Exhaust device

Description

1 / 24 EXHAUST DEVICE [Technical Field]

[001] The present invention relates to an exhaust device for an internal combustion engine, and more particularly to an exhaust device for an internal combustion engine mounted on a vehicle of the mount type. [Technical Background]

[002] Efforts to mitigate or reduce the impact on climate change have been made continuously and conventionally, and research and development on improving emissions are being conducted in order to achieve this purpose.

[003] In particular, in recent years, regulations on environmental emissions have become more stringent, making it mandatory to monitor the exhaust gas control situation. As a monitoring item, in some cases, a diagnosis of catalyst degradation for exhaust gas purification is included as an item. For example, as disclosed in Patent Document 1 to be listed below, a catalyst degradation state is determined based on the emission values ​​of the exhaust gas sensors, each fixed to the front and rear of the catalyst.

[004] Furthermore, in a vehicle of the mounting type including an exhaust chamber in an exhaust passage, an arrangement is known in which the exhaust gas sensor is attached to an exhaust pipe in the front and rear of the catalyst fixed on an upstream side of the exhaust chamber, for example, as disclosed in Patent Document 2 to be listed below.

[005] To properly diagnose degeneration of Petition 870250087822, dated 09 / 29 / 2025, p. 55 / 94 2 / 24 catalyst in this way, it is important to ensure the reliability and accuracy of detection by the exhaust gas sensors.

[006] In a case where the catalytic converter is fixed on the upstream side of the exhaust chamber and the exhaust gas sensor is fixed on the downstream side of the catalytic converter, the exhaust passage becomes long in the front-to-rear direction of the vehicle, and it may be difficult to ensure clearance for a rear wheel, a swing arm, or similar.

[007] By placing part of the catalyst in the exhaust chamber, it is possible to make the front-to-rear length compact. However, if the exhaust gas sensor is located in the exhaust chamber, the air in the exhaust chamber and the exhaust gases that have passed through the catalyst are mixed. Therefore, it is difficult to place the exhaust gas that has passed through the catalytic converter in direct contact with the exhaust gas sensor, which can reduce the accuracy of the detection. [Technical Status Document] [Patent Document] Patent Document 1: JP 2003-206784 A (Fig. 1) Patent Document 2: JP 2017-214904 A (Figs. 1 to 4) [Summary of the Invention] [Underlying problems to be solved by the invention]

[008] Moreover, in improving emissions, by providing the exhaust gas sensor at the front and rear of the catalyst in the exhaust pipe in order to properly diagnose catalyst degradation for exhaust gas treatment, a problem arises, because before the air present in an exhaust chamber and the exhaust gas that has passed through the catalyst are mixed, the exhaust gas may come into contact with the exhaust gas sensor, which improves the detection accuracy by Petition 870250087822, dated 09 / 29 / 2025, p. 56 / 94 3 / 24 exhaust gas sensor, while also allowing for a compact front-to-rear exhaust system length.

[009] One objective of the present invention is to obtain an exhaust device capable of solving such a problem, and the present invention therefore contributes to mitigating or reducing the influence on climate change. [Means to solve the problems]

[010] In order to solve the above problem, the present invention provides an exhaust device including: an exhaust chamber arranged so that at least part of the exhaust chamber overlaps an internal combustion engine in a top view; An exhaust pipe that runs under the internal combustion engine from an exhaust port on the internal combustion engine and includes an opening portion in the exhaust chamber; a catalyst retention tube, which is retained in the exhaust pipe, at least a part of which is disposed in the exhaust chamber, and which is filled with a catalyst; and an exhaust gas sensor disposed in a protruding sensor attachment portion that is provided in the exhaust pipe so as to penetrate a rear exhaust pipe and the exhaust chamber, the rear exhaust pipe constituting the exhaust pipe, being housed in the exhaust chamber and retaining the catalyst retention tube.

[011] According to the configuration above, when providing the exhaust gas sensor at the front and rear of the catalyst in the exhaust pipe in order to properly diagnose catalyst degradation for exhaust gas treatment, at least one part of the catalyst retention tube that Petition 870250087822, dated 29 / 09 / 2025, p. 57 / 94, eliminates the front-to-rear length of the exhaust device, which is arranged in the exhaust chamber. While a front-to-rear length of the exhaust device is made compact, the exhaust gas sensor is arranged in the exhaust pipe that retains the catalyst retention tube on the downstream side of the catalyst retention tube, so that the exhaust gas can be placed directly in contact with the exhaust gas sensor before the air in the exhaust chamber and the exhaust gas that has passed through the catalyst are mixed, and the accuracy of the detection can be improved. Furthermore, an improvement in emissions is achieved, thus contributing to mitigating or reducing the impact on climate change.

[012] In a preferred embodiment of the present invention, the catalyst retention tube is arranged obliquely with respect to the vehicle's centerline in the front-to-rear direction of the vehicle. By arranging the catalyst retention tube obliquely, the distance in the front-to-rear direction of the exhaust path can be made compact.

