Exhaust gas purifying device of internal combustion engine

Abstract

An exhaust emission control device of an internal combustion engine capable of satisfactorily atomizing a reducing agent and surely securing combustion air. Since the controller of the exhaust emission control device controls the nozzle opening of a variable discharge turbo for spraying urea water, even when the engine is in a low load area of T1 to T2 and a supercharging pressure does not rise normally, the supercharging pressure P suitable for spraying the urea water can be provided by controlling the nozzle opening of the variable discharge turbo so as to be closed more than a normal one (chain double-dashed line), and the urea water can be securely atomized by a part of the supercharging air. Also, since the amount of combustion air supplied to the engine is increased by raising the supercharging pressure to P, satisfactory combustion can be realized and the generation of particulates and the discharge of unburned fuel can be suppressed.

Description

[0001] technology area [0002] The present invention relates to an exhaust gas purifying device for an internal combustion engine, and in particular, to an exhaust gas purifying device that is installed in an exhaust gas passage of an internal combustion engine with a variable exhaust turbocharger and purifies exhaust gas by supplying a reducing agent. Background technique [0003] Currently, it is known that in order to collect particulates (particulate matter) in exhaust gas discharged from internal combustion engines such as diesel engines and reduce NO X amount, and an exhaust gas purification device is installed in the exhaust gas passage of the internal combustion engine. [0004] As an exhaust gas purification device that collects particulates, a device equipped with a diesel particulate filter (DPF: Diesel Particulate Filter) is being developed as a means of reducing NO X (nitrogen oxides) exhaust gas purification device, equipped with NO X Reduction catalyst and NO...

AI Technical Summary

Problems solved by technology

[0009] However, according to Patent Document 2, since the supercharger side of the exhaust turbocharger and the reducing agent spraying device are simply communicated through the air extraction passage, if the engine is operated in a low-load region, the exhaust turbine In the state where the pressure ratio of the supercharger is low and the air flow rate is also small, the air cannot be sufficiently sent to the reducing agent injection device, the reducing agent is difficult to be atomized, and the NO can not be carried out well. X The problem with the reaction of the reducing agent

Moreover, because the exhaust gas temperature is usually low when the boost pressure is low, the NO X The reduction catalyst temperature is also lower, so the reaction is more difficult to proceed

[0010] In addition, in the low-load region, since only a small amount of charge air is sent to the side of the reducing agent injection device, the combustion air of the engine is insufficient, and particles and unburned fuel may increase.

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