DE19743446C2 - Exhaust system for an internal combustion engine - Google Patents

Description

The present invention relates to an exhaust system for an internal combustion engine machine with at least one of the exhaust gases of the internal combustion engine ne flow-through first muffler, in particular reverberation damper, and at least a second silencer, which is parallel to the first muffler is connected to the exhaust gas stream, the he and the second silencer are tuned to different frequencies are true.

Exhaust systems of this type are produced in particular in motor vehicles used moderately to the noise level generated by the vehicle engine to reduce. However, the requirements, which are outlined in the Hin view of the noise emission from internal combustion engines and thus driven vehicles, steadily.

In an exhaust system of this type known from DE 43 30 129 A1 a first designed as an absorption or reflection muffler Silencer with a so-called Helmholtz resonator as second Combined silencer. The abge forming the Helmholtz resonator closed cavity is shunted to the exhaust gas flow closed. While a Helmholtz resonator is a particularly strong one  Sound absorption within a relatively narrow frequency band light, flow-through silencers are characterized by a frequency ß broadband, if weaker sound attenuation. Through the Combination of a Helmholtz resonator with a flow through Silencers are more typical to adapt to noise emissions Combustion engines are comparatively possible because the engines are next to lower noise in a wide frequency range amplified Ge can excite noise in narrower frequency bands.

However, a certain disadvantage of this known exhaust system is that that the exhaust gas back pressure with increasing speed of the internal combustion engine increases, reducing their performance.

An exhaust system of the type mentioned is also from DE 94 06 200 U1 known. In this known exhaust system there are two sounds damper connected in parallel to each other to the exhaust gas stream, the Exhaust inlet opening to the one silencer can be temporarily closed is. The exhaust outlet of the other silencer is one connected further exhaust gas inlet opening of the first silencer, so that the exhaust gas flow flowing through the second silencer starts flowing through the first silencer and then through the exhaust outlet.

DE-GM 68 03 317 finally shows an exhaust system with two in parallel mufflers connected to the exhaust gas flow, but only can be optionally supplied with the exhaust gas flow. The other sound The damper is then completely separated from the exhaust gas flow cannot act as a resonator.

The invention has for its object an exhaust system of the beginning Specify the type mentioned, its flow behavior at the same time good noise reduction behavior compared to the known exhaust systems is improved.

This object is achieved in that the gas outlet from the second Silencer is temporarily lockable, and that the second sound damper acts as a resonator when the gas outlet is closed.

According to the invention, it is not the gas inlet but the gas outlet that is out the second silencer can be temporarily closed and the second one works Silencer with closed gas outlet as a resonator. Thus lies in the exhaust system according to the invention both with the gas off occurs when the gas outlet is closed, a parallel connection of the two silencers. This means that when the gas outlet is open both mufflers are flowed through, with the gas outlet closed only one while the other muffler as a resonator, in particular Helmholtz resonator works.

The advantage of the exhaust system according to the invention is that at high speeds when the gas escapes from the second silencer is opened, a particularly large passage cross section for the exhaust gas current is given. This allows the exhaust gas back pressure at high speed len be kept low. On the other hand, at low speeds through the parallel connection of a flow-through silencer and a particularly good one of a non-flowed resonator silencer Sound absorption can be achieved.

Through the gas outlet opening of the second, which can be temporarily closed The silencer can be connected to the exhaust gas flow parallel to the first silencer  connected second silencer optionally as Helmholtz Resonator or used as a flow-through silencer. Be preferably depending on the operating state of the internal combustion engine So the exhaust opening of the second silencer can be opened or be closed. This allows the second silencer, especially in a lower speed range in which strong, narrowband noise Emissions occur when the Helmholtz resonator acts in addition to the first flow through the silencer to a particularly good Ge noise reduction in this frequency range. From a certain Engine speed is determined by opening the gas outlet of the second Muffler increases the flow cross section of the exhaust system, so that an undesirable increase in exhaust gas back pressure is prevented.

The flow cross-section of the first, continuously flowed sound damper can be proportionate in the exhaust system according to the invention be made small, so that the continuously flowing first exhaust gas muffler has a high damping effect. Nevertheless, the Exhaust gas back pressure not at higher engine speeds impermissible because the flow cross-section by opening the gas opening of the second silencer is increased.

