JP7032108B2 - Internal combustion engine exhaust system - Google Patents

Description

The present invention relates to an exhaust system for an internal combustion engine.

Generally, an exhaust device of an internal combustion engine such as a ship or a vehicle discharges exhaust gas to the outside via a silencer in order to reduce exhaust noise. Examples of such a silencer include an expansion type silencer and a sound absorbing type silencer. The expansion type silencer is provided with an expansion portion having a diameter larger than that of the exhaust pipe. However, in this extended type silencer, when the diameter of the expanded portion is "D", the frequency f having the sound reducing effect is f ≦ 1.2197C / D (“C” is the speed of sound). When the exhaust flow rate is large as in a large internal combustion engine, the inner diameter of the exhaust pipe becomes large from the viewpoint of the allowable pressure loss of the internal combustion engine, and the diameter D of the extended silencer also becomes large accordingly. Therefore, the frequency band having the sound reduction effect is lowered.

Non-Patent Document 1 describes a technique of providing a sound absorbing material on the inner surface of the expansion portion in order to increase the sound reduction effect in a frequency band in which the sound reduction effect is reduced in the expansion type silencer.
Non-Patent Document 2 describes a technique for increasing the number of stages of an extended silencer in order to increase the sound reduction effect.

Leo L. BERANEK, "Noise and Vibration Control", (USA), McGRAW-HILL BOOK COMPANY, January 1, 1971, p362-371. "NOISE AND VIBRATION CONTROL ENGINEERING" by Istvan L. Ver, LEO L. BERANEK, 2nd Edition, John Wiley and Sons, November 11, 2005, p310-329

The extended silencer described in Non-Patent Document 1 has a frequency band of f = n × C / (2L) (n = 1,2,3 ..., L: silencer length) in which the sound reduction effect is reduced. It increases the sound reduction effect, and its frequency band is in the range of f≤2C / D, and it is difficult to extend the sound reduction effect to high frequencies.
The extended silencer described in Non-Patent Document 2 also only increases the sound reduction effect, and it is difficult to increase the frequency in which the sound reduction effect can be obtained.
Therefore, in order to reduce the sound in the high frequency region, it is necessary to separately install and connect an extended silencer and a silencer that has a sound reduction effect up to the high frequency band. There is a problem that is limited.

The present invention has been made in view of the above circumstances, and provides an exhaust device for an internal combustion engine capable of obtaining a sound reduction effect up to a high frequency band while suppressing an increase in size.

The following configuration is adopted to solve the above problems.
According to the first aspect of the present invention, the exhaust device of an internal combustion engine includes a silencer that reduces exhaust noise. The silencer includes a plurality of expansion chambers, a connecting pipe, and a sound absorbing member. The flow path cross-sectional area of the plurality of expansion chambers is expanded as compared with the exhaust pipe. The communication pipe communicates the plurality of expansion chambers in series to form a communication flow path having a smaller flow path cross-sectional area than the expansion chamber. The sound absorbing member is arranged inside the connecting pipe and absorbs the exhaust sound transmitted through the connecting flow path. Inside one of the connecting pipes, a plurality of the connecting flow paths separated by the sound absorbing member are formed.
With this configuration, the sound absorbing member is arranged in the connecting flow path having a smaller flow path cross-sectional area than the expansion chamber. Since the cross-sectional area of the flow path of the connecting pipe is smaller than the cross-sectional area of the flow path of the expansion chamber, the sound absorbing member can obtain the sound reduction effect up to the high frequency band. Further, the sound reduction effect in the low frequency band is obtained by the expansion chamber. Further, by arranging the sound absorbing member inside the connecting pipe, it is possible to reduce the size as compared with the case where the sound absorbing type silencer is separately connected to the expanded type silencer having a plurality of expansion chambers. ..
Therefore, it is possible to obtain a sound reduction effect up to a high frequency band while suppressing the silencer from becoming large in size.
According to the second aspect of the present invention, the connecting pipe in the first aspect is formed in a circular cross section, and the sound absorbing member is formed in a tubular shape having a smaller diameter than the connecting pipe and has a circular cross section as the connecting flow path. The inner connecting flow path formed inside the sound absorbing member and the outer connecting flow path formed between the sound absorbing member and the inner peripheral surface of the connecting tube are provided.
According to the third aspect of the present invention, in the first aspect, the plurality of flat plate-shaped sound absorbing members are formed inside the connecting pipe so that the plurality of connecting flow paths are formed inside the connecting pipe. Are arranged at intervals.

According to the fourth aspect of the present invention, in the exhaust device of the internal combustion engine according to any one of the first to third aspects, the inlet and the outlet of the connecting pipe are in the expansion chamber in the direction in which the exhaust gas flows. It may be arranged on the central portion side of the expansion chamber with respect to the end portion.
With such a configuration, it is possible to suppress the formation of a valley at the frequency at which the sound reduction effect is obtained.

According to the fifth aspect of the present invention, in the exhaust device of the internal combustion engine according to any one of the first to the fourth aspects, the expansion chambers adjacent to each other in the direction in which the exhaust gas flows are formed by the plurality of communication pipes. It may be communicated.
With such a configuration, it is possible to reduce the cross-sectional area of the flow path per connecting pipe while suppressing the increase in the flow path resistance of the exhaust gas. Therefore, the frequency band in which the sound reduction effect can be obtained can be further increased according to the cross-sectional area of the flow path of the connecting pipe.

According to the sixth aspect of the present invention, the sound absorbing member according to any one of the first to fifth aspects may be formed so as to extend in the direction in which the exhaust gas flows.
With such a configuration, the sound absorbing member can be efficiently brought into contact with the exhaust gas inside the connecting pipe, so that the sound absorbing effect can be improved.

According to the seventh aspect of the present invention, the sound absorbing member according to the first to sixth aspects may include an acoustic liner having a sound absorbing effect at a preset predetermined frequency.
By arranging the acoustic liner inside the connecting tube in this way, a sound absorbing effect at a predetermined frequency set in advance can be obtained.

