JP2024043766A - Hydraulic lifting device - Google Patents

Abstract

[Problem] To provide a hydraulic lifting device that allows greater freedom in the layout of components. [Solution] A hydraulic lifting device 100 includes a lift arm 2, a position control lever 6, and a position control transmission mechanism 20. 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 shaft 220 rotates around axis A1 (and axis A2) in response to the displacement of the lever 6. The second shaft 230 rotates around axis A3 in response to the displacement of the feedback rod 9 when the lift arm 2 rotates relative to the first shaft 2. The cam 210 displaces the spool position in response to the respective rotations of the first and second shafts 220, 230. The axis A3 of the second shaft 230 is located above the axis A1 of the first shaft 220. [Selected Figure] Fig. 9

Description

The present invention relates to a hydraulic lifting device that lifts and lowers a lift arm based on 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 is equipped with 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 also includes a position lever and an operating link mechanism. The operating link mechanism transmits the respective displacements to the lift feedback link based on the operation of the position lever and the raising and lowering of the lift arm, and the lift feedback link swings to displace the spool.

The operating link mechanism is broadly divided into a part that transmits the displacement of the position lever and a part that transmits the displacement of the lift arm. The "part that transmits the displacement of the position lever" has a first arm shaft (arm shaft 44). One end of the first arm shaft is connected to the base of the position lever, and the other end is connected to one end of the lift feedback link. In response to the rotation of the position lever, the first arm shaft rotates around its axis and the lift feedback link swings. The "part that transmits the displacement of the lift arm" has a second arm shaft (arm shaft 51). One end of the second arm shaft is connected to a rod that is linked to the lift arm, and the other end is connected to the other end of the lift feedback link. In response to the lifting and lowering of the lift arm, the second arm shaft rotates around its axis and the lift feedback link swings. In other words, the displacement of the lift arm is fed back to the spool via the rod. This allows the height of the lift arm in the lifting and lowering direction to be easily adjusted to the desired height.

JP 2003-000003 A (paragraphs 0015 to 0021, etc.)

This type of hydraulic lifting device has many components, each of which has a wide variety of shapes and sizes. From the perspective of improving the ease of mounting on a work machine and the ease of operation by the operator, there is a growing demand for greater freedom in the layout of each component. On the other hand, in the device of Patent Document 1, the first and second arm shafts are pivotally supported by bosses on both the left and right sides. Since the bosses are provided on the same axis, the first and second arm shafts are arranged coaxially so as to extend in the left-right direction. When the first and second arm shafts are arranged coaxially in this way, the components must be arranged so as not to interfere with each other, which limits the layout.

In view of the above, the present invention makes it possible to easily adjust the height of the lift arm in the vertical direction toward a target height, and to increase the degree of freedom in the layout of component parts. The purpose is to provide a hydraulic lifting device.

The technical means of the present invention for solving this technical problem are characterized by the following: The hydraulic lifting device of the present invention comprises a case, a hydraulic cylinder located inside the case and driven in 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, which allows and regulates 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 lift arm located outside the case and configured to be connected to an operator. a position control lever configured to be displaceable in response to operation of the lift arm; a position feedback rod located outside the case and configured to be displaceable in response to relative rotation of the lift arm; and a position control transmission mechanism which, when the position control lever is operated, transmits the displacement of the position control lever toward the spool, and displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic oil, and, when the lift arm rotates relatively, transmits the displacement of the position feedback rod toward the spool, and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic oil. The position control transmission mechanism includes a first position control shaft that rotates about an axis in response to the 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 about an axis in response to the displacement of the position feedback rod when the lift arm rotates relative to the first position control shaft, and a position control cam that displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic oil in response to the rotation of the first position control shaft when the first position control shaft rotates, and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic oil in response to the rotation of the second position control shaft when the second position control shaft rotates.

In the hydraulic lifting device, the position 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 position control shaft is equipped with a same-direction rotation shaft connected to the other end of the position control lever and rotatable in the same direction as the rotation direction of the position control lever, a reverse-direction rotation shaft connected to the position control cam and rotatable in the opposite direction to the rotation direction of the position 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 position 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 further includes a pump lever located outside the case and 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 operation by an operator; and a pump transmission mechanism that transmits the displacement of the pump lever toward the spool and displaces the position of the spool toward the side allowing the supply and discharge of the hydraulic oil when the pump lever is operated to displace from the first position to the second position, and transmits the displacement of the position feedback rod toward the spool and displaces the position of the spool toward the 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. 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, and a pump cam that displaces the position of the spool toward the side that allows the supply and discharge of the hydraulic oil in response to the rotation of the pump shaft when the pump shaft rotates, and displaces the position of the spool toward the side that restricts the supply and discharge of the hydraulic oil in response to the rotation of the second position control shaft when the second position control shaft rotates.

