Motorcycles

Abstract

Disclosed is a motorcycle in which an undercover 12 fixed to a body frame 2 covers the body from below, a rear part 12r of the undercover is provided extending toward a catalyst device 44, a plate member 15 that extends forward with at least a rear part 15r attached to the lower part of a crankcase 22 is disposed so as to cover the catalyst device 44 from below, an air guide port 17 that guides travel air to the catalyst device 44 is formed between a rear end edge 12re of the undercover 12 and a front end edge 15f of the plate member 15, and when an internal combustion engine 21 swings relative to the body frame 2, the open area of the air guide port 17 increases, whereby a catalyst 44a can be activated quickly during warm-up operation, and the catalyst temperature can be kept from becoming excessively high during high-load operation to reduce the amount of harmful substances emitted.

Description

[Technical Field]

[0001] The present invention relates to a motorcycle equipped with a catalytic converter. [Background technology]

[0002] Efforts aimed at mitigating or reducing the impact of climate change have been ongoing for some time, and to achieve this, research and development is being conducted to reduce emissions of harmful substances. In internal combustion engines mounted on motorcycles, a catalytic converter is installed in the exhaust system to remove harmful substances such as NOx, CO, and HC contained in the exhaust gas.

[0003] Because catalytic converters have low reduction capabilities at room temperature, they are heated by exhaust heat to activate the catalyst and increase purification capabilities, but if the catalyst overheats, its purification capabilities decline and it is damaged. For this reason, the catalytic converter is cooled by utilizing the wind generated by running the vehicle (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-60256

[0005] The motorcycle disclosed in Patent Document 1 has an internal combustion engine in which a cylinder and a cylinder head are stacked in order on a crankcase, and the cylinder axis is tilted forward and approximately horizontal. The engine is supported swingably on a body frame via a link member. The catalytic converter is installed midway in the exhaust pipe extending from the cylinder head, below the cylinder and in front of the crankcase, with its longitudinal direction aligned with the vehicle width direction.

[0006] An undercover that covers the vehicle body from below is attached to the vehicle body frame in front of the catalytic converter. The rear end of the lower surface of the undercover is directed toward the catalytic converter. Therefore, the underside of the undercover can guide the wind generated by the vehicle traveling to the catalytic converter, and the catalytic converter is cooled by using the wind generated by the vehicle traveling, thereby cooling the catalyst loaded inside the catalytic converter. Summary of the Invention [Problem to be solved by the invention]

[0007] The catalytic converter disclosed in Patent Document 1 is attached to the front of the crankcase below the cylinder, and since there is an under cover in front of the catalytic converter, the area below the catalytic converter is always open. Therefore, even if the catalytic converter is heated by exhaust heat during warm-up, the catalytic converter dissipates heat downward, which delays catalyst activation, especially when the engine is cold, and exhaust purification is not immediately achieved.

[0008] Furthermore, since the area below the catalytic converter is always open, even if the underside of the undercover directs the wind from driving toward the catalytic converter, the wind from driving along the underside of the undercover is directed toward the catalytic converter to cool it. However, during high-load operation, it is desirable for the catalytic converter to be cooled more to prevent excessive rises in catalyst temperature.

[0009] Therefore, in order to reduce the amount of harmful substance emissions, it is important to not only quickly activate the catalyst, but also to prevent the catalyst temperature from rising excessively.

[0010] The present invention has been made in consideration of the above points, and its object is to provide a motorcycle that can quickly activate a catalyst during warm-up operation, prevent the catalyst temperature from becoming excessively high during high-load operation, and reduce the amount of harmful substances emitted. This will in turn contribute to mitigating or reducing the impact of climate change. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides: An internal combustion engine, which has a cylinder and a cylinder head stacked on a crankcase and fastened together, is supported swingably on a vehicle frame via a link member, In a motorcycle, a catalytic converter is disposed in front of the crankcase and is disposed midway through an exhaust pipe extending from the cylinder head, an undercover fixed to the vehicle body frame covers the vehicle body from below, and its rear portion extends toward the catalytic converter (44); a plate member having at least a rear portion (15r) attached to a lower portion of the crankcase and extending forward is disposed so as to cover the catalytic device from below; an air guide port for guiding traveling air to the catalytic converter is formed between the rear end edge of the undercover and the front end edge of the plate member; The motorcycle is characterized in that, when the internal combustion engine swings relative to the body frame, an opening area of ​​the air guide port increases.

