JP6742938B2 - Tractor - Google Patents

Description

The present invention relates to a three-point link mechanism that is vertically swingably connected to a rear portion of a vehicle body and that enables attachment of a working device including a cultivating device, and a hydraulic lifting drive that drives the three-point link mechanism up and down. A unit, and a mechanical linkage unit for automatic lifting, which converts the amount of change in the traction load into a lifting operation amount and transmits it to the lifting drive unit during the plowing work in which the plowing device is attached to the three-point link mechanism. Regarding tractors.

The tractor as described above is provided with a mechanical linkage unit for automatic lifting, so that at the time of tilling work, it is possible to automatically raise and lower the tilling device according to the towing load and perform draft control for maintaining the towing load constant. Is configured.

Draft controllable tractors include a draft adjusting lever for setting the working depth, a link mechanism (cylinder shaft and arm, etc.) that links the spool of the control valve to the draft adjusting lever, and load detection that swings back and forth according to the towing load. By providing a member (top link hinge) and a link mechanism (draft feedback link mechanism) that links the spool of the control valve to the load detection member, the traction load can be set to a set value determined by the working depth setting of the draft adjustment lever. Some of them are configured to maintain (for example, see Patent Document 1).

In the tractor described in Patent Document 1, for example, a case of performing plowing work using draft control in a standard field in which the traction load is unlikely to increase due to soil hardness and the fluctuation of the traction load is unlikely to occur, and soil Depending on the traction load, cultivating equipment such as plows and subsoilers can be used depending on the traction load, regardless of the case of performing cultivating work using draft control in a field where the traction load is likely to increase due to the hardness of It is configured to move up and down at standard speed.

Therefore, even if the traction load rises rapidly, the tiller will rise at a standard speed based on the increase in the traction load. As a result, when the traction load rapidly increases, it is not possible to suitably suppress the increase in the traction load, which may cause an engine stall due to the increase in the traction load.

Therefore, in order to avoid an engine stall due to a sudden increase in the towing load, in the tractor equipped with the mechanical linkage unit for automatic lifting described above, the change amount conversion that can be switched between the standard conversion state and the amplification conversion state is possible. It has been proposed by the applicant that the mechanism be provided in a mechanical linkage unit (see, for example, Patent Document 2).

The invention described in Patent Document 2 is, for example, an operator when performing plowing work using draft control in a standard field in which the traction load is unlikely to increase due to soil hardness or the like, and the fluctuation in the traction load is unlikely to increase. However, by switching the change amount conversion mechanism to the standard conversion state, the tiller can be moved up and down according to the traction load at a standard speed suitable for this field. In addition, for example, when performing cultivating work using draft control in a field where the traction load is likely to be large due to soil hardness and the traction load is likely to fluctuate significantly, the operator amplifies the change amount conversion mechanism and converts it. By switching to, it is possible to raise and lower the tiller according to the traction load at a high speed suitable for this field. As a result, the engine stall resulting from the increase in the towing load can be avoided in both the field where the towing load is unlikely to change rapidly and the field where the towing load is likely to change rapidly.

JP 2006-109802 A Japanese Patent Application No. 2016-182005

In the invention described in Patent Document 2, a mechanical linkage unit including a change amount conversion mechanism is used as a load detection member and a load detection member that swing back and forth according to a traction load transmitted via a top link of a three-point link mechanism. A swinging member that is swingably supported, a holding mechanism that biases the swinging member to a predetermined posture with respect to the load detection member, a receiving member that can change its position between an acting position and a retracted position with respect to the swinging member, and , A link mechanism for interlockingly connecting the swinging member and the lifting drive unit, and the like. When the change amount conversion mechanism is in the standard conversion state, the receiving member is located at the retracted position, so that the load detection member and the swing member are integrally swung by the action of the holding mechanism. As a result, the amount of change in the towing load is transmitted to the lifting drive unit as an amount of lifting operation without being amplified, and as a result, the tiller moves up and down at a standard speed. Further, when the change amount conversion mechanism is in the amplification conversion state, the receiving member is located at the operation position, so that the load detection member swings in the increasing direction of the towing load, so that the operation of the holding mechanism is prevented. The load detecting member and the rocking member largely rock relative to each other. As a result, the amount of change in the towing load is amplified and transmitted to the lifting drive unit as the lifting operation amount, and as a result, the tiller moves up and down at a high speed.

However, in the invention described in Patent Document 2, when the fluctuation of the traction load becomes large during the plowing work using the draft control, the load detection member vibrates violently in the front-back direction along with the fluctuation of the traction load at this time. Then, under the influence of the influence, when the load detection member swings in the ascending direction of the towing load, the swing member easily swings excessively with respect to the swing of the load detection member. Further, when the load detection member swings in the direction of decreasing the traction load, the swing of the swing member tends to be delayed with respect to the swing of the load detection member. When excessive swing and swing delay of the swing member with respect to the load detection member occur, chattering may occur in the mechanical linkage unit due to the excessive swing and swing delay, and chattering occurs. When occurs, it becomes difficult to perform highly accurate draft control according to the towing load.

In other words, it is desired to prevent chattering from occurring in the mechanical linkage unit during cultivating work using draft control, and prevent the control accuracy in draft control from being reduced due to chattering.

As a means for solving the above problems,
A tractor according to the present invention includes a three-point link mechanism that is vertically swingably connected to a rear portion of a vehicle body, and that enables attachment of a working device including a tiller, and a hydraulic type that drives the three-point link mechanism up and down. And a mechanical linkage unit for automatic lifting, which converts the amount of change in the traction load into a lifting operation amount and transmits it to the lifting drive unit during the plowing work in which the lifting drive unit and the cultivator are attached to the three-point link mechanism. With and
The mechanical linkage unit includes a load detecting member that swings back and forth according to a traction load transmitted via a top link of the three-point link mechanism, and a biasing member that swings and urges the load detecting member in a direction of decreasing the traction load. A biasing mechanism, a swinging member swingably supported by the load detecting member, a restricting mechanism that restricts swinging of the swinging member with respect to the load detecting member, the swinging member, and the lifting drive unit. And a link mechanism for interlocking
The regulation mechanism includes a receiving member that integrally swings with the load detection member, and a biasing unit that swings and biases the swinging member in a direction of pressing the swinging member against the receiving member.

According to this means, when the load detection member swings back and forth according to the traction load during the tilling work using draft control, the catching tool swings integrally with the load detection member, and the swinging member is attached. It is held in a state of being pressed against the catch by the action of the biasing unit. As a result, for example, even when the traction load fluctuates drastically and the load detection member vibrates back and forth violently during cultivating work, the action of the urging unit causes an excessive movement of the oscillating member relative to the load detection member. It is possible to suppress rocking and rocking delay.

As a result, even if the traction load fluctuates significantly during plowing work using draft control, chattering may occur in the mechanical linkage unit due to excessive swing or swing delay of the swing member with respect to the load detection member. Can be difficult. As a result, it is possible to prevent deterioration of control accuracy in draft control due to chattering.

As one of means for making the present invention more preferable,
The urging unit includes a first urging mechanism that is installed from the load detecting member to the oscillating member or the link mechanism to suppress oscillating of the oscillating member with respect to the load detecting member, and a fixing member of a vehicle body. A second urging mechanism that is installed on the swing member or the link mechanism and that suppresses swing of the load detection member and the swing member in the pulling load increasing direction is provided.

According to this means, when the load detecting member and the swinging member integrally swing, the first biasing mechanism swings with respect to the load detecting member regardless of the forward and backward swing of the load detecting member according to the towing load. The force for suppressing the swing of the member becomes constant. Further, when the load detecting member and the swinging member relatively swing, the first biasing mechanism swings the swinging member relative to the load detecting member as the swinging member swings larger with respect to the load detecting member. The force that suppresses movement increases.

