JP2924724B2 - Agricultural traveling vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agricultural traveling vehicle capable of turning in accordance with soil conditions in a field.

[0002]

2. Description of the Related Art When a tractor is turned on a ridge in a field or the like, the front wheels are turned off and only the rear wheels are driven. A four-wheel drive front wheel with a speed approximately twice as high as the rotation speed, the difference in rotation speed between the front and rear wheels is adjusted, and a brake is applied to the rear wheel inside the turn to reduce the turning radius. .

[0003]

When turning in a field where the soil is soft, if the rear wheel on the inside of the turning is completely fixed by applying a strong brake, the soil is greatly swollen when the rear wheel inside turns. There is a problem. Also, if the braking force of the rear wheel brake is weakened and the inside rear wheel is turned with a slight rotation, roughening of the field can be reduced,
There is a disadvantage that the turning radius becomes large. Therefore, it is necessary to appropriately set the braking force of the rear wheel brake according to the hardness of the soil.

[0004] Further, when turning in a field with soft soil, such as a wetland, in a rear wheel two-wheel drive state, the rear wheels may slip and traveling becomes difficult. Therefore, in a field with soft soil,
It is good to have the front wheel speedup 4WD state. On the other hand, in fields where the soil is hard, such as dry fields and uncultivated fields, turning is easy even in the rear wheel two-wheel drive state, and the rear wheel two-wheel drive state makes the rotation of the front wheel less resistive and roughens the field. Not preferred. Thus, it is necessary to select an appropriate driving mode according to the degree of hardness of the soil.

Therefore, the present invention is to change the braking force of the rear wheel brake and the driving form of the front wheels appropriately in accordance with the soil condition of the field to make a turn suited to the soil condition. In order to achieve the following, it was configured as follows.

[0006]

That is, an agricultural traveling vehicle according to the present invention is provided with a work implement elevating device, and the driving form of the front and rear wheels is at least rear wheel two-wheel drive , front and rear wheel constant-speed four-wheel drive.
A front-wheel rotation sensor that detects front-wheel rotation speed and a rear wheel that detects rear-wheel rotation speed in an agricultural traveling vehicle that can be changed to the front wheel speed-up four- wheel drive state and configured to brake the turning inside rear wheel A rotation sensor, a rotation ratio detecting means for calculating a rotation ratio between the front wheel and the rear wheel based on a result of the detection, and a front-rear rotation at the time of turning according to a rotation ratio of the front wheel and the rear wheel in a rear-wheel two-wheel drive state after the work implement rises. It is characterized by comprising a wheel drive mode and control means for determining the braking force of the rear wheel inside the turn.

[0007] The invention according to claim 2 is the invention according to claim 1.
The control means of the rear wheel two-wheel drive
As the rotation ratio between the front and rear wheels increases,
Front and rear wheel drive mode, rear wheel two-wheel drive mode, front wheel speed-up drive mode
State, the front and rear wheels are driven at a constant speed,
The feature is that the braking force of the rear wheel is set weak .

[0008]

The front wheel rotation speed is detected by the front wheel rotation sensor, and the rear wheel rotation speed is detected by the rear wheel rotation sensor, and the rotation ratio between the front wheel and the rear wheel is calculated based on these detection results. When turning, the work equipment mounted by the work equipment elevating device is raised, but after the work equipment is lifted, the soil condition at that time is indirectly determined by the rotation ratio of the front and rear wheels in the rear wheel two-wheel drive state I do. And in the invention according to claim 1,
The drive mode of the front and rear wheels during turning is changed to the rear two-wheel drive state, front and rear wheel constant-speed four-wheel drive state, front wheel speed-up four-wheel drive state according to the rotation ratio, and the braking force of the rear wheel inside the turn is determined. I do.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tractor will be described as an embodiment of the agricultural traveling vehicle of the present invention, but the present invention is not limited to this.

A tractor 1 shown in FIG. 1 is a front-rear four-wheel drive vehicle, and has front wheels 2 and 2 and rear wheels 3 and 3 at four corners of the body. A front axle case 5 supporting the axles of the front wheels 2, 2 is mounted below the front frame 7, and rear axle cases 6, 6 supporting the rear wheels 3, 3 are mounted on the rear side surface of the transmission case 8. I have. The front axle case 5 is pivotally mounted on the front frame 7 at the center in the left-right direction so as to be able to swing left and right around an axis centered in the front-rear direction, and the front wheels 2, 2 move up and down due to unevenness of the ground. I have.

The engine 1 is located above the center of the front frame 7.
0 is detachably mounted. 11 is a radiator, 1
Reference numeral 2 denotes a cooling fan, and 13 denotes a fan belt, which are disposed in front of the engine 10. Reference numeral 14 denotes a hood, which covers the front and sides of the engine 10 and accessories (not shown).

