DE4330129C2 - Exhaust system of an internal combustion engine - Google Patents

Description

The invention relates to an exhaust system of an internal combustion engine according to the upper concept of the first claim.

Such exhaust systems are used as standard and allow one low noise level.

Such an exhaust system is known by way of example from DE 36 41 942 C2. she shows a single absorption exhaust silencer with a parallel ten resonator, the Helmholtz resonator from a common gas guide volume within the muffler or muffler housing is branched. This results in a reflection point without any possible tuning friendliness.

Another exhaust system is known from DE 20 28 056 A, in which an as Pipe coupling trained through-flow muffler with two more sound dampers is combined, the bag spaces in front of and behind the aforementioned Mufflers are connected to its exhaust pipe and accordingly as Helmholtz resonators can be formed.

The requirements with regard to the noise emission from the internal combustion engine NEN or provided by motor vehicles driven by internal combustion engines are increasing steadily.

It is therefore an object of the invention to provide an exhaust system with a further improvement To create sound absorption, with an adaptation to minor modifications different engines of a motor vehicle type should be possible.

This object of the invention by the features of the first claim solved.

The invention is based on the general idea of both exhaust gas flowed exhaust system of an internal combustion engine front silencer as well  one exhaust muffler with a Helmholtz Equipped resonator to optimize the muffler effect. During a Helmholtz resonator a particularly strong sound attenuation within a relative narrow frequency band allows, characterized by flow through silencers due to a broadband, albeit somewhat weaker sound damping off. An adaptation to noise emissions is therefore more typical Combustion engines are comparatively easy to do because they are smaller Noise in a wide frequency range amplified noise in narrower Can excite frequency bands. This also contributes to the connection of the respective Helmholtz resonator with the help of a before the respective sound damper branching pipe piece takes place.  

According to a preferred embodiment of the invention the Helmholtz resonators as essentially independent, only a silencer with an inlet opening pots designed to provide extensive thermal decoupling the Helmholtz resonators from the hot exhaust gas to ensure flow through mufflers. This can prevent the frequency ver keep the Helmholtz resonators due to excessive heating changes excessively. Because the natural frequency of a Helmholtz Resonators is also strongly dependent on temperature Density of the gases absorbed by the Helmholtz resonator dependent.

Through the independent construction provided according to the invention of the Helmholtz resonators, these become thermal  significantly less stressed and accordingly indicate a significantly lower natural frequency drift. Also the essentially independent arrangement of the Helmholtz Resonators basically offers the possibility that a Helmholtz resonator and the associated exhaust gas flowed silencer have a common partition and accordingly form a common producible unit - and thus also installed or hung together on the vehicle can be. In this case, the desired may be limited This guarantees heating of the Helmholtz resonator be that according to a preferred embodiment of the common partition area less than about a seventh the surface of the housing of the Helmholtz resonator makes. The Helmholtz resonator then also heats up when operating the internal combustion engine significantly less than the muffler through which the exhaust gas flows, since the Helmholtz Resonator as a sack room only when the internal combustion engine starts machine is filled once with a gas cushion and during continuous operation practically only through heat conduction can heat, which is due to the small size of the common seed partition is clearly limited. Here is a Heating of the Helmholtz resonator is also reduced, that heat is released to the environment via its surface becomes.

The housing of the Helmholtz resonator can advantageously due to the limited warming possibly from less temperature-resistant materials, for example wise from an optimal light metal under weight aspects alloy.  

Yet another voting option with the result of one additionally improved sound attenuation exists if too at least one of the Helmholtz resonators is designed as a sound space forms is. For this purpose, this Helmholtz resonator can at least be divided into two chambers, which are separated by an in which there is preferably a short piece of pipe with one another are connected. Such a helmet designed as a sound space holtz resonator acts in the theory of sound absorption as Spring-mass-spring system and allows by tuning of the individual components, namely the spring, which by the formed in a sealed container formed gas and the mass that represents the mass of gas in the pipe section, the optimal sound insulation effect in the required Fre quenz range.

The Helmholtz resonators are preferably each current up the flow through the silencer on the exhaust pipe closed to the flow through the silencer rooms as far as possible to relieve from pulsations of the exhaust gas. hereby there is a risk of excitation of structure-borne noise reduced. Otherwise, this will result in the arrangement flowed absorption damper the life of the Absorbent material increased.

For a particularly good vibration coupling of the Helmholtz resonators to the one flowing through the exhaust pipe Exhaust gas with simple pipe construction guarantee too can, it is provided, the exhaust pipe at the connections of the Helmholtz resonators as an acute-angled pipe fork to form fork ends pointing in the flow direction. This leads to the connections of the Helmholtz resonators practically against the flow direction of the exhaust gas in the exhaust gas flow.  

