Vehicle exhaust pipe structure

Abstract

To provide an exhaust pipe structure of a vehicle which is reduced in an amplification of an air column resonance of an exhaust pipe which is bifurcated or more, and improved in silence performance.SOLUTION: Exhaust pipe structures 10, 20 of a vehicle comprise: mufflers 14, 15 which are arranged at branch pipes 12, 13 branched from one piece of an exhaust pipe 11, and have different capacities; a first branch pipe 12 having a first upstream-side pipe 12a and a first downstream-side pipe 12b; and a second branch pipes 13 having a second upstream-side pipe 13a and a second downstream-side pipe 13b. A second angle θ2 formed of the second upstream-side pipe and the second downstream-side pipe is set smaller than a first angle θ1 formed of the first upstream-side pipe and the first downstream-side pipe.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vehicle exhaust pipe structure with improved sound deadening performance. [Background technology]

[0002] According to vehicle noise regulations, it is desirable for the noise emitted from the exhaust pipe to be small in order to meet legal standards for external noise. For example, in an exhaust pipe structure with two or more tailpipes on one side, it is desirable for the exhaust flow rate of each pipe to be equal in order to achieve a higher noise reduction effect.

[0003] For example, Patent Document 1 discloses a sub-muffler structure for an internal combustion engine in which a bifurcated exhaust pipe is connected by an outer cylinder. In a conventional sub-muffler structure, the downstream end of the exhaust pipe introduced into the axial center of the outer cylinder of the sub-muffler is bifurcated into two outwardly in the left-right direction of the vehicle body by a conduit inside the outer cylinder, and a large number of small holes in the peripheral wall of the conduit connect the inside of the conduit to the space between the outer cylinder and the conduit, using this space to muffle exhaust pipe resonance and high-frequency exhaust noise. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-8250 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if exhaust gas flows equally into the two bifurcated exhaust pipes, the air column resonance of the two exhaust pipes will be amplified in a certain frequency range, resulting in an increase in exhaust sound pressure.

[0006] In view of the above circumstances, the present invention aims to provide an exhaust pipe structure for a vehicle that reduces the amplification of air column resonance in an exhaust pipe that branches into two or more parts, thereby improving noise reduction performance. [Means for solving the problem]

[0007] The vehicle exhaust pipe structure of one aspect of the present invention includes a branch pipe that branches off from a single exhaust pipe and branches off into at least two or more branches, the branch pipe has a first branch pipe and a second branch pipe branched off from the exhaust pipe, the first branch pipe has a first upstream pipe on the upstream side and a first downstream pipe communicating with the downstream side of the first upstream pipe, the second branch pipe has a second upstream pipe on the upstream side and a second downstream pipe communicating with the downstream side of the second upstream pipe, and a first muffler and a second muffler having different volumes are provided downstream of the first downstream pipe and the second downstream pipe, respectively; a second angle formed between the second upstream pipe and the second downstream pipe is set smaller than a first angle formed between the first upstream pipe and the first downstream pipe; The second volume of the second muffler is set to be larger than the first volume of the first muffler, and the number of first punched holes drilled in the first downstream pipe in the first muffler is larger than the number of second punched holes drilled in the second downstream pipe in the second muffler. . [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vehicle exhaust pipe structure that reduces the amplification of air column resonance in an exhaust pipe that branches into two or more parts and improves sound deadening performance. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing an exhaust pipe of a vehicle according to an embodiment of the present invention; [Figure 2] FIG. 1 is a perspective view showing a tail exhaust unit, which is an exhaust pipe structure of a vehicle according to the first embodiment. [Figure 3] FIG. 10 is a partial cross-sectional view showing the configuration of the tail exhaust unit of the first embodiment. [Figure 4] FIG. 10 is a partial cross-sectional view showing the configuration of a tail exhaust unit according to a first modified example. [Figure 5] FIG. 10 is a perspective view showing a tail exhaust unit according to a second modified example; [Figure 6] FIG. 10 is a partial cross-sectional view showing the configuration of a tail exhaust unit according to a second modified example. [Figure 7] Graph showing an example of the change in frequency and damping sound pressure of air column resonance between a conventional structure and the structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of one aspect of the present invention will be described in detail below with reference to the drawings. Note that in the drawings used in the following description, each component is shown at a different scale so that it can be recognized on the drawing, and the present invention is not limited to the number of components, the shape of the components, the size ratio of the components, and the relative positional relationship of the components shown in these drawings.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] The vehicle exhaust pipe 1 shown in Figure 1 has an exhaust manifold 2 connected to the internal combustion engine, which is the power unit, a catalytic converter 3 that purifies harmful exhaust components using a catalyst, and two tail exhaust units 10 and 20, and multiple, in this case four, exhaust pipes 4, 5, 6 and 7 are connected by exhaust pipe connecting members 8 such as ball joints.

