Exhaust device

Abstract

To provide an exhaust device capable of suppressing generation of stress in an exhaust pipe due to heat of a catalyst device.SOLUTION: An exhaust device (30) having a muffler (32) that accommodates a catalyst device (C) and mounted to a power unit (P) includes an exhaust pipe (50) disposed on the downstream side in a flow passage direction of exhaust gas (G) of the power unit (P) relative to a casing (41) that accommodates the catalyst device (C). The exhaust pipe (50) is supported slidably in the flow passage direction relative to the casing (41). An exhaust gas sensor (64) for detecting components of the exhaust gas (G) is mounted to the exhaust pipe (50). The exhaust pipe (50) is supported slidably relative to an interposing pipe (45) fixed to a downstream side end part of the casing (41).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an exhaust system, and more particularly to an exhaust system equipped with a catalytic converter for purifying exhaust gas from an internal combustion engine. [Background technology]

[0002] 2. Description of the Related Art Exhaust systems equipped with catalytic converters for purifying exhaust gas from internal combustion engines have been known.

[0003] Patent Document 1 discloses a configuration in which a cylindrical catalytic device is disposed inside a muffler of an exhaust system, and exhaust pipes are connected to both the upstream and downstream ends of the catalytic device in the flow direction of the exhaust gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-227157 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the configuration of Patent Document 1 did not consider how to deal with the stress that occurs when the catalytic device becomes hot due to the heat of the exhaust gas during operation of the internal combustion engine, particularly due to thermal expansion of the exhaust pipe downstream of the catalytic device.

[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 can suppress the generation of stress in the exhaust pipe due to the heat of the catalytic converter. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention has a first feature in that an exhaust system (30) having a muffler (32) that houses a catalytic device (C) and that is attached to a power unit (P) includes an exhaust pipe (50) that is arranged downstream of a housing (41) that houses the catalytic device (C) in the flow direction of exhaust gas (G) from the power unit (P), and the exhaust pipe (50) is supported so as to be slidable in the flow direction relative to the housing (41).

[0008] A second feature is that an exhaust gas sensor (64) for detecting the components of the exhaust gas (G) is attached to the exhaust pipe (50), and the exhaust pipe (50) is supported slidably relative to an intervening pipe (45) fixed to the downstream end of the housing (41).

[0009] A third feature is that the exhaust gas sensor (64) is attached at a position upstream of the center (Lh) of the entire length (L) of the exhaust pipe (50) in the flow direction of the exhaust gas (G).

[0010] A fourth feature is that the exhaust pipe (50) is made up of a plurality of members (51, 52), and the exhaust gas sensor (64) is attached to the most upstream member of the plurality of members (51, 52). [Effects of the Invention]

[0011] According to a first feature, an exhaust system (30) having a muffler (32) that houses a catalytic converter (C) and that is attached to a power unit (P) includes an exhaust pipe (50) disposed downstream of a housing (41) that houses the catalytic converter (C) in the flow direction of exhaust gas (G) from the power unit (P), and the exhaust pipe (50) is supported slidably in the flow direction relative to the housing (41). While the catalytic converter becomes hot due to the heat of the exhaust gas during operation of a power unit including an internal combustion engine, and the exhaust pipe downstream of the catalytic converter is particularly prone to thermal expansion, the slidable support of the exhaust pipe relative to the housing that houses the catalytic converter prevents stress from occurring between the exhaust pipe and the housing even if the exhaust pipe thermally expands. This increases the stress tolerance of the muffler and improves the heat resistance and durability of the exhaust system.

[0012] According to a second feature, an exhaust gas sensor (64) for detecting components of the exhaust gas (G) is attached to the exhaust pipe (50), and the exhaust pipe (50) is supported slidably relative to an intervening pipe (45) fixed to the downstream end of the housing (41). Therefore, by connecting the exhaust pipe to the downstream side of the housing via the intervening pipe rather than directly, it is possible to increase the tolerance for thermal changes that occur between the housing and the exhaust pipe. As a result, even if the exhaust pipe is configured to be slidable, it is difficult for a gap to occur between the exhaust pipe and the housing, and it is possible to prevent a decrease in the detection accuracy of the exhaust gas sensor.

