Saddle-type vehicle

Abstract

To provide a structure which enables a three-way catalyst and a NOx storage catalyst to be arranged effectively in an exhaust passage of an internal combustion engine at a saddle riding type vehicle.SOLUTION: A saddle riding type vehicle 1 according to one embodiment comprises: a three-way catalyst 53a which is disposed in an exhaust passage of an internal combustion engine 20; and a NOx storage catalyst 53b which is disposed downstream of the three-way catalyst in the exhaust passage. At least a part of a first exhaust purification unit 51d comprising the NOx storage catalyst is exposed to the outer side in a width direction of the vehicle.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a straddle-type vehicle such as a motorcycle. [Background technology]

[0002] Efforts to mitigate or reduce the impact of climate change have been ongoing for some time, and research and development has been conducted to reduce emissions of harmful substances in order to achieve this. Specifically, exhaust purification catalysts, such as three-way catalysts, have been installed in the exhaust passage of internal combustion engines.

[0003] For example, Patent Document 1 discloses that a three-way catalyst and a NOx storage catalyst are arranged in this order from the upstream side in the exhaust passage of an internal combustion engine. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4765991 Summary of the Invention [Problem to be solved by the invention]

[0005] In four-wheeled automobiles, internal combustion engines are operated with lean combustion to improve fuel economy. There is also a desire to introduce lean combustion to improve the fuel economy of the internal combustion engines installed in straddle-type vehicles such as motorcycles. In this case, when an internal combustion engine is operated with lean combustion, there is a risk that a larger amount of nitrogen oxides (NOx) will be released into the atmosphere than during stoichiometric operation. Therefore, it is desirable to provide a NOx storage catalyst in the exhaust system of straddle-type vehicles in order to remove the nitrogen oxides that may be emitted during lean combustion.

[0006] However, while harmful substances in exhaust gases can be effectively reduced by placing a three-way catalyst and a NOx storage catalyst in the exhaust passage of an internal combustion engine as described in Patent Document 1, there are issues with placement in straddle-type vehicles such as motorcycles. For example, NOx storage catalysts have a lower heat resistance temperature than three-way catalysts, so from the standpoint of heat resistance, it is desirable to place them in a different position from the three-way catalyst, but in straddle-type vehicles the space available for placing various components is limited.

[0007] In order to solve the above-mentioned problems, the present application aims to provide a configuration that enables a three-way catalyst and a NOx storage catalyst to be effectively arranged in the exhaust passage of an internal combustion engine in a saddle-ride type vehicle, thereby contributing to mitigating or reducing the impact of climate change. [Means for solving the problem]

[0008] One aspect of the present invention is In a saddle-type vehicle equipped with an internal combustion engine, a three-way catalyst disposed in an exhaust passage of the internal combustion engine; a NOx storage catalyst disposed downstream of the three-way catalyst in the exhaust passage; Equipped with At least a portion of the first exhaust purification unit including the NOx storage catalyst is exposed to the outside in the vehicle width direction. Saddle-type vehicle to provide.

[0009] According to the above configuration, a three-way catalyst and a NOx storage catalyst are arranged in this order from upstream to downstream in the exhaust passage of the internal combustion engine of a saddle-riding vehicle, and at least a portion of the first exhaust purification unit equipped with the NOx storage catalyst is exposed to the outside in the vehicle width direction. Therefore, the NOx storage catalyst of the first exhaust purification unit can be cooled to an appropriate temperature by the running wind, making it possible to prevent deterioration of the NOx storage catalyst due to heat damage. Furthermore, because at least a portion of the first exhaust purification unit equipped with the NOx storage catalyst is exposed to the outside in the vehicle width direction, the first exhaust purification unit equipped with the NOx storage catalyst can be mounted on the saddle-riding vehicle without significantly modifying the arrangement space of various other components of the saddle-riding vehicle. Therefore, according to the above configuration, it is possible to effectively arrange a three-way catalyst and a NOx storage catalyst in the exhaust passage of the internal combustion engine of a saddle-riding vehicle.

[0010] Preferably, at least a portion of the second exhaust purification section equipped with the three-way catalyst is disposed behind the windbreak section. With this configuration, by positioning at least a portion of the second exhaust purification section equipped with the three-way catalyst behind a windbreak section, such as a body cover or a front wheel, it is possible to make it difficult for the wind generated by traveling to hit the second exhaust purification section, thereby making it possible to maintain the temperature of the three-way catalyst at an appropriate temperature.

[0011] Preferably, the upstream end of the first exhaust purification section equipped with the NOx storage catalyst is located at a different position from the downstream end of the first exhaust purification section in the vertical direction of the vehicle. With this configuration, the first exhaust purification section equipped with the NOx storage catalyst can be disposed at an angle or right angle to the horizontal ground plane. Therefore, the wind generated by running can be efficiently applied to the first exhaust purification section equipped with the NOx storage catalyst, particularly to its longitudinally extending surface, and the NOx storage catalyst can be cooled to an appropriate temperature.

[0012] Preferably, when a plane extending toward the center of the vehicle body in the vehicle width direction is defined, the second exhaust purification section including the three-way catalyst intersects with the plane. With this configuration, the three-way catalyst can be positioned more actively behind the windshield function section, making it more difficult for the wind to hit the second exhaust purification section including the three-way catalyst, and making it possible to continue to maintain an appropriate temperature for the three-way catalyst.

[0013] Preferably, the internal combustion engine has a fan at one end of a crankshaft oriented in a vehicle width direction, and the first exhaust purification unit equipped with the NOx storage catalyst is positioned radially outward of the fan about a central axis of rotation of the fan. With this configuration, the first exhaust purification unit equipped with the NOx storage catalyst can be arranged compactly near the fan, thereby saving space.

[0014] Preferably, the internal combustion engine has a fan at one end of a crankshaft oriented in the vehicle width direction, a fan cover is provided axially outward of the fan, the fan cover has an opening that opens downward, the first exhaust purification unit including the NOx storage catalyst is located below the fan cover, and at least a portion of the first exhaust purification unit is covered by the fan cover. With this configuration, the first exhaust purification unit can be suitably cooled by the wind from the fan, and the NOx storage catalyst can be cooled to an appropriate temperature.

[0015] Preferably, the saddle-type vehicle further includes a first sensor provided in the exhaust passage upstream of the NOx storage catalyst and downstream of the three-way catalyst, and a second sensor provided in the exhaust passage downstream of the NOx storage catalyst, and at least one of at least a portion of the first sensor and at least a portion of the second sensor is covered by the fan cover. This configuration can protect at least one of the first sensor and the second sensor from obstacles such as flying stones. Note that, for example, the first sensor may be a temperature sensor, and the second sensor may be an exhaust gas sensor.

[0016] Preferably, the fan cover has a cutout portion in which a sensor provided in the exhaust passage is disposed. This configuration improves accessibility to the sensor, thereby facilitating maintenance of the sensor.

