Saddle-riding type vehicle

Abstract

To provide a configuration in which an exhaust gas sensor can be suitably arranged in an upstream side of an exhaust emission control catalyst while sufficiently securing protection performance of the exhaust gas sensor in an internal combustion engine having a plurality of cylinders mounted on a saddle-riding type vehicle.SOLUTION: A saddle-riding type vehicle 10 includes a collective exhaust pipe 70 in which a plurality of exhaust pipes 68 connected to an exhaust port of each of cylinders are collected, an exhaust purification catalyst 54a disposed in a downstream side thereof, and an exhaust gas sensor 60 provided on an upstream side thereof. Each of the exhaust pipes extends from the corresponding exhaust port positioned above a crankshaft, and the catalyst is arranged below the crankshaft and is arranged at a position overlapped with the crankshaft in a front-rear direction of the vehicle. At least a part of the exhaust gas sensor extends in a region between the plurality of exhaust pipes 68 and an engine body 34B.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a straddle-type vehicle such as a motorcycle equipped with an internal combustion engine.

Background Art

[0002] Conventionally, in motorcycles, it has been common to provide a multi-cylinder engine, that is, an internal combustion engine 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 that connects pairs of exhaust pipes via communication holes, and a radiator disposed in front of the exhaust pipes. 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 arranged in series from left to right. The exhaust pipe of the first cylinder and the exhaust pipe of the second cylinder merge at a merging portion, and the exhaust pipe of the third cylinder and the exhaust pipe of the fourth cylinder merge at a merging portion. Further, by the merging of these merging portions, the four exhaust pipes from the first cylinder to the fourth cylinder finally converge 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, and the first connecting pipe is disposed above the second connecting pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the motorcycle of Patent Document 1 as well, it is desirable to dispose an exhaust purification catalyst in the exhaust passage of the internal combustion engine, but there is no description thereof in Patent Document 1. On the other hand, when providing an exhaust purification catalyst, it is desirable to provide an exhaust gas sensor such as an oxygen sensor upstream thereof and perform, for example, fuel injection control. However, there are various restrictions on the layout of various devices in a motorcycle, and for example, it is not easy to dispose the exhaust gas sensor upstream of the exhaust purification catalyst while sufficiently ensuring the protection performance of the exhaust gas sensor. An object of the present invention is to provide a configuration that enables the exhaust gas sensor to be suitably disposed upstream of the exhaust purification catalyst while sufficiently ensuring the protection performance of the exhaust gas sensor in an internal combustion engine having a plurality of cylinders mounted on a saddle-type vehicle such as a motorcycle.

Means for Solving the Problems

[0005] To achieve the above object, one aspect of the present invention is a saddle-type vehicle equipped with an internal combustion engine having a plurality of cylinders, a collective exhaust pipe to which a plurality of exhaust pipes connected to the exhaust ports of the respective cylinders converge, an exhaust purification catalyst disposed downstream of the collective exhaust pipe, an exhaust gas sensor provided upstream of the exhaust purification catalyst and comprising each of the plurality of exhaust pipes extends from the corresponding exhaust port located above the crankshaft of the internal combustion engine, the catalyst is disposed below the crankshaft and is disposed at a position overlapping the crankshaft of the internal combustion engine in the longitudinal direction of the vehicle, at least a part of the exhaust gas sensor is provided so as to extend into a region between the plurality of exhaust pipes and the engine body of the internal combustion engine characterized in that it is a saddle-type vehicle is provided.

[0006] According to the above configuration, it is possible to effectively utilize the area between the plurality of exhaust pipes and the engine body to arrange the exhaust gas sensor, and it is also possible to arrange the exhaust gas sensor so as to hide it behind the exhaust pipe. Thereby, for example, the exhaust gas sensor can be protected from stones or the like splashed up by the front wheels. Thus, in an internal combustion engine having a plurality of cylinders mounted on a saddle-type vehicle, it becomes possible to suitably arrange the exhaust gas sensor upstream of the exhaust purification catalyst while sufficiently ensuring the protection performance of the exhaust gas sensor.

