DE102010043327A1 - Internal combustion engine for motor car, has switchable bypass arranged parallel to wastegate bypass in turbine housing, and additive catalytic converter arranged in switchable bypass, where wastegate bypass controls wastegate valve - Google Patents

Abstract

The engine (1) has an exhaust system (5) comprising a catalytic converter (10) that is arranged downstream of a turbine (7) of a supercharger (6). A switchable bypass (11) e.g. internal bypass, bypasses a turbine wheel (19). An additive catalytic converter (16) is arranged in the bypass. The bypass is arranged parallel to a wastegate bypass in a turbine housing. The wastegate bypass bypasses the turbine wheel and controls a wastegate valve i.e. wastegate flap. The additive catalytic converter has smaller thermal mass than that of the catalytic converter of the exhaust system. The catalytic converter of the exhaust system and the additive catalytic converter are designed as an oxidation catalytic converter or three-way catalytic converter.

Description

The present invention relates to an internal combustion engine, in particular a motor vehicle. The invention also relates to a turbine of an exhaust gas turbocharger of an internal combustion engine as well as to an exhaust gas turbocharger equipped with such a turbine.

To increase performance, a modern internal combustion engine can be equipped with a charging device, in particular with an exhaust gas turbocharger. If an exhaust-gas turbocharger is used, its turbine is arranged in an exhaust system of the internal combustion engine, and as a rule as close as possible to the internal combustion engine, since the exhaust gas has the highest energy content there.

For exhaust gas purification, it is customary in the exhaust system of an internal combustion engine z. For example, to arrange a catalyst with the aid of which unreacted or only partially reacted fuel residues or intermediates of the combustion reactions can be reacted. For such a catalyst to work properly, it requires a minimum operating temperature, also referred to as a light-off temperature.

In order to comply with the increasingly stringent legislation on pollutant emissions, it is necessary to make the time that passes in a cold start of the internal combustion engine until the catalyst reaches its minimum operating temperature as short as possible. A cold start or a cold start phase designates the start of the internal combustion engine from a state in which the components of the internal combustion engine, in particular engine block and exhaust system, have a temperature which substantially corresponds to the ambient temperature.

To make the cold start for the catalyst as short as possible, it is basically possible to increase the exhaust gas temperature and the amount of exhaust gas through an intervention in the engine control, which is associated with a deteriorated efficiency and increased fuel consumption. Alternatively, a rich combustion mixture can also be generated by an intervention in the engine control, so that comparatively much fuel residues are contained in the exhaust gas. By injecting additional air, so-called secondary air into the exhaust system, combustion of the residual fuel can be achieved within the exhaust system upstream of the catalyst, resulting in an increased exhaust gas temperature. This measure also leads to a reduction of the efficiency or to an increased fuel consumption.

In any case, an exhaust gas turbine contained in the exhaust system is a hindrance for a rapid cold start of the catalyst, since the turbine is arranged regularly upstream of the catalyst in the exhaust system and cold start a heat sink forms, which has a correspondingly large heat capacity due to their relatively large mass. In other words, to heat the catalyst, the turbine must first be heated.

The present invention is concerned with the problem of providing an improved embodiment for an internal combustion engine or for a turbine or for an exhaust gas turbocharger of the aforementioned type, which is characterized in particular by the fact that the time for heating the catalytic converter is reduced during a cold start. also trying to reduce the energy required for this purpose.

This problem is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea of providing, in addition to the respective catalyst, an additional catalyst which is arranged in a bypass which bypasses the turbine. In this case, the bypass opens between the turbine and catalyst again in the main path of the exhaust system, so that the additional catalyst is in open bypass upstream of the catalyst, which can also be referred to below as the main catalyst.

By arranging such an additional catalyst in a bypass surrounding the turbine, the entire thermal mass of the turbine is bypassed, so that directly heating of the additional catalyst can be realized. Furthermore, the exhaust gas upstream of the (main) catalyst anyway has a higher temperature, so that the additional catalyst can heat up more quickly.

In the internal combustion engine according to the invention, the bypass is provided in addition to a wastegate bypass, which is arranged parallel to the bypass of the catalyst. The wastegate bypass is formed in a turbine housing and bypasses the turbine wheel within the turbine housing. The wastegate bypass can be controlled by means of a wastegate valve.

An embodiment in which the bypass containing the additional catalyst is also formed in the turbine housing is particularly expedient.

An embodiment in which the additional catalyst has a smaller thermal mass than the main catalyst is particularly advantageous.

