Exhaust device

Abstract

Disclosed is an exhaust device provided with: an exhaust chamber (65) provided so as to overlap an internal combustion engine (3) in plan view; an exhaust pipe (61) that passes below the internal combustion engine from an exhaust port (36) of the internal combustion engine and has an opening (61c) in the exhaust chamber; a catalyst holding pipe (80) which is held in the exhaust pipe, at least a portion of which is provided in the exhaust chamber, and which is filled with a catalyst (8); and an exhaust gas sensor (91) that is provided on a sensor attachment boss part (93) that is provided on the exhaust pipe (61) so as to penetrate through the exhaust chamber (65) and a rear exhaust pipe (61b) that constitutes the exhaust pipe, is housed in the exhaust chamber, and holds the catalyst holding pipe, and thereby, the exhaust gas sensor (91) is attached to the sensor attachment boss part (93), and the exhaust gas sensor (91) is attached to the sensor attachment boss part (93). When exhaust gas sensors are arranged in front of and behind a catalyst in an exhaust pipe for properly diagnosing deterioration of the catalyst for exhaust gas treatment, the length of an exhaust path in the front-back direction can be compactly set, the detection accuracy of the exhaust gas sensors can be improved, emission can be improved, and climate change or influence can be alleviated.

Description

TECHNICAL FIELD

[0001] The present application relates to an exhaust device, and particularly relates to an exhaust device for an internal combustion engine mounted on a straddle-type vehicle. BACKGROUND

[0002] In the past, efforts for mitigating climate change or reducing the impact have continued, and research related to emission improvement has been conducted for the realization thereof.

[0003] In particular, in recent years, restrictions on environmental load have become strict, and there is an obligation to monitor the control state of exhaust gas. As a monitoring item, deterioration diagnosis of a catalyst that purifies exhaust gas is sometimes included as an item, and for example, as shown in the following Patent Literature 1, the deterioration state of the catalyst is determined based on the output values of exhaust gas sensors installed before and after the catalyst.

[0004] In a straddle-type vehicle having an exhaust chamber in an exhaust passage, as shown in the following Patent Literature 2, for example, a configuration in which an exhaust gas sensor is installed on an exhaust pipe before and after a catalyst installed on the upstream side of the exhaust chamber is known.

[0005] In order to thus properly perform catalyst deterioration diagnosis, it is important to ensure the detection reliability and accuracy of the exhaust gas sensor.

[0006] However, in the case where the catalyst is installed on the upstream side of the exhaust chamber and the exhaust gas sensor on the downstream side of the catalyst, the exhaust passage becomes long in the vehicle front-rear direction, and it is sometimes difficult to ensure the clearance from the rear wheel, swing arm, or the like.

[0007] By providing a part of the catalyst inside the exhaust chamber, it is possible to make the front-rear length compact, but in the case where the exhaust gas sensor is provided inside the exhaust chamber, the air inside the exhaust chamber mixes with the exhaust gas that has passed through the catalyst, and thus it is difficult to make the exhaust gas after passing through the catalyst directly contact the exhaust gas sensor, and the detection accuracy can be reduced.

[0008] PRIOR ART DOCUMENTS

[0009] PATENT LITERATURE

[0010] Patent Literature 1: Japanese Patent Application Publication No. 2003-206784 Figure 1 )

[0011] Patent Literature 2: Japanese Patent Application Publication No. 2017-214904 Figures 1-4 ) SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] However, in emission improvement, the problem is that when an exhaust gas sensor is provided before and after a catalyst in an exhaust pipe for proper deterioration diagnosis of the catalyst for exhaust gas treatment, the front and rear direction length of the exhaust device can be set compactly, and before air in the exhaust chamber mixes with exhaust gas after passing through the catalyst, the exhaust gas can be brought into direct contact with the exhaust gas sensor, thereby improving the detection accuracy of the exhaust gas sensor.

[0014] The present application aims to achieve an exhaust device that can solve the problem, and further contribute to mitigating climate change or reducing the impact.

[0015] Technical solution for solving the technical problem

[0016] To solve the above problem, the exhaust device of the present application has: an exhaust chamber provided to overlap at least a part of an internal combustion engine in plan view; an exhaust pipe having an opening portion in the exhaust chamber from an exhaust port of the internal combustion engine through the lower part of the internal combustion engine; a catalyst holding pipe held by the exhaust pipe, at least a part of which is provided in the exhaust chamber and filled with a catalyst; and an exhaust gas sensor provided to a sensor mounting boss portion provided to the exhaust pipe in such a manner as to pass through the rear exhaust pipe and the exhaust chamber, the rear exhaust pipe constituting the exhaust pipe and housed in the exhaust chamber, holding the catalyst holding pipe.