[0007] Preferably, the exhaust gas sensor is arranged in the collective exhaust pipe. According to this configuration, it becomes possible to sense the exhaust gas in which the exhaust gases discharged from the respective exhaust pipes are mixed in the collective exhaust pipe by using the exhaust gas sensor, and the detection accuracy in the exhaust gas sensor can be improved.

[0008] Preferably, there are two collective exhaust pipes upstream of the catalyst, and at least a part of the two collective exhaust pipes overlaps in a side view of the vehicle. According to this configuration, the collective portion of the exhaust pipes can be arranged compactly.

[0009] Preferably, the exhaust gas sensor is arranged in each of the two collective exhaust pipes, and the two exhaust gas sensors are arranged in the same direction as each other in the vehicle width direction. According to this configuration, mutual interference during the assembly of the two exhaust gas sensors can be prevented, and the efficiency of their assembly can be increased.

Advantages of the Invention

[0010] According to the above aspect of the present invention, since the above configuration is provided, in an internal combustion engine having a plurality of cylinders mounted on a saddle-type vehicle, it becomes possible to suitably arrange the exhaust gas sensor upstream of the exhaust purification catalyst while sufficiently ensuring the protection performance of the exhaust gas sensor.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0012] Hereinafter, a motorcycle 10, which is a saddle-riding type vehicle according to an embodiment of the present invention, will be described with reference to the accompanying drawings. Here, the up-down, front-rear, left-right directions of the vehicle body are defined based on the line of sight of the driver riding on the motorcycle 10. In the drawings, the symbol "UP" is used for the upper side in the vertical direction, the symbol "DW" is used for the lower side, the symbol "FR" is used for the front side in the vehicle front-rear direction, the symbol "RR" is used for the rear side, the symbol "RH" is used for the right side in the vehicle width direction, and the symbol "LH" is used for the left side.

[0013] FIG. 1 shows a left side view of a motorcycle 10, which is a saddle-riding type vehicle according to an embodiment of the present invention. The motorcycle 10 includes a vehicle body frame 12 and a vehicle body cover 13 attached to the vehicle body frame 12. The vehicle body cover 13 covers a fuel tank 15 supported by the vehicle body frame 12 behind a head pipe portion 14, and includes a tank cover 18 connected to a seat 17 behind the fuel tank 15, and a side cover 19 continuous from the lower end of the tank cover 18. Fuel is stored in the fuel tank 15. When operating the motorcycle 10, a passenger including a driver straddles the seat 17.

[0014] A front fork 27 is supported by 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 operating the motorcycle 10, the driver grips the grips at the left and right ends of the steering handle 29.

[0015] A swing arm 32 is connected to the vehicle body frame 12 behind the vehicle so as to be swingable up and down around a pivot 31. A rear wheel WR is rotatably supported by the rear end of the swing arm 32 around an axle 33. An internal combustion engine (hereinafter referred to as an engine) 34 that burns fuel supplied from the fuel tank 15 to generate power is mounted on the vehicle body frame 12 between the front wheel WF and the rear wheel WR. The power of the engine 34 is transmitted to the rear wheel WR via a transmission.

[0016] The vehicle body frame 12 includes the aforementioned head pipe portion 14, a main frame portion extending rearward and downward from the head pipe portion 14, a seat frame portion extending rearward in a substantially horizontal direction from the main frame portion and supporting the seat 17 from below, and a rear frame portion coupled to the seat frame portion. However, detailed description thereof is omitted here.

[0017] Figure 2 shows a left side view of the motorcycle 10 with a part of the body cover 13 removed and a part of the motorcycle 10 represented 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 rotatably supports a crankshaft 35 about a rotation axis 35A, and partitions a cylinder that guides the linear reciprocating motion of a piston 37 on a cylinder axis C that stands obliquely forward. The engine body 34B includes a cylinder block 38, a cylinder head 39 that is coupled to the cylinder block 38 from above and supports a valve operating mechanism 39a, and a head cover 41 that is coupled to the upper end of the cylinder head 39 and covers the valve operating mechanism 39a on the cylinder head 39. 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 disposed behind the crankshaft 35.

