Muffler

Abstract

To improve a silencing effect, in a muffler in which upstream and downstream inner pipes through which exhaust passes are inserted into an outer pipe for silencing.SOLUTION: A muffler comprises an upstream inner pipe that introduces exhaust gas, a downstream inner pipe that discharges exhaust gas, an outer pipe that forms an internal space for silencing around a downstream end part of the upstream inner pipe and an upstream end part of the downstream inner pipe, and a first opening. The first opening allows an exhaust flow path of the downstream inner pipe and the internal space to communicate with each other. The upstream end part of the downstream inner pipe is arranged in the upstream inner pipe via a gap so that it overlaps with the downstream end part of the upstream inner pipe by a predetermined length in a central axis direction in the outer pipe.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a muffler. [Background technology]

[0002] Patent document 1 describes a muffler in which a first exhaust pipe and a second exhaust pipe are inserted into a case outer tube, and the downstream end of the upstream first exhaust pipe is inserted into the upstream end of the downstream second exhaust pipe so that a predetermined gap is created.

[0003] In this muffler, the downstream end of the first exhaust pipe, which is inserted into the second exhaust pipe, is narrowed to reduce the exhaust gas flow and mitigate exhaust pulsation, and noise is further suppressed by turning the internal space of the case outer cylinder into a resonance chamber through the use of gaps. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Jpn. Jpn. Published No. 57-055927 Summary of the Invention [Problem to be solved by the invention]

[0005] In the muffler described in Patent Document 1, the first exhaust pipe on the upstream side is inserted into the second exhaust pipe on the downstream side, so the exhaust flow through the gap is in the opposite direction to the exhaust flow through the first exhaust pipe and the second exhaust pipe, which makes it difficult to obtain a silencing effect through resonance.

[0006] One aspect of the present disclosure has an object to improve the silencing effect in a muffler in which upstream and downstream inner pipes through which exhaust gas passes are inserted into a silencing outer pipe as described above. [Means for solving the problem]

[0007] A muffler according to one embodiment of the present disclosure includes an upstream inner pipe for introducing exhaust gas, a downstream inner pipe for discharging exhaust gas, an outer pipe for forming an internal space for silencing sound around the downstream end of the upstream inner pipe and the upstream end of the downstream inner pipe, and a first opening. The first opening communicates the exhaust flow path of the downstream inner pipe with the internal space. The upstream end of the downstream inner pipe is disposed within the upstream inner pipe via a gap so as to overlap with the downstream end of the upstream inner pipe by a predetermined length in the central axis direction within the outer pipe.

[0008] Therefore, according to the muffler of the present disclosure, the flow of exhaust gas passing through the gap between the upstream inner pipe and the downstream inner pipe coincides with the flow of exhaust gas flowing from the upstream inner pipe to the downstream inner pipe, thereby improving the silencing effect by resonance.

[0009] Here, the muffler of the present disclosure may include a retaining member provided between an outer wall of the upstream end of the downstream inner pipe and an inner wall of the downstream end of the upstream inner pipe, and in this case, the first opening may be formed in either the retaining member or a side surface of the upstream inner pipe.

[0010] Moreover, the muffler of the present disclosure may not have the retaining member, and the first opening may be formed in the side surface of the upstream inner pipe. In this way, by forming the first opening on the side surface of the retaining member or the upstream inner pipe, a passage for exhaust air is formed through the gap between the upstream inner pipe and the downstream inner pipe to the internal space of the outer pipe. Therefore, even in this way, the gap between the upstream inner pipe and the downstream inner pipe can function as a resonance chamber, and the silencing effect by resonance can be improved.

[0011] Next, a second opening may be formed on the side surface of the downstream inner pipe, which connects the exhaust flow passage of the downstream inner pipe to the internal space. In this way, an exhaust passage is formed that runs from the exhaust flow passage of the upstream inner pipe through the gap between the upstream inner pipe and the downstream inner pipe, and through the internal space formed by the outer pipe, to the exhaust flow passage of the downstream inner pipe, and the exhaust is expanded in this passage. Therefore, by configuring the muffler in this way, the silencing effect due to resonance and expansion can be improved.

