Cowling structure of straddle-type vehicle and straddle-type vehicle

A cowling structure of a straddle-type vehicle, comprises a front opening forming section formed with a front opening which opens frontward in a vehicle body; a rear opening forming section formed with a rear opening which is placed rearward relative to the front opening and opens to a rear in the vehicle body; an inclined wall which is placed between a lower portion of the front opening forming section and a lower portion of the rear opening forming section, extends in a forward and rearward direction, and includes an inclined surface inclined to be higher as the inclined surfaces extends in a rearward direction; and an outer side wall protruding upward from an outer side portion of the inclined wall in a vehicle width direction of the vehicle body and extending in the forward and rearward direction.

TECHNICAL FIELD

The present invention relates to the cowling structure of a straddle-type vehicle, which covers the front portion of a vehicle body, and the straddle-type vehicle including the cowling structure.

BACKGROUND ART

In a motorcycle disclosed in Patent Literature 1, a front cowling is provided to cover a vehicle body from the front side of the upper ends of front forks to the side portions of the vehicle body.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In some cases, the motorcycle disclosed in Patent Literature 1 is required to travel more stably at a high speed.

The present invention has been developed to solve the above-described problem, and an object of the present invention is to provide the cowling structure of a straddle-type vehicle which allows the vehicle to travel more stably at a high speed, and the straddle-type vehicle including the cowling structure.

Solution to Problem

To solve the above-described problem, a cowling structure of a straddle-type vehicle of the present invention, comprises a front opening forming section formed with a front opening which opens frontward in a vehicle body; a rear opening forming section formed with a rear opening which is placed rearward relative to the front opening and opens to a rear in the vehicle body; an inclined wall which is placed between a lower portion of the front opening forming section and a lower portion of the rear opening forming section, extends in a forward and rearward direction, and includes an inclined surface inclined to be higher as the inclined surface extends in a rearward direction; and an outer side wall protruding upward from an outer side portion of the inclined wall in a vehicle width direction of the vehicle body and extending in the forward and rearward direction.

When the air flows through the front opening into a region that is rearward relative to the front opening, this air flows along the inclined wall and is discharged to outside the vehicle body through the rear opening. Since the inclined surface of the inclined wall is inclined to be higher as it extends in the rearward direction, the air collides with the inclined surface and thereby a downward force (hereinafter the downward force will be referred to as a “downforce”) is generated in the inclined surface, which causes a force pushing down the wheel to a road surface to be generated. Since the rear opening opens to the rear in the vehicle body, the flow of the air from the front opening toward the rear opening can be facilitated, and reduction of the flow velocity of the air can be suppressed. In addition, the outer side wall can prevent the air flowing along the upper portion of the inclined surface from being diverted to the outward region in the vehicle width direction. Therefore, the downforce can be effectively generated in the inclined surface.

To solve the above-described problem, a straddle-type vehicle of the present invention comprises a vehicle body; and the above-described cowling structure of the straddle-type vehicle, which covers a front portion of the vehicle body.

Advantageous Effects of Invention

In accordance with the present invention, since the downforce can be generated effectively in the inclined surface, the straddle-type vehicle can travel more stably at a high speed.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the preferred embodiments of a straddle-type vehicle of the present invention will be described with reference to the accompanying drawings. The directions stated below are from the perspective of a rider straddling the straddle-type vehicle, and a rightward and leftward direction conforms to a vehicle width direction of the vehicle body. Hereinafter, inward (inside) of the vehicle body in the vehicle width direction will be referred to as “inward (inside),” while outward (outside) of the vehicle body in the vehicle width direction will be referred to as “outward (outside).”

