JP3416632B2 - 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 work vehicle such as an agricultural tractor or a riding type rice transplanter.

[0002]

2. Description of the Related Art An agricultural tractor, which is an example of a work vehicle, is provided with a pair of left and right side brakes capable of independently braking each of the left and right rear wheels. By depressing one of the side brake pedals, one side brake is operated to the braking side. As a result, when the turning operation is performed, braking is applied to the rear wheel on the center side of the turning, thereby enabling a small turn around the rear wheel on the center side of the turning.

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 equipped with a front wheel transmission that can be switched to increase speed, if the front wheels are steered from the straight ahead position to the right or left, the front wheel transmission is switched to the speed increasing state in conjunction with the steering operation, and the center of turning There is an agricultural tractor configured such that the side brake on the side is operated to the braking side (for example, Japanese Patent Laid-Open No. Hei 3
-243429 gazette). As a result, the small-turn turning can be smoothly performed by the speed-up action of the front wheels and the braking action on the rear wheels on the turning center side.

[0004]

With the above-mentioned configuration,
When the front wheels are steered rightward or leftward from the straight-ahead position, the front wheel transmission is switched to the speed increasing state, and only one state in which the side brake on the turning center side is operated to the braking side appears. On the other hand, the work site and work on which the work vehicle travels often change into 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. If only one state is said to be operated by the braking side, paddy fields, upland fields,
Work where a working device (for example, rotary tiller, plow or grass working machine, etc.) is installed at the rear of the work vehicle or work site that changes into various conditions such as a soft field or a hard field,
For work that cannot be adequately performed when a work device (such as a snow blower or front loader) is attached to the front of the work vehicle, making it difficult to perform appropriate turning according to the work site and each state of work. May be.

The present invention provides a work vehicle having two turning functions of a front wheel transmission and a side brake, while avoiding a situation in which the rear wheel on the turning center side is dragged on the ground and roughens the ground. It is an object of the present invention to provide a structure capable of performing an appropriate turn corresponding to a changing work site and each state of work by various work devices.

[0006]

The feature of the present invention resides in that the work vehicle is constructed as follows. [1] Standard state in which power is transmitted to the front wheels so that the front wheels and rear wheels are driven at approximately the same speed, and a speed-up state in which power is transmitted to the front wheels so that the front wheels are driven faster than the rear wheels The front wheel transmission that can be switched between, the pair of left and right side brakes that can brake the selected one of the pair of left and right rear wheels, and the front wheel that is steered from the straight position to the right or left. Front wheel shift operating means for shifting the front wheel transmission to a speed-up state in conjunction with the steering operation, and when the front wheel is steered from the straight-ahead position to the right or left, this front steering operation is interlocked. And a side brake operating means for operating the side brake on the turning center side to the braking side,
In a state in which the shift change operation by the front wheel shift operation means is possible, both the braking turn inhibiting means for preventing the operation by the side brake operation means, the operation by the side brake operation means, and the operation by the front wheel shift operation means are blocked. Steering operation of the front wheels equipped with possible small turning prevention means
In conjunction with the side brake operating means and the front wheel change
A first state in which operation by the quick operating means is both permitted;
The second state in which the braking turning inhibiting means acts, and the small turning
The 3rd state in which the turning deterrent means operates is switched in the normal and reverse order in this order.
The order of operations is set so that they can be changed .

[2] As described in claim 2, both the speed increasing operation by the front wheel shifting operation means interlocked with the steering operation and the braking operation by the side brake operation means interlocked with the steering operation are permitted. 1st state , a second state in which a braking turning inhibiting means that restrains the braking operation by the side brake operating means while allowing only the speed increasing operation by the front wheel shifting operation means, and the speedup by the front wheel shifting operation means The small-turn turning suppression means that restrains both the operation and the braking operation by the side brake operating means is created.
The third state to be used may be configured to be switchable based on a human operation.

[3] As described in claim 3, when the traveling speed state of the airframe is low, the speed-up operation by the front wheel shifting operation means linked to the steering operation and the side brake linked to the steering operation are performed. When both the braking operation by the operating means is allowed and the speed is changed from the low speed state to the higher speed side, only the speed increasing operation by the front wheel shift operating means is allowed and the braking operation by the side brake operating means is restrained . It may be configured to be switched to either the state or the third state in which both the speed-up operation by the front wheel shift operation means and the braking operation by the side brake operation means are restrained.

[4] As described in claim 4, when the traveling speed state of the airframe is low, a speed increasing operation is performed by the front wheel shift operation means linked to the steering operation and a side brake linked to the steering operation. When both the braking operation by the operating means is allowed and the speed is changed from the low speed state to the medium speed state, only the speed increasing operation by the front wheel shift operating means is allowed and the braking operation by the side brake operating means is restricted. It may be configured to be switched to the second state of being activated.

[5] According to a fifth aspect of the present invention, when the traveling speed state of the airframe is low, the speed-up operation is performed by the front wheel shifting operation means linked to the steering operation and the side brake linked to the steering operation. When both the braking operation by the operating means is allowed and the speed is changed from the medium speed state to the high speed state, both the speed increasing operation by the front wheel shift operating means and the braking operation by the side brake operating means are restrained. It may be configured to switch to the third state .

[6] According to a sixth aspect of the present invention, when the traveling speed state of the machine body is a low speed state, speed-up operation is performed by the front wheel shift operation means linked to the steering operation and side brakes linked to the steering operation. When both the braking operation by the operating means is allowed and the speed is changed from the low speed state to the higher speed side, only the speed increasing operation by the front wheel shift operating means is allowed and the braking operation by the side brake operating means is restrained . State , or a third state in which both the speed-up operation by the front wheel shift operation means and the braking operation by the side brake operation means are restrained, and when returned to the low speed state, the steering operation is interlocked. It may be configured to automatically return to the first state in which both the speed increasing operation by the front wheel shift operation means and the braking operation by the side brake operation means linked to the steering operation are permitted.

