Hydraulic lifting device

Abstract

To provide a hydraulic lifting apparatus which can easily increase a separation distance between a connected implement and the grounding surface.SOLUTION: A hydraulic lifting apparatus 100 includes a lift arm 2, a bracket 3, a draft control lever 8 and a draft control transmission mechanism 40 and can execute draft control. The bracket 3 is provided on a rear end of a case 1 and relatively rotates with respect to the case 1 with the other end side 32 as a fulcrum according to a traction load from a connected top link. The bracket 3 includes attachment parts 35a-c, 36a-c which can be attached with a front side end of the top link. In the ascending / descending directions of the implement, a bracket shaft Z2 is positioned on the upper side with respect to a lift arm shaft Z1, and attachment parts 35a-c, 36a-c having shafts Z3, Z4, Z5 are located on the lower side with respect to the bracket shaft Z2.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The present invention relates to a hydraulic lifting device that raises and lowers a lift arm based on hydraulic pressure.

Background Art

[0002] Conventionally, as a hydraulic lifting device that raises and lowers a lift arm based on hydraulic pressure, for example, the device shown in Patent Document 1 is known. This device includes a hydraulic cylinder and a control valve having a spool, and depending on the position of the spool, the supply and discharge of hydraulic oil to the hydraulic cylinder are permitted and regulated. This device further includes a load detection member and a biasing mechanism. The load detection member is provided at the rear end portion of the transmission case and is capable of connecting the front end portion of the top link. Also, the load detection member is swingable according to the traction load of the implement via the top link. The biasing mechanism biases the load detection member to swing.

[0003] When the load detection member swings according to the traction load, the spool is displaced according to the swing via a transmission mechanism. Then, with the implement being connected, the lift arm rises and falls. Thereby, an implement such as a plow also rises and falls, and an appropriate traction load can be maintained. That is, with the above-described configuration, draft control can be executed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The top link connected to this type of hydraulic lifting device is generally rod-shaped, with a defined front and rear end. When the front end of the top link is connected to the mounting part of the hydraulic lifting device, the rear end is positioned higher than the front end. In this case, assuming that the height of the lift arm's axis of rotation, arm length, and range of motion remain unchanged, the lower the position of the front end of the top link moves when the implement is connected, the higher the lower end of the implement is lifted. That is, the distance between the connected implement and the ground increases. Therefore, by positioning the front end of the top link lower, the distance between the connected implement and the ground can be increased, which is often preferable when operating the work equipment.

[0006] On the other hand, the load detection member described in Patent Document 1 above includes a connecting hole and a support shaft. The connecting hole is configured to connect to the front end of the top link. The support shaft pivotably supports the load detection member at the rear end of the transmission case. In terms of the positional relationship between the connecting hole and the support shaft, the connecting hole is located above the support shaft. Therefore, it is not possible to position the front end of the top link sufficiently downwards, making it difficult to increase the distance between the connected implement and the ground.

[0007] Therefore, in view of the above, the present invention aims to provide a hydraulic lifting device that can easily increase the distance between the connected implement and the ground. [Means for solving the problem]

[0008] The technical means of the present invention for solving this technical problem is characterized by the following: The hydraulic lifting device of the present invention comprises a case, a hydraulic cylinder located inside the case and driven in accordance with the supply and discharge of hydraulic fluid, a control valve located inside the case and having a spool in the flow path of the hydraulic fluid, which allows and restricts the supply and discharge of the hydraulic fluid to the hydraulic cylinder according to the position of the spool, a lift arm located outside the case and having one end and the other end defined, wherein the one end is configured to be connectable to an object, and the lift arm is configured to be able to lift and lower the connected object by rotating relative to the case with the other end as a pivot point when the hydraulic cylinder is driven, and a bracket located outside the case and having one end and the other end defined, wherein the one end is configured to be connectable to an object, and the connected object The device comprises: a bracket that rotates relative to the case with the other end as a pivot point in response to a towing load from an object; a draft control lever located outside the case and configured to be displaceable in response to operator operation; a draft feedback rod located outside the case and configured to be displaceable in response to the relative rotation of the bracket; and a draft control transmission mechanism that, when the draft control lever is operated, transmits the displacement of the draft control lever toward the spool and displaces the spool toward the side that allows the supply and discharge of the hydraulic fluid, and when the bracket rotates relative to the spool, transmits the displacement of the draft feedback rod toward the spool and displaces the spool toward the side that restricts the supply and discharge of the hydraulic fluid. The lift arm comprises a lift arm axis which is the axis of relative rotation with respect to the case and extends in a second direction perpendicular to a first direction which is the direction in which the object moves up and down, and the bracket comprises a bracket axis which is the axis of relative rotation with respect to the case and extends in the second direction and is located parallel to the lift arm axis, and a mounting portion which is configured to be able to attach the object and is located below the bracket axis in the first direction.

[0009] In the hydraulic lifting device, the bracket is configured such that the bracket axis is located below the lift arm axis in the first direction.

[0010] In the hydraulic lifting device, the bracket is configured such that the bracket axis is located above the lift arm axis in the first direction.

[0011] The hydraulic lifting device further comprises a bracket shaft, which pivotally supports the other end of the bracket in the case and is arranged coaxially with the bracket axis, and is configured to generate a biasing force when it rotates relative to the traction load.

[0012] In the hydraulic lifting device, the draft control transmission mechanism includes: a first draft control shaft that rotates around an axis in accordance with the displacement of the draft control lever when the draft control lever is operated; a second draft control shaft located above the first draft control shaft in the lifting direction of the object, and that rotates around an axis in accordance with the displacement of the draft feedback rod when the bracket rotates relative to it; and a draft control cam that, when the first draft control shaft rotates, displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid in accordance with the rotation of the first draft control shaft, and when the second draft control shaft rotates, displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid in accordance with the rotation of the second draft control shaft.

[0013] In the hydraulic lifting device, the draft control lever has one end and the other end defined, the one end being configured to be operable by the operator, and the other end being configured to be rotatable relative to the case with respect to the operation, with the other end as the pivot point. The first draft control shaft is connected to the other end of the draft control lever and comprises a same-direction rotating shaft configured to be rotatable in the same direction as the rotation direction of the draft control lever, a reverse-direction rotating shaft connected to the draft control cam and configured to be rotatable in the opposite direction to the rotation direction of the draft control lever, and a rotation transmission unit that transmits the rotation of the same-direction rotating shaft toward the reverse-direction rotating shaft when the draft control lever rotates relative to the other shaft, and rotates the reverse-direction rotating shaft in the opposite direction to the rotation direction of the same-direction rotating shaft.

[0014] The hydraulic lifting device includes a position control lever located outside the case and configured to be displaceable in response to operator operation; a position feedback rod located outside the case and configured to be displaceable in response to the relative rotation of the lift arm; and a position control transmission mechanism that, when the position control lever is operated, transmits the displacement of the position control lever toward the spool and displaces the spool toward the side that allows the supply and discharge of the hydraulic fluid, and when the lift arm rotates relative to the spool, transmits the displacement of the position feedback rod toward the spool and displaces the spool toward the side that restricts the supply and discharge of the hydraulic fluid. The position control transmission mechanism further comprises: a first position control shaft that rotates around an axis in accordance with the displacement of the position control lever when the position control lever is operated; a second position control shaft located above the first position control shaft in the lifting direction of the object, and that rotates around an axis in accordance with the displacement of the position feedback rod when the lift arm rotates relative to it; and a position control cam that, when the first position control shaft rotates, displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid in accordance with the rotation of the first position control shaft, and when the second position control shaft rotates, displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid in accordance with the rotation of the second position control shaft.

[0015] The hydraulic lifting device further comprises: a first displacement transmission unit connected to the second draft control shaft so as to be integrally rotatable and to the draft feedback rod so as to be relative to the bracket, which rotates the second draft control shaft in accordance with the displacement of the draft feedback rod when the bracket rotates relative to the bracket; a second displacement transmission unit connected to the second position control shaft so as to be integrally rotatable and to the position feedback rod so as to be relative to the position feedback rod, which rotates the second position control shaft in accordance with the displacement of the position feedback rod when the lift arm rotates relative to the bracket; and a third displacement transmission unit configured to contact and press against the first displacement transmission unit and to rotate relative to the case in conjunction with the rotation of the second displacement transmission unit, which rotates relative to the case and presses against the first displacement transmission unit while contacting it when the position feedback rod is displaced and the second displacement transmission unit rotates, thereby rotating the first displacement transmission unit.

[0016] In the hydraulic lifting device, either the first draft control shaft or the first position control shaft has a hollow structure and is configured to allow the other to be coaxially fitted into the interior of the first, and either the second draft control shaft or the second position control shaft has a hollow structure and is configured to allow the other to be coaxially fitted into the interior of the first, and the draft control transmission mechanism and the position control transmission mechanism are configured such that the other is coaxially fitted into either the first draft control shaft or the first position control shaft, and the other is coaxially fitted into either the second draft control shaft or the second position control shaft, so that the first draft control shaft and the first position control shaft rotate relative to each other about an axis in response to the displacement of either the draft control lever or the position control lever, and the second draft control shaft and the second position control shaft rotate relative to each other about an axis in response to the displacement of either the draft feedback rod or the position feedback rod.

[0017] The hydraulic lifting device further comprises: a pump lever located outside the case and configured to be displaceable from a first position, which is any position while the supply and discharge of the hydraulic fluid is restricted by the control valve, to a second position different from the first position, in response to the operator's operation; and a pump transmission mechanism that, when the pump lever is operated to be displaced from the first position to the second position, transmits the displacement of the pump lever to the spool and displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid, and when the lift arm rotates relative to the pump lever while it is in the second position, transmits the displacement of the position feedback rod to the spool and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid. The pump transmission mechanism includes a pump shaft that rotates around an axis in accordance with the displacement of the pump lever when the pump lever is operated and displaced from the first position to the second position, and a pump cam that, when the pump shaft rotates, displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid in accordance with the rotation of the pump shaft, and when the second position control shaft rotates, displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid in accordance with the rotation of the second position control shaft.

