WO2023190225A1

WO2023190225A1 - Exhaust device for saddle-ride vehicle

Info

Publication number: WO2023190225A1
Application number: PCT/JP2023/011968
Authority: WO
Inventors: 弘志間平; 卓也大塚; 光司吉田; 大輔堂山
Original assignee: 本田技研工業株式会社
Priority date: 2022-03-30
Filing date: 2023-03-24
Publication date: 2023-10-05

Abstract

The present disclosure is directed to providing a configuration that makes it possible to perform early activation of an exhaust purifying catalyst in a more preferable manner in an internal combustion engine having a plurality of cylinders that is mounted on a saddle-ride vehicle. An exhaust device 46 for a saddle-ride vehicle 10 according to an embodiment is provided with: an exhaust purifying catalyst 54a which is disposed on the downstream side of a collective exhaust pipe 70 into which a plurality of exhaust pipes 68 respectively connected to exhaust ports 39c of respective cylinders are collected; and at least one communication pipe 76 that provides communication between at least two of the exhaust pipes on the upstream side of the collective exhaust pipe. Each of the plurality of the exhaust pipes extends from the corresponding exhaust port positioned over a crank shaft 35 of the internal combustion engine, and the catalyst 54a is disposed under the crank shaft and is disposed in a position overlapping the crank shaft of the internal combustion engine in the longitudinal direction of the vehicle.

Description

Exhaust system for saddle type vehicles

The present invention relates to an exhaust system for a straddle-type vehicle such as a motorcycle equipped with an internal combustion engine.

Conventionally, motorcycles have been equipped with multi-cylinder engines, that is, internal combustion engines having a plurality of cylinders. For example, the motorcycle of Patent Document 1 includes a plurality of exhaust pipes connected to the exhaust ports of each cylinder of a multi-cylinder engine, a connecting pipe connecting pairs of exhaust pipes via a communication hole, and a and a radiator placed in the front. The engine disclosed in Patent Document 1 has four cylinders, and the cylinder arrangement is such that the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder are lined up in series from left to right. The exhaust pipe of the No. 1 cylinder and the exhaust pipe of the No. 2 cylinder merge at the merging point, and the exhaust pipe of the No. 3 cylinder and the exhaust pipe of the No. 4 cylinder merge at the merging portion. Further, by merging these merging parts with each other, the four exhaust pipes of the first to fourth cylinders are finally assembled into a single collecting pipe. A muffler is connected to this collecting pipe, and exhaust gas is discharged from this muffler. The connecting pipe includes a first connecting pipe that connects the exhaust pipes of the first cylinder and the fourth cylinder, and a second connecting pipe that connects the exhaust pipes of the second cylinder and the third cylinder. The tube is arranged above the second connecting tube.

Japanese Patent Application Publication No. 2020-2840

Incidentally, in the motorcycle of Patent Document 1 as well, it is desired that a catalyst purifying catalyst be disposed in the exhaust passage of the internal combustion engine, but Patent Document 1 does not contain any description regarding this. Furthermore, it is desired that the catalyst be activated early, such as when starting the internal combustion engine. An object of the present invention is to provide a configuration that enables early activation of an exhaust purification catalyst in an internal combustion engine having a plurality of cylinders that is mounted on a straddle-type vehicle such as a motorcycle, for example. There is a particular thing.

In order to achieve the above object, a first aspect of the present invention includes:
An exhaust system for a straddle-type vehicle equipped with an internal combustion engine having multiple cylinders,
an exhaust purification catalyst disposed on the downstream side of a collective exhaust pipe where a plurality of exhaust pipes connected to the exhaust port of each cylinder gather;
at least one communication pipe, the communication pipe communicating with at least two of the exhaust pipes on the upstream side of the collective exhaust pipe, each of the plurality of exhaust pipes being connected to the exhaust pipe from the crankshaft of the internal combustion engine. also extends from the corresponding exhaust port located on the upper side;
The exhaust system for a straddle-type vehicle is characterized in that the catalyst is disposed below the crankshaft and at a position overlapping with the crankshaft of the internal combustion engine in the longitudinal direction of the vehicle. provide.

According to the above configuration, the exhaust purification catalyst can be placed below the internal combustion engine, and therefore the distance from the exhaust port to the catalyst can be shortened compared to the case where the exhaust purification catalyst is installed inside the muffler, and the The catalyst can be activated. On the other hand, if the catalyst is placed close to the crankshaft, there is a concern that the exhaust pressure in the exhaust passage upstream of the catalyst will increase and this will affect the output of the internal combustion engine. can improve the output characteristics of As described above, according to the above configuration, it is possible to perform early activation of the exhaust purification catalyst in an internal combustion engine having a plurality of cylinders mounted on a straddle-type vehicle.