According to the eighth aspect of the present invention, the sound absorbing member according to the first to sixth aspects is
By arranging the acoustic metamaterial inside the connecting tube in this way, a sound absorbing effect at a predetermined frequency set in advance can be obtained.

According to the above-mentioned silencer, the sound reduction effect can be obtained up to a high frequency band while suppressing the increase in size.

It is sectional drawing which shows the schematic structure of the silencer of the exhaust device in 1st Embodiment of this invention. It is sectional drawing which shows the schematic structure of the silencer in the 2nd Embodiment of this invention. It is sectional drawing corresponding to FIG. 2 in the 3rd Embodiment of this invention. It is sectional drawing corresponding to FIG. 2 in the 4th Embodiment of this invention. It is sectional drawing which follows the VV line of FIG. 4 in the 4th Embodiment of this invention. It is sectional drawing corresponding to FIG. 5 in the modification of the 4th Embodiment of this invention. It is sectional drawing corresponding to FIG. 2 in the 5th Embodiment of this invention. FIG. 7 is a cross-sectional view taken along the line VIII-VIII of FIG. It is a perspective view of the connecting pipe and the sound absorbing member in the 1st modification of the Embodiment of this invention. It is a perspective view of the connecting pipe and the sound absorbing member in the 1st modification of the Embodiment of this invention.

(First Embodiment)
Next, the exhaust device of the internal combustion engine according to the first embodiment of the present invention will be described with reference to the drawings. The exhaust device exemplified in this first embodiment is an exhaust device for an internal combustion engine included in a ship such as a passenger ship, a car ferry, or a ship. In such a ship, the flow rate of the exhaust gas of the internal combustion engine is large and the space for arranging the silencer is limited as compared with the case of the automobile.

FIG. 1 is a cross-sectional view showing a schematic configuration of a silencer of an exhaust device according to the first embodiment of the present invention.
As shown in FIG. 1, the exhaust device 100 of the first embodiment includes an exhaust pipe 10 and a silencer 20.
The exhaust pipe 10 discharges the exhaust gas of the internal combustion engine E to the outside. The exhaust pipe 10 extends from an internal combustion engine E arranged in the main engine chamber of a ship to a funnel (not shown), for example. For example, when the internal combustion engine E is a multi-cylinder reciprocating engine, the exhaust pipe 10 merges the exhaust gas discharged from the exhaust ports of the plurality of cylinders and then guides the exhaust gas to the funnel.

The silencer 20 is provided in the middle of the exhaust pipe 10 and reduces the exhaust noise transmitted to the outside via the exhaust pipe 10. The silencer 20 mainly includes a plurality of expansion chambers 21, a connecting pipe 22, and a sound absorbing member 23.

The upstream exhaust pipe 10a on the internal combustion engine E side is connected to one of the plurality of expansion chambers 21. Further, the downstream exhaust pipe 10b on the funnel side is connected to the other one of the plurality of expansion chambers 21. These expansion chambers 21 function as so-called expansion type silencers that mute the exhaust noise by expanding the cross-sectional area of the gas flow path through which the exhaust gas flows. In this embodiment, the case where the first expansion chamber 21a and the second expansion chamber 21b, which are two expansion chambers 21, are provided is illustrated, but three or more expansion chambers 21 may be provided. In the following description, when it is not necessary to distinguish between the first expansion chamber 21a and the second expansion chamber 21b, it may be simply referred to as "expansion chamber 21".

The communication pipe 22 communicates a plurality of expansion chambers 21 in series. The connecting pipe 22 forms a connecting flow path 22f, and the flow path cross-sectional area thereof is constant in the length direction thereof and is smaller than the flow path cross-sectional area of the expansion chamber 21. The communication pipe 22 in this embodiment communicates the first expansion chamber 21a to which the upstream exhaust pipe 10a is connected and the second expansion chamber 21b to which the downstream exhaust pipe is connected in series. In this embodiment, the connecting pipe 22 and the exhaust pipe 10 are each formed in a tubular shape having a circular cross section, and exemplify a case where the cross-sectional areas of the respective flow paths are the same.

The sound absorbing member 23 is arranged inside the connecting pipe 22. The sound absorbing member 23 absorbs exhaust sound through the connecting flow path 22f. The sound absorbing member 23 in this embodiment is arranged so as to cover the entire inner surface of the connecting pipe 22 and is fixed to the inner surface of the connecting pipe 22. That is, the sound absorbing member 23 is formed in a tubular shape having substantially the same length as the connecting pipe 22. The sound absorbing member 23 in this embodiment is formed to have a circular cross section like the connecting pipe 22.

Here, the frequency at which the sound reduction effect is obtained inside the connecting pipe 22 changes depending on the cross-sectional area of the flow path of the connecting pipe 22 and the thickness of the sound absorbing member 23. Therefore, among the frequency components constituting the exhaust sound, the cross-sectional area of the flow path of the connecting pipe 22 and the thickness of the sound absorbing member 23 are adjusted according to the frequency of the high frequency band to be reduced. As the sound absorbing member 23 in this embodiment, for example, a sound absorbing material such as rock wool or glass wool can be used. A sound absorbing material such as urethane foam may be used as the sound absorbing member 23 as long as it can withstand the internal temperature of the connecting pipe 22.

Therefore, according to the first embodiment described above, the sound absorbing member 23 is arranged in the connecting flow path 22f having a smaller flow path cross-sectional area than the expansion chamber 21. Since the flow path cross-sectional area of the connecting pipe 22 is smaller than the flow path cross-sectional area of the expansion chamber 21, the sound absorbing member 23 can obtain the sound reduction effect up to the high frequency band. Further, the sound reduction effect in the low frequency band is obtained by the expansion chamber 21. Further, by arranging the sound absorbing member 23 inside the connecting pipe 22, the silencer 20 is smaller than the case where the sound absorbing silencer is separately connected to the expanded silencer having a plurality of expansion chambers 21. Can be achieved. As a result, it is possible to obtain a sound reduction effect up to a high frequency band while suppressing the silencer 20 from becoming large in size.

