Tractor

Abstract

To prevent reduction in accuracy when transmitting a change in a traction load while utilizing an advantage due to the use of an operation cable.SOLUTION: A tractor comprises: a hydraulic lifting and lowering drive unit 9 for lifting- and lowering-driving a three-point link mechanism; a load detection member 21 which oscillates according to a traction load of a work device; and a mechanical linkage unit 22 which transmits an oscillation change amount of the load detection member 21 to the lifting and lowering drive unit. The mechanical linkage unit 22 includes: a first link mechanism 45 which is provided on one side in a left-right direction of a vehicle body frame SF and is linked to the load detection member 21; a second link mechanism 46 which is provided on the other side in the left-right direction of the vehicle body frame SF and is linked to the lifting and lowering drive unit 9; and an operation cable 47 which links the first link mechanism 45 to the second link mechanism 46.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a tractor equipped with a three-point linkage mechanism for attaching a work implement so that the implement can be raised and lowered. [Background technology]

[0002] The above-mentioned tractor is configured to perform plowing or other work with a work implement such as a plow attached to a three-point linkage mechanism, and is equipped with a mechanical linkage unit for draft control that converts changes in the tractive load acting on the work implement during work into a lift operation amount and transmits this to a lift drive unit. Conventionally, there have been tractors that transmit changes in the tractive load to the mechanical linkage unit via an operation cable (see, for example, Patent Document 1).

[0003] In the device described in Patent Document 1, the entire mechanical linkage unit is arranged in a state where it is offset to one side of the vehicle body in the left-right direction, and the operating cable extends toward the rear of the vehicle body, curves in an arc, and then extends back toward the front of the vehicle body and is connected to a relay link mechanism. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-191843 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-described conventional configuration, changes in traction load are transmitted to the lift drive unit via an operating cable, which has the advantage of simplifying the configuration and preventing chattering, enabling smoother transmission, compared to, for example, a configuration in which changes in traction load are transmitted by connecting multiple links.

[0006] However, because the operating cable is routed in a state where it extends toward the rear of the vehicle body, then curves and returns toward the front of the vehicle body, the operating cable is bent with a small radius of curvature. When routed in this state, excessive force is applied to the bent part with a small radius of curvature when pushing or pulling, and there is a risk that the operating cable will not be able to accurately transmit changes in the traction load.

[0007] Therefore, there has been a demand for a system that can take advantage of the advantages of using an operating cable while preventing a decrease in accuracy when transmitting changes in traction load. [Means for solving the problem]

[0008] The tractor according to the present invention is characterized by the fact that it comprises a body frame, a three-point linkage mechanism connected to the rear of the body so that it can swing up and down and to which a work implement can be attached, a lifting drive unit that drives the three-point linkage mechanism up and down, a load detection member that swings in accordance with the towing load of the work implement when the work implement is towed by the body and performing ground work, and a mechanical linkage unit that transmits the amount of swing change of the load detection member to the lifting drive unit, and the mechanical linkage unit comprises a first linkage mechanism provided on one side of the body frame in the left-right direction and linked to the load detection member, a second linkage mechanism provided on the other side of the body frame in the left-right direction and linked to the lifting drive unit, and an operating cable that links the first linkage and the second linkage.

[0009] According to the present invention, the amount of change in the swing of the load detection member is transmitted to the lifting drive unit via the operation cable, resulting in a simple configuration and easy smooth transmission without chattering. The amount of change in the swing of the load detection member, which swings in response to the traction load, is transmitted from the first link mechanism to the second link mechanism via the operation cable, and then from the second link mechanism to the lifting drive unit. Since the first link mechanism is provided on one side of the body frame in the left-right direction and the second link mechanism is provided on the other side of the body frame in the left-right direction, one end and the other end of the operation cable are spaced apart in the left-right direction.

[0010] As a result, the operating cable is provided in a state in which it makes a large detour from one side of the body frame to the other side in the left-right direction, and is bent in a large radius of curvature, which allows the interlocking operation of the operating cable to be performed smoothly and without strain.

[0011] Therefore, it is possible to prevent a decrease in accuracy when transmitting changes in traction load while taking advantage of the advantages of using an operating cable.

[0012] In the present invention, it is preferable that the first link mechanism is provided with a swing operating member that swings in conjunction with the swing of the load detection member around a swing axis different from the swing axis of the load detection member, and that the end of the operating cable on the load detection member side is connected to the swing operating member.

[0013] According to this configuration, the load detection member and the swing operation member swing around different axes, so that the operating cable is not restricted by the way the load detection member swings and displaces, and it is possible to set up the operating cable so that it can be operated smoothly in conjunction with the swing operation member.

