| 摘要 |
A ceramic sintered body fitted into an inner hole through a cylindrical metal outer pipe in the state in which the front end side of the ceramic sintered body is protruded out from the front end of an metal shell, includes: a heating portion to which a positive-pole-side lead is connected in the front end side; and a positive-pole-side electrode lead-out portion having a positive-pole-side electrode portion which is extendedly provided from the positive-pole-side lead in the rear end side. Further, the outer diameter of the positive-pole-side electrode lead-out portion is set to be smaller than that of the negative-pole-side electrode lead-out portion so that the positive-pole-side lead is substantially linear and a sufficient insulation distance between the metal shell functioning as a negative-pole-side terminal and the positive-pole-side lead coil can be secured.
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