Muffler

Abstract

To provide a muffler that can produce a silencing effect at the time of low rotation of an internal combustion engine, and can suppress increase in pressure loss of exhaust gas at the time of high rotation of the internal combustion engine.SOLUTION: A muffler includes an outer shell member, a first exhaust pipe, a second exhaust pipe, and an inflow part. The first exhaust pipe has a first insertion end part inserted into the outer shell member. The second exhaust pipe has a second insertion end part inserted into the outer shell member and is positioned downstream of the first exhaust pipe. The inflow part allows an exhaust gas flowing in the first exhaust pipe to flow into an internal space of the outer shell member. The first insertion end part and the second insertion end part are configured so as to be connected at least at the time of high rotation of an internal combustion engine. The inflow part is configured to open at the time of low rotation of the internal combustion engine, and to close at least at the time of high rotation of the internal combustion engine by thermal elongation in an axial direction of the first exhaust pipe.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a silencer including an outer cylinder, a front end plate and a rear end plate that close openings at both ends of the outer cylinder, a front exhaust pipe having one end inserted into and fixed to the front end plate, and a rear exhaust pipe having one end inserted into and fixed to the rear end plate. In this silencer, exhaust gas emitted from an internal combustion engine flows from the front exhaust pipe through an internal space formed by the outer cylinder to the rear exhaust pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-135440 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, mufflers used in vehicle exhaust systems are generally required to muffle low-frequency exhaust noise when the engine is running at low speed, and to muffle high-frequency exhaust noise and reduce exhaust gas pressure loss when the amount of exhaust gas increases at high engine speeds, etc. Known methods for silencing low-frequency exhaust noise include expanding the exhaust gas, and known methods for silencing high-frequency exhaust noise include absorbing it with sound-absorbing material.

[0005] The silencer of Patent Document 1 described above is configured to expand exhaust gas even when the engine is running at high speed. However, this configuration does not adequately muffle high-frequency exhaust noise, and the exhaust gas flows from the front exhaust pipe through the internal space of the outer cylinder to the rear exhaust pipe, causing the exhaust gas to expand and then compress in the internal space, which is a problem in that it is prone to increasing pressure loss of the exhaust gas.

[0006] One aspect of the present disclosure aims to provide a silencer that can achieve a silencing effect when the internal combustion engine is running at low speeds and can suppress an increase in exhaust gas pressure loss when the internal combustion engine is running at high speeds. [Means for solving the problem]

[0007] One aspect of the present disclosure is a silencer comprising an outer shell member, a first exhaust pipe, a second exhaust pipe, and an inlet portion. The outer shell member defines an interior space. The first exhaust pipe has a first insertion end inserted into the outer shell member, and exhaust gas exhausted from an internal combustion engine flows through the first exhaust pipe. The second exhaust pipe is disposed downstream of the first exhaust pipe. The second exhaust pipe also has a second insertion end inserted into the outer shell member. The inlet portion allows exhaust gas flowing through the first exhaust pipe to flow into the interior space. The first insertion end and the second insertion end are configured to be connected together at least when the internal combustion engine is operating at high revolutions. The inlet portion is configured to open when the internal combustion engine is operating at low revolutions, and to close at least when the internal combustion engine is operating at high revolutions due to thermal expansion of the first exhaust pipe in the axial direction.

[0008] With this configuration, when the internal combustion engine is running at low speeds, exhaust gas flows from the first exhaust pipe into the internal space of the outer shell member through the open inlet, facilitating expansion of the exhaust gas. Furthermore, when the internal combustion engine is running at high speeds, the inlet is blocked due to thermal expansion of at least the first exhaust pipe in the axial direction, causing exhaust gas to flow from the first exhaust pipe to the second exhaust pipe without passing through the internal space, thereby preventing the exhaust gas from expanding and then being compressed. Therefore, a silencing effect is achieved when the internal combustion engine is running at low speeds, and an increase in exhaust gas pressure loss can be suppressed when the internal combustion engine is running at high speeds.

