Exhaust gas cleaner for engine

Abstract

An exhaust gas cleaner of an engine in which cleaning efficiency of Nox is enhanced by preventing clogging of an injection nozzle for supplying a reducing agent to the upstream side of exhaust gas of a reducing catalyst. Using a detection signal S1 of the exhaust gas temperature from an exhaust gas temperature sensor (9), a reducing agent supply unit (6) sets a supply quantity larger than a lower limit of the supply quantity for cooling the inside of an injection nozzle (5) at a temperature below the crystallizing point of urine water and supplies the set supply quantity of urine water to the injection nozzle (5) at the detected exhaust gas temperature. Consequently, the inside of the injection nozzle (5) is cooled at a temperature below the crystallizing point of urine water. Since urine water is not crystallizing in the injection nozzle (5), the injection nozzle (5) can be prevented from clogging and the cleaning efficiency of Nox can be enhanced.

Description

technical field [0001] The present invention relates to an exhaust purification device that uses a reducing agent to reduce and remove nitrogen oxides (NOx) discharged from a diesel engine, a gasoline engine, etc. mounted on a mobile vehicle, and particularly relates to a nozzle that prevents the supply of the reducing agent to the upstream side of the exhaust gas of the reduction catalyst It is an engine exhaust purification device that eliminates the clogging of the nozzle and improves the efficiency of NOx purification treatment when the nozzle is clogged. Background technique [0002] Several exhaust gas purification devices have been proposed as systems for purifying exhaust gas by removing, in particular, NOx among particulate matter (PM) in exhaust gas discharged from an engine. This exhaust purification device is a device that installs a reduction catalyst in the exhaust system of the engine, injects and supplies a reducing agent into the exhaust passage on the upstr...

AI Technical Summary

Problems solved by technology

[0006] However, when the reducing agent supply mechanism is a so-called pneumatic reducing agent supply means that supplies compressed air while supplying urea water to the nozzle, and sprays the urea water after spraying, the compressed air normally supplied to the nozzle cools the inside of the nozzle. , so the temperature inside the nozzle will not rise to 132°C or above, hindering the melting of solid urea

Therefore, crystallized and solidified solid urea may adhere to the inside of the nozzle, causing clogging of the nozzle.

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