JPH0136211B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an improvement in a resistance welding device for spot welding a contact and a pedestal. As is well known, spot welding is a process in which two or more objects to be welded are sandwiched between two electrodes facing each other, and the objects to be welded are joined together by applying pressure and electricity to generate heat from the weld. First, a conventional resistance welding apparatus for performing this type of spot welding will be explained with reference to FIG. In the figure, 1 is an upper main electrode, 2 is a lower main electrode facing the upper main electrode, 3 is a contact, and 4 is a pedestal. Conventionally, as shown in the figure, a contact point and a pedestal were sandwiched between both main electrodes 1 and 2, and electricity was simply applied under pressure. However, when the contact is bonded to the longitudinal end of the pedestal in this manner, bonding failures are likely to occur due to uneven temperature rise at the bonding interface. This situation will be explained based on FIG. In the figure, 5 is a bonding layer, 6 is eluted metal, and 7 is a bonding defect. That is, as shown in the figure, a bonding layer 5 is formed on the end side of the pedestal 4, and the eluted metal 6 drips down considerably. On the other hand, there is a strong tendency for bonding defects 7 such as notches to occur on the opposite side of the end of the pedestal 4. Next, the cause of such bonding failure will be explained based on FIG. 3. As shown in the figure, thermal saturation occurs at the end face of the pedestal 4, but on the opposite side a heat flow C is formed in the longitudinal direction. Therefore, the temperature from point A to point B at the bonding interface is T _A −
It has a steep downward slope as shown in T _B , and as a result of joining, the eluted metal 6 drips on the end side of the pedestal 4, and on the opposite side, a joining defect 7 such as a notch occurs. It is something. This invention was made in order to eliminate the above-mentioned drawbacks, and in addition to a pair of main electrodes that sandwich the contact and the pedestal and are energized under pressure, it is electrically connected to one of the main electrodes, By providing an auxiliary electrode that contacts the pedestal, the present invention attempts to provide a resistance welding device that can uniformize the temperature rise at the bonding interface and achieve stable bonding. Hereinafter, one embodiment of the present invention will be described based on the drawings. In FIG. 4, reference numeral 8 denotes an auxiliary electrode, and a spring 9 is attached to one end surface, and the elastic pressure of this spring 9 causes the other end surface to move to the base 4.
It is in stable contact with the opposite end of the 1
0 is a shunt such as a copper wire, one end of which is electrically attached to the upper main electrode 1 and the other end of which is electrically attached to the auxiliary electrode 8, through which a part of the welding current flows. 11 is the auxiliary electrode 8 and spring 9
This is a guide that stores the auxiliary electrode 8 and prevents it from swinging laterally when it comes into contact with the pedestal 4 and moves up and down, and maintains a good contact state between the auxiliary electrode 8 and the pedestal 4. It is attached to the upper main electrode 1 in an insulated manner. In the above configuration, when the contact 3 and the pedestal 4 are energized under pressure, the welding current mainly flows from the upper main electrode 1 → the contact 3 → the pedestal 4 → the lower main electrode as shown by the solid arrow as shown in FIG. 2 (the reverse may also be the case), but part of it flows from upper main electrode 1 to shunt 10 to
The flow flows from the auxiliary electrode 8 to the pedestal 4 to the lower main electrode 2 (the reverse may also be the case), actively generating heat on the opposite side of the end of the pedestal 4. As a result, the temperature difference between points A and B at the bonding interface between the contact 3 and the pedestal 4 becomes extremely small as T _A - T _B , and bond defects 7 such as dripping of the eluted alloy 6 and notches occur. Therefore, a stable bonded portion with a good bonding layer 5 can be obtained. Further, in the above embodiment, the contact 3 and the pedestal 4
It goes without saying that the temperature rise at point B of the joint interface depends on the magnitude of the shunt current when the welding current is kept constant. The magnitude of this shunt current is determined by the electrical resistance between the shunt 10 and the pedestal 4. When the materials and dimensions of the shunt 10 and the auxiliary electrode 8 are constant, the contact area between the auxiliary electrode 8 and the pedestal 4, that is, the spring 9 Determined by pressure.
This was confirmed by the experimental results shown in Table 1 below, which shows the relationship between the pressure of the spring 9 and the shunt current value.

[Table] The optimum shunt current value that minimizes the temperature difference between points A and B at the bonding interface varies depending on the materials, shapes, dimensions, etc. of the contact 3 and the pedestal 4, and if these changes, the pressure of the spring 9 will change. It is necessary to select the appropriate value for the shunt current. FIG. 6 is a conceptual diagram showing another embodiment of the present invention, the feature of which is that by selecting the pressure of the spring 9 for pressing the auxiliary electrode 8 against the pedestal 4, the magnitude of the shunt current can be adjusted. The point is that it is controlled. Reference numeral 12 denotes a pressure adjustment screw for the spring 9, one end of which is in contact with the spring 9, and is screwed into the guide 11 with a screw machined on the side surface. Therefore, the pressure adjustment screw 12
By rotating the pressure adjustment screw, the pressure of the spring 9 can be adjusted. As in the above embodiment, the pressure adjustment screw 12 allows
By changing the pressure of the spring 9, the pressure of the spring 9 can be selected to an appropriate value, and the shunt current can be adjusted so that the temperature difference between points A and B at the bonding interface between the contact 3 and the pedestal 4 is minimized. The size of can be controlled. As a result, it is possible to obtain a more stable and better joint than in the case of the above embodiment, and even if the materials and dimensions of the contact 3 and the pedestal 4 are changed, springs with different spring constants or dimensions can be used. There is no need to change the spring pressure to 9 each time, and the spring pressure can be easily adjusted, which improves work efficiency. In the above embodiment, a spring was used as a means for pressing the auxiliary electrode, but any means capable of applying pressure, such as an air cylinder or a hydraulic cylinder, may be used. In addition, as a means of guiding shunt current to the auxiliary electrode,
Although a shunt such as a copper wire is used, a structure may be adopted in which a shunt current flows directly from the guide to the auxiliary electrode without insulating the upper main electrode and the guide. As described above, according to the present invention, it is possible to equalize the temperature rise at the bonding interface between the contact and the pedestal, and it is possible to achieve the effect of significantly improving the stability of the bonding.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram showing a conventional device, Fig. 2 is a conceptual diagram showing a joining state of the conventional device, Fig. 3 is an explanatory diagram for explaining the drawbacks of the conventional device, and Fig. 4 is an embodiment of the present invention. Conceptual diagram showing example resistance welding equipment, No. 5
The figure is a conceptual diagram showing a welding state in one embodiment of the present invention, and FIG. 6 is a conceptual diagram showing a resistance welding apparatus according to another embodiment of the invention. In the figure, 1 is an upper main electrode, 2 is a lower main electrode, 3 is a contact, 4 is a pedestal, 8 is an auxiliary electrode, 9 is a spring, 10 is a shunt, and 12 is a pressure adjustment screw. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A pair of main electrodes that sandwich contacts to be joined to each other and a pedestal extending in a predetermined direction from the contacts, and are energized under pressure, one of the main electrodes being electrically connected to the base. A resistance welding device comprising: an auxiliary electrode connected to the pedestal and brought into contact with an extension side of the pedestal; 2. Claim 1, wherein the auxiliary electrode is provided with a pressurizing means for pressurizing the pedestal.
Resistance welding equipment as described in section. 3. The resistance welding apparatus according to claim 2, wherein the pressurizing means includes a pressure regulating device. 4. The resistance welding device according to claim 2 or 3, wherein the pressurizing means is a spring.