WO2015104998A1 - Exhaust muffler - Google Patents

Abstract

An exhaust muffler comprising: an inside pipe-shaped member forming part of an exhaust flow path for an internal combustion engine; and an outside pipe-shaped member configured so as to cover the outside of the inside pipe-shaped member, having a prescribed interval provided therebetween. An upstream-side end section of the outside pipe-shaped member is joined to the outer peripheral surface of the inside pipe-shaped member. The inside pipe-shaped member has a plurality of inside through-holes arranged along the axial direction thereof, having prescribed intervals therebetween in the axial direction. The outside pipe-shaped member has at least one outside through-hole, further on the upstream side than the most upstream inside through-hole among the plurality of inside through-holes.

Description

Exhaust silencer Cross-reference of related applications

This international application claims priority based on Japanese Patent Application No. 2014-1723 filed with the Japan Patent Office on January 8, 2014. The entire contents are incorporated into this international application.

The present invention relates to an exhaust silencer disposed in an exhaust passage of an internal combustion engine.

The exhaust system for automobiles suppresses exhaust noise by an exhaust silencer disposed in the exhaust passage of the internal combustion engine. For example, low-frequency air column resonance generated in a long-length tubular portion is a factor that deteriorates exhaust exhaust noise. Therefore, measures are taken such as reducing the air column resonance by providing a sub-muffler in series with the main muffler.

On the other hand, in Patent Document 1, in order to reduce air column resonance, an inlet pipe and an outlet pipe are inserted into the outer shell of the main muffler, and a number of punching holes are formed in a portion of the inlet pipe located in the outer shell. An exhaust exhaust silencer is disclosed.

Japanese Utility Model Publication No. 6-14023

However, in the conventional exhaust silencer, a sub muffler is provided in addition to the main muffler, and the exhaust pipe is composed of two members, an inlet pipe and an outlet pipe, and thus the structure becomes complicated. was there. In addition, in the conventional exhaust silencer, although low-frequency air column resonance can be reduced, no countermeasure has been taken against exhaust noise in the high frequency region.

In one aspect of the present invention, it is desirable to suppress exhaust noise in a low frequency region and a high frequency region with a simple structure.

An exhaust silencer according to one aspect of the present invention includes an inner tubular member that forms part of an exhaust passage of an internal combustion engine, and an outer tubular member configured to cover the outer side of the inner tubular member with a predetermined interval. The upstream end of the outer tubular member is joined to the outer peripheral surface of the inner tubular member, and the inner tubular member is arranged along the axial direction with a predetermined interval in the axial direction. A plurality of inner through holes, and the outer tubular member has at least one outer through hole upstream of the most upstream inner through hole among the plurality of inner through holes. .

In the exhaust silencer, the inner tubular member has a plurality of inner through holes arranged along the axial direction with a predetermined interval in the axial direction. Therefore, the sound pressure in the inner tubular member when the air column resonance sound is generated can be gradually released and reduced by the plurality of inner through-holes, and the occurrence of standing waves can be suppressed. In addition, by providing the outer through hole in the outer tubular member that covers the outer side of the inner tubular member, the sound pressure in the inner tubular member can be more effectively released and reduced.

Further, the outer tubular member has at least one outer through hole on the upstream side of the innermost through hole on the most upstream side among the plurality of inner through holes. That is, the exhaust gas flowing through the inner tubular member tends to flow downstream from the inner through hole after passing through the inner through hole. Therefore, the vicinity of the outer through hole on the upstream side can be set to a negative pressure. Thereby, the ejection of the exhaust gas from the outer through hole can be suppressed. As a result, while sufficiently obtaining the above-described decompression effect by the outer through hole, it is possible to suppress the heat damage to the peripheral parts due to the ejection of the exhaust gas and to suppress the noise caused by the airflow near the outer through hole.

The inner tubular member has a plurality of inner through-holes arranged along the axial direction with a predetermined interval in the axial direction. The outer tubular member is configured to cover the outer side of the inner tubular member with a predetermined interval. Therefore, a resonance chamber serving as a Helmholtz resonator is formed in a space between each inner through hole of the inner tubular member and the outer tubular member covering the outer side. Thereby, the Helmholtz resonance effect is obtained, and for example, exhaust noise having a specific frequency in a high frequency region can be reduced.

As described above, since the exhaust silencer has a simple structure as described above, it is possible to suppress the exhaust noise at a lower cost and a smaller space than conventional ones. Moreover, since not only exhaust noise in the low frequency region (air column resonance) but also exhaust noise in the high frequency region can be suppressed, it becomes possible to suppress exhaust noise in a wider frequency region than in the past. The exhaust noise suppression effect can be enhanced as a whole.

