Shock absorbing structure of two-wheeled vehicle

A shock absorbing structure of a two-wheeled vehicle capable of sufficiently absorbing shock and desirably maintain the steerability of the two-wheeled vehicle. The structure includes a shock absorbing member projecting from a front wheel, wherein the shock absorbing member is crashed when the vehicle collides with an obstacle so as to absorb shock. A ceiling wall of the shock absorbing member is located at such a position that the ceiling wall does not block a forward viewing area for a driver. A center of a leading end contact surface of the shock absorbing member is located at a position higher than a vertical position of a center of gravity G of both a motorcycle and the driver, and right and left side surfaces of the shock absorbing member are offset to a center of a vehicular body from right and left side surfaces of the motorcycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-023830 filed on Jan. 31, 2001 the entire contents thereof is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a shock absorbing structure for a two-wheeled vehicle including a shock absorbing member projecting from a vehicular body, wherein shock is absorbed by crashing the shock absorbing member.

2. Description of Background Art

A technique regarding a shock absorbing member for a two-wheeled vehicle has been proposed in Japanese Patent Laid-open No. Hei 10-67374 entitled “Vehicular Frame Including Riding Portion.” According to this technique, a vehicle has a deformable element (hereinafter, referred to as “shock absorbing member”) disposed over a front wheel, characterized in that if the vehicle collides with an obstacle, the shock absorbing member is crashed to absorb a shock.

To be more specific, according to the two-wheeled vehicle disclosed in the above document, the shock absorbing member is located at a position higher than a vertical position of a center of a gravity of the whole vehicle, whereby when the vehicle collides with an obstacle, a rear wheel can be prevented from floating upwardly. As a result, it is possible to prevent occurrence of pitching (such as the falling forward or bending backward) of the vehicle.

The above shock absorbing member can absorb a larger shock energy by enlarging a shape of the shock absorbing member, for example, by enlarging the dimensions of the member in the longitudinal direction (length direction of the vehicle), the lateral direction (width direction of the vehicle), and the height direction (vertical direction of the vehicle).

The enlargement of the shape of the shock absorbing member, however, has inconveniences. At first, if the dimensions of the shock absorbing member are enlarged in the height direction (vertical direction of the vehicle) and the longitudinal direction (length direction of the vehicle) so as to enlarge the shape of the shock absorbing member, a forward viewing area for a driver may be blocked by the shock absorbing member.

In addition, if the dimension of the shock absorbing member is enlarged in the lateral direction (width direction of the vehicle) so as to enlarge the shape of the shock absorbing member, right and left side surfaces of the shock absorbing member project outwardly from right and left side surfaces of the vehicular body, with a result that the right and left side surfaces of the shock absorbing member may interfere with an obstacle during the operation of the two-wheeled vehicle.

SUMMARY AND OBJECTS OF THE INVENTION

An object of the present invention is to provide a shock absorbing member of a two-wheeled vehicle, which is capable of sufficiently absorbing shock, desirably maintaining a forward viewing area for a driver, and preventing the shock absorbing member from interfering with an obstacle during the operation of the vehicle.

To achieve the above object, according to the present invention, there is provided a shock absorbing structure of a two-wheeled vehicle including a shock absorbing member projecting from a vehicular body, wherein shock is absorbed by crashing the shock absorbing member. A front end of the shock absorbing member is located in front of a front wheel or in the vicinity of the front wheel. An upper end of the shock absorbing member is located at such a position so that the upper end of the shock absorbing member does not block a forward viewing area for a driver. A center of a leading end contact surface of the shock absorbing member is located at a position higher than a vertical position of a center of gravity of both the vehicle and the driver. Right and left side surfaces of the shock absorbing member are offset to a center of a vehicular body from right and left side surfaces of the vehicular body.

According to the configuration of the shock absorbing structure, the front end of the shock absorbing member is located in front of a front wheel or in the vicinity of the front wheel. Accordingly, if the front end collides with an obstacle, a portion, ranging from the front end to the front wheel, of the shock absorbing member can be efficiently crashed. Such efficient crashing of the shock absorbing member allows desirable absorption of a shock.

