WO2018052056A1

WO2018052056A1 - Tractor

Info

Publication number: WO2018052056A1
Application number: PCT/JP2017/033197
Authority: WO
Inventors: 柳原克己; 木山和也
Original assignee: 株式会社クボタ
Priority date: 2016-09-16
Filing date: 2017-09-14
Publication date: 2018-03-22

Abstract

This tractor is provided with: a hydraulic vertically driving unit 17 for vertically driving a towed tiller; and a mechanical coordination unit 18 for automatic vertical motion, the mechanical coordination unit 18 converting the amount of change in a towed load into a vertical operation amount and transmitting the vertical operation amount to the vertically driving unit 17. The mechanical coordination unit 18 is provided with: a change amount conversion mechanism 33 having a load detection member 36 which rocks forward and backward in response to a towed load; and a link mechanism 34 for connecting in a coordinated manner the change amount conversion mechanism 33 and the vertically driving unit 17. The change amount conversion mechanism 33 has a rocking member 38 supported in a rockable manner by the load detection member 36 and connected in an coordinated manner to the vertically driving unit 17 through the link mechanism 34, and the change amount conversion mechanism 33 is configured so as to amplify, by means of the relative rocking between the load detection member 36 and the rocking member 38, the amount of change in a towed load, which is obtained by the forward and backward rocking of the load detection member 36, and then convert the amplified amount into the vertical operation amount.

Description

Tractor

The present invention relates to a three-point link mechanism that is connected to the rear part of a vehicle body so as to be able to swing up and down, and a hydraulic lift drive that drives a pull-type tillage device attached to the three-point link mechanism together with the three-point link mechanism. The present invention relates to a tractor including a unit and a mechanical linkage unit for automatic lifting that converts a change amount of a traction load into a lifting operation amount and transmits it to the lifting drive unit.

[1]
The tractor as described above includes a draft adjustment lever for setting tillage depth, a link mechanism (such as a cylinder shaft and an arm) that links the spool of the control valve to the draft adjustment lever, and a load detection member that swings back and forth according to the traction load. (Top link hinge) and a second link mechanism (draft feedback link mechanism) that interlocks the spool of the control valve with the load detection member, etc., so that the traction load is determined by the working depth setting of the draft adjustment lever There is one configured so that draft control can be maintained (see, for example, Patent Document 1).

[2]
In the tractor as described above, during a tilling work in which a plow, which is an example of a towing type tillage device, is attached to a three-point link mechanism, the amount of change in towing load is converted into a lifting operation amount, and a lifting drive unit (hydraulic lifting / lowering unit). Some have a mechanical linkage unit (draft feedback link mechanism) for draft control to be transmitted to the apparatus (see, for example, Patent Document 1).

Further, in the tractor as described above, the rotary cover is attached to the three-point link mechanism as an example of a towing type tillage device. Mechanical linkage unit (oscillating link, interlocking link, sensor wire) for automatic tilling depth control that converts the change in tilling depth obtained by the swing displacement into the lifting operation amount and transmits it to the lifting drive unit (control hydraulic circuit) ) (For example, see Patent Document 2).

Since the tractor described in Patent Document 1 includes a mechanical linkage unit for draft control, when performing a plowing work with a plow, draft control can be performed in which the plow automatically moves up and down according to the traction load. Thereby, in this tractor, the traction load can be kept constant, and the occurrence of an engine stall due to the increase in the traction load can be avoided.

Since the tractor described in Patent Document 2 includes a mechanical linkage unit for automatic tillage control, when performing a tilling operation using a rotary tiller, the rear cover is interlocked with the vertical swing of the rear cover according to the tilling depth. Thus, automatic tilling control in which the rotary tiller automatically moves up and down can be performed. Thereby, in this tractor, the plowing operation with high accuracy in which the plowing depth is maintained constant can be performed.

JP 2006-109802 A JP 2005-198665 A

[1]
The problems corresponding to the background art [1] are as follows.
In the tractor described in Patent Document 1, for example, when cultivating work by draft control in a standard field where the traction load is difficult to increase due to the hardness of the soil and the fluctuation of the traction load is difficult to increase, Regardless of whether or not the tillage load is likely to increase and the fluctuation of the tow load tends to be severe, the plow, subsoiler, etc. It is configured to move up and down.
Thereby, even if it is a case where traction load rises rapidly, a tilling device will raise at a standard speed based on a raise of traction load.
For this reason, when the traction load rapidly increases, the increase in the traction load cannot be suitably suppressed, and there is a possibility of causing an engine stall due to the increase in the traction load.

That is, it is desired that engine stall caused by an increase in the traction load can be avoided even when the traction load rapidly increases.

[2]
The problems corresponding to the background art [2] are as follows.

Since the tractor described in Patent Document 1 does not include a mechanical linkage unit for automatic tillage control, the above-described automatic tillage control cannot be performed when performing a tilling operation using a rotary tiller. Therefore, it becomes difficult to perform a highly accurate tilling work in which the tilling depth is maintained constant.

Since the tractor described in Patent Document 2 does not include a mechanical linkage unit for draft control, when performing plowing work with a plow, the draft control described above cannot be performed. There is a risk of causing an engine stall due to the rise.

That is, it is desired to develop a mechanical linkage unit capable of performing draft control suitable for tillage work using a plow and the like and automatic tillage control suitable for tillage work using a rotary tiller.

[1]
The means for solving the problem [1] is as follows.

The tractor according to the present invention includes a three-point link mechanism connected to a rear portion of a vehicle body so as to be swingable up and down, and a hydraulic type that drives a pulling type tiller attached to the three-point link mechanism together with the three-point link mechanism. And a mechanical linkage unit for automatic lifting that converts the amount of change in the traction load into a lifting operation amount and transmits it to the lifting drive unit,
The mechanical linkage unit includes a change amount conversion mechanism having a load detection member that swings back and forth in response to a traction load transmitted through the top link of the three-point link mechanism, the change amount conversion mechanism, and the lifting drive unit. A link mechanism that interlocks and
The change amount conversion mechanism includes a swinging member that is swingably supported by the load detection member and that is linked to the lifting drive unit via the link mechanism. A change amount of the traction load obtained by movement is amplified by relative swinging of the load detection member and the swinging member, and then converted into the lifting operation amount.

According to this means, when a change occurs in the traction load in a cultivating work in which a traction type tilling device such as a plow or a subsoiler is attached to the three-point link mechanism, the load detection member is set according to the amount of change in the traction load at this time. In addition to swinging back and forth, the load detecting member and the swinging member swing relative to each other, so that the amount of change in the traction load is amplified. Then, the amount of change in the traction load after amplification is converted into a lift operation amount and transmitted to the lift drive unit.
As a result, it is possible to quickly raise and lower the towing type tillage device in accordance with changes in the towing load, and as a result, even when the towing load increases rapidly, engine stall due to the increase in towing load can be avoided. Can do.

In addition, since the load detection member and the swing member swing relative to each other, the amount of change in the traction load can be greatly amplified while narrowing the swing range of the load detection member and the swing member. Thereby, the front-rear length of the space required for installation of the change amount conversion mechanism having the load detection member and the swing member can be shortened.
As a result, it is possible to avoid an engine stall caused by a sudden increase in the traction load while suppressing an increase in the size of the vehicle body that increases the overall length of the vehicle body.

As one of the means for making the present invention more suitable,
The change amount conversion mechanism converts a change amount of the traction load into the lift operation amount without amplifying the change amount, and a first conversion state that amplifies the change amount of the traction load and then converts it into the lift operation amount. It is configured to be switchable between two conversion states,
When the change amount conversion mechanism is in the first conversion state, due to the integral swinging of the load detecting member and the swinging member, the change amount of the traction load is not amplified and the lift drive unit is used as the lift operation amount. Communicated to
When the change amount conversion mechanism is in the second conversion state, the change amount of the traction load is amplified by the relative swinging of the load detecting member and the swinging member, and the lift drive unit is used as the lift operation amount. Reportedly.

According to this means, for example, when plowing or subsoiler is used in a standard field where the traction load is difficult to increase due to soil hardness and the traction load does not fluctuate easily, If the conversion mechanism is switched to the first conversion state, a tilling device such as a plow or subsoiler can be raised or lowered according to the traction load at a standard speed suitable for this field. As a result, it is possible to avoid an engine stall due to an increase in the traction load while performing draft control with a gentle change in tilling depth.
In addition, for example, when plowing or sub-soiler is used in a field where the traction load is likely to increase due to the hardness of the soil and the traction load tends to fluctuate, the operator converts the change amount conversion mechanism to the second conversion amount. If it switches to a state, tillage devices, such as a plow and a subsoiler, can be raised / lowered according to traction load at high speed suitable for this field. As a result, even when the traction load suddenly increases, engine stall due to the increase in traction load can be avoided.

As one of the means for making the present invention more suitable,
The mechanical linkage unit includes an operation tool for switching the change amount conversion mechanism between the first conversion state and the second conversion state.

According to this means, the operator can easily switch the change amount conversion mechanism between the first conversion state and the second conversion state by operating the operation tool.

As one of the means for making the present invention more suitable,
The change amount conversion mechanism includes a holding mechanism that biases the swing member to a predetermined posture with respect to the load detection member,
The operation tool includes a receiving member that moves between a non-receiving position and a receiving position,
When the receiving member is located at the non-receiving position, the receiving member is removed from the swinging region of the swinging member and does not receive the swinging member, whereby the load detection member and the swinging member are Oscillates integrally by the holding action of the holding mechanism,
When the receiving member is positioned at the receiving position, the receiving member is positioned within the swinging region of the swinging member and receives the swinging member, whereby the load detection member and the swinging member are The relative swinging against the holding action of the holding mechanism is allowed.

According to this means, the change amount conversion mechanism includes the holding mechanism and the operation tool only includes the receiving member. When the receiving member is in the non-receiving position, the change amount conversion mechanism swings with the load detection member. A first conversion state in which the member swings integrally can be obtained. In addition, when the receiving member is in the receiving position, a second conversion state in which relative change between the load detection member and the swing member is allowed in the change amount conversion mechanism can be obtained.
As a result, it is possible to surely switch the change amount conversion mechanism between the first conversion state and the second conversion state while simplifying the configuration.

