JP7289726B2 - tractor - Google Patents

Description

The present invention relates to tractors.

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 disclosed in Patent Document 1 adjusts the amount of lifting operation according to the amount of change in traction load detected via the top link of the three-point link mechanism. valve, etc.). The lift drive unit lifts and lowers the three-point link mechanism according to the amount of lifting operation, so that the traction-type tillage device (for example, plow) attached to the three-point link mechanism automatically moves according to the traction load. ascend and descend. As described above, the tractor of Patent Document 1 can perform draft control when performing tillage work using a traction type tillage device, so that the traction load can be maintained constant, and even if the traction load increases, the draft control can be performed. It is possible to avoid the occurrence of an engine stall caused by this.

As an example of a tractor equipped with a hydraulic lifting device, Patent Document 2 discloses a tractor equipped with a mechanical linkage unit for automatic plowing depth control.

The mechanical linkage unit (intermediate link mechanism) for automatic plowing depth control of Patent Document 2 is detected via a link mechanism (swing arm, linkage link, linkage link, sensor wire, etc.) provided in the rotary tillage device. The amount of lifting operation corresponding to the amount of change in plowing depth is transmitted to the lifting drive unit (position control valve, etc.). The elevation drive unit drives the 3-point link mechanism up and down according to the amount of elevation operation, thereby automatically raising and lowering the rotary tillage device attached to the 3-point link mechanism according to the plowing depth. In this way, the tractor of Patent Document 2 can perform automatic tillage depth control when performing tillage work using a rotary tillage device. can be done.

Japanese Patent Application Laid-Open No. 2006-109802 Japanese Patent Application Laid-Open No. 2003-102208

The tractor of Patent Document 1 does not have a mechanical linkage unit for automatic plowing depth control. Therefore, when performing tillage work with a rotary tillage device, automatic tillage depth control cannot be performed, and it has been difficult to perform highly accurate tillage work in which the tillage depth is kept constant.

The tractor of Patent Document 2 does not have a mechanical linkage unit for draft control. Therefore, when performing tillage work with a towing type tillage device, draft control cannot be performed, and there is a risk of causing an engine stall due to an increase in towing load.

In order to accommodate both plowing operations, it is envisaged that the hydraulic lifting device comprises both a mechanical linkage unit for automatic plowing depth control and a mechanical linkage unit for draft control.

However, there is a problem that the structure of the hydraulic lifting device tends to be complicated by providing both mechanical linkage units. As the structure becomes more complicated, maintenance tends to take longer, and chattering is more likely to occur due to the large number of link members that constitute the mechanical linkage unit.

Therefore, it is an object of the present invention to provide a tractor that can perform draft control and automatic plowing depth control and that does not easily complicate the structure of the hydraulic lift device.

A tractor according to one aspect includes a three-point link mechanism to which a cultivator can be attached, a hydraulic lifting drive unit that drives the three-point link mechanism up and down, and a lifting operation amount of the three-point link mechanism that is controlled by the lifting drive unit. and a mechanical linkage unit that communicates to. The mechanical linkage unit has a cable for selectively transmitting the amount of change in traction load and the amount of change in plowing depth, and a mechanical link mechanism interlockingly connected to the cable and the elevation drive unit. A first connecting portion, which is a connecting portion on one side of the cable, is connected to the mechanical link mechanism. By switching the connecting destination of the second connecting portion, which is the connecting portion on the other side of the cable, a first lifting operation amount corresponding to the amount of change in the traction load and a second lifting operation amount corresponding to the amount of change in the tillage depth. and the operation amount is selected as the elevation operation amount to be transmitted to the elevation drive unit.

In order to switch the connection destination of the second connection part of the cable, the mechanical link mechanism connected to the first connection part of the cable is a link mechanism common to both the draft control and the automatic plowing depth control. Therefore, similar functions of the draft control and the automatic plowing depth control can be combined into one link mechanism, so that the structure of the hydraulic lift device can be made difficult to complicate.

In addition, cables are more flexible than plate-like or rod-like link members used in general mechanical link mechanisms. 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 prevented from becoming complicated.

In addition, by switching the connection destination of the cable with a wide movable range by flexibility, it is possible to easily perform the work of switching between the draft control and the automatic plowing depth control.

According to a preferred aspect, when the first elevation operation amount is selected as the elevation operation amount, the tractor includes an attachment portion for draft control to which the second connection portion is attached; and a mounting portion for automatic plowing depth control to which the second connecting portion is mounted when an amount is selected as the lifting operation amount. The attachment portion for draft control may be positioned forward of the front end of the top link of the three-point linkage. The mounting portion for automatic plowing depth control may be positioned rearward of the rear end of the top link.

When switching between the draft control and the automatic plowing depth control, the operator can work between the front end and the rear end of the top link in a side view of the tractor. Switching work can be easily performed.

According to a preferred aspect, the tractor may have a mounting portion to which the second connecting portion is mounted when the first elevation operation amount is selected as the elevation operation amount. The cable may have a portion extending from the second connection toward the rear of the tractor. The second connecting part may be attached to the attachment part toward the front of the tractor.

When the operator positioned behind the tractor selects the first elevation operation amount as the elevation operation amount, that is, when switching to the draft control, the operator is more inclined than the portion extending toward the rear of the tractor (extending portion). By gripping the extension portion so that the second connecting portion is located on the front side of the operator, it becomes easier to carry the second connecting portion to the mounting portion. Therefore, the operator can easily switch to the draft control.

