Exhaust system

Abstract

To provide an exhaust system capable of developing sufficient silence effects by making effective use of a limited space.SOLUTION: An exhaust system includes a chamber (41) arranged below an engine, an inlet pipe (50) for guiding exhaust gas from an exhaust pipe to the chamber, a tail pipe (61) for exhausting the exhaust gas from the chamber to the outside, a first partition wall (43) for partitioning the inside of the chamber into a pair of right and left spaces, and a second partition wall (44) for partitioning one of the pair of right and left spaces into a pair of front and rear spaces. The other of the pair of right and left spaces becomes a first expansion chamber (45) into which the inlet pipe enters, the rear side of the pair of front and rear spaces becomes a second expansion chamber (46) downstream of the first expansion chamber, and the front side of the pair of front and rear spaces becomes a third expansion chamber (47) downstream of the second expansion chamber where the tail pipe enters.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an exhaust system. [Background technology]

[0002] In the exhaust system of a saddle-type vehicle, a sound-absorbing chamber is provided downstream of an exhaust pipe extending from the engine. When exhaust gas flows from the exhaust pipe into the chamber, the exhaust gas expands inside the chamber, attenuating the energy of the exhaust sound. One known exhaust device of this type has a chamber disposed below the engine (see, for example, Patent Document 1). Inside the chamber described in Patent Document 1, multiple expansion chambers are formed by partitions, and after the exhaust gas repeatedly expands as it passes through the multiple expansion chambers, the exhaust gas is discharged from the downstream expansion chamber to the outside through the tailpipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-160915 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the chamber described in Patent Document 1 is disposed below the engine, there are cases where the chamber volume cannot be sufficiently secured due to the bank angle and the relationship with surrounding parts. Although multiple expansion chambers are formed inside the chamber to provide sound deadening measures, it is difficult to secure a large volume for the multiple expansion chambers in the limited space below the engine because the multiple expansion chambers are arranged in a front-to-rear configuration. As a result, there is a risk that the exhaust gas will not be able to expand completely, reducing the sound deadening effect.

[0005] The present invention has been made in consideration of the above-mentioned points, and has an object to provide an exhaust device that can effectively utilize a limited space and obtain a sufficient sound-absorbing effect. [Means for solving the problem]

[0006] An exhaust device according to one embodiment of the present invention is an exhaust device that purifies exhaust gas exhausted from an engine through an exhaust pipe, and includes a chamber disposed below the engine, an inlet pipe that guides exhaust gas from the exhaust pipe to the chamber, a tail pipe that discharges exhaust gas from the chamber to the outside, a first partition wall that divides the inside of the chamber into a pair of left and right spaces, and a second partition wall that divides one of the pair of left and right spaces into a pair of front and rear spaces. a first communication pipe extending laterally and penetrating the first partition wall, and a second communication pipe extending forward and backward and penetrating the second partition wall; the other of the pair of left and right spaces is a first expansion chamber into which the inlet pipe enters, the rear side of the pair of front and rear spaces is a second expansion chamber downstream of the first expansion chamber, and the front side of the pair of front and rear spaces is a third expansion chamber downstream of the second expansion chamber into which the tail pipe enters. The first expansion chamber and the second expansion chamber communicate with each other through the first communication pipe, the second expansion chamber and the third expansion chamber communicate with each other through the second communication pipe, and the first communication pipe overlaps with an inlet of the second communication pipe in a rear view. This solves the above problem. Effect of the Invention