Reference numeral 16 denotes a steering wheel. When the steering wheel is rotated left and right, the front wheels 2 are steered and swung right and left. The turning angle of the handle 16 is detected by a turning angle sensor 17. As shown in FIG. 2, in the vicinity of the handle 16, there are provided a finger-operated lifting / lowering lever 18 for raising and lowering the work implement to a set raising position and a lowering position, a 4WD switch 19 for switching a control mode of a driving mode, and the like. Have been. The 4WD switch 19 is an OFF switch 19a that is turned off when the vehicle is traveling on the road and when the loader is working.
And an ON switch 19b that is turned ON during normal work other than the loader work.

Fenders 21 and 21 are mounted from the front of the left and right rear wheels 3 and upward, and a seat 22 is provided between the left and right fenders 21 and 21. The driver's foot below the seat 22 is a substantially flat floor 23. Right and left rear wheel brake pedals 24, 24 are provided on the front right side of the floor 23. A position lever 25 is provided on the side of the seat 22 for changing the vertical position of the work implement.

At the rear of the machine body, lift arms 27, 27 which are vertically turned by an elevating hydraulic cylinder 26 are provided. At the bases of the lift arms 27, 27, a lift arm sensor 28 for detecting the angle of the arm is provided. The distal ends of the lift arms 27, 27 and the intermediate portions of the lower links 27a, 27a for mounting the working machine are connected by lift rods 27b, 27b.
By raising and lowering the 7, 27, a working machine such as a rotary tilling device mounted on the rear end of the lower link 27a, 27a is moved up and down. Also,
One of the lift rods 27b (the right side in the illustrated example) is a left-right tilt hydraulic cylinder 55, and the right-left tilt of the working machine is adjusted by expanding and contracting the hydraulic cylinder. In addition, a top link 27d is attached above the lower links 27a, 27a and in the center of the left and right, and the lower link 27
The working machine is supported by a three-point link mechanism composed of a, 27a and a top link 27d.

FIG. 3 is a power system diagram of the tractor, and the power system will be described based on the diagram.

The rotational power of the engine 10 is input to the transmission case 8. A main clutch 30 is provided at the entrance of the transmission case 8 so as to switch on and off the transmission. The power that has passed through the main clutch 30 is transmitted and branched to two systems, a driving power for driving the front wheels and the rear wheels, and a PTO driving force for extracting external power.

The traveling driving force is transmitted to a rear wheel differential device 36 by a rear wheel drive rotating shaft 35 via a reverse transmission 31, a main transmission 32, and an auxiliary transmission 33. The output shafts 37, 37 project right and left from the rear wheel differential device 36, and the driving force of the output shafts 37, 37 is transmitted to the transmission mechanism in the rear axle cases 6, 6 to drive the left and right rear wheels 3, 3. .

The left and right output shafts 37, 37 are provided with rear wheel brake devices 40, 40 individually operated by the rear wheel brake pedals 24, 24, respectively. It can be braked.
Further, the rear wheel brake devices 40, 40 are also operated by brake hydraulic cylinders 41, 41 for automatically braking the rear wheels inside the turning when turning.

The structure of the operation unit of the rear wheel brake device is shown in FIG.
It is like. That is, the brake operation shaft 42a
The front end of a brake arm 42b integrally formed with the brake pedal 42 is connected to the rear end of a brake rod 42c interlocking with the brake pedal 24. When the brake pedal 24 is depressed, the brake arm 42b turns forward (to the right in FIG. 4). Move
The rear wheel brake is applied. The tip of the piston 41a of the brake hydraulic cylinder 41 is in contact with the rear surface of the tip of the brake arm 42b.
When 1a protrudes, the brake arm 42b rotates to the front side to apply the rear wheel brake. When the depressing operation of the brake pedal 24 and the projecting operation of the piston 41a are released, the brake arm 42b is pulled back to the rear side by the action of the return spring 42d, and the rear wheel brake is in a non-operating state.

With the above structure, even when the brake hydraulic cylinder 41 performs automatic braking, the brake pedal 2
4 is prioritized, and the agricultural traveling vehicle can be stopped urgently. Further, even if the control system for automatic braking by the brake hydraulic cylinder 41 fails, the rear wheel brake device 40 during turning can be operated by manual operation using the brake pedal 24, which hinders running during turning. Does not occur. Furthermore, the automatic braking by the brake hydraulic cylinder 41 is intentionally stopped, and the rear wheel brake device 40 during turning can be operated by manual operation using the brake pedal 24.