Even if a Helmholtz resonator with one from the exhaust gas flowed mufflers in a common housing is arranged is for the connection of the two housing parts such a pipe fork outside the housing intended. On the one hand, this causes thermal stress of the Helmholtz resonator is reduced. On the other hand, by different lengths of the forked pipe pieces an additional frequency tuning, especially of the Helmholtz Resonators can be achieved.

Moreover, the advantageous features of Invention on the claims and the following explanations a particularly preferred embodiment based on referred to the drawing.

It shows

Fig. 1 is a plan view of the exhaust system,

Fig. 2 shows the associated side view and

Fig. 3 is a more constructive representation of the pre-silencer in plan view.

The exhaust system shown has a front silencer 1 and a rear silencer 2 . The front silencer 1 and the rear silencer 2 are connected to each other by an exhaust pipe 3 , which also introduces the exhaust gases of an internal combustion engine, not shown, into the front silencer 1 . Via an end pipe 4 ge the exhaust gases finally out of the rear silencer 2 to the outside.

Both upstream of the front silencer 1 and upstream of the rear silencer 2 each branch off from the exhaust pipe 3 a short pipe section 5 , which leads to a Helmholtz resonator 6 a and 6 b, respectively. These two Helmholtz resonators are designed as essentially independent silencer pots, which only have an inlet opening adapted to the mouth region of the pipe section 5 . While the Helmholtz resonator 6 b is suspended completely independently, the Helmholtz resonator 6 a has a common partition 7 with the associated front silencer 1 .

The Helmholtz resonator 6 b is designed as a so-called sound space and has an internal partition 8 , which is provided with a transition opening 9 with a pipe section 10 inserted therein. Thus, the reverberator 2 associated Helmholtz resonator 6 b is divided into two chambers 11 a and 11 b.

According to FIG. 3, the Helmholtz resonator 6 a and the front silencer 1 have a common housing which is approximately V-shaped in plan view with an arcuate transition between the V-legs. As can be seen from Fig. 1 bar, the transition region between the V-legs has a particularly small cross-section, which widens towards the ends of the V-legs. The housing can be composed of two half-shells in a generally known manner.

The partition 7 is arranged within the housing near a vertical center plane. On both sides of this partition 7 , the exhaust pipe 3 or the pipe section 5 open into a respective housing half, the pipe section 5 protruding only a limited part into the interior of the associated housing half and connecting the interior of this housing half with the exhaust pipe 3 .

For stiffening, the pipe section 5 assigned to the housing half can be provided with a perforated transverse wall 12 .

The exhaust pipe 3 is passed through the housing half assigned to it, approximately in its longitudinal direction, and connected to the interior of this housing half via perforations in its wall. To stiffen this housing half is a transverse wall 13 which is designed as a sliding seat for the exhaust pipe 3 .

In the area of the perforations, the exhaust pipe 3 is covered with chrome steel wool within the associated housing half. For the rest, the housing half mentioned is filled with basalt stone wool. The front silencer 1 thus forms a so-called absorption damper, which is characterized by a broadband damping of noise. The filling of chrome steel or basalt stone wool or the like necessary for such a damper offers the additional advantage in the present case that the hot exhaust gases can only act on the wall of the front silencer 1 and the partition 7 with reduced intensity, as a result of which a reduced thermal Coupling between the front silencer 1 and the Helmholtz resonator 6 a is effected. In addition, the heat transfer between the front silencer 1 and the Helmholtz resonator 6 a is also effectively limited by sam that the housing cross section in the region of the partition 7 is comparatively small and the Helmholtz resonator 6 a by means of the pipe section 5 also from its connection area on Exhaust pipe 3 has a greater distance. In addition, the exhaust pipe 3 within the pre-silencer 1 near the partition 7 have no or comparatively few perforations, while 13 at a greater distance from the partition 7 and in particular in the flow direction behind the transverse wall, perforations are present in increased numbers.

The front silencer 1 and the Helmholtz resonator 6 a housing can be held without separate housing attachments on the vehicle alone through the exhaust pipe 3 , the suspensions of the exhaust pipe 3 can be arranged in greater distance from the front silencer 1 .

The housing of the rear silencer 2 and the Helmholtz resonator 6 b have a largely similar shape and can accordingly be fastened to the vehicle with similar holding elements. At the same time, the opportunity is offered to replace the positions of the rear silencer 2 and the Helmholtz resonator 6 b, in order to enable a modified frequency-wise tuning of the exhaust system without major design effort. With such an interchanged arrangement, the flow path between front silencer 1 and tail pipe 4 is shortened. On the other hand, the Helmholtz resonator 6 b is then connected to the exhaust pipe 3 with a significantly longer pipe section 5 .