[0007] According to an exhaust device of one aspect of the present invention, the first expansion chamber and the second and third expansion chambers are formed on the left and right sides inside the chamber, and the second expansion chamber and the third expansion chamber are formed on the front and rear sides. The direction of the flow of exhaust gas from the first expansion chamber to the second expansion chamber and the direction of the flow from the second expansion chamber to the third expansion chamber cross each other. It becomes difficult for the exhaust gas to flow directly from the first expansion chamber to the third expansion chamber, and the exhaust gas can be sufficiently expanded in the first to third expansion chambers. Even if the chamber is arranged in a limited space below the engine, by forming the first to third expansion chambers inside the chamber, the exhaust gas can be expanded in stages, thereby improving the sound silencing performance of the chamber. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a left side view of the engine and its periphery according to the present embodiment. [Diagram 2] FIG. 2 is a right side view of the engine and its periphery according to the present embodiment. [Diagram 3] FIG. 2 is a top view of the exhaust device of the present embodiment. [Figure 4]FIG. 2 is a side view of the exhaust device of the present embodiment. [Diagram 5] FIG. 2 is a perspective view showing an internal structure of a chamber according to the present embodiment. [Figure 6] FIG. 2 is a perspective view of the chamber with the upper outer body removed in this embodiment. [Figure 7] FIG. 2 is a top view showing the internal structure of the chamber of the present embodiment. [Figure 8] FIG. 2 is a rear view showing the internal structure of the chamber of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An exhaust device according to one embodiment of the present invention purifies exhaust gas exhausted from an engine through an exhaust pipe. A chamber is disposed below the engine, and exhaust gas is guided from the exhaust pipe to the chamber through an inlet pipe, and exhaust gas is discharged from the chamber to the outside through a tail pipe. The inside of the chamber is divided into a pair of left and right spaces by a first partition wall, and one of the pair of left and right spaces is divided into a pair of front and rear spaces by a second partition wall. The other of the pair of left and right spaces is a first expansion chamber into which the inlet pipe enters, the rear side of the pair of front and rear spaces is a second expansion chamber downstream of the first expansion chamber, and the front side of the pair of front and rear spaces is a third expansion chamber into which the tail pipe enters downstream of the second expansion chamber. In this way, the first expansion chamber and the second and third expansion chambers are formed separately on the left and right sides inside the chamber, and the second expansion chamber and the third expansion chamber are formed separately on the front and rear sides. The direction of the flow of exhaust gas from the first expansion chamber to the second expansion chamber and the direction of the flow from the second expansion chamber to the third expansion chamber intersect. It becomes difficult for the exhaust gas to flow directly from the first expansion chamber to the third expansion chamber, and the exhaust gas can be sufficiently expanded in the first to third expansion chambers. Even if the chamber is placed in a limited space below the engine, by forming the first to third expansion chambers inside the chamber, the exhaust gas can be expanded in stages, improving the soundproofing performance of the chamber. EXAMPLES

[0010] Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings. Fig. 1 is a left side view of the engine and its surroundings in this embodiment. Fig. 2 is a right side view of the engine and its surroundings in this embodiment. In the following drawings, the arrow FR indicates the front of the vehicle, the arrow RE indicates the rear of the vehicle, the arrow L indicates the left side of the vehicle, and the arrow R indicates the right side of the vehicle.

[0011] 1 and 2, engine 10 is a parallel two-cylinder engine with a cylinder block 12 disposed on top of a crankcase 11. A cylinder head 13 is attached to the top of the cylinder block 12, and a head cover (not shown) is attached to the top of the cylinder head 13. An oil pan 14 in which oil for lubrication and cooling is stored is attached to the bottom of the crankcase 11. A magneto cover 15 that covers a magneto chamber inside the case is attached to the left side of the crankcase 11, and a clutch cover 16 that covers a clutch chamber inside the case is attached to the right side of the crankcase 11.

[0012] The engine 10 is supported by a pair of left and right main frames 21 of a saddle-ride type vehicle. A swing arm 22 that supports a rear wheel (not shown) is supported swingably on the pair of main frames 21. The swing arm 22 is connected to a rear suspension 23 for cushioning the rear wheel. An upper end of the rear suspension 23 is connected to the main frames 21, and a lower end of the rear suspension 23 is connected to the swing arm 22 via a link arm 24 and a link bracket 25. In addition, a chamber 41 of an exhaust device 30 is supported on the lower part of the pair of main frames 21 via left and right brackets 42a, 42b.

[0013] Exhaust gas flows into the chamber 41 through the pair of exhaust pipes 31a, 31b, and is exhausted from the chamber 41 to the outside via the muffler 35. A plurality of expansion chambers are formed inside the chamber 41, and the exhaust gas expands stepwise in each expansion chamber, thereby attenuating the energy of the exhaust sound. However, since the chamber 41 is disposed in a limited space below the engine 10, it is difficult to secure a plurality of large expansion chambers inside the chamber 41. Therefore, the chamber 41 of this embodiment makes it difficult for the exhaust gas to flow directly between the plurality of expansion chambers, and the exhaust gas is sufficiently expanded in each expansion chamber, improving the sound deadening performance.

[0014] The detailed configuration of the exhaust device will be described below with reference to Fig. 3 to Fig. 6. Fig. 3 is a top view of the exhaust device of this embodiment. Fig. 4 is a side view of the exhaust device of this embodiment. Fig. 5 is a perspective view showing the internal structure of the chamber of this embodiment. Fig. 6 is a perspective view of the chamber with the upper outer body removed of this embodiment.

[0015] As shown in Figures 3 and 4, the exhaust device 30 reduces the exhaust noise of exhaust gas exhausted from the engine 10 (see Figure 1) through exhaust pipes 31a, 31b and purifies the exhaust gas. The exhaust pipes 31a, 31b extend downward from the front surface of the engine 10, and the exhaust pipes 31a, 31b are collected together by a collecting pipe 32 and connected to an inlet pipe 50. A mounting boss 38 for an upstream exhaust gas sensor (not shown) is formed on the outer circumferential surface of the collecting pipe 32. The upstream exhaust gas sensor detects the average oxygen concentration of the exhaust gas flowing in from the exhaust pipes 31a, 31b. The detection result of the upstream exhaust gas sensor is used for feedback control of the fuel injection amount.

