EP4650580A1

EP4650580A1 - Exhaust device for internal combustion engine

Info

Publication number: EP4650580A1
Application number: EP23923982.5A
Authority: EP
Inventors: Ryosuke Kinoshita; Naoki Sakamoto; Hiroyuki Kurino; Ryota Yamada; Xiaochen Wang; Rikumo Tachibana; Ryosuke Ibata; Ryota Takahashi; Satoru Maki
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2023-02-21
Filing date: 2023-02-21
Publication date: 2025-11-19
Also published as: JPWO2024176328A1; WO2024176328A1; EP4650580A4; CN121002270A

Abstract

An exhaust device 39 for an internal combustion engine 10, which is mounted on a straddle type vehicle 10 according to an embodiment of the present invention includes: an exhaust gas purification catalyst 48a provided in an exhaust passage 52 of the internal combustion engine E; and an exhaust gas sensor 46 provided on a downstream exhaust passage 52b on a downstream side of the exhaust gas purification catalyst 48a. The exhaust gas sensor 46 is provided on a connection portion 70, which is welded with the exhaust pipe 50 defining and forming the downstream exhaust passage 52b, so that the exhaust gas sensor 46 is inclined obliquely with respect to an exhaust flow direction EF. A welding start portion B1 in a weld portion 70W around the connection portion 70 to be connected with the exhaust pipe 50 is located on a non-upstream side in the exhaust flow direction EF of the exhaust gas sensor 46.

Description

[Technical Field]

The present invention relates to an exhaust device for an internal combustion engine mounted on a straddle type vehicle such as a motorcycle.

[Background Art]

Efforts for the purpose of mitigating climate changes or reducing the influence have been continuously made, conventionally, and research and development on emission improvement have been conducted for the purpose of achieving this. For example, in internal combustion engines for vehicles including straddle type vehicles such as motorcycles, various studies have been made on the provision of an exhaust gas sensor on an exhaust passage of an internal combustion engine and control of fuel injection in accordance with an output of the exhaust gas sensor in order to purify the exhaust gas.
For example, Patent Document 1 discloses that an attachment portion into which an oxygen concentration sensor is screwed is provided in a straight pipe portion of an exhaust manifold of an internal combustion engine for a motorcycle that is a scooter-type vehicle. Such an attachment portion is welded to the straight pipe portion of the exhaust manifold, and a screwed portion (a female screw) corresponding to a screwing portion (a male screw) of the oxygen concentration sensor is provided on an inner circumferential surface of the attachment portion. Such an attachment portion is obliquely welded to the straight pipe portion of the exhaust manifold, and in the attached state, a protector side (an oxygen detection side) of the oxygen concentration sensor is obliquely inserted into the exhaust manifold from an upstream side to a downstream side of the exhaust gas. That is, an output signal line side (a wiring side) of the oxygen concentration sensor is located on a cylinder head side of the engine. This makes it possible to reduce the flow path resistance of the exhaust gas in the exhaust manifold, and to perform precise oxygen concentration measurement without hindering the flow of the exhaust gas.

[Prior Art Document]

[Patent Document]

Patent Document 1: JP 2006-170938 A

[Summary of the Invention]

[Underlying Problems to be solved by the Invention]

In the emission improvement, by the way, there is a demand for further improving detection accuracy of the exhaust gas sensor such as the above oxygen concentration sensor. For example, when the above attachment portion for attaching the exhaust gas sensor, in other words, a connection portion is provided by being welded to the exhaust pipe, the welding is continuously performed over the entire circumference of such a connection portion, and the welding is performed to reach a position that overlaps a welding start portion. That is, in the welding, the welding start portion and a welding end portion overlap each other. For this reason, in the welding start portion (that is, the welding end portion), a weld bead may be thicker than the other portions. Hence, the weld bead, that is, the back bead may easily appear inside the exhaust pipe. Depending on the protrusion amount of such a back bead, the flow of the exhaust gas toward the exhaust gas sensor may be influenced. In particular, in a case where the exhaust gas sensor is disposed obliquely with respect to the exhaust flow direction, the protrusion amount on a tip end side of a sensor detection unit into the exhaust passage is smaller than that of a case where the exhaust gas sensor is disposed at a right angle to the exhaust flow direction. Therefore, the influence of the back bead on the flow of the exhaust gas may further intensively decide the detection capability.
Then, with regard to the influence of the back bead on the exhaust gas sensor, consideration is desirably given, in particular, to the exhaust gas sensor provided on the downstream side of an exhaust gas purification catalyst in the exhaust passage of the internal combustion engine. This is because the exhaust gas passes through the exhaust gas purification catalyst, and then the flow of the exhaust gas is easily disturbed by influence of the exhaust pressure, in some cases. The component detection of the exhaust gas by the exhaust gas sensor provided on the downstream side of the exhaust gas purification catalyst may be more difficult than the detection by the exhaust gas sensor provided on the upstream side of the exhaust gas purification catalyst.
An object of the present invention is to provide, in an exhaust device for an internal combustion engine mounted on a straddle type vehicle such as a motorcycle, a configuration capable of reducing the influence of a weld bead of a connection portion of an exhaust gas sensor on detection accuracy of the exhaust gas sensor, in a case where the exhaust gas sensor is provided to be obliquely inclined with respect to an exhaust passage, on a downstream side of an exhaust gas purification catalyst. This contributes to mitigating climate changes or reducing the influence, accordingly.

[Means to solve the Problems]

In order to achieve the above object, according to one aspect of the present invention,
an exhaust device for an internal combustion engine mounted on a straddle type vehicle is provided, the exhaust device including:

an exhaust gas purification catalyst provided in an exhaust passage of the internal combustion engine; and
an exhaust gas sensor provided on a downstream exhaust passage on a downstream side of the exhaust gas purification catalyst, in which
the exhaust gas sensor is provided on a connection portion welded with an exhaust pipe defining and forming the downstream exhaust passage, so that the exhaust gas sensor is inclined obliquely with respect to an exhaust flow direction, and
a welding start portion in a weld portion around the connection portion to be connected with the exhaust pipe is located on a non-upstream side in the exhaust flow direction of the exhaust gas sensor.