[0017] According to the above structure, when an exhaust gas sensor is provided before and after a catalyst in an exhaust pipe for proper deterioration diagnosis of the catalyst for exhaust gas treatment, by providing at least a part of the catalyst holding pipe, which suppresses the front and rear length of the exhaust device, in the exhaust chamber, the front and rear direction length of the exhaust path can be set compactly, and by providing the exhaust gas sensor to the exhaust pipe holding the catalyst holding pipe on the downstream side of the catalyst holding pipe, the exhaust gas can be brought into direct contact with the exhaust gas sensor before air in the exhaust chamber mixes with exhaust gas after passing through the catalyst, so the detection accuracy can be improved. Furthermore, emission improvement is achieved, and further contributes to mitigating climate change or reducing the impact.

[0018] According to the preferred embodiment of the present application, the catalyst holding pipe is provided obliquely with respect to the vehicle center line in the vehicle front and rear direction, and by obliquely providing the catalyst holding pipe, the front and rear direction distance of the exhaust path can be made compact.

[0019] According to the preferred embodiment of the present application, the downstream end portion of the exhaust pipe in which the exhaust gas sensor is provided is arranged along the inner wall surface of the exhaust chamber so as to abut against the inner wall surface of the exhaust chamber. By arranging the exhaust gas sensor close to the inner wall surface of the exhaust chamber, the amount of recess of the exhaust chamber for arranging the exhaust gas sensor can be reduced compared to the case where the exhaust gas sensor is arranged 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.

[0020] According to the preferred embodiment of the present application, the downstream end portion of the exhaust pipe has a reduced diameter structure.

[0021] If water splashes on the detection portion of the exhaust gas sensor, it is possible that the detection portion of the exhaust gas sensor is sharply cooled and becomes a cause of a decrease in the detection accuracy of the exhaust gas sensor, but by forming a reduced diameter structure, water accumulated in the exhaust chamber at the time of backflow of gas due to exhaust pulsation, external gas intruding from the drain hole, and the like are less likely to come into contact with the exhaust gas sensor, and it is possible to prevent an influence on the sensing accuracy of the exhaust gas sensor.

[0022] According to the preferred embodiment of the present application, the reduced diameter structure of the downstream end portion of the exhaust pipe is asymmetric with respect to the center line in the exhaust chamber of the exhaust pipe when viewed in a direction perpendicular to the flow direction of exhaust gas flowing in the exhaust pipe.

[0023] Therefore, the exhaust gas sensor is less likely to be affected by water and gas, and an influence on the sensing accuracy is prevented, and by forming the reduced diameter structure to be asymmetric to the left and right, the downstream end portion of the exhaust pipe is not excessively throttled, and thus is less likely to become a resistance to the flow of exhaust gas, and it is possible to improve the drivability.

[0024] According to the preferred embodiment of the present application, when the exhaust device is viewed from above, the exhaust gas sensor is arranged offset with respect to a center extension line passing through the center of the length direction of the catalyst holding pipe, and the downstream end portion of the exhaust pipe on the side where the exhaust gas sensor is provided is reduced in diameter so as to gradually approach the center extension line from the portion on the downstream side of the exhaust gas sensor.

[0025] By reducing the downstream end portion of the exhaust pipe on the side where the exhaust gas sensor is provided in diameter so as to gradually approach the center extension line, the flow rate of the gas flowing on the exhaust gas sensor side can be relatively reduced, and sensing of the exhaust gas becomes easy.

[0026] Effects of the Invention

[0027] According to the exhaust device of the present application, when an exhaust gas sensor is provided before and after the catalyst in the exhaust pipe in order to appropriately perform deterioration diagnosis of the catalyst for exhaust gas treatment, by providing at least a part of the catalyst holding pipe that suppresses the length of the exhaust device in the front-rear direction in the exhaust chamber, the length of the exhaust passage in the front-rear direction can be compactly provided, and by providing the exhaust gas sensor on the exhaust pipe of the catalyst holding pipe on the downstream side of the catalyst holding pipe, the exhaust gas can be brought into contact with the exhaust gas sensor directly before the air in the exhaust chamber is mixed with the exhaust gas after passing through the catalyst, so that the detection accuracy can be improved. Moreover, improvement of emission is achieved, and further, contribution to mitigation of climate change or reduction of influence is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a left side elevation diagram of a partial cross section of the motorized two-wheeled vehicle of the present embodiment except for the vehicle body cover.