[0016] The inlet pipe 50 connects the first catalyst 36 and the second catalyst 37 (see FIG. 5) via a connecting pipe 51. The upstream side of the connecting pipe 51 is outside the chamber 41, and the first catalyst 36 is disposed on the upstream side of this connecting pipe 51. The downstream side of the connecting pipe 51 is inserted into the chamber 41, and the second catalyst 37 is disposed on the downstream side of this connecting pipe 51. A mounting boss 39 for a downstream exhaust gas sensor (not shown) is formed on the outer circumferential surface of the connecting pipe 51 between the first and second catalysts 36, 37. The downstream exhaust gas sensor detects the average oxygen concentration of the exhaust gas flowing in from the exhaust pipes 31a, 31b. The detection result of the downstream exhaust gas sensor is used for feedback control of the fuel injection amount and for diagnosing catalyst deterioration.

[0017] As exhaust gas flows from the exhaust pipes 31a, 31b into the inlet pipe 50, air pollutants contained in the exhaust gas, such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), are purified by the first and second catalysts 36, 37. As exhaust gas flows from the inlet pipe 50 into the chamber 41, the exhaust gas expands in each expansion chamber in the chamber 41, reducing exhaust noise. A muffler 35 (see FIG. 2) is connected to the downstream side of the chamber 41 via a tail pipe 61, and exhaust gas that has passed through the chamber 41 is exhausted to the outside from the muffler 35. Because exhaust noise is reduced in the chamber 41, the expansion chambers of the muffler 35 are made smaller, thereby realizing a reduction in the size of the muffler 35.

[0018] The chamber 41 is positioned below the engine 10 and behind the oil pan 14 (see FIG. 1). The chamber 41 is box-shaped, and an inlet pipe 50 is inserted into the right side of the front wall of the chamber 41, and a tail pipe 61 extends rearward from the right side of the rear wall of the chamber 41. The inlet pipe 50 guides exhaust gas from the exhaust pipes 31a, 31b to the chamber 41, and the tail pipe 61 discharges the exhaust gas from the chamber 41 to the outside. In addition, brackets 42a, 42b are provided on both left and right side walls of the chamber 41, and the chamber 41 is attached to the lower part of the main frame 21 (see FIG. 1) via the brackets 42a, 42b.

[0019] As shown in Fig. 5, the inside of the chamber 41 is divided into a pair of left and right spaces by a first partition wall 43 extending in the front-rear direction. Furthermore, the left space of the pair of left and right spaces is divided into a pair of front and rear spaces by a second partition wall 44 extending in the front-rear direction. The right space of the pair of left and right spaces is a first expansion chamber 45 into which the inlet pipe 50 enters. The rear space of the pair of front and rear spaces is a second expansion chamber 46 downstream of the first expansion chamber 45. The front space of the pair of front and rear spaces is a third expansion chamber 47 downstream of the second expansion chamber 46 into which the tail pipe 61 enters.

[0020] In this way, the rear side of the first expansion chamber 45 and the second expansion chamber 46 are adjacent to each other in the left-right direction, and the front side of the first expansion chamber 45 and the third expansion chamber 47 are adjacent to each other in the left-right direction. The first expansion chamber 45 has the largest volume, the second expansion chamber 46 has the second largest volume, and the third expansion chamber 47 has the smallest volume. An inlet pipe 50 is provided on the front wall of the chamber 41, and the first catalyst 36 upstream of the inlet pipe 50 is disposed outside the chamber 41, and the second catalyst 37 downstream of the inlet pipe 50 is disposed inside the chamber 41. The second catalyst 37 is disposed in parallel to the first partition wall 43 in the first expansion chamber 45.

[0021] A straight first communication pipe 53 is provided on the rear end side of the first partition 43, and a straight second communication pipe 57 is provided on the right end side (the other side in the left-right direction) of the second partition 44. The first communication pipe 53 extends left and right and penetrates the first partition 43, and the first expansion chamber 45 and the second expansion chamber 46 communicate with each other through the first communication pipe 53. The second communication pipe 57 extends front and rear and penetrates the second partition 44, and the second expansion chamber 46 and the third expansion chamber 47 communicate with each other through the second communication pipe 57. Inside the chamber 41, the first and second communication pipes 53 and 57 are arranged so that their extending directions intersect.

[0022] A tail pipe 61 bent in a generally crank shape is provided on the left end side (one side in the left-right direction) of the second partition 44. The tail pipe 61 extends in the front-rear direction to the left of the second communication pipe 57, passes through the second partition 44, then extends in the left-right direction in front of the first communication pipe 53, passes through the first partition 43, and further extends diagonally rearward to the right and passes through the rear wall of the chamber 41. That is, the tail pipe 61 extends in the front-rear direction from the third expansion chamber 47 to the second expansion chamber 46, extends in the left-right direction from the second expansion chamber 46 to the first expansion chamber 45, and extends from the right corner of the rear wall of the first expansion chamber 45 to the outside of the chamber 41.

