JPH09155557A - Resistance welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the resistance welding equipment which is free from variance of welding resistance at each welding point and has uniform welding quality and in which an insulation member is used for a welding stage. SOLUTION: Respective one ends of plural welding power sources 1a, 1b are connected in common to a ground electrode 4 and these other ends are respectively connected to respective welding electrodes 2a, 2b, the contact resistance of the ground electrode 4 for an object 7b to be welded is smaller as compared to contact resistance of the plural piece welding power sources 1a, 1b, the electric current passing the ground electrode 4 is made to reverse phase and is simultaneously caused to flow from the plural piece welding power sources 1a, 1b to the objects 7b, 7a to be welded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-spot resistance welding apparatus having a plurality of welding power sources and welding electrodes, and more particularly to a multi-point simultaneous resistance welding apparatus.

[0002]

2. Description of the Related Art As a conventional multi-point simultaneous resistance welding apparatus, a series type is shown in FIG. 7 and an opposed type is shown in FIG. The multi-point simultaneous resistance welding apparatus shown in FIG. 7 includes a single welding power source 11 and two welding electrodes 12a and 12b connected to both ends of the welding power source 11 via electric wires.
Then, of the objects to be welded 14a and 14b stacked on the welding stage 13, the welding electrodes 12a and 12b are brought into contact with the objects to be welded 14b in the upper layer to apply a pressing force, and the welding power source 11 supplies electricity. Between the two welding electrodes 12a and 12b, an electric current is caused to flow from the upper layer welded object 14b to the lower layer welded object 14a and the upper layer welded object 14b, and the joule is generated by the current flowing through the two welding electrodes 12a and 12b. The upper layer welded object 14b and the lower layer welded object 14a are locally heated and melted by heat, and the upper layer welded object 14b and the lower layer welded object 14a are spot-welded at welding points g and h. is there.

The opposed multi-point simultaneous resistance welding apparatus shown in FIG. 8 is equipped with a plurality of welding power sources 15a and 15b. Each of the welding power sources 15a and 15b has one end connected to the welding electrodes 16a and 16b via an electric wire and the other end connected to a metal welding stage 17 via an electric wire. And each welding power supply 15a, 15b comprises each welding circuit. Note that 18a and 18b
Is an object to be welded.

[0004]

However, since the conventional multi-point simultaneous resistance welding apparatus shown in FIG. 7 has two welding points g and h which are in series in one welding circuit, each welding point g and h. Due to the difference in the welding resistance of the, the quality of the welding varied. Moreover, since the conventional multipoint simultaneous resistance welding apparatus shown in FIG. 8 uses the welding stage 17 as an electrode,
The object to be welded 18a has been limited to one that can be electrically connected to the welding stage 17.

Therefore, an object of the present invention is to provide a resistance welding apparatus which is not affected by variations in welding resistance at each welding point, has uniform welding quality, and can use an insulating member for a welding stage. To do.

[0006]

In order to achieve the above object, the present invention has a plurality of welding power sources each having one end connected to an individual welding electrode and the other ends commonly connected to a ground electrode. The contact resistance of the ground electrode with respect to the object to be welded is smaller than the contact resistance of the welding electrode, and a current having an opposite phase to the ground electrode is simultaneously supplied from the plurality of welding power sources to the object to be welded. Characterize.

As described above, according to the present invention, each welding power source circuit is composed of a plurality of welding power sources, and the currents of opposite phases are passed through the ground electrode. The electrode does not generate heat. Further, even if there are variations in a plurality of welding resistances, those welding variations can be reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic form view of an embodiment of the resistance welding apparatus of the present invention, and FIG. 2 is a partial schematic explanatory view of FIG. In this embodiment, a plurality of commercial frequencies,
For example, it has two welding power sources 1a and 1b. One end of the welding power source 1a, 1b is connected to the welding electrode 2a via an electric wire,
2b, and the other end is commonly connected to the ground electrode 4 via the switches 3a and 3b. The welding power sources 1a and 1b are connected to the same polarity via the switches 3a and 3b and the ground electrode 4.

