JPH0194022A - Front wheel speed change constitution for work vehicle - Google Patents

Abstract

PURPOSE:To enable rapid turning while work grounds are ruined less by enabling an acceleration ratio of front wheels to rear wheels at the time of turning to be changeable depending on operational running speeds suitable to work sites. CONSTITUTION:No.1, No.2 and No.3 control valves 17, 18 and 19 of an electromagnetic actuation type are provided, which feed working oil supplied from a pump 16 to each hydraulic clutch 12, 13, and 14, each of these control valves 17, 18, and 19 is energized to the oil discharging side, that is, the discharging side of the clutches. Signals from limit switches 21a, 21b and 21d detecting the actuating position of the auxiliary speed change lever in an auxiliary speed change device capable of changing speeds in four steps, a potentiometer 23 detecting the steering actuation angle of a steering handle 22 and from a four wheel drive switch 24 are inputted into a control device 20 directing actuation signals to each of the control valves 17, 18 and 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a front wheel transmission structure of a four-wheel drive type working vehicle, typified by an agricultural tractor.

[Conventional technology]

In an agricultural tractor, which is an example of a four-wheel drive type work vehicle, as disclosed in, for example, Japanese Unexamined Patent Publication No. 60-4470, there is a standard drive state in which power is transmitted at a drive speed approximately equal to the rear wheel drive speed; Models have appeared that are equipped with front wheel transmissions that can be operated to switch between an accelerated drive state in which transmission is performed at a drive speed greater than the rear wheel drive speed, and with this disclosed structure, the steering wheel cannot be operated beyond a set angle. When you operate in the direction of
The front wheel transmission is configured to be switched from the standard drive side to the speed-up drive side, thereby making it possible to perform sharp turns relatively easily even on soft ground.

[Problem that the invention seeks to solve]

The working ground on which agricultural tractors travel varies widely, such as fields, wet fields, and lawns, but with conventional configurations, the speed increasing ratio of the front wheels to the rear wheels is constant during the speed increasing drive state. Because of this, when turning, the driving conditions of the front wheels and the turning conditions of the front of the aircraft did not match well, and there were cases where the front wheels would ruin the work surface. Furthermore, if the front wheel transmission is switched to the speed-increasing drive side when a steering operation is performed while the vehicle is traveling at a relatively high speed, the vehicle will make a sharp turn at high speed, resulting in a dangerous situation.

The present invention has focused on the above-mentioned problem, and aims to provide a structure that allows safe turning without particularly disturbing the working ground.

[Means for solving problems]

A feature of the present invention is that, in the front wheel transmission structure of a work vehicle as described above, the front wheel transmission is prevented from increasing the speed in a high-speed driving state exceeding a set speed, and in a low-speed driving state below the set speed. The present invention is provided with a control means for changing the speed increasing ratio of the front wheels to the rear wheels on the speed increasing drive side of the front wheel transmission according to the driving condition, and its functions and effects are as follows.

[For production]

-i, the working traveling speed on a relatively flat working area such as a grassy field is relatively high, and the working traveling speed on a rough ground with severe irregularities is relatively low.

Therefore, depending on the driving condition, the speed increase ratio in the speed increase drive state that appears when turning is set to a small value (such as 2 times) when the speed is relatively high. In general fields where there is no need to worry about rough ground, it is possible to set a large speed increase ratio (such as 3 times).

If the aircraft is traveling at a high speed higher than the set speed during such a turn, the front wheel transmission will not be switched to the speed-increasing drive side and will remain in the standard drive state, and normal turns will not be possible. You will be killed.

〔Effect of the invention〕

As described above, it has become possible to change the speed increase ratio of the front wheels to the rear wheels when turning in accordance with the working speed suitable for the work area, and it has become possible to make sharp turns without disturbing the work ground. This has improved safety by preventing situations such as sharp turns at high speeds.

〔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 Figure 3, power from the engine (1) is transmitted to the main transmission (not shown) and sub-transmission (not shown) in the mission case (3) via the main clutch (2). At the same time, the power branched from just before the rear wheel differential mechanism (15) passes through the front wheel transmission (5) and can be freely steered from the front export power shaft (6). is transmitted to the front wheels (7).