In the hydraulic lifting device, the pumper lever has one end and the other end, the one end is operable by the operator, and the pumper lever is configured to be displaced in accordance with the operation, using the other end as a fulcrum. The pump lever includes a rotation regulating portion configured to be rotatable relative to the case and regulating the relative rotation of the pumper lever.

The hydraulic lifting device is a bracket that is located outside the case and has one end and the other end, and the one end is configured to be connectable to a target object, and the one end is configured to be connectable to a target object. a bracket that rotates relative to the case using the other end as a fulcrum in response to a traction load; a draft control lever located outside the case and configured to be displaceable in response to an operator's operation; a draft feedback rod located outside the case and configured to be displaceable in accordance with relative rotation of the bracket; and a draft feedback rod configured to direct displacement of the draft control lever toward the spool when the draft control lever is operated. and displacing the position of the spool toward a side that allows supply and discharge of the hydraulic oil, and transmitting the displacement of the draft feedback rod toward the spool when the bracket rotates relative to the spool; The apparatus further includes a draft control transmission mechanism that displaces the position of the spool toward a side where supply and discharge of the hydraulic oil is restricted. 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 about the target object more than the first draft control shaft. a second draft control shaft that is located on the upper side in the vertical direction of the bracket and rotates about an axis in accordance with the displacement of the draft feedback rod when the bracket rotates relative to the bracket; and a second draft control shaft that rotates 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 permitted according to the rotation of the first draft control shaft, and when the second draft control shaft rotates, the second draft control shaft and a draft control 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 spool.

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

According to the present invention, the height of the lift arm 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.

1 is an overall perspective view of a hydraulic lifting device according to an embodiment of the present invention. FIG. 2 is a right side view of the hydraulic lifting device shown in FIG. 1. FIG. 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 an overall perspective view of each transmission mechanism in the hydraulic lifting device shown in FIG. 1 . 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. 2 is an overall view of a position control transmission mechanism in the hydraulic lifting device shown in FIG. 1. FIG. FIG. 2 is an overall view of a pump transmission mechanism in the hydraulic lifting device shown in FIG. 2 is an overall view of a draft control transmission mechanism in the hydraulic lifting device shown in FIG. 1. FIG. 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.

Embodiments of the present invention will be described below based on the drawings.

<Overall configuration of hydraulic lifting device>
FIG. 1 is an overall perspective view of a hydraulic lifting device 100 according to an 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, for example, on an agricultural vehicle such as a tractor. More specifically, the hydraulic lifting device 100 is mounted at the rear of a tractor or the like and above 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 21 of the lift arm 2 is connected to a lower link via a lift link. An end of a top link is connected to one end 31 of the bracket 3. An implement is connected to the rear of the top link and the lower link. As the lift arm 2 rotates relative to the case 1, 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 shown in Figures 1 to 4, the hydraulic lifting device 100 includes a case 1, a lift arm 2, a bracket 3, 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 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 transmission mechanism 20, 30, and 40 will be described in detail later.

Case 1 is a housing, and the bottom surface of case 1 is open. The two lift arms 2 are located at the rear outside of the case 1, one each on both left and right sides. In each lift arm 2, one end side 21 and the other end side 22 are defined. One end side 21 is configured to be connectable to a lift link (not shown). The other end side 22 is pivotally supported at both ends of a shaft 23 that passes through both left and right side surfaces from inside the case 1 (see FIGS. 5 and 6). Each lift arm 2 projects rearward from the other end side 22 toward the one end side 21. Each lift arm 2 rotates relative to the case 1 using the other end side 22 as a fulcrum when the hydraulic cylinder 4 is driven. That is, the one end side 21 can swing vertically using the other end side 22 as a fulcrum.