According to the above configuration, the welding start portion is located on the non-upstream side in the exhaust flow direction of the exhaust gas sensor. Therefore, the welding start portion is not located on the upstream side of the exhaust gas sensor, and it becomes possible to suppress the weld bead on the upstream side of the downstream exhaust gas sensor becoming thick, so that the flow of the exhaust gas from the exhaust gas purification catalyst toward the downstream exhaust gas sensor can be more suitably maintained. Therefore, in the exhaust device for the internal combustion engine mounted on the straddle type vehicle, it becomes possible to reduce the influence of the weld bead of the connection portion of the downstream exhaust gas sensor on the detection accuracy of the downstream exhaust gas sensor on the downstream side of the exhaust gas purification catalyst. Therefore, the detection accuracy of the exhaust gas sensor can be improved.
In a case where a virtual plane is defined to pass through an intersection point between an extension plane of a surface of the exhaust pipe and an axis of the connection portion, and is orthogonal to the exhaust flow direction, the welding start portion is preferably located on a downstream side in the exhaust flow direction of the virtual plane. According to this configuration, the welding start portion in the weld portion around the connection portion can be more reliably located on the non-upstream side in the exhaust flow direction of the exhaust gas sensor.
The welding start portion is preferably located in a region within a downstream width of the connection portion. According to this configuration, the welding start portion in the weld portion around the connection portion can be more reliably located on the downstream side in the exhaust flow direction of the exhaust gas sensor. This enables further suppression of the influence of hindering the flow of the exhaust gas by the weld bead, and thus enables further improvement in the detection accuracy of the downstream exhaust gas sensor.
In a case where a virtual plane is defined to pass through an intersection point between an extension plane of a surface of the exhaust pipe and an axis of the connection portion, and is orthogonal to the exhaust flow direction, an inclination of an axis of the exhaust gas sensor with respect to the virtual plane is preferably equal to or larger than 10 degrees and equal to or smaller than 45 degrees. According to this configuration, the sensor detection unit of the exhaust gas sensor can be sufficiently spaced apart from the inner wall surface of the exhaust pipe, and the sensor detection unit itself becoming resistance of the exhaust flow can also be effectively suppressed.
The exhaust gas sensor preferably includes a sensor detection unit located in the exhaust passage and a sensor body portion extending on an outside of the exhaust passage, and the sensor detection unit may be located on a downstream side in the exhaust flow direction of the sensor body portion. According to this configuration, the sensor detection unit of the exhaust gas sensor can be disposed along the exhaust flow direction. Therefore, even if the flow velocity of the exhaust gas around the exhaust gas sensor is very high, the pressure loss of the exhaust gas by the exhaust gas sensor can be reduced.
The purification device preferably includes the exhaust gas purification catalyst in an inside, the purification device having a main body portion in which a carrier carrying the exhaust gas purification catalyst is disposed, and a reduced-diameter portion connected with a downstream side in the exhaust flow direction of the main body portion and reducing in diameter toward the downstream side in the exhaust flow direction, and the connection portion may be located on the downstream side in the exhaust flow direction of the reduced-diameter portion, the exhaust gas sensor including a sensor detection unit located in the exhaust passage, and a sensor body portion extending on an outside of the exhaust passage, the sensor detection unit being located on the downstream side in the exhaust flow direction of the sensor body portion. According to this configuration, the exhaust gas sensor can be located on the downstream side of the reduced diameter portion of the purification device, and the sensor detection unit of the exhaust gas sensor can be disposed along the exhaust flow direction. Therefore, even if the flow velocity of the exhaust gas that has passed through the purification device and then flows around the downstream exhaust gas sensor is very high, the pressure loss of the exhaust gas by the downstream exhaust gas sensor can be reduced.

[Effects of the Invention]

According to the above one aspect of the present invention, with the provision of the above configuration, in the exhaust device for the internal combustion engine mounted on the straddle type vehicle, it becomes possible to reduce the influence of the weld bead of the connection portion of the exhaust gas sensor on the detection accuracy of the exhaust gas sensor, in a case where the exhaust gas sensor is provided to be obliquely inclined with respect to an exhaust passage on a downstream side of an exhaust gas purification catalyst.

[Brief Description of Drawings]

Fig. 1 is a left side view of a motorcycle that is a straddle type vehicle according to one embodiment of the present invention.
Fig. 2 is a front view of a part of the motorcycle of Fig. 1.
Fig. 3 is a bottom view of a part of the motorcycle of Fig. 1.
Fig. 4 is a view illustrating a part of an exhaust device for an internal combustion engine of the motorcycle of Fig. 1 according to a modification.
Fig. 5 is an enlarged perspective view of an exhaust gas sensor of the exhaust device for the internal combustion engine in the motorcycle of Fig. 1 and a periphery of its attachment portion.
Fig. 6 is an enlarged view of the exhaust gas sensor and a periphery of its attachment portion in the exhaust device that is detached from the motorcycle of Fig. 1.
Fig. 7 is an enlarged cross-sectional view of the periphery of the exhaust gas sensor illustrated in Fig. 6.
Fig. 8 is a view of the exhaust gas sensor when viewed from a cut surface of an exhaust pipe that is cut on a downstream side of the exhaust gas sensor illustrated in Fig. 6.
Fig. 9 is a schematic cross-sectional view of a weld portion when two plate members are welded together by arc welding.
Fig. 10 is a plan view of a periphery of a connection portion of the exhaust gas sensor illustrated in Fig. 6, and is a schematic view illustrating a welding start portion in a weld portion around the connection portion and a welding direction from the welding start portion.

