DE102007007946B4 - Multi-flow exhaust system with crosstalk - Google Patents

Abstract

Exhaust system for an internal combustion engine with several combustion chambers, in which a discontinuous gas exchange can be carried out, with exhaust gas discharged from the combustion chambers being routable in at least two main exhaust gas pipes (2, 3), a first main exhaust gas pipe (2) having a first crosstalk path (4) and a second The main exhaust pipe (3) is assigned a second crosstalk path (5), with at least one first crosstalk opening (2b) between the first crosstalk path (4) and the first main exhaust pipe (2) and between the second crosstalk path (5) and the second main exhaust pipe (3) at least one second crosstalk opening (3b) are provided, and between the first crosstalk path (4) and the second crosstalk path (5) a third crosstalk path (6) is provided which connects to the first crosstalk path (4) via at least one third crosstalk opening (7f, 8a) and with the second crosstalk path (5) via at least one fourth crosstalk opening (7g, 9a) is connected so that sound waves can run through these crosstalk sections (4, 5, 6) between the main exhaust pipes (2, 3), the third crosstalk section (6) essentially spatially parallel to ...

Description

The invention relates to an exhaust system for an internal combustion engine having a plurality of combustion chambers, in which discontinuously a gas exchange is vornehmbar, wherein discharged from the combustion chambers exhaust gas can be performed in at least two main exhaust pipes, wherein a first main exhaust pipe with a first exhaust gas flow a first crosstalk and a second main exhaust pipe with a second crosstalk is associated with a second exhaust stream, wherein between the first crosstalk and the first main exhaust pipe at least a first crosstalk opening and between the second crosstalk and the second main exhaust pipe at least a second crosstalk opening are provided.

The invention generally relates to a noise modification apparatus in which gas can be passed in at least two main gas pipelines, wherein a first crosstalk and a second main gas piping (with a second gas flow) are associated with a second crosstalk path to a first main gas piping.

From the DE 103 31 620 A1 on which the preamble of claim 1 is based, an exhaust system for the internal combustion engine of a motor vehicle is known in which two exhaust pipes are acoustically coupled to each other by means of a two-part crosstalk. The crosstalk path is formed in a common housing such that the housing is divided by a partition wall into two chambers, which are connected to each other via an opening or perforation, each exhaust pipe is associated with a respective chamber. The proposed crosstalk is intended to improve the noise during operation of the internal combustion engine and thus serves as a device for noise modification.

From the JP 58 093 919 A is also known an exhaust system for an internal combustion engine of a motor vehicle, in which two exhaust pipes are acoustically coupled to each other by means of a crosstalk in a common housing. The housing is divided into two chambers, which are connected to each other via openings, each exhaust pipe is associated with a respective chamber. Again, the proposed crosstalk serves to improve the noise during operation of the internal combustion engine and thus as a device for noise modification.

The object of the invention is in contrast to enable a further optimization of the noise in an internal combustion engine with the simplest possible means and with good space utilization.

This object is achieved by an exhaust system with the features of claim 1. Advantageous embodiments and further developments of the invention are the subject of the dependent claims 2 to 10.

The exhaust system according to the invention has a first crosstalk, a second crosstalk and a third crosstalk, wherein the first crosstalk and / or the second crosstalk within one the first main exhaust pipe and / or within a second main exhaust pipe at least partially enclosing tubular element is formed. Particularly preferred here is a double-walled design of at least one of the main exhaust pipes, so that in a hollow wall of a main exhaust pipe in a particularly simple manner an associated crosstalk can be accommodated.

With this construction, the greatest possible length of the crosstalk distance can be achieved in a particularly small installation space. In particular, a comparatively long acoustically effective crosstalk distance between the main exhaust gas pipes can be produced at a predeterminable (small) installation space length along the axial extent of the main exhaust gas pipelines. First, second and third crosstalk are connected in series and connected by a plurality of spaced apart crosstalk openings (openings, perforations, acoustically permeable membrane, etc.). The crosstalks are, for example, accommodated in a space with a length / width ratio of less than five.

In one embodiment of the invention, the current in the crosstalk distances with the gas flow sound waves at least twice by approximately 180 ° are deflected. When crossing into a main exhaust pipe or out of a main exhaust pipe, a 180 ° deflection may also take place. In a preferred manner, crosstalk openings are provided in the region of deflection points and thus spaced as far as possible from each other.

In a further embodiment of the invention, the crosstalk sections are formed within a common housing with at least two internal separating walls separating the crosstalk paths. This results in a particularly simple construction of the system. The partitions may be designed as preferably concentrically arranged sheet metal shells.