As one of the means for making the present invention more suitable,
When the receiving member is located at the receiving position, the load detecting member and the swinging member are integrally swung by the holding action of the holding mechanism while the swinging member is not received by the receiving member. While the moving member is moving and is being received by the receiving member, relative swinging of the load detecting member and the swinging member against the holding action of the holding mechanism is allowed.

According to this means, even when the receiving member is located at the receiving position, the swing displacement amount of the load detecting member based on the traction load is until the swing member reaches a predetermined amount that can be received by the receiving member. When the load detection member and the swing member swing together, the amount of change in the traction load is transmitted to the lift drive unit as a lift operation amount without being amplified. When the swing displacement amount of the load detection member exceeds a predetermined amount, the swing member is received by the receiving member, and the load detection member and the swing member swing relative to each other. Is amplified and transmitted to the lift drive unit as a lift operation amount.
As a result, in a work situation where the traction load slightly exceeds the set value and there is no possibility of causing an engine stall, the lifting drive unit is in the work situation at this time even if the change amount conversion mechanism is in the second conversion state. A tilling device such as a plow or subsoiler is driven up and down according to the traction load at a suitable standard speed.
Also, in working situations where the traction load greatly exceeds the set value and the engine stall is likely to occur, the elevating drive unit pulls the tillage device such as plow and subsoiler at a high speed suitable for the working situation at this time. Drive up and down according to
As a result, even in a work situation where the traction load slightly exceeds the set value, the elevating drive unit lowers the durability of the elevating drive unit due to the elevating drive unit driving the tillage device at an unnecessarily high speed. While avoiding the fear, it is possible to avoid an engine stall caused by a sudden increase in the traction load.

As one of the means for making the present invention more suitable,
A roller that is rotatable about an axis parallel to the axis of oscillation of the oscillation member is provided at a receiving position of the oscillation member of the reception member.

According to this means, when the swinging member slides relative to the receiving member due to relative swinging of the load detection member and the swinging member in the second conversion state of the change amount conversion mechanism, The roller rotates in the sliding direction.
Accordingly, the swing member smoothly slides with respect to the receiving member, and the load detection member and the swing member smoothly swing relative to each other.
As a result, it is possible to smoothly perform the draft control in the second conversion state of the change amount conversion mechanism.

As one of the means for making the present invention more suitable,
The holding mechanism includes a stopper that restricts the swinging member from swinging in the direction in which the three-point link mechanism is lowered with respect to the load detection member, and the swinging member is provided with swinging toward the stopper. And a spring.

According to this means, the load detecting member and the swinging member can be swung integrally when the change amount conversion mechanism is in the first conversion state with a simple configuration including only a stopper and a spring. When the conversion mechanism is in the second conversion state, the load detection member and the swing member can be relatively swung.
As a result, the change amount conversion mechanism can be suitably switched between the first conversion state and the second conversion state while simplifying the configuration.

As one of the means for making the present invention more suitable,
The said operation tool is arrange | positioned adjacent to the said driver seat in the back location of the driver seat in a vehicle body.

According to this means, the operator can operate the operation tool by extending his hand toward the rear part of the driver seat while sitting on the driver seat, and the conversion state of the change amount conversion mechanism is easy. You can switch to

As one of the means for making the present invention more suitable,
The change amount conversion mechanism is disposed adjacent to the driver seat at a location behind the driver seat in the vehicle body.

According to this means, the operator can easily confirm the operating state of the change amount conversion mechanism by visually observing the rear portion of the driver seat while being seated on the driver seat.
Further, since the rear portion of the driver seat is not covered with a cover or the like, the change amount conversion mechanism can be easily maintained.

[2]
The means for solving the problem [2] is as follows.

The tractor according to the present invention is a tractor that can be operated by attaching a tillage device,
A three-point link mechanism that is connected to the rear part of the vehicle body so as to swing up and down, and to which the tilling device can be attached, a hydraulic lifting drive unit that drives the three-point link mechanism to move up and down, a change amount of the traction load, and a tilling depth A mechanical linkage unit for automatic raising / lowering that selectively converts any one of the change amounts into an elevation operation amount and transmits it to the elevation drive unit,
The mechanical linkage unit includes a change amount conversion mechanism that can be switched between a first linkage conversion state and a second linkage conversion state, and a link mechanism that interlocks and connects the change amount conversion mechanism and the elevating drive unit. Prepared,
The change amount conversion mechanism includes a load detection member that swings back and forth according to a traction load transmitted through the top link of the three-point link mechanism, and a swing member that swings according to the tilling depth of the tilling device. Have
When the change amount conversion mechanism is switched to the first linkage conversion state, the change amount conversion mechanism can convert the change amount of the traction load obtained by swinging the load detection member back and forth into the lift operation amount. become,
When the change amount conversion mechanism is switched to the second linkage conversion state, the change amount conversion mechanism can convert the change amount of the tilling depth obtained by swinging of the swing member into the lifting operation amount. Become.

According to this means, when performing a tilling work using a plow, a subsoiler, etc., the mechanical linkage unit is placed in the draft control state (first linkage state) by attaching the plow, the subsoiler, etc. to the three-point link mechanism. In this draft control state, when an operator switches the change amount conversion mechanism to the first linkage conversion state, a draft in which a plow, a subsoiler, and the like automatically move up and down according to the traction load during a tilling operation. Control is performed. As a result, it is possible to avoid the occurrence of engine stall due to an increase in traction load.
In addition, when performing a tilling operation using a rotary tiller or the like, the mechanical linkage unit is placed in the automatic tilling control state (second linkage state) by attaching the rotary tiller or the like to the three-point link mechanism. In this automatic tilling control state, when the operator switches the change amount conversion mechanism to the second linkage conversion state, the rotary tiller and the like automatically move up and down according to the tilling depth during the tilling work. Automatic plowing control is performed. As a result, it is possible to perform a highly accurate tilling work in which the tilling depth is maintained constant.
In other words, this tractor is equipped with the mechanical linkage unit having the above-described configuration, so that the above-described draft control can be performed when performing a tilling operation using a plow, a subsoiler, or the like, and a tilling operation using a rotary tiller or the like. When performing, automatic plowing control mentioned above can be performed.

As one of the means for making the present invention more suitable,
The mechanical linkage unit includes an operation tool that switches the change amount conversion mechanism between the first linkage conversion state and the second linkage conversion state.

According to this means, the operator can easily switch the change amount conversion mechanism between the first linkage conversion state and the second linkage conversion state by operating the operation tool.

As one of the means for making the present invention more suitable,
The swing member is supported swingably on the load detection member,
The operation tool is in contact with the load detection member to prevent the load detection member from swinging back and forth, and non-contact allowing the load detection member to swing back and forth without contacting the load detection member. A contact member that moves across the position,
When the contact member is in the non-contact position, the load detection member swings back and forth, whereby the amount of change in the traction load is transmitted to the lift drive unit as the lift operation amount,
When the contact member is in the contact position, the swinging member independently swings in a state where the load detection member does not swing back and forth, whereby the change amount of the tilling depth is transmitted to the lift drive unit as the lift operation amount. It is done.

According to this means, when the contact member is in the non-contact position, the change amount conversion mechanism is in the first linkage conversion state described above, and when the contact member is in the contact position, the change amount conversion mechanism is in the second linkage described above. Conversion state.
This prevents the load detection member from swinging back and forth according to the traction load transmitted through the top link in automatic tilling control during tillage work using a rotary tiller and the like. There is no possibility that the change amount of the traction load is input to the change amount conversion mechanism due to the movement.
As a result, in the automatic tilling control based on the change amount of the tilling depth, it is possible to avoid the possibility that the work accuracy is reduced due to the change amount of the traction load being input to the change amount conversion mechanism.

As one of the means for making the present invention more suitable,
A first conversion state and a second conversion state as the first linkage conversion state,
The change amount conversion mechanism can be switched between the first conversion state and the second conversion state by operating the operation tool, and urges the swing member to a predetermined posture with respect to the load detection member. Holding mechanism to
When the change amount conversion mechanism is in the first conversion state, the load detection member and the swing member swing together by the holding action of the holding mechanism, and the traction obtained by swinging back and forth of the load detection member The amount of change in the load is not amplified and is transmitted to the lift drive unit as the lift operation amount,
When the change amount conversion mechanism is in the second conversion state, the load detection member and the swing member are allowed to swing relative to each other against the holding action of the holding mechanism, and the load detection member swings back and forth. The obtained change amount of the traction load is amplified and transmitted to the elevating drive unit as the elevating operation amount.

According to this means, for example, when plowing or subsoiling is performed in a standard field where the traction load is difficult to increase due to soil hardness and the traction load does not fluctuate easily, By operating and switching the change amount conversion mechanism to the first conversion state, the plow, the subsoiler, and the like can be raised and lowered according to the traction load at a standard speed suitable for this field. As a result, it is possible to avoid the occurrence of engine stall due to an increase in the traction load while performing draft control with a gentle change in tilling depth.
In addition, for example, when plowing or plow sowing is performed in a field where the traction load is likely to increase due to the hardness of the soil and the traction load is likely to fluctuate, the operator operates the operation tool to change the amount of change. When the conversion mechanism is switched to the second conversion state, the plow, the subsoiler, and the like can be lifted and lowered according to the traction load at a high speed suitable for the field. As a result, it is possible to avoid the occurrence of engine stall due to a sudden increase in the traction load.

According to this means, the load detecting member and the swinging member can be integrally swung in the first conversion state with a simple configuration including only the stopper and the spring. In the second conversion state, relative swinging between the load detection member and the swinging member can be allowed.
As a result, the change amount conversion mechanism can be suitably switched between the first conversion state and the second conversion state while simplifying the configuration.

As one of the means for making the present invention more suitable,
The load detecting member includes a first connecting part to which a long top link is connected and a second connecting part to which a bracket for supporting the short top link is connected.

According to this means, for example, when performing a tilling work by a rotary tiller, the specification of the three-point link mechanism is a standard link specification including a long top link and left and right lower links, and a short top link and left and right lower links. It can be easily changed to a special link specification with
And when the specification of the three-point link mechanism is changed from the standard link specification to the special link specification, the lift drive amount of the rotary tiller with respect to the lift operation amount of the lift drive unit becomes large, and the highest lift position of the rotary tiller is high. Become.
As a result, for example, when plowing work with a rotary tiller at a work site with a high hail, the specification of the three-point link mechanism is changed from the standard link specification to the special link specification. It is easy to avoid the possibility that the rotary tiller will come into contact with a high ridge when performing a coasting turn or the like.

