DE102007053932A1 - Exhaust system and method for operating the same - Google Patents

Abstract

Exhaust system for an internal combustion engine of a motor vehicle, comprising a first exhaust line with a first engine near catalytic converter, a second exhaust line parallel to the first exhaust line and a second combustion engine remote catalyst, wherein the first catalyst has a smaller and the second catalyst has a larger flow area and method for operating such exhaust system.

Description

The The invention relates to an exhaust system for an internal combustion engine Motor vehicle comprising a first exhaust system with a first close to the engine Catalyst, a second exhaust line parallel to the first exhaust gas line and a second combustion engine remote catalyst. "Brennkraftmaschinennah" and "Brennkraftmaschinenfern" refers to it in particular relative to the arrangement of the two catalysts to each other.

primary catalytic converters intended to minimize exhaust pollutant emissions in particular reach their operating temperature very quickly in the cold start phase, in the desired reduction of the pollutant content in the exhaust gas he follows. They are therefore common Internal combustion engine arranged close to the exhaust manifold. For a quick warming it is as well Cheap, if the precatalyst has a small flow cross-section. Especially at higher Engine revs provides such a catalyst low flow cross-section however, a flow resistance which increased one Rider pressure conditionally and to performance losses and increased fuel consumption leads.

Regarding Performance and fuel consumption would be a large flow area in the catalyst Cheap. An enlargement of the However, catalyst for reducing the throttle effect is in the Usually not possible because then the catalyst reaches its operating temperature too late would.

task The invention is to provide an exhaust system mentioned above, with the one hand, in particular during a cold start of the internal combustion engine allows a rapid achievement of the catalyst operating temperature and at the same time, in particular in a full load operation of the internal combustion engine performance degradation and an elevated one Fuel consumption reduced by the throttling effect of the catalyst become. Furthermore to provide a method for operating such an exhaust system become,

The solution The task takes place with an exhaust system with the characteristics of Claim 1, the first catalyst, a lower and the second catalyst has a larger flow cross-section. "Lower Flow cross section "and" larger flow cross-section "refers in particular on the relationship the flow cross sections the two catalysts relative to each other. Because of its low Flow area the first catalyst reaches its operating temperature very quickly and is very fast for an effective exhaust gas purification available, the second catalyst has due to its larger flow cross section a low throttle effect and allows a power and Consumption-optimal operation of the internal combustion engine.

In addition, will the object with a method having the features of the claim 6 solved by the exhaust stream is passed substantially through the first catalyst when the temperature of the exhaust system is below a predetermined temperature lies. As a result, a particularly rapid heating is achieved when the exhaust system is still cold.

Especially preferred embodiments the exhaust system according to the invention and a particularly preferred embodiment of the method according to the invention are the subject of the dependent claims.

Preferably is the second catalyst associated with the second exhaust line, so that two mutually parallel exhaust strands each have a catalyst exhibit.

It has proved to be particularly advantageous if the first and the second exhaust gas line flow downstream into a common exhaust gas line and the second catalytic converter is assigned to the common exhaust gas line. In addition, it is considered advantageous if the first and the second exhaust line branch off upstream from a common exhaust line. Then it is expediently in the region of the branch and / or the mouth of a control valve ( 116 ) for controlling the exhaust gas flow between the first and second exhaust gas line ( 104 . 106 ) intended. It has proved to be favorable to operate the control flap (s) controlled or regulated.

A Particularly preferred embodiment of the method according to the invention is characterized by the fact that the exhaust gas flow essentially through the second catalyst is passed when the temperature of the exhaust system is above a predetermined temperature. This will be added warm exhaust system the throttle loss through the catalyst significantly reduced.

following are particularly preferred embodiments of the invention with reference to figures closer explains thereby show schematically and by way of example

1 an exhaust system comprising a catalyst with a smaller flow cross-section and a catalyst with a larger flow cross-section, wherein either both catalysts or only the catalyst with the larger flow cross-section is / can be flowed through and

2 an exhaust system comprising a catalyst having a smaller flow cross section and a catalyst having a larger flow cross section, wherein either the catalyst with the smaller flow cross section or the catalyst with the larger flow cross section can be flowed through.

