TECHNICAL FIELD
[0001]
The present invention relates to a transmission device for a
work vehicle including a predetermined transmission mechanism
having a plurality of forward gear shift stages for the work vehicle
to move forward and a reverse gear shift stage for the work vehicle
to move backward.
BACKGROUND ART
[0002]
Patent Literature 1 discloses a transmission device for a
work vehicle including a predetermined transmission mechanism
having a plurality of forward gear shift stages for the work vehicle
to move forward and a reverse gear shift stage for the work vehicle
to move backward. Even when the work vehicle does not include a
shuttling mechanism that requires a gear shaft for switching
between forward and backward motions, the predetermined
transmission mechanism enables an operator to switch between
forward and backward motions, which saves manufacturing cost.
CITATION LIST
PATENT LITERATURE
[0003]
Patent Literature 1: JP 2003-54283 A
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0004]
Using the predetermined transmission mechanism to switch
between forward and backward motions tends to cause an increase in
speed difference between forward and backward motions. Every time
an operator switches between forward and backward motions, the
operator switches gears of another transmission mechanism or
controls the accelerator pedal or the brake pedal to decrease the
speed difference between forward and backward motions. For this
reason, switching between forward and backward motions by the
predetermined transmission mechanism tends to impose a complicated
operation on the operator, which leaves room for improvement in
operability.
[0005]
In order to solve the problem, an object of the present
invention is to provide a transmission device for a work vehicle
including a predetermined transmission mechanism having a plurality
of forward gear shift stages for the work vehicle to move forward
3
and a reverse gear shift stage for the work vehicle to move backward,
the transmission device being capable of enhancing operability in
switching between the forward and reverse gear shift stages.
SOLUTION TO PROBLEM
[0006]
A transmission device for a work vehicle according to an
aspect includes a predetermined transmission mechanism having a
plurality of forward gear shift stages for the work vehicle to move
forward and a reverse gear shift stage for the work vehicle to move
backward. The plurality of forward gear shift stages includes: a
low-speed gear shift stage having the largest gear ratio among the
plurality of forward gear shift stages; and a predetermined gear
shift stage having a gear ratio closest to a gear ratio of the
reverse gear shift stage among the plurality of forward gear shift
stages.
BRIEF DESCRIPTION OF DRAWINGS
[0007]
Fig. 1 is a left side view of a work vehicle according to an
embodiment.
Fig. 2 is a perspective view of a driver space according to
the embodiment as viewed from upper left front;
Fig. 3 is a perspective view of an auxiliary transmission
mechanism according to the embodiment as viewed from upper left
front.
Fig. 4 is a right side view of the auxiliary transmission
mechanism according to the embodiment.
Fig. 5 is a front view of the auxiliary transmission mechanism
according to the embodiment.
Fig. 6 is a schematic view illustrating a part of a
transmitting system according to the embodiment.
Fig. 7A is a schematic view illustrating a range of motion
of a main gear shifting lever according to the embodiment. Fig.
7B is a schematic view illustrating a range of motion of an
auxiliary gear shifting lever according to the embodiment.
Fig. 8 is a right side view of the auxiliary transmission
mechanism according to the embodiment.
DESCRIPTION OF EMBODIMENTS
[0008]
[Summary of Embodiment]
A transmission device for a work vehicle according to an
embodiment includes a predetermined transmission mechanism (an
auxiliary transmission mechanism 50 in the embodiment) having a
plurality of forward gear shift stages for the work vehicle to move
forward and a reverse gear shift stage for the work vehicle to move
backward. The plurality of forward gear shift stages includes: a
4
low-speed gear shift stage having the largest gear ratio among the
plurality of forward gear shift stages; and a predetermined gear
shift stage (a medium-speed gear shift stage in the embodiment)
having a gear ratio closest to a gear ratio of the reverse gear
shift stage among the plurality of forward gear shift stages.
[0009]
Since a predetermined gear has a gear ratio closest to that
of the reverse gear shift stage, when switching between forward
and backward motions, an operator switches between the
predetermined gear and the reverse gear shift stage, thereby
decreasing the speed difference between forward and backward
motions as compared with a case where the predetermined gear is
shifted into another forward gear shift stage. This makes it easier
to omit the complicated operation imposed on the operator to
decrease the speed difference between forward and backward motions,
which enhances operability in switching between the forward and
reverse gear shift stages. In addition, since the predetermined
gear has a gear ratio smaller than that of a low-speed gear, it is
possible to make the forward speed faster than the low-speed gear,
which enables reduction in working time as compared with a case
where the work vehicle moves forward in the low-speed gear.
