Patent ID: 6603246
Filing Date: 2003-08-05
Classification: H01T

Abstract:
A spark plug used for cogeneration purpose and requiring a re-gapping adjustment after a period of use, comprising:a central electrode; an insulator provided around said central electrode; a metal fitting provided around said insulator; a grounding electrode having one end connected to said metal fitting and the other end located in opposed relationship with said central electrode; and noble metal tips attached on opposed surfaces of said central electrode and said grounding electrode, wherein a discharging gap is formed between the noble metal tip of said central electrode and the noble metal tip of said grounding electrode, said noble metal tips of the electrodes are disposed in such a manner that said discharging gap has a first gap at one side closer to said one end of said grounding electrode and a second gap at an opposite side closer to said other end of said grounding electrode, with said first gap being shorter than said second gap, a first straight line connecting both edges of said noble metal tip attached on said grounding electrode inclines by an angle &agr; of 2Â° to 10Â° with respect to a second straight line connecting both edges of said noble metal tip attached on said central electrode, where said both edges of said noble metal tip of said grounding electrode and both edges of said noble metal tip of said central electrode cooperatively define said first gap and said second gap, and a minimum distance of said discharging gap is within a range from 0.2 mm to 0.5 mm.