Due to the smaller thermal mass, the additional catalyst can be heated much faster to its minimum operating temperature with the same amount of exhaust gas and the same exhaust gas temperature than the main catalyst. Thus, the required catalytic treatment of the exhaust gases can be realized much faster by the additional catalyst. This applies both to embodiments in which the heat energy of the exhaust gas is increased via the engine control and which operate with or without secondary air, as well as for embodiments which manage without such measures. In this case, the invention utilizes the knowledge that only a comparatively small amount of exhaust gas is produced during a cold start since, as a rule, full power or high rotational speeds are not required immediately when starting the internal combustion engine. Accordingly, the additional catalyst can be dimensioned significantly smaller than the main catalyst, which must still have a tolerable flow resistance at full load.

Preferably, the main catalyst and the additional catalyst may have different catalytic coatings and / or flow resistance and / or pore sizes and / or storage capacity or adsorption capacity for certain exhaust gas components, whereby the two catalysts can be adapted to different environmental parameters, on the one hand during hot operation for apply to the main catalyst and on the other hand apply to the additional catalyst during cold start. In particular, therefore, the additional catalyst can be designed so that its light-off temperature is lower than the light-off temperature of the main catalyst.

According to an advantageous embodiment, the catalyst of the exhaust system can be designed as an oxidation catalyst or as a 3-way catalyst. The additional catalyst can also be designed as an oxidation catalyst or as a 3-way catalyst. In principle, both the main catalyst and the additional catalyst can either each be an oxidation catalyst or in each case a 3-way catalyst. Preferably, however, the main catalyst and the supplemental catalyst are configured differently, namely with respect to different goals. While the main catalytic converter in warm operation from idle to full load is to achieve sufficient exhaust gas purification, the additional catalytic converter only has to achieve an efficient improvement of the emission values for the cold start. This can be realized with different catalytic coatings. For example, the additive catalyst may have a higher noble metal content in the catalytically active coating than the main catalyst to reduce the light-off temperature. Furthermore, the additional catalyst may be designed so that it can be used for certain exhaust gas components, the z. Example, require relatively high reaction temperatures, a certain storage capacity or adsorption has, the desorption of these exhaust components then takes place later, when the main catalyst has reached its operating temperature, so that then released at the additional catalyst exhaust components in the subsequent main catalyst can be.

According to another advantageous embodiment, the bypass may be formed in a turbine housing of the turbine, so that then the additional catalyst is arranged in the turbine housing. The bypass is designed in this case with respect to the turbine as an internal bypass. In principle, the bypass can alternatively be configured with respect to the turbine as an external bypass. In an internal bypass results in a particularly compact design for the bypass with additional catalyst arranged therein. Suitably, the bypass within the turbine housing is designed such that it bypasses a turbine wheel rotatably arranged in the turbine housing. In particular, the bypass thus branches off from a main path, which is passed through the turbine housing, in which the turbine wheel is arranged, upstream of the turbine wheel, and is also reconnected to the main path within the turbine housing downstream of the turbine wheel. By integrating the bypass and the additional catalyst in the turbine housing, the invention in a conventional internal combustion engine can be realized simply by mounting the turbine presented here with integrated bypass and integrated additional catalyst instead of a conventional turbine.

While the preferred internal bypass within the turbine bypasses the turbine wheel, the external bypass bypasses the entire turbine or its turbine housing.

The bypass is switchable, so it can be opened and locked. When the bypass is blocked, the additional catalytic converter is deactivated and the entire exhaust gas flow is then guided through the turbine to act on the turbine wheel. To realize the switchability of the bypass, a bypass valve, z. B. a bypass damper, be provided for opening and locking the bypass. Particularly useful is an embodiment in which the bypass valve designed as a bypass valve is mounted pivotably on the turbine housing.

According to an advantageous embodiment, the bypass valve, in particular the bypass flap, may be mounted on the turbine housing such that it opens against the exhaust gas flow direction and against the exhaust gas pressure prevailing upstream of the turbine wheel. This ensures that the bypass valve is biased at higher exhaust pressures, ie at higher loads and subsequently with deactivated bypass by the exhaust pressure in its closed position or blocking position, which favors proper functioning of the turbine.

Suitably, the bypass valve, in particular the bypass flap, be configured as a flow guide, so that it deflects at least part of the exhaust gas flow in the direction of bypass in the open state. As a result, the effectiveness of the bypass and thus the heating of the additional catalyst can be supported.

