JP6637861B2 - Tractor - Google Patents

Description

  The present invention relates to a tractor to which a tilling device can be attached and which can work, and more specifically, a three-point link mechanism which is vertically swingably connected to a rear portion of a vehicle body and to which the tilling device can be attached, and which raises and lowers the three-point link mechanism. The present invention relates to a tractor including a hydraulic lifting / lowering drive unit to be driven, and a mechanical linking unit for automatic lifting / lowering that converts a change in traction load or a change in plowing depth into a lifting / lowering operation amount and transmits the same to the lifting / lowering drive unit.

  In the tractor as described above, during plowing work in which a plow, which is an example of a tow-type tillage device, is attached to a three-point link mechanism, the amount of change in the tow load is converted into a lift operation amount, and a lift drive unit (hydraulic lift) Some devices are provided with a mechanical linkage unit (draft feedback link mechanism) for draft control to be transmitted to a device (for example, see Patent Document 1).

  Further, in the tractor as described above, a rotary cover, which is an example of a traction type tillage device, is mounted on the rotary tillage device at the time of the tillage work attached to the three-point link mechanism so that the rotary tillage device can swing vertically. A mechanical linking unit for automatic plowing depth control (oscillating link, interlocking link, sensor wire) which converts the amount of change in the plowing depth obtained by the swinging displacement into a lifting / lowering operation amount and transmits it to a lifting / lowering drive unit (control hydraulic circuit) ) (For example, see Patent Document 2).

  The tractor described in Patent Literature 1 includes a mechanical linking unit for draft control, so that when performing plowing work with a plow, draft control in which the plow is automatically raised and lowered in accordance with the traction load can be performed. As a result, in this tractor, the traction load can be kept constant, and the occurrence of engine stall due to the increase in the traction load can be avoided.

  Since the tractor described in Patent Literature 2 includes the mechanical linkage unit for automatic tillage depth control, when performing tillage work with a rotary tillage device, the tractor is interlocked with the vertical swing of the rear cover according to the tillage depth. The automatic tillage control, in which the rotary tiller automatically moves up and down, can be performed. Thereby, in this tractor, highly accurate tillage work in which the tillage depth is kept constant can be performed.

JP-A-2006-109802 (paragraph numbers 0017 to 0029, FIGS. 1 to 7) JP-A-2005-198665 (paragraph numbers 0038 to 0045, FIGS. 1 to 7)

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

  The tractor described in Patent Literature 2 does not include a mechanical linking unit for draft control. Therefore, when performing tilling work with a plow, the above-described draft control cannot be performed. There is a possibility that engine stall due to the rise may be caused.

  That is, there is a demand for the development of a mechanical linkage unit that can perform draft control suitable for plowing work using a plow or the like and automatic plowing depth control suitable for plowing work using a rotary tillage device.

As means for solving the above problems,
The tractor according to the present invention is a tractor capable of working by attaching a tilling device,
A three-point link mechanism that is vertically swayably connected to a rear portion of the vehicle body and to which the tilling device can be attached; a hydraulic lifting and lowering drive unit that drives the three-point link mechanism up and down; A mechanical linkage unit for automatic ascending and descending, which selectively converts any one of the amounts of change into an ascending / descending operation amount and transmits it to the ascending / descending drive unit,
The mechanical linkage unit includes a change amount conversion mechanism switchable between a first conversion state and a second conversion state, a link mechanism that interlocks the change amount conversion mechanism and the elevation drive unit, and the change amount conversion mechanism. An operating tool for switching a mechanism between the first conversion state and the second conversion state,
The change amount conversion mechanism is a load detection member that swings back and forth according to a traction load transmitted through a top link of the three-point link mechanism, and is swingably supported by the load detection member, A rocking member that rocks according to the plowing depth, and a holding mechanism that can hold the rocking member in a predetermined posture with respect to the load detection member ,
When the change amount conversion mechanism is switched to the first 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 lifting operation amount. ,
When the change amount conversion mechanism is switched to the second conversion condition, the change amount conversion mechanism, Ri convertible der the variation of the Kofuka obtained by swinging of the swinging member to the lifting operation amount ,
The change amount conversion mechanism can be switched between a standard conversion state included in the first conversion state and an amplification conversion state included in the first conversion state by operating the operation tool,
When the change amount conversion mechanism is in the standard conversion state, the load detecting member and the swinging member swing together as a result of the holding action of the holding mechanism, and the traction load obtained by forward and backward swinging of the load detecting member. The amount of change is transmitted to the lifting drive unit as the lifting operation amount without being amplified,
When the change amount conversion mechanism is in the amplification conversion state, relative swing between the load detection member and the swing member is allowed, and the change amount of the traction load obtained by the forward and backward swing of the load detection member is amplified. Then, the lift operation amount is transmitted to the lift drive unit .

According to this means, when tilling work is performed by a plow or a subsoiler, the mechanical linkage unit is placed in a draft control state by attaching the plow or the subsoiler to the three-point link mechanism. In this draft control state, if the operator operates the operating tool to switch the change amount conversion mechanism to the first conversion state, during plowing work, the plow, the subsoiler, and the like are automatically turned on according to the traction load. Draft control is performed to move up and down. As a result, it is possible to avoid occurrence of engine stall due to an increase in the traction load.
Further, when tilling work is performed using a rotary tilling device or the like, the mechanical linking unit is in an automatic tilling depth control state by attaching the rotary tilling device or the like to the three-point link mechanism. In this automatic plowing depth control state, when the operator operates the operating tool to switch the change amount conversion mechanism to the second conversion state, during the plowing operation, the rotary plowing device or the like according to the plowing depth. The automatic plowing depth control is automatically performed. As a result, highly accurate tillage work in which the tillage depth is kept constant can be performed.
That is, in this tractor, by providing the mechanical linkage unit having the above-described configuration, the above-described draft control can be performed when performing plowing work using a plow, a subsoiler, or the like. , The above-mentioned automatic plowing depth control can be performed.
According to this means, for example, when performing tilling work with a plow or a subsoiler or the like in a standard field where the traction load is difficult to increase due to the hardness of the soil and the variation in the traction load is unlikely to be intense, the operator may use the operating tool. By operating the change amount conversion mechanism to the standard conversion state, the plow, the subsoiler, and the like can be moved up and down according to the traction load at a standard speed suitable for this field. As a result, it is possible to avoid the occurrence of the engine stall caused by the increase in the traction load while performing the draft control in which the change in the plowing depth is gentle.
Further, for example, when performing a tilling operation with a plow or a subsoiler in a field where the traction load is likely to be large due to the hardness of the soil and the traction load is apt to fluctuate greatly, the operator operates the operation tool to change the amount of change. If the conversion mechanism is switched to the amplification conversion state, the plow, the subsoiler, and the like can be moved up and down at a high speed suitable for the field according to the traction load. As a result, it is possible to avoid the occurrence of engine stall due to a sudden increase in the traction load.

