JP3146068B2 - Work vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a turning operation in a working vehicle such as an agricultural tractor or a riding rice transplanter.

[0002]

2. Description of the Related Art Some agricultural tractors, which are an example of a working vehicle, include a pair of left and right side brakes capable of independently braking left and right rear wheels. By depressing one of the side brake pedals, one of the side brakes is operated to the braking side. Thereby, by turning the rear center wheel on the turning center during the turning operation, it is possible to make a small turn around the rear wheel on the turning center side.

In recent years, power is transmitted to the front wheels so that the front wheels and the rear wheels are driven at substantially the same speed, and power is transmitted to the front wheels so that the front wheels are driven at a higher speed than the rear wheels. When the front wheels are steered to the right or left from the straight ahead position by switching the front wheel transmission to the speed increasing state, the front wheel transmission is switched to the speed increasing state in conjunction with the steering operation, and the turning center is turned. There is an agricultural tractor configured such that the side brake on the side is operated to the braking side (for example, Japanese Unexamined Patent Publication No.
-243429). Thereby, the small turning can be smoothly performed by the speed increasing action of the front wheels and the braking action to the rear wheels on the turning center side.

[0004]

With the above configuration,
When the front wheels are steered to the right or left from the straight running position, the front wheel transmission is switched to the speed-up state, and only one state appears, in which the side brake on the turning center side is operated to the braking side. On the other hand, the work place and work where the work vehicle travels often change in various states depending on the situation. Therefore, as described above, the front wheel transmission is switched to the speed increasing state, and the side brake on the turning center side is operated. Only one state appears to be operated on the braking side,
A work site that changes to various states such as a soft field or a hard field, work when a working device (for example, a rotary tilling device, a plow or a pasture working machine, etc.) is attached to a rear portion of a work vehicle,
It is not possible to sufficiently cope with work when a work device (for example, a snowplow or a front loader, etc.) is attached to the front of the work vehicle, making it difficult to perform appropriate turning according to the work place and each state of work. May be.

The present invention provides a work vehicle having two turning functions, a front wheel transmission and a side brake, in various ways while avoiding a state in which the rear wheel on the turning center side drags the ground and roughens the ground. It is an object of the present invention to provide a configuration in which a proper turning can be performed in accordance with a changing work place and each state of work by various work devices.

[0006]

The feature of the present invention resides in the construction of a working vehicle as follows. [1] In a standard state in which power is transmitted to the front wheels so that the front wheels and the rear wheels are driven at substantially the same speed, and in an increased state in which power is transmitted to the front wheels so that the front wheels are driven at a higher speed than the rear wheel. A switchable front wheel transmission, a pair of left and right side brakes capable of braking a selected one of a pair of left and right rear wheels, and the side brakes can be operated on the braking side until the rear wheels stop substantially until the rear wheels stop. A pair of left and right side brake pedals, first operating means for switching the front wheel transmission to a speed increasing state in conjunction with the steering operation when the front wheels are steered to the right or left from the straight traveling position, and the front wheels When the vehicle is steered to the right or to the left from the straight-ahead position, a second operating means for operating the side brake on the turning center side to the braking side in conjunction with the steering operation is provided. Front wheel changes in conjunction with steering to the left First setting means for setting an operation state in which the speed device is switched to an increased speed state, and a stop state in which the speed device is not switched, and a turning center side on the turning center side in conjunction with a steering operation of the front wheels from the straight traveling position to the right or left. The maximum braking force at the end of the operation stroke when the side brake is operated toward the braking side is the maximum braking force in the weak braking state where the rear wheel does not stop almost in the stopped state, and in the forced movement state where the braking force is stronger than the weak braking state . Any one set
And second setting means capable of selectively switching to a braking force .

[0007] [2] In the configuration of [1], so as to set the operating state and a stopped state based on the running speed condition of the aircraft, have configured the first setting means.

[0008] [3] In the configuration of the [2], as the traveling speed state of the aircraft becomes possible to set the operating state and a slow state, you have configured the first setting means.

[0009] [4] In the configuration of the [2] or [3], the running speed condition of the aircraft so that the high speed state is a stopped state is forcibly set, there constitute a first setting means .

[5] Power from the engine is transmitted through the main transmission and the auxiliary transmission.
Work vehicle configured to transmit power to the rear and front wheels
In the standard state of transmitting power to the front wheels so that the front wheels and the rear wheels are driven at substantially the same speed, and in the speed increasing state of transmitting power to the front wheels so that the front wheels are driven at a higher speed than the rear wheels A front-wheel transmission that can be freely switched, a pair of left and right side brakes that can brake a selected one of a pair of left and right rear wheels, and a stop in which the rear wheels substantially stop the side brakes
A pair of left and right side brakes that can be operated to the braking side until the state
A pedal, first operation means for switching the front wheel transmission to a speed increasing state in conjunction with the steering operation when the front wheels are steered to the right or left from the straight ahead position; When the steering operation is performed from right to left or from left to right, there is provided second operating means for operating the side brake on the turning center side to the braking side in conjunction with the steering operation, and the right or left from the straight traveling position of the front wheels. First setting means for setting an operating state in which the front wheel transmission is switched to a speed increasing state in conjunction with a steering operation to the left, and a stop state in which the switching operation is not performed; and a right or left direction from the straight traveling position of the front wheels. End of the operation stroke when the side brake on the turning center side is operated to the braking side in conjunction with the steering operation of
The maximum braking force at the end is selected as one of a set braking force of a weak braking state in which the rear wheel is not substantially stopped and a forced braking state in which the braking force is stronger than the weak braking state.
Switchable second setting means, further comprising:
2 Switching between the weak braking state and the forced operation by the setting means
Means that the sub-transmission lever operating the sub-transmission is in the low-speed position
The sub-shift lever is in the high-speed position
Switching to the forced operation state is not
It is configured to work .