[0018] In the hydraulic lifting device, the pump lever has one end and the other end defined, the one end is configured to be operable by the operator, and the other end is configured to be rotatable relative to the case with respect to the operation, with respect to the other end as the pivot point, and the pump lever is provided with a rotation restricting part that restricts the relative rotation of the pump lever. [Effects of the Invention]

[0019] According to the present invention, the distance between the connected implement and the ground can be easily increased. [Brief explanation of the drawing]

[0020] [Figure 1]It is an overall perspective view of a hydraulic lifting device according to a first embodiment of the present invention. [Figure 2] It is a right side view of the hydraulic lifting device shown in FIG. 1. [Figure 3] It is a left side view of the hydraulic lifting device shown in FIG. 1. [Figure 4] It is a bottom view of the hydraulic lifting device shown in FIG. 1. [Figure 5] It is a perspective view showing a part of the drive system inside the case of the hydraulic lifting device shown in FIG. 1. [Figure 6] It is a perspective view showing a part of the drive system inside the case of the hydraulic lifting device shown in FIG. 1. [Figure 7] It is a left side view of the rear side of the hydraulic lifting device shown in FIG. 1, and is a view showing the positional relationship of each shaft. [Figure 8] It is an overall perspective view of each transmission mechanism in the hydraulic lifting device shown in FIG. 1. [Figure 9] It is an enlarged view of the main part showing the positional relationship of each cam and spool in the hydraulic lifting device shown in FIG. 1. [Figure 10] It is an overall view of the position control transmission mechanism in the hydraulic lifting device shown in FIG. 1. [Figure 11] It is an overall view of the pump transmission mechanism in the hydraulic lifting device shown in FIG. 1. [Figure 12] It is an overall view of the draft control transmission mechanism in the hydraulic lifting device shown in FIG. 1. [Figure 13] It is an overall schematic view showing the positional relationship of the components of each transmission mechanism in the hydraulic lifting device shown in FIG. 1. [Figure 14] It is a left side view of a hydraulic lifting device according to a second embodiment of the present invention. [Figure 15] It is a left side view of the rear side of the hydraulic lifting device shown in FIG. 14, and is a view showing the positional relationship of each shaft. [Figure 16] It is a perspective view showing the configuration near the front end of each feedback rod in the hydraulic lifting device shown in FIG. 14. [Figure 17] It is an overall schematic view showing the positional relationship of the components of each transmission mechanism in the hydraulic lifting device shown in FIG. 14. [Figure 18] Figure 14 shows the component diagrams of the position feedback rod, second displacement transmission mechanism, third displacement transmission mechanism, and fourth displacement transmission mechanism in the hydraulic lifting device. [Figure 19] Figure 14 shows the component configuration diagram of the draft feedback rod and the first displacement transmission mechanism in the hydraulic lifting device. [Modes for carrying out the invention]

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0022] [First Embodiment] First, a first embodiment of the present invention will be described.

[0023] <Overall configuration of the hydraulic lifting system> Figure 1 is an overall perspective view of the hydraulic lifting device 100 according to the first embodiment of the present invention. Figures 2 and 3 are side views of the hydraulic lifting device 100. Figure 4 is a bottom view of the hydraulic lifting device 100. The left / right, up / down, and front / back arrows shown as appropriate in each figure correspond to the left direction / right direction, the up direction / down direction, and the front direction / rear direction, respectively.

[0024] The hydraulic lifting device 100 is mounted on an agricultural vehicle such as a tractor. More specifically, the hydraulic lifting device 100 is mounted at the rear of the tractor or the like, on top of the transmission case. One end 21 of the lift arm 2 and one end 31 of the bracket 3 protrude rearward from the mounted hydraulic lifting device 100. One end 21 of the lift arm 2 is connected to the lower link via a lift link. The end of the top link is connected to one end 31 of the bracket 3. An implement is connected to the rear of the top link and the lower link. The connected implement can be raised and lowered vertically relative to the agricultural vehicle via the top link and the lower link as the lift arm 2 rotates relative to the case 1. In this embodiment, the direction of raising and lowering of the implement corresponds to the vertical direction and corresponds to the first direction.

[0025] As shown in Figures 1 to 4, the hydraulic lifting device 100 comprises a case 1, a lift arm 2, a lift arm shaft 23, a bracket 3, a bracket shaft 33, a hydraulic cylinder 4, a control valve 5, a position control lever 6, a pump lever 7, a draft control lever 8, a position feedback rod 9, and a draft feedback rod 10. Bracket 3 will be described in detail later. The hydraulic lifting device 100 also comprises a position control transmission mechanism 20, a pump transmission mechanism 30, and a draft control transmission mechanism 40. Each of the transmission mechanisms 20, 30, and 40 will also be described in detail later.

[0026] Case 1 is an enclosure, and its bottom surface is open. Two lift arms 2 are located on the left and right sides, one on each side, at the rear outside of Case 1. Each lift arm 2 has a defined end 21 and other end 22. The end 21 is configured to be connectable to a lift link (not shown). The other end 22 is pivotally supported at both ends of a lift arm shaft 23 that penetrates both sides of Case 1 from the inside (see Figures 5 and 6). Each lift arm 2 protrudes rearward from the other end 22 toward the one end 21. When the hydraulic cylinder 4 is driven, each lift arm 2 rotates relative to Case 1 with the other end 22 as the pivot point. That is, with the other end 22 as the pivot point, the one end 21 can swing vertically.

[0027] As shown in Figures 1, 5, and 6, the lift arm 2 is equipped with a lift arm axis Z1, which is the axis of rotation relative to the case 1. In this embodiment, the direction of the lift arm axis Z1 corresponds to the left-right direction and is the second direction. The direction of the lift arm axis Z1 (second direction) is perpendicular to the upward and downward direction of the implement (first direction). The lift arm shaft 23 is arranged coaxially with the lift arm axis Z1.

[0028] Figures 5 and 6 show a part of the drive system inside the case 1. As shown in Figures 4 to 6, the hydraulic cylinder 4 is connected to a hydraulic fluid circuit (not shown) and is driven in accordance with the supply and discharge of the hydraulic fluid. The hydraulic cylinder 4 contains a piston 41 and a piston rod 42. In accordance with the supply and discharge of hydraulic fluid inside the hydraulic cylinder 4, the piston 41 and piston rod 42 move relative to the case 1 in the front-rear direction. In the internal space of the case 1, the rear end of the piston rod 42 is connected to the rotating tip of the crank arm 43. Also, the pivot point of the crank arm 43 is connected to the center of the lift arm shaft 23 in the left-right direction. As a result, the relative movement of the piston 41 and piston rod 42 in the front-rear direction is converted into rotation of the lift arm shaft 23.

[0029] As shown in Figure 4, the hydraulic cylinder 4 is positioned within the internal space of the case 1 such that the axes of the piston 41 and piston rod 42 are aligned in the front-rear direction and are positioned towards the front left. The space between the hydraulic cylinder 4 and the upper and right inner walls of the case 1 houses parts of the transmission mechanisms 20, 30, and 40, which will be described later. A hydraulic fluid control valve 5 is housed between the hydraulic cylinder 4 and the right inner wall of the case 1.

[0030] The control valve 5 has a hydraulic fluid passage formed inside and is interposed in the hydraulic fluid circuit. Other components connected to and interposed in this circuit include a hydraulic pump, relief valve, flow path switching valve, safety valve, and drop control valve. These components are either integrated with the case 1 or are separate components. The control valve 5 is located to the right of the hydraulic cylinder 4 within the internal space of the case 1. The control valve 5 has a spool 51 within the hydraulic fluid passage. The front end 51a of the spool 51 is exposed outside the hydraulic fluid passage of the control valve 5. The spool 51 is displaceable in the front-rear direction relative to the housing of the control valve 5. The spool 51 is constantly biased forward by a spring.

[0031] The front end 51a of the spool 51 is pressed backward against the biasing force by the cams of the transmission mechanisms 20, 30, and 40. At this time, the position of the spool 51 is displaced backward, allowing the supply of hydraulic fluid to the hydraulic cylinder 4. As hydraulic fluid is supplied to the hydraulic cylinder 4, the piston 41 and piston rod 42 are displaced, and the lift arm 2 rotates relative to them via the crank arm 43 and lift arm shaft 23. On the other hand, when the pressing by the cams of the transmission mechanisms 20, 30, and 40 is released, the position of the spool 51 is displaced forward along the biasing force, restricting the supply of hydraulic fluid to the hydraulic cylinder 4. As a result, the displacement of the piston 41 and piston rod 42, and the rotation of the crank arm 43 and lift arm shaft 23 are restricted, and the position (height) of the lift arm 2, which was rotating relative to it, is fixed.

[0032] As shown in Figures 1 and 2, the position control lever 6, the pump lever 7, and the draft control lever 8 are located on the outside and right side of the case 1, and are positioned in front of the lift arm 2. The position control lever 6 has one end 61 and the other end 62. The one end 61 is configured to be operable by the operator. The other end 62 is pivotally supported at the right end of the first position control shaft 220, which penetrates the right side from inside the case 1 (see Figures 8 and 10). The position control lever 6 protrudes upward from the other end 62 toward the one end 61. When the one end 61 of the position control lever 6 is operated by the operator, it rotates relative to the case 1 with the other end 62 as the pivot point, as a displacement corresponding to the operation. That is, the one end 61 can swing in the front-rear direction with the other end 62 as the pivot point.

[0033] In the pump lever 7, one end 71 and the other end 72 are defined. The one end 71 is configured to be operable by the operator. A grip (not shown) that can be grasped by the operator may be provided separately. The other end 72 is pivotally supported at the right end of the pump shaft 320 that penetrates the right side from inside the case 1 (see Figures 8 and 11). The pump lever 7 protrudes upward from the other end 72 toward the one end 71. The other end 72 of the pump lever 7 is located above the other end 62 of the position control lever 6. When the one end 71 of the pump lever 7 is operated by the operator, it rotates relative to the case 1 with the other end 72 as the pivot point, as a displacement corresponding to the operation. That is, the one end 71 can swing in the front-rear direction with the other end 72 as the pivot point. More specifically, the pump lever 7 is configured to be displaceable from a first position, which is any position when the supply and discharge of hydraulic fluid is restricted by the control valve 5, to a second position different from the first position, in response to the operator's operation.

[0034] Here, "the state in which the supply and discharge of hydraulic fluid is restricted by the control valve 5" refers, for example, to the state after the position of the spool 51 has been displaced toward the side that restricts the supply and discharge of hydraulic fluid due to the displacement of the position feedback rod 9. The relationship between "first position" and "second position" is that the positions of the one end 71 are different from each other. For example, the one end 71 in the second position may be located in front of or behind the one end 71 in the first position. The position of the spool 51 is displaced toward the side that allows the supply and discharge of hydraulic fluid due to the movement of the one end 71.

[0035] The pump lever 7 has a detent mechanism to prevent the relative rotation from returning. In this embodiment, the detent mechanism functions only on the downward side of the pump lever 7, but it may also function on the upward side of the pump lever 7. In addition to the detent mechanism, the pump lever 7 is equipped with a rotation restricting part 74 that restricts the relative rotation of the pump lever 7. The rotation restricting part 74 may be indirectly fixed to the case 1, for example, via a plate 73 provided on the case 1. The rotation restricting part 74 is equipped with a protruding member 74a that protrudes forward. The protruding member 74a is located behind the pump lever 7, and the front end of the protruding member 74a can intersect with the radial trajectory of the pump lever 7. Therefore, if one end 71 is continuously swung backward, the pump lever 7, which rotates counterclockwise relative to the pump lever 7 in Figure 2, will eventually come into contact with the front end of the protruding member 74a. At this time, the relative rotation of the pump lever 7 is restricted. As a result of restricting relative rotation, the lifting height of the connected implements can be easily adjusted to any desired position.

[0036] Furthermore, the position of the front end of the protruding member 74a can be adjusted in the front-rear direction by a length adjustment mechanism such as a screw. That is, the position in which the pump lever 7 contacts the protruding member 74a can also be adjusted in the front-rear direction. Therefore, the relative rotation of the pump lever 7 is restricted further forward as the position of the front end of the protruding member 74a is displaced further forward.

