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US 6,632,381 B2Granted
Production process for alumina based insulator
AssigneeNgk Spark Plug Co., Ltd.
InventorMakoto Sugimoto
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AssigneeNgk Spark Plug Co., Ltd.
InventorMakoto Sugimoto
Estimating the term…
In insulator including alumina as a main component, a Na component in the insulator is set in the range of 0.07 to 0.5 wt % as Na2O. While the Na component content is as high as to have conventionally been regarded to be beyond the common sense, with this range of the Na component content, insulation resistance, mechanical strength and the like at high temperature are unexpectedly not reduced and an insulator with performances comparable to those of an insulator from conventional low soda alumina lower in Na component content than the above described range can be obtained. As a result, medium soda alumina and regular soda alumina that are much lower in cost than conventionally used low soda alumina can be used instead of the low soda alumina, so that dramatic reduction in production costs of insulator 2 for a spark plug 100 and in addition, of the spark plug 100 using the insulator 2 are realized.
A production process for an alumina based insulator for a spark plug, wherein a raw material powder prepared by mixing additive element based raw materials including one or more selected from the group consisting of Si, Ca, Mg, Ba, Zn and B components at a total content in the range of 0.1 to 15 parts by weight respectively as values converted into SiO2, CaO, MgO, BaG, ZnO and B2O3 into 85 to 98 parts by weight of alumina powder, and including an alumina powder having a Na component content of from 0.07 to 0.65 wt % as a value converted into Na2O, the powder particles of which have in the surface regions a Na component in the range of 0.01 to 0.2 wt % as a value converted into Na2O as a main component, is formed into a prescribed insulator shape as a green body and the green body is sintered,
Dependencies are inferred from the claim text.