0001]The present disclosure relates to tractors.
Background technology
[0002]
　Conventionally, a three-point link mechanism to which a tilling device can be attached, a hydraulic elevating drive unit that elevates and drives the three-point link mechanism, and a mechanical linkage unit that transmits the elevating operation amount of the three-point link mechanism to the elevating drive unit. Is known (see, for example, Patent Document 1).
[0003]
　The mechanical linkage unit includes a load detection member that detects the amount of change in the traction load via a three-point link mechanism, and a mechanical link mechanism that transmits the amount of lift operation according to the amount of change in the traction load to the lift drive unit. Have. As a result, the elevating drive unit moves the three-point link mechanism up and down, so that the tilling device attached to the three-point link mechanism can automatically move up and down according to the traction load.
Prior art literature
Patent documents
[0004]
Patent Document 1: Japanese Unexamined Patent Publication No. 2006-109802
Outline of the invention
[0005]
　Generally, in a mechanical link mechanism, since there is a distance from the load detection member to the elevating drive unit, the amount of change in the traction load is transferred to the elevating drive unit by interlocking and connecting a plurality of plate-shaped or rod-shaped link members. I'm telling you.
[0006]
　Here, since a plurality of link members are used in the mechanical link mechanism, the structure of the mechanical link mechanism tends to be complicated. The more complicated the mechanical link mechanism, the longer it takes to maintain, and the more chattering is likely to occur due to the large number of link members.
[0007]
　Therefore, it is an object of the present invention to provide a tractor in which the structure of the mechanical link mechanism is less likely to be complicated.
[0008]
　The tractor according to one aspect is a three-point link mechanism to which a tilling device can be attached, a hydraulic elevating drive unit that elevates and drives the three-point link mechanism, and the elevating operation amount of the three-point link mechanism. It is equipped with a mechanical linkage unit that conveys information to. The mechanical linkage unit includes a load detection member that detects a change in the traction load via the three-point link mechanism, and a cable that is interlocked according to the change in the traction load detected by the load detection member. It has a mechanical link mechanism that is interlocked with the cable and the elevating drive unit and transmits the elevating operation amount according to the change amount of the traction load to the elevating drive unit.
A brief description of the drawing
[0009]
FIG. 1 is a right side view of the tractor according to the first embodiment.
FIG. 2 is a right side view of the hydraulic lifting device according to the first embodiment.
FIG. 3 is a hydraulic circuit diagram for raising and lowering according to the first embodiment.
FIG. 4 is a perspective view of the load detection mechanism according to the first embodiment as viewed from the upper left front.
FIG. 5 is a cross-sectional view taken along the line 5A-5A of FIG.
FIG. 6 is a right side view for explaining the intermediate link mechanism according to the first embodiment.
FIG. 7 is a right side view of the hydraulic lifting device according to the modified example.
FIG. 8 is a perspective view of the load detection mechanism according to the modified example as viewed from the upper right rear.
FIG. 9 is a rear view of the load detection mechanism according to the modified example as viewed from the rear.
FIG. 10 is a right side view of a load detection mechanism according to a modified example.
FIG. 11 is a right side view of a load detection mechanism according to a modified example.
FIG. 12 is a right side view of the tractor according to the second embodiment.
FIG. 13 is a right side view of the hydraulic lifting device according to the second embodiment.
Embodiment for carrying out the invention
[0010]
　[Summary of Embodiment] The
　tractor according to one embodiment includes a three-point link mechanism to which a tilling device can be attached, a hydraulic elevating drive unit for elevating and lowering the three-point link mechanism, and an elevating operation of the three-point link mechanism. A mechanical linkage unit that transmits an amount to the elevating drive unit is provided. The mechanical linkage unit includes a load detection member that detects a change in the traction load via the three-point link mechanism, and a cable that is interlocked according to the change in the traction load detected by the load detection member. It has a mechanical link mechanism that is interlocked with the cable and the elevating drive unit and transmits the elevating operation amount according to the change amount of the traction load to the elevating drive unit.
[0011]
　As a result, in the mechanical linkage unit, the cable can take a part of the transmission path for transmitting the change amount of the traction load from the load detection member to the elevating drive unit. Therefore, the amount of change in the traction load can be transmitted to the elevating drive unit without increasing the number of plate-shaped or rod-shaped link members constituting the mechanical link mechanism. As a result, it is possible to suppress an increase in the number of link members, and it is possible to make the structure of the mechanical link mechanism less complicated.
[0012]
　According to a preferred embodiment, the cable may have a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side. The cable may have a portion extending rearward of the tractor from the second connecting portion. One end of the cable is connected to the mechanical link mechanism towards the front of the tractor, and the other end of the cable towards the front of the tractor is the load detecting member. May be linked to. As a result, the operator located behind the tractor can follow the cable from the rear of the tractor and recognize each connection portion. Therefore, the operator can easily perform maintenance work such as cable inspection and replacement work.
[0013]
　According to a preferred embodiment, the cable may have a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side. The tractor may have a mounting portion to which the second connecting portion is mounted, and may have a swinging member that swings back and forth in response to the front-back swing of the load detecting member. In the side view of the tractor, when the second connecting portion swings forward together with the swinging member, the first connecting portion is pulled backward and the second connecting portion swings backward together with the swinging member. The cable may then extend while curving so that the first connecting portion is pulled forward. The second connecting portion may be attached to the mounting portion at a position higher than that of the first connecting portion. By bending the cable during maintenance work, the operator can carry the second connecting portion to the mounting portion without the operator moving significantly. In addition, since the second connecting portion is at a higher position than the first connecting portion, it can be attached at a position close to the height of the operator's line of sight. The worker can easily perform the maintenance work.
[0014]
　According to a preferred embodiment, the cable may have an inner cable that swings in response to the front-back swing of the swing member, and a cover portion that covers the outside of the inner cable. It may have a cable fixing portion for fixing the cover portion. By fixing the cover portion with the cable fixing portion, the swing path of the inner cable can be fixed, and the inner cable can be stably swung according to the front-back swing of the swing member. As a result, the mechanical linkage unit can accurately transmit the elevating operation amount according to the change amount of the traction load to the elevating drive unit, so that high-quality draft control can be executed.
[0015]
　According to a preferred embodiment, the tractor may have a rocking member that swings back and forth in response to the back and forth swing of the load detecting member. The mechanical linking unit may have a sensitivity adjusting mechanism for adjusting the operating sensitivity when the elevating drive unit is interlocked with the swing member. The cable may be connected to the swing member and the sensitivity adjusting mechanism. Since the cable directly connects the swing member and the sensitivity adjustment mechanism, the number of link members connecting the swing member and the sensitivity adjustment mechanism can be reduced, and the structure of the hydraulic lifting device becomes complicated. hard.
[0016]
　According to a preferred embodiment, at least a portion of the mechanical linkage may be located posterior to the front end of the lower link of the three-point linkage. Since the mechanical link mechanism can be easily confirmed from the rear of the tractor, maintainability can be improved.
[0017]
　According to a preferred embodiment, the cable may have a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side. The mounting portion to which the second connecting portion is mounted may be located above the load detecting member. This makes it easy to check the second connecting portion and the mounting portion from the rear of the tractor, and it is easy to attach and detach the second connecting portion. Therefore, maintenance work can be easily performed. Further, it is not necessary to provide a space for mounting the second connecting portion in front of the load detecting member.
[0018]
　According to a preferred embodiment, the cable may have a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side. The mechanical linking unit may have a first mounting portion to which the first connecting portion is mounted and a second mounting portion to which the second connecting portion is mounted. The second mounting portion may be located behind the first mounting portion in a state where the traction load is not applied. As a result, since the distance from the rear of the tractor to the second mounting portion is shorter than that of the first mounting portion, it is easy to mount and remove the second connecting portion from the rear of the tractor. Therefore, maintenance work can be easily performed.
[0019]
　According to a preferred embodiment, the mechanical linking unit has an amplification swing member that is swingably supported by the load detection member and swings back and forth in response to the front-back swing of the load detection member. good. The amount of change in the traction load may be amplified by the front-back swing of the amplification swing member. This makes it possible to quickly raise and lower the tilling device according to changes in the traction load. As a result, even when the traction load suddenly increases, it is possible to avoid engine stall due to the increase in the traction load.
[0020]
　According to a preferred embodiment, a state in which the elevating operation amount according to the amount of change in the traction load amplified by the anteroposterior oscillating member is transmitted to the elevating drive unit, and the amplification oscillating member. The state in which the elevating operation amount according to the change amount of the traction load that is not amplified by the front-rear swing may be transmitted to the elevating drive unit may be switched. As a result, the operator can drive the three-point link mechanism up and down according to the condition of the soil in which the towing operation is performed (for example, the hardness of the soil, the content ratio of stones, rocks, trees, etc.).
[0021]
　According to a preferred embodiment, the first connecting portion, which is the connecting portion on one side of the cable, may be connected to the mechanical link mechanism. The cable may selectively transmit the change amount of the traction load and the change amount of the tillage depth. By switching the connection destination of the second connecting portion, which is the connecting portion on the other side of the cable, the first elevating operation amount according to the change amount of the traction load and the second elevating operation amount according to the change amount of the tillage depth. Either one of the operation amount is selected as the elevating operation amount transmitted to the elevating drive unit.
