JPS63130434A - Four-wheel drive working truck - Google Patents

Abstract

PURPOSE:To relieve impact of switching operation of a front wheel speed change gear at the time of turning a working truck, by disconnecting transmission of power to a front wheel when a steering wheel for the front wheel is operated by a first setting angle or more and less than a second setting angle, and operating the front wheel power transmission to the speed increase side when the steering wheel is operated over the second setting angle. CONSTITUTION:During the time when a steering wheel 20 for front wheel is operated by a first setting angle theta1 or more and less than a second setting angle theta2, power transmission to a front wheel 1 is disconnected, and when the steering wheel 20 is operated over the second setting angle theta2, a front wheel speed change gear 10 is operated to the speed increase side. In such arrangement, two-wheel drive condition of rear wheel appears immediately before the front wheel speed change gear 10 is switched to speed increase condition so as to relieve droppage of speed at the start of turning during two-wheel drive condition. When the front wheel 1 is brought into speed increase condition subsequently, the impact is reduced because the difference from previous driving speed is lower than conventional one. Consequently, switching impact of the front wheel speed change gear 10 can be relieved when a working truck is turned.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a transmission system for steerable front wheels that has two states: a standard drive state where power is transmitted at a drive speed approximately equal to the rear wheel drive speed; The present invention relates to a four-wheel drive type work vehicle equipped with a front wheel transmission that switches to an increased speed drive state in which transmission is performed at a high drive speed.

[Conventional technology]

In recent years, models equipped with front wheel transmissions have appeared as mentioned above, and by operating this front wheel transmission to the speed-increasing drive side when turning, it is possible to make sharp turns without disturbing the ground, and even on soft ground. It can be done.

An example of the configuration of the operation system of a front wheel transmission is disclosed in Japanese Patent Application Laid-Open No. 59-17
It is disclosed in Japanese Patent No. 6121. This is a configuration in which the steering wheel and the front wheel transmission are linked, and when the vehicle is steered beyond a set angle in the straight-ahead state, the front wheel transmission is switched from the standard drive state to the speed-up drive state.

[Problem that the invention seeks to solve]

When a general four-wheeled vehicle turns, the turning radius of the front wheels becomes larger than the turning radius of the rear wheels, resulting in what is called a difference between the inner and outer wheels. Therefore, for a four-wheel drive vehicle to turn smoothly,
It is preferable that the drive speed of the front wheels is made slightly faster than the drive speed of the rear wheels, depending on the difference between the inner and outer wheels.

However, when turning with the aforementioned four-wheel-drive work vehicle, the drive speeds of the front and rear wheels are still the same at the beginning of the turn.
The drive speed of the front wheels becomes slower than the drive speed suitable for the previous turn, and the front wheels appear to be in a state where the brakes are applied. After that, when the steering angle of the front wheels is operated beyond the set angle and the front wheels enter a speed-increasing drive state, the front wheels are braked and the driving speed decreases slightly, but the front wheels suddenly become faster than the rear wheels. The vehicle is pulled at high speed, and the sudden acceleration causes a shock, which makes the ride uncomfortable for the operator and is also unfavorable in terms of safety. This phenomenon is often seen in long wheel base four-wheel drive work vehicles where the difference between the inner and outer wheels is large.

Here, the present invention focuses on the above-mentioned points, and aims to alleviate the shock when switching the front wheel transmission during a turn.

[Means for solving problems]

A feature of the present invention is that in a snow-covered four-wheel-drive work vehicle, while the steering wheel for steering the front wheels is operated at a first setting angle or more and a second setting angle or less, power transmission to the front wheels is cut off. and when the steering wheel is operated beyond the second setting angle, the front wheel transmission is operated to the speed increasing drive side, and its operation and effect are as follows. .

[For production]

With the configuration described above, immediately before the front wheel transmission changes from the standard drive state to the increased speed drive state, the two rear wheels
A wheel drive condition appears. During this period, the apparent braking state of the front wheels disappears, and the reduction in speed at the start of a turn in the standard drive state is alleviated during this two-wheel drive state.

After that, when the front wheels enter the speed-increasing drive state, the difference between the traveling speed in the two-wheel drive state before entering the speed-increasing drive state and the traveling speed when the speed-increasing drive state is entered is greater than in the conventional configuration. Since it is small, the shock at this time will be less.

〔Effect of the invention〕

As described above, it is possible to reduce the shock when turning by utilizing the speed increasing effect of the front wheel transmission, thereby improving the ride comfort and safety of the four-wheel drive type work vehicle.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A four-wheel drive agricultural tractor, which is one embodiment of the present invention, will be described below with reference to the drawings.