[0012] According to this configuration, when the internal combustion engine swings relative to the body frame, the front end edge of the plate member that swings together with the internal combustion engine moves downward away from the rear end edge of the undercover, thereby forming an air guide port between the rear end edge of the undercover and the front end edge of the plate member that guides the running wind to the catalytic device. Furthermore, when the internal combustion engine is not swinging relative to the body frame, the air guide port is not formed, and the rear of the undercover is covered by the plate member, thereby covering the lower part of the catalytic converter.

[0013] Therefore, when the catalytic converter is warmed up, the bottom of the catalytic converter is covered with a plate member, so that heat is radiated downwards to a minimum, and there is no wind until the vehicle is moving. This allows the catalytic converter to be heated efficiently by exhaust heat, promoting catalyst activation and reducing the emission of harmful substances contained in exhaust gases. When the vehicle is traveling, the wind from the vehicle enters the air guide port and is guided to the catalytic converter, thereby cooling the catalytic converter and maintaining the purification capacity of the catalytic converter.

[0014] When the internal combustion engine is operating under high load, such as during acceleration while driving, a large load is applied to the body frame, causing the internal combustion engine to swing significantly relative to the body frame, and the plate member also swings, opening the air guide port widely, so that a large amount of traveling wind can be directed into the catalytic device, further cooling the catalytic device. Therefore, excessive increases in catalyst temperature during high-load operation can be prevented, the deterioration of exhaust purification capacity can be prevented, and harmful substances contained in exhaust gas can be reduced.

[0015] In a preferred embodiment of the present invention, A pair of left and right guide protrusions protruding downward on the lower surface of the undercover are provided on the left and right sides in the vehicle width direction, respectively, to define an air guide passage therebetween that guides the traveling wind to the air guide port.

[0016] According to this configuration, a pair of left and right guide protrusions that protrude downward on the left and right sides of the vehicle width direction are provided at the rear of the undercover, and the pair of left and right guide protrusions form an air guide passage between them that guides the traveling wind to the air guide port.Therefore, the traveling wind along the underside of the undercover can be smoothly guided to the air guide port by the air guide passage between the pair of left and right guide protrusions, and the catalytic device can be cooled efficiently.

[0017] In a preferred embodiment of the present invention, The distance between the pair of left and right guide protrusions in the vehicle width direction increases toward the front.

[0018] With this configuration, the widthwise spacing between the pair of left and right guide protrusions increases as they move forward, so that as much of the traveling wind as possible can be taken into the air guide passage and guided to the air guide port and then to the catalytic converter, which is expected to have a significant cooling effect. [Effects of the Invention]

[0019] In this invention, the catalytic converter is covered with a plate member underneath during warm-up, minimizing heat radiation downward, and there is no wind until the vehicle is moving. This allows the catalytic converter to be efficiently heated by exhaust heat, promoting catalyst activation and reducing the emission of harmful substances contained in exhaust gases. In addition, during high-load operation, a large load is applied to the body frame, causing the internal combustion engine to swing significantly relative to the body frame, and the plate member also swings, opening the air intake port widely.This allows a large amount of running wind to be directed into the catalytic device, further cooling the catalytic device.This prevents excessive increases in catalyst temperature during high-load operation, prevents a decrease in exhaust purification capacity, and reduces the amount of harmful substances contained in exhaust gases. This will in turn contribute to mitigating or reducing the impact of climate change. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a right side view of a motorcycle according to one embodiment of the present invention. [Figure 2] FIG. 2 is a left rear bottom perspective view of a central main part of the motorcycle. [Figure 3] FIG. 2 is a bottom view of a central main part of the motorcycle. [Figure 4] 3 is a left side cross-sectional view of a central main part of the motorcycle in a state where the internal combustion engine is not swinging relative to the body frame. FIG. [Figure 5] 4 is a left side cross-sectional view of a central main part of the motorcycle in a state where the internal combustion engine is swung relative to the body frame. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall side view of a motorcycle 1, which is a straddle-type vehicle according to a first embodiment of the present invention. In the description and claims of this specification, the directions of front, back, left, right, up and down shall follow the normal standard of the forward direction being the straight-ahead direction of the motorcycle 1 according to this embodiment, and in the drawings, FR indicates the forward direction, LH indicates the left, RH indicates the right, and UP indicates the up direction.

