JP6276032B2 - Exhaust silencer - Google Patents

Description

  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 tubular section may cause deterioration of exhaust noise, and measures to reduce air column resonance by providing a sub-muffler in series with the main muffler Has been taken.

  On the other hand, Patent Document 1 has a structure in which an inlet pipe and an outlet pipe into which an exhaust pipe is divided into two are inserted into an outer shell of a main muffler, and a number of punching holes are formed in a portion located in the outer shell of the inlet pipe. A silencer for reducing air column resonance is disclosed.

Japanese Utility Model Publication No. 6-14023

  However, the conventional exhaust silencer has a problem that the structure becomes complicated because a sub muffler is provided in addition to the main muffler and the exhaust pipe is divided in the main muffler. In addition, although low-frequency air column resonance can be reduced, no countermeasures have been taken against high-frequency exhaust noise.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an exhaust silencer that can suppress exhaust noise in low and high frequency regions with a simple structure.

  An exhaust silencer of the present invention includes an inner tubular member that forms a part of an exhaust flow path of an internal combustion engine, and an outer tubular member that covers the outer side of the inner tubular member with a predetermined interval, and the outer tubular member The upstream end of the inner tubular member is joined to the outer peripheral surface of the inner tubular member, and the inner tubular member has a plurality of inner through holes arranged at predetermined intervals in the axial direction, The outer tubular member has at least one outer through hole upstream of the innermost through hole on the most upstream side.

  In the exhaust silencer of the present invention, the inner tubular member has a plurality of inner through holes arranged at predetermined intervals 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 standing wave 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.

  The outer tubular member has at least one outer through hole on the upstream side of the most upstream inner through hole, that is, on the side opposite to the exhaust direction (downstream side). 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, it is possible to prevent thermal damage to peripheral parts due to the ejection of exhaust gas and to suppress noise caused by airflow in the vicinity of the outer through-hole while obtaining the above-described decompression effect due to the outer through-hole.

  The inner tubular member has a plurality of inner through-holes arranged at predetermined intervals in the axial direction, and the outer tubular member covers the outer side of the inner tubular member with predetermined intervals. 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 of the present invention has a simple structure as described above, it is possible to achieve suppression of exhaust noise at a lower cost and space saving than in the past. 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.

  Moreover, the diameter-reduced part formed by reducing a diameter may be provided in the downstream edge part of the said inner side 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 passage. In this case, the heat damage to the peripheral parts due to the ejection of the exhaust gas from the outer through hole of the outer tubular member while sufficiently obtaining the effect of the present invention that suppresses the exhaust noise in the low frequency and high frequency regions with a simple structure. Can be further prevented.

  In the exhaust silencer of the present invention, 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, 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 AA in FIG. 4. FIG. 5 is a cross-sectional view taken along line B-B 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.

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 that forms 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. This will be described in detail below.

  As shown in FIG. 1, an exhaust system 8 using an exhaust silencer 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. A front pipe 81, a muffler 82, and a tail pipe 83 are provided.

  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, the downstream end of the exhaust flow path.

  As shown in FIGS. 2 and 3, the exhaust silencer 1 has a double-pipe structure composed of 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 with a certain interval in the radial direction. The upstream end 311 of the outer tubular member 3 is gradually reduced in diameter toward the upstream side, and 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 inner through holes 22 are arranged in a line at regular intervals in the axial direction (exhaust 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 that penetrates 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 disposed at predetermined intervals 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 standing wave. 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.

  The outer tubular member 3 has one outer through hole 32 on the upstream side of the most upstream inner through hole 22 (22a), that is, on the side opposite to the exhaust direction (downstream side). 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 prevent thermal damage to peripheral parts due to the emission of exhaust gas and to suppress noise caused by airflow 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 at predetermined intervals in the axial direction, and the outer tubular member 3 covers the outer side of the inner tubular member 2 with predetermined intervals. ing. 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 equation (1) in FIG. The exhaust noise of a specific frequency (resonance frequency f ₀ ) in the high frequency region can be reduced by the Helmholtz resonance effect.

  7, 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 side) (Hole diameter of the through hole 22), L: 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 achieve suppression of exhaust noise at a lower cost and space saving than in the past. Moreover, since not only exhaust noise (air column resonance sound) in a low frequency region (for example, 100 to 800 Hz) but also exhaust noise in a high frequency region (for example, 1600 to 4000 Hz) can be suppressed, the exhaust gas is exhausted as compared with the conventional case. Noise can be suppressed in a wide frequency range, and the exhaust noise suppression effect can be enhanced as a whole.

  In the exhaust silencer 1, the downstream end 312 of the outer tubular member 3 opens 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, while sufficiently obtaining the effect of the present invention that suppresses the exhaust noise in the low frequency and high frequency regions with a simple structure, the thermal damage to the peripheral parts due to the emission of the exhaust gas from the outer through hole 32 of the outer tubular member 3 is prevented. This can be further prevented.

(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 whose radial cross section is circular. 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 (exhaust direction) Four rows are formed at equal intervals in the direction. In addition, two rows of inner through-hole groups 23 (23a, 23c) are formed at positions facing the radial direction in the short diameter portion of the outer tubular member 3, and the other two rows of inner through-hole groups 23. (23b, 23d) is formed at a position 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, if the distance L between the inner tubular member 2 and the outer tubular member 3 is different from the equation (1) in FIG. 7, the resonance frequency f ₀ of the Helmholtz resonator is different.

  Therefore, exhaust noise of a plurality of different frequencies (two types of frequencies in the present 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 released more effectively and reduced, and in particular, the effect of suppressing standing waves can be enhanced.

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

Claims (4)

An inner tubular member that forms part of the exhaust flow path of the internal combustion engine;
An outer tubular member covering 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 at predetermined intervals in the axial direction,
The outer tubular member has at least one outer through hole upstream of the innermost through hole on the most upstream side,
The downstream end of the outer tubular member is open toward the downstream side;
Exhaust silencer characterized by. An inner tubular member that forms part of the exhaust flow path of the internal combustion engine of the vehicle;
An outer tubular member covering 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 at predetermined intervals in the axial direction,
The outer tubular member has at least one outer through hole upstream of the innermost through hole on the most upstream side,
The at least one outer through hole faces a lower side of the vehicle ;
The downstream end of the outer tubular member is open toward the downstream side;
Exhaust silencer characterized by. 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. The exhaust silencer according to any one of claims 1 to 3 , wherein the exhaust silencer is disposed at a downstream end of the exhaust passage.

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