Spark plug construction

摘要

A spark plug is disclosed and comprises: a metal tube which interiorly defines an axis and is externally-threaded for engine block engagement; an insulator having a portion which is disposed inside the tube and extends therebeyond; a positive electrode extending through the insulator and projecting beyond the extending portion of the insulator; and an annular ground electrode coupled to the tube. The electrodes are configured such that a spark gap defined therebetween comprises an elongate channel which opens axially and away from said insulator and is substantially unobstructed in the axial direction. The ground defines a void having: a central portion occupied by the positive electrode in use; an annular channel surrounding the central portion; and a plurality of lobes, each being positioned with respect to the central portion in a manner analogous to the placement of the planet gears with respect to the sun gear in a planetary gear.

主权项

1. A spark plug for use with an engine block/cylinder head, said spark plug comprising:
a metal tube which is orientated coaxially about and defines a longitudinal axis and is externally-threaded for engagement in a corresponding threaded bore in said engine block in use; an insulator having a portion disposed inside the tube, which portion extends axially beyond the tube; a positive electrode extending through the insulator and projecting beyond the portion of the insulator that extends beyond the tube; a ground electrode coupled to the metal tube, wherein the positive and ground electrodes are configured such that a spark gap defined between the positive and ground electrodes comprises an elongate channel which opens axially and away from said insulator and is substantially unobstructed in the axial direction; wherein the ground electrode is annular and defines a void having: a central portion which is occupied by the positive electrode in use; an annular channel surrounding the central portion; a plurality of lobes, each being positioned with respect to the central portion in a manner analogous to the placement of the planet gears with respect to the sun gear in a planetary gear; wherein the plurality of lobes consists of three to seven lobes; and, wherein if R1 is the radius of each lobe R2 is the distance from the axis of each lobe to the axis of the central portion R3 is the outer radius of the ground electrode R4 is the outer radius of the annular channel R1:R2:R3:R4:R5 is about 0.12: 0.305: 0.475: 0.25.