On the other hand, the second urging mechanism is configured so that the load detection member and the swinging member integrally swing, and the load detection member and the swinging member relatively swing. The greater the swinging of the load detection member in the increasing direction of the towing load, the greater the force for suppressing the swinging of the load detecting member and the swinging member in the increasing direction of the towing load. Further, the second biasing mechanism swings with respect to the load detection member as the load detection member swings largely in the ascending direction of the towing load when the load detection member and the swing member relatively swing. The greater the swing of the moving member, the greater the force that restrains the load detection member and the swing member from swinging in the pulling load increasing direction. As a result, the second biasing mechanism causes the load detection member and the swing member to swing relative to each other as compared to the case where the load detection member and the swing member integrally swing. The force that suppresses the swinging of the moving member in the direction of increasing the traction load increases.

That is, the second urging mechanism causes the load detection member to pull the traction load regardless of whether the load detection member and the swing member integrally swing or whether the load detection member and the swing member relatively swing. The greater the swing in the ascending direction of the load detection member, the greater the force that suppresses the swing of the load detecting member and the swinging member in the pulling load rising direction becomes, and the swinging of the load detecting member and the swinging member in the pulling load rising direction becomes larger. It functions as a damper to damp the motion.

As a result, regardless of whether the load detection member and the rocking member integrally rock, or when the load detection member and the rocking member relatively rock, the traction load fluctuates significantly and the load detection member is When it vibrates back and forth violently, due to the action of the second biasing mechanism, excessive rocking and rocking delay of the rocking member with respect to the load detecting member can be suppressed more effectively.

In the case where the load detection member and the swing member relatively swing, when the fluctuation of the traction load becomes large and the load detection member and the swing member swing relatively, the first biasing mechanism and the first biasing mechanism Due to the action of the urging mechanism, it is possible to more effectively suppress excessive swing and swing delay of the swing member with respect to the load detection member.

Since it is not necessary to take measures only when the fluctuation of the towing load becomes large by the action of the first urging mechanism, the measures can be taken only by the action of the first urging mechanism. As a result, it is possible to avoid the inconvenience that the rocking member is hard to rock.

As a result, chattering in the mechanical linkage unit due to excessive rocking and rocking delay of the rocking member with respect to the load detection member, etc. It can be made more reliable and less likely to occur. As a result, it is possible to more reliably prevent a decrease in control accuracy in draft control due to chattering.

As one of means for making the present invention more preferable,
The first biasing mechanism includes a first tension spring that is installed from the load detection member to the swing member or the link mechanism, and a second tension spring having a diameter smaller than that of the first tension spring.
The second tension spring extends from the load detection member to the swing member or the link mechanism through the inside of the first tension spring.

According to this means, the outer diameter of the first biasing mechanism can be made smaller than that in the case where the first biasing mechanism is constituted by a single tension spring. As a result, the high tension required for the first biasing mechanism can be secured without increasing the size of the first biasing mechanism, and it is easy to avoid the disadvantage that the first biasing mechanism interferes with the peripheral members. Become.

It is a right view of the tractor with which the plow was attached to the three-point link mechanism. It is a right view of the tractor in which the rotary tiller was attached to the three-point link mechanism. FIG. 6 is a right side view of a vertical section of an essential part showing the configurations of a lifting drive unit and a mechanical linkage unit. FIG. 3 is a plan view of a main part showing a configuration of a lifting drive unit and a mechanical linkage unit. FIG. 3 is an exploded perspective view of essential parts showing the configurations of a lifting drive unit and a mechanical linkage unit. FIG. 8 is a right side elevational view in vertical cross-section of essential parts showing an operating state of the lifting drive unit when the tilling device is stopped moving up and down by holding the position of the height setting lever on the lower setting side. FIG. 6 is a right side elevational view in longitudinal cross-section of essential parts showing an operating state of the lifting drive unit when the tilling device is raised in association with the swing operation of the height setting lever in the high position setting direction. FIG. 6 is a right side elevational view in vertical cross-section of essential parts showing an operating state of the lifting drive unit when the tiller is stopped moving up and down by holding the position of the height setting lever on the high setting side. FIG. 4 is an exploded perspective view of a main part showing a configuration of a change amount conversion mechanism and the like. FIG. 6 is a rear view of the main part showing the configuration of a change amount conversion mechanism and the like. FIG. 5 is a sectional view taken along line XI-XI in FIG. 4. FIG. 6 is a right side vertical cross-sectional view of a main part showing the operating states of the mechanical linkage unit and the lifting drive unit when the traction load does not exceed the set value in the standard conversion state of the change amount conversion mechanism. FIG. 6 is a right side vertical cross-sectional view of a main part showing an operating state of a mechanical linkage unit and a lifting drive unit when a traction load exceeds a set value in a standard conversion state of a change amount conversion mechanism. FIG. 6 is a right side vertical cross-sectional view of a main part showing an operating state of a mechanical linkage unit and a lifting drive unit when a traction load does not exceed a set value in an amplification conversion state of a change amount conversion mechanism. FIG. 6 is a right side vertical cross-sectional view of a main part showing an operating state of a mechanical linkage unit and a lifting drive unit when a traction load exceeds a set value in an amplification conversion state of a change amount conversion mechanism. FIG. 6 is a right side vertical cross-sectional view of essential parts showing an operating state of the mechanical linkage unit and the lifting drive unit when the tilling depth reaches the set tilling depth in the second converting state of the change amount converting mechanism. FIG. 6 is a right side vertical cross-sectional view of essential parts showing an operating state of the mechanical linkage unit and the lifting drive unit when the working depth is deeper than the set working depth in the second conversion state of the change amount conversion mechanism.

Hereinafter, an example of a mode for carrying out the present invention will be described with reference to the drawings.
The direction indicated by the arrow F in FIGS. 1 and 2 is the front side of the tractor, and the direction indicated by the arrow U is the upper side of the tractor.

As shown in FIGS. 1 and 2, a tractor exemplified in the present embodiment includes a front frame 1 arranged at a front part of a vehicle body, an engine 2 connected to a rear part of the front frame 1, and a lower rear end portion of the engine 2. To the clutch housing 3, the intermediate frame 4 connected to the rear end of the clutch housing 3, the rear frame combined transmission case connected to the rear end of the intermediate frame 4 (hereinafter, referred to as T/M case) 5, left and right front wheels 6 arranged on the left and right of the front frame 1, left and right rear wheels 7 arranged on the left and right of the T/M case 5, left and right rear fenders 8 covering the left and right rear wheels 7, and a vehicle body It is equipped with a boarding-type driving section 9 arranged in the rear part.

Although illustration is omitted, the power from the engine 2 is supplied to the T/M case 5 via the main clutch built in the clutch housing 3 and the transmission shaft covered with the intermediate frame 4. It is transmitted to the transmission. Then, the power after shifting by the main transmission is transmitted to the left and right front wheels 6 and the left and right rear wheels 7 via the auxiliary transmission incorporated in the T/M case 5.

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

At the rear of the T/M case 5, a three-point link mechanism 12 that allows attachment of a work device is connected so as to be vertically swingable. The three-point link mechanism 12 includes a single top link 13, left and right lower links 14, and the like. Thus, when performing cultivating work with this tractor, the towed cultivating device 15, which is an example of a working device, can be attached to the three-point link mechanism 12.