[0014] In the present invention, it is preferable that the operating cable extends in the up-down direction from a connected point at each of a connecting point to the first link mechanism and a connecting point to the second link mechanism.

[0015] With this configuration, the operating cable can be prevented from protruding in the fore-and-aft direction of the vehicle body, and there is less risk of the operating cable coming into contact with the lift arm or three-point link mechanism, etc., allowing for smooth lifting and lowering of the work equipment.

[0016] In the present invention, it is preferable that the operating cable extends from a connection point to the first link mechanism, passes through a rear region of the body frame, and extends to a connection point to the second link mechanism.

[0017] According to this configuration, the operating cable passes through the rear area of ​​the body frame, so it can be routed along the body frame and can be held in a stable position without stretching unstably through the air.

[0018] The present invention In the meantime, The vehicle is provided with a transmission case located at the rear of the vehicle body frame, and a PTO shaft that is provided in a state where it protrudes rearward from the rear of the transmission case and is capable of outputting power to be transmitted to the working device. R, The operating cable extends downward from a position higher than the PTO shaft, passes below the PTO shaft, and extends to a position higher than the PTO shaft. This is preferable.

[0019] According to this configuration Ba, manipulation The operating cable extends downward from a position higher than the PTO shaft, passes under the PTO shaft, and extends to a position higher than the PTO shaft. The PTO shaft is provided at a low position corresponding to the working device in order to output power to the working device.

[0020] By extending the operating cable in this manner, it passes through the area below the PTO shaft, making a large detour and bending it in a large radius of curvature, which allows for smooth operation of the operating cable.

[0021]

[0022] In the present invention, it is preferable that the operating cable is routed along the rear wall of the transmission case, a locking member is provided at a location on the rear wall corresponding to the area below the PTO shaft, and the middle portion of the operating cable is locked and held by the locking member.

[0023] According to this configuration, the operating cable is arranged along the rear wall of the transmission case and is locked and held by a locking member on the lower side of the PTO shaft, so that the operating cable does not extend unstably in the air or swing freely, but can be held in a stable position along the rear wall of the transmission case.

[0024] In the present invention, it is preferable that the operation cable is provided in a state in which an end of the operation cable on the lift drive unit side is located forward of the rear wall of the transmission case.

[0025] According to this configuration, the end of the operation cable on the lift drive unit side is located forward of the rear wall, so the operation cable extends toward the front while following the rear wall, making it easy to avoid the operation cable protruding rearward.

[0026] In the present invention, it is preferable that the operating cable is arranged such that the end of the operating cable facing the load detection member is located on one side of the left-right direction of the transmission case, and the end of the operating cable facing the lifting drive unit is located on the other side of the left-right direction of the transmission case.

[0027] According to this configuration, the operation cable has both end portions spaced apart in the left-right direction, so that the entire cable can be bent in a large circle with a large radius of curvature without strain.

[0028] In the present invention, it is preferable that the operation cable is provided such that the end of the operation cable on the load detection member side and the end of the operation cable on the lifting drive unit side each extend along the vertical direction.

[0029] With this configuration, the operating cable can be prevented from protruding in the fore-and-aft direction of the vehicle body, there is less risk of the operating cable coming into contact with the lift arm or three-point link mechanism, etc., and the lifting and lowering operation of the work device can be performed smoothly. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. [Figure 2] FIG. 2 is a right side view of a main part showing the configuration of the lift drive unit and the mechanical linkage unit. [Figure 3] FIG. 2 is a plan view of the main parts showing the configuration of the lift drive unit and the mechanical linkage unit. [Figure 4] FIG. 2 is a rear view of the main part showing the configuration of the lift drive unit and the mechanical linkage unit. [Figure 5] FIG. 2 is a left side view of a main part showing the configuration of a lift drive unit and a mechanical linkage unit. [Figure 6] FIG. 2 is an exploded perspective view of a main part showing the configuration of a mechanical linkage unit. [Figure 7] FIG. 2 is an exploded perspective view of a main part showing the configuration of a mechanical linkage unit. [Figure 8] FIG. 2 is a cross-sectional plan view of a main part showing the configuration of a mechanical linkage unit. [Figure 9] FIG. 2 is an exploded perspective view showing a valve operating mechanism. [Figure 10] FIG. 2 is a linkage system diagram showing the linkage configuration of a mechanical linkage unit. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the direction indicated by the "F" arrow indicates the front side of the vehicle, the direction indicated by the "B" arrow indicates the rear side of the vehicle, the direction indicated by the "L" arrow indicates the left side of the vehicle, and the direction indicated by the "R" arrow indicates the right side of the vehicle. Therefore, the width direction of the vehicle corresponds to the left-right direction.