[0011]

[6] In the configuration of [5] , the second setting means is configured so that the braking force is forcibly changed to zero when the traveling speed state of the body is high.

[0013]

[7] In the configuration of [5] , the first setting means is configured so that the stop state is forcibly set when the traveling speed state of the aircraft is a high speed state, and the braking force is reduced. The second setting means is configured so as to be forcibly changed to zero.

[0015]

According to the first aspect of the present invention, when the front wheels are steered to the right or left from the straight traveling position, the front wheel transmission is switched to the speed increasing state, and the side brake on the turning center side is operated. Operated on the braking side. In this case, even if the work place where the work vehicle runs and the state of the work change, the front wheel transmission is operated and stopped so as to adapt to the work place that variously changes and the state of work by various work devices. End of operation stroke when setting to the state or when the side brake on the turning center side is operated to the braking side
Or you can set by selecting one of strong force dynamic state of the braking force than the maximum braking force weak braking state and a weak braking state in.

According to the first aspect of the present invention, at the end of the operation stroke when the side brake on the turning center side is operated to the braking side.
Maximum braking force of the, can be set to a weak braking state.
In this weak braking state, the rear wheel does not stop at the turning center side (weak braking state) but is in a state in which the rear wheel rotates to some extent. Therefore, when the front wheel is steered to the right or left from the straight traveling position, By operating the center side brake in a weak braking state, it is possible to suppress a situation in which the rear wheel on the turning center side drags the ground and roughens the ground. Further, according to the first aspect of the present invention, when the side brake on the turning center side is operated to the braking side, it is determined at the end of the operation stroke.
By setting the large braking force to the forced movement state, it is possible to perform a small turning with a smaller turning radius. Further, this work vehicle is provided with a pair of left and right side brakes that can independently operate the left and right rear wheels and a pair of left and right side brake pedals that can be manually operated, so that the braking force is insufficient. In this case, if the side brake pedal is strongly depressed, the side brake can be operated on the braking side until the rear wheel is substantially stopped.

[II] According to the feature of the second aspect, similar to the case of the first aspect, the "action" described in the above [I] is provided, and in addition, the following "action" is provided. ing. When setting the front wheel transmission in the operating state and the stopped state, the setting may be performed not only based on the work place and the state of the work, but also based on the traveling speed state of the aircraft. According to the feature of the second aspect, the front wheel transmission can be set based on the traveling speed state of the aircraft even if the operator does not artificially set the front wheel transmission to the operating state and the stop state based on the traveling speed state of the aircraft. It is automatically set to the operation state and the stop state.

[III] According to the feature of claim 3, the "action" described in the above [II] is provided similarly to the case of claim 2, and in addition, the following "action" is provided. ing. When the traveling speed state of the aircraft is low, the traveling speed of the aircraft when the front wheels are steered to the right or left from the straight ahead position also becomes low, so even if the front wheel transmission is in the operating state, it is in the stopped state. Even so,
The turn can be performed without any trouble. According to the third aspect of the present invention, when the traveling speed state of the body is low, the front wheel transmission can be set to the operating state. The front wheel transmission can be set to an active state and a stopped state to adapt to the state.

[IV] According to the feature of claim 4, similar to the case of claim 2 or 3, the "action" described in the above [II] [III] is provided. Has "action".
When the traveling speed state of the aircraft is high speed, the traveling speed of the aircraft when the front wheels are steered to the right or left from the straight ahead position also becomes high. The body is in a state of making a small turn at high speed, which is not preferable in terms of riding comfort. According to the features of claim 4,
When the traveling speed state of the body is a high speed state, the front wheel transmission is forcibly set to the stop state, so that the state in which the body makes a small turn at high speed during the turning operation is avoided.

[V] According to the feature of claim 5, similar to the case of claim 1, the "action" described in the above [I] is provided, and in addition, the following "action" is provided. ing. According to the feature of claim 5, the weak braking state by the second setting means and the cutoff of the forcible movement are set.
Change the operating position of the sub-transmission lever that operates the sub-transmission.
The sub-transmission lever is set to the low speed position.
The above change is permitted while the
Forced operation when the lever is operated to the high speed position
Switching to is disabled. Accordingly
The front wheel is steered to the right or left from the straight position
When the side brake on the turning center side of the is operated to the braking side
The braking force of the
State can be changed and configuration for that
Means for detecting switching of the traveling speed by using the auxiliary transmission lever
The structure can be easily configured by utilizing the above.

