PURPOSE: To secure the sufficient durability against the thermal stress caused by the temperature difference between a center electrode and an outer cylinder by providing a shed part on a projecting part of the center electrode, and combining this cap part with the outer cylinder in the axial direction of the center electrode in a compressive manner.
CONSTITUTION: A honey-comb shaped carrier 4 is formed by coiling metallic foils 2, 3 around a center electrode 1, and at the same time, the carrier 4 is stored and mounted so as to be brought into internal contact with an outer cylinder 5 constituting the other electrode. The center electrode 1 is made to penetrate the outer cylinder 5 to be projected outward, and the catalyst is heated by supplying an electric current between the projected part of the center electrode 1 and the outer cylinder 5. In particular, a shed part, i.e., a collar part 11 of an electrode seat 7 is provided on the projected part of the center electrode 1, and this collar part 11 and the outer clinder 5 are combined with each other in the axial direction of the center electrode 1 in an expandable manner. Thus, the thermal stress of the center electrode 1 is absorbed by a compressively combined part 12 between the collar part 11 of the electrode seat 7 and the outer cylinder 5, and the durability can be secured without exertion of the shearing force and bending moment.
NIPPON SOKEN
NIPPON STEEL CORP