JP6112035B2 - Indirect spot welding equipment - Google Patents

Description

  The present invention relates to an indirect spot welding apparatus.

  Conventionally, resistance spot welding, mainly direct spot welding, has been used for welding automobile bodies and parts, but recently, series spot welding, indirect spot welding, and the like have been used.

  The characteristics of the above three types of spot welding will be described with reference to FIGS.

  In any spot welding, there is no change in that at least two superposed metal plates are joined by welding.

  FIG. 1 is a diagram showing a direct spot welding method. In this welding method, a current is passed while pressing the upper and lower sides of the two metal plates 1 and 2 sandwiched between a pair of electrodes 3 and 4, and the resistance heating of the metal plates 1 and 2 is used to This is a method for obtaining a welded portion 5 having a shape. In each of the electrodes 3 and 4, the pressurization control devices 6 and 7 and the current control device 8 control the pressure and the current value to be energized.

  FIG. 2 is a diagram showing a series spot welding method. In this welding method, a current is applied to the two stacked metal plates 11 and 12 while applying pressure to the pair of electrodes 13 and 14 arranged at positions away from the same surface side (in the same direction). It is a method of obtaining the welded parts 15-1 and 15-2. In each of the electrodes 13 and 14, the pressurization control devices 6 and 7 and the current control device 8 control the applied pressure and the current value to be energized.

  FIG. 3 is a diagram showing an indirect spot welding method. In this welding method, the two metal plates 21 and 22 are pressed against each other while pressing the electrode 23 against one metal plate 21, and on the other metal plate 22 at a position away from the electrode 23. This is a method of forming a spot-like welded portion 25 on the metal plates 21 and 22 by attaching a power supply terminal 24 and energizing between them.

  Of the three types of welding methods described above, direct spot welding is used when there is sufficient space and an opening that sandwiches the metal plate from above and below is obtained. However, in actual welding, there are many cases where there is not enough space or the metal plate cannot be sandwiched from above and below with a closed cross-sectional structure. In such cases, the series spot welding method or the indirect spot welding method is used. Used.

  When the series spot welding method or indirect spot welding method is used for the above applications, the stacked metal plates are pressed by the electrode only from one direction, and the opposite side becomes unsupported. Yes. Therefore, in the series spot welding method and the indirect spot welding method, it is not possible to apply a high applied pressure locally to the welded portion as in the direct spot welding method in which the metal plate is sandwiched between the electrodes from both sides. Further, since the electrode sinks into the metal plate during energization, the contact state between the electrode-metal plate and the metal plate-metal plate changes. For these reasons, there is a problem in that the current energization path is not stable between the stacked metal plates, and it is difficult to form a melt-bonded portion.

  Patent Documents 1 to 9 propose techniques for solving the above problems.

  In Patent Document 1, in series spot welding, an applied current at the initial stage of welding is applied at 1.5 times or more of the subsequent steady current, and a large current is applied at the initial stage of welding to form a nugget. A technique for flowing is disclosed.

  In Patent Document 2, in series spot welding, a seat surface that is one step higher than the general portion is partially formed at a portion where the electrode of one metal plate is pressed and contacted, and the tip of the electrode is formed into a spherical surface. A technique is disclosed in which an electrode is welded in pressure contact with a seating surface so as to crush the seating surface.

  Patent Document 3 discloses a technique for alternately repeating a time zone in which a current value is kept high and a time zone in which a current value is kept low during energization of indirect spot welding or series spot welding. Further, Patent Document 3 discloses a technique for gradually increasing the current value in the time period in which the current value is kept high as the time period in which the current value is kept high and the time period in which the current value is kept low are alternately repeated. Has been.

In the indirect spot welding method, the inventors set the current value to be energized to be constant from the energization start to the end, and the electrode pressure is divided into two time zones t ₁ and t ₂ from the energization start, Patent Document 4 discloses a technique using two-stage control in which pressure is applied with a pressure F ₁ in the first time zone t ₁ and then pressure is applied with a pressure F ₂ lower than F _{1 in} the next time zone t ₂ . is suggesting.

In addition, in the indirect spot welding method in Patent Document 4, the present inventors have applied pressure F ₁ , current value C ₁ , and subsequent values in the first time zone t1 divided into two time zones t1 and t2 from the start of energization. It is found that welding can be carried out more effectively by defining the pressing force F ₂ and current value C ₂ in the time zone t2 in the following formulas (1) to (4). Proposed in Patent Document 5. T is the total thickness (mm) of the stacked metal plates.