In this embodiment, the plow 15A, which is an example of the towed tiller 15, is attached to the three-point link mechanism 12 (see FIG. 1) and the rotary tiller that is an example of the towed tiller 15. The state in which the device 15B is attached to the three-point link mechanism 12 (see FIG. 2) is illustrated, but the three-point link mechanism 12 includes a towed cultivator such as a disc harrow, a cultivator, and a subsoiler. The device 15 can be attached. Further, the three-point link mechanism 12 can be equipped with a working device such as a mower or a seeder in addition to the towed tiller.

As shown in FIGS. 1 to 8, the tractor includes a mechanically-operated hydraulic lifting device 16. The hydraulic lifting device 16 includes a hydraulic lifting drive unit 17 that lifts and lowers the tilling device 15 together with the three-point link mechanism 12, and a pulling load during the tilling work in which the tilling device 15 is attached to the three-point link mechanism 12. A mechanical linkage unit 18 for automatic lifting is provided, which selectively converts one of the change amount and the change amount of the working depth into a lift operation amount and transmits it to the lift drive unit 17.

The lift drive unit 17 includes left and right lift arms 20 that suspend and support the left and right lower links 14 via left and right support members 19, a hydraulic cylinder 21 that vertically swings the left and right lift arms 20, and a hydraulic cylinder 21. Of the control valve 22, the height setting lever 23 for setting the control target height of the tiller 15, the friction type holding mechanism 24 for holding the height setting lever 23 at an arbitrary operation position, and the control valve 22. A first link mechanism 25 for interlocking the spool 22A with the height setting lever 23, a feedback link mechanism 26 for interlocking the spool 22A with the left and right lift arms 20, and the like are provided. The control valve 22 is internally provided with a biasing means (not shown) for biasing the spool 22A to return to the lowered position on the front side of the vehicle body.

The first link mechanism 25 is provided on the spool 22A of the control valve 22 and the first swing arm 27 that comes into contact with the linking portion 23A of the height setting lever 23 from the rear side of the vehicle body (the high setting side of the height setting lever 23). A balance arm 28 supported so as to be swingable back and forth, a first crank shaft 29 extending from a swing center of the first swing arm 27 to an upper end portion of the balance arm 28, and the like are provided. When the height setting lever 23 is oscillated in the high position setting direction (rearward direction of the vehicle body), the first link mechanism 25 causes the spool 22A of the control valve 22 to act as an urging means in association with the operation. Move from neutral position to raised position against. In the first link mechanism 25, when the height setting lever 23 is oscillated in the lower setting direction (the vehicle body front direction), the spool 22A of the control valve 22 is neutralized by the action of the urging means in conjunction with the operation. Allowing to move from position to lowered position.

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

With the above configuration, when the operator operates the height setting lever 23 to increase the control target height of the tiller 15, the first link mechanism 25 causes the spool 22A of the control valve 22 to move along with this operation. The neutral position is moved to the raised position (see FIG. 7). This causes the left and right lift arms 20 and the tiller 15 to rise. Then, when the tiller 15 reaches the control target height by this rise, the feedback link mechanism 26 moves the spool 22A of the control valve 22 from the raised position to the neutral position in conjunction with this (see FIG. 8). As a result, the left and right lift arms 20 and the tiller 15 stop rising.

Further, when the operator lowers the control target height of the tiller 15 by operating the height setting lever 23, the first link mechanism 25 moves from the neutral position of the spool 22A to the lowered position with this operation. The movement is allowed, and the spool 22A moves from the neutral position to the lowered position by the action of the biasing means. This causes the left and right lift arms 20 and the tiller 15 to descend. Then, when the tiller 15 reaches the control target height by this lowering, the feedback link mechanism 26 moves the spool 22A of the control valve 22 from the lowering position to the neutral position in conjunction with this. As a result, the left and right lift arms 20 and the tiller 15 stop descending.

That is, in this tractor, by providing the above-described lifting drive unit 17, it is possible to favorably perform the position control for vertically moving the tiller 15 to the arbitrary control target height set by the operation of the height setting lever 23. You can By this position control, it is possible to set the plowing depth during the plowing work to any depth.

As shown in FIGS. 1 to 5 and 9 to 17, the mechanical linkage unit 18 includes a change amount conversion mechanism 33 that can switch between a first conversion state and a second conversion state, and a change amount conversion mechanism 33. The operation tool 35 for switching between the first conversion state and the second conversion state is provided. The change amount conversion mechanism 33 includes a load detection member 36 that swings back and forth according to a traction load transmitted via the top link 13, and a biasing force that swings the load detection member 36 rearward of the vehicle body, which is a direction in which the traction load decreases. A biasing mechanism 49, a swinging member 38 swingably supported by the load detecting member 36, a restricting mechanism 52 for restricting swinging of the swinging member 38 with respect to the load detecting member 36, and the swinging member 38 and a lifting drive unit. A second link mechanism 34 for interlockingly connecting with 17 and the like are provided. The rocking member 38 rocks in accordance with the tilling depth of the tiller 15 when interlocked with the grounding body 37 (see FIGS. 2 and 16 to 17) that detects the tilling depth of the tiller 15.

In the first conversion state of the change amount conversion mechanism 33, the swinging of the swinging member 38 with respect to the load detecting member 36 is performed by the restricting mechanism 52 while the load detecting member 36 is allowed to swing back and forth according to the traction load. It is regulated. In the second conversion state of the change amount conversion mechanism 33, the swing of the swinging member 38 with respect to the load detecting member 36 is prevented by the restricting mechanism 52 while the load detecting member 36 is prevented from swinging back and forth according to the towing load. It is regulated.

Of the various tilling devices 15, the plow 15A (see FIG. 1), the subsoiler, and the like do not include the grounding body 37. The rotary tiller 15B (see FIG. 2) is provided with a rear cover that functions as a grounding body 37 so as to be vertically swingable. Therefore, for example, in the cultivating work in which the plow 15A is attached to the three-point link mechanism 12, the mechanical linkage unit 18 is in the first linkage state in which the interlocking linkage between the swinging member 38 and the grounding body 37 is released. (See FIGS. 1, 3-5, 9-15). Further, in the cultivating work in which the rotary cultivating device 15B is attached to the three-point link mechanism 12, in the mechanical linkage unit 18, the swing member 38 and the grounding body 37 are interlocked and coupled via the third link mechanism 39. The second linked state is established (see FIGS. 2 and 16 to 17).

When the change amount conversion mechanism 33 is switched to the above-described first conversion state in the first linkage state of the mechanical linkage unit 18, the load detection member 36 is allowed to swing back and forth according to the traction load, and the regulation mechanism 52 of the regulation mechanism 52 moves. The load detection member 36 and the swinging member 38 can swing together as a result of the action. As a result, the change amount conversion mechanism 33 can convert the change amount of the traction load obtained by swinging the load detection member 36 back and forth into the up/down operation amount (FIGS. 1, 3 to 5, and 9 to 9 ). 15).

When the change amount conversion mechanism 33 is switched to the second conversion state described above in the second linkage state of the mechanical linkage unit 18, the load detection member 36 is prevented from swinging back and forth according to the traction load, and the regulation mechanism 52 of the regulation mechanism 52 is blocked. The swing member 38 can swing with respect to the load detection member 36 against the action. As a result, the change amount conversion mechanism 33 can convert the change amount of the working depth obtained by the swinging of the swinging member 38 that interlocks with the grounding body 37 into the raising/lowering operation amount (FIGS. 2 and 16-). 17).