It is a right view of the tractor where the plow was attached to the three-point link mechanism in the first embodiment. It is a right view of the tractor in which the rotary tiller was attached to the three-point link mechanism in the first embodiment. It is a vertical right side view of the principal part which shows the structure of the raising / lowering drive unit and mechanical linkage unit in 1st Embodiment. It is a top view of the principal part which shows the structure of the raising / lowering drive unit and mechanical linkage unit in 1st Embodiment. It is a disassembled perspective view of the principal part which shows the structure of the raising / lowering drive unit and mechanical linkage unit in 1st Embodiment. It is a vertical development right side view of the important section showing the operation state of the raising / lowering drive unit when the tillage device stops raising and lowering by holding the position on the lower setting side of the height setting lever. It is a vertical development right side view of the principal part showing the operation state of the raising / lowering drive unit when the tilling device is raised in conjunction with the swinging operation of the height setting lever in the high position setting direction. It is a vertical development right side view of the important section which shows the operation state of the raising / lowering drive unit when the tillage device stops raising and lowering by holding the position of the height setting lever on the high position setting side. It is a disassembled perspective view of the principal part which shows structures, such as a variation | change_quantity conversion mechanism in 1st Embodiment. It is a rear view of the principal part which shows structures, such as a variation | change_quantity conversion mechanism in 1st Embodiment. FIG. 6 is a sectional view taken along line XI-XI in FIG. 4. It is a vertical right view of the principal part which shows the operation state of the mechanical linkage unit and the raising / lowering drive unit when the traction load does not exceed the set value in the first conversion state of the change amount conversion mechanism in the first embodiment. It is a vertical right view of the principal part which shows the operation state of a mechanical linkage unit and a raising / lowering drive unit when a traction load exceeds a setting value in the 1st conversion state of the variation | change_quantity conversion mechanism in 1st Embodiment. It is a vertical right view of the principal part which shows the operation state of a mechanical linkage unit and a raising / lowering drive unit when the traction load is not over the setting value in the 2nd conversion state of the variation | change_quantity conversion mechanism in 1st Embodiment. It is a vertical right view of the principal part which shows the operation state of a mechanical linkage unit and a raising / lowering drive unit when a traction load exceeds a setting value in the 2nd conversion state of the variation | change_quantity conversion mechanism in 1st Embodiment. It is a vertical right side view of the principal part which shows the operation state of the mechanical linkage unit and the raising / lowering drive unit when the tilling depth reaches the set tilling depth in the second linkage conversion state of the change amount conversion mechanism in the first embodiment. . It is a vertical right side view of the principal part which shows the operation state of the mechanical linkage unit and the raising / lowering drive unit when the tilling depth is deeper than the set tilling depth in the second linkage conversion state of the change amount conversion mechanism in the first embodiment. . It is a right view of the tractor with which the plow was attached to the three-point link mechanism in 2nd Embodiment. It is a vertical right side view of the principal part which shows the structure of the raising / lowering drive unit and mechanical linkage unit in 2nd Embodiment. It is a vertical right view of the principal part which shows the operation state of a mechanical linkage unit and a raising / lowering drive unit when the traction load is not over the setting value in 2nd Embodiment. It is a vertical right view of the principal part which shows the operation state of a mechanical linkage unit and a raising / lowering drive unit when a traction load exceeds a setting value in 2nd Embodiment.

[First Embodiment]
Hereinafter, a first embodiment, which is an example of a mode for carrying out the present invention, will be described with reference to the drawings.
The direction indicated by the arrow F shown in FIG. 1 is the front side of the tractor, and the direction indicated by the arrow U is the upper side of the tractor.

As shown in FIGS. 1 and 2, the tractor illustrated in the first embodiment includes a front frame 1 disposed at the front of the vehicle body, an engine 2 connected to the rear of the front frame 1, and a rear end of the engine 2. The clutch housing 3 connected to the lower portion, the intermediate frame 4 connected to the rear end portion of the clutch housing 3, and the transmission case serving as a rear frame connected to the rear end portion of the intermediate frame 4 (hereinafter referred to as a T / M case). 5) Left and right front wheels 6 arranged on the left and right of the front frame 1, left and right rear wheels 7 arranged on the left and right of the T / M case 5, left and right rear fenders 8 covering the left and right rear wheels 7, and the vehicle body And a boarding type driving unit 9 disposed at the rear of the vehicle.

Although not shown, the power from the engine 2 is supplied from the main clutch built in the clutch housing 3 and the transmission shaft covered by the intermediate frame 4 to the main power built in the T / M case 5. It is transmitted to the transmission. Then, the power after the shift by the main transmission is transmitted to the left and right front wheels 6 and the left and right rear wheels 7 via an auxiliary transmission built in the T / M case 5 or the like.

As shown in FIGS. 1 and 2, the driving unit 9 includes a steering wheel 10 for front wheel steering, a driving seat 11 disposed between the left and right rear fenders 8, and the like.

A three-point link mechanism 12 that enables attachment of the working device is connected to the rear portion of the T / M case 5 so as to be swingable up and down. The three-point link mechanism 12 includes a single top link 13 and left and right lower links 14. Thereby, when performing a tilling operation with this tractor, a towed tilling device 15 which is an example of a working device can be attached to the three-point link mechanism 12.

In the first embodiment, a plow 15A, which is an example of a towing type tilling device 15, is attached to the three-point link mechanism 12 (see FIG. 1), and a rotary, which is an example of a towing type tilling device 15. The state where the tilling device 15B is attached to the three-point link mechanism 12 (see FIG. 2) is illustrated, but the three-point link mechanism 12 includes a traction type such as a disk harrow, a cultivator, and a sub soiler. A tilling device 15 can be attached.

As shown in FIGS. 1 to 8, the tractor includes a mechanically linked hydraulic lifting device 16. The hydraulic lifting / lowering device 16 selectively lifts / lowers either the hydraulic lifting / lowering drive unit 17 that drives the tilling device 15 up / down together with the three-point link mechanism 12, and the change amount of the traction load or the change amount of the tilling depth. A mechanical linkage unit 18 for automatic raising / lowering that is converted into an operation amount and transmitted to the raising / lowering drive unit 17 is provided.

The elevating drive unit 17 includes left and right lift arms 20 that suspend and support the left and right lower links 14 via left and right support members 19, a hydraulic cylinder 21 that drives the left and right lift arms 20 to swing up and down, and a hydraulic cylinder 21. A control valve 22 that controls the operation of the tiller 15, a height setting lever 23 that sets the control target height of the tilling device 15, a friction-type holding mechanism 24 that holds the height setting lever 23 at an arbitrary operation position, A first link mechanism 25 that links the spool 22A to the height setting lever 23, a feedback link mechanism 26 that links the spool 22A to the left and right lift arms 20, and the like are provided. The control valve 22 includes an urging means (not shown) for urging the spool 22A to return to the lowered position on the front side of the vehicle body.

The first link mechanism 25 can swing back and forth on the first swing arm 27 that contacts the height setting lever 23 from the rear side of the vehicle body (the higher position setting side of the height setting lever 23) and the spool 22A of the control valve 22. And the first crankshaft 29 extending from the swing center of the first swing arm 27 to the upper end of the balance arm 28, and the like. When the height setting lever 23 is swung in the high position setting direction (rear direction of the vehicle body), the first link mechanism 25 causes the spool 22A of the control valve 22 to act as an urging means in conjunction with the operation. Move it from the neutral position to the raised position. In the first link mechanism 25, when the height setting lever 23 is swung in the lower setting direction (front direction of the vehicle body), the spool 22A of the control valve 22 is neutralized by the action of the biasing means in conjunction with the operation. Allow movement from position to lowered position.

The feedback link mechanism 26 includes a linkage rod 30 extending from the right lift arm 20 to the front side of the vehicle body, a second swing arm 31 interlocking with the left and right lift arms 20 via the linkage rod 30, and a second swing arm. A second crankshaft 32 extending from the swing center of 31 to the lower end of the balance arm 28, and the like. When the tillage device 15 reaches the control target height, the feedback link mechanism 26 moves the spool 22A of the control valve 22 from the raised position or the lowered position to the neutral position in conjunction with the arrival.

With the above configuration, when the operator operates the height setting lever 23 to increase the control target height of the tilling device 15, the first link mechanism 25 pulls the spool 22 A of the control valve 22 along with this operation. Move from the neutral position to the raised position (see FIG. 7). Thereby, the tillage device 15 rises together with the left and right lift arms 20. When the tiller 15 reaches the control target height due to this rise, the feedback link mechanism 26 moves the spool 22A of the control valve 22 from the raised position to the neutral position (see FIG. 8). As a result, the tilling device 15 stops rising together with the left and right lift arms 20.
When the operator operates the height setting lever 23 to lower the control target height of the tilling device 15, the first link mechanism 25 moves from the neutral position of the spool 22A to the lowered position along with this operation. The movement is allowed, and the spool 22A is moved from the neutral position to the lowered position by the action of the urging means. Thereby, the tilling device 15 descends together with the left and right lift arms 20. Then, when the tilling device 15 reaches the control target height by this lowering, the feedback link mechanism 26 moves the spool 22A of the control valve 22 from the lowered position to the neutral position in conjunction with this. Thereby, the tilling device 15 stops descending together with the left and right lift arms 20.

That is, in this tractor, by providing the above-described lifting drive unit 17, position control for moving the tillage device 15 up and down to an arbitrary control target height set by the operation of the height setting lever 23 is favorably performed. Can do. And by this position control, the tilling depth at the time of tillage work can be set to an arbitrary depth.

As shown in FIGS. 1 to 5 and FIGS. 9 to 17, the mechanical linkage unit 18 includes a change amount conversion mechanism 33 and a change amount conversion mechanism 33 that can be switched between a first linkage conversion state and a second linkage conversion state. And a second link mechanism 34 that interlocks the lift drive unit 17 and an operation tool 35 that switches the change amount conversion mechanism 33 between a first linkage conversion state and a second linkage conversion state. The change amount conversion mechanism 33 includes a load detection member 36 that swings back and forth according to the traction load transmitted through the top link 13, and a grounding body 37 that detects the plowing depth of the tilling device 15 (FIGS. 2, 16 to 17). And a swinging member 38 that swings in accordance with the tilling depth of the tilling device 15.

