The present invention relates to a mixer apparatus for an exhaust gas aftertreatment system of a motor vehicle, which apparatus has a, for example, cylindrical housing having an enveloping wall, a first end wall, and a second end wall; an injection opening for an exhaust gas aftertreatment agent being embodied in the enveloping wall; and at least one flow-directing element extending in curved fashion, which directs an exhaust gas flow from at least one inlet opening to an outlet opening embodied in the second end wall, being disposed in the housing.

The present invention further relates to an exhaust gas aftertreatment system having such a mixer apparatus, and to a motor vehicle having a corresponding exhaust gas aftertreatment system.

BACKGROUND INFORMATION

A variety of methods and apparatuses that serve to reduce hazardous constituents of an exhaust gas are available for the aftertreatment of exhaust gases, in particular of diesel engines. One method often used is “selective catalytic reduction” (SCR) for reducing nitrogen oxide constituents in the exhaust gas. Here an aqueous urea solution, constituting an exhaust gas aftertreatment agent, is injected into the exhaust gas flow, mixes with the exhaust gas, and reacts downstream in a catalyst, together with the exhaust gas, in order to reduce nitrogen oxides. The result of the exhaust gas aftertreatment can be optimized by improved blending of the exhaust gas aftertreatment agent and the exhaust gas. It is conventional, for example, to provide, for mixing, a mixer apparatus such as the one described, for example, in German Patent Application No. DE 10 2013 005 206 B3. This mixer apparatus has in the housing a helically extending flow-directing element, the result of which is that the exhaust gas flow acquires a swirl and that a mixing section of the greatest possible length is made available in only a small space. The flow-directing element guides the exhaust gas flow from the inlet opening to an outlet opening in the second end wall, where the mixture of exhaust gas flow and exhaust gas aftertreatment agent emerges from the mixing apparatus and is delivered to the SCR catalyst. Because exhaust gas regulations are constantly becoming more stringent, great effort is being expended on improving fuel efficiency and at the same time reducing emissions, in particular the nitrogen oxide portion, in exhaust gas. One of the consequences of this is that the temperature of the exhaust gas flow decreases. This has the disadvantage, for the SCR catalyst, that it is more difficult to reach the reaction temperature necessary for reduction of the nitrogen oxide constituents. Normally the SCR catalyst is disposed far away from the internal combustion engine, with the result that further temperature losses occur. The closer to the internal combustion engine the catalyst is located, or the shorter the distance the exhaust gas flow must travel from the internal combustion engine to the catalyst, the better the aftertreatment result for many operating states.

German Patent Application No. DE 10 2016 211 703 A1, the disclosure of which is expressly incorporated into the description of the present invention by reference, discloses a mixer apparatus for an exhaust gas aftertreatment system of a motor vehicle, which apparatus has a cylindrical housing having an enveloping wall, a first end wall, and a second end wall; an injection opening for an exhaust gas aftertreatment agent being embodied in the enveloping wall. The exhaust gas flows from at least one inlet opening in a first end wall to an outlet opening in a second end wall, the at least one inlet opening allowing much of the incoming flow of exhaust gas to flow into the mixer apparatus.

SUMMARY

A mixer apparatus according to an example embodiment of the present invention may have the advantage that even further improved mixing of the exhaust gas and exhaust gas aftertreatment agent occurs in a small space, the mixer apparatus and the downstream catalyst being capable of being disposed close to the internal combustion engine but nevertheless ensuring a sufficient mixing path for sufficient mixing. Provision is made here, particularly advantageously, that at least a substantial region of the metering axis proceeding from the injection opening is located, with respect to inflowing exhaust gas, in the shelter of an opening-free region of the first end wall, so that a stream of reducing agent can propagate in protected fashion and can nevertheless become intimately mixed with exhaust gas in a very small space. Suitable provision of opening-free regions can at the same time enable improved (especially in thermomechanical terms) fastening of flow-directing elements on the first end wall that is located close to or in the region of an inlet opening.

Further advantages and preferred features and feature combinations are evident in particular from the disclosure herein.

The present invention will be discussed below in further detail with reference to the figures.