[7] As described in claim 7, the steering angle of the front wheels for detecting the set angle for operating the front wheel shift operating means and the set angle for operating the side brake operating means. One steering angle detecting means may be provided, and the front wheel shift operating means and the side brake operating means may be integrally configured .

[0013]

[8] As described in claim 8 , the braking operation by the side brake operating means interlocked with the steering operation of the front wheels may be a weak braking state in which the rear wheels are not substantially stopped. .

[9] As described in claim 9, the speed-up operation by the front wheel shift operation means linked to the steering operation and the braking operation by the side brake operation means linked to the steering operation are performed by hydraulic pressure. The hydraulic actuator operated by the front wheel shift operating means and the hydraulic actuator operated by the side brake operating means may have different operating pressures.

[10] As described in claim 10, the operating pressure of the speed-up operation in the front wheel shift operation means linked to the steering operation is changed to the braking pressure in the side brake operation means linked to the steering operation. It is better to set it lower than the operating pressure.

[0017]

[I] According to the feature of claim 1, when the front wheels are steered from the straight-ahead position to the right or left, the front wheel transmission is switched to the speed increasing state, and the side brake on the turning center side is operated. It is operated on the braking side. In this way, while the front wheel speed-increasing state associated with the steering operation and the braking operation state associated with the steering operation can be automatically switched, the shift-changing operation can be performed by the front-wheel shift operating means. By providing the brake turning inhibiting means for inhibiting the operation by the side brake operating means, it is possible to maintain the linkage of the front wheel speed increase with respect to the steering operation and to inhibit only the braking linkage. Further, by providing a small turning restraint means capable of blocking both the operation by the side brake operating means and the operation by the front wheel shift operating means, it is possible to link the front wheel acceleration operation and the rear wheel braking operation with respect to the steering operation. Disable both automatic switching operation to, and run in a completely independent operating state without the above linked operation,
You can also switch quickly. Furthermore, in claim 1
In the invention, the side brake is interlocked with the steering operation of the front wheels.
The operation by the rake operation means and the front wheel shift operation means
The first state, in which both are allowed, and the braking turning inhibiting means act
And a second state in which the small-turn turning inhibiting means acts.
The operation order so that the three states can be switched between forward and reverse in this order
Has been set. Therefore, for example, in the first state
Suddenly switched from the driving mode in the third mode to the driving mode in the third state.
As if you were accustomed to turning in a small circle,
When it makes a large turn, the expansion of the aircraft outside than expected
It may be confusing to turn around, or conversely, in the third state
The running form is suddenly switched to the running form in the first state.
As if you were accustomed to turning around,
If you make a small turn, the inside of the aircraft will be cut more than expected
There is a possibility that you may be confused about the turning, but
In the invention according to claim 1, in the middle of the operation sequence, the front wheel shift
While the gear shifting operation can be performed using the operating means,
Brake turning inhibiting means for preventing operation by rake operating means
Since the second state in which is operated is set,
It is possible to carry stable aircraft due to the low possibility
Of.

[II] According to the characteristics of claim 2, the "action" described in [I] is provided as in the case of claim 1, and in addition to this, the following "action" is provided. ing. As described in claim 2, the speed increasing operation by the front wheel shift operating means and the braking operation by the side brake operating means are performed.
A first state in which both are allowed in conjunction with the steering operation, and a braking turning restraining means for restricting the braking operation by allowing only the speed increasing operation are operated.
Since it is configured to be switchable between a second state for use and a third state in which the small-turn turning inhibiting means for restraining both speed-up operation and braking operation act on the basis of human operation, the situation of the work site and Appropriate turning conditions can be arbitrarily set according to the type of work.

[III] According to the feature of claim 3, as in the case of claim 1 or 2, it has the same "action" as in the case of [I] and [II]. It has such a "action". As described in claim 3,
When the traveling speed state of the aircraft is a low speed state, both the speed increasing operation by the front wheel shifting operation means linked with the steering operation and the braking operation by the side brake operation means linked with the steering operation are allowed,
When the speed is changed from the low speed state to the higher speed side, the second state in which only the speed increasing operation of the front wheel shift operating means is allowed and the braking operation of the side brake operating means is restrained, or the speed increase by the front wheel shift operating means is performed. By configuring the operation and the braking operation by the side brake operating means to be switched to any of the third states in which both are restrained, it is easy to perform work in a turning form that matches the traveling speed and work conditions. That is, for example,
In general plowing work in paddy fields, dry fields, and wet fields, both speed-up operation and braking operation linked to steering operation are allowed in a low-speed running state, and in the speed range higher than the low-speed state, a ridge is formed. When cultivating along the shore, cultivating along the wall of the house, or pulling the plow, the braking operation linked to the steering operation is restrained by allowing only the front wheel speed increase.In addition, when the vehicle is traveling on the road or when the aircraft is simply moving, it increases with the steering operation. It can be appropriately used such that both the fast operation and the braking operation are restrained.