[0017] Preferably, at least a portion of the first exhaust purification section including the NOx storage catalyst is located inside a brake pedal in the vehicle width direction and is covered by the brake pedal. According to this configuration, by covering at least a portion of the first exhaust purification section including the NOx storage catalyst with the brake pedal, the protection performance of the NOx storage catalyst can be improved. [Effects of the Invention]

[0018] According to the above aspect of the present invention, since the above configuration is provided, it becomes possible to effectively arrange a three-way catalyst and a NOx storage catalyst in the exhaust passage of an internal combustion engine in a straddle-type vehicle. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is an overall right side view of a motorcycle according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged left side view of a portion of the vehicle of FIG. [Figure 3] 2 is a side view of a power unit, an intake device, and an exhaust device of the motorcycle of FIG. 1. [Figure 4] FIG. 4 is a plan view of FIG. 3. [Figure 5] FIG. 2 is a bottom view of a portion of the motorcycle. [Figure 6] FIG. 2 is a partial cross-sectional view taken along the crankshaft of the internal combustion engine of the power unit. [Figure 7] FIG. 2 is an overall left side view of the motorcycle of FIG. 1. [Figure 8] FIG. 2 is a front view of a portion of the motorcycle of FIG. [Figure 9] FIG. 2 is a perspective view of a fan cover of the motorcycle of FIG. 1. [Figure 10]FIG. 2 is a schematic diagram of the motorcycle of FIG. 1 as seen from the front of the vehicle. [Figure 11] 10 is a graph showing experimental results. [Figure 12] FIG. 10 is an overall left side view of a motorcycle according to a second embodiment of the present invention. [Figure 13] FIG. 13 is a front view of a portion of the motorcycle of FIG. 12. [Figure 14] FIG. 13 is a schematic diagram of the motorcycle of FIG. 12 as seen from the front of the vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a first embodiment of the present invention will be described. Fig. 1 shows a side view of a scooter-type motorcycle 1 according to this embodiment. In the explanations in this specification, the directions of front, back, left, right, and up and down will follow the usual standard of the straight-ahead direction of the motorcycle 1 in this embodiment being the forward direction, and in the drawings, FR indicates the forward direction, RE indicates the rearward direction, LH indicates the leftward direction, RH indicates the rightward direction, UP indicates the upward direction, and DW indicates the downward direction.

[0021] As shown in FIG. 1, a front body 1F and a rear body 1R are connected via a low floor portion 1C, and a body frame F that forms the skeleton of the body is generally composed of a down tube 3 and a main pipe 4. That is, a down tube 3 extends downward from a head pipe 2 at the front part 1F of the vehicle body, bends horizontally at its lower end and extends rearward below the floor part 1C, and is connected at its rear end to a pair of left and right main pipes 4, which form an inclined section 4a that extends diagonally upward and rearward from the connected section, and the upper part of the inclined section 4a is further bent to form a horizontal section 4b that extends rearward approximately horizontally.

[0022] In the front body portion 1F, the head pipe 2 and the vertically oriented portions of the down tube 3 are covered from the front and rear by the front cover 1a and leg shield 1b, in the floor portion 1C, the vertically oriented portions of the down tube 3 are covered by the lower side cover 1c, and in the rear body portion 1R, the main pipe 4 is covered on the left, right, and rear sides by the body cover 1d. The lower side cover 1c, which covers the underside of the vehicle, extends from the bottom of the front cover 1a toward the rear of the vehicle and covers part of the right side of the power unit P, as shown in Figures 2 and 7. The front cover 1a, leg shield 1b, lower side cover 1c, and body cover 1d are included in the body cover BC.

[0023] A storage box 5 and a fuel tank (not shown) are supported at the front and rear between the pair of main pipes 4, and a seat 7 is disposed above the storage box 5 and the fuel tank to cover them. On the other hand, at the front body 1F, a handlebar 8 is provided above and journalled on the head pipe 2, and a front fork 9 extends below and journalled at its lower end to a front wheel 10.

[0024] As shown in Fig. 1, a support bracket 11 is provided to protrude rearward, located approximately halfway along the longitudinal direction of the inclined portion 4a of the main pipe 4. As shown in Fig. 2, a hanger 22h is provided to protrude diagonally upward from the top of the power unit P. The support bracket 11 of the main pipe 4 and the hanger 22h are connected via a link member 12, and this link mechanism connects and supports the power unit P to the main pipe 4 so that it can swing.

[0025] 3, a single-cylinder, four-stroke, air-cooled internal combustion engine 20 is mounted in the front of the power unit P. A cylinder block 23, a cylinder head 24, and a head cover 25 are sequentially stacked on top of each other in a crankcase 22 that supports a crankshaft 21 oriented in the vehicle width direction and protrude forward in a posture that is tilted forward to a nearly horizontal state. Here, the portion of the internal combustion engine 20 including the crankcase 22, the cylinder block 23, the cylinder head 24, and the head cover 25 is referred to as an engine body B.

[0026] Referring to Figure 6, the crankcase 22 is split into left and right parts, a left crankcase part 22L and a right crankcase part 22R, and the crankshaft 21 oriented in the vehicle width direction is rotatably supported by the left crankcase part 22L and the right crankcase part 22R via main bearings 21b, 21b, respectively.

[0027] An AC generator 55 is provided on the right shaft portion of the crankshaft 21, and a centrifugal cooling fan 56 is integrally attached to an outer rotor 55r of the AC generator 55. A fan cover 57 that covers the right crankcase portion 22R from the right side houses the centrifugal cooling fan 56. Referring also to Figure 2, the fan cover 57 is formed with a grill 57g that serves as an outside air inlet facing the centrifugal cooling fan 56. In this way, the centrifugal cooling fan 56 is an air-cooled fan and may be simply referred to as a fan.

[0028] 6, the left crankcase 22L extends rearward and doubles as a transmission case, and a transmission case cover 65 covers the transmission case (left crankcase) 22L from the left side, with the belt-type continuously variable transmission 60 disposed inside. A drive chain sprocket 58 is provided adjacent to the main bearing 21b on the left shaft portion of the crankshaft 21, and a drive pulley 61 of the belt-type continuously variable transmission 60 is provided on the end of the left shaft.

[0029] Power is transmitted to the valve mechanism on the cylinder head 24 side by a cam chain 59 wound around a drive chain sprocket 58 . 1 and 3, the reduction gear output shaft of the reduction mechanism 64 provided at the rear of the belt-type continuously variable transmission 60 is the rear axle 28a, and the rear wheel 28 is provided on the rear axle 28a. A rear cushion (not shown) is interposed between the upper end of the rear part of the transmission case 22L that houses the reduction mechanism 64 and the upper bent part of the main pipe 4.

[0030] 3, a driven pulley 63 of the belt-type continuously variable transmission 60 is journaled on a reducer input shaft 64a of the reduction mechanism 64, a belt 62 is wound around a drive pulley 61 provided on the crankshaft 21 and the driven pulley 63 provided on the reducer input shaft 64a, and the power of the internal combustion engine 20 is transmitted to the driven pulley 63 via the belt 62, and the rotation of the driven pulley 63 is transmitted to the reducer input shaft 64a of the reduction mechanism 64 via a centrifugal clutch (not shown), and is then reduced in speed by the reduction mechanism 64 before being transmitted to the rear wheel 28. As shown in FIG. 6, an outside air intake fan 61F is formed on the left pulley half of the drive pulley 61.

[0031] A shroud 70, which is an air guide member as shown in Figure 6, surrounds the cylinder block 23 and the cylinder head 24, and the right side of the shroud 70 is connected to the fan cover 57. Therefore, air can be blown through the shroud 70 to various parts of the cylinder block 23 and the cylinder head 24, for example, around the outlet of the exhaust port 24b of the cylinder head 24 of the internal combustion engine 20.