1.2 F ₂ ≦ F ₁ ≦ 5 F ₂ (1)
0.25 C ₂ ≦ C ₁ ≦ 0.85 C ₂ (2)
35 T ^2.3 ≤ F ₂ ≤ 170 T ^1.9 (3)
2 T ^0.5 ≦ C ₂ ≦ 5.5 T ^0.9 (4)
Further, the inventors have developed the above-described technique, and in the indirect spot welding method of Patent Document 5, the _first time is divided into three time zones t ₁ , t ₂ , and t ₃ from the start of energization. In the band t ₁ , pressurization is performed with the pressurizing force F ₁ and energization is performed at the current value C _{1. In} the next time zone t ₂ , pressurization is performed with the pressurizing force F ₂ lower than F ₁ and the current value C is higher than C _1. energized with _2, further in the next time period t _3, developed a technology for conducting a high current value C ₃ than pressurize and C ₂ at low pressure F ₃ than same or F ₂ and F _2, This was proposed in Patent Document 6.

In addition, in the indirect spot welding method disclosed in Patent Document 6, the inventors have applied pressure F ₁ and current value C in the first time zone t1 divided into three time zones t1, t2, and t3 from the start of energization. ₁ , pressurizing force F ₂ and current value C _{2 in} the next time zone t ₂ , and further pressurizing force F ₃ and current value C ₃ in the next time zone t ₃ are respectively limited to the following formulas (5) to (10): Thus, it was found that it can be carried out more effectively, and this was proposed in Patent Document 7.

1.2 F ₂ ≦ F ₁ ≦ 3F ₂ (5)
0.25 C ₂ ≦ C ₁ ≦ 0.9 C ₂ (6)
F ₃ ≦ F ₂ ≦ 3F ₃ (7)
0.5 C ₃ ≦ C ₂ ≦ 0.9 C ₃ (8)
30 T ^2.1 ≤ F ₃ ≤ 170 T ^1.9 (9)
2 T ^0.5 ≦ C 3 ≦ 5.5 T ^0.9 (10)
In addition, in the indirect spot welding, the inventors have electrically insulated the overlapping surface between the metal plates except for the place where the welding is performed, thereby suppressing the dispersion of current during welding and stably producing the molten nugget. A forming technique was developed and proposed in Patent Document 8.

  Furthermore, the inventors have developed a technique for performing welding in a state in which a viscous substance having an insulating property is interposed on the entire overlapping surface between metal plates in indirect spot welding, and proposed in Patent Document 9 did.

Japanese Patent Laid-Open No. 11-333569 JP 2002-239742 A JP 2006-198676 A JP 2010-194609 A JP 2012-035278 A Japanese Patent Application Laid-Open No. 2011-194459 JP 2012-91203 A JP 2011-50977 A JP 2012-157888 A

  In the indirect spot welding method, heat generation and melting due to energization occur at a site where the power supply terminal contacts with a member in which at least two metal plates are superposed, and the member may be deformed or deteriorated, resulting in poor quality. . However, in order to solve such a problem, there is no disclosure in Cited Documents 1 to 9 regarding the structure in which the power supply terminal contacts the member.

  The present invention has been made with respect to such problems, and an object thereof is to reduce or prevent the occurrence of heat generation and melting due to energization and the occurrence of poor quality due to deformation and deterioration of members.

As a result of intensive studies to solve the above problems, the present inventors have obtained the following knowledge.
a) When the superposed steel plates are pressed with an electrode (welding electrode) only from one surface side and indirect spot welding is performed on the opposite side without support, the power supply terminal is connected to the other surface as the other electrode. It attaches to the position which the metal plate of the side spaced apart, and it supplies with electricity between a welding electrode and this electric power feeding terminal. At this time, heat generation and melting due to energization occur at a portion where the member and the power supply terminal are in contact with each other, and the member may be deformed or deteriorated, resulting in poor quality.
b) In order to overcome the above problem, it is necessary to increase the contact area between the member and the power supply terminal, thereby reducing the current density at the contact portion and preventing excessive heat generation. However, while the member used for welding may have a complicated shape, the power supply terminal needs to have a shape that can secure a sufficient contact area even with a surface with various curvatures. Therefore, it is necessary to make the power supply terminal follow the curved surface of the member.
c) The structure for bringing the power supply terminal into contact with the power supply terminal as described above is preferably a simple structure from the viewpoint of production cost and maintenance, and a structure that can use a general-purpose product for the consumable part. .