According to a preferred aspect, the tractor has a load detection member that swings back and forth according to the traction load transmitted through the top link of the three-point linkage mechanism, and a mounting portion to which the second connecting portion is mounted. and a swing member that swings back and forth according to the back and forth swing of the load detection member. In a side view of the tractor, when the second connecting portion swings forward together with the swinging member, the first connecting portion is pulled rearward, and the second connecting portion swings backward together with the swinging member. The cable may then bend and extend such that the first connecting portion is pulled forward. The second connection part may be attached to the attachment part at a position higher than the first connection part.

When switching to the draft control, the operator bends the cable so that the operator can carry the second connecting part to the attachment part without moving much. In addition, since the second connecting portion is positioned higher than the first connecting portion, it can be attached at a position close to the line of sight of the operator. The operator can easily switch to draft control.

According to a preferred aspect, the cable may include an inner cable that swings according to the back-and-forth swing of the swing member, and a cover portion that covers the outer side of the inner cable. A cable fixing portion may be provided 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 back and forth swing of the swing member. As a result, the mechanical linkage unit can accurately transmit the elevation operation amount corresponding to the amount of change in the traction load to the elevation drive unit, so that high-quality draft control can be performed.

According to a preferred aspect, the tractor includes a load detection member that swings back and forth according to the traction load transmitted through the top link of the three-point link mechanism, and a load detection member that swings back and forth according to the back and forth swing of the load detection member. and a rocking member that rocks. The mechanical linkage unit may have a sensitivity adjustment mechanism that adjusts the operating sensitivity when the elevation drive unit is linked with the rocking member. The cable may be connected to the swing member and the sensitivity adjustment mechanism.

Since the cable directly connects the swinging member and the sensitivity adjusting mechanism, the number of link members connecting the swinging member and the sensitivity adjusting mechanism can be reduced, and the structure of the hydraulic lifting device becomes complicated. hard.

According to a preferred aspect, at least part of the mechanical link mechanism may be positioned rearward of the front end of the lower link of the three-point link mechanism.

Since it becomes easy to check the said mechanical link mechanism from the back of a tractor, maintainability can be improved.

According to a preferred aspect, the tractor includes a load detection member that swings back and forth according to the traction load transmitted through the top link of the three-point link mechanism, and the first elevation operation amount as the elevation operation amount. If selected, it may have a mounting portion to which the second coupling portion is mounted. The attachment portion may be positioned above the load detection member.

As a result, when switching from automatic plowing depth control to draft control, it is easy to confirm the second connecting portion and the attachment portion from the rear of the tractor, and to easily switch the connection destination of the second connecting portion. Therefore, the switching work can be easily performed.

According to a preferred aspect, a hitch device for connecting the tillage device may be provided at the rear of the three-point linkage. 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 an attachment portion to which the second connecting portion is attached when the second elevation operation amount is selected as the elevation operation amount.

As a result, since the second connecting portion of the cable is directly attached to the linking member of the hitch device, compared to the case where the second connecting portion of the cable is attached on the front side of the three-point linkage mechanism, the change in plowing depth is It is possible to reduce the number of members for transmitting the amount to the cable.

FIG. 1 is a right side view (No. 1) of the tractor according to the embodiment. FIG. 2 is a right side view (No. 1) of the hydraulic lifting device according to the embodiment. FIG. 3 is a hydraulic circuit diagram for lifting according to the embodiment. FIG. 4 is a perspective view of the load detection mechanism according to the embodiment as seen from the upper left front. FIG. 5 is a cross-sectional view taken along line 5A--5A of FIG. FIG. 6 is a right side view for explaining the intermediate link mechanism according to the embodiment; FIG. 7 is a right side view (No. 2) of the tractor according to the embodiment. FIG. 8 is a right side view (No. 2) of the hydraulic lifting device according to the embodiment.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In addition, in the following description of the drawings, the same or similar reference numerals are given to the same or similar parts. However, it should be noted that the drawings are schematic, and the ratio of each dimension is different from the actual one. Therefore, specific dimensions and the like should be determined with reference to the following description. In addition, portions having different dimensional relationships and ratios may also be included between the drawings. In the present specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals to omit redundant description, and elements that are not directly related to the present invention are omitted from the drawings.

(1) Schematic Configuration of Tractor Equipped with Traction-Type Tillage Device A schematic configuration of a tractor equipped with a traction-type cultivator will be described with reference to FIG. FIG. 1 is a right side view (No. 1) of the tractor according to the embodiment. Arrow F shown in the drawings indicates the forward direction (forward) of the tractor, arrow B indicates the rearward direction (backward) of the tractor, arrow U indicates the upward direction (upward) of the tractor, and arrow D indicates the downward direction (upward) of the tractor. arrow R indicates the rightward direction (rightward) of the tractor, and arrow L indicates the leftward direction (leftward) 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. As shown in FIG.

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 ride-on driving section 27, a cylinder case 28, and the like.

The frame 21 has a front frame 21</b>F positioned at the front of the vehicle body 2 and an intermediate frame 21</b>M connected to the rear end of the clutch housing 23 . The engine 22 is connected to the rear portion of the front frame 21F. The clutch housing 23 is connected to the lower rear end of the engine 22 . The T/M case 24 is connected to the rear end 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 sides of the front frame 21F and left and right rear wheels 25B arranged on the left and right sides 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 positioned between the left and right rear fenders 26 . A control valve 63 and the like, which will be described later, are housed in the cylinder case 28 . A driver's seat is arranged above the cylinder case 28 .

Although not shown, the power from the engine 22 passes through the main clutch built in the clutch housing 23, the transmission shaft covered with the intermediate frame 21M, and the like, to the main body built in the T/M case 24. transmitted to the transmission. Power after shifting by the main transmission is transmitted to the wheels 25 via the sub-transmission or the like built in the T/M case 24 .

