exhaust system

Abstract

To provide an exhaust device that can achieve both a silencing effect and high torque of a power unit. [Solution] In an exhaust system (30) having a muffler (33) for silencing exhaust gas (G) from a power unit (P) including an internal combustion engine, the muffler (33) is configured such that an inner tube (41) containing a plurality of inner pipes (37, 38) is disposed inside an outer tube (36) that serves as an outer shell of the muffler (33), and an expansion chamber (42) is formed between the inner tube (41) and the outer tube (36) by widening the gap between the inner tube (41) and the outer tube (36) more than in other parts, and a plurality of communication holes (50a, 50b, 50c) are formed in the inner tube (41) in a part that forms the expansion chamber (42). The communication holes (50a, 50b, 50c) are formed near the ends of the inner pipes (37, 38) in a side view of the muffler (33).

Description

[Technical Field]

[0001] The present invention relates to an exhaust system, and more particularly to an exhaust system that purifies and silences exhaust gas from a power unit including an internal combustion engine before discharging it. [Background technology]

[0002] BACKGROUND ART Conventionally, in an exhaust system that purifies and silences exhaust gas from a power unit including an internal combustion engine before discharging it, a configuration in which a plurality of punched holes are provided in an inner pipe disposed inside a muffler in order to enhance the silencing effect has been known.

[0003] Patent Document 1 discloses an exhaust device in which a plurality of punched holes are provided at the front end of an inner pipe connected to an outlet hole of a muffler. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-214462 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, if multiple punched holes are provided in the inner pipe arranged inside the muffler, the silencing effect is enhanced, but the exhaust gas is allowed to escape more easily, which makes it easier to reduce the torque of the power unit.Therefore, there is still room for improvement in order to obtain an exhaust system that can achieve both silencing effect and high torque of the power unit.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust system that solves the above-mentioned problems of the prior art and achieves both a silencing effect and high torque of the power unit. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an exhaust system (30) having a muffler (33) for silencing exhaust gas (G) from a power unit (P) including an internal combustion engine, wherein the muffler (33) is configured such that an inner tube (41) containing a plurality of inner pipes (37, 38) is disposed inside an outer tube (36) that serves as the outer shell of the muffler (33), and an expansion chamber (42) is provided between the inner tube (41) and the outer tube (36) by widening the gap between the inner tube (41) and the outer tube (36) more than in other parts, and a plurality of communication holes (50a, 50b, 50c) are formed in the inner tube (41) in the part that constitutes the expansion chamber (42).

[0008] A second feature of the muffler (33) is that the communication holes (50a, 50b, 50c) are formed near the ends of the inner pipes (37, 38) in a side view of the muffler (33).

[0009] A third feature of the present invention is that the expansion chamber (42) is formed by forming a part of the inner cylinder (41) into a flat plate portion (41a), and the communication holes (50a, 50b, 50c) are formed in the flat plate portion (41a).

[0010] A fourth feature of the present invention is that the expansion chamber (42) is provided on the inner side of the muffler (33) in the vehicle width direction.

[0011] A fifth feature is that the diameter of the communication holes (50a, 50b, 50c) changes according to the distance between the outer cylinder (36) and the flat plate portion (41a).

[0012] Furthermore, a sixth feature is that a plurality of punched holes (38a) are formed in a portion of the inner pipe (37, 38), and at least a portion of the communication holes (50a, 50b, 50c) are positioned so as to overlap with the punched holes (38a) in a side view of the muffler (33). [Effects of the Invention]

[0013] According to a first feature, in an exhaust system (30) having a muffler (33) that silences exhaust gas (G) from a power unit (P) including an internal combustion engine, the muffler (33) is configured such that an inner tube (41) that houses a plurality of inner pipes (37, 38) is disposed inside an outer tube (36) that serves as an outer shell of the muffler (33), and an expansion chamber (42) is provided between the inner tube (41) and the outer tube (36) by widening the gap between the inner tube (41) and the outer tube (36) more than in other parts. A plurality of communication holes (50a, 50b, 50c) are formed in the inner tube (41) at a part that constitutes the expansion chamber (42). This allows communication between the expansion chamber formed between the inner tube and the outer tube and the inside of the inner tube that houses the inner pipes, thereby enhancing the silencing effect of the muffler.

