JP7457046B2 - Exhaust pipe - Google Patents

Description

The present disclosure relates to an exhaust pipe.

BACKGROUND ART There is a known technique for attenuating vehicle exhaust pipe noise by using sound wave interference due to Helmholtz resonance or side branches. As an example, in the technique disclosed in Patent Document 1, a resonance chamber and a resonance pipe are formed in a gap between an inner pipe and an outer pipe in an exhaust pipe having a double pipe structure. Then, the Helmholtz resonance attenuates noise at a frequency depending on the volume of the resonance chamber, the length of the resonance tube, and the like.

Japanese Patent Application Publication No. 2020-112063

However, although the technique disclosed in Patent Document 1 can attenuate noise at a specific frequency, there is a desire to suppress noise in a wider band.
One aspect of the present disclosure aims to suppress noise in a wider band.

One aspect of the present disclosure is an exhaust pipe that is mounted on a vehicle, and includes an inner pipe, an outer pipe, an opening, a closing portion, and at least one closing portion. The inner tube is configured to allow exhaust gas to flow down. The outer tube is arranged outside the inner tube so as to form a double tube, and forms a muffling chamber between the outer tube and the inner tube. The opening opens the muffling chamber at the first end of the double tube. A closure closes off the sound deadening chamber at the second end of the double tube. The closing portion is provided apart from the opening and the closing portion, and by closing the silencing chamber, divides the silencing chamber into an upstream silencing region and a downstream silencing region in the exhaust gas flow direction. Moreover, the closing part has at least one flow path that communicates the upstream silencing area and the downstream silencing area.

According to the above configuration, a silencing effect due to resonance in the entire silencing chamber and a silencing effect due to resonance in each silencing area of the silencing chamber formed by the closing portion can be obtained. Therefore, noise in a wider band can be suppressed compared to the case where no blocking part is provided and the sound is muffled by resonance throughout the muffling chamber.

In one aspect of the present disclosure, the area of the opening may be larger than the area of a cross section of the flow path of the closing portion perpendicular to the flow direction of exhaust gas.
According to the above configuration, since the area of the opening of the silencing chamber becomes larger, it becomes easier for sound waves to enter the silencing chamber, and resonance is more likely to occur in the entire silencing chamber and in each silencing area. Therefore, noise in a wider band can be suppressed favorably.

In one aspect of the present disclosure, a cross section of the outer pipe parallel to the flow direction of the exhaust gas in a portion where the blocking portion is not located extends along the flow direction of the exhaust gas from a first end to a second end in the flow direction of the exhaust gas. It's okay.

According to the above configuration, the space for arranging the exhaust pipe can be suppressed.
In one aspect of the present disclosure, the outer tube may have a recess that is depressed toward the inner tube, and the closing portion may have a recess.

According to the above configuration, a closed portion can be formed satisfactorily.
In one aspect of the present disclosure, the number of occlusions may be one.
According to the above configuration, a good sound deadening effect due to resonance can be obtained in each sound deadening region of the sound deadening chamber divided by the blocking portion. Therefore, noise in a wider band can be suppressed favorably.

In one aspect of the present disclosure, the first end of the double pipe may be located upstream in the flow direction of the exhaust gas.
According to the above-mentioned configuration, sound waves can easily enter the sound absorbing chamber, and resonance can easily occur in the entire sound absorbing chamber and in each sound absorbing region of the sound absorbing chamber, thereby making it possible to effectively suppress noise over a wider frequency range.

FIG. 3 is a transparent side view of the exhaust pipe. FIG. 2 is a sectional view taken along line II-II in FIG. 1; FIG. 2 is a sectional view taken along line III-III in FIG. 1; It is a graph which shows the measurement result of the amount of silence of an exhaust pipe. FIG. 7 is a transparent side view of the vicinity of a blockage in an exhaust pipe of a modified example. FIG. 7 is a transparent side view of the vicinity of a blockage in an exhaust pipe of a modified example.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that the embodiments of the present disclosure are not limited to the embodiments described below, and may take various forms as long as they fall within the technical scope of the present disclosure.