In a further embodiment of the invention, the crosstalk sections are arranged within a common housing, which surrounds at least one of the main exhaust pipe at least in sections. In this way, a third crosstalk between an outer wall of the common housing and a main exhaust pipe or between an outer wall of the common housing and a wall of the first and / or the second crosstalk can be formed.

In a further embodiment of the invention, the first crosstalk opening provided between the first main exhaust pipe and the first crosstalk path extends along a first peripheral area and along a first length of the first main exhaust pipe. The first crosstalk opening may, for example, be designed as a perforation in a part of the wall of the first main exhaust pipe and extend over a range of 90 ° to 360 ° of the circumference of this wall.

In a further embodiment of the invention, the second crosstalk opening provided between the second main exhaust pipe and the second crosstalk extends along a first peripheral area and along a first length of the second main exhaust pipe. The second crosstalk opening may, for example, be designed as a perforation in a part of the wall of the second main exhaust pipe and extend over a range of 90 ° to 360 ° of the circumference of this wall.

In a further embodiment of the invention, the third crosstalk opening provided between the first crosstalk path and the third crosstalk path extends along a first circumferential region and along a first longitudinal segment of the first crosstalk path. Based on the first crosstalk distance, the third crosstalk opening is preferably arranged as far as possible from the first crosstalk opening. Analogously, the fourth crosstalk opening provided between the second crosstalk path and the third crosstalk path extends along a first circumferential region and along a first longitudinal segment of the second crosstalk path. Based on the second crosstalk distance, the fourth crosstalk opening is preferably arranged as far as possible from the second crosstalk opening.

In a further embodiment of the invention, the sum of the lengths of the first, the second and the third crosstalk is greater than twice, in particular greater than 2.5 times the length of the common housing. According to the present invention, theoretically there are no limits to the summed length of all crosstalk paths when providing a fourth, fifth, or nth crosstalk path connected in series with the first, second, and third crosstalk paths.

In a further embodiment of the invention, the sum of the lengths of the first, the second and the third crosstalk distance corresponds approximately to three times the length of the common housing. This results preferably from the fact that three spatially parallel crosstalk paths are interconnected in a zigzag-shaped manner and each crosstalk path extends through approximately the entire length of the housing.

The above and other features and advantages of the invention will become more apparent from the following description of preferred, non-limiting embodiments of the invention with reference to the accompanying drawings. Show:

1a a schematic cross-sectional view of a first embodiment of an exhaust system;

1b a schematic longitudinal sectional view of the first embodiment;

2a a schematic cross-sectional view of a second embodiment of an exhaust system; and

2 B a schematic longitudinal sectional view of the second embodiment.

A not shown reciprocating internal combustion engine of a motor vehicle (eg., Passenger cars) has in known manner a plurality of cylindrical combustion chambers ("cylinder"), in which a fuel / air mixture in a 2- or 4-stroke process is intermittently burned, wherein after each combustion process from each cylinder a certain amount of exhaust gas in an exhaust system 1 is ejected. For collecting a plurality of exhaust gas streams discharged from the individual cylinders, exhaust manifolds are provided in which the exhaust gases are combined to form (main) exhaust gas streams. In this case, those partial exhaust streams are preferably combined, which originate from cylinders of a common cylinder bank of the internal combustion engine. In a further preferred manner, so-called V6, V8, V10 or V12 engines result in two cylinder banks, in each of which half of the cylinders of the internal combustion engine are combined to form 3-, 4-, 5- or 6-cylinder banks.

For receiving and forwarding the (main) exhaust gas flows are for an internal combustion engine with two cylinder banks thus two main exhaust pipes 2 . 3 provided, which are shown in the figures. In a manner known per se, corresponding to the firing order of the individual cylinders of a bank, there are pressure surges or sound waves in the respective main exhaust gas pipeline 2 . 3 that can overlap and / or erase. This is on the DE 103 31 620 A1 Reference is made, are included in the further explanation of the acoustics in an exhaust system and for influencing the sound characteristics of an exhaust system of an internal combustion engine.

For a targeted constructive influence on the sound behavior and the pressure conditions in the exhaust system 1 are three or more crosstalk according to the invention 4 . 5 . 6 provided between the main exhaust pipes 2 . 3 are switched and over the main exhaust pipes 2 . 3 acoustically coupled with each other.

