Silencer

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2010 008 403.4 filed Feb. 18, 2010, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a silencer (also known as a muffler), particularly a rear silencer, for an exhaust system of a combustion engine, particularly of a motor vehicle.

[0003] In an exhaust system a so-called rear silencer is usually located at an end section of the exhaust system on the outlet side. An outlet pipe leading out of the rear silencer usually forms a so-called tailpipe or is connected to such a tailpipe. The tailpipe has the mouth opening of the exhaust system that is open to the environment. Usually a silencer comprises a housing in which an outlet chamber is located and the outlet pipe is led out from said outlet chamber. For damping low-frequency noises it is usual to construct the outlet pipe of the rear silencer or the tailpipe comparatively long. Comparatively much space is required for this. Particularly in the case of smaller vehicles only little space is available. The use of very long outlet pipes or tailpipes is of increased importance especially with smaller combustion engines with for example three or four cylinders, particularly if the sound damping altogether is to be realized using less space and less weight.

[0004] The present invention deals with the problem of stating an improved embodiment for a silencer of the type mentioned at the outset, which is particularly characterized by a reduced construction volume.

[0005] According to the invention, a silencer is provided, particularly a rear silencer, for an exhaust system of a combustion engine, particularly of a motor vehicle. The silencer comprises a housing in which an outlet chamber is located. An outlet pipe arrangement leads out of the housing. The outlet pipe is fluidically connected to the outlet chamber on the inlet side. The outlet pipe arrangement is developed as pipe-in-pipe arrangement, comprising at least one deflection pipe closed on one side and arranged in the housing and an outlet pipe leading out of the housing.

[0006] The invention is based on the general idea of developing the outlet pipe not as a single pipe but as a pipe arrangement, namely as pipe-in-pipe arrangement. Such a pipe-in-pipe arrangement comprises at least one deflection pipe closed on one end and arranged in the housing of the silencer and an outlet pipe led out of the housing. Through the pipe-in-pipe arrangement, a comparatively long flow path can be realized with short length, which is carried out with the help of suitable deflections. The pipe-in-pipe arrangement can be constructed substantially shorter than a comparable pipe with identical flow length. Investigations have shown that the pipe-in-pipe arrangement achieves damping equivalent to that of a continuous pipe with respect to the low frequencies. At higher frequencies, an even better damping effect is achieved which is attributed to the cross-sectional jumps in the region of the flow deflections.

[0007] The proposed design thus allows a space-reduced realization of a silencer with long flow path in the “outlet pipe” or in the outlet pipe arrangement, with which the desired damping effect for low interference frequencies is additionally guaranteed.

[0008] According to an advantageous embodiment the pipe-in-pipe arrangement can create a flow path which from the outlet chamber to the outlet pipe comprises at least two 180° deflections. Because of this, a three-way layering for the exhaust flow is obtained, which ultimately results in a significant shortening of the outlet pipe arrangement compared with a single pipe.

[0009] With another embodiment it can be provided that the deflection pipe on its closed side comprises a bottom that is concavely curved towards the outlet pipe. Because of this, the through-flow resistance of the silencer can be reduced. In addition or alternatively, the housing or an outer pipe enveloping the deflection pipe can have a bottom that is concavely curved towards the deflection pipe on its side facing the open side of the deflection pipe. Because of this, the 180° deflection is favored, which reduces the through-flow resistance of the silencer.

[0010] A further optional measure for reducing the flow resistance is the provision of a flow deflection contour on an open side of the deflection pipe. With the help of such a flow deflection contour a resistance-reducing flow deflection can likewise be promoted. This can for example be a deflection collar deflecting the flow to the outside or a rounded-off end region likewise favoring the circulation.

[0011] According to another advantageous embodiment it can be provided to equip the outlet pipe on its inlet side, that is within the deflection pipe, with a perforation. Such a perforation can reduce the development of higher-frequency noises. In addition or alternatively the outlet pipe can be fastened to the deflection pipe on its inlet side. This produces a stabilization of the outlet pipe within the pipe-in-pipe arrangement. Fastening of the outlet pipe to the deflection pipe can more preferably be carried out also in the region of the perforation.

[0012] It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated, but also in other combinations or by themselves, without leaving the scope of the present invention.

[0013] Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters refer to same or similar or functionally same components. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

[0023] Referring to the drawings in particular, according to FIGS. 1 and 2 a silencer 1, which preferably is a rear silencer, comprises a housing 2 having an outlet chamber 3. An outlet pipe arrangement 4 is led out of the housing 2, namely in such a manner that the outlet pipe arrangement 4 on the inlet side is fluidically connected to the outlet chamber 3 located in the housing 2.

[0024] The silencer 1 in the installed state is incorporated in an exhaust system 5 which is only partially evident here and which belongs to a combustion engine that is not shown here, which can preferentially be arranged in a motor vehicle. Provided that the silencer 1 is preferably developed as rear silencer 1, it is located in an end region of the exhaust system 5 on the outlet end. In particular, the outlet pipe arrangement 4 led out of the housing 2 comprises a so-called tailpipe 6 of the exhaust system 5 or is connected to said tailpipe 6. The tailpipe 6 is characterized in that it comprises the mouth opening of the exhaust system 5 on the outlet side or of the respective line of the exhaust system 5. The rear silencer 1 is thus located on the tailpipe 6 or near the tailpipe 6.

[0025] With the silencer 1 introduced here the outlet pipe arrangement 4 is designed as pipe-in-pipe arrangement 7. The latter comprises at least one deflection pipe 8 and one outlet pipe 9. The deflection pipe 8 is arranged in the housing 2 and is closed on one side. The outlet pipe 9 is arranged in the deflection pipe 8 and led out of the housing 2. Provided that it is a rear silencer 1, the outlet pipe 9 can be connected to the tailpipe 6 or directly merge with the tailpipe 6 or itself form the tailpipe 6.

