JP2024043765A - Hydraulic lifting apparatus - Google Patents

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

The present invention relates to a hydraulic lifting device that raises and lowers a lift arm using hydraulic pressure.

Conventionally, a hydraulic lifting device that raises and lowers a lift arm based on hydraulic pressure is known, for example, as shown in Patent Document 1. This device includes a hydraulic cylinder and a control valve having a spool, and the supply and discharge of hydraulic oil to the hydraulic cylinder is permitted and restricted depending on the position of the spool. This device further includes a load detection member and a biasing mechanism. The load detection member is provided at the rear end of the transmission case, and can be connected to the front end of the top link. The load detection member is also capable of swinging in response to the towing load of the implement via the top link. The biasing mechanism biases the load detection member to swing.

When the load detection member swings in response to the traction load, the spool is displaced in response to the swing via the transmission mechanism. Then, the lift arm moves up and down with the implement connected. As a result, implements such as plows can also be raised and lowered, and an appropriate tractive load can be maintained. That is, the above-described configuration allows draft control to be executed.

JP 2018-153118 (Paragraph 0039, Figure 3, etc.)

The top link connected to this type of hydraulic lifting device is generally rod-shaped, with a defined front end 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. If the height of the rotation shaft of the lift arm, the arm length, and the range of rotation do not change, the lower the position of the front end of the top link moves downward when the implement is connected, the higher the bottom end of the implement is lifted. In other words, 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 preferable in many situations when operating the work machine.

On the other hand, the load detection member of the above-mentioned Patent Document 1 includes a connecting hole and a support shaft. The connecting hole is configured so that the front end side of the top link can be connected. The support shaft supports the load detection member at the rear end of the transmission case so that the load detection member can swing. In terms of the positional relationship between the connecting hole and the support shaft, the connecting hole is located above the support shaft. For this reason, the front end side of the top link cannot be positioned sufficiently downward, making it difficult to increase the distance between the connected implement and the ground.

Therefore, in view of the above, an object of the present invention is to provide a hydraulic lifting device that can easily increase the distance between a connected implement and the ground.

The technical means of the present invention for solving this technical problem are characterized as follows. The hydraulic lifting device of the present invention comprises a case, a hydraulic cylinder located inside the case and driven in response to the supply and discharge of hydraulic oil, a control valve located inside the case and having a spool in a flow path of the hydraulic oil, the control valve allowing and regulating the supply and discharge of the hydraulic oil to the hydraulic cylinder depending on the position of the spool, a lift arm located outside the case and having one end and the other end defined, the one end being configured to be connectable to an object and configured to rotate relative to the case with the other end as a fulcrum when the hydraulic cylinder is driven, thereby lifting and lowering the connected object, and a bracket located outside the case and having one end and the other end defined, the one end being configured to be connectable to an object and configured to lift and lower the connected object. the draft control transmission mechanism comprises: a bracket that rotates relative to the case with the other end as a fulcrum in response to a towing load from an object; a draft control lever that is located outside the case and configured to be displaceable in response to operation by an operator; a draft feedback rod that is 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 position of the spool toward a side that allows supply and discharge of the hydraulic oil, and, when the bracket rotates relatively, transmits the displacement of the draft feedback rod toward the spool and displaces the position of the spool toward a side that restricts supply and discharge of the hydraulic oil. The lift arm has a lift arm axis which is the axis of the relative rotation with respect to the case and extends in a second direction perpendicular to a first direction in which the object is raised and lowered, and the bracket has a bracket axis which is the axis of the relative rotation with respect to the case and extends in the second direction, and which is positioned parallel to the lift arm axis, and a mounting portion which is configured to be able to mount the object and is positioned lower in the first direction than the bracket axis.

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.

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.

The hydraulic lifting device further includes a bracket shaft that supports the other end of the bracket on the case, is arranged coaxially with the bracket shaft, and is configured to generate a biasing force when the bracket rotates relative to the traction load.

In the hydraulic lifting device, the draft control transmission mechanism includes a first draft control shaft that rotates around an axis according to displacement of the draft control lever when the draft control lever is operated, and a first draft control shaft that rotates around an axis according to displacement of the draft control lever. a second draft control shaft that is located above the shaft in the vertical direction of the object and rotates around an axis according to displacement of the draft feedback rod when the bracket rotates relative to the target; and the first draft control shaft. When the shaft rotates, the position of the spool is displaced toward a side where supply and discharge of the hydraulic oil is permitted according to the rotation of the first draft control shaft, and when the second draft control shaft rotates, A draft control cam that displaces the position of the spool toward a side that regulates supply and discharge of the hydraulic oil in accordance with rotation of the second draft control shaft.

In the hydraulic lifting device, the draft control lever has one end and the other end defined, the one end is operable by the operator, and is rotatable relative to the case with the other end as a fulcrum for displacement in response to the operation. The first draft control shaft is connected to the other end of the draft control lever and includes a same-direction rotation shaft configured to rotate in the same direction as the rotation direction of the draft control lever, a reverse-direction 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, and a rotation transmission unit that transmits the rotation of the same-direction rotation shaft to the reverse-direction rotation shaft when the draft control lever rotates relative to the case, and rotates the reverse-direction rotation shaft in the opposite direction to the rotation direction of the same-direction rotation shaft.

The hydraulic lifting device includes a position control lever located outside the case and configured to be displaceable according to an operation by an operator, and a position control lever located outside the case and configured to be displaced according to relative rotation of the lift arm. a position feedback rod configured to transmit a displacement of the position control lever toward the spool when the position control lever is operated, and a position feedback rod configured to allow the position of the spool to be supplied and discharged in the hydraulic fluid; and transmits the displacement of the position feedback rod toward the spool when the lift arm relatively rotates, and the position of the spool is directed toward a side that regulates supply and discharge of the hydraulic oil. A position control transmission mechanism for causing displacement. The position control transmission mechanism includes a first position control shaft that rotates around an axis in response to displacement of the position control lever when the position control lever is operated, and a first position control shaft that rotates around the axis in response to displacement of the position control lever; a second position control shaft that is located on the upper side in the vertical direction of the lift arm and rotates around an axis according to the displacement of the position feedback rod when the lift arm rotates relative to the second position control shaft; and when the first position control shaft rotates. In accordance with the rotation of the first position control shaft, the position of the spool is displaced toward a side where supply and discharge of the hydraulic oil is permitted, and when the second position control shaft rotates, the second position control shaft is moved. The apparatus further includes a position control cam that displaces the position of the spool toward a side that regulates supply and discharge of the hydraulic oil in accordance with rotation of the shaft.

The hydraulic lifting device is connected to the second draft control shaft so as to be integrally rotatable, and is also connected to the draft feedback rod so as to be relatively rotatable, and when the bracket rotates relative to the bracket, the hydraulic lifting device responds to the displacement of the draft feedback rod. Accordingly, a first displacement transmitting section that rotates the second draft control shaft is connected to the second position control shaft so as to be integrally rotatable, and is connected to the position feedback rod so as to be relatively rotatable, and the lift arm a second displacement transmitting part that rotates the second position control shaft according to the displacement of the position feedback rod when the position feedback rod rotates relative to the second position control shaft; The second displacement transmitting section is configured to rotate relative to the case in conjunction with the rotation of the second displacement transmitting section, and when the position feedback rod is displaced and the second displacement transmitting section rotates, the second displacement transmitting section rotates relative to the case. The apparatus further includes a third displacement transmitting part that rotates the first displacement transmitting part by pressing the first displacement transmitting part while contacting the first displacement transmitting part.

In the hydraulic lifting device, one of the first draft control shaft and the first position control shaft has a hollow structure and is configured so that the other can be coaxially inserted into the inside of the first draft control shaft, and one of the second draft control shaft and the second position control shaft has a hollow structure and is configured so that the other can be coaxially inserted into the inside of the first draft control shaft and the second position control shaft, and the draft control transmission mechanism and the position control transmission mechanism are configured so that the other is coaxially inserted into either the first draft control shaft or the first position control shaft, and the other is coaxially inserted 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 relatively to each other about their axes 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 relatively to each other about their axes in response to the displacement of either the draft feedback rod or the position feedback rod.

The hydraulic lifting device is located outside the case, and is moved in response to an operator's operation from a first position that is an arbitrary position when supply and discharge of the hydraulic oil is regulated by the control valve. , a pumper lever configured to be displaceable to a second position different from the first position; and a pumper lever configured to be able to be displaced from the first position to the second position; The transmission is transmitted to the spool, and the position of the spool is displaced toward the side where supply and discharge of the hydraulic oil is permitted, and the lift arm is rotated relative to the pump lever in the second position. The pump transmission mechanism further includes a pump transmission mechanism that transmits the displacement of the position feedback rod toward the spool and displaces the position of the spool toward a side that restricts supply and discharge of the hydraulic oil. The pumper transmission mechanism includes a pumper shaft that rotates around an axis in accordance with displacement of the pumper lever, and a pumper shaft that rotates when the pumper lever is operated and displaced from the first position to the second position. When the pump shaft rotates, the position of the spool is displaced toward a side that allows supply and discharge of the hydraulic oil, and when the second position control shaft rotates, the second position control shaft a pump cam that displaces the position of the spool toward a side that regulates supply and discharge of the hydraulic oil in response to rotation of the pump cam.

In the hydraulic lifting device, the pump lever has one end and the other end defined, the one end is operable by the operator, and the other end is rotatable relative to the case as a displacement in response to the operation, with the other end as a fulcrum, and includes a rotation restriction section that restricts the relative rotation of the pump lever.