[0012] On the other hand, a sound absorbing material and a cover member that covers the sound absorbing material may be provided around the downstream inner pipe. In this case, a second opening that connects the space around the sound absorbing material to the internal space may be formed in the cover member or between the cover member and the outer wall of the downstream inner pipe.

[0013] In this way, an exhaust passage is formed that leads from the exhaust flow path of the upstream inner pipe through the gap between the upstream inner pipe and the downstream inner pipe, the internal space formed by the outer pipe, and the space around the sound absorbing material to the exhaust flow path of the downstream inner pipe. Therefore, even with a muffler configured in this way, the silencing effect due to resonance and expansion can be improved.

[0014] Next, the upstream end of the downstream inner pipe may be flared or tapered so that the tip side expands outward, thereby preventing a part of the exhaust gas flowing from the upstream inner pipe to the downstream inner pipe from hitting the upstream end of the downstream inner pipe, thereby preventing a decrease in the silencing effect.

[0015] Also, an opening / closing valve that opens more as the exhaust flow rate increases may be provided inside the downstream inner pipe. In this way, when the exhaust flow rate is low, the proportion of exhaust gas flowing through the gap between the upstream inner pipe and the downstream inner pipe can be increased, thereby enhancing the above-mentioned silencing effect. When the exhaust flow rate is high, the opening / closing valve is opened to increase the flow rate of exhaust gas flowing through the downstream inner pipe, thereby suppressing an increase in pressure loss caused by the muffler.

[0016] The inner space may be provided with a separator that divides the inner space. In this way, the exhaust gas passes through the separator, expanding the exhaust gas and enhancing the sound deadening effect. The separator can also increase the strength of the outer tube. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a cross-sectional view illustrating a configuration of a muffler according to the first embodiment. [Diagram 2]FIG. 2 is an explanatory diagram illustrating the flow of exhaust gas in the muffler shown in FIG. [Diagram 3] FIG. 2 is an explanatory diagram showing a principle model of Hertzholtz resonance caused by the muffler shown in FIG. 1. [Figure 4] 1. FIG. 4 is an explanatory diagram illustrating a modified example of the muffler shown in FIG. [Diagram 5] FIG. 6 is a cross-sectional view illustrating a configuration of a muffler according to a second embodiment. [Figure 6] FIG. 11 is a cross-sectional view showing the configuration of a muffler according to a third embodiment. [Figure 7] FIG. 11 is a cross-sectional view showing the configuration of a muffler according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. [First embodiment] [composition] As shown in FIG. 1, the muffler 2 of this embodiment includes an upstream inner pipe 10 that introduces exhaust gas, a downstream inner pipe 20 that discharges exhaust gas, and an outer pipe 40 that forms an internal space 42 for silencing sound around the downstream end 12 of the upstream inner pipe 10 and the upstream end 22 of the downstream inner pipe 20.

[0019] The upstream inner pipe 10 and the downstream inner pipe 20 are both cylindrical in shape. The upstream inner pipe 10 and the downstream inner pipe 20 are arranged in the outer pipe 40 such that the central axes of the downstream end 12 and the upstream end 22 coincide with each other.

[0020] Also, the upstream end 22 of the downstream inner pipe 20 has a diameter smaller than that of the upstream inner pipe 10 by a predetermined length from the tip in the central axial direction so that it can be inserted into the downstream end 12 of the upstream inner pipe 10. Then, the upstream end 22 of the downstream inner pipe 20, which has a smaller diameter than the upstream inner pipe 10, is inserted into the downstream end 12 of the upstream inner pipe 10.

[0021] The upstream end 22 of the downstream inner pipe 20 has a main body 22A extending with the same diameter, and a tip end 22B on the tip side of the main body 22A that is tapered and expands linearly toward the tip. This is to prevent the exhaust gas flowing through the upstream inner pipe 10 from hitting the edge of the tip end 22B of the upstream end 22 of the downstream inner pipe 20, turbulent exhaust gas, and generating airflow noise. However, the tip end 22B of the upstream end 22 of the downstream inner pipe 20 does not necessarily need to be tapered, and the same effect can be obtained even if it has a flare shape that expands in a curved manner toward the tip (in other words, a trumpet shape).

