JPH1189346A - Four-wheel drive paddy field work vehicle - Google Patents

Abstract

(57) [Problem] A front wheel transmission is automatically switched to a speed increasing state during turning, and a side brake of a rear wheel on a turning center side is automatically operated to a braking side. In a wheel drive type paddy field working vehicle, the surface roughness during turning is suppressed. SOLUTION: As the steering angle of a front wheel 1 from a straight traveling position A increases, the braking force of a side brake 35 on the turning center side is changed to a stronger side, and the steering angle of the front wheel 1 from the straight traveling position A decreases. In other words, the braking force of the side brake 35 on the turning center side is changed to the weak side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling system in a four-wheel-drive paddy working vehicle such as a riding rice transplanter or a riding direct sowing machine.

[0002]

2. Description of the Related Art In a riding type rice transplanter, which is an example of a four-wheel drive type paddy field working vehicle, a standard condition in which the front and rear wheels are driven at substantially the same speed, and the front wheel is driven at a higher speed than the rear wheel It has been proposed to provide a front wheel transmission that can be freely switched to a speed-up state. As a result, when the planting process has been completed and the aircraft has reached the edge of the ridge, the front wheel transmission is automatically switched to the speed increasing state with the start of turning, and the right and left rear wheels are operated. It has been proposed that, of the side brakes that can be independently braked, the side brake on the turning center side is automatically operated to the braking side, so that a small turning can be performed at the ridge. I have.

[0003]

In a four-wheel drive paddy working vehicle, the front wheel transmission is switched to a speed increasing state as described above, and the side brake on the turning center side is operated to the braking side to turn. If this is done, a small turn can be performed, but on the contrary, the rice field will often be roughened. If the rice field at the edge of the ridge is roughened in this way, for example, when running on the edge of the ridge in a riding type rice transplanter and planting the seedlings, it is necessary to level the ridge sufficiently beforehand for seedlings. Planting may be difficult. The present invention provides a four-wheel-drive paddy working vehicle configured such that a front wheel transmission is automatically switched to a speed-up state when turning, and a side brake on the turning center side is automatically operated on the braking side. It is an object of the present invention to make it possible to make a turn while keeping the rice field as rough as possible.

[0004]

[Means for Solving the Problems]

[I] In the paddy field work vehicle, since the turning center side rear wheel of the front wheels and the rear wheels is closest to the turning center of the body, and the turning radius of the turning center side rear wheel is the smallest. When the front wheel transmission is switched to the speed increasing state, and the side brake on the turning center side is operated to the braking side, when turning,
In this state, the rear wheel on the turning center side turns sideways on the spot without moving, and the rear wheel on the turning center side is in a state of roughening the rice field.

According to the first aspect of the present invention, when turning, the front wheel transmission is switched to the speed increasing state, and among the side brakes capable of independently braking the right and left rear wheels, the side brake on the turning center side is used. As the steering angle of the front wheel from the straight running position increases, the braking force of the side brake on the turning center side changes to the strong side, and conversely, the steering angle of the front wheel from the straight running position Is smaller, the braking force of the side brake on the turning center side is changed to a weaker side.

If the braking force of the side brake on the turning center side is changed to the weaker side as the steering angle of the front wheel from the straight traveling position becomes smaller, the turning radius is particularly small. If it is not necessary to make a small turn, the turning center side rear wheel will rotate to some extent and move, and if the turning center side rear wheel does not move and turns sideways on the spot You can avoid such situations. Conversely, when it is necessary to make a small turn with a small turning radius, such as an increase in the steering angle of the front wheels from the straight traveling position, the front wheel transmission is switched to the speed increasing state during turning, and the turning center side is turned. Since the braking force of the side brake is changed to the strong side, a small turning with a small turning radius can be performed without any trouble.

[II] According to the feature of the second aspect, similar to the case of the first aspect, it has the "action" of the above-mentioned [I], and in addition to this, has the following "action". ing. According to the feature of claim 2, the side brake on the turning center side is repeatedly operated on the braking side and the braking release side at the time of turning, and the ratio of the operation time on the braking side to the operation time on the braking release side becomes larger. By performing the change operation, the braking force of the side brake on the turning center side is changed to the strong side. When the side brake on the turning center side is repeatedly operated on the braking side and the braking release side in this way, the rear wheel on the turning center side stops (or slightly rotates) and repeats the rotating movement during the turning. As a result, it is possible to further avoid a state in which the rear wheel on the turning center side turns sideways without moving.