The present invention is based on the above findings and has the following characteristics.
[1] A member in which at least two metal plates are overlapped is pressed against the metal plate while pressing the welding electrode from one surface side, and the metal plate on the other surface side is separated from the welding electrode. An indirect spot welding apparatus in which a power feeding terminal is brought into contact with a drive unit to conduct welding between a welding electrode and the power feeding terminal,
The power feeding terminal is an indirect spot welding apparatus in which four or more contact electrodes are arranged in parallel on a pedestal made of a conductor.
[2] The power feeding terminal is attached to the drive unit via an elastic body that is elastically deformable in at least one of the drive axis direction of the drive unit and the direction orthogonal to the drive axis direction. The indirect spot welding apparatus described.
[3] The indirect spot welding apparatus according to [2], wherein the elastic body is a coil spring.

  The indirect spot device according to the present invention can reduce heat generation and melting due to energization at a portion where the member and the power supply terminal are in contact, and can eliminate quality defects due to deformation and alteration of the member.

It is a figure which shows the direct spot welding method. It is a figure which shows a series spot welding method. It is a figure which shows the indirect spot welding method. It is a figure which shows the structure of the electric power feeding terminal of the indirect spot apparatus which concerns on embodiment of this invention. It is a figure which shows a part of indirect spot apparatus which concerns on embodiment of this invention. It is a figure which shows the indirect spot apparatus used in the Example. It is a figure which shows the state which is making the planar lower board contact the electric power feeding terminal horizontally. It is a figure which shows the state which makes the planar lower board incline and contact the electric power feeding terminal. It is a figure which shows the state which is contacting horizontally the lower board which has a convex curved surface to an electric power feeding terminal. It is a figure which shows the state which made the lower board which has a convex curve to the electric power feeding terminal incline and is made to contact. It is a figure which shows the state which is making the lower board which has a concave curved surface horizontally contact the electric power feeding terminal. It is a figure which shows the state which made the lower board which has a concave curved surface in contact with the electric power feeding terminal inclined.

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

  FIG. 4 is a diagram showing a power supply terminal of the indirect spot welding apparatus according to the embodiment of the present invention. The indirect spot welding apparatus according to the present invention presses a welding electrode against a metal plate from one side while pressing the welding electrode against a member in which at least two metal plates are overlapped, and is applied to the metal plate on the other side. In this case, the power supply terminal is brought into contact with a position separated from the welding electrode, and welding is performed by energizing between the welding electrode and the power supply terminal.

  Fig.4 (a) is the figure which looked at the electric power feeding terminal of the indirect spot welding apparatus which concerns on embodiment of this invention from the top, and FIG.4 (b) is the figure which looked at the electric power feeding terminal from the side.

  As shown in FIGS. 4A and 4B, the power supply terminal 41 has a base 42 made of a conductor. Four contact electrodes 43 are provided in parallel on the pedestal 42 via adapters 44. Here, “parallel” means that a plurality of rows of contact electrodes 43 arranged at a predetermined interval are provided. In the example of FIG. 4A, two contact electrodes 43 are provided in two rows.

  The contact electrode 43 has a cylindrical shape with a diameter of 5 to 20 mm, and the tip of the cylinder is formed in a convex curved shape. The curved surface at the tip may have a shape having a two-step curvature. For example, it can be configured such that the radius of curvature is 4 to 15 mm in a region exceeding 2 to 5 mm from the center of the circle, and the inner radius of curvature is 30 to 60 mm.

  By forming the tip of the contact electrode 43 in a curved shape, the contact electrode 43 can be stably brought into contact with the member even when the contact surface of the member has a gentle concave shape, and a predetermined contact area is ensured. be able to. Further, since the four contact electrodes 43 having a curved surface are in contact with the member at the same time, the current flowing from one contact electrode 43 to the member can be suppressed to a low level. The contact electrode 43 disposed on the pedestal 42 is configured to be detachable, and can be easily replaced when the tip of the contact electrode 43 deteriorates.

  A terminal block 45 is provided on the side surface of the pedestal 42 to receive power from a power source (not shown). Two or more terminal blocks 45 may be provided. In addition, the pedestal 42 is provided with a cooling water inlet 46 to which cooling water for cooling the contact electrode 43 is supplied and a cooling water outlet 47 from which the cooling water is discharged.

  FIG. 5 is a diagram showing a configuration of the indirect spot device according to the embodiment of the present invention. The power supply terminal 41 configured as described above is attached to the drive unit 52 via the elastic body 51. The elastic body 51 is configured to be elastically deformable in at least one of the drive shaft direction of the drive unit 52 and the direction orthogonal to the drive shaft direction.