[0022] Next, the upstream end 22 of the downstream inner pipe 20 is inserted into the downstream end 12 of the upstream inner pipe 10, so that a part of the upstream inner pipe 10 and a part of the downstream inner pipe 20 overlap in the central axial direction. In this overlapping portion 32, an annular gap 34 is provided between the upstream inner pipe 10 and the downstream inner pipe 20. A retaining member 30 is provided in part of this gap 34. As a result, in the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20, the retaining member 30 can retain the gap 34.

[0023] The holding member 30 holds the upstream inner pipe 10 and the downstream inner pipe 20 slidably in the central axial direction, and is composed of, for example, a mesh member formed in a mesh shape with metal wires. The holding member 30 is disposed on the tip side of the downstream end 12 of the upstream inner pipe 10 in an overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20. The holding member 30 is fixed by welding to either the inner circumferential surface of the upstream inner pipe 10 or the outer circumferential surface of the downstream inner pipe 20. The holding member 30 is disposed on the downstream side of a hole 14, which will be described later, in the overlapping portion 32.

[0024] A hole 14 is formed in the sidewall of the downstream end 12 of the upstream inner pipe 10 upstream of the retaining member 30. This hole 14 communicates between a gap 34 in an overlapping portion 32 of the upstream inner pipe 10 and the downstream inner pipe 20 and an internal space 42 of the outer pipe 40, and corresponds to an example of a first opening of the present disclosure.

[0025] Additionally, an overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20 is disposed upstream of the outer pipe 40, and the downstream inner pipe 20 is disposed within the outer pipe 40, extending downstream of the overlapping portion 32. A hole 24 is formed in the side wall of the downstream inner pipe 20, downstream of the outer pipe 40, to communicate the internal space 42 of the outer pipe 40 with the exhaust passage of the downstream inner pipe 20. This hole 24 corresponds to an example of a second opening of the present disclosure. [effect] As shown in FIG. 2, in the muffler 2 of this embodiment, a portion of the exhaust gas flowing from the upstream inner pipe 10 to the downstream inner pipe 20 flows into the gap 34 of the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20 in a forward direction along the flow of the exhaust gas in the upstream inner pipe 10.

[0026] Then, a portion of the exhaust gas that flows into the gap 34 flows through the hole 14 of the upstream inner pipe 10 into the internal space 42 of the outer pipe 40, and further flows from the internal space 42 of the outer pipe 40 through the hole 24 formed in the side wall of the downstream inner pipe 20 into the exhaust passage of the downstream inner pipe 20.

[0027] Therefore, according to the muffler 2 of this embodiment, the hole 14 as the first opening provided in the upstream inner pipe 10 serves as the expanded hole, and the hole 24 as the second opening provided in the downstream inner pipe 20 serves as a flow path for exhaust gas from the expanded hole, thereby increasing the expanded silencing effect. Also, the gap 34 between the upstream inner pipe 10 and the downstream inner pipe 20 can be made to function as a resonance pipe to obtain a resonance silencing effect.

[0028] Therefore, according to the muffler 2 of the present embodiment, noise can be suppressed by the expanded sound deadening effect and the resonant sound deadening effect, and a better sound deadening effect can be achieved than the muffler described in Patent Document 1. The expanded sound deadening effect and the resonant sound deadening effect can be adjusted by appropriately changing the number of holes 14 as the first openings and holes 24 as the second openings.

[0029] Furthermore, by providing a tail pipe 50 downstream of the downstream inner pipe 20 as shown by the dotted line in FIG. 2, the muffler 2 of this embodiment can be used as a rear muffler that discharges exhaust gas from the tail pipe 50 to the outside.

[0030] In this way, when the muffler 2 is used as a rear muffler, a principle model of Helmholtz resonance can be constructed that is composed of the first resonance tube, the first resonance volume, the second resonance tube, and the second resonance volume shown in FIG.