Further, the sound absorbing member 23 is formed so as to extend in the direction in which the exhaust gas flows. Therefore, the sound absorbing member 23 can be efficiently brought into contact with the exhaust gas inside the connecting pipe 22, and the sound absorbing effect of the sound absorbing member 23 can be improved. In addition, it is possible to prevent the flow of exhaust gas from being obstructed by the sound absorbing member 23.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings. This second embodiment differs only in that a duct is provided in the connecting pipe 22 of the first embodiment described above. Therefore, the same parts as those in the first embodiment described above will be described with the same reference numerals.

FIG. 2 is a cross-sectional view showing a schematic configuration of a silencer according to a second embodiment of the present invention.
As shown in FIG. 2, the exhaust device 200 in the second embodiment includes an exhaust pipe 10 and a silencer 220, as in the first embodiment described above. The silencer 220 is provided in the middle of the exhaust pipe 10 and reduces the exhaust noise transmitted to the outside via the exhaust pipe 10. The silencer 220 mainly includes a plurality of expansion chambers 221s, a connecting pipe 222, and a sound absorbing member 23.

In the silencer 220 in the second embodiment, the first expansion chamber 221a and the second expansion chamber 221b are integrally formed by the silencer housing 220h and the partition wall 220s. The internal space of the silencer housing 220h is partitioned by a partition wall 220s into a first space S1 which is an internal space of the first expansion chamber 221a and a second space S2 which is an internal space of the second expansion chamber 221b. .. The first expansion chamber 221a includes an exhaust inlet O1 into which the exhaust gas flows in, and the second expansion chamber 221b includes an exhaust outlet O2 in which the exhaust gas flows out. The first expansion chamber 221a and the second expansion chamber 221b each function as an expansion type silencer that expands the cross-sectional area of the gas flow path through which the exhaust gas flows to muffle the sound. In the following description, when it is not necessary to distinguish between the first expansion chamber 221a and the second expansion chamber 221b, it may be simply referred to as "expansion chamber 221".

The communication pipe 222 communicates a plurality of expansion chambers 221, that is, the first expansion chamber 221a and the second expansion chamber 221b in series, similarly to the communication pipe 22 of the first embodiment. The connecting pipe 222 in the second embodiment penetrates a part of the partition wall 220s and extends in a direction intersecting the partition wall 220s. The flow path cross-sectional area of the connecting pipe 222 is constant in the length direction thereof, and is smaller than the flow path cross-sectional area of the first expansion chamber 221a and the second expansion chamber 221b.

The connecting pipe 222 has a first duct portion D1 projecting from the partition wall 220s toward the center of the first space S1 and a second duct portion projecting from the partition wall 220s toward the center of the second space S2. It is equipped with D2. By providing the first duct portion D1, the inlet 222i of the connecting pipe 222 is opened at the position of the partition wall 220s, that is, on the side closer to the exhaust inlet O1 than the position on the most downstream side of the first expansion chamber 221a. Similarly, by providing the second duct portion D2, the outlet 222o of the connecting pipe 222 opens at the position of the partition wall 220s, that is, on the side closer to the exhaust outlet O2 than the position on the most upstream side of the second expansion chamber 221b. ing.

The sound absorbing member 23 is arranged inside the connecting pipe 222 as in the first embodiment. The sound absorbing member 23 absorbs exhaust sound through the connecting flow path 222f. The sound absorbing member 23 in the second embodiment has the same configuration as the sound absorbing member 23 in the first embodiment, is arranged so as to cover the entire inner surface of the connecting pipe 222, and is fixed to the inner surface of the connecting pipe 222. .. That is, the sound absorbing member 23 is formed in a tubular shape having substantially the same length as the connecting pipe 222. The sound absorbing member 23 in this embodiment is formed to have a circular cross section like the connecting pipe 222. The cross-sectional area of the flow path of the connecting pipe 222 and the thickness of the sound absorbing member 23 are adjusted according to the frequency band to be sound-reduced, as in the first embodiment.

Therefore, according to the second embodiment described above, the sound absorbing member 23 is arranged in the connecting flow path having a smaller flow path cross-sectional area than the expansion chamber 221 as in the first embodiment. Since the flow path cross-sectional area of the connecting pipe 222 is smaller than the flow path cross-sectional area of the expansion chamber 221, the sound absorbing member 23 can obtain the sound reduction effect up to the high frequency band. Further, the sound reduction effect in the low frequency band is obtained by the expansion chamber 221. Further, by arranging the sound absorbing member 23 inside the connecting pipe 222, the silencer 220 is smaller than the case where the sound absorbing silencer is separately connected to the expanded silencer having a plurality of expansion chambers 221. Can be achieved. As a result, it is possible to obtain a sound reduction effect up to a high frequency band while suppressing the silencer 220 from becoming large in size.

Further, the sound absorbing member 23 is formed so as to extend in the direction in which the exhaust gas flows. Therefore, the sound absorbing member 23 can be efficiently brought into contact with the exhaust gas inside the connecting pipe 222, and the sound absorbing effect of the sound absorbing member 23 can be improved. Further, it is possible to prevent the flow of the exhaust gas from being obstructed by the sound absorbing member 23.

Further, the first expansion chamber 221a and the second expansion chamber 221b can be integrally formed by the silencer housing 220h and the partition wall 220s. Therefore, the total length of the silencer 220 can be shortened as compared with the case where the first expansion chamber 221a and the second expansion chamber 221b are formed apart from each other.

Further, the connecting pipe 222 includes a first duct portion D1 and a second duct portion D2. Therefore, the inlet 222i of the connecting pipe 222 is arranged closer to the center of the first expansion chamber 221a than the end of the first expansion chamber 221a in the direction in which the exhaust gas flows, and the outlet 222o of the connecting pipe 222 is the second expansion chamber. It is arranged closer to the center of the second expansion chamber 221b than the end of the 221b. As a result, in particular, in the low frequency band sound reduction effect obtained by the first expansion chamber 221a and the second expansion chamber 221b, it is possible to suppress the formation of a so-called valley in which the sound reduction effect is reduced at a predetermined frequency.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to the drawings. This third embodiment differs from the first embodiment described above in the number of connecting pipes. Therefore, the same parts as those in the first embodiment described above will be described with the same reference numerals.