[III] According to the feature of claim 3, similar to the case of claim 1 or 2, the "action" described in the above [I] or [II] is provided. Has "action". According to the feature of the third aspect, when the steering angle of the front wheel from the straight traveling position is increased, the degree of the operation of changing the braking force of the side brake on the turning center side to the strong side is not constant, and the steering force is changed from the straight traveling position of the front wheel. When the steering angle increases, the braking force of the side brake on the turning center side is not changed much to the strong side, or conversely, the braking force of the side brake on the turning center side is largely changed to the strong side. The degree to which the braking force is changed to the high side can be changed. Accordingly, the degree to which the braking force of the side brake on the turning center side is changed to the strong side in accordance with the state of the paddy field (hardness of mud on the field surface, depth of the cultivator, etc.), work form, or the like, is appropriately adjusted. Can be set and changed.

[IV] According to the feature of claim 4, similar to the case of claim 3, the "action" described in the above-mentioned [I], [II], and [III] is provided. It has various “actions”. If the mud on the rice field is soft, it means that a lot of water is present on the rice field, so even if the rice field is roughened with the mud being soft, the rough surface often disappears naturally. On the other hand, when the mud on the rice field is hard, it means that there is not much water on the rice field. Therefore, if the rice field is roughened while the mud is hard, the rough rice field may not disappear.

As a result, the degree of change in the braking force of the side brake on the turning center side to the strong side is increased as the mud on the paddy surface is softer. If the degree to which the braking force of the side brake is changed to the strong side is made small, especially when the mud on the rice field is hard, the rear wheel on the turning center side does not move and The situation of changing direction can be further avoided. On the other hand, when the mud on the rice field is soft, a small turning radius with a small turning radius can be performed without hindrance to roughening of the rice field.

[V] According to the features of claim 5, claim 3
As in the case of (1), the "action" described in the preceding section [I] [II] [III] is provided, and in addition to this, the following "action" is provided. In the paddy field work vehicle, the front and rear wheels sink from the surface of the rice field, and the front wheels and the rear wheels are in contact with the cultivator below the surface of the ground and the vehicle travels. The resistance applied to the fuselage will be large. With this configuration, as in the feature of claim 5, when the depth of the cultivator is deeper, the degree of the operation of changing the braking force of the side brake on the turning center side to the strong side is increased,
In addition to switching the front wheel transmission to the speed increasing state,
By strongly operating the side brake on the turning center side toward the braking side, it is possible to avoid a situation in which the turning radius increases due to the resistance applied to the aircraft body even though the steering angle of the front wheel from the straight traveling position is large.

[VI] According to the feature of claim 6, similar to the case of claim 3, the "action" described in the above [I], [II], and [III] is provided. It has various “actions”. Generally, there is a tendency that the higher the traveling speed of the body, the larger the turning radius due to the centrifugal force at the time of turning. With this configuration, as the traveling speed of the vehicle body increases, the degree of the operation of changing the braking force of the side brake on the turning center side to the high side increases as the traveling speed of the aircraft increases, so that the front wheel transmission increases. In addition to switching to the high speed state, the side brake on the turning center side is strongly operated to the braking side, so that the steering angle from the straight ahead position of the front wheel is large, but turning due to centrifugal force during turning The situation where the radius becomes large can be avoided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a seedling planting device 3 is provided with a link mechanism 4 and a rear portion of a body supported by a pair of left and right front wheels 1 and a pair of left and right rear wheels 2 which can be steered. A riding type rice transplanter, which is an example of a four-wheel drive type paddy working vehicle, is connected by a hydraulic cylinder 5 so as to be able to move up and down freely.

Next, the traveling transmission system of the riding type rice transplanter will be described. As shown in FIG. 2, the power of an engine 6 disposed at the front of the body is transmitted to a transmission case 9 at the rear of the body via a main clutch 7 and a transmission shaft 8. The power transmitted to the transmission case 9 is transmitted to a hydrostatic continuously variable transmission 10 capable of steplessly shifting the gears forward and backward, and a subtransmission 11 capable of being variablely shifted to a high and low gear.
And transmitted to the right and left rear wheels 2 via the rear wheel differential device 12. The power branched immediately before the rear wheel differential device 12 is transmitted to the right and left front wheels 1 via a hydraulically operated front wheel transmission device 13, a transmission shaft 14, and a front wheel differential device 15.