[0031] Here, the first resonance pipe is formed in the region from the rear end of the tail pipe 50 to the tip of the upstream end 22 of the downstream inner pipe 20, and the first resonance volume is formed in the upstream inner pipe 10 at the tip of the downstream inner pipe 20. The second resonance pipe is formed in the region from the tip of the upstream end 22 of the downstream inner pipe 20 to the hole 14 in the gap 34, and the second resonance volume is formed in the internal space 42 of the outer pipe 40.

[0032] Therefore, by using the muffler 2 as a rear muffler, the route from the rear end of the tailpipe 50 to the second resonance volume formed by the internal space 42 of the outer pipe 40 is made more complex, thereby suppressing the amplification of sound due to Helmholtz resonance of the tailpipe 50.

[0033] [Variations] In this embodiment, it has been described that in the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20, a hole 14 as a first opening is provided in the side wall of the upstream inner pipe 10, thereby causing the gap 34 in the overlapping portion 32 to function as a resonance pipe.

[0034] However, the hole 14 as the first opening does not necessarily have to be provided in the upstream inner pipe 10. As illustrated in FIG. 4, the same effect as in the above embodiment can be obtained by forming the first opening by cutting out a part of the retaining member 30 to form the gap 34.

[0035] Furthermore, since the upstream inner pipe 10 and the downstream inner pipe 20 are hermetically fixed to the upstream and downstream opening portions of the outer pipe 40, the gap 34 in the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20 can sometimes be formed without using a retaining member 30.

[0036] Furthermore, when a gap 34 is formed in the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20 without using the retaining member 30 in this manner, the gap 34 can function as a first opening, thereby achieving the above-mentioned sound-proofing effect due to expansion and resonance. [Second embodiment] As shown in Fig. 5, the muffler 4 of this embodiment has the same basic configuration as the muffler 2 of the first embodiment. Therefore, in this embodiment, the same components as those of the muffler 2 of the first embodiment are denoted by the same reference numerals in Fig. 5 as in Fig. 1, and detailed descriptions thereof will be omitted.

[0037] The muffler 4 of this embodiment differs from the muffler 2 of the first embodiment in that a sound absorbing material 44 and a cover member 46 covering the sound absorbing material 44 are provided around the downstream inner pipe 20, and holes 48 serving as second openings are provided in the side wall of the cover member 46. The side wall of the downstream inner pipe 20 is provided with a plurality of holes 26 that communicate with the interior of the cover member 46 in which the sound absorbing material 44 is housed.

[0038] According to the muffler 4 of the present embodiment configured as described above, not only can it obtain the same effects as the muffler 2 of the first embodiment, but also the sound-absorbing material 44 provided around the downstream inner pipe 20 can further enhance the sound-dampening effect in the high frequency range.

[0039] In this embodiment, a hole 48 serving as a second opening is provided in the side wall of the cover member 46 that covers the sound-absorbing material 44. However, if the cover member 46 is not fixed in a sealed state to the outer wall of the downstream inner pipe 20, it is not necessary to provide a hole 48 in the side wall of the cover member 46.

[0040] In other words, when the cover member 46 is not fixed in a sealed state to the outer wall of the downstream inner pipe 20, a gap 34 through which exhaust air passes exists between the cover member 46 and the outer wall of the downstream inner pipe 20, and this gap may be utilized as the second opening. [Third embodiment] As shown in Fig. 6, the muffler 6 of this embodiment has the same basic configuration as the muffler 2 of the first embodiment. Therefore, in this embodiment, the same components as those of the muffler 2 of the first embodiment are denoted by the same reference numerals in Fig. 6 as in Fig. 1, and detailed descriptions thereof will be omitted.

[0041] A muffler 6 of this embodiment differs from the muffler 2 of the first embodiment in that an opening / closing valve 60 is provided inside the downstream inner pipe 20, the opening of which increases as the exhaust flow rate increases. According to the muffler 6 of this embodiment configured in this manner, not only can the same effects as the muffler 2 of the first embodiment be obtained, but also when the exhaust flow rate is low, the opening of the opening / closing valve 60 can be reduced to enhance the silencing effect through expansion and resonance.

