Tractor

Abstract

To prevent an operation cable from becoming obstruction for operation of a movable member located on a vehicle body rear part side while utilizing an advantage due to use of the operation cable.SOLUTION: A tractor comprises: a lifting and lowering drive unit 9 for lifting- and lowering-driving a three-point link mechanism 20; and a mechanical linkage unit 22 which transmits an oscillation change of a load detection member 21 that oscillates according to a traction load of a work device to the lifting and lowering drive unit 9. The mechanical linkage unit 22 includes an operation cable 47 which cooperates according to an oscillation amount of the load detection member 21. The operation cable 47 is provided such that an upper side end and a lower end side respectively extend along a vertical direction and the lower end side is located on a front side with respect to the upper side end.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 plow or other implement 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 implement during work into a lift operation amount and transmits this to a lift drive unit. Conventionally, the mechanical linkage unit has transmitted changes in the tractive load 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-mentioned conventional configuration, the change in traction load is transmitted to the lift drive unit via the operation cable. Linkage Compared to systems that transmit changes in tractive load by connecting the wheels, this system has the advantage of simplifying the configuration, preventing chattering, and ensuring smooth transmission.

[0006] However, since the operating cable is routed in a curved state after extending toward the rear of the vehicle, there is a high risk that it may come into contact with the three-point link mechanism located at the rear of the vehicle, which could result in the lifting and lowering operation not working properly, which has some disadvantages.

[0007] Therefore, there was a demand for a system that would take advantage of the advantages of using an operating cable while not interfering with the operation of the three-point linkage mechanism located at the rear of the vehicle. [Means for solving the problem]

[0008] A characteristic configuration of a tractor according to the present invention includes a three-point link mechanism connected to the rear of a vehicle body so as to be able to swing up and down and to which a work implement can be attached, a lifting drive unit that drives the three-point link mechanism to move 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 vehicle body and performing ground work, and a mechanical linkage unit that transmits swing changes of the load detection member to the lifting drive unit, and Linkage The operation cable is provided with an operation cable for detecting the load, and the operation cable is provided such that an upstream end of the operation cable on the load detection member side and a downstream end of the operation cable on the lifting drive unit side each extend in a vertical direction or an up-down direction close to the vertical direction, and the downstream end is positioned further forward than the upstream end.

[0009] According to the present invention, swing changes in the load detector are transmitted to the lifting drive unit via the control cable, which is simpler than a system that connects multiple links and facilitates smooth transmission without chattering. The control cable has an upstream end on the load detector side and a downstream end on the lifting drive unit side that each extend vertically or in a vertical direction close to vertical. The downstream end of the control cable is positioned forward of the upstream end, so the entire control cable passes closer to the front of the vehicle body than the upstream end. As a result, the control cable does not protrude toward the rear of the vehicle body, reducing the risk of contact with a three-point linkage or the like located at the rear of the vehicle body, allowing for smooth lifting and lowering of the work equipment.

[0010] Therefore, while taking advantage of the advantages of using an operating cable, it is possible to avoid interfering with the operation of the three-point linkage mechanism located at the rear of the vehicle.

[0011] In the present invention, the mechanical linking unit is provided with a mechanism for detecting the swing of the load detecting member around a swing axis different from the swing axis of the load detecting member. Linkage It is preferable that the device is provided with a swinging operation member that swings in a direction perpendicular to the horizontal axis, the upstream end of the operating cable being connected to the swinging operation member, and the swinging operation member being configured to swing up and down around a horizontal position in response to operation of the operating cable that extends in a vertical direction or an up-down direction close to the vertical direction.

[0012] 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.

[0013] When the swing operation member is swung in response to the operation of the control cable, the swing operation member swings up and down around a horizontal position, so the connecting portion between the control cable and the swing operation member has a small amount of horizontal swing. As a result, at the portion where the outer periphery (outer cable) on the upstream side of the control cable is supported, the sliding portion (inner cable) and the fixed portion (outer cable) do not rub strongly against each other, reducing the risk of wear.

[0014] In the present invention, it is preferable that the mechanical linkage unit is provided with a first relay arm to which the downstream end of the operating cable is connected, and that the first relay arm is configured to swing up and down around a horizontal position in response to operation of the operating cable, which extends along a vertical direction or an up-down direction close to that.

[0015] With this configuration, when the first relay arm is swung in response to operation of the control cable, the first relay arm sways up and down around a horizontal position, so the amplitude of horizontal swing at the connection point between the control cable and the first relay arm is small. As a result, at the point where the outer periphery (outer cable) on the downstream side of the control cable is supported, the sliding portion (inner cable) and the fixed portion (outer cable) do not rub against each other strongly, reducing the risk of wear.