[0022] In this embodiment, the motorcycle 1 is specifically a scooter-type motorcycle. In this motorcycle 1, a front body 1A and a rear body 1B are connected via a low footrest (floor) 1C, and a body frame 2 that forms the skeleton of the body is generally composed of a down frame 4 and a main frame 5. That is, a down frame 4 extends downward from a head pipe 3 in the front body portion 1A, and lower frame portions 5a of a pair of left and right main frames 5 are connected to the lower ends of the down frame 4 and extend rearward and approximately horizontally. The main frames 5 extend diagonally rearward and upward from the rear ends of the lower frame portions 5a and form a pair of left and right inclined portions 5b, and the upper portions of the inclined portions 5b are further bent to form a pair of left and right horizontal portions 5c that extend rearward and approximately horizontally.

[0023] A storage box (not shown) is supported on the inclined portion 5b and horizontal portion 5c of the main frame 5, and a passenger seat 6 is arranged above the storage box. On the other hand, at the front body portion 1A, a handlebar 7 is provided above and journalled on the head pipe 3, and a front fork 8 extends below and journalled at its lower end to a front wheel 9. A frame side bracket 5bb protrudes rearward from the inclined portion 5b of the main frame 5, and a power unit side bracket 20b is attached to the frame side bracket 5bb via a link member 18, and a swing-type power unit (hereinafter simply referred to as the "power unit") 20 is connected and supported so that it can swing up and down. That is, the motorcycle 1 of this embodiment employs an upper link support structure for the power unit 20.

[0024] At the front body portion 1A, the head pipe 3 and the down frame 4 are covered from the front and rear by a front cover 10a and a leg shield 10b. The footrest (floor portion) 1C is provided on a pair of left and right lower frame portions 5a of the main frame 5 of the vehicle body frame 2, and the upper part of the lower frame portions 5a is covered by a floor cover 10c, and the left and right sides are covered in the front-to-rear direction by floor side covers 10d.

[0025] At the rear portion 1B of the vehicle body, a fuel tank 28 is attached to the horizontal portion 22c of the main frame 22 below and behind the passenger seat 6, and the inclined portion 22b and horizontal portion 22c of the main frame 22 are covered on the left, right and rear sides by a body cover 10e. In addition, a front fender 11 is provided above the front wheel 14.

[0026] In the motorcycle 1 of this embodiment, the lower part of the footrest portion (floor portion) 1C is covered by an undercover 12 attached to the lower frame portion 5a of the main frame 5 from below. Each of the covers 10a to 10e is made of an appropriate material. The undercover 12 is preferably made of a resin material, but is not limited to this.

[0027] The power unit 20 is provided with an internal combustion engine 21 and a power transmission section 31 having a belt-type continuously variable transmission 31a installed rearward from the internal combustion engine 21, and a rear wheel 33 is mounted on a rear axle 32a, which is the output shaft of a reduction gear mechanism 32 provided at the rear of the power transmission section 31. A rear cushion (not shown) is interposed between the rear of the power transmission unit 31 and the horizontal portion 5c at the rear of the main frame 5.

[0028] The internal combustion engine 21 has a crankcase 22 that supports a crankshaft 22a rotatably in the vehicle width direction, i.e., the left-right direction, and a cylinder 23 and a cylinder head 24 are stacked in order from the crankcase 22 forward and are fastened with the cylinder axis C tilted significantly forward and nearly horizontal, and a head cover 25 is placed on top of the cylinder head 24. As shown in Figure 4, the link member 18 is connected to the power unit side bracket 20b provided on the upper part of the crankcase 22, so that the internal combustion engine 21 swings integrally with the power unit 20 relative to the body frame 2 via the link member 18. The crankcase 22 has a left-right split structure, with the left half extending rearward as a single unit to form a power transmission section 31 .

[0029] Referring to Figure 4, which shows a cross section of the internal combustion engine 21, a combustion chamber 41 is formed between the top surface of a piston 40 that reciprocates within the cylinder bore of the cylinder 23 and a cylinder head 43. An intake port 41i extends upward from the combustion chamber 41 of the cylinder head 24, which is tilted significantly forward, and an exhaust port 41e extends downward. H The cylinder head 24 is provided with an intake valve 51 that opens and closes the intake valve opening where the intake port 41i opens to the combustion chamber 41, and an exhaust valve 52 that opens and closes the exhaust valve opening where the exhaust port 41e opens to the combustion chamber 41, and is provided with a valve operating mechanism 50 that drives the intake valve 51 and the exhaust valve 52 at a predetermined timing with respect to the combustion stroke of the internal combustion engine 21.

[0030] An intake pipe 42 bends rearward and extends from the inlet of an intake port 41i at the top of the cylinder head 24 of the internal combustion engine 21, which is tilted forward significantly. In addition, an approximately cylindrical catalytic converter 44 is installed midway through the exhaust pipe 43 connected to the outlet of the exhaust port 41e at the bottom of the cylinder head 24, and a catalyst 44a, such as a three-way catalyst, for purifying the exhaust gas is loaded inside the catalytic converter 44.

[0031] Referring to Figure 4 (and Figure 5), the catalytic converter 44 is positioned below the cylinder head 24, which is tilted forward significantly, and in front of the crankcase 22, and is supported on the cylinder head 24 by a front support stay 48 and on the crankcase 22 by a rear support stay 49. The catalytic converter 44 is cylindrical and disposed near the center of the vehicle width direction with its longitudinal direction oriented in the left-right direction of the vehicle.

[0032] The exhaust pipe 43 is made up of an upstream exhaust pipe 43 a upstream of the catalytic device 44 and a downstream exhaust pipe 43 b downstream of the catalytic device 44 . Referring to FIG. 3, the upstream exhaust pipe 43a extends downward from the outlet of the exhaust port 41e, then bends to the left, and then makes a large curve from the left below the cylinder head 24 to face right, where it is connected to the right end of the catalytic converter 44. Referring to FIG. 1, downstream exhaust pipe 43b extends rightward from the right end of catalytic converter 44, then bends rearward, extends slightly diagonally downward and rearward along the right side of the vehicle, and is connected to muffler 45 that is attached to crankcase 22 and disposed on the right side of rear wheel 33.

[0033] Referring to Figures 2 and 4, the undercover 12 covering the underside of the footrest portion (floor portion) 1C is a generally horizontal plate that is installed on the lower edges of the left and right floor side covers 10d, 10d that are bent inward. It extends rearward from the front at a slight downward incline from the horizontal, bends upward at the lowest end 12x, and the rear portion 12r behind the lowest end 12x extends toward the catalytic converter 44. A rear portion 12r of the undercover 12 extends obliquely upward toward the catalytic converter 44, and its rear edge 12re is located slightly in front of the catalytic converter 44.

[0034] Referring to Figures 2 and 3, a pair of left and right guide protrusions 13L, 13R, which are long in the front and rear and protrude downward on the left and right sides of the vehicle width direction, are erected on the underside of the undercover 12, forming an air guide passage 14 between them that guides the wind while the vehicle is running. The rear ends 13Le, 13Re of the left and right guide protrusions 13L, 13R are located at the rear edge 12re of the undercover 12, and the catalytic device 44 oriented in the left-right direction is located within the left-right width of the rear ends 13Le, 13Re of the left and right guide protrusions 13L, 13R, so that the catalytic device 44 can face the air guide passage 14 between the guide protrusions 13L, 13R.

[0035] As shown in FIG. 3, the left and right guide protrusions 13L, 13R are formed so that the distance between them in the left and right vehicle width direction increases toward the front. As shown in FIG. 2, the left and right guide protrusions 13L, 13R increase in height from the front to the rear in the longitudinal direction of the vehicle, reaching a maximum height just before the rear ends 13Le, 13Re, and then rapidly decreasing in height behind them to reach the rear ends 13Le, 13Re.

[0036] Therefore, when the motorcycle 1 is traveling, the wind blowing along the underside of the undercover 12 at the bottom of the vehicle body can be drawn into the air guide passage 14 in as large a volume as possible and guided to the catalytic device 44 by the pair of left and right guide protrusions 13L, 13R, the widthwise spacing of which increases as the vehicle moves forward. A plurality of long guide ridges may be provided in the front-rear direction between the left and right guide ridges 13L, 13R, which can smooth the flow of wind while traveling.

[0037] In the motorcycle 1, a plate member 15 is fixed at its rear portion 15r to the bottom of the crankcase 22 and extends forward, and is disposed so as to cover the catalytic converter 44 from below. 3 and 4, plate member 15 is a rectangular plate member, and has a pair of left and right elongated mounting ribs 15b, 15b standing upright on the rear portion 15r of the upper surface. On the other hand, the crankcase 22 has a lower surface formed with a bulging portion 22b that bulges downward in a rectangular shape. The plate member 15 is made of, but not limited to, a resin material.

[0038] The left and right mounting ribs 15b, 15b on the upper surface of the plate member 15 are fitted onto the outer surfaces of the left and right side walls of the bulge portion 22b on the underside of the crankcase 22, and fastened with bolts 16, thereby fixing the rear portion 15r of the plate member 15 to the bulge portion 22b on the underside of the crankcase 22. The plate member 15, whose rear portion 15r is fixed to the underside of the crankcase 22, extends forward as shown in FIG. 4 to cover the lower portion of the catalytic converter 44 located below the cylinder 23 and in front of the crankcase 22.

[0039] The fixing of the plate member 15 to the lower part of the crankcase 22 is not limited to the manner of this embodiment, and may be done in another manner as appropriate, as long as the plate member is attached so that at least its rear part is attached to the lower part of the crankcase and extends forward.

[0040] The plate member 15 fixed to the crankcase 22 swings integrally with the internal combustion engine 21 which swings relative to the body frame 2 via the link member 18 . When no load is applied to the body frame 2, the front end edge 15f of the plate member 15 is close to the rear end edge 12re of the undercover 12, as shown in FIG. When a load is applied to the body frame 2 and the internal combustion engine 21 swings relative to the body frame 2, the plate member 15 swings downward together with the internal combustion engine 21, and as shown in Figure 5, the front end edge 15f of the plate member 15 moves downward away from the rear end edge 12re of the undercover 12, thereby forming an air guide port 17 between the rear end edge 12re of the undercover 12 and the front end edge 15f of the plate member 15 to guide the wind while driving to the catalytic device 44.

[0041] Since the internal combustion engine 21, the plate member 15, and the catalytic converter 44 swing together relative to the body frame 2, as shown in Figure 5, the catalytic converter 44 is positioned in a location facing the air intake 17 formed between the rear end edge 12re of the undercover 12 and the front end edge 15f of the plate member 15. Referring to Figure 5, when the vehicle is traveling, the wind flows rearward along the underside of the undercover 12, is guided by the left and right guide protrusions 13L, 13R, enters the air guide port 17, and is effectively guided to the catalytic converter 44, thereby cooling the catalytic converter 44.

[0042] The motorcycle 1 according to the embodiment of the present invention described in detail above has the following advantages. As shown in FIG. 4, when the motorcycle 1 is not being ridden and no load such as a weight is applied to the body frame 2, the front end edge 15f of the plate member 15 is close to the rear end edge 12re of the undercover 12, so that the plate member 15 covers the rear of the undercover 12 and covers the underside of the catalytic converter 44.

[0043] When a passenger gets in the vehicle and a load is applied to the body frame 2, the internal combustion engine 21 swings relative to the body frame 2, and the front end edge 15f of the plate member 15, which swings together with the internal combustion engine 21, moves downward away from the rear end edge 12re of the undercover 12, thereby forming an air guide port 17 between the rear end edge 12re of the undercover 12 and the front end edge 15f of the plate member 15, which guides the wind from the vehicle toward the catalytic converter 44. Figure 5 shows a state in which, when a high load is applied to the body frame during driving, the internal combustion engine 21 swings significantly relative to the body frame 2, causing the air intake 17 to open widely; however, when a passenger is simply in the vehicle, the opening of the air intake 17 shown in Figure 5 is smaller.

[0044] Therefore, when the vehicle is warming up, the driver gets in and forms the air inlet 17 that guides the wind toward the catalytic converter 44. However, the air inlet 17 is small and the catalytic converter 44 is covered from below by the plate member 15, so there is little heat dissipation downward, and this is until the vehicle starts moving. Since there is no wind, the catalytic converter 44 can be efficiently heated by the exhaust heat, which promotes catalyst activation, especially when the vehicle is cold, and reduces the emission of harmful substances contained in the exhaust gas. Furthermore, since the catalyst device 44 can be efficiently heated by exhaust heat, there is no need to shorten the upstream exhaust pipe 43a upstream of the catalyst device 44, and the catalyst device 44 can be easily positioned at an optimum position.