Of the various tillage devices 15 that can be connected to the three-point link mechanism 12, the plow 15A (see FIG. 1), the subsoiler, and the like do not include the grounding body 37. The rotary tiller 15B (see FIG. 2) includes a rear cover that functions as a grounding body 37 so as to be swingable up and down. Therefore, in a state where the plow 15A is attached to the three-point link mechanism 12, the mechanical linkage unit 18 enters the draft control state (first linkage state) in which the interlocking connection between the swing member 38 and the grounding body 37 is released. (See FIG. 1, FIGS. 3 to 5, and FIGS. 9 to 15). In the state where the rotary tiller 15B is attached to the three-point link mechanism 12, the mechanical linkage unit 18 includes an automatic tiller in which the swing member 38 and the grounding body 37 are interlocked and connected via the third link mechanism 39. A deep control state (second linkage state) is established (see FIGS. 2 and 16 to 17).

In the draft control state of the mechanical linkage unit 18, when the change amount conversion mechanism 33 is switched to the first linkage conversion state described above, the change amount conversion mechanism 33 is provided with a traction load obtained by swinging the load detection member 36 back and forth. Can be converted into a lift operation amount (see FIGS. 1, 3 to 5, and FIGS. 9 to 15).
In the automatic plowing depth control state of the mechanical linkage unit 18, when the change amount conversion mechanism 33 is switched to the second linkage conversion state described above, the change amount conversion mechanism 33 is obtained by swinging of the swing member 38. It is possible to convert the amount of change in depth into the amount of lift operation (see FIGS. 2 and 16 to 17).
As a result, when plowing work is performed with the plow 15A in this tractor, the plow 15A is attached to the three-point link mechanism 12, so that the mechanical linkage unit 18 enters the draft control state (first linkage state). In this draft control state, when the operator operates the operation tool 35 and switches the change amount conversion mechanism 33 to the first linkage conversion state, the plow 15A is set according to the traction load during the tilling work. Draft control is performed to automatically move up and down. As a result, it is possible to avoid engine stall due to an increase in traction load.
In addition, when performing the tilling work by the rotary tiller 15B in this tractor, the rotary tiller 15B is attached to the three-point link mechanism 12, and the swing member 38 and the grounding body 37 are connected via the third link mechanism 39. As a result of the interlocking connection, the mechanical linkage unit 18 enters the automatic tilling depth control state (second linkage state). And in this automatic tilling control state, if an operator operates the operation tool 35 and switches the change amount conversion mechanism 33 to the conversion state for 2nd linkage, according to tilling work at the time of tilling work Automatic tilling control in which the rotary tiller 15B automatically moves up and down in conjunction with the vertical swing of the grounding body (rear cover) 37 is performed. As a result, it is possible to perform a highly accurate tilling work in which the tilling depth is maintained constant.
In other words, the tractor includes the mechanical linkage unit 18 having the above-described configuration, so that the above-described draft control can be performed when performing the tilling work by the plow 15A. Moreover, when performing the tilling work by the rotary tiller 15B, the above-described automatic tilling control can be performed.

As shown in FIGS. 3 to 5, FIGS. 9 to 10, and FIGS. 12 to 17, the swing member 38 is supported by the load detection member 36 so as to be swingable. The operation tool 35 is in contact with the load detection member 36 to prevent the load detection member 36 from swinging back and forth, and is not contacted to allow the load detection member 36 to swing back and forth without contacting the load detection member 36. The contact member 40 which moves over a position is provided. When the contact member 40 is in the non-contact position, the load detection member 36 swings back and forth, so that the amount of change in the traction load is transmitted to the lift drive unit 17 as the lift operation amount. Further, when the contact member 40 is in the contact position, the swinging member 38 swings independently while the load detection member 36 does not swing back and forth, whereby the amount of change in tilling depth is transmitted to the lift drive unit 17 as the lift operation amount. .
That is, when the contact member 40 is in the non-contact position, the change amount conversion mechanism 33 is in the first linkage conversion state described above, and when the contact member 40 is in the contact position, the change amount conversion mechanism 33 is in the second state described above. The conversion state for linkage is entered.
Thereby, in the automatic tilling control at the time of tillage work by the rotary tiller 15B, the load detection member 36 does not swing back and forth according to the traction load transmitted through the top link 13, and thus the load detection member 36 There is no possibility that the change amount of the traction load is input to the change amount conversion mechanism 33 due to the back-and-forth swing.
As a result, in the automatic tilling control based on the change amount of the tilling depth, it is possible to avoid the possibility that the work accuracy is reduced due to the change amount of the traction load being input to the change amount conversion mechanism 33.

2 and FIGS. 16 to 17, the grounding body 37 of the rotary tiller 15B is spring-biased in the descending direction (grounding direction). The third link mechanism 39 includes a reversing arm 41 supported by the rotary tiller 15B, a linkage rod 42 extending between the grounding body 37 and the reversing arm 41, a control cable 43 extending between the reversing arm 41 and the swinging member 38, and the like. I have. Then, one end of the control cable 43 is detachably pin-connected to a portion above the swing fulcrum in the swing member 38.

On the upper side of the swing member 38, a plurality of connection holes 38A for a control cable are formed. Thereby, the connection position of the control cable 43 with respect to the swing member 38 can be changed, and by this change, the swing displacement amount of the swing member 38 with respect to the swing displacement amount of the grounding body 37 can be changed. As a result, in the automatic tilling control, it is possible to adjust the responsiveness when the rotary tiller 15B moves up and down in conjunction with the vertical swing of the grounding body 37 according to the tilling depth.
In the first embodiment, an example in which two connecting holes 38A are formed in the swinging member 38 as the plurality of connecting holes 38A is illustrated. However, three or more connecting holes 38A include the swinging member 38. It may be formed.

As shown in FIGS. 1, 3 to 5, and 10 to 15, the three-point link mechanism 12 to which the plow 15 A is attached has the front end portion of the top link 13 connected to the load detection member 36 via the first connection pin 44. It is connected. Further, the front end portions of the left and right lower links 14 are connected to the left and right brackets 45 provided at the rear end portion of the T / M case 5 via left and right second connection pins 46. With this connection structure, the traction load during the tilling work acts on the load detection member 36 via the top link 13.

As shown in FIGS. 3 to 5 and FIGS. 9 to 17, the load detection member 36 swings in the front-rear direction via the first support shaft 48 on the support member 47 fixed to the rear end of the T / M case 5. It is supported so that it can be displaced. The mechanical linkage unit 18 includes a biasing mechanism 49 that swings and biases the load detection member 36 in a direction against the traction load applied to the load detection member 36 (rear direction of the vehicle body), and swings the load detection member 36 back and forth. A limiting mechanism 50 that limits the range is provided. The load detecting member 36 is held in a reference posture extending vertically upward from the first support shaft 48 by the action of the biasing mechanism 49 and the limiting mechanism 50. Then, when the traction load exceeds the set value, the load detection member 36 swings and displaces from the reference posture to the front side of the vehicle body against the action of the urging mechanism 49 in conjunction with the increase of the traction load, and In conjunction with the decrease in the traction load, the urging mechanism 49 swings and displaces to the rear side of the vehicle body to return to the reference posture. The free end of the load detection member 36 is provided with a second support shaft 51 that supports the swing member 38 so as to be swingable.

As shown in FIGS. 3 to 10 and 12 to 17, the change amount conversion mechanism 33 includes a holding mechanism 52 that urges the swing member 38 to return to a predetermined posture with respect to the load detection member 36. When the rocking member 38 is linked to the grounding body 37, the rocking member 38 is connected and set so that the predetermined posture of the rocking member 38 corresponds to the lowest position of the grounding body 37. In the swing member 38, the second link mechanism 34 described above is pin-connected to a portion below the swing support point of the swing member 38. The second link mechanism 34 includes an operation arm 53 supported by the linkage portion 27A of the first swing arm 27 so as to be able to swing back and forth, a reversing arm 54 for reversing the operation direction, and one end of the operation arm 53 and the reversing arm 54. And a second linkage member 56 extending between the other end of the reversing arm 54 and the swinging member 38. The linkage portion 27A of the first swing arm 27 is formed in a U shape in plan view. The operating arm 53 swings in the rear direction of the vehicle body (the high position setting direction of the height setting lever 23), so that the linkage portion 27A of the first rocking arm 27 from the front side of the vehicle body (the low position setting side of the height setting lever 23). To touch.
With this configuration, when the change amount conversion mechanism 33 is switched to the first linkage conversion state in the draft control state of the mechanical linkage unit 18, when the traction load increases, the holding mechanism 52 is held in conjunction with the increase. Due to the action, the load detecting member 36 and the swinging member 38 swing integrally with the front side of the vehicle body. When the traction load decreases, the load detection member 36 and the swing member 38 swing integrally with the rear side of the vehicle body by the holding action of the holding mechanism 52 in conjunction with the decrease.
When the load detection member 36 and the swing member 38 swing integrally with the front of the vehicle body, the operation arm 53 swings in the rear direction of the vehicle in conjunction with this integral swing. The linkage portion 27A of the first swing arm 27 is pressed backward in the vehicle body. As a result, the first swing arm 27 swings backward in the vehicle body, and the spool 22A of the control valve 22 linked to the first swing arm 27 rises from the neutral position against the action of the biasing means. (See FIG. 13). As a result, the plow 15A rises together with the left and right lift arms 20.
Further, when the load detection member 36 and the swing member 38 integrally swing to the rear side of the vehicle body, the operation arm 53 swings in the front direction of the vehicle body in conjunction with the integral swing, and this swing causes the operation arm 53 to swing. Is separated from the linkage portion 27A of the first swing arm 27 in the front direction of the vehicle body. As a result, the first swing arm 27 is allowed to swing forward in the vehicle body, and the spool 22A of the control valve 22 is moved from the neutral position to the lowered position by the action of the biasing means. As a result, the plow 15A is lowered together with the left and right lift arms 20.
On the other hand, when the change amount conversion mechanism 33 is switched to the second linkage conversion state in the automatic plowing depth control state of the mechanical linkage unit 18, when the plowing depth becomes deep and the grounding body 37 rises, the rise is linked. Thus, the swinging member 38 swings independently in the backward tilting direction with respect to the load detection member 36 against the bias of the holding mechanism 52. Further, when the grounding body 37 descends due to the shallow tillage depth, the swinging member 38 independently swings forwardly with respect to the load detecting member 36 by the urging of the holding mechanism 52 in conjunction with the lowering. To do.
When the swing member 38 swings independently in the backward tilt direction, the operation arm 53 swings in the rear direction of the vehicle body in conjunction with the independent swing, and the operation arm 53 is moved to the first swing arm by this swing. 27 linking portions 27A are pushed backward in the vehicle body. As a result, the first swing arm 27 swings backward in the vehicle body, and the spool 22A of the control valve 22 linked to the first swing arm 27 rises from the neutral position against the action of the biasing means. (See FIG. 17). As a result, the rotary tiller 15 B rises together with the left and right lift arms 20.
When the swing member 38 swings independently in the forward tilt direction, the operation arm 53 swings in the front direction of the vehicle body in conjunction with the independent swing, and this swing causes the operation arm 53 to move to the first swing arm. It leaves | separates in the vehicle body front direction from 27 linkage part 27A. As a result, the first swing arm 27 is allowed to swing forward in the vehicle body, and the spool 22A of the control valve 22 is moved from the neutral position to the lowered position by the action of the biasing means. As a result, the rotary tiller 15B is lowered together with the left and right lift arms 20.