[1. overview]
The exhaust pipe 1 of this embodiment is mounted on a vehicle and forms a flow path for exhaust gas from the vehicle's engine (see FIG. 1). Further, the exhaust pipe 1 includes a double pipe 2 that functions as a muffler.

Specifically, the exhaust pipe 1 extends straight in the direction of the axis 1A, as an example, and the exhaust gas flows down from the upstream side to the downstream side in the direction of the axis 1A. Further, the exhaust pipe 1 includes an inner pipe 3 and an outer pipe 4 that constitute a double pipe 2, and a closing portion 5. The inner tube 3 and the outer tube 4 have a circular cross section (hereinafter referred to simply as a cross section) perpendicular to the axis 1A (see FIG. 2).

[2. Outer tube]
The outer tube 4 extends straight in the direction of the axis 1A, is disposed outside the inner tube 3, and includes an inlet portion 40, an enlarged diameter portion 41, and a main body portion 42 (see FIG. 1).

The inlet portion 40 is a cylindrical portion that forms an inlet for exhaust gas into the exhaust pipe 1 .
The expanded diameter section 41 is connected to the downstream end of the inlet section 40, and expands the cross section of the outer pipe 4 downstream.

The main body portion 42 is a cylindrical portion connected to the downstream end of the enlarged diameter portion 41, and the cross-sectional diameter of the main body portion 42 is larger than the cross-sectional diameter of the inlet portion 40.
[3. Inner tube]
The inner tube 3 extends straight in the direction of the axis 1A and is disposed inside the main body 42 of the outer tube 4, and the inner tube 3 and the main body 42 of the outer tube 4 form a double tube 2. (See Figure 1). The inner tube 3 includes a main body portion 30, an enlarged diameter portion 31, and an outlet portion 32.

The main body portion 30 is a cylindrical portion that forms an inlet for exhaust gas into the inner tube 3 .
The enlarged diameter portion 31 is connected to the downstream end of the main body portion 30, and enlarges the cross section of the inner tube 3 toward the downstream side.

The outlet portion 32 is a cylindrical portion connected to the downstream end of the enlarged diameter portion 31, and the diameter of the cross section of the outlet portion 32 is larger than the diameter of the cross section of the enlarged diameter portion 31. . Further, the outlet portion 32 is joined to the downstream end of the main body portion 42 of the outer tube 4.

[4. Double pipe]
As described above, the inner tube 3 and the main body portion 42 of the outer tube 4 form the double tube 2 that extends straight in the direction of the axis 1A (see FIG. 1). The inner tube 3 and the main body part 42 are arranged so that their cross sections are concentric, and the axis 1A passes through the center of the cross sections of the inner tube 3 and the main body part 42.

Then, the exhaust gas flowing down the double pipe 2 passes through the inner pipe 3 and flows out of the exhaust pipe 1. Further, the space between the main body portion 30 and enlarged diameter portion 31 of the inner tube 3 and the main body portion 42 of the outer tube 4 functions as a muffling chamber 20 for suppressing the noise of exhaust gas.

Specifically, there is a gap surrounding the opening of the inner tube 3 between the upstream end of the main body 30 of the inner tube 3 and the main body 42 of the outer tube 4. An opening 21 is formed at the upstream end of the pipe 2 to open the silencing chamber 20 (see FIG. 2). The opening 21 of the muffling chamber 20 has the same shape as the cross section of the muffling chamber 20 .

Further, the outer circumferential surface of the outlet portion 32 of the inner tube 3 is in contact with the downstream end of the main body portion 42 of the outer tube 4, and these parts allow the downstream end of the double tube 2 to , a closing part 22 is formed to close the downstream end of the muffling chamber 20.

Therefore, the upstream end of the main body 30 of the inner tube 3 and the downstream end of the enlarged diameter section 31 of the inner tube 3 are the same as the upstream end of the silencing chamber 20 and the downstream end of the expanded diameter section 31 of the inner tube 3, respectively. This corresponds to the end. Hereinafter, the distance along the axis 1A between the upstream end and the downstream end of the silencing chamber 20 will be referred to as L1. L1 corresponds to the entire length of the silencing chamber 20. Specifically, L1 is the length from the upstream end surface of the main body portion 30 in the inner tube 3 to the boundary between the enlarged diameter portion 31 and the outlet portion 32.