In a first embodiment according to 1a and 1b is the main exhaust piping 2 . 3 a metallic housing 7 assigned to the main exhaust pipes 2 . 3 partially encloses. The housing 7 has an outer wall 7a on, the three crosstalk tracks 4 . 5 . 6 limited to the outside. Furthermore, within the housing 7 two partitions 7b . 7c provided the crosstalk routes 4 . 5 . 6 delimit against each other and the firm (for example by welding) with the outer wall 7a are connected.

In particular, according to the first embodiment, the structure described below is realized: a first main exhaust pipe 2 is from a first crosstalk track 4 surrounded, so that both have a common wall 2a exhibit. The first crosstalk track 4 in turn is mostly from the outer wall 7a of the common housing 7 as well as from a first internal partition 7b limited. A second main exhaust pipe 3 is from a second crosstalk track 5 surrounded, so that both have a common wall 3a exhibit. The second crosstalk track 5 in turn is mostly from the outer wall 7a of the common housing 7 as well as from a second internal partition 7c limited.

Between the first crosstalk 4 and the second crosstalk 5 is a third crosstalk track 6 formed, partly from the outer wall 7a the common housing, partly from the first inner partition 7b and partly from the second internal partition 7c is limited. In a modified embodiment, the third crosstalk can also be accommodated in a separate tubular element, in which case can be omitted at least one internal partition.

In the common wall 2a of first main exhaust pipeline 2 and first crosstalk 4 is a first crosstalk opening 2 B provided along a substantial part of the circumference of the first main exhaust pipe 2 extends and, for example, as a perforation or other breakthrough or acoustically permeable membrane in the wall 2a is executed. The size or dimension of the first crosstalk opening 2 B is dependent on the desired or to be avoided throttling effect and depending on the desired length of the first crosstalk 4 adjustable.

The positioning of the crosstalk opening 2 B in the axial direction (parallel to the main flow direction of the exhaust gas) is near a rear end wall 7d of the common housing 7 or adjoining it. Alternatively, the first crosstalk opening 2 B of course also near the front wall 7e of the housing 7 be provided. In a modified embodiment, an adjustable closure element may be provided to limit the extent of the first crosstalk opening 2 B to be able to adjust during operation of the internal combustion engine.

In the common wall 3a from second main exhaust pipeline 3 and second crosstalk 5 is a second crosstalk opening 3b provided along a substantial part of the circumference of the second main exhaust pipe 3 extends and, for example, as a perforation or other breakthrough or acoustically permeable membrane in the wall 3a is executed. The size or dimension of the crosstalk opening 3b is dependent on the throttling effect and depending on the desired length of the second crosstalk 5 adjustable. The positioning of the second crosstalk opening 3b in the axial direction (parallel to the main flow direction of the exhaust gas) is near the front end wall 7e (alternatively the rear end wall 7d ) of the common housing 7 or adjoining it. In a modified embodiment, an adjustable closure element can also be provided here, to the extent of the second crosstalk opening 3b to be able to adjust during operation of the internal combustion engine.

In the first internal partition 7b is a third crosstalk opening 7f provided while in the second internal partition 7c a fourth crosstalk opening 7g is arranged. About the third and fourth crosstalk communication communicates the third crosstalk 6 on the one hand with the first crosstalk track 4 and on the other with the second crosstalk 5 , The length of the third crosstalk 6 is essentially due to the distance between the third crosstalk opening 7f and the fourth crosstalk opening 7g Are defined. Accordingly, the third crosstalk opening 7f adjacent to the front end wall 7e and the fourth crosstalk opening 7g adjacent to the rear end wall 7d of the housing 7 (Alternatively, vice versa) arranged to a maximum length of the third crosstalk 6 to achieve.

A ratio of length to width of the housing 7 may be chosen in this way, for example, less than ten or preferably less than five. The sum of the lengths of the first, the second and the third crosstalk is as set out greater than two times, in particular greater than 2.5 times the length of the common housing 7 ; approximately the sum of the lengths of the crosstalk can be three times the length of the housing.

During operation of the internal combustion engine, as mentioned, two (main) exhaust gas streams enter the main exhaust pipelines 2 . 3 , In this case, sound waves introduced into these exhaust gas streams can originate from the first main exhaust gas pipeline 2 over the first crosstalk opening 2 B after a 180 ° deflection into the first crosstalk 4 reach; from there and after another 180 ° deflection over the third crosstalk opening 7f in the third crosstalk 6 which are essentially centered in the housing 7 is arranged; then over the fourth crosstalk opening 7g and another 180 ° deflection into the second crosstalk 5 that the second main exhaust pipeline 3 completely surrounds, and from there, after another 180 ° deflection through the second crosstalk opening 3b into the second main exhaust pipeline 3 ,