Next, the front wheel transmission 13 will be described. As shown in FIG. 2, a standard gear 17 and a speed-increasing gear 18 are fitted on a support shaft 16 connected to the transmission shaft 14 so as to be rotatable relative to each other, and the power branched immediately before the rear wheel differential device 12 is transmitted. The power is transmitted to the standard gear 17 and the speed increasing gear 18 via the shaft 21. A standard clutch 19 of a friction multi-plate type and a hydraulic operation type is provided between the support shaft 16 and the standard gear 17, and a friction multi-plate type and a hydraulic operation type of speed increase between the support shaft 16 and the speed increasing gear 18. A clutch 20 is provided. Accordingly, when the standard clutch 19 is operated to the transmission side, power is transmitted to the front wheel differential device 15 in a standard state in which the front wheel 1 and the rear wheel 2 are driven at substantially the same speed.
When the speed increasing clutch 20 is operated to the transmission side, the front wheel differential device 1 is driven in a speed increasing state in which the front wheels 1 are driven at a higher speed than the rear wheels 2.
Power is transmitted to 5.

As shown in FIG. 2, a pair of left and right side brakes 35 capable of independently braking the right and left rear wheels 2 and a pair of left and right side brakes capable of operating the side brakes 35 independently on the braking side. A pedal 36 is provided. Single-acting operation cylinders 33R and 33L are provided, which can operate the right and left side brakes 35 on the braking side. The operation cylinders 33R and 33L are extended by supplying hydraulic oil to the operation cylinders 33R and 33L. Then, the side brake 35 is operated to the braking side, and by discharging the hydraulic oil of the operation cylinders 33R and 33L,
The operation cylinders 33R and 33L contract, and the side brake 35 is operated to the brake release side.

Next, the structure of the hydraulic circuit of the front wheel transmission 13 and the right and left operation cylinders 33R and 33L will be described. As shown in FIG. 3, hydraulic oil from a pump 24 is supplied to the front wheel transmission 13 via an electromagnetic switching valve 27 and oil passages 26 and 29. In the electromagnetic switching valve 27,
Hydraulic oil is supplied to the standard clutch 19 to
And a speed increasing position 27B for supplying hydraulic oil to the speed increasing clutch 20 to operate the speed increasing clutch 20 on the transmission side. It is biased to position 27A.

An oil passage 30 branches from an oil passage 29 connecting the electromagnetic switching valve 27 and the speed increasing clutch 20.
Are connected to the right and left operation cylinders 33R, 33L via the electromagnetic operation valve 31 and the electromagnetic switching valve 32. In the solenoid operated valve 31, right and left operation cylinders 33R,
A brake position 31A for supplying hydraulic oil to 33L and a brake release position 31B for discharging hydraulic oil from the right and left operation cylinders 33R and 33L are provided, and the electromagnetic operation valve 31 is biased by a spring to the brake release position 31B. Have been.

In the electromagnetic switching valve 32, hydraulic oil is supplied to the right operating cylinder 33R and hydraulic oil is discharged from the left operating cylinder 33L.
The left braking position 32L for discharging the hydraulic oil of R and supplying the hydraulic oil to the left operating cylinder 33L, the right and left operating cylinders 3
A brake release position 32N for discharging the 3R and 33L hydraulic oil is provided, and the electromagnetic switching valve 32 is biased to the brake release position 32N by a spring.

Next, the raising and lowering control of the seedling planting apparatus 3 during planting traveling will be described. As shown in FIGS. 3 and 1, the rear portion of the sensor float 34 provided at the lower left and right center of the seedling planting device 3 is supported so as to be able to swing up and down around a horizontal axis P1. The detection arm 37 a of the provided potentiometer 37 and the front part of the sensor float 34 are connected by a link rod 38. Spring 3
9, the front part of the sensor float 34 is urged downward via the detection arm 37a and the link rod 38. The detection value of the potentiometer 37 of the sensor float 34 is input to the control device 42, and the detection value of the potentiometer 37 indicates the vertical distance between the front part of the sensor float 34 and the seedling planting device 3 (potentiometer 37). .