Preferably, each of the plurality of exhaust pipes is curved between the corresponding exhaust port and the collective exhaust pipe so that the plurality of exhaust pipes widens in the vehicle width direction. According to this configuration, the length of the exhaust passage on the upstream side of the catalyst can be made longer. Therefore, for example, the output characteristics of the internal combustion engine in a high rotation range can be improved.

Preferably, the communication pipe is provided so as to extend in a region between the plurality of exhaust pipes and the engine body of the internal combustion engine. According to this configuration, the communication pipe can be arranged compactly.

Preferably, at least a portion of the exhaust gas sensor provided upstream of the catalyst is arranged in a region between the plurality of exhaust pipes and the engine body of the internal combustion engine. According to this configuration, the exhaust gas sensor can be disposed by effectively utilizing the area between the exhaust pipe and the engine body, and the exhaust gas sensor is placed behind the exhaust pipe, that is, on the back side thereof, so that the exhaust gas sensor at least partially overlaps with the exhaust pipe. Therefore, the protection performance of the exhaust gas sensor can be improved.

Preferably, the communication pipe is connected to the corresponding exhaust pipe via a connecting pipe member. According to this configuration, it is possible to attach the communication pipe flexibly corresponding to the shape of the exhaust pipe.

Preferably, the communication pipe is configured by connecting at least two pipe members. According to this configuration, it becomes easy to adjust the assembly error of the communication pipe.

The second aspect of the present invention is
An exhaust system for an internal combustion engine for a straddle-type vehicle,
An exhaust purification catalyst disposed on the downstream side of a collective exhaust pipe in which a plurality of exhaust pipes connected to exhaust ports of each cylinder are assembled, the catalyst being arranged with respect to the crankshaft of the internal combustion engine in the direction of the cylinder axis. an exhaust purification catalyst located on the opposite side of the exhaust port;
Provided is an exhaust system for an internal combustion engine, comprising at least one communication pipe, the communication pipe communicating at least two of the exhaust pipes on the upstream side of the collective exhaust pipe.

According to the configuration of the second aspect, the exhaust purification catalyst can be placed near the crankshaft, so the distance from the exhaust port to the catalyst can be shortened compared to the case where the exhaust purification catalyst is installed in the muffler. It is possible to activate the catalyst at an early stage. On the other hand, if the catalyst is placed close to the crankshaft, the exhaust pressure in the exhaust passage on the upstream side of the catalyst tends to increase, which may affect the output of the internal combustion engine.However, by attaching the above communication pipe to the exhaust pipe, the internal combustion The output characteristics of the engine can be improved. As described above, according to the above configuration, it is possible to perform early activation of the exhaust purification catalyst in an internal combustion engine having a plurality of cylinders mounted on a straddle-type vehicle.

According to the first aspect or the second aspect of the present invention, since the above configuration is provided, early activation of the exhaust purification catalyst is more suitable in an internal combustion engine having a plurality of cylinders mounted on a straddle type vehicle. It becomes possible to do so.

FIG. 1 is a left side view of a motorcycle, which is a straddle-type vehicle, according to an embodiment of the present invention. FIG. 2 is a left side view of the motorcycle shown in FIG. 1 with a part of the body cover removed and a part of the motorcycle shown in cross section. 3 is a side view of an exhaust system for an internal combustion engine mounted on the motorcycle shown in FIG. 1. FIG. FIG. 4 is a perspective view of the upstream portion of the exhaust system of FIG. 3. FIG. 5 is a bottom view of a portion of the exhaust system 46 shown in FIG. 3, viewed from below the motorcycle. FIG. 6 is a front view of a portion of the exhaust system shown in FIG. 3, viewed from the front of the vehicle. FIG. 7 is a front view of the motorcycle of FIG. 1 from the front with a part of the body cover removed. FIG. 8 is an enlarged view of a portion of the left side view of the motorcycle shown in FIG. 1. FIG. FIG. 9 is a perspective view of a portion of the exhaust system of FIG. 3. FIG. 10 is a perspective view of a portion of a modification of the exhaust device of FIG. 3. FIG.