[5. Occlusion]
As an example, one closing portion 5 is provided in the silencing chamber 20 so as to be spaced apart from the opening 21 and the closing portion 22 (in other words, both ends of the silencing chamber 20) (see FIG. 1). The distance between the upstream end of the silencing chamber 20 and the upstream end of the closing section 5 is set to L2. Specifically, L2 is the length of the inner tube 3 from the upstream end surface of the main body portion 30 to the upstream end surface of the closing portion 5. Further, the distance between the upstream end of the closing portion 5 and the downstream end of the silencing chamber 20 is set to L3. Specifically, L3 is the length from the upstream end surface of the closing portion 5 to the boundary between the enlarged diameter portion 31 and the outlet portion 32. Note that L2 and L3 are numerical values larger than 0, and these numerical values are appropriately determined depending on the noise band for which the amount of silencing is desired to be increased.

The closing portion 5 blocks the silencing chamber 20, thereby dividing the silencing chamber 20 into a first silencing area 20A located on the upstream side and a second silencing area 20B located on the downstream side. Note that L2 and L3 correspond to the lengths of the first and second silencing areas 20A and 20B, respectively.

As an example, the closing portion 5 is constituted by an intervening object disposed between the main body portion 30 of the inner tube 3 and the main body portion 42 of the outer tube 4. Moreover, a wire mesh is used as an example of the inclusion. The inclusion is held between the outer circumferential surface of the main body 30 of the inner tube 3 and the inner circumferential surface of the main body 42 of the outer tube 4. It is possible to slide against inclusions. Note that the inclusion is joined to one of the main body part 30 of the inner tube 3 or the main body part 42 of the outer tube 4, and the main body part 30 of the inner tube 3 or the main body part of the outer tube 4 that is not joined to the inclusion. 42 may be slidable relative to the inclusion.

The closing part 5 has two flow paths 50 that communicate the first silencing area 20A and the second silencing area 20B (see FIG. 3). These channels 50 face each other across the axis 1A. Note that the closing portion 5 may have one or three or more flow paths 50. That is, in the present embodiment, the closed portion 5 is formed by an inclusion that partially closes the area surrounding the inner tube 3 in the muffling chamber 20 . The area of the opening 21 of the silencing chamber 20 is larger than the sum of the cross-sectional areas of each flow path 50 of the closing portion 5 (hereinafter referred to as the total area). Note that the flow path 50 may be formed by denting a part of the inclusion in the radial direction. Alternatively, for example, a plurality of inclusions may be arranged with gaps in the circumferential direction, and the flow path 50 may be formed by the gaps between the inclusions.

In addition, the cross sections of the main bodies 30 and 42 of the inner tube 3 and outer tube 4 parallel to the axis 1A extend from the upstream end to the downstream end of the axis 1A (in other words, in the flow direction of exhaust gas). ). Therefore, the parallel cross section of the portion of the main body portion 42 of the outer tube 4 that faces each of the silencing areas 20A and 20B of the silencing chamber 20 (in other words, the portion where the closing portion 5 is not located) is located on the upstream side. It extends along the axis 1A from the end to the downstream end. In other words, the parallel cross section of the portion extends parallel or substantially parallel to the axis 1A.

[6. Sound deadening effect due to blockage]
The muffling chamber 20 formed in the double pipe 2 functions as a side branch type muffler (see FIG. 1). Further, by providing the closing portion 5 in the silencing chamber 20, a silencing effect due to resonance in the entire silencing chamber 20 and a silencing effect due to resonance in each of the first and second silencing regions 20A can be obtained.

Specifically, the silencing effect of the entire silencing chamber 20 is caused by resonance of a frequency corresponding to L1, which is the entire length of the silencing chamber 20. Further, the silencing effect due to resonance in the first and second silencing regions 20A and 20B is caused by resonance of frequencies corresponding to the lengths L2 and L3, which are the lengths of the first and second silencing regions 20A and 20B, respectively. Therefore, the noise band in which the degree of attenuation increases changes depending on the values of L1 to L3.