[013] In a preferred embodiment of the present invention, a downstream end portion of the exhaust pipe, in which the exhaust gas sensor is disposed, is disposed together with an inner wall surface of an exhaust chamber.

[014] By placing the exhaust gas sensor close to the inner wall surface of the exhaust chamber, the amount of exhaust chamber recess required to place the exhaust gas sensor can be reduced, compared to a case where the exhaust gas sensor is placed in the center of the exhaust chamber, and the detection accuracy of the exhaust gas sensor can be improved while ensuring the capacity of the exhaust chamber. Petition 870250087822, dated 09 / 29 / 2025, p. 58 / 94 5 / 24

[015] In a preferred embodiment of the present invention, a downstream end portion of the exhaust pipe has a reduced diameter structure.

[016] When water is splashed onto the exhaust gas sensor detection unit, the detection unit can cool down rapidly, causing a decrease in the detection accuracy of the exhaust gas sensor detection unit. However, by adopting a reduced diameter structure, the water accumulated in the exhaust chamber at the time of gas reflux due to exhaust pulsation, the outside air that entered through a drain hole, or similar, hardly comes into contact with the exhaust gas sensor, making it possible to avoid influencing the detection accuracy of the exhaust gas sensor.

[017] In a preferred embodiment of the present invention, the reduced diameter structure of the downstream end portion of the exhaust pipe is asymmetrical from left to right with respect to a centerline in the exhaust chamber of the exhaust pipe, when viewed in a direction perpendicular to a flow direction of an exhaust gas flowing in the exhaust pipe.

[018] Therefore, the exhaust gas sensor is hardly influenced by water or gas, while at the same time avoiding the influence of water or gas on detection accuracy, and the reduced diameter structure is made asymmetrical from left to right. Thus, the downstream end portion of the exhaust pipe is not excessively narrowed and thus hardly any resistance to the exhaust gas flow occurs, improving drivability.

[019] In a preferred embodiment of the present invention, in a top view of the exhaust device, the exhaust gas sensor is arranged offset from an extension line. Petition 870250087822, dated 09 / 29 / 2025, p. 59 / 94 6 / 24 central, which passes through a center in a longitudinal direction of the catalyst retention tube, and a downstream portion, relative to the exhaust gas sensor, of the downstream end portion of the exhaust tube, on one side where the exhaust gas sensor is located, is reduced in diameter to gradually approach the central extension line.

[020] By reducing the diameter of the downstream end portion of the exhaust pipe on the side where the exhaust gas sensor is located so as to gradually approach the center extension line, the flow velocity of the gas flow on the exhaust gas sensor side can be relatively reduced, and the exhaust gas is easily detected. [Effects of the Invention]

[021] According to the exhaust device of the present invention, by providing the exhaust gas sensor at the front and rear of the catalyst in the exhaust pipe in order to properly diagnose catalyst degradation for exhaust gas treatment, at least a portion of the catalyst retention tube that suppresses the front-to-rear length of the exhaust device is disposed in the exhaust chamber, and while a length in a front-to-rear direction of the exhaust device is made compact, the exhaust gas sensor is disposed in the exhaust pipe that carries the catalyst retention tube on the downstream side of the catalyst retention tube, so that the exhaust gas can be placed directly in contact with the exhaust gas sensor, before the air in the exhaust chamber and the exhaust gas that has passed through the catalyst are mixed, and the accuracy of the detection can be improved.Furthermore, an improvement in emissions is achieved, thus contributing to mitigating or reducing the impact on climate change. Petition 870250087822, dated 09 / 29 / 2025, pp. 60 / 94 7 / 24 climate. [Brief Description of the Drawings]

[022] Fig. 1 is a schematic left elevation view of a motorcycle according to the present embodiment, partially including a cross-section, except for a vehicle body cover.

[023] Fig. 2 is a left side view illustrating only an exhaust device that is withdrawn, in a direction illustrated in Fig. 1.

[024] Fig. 3 is a plan view of the exhaust device, when viewed in the direction of arrow III in Fig. 2, i.e., a top view.

[025] Fig. 4 is an enlarged side view in cross section of an exhaust pipe and an exhaust chamber taken along line IV-IV in Fig. 3.

[026] Fig. 5 is a partially enlarged view of the exhaust pipe and exhaust chamber, in a direction illustrated in Fig. 3, i.e., a top view.

[027] Fig. 6 is a perspective view of a front portion of the exhaust chamber, when viewed obliquely from the upper left front.

[028] Fig. 7 is a schematic cross-sectional view of a vehicle body taken substantially along line VII-VII in Fig. 1 and directed toward a front side of a vehicle. [Modes of carrying out the invention]

[029] An exhaust device according to an embodiment of the present invention will be described with reference to Figs. 1 to 7.