The driving force of the rear wheel drive rotary shaft 35 is also transmitted to a front wheel drive rotary shaft 43 provided in parallel with the rear wheel drive rotary shaft 35. The front wheel drive rotation shaft 43 is provided with a 4WD switching device 44. The 4WD switching device 44 is in the “front-rear wheel constant speed four-wheel drive (4WD)” state in which the average rotation speed (peripheral speed) of the rear wheels 3 and 3 and the front wheels 2 and 2 is almost constant, and the rotation of the front wheels 2 and 2 A "front wheel speed-up four-wheel drive" state in which the peripheral speed ratio is almost twice the rotational speed of the rear wheels 3 and 3, and "the front wheels 2 and 2 are turned off to drive only the rear wheels 3 and 3" This is a device that switches to the "rear wheel two-wheel drive (2WD)" state. Next, based on FIG.
The specific configuration of the 4WD switching device 44 will be described.

The front wheel drive rotary shaft 43 is provided with a 4WD switching device 4.
4 is separated into an input shaft 43a and an output shaft 43b, and an end of the output shaft 43b is rotatably fitted to a first clutch boss 80 which rotates integrally with the input shaft 43a. The first clutch gear 81 is engaged with the spline portion of the first clutch boss 80, and the first clutch gear is always meshed with the first counter gear 82. Also, the connecting transmission shaft 8
4, a second counter gear 85 connected to the first counter gear 82 so as to rotate integrally therewith, and a second clutch gear 87 formed on a second clutch boss 86 rotatable on the output shaft 43b. Are engaged.

Therefore, when the input shaft 43a rotates, the first clutch boss 80 and the second clutch boss 86 rotate simultaneously, and when the input shaft 43a stops, the first and second clutch bosses 80 and 86 stop simultaneously. . First clutch gear 8
The speed of the first counter gear 82 is increased by 1 and the speed of the second clutch gear 87 is further increased by the second counter gear 85. The second clutch boss 86 makes two rotations while the first clutch boss 80 makes one rotation. .

The first clutch boss 80 and the second clutch boss 86 are rotatably provided facing the outer peripheral portion of the output side shaft 43b, and the first clutch boss 80 and the output side shaft 43b are transmitted and received by the constant speed clutch C1. The second clutch boss 86 and the output shaft 43b are connected to the speed increasing clutch C2.
The transmission can be turned on and off. The constant speed clutch C1 and the speed increasing clutch C2 have the following configuration.

Between the first clutch boss 80 and the second clutch boss 86, a plurality of friction plates 90,... Rotating integrally with the clutch boss side, and a plurality of friction plates 90,. Are integrally mounted on the spline portion of the output side shaft 43b, and the first piston 92 for engaging and disengaging a constant speed clutch is provided on both sides of a partition wall 91a of the clutch drum 91. And a speed-increasing clutch on / off second piston 93 are provided. Then, a part of the lubricating oil filled in the transmission case 8 is suctioned and pressurized by a pump (not shown), and is separated from the first piston 92 of the constant velocity clutch C1 via the solenoid switching control valve 61. By supplying either the first oil chamber 96 between the walls 91a or the second oil chamber 97 between the second piston 93 of the speed increasing clutch C2 and the partition wall 91a, the first piston 92 or the second Piston 9
3 is activated.

FIG. 5 shows a state in which the switching control valve 61 is in a neutral state. In this neutral state, both the constant speed clutch C1 and the speed increasing clutch C2 are in the off state, and the rotation of the input side shaft 43a is transmitted to the output side shaft 43b. Don't tell. When the 4WD solenoid 61a of the switching control valve 61 is energized from the state shown in the figure, high-pressure oil flows into the first oil chamber 96, the constant-speed clutch C1 is engaged, and the rotation of the input shaft 43a is transmitted to the output shaft 43b. Also,
When the front wheel speed increasing solenoid 61b of the switching control valve 61 is energized, high pressure oil flows into the second oil chamber 97 and the speed increasing clutch C2
Are connected, and the rotation of the input side shaft 43a is doubled and transmitted to the output side shaft 43b.

Therefore, when the constant speed clutch C1 is "ON" and the speed increasing clutch C2 is "OFF", the front wheels 2, 2 and the rear wheels 3,
The front and rear wheel constant-speed four-wheel drive (4
WD), and when the constant speed clutch C1 is “disengaged” and the speed increasing clutch C2 is “on”, the peripheral speed of the front wheels 2, 2 is twice the peripheral speed of the rear wheels 3, 3, “front wheel increase”. Speed 4WD)
When both clutches C1 and C2 are "off", the rear wheels 3, 3
It is a "rear two-wheel drive" that drives only the rear wheel.

The input shaft 43a and the output shaft 43b are provided with a rear wheel rotation sensor 45 and a front wheel rotation sensor 46 for detecting the rotation speed of each shaft. The rotation speed of the input shaft is proportional to the average rotation speed of the left and right rear wheels, and the rotation speed of the output shaft is proportional to the average rotation speed of the left and right front wheels. In this embodiment, when the output shaft makes one rotation while the input shaft makes one rotation,
The rotation speed of the front wheel and the rotation speed of the rear wheel coincide.