As shown by lines 6 to 8 of the graph in FIG. 4, the exhaust pipe 1 of this embodiment suppresses noise in a wider range than when the blockage portion 5 is removed from the exhaust pipe 1. That is, line 6 shows the measurement result of the amount of silencing of exhaust pipe 1 from which blockage portion 5 was removed. Note that the exhaust pipe 1 has a length L1 of 700 mm. Moreover, line 7 shows the measurement results of the amount of damping of the exhaust pipe 1 when L1=700 mm, L2=200 mm, and L3=500 mm. Moreover, line 8 shows the measurement results of the amount of damping of the exhaust pipe 1 when L1=700 mm, L2=350 mm, and L3=350 mm.

According to the graph of FIG. 4, in the low frequency band, the exhaust pipe 1 without the blockage part 5 and each exhaust pipe 1 with the blockage part 5 have similar correspondences between the frequency and the amount of silencing. That is, with respect to noise in the low frequency band, the exhaust pipe 1 having the blocking part 5 has the same level of muffling effect as each exhaust pipe 1 not having the blocking part 5. On the other hand, in the high frequency band, there is a difference in the correspondence between the frequency of these exhaust pipes 1 and the amount of silencing, and each exhaust pipe 1 with a blockage part 5 is different from the exhaust pipe 1 without a blockage part 5. Compared to this, there is a lot of noise reduction.

That is, by providing the blocking portion 5, the amount of noise reduction in the high frequency band can be increased while maintaining the amount of noise reduction in the low frequency band. That is, by providing the blocking portion 5, the noise band to be suppressed is expanded to the high frequency side.

Moreover, lines 6 and 7 indicate that when the numerical values of L2 and L3 are different, the bands of noise in which the amount of silencing increases will be different in the high frequency band. Therefore, by adjusting L2 and L3 according to the characteristics of the noise generated in the vehicle in which the exhaust pipe 1 is mounted, the noise can be suitably suppressed.

[7. Modified example of occluded part]
In the exhaust pipe 1 of this embodiment, all or a portion of the closing portion 5 may be configured by the shape of the inner pipe 3 and/or the outer pipe 4.

Specifically, for example, a recess 43 may be provided in the main body 42 of the outer tube 4 so as to go around the main body 42 and sink toward the inner tube 3 (see FIG. 5). Then, the wire mesh 51 may be placed between the bottom of the recess 43 and the main body 30 of the inner tube 3 in the same manner as in this embodiment. That is, the closing portion 5 may be configured by the recess 43 and the wire mesh 51.

Further, for example, a concave portion may be provided in the main body portion 42 of the outer tube 4 so as to go around the main body portion 42 and whose bottom portion abuts the main body portion 30 of the inner tube 3. By forming a groove in the bottom of the recess, at least one channel may be formed between the bottom and the main body 30, which communicates the first silencing region 20A and the second silencing region 20B. . That is, the closing portion may be formed by the recessed portion of the main body portion 42 of the outer tube 4 without providing an intervening material such as the wire mesh 51.

By doing so, the closed portion can be formed satisfactorily.
In addition, also in these cases, the cross section parallel to the axis 1A of the portion of the main body portion 42 of the outer tube 4 where the closing portion 5 is not located (in other words, the portion other than the recessed portion) is the upstream end. It may extend along the axis 1A from the end to the downstream end.

Further, it is preferable that the length of the main body portion 42 other than the recessed portion in the direction of the axis 1A is longer than the length of the closure portion 5 in the direction of the axis 1A. That is, it is preferable that the portion of the main body 42 extending along the axis 1A be longer than the recessed portion of the main body 42.

Further, for example, a convex portion 33 may be formed on the main body portion 30 of the inner tube 3 so as to extend toward the outer tube 4 so as to go around the main body portion 30 (see FIG. 6). Then, the wire mesh 51 may be placed between the top of the convex portion 33 and the main body portion 42 of the outer tube 4 in the same manner as in this embodiment. That is, the convex portion 33 and the wire mesh 51 may constitute the closing portion 5.

Further, for example, a convex portion may be formed on the main body portion 30 of the inner tube 3 so as to go around the main body portion 30 and whose top portion abuts the main body portion 42 of the outer tube 4. By forming a groove at the top of the convex portion, at least one channel may be formed between the top and the main body 42 to communicate the first silencing region 20A and the second silencing region 20B. good. That is, the closed portion may be formed by the convex portion of the main body portion 30 of the inner tube 3 without providing an intervening material such as the wire mesh 51.