According to the present invention, it is easy to increase the distance between the connected implement and the ground.

1 is an overall perspective view of a hydraulic lifting device according to a first embodiment of the present invention. FIG. 2 is a right side view of the hydraulic lifting device shown in FIG. 1 . FIG. 2 is a left side view of the hydraulic lifting device shown in FIG. 1. FIG. FIG. 2 is a bottom view of the hydraulic lifting device shown in FIG. 1 . FIG. 2 is a perspective view showing a part of a drive system inside a case of the hydraulic lifting device shown in FIG. 1 . FIG. 2 is a perspective view showing a part of a drive system inside a case of the hydraulic lifting device shown in FIG. 1 . FIG. 2 is a left side view of the rear side of the hydraulic lifting device shown in FIG. 1 , showing the positional relationship of each shaft. 2 is an overall perspective view of each transmission mechanism in the hydraulic lifting device shown in FIG. 1. FIG. FIG. 2 is an enlarged view of essential parts showing the positional relationship of each cam and spool in the hydraulic lifting device shown in FIG. 1. FIG. FIG. 2 is an overall view of a position control transmission mechanism in the hydraulic lifting device shown in FIG. 1 . 2 is an overall view of a pump transmission mechanism in the hydraulic lifting device shown in FIG. 1. FIG. FIG. 2 is an overall view of a draft control transmission mechanism in the hydraulic lifting device shown in FIG. 1 . 2 is an overall schematic diagram showing the positional relationship of components of each transmission mechanism in the hydraulic lifting device shown in FIG. 1 . FIG. FIG. 6 is a left side view of a hydraulic lifting device according to a second embodiment of the present invention. FIG. 15 is a left side view of the rear side of the hydraulic lifting device shown in FIG. 14, and is a diagram showing the positional relationship of each axis. FIG. 15 is a perspective view showing a configuration in the vicinity of the front end portion of each feedback rod in the hydraulic lifting device shown in FIG. 14. 15 is an overall schematic diagram showing the positional relationship of the components of each transmission mechanism in the hydraulic lifting device shown in FIG. 14. FIG. 15 is a component configuration diagram of a position feedback rod, a second displacement transmission mechanism, a third displacement transmission mechanism, and a fourth displacement transmission mechanism in the hydraulic lifting device shown in FIG. 14. 15 is a component configuration diagram of a draft feedback rod and a first displacement transmission mechanism in the hydraulic lifting device shown in FIG. 14. FIG.

Hereinafter, each embodiment of the present invention will be described based on the drawings.

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

<Overall configuration of hydraulic lifting device>
FIG. 1 is an overall perspective view of a hydraulic lifting device 100 according to a first embodiment of the present invention. 2 and 3 are side views of the hydraulic lifting device 100. FIG. 4 is a bottom view of the hydraulic lifting device 100. Left/right, up/down, front/back of the arrows appropriately shown in each figure correspond to left/right direction, upward/downward direction, and front/backward direction, respectively.

The hydraulic lifting device 100 is mounted on an agricultural vehicle such as a tractor. More specifically, the hydraulic lifting device 100 is mounted on the rear of the tractor or the like, on the upper part of the transmission case. One end side 21 of the lift arm 2 and one end side 31 of the bracket 3 protrude rearward from the mounted hydraulic lifting device 100. One end side 21 of the lift arm 2 is connected to the lower link via a lift link. An end of the top link is connected to one end side 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 in the vertical direction 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 lifting and lowering direction of the implement corresponds to the vertical direction, which is the first direction.

As shown in Figures 1 to 4, the hydraulic lifting device 100 includes 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. The bracket 3 will be described in detail later. The hydraulic lifting device 100 also includes 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.

The case 1 is a housing, and the bottom of the case 1 is open. Two lift arms 2 are located on the outside rear of the case 1, one on each of the left and right sides. Each lift arm 2 has one end 21 and the other end 22. The one end 21 is configured to be connectable to a lift link (not shown). The other end 22 is supported by both ends of a lift arm shaft 23 that penetrates both the left and right sides from inside the case 1 (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 the case 1 with the other end 22 as a fulcrum. In other words, the one end 21 can swing up and down with the other end 22 as a fulcrum.

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

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 oil circuit (not shown) and is driven in response to the supply and discharge of the hydraulic oil. The hydraulic cylinder 4 has a piston 41 and a piston rod 42 inside. In response to the supply and discharge of the hydraulic oil inside the hydraulic cylinder 4, the piston 41 and the 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 side of the piston rod 42 is connected to the rotating tip side of the crank arm 43. In addition, the rotation fulcrum side of the crank arm 43 is connected to the center part of the lift arm shaft 23 in the left-right direction. As a result, the relative movement of the piston 41 and the piston rod 42 in the front-rear direction is converted into the rotation of the lift arm shaft 23.

As shown in FIG. 4, the hydraulic cylinder 4 is arranged in the internal space of the case 1 so that the axes of the piston 41 and the piston rod 42 extend along the front-rear direction and are closer to the left front. A portion of each transmission mechanism 20, 30, 40, which will be described later, is accommodated between the hydraulic cylinder 4 and the upper inner wall and right inner wall of the case 1. Further, a hydraulic oil control valve 5 is housed between the hydraulic cylinder 4 and the right inner wall of the case 1.

The control valve 5 has a flow path for hydraulic oil formed therein, and is interposed in a hydraulic oil circuit. In addition, a hydraulic pump, relief valve, flow path switching valve, safety valve, drop adjustment valve, etc. are also connected and installed in the circuit. These parts are configured integrally with the case 1 or separately. The control valve 5 is located on the right side of the hydraulic cylinder 4 in the internal space of the case 1. The control valve 5 has a spool 51 in the hydraulic oil flow path. A front end side 51a of the spool 51 is exposed outside the hydraulic oil flow path of the control valve 5. The spool 51 is movable in the front-rear direction relative to the housing of the control valve 5. The spool 51 is always urged forward by a spring.

The front end side 51a of the spool 51 is pressed backward against the biasing force by the cams of each transmission mechanism 20, 30, 40. At this time, the position of the spool 51 is displaced backward, allowing the supply of hydraulic oil to the hydraulic cylinder 4. As hydraulic oil is supplied to the hydraulic cylinder 4 and the piston 41 and piston rod 42 are displaced, the lift arm 2 rotates relatively through the transmission of the crank arm 43 and the lift arm shaft 23. On the other hand, when the pressure by the cams of each transmission mechanism 20, 30, 40 is released, the position of the spool 51 is displaced forward along the biasing force, and the supply of hydraulic oil to the hydraulic cylinder 4 is restricted. 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 that was rotating relatively is fixed.

1 and 2, the position control lever 6, the pump lever 7, and the draft control lever 8 are located on the right side outside the case 1, and are located forward 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 an operator. The other end 62 is supported by the right end of a first position control shaft 220 that penetrates the right side from inside the case 1 (see Figs. 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 is operated by an operator, the position control lever 6 rotates relative to the case 1 with the other end 62 as a fulcrum, as a displacement according to the operation. That is, the one end 61 can swing in the front-rear direction with the other end 62 as a fulcrum.

In the pumper lever 7, one end side 71 and the other end side 72 are defined. One end side 71 is configured to be operable by an operator. Separately, a grip (not shown) that can be held by the operator may be provided. The other end 72 is pivotally supported at the right end of a pump shaft 320 that passes through the right side surface from inside the case 1 (see FIGS. 8 and 11). The pumper lever 7 projects upward from the other end side 72 toward the one end side 71. The other end side 72 of the pumper lever 7 is located above the other end side 62 of the position control lever 6. When one end side 71 is operated by an operator, the pumper lever 7 rotates relative to the case 1 with the other end side 72 as a fulcrum as a displacement according to the operation. That is, the one end side 71 can swing back and forth using the other end side 72 as a fulcrum. More specifically, the pumper lever 7 is moved from a first position, which is an arbitrary position when supply and discharge of hydraulic oil is regulated by the control valve 5, to the first position according to the operator's operation. It is configured to be able to be displaced to a second position different from the first position.

Here, the "state in which the supply and discharge of hydraulic oil is restricted by the control valve 5" refers to, for example, a state after the position of the spool 51 has been displaced toward the restricting side of the supply and discharge of hydraulic oil due to the displacement of the position feedback rod 9. The relationship between the "first position" and the "second position" only needs to be such that the positions of the one end side 71 are different from each other. For example, the one end side 71 in the second position may be located forward or rearward of the one end side 71 in the first position. The positional movement of the one end side 71 displaces the position of the spool 51 toward the allowing side of the supply and discharge of hydraulic oil.

The pumper lever 7 has a detent mechanism as a detent for relative rotation. In this embodiment, the detent mechanism functions only on the lowering side of the pumper lever 7, but in addition to this, it may also function on the raising side of the pumper lever 7. In addition to the detent mechanism, the pumper lever 7 includes a rotation regulating portion 74 that regulates relative rotation of the pumper lever 7. The rotation restricting portion 74 may be indirectly fixed to the case 1 via a plate 73 provided on the case 1, for example. The rotation restricting portion 74 includes a protrusion member 74a that protrudes forward. The protruding member 74a is located at the rear of the pumper lever 7, and the front end of the protruding member 74a can intersect with the radial locus of the pumper lever 7. Therefore, if the one end side 71 continues to swing backward, the pumper lever 7, which rotates counterclockwise in FIG. 2, will eventually come into contact with the front end of the protruding member 74a. At this time, the relative rotation of the pumper lever 7 is restricted. As a result of restricting relative rotation, the vertical height of the connected implements can be easily adjusted to any desired position.