[0018] As shown in FIG. 2, an intake device that supplies an air-fuel mixture toward the engine body 34B of the engine 34 and an exhaust device 46 that discharges the exhaust gas of the engine body 34B toward the rear of the vehicle are connected to the engine body 34B of the engine 34. The intake device is coupled to the rear wall of the cylinder head 39 and forms 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 into the intake port 39b of the cylinder head 39 by the action of a throttle valve, and an air cleaner that purifies the outside air supplied to the engine 34. A fuel injection valve that injects fuel facing the intake port 39b of the cylinder head 39 is also provided.

[0019] Fig. 3 shows a side view of the exhaust device 46. In Fig. 3, the exhaust device 46 is shown in the posture when mounted on the motorcycle 10. Fig. 4 shows a perspective view of the upstream portion of the exhaust device 46. Note that the cover member 44 in Figs. 3 and 4 is provided on the right side surface of the motorcycle 10 to protect the driver from the heat of the exhaust gas. Fig. 5 shows a bottom view of a part of the exhaust device 46 as seen from below the motorcycle 10. In Fig. 5, the wheels WF, WR and the approximate contour line of the motorcycle 10 are shown to facilitate understanding of the arrangement of the exhaust device 46 in the motorcycle 10, and the illustration of the communication pipe described later is omitted. Fig. 6 shows a front view of a part of the exhaust device 46 shown in Fig. 3 as seen from the front of the vehicle.

[0020] The exhaust device 46 is coupled to the front wall of the cylinder head 39 and forms an exhaust passage 50 together with the exhaust port 39c of the cylinder head 39. The exhaust device 46 is arranged on the motorcycle 10 so as to pass under the engine body 34B and extend rearward. The exhaust device 46 includes, in the exhaust passage 50 in order from the upstream side, a purification device 54 provided with an exhaust purification catalyst 54a, and a muffler 56 having a silencing function of the engine 34 provided on the downstream side of the purification device 54. As shown in Figs. 1 and 2, the engine body 34B is provided on the vehicle body frame 12 such that the front wall of the cylinder head 39 faces forward and obliquely downward in the vehicle longitudinal direction.

[0021] Now, the engine 34 is an internal combustion engine having a plurality of cylinders, and more specifically, is an in-line four-cylinder water-cooled engine. Here, the cylinder arrangement of the engine 34 is the first (♯1) cylinder, the second (♯2) cylinder, the third (#3) cylinder, and the fourth (♯4) cylinder from left to right. The ignition order by the spark plugs provided so as to face the combustion chambers 58 of the respective cylinders is in the order of the ♯1 cylinder, the ♯2 cylinder, the ♯4 cylinder, and the ♯3 cylinder (in the order of 1-2-4-3).

[0022] 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 (e.g., CPU) and a memory (e.g., 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 the inputs from these sensors, and controls the operations of, for example, a fuel injection valve, an ignition 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 have a mechanically operated configuration.

[0023] In addition, an exhaust gas sensor 60 provided upstream of the purification device 54 including the exhaust purification catalyst 54a and an exhaust gas sensor 62 provided downstream of the purification device 54 including the exhaust purification catalyst 54a are also connected to the ECU. The ECU performs correction control of fuel injection control based on the operating state, for example, based on the inputs from the exhaust gas sensors 60 and 62. The exhaust gas sensors 60 and 62 are each oxygen sensors, but may be, for example, air-fuel ratio (A / F) sensors. In addition, a brake operation unit and the like are 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.

[0024] Furthermore, the engine 34 is a water-cooled engine, and a water jacket is formed so that cooling water circulates around the cylinder block, and a radiator 66, which is a heat exchanger that cools the cooling water supplied to the water jacket, is provided. The radiator 66 is disposed in front of the engine 34, and as shown in FIG. 1, is disposed between the front wheels WF and the engine body 34B in the vehicle longitudinal direction. The upper part of the radiator 66 is coupled to the vehicle body frame 12 via a bracket, and the lower part thereof is coupled to the cylinder block 38 via another bracket and is supported thereby. A fan is attached to the back surface, that is, the rear side of the radiator 66 so as to be positioned substantially in front of the cylinder head 38.

[0025] Here, the exhaust device 46 of the engine 34 mounted on the motorcycle 10 will be described in more detail.