With the above-described configuration, when the plough 15A is cultivated in this tractor, the mechanical linkage unit 18 is brought into the first linkage state by mounting the plow 15A to the three-point link mechanism 12. Then, in this first linked state, the operator operates the operation tool 35 to switch the change amount conversion mechanism 33 to the first conversion state, so that the plow 15A automatically operates according to the towing load during the tilling work. Draft control to move up and down can be performed. As a result, it is possible to avoid the occurrence of engine stall due to the increase in traction load.

Further, in the case of performing the cultivating work by the rotary cultivating device 15B in this tractor, the rotary cultivating device 15B is attached to the three-point link mechanism 12, and the swinging member 38 and the grounding body 37 act as the third link mechanism 39. The mechanical linkage unit 18 is brought into the second linkage state by being interlocked and coupled via. Then, in this second linked state, the operator operates the operation tool 35 to switch the change amount conversion mechanism 33 to the second conversion state, so that at the time of tilling work, a grounding body (rear cover) corresponding to the working depth is obtained. ) It is possible to perform automatic tilling depth control in which the rotary tiller 15B automatically moves up and down in conjunction with the vertical swing of 37. As a result, it is possible to perform high-precision plowing work in which the plowing depth is maintained constant.

That is, in this tractor, when the mechanical linkage unit 18 having the above-described configuration is provided, when performing the plowing work with the plow 15A, the draft control suitable for the plowing work with the plow 15A can be performed. Further, when the tilling work is performed by the rotary tiller 15B, automatic tilling depth control suitable for the tilling work by the rotary tiller 15B can be performed.

Although illustration is omitted, in this tractor, as work other than tilling work, for example, mowing work in which a mower is attached to the three-point link mechanism 12 or sowing work in which a seeder is attached to the three-point link mechanism 12, In such a case, since the working devices such as the mower and the seeder do not include the grounding body 37 for detecting the working depth, the mechanical linkage unit 18 is in the first linkage state. Then, in mowing work or sowing work, the operator operates the operation tool 35 to switch the change amount conversion mechanism 33 to the second conversion state, so that the load detection member 36 swings back and forth according to the towing load. Is blocked. As a result, it is possible to avoid the possibility that the mower, the seeder, or the like automatically moves up and down according to the towing load during the mowing work or the sowing work.

As shown in FIGS. 3 to 5, 9 to 10 and 12 to 17, the operating tool 35 is in contact with the load detecting member 36 to prevent the load detecting member 36 from swinging forward and backward, and the load detecting member. A plate-shaped contact member 40 that moves to a retracted position that allows the load detection member 36 to swing back and forth without contacting the load 36 is provided. Then, when the contact member 40 is in the retracted position, the load detection member 36 is allowed to swing back and forth according to the pulling load, and the load detection member 36 and the swinging member 38 can integrally swing by the action of the regulation mechanism 52. Thus, the change amount of the traction load is transmitted to the lifting drive unit 17 as the lifting operation amount. Further, when the contact member 40 is in the working position, the front-back swing of the load detection member 36 according to the pulling load is prevented, and the swing member 38 can swing with respect to the load detection member 36 against the action of the regulation mechanism 52. Then, the change amount of the working depth is transmitted to the lifting drive unit 17 as the lifting operation amount.

That is, when the contact member 40 is in the retracted position, the change amount conversion mechanism 33 is in the first conversion state described above, and when the contact member 40 is in the operation position, the change amount conversion mechanism 33 is in the second conversion state described above. Become.

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

As shown in FIGS. 3, 5, 9, and 12 to 17, a plurality of connecting holes 38A for the control cable are formed on the upper side of the swinging member 38. Thereby, the connecting position of the control cable 43 to the swing member 38 can be changed, and by this change, the swing displacement amount of the swing member 38 with respect to the swing displacement amount of the grounding body 37 can be changed. As a result, in the automatic tillage depth control, the responsiveness when the rotary tiller 15B moves up and down can be adjusted in association with the vertical swing of the grounding body 37 according to the tillage depth.

In the present embodiment, two connecting holes 38A are formed in the swinging member 38 as the plurality of connecting holes 38A, but three or more connecting holes 38A are formed in the swinging member 38. It may have been done.

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

As shown in FIGS. 3 to 5 and 9 to 17, the load detection member 36 swings in the front-rear direction on the support bracket 47 fixed to the rear end of the T/M case 5 via the first support shaft 48. It is displaceably supported. The mechanical linkage unit 18 includes a limiting mechanism 50 that limits the front-back swing range of the load detection member 36. The load detection member 36 is held in a reference posture extending vertically upward from the first support shaft 48 by the action of the biasing mechanism 49 and the limiting mechanism 50 described above. Then, when the traction load exceeds the set value, the load detection member 36 swings from the reference posture to the front side of the vehicle body against the action of the urging mechanism 49 in association with the increase of the traction load, and In association with the decrease in the towing load, the urging mechanism 49 causes the vehicle body to swing rearward and return to the reference posture. The free end portion of the load detection member 36 is provided with a second support shaft 51 that swingably supports the swing member 38.

As shown in FIGS. 3 to 10 and 12 to 17, the swinging member 38 is held in a predetermined posture with respect to the load detecting member 36 by the action of the regulation mechanism 52. The swinging member 38 is connected and set so that the predetermined posture of the swinging member 38 corresponds to the lowermost position of the grounding body 37 when the swinging member 38 is linked to the grounding body 37. The second link mechanism 34 described above is pin-connected to the swing member 38 at a portion below the swing fulcrum (second support shaft 51) of the swing member 38. The second link mechanism 34 includes an operation arm 53 that is swingably supported by the linkage portion 27A of the first swing arm 27, an inversion arm 54 that inverts the operation direction, and one end of the operation arm 53 and the inversion arm 54. And a second linking member 56 extending over the other end of the reversing arm 54 and the swinging member 38. The linking portion 27A of the first swing arm 27 is formed in a U shape in plan view. The operation arm 53 swings in the rearward direction of the vehicle body (the direction in which the height setting lever 23 is set to the higher position), so that the operating arm 53 moves from the vehicle body front side (the lower position setting side of the height setting lever 23) to the linkage portion 27A of the first swing arm 27. To contact.

With this configuration, when the change amount conversion mechanism 33 is switched to the first conversion state when the mechanical linkage unit 18 is in the first linkage state, when the traction load increases, the regulation mechanism 52 works in conjunction with this increase. The load detection member 36 and the swinging member 38 swing together to the front side of the vehicle body. Further, when the towing load is reduced, the load detection member 36 and the swinging member 38 swing integrally toward the rear side of the vehicle body by the action of the regulation mechanism 52 in conjunction with this reduction.

When the load detecting member 36 and the swinging member 38 integrally swing toward the front side of the vehicle body, the operation arm 53 swings rearward of the vehicle body in conjunction with this integral swinging, and this swinging causes the operation arm 53 to move. The linking portion 27A of the first swing arm 27 is pushed rearward of the vehicle body. As a result, the first swing arm 27 swings in the rearward direction of the vehicle body, and the spool 22A of the control valve 22 linked to the first swing arm 27 resists the action of the biasing means and moves up from the neutral position to the raised position. (See FIG. 13). As a result, the plow 15A moves up together with the left and right lift arms 20.

Further, when the load detection member 36 and the swing member 38 integrally swing toward the rear side of the vehicle body, the operation arm 53 swings in the front direction of the vehicle body in conjunction with the integral swing, and this swing causes the operation arm 53 to swing. Moves away from the linkage portion 27A of the first swing arm 27 in the vehicle body front direction. As a result, the swing of the first swing arm 27 in the front direction of the vehicle body is allowed, and the spool 22A of the control valve 22 moves from the neutral position to the lowered position by the action of the biasing means. As a result, the plows 15A descend together with the left and right lift arms 20.

