exhaust system

Abstract

To provide an exhaust device enabling both of output improvement and muffling effects when opening an exhaust valve.SOLUTION: An exhaust device (30) includes: a muffler (34) having an expansion chamber (A); a discharge exhaust pipe (55) for discharging combustion gas (G) from the muffler (34); and an exhaust valve mechanism (40) that regulates a flow rate of the combustion gas (G) by using an opening / closing type exhaust valve (42). The discharge exhaust pipe (55) is coupled to the expansion chamber (A), and the exhaust valve (42) is provided in an upstream side exhaust pipe (50) for introducing the combustion gas (G) to the expansion chamber (A). The exhaust device is configured to introduce the combustion gas (G) to the expansion chamber (A) even while the exhaust valve (42) is closed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an exhaust system, and more particularly to an exhaust system equipped with an exhaust valve mechanism that adjusts the flow rate of combustion gas with an open / close type exhaust valve. [Background technology]

[0002] BACKGROUND ART Conventionally, in an exhaust system that purifies and silences combustion gases from an internal combustion engine before discharging them, a configuration that includes an exhaust valve mechanism that adjusts the flow rate of the combustion gases with an exhaust valve such as a butterfly valve has been known.

[0003] Patent Document 1 discloses an exhaust device in which an exhaust valve mechanism is attached to a connecting pipe connected to the upstream side of a muffler having an expansion chamber for combustion gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-85954 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration of Patent Document 1, when the exhaust valve is opened, the combustion gas is discharged to the outside of the muffler through a straight pipe without passing through the expansion chamber inside the muffler. This means that while output at high speeds is likely to improve, there is the problem that the exhaust noise is likely to become louder.

[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 that can achieve both improved output and a silencing effect when the exhaust valve is open. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an exhaust system (30) having a muffler (34) provided with an expansion chamber (A), an exhaust pipe (55) for discharging combustion gas (G) from the muffler (34), and an exhaust valve mechanism (40) for adjusting the flow rate of the combustion gas (G) with an open / close exhaust valve (42), wherein the exhaust pipe (55) is connected to the expansion chamber (A), and the exhaust valve (42) is provided in an upstream exhaust pipe (50) that introduces the combustion gas (G) into the expansion chamber (A).

[0008] A second feature of the present invention is that the combustion gas (G) is introduced into the expansion chamber (A) even when the exhaust valve (42) is closed.

[0009] A third feature is that the exhaust device (30) is attached to a vehicle (1) having a step holder (20) that supports a step bar (19) on which a passenger places their feet, and at least a portion of the exhaust valve mechanism (40) overlaps the step holder (20) in the fore-and-aft direction when viewed from the side of the vehicle body of the vehicle (1).

[0010] A fourth feature is that the cylindrical outer shell member (60) that houses the upstream exhaust pipe (50) is inclined so that the rear side of the vehicle body is positioned more outward in the vehicle width direction than the front side of the vehicle body in a plan view of the vehicle (1).

[0011] A fifth feature is that the upstream exhaust pipe (50) and the discharge exhaust pipe (55) at least partially overlap each other when viewed from the upstream side of the flow path of the combustion gas (G). [Effects of the Invention]

[0012] According to a first feature, an exhaust device (30) includes a muffler (34) provided with an expansion chamber (A), an exhaust pipe (55) that discharges combustion gas (G) from the muffler (34), and an exhaust valve mechanism (40) that adjusts the flow rate of the combustion gas (G) with an open / close exhaust valve (42). The exhaust pipe (55) is connected to the expansion chamber (A), and the exhaust valve (42) is provided in an upstream exhaust pipe (50) that introduces the combustion gas (G) into the expansion chamber (A). Therefore, by opening the exhaust valve, the combustion gas is introduced into the expansion chamber via the upstream exhaust pipe and is further discharged to the outside of the muffler from the exhaust pipe connected to the expansion chamber. Therefore, when the exhaust valve is opened, the combustion gas flows linearly, thereby increasing the output of the internal combustion engine, and the combustion gas expands in the expansion chamber, thereby improving the silencing effect.