As one of means for making the present invention more suitable,
Before SL operation device, allows the contact position to prevent longitudinal oscillation of the load detection member in contact with the load detection member, the longitudinal oscillation of the load detection member without contacting the load detection member non A contact member that moves across the contact position,
When the contact member is at the non-contact position, the amount of change in the traction load is transmitted to the lifting drive unit as the lifting operation amount by the load detection member swinging back and forth,
When the contact member is at the contact position, the swing member swings independently in a state where the load detection member does not swing back and forth, so that the amount of change in the tillage depth is transmitted to the lift drive unit as the lift operation amount. Can be

According to this means, when the contact member is in the non-contact position, the change amount conversion mechanism is in the first conversion state described above, and when the contact member is in the contact position, the change amount conversion mechanism is in the second conversion state described above. Become.
As a result, in the automatic plowing depth control during the tilling operation by the rotary tilling device or the like, the load detecting member does not swing back and forth according to the traction load transmitted through the top link, and thus the load detecting member swings back and forth. 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 plowing depth control based on the amount of change in the plowing depth, it is possible to avoid the possibility that the work accuracy is reduced due to the input of the amount of change in the traction load to the change amount conversion mechanism.

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

According to this means, the load detection member and the swinging member can be swung together in the standard conversion state with a simple configuration having only the stopper and the spring. Further, in the amplification conversion state, relative swing between the load detection member and the swing member can be allowed.
As a result, it is possible to preferably switch between the standard conversion state and the amplification conversion state of the change amount conversion mechanism while simplifying the configuration.

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

According to this means, the operator can easily confirm the conversion state of the change amount conversion mechanism by visually observing the rear part of the driver's seat while sitting on the driver's seat.
Further, since the rear part of the driver's seat is not covered with a cover or the like, maintenance of the change amount conversion mechanism can be easily performed.

As one of means for making the present invention more suitable,
The operating tool is disposed adjacent to the driver seat at a position behind the driver seat in the vehicle body.

  According to this means, the operator can operate the operating tool by reaching the rear part of the driver's seat while sitting on the driver's seat, thereby facilitating the conversion state of the change amount conversion mechanism. You can switch to

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

According to this means, for example, when performing tilling work with a rotary tilling device, the specifications of the three-point link mechanism, the standard link specifications including a long top link and left and right lower links, a short top link and left and right lower links It can be easily changed to a special link specification with
When the specification of the three-point link mechanism is changed from the standard link specification to the special link specification, the lifting drive amount of the rotary tilling device with respect to the lifting operation amount of the lifting drive unit is increased, and the highest position of the rotary tilling device is increased. Become.
As a result, for example, when performing tilling work using a rotary tilling device in a work site having a high ridge, by changing the specification of the three-point link mechanism from the standard link specification to the special link specification, it is possible to perform traveling over the ridge. It is easy to avoid the possibility that the rotary tilling device will contact a high ridge when performing a ridge turn or the like.

It is a right side view of the tractor in which the plow was attached to the three-point link mechanism. It is a right view of the tractor in which the rotary tilling device was attached to the three-point link mechanism. It is a vertical right side view of a main part showing a configuration of a lifting drive unit and a mechanical linkage unit. It is a top view of an important section showing composition of a raising and lowering drive unit and a mechanical type link unit. FIG. 3 is an exploded perspective view of a main part showing a configuration of a lifting drive unit and a mechanical linkage unit. It is a vertical development right side view of an important section showing an operation state of an up-and-down drive unit when a tillage device stops raising and lowering by holding a position of a height setting lever on a lower setting side. It is a vertical development right side view of an important section showing an operation state of an up-and-down drive unit when a tillage device rises in conjunction with rocking operation of a height setting lever in a high setting direction. It is a vertical development right side view of an important section showing an operation state of an up-and-down drive unit, when a tillage device stops raising and lowering by holding a position of a height setting lever on a high setting side. FIG. 3 is an exploded perspective view of a main part showing a configuration of a change amount conversion mechanism and the like. FIG. 4 is a rear view of a main part showing a configuration of a change amount conversion mechanism and the like. It is XI-XI sectional drawing in FIG. FIG. 8 is a vertical right side view of a main part showing an operation state of the mechanical linking unit and the lifting drive unit when the traction load does not exceed a set value in a standard conversion state of the change amount conversion mechanism. It is a vertical right side view of an important section showing an operation state of a mechanical linkage unit and a lifting drive unit when a traction load exceeds a set value in a standard conversion state of a change amount conversion mechanism. FIG. 7 is a vertical right side view of a main part showing an operating state of a mechanical linking unit and a lifting drive unit when a traction load does not exceed a set value in an amplification conversion state of a change amount conversion mechanism. It is a vertical right side view of an important section showing an operation state of a mechanical linkage unit and an elevating drive unit when a traction load exceeds a set value in an amplification conversion state of a change amount conversion mechanism. It is a vertical right side view of an important section showing an operation state of a mechanical linkage unit and an elevating drive unit when a plowing depth reaches a set plowing depth in a second conversion state of a change amount conversion mechanism. It is a vertical right side view of an important section showing an operation state of a mechanical linkage unit and a raising / lowering drive unit when the plowing depth is deeper than a set plowing depth in a second conversion state of the change amount conversion mechanism.

