US Patent 7354558 Exhaust gas purification system

An exhaust gas purification system includes a honeycomb structural member and a center electrode. The honeycomb structural member is disposed in an exhaust emission flow path from an engine. The center electrode extends along an axis of the honeycomb structural member from an upstream side thereof. A voltage of a polarity opposite from the polarity of the honeycomb structural member is applied to the center electrode. Sub-electrodes are further provided for controlling an electric field between the center electrode and the honeycomb structural member.