Patent ID: 7758833

Claim:
An exhaust gas purifying apparatus for an internal combustion engine, said exhaust gas purifying apparatus comprising: NOx removing means provided in an exhaust system of said engine; a particulate filter provided in said exhaust system; temperature detecting means for detecting a temperature of said exhaust system; sulfur oxide removing means for performing a process for removing sulfur oxide accumulated in said NOx removing means by supplying reducing components to said exhaust system so as to place the exhaust gases of said engine in a reducing state; regeneration means for performing a regeneration process for burning particulates trapped in said particulate filter by performing a temperature control operation so that the exhaust system temperature coincides with a target temperature; and switching control means for performing a switching control which makes said sulfur oxide removing means and said regeneration means alternately operate, when it is determined to be necessary to perform at least one of removal of the sulfur oxide in said NOx removing means and regeneration of the particulate filter, wherein said switching control means stops operation of said regeneration means when the exhaust system temperature stays in a predetermined control range in the vicinity of the target temperature for a predetermined time period during the operation of said regeneration means, and starts operation of said sulfur oxide removing means, wherein said switching control means stops operation of said sulfur oxide removing means when the exhaust system temperature has deviated from a predetermined limit range during the operation of said sulfur oxide removing means, and starts operation of said regeneration means.