Reference numeral 5 is a welding stage.
An insulator 6 is disposed on the top of the. Further, the objects to be welded 7a and 7b are placed on the insulator 6 in an overlapping manner.

The area of the surface of the ground electrode 4 that contacts the object to be welded 7b (filled portion) is larger than the area of the surface of the welding electrodes 2a and 2b that contacts the object to be welded 5b (filled portion). The contact resistance of the ground electrode 4 is smaller than the contact resistance of the welding electrodes 2a and 2b. In addition,
Reference characters a and b denote welding points of the objects to be welded 7a and 7b, respectively.

The welding power supply circuit of this embodiment can be realized by a transformer T with a midpoint tap as shown in FIG. The primary winding N1 of the transformer T is connected to a commercial power source, and the switch 3 is provided on the primary winding N1. The switch 3 has a function of turning on the switches 3a and 3b in the welding power source circuit of FIG. 1 in synchronization.
When a switch is provided on the side of the secondary winding N2, the switch 3 becomes switches 3a and 3b as indicated by the broken line. The secondary winding N2 of the transformer T is provided with a middle point tap, the ground electrode 4 is connected to this middle point tap, and the welding electrode 2a is connected to the winding start end of the secondary winding.
The welding electrode 2b is connected to the winding end. The welding power source 1a is composed of the upper winding of the secondary winding N2 of the transformer T, and the welding power supply 1b is composed of the lower winding of the secondary winding N2 of the transformer T.

Next, the mode of welding in this embodiment will be described. In FIGS. 1 and 2, the objects to be welded 7a and 7b are placed on the insulator 6 placed on the welding stage 5 in an overlapping manner. Two welding points a and b on the objects to be welded 7a and 7b
Welding electrodes 2a and 2b are respectively arranged in
The ground electrode 4 is arranged at a substantially middle portion between the welding electrodes 2a and 2b. Then, an appropriate pressure is applied to the welding electrodes 2a and 2b, the switches 3a and 3b are synchronously turned on, and currents are made to flow from the welding power sources 1a and 1b to the two objects to be welded 7b and 7a, respectively. Spot welding at.

In this case, as shown in FIG. 3, the welding power source 1
A loop current ia flows in the circuit of a through the welding electrode 2a, the objects to be welded 7b, 7a and the ground electrode 4, and in the circuit of the welding power source 1b, the ground electrode 4, the two objects to be welded 7b, 7a and Loop current ib via welding electrode 2b
Flows. Therefore, the loop current ia and the loop current i
b will flow through the ground electrode 4 in the opposite direction, and will cancel each other out. In FIG. 2, the ground electrode 4 is disposed on the upper layer welded object 7b, but when the lower layer welded object 7a is wide, the lower layer welded object 7a is indicated by a broken line 4a. The upper position is preferable because the current that bypasses the object to be welded 7b decreases and the amount of welding current passing through the welding point increases.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, four welding power sources 1c
Of the two welding power sources 1c and 1e and the remaining two welding power sources 1d and 1f have different polarities. One end of each of these welding power sources 1c to 1f has a switch 3c to 3f.
Are connected to the welding electrodes 2c to 2f, respectively. The other ends of these welding power sources 1c to 1f are commonly connected to the ground electrode 4. Therefore, the four welding power sources 1c to 1f constitute four parallel circuits via the ground electrode 4. The other configurations are similar to those of the first embodiment, and therefore, the same numbers are given and the description thereof is omitted. Next, the mode of welding in this embodiment will be described. Similar to the first embodiment, the objects to be welded 7a, 7b are placed on the insulator 6 arranged on the welding stage 5.
Place them on top of each other. The welding electrodes 2c to 2f are arranged at predetermined positions on the four welding points c to f of the objects to be welded 7a and 7b, and the ground electrode 4 is arranged at an appropriate portion of the object to be welded 7b. Then, an appropriate pressure is applied to the welding electrodes 2c to 2f, the switches 3c to 3f are synchronously turned on, and the welding power source 1c to
From 1f, electric currents are respectively applied to the objects to be welded 7b and 7a to perform spot welding at welding points cf. Welding power source with same polarity 1
c and 1e and welding power sources 1d and 1f of opposite polarities, currents in opposite directions flow as indicated by arrows, and the currents passing through the ground electrode 4 cancel each other out. Become. Next, Table 1 shows a comparative example of the welding strength [kg] between the welding points a and b and the welding points g and h in the first embodiment shown in FIG. 1 and the conventional example shown in FIG.