[0022]
　The mechanical link mechanism connected to the first connection portion of the cable for switching the connection destination of the second connection portion of the cable is a link mechanism common to both draft control and automatic tillage control. Therefore, since it is possible to combine similar functions in the draft control and the automatic plowing depth control into one link mechanism, it is possible to make the structure of the hydraulic lifting device less complicated. In addition, the cable has flexibility as compared with a plate-shaped or rod-shaped link member used in a general mechanical link mechanism. Therefore, the degree of freedom in arranging the connection destination of the cable is increased, and the structure of the hydraulic lifting device can be made less complicated. In addition, by switching the connection destination of the cable having a wide movable range due to the flexibility, the switching work between the draft control and the automatic plowing depth control can be easily performed.
[0023]
　According to a preferred embodiment, the tractor has a draft control mounting portion to which the second connecting portion is mounted and the second lifting operation when the first lifting operation amount is selected as the lifting operation amount. When the amount is selected as the elevating operation amount, it may have a mounting portion for automatic tillage control to which the second connecting portion is mounted. The draft control mounting portion may be located in front of the front end of the top link of the three-point link mechanism. The mounting portion for automatic plowing depth control may be located behind the rear end of the top link. When switching between draft control and automatic tillage control, the operator can work between the front and rear ends of the top link in the side view of the tractor, and the draft control and automatic tillage control can be used. Switching work can be easily performed.
[0024]
　According to a preferred embodiment, the tractor may have an attachment portion to which the second connecting portion is attached when the first elevating operation amount is selected as the elevating operation amount. The cable may have a portion extending rearward of the tractor from the second connecting portion. The second connecting portion may be attached to the mounting portion toward the front of the tractor. When the operator located behind the tractor selects the first elevating operation amount as the elevating operation amount, that is, when switching to draft control, the operator extends toward the rear of the tractor (extended part). By gripping the extending portion so that the second connecting portion is located on the front side of the operator, the second connecting portion can be easily carried to the mounting portion. Therefore, the worker can easily perform the work of switching to the draft control.
[0025]
　According to a preferred embodiment, the tractor has a load detecting member that swings back and forth in response to the traction load transmitted via the top link of the three-point link mechanism, and a mounting portion to which the second connecting portion is attached. It may also have a swing member that swings back and forth in response to the front-back swing of the load detection member. In the side view of the tractor, when the second connecting portion swings forward together with the swinging member, the first connecting portion is pulled backward and the second connecting portion swings backward together with the swinging member. The cable may then extend while curving so that the first connecting portion is pulled forward. The second connecting portion may be attached to the mounting portion at a position higher than that of the first connecting portion. By bending the cable when switching to draft control, the operator can carry the second connecting portion to the mounting portion without the operator moving significantly. In addition, since the second connecting portion is at a higher position than the first connecting portion, it can be attached at a position close to the height of the operator's line of sight. The operator can easily perform the work of switching to the draft control.
[0026]
　According to a preferred embodiment, the cable may have an inner cable that swings in response to the front-back swing of the swing member, and a cover portion that covers the outside of the inner cable. It may have a cable fixing portion for fixing the cover portion. By fixing the cover portion with the cable fixing portion, the swing path of the inner cable can be fixed, and the inner cable can be stably swung according to the front-back swing of the swing member. As a result, the mechanical linkage unit can accurately transmit the elevating operation amount according to the change amount of the traction load to the elevating drive unit, so that high-quality draft control can be executed.
[0027]
　According to a preferred embodiment, the tractor has a load detecting member that swings back and forth according to the traction load transmitted via the top link of the three-point link mechanism, and a load detecting member that swings back and forth according to the back and forth swing of the load detecting member. It may have an oscillating member and an oscillating member. The mechanical linking unit may have a sensitivity adjusting mechanism for adjusting the operating sensitivity when the elevating drive unit is interlocked with the swing member. The cable may be connected to the swing member and the sensitivity adjusting mechanism. Since the cable directly connects the swing member and the sensitivity adjustment mechanism, the number of link members connecting the swing member and the sensitivity adjustment mechanism can be reduced, and the structure of the hydraulic lifting device becomes complicated. hard.
[0028]
　According to a preferred embodiment, at least a portion of the mechanical linkage may be located posterior to the front end of the lower link of the three-point linkage. Since the mechanical link mechanism can be easily confirmed from the rear of the tractor, maintainability can be improved.
[0029]
　According to a preferred embodiment, the tractor includes a load detecting member that swings back and forth according to the traction load transmitted via the top link of the three-point link mechanism, and the first elevating operation amount is the elevating operation amount. When selected, it may have a mounting portion to which the second connecting portion is mounted. The mounting portion may be located above the load detecting member. This makes it easy to check the second connecting portion and the mounting portion from the rear of the tractor when switching from the automatic plowing depth control to the draft control, and it is easy to switch the connecting destination of the second connecting portion. Therefore, the switching work can be easily performed.
[0030]
　According to a preferred embodiment, the rear part of the three-point linkage may be provided with a hitch device for connecting the tilling device. The hitch device may have a linking member that swings back and forth according to the amount of change in the plowing depth. The linking member may have a mounting portion to which the second connecting portion is attached when the second elevating operation amount is selected as the elevating operation amount. As a result, the second connecting portion of the cable is directly attached to the linking member of the hitch device, so that the cultivation depth changes as compared with the case where the second connecting portion of the cable is attached to the front side of the three-point link mechanism. The number of members for transmitting the amount to the cable can be reduced.
[0031]
　Conventionally, a tractor equipped with a hydraulic lifting device is widely known. As such a tractor, Patent Document 1 discloses a tractor provided with a mechanical linkage unit for draft control. The mechanical linkage unit (draft feedback link mechanism) for draft control of Patent Document 1 is an elevating drive unit (control) that controls the elevating operation amount according to the amount of change in the traction load detected via the top link of the three-point link mechanism. It is informed to the valve etc.). The elevating drive unit automatically elevates and drives the three-point link mechanism according to the amount of elevating operation, so that the traction-type tilling device (for example, a plow) attached to the three-point link mechanism automatically responds to the traction load. Go up and down. As described above, the tractor of Patent Document 1 can perform draft control when the tractor is cultivated by the traction type tilling device, so that the traction load can be kept constant and the traction load can be increased. It is possible to avoid the occurrence of the engine stall caused by it.
[0032]
　Further, as an example of a tractor provided with a hydraulic lifting device, Japanese Patent Application Laid-Open No. 2003-102208 (hereinafter referred to as Patent Document 2) discloses a tractor provided with a mechanical linking unit for automatic tillage depth control. .. The mechanical linkage unit (intermediate link mechanism) for automatic tillage control of Patent Document 2 is detected via a link mechanism (swing arm, interlocking link, interlocking link, sensor wire, etc.) provided in the rotary tillage device. The amount of elevating operation according to the amount of change in plowing depth is transmitted to the elevating drive unit (position control valve, etc.). The elevating drive unit automatically elevates and lowers the three-point link mechanism according to the amount of elevating operation, so that the rotary tilling device attached to the three-point link mechanism automatically elevates and descends according to the cultivation depth. As described above, the tractor of Patent Document 2 can perform automatic tillage depth control when the tillage work is performed by the rotary tillage device, so that the tillage work with high accuracy in which the tillage depth is kept constant is performed. Can be done.
[0033]
　The tractor of Patent Document 1 does not include a mechanical linkage unit for automatic tillage depth control. Therefore, when the tilling work is performed by the rotary tilling device, the automatic tilling depth control cannot be performed, and it is difficult to perform the tilling work with high accuracy in which the tilling depth is kept constant. On the other hand, the tractor of Patent Document 2 does not include a mechanical linkage unit for draft control. Therefore, when the tilling work is performed by the traction type tilling device, the draft control cannot be performed, and there is a possibility that the engine stalls due to the increase in the traction load. To accommodate both tillage operations, it is envisioned that the hydraulic lift will be equipped with both a mechanical linkage unit for automatic tillage control and a mechanical linkage unit for draft control. However, by providing both mechanical linkage units, there is a problem that the structure of the hydraulic lifting device tends to be complicated. The more complicated the structure, the longer it takes to maintain, and the more chattering is likely to occur due to the large number of link members constituting the mechanical linking unit. Therefore, in order to provide a tractor capable of performing draft control and automatic tillage control and in which the structure of the hydraulic elevating device is less likely to be complicated, the tractor may have the following configuration.
[0034]
　The tractor according to one aspect is a three-point link mechanism to which a tilling device can be attached, a hydraulic elevating drive unit that elevates and drives the three-point link mechanism, and the elevating operation amount of the three-point link mechanism. It is equipped with a mechanical linkage unit that conveys information to. The mechanical linking unit includes a cable that selectively transmits a change in traction load and a change in tillage depth, and a mechanical link mechanism that is interlocked and connected to the cable and the elevating drive unit. The first connecting portion, which is the connecting portion on one side of the cable, is connected to the mechanical link mechanism. By switching the connection destination of the second connecting portion, which is the connecting portion on the other side of the cable, the first elevating operation amount according to the change amount of the traction load and the second elevating operation amount according to the change amount of the tillage depth. Either one of the operation amount is selected as the elevating operation amount transmitted to the elevating drive unit.
[0035]
　Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the ratio of each dimension is different from the actual one. Therefore, the specific dimensions, etc. should be determined in consideration of the following explanation. In addition, there may be a portion where the relationship and ratio of the dimensions of the drawings are different from each other. In the present specification and the drawings, elements having substantially the same function and configuration are designated by the same reference numerals to omit duplicate description, and elements not directly related to the present disclosure are omitted from the illustration.
