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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 Art

[0002] Patent Document 1 describes a muffler in which a first exhaust duct and a second exhaust duct are inserted into an outer case cylinder, and the downstream end of the first exhaust duct on the upstream side is inserted into the upstream end of the second exhaust duct on the downstream side so that a predetermined gap is formed.

[0003] In this muffler, by reducing the diameter of the downstream end of the first exhaust duct inserted into the second exhaust duct, the exhaust gas flow is reduced to alleviate the pulsation of the exhaust, and further, by resonating the internal space of the outer case cylinder with the gap, noise is suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the muffler described in Patent Document 1 above, since the first exhaust duct on the upstream side is inserted into the second exhaust duct on the downstream side, the flow of the exhaust passing through the gap is in the opposite direction to the direction of the exhaust flowing through the first exhaust duct and the second exhaust duct. For this reason, there is a problem that it is difficult to obtain a noise reduction effect by resonance.

[0006] One aspect of the present disclosure aims to enhance the noise reduction effect in a muffler in which inner pipes on the upstream side and the downstream side through which exhaust passes are inserted into an outer pipe for noise reduction.

Means for Solving the Problems

[0007] A muffler according to one aspect of the present disclosure comprises an upstream inner pipe for introducing exhaust gas, a downstream inner pipe for discharging exhaust gas, an outer pipe that forms a sound-dampening internal space 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 connects the exhaust gas flow path of the downstream inner pipe to the internal space. The upstream end of the downstream inner pipe is positioned within the upstream inner pipe with a gap between them, such that it overlaps with the downstream end of the upstream inner pipe by a predetermined length in the direction of the central axis within the outer pipe.

[0008] Therefore, according to the muffler of this disclosure, the exhaust flow passing through the gap between the upstream inner tube and the downstream inner tube coincides with the exhaust flow from the upstream inner tube to the downstream inner tube. As a result, the sound-dampening effect due to resonance can be enhanced.

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

[0010] Furthermore, the muffler of this disclosure may lack the above-mentioned retaining member and may have a first opening formed on the side surface of the upstream inner tube. In this way, by forming a first opening on the side surface of the retaining member or the upstream inner tube, the first opening creates an exhaust passage that passes through the gap between the upstream inner tube and the downstream inner tube to the internal space of the outer tube. Therefore, even in this manner, the gap between the upstream inner tube and the downstream inner tube can function as a resonance chamber, thereby enhancing the sound-dampening effect due to resonance.

[0011] Next, a second opening may be formed on the side of the downstream inner pipe, connecting the exhaust passage of the downstream inner pipe with the internal space. In this way, an exhaust passage is formed from the exhaust passage of the upstream inner pipe, through the gap between the upstream and downstream inner pipes, and the internal space formed by the outer pipe, to the exhaust passage of the downstream inner pipe, and the exhaust is expanded in this passage. Therefore, by configuring the muffler in this way, the sound-dampening effect due to resonance and expansion can be enhanced.

[0012] On the other hand, 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 with 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 from the exhaust flow path of the upstream inner pipe, through the gap between the upstream and downstream inner pipes, 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 if the muffler is configured in this way, the sound-dampening effect due to resonance and expansion can be enhanced.

[0014] Furthermore, the upstream end of the downstream inner pipe may have a flared or tapered shape that widens outward at the tip. This prevents some 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, thus suppressing a decrease in the sound-dampening effect.

[0015] Furthermore, an on / off valve may be provided inside the downstream inner pipe, the opening degree of which increases as the exhaust flow rate increases. In this way, when the exhaust flow rate is low, the proportion of exhaust flowing through the gap between the upstream and downstream inner pipes can be increased, thereby enhancing the noise reduction effect mentioned above. Also, when the exhaust flow rate is high, opening the on / off valve increases the flow rate of exhaust flowing through the downstream inner pipe, thereby suppressing the increase in pressure loss generated in the muffler.

[0016] Furthermore, the internal space may be divided by a separator. In this way, the exhaust gas passes through the separator, expanding the exhaust and enhancing the sound-dampening effect. The separator can also be used to increase the strength of the outer pipe. [Brief explanation of the drawing]

[0017] [Figure 1] This is a cross-sectional view showing the configuration of the muffler according to the first embodiment. [Figure 2]It is an explanatory diagram for explaining the exhaust flow inside the muffler shown in FIG. 1. [Figure 3] It is an explanatory diagram showing a principle model of Helmholtz resonance by the muffler shown in FIG. 1. [Figure 4] It is an explanatory diagram showing a modified example of the muffler shown in FIG. 1. [Figure 5] It is a cross-sectional view showing the configuration of the muffler of the second embodiment. [Figure 6] It is a cross-sectional view showing the configuration of the muffler of the third embodiment. [Figure 7] It is a cross-sectional view showing the configuration of the muffler of the fourth embodiment. [Embodiments for Carrying Out the Invention]

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [First Embodiment] [Configuration] As shown in FIG. 1, the muffler 2 of the present embodiment includes an upstream inner pipe 10 for introducing exhaust, a downstream inner pipe 20 for discharging exhaust, and an outer pipe 40 that forms a sound-absorbing internal space 42 around the downstream end portion 12 of the upstream inner pipe 10 and the upstream end portion 22 of the downstream inner pipe 20.

