Exhaust gas emission control device i.e. selective catalytic reduction system, for e.g. diesel engine, has urea solution injecting valve opening based on freezing condition change to convey agent remaining in supplying circle into pipe

摘要

The device has an electronic control unit (ECU) (30) opening a urea solution injecting valve (15) to inject the agent from a reducing agent supplying mechanism, into an exhaust pipe (11) to induce a specific emission control reaction in an exhaust gas catalyzer. The ECU monitors a freezing condition change after stopping of an engine and a change of the agent remaining in a reducing agent supplying circle including the mechanism and the valve, from liquid to solid phase. The valve opens based on the monitored change to convey the agent that is remaining in the circle, into the pipe.