Spark plug and method of manufacturing the same
US6274971A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 18, 1999 |
| Grant date | Aug 14, 2001 |
| Priority date | — |
| Expiry date | May 18, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01T13/38
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A glaze layer formed on the surface an alumina-based insulator of a resistor spark plug contains SiO.sub.2 (18 to 35% by weight), B.sub.2 O.sub.3 (25 to 40% by weight), ZnO (10 to 25% by weight), BaO (7 to 20% by weight), Na.sub.2 O (3 to 9% by weight), and K.sub.2 O (3 to 9% by weight). Since the difference between the coefficients of linear expansion of the glaze and that of the alumina-based insulating material is relatively small, the glaze layer is less susceptible to cracks and the like. Also, since the glaze has a softening point lower than that of conventional lead-silicate-glass-based glaze, the glost-firing temperature can be as low as 800.degree. to 950.degree. C. Therefore, even in the case where glost firing is performed concurrently with a glass sealing step, a center electrode and a terminal metal piece are less susceptible to oxidation. Further, even though the content of the alkali metal component is high, a good insulating performance is obtained so that excellent flashover resistance is attained.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.