Motor vehicles – Special wheel base – Having only two wheels
Reexamination Certificate
1999-09-10
2001-09-18
Olszewski, Robert P. (Department: 2167)
Motor vehicles
Special wheel base
Having only two wheels
C180S219000
Reexamination Certificate
active
06290017
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a body frame structure of a two-wheeled motor vehicle provided with a swing arm type rear suspension.
2. Description of the Background Art
Many two-wheeled motor vehicles are provided with a so-called swing arm type rear suspension. That is, a swing arm for a rear wheel is secured to a body frame and at the same time it is suspended from the body frame through a rear suspension. Generally, once characteristics of a rear suspension are determined, a layout relation thereof (e.g. mounting position and inclination) to a swing arm is mostly determined. This form of rear suspension is shown in a “saddle type vehicle” as disclosed in Japanese Patent Laid-open No. Hei 2-74487.
According to
FIGS. 1
to
3
and
6
of the publication, a pair of upper frame members are extended backward and downward from a head pipe
4
, a front end portion of a rear fork is mounted between rear lower portions of the upper frame members
14
, a rear end portion of a damper
8
is secured to a longitudinally intermediate position of the rear fork, and a front end portion of the damper
8
is attached to a cross member
15
mounted between the upper frame members
14
.
FIGS. 2 and 3
show the cross member
15
mounted between straight portions of the upper frame members
14
as seen from the side, an arm (with no reference numeral affixed thereto) is extended upwardly from the cross member
15
and the front end portion of the damper
8
is attached to an upper end of the arm, so that the damper
8
extends nearly in parallel with the above straight portions. Thus, the front end portion of the damper
8
is secured to the cross member
15
in an offset manner with the side view.
It is desirable that the center of gravity of the two-wheeled motor vehicle
1
be as low as possible, and it is therefore desirable that fuel tank
11
be disposed at a low position on the vehicle. The height of the fuel tank
11
, which is disposed in front of a seat
12
, is set so as to be appropriate in vehicular driving relative to the level of the seat
12
. In view of these points it is also desired that the upper frame members
14
extending below the fuel tank
11
be positioned low on the vehicle.
In the above conventional technique, the upper frame members
14
are positioned relatively low and the damper
8
is disposed above the upper frame members
14
and substantially in parallel with the straight portions of the upper frame members with side view.
As shown in
FIG. 2
of the above publication, the front end portion of the damper
8
is attached to the cross member
15
in an upwardly offset manner. Consequently, a torsional moment is induced in the cross member
15
due to the eccentric load of the damper
8
. Thus, it is required that the rigidity of the cross member
15
be enhanced, which results in an increase in both weight and cost.
One measure for preventing such an inconvenience is to raise the height of the cross member
15
up to the level of the front end portion of the damper
9
. This can be done by raising the height of the entire upper frame members
14
up to the level of the cross member
15
. However, if the upper frame members
14
are raised, they will interfere with the edge of the fuel tank
11
or of the seat
12
. To avoid this interference, the edge of the fuel tank
11
or of the seat
12
must be made wider. However, this is undesirable because an increase of the vehicle width will result.
Accordingly, in connection with a two-wheeled motor vehicle having a front end portion of a rear suspension damper
9
attached to an upper part of a body frame, it is an object of the present invention to provide a technique capable of (1) reducing the weight and cost of the body frame and (2) setting a fuel tank and a seat at optimum heights without changing their shapes and sizes.
SUMMARY OF THE INVENTION
In order to achieve the above-mentioned objects, a two-wheeled motor vehicle is disclosed having a pair of right and left main frames extending backward and downward from a head pipe, a cross member mounted between straight portions of the main frames as seen from the side, and a front end portion of a rear suspension secured to the cross member. The rear suspension extends approximately in parallel with the straight portions, and a body frame structure is provided having expanded portions formed locally upward from the straight portions of the main frames. The cross member is mounted between the expanded portions, and the front end portion of the rear suspension is secured to a vertical center of the rear side of the cross member.
Because the front end portion of the rear suspension is attached to the center of the cross member, an eccentric load exerted on the cross member from the rear suspension will be decreased. The cross member has a margin in point of rigidity because a torsional moment is not induced therein. As a result, the diameter and thickness of its material can be made much smaller, and a reduction in weight and cost of the body frame can be attained.
It is only the locally expanded portions that project upward from the main frames, with the cross member being mounted between the expanded portions. Thus, because of a local projection, there is no danger of interference of the main frames with the edge of a fuel tank or of a seat. Therefore, it is not necessary to change the shapes and sizes of the fuel tank and the seat. In addition, it is possible to set them at optimum heights.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4706774 (1987-11-01), Tsuboi
patent: 4744579 (1988-05-01), Roatta
patent: 5016725 (1991-05-01), Muramatsu
patent: 5284221 (1994-02-01), Warne
patent: 5377776 (1995-01-01), Saiki
patent: 5857538 (1999-01-01), Chambers
patent: 5921339 (1999-07-01), Matsuura
patent: 5975230 (1999-11-01), Bourget
patent: 0330557A2 (1989-08-01), None
patent: 213577 (1985-10-01), None
patent: A2-74487 (1990-03-01), None
patent: 5-77777 (1993-03-01), None
Birch & Stewart Kolasch & Birch, LLP
Cuff Michael
Honda Giken Kogyo Kabushiki Kaisha
Olszewski Robert P.
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