1 shows an exhaust system 100 comprising a catalyst 108 with a smaller flow cross-section and a catalyst 110 with larger flow cross-section, either with both catalysts 108 . 110 or just the catalyst 110 with the larger flow cross-section is / can be flowed through.

A precatalyst of the exhaust system not shown here 100 a motor vehicle internal combustion engine is designed in two parts. An exhaust duct 102 shares in a branch in two mutually parallel exhaust strands 104 . 106 on, the downstream again in a common exhaust duct 114 lead. The first exhaust system 104 includes a first engine-near catalyst 108 with a smaller flow cross section, the second exhaust line 106 includes a second combustion engine remote catalyst 110 with larger flow cross-section.

The catalyst 108 with a smaller flow cross-section heats up quickly during operation of the internal combustion engine, since it has a low heat capacity. In addition, a rapid heating of the catalyst 108 supported by the fact that it is located close to the engine near the exhaust manifold and leaves only a limited flow through lets. The catalyst 110 with larger flow cross-section provides only a low flow resistance in the exhaust system 106 and thus causes only a low back pressure, which is advantageous in terms of consumption and performance of the internal combustion engine.

At the junction upstream of the two exhaust lines 104 . 106 is a control flap 116 for controlling the exhaust gas flow between the first and second exhaust gas line 104 . 106 intended. By means of the control flap 116 the exhaust gas flow during operation of the internal combustion engine either the first or the second exhaust line 104 . 106 or both exhaust lines 104 . 106 be forwarded. The control flap 116 can be operated continuously or discretely. The control flap 116 is passively pressure actuated or actively actuated by means of an actuator. In this case, an electromotive, pneumatic or hydraulic actuator can be used. In an actuator operation, a control device is provided for controlling the actuator, which controls the actuator on the basis of external parameters such as exhaust gas pressure, engine speed, exhaust gas temperature and / or catalyst temperature, and / or stored in the control device parameters. Alternatively or in addition to the branch-side control flap 116 may a control valve (not shown) in the mouth region of the two exhaust gas lines 104 . 106 in the exhaust duct 114 be provided.

In the case of a cold exhaust system, in particular in the starting phase, the exhaust gas flow is through the first exhaust gas line 104 and with it through the catalyst 108 directed. This heats up quickly to operating temperature, so that already in the start-up phase, a good reduction in pollutants is achieved. The exhaust gas flow is particularly through the catalyst at low engine speeds, where a limited exhaust gas flow prevails 108 directed. The exhaust gas flow is then through the catalyst 108 passed when the temperature of the exhaust system is below a predetermined temperature.

At higher engine speeds and higher exhaust volume, the exhaust flow through the second exhaust line 106 and with it through the catalyst 110 passed with a larger flow cross-section. The exhaust gas flow is then through the catalyst 110 passed when the temperature of the exhaust system is above a predetermined temperature.

As described, the diversion of the exhaust gas flow can be effected continuously or discretely, regulated or parameter-dependent controlled. The exhaust gas flow can then also through the second exhaust line 106 be passed when the temperature of its catalyst 110 is more suitable for optimum operation than the temperature of the first catalyst 108 , Likewise, a diversion of the exhaust gas flow toward the second exhaust gas line 106 take place if its catalyst 110 has reached a predetermined minimum temperature, in particular its operating temperature.

When the exhaust gas flow is substantially through the second exhaust line 106 is passed, is a further increase in temperature of the first catalyst 108 avoided and the second catalyst 110 is effective. Because the catalyst 110 a larger flow area than the catalyst 108 has, represents a only a small flow resistance and thus enables a performance and consumption-optimized operation of the internal combustion engine.