[0016] In the present invention, a second relay arm that swings integrally with the first relay arm; Linkage Linked Linkage a member, and the second relay arm is configured to swing back and forth in accordance with the operation of the operation cable, and Linkage It is preferable that the load detecting member is configured to move back and forth to transmit swing changes of the load detecting member to the lifting drive unit.

[0017] According to this configuration, the operation cable is moved in the up and down direction, Linkage The members can be arranged along the front-rear direction, and the mechanical linking unit can be made compact in the vertical direction.

[0018] In the present invention, the mechanical linking unit is provided with a mechanism for detecting the swing of the load detecting member around a swing axis different from the swing axis of the load detecting member. Linkage It is preferable that the load detection member has a swing operation member that swings relative to the load detection member, a support frame that swingably supports the load detection member is provided in a state supported by the vehicle body frame, a support member that swingably supports the swing operation member is provided in a state supported by the support frame, the operation cable has an inner cable and an outer cable that slidably supports the inner cable by being inserted outside, and the upstream end of the outer cable is supported in a fixed position by the support member.

[0019] According to this configuration, the support member is supported by a firmly installed support frame, and this support member can stably support the swing support member and the upstream end of the outer cable. Furthermore, because the support member that supports the swing support member is used to support the upstream end of the outer cable, there is no need to provide a dedicated member for supporting the outer cable, and the configuration can be simplified by sharing the member.

[0020] In the present invention, it is preferable that the operating cable includes an inner cable and an outer cable that slidably supports the inner cable, and that a bracket that supports the downstream end of the outer cable is provided in a state that the bracket is supported by the vehicle frame.

[0021] According to this configuration, the downstream end of the outer cable can be stably supported by the body frame via the bracket. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. [Figure 2] FIG. 2 is a right side view of the 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

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 .

[0032] 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.

[0033] [Drive lift unit] The lift drive unit 9 includes a hydraulic cylinder 26 as an actuator for driving the left and right lift arms 25 to swing up and down, a hydraulic control valve 27 as a control unit for controlling the supply and discharge of hydraulic oil to the hydraulic cylinder 26, a height setting lever 28 for setting the control target height of the working device 12, and a spool 27A of the hydraulic control valve 27 by operating the height setting lever 28 and the mechanical linkage unit 22. Linkage and a valve operating mechanism 29 for operating the spool 27A on the left and right lift arms 25. Linkage The hydraulic control valve 27 is equipped with a feedback link mechanism 30 that returns the spool 27A to a lowered position toward the front of the vehicle body. The hydraulic control valve 27 is equipped with an internal biasing means (not shown) that biases the spool 27A back to its 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.

[0034] 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.

[0035] The valve operating mechanism 29 is operated by swinging the height setting lever 28. Linkage The valve operating mechanism 29 moves the spool 27A of the hydraulic control valve 27 from the neutral position to the raised position or the lowered position in response to the operation of the mechanical linkage unit 22.

[0036] The feedback link mechanism 30 includes a connecting link 35 extending from the left lift arm 25 toward the front of the vehicle body, an operating member 36 that engages with the other end of the balance arm 33 via the connecting link 35, and the like. When the working device 12 reaches the target height, the feedback link mechanism 30 notifies the user of the arrival of the target height. LinkageThis moves the spool 27A of the hydraulic control valve 27 from the raised or lowered position to the neutral position.

[0037] The operating arm 32 has a long hole 32a formed along the swing direction. Linkage The portion 28a is extended, Linkage Portion 28a is provided with pin 28b that fits into elongated hole 32a and engages with it. When height setting lever 28 is operated to the height-increasing side (rearward), operating arm 32 swings rearward via pin 28b, and spool 27A is operated to the raised position. When hydraulic cylinder 26 operates to raise lift arm 25 to a position corresponding to the set height of height setting lever 28, feedback link mechanism 30 is operated to return spool 27A to the neutral position, and lift arm 25 is maintained at the set height suitable for tilling work.

[0038] 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.

[0039] [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.

[0040] 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. Also, 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 plowing acts on the load detection member 21 via the top link 20b.

[0041] When the traction load becomes large, the load detection member 21 detects the increase in the traction load. Linkage Then, the vehicle body is swung forward from the standard position (standby state) against the biasing force of the coil spring 39, and the traction load is reduced. Linkage Then, the biasing force of the coil spring 39 causes the arm 31 to swing rearward and return to the reference position.