Note that the position of the front end of the protruding member 74a can be adjusted in the front-rear direction using a length adjustment mechanism such as a screw. That is, the position where the pumper lever 7 contacts the protrusion member 74a is also adjusted in the front-rear direction. Therefore, the relative rotation of the pumper lever 7 is regulated more toward the front as the position of the front end of the protrusion member 74a is displaced forward.

In the draft control lever 8, one end side 81 and the other end side 82 are respectively defined. The one end side 81 is configured to be operable by an operator. The other end side 82 is supported by the right end of the first draft control shaft 420 that 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 side 82 toward the one end side 81. The other end side 82 of the draft control lever 8 is positioned coaxially with the other end side 62 of the position control lever 6. The draft control lever 8 is positioned to the left of the position control lever 6. When the one end side 81 of the draft control lever 8 is operated by an operator, the draft control lever 8 rotates relative to the case 1 with the other end side 82 as a fulcrum as a displacement according to the operation. In other words, the one end side 81 can swing in the forward and backward directions with the other end side 82 as a fulcrum.

As shown in FIGS. 3 to 6, the position feedback rod 9 and the draft feedback rod 10 are located on the outside and left side of the case 1, and extend in the front-rear direction. The rear end side 91 of the position feedback rod 9 is connected to the lower end of the cam 24 so as to be relatively rotatable. 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 together, and the lower end of the cam 24 swings back and forth. Accordingly, the position feedback rod 9 can be displaced in the front-rear direction.

The front end side 92 of the position feedback rod 9 is connected to the lower end of the cam 230a so as to be relatively rotatable. The cam 230a is pivotally supported at the left end of a second position control shaft 230 that passes through the left side surface from inside the case 1, and protrudes downward (see FIGS. 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, and the second position control shaft 230 is relatively rotatable.

The rear end 101 of the draft feedback rod 10 is connected to the lower end of the joint 34. The joint 34 is fixed integrally 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-to-rear direction. In response to this, the draft feedback rod 10 is capable of displacement in the front-to-rear direction.

The front end side 102 of the draft feedback rod 10 is connected to the lower end of the cam 430a so as to be rotatable relative to the cam 430a. A part of the front end side 102 is composed of a spring 102a. The cam 430a is supported by 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 side 102 with the cam 430a is higher than the connection position of the front end side 92 of the position feedback rod 9 with 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, and the second draft control shaft 430 is capable of rotating relative to the cam 430. In particular, when the draft feedback rod 10 is displaced forward, the spring 102a slightly shrinks from the 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 backward, the spring 102a does not interfere (does not stretch).

<Bracket configuration>
As shown in Figures 1, 5 and 6, the bracket 3 is located rearward of the other end 22 of the lift arm 2 and at the outer rear end of the case 1. One end 31 and the other end 32 are defined in the bracket 3. The one end 31 is configured to be connectable to a top link (not shown). That is, in this embodiment, the bracket 3 is a so-called top link bracket. The other end 32 is journaled by a bracket shaft 33 connected to the case 1 at both ends. The bracket 3 rotates relative to the case 1 with the other end 32 as a fulcrum in response to a traction load from the connected top link (i.e., an implement).

The bracket 3 has a bracket axis Z2, which is an axis of relative rotation with respect to the case 1. The bracket axis Z2 is positioned parallel to the lift arm axis Z1. In this embodiment, the direction of the bracket axis Z2 corresponds to the left-right direction, which is equivalent to the second direction. The direction of the bracket axis Z2 (second direction) is perpendicular to the lifting and lowering direction of the implement (first direction). The bracket shaft 33 is arranged coaxially with the bracket axis Z2.

The bracket 3 has a left side plate 35 and a right side plate 36. The left side plate 35 and the right side plate 36 are disposed on the left and right sides, respectively, of approximately the center in the left-right direction at the outer rear end of the case 1. The faces of the left side plate 35 and the right side plate 36 face each other parallel to each other with a specified distance between them. The left side plate 35 and the right side plate 36 each have approximately the same shape, extend rearward from the other end side 32, and further protrude diagonally downward toward the one end side 31 at the rear.

Further, the bracket 3 includes attachment portions 35a, 35b, 35c, 36a, 36b, and 36c, and a link pin 37. The attachment parts 35a, 35b, and 35c are circular through holes, and are provided in the left side plate 35. The attachment parts 36a, 36b, and 36c are circular through holes, and are provided in the right side plate 36. The attachment parts 35a and 36a are arranged coaxially with the left-right axis Z3. The attachment parts 35b and 36b are arranged coaxially with the left-right axis Z4. The attachment parts 35c and 36bc are arranged coaxially with the left-right axis Z5. The axes Z3, Z4, and Z5 are each located parallel to the bracket axis Z2.

The link pin 37 can be coaxially engaged with one set selected from the attachment parts 35a, 36a, the attachment parts 35b, 36b, and the attachment parts 35c, 36c. As an example, a state in which the link pin 37 is fitted to the attachment parts 35c and 36c is illustrated. When attaching the top link to the bracket 3, a mating hole at the end of the top link is arranged coaxially between the selected pair of attachment parts 35a-c, 36a-c, and the link pin 37 Attach the mating hole at the end of the top link. Thereby, the top link is relatively rotatably connected to the bracket 3 via the link pin 37 at its end.

The bracket shaft 33 is configured to generate a biasing force when it rotates relative to the implement in response to the towing load. The bracket shaft 33 has, for example, a torsion bar structure, and generates a biasing force in the opposite rotation direction to the rotation load around the bracket axis Z2. More specifically, when the top link is connected by the link pin 37 and the one end side 31 swings rearward in response to the towing load, the bracket 3 rotates relative to the bracket axis Z2. In this case, the direction of relative rotation is counterclockwise when viewed from the left side (see Figures 3 and 7). In response to this, the bracket shaft 33 generates a biasing force in the clockwise direction when viewed from the left side. On the other hand, when the one end side 31 swings forward in response to the towing load, the bracket 3 also rotates relative to the bracket axis Z2. In this case, the direction of relative rotation is clockwise when viewed from the left side. In response to this, the bracket shaft 33 generates a biasing force in the counterclockwise direction when viewed from the left side. In this way, the one end side 31 can swing back and forth while being biased, with the other end side 32 as the fulcrum.

As shown in FIG. 7, the bracket shaft 33 is located rearward of the lift arm shaft 23. The bracket axis Z2 of the bracket shaft 33 is located lower than the lift arm axis Z1 of the lift arm shaft 23 by a height H1 in the vertical direction. The mounting parts 35a, 35b, and 35c are located rearward of the bracket shaft 33. The mounting parts 35a, 35b, and 35c are arranged in this order on the left side plate 35 from the upper left to the lower right. The positional relationship of the mounting parts 36a to c is similar to that of the mounting parts 35a to c. The axis Z3 of the mounting part 35a is located lower than the bracket axis Z2 by a height H2a in the vertical direction. The axis Z4 of the mounting part 35b is located lower than the bracket axis Z2 by a height H2b in the vertical direction. The axis Z5 of the mounting part 35c is located lower than the bracket axis Z2 by a height H2c in the vertical direction. In this embodiment, the positional relationship of each axis Z1 to Z5 is parallel to one another in the left-right direction, and the heights are H1<H2a<H2b<H2c, but is not limited to this.

<Configuration of transmission mechanism>
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, 40 is configured to transmit the displacement of each lever 6, 7, 8 and the displacement of each rod 9, 10 toward a spool 51 of the control valve 5. The displacements input to each transmission mechanism 20, 30, 40 are finally collected into a position control cam 210, a pumper cam 310, and a draft control cam 410, and displace each of the cams 210, 310, 410, respectively.

Figure 9 is an enlarged view of the main parts showing the positional relationship of each cam 210, 310, 410 and the spool 51 inside the case 1. As shown in Figure 8, the position control cam 210, the pumper cam 310 and the draft control cam 410 are each approximately "E" shaped 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 with a gap between them. Each cam 210, 310 and 410 is provided with a pin that penetrates approximately the center in the vertical direction in the left-right direction to position it. Each cam 210, 310 and 410 can rotate relatively around the pin. As the position control cam 210, pump cam 310, and draft control cam 410 are displaced, the upper end sides 212, 312, 412 and the lower end sides 213, 313, 413 can swing forward and backward.

In response to the swinging motion, the respective protrusions 211, 311, 411 can swing in the front-rear direction together. When the protrusions 211, 311, 411 swing rearward and displace, the front end 51a of the spool 51 is pressed by the protrusions 211, 311, 411 and displaced rearward. Next, when the protrusions 211, 311, 411 swing forward and displace, the spool 51 displaces forward in response to the biasing force of the spring. In this way, the spool 51 of the control valve 5 is also displaced in response to the respective displacements of the cams 210, 310, 410. The specific operation of the respective cams 210, 310, 410 will be explained together with the detailed explanation of the respective transmission mechanisms 20, 30, 40.

Hereinafter, the respective 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.

<<Position control transmission mechanism>>
FIG. 10 is an overall view of the position control transmission mechanism 20. As shown in FIG. 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.

The first position control shaft 220 includes a co-rotating shaft 221 , a reverse-rotating shaft 222 , and a rotation transmitting section 223 . The co-rotating shaft 221 extends in the left-right direction and has an axis A1 parallel to the left-right direction. The same direction rotating shaft 221 is connected to the other end 62 of the position control lever 6 at its right end. The same direction rotating shaft 221 is rotatable around the axis A1 in the same direction as the rotation direction of the position control lever 6. A cam 221a that projects upward is provided on the left end side of the co-rotating shaft 221. The cam 221a can swing back and forth in accordance with the rotation of the co-rotating shaft 221 about the axis A1.

