode 20 with respect to the support portion 40 The inner electrode moving means (cylinder 60 in the present embodiment) for moving the electrode in the axial direction and the coaxial electrode moving means (the elevator 70 in the present embodiment) for moving the entire coaxial electrode 30 in the central axis direction via the support portion 40. ). The outer electrode 10 and the inner electrode 20 are connected to a power source 80 via a coil 81 as shown in FIG. A cylindrical insulating member 90 is disposed between the outer electrode 10 and the inner electrode 20 in the radial direction. In the present embodiment, the center axis direction of the coaxial electrode 30 is a vertical direction, and the coaxial electrode 30 is lowered to bring the outer electrode 10 and the tip of the inner electrode 20 into contact with the upper surface of the workpiece W.

The outer electrode 10 is made of a metal material (for example, Cr—Cu alloy) in a substantially cylindrical shape, and is arranged with the tip portion directed downward. As shown in FIG. 2, the distal end portion 11 of the outer electrode 10 gradually decreases in thickness toward the distal end side (downward). In this embodiment, the distal end portion 11 forms an arc shape that swells downward in the axial section. is doing. As shown in FIGS. 3 and 4, the outer electrode 10 has notch portions 12 extending from the distal end portion 11 to the proximal end side (upward) at a plurality of locations at equal intervals in the circumferential direction (six locations in the illustrated example). Formed. In the present embodiment, the circumferential width L ₁ of the notch 12 is set to be smaller than the circumferential interval L ₂ between the adjacent notches 12 (see FIG. 4).

  As shown in FIG. 2, the spring 50 as the outer electrode moving means is arranged in a compressed state between the upper end portion of the outer electrode 10 and the support portion 40, so that the outer electrode 10 is always biased downward. Is done. Further, the downward movement of the outer electrode 10 is restricted by a holding portion 41 provided in the support portion 40. Specifically, a locking portion 13 protruding to the outer diameter is formed at the upper end portion of the outer electrode 10, and a protruding portion 42 facing the inner diameter is formed at the lower end portion of the holding portion 41. By engaging the portion 42 in the axial direction, the movement of the outer electrode 10 downward from the engaging portion is restricted.

  The inner electrode 20 is formed of a metal material (for example, Cr—Cu alloy) and is inserted into the inner periphery of a cylindrical insulating member 90 fixed to the inner peripheral surface of the outer electrode 10. The inner electrode 20 is provided so as to be movable relative to the outer electrode 10 in the axial direction. In this embodiment, the inner electrode 20 is provided so as to be slidable with respect to the insulating member 90. The tip (lower end) 21 of the inner electrode 20 has a tapered shape as shown in FIG. 5, and specifically, a flat surface 22 formed at the tip and the outer diameter gradually from the flat surface 22 upward. And a conical surface 23 which is enlarged. The apex angle α of the conical surface 23 is set within a range of 100 to 170 degrees, for example, 140 degrees.

  The cylinder 60 as the inner electrode moving means is attached to the support portion 40 as shown in FIG. 1, and when the pressure in the cylinder 60 is increased, the inner electrode 20 is pushed downward with respect to the support portion 40.

  Hereinafter, an example of a welding method using the resistance welding apparatus having the above configuration will be described.

  First, as shown in FIG. 1, the tip of the inner electrode 20 is protruded downward from the tip of the outer electrode 10, and the entire coaxial electrode 30 is lowered by the elevator 70 in this state, and shown in FIG. In this way, the tip 21 of the inner electrode 20 is brought into contact with the upper surface of the workpiece W. When the coaxial electrode 30 is continuously lowered, the inner electrode 20 moves backward relatively against the pressure in the cylinder 60 (actually, the cylinder 60 or the like is in a state where the inner electrode 20 is in contact with the workpiece W and is stationary). Descent). At this time, the tip 21 of the inner electrode 20 is pressed against the workpiece W by the pressure inside the cylinder 60.

  When the coaxial electrode 30 is further lowered, as shown in FIG. 7, the distal end portion 11 of the outer electrode 10 comes into contact with the work W, and the outer electrode 10 approaches the support portion 40 against the elastic force of the spring 50. Move relative to each other (actually, the support portion 40 and the like are lowered while the outer electrode 10 and the inner electrode 20 are in contact with the workpiece W and are stationary).