[0037] In the draft control lever 8, one end 81 and the other end 82 are defined. The one end 81 is configured to be operable by the operator. The other end 82 is pivotally supported at the right end of the first draft control shaft 420, which penetrates the right side from inside the case 1 (see Figures 8 and 12). The draft control lever 8 protrudes upward from the other end 82 toward the one end 81. The other end 82 of the draft control lever 8 is coaxially positioned with respect to the other end 62 of the position control lever 6. The draft control lever 8 is located to the left of the position control lever 6. When the one end 81 of the draft control lever 8 is operated by the operator, it rotates relative to the case 1 with the other end 82 as the pivot point, as a displacement corresponding to the operation. That is, the one end 81 can swing in the front-rear direction with the other end 82 as the pivot point.

[0038] As shown in Figures 3 to 6, the position feedback rod 9 and the draft feedback rod 10 are located on the outside of the case 1, on the left side, and each extends in the front-rear direction. The rear end 91 of the position feedback rod 9 is rotatably connected to the lower end of the cam 24. The cam 24 is coaxially fixed to the lift arm shaft 23 of the left lift arm 2 and protrudes downward. When the lift arm 2 rotates relative to the case 1, the cam 24 also rotates integrally, and the lower end of the cam 24 swings in the front-rear direction. Accordingly, the position feedback rod 9 is displaceable in the front-rear direction.

[0039] The front end 92 of the position feedback rod 9 is rotatably connected to the lower end of the cam 230a. The cam 230a is pivotally supported at the left end of the second position control shaft 230, which penetrates the left side from inside the case 1 and protrudes downward (see Figures 8 and 10). When the position feedback rod 9 is displaced in the longitudinal direction, the lower end of the cam 230a swings in the longitudinal direction, allowing the second position control shaft 230 to rotate relative to it.

[0040] The rear end 101 of the draft feedback rod 10 is connected to the lower end of the joint 34. The joint 34 is integrally fixed to the left side plate 35 of the bracket 3 and protrudes downward to the left. When the bracket 3 rotates relative to the case 1, the joint 34 also rotates integrally, and the lower end of the joint 34 swings in the front-rear direction. Accordingly, the draft feedback rod 10 is displaceable in the front-rear direction.

[0041] The front end 102 of the draft feedback rod 10 is rotatably connected to the lower end of the cam 430a. Part of the front end 102 is composed of a spring 102a. The cam 430a is pivotally supported at the left end of the second draft control shaft 430, which penetrates the left side from inside the case 1, and protrudes downward to the left (see Figures 8 and 12). The connection position of the front end 102 to the cam 430a is higher than the connection position of the front end 92 of the position feedback rod 9 to the cam 230a. When the draft feedback rod 10 is displaced in the front-rear direction, the lower end of the cam 430a swings in the front-rear direction, allowing the second draft control shaft 430 to rotate relative to it. In particular, when the draft feedback rod 10 is displaced forward, the spring 102a compresses slightly from its mounting length, and the cam 430a swings forward while being biased by the spring 102a. On the other hand, when the draft feedback rod 10 is displaced rearward, the spring 102a does not interfere (does not stretch).

[0042] <Bracket configuration> As shown in Figures 1, 5, and 6, the bracket 3 is located behind the other end 22 of the lift arm 2 and at the outer rear end of the case 1. The bracket 3 has one end 31 and the other end 32. The one end 31 is configured to be connectable to a top link (not shown). In other words, in this embodiment, the bracket 3 is a so-called top link bracket. The other end 32 is pivotally supported by a bracket shaft 33 connected to both ends of the case 1. The bracket 3 rotates relative to the case 1 with the other end 32 as the pivot point in response to the traction load from the connected top link (i.e., implement).

[0043] Bracket 3 is equipped with a bracket axis Z2, which is the axis of rotation relative to case 1. The bracket axis Z2 is located parallel to the lift arm axis Z1. In this embodiment, the direction of the bracket axis Z2 corresponds to the left-right direction and is the second direction. The direction of the bracket axis Z2 (second direction) is perpendicular to the upward and downward direction of the implement (first direction). The bracket shaft 33 is arranged coaxially with the bracket axis Z2.

[0044] Bracket 3 comprises a left plate 35 and a right plate 36. The left plate 35 and the right plate 36 are positioned at the outer rear end of case 1, to the left and right of approximately the center in the left-right direction, respectively. The surfaces of the left plate 35 and the right plate 36 are parallel to each other and face each other with a predetermined distance between them. The left plate 35 and the right plate 36 each have substantially the same shape, extending to the rear from the other end 32 and further projecting toward one end 31 diagonally downward and rearward.

[0045] Bracket 3 also includes mounting parts 35a, 35b, 35c, 36a, 36b, 36c and link pins 37. Mounting parts 35a, 35b, and 35c are circular through holes and are provided on the left side plate 35. Mounting parts 36a, 36b, and 36c are circular through holes and are provided on the right side plate 36. Mounting parts 35a and 36a are arranged coaxially with the left-right axis Z3. Mounting parts 35b and 36b are arranged coaxially with the left-right axis Z4. Mounting parts 35c and 36bc are arranged coaxially with the left-right axis Z5. Axes Z3, Z4, and Z5 are each located parallel to the bracket axis Z2.

[0046] The link pin 37 can be coaxially fitted to one set selected from among the mounting portions 35a, 36a, mounting portions 35b, 36b, and mounting portions 35c, 36c. As an example, the diagram shows the link pin 37 fitted to the mounting portions 35c, 36c. When attaching the top link to the bracket 3, the fitting holes of the top link end are coaxially positioned between the selected set of mounting portions 35a-c, 36a-c, and the link pin 37 is used to fit the top link end, including the fitting holes. As a result, the top link is connected to the bracket 3 via the link pin 37 at its end, allowing it to rotate relative to the bracket 3.

[0047] The bracket shaft 33 is configured to generate a biasing force during relative rotation according to the towing load of the implement. The bracket shaft 33 has, for example, a torsion bar structure, and a biasing force is generated in the reverse rotation direction with respect to the rotational load around the bracket axis Z2. More specifically, when one end side 31 swings rearward according to the towing load in a state where the top link is connected by the link pin 37, the bracket 3 rotates relatively around the bracket axis Z2. In this case, the direction of relative rotation is counterclockwise in a left side view (see FIGS. 3 and 7). Accordingly, the bracket shaft 33 generates a biasing force in the clockwise direction in a left side view. On the other hand, when one end side 31 swings forward according to the towing load, the bracket 3 also rotates relatively around the bracket axis Z2. In this case, the direction of relative rotation is clockwise in a left side view. Accordingly, the bracket shaft 33 generates a biasing force in the counterclockwise direction in a left side view. Thus, with the other end side 32 as a fulcrum, the one end side 31 can swing back and forth while being biased.

[0048] As shown in FIG. 7, the bracket shaft 33 is located behind the lift arm shaft 23. The bracket axis Z2 of the bracket shaft 33 is located lower by a height H1 in the vertical direction than the lift arm axis Z1 of the lift arm shaft 23. The attachment portions 35a, 35b, 35c are located behind the bracket shaft 33. The attachment portions 35a, 35b, 35c are arranged in parallel on the left side plate 35 from the upper left to the lower right in this order. Note that the positional relationship of the attachment portions 36a to c is the same as that of the attachment portions 35a to c. The axis Z3 of the attachment portion 35a is located lower by a height H2a in the vertical direction than the bracket axis Z2. The axis Z4 of the attachment portion 35b is located lower by a height H2b in the vertical direction than the bracket axis Z2. The axis Z5 of the attachment portion 35c is located lower by a height H2c in the vertical direction than the bracket axis Z2. In the present embodiment, the positional relationship of the respective axes Z1 to Z5 is parallel to each other in the left - right direction and H1 < H2a < H2b < H2c, but it is not limited to this.

[0049] <Configuration of the transmission mechanism> As shown in Figures 8 to 13, the hydraulic lifting device 100 includes a position control transmission mechanism 20, a pumper transmission mechanism 30, and a draft control transmission mechanism 40. Each transmission mechanism 20, 30, and 40 is configured to transmit the displacement of each lever 6, 7, and 8, and the displacement of each rod 9 and 10, to the spool 51 of the control valve 5. The displacements input to each transmission mechanism 20, 30, and 40 are ultimately aggregated into the position control cam 210, the pumper cam 310, and the draft control cam 410, causing each of the cams 210, 310, and 410 to displace, respectively.

[0050] Figure 9 is a magnified view of the main parts showing the positional relationship of each cam 210, 310, 410 and the spool 51 inside case 1. As shown in Figure 8, the position control cam 210, the pumper cam 310, and the draft control cam 410 each have an approximately "E" shape when viewed from the left side. From left to right, the draft control cam 410, the position control cam 210, and the pumper cam 310 are arranged in this order, overlapping each other with some space between them. Each cam 210, 310, and 410 is provided with a pin that penetrates from left to right through its approximate vertical center, allowing for positioning. Each cam 210, 310, and 410 can rotate relative to each other using this pin as a pivot. The position control cam 210, the pump cam 310, and the draft control cam 410 are designed so that their upper ends 212, 312, 412 or lower ends 213, 313, 413 can swing in the front-rear direction.

[0051] In accordance with this oscillation, each of the protrusions 211, 311, and 411 is also able to swing integrally in the front-rear direction. When the protrusions 211, 311, and 411 swing to the rear and are displaced, the front end 51a of the spool 51 is pressed by the protrusions 211, 311, and 411 and displaced to the rear. Subsequently, when the protrusions 211, 311, and 411 swing to the front and are displaced, the spool 51 is displaced to the front in accordance with the biasing force of the spring. In this way, the spool 51 of the control valve 5 is displaced in accordance with the displacement of each of the cams 210, 310, and 410. The specific operation of each of the cams 210, 310, and 410 will be explained together when the details of each transmission mechanism 20, 30, and 40 are described.

[0052] The configurations of the position control transmission mechanism 20, the pump transmission mechanism 30, and the draft control transmission mechanism 40 will be described in detail below.

[0053] <<Position Control Transmission Mechanism>> Figure 10 is an overall view of the position control transmission mechanism 20. As shown in Figure 10, the position control transmission mechanism 20 includes a position control cam 210, a first position control shaft 220, and a second position control shaft 230.

[0054] The first position control shaft 220 comprises a co-rotating shaft 221, a reverse-rotating shaft 222, and a rotation transmission unit 223. The co-rotating shaft 221 extends in the left-right direction and has an axis A1 parallel to the left-right direction. The co-rotating shaft 221 is connected at its right end to the other end 62 of the position control lever 6. The co-rotating shaft 221 is rotatable around axis A1 in the same direction as the rotation direction of the position control lever 6. A cam 221a protruding upward is provided at the left end of the co-rotating shaft 221. The cam 221a is oscillating in the front-back direction in accordance with the rotation of the co-rotating shaft 221 around axis A1.

