Emission control system

Abstract

An emission control system, includes: an exhaust pipe portion, adapted to guide exhaust gas from an engine to outside; a catalyst, accommodated in the exhaust pipe portion; an additive injection valve, provided at the exhaust pipe portion located at upstream side of the catalyst, and configured to inject additives to be supplied to the catalyst toward a flow of the exhaust gas in the exhaust pipe portion. The exhaust pipe portion has a flow path section located at upstream side of the catalyst, which intersects an injection flow of the additives injected by the additive injection valve, and the flow path section is made to have substantially the same shape as an injection region of the injection flow which confronts the exhaust gas.

Description

BACKGROUND OF THE INVENTION[0001]For purification of exhaust emissions from a car (a vehicle) having a diesel engine, an emission control system is used in which a adsorption type NOx catalyst, a selective reduction type NOx catalyst and a diesel particulate filter are combined together to prevent the emission of NOx (oxides of nitrogen) and PM (particulate matter) which are contained in exhaust emissions from a diesel engine to the atmosphere[0002]An emission control system like this adopts a construction in which a catalyst referred to as a pre-stage catalyst such as an oxidation catalyst, a NOx trap catalyst or a selective reduction type NOx catalyst is provided in an interior of an exhaust pipe portion which expels exhaust gases discharged from the engine to the outside thereof, and a fuel injection valve (such as one for adding a reducing agent) which injects a fuel required for reaction of the catalyst to an upstream side of the catalyst, for example, the oxidation catalyst.[0...

AI Technical Summary

Benefits of technology

[0022]A release portion where a contact with the injection flow of the additives which is deflected as a result of collision with the exhaust gas is avoided, may be formed at a downstream part of the exhaust pipe portion which intersects the injection flow of the additives.

Problems solved by technology

However, as it is required that a location where a catalyst is installed is secured in the vicinity of an exhaust side of an engine in order to meet the recent tendency of enhancing the exhaust emission purifying efficiency at the time of cold start, it becomes difficult to ensure such a sufficient fuel spray travel.

To make this happen, it becomes difficult to ensure a long enough fuel spray travel for mixture of fuel with exhaust gases between the fuel injection valve and the catalyst.

From the reasons regarding the installation of the fuel injection valve and the catalyst, the situation in which the fuel spray travel for mixture of fuel with exhaust gases becomes difficult to be ensured is seen not only the emission control system in which the bent portion is provided in the exhaust pipe but also in an emission control system in which no such bent portion is provided.

However, even with this proposed emission control system, from the limitations on the installation of the fuel injection valve and the catalyst, which are similar to the aforesaid one, there still remains the situation in which the fuel spray travel for mixture of fuel with exhaust gases is difficult to be ensured.

Due to this, in an emission control system, it remains difficult to mix injected fuel with exhaust gases sufficiently.

This has caused a problem that uniformly atomized fuel is difficult to be supplied to a catalyst and hence the catalyst cannot fulfill its function.

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