  As the elastic body 51, for example, a coiled spring can be used.

  The drive unit 52 has an extendable part 53 and a fixed part 54. The expansion / contraction part 53 is movable in the vertical direction of the drawing with respect to the fixed part 54. As a drive mechanism of the drive unit 52, a pneumatic type, a hydraulic type, and a servo motor type can be used.

  The power supply cable 55 is attached to a terminal block 56 disposed on the fixed portion 54 of the drive unit 52. A highly flexible connector 57 is attached to the terminal block 56. The connector 57 is connected to the terminal block 45 of the power feeding terminal 41. As the connector 57, it is possible to use a superposed metal foil such as copper or a braided thin wire.

  Next, the effect of the indirect spot welding apparatus configured as described above will be described. Heat generation and melting due to energization occur at the portion that contacts the power supply terminal 41 of the member to be welded. In order to avoid quality defects due to deformation and alteration of the member, it is necessary to reduce or prevent this heat generation and melting. There is. In order to reduce or prevent melting, it is necessary to increase the contact area between the member and the power supply terminal 41 to reduce the current density and prevent excessive heat generation.

  However, the member used for welding may have a complicated shape, and the structure in which the power supply terminal 41 is brought into contact with the member needs to ensure a sufficient contact area even on a surface with various curvatures.

  Therefore, in the present invention, the contact area is increased and the current density is decreased by providing the four contact electrodes 43 on the power supply terminal 41. In the present invention, the contact surface of the power supply terminal 41 is made to follow the shape of the member by connecting the power supply terminal 41 to the drive unit 52 via the elastic body 51. Thereby, the contact area of the contact electrode 43 and a member can be enlarged, and a current density can be lowered | hung. Thereby, the heat generation / melting of the member can be reduced or prevented, and the quality defect due to the deformation or alteration of the member can be reduced.

  In the above description, the four contact electrodes 43 are arranged on the power supply terminal 41. However, if the number of the power supply terminals 41 is four or more, sufficient contact contact with the member is ensured. And the effects of the present invention can be achieved.

In order to verify the effect of the present invention example, indirect spot welding was performed using the present invention example , a reference example, and a comparative example. FIG. 6 is a view showing an indirect spot welding apparatus used as an example of the present invention.

In the example of the present invention , the reference example, and the comparative example, as the members to be welded, those obtained by superposing the upper plate 61 and the lower plate 62 were used. The upper plate 61 and the lower plate 62 have a plate thickness of 1.0 mm, have the chemical components shown in Table 1, and have a tensile strength of 270 N / mm ² or more (SPC270 ). Two places of the lower plate 62 were supported by a jig 64 so as to sandwich the welded portion 63. The interval W between the two jigs 64 was 50 mm.

  The welding electrode 65 was pressed against the upper plate 61. The pressurization of the welding electrode 65 is controlled by a pressurization control device 67. The current flowing between the welding electrode 65 and the contact electrode 43 is controlled by a current control device 68.

  As shown in FIG. 6, the drive unit 52 is arranged below the position P of the lower plate 62 that is separated from the welded portion 63, and the power supply terminal 41 is brought into contact with the lower plate 62 at this position P.

  The structure of the power supply terminal 41 is different from that according to the present invention. The shape of the power supply terminal 41 according to the present invention is as shown in FIG. Four contact electrodes 43 are arranged in parallel on a base 42 made of a conductor. The shape of the contact electrode 43 is a cylinder having a diameter of 13 mm, and the tip of the cylinder has a curved surface (DR electrode). The contact electrode 43 has a curved surface with a radius of curvature of 40 mm when the radius is 3 mm or less from the center of the circle, and has a two-step curvature with a radius of curvature of 8 mm within a range exceeding the radius of 3 mm from the center of the circle.

  On the other hand, the power supply terminal used as a comparative example has a cylindrical shape with a diameter of 38 mm and has a shape in which only one contact electrode is arranged. The tip shape of the contact electrode is flat.

  Moreover, the structure which makes a power supply terminal contact a member also used the thing according to this invention, and a thing different from this invention. In the structure according to the present invention, the power supply terminal 41 is attached to the drive unit 52 via a coiled spring that can be elastically deformed in the drive axis direction of the drive unit 52 and in a direction orthogonal to the drive axis direction ( There is an elastic body 51). On the other hand, in a structure different from the present invention, the power supply terminal 41 is attached to the drive unit 52 via a rigid support (no elastic body 51).

  Table 2 shows combinations of the power supply terminal and the structure in which the power supply terminal is in contact with the member.

