JPH07156676A - 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:Steering front wheels 1, rear wheels 2 driven through a gear transmission 4, right/left HSTs 6, 7 capable of individually driving the right/left front wheels 1, steering angle detecting means for detecting a steering amount of the front wheels 1 and a rear wheel speed detecting means for detecting a drive speed of the rear wheels 2 are respectively provided. Also a control means for connecting delivery amount change adjusting electrically-operated cylinder of these HSTs 6, 7 and pumps 8, 9, steering angle detecting means and the rear wheel speed detecting means, so that each HST 6, 7 is operated to be 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, is provided. Theoretically, a wheel slip at the time of turn running is set to zero.

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 wheel and rear wheel differential 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]

To achieve the above object, the present invention is directed to a steering front wheel, a rear wheel driven through a gear transmission, and left and right HSTs capable of separately driving left and right front wheels.
The steering angle detecting means for detecting the steering amount of the front wheels and the rear wheel speed detecting means for detecting the driving speed of the rear wheels are respectively provided, and each HST is based on the driving speed of the rear wheels in a state in which the ground slip of the front wheels does not occur. So that these HS
It is characterized in that it is provided with a control means that links the T operation means, the steering angle detection means, and the rear wheel speed detection means.

[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, in the straight traveling, the front wheels and the rear wheels are driven at a constant speed, and in the turning traveling, the front wheels are accelerated by the radius difference between the front wheels and the rear wheels.
The drive speed of ST is controlled. Further, by providing a difference in the driving speed between the left and right HSTs, it becomes possible to absorb the speed difference between the left and right front wheels during turning. 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 when turning is 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.

For example, when a belt continuously variable transmission is adopted, a forward / reverse switching mechanism and a neutral developing mechanism are separately required, but in the case of the present invention in which the front wheels are driven by HST, a normal rotation ( It can show forward (forward), neutral (stop or two-wheel drive with only rear wheels), and reverse (reverse). Further, since the present application is a so-called 2-pump / 2-motor structure, 1 pump / 2
This is significant in that each pump can be constructed of a small capacity type as compared with a motor structure that drives the front wheels, and the structure and control structure of the front wheel drive system as a whole can be simplified.

Further, since the rear wheels are driven by a gear transmission, the driving force can be efficiently transmitted to the road surface and a large traction force is required as compared with a structure in which power is transmitted by a hydraulic motor or a belt mechanism, for example. A suitable drive system is formed by a work machine having many parts.

[0009]

As a result, the left-right independent HST hydraulic control structure that continuously changes the rotational speed of the front wheels with respect to the rear wheels that are gear-driven, with respect to the drive speed difference between the front wheels and the rear wheels that occurs during turning, It was possible to secure a strong traction force and to reduce or eliminate slippage and earth pushing while achieving simplification of the transmission structure and to obtain a four-wheel drive traveling state more suitable for a working machine.

[0010]

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 for the rear wheels, 5 is a rear wheel diff mechanism, and 6 is a left front wheel. HSTs, 7 are HSTs (hydrostatic stepless transmissions) for the right front wheel, and left and right HSTs 6, 7 have variable displacement hydraulic pumps 8, 9 and hydraulic motors 10, 11. The power of the engine 3 is input to the left and right hydraulic pumps 8 and 9 via the distribution mechanism 25.

The hydraulic motors 7 and 8 and the front wheels 1 and 1 are interlocked with each other via a gear reduction mechanism 21, and each gear reduction mechanism 21.
A front wheel rotation speed sensor 12 for detecting the rotation speed of the front wheel 1 is provided for each, and electric actuators (solenoid, electric cylinder, etc.) 13, 14 for variably setting the tilt angles of the hydraulic pumps 8, 9 swash plates. Is equipped with.

As shown in FIG. 2, a first potentiometer (corresponding to a steering angle detecting means) 16 for detecting the amount of rotation of the steering wheel 15 and a gear shift lever 17 of the gear transmission 4 are also provided.
A second potentiometer (corresponding to rear wheel speed detecting means) 18 for detecting the operating position of the front wheel 1 and a turning angle sensor 19 for detecting the actual turning angle of the front wheel 1 by a power steering device (not shown). 1st and 2nd
Potentiometers 16 and 18, break angle sensor 19, front wheel rotational speed sensor 12, left and right electric actuators 13 and 14, digital speed setting device 23, and two-wheel drive state and four-wheel drive state by front wheels 1 and 1 A changeover switch 24 for selecting is connected to the control means 20 to form a drive control circuit L.