[0055] The reverse-rotating shaft 222 extends in the left-right direction and has an axis A2 parallel to the left-right direction. Axis A2 is located above and slightly in front of axis A1. That is, the same-direction rotating shaft 221 and the reverse-rotating shaft 222 are arranged to have different axes from each other. As shown by the dashed line in Figure 10 and in Figure 13, the reverse-rotating shaft 222 has a hollow structure along axis A2, and the reverse-rotating shaft 422 of the first draft control shaft 420 can be coaxially fitted inside it.

[0056] A cam 222a protruding downward is provided on the right end of the reverse-rotating shaft 222. In accordance with the forward and backward oscillation of the cam 222a, the reverse-rotating shaft 222 can rotate around axis A2 in the opposite direction to the rotation direction of the position control lever 6. A cam 222b protruding downward is provided on the left end of the reverse-rotating shaft 222. The cam 222b can swing in the forward and backward direction in accordance with the rotation of the reverse-rotating shaft 222 around axis A2.

[0057] The rotation transmission unit 223 is a plate that extends in the front-rear direction. The rear side of the rotation transmission unit 223 is rotatably connected to the upper end of the cam 221a, and the front side of the rotation transmission unit 223 is rotatably connected to the lower end of the cam 222a. The rotation transmission unit 223 is configured to cause the cam 222a to swing in the front-rear direction in response to the front-rear swinging of the cam 221a.

[0058] In the first position control shaft 220 configured in this way, when the position control lever 6 is operated, the same-direction rotating shaft 221 rotates around axis A1 and the opposite-direction rotating shaft 222 rotates around axis A2, in accordance with the displacement of the position control lever 6. More specifically, when the position control lever 6 is operated and both the position control lever 6 and the same-direction rotating shaft 221 rotate in direction R1, the cam 221a swings forward. Direction R1 corresponds to a clockwise direction when viewed from right to left. In accordance with the forward swing of the cam 221a, the cam 222a also swings forward via the rotation transmission unit 223. In accordance with the forward swing of the cam 222a, the opposite-direction rotating shaft 222 rotates in direction R2, which is opposite to direction R1. Direction R2 corresponds to a counterclockwise direction when viewed from right to left.

[0059] On the other hand, when the position control lever 6 is operated, and both the position control lever 6 and the same-direction rotating shaft 221 rotate in direction R2, the cam 221a swings backward. In response to the backward swing of the cam 221a, the cam 222a also swings backward via the rotation transmission unit 223. In response to the backward swing of the cam 222a, the reverse-direction rotating shaft 222 rotates in direction R1, which is opposite to direction R2. In other words, the rotation transmission unit 223 transmits the rotation of the same-direction rotating shaft 221 to the reverse-direction rotating shaft 222, and also causes the reverse-direction rotating shaft 222 to rotate in the opposite direction to the rotation of the same-direction rotating shaft 221.

[0060] The second position control shaft 230 extends in the left-right direction and has an axis A3 parallel to the left-right direction. Axis A3 is located above axis A2. That is, the first position control shaft 220 and the second position control shaft 230 are arranged to have different axes from each other, and the second position control shaft 230 is located above the first position control shaft 220.

[0061] A cam 230a protruding downward is provided on the left end of the second position control shaft 230. The front end 92 of the position feedback rod 9 is connected to the lower end of the cam 230a so as to be rotatable relative to it. In accordance with the forward and backward oscillation of the cam 230a, the second position control shaft 230 is rotatable around axis A3.

[0062] A cam 230b is provided slightly to the right of the center of the second position control shaft 230 in the left-right direction, protruding upward. The cam 230b is capable of swinging in the front-rear direction in accordance with the rotation of the second position control shaft 230 around axis A3. An extension 231 of the same diameter is provided at the right end of the second position control shaft 230. The extension 231 extends coaxially to the right from the cam 230b to axis A3.

[0063] The second position control shaft 230, configured in this way, rotates around axis A3 in accordance with the displacement of the position feedback rod 9 when the lift arm 2 rotates relative to it. More specifically, when the cam 24 swings backward due to the upward swing of the lift arm 2, the position feedback rod 9 is displaced backward. In accordance with the backward displacement of the position feedback rod 9, the cam 230a swings backward. In accordance with the backward swing of the cam 230a, the second position control shaft 230 rotates in direction R1.

[0064] On the other hand, when the cam 24 swings forward due to the downward swing of the lift arm 2, the position feedback rod 9 is displaced forward. In response to the forward displacement of the position feedback rod 9, the cam 230a swings forward. In response to the forward swing of the cam 230a, the second position control shaft 230 rotates in direction R2, which is opposite to direction R1.

[0065] In the position control cam 210, a protrusion 211, an upper end 212, and a lower end 213 are defined. The protrusion 211 protrudes rearward from approximately the center in the vertical direction and, as described above, is capable of contacting the front end 51a of the spool 51. The upper end 212 is rotatably connected to the cam 230b of the second position control shaft 230. The lower end 213 is rotatably connected to the cam 222b of the reverse rotation shaft 222 (first position control shaft 220).

[0066] When the position control lever 6 is operated, the position control lever 6 and the same-direction rotating shaft 221 rotate in direction R2, and the opposite-direction rotating shaft 222 rotates in direction R1, causing the cam 222b to swing to the rear. In response to the rearward swing of the cam 222b, the lower end 213 of the position control cam 210 also swings to the rear, and the protruding portion 211 is also displaced to the rear. As a result, the spool 51 is displaced toward the side where the supply and discharge of hydraulic fluid is permitted (i.e., the rear). This displacement of the spool 51 causes the lift arm 2 to swing upward.

[0067] Next, the upward swing of the lift arm 2 causes the second position control shaft 230 to rotate in direction R1, and the cam 230b swings forward. In response to the forward swing of the cam 230b, the upper end 212 of the position control cam 210 also swings forward, and the protruding portion 211 is also displaced forward. As a result, the spool 51 is displaced toward the side that restricts the supply and discharge of the hydraulic fluid (i.e., the front side). This displacement of the spool 51 causes the lift arm 2, which is swinging upward, to stop.

[0068] <<Pumper transmission mechanism>> Figure 11 is an overall view of the pumper transmission mechanism 30. As shown in Figure 11, the pumper transmission mechanism 30 comprises a pumper cam 310, a pumper shaft 320, and a rotational transmission unit 330.

[0069] The pump shaft 320 extends in the left-right direction and is positioned coaxially with axis A3. As shown by the dashed line in Figure 11 and in Figure 13, the pump shaft 320 has a hollow structure along axis A3, and the extension 231 of the second position control shaft 230 can be coaxially fitted inside it.

[0070] The pump shaft 320 is connected to the other end 72 of the pump lever 7 at its right end. The pump shaft 320 is rotatable around axis A3 in the same direction as the rotation of the pump lever 7. A cam 320a protruding downward is provided at the left end of the pump shaft 320. The cam 320a is oscillating in the front-back direction in accordance with the rotation of the pump shaft 320 around axis A3.

[0071] The rotation transmission section 330 is a plate extending in the vertical direction and is arranged coaxially with the axis A2. As shown by the dashed line in Figure 11 and in Figure 13, the rotation transmission section 330 has a fitting hole along the axis A2, into which the reverse rotation shaft 222 of the first position control shaft 220 can be coaxially fitted. The upper side of the rotation transmission section 330 is rotatably connected to the lower end of the cam 320a, and the lower side of the rotation transmission section 330 is rotatably connected to the lower end 313 of the pumper cam 310. The rotation transmission section 330 is configured to cause the lower end 313 to swing in the front-rear direction in response to the front-rear swinging of the cam 320a.

[0072] The pump shaft 320 configured in this way rotates around axis A3 in accordance with the displacement of the pump lever 7 when the pump lever 7 is operated. More specifically, when the pump shaft 320 rotates in direction R1 due to the operation of the pump lever 7, the cam 320a swings to the rear. In accordance with the swing of the cam 320a to the rear, the rotation transmission unit 330 rotates in direction R2, which is opposite to direction R1.

[0073] On the other hand, when the pump lever 7 is operated and the pump shaft 320 rotates in direction R2, the cam 320a swings forward. In response to the forward swing of the cam 320a, the rotation transmission unit 330 rotates in direction R1, which is opposite to direction R2.

[0074] In the pump cam 310, a protruding portion 311, an upper end portion 312, and a lower end portion 313 are defined. The protruding portion 311 protrudes rearward from approximately the center in the vertical direction and, as described above, is capable of contacting the front end portion 51a of the spool 51. The upper end portion 312 is rotatably connected to the cam 230b of the second position control shaft 230. More specifically, as shown in Figure 13, the upper end portion 312 is interposed between the cam 230b and the upper end portion 212 of the position control cam 210. The cam 230b and the upper end portions 312 and 212 are pinned together so that they can swing integrally in response to the swing of the cam 230b. The lower end portion 313 is rotatably connected to the lower side of the rotation transmission portion 330.

[0075] With the supply and discharge of hydraulic fluid restricted by the control valve 5, the pump lever 7, which is in the first position, is displaced to the second position. When the pump lever 7 is operated and the pump lever 7 and the pump shaft 320 each rotate in direction R2, the cam 320a swings forward and the rotation transmission unit 330 rotates in direction R1. In accordance with the rotation of the rotation transmission unit 330 in direction R1, the lower end side 313 of the pump cam 310 also swings backward, and the protruding portion 211 is also displaced backward. As a result, the spool 51 is displaced toward the side where the supply and discharge of hydraulic fluid is permitted (i.e., the rear). In accordance with the displacement of the spool 51, the lift arm 2 swings upward.

[0076] Next, the upward swing of the lift arm 2 causes the second position control shaft 230 to rotate in direction R1, and the cam 230b swings forward. In response to the forward swing of the cam 230b, the upper end 312 of the pumper cam 310, along with the upper end 212 of the position control cam 210, also swings forward, and the protruding portion 311 is also displaced forward. As a result, the spool 51 is displaced toward the side that restricts the supply and discharge of the hydraulic fluid (i.e., the front side). In response to the displacement of the spool 51, the lift arm 2, which had been swinging upward, stops.

[0077] <<Draft control transmission mechanism>> Figure 12 is an overall view of the draft control transmission mechanism 40. As shown in Figure 12, the draft control transmission mechanism 40 comprises a draft control cam 410, a first draft control shaft 420, and a second draft control shaft 430.

[0078] The first draft control shaft 420 comprises a co-rotating shaft 421, a reverse-rotating shaft 422, and a rotation transmission unit 423. The co-rotating shaft 421 extends in the left-right direction and is arranged coaxially with axis A1. As shown by the dashed line in Figure 11 and in Figure 12, the co-rotating shaft 421 has a hollow structure along axis A1, and the co-rotating shaft 221 of the first position control shaft 220 can be coaxially fitted inside it. The co-rotating shaft 421 is connected to the other end 82 of the draft control lever 8 at its right end. The co-rotating shaft 421 is rotatable around axis A1 in the same direction as the rotation direction of the draft control lever 8. A cam 421a is provided on the left end of the co-rotating shaft 421, protruding upward so as to be adjacent to the right side of the cam 221a. The cam 421a is oscillating in the front-back direction in accordance with the rotation of the co-rotating shaft 421 around axis A1. Each of the oscillating cams 421a and 221a is capable of contacting the stay. When contact is made with the stay, the oscillation of each cam 421a and 221a is restricted, and the operation of each lever 6 and 8 is also restricted. In other words, by adjusting the contact position between each cam 421a and 221a and the stay, the operating range of each lever 6 and 8 can be set. For example, in this embodiment, the operating range may be set so that the operating angle of each lever 6 and 8 is 45 degrees.