[0036]
　[First Embodiment]
　(1) Schematic configuration
　of a tractor A schematic configuration of a tractor will be described with reference to FIG. FIG. 1 is a right side view of the tractor according to the embodiment. The arrow F shown in the drawing indicates the front direction (forward) of the tractor, the arrow B indicates the rear direction (rear direction) of the tractor, the arrow U indicates the upward direction (upward) of the tractor, and the arrow D indicates the downward direction (upward) of the tractor. Downward), arrow R indicates the right direction (right side) of the tractor, and arrow L indicates the left direction (left side) of the tractor. As shown in FIG. 1, the tractor 1 exemplified in this embodiment includes a vehicle body 2, a three-point link mechanism 3, and a hydraulic lifting device 5. The vehicle body 2 includes a frame 21, an engine 22, a clutch housing 23, a transmission case (hereinafter referred to as a T / M case) 24, wheels 25, a rear fender 26, a boarding-type driving unit 27, a cylinder case 28, and the like.
[0037]
　The frame 21 has a front frame 21F located at the front of the vehicle body 2 and an intermediate frame 21M connected to the rear end of the clutch housing 23. The engine 22 is connected to the rear part of the front frame 21F. The clutch housing 23 is connected to the lower part of the rear end of the engine 22. The T / M case 24 is connected to the rear end portion of the intermediate frame 21M. The T / M case 24 is also used as a rear frame. The wheels 25 have left and right front wheels 25F arranged on the left and right of the front frame 21F, and left and right rear wheels 25B arranged on the left and right of the T / M case 24. The rear fender 26 covers the left and right rear wheels 25B. The driving unit 27 has a steering wheel 271 for steering the front wheels and a driver's seat 272 located between the left and right rear fenders 26. The cylinder case 28 accommodates a control valve 63 and the like, which will be described later. A driver's seat is arranged above the cylinder case 28.
[0038]
　Although not shown, the power from the engine 22 is mainly built in the T / M case 24 via the main clutch built in the clutch housing 23, the transmission shaft covered with the intermediate frame 21M, and the like. It is transmitted to the transmission. The power after shifting by the main transmission is transmitted to the wheels 25 via the auxiliary transmission or the like built in the T / M case 24.
[0039]
　The tilling device 4 can be attached to the three-point link mechanism 3. The three-point link mechanism 3 is connected to the rear portion of the T / M case 24 so as to be swingable up and down. The three-point link mechanism 3 has a single top link 3A and left and right lower links 3B. When the tilling work is performed by the tractor 1, the traction type tilling device 4A can be attached to the three-point link mechanism 3. In this embodiment, as an example of the tractor type tilling device 4A, a state in which a plow is attached to the three-point link mechanism 3 is shown. A disc halo, a cultivator, a subsoiler, and the like can be attached to the three-point link mechanism 3 as a tractor-type tillage device 4A.
[0040]
　As shown in FIG. 1, the front end portion of the top link 3A is connected to a load detection mechanism 71 (load detection member 711) described later via a connecting pin. Further, the front ends of the left and right lower links 3B are connected to the left and right brackets provided at the rear ends of the T / M case 24 via the left and right connecting pins. Due to this connection structure, the traction load during the tilling work acts on the load detection member 711 via the top link 3A.
[0041]
　The hydraulic lifting device 5 is a machine-linked device. The hydraulic lifting device 5 is arranged on the rear side of the tractor. The configuration of the hydraulic lifting device 5 is shown below.
[0042]
　(2) Configuration of Hydraulic Lifting Device The configuration
　of the hydraulic lifting device according to the present embodiment will be described with reference to FIGS. 1 to 6. FIG. 2 is a right side view of the hydraulic lifting device according to the embodiment. FIG. 3 is a hydraulic circuit diagram for raising and lowering according to the embodiment. FIG. 4 is a perspective view of the load detection mechanism according to the embodiment as viewed from the upper left front. FIG. 5 is a cross-sectional view taken along the line 5A-5A of FIG. FIG. 6 is a right side view for explaining the intermediate link mechanism according to the embodiment.
[0043]
　As shown in FIG. 2, the hydraulic elevating device 5 (tractor 1) includes a hydraulic elevating drive unit 6 and a mechanical linking unit 7. The elevating drive unit 6 can elevate and drive the three-point link mechanism 3. The tilling device 4 attached to the three-point link mechanism 3 moves up and down according to the ascending / descending drive of the three-point link mechanism 3. The mechanical linkage unit 7 transmits the elevating operation amount of the three-point link mechanism 3 to the elevating drive unit 6. Details of the mechanical linkage unit 7 will be described later. The elevating drive unit 6 has a left and right lift arm 61, a lift cylinder 62, a control valve 63, a balance arm 64, a position arm 65, a position arm shaft 65A, a feedback arm shaft 66A, a position lever 67, and a position plate 68.
[0044]
　As shown in FIG. 1, the left and right lift arms 61 suspend and support the left and right lower links 3B via the left and right support members. The lift arm 61 is hydraulically driven by the lift cylinder 62 so as to be able to swing up and down. The lift cylinder 62 lifts and lowers the three-point link mechanism 3 via the lift arm 61. The lift cylinder 62 is housed in a cylinder case 28.
[0045]
　The control valve 63 controls the lift cylinder 62. As shown in FIG. 3, the control valve 63 may include a spool 631, a lowering valve 632, a relief valve 633, an unload valve 634, and the like. The control valve 63 may be connected to the lift cylinder 62 via a drop speed adjusting valve. The control valve 63 is housed in the cylinder case 28. The spool 631 is always urged in the downward direction D by an urging means (for example, a spring).
[0046]
　The balance arm 64 is swingably connected to the end of the spool 631. A position arm shaft 65A is locked and connected to one end of the balance arm 64 via an operation pin, and a feedback arm shaft 66A is engaged to the other end of the balance arm 64 via an operation pin. It is stopped and connected. The feedback arm shaft 66A is interlocked with the lift arm 61 via a feedback link mechanism (not shown).
[0047]
　The position arm 65 is fixed to the outer end of the position arm shaft 65A. When the position arm 65 is rotated, the balance arm 64 swings around the locking point of the feedback arm shaft 66A with the operation pin. As a result, the spool 631 shifts to the ascending side or the descending side, and the lift arm 61 performs a drive ascending operation or a self-weight lowering operation. The operation of the lift arm 61 is transmitted via the feedback link mechanism and converted into rotation of the feedback arm shaft 66A. When the feedback arm shaft 66A is rotated, the spool 631 is shifted in the opposite direction via the balance arm 64. The spool 631 returns to the neutral position when the feedback arm shaft 66A is rotated to a predetermined rotation position corresponding to the rotation operation position of the position arm 65. In this way, by arbitrarily rotating the position arm 65, the lift arm 61 can be raised and lowered to a position corresponding to the position arm 65.
[0048]
　The position lever 67 sets the control target height of the tilling device 4. The position lever 67 is arranged on the right side of the driver's seat. The position lever 67 is arranged so as to be swingable back and forth around the fulcrum a located near the rear side of the position arm 65. The fulcrum a is a fulcrum common to the control adjustment lever 751 described later. The position lever 67 is arranged on the driver's seat 272 side (left side) of the control adjustment lever 751. The position lever 67 is interlocked with the position arm 65 via the elongated hole 65h and the position plate 68. Since the spool 631 is urged in the downward direction D by the urging means, the position arm 65 is urged to rotate clockwise in a side view from the right side (see FIG. 2 and the like). As a result, the rear end of the elongated hole 65h is engaged with and in contact with the position plate 68.
[0049]
　As the position lever 67 swings backward (counterclockwise in FIG. 2) with the fulcrum a as the axis, the position arm 65 engaged and supported by the position plate 68 resists the urging force. And is rotated backward (counterclockwise in FIG. 2). As a result, the lift arm 61 rises to a position corresponding to the position arm 65. On the other hand, as the position lever 67 is swung toward the front F (clockwise in FIG. 2) with the fulcrum a as the axis, the position arm 65 that is urged to rotate becomes the position lever 67. It follows and rotates. As a result, the lift arm 61 descends to the position corresponding to the position arm 65.
[0050]
　Next, the details of the mechanical linkage unit 7 will be described. The mechanical linkage unit 7 includes a load detection mechanism 71, an urging mechanism 72, a limiting mechanism 73, an operating tool 74, an intermediate link mechanism 75, and a cable 78. As shown in FIG. 2, the vehicle body 2 has a first cable fixing portion 241 to which a cover portion 78B described later is fixed on the intermediate link mechanism 75 side at the rear end of the vehicle body 2 (T / M case 24). You can do it. Further, as shown in FIGS. 2, 4 and 5, a support member 91 is fixed to the rear end of the vehicle body 2 (cylinder case 28). The support member 91 extends in the vertical direction outside the vertical wall portion 911 connected to the rear portion of the vehicle body 2 (cylinder case 28), the linking portion 912 which is U-shaped in the top view, and the vertical wall portion 911 in the lateral direction. It has an outer wall portion 913, a swing support portion 914 that supports the swing member 715 described later, and a second cable fixing portion 915 to which the cover portion 78B is fixed. The linking portion 912 has left and right side portions 912A extending rearward from the vertical wall portion 911, and a rear portion 912B extending laterally so as to connect the left and right side portions 912A.
[0051]
　The load detection mechanism 71 detects the amount of change in the traction load via the three-point link mechanism 3, and transmits the amount of change in the traction load to the intermediate link mechanism 75 via the cable 78. The load detection mechanism 71 has a load detection member 711 and a swing member 715.
[0052]
　The load detecting member 711 detects the amount of change in the traction load via the three-point link mechanism 3. The load detection member 711 is supported by the support member 91 so that it can be oscillated and displaced in the front-rear direction via the first support shaft 92. The load detection member 711 swings back and forth according to the traction load transmitted via the top link 3A. The load detection member 711 includes left and right side wall portions 711A, vertical wall portions 711B to which the side wall portions 711A are fixed, connecting holes 711C formed in the side wall portions 711A, extension portions 711E extending forward from the vertical wall portions 711B, and swinging. It has a contact portion 711F, which comes into contact with the member 715.
