Exhaust system

p0001The present invention relates to an exhaust system for an internal combustion engine, in particular in a motor vehicle, having the features of the preamble of claim 1.

p0002For passenger cars with powerful internal combustion engines, which are preferably configured as a V-type engines, the exhaust gases are often out of the two cylinder banks through two manifolds in two exhaust lines to a common silencer or two separate mufflers. The two exhaust lines in this case run vehicle underbody in a tunnel, which regularly includes heat shields upwards and sideways. Down, the lower ground clearance, an imaginary boundary of the tunnel. Furthermore, can often be found for acoustic reasons a middle silencer, which must be arranged in the central area of ​​the plant. Here, each exhaust line, a separate middle silencer be assigned. Likewise, two exhaust lines, a common middle muffler are assigned. Anyway, the respective middle silencer must also be accommodated in the tunnel, which regularly leads to space problems, since the respective middle silencer must have a certain minimum volume in order to fulfill its acoustic feature.

p0003From the <patcit id="pcit0001" dnum="DE4106918A1"><text>DE 41 06 918 A1</text></patcit> is a generic exhaust system is known in which two separately controllable sound transmission equipment upstream of catalysts are arranged, which are arranged in the two exhaust gas lines. Downstream of these catalysts are the two exhaust gas lines, a common middle muffler and downstream of them associated with a common silencer.

p0004From the <patcit id="pcit0002" dnum="EP1400666A1"><text>EP 1400666 A1</text></patcit> An exhaust system is known, which comprises two separate exhaust-gas lines for discharging exhaust gases of an internal combustion engine. Furthermore, the known exhaust system includes a switchable sound transmission device which couples the two exhaust lines for the transmission of airborne sound together. With the aid of a control means controlling the sound transmission device can be activated and deactivated, this being done in dependence of at least one operating parameter of the internal combustion engine. The operating parameters in this case are, for example, the speed and / or the load of the internal combustion engine. In the prior art exhaust system, the one sound transmission means is arranged downstream of two catalysts arranged in each one of the exhaust strands. the upstream sound transmission device is positioned Further silencers, which are assigned to the individual exhaust lines separately and each form a middle silencer and a rear silencer.

p0005The known exhaust system is advantageously operated so that at low speeds the sound transmission device is active. Silencers, which are assigned to the exhaust gas lines are acoustically designed for interfering frequencies, which occur at low speeds. At higher speeds the sound transmission means is deactivated, whereby the effective interference frequencies due to the specific assignment of the separate exhaust gas lines is halved to individual cylinders of the internal combustion engine. Thus can be achieved for two speed ranges that are available through the spurious frequencies correlated, effective sound damping. The disadvantage here is the restriction of the damping effect on only two speed ranges. Furthermore, the activation of the sound transmission device at low speeds may result in a reduction of the available engine torque due to adverse effects on the gas exchange process in the cylinders of the engine.

p0006Here is where the present invention. The present invention addresses the problem of specifying an improved embodiment for an exhaust system of the type mentioned, in particular, is characterized in that the space required is reduced.

p0007This problem is achieved by the subject matter of the independent claim. Advantageous embodiments are subject of the dependent claims.

p0008The invention is based on the general idea to dispense with a central silencer. The associated with the installation of a center muffler space problems can be avoided thereby. This is made possible by the fact that the two exhaust lines are acoustically coupled with two switchable sound transmission facilities that are spaced from each other in the exhaust gas flow direction. This can improve variability of the adjustable switching states are realized. Of elevated interest are at least three different switching states, namely a first switching state in which both the sound transmission means are deactivated, a second switching state, wherein the one sound transmission means is activated, while the other sound transmission device is deactivated, and a third switching state in which activates both sound transmission means are. It has been shown that the different switching states give significant effects on the torque of the exhaust system equipped with the internal combustion engine. In particular can be in the first switching state, the torque increase significantly when this low rotational speeds of the internal combustion engine is associated, so operating conditions in which a high torque is particularly desirable. Furthermore, it has been shown that the damping effect of the exhaust system is better adapted to different operating conditions of the engine by the three different switching states. With appropriate design and positioning of the sound transmission means, the damping effect of the exhaust system can now be overall improved so that the invention can be dispensed with a central silencer.

p0009Furthermore, the sound transmission means at the exhaust system of the invention are disposed downstream of the catalysts, which are provided in the two exhaust gas lines.

p0010Particularly advantageously, an embodiment has been shown in which the upstream first sound transmission device is deactivated in the second operating state, while the downstream second sound transmission device is activated. In the second switching state, for example, be increased for medium speeds, the torque.

p0011Suitably assigns a controller to the switching states of different speed ranges. Here, the first switching state is associated with a lower speed range, while the second switching state is associated with a medium speed range and the third switching state is associated with a higher speed range.

