JP2010092678A - Muffler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffler capable of preventing deterioration of muffling performance due to condensed water. <P>SOLUTION: The muffler includes an exhaust gas passage (22) penetrating a case (21) and a sound absorbing member (30) surrounding a periphery of the exhaust gas passage (22) and enclosed inside the case (21). The exhaust gas passage (22) is provided with a plurality of small holes (22a) open toward the inside of the case (21), and between the exhaust gas passage (22) and the sound absorbing member (30), there is provided a thin film (23) through which liquid does not pass but sound wave does. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silencer for reducing the generated sound of exhaust gas, and more particularly to a silencer that can prevent deterioration of the silencing performance due to condensed water.

  A fuel cell is a cell that obtains an electromotive force by reacting hydrogen and oxygen. Since fuel cells do not emit harmful gases, they are being developed as energy sources for automobiles and the like.

  When this fuel cell is mounted on a vehicle, since a large amount of water vapor is contained in the exhaust gas, a large amount of condensed water is generated when the water vapor is cooled in the vicinity of the silencer exposed to the outside air. If this condensed water stays inside the silencer, there may be a problem that the sound absorbing performance deteriorates due to permeation into the sound absorbing member, or the accumulated condensed water corrodes.

  In order to solve such a problem, an exhaust device (see Patent Document 1) is known in which condensed water accumulated in the muffler is caused to flow down into the sub-muffler, and this condensed water is discharged from the Pitot tube by the flow of exhaust gas. .

  There is also known a silencer (see Patent Document 2) in which generated water is dropped by a columnar member provided in the silencer, the generated water is accumulated in a buffer, and the accumulated produced water is discharged by a drain valve.

There is also known an exhaust device (see Patent Document 3) provided with a water amount adjusting hole for collecting a predetermined amount of condensed water contained in exhaust gas in a sound absorbing chamber in the muffler.
Japanese Patent Laid-Open No. 10-30435 JP 2005-171874 A JP 2005-188312 A

  As described above, when the condensed water accumulated in the silencer is discharged using a pitot tube or a small hole opened for drainage, clogging of the pitot tube occurs due to the influence of the sound absorbing material. It is easy and may not drain smoothly. In addition, the small holes are likely to be clogged with mud and dust when the vehicle is running. When these pitot tubes and small holes are clogged, there has been a problem that the sound deadening performance is greatly reduced.

  In cold regions, the condensed water remaining in the Pitot tube and small holes may freeze. If these pitot tubes and small holes are closed due to freezing of condensed water, there is a problem that the noise reduction performance is deteriorated or the system cannot be started when the system is started.

  The present invention has been made in view of such problems, and a silencer that can improve durability without deteriorating the silencing performance by preventing the condensed water from entering the silencer. The purpose is to provide.

  The invention according to claim 1 is a silencer connected to an exhaust system of a fuel cell, and an exhaust gas passage penetrating a case, and a sound absorbing material that surrounds the exhaust gas passage and is filled in the case And the exhaust gas passage includes a plurality of small holes that open into the case, and a thin film that does not pass liquid but passes sound waves between the exhaust gas passage and the sound absorbing member. It is characterized by having.

  The invention according to claim 2 is the silencer according to claim 1, wherein the thin film is provided in close contact with the periphery of the exhaust gas passage.

  The invention according to claim 3 is the silencer according to claim 1, wherein the thin film is provided in close contact with an inner peripheral surface of the exhaust gas passage.

  Invention of Claim 4 is a silencer as described in any one of Claim 1 to 3, Comprising: The said thin film is provided only in the location corresponding to the position of the small hole provided in the said exhaust-gas channel | path. It is characterized by being able to.

  The invention according to claim 5 is the silencer according to claim 1, wherein the sound absorbing member is filled in the case at a predetermined interval from the exhaust gas passage, and the thin film is formed on the sound absorbing member. , And is provided in close contact with the surface facing the exhaust gas passage.