First of all, a situation in which it is necessary to apply a downforce to the vehicle body of a straddle-type vehicle10of the present embodiment will be described. In the straddle-type vehicle10, each of side cowlings44a,44bis inclined in an outward direction of the vehicle width direction, from its front end portion to its rear end portion, and thereby diverts air flowing toward the rider's legs. The rear end portions of the side cowlings44a,44bare located in the vicinity of a radiator core22a. The air which has flowed through the radiator core22aflows to a rear region and to a lower region within the vehicle width of the vehicle body, while preventing an interference with the side cowlings44a,44b. The side cowlings44a,44bserve to guide the air to the radiator core22a. The front ends of the inner side surfaces of the side cowlings44a,44bin the vehicle width direction are located in front of the radiator core22a. The upper portion of the space formed between the left side cowling44aand the right side cowling44bis closed by a head lamp unit56, a front cowling42, or the like. An opening is provided between the pair of left and right side cowlings44a,44b, to introduce the air into the vehicle body. The radiator core22ais disposed between the side cowlings44a,44band rearward relative to the front end portions of the side cowlings44a,44b. In this configuration, the air is guided in the rearward direction from the front ends of the side cowlings44a,44bthrough the space formed between the side cowlings44a,44b. This air is guided to the radiator core22awithout being diverted to an outward region in the vehicle width direction.

If a large amount of air is guided to the space formed between the side cowlings44a,44bwhile the vehicle10is traveling at a high speed, the air guided to the space formed between the side cowlings44a,44bcauses a force for raising a front wheel26to be generated in the vehicle10, so that the grounding load of the front wheel26tends to be reduced. In the present embodiment, the front surface of the radiator core22aand the front surface of the cylinder of an engine20are inclined in the rearward direction as they extend in a downward direction. In this structure, the force for raising the front wheel26tends to act on the vehicle body. In the present embodiment, by using a front cowling structure14which will be described later, the downforce is generated to push down the front cowling42, by the air which collides with the surface of the front cowling42facing upward. In this way, it becomes possible to suppress reduction of the grounding load of the front wheel26, and easily transmit driving power and a braking force from the front wheel26to the road surface, while the vehicle10is traveling at a high speed. Since the downforce is generated and the grounding load of the front wheel26is increased irrespective of the air guided to the space formed between the side cowlings44a,44b, the driving power and the braking force applied from the front wheel26to the road surface can be increased, and a traveling performance can be improved.

Hereinafter, the configuration of the straddle-type vehicle10or the like will be specifically described.FIG. 1is a plan view showing the configuration of the straddle-type vehicle10according to the embodiment.FIG. 2is a front view showing the configuration of the straddle-type vehicle10. The straddle-type vehicle10of the present embodiment is a motorcycle and receives the air from the front, while the straddle-type vehicle10is traveling. As shown inFIG. 1, the straddle-type vehicle10includes a vehicle body12, and the front cowling structure14covering the front portion of the vehicle body12.

As shown inFIG. 1, the vehicle body12includes a vehicle body frame18, the engine20mounted to the vehicle body frame18, and a cooling device22for cooling the engine20. The cooling device22includes the radiator core22afor performing heat exchange between the air and a coolant which has taken heat out of the engine20. The radiator core22ais placed in front of the engine20in such a manner that the surface of the radiator core22awhich receives the air faces the front.

As shown inFIG. 2, the vehicle body12includes a pair of left and right front forks24a,24bprovided at the front portion of the vehicle body frame18(FIG. 1), the front wheel26mounted to the front forks24a,24b, a swing arm (not shown) provided at the rear portion of the vehicle body frame18(FIG. 1), a rear wheel28mounted to the swing arm, and a front fender30.

As shown inFIG. 1, the vehicle body12further includes a steering handle34, a fuel tank36placed rearward relative to the steering handle34, and a seat38placed behind the fuel tank36. The steering handle34is provided with a pair of left and right grips40a,40b. The rider straddles the seat38, grips the grips40a,40b, and steers the steering handle34.

As shown inFIG. 2, the front cowling structure14includes the front cowling42placed above the front fender30and in front of the upper ends of the front forks24a,24b, to cover the vehicle body12, and the pair of left and right side cowlings44a,44bplaced on the left and right sides of the front forks24a,24b, respectively, to cover the vehicle body12. The front cowling structure14is a portion exposed to the front, when the vehicle body is viewed from the front. The front cowling structure14may be constituted by a single member, or may include a plurality of members which are coupled to each other. The front cowling structure14has an outer shape in which right and left outer edges extend to be spaced apart from each other in an outward direction of the vehicle width direction, from its front end toward its rear portion, and upper and lower outer edges are spaced apart from each other in a vertical direction, from the front end. In the present embodiment, the front cowling structure14includes aerodynamic devices46a,46bfor generating the downforce.

