PURPOSE: To determine the axial direction length of the electric discharge connection area of a metal foil before connection to be larger than the same length of the non-electric discharge connection area in the carrier for purification of an exhaust gas from an automotive internal combustion engine, and restrict the spread of an electric current route to enhance thermal efficiency.
CONSTITUTION: A metal corrugated foil 11 and a metal plane foil 12 of aluminum-containing stainless steel are connected partially at a part where both foils come in contact with each other using a laser beam welding method. Then the foils are baked in air or an oxidation atmosphere to prepare a heater foil coated with insulating oxide. In this case, the length in an axial direction of a part corresponding to both inner peripheral part 15 and euter peripheral part 16 of a winding is determined to be larger than the length in an axial direction of a part against an intermediate part 17 by the length of a part which is molten by electric discharge connection, when the corrugated foil 11 and the plane foil 12 are wound around a center electrode 13 in the form of a multi-layer. That is, the longitudinal width of the inner peripheral part 15 and the outer peripheral part 16 is greater the than longitudinal width of the intermediate part 17.
YOSHINAGA TORU
FUJISHIRO OSAMU
NIPPON SOKEN
NIPPON STEEL CORP