[0042] In other words, when the exhaust flow rate is low, the opening of the opening / closing valve 60 becomes smaller, and a larger proportion of the exhaust flows through the gap 34 between the upstream inner pipe 10 and the downstream inner pipe 20, thereby improving the soundproofing effect compared to the muffler 2 of the first embodiment.

[0043] Furthermore, when the flow rate of the exhaust gas is high, the on-off valve 60 is opened, so that the flow rate of the exhaust gas flowing through the downstream inner pipe 20 is increased, thereby making it possible to suppress an increase in pressure loss occurring in the muffler 6. [Fourth embodiment] As shown in Fig. 7, the muffler 8 of this embodiment has the same basic configuration as the muffler 2 of the first embodiment. Therefore, in this embodiment, the same components as those of the muffler 2 of the first embodiment are denoted by the same reference numerals in Fig. 7 as in Fig. 1, and detailed descriptions thereof will be omitted.

[0044] A muffler 8 of the present embodiment differs from the muffler 2 of the first embodiment in that a separator 70 that divides the internal space 42 into an upstream side and a downstream side is provided inside the outer pipe 40. The separator 70 is provided with holes (not shown) that allow exhaust gas to pass from the upstream side to the downstream side of the internal space 42.

[0045] Therefore, according to the muffler 8 of the present embodiment, the exhaust gas passes through the separator 70 in the internal space 42, so that the number of times the exhaust gas is expanded can be increased compared to the muffler 2 of the first embodiment, and the silencing effect due to the expansion can be improved. In addition, the separator 70 can also increase the strength of the outer pipe 40. [Other embodiments] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0046] For example, the configurations described in the first embodiment and its modified examples can be applied to the mufflers of the second to fourth embodiments to obtain the same effects as those described above. In addition, multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0047] Furthermore, in addition to the muffler described above, the technology of the present disclosure can be realized in various forms, such as an exhaust system that includes a muffler as a component, and a method for reducing exhaust noise. [Explanation of symbols]

[0048] 2-8...muffler, 10...upstream inner pipe, 12...downstream end portion, 14...hole (first opening), 20...downstream inner pipe, 22...upstream end portion, 24, 48...hole (second opening), 30...retaining member, 34...gap, 40...outer pipe, 42...internal space, 44...sound-absorbing material, 46...cover member, 60...opening / closing valve, 70...separator.

Claims

1. an upstream inner pipe for introducing exhaust gas; a downstream inner pipe for discharging the exhaust gas; an outer pipe that defines an internal space for silencing noise around a downstream end of the upstream inner pipe and an upstream end of the downstream inner pipe; a first opening communicating the exhaust passage of the downstream inner pipe with the internal space; Equipped with A muffler, wherein the upstream end of the downstream inner pipe is arranged within the upstream inner pipe via a gap so as to overlap with the downstream end of the upstream inner pipe by a predetermined length in the central axis direction within the outer pipe.

2. a retaining member provided between an outer wall of the upstream end of the downstream inner pipe and an inner wall of the downstream end of the upstream inner pipe, The muffler according to claim 1 , wherein the first opening is formed in at least one of the retaining member and a side surface of the upstream inner pipe.

3. The muffler according to claim 1 , wherein the first opening is formed in a side surface of the upstream inner pipe.

4. The muffler according to any one of claims 1 to 3, wherein a second opening is formed on a side surface of the downstream inner pipe, the second opening communicating the exhaust flow path of the downstream inner pipe with the internal space.

5. a sound absorbing material and a cover member that covers the sound absorbing material are provided around the downstream inner pipe, A muffler as described in any one of claims 1 to 3, wherein a second opening is formed in the cover member or between the cover member and an outer wall of the downstream inner pipe, the second opening communicating between a space around the sound-absorbing material and the internal space.

6. The muffler according to any one of claims 1 to 3, wherein the upstream end of the downstream inner pipe has a tip side that is flared or tapered and expands outward.

7. The muffler according to any one of claims 1 to 3, further comprising an opening / closing valve disposed inside the downstream inner pipe, the opening of which increases as the flow rate of the exhaust gas increases.

8. The muffler according to any one of claims 1 to 3, wherein a separator is provided in the internal space to divide the internal space in the central axis direction.

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