As shown inFIG. 2, the upper surface of the front cowling42has an inclined surface42awhich is inclined to be higher as it extends in the rearward direction. The front cowling42supports a windshield48. A pair of left and right side mirrors60a,60bare attached to the front cowling42.

As shown inFIG. 2, the front end portion42bof the front cowling42is formed with a pair of left and right openings62a,62bwhich are opened to the front. In the present embodiment, a ram duct63is connected to the left opening62a. The air taken into the ram duct63through the opening62ais supplied to the engine20(FIG. 1) via an air cleaner or the like which is not shown. A radiator opening23is provided below the front cowling42to supply the air to the radiator core22a. Alternatively, the ram duct63may be connected to the right opening62b.

As shownFIG. 1, each of the pair of left and right side cowlings44a,44bhas a plate shape in which it gradually protrudes in the outward direction, from its front end toward its rear portion. As shown inFIG. 2, when the vehicle body is viewed from the side, the side cowlings44a,44bare mounted to the vehicle body12in such a manner that the upper portions of the side cowlings44a,44boverlap with the outer side portions64a,64b, respectively, and are apart from the outer side portions64a,64b, respectively, in the vehicle width direction. The outer side portions14a,14bof the front cowling structure14are formed by the side cowlings44a,44b, respectively. In this configuration, each of the outer side portions14a,14bof the front cowling structure14is provided with a swelling section83which gradually swells in the outward direction, from its front end toward its rear end, and reduces an air resistance, and a wind deflecting section81which diverts in the outward direction the air flowing toward the rider. The front cowling structure14includes the outer side portion14alocated on the outer surface in the vehicle width direction. The swelling section83is located at the front portion of the outer side portion14a, and gradually swells in the outward direction of the vehicle width direction, from its front end toward its rear portion. In the present embodiment, the swelling section83includes an inclined wall80, an outer side wall82, and an upper wall86. When the vehicle body is viewed from the front, the wind deflecting sections81overlap with the rider straddling the vehicle, and are located in front of the rider. To prevent the air from colliding with the rider, the wind deflecting sections81are located at relatively outer portions, respectively, of the front cowling structure14. In the present embodiment, each of the wind deflecting sections81includes the side portion of the front cowling42, and the corresponding side cowling44a,44b.

FIG. 3is a front view showing the configuration of the aerodynamic device46aprovided at the left half part of the front cowling structure14.FIG. 4is a perspective view showing in an enlarged manner the configuration of the left half part of the front cowling structure14, when viewed from the front and the right.FIG. 5is a longitudinal sectional view schematically showing the configuration of the left aerodynamic device46a, when viewed from the left. In the present embodiment, the left aerodynamic device46aincludes the front cowling42and the left side cowling44a, while the right aerodynamic device46bincludes the front cowling42and the right side cowling44b. The left aerodynamic device46aand the right aerodynamic device46bare symmetric in the rightward and leftward direction. Hereinafter, regarding the configurations of the aerodynamic devices46a,46b, the left aerodynamic device46awill be mainly described.

As shown inFIGS. 3 and 4, the aerodynamic device46aincludes a lift force generating section66which generates the downforce which is a downward lift force, by use of the air, and a guide section68which guides the ram air to the lift force generating section66. The lift force generating section66is provided at the outer side portion14aof the front cowling structure14. The guide section68is provided at the front end portion14cof the front cowling structure14. The aerodynamic device46ais provided at the side portion of the front cowling structure14in the vehicle width direction. The aerodynamic device46ais placed above the radiator opening23, is provided at the front portion of the front cowling structure14, and located in front of the front fork24a,24b. Since the aerodynamic devices46a,46bare placed in front of the front forks24a,24b, respectively, moment forces pushing down the front forks24a,24b, respectively, can be increased, when the downforces are generated. In this way, the aerodynamic devices46a,46bare preferably placed at a location that is as forward as possible. The aerodynamic device46ais provided at the side portion of the front cowling that is outward relative to the upper surface of the front cowling42. The aerodynamic device46ais located rearward relative to the windshield48and the side mirror60a. The aerodynamic device46ais set to be as high as the handle grip40a, and laterally relative to the head lamp unit56.