The silencer arrangement according to the invention can basically can be used as a front, main or rear silencer. However, use as a rear muffler is preferred, since this is due to the lower exhaust gas temperature especially with the resonator larger Damping effects can be achieved.

Through the second one connected in parallel to the first silencer Silencers can achieve optimal tuning of the exhaust system become. In particular, the two can be parallel to each other in the exhaust gas flow  switched flow-through silencers independently others can be tuned to different frequencies, one too strong increase in the exhaust gas back pressure is prevented by the fact that both silencers as at least temporarily flowed through silencers are trained. In addition, the size of the exhaust system overall be kept relatively small because of the Flow through both mutually parallel silencers whose flow Mung cross section can be made smaller than with silencer pairs with only one silencer flowed through.

In particular, the first silencer is on high frequencies and the second silencer tuned to low frequencies.

According to further embodiments of the invention, both silencers can fer each trained as an absorption and / or reflection silencer det be. Depending on the requirements for sound insulation, the can suitable type of silencer can be selected.  

The two silencers can each have one, two or more chambers include. Through the two- or multi-chamber training of the sound Additional tuning options for certain frequencies are dampened zen created, both with flow through the silencer and also closed with a silencer acting as a Helmholtz resonator exhaust outlet. The vote takes place in the Chamber-protruding pipe sections, the length of which corresponds to the respective Tuning frequency is selected. The tonal spaces thus formed act as Spring-mass-spring system, in which the spring through the in the Chamber recorded gas and the mass by the mass of gas in the tube piece is formed. By coordinating the individual components so the optimal sound insulation effect in the desired Fre quenz range.

In addition to the first and second silencers, at least one can another silencer acting as a resonator in the shunt be connected to the exhaust gas flow. The further silencer fer like the second silencer also temporarily from the exhaust gas be flowable. This further increases the voting options and accordingly further improved the sound absorption.

According to a further embodiment of the invention, the first and the second silencer with its inlet opening at one end of each first fork-shaped pipe section of an engine-side exhaust pipe closed. This has the advantage, among other things, that the second one is preferred Silencers designed as a Helmholtz resonator vibrationally is particularly well coupled to the exhaust gas flow, since the mouth of the second muffler points the flow direction of the exhaust gas.  By a second fork-shaped pipe section, the from the first and the second muffler emerging exhaust gas flows another embodiment of the invention can be reunited. al Alternatively, the two exhaust gas streams can each be sent to a separa exhaust pipe on the exhaust side must be connected.

In exhaust systems with two separate exhaust gases coming from the engine Pipes are the first and the second silencer preferably on double fork-shaped cross piece connected. This is a ver mixing and distribution of the two exhaust gas flows to both Silencer guaranteed.

According to another embodiment of the invention, the first and the second silencer can be housed in a common housing. As a result, the exhaust system can be designed to be particularly space-saving the.

An embodiment of the invention is shown in the drawing and is described below. It shows, each in a schematic Presentation:

Fig. 1 shows a portion of a first variant of an inventive SEN exhaust system,

Fig. 2 sections of further variants of inventive exhaust systems and

Fig. 3-5, respectively a portion of another variant of an OF INVENTION to the invention the exhaust system.

The section shown in Fig. 1 of an exhaust system according to the invention comprises on the one hand with the exhaust outlet of an internal combustion engine and on the other hand with an exhaust port connected exhaust pipe 1 , egg nen from the exhaust gases supplied according to arrow I through the first muffler 2 and a second muffler 3rd The inlet opening 5 of the first muffler 2 and the inlet opening 6 of the second muffler 3 are connected to a section of the exhaust pipe 1 on the engine side via a first pipe section 4 which is forked at an acute angle. The outlet opening 7 of the first muffler 2 and the outlet opening 8 of the second muffler 3 are connected via a second pipe section 9 forked at an acute angle to a section of the exhaust pipe 1 on the exhaust side. As indicated by the pipe sections 10 and 11 in the first muffler 2 , this is designed as a continuously flowed reflection muffler. The second muffler 3 , as shown, is designed as a reflection muffler. For this purpose, 3 pipe sections 12 and 13 are provided in the silencer. The two silencers 2 and 3 can each be tuned to specific frequency ranges over the length of the pipe sections 10 , 11 and 12 , 13 .

