Patent ID: 6865882

Claim:
A device for purifying exhaust gas of a diesel engine, said device comprising: a first continuous regeneration type diesel particulate filter arranged in the exhaust gas passage of the diesel engine, said first continuous regeneration type diesel particulate filter including a diesel particulate filter member and a catalyst positioned on the upstream side of said diesel particulate filter member; a by-path having a first end connected to the exhaust gas passage upstream of said first continuous regeneration type diesel particulate filter, and a second end connected to the exhaust gas passage upstream of said first continuous regeneration type diesel particulate filter so that said by-path bypasses a portion of the exhaust gas passage on the upstream side of said first continuous regeneration type diesel particulate filter; a second continuous regeneration type diesel particulate filter disposed in said by-path, said second continuous regeneration type diesel particulate filter including a diesel particulate filter member and a catalyst positioned on the upstream side of said diesel particulate filter member; a change over valve for changing over the flow passage of the exhaust gas, arranged in said exhaust gas passage between the first end and the second end of said by-path; exhaust gas temperature-elevating means for elevating the temperature of the exhaust gas of the diesel engine; exhaust gas temperature region detecting means for detecting the exhaust gas temperature region of the diesel engine; and control means for controlling said exhaust gas temperature-elevating means and said change-over valve based on the exhaust gas temperature region of the diesel engine, detected by said exhaust gas temperature region detecting means; wherein, when the exhaust gas temperature region of the diesel engine, detected by said exhaust gas temperature region detecting means, is a temperature region lower than a predetermined temperature region, said control means actuates said exhaust gas temperature-elevating means and controls said change-over valve so that the exhaust gas passes through said second continuous regeneration type diesel particulate filter.