Patent ID: 7618596

Claim:
An exhaust gas purification system comprising a first honeycomb filter comprising a honeycomb structure having a large number of through channels formed in the axial direction and partitioned by porous partition walls, each of the through channels having a first end at one end of the filter and a second end at an opposite end of the filter, wherein a first group of the through channels have a relatively large open area of cell in a cross-section parallel to the end face and are plugged only at the first end, and a second group of the through channels have a relatively small open area of cell in the end face cross-section and are not plugged, wherein there is further installed behind said first honeycomb filter a second honeycomb filter comprising a honeycomb structure having a large number of through channels formed in the axial direction and partitioned by porous partition walls; a first group of the through channels of the second honeycomb filter being plugged only at a first end and a second group of the through channels of the second honeycomb filter being plugged only at a second end, and the cross-sectional areas of the through channels are substantially uniform in the axial direction.