In addition, also in these cases, the cross section of the main body portion 42 of the outer tube 4 parallel to the axis 1A may extend along the axis 1A from the upstream end to the downstream end.
In addition, protrusions and recesses are similarly provided in each of the main bodies 30 and 42 of the inner tube 3 and outer tube 4, and inclusions are similarly provided between the tops of the protrusions and the bottoms of the recesses. By providing this, a closed portion may be formed. Further, the top of the convex portion and the bottom of the concave portion are brought into contact with each other, and at least one flow path is formed between these portions, and a closed portion is formed by the convex portion and the concave portion without providing an intervening material. Good too.

[8. effect]
(1) According to the above embodiment, a silencing effect due to resonance in the entire silencing chamber 20 and a silencing effect due to resonance in each of the silencing regions 20A and 20B of the silencing chamber 20 formed by the blocking portion 5 can be obtained. Therefore, noise in a wider band can be suppressed compared to the case where the blocking part 5 is not provided and the sound is muffled by resonance in the entire muffling chamber 20.

(2) Furthermore, the area of the opening 21 of the silencing chamber 20 is larger than the total cross-sectional area of each flow path 50 of the closing portion 5. This increases the area of the opening 21, making it easier for sound waves to enter the silencing chamber 20, making it easier for resonance to occur throughout the silencing chamber 20 and in each of the silencing regions 20A and 20B. Therefore, noise in a wider band can be suppressed favorably.

(3) In addition, in the main body portion 42 of the outer tube 4, a section parallel to the axis 1A extends from the upstream end to the downstream end of the axis 1A. extends along the Therefore, the space for arranging the exhaust pipe 1 can be reduced.

(4) Moreover, the closing part 5 has a wire mesh as a holding object, and the inner tube 3 and/or the outer tube 4 can slide against the wire mesh. Therefore, when thermal elongation occurs in the double tube 2, the difference in thermal elongation between the inner tube 3 and the outer tube 4 can be absorbed, and buckling can be suppressed.

In addition, in a muffler with a double-pipe structure that performs noise reduction using Helmholtz resonance or side branches, the part that closes the end of the silencing chamber between the inner pipe and the outer pipe is configured with a wire mesh, and the inner pipe and A technique for absorbing the difference in thermal expansion between the outer tube and the outer tube is known. In addition, in a similar muffler, there is a technology that absorbs the difference in thermal expansion between the inner tube and the outer tube by arranging a wire mesh at the end of the silencing chamber and forming the opening of the silencing chamber with the wire mesh. Are known.

In these mufflers, if the density of the wire mesh is low, it becomes difficult for sound waves to be reflected at the ends of the silencing chamber, which may reduce the silencing effect due to resonance. For this reason, it is necessary to make the wire mesh high in density, which results in an increase in cost. On the other hand, according to the embodiment described above, the density of the wire mesh has less influence on the silencing effect, and the density of the wire mesh can be lowered. Therefore, an increase in cost can be suppressed.

(5) Furthermore, the opening 21 of the silencing chamber 20 is located at the upstream end of the double pipe 2. Therefore, sound waves easily enter the muffling chamber 20, and resonance is likely to occur in the muffling chamber 20 as a whole and in each of the muffling regions 20A and 20B of the muffling chamber 20. Therefore, noise in a wider band can be suppressed favorably.

[9. Other embodiments]
(1) In the above embodiment, the opening 21 of the double pipe 2 may be located on the downstream side, and the closing portion 22 may be located on the upstream side. Specifically, for example, the outlet portion 32 of the inner tube 3 may be placed on the upstream side, and the main body portion 30 may be placed on the downstream side. Further, for example, the opening of the exhaust pipe 1 on the side where the outlet portion 32 of the inner pipe 3 and the main body portion 42 of the outer pipe 4 are located may be used as the inlet of the exhaust gas into the exhaust pipe 1.