As shown inFIGS. 3 and 4, the lift force generating section66includes a tubular portion70having a horizontal cross-section of a substantially rectangular shape. As shown inFIG. 5, the front portion of the tubular portion70is provided with a front opening forming section72formed with a front opening72awhich opens to the front. A space is formed to allow the space formed in front of the vehicle body and the front opening72ato be in communication with each other. Through this space, the air flowing in the rearward direction from the front of the vehicle body can be introduced into the front opening72a. In the same manner, a space is formed to allow the space formed rearward relative to the vehicle body and the rear opening to be in communication with each other. Through this space, the air which has flowed in the rearward direction through the rear opening76acan be discharged to an outside space formed rearward relative to the vehicle body. An introduction port forming section74formed with an introduction port74ais provided in front of the front opening forming section72, at the front portion of the tubular portion70. The introduction port74aopens to the inside in the vehicle width direction. The introduction port74ais configured to flow the air which has been guided by the guide section68, toward the front opening72a. The rear portion of the tubular portion70is provided with a rear opening section76formed with the rear opening76awhich opens to the rear in the vehicle body.

As shown inFIG. 5, in the interior of the tubular portion70, an air passage R is provided to extend over a region from the introduction port74ato the rear opening76a, through the front opening72a. The front opening72ahas an opening area which is smaller than an opening area of the rear opening76aand smaller than an opening area of the introduction port74a. In other words, the cross-sectional area of the passage R is reduced at the front opening72a. Therefore, the flow velocity of the air flowing through the passage R is increased at the front opening72a.

As shown inFIG. 5, the bottom portion of the tubular portion70includes the inclined wall80having an inclined surface80awhich is smoothly inclined to be higher as it extends in the rearward direction. The inclined wall80is placed to extend continuously between the lower portion of the front opening forming section72and the lower portion of the rear opening forming section76. The inclined surface80aof the inclined wall80is the upper surface of the inclined wall80. The inclined surface80aof the inclined wall80connects the lower end of the front opening72ato the lower end of the rear opening76ain the forward and rearward direction, and extends in the forward and rearward direction. In the present example, the rear opening72ais placed outward in the vehicle width direction relative to the front opening72a. Therefore, the inclined surface80aextends in the outward direction of the vehicle width direction from its front end toward its rear portion. Specifically, the inclined surface80ais gradually curved in the outward direction of the vehicle width direction as it extends in the rearward direction. The inclined surface80aof the inclined wall80has a shape in which a dimension in the forward and rearward direction is greater than a dimension in the vertical direction. In the present example, the rear end portion of the inclined wall80ais located rearward relative to the windshield48. Specifically, the rear end portion of the inclined wall80aextends to the location of the front fork24a,24bin the forward and rearward direction. Since the side surface of the front cowling42is formed with the inclined surface80a, the length of the inclined surface80ain the forward and rearward direction can be increased easily, compared to a case where the upper surface of the front cowling42is formed with the inclined surface. Since the side surface of the front cowling42is formed with the inclined surface80a, it becomes possible to prevent the air discharged from the rear opening76afrom flowing toward the rider. As shown inFIG. 3, in the present embodiment, the inclined wall80is integrated with the inner side surface of the side cowling44aprovided at the outer side portion14aof the front cowling structure14. In other words, the inclined wall80is located inward relative to the swelling section83. The inclined surface80ais located outward in the vehicle width direction relative to the windshield48.

As shown inFIG. 3, an outer side wall82protrudes upward from an outer side portion80bof the inclined wall80and extends in the forward and rearward direction. In the present embodiment, the outer side wall82is formed by the side cowling44aprovided at the outer side portion14aof the front cowling structure14. The outer side wall82is located inward relative to the outer side end of the grip40aattached to the steering handle34, and above the front wheel26. The front end portion of the outer side wall82is formed with a curved portion82awhich is curved in an inward direction to close the front end of the tubular portion70. The outer side wall82makes it possible to prevent a situation in which the air flowing into the passage R through the introduction port74ais diverted in the outward direction.

