Corona igniter having controlled location of corona formation

摘要

A corona igniter 20 includes an insulator 28 surrounding a central electrode 24 and a shell 30 surrounding the insulator 28. The shell 30 presents a shell gap 38 having a shell gap width ws between a shell lower end 34 and a shell inner surface 90 or shell outer surface 92. The shell 30 has a shell thickness ts decreasing toward the shell lower end 34 allowing the shell gap width ws to increase toward the shell lower end 34. The shell gap 38 is open at the shell lower end 34 allowing air to flow therein, and the shell gap width ws is greatest at the shell lower end 34. The increasing shell gap width ws enhances corona discharge 22 along the insulator 28 between the central electrode 24 and shell 30.

主权项

1. A corona igniter for providing a corona discharge, comprising:
a central electrode formed of an electrically conductive material extending from an electrode terminal end for receiving a high radio frequency voltage to an electrode firing end for emitting a radio frequency electric field to ionize a fuel-air mixture and provide a corona discharge, said central electrode including a firing tip extending radially outwardly from said electrode firing end to present a tip diameter, an insulator formed of an electrically insulating material disposed around said central electrode and extending longitudinally from an insulator upper end to an insulator nose end, said insulator presenting an insulator outer surface extending between said insulator upper end and said insulator nose end, said insulator presenting an insulator nose diameter at said insulator nose end being less than said tip diameter of said firing tip, a shell formed of an electrically conductive metal material disposed around said insulator and extending longitudinally from a shell upper end toward said insulator nose end to a shell lower end, said shell presenting a shell inner surface facing said insulator outer surface and a shell outer surface extending between said shell lower end and said shell upper end, said shell presenting a shell gap having a shell gap width (ws) between said insulator outer surface and said shell inner surface, said shell gap being open at said shell lower end allowing air to flow therein, and said shell gap width (ws) increasing toward said shell lower end.