[030] In the present embodiment, an internal combustion engine is an internal combustion engine mounted in a vehicle of the type to be mounted, and the vehicle of the type to be mounted indicates a case of a motorcycle 1, and directions such Petition 870250087822, dated 09 / 29 / 2025, p. 61 / 94 8 / 24 as front, rear, left, right, and up and down in the claims and description of this specification correspond respectively to the directions of the motorcycle in this embodiment.

[031] In the drawings, the arrow FR indicates the front of the vehicle, LH indicates the left of the vehicle, RH indicates the right of the vehicle and UP indicates the top of the vehicle.

[032] Fig. 1 is a schematic left elevation view of a motorcycle 1 according to the present embodiment, including partially a cross section, except for a vehicle body cover.

[033] As illustrated in Fig. 1, in a vehicle chassis 2 of the motorcycle 1 in the present embodiment, a pair of main structures 21 extend slightly downward from a steering tube 20 to the rear, then additionally forming flexed portions 21a flexing downward in a side view, forming sharply inclined portions 21b and reaching a pivot structure 22.

[034] Furthermore, a pair of lower left and right structures 23 extending downwards from the steering tube 20 at a sharply oblique angle are substantially parallel to the sharply inclined portions 21b of the main structures 21 in a side view.

[035] A pair of left and right seat rails 24 extend rearward from the flexed portions 21a of the main structures 21, and a pair of left and right rear supports 25, which couple the rear portions of the seat rails 24 to the pivot structure 22, support the seat rails 24.

[036] The main left and right structures 21, the left and right flexed portions 21a, the sharply inclined portions Petition 870250087822, dated 09 / 29 / 2025, pp. 62 / 94 9 / 24 left and right 21b and the left and right seat rails 24 are connected by a plurality of transverse members 26 which are provided in appropriate positions.

[037] In vehicle chassis 2, as described above, a front fork 11 is pivotally supported by the steering tube 20, and a front wheel 12 is pivotally supported by a lower end of the front fork 11.

[038] In the pivot structure 22, which is connected to a lower portion of the sharply inclined portion 21b of the main structure 21, a swing arm 13 having a supported front end extends rearward, a rear wheel 14 is pivotally supported on a rear end of the swing arm 13, and a rear shock absorber 15 is interposed between the swing arm 13 and the vehicle chassis 2.

[039] A fuel tank 16 is mounted on the front portions of the main structures 21, and a passenger seat 17 is provided at the rear of the fuel tank 16, so as to be supported by the seat rails 24.

[040] In the present embodiment, in the motorcycle 1, the internal combustion engine 3 is mounted below the main structures 21 and in the front part of the sharply inclined portions 21b. In the internal combustion engine 3, a front portion of a crankcase 30 is attached to a support 23a, which is fixed to a lower end of the lower structure 23, and a rear portion of the crankcase 30 is attached to the pivot structure 22 and suspended.

[041] The internal combustion engine 3 in the present embodiment includes a transmission 4 in a rear portion in the crankcase 30 to constitute a so-called power unit, and is a four-stroke, single-cylinder, air-cooled internal combustion engine mounted on the motorcycle 1 with Petition 870250087822, dated 09 / 29 / 2025, pp. 63 / 94 10 / 24 a crankshaft 31 oriented in a motorcycle vehicle width direction 1, i.e., in the left-right direction.

[042] A main shaft, not illustrated, and an intermediate shaft 42 of the transmission 4 are provided in a rear portion in the crankcase 30 in parallel with the crankshaft 31, and the intermediate shaft 42 penetrates through the crankcase 30 to the left and projects outwards to be a final output shaft of the power unit and includes an output sprocket 43 in a protruding portion. A drive chain 44, which is wound around the output sprocket 43, is connected to a driven sprocket 45 on the rear wheel side 14 to constitute a chain transmission mechanism, and dynamic power is transferred to the rear wheel 14.

[043] The internal combustion engine 3 is suspended in an attitude in which a cylinder block 32, a cylinder head 33 and a cylinder head cover 34 are placed vertically while slightly inclining a cylinder shaft forward in the crankcase 30.

[044] An intake tube 51, in connection with an intake port 35, extends rearward from the cylinder head 33 of the internal combustion engine 3, and an intake system passage reaches an air filter box 55 via an intake member 50, including the intake tube 51, a throttle body 52, a connecting tube 53 and the like.

[045] On the front part of the cylinder head 33, an exhaust device 6 is configured in such a way that an exhaust pipe 61, in connection with an exhaust orifice 36, extends and bends downwards and extends backwards, under the internal combustion engine 3, and an exhaust passage reaches a silencer 69 on the right side of the rear wheel 14 through an exhaust chamber 65.

[046] Fig. 2 is a left side view illustrating only the device. Petition 870250087822, dated 09 / 29 / 2025, pp. 64 / 94 11 / 24 exhaust 6, which includes the exhaust pipe 61, the exhaust chamber 65 and the muffler 69, and which is removed in a direction illustrated in Fig. 1.

