To restrain flash-over while maintaining durability of an electrical insulator.
A spark plug comprises: an electric insulator having a shaft hole penetrating in an axial line direction, and having a step part projecting outward in a radial direction on its own outer periphery; a center electrode provided on a tip side of the shaft hole; a cylindrical main metal fitting having a receiving part projecting inward in the radial direction on its own inner periphery, and holding the electric insulator while the step part is locked with the receiving part; and a packing arranged between the step part and the receiving part and contacting them. In the electric insulator, arithmetic average roughness Ra1 of an outer surface of a portion nearer the tip side than a position contacting the packing is 3 μm or more and 15 μm or less.
| JP6313745 | Corona igniter with improved electrical performance |
| JP2006120649 | SPARK PLUG AND IGNITION APPARATUS UTILIZING THE SAME |
| JP3902756 | SPARK PLUG |
SAJI TOSHIMASA
HONDA TOSHITAKA
| JP2003303661A | 2003-10-24 | |||
| JPH06176848A | 1994-06-24 | |||
| JPH0476289U | 1992-07-03 | |||
| JP2002175863A | 2002-06-21 |
| WO2010082409A1 | 2010-07-22 |
Yoko Matsuoka
Next Patent: SOLID BATTERY AND METHOD FOR MANUFACTURING THE SAME