Of course, the described path can also be reversed by sound waves. In this way, pressure waves, vibrations or shocks in the range of crosstalk can 4 . 5 . 6 run against each other and reinforce each other and / or extinguish. Depending on requirements, a preferred length geometry of the crosstalk sections can thus be selected in order to achieve a superposition of pressure waves. In this case, overlays are to be influenced in particular by the fact that a summed length of the crosstalk paths adapted to specific wavelengths is selected. In general, the largest possible overlay distance should be provided, which is present in a small axial space between the front and the rear end wall 7e . 7d of the housing 7 is accomplished in that within the at least three crosstalk sections 4 . 5 . 6 an at least two-fold deflection of pressure waves is achieved and all crosstalk distances are arranged spatially parallel and adjacent to each other. In a preferred manner, a significant restriction within the crosstalk 4 . 5 . 6 avoided by the traversed cross-sectional areas of the crosstalk paths are at least approximately as large as those of the main exhaust pipes 2 . 3 ,

Due to the described functionality, the arrangement according to the invention is generally suitable as a device for noise modification on a system with double-flow gas flow, in which the first main gas pipeline 2 (with a first gas stream) the first crosstalk 4 and the second main gas pipeline 3 (with a second gas stream) the second crosstalk 5 assigned. Between first crosstalk 4 and second crosstalk 5 is a third crosstalk track 6 provided, with the main gas piping 2 - 3 over these crosstalks 4 - 6 are acoustically coupled together and the third crosstalk 6 in particular spatially parallel to the first and the second crosstalk, preferably adjacent to this is arranged.

A modified second embodiment of an exhaust system is in the 2a and 2 B shown. The configuration is essentially the same as that of 1a and 1b ,

Again, the main exhaust piping is 2 . 3 a housing 7 assigned to the main exhaust pipes 2 . 3 partially encloses along a certain length range. The housing 7 has an outer wall 7a on, furthermore, are inside the housing 7 two cylindrical partitions 8th . 9 provided the crosstalk routes 4 . 5 . 6 demarcate each other. Thus, according to the second embodiment, the structure described below is realized.

A first main exhaust pipeline 2 is from a first crosstalk track 4 surrounded by a ring, with a wall 2a the first main exhaust pipe as the inner wall of the crosstalk 4 serves. The first crosstalk track 4 For its part, it is essentially completely inside the outer wall 7a of the common housing 7 arranged. Preferred are the first main exhaust pipe 2 and the first crosstalk track 4 housed in a double-walled cylindrical tube, the outer wall as a partition 8th serves. A second main exhaust pipe 3 is from a second crosstalk track 5 surrounded, being a common wall 3a at the same time the main exhaust pipe outside limits and an inner wall of the crosstalk 5 represents. Preferred are the second main exhaust pipe 3 and the second crosstalk 5 housed in a double-walled cylindrical tube, the outer wall as a partition 9 serves. The second crosstalk track 5 is in turn completely at a distance from the outer wall 7a of the common housing 7 enclosed. Thus, between the cylindrical partitions 8th . 9 and the outer wall 7a of the housing 7 a cavity formed as a third crosstalk 6 serves.

In modified embodiments, further crosstalk sections are housed in further tubular elements, which may also be arranged concentrically to the flow axes of the main exhaust pipes or between the first and the second crosstalk.

In the common wall 2a of first main exhaust pipeline 2 and first crosstalk 4 is - like out 2 B apparent - a first crosstalk opening 2 B provided along a substantial part of the circumference of the first main exhaust pipe 2 extends. Preferably, the crosstalk opening is a perforation with a plurality of round or elongated holes, as an annular open aperture in the wall 2a or executed in the form of one or more Hutzen. It allows acoustic coupling of the first main exhaust pipe 2 with the first crosstalk 4 and, by the way, has the same functionality as that in the first embodiment 1a and 1b ,

In the common wall 3a from second main exhaust pipeline 3 and second crosstalk 5 is analogous to the first embodiment, a second crosstalk opening 3b intended. A third crosstalk opening 8a and a fourth crosstalk opening 9a each provide an acoustic coupling between first crosstalk 4 and third crosstalk 6 or between the second crosstalk 5 and third crosstalk 6 , Similar to the first embodiment, adjacent crosstalk openings are preferably arranged at a distance from each other, which is approximately the axial length of the housing 7 corresponds, so that the longest possible crosstalk between first crosstalk 2 B and fourth crosstalk opening 9a is reached.