Therefore, when the seedling planting device 3 moves up and down while the sensor float 34 follows the ground surface as the aircraft advances, the sensor float 34 moves around the horizontal axis P1.
Is moved up and down, the control device 42 operates the control valve 28 so that the detection value of the potentiometer 37 becomes the set value C (so that the detection arm 37a of the potentiometer 37 becomes the posture of the set value C). Then, the hydraulic cylinder 5 is operated to expand and contract, and the seedling planting apparatus 3 is automatically moved up and down. Thereby, the seedling planting apparatus 3 is maintained at the set height from the rice field, and the planting depth of the seedlings by the seedling planting apparatus 3 is maintained at the set value.

Next, the change of the control sensitivity in the above-mentioned elevation control will be described. As shown in FIG. 3, a sensitivity setting dial 41 that can be operated artificially is provided on the control unit of the aircraft, and the set value of the sensitivity setting dial 41 is set in the control device 4.
2 has been entered. In this case, if the driver determines that the mud on the rice field is hard, the sensitivity setting dial 41 may be operated to the insensitive side, and if the driver determines that the mud on the rice field is soft, the sensitivity setting dial 41 is moved to the sensitive side. You just need to do it.

When the sensitivity setting dial 41 is operated to the insensitive side, the set value C shown in FIG. 3 is automatically changed to the upward insensitive side, and the detection value of the potentiometer 37 is changed to the upward set value. C (so that the detection arm 37a of the potentiometer 37 has the upward set value C), the seedling planting apparatus 3 is automatically moved up and down. At this upward set value C, the posture of the sensor float 34 is on the front upward side, so that the contact area of the sensor float 34 on the rice field surface is reduced, the spring 39 is compressed, and the urging force of the spring 39 is increased. Float 34
Is changed to the insensitive side (the control sensitivity of the elevation control).

Conversely, when the sensitivity setting dial 41 is operated to the sensitive side, the set value C shown in FIG. 3 is automatically changed to the downward sensitive side, and the detection value of the potentiometer 37 is changed to the downward set value C. (So that the detection arm 37a of the potentiometer 37 is in the posture of the downward set value C), the seedling planting apparatus 3 is automatically moved up and down. At this downward set value C, the attitude of the sensor float 34 is on the forward and downward side, so that the contact area of the sensor float 34 to the rice paddle surface is increased, the spring 39 is extended, and the urging force of the spring 39 is weakened. The sensitivity of the float 34 to follow the ground surface (the control sensitivity of the elevation control) is changed to the sensitive side.

Next, a description will be given of a state of turning on a ridge. As shown in FIGS. 2 and 3, a pitman arm 22 for steering the front wheel 1 is provided, and a potentiometer 23 for detecting right and left steering angles of the pitman arm 22 from the straight traveling position A is provided. , The detection value of the potentiometer 23 is input to the control device 42. As a result, when one planting process is completed and the aircraft reaches the ridge, the driver greatly raises the seedling planting device 3 to operate the planting plant shown in FIG.
Then, the front wheel 1 (pitman arm 22) is steered right or left from the straight traveling position A by the steering handle 40 shown in FIG. In this state, the front wheel transmission 13 is still in the standard state, and the right and left side brakes 35 are not operated on the braking side.

In this case, the pitman arm 22 is steered from the straight traveling position A to the right, for example, to the right first set angle A.
When the number reaches 1, the control device 42 operates the electromagnetic switching valve 27 from the standard position 27A to the speed increasing position 27B, and switches the front wheel transmission 13 from the standard state to the speed increasing state, as shown in FIG. At the right and left first set angles A1, the right and left side brakes 35 have not yet been operated to the braking side.

Next, when the pitman arm 22 is further steered to the right from the first set angle A1 on the right, FIG.
As shown in the figure, the electromagnetic switching valve 32 is operated from the braking release position 32N to the right braking position 32R by the control device 42, and the electromagnetic operation valve 31 is moved to the braking position 31A and the braking release position 31B.
Are repeatedly and alternately operated. In this case, FIG.
As shown in the figure, one cycle T in which the solenoid operated valve 31 is operated to the braking position 31A and the braking release position 31B is set to be relatively long, and the solenoid operated valve 31 is moved to the braking position 31.
A and the brake release position 31B are alternately and repeatedly operated at a relatively low speed.