In the draft control state of the mechanical linkage unit 18 described above, the feedback link mechanism 26 is activated when the integral swinging of the load detecting member 36 and the swinging member 38 corresponding to the traction load is stopped by the rising or lowering of the plow 15A. In conjunction with the swing stop, the spool 22A of the control valve 22 is moved from the raised position or the lowered position to the neutral position. Thereby, the plow 15A stops ascending or descending together with the left and right lift arms 20.
When the independent oscillating of the oscillating member 38 according to the tilling depth is stopped by the raising or lowering of the rotary tiller 15B in the automatic tilling control state of the mechanical linkage unit 18 described above, the feedback link mechanism 26 In conjunction with the stop, the spool 22A of the control valve 22 is moved from the raised position or the lowered position to the neutral position. As a result, the rotary tiller 15 B stops moving up or down together with the left and right lift arms 20.

With the above configuration, the tractor includes the mechanical linkage unit 18 having the above-described configuration, so that the above-described draft control can be performed satisfactorily when performing the tilling work using the plow 15A. Further, when performing the tilling work by the rotary tiller 15B, the above-described automatic tilling control can be favorably performed.

As shown in FIGS. 3 to 5, 9 to 10, and 12 to 17, the holding mechanism 52 swings in a direction in which the swing member 38 moves the three-point link mechanism 12 downward relative to the load detection member 36. And a spring 58 for swinging and biasing the swinging member 38 toward the stopper 57.
That is, the load detecting member 36 and the swinging member 38 can be swung integrally with a simple configuration including only the stopper 57 and the spring 58 and when the change amount converting mechanism 33 is in the first linkage converting state. In addition, when the change amount conversion mechanism 33 is in the second linkage conversion state, the swing member 38 can be swung independently with respect to the load detection member 36.
As a result, it is possible to suitably switch the change amount conversion mechanism 33 between the first linkage conversion state and the second linkage conversion state while simplifying the configuration.

The stopper 57 is supported by the load detection member 36. The spring 58 is installed over the load detection member 36 and the second linkage member 56.

As shown in FIGS. 3 to 5, 9 to 10, and 12 to 15, the change amount conversion mechanism 33 uses the first conversion state (see FIGS. 12 to 13) and the second conversion state (see FIGS. 12 to 13) as the first linkage conversion state. 14 to 15). The change amount conversion mechanism 33 is switched between the first conversion state and the second conversion state by the operation of the operation tool 35 described above.
When the change amount conversion mechanism 33 is in the first conversion state, the load detecting member 36 and the swinging member 38 swing together by the holding action of the holding mechanism 52, and the integrated swinging causes The amount of change in the traction load obtained by swinging is not amplified and transmitted to the elevating drive unit 17 as the elevating operation amount (see FIGS. 12 to 13).
Further, when the change amount conversion mechanism 33 is in the second conversion state, relative swinging of the load detecting member 36 and the swinging member 38 against the holding action of the holding mechanism 52 is allowed, and load detection is performed by this relative swinging. The amount of change in the traction load obtained by swinging the member 36 back and forth is amplified and transmitted to the lift drive unit 17 as a lift operation amount (see FIGS. 14 to 15).
Thereby, for example, when plowing work with the plow 15A is performed in a standard field where the traction load is difficult to increase due to the hardness of the soil and the fluctuation of the traction load is difficult to increase, the operator operates the operation tool 35. When the change amount conversion mechanism 33 is switched to the first conversion state, the plow 15A can be raised and lowered according to the traction load at a standard speed suitable for this field. As a result, it is possible to avoid an engine stall due to an increase in the traction load while performing draft control with a gentle change in tilling depth.
Further, for example, when plowing work with the plow 15A is performed in a field where the traction load is likely to increase and the traction load is likely to fluctuate due to the hardness of the soil, the operator operates the operation tool 35 to change the amount of change. By switching the conversion mechanism 33 to the second conversion state, the plow 15A can be lifted and lowered according to the traction load at a high speed suitable for this field. As a result, it is possible to avoid an engine stall due to a sudden increase in the traction load.

As shown in FIGS. 3 to 5, FIGS. 9 to 10, and FIGS. 12 to 17, the operating tool 35 includes a receiving member 59 that moves between a non-receiving position and a receiving position. When the receiving member 59 is positioned at the non-receiving position, the load detecting member 36 and the swinging member 38 are moved by the holding action of the holding mechanism 52 by the receiving member 59 being out of the swinging region of the swinging member 38. Swings together. In addition, when the receiving member 59 is positioned at the receiving position, the holding member 59 is positioned within the swinging region of the swinging member 38, and the holding mechanism is in a state where the swinging member 38 is not received by the receiving member 59. While the load detecting member 36 and the swinging member 38 swing integrally by the holding action of 52, and the swinging member 38 is received by the receiving member 59, load detection against the holding action of the holding mechanism 52 is detected. The relative swinging of the member 36 and the swinging member 38 is allowed.
That is, in addition to the holding mechanism 52 described above, the operation tool 35 is simply provided with the receiving member 59. When the receiving member 59 is in the non-receiving position, the load detecting member 36 and the swinging member 38 are integrated. The first conversion state of the swinging change amount conversion mechanism 33 can be obtained. Further, when the receiving member 59 is in the receiving position, the second conversion state of the change amount conversion mechanism 33 in which the relative swinging of the load detection member 36 and the swinging member 38 is allowed can be obtained.
As a result, it is possible to satisfactorily switch the change amount conversion mechanism 33 between the first conversion state and the second conversion state while simplifying the configuration.

In the second conversion state of the change amount conversion mechanism 33, when the load detection member 36 is in the reference posture, a gap is secured between the swing member 38 and the receiving member 59. Therefore, until the swing displacement amount from the reference posture of the load detection member 36 based on the traction load reaches a predetermined amount at which the swing member 38 contacts the receiving member 59, the receiving member 59 is not swung. By not receiving 38, the load detection member 36 and the swing member 38 swing integrally. When the swing displacement amount from the reference posture of the load detection member 36 becomes a predetermined amount or more, the load detection member 36 and the swing member 38 swing relative to each other when the receiving member 59 receives the swing member 38. .
As a result, in a work situation where the traction load slightly exceeds the set value and there is no possibility of causing an engine stall, the plow 15A can move at a standard speed even if the change amount conversion mechanism 33 is in the second conversion state. It is driven up and down accordingly.
As a result, even in a work situation where the traction load slightly exceeds the set value, it is possible to avoid the possibility that the durability of the elevating drive unit 17 is reduced due to raising and lowering the plow 15A at an unnecessarily high speed. Can do.

In the second conversion state of the change amount conversion mechanism 33, when the relative swing between the load detection member 36 and the swing member 38 is allowed, when the traction load increases, the load detection member 36 is interlocked with the increase. While swinging to the front side of the vehicle body, the swinging member 38 swings relative to the backward tilting direction against the bias of the holding mechanism 52. When the traction load decreases, the load detection member 36 swings to the rear side of the vehicle in conjunction with the decrease, and the swing member 38 relatively swings in the forward tilt direction by the urging of the holding mechanism 52. .
When the load detecting member 36 swings to the front side of the vehicle body and the swinging member 38 relatively swings in the backward tilt direction, the operation arm 53 swings in the rear direction of the vehicle body in conjunction with this relative swinging. By swinging, the operation arm 53 presses the linkage portion 27A of the first swing arm 27 in the rear direction of the vehicle body. As a result, the first swing arm 27 swings backward in the vehicle body, and the spool 22A of the control valve 22 linked to the first swing arm 27 rises from the neutral position against the action of the biasing means. (See FIG. 15). As a result, the plow 15A rises together with the left and right lift arms 20.
Further, when the load detection member 36 swings to the rear side of the vehicle body and the swing member 38 relatively swings forward, the operation arm 53 swings forward of the vehicle body in conjunction with the relative swing, With this swing, the operation arm 53 is separated from the linkage portion 27A of the first swing arm 27 in the front direction of the vehicle body. As a result, the first swing arm 27 is allowed to swing forward in the vehicle body, and the spool 22A of the control valve 22 is moved from the neutral position to the lowered position by the action of the biasing means. As a result, the plow 15A is lowered together with the left and right lift arms 20.

In the second conversion state of the change amount conversion mechanism 33 described above, the feedback link mechanism 26 stops when the relative swinging of the load detecting member 36 and the swinging member 38 according to the traction load is stopped by the raising or lowering of the plow 15A. In conjunction with this oscillation stop, the spool 22A of the control valve 22 is operated from the raised position or the lowered position to the neutral position. As a result, the plow 15 A stops ascending or descending together with the left and right lift arms 20.