Next, to explain the front wheel transmission (5) in detail, as shown in Fig. 1, the transmission shaft receives and receives the power from just before the rear wheel differential mechanism (15) with respect to the front export power shaft (6). (8) are arranged in parallel, and the standard drive gear (9) is connected to this transmission shaft (8).
), first speed increasing drive gear (10), second speed increasing drive gear (1
1) is fixed. On the other hand, the front export force axis (6)
A multi-disc type first hydraulic clutch (12), second hydraulic clutch (13), and third hydraulic clutch (14) are attached to each of the hydraulic clutches (12), (13), (14).
) gears (12a), (13a), (14a)
are the standard drive gear (9) and the first speed increasing drive gear (1o).
, meshes with the second speed-increasing drive gear (11). With the above structure, when the first hydraulic clutch (12) is engaged, power is transmitted so that the driving speeds of the front and rear wheels (7) and (4) are approximately equal, and when the second hydraulic clutch (13) is engaged, the power is transmitted to the front wheels (7) and (4) so that the drive speeds are approximately equal. The power is transmitted so that the rear wheels (7) are driven at approximately twice the speed of the rear wheels (4), and the third hydraulic clutch (14
), power is transmitted so that the front wheels (7) are driven at approximately three times the speed of the rear wheels (4).

Next, each of the hydraulic clutches (12), (13),
To explain in detail the hydraulic oil supply system for (14), as shown in FIG.
14) Electromagnetically operated No. 1.2.3 control valve (1
7), (18).

(19) are provided, and each of these control valves (17), (
18).

(19) is biased toward the oil drain side, that is, toward the clutch disengagement side. Each of the control valves (17), (18), (1
9) includes a limit switch (21a) that detects the operating position of an auxiliary gear shift lever (not shown) in a auxiliary transmission capable of shifting into four stages.

(21b), (21c), (21d), a potentiometer (23) that detects the steering angle of the steering wheel (22), and signals from the four-wheel drive switch (24) are input.

Next, the flow of control within the control device (20) will be described. As shown in FIGS. 1 and 2, the four-wheel drive switch (20)
4) is OFF, each control valve (17).

No operation signal is issued to (1B) and (19), and each hydraulic clutch (12), (13), and (14) is disengaged, resulting in a rear two-wheel drive state, and the four-wheel drive switch (24) is in a disengaged state. ) is ON, the first control valve (17
), the first hydraulic clutch (12) is engaged, and in this state the front and rear wheels (7), (4)
are driven at approximately the same speed.

When the control handle (22) is steered beyond the set angle and the aircraft starts turning, the following operations are performed. That is, when the sub-shift lever is operated to the low speed position of 1st or 2nd speed, an operation signal is issued to the third control valve (19), the third hydraulic clutch (14) is engaged, and the front wheel ( 7) is driven at approximately three times the speed of the rear wheels (4) and the sub-shift lever is operated to the middle speed position of 3rd gear, an operation signal is issued to the second control valve (18). Second
The hydraulic clutch (13) is engaged, and the front wheels (7) are driven at approximately twice the speed of the rear wheels (4). On the other hand, when the sub-shift lever is operated to the high speed position of 4th gear, the operation signal is issued to the first control valve (17) regardless of the steering operation of the control handle (22). It continues like that.

[Another example]

The speed increasing drive side of the front wheel transmission (5) is configured as a belt-type or disc-type continuously variable transmission, and a vehicle speed sensor is provided to detect the traveling speed of the aircraft, so that when turning at a vehicle speed below a set speed, It is also possible to adopt a structure in which the driving speed of the front wheels (7) is continuously changed according to the vehicle speed.

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 front wheel transmission structure for a working vehicle according to the present invention, FIG. 1 is a diagram showing the front wheel transmission, a control device, a steering wheel, and a linked state, and FIG. 2 is a diagram showing the flow of control in the control device. Flowchart, FIG. 3 is an overall side view of the agricultural tractor. (4)...Rear wheel, (5)...Front wheel transmission, (7)...Front wheel, (20)...
Control device, (22)... control handle.

Claims (1)

[Claims] The transmission system to the front wheels (7), which can be steered freely, is switched between a standard drive state in which the transmission is transmitted at a speed approximately equal to the rear wheel drive speed, and an increased speed drive state in which the transmission is transmitted at a drive speed greater than the rear wheel drive speed. A work vehicle is equipped with a front wheel transmission (5) that can be operated, and is linked so that the front wheel transmission (5) is switched to the speed-increasing drive side by a steering operation of a steering handle (22) at a set angle or more. The front wheel transmission structure prevents the front wheel transmission (5) from increasing the speed in a high-speed driving state exceeding a set speed, and also prevents the front wheel transmission (5) from increasing the speed in a low-speed driving state below the set speed, depending on the driving state. A front wheel transmission structure for a work vehicle, which includes a control means (20) for changing the speed increase ratio of a front wheel (7) to a rear wheel (4) on the speed increase drive side of a transmission (5).