A cultivator 4 can be attached to the three-point linkage 3 . The three-point link mechanism 3 is connected to the rear part of the T/M case 24 so as to be able to swing vertically. The three-point link mechanism 3 has a single top link 3A and left and right lower links 3B. When the tractor 1 is used for tillage work, the three-point link mechanism 3 can be attached with a traction-type tillage device 4A.

In addition, in this embodiment, a state in which a plow is attached to the three-point link mechanism 3 is shown as an example of the traction type tillage device 4A. A disk harrow, a cultivator, a subsoiler, and the like can also be attached to the three-point link mechanism 3 as a traction type tillage device 4A.

As shown in FIG. 1, the front end of the top link 3A is connected via a connecting pin to a load detection mechanism 71 (load detection member 711), which will be described later. Further, the front ends of the left and right lower links 3B are connected to left and right brackets provided at the rear end of the T/M case 24 via left and right connecting pins. Due to this connection structure, the traction load during tillage work acts on the load detection member 711 via the top link 3A.

The hydraulic lifting device 5 is a mechanically 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.

(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. FIG. 2 is a right side view (No. 1) of the hydraulic lifting device according to the embodiment. FIG. 3 is a hydraulic circuit diagram for lifting according to the embodiment. FIG. 4 is a perspective view of the load detection mechanism according to the embodiment as seen from the upper left front. FIG. 5 is a cross-sectional view taken along line 5A--5A of FIG. FIG. 6 is a right side view for explaining the intermediate link mechanism according to the embodiment;

As shown in FIG. 2 , the hydraulic lift device 5 (tractor 1 ) includes a hydraulic lift drive unit 6 and a mechanical linkage unit 7 . The lift drive unit 6 can drive the three-point link mechanism 3 to lift. The cultivator 4 attached to the three-point link mechanism 3 moves up and down according to the elevation drive of the three-point link mechanism 3 . The mechanical linkage unit 7 transmits the lifting operation amount of the three-point link mechanism 3 to the lifting drive unit 6 . Details of the mechanical linkage unit 7 will be described later.

The elevation drive unit 6 has left and right lift arms 61 , lift cylinders 62 , control valves 63 , balance arms 64 , position arms 65 , position arm shafts 65A, feedback arm shafts 66A, position levers 67 and position plates 68 .

As shown in FIG. 1, the left and right lift arms 61 suspend and support the left and right lower links 3B via left and right support members. The lift arm 61 is hydraulically driven by a lift cylinder 62 so as to be vertically swingable. The lift cylinder 62 vertically drives the three-point link mechanism 3 via the lift arm 61 . The lift cylinder 62 is housed in the cylinder case 28 .

A control valve 63 controls the lift cylinder 62 . As shown in FIG. 3, control valve 63 may include spool 631, lowering valve 632, relief valve 633, unload valve 634, and the like. The control valve 63 may be connected with the lift cylinder 62 via a falling speed adjusting valve. The control valve 63 is housed in the cylinder case 28 . The spool 631 is constantly biased in the downward direction D by biasing means (for example, a spring).

The balance arm 64 is pivotably connected to the end of the spool 631 . A position arm shaft 65A is engaged with one end of the balance arm 64 via an operation pin, and a feedback arm shaft 66A is engaged with the other end of the balance arm 64 via an operation pin. connected. The feedback arm shaft 66A is interlocked with the lift arm 61 via a feedback link mechanism (not shown).

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 with the operation pin of the feedback arm shaft 66A. As a result, the spool 631 shifts to the ascending side or descending side, and the lift arm 61 performs the driven ascending operation or the self-weight descending 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. As the feedback arm shaft 66A is rotated, the spool 631 is shifted via the balance arm 64 in the opposite direction. The spool 631 returns to neutral when the feedback arm shaft 66A is rotated to a predetermined rotation position corresponding to the rotation operation position of the position arm 65. As shown in FIG. By arbitrarily rotating the position arm 65 in this manner, the lift arm 61 can be moved up and down to a position corresponding to the position arm 65 .

The position lever 67 sets the control target height of the tillage device 4 . The position lever 67 is arranged on the right lateral side of the driver's seat. The position lever 67 is arranged so as to be able to swing back and forth around a fulcrum a located in the vicinity of the rear side of the position arm 65 . A fulcrum a is a common fulcrum with a control adjustment lever 751, which will be described later. The position lever 67 is arranged closer to the driver's seat 272 (left side) than the control adjustment lever 751 is. The position lever 67 is interlocked with the position arm 65 via a long hole 65 h and a 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, etc.). As a result, the rear end of the elongated hole 65h is engaged with and abuts on the position plate 68. As shown in FIG.

As the position lever 67 swings rearward (counterclockwise in FIG. 2) about the fulcrum a, the position arm 65 engaged with and supported by the position plate 68 resists the urging force. is rotated backward (counterclockwise in FIG. 2). Thereby, the lift arm 61 rises to a position corresponding to the position arm 65 . On the other hand, as the position lever 67 swings forward F (clockwise direction in FIG. 2) about the fulcrum a, the position arm 65 which is biased to rotate moves toward the position lever 67. Follow and rotate. Thereby, the lift arm 61 is lowered to a position corresponding to the position arm 65 .

Next, the details of the mechanical linkage unit 7 will be described. The mechanical linkage unit 7 has a load detection mechanism 71 , an urging mechanism 72 , a restriction 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 (to be 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 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 includes a vertical wall portion 911 connected to the rear portion of the vehicle body 2 (cylinder case 28), a connecting portion 912 which is U-shaped when viewed from above, and extends vertically outside the vertical wall portion 911 in the lateral direction. a rocking support portion 914 that supports a rocking member 715, which will be described later, and a second cable fixing portion 915 to which the cover portion 78B is fixed. The connecting portion 912 has left and right side portions 912A extending rearward from the vertical wall portion 911 and rear portions 912B extending in the lateral direction so as to connect the left and right side portions 912A.