With the above-described configuration, the tractor includes the mechanical linkage unit 18 having the above-described configuration, so that it is possible to select draft control in consideration of soil hardness and the like that differ from field to field. As a result, the plowing work by the plow 15A can be performed satisfactorily regardless of the soil hardness and the like which differ from field to field.

A roller 60 that is rotatable about an axis parallel to the axis of oscillation of the oscillation member 38 is provided at a location where the oscillation member 38 of the reception member 59 is received.
With this configuration, when the swinging member 38 slides on the receiving member 59 due to relative swinging of the load detecting member 36 and the swinging member 38 in the second conversion state of the change amount converting mechanism 33, Along with the sliding, the roller 60 rotates in the sliding direction.
As a result, the swinging member 38 slides smoothly with respect to the receiving member 59, and the load detection member 36 and the swinging member 38 smoothly swing relative to each other.
As a result, the draft control in the second conversion state of the change amount conversion mechanism 33 can be performed smoothly.

As shown in FIGS. 1 and 2, the change amount conversion mechanism 33 is disposed adjacent to the driver seat 11 at a location behind the driver seat 11 in the vehicle body. Thus, the operator can easily confirm the operating state of the change amount conversion mechanism 33 by visually observing the rear part of the driver seat 11 while sitting on the driver seat 11.
Further, the rear portion of the driver seat 11 is not covered with a cover or the like, so that the change amount conversion mechanism 33 can be easily maintained.

The operating tool 35 is disposed adjacent to the driver seat 11 at a location behind the driver seat 11 in the vehicle body. As a result, the operator can operate the operation tool 35 by extending the hand toward the rear portion of the driver seat 11 while sitting on the driver seat 11, and the change amount conversion mechanism 33 is set to the first position. The conversion state, the second conversion state, and the second linkage conversion state can be easily switched.

As shown in FIGS. 3 to 5, 9 to 10, and 12 to 17, the operating tool 35 includes a swing plate 61 that is swingably supported by the support member 47 described above in the left-right direction, and a swing plate. An operation handle 62 extending forward from 61 is provided. A plate-like contact member 40 is provided on the left side portion of the swing plate 61, and a receiving member 59 is provided on the right side portion of the swing plate 61. The operation tool 35 swings in the left-right direction around the axis X extending in the front-rear direction. The operation tool 35 is alternatively held at one of the first operation position, the second operation position, and the third operation position by a detent mechanism 63 provided across the support member 47 and the swing plate 61. .
When the operation tool 35 is held at the first operation position on the right side, the contact member 40 is positioned at the non-contact position, and the receiving member 59 is positioned at the non-receiving position. As a result, the change amount conversion mechanism 33 enters the first conversion state for draft control.
When the operation tool 35 is held at the second operation position between the left and right, the contact member 40 is positioned at the non-contact position, and the receiving member 59 is positioned at the receiving position. As a result, the change amount conversion mechanism 33 enters the second conversion state for draft control.
When the operation tool 35 is held at the left third operation position, the contact member 40 is positioned at the contact position, and the receiving member 59 is positioned at the non-receiving position. As a result, the change amount conversion mechanism 33 enters the second linkage conversion state for automatic tilling control.
That is, the operator switches the operation position of the operation tool 35 to change the change amount conversion mechanism 33 to the first conversion state for draft control, the second conversion state for draft control, and the automatic plowing depth control. It is possible to easily switch to the second linkage conversion state.

As shown in FIGS. 3, 5, and 9 to 17, the load detection member 36 includes left and right side wall portions 36A having through holes 36a facing each other. The support member 47 includes a vertical wall portion 47A connected to the rear portion of the vehicle body, and a U-shaped linkage portion 47B extending rearward from the vertical wall portion 47A and entering between the left and right side wall portions 36A. ing. In the linkage portion 47B, left and right elongated holes 47a that are long in the front-rear direction are formed at locations facing the through holes 36a of the side wall portions 36A. The limiting mechanism 50 described above is formed by the through holes 36a of the load detection member 36, the long holes 47a of the support member 47, the linkage pins 64 inserted into the through holes 36a and the long holes 47a, and the like. It is configured.
That is, the forward / backward swing range of the load detection member 36 is limited and set by the longitudinal length of each of the long holes 47 a formed in the support member 47.

The limiting mechanism 50 includes a rubber block 65 that is fitted into a space between the vertical wall portion 47A of the support member 47 and the linkage portion 47B. In the rubber block 65, a long hole 65 a having a front and rear length shorter than that of the long hole 47 a of the support member 47 is formed at a position facing the long hole 47 a of the support member 47. And the linkage pin 64 is inserted in this long hole 65a.
Thereby, when the restriction mechanism 50 restricts the forward / backward swing of the load detection member 36, the linkage pin 64 of the restriction mechanism 50 collides with the rubber block 65, so that the linkage pin 64 contacts the linkage portion 47 B of the support member 47. Generation of noise due to collision can be prevented.

As shown in FIGS. 3 to 6 and FIGS. 12 to 17, the mechanical linkage unit 18 includes a sensitivity adjustment mechanism 66 that adjusts the operation sensitivity when the elevating drive unit 17 is interlocked with the swing member 38. The sensitivity adjustment mechanism 66 includes a sensitivity adjustment lever 67 disposed so as to be held at an arbitrary operation position in the operation unit 9, a linkage member 69 extending from the sensitivity adjustment lever 67 to the support shaft 68 of the reversing arm 54, and the reversing arm 54. A support member 70 that supports the support shaft 68 so as to be displaceable in the front-rear direction is provided. When the support position of the support shaft 68 by the support member 70 is changed in the front-rear direction by the swinging operation of the sensitivity adjustment lever 67 in the front-rear direction, the sensitivity adjustment mechanism 66 performs the first swing in conjunction with this change. The gap 71 between the linkage portion 27A of the arm 27 and the operation arm 53 is changed. Thereby, the operation sensitivity when the raising / lowering drive unit 17 interlock | cooperates with the rocking | swiveling member 38 can be adjusted.

The sensitivity adjustment mechanism 66 is more sensitive to the operation sensitivity when the lifting drive unit 17 is interlocked with the swing member 38 as the gap 71 described above becomes smaller, and when the traction load exceeds the set value and the plow 15A rises. Responsiveness is improved.
In the sensitivity adjustment mechanism 66, as the gap 71 is increased, the operation sensitivity when the elevating drive unit 17 is interlocked with the swinging member 38 becomes insensitive, and when the traction load exceeds the set value and the plow 15A rises. Responsiveness deteriorates.
As a result, for example, the plow 15A frequently moves up and down and hunts by making the above-mentioned operation sensitivity insensitive as the change in the traction load becomes more intense due to the field conditions such as intense field undulations. The fall of the plowing work precision which originated can be prevented.

As shown in FIGS. 1 to 3, 5, 9, and 11 to 17, the load detection member 36 has a long top link 13 A (see FIGS. 1, 3, 5, 9, and 11 to 15). A first connecting portion 36B to be connected and a second connecting portion 36C to which a bracket 72 (see FIGS. 2 and 16 to 17) for supporting the short top link 13B is connected are provided.
Thereby, for example, when performing the tilling work by the rotary tiller 15B, the specification of the three-point link mechanism 12 is changed to the standard link specification including the long top link 13A and the left and right lower links 14, the short top link 13B and the left and right The special link specification including the lower link 14 can be easily changed.
When the specification of the three-point link mechanism 12 is changed from the standard link specification to the special link specification, the up / down drive amount of the rotary tiller 15B with respect to the up / down operation amount of the up / down drive unit 17 is increased, and the maximum of the rotary tiller 15B is increased. The ascending position becomes higher.
As a result, for example, when performing a tilling work with the rotary tiller 15B in a work site having a high hail, the specification of the three-point link mechanism 12 is changed from the standard link specification to the special link specification, thereby exceeding the hail. It becomes easy to avoid the possibility that the rotary tiller 15B comes into contact with a high ridge when performing traveling, side turning, or the like.

The load detecting member 36 includes a single connecting hole that enables pin connection of the long top link 13A as the first connecting portion 36B. Further, the load detection member 36 includes two upper and lower connecting holes that enable pin connection of the bracket 72 as the second connecting portion 36C.

[Second Embodiment]
Hereinafter, a second embodiment which is an example of a mode for carrying out the present invention will be described with reference to the drawings.
Since the tractor exemplified in the second embodiment is the same as the tractor exemplified in the first embodiment except for the configuration of the mechanical linkage unit 18 for automatic lifting and lowering, the following configuration is the same. Only the configuration of the mechanical linkage unit 18 for automatic elevation will be described.
Also in the second embodiment, the direction indicated by the arrow F shown in FIG. 18 is the front side of the tractor, and the direction indicated by the arrow U is the upper side of the tractor.

As shown in FIGS. 18 to 21, the mechanical linkage unit 18 for automatic raising and lowering exemplified in the second embodiment includes a towed tiller 15 such as a plow 15A or a subsoiler (not shown) and a three-point link mechanism 12. At the time of the tilling work attached to the vehicle, the amount of change in the traction load is converted into a lifting operation amount and transmitted to the hydraulic lifting drive unit 17.
That is, the mechanical linkage unit 18 for automatic raising / lowering is configured for draft control that enables only draft control for automatically raising / lowering the tilling device 15 according to the traction load during tilling work.

The mechanical linkage unit 18 includes a change amount conversion mechanism 33 having a load detection member 36 that swings back and forth in accordance with a traction load transmitted through the top link 13 of the three-point link mechanism 12, and the change amount conversion mechanism 33. A second link mechanism 34 that interlocks the drive unit 17 is provided. The configuration of the second link mechanism 34 is the same as the configuration exemplified in the first embodiment.

The change amount conversion mechanism 33 includes a swinging member 38 that is swingably supported by the load detection member 36 and that is linked to the lifting drive unit 17 via the second link mechanism 34. The amount of change in the traction load obtained by swinging back and forth is amplified by the relative swinging of the load detecting member 36 and the swinging member 38, and then converted into a lift operation amount.

With this configuration, for example, when a change occurs in the traction load in the plowing work in which the plow 15A is attached to the three-point link mechanism 12 as the traction-type cultivator 15, the load detection member according to the amount of change in the traction load at this time In addition to the back and forth swinging of 36, the load detecting member 36 and the swinging member 38 swing relative to each other, so that the amount of change in the traction load is amplified. Then, the amount of change in the traction load after amplification is converted into a lifting operation amount and transmitted to the lifting drive unit 17.
As a result, the plow 15A can be quickly moved up and down in accordance with the change in the traction load. As a result, even when the traction load increases rapidly, an engine stall due to the increase in the traction load can be avoided.