The reverse rotation shaft 222 extends in the left-right direction and has an axis A2 that is parallel to the left-right direction. The axis A2 is located diagonally above and forward of the axis A1. That is, the same-direction rotation shaft 221 and the reverse-direction rotation shaft 222 are arranged to have different axes. As shown in the dashed line portion of FIG. 10 and in FIG. 13, the reverse rotation shaft 222 has a hollow structure along the axis A2, and the reverse rotation shaft 422 of the first draft control shaft 420 can be coaxially inserted therein.

A cam 222a that protrudes downward is provided on the right end side of the reverse rotation shaft 222. In response to the back-and-forth rocking of the cam 222a, the reverse rotation shaft 222 can rotate around the axis A2 in a direction opposite to the rotation direction of the position control lever 6. A cam 222b that protrudes downward is provided on the left end side of the reverse rotation shaft 222. The cam 222b can swing back and forth in response to the rotation of the reverse rotation shaft 222 about the axis A2.

The rotation transmission section 223 is a plate extending in the front-rear direction. The rear side of the rotation transmission section 223 is rotatably connected to the upper end of the cam 221a, and the front side of the rotation transmission section 223 is rotatably connected to the lower end of the cam 222a. The rotation transmission section 223 is configured to swing the cam 222a in the front-back direction in response to the swing of the cam 221a in the front-back direction.

In the first position control shaft 220 configured in this manner, when the position control lever 6 is operated, the same-direction rotating shaft 221 rotates around axis A1 and the reverse-direction rotating shaft 222 rotates around axis A2 in response to the displacement of the position control lever 6. More specifically, when the position control lever 6 and the same-direction rotating shaft 221 each rotate in direction R1 by operating the position control lever 6, the cam 221a swings forward. Direction R1 corresponds to the clockwise direction when viewed from right to left. In response to the swinging of the cam 221a forward, the cam 222a also swings forward via the rotation transmission part 223. In response to the swinging of the cam 222a forward, the reverse-direction rotating shaft 222 rotates in direction R2 opposite to direction R1. Direction R2 corresponds to the counterclockwise direction when viewed from right to left.

On the other hand, when the position control lever 6 and the co-rotating shaft 221 rotate in the direction R2 due to the operation of the position control lever 6, the cam 221a swings rearward. As the cam 221a swings rearward, the cam 222a also swings rearward via the rotation transmission section 223. In response to the rearward rocking of the cam 222a, the reverse rotation shaft 222 rotates in the direction R1 opposite to the direction R2. That is, the rotation transmitting unit 223 transmits the rotation of the same-direction rotating shaft 221 to the opposite-direction rotating shaft 222, and rotates the opposite-direction rotating shaft 222 in a direction opposite to the rotation direction of the same-direction rotating shaft 221. It looks like this.

The second position control shaft 230 extends in the left-right direction and has an axis A3 that is parallel to the left-right direction. The axis A3 is located above the axis A2. In other words, the first position control shaft 220 and the second position control shaft 230 are arranged to have different axes, and the second position control shaft 230 is located above the first position control shaft 220.

A cam 230a that protrudes downward is provided on the left end side of the second position control shaft 230. A front end side 92 of the position feedback rod 9 is connected to the lower end of the cam 230a so as to be relatively rotatable. The second position control shaft 230 is rotatable around the axis A3 in response to the back-and-forth rocking of the cam 230a.

A cam 230b that protrudes upward is provided slightly to the right of the center of the second position control shaft 230 in the left-right direction. The cam 230b can swing back and forth in response to the rotation of the second position control shaft 230 about the axis A3. An extension 231 of the same diameter is provided on the right end side of the second position control shaft 230. The extension 231 extends from the cam 230b to the right coaxially with the axis A3.

The second position control shaft 230 configured in this manner rotates around the axis A3 in accordance with the displacement of the position feedback rod 9 when the lift arm 2 rotates relative to the other. More specifically, when the cam 24 swings rearward due to upward swinging of the lift arm 2, the position feedback rod 9 is displaced rearward. In response to the rearward displacement of the position feedback rod 9, the cam 230a swings rearward. In response to the rearward rocking of the cam 230a, the second position control shaft 230 rotates in the direction R1.

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 a direction R2 opposite to the direction R1.

In the position control cam 210, a protrusion 211, an upper end side 212, and a lower end side 213 are defined. The protruding portion 211 protrudes rearward from the substantially central portion in the vertical direction, and can come into contact with the front end side 51a of the spool 51 as described above. The upper end side 212 is connected to a cam 230b of the second position control shaft 230 so as to be relatively rotatable. The lower end side 213 is connected to a cam 222b of a reverse rotation shaft 222 (first position control shaft 220) so as to be relatively rotatable.

When the position control lever 6 is operated, the position control lever 6 and the same-direction rotating shaft 221 each rotate in direction R2, and the reverse-direction rotating shaft 222 rotates in direction R1, the cam 222b swings rearward. In response to the swinging rearward of the cam 222b, the lower end side 213 of the position control cam 210 also swings rearward, and the protrusion 211 is also displaced rearward. This causes the spool 51 to displace toward the side that allows the supply and discharge of hydraulic oil (i.e., the rear side). The displacement of the spool 51 causes the lift arm 2 to swing upward.

Next, as the lift arm 2 swings upward, the second position control shaft 230 rotates in the direction R1, and the cam 230b swings forward. In response to the forward swinging of the cam 230b, the upper end side 212 of the position control cam 210 also swings forward, and the protrusion 211 is also displaced forward. As a result, the spool 51 is displaced toward the side where supply and discharge of hydraulic oil is restricted (ie, the front side). The displacement of the spool 51 causes the lift arm 2 swinging upward to stop.

<<Pumper transmission mechanism>>
11 is an overall view of the pump transmission mechanism 30. As shown in FIG. 11, the pump transmission mechanism 30 includes a pump cam 310, a pump shaft 320, and a rotation transmission portion 330.

The pump shaft 320 extends in the left-right direction and is disposed coaxially with the axis A3. As shown in the dashed line in FIG. 11 and in FIG. 13, the pump shaft 320 has a hollow structure along the axis A3, and the extension portion 231 of the second position control shaft 230 can be coaxially inserted into the inside of the pump shaft 320.

The pump shaft 320 is connected at its right end to the other end 72 of the pump lever 7. The pump shaft 320 is rotatable around axis A3 in the same direction as the rotation of the pump lever 7. A cam 320a that protrudes downward is provided at the left end of the pump shaft 320. The cam 320a is oscillating back and forth in response to the rotation of the pump shaft 320 around axis A3.

The rotation transmission unit 330 is a plate that extends in the vertical direction and is arranged coaxially with the axis A2. As shown in the dashed line in FIG. 11 and in FIG. 13, the rotation transmission unit 330 has a mating hole along the axis A2, into which the reverse rotation shaft 222 of the first position control shaft 220 can be coaxially inserted. The upper side of the rotation transmission unit 330 is rotatably connected to the lower end of the cam 320a, and the lower side of the rotation transmission unit 330 is rotatably connected to the lower end side 313 of the pump cam 310. The rotation transmission unit 330 swings the lower end side 313 in the vertical direction in response to the swinging of the cam 320a in the vertical direction.

When the pump lever 7 is operated, the pump shaft 320 configured in this manner rotates around axis A3 in response to the displacement of the pump lever 7. More specifically, when the pump shaft 320 rotates in direction R1 by operating the pump lever 7, the cam 320a swings rearward. In response to the swinging rearward of the cam 320a, the rotation transmission part 330 rotates in direction R2, which is opposite to direction R1.

On the other hand, when the pumper lever 7 and the pumper shaft 320 are rotated in the direction R2 by operating the pumper lever 7, the cam 320a swings forward. In response to the frontward swinging of the cam 320a, the rotation transmitting section 330 rotates in the direction R1 opposite to the direction R2.

In the pumper cam 310, a protrusion 311, an upper end side 312, and a lower end side 313 are defined. The protruding portion 311 protrudes rearward from the substantially central portion in the vertical direction, and can come into contact with the front end side 51a of the spool 51 as described above. The upper end side 312 is connected to the cam 230b of the second position control shaft 230 so as to be relatively rotatable. More specifically, as shown in FIG. 13, the upper end side 312 is interposed between the cam 230b and the upper end side 212 of the position control cam 210. The cam 230b and the upper end sides 312, 212 are pinned together so that the upper end sides 312, 212 can swing together in response to the swing of the cam 230b. The lower end side 313 is connected to the lower side of the rotation transmission section 330 so as to be relatively rotatable.

In a state where the supply and discharge of hydraulic oil is regulated by the control valve 5, the pumper lever 7 located at the first position is moved to the second position. When the pumper lever 7 and the pumper shaft 320 rotate in the direction R2 by operating the pumper lever 7, the cam 320a swings forward, and the rotation transmitting section 330 rotates in the direction R1. In accordance with the rotation of the rotation transmission section 330 in the direction R1, the lower end side 313 of the pump cam 310 also swings rearward, and the protrusion 211 is also displaced rearward. As a result, the spool 51 is displaced toward the side (ie, the rear side) that allows supply and discharge of hydraulic oil. According to the displacement of the spool 51, the lift arm 2 swings upward.

Next, as the lift arm 2 swings upward, the second position control shaft 230 rotates in the direction R1, and the cam 230b swings forward. As the cam 230b swings forward, the upper end 212 of the position control cam 210 as well as the upper end 312 of the pump cam 310 swings forward, and the protrusion 311 also moves forward. As a result, the spool 51 is displaced toward the side where supply and discharge of hydraulic oil is restricted (ie, the front side). In response to the displacement of the spool 51, the lift arm 2, which had been swinging upward, stops.