[Modes for carrying out the Invention]

Hereinafter, a motorcycle 10, which is a straddle type vehicle according to one embodiment of the present invention, will be described with reference to the accompanying drawings. Here, upper, lower, front, rear, right, and left of the vehicle body are defined based on the line of sight of a driver who is seated on the motorcycle 10. In the drawings, reference sign "UP" is used for an upper side in an up-down direction, reference sign "DW" is used for a lower side, reference sign "FR" is used for a front side in a vehicle front-rear direction, reference sign "RR" is used for a rear side, reference sign "RH" is used for a right side in a vehicle width direction, and reference sign "LH" is used for a left side.
Fig. 1 is a left side view of the motorcycle 10, that is, a side view on the right side of the vehicle body. Fig. 2 is a front view, that is, illustrates a front surface of a part of the motorcycle 10. Fig. 3 is a bottom view of a part of the motorcycle 10 of Fig. 1.
The motorcycle 10 includes: a power unit; and a vehicle body frame 12, on which electric components are mounted. A main tube (not illustrated) of the vehicle body frame 12 extends rearward from a head pipe 14, which is located in a front end portion. A fuel tank 18, in the inside of which fuel is stored, is disposed on a rear side of the head pipe 14. A seat 20, on which a driver is seated, is mounted on a rear side of the fuel tank 18. A footrest 22, which serves as a footrest for a driver to place its foot during driving, is provided below the seat 20.
A brake pedal 24 for a rear wheel WR, which is a drive wheel, is provided in the vicinity of the footrest 22, on the right side of the vehicle body illustrated in Fig. 1. On the brake pedal 24, a rear end portion 24r, which is located on a rear side of the footrest 22, is pivotally supported, and a front end portion 24f, which is located on a front side relative to the footrest 22, is provided to be swingable up and down. In a side view of the motorcycle 10 in Fig. 1, the brake pedal 24 is shaped to first extend substantially horizontally from the rear end portion 24r toward the front end portion 24f and then be slightly inclined forward and upward. That is, the brake pedal 24 extends in a front-rear direction without being substantially inclined in an up-down direction in a side view of the motorcycle 10. The front end portion 24f of the brake pedal 24 functions as a pedal portion, is located on a right lateral side of a front end side part of a crankcase 30 to be described later, is also located at substantially the same height as the footrest 22, and can be stepped on to be operated by the driver's foot placed on the footrest 22.
Furthermore, in the vicinity of the footrest 22 on the right side of the vehicle body illustrated in Fig. 1, in particular, a kick pedal 25 is provided on an upper side of the footrest 22. The kick pedal 25 includes: a rear end portion 25r, which is located on a substantially upper side of the footrest 22; and a front end portion 25f, which is located in the vicinity of a rear portion of a cylinder head 34 of an engine main body 26 of an internal combustion engine E of the power unit. The kick pedal 25 first extends upward toward the front end portion 25f from the rear end portion 25r, and is then curved forward. The kick pedal 25 is unfolded to extend outward in the vehicle width direction when it is used. The front end portion 25f of the kick pedal 25 functions as a pedal portion, and is stepped on by the driver's foot. Stepping on in such a manner causes the kick pedal 25 to turn in a predetermined range around the rear end portion 25r, and is capable of starting up the internal combustion engine E.
The engine main body 26 of the internal combustion engine E is suspended on the main tube in the vehicle body frame 12. The engine main body 26 includes: the above-described crankcase 30; a cylinder block 32; a cylinder head 34; and a head cover 36, which are sequentially provided above the crankcase 30. The cylinder block 32 in a forward inclined state is coupled with an upper side of the crankcase 30. Therefore, as illustrated in Fig. 1, a cylinder axis C of the cylinder of the engine main body 26 is inclined obliquely forward from the crankshaft of the crankcase 30 toward the cylinder head 34. Note that the crankshaft extends in the vehicle width direction, and is substantially orthogonal to the up-down direction and the front-rear direction. In Fig. 1, a rotation axis 38 of the crankshaft is illustrated.
An upper end (an upstream end) of an exhaust pipe 40 of the exhaust device 39 for the internal combustion engine E is connected with the cylinder head 34 of the engine main body 26. The exhaust gas discharged from the combustion chamber (not illustrated) flows through the exhaust pipe 40, and is discharged from a muffler 42, which is located on a right lateral side of the rear wheel WR, that is, located on a right lateral rear side of the vehicle body. Exhaust gas sensors 44 and 46 and a purification device 48 are provided on the front end side, that is, on an upstream side of the muffler 42. Note that an exhaust port of the cylinder head 34, the exhaust pipe 40, the purification device 48, an exhaust pipe 50, and the muffler 42 are connected in this order in an exhaust flow direction, and each of them defines a part of an exhaust passage 52.
Note that a front fork 54 is rotatably supported on a front end portion of the main tube via a steering shaft provided in the head pipe 14. A handlebar 56 is provided on an upper end portion of the steering shaft, and grips 58 are respectively attached to both end portions of the handlebar 56. A front wheel WF is rotatably supported by lower portions of the front fork 54. An upper side of the front wheel WF is partially covered with a front fender 60.
In addition, the rear wheel WR, to which dynamic power of the internal combustion engine E is transmitted, is rotatably supported on a rear side of the engine main body 26 via a swing arm. A suspension 62, which mitigates an impact from a road surface, is disposed between the swing arm and the vehicle body frame 12. A rear fender 64 is disposed on a rear upper side of the rear wheel WR, that is, on a rear side of the seat 20.
As described above, by the way, the exhaust pipe 40 of the exhaust device 39 is connected with a front wall of the cylinder head 34 of the engine main body 26, and the purification device 48 and the muffler 42 are disposed on the downstream side sequentially from the upstream side. The purification device 48 is configured to have a function of purifying the exhaust gas, and particularly accommodates an exhaust gas purification catalyst 48a in its inside, that is, includes a carrier 48b, which carries the catalyst 48a. Here, the carrier 48b includes a honeycomb base material in which a plurality of cells, which extend from an inflow end face (an upstream end face) to an outflow end face (a downstream end face) of the exhaust gas, and which is partitioned and formed by porous partition walls. The catalyst 48a is carried on the partition walls of such a honeycomb base material. Here, the catalyst 48a is a three-way catalyst (TWC), and has a function (that is, a three-way purification function) of purifying HC in the exhaust gas by oxidizing or reducing HC in the exhaust gas to H₂O and CO₂, CO to CO₂, and NOx to N₂. The carrier 48b is made of, for example, an oxide such as alumina, silica, zirconia, titania, ceria, or zeolite, and the three-way catalyst contains, for example, a noble metal such as platinum, palladium, or rhodium.
In the exhaust passage 52, the exhaust gas sensor 44 is provided on an exhaust passage (an upstream exhaust passage) 52a on the upstream side of the purification device 48, and the exhaust gas sensor 46 is provided on an exhaust passage (a downstream exhaust passage) 52b on the downstream side of the purification device 48. Here, the exhaust gas sensors 44 and 46 are each an oxygen (O₂) sensor that outputs a signal corresponding to the oxygen concentration in the exhaust gas, but may be, for example, an LAF sensor (linear air fuel ratio sensor) that is one type of air-fuel ratio sensors. The muffler 42 is configured to have a silencing function.