[0053]
　The vertical wall portion 711B is provided on the free end side (upper side) of the load detection member 711. A linking portion 912 of the support member 91 is inserted between the left and right vertical wall portions 711B. A top link bracket that supports the top link 3A or the top link 3A can be connected to the connecting hole 711C. The extending portion 711E extends forward from the vertical wall portion 711B. The extending portion 711E is arranged on the right side of the side wall portion 711A. The contact portion 711F extends to the right from the extension portion 711E at the front portion of the extension portion 711E. As a result, when the load detection member 711 swings forward in response to an increase in the traction load, the contact portion 711F moves forward and comes into contact with the swing member 715.
[0054]
　The swing member 715 swings back and forth according to the front-back swing of the load detection member 711. The swing member 715 is supported by the swing support portion 914 via a second support shaft 914A extending in the lateral direction. The swing member 715 can swing around the fulcrum b passing through the axis of the second support shaft 914A. The swing member 715 swings forward by being pushed forward by the contact portion 711F that moves forward. When there is no contact with the contact portion 711F (that is, when no forward force acts from the contact portion 711F), the swing member 715 swings backward by an urging mechanism (not shown). For example, the swing member 715 is pulled back to a predetermined position by the spring force of the torsion spring attached to the second support shaft 914A.
[0055]
　The rocking member 715 has a second mounting portion 715A to which the cable 78 (second connecting portion 782 described later) is mounted. The second mounting portion 715A is arranged on the free end side. Further, the second mounting portion 715A is located above the load detecting member 711. Further, the second mounting portion 715A is located behind the front end of the lower link 3B. Further, the second mounting portion 715A is located behind the first mounting portion 752A, which will be described later, in a state where no traction load is applied. Further, the second mounting portion 715A is located in front of the front end of the top link 3A. The second mounting portion 715A is a mounting portion for draft control. When the first elevating operation amount according to the change amount of the traction load is selected as the elevating operation amount transmitted to the elevating drive unit 6, the second connecting portion 782 is attached to the second mounting portion 715A toward the front. ..
[0056]
　The urging mechanism 72 swings and urges the load detecting member 711 in a direction (rearward) that opposes the traction load applied to the load detecting member 711. As shown in FIG. 5, the urging mechanism 72 may be configured by a spring having elasticity in the front-rear direction.
[0057]
　The limiting mechanism 73 limits the range of forward / backward swing of the load detecting member 711. The limiting mechanism 73 may be composed of a through hole 711h, an elongated hole 912h, a rubber block 73b, and a linking pin 73p. The through hole 711h is formed in the load detecting member 711. Specifically, the through hole 711h is formed so as to face each of the left and right side wall portions 711A. The elongated hole 912h is a hole formed in the support member 91 that is long in the front-rear direction. Specifically, the elongated hole 912h is formed at a position facing the through hole 711h in each of the left and right side portions 912A of the linking portion 912. The rubber block 73b is fitted into the space between the vertical wall portion 911 of the support member 91 and the linking portion 912 (side portion 912A and rear portion 912B). The rubber block 73b is formed with a long hole 73h having a shorter front-rear length than the long hole 912h of the support member 91 at a position facing the long hole 912h of the support member 91. The linking pin 73p is inserted into each through hole 711h, each elongated hole 912h, and each elongated hole 73h.
[0058]
　The front-rear swing range of the load detection member 711 is limited and set by the front-rear length of each elongated hole 912h of the support member 91. When the limiting mechanism 73 limits the back-and-forth swing of the load detecting member 711, the linking pin 73p of the limiting mechanism 73 collides with the rubber block 73b.
[0059]
　The load detecting member 711 is held in a reference posture extending vertically upward from the first support shaft 92 by the action of the urging mechanism 72 and the limiting mechanism 73. When the traction load exceeds a predetermined value, the load detection member 711 swings forward from the reference posture against the action of the urging mechanism 72 in conjunction with the increase in the traction load. Further, the load detection member 711 swings backward due to the action of the urging mechanism 72 in conjunction with the decrease in the traction load, and returns to the reference posture.
[0060]
　The operating tool 74 switches between a first state in which the load detecting member 711 detects the traction load and a second state in which the load detecting member 711 does not detect the traction load. The operating tool 74 extends rearward from the rocking plate 741 oscillating laterally to the support member 91, the operating handle 742 extending upward from the rocking plate 741, and the rocking plate 741. It has a contact member 743. The contact member 743 moves between the non-contact position and the contact position. At the non-contact position (first operation position P1), the contact member 743 does not come into contact with the load detection member 711 (vertical wall portion 711B) and allows the load detection member 711 to swing back and forth. On the other hand, at the contact position, the contact member 743 contacts the load detection member 711 to prevent the load detection member 711 from swinging back and forth. At the contact position (second operation position P2), the contact member 743 is sandwiched between the vertical wall portion 711B and the rocking plate 741.
[0061]
　The operating tool 74 swings laterally around an axial center extending in the front-rear direction. The operating tool 74 is selectively held at one of the first operating position P1 (left side) and the second operating position P2 (right side) by the detent mechanism. When the operating tool 74 is held at the first operating position P1, the contact member 743 is located at the non-contact position, and the load detecting mechanism 71 is in the first state. On the other hand, when the operation tool 74 is held at the second operation position P2, the contact member 743 is located at the contact position, and the load detection mechanism 71 is in the second state. The operator can perform draft control by moving the operation tool 74 to the first operation position P1.
[0062]
　Next, the intermediate link mechanism 75 will be described. The intermediate link mechanism 75 is a mechanical link mechanism. As shown in FIG. 2, the intermediate link mechanism 75 is interlocked and connected to the cable 78 and the elevating drive unit 6. The intermediate link mechanism 75 transmits the elevating operation amount according to the change amount of the traction load to the elevating drive unit 6. The intermediate link mechanism 75 includes a control adjusting lever 751, a cable connecting arm 752, a linking plate 753, an adjusting arm 754, and a linking rod 755.
[0063]
　The control adjustment lever 751 is a lever for adjusting the draft control. The control adjustment lever 751 can swing back and forth around the fulcrum a.
[0064]
　The cable connecting arm 752 can swing back and forth around the fulcrum c. The cable connecting arm 752 serves as a connecting destination on one side of the cable 78. The cable connecting arm 752 has a first mounting portion 752A to which the cable 78 is mounted. Specifically, a first connecting portion 781, which will be described later, is attached to the first mounting portion 752A. The cable connecting arm 752 is equipped with a tension spring (not shown) for oscillating forward. The cable connecting arm 752 has a cam surface S formed in a convex shape on the rear end side (the side on the roller 754r side described later) of the cable connecting arm 752.
[0065]
　The linkage plate 753 extends rearward from the base end of the control adjustment lever 751 (a support shaft extending from the right side surface of the cylinder case 28 in the right direction R). The linkage plate 753 can swing around the fulcrum a. The relative positions of the control adjustment lever 751 and the linkage plate 753 are fixed. Therefore, in response to the operation of the control adjustment lever 751, the linkage plate 753 also rotates around the fulcrum a.
[0066]
　The adjustment arm 754 is attached so as to be swingable back and forth around the fulcrum d at the tip (rear end) of the linking plate 753. A roller 754r as a cam follower is attached to the adjustment arm 754. Further, the adjustment arm 754 is equipped with a torsion spring that oscillates the adjustment arm 754 forward. The roller 754r abuts from the rear on the cam surface S of the cable connecting arm 752 due to the forward urging swing of the adjustment arm 754, and follows the cam surface S.
[0067]
　The linking rod 755 is erected over the position arm 65 and the cable connecting arm 752. The linking rod 755 transmits the swing displacement of the adjustment arm 754 according to the cam surface S of the roller 754r to the position arm 65.
[0068]
　As shown in FIG. 1, at least a part of the intermediate link mechanism 75 is located behind the front end of the lower link 3B of the three-point link mechanism 3. In the embodiment, at least a part of the cable connecting arm 752 and at least a part of the adjusting arm 754 are located behind the front end of the lower link 3B. The intermediate link mechanism 75 (mechanical linkage unit 7) has a sensitivity adjusting mechanism that adjusts the operating sensitivity when the elevating drive unit 6 is interlocked with the swing member 715. In the present embodiment, the sensitivity adjusting mechanism is composed of a control adjusting lever 751, a cable connecting arm 752, a linking plate 753, an adjusting arm 754, and a linking rod 755.
[0069]
　Since the relative position between the control adjustment lever 751 and the linkage plate 753 is fixed, the operator operates the control adjustment lever 751 to position the control adjustment lever 751 rearward (counterclockwise in FIG. 6). The linkage plate 753 rotates downward around the fulcrum a (counterclockwise in FIG. 6), and the fulcrum d is displaced downward. As a result, the distance between the contact point of the roller 754r with respect to the cable connecting arm 752 and the fulcrum c of the cable connecting arm 752 becomes smaller, and the lever ratio for bringing the adjusting arm 754 into contact with the cable connecting arm 752 by the control adjusting lever 751. Becomes smaller. Therefore, the rotation of the adjustment arm 754 becomes sensitive to the rotation of the cable connecting arm 752. That is, the operating sensitivity of the elevating drive unit 6 becomes sensitive to the swing of the swing member 715, and the responsiveness when the tilling device 4A rises when the traction load exceeds a predetermined value is improved.