[IV] According to the characteristics of claim 4, as in the case of claims 1, 2, or 3, the above [I] [II] [I
II] is provided with the “action”, and in addition to this, the following “action” is provided. According to a fourth aspect of the present invention, when the traveling speed state of the airframe is low, a speed increasing operation by the front wheel shift operation means linked with the steering operation and a braking operation by the side brake operation means linked with the steering operation. If both are allowed and the speed is changed to a medium speed state rather than a low speed state,
If it is configured such that only the speed-increasing operation of the front wheel shift operation means is allowed and the braking operation by the side brake operation means is switched to the second state , a low-speed traveling state and a medium-speed traveling state higher than this can be achieved. In any of the traveling states described above, the turning form adapted to the traveling speed and the working situation is selected.

[V] According to the feature of claim 5, as in the case of claim 1, 2, or 3, the above [I] [II] [II
I] is provided with the “action” described above, and in addition to this, the following “action” is provided. As described in claim 5, when the traveling speed state of the airframe is low, a speed-up operation by the front wheel shift operation means linked to the steering operation and a braking operation by the side brake operation means linked to the steering operation. If both are allowed and the speed is changed to a higher speed than the medium speed, the state is switched to the third state in which both the speed increasing operation by the front wheel shift operating means and the braking operation by the side brake operating means are restrained . With such a configuration, the turning form adapted to the traveling speed and the work situation is selected in both traveling states of the low speed traveling state and the high speed traveling state higher than the medium speed.

[VI] According to the characteristics of claim 6, the "action" described in [I] to [V] is provided as in the case of claims 1 to 5, and in addition to this, the following is provided. It has the "action". According to the sixth aspect of the present invention, the turning mode adapted to the traveling speed and the working condition is selected as described above, and when returning to the low speed state, the front wheel shifting operation means interlocked with the steering operation. Is automatically returned to the first state in which both the speed increasing operation and the braking operation by the side brake operating means interlocking with the steering operation are permitted, so whether or not the control mode in the predetermined low speed state has been returned is determined. No confirmation is required.

[VII] According to the features of claim 7, the contract
As in the case of the requirements 1 to 3, described in the above [I] to [III].
In addition to the above "action", the following
It has "action". The steering angle of the front wheels is provided with one steering angle detecting means for detecting a set angle for operating the front wheel shift operating means and a set angle for operating the side brake operating means, If the operating means and the side brake operating means are configured as an integrated control valve, it is necessary to separately provide two steering angle detecting means for front wheel acceleration and steering angle detecting means for side brakes. In addition, there is no need for linking means for linking the control valves constituting the front wheel shift operating means and the control valves constituting the side brake operating means while individually controlling them in separate circuits.

[0024]

[VIII] According to the feature of claim 8,
Similar to the case of claims 1 to 7, the above "I " to "VII " have the "action", and in addition to this, the following "action" is provided. As described in claim 8, when the braking operation by the side brake operating means interlocked with the steering operation of the front wheels is set to a weak braking state that does not result in a stopped state in which the rear wheels substantially stop, the braking operation at the time of the braking operation is performed. It is possible to avoid locking the rear wheel on the turning center side and avoid the situation where the rear wheel is dragged while being locked.

[IX] According to a feature of claim 9,
Similar to the cases of Items 1 to 8, the "action" described in the above [I] to [VIII] is provided, and in addition to this, the following "action" is provided. As described in claim 9 , the hydraulic actuator performs the speed increasing operation by the front wheel shift operating means linked to the steering operation and the braking operation by the side brake operating means linked to the steering operation. If the hydraulic pressures of the hydraulic actuators operated by the front wheel shift operation means and the hydraulic actuators operated by the side brake operation means are made different from each other, the operating pressure suitable for the front wheel speed-up operation and the braking operation can be achieved. It is possible to set an operating pressure suitable for

[X] According to the features of claim 10,
Similar to the case of the item 9, the “action” described in the above [IX] is provided, and in addition to this, the following “action” is provided. As set forth in claim 10, the operating pressure of the speed increasing operation of the front wheel shift operating means linked to the steering operation is set lower than the operating pressure of the braking operation of the side brake operating means linked to the steering operation. Then, the speed increasing operation by the front wheel shift operation means can be performed with a low pressure until the operating pressure is generated during the braking operation.

[0028]

With the above-described structure, the front wheel speed-increasing state associated with the steering operation and the braking operation state associated with the steering operation can be automatically switched.
In the state where the shift change operation by the front wheel shift operation means is possible,
By providing the braking / turning inhibiting means for inhibiting the operation by the side brake operating means, it is possible to maintain the linkage of the front wheel speed increase with respect to the steering operation and to inhibit the linkage of the braking only. In this way, maintaining the linkage of front wheel acceleration to the steering operation and suppressing only the linkage of braking makes it possible to perform plowing work at the edge of the ridge or when turning at the end of the house, or It is possible to obtain an effective turning form when it is not desired to turn the machine body too rapidly, such as when performing plow towing work. Further, by providing a small turning restraint means capable of blocking both the operation by the side brake operating means and the operation by the front wheel shift operating means, it is possible to link the front wheel acceleration operation and the rear wheel braking operation with respect to the steering operation. It is also possible to quickly disable the automatic switching operation to and to perform the traveling in the completely independent operation state without the above-described linked operation. Further, in the invention according to claim 1, the steering operation of the front wheels is performed.
The side brake operating means and the front wheel
A first state in which both operations by the gear shift operation means are permitted, and
The second state in which the braking turning inhibiting means acts, and the small turn
The third state in which the turning suppression means acts is reversed in this order.
Since the operation order is set so that it can be switched, small turns
The aircraft swelled outward more than expected as if you were used to turning
While turning, or conversely, the feeling that you are used to turning around
So that the aircraft turns while cutting inward more than expected
However, the possibility of confusion in the operation feeling is reduced and
There is an advantage that it is easy to carry out a fixed aircraft run.