The load detection mechanism 71 detects the amount of change in 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 .

The load detection member 711 detects the amount of change in traction load via the three-point link mechanism 3 . The load detection member 711 is supported by the support member 91 so as to be swingably displaceable 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 through the top link 3A.

The load detection member 711 includes left and right side wall portions 711A, a vertical wall portion 711B to which the side wall portions 711A are fixed, a connecting hole 711C formed in the side wall portion 711A, an extension portion 711E extending forward from the vertical wall portion 711B, and a swinging member. It has a contact portion 711</b>F that contacts the member 715 .

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. The top link 3A or a top link bracket that supports the top link 3A can be connected to the connection 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 rightward 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 traction load, the contact portion 711</b>F moves forward and comes into contact with the swing member 715 .

The rocking member 715 rocks back and forth in accordance with the back and forth rocking of the load detecting member 711 . The rocking member 715 is supported by the rocking support portion 914 via a laterally extending second support shaft 914A. The swing member 715 can swing around a fulcrum b passing through the axis of the second support shaft 914A. The swinging member 715 swings forward by being pushed forward from the contact portion 711F that moves forward. When there is no contact with the contact portion 711F (that is, when no forward force is exerted 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 backward to a predetermined position by the spring force of a torsion spring attached to the second support shaft 914A.

The swinging member 715 has a second attachment portion 715A to which the cable 78 (second connecting portion 782 described later) is attached. The second attachment portion 715A is arranged on the free end side. Also, the second attachment portion 715A is positioned above the load detection member 711 . In addition, the second attachment portion 715A is positioned rearward of the front end of the lower link 3B. In addition, the second mounting portion 715A is located behind the first mounting portion 752A, which will be described later, in a state in which no traction load is applied. Also, the second attachment portion 715A is positioned forward of the front end of the top link 3A. The second mounting portion 715A is a mounting portion for draft control. When the first elevation operation amount corresponding to the amount of change in traction load is selected as the elevation operation amount to be transmitted to the elevation drive unit 6, the second connecting portion 782 is attached to the second attachment portion 715A toward the front. .

The biasing mechanism 72 swings and biases the load detection member 711 in a direction (backward) against the traction load applied to the load detection member 711 . As shown in FIG. 5, the biasing mechanism 72 may be configured by a spring having elasticity in the front-rear direction.

The limit mechanism 73 limits the front-rear swing range of the load detection member 711 . The restriction mechanism 73 may be composed of a through hole 711h, an elongated hole 912h, a rubber block 73b, and a linking pin 73p. A through hole 711 h is formed in the load detection member 711 . Specifically, the through holes 711h are formed so as to face the left and right side wall portions 711A, respectively. The long hole 912h is a hole formed in the support member 91 and elongated in the front-rear direction. Specifically, the long hole 912h is formed in each of the left and right side portions 912A of the linking portion 912 at a location facing the through hole 711h. The rubber block 73b is fitted in 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 an elongated hole 73h having a shorter longitudinal length than the elongated hole 912h of the support member 91 at a location facing the elongated hole 912h of the support member 91 . The linking pin 73p is inserted into each through hole 711h, each long hole 912h, and each long hole 73h.

The front-rear swing range of the load detection member 711 is limited by the front-rear length of each elongated hole 912 h of the support member 91 . When the restriction mechanism 73 restricts the front-rear swing of the load detecting member 711, the linking pin 73p of the restriction mechanism 73 collides with the rubber block 73b.

The load detecting member 711 is held in a reference posture vertically extending upward from the first support shaft 92 by the action of the biasing 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 biasing mechanism 72 in conjunction with the increase of the traction load. Further, the load detection member 711 is pivotally displaced rearward by the action of the biasing mechanism 72 in conjunction with the reduction of the traction load and returns to the reference posture.

The operation tool 74 switches the load detection mechanism 71 between a first state in which the load detection member 711 detects the traction load and a second state in which the load detection member 711 does not detect the traction load.

The operation tool 74 includes a rocking plate 741 laterally rockably supported by the support member 91 , an operation handle 742 extending upward U from the rocking plate 741 , and extending rearward from the rocking plate 741 . a contact member 743; Contact member 743 moves between a non-contact position and a contact position. At the non-contact position (first operating position P1), the contact member 743 does not contact 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 operating position P2), the contact member 743 is sandwiched between the vertical wall portion 711B and the rocking plate 741 .

The operation tool 74 swings sideways around an axis extending in the front-rear direction. The operating tool 74 is selectively held at either the first operating position P1 (left side) or 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 positioned at the non-contact position and the load detection mechanism 71 is in the first state. On the other hand, when the operating tool 74 is held at the second operating position P2, the contact member 743 is positioned 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.

Next, the intermediate link mechanism 75 will be explained. The intermediate link mechanism 75 is a mechanical link mechanism. As shown in FIG. 2 , the intermediate link mechanism 75 is interlocked with the cable 78 and the elevation drive unit 6 . The intermediate link mechanism 75 transmits to the elevation drive unit 6 the elevation operation amount corresponding to the amount of change in the traction load.

The intermediate link mechanism 75 has a control adjustment lever 751 , a cable connection arm 752 , a link plate 753 , an adjustment arm 754 and a link rod 755 .

The control adjustment lever 751 is a lever for adjusting draft control. The control adjusting lever 751 can swing back and forth around the fulcrum a.

The cable connecting arm 752 can swing back and forth around the fulcrum c. The cable connecting arm 752 serves as a connection destination of one side of the cable 78 . The cable connecting arm 752 has a first attachment portion 752A to which the cable 78 is attached. Specifically, a first connecting portion 781, which will be described later, is attached to the first attaching portion 752A.