[0014] According to the second feature, the communication holes (50a, 50b, 50c) are formed near the ends of the inner pipes (37, 38) in a side view of the muffler (33). Therefore, by providing the communication holes in areas where the flow velocity of the exhaust gas is high and the pressure fluctuations are large, it is possible to enhance the silencing effect and suppress a reduction in the torque of the power unit.

[0015] According to the third feature, the expansion chamber (42) is formed by forming a part of the inner cylinder (41) into a flat plate portion (41a), and the communication holes (50a, 50b, 50c) are formed in the flat plate portion (41a). This makes it possible to easily form the expansion chamber and facilitates the processing of forming the communication holes.

[0016] According to the fourth feature, the expansion chamber (42) is provided on the vehicle widthwise inner side of the muffler (33). This means that the expansion chamber portion, which is likely to become hot due to the heat of the exhaust gas, is located on the vehicle widthwise inner side, thereby reducing the possibility that passengers or the like will come into contact with the portion that becomes hot, and preventing the portion that is easily visible from the outside from becoming burnt due to heat, thereby reducing the appearance.

[0017] According to the fifth feature, the diameter of the communication holes (50a, 50b, 50c) changes according to the distance between the outer tube (36) and the flat plate portion (41a). For example, by making the diameter smaller where the distance between the outer tube and the flat plate portion is short and making the diameter larger where the distance between the outer tube and the flat plate portion is long, it is possible to reduce the bias in the pressure acting on the wall of the expansion chamber and equalize the inflow pressure of the exhaust gas into the expansion chamber.

[0018] According to the sixth feature, a plurality of punched holes (38a) are formed in a portion of the inner pipe (37, 38), and at least a portion of the communication holes (50a, 50b, 50c) are provided at positions overlapping with the punched holes (38a) in a side view of the muffler (33). Therefore, by providing communication holes in a portion where the flow velocity of the exhaust gas is high and where the exhaust gas is diffused radially outward by the punched holes, the silencing effect of the muffler can be improved. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a right side view of a motorcycle to which an exhaust system according to an embodiment of the present invention is applied. [Figure 2] FIG. 2 is a perspective view of the muffler as seen from the left rear. [Figure 3] FIG. 2 is a perspective view showing a state in which an outer cylinder is removed from the muffler. [Figure 4] FIG. 2 is a left side view of the muffler with the outer cylinder removed. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. Figure 1 is a right side view of a motorcycle 1 to which an exhaust system 30 according to one embodiment of the present invention is applied. The motorcycle 1 is a straddle-type vehicle that travels by transmitting the driving force of a power unit P, which is an integrated configuration of an internal combustion engine and a transmission, to a rear wheel WR.

[0021] A head pipe F1 that rotatably supports a steering stem (not shown) is provided at the front end of a pair of left and right main frames F2 that make up the body frame F. A top bridge 20 and a bottom bridge 21 that support a pair of left and right front forks 2 are fixed to the upper and lower ends, respectively, of the steering stem.

[0022] A front wheel WF is rotatably supported at the lower end of the front fork 2. A front fender 3 that covers the upper part of the front wheel WF is attached to the front fork 2. A steering handlebar 7 is fixed to the upper part of the top bridge 20. A headlight 5 and a meter device 6 are disposed in front of the head pipe F1. A pair of left and right front flasher lamps 4 are attached to the sides of the headlight 5.

[0023] A fuel tank 8 is disposed on top of the main frame F2. A pair of left and right pivot plates 16 are attached to the lower part of the main frame F2, which extends rearward from the head pipe F1 and then curves downward. A rear frame F4, which supports a front seat 9 and a rear seat 11, is connected to the rear of the main frame F2. A power unit P, to which an exhaust device 30 is attached, is suspended below the main frame F2 and in front of the pivot plates 16. A center stand 15 is pivotally supported on the lower end of the main frame F2 so as to be swingable.

