Exhaust device for internal combustion engine

Description

1 / 26 EXHAUST DEVICE FOR INTERNAL COMBUSTION ENGINE [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 influence on climate change have been made continuously and conventionally, and research and development on emissions improvement is 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 emission control status of internal combustion engines. As a monitoring item, in some cases a diagnosis of catalyst degradation is included for exhaust gas purification. For example, as disclosed in Patent Document 1 to be listed below, a catalyst degradation state is determined based on the emission values ​​of 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, the arrangement 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 is known, for example, as disclosed in Patent Document 2 to be listed below.

[005] In order to diagnose catalyst degeneration Petition 870250087866, dated 09 / 29 / 2025, p. 46 / 86 2 / 26 properly in this way, it is important to ensure the reliability and accuracy of the exhaust gas sensors' detection.

[006] However, 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 the like.

[007] In order to solve this, in a case where part of the catalyst is stored in the exhaust chamber and the exhaust gas sensor is arranged in an exhaust pipe on its downstream side, it is necessary to provide a sensor mounting protrusion to penetrate the exhaust chamber and a plurality of members of the exhaust pipe. However, each member expands or contracts due to the thermal influence of the catalyst, thus causing distortion in the sensor mounting protrusion. Therefore, the durability, detection reliability and accuracy of the exhaust gas sensor may be affected. [Technical Status Document] [Patent Document]

[008] 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]

[009] In improving emissions, incidentally, by providing the exhaust gas sensor at the front and rear of the catalyst in the exhaust pipe in an exhaust device for an internal combustion engine, including an exhaust chamber, also in a case where a part of the catalyst in the exhaust pipe is disposed in the exhaust chamber in order to suppress a Petition 870250087866, dated 09 / 29 / 2025, p. 47 / 86 3 / 26 front-to-rear length of the exhaust device, there is a problem where the distortion that occurs in a portion of the sensor mounting protrusion of the exhaust gas sensor on the downstream side of the catalyst can be mitigated, so that the durability, detection reliability and accuracy of the exhaust gas sensor are improved by reducing the load that occurs on the sensor mounting protrusion portion.

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

[011] In order to solve the above problem, the present invention provides an exhaust device for an internal combustion engine, the exhaust device including: an exhaust chamber; an exhaust pipe connected to an exhaust port of an internal combustion engine and including an opening portion in the exhaust chamber; a catalyst retention tube retained in the exhaust pipe, at least a portion of the catalyst retention tube being disposed in the exhaust chamber; and an exhaust gas sensor disposed in a sensor attachment protrusion portion, which penetrates the exhaust pipe and exhaust chamber on a downstream side of the catalyst retention tube, and which is provided in the exhaust pipe, in which a connecting portion of the exhaust pipe, an exhaust chamber, and a front exhaust gas flow end portion of a rear exhaust pipe, which constitutes the exhaust pipe, which is stored in the Petition 870250087866, dated 09 / 29 / 2025, p. 48 / 86 4 / 26 exhaust chamber, and which retains the catalyst retention tube, forms an exhaust tube slide retention portion in which the exhaust tube is slidably fitted into an opening of the exhaust chamber, and a connecting portion between the catalyst retention tube and the exhaust tube forms a catalyst slide retention portion in which the catalyst retention tube is slidably fitted with an inner surface of the exhaust tube.

[012] 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, in a case where a part of the catalyst in the exhaust pipe is disposed in the exhaust chamber in order to suppress the front-to-rear length of the exhaust device, it is necessary to dispose of the exhaust gas sensor on the downstream side so as to penetrate a plurality of members, such as the exhaust chamber and the exhaust pipe, thus causing problems of expansion or contraction and distortion of each member due to heat.