The top portion of the tubular portion70is provided with a plate-shaped upper wall86having a smooth inclined surface86awhich is inclined to be higher as it extends in the rearward direction. As shown inFIG. 5, the upper wall86extends continuously over a region from the introduction port forming section74to the rear opening forming section76through the front opening forming section72. The inclination angle of the inclined surface86aof the upper wall86with respect to a horizontal plane is set to be greater than that of the inclined surface80aof the inclined wall80with respect to the horizontal plane. Because of this structure, the opening area of the rear opening76ais greater than that of the front opening72a. The rear end of the upper wall86is located in front of the rear end of the inclined wall80. The rear opening76ais inclined to be lower as it extends in the rearward direction. Because of this structure, the opening area of the rear opening76ais also greater than that of the front opening72a. As shown inFIG. 3, in the present embodiment, the upper wall86is integrated with the inner side surface of the side cowling44a, along with the inclined wall80and the outer side wall82. The upper wall86makes it possible to prevent the air flowing into the passage R through the introduction port74afrom being diverted in the upward direction.

As shown inFIG. 3, the outer side portion of the upper surface of the inclined surface86ais formed with a protruding portion88protruding in the upward direction and extending in the forward and rearward direction. The protruding portion88has a semicircular cross-section (horizontal section). A stepped portion88awith a height increased in the outward direction is formed by the protruding portion88. The stepped portion88amakes it possible to prevent the air flowing along the upper portion of the inclined surface86afrom being diverted in the outward direction. The shape of the cross-section (horizontal section) of the protruding portion88is not particularly limited, and may be, for example, a triangular shape, a rectangular shape, or an inverted-L shape.

As shown inFIG. 3, an inner side wall90is provided above the inner side portion80cof the inclined wall80to extend in the forward and rearward direction. In the present embodiment, the inner side wall90is formed by the outer side portion64aof the front cowling42. In this way, a tubular shape with a rectangular cross-section formed with the front opening72aand the rear opening76ais formed by the inclined wall80, the outer side wall82, the upper wall86, and the inner side wall90. This makes it possible to prevent the air introduced through the front opening72afrom leaking to an outside region through a region other than the rear opening76a. The front opening72aopens to the front, and has a passage cross-sectional area in which a dimension in the vertical direction is greater than a dimension in the vehicle width direction. This makes it possible to increase the amount of the air introduced through the front opening72a, while preventing an increase in the size of the vehicle body in the vehicle width direction. The rear opening76aopens to the rear, and has a passage cross-sectional area in which a dimension in the forward and rearward direction is greater than a dimension in the vehicle width direction. This makes it possible to increase the amount of the air discharged through the front opening72a, while preventing an increase in the size of the vehicle body in the vehicle width direction. The upper end portion of the front opening72ais preferably located below the lower end portion of the rear opening76a. In this configuration, the air travelling horizontally in the rearward direction through a region that is in the vicinity of the upper end portion of the front opening72acollides with the inclined surface80abefore the air reaches the rear opening76a, which can easily increase the downforce.

The passage cross-sectional area is gradually reduced from the front opening72atoward the rear opening76a. Specifically, the inclined surface80ahas a shape in which a dimension in the vehicle width direction is gradually reduced, as it extends in the rearward direction. This makes it possible to suppress reduction of the flow velocity of the air flowing along the upper portion of the inclined surface80a, and increase the flow velocity of the air flowing along the upper portion of the inclined surface80aas the air travels in the rearward direction. In the front cowling structure14, the aerodynamic devices46a,46bare provided in the swelling sections which swell in the outward direction of the vehicle width direction, as the wind deflecting sections81which divert the air flowing to a region which is in the vicinity of the handle34, to an outward region in the vehicle width direction. This makes it possible to obtain the downforce while preventing an undesired increase in the size of the front cowling structure14in the vehicle width direction. The inner side wall90makes it possible to prevent the air flowing into the passage R through the introduction port74afrom being diverted to an inward region.