Hereinafter, a motorcycle 10, which is a straddle-type vehicle according to an embodiment of the present invention, will be described with reference to the accompanying drawings. Here, the up, down, front, back, left, and right directions of the vehicle body are defined based on the line of sight of the driver riding the motorcycle 10. In the figure, the upper side in the vertical direction is marked with the code "UP", the lower side with the code "DW", the front side in the longitudinal direction of the vehicle with the code "FR", and the rear side with the code "RR". The symbol "RH" is used for the right side in the vehicle width direction, and the symbol "LH" is used for the left side.

FIG. 1 shows a left side view of a motorcycle 10 that is a straddle-type vehicle according to an embodiment of the present invention. The motorcycle 10 includes a body frame 12 and a body cover 13 attached to the body frame 12. The vehicle body cover 13 covers the fuel tank 15 supported by the vehicle body frame 12 behind the head pipe section 14, and is continuous from the lower end of the tank cover 18 with a tank cover 18 connected to the seat 17 at the rear of the fuel tank 15. It has a side cover 19. Note that fuel is stored in the fuel tank 15. When driving the motorcycle 10, passengers including the driver straddle the seat 17.

A front fork 27 is supported on the head pipe portion 14 so as to be steerable. A front wheel WF is rotatably supported by the front fork 27 around an axle 28. A steering handle 29 is coupled to the upper end of the front fork 27. When driving the motorcycle 10, the driver grasps grips at the left and right ends of the steering handle 29.

A swing arm 32 is connected to the vehicle body frame 12 at the rear of the vehicle so as to be able to swing up and down about a pivot 31. A rear wheel WR is rotatably supported at the rear end of the swing arm 32 around an axle 33. An internal combustion engine (hereinafter referred to as engine) 34 that generates power by burning fuel supplied from a fuel tank 15 is mounted on the vehicle body frame 12 between the front wheels WF and the rear wheels WR. The power of the engine 34 is transmitted to the rear wheel WR via a transmission device.

The vehicle body frame 12 includes the aforementioned head pipe section 14, a main frame section extending backward from the head pipe section 14, and a seat frame section extending rearward in a substantially horizontal direction from the main frame section and supporting the seat 17 from below. and a rear frame portion coupled to the seat frame portion, but a detailed explanation thereof will be omitted here.

FIG. 2 shows a left side view of the motorcycle 10 with part of the body cover 13 removed and a part of the motorcycle 10 shown in cross section. The engine body 34B of the engine 34 is disposed below the aforementioned main frame and connected to the main frame. The engine body 34B is coupled from above to a crankcase 36 that supports a crankshaft 35 rotatably around a rotational axis 35A, and guides linear reciprocating motion of a piston 37 on a cylinder axis C that stands diagonally forward. A cylinder block 38 that partitions the cylinders; a cylinder head 39 that is connected to the cylinder block 38 from above and supports a valve train 39a; and a cylinder head 39 that is connected to the upper end of the cylinder head 39 and that supports a valve train 39a on the cylinder head 39. A head cover 41 that covers the head cover 41 is provided. The crankcase 36 houses a transmission that is connected to the crankshaft 35 and outputs the power of the crankshaft 35 at a specified gear ratio. The transmission is arranged behind the crankshaft 35.

As shown in FIG. 2, the engine body 34B of the engine 34 includes an intake device that supplies air-fuel mixture toward the engine body 34B, and an exhaust device 46 that discharges exhaust gas from the engine body 34B toward the rear of the vehicle. are connected. The intake device is coupled to the rear wall of the cylinder head 39, and defines an intake passage together with the intake port 39b of the cylinder head 39.
The intake device includes a throttle body that adjusts the flow rate of air flowing to the intake port 39b of the cylinder head 39 by the function of a throttle valve, and an air cleaner that purifies the outside air supplied to the engine 34. Note that a fuel injection valve is also provided that faces the intake port 39b of the cylinder head 39 and injects fuel.

FIG. 3 shows a side view of the exhaust device 46. In FIG. 3, the exhaust device 46 is shown in the attitude when mounted on the motorcycle 10. Further, FIG. 4 shows a perspective view of the upstream side portion of the exhaust device 46.
Note that the cover member 44 in FIGS. 3 and 4 is provided on the right side of the motorcycle 10 to protect the driver from the heat of the exhaust gas. FIG. 5 shows a bottom view of a portion of the exhaust system 46 viewed from below the motorcycle 10. In FIG. 5, rough outlines of the wheels WF, WR and the motorcycle 10 are shown to make it easier to understand the arrangement of the exhaust device 46 in the motorcycle 10, and illustration of a communication pipe to be described later is omitted. FIG. 6 shows a front view of a part of the exhaust system 46 shown in FIG. 3 as seen from the front of the vehicle.