[0021]

[VI] According to the feature of claim 6, the same as in claim 5,
The “action” described in [V] is provided, and in addition, the following “action” is provided. When the traveling speed of the aircraft is high, the traveling speed of the aircraft when the front wheels are steered to the right or left from the straight ahead position also increases, so the side brake on the turning center side moves to the braking side during the turning operation. When operated, the aircraft is in a state of making a small turn at high speed, which is not preferable in terms of riding comfort. According to the feature of claim 6 , when the traveling speed state of the aircraft is a high speed state, the braking force when the side brake on the turning center side is operated to the braking side is forcibly zero, that is, the side on the turning center side is forced. Since the brake is not operated on the braking side, a state in which the aircraft makes a small turn at high speed during the turn operation is avoided.

[0023]

[0024]

[VII] According to the feature of claim 7, the same as in claim 5,
The “action” described in [V] is provided, and in addition, the following “action” is provided. When the traveling speed state of the aircraft is high speed, the traveling speed of the aircraft when the front wheels are steered to the right or left from the straight ahead position also becomes high. The body is in a state of making a small turn at high speed, which is not preferable in terms of riding comfort. Similarly, when the traveling speed state of the aircraft is high speed, if the side brake on the turning center side is operated to the braking side during the turning operation, the aircraft will make a small turn at high speed, and the Is not preferred.

According to a seventh aspect of the present invention, when the traveling speed of the body is high, the front wheel transmission is forcibly set to the stop state, and the side brake on the turning center side is operated to the braking side. In this case, the braking force at that time is forcibly zero, that is, the side brake on the turning center side is not operated on the braking side, so that the state in which the aircraft makes a small turn at high speed during the turning operation is avoided.

[0027]

According to the first aspect of the present invention, the front wheel transmission is switched to the speed increasing state during the turning operation by providing the two turning functions of the front wheel transmission and the side brake, and the side brake on the turning center side is operated. In a work vehicle configured to be operated on the braking side, the front wheel transmission can be set to the operating state and the stopped state, and the maximum braking force at the end of the operation stroke when the side brake on the turning center side is operated on the braking side Can be changed to a weak braking state and a forced movement state in which the braking force is stronger than the weak braking state, so that appropriate turning adapted to various states of work at variously changing work sites and various working devices. And the turning performance of the work vehicle could be improved. According to the feature of the first aspect, in a work vehicle having two turning functions of a front wheel transmission and a side brake, the turning center side rear wheel is rotated to some extent in a weak braking state, and the turning center side rear wheel is rotated. Can be suppressed from dragging the ground and ruining the ground. In other words, in a field that is repeatedly used, if the roughness of the field in a place where frequent turning is performed becomes large, it becomes difficult to perform the turning operation itself accurately, or it becomes difficult to perform the process after turning as initial. However, in the present invention, it is possible to suppress the roughening of the field as much as possible by using the configuration capable of the weak braking state as described above, so that the small turning performance of the work vehicle can be improved. According to the first aspect of the present invention, when the side brake on the turning center side is operated to the braking side, the operation stroke at the end of the operation stroke is reduced.
By setting the maximum braking force in the forced movement state, it is possible to perform a small turning with a smaller turning radius, and it is possible to improve the turning performance of the work vehicle.
In other words, if the degree of the weak braking is set to a certain value, there is a possibility that a considerable difference occurs in the manner of applying the weak braking depending on the unevenness of the field to be used and the degree of hardness and softness. For this reason, as a certain degree of weak braking,
Although it may be possible to set only the greatest common denominator value that is not suitable for avoiding roughening of the field, in the present invention, weak braking and a stronger braking state can be selected, It is easy to set the above-mentioned weak braking to a value that is assumed to be sufficient to suppress the roughening of the field, and therefore, it is possible to select a weak braking or a forced operation state suitable for the conditions of the field. Furthermore, since this work vehicle is provided with a pair of left and right side brake pedals that can be manually operated with a pair of left and right side brakes that can independently brake the left and right rear wheels, when the braking force is insufficient. When the side brake pedal is strongly depressed, the side brake can be operated on the braking side until the rear wheel is substantially stopped.

According to the features of claim 2, the "effect of the invention" of claim 1 is provided as in the case of claim 1, and in addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to the second aspect of the present invention, the front wheel transmission is automatically set to the operation state and the stop state based on the traveling speed state of the body, so that the operation by the operator is reduced, and the operability is reduced. It was good.

According to the feature of the third aspect, the "effect of the invention" of the second aspect is provided similarly to the case of the second aspect, and in addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to the feature of the third aspect, it is noted that when the traveling speed state of the body is a low speed state, it is possible to turn without any trouble regardless of whether the front wheel transmission is operating or stopped. By configuring the transmission so that it can be set to the operating state, small turning can be accurately performed according to the operating state of the front wheel transmission.

According to the feature of claim 4, claim 2 or 3
The effect of the invention according to claim 2 or 3 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 the fourth aspect, when the traveling speed state of the body is a high speed state, the front wheel transmission is forcibly set to the stop state, and the state in which the body makes a small turn at high speed is avoided beforehand, so that the work is performed. The ride comfort of the car was prevented from being reduced.

