Honeycomb filter and exhaust gas purification system

Abstract

A honeycomb filter is provided comprising a honeycomb structure having a large number of through channels formed in an 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 are plugged only at the first end, and a second group of the through channels are not plugged. A honeycomb structure is further provided having through channels with a relatively large frontal area and through channels with a relatively small frontal area, and wherein all the through channels with a relatively large frontal area are the first group, and all the through channels with a relatively small frontal area are in the second group. A honeycomb filter is also provided with a catalyst component carried on a surface of the partition walls and / or a surface of pores present in an inside of the partition walls.

Description

[0001]This is a Continuation of application Ser. No. 10 / 778,051 filed Feb. 17, 2004. The disclosure of the prior application is hereby incorporated by reference herein in its entirety.FIELD OF THE INVENTION AND THE RELATED ART STATEMENT[0002]The present invention relates to a honeycomb filter used to collect particulate matters in exhaust gas discharged from combustion engines such as a diesel engine.[0003]A large amount of particulate matters (fine particulate substances) including soot (a black smoke of carbon) as a major component are contained in exhaust gas discharged from a diesel engine, gasoline lean burn engine, or gasoline direct-injection engine. Since particulate matters cause environmental pollution if emitted into the atmosphere, a filter to collect the particulate matters is mounted in the exhaust gas system for a diesel engine.[0004]The honeycomb filter used for such a purpose has a honeycomb structure having many through channels 13 partitioned by porous partition w...

AI Technical Summary

Problems solved by technology

However, the honeycomb filters of the above configuration have a problem of a high pressure loss since all through channels are plugged on one end face.

However, in a conventional honeycomb filter, solids such as ash and iron oxide which cannot be removed by combustion are gradually accumulated and clog the filter.

Therefore, such conventional honeycomb filters have a problem in thermal shock resistance due to heat expansion and the like of the plugging portions on the end face on the inlet port side.

For this reason, it has been difficult to use such filters for purifying exhaust gas from gasoline engines discharging exhaust gas at a temperature higher than that of diesel engines in a temperature fluctuation range greater than that of diesel engines.

In addition, particulate matters adhere to the plugging portions of through channels on the end face on the exhaust gas inlet port side of the honeycomb filters and deposit around the adhered particulate matters as a core, causing even the openings of the through channels of which the end face is not plugged on the exhaust gas inlet port side to clog.

This causes another problem of rapidly increasing a pressure loss in the filter.

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