The bracket 3 is located outside the case 1 and on the rear side of the other end 22 of the lift arm 2. In the bracket 3, one end side 31 and the other end side 32 are defined. One end side 31 is configured to be connectable to a top link (not shown). The other end 32 is supported by a shaft 33 that is connected at both ends to the case 1 (see FIGS. 5 and 6). The shaft 33 has, for example, a torsion bar structure, so that a biasing force is generated in the opposite rotational direction in response to a rotational load around the shaft. The axial center of the shaft 33 is located lower and rearward than the axial center of the shaft 23. The bracket 3 protrudes diagonally downward and rearward from the other end side 32 toward the one end side 31. The connecting portion of the top link in the bracket 3 is located below each of the shafts 23 and 33. The bracket 3 rotates relative to the case 1 using the other end side 32 as a fulcrum in response to the traction load from the connected top link (namely, the implement). That is, the one end side 31 can swing back and forth while being biased, using the other end side 32 as a fulcrum.

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 in the left-right direction of the shaft 23. 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 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 hydraulic oil flow path formed inside and is interposed in the hydraulic oil circuit. Other components connected to and interposed in the circuit include a hydraulic pump, a relief valve, a flow path switching valve, a safety valve, and a drop adjustment valve. These components are configured as either one with the case 1 or as separate components. The control valve 5 is located to the right 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. The 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 displaceable in the front-rear direction relative to the housing of the control valve 5. The spool 51 is constantly biased forward by a spring.

The front end side 51a of the spool 51 is pressed rearward by the cams of the respective transmission mechanisms 20, 30, and 40 against the urging force. At this time, the position of the spool 51 is displaced rearward, and supply of hydraulic oil to the hydraulic cylinder 4 is permitted. 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 transmission from the crank arm 43 and the shaft 23. On the other hand, when the pressure by the cam of each transmission mechanism 20, 30, 40 is released, the position of the spool 51 is displaced forward along the force, and the supply of hydraulic oil to the hydraulic cylinder 4 is regulated. As a result, the displacement of the piston 41 and the piston rod 42 and the rotation of the crank arm 43 and the shaft 23 are respectively restricted, and the position (height) of the lift arm 2 that has been relatively rotating is fixed.

As shown in FIGS. 1 and 2, the position control lever 6, the pumper lever 7, and the draft control lever 8 are located on the outside of the case 1, on the right side, and in front of the lift arm 2, respectively. are doing. In the position control lever 6, one end side 61 and the other end side 62 are defined. One end side 61 is configured to be operable by an operator. The other end side 62 is pivotally supported at the right end portion of a first position control shaft 220 that passes through the right side surface from inside the case 1 (see FIGS. 7 and 9). The position control lever 6 projects upward from the other end side 62 toward the one end side 61. When one end 61 of the position control lever 6 is operated by an operator, the position control lever 6 rotates relative to the case 1 about the other end 62 as a fulcrum as a displacement corresponding to the operation. That is, the one end side 61 can swing back and forth using the other end side 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. 7 and 10). 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.

The position of the front end of the protruding member 74a can be adjusted in the front-rear direction by a length adjustment mechanism such as a screw. In other words, the position where the pump lever 7 abuts against the protruding member 74a can also be adjusted in the front-rear direction. Therefore, the relative rotation of the pump lever 7 is restricted further forward as the position of the front end of the protruding member 74a is displaced forward.

The draft control lever 8 has one end 81 and the other end 82. The one end 81 is configured to be operable by an operator. The other end 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 7 and 11). The draft control lever 8 protrudes upward from the other end 82 toward the one end 81. The other end 82 of the draft control lever 8 is positioned coaxially with the other end 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 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 82 as a fulcrum, as a displacement according to the operation. That is, the one end 81 can swing in the forward and backward directions with the other end 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 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 92 of the position feedback rod 9 is connected to the lower end of the cam 230a so as to be capable of relative rotation. The cam 230a is journalled at the left end of the second position control shaft 230, which penetrates the left side from inside the case 1, and protrudes downward (see Figures 7 and 9). When the position feedback rod 9 is displaced in the front-rear direction, the lower end of the cam 230a swings in the front-rear direction, allowing the second position control shaft 230 to rotate relatively.

A rear end side 101 of the draft feedback rod 10 is connected to a lower end of the joint 34. The joint 34 is integrally fixed to the left side surface of the bracket 3 and protrudes downward to the left side. When the bracket 3 rotates relative to the case 1, the joint 34 also rotates together, and the lower end of the joint 34 swings back and forth. Accordingly, the draft feedback rod 10 is movable in the front-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 relatively rotatable. A part of the front end side 102 is constituted by a spring 102a. The cam 430a is pivotally supported at the left end of a second draft control shaft 430 that passes through the left side surface from inside the case 1, and protrudes downward to the left (see FIGS. 7 and 11). 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 longitudinal direction, the lower end of the cam 430a swings in the longitudinal direction, and the second draft control shaft 430 is relatively rotatable. In particular, when the draft feedback rod 10 is displaced forward, the spring 102a is slightly compressed from its installation 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).