The power via the 4WD switching device 44 is taken out to the front of the transmission case 8 and further transmitted to the front axle case 5 via the front wheel transmission shaft 48. A front differential device 49 is provided at the center in the left-right direction of the front axle case 5, and the power input to the front axle case 5 drives the left and right front wheels 2, 2 via the front differential device 49.

On the other hand, the PTO driving force is transmitted to the PTO transmission 5
After passing through 0, it is taken out to the PTO shaft 51 projecting rearward from the back of the transmission case 8. A transmission shaft to various working machines (not shown) is detachably connected to the protruding portion of the PTO shaft 51 by transmission.

The hydraulic device of the tractor 1 has the structure shown in FIG. That is, the main hydraulic pump 53 and the power steering hydraulic pump 54 are provided, and the lifting hydraulic cylinder 26, the left and right tilt hydraulic cylinder 55, the 4WD switching device 44, the brake hydraulic cylinders 41, 41 Is operated, and the power steering device 56 is operated by the pressure oil sent from the power steering hydraulic pump 54. In the figure,
Reference numeral 57 denotes a flow dividing valve for branching and supplying pressure oil to a circuit for operating the elevating hydraulic cylinder 26 and a circuit for operating the right-and-left tilting hydraulic cylinder 55; 58, an elevating / lowering hydraulic valve for controlling the elevating hydraulic cylinder 26; Hydraulic cylinder 5
Reference numeral 61 denotes the solenoid switching control valve for switching the 4WD switching device 44.

Reference numerals 62 (L) and 62 (R) denote proportional solenoid pressure reducing valves provided in oil passages to the left and right brake hydraulic cylinders 41 (L) and 41 (R).
(L), the internal pressure of each cylinder changes in accordance with the amount of current supplied to 62a (R), whereby the rear wheel brake devices 40, 40
Brake pressure is adjusted.

The tractor 1 controls traveling during turning of the machine body and lifting and lowering of the working machine by the control device shown in the block diagram of FIG. The controller that controls these controls includes a traveling controller 70A and a lifting controller 70B, and both controllers are communicably connected. The travel controller 70A includes a CPU 71, an E ² PROM 7
2. ROM 73, each interface 74, 75, 7
6, an A / D converter 77, and a current detection circuit 78. The CPU 71 is a rotation speed calculation unit and a control unit.

A signal from the elevation controller 70B, 4
The signal from the WD switch 19 and each of the sensors 17 and 2
8, 45 and 46 and the feedback signal from the current detection circuit 78 are used as the CP of the travel controller 70A.
It is sent to U71. The CPU 71 performs predetermined data processing on the input data based on a program provided from the ROM 73, and in response to an output request obtained thereby, each of the solenoids 61a, 61b, 62 (L), 62
(R) and outputs it to the display devices 79. Intermediate data and output data obtained by the data processing may be E ² PR
The data is stored or rewritten in the OM 72 and transmitted to the elevation controller 70B.

FIGS. 8 to 11 and 12 are flowcharts of the control. Next, the details of the traveling control during the turning of the aircraft will be specifically described according to the record at the time of a certain turning shown in FIG.

4WD switch 19 is ON switch 1
If it is determined that the vehicle has turned on by pressing 9b and that the turning of the aircraft has been started from the detection value of the turning angle sensor 17 (at the point A in FIG. 13), based on the determination at the time of going straight (description omitted), Set the braking force for the rear wheel inside the turning, and select the preferred driving mode. In FIG. 13, "front wheel speed-up four-wheel drive" is selected.

Thereafter, a fixed time T ₀ (for example, 1.2 seconds)
Is forcibly switched to the "rear two-wheel drive" (Fig. 13
B point), and the predetermined time T ₁ (for example, 0.2
Seconds), the front wheel rotation sensor 46 and the rear wheel rotation sensor 4
Rotation ratio between the front wheels and the rear wheels than the detection value of 5 (front wheel rotational speed / rear wheel speed) to calculate the Y _n, preset difference between the reference rotation ratio Y, i.e. change speed ratio SLP _n (= Y- Based on Y _n ), the braking force and the driving form of the rear inner wheel thereafter are determined (at the point C in FIG. 13).

The reference rotation ratio Y is a value set according to the current brake pressure _Pn , and is a rotation ratio between the front wheels and the rear wheels on the basis of turning on extremely hard soil. FIG. 16 is a graph showing the relationship between the brake pressure _Pn and the reference rotation ratio Y.
It is represented by a function of 0.03 × P _n +1.5. This function is set based on the data of the rotation ratio of the front and rear wheels obtained as a result of turning on the hard ground such as asphalt while changing the rear wheel braking force (brake pressure _Pn ). In this embodiment, the reference rotation ratio Y is corrected to a corrected reference rotation ratio Y 'in consideration of a brake pressure change due to a temperature change.