[047] Fig. 3 is a plan view of the exhaust device 6, when viewed in the direction of arrow III in Fig. 2, i.e., a top view.

[048] Fig. 4 is an enlarged side view in cross section of exhaust pipe 61 and exhaust chamber 65 taken along line IV-IV in Fig. 3.

[049] Fig. 5 is a partially enlarged view of the exhaust pipe 61 and the exhaust chamber 65, in a direction illustrated in Fig. 3, i.e., a top view.

[050] As illustrated in Fig. 2, in the exhaust device 6 for the internal combustion engine 3 in the present embodiment, a front exhaust pipe (an “exhaust pipe” in the present invention) 61a of the exhaust pipe 61, in connection with the exhaust orifice 36, extends under the internal combustion engine 3 and is connected to the exhaust chamber 65.

[051] As illustrated in Fig. 3, at least part of the exhaust chamber 65 is arranged to overlap the internal combustion engine 3 in a top view.

[052] As illustrated in Fig. 4, a rear end 62 of the exhaust gas flow of the front exhaust pipe 61a which constitutes the exhaust pipe 61 is fitted with an opening 66, which is formed in an outer casing 65a, in relation to the exhaust chamber 65, and a part of the fitting portion forms a front exhaust pipe fastening portion 73a, which fastens the exhaust pipe 61 and the outer casing 65a of the exhaust chamber 65 by welding or the like.

[053] Note that a drain hole, not shown, is for discharging moisture from the exhaust gas condensation in the exhaust chamber. Petition 870250087822, dated 09 / 29 / 2025, pp. 65 / 94 12 / 24 is provided in a bottom portion of the exhaust chamber 65.

[054] A rear exhaust pipe (the “exhaust pipe” 61 in the present invention) 61b, which constitutes the exhaust pipe 61 with a predetermined clearance in an extension direction from a rear end 62 of the front exhaust pipe 61a, extends and is housed in the exhaust chamber 65, and is retained on an inner surface of the outer casing 65a of the exhaust chamber 65.

[055] A connecting portion between the exhaust chamber 65 and the front exhaust gas flow end portion 63 of the rear exhaust pipe 61b, which is housed in the exhaust chamber 65, and which retains a catalyst retention tube 80 to be described later, forms a sliding exhaust pipe retention portion 71 in which the exhaust pipe 61 is slidably fitted into the opening 66 of the exhaust chamber 65. Thus, it becomes possible to allow the opening 66 to expand or contract in an axial direction of the pipe caused by the thermal expansion of the rear exhaust pipe 61b.

[056] It is worth noting that, in the present embodiment, the sliding retaining portion of the exhaust pipe 71 is formed on the front end portion 63 of the rear exhaust pipe 61b, but may be displaced in a downstream direction from the front end portion 63.

[057] The rear end of the rear exhaust pipe 61b, that is, a downstream end portion 64 of the exhaust pipe 61, includes an opening portion 61c in the exhaust chamber 65.

[058] As illustrated in Fig. 5, the rear exhaust pipe 61b includes a rear exhaust pipe protruding portion 73b, which is attached to the outer casing 65a of the exhaust chamber 65 by partial welding or similar means in the vicinity of a downstream sensor protruding portion 93 to be Petition 870250087822, dated 09 / 29 / 2025, pp. 66 / 94 13 / 24 described later, and prevents the positional displacement of the outer casing 65a of the exhaust chamber 65 in relation to the protruding downstream sensor mounting portion 93.

[059] It is worth noting that, in the present embodiment, the front exhaust pipe 61a and the rear exhaust pipe 61b are partially separated from each other in the exhaust chamber 65. However, they function in an integrated manner as the exhaust pipe 61. Hereafter, they will be collectively referred to as exhaust pipe 61, including the description in the claims.

[060] The catalyst retaining tube 80 is fixed to the front exhaust pipe 61a, extends into the interior of the rear exhaust pipe 61b and is retained inside the exhaust pipe 61 (61a, 61b). Its upstream end 80a is fixed to an inner surface of the front exhaust pipe 61a. The catalyst retaining tube 80 is slidably fitted to the inner surface of the rear pipe 61b, forms a sliding catalyst retaining portion 72 and is connected. This allows for expansion or contraction in the axial direction of the rear pipe 61b caused by the thermal expansion of the catalyst retaining tube 80.

[061] It is worth noting that, as illustrated in Fig. 3, the catalyst retention tube 80 is arranged obliquely in relation to a central line X of the vehicle in the front-to-rear direction of the vehicle, and the length in the front-to-rear direction of the exhaust passage is made compact.

[062] The catalyst retention tube 80 is filled with a catalyst 8 for exhaust gas treatment, for example, a three-way catalyst for the combined purification of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx).