Therefore, the solenoid operated valve 31 is moved to the braking position 31A.
Is operated, the operating oil is supplied to the right operating cylinder 33R on the turning center side, and the right side brake 3
5 is operated to the braking side and the solenoid operated valve 31 is operated to the braking release position 31B, the hydraulic oil of the right operating cylinder 33R, which is the turning center side, is discharged, and the right side brake 35 is released. Operated to the side. As a result, during turning, the rear wheel 2 on the turning center side stops (or slightly rotates).
(The state in which the side brake 35 on the turning center side is operated to the braking side) and the rotational movement (the state in which the side brake 35 on the turning center side is operated on the braking release side) is repeated. .

As shown in FIG. 5, the cycle T of the solenoid operated valve 31
In the first embodiment, the first operation time T1 during which the electromagnetic operation valve 31 is operated at the braking position 31A and the second operation time T2 during which the electromagnetic operation valve 31 is operated at the braking release position 31B are configured to be freely changeable. The ratio of the operation time T1 (braking ratio (T1 / T) is configured to be changeable. As a result, the pitman arm 22 is moved from the right first set angle A1 as shown by the braking characteristic B1 shown by the solid line in FIG. When the steering operation is further started to the right, as the steering angle of the pitman arm 22 increases from the first set angle A1 on the right, the braking ratio (T1 / T) is changed to be increased in proportion to the steering angle. When the steering angle of the pitman arm 22 reaches the right second set angle A2 (the first operation time T1 becomes longer and the second operation time T2 becomes shorter), the braking ratio (T1 / T) is obtained.
Is held at the set value D.

This set value D is not "1.0". Even if the braking ratio (T1 / T) reaches the set value D, the second set shown in FIG.
The operation time T2 does not become “0”. Accordingly, when the pitman arm 22 exceeds the right or left second set angle A2,
Even if the vehicle is steered to the right or left and turned, the rear wheel 2 on the turning center side stops (or slightly rotates) during this turning (the side brake 35 on the turning center side is operated to the braking side). State), and rotational movement (a state in which the side brake 35 on the turning center side is operated to the brake release side).

As shown in FIG. 3, the sensitivity setting dial 41
If the driver determines that the mud on the rice field is hard as described above, the driver operates the sensitivity setting dial 41 to the insensitive side, and the driver sets the mud on the rice field. Is determined to be soft, the driver operates the sensitivity setting dial 41 to the sensitive side. This allows
As the sensitivity setting dial 41 is operated on the insensitive side (the side where the mud on the rice field is hard), the braking characteristic B1 indicated by the solid line as shown in FIG.
However, as shown in the braking characteristic B2 of the one-dot chain line, the operation is changed to a small one (the degree of change operation to the strong side is small), and accordingly, the right and left second set angles A2 are changed. Is also changed to the large side.

Conversely, as the sensitivity setting dial 41 is operated to the more sensitive side (the side where the mud on the paddy surface is softer), the braking characteristic B1 indicated by the solid line as shown in FIG. Is changed to a large one (the degree of change operation to the strong side is large), and accordingly, the right and left second set angles A2 are also changed to the small side. In this case, the sensitivity setting dial 41 and the braking characteristics B1,
B2 and B3, the braking characteristics B1 and B shown in FIG.
A change switch (not shown) that can arbitrarily change the inclination of B2 and B3 is also provided.

[First Embodiment of the Invention] FIGS. 1 and 3
As shown in the figure, a potentiometer 43 for detecting the vertical angle of the link mechanism 4 with respect to the airframe is provided at the base of the link mechanism 4 so that the seedling planting apparatus 3 is automatically maintained at the set height from the rice field as described above. During the vertical lifting operation,
The depth of the cultivator (the depth from the rice field to the cultivator where the front wheel 1 and the rear wheel 2 sink and contact the ground) can be detected by the detection value of the potentiometer 43.

As a result, as the depth of the cultivator decreases, the braking characteristic B1 indicated by the solid line is changed to the one having a smaller inclination as indicated by the braking characteristic B2 indicated by the alternate long and short dash line as shown in FIG. The degree of the change operation is small), the right and left second set angles A2 are changed to the large side, and the deeper the depth of the cultivator, the more the two-point braking characteristic B1 as shown in FIG. As shown by the braking characteristic B3 of the dashed line, the operation is changed to one with a large inclination (the degree of change operation to the strong side is large), and the right and left second set angles A2 are changed to the small side. You may comprise.