The exhaust device 46 is coupled to the front wall of the cylinder head 39 and defines an exhaust passage 50 together with the exhaust port 39c of the cylinder head 39. The exhaust device 46 is arranged in the motorcycle 10 so as to pass under the engine body 34B and extend rearward. The exhaust device 46 includes, in order from the upstream side in the exhaust passage 50, a purification device 54 that includes an exhaust purification catalyst 54a, and a muffler 56 that has a muffler function for the engine 34 and is provided downstream of the purification device 54. As shown in FIGS. 1 and 2, the engine main body 34B is provided on the vehicle body frame 12 so that the front wall of the cylinder head 39 faces forward in the longitudinal direction of the vehicle and diagonally downward.

Now, the engine 34 is an internal combustion engine having a plurality of cylinders, and more specifically, an in-line four-cylinder water-cooled engine. Here, the cylinder arrangement of the engine 34 is assumed to be a first (#1) cylinder, a second (#2) cylinder, a third (#3) cylinder, and a fourth (#4) cylinder from left to right. The ignition order by the spark plugs provided facing the combustion chamber 58 of each cylinder is the order of #1 cylinder, #2 cylinder, #4 cylinder, and #3 cylinder (1-2-4-3 order).

A control device such as the engine 34, that is, an ECU (engine control unit) has a configuration as a computer. That is, the ECU includes a processor (eg, CPU) and memory (eg, ROM, RAM). Output signals from various sensors are input to the ECU.
For example, engine load sensors such as an engine speed sensor and a throttle opening sensor are connected to the ECU. The ECU analyzes the operating state based on inputs from these sensors, and controls the operation of, for example, a fuel injection valve, a spark plug, and a throttle valve based on the analyzed operating state. Note that the throttle valve is not limited to an electronically controlled type, and may be provided with a mechanically operated type.

The ECU also includes an exhaust gas sensor 60 provided upstream of the purification device 54 including the exhaust purification catalyst 54a, an exhaust gas sensor 62 provided downstream of the purification device 54 provided with the exhaust purification catalyst 54a, etc. is also connected. The ECU performs correction control of fuel injection control based on the operating state, for example, based on inputs from the

exhaust gas sensors

60 and 62. The

exhaust gas sensors

60 and 62 are each oxygen sensors, but may also be air-fuel ratio (A/F) sensors, for example. Other components such as a brake operating section are also connected to the ECU. An exhaust control valve 64 is provided downstream of the purification device 54, and the operation of this exhaust control valve 64 is also controlled by the ECU here.

Further, the engine 34 is a water-cooled engine, and a water jacket is formed around the cylinder block so that cooling water circulates, and a heat exchanger is provided to cool the cooling water fed to the water jacket. A radiator 66 is provided. The radiator 66 is disposed in front of the engine 34, and as shown in FIG. 1, is disposed between the front wheel WF and the engine body 34B in the longitudinal direction of the vehicle. The upper part of the radiator 66 is connected to the vehicle body frame 12 via a bracket, and the lower part of the radiator 66 is connected to the cylinder block 38 via another bracket, and is supported thereby. A fan is attached to the rear side of the radiator 66 so as to be located substantially in front of the cylinder head 38.

Here, the exhaust system 46 of the engine 34 mounted on the motorcycle 10 will be explained in more detail.

The exhaust device 46 includes a plurality of exhaust pipes 68 connected to the exhaust port 39c of each cylinder, a collective exhaust pipe 70 where these exhaust pipes 68 are collected, and an exhaust gas purifying pipe disposed downstream of the collective exhaust pipe 70. The purification device 54 includes a catalyst 54a, a downstream exhaust pipe 72 connected to the downstream side of the purification device 54, and a muffler 56 connected to the downstream side of the downstream exhaust pipe 72. Here, since the engine 34 has four cylinders, four exhaust pipes 68 are provided. Two adjacent exhaust pipes 68 among the four exhaust pipes 68 are connected to a corresponding collective exhaust pipe 70, and this collective exhaust pipe 70 is connected to the purifier 54. That is, as shown in FIG. 4, the exhaust pipe 68a of the #1 cylinder and the exhaust pipe 68b of the #2 cylinder are connected to the first collective exhaust pipe 70a, and the exhaust pipe 68c of the #3 cylinder and the exhaust pipe of the #4 cylinder are connected to the first collective exhaust pipe 70a. 68d is connected to the second collective exhaust pipe 70b, and these

collective exhaust pipes

70a and 70b are connected to the purifier 54. The two

exhaust pipes

70a and 70b on the upstream side of the purification device 54 including the exhaust purification catalyst 54a are placed next to each other in the vehicle width direction and are substantially integrated.