  For each of the combinations in Table 2, welding was performed by bringing the member (lower plate 62) and the power supply terminal into contact with each other in six states. 7 to 12 show six contact states. 7 to 12 show only the power feeding terminal contact portion of FIG.

  In FIG. 7, the planar lower plate 62 is in horizontal contact with the power feeding terminal 41 (planar horizontal). In FIG. 8, the planar lower plate 62 is brought into contact with the power supply terminal 41 by inclining (planar inclination). The inclination angle is 5 °.

  In FIG. 9, a lower plate 62 having a convex curved surface is in horizontal contact with the power supply terminal 41 (convex curved horizontal). The curvature of the convex curved surface of the lower plate 62 is a curvature radius of 100 mm. In FIG. 10, the lower plate 62 having a convex curved surface is brought into contact with the power feeding terminal 41 (inclined convex curved surface). The curvature of the convex curved surface is a curvature radius of 100 mm. The inclination angle is 5 °.

  In FIG. 11, the lower plate 62 having a concave curved surface is in horizontal contact with the power supply terminal 41 (horizontal concave curved surface). The curvature of the concave curved surface of the lower plate 62 is a radius of curvature of 100 mm. In FIG. 12, the lower plate 62 having a concave curved surface is brought into contact with the power supply terminal 41 by inclining (concave curved surface inclination). The curvature of the concave curved surface is a curvature radius of 100 mm. The inclination angle is 5 °.

In the present invention example , the reference example, and the comparative example, power is supplied from the power supply cable 55 to the power supply terminal 41 in a state where the lower plate 62 and the power supply terminal 41 are in contact with each other in the above-described six contact states. The power supply terminal 41 was energized.

  The welding conditions are as shown in Table 3.

  The results are shown in Table 4.

  In Table 4, the external appearance state of the power feeding terminal contact portion of FIG. 6 is shown. “No change” in the table indicates that there is no change in the shape and properties of the surface, and that heat generation due to energization, deformation due to melting, and alteration are prevented. “Indentation” is a state in which a member softens due to heat generation or melting due to energization, and the tip shape of the electrode is deformed as if transferred, resulting in poor quality. “Burn” is a state in which the surface of the member is oxidized by heat generated by energization, and is a state in which it can be estimated that the member is heated to 600 to 700 ° C. or higher. In the case of a steel material, if the material is heated to a temperature higher than this temperature, the material may change in quality, resulting in a loss of properties imparted during production, resulting in poor quality.

As shown in Table 4, in Example 1 of the present invention, “no change” was obtained in the contact state of all the power supply terminals. In the case of the reference example , “indentation” and “burn” occurred in the case of plane inclination, convex curve inclination, and concave curve inclination, but “no change” in other cases.

  On the other hand, in Comparative Example 1, “indentation” and “burnt” all occurred except that “no change” was obtained only in the case of horizontal and flat planes. Further, in Comparative Example 2, “indentation” and “burnt” occurred in all cases except that “no change” was obtained only in the case of a horizontal plane.

  From the above, it has been found that by providing the four contact electrodes 43 on the power supply terminal 41, the heat generation and melting of the member can be reduced. Further, it has been found that the heat generation and melting of the member can be further reduced by attaching the power supply terminal 41 to the drive unit 52 via the elastic body 51.

1, 2, 11, 12, 21, 22 Metal plate 3, 4, 13, 14, 23 Electrode 5, 15-1, 15-2, 25, 63 Welded portion 6, 7, 67 Pressure control device 8, 68 Current control device 24 Power supply terminal 41 Power supply terminal 42 Base 43 Contact electrode 44 Adapter 45 Terminal block 46 Cooling water inlet 47 Cooling water outlet 51 Elastic body 52 Drive unit 53 Extending and contracting part 54 Fixing part 55 Power feeding cable 56 Terminal block 57 Connector 61 Upper plate 62 Lower plate 64 Jig 65 Welding electrode

Claims (1)

At least two metal plates are pressed against each other while pressing the welding electrode against the metal plate from one side, and the power supply terminal is placed at a position separated from the welding electrode on the other side. An indirect spot welding apparatus that performs welding by bringing a welding unit into contact with the welding electrode and the power supply terminal,
The power supply terminal is an elastic material in which four or more contact electrodes are arranged in parallel on a pedestal made of a conductor and elastically deformable in the drive axis direction of the drive unit and in a direction perpendicular to the drive axis direction. Attached to the drive unit through the body,
An indirect spot welding apparatus in which the elastic body is a coil spring .

Images