[0009] In one aspect of the present disclosure, one of the first insertion end and the second insertion end may have an expanded diameter so as to be able to cover the periphery of the other. The inflow portion may be a gap formed between the first insertion end and the second insertion end in the axial direction of the first exhaust pipe or in the radial direction of the first exhaust pipe.

[0010] According to this configuration, the inlet can be easily formed by arranging the second exhaust pipe relative to the first exhaust pipe so that there is an axial or radial gap between the first and second insertion ends. Furthermore, because the radial sizes of the first and second insertion ends are different, the inlet is likely to be blocked even if the axis of the first exhaust pipe is displaced radially at least when the first exhaust pipe thermally elongates in the axial direction.

[0011] In one aspect of the present disclosure, one of the first and second insertion ends may be arranged to be inserted into the other. The inlet may be a hole provided in the first or second insertion end near a region where the first and second insertion ends overlap, and communicating the inside and outside of the first exhaust pipe or the second exhaust pipe.

[0012] According to this configuration, the inflow portion can be easily blocked by closing the hole provided in the first insertion end portion or the second insertion end portion due to thermal expansion of at least the first exhaust pipe in the axial direction.

[0013] In one aspect of the present disclosure, an end face of the first insertion end portion and an end face of the second insertion end portion may be configured to be able to abut against each other, and the inlet portion may be a gap formed in the axial direction between the end face of the first insertion end portion and the end face of the second insertion end portion.

[0014] According to this configuration, the inlet can be easily formed by arranging the second exhaust pipe relative to the first exhaust pipe so that there is an axial gap between the end faces of the first and second insertion ends. Also, the inlet can be easily closed by bringing the end faces of the first and second insertion ends into contact due to thermal expansion of at least the first exhaust pipe in the axial direction.

[0015] One aspect of the present disclosure may further include a buffer member disposed between the first insertion end and the second insertion end when the inlet is closed. According to this configuration, the buffer member can suppress abnormal noise that occurs when the first exhaust pipe and the second exhaust pipe collide due to vibration. [Brief explanation of the drawings]

[0016] [Figure 1] Fig. 1A is a cross-sectional view of the silencer taken along the axial direction when the internal combustion engine is stopped and at low revolutions, and Fig. 1B is a cross-sectional view of the silencer taken along the axial direction when the internal combustion engine is at high revolutions. [Figure 2] Fig. 2A is a cross-sectional view showing the internal structure of the silencer of the first modified example when the internal combustion engine is stopped and at low revolutions, and Fig. 2B is a cross-sectional view showing the internal structure of the silencer of the first modified example when the internal combustion engine is at high revolutions. [Figure 3] Fig. 3A is a cross-sectional view showing the internal structure of the silencer of the second modified example when the internal combustion engine is stopped and at low revolutions, and Fig. 3B is a cross-sectional view showing the internal structure of the silencer of the second modified example when the internal combustion engine is at high revolutions. [Figure 4] Fig. 4A is a cross-sectional view showing the internal structure of the silencer of the third modified example when the internal combustion engine is stopped and at low revolutions, and Fig. 4B is a cross-sectional view showing the internal structure of the silencer of the third modified example when the internal combustion engine is at high revolutions. [Figure 5] Fig. 5A is a cross-sectional view showing the internal structure of the silencer of the fourth modified example when the internal combustion engine is stopped and at low revolutions, and Fig. 5B is a cross-sectional view showing the internal structure of the silencer of the fourth modified example when the internal combustion engine is at high revolutions. [Figure 6] Fig. 6A is a cross-sectional view showing the internal structure of the silencer of the fifth modified example when the internal combustion engine is stopped and at low revolutions, and Fig. 6B is a cross-sectional view showing the internal structure of the silencer of the fifth modified example when the internal combustion engine is at high revolutions. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration] 1A is a device for reducing exhaust noise used in an exhaust system that constitutes an exhaust gas flow path of an internal combustion engine. Muffler 100 includes an outer shell member 1, a first exhaust pipe 2, a second exhaust pipe 3, an inlet portion 4, and a buffer member 5.

