The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 16, 2000
Filed:
Apr. 14, 1999
Chiaki Kumada, Gifu, JP;
NGK Spark Plug Co., Ltd., Nagoya, JP;
Abstract
A glow plug has a sheath heater, a heating coil and a control coil. The sheath heater has a sheath tube having a closed leading end. The heating coil is disposed adjacent to the leading end of a projection of the sheath tube beyond a main metal shell. The control coil is connected in series to the rear end of the heating coil and arranged to be heated by the heating coil to raise the electrical resistance to control the supply of electric power to the heating coil. The projection of the sheath tube has a substantially uniform outer diameter in the axial direction and the outer diameter is between 3.0 mm to 4.4 mm. Therefore, a temperature rising characteristic at the surface of the leading end of the sheath tube has a peak temperature TP in an initial stage of energization and saturates at a temperature not higher than the peak temperature TP.