Hereinafter, an example of an embodiment for carrying out the present invention will be described with reference to the drawings.
The direction indicated by the arrow F 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, a tractor exemplified in the present embodiment includes a front frame 1 disposed at a front portion of a vehicle body, an engine 2 connected to a rear portion of the front frame 1, and a lower rear end of the engine 2. , An intermediate frame 4 connected to the rear end of the clutch housing 3, and a transmission case (hereinafter, referred to as a T / M case) serving also as a rear frame connected to the rear end of the intermediate frame 4. 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 It is provided with a riding type driving unit 9 arranged at the rear.

  Although not shown, the power from the engine 2 is supplied to the T / M case 5 via a main clutch built in the clutch housing 3 and a transmission shaft covered with the intermediate frame 4. It is transmitted to the transmission. Then, the power after shifting 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 or the like built in the T / M case 5.

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

  At the rear of the T / M case 5, a three-point link mechanism 12 for attaching a working device is vertically swingably connected. The three-point link mechanism 12 includes a single top link 13, left and right lower links 14, and the like. Thereby, when performing the tilling work with this tractor, the traction type tilling device 15 which is an example of the working device can be attached to the three-point link mechanism 12.

  In this embodiment, the plow 15A, which is an example of the traction-type tilling device 15, is attached to the three-point link mechanism 12 (see FIG. 1), and the rotary tilling device, which is an example of the traction-type tilling device 15, is shown. 15B is attached to the three-point link mechanism 12 (see FIG. 2), but the three-point link mechanism 12 has a traction type tilling device such as a disk harrow, a cultivator, and a subsoiler. 15 can be attached.

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

  The lifting drive unit 17 includes left and right lift arms 20 for suspending and supporting the left and right lower links 14 via left and right support members 19, a hydraulic cylinder 21 for vertically swinging the left and right lift arms 20, and a hydraulic cylinder 21. Control valve 22 for controlling the operation of the cultivator 15, a height setting lever 23 for setting the control target height of the tillage device 15, a friction type holding mechanism 24 for holding the height setting lever 23 at an arbitrary operation position, A first link mechanism 25 for interlocking the spool 22A with the height setting lever 23, a feedback link mechanism 26 for interlocking the spool 22A with 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 and the spool 22A of the control valve 22 that come into contact with the height setting lever 23 from the rear side of the vehicle (the high setting side of the height setting lever 23). , A 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 setting direction (rearward 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 from the neutral position to the raised position in opposition. When the height setting lever 23 is swung in the low setting direction (vehicle forward direction), the first link mechanism 25 causes the spool 22A of the control valve 22 to be neutralized by the action of the urging means in conjunction with the operation. Move from the position to the lowered position.

  The feedback link mechanism 26 includes a link rod 30 extending from the right lift arm 20 to the vehicle body front side, a second swing arm 31 linked with the left and right lift arms 20 via the link 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 is provided. 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 reaching.

With the above configuration, when the operator operates the height setting lever 23 to increase the control target height of the tillage device 15, the first link mechanism 25 causes the spool 22A of the control valve 22 to move with the operation. Move from the neutral position to the raised position (see FIG. 7). Thereby, the tillage device 15 moves up together with the left and right lift arms 20. Then, when the tillage device 15 reaches the control target height by this ascent, the feedback link mechanism 26 moves the spool 22A of the control valve 22 from the ascent position to the neutral position in conjunction with this (see FIG. 8). Thereby, the tillage device 15 together with the left and right lift arms 20 stops rising.
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 the spool 22A from the neutral position to the lowered position with this operation. The movement is allowed, and the spool 22A moves from the neutral position to the lowered position by the action of the urging means. Thereby, the tillage device 15 moves down together with the left and right lift arms 20. Then, when the tillage device 15 reaches the control target height by this lowering, in conjunction with this, the feedback link mechanism 26 moves the spool 22A of the control valve 22 from the lowering position to the neutral position. Thereby, the tillage device 15 together with the left and right lift arms 20 stops descending.

  In other words, in this tractor, by providing the above-described lifting drive unit 17, it is possible to satisfactorily perform position control for raising and lowering the tillage device 15 to an arbitrary control target height set by operating the height setting lever 23. Can be. And by this position control, the plowing depth during the plowing operation 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 that can be switched between a first conversion state and a second conversion state, the change amount conversion mechanism 33, and a lifting drive unit. 17 and an operation tool 35 for switching the change amount conversion mechanism 33 between the first conversion state and the second conversion state. The change amount conversion mechanism 33 includes a load detection member 36 that swings back and forth according to a traction load transmitted via the top link 13 and a ground contact body 37 that detects the tillage depth of the tillage device 15 (FIGS. 2, 16 to 17). The swinging member 38 swings in accordance with the tillage depth of the tillage device 15 by being interlocked and connected with the tilling device 15.

  Among 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 tillage device 15B (see FIG. 2) includes a rear cover that functions as a ground contact body 37 so as to be vertically swingable. Therefore, in a state where the plow 15A is attached to the three-point link mechanism 12, the mechanical linkage unit 18 is in a draft control state in which the interlocking connection between the swing member 38 and the grounding body 37 is released (FIGS. 1, FIG. 3 to 5, see FIGS. 9 to 15). When the rotary tillage device 15 </ b> B is attached to the three-point link mechanism 12, the mechanical linking unit 18 performs automatic plowing in which the swinging member 38 and the grounding body 37 are interlocked and connected via the third link mechanism 39. It becomes a deep control state (see FIG. 2, FIGS. 16 to 17).