<Configuration of transmission mechanism>
7 to 12, 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 to a spool 51 of the control valve 5. The displacements input to each transmission mechanism 20, 30, 40 are finally collected in 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.

FIG. 8 is an enlarged view of main parts showing the positional relationship between the cams 210, 310, 410 and the spool 51 inside the case 1. As shown in FIG. 8, the position control cam 210, the pumper cam 310, and the draft control cam 410 each have a substantially "E" shape when viewed from the left side. From the left side to the right side, the draft control cam 410, the position control cam 210, and the pump cam 310 are arranged in this order so as to be overlapped with each other at intervals. Each of the cams 210, 310, and 410 is provided with a pin that passes through the substantially central portion of each cam in the vertical direction in the left-right direction for positioning. Each of the cams 210, 310, and 410 can rotate relative to each other using the pin as a support shaft. As the position control cam 210, pumper cam 310, and draft control cam 410 are displaced, their respective upper end sides 212, 312, 412 or lower end sides 213, 313, 413 can swing in the front-rear direction.

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. 9 is an overall view of the position control transmission mechanism 20. As shown in FIG. 9, 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 same-direction rotating shaft 221, a reverse-direction rotating shaft 222, and a rotation transmission unit 223. The same-direction rotating shaft 221 extends in the left-right direction and has an axis A1 that is parallel to the left-right direction. The right end of the same-direction rotating shaft 221 is connected to the other end 62 of the position control lever 6. 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 protrudes upward is provided on the left end of the same-direction rotating shaft 221. The cam 221a is oscillating in the front-rear direction in response to the rotation of the same-direction rotating shaft 221 around 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. 9 and in FIG. 12, 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 of the second position control shaft 230. The front end 92 of the position feedback rod 9 is connected to the lower end of the cam 230a so as to be capable of relative rotation. In response to the forward and backward swing of the cam 230a, the second position control shaft 230 can rotate around the axis A3.

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 axis A3 in response to the displacement of the position feedback rod 9 when the lift arm 2 rotates relative to the lift arm 2. More specifically, when the cam 24 swings rearward due to the lift arm 2 swinging upward, 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 swing of the cam 230a, the second position control shaft 230 rotates in 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 rocking of the cam 230a, the second position control shaft 230 rotates in a direction R2 opposite to the direction R1.

The position control cam 210 has a protruding portion 211, an upper end side 212, and a lower end side 213. The protruding portion 211 protrudes rearward from approximately the center in the vertical direction, and as described above, is capable of abutting against the front end side 51a of the spool 51. The upper end side 212 is connected to the cam 230b of the second position control shaft 230 so as to be capable of relative rotation. The lower end side 213 is connected to the cam 222b of the reverse direction rotation shaft 222 (first position control shaft 220) so as to be capable of relative rotation.

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>>
FIG. 10 is an overall view of the pump transmission mechanism 30. As shown in FIG. 10, the pump transmission mechanism 30 includes a pump cam 310, a pump shaft 320, and a rotation transmission section 330.

Pumper shaft 320 extends in the left-right direction and is arranged coaxially with axis A3. As shown in the broken line part in FIG. 10 and in FIG. 12, the pumper shaft 320 has a hollow structure along the axis A3, into which the extension part 231 of the second position control shaft 230 can be coaxially fitted. It has become.

The pumper shaft 320 is connected to the other end 72 of the pumper lever 7 at its right end. The pumper shaft 320 is rotatable around the axis A3 in the same direction as the rotational direction of the pumper lever 7. A cam 320a that projects downward is provided on the left end side of the pumper shaft 320. The cam 320a can swing back and forth in accordance with the rotation of the pump shaft 320 about the axis A3.