FIG. 3 is a cross-sectional view corresponding to FIG. 2 in the third embodiment of the present invention.
As shown in FIG. 3, the exhaust device 300 in the third embodiment includes an exhaust pipe 10 and a silencer 320, as in the first embodiment described above. The silencer 320 is provided in the middle of the exhaust pipe 10 and reduces the exhaust noise transmitted to the outside via the exhaust pipe 10. The silencer 320 mainly includes a plurality of expansion chambers 321 and a plurality of connecting pipes 322 and a sound absorbing member 323.

Similar to the silencer 220 of the second embodiment, the silencer 320 in the third embodiment integrates the first expansion chamber 321a and the second expansion chamber 321b, which are two expansion chambers 321 by the silencer housing 320h and the partition wall 320s. Is formed in. The internal space of the silencer housing 320h is partitioned by a partition wall 320s into a first space S1 which is an internal space of the first expansion chamber 321a and a second space S2 which is an internal space of the second expansion chamber 321b. .. The first expansion chamber 321a includes an exhaust inlet O1 into which the exhaust gas flows in, and the second expansion chamber 321b includes an exhaust outlet O2 in which the exhaust gas flows out. The first expansion chamber 321a and the second expansion chamber 321b each function as an expansion type silencer that expands the cross-sectional area of the gas flow path through which the exhaust gas flows to muffle the sound. In the following description, when it is not necessary to distinguish between the first expansion chamber 321a and the second expansion chamber 321b, it may be simply referred to as "expansion chamber 321".

The plurality of communication pipes 322 communicate the first expansion chamber 321a and the second expansion chamber 321b in series, respectively. In other words, the plurality of connecting pipes 322 are connected in parallel between the first expansion chamber 321a and the second expansion chamber 321b. These connecting pipes 322 penetrate a part of the partition wall 320s and extend in a direction intersecting the partition wall 320s. In this third embodiment, the case where two connecting pipes 322a and 322b are provided is illustrated, but three or more connecting pipes 322 may be provided.

The flow path cross-sectional area of these connecting pipes 322a and 322b is constant in the length direction thereof, and is smaller than any of the flow path cross-sectional areas of the first expansion chamber 321a and the second expansion chamber 321b. Here, in the second embodiment, the case where the flow path cross-sectional areas of the connecting pipes 322a and 322b are the same is illustrated. However, the flow path cross-sectional areas of the connecting pipes 322a and 322b may be different from each other. When the flow path cross-sectional areas are formed so as to be different from each other in this way, the frequency characteristics of the sound reduction effect obtained by the respective connecting pipes 322a and 322b can be made different, so that the sound reduction effect can be obtained over a wider frequency band. Is obtained.

Similar to the connecting pipe 222 of the second embodiment, the connecting pipes 322a and 322b have a first duct portion D1 projecting from the partition wall 320s toward the center of the first space S1 and a second duct portion D1 from the partition wall 320s. A second duct portion D2 projecting toward the central portion of the space S2 is provided. By providing the first duct portion D1, the inlet 322i of the connecting pipes 322a and 322b opens at the position of the partition wall 320s, that is, on the side closer to the exhaust inlet O1 than the position on the most downstream side of the first expansion chamber 321a. There is. Similarly, by providing the second duct portion D2, the outlets 322o of the connecting pipes 322a and 322b are located closer to the exhaust outlet O2 than the position of the partition wall 320s, that is, the position on the most upstream side of the second expansion chamber 321b. It is open.

The sound absorbing member 323 is arranged inside the connecting pipes 322a and 322b, respectively, like the sound absorbing member 23 of the first and second embodiments. The sound absorbing member 323 absorbs exhaust sound through the connecting flow path 322f in the connecting pipes 322a and 322b. The sound absorbing member 323 in the third embodiment is arranged so as to cover the entire inner surface of the connecting pipe 322 and is fixed to the inner surface of the connecting pipe 322. That is, the sound absorbing member 323 is formed in a tubular shape having substantially the same length as the connecting pipe 322. The sound absorbing member 323 in the third embodiment is formed to have a circular cross section like the connecting pipe 322.

The cross-sectional area of the flow path of the connecting pipe 322 and the thickness of the sound absorbing member 323 are adjusted according to the frequency band to be sound-reduced, as in the first embodiment. That is, the thickness of the sound absorbing member 323 arranged in the connecting pipe 322a and the thickness of the sound absorbing member 323 arranged in the connecting pipe 322b can be made different from each other. By making the thicknesses of the sound absorbing members 323 different from each other in this way, it is possible to widen the frequency band in which the sound reduction effect can be obtained, as in the case where the flow path cross-sectional areas of the connecting pipes 322a and 322b are made different. In order to widen the frequency band in which the sound reduction effect can be obtained, the cross sections of the flow paths of the connecting pipes 322a and 322b may be different from each other, and the thickness of the sound absorbing member 323 may be different from each other.

On the other hand, when the flow path cross-sectional areas of the connecting pipes 322a and 322b are the same and the thickness of the sound absorbing member 323 is the same, the frequency characteristics of the sound reduction effect are the same. The sound reduction effect can be increased.

Therefore, according to the third embodiment described above, the sound absorbing member 323 is arranged in the connecting flow path 322f having a smaller flow path cross-sectional area than the expansion chamber 321 as in the first embodiment. Since the flow path cross-sectional area of the connecting pipe 322 is smaller than the flow path cross-sectional area of the expansion chamber 321, the sound absorbing member 323 can obtain the sound reduction effect up to the high frequency band. Further, the sound reduction effect in the low frequency band is obtained by the expansion chamber 321. Further, by arranging the sound absorbing member 323 inside the connecting pipe 322, the silencer 320 is smaller than the case where the sound absorbing silencer is separately connected to the expanded silencer having the plurality of expansion chambers 321. Can be achieved. As a result, it is possible to obtain a sound reduction effect up to a high frequency band while suppressing the silencer 320 from becoming large in size.