[0013] According to the third feature, the exhaust gas sensor (64) is attached at a position upstream of the center (Lh) of the entire length (L) of the exhaust pipe (50) in the flow direction of the exhaust gas (G), and thus the exhaust gas sensor is spaced apart from the downstream end of the exhaust pipe, thereby preventing exhaust gas that flows back from the expansion chamber of the muffler into the exhaust pipe from coming into contact with the exhaust gas sensor, thereby maintaining the detection accuracy of the exhaust gas sensor.

[0014] According to the fourth feature, the exhaust pipe (50) is made up of a plurality of members (51, 52), and the exhaust gas sensor (64) is attached to the most upstream member of the plurality of members (51, 52), thereby maintaining the detection accuracy of the exhaust gas sensor. [Brief explanation of the drawings]

[0015] [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 attached. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 3 is a cross-sectional view taken along line III-III in FIG. 2 (a sensor mounting portion is shown). [Figure 4] FIG. 4 is an enlarged cross-sectional view showing the sliding structure of the exhaust pipe. [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 line VI-VI in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] A preferred embodiment 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 equipped with an exhaust system 30 according to this embodiment. The motorcycle 1 is a scooter-type straddle-type vehicle having a low step floor 19 on which the rider places their feet between a steering handlebar 9 and a seat 10.

[0017] A pair of left and right front forks 2 that pivotally support a front wheel WF are supported at the front end of the body frame. A front fender 3 that covers the upper part of the front wheel WF is attached to the front forks 2, which are steered by a steering handlebar 9. A pair of left and right rearview mirrors 8 are disposed on top of a handlebar cover 7 that covers the steering handlebar 9. A pair of left and right side cowls 4 cover a position near the top of the front forks 2. A front cowl 5 that supports a headlight 6 is connected to the front of the side cowls 4. A leg shield 20 that faces the rider's feet is connected to the rear of the side cowls 4.

[0018] A unit swing type power unit P located behind the under cowl 18 is pivotally supported on the body frame covered by the under cowl 18. A rear wheel WR serving as a drive wheel is pivotally supported at the rear of the power unit P. The power unit P is suspended from the body frame by a rear cushion 15 at a position towards the rear. A center stand 17 is pivotally supported below the power unit P so that it can pivot.

[0019] An exhaust system 30 is attached to a power unit P including an internal combustion engine. The exhaust system 30 has an exhaust pipe 30 connected to the cylinder head of the internal combustion engine and a muffler 32 serving as a silencer. A muffler cover 12 is attached to the upper part of the muffler 32. A pair of left and right rear cowls 11 supporting the seat 10 are attached to the rear of the vehicle with a grab bar 13 and a tail light unit 14, and a rear fender 16 is disposed below the tail light unit 14.

[0020] Figure 2 is a cross-sectional view taken along line II-II in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 2 (the sensor mounting portion is shown). A catalytic device C that purifies exhaust gas G is housed in muffler 32 of exhaust system 30. Muffler 32 has a tapered connecting pipe 46 connected to the rear of exhaust pipe 31, a cylindrical portion 49 connected to the rear of connecting pipe 46, a tapered muffler front portion 33 connected to the rear of cylindrical portion 49, a muffler outer shell 39 connected to the rear of muffler front portion 33, and a muffler rear portion 48 connected to the rear of muffler outer shell 39.