[0070]
　On the other hand, as the control adjustment lever 751 is positioned forward (clockwise in FIG. 6), the linkage plate 753 rotates upward around the fulcrum a (clockwise in FIG. 6), and the fulcrum d is displaced upward. As a result, the distance between the contact point of the roller 754r with respect to the cable connecting arm 752 and the fulcrum c of the cable connecting arm 752 becomes large, and the lever ratio for bringing the adjusting arm 754 into contact with the cable connecting arm 752 by the control adjusting lever 751. Becomes larger. Therefore, the rotation of the adjustment arm 754 becomes insensitive to the rotation of the cable connecting arm 752. That is, the operating sensitivity of the elevating drive unit 6 becomes insensitive to the swing of the swing member 715, and the responsiveness when the tilling device 4A rises when the traction load exceeds a predetermined value becomes slow.
[0071]
　Next, the cable 78 will be described. The cable 78 is interlocked according to the amount of change in the traction load detected by the load detection member 711. The cable 78 is interlocked and connected to the load detection mechanism 71 and the elevating drive unit 6. Specifically, the cable 78 is connected to the swing member 715 and the sensitivity adjusting mechanism. One end of the cable 78 is connected to the intermediate link mechanism 75 toward the front of the tractor 1. The other end of the cable 78 is connected to the load detecting member 711 toward the front of the tractor 1. The cable 78 has a first connecting portion 781 that is a connecting portion on one side of the cable 78, and a second connecting portion 782 that is a connecting portion on the other side of the cable 78.
[0072]
　The first connecting portion 781 is connected on the intermediate link mechanism 75 side. Specifically, the first connecting portion 781 is connected to the cable connecting arm 752. The second connecting portion 782 is connected on the load detecting member 711 (load detecting mechanism 71) side. The second connecting portion 782 is connected to the swing member 715. The second connecting portion 782 is attached to the second mounting portion 715A at a position higher than that of the first connecting portion 781.
[0073]
　The cable 78 is a push-pull cable. The cable 78 has an inner cable 78A and a cover portion 78B. The inner cable 78A swings in response to the swing of the load detection member 711. The inner cable 78A can move inside the outer cable 78B3 described later. The first connecting portion 781 is arranged at one end of the inner cable 78A, and the second connecting portion 782 is arranged at the other end of the inner cable 78A. Therefore, the inner cable 78A is directly connected to the swing member 715. Further, the inner cable 78A is directly connected to the cable connecting arm 752.
[0074]
　The cover portion 78B covers the outside of the inner cable 78A. The cover portion 78B has a first fixing portion 78B1 fixed to the first cable fixing portion 241, a second fixing portion 78B2 fixed to the second cable fixing portion 915, and an outer cable 78B3. The first fixing portion 78B1 is located at the end of the outer cable 78B3 on the intermediate link mechanism 75 side, and the second fixing portion 78B2 is located at the end of the outer cable 78B3 on the load detecting member 711 side. The second fixing portion 78B2 is fixed to the second cable fixing portion 915 at a position higher than the first connecting portion 781.
[0075]
　As shown in FIGS. 2 and 4, the cable 78 has a portion (extending portion E) extending rearward of the tractor 1 from the second connecting portion 782. Further, the cable 78 extends while being curved. Specifically, in the side view of the tractor 1, the cable 78 extends in a C-shape or a U-shape. Therefore, in the side view of the tractor 1, when the second connecting portion 782 swings forward together with the swing member 715, the first connecting portion 781 is pulled backward. Further, when the second connecting portion 782 swings backward together with the swing member 715, the first connecting portion 781 is pulled forward. That is, when the force of the front direction F acts on the second connecting portion 782, the force of the rear direction B acts on the first connecting portion 781, and when the force of the rear direction B acts on the second connecting portion 782, the first connecting portion acts. A force in the forward direction F acts on 781.
[0076]
　Next, draft control will be described. When the tractoring work is performed using the traction type tilling device 4A and the traction load of the traction type cultivating device 4A becomes larger than a predetermined value, the load detection member 711 swings forward, so that the rocking member The 715 is pushed by the contact portion 711F and swings forward. As a result, when the second connecting portion 782 of the cable 78 swings forward together with the swing member 715, the first connecting portion 781 is pulled backward. As a result, the cable connecting arm 752 rotates backward around the fulcrum c, and the adjusting arm 754 follows the cable connecting arm 752 and swings backward. The linking rod 755 is pulled backward together with the adjustment arm 754, and the position arm 65 rotates rearward around the position arm shaft 65A. As a result, the lift arm 61 rises to a position corresponding to the position after the rotation of the position arm 65. The displacement of the position arm 65 corresponds to the amount of lifting operation. Therefore, the control valve 63 controls the lift cylinder 62 according to the lifting operation amount (displacement amount of the position arm 65).
[0077]
　When the load of the tilling device 4 falls below a predetermined value as the lift arm 61 rises, the raising operation of the lift arm 61 stops. Since the draft control in which the tilling device 4A automatically moves up and down according to the traction load during the tilling work can be performed, it is possible to avoid the occurrence of engine stall due to the increase in the traction load.
[0078]
　With the above configuration, in the mechanical linkage unit 7, the cable 78 can bear a part of the transmission path for transmitting the change amount of the traction load from the load detection member 711 to the elevating drive unit 6. Therefore, the amount of change in the traction load can be transmitted to the elevating drive unit 6 without increasing the number of plate-shaped or rod-shaped link members constituting the mechanical intermediate link mechanism 75. As a result, it is possible to suppress an increase in the number of link members, and it is possible to make the structure of the mechanical link mechanism less complicated.
[0079]
　Further, the cable 78 has an extending portion E extending from the second connecting portion 782 toward the rear of the tractor 1. Further, one end of the cable 78 is connected to the intermediate link mechanism 75 toward the front, and the other end of the cable 78 is received forward and connected to the load detection member 711. As a result, the operator located behind the tractor 1 can follow the cable 78 from the rear of the tractor and recognize each connecting portion (first connecting portion 781 and second connecting portion 782). As a result, the operator can easily perform maintenance work such as inspection and replacement work of the cable 78. In addition, the worker carries the second connecting portion 782 to the second mounting portion 715A by grasping the extending portion E so that the second connecting portion 782 is located in front of the worker with respect to the extending portion E. It will be easier. Therefore, the operator can easily attach the second connecting portion 782 and easily perform the maintenance work.
[0080] [0080]
　Further, in the side view of the tractor 1, when the second connecting portion 782 swings forward together with the swinging member 715, the first connecting portion 781 is pulled backward, and the second connecting portion 782 moves backward together with the swinging member 715. The cable 78 extends while bending so that the first connecting portion 781 is pulled forward when it swings. In addition, the second connecting portion 782 is attached to the first mounting portion 752A at a position higher than that of the first connecting portion 781. By bending the cable 78 during maintenance work, the operator can carry the second connecting portion 782 to the mounting portion without the operator moving significantly. In addition, since the second connecting portion 782 is at a higher position than the first connecting portion 781, it can be attached at a position close to the height of the operator's line of sight. The worker can easily perform the maintenance work.
[0081]
　Further, the tractor 1 has a cable fixing portion (first cable fixing portion 241 and second cable fixing portion 915). By fixing the cover portion 78B with the cable fixing portion, the inner cable 78A can be stably swung. As a result, the mechanical linkage unit 7 can accurately transmit the elevating operation amount according to the change amount of the traction load to the elevating drive unit 6, so that high-quality draft control can be executed.
[0082]
　Further, the cable 78 is connected to the swing member 715 and the sensitivity adjusting mechanism. As a result, the number of link members connecting the swing member 715 and the sensitivity adjusting mechanism can be reduced, and the structure of the hydraulic lifting device 5 is less likely to be complicated.
[0083]
　Further, at least a part of the intermediate link mechanism 75 is located behind the front end of the lower link 3B. This makes it easier to check the intermediate link mechanism 75 from the rear of the tractor 1, so that maintainability can be improved.
[0084]
　Further, the second mounting portion 715A is located above the load detecting member 711. As a result, when the second mounting portion 715A is visually recognized from the rear of the tractor 1, the second mounting portion 715A can be visually recognized above the load detecting member 711, and the load detecting member 711 is unlikely to overlap with the second mounting portion 715A. Become. It is easy to check the second connecting portion and the mounting portion from the rear of the tractor 1, and it is easy to attach and detach the second connecting portion 782. Therefore, the switching work can be easily performed. Further, it is not necessary to provide a space for providing the second mounting portion 715A in front of the load detecting member 711.
[0085]
　The second mounting portion 715A is located behind the front end of the lower link 3B. Since the distance from the rear of the tractor 1 to the second mounting portion 715A is closer than the front end of the lower link 3B, it is easy to mount and remove the second connecting portion 782 from the rear of the tractor 1. Therefore, maintenance work can be easily performed.
[0086]
　Further, the second mounting portion 715A is located behind the first mounting portion 752A in a state where no traction load is applied. Since the distance from the rear of the tractor 1 to the second mounting portion 715A is shorter than that of the first mounting portion 752A, it is easy to mount and remove the second connecting portion 782 from the rear of the tractor 1. Therefore, maintenance work can be easily performed.
[0087]
　[Modification Example]
　Next, a modification example according to the first embodiment will be described with reference to FIGS. 7 to 11. FIG. 7 is a right side view of the hydraulic lifting device according to the modified example. FIG. 8 is a perspective view of the load detection mechanism according to the modified example as viewed from the upper right rear. FIG. 9 is a rear view of the load detection mechanism according to the modified example as viewed from the rear. FIG. 10 is a right side view of the load detection mechanism according to the modified example. FIG. 11 is a right side view of the load detection mechanism according to the modified example. It should be noted that the same configuration as described above is omitted from the description.