According to the second aspect of the present invention, the first state in which the speed-up operation by the front wheel shift operation means and the braking operation by the side brake operation means are both permitted in conjunction with the steering operation, and the speed-up operation. Brake and turn deterrent hand that restricts braking operation by allowing only
There are a second state in which the step operates and a third state in which the small-turn turning inhibiting means for restraining both the speed increasing operation and the braking operation acts .
Switching can be performed based on human operation, and appropriate turning conditions can be arbitrarily set according to the situation of the work place and the type of work.

As described in claim 3, the speed-up operation of the front wheel shift operation means and the braking operation by the side brake operation means are configured to be associated with the machine traveling speed, so that, for example, in paddy fields, dry fields, and wet fields. In general plowing work, in a low-speed running state, both speed-up operation and braking operation linked to the steering operation are allowed, and in the speed range on the higher speed side than the low-speed state,
When cultivating on the edge of the ridge, plowing on the wall of the house, or pulling the plow, only the front wheels are allowed to accelerate and the braking operation linked to the steering operation is restrained.In addition, when driving on the road or when the aircraft is simply moving, it is accompanied by the steering operation. It is possible to easily perform work in a turning form that suits the traveling speed and the working conditions by appropriately selecting the proper use such as controlling both the speed-up operation and the braking operation.

According to a fourth aspect of the present invention, when the traveling speed state of the airframe is low, the front wheel shifting operation means interlocked with the steering operation and the side brake operation means interlocked with the steering operation. When both the braking operation of the front wheel shifting operation means is changed to a middle speed state of a higher speed than the low speed state, only the speed increasing operation of the front wheel shift operation means is allowed and the braking operation of the side brake operation means is restrained . When configured to be switched to a state, an appropriate turning form at a traveling speed adapted to the work situation is selected in any traveling state of a low speed traveling state and a medium speed traveling state higher than this, particularly In addition, in order to perform work while avoiding a situation in which a work device extended to the rear of the aircraft, such as turning around a ridge or inside a house, collides with a ridge or a house wall due to a sharp turn of the aircraft. It is suitable.

According to a fifth aspect of the present invention, when the traveling speed state of the airframe is low, the front wheel shifting operation means interlocked with the steering operation and the side brake operation means interlocked with the steering operation. And the braking operation of the side brake operating means are both restrained when both the braking operation of the front wheel shifting operation means and the braking operation of the front wheel shifting operation means are changed to a high speed state that is higher than the medium speed state. If it is configured to be switched to, the appropriate turning form at the traveling speed adapted to the work situation is selected in both the low-speed traveling state and the high-speed traveling state that is higher than the medium-speed state. Since the state in which the machine body makes a small turn at a high speed is avoided when moving in the field or traveling on the road, it is possible to prevent deterioration of the riding comfort of the work vehicle.

According to a sixth aspect of the present invention, in addition to the turning form adapted to the traveling speed and the working condition as described above, when the speed is returned to the low speed state, the front wheel shifting operation means interlocked with the steering operation. The first state that allows both the speed-up operation of the vehicle and the braking operation by the side brake operation means linked to the steering operation.
Since it returns to the state, it is not necessary to confirm whether or not the control mode is automatically returned to the predetermined low speed state, and the operability is significantly improved.

According to a seventh aspect of the present invention, one steering angle for detecting the steering angle of the front wheels for detecting the set angle for operating the front wheel shift operating means and the set angle for operating the side brake operating means. If the front wheel shift operating means and the side brake operating means are provided with an integrated control valve, the steering angle detecting means for front wheel acceleration and the steering angle for side braking are provided. It is not necessary to separately provide two of the detecting means, and the control valve that constitutes the front wheel shift operating means and the control valve that constitutes the side brake operating means are operated separately while individually controlling them in separate circuits. Since no such linking means is required, the structure can be simplified.

[0035]

As described in claim 8 , the braking operation by the side brake operating means interlocked with the steering operation of the front wheels is set to a weak braking state in which the rear wheels do not substantially stop and the braking operation is performed. It is possible to avoid locking the rear wheel on the side of the turning center during operation, and to prevent the ground from being rough due to the rear wheel being dragged while being locked.

According to a ninth aspect of the present invention, the hydraulic actuator performs the speed increasing operation by the front wheel shifting operation means linked to the steering operation and the braking operation by the side brake operation means linked with the steering operation by the hydraulic actuator. If the hydraulic actuators operated by the front wheel shift operating means and the hydraulic actuators operated by the side brake operating means are configured to have different operating pressures from each other, the operating pressures suitable for the front wheel speed-up operation can be obtained. It is possible to set the operating pressure suitable for the braking operation, and it is possible to easily configure the front wheel acceleration at the appropriate timing associated with the steering and the braking operation at the appropriate operating pressure.

According to a tenth aspect of the present invention , the operating pressure of the speed increasing operation of the front wheel shift operating means linked to the steering operation is calculated from the operating pressure of the braking operation of the side brake operating means linked to the steering operation. If the value is set to a low value, the front wheel shifting operation means can perform the speed increasing operation with a low pressure until the operating pressure is generated during the braking operation, and the operating pressure of each hydraulic actuator can be easily controlled.

[0039]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of a four-wheel drive type agricultural tractor which is an example of a work vehicle. An engine (not shown) is provided at the front of the machine supported by front wheels 1 and rear wheels 2, and a mission case 4 is provided at the rear. The agricultural tractor is configured with.

