Exhaust system

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 device, and particularly to an exhaust device provided with a catalyst device for purifying exhaust gas of an internal combustion engine.

Background Art

[0002] Conventionally, an exhaust device provided with a catalyst device for purifying exhaust gas of an internal combustion engine has been known.

[0003] Patent Document 1 discloses a configuration in which a cylindrical catalyst device is disposed inside a muffler of an exhaust device, and exhaust pipes are connected to both end portions on the upstream side and the downstream side of the catalyst device in the flow path direction of the exhaust gas.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the configuration of Patent Document 1, during the operation of the internal combustion engine, the catalyst device becomes high temperature due to the heat of the exhaust gas, and particularly, no consideration has been given to the countermeasure against the stress generated by the thermal expansion of the exhaust pipe on the downstream side of the catalyst device.

[0006] An object of the present invention is to solve the above problems of the prior art and provide an exhaust device capable of suppressing the generation of stress in the exhaust pipe due to the heat of the catalyst device.

Means for Solving the Problems

[0007] To achieve the above objective, the present invention provides an exhaust system (30) attached to a power unit (P), which has a muffler (32) housing a catalytic converter (C), and is characterized in that it comprises an exhaust pipe (50) disposed downstream of the housing (41) housing the catalytic converter (C) in the flow direction of the exhaust gas (G) of the power unit (P), and the exhaust pipe (50) is supported so as to be slidable relative to the housing (41) in the flow direction.

[0008] Furthermore, 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 slidably supported with respect to an intervening pipe (45) fixed to the downstream end of the housing (41).

[0009] Furthermore, a third feature is that the exhaust gas sensor (64) is mounted at a position upstream of the central part (Lh) of the total length (L) of the exhaust pipe (50) in the flow direction of the exhaust gas (G).

[0010] Furthermore, the exhaust pipe (50) is composed of multiple members (51, 52), and the exhaust gas sensor (64) is attached to the upstreammost of these multiple members (51, 52), which is a fourth characteristic feature. [Effects of the Invention]

[0011] According to the first feature, the exhaust system (30) attached to the power unit (P) has a muffler (32) that houses a catalytic converter (C), and includes an exhaust pipe (50) disposed downstream of the housing (41) that houses the catalytic converter (C) in the direction of the flow path of the exhaust gas (G) of the power unit (P). The exhaust pipe (50) is slidably supported relative to the housing (41) in the direction of the flow path. During operation of the power unit including the internal combustion engine, the catalytic converter becomes hot due to the heat of the exhaust gas, and in particular, the exhaust pipe downstream of the catalytic converter is prone to thermal expansion. However, because this exhaust pipe is slidably supported relative to the housing that houses the catalytic converter, it is possible to prevent stress from being generated between the exhaust pipe and the housing even if the exhaust pipe expands due to thermal expansion. This increases the stress tolerance of the muffler and improves the heat resistance and durability of the exhaust system.

[0012] According to the second feature, 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 slidably supported with respect to an intervening pipe (45) fixed to the downstream end of the housing (41). Therefore, by connecting the exhaust pipe via an intervening pipe rather than directly connecting it to the downstream side of the housing, 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, gaps are less likely to occur between the exhaust pipe and the housing, and a decrease in the detection accuracy of the exhaust gas sensor can be prevented.

[0013] According to the third feature, the exhaust gas sensor (64) is mounted upstream of the central part (Lh) of the total length (L) of the exhaust pipe (50) in the direction of the flow of the exhaust gas (G). By separating the exhaust gas sensor from the downstream end of the exhaust pipe, it is possible to prevent exhaust gas flowing back into the exhaust pipe from the expansion chamber of the muffler from coming into contact with the exhaust gas sensor. This makes it possible to maintain the detection accuracy of the exhaust gas sensor.

[0014] According to the fourth feature, the exhaust pipe (50) is composed of multiple members (51, 52), and the exhaust gas sensor (64) is attached to the upstream member among the multiple members (51, 52), so that the detection accuracy of the exhaust gas sensor can be maintained. [Brief explanation of the drawing]

[0015] [Figure 1] This is a right side view of a motorcycle equipped with an exhaust system according to this embodiment. [Figure 2] This is a cross-sectional view taken along line II-II in Figure 1. [Figure 3] Figure 2 shows a cross-sectional view taken along line III-III (the sensor mounting area is shown). [Figure 4] This is an enlarged cross-sectional view showing the sliding structure of the exhaust pipe. [Figure 5] Figure 2 is a cross-sectional view along the VV line. [Figure 6] Figure 6 is a cross-sectional view taken along the line VI-VI in Figure 5. [Modes for carrying out the invention]

[0016] 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 the exhaust device 30 according to this embodiment is attached. The motorcycle 1 is a scooter-type saddle vehicle having a low step floor 19 on which the driver places their feet between the steering handle 9 and the seat 10.