[0088]
　The mechanical linkage unit 7 in the modified example has an amplification swing member 77. The amplification swing member 77 is swingably supported by the load detection member 711. Specifically, the amplification swing member 77 is supported by the load detection member 711 via a third support shaft 773 extending in the lateral direction. As a result, the amplification swing member 77 can swing around the fulcrum f. The upper portion of the amplification rocking member 77 is located above the fulcrum f, and the lower portion of the amplification rocking member 77 is located below the fulcrum f.
[0089]
　Further, the amplification swing member 77 swings back and forth according to the front-back swing of the load detection member 711. The amount of change in the traction load is amplified by the back-and-forth swing of the amplification swing member 77. A contact roller 775 that can rotate around the fulcrum of the fourth support shaft 774 is attached to the amplification swing member 77 via a fourth support shaft 774 that extends laterally. Specifically, the contact roller 775 is attached to the lower part of the amplification swing member 77. The contact roller 775 comes into contact with the rocking member 715.
[0090]
　The load detection mechanism 71 has an amplification contact portion 711G that contacts the amplification swing member 77. The amplification contact portion 711G extends laterally outward from the side wall portion 711A (in this modification, from the right side wall portion 711A to the right direction L). In this modification, unlike the first embodiment, the load detection mechanism 71 does not have the extension portion 711E and the contact portion 711F.
[0091]
　The operating tool 74 has a receiving portion 745 that receives the amplification swing member 77. The receiving portion 745 has a receiving roller 745A for receiving the amplification rocking member 77 and a support portion 745B for supporting the receiving roller 745A. Further, the operating tool 74 switches between the first state, the second state, and the third state. As described above, the first state is the state in which the load detecting member 711 detects the traction load. In the first state, the elevating operation amount according to the amount of change in the traction load that is not amplified by the front-rear oscillation of the amplification oscillating member 77 is transmitted to the elevating drive unit 6. The second state is a state in which the load detecting member 711 does not detect the traction load. The third state is a state in which the elevating operation amount according to the amount of change in the traction load amplified by the front-rear oscillating member 77 is transmitted to the elevating drive unit. Therefore, in the third state, the amount of change in the traction load detected by the load detection member 711 is amplified.
[0092]
　As shown in FIG. 9, the operation tool 74 is selectively held at one of the first operation position P1 (right side), the second operation position P2 (left side), and the third operation position (center). .. When the operating tool 74 is held at the first operating position P1, the contact member 743 is positioned at the non-contact position. In addition, the receiving portion 745 does not come into contact with the amplification swing member 77. The load detection mechanism 71 is in the first state. When the operating tool 74 is held at the second operating position P2, the contact member 743 is located at the contact position, and the load detecting mechanism 71 is in the second state. When the operating tool 74 is held at the third operating position P3, the contact member 743 is positioned at the non-contact position. In addition, the receiving portion 745 comes into contact with the amplification swing member 77. The load detection mechanism 71 is in the third state.
[0093]
　As shown in FIG. 10, in the first state, when the load detection member 711 swings forward in response to an increase in the traction load, the amplification contact portion 711G moves forward. By moving the amplification contact portion 711G forward, the amplification swing member 77 is pushed forward. Here, since the receiving portion 745 (reception roller 745A) does not come into contact with the amplification swing member 77, the amplification swing member 77 is pushed forward as it is by the amount corresponding to the swing of the load detection member 711. The contact roller 775 that comes into contact with the swing member 715 moves forward by the amount that the amplification swing member 77 is pushed forward, and the swing member 715 swings forward according to the amount of movement of the contact roller 775. do. As a result, when the second connecting portion 782 of the cable 78 swings forward together with the swing member 715, the first connecting portion 781 is pulled backward.
[0094]
　As shown in FIG. 11, in the third state, as in the first state, when the load detecting member 711 swings forward in response to an increase in the traction load, the amplification contact portion 711G moves forward and the amplification swing The moving member 77 is pushed forward. Here, since the receiving portion 745 (reception roller 745A) comes into contact with the amplification swing member 77, the upper portion of the amplification rocking member 77 is not pushed forward, while the lower portion of the amplification rocking member 77 is forward. Is pushed out to. As a result, in FIG. 11, the amplification swing member 77 swings counterclockwise around the fulcrum f. Therefore, the amplification swing member 77 swings relative to the load detection member 711. As a result, the lower part of the amplification swing member 77, specifically, the contact roller 775, moves forward by the amount of swing of the amplification swing member 77 in addition to the swing amount of the load detection member 711. Since the contact roller 775 moves forward by the amount that the amplification swing member 77 is pushed forward, in the third state, even if the traction load is the same as in the first state, the swing member 715 is the first. It swings forward from the state. Therefore, the amount of change in the traction load is increased by the swing of the amplification swing member 77.
[0095]
　As described above, in the modified example, the amount of change in the traction load is amplified by the back-and-forth swing of the amplification swing member 77. As a result, the tilling device 4A can be quickly moved up and down according to the change in the traction load. As a result, even when the traction load suddenly increases, it is possible to avoid engine stall due to the increase in the traction load.
[0096]
　Further, the third state in which the elevating operation amount according to the change amount of the traction load amplified by the front-rear swing of the amplification swing member 77 is transmitted to the lift drive unit 6, and the front-back swing of the amplification swing member 77 amplifies the amount. The first state in which the elevating operation amount according to the change amount of the traction load that has not been performed is transmitted to the elevating drive unit 6 is switched. As a result, the operator can drive the three-point link mechanism 3 up and down according to the condition of the soil in which the towing operation is performed (for example, the hardness of the soil, the content ratio of stones, rocks, trees, etc.).
[0097]
　The vehicle body 2 may have a fourth cable fixing portion 244 to which the cover portion 78B is fixed. The front end portion of the fourth cable fixing portion 244 is supported, and the fourth cable fixing portion 244 may extend rearward to the rear end portion of the fourth cable fixing portion 244, which is a spiral portion extending in a spiral shape. May be provided. The cover portion 78B may be inserted into this spiral portion. The cover portion 78B may be fixed by inserting the cover portion 78B into the spiral portion. As a result, the cover portion 78B is fixed at three points of the first fixing portion 78B1, the second fixing portion 78B2, and the fourth cable fixing portion 244, so that the cover portion 78B swings due to vibration due to running or the like. Can be suppressed. As a result, the vibration of the first fixing portion 78B1 and the second fixing portion 78B2 is suppressed, the load applied to the first mounting portion 752A and the second mounting portion 715A is reduced, and the first mounting portion 752A and the second mounting portion 715A are reduced. Damage can be reduced.
[0098]
　[Second Embodiment]

　Hereinafter, the second embodiment will be described. The tractor 1 may be replaceable with a towed tiller 4A and a rotary tiller 4B. In the first embodiment, the tractor 1 provided with the traction type tilling device 4A has been described. Therefore, the tractor 1 provided with the rotary tilling device 4B will be described with reference to FIGS. 12 and 13. FIG. 12 is a right side view of the tractor according to the second embodiment. FIG. 13 is a right side view of the hydraulic lifting device according to the second embodiment. It should be noted that the same configuration as described above is omitted from the description.
[0099]
　As shown in FIGS. 12 and 13, a rotary tiller 4B can be attached to the three-point link mechanism 3. The rotary tillage device 4B can be attached to and detached from the tractor 1 (three-point link mechanism 3) by attaching and detaching the rotary tillage device 4B via the hitch device 8. The hitch device 8 is provided at the rear of the three-point link mechanism 3. The hitch device 8 is for connecting the tilling device 4 (rotary tilling device 4B).
[0100]
　The hitch device 8 has a linking member 81 and a third cable fixing portion 83. The linking member 81 swings back and forth together with the swing arm 45 described later. Therefore, the linking member 81 swings back and forth according to the amount of change in plowing depth. The linking member 81 has a third mounting portion 813 to which the second connecting portion 782 is mounted. The third mounting portion 813 is a mounting portion for automatic plowing depth control. When the second elevating operation amount according to the change amount of the tillage depth is selected as the elevating operation amount transmitted to the elevating drive unit 6, the second connecting portion 782 is attached to the third mounting portion 813. The third mounting portion 813 is located behind the rear end of the top link 3A. The cover portion 78B is fixed to the third cable fixing portion 83. A bracket 35 that supports the top link 3A is attached to the load detecting member 711. The top link 3A is shorter than the top link 3A in FIG.
[0101]
　The rotary tillage device 4B includes a rotor section 41, a tillage cover 42 that covers the rotor section 41 from above, a grounding body (rear cover) 43 that detects a change in the tillage depth of the rotary tillage device 4B, a transmission case section 44, and a transmission case section. The 44 has a swing arm 45 that can swing back and forth, and a linking link 46 that is erected over the lower free end of the swing arm 45 and the grounding body 43. The ground contact body 43 is a rear cover that prevents the scattering of soil during tillage and averages the tillage traces. The grounding body 43 is mounted on the rear end of the tillage cover 42. The grounding body 43 can swing up and down around the fulcrum e.
[0102]
　A linking member 81 is rotatably mounted on the rear portion of the three-point link mechanism 3 with the central portion of the linking member 81 as a fulcrum. When the rotary tilling device 4B is connected to the three-point link mechanism 3 via the hitch device 8, one end of the linking member 81 is engaged and connected to the engaging recess (not shown) formed in the swing arm 45. As a result, the linking member 81 rotates in accordance with the swing of the swing arm 45. A third mounting portion 813 is provided at the other end of the linking member 81. The second connecting portion 782 of the cable 78 is attached to the third mounting portion 813. As a result, the ground body 43 and the control valve 63 are linked via the cable 78.