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 (high, medium and low three-stage gear shift type) (not shown), or It is transmitted from the rear wheel differential mechanism 5 to the left and right rear wheels 2 via a second auxiliary transmission device (a two-stage gear shift type of neutral and ultra-low speed) (not shown). The power branched from 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 normal state in which the front wheels 1 are driven at substantially the same speed as the rear wheels 2 and a state in which the front wheels 1 are driven at a higher speed than the rear wheels 2. It is possible to perform switching operation between two states, that is, a transmission speed increasing state. As shown in FIG. 1, the shift member 9 for switching between the standard state and the speed-up state is urged toward the side of engagement with the standard gear 20 by the spring 10, and normally the shift member 9 is moved to the standard gear 20. The occlusion is in a standard condition. 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 side of the drawing and the friction clutch 21 is pressed and operated to increase the speed. Is obtained.

As shown in FIG. 1, for the left and right rear wheels 2,
Side brakes 11R and 11L capable of independently braking are provided. As shown in FIGS. 1 and 9, a pair of left and right side brake pedals 12R and 12L are arranged on the right side of the floor surface of the control section.
2R, 12L and the side brakes 11R, 11L are interlockingly connected via the cylinders 13R, 13L and the linkage rod 14.

With the above structure, the left and right side brakes 12R and 11L can be independently operated by depressing the left and right side brake pedals 12R and 12L. Cylinder 1 as shown in FIG.
3R and 13L are urged toward the extension side by a spring 13a,
By supplying hydraulic oil to contract the cylinders 13R and 13L, the left and right side brakes 11R and 11L can be operated to the braking side.

Next, a description will be given of how the steering operation of the front wheels 1 and the left and right side brakes 11R and 11L and the front wheel transmission 6 are linked. As shown in FIGS. 1 and 2, the pump 15
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-ahead 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, 13L of the left and right side brake pedals 12R, 12L are drained.
N, the hydraulic oil from the pump 15 is supplied to the oil chamber of the front wheel transmission 6 and the right cylinder 13R, and the left cylinder 13 is supplied.
The right turning position 16R in which L is in the oil drain state and the left turning position 16L in which 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 in the oil drain state are included. The control valve 16 is of a position switching type, and is configured such that the front wheel shift operating means and the side brake operating means are combined.

As shown in FIG. 1, a fan-shaped cam plate 18 is fixed to the pitman arm 17 for steering operation of the front wheels 1, and a spool 16a of the control valve 16 abuts on the cam plate 18 to make a spool. A spring 16b for urging 16a toward the contact side is provided. The state shown in FIG. 1 is a state in which the front wheels 1 are operated to the straight-ahead position, and the control valve 16 moves to the straight-ahead position 16N.
It is in the state of being operated. In this state, the left and right side brakes 11R and 11L are in a 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 from the state shown in FIG. 1 over the set angle, the spool 16a of the control valve 16 is pushed rightward by the cam plate 18 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 device 6 is operated to be turned on, and the front wheel 1 is driven at a higher speed than the rear wheel 2, and the right cylinder 13 is driven.
R contracts and the right side brake 11R is operated to the braking side.

On the contrary, when the front wheel 1 is steered to the left from the state shown in FIG. 1 over the set angle, the spool 1 of the control valve 16 is moved.
6a moves to the left in the plane of the drawing to the left turning position 16L, and hydraulic oil is supplied to the left cylinder 13L and the front wheel transmission 6. Therefore, the friction clutch 21 of the front wheel transmission 6 is operated to be operated, and the front wheel 1 is driven at a higher speed than the rear wheel 2, resulting in the speed increasing state, 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 and 11R as described above are operated by the switching lever 3.
It is configured such that the operation of L to the braking side and the operation of switching the front wheel transmission 6 to the speed increasing state are performed and the state of not performing the switching operation. Next, the switching structure will be described. . As shown in FIGS. 2 and 1, a pressure regulating valve 19 is connected to the oil passage 28, and the pressure regulating valve 19 supports a valve body 19a, a spring 19b for urging the valve body 19a toward the closing side, and a rear end of the spring 19b. The support member 19c is provided.
As a result, when the pressure in the oil passage 28 exceeds the pressure set by the spring 19b, the valve body 19a opens to the right on the paper surface and the working 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 urging 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
Reference numeral 9 denotes a pair of notches 29a and 29b and a drain hole 29.
1st land part 29A provided with c, and 1st circular arc surface 29
The second land portion 29B including the d and the second circular arc surface 29e is provided, and the rear end of the support member 19c of the pressure regulating valve 19 is abutted against the first circular arc surface 29d, and the support member 1 is formed.
The position of 9c is decided. Spool 2 of switching valve 24
An operation plate 30 is fixed to the tip of the switching lever 3
The operation plate 30 and the operation plate 30 are interlockingly connected by a connecting rod 22.

The state shown in FIG. 1 is a state in which the switching lever 3 is operated to the first position B1. In this state, the hydraulic oil from the pump 15 is supplied to the control valve 16 via the first cutout portion 29a in the spool 29 of the switching valve 24 and the oil passage 28. Support member 19c for pressure regulating valve 19
Is pushed to the left side of the drawing by the first arc surface 29d of the spool 29, the spring 19b of the pressure regulating valve 19 is compressed, and the action of the pressure regulating valve 19 causes the working hydraulic pressure to be supplied to the control valve 16. The second set pressure P2 described below is maintained.

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 at the first set pressure P1, the side brake 11 is operated.
R and 11L are not operated to the braking side. At the 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 in a state of being dragged as the vehicle body advances, this dragging action causes the side brakes 11R and 11L.
And the rear wheel 2 on the braking side is rotated.