On the other hand, when the change amount conversion mechanism 33 is switched to the second conversion state in the second linkage state of the mechanical linkage unit 18, when the plowing depth becomes deep and the grounding body 37 rises, the rocking motion is interlocked with this rise. The moving member 38 independently swings in the backward tilting direction with respect to the load detecting member 36 against the action of the regulation mechanism 52. Further, when the plowing depth becomes shallow and the grounding body 37 descends, the swinging member 38 independently swings in the forward tilting direction with respect to the load detecting member 36 by the action of the regulating mechanism 52 in conjunction with this descending. ..

When the swing member 38 independently swings in the backward tilt direction, the operation arm 53 swings in the rearward direction of the vehicle body in conjunction with this independent swing, and this swing causes the operation arm 53 to move to the first swing arm. The linkage portion 27A of 27 is pushed rearward of the vehicle body. As a result, the first swing arm 27 swings in the rearward direction of the vehicle body, and the spool 22A of the control valve 22 linked to the first swing arm 27 resists the action of the biasing means and moves up from the neutral position to the raised position. (See FIG. 17). As a result, the rotary tiller 15B rises together with the left and right lift arms 20.

When the swing member 38 independently swings in the forward tilt direction, the operation arm 53 swings in the vehicle body front direction in conjunction with this independent swing, and this swing causes the operation arm 53 to move to the first swing arm. It moves away from the linking portion 27A of 27 in the front direction of the vehicle body. As a result, the swing of the first swing arm 27 in the front direction of the vehicle body is allowed, and the spool 22A of the control valve 22 moves from the neutral position to the lowered position by the action of the biasing means. As a result, the rotary tiller 15B descends together with the left and right lift arms 20.

In the first linking state of the mechanical linking unit 18, the feedback link mechanism 26 stops the integral swinging of the load detecting member 36 and the swinging member 38 according to the pulling load due to the raising or lowering of the plow 15A, Interlocking with this swing stop, the spool 22A of the control valve 22 is moved from the raised position or the lowered position to the neutral position. As a result, the plows 15A stop moving up and down together with the left and right lift arms 20.

In the second linked state of the mechanical linkage unit 18 described above, the feedback link mechanism 26 stops the swing when the independent swing of the swing member 38 according to the working depth is stopped by the raising or lowering of the rotary tiller 15B. In conjunction with, the spool 22A of the control valve 22 is moved from the raised position or the lowered position to the neutral position. As a result, the rotary tiller 15B stops moving up and down together with the left and right lift arms 20.

With the above configuration, this tractor is provided with the mechanical linkage unit 18 having the above-described configuration, so that the above-mentioned draft control can be satisfactorily performed when the plowing work by the plow 15A is performed. Further, when the tilling work is performed by the rotary tiller 15B, the above-mentioned automatic tilling depth control can be favorably performed.

As shown in FIGS. 3 to 5, 9 to 10 and 12 to 15, the change amount conversion mechanism 33 has a standard conversion state (see FIGS. 12 to 13) and an amplification conversion state (see FIGS. 14 to 15) as the first conversion state. See) and. The change amount conversion mechanism 33 switches between the standard conversion state and the amplification conversion state by the operation of the operation tool 35 described above. Then, when the change amount conversion mechanism 33 is in the standard conversion state, the load detection member 36 and the swinging member 38 integrally swing due to the action of the regulation mechanism 52, and the swinging of the load detection member 36 back and forth is performed by this integral swinging. The amount of change in the traction load obtained in step 1 is transmitted to the up-and-down drive unit 17 as an up-and-down operation amount without being amplified (see FIGS. 12 to 13). Further, when the change amount conversion mechanism 33 is in the amplification conversion state, relative swing of the load detection member 36 and the swing member 38 against the action of the regulation mechanism 52 is allowed, and this relative swing allows the load detection member 36 to move. The amount of change in the traction load obtained by the forward and backward swing is amplified and transmitted to the elevating drive unit 17 as the elevating operation amount (see FIGS. 14 to 15).

As a result, for example, when performing plowing work with the plow 15A in a standard field where the traction load is unlikely to increase due to soil hardness and the traction load does not fluctuate significantly, the operator operates the operation tool 35. By switching the change amount conversion mechanism 33 to the standard conversion state, the plow 15A can be moved up and down according to the traction load at a standard speed suitable for this field. As a result, it is possible to avoid the engine stall due to the increase in the towing load while performing the draft control in which the change in the working depth is gentle.

In addition, for example, when performing plowing work by the plow 15A in a field where the traction load is likely to be large due to soil hardness and the traction load is likely to vary significantly, the operator operates the operation tool 35 to convert the change amount. By switching the mechanism 33 to the amplification conversion state, the plow 15A can be moved up and down according to the traction load at a high speed suitable for this field. As a result, it is possible to avoid an engine stall resulting from a sharp increase in the traction load.

As shown in FIGS. 3 to 5, FIGS. 9 to 10 and FIGS. 12 to 17, the operation tool 35 includes a roller 60 as a receiving member that moves between the retracted position and the operating position. Then, when the roller 60 is located at the retracted position, the roller 60 moves out of the swing region of the swing member 38, so that the load detection member 36 and the swing member 38 integrally swing due to the action of the regulation mechanism 52. Further, when the roller 60 is located at the working position, the roller 60 enters the swing area of the swing member 38. Then, until the swing member 38 is received by the roller 60, the load detection member 36 and the swing member 38 integrally swing by the action of the regulation mechanism 52. Further, while the swing member 38 is being received by the roller 60, the load detection member 36 and the swing member 38 relatively swing against the action of the regulation mechanism 52.

That is, by providing the operation tool 35 with the roller 60, when the roller 60 is in the retracted position, the standard conversion state of the change amount conversion mechanism 33 in which the load detection member 36 and the swing member 38 integrally swing can be obtained. it can. Further, when the roller 60 is in the operating position, it is possible to obtain the amplification conversion state of the change amount conversion mechanism 33 in which the relative swing between the load detection member 36 and the swing member 38 is allowed.

As shown in FIG. 14, in the amplification conversion state of the change amount conversion mechanism 33, when the load detection member 36 is in the reference posture described above, a gap is secured between the swing member 38 and the roller 60. Therefore, the roller 60 does not receive the swing member 38 until the swing displacement amount of the load detection member 36 based on the traction load from the reference posture reaches a predetermined amount at which the swing member 38 contacts the roller 60. As a result, the load detection member 36 and the swinging member 38 swing together. Then, when the amount of swing displacement of the load detection member 36 from the reference posture becomes equal to or greater than a predetermined amount, the roller 60 receives the swing member 38, so that the load detection member 36 and the swing member 38 relatively swing.

As a result, in a work situation in which the traction load slightly exceeds the set value and engine stall is unlikely to occur, the plow 15A is a standard one depending on the traction load even when the change amount conversion mechanism 33 is in the amplification conversion state. Driven up and down at speed. As a result, even in a work situation in which the towing load slightly exceeds the set value, it is possible to avoid the possibility of lowering the durability of the lifting drive unit 17 due to raising and lowering the plow 15A at a high speed according to the towing load. can do.

As shown in FIG. 15, when the swinging member 38 is in contact with the roller 60 in the amplification conversion state of the change amount conversion mechanism 33, when the towing load increases, the load detecting member 36 is interlocked with this increase. Rocks toward the front side of the vehicle body, and the rocking member 38 relatively rocks in the backward tilt direction against the action of the restricting mechanism 52. When the towing load decreases, the load detecting member 36 swings rearward of the vehicle body in conjunction with this decrease, and the swinging member 38 relatively swings in the forward tilt direction by the action of the restricting mechanism 52.

