MULTIPOLAR SPARK PLUG

Japanese Patent JP3874840

B2

PROBLEM TO BE SOLVED: To improve the ignition property by forming a central electrode tip with a large diameter, setting the outer diameter of the large diameter part larger than the outer diameter of the central electrode by a prescribed value, and setting (thickness of large diameter part)/(axial distance of discharge surface) to a prescribed value.
SOLUTION: A dipolar spark plug A has a central electrode tip 32 formed with a large diameter, the outer diameter d2 (&phiv 2.5) of this large diameter part 31 is set larger than the outer diameter d1 (&phiv 2.0) of a central electrode 3 by 0.5mm, and [thickness T1 (0.4mm) of the large diameter part 31]/[axial distance L (1.5mm) of discharge surface] is set to about 0.27. Since a spark discharge is thus caused between a discharge surface front side 411 and the part 31, A/F lean limit is improved by about 1, and satisfactory ignition property can be held. Further, since the diameter difference is 0.5mm, the temperature of the large diameter part (central electrode 3 tip) is never remarkably increased, and the wear of the electrode tip part by spark discharge is minimized. Thus, in the plug A, the reduction in spark wear resistance of the electrode 3 is almost eliminated by providing the part 31.

JP4434509	Spark plug
WO/2010/038611	SPARK PLUG FOR INTERNAL COMBUSTION ENGINE

Kozo Amano
Yoshihiro Matsubara

JP14691796A

January 31, 2007

June 10, 1996

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Nippon Special Ceramics Co., Ltd.

H01T13/20; H01T13/46; (IPC1-7): H01T13/46; H01T13/20

JP61253785A
JP2204988A
JP59071280A
JP7235363A
JP4196080A
JP1176690A
JP5644464A
JP5667186A
JP1161691A
JP2220385A
JP8171976A
JP57188284U
JP62195993U

Kenji Ishiguro

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