[063] It is worth noting that catalyst 8 is not limited to the three-way catalyst and includes a case where different types of catalysts are arranged in Petition 870250087822, dated 09 / 29 / 2025, pp. 67 / 94 14 / 24 a longitudinal direction of the catalyst 8, which is illustrated. Furthermore, the catalyst 8 in the present embodiment is supported in a honeycomb structure, so that the exhaust gases can react as they pass through it.

[064] The catalyst retaining tube 80 is supported on the inner surfaces of the front exhaust pipe 61a and the rear exhaust pipe 61b, and a portion of the catalyst retaining tube 80 is disposed in the exhaust chamber 65.

[065] By providing the exhaust gas sensor 91 at the front and rear of the catalyst 8 in order to properly diagnose degradation of the catalyst 8 for exhaust gas treatment, in a case where a part of the catalyst 8 in the exhaust pipe 61 is disposed in the exhaust chamber 65 in order to suppress the front-to-rear length of the exhaust device 6, it is necessary to dispose of the exhaust gas sensor 91 on the downstream side so as to penetrate a plurality of members, such as the exhaust chamber 65 and the exhaust pipe 61, thus causing problems of expansion or contraction and distortion of each member due to heat.

[066] However, a connecting portion between the rear exhaust pipe 61b and the exhaust chamber 65 forms the exhaust pipe sliding retaining portion 71, and a connecting portion between the catalyst retaining pipe 80 and the rear exhaust pipe 61b forms the catalyst sliding retaining portion 72. Therefore, it becomes possible to release the displacement of each member caused by thermal expansion and mitigate the distortion that occurs in the protruding downstream sensor mounting portion 93 of the exhaust gas sensor 91, which is provided in the exhaust pipe 61 so as to penetrate the exhaust chamber 65 and the exhaust pipe 61, so that the durability, detection reliability and accuracy of the exhaust gas sensor 91 can be improved by reducing the load that occurs in the protruding portion of Petition 870250087822, dated 09 / 29 / 2025, pp. 68 / 94 15 / 24 downstream sensor mounting 93.

[067] This modality will be described in more detail below.

[068] In the exhaust pipe 61, the exhaust gas sensor 91 is provided on the upstream and downstream side of the catalyst 8 in order to detect a state of exhaust gas purification by the catalyst 8 and also to detect a degradation of the catalyst 8.

[069] The exhaust gas sensor 91 is, for example, an O2 sensor or an air-fuel ratio sensor (AFR sensor), but the type is not limited in the present embodiment.

[070] As illustrated in Figures 2 and 3, the exhaust gas sensor on the upstream side is arranged in a protruding upstream sensor mounting portion 92, which is provided at a front end of the front exhaust pipe 61a, but the exhaust gas sensor itself on the upstream side is not shown.

[071] As illustrated in Fig. 4, the exhaust gas sensor 91 on the downstream side is disposed in the downstream sensor mounting protruding portion 93, which is provided in the rear exhaust pipe 61b extending downstream from a downstream end 80b of the catalyst retaining tube 80 in the exhaust gas chamber 65, but the downstream sensor mounting protruding portion 93 penetrates the rear exhaust pipe 61b and the exhaust chamber 65, and is provided in the rear exhaust pipe 61b.

[072] The catalyst retaining tube 80 is retained by the rear exhaust pipe 61b via the sliding catalyst retaining portion 72, and thus the expansion and contraction in the axial direction of the rear exhaust pipe 61b, caused by the thermal expansion of the catalyst retaining tube 80, are suppressed, so that the distortion that occurs in the protruding retaining portion is eliminated. Petition 870250087822, dated 09 / 29 / 2025, p. 69 / 94 16 / 24 of downstream sensor 93, which is provided to penetrate both the exhaust chamber 65 and the rear exhaust pipe 61b, can be mitigated, and the durability, detection reliability and accuracy of the exhaust gas sensor 91 can be improved by reducing the load that occurs on the protruding mounting portion of downstream sensor 93.

[073] As described above, by placing at least part of the catalyst retention tube 80 in the exhaust chamber 65, the front-to-rear length of the exhaust passage is made compact. By placing the exhaust gas sensor 91 in the rear exhaust tube 61b on the downstream side of the catalyst retention tube 80, the exhaust gases can be placed directly in contact with the exhaust gas sensor 91 before the air in the exhaust chamber 65 and the exhaust gases that have passed through the catalyst 8 are mixed, so that the detection accuracy of the exhaust gas sensor 91 can be improved.

[074] As illustrated in Fig. 3, in the present embodiment, the front exhaust pipe 61a includes a bent portion 61d, which is spaced to the right in the vehicle width direction from the vehicle centerline X on the upstream end side 80a of the catalyst retaining pipe 80, and is bent on the upstream side of the catalyst 8, and a bent portion 65d forms an enlarged diameter structure 65e.