[0029] Figure 2 is a left side elevation diagram of the exhaust device shown in Figure 1

[0030] Figure 3 is a plan view of the exhaust device in III direction, i.e., plan view in Figure 2

[0031] Figure 4 is a side enlarged sectional view of the exhaust pipe and the exhaust chamber in IV-IV direction in Figure 3

[0032] Figure 5 is a partial enlarged view of the exhaust pipe and the exhaust chamber in the direction shown in Figure 3

[0033] Figure 6 is a perspective view of the front portion of the exhaust chamber viewed from the left oblique front upper side.

[0034] Figure 7 is a vehicle body cross section diagram in the VII-VII direction in Figure 1 DETAILED DESCRIPTION

[0035] The exhaust device of the present application will be described based on an embodiment. Figures 1-7 In the present embodiment, the internal combustion engine is an internal combustion engine mounted on a straddle-type vehicle, and the straddle-type vehicle indicates a case of a motorized two-wheeled vehicle, and the front-rear-left-right-up-down directions and the like in the claims and the description of the present specification are in accordance with the directions of the motorized two-wheeled vehicle of the present embodiment.

[0036]

[0037] ​​​​​​In the diagram, the arrows FR indicate the front of the vehicle, LH indicates the left side of the vehicle, RH indicates the right side of the vehicle, and UP indicates the top of the vehicle.

[0038] Figure 1 This is a schematic left elevation view of a partial cross-section of the motorized two-wheeled vehicle 1 of this embodiment, excluding the body cover.

[0039] like Figure 1 As shown, in the frame 2 of the motorized two-wheeled vehicle 1 of this embodiment, the left and right main frames 21 extend slightly downward from the head tube 20 to the rear, and then bend downward in a side view to form a curved section 21a, forming a steeply tilted section 21b that reaches the pivot frame 22.

[0040] In addition, when viewed from the side, the left and right lower frames 23 extend downward from the head tube 20 at a steep angle, roughly parallel to the steeply inclined portion 21b of the main frame 21.

[0041] A pair of left and right seat tracks 24 extend rearward from the curved portion 21a of the main frame 21, and a pair of left and right rear support rods 25 connect the rear part of the seat tracks 24 to the pivot frame 22 to support the seat tracks 24.

[0042] The left and right main frames 21, the left and right curved sections 21a, the left and right steeply tilted sections 21b, and the left and right seat tracks 24 are connected by a plurality of intersecting parts 26 located in appropriate positions.

[0043] In the frame 2 described above, a front fork 11 is pivotally supported at the head tube 20, and a front wheel 12 is axled at its lower end.

[0044] On the pivot frame 22, which is connected to the lower part of the steeply inclined section 21b of the main frame 21, a swing arm 13 supported at the front end extends rearward, with a rear wheel 14 axled at its rear end, and a rear shock absorber 15 is clamped between the swing arm 13 and the frame 2.

[0045] A fuel tank 16 is mounted on the front of the main frame 21, and an occupant seat 17 is mounted behind the fuel tank 16 and supported on the seat rail 24.

[0046] In this embodiment, the motorized two-wheeled vehicle 1 is equipped with an internal combustion engine 3 below the main frame 21 and in front of its steeply tilted portion 21b. The internal combustion engine 3 is suspended by fastening the front part of its crankcase 30 to a bracket 23a installed at the lower end of the lower frame 23 and fastening the rear part of the crankcase 30 to a pivot frame 22.

[0047] In this embodiment, the internal combustion engine 3 has a transmission 4 at the rear of the crankcase 30, forming a so-called power unit. The crankshaft 31 of the internal combustion engine is oriented in the width direction of the motorized two-wheeled vehicle 1, i.e., the left-right direction, and is mounted on the air-cooled single-cylinder four-stroke cycle internal combustion engine of the motorized two-wheeled vehicle 1.

[0048] Within the rear of the crankcase 30, parallel to the crankshaft 31, are a main shaft and a countershaft 42 (not shown) of the transmission 4. The countershaft 42 extends to the left through the crankcase 30 and protrudes outward, becoming the final output shaft of the power unit. An output sprocket 43 is located at the protruding part. A drive chain 44 wound around the output sprocket 43 is mounted on a driven sprocket 45 on the side of the rear wheel 14, forming a chain transmission mechanism that transmits power to the rear wheel 14.

[0049] The internal combustion engine 3 is suspended on the crankcase 30 in a posture in which the cylinder axis is tilted slightly forward and the cylinder block 32, cylinder head 33, and cylinder head cover 34 are raised.