The rotation transmission section 330 is a plate extending in the vertical direction, and is arranged coaxially with the axis A2. As shown in the broken line part in FIG. 10 and in FIG. It is possible to insert it. The upper side of the rotation transmitting section 330 is rotatably connected to the lower end of the cam 320a, and the lower side of the rotation transmitting section 330 is rotatably connected to the lower end side 313 of the pumper cam 310. The rotation transmission section 330 is configured to swing the lower end side 313 in the front-back direction in response to the swing of the cam 320a in the front-back 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 pump cam 310, a protruding portion 311, an upper end side 312, and a lower end side 313 are each defined. The protruding portion 311 protrudes rearward from approximately the center in the vertical direction, and as described above, can abut against the front end side 51a of the spool 51. The upper end side 312 is connected to the cam 230b of the second position control shaft 230 so as to be capable of relative rotation. More specifically, as shown in FIG. 12, 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 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 part 330 so as to be capable of relative rotation.

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>>
FIG. 11 is an overall view of the draft control transmission mechanism 40. As shown in FIG. 11, 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 co-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 same direction 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 is capable of contacting 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 protruding downward is provided on the right end of the reverse rotation shaft 422, adjacent to the right side of the cam 222a. In response to the forward and backward swing of the cam 422a, the reverse rotation shaft 422 can rotate around the axis A2 in the opposite direction to the rotation direction of the draft control lever 8. A cam 422b protruding downward is provided on the left end of the reverse rotation shaft 422. The cam 422b can swing forward and backward in response to the rotation of the reverse rotation shaft 422 around 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. 11 and in FIG. 12, 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 the axis A3 in accordance with the displacement of the draft feedback rod 10 when the bracket 3 rotates relative to the other. More specifically, when the joint 34 swings rearward due to rearward rocking of the bracket 3, the draft feedback rod 10 is displaced rearward without the spring 102a extending from its attachment length. In response to the rearward displacement of the draft feedback rod 10, the cam 430a swings rearward. In response to the rearward rocking of the cam 430a, the second draft control shaft 430 rotates in the 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 Figures 11 and 12, 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. In other words, the protrusion 102b can intersect with the radial trajectory of the cam 230a.

Therefore, for example, when the position feedback rod 9 continues to be displaced rearward, the cam 230a, which is relatively rotated rearward, will eventually come into contact with the protrusion 102b. After the contact, when the position feedback rod 9 is further displaced rearward, the cam 230a presses 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 is not displaced rearward, and the bracket 3 does not swing. On the other hand, in conjunction with the protrusion 102b being pushed rearward, the cam 430a also swings rearward, and the second draft control shaft 430 rotates in the direction R1.

The draft control cam 410 has a protruding portion 411, an upper end side 412, and a lower end side 413. The protruding portion 411 protrudes rearward from approximately the center in the vertical direction, and as described above, can abut against the front end side 51a of the spool 51. The upper end side 412 is connected to the cam 430b of the second draft control shaft 430 so as to be capable of relative rotation. The lower end side 413 is connected to the cam 422b of the reverse direction rotation shaft 422 (first draft control shaft 420) so as to be capable of relative rotation.

The operation associated with the operation of the draft control lever 8 will be described below. The premise of operation is that a traction load from the top link (implement) is applied to the bracket 3, the bracket 3 is oscillated according to the traction load, and the spool 51 is positioned in a neutral state. It is assumed that there is In this state, when the draft control lever 8 and the same direction rotating shaft 421 are rotated in the direction R2 by operating the draft control lever 8, and the opposite direction rotating shaft 422 is rotated in the direction R1, the cam 422b is moved to the rear side. oscillate. In accordance with the rearward swinging of the cam 422b, the lower end side 413 of the draft control cam 410 also swings rearward, and the protrusion 411 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. 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 penetrating the ground, the degree of tillage depth decreases. Also, if the lower end of the implement is separated from the ground, the separation distance increases. Therefore, the traction load from the top link to the bracket 3 changes, and the bracket 3 rotates relative to the top link in response. 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 embodiment of the present invention includes the lift arm 2, the position control lever 6, and the position control transmission mechanism 20. 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 rotates around the axis A1 (and axis A2) according to the displacement of the position control lever 6 when the position control lever 6 is operated. The second position control shaft 230 rotates around the axis A3 according to the displacement of the position feedback rod 9 when the lift arm 2 rotates relative to the other. When the first position control shaft 220 rotates, the position control cam 210 displaces the position of the spool 51 toward the side where supply and discharge of hydraulic oil is permitted according 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 in accordance with the rotation of the second position control shaft 230 toward the side where supply and discharge of hydraulic oil is restricted. Therefore, the height of the lift arm 2 in the vertical direction can be easily adjusted to a target height.