[0015]

[Table 1]

From Table 1, it is understood that the deviation σ of the variation in welding strength is smaller in this embodiment than in the conventional example. Regarding the welding strength, the present example and the conventional example are almost the same.

Next, referring to the electrical equivalent circuit of this embodiment shown in FIG. 1 (FIG. 5) and the electrical equivalent circuit of the conventional example shown in FIG. 7 (FIG. 6), the welding point a (g) is determined. Welding resistance Ra (R
g), the welding current when the welding resistance Rb (Rh) of the welding point b (h) is changed from 1/1 to 1/2, and the heat generation amount at the welding resistance Ra (Rb) and the welding resistance Rg (Rh). Regarding these heat generation ratios, Table 2 shows the case of this embodiment and Table 3 shows the case of the conventional example.
In this embodiment, the ground resistance R4 is set to be smaller than the welding resistances Ra and Rb. In the present embodiment, Ra is the welding resistance at the welding point a, and Rb is the welding point b.
, R4 is the contact resistance of the ground electrode 4, Qa is the amount of heat generated at the welding point a, and Qb is the amount of heat generated at the welding point b. Since the welding power sources 1a and 1b are connected in the same polarity, the loop current ia passing through the welding resistance Ra and the loop current ib passing through the welding resistance Rb are the contact resistance R4 of the ground electrode 4.
Will flow in the opposite direction as indicated by the arrow.

In the conventional example, Rg is the welding resistance at the welding point g, Rh is the welding resistance at the welding point h, and Qg is the welding point g.
Of the welding point h, and Qh is the heating value of the welding point h. Then, the loop current IG flows as the welding current through the welding resistances Rg and Rh.

[0019]

[Table 2]

[0020]

[Table 3]

From Tables 2 and 3 above, in the present embodiment in which the ground electrode is provided and the currents flowing through the ground electrode are set in opposite directions to cancel each other, even if the welding resistances Ra and Rb vary, It is possible to reduce the heat generation ratio of the welding resistances Ra and Rb, that is, the welding variation.

[0022]

As described above, according to the present invention, since a plurality of welding power sources are connected in parallel to the ground electrode and currents of opposite phases are passed through the ground electrode, the currents flowing through the ground electrode are canceled out. The ground electrode does not generate heat. Further, even if there are variations in a plurality of welding resistances, those welding variations can be reduced. Also, an insulating material can be used for the welding stage.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of a resistance welding apparatus of the present invention.

FIG. 2 is a partially omitted perspective view of FIG. 1;

FIG. 3 is a power supply equivalent circuit diagram of the first embodiment shown in FIG.

FIG. 4 is a schematic configuration diagram of a second embodiment of the resistance welding apparatus of the present invention.

5 is an electrical equivalent circuit diagram of FIG.

FIG. 6 is an electrical equivalent circuit diagram of a conventional example.

FIG. 7 is a schematic configuration diagram of a conventional series-type multi-point simultaneous resistance welding device.

FIG. 8 is a schematic configuration diagram of a conventional opposed multi-point simultaneous resistance welding apparatus.

[Explanation of symbols]

1a, 1b, 1c, 1d, 1e, 1f Welding power sources 2a, 2b, 2c, 2d, 2e, 2f Welding electrodes 3a, 3b, 3c, 3d, 3e, 3f Switch 4 Ground electrode 5 Welding stage 6 Insulator 7a , 7b Objects to be welded a, b, d, d, e, f Welding points

Claims (1)

[Claims] 1. One end of each of a plurality of welding power sources is connected to an individual welding electrode, and the other ends thereof are commonly connected to a ground electrode, and the contact resistance of the ground electrode with respect to an object to be welded is that of the welding electrode. A resistance welding apparatus characterized in that a current, which is smaller than a contact resistance, is made to flow from the plurality of welding power sources to the object to be welded at the same time in an opposite phase to the ground electrode.