[Second Alternative Embodiment of the Invention] As shown in FIG. 3, a speed sensor 44 for detecting the running speed of the body from the rotation speed of the rear wheel 2 is provided.
As shown in FIG. 4, the braking characteristic B1 of the solid line is changed to the one having a small inclination as indicated by the braking characteristic B2 of the one-dot chain line (the degree of the change operation to the strong side is small), and the right and left As the set angle A2 is changed to the large side and the traveling speed of the aircraft is higher, the braking characteristic B indicated by the solid line as shown in FIG.
As shown in the braking characteristic B3 of the two-dot chain line, 1 is operated to change to the one with a large inclination (the degree of operation to change to the strong side is large), and the right and left second set angles A2 are changed to the small side It may be configured to be operated.

In the configuration shown in FIGS. 2 and 4, the pitman arm 22 is moved from the straight traveling position A to right and left third set angles (not shown) on the straight traveling position A side of the right and left first set angles A1. ), The side brake 35 on the turning center side starts to be operated to the braking side. Next, when the pitman arm 22 reaches the first set angle A1, the front wheel transmission 13
Is switched from the standard state to the speed increasing state, and the braking characteristics B1,
Based on B2 and B3, the braking ratio (T1 / T) may be changed to a larger one.

[0037]

According to the first aspect of the present invention, the front wheel transmission is automatically switched to the speed increasing state when turning, and the side brake on the turning center side is automatically operated on the braking side. In a four-wheel drive type paddy working vehicle, the braking force of the side brake on the turning center side is changed to a weaker side as the steering angle of the front wheel from the straight traveling position becomes smaller, and particularly the front wheel When the steering angle from the straight traveling position is small, roughening of the rice field by the rear wheel on the turning center side can be suppressed, and the traveling performance of a four-wheel drive type paddy working vehicle can be improved. Was. In this case, if it is necessary to make a small turn with a small turning radius, the front wheel transmission is switched to an increased speed state during the turn,
Since the braking force of the side brake on the turning center side is changed to the strong side and a small turning with a small turning radius can be performed without any trouble, the running performance in this aspect is not reduced.

According to the features of the second aspect, the "effect of the invention" of the first aspect is provided similarly to the case of the first aspect. In addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to the second aspect of the invention, the side brake on the turning center side is repeatedly operated on the braking side and the braking release side during turning, and the rear wheel on the turning center side stops (or slightly rotates) and moves while rotating. By configuring to repeat, the roughening of the rice field due to turning sideways on the spot without moving the rear wheel on the turning center side can be further avoided, and the four-wheel drive type paddy field The running performance of the work vehicle was further improved.

According to the feature of claim 3, claim 1 or 2
"Effects of the Invention" of Claim 1 or 2 as in the case of
In addition to this “effect of the invention”, the following “effect of the invention” is provided. According to the feature of claim 3, the braking force of the side brake on the turning center side is changed to the strong side in accordance with the state of the paddy field (hardness of mud on the rice field, depth of the cultivator, etc.), work form, and the like. Since the degree can be set and changed to an appropriate level, it is possible to turn appropriately while suppressing roughening of the rice field, and it is possible to further improve the traveling performance of the four-wheel drive type paddy working vehicle Was.

According to the feature of the fourth aspect, the "effect of the invention" of the third aspect is provided similarly to the case of the third aspect, and in addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to the feature of claim 4, by changing the degree of the operation of changing the braking force of the side brake on the turning center side to the strong side in accordance with the characteristic of the roughness due to the hardness of the mud on the paddy surface, Thus, roughening of the rice field due to the rear wheel on the turning center side can be further suppressed, and the traveling performance of the four-wheel drive type paddy working vehicle can be further improved. In this case, in a state where the mud on the rice field is soft, a small turning radius with a small turning radius can be performed without hindrance while roughening the rice field, so that the running performance on this surface is not reduced.