[0023] A cylindrical cap 62 with a bottom is attached to the front end of the tail pipe 61. The front end of the cap 62 is closed, and a large number of punched holes are formed on the outer circumferential surface of the cap 62. The inlet of the tail pipe 61 is formed by the large number of punched holes. A bulge 49 that expands the third expansion chamber 47 forward is formed on the left side of the front wall of the chamber 41, and the cap 62 of the tail pipe 61 is positioned inside this bulge 49. Since the inlet of the tail pipe 61 is a punched hole in the cap 62, the inlet of the tail pipe 61 is narrowed, making it easier to keep exhaust gas inside the bulge 49.

[0024] 5 and 6, the right half of the outer wall of the chamber 41 has a two-layer structure in which sound-absorbing material 73 is packed between an outer body 71 and an inner body 72, and the left half of the outer wall of the chamber 41 has a single-layer structure of the outer body 71. The first expansion chamber 45 is surrounded by the two-layer outer wall, and the second expansion chamber 46 and the third expansion chamber 47 are surrounded by the single-layer outer wall. A pair of upper and lower large plates 74 that cover the outer body 71 from the inside are arranged in the second expansion chamber 46, and a pair of upper and lower small plates 76 that cover the outer body 71 from the inside are arranged in the third expansion chamber 47.

[0025] The upper large plate 74 extends from the top surface of the second expansion chamber 46 to the left side, and the lower large plate 74 extends from the bottom surface of the second expansion chamber 46 to the left side. The upper small plate 76 extends from the top surface of the third expansion chamber 47 to the left side, and the lower small plate 76 extends from the bottom surface of the third expansion chamber 47 to the left side. Shallow depressions 75, 77 are formed on the surfaces of the large plate 74 and the small plate 76, and these depressions 75, 77 are filled with sound-absorbing material (not shown). Although not shown, the large plate 74 and the small plate 76 have numerous punched holes formed therein.

[0026] A partition plate 78 is attached to the left side surface of the first partition 43 in a predetermined range from the rear end of the second catalyst 37 to the front of the tail pipe 61. A sound absorbing material (not shown) is filled between the first partition 43 and the partition plate 78. In this way, the first expansion chamber 45 with the largest volume is formed of a two-layered outer wall or partition, and the second and third expansion chambers 46 and 47 are also partially formed of two-layered outer walls or partitions. This makes it possible to improve the sound absorbing performance without increasing the size of the chamber 41. In addition, the two-layered structure is minimized to suppress an increase in weight and to make it difficult for heat to be trapped. For example, glass wool is used as the sound absorbing material 73.

[0027] Hereinafter, the positional relationship of the members inside the chamber will be described with reference to Figures 7 and 8. Figure 7 is a top view showing the internal structure of the chamber of this embodiment. Figure 8 is a rear view showing the internal structure of the chamber of this embodiment.

[0028] As shown in FIG. 7, a first expansion chamber 45 is formed in the right half of the chamber 41, a second expansion chamber 46 is formed on the rear side of the left half of the chamber 41, and a third expansion chamber 47 is formed on the front side of the left half of the chamber 41. An outlet 52 of an inlet pipe 50 (second catalyst 37) is located in the middle of the first expansion chamber 45 in the front-rear direction, and an inlet 54 of a first communication pipe 53 is located on the rear side of the first expansion chamber 45. An outlet 55 of the first communication pipe 53 is located on the rear side of the second expansion chamber 46, and an inlet 58 of a second communication pipe 57 is located in the middle of the second expansion chamber 46 in the front-rear direction. An outlet 59 of the second communication pipe 57 is located on the rear side of the third expansion chamber 47, and a cap 62 of a tail pipe 61 is located inside the bulging portion 49.

[0029] Exhaust gas flows into the first expansion chamber 45 from the outlet 52 of the inlet pipe 50, and then flows from the first expansion chamber 45 into the inlet 54 of the first communication pipe 53. The inlet pipe 50 is inclined so as to become higher toward the rear, and the left and right extension parts 63 of the tail pipe 61 overlap the outlet 52 of the inlet pipe 50 in front of the first communication pipe 53 in a rear view (see FIG. 8). The flow of exhaust gas is blocked by the left and right extension parts 63 of the tail pipe 61 in front of the first communication pipe 53, making it difficult for the exhaust gas to flow directly from the outlet 52 of the inlet pipe 50 to the inlet 54 of the first communication pipe 53. This makes it easier for the exhaust gas to expand sufficiently in the first expansion chamber 45.