  According to the first aspect of the present invention, since a thin film-like thin film that does not pass liquid but passes sound waves is provided between the exhaust gas passage and the sound absorbing member, liquid (for example, from the exhaust gas passage to the sound absorbing member) Condensed water) can be prevented from penetrating, and deterioration of the sound deadening performance and corrosion of the case due to this liquid can be prevented.

  According to the invention described in claim 2, since the thin film is provided in close contact with the periphery of the exhaust gas passage, it is possible to prevent liquid (for example, condensed water) from penetrating from the exhaust gas passage to the sound absorbing member. .

  According to the invention described in claim 3, since the thin film is provided in close contact with the inner peripheral surface of the exhaust gas passage, it prevents the liquid (for example, condensed water) from penetrating from the exhaust gas passage to the sound absorbing member. Can do.

  According to the fourth aspect of the present invention, since the thin film is provided only at a position corresponding to the position of the small hole provided in the exhaust gas passage, liquid (for example, condensed water) permeates from the exhaust gas passage to the sound absorbing member. This can be prevented and the manufacturing cost can be reduced.

  According to the fifth aspect of the present invention, the sound absorbing member is filled in the case at a predetermined interval from the exhaust gas passage, and the thin film is provided in close contact with the surface of the sound absorbing member facing the exhaust gas passage. It is possible to prevent a liquid (for example, condensed water) from penetrating from the gas passage to the sound absorbing member, and to exhibit a silencing performance in a wide range from a medium frequency to a high frequency.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory diagram of a silencer 1 centered on a silencer 10 according to an embodiment of the present invention.

  The silencer 1 of the present invention includes a fuel cell stack 2 mounted on a vehicle and an exhaust system 3. A silencer 10 is connected to the exhaust system 3. The silencer 10 reduces noise generated by exhaust gas discharged from the fuel cell stack 2. The exhaust gas that has passed through the silencer 10 is discharged to the atmosphere.

  The fuel cell stack 2 obtains an electromotive force by reacting a fuel gas (hydrogen) with an oxidant gas (air). At this time, water is generated by the reaction between hydrogen and oxygen. The generated water is discharged as exhaust gas together with unreacted gas mainly as water vapor.

  Since the exhaust system 3 mounted on the vehicle is exposed to the outside air, the temperature of the exhaust gas decreases when passing through the exhaust system 3. Therefore, condensed water is generated in the silencer 10. This condensed water may affect the silencing performance of the silencer 10.

  Specifically, when condensed water enters the silencer 10, the condensed water penetrates into the sound absorbing member 30 (see FIG. 2) constituting the silencer 10, and the air layer of the sound absorbing member 30 is exclusively used. The area is reduced and the noise reduction performance is reduced. Moreover, when condensed water accumulates inside the silencer 10, corrosion occurs in the silencer 10 due to the condensed water, and the durability of the silencer 10 decreases.

  With respect to such a problem, in the embodiment of the present invention, by providing a characteristic configuration as described below, there is a problem that may occur due to condensed water without deteriorating the silencing performance of the silencer 10. To prevent.

  FIG. 2 is a cross-sectional view showing a configuration of the silencer (muffler) 10 according to the embodiment of the present invention.

  The silencer (muffler) 10 includes a substantially cylindrical case 21, an exhaust pipe 22 that is an exhaust gas passage, and a sound absorbing member 30.

  The case 21 is configured by a cylindrical or elliptical case that determines the shape of the silencer 10. The material of the case 21 may be metal, non-ferrous metal, resin, or the like. The end plate 21a and 21b which obstruct | occlude the opening part of the case 21 are joined to the both ends of the case 21. As shown in FIG.

  The case 21 is provided with a tubular exhaust pipe 22 through which exhaust gas flows. The material of the exhaust pipe 22 may be metal, non-ferrous metal, resin, or the like. The exhaust pipe 22 is supported by end plates 21a and 21b, respectively, one of which communicates with the fuel cell stack 2 from the exhaust system 3, and the other is opened to the atmosphere. In addition, the arrow in a figure shows the flow direction of exhaust gas.