When the change amount conversion mechanism 33 is switched to the above-described first conversion state in the draft control state of the mechanical linkage unit 18, the change amount conversion mechanism 33 changes the traction load obtained by swinging the load detection member 36 back and forth. It is possible to convert the amount into a lifting operation amount (see FIGS. 1, 3 to 5, and 9 to 15).
When the change amount conversion mechanism 33 is switched to the above-described second conversion state in the automatic plowing depth control state of the mechanical linkage unit 18, the change amount conversion mechanism 33 adjusts the plowing depth obtained by the swing of the swing member 38. The change amount can be converted into a lifting operation amount (see FIGS. 2 and 16 to 17).
Accordingly, when the plow 15A is used in the tractor to perform the tilling operation, the plow 15A is attached to the three-point link mechanism 12, so that the mechanical linkage unit 18 is in the draft control state. Then, in this draft control state, if the operator operates the operating tool 35 to switch the change amount conversion mechanism 33 to the first conversion state, the plow 15A automatically operates according to the traction load during the tilling operation. Draft control is performed to move up and down. As a result, it is possible to avoid occurrence of engine stall due to an increase in the traction load.
Also, when performing tilling work with the rotary tilling device 15B in this tractor, the rotary tilling device 15B is attached to the three-point link mechanism 12, and the rocking member 38 and the grounding body 37 are connected via the third link mechanism 39. By the interlocking connection, the mechanical linkage unit 18 enters the automatic plowing depth control state. In this automatic plowing depth control state, when the operator operates the operating tool 35 to switch the change amount conversion mechanism 33 to the second conversion state, the grounding body according to the plowing depth during the plowing operation. Automatic tilling depth control is performed in which the rotary tilling device 15B automatically moves up and down in conjunction with the vertical swing of the (rear cover) 37. As a result, highly accurate tillage work in which the tillage depth is kept constant can be performed.
That is, in the tractor, by providing the mechanical linkage unit 18 having the above-described configuration, the above-described draft control can be performed when the tilling operation is performed by the plow 15A. In addition, when performing the tillage operation by the rotary tillage device 15B, the above-described automatic tillage depth 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 swingably supported by the load detection member 36. The operating tool 35 has a contact position at which the load detecting member 36 comes into contact with the load detecting member 36 to prevent the longitudinal movement of the load detecting member 36 and a non-contact position at which the load detecting member 36 does not It has a contact member 40 that moves across the position. Then, when the contact member 40 is at the non-contact position, the amount of change in the traction load is transmitted to the lifting drive unit 17 as the lifting operation amount by the load detection member 36 swinging back and forth. Further, when the contact member 40 is in the contact position, the swing member 38 swings independently in a state where the load detecting member 36 does not swing back and forth, so that the amount of change in the tillage depth is transmitted to the lifting drive unit 17 as a lifting 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 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 conversion state. become.
Thereby, in the automatic tillage depth control during the tillage operation by the rotary tillage device 15B, the load detection member 36 does not swing back and forth according to the traction load transmitted through the top link 13, and therefore, the load detection member 36 There is no possibility that the amount of change in the traction load is input to the change amount conversion mechanism 33 due to the swinging back and forth.
As a result, in the automatic plowing depth control based on the amount of change in the plowing depth, it is possible to avoid a possibility that the work accuracy is reduced due to the input of the amount of change in the traction load to the change amount conversion mechanism 33.

  As shown in FIG. 2 and FIGS. 16 to 17, the ground contact body 37 of the rotary tillage device 15 </ b> B is spring-biased in a downward direction (ground contact direction). The third link mechanism 39 includes a reversing arm 41 supported by the rotary tillage device 15B, a link rod 42 extending between the grounding body 37 and the reversing arm 41, and a control cable 43 extending between the reversing arm 41 and the swing member 38. Have. One end of the control cable 43 is detachably pin-connected to a portion of the swing member 38 above the swing fulcrum.

A plurality of connection holes 38A for control cables are formed on the upper side of the swing member 38. Thus, the connection position of the control cable 43 to the swing member 38 can be changed, and by this change, the swing displacement amount of the swing member 38 relative to the swing displacement amount of the grounding body 37 can be changed. As a result, in the automatic tillage depth control, it is possible to adjust the responsiveness when the rotary tillage device 15B moves up and down in conjunction with the vertical swing of the ground contact body 37 according to the tillage depth.
In the present 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, but three or more connecting holes 38A are formed in the swinging member 38. It may be.

  As shown in FIGS. 1, 3 to 5, and 10 to 15, in the three-point link mechanism 12 to which the plow 15 </ b> A is attached, the front end of the top link 13 is connected to the load detection member 36 via the first connection pin 44. Are linked. The front ends of the left and right lower links 14 are connected via left and right second connection pins 46 to left and right brackets 45 provided at the rear end of the T / M case 5. With this connection structure, the traction load during the tilling operation 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 a first support shaft 48 on a support member 47 fixed to the rear end of the T / M case 5. It is displaceably supported. The mechanical linking unit 18 includes an urging mechanism 49 that oscillates the load detecting member 36 in a direction (rearward direction of the vehicle body) against a traction load applied to the load detecting member 36, and swings the load detecting member 36 back and forth. A limiting mechanism 50 for limiting the range. 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 urging mechanism 49 and the limiting mechanism 50. When the traction load exceeds the set value, the load detection member 36 swings from the reference posture to the front of the vehicle body against the action of the urging mechanism 49 in conjunction with the increase in the traction load, and In conjunction with the reduction in the traction load, the urging mechanism 49 swings back to the rear of the vehicle body and returns 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 swing.

