| 摘要 |
PURPOSE: To perform high reliable welding between sheet metals of conductive material by measuring resistance in the vicinity of a zone to be welded between sheet metals lapped for welding, and comparing a measured value with a predetermined value. CONSTITUTION: Two sheet metals of conductive material are touchingly arranged in a zone to be welded. Next, a first and second electrodes placed over an area to be welded are brought into contact with the top face of the upside sheet metal. A small electric current is caused to flow between these two electrodes to measure a resistance. When this measured value exceeds a predetermined value, contact condition between the sheet metals and the electrodes is improved. Secondly, a resistance between at least one of the first and second electrodes mentioned above and a third electrode which is brought into contact with the lower sheet metal in the place adjacent to the area to be welded is measured. When this measured value is compared with the predetermined value and is smaller than the latter, the both sheet metals are welded by supplying electric welding energy between the first and second electrodes. On the other hand, when the measured value mentioned above exceeds the predetermined value, the vicinity of a zone to be welded of the both sheet metals is applied with cleaning treatment, and welding is performed under condition in which a measured value is smaller than the predetermined value.
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