WO2010009929A1 - Exhaust gas aftertreatment device for a spark-ignited internal combustion engine - Google Patents

Abstract

The invention relates to an exhaust gas aftertreatment device (3) for spark-ignition engines, wherein a particulate filter is also integrated in a primary catalytic converter (7). It is thereby possible to reliably meet limits regarding particulate mass and number of particles at low additional cost in the future too.

Description

 description

title

Exhaust after-treatment device for an internal combustion engine with spark ignition

State of the art

The invention is based on an exhaust aftertreatment device

Internal combustion engine, which operates according to the Otto method, with a precatalyst and a main catalyst, as it is known for example from DE 102 55 308.4.

So far, only the components HC, NOx and CO ₂ were limited by respective limits in the gasoline engine in the exhaust gases. With the EUV and EUVI limit values coming into force in the future, the particles in the exhaust gases will also be limited. Initial investigations have shown that these limit values and above all the limit value for the number of particles provided for in the EUVI standard can not be readily controlled by internal engine measures, such as a suitable control of the internal combustion engine.

This is especially true when the gasoline engine is equipped with direct injection. In the case of direct gasoline injection (BDE), as a result of the process, more particulates in the exhaust gases occur compared with intake manifold injection (SRE).

Disclosure of the invention

The invention has for its object to provide an exhaust aftertreatment device, which is simple in construction and in which the required limits in terms of particle number and particle mass can be safely adhered to without significant application effort. This object is achieved in an exhaust aftertreatment device for an internal combustion engine with spark ignition, comprising a precatalyst and a main catalyst, wherein the precatalyst has a housing, achieved in that in the housing of the precatalyst, a particulate filter is integrated.

The inventive integration of a particulate filter in the precatalyst, it is possible to comply with relatively low cost regardless of the combustion process used, namely manifold injection, direct injection or a combination of both, the particle limits at relatively low cost.

In addition, by integrating the particulate filter into the precatalyst of the

Engine compartment existing space to be used optimally and it does not have to be avoided on the underbody of the vehicle.

In the context of the invention, the term "precatalyst" also includes a main catalytic converter close to the engine, since both catalysts have in common that they are arranged close to the engine and therefore are exposed to comparatively hot exhaust gases. to dispense with additional sensors.

The fact that the particulate filter is integrated in the already existing housing of the precatalyst, eliminating the cost of a separate housing of the particulate filter and the "Canning" of the particulate filter. If, as in a particularly advantageous embodiment of the

Provided invention, the precatalyst and the particulate filter are arranged on a common carrier, the cost of an additional carrier can be omitted. This means that the additional costs for the particulate filter, which according to the invention is integrated into the precatalyst, are very low.

Because of the close-to-the-engine arrangement of the particulate filter integrated into the precatalyst according to the invention and the modes of operation known in a gasoline engine, it is ensured that the particulate filter is regenerated independently, that is to say without the initiation of a special regeneration mode of operation. As a result, the clogging of the particulate filter over the entire life of the exhaust aftertreatment device is effectively avoided.

This results from the fact that the gasoline engine in homogeneous operation under normal driving conditions in the vicinity of the engine reaches exhaust gas temperatures of 550 ⁰ C. This temperature is above the regeneration or burnout temperature for a particulate filter. In addition, in the raw exhaust gas of the gasoline engine in homogeneous operation Residual oxygen content of at least 0.5% present, which allows the oxidation of the soot stored in the particulate filter during regeneration. Therefore, additional measures to raise the temperature of the exhaust gas in the homogeneous operation of the internal combustion engine are not required.

In stratified operation of a gasoline engine, the exhaust gas temperatures are at a much lower temperature level between 180 ⁰ C and 400 ⁰ C. Therefore, an independent burn-off or regeneration of the particulate filter in stratified operation is not always readily possible.

In a gasoline engine, however, it is easily possible to switch back to homogeneous operation from time to time in order to raise the temperature level to the required value.

As in gasoline engines, which can work in lean operation, always a NOx storage catalyst is present, and you have to switch back to the regeneration of the NOx storage catalytic converter inevitably in the homogeneous mode, at the same time with the regeneration of the storage catalytic converter and the particulate filter is regenerated. In other words: Due to the already existing control functions of the internal combustion engine, which cause the periodic regeneration of the NOx storage catalytic converter, the regeneration of the close-coupled particle filter according to the invention is simultaneously initiated. This means that separate functions or applications for the regeneration of the particulate filter are not required, but this takes place without further action at the same time as the regeneration of the NOx storage catalytic converter.