[0013] According to the second feature, the exhaust device is configured so that the combustion gas (G) is introduced into the expansion chamber (A) even when the exhaust valve (42) is closed, thereby making it possible to obtain an exhaust device in which the combustion gas is introduced into the expansion chamber regardless of whether the exhaust valve is open or closed. This makes it possible to manufacture exhaust devices with and without an exhaust valve mechanism while using many common parts, thereby reducing manufacturing costs.

[0014] According to a third feature, the exhaust device (30) is attached to a vehicle (1) having a step holder (20) that supports a step bar (19) on which a passenger places their feet, and at least a portion of the exhaust valve mechanism (40) overlaps the step holder (20) in the fore-and-aft direction when viewed from the side of the vehicle body of the vehicle (1). Therefore, when viewed from the side of the vehicle body, the valve drive cable extending upward and forward from the exhaust valve device is easily hidden by the step holder, thereby improving the appearance of the vehicle.

[0015] According to a fourth feature, the cylindrical outer shell member (60) that houses the upstream exhaust pipe (50) is inclined so that the rear side of the vehicle body is positioned more outward in the vehicle width direction than the front side in a plan view of the vehicle (1), and the inclination of the outer shell member creates space on the inner side in the vehicle width direction, making it possible to install an exhaust valve mechanism. This makes it possible to prevent the exhaust device from becoming large.

[0016] According to the fifth feature, when viewed from the upstream side of the flow path of the combustion gas (G), the upstream exhaust pipe (50) and the discharge exhaust pipe (55) at least partially overlap each other. Therefore, when an exhaust valve is opened, the combustion gas is more likely to flow linearly from the upstream exhaust pipe to the discharge exhaust pipe, thereby achieving even better output characteristics. [Brief explanation of the drawings]

[0017] [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 an enlarged view of a portion of FIG. [Figure 3] FIG. 2 is a left side view showing the internal structure of the muffler. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5] FIG. 3 is a cross-sectional view taken along line VV in FIG. 2. [Figure 6] FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. [Figure 7] FIG. 2 is a left side view showing the internal structure of a muffler that does not have an exhaust valve mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. Fig. 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. Fig. 2 is a partially enlarged view of Fig. 1. 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 via a drive chain 18.

[0019] 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 8 and a bottom bridge 5 that support a pair of left and right front forks 2 are fixed to the upper and lower ends, respectively, of the steering stem.

[0020] 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 10 that supports a pair of left and right rearview mirrors 9 is fixed to the top of the top bridge 8. A headlight 4 and a meter device 7 are disposed in front of the head pipe F1.

[0021] A fuel tank 11 is disposed on top of the main frame F2. A pivot frame F3 supporting a pivot 22 that pivotally supports a swing arm 17 so that it can swing freely is connected to the rear end of the main frame F2, which extends rearward and downward from the head pipe F1. A step holder 20 supporting a step bar 19 on which the rider places their feet is attached to a position near the bottom of the pivot frame F3. The step holder 20 includes a heel guard 20a that supports the rider's heels. 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 frame F3.

[0022] A swing arm 17, which rotatably supports the rear wheel WR, is suspended from the main frame F2 at a position near the front by a rear cushion 24. A rear frame (not shown) is connected to the rear end of the main frame F2, supporting the seat 12 on which the rider sits and the rear cowl 14 in which the taillight unit 15 is embedded. A pair of left and right tandem step holders 13 and a rear fender 16 that covers the upper part of the rear wheel WR are supported by the lower part of the rear cowl 14.

[0023] The exhaust system 30 comprises an exhaust pipe 31 connected to the exhaust port of the internal combustion engine that constitutes the power unit P, a catalyst housing section 32 connected to the rear of the exhaust pipe 31, a connecting pipe 33 connected to the rear of the catalyst housing section 32, and a muffler 34 connected to the rear of the connecting pipe 33. The muffler 34 is suspended from the tandem step holder 13 on the right side in the vehicle width direction by an attachment stay 36. A plate-shaped heat guard 35 is attached to the top of the muffler 34 to protect the rider's feet from heat. An exhaust valve mechanism 40 that adjusts the flow rate of combustion gases by an open / close exhaust valve is provided in a small-diameter section located at the front end of the muffler 34. The exhaust valve mechanism 40 includes a rotary shaft 41 that supports the exhaust valve (see FIG. 3).