As shown in Fig. 3, an engine (4), a main clutch (5), a transmission, and an engine (4), a main clutch (5), a transmission A lift arm (8) that carries a case (6) and a control unit (7), connects various work devices such as a rotary tiller to the rear of the aircraft so that it can be raised and lowered, and a PTO shaft (9) that transmits power to the work devices. This is a four-wheel drive agricultural tractor.

Regarding the power transmission system of agricultural tractors, as shown in Figures 3 and 2, power from the engine (4) is transmitted through the main clutch (5) to the main transmission and auxiliary transmission in the transmission case (6). The transmission is transmitted to the transmission (not shown), and is transmitted from the rear wheel differential drive shaft (12) to the rear wheel differential mechanism (2a).
At the same time, the power branched from the rear wheel differential drive shaft (12) is transmitted to the front wheel transmission (10), and then to the front wheel differential mechanism (1a) via the front export power shaft (15). be.

As shown in FIG. 2, the front wheel transmission (10) has a front export power shaft (15) installed in parallel with the rear wheel differential drive shaft (12), and a first output power shaft (15) on the rear wheel differential drive shaft (12). - The second drive gears (13) and (14) are fixed. The first and second driven gears (16) and (17) that mesh with the first and second drive gears (13) and (14) are freely fitted onto the front export force shaft (15). A first hydraulic clutch (18) is connected between the first driven gear (16) and the front export force shaft (15), and a first hydraulic clutch (18) is connected between the second driven gear (17) and the front export force shaft (15).
) is configured with a second hydraulic clutch (19).

When the first hydraulic clutch (18) is in the engaged state, the front wheels (1) and the rear wheels (2) are in a standard drive state where the drive speeds are approximately equal, and when the second hydraulic clutch (19) is in the engaged state, the front wheels (1) and the rear wheels (2) are in the standard drive state. The drive speed of the rear wheel (1) becomes faster than that of the rear wheel (2), and when both the first and second wave pressure clutches (18) and (19) are disengaged, the rear wheel (2) )
This means that only two-wheel drive is possible.

Next, the operation system of the front wheel transmission (10) will be described in detail. As shown in FIG. 1, the knuckle arm (21) of the front wheel (1) is steered by the steering handle (20).
Potentiometer-type steering angle detection sensor (2
2), and a signal from a steering angle detection sensor (22) is input to a control device (23). Front wheel (1)
The steering angle changes from the straight forward position (θ.) to the first set angle (θ1
), the first gear of the front wheel transmission (10)
A control valve (24) for supplying and discharging pressure oil to and from the second hydraulic clutches (18) and (19) is connected to the first hydraulic clutch (18).
is operated on the pressure oil supply side to the standard drive state (4W
D-1).

The control valve (24) has three positions in a neutral position for draining oil from the first hydraulic clutch (18) pressure oil supply side, the second hydraulic clutch (19) pressure oil supply side, and both wave pressure clutches (18) and (19). It is composed of three positions, is electromagnetic, and has a neutral return type.

When the steering wheel (20) is operated to make a sharp turn and the steering angle of the front wheels (1) exceeds the first set angle (θ1), the operation signal to the control valve (24) is cut off. The control valve (24) is in a neutral state, the first and second hydraulic clutches (18) and (19) are in a disengaged state, and the rear wheel (24) is in a neutral state.
) is the only two-wheel drive type G (2wD). Furthermore, when the steering handle (20) is operated and the steering angle of the front wheels (1) exceeds the second setting angle (θ2), the control device (20)
3), the control valve (24) is operated to the pressure oil supply side of the second hydraulic clutch (19), and the front wheel transmission (10) is switched to the speed-up drive state (4WD-n). It is.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of a four-wheel drive type work vehicle according to the present invention,
FIG. 1 is a diagram showing the state of connection between the steering handle and the front wheel transmission, FIG. 2 is a side view of the front wheel transmission, and FIG. 3 is a side view of the entire agricultural tractor. (1)...Front wheel, (10)...Front wheel transmission, (20)...Control handle, (θ1)
...First setting angle, (θ2) ...Second
Setting angle.

Claims (1)

[Claims] The transmission system for the steerable front wheels (1) switches between a standard drive state in which power is transmitted at a drive speed approximately equal to the rear wheel drive speed, and an increased speed drive state in which power is transmitted at a drive speed greater than the rear wheel drive speed. A four-wheel drive work vehicle equipped with a device (10), a control handle (20) for steering the front wheels (1);
is greater than or equal to the first set angle (θ_1) and the second set angle (θ_2
), the power transmission to the front wheels (1) is cut off, and when the steering wheel (20) is operated beyond the second setting angle (θ_2), the front wheel transmission (1) is operated.
0) is configured to be operated to the speed-increasing drive side.