[013] However, a connecting portion between the exhaust pipe and the exhaust chamber forms the exhaust pipe slide retaining portion, and a connecting portion between the catalyst retaining pipe and the exhaust pipe forms the catalyst slide retaining portion. Therefore, it becomes possible to release the displacement of each member caused by thermal expansion and mitigate the distortion that occurs in the sensor mounting protrusion portion downstream of the exhaust gas sensor, which is provided in the exhaust pipe so as to penetrate the exhaust chamber and the exhaust pipe, so that the durability, detection reliability and accuracy of the exhaust gas sensor can be improved by reducing the load. Petition 870250087866, dated 09 / 29 / 2025, page 49 / 86 5 / 26 that occurs in the downstream sensor mounting protrusion portion. Furthermore, improved emissions are achieved and a corresponding contribution is made to mitigating or reducing the impact on climate change.

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

[015] The downstream end portion of the exhaust pipe has a reduced diameter structure, thus making it possible to prevent water accumulated in the exhaust chamber at the time of exhaust gas reflux due to exhaust pulsation, outside air that entered through a drain hole or similar from coming into contact with the exhaust gas sensor, so that the durability, detection reliability and accuracy of the exhaust gas sensor can be improved.

[016] In a preferred embodiment of the present invention, the reduced diameter structure of the downstream end portion of the exhaust pipe is asymmetrical left-right with respect to a centerline (Y) in an exhaust chamber of the exhaust pipe, when viewed in a direction perpendicular to a flow direction (F) of exhaust gases flowing in the exhaust pipe (61).

[017] Therefore, the exhaust gas sensor is hardly affected by water or gases, and the durability, detection reliability and accuracy of the exhaust gas sensor can be improved.

[018] Furthermore, by making the reduced diameter structure asymmetrical left-right, the downstream end portion of the exhaust pipe is not excessively narrowed and thus resistance to the flow of exhaust gases hardly occurs, and drivability can be improved.

[019] In a preferred embodiment of the present invention, Petition 870250087866, dated 09 / 29 / 2025, page 50 / 86 6 / 26 in a top view, the exhaust gas sensor is arranged to be offset relative to a central extension line that 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 arranged, is reduced in diameter to gradually approach the central extension line.

[020] In this way, by reducing the diameter of the downstream end portion of the exhaust pipe on the side where the exhaust gas sensor is located to gradually approach the center extension line, the exhaust gas flow velocity on the exhaust gas sensor side can be relatively reduced, and sensing the exhaust gases is facilitated.

[021] In a preferred embodiment of the present invention, a downstream end portion of the exhaust pipe, on one side where the exhaust gas sensor is disposed, is arranged to be in contact with an inner wall surface of the exhaust chamber.

[022] In this way, by arranging the exhaust pipe to be in contact with the inner wall surface of the exhaust chamber, the heat from the high-temperature exhaust pipe is dissipated through the exhaust chamber and thus the movement of the exhaust pipe due to a temperature change is suppressed, so that the distortion that occurs in the sensor mounting protrusion portion can be mitigated, and the durability, detection reliability and accuracy of the exhaust gas sensor can be improved by reducing the load that occurs in the sensor mounting protrusion portion.

[023] In a preferred embodiment of the present invention, Petition 870250087866, dated 09 / 29 / 2025, p. 51 / 86 7 / 26 a side portion of the exhaust chamber includes a recessed portion that is recessed from above and a side, and the exhaust gas sensor is arranged such that an exhaust gas sensor sensing unit faces downwards relative to the recessed portion.

[024] By providing the recessed portion in the exhaust chamber in such a way, it becomes possible to improve the access performance of a tool in disposing of the exhaust gas sensor. [Effects of the Invention]

[025] According to the exhaust device for the internal combustion engine according to the present invention, 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, in a case where a part of the catalyst in the exhaust pipe is disposed in the exhaust chamber in order to suppress the front-to-rear length of the exhaust device, it is necessary to dispose of the exhaust gas sensor on the downstream side so as to penetrate a plurality of members, such as the exhaust chamber and the exhaust pipe, thus causing problems of expansion or contraction and distortion of each member due to heat.