[0024] In this embodiment, in a side view of the vehicle body, the rear end of the heel guard 20a, which is part of the step holder 20, is located rearward of the front end of the pivot shaft 41 that supports the exhaust valve. In other words, at least a part of the exhaust valve mechanism 40 is configured to overlap the step holder 20 in the front-to-rear direction.

[0025] 3 is a left side view showing the internal structure of muffler 34. The outer shell of muffler 34, which is mainly made up of thin metal plate members and pipe members, consists of a front outer shell 60 that forms a small diameter portion, a tapered outer shell 61 that connects to the rear part of front outer shell 60, a large-diameter main outer shell 62 that connects to the rear part of tapered outer shell 61, and a rear outer shell 63 that connects to the rear part of main outer shell 62.

[0026] An upstream exhaust pipe 50 is disposed inside the front outer shell 60 and the tapered outer shell 61. A punched pipe 53 having a plurality of through holes formed therein is connected to the front end of the upstream exhaust pipe 50, and a connecting member 54 for connecting a muffler 34 to the rear end of the connecting pipe 33 (see FIGS. 1 and 2) is connected to the front end of the punched pipe 53.

[0027] The exhaust valve mechanism 40 uses an exhaust valve 42 that opens and closes with the driving force of an actuator to adjust the flow rate of combustion gas G flowing through the upstream exhaust pipe 50. The exhaust valve 42 is a butterfly valve made of a circular thin plate member, and is fixed to a rotating shaft 41 that rotates with the driving force of an actuator.

[0028] An annular first partition wall 51 is disposed downstream of the exhaust valve mechanism 40, between the upstream exhaust pipe 50 and the front outer shell 60. The first partition wall 51 is provided with a plurality of curved, elongated through-holes 52 through which combustion gas G passes when the exhaust valve 42 is closed. Meanwhile, a vertically elongated second partition wall 37 is disposed at a position toward the rear of the tapered outer shell 61. As a result, a front expansion chamber C is formed between the first partition wall 51 and the second partition wall 37.

[0029] The rear end of the upstream exhaust pipe 50 and the front end of the second pipe 57 each pass through the second partition 37. A vertically elongated third partition 58 is disposed inside the main outer shell 62, and a vertically elongated fourth partition 59 is disposed inside the rear outer shell 63.

[0030] The rear side of the second pipe 57 penetrates the third partition 58 at a position near the bottom of the main outer shell 62 and extends rearward to a position close to the fourth partition 59. A third pipe 56 extending in the front-to-rear direction penetrates the third partition 58 at a position near the top of the third partition 58, and the front end of an exhaust pipe 55 penetrates approximately the center of the third partition 58. The front end of the third pipe 56 extends forward to a position close to the second partition 37, and the rear end of the third pipe 56 extends rearward to a position close to the fourth partition 59. The rear end of the exhaust pipe 55 penetrates the fourth partition 59 and faces outward from an opening provided in the rear outer shell 63.

[0031] With the above-described configuration, a central expansion chamber A is formed between the second partition 37 and the third partition 58, and a rear expansion chamber B is formed between the third partition 58 and the fourth partition 59. When the exhaust valve 42 is closed, such as when the internal combustion engine is running at low speed, combustion gas G flows rearward around the outside of the upstream exhaust pipe 50 through the through-holes in the punched pipe 53 and is introduced into the front expansion chamber C through the through-holes 52 in the first partition 51.

[0032] Next, the combustion gas G introduced into the front expansion chamber C passes through the second pipe 57 into the rear expansion chamber B, and further passes through the third pipe 56 into the central expansion chamber A. Then, the combustion gas G introduced into the central expansion chamber A passes through the exhaust pipe 55 and is discharged to the outside of the muffler 34.

[0033] On the other hand, when the exhaust valve 42 is opened during high rotation of the internal combustion engine, the combustion gas G is introduced directly into the central expansion chamber A through the upstream exhaust pipe 50. The combustion gas G introduced into the central expansion chamber A is then discharged to the outside of the muffler 34 through the discharge exhaust pipe 55. In other words, the combustion gas G introduced from the front of the muffler 34 mainly passes through the central expansion chamber A and is discharged to the rear of the muffler 34.