As illustrated in Fig. 1, the exhaust passage 52, which is continuous from the exhaust port of the cylinder head 34 of the engine main body 26, extends on a front side of the engine main body 26, that is, extends outward, then extends downward, further extends rearward passing below the engine main body 26, and extends to reach the right side of the rear wheel WR. That is, the exhaust device 39 extends from the front side of the engine main body 26 of the internal combustion engine E to the lower side, and extends on the right rear side passing on the right lower side of the engine main body 26. As illustrated in Figs. 1 to 3, the purification device 48 is located on the right lower side of the engine main body 26 in a lower part of the vehicle, and is particularly located on the lower side of the crankcase 30. The purification device 48 is disposed to extend substantially horizontally below the engine main body 26 in Fig. 1. Therefore, as illustrated in the front view of the motorcycle 10 of Fig. 2 and the bottom view of the motorcycle 10 of Fig. 3, in a case where a central virtual plane CIS extending on the center in the left-right direction from the front toward the rear of the motorcycle 10 is defined, the purification device 48 is located on its right side, and is provided in the motorcycle 10 so that a downstream portion of the purification device 48 slightly faces outer side in the vehicle width direction than an upstream portion. Note that the central virtual plane CIS can be defined to be orthogonal to the vehicle width direction and also divide each the front wheel WF and the rear wheel WR into substantially two parts.
The exhaust pipe 50, which defines and forms the downstream exhaust passage 52b extending rearward from the purification device 48, extends rearward from a downstream end portion of the purification device 48 on the right rear lower side of the crankcase 30 of the engine main body 26. In the side view of Fig. 1, the exhaust pipe 50 is provided to extend in the vehicle front-rear direction substantially along the brake pedal 24. As illustrated in Figs. 1 to 3, the exhaust pipe 50 extends to be slightly inclined upward and also slightly inclined to the vehicle outer side from the upstream end portion connected with the purification device 48 toward the downstream side in the exhaust flow direction, that is, the vehicle rear side, and is then connected with the muffler 42. The muffler 42 extends in the vehicle front-rear direction on the right side of the rear wheel WR, and is disposed to be slightly inclined upward toward the downstream side in the exhaust flow direction.
The above-described exhaust gas sensor (hereinafter, the downstream exhaust gas sensor) 46 on the downstream side of the purification device 48 is provided on the exhaust pipe 50, which defines and forms the downstream exhaust passage 52b that is an exhaust passage on the downstream side of the purification device 48. Here, as illustrated in Fig. 1, the downstream exhaust gas sensor 46 is disposed, on an upper side of the exhaust pipe 50, at a position closer to the rear end portion 24r between the rear end portion 24r and the front end portion 24f of the brake pedal 24. In addition, as illustrated in Figs. 2 and 3, the downstream exhaust gas sensor 46 is located on an upper inner side of the exhaust pipe 50. Therefore, in the front view of the motorcycle 10 of Fig. 2, a connection portion 70 of the downstream exhaust gas sensor 46 to the exhaust pipe 50 is hidden behind the purification device 48, and the downstream exhaust gas sensor 46 is also partially hidden back behind the purification device 48. Therefore, it becomes possible to protect the downstream exhaust gas sensor 46 suitably from a flying object such as a stone bounced up by the front wheel WF. Furthermore, as illustrated in Fig. 1, the downstream exhaust gas sensor 46 is provided on the exhaust pipe 50 so as to be inclined obliquely with respect to the exhaust flow direction. Thus, in the front view of the motorcycle 10 of Fig. 2, the protrusion amount of the downstream exhaust gas sensor 46 from the exhaust pipe 50 is smaller than that of a case of being attached to the exhaust pipe 50 at a right angle to the exhaust flow direction. Therefore, it becomes possible to more suitably protect the downstream exhaust gas sensor 46 from a flying object.
As illustrated in Fig. 1, the downstream exhaust gas sensor 46, which is disposed on the upper inner side of the exhaust pipe 50 to be hidden on the rear side of the purification device 48, is located on the rear side of and slightly below the footrest 22 extending substantially parallel to the purification device 48 so as to protrude on a right outer side of the purification device 48. Therefore, it becomes possible to protect the downstream exhaust gas sensor 46 suitably on an inner side of the foot of the driver without being influenced by the driver's operation on the brake pedal 24.
Note that in Figs. 1 to 3, it is possible to visually recognize the exhaust gas sensor 46 from the outside of the vehicle body, so that attachment workability and maintenance workability can be maintained satisfactorily.
Here, the above-described exhaust gas sensor (hereinafter, the upstream exhaust gas sensor) 44, which is provided on the exhaust passage 52a on the upstream side of the purification device 48, is attached to the cylinder head 34. The upstream exhaust gas sensor 44 is capable of detecting the oxygen concentration of the exhaust gas in the exhaust port defined and formed on the cylinder head 34. However, the upstream exhaust gas sensor 44 is not limited to the provision of facing the exhaust port, and may be provided on the exhaust pipe 40 as illustrated in Fig. 4. Fig. 4 is a view illustrating the exhaust pipe 40, the purification device 48, and the exhaust pipe 50, which respectively define and form portions of the exhaust passage 52 extending from the engine main body 26 of the internal combustion engine E. Unlike the exhaust device 39 for the internal combustion engine E illustrated in Fig. 1, Fig. 4 illustrates the upstream exhaust gas sensor 44, which is provided on the exhaust pipe 40 according to a modification. In this manner, the upstream exhaust gas sensor 44 can be provided at any position between the position of the exhaust port and an upstream end of a main body portion 48d of the purification device 48, in which the carrier 48b for carrying the exhaust gas purification catalyst 48a is accommodated.
Note that a control device, that is, an ECU (engine control unit) for the internal combustion engine E or the like is not illustrated, but is mounted on the motorcycle 10, and has a configuration as a computer. That is, the ECU includes a processor (for example, CPU) and a memory (for example, ROM and RAM). Output signals from various sensors are input into the ECU. For example, in addition to engine load sensors such as an engine rotation speed sensor and a throttle opening sensor, the upstream exhaust gas sensor 44 and the downstream exhaust gas sensor 46, which have been described above, are connected with the ECU. The ECU analyzes operation states based on the inputs from these sensors, and controls, for example, the respective operations of a fuel injection valve, an ignition plug, and a throttle valve, which are not illustrated, based on the analyzed operation states. For example, the ECU controls the fuel injection from the fuel injection valve so that the purification device 48 suitably purifies the exhaust gas, based on the inputs respectively from the upstream exhaust gas sensor 44 and the downstream exhaust gas sensor 46 (or the outputs from them). However, the throttle valve is not limited to an electronic control type, and may have a configuration of a mechanical operation type.