[0050] The intake pipe 51 is connected to its intake port 35 and extends rearward from the cylinder head 33 of the internal combustion engine 3. The intake system passage reaches the air filter housing 55 via the intake component 50, which consists of the intake pipe 51, the throttle body 52, and the connecting pipe 53.

[0051] An exhaust device 6 is formed in front of the cylinder head 33. The exhaust device 6 is connected to its exhaust port 36 so that the exhaust pipe 61 extends and bends downward, extending downward and rearward in the internal combustion engine 3. The exhaust path reaches the muffler 69 on the right side of the rear wheel 14 via the exhaust chamber 65.

[0052] Figure 2 Is Figure 1 The left side view shown is of the exhaust device 6, which includes the exhaust pipe 61, the exhaust chamber 65, and the muffler 69, and is shown in the direction indicated.

[0053] Figure 3 express Figure 2 The exhaust device 6 is viewed from the III direction, i.e., from above.

[0054] Figure 4 yes Figure 3 The enlarged side cross section of the exhaust pipe 61 and exhaust chamber 65 viewed from the IV-IV direction.

[0055] Figure 5 Based on Figure 3 The direction shown is a partial enlarged view of the exhaust pipe 61 and exhaust chamber 65 from above.

[0056] like Figure 2 As shown, in the exhaust device 6 of this embodiment, the front exhaust pipe ("exhaust pipe" in this invention) 61a of the exhaust pipe 61 connected to the exhaust port 36 extends downward toward the internal combustion engine 3 and is connected to the exhaust chamber 65.

[0057] like Figure 3 As shown, the exhaust chamber 65 is arranged such that at least a portion of it overlaps with the internal combustion engine 3 when viewed from above.

[0058] likeFigure 4 As shown, the exhaust gas flow rear end 62 of the front exhaust pipe 61a constituting the exhaust pipe 61 is fitted with the opening 66 formed in the outer shell 65a of the exhaust chamber 65 relative to the exhaust chamber 65. A part of the fitting portion constitutes the front exhaust pipe fixing portion 73a, which fixes the exhaust pipe 61 to the outer shell 65a of the exhaust chamber 65 by welding or the like.

[0059] In addition, a drain hole (not shown) is provided at the bottom of the exhaust chamber 65 to drain the moisture from the exhaust gas condensed inside the exhaust chamber 65.

[0060] Inside the exhaust chamber 65, a rear exhaust pipe ("exhaust pipe" in this invention) 61b, which constitutes the exhaust pipe 61, is provided and housed in the extension direction of the rear end 62 of the front exhaust pipe 61a with a predetermined gap, and is held on the inner surface of the outer shell 65a of the exhaust chamber 65.

[0061] The exhaust gas flow front end 63 of the rear exhaust pipe 61b, which is housed in the exhaust chamber 65 and holds the catalyst holding tube 80 described later, is connected to the exhaust chamber 65 to form an exhaust pipe sliding holding part 71. This allows the exhaust pipe 61b to slide within the opening 66 of the exhaust chamber 65, thus enabling the rear exhaust pipe 61b to expand and contract in the axial direction relative to the opening 66 due to thermal expansion.

[0062] Furthermore, in this embodiment, the exhaust pipe sliding retaining portion 71 is formed at the front end portion 63 of the rear exhaust pipe 61b, but it can also be offset from the front end portion 63 in the downstream direction.

[0063] The rear end of the rear exhaust pipe 61b, i.e. the downstream end 64 of the exhaust pipe 61, has an opening 61c in the exhaust chamber 65.

[0064] like Figure 5 As shown, the rear exhaust pipe 61b has a rear exhaust pipe fixing part 73b near the downstream sensor mounting boss 93 (described later) that is fixed to the outer shell 65a of the exhaust chamber 65 by partial welding or the like, to prevent the outer shell 65a of the exhaust chamber 65 from shifting relative to the downstream sensor mounting boss 94.

[0065] It should be noted that, in this embodiment, the front exhaust pipe 61a and the rear exhaust pipe 61b are separated within the exhaust chamber 65, but they function as an integral part of the exhaust pipe 61, as described in the claims. Hereinafter, both are referred to as exhaust pipe 61.

[0066] The catalyst holding pipe 80 is fixed in the front exhaust pipe 61a and extends into the rear exhaust pipe 61b, is held inside the exhaust pipe 61 (61a, 61b), and its upstream end 80a is fixed to the inner surface of the front exhaust pipe 61a. The catalyst holding pipe 80 is slidably fitted to the inner surface of the rear pipe 61b, and a catalyst sliding holding portion 72 is formed and connected. Thus, thermal expansion of the catalyst holding pipe 80 relative to the rear pipe 61b is allowed to cause expansion and contraction in the pipe axis direction.