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

The first draft control shaft 420 includes a co-rotating shaft 421 , a reverse-rotating shaft 422 , and a rotation transmitting section 423 . The co-rotating shaft 421 extends in the left-right direction and is disposed coaxially with the axis A1. As shown in the broken line part in FIG. 11 and in FIG. 12, the co-rotating shaft 421 has a hollow structure along the axis A1, and the co-rotating shaft 221 of the first position control shaft 220 is coaxially inserted therein. It can be inserted into. The co-rotating shaft 421 is connected to the other end 82 of the draft control lever 8 at its right end. The same direction rotating shaft 421 is rotatable around the axis A1 in the same direction as the rotation direction of the draft control lever 8. A cam 421a that protrudes upward is provided on the left end side of the co-rotating shaft 421 so as to be adjacent to the right side of the cam 221a. The cam 421a can swing back and forth in accordance with the rotation of the co-rotating shaft 421 about the axis A1. Note that each swinging cam 421a, 221a can come into contact with the stay. When in contact with the stay, the swinging of each cam 421a, 221a is restricted, and the operation of each lever 6, 8 is also restricted. That is, by adjusting the contact position between each cam 421a, 221a and the stay, the operating range of each lever 6, 8 can be set. For example, in this embodiment, the operating range may be set so that the operating angle of each lever 6, 8 is 45 degrees.

The reverse rotation shaft 422 extends in the left-right direction and is arranged coaxially with the axis A2. That is, the same direction rotating shaft 421 and the opposite direction rotating shaft 422 are arranged to have different axes. As shown in the broken line in FIG. 11 and in FIG. 12, the reverse rotation shaft 422 is fitted inside the reverse rotation shaft 222 of the first position control shaft 220.

A cam 422a that protrudes downward is provided on the right end side of the reverse rotation shaft 422 so as to be adjacent to the right side of the cam 222a. In response to the back and forth rocking of the cam 422a, the reverse rotation shaft 422 can rotate around the axis A2 in a direction opposite to the rotation direction of the draft control lever 8. A cam 422b that protrudes downward is provided on the left end side of the reverse rotation shaft 422. The cam 422b can swing back and forth in response to the rotation of the reverse rotation shaft 422 about the axis A2.

The rotation transmission part 423 is a plate extending in the front-rear direction adjacent to the right side of the rotation transmission part 223. The rear side of the rotation transmission part 423 is rotatably connected to the upper end of the cam 421a, and the front side of the rotation transmission part 423 is rotatably connected to the lower end of the cam 422a. The rotation transmission part 423 swings the cam 422a in the front-rear direction in response to the swinging of the cam 421a in the front-rear direction.

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 the axis A1 and rotates in the opposite direction according to the displacement of the draft control lever 8. Shaft 422 rotates around axis A2. More specifically, when the draft control lever 8 and the co-rotating shaft 421 rotate in the direction R1 by operating the draft control lever 8, the cam 421a swings forward. In response to the forward swinging of the cam 421a, the cam 422a also swings forward via the rotation transmission section 423. In response to the forward rocking of the cam 422a, the reverse rotation shaft 422 rotates in a direction R2 opposite to the direction R1.

On the other hand, when the draft control lever 8 and the co-rotating shaft 421 rotate in the direction R2 due to the operation of the draft control lever 8, the cam 421a swings rearward. As the cam 421a swings rearward, the cam 422a also swings rearward via the rotation transmission section 423. In response to the rearward rocking of the cam 422a, the reverse rotation shaft 422 rotates in the direction R1 opposite to the direction R2. That is, the rotation transmitting unit 423 transmits the rotation of the same-direction rotating shaft 421 to the opposite-direction rotating shaft 422, and rotates the opposite-direction rotating shaft 422 in a direction opposite to the rotation direction of the same-direction rotating shaft 421. It looks like this.

The second draft control shaft 430 extends in the left-right direction and is arranged coaxially with the axis A3. As shown in the dashed line in FIG. 12 and in FIG. 13, the second draft control shaft 430 has a hollow structure along the axis A3, and the second position control shaft 230 can be coaxially inserted therein. That is, the first draft control shaft 420 and the second draft control shaft 430 are arranged to have different axes, and the second draft control shaft 430 is located above the first draft control shaft 420.

A cam 430a that protrudes 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 capable of relative rotation. In response to the forward and backward swing of the cam 430a, the second draft control shaft 430 can rotate around the axis A3.

A cam 430b that protrudes upward is provided on the right end of the second draft control shaft 430. The cam 430b can swing back and forth in response to the rotation of the second draft control shaft 430 about the axis A3.

The second draft control shaft 430 configured in this manner rotates around axis A3 in response to the displacement of the draft feedback rod 10 when the bracket 3 rotates relative to the bracket 3. More specifically, when the joint 34 swings rearward due to the bracket 3 swinging rearward, the draft feedback rod 10 is displaced rearward without the spring 102a extending from the mounting length. In response to the rearward displacement of the draft feedback rod 10, the cam 430a swings rearward. In response to the rearward swing of the cam 430a, the second draft control shaft 430 rotates in direction R1.

On the other hand, when the joint 34 swings forward as the bracket 3 swings forward, the draft feedback rod 10 is displaced forward. In this case, the draft feedback rod 10 is displaced while the spring 102a is slightly contracted from the installation length. By contracting the spring 102a in this manner, hunting associated with input can be suppressed. For example, the spring constant of the spring 102a may be adjusted so that the hunting can be appropriately suppressed. In response to the forward displacement of the draft feedback rod 10, the cam 430a swings forward. In response to the forward rocking of the cam 430a, the second draft control shaft 430 rotates in a direction R2 opposite to the direction R1.

As shown in FIGS. 12 and 13, a protrusion 102b is further provided on the front end side 102 of the draft feedback rod 10. The protrusion 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. That is, the protruding portion 102b can intersect with the radial locus of the cam 230a.

For this reason, for example, if the position feedback rod 9 continues to be displaced rearward, the cam 230a, which rotates relatively rearward, will eventually come into contact with the protrusion 102b. If the position feedback rod 9 is displaced further rearward after the contact, the cam 230a will press the protrusion 102b rearward, causing the spring 102a to contract. 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 rearward, the cam 430a will also swing rearward, and the second draft control shaft 430 will rotate in the direction R1.

In the draft control cam 410, a protrusion 411, an upper end side 412, and a lower end side 413 are defined. The protruding portion 411 protrudes rearward from the substantially central portion in the vertical direction, and can come into contact with the front end side 51a of the spool 51, as described above. The upper end side 412 is connected to a cam 430b of the second draft control shaft 430 so as to be relatively rotatable. The lower end side 413 is connected to a cam 422b of a reverse rotation shaft 422 (first draft control shaft 420) so as to be relatively rotatable.

The operation associated with the operation of the draft control lever 8 will be described below. As a premise for operation, it is assumed that a traction load from the top link (implement) is applied to the bracket 3, the bracket 3 is oscillated and displaced in response to the traction load, and the spool 51 is positioned in a neutral state. In this state, when the draft control lever 8 is operated, the draft control lever 8 and the same-direction rotating shaft 421 rotate in the direction R2, and the opposite-direction rotating shaft 422 rotates in the direction R1, the cam 422b swings rearward. In response to the swinging rearward of the cam 422b, the lower end side 413 of the draft control cam 410 also swings rearward, and the protrusion 411 also displaces rearward. As a result, the spool 51 is displaced toward the side that allows the supply and discharge of hydraulic oil (i.e., the rearward side). The displacement of the spool 51 causes the lift arm 2 to swing upward.

Next, as the lift arm 2 swings upward, the implement connected to the lift arm 2 is also displaced upward. For example, if the lower end of the implement is intruding into the ground, the degree of plowing depth will be reduced. Further, when the lower end of the implement is separated from the ground, the separation distance increases. Therefore, the traction load applied from the top link to the bracket 3 changes, and the bracket 3 rotates relative to it accordingly. Due to the relative rotation of the bracket 3, the second draft control shaft 430 rotates in the direction R1, and the cam 430b swings forward.

On the other hand, when the cam 230a presses the protrusion 102b rearward due to upward swinging of the lift arm 2, the spring 102a of the draft feedback rod 10 contracts. On the other hand, the cam 430a also swings rearward in conjunction with the protrusion 102b being pushed rearward. Also in this case, the second draft control shaft 430 rotates in the direction R1, and the cam 430b swings forward.

In response to the forward swinging of the cam 430b, the upper end side 412 of the draft control cam 410 also swings forward, and the protrusion 411 is also displaced forward. As a result, the spool 51 is displaced toward the side where supply and discharge of hydraulic oil is restricted (ie, the front side). The displacement of the spool 51 causes the lift arm 2, which swings upward, to stop.

