Motor vehicles – Special wheel base – Having only two wheels
Reexamination Certificate
2002-05-10
2004-01-20
Morris, Lesley D. (Department: 3619)
Motor vehicles
Special wheel base
Having only two wheels
C180S227000, C280S285000
Reexamination Certificate
active
06679347
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-177535 filed on Jun. 12, 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 frame structure of a motorcycle in which a connecting tube for introducing air from an air cleaner into a carburetor is disposed in the vicinity of the rear end portion of the vehicle body frame.
2. Description of the Background Art
The motorcycle includes a vehicle body frame as a framework for supporting an engine and other members. A vehicle body frame is disclosed in Japanese Patent Laid-Open No. 84190/1995 entitled “FRAME STRUCTURE IN VEHICLES SUCH AS A MOTORCYCLE.” This frame structure will be described below referring to
FIG. 3
of this publication which corresponds to
FIG. 9
in the drawings.
FIG. 9
is a side view of the motorcycle including a frame structure of the related art, showing a state in which a vehicle body frame
150
of a motorcycle comprises a pair of left and right main pipes
152
,
153
extending from the head pipe
151
to the rear of the vehicle body. A pair of left and right brackets
154
,
155
are joined to the rear end portion
152
a
,
153
a
of the main pipes
152
,
153
respectively. A pair of left and right down tubes
156
,
157
extend from the lower end portion
154
a
,
155
a
of the bracket
154
,
155
to the front of the vehicle body.
An engine
160
is mounted between the left and right main pipes
152
,
153
, and the left and right down tubes
156
,
157
. A carburetor
161
is connected to the engine
160
with a connecting tube
162
extending from the carburetor
161
along the rear end portion
152
a
of the left main pipe
152
. An air cleaner
163
is connected to the connecting tube
162
.
Accordingly, air from the air cleaner
163
is introduced into the carburetor
161
via the connecting tube
162
. The introduced air may be supplied to the engine after fuel is mixed with the air.
An important requirement for maintaining optimum engine performance of the motorcycle is to supply air to the carburetor
161
in a suitable manner. In order to supply air to the carburetor
161
in a suitable manner, it is necessary for the air to flow from the air cleaner
163
smoothly in the connecting tube
162
.
In order to ensure smooth flow of air in the connecting tube
162
, it is necessary to form the flow path of the connecting tube
162
in a naturally curved shape, and in order to form it in a naturally curved shape, it is necessary to reserve an enough space for disposing the connecting tube
162
.
Since the rear end portion
152
a
of the left main pipe
152
is exposed to the space where the connecting tube
162
is to be disposed, whether or not enough space can be reserved largely depends on the shape of the left main pipe
152
.
The left and right main pipes
152
,
153
constituting the vehicle body frame
150
of a motorcycle generally tends to use many extruded moldings, and thus the thickness of the cross section of the left main pipe
152
is constant from the front end portion
152
b
through the rear end portion
152
a.
In addition, the left and right main pipes
152
,
153
have to be thick enough to ensure rigidity of the vehicle frame
150
. Therefore, the thickness of the rear end portion
152
a
of the left main pipe
152
increases, and thus enough space for disposing the connecting tube
162
cannot be reserved.
Therefore, the flow path of the connecting tube
162
cannot be formed into a naturally curved shape, and thus smooth flow of air in the connecting tube
162
cannot be ensured, which makes it difficult to maintain the engine performance of the motorcycle in a suitable condition.
SUMMARY AND OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide a frame structure for a motorcycle in which the connecting tube can be configured in a shape that ensures smooth flow of air.
In order to achieve the aforementioned object, the present invention is directed to a motorcycle wherein a pair of left and right mainframes extend from a head pipe to the rear of the vehicle body. A pivot plate is joined to the rear ends of the mainframes. A rear swing arm extends rearwardly from the pivot plate. An air cleaner is mounted above the rear swing arm with the air cleaner being connected to the carburetor via a connecting tube. The carburetor is connected to the engine located below the mainframe. The pivot plate is a member formed by casting or forging wherein the pivot plate extends to a position above the rear end portion of the mainframe so that a prescribed portion of the pivot plate faces towards the outer surface of the connecting tube. The prescribed portion is formed with a recess for accommodating the outer surface of the connecting tube and a rear shock absorber is provided for supporting the rear swing arm that is mounted on the upper end portion of the pivot plate extending to the position above the mainframe.
By employing a member formed by casting or forging as a pivot plate, a recess for accommodating the outer surface of the connecting tube may be formed at a prescribed portion on the pivot plate during the process of forming the pivot plate. In this manner, by forming a recess at the prescribed portion, a space for disposing the connecting tube may be increased.
By reserving enough space, freedom of determination of the shape of the connecting tube increases and thus the connecting tube may be formed in a shape that allows smooth flow of air therein.
The present invention is directed to including an end face of the rear end portion of the mainframe that is inclined in such a manner that the upper portion is positioned forward of the lower portion.
By inclining the end face of the rear end portion of the mainframe in such a manner that the upper portion is positioned forward of the lower portion, the end face of the rear end portion of the mainframe may be tipped forward to set the mainframe apart from the connecting tube.
By setting the mainframe apart from the connecting tube, the prescribed portion of the pivot frame may face towards the outer surface of the connecting tube. By forming a recess on the prescribed portion, the space in which the connecting tube is to be disposed may be increased.
Therefore, the freedom of determining the shape of the connecting tube may be increased.
In addition, by tipping forward the end face of the rear end portion of the mainframe, the joint between the mainframe and the pivot plate may be elongated. Therefore, the strength of the joint may be increased.
The present invention includes a rear end portion of the mainframe that is positioned in the vicinity of the rear end portion of the carburetor.
By positioning the rear end portion of the mainframe in the vicinity of the rear end portion of the carburetor, the rear end portion of the mainframe may be set apart from the connecting tube more positively, so that the prescribed portion of the pivot frame may face towards the outer surface of the connecting tube. By forming a recess on the prescribed portion, the space for disposing the connecting tube may be increased. Therefore, the freedom of determining the shape of the connecting tube is increased.
The present invention includes a rear end portion of the mainframe that is positioned forward of the rear end portion of the carburetor.
By positioning the rear end portion of the mainframe forward of the rear end portion of the carburetor, the rear end portion of the mainframe may be set apart from the connecting tube more positively. Therefore, the prescribed portion of the pivot frame may easily face towards the outer surface of the connecting tube.
Therefore, since the prescribed portion of the pivot frame may face towards the outer surface of the connecting tube relatively easily, the recess may be provided at the suitable position.
Further scope of applicability of the present invention will become apparent from the
Honda Giken Kogyo Kabushiki Kaisha
Lum L.
Morris Lesley D.
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