CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/EP2019/054933, filed on Feb. 28, 2019, which claims the benefit of German Patent Application No. 10 2018 104 599.9, filed on Feb. 28, 2018. The entire disclosures of the above applications are incorporated herein by reference.

FIELD

The disclosure relates to an exhaust gas conduction system for a gasoline engine, comprising an exhaust gas line which can be connected to an exhaust manifold of the gasoline engine, an intake line which can be connected to an intake manifold of the gasoline engine, and a charge air compressor which is arranged in the intake line, and a turbine which is arranged in the exhaust gas line, wherein the exhaust gas line has at least one bypass line with a bypass throttle valve, said line branching off from the exhaust gas line upstream of the turbine and branching back into the exhaust gas line at an opening downstream of the turbine, and wherein at least one exhaust gas recirculation line with an EGR throttle valve is provided, said line opening into the intake line, wherein the exhaust gas recirculation line branches off at a branch on the bypass line, wherein the bypass throttle valve is arranged upstream of the branch of the exhaust gas recirculation line, and wherein an exhaust gas valve is provided in the exhaust gas line upstream of the opening of the bypass line.

The disclosure further relates to a method for operating a gasoline engine, comprising such an exhaust gas conduction system.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

An exhaust gas conduction system for a gasoline engine is already known from DE 10 2015 108 223 A1. The exhaust gas conduction system has an exhaust gas recirculation line which opens in the intake line upstream of the compressor. Additionally, a bypass line is provided for the turbine, on which the exhaust gas recirculation line branches off. A particle filter is arranged in the exhaust gas recirculation line, wherein the particle filter has a catalytically active coating for converting CO, HC and NOx.

An exhaust gas conduction system for a gasoline engine is also known from WO 2015/004497 A1. The bypass line and the exhaust gas recirculation line are connected via a 3-2-way valve, wherein the exhaust gas recirculation line branches off upstream of the turbine and opens out downstream of the compressor.

An exhaust gas conduction system for a gasoline engine with an exhaust gas recirculation line is also known from U.S. Pat. No. 9,593,619, B2.

DE 20 2017 105 126 U1 describes an exhaust gas conduction system with an exhaust gas recirculation line and a bypass line, wherein a particle filter is provided which is positioned in the bypass line upstream of the branch of the exhaust gas recirculation line.

Unlike with a diesel engine, the particle filter of a gasoline engine regenerates largely without additional active measures, i.e. under normal gasoline engine framework conditions, the particle mass retained until that point (soot particles with accumulated or embedded hydrocarbons) essentially converts to CO2 or H20 in the combustion process. For this purpose, sufficiently high exhaust gas temperatures of over 500° C. and oxygen are required in order for combustion to occur. This exhaust gas temperature is achieved in a very wide range of operations of the gasoline engine. Since the majority of gasoline engines are operated stoichiometrically, the oxygen content in the exhaust gas may be too low for a full combustion of the particle mass contained in the filter. In such cases, in transient mode, the usual overrun cut-off phases of the gasoline engine help in which the injection of the engine is switched off for consumption reasons due to the lack of load requirement by the driver.

In engine brake mode, pure air is flushed through the exhaust gas system as a result of the motored engine. This uncombusted air comes into contact with the particles in the particle filter that have been previously heated. If the temperature is sufficiently high, these particles catch fire and combust to gases that can escape through the particle filter. As a result, the particle filter is purified.

Fundamentally, a differentiation is made between three variants of the exhaust gas recirculation, depending on the branch of the EGR line from the exhaust gas line and the opening of the EGR line in the intake line. The combination of the branch of the EGR line upstream of the turbine or turbines and the opening of the EGR line downstream of the compressor or compressors is known as high-pressure EGR (HD-EGR or HP-EGR). The combination of the branch of the EGR line upstream of the turbine or turbines and the opening of the EGR line upstream of the compressor or compressors is known as maximum-pressure EGR (MD-EGR or MP-EGR). The combination used in connection with this disclosure of the branch of the EGR line downstream of the turbine or turbines and the opening upstream of the compressor or compressors is known as low-pressure EGR (ND-EGR or LP-EGR).

SUMMARY

This section provides a general summary of the disclosure, and is not a com-prehensive disclosure of its full scope or all of its features.

The object that forms the basis of the disclosure is to form and arrange an exhaust gas conduction system for a gasoline engine such that an exhaust gas recirculation is possible with an extended range of application.

The object is attained according to the disclosure in such a manner that a particle filter is arranged in the bypass line downstream of the branch of the exhaust gas recirculation line. The bypass line can thus be formed particle filter-free upstream of the branch of the exhaust gas recirculation line. As a result, it is achieved that the particle filter can be used in the EGR line not only in EGR mode, but also in bypass mode, as a result of which in cold start mode in particular, a very rapid heating or light-off is ensured. This is in particular due to the fact that the particle filter is designed for the exhaust gas volume flow to be recirculated; in other words, it is relatively small. When the gasoline engine is in partial load mode, when the bypass throttle valve is closed and the exhaust gas valve is open, the EGR exhaust gas flow is accordingly branched downstream of the turbine and flows through the particle filter in the other direction.