When the load detection member 36 swings toward the front side of the vehicle body and the swinging member 38 relatively swings toward the rearward tilt direction, the operation arm 53 swings toward the rearward direction of the vehicle body in conjunction with this relative swing. The swing operation causes the operation arm 53 to press the linking portion 27A of the first swing arm 27 rearward of the vehicle body. As a result, the first swing arm 27 swings in the rearward direction of the vehicle body, and the spool 22A of the control valve 22 linked to the first swing arm 27 resists the action of the biasing means and moves up from the neutral position to the raised position. Move to. As a result, the plow 15A moves up together with the left and right lift arms 20.

Further, when the load detection member 36 swings toward the rear side of the vehicle body and the swinging member 38 relatively swings in the forward tilt direction, the operation arm 53 swings forward in the vehicle body in conjunction with the relative swing. This swing causes the operation arm 53 to move away from the linking portion 27A of the first swing arm 27 in the vehicle body front direction. As a result, the swing of the first swing arm 27 in the front direction of the vehicle body is allowed, and the spool 22A of the control valve 22 moves from the neutral position to the lowered position by the action of the biasing means. As a result, the plows 15A descend together with the left and right lift arms 20.

The feedback link mechanism 26, when the relative swing between the load detection member 36 and the swing member 38 according to the pulling load is stopped by the rise or fall of the plow 15A in the amplification conversion state of the change amount conversion mechanism 33 described above, Interlocking with the swing stop, the spool 22A of the control valve 22 is operated from the raised position or the lowered position to the neutral position. As a result, the plows 15A stop moving up and down together with the left and right lift arms 20.

With the above-described configuration, this tractor is provided with the mechanical linkage unit 18 having the above-described configuration, so that it is possible to select draft control that takes into consideration soil hardness, etc., which differs for each field. As a result, it is possible to satisfactorily perform the plowing work with the plow 15A regardless of the hardness of the soil which is different for each field.

As shown in FIGS. 1-2 and 4, the change amount conversion mechanism 33 is disposed in the vehicle body at a position behind the driver's seat 11 and adjacent to the driver's seat 11. Thereby, the operator can easily confirm the conversion state of the change amount conversion mechanism 33 by visually observing the rear part of the driver seat 11 while being seated on the driver seat 11. Further, since the upper portion of the rear portion of the driver's seat 11 is not covered with a cover or the like, the change amount conversion mechanism 33 can be easily maintained.

The operation tool 35 is arranged at a position behind the driver's seat 11 in the vehicle body and adjacent to the driver's seat 11. As a result, the worker can operate the operation tool 35 by extending the hand toward the rear part of the driver's seat 11 while sitting on the driver's seat 11, and the change amount conversion mechanism 33 is converted to the standard. The state, the amplification conversion state, and the second conversion state can be easily switched.

As shown in FIGS. 3 to 5, FIGS. 9 to 10 and FIGS. 12 to 17, the operation tool 35 includes a swing plate 61 which is swingably supported in the left and right directions by the support bracket 47 described above, and a swing plate. An operation handle 62 extending forward from 61 is provided. The contact member 40 described above extends rearward from the left side portion of the swing plate 61. Further, the left and right support members 59 that support the roller 60 described above extend rearward from the right side portion of the swing plate 61. The operation tool 35 swings in the left-right direction about an axis X extending in the front-rear direction. The operation tool 35 is selectively held by the detent mechanism 63 provided over the support bracket 47 and the swing plate 61 at any one of the first operation position, the second operation position, and the third operation position. ..

When the operation tool 35 is held at the first operation position on the right side, the contact member 40 and the roller 60 are located at the retracted position. As a result, the change amount conversion mechanism 33 becomes the standard conversion state of the first conversion states for draft control.

When the operation tool 35 is held at the second operation position in the middle between the left and right, the contact member 40 is located at the retracted position and the roller 60 is located at the working position. As a result, the change amount conversion mechanism 33 is in the amplification conversion state of the first conversion states for draft control.

When the operation tool 35 is held in the third operation position on the left side, the contact member 40 is located at the working position and the roller 60 is located at the retracted position. As a result, the change amount conversion mechanism 33 is in the second conversion state for automatic plowing depth control.

That is, the operator switches the operation position of the operation tool 35 to change the change amount conversion mechanism 33 to the standard conversion state for draft control, the amplification conversion state for draft control, and the second conversion state for automatic plowing control. It can be easily switched to the conversion state.

As shown in FIGS. 3 to 5, 9 to 10 and 12 to 17, when the roller 60 is in the operating position, the rotation axis of the roller 60 is parallel to the swing axis of the swing member 38. Is set to be. With this setting, when the change amount conversion mechanism 33 is in the amplification conversion state, when the swing member 38 slides with respect to the roller 60 due to the relative swing of the load detection member 36 and the swing member 38, the slide is performed. With the movement, the roller 60 rotates in the sliding direction of the swing member 38. As a result, the swing member 38 slides smoothly with respect to the roller 60, and the load detection member 36 and the swing member 38 smoothly swing relative to each other. As a result, the draft control in the amplification conversion state of the change amount conversion mechanism 33 can be smoothly performed.

As shown in FIGS. 3, 5, and 9 to 17, the load detection member 36 includes left and right side wall portions 36A having opposing through holes 36a. The support bracket 47 includes a vertical wall portion 47A connected to the rear portion of the vehicle body, and a U-shaped linking portion 47B that extends rearward from the vertical wall portion 47A and enters between the left and right side wall portions 36A. ing. The linking portion 47B is formed with left and right long holes 47a that are long in the front-rear direction, at positions of the side wall portions 36A facing the through holes 36a. The limiting mechanism 50 described above is configured by the through holes 36a of the load detecting member 36, the long holes 47a of the support bracket 47, and the linking pins 64 inserted into the through holes 36a and the long holes 47a. It is configured. That is, the front-back swing range of the load detection member 36 is limited and set by the front-back length of each elongated hole 47 a formed in the support bracket 47.

The limiting mechanism 50 includes a rubber block 65 fitted in a space between the vertical wall portion 47A of the support bracket 47 and the linking portion 47B. In the rubber block 65, a long hole 65a having a front-rear length shorter than that of the long hole 47a of the support bracket 47 is formed at a position facing the long hole 47a of the support bracket 47. The linking pin 64 is inserted into the long hole 65a.

As a result, when the limiting mechanism 50 limits the back-and-forth swing of the load detection member 36, the linking pin 64 of the limiting mechanism 50 collides with the rubber block 65, so that the linking pin 64 contacts the linking portion 47B of the support bracket 47. It is possible to prevent the generation of noise due to a collision.

As shown in FIGS. 3 to 6 and FIGS. 12 to 17, the mechanical linkage unit 18 includes a sensitivity adjustment mechanism 66 that adjusts the operation sensitivity when the lifting drive unit 17 is interlocked with the swing member 38. The sensitivity adjusting mechanism 66 includes a sensitivity adjusting lever 67 arranged to be able to hold a position at an arbitrary operation position in the operating unit 9, a linking member 69 extending from the sensitivity adjusting lever 67 to a support shaft 68 of the reversing arm 54, and the reversing arm 54. The support member 70, which supports the support shaft 68 so as to be displaceable in the front-rear direction, is provided. When the supporting position of the support shaft 68 by the support member 70 is changed in the front-rear direction by the swinging operation of the sensitivity adjusting lever 67 in the front-rear direction, the sensitivity adjusting mechanism 66 interlocks with this change to make the first swinging motion. The gap 71 between the linking portion 27A of the arm 27 and the operation arm 53 is changed. This makes it possible to adjust the operation sensitivity when the lifting drive unit 17 is interlocked with the swing member 38.