According to the configuration of the shock absorbing member, the upper end of the shock absorbing member is located at such a position that the upper end the shock absorbing member does not block a forward viewing area for a driver. Accordingly, the forward viewing area of the driver can be desirably maintained.

According to the configuration of the shock absorbing member, the center of a leading end contact surface of the shock absorbing member is located at a position higher than a vertical position of a center of gravity of both the vehicle and the driver. Since the center of a leading end contact surface of the shock absorbing member is located at a position higher than a vertical position of a center of gravity of both the vehicle and the driver, if the front end of the shock absorbing member collides with an obstacle during the operation of the two-wheeled vehicle, a moment to press down the vehicular body acts around the front end of the shock absorbing member, to thereby prevent a rear wheel from being floated up.

According to the configuration of the shock absorbing member, right and left side surfaces of the shock absorbing member are offset to a center of a vehicular body from right and left side surfaces of the vehicular body. Accordingly, it is possible to prevent the shock absorbing member from being brought into contact with an obstacle during the operation of the two-wheeled vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. It is to be noted that the drawings should be viewed in the direction of the characters.

FIG. 1is a side view of a two-wheeled vehicle including a shock absorbing structure of the present invention. In this embodiment, the two-wheeled vehicle is exemplified by a motorcycle10.

The motorcycle10is a scooter-type vehicle mainly including a body frame11, a front fork12mounted to a head pipe11a of the body frame11, a front wheel13mounted to the front fork12, a handlebar14connected to the front fork12and a swing unit15(including an engine15aand a transmission mechanism15b) mounted to a rear portion of the body frame11. A rear wheel16is mounted to a rear portion of the swing unit15. A seat17is disposed on an upper rear portion of the body frame11. A front cover18ais provided for covering a front portion of the head pipe11a.A center cover18bextends rearwardly from the front cover18afor covering a central portion of the body frame11. A side cover18cextends rearwardly from the center cover18bfor covering a rear portion of the body frame11. A shock absorbing member20of the present invention provided on the front cover18a.

The shock absorbing structure20is configured by mounting a frame body22of a shock absorbing member21to the front cover18a,for example, by means of fastening means (not shown), and providing a plurality of reinforcing ribs30in a space25of the frame body22.

The frame body22includes a ceiling wall23bent at its approximately center portion, into an approximately V-shape, and a peripheral wall24provided on a periphery of the ceiling wall23. A rear end24dof the peripheral wall24is mounted to the front cover18a.

The frame body22can be mounted to both the front cover18aand the body frame11. This makes it possible to more forcibly mount the shock absorbing member21to the vehicular body.

The shock absorbing structure20is a structure made of resin, which is configured such that a front end (leading end contact surface)24aof the shock absorbing member21is offset forwardly from the front wheel13by a distance L1, wherein if the motorcycle10collides with an obstacle, then shock is absorbed by crashing the shock absorbing member21.

The distance L1may be suitably set depending on the type of the motorcycle10.

The shock absorbing structure20may be configured such that the front end24aof the shock absorbing member21is located in the vicinity of the front wheel13. In summary, the shock absorbing structure20may be a structure made of resin configured such that if the motorcycle10collides with an obstacle, then shock can be absorbed by crashing the shock absorbing member21.

FIG. 2is a plan view of the two-wheeled vehicle including the shock absorbing structure of the present invention. Referring toFIG. 2, the shock absorbing member21is mounted to the front end of the front cover18a,wherein right and left side surfaces24cand24bof the shock absorbing member21are each offset to a center28of the vehicular body from the right and left side surfaces of the vehicular body, that is, end surfaces14band14aof the right and left handlebars14by a distance W.

It is to be noted that the peripheral wall24includes the front end24aas a front wall, the right and left side walls24cand24b,and the rear wall24d.

Since the right and left side surfaces24cand24bof the shock absorbing member21are offset to the center28of the vehicular body from the end surfaces14band14aof the right and left handlebars14, it is possible to prevent the shock absorbing member21from being brought into contact with an obstacle during the operation of the motorcycle10and hence to desirably maintain the steerability of the motorcycle10.

