Foley & Lardner
Ceramic heater
 The invention relates to a ceramic heater for use, e.g., as a glow plug for a diesel engine or as an igniter for an oil or gas burner. The ceramic heater has a nonoxide ceramic body having a heating part and a supporting part and a heating resistor embedded in the heating part of the ceramic body. The material of the heating resistor is W, WC, tungsten alloy or a metal nitride such as TiN or TaN. According to the invention the heating part of the ceramic body is formed of aluminum nitride ceramic, which is high in heat conductivity and resistant to oxidation at high temperatures, at least in a core region in contact with the heating resistor, and the supporting part is formed of silicon nitride ceramic which is low in heat conductivity at least in a surface region. The ceramic body is made by uniting a heating part entirely formed of aluminum nitride ceramic and a supporting part entirely formed of silicon nitride ceramic with interposal of a joint part which is formed of mixed ceramic of aluminum nitride and silicon nitride with a gradient of the proportion of aluminum nitride to silicon nitride, or by thoroughly covering a core formed of aluminum nitride ceramic with silicon nitride ceramic. 
NGK Spark Plug Co., Ltd.
H F H
H05B F23Q H05B
inventional inventional inventional
Kazuho Kiminori Yasuhiko Masakazu Shunkichi
Tatematsu Horiki Suzuki Iwai Nozaki