The braking force (brake pressure) and driving mode of the rear inner wheel are determined according to the rules shown in FIG.

For example, when the ground is turning in a hard field such as a dry field or an uncultivated field, the variable rotation ratio SLP _n ≦ 0.3
In this case, the brake pressure _{Pn is set} to “strong” (in the embodiment, 20 kgf / cm ² ), and the drive form is set to “rear wheel two-wheel drive (2
WD) ". Therefore, the vehicle can be turned without damaging the field without the rotation of the front wheel turning, and the braking force on the rear wheel inside the turning can be increased, so that a quick turning with a small turning radius can be performed.

When the ground, such as a wetland or a cultivated field, is turning in a relatively soft field, the variable rotation ratio SLP _n = 0.3 to 0.5, and in this case, the brake pressure P _n to “weak (10-16 kgf / cm ^{2 in the} example)”
And set weaker the greater the value of the variation speed ratio SLP _n,
The drive form will be "Front wheel speedup 4WD". Therefore, the braking force of the turning inside rear wheel is weakened according to the degree of slip, and the turning is performed while the turning inside rear wheel is rotated to some extent, and while the propulsion force is appropriately given by the rotation of the front and rear wheels, and A quick and reliable turn with little roughness and a relatively small turning radius can be performed.

Further, for example, when the vehicle cannot be propelled in a super wet field or the like and cannot turn, the variable rotation ratio SLP _n ≧
In this case, the brake pressure _{Pn is set} to “extremely weak (5 kgf / cm ² in the embodiment)” and the drive mode is set to “front and rear wheel constant speed four-wheel drive (4WD)”. Therefore, while making the braking force of the inside rear wheel extremely low, and applying a very weak brake on the inside rear wheel, the vehicle makes a large turn with the front and rear wheels at a constant speed of 4WD, and the wheel goes into the ground and sinks. The tractor can turn while avoiding a situation in which the tractor cannot escape on its own.

[0043] Although the detected rotation ratio Y _n for determining the variation rotation ratio SLP _n is detected every moment, the detected rotation ratio when determining the braking force and the driving mode of the turning inner rear wheel Y
_n is "rear wheel 2WD" rather than using the value detected immediately after switching, a value detected when the switching constant time T ₁ after has elapsed. The reason for this is that the rotation of the front wheel, whose drive has been cut off, does not change instantaneously to a predetermined rotation, but gradually changes due to the viscosity of the operating oil of the hydraulic clutch, etc., depending on the condition of the soil. Since it changes to a predetermined rotation, in order to perform accurate control according to the state of the soil, the rotation ratio is detected after a certain period of time after switching to `` rear wheel 2WD '' It is. Of length 0.2 to 0.3 seconds this time T _1, is preferably set to 0.2 seconds. This value is a time when it is relatively clear that the rotation ratio has changed according to the soil condition in a short time as possible, and is an optimum value obtained by an experiment. Further, the time T ₁ is appropriately corrected according to the temperature of the operating oil for operating the clutch.
The correction method will be described later.

[0044] When the above control is "front-wheel acceleration four wheel drive" output, after a predetermined time T ₀ has elapsed, switch back to "rear wheel 2WD", optimal braking force and the driving mode of the turning inner rear wheel (Time point D in FIG. 13). When the “rear two-wheel drive” is output by the above control, the state of the “rear two-wheel drive” is continued (time point E in FIG. 13).

The predetermined time T ₀ is suitably from 0.8 to 1.5 seconds, of which 1.2 seconds is optimal. The value of T _{0 is} a value that satisfies the condition that the speed of turning by the “front wheel speedup four-wheel drive” is maintained to some extent and that it is possible to quickly adapt to changes in soil conditions during turning. Yes, it is the optimal value obtained by experiment. If T ₀ is smaller than the above range, the front wheel rotation does not sufficiently increase, and the turning speed decreases. On the other hand, if T ₀ is larger than the above range, the ability to follow changes in the soil condition will be reduced. Generally, the time required for turning is 5 to 6 seconds, and about 10 seconds at a slow speed. Therefore, the rear wheel braking force and the driving mode corresponding to the soil state are changed to about 5 to 10 times during turning.