[0032] The tractor shown in Figure 1 is equipped with a pair of left and right front wheels 1, a pair of left and right rear wheels 2, a front frame 3, an intermediate frame 4, a clutch housing 5, a transmission case 6, a driver's section 7, and a pair of left and right rear fenders 8.

[0033] A pair of left and right front wheels 1 are journaled on a front frame 3 located at the front of the vehicle body and are located laterally outboard of the front frame 3. A clutch housing 5 is located between the front frame 3 and an intermediate frame 4. A transmission case 6 is connected to the rear end of the intermediate frame 4. The clutch housing 5 and transmission case 6 also serve as the body frame of the tractor. In other words, the front frame 3, intermediate frame 4, clutch housing 5, transmission case 6, etc. are connected together to form the body frame SF of the tractor. A rear support case 10 that supports a lifting drive unit 9 (described later) is provided above the transmission case 6.

[0034] An engine E is mounted and supported on the rear of the front frame 3, and a clutch housing 5 is connected to the lower rear end of the engine E. In addition, a pair of left and right rear wheels 2 are journaled on the transmission case 6, positioned on the left and right outer sides of the transmission case 6.

[0035] Although not shown in the figures, the clutch housing 5 houses a main clutch and other components, the intermediate frame 4 is provided with a transmission shaft, and the transmission case 6 houses a main transmission, an auxiliary transmission, and other components. Power from the engine E is transmitted to a pair of left and right front wheels 1 and a pair of left and right rear wheels 2 via the main clutch, transmission shaft, main transmission, auxiliary transmission, and other components. A PTO shaft 13 is provided that protrudes rearward from the rear of the transmission case 6 and is capable of outputting power to be transmitted to a working device 12.

[0036] The driver's section 7 is located at the rear of the vehicle body and is configured to allow an operator to ride in it. The driver's section 7 is equipped with a steering wheel 14 and a driver's seat 15. Rear fenders 8 are located on the left and right sides of the driver's seat 15 on the outer side of the vehicle body, and the rear fenders 8 cover the left and right rear wheels 2 from above. The transmission case 6 is located below the driver's seat 15.

[0037] A front protective frame 16 is provided at the front-rear intermediate portion of the vehicle body, rising from both the left and right sides of the intermediate frame 4 and extending in a detouring upward direction. Also, a rear protective frame 17 is provided at the rear of the vehicle body, positioned behind the driver's seat 15, rising from the left and right lateral portions of the transmission case 6 and extending in a detouring upward direction. The rear protective frame 17 has left and right legs 18 formed upright from the transmission case 6 and an upper arch portion 19, and is provided lower than the front protective frame 16.

[0038] A three-point linkage 20 is connected to the rear of the transmission case 6 so that it can swing up and down. The three-point linkage 20 has left and right lower links 20a and left and right central top links 20b, and supports a working implement 12 so that it can be raised and lowered. The working implement 12 shown in Figure 1 is a plow. As the working implement 12, for example, a tow-type working implement 12 such as a disc harrow, cultivator, subsoiler, rotary, etc. can be attached, but is not limited to these.

[0039] Left and right lift arms 25 are provided to suspend and support the left and right lower links 20 a of the three-point link mechanism 20 via the left and right lift rods 23 .

[0040] The machine is equipped with a hydraulic lifting drive unit 9 that drives the three-point link mechanism 20 to raise and lower while the working implement 12 is connected, a load detection member 21 that swings in accordance with the towing load of the working implement 12 when the working implement 12 is towed by the vehicle body and performing ground work, and a mechanical linkage unit 22 that transmits swing changes of the load detection member 21 to the lifting drive unit 9.

[0041] [Drive lift unit] The lifting drive unit 9 includes a hydraulic cylinder 26 as an actuator that drives the left and right lift arms 25 to swing up and down, a hydraulic control valve 27 as a control unit that controls the supply and discharge of hydraulic oil to the hydraulic cylinder 26, a height setting lever 28 that sets the control target height of the working device 12, a valve operating mechanism 29 that links a spool 27A of the hydraulic control valve 27 by operating the height setting lever 28 and the mechanical linkage unit 22, and a feedback link mechanism 30 that links the spool 27A to the left and right lift arms 25. The hydraulic control valve 27 includes an internal biasing means (not shown) that biases the spool 27A back to a lowered position toward the front of the vehicle body. The height setting lever 28 is supported by the rear support case 10 so as to be swingable back and forth about the axis of a horizontal lever support shaft 31, and extends above the rear fender 8 to the right of the driver's seat 15.