According to the feature of claim 5, the "effect of the invention" of the above-mentioned claim 1 is provided similarly to the case of the claim 1, and in addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to the feature of claim 5, the second setting is provided.
Switching between the weak braking state and the forced operation by the
Based on the operating position of the auxiliary transmission lever that operates the transmission
So that the front wheels are steered right or left from the straight-ahead position.
The side brake on the turning center side when the direction operation is performed is braked
The braking force when the vehicle is operated to the
To be able to change the setting to an appropriate state
I have to. In addition, as a configuration for that,
Use the bar as a means to detect the switching state of the traveling speed
There is an effect that the structure can be simplified.

[0032]

According to the feature of claim 6, the "effect of the invention" of the above-mentioned claim 5 is provided similarly to the case of the claim 5, 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, when the traveling speed state of the body is a high speed state, the braking force when the side brake on the turning center side is operated to the braking side is forcibly changed to a state of zero, and the body is operated. Thus, it is possible to prevent a state in which the vehicle makes a small turn at high speed, thereby preventing a decrease in the riding comfort of the work vehicle.

[0034]

According to the feature of the seventh aspect, similar to the fifth aspect, the "effect of the invention" of the fifth aspect is provided, and in addition to the "effect of the invention", the following "invention" is provided. Of the effect. According to a seventh aspect of the present invention, when the traveling speed state of the body is high, the front wheel transmission is forcibly set to the stop state and the braking when the side brake on the turning center side is operated to the braking side. Since the power is forcibly changed to the zero state and the state in which the aircraft turns at high speed in a small turn is avoided beforehand, it is possible to prevent the riding comfort of the work vehicle from lowering.

[0036]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a four-wheel drive type agricultural tractor, which is an example of a working vehicle, in which an engine (not shown) is provided at a front portion of a body supported by a front wheel 1 and a rear wheel 2, and a transmission case 4 is provided at a rear portion. And the agricultural tractor is provided.

The power of the engine is supplied from the main transmission (multi-stage gear shift type) (not shown) of the transmission case 4 to the first sub-transmission (three-stage high-medium-low gear shift type) (not shown), or The power is transmitted from the rear wheel differential mechanism 5 to the left and right rear wheels 2 via a second auxiliary transmission (neutral and ultra-low speed two-speed gear shift type) (not shown). The power branched immediately before the rear wheel differential mechanism 5 is transmitted to the left and right front wheels 1 via the front wheel transmission 6, the front wheel output shaft 7, and the front wheel differential mechanism 8.

The front wheel transmission 6 shown in FIG. 1 has a standard state in which the front wheel 1 is driven at substantially the same speed as the rear wheel 2 for transmission, and a state in which the front wheel 1 is driven at a higher speed than the rear wheel 2. The operation can be switched between two states of a speed increasing state in which the power is transmitted. As shown in FIG. 1, a shift member 9 for switching between the standard state and the speed-up state is urged by a spring 10 toward an occlusal side with the standard gear 20. It is in a standard condition after biting. When hydraulic oil is supplied to an oil chamber (not shown) formed between the shift member 9 and the standard gear 20, the shift member 9 slides to the left in the drawing and presses the friction clutch 21 to operate to increase the speed. Is obtained.

As shown in FIG. 1, the left and right rear wheels 2
Side brakes 11R and 11L that can be independently braked are provided. As shown in FIGS. 1 and 9, a pair of left and right side brake pedals 12R and 12L are disposed on the right side of the floor of the control unit.
The 2R, 12L and the side brakes 11R, 11L are interlockingly connected via the cylinders 13R, 13L and the link rod 14.

With the above structure, the left and right side brakes 11R, 11L can be independently operated to the braking side by depressing the left and right side brake pedals 12R, 12L. As shown in FIG.
3R and 13L are urged to the extension side by a spring 13a,
By supplying hydraulic oil and contracting the cylinders 13R and 13L, the left and right side brakes 11R and 11L can be operated to the braking side.

Next, the linkage between the steering operation of the front wheel 1 and the left and right side brakes 11R and 11L and the front wheel transmission 6 will be described. As shown in FIG. 1 and FIG.
Is supplied to the left and right side brakes 11R and 11L and the front wheel transmission 6 via the switching valve 24, the oil passage 28 and the control valve 16. The control valve 16 is a straight-moving position 16 in which the oil chamber between the shift member 9 and the standard gear 20 in the front wheel transmission 6 and the cylinders 13R and 13L of the left and right side brake pedals 12R and 12L are drained.
N, supply hydraulic oil from the pump 15 to the oil chamber of the front wheel transmission 6 and the right cylinder 13R,
L is a right turn position 16R where oil is drained, and a left turn position 16L where hydraulic oil is supplied to the oil chamber of the front wheel transmission 6 and the left cylinder 13L and the right cylinder 13R is drained. It is a position switching type.

As shown in FIG. 1, a fan-shaped cam plate 18 is fixed to a pitman arm 17 for steering operation of the front wheel 1, and a spool 16a of the control valve 16 comes into contact with the cam plate 18, and A spring 16b for urging the contact 16a toward the contact side is provided. The state shown in FIG. 1 is a state in which the front wheel 1 is being operated to the straight traveling position, and the control valve 16 is in the straight traveling position 16N.
Is being operated. In this state, the left and right side brakes 11R and 11L are in the non-braking state, the shift member 9 of the front wheel transmission 6 is engaged with the standard gear 20, and the front wheel 1 is driven at substantially the same speed as the rear wheel 2. Has become.