Further, when a fluctuating rotation ratio (SLP _n ≧ 0.5) larger than the fluctuating rotation ratio (SLP _n = 0.3 to 0.5) at the time of switching to the “front wheel speed increasing four-wheel drive” is detected. Is
"Rear wheel two-wheel drive" even within time T ₁ or after time T ₁
Even after is selected, at that time, it is switched to "Front wheel speedup four-wheel drive" and the braking force of the rear inner wheel is set to "weak" or "extremely weak" (time point F in FIG. 13). . As shown in the graph of FIG.
It determined according to the time T ₂ of the from switches to "rear wheel 2WD" to the changing rotation ratio is detected. With such a control, even if the soil suddenly becomes very soft during the turning and slips, the state is quickly switched to an appropriate turning state.

Hereinafter, a correction process based on a temperature change will be described. Brake solenoids 61a (L), 61a
In (R), the temperature changes under the influence of the hydraulic oil. If the coil resistance of the solenoid changes due to this temperature change, even if the brake solenoids 61a (L) and 61a (R) are driven with the same ON-Duty output, the amount of current actually flowing through the coil differs, and the rear wheel The braking force changes. As shown in FIG. 18, the brake ON-Dut
Even if y is the same, the lower the oil temperature, the greater the amount of current actually flowing through the solenoid coil. In order to correct the change in the rear wheel braking force due to the oil temperature, FIG.
The brake ON-Duty correction processing shown in the flowchart of FIG.

In the processing procedure, first, an actual drive current actually flowing through the brake solenoid 61a (L) or 61a (R) is detected by the current detection circuit 78. Then, the actual drive current and the solenoid 61a (L) or 61a
Actual drive brake ON-Dut actually output in (R)
y, and a correction brake ON-Duty for correcting the actual drive brake ON-Duty from the difference between the two, and a temperature of the working oil at that time, that is, an assumed oil temperature H assumed from the difference between the two. Is calculated.

Since the disengagement operation of the hydraulic clutch also changes depending on the temperature of the working oil, the time T ₁ is corrected from the assumed oil temperature H. Figure 17 is a diagram showing the relationship between oil temperature and time T _1. As apparent from the figure, the time T ₁ in oil temperature is lower region lengthened in accordance with the oil temperature is above a certain level (about 20 ° C. C.) to become the time T ₁ that the oil temperature constant. Changes in the time T ₁ corresponds to the dynamic viscosity characteristics of the oil.

A temperature rise recording timer is started simultaneously with the start of the engine, and the time T _U and the assumed oil temperature H at that time are stored in the E ² PROM 72. And
When applying the rear wheel brake for the first time after the next engine start,
Correction brake ON-Du corresponding to elapsed time from start
Drive with the output corrected by ty. As a result, the brake operation immediately after the start of the engine, in which the oil temperature rises rapidly and requires a large correction, can be performed with an appropriate braking force.

By the way, the current detection of the brake solenoid in the brake ON-Duty correction processing is performed after a short time has passed after the drive, taking into account the response delay of the current detection circuit 78. The elapsed time after the drive is about 0.2 seconds. If it is longer, the time T ₁ (0.2 to 0.3
If (sec) is shortened by the correction, the current detection may not be able to catch up.

In calculating the correction brake ON-Duty in the brake ON-Duty correction process, the ON time correction amount increases as the difference between the detected actual drive current and the current scheduled from the actual drive brake ON-Duty increases. I do. Therefore, as for the correction brake ON-Duty in the brake ON-Duty correction processing, the ON time has a larger correction amount as the temperature change is larger.

As described above, the brake ON-Duty
After the correction processing, the current actual drive brake ON-Dut
A reference rotation ratio Y is calculated from y, and a corrected reference rotation ratio Y ′ is calculated from the assumed oil temperature H and the reference rotation ratio Y. And
Correction reference rotation ratio Y 'and set time T ₁ rotation ratio after Y
than the difference between _n, it calculates a variation speed ratio SLP _n, determining the brake pressure of the drive mode and rear wheel inner rear wheel as described above.

The brake output of the rear inner wheel is determined as follows. Brake O according to variable speed ratio SLP _n
Set the N-Duty, then set the correct brake ON-Duty than the value of the time T ₁ and the detection rotation ratio Y _n from when the "rear wheel 2WD". And the cutting angle sensor 1
After reading the seven values, the steering wheel turns right or left to the rear wheel brake operation position (1.2 + 0.2; -0 rotation), and the rear wheel brake operation condition (described later) is satisfied, and a brake output request is issued. If there is, the drive ON-Duty of the previous drive
To the corrected brake ON-duty calculated by the brake ON-Duty correction process.
Output in Duty. Until it detects the next change rotation ratio SLP _n, continues to output in the brake ON-Duty. Thus, the brake ON-Duty at the time of the previous drive is
By determining the output in consideration of the above, it is possible to cope with fluctuations in the braking force due to an increase in the oil temperature.