A further regeneration of the particulate filter without separate activation results from the operating mode "catalyst heating." This mode of operation is initiated in a gasoline engine both in homogeneous operation and in stratified operation after each cold start In this operating mode, the temperature of the exhaust gases by engine-side measures, such as a injection with multiple injections and late ignition angles at a BDE internal combustion engine, as well as late ignition angles raised in a gasoline engine having intake manifold injection. thus, the exhaust gas temperature rises in the vicinity of the pre-catalyst or of the particulate filter according to the invention to values greater than 600 ⁰ C, so that by the operating mode "catalytic converter heating "reliably after the engine start the regeneration of the particulate filter is triggered.

In gasoline engines, which work with stratified charge, also a homogenous phase for heating the engine and the catalyst system is followed. This means that both in gasoline engines with intake manifold injection and gasoline direct injection gasoline engines and the various operating modes known in gasoline engines, such as homogeneous operation, homogeneous lean operation, homogeneous stratified operation, homogeneous knock protection operation and layer catalyst heating in sufficiently short Intervals the exhaust gas temperatures are so high that the regeneration of the particulate filter is triggered.

A sensor system of the exhaust aftertreatment device, which monitors the state of the particulate filter and control functions within the engine control, which trigger a regeneration of the particulate filter, are therefore not required. Therefore, the control unit is not charged additionally and the application of the internal combustion engine to a specific vehicle type or a specific purpose is not complicated by the invention built-in close particulate filter according to the invention.

In internal combustion engines, which operate exclusively in homogeneous operation, can be completely dispensed with a control strategy for the regeneration due to the above boundary conditions.

In internal combustion engines, which may also work for a long time in stratified operation, a model-based functionality can be provided, which switches back to the homogeneous operation at too long operation below the regeneration conditions and thus triggers the regeneration of the particulate filter.

These regeneration conditions are either present as a measure of the exhaust gas temperature or are mapped in a corresponding temperature model in the control unit.

Of course, it would also be possible to implement a particulate filter loading model that monitors particle entry into the combined particulate filter and precatalyst and, if necessary, triggers regeneration through the switchover mode.

A particularly advantageous construction of the particle filter according to the invention provides that the particle filter has a carrier, in particular a ceramic carrier, which takes over the filter function and this carrier is provided with catalytically active coatings, so that the particle filter also acts as a precatalyst.

Since in gasoline engines, the amounts of particulate matter compared to a diesel engine are significantly lower and also due to the above-described favorable operating conditions of the inventive combined precatalyst and particulate filter, the burning of the particulate filter is always guaranteed, the volume of the invention Particle filter are relatively small. For example, it is possible to limit the volume of the combined primary catalytic converter and particle filter to 0.5 times the displacement of the internal combustion engine.

Further advantages and advantageous embodiments of the invention are the following drawings, the description and the claims removable. All of the features disclosed in the drawing, the description and the claims can be essential to the invention both individually and in any combination with one another.

Show it:

Figure 1 shows the schematic structure of an inventive

Exhaust treatment device; and

Figure 2 shows an embodiment of a particulate filter according to the invention.

In Figure 1, an internal combustion engine 1 with an exhaust gas aftertreatment device 3 is greatly simplified and shown schematically. The exhaust aftertreatment device 3 comprises an exhaust pipe 5, a combined primary catalyst according to the invention and

Particle filter 7 and a main catalyst 11. The flow direction of the exhaust gas through the exhaust pipe 5 is indicated by arrows 9. In the exemplary embodiment illustrated in FIG. 1, the precatalyst and particulate filter 7 according to the invention comprises a cylindrical housing 16 in which a rotationally symmetrical filter element 18, which is also cylindrical overall, is arranged. Of course, the invention is not limited to these geometries. The main catalytic converter 11 can be designed as a NOx storage catalytic converter in the case of layer concepts.