In the exhaust silencer, the downstream end of the outer tubular member may be open toward the downstream side. In this case, since the downstream end of the outer tubular member is open in the exhaust direction, the sound pressure in the inner tubular member when air column resonance is generated can be more effectively released and reduced. Can do.

Further, a diameter-reduced portion having a reduced diameter may be provided at the downstream end of the inner tubular member. That is, the inner side of the inner tubular member is higher in pressure than the outer side of the inner tubular member (between the inner tubular member and the outer tubular member), but by providing a reduced diameter portion at the downstream end of the inner tubular member. The pressure difference between the inner side and the outer side of the inner tubular member can be further increased compared to the case where the reduced diameter portion is not provided. Thereby, the exhaust gas flowing in the inner tubular member can easily flow into the space between the inner tubular member and the outer tubular member through the inner through hole. As a result, it is possible to suppress abnormal noise (edge tone) generated when the exhaust gas flowing in the inner tubular member collides with the inner wall surface portion (edge) of the inner through hole.

Further, the exhaust silencer may be arranged at the downstream end of the exhaust flow path. In this case, the heat damage to the peripheral parts due to the ejection of the exhaust from the outer through hole of the outer tubular member is further improved while sufficiently obtaining the effect of suppressing the exhaust noise in the low frequency region and the high frequency region with a simple structure. It can be surely suppressed.

In the exhaust silencer, the inner through hole of the inner tubular member refers to a hole that connects the inner side and the outer side of the inner tubular member. The inner through-hole includes, for example, one formed by penetrating the inner tubular member in the thickness direction, one formed by cutting and raising a part of the inner tubular member, and the like.

In addition to the exhaust silencer described above, one aspect of the present invention can be realized in various forms such as an exhaust system including an exhaust silencer and an exhaust silencer method.

It is explanatory drawing which shows the structure of the exhaust system in 1st Embodiment. It is a perspective view which shows the exhaust silencer in 1st Embodiment. It is a perspective view which shows the inner side tubular member and the outer side tubular member in 1st Embodiment. It is sectional drawing which shows the axial cross section of the exhaust silencer in 1st Embodiment. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 4. It is sectional drawing which shows the inner side through-hole and outer side tubular member of an inner tubular member in 1st Embodiment. It is a perspective view which shows the exhaust silencer in 2nd Embodiment. It is arrow sectional drawing corresponding to FIG. 5 in 2nd Embodiment. It is sectional drawing which shows the axial direction cross section of the exhaust silencer in 3rd Embodiment.

DESCRIPTION OF SYMBOLS 1 ... Exhaust silencer 2 ... Inner tubular member 22 ... Inner through-hole 214 ... Outer peripheral surface (outer peripheral surface of inner tubular member)
3 ... Outer tubular member 311 ... Upstream end (upstream end of outer tubular member)
32 ... Outside through hole

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
As shown in FIGS. 1 to 6, the exhaust silencer 1 includes an inner tubular member 2 forming a part of an exhaust passage of an engine (internal combustion engine) and an outer side of the inner tubular member 2 with a predetermined interval. And an outer tubular member 3 for covering. The upstream end 311 of the outer tubular member 3 is joined to the outer peripheral surface 214 of the inner tubular member 2. The inner tubular member 2 has a plurality of inner through-holes 22 arranged at predetermined intervals in the axial direction. The outer tubular member 3 has at least one outer through hole 32 on the upstream side of the innermost through hole 22 (22a) on the most upstream side. Hereinafter, the exhaust silencer 1 will be described in detail.

An exhaust system 8 using the exhaust silencer 1 shown in FIG. 1 is installed under the floor of an automobile and forms an exhaust passage that serves as a passage for exhaust gas (exhaust gas) exhausted from an engine. As shown in FIG. 1, the exhaust system 8 includes a front pipe 81, a muffler 82, and a tail pipe 83.

The front pipe 81 is an exhaust pipe that forms an exhaust passage (upstream exhaust passage) from the upstream side of the muffler 82 in the exhaust direction (direction indicated by arrow F) to the inside of the muffler 82. Further, the tail pipe 83 forms an exhaust passage (downstream exhaust passage) having a relatively long length to the downstream side in the exhaust direction from the muffler 82 (specifically, the downstream opening 831 serving as an exhaust gas outlet). This is an exhaust pipe.

The exhaust silencer 1 constitutes a part of the tail pipe 83. In the present embodiment, the exhaust silencer 1 is disposed at the downstream end of the tail pipe 83, that is, at the downstream end (most downstream portion) of the exhaust flow path.