[0013] The catalytic converter 3 is provided midway through the exhaust pipe 5. The rear exhaust pipe 7 connected to the two tail exhaust units 10, 20 is a collapsed Y-shaped exhaust pipe.

[0014] The vehicle's exhaust pipe 1 is provided on the underside of the vehicle body on which the internal combustion engine is mounted, and exhaust gas from the exhaust manifold 2 passes through four exhaust pipes 4, 5, 6, and 7 from the front of the vehicle body to the rear of the vehicle body, and is discharged to the outside from two tail exhaust units 10 and 20.

[0015] As the exhaust gas passes through the exhaust pipe 5, the catalytic converter 3 removes air pollutants such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx).

[0016] Here, the two tail exhaust units 10, 20 that are the exhaust pipe structure of the vehicle of this embodiment will be described in detail below. Note that the two tail exhaust units 10, 20 have the same configuration and are symmetrical on the left and right, so only the tail exhaust unit 10 located on the right side as viewed from the front of the vehicle will be described as an example.

[0017] The tail exhaust unit 10 (20) is made of metal such as stainless steel, and as shown in Figure 2, has an outside tail pipe 12, which is one branch pipe located on the outside in the vehicle width direction, and an inside tail pipe 13, which is the other branch pipe located on the inside in the vehicle width direction, branched from a main tail pipe 11, which is an exhaust pipe connected to the exhaust pipe 7. The outside tail pipe 12 and the inside tail pipe 13 have the same pipe diameter and are set to be the same pipe length.

[0018] An outside muffler 14, which is an outside chamber (also called a silencer or muffler), is provided midway through the outside tail pipe 12, and an inside muffler 15, which is an inside chamber (also called a silencer or muffler), is provided midway through the inside tail pipe 13. Muffler cutters 16 and 17 are provided at the pipe ends of the outside tail pipe 12 and the inside tail pipe 13, respectively.

[0019] The outside tail pipe 12 has an outside tail upstream pipe 12 a and an outside tail downstream pipe 12 b branching off from the main tail pipe 11 .

[0020] The inside tail pipe 13 has an inside tail upstream pipe 13a and an inside tail downstream pipe 13b that branch off from the main tail pipe 11. The inside tail upstream pipe 13a is connected to the outside tail upstream pipe 12a on the main tail pipe 11 side.

[0021] The outside tail upstream pipe 12a extends in the vehicle width outward direction with its longitudinal hole axis P1 at a predetermined angle relative to the hole axis O, which is the longitudinal axis of the main tail pipe 11. The outside tail downstream pipe 12b extends with its hole axis X1 forming a first angle θ1 with respect to the hole axis P1 of the outside tail upstream pipe 12a. The hole axis O of the main tail pipe 11 and the longitudinal hole axis X1 of the outside tail downstream pipe 12b are approximately parallel to each other.