[0034] 4 is a cross-sectional view taken along line IV-IV in FIG. 2. The same reference numerals as those used above indicate the same or equivalent parts. The upstream exhaust pipe 50 penetrates approximately the center of the second partition wall 37, and the exhaust exhaust pipe 55 (see FIG. 3) is disposed at a position overlapping the upstream exhaust pipe 50 when viewed from the upstream side of the flow path of the combustion gas G. As a result, when the exhaust valve 42 is opened, the combustion gas G flows linearly from the upstream exhaust pipe 50 toward the exhaust exhaust pipe 55, thereby achieving even better output characteristics.

[0035] Fig. 5 is a cross-sectional view taken along line VV in Fig. 2. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 2. The same reference numerals as those used above indicate the same or equivalent parts. The muffler 34 is disposed on the right side in the vehicle width direction of the motorcycle 1, and the front outer shell 60 constituting the small diameter portion of the muffler 34 is disposed at an angle so that the rear side of the vehicle body is positioned more outward in the vehicle width direction than the front side in a plan view of the vehicle body. The exhaust valve mechanism 40 is attached to the left side in the vehicle width direction of this front outer shell 60. This makes it possible to attach the exhaust valve mechanism 40 by utilizing the space created on the inner side in the vehicle width direction by the inclination of the front outer shell 60, thereby preventing the exhaust device 30 from becoming larger.

[0036] The exhaust valve mechanism 40 includes a rotating shaft 41 to which an exhaust valve 42 is attached, a disk-shaped pulley 47 fixed to the end of the rotating shaft 41, and a return spring 46 that returns the pulley 47 to its initial position (closed state). Two valve drive cables 44, 45 wound around the pulley 47 extend upward and forward from the top surface of a case member 43 that houses the pulley 47 and the return spring 46.

[0037] As described above, the step holder 20, which supports the step bar 19 on which the rider places his or her foot, is attached to the rear of the pivot frame F3 on the right side in the vehicle width direction. The brake pedal 21 is pivotally supported on the inside of the step holder 20 in the vehicle width direction. In this embodiment, the rear end of the heel guard 20a, which constitutes a part of the step holder 20, is located rearward of the front end of the pivot shaft 41 of the exhaust valve 42 in a side view of the vehicle body. In other words, at least a portion of the exhaust valve mechanism 40 is configured to overlap the step holder 20 in the front-to-rear direction. As a result, the valve drive cables 44, 45 extending upward and forward from the case member 43 are easily hidden by the step holder 20 and the heel guard 20a in a side view of the vehicle body, thereby improving the appearance of the motorcycle 1.

[0038] 7 is a left side view showing the internal structure of the muffler 34a that does not have the exhaust valve mechanism 40. The muffler 34a is configured to accommodate different specifications of the power unit of the same model, without the exhaust valve mechanism 40, while maintaining a common external appearance. With the removal of the exhaust valve mechanism 40, the upstream exhaust pipe 50 has also been removed.

[0039] 3 and 4, the only differences are the shapes and structures of the punched pipe 53a, front outer shell 60a, second partition wall 37a, and exhaust pipe 55a, and the other parts are common, thereby achieving a significant reduction in manufacturing costs. Note that the exhaust pipe 55a in this embodiment has an extended overall length to adjust the exhaust noise.

[0040] In this muffler 34a, the combustion gas G introduced from the connecting pipe 33 is introduced directly into the front expansion chamber C, then passes through the second pipe 57 into the rear expansion chamber B, and further passes through the third pipe 56 into the central expansion chamber A. Then, the combustion gas G introduced into the central expansion chamber A passes through the discharge exhaust pipe 55a and is discharged to the outside of the muffler 34a.