The drive control circuit L functions in both the two-wheel drive state and the four-wheel drive state. (1) Two-wheel drive To show the two-wheel drive state, the transmission lever 17 is operated to the neutral position N to cut off the transmission to the rear wheels 2, and the changeover switch 24 is operated to the "two-wheel drive" position. Speed setting device 2
3 and the control means 20 are linked and connected. In this state, when the speed setting device 23 is pushed to input the desired traveling direction and traveling speed, the left and right HSTs 6 and 7 are driven by the electric actuators 13 and 14 so that the speed is revealed.
Operated by.

When the vehicle goes straight ahead, the left and right front wheels 1, 1 are controlled so as to be driven at a constant speed, and when turning, each HST 6, 7 is controlled so that a speed difference corresponding to the turning radius difference is added from the information of the first potentiometer 16. Is controlled so that the front wheels 1, 1 are driven, and the rear wheels 2, 2 rotate freely.

(2) Four-wheel drive To display the four-wheel drive state, set the changeover switch 24 to "4.
To the "drive" position to set the speed setting device 23 and the control means 20.
Breaks the relationship with. Then, a state appears in which the drive speed of the front wheels 1 is automatically set according to the drive speed of the rear wheels 2. That is, when the speed change lever 17 is operated to set the traveling direction (forward or reverse) and the traveling speed (shift speed), 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 the information, the electric actuators 13 and 14 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. At the time of turning (for example, 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 speed required for the front wheels 1 and 1 and the driving speed difference due to the relative radius difference are calculated, and the arithmetic values thereof are calculated. The HSTs 6 and 7 are operated so as to be issued. Needless to say, the differential mechanism 5 absorbs the relative speed difference between the left and right rear wheels of the rear wheels 2, 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 FIGS. 3 and 4, control valves V _{1 and} V ₂ such as electromagnetic proportional control valves are provided in connection oil passages between the hydraulic pumps 8 a and 9 a and the hydraulic motors 10 and 11. A structure in which the front wheels 1, 1 are driven by the HSTs 6, 7 having a structure in which the In this case, the control structure is such that the electric actuators 13 and 14 for tilting angle operation shown in FIG. 4 switch and operate these control valves V _{1 and} V ₂ (the hydraulic pumps 8a and 9a are of a variable displacement type, and the control means). It may be a composite operation structure in which adjustment is made by 20).

In the two-wheel drive state, the speed setting device 2
Instead of 3, the speed is set by operating the pedal 26. That is, the third potentiometer 30 that detects the operation amount of the speed control pedal 26 is connected to the control device 20 to operate the electric actuators 13 and 14, and the relative speed difference between the left and right front wheels 1 and 1 during turning is automatically. Controlled by.

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 the 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.

In the present application, the "front wheel 1" in the claims is claimed.
The description "in a state where no slippage to the ground occurs" 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 another control block diagram of the drive system.

FIG. 5 is a system diagram showing a conventional drive system structure.

[Explanation of symbols]

 1 Front Wheel 2 Rear Wheel 4 Gear Transmission 6 Left HST 7 Right HST 13, 14 Operating Means 16 Steering Angle Detecting Means 18 Rear Wheel Speed Detecting Means 20 Control Means

Claims (1)

[Claims] 1. Steering front wheel (1), gear transmission (4)
Rear wheels (2) driven via the left and right front wheels (1),
Left and right HST (6) that can drive (1) separately,
(7), steering angle detecting means (16) for detecting the steering amount of the front wheel (1), and rear wheel speed detecting means (18) for detecting the driving speed of the rear wheel (2), respectively, and the front wheel Based on the drive speed of the rear wheel (2), the HST (6),
These HSTs (6) and (7) are operated so that (7) is operated.
Four-wheel drive working machine provided with control means (20) for linking the operating means (13), (14), the steering angle detecting means (16), and the rear wheel speed detecting means (18). Drive controller.