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US 5,565,157 AGranted
Method of making a spark plug insulator
AssigneeNgk Spark Plug Co., Ltd.
InventorsMakoto Sugimoto, Masahiro Konishi, Hiroyuki Tanabe, Kenichi Nishikawa
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Abstract
In a spark plug insulator for use in an internal combustion engine, a sintered body has boron nitride and a metal oxide, the boron nitride of the sintered body being 80% or exceeding 80% by weight, and the sintered body having a thermal expansion coefficient of less than 5.0.times.10-.sup.6 /.degree.C. The metal oxide is selected alone or combination from the group consisting of magnesium oxide, calcium oxide, silicon oxide, boron oxide, yttrium oxide and aluminum oxide.
Claims2
A method of making a spark plug insulator comprising steps of:
- mixing a powder of boron nitride (BN), an additive and ethanol to form a mixture within a nylon pot mill by means of nylon ball, the boron nitride being 80% or exceeding 80% by weight;
- drying the mixture for about 10 hours in a vacuum environment;
- pulverizing the dried mixture so that its grain size is less than 350 .mu.m;
- forcing the pulverized mixture into a tubular carbon die;
- sintering the mixture in the carbon die by means of hot press in a nitrogen atmosphere under about 50 MPa at 1800.degree..about.1900.degree. C. for 5.about.10 hours so as to form a boron nitride based compact body;
- and
- releasing the boron nitride based compact body from the carbon die.
4 more elements
Dependencies are inferred from the claim text.