JPH07156675A - Drive control device for four-wheel driven work machine - Google Patents

Abstract

PURPOSE:To decrease damaging a rice field at the time of turning due to slipping and earth pressing, by reconsidering a four-wheel drive structure. CONSTITUTION:In a four-wheel driven tractor, a steering front wheel 1 is driven by a single oil hydraulic pump 6 and right/left oil hydraulic motors 7, 8, to drive a rear wheel 2 by a gear through a differential mechanism 5. A steering angle detecting means for detecting a steering amount of the front wheel 1 and a rear wheel speed detecting means for detecting a drive speed of the rear wheel 2 are respectively provided, and a control means for connecting both solenoid proportional control valves 9, 10, steering angle detecting means and the rear wheel speed detecting means, so that maipulated variable of the control valves 9, 10 relating to the oil hydraulic motors 7, 8 is set to be adjusted, based on the drive speed of the rear wheel 2 in a condition that a slip against the ground of the front wheel 1 is not generated on calculation by realizing the drive speed of each wheel corresponding to a turning radius, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a working machine such as a tractor and a rice transplanter, and more particularly to a drive control device for a four-wheel drive type working machine suitable for traveling on rough roads and traveling under heavy load.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 2-28 discloses a four-wheel drive structure.
As shown in Japanese Laid-Open Patent Publication No. 022, the drive force is generally input to both the front and rear wheel diff mechanisms by gear transmission. For example, as shown in FIG.
There is also a hydraulic drive structure in which the power after passing through ST27 is input to both the front wheel and rear wheel differential mechanisms 28, 5 by a gear distribution mechanism 29.

[0003]

The gear transmission structure is excellent in that a reliable driving force can be transmitted to the front and rear wheels, and the hydraulic drive structure is useful as a four-wheel drive means that can easily take out continuously variable power. In either structure, a problem may occur when making a small turn. That is, in turning, there is a difference in speed between the rear wheels and the front wheels due to the difference in turning radius, but in any of the structures described above, the peripheral speed of the front wheels and the peripheral speed of the rear wheels are always or substantially constant. Therefore, the front wheels or the rear wheels are running while slipping. Therefore, especially in a small turn where it becomes noticeable, there is a possibility that the field is roughened by slippage or earth pushing, and it is difficult to make a small turn for four-wheel drive, and there is room for improvement.

In the former publication, when the cutting angle of the front wheels exceeds a certain degree, the rotational peripheral speed of the front wheels is increased so as to be faster than that of the rear wheels, so that a small turn can be made with less slip on the ground. However, the condition for shifting the front wheels is unique, and the range in which the above-described slip and earth pushing can be dealt with is limited. An object of the present invention is to review the four-wheel drive structure so that slippage and earth pushing will lessen the damage to the field during turning.

[0005]

In order to achieve the above object, the present invention provides a hydraulic motor capable of individually driving a rear drive wheel, a front steering wheel, and left and right front wheels, and a unit for supplying pressure oil to these hydraulic motors. One hydraulic pump, steering angle detecting means for detecting the steering amount of the front wheels, and rear wheel speed detecting means for detecting the driving speed of the rear wheels are provided respectively, and the driving speed of the rear wheels is adjusted so that the front wheels do not slip to ground. In order to adjust and set the operation amount of the control valve with respect to the hydraulic motor based on the above, the control valve, the steering angle detecting means, and the rear wheel speed detecting means are provided in a linked manner.

[0006]

In the above characteristic structure, the drive speed of the front wheels is controlled with reference to the drive speed of the rear wheels. That is, the driving speed of the hydraulic motor for the front wheels is controlled so that the front wheels and the rear wheels are driven at a constant speed in the straight traveling, and the front wheels are accelerated in an amount corresponding to the radius difference between the front wheels and the rear wheels in the turning traveling. Of. In turning, it also becomes possible to absorb the rotational speed difference between the left and right front wheels. In other words, since the left and right front wheel rotation speeds can be controlled independently of each other, the rotation speed required for the front wheels when the rear wheel is used as a reference during turning can be obtained regardless of the turning radius. A large driving force can be expressed without causing the field to become rough due to the pushing or reducing the field. Further, for example, when a belt continuously variable transmission is adopted, a forward / reverse rotation switching mechanism and a neutral appearance mechanism are separately required, but in the present invention in which the rotation speed of the front wheels is controlled by a hydraulic motor and a proportional control valve, Forward rotation (forward) without a separate mechanism,
Neutral (stop or two-wheel drive with only rear wheels) and reverse rotation (reverse) can appear.