[0017] At the front end of the vehicle body frame, a pair of left and right front forks 2 that rotatably support the front wheels WF are supported. A front fender 3 that covers the upper part of the front wheels WF is attached to the front forks 2 that are steered by the steering handle 9. On the upper part of the handle cover 7 that covers the steering handle 9, a pair of left and right rearview mirrors 8 are arranged. The position near the upper part of the front forks 2 is covered by a pair of left and right side cowls 4. At the front part of the side cowl 4, a front cowl 5 that supports the headlight 6 is connected. At the rear part of the side cowl 4, a leg shield 20 that faces the driver's feet is connected.

[0018] The unit swing type power unit P located behind the under cowl 18 is swingably supported by the vehicle body frame covered by the under cowl 18. At the rear part of the power unit P, a rear wheel WR as a drive wheel is rotatably supported. The power unit P is suspended by the rear cushion 15 at a position closer to the rear by the vehicle body frame. At the lower part of the power unit P, a center stand 17 is swingably supported.

[0019] The power unit P including the internal combustion engine has an exhaust device 30 having an exhaust pipe 30 connected to the cylinder head of the internal combustion engine and a muffler 32 as a silencer. A muffler cover 12 is attached to the upper part of the muffler 32. At the rear parts of a pair of left and right rear cowls 11 that support the seat 10, a grab bar 13 and a tail light device 14 are attached, and a rear fender 16 is arranged below the tail light device 14.

[0020] Figure 2 is a sectional view taken along line II-II of Figure 1. Further, Figure 3 is a sectional view taken along line III-III of Figure 2 (the sensor attachment portion is shown). A catalyst device C for purifying the exhaust gas G is housed in the muffler 32 of the exhaust device 30. The muffler 32 includes a tapered connecting pipe 46 connected to the rear part of the exhaust pipe 31, a cylindrical portion 49 connected to the rear part of the connecting pipe 46, a tapered muffler front portion 33 connected to the rear part of the cylindrical portion 49, a muffler outer shell 39 connected to the rear part of the muffler front portion 33, and a muffler rear portion 48 connected to the rear part of the muffler outer shell 39.

[0021] The muffler inner shell 38 is supported on the inner wall of the muffler outer shell 39 via a plurality of buffer members 47, and the first partition wall 42 and the second partition wall 44 are supported on the inner wall of the muffler inner shell 38. The first partition wall 42 and the second partition wall 44 are connected to the rear part of the cylindrical portion 49 and house a catalyst device C for purifying the exhaust gas G, an exhaust pipe 50 supported at the rear part of the housing 41, a punching pipe 35 provided with a large number of through holes to enhance the sound absorption effect, an air supply pipe 37 that sends the exhaust gas G backward from an expansion chamber formed in front of the punching pipe 35, and an exhaust port pipe 40 connected to the rear part of the air supply pipe 37 to form an exhaust port.

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

[0023] The exhaust pipe 50 supported at the rear part of the housing 41 for housing the catalyst device C is composed of a tapered pipe 51 on the upstream side in the flow path direction of the exhaust gas and a rear pipe 52 connected to the rear part of the tapered pipe 51. The boss 63 for supporting the exhaust gas sensor 64 is attached to the tapered pipe 51 by an attachment member 62. The exhaust device 30 according to the present embodiment is characterized in that the exhaust pipe 50 is supported slidably with respect to the housing 41. Each pipe, partition wall, etc. can be made of various metals such as stainless steel, aluminum, titanium, etc.

[0024] Figure 4 is an enlarged cross-sectional view showing the sliding structure of the exhaust pipe 50. The same reference numerals indicate the same or equivalent parts. As described above, the exhaust pipe 50 consists of a tapered pipe 51 on the upstream side in the flow direction of the exhaust gas G and a rear pipe 52 connected to the downstream side of the tapered pipe 51. An annular intervening pipe 45 is fixed to the downstream end of the housing 41 that houses the catalyst by a weld bead B. The exhaust pipe 50 is slidably supported in the sliding section S with respect to the intervening pipe 45 and the second partition wall 44.

[0025] In this embodiment, the exhaust system 30 has an exhaust pipe 50 that is slidably supported relative to the housing 41 in the direction of the exhaust gas G flow path. Therefore, when the power unit P, including the internal combustion engine, is in operation, the catalytic converter C becomes hot due to the heat of the exhaust gas, and in particular the exhaust pipe 50 downstream of the catalytic converter C is prone to thermal expansion. However, because the exhaust pipe 50 is slidably supported relative to the housing 41 that houses the catalytic converter C, it is possible to prevent stress from being generated between the exhaust pipe 50 and the housing 41 even if the exhaust pipe 50 expands due to heat. This increases the stress tolerance of the muffler 32 and improves the heat resistance and durability of the exhaust system 30.