As described above, the downstream exhaust gas sensor 46 is provided on the exhaust pipe 50 so as to be inclined obliquely with respect to an exhaust flow direction EF. Fig. 5 is an enlarged perspective view of the downstream exhaust gas sensor 46 and the periphery of its attachment portion. The downstream exhaust gas sensor 46 is provided on the connection portion 70, which is welded with the exhaust pipe 50 defining and forming the downstream exhaust passage 52b, so that the downstream exhaust gas sensor 46 is inclined obliquely with respect to the exhaust flow direction EF. The connection portion 70 denotes a connection member, that is, a connection holder, here, more specifically, a boss member having a tubular shape, includes a through hole 70h (see Fig. 7) having an axis 70a, and serves as a member of insertion welding. As illustrated in Fig. 5, the connection portion 70 is connected to an attachment hole 50h of the exhaust pipe 50 by welding, here, arc welding. A weld bead 70b, which extends over the entire circumference of the connection portion 70, is formed around the connection portion 70 so as not to leave a gap between the connection portion 70 and the exhaust pipe 50.
Here, Fig. 6 is an enlarged view of the downstream exhaust gas sensor 46 and the periphery of its attachment portion in the exhaust device 39, which is removed from the motorcycle 10, and Fig. 7 is an enlarged cross-sectional view of the periphery of the downstream exhaust gas sensor 46. However, in Figs. 6 and 7, the weld bead 70b is omitted, and in Fig. 7, the downstream exhaust gas sensor 46 is not illustrated in cross-section. In addition, Fig. 8 is a view of the exhaust gas sensor 46 when viewed from a cut surface of the exhaust pipe 50, which is cut at a position on a downstream side of the downstream exhaust gas sensor 46 illustrated in Fig. 6.
A screwed portion (a female screw portion) 70c for attaching the downstream exhaust gas sensor 46 is formed in the connection portion 70 on an inner circumferential surface 70i, which defines and forms the through hole 70h having a substantially cylindrical shape that extends straight. A screwing portion (a male screw portion) 46b corresponding to the screwed portion 70c is formed on an outer circumference of the downstream exhaust gas sensor 46. Thus, the downstream exhaust gas sensor 46 is screwed (threaded) into the connection portion 70. In this situation, an abutting portion 46c, which annularly bulges in the radial direction of the downstream exhaust gas sensor 46, comes into contact with, and then abuts an abutted portion 70d of the connection portion 70. The downstream exhaust gas sensor 46 is attached to the connection portion 70 in this manner, and thus an axis 46a of the downstream exhaust gas sensor 46 coincides with the axis 70a of the through hole 70h, which is defined and formed by the inner circumferential surface 70i of the connection portion 70. In addition, their axes 46a and 70a intersect an axis 50a, which extends in the exhaust flow direction EF of the exhaust pipe 50. Therefore, here, the portion of the exhaust pipe 50 on which the connection portion 70 is provided is a pipe portion (a straight pipe portion) that extends substantially straight, and thus the axis 50a of the exhaust pipe 50, the axis 70a of the connection portion 70, and the axis 46a of the downstream exhaust gas sensor 46 extend substantially on an identical plane. Note that the axes 46a and 70a may extend not to intersect the axis 50a of the exhaust pipe 50, that is, not to intersect at one point and to be spaced apart by a distance within a certain allowable range.
The connection portion 70 is obliquely welded with the exhaust pipe 50, and includes a tip end attachment portion 70e, which is formed so that the axis 70a is inclined with respect to the exhaust flow direction EF of the downstream exhaust passage 52b. The tip end attachment portion 70e is curved along the curved shape of the exhaust pipe 50 having a substantially circular cross-section, and has a concave curved surface inclined with respect to the axis 70a. The tip end attachment portion 70e is located to be closer to the exhaust pipe 50 than the abutted portion 70d in the direction of the axis 70a of the connection portion 70, and is located at one end portion, that is, a tip end portion of the connection portion 70 in the direction of the axis 70a. Note that the other end portion of the connection portion 70 in the direction of the axis 70a is the above-described abutted portion 70d. The circumference of the tip end attachment portion 70e is welded, and thus the connection portion 70 is attached to the hole 50h of the exhaust pipe 50 so that the connection portion 70 does not protrude into the downstream exhaust passage 52b.
The exhaust gas sensor 46 is attached to the connection portion 70, which is attached to the exhaust pipe 50 in this manner, a sensor detection unit 46d on its tip end is located in the downstream exhaust passage 52b, and a sensor body portion 46e including the above-described abutting portion 46c extends on the outside of the downstream exhaust passage 52b. Then, the inclination of the downstream exhaust gas sensor 46 with respect to the exhaust flow direction EF is determined so that the sensor detection unit 46d is located on a downstream side in the exhaust flow direction EF of the sensor body portion 46e. This enables the provision of the sensor detection unit 46d in the downstream exhaust passage 52b of the exhaust pipe 50 so as to smoothly follow the exhaust gas flowing in the exhaust flow direction EF.
With regard to the inclination of the downstream exhaust gas sensor 46, in a case where a virtual plane EIS is defined to be orthogonal to the exhaust flow direction EF as illustrated in Fig. 7, an inclination θ of the axis 46a of the downstream exhaust gas sensor 46 with respect to such a virtual plane EIS may be equal to or larger than 10 degrees and equal to or smaller than 45 degrees. In consideration of the hole 50h of the exhaust pipe 50, the virtual plane EIS may be determined to pass through an intersection point CP between an extension plane of a surface 50s of the exhaust pipe 50 and the axis 70a of the connection portion 70 and to be orthogonal to the exhaust flow direction EF. By setting the inclination θ to equal to or larger than 10 degrees, it becomes possible to reduce the protrusion amount of the sensor detection unit 46d in the downstream exhaust passage 52b, as compared with a case where the inclination θ is smaller than 10 degrees, and it becomes possible to suppress the sensor detection unit 46d becoming resistance to the flow of the exhaust gas. In addition, by setting the inclination θ to equal to or smaller than 45 degrees, it becomes possible to ensure the distance to be equal to or longer than a predetermined distance between the sensor detection unit 46d and the exhaust pipe 50 itself or the weld bead 70b, that is, a back bead B to be described later, as compared with a case where the inclination θ is set to an angle larger than 45 degrees.