Further, since the load detection member 36 and the swing member 38 swing relative to each other, it is possible to greatly amplify the change amount of the traction load while narrowing the swing range of the load detection member 36 and the swing member 38. Thereby, the front-rear length of the space required for installation of the change amount conversion mechanism 33 having the load detection member 36 and the swing member 38 can be shortened.
As a result, it is possible to avoid an engine stall caused by a sudden increase in the traction load while suppressing an increase in the size of the vehicle body that increases the overall length of the vehicle body.

As shown in FIGS. 19 to 21, the load detection member 36 is supported by a support member 47 fixed to the rear end of the T / M case 5 through a first support shaft 48 so as to be able to swing and displace in the front-rear direction. ing. The free end portion of the load detection member 36 is provided with a second support shaft 51 that supports the swing member 38 so as to swing back and forth. In the swing member 38, the above-described second link mechanism 34 is pin-connected to a portion below the swing support point (second support shaft 51) of the swing member 38.

The mechanical linkage unit 18 includes a biasing mechanism 49 that swings and biases the load detection member 36 in a direction against the traction load applied to the load detection member 36 (rear direction of the vehicle body), and swings the load detection member 36 back and forth. A limiting mechanism 50 that limits the range is provided. The configurations of the urging mechanism 49 and the limiting mechanism 50 are the same as the configurations exemplified in the first embodiment.

The load detection member 36 is held in a reference posture extending vertically upward from the first support shaft 48 by the action of the biasing mechanism 49 and the limiting mechanism 50. Then, when the traction load exceeds the set value, the load detection member 36 swings and displaces from the reference posture to the front side of the vehicle body against the action of the urging mechanism 49 in conjunction with the increase of the traction load, and In conjunction with the decrease in the traction load, the urging mechanism 49 swings and displaces to the rear side of the vehicle body to return to the reference posture.

The change amount conversion mechanism 33 has a holding mechanism 52 that urges the swing member 38 to return to a predetermined posture with respect to the load detection member 36. The holding mechanism 52 restricts the swing member 38 from swinging in the direction in which the three-point link mechanism 12 is lowered with respect to the load detection member 36, and swings the swing member 38 toward the stopper 57. A spring 58 that is urged to move is provided. The stopper 57 is supported by the load detection member 36. The spring 58 is extended over the load detection member 36 and the second linkage member 56 of the second link mechanism 34.

The change amount conversion mechanism 33 has a receiving member 59 arranged in the swing region of the swing member 38 so that the upper side of the swing member 38 can be received from the front side of the vehicle body. The receiving member 59 is supported by the upper end portion of the support member 47.

The change amount conversion mechanism 33 is configured such that a gap is secured between the swing member 38 and the receiving member 59 when the load detection member 36 is in the reference posture.
Therefore, until the swing displacement amount from the reference posture of the load detection member 36 based on the traction load reaches a predetermined amount at which the swing member 38 contacts the receiving member 59, the receiving member 59 is not swung. By not receiving 38, the load detecting member 36 and the swinging member 38 swing together by the holding action of the holding mechanism 52. As a result, the amount of change in the traction load obtained by swinging the load detection member 36 back and forth is transmitted to the lift drive unit 17 as a lift operation amount without being amplified.
When the swing displacement amount of the load detection member 36 from the reference posture becomes a predetermined amount or more, the receiving member 59 receives the swing member 38, whereby the load detection member 36 resists the holding action of the holding mechanism 52. Relative rocking with the rocking member 38 is allowed. As a result, the amount of change in the traction load obtained by swinging the load detection member 36 back and forth is amplified by the relative swing between the load detection member 36 and the swing member 38 and then transmitted to the lift drive unit 17 as the lift operation amount. It is done.
That is, in a work situation where the traction load slightly exceeds the set value and there is no possibility of causing engine stall, the lifting drive unit 17 responds to the traction load with the plow 15A at a standard speed suitable for the work situation at this time. Drive up and down.
Further, in a work situation where the traction load greatly exceeds the set value and the possibility of causing an engine stall is high, the lift drive unit 17 lifts and lowers the plow 15A according to the traction load at a high speed suitable for the work situation at this time. Drive.
As a result, even in a work situation where the traction load slightly exceeds the set value, the elevating drive unit 17 has the durability of the elevating drive unit 17 due to the elevating drive unit 17 driving the plow 15A up and down at an unnecessarily high speed. While avoiding the possibility of a decrease, it is possible to avoid an engine stall caused by a sudden increase in the traction load.

As shown in FIGS. 18 to 21, when the relative swing between the load detection member 36 and the swing member 38 is allowed, the change amount conversion mechanism 33 is linked to the increase and the load is increased. The detection member 36 swings to the front side of the vehicle body, and the swing member 38 relatively swings in the backward tilt direction against the urging force of the holding mechanism 52. When the traction load decreases, the load detection member 36 swings to the rear side of the vehicle in conjunction with the decrease, and the swing member 38 relatively swings in the forward tilt direction by the urging of the holding mechanism 52. .
When the load detecting member 36 swings to the front side of the vehicle body and the swinging member 38 relatively swings in the backward tilt direction, the operation arm 53 swings in the rear direction of the vehicle body in conjunction with this relative swinging. By swinging, the operation arm 53 presses the linkage portion 27A of the first swing arm 27 in the rear direction of the vehicle body. As a result, the first swing arm 27 swings backward in the vehicle body, and the spool 22A of the control valve 22 linked to the first swing arm 27 rises from the neutral position against the action of the biasing means. Move to. As a result, the plow 15A rises together with the left and right lift arms 20.
Further, when the load detection member 36 swings to the rear side of the vehicle body and the swing member 38 relatively swings forward, the operation arm 53 swings forward of the vehicle body in conjunction with the relative swing, With this swing, the operation arm 53 is separated from the linkage portion 27A of the first swing arm 27 in the front direction of the vehicle body. As a result, the first swing arm 27 is allowed to swing forward in the vehicle body, and the spool 22A of the control valve 22 is moved from the neutral position to the lowered position by the action of the biasing means. As a result, the plow 15A is lowered together with the left and right lift arms 20.
When the relative swinging of the load detecting member 36 and the swinging member 38 according to the traction load is stopped by raising or lowering the plow 15A, the feedback link mechanism 26 of the lifting drive unit 17 is interlocked with the swinging stop. However, the spool 22A of the control valve 22 is operated from the raised position or the lowered position to the neutral position. Thereby, the plow 15A stops ascending or descending together with the left and right lift arms 20.

As shown in FIGS. 19 to 21, a roller 60 that is rotatable around an axis parallel to the axis of oscillation of the oscillation member 38 is provided at the receiving position of the oscillation member 38 of the reception member 59. .
With this configuration, when the swing member 38 slides relative to the receiving member 59 due to the relative swing between the load detection member 36 and the swing member 38 in the change amount conversion mechanism 33, The roller 60 rotates in the sliding direction.
As a result, the swinging member 38 slides smoothly with respect to the receiving member 59, and the load detecting member 36 and the swinging member 38 smoothly swing relative to each other, so that the draft control can be performed smoothly. it can.

As shown in FIG. 18, the change amount conversion mechanism 33 is disposed adjacent to the driver seat 11 at a location behind the driver seat 11 in the vehicle body. Thus, the operator can easily confirm the operating state of the change amount conversion mechanism 33 by visually observing the rear part of the driver seat 11 while sitting on the driver seat 11.
Further, the rear portion of the driver seat 11 is not covered with a cover or the like, so that the change amount conversion mechanism 33 can be easily maintained.

20 to 21, the mechanical linkage unit 18 includes a sensitivity adjustment mechanism 66 that adjusts the operation sensitivity when the elevating drive unit 17 is interlocked with the swing member 38. The sensitivity adjustment mechanism 66 is the same as the configuration exemplified in the first embodiment. Thus, for example, as the change in the traction load becomes larger due to the field condition such as the undulation of the field, the operation described above is performed. By making the sensitivity insensitive, it is possible to prevent a decrease in tillage work accuracy due to the plow 15A being frequently lifted and hunted.

[Another embodiment]
The present invention is not limited to the configurations exemplified in the first embodiment and the second embodiment described above, and representative other embodiments relating to the present invention will be exemplified below.

[1] The tractor configuration can be variously changed.
For example, the tractor may be configured in a semi-crawler specification including left and right crawlers instead of the left and right rear wheels 7.
For example, the tractor may be configured in a full crawler specification including left and right crawlers instead of the left and right front wheels 6 and the left and right rear wheels 7.
For example, the tractor may be configured to have an electric specification including an electric motor instead of the engine 2.
For example, the tractor may be configured in a hybrid specification including the engine 2 and an electric motor.

[2] The working device attached to the three-point link mechanism 12 may be a mower or a seeder other than the tilling device.
When the mower or the sowing machine is attached to the three-point link mechanism 12, the operator places the operation tool 35 at the third operation position and converts the change amount conversion mechanism 33 into the second linkage conversion. By switching to the state, it is possible to prevent the load detection member 36 from swinging back and forth according to the traction load, and it is possible to avoid the possibility that the mower or the seeding machine is moved up and down by the traction load during the work.

[3] Various changes can be made to the configuration of the lifting drive unit 17.
For example, the elevating drive unit 17 may be configured to include a hydraulic motor or the like instead of the hydraulic cylinder 21.
For example, the elevating drive unit 17 may be configured to include an urging unit that urges the spool 22 A of the control valve 22 to return to the lowered position outside the control valve 22.

[4] The mechanical linkage unit 18 is, for example, supported as a swing member 38 by a swing control member 38 for swing control supported by a load detection member 36 and a support member 47 so as to swing. And a swing control member 38 for automatic plowing depth control, and a link control mechanism 34 for linking and connecting the swing control member 38 for draft control to the lifting drive unit 17 as a link mechanism 34. A link mechanism 34 for automatic tilling control that interlocks and connects a rocking member 38 for depth control to the lifting drive unit 17, and a load detecting member 36 and a rocking member 38 for draft control by operation of the operation tool 35. A first conversion state in which the rocking member 38 for automatic plowing depth control is permitted and the rocking member 38 for automatic tilling control is prevented from swinging, and the relative rocking of the load detecting member 36 and the rocking member 38 for draft control. Acceptable and automatic The second conversion state in which the swing member 38 for depth control is prevented from swinging, the swing detection member 36 and the swing member 38 for draft control are prevented from swinging and the swing member 38 for automatic tilling control. It may be configured to switch to the second linkage conversion state that allows the oscillation of the second linkage.