[0019] Both the upstream inner pipe 10 and the downstream inner pipe 20 are cylindrical. The upstream inner pipe 10 and the downstream inner pipe 20 are arranged such that the central axes of the downstream end portion 12 and the upstream end portion 22 coincide within the outer pipe 40.

[0020] In addition, the upstream end portion 22 of the downstream inner pipe 20 has a diameter smaller than that of the upstream inner pipe 10 by a predetermined length in the central axis direction from the tip so as to be insertable into the downstream end portion 12 of the upstream inner pipe 10. And in the downstream inner pipe 20, the upstream end portion 22 having a diameter smaller than that of the upstream inner pipe 10 is inserted into the downstream end portion 12 of the upstream inner pipe 10.

[0021] The upstream end 22 of the downstream inner pipe 20 has a main body 22A that extends with the same diameter, and a tapered tip 22B at the tip end of the main body 22A that widens linearly toward the tip. This is to suppress the generation of airflow noise caused by exhaust gases flowing through the upstream inner pipe 10 hitting the edge of the tip 22B of the upstream end 22 of the downstream inner pipe 20, which turbulences the exhaust gases. However, the tip 22B of the upstream end 22 of the downstream inner pipe 20 does not necessarily have to be tapered; the same effect can be obtained by making it a flared shape (in other words, a trumpet shape) that widens in a curve toward the tip.

[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 portion of the upstream inner pipe 10 and a portion of the downstream inner pipe 20 overlap in the direction of the central axis. 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 a portion of this gap 34. As a result, the retaining member 30 can hold the gap 34 in the overlapping portion 32 of the upstream inner pipe 10 and the downstream inner pipe 20.

[0023] The retaining member 30 holds the upstream inner pipe 10 and the downstream inner pipe 20 so that they can slide in the direction of the central axis, and is made of a mesh member formed in a mesh shape using metal wire, for example. The retaining member 30 is positioned at the tip of the downstream end 12 of the upstream inner pipe 10 in the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20. The retaining 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 retaining member 30 is provided downstream of the hole 14, which will be described later, in the overlapping portion 32.

[0024] Furthermore, at the downstream end 12 of the upstream inner pipe 10, a hole 14 is drilled in the side wall upstream of the retaining member 30. This hole 14 connects the gap 34 between the overlapping portion 32 of the upstream inner pipe 10 and the downstream inner pipe 20 with the internal space 42 of the outer pipe 40, and corresponds to an example of the first opening of this disclosure.

[0025] Furthermore, the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20 is located on the upstream side of the outer pipe 40, and the downstream inner pipe 20 is located within the outer pipe 40, extending downstream from the overlapping portion 32. A hole 24 is drilled in the side wall of the downstream inner pipe 20, on the downstream side of the outer pipe 40, to connect 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 the second opening in this disclosure. [effect] As shown in Figure 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 between the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20 in the forward direction along with the exhaust gas flow in the upstream inner pipe 10.

[0026] Then, a portion of the exhaust gas that flows into the gap 34 flows into the internal space 42 of the outer pipe 40 through the hole 14 of the upstream inner pipe 10, 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, which serves as the first opening in the upstream inner pipe 10, becomes an expansion hole, and the hole 24, which serves as the second opening in the downstream inner pipe 20, becomes a passage for exhaust gas from the expansion hole, thereby increasing the expansion sound-dampening effect. Furthermore, the gap 34 between the upstream inner pipe 10 and the downstream inner pipe 20 can be made to function as a resonant pipe, thereby obtaining a resonant sound-dampening effect.

[0028] Therefore, according to the muffler 2 of this embodiment, noise can be suppressed by this expanded sound-dampening effect and resonance sound-dampening effect, and a better sound-dampening effect can be achieved compared to the muffler described in Patent Document 1. The expanded sound-dampening effect and resonance sound-dampening effect can be adjusted by appropriately changing the number of holes 14 as the first opening and holes 24 as the second opening.

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

[0030] Thus, when muffler 2 is used as a rear muffler, a Helmholtz resonance principle model can be constructed consisting of the first resonant tube, first resonant volume, second resonant tube, and second resonant volume shown in Figure 3.

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

[0032] Therefore, by using muffler 2 as a rear muffler, the route from the rear end of the tailpipe 50 to the second resonant volume formed in 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] [Differentiation] In this embodiment, in the overlapping portion 32 between the upstream inner pipe 10 and the downstream inner pipe 20, a hole 14 is provided as a first opening in the side wall of the upstream inner pipe 10, thereby allowing the gap 34 in the overlapping portion 32 to function as a resonant tube.

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

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

[0036] Furthermore, if 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 holding member 30, the gap 34 can function as a first opening, thereby achieving the aforementioned sound-dampening effect through expansion and resonance. [Second Embodiment] As shown in Figure 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 reference numerals as in Figure 1 are used in Figure 5 for components that are the same as those in the muffler 2 of the first embodiment, and detailed explanations are omitted.