[0024] The pivot plate 16 supports a pivot 17 that pivotally supports a swing arm 22 so that it can swing freely. A pair of left and right step bars 19 on which the driver places his feet are disposed below and in front of the pivot plate 16. A brake pedal 18 is pivotally supported so that it can swing behind the step bar 19 on the right side in the vehicle width direction. The swing arm 22 that pivotally supports the rear wheel WR so that it can rotatably swing is suspended from the rear frame F4 by a pair of left and right rear cushions 10 at a position near the rear of the swing arm 22. A rear fender 12 that covers the upper part of the rear wheel WR is attached to the rear frame F4, and a taillight unit 14 and a pair of left and right rear flashers 13 are attached to the rear of the rear fender 12.

[0025] The exhaust device 30 comprises an exhaust pipe 31 connected to the exhaust port of the internal combustion engine that constitutes the power unit P, a catalyst storage section 32 connected to the rear of the exhaust pipe 31, and a muffler 33 connected to the rear of the catalyst storage section 32.

[0026] 2 is a perspective view of the muffler 33 as seen from the left rear. The muffler 33 includes a connecting portion 45 connected to the rear portion of the catalyst housing portion 32, a tapered tubular front outer shell 34 connected to the rear portion of the connecting portion 45, an outer tube 36 as a cylindrical outer shell connected to the rear portion of the front outer shell 34, and a tapered tubular rear outer shell 39 connected to the rear portion of the outer tube 36. A muffler stay 35 is attached to a position near the front of the muffler outer shell 36 for suspending the muffler 33 from the pivot plate 16. A first inner pipe 37 communicating with the connecting portion 45 and a second inner pipe 38 communicating with an exhaust port that discharges exhaust gas G from the expansion chamber rearward are housed inside the muffler outer shell 36.

[0027] Fig. 3 is a perspective view showing the state in which the outer cylinder 36 has been removed from the muffler 33. Fig. 4 is a left side view showing the state in which the outer cylinder 36 has been removed from the muffler 33, and Fig. 5 is a cross-sectional view taken along line VV in Fig. 4. The same reference numerals as those used above indicate the same or equivalent parts. The first inner pipe 37 and the second inner pipe 38 are housed in an inner cylinder 41 disposed inside the outer cylinder 36. A flat plate portion 41a is formed on the inner side of the inner cylinder 41 in the vehicle width direction, and the gap formed by this between the inner cylinder 41 and the outer cylinder 36 functions as an expansion chamber 42 for the exhaust gas G.

[0028] This embodiment is characterized in that communication holes 50a, 50b, and 50c are formed in the flat plate portion 41a that constitutes the expansion chamber 42. This allows communication between the expansion chamber 42, which is formed between the inner tube 41 and the outer tube 36, and the inside of the inner tube 41, which houses the inner pipes 37 and 38, thereby improving the silencing effect of the muffler 33. Furthermore, the communication holes 50a, 50b, and 50c are formed near the front end of the second inner pipe 38 in a side view of the muffler 32. Thus, by providing the communication holes 50a, 50b, and 50c in a portion where the flow velocity of the exhaust gas G is high and the pressure fluctuations are large, it is possible to suppress a reduction in the torque of the power unit P while improving the silencing effect.

[0029] In this embodiment, the expansion chamber 42 is formed by forming the flat plate portion 41a in the inner cylinder 41, which makes it easy to form the expansion chamber 42 and also makes it easy to drill the communication holes 50a, 50b, and 50c. Furthermore, since the expansion chamber 42 is provided on the inner side of the muffler 33 in the vehicle width direction, the portion of the expansion chamber G that is likely to become hot due to the heat of the exhaust gas G is disposed on the inner side in the vehicle width direction, which reduces the possibility that an occupant or the like will come into contact with the portion that becomes hot and prevents a portion that is easily visible from the outside from becoming browned due to heat, which would degrade the appearance.

[0030] In addition, in this embodiment, the diameter of the first communication hole 50a is set smaller than the second communication hole 50b and the third communication hole 50c. This is because the diameter is smaller where the outer cylinder 36 is close to the flat plate portion 41a and larger where the outer cylinder 36 is farther from the flat plate portion 41a, thereby reducing uneven pressure acting on the wall of the expansion chamber 42 and making it possible to equalize the pressure of the exhaust gas G flowing into the expansion chamber 42. Furthermore, in this embodiment, the total area of ​​the communication holes is optimized, thereby improving the noise reduction effect and torque reduction effect.