It is particularly advantageous if the bypass valve, in particular the bypass valve, in the open state at least partially blocks an exhaust main path leading to the turbine wheel. This also favors the flow through the bypass and thus the heating of the additional catalyst when the bypass is open.

According to the invention, the bypass is provided in addition to a parallel, formed in the turbine housing wastegate bypass, which also bypasses the turbine wheel and which is controllable with a wastegate valve. Such a controllable wastegate bypass serves to regulate the power of the turbine or of an exhaust gas turbocharger equipped with the turbine. The here presented bypass with additional catalyst is provided in addition to this wastegate bypass. In particular, the wastegate valve is additionally and completely independent of the bypass valve or designed by the bypass valve. In particular, the wastegate valve, if designed as a wastegate flap, may be mounted on the turbine housing such that the wastegate flap opens with the exhaust gas flow direction and with the exhaust gas pressure prevailing upstream of the turbine wheel. Thus, the exhaust gas pressure supports the opening movement of the wastegate flap.

Finally, the present invention relates to a turbine with integrated bypass and an exhaust gas turbocharger with such a turbine.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Show, in each case schematically,

1 a greatly simplified schematic diagram of an internal combustion engine,

2 a sectional view of a turbine,

3 a further sectional view of the turbine according to section lines III in 2 when the bypass is open,

4 a sectional view as in 3 , but with closed bypass.

Corresponding 1 includes an internal combustion engine 1 , which is preferably arranged in a motor vehicle, a fresh air system 2 for supplying fresh air to cylinders 3 an engine block 4 the internal combustion engine 1 , Furthermore, the internal combustion engine 1 an exhaust system 5 for discharging exhaust gas from the cylinders 3 on. In the internal combustion engine 1 it is a supercharged internal combustion engine, this with an exhaust gas turbocharger 6 equipped, its turbine 7 in the exhaust system 5 is arranged and its compressor 8th in the fresh air system 2 is arranged. In the usual way are turbine 7 and compressors 8th or a turbine wheel 19 and a compressor wheel 28 about a common wave 9 together in drive connection.

In the exhaust system 5 is downstream of the turbine 7 at least one catalyst 10 arranged hereinafter also as the main catalyst 10 referred to as. Preferably, it is the main catalyst 10 around an oxidation catalyst or a 3-way catalyst.

The internal combustion engine 1 is also with a bypass 11 equipped with the help of a bypass valve 12 is switchable and the turbine 7 bypasses. In the example of 1 is the bypass 11 designed as an external bypass, the turbine 7 handles externally. Accordingly, in 1 a branch point 13 in which the bypass 11 from an exhaust pipe 14 the exhaust system 5 branches off, upstream of the turbine 7 arranged while a discharge point 15 in which the bypass 11 back to the exhaust pipe 14 connected downstream of the turbine 7 is arranged. Furthermore, there is this discharge point 15 upstream of the main catalyst 10 , In the bypass 11 is an additive catalyst 16 arranged, with the bypass open 11 upstream of the main catalyst 10 is arranged and connected in series with this. The additional catalyst 16 is preferably designed as an oxidation catalyst or as a 3-way catalyst. In principle, the additional catalyst 16 have the same catalytic coating as the main catalyst 10 , However, preferred are main catalyst 10 and additional catalyst 16 equipped with different catalytic coatings to the two catalysts 10 . 16 better adapted to their different purposes. The main catalyst 10 must in warm operation as possible for all operating conditions of the internal combustion engine 1 , So in particular from idle to full load, ensure sufficient emission reduction. In contrast, the additional catalyst must 16 bring about a reduction of pollutants only for the relatively short-term cold start operation. For this he must address early, so have a very low light-off temperature. Furthermore, he does not have to be able to implement all pollutants. It may be sufficient, certain pollutants, such as. As hydrocarbons, nitrogen oxides and / or particles to adsorb, at least until the main catalyst 10 has reached its operating temperature. Then the additional catalyst 16 either react or release or adsorb the adsorbed pollutants at a sufficiently elevated temperature, so that they are the main catalyst 10 can be supplied and implemented therein.

With the help of a control device 17 can the bypass valve 12 to open and lock the bypass 11 be operated. In particular, the controller 17 for a cold start of the internal combustion engine 1 the bypass 11 open and thereby activate, so that the exhaust of the cylinder 3 the bypass 11 and thus the additional catalyst 16 flow through before becoming the main catalyst 10 reach.