[0030] In rear view, the inlet 54 of the first communication pipe 53 is located below the left and right extension parts 63 of the tail pipe 61 (see FIG. 8), and the outlet 52 of the inlet pipe 50 and the inlet 54 of the first communication pipe 53 are vertically misaligned. Also, the orientations of the inlet pipe 50 and the first communication pipe 53 cross, and the first communication pipe 53 partially overlaps the outlet 52 of the inlet pipe 50 in the first expansion chamber 45 in rear view (see FIG. 8). This makes it difficult for exhaust gas to flow directly from the outlet 52 of the inlet pipe 50 to the inlet 54 of the first communication pipe 53, making it easier for the exhaust gas to expand in the first expansion chamber 45.

[0031] Exhaust gas flows into the second expansion chamber 46 from the outlet 55 of the first communication pipe 53, and from the second expansion chamber 46 into the inlet 58 of the second communication pipe 57. The second communication pipe 57 is at approximately the same height as the left and right extension parts 63 of the tail pipe 61, and the left and right extension parts 63 of the tail pipe 61 overlap the inlet 58 of the second communication pipe 57 in front of the first communication pipe 53 in a rear view (see FIG. 8). The flow of exhaust gas is blocked by the left and right extension parts 63 of the tail pipe 61 in front of the first communication pipe 53, making it difficult for the exhaust gas to flow directly from the outlet 55 of the first communication pipe 53 to the inlet 58 of the second communication pipe 57. This makes it easy for the exhaust gas to expand sufficiently in the second expansion chamber 46.

[0032] In rear view, the outlet 55 of the first communication pipe 53 is located below the left and right extension parts 63 of the tail pipe 61 (see FIG. 8), and the outlet 55 of the first communication pipe 53 and the inlet 58 of the second communication pipe 57 are vertically misaligned. In addition, the orientations of the first communication pipe 53 and the second communication pipe 57 cross, and the first communication pipe 53 overlaps the inlet 58 of the second communication pipe 57 in the second expansion chamber 46 in rear view (see FIG. 8). This makes it difficult for exhaust gas to flow directly from the outlet 55 of the first communication pipe 53 to the inlet 58 of the second communication pipe 57, making it easier for the exhaust gas to expand in the second expansion chamber 46.

[0033] The exhaust gas flows into the third expansion chamber 47 from the outlet 59 of the second communication pipe 57, and the exhaust gas flows into the cap 62 of the tail pipe 61 from the third expansion chamber 47. As described above, the second communication pipe 57 is provided on the right end side of the second partition wall 44, and the front and rear extension parts 64 of the tail pipe 61 are provided on the left end side of the second partition wall 44. The bulge 49 is formed in the front wall of the chamber 41, and the outlet 59 of the second communication pipe 57 faces the base part of the bulge 49, and the cap 62 of the tail pipe 61 faces the top part of the bulge 49. Therefore, the exhaust gas from the outlet 59 of the second communication pipe 57 is diffused not only inside the bulge 49 but also over a wide range.

[0034] The outlet 59 of the second communication pipe 57 is positioned behind the third expansion chamber 47, and the cap 62 of the tail pipe 61 is positioned inside the bulging portion 49 forward of the outlet 59 of the second communication pipe 57. The front and rear extension portions 64 of the second communication pipe 57 and the tail pipe 61 are parallel, and the outlet 59 of the second communication pipe 57 and the cap 62 of the tail pipe 61 are misaligned in the front and rear. It becomes difficult for the exhaust gas to flow directly from the outlet 59 of the second communication pipe 57 to the cap 62 of the tail pipe 61, and the exhaust gas easily expands in the third expansion chamber 47. Since the cap 62 is positioned inside the bulging portion 49, the volume of the bulging portion 49 is effectively utilized for the expansion of the exhaust gas.

[0035] In this way, it is difficult for exhaust gas to flow directly from the first expansion chamber 45 to the second expansion chamber 46, it is difficult for exhaust gas to flow directly from the second expansion chamber 46 to the third expansion chamber 47, and it is difficult for exhaust gas to flow directly from the third expansion chamber 47 to the tail pipe 61. The exhaust gas is sufficiently expanded in the first to third expansion chambers 45-47, improving the silencing performance of the chamber 41. Since the exhaust gas is expanded stepwise in the first to third expansion chambers 45-47 and the energy of the exhaust sound is significantly attenuated, it is possible to arrange the chamber 41 in a narrow space below the engine 10.

[0036] The inlet pipe 50 and the second communication pipe 57 extend parallel to the front and rear extension portions 64 of the tail pipe 61, and the first communication pipe 53 extends parallel to the left and right extension portions 63 of the tail pipe 61. The left and right extension portions 63 of the tail pipe 61 cross the inlet pipe 50 and the second communication pipe 57 in front of the first communication pipe 53. The first communication pipe 53 is formed shorter than the distance L from the left end of the second communication pipe 57 to the right end of the inlet pipe 50 (second catalyst 37) (see FIG. 8). The left and right extension portions 63 of the tail pipe 61 are formed longer than the distance L from the left end of the second communication pipe 57 to the right end of the inlet pipe 50 (second catalyst 37) in the left-right direction (see FIG. 8).