As shown in FIGS. 3 to 10 and FIGS. 12 to 17, the change amount conversion mechanism 33 includes a holding mechanism 52 that urges the swinging member 38 to return to a predetermined posture with respect to the load detection member 36. When the swing member 38 is connected to the grounding body 37 in an interlocking manner, the swinging member 38 is connected and set so that the predetermined posture of the swinging member 38 corresponds to the lowest position of the grounding body 37. The above-mentioned second link mechanism 34 is connected to the swing member 38 by a pin at a position below the swing fulcrum of the swing member 38. The second link mechanism 34 includes an operation arm 53 supported by the linking 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. , A second linking member 56 extending between the other end of the reversing arm 54 and the swinging member 38, and the like. The linking portion 27A of the first swing arm 27 is formed in a U-shape in plan view. The operation arm 53 swings in the rearward direction of the vehicle body (the direction in which the height setting lever 23 is set to a higher position), so that the linking portion 27A of the first swing arm 27 is moved from the vehicle body front side (the lower setting side of the height setting lever 23). Contact
With this configuration, when the change amount conversion mechanism 33 is switched to the first conversion state in the draft control state of the mechanical linkage unit 18, when the traction load increases, the holding action of the holding mechanism 52 is performed in conjunction with the rise. The load detecting member 36 and the swing member 38 swing integrally with the vehicle body front side. When the towing load decreases, the load detecting member 36 and the swinging member 38 swing integrally to the rear side of the vehicle body by the holding action of the holding mechanism 52 in conjunction with the decrease.
When the load detecting member 36 and the swinging member 38 swing integrally to the front side of the vehicle body, the operation arm 53 swings in the rearward direction of the vehicle body in conjunction with the integrated swinging, and the swinging operation causes the operation arm 53 to swing. The linking portion 27A of the first swing arm 27 is pressed rearward 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 is raised from the neutral position against the action of the urging means. (See FIG. 13). As a result, the plow 15A moves up together with the left and right lift arms 20.
When the load detecting member 36 and the swinging member 38 swing integrally to the rear side of the vehicle body, the operating arm 53 swings forward in the vehicle body in conjunction with the swinging together, and the swinging operation of the operating arm 53 Moves away from the linking portion 27A of the first swing arm 27 in the forward direction of the vehicle body. Thereby, the first swing arm 27 is allowed to swing forward of 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 urging means. As a result, the plow 15A descends 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 conversion state in the automatic plowing depth control state of the mechanical linkage unit 18, when the plowing depth is increased and the ground contact body 37 is raised, The swing member 38 independently swings in the backward tilt direction with respect to the load detection member 36 against the bias of the holding mechanism 52. Further, when the tillage depth becomes shallow and the ground contacting body 37 descends, the swinging member 38 is independently pivoted in the forward tilt direction with respect to the load detecting member 36 by the urging of the holding mechanism 52 in conjunction with the descending. I do.
When the swing member 38 swings independently in the backward tilt direction, the operation arm 53 swings in the rearward direction of the vehicle body in conjunction with the independent swing, and the swing causes the operation arm 53 to move to the first swing arm. 27 is pressed in the rearward 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 is raised from the neutral position against the action of the urging means. (See FIG. 17). As a result, the rotary tillage device 15B moves up 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 forward in the vehicle body in conjunction with the independent swing, and the swing causes the operation arm 53 to move to the first swing arm. 27 is separated from the link 27A in the forward direction of the vehicle body. Thereby, the first swing arm 27 is allowed to swing forward of 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 urging means. As a result, the rotary tillage device 15B descends together with the left and right lift arms 20.

In the draft control state of the mechanical linkage unit 18, the feedback link mechanism 26 stops the swing of the load detection member 36 and the swing member 38 according to the traction load by raising or lowering 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. As a result, the plow 15A stops moving up or down together with the left and right lift arms 20.
In the automatic plowing control state of the mechanical linking unit 18 described above, when the independent rocking of the rocking member 38 according to the plowing depth is stopped by the raising or lowering of the rotary plow 15B, the feedback link mechanism 26 makes this rocking. 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. Accordingly, the rotary tillage device 15B stops lifting or lowering 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 when the tilling operation is performed by the plow 15A, the above-described draft control can be favorably performed. In addition, when performing the tillage operation by the rotary tillage device 15B, the above-described automatic tillage depth control can be favorably performed.

As shown in FIGS. 3 to 5, 9 to 10, and 12 to 17, the holding mechanism 52 swings the swinging member 38 in the direction of lowering the three-point link mechanism 12 with respect to the load detection member 36. And a spring 58 for oscillatingly urging the swing member 38 toward the stopper 57.
That is, with a simple configuration including only the stopper 57 and the spring 58, when the change amount conversion mechanism 33 is in the first conversion state, the load detection member 36 and the rocking member 38 can be rocked integrally, When the change amount conversion mechanism 33 is in the second conversion state, the swing member 38 can be independently swung with respect to the load detection member 36.
As a result, it is possible to preferably switch the change amount conversion mechanism 33 between the first conversion state and the second conversion state while simplifying the configuration.

  The stopper 57 is supported by the load detection member 36. The spring 58 extends over the load detecting member 36 and the second linking member 56.

As shown in FIGS. 3 to 5, 9 to 10, and 12 to 15, the change amount conversion mechanism 33 includes a standard conversion state (see FIGS. 12 to 13) and an amplification conversion state (FIGS. 14 to 15) as the first conversion state. See). The change amount conversion mechanism 33 is switched between the standard conversion state and the amplification conversion state by operating the operation tool 35 described above.
When the change amount conversion mechanism 33 is in the standard conversion state, the load detecting member 36 and the swinging member 38 swing together as a result of the holding action of the holding mechanism 52, and due to the integrated swing, the load detecting member 36 swings back and forth. The amount of change in the traction load obtained by the movement is transmitted to the lifting drive unit 17 as the lifting operation amount without being amplified (see FIGS. 12 and 13).
When the change amount conversion mechanism 33 is in the amplification conversion state, relative swing between the load detection member 36 and the swing member 38 that resists the holding action of the holding mechanism 52 is allowed. The amount of change in the traction load obtained by the swinging movement 36 is amplified and transmitted to the lifting drive unit 17 as a lifting operation amount (see FIGS. 14 and 15).
Thereby, for example, when performing the tilling work by the plow 15A in a standard field where the traction load is hardly increased due to the hardness of the soil and the fluctuation of the traction load is hardly increased, the operator operates the operation tool 35 to operate the plow 15A. If the change amount conversion mechanism 33 is switched to the standard conversion state, the plow 15A can be raised and lowered at a standard speed suitable for the field according to the traction load.
As a result, it is possible to avoid the occurrence of the engine stall caused by the increase in the traction load while performing the draft control in which the change in the plowing depth is gentle.
Further, for example, when performing a tilling operation with the plow 15A 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 greatly, the operator operates the operation tool 35 to convert the change amount. By switching the mechanism 33 to the amplification conversion state, the plow 15A can be moved up and down at a high speed suitable for the field according to the traction load. As a result, it is possible to avoid the occurrence of 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 located at the non-receiving position, the receiving member 59 is removed from the swing region of the swing member 38, and the load detecting member 36 and the swing member 38 Swings together. Further, when the receiving member 59 is located at the receiving position, the receiving member 59 is located within the swinging region of the swinging member 38, and the holding mechanism is provided while the swinging member 38 is not received by the receiving member 59. While the load detecting member 36 and the swinging member 38 swing together by the holding action of the 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 performed. The relative swing between the member 36 and the swing member 38 is allowed.
That is, in addition to the holding mechanism 52 described above, the operating tool 35 is provided with only the receiving member 59, and when the receiving member 59 is in the non-receiving position, the load detecting member 36 and the swing member 38 are integrated. A standard conversion state of the oscillating change amount conversion mechanism 33 can be obtained. Further, when the receiving member 59 is at the receiving position, it is possible to obtain the amplification conversion state of the change amount conversion mechanism 33 in which the relative swing between the load detection member 36 and the swing member 38 is allowed.
As a result, it is possible to favorably switch between the standard conversion state and the amplification conversion state of the change amount conversion mechanism 33 while simplifying the configuration.