Upstream of the precatalyst 7, a first lambda probe 13 is provided. Between the precatalyst according to the invention and particulate filter 7 and the main catalyst 11, which may be formed as a NOx storage catalyst, a temperature sensor 15 is provided. Downstream of the main catalytic converter 11, a second lambda probe and / or NOx sensor 17 is provided. These probes 13, 15 and 17, are anyway present in conventional exhaust aftertreatment devices with a pre-catalyst 7 and a main catalyst 11, which is designed as a NOx storage catalyst. Therefore, in the exhaust aftertreatment device 3 according to the invention, in which a particle filter is integrated into the precatalyst 7, no additional sensor system is required.

FIG. 2 shows a longitudinal section through an exemplary embodiment of a filter element 18 according to the invention. The filter element 18 is inventively combined Pre-catalyst and particulate filter used in the exhaust aftertreatment device 3 of an operating according to the Otto method internal combustion engine 1 with spark ignition.

The filter element 18 is made as an extruded shaped body of a porous ceramic material, such as cordierite. The filter element 18 is flowed through in the direction of the arrows 9 by the exhaust gas, not shown. An entrance surface has the reference numeral 22 in FIG. 2, while an exit surface in FIG. 2 has the reference numeral 24.

Parallel to a longitudinal axis 26 of the filter element 18 extend a plurality of inlet channels 28 in alternation with outlet channels 30. The inlet channels 28 are closed at the outlet surface 24. The sealing plugs are shown in FIG. 2 without reference numerals. In contrast, the outlet channels 30 are open at the outlet surface 24 and closed in the region of the inlet surface 22.

The flow path of the unpurified exhaust gas thus leads into one of the inlet channels 28 and from there through a filter wall 34 into one of the outlet channels 30. This is illustrated by the arrows 32 by way of example.

In the exemplary embodiment according to FIG. 2, a sealing ring 36 is formed both in the region of the inlet surface 22 and in the region of the outlet surface 24. The sealing ring is usually made of the same or at least a similar material as the filter element 18 and is inextricably connected to the filter element 18 during sintering. The sealing rings 36 facilitate the sealing of the filter element 18 in the housing 16.

The combined filter element 18 according to the invention combines the functionality of a wallflow particulate filter with the functionality of a three-way catalyst. This can be done, for example, by coating the ceramic carrier of the filter element 18 with correspondingly catalytically active substances so that the filter element 18 simultaneously acts as a three-way catalyst.

Claims

claims An exhaust aftertreatment device for a spark-ignition internal combustion engine comprising a pre-catalyst (7) and a main catalytic converter (11) or a main catalytic converter (11) close to the engine, wherein the primary catalytic converter (7) or the main catalytic converter close to the engine comprises a housing (16), characterized in that the housing (16) is integrated with a particle filter (18). 2. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the pre-catalyst (7) and the particulate filter (18) are arranged on a common carrier. 3. exhaust gas treatment device according to claim 2, characterized in that the carrier of the precatalyst (7) is designed as a porous filter element (18), and that the filter element (18) is coated with catalytically active substances. 4. exhaust aftertreatment device according to one of the preceding claims, characterized in that the particle filter (18) is made of a ceramic material. 5. Filter element according to one of the preceding claims, characterized in that the particulate filter (18) consists of aluminum-magnesium silicate, preferably cordierite, titanium dioxide (TiO2), silicon carbide (SiC) and / or aluminum titanate. 6. exhaust gas aftertreatment device according to claim 2 or 3, characterized in that the particle filter (18) made of a metallic material, in particular a metal fabric is made. 7. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the main catalytic converter (11) is designed as a NOx storage catalytic converter. 8. Exhaust after-treatment device according to one of the preceding claims, characterized in that the particle filter (18) and the NOx storage catalytic converter (11) are arranged on a common carrier. 9. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the exhaust gas aftertreatment device (3) comprises a first lambda probe (13), a temperature sensor (17), a second lambda probe and / or a NOx sensor (17). 10. Exhaust after-treatment device according to one of the preceding claims, characterized in that it is suitable for use on an internal combustion engine (1) with direct injection (BDE) and / or intake manifold injection (SRE). 11. A method for exhaust aftertreatment of the exhaust gas of an internal combustion engine with spark ignition, wherein the exhaust gas flows through a pre-catalyst and a main catalyst or a main catalyst close to the engine, wherein the pre-catalyst or the main engine-near catalyst has a housing, characterized in that the exhaust gas also integrated in the housing Traps particulate filter.