Patent ID: 8963408
Filing Date: 2015-02-24
Classification: H01T

Abstract:
1. A spark plug for internal combustion engines, comprising: a cylindrical housing formed to have a top end portion, wherein the housing has a length-wise direction defined as an axial direction, a circumferential direction, a radial direction, and the housing has a tip-end side and a base-end side in the axial direction; a cylindrical insulation porcelain held inside the housing; a center electrode formed to have a top end portion and held inside the insulation porcelain such that the top end portion protrudes from the insulation porcelain; a ground electrode which protrudes from the top end portion of the housing such that there is left a spark discharge gap between the ground electrode and the center electrode; a first projection which projects from a first position on the top end portion of the housing to the tip-end side, the first position being set to be opposed to the ground electrode with the center electrode therebetween, a second projection which projects from a second position on the top end portion of the housing to the tip-end side, the second position being closer to the ground electrode than to the first projection, and a third projection which projects from a third position on the top end portion of the housing to the tip-end side, the third position being closer to the first projection than to the ground electrode, wherein the second and third projections have widths in the circumferential direction, wherein the widths are smaller than a width of the ground electrode in the circumferential direction at positions of the second and third projections, the positions of the second and third projections being the closest to the spark discharge gap in the axial direction.