[0018] The outer shell member 1 is a metal member that forms an internal space 11. In this embodiment, the outer shell member 1 has a shell 12 and two end plates 13 and 14. Shell 12 is a cylindrical member. Two end plates 13, 14 are arranged facing each other to close openings at both ends of shell 12. End plate 13 has a through hole into which first exhaust pipe 2 is inserted, and end plate 14 has a through hole into which second exhaust pipe 3 is inserted.

[0019] The first exhaust pipe 2 is a metal pipe through which exhaust gas G discharged from the internal combustion engine flows. The first exhaust pipe 2 forms a flow path that introduces the exhaust gas G into the outer shell member 1. The first exhaust pipe 2 extends along the central axis A and is cylindrical with a constant diameter. The downstream end of the first exhaust pipe 2 is inserted into the outer shell member 1 and disposed in the internal space 11. The downstream end of the first exhaust pipe 2 will hereinafter be referred to as the first insertion end 21.

[0020] The second exhaust pipe 3 is a metal pipe located downstream of the first exhaust pipe 2. The second exhaust pipe 3 forms a flow path for discharging exhaust gas G introduced into the outer shell member 1. The second exhaust pipe 3 extends along a central axis and is cylindrical. The central axis of the second exhaust pipe 3 is located on the same straight line as the central axis A of the first exhaust pipe 2. The upstream end of the second exhaust pipe 3 is inserted into the outer shell member 1 and is located in the internal space 11. The upstream end of the second exhaust pipe 3 will hereinafter be referred to as the second insertion end 31.

[0021] In this embodiment, the second insertion end portion 31 has an inner diameter larger than the outer diameter of the first insertion end portion 21 of the first exhaust pipe 2, and is expanded in diameter so as to cover the periphery of the first insertion end portion 21. Specifically, the second exhaust pipe 3 has a main body portion 32, a tapered portion 33, and an expanded portion 34.

[0022] The main body portion 32 is a portion with a constant diameter, and has approximately the same diameter as the first exhaust pipe 2. The expanded portion 34 is a portion with a constant diameter that is larger than the main body portion 32. In other words, the expanded portion 34 is a portion of the second exhaust pipe 3 that has been subjected to expansion processing to increase the diameter of the second exhaust pipe 3. The expanded portion 34 is provided at the second insertion end portion 31 of the second exhaust pipe 3. The tapered portion 33 is a portion that connects the main body portion 32 and the expanded portion 34, and is formed in a tapered shape that increases in diameter toward the second insertion end portion 31.

[0023] As shown in FIG. 1A, in this embodiment, the second exhaust pipe 3 is disposed close to the first exhaust pipe 2 with a gap therebetween in the axial direction along the central axis A. As a result, a gap is formed in the axial direction between the first insertion end portion 21 of the first exhaust pipe 2 and the second insertion end portion 31 of the second exhaust pipe 3. The width of this gap is set to about several millimeters. In this embodiment, this gap functions as an inlet portion 4, which will be described later.

[0024] The inlet portion 4 is a portion that allows the exhaust gas G flowing through the first exhaust pipe 2 to flow into the internal space 11. The inlet portion 4 is configured to be open or closed depending on the rotation speed of the internal combustion engine. The state in which the inlet portion 4 is open means that a gap is formed between the first insertion end portion 21 and the second insertion end portion 31 in the axial direction, as shown in FIG. 1A.