[0067] Further, as shown in Figure 3 the catalyst holding pipe 80 is disposed obliquely relative to the vehicle center line X in the vehicle front-rear direction, so that the front-rear direction length of the exhaust passage is compact.

[0068] A catalyst 8 for exhaust gas treatment, such as a three-way catalyst that purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) together, is filled in the catalyst holding pipe 80.

[0069] Further, the catalyst 8 is not limited to a three-way catalyst, and cases where different types of catalysts are arranged in the length direction of the illustrated catalyst 8 are also included. In addition, the catalyst 8 of the present embodiment is supported on a honeycomb structure in such a manner that exhaust gas can pass through while reacting.

[0070] The catalyst holding pipe 80 is held across the inner surfaces of the front exhaust pipe 61a and the rear exhaust pipe 61b, and thus a portion of the catalyst holding pipe 80 is disposed in the exhaust chamber 65.

[0071] When an exhaust gas sensor 91 is provided in front of and behind the catalyst 8 in order to properly perform degradation diagnosis of the catalyst 8 for exhaust gas treatment, in cases where a portion of the catalyst 8 in the exhaust pipe 61 is arranged in the exhaust chamber 65 in order to suppress the front-rear length of the exhaust device 6, the downstream-side exhaust gas sensor 91 needs to be provided so as to pass through a plurality of members such as the exhaust chamber 65 and the exhaust pipe 61, and problems of expansion and strain of each member caused by heat arise, but since the connection portion of the rear exhaust pipe 61b and the exhaust chamber 65 forms the exhaust pipe sliding holding portion 71 and the connection portion of the catalyst holding pipe 80 and the rear exhaust pipe 61b forms the catalyst sliding holding portion 72, the displacement of each member caused by thermal expansion can be released, the strain that arises in the downstream sensor mounting boss portion 93 of the exhaust gas sensor 91 provided in the exhaust pipe 61 so as to simultaneously pass through the exhaust chamber 65 and the exhaust pipe 61 can be alleviated, the durability and detection reliability and accuracy of the exhaust gas sensor 91 can be improved by reducing the load that arises in the downstream sensor mounting boss portion 93.

[0072] In the present embodiment, the following is further specifically described.

[0073] In the exhaust pipe 61, in order to detect the state of the exhaust gas purification based on the catalyst 8, in addition, the deterioration of the catalyst 8 is detected, and an exhaust gas sensor 91 is provided on the upstream side and the downstream side of the catalyst 8.

[0074] The exhaust gas sensor 91 is, for example, an O2 sensor, an LAF sensor (air-fuel ratio sensor), but the kind is not limited in the embodiment.

[0075] As shown in Figs. 1 and 2, the upstream side exhaust gas sensor is provided on an upstream sensor mounting boss portion 92 provided on the front end side of the front exhaust pipe 61a, but the drawing of the upstream side exhaust gas sensor itself is omitted. Figure 2 Figure 3 As shown in Figs. 1 and 2, the upstream side exhaust gas sensor is provided on an upstream sensor mounting boss portion 92 provided on the front end side of the front exhaust pipe 61a, but the drawing of the upstream side exhaust gas sensor itself is omitted.

[0076] As shown in Figs. 1 and 2, the upstream side exhaust gas sensor is provided on an upstream sensor mounting boss portion 92 provided on the front end side of the front exhaust pipe 61a, but the drawing of the upstream side exhaust gas sensor itself is omitted. Figure 4 As shown in Figs. 1 and 2, the upstream side exhaust gas sensor is provided on an upstream sensor mounting boss portion 92 provided on the front end side of the front exhaust pipe 61a, but the drawing of the upstream side exhaust gas sensor itself is omitted.

[0077] As described above, by providing at least a part of the catalyst holding pipe 80 in the exhaust gas chamber 65, the front-rear direction length of the exhaust gas path can be compactly provided, by providing the exhaust gas sensor 91 on the downstream side of the catalyst holding pipe 80 on the rear exhaust pipe 61b, the exhaust gas can be brought into contact with the exhaust gas sensor 91 directly before the air in the exhaust gas chamber 65 and the exhaust gas after passing through the catalyst 8 are mixed, and thus the detection accuracy of the exhaust gas sensor 91 can be improved.

