Patent ID: 8209958

Claim:
An engine exhaust emission purification apparatus comprising: a reduction catalytic converter disposed in an engine exhaust system to reduce and purify nitrogen oxides by using a liquid reducing agent, wherein the liquid reducing agent is a urea aqueous solution; an injection nozzle that supplies by injection the liquid reducing agent to a flow of an exhaust emission upstream from the reduction catalytic converter; a nozzle temperature detecting device for detecting a temperature of the nozzle of the injection nozzle; a temperature maintenance device for maintaining a temperature of at least a part of a liquid reducing agent supply system including the injection nozzle and piping of the injection nozzle at a temperature equal to or higher than a melting point of urea, wherein the temperature maintenance device comprises a heating device that heats at least a part of the liquid reducing agent supply system and a heating control device that controls the heating device, and wherein the heating control device controls actuation of the heating device based on the temperature of the nozzle detected by the nozzle temperature detecting device.