In addition, as illustrated in Fig. 6, the connection portion 70 is provided to locate the sensor detection unit 46d of the downstream exhaust gas sensor 46 in a position spaced apart by a distance within a predetermined distance range (a first predetermined distance range) in the exhaust flow direction EF from a downstream end 48c of the carrier 48b carrying the exhaust gas purification catalyst 48a of the purification device 48. The first predetermined distance range can be determined as a range that enables the sensor detection unit 46d of the downstream exhaust gas sensor 46 to be located in a region where the exhaust gas that has passed through the purification device 48, that is, the exhaust gas purification catalyst 48a is uniformly diffused to some extent in the downstream exhaust passage 52b. Further, it is sufficient to determine the first predetermined distance range so that the heat of the exhaust gas purification catalyst 48a, that is, the carrier 48b for carrying the purification device 48 does not affect the downstream exhaust gas sensor 46. Here, the purification device 48 includes: the main body portion 48d in which the carrier 48b carrying the exhaust gas purification catalyst 48a is disposed; and a reduced diameter portion 48e, which is connected with the downstream side in the exhaust flow direction EF of the main body portion 48d, and which is reduced in diameter toward the downstream side in the exhaust flow direction EF. Therefore, it is sufficient to set the first predetermined distance range to a distance by which the sensor detection unit 46d of the downstream exhaust gas sensor 46 is located on a downstream side of the reduced diameter portion 48e. Note that the first predetermined distance range may be determined in association with the average diameter of the exhaust pipe 50, but without being limited to this, may be determined in accordance with, for example, the shape of the exhaust pipe 50, the size of the motorcycle 10, and/or the size of the internal combustion engine E.
Furthermore, the connection portion 70 is provided to locate the sensor detection unit 46d of the downstream exhaust gas sensor 46 in a position spaced apart by a distance within a second predetermined distance range in the exhaust flow direction EF from a drain hole 51h for removing the condensed water in the exhaust passage 52. As illustrated in Fig. 1, the drain hole 51h is provided on a downstream side in the exhaust flow direction EF of the downstream exhaust gas sensor 46, and is provided in the vicinity of an upstream end of the muffler 42. Note that the drain hole 51h may be provided on the exhaust pipe 50. The atmosphere can enter from the drain hole 51h. If the downstream exhaust gas sensor 46 is too close to the drain hole 51h, the downstream exhaust gas sensor 46 will be influenced by the oxygen in the atmosphere that has entered. For this reason, the above second predetermined distance range is determined to reduce this influence. The second predetermined distance range may be defined to enable a compact arrangement of the downstream exhaust gas sensor 46 in the motorcycle 10. Note that the second predetermined distance range may be determined in association with the average diameter of the exhaust pipe 50, but without being limited to this, may be determined in accordance with, for example, the shape and/or arrangement of the exhaust pipe 50.
In the arc welding for connecting the connection portion 70 with the exhaust pipe 50, by the way, the weld bead 70b is normally generated not only on the front side (on the outside of the exhaust pipe 50) where the electrode is located but also on the back side (on the inside of the exhaust pipe 50). For example, Fig. 9 illustrates a schematic cross-sectional view of a weld portion in which two plate members M1 and M2 are welded together by arc welding. In Fig. 9, the plate members M1 and M2 are welded together by arc welding, and a weld bead MB is formed between the plate members M1 and M2. In Fig. 9, in a case where an upper surface MU is set as a front side, that is, a welding operation side, it can be seen that the weld bead MB also protrudes on a lower surface MD on the opposite side in Fig. 9.
Such a weld bead on the back side, that is, the back bead B can also be formed when the connection portion 70 is welded with the exhaust pipe 50. In particular, in welding the connection portion 70 having a tubular shape, the weld bead 70b, which is continuous around the connection portion 70, is formed. As schematically illustrated in Fig. 10, the weld bead 70b starts from a welding start portion B1, is continuously formed around the connection portion 70 from the welding start portion B1, and ends at a welding end portion B2, which overlaps the welding start portion B1. In this manner, since the welding start portion B1 overlaps the welding end portion B2, there is a possibility that the weld bead 70b in the welding start portion B1 is larger in thickness than those of the other portions, the back bead B in the welding start portion B1 is also larger in thickness than those of the other portions, and the protrusion amount into the exhaust pipe 50 is larger than those of the other portions. For this reason, also in a case where the weld bead 70b is formed and the back bead B budges around the connection portion 70, that is, in an inner region 50hi of the attachment hole 50h as illustrated in Fig. 8, here, the welding start portion B1 in a weld portion 70W around the connection portion 70 to be connected with the exhaust pipe 50 is located on a non-upstream side in the exhaust flow direction EF of the downstream exhaust gas sensor 46 in order to reduce the influence of the back bead B on the detection accuracy of the downstream exhaust gas sensor 46 (see Fig. 10). Note that the "non-upstream side" denotes any side other than the upstream side of the downstream exhaust gas sensor 46 in the exhaust flow direction EF. For example, the welding start portion B1 on the non-upstream side of the downstream exhaust gas sensor 46 can be set in a position where the exhaust gas does not directly reach the sensor detection unit 46d when the exhaust gas passes around the back bead in the welding start portion B1 in the exhaust flow direction EF. Note that in Fig. 10, the welding direction from the welding start portion B1 is indicated by an arrow A1 in the clockwise direction, but without being limited to this, the welding direction may be the counterclockwise direction.
Specifically, here, the welding start portion B1 passes through the intersection point CP between an extension plane of the surface of the exhaust pipe 50 and the axis 70a of the connection portion 70, and is located on the downstream side in the exhaust flow direction EF relative to the above virtual plane EIS (see Fig. 7), which is defined to be orthogonal to the exhaust flow direction EF. That is, in Fig. 10, in the exhaust flow direction EF, the welding start portion B1 is located on the downstream side of the virtual plane EIS.
In addition, in the present embodiment, in order to more reliably prevent the influence of the back bead B in the position of the welding start portion B1, the welding start portion B1 is located in a region within a downstream width 70r of the connection portion 70. As illustrated in Fig. 10, in a case where the length of the connection portion 70 in the direction orthogonal to the exhaust flow direction EF is defined as the width of the connection portion 70, that is, the downstream width 70r, the region within the downstream width 70r of the connection portion 70 denotes a region that extends to the downstream side of the connection portion 70 within the width 70r of the connection portion 70, in the exhaust flow direction EF.
A characteristic configuration of the exhaust device 39 for the internal combustion engine E in the motorcycle 10 having the above configuration, and its operation and effects will be described below.