Each of the plurality of exhaust pipes 68 is connected to the front wall of the engine body 34B, extends diagonally forward and downward from the front wall, then curves rearward, and is shaped to face downward of the engine body 34B. It is. Each of the plurality of exhaust pipes 68 is provided to extend from a corresponding exhaust port 39c located above the crankshaft 35 of the engine 34. Then, the plurality of exhaust pipes 68 are connected to a collective exhaust pipe 70 to gather together. The collective exhaust pipe 70 is connected to a purification device 54 located below the engine body 34B. The downstream exhaust pipe 72 further extends rearward, curves to the right in the vehicle width direction, extends upward on the right side of the vehicle body, extends rearward, and connects to the muffler 56. As a result, the exhaust gas discharged from the combustion chamber 58 to the exhaust port 39c of the cylinder head of the engine body 34B of the engine 34 passes through the exhaust device 46 and is discharged through the exhaust outlet on the downstream side of the muffler 56. Note that the purifying device 54 is positioned below the crankshaft 35 of the engine 34. As shown in FIG. 5, when defining a central imaginary plane IS extending in the front-rear direction of the motorcycle 10, the purifier 54 is provided so as to intersect with the central imaginary plane IS and extend in the front-rear direction. Note that the central virtual plane IS is substantially perpendicular to the crankshaft 35 and the

axles

28 and 33, and approximately bisects each of the front wheel WF and the rear wheel WR.

As shown in FIGS. 1 to 4, each of the exhaust pipes 68 is curved so as to be convex toward the front of the vehicle. Each of the plurality of exhaust pipes 68 is curved between the corresponding exhaust port 39c and the collective exhaust pipe 70 so that the plurality of exhaust pipes 68 widen in the vehicle width direction. The four exhaust pipes 68 are curved to widen in the vehicle width direction. This flare of the exhaust pipes 68 is designed to space the exhaust pipes 68 apart from each other. Therefore, in FIG. 7, which is a front view of the motorcycle 10 seen from the front with part of the body cover 13 removed, parts of the

exhaust pipes

68a and 68d on both sides are exposed.

Here, FIG. 8 shows an enlarged view of a portion of the left side view of the motorcycle 10 in FIG. 1. In FIG. 8, a line L1 that extends vertically perpendicular to the longitudinal direction of the vehicle and passes through the rotational axis 35A of the crankshaft 35, a line L2 that passes through the rotational axis 35A and approximately the center 39d of the exhaust port 39c, and a line parallel to the line L1. and the exhaust pipe 68. Here, a line L3 is a tangent that touches the exhaust pipe 68a at a contact point L3a, and a line L4 passing through the intersection L4a of the longitudinal axis 54L of the purifier 54 and the line L1 and the above-mentioned contact L3a. Pull. Since FIG. 8 is a view of the motorcycle 10 viewed from the left side in the vehicle width direction, the line L1 and the line L3 are orthogonal to the vehicle longitudinal direction. Note that the line L3 may be a line that is parallel to the line L1 and passes through the inflection point of the exhaust pipe 68a in FIGS. It is preferable that the line passes through an intersection L4a between the longitudinal axis 54L and the line L1.

As is clear from FIG. 8, the line L1 intersects the purification device 54 equipped with the exhaust purification catalyst 54a. That is, the exhaust purification catalyst 54a is disposed below the crankshaft 35 and at a position overlapping the crankshaft 35 of the engine 34 in the longitudinal direction of the motorcycle 10. The exhaust gas sensor 60 on the upstream side of the purification device 54 including the exhaust purification catalyst 54a is provided in each of the collective exhaust pipes 70, and is located in the area shown in FIG. 8 surrounded by the four lines L1, L2, L3, and L4. Part of it is located in In addition, from another viewpoint, at least a portion of each of the exhaust gas sensors 60 is arranged in a region R (see FIG. 8) between the plurality of exhaust pipes 68 and the engine body 34B of the engine 34. In this way, the catalyst 54a is disposed below the engine body 34B and close to the engine body 34B, and as a result, a part of the exhaust passage 50 from the exhaust port 39c to the catalyst 54a is arranged such that, for example, the catalyst 54a is disposed in the muffler 56. It is much shorter than it would otherwise be.