[075] Arranging the bent portion 65d in this way makes it possible to ensure a necessary exhaust pipe length for the exhaust pipe 61, while shortening the front-to-rear arrangement distance. The enlarged diameter structure arrangement 65e in the bent portion 65d makes it possible to uniformly disperse, in the front exhaust pipe 61a, the exhaust gas flow that is unevenly present in the front exhaust pipe 61a on the upstream side of the catalyst 8. By uniformly placing the exhaust gases in contact Petition 870250087822, dated 09 / 29 / 2025, pp. 70 / 94 17 / 24 with an upstream end surface of catalyst 8, the irregular flow of exhaust gas to catalyst 8 can be suppressed, and the detection accuracy of the exhaust gas sensor 91 that has passed through catalyst 8 can be improved.

[076] As illustrated in Figures 4 and 5, the downstream end portion 61c of the rear exhaust pipe 64 is reduced in diameter. When water that has accumulated in the exhaust chamber 65 at the time of the reflux of exhaust gases due to exhaust pulsation, outside air that has entered through a drain hole, or similar, comes into contact with the exhaust gas sensor 91, rapid cooling can cause a decrease in the detection accuracy of a detection unit 91a of the exhaust gas sensor 91. However, this can be avoided by the reduced diameter of the downstream end portion 64, which prevents influence on the detection accuracy of the exhaust gas sensor 91.

[077] Therefore, the durability, detection reliability and accuracy of the exhaust gas sensor 91 are improved.

[078] Furthermore, as illustrated in Fig. 5, the reduced diameter structure of the downstream end portion 64 of the rear exhaust pipe 61b is formed to be asymmetrical from left to right in a top view with respect to a Y-axis centerline in the exhaust chamber of the rear exhaust pipe 61b. Therefore, the downstream end portion 64 of the rear exhaust pipe 61b is not excessively narrowed and thus hardly any resistance to exhaust gas flow occurs, improving drivability.

[079] Additionally, as illustrated in Fig. 5, the exhaust gas sensor 91 is positioned offset from a central extension line Z that passes through the center in the longitudinal direction of the pipe. Petition 870250087822, dated 09 / 29 / 2025, pp. 71 / 94 18 / 24 catalyst retention 80 in a top view. A downstream portion, relative to the exhaust gas sensor 91, of the downstream end portion 64 of the rear exhaust pipe 61b, on the side where the exhaust gas sensor 91 is located, is reduced in diameter to gradually approach the central extension line Z.

[080] Therefore, the exhaust gas flow velocity on the exhaust gas sensor side 91 can be relatively reduced, making it easier to detect the exhaust gases.

[081] Furthermore, the downstream end portion 64 of the rear exhaust pipe 61b, on the side where the exhaust gas sensor 91 is disposed, is arranged to be in contact with an inner wall surface 65b of the exhaust chamber 65 in a top view.

[082] Therefore, the heat from the high-temperature rear exhaust pipe 61b is dissipated through the exhaust chamber 65, and thus the movement of the rear exhaust pipe 61b due to a temperature change is suppressed, so that the distortion that occurs in the protruding downstream sensor mounting portion 93 of the exhaust gas sensor 91 can be mitigated, and the durability, detection reliability and accuracy of the exhaust gas sensor 91 can be improved by reducing the load that occurs in the protruding downstream sensor mounting portion 93.

[083] Furthermore, by placing the exhaust gas sensor 91 closer to the inner wall surface of the exhaust chamber 65, the amount of recess in the exhaust chamber 65 required to place the exhaust gas sensor 91 can be reduced, compared to a case where the exhaust gas sensor 91 is placed in the center of the exhaust chamber 65, so that the detection accuracy of the exhaust gas sensor 91 can be improved while ensuring the capacity of the exhaust chamber 65. Petition 870250087822, dated 09 / 29 / 2025, pp. 72 / 94 19 / 24

[084] Fig. 6 is a perspective view of the front portion of the exhaust chamber 65, when viewed obliquely from the upper left front.

[085] As illustrated in Figures 2, 3 and 6, the recessed portion 65c, which is recessed from above and on a left lateral side, is formed in a left lateral portion of the exhaust chamber 65. The exhaust gas sensor 91 is arranged in the recessed portion 65c so that the sensing unit 91a faces downwards.

[086] It is worth noting that the recess portion 65c is provided in the exhaust chamber 65 and thus improving the access performance of a tool when positioning the exhaust gas sensor 91.

[087] Furthermore, the recessed portion 65c has an inclined shape to have a slightly descending gradient towards the left side. When water, such as rain, is splashed into the exhaust chamber 65, it hardly accumulates and flows easily.

[088] Fig. 7 is a schematic cross-sectional view of the vehicle chassis, substantially taken along line VII-VII in Fig. 1 and directed to a front side of the vehicle, and illustrates a cross-section on a rear side of the protruding downstream sensor mounting portion 93 in the exhaust chamber 65.