<Effects of embodiment>
As described above, the hydraulic lifting device 100 according to the first embodiment of the present invention includes the lift arm 2, the bracket 3, the draft control lever 8, and the draft control transmission mechanism 40. This allows draft control to be executed. The lift arm 2 rotates relative to the case 1 using the other end 22 as a fulcrum 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 using the other end side 32 as a fulcrum in response to a traction load from a connected top link (namely, an implement). Further, the bracket 3 includes attachment portions 35a, 35b, 35c, 36a, 36b, and 36c configured to allow attachment of the front end of the top link. Here, the lift arm 2 includes a lift arm axis Z1 that is an axis of relative rotation with respect to the case 1. The bracket 3 includes a bracket axis Z2 that is an axis of relative rotation with respect to the case 1, and further includes axes Z3, Z4, and Z5 of the mounting portions 35a to 35c, and 36a to c. The lift arm axis Z1, the bracket axis Z2, and the respective axes Z3, Z4, and Z5 are arranged in a direction (second direction, in this embodiment) perpendicular to the up-and-down direction (first direction, in this embodiment, the vertical direction) of the implement. They extend in the left-right direction) 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 parts 35a to 35c, 36a to 36a have the respective axes Z3, Z4, and Z5 below the bracket axis Z2. c is located (see Figure 7).

By connecting the front end of the top link to the mounting parts 35a-c, 36a-c configured in this manner, 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 a configuration in which the mounting parts 35a-c, 36a-c are positioned above the bracket axis Z2, the front end of the top link can be positioned further downward, and the distance can be increased. For example, even if a working machine to which the hydraulic lifting device 100 of the first embodiment is applied tilts relative to the ground when traveling on uneven ground, uneven ground, slopes, etc., the distance between the implement and the ground can be increased, so that contact between the implement and the ground can be suppressed. More specifically, when a tractor equipped with the hydraulic lifting device 100 of this embodiment crosses a ridge, the implement does not come into contact with the ground, and the ridge is not destroyed.

Furthermore, in the first embodiment, a bracket shaft 33 is particularly provided. The bracket shaft 33 pivotally supports the other end side 32 of the bracket 3 on the outer rear end of the case 1, and is arranged coaxially with the bracket axis Z2. The bracket shaft 33 is configured to generate an urging force during relative rotation according to the traction load. According to this, the bracket shaft 33 can be provided with a biasing function required for executing draft control. That is, the bracket shaft 33 serves both as a support shaft for the bracket 3 and as a biasing mechanism, and there is no need to add a separate biasing mechanism. Therefore, it is no longer necessary to interpose a biasing mechanism between the one end side 31 of the bracket 3 and the case 1, for example, as in the conventional case. Therefore, it is possible to increase the room for positioning the bracket shaft Z2 or the attachment portions 35a to 35c, 36a to 36c further downward.

In addition, particularly in the first embodiment, the draft control transmission mechanism 40 includes 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 the axis A1 (and axis A2) according to the displacement of the draft control lever 8 when the draft control lever 8 is operated. The second draft control shaft 430 rotates around the axis A3 in response to the displacement of the draft feedback rod 10 when the bracket 3 rotates relative to the other. 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 supply and discharge of hydraulic oil in response to 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 regulates the supply and discharge of hydraulic oil according to the rotation of the second draft control shaft 430. Therefore, the elevation height of the lift arm 2 can be easily adjusted so that the traction load on the bracket 5 reaches a target level.

The second draft control shaft 430 is located above the first draft control shaft 420 in the lifting 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 lower side of the second draft control shaft 430 to be effectively used as a storage space for components. For this reason, for example, as shown in FIG. 8, the hydraulic cylinder 4 is stored below the second draft control shaft 430 and to the left of the first draft control shaft 420, thereby making it possible to reduce the overall size of the hydraulic lifting device 100. In this way, the degree of freedom in the layout of the components can be increased.

Therefore, the lifting height of the lift arm 2 can be easily adjusted so that the traction load on the bracket 5 reaches a target level, and the degree of freedom in the layout of the component parts can be increased. Moreover, the hydraulic cylinder 4, which is heavy among the components, can be arranged below in the internal space of the hydraulic lifting device 100. Therefore, the position of the center of gravity of the hydraulic lifting device 100 can be adjusted over a wide range.

For example, in the first embodiment, the draft control lever 8 is defined by one end side 81 and the other end side 82, and the one end side 81 is configured to be operable by the operator, and the other end side is configured to be able to be operated by the operator. It is configured to be rotatable relative to the case 1 about the side 82 as a fulcrum. The first draft control shaft 420 includes a co-rotating shaft 421 , a reverse-rotating shaft 422 , and a rotation transmitting section 423 . The same direction rotation shaft 421 is connected to the other end side 82 of the draft control lever 8 and is configured to be rotatable in the same direction as the rotation direction of the draft control lever 8. The reverse rotation shaft 422 is connected to the draft control cam 410 and is configured to be rotatable in a direction opposite to the rotation direction of the draft control lever 8. The rotation transmitter 423 transmits the rotation of the same-direction rotating shaft 421 to the opposite-direction rotating shaft 422 when the draft control lever 8 rotates relative to the draft control lever 8 , and also transmits the rotation of the same-direction rotating shaft 421 to the opposite-direction rotating shaft 421 . Rotate in the opposite direction.

According to this, the same direction rotating shaft 421 and the reverse direction rotating shaft 422 can be arranged with different axes via the rotation transmission part 423. For example, as shown in FIG. 12, the position of the axis A1 of the same direction rotating shaft 421 and the position of the axis A2 of the reverse direction rotating shaft 422 can be made different from each other. Therefore, the same direction rotating shaft 421 and the reverse direction rotating shaft 422 can be laid out without interfering with the arrangement of the hydraulic cylinder 4, the control valve 5, etc. That is, the degree of freedom of the layout of the first draft control shaft 420 and the draft control lever 8 can be 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 part 423, the displacement amount of the draft control cam 410 (the displacement amount of the spool 51) relative to the displacement amount of the draft control lever 8 can be adjusted. Therefore, the operating range of the draft control lever 8 can be adjusted so that it is easy for the operator to operate.

In the first embodiment, the position control lever 6 and the position control transmission mechanism 20 are particularly provided. 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. When the position control lever 6 is operated, the first position control shaft 220 rotates around the axis A1 (and axis A2) in response to the displacement of the position control lever 6. When the lift arm 2 rotates relative to the axis A1, the second position control shaft 230 rotates around the axis A3 in response to the displacement of the position feedback rod 9. When the first position control shaft 220 rotates, the position control cam 210 displaces the position of the spool 51 toward the allowable side of the supply and discharge of hydraulic oil in response to 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 restrictive side of the supply and discharge of hydraulic oil in response to the rotation of the second position control shaft 230. This allows the height of the lift arm 2 in the lifting direction to be easily adjusted to the desired height.

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. According to this, the lower side of the second position control shaft 230 can be effectively used as a space for accommodating components. For this reason, for example, as shown in FIG. 8, the hydraulic cylinder 4 is housed below the second position control shaft 230 and on the left side of the first position control shaft 220, so that the hydraulic lifting device 100 can be operated. The overall size can be made smaller. In this way, the degree of freedom in layout of component parts can be increased.

As a result, the height of the lift arm 2 in the lifting direction can be easily adjusted to the desired height, and the degree of freedom in the layout of the components can be increased. In addition, the hydraulic cylinder 4, which is the heaviest of the components, can be positioned lower in the internal space of the hydraulic lifting device 100. This allows the position of the center of gravity of the hydraulic lifting device 100 to be adjusted over a wide range.

In the first embodiment, the position control lever 6 has one end 61 and the other end 62, and the one end 61 is configured to be operable by an operator, and is configured to rotate relative to the case 1 with the other end 62 as a fulcrum, as a displacement according to the operation. The first position control shaft 220 includes a same-direction rotating shaft 221, a reverse-direction rotating shaft 222, and a rotation transmission unit 223. The same-direction rotating shaft 221 is connected to the other end 62 of the position control lever 6 and is configured to be rotatable in the same direction as the rotation direction of the position control lever 6. The reverse-direction rotating shaft 222 is connected to the position control cam 210 and is configured to be rotatable in the opposite direction to the rotation direction of the position control lever 6. When the position control lever 6 rotates relative to the case 1, the rotation transmission unit 223 transmits the rotation of the same-direction rotating shaft 221 to the reverse-direction rotating shaft 222, and rotates the reverse-direction rotating shaft 222 in the opposite direction to the rotation direction of the same-direction rotating shaft 221.

According to this, the same direction rotating shaft 221 and the opposite direction rotating shaft 222 can be arranged with different axes via the rotation transmitting part 223. For example, as shown in FIG. 10, the position of the axis A1 of the same direction rotating shaft 221 and the position of the 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. That is, the degree of freedom in the layout of the first position control shaft 220 and the position control lever 6 can be increased, and for example, a layout that is easy for the operator to operate can be adopted. Furthermore, by changing the link ratio in the rotation transmission section 223, the amount of displacement of the position control cam 210 (the amount of displacement of the spool 51) relative to the amount of displacement of the position control lever 6 can be adjusted. Therefore, the operating range of the position control lever 6 can be adjusted to make it easier for the operator to operate.

In particular, 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 one can be coaxially inserted into the other. In particular, either the second draft control shaft 430 or the second position control shaft 230 has a hollow structure and is configured so that one can be coaxially inserted into the other.

More specifically, as shown in FIGS. 10, 12, and 13, the same direction rotating shaft 221 of the first position control shaft 220 is coaxial with the same direction rotating shaft 421 of the first draft control shaft 420. It will be inserted. The reverse rotation shaft 422 of the first draft control shaft 420 is coaxially fitted into the reverse rotation 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 the 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 the axis A3. According to this, the other shaft can be accommodated inside one shaft, and a space can be secured by the amount of space accommodated in the shaft. Therefore, the degree of freedom in layout of component parts can be further increased.