A tension spring (not shown) is attached to the cable connecting arm 752 for swinging and biasing it forward. The cable connecting arm 752 has a cam surface S that is convexly curved on the rear end side of the cable connecting arm 752 (the side on the roller 754r side, which will be described later).

The linking plate 753 extends rearward from the base end of the control adjustment lever 751 (a support shaft extending in the right direction R from the right side surface of the cylinder case 28). The link plate 753 can swing around the fulcrum a. The relative positions of the control adjustment lever 751 and the link plate 753 are fixed. Therefore, according to the operation of the control adjusting lever 751, the linking plate 753 also rotates around the fulcrum a.

The adjustment arm 754 is attached to the front end (rear end) of the link plate 753 so as to be able to swing back and forth around the fulcrum d. A roller 754r is attached to the adjustment arm 754 as a cam follower. A torsion spring is attached to the adjustment arm 754 to swing the adjustment arm 754 forward. The forward biasing swing of the adjustment arm 754 causes the roller 754r to abut on the cam surface S of the cable connecting arm 752 from behind and follow the cam surface S. As shown in FIG.

A linking rod 755 spans the position arm 65 and the cable linking arm 752 . The linking rod 755 transmits to the position arm 65 the swinging displacement of the adjusting arm 754 according to the cam surface S of the roller 754r.

As shown in FIG. 1 , at least part of the intermediate link mechanism 75 is positioned rearward of the front end of the lower link 3B of the three-point link mechanism 3 . In the embodiment, at least part of the cable connecting arm 752 and at least part of the adjusting arm 754 are positioned rearward of the front end of the lower link 3B.

The intermediate link mechanism 75 (mechanical linkage unit 7 ) has a sensitivity adjustment mechanism that adjusts the operating sensitivity when the elevation drive unit 6 is linked with the swing member 715 . In this embodiment, the sensitivity adjustment mechanism is composed of a control adjustment lever 751 , a cable connection arm 752 , a connection plate 753 , an adjustment arm 754 and a connection rod 755 .

Since the relative positions of the control adjustment lever 751 and the linking plate 753 are fixed, the operator operates the control adjustment lever 751 to position the control adjustment lever 751 rearward (counterclockwise in FIG. 6). The linking 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 abutment point of the roller 754r on the cable connecting arm 752 and the fulcrum c of the cable connecting arm 752 is reduced, and the lever ratio for bringing the adjusting arm 754 into contact with the cable connecting arm 752 by the control adjusting lever 751 is reduced. becomes smaller. Therefore, the rotation of the adjustment arm 754 is sensitive to the rotation of the cable connecting arm 752 . That is, the operating sensitivity of the elevation drive unit 6 becomes sensitive to the swinging motion of the swinging member 715, and the responsiveness when the tillage device 4A is lifted when the traction load exceeds a predetermined value is improved.

On the other hand, as the control adjustment lever 751 is moved forward (clockwise in FIG. 6), the linking 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 abutment point of the roller 754r on the cable connecting arm 752 and the fulcrum c of the cable connecting arm 752 increases, and the control adjusting lever 751 causes the adjusting arm 754 to contact the cable connecting arm 752. becomes larger. Therefore, the rotation of the adjustment arm 754 is insensitive to the rotation of the cable connecting arm 752 . That is, the operating sensitivity of the elevation drive unit 6 to the swing of the swing member 715 becomes insensitive, and the responsiveness when the tillage device 4A rises when the traction load exceeds a predetermined value becomes slow.

Next, the cable 78 will be explained. The cable 78 interlocks according to the amount of change in traction load detected by the load detection member 711 . The cable 78 is interlocked with the load detection mechanism 71 and the lift drive unit 6 . Specifically, the cable 78 is connected to the swing member 715 and the sensitivity adjustment 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 detection 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 .

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 side of the load detecting member 711 (load detecting mechanism 71). The second connecting portion 782 is connected to the swing member 715 . The second connecting portion 782 is attached to the second attaching portion 715A at a position higher than the first connecting portion 781 .

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 according to the swinging of the load detecting member 711. As shown in FIG. The inner cable 78A can move inside an outer cable 78B3, which will be described later.

A first connecting portion 781 is arranged at one end of the inner cable 78A, and a 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. As shown in FIG. Also, the inner cable 78A is directly connected to the cable connecting arm 752 .

The cover portion 78B covers the outer side 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 positioned at the end of the outer cable 78B3 on the intermediate link mechanism 75 side, and the second fixing portion 78B2 is positioned 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. As shown in FIG.

As shown in FIGS. 2 and 4 , the cable 78 has a portion (extending portion E) extending from the second connecting portion 782 toward the rear of the tractor 1 . Also, the cable 78 extends while curving. Specifically, when the tractor 1 is viewed from the side, the cable 78 extends in a C-shape or a U-shape. Therefore, in a 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 rearward. Further, when the second connecting portion 782 swings backward together with the swinging member 715, the first connecting portion 781 is pulled forward. That is, when the force in the forward direction F acts on the second connecting portion 782, the force in the backward direction B acts on the first connecting portion 781, and when the force in the backward direction B acts on the second connecting portion 782, the first connecting portion A force in the forward direction F acts on 781 .

Next, draft control will be described. Cultivation work is performed using the towed tillage device 4A, and when the towing load of the towed tillage device 4A becomes greater than a predetermined value, the load detection member 711 is swung forward, thereby causing the swinging member to move forward. 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 swinging member 715, the first connecting portion 781 is pulled rearward. 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 connecting rod 755 is pulled rearward together with the adjustment arm 754, and the position arm 65 rotates rearward about the position arm shaft 65A. As a result, the lift arm 61 rises to a position corresponding to the position after the position arm 65 has been rotated. It should be noted that 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 amount of elevation operation (the amount of displacement of the position arm 65).