[0079] The reverse-rotating shaft 422 extends in the left-right direction and is arranged coaxially with axis A2. That is, the same-direction rotating shaft 421 and the reverse-direction rotating shaft 422 are arranged to have different axes from each other. As shown by the dashed line in Figure 11 and in Figure 12, the reverse-direction rotating shaft 422 is fitted inside the reverse-direction rotating shaft 222 of the first position control shaft 220.

[0080] On the right end of the reverse-rotating shaft 422, a cam 422a is provided that protrudes downward, adjacent to the right side of cam 222a. In accordance with the forward and backward oscillation of cam 422a, the reverse-rotating shaft 422 can rotate around axis A2 in the opposite direction to the rotation direction of the draft control lever 8. On the left end of the reverse-rotating shaft 422, a cam 422b is provided that protrudes downward. Cam 422b can swing in the forward and backward direction in accordance with the rotation of the reverse-rotating shaft 422 around axis A2.

[0081] The rotation transmission unit 423 is a plate that extends in the front-rear direction and is adjacent to the right side of the rotation transmission unit 223. The rear side of the rotation transmission unit 423 is rotatably connected to the upper end of the cam 421a, and the front side of the rotation transmission unit 423 is rotatably connected to the lower end of the cam 422a. The rotation transmission unit 423 is configured to cause the cam 422a to swing in the front-rear direction in response to the front-rear swinging of the cam 421a.

[0082] In the first draft control shaft 420 configured in this way, when the draft control lever 8 is operated, the same-direction rotating shaft 421 rotates around axis A1 and the opposite-direction rotating shaft 422 rotates around axis A2, depending on the displacement of the draft control lever 8. More specifically, when the draft control lever 8 is operated and both the draft control lever 8 and the same-direction rotating shaft 421 rotate in direction R1, the cam 421a swings forward. In response to the forward swing of the cam 421a, the cam 422a also swings forward via the rotation transmission unit 423. In response to the forward swing of the cam 422a, the opposite-direction rotating shaft 422 rotates in direction R2, opposite to direction R1.

[0083] On the other hand, when the draft control lever 8 is operated, causing the draft control lever 8 and the same-direction rotating shaft 421 to rotate in direction R2, the cam 421a swings backward. In response to the backward swing of the cam 421a, the cam 422a also swings backward via the rotation transmission unit 423. In response to the backward swing of the cam 422a, the reverse-direction rotating shaft 422 rotates in direction R1, which is opposite to direction R2. That is, the rotation transmission unit 423 transmits the rotation of the same-direction rotating shaft 421 to the reverse-direction rotating shaft 422, and also causes the reverse-direction rotating shaft 422 to rotate in the opposite direction to the rotation of the same-direction rotating shaft 421.

[0084] The second draft control shaft 430 extends in the left-right direction and is positioned coaxially with axis A3. As shown by the dashed line in Figure 12 and in Figure 13, the second draft control shaft 430 has a hollow structure along axis A3, and the second position control shaft 230 can be coaxially fitted inside it. That is, the first draft control shaft 420 and the second draft control shaft 430 are positioned so that they have different axes from each other, and the second draft control shaft 430 is located above the first draft control shaft 420.

[0085] A cam 430a protruding downward is provided on the left end of the second draft control shaft 430. The front end 102 of the draft feedback rod 10 is connected to the lower end of the cam 430a so as to be rotatable relative to it. The second draft control shaft 430 is rotatable around axis A3 in accordance with the forward and backward oscillation of the cam 430a.

[0086] A cam 430b that protrudes upward is provided on the right end of the second draft control shaft 430. The cam 430b is capable of swinging in the front-rear direction in accordance with the rotation of the second draft control shaft 430 around axis A3.

[0087] The second draft control shaft 430, configured in this way, rotates around axis A3 in accordance with the displacement of the draft feedback rod 10 when the bracket 3 rotates relative to it. More specifically, when the joint 34 swings to the rear due to the swing of the bracket 3 to the rear, the draft feedback rod 10 is displaced to the rear without the spring 102a extending beyond its mounting length. In accordance with the rearward displacement of the draft feedback rod 10, the cam 430a swings to the rear. In accordance with the rearward swing of the cam 430a, the second draft control shaft 430 rotates in direction R1.

[0088] On the other hand, when the joint 34 swings forward due to the forward swinging of the bracket 3, the draft feedback rod 10 is displaced forward. In this case, the draft feedback rod 10 is displaced while the spring 102a is slightly compressed from its mounting length. This compression of the spring 102a suppresses hunting associated with the input. The spring constant of the spring 102a may be adjusted, for example, to appropriately suppress this hunting. In response to the forward displacement of the draft feedback rod 10, the cam 430a swings forward. In response to the forward swinging of the cam 430a, the second draft control shaft 430 rotates in the direction R2 opposite to the direction R1.

[0089] As shown in Figures 12 and 13, the front end 102 of the draft feedback rod 10 is further provided with a projection 102b. The projection 102b protrudes to the right and is located above the position feedback rod 9 and behind the cam 230a of the second position control shaft 230. In other words, the projection 102b can intersect with the radial trajectory of the cam 230a.

[0090] Therefore, for example, if the position feedback rod 9 continues to be displaced rearward, the cam 230a, which rotates relative to it rearward, will eventually come into contact with the protrusion 102b. After contact, if the position feedback rod 9 is displaced further rearward, the cam 230a will press the protrusion 102b to the rear, causing the spring 102a to compress. As a result, the portion of the draft feedback rod 10 rearward of the spring 102a will not be displaced rearward, and the bracket 3 will not swing. On the other hand, in conjunction with the protrusion 102b being pressed to the rearward side, the cam 430a also swings to the rearward side, and the second draft control shaft 430 rotates in direction R1.

[0091] In the draft control cam 410, a protrusion 411, an upper end 412, and a lower end 413 are defined. The protrusion 411 protrudes rearward from approximately the center in the vertical direction and, as described above, is capable of contacting the front end 51a of the spool 51. The upper end 412 is rotatably connected to the cam 430b of the second draft control shaft 430. The lower end 413 is rotatably connected to the cam 422b of the reverse rotation shaft 422 (first draft control shaft 420).

[0092] The operation of the draft control lever 8 is described below. As a prerequisite for operation, it is assumed that a traction load from the top link (implement) is applied to the bracket 3, and that the bracket 3 is in a state of oscillation displacement in accordance with this traction load, with the spool 51 in a neutral position. In this state, when the draft control lever 8 is operated, the draft control lever 8 and the same-direction rotating shaft 421 each rotate in direction R2, and the opposite-direction rotating shaft 422 rotates in direction R1, causing the cam 422b to swing to the rear. In response to the swing of the cam 422b to the rear, the lower end side 413 of the draft control cam 410 also swings to the rear, and the protruding portion 411 is also displaced to the rear. As a result, the spool 51 is displaced toward the side that allows for the supply and discharge of hydraulic fluid (i.e., the rear). Due to this displacement of the spool 51, the lift arm 2 swings upward.

[0093] Next, the upward swing of the lift arm 2 causes the implement connected to the lift arm 2 to also be displaced upward. For example, if the lower end of the implement is in contact with the ground, the degree of tillage depth decreases. Also, if the lower end of the implement is separated from the ground, the separation distance increases. Consequently, the traction load from the top link to the bracket 3 changes, and in response, the bracket 3 rotates relative to it. Due to the relative rotation of the bracket 3, the second draft control shaft 430 rotates in direction R1, and the cam 430b swings forward.

[0094] On the other hand, when the upward swing of the lift arm 2 causes the cam 230a to press the projection 102b to the rear, the spring 102a of the draft feedback rod 10 compresses. On the other hand, in conjunction with the projection 102b being pressed to the rear, the cam 430a also swings to the rear. In this case as well, the second draft control shaft 430 rotates in direction R1, and the cam 430b swings to the front.

[0095] As the cam 430b swings forward, the upper end 412 of the draft control cam 410 also swings forward, and the protruding portion 411 is also displaced forward. This causes the spool 51 to be displaced toward the side that restricts the supply and discharge of the hydraulic fluid (i.e., the front side). This displacement of the spool 51 stops the lift arm 2 which swings upward.

[0096] <Effects of the Embodiment> As described above, the hydraulic lifting device 100 according to the first embodiment of the present invention comprises a lift arm 2, a bracket 3, a draft control lever 8, and a draft control transmission mechanism 40. This enables draft control. The lift arm 2 rotates relative to the case 1 with its other end 22 as a pivot point in order to raise and lower the connected implement. The bracket 3 is provided at the rear end of the case 1 and rotates relative to the case 1 with its other end 32 as a pivot point in accordance with the traction load from the connected top link (i.e., the implement). The bracket 3 also comprises mounting parts 35a, 35b, 35c, 36a, 36b, and 36c to which the front end of the top link can be attached. Here, the lift arm 2 has a lift arm axis Z1 which is the axis of rotation relative to the case 1. The bracket 3 has a bracket axis Z2 which is the axis of rotation relative to the case 1, and also comprises axes Z3, Z4, and Z5 of the mounting parts 35a~c and 36a~c. The lift arm axis Z1, the bracket axis Z2, and the axes Z3, Z4, and Z5 extend in a direction perpendicular to the vertical direction of the implement (first direction, vertical direction in this embodiment) (second direction, left-right direction in this embodiment), and are parallel to each other. In the first direction, the bracket axis Z2 is located below the lift arm axis Z1, and the mounting portions 35a~c and 36a~c, each having axes Z3, Z4, and Z5, are located below the bracket axis Z2 (see Figure 7).

[0097] By connecting the front end of the top link to the mounting parts 35a~c and 36a~c configured in this way, the front end of the top link can be positioned sufficiently downward. Therefore, the distance between the connected implement and the ground can be easily increased. In particular, compared to configurations where the mounting parts 35a~c and 36a~c are located above the bracket axis Z2, the front end of the top link can be positioned even lower, and the above-mentioned distance can be increased even further. For example, when a work implement to which the hydraulic lifting device 100 of the first embodiment is applied travels on uneven ground, bumpy ground, slopes, etc., even if it tilts relative to the ground, the distance between the implement and the ground can be increased, thus suppressing contact between the implement and the ground. More specifically, when a tractor equipped with the hydraulic lifting device 100 of this embodiment crosses a ridge, the implement can be prevented from contacting the ground, thus preventing the ridge from collapsing.