[5] The configuration of the change amount conversion mechanism 33 can be variously changed.
For example, the change amount conversion mechanism 33 may be configured to include the first conversion state and the second conversion state without including the second linkage conversion state.
For example, the change amount conversion mechanism 33 includes a first conversion state in which the load detection member 36 is connected to the link mechanism 34 and a second conversion state in which the swing member 38 is connected to the link mechanism 34 by operating the operation tool 35. The structure which switches to and may be sufficient.
For example, the change amount conversion mechanism 33 may be configured to include only the first conversion state as the first linkage conversion state.
For example, in the change amount conversion mechanism 33, the swing member 38 is swingably supported by a support member 47 that supports the load detection member 36, and the load detection member 36 is coupled to the link mechanism 34 by operation of the operation tool 35. The first linkage conversion state may be switched to the second linkage conversion state in which the swing member 38 is connected to the link mechanism 34.
For example, the change amount conversion mechanism 33 includes, as the swing member 38, a draft control swing member 38 swingably supported by the load detection member 36, and an automatic tiller supported by the support member 47 swingably. A swing control member 38 for depth control. By operating the operation tool 35, a first linkage conversion state in which the swing control member 38 for draft control is connected to the link mechanism 34, and a swing for automatic tilling depth control. The configuration may be such that the moving member 38 switches to the second linkage conversion state connected to the link mechanism 34. In this configuration, the first conversion state and the second conversion state can be provided as the first linkage conversion state.

[6] The configuration of the load detection member 36 can be variously changed.
For example, the load detection member 36 may be configured such that the upper end portion thereof is supported by the support member 47 via the first support shaft 48.
For example, the load detection member 36 may be configured so as to be swingable back and forth on the support member 37 via a first support shaft 48 that is vertically long.

[7] For example, the holding mechanism 52 swings the swing member 38 in a predetermined posture and a spring receiving member fixed at a position facing the swing member 38 in a predetermined posture in the axial direction of the second support shaft 51. You may comprise from the torsion spring to urge. In this configuration, the torsion spring is assembled in a state in which the coil portion of the torsion spring is externally fitted to the second support shaft 51 and both ends of the torsion spring sandwich the spring receiving member and the swing member 38 in a predetermined posture. It is done.

The present invention is applied to a tractor including a hydraulic lifting drive unit that lifts and lowers a towed tilling device attached to a three-point link mechanism together with a mechanical linkage unit for automatic lifting. be able to.

DESCRIPTION OF SYMBOLS 11 Driver's seat 12 3-point link mechanism 13 Top link 13A Long top link 13B Short top link 15 Tillage device 17 Lift drive unit 18 Mechanical linkage unit 33 Change conversion mechanism 34 Link mechanism 35 Operation tool 36 Load detection member 36B 1st connection Part 36C Second connecting part 38 Oscillating member 40 Contact member 52 Holding mechanism 57 Stopper 58 Spring 59 Receiving member 60 Roller 72 Bracket

Claims

A three-point link mechanism coupled to the rear portion of the vehicle body so as to be able to swing up and down; a hydraulic lift drive unit that drives the pull-type tillage device attached to the three-point link mechanism together with the three-point link mechanism; A mechanical linkage unit for automatic lifting and lowering, which converts a change amount of the load into a lifting operation amount and transmits it to the lifting drive unit;
The mechanical linkage unit includes a change amount conversion mechanism having a load detection member that swings back and forth in response to a traction load transmitted through the top link of the three-point link mechanism, the change amount conversion mechanism, and the lifting drive unit. A link mechanism that interlocks and
The change amount conversion mechanism includes a swinging member that is swingably supported by the load detection member and that is linked to the lifting drive unit via the link mechanism. A tractor configured to amplify a change amount of the traction load obtained by movement by a relative swing between the load detection member and the swing member, and then convert the amplified amount into the lift operation amount.
The change amount conversion mechanism converts a change amount of the traction load into the lift operation amount without amplifying the change amount, and a first conversion state that amplifies the change amount of the traction load and then converts it into the lift operation amount. It is configured to be switchable between two conversion states,
When the change amount conversion mechanism is in the first conversion state, due to the integral swinging of the load detecting member and the swinging member, the change amount of the traction load is not amplified and the lift drive unit is used as the lift operation amount. Communicated to
When the change amount conversion mechanism is in the second conversion state, the change amount of the traction load is amplified by the relative swinging of the load detecting member and the swinging member, and the lift drive unit is used as the lift operation amount. A tractor according to claim 1 to be communicated.
The tractor according to claim 2, wherein the mechanical linkage unit includes an operation tool for switching the change amount conversion mechanism between the first conversion state and the second conversion state.
The change amount conversion mechanism includes a holding mechanism that biases the swing member to a predetermined posture with respect to the load detection member,
The operation tool includes a receiving member that moves between a non-receiving position and a receiving position,
When the receiving member is located at the non-receiving position, the receiving member is removed from the swinging region of the swinging member and does not receive the swinging member, whereby the load detection member and the swinging member are Oscillates integrally by the holding action of the holding mechanism,
When the receiving member is positioned at the receiving position, the receiving member is positioned within the swinging region of the swinging member and receives the swinging member, whereby the load detection member and the swinging member are The tractor according to claim 3, wherein relative swinging against the holding action of the holding mechanism is allowed.
When the receiving member is located at the receiving position, the load detecting member and the swinging member are integrally swung by the holding action of the holding mechanism while the swinging member is not received by the receiving member. And while the swinging member is received by the receiving member, relative swinging of the load detecting member and the swinging member against the holding action of the holding mechanism is allowed. Item 5. The tractor according to item 4.
The tractor according to claim 4 or 5, wherein a roller that is rotatable around an axis parallel to the swing axis of the swing member is provided at a receiving position of the swing member in the receiving member.
The holding mechanism includes a stopper that restricts the swinging member from swinging in the direction in which the three-point link mechanism is lowered with respect to the load detection member, and the swinging member is provided with swinging toward the stopper. The tractor according to any one of claims 4 to 6, further comprising an urging spring.
The tractor according to any one of claims 3 to 7, wherein the operation tool is disposed adjacent to the driver seat at a location behind the driver seat in a vehicle body.
The tractor according to any one of claims 1 to 8, wherein the change amount conversion mechanism is disposed adjacent to the driver seat at a location behind the driver seat in a vehicle body.
A tractor that can be operated with a tillage device,
A three-point link mechanism that is connected to the rear part of the vehicle body so as to swing up and down, and to which the tilling device can be attached, a hydraulic lifting drive unit that drives the three-point link mechanism to move up and down, a change amount of the traction load, and a tilling depth A mechanical linkage unit for automatic raising / lowering that selectively converts any one of the change amounts into an elevation operation amount and transmits it to the elevation drive unit,
The mechanical linkage unit includes a change amount conversion mechanism that can be switched between a first linkage conversion state and a second linkage conversion state, and a link mechanism that interlocks and connects the change amount conversion mechanism and the elevating drive unit. Prepared,
The change amount conversion mechanism includes a load detection member that swings back and forth according to a traction load transmitted through the top link of the three-point link mechanism, and a swing member that swings according to the tilling depth of the tilling device. Have
When the change amount conversion mechanism is switched to the first linkage conversion state, the change amount conversion mechanism can convert the change amount of the traction load obtained by swinging the load detection member back and forth into the lift operation amount. become,
When the change amount conversion mechanism is switched to the second linkage conversion state, the change amount conversion mechanism can convert the change amount of the tilling depth obtained by swinging of the swing member into the lifting operation amount. A tractor.
The tractor according to claim 10, wherein the mechanical linkage unit includes an operation tool for switching the change amount conversion mechanism between the first linkage conversion state and the second linkage conversion state.
The swing member is supported swingably on the load detection member,
The operation tool is in contact with the load detection member to prevent the load detection member from swinging back and forth, and non-contact allowing the load detection member to swing back and forth without contacting the load detection member. A contact member that moves across the position,
When the contact member is in the non-contact position, the load detection member swings back and forth, whereby the amount of change in the traction load is transmitted to the lift drive unit as the lift operation amount,
When the contact member is in the contact position, the swinging member independently swings in a state where the load detection member does not swing back and forth, whereby the change amount of the tilling depth is transmitted to the lift drive unit as the lift operation amount. The tractor according to claim 11.
A first conversion state and a second conversion state as the first linkage conversion state,
The change amount conversion mechanism can be switched between the first conversion state and the second conversion state by operating the operation tool, and urges the swing member to a predetermined posture with respect to the load detection member. Holding mechanism to
When the change amount conversion mechanism is in the first conversion state, the load detection member and the swing member swing together by the holding action of the holding mechanism, and the traction obtained by swinging back and forth of the load detection member The amount of change in the load is not amplified and is transmitted to the lift drive unit as the lift operation amount,
When the change amount conversion mechanism is in the second conversion state, the load detection member and the swing member are allowed to swing relative to each other against the holding action of the holding mechanism, and the load detection member swings back and forth. The tractor according to claim 12, wherein the obtained change amount of the traction load is amplified and transmitted to the lifting drive unit as the lifting operation amount.
The holding mechanism includes a stopper that restricts the swinging member from swinging in the direction in which the three-point link mechanism is lowered with respect to the load detection member, and the swinging member is provided with swinging toward the stopper. The tractor according to claim 13, comprising a spring for biasing.
The tractor according to any one of claims 11 to 14, wherein the operation tool is disposed adjacent to the driver seat at a location behind the driver seat in a vehicle body.
The tractor according to any one of claims 10 to 15, wherein the change amount conversion mechanism is disposed adjacent to the driver seat at a location behind the driver seat in a vehicle body.
The load detection member includes a first connecting portion to which a long top link is connected, and a second connecting portion to which a bracket for supporting the short top link is connected. The described tractor.