In the first embodiment, the pump lever 7 and the pump transmission mechanism 30 are particularly provided. The pump lever 7 is configured to be displaceable from a first position to a second position in response to the operation of the operator. The pump transmission mechanism 30 includes a pump cam 310, a pump shaft 320, and a second position control shaft 230. When the pump lever 7 is operated to be displaced from the first position to the second position, the pump shaft 320 rotates around the axis A3 in response to the displacement of the pump lever 7. When the pump shaft 7 rotates, the pump cam 310 displaces the position of the spool 51 toward the permitting side of the supply and discharge of the hydraulic oil in response to the rotation of the pump shaft 7, and when the second position control shaft 230 rotates, the pump cam 310 displaces the position of the spool 51 toward the restricting side of the supply and discharge of the hydraulic oil in response to the rotation of the second position control shaft 230. Therefore, the lift arm 2 can be easily raised and lowered according to the operator's request.

For example, as in the first embodiment, when the rotation transmission unit 330 is provided in the pump transmission mechanism 30, the pump shaft 320 and the lower end side 313 of the pump cam 310 can be arranged on different axes via the rotation transmission unit 330 (see FIG. 11). Therefore, the pump shaft 320 can be laid out without interfering with the arrangement of the hydraulic cylinder 4, the control valve 5, etc. In other words, the degree of freedom of layout of the pump shaft 320 and the pump lever 7 can be 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 330, the displacement amount of the pump cam 310 (displacement amount of the spool 51) relative to the displacement amount of the pump lever 7 can be adjusted. Therefore, the operating range of the pump lever 7 can be adjusted so that it is easy for the operator to operate.

In the first embodiment, the pump lever 7 has one end 71 and the other end 72, and the one end 71 is configured to be operable by the operator, and is configured to rotate relative to the case 1 with the other end 72 as a fulcrum, as a displacement according to the operation. Furthermore, a rotation restriction unit 74 is provided to restrict the relative rotation of the pump lever 7. This allows the lifting height of the implement by the operation of the pump lever 7 to be intentionally restricted to any position. For example, if the implement is raised too high, the center of gravity position also rises, increasing the risk of tipping over. In particular, when using a relatively heavy implement (e.g., a plow, etc.) on a slope, the risk of tipping over is often high. In such cases, the lifting height of the implement can be appropriately restricted, improving safety. On the other hand, by restricting the lifting height of the implement to the minimum necessary height, the time until the implement hits the ground can be shortened, for example, when lowering the implement after turning during a work interruption. This reduces downtime and improves work efficiency.

[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 points. In the hydraulic lifting device 100 of the second embodiment, the configuration of the bracket 3 differs from that of the first embodiment. Also, the hydraulic lifting device 100 of the second embodiment differs from that of the first embodiment in that a predetermined mechanism is 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. Other than these points, the second embodiment is the same as the first embodiment. Only the differences between the first embodiment and the second embodiment will be described below. Note that the same reference numerals are used for the components of the second embodiment that are the same or equivalent to those of the first embodiment, and the description thereof will be omitted.

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 have substantially the same shape, extend from the other end side 32 to the rear side, and further extend from the lower end side 32 to the rear side. It protrudes towards 31. The attachment parts 35a, 35b, and 35c are arranged in this order vertically downward from above on the left side plate 35. Note that the positional relationship of the attachment parts 36a to 36c is also the same as that of the attachment parts 35a to 35c.

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 this embodiment, the positional relationship of each axis Z1 to Z5 is parallel to each other in the left-right direction, and the heights are H4a<H3<H4b<H4c, but is not limited to this.

FIG. 16 is a perspective view showing the configuration near the front end of each feedback rod 9, 10 in the hydraulic lifting device 100 of the second embodiment. FIG. 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 FIG. 13. As shown in FIG. 14, FIG. 16, and FIG. It is located in . On the other hand, the draft feedback rod 10 is located on the outer side of the position feedback rod 9 on the front side of the substantially intermediate portion of each of the feedback rods 9 and 10 . The hydraulic lifting device 100 of the second embodiment includes a cam 430a, a cam 230a, and a cam 11a at the front ends of the position feedback rod 9 and the draft feedback rod 10. In this embodiment, the cam 430a, the cam 230a, and the cam 11a correspond to a first displacement transmission section, a second displacement transmission section, and a third displacement transmission section. Hereinafter, the cam 430a, the cam 230a, and the cam 11a will be referred to as a first displacement transmitting section 430a, a second displacement transmitting section 230a, and a third displacement transmitting section 11a.

The first displacement transmission part 430a is connected to the left end side of the second draft control shaft 430 so as to be rotatable together with the second draft control shaft 430. The first displacement transmission part 430a is capable of swinging in the front-rear direction about axis A3. The lower end part of the first displacement transmission part 430a is connected to the front end side 102 of the draft feedback rod 10 so as to be rotatable relative to the second draft control shaft 430. Therefore, when the bracket 3 rotates relative to the second draft control shaft 430, the first displacement transmission part 430a rotates the second draft control shaft 430 in response to the displacement of the draft feedback rod 10.

The second displacement transmission part 230a is connected to the left end side of the second position control shaft 230 so as to be rotatable together with the second position control shaft 230. The second displacement transmission part 230a is capable of swinging in the front-rear direction about axis A3. The lower end part of the second displacement transmission part 230a is connected to the front end side 92 of the position feedback rod 9 so as to be rotatable relative to the second position control shaft 230. Therefore, when the lift arm 2 rotates relative to the second position control shaft 230, the second displacement transmission part 230a rotates the second position control shaft 230 in response to the displacement of the position feedback rod 9.

The third displacement transmitting portion 11a is a substantially triangular flat plate, and a fulcrum portion 11a1 is provided approximately at the center thereof. The fulcrum portion 11a1 is connected to a projection portion projecting leftward from the left side surface of the case 1 via a stepped bolt so as to be relatively rotatable. Thereby, the third displacement transmitting part 11a can rotate relative to the case 1 about the fulcrum part 11a1. The third displacement transmitting section 11a is configured to be able to press the first displacement transmitting section 430a when its front end side comes into contact with the first displacement transmitting section 430a. The rear end side of the third displacement transmission section 11a is connected to the second displacement transmission section 230a via the fourth displacement transmission section 11b.

The fourth displacement transmission part 11b is a generally rectangular flat plate, and the third displacement transmission part 11a and the second displacement transmission part 230a are connected at both ends thereof so as to be capable of relative rotation. The connection part of the fourth displacement transmission part 11b to the second displacement transmission part 230a is located above the front end side 92 of the position feedback rod 9.

As shown in FIG. 18, for example, when the position feedback rod 9 is displaced rearward by the swinging of the lift arm 2, the second displacement transmission part 230a swings rearward and rotates the second position control shaft 230 in the direction R1 around the axis A3. At this time, in conjunction with the second displacement transmission part 230a, the fourth displacement transmission part 11b displaces rearward and rotates the third displacement transmission part 11a around the fulcrum part 11a1. As a result, the front end side 11a2 of the third displacement transmission part 11a swings forward.

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

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

Further, in the second embodiment, in particular, a first displacement transmitting section 430a, a second displacement transmitting section 230a, a third displacement transmitting section 11a, and a fourth displacement transmitting section 11b are provided near the front end of each feedback rod 9, 10. , equipped. The third displacement transmitting section 11a is configured such that its front end side 11a2 can come into contact with the rear end side 430a1 of the first displacement transmitting section 430a and press the third displacement transmitting section 11a. The third displacement transmitting section 11a is adapted to rotate in conjunction with the rotation of the second displacement transmitting section 230a via the fourth displacement transmitting section 11b, using the fulcrum section 11a1 as a fulcrum (see FIGS. 19).

Therefore, in order to link the second draft control shaft 430 with the rotation of the second position control shaft 230, the displacement of the second displacement transmission part 230a can be transmitted to the first displacement transmission part 430a via the third displacement transmission part 11a. In the third displacement transmission part 11a, the input from the second displacement transmission part 230a can be turned into a rotational displacement with the fulcrum part 11a1 as the fulcrum. On the other hand, the first displacement transmission part 430a that receives a load from the third displacement transmission part 11a also turns and displaces. Therefore, the load direction and the displacement direction can be brought closer to each other, so that the application of excessive force can be suppressed. Furthermore, the relatively strong front end side 11a2 of the third displacement transmission part 11a and the rear end side 430a1 of the first displacement transmission part 430a can be used as the abutment/pressure part. For example, a configuration in which the swinging second displacement transmission part 230a abuts and presses against the draft feedback rod 10 to link the second draft control shaft 430 can be considered. In this case, the input from the second displacement transmission part 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, the configuration of the second embodiment can reliably transmit the displacement while suppressing bending or deformation of the linked parts.

[Modification]
In the first embodiment, the draft feedback rod 10 is provided with a protruding portion 102b, and the oscillating cam 230a abuts against and presses the protruding portion 102b. Alternatively, the first displacement transmission portion 430a, the second displacement transmission portion 230a, and the third displacement transmission portion 11a of the second embodiment may be provided near the front ends of the feedback rods 9 and 10, and the displacement of the second displacement transmission portion 230a may be transmitted to the first displacement transmission portion 430a via the third displacement transmission portion 11a.

In each of the above embodiments, the bracket shaft 33 is configured to generate a biasing force during relative rotation according to the traction load, but instead, for example, the other end side 32 of the bracket 3 is It may also have only the function of being pivotally supported at the outer rear end of. In this case, the bracket shaft 33 does not have the biasing function required to perform draft control. For this reason, for example, a separate biasing mechanism may be interposed between the case 1 and the bracket 3, the bracket axis Z2 may be positioned below or above the lift arm axis Z1 to the extent possible, and the mounting portions 35a to 35c may be , 36a to 36c may be located below the bracket axis Z2 to the extent possible.