[0098] Furthermore, in the first embodiment in particular, a bracket shaft 33 is provided. The bracket shaft 33 pivotally supports the other end 32 of the bracket 3 at the outer rear end of the case 1 and is arranged coaxially with the bracket shaft Z2. The bracket shaft 33 is configured to generate a biasing force when it rotates relative to the traction load. This allows the bracket shaft 33 to have the biasing function required for the execution of draft control. In other words, the bracket shaft 33 serves as both the support shaft and the biasing mechanism of the bracket 3, eliminating the need to add a separate biasing mechanism. Therefore, as in the conventional method, it is no longer necessary to interpose a biasing mechanism, for example, between one end 31 of the bracket 3 and the case 1. This allows for greater space to position the bracket shaft Z2 or the mounting portions 35a~c, 36a~c further down.

[0099] Furthermore, in the first embodiment in particular, the draft control transmission mechanism 40 comprises a draft control cam 410, a first draft control shaft 420, and a second draft control shaft 430. The first draft control shaft 420 rotates around axis A1 (and axis A2) in accordance with the displacement of the draft control lever 8 when the draft control lever 8 is operated. The second draft control shaft 430 rotates around axis A3 in accordance with the displacement of the draft feedback rod 10 when the bracket 3 rotates relative to it. When the first draft control shaft 420 rotates, the draft control cam 410 displaces the position of the spool 51 toward the side that allows the supply and discharge of hydraulic fluid in accordance with the rotation of the first draft control shaft 420. When the second draft control shaft 430 rotates, the draft control cam 410 displaces the position of the spool 51 toward the side that restricts the supply and discharge of hydraulic fluid in accordance with the rotation of the second draft control shaft 430. Therefore, the lifting height of the lift arm 2 can be easily adjusted so that the traction load on the bracket 5 reaches the desired size.

[0100] The second draft control shaft 430 is located above the first draft control shaft 420 in the vertical direction of the top link (implement). In this embodiment, the axis A3 of the second draft control shaft 430 is located above the axis A1 of the first draft control shaft 420. This allows the space below the second draft control shaft 430 to be effectively utilized as a space for housing components. For example, as shown in Figure 8, the hydraulic cylinder 4 is housed below the second draft control shaft 430 and to the left of the first draft control shaft 420, allowing the hydraulic lifting device 100 to be made smaller overall. In this way, the degree of freedom in the layout of components can be greatly increased.

[0101] Therefore, the lifting height of the lift arm 2 can be easily adjusted so that the traction load on the bracket 5 reaches the desired size, and the degree of freedom in the layout of the components can be greatly increased. In addition, the hydraulic cylinder 4, which is the heaviest component, can be placed at the bottom of the internal space of the hydraulic lifting device 100. As a result, the position of the center of gravity of the hydraulic lifting device 100 can be adjusted over a wide range.

[0102] For example, in the first embodiment, the draft control lever 8 has one end 81 and the other end 82 defined, with the one end 81 being operable by the operator and configured to rotate relative to the case 1 with the other end 82 as a pivot point as a displacement corresponding to the operation. The first draft control shaft 420 includes a co-rotating shaft 421, a reverse-rotating shaft 422, and a rotation transmission unit 423. The co-rotating shaft 421 is connected to the other end 82 of the draft control lever 8 and is configured to rotate in the same direction as the rotation direction of the draft control lever 8. The reverse-rotating shaft 422 is connected to the draft control cam 410 and is configured to rotate in the opposite direction to the rotation direction of the draft control lever 8. When the draft control lever 8 rotates relative to the case, the rotation transmission unit 423 transmits the rotation of the co-rotating shaft 421 toward the reverse-rotating shaft 422 and rotates the reverse-rotating shaft 422 in the opposite direction to the rotation direction of the co-rotating shaft 421.

[0103] According to this, the same-direction rotating shaft 421 and the opposite-direction rotating shaft 422 can be arranged on different axes via the rotation transmission unit 423. For example, as shown in Figure 12, the position of axis A1 of the same-direction rotating shaft 421 and the position of axis A2 of the opposite-direction rotating shaft 422 can be made different from each other. Therefore, the same-direction rotating shaft 421 and the opposite-direction rotating shaft 422 can be laid out without interfering with the arrangement of the hydraulic cylinder 4, control valve 5, etc. In other words, the degree of freedom in the layout of the first draft control shaft 420 and the draft control lever 8 can be greatly increased, and for example, a layout that is easy for the operator to operate can be adopted. In addition, by changing the link ratio in the rotation transmission unit 423, the amount of displacement of the draft control cam 410 (the amount of displacement of the spool 51) can be adjusted in relation to the amount of displacement of the draft control lever 8. Therefore, the operating range of the draft control lever 8 can be adjusted to be easy for the operator to operate.

[0104] In addition, in the first embodiment in particular, a position control lever 6 and a position control transmission mechanism 20 are provided. The position control transmission mechanism 20 comprises a position control cam 210, a first position control shaft 220, and a second position control shaft 230. The first position control shaft 220 rotates around axis A1 (and axis A2) in accordance with the displacement of the position control lever 6 when the position control lever 6 is operated. The second position control shaft 230 rotates around axis A3 in accordance with the displacement of the position feedback rod 9 when the lift arm 2 rotates relative to it. When the first position control shaft 220 rotates, the position control cam 210 displaces the position of the spool 51 toward the side that allows the supply and discharge of hydraulic fluid in accordance with the rotation of the first position control shaft 220. When the second position control shaft 230 rotates, the position control cam 210 displaces the position of the spool 51 toward the side that restricts the supply and discharge of hydraulic fluid in accordance with the rotation of the second position control shaft 230. Therefore, the height of the lift arm 2 in the vertical direction can be easily adjusted to the desired height.

[0105] The second position control shaft 230 is located above the first position control shaft 220 in the vertical direction of the top link (implement). In this embodiment, the axis A3 of the second position control shaft 230 is located above the axis A1 of the first position control shaft 220. This allows the space below the second position control shaft 230 to be effectively utilized as a space for housing components. For example, as shown in Figure 8, the hydraulic cylinder 4 is housed below the second position control shaft 230 and to the left of the first position control shaft 220, allowing the hydraulic lifting device 100 to be made smaller overall. In this way, the degree of freedom in the layout of components can be greatly increased.

[0106] Therefore, the height of the lift arm 2 in the vertical direction can be easily adjusted to the desired height, and the degree of freedom in the layout of the components can be greatly increased. In addition, the hydraulic cylinder 4, which is the heaviest component, can be placed at the bottom of the internal space of the hydraulic lifting device 100. As a result, the position of the center of gravity of the hydraulic lifting device 100 can be adjusted over a wide range.

[0107] Furthermore, in the first embodiment in particular, the position control lever 6 has one end 61 and the other end 62 defined, with the one end 61 being operable by the operator and configured to rotate relative to the case 1 with the other end 62 as a pivot point as a displacement corresponding to the operation. The first position control shaft 220 comprises a co-rotating shaft 221, a reverse-rotating shaft 222, and a rotation transmission unit 223. The co-rotating shaft 221 is connected to the other end 62 of the position control lever 6 and is configured to rotate in the same direction as the rotation direction of the position control lever 6. The reverse-rotating shaft 222 is connected to the position control cam 210 and is configured to rotate in the opposite direction to the rotation direction of the position control lever 6. When the position control lever 6 rotates relative to the position control lever 6, the rotation transmission unit 223 transmits the rotation of the co-rotating shaft 221 toward the reverse-rotating shaft 222 and rotates the reverse-rotating shaft 222 in the opposite direction to the rotation direction of the co-rotating shaft 221.

[0108] According to this, the same-direction rotating shaft 221 and the opposite-direction rotating shaft 222 can be arranged on different axes via the rotation transmission unit 223. For example, as shown in Figure 10, the position of axis A1 of the same-direction rotating shaft 221 and the position of axis A2 of the opposite-direction rotating shaft 222 can be made different from each other. Therefore, the same-direction rotating shaft 221 and the opposite-direction rotating shaft 222 can be laid out without interfering with the arrangement of the hydraulic cylinder 4, control valve 5, etc. In other words, the degree of freedom in the layout of the first position control shaft 220 and the position control lever 6 can be greatly increased, and for example, a layout that is easy for the operator to operate can be adopted. In addition, by changing the link ratio in the rotation transmission unit 223, the amount of displacement of the position control cam 210 (the amount of displacement of the spool 51) can be adjusted in relation to the amount of displacement of the position control lever 6. Therefore, the operating range of the position control lever 6 can be adjusted to be easy for the operator to operate.

[0109] Furthermore, in the first embodiment, either the first draft control shaft 420 or the first position control shaft 220 has a hollow structure and is configured so that the other can be coaxially fitted inside the other. Either the second draft control shaft 430 or the second position control shaft 230 has a hollow structure and is configured so that the other can be coaxially fitted inside the one.

[0110] More specifically, as shown in Figures 10, 12, and 13, the coaxial rotating shaft 221 of the first position control shaft 220 is coaxially fitted into the coaxial rotating shaft 421 of the first draft control shaft 420. The reverse rotating shaft 422 of the first draft control shaft 420 is coaxially fitted into the reverse rotating shaft 222 of the first position control shaft 220. The second position control shaft 230 is coaxially fitted into the second draft control shaft 430. Depending on the displacement of either the position control lever 6 or the draft control lever 8, the first position control shaft 220 and the first draft control shaft 420 rotate relative to each other around axes A1 and A2. Depending on the displacement of either the position feedback rod 9 or the draft feedback rod 10, the second position control shaft 230 and the second draft control shaft 430 rotate relative to each other around axis A3. According to this design, one shaft can be housed inside the other, freeing up space by the amount the shafts are housed in. This further increases the degree of freedom in the layout of the components.

[0111] In addition, the first embodiment includes a pump lever 7 and a pump transmission mechanism 30. The pump lever 7 is configured to be displaceable from a first position to a second position in response to the operator's operation. The pump transmission mechanism 30 includes a pump cam 310, a pump shaft 320, and a second position control shaft 230. The pump shaft 320 rotates around axis A3 in accordance with the displacement of the pump lever 7 when the pump lever 7 is operated and displaced from the first position to the second position. The pump cam 310 displaces the position of the spool 51 toward the side that allows the supply and discharge of hydraulic fluid in accordance with the rotation of the pump shaft 7 when the pump shaft 7 rotates, and displaces the position of the spool 51 toward the side that restricts the supply and discharge of hydraulic fluid in accordance with the rotation of the second position control shaft 230 when the second position control shaft 230 rotates. As a result, the lift arm 2 can be easily raised and lowered according to the operator's request.

[0112] For example, as in the first embodiment, when the pump transmission mechanism 30 is provided with a rotational transmission section 330, the pump shaft 320 and the lower end 313 of the pump cam 310 can be arranged on different axes via the rotational transmission section 330 (see Figure 11). Therefore, the pump shaft 320 can be laid out without interfering with the arrangement of the hydraulic cylinder 4, control valve 5, etc. In other words, the degree of freedom in the layout of the pump shaft 320 and the pump lever 7 can be greatly increased, and for example, a layout that is easy for the operator to operate can be adopted. In addition, by changing the link ratio in the rotational transmission section 330, the amount of displacement of the pump cam 310 (the amount of displacement of the spool 51) can be adjusted in relation to the amount of displacement of the pump lever 7. Therefore, the operating range of the pump lever 7 can be adjusted to be easy for the operator to operate.