(2) In the above embodiment, N (N is an integer of 2 or more) closing portions 5 may be provided in the muffling chamber 20 of the double pipe 2. The distance between the opening 21 of the silencing chamber 20 and each closing portion 5 may be determined depending on the noise band for which the amount of silencing is desired to be increased. As a result, N+1 silencing regions are formed in the silencing chamber 20, and in each silencing region, a silencing effect is produced by resonance at a frequency corresponding to the length of the silencing region. Therefore, noise in a wider band can be suppressed.

Further, in this case, it is preferable that the area of the opening 21 of the silencing chamber 20 is larger than the total area of the cross section of each flow path in each closing part 5.
(3) In the above embodiment, the double pipe 2 is not limited to a shape that extends straight in the direction of the axis 1A, but may have a curved or bent shape, for example. Furthermore, the main bodies 30 and 42 of the inner tube 3 and outer tube 4 constituting the double tube 2 are arranged so that their cross sections are concentric, but the position of the main bodies 30 and 42 is not limited to this. It can be determined as appropriate. Further, the cross sections of the inner tube 3 and the outer tube 4 are not limited to circular shapes, and may be determined as appropriate.

(4) Multiple functions of one component in the above embodiment may be realized by multiple components, and one function of one component may be realized by multiple components. . Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or one function realized by a plurality of constituent elements may be realized by one constituent element. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of other embodiments.

DESCRIPTION OF SYMBOLS 1... Exhaust pipe, 1A... Axis line, 2... Double pipe, 20... Silencing chamber, 20A... First silencing area, 20B... Second silencing area, 21... Opening, 22... Closed part, 3... Inner pipe, 30... Main body part, 4... Outer pipe, 42... Main body part, 5... Closure part, 50... Channel.

Claims (6)

An exhaust pipe installed in a vehicle,
an inner tube configured to flow the exhaust gas and extending along a linear axis ;
an outer tube disposed outside the inner tube to form a double tube, extending along the axis, and forming a muffling chamber between the inner tube and the inner tube;
an opening that opens the sound deadening chamber at a first end of the double pipe;
a closing part that closes off the sound deadening chamber at a second end of the double pipe;
At least one at least one spaced apart from the opening and the closing part, which blocks the muffling chamber to divide the muffling chamber into an upstream muffling area and a downstream muffling area in the flow direction of the exhaust gas. a blockage portion;
The closing part has at least one flow path that communicates the upstream silencing area and the downstream silencing area,
The portions of the inner tube and the outer tube located in the respective sound-deadening regions have cross sections parallel to the axis that extend parallel or substantially parallel to the axis from a first end to a second end in the direction of the axis. ,
Each sound deadening region is configured to perform sound deadening by resonance of a frequency corresponding to the length of the sound deadening region in the direction of the axis.
Exhaust pipe. An exhaust pipe installed in a vehicle,
an inner pipe configured to allow exhaust gas to flow down;
an outer tube disposed outside the inner tube to form a double tube and forming a muffling chamber between the inner tube and the inner tube;
an opening that opens the sound deadening chamber at a first end of the double pipe;
a closing part that closes off the sound deadening chamber at a second end of the double pipe;
At least one at least one spaced apart from the opening and the closing part, which blocks the muffling chamber to divide the muffling chamber into an upstream muffling area and a downstream muffling area in the flow direction of the exhaust gas. a blockage portion;
The closing part has at least one flow path that communicates the upstream silencing area and the downstream silencing area,
The outer tube has a recess that is depressed toward the inner tube,
The closing portion has the recess.
Exhaust pipe. The exhaust pipe according to claim 2 ,
A cross section parallel to the flow direction of the exhaust gas of a portion of the outer pipe where the blocking portion is not located extends along the flow direction of the exhaust gas from a first end to a second end in the flow direction of the exhaust gas. An exhaust pipe according to any one of claims 1 to 3 ,
an area of the opening is larger than an area of a cross section of the flow passage of the obstruction portion perpendicular to a flow direction of the exhaust gas. The exhaust pipe according to any one of claims 1 to 4 ,
The number of the blocking parts is one. Exhaust pipe. The exhaust pipe according to any one of claims 1 to 5 ,
The first end of the double pipe is located on the upstream side in the flow direction of the exhaust gas. Exhaust pipe.

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