[0026] The exhaust device 46 includes a plurality of exhaust pipes 68 connected to the exhaust ports 39c of the respective cylinders, a collective exhaust pipe 70 to which these exhaust pipes 68 converge, a purification device 54 provided with an exhaust purification catalyst 54a disposed on the downstream side of the collective exhaust pipe 70, 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. And, two adjacent exhaust pipes 68 out of the four exhaust pipes 68 are connected to the corresponding collective exhaust pipe 70, and this collective exhaust pipe 70 is connected to the purification device 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, the exhaust pipe 68c of the #3 cylinder and the exhaust pipe 68d of the #4 cylinder are connected to the second collective exhaust pipe 70b, and those collective exhaust pipes 70a, 70b are connected to the purification device 54. Incidentally, the two collective exhaust pipes 70a, 70b on the upstream side of the purification device 54 provided with the exhaust purification catalyst 54a are adjacent to each other in the vehicle width direction and are substantially integrated.

[0027] Each of the plurality of exhaust pipes 68 is connected to the front wall of the engine body 34B, extends obliquely forward and downward from the front wall, then curves rearward, and is shaped to face downward of the engine body 34B. Each of the plurality of exhaust pipes 68 is provided so as to extend from a corresponding exhaust port 39c located above the crankshaft 35 of the engine 34. And the plurality of exhaust pipes 68 gather by connecting to a collective exhaust pipe 70. The collective exhaust pipe 70 is connected to a purification device 54 disposed below the engine body 34B. And the downstream exhaust pipe 72 further extends rearward, curves to the right side in the vehicle width direction, extends upward on the right side of the vehicle body, extends rearward, and is connected to the muffler 56. Thereby, 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 purification device 54 is positioned below the crankshaft 35 of the engine 34. And as shown in FIG. 5, when a central virtual plane IS extending in the front-rear direction of the motorcycle 10 is defined, the purification device 54 is provided so as to intersect the central virtual plane IS and extend in the front-rear direction. Note that the central virtual plane IS is substantially orthogonal to the crankshaft 35, the axles 28 and 33, and substantially bisects each of the front wheel WF and the rear wheel WR.

[0028] As shown in FIGS. 1 to 4, each of the exhaust pipes 68 is curved so as to bulge toward the front of the vehicle. And 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 spread in the vehicle width direction. The four exhaust pipes 68 are curved so as to spread in the vehicle width direction. This spread of the exhaust pipes 68 is designed to separate the exhaust pipes 68 from each other. Therefore, in FIG. 7 which is a front view in a front view of the motorcycle 10 with a part of the body cover 13 removed as seen from the front, a part of the exhaust pipes 68a and 68d on both sides appears.

[0029] Here, an enlarged view of a part of the left side view of the motorcycle 10 in FIG. 1 is shown in FIG. 8. In FIG. 8, a line L1 that extends vertically and intersects the vehicle front-rear direction and passes through the rotation axis line 35A of the crankshaft 35, a line L2 that passes through the rotation axis line 35A and through the approximate center 39d of the exhaust port 39c, a line L3 that is parallel to the line L1 and is a tangent line that contacts the exhaust pipe 68 here, the exhaust pipe 68a at the contact point L3a, and a line L4 that passes through the intersection point L4a of the longitudinal axis 54L of the purification device 54 and the line L1 and the aforementioned contact point L3a are drawn. Since FIG. 8 is a view of the motorcycle 10 seen from the left side in the vehicle width direction, the line L1 and the line L3 are perpendicular to the vehicle front-rear 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. 1 and 8. In this case, the line L4 may be a line that passes through the inflection point and the intersection point L4a of the longitudinal axis 54L of the purification device 54 and the line L1.

[0030] As is clear from FIG. 8, the line L1 intersects the purification device 54 provided with the exhaust purification catalyst 54a. That is, the exhaust purification catalyst 54a is disposed below the crankshaft 35 and is disposed at a position overlapping the crankshaft 35 of the engine 34 in the front-rear direction of the motorcycle 10. The exhaust gas sensors 60 on the upstream side of the purification device 54 provided with the exhaust purification catalyst 54a are provided in each of the collective exhaust pipes 70, and a part thereof is located in the region of FIG. 8 surrounded by the four lines L1, L2, L3, and L4. In another view, at least a part of each of the exhaust gas sensors 60 is disposed in a region R (see FIG. 8) between the plurality of exhaust pipes 68 and the engine body 34B of the engine 34. Thus, the catalyst 54a is disposed near the engine body 34B below the engine body 34B. As a result, a part of the exhaust passage 50 from the exhaust port 39c to the catalyst 54a is made considerably shorter compared to the case where the catalyst 54a is disposed in the muffler 56, for example.