In the two-wheeled vehicle shown inFIG. 2, the end surfaces14band14aof the right and left handlebars14are taken as the right and left side surfaces of the vehicular body; however, the present invention is not limited thereto but may be applied to a two-wheeled vehicle in which other members are taken as the right and left side surfaces of the vehicular body.

FIG. 3is a side view of the two-wheeled vehicle including the shock absorbing structure of the present invention, showing an operational state of the two-wheeled vehicle. Referring toFIG. 3, the upper end (ceiling wall or top wall)23of the shock absorbing member2l is located at such a position that the upper end23does not block the forward viewing area for a driver40, that is, located under a forward viewing area line29of the driver40.

By locating the ceiling wall23of the shock absorbing member21at such a position that the ceiling wall23located thereat does not block the forward viewing area of the driver40, it is possible to desirably maintain the forward viewing area of the driver40, and hence to desirably maintain the steerability of the motorcycle10.

The forward viewing area line29is defined as a line of sight along which the driver40looks at a position P on a road45, the position which is separated from the front end24aof the shock absorbing member21by a distance L2, over the shock absorbing member21. The distance L2may be suitably set depending on the type of motorcycle10.

As shown inFIG. 3, a center24eof the front end (leading end contact surface)24aof the shock absorbing member21is located at a position higher than a vertical position of a center of gravity G of both the vehicle (motorcycle)10and the driver40by a distance H.

Letting the height of the front end (leading end contact surface)24abe 2×H2, the center24eis located at a height H2from a lower end26of the shock absorbing member21.

Since the center24eof the front end24aof the shock absorbing member21is set at a position higher than a vertical position of the center of gravity G of both the motorcycle10and the driver40, if the front end24aof the shock absorbing member21collides with an obstacle during the operation of the motorcycle10, a moment (in the backward turn direction) to press down the vehicular body of the motorcycle10acts around the front end24aof the shock absorbing member21, to prevent the rear wheel16from floating upwardly, that is, to prevent the occurrence of pitching of the vehicular body.

FIG. 4is a sectional view taken on line4—4ofFIG. 1showing one example of the shock absorbing member21.

The peripheral wall24of the frame body22is a wall portion formed into an approximately U-shape in cross-section. The peripheral wall24includes the front end24alocated at a front end of the ceiling wall23(seeFIG. 1) in such a manner as to extend in a straight line in the width direction. The left side wall24bextends rearwardly from a left end of the front end24awhile being curved partially (specifically, at its front end). The right side wall24cextends rearwardly from a right end of the front end24awhile being curved partially (specifically, at its front end). The rear wall24dextends so as to connect rear ends of the right and left side walls24cand24bto each other while being curved into a shape following that of the front cover18a.

With this provision of the peripheral wall24on the periphery of the ceiling wall23, the space25can be formed in the frame body22.

In the shock absorbing member21, a plurality of reinforcing ribs30are formed in the space25of the frame body22, to partition the space25of the frame body22into a plurality of cavity portions32, wherein some of the reinforcing ribs30, which are designated by reference numerals30ato30g,are partially thinned to form thin wall portions35ato35g,respectively.

The plurality of reinforcing ribs30may be arranged so as to give a specific strength to the frame body22.

It is to be noted that the arrangement of the reinforcing ribs30is not limited to that shown inFIG. 2but may be arbitrarily changed in accordance with a desired strength of the shock absorbing member21.

Of the reinforcing ribs30to which a compressive force is applied, the suitable reinforcing ribs30ato30gare selected, and the reinforcing ribs30ato30gthus selected are partially thinned to form the thin wall portions35ato35gtherefor, respectively.

To be more specific, pairs of the reinforcing ribs30ato30gare provided, each pair (for example,30aand30a) being provided on the right and left sides of the shock absorbing member21in such a manner as to be bilaterally symmetric with respect to an axis37, are selected and the pairs of right and left reinforcing ribs30ato30gare partially thinned to form the thin wall portions35ato35g,respectively.

With this shock absorbing member21, when a shock F acts on the front end24aas shown by a white arrow, a compressive force is axially applied to the right side reinforcing ribs30ato30gand also to the left side reinforcing ribs30ato30g.As a result, the thin wall portions35ato35gare broken or deformed, whereby a central portion27of the shock absorbing member21is overall crashed.