When the load of the cultivator 4 falls below a predetermined value as the lift arm 61 rises, the lifting operation of the lift arm 61 stops. Since draft control can be performed to automatically raise and lower the tillage device 4A according to the traction load during tillage work, it is possible to avoid the occurrence of an engine stall due to an increase in the traction load.

(3) Tractor Equipped with Rotary Cultivator Next, a tractor equipped with a rotary cultivator will be described with reference to FIGS. 7 and 8. FIG. FIG. 7 is a right side view (No. 2) of the tractor according to the embodiment. FIG. 8 is a right side view (No. 2) of the hydraulic lifting device according to the embodiment. It should be noted that description of the same configuration as described above is omitted.

As shown in FIGS. 7 and 8, the three-point link mechanism 3 can be attached with a rotary tillage device 4B. 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. As shown in FIG. A hitch device 8 is provided at the rear of the three-point linkage mechanism 3 . The hitch device 8 is for connecting the tillage device 4 (rotary tillage device 4B).

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 a swing arm 45, which will be described later. Therefore, the linking member 81 swings back and forth according to the amount of change in tillage depth. The linking member 81 has a third attachment portion 813 to which the second linking portion 782 is attached. The third mounting portion 813 is a mounting portion for automatic plowing depth control. When the second lifting operation amount corresponding to the amount of change in plowing depth is selected as the lifting operation amount to be transmitted to the lifting drive unit 6 , the second connecting portion 782 is attached to the third mounting portion 813 . The third mounting portion 813 is positioned rearward of the rear end of the top link 3A. A cover portion 78B is fixed to the third cable fixing portion 83 .

A bracket 35 for supporting the top link 3A is attached to the load detecting member 711. As shown in FIG. Top link 3A is shorter than top link 3A in FIG.

The rotary tillage device 4B includes a rotor portion 41, a tillage cover 42 covering the rotor portion 41 from above, a grounding member (rear cover) 43 for detecting the amount of change in the tillage depth of the rotary tillage device 4B, a transmission case portion 44, and a transmission case portion. 44 has a rocking arm 45 that can rock back and forth, and a connecting link 46 that spans the lower free end of the rocking arm 45 and the grounding member 43 .

The grounding body 43 is a rear cover that prevents soil from scattering during tillage and evens out tillage marks. A grounding member 43 is provided at the rear end of the tillage cover 42 . The grounding body 43 can swing up and down around the fulcrum e.

A linking member 81 is provided at the rear portion of the three-point link mechanism 3 so as to be rotatable about the central portion of the linking member 81 as a fulcrum. When the rotary tillage device 4B is connected to the three-point link mechanism 3 via the hitch device 8, one end of the connecting member 81 is engaged and connected to an engagement recess (not shown) formed in the swing arm 45. As shown in FIG. 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 connecting member 81 . A second connection portion 782 of the cable 78 is attached to the third attachment portion 813 . Thereby, the grounding member 43 and the control valve 63 are linked via the cable 78 .

Next, automatic plowing depth control will be described. When the rotary tillage device 4B is used for tillage work and the rotary tillage device 4B becomes deeper than the target tillage depth, the grounding member 43 is lifted and swung accordingly. As a result, the linking link 46 moves forward, the swing arm 45 swings forward, and the linking member 81 rotates counterclockwise. Due to the rotation of the linking member 81, the second linking portion 782 of the cable 78 is pulled rearward, and the first linking portion 781 is also pulled rearward. As a result, similarly to the draft control, 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 the lift arm 61 rises, the rotary tillage device 4B rises to a position corresponding to the position after the position arm 65 rotates. Then, when the grounding member 43 is restored to its original posture, the rising operation is stopped and the original plowing depth is restored.

On the other hand, when the rotary tillage device 4B is used for tillage work, and the rotary tillage device 4B becomes shallower than the target tillage depth, the grounding member 43 hangs down and swings accordingly, thereby causing the cable 78 to become loose. The inner cable 78A is loosened. Here, since the cable connecting arm 752 is biased to swing forward (clockwise in FIG. 8) by the tension spring, when the inner cable 78A is loosened, the cable connecting arm 752 takes up the slack of the inner wire 36a. Swing forward (clockwise) to absorb. As a result, the adjustment arm 754 follows the cable connection arm 752 and swings forward. The connecting rod 755 is pushed forward together with the adjusting arm 754, and the position arm 65 rotates forward about the position arm shaft 65A. As a result, the lift arm 61 is lowered and the rotary tillage device 4B is lowered to a position corresponding to the position after the position arm 65 has been rotated. Then, when the grounding member 43 is restored to its original posture, the lowering operation is stopped and the original plowing depth is restored.

In addition, 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 enters 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.

With the above configuration, by switching the connecting destination of the second connecting portion 782 of the cable 78, the first lifting operation amount corresponding to the amount of change in the traction load and the second lifting operation amount corresponding to the amount of change in the plowing depth can be obtained. is selected as the elevation operation amount to be transmitted to the elevation drive unit 6. Thereby, the cable 78 can selectively transmit the amount of change in traction load and the amount of change in plowing depth.

Specifically, when the second attachment portion 715A of the swing member 715 is selected as the connection destination of the second connection portion 782, the first elevation operation amount is transmitted to the elevation drive unit 6 as the elevation operation amount. The lift drive unit 6 controls the lift cylinder 62 according to the first lift operation amount (that is, the amount of change in traction load). Therefore, the traction type tillage device 4A can be automatically raised and lowered according to the towing load during tillage work.