  Inside the case 21, the exhaust pipe 22 is provided with a small hole 22 a at its main point. The small hole 22a communicates from the inside of the exhaust pipe 22 to the inside of the case 21 and is configured to guide sound waves contained in the exhaust gas to the sound absorbing member 30 of the silencer 10.

  In the example shown in FIG. 2, the exhaust pipe 22 is provided with several circumferential small holes 22a, and these are provided in five rows in the exhaust gas flow direction.

  The sound absorbing member 30 is provided inside the case 21 so as to surround the exhaust pipe 22. The sound absorbing member 30 is made of a material containing many air layers, such as glass wool, sound absorbing urethane, and sound absorbing pellets. The sound wave transmitted from the small hole 22a of the exhaust pipe 22 is attenuated by this air layer.

  The sound wave is transmitted from the small hole 22 a to the sound absorbing member 30 when passing through the exhaust pipe 22. The sound absorbing member 30 includes a large amount of an air layer therein, and sound waves attenuate when passing through the sound absorbing member 30. The attenuated sound wave passes through the small hole 22a and returns to the exhaust pipe 22. Further, the exhaust gas does not pass through the small hole 22a, but is passed through the exhaust pipe 22 as it is and then released into the atmosphere.

  A thin film sheet 23 is provided around the exhaust pipe 22.

  Specifically, as shown in FIG. 2, a thin film sheet 23 is provided between the exhaust pipe 22 and the sound absorbing member 30 so as to be in close contact with the periphery of the exhaust pipe 22. The membrane sheet 23 is made of a material that allows sound waves to pass but not liquid (for example, water).

  The membrane sheet 23 prevents the condensed water generated in the silencer 10 from entering the sound absorbing member 30. The condensed water generated in the silencer 10 is pushed out from the exhaust pipe 22 by the pressure of the exhaust gas. On the other hand, the sound wave passes through the membrane sheet 23 and is transmitted into the sound absorbing member 30. This sound wave is attenuated by the sound absorbing member 30 as described above.

  With such a configuration, the silencing performance can be exhibited without the condensed water penetrating into the silencer 10.

  The efficiency with which sound waves are transmitted through the membrane sheet 23 varies depending on the material, film thickness, and the like of the membrane sheet 23. Therefore, it is possible to control the silencing performance by selecting these materials and film thicknesses.

  As the material of the film sheet 23, for example, a thin film of metal, resin, rubber, or the like can be used. Since the exhaust gas temperature of the fuel cell stack 2 is lower than the exhaust gas temperature of an internal combustion engine such as a gasoline engine (approximately less than 100 ° C.), it is possible to use a material having a low heat resistance temperature. Since resin and rubber are excellent in workability as compared with metal, the use of these resin and rubber as the material of the membrane sheet 23 can reduce the manufacturing cost of the silencer 10.

  The membrane sheet 23 is fixed to the exhaust pipe 22 or the sound absorbing member 30 by adhesion, caulking, brazing, welding, or the like. Moreover, when using resin and rubber | gum, it can form and adhere | attach by thermoplastic deformation. Note that the fixing method is not limited to these methods, and any fixing method may be used as long as condensed water does not enter the sound absorbing member 30 from the exhaust pipe 22.

  FIG. 3 is a cross-sectional view showing another configuration of the silencer 10 according to the embodiment of the present invention.

  In the example shown in FIG. 2 described above, the membrane sheet 23 is disposed between the exhaust pipe 22 and the sound absorbing member 30. On the other hand, in the configuration example shown in FIG. 3, it is provided not on the outer periphery of the exhaust pipe 22 but on the inner peripheral side of the exhaust pipe 22.

  In the example shown in FIG. 2 described above, since the membrane sheet 23 is provided on the outer peripheral side of the exhaust pipe 22, the small hole 22 a is recessed from the inner peripheral surface of the exhaust pipe 22 due to the pipe thickness of the exhaust pipe 22. Become. Therefore, the condensed water may remain in the small holes 22a and freeze at a low temperature.

  When the condensed water freezes in the small hole 22a, the efficiency of transmitting the sound wave of the exhaust gas to the sound absorbing member 30 inside the silencer 10 is lowered, so that the sound deadening performance may be lowered.