[0037] As described above, the flow of exhaust gas is blocked by the left and right extension parts 63 of the tail pipe 61 in front of the first communication pipe 53 in the first expansion chamber 45 and the second expansion chamber 46. It becomes difficult for the exhaust gas to flow directly from the outlet 52 of the inlet pipe 50 to the inlet 54 of the first communication pipe 53, and it becomes difficult for the exhaust gas to flow directly from the outlet 55 of the first communication pipe 53 to the inlet 58 of the second communication pipe 57. Therefore, the exhaust gas can be sufficiently expanded in the first and second expansion chambers 45 and 46, improving the sound deadening performance of the chamber 41. The tail pipe 61 functions as a barrier that blocks the flow of exhaust gas in the first and second expansion chambers 45 and 46.

[0038] The first expansion chamber 45 is entirely surrounded by a two-layered outer wall, and the second and third expansion chambers 46, 47 are partially surrounded by a two-layered outer wall. The large plate 74 of the second expansion chamber 46 is arranged so as to overlap the outlet 55 side of the first communication pipe 53 and the inlet 58 side of the second communication pipe 57 in a plan view. The outlet 55 of the first communication pipe 53 faces a side portion of the lower large plate 74 (see FIG. 8). The small plate 76 of the third expansion chamber 47 is arranged so as to overlap the outlet 59 side of the second communication pipe 57 behind the bulging portion 49 in a plan view. The sound deadening effect of the chamber 41 is enhanced by forming a two-layered structure around the communication pipes 53, 57 where exhaust gas is concentrated.

[0039] As described above, according to this embodiment, the first expansion chamber 45 and the second and third expansion chambers 46, 47 are formed on the left and right sides inside the chamber 41, and the second expansion chamber 46 and the third expansion chamber 47 are formed on the front and rear sides. The direction of the flow of the exhaust gas from the first expansion chamber 45 to the second expansion chamber 46 and the direction of the flow from the second expansion chamber 46 to the third expansion chamber 47 cross each other. It becomes difficult for the exhaust gas to flow directly from the first expansion chamber 45 to the third expansion chamber 47, and the exhaust gas can be sufficiently expanded in the first to third expansion chambers 45-47. Even if the chamber 41 is arranged in a limited space below the engine 10, the exhaust gas can be expanded stepwise by forming the first to third expansion chambers 45-47 inside the chamber 41, thereby improving the sound deadening performance of the chamber 41.

[0040] In this embodiment, the first expansion chamber is formed on the right side of the chamber, and the second and third expansion chambers are formed on the left side of the chamber, but the first expansion chamber may be formed on the left side of the chamber, and the second and third expansion chambers may be formed on the right side of the chamber.

[0041] In addition, in this embodiment, the first communication pipe extends to the left and right, but the first communication pipe only needs to communicate between the first expansion chamber and the second expansion chamber. For example, the first communication pipe may extend diagonally.

[0042] In addition, in this embodiment, the second communication pipe extends in the front-rear direction, but the second communication pipe only needs to communicate between the second expansion chamber and the third expansion chamber. For example, the second communication pipe may extend obliquely.

[0043] In this embodiment, the outer wall of the chamber surrounding the second and third expansion chambers has a partial two-layer structure, but the outer wall of the chamber surrounding the second and third expansion chambers may have a single-layer structure as a whole. Also, the outer wall of the chamber may have a two-layer structure or a single-layer structure as a whole.

[0044] In this embodiment, the partition plate is attached to the first partition in a predetermined range from the rear end of the second catalyst to the front of the tail pipe, but the predetermined range to which the partition plate is attached can be changed as appropriate. For example, it is sufficient that the partition plate is attached to the first partition in a predetermined range from the front position of the inlet pipe to the front position of the first connecting pipe.

[0045] In addition, in this embodiment, the left and right extensions of the tail pipe are arranged in the first and second expansion chambers, but the tail pipe does not have to be arranged in the first and second expansion chambers. For example, the tail pipe may extend from the third expansion chamber to the outside of the chamber.

[0046] Furthermore, in this embodiment, a bulging portion is formed in the chamber, but as long as a sufficient volume of the third expansion chamber can be ensured, the chamber does not necessarily need to have a bulging portion.

[0047] In addition, in this embodiment, the inlet of the tail pipe is formed by a punched hole in the cap, but the shape of the inlet of the tail pipe is not particularly limited as long as it allows exhaust gas to flow in.