[0078]

[0079] As shown in Figs. 1 and 2, the upstream side exhaust gas sensor is provided on an upstream sensor mounting boss portion 92 provided on the front end side of the front exhaust pipe 61a, but the drawing of the upstream side exhaust gas sensor itself is omitted. Figure 3

[0080] ​​​By so providing the bent portion 65d, the exhaust pipe 61 can ensure a necessary exhaust pipe length while shortening the front-rear arrangement distance, by providing the diameter-enlarged structure 65e at the bent portion 65d, the exhaust gas flow in the front exhaust pipe 61a on the upstream side of the catalyst 8 can be made to uniformly disperse in the front exhaust pipe 61a, by making the exhaust gas uniformly contact the upstream end surface of the catalyst 8, the exhaust gas bias flow with respect to the catalyst 8 can be suppressed, and the detection accuracy of the exhaust gas sensor 91 after passing through the catalyst 8 can be improved.

[0081] As shown in Figure 4 , Figure 5 , the downstream end portion 64 of the rear exhaust pipe 61b is reduced in diameter. When backflow of exhaust gas occurs due to exhaust pulsation, if water accumulated in the exhaust chamber 65, external gas intruding from the drain hole, or the like contacts the exhaust gas sensor 91, it can be possible that the detection accuracy of the detection portion 91a of the exhaust gas sensor 91 is reduced due to sudden cooling, but this situation can be prevented by the reduced diameter of the downstream end portion 64, and the sensing accuracy of the exhaust gas sensor 91 can be prevented from being affected.

[0082] In addition, the durability and detection reliability and accuracy of the exhaust gas sensor 91 are thus improved.

[0083] Furthermore, as shown in Figure 5 , the reduced diameter structure of the downstream end portion 64 of the rear exhaust pipe 61b is formed to be non-symmetrical with respect to the exhaust chamber inner center line Y left and right in plan view. Thus, the downstream end portion 64 of the rear exhaust pipe 61b is not excessively throttled, and thus the resistance to the exhaust gas flow is less likely to occur, and the drivability is improved.

[0084] In addition, as shown in Figure 5 , the exhaust gas sensor 91 is provided at a position offset with respect to a center extension line Z passing through the length direction center of the catalyst holding pipe 80 in plan view, and the portion of the downstream end portion 64 of the rear exhaust pipe 61b on the exhaust gas sensor 91 side on the downstream side with respect to the exhaust gas sensor 91 is reduced in diameter so as to gradually approach the center extension line Z.

[0085] Thus, the flow rate of the exhaust gas flow on the exhaust gas sensor 91 side can be relatively reduced, and the sensing of the exhaust gas becomes easier.

[0086] Furthermore, the downstream end portion 64 of the rear exhaust pipe 61b on the exhaust gas sensor 91 side is provided so as to contact the inner wall surface 65b of the exhaust chamber 65 in plan view.

[0087] Therefore, heat of the high-temperature rear exhaust pipe 61b is dissipated via the exhaust chamber 65, so that movement of the rear exhaust pipe 61b caused by temperature change is suppressed, strain generated at the downstream sensor mounting boss portion 93 of the exhaust gas sensor 91 is mitigated, durability and detection reliability and accuracy of the exhaust gas sensor 91 are improved by reducing load generated at the downstream sensor mounting boss portion 93.

[0088] In addition, by disposing the exhaust gas sensor 91 close to the inner wall surface of the exhaust chamber 65, compared with the case where the exhaust gas sensor 91 is disposed at the center of the exhaust chamber 65, the amount of recess of the exhaust chamber 65 for disposing the exhaust gas sensor 91 can be reduced, the capacity of the exhaust chamber 65 can be ensured, and the detection accuracy of the exhaust gas sensor 91 can be improved.

[0089] Figure 6 is a perspective view of the front portion of the exhaust chamber 65 viewed from the left obliquely front upper side.

[0090] As shown in Figure 2 , Figure 3 , Figure 6 , a recessed portion 65c recessed from the upper side and the left side is formed at the left side portion of the exhaust chamber 65, and the exhaust gas sensor 91 is disposed so that the detection portion 91a thereof faces downward with respect to the recessed portion 65c.

[0091] Further, by providing the recessed portion 65a in the exhaust chamber 65, the accessibility of a tool when the exhaust gas sensor 91 is disposed is improved.

[0092] In addition, the shape of the recessed portion 65a is inclined so as to slightly have a downward slope toward the left side, and becomes a shape in which water is less likely to accumulate and is likely to flow when water such as rain splashes into the exhaust chamber 65.

[0093] Figure 7 is a vehicle body cross-sectional view in the direction of VII-VII in Figure 1 , indicating a rear cross section of the downstream sensor mounting boss portion 93 in the exhaust chamber 65.