As shown inFIGS. 3 and 4, the guide section68is configured to guide the air in such a manner that the air which reaches a front region Q is gathered at the front opening72a. The front region Q is defined as a region which is in front of the front opening72a. In the present embodiment, the front region Q is located inward in the vehicle width direction relative to the front opening72a. The guide section68is integrated with the front cowling42in such a manner that the guide section68is located in front of the front opening72aand inward relative to the front opening72a. The guide section68includes a first guide surface96aformed below the opening62a, a second guide surface96bformed between the upper edge of the first guide surface96aand the lower edge of the opening62a, and a third guide surface96cformed inward relative to the first guide surface96aand the second guide surface96b. Each of the first guide surface96a, the second guide surface96band the third guide surface96cfaces the front to receive the air.

The first guide surface96ais a smooth inclined surface which is inclined to be higher as the first guide surface96aextends in the rearward direction. The second guide surface96bis a smooth inclined surface which is inclined to be lower as the second guide surface96bextends in the rearward direction. A V-shaped groove98which is recessed in the rearward direction is formed by the first guide surface96aand the second guide surface96b. A trough line98aof the groove98extends in a straight-line shape and is inclined with respect to the vehicle width direction in such a manner that the trough line98abecomes higher and extends in the rearward direction, as it extends in the outward direction. Since the V-shaped groove98is inclined in the upward direction as it extends in the outward direction, the outer portion of the groove98guides the air in a greater amount than the inner portion of the groove98does. By increasing the depth of the V-shaped groove98, or inclining the groove98in the upward direction, it becomes possible to prevent the air from leaking from the guide section, even when the amount of the air to be guided is increased. The outer end portion of the groove98is located inward relative to the introduction port74a. When viewed from the front, the dimension in the vertical direction and the dimension in the vehicle width direction, of the first guide surface96aare greater than those of the second guide surface96b. In addition, the projection area of the first guide surface96afrom the front is greater than that of the second guide surface96b. The third guide surface96cis inclined with respect to the vehicle width direction in such a manner that the third guide surface96cis located at the front as it extends in the inward direction.

Since the outer side portion of the inclined wall80in the vehicle width direction is formed with the outer side wall82protruding upward, it becomes possible to prevent the air flowing in the rearward direction along the inclined wall80from being diverted from the inclined wall80to an outward region in the vehicle width direction. In a case where the inclined wall80is curved in the outward direction of the vehicle width direction, a force tends to be applied to the outward region in the vehicle width direction, by a centrifugal force. However, since the outer side portion of the inclined wall80is formed with the outer side wall82protruding upward, it becomes possible to suitably prevent the air from being diverted to the outward region in the vehicle width direction. When viewed from the front, the projection area of the guide section68is greater than the area of the front opening72a. This makes it possible to increase the amount of the air guided to the interior of the front opening72a, compared to a case where the front opening72afaces the front. In particular, since the guide section68is provided at the front portion of the front cowling structure14, the air with a high pressure can be guided to the front opening72a. The above-described trough line of the guide groove98preferably has a shape in which the trough line has a greater depth as it extends in the outward direction. The guide groove98is located at the lower region of the front portion of the front cowling42. More specifically, the guide groove98is located below the center in the vehicle width direction, of the front portion of the front cowling42, to be precise, below the head lamp unit56or the opening of the ram duct63. In this structure, the inclined surface80aof the inclined wall80can be extended in the rearward direction from a lower position. This makes it possible to increase the length of the inclined surface80ain a state in which the angle of the inclined surface80ais fixed at a predetermined value.

The introduction port74ahas a shape in which a dimension in the vertical direction is greater than a dimension in the forward and rearward direction. The introduction port forming section74connects the introduction port74ato the front opening72a, and guides the air introduced into the introduction port74ato the front opening72awhile changing the direction of the air. Specifically, the outer side portions14a,14bare formed with the curved surfaces, respectively, extending gradually in the rearward direction, from their front end portions toward outward regions, when viewed from the front. The air gathered by the guide surfaces96a,96b,96cin the above-described manner, can be flowed in the rearward direction, and guided to the front opening, while preventing reduction of the flow velocity of the air. In addition, since the introduction port forming section74is formed with the curved surface, the front opening72acan be covered when viewed from the front. As a result, the external appearance of the vehicle can be improved.