In the internal combustion engine E, which is mounted on the motorcycle 10 of a straddle type vehicle, the exhaust device 39 is connected with the engine main body 26. The exhaust device 39 includes the exhaust gas purification catalyst 48a, which is provided in the exhaust passage 52, and the downstream exhaust gas sensor 46, which is provided on a downstream exhaust passage 52b on the downstream side of the exhaust gas purification catalyst 48a. The downstream exhaust gas sensor 46 is provided on the connection portion 70, which is welded with the downstream exhaust pipe 50 defining and forming the downstream exhaust passage 52b, so that the downstream exhaust gas sensor 46 is inclined obliquely with respect to the exhaust flow direction EF. Then, the welding start portion B1 in the weld portion 70W around the connection portion 70 to be connected with the exhaust pipe 50 is located on the non-upstream side in the exhaust flow direction EF of the downstream exhaust gas sensor 46. According to this configuration, the welding start portion B1 is located on the non-upstream side in the exhaust flow direction EF of the downstream exhaust gas sensor 46. Therefore, the welding start portion B1 is not located on the upstream side of the downstream exhaust gas sensor 46, and it becomes possible to suppress the weld bead 70b on the upstream side of the downstream exhaust gas sensor 46 becoming thick, so that the flow of the exhaust gas from the exhaust gas purification catalyst 48a toward the downstream exhaust gas sensor 46 can be more suitably maintained. Thus, in the exhaust device 39 for the internal combustion engine E mounted on the motorcycle 10, it becomes possible to reduce the influence of the weld bead 70b of the connection portion 70 of the downstream exhaust gas sensor 46 on the detection accuracy of the downstream exhaust gas sensor 46, on the downstream side of the exhaust gas purification catalyst 48a. Therefore, the detection accuracy of the downstream exhaust gas sensor 46 can be improved.
In particular, in the present embodiment, the welding start portion B1 is located on the downstream side in the exhaust flow direction EF of the virtual plane EIS. According to this configuration, the welding start portion B1 in the weld portion 70W around the connection portion 70 can be more reliably located on the non-upstream side in the exhaust flow direction EF of the downstream exhaust gas sensor 46. Therefore, the above operation and effects are achievable.
In addition, in the present embodiment, furthermore, the welding start portion B1 is located in a region within the downstream width 70r of the connection portion 70. According to this configuration, the welding start portion B1 in the weld portion 70W around the connection portion 70 can be more reliably located on the downstream side in the exhaust flow direction EF of the downstream exhaust gas sensor 46. This enables further suppression of the influence of hindering the flow of the exhaust gas by the weld bead 70b, and thus enables further improvement in the detection accuracy of the downstream exhaust gas sensor 46. Note that the welding start portion B1 is not limited to being located in the region within the downstream width 70r of the connection portion 70, and can be located at any position on the non-upstream side in the exhaust flow direction EF of the downstream exhaust gas sensor 46.
In addition, the inclination θ of the axis 46a of the downstream exhaust gas sensor 46 with respect to the virtual plane EIS may be equal to or larger than 10 degrees and equal to or smaller than 45 degrees. According to this configuration, the sensor detection unit 46d of the downstream exhaust gas sensor 46 can be sufficiently spaced apart from the inner wall surface 50i of the exhaust pipe 50 (see Fig. 8), and the sensor detection unit 46d itself becoming resistance of the exhaust flow can also be effectively suppressed.
The connection portion 70 is provided to locate the sensor detection unit 46d of the downstream exhaust gas sensor 46 in a position spaced apart from the downstream end 48c of the carrier 48b carrying the exhaust gas purification catalyst 48a by a distance within a first predetermined distance range in the exhaust flow direction. According to this configuration, the downstream exhaust gas sensor 46 can be provided in a place spaced apart from the exhaust gas purification catalyst 48a by an appropriate distance. Therefore, the exhaust gas uniformly diffused to some extent in the exhaust pipe 50 can be easily applied to the sensor detection unit 46d, so that the detection accuracy of the downstream exhaust gas sensor 46 can be substantially improved. In addition, according to this configuration, although the exhaust gas purification catalyst 48a, that is, the purification device 48 can have a high temperature, the downstream exhaust gas sensor 46 can be appropriately spaced apart from the exhaust gas purification catalyst 48a, so that the performance of the downstream exhaust gas sensor 46 can be suitably maintained.
Further, the connection portion 70 is provided to locate the sensor detection unit 46d of the downstream exhaust gas sensor 46 in a position spaced apart from the drain hole 51h for removing the condensed water in the exhaust passage 52 by a distance within a second predetermined distance range in the exhaust flow direction. According to this configuration, it becomes possible to suppress the influence of oxygen in atmosphere that can enter from the drain hole 51h on the downstream exhaust gas sensor 46.
Furthermore, the downstream exhaust gas sensor 46 further includes: the sensor detection unit 46d, which is located in the exhaust passage 52; and the sensor body portion 46e, which extends on the outside of the exhaust passage 52. Then, the sensor detection unit 46d is located on the downstream side of the sensor body portion 46e in the exhaust flow direction EF. According to this configuration, the sensor detection unit 46d of the downstream exhaust gas sensor 46 can be disposed along the exhaust flow direction EF. Therefore, even if the flow velocity of the exhaust gas around the downstream exhaust gas sensor 46 is very high, the pressure loss of the exhaust gas by the downstream exhaust gas sensor 46 can be reduced.
In addition, the purification device 48 including, in its inside, the exhaust gas purification catalyst 48a includes: the main body portion 48d in which the carrier 48b carrying the exhaust gas purification catalyst 48a is disposed; and the reduced diameter portion 48e, which is connected with the downstream side in the exhaust flow direction EF of the main body portion 48d, and which is reduced in diameter toward the downstream side in the exhaust flow direction EF. Then, the connection portion 70 is located on the downstream side of the reduced diameter portion 48e in the exhaust flow direction EF. As described above, the downstream exhaust gas sensor 46 includes: the sensor detection unit 46d, which is located in the exhaust passage 52; and the sensor body portion 46e, which extends on the outside of the exhaust passage 52. The sensor detection unit 46d is located on the downstream side of the sensor body portion 46e in the exhaust flow direction EF. According to this configuration, the downstream exhaust gas sensor 46 can be located on the downstream side of the reduced diameter portion 48e of the purification device 48, and in addition, the sensor detection unit 46d of the downstream exhaust gas sensor 46 can be disposed along the exhaust flow direction EF. Therefore, even if the flow velocity of the exhaust gas that has passed through the purification device 48 and then flows around the downstream exhaust gas sensor 46 is very high, the pressure loss of the exhaust gas by the downstream exhaust gas sensor 46 can be reduced.
Heretofore, embodiments and modifications in the present invention have been described. However, the present invention is not limited to them. Various substitutions and changes can be made without departing from the spirit and scope of the present invention defined by the claims of the present application.
The number of cylinders of the internal combustion engine mounted on the straddle type vehicle to which the present invention is applied is not particularly limited, and the number of cylinders of the internal combustion engine may be one, that is, a single cylinder, or may be two or more.
Note that with regard to the downstream exhaust gas sensor 46, the position of the welding start portion B1 of the weld portion 70W in the connection portion 70 has been described above. The above description of the downstream exhaust gas sensor 46, for example, the position of the welding start portion B1, may be similarly applied to the upstream exhaust gas sensor 44.

