Exhaust gas purifying apparatus for engine

An exhaust gas purifying apparatus for an engine comprising:

• a reduction catalyst which is arranged in an exhaust system of an engine, for reducing and purifying nitrogen oxide in an exhaust gas using a reducing agent;
• reducing agent supply means having an injection nozzle which is supplied with a reducing agent together with compressed air and atomizes said reducing agent, and which injection-supplies this to an exhaust gas on an upstream side of said reduction catalyst inside an exhaust gas passage of said exhaust system;
• and
• temperature detection means which is provided in the vicinity of said injection nozzle on the upstream side of the exhaust gas passage, and which detects the exhaust gas temperature inside said exhaust gas passage;
• wherein
• said reducing agent supply means is provided with pressure detection means for detecting an internal pressure of said injection nozzle, and uses a detection signal of the internal pressure of said injection nozzle to stop supply of compressed air and reducing agent to the injection nozzle when the internal pressure reaches or exceeds a predetermined value, and uses a detection signal of the exhaust gas temperature from said temperature detection means to restart supply of compressed air and reducing agent to the injection nozzle when the exhaust gas temperature in the vicinity of the injection nozzle reaches or exceeds the melting point of the reducing agent.