Furthermore, the exhaust device 46 is provided with a communication pipe 76 that communicates the two exhaust pipes 68 on the upstream side of the collective exhaust pipe 70. Here, two

communication pipes

76a and 76b are provided. The first communication pipe 76a is provided to connect the exhaust pipe 68a of the #1 cylinder and the exhaust pipe 68d of the #4 cylinder, and enables mutual movement of exhaust gas between the

exhaust pipes

68a and 68d. . The second communication pipe 76b is provided to connect the exhaust pipe 68b of the #2 cylinder and the exhaust pipe 68c of the #3 cylinder, and enables mutual movement of exhaust gas between the

exhaust pipes

68b and 68c. . The first communication pipe 76a and the second communication pipe 76b are each provided to extend generally parallel to the vehicle width direction. As can be understood from FIGS. 4 and 6, the first communication pipe 76a is positioned lower than the second communication pipe 76b, but the first communication pipe 76a is located at the same height as the second communication pipe 76b, or the second communication pipe 76a is positioned lower than the second communication pipe 76b. It may be provided above the pipe 76b.

As shown in FIG. 4, the first communication pipe 76a has a seam or connection part therebetween, and is configured by connecting two pipe members P, but is configured by connecting three or more pipe members. may be done. This also applies to the second communication pipe 76b, which is constructed of a single pipe member here, and the second communication pipe 76b may also be constructed by connecting at least two pipe members. Note that it is also possible to configure the first communication pipe 76a with a single pipe member.

As shown in FIG. 4, the

communication pipes

76a, 76b are connected to the corresponding exhaust pipes 68 via connecting pipe members 78. The connecting pipe member 78 has a connection shape corresponding to the curved shape of the connection point of the exhaust pipe 68.

As shown in FIG. 8, the first communication pipe 76a is provided so as to generally extend in the area of FIG. 8 surrounded by four lines L1, L2, L3, and L4. From another perspective, the first communication pipe 76a generally extends in the region R between the plurality of exhaust pipes 68 and the engine body 34B of the engine 34. On the other hand, the second communication pipe 76b is not located in front of the plurality of exhaust pipes 68, but is arranged so as not to protrude into the region R. Note that the second communication pipe 76b may also be provided so as to protrude and extend into the region R similarly to the first communication pipe 76a.

FIG. 9 shows an enlarged perspective view of a part of the exhaust system 46 centered on the collective exhaust pipe 70, which at least partially overlaps in the side view of the motorcycle 10 shown in FIGS. 1 and 8, for example. The two exhaust gas sensors 60 provided in each of the first collective exhaust pipe 70a and the second collective exhaust pipe 70b are attached facing the same side, and are arranged facing the same direction in the vehicle width direction. has been done. Here, the two exhaust gas sensors 60 are arranged toward the left side in the vehicle width direction.

The characteristic configuration, operation, and effects of the exhaust device 46 having the above configuration will be described below.

The motorcycle 10 is equipped with an engine 34 having multiple cylinders. The exhaust system 46 of the engine 34 includes an exhaust purification catalyst 54a disposed downstream of a collective exhaust pipe 70 where a plurality of exhaust pipes 68 connected to the exhaust ports 39c of each cylinder are assembled, and an exhaust purification catalyst 54a disposed upstream of the collective exhaust pipe 70. A communication pipe 76 is provided on the side to communicate with a corresponding exhaust pipe 68. Each of the plurality of exhaust pipes 68 extends from a corresponding exhaust port 39c located above the crankshaft 35, and is connected to a collective exhaust pipe 70, which has a catalyst 54a downstream thereof. Connect directly to device 54. The catalyst 54a is disposed below the crankshaft 35 and at a position overlapping the crankshaft 35 of the engine 34 in the longitudinal direction of the vehicle (in FIG. 54 intersect). According to this configuration, the exhaust purification catalyst 54a can be arranged below the engine 34, and therefore the distance from the exhaust port 39c to the catalyst 54a is longer than when the exhaust purification catalyst 54a is provided inside the muffler 56. can be shortened, and the catalyst 54a can be activated early. On the other hand, if the catalyst 54a is placed close to the crankshaft 35, the exhaust pressure in the exhaust passage upstream of the catalyst 54a will increase, which may affect the output of the engine 34.However, a communication pipe 76 is attached to the exhaust pipe 68. By doing so, the output characteristics of the engine can be improved. In this way, according to the above configuration, it is possible to perform early activation of the exhaust purification catalyst 54a in the engine 34 that is mounted on the motorcycle 10 and has a plurality of cylinders.