[089] As illustrated in Fig. 7, a harness 91b of the exhaust gas sensor 91, which is fixed in the recessed portion 65a of the exhaust chamber 65, is locked in a support 26a, which is fixed to the transverse member 26 extending upwards and present nearby. By locking the harness 91b in the support 26a once in this way, even if the arrangement configuration of the exhaust gas sensor 91 of the exhaust chamber 65 is changed, it is possible to handle it easily, and the harness 91b is routed stably and Petition 870250087822, dated 09 / 29 / 2025, pp. 73 / 94 20 / 24 insurance.

[090] The exhaust device 6 in the present embodiment described above has the following characteristics.

[091] That is, the exhaust chamber 65, which is arranged so that at least part of the exhaust chamber 65 overlaps an internal combustion engine 3 in a top view; the exhaust pipe 61, which passes under the internal combustion engine 3 from an exhaust port 36 of the internal combustion engine 3, and which includes an opening portion (61c) in the exhaust chamber (65); the catalyst retaining tube 80, which is retained in the exhaust pipe 61, and at least part of which is arranged in the exhaust chamber 65, and which is filled with a catalyst 8; and the exhaust gas sensor 91, disposed in a protruding sensor mounting portion 93 which is provided in the exhaust pipe 61b so as to penetrate a rear exhaust pipe 61b and the exhaust chamber 65, the rear exhaust pipe 61b constituting the exhaust pipe 61, being housed in the exhaust chamber 65 and retaining the catalyst retention pipe 80, are included.

[092] Thus, in providing the exhaust gas sensor at the front and rear of the catalyst in the exhaust pipe in order to properly diagnose catalyst degradation for exhaust gas treatment, it is necessary to suppress the front-to-rear length of the exhaust device 6. However, at least part of the catalyst retention tube 80 is disposed in the exhaust chamber 65, while a length in a front-to-rear direction of the exhaust device 6 is made compact, the exhaust gas sensor 91 is disposed in the rear exhaust pipe 61b on the downstream side of the catalyst retention tube 80, so that the exhaust gases can be placed in direct contact with the exhaust gas sensor 91 before the air in the exhaust chamber 65 and the exhaust gases Petition 870250087822, dated 09 / 29 / 2025, pp. 74 / 94 21 / 24 that passed through catalyst 8 are mixed, and the detection accuracy can be improved. Furthermore, an improvement in emissions is achieved, consequently contributing to mitigating or reducing the impact on climate change.

[093] As illustrated in Figure 3, the catalyst retention tube 80 is arranged obliquely in relation to the vehicle's centerline X in the front-to-rear direction of the vehicle. By arranging the catalyst retention tube 80 obliquely, the distance in the front-to-rear direction of the exhaust path can be made compact.

[094] As illustrated in Figure 5, the downstream end portion 64 of the rear exhaust pipe 61b in which the exhaust gas sensor 91 is disposed, is disposed in contact with the inner wall surface 65b of the exhaust chamber 65. By disposing of the exhaust gas sensor 91 close to the inner wall surface of the exhaust chamber 65, a quantity of exhaust chamber 65 recess for disposing of the exhaust gas sensor 91 can be reduced, compared to a case where the exhaust gas sensor 91 is disposed in the center of the exhaust chamber, and the detection accuracy of the exhaust gas sensor 91 can be improved while ensuring the capacity of the exhaust chamber 65.

[095] The downstream end portion 64 of the rear exhaust pipe 61b has the reduced diameter structure 67.

[096] When water is splashed onto the 91a detection unit of the exhaust gas sensor 91, the 91a detection unit can be rapidly cooled, causing a decrease in the detection accuracy of the 91a detection unit of the exhaust gas sensor 91. However, by adopting the reduced diameter structure 67, the water accumulated in the exhaust chamber 65 at the time of gas reflux due to exhaust pulsation, the outside air that entered through a Petition 870250087822, dated 09 / 29 / 2025, pp. 75 / 94 22 / 24 drain hole, or similar, hardly comes into contact with exhaust gas sensor 91, making it possible to avoid influencing the detection accuracy of exhaust gas sensor 91.

[097] The reduced diameter structure 67 of the downstream end portion 64 of the rear exhaust pipe 61b is asymmetrical from left to right with respect to the centerline Y in the exhaust chamber of the rear exhaust pipe 61b, when viewed in a direction perpendicular to a flow direction F of the exhaust gas flowing in the exhaust pipe 61.

[098] Therefore, the exhaust gas sensor 91 is hardly influenced by water or gas, while at the same time avoiding the influence of water or gas on detection accuracy, and the reduced diameter structure 67 is made asymmetrical from left to right. Therefore, the downstream end portion 64 of the rear exhaust pipe 61b is not excessively narrowed and thus hardly any resistance to exhaust gas flow occurs, improving drivability.

