Wegner & Bretschneider
Wide thermal range spark plug
 A spark plug including an insulator body provided with a center bore and a bottom end defining a discharge end of the insulator body and a discharge center electrode formed in a region of the discharge end of the insulator body; a spark plug including thermal conductivity-controling material comprising spherical metal powder as an essential element thereof in the center bore providing function to control thermal conductivity of the spark plug. The conductivity controling material further comprises refractory powder and glass powder. The controling material is also composed of spherical metal powder coated with a ceramic layer of a mixture thereof with the spherical metal powder. The spark plug with the controling material permits an increasing conductance according to temperature rise to provide a thermally wide-ranged spark plug. 
NGK Spark Plug Co., Ltd.
F H
F02B H01T
additional inventional
Shunichi Kanemitsu Yasuhiko
Takagi Nishio Suzuki