[0022] On the other hand, the inside tail upstream pipe 13a has a longitudinal hole axis P2 that forms a predetermined angle with respect to the hole axis O of the main tail pipe 11, and extends in the vehicle width direction opposite to the outside tail upstream pipe 12a. The inside tail upstream pipe 13a is connected to the outside tail upstream pipe 12a in the vicinity of the main tail pipe 11.

[0023] Therefore, the exhaust gas from the main tail pipe 11 flows more toward the outside tail upstream pipe 12a and is discharged at a smaller flow rate toward the inside tail upstream pipe 13a.

[0024] The inside tail downstream pipe 13b extends such that its hole axis X2 forms a second angle θ2 (θ2<θ1) with respect to the hole axis P2 of the inside tail upstream pipe 13a that is smaller than the first angle θ1. That is, the first angle θ1 is larger than the second angle θ2 (θ1>θ2).

[0025] The hole axis O of the main tail pipe 11 and the hole axis X2 of the inside tail downstream pipe 13b are also substantially parallel to each other. That is, the hole axes X1, X2 of the outside tail downstream pipe 12b and the inside tail downstream pipe 13b extend substantially parallel to each other.

[0026] The outside tail downpipe 12b is a punching pipe having a plurality of holes 23 formed in the middle portion, and the housing 21 of the outside muffler 14 is connected so as to cover these plurality of holes 23. Also, the inside tail downpipe 13b is also a punching pipe having a plurality of holes 33 formed in the middle portion, and the housing 31 of the inside muffler 15 is connected so as to cover these plurality of holes 33.

[0027] The outside muffler 14 and the inside muffler 15 have a structure for reducing the so-called resonance exhaust sound. Note that the outside muffler 14 and the inside muffler 15 can also be applied to various muffler structures such as a so-called absorption type structure in which a sound absorbing material such as glass wool or steel wool is filled in the housings 21 and 31, a so-called expansion type structure in which pipes are connected to both ends of the housings 21 and 31, and a so-called partition type structure in which a plurality of partitions are provided in the housings 21 and 31.

[0028] The housing 21 of the outside muffler 14 of the present embodiment is a substantially cylindrical body having an inner diameter D1 with both end faces that close the front and rear circumferences of the outside tail downpipe 12b. Also, the housing 31 of the inside muffler 15 is also a substantially cylindrical body having an inner diameter D2 larger than the inner diameter D1 with both end faces that close the front and rear circumferences of the inside tail downpipe 13b. Also, the lengths of the housings 21 and 31 in the front and rear directions are set to be the same.

[0029] In the tail exhaust unit 10(20) of the present embodiment, the capacity (volume) A1 of the internal space formed by the housing 21 of the outside muffler 14 is set to be smaller (A1 < A2) than the capacity (volume) A2 of the internal space formed by the housing 31 of the inside muffler 15. That is, the outside muffler 14 is set to have a smaller capacity than the inside muffler 15, and the inside has different volumes. In other words, the inside muffler 15 is set to have a larger internal space and a larger capacity than the outside muffler 14.

[0030] The outside muffler 14 and the inside muffler 15 may have different capacities, and the front-rear lengths of the housings 21, 31 may not be the same.

[0031] The tail exhaust unit 10 (20) configured as described above has two outside tail pipes 12 and two inside tail pipes 13, each of which is provided with two outside mufflers 14 and two inside mufflers 15 with different capacities (volumes) A1 and A2, which are designed to muffle sounds of specific frequencies generated by resonance in each pipe.

[0032] That is, the tail exhaust unit 10 (20) is configured such that the capacities (volumes) A1, A2 of the outside muffler 14 and the inside muffler 15 are unequal, with the capacity (volume) A2 of the inside muffler 15 provided on the inside tail pipe 13 side, which has a lower flow rate, being larger than the capacity (volume) A1 of the outside muffler 14 provided on the outside tail pipe 12 side. This causes a phase shift in the resonance caused by the outside tail pipe 12 and the inside tail pipe 13, which branch off from the main tail pipe 11, reducing the amplification of air column resonance.