Since the rear wheel braking force changes depending on the oil temperature as described above, the OFF timing of the rear wheel brake output is adjusted according to the assumed oil temperature H. For example, when the oil temperature is low, the viscosity of the hydraulic oil is high and the rear wheel brake is in a poorly released state, so the brake release operation is started earlier.

The information on the temperature correction obtained by the data processing is sent from the traveling controller 70A to another control device, for example, the elevation controller 70B.
Used for temperature correction of a proportional solenoid valve for elevation control.

For the operation of the rear wheel brake during turning,
There are the following operating conditions: (1) It must be within 20 seconds after the working machine has been raised. If the work is interrupted on the ridge, it is dangerous if the rear wheel is in a one-brake state when resuming, so this is to prevent this.

(2) The handle operates about 1.2 turns from the neutral position (see FIG. 19). The time during which the rotary tilling device comes out of the soil during tilling work is considered.

(3) After the output in one direction is turned off, the output in the opposite direction is not performed for 10 seconds. Immediately after the start of the work or immediately after the end of the turn, the steering wheel may be operated greatly to align the course with the work line.

(4) The automatic rear wheel brake does not operate during reverse travel. This prevents a change of direction at the headland from becoming inconsistent with the operator's will.

Next, the lifting control of the working machine mounted on the tractor will be described. For raising and lowering the working machine, the operation of raising and lowering the working machine to a height corresponding to the operating position of the lever by operating the position lever 25, and the operation between the working height and the non-working height by operating the lifting lever 18 There is an operation of raising and lowering and an automatic raising operation at the time of turning to automatically raise the working height from the working height to the non-working height in conjunction with the turning operation of the body.

There are the following operating conditions for the automatic ascent operation during turning. (1) Five seconds or more have passed since the lowering of the work equipment. This is to prevent the working machine from rising during the alignment.

(2) The steering wheel is switched from the straight traveling range (± １ ／ rotation) to the ascending range (about 1/2 rotation or more),
When the following conditional expression is satisfied. θ + (2 · P _n / P _max ) × Δθ ≧ θ _AL where θ: steering angle [deg] from the straight running state of the steering wheel P _n : brake pressure [kgf / cm ² ] P _max : maximum brake pressure (20 [Kgf / cm ² ]) Δθ: steering wheel operating speed [deg / 100msec] Δθ = (current steering wheel turning angle θ)-(handle turning angle before 100msec θ ') θ _AL : steering wheel turning angle for forcible lift-up operation _Specifically , it is assumed that θ _AL = 360 ° (+ 0.2 °, −0 °). This value does not work when turning, when an unfamiliar operator staggers when turning straight and turns the handle sharply, or when the handle is quickly returned after being picked up in a wet field or a rough field. This is an appropriate value for the setting, and is a value set as a preferable value by an experiment.

According to the conditional expression, when the steering wheel is in the range A (lift-up range), the larger the operation angle θ, the larger the operation speed Δθ, or the larger both,
It is easy to satisfy the conditional expression, and the automatic ascent operation during turning is activated quickly. Incidentally, even the most slow operating speed, if it exceeds the handle turning angle theta is theta _AL, turning automatic increase operation forcibly actuated. In addition, the higher the brake pressure, the faster the turning speed, so that the automatic ascent operation during turning is operated faster.

(3) When the work machine is lowered by the position lever 25 or the elevating lever 18 during the ascent while turning, the work machine does not descend. This is to prevent the work implement from lowering due to erroneous operation of the position lever 25 or the elevating lever 18. In particular, since the lifting lever 18 is provided near the handle 16, erroneous operation is likely to occur during turning.

FIG. 20 shows a general form of operation of a tractor in a paddy field or a field. A method of operating a tractor (agricultural traveling vehicle) of the present invention when making a headland turn at a portion M in the drawing will be described (see Table 1).

[0067]

[Table 1]

When approaching the headland, the operator operates the handle. Then, the work equipment rises,
The driving mode is switched to a preferable driving mode such as "Front wheel speed increasing four-wheel drive" or "Rear wheel two-wheel drive", and the brake is applied to the rear wheel inside the turning under a preferable braking force, so that the aircraft turns. During the turn, the optimal drive mode and rear wheel braking force are selected by the turning traveling control, so that the field is not roughened,
Moreover, quick turning can be performed.

When the turning is completed, the operator returns the steering wheel to the straight traveling range. Then, the driving mode is switched from the driving mode at the time of turning to the driving mode at the time of straight traveling (usually “front and rear wheels at a constant speed 4WD”), the brakes of the rear wheels are released, and the tractor is in a straight traveling state.

Subsequently, the operator operates the steering wheel as necessary to perform alignment, and then lowers the working machine with the position lever 25 or the lifting lever 18. Thereby, the work machine is lowered.