In the amplification 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 of the load detecting member 36 based on the towing load from the reference posture reaches a predetermined amount at which the swing member 38 contacts the receiving member 59, the receiving member 59 is By not receiving 38, the load detecting member 36 and the swing member 38 swing together. When the swing displacement amount of the load detection member 36 from the reference posture becomes equal to or more than a predetermined amount, the load detection member 36 and the swing member 38 relatively swing by the receiving member 59 receiving the swing member 38. .
Accordingly, in a work situation where the traction load slightly exceeds the set value and there is no possibility of causing engine stall, even when the change amount conversion mechanism 33 is in the amplification conversion state, the plow 15A can move to a standard position in accordance with the traction load. It is driven up and down at a speed.
As a result, even in a work situation where the towing load slightly exceeds the set value, it is possible to avoid the possibility that the durability of the lifting drive unit 17 is reduced due to raising and lowering the plow 15A at a high speed according to the towing load. can do.

When the relative swing between the load detection member 36 and the swing member 38 is allowed in the amplification conversion state of the change amount conversion mechanism 33, when the traction load increases, the load detection member 36 While swinging forward, the swing member 38 relatively swings in the backward tilt direction against the bias of the holding mechanism 52. When the towing load decreases, the load detecting member 36 swings to the rear of the vehicle body in conjunction with the decrease, and the swinging member 38 relatively swings in the forward leaning direction by the urging of the holding mechanism 52. .
When the load detecting member 36 swings to the front of the vehicle body and the swing member 38 relatively swings in the backward tilt direction, the operation arm 53 swings in the rearward direction of the vehicle body in conjunction with the relative swing. By the swing, the operation arm 53 presses the linking portion 27A of the first swing arm 27 in the rearward 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 is raised from the neutral position against the action of the urging means. (See FIG. 15). As a result, the plow 15A moves up together with the left and right lift arms 20.
Further, when the load detecting member 36 swings to the rear side of the vehicle body and the swinging member 38 relatively swings in the forward tilt direction, the operation arm 53 swings forward in the vehicle body in conjunction with the relative swing, This swing causes the operation arm 53 to move away from the linking portion 27A of the first swing arm 27 in the forward direction of the vehicle body. Thereby, the first swing arm 27 is allowed to swing forward of 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 urging means. As a result, the plow 15A descends together with the left and right lift arms 20.

  When the relative swing between the load detecting member 36 and the rocking member 38 according to the traction load is stopped by raising or lowering the plow 15A in the amplification conversion state of the change amount converting mechanism 33 described above, the feedback link mechanism 26 In conjunction with the stop of the swing, 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 15A stops moving up or down together with the left and right lift arms 20.

  With the above configuration, this tractor includes the mechanical linkage unit 18 having the above-described configuration, so that it is possible to select a draft control that takes into account different soil hardness for each field. As a result, the plowing operation using the plow 15A can be performed satisfactorily irrespective of the hardness of the soil that varies from field to field.

A roller 60 rotatable around an axis parallel to the swing axis of the swing member 38 is provided at a position where the swing member 38 is received in the receiving member 59.
With this configuration, when the swing member 38 slides with respect to the receiving member 59 due to relative swing between the load detection member 36 and the swing member 38 in the amplification conversion state of the change amount conversion mechanism 33, The roller 60 rotates in the sliding direction with the movement.
As a result, the swing member 38 slides smoothly with respect to the receiving member 59, and the load detection member 36 and the swing member 38 relatively smoothly swing.
As a result, the draft control in the amplification conversion state of the change amount conversion mechanism 33 can be smoothly performed.

As shown in FIGS. 1 and 2, the change amount conversion mechanism 33 is disposed adjacent to the driver's seat 11 at a position behind the driver's seat 11 in the vehicle body. Thus, the worker can easily check the conversion 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, since the rear part of the driver's seat 11 is not covered with a cover or the like, maintenance of the change amount conversion mechanism 33 is facilitated.

  The operating tool 35 is disposed at a position behind the driver's seat 11 on the vehicle body and adjacent to the driver's seat 11. Thereby, the operator can operate the operating tool 35 by reaching his / her hand toward the rear part of the driver's seat 11 while sitting on the driver's seat 11, and the standard conversion of the change amount conversion mechanism 33 is performed. The state, the amplification conversion state, and the second conversion state can be easily switched.

