Rear fork attachment structure for motorcycle

Details Rear fork attachment structure for motorcycle Rear fork attachment structure for motorcycle

1999-09-10

2001-02-20

Hurley, Kevin (Department: 3619)

Motor vehicles

Special wheel base

Having only two wheels

C280S284000

Reexamination Certificate

active

06189638

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a rear fork attachment structure for motorcycles.
2. Description of Related Art
Many motorcycles have a rear wheel suspension device including a rear fork (corresponding to a swing arm) for a rear wheel which is vertically swingably mounted on a vehicle body frame, and a rear suspension by which the rear fork is suspended from the vehicle body frame. One such rear wheel suspension device is known from Japanese utility model publication No. 62-60491 entitled “Swing arm attachment structure for motorcycles”, for example.
According to the above related art, as shown in
FIG. 1
of the above publication, an attachment
4
of a swing arm extends between right and left ends
1
′,
1
of a frame having a predetermined width, and the right and left ends
1
′ and
1
and the attachment
4
are coupled together by a pivot bolt
11
(the reference numerals shown herein and below are the same as those in the publication).
According to the above related art, a collar
8
held against an inner end surface of the right end
1
′, bearings
9
, and a collar
7
are fitted over the pivot bolt
11
, and fastened together with the right and left ends
1
′,
1
by the pivot bolt
11
and a nut
13
. Since these parts
7
through
9
, right and left ends
1
′,
1
, and the attachment
4
have manufacturing tolerances, it is necessary to provide a clearance in view of an assembling tolerance between the right and left ends
1
′,
1
. In order to assemble the parts
7
through
9
between the right and left ends
1
′,
1
without any clearance, an adjustment collar
10
is employed to make axial adjustments along the pivot bolt
11
. Since there is no clearance, when the pivot bolt
11
and the nut
13
are tightened together, any bending moments due to the tightening forces do not act on the right and left ends
1
′,
1
.
An engine is integrally mounted on the frame and has an engine case which is extremely rigid as is well known in the art. If an extremely rigid case is used, then it can increase the rigidity of a portion of the frame on which a rear fork is mounted. For example, the rear fork is supported by the engine case and the right and left ends of the frame. Consequently, the rigidity with which to support the rear fork is higher than if the rear fork is supported by only the right and left ends
1
′,
1
of the frame as is the case with the prior art.
However, unless both a clearance between the rear fork and the engine case and a clearance between the rear fork and the frame are eliminated, when the pivot bolt
11
and the nut
13
are tightened together, bending moments due to the tightening forces act on the rear fork and the frame. Therefore, it is necessary to take some measures against the application of such bending moments.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a technique for supporting a rear fork with a pivot portion of an engine and right and left pivot supports of a vehicle body frame while attaching right and left arms of the rear fork reliably to the pivot portion and the right and left pivot supports without undue attachment loads imposed thereon.
To achieve the above object, according to a first aspect of the present invention, a rear fork attachment structure is for a motorcycle having an engine disposed substantially centrally in a vehicle body, right and left arms of a rear fork extending over right and left sides of a pivot portion of the engine, right and left pivot supports depending from the vehicle body frame and extending over right and left sides of the right and left arms. Furthermore, the left pivot support, the left arm, the pivot portion, the right arm, and the right pivot support are coupled together by a single pivot shaft. The rear fork attachment structure includes the right and left pivot supports having adjustment bolts with respective pivot shaft insertion holes, the adjustment bolts being capable of adjusting distances between the right and left arms and the right and left pivot supports.
The centers of the right and left pivot supports are aligned with the center of the pivot portion, and the right and left arms are pulled in between the right and left pivot supports and the pivot portion, followed by aligning the centers of right and left attachments with the center of the pivot portion.
The distance between the right arm and the right pivot support is adjusted by the right adjustment bolt for eliminating a clearance between the pivot portion and the right arm and a clearance between the right arm and the right pivot support. The distance between the left arm and the left pivot support is adjusted by the left adjustment bolt for eliminating a clearance between the pivot portion left arm and a clearance between the left arm and left pivot support.
Since there is no clearance, when the pivot shaft is tightened from both sides of the right and left pivot supports, any bending moments due to the tightening forces do not act on the vehicle body frame and the rear fork. Therefore, the right and left arms of the rear fork can reliably be mounted on the pivot portion of the engine and the right and left pivot supports without undue attachment loads imposed thereon. Furthermore, no special dimensional management for the parts is necessary in the area where the rear fork is mounted.
According to the first aspect of the present invention, the rear fork is pivotally supported on the pivot shaft by bearings, the bearings including a bearing mounted in one of the right and left arms so as to have a prescribed axial position thereof and a bearing mounted in the other of the right and left arms so as not to have a prescribed axial position thereof.
When one of the adjustment bolts on the right and left arms is adjusted, the position of the rear fork with respect to the center of the vehicle body is automatically established. Accordingly, the right and left adjustment bolts may simply be adjusted without paying attention to the positioning of the rear fork, and hence the adjustment operation can easily be performed.
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: 5964312 (1999-10-01), Maldonado
patent: 62-60491 U (1987-04-01), None
patent: 6-87481 (1994-03-01), None

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