[0007]

As a result, the hydraulic control structure that continuously changes the rotational speed of the front wheels with respect to the rear wheels to the drive speed difference between the front wheels and the rear wheels that occurs during turning makes slipping while simplifying the transmission structure. There was no or less soil pushing, and it was possible to obtain a four-wheel drive running condition suitable for a working machine.

[0008]

Embodiments of the present invention will be described below with reference to the drawings in the case of a tractor which is an example of a working machine.
The drive system of the tractor is shown in FIG. 1, 1 is a steering front wheel, 2 is a driving rear wheel, 3 is an engine, 4 is a gear transmission, 5 is a rear wheel diff mechanism, and 6 is a single variable displacement hydraulic pressure. pump,
Reference numerals 7 and 8 are left and right front wheel drive hydraulic motors, and 9 and 10 are left and right electromagnetic proportional control valves.

The hydraulic motors 7 and 8 and the front wheels 1 and 1 are interlocked via a gear reduction mechanism 11, and each gear reduction mechanism 11 is connected.
A front wheel rotation speed sensor 12 for detecting the rotation speed of the front wheel 1 is provided for each, and a pump rotation detection sensor 13 for detecting the rotation speed of the hydraulic pump 6 and a tilt angle of the pump swash plate are variably set. An electric actuator (solenoid, electric cylinder, etc.) 14 is provided.

Further, as shown in FIG. 2, the steering handle 15
First potentiometer (corresponding to steering angle detection means) 16 for detecting the amount of rotation of the gearshift lever 1 of the gear transmission 4
A second potentiometer (corresponding to rear wheel speed detecting means) 18 for detecting the operating position of 7 and a turning angle sensor 19 for detecting the actual turning angle of the front wheel 1 by a power steering device (not shown) are provided, respectively. The first and second potentiometers 16 and 18, the cutting angle sensor 19,
The drive control circuit L is configured by connecting the front wheel rotation speed sensor 12, the pump rotation detection sensor 13, the electric actuator 14, and the left and right electromagnetic proportional control valves 9 and 10 described above to the control means 20.

The function of the drive control circuit L is as follows. That is, when the speed change lever 17 is operated to set the traveling direction (forward or reverse) and the traveling speed (for example, 3 speeds), the information is transmitted from the second potentiometer 18 to the control means 20, and the information and the first potentiometer 16 are transmitted.
Based on this information, the electric actuator 14 and the left and right electromagnetic proportional control valves 9 and 10 are operated to control the rotational peripheral speed of the front wheels.

When traveling straight ahead, the peripheral speeds of the front wheels 1 and 1 are controlled so that the peripheral speeds of the rear wheels 2 and 2 coincide with each other. For example, the opening amounts of the left and right control valves 9 and 10 are set to the same amount in a half open state, and the rotational peripheral speed of the front wheel 1 is set by adjusting the discharge amount of the hydraulic pump 6. (The control valves 9 and 10 may be fully opened, and the rotational speed of the front wheel 1 may be adjusted and set only by the hydraulic pump 6.)

At the time of turning right, the front wheels 1, 1 are driven at a higher speed than the rear wheels 2, 2. That is, the second potentiometer 1
The turning radii of the front wheels 1 and 1 and the rear wheels 2 and 2 are calculated from the information of 8, and the rotational peripheral speeds required for the front wheels 1 and 1 are also calculated. The driving speed difference due to the relative radius difference between the left and right front wheels 1 and 1 slightly increases the opening degree of the left control valve 9 and slightly decreases the opening degree of the right control valve 10, and the relative speed difference between the front and rear wheels 1 and 2. Is handled by increasing the discharge amount of the hydraulic pump 6 by the electric actuator 14. (By keeping the left control valve 9 fully open and decreasing the opening degree of the right control valve 10, the front wheel 1,
It is also possible to absorb the relative radius difference of 1 and further increase the discharge amount of the hydraulic pump 6. ) When turning left, the above is the reverse of when turning right. Needless to say, the differential mechanism 5 absorbs the relative speed difference between the rear wheels 2 and 2.