Accordingly, by sufficiently crashing the shock absorbing member21, the shock power can be positively absorbed.

In addition, since the configuration of the right side reinforcing ribs30ato30gis the same as that of the left side reinforcing ribs30ato30g,only the right side reinforcing ribs30ato30gwill be hereinafter be described.

A function of the above-described shock absorbing structure20of the present invention will be described below.

FIGS.5(a) and5(b) are views illustrating a function of a comparative example.

Referring to FIG.5(a), if a front end52of a shock absorbing member51collides with an obstacle42during the operation of a two-wheeled vehicle50, a shock F generated by the collision acts on a position lower than a vertical position of a center G1of gravity of both the two-wheeled vehicle50and a driver40by a height H1.

Accordingly, at the center G1of gravity, as shown by an arrow, there occurs a moment M1which acts counterclockwise around the front end52of the shock absorbing member51.

Referring to FIG.5(b), a rear wheel53of the two-wheeled vehicle50floats upwardly as shown by an arrow (1), resulting in pitching of the vehicle50.

FIGS.6(a) and6(b) are views illustrating a function of the shock absorbing structure of the present invention.

Referring to FIG.6(a), if the front end24aof the shock absorbing member21collides with an obstacle42during the operation of the motorcycle10, a shock generated by the collision acts on a position higher than a vertical position of the center of gravity G of both the motorcycle10and the driver40by a distance H.

Accordingly, at the center of gravity G, as shown by an arrow, there occurs a moment M2which acts clockwise around the front end24aof the shock absorbing member21.

Referring to FIG.6(b), it is possible to prevent the rear wheel16of the motorcycle10from floating upwardly, and hence to prevent the occurrence of pitching of the motorcycle10.

In the embodiment, some of the reinforcing ribs30, that is, the reinforcing ribs30ato30gare partially thinned to form the thin wall portions35ato35gtherefor; however, the present invention is not limited thereto. For example, all of the reinforcing ribs30may be partially thinned to form the thin wall portions therefor, and further the thin wall portions35ato35gmay be formed at arbitrary positions of the reinforcing ribs30ato30g.

With a suitable provision of the thin wall portions, a desired crashing form or a desired shock absorbing characteristic can be obtained.

In the embodiment, the shock absorbing member21is made from a resin; however, it may be made from another material such as an aluminum alloy or a steel.

In the embodiment, the shock absorbing member21is mounted to the front end of the vehicular body. However, the shock absorbing member21may be mounted to the rear end or each of the right and left side surfaces of the vehicular body. Even in this case, the same effect as that obtained by the embodiment can be obtained.

In the embodiment, the two-wheeled vehicle is exemplified by the motorcycle10. However, it may be a scooter or a bicycle with a motor.

The present invention having the above-described configurations exhibits the following effects. According to the present invention, the front end of the shock absorbing member is located in front of a front wheel or in the vicinity of the front wheel. Accordingly, if the front end collides with an obstacle, a portion, ranging from the front end to the front wheel, of the shock absorbing member can be efficiently crashed.

Also, the upper end of the shock absorbing member is located at such a position that the upper end the shock absorbing member located thereat does not block a forward viewing area for a driver. Accordingly, it is possible to desirably keep the forward viewing area of the driver, and hence to desirably maintain the steerability of the two-wheeled vehicle.

Further, the center of a leading end contact surface of the shock absorbing member is located at a position higher than a vertical position of a center of gravity of both the vehicle and the driver. Since the center of a leading end contact surface of the shock absorbing member is located at a position higher than a vertical position of a center of gravity of both the vehicle and the driver, if the front end of the shock absorbing member collides with an obstacle during the operation of the two-wheeled vehicle, a moment to press down the vehicular body acts around the front end of the shock absorbing member, to thereby prevent a rear wheel from floating upwardly.

Additionally, right and left side surfaces of the shock absorbing member are offset to a center of a vehicular body from right and left side surfaces of the vehicular body. Accordingly, it is possible to prevent the shock absorbing member from being brought into contact with an obstacle during the operation of the two-wheeled vehicle, and hence to desirably maintain the steerability of the two-wheeled vehicle.