[0048] The exhaust system of this embodiment can also be applied as appropriate to other straddle-type vehicles, such as buggy-type three-wheeled motor vehicles. Here, the term "saddle-type vehicle" is not limited to vehicles in general on which a rider sits astride a seat, but also includes scooter-type vehicles on which a rider does not sit astride a seat.

[0049] As described above, the exhaust device (30) of this embodiment is an exhaust device that purifies exhaust gas exhausted from the engine (10) through the exhaust pipes (31a, 31b), and includes a chamber (41) arranged below the engine, an inlet pipe (50) that guides exhaust gas from the exhaust pipe to the chamber, a tail pipe (61) that discharges exhaust gas from the chamber to the outside, a first partition wall (43) that divides the inside of the chamber into a pair of left and right spaces, and a second partition wall (44) that divides one of the pair of left and right spaces into a pair of front and rear spaces, the other of the pair of left and right spaces being a first expansion chamber (45) into which the inlet pipe enters, the rear side of the pair of front and rear spaces being a second expansion chamber (46) downstream of the first expansion chamber, and the front side of the pair of front and rear spaces being a third expansion chamber (47) downstream of the second expansion chamber into which the tail pipe enters. According to this configuration, the first expansion chamber and the second and third expansion chambers are formed on the left and right sides inside the chamber, and the second expansion chamber and the third expansion chamber are formed on the front and rear sides. The direction of the flow of exhaust gas from the first expansion chamber to the second expansion chamber and the direction of the flow from the second expansion chamber to the third expansion chamber cross each other. It becomes difficult for the exhaust gas to flow directly from the first expansion chamber to the third expansion chamber, and the exhaust gas can be sufficiently expanded in the first to third expansion chambers. Even if the chamber is arranged in a limited space below the engine, by forming the first to third expansion chambers inside the chamber, the exhaust gas can be expanded in stages, improving the sound deadening performance of the chamber.

[0050] In the exhaust device of this embodiment, a first communication pipe (53) extending left and right and penetrating the first partition wall, and a second communication pipe (57) extending front and rear and penetrating the second partition wall are provided, the first expansion chamber and the second expansion chamber communicate with each other through the first communication pipe, and the second expansion chamber and the third expansion chamber communicate with each other through the second communication pipe, and the first communication pipe overlaps the inlet (58) of the second communication pipe in a rear view. With this configuration, the directions of the first communication pipe and the second communication pipe cross, making it difficult for exhaust gas to flow directly from the outlet of the first communication pipe to the inlet of the second communication pipe. Therefore, exhaust gas can be sufficiently expanded in the second expansion chamber to improve the sound deadening performance of the chamber.

[0051] In the exhaust system of this embodiment, the tail pipe extends forward and backward, penetrates the second partition wall, and then extends left and right, penetrating the first partition wall, and the left and right extension portions (63) of the tail pipe overlap the inlet of the second communicating pipe in front of the first communicating pipe in rear view. With this configuration, the flow of exhaust gas is blocked by the left and right extension portions of the tail pipe in front of the first communicating pipe, making it difficult for exhaust gas to flow directly from the outlet of the first communicating pipe to the inlet of the second communicating pipe. Therefore, the exhaust gas can be sufficiently expanded in the second expansion chamber, improving the silencing performance of the chamber.

[0052] In the exhaust system of this embodiment, the left and right extensions of the tail pipe overlap the outlet (52) of the inlet pipe in front of the first communication pipe in rear view. With this configuration, the flow of exhaust gas is blocked by the left and right extensions of the tail pipe in front of the first communication pipe, making it difficult for exhaust gas to flow directly from the outlet of the inlet pipe to the inlet of the first communication pipe. Therefore, the exhaust gas can be sufficiently expanded in the first expansion chamber to improve the silencing performance of the chamber.

[0053] In the exhaust device of this embodiment, the left and right extending portions of the tail pipe are longer than the distance from one left and right end of the second communication pipe to the other left and right end of the inlet pipe. With this configuration, the flow of exhaust gas is blocked by the left and right extending portions of the tail pipe in front of the first communication pipe in the first expansion chamber and the second expansion chamber. It becomes difficult for exhaust gas to flow directly from the outlet of the inlet pipe to the inlet of the first communication pipe, and it becomes difficult for exhaust gas to flow directly from the outlet of the first communication pipe to the inlet of the second communication pipe. Therefore, the exhaust gas can be sufficiently expanded in the first and second expansion chambers to improve the sound deadening performance of the chamber.

