Patent ID: 8847494

Claim:
An ignition system for a plasma jet ignition plug comprising: a plasma jet ignition plug having a center electrode, a ground electrode, and a cavity surrounding at least a portion of a gap formed between the center electrode and the ground electrode to form a discharge space; a voltage application section for applying voltage across the gap, wherein the voltage is supplied to the gap solely by said voltage application section; a plug cap unit having an electrical conductor electrically connecting the plasma jet ignition plug and a plug cord to which voltage from the voltage application section is applied and that is connected to the plasma jet ignition plug; a capacitance section having a capacitance and provided in parallel with the plasma jet ignition plug, said capacitance section comprising: an electrical conductor that is electrically connected to both the plasma jet ignition plug and the voltage application section at a location between the plasma jet ignition plug and the voltage application section, and a unit built-in section having a capacitance equal to or greater than that of the plasma jet ignition plug, the unit built-in section built into the plug cap unit, wherein the capacitance section is connected at one end to the electrical conductor of the plug cap unit and is grounded at the other end; and a shield formed of a conductive material, said shield is grounded and disposed around the unit built-in section and the electrical conductor, wherein the shield and the electrical conductor have a capacitance of 25 pF or less between the shield and the electrical conductor.