| 摘要 |
PURPOSE:To improve the durability of a heating part and contrive to prevent the heating element from over-heating due to a self-control by a method wherein an electric current limiting resistance element is connected to a ceramic heater in series, the ceramic heater is made by sinter forming after imbedding of a heating wire made of high heat-resisting metal in a ceramic powder material. CONSTITUTION:A coil-shaped heating wire 2 is imbedded in a ceramic powder material which is mainly composed of Si3N4, SiC and the like, and preformed in cylindrical shape, then the ceramic is sintered by a hot-press method, thus, the external form of a ceramic heater 1 is finished by abrasion or grinding process. A metal outer cylinder 3 is fitted and brazed at the outer side of a rear half part, simultaneously, one end 2a of a heating wire 2 is connected to the outer side of the rear half part. The metal outer cylinder 3 is brazed to be (-) side electrode on a bore at the end part of a fitting 4, meanwhile, the other end 2b of the heating wire 2 is brazed to a cap 5 fitted to the rear end part of the ceramic heater 1, and connected to a metal coil-shaped resistance element 7 via a lead rod 6 welded to the cap 5, the other end of the resistance element 7 is welded to a center shaft 8. A heat-resistant insulating filler material 9 such as MgO or glass and the like is filled inside of the bore of the fitting 4 and the metal outer cylinder 3. The center shaft 8 is formed to be (+) electrode by locking and fixing to the fitting 4 with a circular nut 11 by interposing an insulating element 10 between the shaft and the fitting. |