When the front wheel 1 is steered to the right by a set angle or more from the state shown in FIG. 1, the spool 16a of the control valve 16 is pushed by the cam plate 18 to the right in the drawing, to the right turning position 16R. The hydraulic oil is supplied to the right cylinder 13R and the front wheel transmission 6. Therefore, the friction clutch 21 of the front wheel transmission 6 is engaged, and the front wheel 1 is driven at a higher speed than the rear wheel 2 so as to be in a speed increasing state.
R contracts and the right side brake 11R is operated to the braking side.

Conversely, when the front wheel 1 is steered to the left by a predetermined angle or more from the state shown in FIG.
6a moves to the left in the drawing to the left turning position 16L, and the hydraulic oil is supplied to the left cylinder 13L and the front wheel transmission 6. Accordingly, the friction clutch 21 of the front wheel transmission 6 is engaged and the front wheel 1 is driven at a higher speed than the rear wheel 2 to be in a speed-up state, in which the left cylinder 13L contracts and the left side brake 11L brakes. Operated to the side.

In this agricultural tractor, the automatic side brakes 11R, 11
The operation is performed to switch between the state where the operation of L on the braking side and the operation of switching the front wheel transmission 6 to the speed increasing state and the state where the operation is not performed. Next, this switching structure will be described. . As shown in FIGS. 2 and 1, a pressure regulating valve 19 is connected to the oil passage 28. The pressure regulating valve 19 supports a valve body 19a, a spring 19b for urging the valve body 19a to the closing side, and a rear end of the spring 19b. And a supporting member 19c.
As a result, when the pressure in the oil passage 28 exceeds the pressure set by the spring 19b, the valve body 19a opens rightward on the drawing surface, and the hydraulic oil is discharged through the drain oil passage 38. The supplied operating oil pressure is the spring 19 of the pressure regulating valve 19.
It is determined by the biasing force of b, that is, the position of the support member 19c of the spring 19b.

As shown in FIG. 2, the spool 2 of the switching valve 24
9 is a pair of notches 29a and 29b and a drain hole 29.
c first land portion 29A and first circular arc surface 29
d and a second land portion 29B having a second arc surface 29e. The rear end of the support member 19c of the pressure regulating valve 19 is applied to the first arc surface 29d, and the support member 1
The position of 9c is determined. Spool 2 of switching valve 24
The operation plate 30 is fixed to the tip of the switching lever 9 and the switching lever 3
And the operation plate 30 are interlocked and connected by a link rod 22.

The state shown in FIG. 1 is a state in which the switching lever 3 is being operated to the first position B1. In this state, the operating oil from the pump 15 is supplied to the control valve 16 via the first cutout portion 29 a in the spool 29 of the switching valve 24 and the oil passage 28. Support member 19c for pressure regulating valve 19
Is pressed to the left by the first arcuate surface 29d of the spool 29, the spring 19b of the pressure regulating valve 19 is compressed, and the hydraulic pressure supplied to the control valve 16 is reduced by the action of the pressure regulating valve 19. It is maintained at a second set pressure P2 described later.

As shown in FIG. 7, the front wheel transmission 6 is switched from the standard state to the speed increasing state at a relatively low first set pressure P1, but the side brake 11 is operated at the first set pressure P1.
R and 11L are not operated on the braking side. At a second set pressure P2 higher than the first set pressure P1, the side brake 11
R and 11L are operated in the weak braking state, and the front wheel transmission 6 is also switched from the standard state to the speed increasing state. The weak braking state of the side brakes 11R and 11L means that when the rear wheel 2 on the braking side is dragged as the body advances, the drag action is performed by the side brakes 11R and 11L.
And the rear wheel 2 on the braking side is rotated.

As shown in FIGS. 2 and 1, in the state where the switching lever 3 is operated to the first position B1, when the front wheel 1 is steered to the right or left by a predetermined angle or more as described above,
When the spool 16a of the control valve 16 is slid by the cam plate 18, the hydraulic oil is supplied to the right or left cylinder 13R, 1R.
It is supplied to the front wheel transmission 6.

In this case, the operating hydraulic pressure supplied as described above is maintained at the second set pressure P2 by the action of the pressure regulating valve 19. Accordingly, as shown by the solid line A2 in FIG. 7, the friction clutch 21 of the front wheel transmission 6 is engaged and the front wheel 1 is driven at a higher speed than the rear wheel 2, so that the right or left cylinder 13R is increased. , 13L contracts, and the right or left side brake 11R, 11L is operated to a weak braking state.
Accordingly, a very small turning can be performed by the pulling action in the turning direction by the increased front wheel 1 and the weak braking action on the rear wheel 2 on the turning center side. In this case, when the rear wheel 2 on the braking side is dragged with the turning of the aircraft, the rear wheel 2 on the braking side is rotated.
The ground is less likely to be roughened by the rear wheel 2 on the braking side.