In the sensitivity adjusting mechanism 66, as the above-mentioned gap 71 becomes smaller, the operation sensitivity when the elevating drive unit 17 interlocks with the swing member 38 becomes more sensitive, and when the pulling load exceeds the set value and the plow 15A rises. Responsiveness is improved.

In the sensitivity adjustment mechanism 66, the larger the above-mentioned gap 71, the less sensitive the operation sensitivity when the elevating drive unit 17 is interlocked with the swing member 38, and when the pulling load exceeds the set value and the plow 15A rises. Responsiveness deteriorates.

As a result, for example, as the traction load changes more drastically due to the field conditions such as the undulation of the field, the plow 15A is frequently moved up and down to cause hunting. It is possible to prevent a decrease in the precision of the tilling work due to this.

As shown in FIGS. 3 to 4, 6, and 12 to 17, the support member 70 is fixed to the lower right portion of the seat support member 73 attached to the rear end of the T/M case 5. The support member 70 has a recess 70A that is long in the front-rear direction and extends rearward from the front end of the support member 70, and thus supports the support shaft 68 of the reversing arm 54 so that the position of the support shaft 68 can be changed in the front-rear direction.

As shown in FIGS. 3 to 5, FIGS. 9 to 10, and 12 to 17, the restricting mechanism 52 causes the receiving member 57 that integrally swings with the load detection member 36 and the swinging member 38 to the receiving member 57. An urging unit 58 for oscillating in the pressing direction is provided.

With the above configuration, when the load detection member 36 swings back and forth according to the towing load during the tilling work using draft control, the catch 57 swings integrally with the load detection member 36 and the swing member. 38 is held in a state of being pressed against the catch 57 by the action of the biasing unit 58. Thus, for example, even when the traction load fluctuates drastically and the load detection member 36 rocks back and forth violently during cultivating work, the urging unit 58 acts to rock the load detection member 36. It is possible to suppress excessive swing and swing delay of the member 38.

As a result, even if the traction load fluctuates significantly during the plowing work using the draft control, in the mechanical linkage unit 18, the swinging member 38 causes excessive swinging and swinging delay with respect to the load detecting member 36. Chattering can be made less likely to occur. As a result, it is possible to prevent deterioration of control accuracy in draft control due to chattering.

As shown in FIGS. 3 to 5, 10, and 12 to 17, the urging unit 58 is erected from the load detecting member 36 to the second linking member 56 of the second link mechanism 34 and swings with respect to the load detecting member 36. The first urging mechanism 74 that suppresses the swing of the member 38, and the seat support member 73 that is a fixed member of the vehicle body are installed on the second linking member 56 so as to extend the pulling load increasing direction of the load detection member 36 and the swing member 38. And a second urging mechanism 75 that suppresses swinging to the.

With the above configuration, when the load detection member 36 and the swing member 38 integrally swing, the first biasing mechanism 74 detects the load regardless of whether the load detection member 36 swings back and forth according to the traction load. The force that suppresses the swing of the swing member 38 with respect to the member 36 becomes constant. When the load detecting member 36 and the swinging member 38 relatively swing, the first biasing mechanism 74 swings the swinging member 38 largely with respect to the load detecting member 36 as the traction load increases. As a result, the force that suppresses the rocking of the rocking member 38 in the pulling load increasing direction relative to the load detecting member 36 increases.

On the other hand, in the second urging mechanism 75, both when the load detection member 36 and the rocking member 38 rock integrally, and when the load detection member 36 and the rocking member 38 rock relative to each other. Also, as the load detection member 36 swings in the increasing direction of the traction load as the traction load increases, the force for suppressing the swinging of the load detecting member 36 and the swinging member 38 in the traction load increasing direction increases. Become. In addition, when the load detecting member 36 and the swinging member 38 swing relative to each other, the second biasing mechanism 75 causes the load detecting member 36 to swing greatly in the direction of increasing the towing load, when the load detecting member 36 swings relatively. The larger the swinging member 38 swings with respect to 36, the greater the force that suppresses the swinging of the load detection member 36 and the swinging member 38 in the pulling load increasing direction. As a result, in the second biasing mechanism 75, when the load detection member 36 and the swinging member 38 relatively swing, rather than when the load detection member 36 and the swinging member 38 swing together. The force that suppresses the swing of the load detection member 36 and the swing member 38 in the pulling load increasing direction increases.

In other words, the second urging mechanism 75 loads the load regardless of whether the load detection member 36 and the swing member 38 swing integrally or when the load detection member 36 and the swing member 38 relatively swing. The greater the swing of the detection member 36 in the increasing direction of the traction load, the larger the force that suppresses the swing of the load detecting member 36 and the swinging member 38 in the pulling load increasing direction becomes, and the load detecting member 36 and the swinging motion increase. It functions as a damper that damps the swing of the member 38 in the direction of increasing the traction load.

As a result, the traction load varies greatly regardless of whether the load detection member 36 and the swinging member 38 swing integrally or when the load detection member 36 and the swinging member 38 relatively swing. When the load detection member 36 vibrates back and forth violently, the action of the second biasing mechanism 75 can more effectively suppress excessive rocking and operation delay of the rocking member 38 with respect to the load detection member 36. it can.

Further, when the load detection member 36 and the swing member 38 are relatively swung, if the fluctuation of the traction load is so great that the load detection member 36 and the swing member 38 are relatively swung relatively, Due to the action of the biasing mechanism 74 and the second biasing mechanism 75, excessive swing and swing delay of the swing member 38 with respect to the load detection member 36 can be suppressed more effectively.

Further, since it is not necessary to take the measure when the fluctuation of the towing load becomes severe only by the action of the first urging mechanism 74, the measure can be taken only by the action of the first urging mechanism 74. It is possible to avoid the inconvenience that it becomes difficult for the swinging member 38 to swing with respect to 36.

As a result, chattering in the mechanical linkage unit due to excessive swing and swing delay of the swing member 38 with respect to the load detection member 36, even if the towing load fluctuates significantly during plowing work using draft control. Can be more reliably and preferably less likely to occur. As a result, it is possible to more reliably prevent a decrease in control accuracy in draft control due to chattering.

As shown in FIGS. 3, 5, 9-10, and 12-17, the first urging mechanism 74 includes a first tension spring 76 that extends from the load detection member 36 to the second linkage member 56, and a first tension spring 76. The second tension spring 77 has a diameter smaller than that of the first tension spring 76. The second extension spring 77 extends from the load detection member 36 to the second linkage member 56 through the inside of the first extension spring 76.

With this configuration, the outer diameter of the first biasing mechanism 74 can be made smaller than that in the case where the first biasing mechanism 74 is configured by a single tension spring. As a result, the high tension required for the first urging mechanism 74 can be secured without increasing the size of the first urging mechanism 74, and the inconvenience that the first urging mechanism 74 interferes with the peripheral members, etc. It is easy to avoid.

As shown in FIGS. 3 to 5 and FIGS. 12 to 17, the second urging mechanism 75 is supported by the first boss member 78 and the second linkage member 56 fixed to the seat support member 73 so as to be capable of swinging back and forth. A second boss member 79, a rod 80 installed between the first boss member 78 and the second boss member 79, a compression spring 81 externally fitted to the rod 80, a spring receiver 82 that receives the rear end of the compression spring 81, and , A positioning pin 83 for positioning the spring receiver 82 with respect to the rod 80, and the like. The first boss member 78 slidably supports the front side of the rod 80 and receives the front end of the compression spring 81. The rear end of the rod 80 is pin-connected to the second boss member 79. On the rear end side of the rod 80, three through-holes 80 a that allow the mounting position of the positioning pin 83 with respect to the rod 80 to be changed are formed.