[0042] As shown in Figures 9 and 10, the valve operating mechanism 29 includes an operating arm 32 that can be swung by operating the height setting lever 28 and the mechanical linkage unit 22, a balance arm 33 that is supported on the spool 27A of the hydraulic control valve 27 so as to be able to swing back and forth around the vertical axis, and an operating member 34 that is swung in conjunction with the swing of the operating arm 32 and is movably engaged with one end of the balance arm 33.

[0043] The valve operating mechanism 29 moves the spool 27A of the hydraulic control valve 27 from the neutral position to the raised position or lowered position in conjunction with the swing operation of the height setting lever 28. The valve operating mechanism 29 also moves the spool 27A in response to the operation of the mechanical linkage unit 22.

[0044] The feedback link mechanism 30 includes a connecting link 35 extending from the left lift arm 25 toward the front of the vehicle body, and an operating member 36 that engages with the other end of the balance arm 33 via the connecting link 35. When the working implement 12 reaches the target height, the feedback link mechanism 30 moves the spool 27A of the hydraulic control valve 27 from the raised or lowered position to the neutral position in response to the reaching of the target height.

[0045] The operating arm 32 has a slot 32a formed in the swing direction. An interlocking portion 28a extends downward and forward from the height setting lever 28, and a pin 28b that fits into the slot 32a is provided in the interlocking portion 28a. When the height setting lever 28 is operated to the height-increasing side (rearward), the operating arm 32 swings rearward via the pin 28b, and the spool 27A is operated to the raised position. When the hydraulic cylinder 26 operates to raise the lift arm 25 to a position corresponding to the set height of the height setting lever 28, the feedback link mechanism 30 is operated to return the spool 27A to its neutral position, and the lift arm 25 is maintained at the set height suitable for tilling work.

[0046] When the operating arm 32 is pulled rearward due to an increase in the traction load by operating the mechanical linkage unit 22 described below, the long hole 32a allows it to swing rearward, allowing the lift arm 25 to be raised.

[0047] [Load detection member] 5 and 6, the load detection member 21 is supported by a rear frame 37 fixed to the rear end of the rear support case 10 so as to be swingably displaceable in the front-to-rear direction via a horizontal support shaft 38 at the bottom. The load detection member 21 is biased to swing toward the rear of the vehicle body by a coil spring 39 provided on the front side. In addition, the range of swinging of the load detection member 21 for the front and rear is limited by a limiting mechanism consisting of an elongated hole 40 formed in the rear frame 37 and a pin 41 provided on the load detection member 21.

[0048] As shown in Fig. 5, the front end of the top link 20b of the three-point linkage 20 is connected to the load detection member 21 via a connecting pin 42. As shown in Fig. 1, the front ends of the left and right lower links 20a are connected to left and right brackets 43 provided at the rear end of the transmission case 6 via left and right connecting pins 44. With this connection structure, the traction load during tilling work acts on the load detection member 21 via the top link 20b.

[0049] When the traction load becomes large, the load detection member 21 swings from the standard position (standby state) toward the front of the vehicle body against the biasing force of the coil spring 39 in conjunction with the increase in the traction load, and swings toward the rear of the vehicle body due to the biasing force of the coil spring 39 in conjunction with the decrease in the traction load, returning to the standard position.

[0050] [Mechanical linkage unit] The mechanical linkage unit 22 is configured to transmit the swing displacement caused by the traction load of the load detection member 21 to the operating arm 32 of the valve operating mechanism 29. As shown in Fig. 4, the mechanical linkage unit 22 is provided with: a first linkage mechanism 45 provided on the left side, which is one side in the left-right direction of the body frame SF, and interlocked with the load detection member 21; a second linkage mechanism 46 provided on the right side, which is the other side in the left-right direction of the body frame SF, as an operating linkage mechanism interlocked with the lift drive unit 9; and an operating cable 47 interlocking and interlocking the first linkage mechanism 45 and the second linkage mechanism 46.

[0051] The first link mechanism 45 will now be described. As shown in Figures 5, 6 and 10, the first link mechanism 45 is provided with an interlocking member 48 that is provided on the left side of the upper part of the load detection member 21 and that swings in conjunction with the load detection member 21, and a swing operating member 50 that is supported so as to be swingable around the horizontal axis by a bracket 49 that serves as a support member fixed to the rear frame 37.

