Patent ID: 7808166

Claim:
A spark plug comprising: a tubular metal shell having an end; an insulator retained in the metal shell with an end thereof protruding from the end of the metal shell; a center electrode secured in the insulator such that an end of the center electrode protrudes from the end of the insulator; and a ground electrode including a proximal portion, a distal portion, and an intermediate portion between the proximal and distal portions, the proximal portion being fixed to the end of the metal shell and extending in an axial direction of the center electrode in an axial range between the ends of the metal shell and the insulator, the distal portion extending first in the axial direction of the center electrode and then in a radial direction of the center electrode to face the end of the center electrode in the axial direction through a spark gap formed therebetween, the intermediate portion extending in the axial direction of the center electrode in an axial range between the ends of the insulator and the center electrode, the intermediate portion having a thickness surface that is perpendicular to the radial direction of the center electrode in which the distal portion of the ground electrode extends and defines a thickness L 3 of the intermediate portion in a thicknesswise direction of the intermediate portion, the thicknesswise direction being perpendicular to both the axial direction of the center electrode and the radial direction of the center electrode in which the distal portion of the ground electrode extends, the intermediate portion also having a width surface that is perpendicular to the thickness surface and defines a width L 4 of the intermediate portion in a widthwise direction of the intermediate portion, the widthwise direction being perpendicular to both the thicknesswise direction and the axial direction of the center electrode, the thickness L 3 of the intermediate portion being smaller than the width L 4 of the intermediate portion.