[0041] As described above, the exhaust device 30 according to the present invention has the muffler 34 provided with the central expansion chamber A, the exhaust exhaust pipe 55 that discharges the combustion gas G from the muffler 34, and the exhaust valve mechanism 40 that adjusts the flow rate of the combustion gas G with the open / close exhaust valve 42, in which the exhaust exhaust pipe 55 is connected to the central expansion chamber A and the exhaust valve 42 is provided in the upstream exhaust pipe 50 that introduces the combustion gas G into the central expansion chamber A. Therefore, by opening the exhaust valve 42, the combustion gas G is introduced into the central expansion chamber A via the upstream exhaust pipe 50 and is then discharged to the outside of the muffler 34 from the exhaust exhaust pipe 55 connected to the central expansion chamber A. When the exhaust valve 42 is opened, the combustion gas G flows in a straight line, thereby increasing the output of the internal combustion engine, and the combustion gas G expands in the central expansion chamber A, thereby improving the silencing effect.

[0042] Furthermore, since the exhaust device 30 is configured so that combustion gas G is introduced into the central expansion chamber A even when the exhaust valve 42 is closed, it is possible to obtain an exhaust device 30 in which combustion gas G is introduced into the central expansion chamber A regardless of the open / close state of the exhaust valve 42. This makes it possible to separately manufacture exhaust devices 34 that have the exhaust valve mechanism 40 and exhaust devices 34a that do not have the exhaust valve mechanism 40 while using many common parts, thereby reducing manufacturing costs.

[0043] Furthermore, when viewed from the upstream side of the flow path of the combustion gas G, the upstream exhaust pipe 50 and the exhaust exhaust pipe 55 at least partially overlap, so when the exhaust valve 42 is opened, the combustion gas G tends to flow linearly from the upstream exhaust pipe 50 toward the exhaust exhaust pipe 55, thereby achieving even better output characteristics.

[0044] The configuration of the motorcycle, the number of cylinders of the internal combustion engine, the shape and structure of the exhaust system, the materials and shapes of the outer shells and partitions that make up the muffler, the pipe materials, the arrangement and structure of the exhaust valve mechanism, the shape and structure of the exhaust valves, the volume ratios of the front expansion chamber, the central expansion chamber, and the rear expansion chamber are not limited to those described in the above embodiment and can be modified in various ways. For example, the total number of expansion chambers may be four or more. The exhaust system according to the present invention is not limited to motorcycles and can be applied to various vehicles, such as three-wheeled vehicles and four-wheeled vehicles, that use a power unit including an internal combustion engine as a drive source. [Explanation of symbols]

[0045] 1...motorcycle (vehicle), 30...exhaust system, 34...muffler, 40...exhaust valve mechanism, 42...exhaust valve, 50...upstream exhaust pipe, 55...discharge exhaust pipe, 51...first partition wall, 37...second partition wall, 58...third partition wall, 59...fourth partition wall, 57...second pipe, 56...third pipe, 60...front outer shell (outer shell member), A...central expansion chamber (expansion chamber), B...rear expansion chamber, C...front expansion chamber, G...combustion gas

Claims

1. An exhaust device (30) having a muffler (34) provided with an expansion chamber (A), an exhaust pipe (55) for discharging combustion gas (G) from the muffler (34), and an exhaust valve mechanism (40) for adjusting the flow rate of the combustion gas (G) with an open / close type exhaust valve (42), The exhaust pipe (55) is connected to the expansion chamber (A), the exhaust valve (42) is provided in an upstream exhaust pipe (50) that introduces the combustion gas (G) into the expansion chamber (A); a cylindrical outer shell member (60) that houses the upstream exhaust pipe (50) is inclined so that the rear side of the vehicle body is positioned more outward in the vehicle width direction than the front side of the vehicle body in a plan view of the vehicle (1) to which the exhaust device (30) is attached; The exhaust system has an exhaust valve mechanism (40) disposed inside the outer shell member (60) in the vehicle width direction.

2. An exhaust device as described in claim 1, wherein when viewed from the upstream side of the flow path of the combustion gas (G), the upstream exhaust pipe (50) and the discharge exhaust pipe (55) at least partially overlap.

3. 3. The exhaust system according to claim 1, wherein the combustion gas (G) is introduced into the expansion chamber (A) even when the exhaust valve (42) is closed.

4. The exhaust device (30) is attached to a vehicle (1) having a step holder (20) that supports a step bar (19) on which a passenger places their feet, 3. The exhaust system according to claim 1, wherein at least a portion of the exhaust valve mechanism (40) overlaps with the step holder (20) in the front-rear direction in a side view of the vehicle body of the vehicle (1).

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