The Helmholtz resonator 6 b is subjected to particularly little thermal stress, so that its housing is particularly suitable for production from light metal. In this case, it can be provided, if necessary, to produce the housing base connected to the pipe section 5 , such as the pipe section 5 or the exhaust pipe 3, from steel and to manufacture only the remaining housing part from light metal.

Claims (19)

1. Exhaust system of an internal combustion engine with an exhaust pipe ( 3 ), which leads the exhaust gas in succession through at least one exhaust gas flow through the pre-silencer ( 1 ) and at least one exhaust gas flow through the exhaust silencer ( 2 ), characterized in that the exhaust pipe ( 3 ) both before a pipe piece ( 5 ) leading to a Helmholtz resonator ( 6 a, 6 b) branches off the front silencer ( 1 ) and in front of the rear silencer ( 2 ). 2. Exhaust system according to claim 1, characterized in that the Helmholtz resonator ( 6 a, 6 b) is designed as a substantially independent, only one inlet opening having a silencer pot. 3. Exhaust system according to claim 1 or 2, characterized in that the Helmholtz resonators ( 6 a, 6 b) each have approximately the same volume as the adjacent front silencer ( 1 ) or rear silencer ( 2 ). 4. Exhaust system according to one of claims 1 to 3, characterized in that the front silencer ( 1 ) and the associated Helmholtz resonator ( 6 a) have a common housing. 5. Exhaust system according to one of claims 1 to 4, characterized in that the rear silencer ( 2 ) and the associated Helmholtz resonator ( 6 b) have separate housings. 6. Exhaust system according to claim 4 or 5, characterized in that a comparatively low heat transfer occurs between the front silencer ( 1 ) and the associated Helmholtz resonator ( 6 a) forming parts of the common housing. 7. Exhaust system according to claim 6, characterized in that the housing parts are separated from one another by a common partition ( 7 ), the area of which makes up less than a seventh of the surface of the housing part of the Helmholtz resonator ( 6 a). 8. Exhaust system according to one of claims 1 to 7, characterized in that at least one of the Helmholtz resonators ( 6 b) is designed as a sound space and for this purpose is divided into at least two chambers ( 11 a, 11 b) which are separated by a transfer opening ( 9 ) are connected to each other with a piece of pipe ( 10 ). 9. Exhaust system according to one of claims 4 to 8, characterized in that the approximately V-shaped common housing of the front silencer ( 1 ) and the associated Helmholtz resonator ( 6 a) through the common partition ( 7 ) in the transition area the V-leg is divided. 10. Exhaust system according to claim 9, characterized in that the exhaust pipe ( 3 ) is forked before the transition region between the V-legs of the common housing and the fork ends on both sides of the partition open into the associated housing parts. 11. Exhaust system according to claim 9 or 10, characterized in that the housing, which forms the front silencer ( 1 ), is flowed through substantially in the longitudinal direction - from the V tip to the end of the V leg. 12. Exhaust system according to one of claims 1 to 11, characterized in that the front silencer ( 1 ) is designed as an absorption damper and is penetrated by a perforated part of the exhaust pipe ( 3 ). 13. Exhaust system according to claim 12, characterized in that in the area of the perforations a first order of metal wool, in particular chrome steel wool, is arranged and that the housing of the pre-silencer ( 1 ) is otherwise filled with mineral wool, in particular basalt stone wool. 14. Exhaust system according to one of claims 9 to 13, characterized in that the housing part forming the front silencer ( 1 ) is reinforced by a transverse wall ( 13 ) with a sliding seat for the exhaust pipe passing through this housing part ( 3 ). 15. Exhaust system according to claim 14, characterized in that the transverse wall ( 13 ) is perforated. 16. Exhaust system according to one of claims 1 to 15, characterized in that the after-muffler through which the exhaust gas flows ( 2 ) is essentially designed as a reflection damper with a plurality of resonators through which flow. 17. Exhaust system according to one of claims 5 to 16, characterized in that the housing pots of the rear silencer ( 2 ) and the associated Helmholtz resonator ( 6 b) are arranged side by side and the exhaust pipe ( 3 ) is forked near one of the housing pots and accordingly fork parts are available with different lengths. 18. Exhaust system according to claim 17, characterized in that the Helmholtz resonator ( 6 b) is arranged on the shorter fork branch. 19. Exhaust system according to one of claims 1 to 18, characterized in that the Helmholtz resonators ( 6 a, 6 b), in particular the rear silencer ( 2 ) associated Helmholtz resonator ( 6 b), at least partially have a housing made of light metal ,