[026] However, a connecting portion between the exhaust pipe and the exhaust chamber forms the exhaust pipe slide retaining portion, and a connecting portion between the catalyst retaining pipe and the exhaust pipe forms the catalyst slide retaining portion. Therefore, it becomes possible to release the displacement of each member caused by thermal expansion and mitigate the distortion that occurs in the sensor mounting protrusion portion downstream of the exhaust gas sensor, which is provided in the exhaust pipe so as to penetrate the exhaust chamber and the pipe. Petition 870250087866, dated 09 / 29 / 2025, page 52 / 86 8 / 26 exhaust, so that the durability, detection reliability and accuracy of the exhaust gas sensor can be improved by reducing the load that occurs on the downstream sensor mounting protrusion portion. In addition, improved emissions are achieved and a corresponding contribution is made to mitigating or reducing the impact on climate change. [Brief Description of the Drawings]

[027] 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.

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

[029] 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.

[030] 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.

[031] 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.

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

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

[034] An exhaust device for an internal combustion engine according to an embodiment of the present invention will be described with Petition 870250087866, dated 09 / 29 / 2025, p. 53 / 86 9 / 26 reference to Figs. 1 to 7.

[035] In the present embodiment, an internal combustion engine 3 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 an instance of a motorcycle 1, and directions such as front, rear, left, right and up and down in the claims and description of the present specification correspond respectively to the directions of the motorcycle in the present embodiment.

[036] 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.

[037] 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.

[038] As illustrated in Fig. 1, in the vehicle body 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 folded portions 21a to fold downward in a side view, forming sharply inclined portions 21b and reaching a pivot structure 22.

[039] Furthermore, a pair of lower left and right structures 23 extending downward 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.

[040] A pair of left and right seat rails 24 extend rearward from the folded portions 21a of the main structures 21, and a pair of left and right rear feet 25, which couple the rear portions of the seat rails 24 to the pivot structure 22, support the seat rails 24. Petition 870250087866, dated 09 / 29 / 2025, page 54 / 86 10 / 26

[041] The main left and right structures 21, the left and right bent portions 21a, the sharply inclined left and right portions 21b and the left and right seat rails 24 are connected by a plurality of transverse members 26, which are provided in appropriate positions.

[042] In the vehicle body 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.

[043] 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 body 2.

[044] A fuel tank 16 is attached to 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.

[045] 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 clamp 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 is suspended.

[046] 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 an internal combustion engine of cycle Petition 870250087866, dated 09 / 29 / 2025, pp. 55 / 86 11 / 26 four-stroke, single-cylinder, air-cooled engine, mounted on motorcycle 1 with a crankshaft 31 oriented in a vehicle width direction of motorcycle 1, i.e., in the left-to-right direction.

[047] 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.

[048] 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.

[049] 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 choke body 52, a connecting tube 53 and the like.

[050] 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 port 36, extends and bends downwards and extends backwards, below 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. Petition 870250087866, dated 09 / 29 / 2025, pp. 56 / 86 12 / 26

[051] Fig. 2 is a left side view illustrating only the exhaust device 6, which includes the exhaust pipe 61, the exhaust chamber 65 and the silencer 69, and which is removed, in a direction illustrated in Fig. 1.

[052] 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.

[053] 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.

[054] 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.

[055] 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 port 36, extends below the internal combustion engine 3 and is connected to the exhaust chamber 65.

[056] 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.

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

[058] Note that a drainage hole, not illustrated, for Petition 870250087866, dated 09 / 29 / 2025, p. 57 / 86 13 / 26 Discharging the moisture from condensed exhaust gases in exhaust chamber 65 is provided in a bottom portion of exhaust chamber 65.

[059] 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, is extended and stored in the exhaust chamber 65, and is retained on an inner surface of the outer casing 65a of the exhaust chamber 65.

[060] 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 stored in the exhaust chamber 65, and which retains a catalyst retention tube 80 to be described later, forms an exhaust pipe slide 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 the axial pipe direction caused by the thermal expansion of the rear exhaust pipe 61b.