Although in the present embodiment, the second guide surface96bis made lower as it extends in the rearward direction, the second guide surface96bmay extend in a direction perpendicular to the horizontal plane, or may be made higher as it extends in the rearward direction. In a case where the second guide surface96bis made higher as it extends in the rearward direction, the inclination angle of the second guide surface96ais desirably set to be greater than that of the first guide surface96a, to form the V-shaped groove98.

While the straddle-type vehicle10ofFIG. 2is traveling, the front cowling structure14receives the air from the front. The air flows from the front of the front cowling structure14and reaches the front region Q. The first guide surface96asuppresses the air from being diverted in the downward direction. The second guide surface96bsuppresses the air from being diverted in the upward direction. The third guide surface96csuppresses the air from being diverted in the inward direction. A part of the air which has reached the front region Q is thus gathered at the groove98. This air is guided in the outward direction by the groove98. The direction of the part of the air is changed by the introduction port forming section74. The air is supplied to the front opening72athrough the introduction port74a. As shown inFIG. 5, the air supplied to the front opening72aflows through the front opening72aand into a region which is rearward relative to the front opening72a. The air flows along the upper portion of the inclined surface80aand flows in the rearward direction to a region outside the vehicle body through the rear opening76a. Since the inclined surface80ais inclined to be higher as it extends in the rearward direction, the air collides with the inclined surface80aand thus the downforce is generated. This makes it possible to prevent the front wheel26(FIG. 2) from coming off the ground. As a result, the straddle-type vehicle10can travel more stably at a high speed.

As shown inFIG. 5, since the rear opening76aopens to the rear in the vehicle body, it becomes possible to prevent the air flowing from the front opening72atoward the rear opening76afrom becoming stagnant or stuck. Thus, movement of the air can be facilitated, and reduction of the flow velocity of the air can be suppressed. Since the passage R located above the inclined surface80ais constituted by the tubular portion70, it becomes possible to suppress the air from being diverted from the passage R to regions which are above and below the passage R and to regions which are inward and outward in the vehicle width direction relative to the passage R. Further, since the air is gathered by the guide section68, the air which collides with a region with an area greater than that of the front opening can be guided to the front opening. This makes it possible to increase the pressure (flow rate) of the air supplied to the front opening72a. Moreover, the flow velocity of the air can be increased at the front opening72ahaving a reduced cross-sectional area. Therefore, the air flowing at a high speed can collide with the inclined surface80a. In this way, the downforce can be generated effectively.

As shown inFIG. 5, the introduction port forming section74has the first introduction port74awhich is located in front of the front opening72aand opens to the inside in the vehicle width direction, while the guide section68is located inward relative to the front opening72aand the introduction port74aand in front of the front opening72aand the introduction port74a. In this structure, the air gathered by the guide section68is easily guided from the introduction port74ato the front opening72a. As shown inFIG. 3, since the outer side wall82of the aerodynamic device46ais constituted by the side cowling44a,44b, the dimension of the guide section68in the vehicle width direction can be increased. The guide section68is capable of gathering a large amount of air. Since the guide section68is integrated with the front cowling42(FIG. 3), the number of members can be reduced.

As shown inFIGS. 3 and 4, the first guide surface96aof the guide section68, the inclined surface86aof the aerodynamic device46a, and the inclined surface42aof the front cowling42are inclined to be higher as they extend in the rearward direction. Therefore, the downforce can also be generated by the collision of the air with the first guide surface96a, the inclined surface86a, and the inclined surface42a.

As shown inFIG. 2, since the aerodynamic devices46a,46bare provided at the outer side surfaces of the left and right outer side portions64a,64bof the front cowling42, the downforce can be well balanced in the vehicle width direction. Since the outer side wall82(FIG. 3) is located inward relative to the outer side end of the grip40aattached to the steering handle34(FIG. 1) and above the front wheel26, a bank angle is not reduced.

A part of the air which has reached the front region Q (FIG. 3) collides with the first guide surface96aand thereby flows in the upward direction. This air flows into the ram duct63through the opening62a. Therefore, a greater amount of air can be supplied to the engine20(FIG. 1).