[0042] [Mechanical linkage unit] The mechanical linkage unit 22 is configured to transmit the swing displacement of the load detection member 21 due to the traction load to the operation arm 32 of the valve operation mechanism 29. As shown in FIG. 4, the mechanical linkage unit 22 is provided on the left side of the body frame SF in the left-right direction, and is connected to the load detection member 21. Linkage The first link mechanism 45 is connected to the lift drive unit 9, and is provided on the right side of the body frame SF as the other side in the left-right direction. Linkage The second link mechanism 46 is a linked operation link mechanism, and the first link mechanism 45 and the second link mechanism 46 are Linkage and an operating cable 47 for linking the same.

[0043] The first link mechanism 45 will now be described. As shown in FIGS. 5, 6 and 10, the first link mechanism 45 is provided on the left side of the upper part of the load detection member 21. Linkage and sway Linkage The rear frame 37 is provided with a swing operation member 50 supported by a bracket 49 as a support member fixed to the rear frame 37 so as to be swingable about a horizontal axis.

[0044] Linkage The member 48 is formed in the shape of a strip that is long in the vertical direction, and the 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. Linkage A receiving member 51 is provided at the rear side of the swing fulcrum of the member 48, and when the load detection member 21 swings forward, it is received by the receiving member 51. Linkage Component 48 Linkage The arm is configured to swing forward.

[0045] The swing operation member 50 has an upper arm portion 52 and a lower arm portion 53, and is formed as a plate body formed in 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. Linkage As the member 48 swings forward, Linkage A contact roller 56 supported on the lower end of member 48 is configured to be able to contact the upper arm portion 52, and the end of the operating cable 47 on the load detection member 21 side is connected to the swinging end of the lower arm portion 53.

[0046] The swing operation member 50 has an upper arm portion 52 which is supported by a coil spring 57 attached to a support shaft 55. Linkage Therefore, in the initial state where no traction load is applied, the upper arm portion 52 is Linkage It comes into contact with the member 48 .

[0047] When the load detection member 21 swings forward from the standby position due to the traction load, Linkage The member 48 and the upper arm portion 52 Linkage The lower arm 53 swings forward, and the lower arm 53 swings upward, pulling the operating cable 47 upward. When the pulling load is removed, the lower arm 53 returns to its initial state. The lower arm 53 is configured to swing up and down around a horizontal position in response to the operation of the operating cable 47, which extends in the vertical direction.

[0048] The first link mechanism 45 has a function to detect the swing displacement of the load detection member 21. LinkageThe change amount adjustment mechanism 58 is provided, which can change the amount of relative displacement of the member 48 in two stages. As shown in Figs. 3 to 6, the change amount adjustment mechanism 58 includes a base member 59 supported on the rear frame 37 so as to be rotatable about the longitudinal axis X, a grip operation unit 60 that swings the base member 59, and an operation restriction unit 61 supported on the base member 59. The operation restriction unit 61 moves in accordance with the rotation of the base member 59. Linkage It is possible to switch between a state in which it is positioned within the movement area of ​​the member 48 (the state shown in FIGS. 4 and 5) and a state in which it is positioned outside the movement area.

[0049] When the base member 59 is rotated counterclockwise in FIG. 4 about the longitudinal axis X from the state shown in FIGS. 4 and 5 so that the operation restricting portion 61 is out of the range of movement, Linkage The member 48 swings integrally with the load detection member 21. When the operation restricting portion 61 is located in the movement range, Linkage The upper part of the member 48 above the support shaft 48A comes into contact with the operation restricting portion 61 during the swinging movement. Linkage The amount of operation of the member 48 increases. 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.

[0050] The second link mechanism 46 will now be described. As shown in FIGS. 2 to 4, 7, and 10, the second link mechanism 46 is connected to a linking member 62 having a generally L-shaped configuration in a side view, one end of which is connected to an operation cable 47, and the other end of the linking member 62 is connected to the operation cable 47, which is pushed or pulled in response to the swing of the linking member 62, thereby transmitting the amount of operation. Linkage A push-pull rod 63 extending in the forward and backward directions is connected to the rear end of the push-pull rod 63, and the push-pull rod 63 is connected to the rear end of the push-pull rod 63. Linkage and an operating arm 64 as a downstream swing arm that swings along the valve operating mechanism 29. The operating arm 64 is rotatably supported by the operating arm 32 of the valve operating mechanism 29.

[0051] As shown in Fig. 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] As shown in FIGS. 2 and 7, the spool 27A is connected to the load detection member 21. Linkage The sensitivity adjustment mechanism 72 is provided with a sensitivity adjustment lever 73 provided on the right side of the driver's seat 15, an operating member 74 extending from the sensitivity adjustment lever 73 to the lateral support shaft 67 of the linking member 62, and a support bracket 75 on the vehicle body side 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.

[0057] 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.