As in the first embodiment, the crosstalks are 4 . 5 . 6 with their longest extent substantially parallel to each other and parallel to the main flow direction in the main exhaust pipes 2 . 3 oriented so that in the crosstalk distances results in a multiple 180 ° deflected sound wave propagation.

Analogous to the first embodiment, a system according to 2a and 2 B in a slightly modified form generally serve as a device for noise modification for two gas streams.

With the help of the here proposed devices with multi-divided housing a targeted Klangcharakteroptimierung is possible because the length and cross-sectional geometries of the crosstalk paths are adapted to the present in the system during operation (pressure or sound) wavelengths. Likewise, the sound characteristics can be influenced by means of the opening cross sections and throttle effects of the crosstalk openings (by means of adjustable openings also during operation). It is also possible to introduce known absorption materials (for example steel wool or foams) at several points into the system in order to achieve specific damping effects. In the system according to the invention, the height of the influenceable subdivisions of the sound waves is no longer determined primarily by the cross-sectional areas of the crosstalk paths. There is no adverse effect on the main exhaust gas flows and thus no negative impact on performance, consumption and emissions of the internal combustion engine.

Claims (10)

Exhaust system for an internal combustion engine having a plurality of combustion chambers in which discontinuously a gas exchange is vornehmbar, wherein discharged from the combustion chambers exhaust gas in at least two main exhaust pipes ( 2 . 3 ) is feasible, wherein a first main exhaust pipe ( 2 ) a first crosstalk path ( 4 ) and a second main exhaust pipe ( 3 ) a second crosstalk path ( 5 ) are assigned, wherein between the first crosstalk ( 4 ) and the first main exhaust pipeline ( 2 ) at least a first crosstalk opening ( 2 B ) and between the second crosstalk path ( 5 ) and the second main exhaust pipe ( 3 ) at least a second crosstalk opening ( 3b ) are provided, and between first crosstalk ( 4 ) and second crosstalk ( 5 ) a third crosstalk path ( 6 ) provided with the first crosstalk path ( 4 ) via at least a third crosstalk opening ( 7f . 8a ) and with the second crosstalk path ( 5 ) via at least a fourth crosstalk opening ( 7g . 9a ), so that sound waves through these crosstalk tracks ( 4 . 5 . 6 ) between the main exhaust pipes ( 2 . 3 ), the third crosstalk path ( 6 ) is arranged substantially spatially parallel to the first and / or the second crosstalk path , characterized in that the first crosstalk path ( 4 ) and / or the second crosstalk path ( 5 ) within a first main exhaust pipeline ( 2 ) and / or within a second main exhaust pipeline ( 3 ) at least partially enclosing tubular element ( 8th . 9 ) are formed. Exhaust system according to claim 1, characterized in that the crosstalk paths ( 4 . 5 . 6 ) are designed and arranged such that the crosstalk paths ( 4 . 5 . 6 ) passing sound waves at least twice by about 180 °. Exhaust system according to one of the preceding claims 1 to 2, characterized in that the crosstalk paths ( 4 . 5 . 6 ) within a common housing ( 7 ) with at least two internal dividing walls separating the crosstalk paths ( 7b . 7c ; 8th . 9 ) are formed. Exhaust system according to one of the preceding claims 1 to 3, characterized in that the crosstalk paths ( 4 . 5 . 6 ) within a common housing ( 7 ) are arranged, the at least one of the main exhaust pipes ( 2 . 3 ) encloses at least in sections. Exhaust system according to one of the preceding claims 1 to 4, characterized in that the first crosstalk opening ( 2 B ) along a first peripheral region and along a first longitudinal section of the first main exhaust pipeline ( 2 ). Exhaust system according to one of the preceding claims 1 to 5, characterized in that the second crosstalk opening ( 3b ) along a first peripheral region and along a first longitudinal section of the second main exhaust pipeline ( 3 ). Exhaust system according to one of the preceding claims 1 to 6, characterized in that the third crosstalk opening ( 7f . 8a ) along a first circumferential region and along a first longitudinal segment of the first crosstalk path (FIG. 4 ). Exhaust system according to one of the preceding claims 1 to 7, characterized in that the fourth crosstalk opening ( 7g . 9a ) along a first circumferential region and along a first longitudinal segment of the second crosstalk path (FIG. 5 ). Exhaust system according to one of the preceding claims 3 to 8, characterized in that the sum of the lengths of the first, the second and the third crosstalk distance is greater than twice the length of the common housing ( 7 ). Exhaust system according to one of the preceding claims 3 to 9, characterized in that the sum of the lengths of the first, the second and the third crosstalk distance is approximately three times the length of the common housing ( 7 ) corresponds.

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