[0113] Furthermore, in the first embodiment in particular, the pump lever 7 has one end 71 and the other end 72 defined, with the one end 71 being operable by the operator and the other end 72 being rotatable relative to the case 1 as a displacement corresponding to the operation. In addition, a rotation restricting part 74 is provided to restrict the relative rotation of the pump lever 7. This makes it possible to intentionally restrict the height to which the implement is raised by operating the pump lever 7 so that it is at an arbitrary position. For example, if the implement is raised too high, the center of gravity also rises, increasing the risk of tipping over. In particular, the risk of tipping over is often high when using relatively heavy implements (e.g., plows) on slopes. In such cases, the height to which the implement is raised can be appropriately restricted, improving safety. On the other hand, by restricting the height to which the implement is raised to the minimum necessary height, the time until the implement touches the ground can be shortened when lowering the implement, for example, after turning during work interruptions. Therefore, the time spent interrupting work can be reduced, and work efficiency can be improved accordingly.

[0114] [Second Embodiment] Next, a second embodiment of the present invention will be described. The hydraulic lifting device 100 according to the second embodiment of the present invention differs from the first embodiment described above in the following respects. In the hydraulic lifting device 100 of the second embodiment, the configuration of the bracket 3 differs from that of the first embodiment. In addition, a predetermined mechanism has been added near the front end of each feedback rod 9, 10 in order to interlock the second draft control shaft 430 with the rotation of the second position control shaft 230, which is another difference from the first embodiment. Aside from these points, the second embodiment is the same as the first embodiment. Hereinafter, only the differences between the second embodiment and the first embodiment will be described. Note that in the components of the second embodiment, those that are the same or equivalent as those in the first embodiment will be denoted by the same reference numerals and their description will be omitted.

[0115] FIG. 14 is a left side view of the hydraulic lifting device 100 of the second embodiment and corresponds to FIG. 3. FIG. 15 is a diagram showing the positional relationship of each axis in the hydraulic lifting device 100 of the second embodiment and corresponds to FIG. 7. As shown in FIGS. 14 and 15, the left side plate 35 and the right side plate 36 of the bracket 3 each have substantially the same shape, extend rearward from the other end side 32, and further project toward the lower one end side 31. The mounting portions 35a, 35b, 35c are arranged in parallel on the left side plate 35 vertically downward in this order from above. Note that the positional relationship of the mounting portions 36a to c is the same as that of the mounting portions 35a to c.

[0116] As shown in FIG. 15, the bracket axis Z2 of the bracket shaft 33 is located above the lift arm axis Z1 of the lift arm shaft 23 by a height H3 in the vertical direction. The axis Z3 of the mounting portion 35a is located below the bracket axis Z2 by a height H4a in the vertical direction. The axis Z4 of the mounting portion 35b is located below the bracket axis Z2 by a height H4b in the vertical direction. The axis Z5 of the mounting portion 35c is located below the bracket axis Z2 by a height H4c in the vertical direction. In the present embodiment, the positional relationship of the axes Z1 to Z5 is parallel to each other in the left-right direction and H4a < H3 < H4b < H4c, but it is not limited to this.

[0117] Figure 16 is a perspective view showing the configuration near the front ends of each feedback rod 9, 10 in the hydraulic lifting device 100 of the second embodiment. Figure 17 shows the positional relationship of the components of each transmission mechanism in the hydraulic lifting device 100 of the second embodiment and corresponds to Figure 13. As shown in Figures 14, 16, and 17, behind the approximately midpoint of each feedback rod 9, 10, the draft feedback rod 10 is located between the position feedback rod 9 and the left side of the case 1. On the other hand, in front of the approximately midpoint of each feedback rod 9, 10, the draft feedback rod 10 is located outside the position feedback rod 9. The hydraulic lifting device 100 of the second embodiment is equipped with cams 430a, 230a, and 11a at the front ends of the position feedback rod 9 and the draft feedback rod 10. In this embodiment, cams 430a, 230a, and 11a correspond to the first displacement transmission unit, the second displacement transmission unit, and the third displacement transmission unit. Hereinafter, cam 430a, cam 230a, and cam 11a will be referred to as the first displacement transmission unit 430a, the second displacement transmission unit 230a, and the third displacement transmission unit 11a.

[0118] The first displacement transmission unit 430a is connected to the left end of the second draft control shaft 430 so as to be able to rotate integrally with the second draft control shaft 430. The first displacement transmission unit 430a is able to swing in the front-rear direction about axis A3. The lower end of the first displacement transmission unit 430a is connected to the front end 102 of the draft feedback rod 10 so as to be able to rotate relative to it. Therefore, when the bracket 3 rotates relative to it, the first displacement transmission unit 430a rotates the second draft control shaft 430 in accordance with the displacement of the draft feedback rod 10.

[0119] The second displacement transmission unit 230a is connected to the left end of the second position control shaft 230 so as to be able to rotate integrally with the second position control shaft 230. The second displacement transmission unit 230a is able to swing in the front-rear direction about axis A3. The lower end of the second displacement transmission unit 230a is connected to the front end 92 of the position feedback rod 9 so as to be able to rotate relative to it. Therefore, when the lift arm 2 rotates relative to it, the second displacement transmission unit 230a rotates the second position control shaft 230 in accordance with the displacement of the position feedback rod 9.

[0120] The third displacement transmission section 11a is a roughly triangular flat plate, with a pivot point 11a1 provided approximately in its center. The pivot point 11a1 is connected to a projection that protrudes to the left from the left side of the case 1 via a stepped bolt so as to be rotatable relative to it. As a result, the third displacement transmission section 11a is rotatable relative to the case 1 with the pivot point 11a1 as its axis. The third displacement transmission section 11a is configured to press against the first displacement transmission section 430a when its front end comes into contact with it. The rear end of the third displacement transmission section 11a is connected to the second displacement transmission section 230a via the fourth displacement transmission section 11b.

[0121] The fourth displacement transmission section 11b is a substantially rectangular flat plate, and the third displacement transmission section 11a and the second displacement transmission section 230a are connected to it at both ends so as to be rotatable relative to each other. The connection point of the fourth displacement transmission section 11b in the second displacement transmission section 230a is located above the front end side 92 of the position feedback rod 9.

[0122] As shown in Figure 18, for example, when the position feedback rod 9 is displaced rearward due to the swinging of the lift arm 2, the second displacement transmission unit 230a swings to the rear and rotates the second position control shaft 230 around axis A3 in direction R1. At this time, in conjunction with the second displacement transmission unit 230a, the fourth displacement transmission unit 11b is displaced rearward and rotates the third displacement transmission unit 11a with the pivot point 11a1 as the pivot. As a result, the front end side 11a2 of the third displacement transmission unit 11a swings to the front.

[0123] As shown in Figure 19, the front end 11a2 of the third displacement transmission part 11a, which swings forward, approaches the first displacement transmission part 430a and eventually contacts and presses against the rear end 430a1. The rear end 430a1 is configured to be a round rod shape extending to the left and right. As a result, the first displacement transmission part 430a swings backward and rotates the second draft control shaft 430 around axis A3 in direction R1. The backward swing of the first displacement transmission part 430a causes the spring 102a to compress. As a result, the part of the draft feedback rod 10 behind the spring 102a does not displace backward, and the bracket 3 does not swing.

[0124] As described above, in the hydraulic lifting device 100 according to the second embodiment of the present invention, in the first direction, the bracket shaft Z2 is located above the lift arm shaft Z1, and the mounting portions 35a~c and 36a~c, each having shafts Z3, Z4, and Z5, are located below the bracket shaft Z2 (see Figure 15). By connecting the front end of the top link to the mounting portions 35a~c and 36a~c configured in this way, the front end of the top link can be positioned sufficiently downward even when the bracket shaft Z2 is located above the lift arm shaft Z1. Therefore, the same effects as those obtained in the first embodiment described above can be obtained.

[0125] Furthermore, in the second embodiment in particular, a first displacement transmission unit 430a, a second displacement transmission unit 230a, a third displacement transmission unit 11a, and a fourth displacement transmission unit 11b are provided near the front ends of each feedback rod 9, 10. The third displacement transmission unit 11a is configured to abut and press against the rear end 430a1 of the first displacement transmission unit 430a at its front end 11a2. The third displacement transmission unit 11a rotates in conjunction with the rotation of the second displacement transmission unit 230a via the fourth displacement transmission unit 11b, with the pivot point 11a1 as the pivot point (see Figures 18 and 19).

[0126] Therefore, in order to synchronize the rotation of the second position control shaft 230 with the rotation of the second draft control shaft 430, the displacement of the second displacement transmission unit 230a can be transmitted to the first displacement transmission unit 430a via the third displacement transmission unit 11a. In the third displacement transmission unit 11a, the input from the second displacement transmission unit 230a can be converted into rotational displacement with the pivot point 11a1 as the pivot. On the other hand, the first displacement transmission unit 430a, which receives the load from the third displacement transmission unit 11a, also undergoes rotational displacement. Therefore, the load direction and the displacement direction can be brought closer together, thereby suppressing the application of excessive force. Furthermore, the relatively strong front end 11a2 of the third displacement transmission unit 11a and the rear end 430a1 of the first displacement transmission unit 430a can be used as contact and pressing points. For example, a configuration in which the oscillating second displacement transmission unit 230a is brought into contact with and pressed against the draft feedback rod 10 to link the second draft control shaft 430 is also conceivable. In this case, the input from the second displacement transmission unit 230a is directly transmitted to the draft feedback rod 10, which may cause bending or deformation of the draft feedback rod 10. On the other hand, as described above, according to the configuration of the second embodiment, displacement can be reliably transmitted while suppressing bending or deformation of the linked parts.

[0127] [Differentiation] In the first embodiment described above, a projection 102b is provided on the draft feedback rod 10, and the swinging cam 230a contacts and presses against the projection 102b. Alternatively, the first displacement transmission unit 430a, the second displacement transmission unit 230a, and the third displacement transmission unit 11a of the second embodiment may be provided near the front end of each feedback rod 9, 10, and the displacement of the second displacement transmission unit 230a may be transmitted to the first displacement transmission unit 430a via the third displacement transmission unit 11a.

[0128] In each of the above embodiments, the bracket shaft 33 is configured to generate a biasing force when it rotates relative to the traction load. However, instead, for example, it may only have the function of pivotally supporting the other end 32 of the bracket 3 on the outer rear end of the case 1. In this case, the bracket shaft 33 does not have the biasing function required for the execution of draft control. For this reason, for example, a separate biasing mechanism may be interposed between the case 1 and the bracket 3, and the bracket shaft Z2 may be positioned below or above the lift arm shaft Z1 as far as possible, and the mounting portions 35a~c, 36a~c may be positioned below the bracket shaft Z2 as far as possible.