As described above, the operator only needs to operate the steering wheel from the start of the turn to the end of the turn, and all the other operations necessary for the turn are automatically performed, so that the steering is extremely simple. At the end of the turn, the operator lowers the work implement by operating it. This is an operation necessary to prevent the work implement from descending due to malfunction and to determine the timing of the work implement lowering at the operator's will. . If this work machine lowering operation is performed by the raising / lowering lever 18, only the fingertip is moved lightly, so that the operation can be performed while holding the handle with both hands, and there is no burden.

[0072]

As described above, the agricultural traveling vehicle according to the present invention is provided with the work implement elevating device, and the driving form of the front and rear wheels is at least a rear wheel two-wheel drive state, a front and rear wheel constant-speed four-wheel drive state. In an agricultural traveling vehicle that can be changed to the front wheel speed-up four-wheel drive state and configured to brake the turning inside rear wheel, the state of the soil is detected from the rotation ratio of the front and rear wheels, and the driving form of the front and rear wheels according to this By determining the braking force of the rear wheel on the inside of the turn, it is possible to perform a quick turn without damaging the soil. More specifically, when the front wheel is driven in the non-drive state, the braking force of the rear inner wheel is set to be weaker in the case of driving in the speed increasing state than in the case of the non-driving state, and furthermore, the same speed as the rear wheel is set. When the vehicle is driven by the vehicle, the braking force of the rear wheel on the inside of the turn is set to be weaker correspondingly, and a quick turn without soiling can be performed.

[Brief description of the drawings]

FIG. 1 is an overall side view of a tractor.

FIG. 2 is a diagram illustrating a main part of a tractor.

FIG. 3 is a transmission system diagram.

FIG. 4 is a diagram illustrating an operation unit of the rear wheel brake device.

FIG. 5 is a sectional view of a 4WD switching device.

FIG. 6 is a hydraulic circuit diagram.

FIG. 7 is a block diagram of a control device.

FIG. 8 is a first flowchart of a turning traveling control.

FIG. 9 is a second flowchart of the running control during turning.

FIG. 10 is a third flowchart of the running control during turning.

FIG. 11 is a third flowchart of the running control during turning.

FIG. 12 is a flowchart of a brake ON-duty correction process.

FIG. 13 is a time chart of the front wheel speed-up four-wheel drive output, the rotation ratio, and the braking force set value.

FIG. 14 is a graph showing a control rule for determining a brake pressure and a drive mode based on a variable rotation ratio.

FIG. 15 is a graph showing a control rule for determining a brake pressure based on a time from when the rear two-wheel drive is switched to when a variable rotation ratio is detected.

FIG. 16 is a graph showing a relationship between a brake pressure and a reference rotation ratio.

FIG. 17 is a graph showing a relationship between an oil temperature and a set time.

FIG. 18 is a graph showing a relationship between a brake ON-Duty and a detected current amount.

FIG. 19 is a view showing a steering angle;

FIG. 20 is a diagram showing a working form by a tractor.

[Explanation of symbols]

 Reference Signs List 1 tractor (agricultural traveling vehicle) 2 front wheel 3 rear wheel 16 handle 17 turning angle sensor 40 rear wheel brake device 44 4WD switching device 45 rear wheel rotation sensor 46 front wheel rotation sensor 61a 4WD solenoid 61b front wheel speed increasing solenoid 62a brake solenoid 70A traveling controller 71 CPU (rotation ratio calculation means, control means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-154939 (JP, A) JP-A-3-246152 (JP, A) JP-A-2-20463 (JP, A) JP-A-63-1988 247172 (JP, A) JP-A-8-282339 (JP, A) JP-A-2-64471 (JP, U) JP-A 52-75327 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60T 8/58 B60K 41/26 B62D 11/08

Claims (2)

(57) [Claims] 1. A drive unit for a front and rear wheel, a front and rear wheel constant-speed four-wheel drive state,
A front wheel rotation sensor for detecting a front wheel rotation speed and a rear wheel rotation sensor for detecting a rear wheel rotation speed in an agricultural traveling vehicle that can be changed to a front wheel speedup four- wheel drive state and configured to brake a turning inside rear wheel. A rotation ratio detecting means for calculating a rotation ratio between the front wheel and the rear wheel based on a result of the detection, and front and rear wheel drive during turning according to a rotation ratio between the front wheel and the rear wheel in a rear wheel two-wheel drive state after the work implement rises. An agricultural traveling vehicle comprising a form and control means for determining a braking force of a rear wheel inside a turn. 2. The control means according to claim 1, wherein the control means is provided on a work machine.
The rotation ratio between the front and rear wheels in the rear two-wheel drive
The front and rear wheel drive configuration during turning
Two-wheel drive state, front wheel speed-up drive state, front and rear wheel constant velocity drive state
Change the braking force of the rear wheel inside the
Agricultural vehicles, characterized in that the.