[Reference Signs List]

10: Motorcycle (straddle type vehicle)
12: Vehicle body frame
14: Head pipe
22: Footrest
24: Brake pedal
25: Kick pedal
26: Engine main body
30: Crankcase
38: Rotation axis of crankshaft
39: Exhaust device
40: Exhaust pipe
42: Muffler
44: Exhaust gas sensor
46: Exhaust gas sensor (downstream exhaust gas sensor)
48: Purification device
48a: Exhaust gas purification catalyst
50: Exhaust pipe
70: Connection portion
70b: Weld bead
70W: Weld portion
B1: Welding start portion
B2: Welding end portion

Claims

An exhaust device (39) for an internal combustion engine (E) mounted on a straddle type vehicle (10), the exhaust device (39) comprising:
an exhaust gas purification catalyst (48a) provided in an exhaust passage (52) of the internal combustion engine (E); and

an exhaust gas sensor (46) provided on a downstream exhaust passage (52b) on a downstream side of the exhaust gas purification catalyst (48a), wherein

the exhaust gas sensor (46) is provided on a connection portion (70) welded with an exhaust pipe (50) defining and forming the downstream exhaust passage (52b), so that the exhaust gas sensor (46) is inclined obliquely with respect to an exhaust flow direction (EF), and

a welding start portion (B1) in a weld portion (70W) around the connection portion (70) to be connected with the exhaust pipe (50) is located on a non-upstream side in the exhaust flow direction (EF) of the exhaust gas sensor (46).
The exhaust device (39) as claimed in claim 1, wherein
in a case where a virtual plane (EIS) is defined to pass through an intersection point (CP) between an extension plane of a surface (50s) of the exhaust pipe (50) and an axis (70a) of the connection portion (70), and is orthogonal to the exhaust flow direction (EF), the welding start portion (B1) is located on a downstream side in the exhaust flow direction (EF) of the virtual plane (EIS).
The exhaust device (39) as claimed in claim 1 or 2, wherein
the welding start portion (B1) is located in a region within a downstream width (70r) of the connection portion (70).
The exhaust device (39) as claimed in one of claims 1 to 3, wherein
in a case where the virtual plane (EIS) is defined to pass through an intersection point (CP) between an extension plane of a surface (50s) of the exhaust pipe (50) and an axis (70a) of the connection portion (70), and is orthogonal to the exhaust flow direction (EF), an inclination (θ) of an axis (46a) of the exhaust gas sensor (46) with respect to the virtual plane (EIS) is equal to or larger than 10 degrees and equal to or smaller than 45 degrees.
The exhaust device (39) as claimed in one of claims 1 to 4, wherein
the exhaust gas sensor (46) includes a sensor detection unit (46d) located in the exhaust passage (52) and a sensor body portion (46e) extending on an outside of the exhaust passage (52), and

the sensor detection unit (46d) is located on a downstream side in the exhaust flow direction (EF) of the sensor body portion (46e).
The exhaust device (39) as claimed in one of claims 1 to 4, wherein
the purification device (48) includes the exhaust gas purification catalyst (48a) in an inside, the purification device (48) having a main body portion (48d) in which a carrier (48b) carrying the exhaust gas purification catalyst (48a) is disposed, and a reduced-diameter portion (48e) connected with a downstream side in the exhaust flow direction (EF) of the main body portion (48d) and reducing in diameter toward the downstream side in the exhaust flow direction (EF), and

the connection portion (70) is located on the downstream side in the exhaust flow direction (EF) of the reduced-diameter portion (48e),

the exhaust gas sensor (46) including a sensor detection unit (46d) located in the exhaust passage (52), and a sensor body portion (46e) extending on an outside of the exhaust passage (52),

the sensor detection unit (46d) being located on the downstream side in the exhaust flow direction (EF) of the sensor body portion (46e).