  On the other hand, in the configuration example shown in FIG. 3, the membrane sheet 23 is provided on the inner peripheral surface of the exhaust pipe 22, so that no concave shape is formed inside the silencer 10, and condensed water does not stay. Thereby, the problem which generate | occur | produces by freezing of condensed water can be prevented.

  The inner surface of the exhaust pipe 22 may have a concave shape corresponding to the film thickness of the membrane sheet 23 so that no step is generated between the inner surface of the exhaust pipe 22 and the membrane sheet 23.

  FIG.4 and FIG.5 is sectional drawing which shows another structure of the silencer 10 of embodiment of this invention.

  As described above, the small hole 22a of the exhaust pipe 22 can be appropriately changed according to the silencing performance.

  In the example shown in FIG. 2, the small holes 22a are provided in five rows in the exhaust gas flow direction. On the other hand, in the example shown in FIG. 4, only two rows of small holes 22a are provided in the exhaust gas flow direction.

  As described above, the configuration of the small hole 22a of the exhaust pipe 22 can arbitrarily change the exhaust gas silencing performance.

  Depending on the position of the small hole 22 a, it is not necessary to provide the membrane sheet 23 from the upstream side to the downstream side of the exhaust pipe 22. Specifically, as shown in FIG. 5, a membrane sheet 23 may be provided so as to cover the periphery of a part of the exhaust pipe 22 in correspondence with the location where the small hole 22 a is provided. In other words, it is sufficient that the condensed water does not penetrate from the exhaust pipe 22 to the sound absorbing member 30. By comprising in this way, the material of the film | membrane sheet 23 and a process man-hour can be reduced, and manufacturing cost can be held down.

  FIG.6 and FIG.7 is sectional drawing which shows another structure of the silencer 10 of embodiment of this invention.

  In the configuration example shown in FIG. 6, the sound absorbing member 30 is not filled in the case 21, but a hollow portion is provided around the exhaust pipe 22. That is, the sound absorbing member 30 is filled in the case 21 at a predetermined interval from the exhaust pipe 22.

  With this configuration, an air layer can be provided inside the silencer 10. Thereby, it becomes possible to exhibit the silencing performance by the air layer and the sound absorbing member 30, and for example, the silencing performance in a wide range from the medium frequency to the high frequency can be achieved.

  Furthermore, as another configuration example of the structure in which the air layer is provided inside the silencer 10, as shown in FIG. 7, the membrane sheet 23 is provided not on the periphery of the exhaust pipe 22, but on the surface of the sound absorbing member 30. Anyway.

  With the configuration as shown in FIG. 7, sound waves are guided to the air layer without being attenuated by the membrane sheet 23, so that the silencing effect by the air layer is increased. However, in such a configuration, condensed water may accumulate in the air layer inside the silencer 10. Therefore, it is preferable to provide the silencer 10 with a mechanism (for example, a Pitot tube) for discharging the condensed water.

  As described above, in the embodiment of the present invention, the silencer 10 includes the membrane sheet 23 between the exhaust pipe 22 through which the exhaust gas flows and the sound absorbing member 30 that silences the sound wave included in the exhaust gas. . Since the membrane sheet 23 is made of a material that allows sound waves to pass but not liquid, the condensed water does not penetrate into the sound absorbing member 30, and the condensed water can be easily discharged out of the silencer. Thereby, durability of a silencer can be improved, without reducing a silencing performance.

  FIG. 8 is a graph showing experimental results of the silencing performance of the silencer 10 according to the embodiment of the present invention.

  The graph shown in FIG. 8 illustrates the silencing performance of the silencer 10 provided with the membrane sheet 23 compared to a configuration not provided with the membrane sheet 23.

The horizontal axis of the graph represents the exhaust gas flow rate [m ³ / min] per minute. The vertical axis of the graph represents the sound wave level comparison result [dB] when the sound wave level of the configuration without the membrane sheet 23 is zero. The comparison result indicates that the sound wave is attenuated and the sound deadening performance is higher than the configuration without the membrane sheet 23 in the case of the positive side, and the sound deadening performance is lower in the case of the negative side.