On the other hand, when the third attachment portion 813 of the hitch device 8 is selected as the connection destination of the second connection portion 782, the second elevation operation amount is transmitted to the elevation drive unit 6 as the elevation operation amount. The lift drive unit 6 controls the lift cylinder 62 according to the second lift operation amount (that is, the amount of change in tillage depth). Therefore, the rotary tillage device 4B can be automatically raised and lowered according to the tillage depth during tillage work.

As described above, the intermediate link mechanism 75 connected to the first connection portion 781 is a link mechanism common to both the draft control and the automatic plowing depth control in order to switch the connection destination of the second connection portion 782 . Therefore, similar functions of the draft control and the automatic plowing depth control can be combined into one link mechanism, so the structure of the hydraulic lifting device 5 can be made difficult to complicate.

In addition, the second attachment portion 715A is located forward of the front end of the top link 3A. The third mounting portion 813 is positioned rearward of the rear end of the top link. When switching between the draft control and the automatic plowing depth control, 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. can be easily switched.

Moreover, the cable 78 is more flexible than plate-like or rod-like link members used in general mechanical link mechanisms. Therefore, the degree of freedom in arranging the connection destination of the cable 78 is increased, and the structure of the hydraulic lifting device 5 can be prevented from becoming complicated.

In addition, switching between the draft control and the automatic plowing depth control can be easily performed by switching the connecting destination of the cable 78 with a wide movable range due to flexibility.

The cable 78 also has an extension 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 attachment portion 715A toward the front. As a result, the operator positioned behind the tractor 1 can grasp the extension part E so that the second connection part 782 is positioned on the front side of the operator relative to the extension part E, thereby moving the second connection part 782. It becomes easier 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.

Further, when the second connecting portion 782 swings forward together with the swinging member 715 in a side view of the tractor 1 , the first connecting portion 781 is pulled rearward, and the second connecting portion 782 swings backward along with the swinging member 715 . The cable 78 extends while bending so that the first connecting portion 781 is pulled forward when rocked. In addition, the second connecting portion 782 is attached to the first attaching portion 752A at a position higher than the first connecting portion 781 . By bending the cable 78 during maintenance work, the worker can carry the second connecting portion 782 to the mounting portion without having to move much. In addition, since the second connecting portion 782 is positioned higher than the first connecting portion 781, it can be attached at a position close to the line of sight of the operator. The operator can easily switch to draft control.

The tractor 1 also has cable fixing portions (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 elevation operation amount corresponding to the amount of change in the traction load to the elevation drive unit 6, so that high-quality draft control can be performed.

Also, the cable 78 is connected to the swing member 715 and the sensitivity adjustment mechanism. As a result, the number of link members connecting the swing member 715 and the sensitivity adjustment mechanism can be reduced, and the structure of the hydraulic lift device 5 is less complicated.

At least part of the intermediate link mechanism 75 is positioned rearward of 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, thereby improving maintainability.

Also, the second attachment portion 715A is positioned above the load detection member 711 . As a result, when the second mounting portion 715A is viewed from behind the tractor 1, the second mounting portion 715A can be viewed above the load detecting member 711, and the load detecting member 711 is less likely to overlap the second mounting portion 715A. Become. It is easy to check the second connecting portion and the attaching portion from the rear of the tractor 1, and to attach and detach the second connecting portion 782 easily. Therefore, the switching work can be easily performed. In addition, it is not necessary to provide a space for the second attachment portion 715A in front of the load detection member 711 .

The second attachment portion 715A is located rearward of 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 shorter than the front end of the lower link 3B, the second connecting portion 782 can be easily mounted and removed from the rear of the tractor 1. Therefore, the switching work can be easily performed.

The hitch device 8 also has a linking member 81 that swings back and forth according to the amount of change in tillage depth. The linking member 81 has a third attachment portion 813 to which the second linking portion 782 is attached. As a result, the second connecting portion 782 of the cable 78 is directly attached to the connecting member 81 of the hitch device 8, so compared to the case where the second connecting portion 782 of the cable 78 is attached on the front side of the three-point linkage mechanism 3. As a result, the number of members for transmitting the amount of change in plowing depth to the cable 78 can be reduced.

Also, in a state where no traction load is applied, the second mounting portion 715A is positioned rearward of the first mounting portion 752A. Since the distance from the rear of the tractor 1 to the second mounting portion 715A is shorter than the distance from the first mounting portion 752A, the second connecting portion 782 can be easily mounted and removed from the rear of the tractor 1. Therefore, the switching work can be easily performed.

(4) Other Embodiments Although the present invention has been described in detail using the above-described embodiments, it should be apparent to those skilled in the art that the present invention is not limited to the embodiments described herein. is. The present invention can be implemented with modifications and variations without departing from the spirit and scope of the invention defined by the claims. Accordingly, the descriptions herein are for the purpose of illustration and description, and are not intended to have any limiting meaning with respect to the present invention.

Various modifications of the configuration of the tractor 1 are possible. For example, the tractor 1 may be configured as a semi-crawler specification having left and right crawlers in place of the left and right rear wheels 25B. For example, the tractor 1 may be configured as a full crawler specification having left and right crawlers in place of the left and right wheels 25 . For example, the tractor 1 may be configured with an electric motor instead of the engine 22 . For example, the tractor 1 may be configured as a hybrid specification including the engine 22 and an electric motor.

The configuration of the elevation drive unit 6 and the configuration of the mechanical linkage unit 7 can be modified in various ways. For example, cable 78 may have a portion that extends toward the side of tractor 1 . That is, when the tractor 1 is viewed from the rear (seen from the rear of the tractor 1), the extension E may extend laterally. A worker positioned on the side of the tractor 1 grips the extension part E so that the second connection part 782 is positioned on the front side of the operator relative to the extension part E, thereby moving the second connection part 782. It becomes easier 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.