p0012Further important features and advantages of the invention will be apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

p0013It is understood that the features mentioned above and those yet to be explained not only in the particular combination indicated but also in other combinations or alone without departing from the scope of the present invention.

p0014Preferred embodiments of the invention are illustrated in the drawings and are explained in the following description, wherein like reference numerals refer to identical or similar or functionally identical components.

p0015The drawings show schematically,<dl id="dl0001"><dt>Fig. 1</dt><dd>a greatly simplified, circuit diagram-like Prinzip- illustration of an exhaust system according to the invention,</dd><dt>FIG. 2</dt><dd>a view as in <figref idrefs="f0001">Fig. 1</figref>But direction at a proper generic type exhaust system.</dd></dl>

p0016According to <figref idrefs="f0001">Fig. 1 and 2</figref> an exhaust system 1 has two separate exhaust lines 2 and 3. The exhaust system 1 serves to dissipate the exhaust gases in an internal combustion engine 4, which can be arranged in particular in a motor vehicle. Here, the two exhaust lines 2, 3 different cylinders 5 of the engine 4 are assigned. In the example shown without loss of generality, a six-cylinder engine. In general, the two exhaust lines 2, 3 are each assigned to a group of cylinders 5, which are selected such that the cylinder 5 of a group of cylinders and the cylinder 5 of the other cylinder group have their strokes applied alternately in a preferred construction of the exhaust system. 1

p0017Similarly, the cylinder groups can be selected so that parallel working cylinders are arranged in different groups of cylinders. This is especially true for gröβere engines, such as V-eight or twelve V-engines.

p0018The exhaust system 1 also includes a first switchable sound transmission means 7, which is designed such that it can couple the two exhaust lines 2, 3 for the transmission of airborne sound together. In addition, the exhaust system 1 of the invention comprises a second switchable sound transmission device 8 which is designed such that it can couple the two exhaust lines 2, 3 downstream of the first sound transmission device 7 for transmission of airborne each other.

p0019To switch or to operate the two sound transmission means 7 a control device 9 is provided. This is designed so that they both sound transmission means 7, 8 depending on at least one operating parameter of the internal combustion engine 4 can control to activate and deactivate. In each activated state a sound transmission between the two exhaust lines 2, 3 by the respective sound transmission means 7, 8 takes place in the deactivated state, however, the transmission of sound between the two exhaust lines 2, 3 by the respective sound transmission means 7, 8. The control device 9 is omitted in the present invention also in such a way that they can control 8 of an operating parameter of the internal combustion engine 4 for the realization of at least three different switching states, the two sound transmission means 7 depending least. In a first switching state, both sound transmission means 7, 8 are deactivated. In a second switching state, one of the sound transmission means 7, 8 is activated, while the other sound transmission device 7, 8 is deactivated. In a third switching state then both sound transmission means 7, 8 are activated. Preferably, the control device 9 controls the sound transmission means 7, 8 for the realization of the second switching state so that the upstream first sound transmission device 7 is turned off and that the downstream second sound transmission device 8 is activated. The operating parameters of the internal combustion engine 4, the control device 9 is preferably used a speed of the internal combustion engine 4, to operate the sound transmission means 7, 8 in dependence on the speed.

p0020Particularly advantageous is an embodiment in which the controller 9 is configured such that it divides the speed range of the engine 4 in total in three speed ranges. In a lower speed range, the control means 9 actuates the sound transmission means 7, 8 for adjusting the first switching state. In a middle speed range, the control device 9 to the acoustic transmission devices 7, 8 to the second switching state. In the upper speed range, the controller 9 then realized the third switching state. The corresponding speed information obtained, the controller 9 for example of an engine control unit, not shown here. In particular, the control device 9 can be integrated as hardware in such a motor control device or implemented in software.

p0021For example, for e include speeds up to 1,500 rev / min inen six-cylinder engine, the lower speed range, while the average speed range may include speeds of 1,500 rev / min to about 2,500 r / min. The upper speed range can then have speeds from 2,500 r / min.

p0022According to <figref idrefs="f0001">Fig. 1 and 2</figref> 10 may be disposed in each exhaust line 2, 3, a catalyst. In general, these are in each case by an oxidation catalyst, are reacted with the unburned hydrocarbons and carbon monoxide. As a rule, such a catalyst 10 2 is relatively close to the internal combustion engine 4, in particular immediately after an exhaust manifold or manifold 11 contains Furthermore, in the embodiments shown here, each exhaust line a silencer 12 may These mufflers 12 in particular called silencer act whose outlet for tailpipe 13 of the respective exhaust line 2, 3 leads. Instead of two separate, respective one of the exhaust pipes 2, 3 associated with mufflers 12 can in principle also a common silencer may be provided which is then associated with the two exhaust gas lines 2; 3.