[061] Note that, in the present embodiment, the exhaust pipe slide retaining portion 71 is formed on the front end portion 63 of the rear exhaust pipe 61b, but may be deflected in a downstream direction from the front end portion 63.

[062] 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.

[063] As illustrated in Fig. 5, the rear exhaust pipe 61b includes a rear exhaust pipe attachment 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 attachment protrusion portion 93 Petition 870250087866, dated 09 / 29 / 2025, pp. 58 / 86 14 / 26 to be described later, and prevents the positional displacement of the outer casing 65a of the exhaust chamber 65 in relation to the downstream sensor mounting protrusion portion 94.

[064] Note 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 integrally as the exhaust pipe 61. Hereafter, they will be collectively referred to as exhaust pipe 61, including the description in the claims.

[065] The catalyst retaining tube 80 is affixed to the front exhaust pipe 61a, extends over the inside of the rear exhaust pipe 61b and is retained within the exhaust pipe 61 (61a, 61b). Its upstream end 80a is affixed to an inner surface of the front exhaust pipe 61a. The catalyst retaining tube 80 is slidingly fitted to the inner surface of the rear pipe 61b, forms a catalyst slide 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.

[066] Note that, as illustrated in Fig. 3, the catalyst retention tube 80 is arranged obliquely with respect to a vehicle centerline X 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.

[067] The catalyst retention tube 80 is filled with a catalyst 8 for exhaust gas treatment, for example, a three-way catalyst for purifying hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) all together.

[068] Note that catalyst 8 is not limited to the three-way catalyst and includes a case where different types of catalysts are arranged in a Petition 870250087866, dated 09 / 29 / 2025, page 59 / 86 15 / 26 longitudinal direction of catalyst 8, which is illustrated. Furthermore, catalyst 8 in the present embodiment is supported on a honeycomb structure so that the exhaust gases can react as they pass through.

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

[070] 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.

[071] However, a connecting portion between the rear exhaust pipe 61b and the exhaust chamber 65 forms the exhaust pipe slide retaining portion 71, and a connecting portion between the catalyst retaining pipe 80 and the rear exhaust pipe 61b forms the catalyst slide 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 downstream sensor mounting protrusion 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 protrusion portion. Petition 870250087866, dated 09 / 29 / 2025, pp. 60 / 86 16 / 26 downstream sensor mounting 93.

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

[073] 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 the degradation of the catalyst 8.

[074] 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.

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

[076] As illustrated in Fig. 4, the exhaust gas sensor 91 on the downstream side is disposed in the downstream sensor attachment protrusion portion 93, which is provided in the rear exhaust pipe 61b extending downstream from a downstream end 80b of the catalyst retention pipe 80 in the exhaust gas chamber 65, but the downstream sensor attachment protrusion portion (a “sensor attachment protrusion portion” in the present invention) 93 penetrates the rear exhaust pipe 61b and the exhaust gas chamber 65, and is provided in the rear exhaust pipe 61b.

[077] The catalyst retaining tube 80 is retained by the rear exhaust pipe 61b via the catalyst slide retaining portion 72 and thus 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, Petition 870250087866, dated 09 / 29 / 2025, pp. 61 / 86 17 / 26 so that the distortion that occurs in the downstream sensor mounting protrusion portion 93, which is provided to penetrate both the exhaust chamber 65 and the rear exhaust pipe 61b, can be mitigated, and durability, detection reliability and accuracy of the exhaust gas sensor 91 can be improved by reducing the load that occurs in the downstream sensor mounting protrusion portion 93.

[078] As described above, by placing at least part of the catalyst retention tube 80 in the exhaust chamber 65, the length in the front-to-rear direction 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 together, so that the detection accuracy of the exhaust gas sensor 91 can be improved.

[079] 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.