As shown in FIGS. 2 and 3, the exhaust silencer 1 has a double tube structure constituted by an inner tubular member 2 and an outer tubular member 3. The inner tubular member 2 is formed in a circular tube shape and has a circular cross section in the radial direction. Similar to the inner tubular member 2, the outer tubular member 3 is formed in a circular tube shape and has a circular cross section in the radial direction. The inner diameter of the outer tubular member 3 is larger than the outer diameter of the inner tubular member 2. The inner tubular member 2 is inserted into the outer tubular member 3 except for a part on the upstream side.

As shown in FIG. 4, the inner tubular member 2 forms a part of the exhaust passage. The upstream end portion 211 of the inner tubular member 2 is joined to the pipe portion immediately upstream thereof by, for example, welding. An inner opening 213 that opens toward the downstream side is formed at the downstream end 212 of the inner tubular member 2. The inner opening 213 corresponds to the above-described downstream opening 831 serving as an exhaust gas outlet.

The outer tubular member 3 is disposed so as to cover the outer side of the inner tubular member 2. The outer tubular member 3 is disposed with a certain distance in the radial direction between the outer tubular member 3 and the inner tubular member 2. The upstream end 311 of the outer tubular member 3 is gradually reduced in diameter toward the upstream side. Further, the upstream end 311 of the outer tubular member 3 is joined to the outer peripheral surface 214 of the inner tubular member 2 by welding, for example, and is closed. At the downstream end 312 of the outer tubular member 3, an outer opening 313 that opens toward the downstream side is formed between the outer tubular member 3 and the inner tubular member 2.

As shown in FIGS. 4 and 5, the inner tubular member 2 is formed with a plurality of inner through holes 22 penetrating in the radial direction. In the present embodiment, a predetermined number of the inner through holes 22 are arranged in a line at regular intervals in the axial direction with the same circumferential position (without changing the circumferential position). In addition, the inner through-hole group 23 including the predetermined number of inner through-holes 22 arranged as a group is formed in five rows at equal intervals in the circumferential direction.

As shown in FIGS. 4 and 6, the outer tubular member 3 is formed with one outer through hole 32 penetrating in the radial direction. The outer through hole 32 is arranged on the upstream side of the inner through hole 22 (22a) formed on the most upstream side. The outer through hole 32 is formed to open to the vehicle lower side. The inner diameter of the outer through hole 32 is larger than the inner diameter of the inner through hole 22.

Next, the effect in the exhaust silencer 1 of this embodiment is demonstrated.
In the exhaust silencer 1 of the present embodiment, the inner tubular member 2 has a plurality of inner through holes 22 arranged along the axial direction with a predetermined interval in the axial direction. Therefore, the sound pressure in the inner tubular member 2 when the air column resonance sound is generated can be gradually released and reduced by the plurality of inner through holes 22 to suppress the occurrence of standing waves. Moreover, by providing the outer through-hole 32 in the outer tubular member 3 that covers the outer side of the inner tubular member 2, the sound pressure in the inner tubular member 2 can be more effectively released and reduced.

Further, the outer tubular member 3 has one outer through hole 32 on the upstream side of the innermost through hole 22 (22a) on the most upstream side among the plurality of inner through holes 22. That is, after the exhaust gas flowing through the inner tubular member 2 passes through the inner through hole 22, it tends to flow downstream from the inner through hole 22 that has passed therethrough. Therefore, the vicinity of the outer through hole 32 on the upstream side can be set to a negative pressure. Thereby, the ejection of the exhaust gas from the outer through hole 32 can be suppressed. As a result, it is possible to suppress the heat damage to the peripheral parts due to the emission of the exhaust gas and to suppress the noise caused by the air current in the vicinity of the outer through-hole 32 while sufficiently obtaining the pressure reducing effect by the outer through-hole 32 described above.

The inner tubular member 2 has a plurality of inner through holes 22 arranged along the axial direction with a predetermined interval in the axial direction. The outer tubular member 3 is configured to cover the outer side of the inner tubular member 2 with a predetermined interval. Therefore, a resonance chamber serving as a Helmholtz resonator is formed in a space between each inner through hole 22 of the inner tubular member 2 and the outer tubular member 3 covering the outside. Thereby, the Helmholtz resonance effect is obtained, and exhaust noise having a specific frequency in the high frequency region can be reduced.