As shown in FIGS. 3 to 5, FIGS. 9 to 10, and FIGS. 12 to 17, the operating tool 35 includes a swing plate 61 supported by the above-described support member 47 so as to swing in the left-right direction, and a swing plate. An operation handle 62 extending forward from the main body 61 is provided. The plate-shaped contact member 40 is provided on the left side of the swinging plate 61, and the receiving member 59 is provided on the right side of the swinging plate 61. The operation tool 35 swings left and right around an axis X extending in the front and rear direction. The operation tool 35 is selectively held at one of the first operation position, the second operation position, and the third operation position by a detent mechanism 63 provided over the support member 47 and the swing plate 61. .
When the operation tool 35 is held at the right first operation position, the contact member 40 is located at the non-contact position, and the receiving member 59 is located at the non-receiving position. As a result, the change amount conversion mechanism 33 enters a standard 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 located at the non-contact position, and the receiving member 59 is located at the receiving position. As a result, the change amount conversion mechanism 33 enters an amplification conversion state for draft control.
When the operation tool 35 is held at the third operation position on the left side, the contact member 40 is located at the contact position, and the receiving member 59 is located at the non-receiving position. As a result, the change amount conversion mechanism 33 enters the second conversion state for automatic plowing depth control.
That is, the operator switches the operation position of the operating tool 35 to change the change amount conversion mechanism 33 to the standard conversion state for draft control, the amplification conversion state for draft control, and the second conversion state for automatic plowing depth control. You can easily switch to the conversion state.

As shown in FIGS. 3, 5, and 9 to 17, the load detection member 36 includes left and right side walls 36A having opposed through holes 36a. The support member 47 includes a vertical wall portion 47A connected to the rear portion of the vehicle body, and a U-shaped connecting portion 47B extending in a rearward direction from the vertical wall portion 47A and entering between the left and right side wall portions 36A. ing. In the linking portion 47B, left and right long holes 47a long in the front-rear direction are formed at locations where the side walls 36A face the through holes 36a. The above-described limiting mechanism 50 includes the through holes 36a of the load detecting member 36, the long holes 47a of the support member 47, and the link pins 64 inserted into the through holes 36a and the long holes 47a. It is configured.
That is, the longitudinal swing range of the load detecting member 36 is limited 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 linking portion 47B. The rubber block 65 has a long hole 65 a having a front-rear length shorter than the long hole 47 a of the support member 47 at a position facing the long hole 47 a of the support member 47. The link pin 64 is inserted into the elongated hole 65a.
Thereby, when the limiting mechanism 50 limits the forward and backward swing of the load detecting member 36, the linking pin 64 of the limiting mechanism 50 collides with the rubber block 65. 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 lifting 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 able to hold a position at an arbitrary operation position in the driving unit 9, a linking member 69 extending from the sensitivity adjustment lever 67 to the support shaft 68 of the reversing arm 54, and a reversing arm 54. A support member 70 for supporting 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 swing operation of the sensitivity adjustment lever 67 in the front-back direction, the sensitivity adjustment mechanism 66 performs the first swing The gap 71 between the linking portion 27A of the arm 27 and the operation arm 53 is changed. Thereby, the operation sensitivity when the lifting drive unit 17 is interlocked with the swing member 38 can be adjusted.

The sensitivity adjusting mechanism 66 is configured such that the smaller the gap 71 becomes, the more sensitive the operation sensitivity when the lifting / lowering drive unit 17 is interlocked with the swing member 38 becomes, and the more the plow 15A rises when the traction load exceeds the set value. Responsiveness improves.
The sensitivity adjusting mechanism 66 is configured such that the larger the gap 71 is, the less sensitive the operation sensitivity when the lifting / lowering drive unit 17 is interlocked with the swing member 38 becomes, and the more the plow 15A rises when the traction load exceeds the set value. Responsiveness deteriorates.
As a result, for example, due to a field condition such as a rugged field, the more the traction load changes, the more insensitive the above-mentioned operation sensitivity becomes, so that the plow 15A frequently moves up and down and hunts. It is possible to prevent a decrease in the tilling work accuracy due to this.

As shown in FIGS. 1 to 3, 5, 9, and 11 to 17, the load detecting member 36 has a long top link 13 </ b> 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, 16 to 17) supporting the short top link 13B are connected are provided.
Thereby, for example, when performing the tilling work by the rotary tilling device 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, and the short top link 13B and the left and right It can be easily changed to a special link specification having the lower link 14.
When the specification of the three-point link mechanism 12 is changed from the standard link specification to the special link specification, the lifting drive amount of the rotary plow 15B with respect to the lifting operation amount of the lifting drive unit 17 becomes large, and The ascent position is higher.
As a result, for example, when the tilling work is performed by the rotary tilling device 15B in a work site having a high ridge, the specification of the three-point link mechanism 12 is changed from the standard link specification to the special link specification, so that the ridge crossing is performed. When running or turning at the edge of a ridge, the possibility that the rotary tillage device 15B comes into contact with a high ridge can be easily avoided.

  The load detection member 36 has a single connection hole that enables the long top link 13A to be pin-connected as the first connection portion 36B. The load detecting member 36 includes two upper and lower connection holes that enable the bracket 72 to be connected to pins as the second connection portion 36C.

[Another embodiment]
The present invention is not limited to the configuration exemplified in the above-described embodiment. Hereinafter, another representative embodiment of the present invention will be exemplified.

[1] The configuration of the tractor can be variously changed.
For example, the tractor may be configured as a semi-crawler specification including left and right crawlers in place of the left and right rear wheels 7.
For example, the tractor may be configured as a full crawler specification including left and right crawlers in place of the left and right front wheels 6 and 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 to have a hybrid specification including the engine 2 and the 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.
Then, at the time of work traveling in which a mower or a seeder is attached to the three-point link mechanism 12, the operator positions the operation tool 35 at the third operation position and sets the change amount conversion mechanism 33 to the second conversion state. By switching, 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, the seeder, or the like is moved up and down by the traction load during operation.

[3] The configuration of the lifting drive unit 17 can be variously changed.
For example, the lifting drive unit 17 may be configured to include a hydraulic motor or the like instead of the hydraulic cylinder 21.
For example, the lifting drive unit 17 may have a configuration in which a biasing unit that biases the spool 22 </ b> A of the control valve 22 to return to the lowered position is provided outside the control valve 22.