[0026] Furthermore, since the exhaust pipe 50 is slidably supported with respect to the intervening pipe 45, connecting the exhaust pipe 50 via the intervening pipe 45, rather than directly connecting it to the downstream side of the housing 41, makes it 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 slide, a gap is less likely to occur between the exhaust pipe 50 and the housing 41, preventing 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 indicate the same or equivalent parts. The tapered pipe 51 and the 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 through a through hole 51a formed in the flat portion of the tapered pipe 51.

[0028] The exhaust gas sensor 64 is mounted upstream of the central part Lh of the total length L of the exhaust pipe 50 in the flow direction of the exhaust gas G. This separates the exhaust gas sensor 64 from the downstream end of the exhaust pipe 50, thus controlling the muffler. 32 This prevents exhaust gas G flowing back from the expansion chamber into the exhaust pipe 50 from coming into contact with the exhaust gas sensor 64. This prevents a decrease in the detection accuracy of the exhaust gas sensor 64.

[0029] Furthermore, since 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 tapered section 51b that gradually narrows in diameter toward the downstream side, and a flat section 51c that has the same width as the tapered section 51b but does not narrow in diameter toward the downstream side, and the exhaust gas sensor 64 is attached to this flat section 51c. The central axis O of the exhaust gas sensor 64 is inclined such that the harness attachment section 64b to which the harness H is attached is located upstream of the sensor section 64a of the exhaust gas sensor 64. This makes it possible to position the exhaust gas sensor 64 perpendicular to the flow of exhaust gas G which is bent toward the flat section 51c upon contact with the inner wall of the tapered section 51b. This prevents a decrease in the detection accuracy of the exhaust gas sensor 64.

[0030] As described above, the exhaust system 30 according to the present invention includes an exhaust pipe 50 disposed downstream of the housing 41 housing the catalytic converter C in the flow direction of the exhaust gas G, and the exhaust pipe 50 is supported so as to be slidable relative to the housing 41 in the flow direction. Therefore, when the power unit P including the internal combustion engine is in operation, the catalytic converter C becomes hot due to the heat of the exhaust gas G, and in particular the exhaust pipe 50 downstream of the catalytic converter C is prone to thermal expansion. However, because the exhaust pipe 50 is supported so as to be slidable relative to the housing 41 housing the catalytic converter C, it is possible to prevent stress from being generated between the exhaust pipe 50 and the housing 41 even if the exhaust pipe 50 expands due to thermal expansion. This increases the stress tolerance of the muffler 32 and improves the heat resistance and durability of the exhaust system 30.

[0031] The form 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 material of the exhaust pipe and bulkhead, the number of components constituting the exhaust pipe, the setting of the fitting strength of the sliding part, etc., are not limited to the above embodiment and can be modified in various ways. The exhaust system according to the present invention is not limited to motorcycles, but can be applied to various vehicles that use a power unit including an internal combustion engine as a driving source, such as three-wheeled and four-wheeled vehicles. [Explanation of symbols]

[0032] 1...Motorcycle (vehicle), 30...Exhaust system, 32...Muffler, 41...Housing, 45...Intermediate pipe, 50...Exhaust pipe, 51...Tapered pipe (multiple components), 52...Rear pipe (multiple components), 64...Exhaust gas sensor, C...Catalytic converter, P...Power unit, G...Exhaust gas, L...Total length of exhaust pipe, Lh...Midpoint of the total length of exhaust pipe

Claims

1. In an exhaust system (30) attached to a power unit (P), which has a muffler (32) housing a catalytic converter (C), The housing (41) that houses the catalyst device (C) is provided with an exhaust pipe (50) disposed downstream in the flow direction of the exhaust gas (G) of the power unit (P), The exhaust pipe (50) is supported so as to be slidable in the flow path direction relative to the housing (41), An exhaust system characterized in that the rear portion of the exhaust pipe (50) is slidably supported with respect to a second bulkhead (44) fixed to the muffler (32).

2. The exhaust system according to claim 1, characterized in that the exhaust pipe (50) is housed inside the muffler (32).

3. An exhaust gas sensor (64) for detecting the components of the exhaust gas (G) is attached to the exhaust pipe (50). The exhaust device according to claim 1, characterized in that the exhaust pipe (50) is slidably supported with respect to an intervening pipe (45) fixed to the downstream end of the housing (41).

4. The exhaust system according to claim 3, characterized in that the exhaust pipe (50) is attached to the muffler outer shell (39) via a boss (63) and a support plate (61) that support the exhaust gas sensor (64).

5. The exhaust device according to claim 1, characterized in that the rear end of the exhaust pipe (50) is open to the expansion chamber of the muffler (32).

6. The exhaust system according to claim 3, characterized in that the exhaust gas sensor (64) is mounted at a position upstream of the central portion (Lh) of the total length (L) of the exhaust pipe (50) in the flow direction of the exhaust gas (G).

7. The exhaust pipe (50) is composed of a plurality of members (51, 52), The exhaust system according to claim 3 or 6, characterized in that the exhaust gas sensor (64) is attached to the most upstream of the plurality of members (51, 52).

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