[0021] A muffler inner shell 38 is supported on the inner wall of the muffler outer shell 39 via a plurality of buffer members 47, and a first partition 42 and a second partition 44 are supported on the inner wall of the muffler inner shell 38. The first partition 42 and the second partition 44 support a housing 41 that is connected to the rear of the cylindrical portion 49 and that houses a catalytic device C that purifies exhaust gas G, an exhaust pipe 50 that is supported on the rear of the housing 41, a punched pipe 35 that is provided with a number of through holes to improve the silencing effect, an air supply pipe 37 that sends exhaust gas G rearward from an expansion chamber formed in front of the punched pipe 35, and an exhaust port pipe 40 that is connected to the rear of the air supply pipe 37 and forms an exhaust port.

[0022] The muffler outer shell 39 is provided with a mounting hole 60 for mounting an exhaust gas sensor 64 (see FIG. 6) that detects the components of the exhaust gas G. A boss 63 in which the mounting hole 60 is formed is supported by a support plate 61, and a connecting plate 65 for mounting the support plate 61 to the outer shell 39 is connected to the outer periphery of the support plate 61.

[0023] The exhaust pipe 50, which is supported at the rear of the housing 41 that houses the catalytic device C, consists of a tapered pipe 51 on the upstream side in the exhaust gas flow direction, and a rear pipe 52 connected to the rear of the tapered pipe 51. A boss 63 that supports an exhaust gas sensor 64 is attached to the tapered pipe 51 by a mounting member 62. The exhaust system 30 according to this embodiment is characterized in that the exhaust pipe 50 is supported so as to be slidable relative to the housing 41. Each pipe, partition wall, etc. can be made of various metals such as stainless steel, aluminum, titanium, etc.

[0024] 4 is an enlarged cross-sectional view showing the sliding structure of the exhaust pipe 50. The same reference numerals as those used above indicate the same or equivalent parts. As described above, the exhaust pipe 50 comprises the tapered pipe 51 on the upstream side in the flow direction of the exhaust gas G, and the rear pipe 52 connected to the downstream side of the tapered pipe 51. An annular intermediate pipe 45 is fixed by a weld bead B to the downstream end of the casing 41 that houses the catalyst. The exhaust pipe 50 is supported by a sliding portion S so as to be slidable relative to the intermediate pipe 45 and the second partition wall 44.

[0025] In the exhaust device 30 according to this embodiment, the exhaust pipe 50 is supported so as to be slidable relative to the housing 41 in the flow direction of the exhaust gas G. Therefore, while the catalytic device C becomes hot due to the heat of the exhaust gas during operation of the power unit P including the internal combustion engine, and the exhaust pipe 50 downstream of the catalytic device C is particularly prone to thermal expansion, since the exhaust pipe 50 is supported so as to be slidable relative to the housing 41 that houses the catalytic device C, it is possible to prevent stress from occurring between the exhaust pipe 50 and the housing 41 even if the exhaust pipe 50 thermally expands. This increases the stress tolerance of the muffler 32, and improves the heat resistance and durability of the exhaust device 30.

[0026] Furthermore, because the exhaust pipe 50 is supported so as to be able to slide relative to the intervening pipe 45, by connecting the exhaust pipe 50 via the intervening pipe 45 rather than directly connecting it to the downstream side of the housing 41, it is possible to increase the tolerance for thermal changes that occur between the housing 41 and the exhaust pipe 50. As a result, even if the exhaust pipe 50 is configured to be able to slide, it is unlikely that a gap will occur between the exhaust pipe 50 and the housing 41, and it is possible to prevent a decrease in the detection accuracy of the exhaust gas sensor 64.

[0027] Figure 5 is a cross-sectional view taken along line VV in Figure 2. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5. The same reference numerals as those used above indicate the same or equivalent parts. The tapered pipe 51 and rear pipe 52 are fixed together by a weld bead B. The sensor portion 64a of the exhaust gas sensor 64 faces the exhaust passage from a through-hole 51a formed in the flat portion of the tapered pipe 51.

[0028] The exhaust gas sensor 64 is attached at a position upstream of the center portion Lh of the entire length L of the exhaust pipe 50 in the flow direction of the exhaust gas G. By separating the exhaust gas sensor 64 from the downstream end of the exhaust pipe 50, it is possible to prevent the exhaust gas G that flows back into the exhaust pipe 50 from coming into contact with the exhaust gas sensor 64. This makes it possible to prevent a decrease in the detection accuracy of the exhaust gas sensor 64.