[0052] The interlocking member 48 is formed in the shape of a strip that is long in the vertical direction, and its vertical middle portion is supported by the load detecting member 21 so as to be swingable around the axis of the horizontal support shaft 48A. A receiving member 51 is provided on the load detecting member 21 at a location on the rear side of the swing fulcrum portion of the interlocking member 48, and when the load detecting member 21 swings forward, it is received by the receiving member 51 and the interlocking member 48 swings forward in conjunction with it.

[0053] The swing operation member 50 has an upper arm portion 52 and a lower arm portion 53, and is formed from a plate body formed into a substantially L-shape in side view. The swing operation member 50 is swingably supported at its middle portion by a bracket 49 via a horizontal support shaft 55. The bracket 49 is connected and fixed to the rear frame 37. A contact roller 56 supported on the lower end of the interlocking member 48 is configured to be able to come into contact with the upper arm portion 52 as the interlocking member 48 swings forward, and the swing end of the lower arm portion 53 is connected to the end of the operation cable 47 on the load detection member 21 side.

[0054] The swing operation member 50 is biased by a coil spring 57 attached to a support shaft 55 to rotate the upper arm portion 52 in a direction approaching the interlocking member 48. Therefore, in the initial state where no traction load is applied, the upper arm portion 52 is in contact with the interlocking member 48.

[0055] When the load detection member 21 swings forward from the standby position due to a traction load, the interlocking member 48 and the upper arm 52 swing forward in unison, and the lower arm 53 swings upward, pulling the operation cable 47 upward. When the traction load is removed, the initial state is restored. The lower arm 53 is configured to swing up and down around a horizontal position in response to operation of the operation cable 47, which extends in the vertical direction.

[0056] The first link mechanism 45 is provided with a change amount adjustment mechanism 58 that can change the amount of relative displacement of the interlocking member 48 with respect to the pivotal displacement of the load detection member 21 in two stages. As shown in FIGS. 3 to 6, the change amount adjustment mechanism 58 includes a base member 59 that is supported on the rear frame 37 so as to be rotatable about the longitudinal axis X, a grip operation unit 60 that operates to pivot the base member 59, and an operation restriction unit 61 that is supported on the base member 59. The operation restriction unit 61 is switchable between a state in which it is located within the movement range of the interlocking member 48 as the base member 59 pivots (the state shown in FIGS. 4 and 5) and a state in which it is located outside the movement range.

[0057] 4 and 5 about the longitudinal axis X in the counterclockwise direction in FIG. 4, when the operation regulating unit 61 is moved out of the range of movement, the interlocking member 48 swings integrally with the load detecting member 21. When the operation regulating unit 61 is located within the range of movement, a portion of the interlocking member 48 above the support shaft 48A comes into contact with the operation regulating unit 61 midway through the swing, increasing the amount of operation of the interlocking member 48. This makes it possible to change the amount of operation transmitted to the operating arm 32 in response to the amount of displacement of the load detecting member 21, for example, depending on differences in the hardness of the soil in the field.

[0058] The second link mechanism 46 will now be described. 2 to 4, 7, and 10, second link mechanism 46 is provided with: a linking member 62 that is generally L-shaped in side view and has one end connected to operation cable 47; a push / pull rod 63 extending forward and backward as a linking member that is connected to the other end of linking member 62 and is pushed or pulled in response to the swing of linking member 62 to transmit the amount of operation; and an operating arm 64 that is connected to the rear end of push / pull rod 63 and serves as a downstream swing arm that swings in conjunction with the pushing and pulling. Actuating arm 64 is rotatably supported by operating arm 32 of valve operating mechanism 29.

[0059] 4, a second link mechanism 46 is provided so as to pass through a lateral portion of the lift arm 25. The second link mechanism 46 is provided so as to pass between the right lift arm 25 and the right leg 18 of the rear protective frame 17.

[0060] The linking member 62 is integrally formed in a generally L-shape and includes a first relay arm 65 to which the downstream end of the operation cable 47 is connected, and a second relay arm 66 that swings integrally with the first relay arm 65. The linking member 62 is supported by a support bracket 68 so as to be swingable around the axis of a horizontal support shaft 67 provided in the middle portion.

[0061] The operating cable 47 is connected to the swinging end of the first relay arm 65, and the front end of the push / pull rod 63 is connected to the swinging end of the second relay arm 66. When the linking member 62 swings via the operating cable 47 in response to the swing of the load detection member 21, the push / pull rod 63 is operated, and the operating arm 64 swings by an operating amount corresponding to the swing amount of the load detection member 21. As the operating arm 64 swings, the operating arm 32 swings.