For example, as shown in FIG. 7, a resonance chamber 41 serving as a Helmholtz resonator is formed in a space between each inner through hole 22 of the inner tubular member 2 and the outer tubular member 3 covering the outside. In this case, the resonance frequency f ₀ of the Helmholtz resonator can be obtained from the following formula (1). The exhaust noise of a specific frequency (resonance frequency f ₀ ) in the high frequency region can be reduced by the Helmholtz resonance effect.

 

In the above formula (1), c: sound velocity, P: aperture ratio of the inner through hole 22 of the inner tubular member 2, t: plate thickness of the inner tubular member 2, δ: 0.8d (d: inner through hole) 22 is a distance between the inner tubular member 2 and the outer tubular member 3. For example, by changing the opening ratio P of the inner through-hole 22 of the inner tubular member 2 and the distance L that is the distance between the inner tubular member 2 and the outer tubular member 3, exhaust noise having a specific frequency in the high frequency region is selectively selected. Can be reduced. Here, the opening ratio P is the opening area of the inner through hole (the total of the opening areas if there are a plurality of inner through holes) or the area of an arbitrary portion where the inner through hole is formed (for example, the inner through hole is formed). Divided by the area of the outer surface of the inner tubular member to be obtained.

As described above, since the exhaust silencer 1 of the present embodiment has the simple structure as described above, it is possible to realize suppression of exhaust noise at a lower cost and space saving than in the past. Further, not only exhaust noise (air column resonance) in the low frequency region (for example, 100 to 800 Hz) but also exhaust noise in the high frequency region (for example, 1600 to 4000 Hz) can be suppressed. Noise can be suppressed in a wide frequency range, and the exhaust noise suppression effect can be enhanced as a whole.

Further, in the exhaust silencer 1, the downstream end 312 of the outer tubular member 3 is opened toward the downstream side. That is, the downstream end 312 of the outer tubular member 3 opens in the exhaust direction. An outer opening 313 is formed at the downstream end 312 of the outer tubular member 3. Therefore, the sound pressure in the inner tubular member 2 when air column resonance is generated can be more effectively released and reduced by the outer opening 313.

Further, the outer through hole 32 of the outer tubular member 3 is formed to open to the vehicle lower side. Therefore, it is possible to further reduce the influence of thermal damage to peripheral components due to the ejection of exhaust gas from the outer through hole 32 of the outer tubular member 3.

Further, the exhaust silencer 1 is disposed at the downstream end of the exhaust passage. Therefore, the heat damage to the peripheral parts due to the ejection of the exhaust gas from the outer through-hole 32 of the outer tubular member 3 is more surely obtained while sufficiently obtaining the effect of suppressing the exhaust noise in the low frequency region and the high frequency region with a simple structure. Can be suppressed.

(Embodiment 2)
In the present embodiment, as shown in FIGS. 8 and 9, the radial sectional shape of the outer tubular member 3 is changed.

As shown in FIGS. 8 and 9, the outer tubular member 3 has an elliptical radial cross section, unlike the inner tubular member 2 having a circular radial cross section. Therefore, the distance between the inner tubular member 2 and the outer tubular member 3 is not constant in the circumferential direction. That is, the distance between the inner tubular member 2 and the outer tubular member 3 varies depending on the circumferential position.

As shown in FIG. 9, in the inner tubular member 2, the inner through-hole group 23 including a predetermined number of inner through-holes 22 arranged in a line at regular intervals in the axial direction is equally spaced in the circumferential direction. 4 rows are formed. Further, two rows of the inner through hole groups 23 (23 a, 23 c) are formed at positions facing the radial direction in the short diameter portion of the outer tubular member 3. The other two rows of inner through hole groups 23 (23 b, 23 d) are formed at positions facing the radial direction in the long diameter portion of the outer tubular member 3.

That is, in the inner tubular member 2, the portion in which the inner through hole 22 of the inner through hole group 23 a is formed and the portion in which the inner through hole 22 of the inner through hole group 23 c is formed are the same as the outer tubular member 3. The distance between them is the same. The distance between the outer tubular member 3 is the same as the portion of the inner through hole group 23b where the inner through hole 22 is formed and the portion of the inner through hole group 23d where the inner through hole 22 is formed. is there.

In the inner tubular member 2, the portions where the inner through holes 22 of the inner through hole groups 23 b and 23 d are formed are compared to the portions where the inner through holes 22 of the inner through hole groups 23 a and 23 c are formed. The distance between the outer tubular member 3 is large. Other basic configurations are the same as those in the first embodiment.