[0031] Furthermore, this embodiment is characterized in that a plurality of punched holes 38a are formed in the front end of the second inner pipe 38, and the two second communication holes 50b and the two third communication holes 50c are provided at positions that overlap the punched holes 38a in a side view of the muffler 33. This makes it possible to improve the silencing effect of the muffler 33 by providing communication holes in a portion where the flow velocity of the exhaust gas G is high and which is diffused radially outward by the punched holes 38a.

[0032] As described above, according to the exhaust device 30 of this embodiment, the muffler 33 is configured such that the inner tube 41, which houses the first inner pipe 37 and the second inner pipe 38, is arranged inside the outer tube 36, which serves as the outer shell of the muffler 33. An expansion chamber 42 is provided between the inner tube 41 and the outer tube 42 by widening the gap between the inner tube 41 and the outer tube 36 more than in other parts. Communication holes 50a, 50b, 50c are formed in the part of the inner tube 41 that constitutes the expansion chamber 42. Therefore, by connecting the expansion chamber 42 formed between the inner tube 41 and the outer tube 36 to the inside of the inner tube 41, it is possible to enhance the sound-absorbing effect of the muffler 33.

[0033] The configuration of the motorcycle, the displacement and number of cylinders of the internal combustion engine, the shape and structure of the exhaust device, the shape and structure of the inner and outer cylinders that make up the muffler, the shape and material of the inner pipe, the shape and capacity of the expansion chamber, the size and number of the communication holes and punched holes, the total area of ​​the communication holes, etc. are not limited to the above-described embodiments and can be modified in various ways. The exhaust device according to the present invention is not limited to motorcycles, but can be applied to various vehicles such as three-wheeled and four-wheeled vehicles that are driven by a power unit that includes an internal combustion engine. [Explanation of symbols]

[0034] 1...motorcycle, 30...exhaust system, 33...muffler, 36...outer cylinder, 37...first inner pipe (inner pipe), 38...second inner pipe (inner pipe), 38a...punched hole, 41...inner cylinder, 41a...flat plate portion, 42...expansion chamber, 50a...first communication hole (communication hole), 50b...first communication hole (communication hole), 50c...first communication hole (communication hole), P...power unit, G...exhaust gas

Claims

1. An exhaust system (30) having a muffler (33) for silencing exhaust gas (G) from a power unit (P) including an internal combustion engine, The muffler (33) is configured such that an inner cylinder (41) containing a plurality of inner pipes (37, 38) is disposed inside an outer cylinder (36) serving as an outer shell of the muffler (33), and an expansion chamber (42) is provided between the inner cylinder (41) and the outer cylinder (36) by widening a part of a cylindrical gap formed between the inner cylinder (41) and the outer cylinder (36) as a flat plate portion (41a) of the inner cylinder (41) more than the other cylindrical gaps. A plurality of communication holes (50a, 50b, 50c) are formed in the inner cylinder (41) at a portion that constitutes the expansion chamber (42), The exhaust device is characterized in that the communication holes (50a, 50b, 50c) are formed in the flat plate portion (41a).

2. 2. The exhaust system according to claim 1, wherein the communication holes (50a, 50b, 50c) are formed near the ends of the inner pipes (37, 38) in a side view of the muffler (33).

3. 3. The exhaust system according to claim 1, wherein the expansion chamber (42) is provided on an inner side of the muffler (33) in the vehicle width direction.

4. 2. The exhaust device according to claim 1, wherein the diameter of the communication holes (50a, 50b, 50c) changes in accordance with the distance between the outer cylinder (36) and the flat plate portion (41a).

5. A plurality of punched holes (38a) are formed in a part of the inner pipe (37, 38), 3. The exhaust device according to claim 1, wherein at least a portion of the communication holes (50a, 50b, 50c) is positioned so as to overlap with the punched hole (38a) in a side view of the muffler (33).

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