Further, the sound absorbing member 323 is formed so as to extend in the direction in which the exhaust gas flows. Therefore, the sound absorbing member 323 can be efficiently brought into contact with the exhaust gas inside the connecting pipe 322, and the sound absorbing effect of the sound absorbing member 323 can be improved. In addition, it is possible to prevent the flow of exhaust gas from being obstructed by the sound absorbing member 323.

Further, the first expansion chamber 321a and the second expansion chamber 321b can be integrally formed by the silencer housing 320h and the partition wall 320s. Therefore, the total length of the silencer 320 can be shortened as compared with the case where the first expansion chamber 321a and the second expansion chamber 321b are formed separately.

Further, the connecting pipe 322 includes a first duct portion D1 and a second duct portion D2. Therefore, the inlet 322i of the connecting pipe 322 is arranged closer to the center of the first expansion chamber 321a than the end of the first expansion chamber 321a in the direction in which the exhaust gas flows, and the outlet 322o of the connecting pipe 322 is the second expansion chamber. It is arranged closer to the center than the end of 321b. As a result, it is possible to suppress the formation of a valley in which the sound reduction effect is reduced, particularly in the low frequency band sound reduction effect obtained by the first expansion chamber 321a and the second expansion chamber 321b.

Further, the first expansion chamber 321a and the second expansion chamber 321b that are adjacent to each other in the direction in which the exhaust gas flows are communicated with each other by a plurality of communication pipes 322. Therefore, it is possible to reduce the flow path cross-sectional area per connecting pipe 322 while suppressing the increase in the flow path resistance of the exhaust gas, and the sound reduction effect is obtained according to the flow path cross-sectional area of the connecting pipe 322. The frequency band that can be obtained can be further increased.

In the third embodiment described above, the case where the first expansion chamber 321a and the second expansion chamber 321b are integrally formed has been described, but as in the first embodiment, the first expansion chamber 321a and the first expansion chamber 321a and the first expansion chamber 321b have been described. (Ii) When the expansion chambers 321b are formed apart from each other, the first expansion chamber 321a and the second expansion chamber 321b may be communicated with each other by a plurality of communication pipes 322a and 322b.

Next, a fourth embodiment of the present invention will be described with reference to the drawings. This fourth embodiment differs from the above-mentioned second embodiment in the arrangement of the sound absorbing member. Therefore, the same parts as those in the second embodiment described above will be described with the same reference numerals.
FIG. 4 is a cross-sectional view corresponding to FIG. 2 in the fourth embodiment of the present invention. FIG. 5 is a cross-sectional view taken along the line VV of FIG. 4 in the fourth embodiment of the present invention.

As shown in FIG. 4, the exhaust device 400 in the fourth embodiment includes an exhaust pipe 10 and a silencer 420, as in the first embodiment described above. The silencer 420 is provided in the middle of the exhaust pipe 10 and reduces the exhaust noise transmitted to the outside via the exhaust pipe 10. The silencer 420 mainly includes a plurality of expansion chambers 221s, a connecting pipe 222, and a sound absorbing member 423.

In the silencer 420 in the fourth embodiment, as in the second embodiment, the silencer housing 220h and the partition wall 220s integrally form the first expansion chamber 221a and the second expansion chamber 221b, which are two expansion chambers 221. Has been done. The internal space of the silencer housing 220h is partitioned by a partition wall 220s into a first space S1 which is an internal space of the first expansion chamber 221a and a second space S2 which is an internal space of the second expansion chamber 221b. .. The first expansion chamber 221a includes an exhaust inlet O1 into which the exhaust gas flows in, and the second expansion chamber 221b includes an exhaust outlet O2 in which the exhaust gas flows out. The first expansion chamber 221a and the second expansion chamber 221b each function as an expansion type silencer that expands the cross-sectional area of the gas flow path through which the exhaust gas flows to muffle the sound.

The communication pipe 222 communicates a plurality of expansion chambers 221 in series, similarly to the communication pipe 22 of the first embodiment. The connecting pipe 222 in the fourth embodiment penetrates a part of the partition wall 220s and extends in a direction intersecting the partition wall 220s. The flow path cross-sectional area of the connecting pipe 222 is constant in the length direction thereof, and is smaller than any of the flow path cross-sectional areas of the first expansion chamber 221a and the second expansion chamber 221b.

The connecting pipe 222 includes a first duct portion D1 projecting from the partition wall 220s toward the center of the first space S1 and a second duct portion D2 projecting from the partition wall 220s toward the center of the second space S2. , Is equipped. By providing the first duct portion D1, the inlet 222i of the connecting pipe 222 is opened at the position of the partition wall 220s, that is, on the side closer to the exhaust inlet O1 than the position on the most downstream side of the first expansion chamber 221a. Similarly, by providing the second duct portion D2, the outlet 222o of the connecting pipe 222 opens at the position of the partition wall 220s, that is, on the side closer to the exhaust outlet O2 than the position on the most upstream side of the second expansion chamber 221b. ing.

As shown in FIGS. 4 and 5, the sound absorbing member 423 is arranged inside the connecting pipe 222 as in the second embodiment. The sound absorbing member 423 absorbs exhaust sound inside the connecting pipe 222. The sound absorbing member 423 in the fourth embodiment forms a plurality of connecting flow paths F through which the exhaust gas passes inside one connecting pipe 222.

The sound absorbing member 423 exemplified in the fourth embodiment is formed in a tubular shape having a circular cross section with a diameter smaller than that of the connecting pipe 222. The sound absorbing member 423 is formed to have substantially the same length as the connecting pipe 222. The sound absorbing member 423 is supported by a support member (not shown) extending in the radial direction of the connecting pipe 222 with respect to the inner surface of the connecting pipe 222. The sound absorbing member 23 in this embodiment is formed to have a circular cross section like the connecting pipe 222. The cross-sectional area of the flow path of the connecting pipe 222 and the thickness of the sound absorbing member 23 are adjusted according to the frequency band to be sound-reduced, as in the first embodiment.