[0031] Further, in the exhaust device 46, a communication pipe 76 for communicating two exhaust pipes 68 is provided 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 so as to connect the exhaust pipe 68a of the #1 cylinder and the exhaust pipe 68d of the #4 cylinder, enabling mutual movement of exhaust gas between these exhaust pipes 68a and 68d. The second communication pipe 76b is provided so as to connect the exhaust pipe 68b of the #2 cylinder and the exhaust pipe 68c of the #3 cylinder, enabling mutual movement of exhaust gas between these exhaust pipes 68b and 68c. The first communication pipe 76a and the second communication pipe 76b are each provided so as to extend substantially parallel in the vehicle width direction. As can be understood from FIGS. 4 and 6, the first communication pipe 76a is positioned below the second communication pipe 76b, but it may also be provided at the same height as the second communication pipe 76b or above the second communication pipe 76b.

[0032] As shown in FIG. 4, the first communication pipe 76a has a joint, that is, a connection part therebetween and is constituted by connecting two pipe members P, but it may also be constituted by connecting three or more pipe members. This is the same for the second communication pipe 76b which is constituted by a single pipe member here, and the second communication pipe 76b may also be constituted by connecting at least two pipe members. Note that it is also possible to constitute the first communication pipe 76a with a single pipe member.

[0033] As shown in FIG. 4, the communication pipes 76a and 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 location of the exhaust pipe 68.

[0034] As shown in FIG. 8, the first communication pipe 76a is provided so as to generally extend into the region of FIG. 8 surrounded by the four lines L1, L2, L3, and L4. And, in another view, the first communication pipe 76a generally extends into 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 in the same manner as the first communication pipe 76a.

[0035] FIG. 9 shows an enlarged perspective view of a part of the exhaust device 46 centered on the collective exhaust pipe 70 at least partially overlapping in the side view of the motorcycle 10 of 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 in the same direction as each other in the vehicle width direction. Here, the two exhaust gas sensors 60 are arranged facing the left side in the vehicle width direction.

[0036] The characteristic configuration, operation, and effects of the motorcycle 10, which is a saddle-riding type vehicle having the above configuration, will be described below.

[0037] The motorcycle 10 equipped with an engine 34 having a plurality of cylinders includes a collective exhaust pipe 70 where a plurality of exhaust pipes 68 connected to the exhaust ports 39c of each cylinder converge, an exhaust purification catalyst 54a disposed on the downstream side of the collective exhaust pipe 70, and an exhaust gas sensor 60 provided on the upstream side of the exhaust purification catalyst 54a. Each of the plurality of exhaust pipes 68 extends from a corresponding exhaust port 39a located above the crankshaft 35 of the engine 34. The catalyst 54a is disposed below the crankshaft 35 and is arranged at a position overlapping the crankshaft 35 of the engine 34 in the vehicle longitudinal direction. And at least a part of the exhaust gas sensor 60 is provided so as to extend into the 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 arranged by effectively utilizing the region R between the plurality of exhaust pipes 68 and the engine body 34B. Also, the exhaust gas sensor 60 can be arranged so as to be hidden behind the exhaust pipe 68. Thereby, for example, the exhaust gas sensor 60 can be protected from stones splashed up by the front wheel WF or the like. Thus, in the engine 34 having a plurality of cylinders mounted on the motorcycle 10, it becomes possible to suitably arrange the exhaust gas sensor 60 on the upstream side of the exhaust purification catalyst 54a while sufficiently ensuring the protection performance of the exhaust gas sensor 60.

[0038] Also, the exhaust gas sensor 60 is arranged in the collective exhaust pipe 70. According to this configuration, it becomes possible to sense the exhaust gas in which the exhaust gases discharged from the respective exhaust pipes 68 are mixed in the collective exhaust pipe 70 by using the exhaust gas sensor 60, and the detection accuracy of the exhaust gas sensor 60 can be improved.