Next, when the switching lever 3 is operated to the second position B2, the spool 29 of the switching valve 24 is rotated clockwise by a predetermined angle from the state shown in FIG. In this case, the portion of the first arc surface 29d of the spool 29 that contacts the support member 19c of the pressure regulating valve 19 is slightly retracted rightward on the paper. Along with this, the support member 19c also slides to the right in the drawing to slightly weaken the urging force of the spring 19b, and the operating oil pressure supplied to the control valve 16 is maintained at the first set pressure P1 lower than the second set pressure P2. You.

In this state, when the front wheel 1 is steered to the right or left by a predetermined angle or more to supply the hydraulic oil to the right or left cylinders 13R, 13L and the front wheel transmission 6, the dashed line in FIG. As shown in A1, the friction clutch 21 of the front wheel transmission 6 is engaged, and the speed increasing state in which the front wheel 1 is driven at a higher speed than the rear wheel 2 appears. On the other hand, the right or left cylinders 13R, 13L do not contract, and the right or left side brakes 11R, 11L are not operated on the braking side. Thereby, a smooth small turning can be performed by the pulling action in the turning direction by the increased speed front wheel 1. In this case, since the left and right rear wheels 2 are also driven, the rear wheel 2 on the turning center side is not dragged, and the ground is not roughened by the rear wheel 2 on the turning center side.

Next, as shown in FIG.
When operated to the position B3, the spool 29 of the switching valve 24
From the state shown in FIG. 2, the operation is further rotated clockwise by a predetermined angle. In this case, the first
The drain hole 29c of the land portion 29A communicates with the drain oil passage 39. As a result, the hydraulic oil from the pump 15
The air is discharged through the drain hole 29c of the land 29A and the drain oil passage 39.

In this state, even if the front wheel 1 is steered to the right or left by more than the set angle, the right or left cylinders 13R and 13L and the front wheel transmission 6 are moved as shown by the two-dot chain line A4 in FIG. No hydraulic oil is supplied. Accordingly, the front wheel transmission 6 maintains the normal state during the turning operation, the right or left side brakes 11R and 11L are not operated on the braking side, and the four wheels of the front wheel 1 and the rear wheel 2 have substantially the same speed. The turning is performed in the state driven by.

In this agricultural tractor, the automatic operation of the side brakes 11R and 11L to the braking side as described above during the turning operation at high speed traveling, and the front wheel transmission 6
The switching operation to the speed increasing state is not performed, and this structure will be described next. As shown in FIG. 3, the operation shaft 23 of the first auxiliary transmission and the operation shaft 25 of the second auxiliary transmission project from the lateral side surface of the transmission case 4. 1 The operation member 26 and the operation plate 27 are fixed. A sub-transmission lever (not shown) of the first and second sub-transmissions, and a first operation member 26 and an operation plate 27 are interlocked by link rods 28 and 31. The operation plate 27 has a T-shaped long hole 27a, and a link rod 28 connected to the first operation member 26.
Is inserted into the long hole 27a of the operation plate 27.

Around the horizontal axis P1 of the transmission case 4,
A curvilinear second operating member 32 is swingably supported, and the lower end of the second operating member 32 is pin-connected to the operating plate 27. A bracket 34 is supported on the upper end of the first operation member 23 so as to be freely swingable around a horizontal axis P2.
4 is connected. The end of the outer 33b of the release wire 33 is freely swingably supported around the horizontal axis P3 at the upper end of the second operation member 32. As shown in FIGS. 3 and 2, the other end of the inner wire 33 a of the release wire 33 is connected to the operation plate 30 of the switching valve 24.

The first and second subtransmissions operated by the subtransmission lever are arranged in parallel with the transmission system, and when one is operated in one shift position, the other is in the neutral position. exist. The state shown in FIG. 3 is a state in which the sub-transmission lever is operated to the low speed position (the first sub-transmission is in the low speed position and the second sub-transmission is in the neutral position), and the first operating member 26 is in the low-speed position F1. It is located in. In this state, the inner wire 33a of the release wire 33 is not pulled toward the first and second operation members 26 and 32.

As a result, as shown in FIG. 2, the switching lever 3 can be operated to the first position B1, and the automatic operation of the side brakes 11R and 11L to the weak braking state during the turning operation as described above. The switching operation of the front wheel transmission 6 to the speed increasing state is performed. It is also possible to operate the switching lever 3 to the second and third positions B2 and B3, a state in which only the switching operation of the front wheel transmission 6 to the speed increasing state is performed at the time of the turning operation, and an automatic side shift operation at the time of the turning operation. Brake 11R, 1
It is possible to select a state in which both the 1L braking operation and the switching operation of the front wheel transmission 6 to the speed increasing state are not performed. As described above, in the state where the sub-transmission lever is operated to the low speed position, the switching lever 3 is moved to the first, second, and third positions B1,
By operating B2 and B3, three states can be selected (see FIG. 8).

Next, as shown in FIG. 4, when the sub-transmission lever is operated to the middle speed position (the first sub-transmission is in the middle speed position and the second sub-transmission is in the neutral position), the first operating member 26 is The rocking operation is performed in the clockwise direction to reach the middle speed position F2. In this state, the inner wire 33a of the release wire 33 is slightly pulled toward the first and second operation members 26 and 32. Thereby, the operation plate 30 of the switching valve 24 is rotated clockwise by a predetermined angle from the state shown in FIG.

