JPH0221186Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a spot welding electrode for stacking and spot welding a plurality of steel plates, and in particular for spot welding steel plates having a non-conductive thin film on at least one surface. This invention relates to spot welding electrodes.

[Conventional technology]

When joining multiple composite steel plates coated with an organic coating such as acrylic or epoxy on one or both sides of the thin steel plates by spot welding, conventionally, as disclosed in JP-A No. 58-97487, a file is used. It is known that spot welding is performed after the paint layer on the surface of a steel plate is broken by staking.

[Problem that the invention attempts to solve]

However, this method requires two steps: filing and spot welding, which is time-consuming and
Since holes are made in two stacked composite steel plates during sanding, there is a problem in that even after spot welding, protrusions remain and the flatness of the steel plates is impaired.

The object of the present invention is to provide a spot welding electrode device that requires fewer steps and does not impair the flatness of a steel plate.

[Means for solving problems]

In order to achieve the above purpose, in this invention,
A mechanism shall be provided to rotate the spot welding electrode when pressing it against the steel plate.

[Effect]

According to this, the paint layer on the surface of the steel plate against which the spot welding electrode is pressed is partially torn by the pressing rotation of the electrode, and the electrical resistance between the spot welding electrode and the steel plate is reduced, resulting in desired welding. Therefore, sanding can be omitted, and the steel plate does not have any protrusions.

[Embodiment] Fig. 1 shows a longitudinal section of an embodiment of the present invention, and Fig. 2 shows its external appearance. In addition, Figure 1 is - of Figure 2.
FIG.

One of the spot welding electrodes 1 and 2 2 is supported by an arm 4, and its position in the vertical direction is set by this arm 4. It does not move up and down during welding. Two composite steel plates are placed on the lower electrode 2 in a stacked manner. The upper electrode 1 is fixed to the lower end of the electrode holder 7. The electrode holder 7 is hollow and has a conduit 15 disposed therein. At the upper end of the electrode holder 7 are sleeve connectors 16 and 1 for introducing cooling water.
7 is fixed. Cooling water entering the electrode holder 7 from the connector 16 passes through the conduit 15 to the upper electrode 1, then passes through the inner space of the electrode holder 7 to the connector 17, and exits to the outside.

The electrode holder 7 is vertically movable and rotatably supported by the holder support member 5 through a bearing 6 integrated with the holder support member 5 . A compression coil spring 8 built into the support member 5 drives the electrode holder 7 downward. As a result, the electrode holder 7 protrudes from the holder support member 5, as shown in FIG.

An inclined cam groove 10 is formed in the large diameter cylindrical portion of the holder support member 5. A tracing roller 9 is pivotally attached to the electrode holder 7.
is engaged with the cam groove 10. Holder support member 5
A positioning screw 12 is attached to the upper end, and the lower end of this screw 12 faces the end member 11 at the upper end of the electrode holder 7 .

The holder support member 5 is fixed to the vertically movable arm 3. The arm 3 is connected to a lifting mechanism (based on an air cylinder, not shown), and is driven downward when performing spot welding at one point, and is driven upward when the welding is completed.

When two composite steel plates are placed one on top of the other between electrodes 1 and 2 in the state shown in Fig. 1, and the arm 3 is driven downward, the entire electrode device shown in Fig. 2 first descends, and electrode 1 hits the steel plate. . When the electrode 1 hits the steel plate, the steel plate prevents the electrode holder 7 from descending, so the holder support member 5 descends while the holder 7 remains substantially stationary. At this time, the spring 8 is compressed and the roller 9 is pushed down by the cam groove 10, so the roller 9 moves along the cam groove. That is, the roller 9 rotates around the axis of the holder 7, and thereby the electrode holder 7 and the electrode 1 rotate around the axis. When the roller 9 reaches the upper end of the cam groove 10, or before that, the screw 12 is inserted into the end member 11 of the holder 7.
When the lower end of the support member 5 and the holder 7 are integrally driven downward, the predetermined force applied to the arm 3 is directly applied to the electrode 1. Therefore, electrode 1
rotates (forward rotation) after its lower end touches the steel plate until the predetermined force is applied, and during this rotation, the repulsive force of the spring 8 is applied to the electrode 1. The maximum rotation angle of the electrode 1 is determined by the length of the cam groove 10, and the rotation angle of the electrode 1 can be adjusted within this range using the screw 12. The pressing force applied to the electrode 1 while the electrode 1 is rotating forward is determined by the strength of the spring 8.