In particular, in the above internal combustion engine, the ignition order is #1 cylinder, #2 cylinder, #4 cylinder, and #3 cylinder (1-2-4-3 order). One of the two

communication pipes

76a and 76b, the first communication pipe 76a, is provided to connect the exhaust pipe 68a of the #1 cylinder and the exhaust pipe 68d of the #4 cylinder, and the other, the second communication pipe 76b is provided to connect the exhaust pipe 68b of the #2 cylinder and the exhaust pipe 68c of the #3 cylinder. In this way, the exhaust pipes 68 of the cylinders whose ignition intervals are distant, in other words, the exhaust pipes 68 of the cylinders whose exhaust strokes are temporally distant, are connected by the communication pipe 76, so that the exhaust pipes 68 of the cylinders whose ignition intervals are distant from each other in terms of time are connected by the communication pipe 76, so that the exhaust pipes 68 of the cylinders whose ignition intervals are distant from each other, or in other words, the exhaust pipes 68 of the cylinders whose exhaust strokes are temporally distant are connected by the communication pipe 76. The exhaust gas can flow not only to the corresponding exhaust pipe 68 but also to the exhaust pipes 68 of other cylinders connected via the communication pipe 76. Therefore, even if the distance of the exhaust passage from the exhaust port 39c to the catalyst 54a is shortened, the length of the exhaust passage can be more preferably substantially increased.

Further, in the exhaust system 46, each of the plurality of exhaust pipes 68 is curved between the corresponding exhaust port 39c and the collective exhaust pipe 70 so that the plurality of exhaust pipes widens in the vehicle width direction.
According to this configuration, the length of the exhaust passage on the upstream side of the catalyst 54a can be made longer.
Therefore, for example, the output characteristics of the engine 34 in a high rotation range can be improved.

Furthermore, the

communication pipes

76, 76a are provided so as to extend in the region R (see, for example, FIG. 8) between the plurality of exhaust pipes 68 and the engine body 34B of the engine 34. According to this configuration, the communication pipe 76 can be arranged compactly.

Furthermore, at least a portion of the exhaust gas sensor 60 provided upstream of the catalyst 54a is arranged in a region R between the plurality of exhaust pipes 68 and the engine body 34B of the engine 34. According to this configuration, the exhaust gas sensor 60 can be disposed by effectively utilizing the area R between the exhaust pipe 68 and the engine body 34B, and the exhaust gas sensor 60 can be placed behind the exhaust pipe 68, that is, on the back side of the exhaust pipe. The exhaust gas sensor 68 can be arranged so as to at least partially overlap the exhaust gas sensor 68, thereby improving the protection performance of the exhaust gas sensor 60.

Further, the communication pipe 76 is connected to the corresponding exhaust pipe 68 via a connecting pipe member 78. According to this configuration, the communication pipe 76 can be attached flexibly to the shape of the exhaust pipe 68.

The communication pipe 76 is configured by connecting at least two pipe members, here two pipe members P. According to this configuration, it becomes easy to adjust the assembly error of the communication pipe 76 at the connecting portion of these pipe members P.

The exhaust system 46 of the engine 34 for the motorcycle 10 includes an exhaust purification catalyst 54a disposed on the downstream side of a collective exhaust pipe 70 where a plurality of exhaust pipes 68 connected to the exhaust ports 39c of each cylinder gather. Be prepared. As shown in FIG. 2, the catalyst 54a is located on the opposite side of the exhaust port 39c with respect to the crankshaft 35 of the engine 34 in the direction of the cylinder axis C. The exhaust device 46 also includes at least one communication pipe, in this case two communication pipes 76 . The communication pipe 76 connects at least two exhaust pipes, here two exhaust pipes 68 , on the upstream side of the collective exhaust pipe 70 . According to this configuration, the exhaust purification catalyst 54a can be placed near the crankshaft 35, and therefore the distance from the exhaust port 39c to the catalyst 54a can be shortened compared to the case where the catalyst 54a is provided in the muffler. The catalyst 54a can be activated early. On the other hand, if the catalyst 54a is disposed close to the crankshaft 35, the exhaust pressure in the exhaust passage upstream of the catalyst 54a is likely to increase, which may affect the output of the engine 34. By installing this, the output characteristics of the engine 34 can be improved.