In this state, the switching lever 3 cannot be operated to the first position B1 as shown in FIG. 2, and the switching lever 3 can be operated to the second and third positions B2 and B3. Become. When the sub-shift lever is operated from the low speed position to the middle speed position while the switching lever 3 is being operated to the first position B1, the switching lever 3 is moved from the first position B1 to the second position B2 by the pulling action of the inner 33a. Switching operation is performed. As described above, when the sub-transmission lever is operated to the middle speed position, the switching lever 3 is moved to the second and third positions B.
The user can operate 2 and B3 to select 2 states (see FIG. 8).

Next, as shown in FIG. 5, when the sub-transmission lever is operated to the high-speed position (the first sub-transmission is in the high-speed position and the second sub-transmission is in the neutral position), the first operating member 26 is moved clockwise in the drawing. To reach the high-speed position F3. In this state, the inner 33a of the release wire 33 is
And the second operation member 26, 32 is largely pulled. As a result, the operation plate 30 of the switching valve 24 in FIG. 2 is largely rotated clockwise in FIG.

In this state, the switching lever 3 cannot be operated to the first and second positions B1 and B2,
The switching lever 3 can be operated only to the third position B3. When the sub-shift lever is operated from the low-speed and medium-speed positions to the high-speed position while the switching lever 3 is being operated to the first and second positions B1 and B2, the switching lever 3 is pulled by the inner member 33a. From the second position B1, B2 to the third position B3
Is switched. As described above, in a state where the sub-transmission lever is operated to the high-speed position, the switching lever 3 can be operated only to the third position B3 (see FIG. 8).

Next, when the sub-transmission lever is operated to the ultra-low speed position, the first operation member 26 is operated to the neutral position N as shown in FIG. 6, and the second operation member 32 is operated by the operation plate 27 as shown in FIG. From the state, it is operated to the ultra-low speed position C in FIG. In this case, the operation of the first operation member 26 causes the release wire 33 to move.
Is pulled to the first operation member 26 side, and accordingly, the second operation member 3 on the outer 33b side is
2 is also operated in the same direction, so that the inner 3 is actually
3a is not brought into the state of being pulled to the first operation member 26 side. As a result, the switching lever 3 is moved to the first, second and third positions B in the same manner as when the sub-transmission lever is operated to the low speed position.
By operating the buttons 1, B2, and B3, three states can be selected (see FIG. 8).

When the spool 29 of the switching valve 24 shown in FIG.
9, the second arc surface 29e of the second land portion 29B abuts against the support member 19c of the pressure regulating valve 19, and the hydraulic oil from the pump 15 is supplied to the control valve 16 via the notch portion 29b of the first land portion 29A. Supplied to In this case, the support member 19c of the pressure regulating valve 19 moves the first circular surface 29d of the second land portion 29B while the switching lever 3 is being operated to the first position B1.
Is pressed to the left in the drawing from the state in contact with.

Thus, the operating oil pressure supplied to the control valve 16 by the operation of the pressure regulating valve 19 is maintained at the third set pressure P3 higher than the second set pressure P2. At the third set pressure P3 as shown by the solid line A3 in FIG.
1R and 11L are in the forced operation state, and the front wheel transmission 6 is also switched from the standard state to the speed increasing state. The forced operation state of the side brakes 11R and 11L is a state where the rear wheel 2 on the braking side substantially stops regardless of the progress of the machine body.

Therefore, in this state, if the front wheel 1 is steered beyond a set angle, a pulling action in the turning direction by the accelerated front wheel 1 and a strong braking action on the rear wheel 2 on the turning center side are obtained. A very small turn can be performed. In this state, the switching lever 3 is moved to the second and third positions B.
2 and B3, the dashed line A in FIG.
The state of 1 and the two-dot chain line A4 is obtained.

[Another Embodiment] In the embodiment shown in FIG.
3a was connected to the first operation member 26, and the outer 33b was connected to the second operation member 32. The relationship was reversed, and the inner 33a was connected to the second operation member 32, and the outer 33b was connected.
b may be connected to the first operation member 26. In the above-described embodiment, the first and second auxiliary transmissions are arranged in parallel to the transmission system. However, the first and second auxiliary transmissions may be arranged in series to the transmission system.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the attached drawings by the description.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a link state of a left and right side brake, a front wheel transmission, a control valve and a switching valve, and a hydraulic circuit.

FIG. 2 is a diagram showing a hydraulic circuit of a switching valve, a control valve, and a pressure regulating valve, and an associated state of a switching valve, a switching lever, and a release wire.

FIG. 3 is a side view of the vicinity of first and second operating members when the sub-transmission lever is operated to a low speed position.

FIG. 4 is a side view of the vicinity of first and second operating members in a state where the sub shift lever is operated to a middle speed position.

FIG. 5 is a side view of the vicinity of the first and second operation members in a state where the sub-transmission lever is operated to a high-speed position.

FIG. 6 is a side view of the vicinity of the first and second operating members in a state where the sub shift lever is operated to the ultra-low speed position.

FIG. 7 is a diagram showing a relationship between operating pressures of a side brake and a front wheel transmission and a steering angle of a front wheel.