[0025] The state in which the inlet section 4 is closed refers to a state in which the first insertion end 21 is inserted into the second insertion end 31, and the first insertion end 21 and the second insertion end 31 are connected to close the gap, as shown in FIG. 1B . In the example shown in FIG. 1B , when the inlet section 4 is closed, the first insertion end 21 is inserted up to the downstream end of the expanded section 34. Note that, when the inlet section 4 is closed, the axial position of the first insertion end 21 within the second insertion end 31 is not limited thereto. For example, only the tip of the first insertion end 21 may be inserted into the second insertion end 31. Specifically, the first insertion end 21 may be inserted so as to stop just before the downstream end of the expanded section 34. Furthermore, for example, the first insertion end 21 may be inserted up to the tapered section 33.

[0026] In this embodiment, as described above, the second exhaust pipe 3 is disposed with an axial gap from the first exhaust pipe 2, so the inlet portion 4 is open when the internal combustion engine is stopped, i.e., when the rotation speed of the internal combustion engine is zero. The inlet portion 4 also opens when the rotation speed of the internal combustion engine is low, i.e., when the exhaust gas G is at a low temperature.

[0027] On the other hand, when the internal combustion engine is rotating at high speeds, the first exhaust pipe 2 and the second exhaust pipe 3 thermally expand in the axial direction so that they approach each other, causing the first insertion end 21 to be inserted into the second insertion end 31, and the first insertion end 21 and the second insertion end 31 to be connected, thereby closing the inlet portion 4. When the internal combustion engine is rotating at high speeds, the exhaust gas G becomes hot. The thermal expansion of the first exhaust pipe 2 and the second exhaust pipe 3 in the axial direction occurs as a result of the first exhaust pipe 2 and the second exhaust pipe 3 thermally expanding due to the high-temperature exhaust gas G flowing through them. In particular, the pipes located closer to the internal combustion engine are more susceptible to thermal expansion. In other words, the first exhaust pipe 2, which is located upstream of the second exhaust pipe 3, is more susceptible to thermal expansion.

[0028] As shown in FIG. 1B , the buffer member 5 is disposed between the first insertion end 21 and the second insertion end 31 when the inlet 4 is closed. Specifically, the buffer member 5 is disposed in a gap formed between the outer circumferential surface of the first insertion end 21 and the inner circumferential surface of the second insertion end 31 when the first insertion end 21 is inserted into the second insertion end 31. The buffer member 5 is a ring-shaped member with a substantially constant thickness in the axial direction. In this embodiment, the buffer member 5 is provided on the outer circumferential surface of the first insertion end 21 so as to extend in the circumferential direction and is fixed by welding or the like. The buffer member may also be fixed to the inner circumferential surface of the second insertion end 31 by welding or the like. The buffer member 5 is made of a wire mesh or the like.

[0029] [2.Effects] According to the embodiment described above in detail, the following effects can be obtained. (2a) When an internal combustion engine is running at low speeds, it is necessary to muffle low-frequency exhaust noise. On the other hand, when an internal combustion engine is running at high speeds, the proportion of low-frequency noise in the exhaust noise generated is low, so there is less need to muffle low-frequency exhaust noise. However, the amount of exhaust gas when an internal combustion engine is running at high speeds is greater than the amount of exhaust gas when it is running at low speeds, and therefore, from the perspective of engine performance, it is necessary to reduce the pressure loss of the exhaust gas when the internal combustion engine is running at high speeds.

[0030] In this embodiment, when the internal combustion engine is running at low speeds, exhaust gas G flows from the first exhaust pipe 2 to the internal space 11 of the outer shell member 1 through the open inlet portion 4 along the arrows shown in FIG. 1A . This facilitates expansion of the exhaust gas G. Therefore, the expansion of the exhaust gas G facilitates silencing of low-frequency exhaust noise. Furthermore, when the internal combustion engine is running at high speeds, the inlet portion 4 is blocked due to thermal expansion of the first exhaust pipe 2 and the second exhaust pipe 3 in the axial direction. Therefore, exhaust gas G flows from the first exhaust pipe 2 to the second exhaust pipe 3 along the arrows shown in FIG. 1B without passing through the internal space 11. This prevents the exhaust gas G from expanding and then being compressed, thereby reducing pressure loss of the exhaust gas G. Therefore, a silencing effect is achieved when the internal combustion engine is running at low speeds, and an increase in pressure loss of the exhaust gas G can be suppressed when the internal combustion engine is running at high speeds. In particular, the amount of exhaust gas G is greater when the internal combustion engine is running at high speeds than when the engine is running at low speeds, significantly suppressing an increase in pressure loss.