[0103]
　Next, automatic plowing depth control will be described. When the rotary tilling device 4B is used for tilling work and the rotary tilling device 4B becomes deeper than the target tilling depth, the grounding body 43 is lifted and rocked accordingly. As a result, the linking link 46 moves forward, the swing arm 45 swings forward, and the linking member 81 rotates counterclockwise. The rotation of the linking member 81 pulls the second connecting portion 782 of the cable 78 rearward and also pulls the first connecting portion 781 rearward. As a result, the cable connecting arm 752 rotates backward around the fulcrum c, and the position arm 65 rotates backward around the position arm shaft 65A, as in the draft control. The lift arm 61 rises and the rotary tiller 4B rises to a position corresponding to the position after the rotation of the position arm 65. Then, when the ground contact body 43 is restored to its original posture, the ascending operation is stopped and the plowing depth is returned to the original depth.
[0104]
　On the other hand, when the rotary tilling device 4B is used for tilling work and the rotary tilling device 4B becomes shallower than the target tilling depth, the grounding body 43 hangs down and swings accordingly, so that the cable 78 The inner cable 78A is loosened. Here, since the cable connecting arm 752 is oscillated forward (clockwise in FIG. 13) by a tension spring, when the inner cable 78A is loosened, the cable connecting arm 752 loosens the inner wire 36a. Swing forward (clockwise) to absorb. As a result, the adjusting arm 754 follows the cable connecting arm 752 and swings forward. The linking rod 755 is pushed forward together with the adjustment arm 754, and the position arm 65 rotates forward around the position arm shaft 65A. As a result, the lift arm 61 is lowered and the rotary tiller 4B is lowered to a position corresponding to the position after the rotation of the position arm 65. Then, when the ground contact body 43 is restored to the original posture, the descending operation is stopped and the plowing depth is returned to the original depth.
[0105]
　When performing automatic plowing depth control, the operating tool 74 is moved to the second operating position P2. As a result, the load detection mechanism 71 is in the second state, and the load detection member 711 does not swing back and forth. Therefore, the amount of change in plowing depth can be detected with high accuracy.
[0106]
　With the above configuration, by switching the connection destination of the second connecting portion 782 of the cable 78, the first elevating operation amount according to the change amount of the traction load and the second elevating operation amount according to the change amount of the tillage depth. Either one of the above is selected as the elevating operation amount transmitted to the elevating drive unit 6. Thereby, the cable 78 can selectively transmit the change amount of the traction load and the change amount of the tillage depth.
[0107]
　Specifically, when the second mounting portion 715A of the swing member 715 is selected as the connection destination of the second connecting portion 782, the first elevating operation amount is transmitted to the elevating drive unit 6 as the elevating operation amount. The elevating drive unit 6 controls the lift cylinder 62 according to the first elevating operation amount (that is, the amount of change in the traction load). Therefore, the traction type tilling device 4A can be automatically raised and lowered according to the traction load during the tilling work.
[0108]
　On the other hand, when the third mounting portion 813 of the hitch device 8 is selected as the connecting destination of the second connecting portion 782, the second elevating operation amount is transmitted to the elevating drive unit 6 as the elevating operation amount. The elevating drive unit 6 controls the lift cylinder 62 according to the second elevating operation amount (that is, the amount of change in plowing depth). Therefore, during the tilling work, the rotary tilling device 4B can be automatically raised and lowered according to the tilling depth.
[0109]
　As described above, the intermediate link mechanism 75 connected to the first connecting portion 781 in order to switch the connecting destination of the second connecting portion 782 is a link mechanism common to both draft control and automatic tillage control. Therefore, since it is possible to combine similar functions in the draft control and the automatic plowing depth control into one link mechanism, the structure of the hydraulic lifting device 5 can be made less complicated.
[0110]
　Further, the second mounting portion 715A is located in front of the front end of the top link 3A. The third mounting portion 813 is located behind the rear end of the top link. The operator can work between the front end and the rear end of the top link 3A in the side view of the tractor 1 when switching between the draft control and the automatic plowing depth control, and the draft control and the automatic plowing depth control can be performed. Switching work with can be easily performed.
[0111]
　Further, the cable 78 has flexibility as compared with a plate-shaped or rod-shaped link member used in a general mechanical link mechanism. Therefore, the degree of freedom in arranging the connection destination of the cable 78 is increased, and the structure of the hydraulic elevating device 5 can be made less complicated.
[0112]
　In addition, by switching the connection destination of the cable 78 having a wide movable range due to the flexibility, the switching work between the draft control and the automatic plowing depth control can be easily performed.
[0113]
　Further, the cable 78 has an extending portion E extending from the second connecting portion 782 toward the rear of the tractor 1. The second connecting portion 782 is attached to the second mounting portion 715A toward the front. As a result, the worker located behind the tractor 1 grips the second connecting portion 782 so that the second connecting portion 782 is located in front of the worker with respect to the extending portion E, thereby holding the second connecting portion 782. It becomes easy to carry to the second mounting portion 715A. Therefore, the operator can easily attach the second connecting portion 782 and easily switch to the draft control.
[0114]
　Further, in the side view of the tractor 1, when the second connecting portion 782 swings forward together with the swinging member 715, the first connecting portion 781 is pulled backward, and the second connecting portion 782 moves backward together with the swinging member 715. The cable 78 extends while bending so that the first connecting portion 781 is pulled forward when it swings. In addition, the second connecting portion 782 is attached to the first mounting portion 752A at a position higher than that of the first connecting portion 781. By bending the cable 78 during maintenance work, the operator can carry the second connecting portion 782 to the mounting portion without the operator moving significantly. In addition, since the second connecting portion 782 is at a higher position than the first connecting portion 781, it can be attached at a position close to the height of the operator's line of sight. The operator can easily perform the work of switching to the draft control.
[0115]
　Further, the tractor 1 has a cable fixing portion (first cable fixing portion 241, second cable fixing portion 915, third cable fixing portion 83). By fixing the cover portion 78B with the cable fixing portion, the inner cable 78A can be stably swung. As a result, the mechanical linkage unit 7 can accurately transmit the elevating operation amount according to the change amount of the traction load to the elevating drive unit 6, so that high-quality draft control can be executed.
[0116]
　Further, the cable 78 is connected to the swing member 715 and the sensitivity adjusting mechanism. As a result, the number of link members connecting the swing member 715 and the sensitivity adjusting mechanism can be reduced, and the structure of the hydraulic lifting device 5 is less likely to be complicated.
[0117]
　Further, at least a part of the intermediate link mechanism 75 is located behind the front end of the lower link 3B. This makes it easier to check the intermediate link mechanism 75 from the rear of the tractor 1, so that maintainability can be improved.
[0118]
　Further, the second mounting portion 715A is located above the load detecting member 711. As a result, when the second mounting portion 715A is visually recognized from the rear of the tractor 1, the second mounting portion 715A can be visually recognized above the load detecting member 711, and the load detecting member 711 is unlikely to overlap with the second mounting portion 715A. Become. It is easy to check the second connecting portion and the mounting portion from the rear of the tractor 1, and it is easy to attach and detach the second connecting portion 782. Therefore, the switching work can be easily performed. Further, it is not necessary to provide a space for providing the second mounting portion 715A in front of the load detecting member 711.
[0119]
　The second mounting portion 715A is located behind the front end of the lower link 3B. Since the distance from the rear of the tractor 1 to the second mounting portion 715A is closer than the front end of the lower link 3B, it is easy to mount and remove the second connecting portion 782 from the rear of the tractor 1. Therefore, the switching work can be easily performed.
[0120]
　Further, the hitch device 8 has a linking member 81 that swings back and forth according to the amount of change in plowing depth. The linking member 81 has a third mounting portion 813 to which the second connecting portion 782 is mounted. As a result, the second connecting portion 782 of the cable 78 is directly attached to the linking member 81 of the hitch device 8, so that the case where the second connecting portion 782 of the cable 78 is attached to the front side of the three-point link mechanism 3 is compared with the case where the second connecting portion 782 of the cable 78 is attached. Therefore, the number of members for transmitting the amount of change in tillage depth to the cable 78 can be reduced.
[0121]
　Further, the second mounting portion 715A is located behind the first mounting portion 752A in a state where no traction load is applied. Since the distance from the rear of the tractor 1 to the second mounting portion 715A is shorter than that of the first mounting portion 752A, it is easy to mount and remove the second connecting portion 782 from the rear of the tractor 1. Therefore, the switching work can be easily performed.
[0122]
　[Other Embodiments]
　Although the present disclosure has been described in detail using the above-described embodiments, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. be. The present disclosure may be implemented as amendments and modifications without departing from the spirit and scope of the present disclosure as determined by the description of the scope of claims. Therefore, the description herein is for purposes of illustration only and has no limiting implications for the present disclosure.
[0123]
　The configuration of the tractor 1 can be changed in various ways. For example, the tractor 1 may be configured as a semi-crawler specification including left and right crawlers instead of the left and right rear wheels 25B. For example, the tractor 1 may be configured to have a full crawler specification including left and right crawlers instead of the left and right wheels 25. For example, the tractor 1 may be configured to have an electric specification provided with an electric motor instead of the engine 22. For example, the tractor 1 may be configured in a hybrid specification including an engine 22 and an electric motor.