In the exhaust system 46 of the motorcycle 10, two collective exhaust pipes 70 were used for the four exhaust pipes 68 from the four cylinders, but a single collective exhaust pipe 70 was used for the four exhaust pipes 68. may be used. FIG. 10 shows a portion of a modified exhaust system 164. A collective exhaust pipe 170 of the exhaust device 164 includes an upstream merging section 172 to which the two exhaust pipes 68 are connected, and a merging section main body 174 where the upstream merging section 172 further converges. An exhaust gas sensor 60 is provided in the collecting section main body 174. By providing the exhaust gas sensor 60 at a location through which exhaust gas from more cylinders passes, detection accuracy by the exhaust gas sensor can be further improved. In addition, the exhaust system 164 is provided with only a communication pipe 76 that connects the exhaust pipe 68b of the #2 cylinder and the exhaust pipe 68c of the #3 cylinder, which corresponds to the second communication pipe 76b, and the exhaust pipe of the #1 cylinder. A communication pipe connecting the exhaust pipe 68a and the #4 cylinder exhaust pipe 68d is not provided. The number of exhaust pipes connected by the communication pipe, the selection of exhaust pipes, etc. can be arbitrarily determined.

Although the embodiments according to the present invention have been described above, the present invention is not limited thereto. Various substitutions and changes can be made without departing from the spirit and scope of the invention as defined by the claims of this application.

The number of cylinders of the internal combustion engine installed in the straddle-type vehicle to which the present invention is applied is not limited to the above embodiment. The number of cylinders of the internal combustion engine may be two or more, and the number of exhaust pipes 68 may be set to a number corresponding to the number of cylinders of the internal combustion engine, preferably the same number as the number of cylinders of the internal combustion engine, and the number of exhaust pipes 68 may be determined to be the same number as the number of cylinders of the internal combustion engine. The number 70 can be set to be less than the number of exhaust pipes 68.

10...Motorcycle (straddle type vehicle)
12...Vehicle body frame 14...Head pipe 15...Fuel tank 17...Seat 34...Internal combustion engine 46...Exhaust device 54a...Exhaust purification catalyst 60...Exhaust gas sensor 68...Exhaust pipe 70...Combined exhaust pipe 76...Communication pipe 78...Connecting pipe Member P...Pipe member

Claims

An exhaust system (46) for a straddle-type vehicle (10) equipped with an internal combustion engine (34) having a plurality of cylinders,
an exhaust purification catalyst (54a) disposed on the downstream side of a collective exhaust pipe (70) where a plurality of exhaust pipes (68) connected to the exhaust port (39c) of each cylinder are gathered;
at least one communication pipe (76), the communication pipe (76) connecting at least two of the exhaust pipes (68) on the upstream side of the collective exhaust pipe (70); Each of the exhaust pipes (68) extends from the corresponding exhaust port (39c) located above the crankshaft (35) of the internal combustion engine (34),
The catalyst (54a) is disposed below the crankshaft (35) and at a position that overlaps with the crankshaft (35) of the internal combustion engine (34) in the longitudinal direction of the vehicle (10). An exhaust system (46) for a straddle-type vehicle (10), characterized in that:
Each of the plurality of exhaust pipes (68) is curved between the corresponding exhaust port (39c) and the collective exhaust pipe (70) so that the plurality of exhaust pipes (68) widen in the vehicle width direction. The exhaust system (46) for a straddle-type vehicle (10) according to claim 1.
The communication pipe (76) is provided so as to extend into a region (R) between the plurality of exhaust pipes (68) and the engine body (34B) of the internal combustion engine (34). An exhaust system (46) for a straddle-type vehicle (10) according to claim 1 or 2.
At least a portion of the exhaust gas sensor (60) provided upstream of the catalyst (54a) is located in a region ( The exhaust system (46) for a straddle-type vehicle (10) according to any one of claims 1 to 3, characterized in that the exhaust system (46) is disposed at a straddle-type vehicle (10).
The saddle according to any one of claims 1 to 4, wherein the communication pipe (76) is connected to the corresponding exhaust pipe (68) via a connecting pipe member (78). Exhaust system (46) for a riding vehicle (10).
The straddle-type vehicle (10) according to any one of claims 1 to 5, wherein the communication pipe (76) is configured by connecting at least two pipe members (P). Exhaust device (46).
An exhaust system (46) for an internal combustion engine (34) for a saddle-type vehicle (10),
An exhaust purification catalyst (54a) disposed on the downstream side of a collective exhaust pipe (70) where a plurality of exhaust pipes (68) connected to the exhaust port (39c) of each cylinder gather, an exhaust purification catalyst (54a) located on the opposite side of the exhaust port (39c) with respect to the crankshaft (35) of the internal combustion engine (34) in the direction of C);
at least one communication pipe (76), the communication pipe (76) communicating with at least two of the exhaust pipes (68) on the upstream side of the collective exhaust pipe (70); An exhaust system (46) for an internal combustion engine (34) characterized by: