WO2024047866A1

WO2024047866A1 - Motorcycle

Info

Publication number: WO2024047866A1
Application number: PCT/JP2022/033115
Authority: WO
Inventors: 義輝及川
Original assignee: 本田技研工業株式会社
Priority date: 2022-09-02
Filing date: 2022-09-02
Publication date: 2024-03-07

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

motorcycle

The present invention relates to a motorcycle equipped with a catalyst device.

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

Since the catalyst device has a low reducing ability at room temperature, the catalyst device is heated by exhaust heat to activate the catalyst and increase the purification ability, but if the catalyst becomes overheated, the purification ability will deteriorate and it will be worn out.
Therefore, the catalytic converter is cooled using the running wind (for example, see Patent Document 1).

JP2019-60256A

The motorcycle disclosed in Patent Document 1 has an internal combustion engine in which a cylinder and a cylinder head are sequentially stacked on a crankcase, and the cylinder axis is tilted forward approximately horizontally, and is swingably supported on a body frame via a link member. ing.
The catalyst device is interposed in the middle of the exhaust pipe extending from the cylinder head, and is disposed below the cylinder and in front of the crankcase, with the vehicle width direction being the longitudinal direction.

An undercover that covers the vehicle body from below is provided in front of the catalyst device and attached to the vehicle body frame.
The rear end of the undercover faces toward the catalyst device.
Therefore, the lower surface of the undercover can guide the traveling wind to the catalyst device, and by using the traveling wind to cool the catalyst device, it is possible to cool the catalyst loaded in the catalyst device.

The catalyst device disclosed in Patent Document 1 is installed below the cylinder and in front of the crankcase. Since there is an undercover in front of the catalyst device, the lower part of the catalyst device is always open.
Therefore, even if the catalytic converter is heated by exhaust heat during warm-up, the catalytic converter radiates heat downward, so the activation of the catalyst is delayed, especially when it is cold, and the exhaust gas is not purified immediately. .

In addition, since the lower part of the catalyst device is always open, even if the lower surface of the undercover guides the traveling wind to the catalyst device, the traveling wind along the lower surface of the undercover is guided to the catalyst device and cools the catalyst device. However, during high-load operation, it is desired that the catalyst device be further cooled in order to suppress an excessive rise in catalyst temperature.

Therefore, in order to reduce the amount of harmful substances emitted, it is important to activate the catalyst early and to suppress excessive rise in catalyst temperature.

The present invention has been made in view of the above, and its objectives are to be able to quickly activate the catalyst during warm-up operation, to prevent the catalyst temperature from becoming excessively high during high-load operation, and to The object of the present invention is to provide a motorcycle that can reduce the amount of harmful substances emitted.
This, in turn, contributes to mitigation or mitigation of the effects of climate change.

In order to achieve the above object, the present invention
An internal combustion engine, in which the cylinder and cylinder head are stacked and integrally connected to the crankcase, is swingably supported by the vehicle body frame via a link member.
In a motorcycle in which a catalyst device interposed in the middle of an exhaust pipe extending from the cylinder head is disposed in front of the crankcase,
An undercover fixed to the vehicle body frame is provided to cover the vehicle body from below and extend its rear part toward the catalyst device (44),
A plate member having at least a rear portion (15r) attached to a lower part of the crankcase and extending forward is disposed to cover the catalyst device from below,
An air guide port is formed between the rear end edge of the undercover and the front end edge of the plate member, and the air guide port guides the traveling wind to the catalyst device.
A motorcycle characterized in that an opening area of the air guide port increases when the internal combustion engine swings relative to the body frame.

According to this configuration, when the internal combustion engine swings with respect to the vehicle body frame, the front end edge of the plate member that swings together with the internal combustion engine separates downward from the rear end edge of the undercover, and the rear end of the undercover An air guide port is formed between the edge and the front edge of the plate member to guide the traveling air to the catalyst device.
Further, when the internal combustion engine is not swinging with respect to the vehicle body frame, no air guide port is formed, so that the plate member covers the rear of the undercover to cover the lower part of the catalyst device.

Therefore, during warm-up operation, the lower part of the catalyst device is covered with a plate member, and there is little heat radiated downward until the vehicle is running. Since there is no running wind, the catalyst device can be efficiently heated by exhaust heat, promoting activation of the catalyst, and suppressing the emission of harmful substances contained in exhaust gas.
When the vehicle is running, running wind enters the air guide port and is guided to the catalyst device to cool the catalyst device, and the purification ability of the catalyst device can be maintained.

During high-load operation of the internal combustion engine, such as when accelerating while driving, a large load is applied to the vehicle body frame, causing the internal combustion engine to swing significantly relative to the vehicle body frame, causing the plate members to swing and opening the air guide port wide. Therefore, a large amount of running air can be guided to the catalyst device to further cool the catalyst device.
Therefore, it is possible to suppress an excessive rise in catalyst temperature during high-load operation, suppress a decrease in exhaust purification ability, and reduce harmful substances contained in exhaust gas.

In a preferred embodiment of the invention,
On the lower surface of the undercover, a pair of left and right guide protrusions that respectively protrude downward in the left and right directions in the vehicle width direction are provided so as to constitute an air guide path that guides the traveling wind to the air guide opening.

According to this configuration, a pair of left and right guide protrusions are provided at the rear part of the undercover, respectively, protruding downward in the left and right directions in the vehicle width direction, and the pair of left and right guide protrusions are provided between each other in the air guide port. Since it forms an air guide path that guides the driving wind, the air guide path between the pair of left and right guide protrusions can smoothly guide the driving wind along the lower surface of the undercover to the air guide port. It can be cooled efficiently.

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

According to this configuration, the distance between the pair of left and right guide protrusions increases as the distance in the vehicle width direction increases toward the front, so that as much wind as possible is taken into the air guide path, guided to the air guide port, and sent to the catalyst device. A great cooling effect can be expected.

In the present invention, during warm-up operation, the lower part of the catalyst device is covered with a plate member, so that less heat is radiated downward until the vehicle is running. Since there is no running wind, the catalyst device can be efficiently heated by exhaust heat, promoting activation of the catalyst, and suppressing the emission of harmful substances contained in exhaust gas.
In addition, during high-load operation, a large load is applied to the vehicle body frame, and the internal combustion engine swings greatly relative to the vehicle body frame, causing the plate members to swing and widen the air guide opening, allowing a large amount of running air to be catalyzed. Since the catalytic converter can be further cooled by directing it to the catalyst device, it is possible to suppress an excessive rise in catalyst temperature during high-load operation, suppress a decline in exhaust purification ability, and reduce harmful substances contained in exhaust gas. be able to.
This, in turn, contributes to mitigation or mitigation of the effects of climate change.

FIG. 1 is a right side view of a motorcycle according to an embodiment of the present invention. FIG. 2 is a left rear bottom perspective view of the main central part of the motorcycle. FIG. 2 is a bottom view of the main central part of the motorcycle. FIG. 3 is a left side cross-sectional view of the main central part of the motorcycle in a state where the internal combustion engine is not swinging with respect to the body frame. FIG. 2 is a left side cross-sectional view of the main central part of the motorcycle in a state in which the internal combustion engine is oscillated with respect to the body frame.

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment based on this invention is described based on FIG. 1 thru|or 5.
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.
Note that in the description of this specification and the claims, the front, rear, left, right, top, and bottom directions are based on the usual standard in which the straight direction of the motorcycle 1 according to the present embodiment is the forward direction, and in the drawings, FR refers to the front direction. , LH indicates left, RH indicates right, and UP indicates upward.

In this embodiment, the motorcycle 1 is specifically a scooter type motorcycle.
In this motorcycle 1, a front body part 1A and a rear body part 1B are connected via a low footrest (floor part) 1C, and a body frame 2, which forms the frame of the body, is generally connected to a down frame 4. It consists of a main frame 5.
That is, the down frame 4 extends downward from the head pipe 3 of the front portion 1A of the vehicle body, and is connected to the lower frame portions 5a of a pair of left and right main frames 5 extending substantially horizontally rearward from the lower end of the down frame 4. The main frame 5 extending diagonally rearward and upward from the rear end of the lower frame portion 5a forms 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 extending rearward substantially horizontally. is formed.

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 disposed above the storage box.
On the other hand, in the front portion 1A of the vehicle body, a handle 7 is provided above the head pipe 3, and a front fork 8 extends downward, and a front wheel 9 is pivotally supported at the lower end of the front fork 8.
A frame-side bracket 5bb is provided on the inclined portion 5b of the main frame 5 so as to protrude rearward, and a power unit-side bracket 20b is attached to the frame-side bracket 5bb via a link member 18. ) 20 are connected and supported so that they can swing up and down.
That is, the motorcycle 1 of this embodiment employs an upper link support structure for the power unit 20.

In the front portion 1A of the vehicle body, the head pipe 3 and down frame 4 are covered from the front and rear by a front cover 10a and a leg shield 10b.
The foot rest (floor part) 1C is provided on a pair of left and right lower frame parts 5a of the main frame 5 of the vehicle body frame 2, and the upper part of the lower frame part 5a is covered by a floor cover 10c, and the left and right sides are respectively in the front and rear directions. covered with floor side cover 10d.

In the rear part 1B of the vehicle body, a fuel tank 28 is attached to the horizontal part 22c of the main frame 22 below the rear of the passenger seat 6, and the inclined part 22b and horizontal part 22c of the main frame 22 are covered on the left and right and rearward by the body cover 10e. be exposed.
Further, a front fender 11 is provided above the front wheel 14.

In the motorcycle 1 of this embodiment, the lower part of the footrest (floor part) 1C is covered by an undercover 12 attached to the lower frame part 5a of the main frame 5 from below.
Each cover 10a-10e is made of a suitable material.
The undercover 12 is preferably formed of a resin material, but is not limited thereto.

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

The internal combustion engine 21 is rotatably supported by a crankcase 22 with a crankshaft 22a oriented in the vehicle width direction, that is, in the left-right direction, and a cylinder 23 and a cylinder head 24 are successively stacked forward from the crankcase 22 to align the cylinder axis. The cylinder head 24 is fastened with the cylinder head C substantially horizontally tilted forward, and a head cover 25 is placed over the cylinder head 24.
As shown in FIG. 4, since the link member 18 is connected to the power unit side bracket 20b provided at the upper part of the crankcase 22, the internal combustion engine 21 is integrally connected to the power unit 20 with respect to the vehicle body frame 2. It swings via the link member 18.
The crankcase 22 has a left-right split structure, with the left half integrally extending rearward to form a power transmission section 31.

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

An intake pipe 42 is bent and extends rearward from the entrance of the intake port 41i at the upper part of the cylinder head 24 of the internal combustion engine 21, which is tilted significantly forward.
Further, a substantially cylindrical catalyst device 44 is interposed in the middle of the exhaust pipe 43 connected to the outlet of the exhaust port 41e at the lower part of the cylinder head 24, and a catalyst device 44 having a substantially cylindrical shape is installed inside the catalyst device 44 for purifying exhaust gas. A catalyst 44a such as a catalyst is loaded.

Referring to FIG. 4 (and FIG. 5), the catalyst device 44 is disposed below the cylinder head 24 that is tilted forward and in front of the crankcase 22, and is supported by the cylinder head 24 by a front support stay 48. At the same time, it is supported by the crankcase 22 by a rear support stay 49.
The catalyst device 44 has a cylindrical shape and is disposed near the center in the vehicle width direction with its longitudinal direction facing in the vehicle width direction.

The exhaust pipe 43 consists of an upstream exhaust pipe 43a upstream from the catalyst device 44 and a downstream exhaust pipe 43b downstream from the catalyst device 44.
Referring to FIG. 3, the upstream exhaust pipe 43a extends downward from the outlet of the exhaust port 41e and then bends to the left, and curves significantly from the left below the cylinder head 24 to face right. By the way, it is connected to the right end of the catalyst device 44.
Referring to FIG. 1, the downstream exhaust pipe 43b extends rightward from the right end of the catalyst device 44, bends rearward, extends backward and slightly diagonally downward on the right side of the vehicle, and is attached to the crankcase 22. and is connected to a muffler 45 located on the right side of the rear wheel 33.

Referring to FIGS. 2 and 4, an undercover 12 that covers the lower part of the footrest (floor part) 1C has a generally horizontal plate shape, and its lower edge is bent inside the left and right floor side covers 10d, 10d. It extends rearward from the front part at a slight downward inclination from the horizontal, bends upward at the lowest end 12x, and the rear part 12r behind the lowest end 12x extends toward the catalyst device 44. ing.
A rear portion 12r of the undercover 12 extends obliquely upward toward the catalyst device 44, and a rear end edge 12re is located somewhat in front of the catalyst device 44.

Referring to FIGS. 2 and 3, on the lower surface of the undercover 12, a pair of left and

right guide protrusions

13L and 13R, which are long in the front and rear, project downward in the left and right directions in the vehicle width direction, and run between each other. It is erected to form an air guide path 14 that guides the wind.
The rear ends 13Le and 13Re of the left and

right guide protrusions

13L and 13R are located at the rear edge 12re of the undercover 12, and within the left and right width of the rear ends 13Le and 13Re of the left and

right guide protrusions

13L and 13R, respectively. , the catalyst device 44 is positioned in the left-right direction, and can face the air guide path 14 between the

guide protrusions

13L and 13R.

As shown in FIG. 3, the left and

right guide protrusions

13L, 13R are formed such that the distance between them in the left and right vehicle width direction increases as they move forward.
Furthermore, as shown in FIG. 2, the height of the left and

right guide protrusions

13L and 13R increases from the front to the rear in the longitudinal direction of the vehicle, and reaches its maximum height in front of the rear ends 13Le and 13Re. At the rear, the height decreases rapidly and reaches the rear ends 13Le and 13Re.

Therefore, when the motorcycle 1 is running, the wind flowing along the lower surface of the undercover 12 at the lower part of the vehicle body is prevented by the pair of left and

right guide protrusions

13L and 13R whose distance in the vehicle width direction increases as the vehicle width direction increases toward the front. As much wind as possible can be taken into the air guiding path 14 and guided to the catalyst device 44.
In addition, a plurality of elongated guide protrusions may be provided in the front-rear direction between the left and

right guide protrusions

13L and 13R, so that the running wind can flow smoothly.

In the present motorcycle 1, a plate member 15 whose rear portion 15r is fixed to the lower part of the crankcase 22 and extends forward is disposed so as to cover the catalyst device 44 from below.
Referring to FIGS. 3 and 4, the plate member 15 is a rectangular plate member, and a pair of left and right long mounting

ribs

15b, 15b are erected on the rear portion 15r of the upper surface.
On the other hand, the lower surface of the crankcase 22 is formed with a bulging portion 22b that bulges downward into a rectangular shape.
The plate member 15 is made of a resin material, but is not limited thereto.

By fitting the left and right mounting ribs 15b on the upper surface of the plate member 15 to the outer surfaces of the left and right side walls of the bulging portion 22b on the lower surface of the crankcase 22 and fastening them with the bolts 16, the lower surface of the crankcase 22 expands. The rear portion 15r of the plate member 15 is fixed to the protruding portion 22b.
As shown in FIG. 4, the plate member 15 whose rear portion 15r is fixed to the lower surface of the crankcase 22 extends forward and covers the lower part of the catalyst device 44 located below the cylinder 23 and in front of the crankcase 22. .

Note that the fixation of the plate member 15 to the lower part of the crankcase 22 is not limited to the aspect of this embodiment, and the plate member may be attached to the lower part of the crankcase so as to extend forward. If it is suitable, it may be done in another mode as appropriate.

The plate member 15 fixed to the crankcase 22 swings together with the internal combustion engine 21, which swings with respect to the vehicle body frame 2 via a link member 18.
When no load is applied to the vehicle body frame 2, the front edge 15f of the plate member 15 is close to the rear edge 12re of the undercover 12, as shown in FIG.
When a load is applied to the vehicle body frame 2 and the internal combustion engine 21 swings relative to the vehicle body frame 2, the plate member 15 swings downward together with the internal combustion engine 21, and as shown in FIG. Since the front edge 15f of the undercover 12 is separated downward from the rear edge 12re of the undercover 12, a guide for guiding the traveling air to the catalyst device 44 is created between the rear edge 12re of the undercover 12 and the front edge 15f of the plate member 15. Wind opening 17 is formed.

Since the internal combustion engine 21, the plate member 15, and the catalyst device 44 swing together with respect to the vehicle body frame 2, the catalyst device 44 is connected to the rear edge 12re of the undercover 12 and the plate member 15, as shown in FIG. It is located at a location facing the air guide port 17 formed between the front edge 15f and the front edge 15f.
Referring to FIG. 5, when the vehicle is traveling, the wind flows backward along the lower surface of the undercover 12, is guided by the left and

right guide protrusions

13L and 13R, enters the air guide port 17, and enters the catalyst device 44. The catalyst device 44 can be cooled effectively.

The embodiment of the motorcycle 1 according to the present invention described in detail above has the following effects.
As shown in FIG. 4, when the motorcycle 1 is not ridden and no load is applied to the body frame 2, the front edge 15f of the plate member 15 is close to the rear edge 12re of the undercover 12. Therefore, the plate member 15 covers the rear of the undercover 12 and covers the lower part of the catalyst device 44.