[0054] In the exhaust system of this embodiment, a bulge (49) that expands the third expansion chamber forward is formed on the outer wall of the chamber, the front and rear extensions of the tail pipe are parallel to the second communication pipe, and the inlet (cap 62) of the tail pipe is positioned inside the bulge forward of the outlet (59) of the second communication pipe. With this configuration, the volume of the third expansion chamber can be expanded by the bulge. The front and rear extensions of the second communication pipe and the tail pipe are parallel, making it difficult for exhaust gas to flow directly from the outlet of the second communication pipe to the inlet of the tail pipe. In addition, by positioning the inlet of the tail pipe inside the bulge, the volume of the bulge can be effectively used for the expansion of the exhaust gas. Therefore, the exhaust gas can be sufficiently expanded in the third expansion chamber to improve the sound deadening performance of the chamber.

[0055] In the exhaust device of this embodiment, the outer wall surrounding the first expansion chamber has a two-layer structure with sound absorbing material (73) packed between the outer body (71) and the inner body (72), and the outer wall surrounding the second expansion chamber and the third expansion chamber has a single-layer structure of the outer body, and a plate (partition plate 78) is attached to the first partition wall in a predetermined range from the front position of the outlet of the inlet pipe to the front position of the first communication pipe, and sound absorbing material is packed between the first partition wall and the plate. According to this configuration, the outer wall and partition wall of the chamber forming the first expansion chamber with the maximum volume have a two-layer structure packed with sound absorbing material. Therefore, it is possible to improve the sound deadening performance without making the chamber larger. In addition, the two-layer structure is minimized to suppress weight increase and to make it difficult for heat to accumulate.

[0056] Although the present embodiment has been described, other embodiments may be made by combining the above-described embodiments and modifications in whole or in part.

[0057] In addition, the technology of the present invention is not limited to the above examples, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to the progress of technology or a different technology derived therefrom, the invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea. [Explanation of symbols]

[0058] 10: Engine 30: Exhaust system 31a: Exhaust pipe 31b: Exhaust pipe 41: Chamber 43: First bulkhead 44: Second bulkhead 45: First expansion chamber 46: Second expansion chamber 47: Third expansion chamber 49 :bulge 50: Inlet pipe 52: Inlet pipe outlet 53: First connecting pipe 57: Second connecting pipe 58: Inlet of second connecting pipe 59: Outlet of the second connecting pipe 61: Tail pipe 62: Cap (tail pipe inlet) 63: Front and rear extensions of the tailpipe 64: Left and right extensions of the tailpipe 71: Outer body 72: Inner Body 73: Sound absorbing material 78: Partition plate (plate)

Claims

1. An exhaust system for purifying exhaust gas exhausted from an engine through an exhaust pipe, a chamber disposed below the engine; an inlet pipe for directing exhaust gas from the exhaust pipe to the chamber; a tail pipe for discharging exhaust gas from the chamber to the outside; a first partition wall that divides the inside of the chamber into a pair of left and right spaces; A second partition wall that divides one of the pair of left and right spaces into a pair of front and rear spaces; a first communication pipe extending laterally and penetrating the first partition wall; a second communication pipe extending forward and backward and penetrating the second partition wall, the other of the pair of left and right spaces is a first expansion chamber into which the inlet pipe enters, A rear side of the pair of front and rear spaces is a second expansion chamber downstream of the first expansion chamber, a third expansion chamber into which the tail pipe enters downstream of the second expansion chamber, and the first expansion chamber and the second expansion chamber communicate with each other through the first communication pipe, the second expansion chamber and the third expansion chamber communicate with each other through the second communication pipe, 13. An exhaust system comprising: an exhaust pipe including: an exhaust passage for exhausting said exhaust pipe; an exhaust passage for exhausting said exhaust pipe;

2. the tail pipe extends forward and backward to penetrate the second bulkhead, and then extends left and right to penetrate the first bulkhead, 2. The exhaust system according to claim 1, wherein left and right extending portions of the tail pipe overlap an inlet of the second communicating pipe in front of the first communicating pipe in a rear view.

3. 3. The exhaust system according to claim 2, wherein left and right extending portions of the tail pipe overlap the outlet of the inlet pipe in front of the first communication pipe in a rear view.

4. 4. The exhaust system according to claim 3, wherein the left and right extending portions of the tail pipe are longer than a distance from one left and right end of the second communication pipe to the other left and right end of the inlet pipe.

5. a bulge portion that expands the third expansion chamber forward is formed on an outer wall of the chamber, The front and rear extending portions of the tail pipe are parallel to the second communication pipe, 5. The exhaust system according to claim 2, wherein an inlet of the tail pipe is positioned forward of an outlet of the second communication pipe and inside the bulging portion.

6. The outer wall surrounding the first expansion chamber has a two-layer structure in which a sound-absorbing material is filled between an outer body and an inner body, and the outer walls surrounding the second expansion chamber and the third expansion chamber have a single-layer structure of the outer body, 6. An exhaust device according to claim 1, wherein a plate is attached to the first partition in a predetermined range from a forward position of the outlet of the inlet pipe to a forward position of the first connecting pipe, and sound-absorbing material is packed between the first partition and the plate.

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