[0010]
The transmission device for a work vehicle and can further
include another transmission mechanism having a plurality of gear
shift stages having different gear ratios. Using another
transmission mechanism to change gear ratios makes it possible to
change the speed of the work vehicle while the speed difference
between forward and backward motions is kept small. This enables
speed adjustment of the work vehicle according to the work to be
done, thereby enhancing work efficiency.
[0011]
The gear ratio of the predetermined gear shift stage to the
gear ratio of the reverse gear shift stage can be at a ratio of
0.8 or more and 1.2 or less to 1. Since the speed difference
between forward and backward motions is decreased, it is easier to
omit the complicated operation imposed on the operator to decrease
the speed difference between forward and backward motions.
[0012]
The plurality of forward gear shift stages can include: the
low-speed gear shift stage; the predetermined gear shift stage; and
a high-speed gear shift stage having the smallest gear ratio among
the plurality of forward gear shift stages. Since the predetermined
gear has a gear ratio smaller than that of a high-speed gear, it
is possible to prevent the forward speed from being too high, which
enables the operator to work stably while switching between forward
and backward motions. In addition, reducing the number of forward
gear shift stages to three facilitates the operator’s work.

CLAIMS
1. A transmission device for a work vehicle comprising a
predetermined transmission mechanism having a plurality of forward
gear shift stages for the work vehicle to move forward and a reverse
gear shift stage for the work vehicle to move backward, wherein
the plurality of forward gear shift stages includes:
a low-speed gear shift stage having the largest gear
ratio among the plurality of forward gear shift stages; and
a predetermined gear shift stage having a gear ratio
closest to a gear ratio of the reverse gear shift stage among the
plurality of forward gear shift stages.
2. The transmission device for a work vehicle according to claim
1, further comprising another transmission mechanism having a
plurality of gear shift stages having different gear ratios.
3. The transmission device for a work vehicle according to claim
1 or 2, wherein
the gear ratio of the predetermined gear shift stage to the
gear ratio of the reverse gear shift stage is at a ratio of 0.8 or
more and 1.2 or less to 1.
4. The transmission device for a work vehicle according to any
one of claims 1 to 3, wherein
the plurality of forward gear shift stages include:
the low-speed gear shift stage;
the predetermined gear shift stage; and
a high-speed gear shift stage having the smallest gear
ratio among the plurality of forward gear shift stages.
5. The transmission device for a work vehicle according to any
one of claims 1 to 4, wherein
the predetermined transmission mechanism includes a
predetermined gear shifting lever controlled by an operator for
shifting gear shift stages in the predetermined transmission
mechanism,
an operation position of the predetermined gear shifting
lever has:
a reverse operation position at which the gear shift
stage is shifted into the reverse gear shift stage; and
a predetermined operation position at which the gear
shift stage is shifted into the predetermined gear shift stage,
and
the predetermined gear shifting lever is configured to move
linearly from the reverse operation position to the predetermined
operation position.
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6. The transmission device for a work vehicle according to any
one of claims 1 to 5, wherein
the predetermined transmission mechanism includes:
a predetermined gear shifting lever controlled by an
operator for shifting gear shift stages in the predetermined
transmission mechanism;
a lever arm configured to rock in front-rear direction
of the work vehicle by an operation of the predetermined gear
shifting lever; and
a lever protector extending upward from a step on which
the operator seated on a driver's seat of the work vehicle places
his/her feet, the lever protector being disposed between the lever
arm and the step, and
the lever protector is configured to stop the lever arm from
rocking forward beyond a predetermined position by contact with the
lever arm.
7. The transmission device for a work vehicle according to claim
6, wherein
the lever protector has an upper end portion being in contact
with the lever arm and chamfered.
8. The transmission device for a work vehicle according to claim
6 or 7, wherein
the lever arm includes a first lever arm and a second lever
arm disposed outside the first lever arm in width direction of the
work vehicle, and
the lever protector includes:
a first lever protector configured to stop the first
lever arm from rocking forward beyond the predetermined position
by contact with the first lever arm; and
a second lever protector configured to stop the second
lever arm from rocking forward beyond the predetermined position
by contact with the second lever arm, the second lever protector
being placed apart from the first lever protector in the width
direction.