Method for producing a ceramic filter for cleaning exhaust gases from a diesel engine

A method for producing a filter composed of an exhaust gas cleaning portion which collects carbon particulates in the exhaust gases emitted from a diesel engine and has an outer peripheral side surface and an outer wall portion which is formed around said side surface so as to be integral therewith, and of which the bulk density is greater than that of said cleaning portion and increases by stages toward the outer surface of said wall portion;

• comprising the steps of:
• winding a plurality of foamed sheets of which the cell density is different from one another around the outer peripheral side surface of an organic foamed body which has a three dimensional network structure provided with a large number of interconnected fine pores, which is formed of the same kind of material as that of said foamed sheets and which has a cell density smaller than that of said foamed sheets, so that the sheet having the larger cell density is outermost;
• immersing said foamed body around which said foamed sheets are wound, into a ceramic slurry bath to adhere said slurry to said foamed body and said foamed sheets;
• drying said slurry adhered to said foamed body and said foamed sheets;
• said immersing and drying steps being repeated until the pores of said outermost sheet are closed by said slurry;
• and
• firing said foamed body and sheets and said dried slurry adhered thereto.

A method for producing a filter composed of an exhaust gas cleaning portion which collects carbon particulates in the exhaust gases emitted from a diesel engine and has an outer peripheral side surface, and an outer wall portion which is formed around said side surface so as to be integral therewith, and of which the bulk density is larger than that of said cleaning portion and increases continuously toward the outer surface of said wall portion;

• comprising the steps of:
• applying pressure to the outer peripheral side surface of an organic foamed body having a three dimensional network structure provided with a large number of interconnected fine pores, while heating said body, so that the bulk density of said body continuously increases toward the outer peripheral side surface thereof,
• immersing said foamed body into a ceramic slurry bath to adhere said slurry to said foamed body;
• drying said slurry adhered to said body;
• said immersing and drying steps being repeated until the pores of said outer peripheral side surface of said body are closed by said slurry;
• and
• firing said foamed body and the dried slurry adhered thereto.