[0031] (2b) In this embodiment, the second exhaust pipe 3 is positioned relative to the first exhaust pipe 2 so that there is an axial gap between the first insertion end 21 and the second insertion end 31, making it easy to form the inlet section 4.

[0032] (2c) In the present embodiment, the second insertion end 31 is provided with an expanded portion 34, and the inner diameter of the second insertion end 31 is larger than the outer diameter of the first insertion end 21. Therefore, even if the central axis A of at least one of the first exhaust pipe 2 and the second exhaust pipe 3 is displaced in the radial direction of the first exhaust pipe 2 when the first exhaust pipe 2 and the second exhaust pipe 3 are thermally stretched in the axial direction, the displacement is absorbed and the first insertion end 21 can be inserted into the second insertion end 31, making it easier for the inlet portion 4 to be blocked.

[0033] (2d) In this embodiment, when the inlet portion 4 is closed, the buffer member 5 is disposed between the first insertion end portion 21 and the second insertion end portion 31. Therefore, the buffer member 5 can suppress abnormal noise when the first exhaust pipe 2 and the second exhaust pipe 3 collide due to vibration.

[0034] 3. Other Embodiments Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above embodiments and can take various forms. For convenience, in Figures 2A to 6B, the outer shell member 1 is omitted from illustration, and only the internal structure of the silencer is shown.

[0035] (3a) In the above embodiment, the expanded portion 34 formed by expanding the pipe is provided at the second insertion end 31 of the second exhaust pipe 3, but the method for expanding the diameter of the second insertion end is not limited to this. For example, as in the internal structure of the silencer of the first modified example shown in Fig. 2A, the second insertion end 31a of the second exhaust pipe 3a may be expanded in diameter by flaring.

[0036] In the first modified example, the second exhaust pipe 3a is also disposed at an axial distance from the first exhaust pipe 2 so that an axial gap is formed between the first insertion end 21 and the second insertion end 31a. Therefore, the inlet portion 4 is open when the internal combustion engine is stopped or at low rotation speeds. Furthermore, as shown in FIG. 2B , when the internal combustion engine is at high rotation speeds, the first insertion end 21 is inserted into the second insertion end 31a due to axial thermal expansion of the first exhaust pipe 2 and the second exhaust pipe 3a, and the first insertion end 21 and the second insertion end 31a are connected to each other, thereby closing the inlet portion 4. When the inlet portion 4 is closed, the buffer member 5, which has a substantially constant thickness in the axial direction, is disposed between the first insertion end 21 and the second insertion end 31a. Specifically, when the first insertion end portion 21 is inserted into the second insertion end portion 31a, the buffer member 5 is arranged to fill the gap formed between the outer peripheral surface of at least the tip of the first insertion end portion 21 and the inner peripheral surface of the second insertion end portion 31. This provides the same effects as those of the above-described embodiments (2a) to (2d).

[0037] (3b) In the first modified example, similar to the embodiment described above, the buffer member 5 has a substantially constant thickness in the axial direction. However, the buffer member does not have to have a constant thickness in the axial direction. For example, as in the internal structure of the silencer of the second modified example shown in FIG. 3A, the buffer member 5a may have a shape in which its thickness gradually increases in the axial direction from the downstream side to the upstream side, so as to conform to the expanding diameter of the second insertion end portion 31a of the second exhaust pipe 3a.