Particularly useful is the additional catalyst 16 in terms of thermal mass smaller dimensioned as the main catalyst 10 , For this purpose, the additional catalyst 16 have a significantly smaller cross-section than the main catalyst 10 , It is accepted that the additional catalyst 16 due to its smaller dimensions only suitable for smaller exhaust gas flow rates, since it has too large a flow resistance at larger exhaust gas flow rates. Too much power loss of the internal combustion engine 1 However, this is not to be feared because of the bypass 11 is activated only for cold start operation and can be deactivated as soon as the main catalyst 10 reaches its minimum operating temperature. During this comparatively short cold start operation, the internal combustion engine 1 Usually operated only at partial load or in lower speed ranges, so that only comparatively small exhaust gas flow rates occur.

While at the in 1 shown embodiment of the bypass 11 designed as an external bypass, the show 2 to 4 an embodiment in which the bypass 11 concerning the turbine 7 as an internal bypass 11 is designed. In other words, the bypass 7 is in a turbine housing 18 the turbine 7 educated. In such an internal bypass 11 is then also the additional catalyst 16 in the turbine housing 18 arranged.

The 2 to 4 show an exhaust gas turbocharger 6 who is in the area of his turbine 7 is cut, in which usually a turbine wheel 19 is rotatably arranged. The turbine wheel 19 this is only in 1 simplified indicated by a broken line, as it is in the sectional views of 2 to 4 is not recognizable. Anyway, the bypass is 11 inside the turbine housing 18 so he arranged the turbine wheel 19 bypasses. For switching the bypass 11 is the bypass valve 12 also in the turbine housing 18 arranged. In the example, the bypass valve 12 as a bypass flap 20 designed with which the bypass 11 can be opened and locked. For this purpose, the bypass flap 20 at the turbine housing 18 around a pivot axis 21 pivoted. It is clear that in principle also other embodiments for the realization of such a bypass valve 12 can be provided.

As in particular from the 3 and 4 shows, is the branch point 13 at the internal bypass 11 inside the turbine housing 18 downstream of an exhaust gas inlet 22 of the turbine housing 18 and upstream of the turbine wheel 19 , Furthermore, there is the discharge point 15 also within the turbine housing 18 , upstream of an exhaust gas outlet 23 of the turbine housing 18 and downstream of the turbine wheel 19 ,

The bypass flap is preferred 20 at the turbine housing 18 stored so that it opens against the exhaust gas flow direction. The exhaust gas flow or its direction is indicated by arrows in the figures 24 indicated. This opens the bypass flap 20 against the exhaust gas pressure upstream of the turbine wheel 19 prevails. However, this means that in the closed position or blocking position of the bypass flap 20 the comparatively high exhaust pressure the bypass flap 20 biased in their closed or locked position. This simplifies the sealing of the bypass flap 20 , Furthermore, this also simplifies a drive, not shown here, for adjusting the bypass flap 20 ,

Appropriately, the bypass flap 20 be designed as a flow guide, so that they as in 3 indicated, in the open state at least part of the exhaust gas flow 24 in the direction of the bypass 11 deflects. In the in the 2 to 4 the embodiment shown is the bypass flap 20 In terms of their shape and positioning also designed or arranged so that they are open to the turbine wheel 19 leading exhaust main path 25 at least partially locks. This fits the bypass flap 20 largely positive fit to the exhaust main path 25 and thereby represents a significant flow resistance in the exhaust main path in the open state 25 what the diversion of the exhaust flow 24 in the bypass 11 supported.

The bypass flap 20 or the bypass valve 12 can in principle also be designed so that at least one intermediate position is adjustable between the closed position for blocking or deactivating the bypass 11 and the open position for enabling or activating the bypass 11 lies, allowing a partial flow of the exhaust gas through the bypass 11 and the additional catalyst 16 flows while the residual current bypasses 11 and the additional catalyst 16 bypasses. If several or any such intermediate positions are adjustable, the part of the exhaust gas flow through the bypass 11 flows, be controlled or adjusted. This is z. B. for hot operation possible, the additional catalyst 16 to regenerate if used during cold start operation to adsorb certain pollutants. Regeneration becomes the additional catalyst 16 freed from the adsorbed pollutants, either directly on the additional catalyst 16 or only at the subsequent main catalyst 10 be implemented.