[080] The arrangement of the folded portion 65d in such a way makes it possible to ensure a necessary exhaust pipe length from the exhaust pipe 61, while shortening a front-to-rear arrangement distance. The enlarged diameter structure arrangement 65e in the folded portion 65d makes it possible to uniformly disperse, in the front exhaust pipe 61a, the flow of exhaust gases present irregularly in the front exhaust pipe 61a on side a. Petition 870250087866, dated 09 / 29 / 2025, pp. 62 / 86 18 / 26 upstream of catalyst 8. By uniformly placing the exhaust gases in contact with an upstream end surface of catalyst 8, the irregular flow of exhaust gases 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.

[081] As illustrated in Figures 4 and 5, the downstream end portion 61c of the rear exhaust pipe 61b is reduced in diameter. When water accumulates in the exhaust chamber 65 at the time of exhaust gas reflux 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, and the influence on the sensing accuracy of the exhaust gas sensor 91 can be avoided.

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

[083] 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 left-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 exhaust gas flow resistance hardly occurs, and drivability is improved.

[084] Additionally, as illustrated in Fig. 5, the exhaust gas sensor 91 is positioned at an offset relative to a central extension line Z, which passes through the center in the longitudinal direction of the tube. Petition 870250087866, dated 09 / 29 / 2025, pp. 63 / 86 19 / 26 of 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.

[085] Therefore, the exhaust gas flow velocity on the exhaust gas sensor side 91 can be relatively reduced, and sensing the exhaust gases is facilitated.

[086] 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.

[087] 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 downstream sensor mounting protrusion 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 downstream sensor mounting protrusion portion 93.

[088] 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 the capacity of the exhaust chamber 65 is guaranteed. Petition 870250087866, dated 09 / 29 / 2025, pp. 64 / 86 20 / 26

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

[090] As illustrated in Figures 2, 3 and 6, the recessed portion 65c, which is recessed from above and on a left side, is formed in a left side 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.

[091] Note that recess portion 65a is provided in the exhaust chamber 65 and thus the access performance of a tool when disposing of the exhaust gas sensor 91 is improved.

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

[093] Fig. 7 is a schematic cross-sectional view of the vehicle body, 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 downstream sensor mounting protrusion portion 93 in the exhaust chamber 65.

[094] As illustrated in Fig. 7, a cable 91b of the exhaust gas sensor 91, which is fixed in the recessed portion 65a of the exhaust chamber 65, is locked in a foot 26a, which is affixed to the transverse member 26 that extends upwards and is present nearby. By locking the cable 91b in the foot 26a once in such a 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 cable 91b is routed stably and safely.

[095] Exhaust device 6 for internal combustion engine 3 Petition 870250087866, dated 09 / 29 / 2025, pp. 65 / 86 21 / 26 in the present modality described above has the following characteristics.

[096] That is to say, the exhaust chamber 65; the exhaust pipe 61, which is connected to the exhaust port 36 of the internal combustion engine 3, and which includes the opening portion 61c in the exhaust chamber 65; the catalyst retaining tube 80, which is retained in the exhaust pipe 61, and at least a part of which is disposed in the exhaust chamber 65; and the exhaust gas sensor 91 disposed in the sensor attachment protrusion portion 93, which penetrates the rear exhaust pipe 61b and the exhaust chamber 65 on the downstream side of the catalyst retaining tube 80, and which is provided in the rear exhaust pipe 61b, are provided.

[097] A connecting portion between the exhaust chamber 65 and the front exhaust gas flow end portion 63 of the rear exhaust pipe 61b, which constitutes the exhaust pipe 61, which is stored in the exhaust chamber 65 and which retains the catalyst retention tube 80, forms the exhaust pipe slide retention portion 71, in which the rear exhaust pipe 61b is slidably fitted into the opening 66 of the exhaust chamber 65, and a connecting portion between the catalyst retention tube 80 and the rear exhaust pipe 61b forms the catalyst slide retention portion 72, in which the catalyst retention tube 80 is slidably fitted with an inner surface of the rear exhaust pipe 61b.