[0062] 2 and 7, there is provided a screw-type distance adjustment unit 69 that can change and adjust the distance between the connection point between the push / pull rod 63 and the second relay arm 66 and the connection point between the push / pull rod 63 and the operating arm 64. Specifically, a threaded portion is formed in the front portion of the push / pull rod 63, and this threaded portion is provided in a state where a cylindrical connector 70 that is supported on the second relay arm 66 so as to be rotatable about a horizontal axis is inserted through this threaded portion.

[0063] Nuts 71 are attached to both the front and rear of the connector 70 on the threaded portion of the push / pull rod 63. By loosening the front and rear nuts 71 and moving the push / pull rod 63 forward or backward, the distance between the connection point between the push / pull rod 63 and the second relay arm 66 and the connection point between the push / pull rod 63 and the operating arm 64 can be changed, and the position can be fixed by tightening the nuts 71 on both sides. The rear end of the push / pull rod 63 is bent approximately 90 degrees in a plan view and pivotally connected to the operating arm 64 so as to be rotatable.

[0064] 2 and 7, a sensitivity adjustment mechanism 72 is provided that adjusts the actuation sensitivity when the spool 27A is interlocked with the load detection member 21. The sensitivity adjustment mechanism 72 includes a sensitivity adjustment lever 73 provided on the right side of the driver's seat 15, an operation member 74 extending from the sensitivity adjustment lever 73 to the lateral support shaft 67 of the linking member 62, and a vehicle-side support bracket 75 that supports the lateral support shaft 67 so that its position can be changed. The sensitivity adjustment lever 73 is supported on the rear support case 10 so as to be swingable back and forth about a lever support shaft 31 that is also shared with the height setting lever 28, and extends above the rear fender 8 to the right of the driver's seat 15. The lever support shaft 31 is provided with a friction retaining portion that retains the sensitivity adjustment lever 73 in any operating position.

[0065] 3 and 8, the support bracket 75 is fixed to the side wall of the rear support case 10 and is bent outward in a generally L-shape in plan view. A long hole 76 that is long in the front-to-rear direction is formed in the outermost vertical surface portion 75a of the support bracket 75. A horizontal support shaft 67 is inserted through this long hole 76 and is provided so as to be movable in the front-to-rear direction along the long hole 76.

[0066] As the sensitivity adjustment lever 73 is swung, the operating member 74 is pushed and pulled, changing the position of the horizontal support shaft 67 back and forth along the elongated hole 76. In conjunction with this, the gap between the operating arm 64 and the connecting portion 32b of the operating arm 32 changes, making it possible to adjust the operating sensitivity when the spool 27A of the hydraulic control valve 27 is connected to the load detection member 21.

[0067] As shown in FIG. 7, the linking portion 32b of the operating arm 32 is provided in a substantially U-shape in plan view, and the operating arm 64 is rotatably supported by a support shaft 64a while positioned inside the linking portion 32b. Operating the sensitivity adjustment lever 73 changes the relative position (reference position) between the operating arm 64 and the operating arm 32 when no traction load is applied. When the operating arm 64 swings from the reference position in conjunction with the load detection member 21, the operating arm 32 can be switched between a state in which it operates sensitively and a state in which it has low responsiveness and low sensitivity in accordance with the change in the reference position.

[0068] 8, a coil spring 77 is provided which rotationally biases the linking member 62 toward the lowering operation side while being fitted onto the horizontal support shaft 67. The coil spring 77 is provided on the inner left-right side of the vertical surface portion 75a of the support bracket 75. The coil spring 77 is configured to rotationally bias the spool 27A of the hydraulic control valve 27 toward the lowered position, i.e., to rotate the first relay arm 65 upward.

[0069] 3 and 7, the operating member 74 is formed in the shape of a strip and is bent midway so that its front side is located on the inner side in the left-right direction and its rear side is located on the inner side in the left-right direction. The front side, to which the sensitivity adjustment lever 73 is connected, is located on the inner side in the left-right direction and is oriented along the front-to-back direction, while the rear side, to which the lateral support shaft 67 is connected, is located on the outer side in the left-to-right direction and is oriented along the front-to-back direction. The intermediate portion between the front side and the rear side is oriented inward in the left-to-right direction as it approaches the front.

[0070] The operating member 74 is positioned on the outer side in the left-right direction of the vertical surface portion 75a of the support bracket 75, supported by the horizontal support shaft 67, and held in position by fastening a nut 78 (see FIG. 8).