[0026] In the shown example the pipe-in-pipe arrangement 7 creates a flow path 10 indicated by arrows which leads from the outlet chamber 3 to the outlet pipe 9 or through the outlet pipe 9 out of the housing 2. Between outlet chamber 3 and outlet pipe 9 this flow path 10 contains at least two 180° deflections 11 and 12 respectively. The first 180° deflection 11 takes place in the housing 2 at the entry into the deflection pipe 8. The second 180° deflection 12 takes place in the deflection pipe 8 at the entry into the outlet pipe 9.

[0027] With the configuration presented here the pipe-in-pipe arrangement 7 comprises an outer channel 13 which is radially formed between the housing 2 and the deflection pipe 8. With another embodiment the outer channel 13 can also be formed between the deflection pipe 8 and an outer pipe which is not shown here, which is arranged within the housing 2 and envelopes the deflection pipe 8. In addition, the pipe-in-pipe arrangement 7 in this case comprises an inner channel 14 which is radially formed between the deflection pipe 8 and the outlet pipe 9. The first 180° deflection 11 connects the outer channel 13 to the inner channel 14. The second 180° deflection 12 connects the inner channel 14 to the interior 15 of the outlet pipe 9.

[0028] Practically, the housing 2, the deflection pipe 8 and the outlet pipe 9 and if applicable the outer pipe are arranged within one another axis-parallel to one another. According to FIG. 3, housing 2, deflection pipe 8 and outlet pipe 9 as well as the outer pipe if applicable can be arranged concentrically to one another. With the embodiment shown in FIG. 4 all involved pipes 8, 9 and the housing 2 are arranged eccentrically to one another. With the embodiment shown in FIG. 5 the outlet pipe 9 is arranged concentrically to the housing 2, while the deflection pipe 8 is arranged eccentrically to the housing 2 and to the outlet pipe 9.

[0029] While FIGS. 3 to 5 show embodiments with circular cross sections, another embodiment is shown in FIG. 6 wherein the deflection pipe 8 and the housing 2 show other round, particularly elliptical or oval cross sections. Selected here is an example which leads to an extremely flat design for the silencer 1. In particular, the deflection pipe 8 and the housing 2 in this case are flattened so far that on the outlet pipe 9 two contact points 16 located diametrically opposite each other are obtained, in which the deflection pipe 8 touches the outlet pipe 9 as well as the housing 2. In the region of these contact points 16 the pipes 8, 9 and the housing 2 can be fastened to one another.

[0030] To reduce the through-flow resistance of the silencer 1 different measures can be realized. For example it is possible to dimension the through-flow capable cross section of the outer channel 13 with respect to the through-flow capable cross section of the inner channel 14 so that the through-flow capable cross section of the outer channel 13 is smaller than the through-flow capable cross section of the inner channel 14. Likewise, the through-flow capable cross section of the outer channel 13 can be identical in size to the through-flow capable cross section of the inner channel 14. Because of this, an excessive pressure increase on overflowing from the outer channel 13 into the inner channel 14 is avoided. In addition or alternatively it can be provided that the through-flow capable cross section of the inner channel 14 is smaller than the through-flow capable cross section of the outlet pipe 9. Likewise, it can also be provided here to select the through-flow capable cross section of the inner channel 14 identical to the through-flow capable cross section of the outlet pipe 9. In general, the through-flow capable cross sections of the outer channel 13, of the inner channel 14 and of the outlet pipe 9 can be matched to one another with respect to a reduced through-flow resistance.

[0031] Optionally it can be provided according to FIG. 2 to provide the deflection pipe 8 on its closed side with a bottom 17 which is concavely curved towards the outlet pipe 9. Because of this, the second 180° deflection 12 can be supported or realized with a reduced flow resistance. In addition or alternatively to this, the housing 2 in the example of FIG. 2 on its side facing the open side of the deflection pipe 8 is equipped with a bottom 18 penetrated by the outlet pipe 9, which bottom is concavely curved towards the deflection pipe 8. Through this shaping of the bottom 18 the first 180° deflection 11 can be supported or realized with a reduced flow resistance.

[0032] According to FIGS. 7 and 8 the deflection pipe 8 can have a flow deflection contour 19 on its open side. This is also a measure to reduce the flow resistance. According to FIG. 7, the flow deflection contour 19 can for example be a deflection collar 20 deflecting the flow towards the outside. In contrast with this, the flow deflection contour 19 according to FIG. 8 can also be a rounded-off end region 21. Other configurations for the flow deflection contour 19 which are not shown here are likewise conceivable.

[0033] With the embodiments of FIGS. 7 and 8 the outlet pipe 9 is provided with a perforation 22 on its inlet side. Such a perforation 22 can impede a noise development upon inflow in the outlet pipe 9. With the embodiment shown in FIG. 7, the outlet pipe 9 protrudes into the deflection pipe 8 so far that it can be fastened to the deflection pipe 8 at its inlet side. In the example, the outlet pipe 9 is fastened to the deflection pipe 8 in the region of its perforation 22, specifically to its space 17. Because of this, the outlet pipe 9 is stabilized within the pipe-in-pipe arrangement 7. In contrast with this, FIG. 8 shows an embodiment wherein the outlet pipe 9 freely standing protrudes into the deflection pipe 8.

[0034] The representations of FIGS. 7 and 8 are half sections, wherein a dash-dotted line 23 represents a symmetry line with respect to which the respective representation can be completed mirror-symmetrically.

[0035] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.