[0033] In other words, in a conventional tail exhaust unit, the outside tail pipe and inside tail pipe that branch into two are approximately the same length, and if the capacity (volume) of the outside muffler and the capacity (volume) of the inside muffler are the same, the antinode and node of the wavelength of the air column resonance in a specific frequency band will match, amplifying the sound pressure.

[0034] Therefore, the tail exhaust unit 10 (20) of this embodiment is structured to prevent amplification of sound pressure by making the capacity (volume) A1 of the outside muffler 14 different from the capacity (volume) A2 of the inside muffler 15 so that the antinodes and nodes of the wavelength of the air column resonance in a specific frequency band do not coincide.

[0035] Therefore, the tail exhaust unit 10(20) can reduce the sound pressure in a specific frequency band generated by the resonance of the outside tail pipe 12 and the inside tail pipe 13, and can reduce the outside vehicle noise. From the above description, the tail exhaust unit 10(20) has an exhaust pipe structure of a vehicle that reduces the amplification of the air column resonance of the two bifurcated exhaust pipes and improves the sound insulation performance. (First modification example)

[0036] As shown in FIG. 4, in the tail exhaust unit 10(20) of this modification example, the number of the plurality of holes 23 formed in the outside tail downstream pipe 12b of the punching pipe in the outside muffler 14 may be made larger than the number of the plurality of holes 33 formed in the inside tail downstream pipe 13b of the punching pipe in the inside muffler 15.

[0037] Even with such a configuration, the tail exhaust unit 10(20) can reduce the sound pressure of a specific frequency as described above, and can reduce the outside vehicle noise. (Second modification example)

[0038] As shown in FIG. 5, it may be a single muffler 18 in which the outside muffler and the inside muffler are integrated. As shown in FIG. 6, in this muffler 18, partition walls 25, 35 are provided inside the muffler housing 19, and the internal spaces on the outside tail pipe 12 side and the inside tail pipe 13 side are separated. That is, the muffler 18 has a structure including an outside muffler and an inside muffler.

[0039] Even in such a configuration of the muffler 18, it is set such that the capacity (volume) A1 of the internal space on the outside tail pipe 12 side is smaller than the capacity (volume) A2 of the internal space on the inside tail pipe 13 side (A1 < A2).

[0040] Even with such a configuration, the tail exhaust unit 10(20) can reduce the sound pressure of a specific frequency as described above, and can reduce the outside vehicle noise.

[0041] In addition to the configuration of this modified example, a configuration in which the number of multiple holes 23 formed in the outside tail downstream pipe 12b of the first modified example is greater than the number of multiple holes 33 formed in the inside tail downstream pipe 13b of the punched pipe in the inside muffler 15 may be combined.

[0042] FIG. 7 shows the attenuation of sound pressure at each frequency by the structures of the tail exhaust unit 10 (20) of the above-described embodiment and the first and second modified examples, compared to the conventional structure.

[0043] As shown in Figure 7, in the conventional structure indicated by the dashed line F0, at frequencies in the commonly used range, for example, 450 Hz to 550 Hz, the nodes and antinodes of the wavelength of the air column resonance coincide and are amplified, resulting in a decrease in the attenuation (dB) by the outside muffler 14 and the inside muffler 15.

[0044] In contrast, the tail exhaust unit 10 (20) having the structure of the above-mentioned embodiment shown by the dotted line F1, the structure of the first modified example shown by the two-dotted line F2, and the structure of the second modified example shown by the three-dotted line F3 has a mismatch between the nodes and antinodes of the wavelength of the air column resonance even at frequencies in the normal operating range, for example, 450 Hz to 550 Hz, so that amplification does not occur, and it is possible to prevent a decrease in the attenuation (dB) by the outside muffler 14 and the inside muffler 15. In other words, since the attenuation sound pressure (dB) is the amount of sound attenuation (quantity of silencing), the larger the value, the better the silencing effect. Therefore, as the attenuation sound pressure (dB) increases, the quantity of silencing increases, and the sound becomes quieter. This makes it possible to reduce sound pressure and reduce noise outside the vehicle. From the above explanation, the tail exhaust unit 10 (20) reduces the amplification of air column resonance in the two bifurcated tail exhaust units 10 (20), resulting in a vehicle exhaust pipe structure with improved silencing performance.