FIG. 8 is a diagram showing a relationship between auxiliary transmission levers (first and second auxiliary transmissions) and operating states of a side brake and a front wheel transmission.

FIG. 9 is a diagram showing a connection state between a side brake pedal and a side brake and a connection cylinder;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front wheel 2 Rear wheel 3, 24 1st setting means, 2nd setting means 6 Front wheel transmission 11R, 11L Side brake 16 1st operating means, 2nd operating means

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI B60T 8/58 B60T 8/58 A B62D 11/08 B62D 11/08 S (56) References JP-A-3-243429 (JP, A) JP-A-2-290725 (JP, A) JP-A-5-262151 (JP, A) JP-A-1-114578 (JP, A) JP-A-2-20462 (JP, A) JP-A-50-51821 ( JP, A) JP-A 2-64471 (JP, U) JP-A 53-148441 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60K 17/28-17/36 B60K 41/00-41/28 B60T 7/12-7/22 B60T 8/00-8/96 B62D 11/00-15/02

Claims (7)

(57) [Claims] 1. A standard state in which power is transmitted to the front wheel (1) so that the front wheel (1) and the rear wheel (2) are driven at substantially the same speed, and the front wheel (1) is moved from the rear wheel (2). A front wheel transmission (6) that can be switched to a speed-up state in which power is transmitted to the front wheels (1) so as to be driven at a high speed, and a selected one of a pair of left and right rear wheels (2) is braked. Possible pair of left and right side brakes (11R), (11L)
And a pair of left and right side brake pedals (12R) and (12L) that can be operated on the braking side until the rear wheels (2) stop substantially by stopping the side brakes (11R) and (11L).
When the front wheel (1) is steered to the right or left from the straight traveling position, the front wheel transmission (6) interlocks with the steering operation.
When the front wheel (1) is steered to the right or left from the straight traveling position, the first operating means (16) for switching the speed to the speed increasing state is interlocked with this steering operation, and A second operating means (16) for operating the side brakes (11R) and (11L) on the braking side, and the front wheel shifter interlocking with the steering operation of the front wheel (1) from the straight traveling position to the right or left. First setting means (3), (24) for setting an operation state in which the device (6) is switched to a speed increasing state and a stop state in which the device (6) is not switched, and to the right or left from the straight traveling position of the front wheel (1). The side brakes (11R), (1
1L) to the braking side at the end of the operation stroke when the rear wheel (2) is substantially stopped. Select and switch to any one of the set braking forces in the forced operation state where the braking force is strong.
A work vehicle, comprising: a replaceable second setting means (3), (24). 2. The work vehicle according to claim 1, wherein the first setting means is configured to set the operation state and the stop state based on a traveling speed state of the body. 3. The work according to claim 2, wherein the first setting means (3) and (24) are configured so that the operating state can be set when the traveling speed state of the body is a low speed state. car. 4. The first setting means (3), (24) is configured such that the stop state is forcibly set when the traveling speed state of the body is a high speed state. 3
The working vehicle described. The power from the engine is transmitted to a main transmission and a sub transmission.
Transmission to rear wheel (2) and front wheel (1) via transmission
In the working vehicle configured as described above, the front wheel (1) is in a standard state where power is transmitted to the front wheel (1) so that the front wheel (1) and the rear wheel (2) are driven at substantially the same speed. A front wheel transmission (6) operable to switch to an increased speed state in which power is transmitted to the front wheels (1) so as to be driven at a higher speed than the rear wheels (2); A pair of left and right side brakes (11R) and (11L) that can brake the selected one
And a pair of left and right side brake pedals (12R) and (12L) that can be operated on the braking side until the rear wheels (2) stop substantially by stopping the side brakes (11R) and (11L).
When the front wheel (1) is steered to the right or left from the straight traveling position, the front wheel transmission (6) interlocks with the steering operation.
When the front wheel (1) is steered to the right or left from the straight traveling position, the first operating means (16) for switching the speed to the speed increasing state is interlocked with this steering operation, and A second operating means (16) for operating the side brakes (11R) and (11L) on the braking side, and the front wheel shifter interlocking with the steering operation of the front wheel (1) from the straight traveling position to the right or left. First setting means (3), (24) for setting an operation state in which the device (6) is switched to a speed increasing state and a stop state in which the device (6) is not switched, and to the right or left from the straight traveling position of the front wheel (1). The side brakes (11R), (1
1L) to the braking side at the end of the operation stroke when the rear wheel (2) is substantially stopped. Select and switch to any one of the set braking forces in the forced operation state where the braking force is strong.
And second changeable setting means (3) and (24).
The operation state and the forced operation are switched by operating the auxiliary transmission.
Make sure that the sub-shift lever
Forgive, with the sub-shift lever in the high-speed position
Is configured to disable switching to the forced operation state.
A working vehicle. As the traveling speed state of wherein the aircraft the brake force to be high speed state is forcibly changed to zero operation, the second setting means (3), wherein you have configured (24) Item 5. The work vehicle according to Item 5 . 7. The first setting means (3), (24) is configured such that the stop state is forcibly set when the traveling speed state of the body is a high speed state, and the braking force is set. The work vehicle according to claim 5 , wherein the second setting means (3), (24) is configured such that the second setting means is forcibly changed to zero.