[0039] Also, the two collective exhaust pipes 70 on the upstream side of the catalyst 54a are provided on the motorcycle 10 such that at least a part of them overlaps in a side view of the motorcycle 10 as shown in FIG. 1 or the like. According to this configuration, the collective portion of the exhaust pipes 68, that is, the collective exhaust pipe 70 can be arranged compactly.

[0040] Furthermore, exhaust gas sensors 60 are arranged in each of the two collective exhaust pipes 70. The two exhaust gas sensors 60 are arranged in the same direction as each other in the vehicle width direction. According to this configuration, mutual interference during the assembly of the two exhaust gas sensors 60 can be prevented, and the efficiency of their assembly can be increased.

[0041] In addition, the exhaust device 46 of the motorcycle 10 includes a communication pipe 76 that communicates the corresponding exhaust pipes 68 on the upstream side of the collective exhaust pipe 70, in addition to an exhaust purification catalyst 54a arranged on the downstream side of the collective exhaust pipe 70 where a plurality of exhaust pipes 68 converge. Each of the plurality of exhaust pipes 68 extends from a corresponding exhaust port 39c located above the crankshaft 35 and is connected to the collective exhaust pipe 70, and this collective exhaust pipe 70 is directly connected to the purification device 54 having the catalyst 54a on its downstream side. The catalyst 54a is arranged below the crankshaft 35 and at a position overlapping the crankshaft 35 of the engine 34 in the vehicle front-rear direction (in FIG. 8, line 1 intersects the purification device 54 that internally supports the catalyst 54a). According to this configuration, the exhaust purification catalyst 54a can be arranged below the engine 34, so that the distance from the exhaust port 39c to the catalyst 54a can be shortened compared to the case where the exhaust purification catalyst 54a is provided in the muffler 56, and the catalyst 54a can be activated earlier. On the other hand, when the catalyst 54a is arranged closer to the crankshaft 35, there is concern that the exhaust pressure in the exhaust passage upstream of the catalyst 54a will increase and affect the output of the engine 34, but by attaching the communication pipe 76 to the exhaust pipe 68, the output characteristics of the engine can be improved. Thus, according to the above configuration, it becomes possible to more suitably activate the exhaust purification catalyst 54a earlier in the engine 34 having a plurality of cylinders mounted on the motorcycle 10.

[0042] Particularly in the above internal combustion engine, the ignition order is in the order of the #1 cylinder, #2 cylinder, #4 cylinder, and #3 cylinder (in the order of 1-2-4-3). And one of the two communication pipes 76a and 76b, the first communication pipe 76a, is provided so as to connect the exhaust pipe 68a of the #1 cylinder and the exhaust pipe 68d of the #4 cylinder, and the other second communication pipe 76b is provided so as to connect the exhaust pipe 68b of the #2 cylinder and the exhaust pipe 68c of the #3 cylinder. In this way, since the exhaust pipes 68 of the cylinders with a separated ignition interval, in other words, the exhaust pipes 68 of the cylinders with an exhaust stroke separated in time are connected by the communication pipe 76, the exhaust gas discharged during the exhaust stroke in a certain cylinder can flow not only into the corresponding exhaust pipe 68 but also into 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 lengthened.

[0043] Also, in the above exhaust device 46, each of the plurality of exhaust pipes 68 is curved so that the plurality of exhaust pipes spread in the vehicle width direction between the corresponding exhaust port 39c and the collective exhaust pipe 70. According to this configuration, the length of the exhaust passage upstream of the catalyst 54a can be made longer. Therefore, for example, the output characteristics of the engine 34 in the high rotation range can be improved.

[0044] Furthermore, the communication pipes 76 and 76a are provided so as to extend into the region R (see FIG. 8 for example) 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.

[0045] Also, the communication pipe 76 is connected to the corresponding exhaust pipe 68 via the connecting pipe member 78. According to this configuration, the communication pipe 76 can be flexibly attached to the shape of the exhaust pipe 68.

[0046] And 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 connection part of those pipe members P.