With the above configuration, the second urging mechanism 75 can change the position of the spring receiver 82 in three stages, and thus, for example, the second urging mechanism 75 can change the position of the spring receiver 82 in accordance with the hardness of the soil in the field that differs depending on the region. The urging force of the urging mechanism 75 can be changed in three stages.

As a result, the risk of chattering in the mechanical linkage unit 18 during cultivating work using draft control can be suppressed more reliably and favorably, regardless of the hardness of soil in the field that differs depending on the region.

As shown in FIGS. 1 to 3, 5, 9, and 11 to 17, the load detection member 36 has a long top link 13A (see FIGS. 1, 3, 5, 9, and 11 to 15). The first connecting portion 36B to be connected and the second connecting portion 36C to which the bracket 72 (see FIGS. 2 and 16 to 17) that supports the short top link 13B are connected are provided.

Thereby, for example, when performing the cultivating work by the rotary cultivating device 15B, the specifications of the three-point link mechanism 12 are the standard link specifications including the long top link 13A and the left and right lower links 14, and the short top link 13B and the left and right short links. The special link specification including the lower link 14 can be easily changed.

When the specification of the three-point link mechanism 12 is changed from the standard link specification to the special link specification, the up-and-down drive amount of the rotary cultivator 15B becomes large with respect to the up-and-down operation amount of the up-and-down drive unit 17, and the maximum value of the rotary cultivator 15B is increased. The ascending position becomes higher.

As a result, for example, when performing cultivating work by the rotary cultivating device 15B in a work site with high ridges, the specifications of the three-point link mechanism 12 are changed from the standard link specifications to the special link specifications to overcome the ridges. It is easy to avoid the possibility that the rotary tiller 15B may come into contact with a high ridge when traveling or turning around the ridge.

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

[Another embodiment]
The present invention is not limited to the configurations illustrated in the above embodiments, and other typical embodiments relating to the present invention will be illustrated below.

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

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

[3] The configuration of the mechanical linkage unit 18 can be modified in various ways.
For example, the mechanical linkage unit 18 includes, as the swing member 38, a swing member 38 for draft control that is swingably supported by the load detection member 36, and an automatic tiller that is swingably supported by a support bracket 47. A deep control rocking member 38 is provided, and as the link mechanism 34, a draft control link mechanism 34 that connects the draft control rocking member 38 to the lifting drive unit 17, and an automatic plowing depth control mechanism. And a link mechanism 34 for automatic plowing control for connecting the rocking member 38 of FIG. 1 to the lifting drive unit 17, and by operating the operation tool 35, the load detecting member 36 and the rocking member 38 for draft control are integrated. While swinging, the standard conversion state of the first conversion state in which the swinging member 38 for automatic tilling depth control is prevented from swinging, and the load detecting member 36 and the swinging member 38 for draft control are relatively swung. Amplification conversion state of the first conversion state that prevents the swinging member 38 for automatic plowing depth control, and swinging of the load detection member 36 and the swinging member 38 for draft control and automatic plowing depth control. It may be configured to switch to a second conversion state in which the swinging member 38 for swinging is swung.
For example, the mechanical linkage unit 18 is configured so that the change amount conversion mechanism 33 can be switched between the standard conversion state and the amplification conversion state, and the change amount conversion mechanism 33 cannot be switched to the second conversion state. May be.
For example, the mechanical linkage unit 18 amplifies the amount of change in the traction load obtained by swinging the load detection member 36 back and forth and converts it into a lift operation amount by amplifying it by the relative swing of the load detection member 36 and the swing member 38. It may be configured to transmit the information to the elevating and lowering drive unit 17 only in this state.

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

[5] The configuration of the regulation mechanism 52 can be variously changed.
For example, in the regulation mechanism 52, the first urging mechanism 74 of the urging unit 58 may be installed from the load detection member 36 to the swing member 38.
For example, in the restricting mechanism 52, the first urging mechanism 74 of the urging unit 58 may be configured by a single tension spring that is installed from the load detecting member 36 to the link mechanism 34.
For example, in the restricting mechanism 52, the first urging mechanism 74 of the urging unit 58 has a tension spring provided from the load detection member 36 to the link mechanism 34 and a torsion spring provided from the load detection member 36 to the swing member 38. A spring may be provided.
For example, in the regulation mechanism 52, the second urging mechanism 75 of the urging unit 58 may be provided on the swing member 38 from the fixed member 73 of the vehicle body.
For example, in the restricting mechanism 52, the second urging mechanism 75 of the urging unit 58 may be configured by a gas damper that is installed from the fixed member 73 of the vehicle body to the swinging member 38 or the link mechanism 34.

[6] The fixing member 73 of the vehicle body on which the second urging mechanism 75 is installed includes, for example, the rear end portion of the T/M case 5 for erection of the second urging mechanism 75 in addition to the seat support member 73. It may be a dedicated member attached to the.

The present invention relates to a three-point link mechanism that is vertically swingably connected to a rear part of a vehicle body and that allows a working device including a cultivating device to be attached, and a hydraulic lifting drive that drives the three-point link mechanism up and down. A unit, and a mechanical linkage unit for automatic lifting, which converts the amount of change in the towing load into a lifting operation amount and transmits it to the lifting drive unit during plowing work in which the plowing device is attached to the three-point link mechanism. Can be applied to tractors.

12 3-point link mechanism 13 Top link 15 Tillage device 17 Elevating drive unit 18 Mechanical linkage unit 34 Link mechanism 36 Load detecting member 38 Swing member 49 Biasing mechanism 52 Restricting mechanism 57 Retaining tool 58 Biasing unit 73 Fixing member 74 First biasing mechanism 75 Second biasing mechanism 76 First tension spring 77 Second tension spring

Claims (3)

A three-point link mechanism that is vertically swingably connected to a rear part of the vehicle body and that enables attachment of a working device including a tiller; and a hydraulic lifting drive unit that drives the three-point link mechanism up and down. And a mechanical linkage unit for automatic lifting, which converts the amount of change in the towing load into an elevating operation amount and transmits it to the elevating and lowering drive unit during cultivating work in which the cultivating device is attached to a three-point link mechanism,
The mechanical linkage unit includes a load detecting member that swings back and forth according to a traction load transmitted via a top link of the three-point link mechanism, and a biasing member that swings and urges the load detecting member in a direction of decreasing the traction load. A biasing mechanism, a swinging member swingably supported by the load detecting member, a restricting mechanism that restricts swinging of the swinging member with respect to the load detecting member, the swinging member, and the lifting drive unit. And a link mechanism for interlocking
The regulation mechanism is a tractor including a receiving member that integrally swings with the load detection member, and a biasing unit that swings and biases the swinging member in a direction of pressing the swinging member against the receiving member. The urging unit includes a first urging mechanism that is installed from the load detecting member to the oscillating member or the link mechanism to suppress oscillating of the oscillating member with respect to the load detecting member, and a fixing member of a vehicle body. The tractor according to claim 1, further comprising: a second urging mechanism that is installed on the swing member or the link mechanism and that restrains the load detection member and the swing member from swinging in a pulling load increasing direction. .. The first biasing mechanism includes a first tension spring that is installed from the load detection member to the swing member or the link mechanism, and a second tension spring having a diameter smaller than that of the first tension spring.
The tractor according to claim 2, wherein the second tension spring passes through the inside of the first tension spring and is installed from the load detection member to the swing member or the link mechanism.

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