[0032] 3, an intake port 24a is formed on the upper surface of a cylinder head 24 of an internal combustion engine 20 in the front part of a power unit P, and an inlet pipe 31 serving as an intake pipe extends upward from the intake port 24a. An exhaust port 24b is formed on the lower surface of the cylinder head 24, and an exhaust pipe 51 extends downward from the exhaust port 24b. An ignition plug 26 is inserted into the cylinder head 24 near the center of the head cover 25, and an oxygen concentration sensor 27 is inserted into the location where the exhaust pipe 51 extends.

[0033] An intake device 30 that draws in outside air and sends it to the internal combustion engine 20 is connected to the intake port 24a of the internal combustion engine 20. The inside of the intake device 30 forms an intake passage through which the intake air sent to the internal combustion engine 20 passes, introducing the intake air into the combustion chamber 20a of the internal combustion engine 20. The intake device 30 comprises an air cleaner device 40 that takes in and purifies outside air, a connecting tube 36 connected to the air cleaner device 40, a throttle body 33 connected to the downstream side of the connecting tube 36, and an inlet pipe 31 connected to the downstream side of the throttle body 33, and these together form an intake system.

[0034] As shown in Figure 4, the air cleaner device 40 of the intake device 30 has an air cleaner case 41 which is made up of left and right unpurified chamber cases 42 and purified chamber cases 43, and a partition section 45 which is arranged between the unpurified chamber case 42 and the purified chamber case 43 and in which an air cleaner element 44 is arranged, dividing the air cleaner element 44 into an unpurified chamber Ca on the unpurified chamber case 42 side and a purified chamber Cb on the purified chamber case 43 side. As shown in Figure 3, an air intake pipe 47, which takes in airflow from running, is disposed in the unpurified chamber case 42 with its opening 47a facing forward. The intake air introduced through the opening 47a passes through the unpurified chamber Ca, passes through the air cleaner element 44, is purified, and is sent to the purified chamber Cb. The purified chamber Cb of the air cleaner device 40 is connected to the throttle body 33 by an elastically deformable connecting tube 36 made of rubber. A fuel injection valve 37 is attached to the top of each of the throttle body 33 and the inlet pipe 31, and injects fuel into the intake passage.

[0035] 5, an exhaust device 50 is connected to the exhaust port 24b of the cylinder head 24. The exhaust device 50 includes an exhaust pipe 51 connected to the exhaust port 24b, and a muffler 52 connected to the rear end of the exhaust pipe 51 and with an atmosphere opening 52a facing rearward of the vehicle, each of which defines a portion of an exhaust passage 50E. Catalytic devices 53a, 53b are housed in the exhaust pipe 51. The exhaust gas emitted from the internal combustion engine 20 flows into the exhaust pipe 51 from the exhaust port 24b, is purified by a catalytic device (hereinafter referred to as the upstream catalytic device) 53a and a catalytic device (hereinafter referred to as the downstream catalytic device) 53b provided midway along the exhaust pipe 51, passes through the muffler 52, and is discharged into the atmosphere from the open-air port 52a.

[0036] The exhaust pipe 51 communicates with the exhaust port 24b, extends downward from the underside of the cylinder head 24, bends diagonally forward to the left, bends further from the rear to the right, bends from the left to the right of the lower part of the crankcase 22, extends rearward, and is connected to a muffler 52 disposed on the right side of the rear wheel 28.

[0037] The exhaust pipe 51 is composed of a catalyst-device-accommodating exhaust pipe 51c in which an upstream catalyst device 53a is accommodated, a catalyst-device-accommodating exhaust pipe 51d in which a downstream catalyst device 53b is accommodated, an upstream exhaust pipe 51a connected to the upstream side of the catalyst-device-accommodating exhaust pipe 51c, an intermediate exhaust pipe 51b connected to the downstream side of the catalyst-device-accommodating exhaust pipe 51c and the upstream side of the catalyst-device-accommodating exhaust pipe 51d, and a downstream exhaust pipe 51e connected to the downstream side of the catalyst-device-accommodating exhaust pipe 51d.

[0038] The upstream exhaust pipe 51a is connected to the exhaust port 24b and extends downward from the underside of the cylinder head 24 (see also Figure 3), then bends diagonally forward to the left and then bends again from the rear to the right to be connected to the catalytic converter-accommodated exhaust pipe 51c.

[0039] The catalyst device-accommodating exhaust pipe 51c is located below the internal combustion engine 20 and is arranged so that exhaust gas flows in the vehicle width direction from the left side to the right side of the vehicle. Here, a central imaginary plane IS extending from the front to the rear of the motorcycle 1 is defined. The central imaginary plane IS is a plane extending to the center of the vehicle body in the vehicle width direction, is perpendicular to the vehicle width direction (left-right direction LH-RH), and in the motorcycle 1, extends so as to substantially bisect the front wheel 10 and the rear wheel 28, respectively, as shown in Figures 5 and 8. As shown in Figure 5, the catalyst device-accommodating exhaust pipe 51c intersects this central imaginary plane IS, and the upstream catalyst device 53a accommodated therein also intersects the central imaginary plane IS. The catalytic converter-accommodating exhaust pipe 51c is disposed so that its upstream end is located on the left side in the vehicle width direction and its downstream end is located on the right side in the vehicle width direction. The upstream end is connected to the upstream exhaust pipe 51a, and the downstream end is connected to the intermediate exhaust pipe 51b.

[0040] An upstream catalytic device 53a is housed inside the catalytic device-housed exhaust pipe 51c, with its axis oriented in the vehicle width direction. The upstream catalytic device 53a is a honeycomb-shaped porous structure with numerous pores extending in its axial direction, and a so-called three-way catalyst (TWC) made of, for example, platinum, rhodium, and palladium is supported on the porous structure as a component that decomposes exhaust gas. Here, the upstream catalytic device 53a of the catalytic device-housed exhaust pipe 51c, which corresponds to the second exhaust purification section, can be simply referred to as a three-way catalyst.

[0041] As shown in Fig. 5, the intermediate exhaust pipe 51b is connected to the downstream side of the catalytic converter-housed exhaust pipe 51c, extends in the vehicle width direction, and then curves rearward. In the vehicle bottom view of Fig. 5, the intermediate exhaust pipe 51b extends rearward in the vehicle front-to-rear direction on the outer side in the vehicle width direction from the crankcase 22 that constitutes the unit case Pc, and is connected to the catalytic converter-housed exhaust pipe 51d. Furthermore, as shown in Figs. 2 and 7, in the vehicle right side view, the intermediate exhaust pipe 51b extends rearward from the right side of the lower part of the power unit P and is connected to the catalytic converter-housed exhaust pipe 51d.

[0042] The catalytic converter-housed exhaust pipe 51d is visible and exposed when viewed from the right side of the vehicle body as shown in Figures 2 and 7, and is particularly visible here than the catalytic converter-housed exhaust pipe 51c. The catalytic converter-housed exhaust pipe 51d extends rearward in the vehicle front-rear direction on the outer side in the vehicle width direction from the crankcase 22 that constitutes the unit case Pc. Furthermore, as shown in Figures 2 and 7, the catalytic converter-housed exhaust pipe 51d extends diagonally downward and rearward in the front-rear direction below the power unit P when viewed from the right side of the vehicle body, and is connected to the downstream exhaust pipe 51e.

