JPH0820354A - Four-wheel steering device for agricultural work vehicle - Google Patents

Abstract

PURPOSE:To lighten the handle action of an agricultural work vehicle 4WS at a low cost. CONSTITUTION:Front and rear wheels 1, 2 are made steerable via a steering mechanism Sa, and the steering mechanism Sa can be operated via the hydraulic cylinder 14 of a power steering device Sb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to agricultural vehicles such as riding lawn mowers and tractors, and more particularly to a four-wheel steering system.

[0002]

2. Description of the Related Art Conventionally, a four-wheel steering device for an agricultural work vehicle such as a riding lawn mower or a tractor has been disclosed in Japanese Utility Model Laid-Open No. 64-1697
A mechanical steering device as shown in Japanese Patent No. 8 or a hydraulic power steering device as shown in Japanese Patent Laid-Open No. 62-175270 is used.

[0003]

The mechanical four-wheel steering system has the disadvantage that the steering wheel operation is heavy, but the cost is easy.

On the other hand, the hydraulic power steering device has an advantage that the steering wheel is lightly operated, but has a disadvantage that the cost is high.

Each of the above-mentioned conventional structures has merits and demerits.

Therefore, if the number of reduction gears in the gear case at the lower end of the handle shaft is increased as a means for lightening the handle operation of the mechanical steering device which is easy to cost, the handle operation becomes light, but the rotation operation of the handle increases. Occurs.

A first object of the present invention is to lighten the handle operation while reducing the cost and suppressing the increase of the handle rotation operation.

A second object of the present invention is to increase the steering angle by using a small hydraulic pump.

[0009]

The characteristic configuration of the first invention is that the front and rear wheels can be steered via a steering link mechanism including a drag rod, a knuckle arm, and a tie rod, and the steering link mechanism is also provided. Is operable via a hydraulic cylinder of the power steering device.

According to a second aspect of the present invention, the steering link mechanism includes a knuckle arm for the front wheels and a knuckle arm for the rear wheels via the drag rods for the front wheels and the drag rods for the rear wheels, respectively. It is configured by connecting to a pitman arm arranged in the center, and the hydraulic cylinder of the power steering device is connected to the pitman arm of the steering link mechanism along the longitudinal direction of the machine body, and the hydraulic cylinders are It is located between the body frames.

[0011]

According to the characteristic construction of the first aspect of the present invention, the mechanical steering link mechanism is configured to be operable via the hydraulic cylinder of the power steering device, and therefore, compared to a pure mechanical steering device. The steering wheel can be operated lightly, and the cost can be reduced as compared with a purely hydraulic power steering device.

According to the characteristic configuration of the second invention, since the hydraulic cylinders of the power steering device are arranged along the longitudinal direction of the machine body, for example, as shown in FIG. 4, the power cylinder 14 of the power steering device is shown. The steering angle can be increased with a small amount of power as compared with the case where the steering wheel is arranged in the lateral direction of the machine body.

That is, when the hydraulic cylinder 14 is arranged along the lateral direction of the machine body, the stalk of the cylinder cannot be long and
The steering angle becomes small, and in order to cope with this, if the lever ratio of the knuckle arm 13 is increased and the knuckle arm 13 is greatly swung with a small stroke to increase the steering angle, power is required. A large pump is required for the power steering device.

However, by disposing the hydraulic cylinders along the vehicle body frame, the stroke can be lengthened, and the steering angle can be increased without increasing the lever ratio.

As described above, since the steering angle is earned by the stroke of the cylinder, power is not required as compared with the one that earns the steering angle by the lever ratio.
A small pump can be used as the pump of the power steering device.

Further, a pitman arm is arranged substantially at the center in the front-rear direction of the machine body so that the front wheel knuckle arm and the rear wheel knuckle arm can be operated via the front wheel drag rod and the rear wheel drag rod. Therefore, as shown in FIG. 4, as in the case of connecting the knuckle arm 13 for the front wheel and the knuckle arm 14 for the rear wheel via the drag rod 10b for the rear wheel, the drag rod for the rear wheel becomes long. There is no such thing as making it easy to bend, and it is possible to avoid having to use a large pump because the rod diameter is made thick as a means for suppressing the bending.

[0017]

According to the first aspect of the present invention, the steering wheel operation is lighter than that of a purely mechanical steering device, and the cost is lower than that of a purely hydraulic power steering device. Be peeled off.

According to the second aspect of the present invention, since the steering angle is earned by the stroke of the cylinder, power is not required as compared with the one that earns the steering angle by the lever ratio. Can be used.

[0019]

Embodiments of the present invention will be described below with reference to a garden tractor equipped with a mower between front and rear wheels of the tractor.

As shown in FIG. 1, an engine 4 is mounted on the front of a vehicle body frame 3 equipped with front and rear wheels 1 and 2, a steering handle 5 is arranged at the center, and a steering seat 6 is arranged on the rear. A mower 8 is movably connected to the lower portion of the vehicle body frame 3 between the front and rear wheels 1 and 2 via a link mechanism 7.

As shown in FIG. 2, the garden tractor is a four-wheel steering type in which the front and rear wheels 1 and 2 can be steered in opposite directions, and a mechanical steering link mechanism Sa is provided in the power steering device Sb. It is configured to be operable via the hydraulic cylinder 14.

The steering link mechanism Sa includes a pitman arm 9 arranged substantially in the center of the machine body in the front-rear direction.
Front wheel drag rod 10a, knuckle arm 11
a, a tie rod 12a, a rear wheel drag rod 10b, a knuckle arm 11b, and a tie rod 12b. The steering link mechanism Sa is disposed above the vehicle body frame 3.

The power steering device Sa is composed of a controller 13 operated by the handle 5 and a hydraulic cylinder 14 operated by the controller 13. The hydraulic cylinder 14 is a pair of left and right body frames 3a, 3a. It is arranged inside along the longitudinal direction of the body.

[Other Embodiments] The farm work vehicle may be a tractor.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

1] Overall side view

FIG. 2 is a plan view of a steering link mechanism.

FIG. 3 is a view taken along the line AA in FIG.

FIG. 4 is a plan view showing a comparative example of a steering link mechanism.

[Explanation of symbols]

 1 Front Wheel 2 Rear Wheel 9 Pitman Arm 10a Front Wheel Drag Rod 10b Rear Wheel Drag Rod 11a Front Wheel Knuckle Arm 11b Rear Wheel Knuckle Arm 12a Front Wheel Tie Rod 12b Rear Wheel Tie Rod 14 Hydraulic Cylinder Sa Steering Link Mechanism Sb Power Steering Device

Claims (2)

[Claims] 1. Front and rear wheels (1) and (2) are connected to drag rods (10a) and (10b) and knuckle arm (11).
a), (11b), tie rods (12a), (12b)
A steering work that is configured to be steerable via a steering link mechanism (Sa) provided with the above, and the steering link mechanism (Sa) can be operated via a hydraulic cylinder (14) of the power steering device (Sb). Car four-wheel steering system. 2. The steering link mechanism (Sa)
A front wheel knuckle arm (11a) and a rear wheel knuckle arm (11b) respectively for the front wheel drag rod (10).
a) and a pitman arm (9) arranged substantially at the center in the front-rear direction of the airframe via a drag rod (10b) for rear wheels.
The hydraulic cylinder (14) of the power steering device (Sb) is connected to the pitman arm (9) of the steering link mechanism (Sa) along the longitudinal direction of the machine body, and Cylinder (1
4) A four-wheel steering device for agricultural vehicles, which is arranged between the left and right body frames.