Next, the effect in the exhaust silencer 1 of this embodiment is demonstrated.
In the exhaust silencer 1 of this embodiment, the inner through-hole 22 (inner through-hole group 23) is formed in a plurality of portions with different distances from the outer tubular member 3 with respect to the inner tubular member 2. Here, when the distance L between the inner tubular member 2 and the outer tubular member 3 is different from the above equation (1), the resonance frequency f ₀ of the Helmholtz resonator is different.

Therefore, exhaust noise having a plurality of different frequencies (two frequencies in this embodiment) in the high frequency region can be reduced by the Helmholtz resonance effect. Thereby, the effect which suppresses the exhaust noise of a high frequency area | region can be heightened further. As a result, exhaust noise in a wider frequency range can be suppressed. Other basic functions and effects are the same as those of the first embodiment.

(Embodiment 3)
The present embodiment is an example in which the configuration of the inner tubular member 2 is changed as shown in FIG.
As shown in the figure, the downstream end portion 212 of the inner tubular member 2 is provided with a reduced diameter portion 24 having a reduced diameter. That is, in the inner tubular member 2, the reduced diameter portion 24 is a portion whose diameter is reduced as compared with other portions. Other basic configurations are the same as those in the first embodiment.

Next, the effect in the exhaust silencer 1 of this embodiment is demonstrated.
In the exhaust silencer 1 of the present embodiment, the inner tubular member 2 has a higher pressure on the inner side of the inner tubular member 2 than on the outer side of the inner tubular member 2 (between the inner tubular member 2 and the outer tubular member 3). By providing the diameter-reduced portion 24 at the downstream end 212, the pressure difference between the inside and the outside of the inner tubular member 2 can be further increased as compared with the case where the diameter-reduced portion 24 is not provided. Thereby, the exhaust gas flowing in the inner tubular member 2 easily flows into the space between the inner tubular member 2 and the outer tubular member 3 through the inner through hole 22. As a result, it is possible to suppress abnormal noise (edge tone) generated when the exhaust gas flowing through the inner tubular member 2 collides with the inner wall surface portion (edge) of the inner through hole 22. Other basic functions and effects are the same as those of the first embodiment.

As described above, the present invention is not limited to Embodiments 1 to 3 described above, and can be implemented in various forms without departing from the technical scope thereof.
(1) In the above embodiment, the exhaust silencer 1 is arranged on the tail pipe 4 as shown in FIG. 1, but the arrangement position of the exhaust silencer 1 is not limited to this. For example, the exhaust silencer 1 may be arranged on the front pipe 81.

(2) In the above embodiment, as shown in FIGS. 4 and 5, a plurality of inner through holes 22 are formed in the inner tubular member 2, but the arrangement position, number, shape, inner diameter, etc. of the inner through holes 22 are as follows. However, the present invention is not limited to this, and various modes can be adopted.

(3) In the said embodiment, as shown in FIG.4, FIG.6, the outer side through-hole 32 of the outer side tubular member 3 is formed in one upstream from the innermost through-hole 22 (22a) of the most upstream side. However, a plurality of them may be formed.

(4) In the above embodiment, as shown in FIG. 4, the outer tubular member 3 has at least one outer through hole upstream of the innermost through hole 22 (22 a) on the most upstream side. In addition to this, the outer through-hole 32 may be provided in another portion (for example, downstream of the most upstream inner through-hole 22 (22a)).

(5) In the above embodiment, as shown in FIG. 4, the outer through hole 32 of the outer tubular member 3 is formed on the upstream side of the innermost through hole 22 (22a) on the most upstream side. It is preferable that the tubular member 2 is disposed in the vicinity of the maximum sound pressure location. In this case, the sound pressure in the inner tubular member 2 can be more effectively released and reduced, and in particular, the effect of suppressing the occurrence of standing waves can be enhanced.

Claims (4)

1. An inner tubular member that forms part of the exhaust flow path of the internal combustion engine;
   An outer tubular member configured to cover the outer side of the inner tubular member with a predetermined interval;
   The upstream end of the outer tubular member is joined to the outer peripheral surface of the inner tubular member,
   The inner tubular member has a plurality of inner through holes arranged along the axial direction with a predetermined interval in the axial direction,
   The exhaust silencer characterized in that the outer tubular member has at least one outer through hole on the upstream side of the innermost through hole on the most upstream side among the plurality of inner through holes.
2. The exhaust silencer according to claim 1, wherein the downstream end portion of the outer tubular member opens toward the downstream side.
3. 3. The exhaust silencer according to claim 1, wherein the downstream end portion of the inner tubular member is provided with a reduced diameter portion having a reduced diameter.
4. The exhaust silencer according to any one of claims 1 to 3, wherein the exhaust silencer is disposed at a downstream end portion of the exhaust passage.

Images