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

In this case, the working hydraulic pressure supplied as described above is maintained at the second set pressure P2 by the action of the pressure regulating valve 19. Therefore, as shown by the solid line A2 in FIG. 7, the friction clutch 21 of the front wheel transmission 6 is turned on and operated, and the front wheel 1 is driven at a higher speed than the rear wheel 2, and the right or left cylinder 13R is activated. , 13L contract and the right or left side brakes 11R, 11L are operated to the weak braking state.
This interlocks with the steering operation of the front wheels to operate the side brakes.
Both operation means and front wheel shift operation means are allowed to operate
This is the first state of the operation. This makes it possible to make a very small small turn 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, the rear wheel 2 on the braking side is accompanied by the turning of the airframe.
When the vehicle is dragged, the rear wheel 2 on the braking side is rotated, so that the rear wheel 2 on the braking side rarely damages the ground.

Next, when the switching lever 3 is operated to the second position B2, the spool 29 of the switching valve 24 is rotated clockwise from the state shown in FIG. 2 by a predetermined angle. In this case, in the first arc surface 29d of the spool 29, the portion of the pressure regulating valve 19 that comes into contact with the support member 19c is slightly retracted to the right of the drawing. Along with this, the supporting member 19c also slides to the right in the plane of the drawing, and the biasing force of the spring 19b is weakened a little, so that the operating hydraulic pressure supplied to the control valve 16 is maintained at the first set pressure P1 lower than the second set pressure P2. It

In this state, when the front wheels 1 are steered to the right or left over a set angle and hydraulic oil is supplied to the right or left cylinders 13R, 13L and the front wheel transmission 6, the alternate long and short dash line in FIG. As indicated by A1, the friction clutch 21 of the front wheel transmission 6 is engaged and operated, and the speed increasing state in which the front wheel 1 is driven at a higher speed than the rear wheel 2 is revealed. On the other hand, the right or left cylinder 13R, 13L does not contract, and the right or left side brake 11R, 11L is not operated to the braking side. This is the second action by the braking turning inhibiting means to be described later.
It is in a state. That is, in the state where the switching valve 24 set in the state where the first set pressure P1 is maintained as described above, the side brake operating unit (control unit) can be operated while the shift switching operation can be performed by the front wheel shift operating unit (control valve 16). It constitutes a braking turning inhibiting means for inhibiting the operation by the valve 16). Accordingly, the pulling action in the turning direction by the speeded up front wheel 1 enables a smooth small turning turn. In this case, since the left and right rear wheels 2 are also driven, the rear wheels 2 on the turning center side
The rear wheel 2 on the turning center side without being dragged.
There is no need to damage the ground.

Next, as shown in FIG. 2, the switching lever 3 is moved to the third position.
When operated to the position B3, the spool 29 of the switching valve 24 becomes
From the state shown in FIG. 2, it is further rotated clockwise by a predetermined angle. In this case, the first spool 29
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 becomes the first
It is discharged through the drain hole 29c of the land portion 29A and the drain oil passage 39. In this way, the switching valve 24 set to maintain the first set pressure P1 and the switching valve 2 thereof.
The switching lever 3 for operating the drain hole 29c of No. 4 to communicate with the drain oil passage 39 is operated by the side brake operating means (control valve 16) and the front wheel shift operating means (control valve 16). A small-turn turning inhibiting means capable of blocking is configured.

Therefore, in this state, even if the front wheel 1 is steered to the right or left beyond the set angle, the chain double-dashed line A in FIG.
As shown in FIG. 4, hydraulic oil is not supplied to the right or left cylinders 13R and 13L and the front wheel transmission 6. As a result, the front wheel transmission 6 maintains the standard state during the turning operation,
The right or left side brake 11R, 11L is also not operated to the braking side, and the turning is performed with the four wheels, the front wheel 1 and the rear wheel 2, being driven at substantially the same speed. This is the above
It is the third state in which the small-turn turning inhibiting means acts, and
The 1st state, the 2nd state, and the 3rd state are the switching levers.
By the operation in 3, it is possible to switch forward and backward in this order.
The operation order is set.

In this agricultural tractor, at the time of turning operation at high speed, the automatic operation of the side brakes 11R and 11L to the braking side as described above and the front wheel transmission 6 are performed.
It is configured so that the switching operation to the speed-increased state is not performed. Next, this structure will be described. As shown in FIG. 3, the operation shaft 23 of the first auxiliary transmission device and the operation shaft 25 of the second auxiliary transmission device project from the lateral side surface of the mission case 4, and the operation shafts 23, 25 have an inverted L-shaped first shaft. 1 The operation member 26 and the operation plate 27 are fixed. Auxiliary speed change levers (not shown) of the first and second auxiliary speed change devices, the first operation member 26, and the operation plate 27 are interlockingly connected by linking rods 28 and 31. The operation plate 27 is provided with a V-shaped elongated hole 27 a, and the connecting rod 28 is connected to the first operation member 26.
The tip 28a of the is inserted into the long hole 27a of the operation plate 27.

Around the horizontal axis P1 of the mission case 4,
The V-shaped second operation member 32 is swingably supported, and the lower end of the second operation member 32 is pin-connected to the operation plate 27. A bracket 34 is supported on the upper end of the first operation member 23 so as to be freely swingable around the horizontal axis P2, and the inner 33a of the release wire 33 is attached to the bracket 3.
4 is connected. An end portion of the outer 33b of the release wire 33 is supported so as to be freely swingable 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 auxiliary transmissions, which are operated to change gears by the auxiliary transmission levers, are arranged in parallel to the transmission system. When one of them is operated to a certain shift position, the other is set to a neutral position. exist. The state shown in FIG. 3 is a state in which the auxiliary transmission lever is operated to the low speed position (the first auxiliary transmission device is in the low speed position and the second auxiliary transmission device is in the neutral position), and the first operating member 26 is in the low speed position F1. Is located in. In this state, the inner 33a of the release wire 33 is not pulled by the first and second operation members 26, 32 side.