When the arm 3 is driven upward after the electrode 1 stops rotating, the holder 7 is first pushed out from the support member 5 by the repulsive force of the spring 8, and the roller 9 rotates along the cam groove 10, thereby lifting the holder. 7 and electrode 1 rotate back.

The pressing force after the electrode 1 stops forward rotation is determined by the downward driving force applied to the arm 3. Arm 3 drive, electrode 1 from start to finish of one spot welding
FIG. 3 shows the timing relationship of forward and backward rotations and welding energization.

In the example shown in Fig. 1, a thin steel plate (thickness 0.6 to 1.6
Composite steel sheet 2 with an organic coating film of acrylic, epoxy, etc. 1 to 5 μm thick on one or both sides of mm)
Overlap spot welding of the sheets was performed. The combination of two composite steel plates is as shown in Figure 4a, where both the front and back sides are coated with paint, and as shown in Figures 4b and 4c, one steel plate is coated on one side and the other is coated. Both sides are coated, and as shown in Figure 4d, both steel plates are coated on only one side.
Good spot welding was obtained in all cases.

As a comparison experiment, when conventional spot welding with non-rotating electrodes was performed for all types, there were random cases where welding was successful and cases where welding was poor, and there was approximately a 50% probability of successful welding. However, with the device of the present invention, 100% good welding can be obtained.

According to the device of the present invention, since the upper electrode 1 is rotated under pressure, it is assumed that the steel plate coating in contact with it is at least partially broken, and the resistance of the uppermost coating layer is almost eliminated. Further, when looking at the welding results, there are many traces of current flowing through the contact portion 1S of the outer contour portion of the lower end surface of the electrode 1. This is electrode 1
Since the electrode rotates around its axis, as shown in Fig. 4e, the closer it is to the outer contour, the larger the movement amount is and the higher the probability of coating peeling. I guess this is because the paint tends to escape outwards on the outer contours.

It is easy to understand that the coating layer directly under the upper electrode 1 is destroyed, but why is the coating layer between the upper steel plate 13 and the lower steel plate 14 and the coating layer on the lower electrode 2 energized by the rotation of the electrode 1? It is unclear whether it will be easier. However, in any of the embodiments shown in Figures 4a to 4d, the apparatus of the present invention provides 100% good spot welding.

In the above embodiment, only the upper electrode 1 is rotated under pressure, but the lower electrode 2 may also be provided with a rotation mechanism like the electrode 1 and rotated under pressure in the same manner. In this case, it is preferable to set the rotation directions of the upper electrode and the lower electrode to be opposite so that the steel plate does not rotate.

[Effects of the Invention] As described above, according to the present invention, composite steel plates such as painted steel plates can be spot welded without sanding. Furthermore, since no protrusions such as squeeze protrusions are produced, the flatness of the steel plate is not impaired.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention,
FIG. 2 is a side view. Note that FIG. 1 is a sectional view taken along the - line in FIG. 2. FIG. 3 is a time chart showing one operation process in spot welding of the electrode device shown in FIG. 1. Figure 4a, Figure 4b, Figure 4
Figures c and 4d are cross-sectional views showing how two steel plates are superimposed to be welded using the electrode device of the present invention, and Figure 4e is a plan view of the covered surface in contact with the electrode 1. 1, 2: Welding electrode, 3, 4: Arm, 5: Holder support member, 6: Bearing, 7: Electrode holder, 8:
Spring, 9: Roller, 10: Cam groove, 11:
End member, 12: Screw, 13, 14: Steel plate, 13
a, 13b, 14a, 14b: paint film, 15: conduit, 16, 17: sleeve connector.

Claims (1)

[Claims for Utility Model Registration] (1) A spot welding electrode; an electrode holder to which the electrode is fixed; a holder support member that supports the electrode holder rotatably around its axis; and the holder support member. An electrode device for spot welding, comprising: a rotational drive means for rotationally driving the electrode holder in conjunction with movement in the direction along the axis. (2) The rotational drive means includes a spring member that drives the electrode holder in a direction protruding from the holder support member, a cam groove of the holder support member, and a spring member that engages with the cam groove and extends along the axis of the cam groove. The spot welding electrode device according to claim (1) of the utility model registration, which comprises an engager of an electrode holder that rotates by movement in a direction.