In the section of the fork-shaped pipe section 9 connected to the outlet opening 8 of the second silencer 3 , a closable exhaust flap 14 is provided. By closing the exhaust flap 14 , an escape of the exhaust gas flow from the second silencer 3 is prevented. The second silencer 3 then acts as a Helmholtz resonator. This resonator 3 can be tuned in the desired manner both over its dimensions, over the length of the assigned sections of the exhaust pipe 1 and over the length of the pipe section 12 and the pipe section 13 . The second silencer 3 can be designed so that its maximum damping performance when the gas outlet opening 8 is in the frequency ranges in which a strong, narrow-band noise emission of the internal combustion engine occurs.

By opening the exhaust flap 14 , a flow-through reflection muffler becomes from the Helmholtz resonator. The exhaust gas supplied to the second muffler 3 is no longer included, but can emerge via the outlet opening 8 and passes via the fork-shaped pipe section 9 into the exhaust-side section of the exhaust pipe 1 , where it merges with the exhaust gas exiting from the first muffler 2 through which the exhaust flows and continues to flow according to arrow II. The second silencer can also be tuned as a reflection silencer, in particular over the length of the pipe sections 12 and 13 .

The exhaust system according to the invention can be tuned in a variety of ways and thus be adapted to different engines and vehicles. The second muffler 3 is tuned, for example, as a Helmholtz resonator to a frequency range around 50 to 100 Hz and is converted, for example, at a speed of approximately 2000 rpm by opening the exhaust flap 14 into a reflection muffler. Due to the design of the second muffler 3 , which is separate from the first muffler 2 , it remains relatively cool despite the flow of hot exhaust gas. This also contributes to the fact that exhaust gas flows through the second muffler 3 only at times, and in the intervening periods is cooled, inter alia, by the airstream.

FIG. 2 shows various versions of the exhaust system according to the invention. Thus, as illustrated, the first muffler as a reflection sound damper 2, as a combined reflection / absorption silencer 2 'or be designed as a pure absorption silencer 2 ". The second muffler 2 can, as shown, as a single-chamber resonator 3 or as multi-chamber be formed resonator 3 '. Instead of the two chambers 15 and 16 of the second muffler 3 also more compartments may be provided. Similarly, the second muffler may be formed as a combined absorption or reflection / absorption silencer. further, Fig. 2 Instead of a single forked pipe section 4, a double fork-shaped cross piece 4 ', the two inlet-side connecting pieces are each closed on one of two mutually parallel motor-side pipe sections 17 and 18 .

In the variant of a gas system according to the invention shown in FIG. 3, the first muffler 2 and the second muffler 3 are each connected to a separate exhaust pipe section 19 , 20 . On the input side, the two mufflers 2 and 3 are closed, as in the variants of FIG. 2, at a double-fork cross piece 4 '.

The variant shown in Fig. 4 largely corresponds to that of Fig. 3, however, the two silencers 2 and 3 are connected to a simple tubular pipe section 4 .

Fig. 5 shows a variant of the exhaust system according to the invention, in which the two silencers 2 and 3 are arranged in a common housing 21 . On the one hand, there is a resonator chamber 22 in the housing 21 , into which a motor-side pipe section 23 opens. On the other hand, the housing 21 is filled with absorption material 24 , which is penetrated by a further motor-side pipe section 25 with a perforated wall. The pipe section 25 is connected to an exhaust pipe section 26 . Finally, the resonator chamber 22 is connected to an exhaust pipe section 27 , in which an exhaust flap 14 is arranged. This configuration is particularly space-saving. It may also be advantageous for reasons of space to design the two silencers 2 and 3 only with a common wall. In these cases too, the two silencers 2 , 3 can each be designed as reflection and / or absorption silencers. In addition, in all cases at least one further silencer can be connected in parallel to the first and second silencers 2 , 3 in the exhaust gas flow I, II. This further muffler is in turn preferably configured as a resonator through which the exhaust gas can flow at times.