[098] When providing the exhaust gas sensor 91 on the front and rear of the catalyst 8 in the exhaust pipe 61 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 mounting protrusion portion 93 on the downstream side so as to Petition 870250087866, dated 09 / 29 / 2025, pp. 66 / 86 22 / 26 penetrate into a plurality of members, such as the exhaust chamber 65 and the rear exhaust pipe 61b, therefore causing problems of expansion or contraction and distortion of each member due to heat.

[099] However, a connecting portion between the rear exhaust pipe 61b and the exhaust chamber 65 forms the exhaust pipe slide retaining portion 71, and a connecting portion between the catalyst retaining pipe 80 and the rear exhaust pipe 61b forms the catalyst slide 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 downstream sensor mounting portion 93 of the exhaust gas sensor 91, which is provided in the rear exhaust pipe 61b so as to penetrate the exhaust chamber 65 and the rear exhaust pipe 61b, 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 downstream sensor mounting protrusion portion 93.Furthermore, improvements in emissions are achieved, and a corresponding contribution is made to mitigating or reducing the impact on climate change.

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

[101] The downstream end portion 64 of the rear exhaust pipe 61b has a reduced diameter structure 67 and thus it becomes possible to prevent water accumulated in the exhaust chamber 65 at the time of exhaust gas reflux due to exhaust pulsation, outside air that entered through a drain hole or similar from coming into contact with the exhaust gas sensor 91, so that the durability, detection reliability and accuracy of the exhaust gas sensor are improved.

[102] The reduced diameter structure 67 of the end portion a Petition 870250087866, dated 09 / 29 / 2025, pp. 67 / 86 23 / 26 downstream 64 of the rear exhaust pipe 61b is asymmetrical left-right with respect to the Y-axis of the exhaust chamber of the rear exhaust pipe 61b, when viewed in a direction perpendicular to the flow direction F of exhaust gases flowing in the exhaust pipe 61.

[103] Therefore, the exhaust gas sensor 91 is hardly affected by water or gases, and the durability, detection reliability and accuracy of the exhaust gas sensor 91 can be improved.

[104] Furthermore, by making the reduced diameter structure 67 asymmetrical left-right, the downstream end portion 64 of the rear exhaust pipe 61b is not excessively narrowed and thus resistance to the flow of exhaust gases hardly occurs, and drivability can be improved.

[105] In a top view, the exhaust gas sensor 91 is arranged to be offset from the central extension line Z, which passes through the 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 rear exhaust tube 61b, on the side where the exhaust gas sensor 91 is arranged, has its diameter reduced to gradually approach the central extension line Z.

[106] Therefore, the exhaust gas flow velocity on the exhaust gas sensor side 91 can be relatively reduced, and sensing the exhaust gases is facilitated.

[107] 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 the inner wall surface 65b of the exhaust chamber 65.

[108] Therefore, the heat from the rear exhaust pipe 61b at high Petition 870250087866, dated 09 / 29 / 2025, pp. 68 / 86 24 / 26 temperature 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 downstream sensor mounting protrusion portion 93 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 downstream sensor mounting protrusion portion 93.

[109] A side portion of the exhaust chamber 65 includes a recessed portion 65c that is recessed from above and a side portion, and the exhaust gas sensor 91 is arranged in such a way that the sensing unit 91a of the exhaust gas sensor 91 faces downwards with respect to the recessed portion 65c.

[110] By providing the recess portion 65c in the exhaust chamber 65 in such a manner, it becomes possible to improve the access performance of a tool in disposing of the exhaust gas sensor 91.

[111] Up to now, although the exhaust device for the internal combustion engine according to an embodiment of the present invention has been described, the present invention is not limited to the embodiment described above and, in addition to the embodiment described above, various modifications can be made without departing from the essence of the present invention.