[0045] In order to reduce the amplification of the air column resonance of the outside tail pipe 12 and the inside tail pipe 13, the capacity (volume) A1 of the outside muffler 14 and the capacity (volume) A2 of the inside muffler 15 need not be approximately the same, so the capacity (volume) A1 of the outside muffler 14 may be configured to be larger than the capacity (volume) A2 of the inside muffler 15.

[0046] Furthermore, although the vehicle exhaust pipe 1 is illustrated as having two tail exhaust units 10, 20, this is not limited to this, and the vehicle may be configured to have one tail exhaust unit 10 (20) on only one side, either the left or right.

[0047] Furthermore, the tail exhaust units 10, 20 are not limited to a configuration in which the tail pipe branches into two, but may be a configuration in which the capacity (volume) of each muffler is set to be different. Note that this technology is not limited to the tail exhaust units 10, 20, but can also be applied to a configuration in which the exhaust pipe branches midway and a muffler is provided.

[0048] The invention described in the above embodiments is not limited to those embodiments, and various modifications can be made in the implementation stage without departing from the gist of the invention. Furthermore, each of the above embodiments includes inventions at various stages, and various inventions can be extracted by appropriate combinations of the disclosed multiple constituent elements.

[0049] For example, if some constituent elements are deleted from all the constituent elements shown in each form, and the stated problem can still be solved and the stated effect can still be obtained, then the configuration from which these constituent elements have been deleted can be extracted as an invention. [Explanation of symbols]

[0050] 1...Vehicle exhaust pipe 2...Exhaust manifold 3...Catalytic converter 4,5,6,7...Exhaust pipe 8...Exhaust pipe connecting member 10,20...Tail exhaust unit 11...Main tailpipe 12...Outside tailpipe 12a…Outside tail upstream pipe 12b...Outside tail downstream pipe 13...Inside tailpipe 13a…Inside tail upstream pipe 13b…Inside tail downstream pipe 14...Outside muffler 15...Inside muffler 16,17...Muffler cutter 18...Muffler 19...Muffler housing 21,31…Housing 23,33…hole 25,35…Bulkhead A1,A2…Capacity (volume) D1,D2…inner diameter O,P1,P2,X1,X2…hole axis

Claims

1. In an exhaust pipe structure for a vehicle, a branch pipe is provided which branches off from a single exhaust pipe and branches off into at least two or more branches, the branch pipe has a first branch pipe and a second branch pipe branched from the exhaust pipe, the first branch pipe has a first upstream pipe on the upstream side and a first downstream pipe communicating with the downstream side of the first upstream pipe, the second branch pipe has a second upstream pipe on the upstream side and a second downstream pipe communicating with the downstream side of the second upstream pipe, a first muffler and a second muffler having different volumes are provided downstream of the first downstream pipe and the second downstream pipe, respectively; a second angle formed between the second upstream pipe and the second downstream pipe is set smaller than a first angle formed between the first upstream pipe and the first downstream pipe; a second volume of the second muffler is set larger than a first volume of the first muffler, An exhaust pipe structure for a vehicle, characterized in that the number of first punched holes drilled in the first downstream pipe in the first muffler is greater than the number of second punched holes drilled in the second downstream pipe in the second muffler.

2. An exhaust pipe structure for a vehicle as described in Claim 1, characterized in that the second upstream pipe is connected at a predetermined angle to the first upstream pipe in the vicinity of the exhaust pipe.

3. 3. The exhaust pipe structure for a vehicle according to claim 1, wherein the first muffler and the second muffler are separated from each other by a partition wall, forming a single, integrated muffler.

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