In the in the 2 to 4 shown preferred embodiment, the turbine 7 also a wastegate bypass 26 on, with the help of a wastegate valve 27 can be controlled. Also the wastegate bypass 26 bypasses the turbine wheel 19 and is inside the turbine 7 So in the turbine housing 18 educated. The wastegate bypass 26 runs in addition and parallel to the bypass 11 , Such a wastegate bypass 26 serves for power control or power control of the exhaust gas turbocharger 6 or the turbine 7 , It is noteworthy that the wastegate valve 27 at the turbine housing 18 is arranged so that it is in the exhaust gas flow direction 24 opens, so with the upstream of the turbine wheel 19 prevailing exhaust pressure opens. As a result, the high exhaust pressure supports opening of the wastegate valve 27 , Accordingly, a not shown here drive the wastegate valve 27 in comparison to a likewise not shown drive of the bypass valve 12 be more elaborate to the wastegate valve 27 to keep closed even at high loads and high exhaust pressures.

Claims (12)

Internal combustion engine, in particular of a motor vehicle, - with an exhaust system ( 5 ) downstream of a turbine ( 7 ) of an exhaust gas turbocharger ( 6 ) at least one catalyst ( 10 ), - with a switchable bypass ( 11 ) for bypassing a turbine wheel ( 19 ) of the turbine ( 7 ) in which an additional catalyst ( 16 ), whereby the bypass ( 11 ) in addition to a parallel, in the turbine housing ( 18 ) formed wastegate bypass ( 26 ) is provided, which is also the turbine wheel ( 19 ) and with a wastegate valve ( 27 ) is controllable. Internal combustion engine according to claim 1, characterized in that the additional catalyst ( 16 ) has a smaller thermal mass than the catalyst ( 10 ). Internal combustion engine according to claim 1 or 2, characterized in that the catalyst ( 10 ) and the additional catalyst ( 16 ) have different catalytic coatings and / or flow resistance and / or pore sizes and / or storage capacity for certain exhaust gas constituents. Internal combustion engine according to one of claims 1 to 3, characterized in that the additional catalyst ( 16 ) is designed so that its light-off temperature is lower than the light-off temperature of the catalyst ( 10 ). Internal combustion engine according to one of claims 1 to 4, characterized in that the turbine ( 7 ) is designed according to one of claims 6 to 12, so that the bypass ( 11 ) in a turbine housing ( 18 ) of the turbine ( 7 ) and the additional catalyst ( 16 ) in the turbine housing ( 18 ) is arranged. Turbine of an exhaust gas turbocharger ( 6 ) an internal combustion engine ( 1 ), in particular a motor vehicle, - with a turbine housing ( 18 ), in which a turbine wheel ( 19 ) is rotatably arranged, - with one in the turbine housing ( 18 ) trained bypass ( 11 ) for bypassing the turbine wheel ( 19 ), - with one in the bypass ( 11 ) arranged additional catalyst ( 16 ), - whereby the bypass ( 11 ) in addition to a parallel, in the turbine housing ( 18 ) formed wastegate bypass ( 26 ) is provided, which is also the turbine wheel ( 19 ) and with a wastegate valve ( 27 ) is controllable. Turbine according to claim 6, characterized in that a bypass flap ( 20 ) for opening and blocking the bypass ( 11 ) on the turbine housing ( 18 ) is pivotally mounted. Turbine according to claim 7, characterized in that the bypass flap ( 20 ) so on the turbine housing ( 18 ) is mounted so that it against the exhaust gas flow direction ( 24 ) and against the upstream of the turbine wheel ( 19 ) prevailing exhaust pressure opens. Turbine according to claim 7 or 8, characterized in that the bypass flap ( 20 ) is designed as a flow guide and in the open state, at least part of the exhaust gas flow ( 24 ) in the direction of the bypass ( 11 ) redirects. Turbine according to one of claims 7 to 9, characterized in that the bypass flap ( 20 ) in the opened state one to the turbine wheel ( 19 ) leading exhaust main path ( 25 ) at least partially blocks. Turbine according to one of claims 6 to 10, characterized in that the additional catalyst ( 16 ) is designed as an oxidation catalyst or as a 3-way catalyst, wherein the bypass ( 11 ) in addition to a parallel, in the turbine housing ( 18 ) formed wastegate bypass ( 26 ) is provided, which is also the turbine wheel ( 19 ) and with a wastegate valve ( 27 ) is controllable. Exhaust gas turbocharger for an internal combustion engine ( 1 ), in particular of a motor vehicle, with a turbine ( 7 ) according to one of claims 6 to 11.

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