As a result, the switching lever 3 can be operated to the first position B1 as shown in FIG. 2, and the automatic side brakes 11R and 11L are automatically operated in the weak braking state as described above during the turning operation. Also, 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, B3, and a state in which only the switching operation to the speed increasing state of the front wheel transmission 6 is performed during the turning operation, and the automatic side operation is performed during the turning operation. Brake 11R, 1
It is possible to select a state in which neither the operation toward the braking side of 1L nor the operation of switching the front wheel transmission 6 to the speed increasing state is performed. As described above, when the auxiliary transmission lever is operated to the low speed position, the switching lever 3 is moved to the first, second, third positions B1,
Three states can be selected by operating B2 and B3 (see FIG. 8).

Next, as shown in FIG. 4, when the auxiliary speed change lever is operated to the medium speed position (the first auxiliary speed change device is in the intermediate speed position and the second auxiliary speed change device is in the neutral position), the first operating member 26 moves to the paper surface. It is rocked in the clockwise direction to reach the medium speed position F2. In this state, the inner 33a of the release wire 33 is slightly pulled to the first and second operation members 26, 32 side. As a result, the operation plate 30 of the switching valve 24 is rotated from the state shown in FIG. 2 in the clockwise direction of the drawing by a predetermined angle.

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 auxiliary shift lever is operated from the low speed position to the medium 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 auxiliary transmission lever is operated to the medium speed position, the switching lever 3 is moved to the second and third positions B.
2 states can be selected by operating 2 or B3 (see FIG. 8).

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

In this state, it becomes impossible to operate the switching lever 3 to the first and second positions B1 and B2,
The switching lever 3 can only be operated to the third position B3. When the sub-gear lever is operated from the low speed / medium speed position 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 moved to the first and second positions by the pulling action of the inner 33a. From the second position B1, B2 to the third position B3
Is switched to. As described above, the switching lever 3 can only be operated to the third position B3 while the auxiliary transmission lever is being operated to the high speed position (see FIG. 8).

Next, when the sub shift lever is operated to the ultra-low speed position, the first operating member 26 is operated to the neutral position N as shown in FIG. 6, and the second operating member 32 is shown in FIG. 3 by the operating plate 27. From the state, it is operated to the ultra-low speed position C in FIG. In this case, the operation of the first operating member 26 causes the release wire 33 to move.
The inner 33a of the second operation member 3 is pulled toward the first operation member 26 side, and accordingly, the second operation member 3 on the outer 33b side is operated.
2 also swings in the same direction, so the inner 3 is actually
3a is not pulled to the side of the first operating member 26 and is not operated. As a result, the switching lever 3 is moved to the 1st, 2nd, 3rd positions B in the same manner as when the auxiliary transmission lever is operated to the low speed position.
It is possible to select three states by operating 1, B2 and B3 (see FIG. 8).

When the spool 29 of the switching valve 24 shown in FIG. 2 is pulled out, rotated by 180 degrees and then inserted again, the spool 2
The second circular arc surface 29e of the second land portion 29B of 9 contacts the support member 19c of the pressure regulating valve 19, and the hydraulic oil from the pump 15 passes through the notch portion 29b of the first land portion 29A to the control valve 16 Is supplied to. In this case, the support member 19c of the pressure regulating valve 19 is in the state in which the switching lever 3 is being operated to the first position B1, the first arc surface 29d of the second land portion 29B.
It is in a state of being pushed to the left side of the paper rather than being in contact with.

As a result, the hydraulic pressure supplied to the control valve 16 by the action of the pressure regulating valve 19 is maintained at the third set pressure P3 which is higher than the second set pressure P2. As shown by the solid line A3 in FIG. 7, at the third set pressure P3, the side brake 1
1R and 11L are forced to operate, 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 in which 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 by the set angle or more, the speeded-up front wheel 1 pulls in the turning direction, and the rear wheel 2 on the turning center side is strongly braked. You can make very small small turns. From this state, move the switching lever 3 to the second and third positions B.
2 and B3, the dashed-dotted line A in FIG.
The states of the one and two-dot chain line A4 are obtained.

[Other Embodiment] In the embodiment shown in FIG. 3, the inner 33a of the release wire 33 is connected to the first operating member 26 and the outer 33b is connected to the second operating member 32. The inner 33a may be connected to the second operating member 32, and the outer 33b may be connected to the first operating member 26. Further, in the above-described embodiment, the first and second auxiliary transmissions are arranged in parallel with the transmission system, but the first and second auxiliary transmissions may be arranged in series with the transmission system.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing left and right side brakes, 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 a linked state of the switching valve with a switching lever and a release wire.

FIG. 3 is a side view of the vicinity of the first and second operation members in a state in which the auxiliary transmission lever is operated to a low speed position.

FIG. 4 is a side view of the vicinity of the first and second operating members in a state in which the auxiliary transmission lever is operated to a medium speed position.

FIG. 5 is a side view of the vicinity of the first and second operation members in a state in which the auxiliary 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 in which the auxiliary transmission lever is operated to an ultra-low speed position.

FIG. 7 is a diagram showing the relationship between the operating pressure of the side brakes and the front wheel transmission and the steering angle of the front wheels.

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 of a side brake pedal and a side brake and a cylinder for connection.

