Land vehicles – Wheeled – Running gear
Reexamination Certificate
1998-10-19
2001-01-09
DePumpo, Daniel G. (Department: 3611)
Land vehicles
Wheeled
Running gear
C280S271000
Reexamination Certificate
active
06170841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steering system for a straddle type four-wheeled all-terrain vehicle (hereinafter abbreviated to “ATV”) and, more specifically, to a steering system capable of limiting the turning of a steering shaft to a predetermined angular turning range.
2. Description of the Related Art
The ATV is capable of traveling rough terrains including sandy places, rugged lands, rocky mountains and rough lands with muddy puddles. A steering shaft is supported for rotation on a body frame of the ATV, and a handlebar is connected to the upper end of the steering shaft. The driver operates the handlebar to steer the ATV. The steering shaft is linked to a wheel support system supporting wheels by a linkage. When the handlebar is operated by the driver, the direction of the wheels is changed for steering. The turning of the steering shaft of the ATV is limited to a predetermined angular turning range by a stopping mechanism similar to a known handlebar stopping mechanism employed in a motorcycle.
Referring to
FIGS. 10 and 11
illustrating a handlebar turning angular turning range adjusting mechanism for a motorcycle, disclosed in JP-A No. 61-196887 (Utility Model), a handlebar
132
is fixedly joined to a lower fork bracket
121
, and stoppers
122
project from the upper surface of the lower fork bracket
121
. A head pipe
130
is fixed to a body frame, and a bracket
154
is fixed to the outer side surface of the head pipe
130
. Stopper bolts
155
are attached to stopper bolt holders
156
fixed to the bracket
154
. When the handlebar
132
is turned on the head pipe
130
by the driver, the lower fork bracket
121
is turned. The handlebar
132
cannot be turned beyond a position where the stopper
122
comes into contact with the stopper bolt
155
. In the motorcycle, the handlebar stopping mechanism is disposed at an upper position near the handlebar to make the handlebar stopping mechanism rigid against force exerted thereon by the handlebar so that the driver is able to recognize the turn of the handlebar to a limit position from the unyielding collision of the stopper bolt
155
against the stopper
122
. The steering shaft of the ATV is combined with a handlebar stopping mechanism similar in principle to the foregoing handlebar stopping mechanism for a motorcycle.
Referring to
FIG. 12
showing a handlebar stopping mechanism employed in a conventional ATV, a handlebar bracket
231
is joined to the upper end of a steering shaft
230
. A handlebar is attached to the handlebar bracket
231
. A stopper
253
provided with a bolt
255
is welded to a side surface of an upper part of the steering shaft
230
. An upper bracket
211
is connected to a body frame F. When the steering shaft
230
is turned to a predetermined angular position, the bolt
255
of the stopper
253
collides with the bracket
211
. An upper bearing unit
212
is attached to the bracket
211
to support the steering shaft
230
for turning. The stopper
253
provided with the bolt
255
is attached to a part of the steering shaft
230
extending upward from the upper bearing unit
212
.
FIGS. 13A and 13B
show the positional relation between the stopper
253
and the bracket
211
when the handlebar is held at a position for straight forward traveling and when the handlebar is turned substantially fully to the right, respectively. The turning of the steering shaft
230
in either direction is limited by the collision of the head of the adjusting bolt
255
with the bracket
211
to limit the turning of the steering shaft
230
to a predetermined angular turning range.
Thus, the handlebar stopping mechanism employed in the ATV, similarly to that employed in a motorcycle, is disposed at an upper position near the handlebar to make the handlebar stopping mechanism rigid against force exerted thereon by the handlebar so that the driver is able to recognize the turn of the handlebar to a limit position from the unyielding collision of the head of the bolt of the stopper against the bracket.
Sometimes intensive shocks that force the direction of the wheels to change suddenly act on the wheels because the ATV travels rough terrains. Those shocks exerted on the wheels are born through a linkage linking a wheel support mechanism and the steering shaft
230
by the stopper attached to the upper part of the steering shaft
230
. The linkage is connected to a lower part of the steering shaft
230
apart from the upper part of the same. Since the stopper is distant from a position on which the shocks are exerted, the steering shaft
230
must be highly rigid and hence the steering shaft
230
is inevitably heavy.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a lightweight, simple steering system for an ATV.
According to one aspect of the present invention, a steering system comprises: a steering shaft supported for turning on a body frame; a handlebar connected to an upper end part of the steering shaft; linkages linking the steering shaft and wheel support mechanisms so that the direction of wheels supported on the wheel support mechanisms is changed when the handlebar is operated. In this steering system, a first shaft-side stopper is disposed on the steering shaft at a position near a part of the same connected to the linkages, a first frame-side stopper is disposed on the body frame at a position corresponding to the first shaft-side stopper, and the turning of the steering shaft relative to the body frame is limited to a predetermined angular turning range by the engagement of the first shaft-side stopper with the first frame-side stopper.
According to the present invention, the first shaft-side stopper is disposed on the steering shaft at a position near the part of the same connected to the linkages to bear shocks exerted on the wheels by the first shaft-side stopper. Accordingly, the steering shaft is not twisted greatly by a torsional moment produced by external shocks, and a section of the steering shaft between a position where external shocks are exerted on the steering shaft and a position where the shaft-side stopper is attached to the steering shaft is short, and therefore the section of the steering shaft has a high torsional rigidity. Consequently, the steering shaft and the associated parts may be of a lightweight construction.
Preferably, the linkages are connected to a lower part of the steering shaft, and the first shaft-side stopper is disposed near the lower end of the steering shaft to construct the steering system in a particularly strong construction.
Preferably, the body frame is provided with a lower bearing unit for supporting the steering shaft at its lower end part, and the lower bearing unit is provided integrally with the first frame-side stopper. The lower bearing unit serving as both a bearing unit and a frame-side stopper reduces the number of component parts and the manufacturing cost of the steering system.
The first shaft-side stopper and the first frame-side stopper can be embodied in various shapes. The first shaft-side stopper may be formed in a shape having projecting parts projecting on the right and the left side of the steering shaft, and the first frame-side stopper may be disposed on the front side of the steering shaft.
The steering shaft may be provided further with a second shaft-side stopper at a position near its upper end, the body frame may be provided further with a second frame-side stopper at a position corresponding to the second shaft-side stopper, the angular position of the steering shaft relative to the body frame when the second shaft-side stopper is in contact with the second frame-side stopper may be substantially the same as that of the steering shaft relative to the body frame when the first shaft-side stopper is in contact with the first frame-side stopper. The steering shaft will not be twisted even if a large torque is applied to the steering shaft by the driver's turning of the handlebar. Accordingly, the collision of the s
Cuff Michael
DePumpo Daniel G.
Kawasaki Jukogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
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