[0129] In each of the above embodiments, the coaxial rotation shaft 221 of the first position control shaft 220 is coaxially fitted into the coaxial rotation shaft 421 of the first draft control shaft 420. Alternatively, the coaxial rotation shaft 221 of the first position control shaft 220 may have a hollow structure, and the coaxial rotation shaft 421 of the first draft control shaft 420 may be coaxially fitted into the coaxial rotation shaft 221 of the first position control shaft 220.

[0130] In each of the above embodiments, the reverse rotation shaft 422 of the first draft control shaft 420 is coaxially fitted onto the reverse rotation shaft 222 of the first position control shaft 220. Alternatively, the reverse rotation shaft 422 of the first draft control shaft 420 may have a hollow structure, and the reverse rotation shaft 222 of the first position control shaft 220 may be coaxially fitted onto the reverse rotation shaft 422 of the first draft control shaft 420.

[0131] In each of the above embodiments, the second position control shaft 230 is coaxially fitted into the second draft control shaft 430. Alternatively, the second position control shaft 230 may have a hollow structure, and the second draft control shaft 430 may be coaxially fitted into the second position control shaft 230.

[0132] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0133] 1: Case 2: Lift arm 21: One end side 22:Other end side 23: Lift arm shaft 3: Bracket 31: One end side 32:Other end side 33: Bracket shaft 35a: Mounting part 35b: Mounting part 35c: Mounting part 36a: Mounting part 36b: Mounting part 36c: Mounting part 4: Hydraulic cylinder 5: Control valve 51: Spool 6: Position control lever 61: One end side 62:Other end side 7: Pompalever 71: One end side 72:Other end side 74: Rotation restricting section 8: Draft control lever 81: One end side 82:Other end side 9: Position Feedback Rod 91: Rear end side 92: Front end side 10: Draft Feedback Rod 101: Rear end side 102: Front end side 11a: Third displacement transmission section 11a1:Fulcrum part 11a2: Front end side 11b: Fourth displacement transmission section 100: Hydraulic lifting device 20: Position control transmission mechanism 210: Position control cam 220: First position control shaft 221: Same-direction rotating shaft 222: Reverse rotation shaft 223: Rotation transmission section 230: Second position control shaft 230a: Second displacement transmission section 30: Pumper transmission mechanism 310: Pompakam 320: Pompa Shaft 330: Rotation transmission section 40: Draft control transmission mechanism 410: Draft control cam 420: 1st Draft Control Shaft 421: Same-direction rotating shaft 422: Reverse rotation shaft 423: Rotation transmission section 430: Second position control shaft 430a: First displacement transmission section 430a1: Rear end side Z1: Lift arm axis Z2: Bracket axis

Claims

1. The case and, A hydraulic cylinder located inside the aforementioned case and driven in accordance with the supply and discharge of hydraulic fluid, A control valve located inside the case and having a spool in the hydraulic fluid passage, the control valve permits and restricts the supply and discharge of the hydraulic fluid to the hydraulic cylinder depending on the position of the spool, A lift arm located outside the case, with one end and the other end defined, wherein the one end is configured to be connectable to an object, and the lift arm is configured to be able to raise and lower the connected object by rotating relative to the case with the other end as a pivot point when the hydraulic cylinder is driven, A bracket located on the outside of the case, with one end and the other end defined, wherein the one end is configured to be connectable to an object, and the bracket rotates relative to the case with the other end as a pivot point in response to the traction load from the connected object, A draft control lever located on the outside of the aforementioned case and configured to be displaceable in response to the operator's actions, A draft feedback rod located on the outside of the case and configured to be displaceable in accordance with the relative rotation of the bracket, A draft control transmission mechanism that, when the draft control lever is operated, transmits the displacement of the draft control lever toward the spool and displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid, and when the bracket rotates relative to it, transmits the displacement of the draft feedback rod toward the spool and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid, In a hydraulic lifting device, The aforementioned lift arm is The lift arm axis is the axis of relative rotation with respect to the case, and extends in a second direction perpendicular to the first direction, which is the upward and downward direction of the object. Equipped with, The aforementioned bracket is The axis of rotation relative to the case, which extends in the second direction, is a bracket axis located parallel to the lift arm axis, A mounting portion is configured to allow the aforementioned object to be attached, and is located below the bracket axis in the first direction, A hydraulic lifting device equipped with a hydraulic lifting mechanism.

2. In the hydraulic lifting device according to claim 1, The aforementioned bracket is The bracket shaft is configured to be located lower in the first direction than the lift arm shaft. Hydraulic lifting device.

3. In the hydraulic lifting device according to claim 1, The aforementioned bracket is The bracket shaft is configured to be positioned above the lift arm shaft in the first direction. Hydraulic lifting device.

4. In the hydraulic lifting device according to claim 2 or claim 3, The bracket shaft is pivotally supported at the other end of the bracket by the case, and is arranged coaxially with the bracket axis, and is configured to generate a biasing force when it rotates relative to the traction load. A hydraulic lifting device further equipped with [features].

5. In the hydraulic lifting device according to claim 2 or claim 3, The aforementioned draft control transmission mechanism is When the draft control lever is operated, a first draft control shaft rotates around its axis in accordance with the displacement of the draft control lever, A second draft control shaft is located above the first draft control shaft in the vertical direction of the object, and rotates around its axis in accordance with the displacement of the draft feedback rod when the bracket rotates relative to it. A draft control cam that, when the first draft control shaft rotates, displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid in accordance with the rotation of the first draft control shaft, and when the second draft control shaft rotates, displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid in accordance with the rotation of the second draft control shaft, A hydraulic lifting device equipped with a hydraulic lifting mechanism.

6. In the hydraulic lifting device according to claim 5, The aforementioned draft control lever is One end and the other end are defined, the one end is configured to be operable by the operator, and the other end is configured to be rotatable relative to the case with respect to the operation, as a displacement corresponding to the operation. The first draft control shaft is A co-rotating shaft is connected to the other end of the draft control lever and configured to rotate in the same direction as the rotation direction of the draft control lever, A reverse rotation shaft connected to the draft control cam and configured to rotate in the opposite direction to the rotation direction of the draft control lever, When the draft control lever rotates relative to the other, the rotation transmission unit transmits the rotation of the same-direction rotating shaft toward the opposite-direction rotating shaft, and rotates the opposite-direction rotating shaft in the opposite direction to the rotation direction of the same-direction rotating shaft. A hydraulic lifting device equipped with a hydraulic lifting mechanism.

7. In the hydraulic lifting device according to claim 5, A position control lever located on the outside of the aforementioned case and configured to be displaceable in response to the operator's actions, A position feedback rod located on the outside of the case and configured to be displaceable in accordance with the relative rotation of the lift arm, A position control transmission mechanism that, when the position control lever is operated, transmits the displacement of the position control lever toward the spool and displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid, and when the lift arm rotates relative to it, transmits the displacement of the position feedback rod toward the spool and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid, In a hydraulic lifting device, The position control transmission mechanism is When the position control lever is operated, a first position control shaft rotates around its axis in accordance with the displacement of the position control lever, A second position control shaft is located above the first position control shaft in the vertical direction of the object, and rotates around its axis in accordance with the displacement of the position feedback rod when the lift arm rotates relative to it. A position control cam that, when the first position control shaft rotates, displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid in accordance with the rotation of the first position control shaft, and when the second position control shaft rotates, displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid in accordance with the rotation of the second position control shaft, A hydraulic lifting device further equipped with [features].

8. In the hydraulic lifting device according to claim 7, A first displacement transmission unit is connected to the second draft control shaft so as to be rotatable integrally with the second draft control shaft and to the draft feedback rod so as to be rotatable relative to the draft feedback rod, and rotates the second draft control shaft in accordance with the displacement of the draft feedback rod when the bracket rotates relative to the first draft control shaft. A second displacement transmission unit is connected to the second position control shaft so as to be rotatable together with the second position control shaft and to the position feedback rod so as to be rotatable relative to the position feedback rod, and rotates the second position control shaft in accordance with the displacement of the position feedback rod when the lift arm rotates relative to the position control shaft. A third displacement transmission unit is configured to contact and press against the first displacement transmission unit, and to rotate relative to the case in conjunction with the rotation of the second displacement transmission unit, and when the position feedback rod is displaced and the second displacement transmission unit rotates, it rotates relative to the case and contacts and presses against the first displacement transmission unit, thereby rotating the first displacement transmission unit. A hydraulic lifting device further equipped with [features].

9. In the hydraulic lifting device according to claim 7, Either the first draft control shaft or the first position control shaft has a hollow structure and is configured such that the other can be coaxially fitted inside the first one. Either the second draft control shaft or the second position control shaft has a hollow structure and is configured such that the other can be coaxially fitted inside the other. The draft control transmission mechanism and the position control transmission mechanism are The other is coaxially fitted into either the first draft control shaft or the first position control shaft, and the other is coaxially fitted into either the second draft control shaft or the second position control shaft, In accordance with the displacement of either the draft control lever or the position control lever, the first draft control shaft and the first position control shaft rotate relative to each other around their respective axes, The second draft control shaft and the second position control shaft are configured to rotate relative to each other around their respective axes in response to the displacement of either the draft feedback rod or the position feedback rod. Hydraulic lifting device.

10. In the hydraulic lifting device according to claim 5, A position control lever located on the outside of the aforementioned case and configured to be displaceable in response to the operator's actions, A position feedback rod located on the outside of the case and configured to be displaceable in accordance with the relative rotation of the lift arm, A position control transmission mechanism that, when the position control lever is operated, transmits the displacement of the position control lever toward the spool and displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid, and when the lift arm rotates relative to it, transmits the displacement of the position feedback rod toward the spool and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid, A pump lever is located outside the case and is configured to be displaceable from a first position, which is any position while the supply and discharge of the hydraulic fluid is restricted by the control valve, to a second position different from the first position, in response to the operator's operation. A pump transmission mechanism that, when the pump lever is operated to displace from the first position to the second position, transmits the displacement of the pump lever toward the spool and displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid, and when the lift arm rotates relative to the pump lever while it is in the second position, transmits the displacement of the position feedback rod toward the spool and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid, Furthermore, The position control transmission mechanism is When the position control lever is operated, a first position control shaft rotates around its axis in accordance with the displacement of the position control lever, A second position control shaft is located above the first position control shaft in the vertical direction of the object, and rotates around its axis in accordance with the displacement of the position feedback rod when the lift arm rotates relative to it. Equipped with, The pumper transmission mechanism is, When the pump lever is operated and displaced from the first position to the second position, the pump shaft rotates around its axis in accordance with the displacement of the pump lever, A pump cam that, when the pump shaft rotates, displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic fluid in accordance with the rotation of the pump shaft, and when the second position control shaft rotates, displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic fluid in accordance with the rotation of the second position control shaft, A hydraulic lifting device equipped with a hydraulic lifting mechanism.

11. In the hydraulic lifting device according to claim 10, The aforementioned pump lever is One end and the other end are defined, the one end is configured to be operable by the operator, and the other end is configured to be rotatable relative to the case with respect to the operation, as a displacement corresponding to the operation. Rotation restricting part that restricts the relative rotation of the pump lever A hydraulic lifting device equipped with a hydraulic lifting mechanism.

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