The functionality of the exhaust system is basically the same for all variants. The two mufflers 2 and 3 are each independently tuned to a specific frequency range, in particular re muffler 2 to high frequencies and muffler 3 to low frequencies. By dividing the exhaust gas flow I, II into two parallel paths, an independent tuning of different frequency ranges is achieved and thereby improved sound absorption. The second silencer 3 can in principle also be designed without an exhaust flap 14 . In this case, the tuning to low frequencies takes place in a different way, in particular by correspondingly small flow cross sections of the associated pipeline sections 12 , 13 and by suitable volumes of the chambers 15 , 16 . The structure of the exhaust system according to the invention therefore has the additional advantage that, in addition to the various variants of the two silencers 2 , 3 shown , a particularly cost-effective variant is also possible, the same components being able to be used in all cases. Only the corresponding mufflers 2 , 3 have to be combined with one another or the exhaust flap 14 inserted or omitted.

The exhaust system according to the invention is preferably used as a rear silencer used and is then taking into account the coordination of Pre-tuned and, if necessary, center silencer. in principle the exhaust system according to the invention can also be used as a preliminary or means silencers are used.

Claims (14)

1.Exhaust system for an internal combustion engine with at least one first muffler ( 2 ), in particular secondary muffler, through which the exhaust gases of the internal combustion engine can flow, and at least one second muffler ( 3 ) which is connected to the exhaust gas flow parallel to the first muffler ( 2 ) first and second mufflers ( 2 , 3 ) are tuned to different frequencies, characterized in that the gas outlet from the second muffler ( 3 ) can be temporarily closed, and that the second muffler ( 3 ) acts as a resonator when the gas outlet is closed. 2. Exhaust system according to claim 1, characterized in that the first silencer ( 2 ) is tuned to high and the second silencer ( 3 ) to low frequencies. 3. Exhaust system according to claim 2, characterized in that the first muffler ( 2 ) is designed as an absorption and / or reflection muffler. 4. Exhaust system according to claim 2 or 3, characterized in that the second muffler ( 3 ) is designed as an absorption and / or reflection muffler. 5. Exhaust system according to one of the preceding claims, characterized in that the gas outlet from the second muffler ( 3 ) is closable depending on the operating state of the internal combustion engine, in particular on the engine speed. 6. Exhaust system according to claim 5, characterized in that the gas outlet from the second muffler ( 3 ) is opened above a predetermined engine speed and closed below it. 7. Exhaust system according to one of the preceding claims, characterized in that the two silencers ( 2 , 3 ) each comprise one, two or more chambers ( 15 , 16 , 22 ). 8. Exhaust system according to one of the preceding claims, characterized in that in addition to the second silencer ( 2 ) at least one further parallel silencer is provided. 9. Exhaust system according to claim 8 characterized, that the additional muffler is preferred temporarily from the exhaust gas flowable resonator is formed. 10. Exhaust system according to one of the preceding claims, characterized in that the first and the second muffler ( 2 , 3 ) are connected with their inlet opening ( 5 , 6 ) to one end of a first fork-shaped pipe section ( 4 ) of an exhaust pipe ( 1 ) , 11. Exhaust system according to one of claims 1 to 9, characterized in that the first and the second silencer ( 2 , 3 ) with their inlet opening ( 5 , 6 ) are each connected to one end of a double fork-shaped cross piece ( 4 '). 12. Exhaust system according to one of the preceding claims, characterized in that the first and the second muffler ( 2 , 3 ) with their outlet opening ( 7 , 8 ) each connected to one end of a second fork-shaped pipe section ( 9 ) of an exhaust pipe ( 1 ) are. 13. Exhaust system according to one of claims 1 to 11, characterized in that the first and the second muffler ( 2 , 3 ) with their outlet opening ( 7 , 8 ) are each connected to a separate exhaust pipe ( 19 , 20 ) on the exhaust side , 14. Exhaust system according to one of the preceding claims, characterized in that the first and the second silencer ( 2 , 3 ) are housed in a common housing ( 21 ).