[4] The mechanical linkage unit 18 is, for example, a swinging member 38, which is swingably supported by the load detection member 36 for draft control, and a swingably supported member 47. A swinging member 38 for controlling the automatic plowing depth, and a link mechanism 34 for linking the swinging member 38 for draft control to the lifting drive unit 17 as a link mechanism; A link mechanism 34 for automatic plowing depth control is provided for linking 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 are operated by operating the operating tool 35. The standard conversion state in which the swinging of the swinging member 38 for automatic plowing depth is prevented and the swinging of the load detecting member 36 and the swinging member 38 for draft control are allowed. Automatic with The amplification conversion state in which the swinging of the swinging member 38 for depth control is prevented, and the swinging of the swinging member 38 for automatic tillage control while preventing the swinging of the load detecting member 36 and the swinging member 38 for draft control. A configuration that switches to the second conversion state in which swing is allowed may be employed.

[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 only the standard conversion state as the first conversion state.
For example, in the change amount conversion mechanism 33, a 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 connected to the link mechanism 34 by operating the operation tool 35. The first conversion state may be switched to a second 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 plow swingably supported by the support member 47. A swing member 38 for depth control, a first conversion state in which the swing member 38 for draft control is connected to the link mechanism 34 by operating the operating tool 35, and a swing member for automatic plowing depth control. 38 may be configured to switch to the second conversion condition to be connected to the link mechanism 34. In this configuration, the standard conversion state and the amplification conversion state can be provided as the first conversion state.

[6] The configuration of the load detection member 36 can be variously changed.
For example, the load detection member 36 may have a configuration in which the upper end is supported by the support member 47 via the first support shaft 48.
For example, the load detecting member 36 may be supported by the supporting member 47 via a vertically long first support shaft 48 so as to be able to swing back and forth.

[7] The holding mechanism 52 swings the swinging member 38 to a predetermined posture, for example, a spring receiving member fixed at a position facing the swinging member 38 in a predetermined posture in the axial direction of the second support shaft 51. It may be constituted by a torsion spring for urging. In this configuration, the torsion spring is assembled such that 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. Can be

  INDUSTRIAL APPLICABILITY The present invention can be applied to a tractor provided with a hydraulic lifting / lowering drive unit for vertically driving a three-point link mechanism to which a tillage device can be attached, and a mechanical linking unit for automatic lifting / lowering.

Reference Signs List 11 Driver's seat 12 Three-point link mechanism 13 Top link 13A Long top link 13B Short top link 15 Tillage device 17 Elevation drive unit 18 Mechanical linkage unit 33 Change amount conversion mechanism 34 Link mechanism 35 Operating tool 36 Load detection member 36B First connection Part 36C Second connecting part 38 Swinging member 40 Contact member 52 Holding mechanism 57 Stopper 58 Spring 72 Bracket

Claims (6)

A tractor that can work with a tilling device attached,
A three-point link mechanism that is vertically swayably connected to a rear portion of the vehicle body and to which the tilling device can be attached; a hydraulic lifting and lowering drive unit that drives the three-point link mechanism up and down; A mechanical linkage unit for automatic ascending and descending, which selectively converts any one of the amounts of change into an ascending / descending operation amount and transmits it to the ascending / descending drive unit,
The mechanical linkage unit includes a change amount conversion mechanism switchable between a first conversion state and a second conversion state, a link mechanism that interlocks the change amount conversion mechanism and the elevation drive unit, and the change amount conversion mechanism. An operating tool for switching a mechanism between the first conversion state and the second conversion state,
The change amount conversion mechanism is a load detection member that swings back and forth according to a traction load transmitted through a top link of the three-point link mechanism, and is swingably supported by the load detection member, A rocking member that rocks according to the plowing depth, and a holding mechanism that can hold the rocking member in a predetermined posture with respect to the load detection member ,
When the change amount conversion mechanism is switched to the first 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 lifting operation amount. ,
When the change amount conversion mechanism is switched to the second conversion condition, the change amount conversion mechanism, Ri convertible der the variation of the Kofuka obtained by swinging of the swinging member to the lifting operation amount ,
The change amount conversion mechanism can be switched between a standard conversion state included in the first conversion state and an amplification conversion state included in the first conversion state by operating the operation tool,
When the change amount conversion mechanism is in the standard conversion state, the load detecting member and the swinging member swing together as a result of the holding action of the holding mechanism, and the traction load obtained by forward and backward swinging of the load detecting member. The amount of change is transmitted to the lifting drive unit as the lifting operation amount without being amplified,
When the change amount conversion mechanism is in the amplification conversion state, relative swing between the load detection member and the swing member is allowed, and the change amount of the traction load obtained by the forward and backward swing of the load detection member is amplified. And the tractor is transmitted to the lifting drive unit as the lifting operation amount . Before SL operation device, allows the contact position to prevent longitudinal oscillation of the load detection member in contact with the load detection member, the longitudinal oscillation of the load detection member without contacting the load detection member non A contact member that moves across the contact position,
When the contact member is at the non-contact position, the amount of change in the traction load is transmitted to the lifting drive unit as the lifting operation amount by the load detection member swinging back and forth,
When the contact member is at the contact position, the swing member swings independently in a state where the load detection member does not swing back and forth, so that the amount of change in the tillage depth is transmitted to the lift drive unit as the lift operation amount. A tractor according to claim 1, wherein The holding mechanism includes a stopper that restricts the swinging member from swinging in a direction to lower the three-point link mechanism with respect to the load detection member, and a swinging member that swings the swinging member toward the stopper. tractor according to claim 1 or 2 and a spring for energizing. The tractor according to any one of claims 1 to 3 , wherein the change amount conversion mechanism is disposed adjacent to the driver's seat at a position behind the driver's seat in the vehicle body. The tractor according to any one of claims 1 to 4 , wherein the operation tool is disposed adjacent to the driver seat at a position behind the driver seat in the vehicle body. The load detection member is longer a first connecting portion which top link is connected, a short top link to any one of the second connecting portion and in which claims 1-5 which comprises a bracket for supporting are connected Tractor as described.

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