[0043] A downstream catalytic device 53b is housed inside the catalytic device-housed exhaust pipe 51d, with its axis generally oriented in the vehicle longitudinal direction. The downstream catalytic device 53b is a honeycomb-shaped porous structure having numerous pores extending in its axial direction, and a so-called NOx storage catalyst containing, for example, platinum and an NOx absorbent is supported on the porous structure for purifying nitrogen oxides (NOx) in the exhaust gas. Here, the downstream catalytic device 53b of the catalytic device-housed exhaust pipe 51d, which corresponds to the first exhaust purification section, may simply be referred to as the NOx storage catalyst. However, the downstream catalytic device 53b, i.e., the NOx storage catalyst, is not limited to this configuration and may have various configurations, such as a precious metal other than platinum. In the NOx storage catalyst, when the internal combustion engine 20 is operating in a fuel-lean state, the NOx in the exhaust gas is absorbed by the NOx absorbent, and when the internal combustion engine 20 is operating in a fuel-rich state (including so-called rich spikes), the NOx is released from the NOx absorbent and reacts with CO and HC to become N2. In this way, the NOx storage catalyst can remove, or purify, the NOx that may be emitted during lean-burn operation, so by arranging the NOx storage catalyst in the exhaust passage 50E, it becomes possible to actively operate the internal combustion engine 20 in a lean-burn state.

[0044] 5, the downstream exhaust pipe 51e is connected to the downstream side of the catalytic converter-accommodating exhaust pipe 51d, and extends rearward in the vehicle longitudinal direction on the outer side in the vehicle width direction from the crankcase 22. Furthermore, as shown in FIGS. 2 and 7, the downstream exhaust pipe 51e is bent and extends obliquely upward from the left side of the lower part of the power unit P in a right side view of the vehicle body, and is connected to a muffler 52 disposed on the right side of the rear wheel 28.

[0045] 2 is a right side view of the vicinity of the power unit P, with a portion of the front side of the fan cover 57 cut away. In the side view of FIG. 2, the catalyst device-accommodating exhaust pipe 51d is located between two curved portions, the intermediate exhaust pipe 51b on the upstream side and the downstream exhaust pipe 51e on the downstream side, and is positioned radially outward of the centrifugal cooling fan 56, particularly radially downward thereof, about the central rotation axis C1 of the centrifugal cooling fan 56, which is covered by the fan cover 57 on one end side of the crankshaft 21 oriented in the vehicle width direction. The central rotation axis C1 of the centrifugal cooling fan 56 coincides with the rotation axis, i.e., the rotation axis line, of the crankshaft 21.

[0046] 2 and 6, a fan cover 57 that constitutes part of the unit case Pc is disposed so as to cover the right side of the centrifugal cooling fan 56. The fan cover 57 is integrally connected to a shroud 70 that surrounds part of the internal combustion engine 20, and covers the right side of the internal combustion engine 20. An eave portion 57d of the fan cover 57 is formed so as to cover the upper part and part of the right side surface of the catalytic converter-accommodated exhaust pipe 51d.

[0047] The fan cover 57 will now be described with reference to Figure 9. The fan cover 57 has a side wall 57a that covers the right side of the fan cover. A grill 57g is formed in the side wall 57a in a circular shape with its center point at the central axis C1 of rotation of the fan 56. When the fan 56 rotates, outside air passes through the grill 57g and is taken into the power unit P. At the upper and rear portions of the periphery of the side wall portion 57a, a peripheral wall portion 57b is erected from the side wall portion 57a ​​toward the internal combustion engine 20. The front edges of the side wall portion 57a ​​and the peripheral wall portion 57b form a shroud joining edge portion 57c that is joined to the shroud 70.

[0048] An eave portion 57d is formed at the lower part of the side wall portion 57a, extending along the catalytic converter-housed exhaust pipe 51d and covering approximately the upper half of the catalytic converter-housed exhaust pipe 51d. Furthermore, as shown in Fig. 2, the eave portion 57d is formed longer in the longitudinal direction of the vehicle than the front-to-rear width of the side wall portion 57a. The eave portion 57d is formed longer than the axial length of the catalytic converter-housed exhaust pipe 51d.

[0049] The eaves portion 57d is composed of an extending portion 57d1 extending outward in the vehicle width direction from the side wall portion 57a, a curved portion 57d2 extending downward from the extending portion 57d1 in a curved shape, and a side wall portion 57d3 extending downward from the curved portion 57d2 and formed to cover a portion of the right side surface of the catalytic converter-accommodated exhaust pipe 51d.

[0050] A notch 57e that opens forward in the vehicle longitudinal direction is formed at the edge of the eaves portion 57d of the fan cover 57. The notch 57e is formed to avoid the temperature sensor 54a. The temperature sensor 54a is a sensor attached immediately upstream of the catalytic converter-accommodating exhaust pipe 51d and corresponds to a first sensor provided in the exhaust passage upstream of the NOx storage catalyst and downstream of the three-way catalyst. As shown in FIG. 2, the notch 57e and the sensor 54a overlap in a side view of the vehicle. Thus, a portion of the temperature sensor 54a is covered by the fan cover 57. The notch 57e has an inclined portion 57f that is inclined obliquely toward the back so that the opening gradually widens. This prevents the temperature sensor 54a from hitting the fan cover 57 and making it difficult to remove the fan cover 57 when the fan cover 57 is removed from the vehicle.

[0051] A cutout opening rearward in the vehicle longitudinal direction may be provided at the rear edge of the extension 57d1 and the curved portion 51d2 of the overhanging portion 57d of the fan cover 57, and the exhaust gas sensor 54b, which is a second sensor provided in the catalytic converter-accommodating exhaust pipe 51d, i.e., the exhaust passage downstream of the NOx storage catalyst, may be disposed in the cutout. This allows a portion of the exhaust gas sensor 54b to be covered by the fan cover 57, similar to the temperature sensor 54a, and at least a portion of the sensor to be protected. Furthermore, providing the exhaust gas sensor 54b in the cutout maintains its accessibility and ensures its ease of removal. The exhaust gas sensor 54b is an LAF (Linear Air-Fuel Ratio) sensor, but may also be an oxygen concentration sensor.

[0052] 9, an opening 57h that opens downward is formed in the extension 57d1 of the eaves portion 57d of the fan cover 57. This opening 57h opens toward the catalyst device-housed exhaust pipe 51d that is located below the fan cover 57 and partially covered by the eaves portion 57d. Therefore, it becomes possible to send air from the centrifugal cooling fan 56 to the catalyst device-housed exhaust pipe 51d and cool the NOx storage catalyst therein.

