Motor vehicles – Having at least one wheel both driven and steerable – With driven axle – mounting two or more wheels – swingable...
Reexamination Certificate
2002-02-15
2004-01-13
Dickson, Paul N. (Department: 3616)
Motor vehicles
Having at least one wheel both driven and steerable
With driven axle, mounting two or more wheels, swingable...
C180S267000, C180S343000, C280S093510, C280S098000
Reexamination Certificate
active
06675925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to working vehicles such as tractors. More particularly, the invention relates to a steering apparatus mounted on such a working vehicle to steer the vehicle by changing directions relative to a vehicle body of right and left wheels.
2. Description of the Related Art
With an agricultural tractor as an example of working vehicles, a turn may be made with a small turning radius on a headland to provide advantages of making the headland small and moving quickly along the headland. For this purpose, a steering technique has been proposed as disclosed in Japanese Laying-open Utility Model Publication S56-36574 and U.S. Pat. No. 5,046,577. In this steering technique, wheels are supported at opposite ends of an axle member to be pivotable about vertical axes, and the axle member in turn is supported at a midpoint transversely of a vehicle body to be pivotable about a vertical axis. The vehicle is steered by changing directions relative to the vehicle body of the axle member and directions relative to the axle member of the right and left wheels. Thus, directions relative to the vehicle body of the wheels are changed by the combination of directional changes relative to the axle member of the wheels and directional changes relative to the vehicle body of the axle member. Compared with a case of employing only the directional changes relative to the axle member of the wheels, this steering mode provides a small turning radius even with an increased maximum steering angle of the wheels.
With the conventional steering technique noted above, when the vehicle is steered, the right and left wheels change directions relative to the vehicle body while sliding to large extents sideways on the ground. To enable the right and left wheels to roll relative to the vehicle body, the axle member has to be supported by the vehicle body to be pivotable also about an axis extending longitudinally of the vehicle body. This requires a complicated construction for attaching the axle member to the vehicle body, and this attaching construction requires a high degree of supporting strength, resulting in disadvantages in terms of cost and weight.
SUMMARY OF THE INVENTION
The object of this invention is to provide a steering apparatus for a working vehicle, which not only can steer wheels by increased steering angles but can reduce sideways sliding of the wheels and enable rolling of the wheels with a relatively inexpensive and lightweight construction.
The above object is fulfilled, according to this invention by a working vehicle comprising:
a vehicle body;
a pair of right and left dirigible wheels each having an axle;
a steering wheel for steering the pair of right and left dirigible wheels;
a pair of wheel supports arranged in right and left positions of the vehicle body;
intermediate cases each supported by one of the wheel supports to be pivotable relative to the one of the wheel supports about a first steering axis extending substantially vertically;
axle cases each attached to a side of one of the intermediate cases opposed to one of the dirigible wheels for supporting the one of the dirigible wheels on one of the axles, each of the axle cases being pivotable relative to one of the intermediate cases about a second steering axis extending substantially vertically; and
a steering control mechanism operable in response to turning of the steering wheel for swinging each of the intermediate cases about the first steering axis and swinging each of the axle cases about the second steering axis, thereby steering the pair of dirigible wheels relative to the vehicle body.
The above construction provides the following advantages. When the steering wheel is turned, the steering control mechanism swings each of the right and left intermediate cases the first steering axis relative to the wheel support, and swings each of the right and left axle cases about the second steering axis relative to one of the intermediate cases. The direction relative to the vehicle body of the right and left wheels changes by both changes in the direction relative to the vehicle body of the intermediate cases and in the direction relative to the intermediate cases of the wheels. This results in a larger maximum steering angle for steering the right and left wheels than where the wheels are steered only about the second steering axes.
Further, each intermediate case is pivotably supported by a wheel support disposed at the left or right side of the vehicle body. The second steering axis serves as a pivotal axis of each dirigible wheel. The first steering axis provides a fulcrum about which the pivotal axis of this wheel is movable longitudinally of the vehicle body. That is, the distance from the fulcrum of movement to the wheel pivotal axis is shorter than the distance from the pivotal axis of an axle member which is a conventional fulcrum of movement to the wheel pivotal axis. Thus, the right and left wheels, when steered, slide sideways over reduced distances over the ground than in the prior art.
An axle member is supported by the vehicle body to be pivotable about a longitudinal axis of the vehicle body, and left wheel support is formed at one end of the axle member and a right wheel support formed at the other end of the axle member. Then, while the axle member is connected in an intermediate position thereof to the vehicle body only to be pivotable about the longitudinal axis of the vehicle body, the right and left wheels change directions by swinging about the second steering axes of the axle cases and swinging about the first steering axis of the intermediate cases, and roll (i.e. swing from side to side) relative to the vehicle body through the axle cases, intermediate cases and axle member.
Thus, with the steering apparatus for a working vehicle according to this invention, changes in the direction relative to the vehicle body of the right and left wheels are effected with larger steering angles than where the right and left wheels are swung only about the second steering axes. The vehicle may be turned with a small turning radius on a headland to diminish the headland. The vehicle may engage in an agricultural operation while running with advantage, such as moving quickly from a finishing point of a preceding patch to a starting point of a next patch.
Moreover, the vehicle may be steered while suppressing side slipping of the wheels on the ground to be less than in the prior art where the axle member swings in the middle position transversely of the vehicle body. Thus the vehicle may run steadily with a reduced chance of sideslipping and other defective running.
Further, the right and left wheels may roll from side to side to maintain the running vehicle body substantially horizontal regardless of irregularities or slopes of the ground. This is achieved by attaching the axle member forming the right and left wheel supports to the vehicle body through the simple mounting structure that only enables the axle member to swing up and down relative to the vehicle body. Thus, the apparatus according to this invention is inexpensive and lightweight.
In the above construction, when the right and left dirigible wheels are in a straight moving state, the second steering axis, preferably, is displaced from the first steering axis longitudinally of the vehicle body.
When changing the direction of a dirigible wheel relative to the vehicle body, the front or rear end of the wheel pivoting about the second steering axis would approach an inward member such as the vehicle body and eventually contact the inward member. Assume that the dirigible wheel is a front wheel and the second steering axis is displaced forwardly from the first steering axis when the wheel is in a straight moving state. When the wheel is turned outward from the straight moving state, the ground-engaging point of the wheel initially moves about the second steering axis and outwardly of the vehicle body. On the other hand, where the second steering axis is aligned with the first steering axis tran
Kawai Isamu
Sumiyoshi Ryohei
Takahashi Seiichi
Yasumi Takashi
Dickson Paul N.
Kubota Corporation
To Toan
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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