As shown inFIG. 1, since each of the outer side portions14a,14bof the front cowling structure14constitutes the swelling section83which swells gradually in the outward direction, from its front end toward its rear portion, when viewed from above, the air resistance can be reduced. In addition, since each of the outer side portions14a,14bof the front cowling structure14constitutes the wind deflecting section for diverting to the outward region, the air flowing toward the rider, the air which collides with the rider can be reduced, and the fatigue of the rider can be mitigated. As shown inFIG. 3, the outer side wall82, the inclined wall80and the upper wall86of the aerodynamic device46aare integrated with the side cowling44aconstituting the wind deflecting section, the number of members can be reduced. Thus, an air resistance reduction effect, a wind deflecting effect, and a stable traveling effect can be obtained with a simplified configuration. In addition, it becomes possible to suppress the outer side wall82, the inclined wall80, and the upper wall86from interfering with the components of the front cowling42. The aerodynamic devices46a,46bare set to be about as high as the grips40a,40bof the handle34, respectively, and are located in front of the grips40a,40b, respectively, for example, below the side mirrors60a,60b, and above the radiator opening23. In this layout, the air flowing to a region which is in the vicinity of the handle34can be reduced. Thus, the wind deflecting effect and the generation of the downforce can be realized.

As shown inFIG. 3, since the outer side surface of the outer edge portion and the outer side surface of the outer side wall82, of the front cowling structure14, are formed as a common surface, it becomes possible to suppress turbulence of the air flowing along the outer side surface of the outer edge portion of the front cowling structure14. Since the outer side surface of the outer edge portion and the outer side surface of the outer side wall82are formed as the common surface, no stepped portion is formed and hence the external appearance is not marred.

As shown inFIG. 3, although in the above-described embodiment, the inclined wall80is integrated with the side cowling44a, the inclined wall80may be integrated with the front cowling42, or may be formed independently of each of the side cowlings44a,44band the front cowling42.

Although in the above-described embodiment, the inclined surface80aextends to be curved in the outward direction of the vehicle width direction, from its front end toward its rear portion, the inclined surface80amay extend in a straight line shape in the outward direction of the vehicle width direction. Further, the inclined wall80may extend in a direction parallel to the forward and rearward direction. The air flowing along the inclined surface80ais preferably deflected to the outward region in the vehicle width direction while the air is flowing from the front opening72ato the rear opening76a. Although in the above-described embodiment, the outer side wall82deflects the air flowing along the inclined surface80ato the outward region in the vehicle width direction, the inner side wall90may deflect the air depending on the shape of the inclined surface80a. For example, the front opening72amay be located at the intermediate portion of the front cowling structure14in the vehicle width direction. In this case, the air introduced into the front opening72ais guided in the outward direction of the vehicle width direction by the inner side wall90, and discharged through the rear opening76a. Such a case may be included in the present invention. In this case, the guide section may be formed at a location that is outward in the vehicle width direction relative to the front opening72aor on the right and left sides of the front opening72ain the vehicle width direction.

As described above, it is sufficient that the guide section is adjacent to the front opening72ain the vehicle width direction. It is sufficient that the guide section is provided with the inclined wall80and the outer side wall82. A guide section which does not include a wall located above the inclined wall80is also included in the present invention. A guide section provided only on one of the right and left sides of the vehicle body is also included in the present invention. Further, a vehicle which does not include the ram duct63is also included in the present invention. The aerodynamic devices46a,46bmay be provided at the upper surface of the front cowling42or the side surfaces of the side cowlings44a,44b. Since the inclined wall80is provided at a portion which diverts the air from the rider for a wind deflecting purpose, the wind deflecting effect can be obtained and the downforce can be generated. The vehicle10can travel more stably at a high speed while reducing a burden on the rider. Since the inclined wall80is located inward relative to the outer edge portion of the front cowling structure14, the turbulence of the air flowing through a region that is in the vicinity of the outer edge of the front cowling structure14can be prevented, and an increase in the air resistance can be suppressed. The cross-sectional area of the passage R at the front opening72amay not be reduced.

The straddle-type vehicle of the present invention may be applied to a straddle-type three-wheeled vehicle or a straddle-type four-wheeled vehicle, as well as the motorcycle of the above-described embodiment.

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