[0071] The coil spring 77 is provided so as to be located on the left-right inward side of the rear portion of the operating member 74. The sensitivity adjustment lever 73 is provided so that its base end portion is located on the left-right inward side of the front portion of the operating member 74, but its upper portion is located on the left-right outward side. Therefore, it is provided so as to be located on the left-right outward side of the front portion of the operating member 74.

[0072] The horizontal support shaft 67 is configured to rotate integrally with the linking member 62. Highly wear-resistant washers 79 are provided at the sliding points between the operating member 74 and the rotating parts of the support bracket 75 to prevent wear.

[0073] The sensitivity adjustment lever 73 and the height setting lever 28 are positioned so that their upper portions are close to each other in the left-right direction to facilitate operation from the driver unit 7. The base end portions of the sensitivity adjustment lever 73 and the height setting lever 28 are spaced apart along the axial direction (left-right direction) of the lever support shaft 31. A push-pull rod 63 is provided so as to pass through this spaced apart portion. The push-pull rod 63 is bent at its front-to-rear midpoint so as to pass between the base end portions of the sensitivity adjustment lever 73 and the height setting lever 28. In this way, the second link mechanism 46 rationally arranges each member to make the left-to-right width as compact as possible.

[0074] [Operation cable] 2, 4, 6, and 10, the operation cable 47 includes an inner cable 47A and an outer cable 47B that slidably supports the inner cable 47A by externally fitting it therearound. The upstream end of the operation cable 47 on the load detection member 21 side (hereinafter simply referred to as the upstream end), specifically the upstream end of the inner cable 47A, is connected to the lower arm portion 53 of the swing operation member 50 in the first link mechanism 45. The downstream end of the operation cable 47 on the lift drive unit 9 side (hereinafter simply referred to as the downstream end), i.e., the downstream end of the inner cable 47A, is connected to the first relay arm 65 of the linkage member 62 in the second link mechanism 46.

[0075] As described above, the lower arm portion 53 of the swing operation member 50 to which the operation cable 47 is connected and the first relay arm 65 of the linking member 62 are configured to swing up and down around a horizontal position, and even if the inner wire 46A slides in conjunction with the swing of the lower arm portion 53 or the first relay arm 65, it is possible to prevent the inner wire 46A from sliding strongly against the end of the outer cable 47B and becoming worn.

[0076] 4, the upstream end of outer cable 47B is supported by an outer cable support member 81 fixed to bracket 49. Bracket 49 is fixedly supported by rear frame 37. The downstream end of outer cable 47B is supported by an outer cable support member 82 serving as a bracket fixedly extended from transmission case 6.

[0077] The connection portion between the downstream end of the inner cable 47A and the first relay arm 65 is located closer to the front of the vehicle body than the connection portion between the upstream end of the inner cable 47A and the lower arm portion 53.

[0078] The upstream end of the operation cable 47 is provided so as to extend in the vertical direction. That is, the upstream end of the inner cable 47A and the outer receiving member 81 are provided at positions spaced apart in the vertical direction while substantially overlapping in a plan view. The downstream end of the operation cable 47 is provided so as to extend in the vertical direction. That is, the downstream end of the inner cable 47A and the outer receiving member 82 are provided at positions spaced apart in the vertical direction while substantially overlapping in a plan view.

[0079] 2, 4, and 5, the operation cable 47 is provided such that the upstream end of the operation cable 47 on the load detection member 21 side and the downstream end of the operation cable 47 on the lift drive unit 9 side each extend in the up-down direction. Also, as shown in FIGS. 1 and 3, the operation cable 47 is provided such that the downstream end is located further forward than the upstream end. The downstream end of the operation cable 47 is provided such that it is located further forward of the rear wall 6A of the transmission case 6.

[0080] As shown in FIG. 4, the operating cable 47 extends downward from a position higher than the PTO shaft 13, passes below the PTO shaft 13, and extends to a position higher than the PTO shaft 13.

[0081] That is, the operating cable 47 is arranged so that the upstream end and downstream end are connected and supported by outer support members 81, 82 at locations above the PTO shaft 13, and the middle portion passes through the area below the PTO shaft 13.

[0082] The operation cable 47 is routed along the rear wall 6A of the transmission case 6. A locking member 83 is provided in a location on the rear wall 6A corresponding to the area below the PTO shaft 13, and an intermediate portion of the operation cable 47 is locked and held by the locking member 83. Therefore, the operation cable 47 curves with a large radius of curvature from the first link mechanism 45 toward the second link mechanism 46, passing through an area below the PTO shaft 13.

[0083] The locking member 83 is elongated and has a length in the left-right direction that is approximately the same as the left-right width of the rear wall 6A of the transmission case 6. By locking the lower intermediate portion of the operation cable 47 over a wide range in the left-right direction in this manner, the operation cable 47 can be maintained in a stable position.