[112] Note that, for convenience of description, the left and right arrangements of the device have been described according to the illustrated embodiment, but without limitation thereto, the left and right arrangements may be reversed. [List of Reference Signs] Motorcycle Vehicle body Internal combustion engine Petition 870250087866, dated 09 / 29 / 2025, pp. 69 / 86 25 / 26 Exhaust device Catalyst Transverse member 26th Foot Cylinder head Exhaust door 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 Double Portion 61e Enlarged diameter structure Rear end Front end portion Downstream end portion Exhaust chamber 65a Outer casing 65b Internal wall surface 65c Recess portion Opening Silencer Exhaust pipe slide retaining portion Catalyst slide retaining portion 73a Front exhaust pipe attachment portion 73b Rear exhaust pipe attachment portion Exhaust gas sensor 91a Detection Unit Petition 870250087866, dated 09 / 29 / 2025, pp. 70-86 26 / 26 91b Cape Upstream sensor mounting protrusion portion Downstream sensor mounting protrusion portion (“sensor mounting protrusion portion” in the present invention) X Center line of the vehicle Y Center line in the exhaust chamber (from the rear exhaust pipe) 61b) Z Central extension line (from catalyst retention tube 80) Petition 870250087866, dated 09 / 29 / 2025, pp. 71 / 86

Claims

1 / 3 CLAIMS 1. Exhaust device for an internal combustion engine, the exhaust device characterized in that it comprises: an exhaust chamber (65); an exhaust pipe (61) connected to an exhaust port (36) of the internal combustion engine (3), and including an opening portion (61c) in the exhaust chamber (65); a catalyst retention tube (80) retained in the exhaust pipe (61) and filled with a catalyst (8), at least a portion of the catalyst retention tube (80) being disposed in the exhaust chamber (65); and an exhaust gas sensor (91) disposed in a sensor mounting protrusion portion (93), which penetrates the exhaust pipe and exhaust chamber (65) on a downstream side of the catalyst retaining tube (80), and which is provided in the exhaust pipe (61), wherein a connecting portion between the exhaust chamber (65) and a front exhaust gas flow end portion (63) of a rear exhaust pipe (61b),which constitutes the exhaust pipe (61), which is stored in the exhaust chamber (65), and which retains the catalyst retention pipe (80), forms an exhaust pipe slide retention portion (71) in which the exhaust pipe (61) is slidably fitted into an opening (66) of the exhaust chamber (65), and a connecting portion between the catalyst retention pipe (80) and the exhaust pipe (61) forms a catalyst slide retention portion (72) in which the catalyst retention pipe (61) is slidably fitted with an inner surface of the exhaust pipe (61).

2. Exhaust device for internal combustion engine, according to claim 1, characterized in that a portion of Petition 870250087866, dated 09 / 29 / 2025, page 72 / 86 2 / 3 downstream end (64) of the exhaust pipe (61) has a reduced diameter structure (67).

3. Exhaust device for internal combustion engine, according to claim 2, characterized in that the reduced diameter structure (67) of the downstream end portion (64) of the exhaust pipe (61) is asymmetrical left-right with respect to a centerline (Y) in an exhaust chamber of the exhaust pipe (61), when viewed in a direction perpendicular to a flow direction (F) of exhaust gases flowing in the exhaust pipe (61).

4. Exhaust device for internal combustion engine, according to claim 2 or 3, characterized in that in a top view, the exhaust gas sensor (91) is arranged to be deflected relative to 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 a side where the exhaust gas sensor (91) is arranged, is reduced in diameter to gradually approach the central extension line (Z).

5. Exhaust device for internal combustion engine, according to claim 1 or 2, characterized in that a downstream end portion (64) of the exhaust pipe (61), on a side where the exhaust gas sensor (61) is disposed, is disposed to be in contact with an inner wall surface (65b) of the exhaust chamber (66).

6. Exhaust device for internal combustion engine, according to claim 5, characterized in that a side portion of the exhaust chamber (65) includes a recessed portion (65c) that is recessed upwards and laterally, and the exhaust gas sensor (91) is arranged such that a sensing unit (91) of the exhaust gas sensor (91) faces downwards relative to the recessed portion (65c).

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