[0037] In the muffler 4 of this embodiment, the difference from the muffler 2 of the first embodiment is 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 a hole 48 serving as a second opening is provided in the side wall of the cover member 46. Furthermore, the side wall of the downstream inner pipe 20 is provided with a plurality of holes 26 that communicate with the inside of the cover member 46 in which the sound-absorbing material 44 is housed.

[0038] With the muffler 4 of this embodiment configured in this way, not only can the same effects as the muffler 2 of the first embodiment be obtained, but 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, it has been described that a hole 48 is provided as a second opening 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 to the outer wall of the downstream inner pipe 20 in a sealed state, it is not necessary to provide a hole 48 in the side wall of the cover member 46.

[0040] In other words, if the cover member 46 is not fixed to the outer wall of the downstream inner pipe 20 in a sealed state, there is a gap 34 through which exhaust gas can pass between the cover member 46 and the outer wall of the downstream inner pipe 20, and this gap may be used as a second opening. [Third Embodiment] As shown in Figure 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 reference numerals as in Figure 1 are used in Figure 6 for components that are the same as those in the muffler 2 of the first embodiment, and detailed explanations are omitted.

[0041] The muffler 6 of this embodiment differs from the muffler 2 of the first embodiment in that an on / off valve 60 is provided inside the downstream inner pipe 20, the on / off valve whose opening degree increases as the exhaust flow rate increases. With the muffler 6 of this embodiment configured in this way, not only can the same effects as the muffler 2 of the first embodiment be obtained, but when the exhaust flow rate is low, the opening degree of the on / off valve 60 can be reduced to enhance the sound-dampening effect through expansion and resonance.

[0042] In other words, when the exhaust flow rate is low, the opening of the on / off valve 60 becomes smaller, which increases the proportion of exhaust flowing through the gap 34 between the upstream inner pipe 10 and the downstream inner pipe 20. As a result, the noise reduction effect can be improved compared to the muffler 2 of the first embodiment.

[0043] Furthermore, when the exhaust flow rate is high, the on / off valve 60 is opened, which increases the flow rate of exhaust gases through the downstream inner pipe 20 and suppresses the increase in pressure loss occurring in the muffler 6. [Fourth Embodiment] As shown in Figure 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 reference numerals as in Figure 1 are used in Figure 7 for components that are the same as those in the muffler 2 of the first embodiment, and detailed explanations are omitted.

[0044] The muffler 8 of this embodiment differs from the muffler 2 of the first embodiment in that a separator 70 is provided inside the outer pipe 40, which divides the internal space 42 into an upstream side and a downstream side. This 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, with the muffler 8 of this embodiment, the exhaust passes through the separator 70 within the internal space 42, which increases the number of exhaust expansion cycles compared to the muffler 2 of the first embodiment and enhances the sound-dampening effect due to the expansion. In addition, the separator 70 can also increase the strength of the outer pipe 40. [Other embodiments] Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented in various modified forms.

[0046] For example, the configuration described in the first embodiment and its modified form can be applied to the mufflers of the second to fourth embodiments to obtain the same effects as described above. Furthermore, multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. In addition, some parts of the configuration of the above embodiment may be omitted. In addition, at least some parts of the configuration of the above embodiment may be added to or replaced with the configuration of other above embodiments.

[0047] Furthermore, the technology disclosed herein can be implemented in various forms, including not only the muffler described above, but also exhaust systems that incorporate a muffler as a component, and methods for reducing exhaust noise. [Explanation of symbols]

[0048] 2-8... Muffler, 10... Upstream inner pipe, 12... Downstream end, 14... Hole (first opening), 20... Downstream inner pipe, 22... Upstream end, 24, 48... Hole (second opening), 30... Retaining member, 34... Gap, 40... Outer pipe, 42... Internal space, 44... Sound absorbing material, 46... Cover member, 60... On / off valve, 70... Separator.

Claims

1. The upstream inner pipe into which the exhaust gas is introduced, The downstream inner pipe for discharging the exhaust gas, An outer pipe that forms a sound-absorbing internal space around the downstream end of the upstream inner pipe and the upstream end of the downstream inner pipe, A first opening that connects the exhaust flow path of the upstream inner pipe with the internal space, Equipped with, The upstream end of the downstream inner pipe is positioned within the upstream inner pipe with a gap between them such that it overlaps with the downstream end of the upstream inner pipe by a predetermined length in the central axis direction within the outer pipe. The downstream inner pipe is surrounded by a sound-absorbing material and a cover member that covers the sound-absorbing material. A muffler wherein a second opening is formed in the cover member, or between the cover member and the outer wall of the downstream inner tube, which connects the space around the sound-absorbing material with the internal space, and the side wall of the downstream inner tube is provided with a plurality of holes that communicate with the inside of the cover member in which the sound-absorbing material is housed.

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

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

4. The muffler according to any one of claims 1 to 3, wherein the upstream end of the downstream inner pipe has a flared or tapered shape that widens outward at the tip.

5. The muffler according to any one of claims 1 to 3, wherein an on / off valve is provided inside the downstream inner pipe, the on / off valve whose opening degree increases as the exhaust flow rate increases.

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

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