[099] In a top view of the exhaust device 6, the exhaust gas sensor 91 is arranged to be offset from a central extension line Z that passes through the center in the longitudinal direction of the catalyst retention tube 80, and a downstream portion, relative to the exhaust gas sensor 91, of the downstream end portion 64 of the rear exhaust tube 61b, on one side where the exhaust gas sensor 91 is arranged, has its diameter reduced to gradually approach the central extension line Z.

[100] By reducing the diameter of the downstream end portion 64 of the rear exhaust pipe 61b on the side where the exhaust gas sensor 91 is located to gradually approach the central extension line Z, the flow velocity of the gas flow from the exhaust gas sensor 91 can be relatively reduced, and the exhaust gas is easily detected. Petition 870250087822, dated 09 / 29 / 2025, pp. 76 / 94 23 / 24

[101] Although the exhaust device according to an embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above and, in addition to the embodiment described above, various modifications may be made without departing from the essence of the present invention.

[102] It is worth noting that, for convenience of description, left and right arrangements of the device have been described in accordance with the illustrated embodiment, but without limitation thereto, the left and right arrangements may be reversed. [List of Reference Signs] Motorcycle Vehicle chassis Internal combustion engine Exhaust device Catalyst Transverse member 26th Support Cylinder head Exhaust hole Exhaust pipe 61a Front exhaust pipe (“exhaust pipe” in the present invention) 61b Rear exhaust pipe (“exhaust pipe” in the present invention) 61c Opening portion 61d Flexed portion 61e Enlarged diameter structure Rear end Front end portion Petition 870250087822, dated 09 / 29 / 2025, pp. 77 / 94 24 / 24 Downstream end portion Exhaust chamber 65a Outer casing 65b Internal wall surface 65c Recess portion Opening Silencer Sliding retaining portion of exhaust pipe Sliding retaining portion of catalyst 73a Front exhaust pipe mounting portion 73b Rear exhaust pipe mounting portion Exhaust gas sensor 91a Detection Unit 91b Whip Protruding portion for upstream sensor mounting Protruding portion for upstream sensor mounting X Center line of the vehicle Y Centerline in the exhaust chamber (from the rear exhaust pipe 61b) Z Central extension line (from catalyst retention tube 80) Petition 870250087822, dated 09 / 29 / 2025, pp. 78 / 94

Claims

1 / 2 CLAIMS 1. Exhaust device, characterized in that it comprises: an exhaust chamber (65) arranged such that at least a portion of the exhaust chamber (65) overlaps an internal combustion engine (3) in a top view; an exhaust pipe (61) passing under the internal combustion engine (3) from an exhaust port (36) of the internal combustion engine (3), the exhaust pipe (61) having an opening portion (61c) open to the exhaust chamber (65) at its downstream end portion (64); a catalyst retention tube (80), which is retained in the exhaust pipe (61), at least a portion of which is disposed in the exhaust chamber (65), and which is filled with a catalyst (8);and an exhaust gas sensor (91) disposed in a protruding sensor attachment portion (93) which is provided in the exhaust pipe (61) so as to penetrate a rear exhaust pipe (61b) and the exhaust chamber (65), the rear exhaust pipe (61b) constituting the exhaust pipe (61), being housed in the exhaust chamber (65) and retaining the catalyst retention pipe (80), and the downstream end portion (64) of the exhaust pipe (61) including a reduced diameter structure (67), the opening portion (61c) opening into the exhaust chamber (65) being provided at a downstream end of the reduced diameter structure (67).

2. Exhaust device according to claim 1, characterized in that the catalyst retention tube (80) is arranged obliquely with respect to a vehicle centerline (X) in a front-to-rear direction. Petition 870250087822, dated 09 / 29 / 2025, p. 89 / 94 2 / 2 3. Exhaust apparatus, according to claim 1 or 2, characterized in that a downstream end portion (64) of the exhaust pipe (61), in which the exhaust gas sensor (91) is disposed, is disposed along an inner wall surface (65b) of an exhaust chamber (65).

4. Exhaust device, according to claim 1, characterized in that the reduced diameter structure (67) of the downstream end portion (64) of the exhaust pipe (61) is asymmetrical from left to right with respect to a centerline (Y) in the exhaust chamber of the exhaust pipe (61), when viewed in a direction perpendicular to a flow direction (F) of an exhaust gas flowing in the exhaust pipe (61).

5. Exhaust device according to claim 4, characterized in that in a top view of the exhaust device, the exhaust gas sensor (91) is arranged offset from a central extension line (Z) passing through a center in a longitudinal direction of the catalyst retention tube (80), and a downstream portion, relative to the exhaust gas sensor (91), of the downstream end portion (64) of the exhaust tube (61), on one side where the exhaust gas sensor (91) is arranged, is reduced in diameter to gradually approach the central extension line (Z). Petition 870250087822, dated 29 / 09 / 2025, pp. 90 / 94

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