[0094] As shown in Figure 7 , the wire harness 91b of the exhaust gas sensor 91 mounted to the recessed portion 65a of the exhaust chamber 65 is caught in a bracket 26a that extends upward and is fixed to a nearby cross member 26. By thus temporarily fixing the wire harness 91b to the bracket 26a, even if the setting of the arrangement of the exhaust gas sensor 91 of the exhaust chamber 65 is changed, it is possible to easily cope with it, and stable and safe wiring of the wire harness 91b is performed.

[0095] The exhaust apparatus 6 of the above-described embodiment has the following features.

[0096] That is, it has: an exhaust chamber 65, which is configured to overlap at least part of the internal combustion engine 3 when viewed from above; an exhaust pipe 61, which passes from the exhaust port 36 of the internal combustion engine 3 through the lower part of the internal combustion engine 3 and has an opening 61c in the exhaust chamber 65; a catalyst holding tube 80, which is held by the exhaust pipe 61, at least part of which is disposed in the exhaust chamber 65 and filled with catalyst 8; and an exhaust gas sensor 91, which is disposed on a sensor mounting boss 93, which is disposed on the rear exhaust pipe 61b in such a way that it passes through the rear exhaust pipe 61b and the exhaust chamber 65, the rear exhaust pipe 61b forming the exhaust pipe 61, housed in the exhaust chamber 65, and holding the catalyst holding tube 80.

[0097] When exhaust gas sensors 91 are installed before and after the catalyst 8 in the exhaust pipe 61 for proper diagnosis of catalyst degradation, it is necessary to suppress the longitudinal length of the exhaust device 6. However, by installing at least a portion of the catalyst holding pipe 80 within the exhaust chamber 65, the longitudinal length of the exhaust device 6 can be compactly arranged. Furthermore, by installing the exhaust gas sensor 91 in the rear exhaust pipe 61b downstream of the catalyst holding pipe 80, the exhaust gas can directly contact the exhaust gas sensor 91 before the air in the exhaust chamber 65 mixes with the exhaust gas after passing through the catalyst 8, thus improving detection accuracy. Moreover, this leads to improved emissions, which in turn helps to mitigate climate change or reduce its impact.

[0098] like Figure 3 As shown, the catalyst retainer pipe 80 is inclined relative to the vehicle centerline X in the front-rear direction of the vehicle. By inclining the catalyst retainer pipe 80, the front-rear distance of the exhaust path can be made compact.

[0099] like Figure 5 As shown, the downstream end 64 of the exhaust pipe 61b, where the exhaust gas sensor 91 is installed, is positioned along the inner wall surface 65b of the exhaust chamber 65 in a manner that connects with the inner wall surface 65b of the exhaust chamber 65. By positioning the exhaust gas sensor 91 close to the inner wall surface 65b of the exhaust chamber 65, compared to the case where it is positioned in the center of the exhaust chamber 65, the amount of recess in the exhaust chamber 65 used to install the exhaust gas sensor 91 can be reduced, thereby improving the detection accuracy of the exhaust gas sensor 91 while ensuring the capacity of the exhaust chamber 65.

[0100] The downstream end 64 of the rear exhaust pipe 61b has a reduced diameter structure 67.

[0101] If water splashes to the detection portion 91a of the exhaust gas sensor 91, there is a possibility that the detection accuracy of the detection portion 91a of the exhaust gas sensor 91 is degraded due to being sharply cooled, but by being formed into the reduced diameter configuration 67, water accumulated in the exhaust chamber 65 at the time of backflow of gas due to exhaust pulsation, external gas intruding from the drain hole, and the like are less likely to contact the exhaust gas sensor 91, and it is possible to prevent the sensing accuracy of the exhaust gas sensor 91 from being affected.

[0102] The reduced diameter configuration 67 of the downstream end portion 64 of the rear exhaust pipe 61b is asymmetric with respect to the center line Y in the exhaust chamber of the rear exhaust pipe 61b when viewed in the vertical direction with respect to the flow direction F of the exhaust gas flowing in the exhaust pipe 61.

[0103] Therefore, the exhaust gas sensor 91 is less likely to be affected by water and gas, and the sensing accuracy is prevented from being affected, and by making the reduced diameter configuration 67 asymmetric to the left and right, the downstream end portion 64 of the rear exhaust pipe 61b is not excessively throttled, and therefore, the resistance to the flow of exhaust gas is less likely to occur, and it is possible to improve the drivability.