[0084] [Another embodiment] Other embodiments are listed below.

[0085] (1) The operating cable 47 may be configured to extend from the connection point to the first link mechanism 45 through the lower area of ​​the body frame SF to the connection point to the second link mechanism 46, or may be configured to pass through the upper side of the body frame SF.

[0086] (2) The operation cable 47 may extend in the front-rear direction from the connecting point to the first link mechanism 45 or the connecting point to the second link mechanism 46, or may extend in the left-right direction.

[0087] (3) The swing operation member 50 may not be provided, and the operation cable 47 may be interlocked with the load detection member 21.

[0088]

[0089] ( 4 ) The middle portion of the operating cable 47 connecting the first link mechanism 45 and the second link mechanism 46 may be routed so as to pass above the PTO shaft 13 .

[0090] ( 5 The load detection member 21 may be supported so as to be swingable around a horizontal support shaft at the top, or may be supported so as to be swingable around a vertical shaft.

[0091] ( 6 As the actuator for driving the three-point link mechanism 20 to move up and down, an electric actuator such as an electric cylinder or an electric motor may be used instead of a hydraulic cylinder.

[0092] ( 7 The tractor configuration can be modified in various ways. For example, it may be configured with crawler travel devices instead of the left and right rear wheels, or it may be configured with crawler travel devices instead of the left and right front wheels and the left and right rear wheels. It may be an electric configuration with an electric motor instead of an engine, or a hybrid configuration with an engine and an electric motor. [Industrial Applicability]

[0093] The present invention is applicable to a tractor equipped with a three-point linkage mechanism that mounts a work implement so that it can be raised and lowered. [Explanation of symbols]

[0094] 6. Transmission case 6A Back wall 9 Lifting drive unit 12 Work equipment 13 PTO shaft 20 Three-point linkage mechanism 21 Load detection member 22 Mechanical Linkage Unit 45 First link mechanism 46 Second link mechanism 47 Control cable 50 Swing operation member 83 Locking member SF body frame

Claims

1. The body frame and a three-point link mechanism connected to the rear of the vehicle body so as to be able to swing up and down and to which a working device can be attached; an elevation drive unit that drives the three-point link mechanism to elevate; a load detection member that swings in response to a towing load of the working device when the working device is towed by the vehicle body and performing ground work; a mechanical linking unit that transmits a swing change amount of the load detecting member to the lifting drive unit, A tractor in which the mechanical linkage unit is provided with a first link mechanism provided on one side of the body frame in the left-right direction and linked to the load detection member, a second link mechanism provided on the other side of the body frame in the left-right direction and linked to the lifting drive unit, and an operating cable that links the first link mechanism and the second link mechanism.

2. The first link mechanism is provided with a swing operation member that swings in conjunction with the swing of the load detection member around a swing axis different from the swing axis of the load detection member, 2. A tractor according to claim 1, wherein an end of the operation cable on the load detection member side is connected to the swing operation member.

3. The tractor according to claim 1 or 2, wherein the operating cable extends in the vertical direction from a connected point at each of a connecting point to the first link mechanism and a connecting point to the second link mechanism.

4. 4. The tractor according to claim 1, wherein the operating cable extends from a connection point to the first link mechanism through a rear region of the body frame to a connection point to the second link mechanism.

5. A transmission case located at the rear of the body frame; a PTO shaft that is provided in a state of protruding rearward from the rear of the transmission case and is capable of outputting power to be transmitted to the working device, 5. The tractor according to claim 1, wherein the operating cable extends downward from a position higher than the PTO shaft, passes below the PTO shaft, and extends to a position higher than the PTO shaft.

6. The operating cable is routed along the rear wall of the transmission case, a locking member is provided at a location of the rear wall corresponding to a region below the PTO shaft, 6. A tractor according to claim 5, wherein an intermediate portion of said operating cable is locked and held by said locking member.

7. The tractor according to claim 6, wherein the operation cable is provided such that an end of the operation cable on the lift drive unit side is located forward of the rear wall of the transmission case.

8. A tractor as described in any one of claims 5 to 7, wherein the operation cable is arranged such that the end of the operation cable facing the load detection member is located on one side of the left-right direction of the transmission case, and the end of the operation cable facing the lifting drive unit is located on the other side of the left-right direction of the transmission case.

9. The tractor according to any one of claims 5 to 8, wherein the operation cable is arranged such that the end of the operation cable on the load detection member side and the end of the operation cable on the lifting drive unit side each extend in the vertical direction.

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