[0047] Note that the exhaust device 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 the respective cylinders converge. As shown in FIG. 2, the catalyst 54a is located on the side opposite to the exhaust port 39c with respect to the crankshaft 35 of the engine 34 in the direction of the cylinder axis C. Further, the exhaust device 46 includes at least one communication pipe, here two communication pipes 76. The communication pipes 76 communicate 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 disposed in the vicinity of the crankshaft 35, and thus 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, and the catalyst 54a can be activated earlier. On the other hand, when the catalyst 54a is disposed closer to the crankshaft 35, there is a concern that the exhaust pressure in the exhaust passage on the upstream side of the catalyst 54a may increase and affect the output of the engine 34. However, by attaching the communication pipe 76 to the exhaust pipe 68, the output characteristics of the engine 34 can be improved.

[0048] In the exhaust device 46 of the motorcycle 10 described above, two collective exhaust pipes 70 are used for the four exhaust pipes 68 from the four cylinders, but a single collective exhaust pipe 70 may be used for the four exhaust pipes 68. FIG. 10 shows a part of a modified exhaust device 164. The collective exhaust pipe 170 of the exhaust device 164 includes an upstream confluence portion 172 to which two exhaust pipes 68 are connected, and a collective portion main body 174 where the upstream confluence portion 172 further converges. An exhaust gas sensor 60 is provided in the collective portion main body 174 of the collective exhaust pipe 170. By providing the exhaust gas sensor 60 at a location where exhaust gas from more cylinders passes through in this way, the detection accuracy by the exhaust gas sensor can be further improved. Further, in the exhaust device 164, only the communication pipe 76 that connects the exhaust pipe 68b of the #2 cylinder and the exhaust pipe 68c of the #3 cylinder, corresponding to the second communication pipe 76b, is provided, and the communication pipe that connects the exhaust pipe 68a of the #1 cylinder and the exhaust pipe 68d of the #4 cylinder is not provided. The number of exhaust pipes connected by the communication pipe, the selection of the exhaust pipes, etc. can be arbitrarily determined.

[0049] Although the embodiments according to the present invention have been described above, the present invention is not limited thereto. Various substitutions and modifications are possible without departing from the spirit and scope of the present invention defined by the claims of this application.

[0050] The number of cylinders of the internal combustion engine mounted on the straddle-type vehicle to which the present invention is applied is not limited to the above embodiments. The number of cylinders of the internal combustion engine may be two or more, the number of exhaust pipes 68 can be determined to be 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 the collective exhaust pipe 70 can be determined to be less than the number of exhaust pipes 68.

Explanation of reference numerals

[0051] 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 gas purification catalyst, 60... Exhaust gas sensor, 68... Exhaust pipe 70... Collective exhaust pipe, 76... Communication pipe, 78... Connecting pipe member, P... Pipe member

Claims

1. A straddle-type vehicle (10) equipped with an internal combustion engine (34) having a plurality of cylinders, a collective exhaust pipe (70) where a plurality of exhaust pipes (68) connected to the exhaust ports (39c) of each cylinder converge, an exhaust purification catalyst (54a) disposed downstream of the collective exhaust pipe (70), and an exhaust gas sensor (60) provided upstream of the exhaust purification catalyst (54a). The vehicle is provided with: Each of the plurality of 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 is positioned to overlap the crankshaft (35) of the internal combustion engine (34) in the longitudinal direction of the vehicle (10). At least a part of the exhaust gas sensor (60) is provided to extend into the region (R) between the plurality of exhaust pipes (68) and the engine body (34B) of the internal combustion engine (34). A straddle-type vehicle (10) characterized by the above.

2. The exhaust gas sensor (60) is disposed in the collective exhaust pipe (70, 170). The straddle-type vehicle (10) according to Claim 1, characterized by the above.

3. There are two collective exhaust pipes (70) upstream of the catalyst (54a). In a side view of the vehicle (10), at least a part of the two collective exhaust pipes (70) overlaps. The straddle-type vehicle (10) according to Claim 1 or 2, characterized by the above.

4. The exhaust gas sensor (60) is disposed in each of the two collective exhaust pipes (70). The two exhaust gas sensors (60) are arranged facing the same direction in the vehicle width direction. The straddle-type vehicle (10) according to Claim 3, characterized by the above.

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