  At this time, the force pressing the outer electrode 10 against the workpiece W increases in accordance with the elastic coefficient of the spring 50 as the spring 50 is compressed. As described above, since the thickness of the distal end portion 11 of the outer electrode 10 decreases downward, the contact area at the contact portion between the outer electrode 10 and the workpiece W can be reduced. In particular, if the tip portion 11 is formed in a circular arc shape as in the present embodiment, as shown in FIG. 8, the outer electrode 10 and the workpiece W are in point contact in the axial cross section (the contact point is indicated by T). Therefore, the contact area between the two becomes very small. Furthermore, in this embodiment, since the notch part 12 is provided in the front-end | tip part 11 of the outer side electrode 10 (refer FIG. 2), the contact area of the outer side electrode 10 and the workpiece | work W becomes still smaller. Thus, by reducing the contact area between the outer electrode 10 and the workpiece W, the surface pressure at the contact portion between the two is increased. For this reason, when the outer electrode 10 is pressed against the workpiece W by the elastic reaction force of the spring 50, the tip 11 of the outer electrode 10 can be slightly bited into the workpiece W as shown in FIG. Therefore, even when a delicate recess is formed on the surface of the workpiece W or the tip 11 of the outer electrode 10, the outer electrode 10 and the workpiece W are absorbed by biting the outer electrode 10 into the workpiece W. Can be reliably contacted. Further, since the surface pressure between the outer electrode 10 and the workpiece W increases, a force for pushing the outer electrode 10 downward (in this embodiment, the elastic reaction force of the spring 50) may be relatively small. Deformation of the workpiece W due to the pressing force can be prevented.

  Thus, the contact of the outer electrode 10 and the inner electrode 20 with the workpiece W is completed. At this time, the outer electrode 10 is pressed against the workpiece W by the elastic reaction force of the spring 50, and the inner electrode 20 is pressed against the workpiece W by the pressure in the cylinder 60.

  In this state, welding is performed by energizing between the outer electrode 10 and the inner electrode 20. As described above, since the outer electrode 10 and the inner electrode 20 are reliably in contact with the workpiece W, the current density can be made uniform in the circumferential direction. In this embodiment, in order to increase the surface pressure between the outer electrode 10 and the workpiece W, the outer electrode 10 is provided with the notches 12, but since the notches 12 are provided at equal intervals in the circumferential direction, that is, Since the contact portion (curved cross-section curved surface) that contacts the workpiece and the non-contact portion (notch portion 12) that does not contact the workpiece are provided at the front end portion of the outer electrode 10 at equal intervals in the circumferential direction, It can be evenly distributed in the circumferential direction.

  By the way, when welding is performed using the coaxial electrode 30, spatter may occur at the contact portion between the inner electrode 20 and the workpiece W. If this spatter adheres to the inner peripheral surface of the outer electrode 10 and falls onto the workpiece W during welding, there is a possibility that energization is hindered. In the present embodiment, since the notch 12 is formed in the outer electrode 10, the sputter generated at the inner periphery of the outer electrode 10 passes through the notch 12 and escapes to the outside, so the inner peripheral surface of the outer electrode 10. The amount of spatter adhering to the substrate can be reduced, and the risk of hindering energization can be reduced.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described.

  In the first embodiment described above, the coaxial electrode 30 is lowered by the elevator 70 to bring the inner electrode 20 into contact with the workpiece W. However, the present invention is not limited to this. For example, as shown in the following second embodiment, the inner electrode 20 may be brought into contact with the workpiece W by pushing out the cylinder 60.

  Specifically, first, as shown in FIG. 10, the coaxial electrode 30 is moved by the elevator 70 in a state where the cylinder 60 is retracted and the distal end portion 21 of the inner electrode 20 is disposed above the distal end portion 11 of the outer electrode 10. Descent. Then, as shown in FIG. 11, the tip 11 of the outer electrode 10 is brought into contact with the workpiece W, and the tip 11 is bitten into the workpiece W by the elastic reaction force of the spring 50 (see FIG. 9). Thereafter, the elevator 70 is stopped, and the inner electrode 20 is pushed downward by the cylinder 60, thereby bringing the tip 21 of the inner electrode 20 into contact with the workpiece W (see FIG. 7).

  As in the first embodiment (see FIGS. 5 to 7), when the inner electrode 20 is brought into contact with the workpiece W by the lowering of the elevator 70, the inner electrode 20 is softened to the workpiece W by slowly lowering the elevator 70. It can be made to contact. As a result, the impact applied to the workpiece W when the inner electrode 20 abuts is reduced, so that deformation of the workpiece W before the start of energization can be suppressed, appearance defects can be avoided, and the energized state can be improved and welding can be performed. The quality can be improved.

  On the other hand, as in the second embodiment (see FIGS. 10 to 11), when the inner electrode 20 is brought into contact with the workpiece W by pushing out the cylinder 60, the inner electrode 20 is pushed out at a stretch by the pressure of the cylinder 60. This can be employed when there is little risk of deformation of the workpiece W, such as when the workpiece W is thick. In this case, it is conceivable that the gap formed between the two metal plates constituting the workpiece W is closed by the impact of the inner electrode 20 due to the extrusion of the cylinder 60.

  Moreover, when the clearance gap is formed between the metal plates of the workpiece | work W, it is also possible to employ | adopt the following 3rd Embodiment. That is, as shown in FIG. 12, the inner electrode 20 is made to recede upward from the outer electrode 10, the coaxial electrode 30 is lowered in this state, and the outer electrode 10 is brought into contact with the workpiece W. When the coaxial electrode 30 is further lowered, the spring 50 is compressed as shown in FIG. 13, the outer electrode 10 is urged downward by the elastic reaction force of the spring 50, and the upper plate W1 is pushed down. As a result, the gap between the upper plate W1 and the lower plate W2 is filled and the two come into contact with each other. Thereafter, as shown in FIG. 14, the inner electrode 20 is pushed downward by a cylinder (not shown) and brought into contact with the workpiece W, and welding is performed by energizing the electrodes. In this way, by filling the gap formed in the workpiece W with the outer electrode 10, the plates W 1 and W 2 of the workpiece W can be brought into contact with each other directly below the inner electrode 20 to be welded. Welding can be performed in a stable state. The inner electrode 20 may be brought into contact with the workpiece W by pushing out the cylinder as described above, or the inner electrode 20 is lowered relative to the outer electrode 10 by compression of the spring 50. You may go by doing.

  Which one of the first to third embodiments is adopted can be easily changed by setting the lowering of the elevator 70 and the timing of pushing out the cylinder 60. What is necessary is just to use suitably according to a use.

  Moreover, although the shape of the front-end | tip part 11 of the outer side electrode 10 has comprised the semicircular arc shape in the axial direction cross section in said embodiment, thickness becomes small gradually toward the front end side. However, the shape is not limited to this as long as it is, for example, an elliptical arc shape or a trapezoidal shape having an axial cross section (not shown) may be used.

  In the above description, the spring 50 is provided as the outer electrode moving means and the cylinder 60 is provided as the inner electrode moving means. However, the present invention is not limited to this. For example, a cylinder may be provided as the outer electrode moving means. In this case, the contact pressure of the outer electrode 10 on the work W can be adjusted by adjusting the pressure in the cylinder.

DESCRIPTION OF SYMBOLS 10 Outer electrode 11 Tip part 12 Notch part 20 Inner electrode 30 Coaxial electrode 40 Support part 50 Spring 60 Cylinder 70 Elevator 80 Power supply 90 Insulation member

Claims (4)

A cylindrical outer electrode and an inner electrode coaxially arranged on the inner periphery of the outer electrode and movable relative to the outer electrode in the central axis direction. A resistance welding device that performs welding by contacting a work and energizing,
A resistance welding apparatus characterized in that the thickness of the tip of the outer electrode is gradually reduced toward the tip.   The resistance welding apparatus according to claim 1, wherein a contact portion that contacts the workpiece and a non-contact portion that does not contact the workpiece are provided at equal intervals in the circumferential direction at a tip portion of the cylindrical outer electrode. This is a method of welding with a resistance welding apparatus having a cylindrical outer electrode and an inner electrode coaxially arranged on the inner periphery of the outer electrode and movable relative to the outer electrode in the central axis direction. And
A resistance welding method for performing welding by bringing the tip of the outer electrode into contact with the work and causing the tip of the inner electrode to come into contact with the work and energizing the inner electrode and the outer electrode in this state. . In the outer electrode formed in a cylindrical shape, the tip is brought into contact with the workpiece, and the workpiece is welded by energizing between the inner electrode arranged coaxially on the inner periphery,
An outer electrode, wherein the thickness of the tip is gradually reduced toward the tip.

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