The turning angle sensor 19 is used for feedback control of the second potentiometer 18 in the power steering device, and the front wheel rotation speed sensor 1 is provided.
It is convenient to make 2 respectively function as feedback control for whether or not the rotation speed as set is expressed.
Further, as shown by a phantom line in FIG. 2, a slip sensor 22 for detecting the slip phenomenon of the front wheels 1 is provided, and when slipping occurs at the drive rotation speed under the control described above, the rotation speed is reduced and the slip is eliminated. This is more convenient.

That is, in this tractor, the rear wheels 2 are driven by the gear transmission 4 and the differential mechanism 5, and the rotational speed of the front wheels 1 is variably controlled with reference to the driving speed of the rear wheels 4.
It is a wheel drive structure and can compensate the speed difference between the front and rear wheels caused by the turning regardless of the turning radius. As a result, as in the case of a conventional general four-wheel drive structure, the rotational peripheral speed of the front wheels is slower than the rotational peripheral speed required for calculation during turning, so that the rear wheel is driven by the driving force of the rear wheels. It becomes possible to solve the problem that the slip and the pushing of the soil in the field, or the small turning braking phenomenon on the pavement occur.

[Other Embodiments] As shown in FIG. 3, the rear wheels 2,
2 also has a hydraulic drive structure, and the above-mentioned drive control circuit L
It is also good to apply. That is, the rear wheel hydraulic pump 2
1 and the rear wheel hydraulic motor 24 are connected via a valve unit 25 having an electromagnetic proportional control valve 25A, and the front wheel hydraulic motors 7 and 8 and the front wheel hydraulic pump 6 are connected to the electromagnetic proportional control valve 9. , 10 are connected via a valve unit 26. In this case, it is convenient to equip the rear wheels 2 and 2 with a slip sensor 23 and control the driving force so as to prevent the front and rear wheels 1 and 2 from slipping as much as possible so that the field is not roughened. Further, it may have a drive structure in which the engine power is transmitted to the rear wheels 2 via HST which is a continuously variable transmission mechanism.

The steering angle detecting means 16 may have a structure for directly detecting the turning angle of the front wheels 1, and the rear wheel speed detecting means 18 may actually be the rotational speed of the rear wheels 2 or the differential mechanism 5. A structure that detects the rotation speed may be used.

By the way, in a front-wheel steering and rear-wheel non-steering structure, the turning radii of the wheels are different during turning.
In the present embodiment, "means for imparting the rotational peripheral speed required for calculation to the front wheels" is established when it is not necessary to consider the slip between the road surface such as the paved road and the road surface. It is also preferable that the phenomenon does not occur. However, on soft grounds such as rice fields, slippage to the ground often does not result in the above calculation.Therefore, a slip sensor, etc. should be added to the calculated rotational peripheral speed so that the wheels grip the ground without slipping. If a means for compensating the driving speed, that is, "a means for controlling the driving speed so that the front wheels grip the ground" is adopted, it is more convenient in that the road surface is prevented from being rough.

That is, the description "in a state where the front wheel 1 does not slip to the ground" in the claims is defined as a concept including any of the above means.

It should be noted that reference numerals are added to 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]

FIG. 1 is a system diagram showing the structure of a tractor drive system.

FIG. 2 is a control block diagram of a drive system.

FIG. 3 is a system diagram showing another structure of a drive system.

FIG. 4 is a system diagram showing a conventional drive system structure.

[Explanation of symbols]

 1 Front Wheel 2 Rear Wheel 6 Hydraulic Pump 7,8 Hydraulic Motor 9,10 Control Valve 16 Steering Angle Detection Means 18 Rear Wheel Speed Detection Means 20 Control Means

Claims (1)

[Claims] 1. Steering front wheels (1) and driving rear wheels (2), left and right front wheels (1), (1) hydraulic motors (7), (8) capable of individually driving, and these hydraulic motors (7). ), (8) a single hydraulic pump (6) for supplying pressure oil, the front wheel (1)
Steering angle detecting means (16) for detecting the steering amount of the rear wheel, and rear wheel speed detecting means (1) for detecting the driving speed of the rear wheel (2).
8), and control valves (9) for the hydraulic motors (7), (8) based on the drive speed of the rear wheels (2) in a state where the front wheels (1) do not slip to ground. These control valves (9), (1) are set so that the operation amount of (10) is adjusted and set.
0), the steering angle detection means (16), and the control means (20) for linking the rear wheel speed detection means (18) with each other.