According to the feature of claim 5, the "effect of the invention" of the above-mentioned claim 3 is provided similarly to the case of the claim 3, and in addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to the feature of the fifth aspect, the degree to which the braking force of the side brake on the turning center side is changed to the strong side is changed according to the depth of the tillage, so that the depth of the tillage is changed. Irrespective of the above, the turning radius can be properly avoided by avoiding the situation where the turning radius becomes large due to the resistance applied to the airframe, so that the traveling performance of the four-wheel drive type paddy working vehicle can be further improved.

According to the feature of claim 6, the "effect of the invention" of claim 3 is provided as in the case of claim 3, and in addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to the feature of the sixth aspect, the degree to which the braking force of the side brake on the turning center side is changed to the strong side is changed in accordance with the traveling speed of the aircraft, thereby being related to the traveling speed of the aircraft. In addition, since the turning radius can be appropriately prevented by avoiding a situation in which the turning radius is increased by the centrifugal force at the time of turning, the traveling performance of the four-wheel drive type paddy working vehicle can be further improved.

[Brief description of the drawings]

FIG. 1 is an overall side view of a riding rice transplanter.

FIG. 2 is a schematic diagram showing a traveling power transmission system.

FIG. 3 is a diagram showing a hydraulic circuit of a front wheel transmission and a side brake.

FIG. 4 is a diagram showing a relationship between a steering angle of a pitman arm from a straight traveling position and a braking ratio of a side brake on a turning center side.

FIG. 5 is a diagram showing an operation state of a solenoid operated valve of a side brake.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front wheel 2 Rear wheel 13 Front wheel transmission 23 Steering angle detecting means 35 Side brake A Straight ahead position T1 Operation time on braking side T2 Operation time on braking release side

Claims (6)

[Claims] A front wheel transmission capable of switching between a standard state in which the front wheels and the rear wheels are driven at substantially the same speed and an increased state in which the front wheels are driven at a higher speed than the rear wheels; A side brake capable of independently braking the wheels, and steering angle detection means for detecting a steering angle of the front wheels from a straight-ahead position; when the front wheels are steered from a straight-ahead position, the front-wheel transmission is provided. A first control means for switching from a standard state to a speed increasing state and operating the side brake on the turning center side to the braking side, and the steering angle on the turning center side increases as the steering angle of the front wheel from the straight traveling position increases. Change the braking force of the side brake to the strong side, and as the steering angle of the front wheels from the straight running position decreases,
A four-wheel drive paddy working vehicle comprising: a second control means for changing the braking force of the side brake on the turning center side to a weaker side. 2. The brake control device according to claim 1, wherein the second control means repeatedly operates the side brake on the turning center side to the braking side and the braking release side, so that as the steering angle of the front wheel from the straight traveling position increases, the braking control on the braking release side increases. Change the ratio of the operation time of the braking side to the operation time to the large side to change the braking force to the high side, and the smaller the steering angle of the front wheel from the straight traveling position, the smaller the operation time of the braking release side to the braking side. The four-wheel drive type paddy working vehicle according to claim 1, wherein the operation time ratio is changed to a small side to change the braking force to a weak side. 3. As the steering angle of the front wheel from the straight running position is increased by the second control means, when the braking force of the side brake on the turning center side is changed to the strong side, the turning force of the side brake on the turning center side is increased. 2. A change means capable of changing the degree to which the braking force is changed to the high side, the change being large or small.
Or a four-wheel-drive paddy working vehicle according to 2. 4. The changing means, wherein the softer the mud on the rice field, the greater the degree to which the braking force of the side brake on the turning center side is changed to the stronger side, and the harder the mud on the rice field,
4. The system according to claim 3, wherein the degree to which the braking force of the side brake on the turning center side is changed to the strong side is reduced.
The described four-wheel drive paddy field working vehicle. 5. The degree of operation of changing the braking force of the side brake on the turning center side to the higher side as the depth of the cultivator increases, and the smaller the depth of the cultivator, the lower the depth of the cultivator. 4. The four-wheel-drive paddy working vehicle according to claim 3, wherein the degree to which the braking force of the side brake on the turning center side is changed to the strong side is reduced. 6. The method according to claim 1, wherein the higher the traveling speed of the body, the greater the degree to which the braking force of the side brake on the turning center side is changed to the higher side, and the lower the traveling speed of the body, the greater the turning center. 4. The four-wheel drive paddy field working vehicle according to claim 3, wherein the degree to which the braking force of the side brake is changed to the high side is reduced.