Further, the sound absorbing member 423 exemplified in the fourth embodiment forms an inner connecting flow path F1 and an outer connecting flow path F2 as a plurality of connecting flow paths F inside the connecting pipe 222. The inner connecting flow path F1 is formed inside the sound absorbing member 423 formed in an annular shape. The outer connecting flow path F2 is formed outside the sound absorbing member 423, that is, between the outer peripheral surface 423a of the sound absorbing member 423 and the inner peripheral surface 222a of the connecting pipe 222.

Here, the inner connecting flow path F1 and the outer connecting flow path F2 function in the same manner as in the case where a plurality of connecting pipes 322 are provided as in the third embodiment described above. That is, when the flow path cross-sectional area of the inner connecting flow path F1 and the flow path cross-sectional area of the outer connecting flow path F2 are different from each other, the frequency characteristics of the sound reduction effect obtained in the inner connecting flow path F1 and the frequency characteristics of the sound reduction effect. It is possible to make the frequency specification of the sound reduction effect obtained by the outer connecting flow path F2 different from that of the frequency specification. Therefore, the sound reduction effect can be obtained over a wider frequency band. On the other hand, when the flow path cross-sectional area of the inner connecting flow path F1 and the flow path cross-sectional area of the outer connecting flow path F2 are the same as each other, the frequency characteristics of the sound reduction effect are the same, so that in that frequency band. The sound reduction effect can be increased. Then, for example, if the total of the flow path cross-sectional area of the inner connecting flow path F1 and the flow path cross-sectional area of the outer connecting flow path F2 is the same as the flow path cross-sectional area of the connecting flow path F of the second embodiment, It is possible to set the frequency band in which the sound reduction effect is obtained to a higher frequency band while making the flow path resistance of the exhaust gas the same.

Therefore, according to the fourth embodiment, the sound absorbing member 423 is arranged in the connecting flow path having a smaller flow path cross-sectional area than the expansion chamber 221 as in the second embodiment. Since the flow path cross-sectional area of the connecting flow paths F1 and F2 formed in the connecting pipe 222 is smaller than the flow path cross-sectional area of the expansion chamber 221, the sound absorbing member 423 can obtain the sound reduction effect up to the high frequency band. Become. Further, the sound reduction effect in the low frequency band is obtained by the expansion chamber 221. Further, by arranging the sound absorbing member 423 inside the connecting pipe 222, the silencer 420 is smaller than the case where the sound absorbing silencer is separately connected to the expanded silencer having a plurality of expansion chambers 221. Can be achieved. As a result, it is possible to obtain a sound reduction effect up to a high frequency band while suppressing the silencer 420 from becoming large in size.

Further, the sound absorbing member 423 is formed so as to extend in the direction in which the exhaust gas flows. Therefore, the sound absorbing member 423 can be efficiently brought into contact with the exhaust gas inside the connecting pipe 222, and the sound absorbing effect of the sound absorbing member 423 can be improved. Further, it is possible to prevent the flow of the exhaust gas from being obstructed by the sound absorbing member 423.

Further, the first expansion chamber 221a and the second expansion chamber 221b can be integrally formed by the silencer housing 220h and the partition wall 220s. Therefore, the total length of the silencer 220 can be shortened as compared with the case where the first expansion chamber 221a and the second expansion chamber 221b are formed apart from each other.

Further, the connecting pipe 222 includes a first duct portion D1 and a second duct portion D2. Therefore, the inlet 222i of the connecting pipe 222 is arranged closer to the center of the first expansion chamber 221a than the end of the first expansion chamber 221a in the direction in which the exhaust gas flows, and the outlet 222o of the connecting pipe 222 is the second expansion chamber. It is arranged closer to the center of the second expansion chamber 221b than the end of the 221b. As a result, it is possible to suppress the formation of a valley in which the sound reduction effect is reduced, particularly with respect to the sound reduction effect in the low frequency band obtained by the first expansion chamber 221a and the second expansion chamber 221b.

Further, since one sound absorbing member 423 can be provided inside one connecting pipe 222 to form a plurality of connecting flow paths F1 and F2, the third embodiment keeps the frequency band in which the sound reduction effect can be obtained as a high frequency band. The number of parts can be reduced as compared with the case where a plurality of connecting pipes 322 are provided as described above.

(Modified example of the fourth embodiment)
FIG. 6 is a cross-sectional view corresponding to FIG. 5 in a modified example of the fourth embodiment of the present invention.
In the fourth embodiment described above, the case where the sound absorbing member 423 is formed into a tubular shape having a circular cross section has been described. However, the shape of the sound absorbing member 423 may be any shape as long as it can form a plurality of connecting flow paths inside one connecting pipe 222.
For example, as in the modified example shown in FIG. 6, a plurality of flat plate-shaped sound absorbing members 423A may be arranged at intervals inside the connecting pipe 222. By doing so, it is possible to form a connecting flow path Fn between the adjacent sound absorbing members 423A. Here, assuming that the number of sound absorbing members 423A is X, X + 1 connecting flow paths Fn are formed.

(Fifth Embodiment)
Next, a fifth embodiment of the present invention will be described with reference to the drawings. This fifth embodiment differs from the above-mentioned second embodiment in the configuration of the connecting pipe. Therefore, the same parts as those of the second embodiment described above will be described with the same reference numerals, and the description overlapping with the second embodiment will be omitted.
FIG. 7 is a cross-sectional view corresponding to FIG. 2 in the fifth embodiment of the present invention. FIG. 8 is a cross-sectional view taken along the line VIII-VIII of FIG.

As shown in FIG. 7, the exhaust device 500 in the fifth embodiment includes an exhaust pipe 10 and a silencer 520. The silencer 520 is provided in the middle of the exhaust pipe 10 and reduces the exhaust noise transmitted to the outside via the exhaust pipe 10. The silencer 520 mainly includes a plurality of expansion chambers 521, a connecting pipe 522, and a sound absorbing member 523.