[0053] An ECU (electronic control unit) (not shown) is provided to control the operation of each part of the internal combustion engine 20. The ECU is configured as a computer and includes a processor (e.g., CPU) and memory (e.g., ROM, RAM), and receives output signals from various sensors. For example, the ECU is connected to an engine load sensor, such as an engine speed sensor and a throttle opening sensor, an oxygen concentration sensor 27, a temperature sensor 54a, and an exhaust gas sensor 54b. The ECU analyzes the operating state based on inputs from these sensors and controls the operation of the spark plug 26, the fuel injector 37, the throttle valve of the throttle body 33, and other components based on the analyzed operating state. This allows the ECU to perform lean-burn operation of the internal combustion engine 20, for example. At this time, the ECU controls the operation of the fuel injector 37 based on inputs from the temperature sensor 54a and the exhaust gas sensor 54b to suitably purify NOx in the downstream catalytic converter 53b of the catalytic converter-accommodating exhaust pipe 51d. Specifically, the ECU generates a so-called rich spike, in which excessive fuel is injected at a predetermined timing.

[0054] The characteristic configuration and effects of the motorcycle 1, which is a saddle-ride type vehicle having the above configuration, will be described below.

[0055] An upstream catalytic device 53a, i.e., a three-way catalyst, and a downstream catalytic device 53b, i.e., a NOx storage catalyst, are arranged in an exhaust passage 50E of the internal combustion engine 20 of the motorcycle 1. In Fig. 5, a plane extending to the center of the vehicle body in the vehicle width direction, i.e., a central imaginary plane IS extending from the front to the rear of the motorcycle 1, intersects with the upstream catalytic device 53a of the catalyst device-housed exhaust pipe 51c but is separated from and does not intersect with the downstream catalytic device 53b of the catalyst device-housed exhaust pipe 51d. In a front view of the motorcycle 1 shown in FIG. 8, at least a portion of the catalyst-equipped exhaust pipe 51d housing the downstream catalytic device 53b is exposed and positioned outward in the vehicle width direction, while the catalyst-equipped exhaust pipe 51c housing the upstream catalytic device 53a is hidden and positioned behind the windscreen WS of the front wheel 10 and the front cover 1a of the body cover BC. This relationship is more clearly seen in FIG. 10, which shows a schematic front view of the motorcycle 1. As such, the catalyst-equipped exhaust pipe 51d equipped with the NOx storage catalyst is positioned outward in the vehicle width direction, with at least a portion of the exhaust pipe 51d exposed outward in the vehicle width direction. In particular, the catalyst-equipped exhaust pipe 51d equipped with the NOx storage catalyst is exposed outward in the vehicle width direction relative to the catalyst-equipped exhaust pipe 51c equipped with the three-way catalyst. In this way, by exposing at least a portion of the catalyst device-accommodating exhaust pipe 51d equipped with a NOx storage catalyst to the outside in the vehicle width direction, the NOx storage catalyst can be cooled to an appropriate temperature by the wind while the vehicle is running, making it possible to prevent deterioration of the NOx storage catalyst due to heat damage. Furthermore, this arrangement in which the exhaust pipe 51d is exposed allows the catalyst device-accommodating exhaust pipe 51d equipped with a NOx storage catalyst to be mounted on the motorcycle 1 without significantly modifying the arrangement space of various other components of the motorcycle 1, for example. Therefore, with the above configuration, it is possible to effectively arrange a three-way catalyst and a NOx storage catalyst in the exhaust passage 50E of the internal combustion engine 20 in the motorcycle 1, which is a saddle-ride type vehicle.5, the catalytic converter-housed exhaust pipe 51d extends rearward in the vehicle longitudinal direction on the outer side in the vehicle width direction of the crankcase 22 that constitutes the unit case Pc, and is therefore disposed on the outer side in the vehicle width direction of the crankcase 22 of the engine body B. This further improves the mountability and cooling capacity of the catalytic converter-housed exhaust pipe 51d equipped with a NOx storage catalyst. However, the extent to which at least a portion, for example, all or part of the catalytic converter-housed exhaust pipe 51d equipped with a NOx storage catalyst is exposed to the outer side in the vehicle width direction should be determined depending on factors such as how much wind hits the catalytic converter-housed exhaust pipe 51d while the motorcycle 1 is traveling, and the acceleration performance of the motorcycle 1. The front view of the motorcycle 1 corresponds to Figure 8 in this case, where the wheels 10, 28 of the motorcycle 1 are facing directly in the fore-and-aft direction, that is, the axles 10a, 28a extending in the vehicle width direction of the wheels 10, 28 are perpendicular to the fore-and-aft direction and perpendicular to the up-and-down direction.

[0056] 5, the catalytic converter-accommodated exhaust pipe 51c, i.e., the upstream catalytic converter 53a, intersects with the central imaginary plane IS extending from the front to the rear of the motorcycle 1, while the catalytic converter-accommodated exhaust pipe 51d, i.e., the downstream catalytic converter 53b, does not intersect with the central imaginary plane IS. In this manner, the upstream catalytic converter 53a, i.e., the three-way catalyst, is positioned closer to the center of the vehicle body in the vehicle width direction than the downstream catalytic converter 53b, i.e., the NOx storage catalyst. Therefore, the upstream catalytic converter 53a, i.e., the three-way catalyst, can be positioned behind the windscreen WS, i.e., the body cover BC and the front wheel 10, or other components that provide a windbreak function. This makes it difficult for the wind to hit the catalytic converter-accommodated exhaust pipe 51c, which includes the three-way catalyst, and enables the temperature of the three-way catalyst to be maintained at an appropriate temperature.

[0057] In particular, the catalyst-equipped exhaust pipe 51c that houses the upstream catalyst 53a is substantially invisible in the front view of the motorcycle 1 in Figure 8, and at least a part of, in this case the entirety of, the catalyst-equipped exhaust pipe 51c, which is the second exhaust purification unit equipped with a three-way catalyst, is located behind the windbreak function unit WS. Therefore, by positioning the catalyst-equipped exhaust pipe 51c equipped with a three-way catalyst behind the windbreak function unit WS, it is possible to make it difficult for the wind from traveling to hit the catalyst-equipped exhaust pipe 51c, and therefore it is possible to maintain the temperature of the three-way catalyst housed therein at an appropriate temperature.

[0058] 2 and 7, the catalytic converter-housed exhaust pipe 51d extends obliquely downward and rearward in the front-to-rear direction below the power unit P in a right side view of the vehicle body. In other words, the upstream end 51du of the catalytic converter-housed exhaust pipe 51d, which is the first exhaust purification unit equipped with a NOx storage catalyst, is located at a different position from the downstream end 51dd of the catalytic converter-housed exhaust pipe 51d in the up-down direction of the motorcycle 1. Because the catalytic converter-housed exhaust pipe 51d is positioned obliquely with respect to the horizontal ground plane, the airflow can be more efficiently directed against the longitudinally extending surface of the catalytic converter-housed exhaust pipe 51d, i.e., the circumferential side surface, compared to when the catalytic converter-housed exhaust pipe 51d is positioned parallel to the horizontal ground plane, thereby cooling the NOx storage catalyst of the catalytic converter-housed exhaust pipe 51d to an appropriate temperature.