[0029] Furthermore, because the exhaust gas sensor 64 is attached to the upstream tapered pipe 51 rather than the downstream rear pipe 52, a decrease in the detection accuracy of the exhaust gas sensor 64 can be prevented. The tapered pipe 51 has a reduced-diameter portion 51b that gradually decreases in diameter toward the downstream side and a flat plate portion 51c that does not decrease in diameter toward the downstream side and has the same width as the reduced-diameter portion 51b. The exhaust gas sensor 64 is attached to this flat plate portion 51c. The central axis O of the exhaust gas sensor 64 is inclined so that the harness attachment portion 64b, to which the harness H is attached, is located upstream of the sensor portion 64a of the exhaust gas sensor 64. This allows the exhaust gas sensor 64 to be disposed perpendicular to the flow of exhaust gas G, which contacts the inner wall of the reduced-diameter portion 51b and is bent toward the flat plate portion 51c. This prevents a decrease in the detection accuracy of the exhaust gas sensor 64.

[0030] As described above, the exhaust device 30 according to the present invention includes the exhaust pipe 50, which is disposed downstream of the housing 41 that houses the catalytic device C in the flow direction of the exhaust gas G, and the exhaust pipe 50 is supported so as to be slidable in the flow direction relative to the housing 41. Therefore, while the catalytic device C becomes hot due to the heat of the exhaust gas G during operation of the power unit P including the internal combustion engine, and the exhaust pipe 50 downstream of the catalytic device C is particularly prone to thermal expansion, since the exhaust pipe 50 is supported so as to be slidable relative to the housing 41 that houses the catalytic device C, it is possible to prevent stress from occurring between the exhaust pipe 50 and the housing 41 even if the exhaust pipe 50 thermally expands. This increases the stress tolerance of the muffler 32, and improves the heat resistance and durability of the exhaust device 30.

[0031] The configuration of the motorcycle, the shape and structure of the exhaust system, the shape and structure of the catalytic converter and housing, the shape and structure of the exhaust pipe, the materials of the exhaust pipe and partition wall, the number of components constituting the exhaust pipe, the fitting strength of the sliding portion, etc. are not limited to the above-described embodiments and can be modified in various ways. The exhaust system according to the present invention is not limited to motorcycles, but can also 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]

[0032] 1...motorcycle (vehicle), 30...exhaust system, 32...muffler, 41...casing, 45...intervening pipe, 50...exhaust pipe, 51...tapered pipe (plural members), 52...rear pipe (plural members), 64...exhaust gas sensor, C...catalyst device, P...power unit, G...exhaust gas, L...total length of exhaust pipe, Lh...central portion of total length of exhaust pipe

Claims

1. An exhaust system (30) having a muffler (32) that houses a catalytic converter (C) and that is attached to a power unit (P), an exhaust pipe (50) disposed downstream of a housing (41) that houses the catalytic device (C) in a flow direction of exhaust gas (G) from the power unit (P); The exhaust device is characterized in that the exhaust pipe (50) is supported so as to be slidable in the flow path direction relative to the housing (41).

2. An exhaust gas sensor (64) for detecting components of the exhaust gas (G) is attached to the exhaust pipe (50), 2. The exhaust system according to claim 1, wherein the exhaust pipe (50) is supported slidably relative to an intermediate pipe (45) fixed to the downstream end of the housing (41).

3. 3. The exhaust system according to claim 2, wherein the exhaust gas sensor is mounted at a position upstream of a center portion of the entire length of the exhaust pipe in the flow direction of the exhaust gas.

4. The exhaust pipe (50) is made up of a plurality of members (51, 52), 4. The exhaust system according to claim 2, wherein the exhaust gas sensor (64) is attached to the most upstream member of the plurality of members (51, 52).

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