Patent ID: 8418668

Claim:
An ignition device for an internal-combustion engine comprising: an electrode structure body comprising an anode, a cathode and a floating electrode; and a pulse power supply to apply a pulse voltage between said anode and said cathode; wherein: a discharge contributing part of said cathode is positioned to be a first distance away from a discharge end of said anode along a surface of said electrode structure body; a discharge contributing part of said floating electrode is positioned to be a second distance shorter than said first distance, away from the discharge end of said anode along the surface of said electrode structure body, and interposed between the discharge end of said anode and the discharge contributing part of said cathode; and said pulse power supply applies a relatively low pulse voltage between said anode and said cathode to generate a pulse discharge in a first discharge region between the discharge end of said anode and the discharge contributing part of said floating electrode, and then applies a relatively high pulse voltage thereto to generate a pulse discharge in a second discharge region between the discharge end of said anode and the discharge contributing part of said cathode.