When a passenger gets on the vehicle and a load is applied to the vehicle body frame 2, the internal combustion engine 21 swings relative to the vehicle body frame 2, and the front edge 15f of the plate member 15 that swings together with the internal combustion engine 21 becomes the rear end of the undercover 12. By separating downward from the edge 12re, an air guide port 17 is formed between the rear edge 12re of the undercover 12 and the front edge 15f of the plate member 15 to guide the running air to the catalyst device 44.
FIG. 5 shows a state in which the internal combustion engine 21 swings greatly relative to the body frame 2 when a high load is applied to the body frame while driving, and the air guide port 17 opens wide. In this case, the opening of the air guide port 17 shown in FIG. 5 is smaller.

Therefore, during warm-up operation, the air guide port 17 is formed to guide the traveling air to the catalyst device 44 when the driver gets on the vehicle, but the air guide port 17 is small and the catalyst device 44 is covered from below by the plate member 15, so that heat dissipation to the bottom is limited. Until it is less and running. Since there is no running wind, the catalyst device 44 can be efficiently heated by the exhaust heat, and the activation of the catalyst can be promoted even when the vehicle is cold, thereby suppressing the emission of harmful substances contained in the exhaust gas.
Further, 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 arranged at an optimal position.

When the vehicle is running, a large load is applied to the vehicle body frame 2, and as shown in FIG. Since the air guide port 17 is opened wide, a large amount of running air can be taken in and guided to the catalyst device 44 to further cool the catalyst device 44.

During high-load operation of the internal combustion engine, such as when accelerating while driving, the plate member 15 swings further downward to open the air guide port 17 more widely, so a larger amount of driving air is taken in, guided to the catalyst device 44, and then catalyzed by the catalyst. Device 44 can be cooled even further.
Therefore, it is possible to suppress an excessive rise in catalyst temperature during high-load operation, suppress a decrease in exhaust purification ability, and reduce harmful substances contained in exhaust gas.
Further, even if the catalyst device 44 is located close to the internal combustion engine 21, it is possible to suppress an excessive rise in catalyst temperature and prevent damage to the catalyst device 44.

In this embodiment, as shown in FIG. 2, a pair of long left and

right guide protrusions

13L and 13R are provided on the lower surface of the undercover 12 and project downward in the left and right directions in the vehicle width direction, respectively. Since the pair of left and

right guide protrusions

13L and 13R constitute an air guide path 14 that guides the traveling wind to the air guide port 17, the pair of left and right guide protrusions direct the traveling wind along the lower surface of the under cover 12 The air can be smoothly guided to the air guide port 17 by the air guide path 14 between 13L and 13R, and the catalyst device 44 can be efficiently cooled.

Furthermore, as shown in FIG. 2, the distance between the pair of left and

right guide protrusions

13L and 13R in the vehicle width direction increases toward the front, so that as much wind as possible is taken into the air guide path 14. It can be guided to the air guide port 17 and then to the catalyst device 44, and a great cooling effect can be expected.

Although the motorcycle according to one embodiment of the present invention has been described above, aspects of the present invention are not limited to the above embodiment, and can be implemented in various forms within the scope of the gist of the present invention. This includes:

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 edge, 13L, 13R...guide protrusion, 14...air guide path, 15...plate member, 15f...front edge, 15r...rear, 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 section, 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...Catalyst device, 45...Muffler, 50...Valve mechanism, 51...Intake valve, 52...Exhaust valve.

Claims

An internal combustion engine (21) in which a cylinder (23) and a cylinder head (24) are stacked and integrally connected to a crankcase (22) is swingably supported by a vehicle body frame (2) via a link member (18). ,
In a motorcycle (1) in which a catalyst device (44) interposed in the middle of an exhaust pipe (43) extending from the cylinder head (24) 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 is provided with a rear portion (12r) thereof extending toward the catalyst device (44),
A plate member (15) that is attached to at least a rear portion (15r) of the lower part of the crankcase (22) and extends forward is disposed to cover the catalyst device (44) from below,
An air guide port (17) is formed between the rear edge (12re) of the undercover (12) and the front edge (15f) of the plate member (15) to guide the running air to the catalyst device (44). ,
A motorcycle characterized in that an opening area of the air guide port (17) increases when the internal combustion engine (21) swings relative to the body frame (2).
On the lower surface of the undercover (12), a pair of left and right guide protrusions (13L, 13R) that protrude downward in the left and right directions in the vehicle width direction guide the running wind to the air guide port (17) between them. The motorcycle according to claim 1, further comprising an air guide path (14).
The motorcycle according to claim 2, wherein the distance between the pair of left and right guide protrusions (13L, 13R) in the vehicle width direction increases toward the front.