[0124]
　The configuration of the elevating drive unit 6 and the configuration of the mechanical linkage unit 7 can be changed in various ways. For example, the cable 78 may have a portion extending laterally of the tractor 1. That is, in the rear view of the tractor 1 (viewed from the rear of the tractor 1), the extending portion E may extend laterally. The worker located on the side of the tractor 1 grips the second connecting portion 782 so that the second connecting portion 782 is located on the front side of the worker with respect to the extending portion E, thereby holding the second connecting portion 782. It becomes easy to carry to the second mounting portion 715A. Therefore, the operator can easily attach the second connecting portion 782, and can easily perform maintenance work and / or switching work to draft control.
[0125]
　In the above embodiment, a swing member that swings back and forth in response to the swing back and forth of the load detection member 711 is provided, and the swing member 715 is provided with a second mounting portion 715A to which the cable 78 is mounted. Not limited. For example, the load detecting member 711 may be provided with the second mounting portion 715A.
[0126]
　In the above embodiment, when the second connecting portion 782 swings forward together with the swing member 715 in the side view of the tractor 1, the first connecting portion 781 is pulled backward and the second connecting portion 782 together with the swing member 715. When swinging backward, the first connecting portion 781 was pulled forward, but the present invention is not limited to this. For example, due to a configuration in which the movement of the swing member 715 is reversed, the first connecting portion 781 is pulled forward when the second connecting portion 782 swings forward, and the second connecting portion 782 swings backward. 1 The connecting portion 781 may be pulled backward.
[0127]
　Further, the linking member 81 was engagedly connected to the swing arm 45 in the engaging recess and was rotatable, but the present invention is not limited to this. For example, the linking link 46 may be connected to the lower free end of the linking member 81. As a result, the linking member 81 may swing back and forth by the linking link 46 without going through the swinging arm 45.
[0128]
　Further, the tractor 1 in the second embodiment may have the load detection mechanism 71 in the modified example of the first embodiment.
[0129]
　The tractor 1 may have a member other than the member described above, or may have only a part of the member described above. Therefore, for example, the elevating drive unit 6 and the mechanical linking unit 7 may have members other than the members described above, or may have only a part of the members described above.
[0130]
　The entire contents of Japanese Patent Application No. 2019-100766 (filed May 29, 2019) and Japanese Patent Application No. 2019-100767 (filed May 29, 2019) are incorporated herein by reference in their entirety. ing.
Code description
[0131]
1: Tractor
3: Three-point link mechanism
4: Tillage device
5: Hydraulic elevating device
6: Elevating drive unit
7: Mechanical linkage unit
71: Load detection mechanism
74: Operating tool
75: Intermediate link mechanism
77: Amplification swing member
78: Cable
78B1: First fixing part
78B2: Second fixing part
78B3: Outer cable
711: Load detection member
715: Swing member
715A: Second mounting part
752A: First mounting part
781: First connecting part
782: First 2 Connection part

WE CLAIMS

[Claim 1]A tractor,
　a three-point link mechanism to which a tilling device can be attached,
　a hydraulic elevating drive unit that elevates and drives the
　three-point link mechanism, and an elevating operation amount of the three-point link mechanism are transmitted to the elevating drive unit. The mechanical linkage unit includes
　a
　　load detection member that detects a change in the traction load via the three-point link mechanism, and the traction load detected by the load detection member
　　. A cable that is interlocked according to
　the amount of change, a mechanical link mechanism that is interlocked with the cable and the elevating drive unit, and transmits the elevating operation amount according to the amount of change in the traction load to the elevating drive unit. Has a tractor.
[Claim 2]
　The cable has a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side, and the cable is connected from the second connecting portion. It has a portion extending rearward of the tractor,
　one end of the cable being connected to the mechanical linkage towards the front of the tractor and
　the other end of the cable. The tractor according to claim 1, wherein the unit is connected to the load detecting member toward the front of the tractor.
[Claim 3]
　The cable has a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side, and the
　mounting portion to which the second connecting portion is attached.
　The second connecting portion swings forward together with the swing member in a side view of the tractor . The cable is curved so that when it moves, the first connecting portion is pulled backward, and when the second connecting portion swings backward together with the swing member, the first connecting portion is pulled forward.
　The tractor according to claim 1 or 2, wherein the second connecting portion is extended and attached to the mounting portion at a position higher than that of the first connecting portion.
[Claim 4]
　A claim that the cable has
　　an inner cable that swings in response to the front-back swing of the swing member, a
　　cover portion that covers the outside of the inner cable, and
　a cable fixing portion that fixes the cover portion. The tractor according to 3.
[Claim 5]
　The mechanical linkage unit has a swing member that swings back and forth in response to the swing back and forth of the load detection member, and the
　mechanically linked unit adjusts the operating sensitivity when the lift drive unit is interlocked with the swing member.
　The tractor according to any one of claims 1 to 4 , wherein the cable has a mechanism and is connected to the swing member and the sensitivity adjusting mechanism.
[Claim 6]
　The tractor according to any one of claims 1 to 5, wherein at least a part of the mechanical link mechanism is located behind the front end of the lower link of the three-point link mechanism.
[Claim 7]
　The cable has a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side, and the
　mounting portion to which the second connecting portion is attached. Is the tractor according to any one of claims 1 to 6, which is located above the load detection member.
[Claim 8]
　The cable has a first connecting portion connected on the mechanical link mechanism side and a second connecting portion connected on the load detecting member side, and the
　mechanical linking unit is the first. The second mounting portion has the first mounting portion to which the connecting portion is mounted and the second mounting portion to which the second connecting portion is mounted, and
　the second mounting portion has the first mounting portion in a state where the traction load is not applied. The tractor according to any one of claims 1 to 7, which is located behind the mounting portion.
[Claim 9]
　The mechanical linkage unit has an amplification swing member that is swingably supported by the load detection member and swings back and forth in response to the front-back swing of the load detection member, and the
　amount of change in the traction load is The tractor according to any one of claims 1 to 8, which is amplified by the front-back swing of the amplification swing member.
[Claim 10]
　The state in which the elevating operation amount corresponding to the change amount of the traction load amplified by the front-rear swing of the amplification swing member is transmitted to the lift drive unit, and the amplification by the front-back swing of the amplification swing member. The tractor according to claim 9, wherein the tractor can be switched between a state in which the elevating operation amount is transmitted to the elevating drive unit according to the amount of change in the traction load that has not been performed.
[Claim 11]
　The first connecting portion, which is the connecting portion on one side of the cable, is connected to the mechanical link mechanism, and the
　cable selectively transmits the change amount of the traction load and the change amount of the tillage depth. By switching the connection destination of the second connecting portion, which is the connecting portion on the other side of
　the cable, the first elevating operation amount according to the change amount of the traction load and the second connection portion according to the change amount of the tillage depth. The tractor according to any one of claims 1 to 10, wherein any one of the elevating operation amount is selected as the elevating operation amount transmitted to the elevating drive unit.
[Claim 12]
　When the first elevating operation amount is selected as the elevating operation amount, the draft control mounting portion to which the second connecting portion is attached and
　the second elevating operation amount are selected as the elevating operation amount. The second connecting portion is provided with a mounting portion for automatic tillage control, and the mounting portion
　for draft control is located in front of the front end of the top link of the three-point link mechanism. The tractor according to claim 11 ,
　wherein the mounting portion for automatic tillage control is located behind the rear end of the top link.
[Claim 13]
　When the first elevating operation amount is selected as the elevating operation amount, the cable has a mounting portion to which the second connecting portion is attached, and the
　cable extends from the second connecting portion toward the rear of the tractor. The tractor according to claim 11 or 12 ,
　wherein the second connecting portion is attached to the mounting portion toward the front of the tractor.
[Claim 14]
　It has a load detection member that swings back and forth according to the traction load transmitted via the top link of the three-point link mechanism, and
　a mounting portion to which the second connecting portion is attached, and swings back and forth of the load detection member. It has a swing member that swings back and forth in response to the
　above, and when the second connecting portion swings forward together with the swing member in the side view of the tractor, the first connecting portion is pulled backward. The cable extends while bending so that the first connecting portion is pulled forward when the second connecting portion swings backward together with the swing member, and
　the second connecting portion extends in a curved manner. 1 The tractor according to any one of claims 11 to 13, which is attached to the mounting portion at a position higher than the connecting portion.
[Claim 15]
　A claim that the cable has
　　an inner cable that swings in response to the front-back swing of the swing member, a
　　cover portion that covers the outside of the inner cable, and
　a cable fixing portion that fixes the cover portion. 14. The tractor according to 14.
[Claim 16]
　It has a load detection member that swings back and forth according to the traction load transmitted via the top link of the three-point link mechanism, and
　a swing member that swings back and forth according to the front-back swing of the load detection member. The
　mechanical linkage unit has a sensitivity adjusting mechanism for adjusting the operating sensitivity when the elevating drive unit is interlocked with the swing member, and the
　cable is connected to the swing member and the sensitivity adjusting mechanism. The tractor according to any one of claims 11 to 15.
[Claim 17]
　The tractor according to any one of claims 11 to 16, wherein at least a part of the mechanical link mechanism is located behind the front end of the lower link of the three-point link mechanism.
[Claim 18]
　A load detection member that swings back and forth according to the traction load transmitted via the top link of the three-point link mechanism, and a
　second connecting portion when the first elevating operation amount is selected as the elevating operation amount.
　The tractor according to any one of claims 11 to 17 , wherein the mounting portion comprises, and the mounting portion is located above the load detecting member.
[Claim 19]
　A hitch device for connecting the tilling device is provided at the rear of the three-point link mechanism, and the hitch device has
　a linking member that swings back and forth according to the amount of change in the tilling depth, and the
　linking member . The tractor according to any one of claims 11 to 18, wherein the tractor has an attachment portion to which the second connecting portion is attached when the second elevating operation amount is selected as the elevating operation amount.