[0058] By pushing and pulling the operating member 74 in accordance with the swinging operation of the sensitivity adjustment lever 73, the position of the horizontal support shaft 67 is changed forward and backward along the elongated hole 76. Linkage Then, the gap between the operating arm 64 and the connecting portion 32b of the operating arm 32 is changed, and the spool 27A of the hydraulic control valve 27 is moved relative to the load detection member 21. Linkage The sensitivity of the operation can be adjusted.

[0059] 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. When the sensitivity adjustment lever 73 is operated, the relative position (reference position) between the operating arm 64 and the operating arm 32 when no traction load is applied changes. LinkageWhen the operating arm 64 swings from the reference position, the operating arm 32 can be switched between a state in which it operates sensitively and a state in which it has low response and low sensitivity in response to changes in the reference position.

[0060] 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.

[0061] 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.

[0062] 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).

[0063] 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.

[0064] 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.

[0065] 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.

[0066] [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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] The upstream end of the operation cable 47 is provided so as to extend in the vertical direction or a vertical direction close to it. 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 or a vertical direction close to it. 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.

[0071] 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 vertically or in a vertical direction close to the vertical 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 position of the operation cable 47 can be maintained in a stable state.

[0076] [Another embodiment] Other embodiments will be listed below.

[0077] (1) Instead of the linking member 62 integrally formed in a roughly L-shape, the push-pull rod 63 may be operated by a single swing arm, a support shaft that rotates integrally with the swing arm, and a swing body that is separate from the swing arm.

[0078] (2) The first relay arm 65 (swing arm) may be configured to swing only in a region above the horizontal position or only in a region below the horizontal position.

[0079] (3) The upstream end of the outer cable 47B may be supported by a dedicated support member that is provided separately.

[0080] (4) The mechanical linking units 22 may be arranged together on one side of the body frame SF in the left-right direction or on the other side of the body frame SF in the left-right direction, rather than being distributed between the left and right.

[0081] (5) The operating cable 47 may be routed so as to pass above the PTO shaft 13.

[0082] (6) The load detection member 21 may be configured to be supported so as to be swingable around a horizontal support shaft at the top, or may be configured to be supported so as to be swingable around a vertical axis.

[0083] (7) 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.

[0084] (8) The tractor configuration can be modified in various ways. For example, the tractor may be configured with crawler travel devices instead of the left and right rear wheels, or 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]

[0085] 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]

[0086] 9 Lifting drive unit 12 Work equipment 20 Three-point linkage mechanism 21 Load detection member 22 Mechanical Linkage Unit 47 Control cable 47A inner cable 47B outer cable 49 Support member 50 Swing operation member 63 LinkageMaterials 65 First relay arm 66 Second relay arm 82 Bracket SF body frame

Claims

1. 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 of the load detecting member to the lifting drive unit, The mechanical linkage unit is provided with an operation cable that is linked in accordance with the swing amount of the load detection member, The operating cable is arranged such that the upstream end of the operating cable on the load detection member side and the downstream end of the operating cable on the lifting drive unit side each extend vertically or in a vertical direction close to that, and the downstream end is positioned further forward than the upstream end.

2. the mechanical linkage unit 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, the upstream end of the operation cable is connected to the swing operation member, 2. The tractor according to claim 1, wherein the swing operation member is configured to swing up and down about a horizontal position in response to operation of the operation cable extending in a vertical direction or a direction close to the vertical direction.

3. the mechanical linkage unit is provided with a first relay arm to which the downstream end of the operation cable is connected, 3. The tractor according to claim 1, wherein the first relay arm is configured to swing up and down around a horizontal position in response to operation of the control cable, which extends in a vertical direction or a direction close to the vertical direction.

4. a second relay arm that swings integrally with the first relay arm; an interlocking member interlocked with the second relay arm, The tractor according to claim 3, wherein the second relay arm is configured to swing back and forth in response to operation of the operating cable, and is configured to move the interlocking member back and forth to transmit swing changes of the load detection member to the lifting drive unit.

5. the mechanical linkage unit 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, a support frame that swingably supports the load detection member is provided in a state supported by a vehicle body frame, a support member that supports the swing operation member so that the swing operation member can swing is provided in a state supported by the support frame, The operating cable includes an inner cable and an outer cable that slidably supports the inner cable by being inserted around it, 5. The tractor according to claim 1, wherein an upstream end of the outer cable is supported by the support member in a positionally fixed state.

6. The operating cable includes an inner cable and an outer cable that slidably supports the inner cable by being inserted around it, 6. The tractor according to claim 1, wherein a bracket for supporting a downstream end of the outer cable is provided in a state supported by a body frame.

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