[0059] Here, we conducted an experiment to investigate the relationship between the inclination of the catalytic converter-accommodating exhaust pipe 51d with respect to the horizontal plane and the temperature of the catalytic converter-accommodating exhaust pipe 51d, and the results of the experiment are shown in Figure 11. The horizontal axis of Figure 11 represents time, with time elapsed as you move to the right, and the vertical axis of Figure 11 represents temperature, with the temperature increasing toward the top. In this experiment, the catalytic converter-accommodating exhaust pipe 51d was positioned in the following orientation, hot exhaust gas was allowed to flow through the catalytic converter-accommodating exhaust pipe 51d, and cool air was blown in from the front, and the temperature change in the catalytic converter-accommodating exhaust pipe 51d was measured. The solid line in the graph of Figure 11 shows the results when the catalytic converter-accommodating exhaust pipe 51d was positioned with its axis perpendicular to the horizontal plane, the dashed-dot line shows the results when the catalytic converter-accommodating exhaust pipe 51d was positioned with its axis tilted approximately 45° with respect to the horizontal plane, and the dashed-dot line shows the results when the catalytic converter-accommodating exhaust pipe 51d was positioned with its axis parallel to the horizontal plane. In this experiment, the catalytic converter-accommodating exhaust pipe 51d was positioned so that its axis was not tilted left or right relative to the cool air blowing from in front of it. In the graph of Fig. 11, the solid line, dashed line, and dashed double-dashed line are arranged from bottom to top. This makes it clear that positioning the upstream end of the catalytic converter-accommodating exhaust pipe 51d at a different position from the downstream end of the catalytic converter-accommodating exhaust pipe 51d in the vertical direction of the vehicle—that is, positioning the catalytic converter-accommodating exhaust pipe 51d at an angle or right angle to the horizontal ground plane—can improve the cooling performance of the catalytic converter-accommodating exhaust pipe 51d, i.e., the NOx storage catalyst, compared to when the catalytic converter-accommodating exhaust pipe 51d is positioned parallel to the horizontal ground plane.

[0060] Furthermore, the internal combustion engine 20 has a centrifugal cooling fan 56 on one end side of the crankshaft 21 oriented in the vehicle width direction, and the catalyst device-accommodated exhaust pipe 51d is positioned radially outward of the centrifugal cooling fan 56, centered on the central rotation axis C1 of the centrifugal cooling fan 56. Therefore, the catalyst device-accommodated exhaust pipe 51d, which is the first exhaust purification part equipped with a NOx storage catalyst, can be compactly arranged near the centrifugal cooling fan 56, thereby achieving space savings.

[0061] The internal combustion engine 20 also has a centrifugal cooling fan 56 on one end side of the crankshaft 21 oriented in the vehicle width direction, and a fan cover 57 is provided on the axial outer side of the centrifugal cooling fan 56, with the fan cover 57 having an opening 57h that opens downward. The catalyst device-accommodated exhaust pipe 51d is located below the fan cover 57, and at least a portion of the catalyst device-accommodated exhaust pipe 51d is covered by the fan cover 57. Therefore, the catalyst device-accommodated exhaust pipe 51d, i.e., the NOx storage catalyst provided therein, can be suitably cooled by the air from the centrifugal cooling fan 56.

[0062] Furthermore, motorcycle 1 is equipped with temperature sensor 54a, a first sensor, provided in the exhaust passage upstream of the NOx storage catalyst in catalyst device-accommodating exhaust pipe 51d and downstream of the three-way catalyst in catalyst device-accommodating exhaust pipe 51c, and exhaust gas sensor 54b, a second sensor, provided in the exhaust passage downstream of the NOx storage catalyst. In particular, temperature sensor 54a is at least partially covered by fan cover 57. This allows at least a portion of temperature sensor 54a to be protected from obstacles such as flying stones. Similarly, exhaust gas sensor 54b may also be at least partially covered by fan cover 57 to enhance its protective performance.

[0063] Furthermore, a cutout 57e is provided in the fan cover 57, and a sensor provided in the exhaust passage, in this case the temperature sensor 54a, is disposed in the cutout 57e. This improves accessibility to the temperature sensor 54a, thereby facilitating maintenance of the temperature sensor 54a. Similarly, the exhaust gas sensor 54b may be disposed in another cutout in the fan cover 57.

[0064] Next, a second embodiment of the present invention will be described. A side view of a motorcycle 101 according to the second embodiment is shown in Fig. 12, and a front view of a portion of the motorcycle 101, that is, a view from the front of the vehicle, is shown in Fig. 13.

[0065] The motorcycle 101 includes a body frame 102 on which a power unit P and electrical components are mounted. The main tubes of the body frame 102 extend rearward from a head pipe 103 located at the front end. A down tube 104 of the body frame 102 is provided so as to extend diagonally downward and rearward from the head pipe 103. A fuel tank 105 containing fuel is disposed behind the head pipe 103. A seat 106 on which a rider sits is mounted behind this fuel tank 105. A footrest 107 on which the rider rests their feet while riding is provided below the seat 106.

[0066] A brake pedal 108 for the rear wheel WR, which is a drive wheel, is provided near a footrest 107 on the right side of the vehicle body shown in FIG. 12. The brake pedal 108 is pivotally supported at a rear end 108r located rearward of the footrest 107, and is provided so that a front end 108f located forward of the footrest 107 can swing up and down. In a side view of the motorcycle 101 in FIG. 12, the brake pedal 108 is initially slanted slightly downward and forward, then becomes generally horizontal, and then further slanted slightly upward and forward, forming a substantially U-shape, as it moves from the rear end 108r to the front end 108f. In other words, the brake pedal 108 extends in the front-to-rear direction without being slanted in the up-and-down direction in a side view of the motorcycle 101. The front end 108f of the brake pedal 108 functions as a pedal portion, is located on the right side of the front end portion of the crankcase 109 described later, and is located at approximately the same height as the footrest 107, so that it can be depressed by the driver's foot placed on the footrest 107.

[0067] Furthermore, a kick pedal 110 is provided near the footrest 107 on the right side of the vehicle body shown in FIG. 12 , particularly above the footrest 107. The kick pedal 110 has a rear end 110r positioned diagonally rearward and upward of the footrest 107 and a front end 110f located near the rear of the cylinder head 112 of the engine body B of the internal combustion engine 111 of the power unit P. As the kick pedal 110 moves from the rear end 110r to the front end 110f, it first extends upward and then curves forward. When in use, the kick pedal 110 unfolds so as to extend outward in the vehicle width direction. The front end 110f of the kick pedal 110 functions as a pedal portion and is depressed by the driver's foot. Depressing the kick pedal 110 rotates the kick pedal 110 around the rear end 110r within a predetermined range, thereby starting the internal combustion engine 111.

[0068] An engine body B of an internal combustion engine 111 is suspended between the main tubes and down tube 104 of the body frame 102. The engine body B includes a crankcase 109 supported on the down tube 104 via a bracket, and a cylinder block 113, a cylinder head 112, and a head cover 114, which are provided in this order above the crankcase 109. The cylinder block 113 is connected above the crankcase 109 in a forward-inclined state. Therefore, as shown in FIG. 12, the cylinder axes 111c of the cylinders of the engine body B are inclined obliquely forward from the crankshaft side of the crankcase 109 toward the cylinder head 112 side. The crankshaft extends in the vehicle width direction and is generally perpendicular to the up-down and front-rear directions. In FIG. 12, a rotational axis 115 of the crankshaft is shown.