[0104] When the exhaust device 6 is viewed from above, the exhaust gas sensor 91 is disposed offset with respect to a center extension line Z passing through the center of the length direction of the catalyst holding pipe 80, and the downstream side portion of the exhaust gas sensor 91 is reduced in diameter in such a manner as to gradually approach the center extension line Z at the downstream end portion 64 of the rear exhaust pipe 61b on the side where the exhaust gas sensor 91 is disposed.

[0105] By reducing the downstream end portion 64 of the rear exhaust pipe 61b on the side where the exhaust gas sensor 91 is disposed in such a manner as to gradually approach the center extension line Z, it is possible to relatively reduce the flow velocity of the gas flow on the exhaust gas sensor 91 side, and the sensing of the exhaust gas becomes easy.

[0106] The above describes an embodiment of the exhaust device of the application, but the application is not limited to the above-described embodiment, and various modifications other than the above can be made within the scope of the gist of the application.

[0107] Further, the left and right arrangement of the device is described in the illustrated embodiment for convenience of explanation, but is not limited thereto, and the left and right arrangement can be reversed.

[0108] Explanation of Reference Numerals

[0109] 1: Motorized two-wheeled vehicle

[0110] 2: Frame

[0111] 3: Internal combustion engine

[0112] 6: Exhaust device

[0113] 8: Catalyst

[0114] 26: cross member

[0115] 26a: bracket

[0116] 33: cylinder head

[0117] 36: exhaust port

[0118] 61: exhaust pipe

[0119] 61a: front exhaust pipe (exhaust pipe in the present invention)

[0120] 61b: rear exhaust pipe (exhaust pipe in the present invention)

[0121] 61c: opening portion

[0122] 61d: curved portion

[0123] 61e: diameter expansion structure

[0124] 62: rear end

[0125] 63: front end portion

[0126] 64: downstream end portion

[0127] 65: exhaust chamber

[0128] 65a: outer shell

[0129] 65b: inner wall surface

[0130] 65c: recessed portion

[0131] 66: opening

[0132] 69: muffler

[0133] 71: exhaust pipe sliding holding portion

[0134] 72: catalyst sliding holding portion

[0135] 73a: front exhaust pipe fixing portion

[0136] 73b: rear exhaust pipe fixing portion

[0137] 91: exhaust gas sensor

[0138] 91a: detection portion

[0139] 91b: wire harness

[0140] 92: upstream sensor mounting boss portion

[0141] 93: downstream sensor mounting boss portion

[0142] X: vehicle center line

[0143] Y: center line in the exhaust chamber (of the rear exhaust pipe 61b)

[0144] Z: center extension line (of the catalyst holding pipe 80)

Claims

1. An exhaust device characterized by, An exhaust device for an internal combustion engine (3) is provided with: an exhaust chamber (65) disposed so as to overlap at least a portion of the internal combustion engine (3) in plan view; an exhaust pipe (61) having an opening portion (61c) in the exhaust chamber (65) from an exhaust port (36) of the internal combustion engine (3) through below the internal combustion engine (3); a catalyst holding pipe (80) held in the exhaust pipe (61), at least a portion of which is disposed in the exhaust chamber (65) and is filled with a catalyst (8); an exhaust gas sensor (91) disposed in a sensor mounting boss portion (93) provided in the exhaust pipe (61) so as to pass through a rear exhaust pipe (61b) constituting the exhaust pipe (61) and housed in the exhaust chamber (65), which holds the catalyst holding pipe (80).

2. The exhaust device according to claim 1, wherein: the catalyst holding pipe (80) is disposed obliquely with respect to a vehicle centerline (X) in a vehicle longitudinal direction.

3. The exhaust device according to claim 1 or 2, wherein: 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 the exhaust chamber (65) so as to abut the inner wall surface (65b) of the exhaust chamber (65).

4. The exhaust device according to claim 1, wherein: the downstream end portion (64) of the exhaust pipe (61) has a reduced diameter structure (67).

5. The exhaust device according to claim 4, wherein: the reduced diameter structure (67) of the downstream end portion (64) of the exhaust pipe (61) is asymmetric with respect to a centerline (Y) in the exhaust chamber of the exhaust pipe (61) in a direction perpendicular to a flow direction (F) of exhaust gas flowing in the exhaust pipe (61) when viewed in a direction perpendicular to the flow direction (F) of the exhaust gas.

6. The exhaust device according to claim 5, wherein: the exhaust gas sensor (91) is disposed offset with respect to a center extension line (Z) passing through a center of a length direction of the catalyst holding pipe (80) when the exhaust device is viewed in plan view, a portion of the downstream end portion (64) of the exhaust pipe (61) on a downstream side from the exhaust gas sensor (91) is reduced in diameter so as to gradually approach the center extension line (Z).

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