p0023correspondingly <figref idrefs="f0001">FIG. 2</figref> it is in principle possible, the exhaust system 1 equipped with at least one middle silencer 14, which may be particularly two exhaust lines 2, 3 assigned together. Depending on the application and depending on the design of the exhaust system 1, it is through the use of the sound transmission means 7, 8 in accordance with<figref idrefs="f0001">Fig. 1</figref> possible to dispense with such a center muffler 14 and yet to ensure adequate soundproofing.

p0024According to <figref idrefs="f0001">Fig. 1 and 2</figref> 7 is arranged on the two exhaust gas lines 2, 3 downstream of the catalysts 10, the first sound transmission device. Furthermore, there is the first sound transmission means 7 upstream of the muffler 12. The second sound transmission means 8 is on two exhaust lines 2, 3 upstream of the muffler 12. In addition, the second sound transmission means 8 is downstream of the first sound transmission means 7 and thus downstream of the catalysts 10th

p0025When in <figref idrefs="f0001">Fig. 1</figref> preferred embodiment shown includes the respective exhaust line 2, 3 upstream of the second sound transmission means 8 no further silencer. Although can upstream of the second sound transmission device 8 quite different exhaust gas treatment devices in the respective exhaust line 2, 3, in particular also downstream of the first sound transmission device 7 is arranged, such as a particulate filter or an SCR catalyst or a denox catalyst, but is not configured exclusively as a Silencer component longer exists. This allows the pressure loss in the respective exhaust line 2, 3 are reduced.

p0026According to the <figref idrefs="f0001">Fig. 1 and 2</figref> may extend parallel to each other, the two exhaust lines 2, 3 in a central region 15th This middle portion extends in the installed state in a tunnel, which is located on the underbody of the vehicle concerned. In the examples shown, the first sound transmission means 7, 3 are arranged at the respective exhaust line 2 in this central region 15 which extends in the tunnel. Additionally or alternatively, can also be selected for the second sound transmission means 8 a positioning in which it is in the running in the tunnel central region 15th

p0027The first sound transmission means 7 is preferably arranged in each exhaust line 2, 3 in an area which is based on a leading of the internal combustion engine 4 for each silencer 12 flow path is less than or equal to 50% of this flow path. Preferably, the first sound transmission means 7 may be positioned at about 30% to 50% or about 40% to 50% or about 50% of this flow path. In contrast, applies to the positioning of the second sound transmission means 8 that is this greater in a region or equal to 50% of said flow path. Preferably, the second sound transmission device 8 is in a range from about 50% to 100% or from about 70% to 100%, or from about 80% to 100% of the flow path. It has been found that an embodiment is particularly advantageous if a flow path between the two sound transmission devices 7, 8 within the respective exhaust branch 2, 3 is at least 50 cm.

p0028The respective acoustic transfer means 7 can 16 and 17 comprise a connection pipe which connects each of the two exhaust lines 2, 3 in communication with each other. Further, the respective sound transmission means 7 each having an actuator 18 and 19, respectively, for. Example, a slide or a flap or a shutter which is configured to allow the respective connecting pipe may be 16, 17 are opened and locked. Further, here, an actuator is in each case still indicated 20 and 21 respectively, which serves for driving the respective actuator 18, 19 and 9 of the operable or controllable with the aid of the control means. In the simplest case, the respective sound transmission means 7, 8 in such a way that only two switching states are set to it, namely an active state with maximum sound transmission or maximum open cross-section of each connecting pipe 16, 17 and an inactive state with no or minimal sound transmission or -locked or minimum open cross-section of each connecting pipe 16, 17. in principle, however, embodiments are conceivable in which at least one of the sound transmission means 7, 8 can realize an intermediate state, at least, wherein the sound transmission between the exhaust gas lines 2, 3 are activated only in part or . is only partially deactivated, so that in particular the flow cross-section in the respective connecting pipe 16, 17 is only partially open or only partially blocked.

The inventive exhaust system 1 operates as follows:

p0029During operation of the internal combustion engine 4 in the lower speed range, ie for example below 1,500 rev / min both sound transmission means 7, 8 are disabled. The exhaust gases of the two cylinder banks 6 are thus removed separately, without leading to an acoustic coupling between the two exhaust gas lines 2; 3. This also interactions between the acoustic coupling and charge exchange processes can be avoided. Such interactions may occur especially at low speeds, since sound waves are pressure pulsations, which can also spread upstream and thereby may affect gas exchange operations adversely in the presence of an acoustic coupling. In the medium speed range, ie above 1,500 r / min and below 2,500 r / min, the second sound transmission means 8 is activated. This can be obtained for the medium speed range, additional torque. In the upper speed range, ie above 2,500 r / min, the first sound transmission means 7 is activated, whereby additional torque is provided. By appropriate adjustment of the common muffler or the two separate silencer 12 and possibly the Middle silencer 14 can be realized for the respective speed range effective sound damping.