In each of the above embodiments, the co-directional rotating shaft 221 of the first position control shaft 220 is coaxially fitted into the co-directional rotating shaft 421 of the first draft control shaft 420. Alternatively, the co-directional rotating shaft 221 of the first position control shaft 220 may have a hollow structure, and the co-directional rotating shaft 421 of the first draft control shaft 420 may be coaxially fitted into the co-directional rotating shaft 221 of the first position control shaft 220.

In each of the above embodiments, the reverse rotation shaft 422 of the first draft control shaft 420 is coaxially fitted into 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 into the reverse rotation shaft 422 of the first draft control shaft 420.

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.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

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 : Attachment part 35b : Attachment part 35c : Attachment part 36a : Attachment part 36b : Attachment part 36c : Attachment part 4 : Hydraulic cylinder 5 : Control valve 51 : Spool 6 : Position control lever 61 : One end side 62 : Other end side 7 : Pumper lever 71 : One end side 72 : Other end side 74 : Rotation regulating part 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 section 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 rotation shaft 222: Reverse Directional rotation shaft 223: Rotation transmission section 230: Second position control shaft 230a: Second displacement transmission section 30: Pumper transmission mechanism 310: Pumper cam 320: Pumper shaft 330: Rotation transmission section 40: Draft control transmission mechanism 410: Draft control cam 420: First draft control shaft 421: Same direction rotation shaft 422: Opposite direction 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 (11)

case and
a hydraulic cylinder located inside the case and driven according to supply and discharge of hydraulic oil;
A control valve located inside the case and having a spool in the flow path of the hydraulic oil, the control valve allowing and regulating supply and discharge of the hydraulic oil to the hydraulic cylinder according to the position of the spool. valve and
A lift arm is located outside the case and has one end and the other end defined, the one end being configured to be connectable to an object, and the other end being connected to the object when the hydraulic cylinder is driven. a lift arm configured to be able to lift and lower the connected object by rotating relative to the case as a fulcrum;
A bracket located outside the case and defined by one end side and the other end side, the one end side is configured to be connectable to a target object, and according to the traction load from the connected target object, a bracket that rotates relative to the case using the other end as a fulcrum;
a draft control lever located outside the case and configured to be movable in response to an operator's operation;
a draft feedback rod located outside the case and configured to be displaceable according to relative rotation of the bracket;
When the draft control lever is operated, the displacement of the draft control lever is transmitted toward the spool, and the position of the spool is displaced toward a side where supply and discharge of the hydraulic oil is permitted, and the bracket is a draft control transmission mechanism that transmits the displacement of the draft feedback rod toward the spool and displaces the position of the spool toward a side that regulates the supply and discharge of the hydraulic oil;
In a hydraulic lifting device equipped with
The lift arm is
a lift arm axis that is an axis of the relative rotation with respect to the case and that is an axis that extends in a second direction orthogonal to a first direction that is the upward and downward direction of the object;
The bracket is
a bracket axis that is an axis of relative rotation with respect to the case and that extends in the second direction and is located parallel to the lift arm axis;
an attachment part configured to be able to attach the object and located below the bracket axis in the first direction;
Hydraulic lifting device with. The hydraulic lifting device according to claim 1,
The bracket is
A hydraulic lifting device configured so that the bracket shaft is located lower than the lift arm shaft in the first direction. The hydraulic lifting device according to claim 1,
The bracket is
A hydraulic lifting device configured so that the bracket shaft is located above the lift arm shaft in the first direction. The hydraulic lifting device according to claim 2 or 3,
a bracket shaft that supports the other end of the bracket on the case, is arranged coaxially with the bracket shaft, and is configured to generate a biasing force when the bracket shaft rotates relative to the case in response to the traction load. In the hydraulic lifting device according to claim 2 or 3,
The draft control transmission mechanism includes:
a first draft control shaft that rotates around an axis in response to displacement of the draft control lever when the draft control lever is operated;
a second draft control shaft that is located above the first draft control shaft in the vertical direction of the object and rotates around an axis in accordance with the displacement of the draft feedback rod when the bracket rotates relative to each other;
When the first draft control shaft rotates, the position of the spool is displaced toward a side where supply and discharge of the hydraulic oil is allowed according to the rotation of the first draft control shaft, and the second draft control shaft is rotated. a draft control cam that, when rotated, displaces the position of the spool in accordance with the rotation of the second draft control shaft toward a side that regulates supply and discharge of the hydraulic oil;
Hydraulic lifting device with. The hydraulic lifting device according to claim 5,
The draft control lever is
One end side and the other end side are defined, and the one end side is configured to be operable by the operator, and configured to be able to rotate relative to the case with the other end side as a fulcrum as a displacement in response to the operation. ,
The first draft control shaft is
a co-rotating shaft connected to the other end of the draft control lever and configured to be rotatable 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 be rotatable in a direction opposite to the rotation direction of the draft control lever;
When the draft control lever relatively rotates, the rotation of the same-direction rotating shaft is transmitted to the opposite-direction rotating shaft, and the opposite-direction rotating shaft is transmitted in a direction opposite to the rotation direction of the same-direction rotating shaft. a rotation transmission unit that rotates the
Hydraulic lifting device with. The hydraulic lifting device according to claim 5,
a position control lever located outside the case and configured to be movable in response to an operation by an operator;
a position feedback rod located outside the case and configured to be displaceable according to relative rotation of the lift arm;
When the position control lever is operated, the displacement of the position control lever is transmitted toward the spool, and the position of the spool is displaced toward the side where supply and discharge of the hydraulic oil is permitted, and the lift arm a position control transmission mechanism that transmits the displacement of the position feedback rod toward the spool and displaces the position of the spool toward a side that regulates supply and discharge of the hydraulic oil when the position feedback rod rotates relative to the
In a hydraulic lifting device equipped with
The position control transmission mechanism is
a first position control shaft that rotates around an axis in response to displacement of the position control lever when the position control lever is operated;
a second position control shaft that is located above the first position control shaft in the lifting direction of the object and rotates around the axis in accordance with the displacement of the position feedback rod when the lift arm rotates relative to the lift arm; ,
When the first position control shaft rotates, the position of the spool is displaced toward a side where supply and discharge of the hydraulic oil is permitted according to the rotation of the first position control shaft, and the second position control shaft is rotated. a position control cam that, when rotated, displaces the position of the spool in accordance with the rotation of the second position control shaft toward a side that regulates supply and discharge of the hydraulic oil;
Hydraulic lifting device further equipped with. The hydraulic lifting device according to claim 7,
The second draft control shaft is connected to the second draft control shaft so as to be integrally rotatable, and is connected to the draft feedback rod so as to be relatively rotatable, and when the bracket rotates relatively, the second a first displacement transmission section that rotates the draft control shaft;
The lift arm is connected to the second position control shaft so as to be integrally rotatable, and is connected to the position feedback rod so as to be relatively rotatable. a second displacement transmission section that rotates a two-position control shaft;
The position feedback rod is configured to be able to abut and press the first displacement transmitting section and to rotate relative to the case in conjunction with rotation of the second displacement transmitting section, and the position feedback rod is displaced and the second displacement transmitting section is moved. a third displacement transmitting section that rotates the first displacement transmitting section by rotating relative to the case and pressing while abutting the first displacement transmitting section when the displacement transmitting section rotates;
Hydraulic lifting device further equipped with. The hydraulic lifting device according to claim 7 or 8,
Either one of the first draft control shaft and the first position control shaft has a hollow structure, and is configured such that the other can be coaxially fitted into the inside of the one;
Either one of the second draft control shaft and the second position control shaft has a hollow structure, and is configured such that the other can be coaxially fitted into the interior of the one;
The draft control transmission mechanism and the position control transmission mechanism are
The other is coaxially fitted into one of the first draft control shaft and the first position control shaft, and the other is fitted into one of the second draft control shaft and the second position control shaft. Fitted coaxially,
In response to 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 axes, and
A hydraulic lifting device configured such that the second draft control shaft and the second position control shaft rotate relative to each other around an axis in response to displacement of either one of the draft feedback rod and the position feedback rod. The hydraulic lifting device according to claim 5,
a pump lever that is located outside the case and is configured to be displaceable from a first position, which is an arbitrary position when the supply and discharge of the hydraulic oil is regulated by the control valve, to a second position different from the first position in response to an operation by an operator;
a pump transmission mechanism that transmits the displacement of the pump lever toward the spool when the pump lever is operated to displace from the first position to the second position, and displaces the position of the spool toward a side allowing the supply and discharge of the hydraulic oil, and transmits the displacement of the position feedback rod toward the spool and displaces the position of the spool toward a side restricting the supply and discharge of the hydraulic oil when the lift arm rotates relatively with the pump lever located at the second position;
Further comprising:
The pump transmission mechanism includes:
a pump shaft that rotates about an axis in response to the displacement of the pump lever when the pump lever is operated to displace from the first position to the second position;
a pump cam that displaces a position of the spool toward a side allowing supply/discharge of the hydraulic oil in response to the rotation of the pump shaft when the pump shaft rotates, and displaces a position of the spool toward a side restricting supply/discharge of the hydraulic oil in response to the rotation of the second position control shaft when the second position control shaft rotates;
A hydraulic lifting device equipped with The hydraulic lifting device according to claim 10,
The pumper lever is
One end side and the other end side are defined, and the one end side is configured to be operable by the operator, and configured to be able to rotate relative to the case with the other end side as a fulcrum as a displacement in response to the operation. ,
A hydraulic lifting device comprising: a rotation regulating section that regulates the relative rotation of the pumper lever.