As with cold starting, in full load mode, during exhaust gas recirculation, the particle filter can be flowed through in the opposite direction in relation to the direction of flow, which leads to a purification of the filter as a result of regeneration.

For this purpose, it can also be advantageous when the at least one particle filter has a catalytically active 3-way coating for converting CO, HC and NOx. Thus, extensive purification of the recirculated exhaust gas is possible. Here, the cooler is protected against contamination and load with excessively acidic exhaust gas, so that optimal cooling is ensured.

Further, it can be advantageous when a cooler is provided within the exhaust gas recirculation line upstream of the EGR throttle valve and downstream of the particle filter. An optimal effect and efficiency of the cooler can be achieved due to the positioning of the cooler downstream of the particle filter.

It can also be advantageous when a 3-way exhaust gas catalytic converter and/or a particle filter is provided in the exhaust gas line. Thus, a purification of the main exhaust gas flow is achieved, in particular following sufficient heating of the exhaust gas.

Here, it can advantageously be provided that downstream of the particle filter and upstream of the opening, the bypass line is free of exhaust gas valves or exhaust gas flaps, or that only one bypass valve is provided in the bypass line downstream of the particle filter and upstream of the opening in order to improve the acoustic properties. For this reason, the exhaust gas conduction system functions without the use of an exhaust gas flap or a valve downstream of the particle filter and before the opening into the main exhaust gas tract. The use of such a bypass valve would only be necessary in cases when unfavorable and disadvantageous pulsation events occur due to the exhaust gas system architecture. This is because a suppression of the pulsation events leads to an improvement in the acoustic properties and to the avoidance of capacity deficits due to an unfavorable formation of the counter-pressure.

It can be of particular importance for the present disclosure when the bypass line is free of connecting lines to the exhaust gas line upstream of the particle filter or upstream of the branch of the exhaust gas recycling line. No further connecting lines are necessary to ensure the correct functioning of the exhaust gas conduction system.

In connection with the formation and arrangement according to the disclosure, it can be advantageous when a charge air recirculation line is provided with a branch downstream of a charge air cooler and an opening between the EGR cooler and the EGR throttle valve. Through the use of a charge air recirculation line, the regeneration intervals for the particle filter can be shortened, since in addition to the overrun mode, i.e. including with a load requirement, an increase in the oxygen content in the exhaust gas can be ensured. This increased oxygen proportion can also be used to regenerate the main particle filter.

Further, it can be advantageous when an exhaust gas diversion is provided, which branches off at a branch downstream of the particle filter and before the opening and which branches back in the exhaust gas line downstream of the 3-way catalytic converter and/or downstream of the particle filter, wherein at least one first diversion valve is positioned between the branch and the opening. Through the use of the exhaust gas diversion, the different pressure losses within the main exhaust gas line can be taken into account. When the exhaust gas has already been purified via the filter catalytic converter in the exhaust gas recirculation line or the bypass line, the 3-way catalytic converter in the main exhaust gas tract or the main particle filter can be bypassed via said diversion.

In addition, it can be advantageous when a diversion section is provided, which branches off between the branch and the first diversion valve and which branches back at an opening downstream of the particle filter, wherein a second diversion valve is provided in the diversion section. The diversion section ensures a bypass of the particle filter in the main exhaust gas tract alone. In this way, a choice can be made as to the point at which the wastegate flow of the bypass line, which flows over the particle filter with the catalytically active 3-way coating in the branch of the exhaust gas recirculation line, is introduced. In other words, before the 3-way catalytic converter, after the 3-way catalytic converter, before the particle filter in the exhaust gas line or after the particle filter in the exhaust gas line. The particle filter in the exhaust gas line can additionally also have a catalytically active 3-way coating.

Furthermore, the object is attained by a method for operating a gasoline engine with an aforementioned exhaust gas conduction system or a corresponding exhaust gas system, in which

a) when the gasoline engine is in cold starting mode, the bypass throttle valve is open and the EGR throttle valve and the exhaust gas valve are closed, so that the exhaust gas flow is guided past the turbine through the bypass line and the particle filter,
b) when the gasoline engine is in partial load mode, the bypass throttle valve is closed and the exhaust gas valve is open, wherein via the EGR throttle valve, depending on the operating point, an exhaust gas mass flow is adjusted within the exhaust gas recirculation line,
c) when the gasoline engine is in full load mode or at least close to full load mode, the EGR throttle valve is closed and the exhaust gas valve is open, wherein via the bypass throttle valve, depending on the operating point, an exhaust gas mass flow is adjusted within the bypass line.

Finally, it can be advantageous when via the charge air recirculation line and the EGR line, charge air is guided into the exhaust gas line and the particle filter in the EGR line and/or the particle filter in the exhaust gas line is regenerated. As already explained above, as a result of a charge air recirculation, the regeneration interval for the particle filter can be shortened, since in different engine operation states, sufficient oxygen can be provided in the exhaust gas.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