[0038] The second modified example also provides the same effects as those of (2a) to (2d) of the above embodiment. Furthermore, in the second modified example, as shown in Fig. 3B, when the inlet portion 4 is closed during high rotation of the internal combustion engine, the buffer member 5a tends to fill the gap between the inner peripheral surface of the second insertion end portion 31a, which is inclined due to the expansion of the diameter, and the outer peripheral surface of the first insertion end portion 21, over the entire axial direction. As a result, when the first insertion end portion 21 is inserted into the second insertion end portion 31a, the buffer member 5a tends to improve the sealing of the gap between the inner peripheral surface of the first insertion end portion 21 and the outer peripheral surface of the second insertion end portion 31a.

[0039] (3c) In the above embodiment and the first and second modified examples, the second exhaust pipes 3, 3a are disposed axially apart from the first exhaust pipe 2, and a gap formed axially between the first insertion end portion 21 and the second insertion end portion 31, 31a functions as the inlet portion 4. However, the configuration of the inlet portion is not limited to this. For example, as in the internal structure of a muffler of a third modified example shown in FIG. 4A , the first exhaust pipe 2 and the second exhaust pipe 3a may be disposed radially apart from each other with the first insertion end portion 21 of the first exhaust pipe 2 inserted into the second insertion end portion 31a of the second exhaust pipe 3a. Specifically, the first exhaust pipe 2 and the second exhaust pipe 3a are disposed such that the first insertion end portion 21 is inserted into the flared second insertion end portion 31a, and a buffer member 5a provided on the outer peripheral surface of the first insertion end portion 21 is disposed radially apart from the inner peripheral surface of the second insertion end portion 31a. As a result, a gap is formed in the radial direction between the buffer member 5a and the second insertion end portion 31a. The width of the gap is set to about several mm. In the third modified example, the gap may function as the inflow portion 4a.

[0040] In the third modified example, the inlet portion 4a is also open when the internal combustion engine is stopped or at low revolutions. Furthermore, as shown in Fig. 4B, when the internal combustion engine is at high revolutions, the inlet portion 4a is closed as the first insertion end portion 21 is further inserted into the second exhaust pipe 3a due to thermal elongation in the axial direction of the first exhaust pipe 2 and the second exhaust pipe 3a. This provides the same effects as (2a), (2c), and (2d) of the above embodiment.

[0041] (3d) In the above embodiment and the first to third modified examples, the second insertion end portions 31, 31a are expanded in diameter so that they can cover the periphery of the first insertion end portion 21. However, the second insertion end portion does not have to be expanded in diameter. For example, as in the internal structure of a silencer of a fourth modified example shown in FIG. 5A, the second exhaust pipe 3b may have a constant diameter, approximately the same as the diameter of the first exhaust pipe 2. In the fourth modified example, a ring-shaped buffer member 5b is provided on the end face of the first insertion end portion 21 and is fixed by welding or the like. The end face of the first insertion end portion 21 and the end face of the second insertion end portion 31b are configured to be able to abut against each other via the buffer member 5b.

[0042] In the fourth modified example, the second exhaust pipe 3b is also disposed with an axial gap relative to the first exhaust pipe 2 so that an axial gap is formed between the end face of the first insertion end 21 (specifically, the buffer member 5b) and the end face of the second insertion end 31b. This results in an axial gap between the buffer member 5b and the second insertion end 31b of the second exhaust pipe 3b. The width of this gap is set to approximately several millimeters. In the fourth modified example, this gap functions as the inlet 4. Therefore, when the internal combustion engine is stopped or running at low speed, the inlet 4 is open. Furthermore, as shown in FIG. 5B , when the internal combustion engine is running at high speed, the inlet 4 is closed by thermal expansion of the first exhaust pipe 2 and the second exhaust pipe 3b in the axial direction, causing the end face of the first insertion end 21 to abut against and connect to the end face of the second insertion end 31b via the buffer member 5b. This provides the same effects as those of the above-described embodiments (2a), (2b), and (2d).