[Explanation of symbols]

1 Front Wheel 2 Rear Wheel 6 Front Wheel Transmission 11R, 11L Side Brake 16 Front Wheel Shift Operating Means, Side Brake Operating Means 18 Steering Angle Detecting Means 3, 24 Small Turn Turning Preventing Means 24 Braking Turning Preventing Means

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-175331 (JP, A) JP-A-3-243429 (JP, A) JP-A-2-20463 (JP, A) JP-A-2- 254068 (JP, A) JP-A-2-290725 (JP, A) JP-A-63-31883 (JP, A) Actually developed 3-8927 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B62D 11/00 B60K 17/00 B60K 41/00

Claims (10)

(57) [Claims] 1. A standard condition 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 an increase in which power is transmitted to the front wheels so that the front wheels are driven at a higher speed than the rear wheels. A front wheel transmission capable of switching to a high speed state, a pair of left and right side brakes capable of braking a selected one of a pair of left and right rear wheels, and a front wheel being steered from a straight position to the right or left. , A front wheel shifting operation means for shifting the front wheel transmission to a speed-up state in synchronism with this steering operation, and when the front wheels are steered to the right or left from the straight-ahead position, this steering operation is performed. And a side brake operating means for operating the side brake on the turning center side to a braking side in an interlocking manner, and blocking the operation by the side brake operating means in a state in which a shift change operation by the front wheel shift operating means is possible. Braking turning suppression Means and the operation by the parking brake operating means, and a both possible blocking maneuverability pivot inhibiting means operated by the front wheel speed change operating unit, the parking brake operating means in conjunction with the front wheel steering operation
And allowing the operation by the front wheel shift operation means together.
1 state and a second state in which the braking turning inhibiting means acts
And a third state in which the small-turn turning inhibiting means acts,
The operation order is set so that it can be switched between forward and reverse in this order.
That work vehicle. 2. A first state in which both speed-up operation by front wheel shift operation means interlocked with steering operation and braking operation by side brake operation means interlocked with steering operation are permitted, and front wheel shift operation means. Brake turning inhibiting means that restrains the braking operation by the side brake operating means while allowing only the speed increasing operation at
Small state that restrains both the second state in which it is activated and the speed-up operation by the front wheel shift operation means and the braking operation by the side brake operation means.
The work vehicle according to claim 1, wherein the work vehicle is configured to be switchable to a third state in which the turning prevention means is actuated based on a manual operation. 3. When the traveling speed state of the airframe is low, both speed-up operation by front wheel shift operation means linked to steering operation and braking operation by side brake operation means linked to steering operation are permitted. Then, when the speed is changed to the higher speed side than the low speed state,
The second state in which only the speed increasing operation by the front wheel shift operating means is permitted to restrain the braking operation by the side brake operating means, or the speed increasing operation by the front wheel shift operating means and the braking operation by the side brake operating means are performed. The work vehicle according to claim 1 or 2, wherein the work vehicle is configured to be switched to any one of a third state in which both are restrained. 4. When the traveling speed state of the aircraft is low, both speed-up operation by the front wheel shift operation means linked to the steering operation and braking operation by the side brake operation means linked to the steering operation are permitted. Then, when the speed is changed from the low speed state to the medium speed state, the state is switched to the second state in which only the speed increasing operation by the front wheel shift operation means is allowed and the braking operation by the side brake operation means is restrained . The work vehicle according to any one of claims 1 to 3, wherein the work vehicle is configured to be formed. 5. When the traveling speed state of the machine body is low, both speed-up operation by the front wheel shift operation means linked to the steering operation and braking operation by the side brake operation means linked to the steering operation are permitted. However, when the speed is changed from the medium speed state to a high speed state, it is possible to switch to a third state in which both the speed increasing operation by the front wheel shift operating means and the braking operation by the side brake operating means are restrained . The work vehicle according to any one of claims 1 to 3. 6. When the traveling speed state of the aircraft is low, both speed-up operation by front wheel shift operation means linked to steering operation and braking operation by side brake operation means linked to steering operation are permitted. Then, when the speed is changed to the higher speed side than the low speed state,
The second state in which only the speed increasing operation by the front wheel shift operating means is permitted to restrain the braking operation by the side brake operating means, or the speed increasing operation by the front wheel shift operating means and the braking operation by the side brake operating means are performed. When the speed is changed to any of the third states in which both are restrained and returned to the low speed state, the speed-up operation is performed by the front wheel shift operation means linked to the steering operation and the side brake operation means linked to the steering operation. The work vehicle according to any one of claims 1 to 5, wherein the work vehicle is configured to automatically return to a first state in which both braking operation is permitted. 7. A steering angle detecting means for detecting a setting angle for operating the front wheel shift operating means and a setting angle for operating the side brake operating means , the steering angle of the front wheels comprising: Moreover, the front wheel shift operation means and the side brake operation means are constituted by an integrated control valve.
The work vehicle according to any one of claims 1 to 6 . Braking operation at 8. The side brake operating means interlocked with the front wheel steering operation, in any one of claims 1 to 7 rear wheels is a weak braking state does not become stopped substantially stopped The work vehicle described. 9. A hydraulic actuator is used to perform speed-up operation by front wheel shift operation means linked to steering operation and braking operation by side brake operation means linked to steering operation. 9. The work vehicle according to claim 1 , wherein the hydraulic actuators operated by the front wheel shift operation means and the hydraulic actuators operated by the side brake operation means have different operating pressures. The 10. working pressure of the speed increasing actuation of the front wheel speed change operation unit in conjunction to the steering operation, it is set lower than the operating pressure of the braking operation at the side brake operating means in conjunction with the steering operation according Item 9. The work vehicle according to item 9 .