  In the graph of FIG. 8, the material of the film sheet 23 is silicon rubber, and the film thickness is 0.3 mm, which is indicated by a dotted line. The film sheet 23 is made of silicon rubber, and the film thickness is 0.5 mm.

According to the experimental results shown in FIG. 8, when the film thickness is 0.3 mm, the exhaust gas flow rate is around 1 to 2 [m ³ / min], compared with the configuration without the film sheet 23. It is shown that it has a good silencing performance. Further, when the exhaust gas flow rate is in the vicinity of 3 [m 3 / min], the noise reduction performance is lower than the configuration without the membrane sheet 23. In general, the exhaust gas flow rate discharged from the fuel cell stack 2 is about 3.5 [m ³ / min] at the maximum, and therefore the influence of the reduction in the noise reduction performance in the vicinity of this flow rate is limited.

  Further, when the film thickness is 0.5 mm, the sound deadening performance equivalent to the configuration without the film sheet 23 is shown over the entire range of the exhaust gas flow rate.

  As is clear from the experimental results shown in the graph of FIG. 8, even when the membrane sheet 23 is provided, the silencing performance is not significantly reduced as compared with the conventional silencer 10 not provided with the membrane sheet 23. Depending on the situation, the silencing performance is improved. In addition, the silencing performance varies depending on the film thickness of the film sheet 23.

  Therefore, by providing the membrane sheet 23, it is possible to provide a silencer that does not impregnate the sound absorbing member 30 with condensed water without deteriorating the silencing characteristics. Further, by selecting the material and film thickness of the film sheet 23, it is possible to appropriately tune the sound deadening characteristic.

  In addition, although embodiment of this invention demonstrated to the example used for the silence of the exhaust gas of the fuel cell stack 2 mounted in a vehicle, it is not restricted to this. For example, the same effect can be obtained by using the silencer 10 to silence the exhaust gas of a home or factory stationary fuel cell.

It is explanatory drawing of the exhaust system of embodiment of this invention. It is sectional drawing which shows the structure of the silencer of embodiment of this invention. It is sectional drawing which shows another structure of the silencer of embodiment of this invention. It is sectional drawing which shows another structure of the silencer of embodiment of this invention. It is sectional drawing which shows another structure of the silencer of embodiment of this invention. It is sectional drawing which shows another structure of the silencer of embodiment of this invention. It is sectional drawing which shows another structure of the silencer of embodiment of this invention. It is explanatory drawing which shows the silencing characteristic of the silencer of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silencer 2 Fuel cell stack 3 Exhaust system 10 Silencer 21 Case 21a, 21b End plate 22 Exhaust pipe 22a Small hole 23 Membrane sheet 30 Sound absorbing member

Claims (5)

A silencer (10) connected to the exhaust system (3) of the fuel cell (2),
An exhaust gas passage (22) that penetrates the case (21), and a sound absorbing member (30) that surrounds the exhaust gas passage (22) and fills the case (21),
The exhaust gas passage (22) includes a plurality of small holes (22a) that open into the case (21),
A silencer comprising a thin film (23) between which the exhaust gas passage (22) and the sound absorbing member (30) do not pass the liquid but the sound wave passes. The muffler according to claim 1,
The silencer, wherein the thin film (23) is provided in close contact with the periphery of the exhaust gas passage (22). The muffler according to claim 1,
The silencer, wherein the thin film (23) is provided in close contact with an inner peripheral surface of the exhaust gas passage (22). The muffler according to any one of claims 1 to 3,
The silencer characterized in that the thin film (23) is provided only at a position corresponding to the position of the small hole (22a) provided in the exhaust gas passage (22). The muffler according to claim 1,
The sound absorbing member (30) is filled in the case (21) at a predetermined interval from the exhaust gas passage (22),
The silencer, wherein the thin film (23) is provided in close contact with a surface of the sound absorbing member (30) facing the exhaust gas passage (22).