[0043] (3e) In the above embodiment and the first to fourth modified examples, the gap formed in the axial or radial direction between the first insertion end portion 21 and the second insertion end portion 31, 31a, 31b functions as the inlet portion 4, 4a. However, the configuration of the inlet portion is not limited to this. For example, as in the internal structure of the muffler of the fifth modified example shown in FIG. 6A, a hole provided in the second exhaust pipe 3c, which has a constant diameter and an inner diameter larger than the outer diameter of the first exhaust pipe 2, and which communicates the inside and outside of the second exhaust pipe 3c may function as the inlet portion 4b. In the fifth modified example, the first exhaust pipe 2 and the second exhaust pipe 3c are connected from the beginning. In other words, the first exhaust pipe 2 and the second exhaust pipe 3c are connected when the internal combustion engine is stopped, running at low speed, and running at high speed. Specifically, the first exhaust pipe 2 and the second exhaust pipe 3c are connected such that the first insertion end 21 is inserted into the second insertion end 31c and the buffer member 5 is disposed in the gap between the outer circumferential surface of the first insertion end 21 and the inner circumferential surface of the second insertion end 31c. The inflow section 4b is provided in the second insertion end 31c near the area where the first insertion end 21 and the second insertion end 31c overlap. Specifically, when the first exhaust pipe 2 and the second exhaust pipe 3c are connected, the inflow section 4b is located downstream of the buffer member 5 that is disposed between the outer circumferential surface of the first insertion end 21 and the inner circumferential surface of the second insertion end 31c. The inflow section 4b may be, for example, a single hole or multiple holes that are provided at intervals in the circumferential direction of the second exhaust pipe 3c.

[0044] In the fifth modified example, the inlet portion 4b is also open when the internal combustion engine is stopped or at low revolutions. Furthermore, as shown in FIG. 6B , when the internal combustion engine is at high revolutions, the first insertion end portion 21 is inserted further into the second exhaust pipe 3c due to thermal expansion of the first exhaust pipe 2 and the second exhaust pipe 3c in the axial direction, and the hole is blocked by the buffer member 5, thereby closing the inlet portion 4b. This provides the same effects as (2a) and (2d) of the above embodiment. Furthermore, the inlet portion 4b can be easily closed by blocking the hole provided in the second exhaust pipe 3c due to thermal expansion of the first exhaust pipe 2 and the second exhaust pipe 3c in the axial direction.

[0045] (3f) In the above embodiment and the first to third modified examples, the second insertion end 31, 31a of the second exhaust pipe 3, 3a is expanded in diameter. However, for example, the first insertion end of the first exhaust pipe may be expanded in diameter so as to be able to cover the second insertion end.

[0046] (3g) In the fifth modified example, the inner diameter of the second exhaust pipe 3c is larger than the outer diameter of the first exhaust pipe 2, and the first insertion end 21 is inserted into the second insertion end 31c, thereby connecting the first exhaust pipe 2 and the second exhaust pipe 3c. However, for example, the inner diameter of the first exhaust pipe may be larger than the outer diameter of the second exhaust pipe, and the second insertion end may be inserted into the first insertion end, thereby connecting the first exhaust pipe and the second exhaust pipe. The first exhaust pipe may be provided with a hole that connects the inside and outside of the first exhaust pipe, and the hole may function as an inlet. In this case, the inlet is located upstream of a buffer member that is arranged between the inner circumferential surface of the first insertion end and the outer circumferential surface of the second insertion end when the first exhaust pipe and the second exhaust pipe are connected.

[0047] (3h) In the above embodiment, the outer shell member 1 has a configuration including the shell 12 and two end plates 13, 14, but the configuration of the outer shell member is not limited to this. For example, the outer shell member may be a cylindrical member whose opposite end portions taper outward and are configured to connect to the first exhaust pipe and the second exhaust pipe, respectively. The cross-sectional shape of the outer shell member is not limited to a circle and may be a polygon.