In the above-described embodiment, the swinging member that swings back and forth according to the front and back swing of the load detection member 711 is provided, and the swinging member 715 is provided with the second attachment portion 715A to which the cable 78 is attached. Not limited. For example, the load detection member 711 may be provided with the second mounting portion 715A.

In the above-described embodiment, when the second connecting portion 782 swings forward together with the swinging member 715 in a side view of the tractor 1 , the first connecting portion 781 is pulled rearward, and the second connecting portion 782 swings together with the swinging member 715 . Although the first connecting portion 781 is pulled forward when it swings backward, the present invention is not limited to this. For example, by reversing the movement of the swinging member 715, the first connecting portion 781 is pulled forward when the second connecting portion 782 swings forward, and the first connecting portion 781 is pulled forward when the second connecting portion 782 swings backward. One connecting portion 781 may be pulled rearward.

In addition, although the linking member 81 is engaged with the swing arm 45 and connected to the engagement recess, it is rotatable, but the present invention is not limited to this. For example, the connecting link 46 may be connected to the lower free end of the connecting member 81 . Thereby, the linking member 81 may be rocked back and forth by the link 46 without the rocking arm 45 .

In addition, the tractor 1 may have members other than the members described above, or may have only a part of the members described above. Therefore, for example, the elevation drive unit 6 and the mechanical linkage unit 7 may have members other than the members described above, or may have only a part of the members described above.

Reference Signs List 1 : Tractor 2 : Car body 3 : Three-point link mechanism 4 : Tillage device 5 : Hydraulic lifting device 6 : Lifting drive unit 7 : Mechanical linkage unit 8 : Hitch device 21 : Frame 22 : Engine 23 : Clutch housing 24 : T /M case 25 : wheel 26 : rear fender 27 : driving unit 28 : cylinder case 61 : lift arm 62 : lift cylinder 63 : control valve 64 : balance arm 65 : position arm 67 : position lever 68 : position plate 71 : load detection mechanism 72 : Biasing mechanism 73 : Limiting mechanism 74 : Manipulator 75 : Intermediate link mechanism 78 : Cable 711 : Load detection member 715 : Swing member

Claims (7)

a tractor,
A three-point link mechanism to which a tillage device can be attached,
a hydraulic lift drive unit that lifts and lowers the three-point link mechanism;
a mechanical linkage unit that transmits the lifting operation amount of the three-point link mechanism to the lifting drive unit;
The mechanical linkage unit is
a cable that selectively transmits the amount of change in traction load and the amount of change in plowing depth;
a mechanical link mechanism interlockingly connected to the cable and the lifting drive unit;
A first connecting portion, which is a connecting portion on one side of the cable, is connected to the mechanical link mechanism,
By switching the connection destination of the second connection portion, which is the connection portion on the other side of the cable, a first elevation operation amount corresponding to the amount of change in the traction load and a second elevation operation amount corresponding to the amount of change in the tillage depth. one of the operation amount and the operation amount is selected as the elevation operation amount to be transmitted to the elevation drive unit;
an attachment portion for draft control to which the second connecting portion is attached when the first elevation operation amount is selected as the elevation operation amount;
a mounting portion for automatic plowing depth control to which the second connecting portion is mounted when the second lifting operation amount is selected as the lifting operation amount;
The mounting portion for draft control is positioned forward of the front end of the top link of the three-point link mechanism,
The mounting portion for automatic plowing depth control is located behind the rear end of the top link,
the cable has a portion extending from the second connecting portion toward the rear of the tractor;
The second connecting portion is attached to the attachment portion for draft control toward the front of the tractor,
The tractor, wherein the mounting portion for automatic plowing depth control is located between the three-point linkage mechanism and the cultivator and provided at the rear of the three-point linkage mechanism. a load detection member that swings back and forth according to the traction load transmitted through the top link of the three-point link mechanism;
a swinging member having a mounting portion to which the second connecting portion is mounted, and swinging back and forth in accordance with the back and forth swing of the load detection member;
In a side view of the tractor, when the second connecting portion swings forward together with the swinging member, the first connecting portion is pulled rearward, and the second connecting portion swings backward together with the swinging member. Then, the cable extends while curving so that the first connecting portion is pulled forward,
The tractor according to claim 1, wherein the second connecting portion is attached to the mounting portion at a position higher than the first connecting portion. The cable is
an inner cable that swings according to the back-and-forth swing of the swing member;
a cover portion that covers the outer side of the inner cable,
3. A tractor according to claim 2, further comprising a cable fixing portion for fixing said cover portion. a load detection member that swings back and forth according to the traction load transmitted through the top link of the three-point link mechanism;
a swinging member that swings back and forth according to the back and forth swing of the load detection member;
The mechanical linkage unit has a sensitivity adjustment mechanism that adjusts the operating sensitivity when the elevation drive unit is linked with the swing member,
The tractor according to any one of claims 1 to 3, wherein the cable is connected to the swing member and the sensitivity adjustment mechanism. 5. The tractor according to any one of claims 1 to 4, wherein at least part of said mechanical link mechanism is located behind the front end of the lower link of said three-point linkage mechanism. a load detection member that swings back and forth according to the traction load transmitted through the top link of the three-point link mechanism;
a mounting portion to which the second connecting portion is mounted when the first lifting operation amount is selected as the lifting operation amount;
The tractor according to any one of claims 1 to 5, wherein the attachment portion is positioned above the load detection member. A hitch device for connecting the cultivator is provided at the rear of the three-point link mechanism,
The hitch device has a linking member that swings back and forth according to the amount of change in the plowing depth,
The tractor according to any one of claims 1 to 6, wherein the linking member has an attachment portion to which the second connecting portion is attached when the second elevation operation amount is selected as the elevation operation amount.

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