Through the use of the catalyst 108 can the catalyst 110 Moreover, be carried out with a larger flow cross-section, as in exhaust systems with only one such catalyst, where due to the heating time always a compromise must be received. In the present case during the heating phase of catalyst 108 take over the exhaust gas purification and this even very quickly. In addition, the catalyst 110 farther away from the internal combustion engine than the catalyst 108 , He is therefore less affected by temperature and can be operated even at high engine power, especially at full load, in its operating range, without a temperature-induced damage threatens.

2 shows an exhaust system 200. comprising a catalyst 208 with a smaller flow cross-section and a catalyst 210 with larger flow cross-section, with either the catalyst 210 with the smaller flow area or the catalyst 210 can be flowed through with the larger flow cross-section.

A precatalyst of the exhaust system not shown here 200. a motor vehicle internal combustion engine is designed in two parts. An exhaust duct 202 shares in a branch in two mutually parallel exhaust strands 204 . 206 on, the downstream again in a common exhaust duct 214 lead. The first exhaust system 204 includes a first engine-near catalyst 208 with a smaller flow cross section, the second exhaust line 206 forms a bypass to the first exhaust system 204 , The common exhaust duct 214 includes a second combustion engine remote catalyst 210 with larger flow cross-section. By means of a control flap 216 can the exhaust gas flow between the first and second exhaust line 204 . 206 be redirected.

For the functionality and advantages will be to the description of 1 Referenced. Essential in the embodiment according to 2 However, that is the catalyst 210 with the larger flow area during operation of the catalyst 210 is already heated with the smaller flow cross-section.

The Exhaust system according to the invention not only in a close to the bend Used in the pre-catalyst, but also in other types of catalysts, for example, a three-way catalyst or a DeNOx catalyst.

With the invention is on the one hand a rapid onset of the catalyst achieved and on the other hand, performance and consumption disadvantages through the catalyst-related flow resistance reduced to a minimum.

Claims (7)

Exhaust system ( 100 . 200. ) for an internal combustion engine of a motor vehicle comprising a first exhaust gas line ( 104 . 204 ) with a first engine-side catalyst ( 108 . 208 ), one to the first exhaust line ( 104 . 204 ) parallel second exhaust line ( 106 . 206 ) and a second combustion engine remote catalyst ( 110 . 210 ), characterized in that the first catalyst ( 108 . 208 ) a lower and the second catalyst ( 110 . 210 ) has a larger flow cross-section. Exhaust system ( 100 ) according to claim 1, characterized in that the second catalyst ( 110 ) the second exhaust line ( 106 ) assigned. Exhaust system ( 200. ) according to claim 1, characterized in that the first and the second exhaust gas line ( 204 . 206 ) downstream in a common exhaust line ( 214 ) and the second catalyst ( 210 ) the common exhaust line ( 214 ) assigned. Exhaust system ( 100 . 200. ) according to one of the preceding claims, characterized in that the first and the second exhaust gas line ( 104 . 106 . 204 . 206 ) upstream of a common exhaust line ( 102 . 202 ) branch off and in the area of the branch and / or the mouth of a control valve ( 116 . 216 ) for controlling the exhaust gas flow between the first and second exhaust gas line ( 104 . 106 . 204 . 206 ) is provided. Exhaust system ( 100 . 200. ) according to one of the preceding claims, characterized in that the control flap (s) ( 116 . 216 ) is controlled or regulated operated / are. Method for operating an exhaust system ( 100 . 200. ) according to one of the preceding claims, characterized in that the exhaust gas flow essentially through the first catalyst ( 108 . 208 ) is conducted when the temperature of the exhaust system is below a predetermined temperature. A method according to claim 6, characterized in that the exhaust gas flow substantially through the second catalyst ( 110 . 210 ) is conducted when the temperature of the exhaust system is above a predetermined temperature.