[0069] An upper end (upstream end) of an upstream exhaust pipe 117 of an exhaust device 116 is connected to a cylinder head 112 of the engine body B. Exhaust gas discharged from a combustion chamber (not shown) flows through the upstream exhaust pipe 117 and is discharged from a muffler 118 located to the right of the rear wheel WR, that is, located at the rear right side of the vehicle body. The exhaust port of the cylinder head 112, the upstream exhaust pipe 117, the catalytic converter housing exhaust pipe 120a, the intermediate exhaust pipe 121, the catalytic converter housing exhaust pipe 120b, and the muffler 118 are connected in this order in the exhaust flow direction, and each defines a part of an exhaust passage 122.

[0070] The catalytic converter-accommodating exhaust pipe 120a corresponds to the catalytic converter-accommodating exhaust pipe 51c that accommodates the upstream catalytic converter 53a, i.e., the three-way catalyst, and has the upstream catalytic converter 53a, i.e., the three-way catalyst, inside. The catalytic converter-accommodating exhaust pipe 120b corresponds to the catalytic converter-accommodating exhaust pipe 51d that accommodates the downstream catalytic converter 53b, i.e., the NOx storage catalyst, and has the upstream catalytic converter 53b, i.e., the NOx storage catalyst, inside.

[0071] A front fork 123 is rotatably supported at the front end of the main tube via a steering shaft provided on the head pipe 103. A handlebar 124 is provided at the upper end of the steering shaft, and grips 125 are attached to both ends of the handlebar 124. A front wheel WF is rotatably supported at the bottom of the front fork 123. The upper part of the front wheel WF is partially covered by a front fender 126.

[0072] A rear wheel WR, to which power from the internal combustion engine 111 is transmitted via a swing arm, is rotatably supported behind the engine body B. A suspension 126 that absorbs shocks from the road surface is disposed between the swing arm and the body frame 102. A rear fender 127 is disposed above and behind the rear wheel WR and behind the seat 106.

[0073] As described above, the upstream exhaust pipe 117 of the exhaust device 116 is connected to the front wall of the cylinder head 112 of the engine body B, and downstream of that, the upstream catalytic device 53a, i.e., the catalytic device-housed exhaust pipe 120a equipped with a three-way catalyst, the intermediate exhaust pipe 121, the downstream catalytic device 53b, i.e., the catalytic device-housed exhaust pipe 120b equipped with a NOx storage catalyst, and the muffler 118 are arranged in this order from the upstream side.

[0074] 12 and 13 , the exhaust passage 122 continuing from the exhaust port of the cylinder head 112 of the engine body B extends to the front of the engine body B, then extends downward, and further extends rearward passing below the engine body B. In other words, the exhaust device 116 extends from the front of the engine body B of the internal combustion engine 111 downward, passes below the engine body B, and extends rearward. The catalytic converter-housed exhaust pipe 120a is positioned on the front side of the engine body B in the vehicle fore-and-aft direction, and is particularly positioned on the front side of the crankcase 109. Therefore, the catalytic converter-housed exhaust pipe 120a is positioned further forward of the front end 108f of the brake pedal 108. Here, because the exhaust passage 122 extends around the engine body B as described above, the catalytic converter-housed exhaust pipe 120a is disposed so as to extend obliquely in the same direction as the cylinder axis 111c in a side view of the motorcycle 101, and to extend obliquely rearward and downward from the upstream side to the downstream side. As shown in the front view of the motorcycle 101 in Figure 13, when a central imaginary plane IS is defined that extends from the front to the rear of the motorcycle 101, the catalyst device-accommodating exhaust pipe 120a is located on the right side of the plane, extending to the right of the front wheel WF in this example and tilted so that its downstream portion is slightly more inward in the vehicle width direction than its upstream portion. A portion of the catalyst device-accommodating exhaust pipe 120a is arranged on the motorcycle 101 so as to be hidden by the surrounding structure of the front wheel WF, specifically, by a windscreen WS such as a front fork 123 and a front fender 126. The central imaginary plane IS can be defined so as to be perpendicular to the vehicle width direction and to substantially bisect the front wheel WF and rear wheel WR.

[0075] On the other hand, the catalytic converter-housed exhaust pipe 120b downstream of the catalytic converter-housed exhaust pipe 120a extends substantially in the longitudinal direction of the vehicle as shown in the side view of Fig. 12, and the downstream end 120bd of the catalytic converter-housed exhaust pipe 120b is located slightly above the upstream end 120bu in the vertical direction of the vehicle. As shown in the front view of the vehicle in Fig. 13, the catalytic converter-housed exhaust pipe 120a equipped with a three-way catalyst is positioned closer to the center of the vehicle than the catalytic converter-housed exhaust pipe 120b equipped with a NOx storage catalyst, and the catalytic converter-housed exhaust pipe 120b tends to be more exposed than the catalytic converter-housed exhaust pipe 120a.

[0076] The positional relationship between the catalytic converter-housed exhaust pipe 120a equipped with a three-way catalyst and the catalytic converter-housed exhaust pipe 120b equipped with a NOx storage catalyst, shown in the front view of the vehicle in Figure 13, is shown in the schematic diagram of Figure 14. From Figure 14, it can be seen more clearly that the NOx storage catalyst in the catalytic converter-housed exhaust pipe 120b is more exposed in the front view of the vehicle than the three-way catalyst in the catalytic converter-housed exhaust pipe 120a.

[0077] As described above, in the motorcycle 101, an upstream catalytic device 53a (i.e., a three-way catalyst) and a downstream catalytic device 53b (i.e., a NOx storage catalyst) are disposed in the exhaust passage 122 of the internal combustion engine 111 mounted on the motorcycle 101. As shown in the front view of the motorcycle 101 in FIGS. 13 and 14, in which the motorcycle 101 is viewed from the front, the catalytic device-housed exhaust pipe 120b that houses the downstream catalytic device 53b is disposed outward in the vehicle width direction, and at least a portion of the exhaust pipe 120b is exposed outward in the vehicle width direction. In particular, the catalytic device-housed exhaust pipe 120b that houses the downstream catalytic device 53b is disposed outward in the vehicle width direction than the catalytic device-housed exhaust pipe 120a that houses the upstream catalytic device 53a, and is particularly exposed here. Therefore, the downstream catalytic device 53b, i.e., the NOx storage catalyst, can be cooled to an appropriate temperature by the wind generated while the motorcycle is traveling, preventing deterioration of the NOx storage catalyst due to heat damage. Furthermore, with this configuration, for example, the catalytic device-housed exhaust pipe 120b equipped with the NOx storage catalyst can be mounted on the motorcycle 101 without significantly modifying the space for arranging various other components of the motorcycle 101. Therefore, even in the motorcycle 101, which is a straddle-type vehicle, it is possible to effectively arrange a three-way catalyst and a NOx storage catalyst in the exhaust passage 122 of the internal combustion engine 20. The extent to which at least a portion of the catalytic device-housed exhaust pipe 120b equipped with the NOx storage catalyst, for example, all or part of it, is exposed to the outside in the vehicle width direction, may be set depending on the degree to which the catalytic device-housed exhaust pipe 120b is exposed to the wind generated while the motorcycle is traveling, the acceleration performance of the motorcycle 101, and the like.

[0078] 13 and 14, the upstream catalytic device 53a, i.e., the three-way catalyst, is positioned closer to the center of the vehicle body, that is, closer to the central imaginary plane IS, than the downstream catalytic device 53b, i.e., the NOx storage catalyst. Therefore, the upstream catalytic device 53a, i.e., the three-way catalyst, of the catalytic device-accommodated exhaust pipe 120a can be intentionally positioned so that it is at least partially hidden behind the windbreak function portion WS, which makes it difficult for the catalytic device-accommodated exhaust pipe 120a equipped with the three-way catalyst to be exposed to the wind while traveling, making it possible to maintain the temperature of the three-way catalyst at an appropriate temperature.