In the silencer 520, the first expansion chamber 521a and the second expansion chamber 521b are integrally formed by the silencer housing 520h and the partition wall 520s. The internal space of the silencer housing 520h is divided into a first space S1 which is an internal space of the first expansion chamber 521a and a second space S2 which is an internal space of the second expansion chamber 521b by a partition wall 520s. .. The first expansion chamber 521a includes an exhaust inlet O1 into which the exhaust gas flows in, and the second expansion chamber 521b includes an exhaust outlet O2 in which the exhaust gas flows out. The first expansion chamber 521a and the second expansion chamber 521b each function as an expansion type silencer that expands the cross-sectional area of the gas flow path through which the exhaust gas flows to muffle the sound. In the following description, when it is not necessary to distinguish between the first expansion chamber 521a and the second expansion chamber 521b, it may be simply referred to as "expansion chamber 521".

The communication pipe 522 communicates the first expansion chamber 521a and the second expansion chamber 521b in series. The connecting pipe 522 in the fifth embodiment penetrates a part of the partition wall 520s and extends in a direction intersecting the partition wall 520s. The communication pipe 522 has a communication flow path F3 that communicates the first expansion chamber 521a and the second expansion chamber 521b with the inner peripheral surface 521c of the expansion chamber 521 (in other words, the inner peripheral surface of the silencer housing 520h). Is forming. The flow path cross-sectional area of the connecting flow path F3 formed by the connecting pipe 522 is constant in the length direction thereof and smaller than the flow path cross-sectional area of the first expansion chamber 521a and the second expansion chamber 521b. There is.

The connecting pipe 522 has a first duct portion D1 projecting from the partition wall 520s toward the center of the first space S1 and a second duct portion projecting from the partition wall 520s toward the center of the second space S2. It is equipped with D2. By providing the first duct portion D1, the inlet 522i of the connecting flow path F3 of the connecting pipe 522 is located closer to the exhaust inlet O1 than the position of the partition wall 520s, that is, the position on the most downstream side of the first expansion chamber 521a. It is open. Similarly, by providing the second duct portion D2, the outlet 522o of the connecting flow path F3 of the connecting pipe 522 is located at the position of the partition wall 520s, that is, at the exhaust outlet O2 from the position on the most upstream side of the second expansion chamber 521b. It is open on the near side.

The sound absorbing member 523 is arranged in the connecting flow path F3 outside the connecting pipe 222. The sound absorbing member 523 absorbs exhaust sound through the connecting flow path F3. The sound absorbing member 523 in the fifth embodiment is arranged so as to cover the entire outer peripheral surface of the connecting pipe 522, and is fixed to the outer peripheral surface of the connecting pipe 522. The sound absorbing member 523 is formed in a tubular shape having substantially the same length as the connecting pipe 522. The sound absorbing member 523 in this embodiment is formed to have a circular cross section like the connecting pipe 522. The cross-sectional area of the flow path of the connecting pipe 522 and the thickness of the sound absorbing member 523 are adjusted according to the frequency band to be sound-reduced, as in the second embodiment. The sound absorbing member 523 may be arranged inside the connecting flow path F3, and is not limited to the above-mentioned arrangement.

Therefore, according to the fifth embodiment described above, the sound absorbing member 523 is arranged in the connecting flow path F3 having a smaller flow path cross-sectional area than the expansion chamber 521. Since the flow path cross-sectional area of the connecting pipe 522 is smaller than the flow path cross-sectional area of the expansion chamber 521, the sound absorbing member 523 can obtain the sound reduction effect up to the high frequency band. Further, the sound reduction effect in the low frequency band is obtained by the expansion chamber 521. Further, by arranging the sound absorbing member 523 inside the connecting flow path F3, the silencer 520 has a silencer 520 as compared with the case where the sound absorbing silencer is separately connected to the expanded silencer having the plurality of expansion chambers 521. It is possible to reduce the size. As a result, it is possible to obtain a sound reduction effect up to a high frequency band while suppressing the silencer 520 from becoming large in size.

Further, the sound absorbing member 523 is formed so as to extend in the direction in which the exhaust gas flows. Therefore, the sound absorbing member 523 can be efficiently brought into contact with the exhaust gas inside the connecting flow path F3, and the sound absorbing effect of the sound absorbing member 523 can be improved. Further, it is possible to prevent the flow of the exhaust gas from being obstructed by the sound absorbing member 523.

Further, the first expansion chamber 521a and the second expansion chamber 521b can be integrally formed by the silencer housing 520h and the partition wall 520s. Therefore, the total length of the silencer 520 can be shortened as compared with the case where the first expansion chamber 521a and the second expansion chamber 521b are formed separately.

Further, the connecting pipe 522 includes a first duct portion D1 and a second duct portion D2. Therefore, the inlet 522i of the connecting flow path F3 is arranged closer to the central portion of the first expansion chamber 521a than the end of the first expansion chamber 521a in the direction in which the exhaust gas flows, and the outlet 522o of the connecting flow path F3 is the second. It is arranged closer to the center of the second expansion chamber 221b than the end of the expansion chamber 221b. As a result, it is possible to suppress the formation of a so-called valley in which the sound reduction effect is lowered at a predetermined frequency, particularly in the low frequency band obtained by the first expansion chamber 521a and the second expansion chamber 521b.

Next, a modification of each embodiment of the present invention will be described with reference to the drawings. This modification is different only in the configuration of the sound absorbing member from each of the above-described embodiments. Therefore, the same parts as those of the above-described embodiments will be described with the same reference numerals. In addition, only the connecting pipe and the sound absorbing member will be described, and other overlapping explanations will be omitted.

(First modification)
FIG. 9 is a perspective view of the connecting pipe and the sound absorbing member in the first modification of the embodiment of the present invention.
In each of the above-described embodiments, the case where the sound absorbing members 23,323,423,523 arranged inside the connecting pipes 22, 222, 322 and outside the connecting pipes 522 are sound absorbing materials such as rock wool and glass wool, respectively. Illustrated. However, for example, as shown in FIG. 7, a sound absorbing member 623 made of an acoustic liner may be arranged. Here, the acoustic liner is formed so as to exert a sound absorbing effect at a predetermined frequency set in advance. That is, in this first modification, the acoustic liner is formed so as to exhibit the sound absorbing effect particularly in the high frequency band among the frequencies included in the exhaust sound. The acoustic liner is composed of a punching plate having a plurality of holes formed therein and a back air layer. The acoustic liner adjusts the acoustic characteristics (in other words, the frequency band that exerts the sound absorbing effect) by adjusting the hole diameter, the aperture ratio, and the thickness of the back air layer of the punching plate. The sound absorbing member 623 arranged outside the connecting pipe 522 is not shown.