[0048] (3i) In the above embodiment and the first to fifth modifications, the silencer 100 is provided with the buffer members 5, 5a, 5b, but for example, the silencer does not have to be provided with the buffer members.

[0049] (3j) In the above embodiment and modified examples 1 to 5, the inflow portions 4, 4a, 4b are closed by thermally expanding the first exhaust pipe 2 and the second exhaust pipes 3, 3a to 3c in the axial direction so that they approach each other. However, for example, the inflow portions 4, 4a, 4b may be closed by thermally expanding only the first exhaust pipe 2 in the axial direction.

[0050] Furthermore, for example, the first exhaust pipe 2 and the second exhaust pipes 3, 3a to 3c may be made of materials with different thermal expansion coefficients. In particular, by making the first exhaust pipe 2, which is more susceptible to the heat of the exhaust gas, out of a material with a higher thermal expansion coefficient than the second exhaust pipes 3, 3a to 3c, it becomes easier to ensure large inflow sections 4, 4a, 4b.

[0051] (3k) For example, the silencer may include a separator that divides the internal space of the outer casing member into multiple chambers in the axial or radial direction. When a separator that divides the internal space into multiple chambers in the axial direction is provided, the separator may be provided with through holes or burring holes that do not inhibit thermal expansion of the first exhaust pipe and the second exhaust pipe.

[0052] (31) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiments may be omitted. Furthermore, 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. [Explanation of symbols]

[0053] 1...outer shell member, 2...first exhaust pipe, 3, 3a to 3c...second exhaust pipe, 4, 4a, 4b...inlet section, 5, 5a, 5b...buffer member, 11...internal space, 12...shell, 13, 14...end plate, 21...first insertion end, 31, 31a to 31c...second insertion end, 32...main body portion, 33...tapered portion, 34...expansion portion, 100...muffler, A...central axis, G...exhaust gas.

Claims

1. A silencer, an outer shell member that forms an internal space; a first exhaust pipe having a first insertion end portion that is inserted into the outer shell member and through which exhaust gas exhausted from the internal combustion engine flows; a second exhaust pipe disposed downstream of the first exhaust pipe, the second exhaust pipe having a second insertion end portion that is inserted into the outer shell member; an inlet portion that allows the exhaust gas flowing through the first exhaust pipe to flow into the internal space; Equipped with the first insertion end portion and the second insertion end portion are configured to be coupled together at least during high rotation speed of the internal combustion engine, The inlet portion is The valve opens when the internal combustion engine is rotating at a low speed, A muffler configured to be closed by thermal expansion of at least the first exhaust pipe in the axial direction when the internal combustion engine is rotating at high speed.

2. 2. The silencer of claim 1, One of the first insertion end portion and the second insertion end portion has a diameter expanded so as to be able to cover the periphery of the other of the first insertion end portion and the second insertion end portion. The inlet portion is a gap formed between the first insertion end portion and the second insertion end portion in the axial direction or in the radial direction of the first exhaust pipe.

3. 2. The silencer of claim 1, one of the first insertion end and the second insertion end is arranged to be inserted into the other, a silencer, wherein the inlet portion is a hole provided in the first insertion end or the second insertion end near a region where the first insertion end and the second insertion end overlap, and which connects the inside and outside of the first exhaust pipe or the second exhaust pipe.

4. 2. The silencer of claim 1, an end surface of the first insertion end portion and an end surface of the second insertion end portion are configured to be able to come into contact with each other; The inlet portion is a gap formed in the axial direction between an end face of the first insertion end portion and an end face of the second insertion end portion.

5. A silencer according to any one of claims 1 to 4, The silencer further comprises a buffer member disposed between the first insertion end and the second insertion end when the inlet is closed.

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