[0079] In particular, at least a portion of the catalytic converter-accommodated exhaust pipe 120a, which is the second exhaust purification unit equipped with a three-way catalyst, is located behind the windbreak function unit WS. Therefore, by positioning the catalytic converter-accommodated exhaust pipe 120a equipped with a three-way catalyst behind the windbreak function unit WS, it is possible to prevent the catalytic converter-accommodated exhaust pipe 120a from being exposed to the wind while traveling, thereby making it possible to maintain the temperature of the three-way catalyst accommodated therein at an appropriate temperature.

[0080] Furthermore, as described above, the downstream end 120bd of the catalytic converter-accommodating exhaust pipe 120b is located slightly above the upstream end 120bu in the vehicle vertical direction when viewed from the right side of the vehicle body in Figure 12. In other words, the upstream end 120bu of the catalytic converter-accommodating exhaust pipe 120b, which is the first exhaust purification unit equipped with a NOx storage catalyst, is located at a different position from the downstream end 120bd of the catalytic converter-accommodating exhaust pipe 120b in the vertical direction of the motorcycle 101. In this way, the catalytic converter-accommodating exhaust pipe 120b can be positioned at an angle with respect to the horizontal ground plane, so that the airflow from traveling can be efficiently directed against the surface extending in the longitudinal direction of the catalytic converter-accommodating exhaust pipe 120b, thereby cooling the catalytic converter 53b of the catalytic converter-accommodating exhaust pipe 120b, i.e., the NOx storage catalyst, to an appropriate temperature. In the motorcycle 101, the catalyst device-accommodating exhaust pipe 120b is only slightly inclined, but as already explained with reference to Fig. 11, the catalyst device-accommodating exhaust pipe 120b may be arranged on the motorcycle 101 with a greater inclination to further improve cooling performance. This inclination should be set depending on the amount of wind that hits the catalyst device-accommodating exhaust pipe 120b when the motorcycle 101 is traveling, the acceleration performance of the motorcycle 101, etc.

[0081] 12, at least a portion of the catalyst device-housed exhaust pipe 120b, which is the first exhaust purification part equipped with the NOx storage catalyst, is located inside the brake pedal 108 in the vehicle width direction and is covered by the brake pedal 108. With this configuration, by covering at least a portion of the catalyst device-housed exhaust pipe 120b equipped with the NOx storage catalyst with the brake pedal 108, it is possible to improve the protection performance of the NOx storage catalyst.

[0082] 12 to 14, it is preferable to install a temperature sensor immediately upstream of the catalyst device-accommodating exhaust pipe 120b and an exhaust gas sensor immediately downstream of the temperature sensor. This allows the NOx in the exhaust gas to be more effectively purified by the NOx storage catalyst under control of an ECU (not shown). Control by the ECU, for example, control related to the lean burn operation of the internal combustion engine 111, is the same as that already explained in the first embodiment, so detailed explanation will be omitted here.

[0083] Although the embodiments and modifications of 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 as defined by the claims of this application.

[0084] For example, the windshield functional part WS is the front wheel 10 and the front cover 1a in the first embodiment, and the front fork 123 and the front fender 126 in the second embodiment, but is not limited to these. Various existing members can function as the windshield functional part WS, and a part or member that functions as a windshield may also be provided as the windshield functional part WS. [Explanation of symbols]

[0085] 1, 101...Motorcycles 20, 111...Internal combustion engine 50, 116...Exhaust system 51c, 51d, 120a, 120b... Catalytic converter housing exhaust pipe 53a, 53b...Catalyst device WS...windbreak function part

Claims

1. In a saddle-type vehicle (1, 101) equipped with an internal combustion engine (20, 111), a three-way catalyst (53a) disposed in an exhaust passage (50E, 122) of the internal combustion engine (20, 111); a NOx storage catalyst (53b) disposed downstream of the three-way catalyst (53a) in the exhaust passage (50E, 122); Equipped with At least a portion of the first exhaust purification section (51d, 120b) including the NOx storage catalyst (53b) is exposed to the outside in the vehicle width direction, The internal combustion engine (20) has a fan (56) at one end of a crankshaft (21) oriented in the vehicle width direction, the first exhaust gas purification section (51d) including the NOx storage catalyst (53b) is positioned radially outward of the fan (56) around a central axis (C1) of rotation of the fan (56); A saddle-type vehicle characterized by:

2. At least a portion of the second exhaust gas purification section (51c, 120a) including the three-way catalyst (53a) is disposed behind the windscreen section (WS).

2. The saddle-type vehicle according to claim 1, wherein the saddle-type vehicle is a vehicle having a saddle-type seat.

3. an upstream end (51du, 120bu) of the first exhaust purification section (51d, 120b) including the NOx storage catalyst (53b) is located at a position different from a downstream end (51dd, 120bd) of the first exhaust purification section (51d, 120b) in the vertical direction of the saddle riding type vehicle (1, 101); 3. The saddle-type vehicle according to claim 1 or 2.

4. When a plane (IS) extending toward the center of the vehicle body in the vehicle width direction is defined, the second exhaust purification section (51c) including the three-way catalyst (53a) has a surface (IS) that intersects with the plane (IS).

3. The saddle-type vehicle according to claim 1 or 2.

5. A saddle-type vehicle (1, 101) equipped with an internal combustion engine (20, 111), a three-way catalyst (53a) disposed in an exhaust passage (50E, 122) of the internal combustion engine (20, 111); a NOx storage catalyst (53b) disposed downstream of the three-way catalyst (53a) in the exhaust passage (50E, 122); Equipped with At least a portion of the first exhaust purification section (51d, 120b) including the NOx storage catalyst (53b) is exposed to the outside in the vehicle width direction, The internal combustion engine (20) has a fan (56) at one end of a crankshaft (21) oriented in the vehicle width direction, a fan cover (57) is provided on the axial outer side of the fan (56); The fan cover (57) has an opening (57h) that opens downward, the first exhaust gas purification section (51d) including the NOx storage catalyst (53b) is located below the fan cover (57); At least a portion of the first exhaust gas purification section (51d) is covered with the fan cover (57). A saddle-type vehicle characterized by:

6. A first sensor (54a) provided in an exhaust passage upstream of the NOx storage catalyst (53b) and downstream of the three-way catalyst (53a); a second sensor (54b) provided in the exhaust passage downstream of the NOx storage catalyst (53b); Further provided with At least one of at least a part of the first sensor (54a) and at least a part of the second sensor (54b) is covered with the fan cover (57).

6. The straddle-type vehicle according to claim 5.

7. The fan cover (57) is provided with a cutout portion (57e), 7. The straddle-type vehicle according to claim 5, wherein a sensor (54a) provided in the exhaust passage is disposed in the notch (57e).

8. At least a part of the first exhaust purification section (120b) including the NOx storage catalyst (53b) is located inside a brake pedal (108) in the vehicle width direction and is covered by the brake pedal (108).

6. The saddle-type vehicle according to claim 1 or 5.

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