(Second modification)
FIG. 10 is a perspective view of a connecting pipe and a sound absorbing member in the first modification of the embodiment of the present invention.
In the first modification described above, the case where the sound absorbing member 623 is made of an acoustic liner has been described. However, as shown in FIG. 10, for example, a sound absorbing member 723 made of an acoustic metamaterial may be arranged inside the connecting pipes 22, 222, 322 and outside the connecting pipe 522. Here, the acoustic metamaterial is a material that artificially generates desired acoustic performance, and exhibits a sound absorbing effect at a predetermined frequency set in advance. That is, in this second modification, the acoustic metamaterial is formed so as to exhibit the sound absorption effect particularly in the high frequency band among the frequencies included in the exhaust sound. Acoustic metamaterials can have a variety of shapes. Although the case where the acoustic metamaterial is formed in a grid pattern is illustrated in FIG. 10, the shape of the acoustic metamaterial is not limited to the grid pattern. The sound absorbing member 723 arranged outside the connecting pipe 522 is not shown.

According to the first and second modifications described above, unlike rock wool and glass wool, there is no scattering due to aging, so that the burden on maintenance can be reduced.

The present invention is not limited to the configurations of the above-described embodiments and modifications, and the design can be changed without departing from the gist thereof.
For example, the case where the exhaust device of each of the above-described embodiments and modifications is an exhaust device of the internal combustion engine E of a ship has been described as an example. However, the present invention is not limited to ships, and may be, for example, an exhaust device for an internal combustion engine of a vehicle such as an automobile.

Further, in each of the above-described embodiments, the case where the sound absorbing members 23,323,423,523,623,723 are formed to have the same length as the connecting pipes 22,222,322,522 has been described. However, the length of the sound absorbing member 23,323,423,523,623,723 is not limited to the above-mentioned length. For example, it may be formed shorter than the connecting pipes 22,222,322,522. Further, the sound absorbing members 23,323,423,523,623,723 may be configured to be intermittently arranged in the longitudinal direction of the connecting pipes 22,222,322,522.

Further, the configurations of the above-described embodiments may be used in combination as appropriate.
Further, in the exhaust devices 100 to 500 of each of the above-described embodiments, the case where two expansion chambers 21,221 and 321,521 are provided respectively has been described. However, a plurality of expansion chambers may be provided, and three or more expansion chambers may be connected in series.

Further, in the first modification and the second modification, the case where the sound absorbing member 623, 723 is made of an acoustic liner or an acoustic metamaterial has been described. However, a sound absorbing material such as rock wool or glass wool, an acoustic liner, and an acoustic metamaterial have been described. And may be appropriately combined to form a sound absorbing member.

10 Exhaust pipe 10a Upstream exhaust pipe 10b Downstream exhaust pipe 20,220,320,420,520 Silencers 21,221,321,521 Expansion chambers 21a, 221a, 321a, 521a First expansion chambers 21b, 221b, 321b, 521b Second Expansion chamber 22,222,322,322a, 322b, 522 Communication pipe 23,323,423,423A, 523,623,723 Sound absorbing member 100,200,300,400,500 Exhaust device 220h, 320h, 520h Silencer housing 220s, 320s, 520s Partition wall 222i, 322i, 522i Entrance 222o, 322o, 522o Exit

Claims (8)

An exhaust device for an internal combustion engine equipped with a silencer that reduces exhaust noise.
The silencer is
A plurality of expansion chambers having a wider flow path cross-sectional area than the exhaust pipe of the internal combustion engine, and
A communication pipe that communicates the plurality of expansion chambers in series to form a communication flow path having a smaller flow path cross-sectional area than the expansion chamber.
A sound absorbing member arranged inside the connecting pipe and absorbing the exhaust sound transmitted through the connecting flow path, and a sound absorbing member.
Equipped with
An exhaust device for an internal combustion engine in which a plurality of the connecting flow paths separated by the sound absorbing member are formed inside one connecting pipe . The connecting pipe is formed with a circular cross section and has a circular cross section.
The sound absorbing member is formed in a tubular shape having a circular cross section with a diameter smaller than that of the connecting pipe.
The connecting flow path includes an inner connecting flow path formed inside the sound absorbing member and an outer connecting flow path formed between the sound absorbing member and the inner peripheral surface of the connecting tube.
The exhaust device for an internal combustion engine according to claim 1. A plurality of flat plate-shaped sound absorbing members are arranged at intervals inside the connecting pipe so that a plurality of the connecting flow paths are formed inside the connecting pipe.
The exhaust device for an internal combustion engine according to claim 1. The entrance and exit of the connecting pipe
The exhaust device for an internal combustion engine according to any one of claims 1 to 3, which is arranged on the central portion side of the expansion chamber with respect to the end portion of the expansion chamber in the direction in which the exhaust gas flows. The exhaust device for an internal combustion engine according to any one of claims 1 to 4, wherein the expansion chambers adjacent to each other in the direction in which the exhaust gas flows are communicated by the plurality of communication pipes. The exhaust device for an internal combustion engine according to any one of claims 1 to 5 , wherein the sound absorbing member is formed so as to extend in a direction in which exhaust gas flows. The sound absorbing member is
The exhaust device for an internal combustion engine according to any one of claims 1 to 6, further comprising an acoustic liner having a sound absorbing effect at a preset predetermined frequency. The sound absorbing member is
The exhaust device for an internal combustion engine according to any one of claims 1 to 6, further comprising an acoustic metamaterial having a sound absorbing effect at a preset predetermined frequency.

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