[0045] When the vehicle is running, a large load is applied to the body frame 2, and as shown in Figure 5, the internal combustion engine 21 swings significantly relative to the body frame 2, and together with this, the plate member 15 swings downward, widening the air guide port 17, thereby taking in a large amount of running air and directing it to the catalytic device 44, thereby further cooling the catalytic device 44.

[0046] When the internal combustion engine is operating under high load, such as during acceleration while traveling, the plate member 15 swings further downward to open the air guide port 17 more widely, thereby taking in a larger amount of traveling air and directing it to the catalytic device 44, thereby further cooling the catalytic device 44. Therefore, excessive increases in catalyst temperature during high-load operation can be prevented, the deterioration of exhaust purification capacity can be prevented, and harmful substances contained in exhaust gas can be reduced. Furthermore, even if the catalytic converter 44 is located close to the internal combustion engine 21, an excessive rise in the catalyst temperature can be suppressed, and damage to the catalytic converter 44 can be prevented.

[0047] In this embodiment, as shown in Figure 2, a pair of long left and right guide ridges 13L, 13R are provided on the underside of the undercover 12, protruding downward on the left and right sides in the vehicle width direction, and the pair of left and right guide ridges 13L, 13R form an air guide passage 14 between them that guides the traveling wind to the air guide opening 17.Therefore, the traveling wind along the underside of the undercover 12 can be smoothly guided to the air guide opening 17 by the air guide passage 14 between the pair of left and right guide ridges 13L, 13R, and the catalytic converter 44 can be cooled efficiently.

[0048] As shown in FIG. 2, the widthwise spacing between the pair of left and right guide protrusions 13L, 13R increases as the vehicle moves forward, so that as much traveling wind as possible can be taken into the air guide passage 14 and guided to the air guide port 17, and then to the catalytic converter 44, which is expected to have a significant cooling effect.

[0049] The above describes a motorcycle according to one embodiment of the present invention, but the aspects of the present invention are not limited to the above embodiment and include various aspects that fall within the scope of the gist of the present invention. [Explanation of symbols]

[0050] 1...Motorcycle, 2...Body frame, 3...Head pipe, 4...Down frame, 5...Main frame, 6...Passenger seat, 7...Handle, 8...Front fork, 9...Front wheel, 12...undercover, 12re...rear end edge, 13L, 13R...guide protrusion portion, 14...air guide passage, 15...plate member, 15f...front end edge, 15r...rear portion, 16...bolt, 17...air guide port, 18...link member 20...power unit, 21...internal combustion engine, 22...crankcase, 23...cylinder, 24...cylinder head, 25...head cover, 28...fuel tank, 31...power transmission part, 31a...belt-type continuously variable transmission, 32...reduction gear mechanism, 33...rear wheel, 40...piston, 41...combustion chamber, 42...intake pipe, 43...exhaust pipe, 44...catalytic device, 45...muffler, 50...valve train, 51...intake valve, 52...exhaust valve.

Claims

1. An internal combustion engine (21) having a crankcase (22) with a cylinder (23) and a cylinder head (24) stacked and integrally fastened together is supported by a body frame (2) via a link member (18) so as to be able to swing. In the motorcycle (1), a catalytic converter (44) is disposed in the middle of an exhaust pipe (43) extending from the cylinder head (24) and is disposed in front of the crankcase (22), an undercover (12) fixed to the vehicle body frame (2) covers the vehicle body from below, and its rear part (12r) extends toward the catalytic converter (44); a plate member (15) having at least a rear portion (15r) attached to a lower portion of the crankcase (22) and extending forward is disposed so as to cover the catalytic converter (44) from below; An air guide port (17) is formed between a rear end edge (12re) of the undercover (12) and a front end edge (15f) of the plate member (15) to guide traveling airflow to the catalytic converter (44), The motorcycle is characterized in that when the internal combustion engine (21) swings relative to the body frame (2), the opening area of ​​the air intake port (17) increases.

2. 2. The motorcycle according to claim 1, wherein a pair of left and right guide protrusions (13L, 13R) protruding downward on the left and right sides in the vehicle width direction are provided on the underside of the undercover (12), forming an air guide passage (14) between them that guides traveling air to the air guide port (17).

3. 3. The motorcycle according to claim 2, wherein the pair of left and right guide ridges (13L, 13R) have a widthwise distance between them that increases toward the front.

Images