The second position control shaft 230 is located above the first position control shaft 220 in the lifting direction of the top link (implement). In this embodiment, the axis A3 of the second position control shaft 230 is located above the axis A1 of the first position control shaft 220. This allows the lower side of the second position control shaft 230 to be effectively used as a storage space for components. For this reason, for example, as shown in FIG. 7, by storing the hydraulic cylinder 4 below the second position control shaft 230 and to the left of the first position control shaft 220, the hydraulic lifting device 100 can be made smaller overall. In this way, the degree of freedom in the layout of the components 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 particular, in this 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 reverse direction rotating shaft 222 can be arranged on different axes via the rotation transmission unit 223. For example, as shown in FIG. 9, the position of the axis A1 of the same direction rotating shaft 221 and the position of the axis A2 of the reverse direction rotating shaft 222 can be made different from each other. Therefore, the same direction rotating shaft 221 and the reverse direction rotating shaft 222 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 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. In addition, by changing the link ratio in the rotation transmission unit 223, the displacement amount of the position control cam 210 (the displacement amount of the spool 51) relative to the displacement amount of the position control lever 6 can be adjusted. Therefore, the operating range of the position control lever 6 can be adjusted so that it is easy for the operator to operate.

In this 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, when the pumper transmission mechanism 30 is provided with the rotation transmission section 330 as in the present embodiment, the pump shaft 320 and the lower end side 313 of the pump cam 310 can be arranged with different axes via the rotation transmission section 330 ( (see Figure 10). Therefore, the pump shaft 320 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 pumper shaft 320 and the pumper lever 7 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 330, the amount of displacement of the pumper cam 310 (the amount of displacement of the spool 51) relative to the amount of displacement of the pumper lever 7 can be adjusted. Therefore, the operating range of the pumper lever 7 can be adjusted to make it easier for the operator to operate.

Further, in this embodiment, in particular, the pumper lever 7 has one end side 71 and the other end side 72 defined, and the one end side 71 is configured to be operable by the operator, and the other end side is configured to be displaced according to the operation. It is configured to be rotatable relative to the case 1 about the fulcrum 72. Further, a rotation regulating portion 74 for regulating relative rotation of the pumper lever 7 is provided. Thereby, the height at which the implement is raised by operating the pumper lever 7 can be intentionally regulated so as to be at an arbitrary position. For example, if the instrument is raised too high, the center of gravity also rises, increasing the risk of falling. In particular, when using a relatively heavy implement (for example, a plow, etc.) on a slope, the risk of overturning often increases. In such a case, the height of the implement can be appropriately regulated and safety can be improved. On the other hand, by regulating the height at which the implement can be raised to the minimum necessary height, for example, when lowering the implement after turning during work interruption, the implement will not touch the ground. You can shorten the time it takes. Therefore, the time required for work interruption can be shortened, and work efficiency can be improved accordingly.

In this embodiment, the bracket 3, the draft control lever 8, and the draft control transmission mechanism 40 are particularly provided. 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. When the draft control lever 8 is operated, the first draft control shaft 420 rotates around the axis A1 (and the axis A2) in response to the displacement of the draft control lever 8. When the bracket 3 rotates relative to the draft control shaft 430, the second draft control shaft 430 rotates around the axis A3 in response to the displacement of the draft feedback rod 10. When the first draft control shaft 420 rotates, the draft control cam 410 displaces the position of the spool 51 toward the allowable side of the supply and discharge of the 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 restrictive side of the supply and discharge of the hydraulic oil in response to the rotation of the second draft control shaft 430. This makes it easy to adjust the lift height of the lift arm 2 so that the traction load on the bracket 5 is the desired magnitude.

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. 7, by storing the hydraulic cylinder 4 below the second draft control shaft 430 and to the left of the first draft control shaft 420, the hydraulic lifting device 100 can be made smaller overall. 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 present embodiment, the draft control lever 8 has one end side 81 and the other end side 82 defined, and the one end side 81 is configured to be operable by the operator, and the other end side is configured to be displaced according to the operation. It is configured to be rotatable relative to the case 1 about the fulcrum 82. 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. 11, 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 particular, in this embodiment, either the first position control shaft 220 or the first draft control shaft 420 has a hollow structure and is configured so that one can be coaxially inserted into the other. In particular, either the second position control shaft 230 or the second draft control shaft 430 has a hollow structure and is configured so that one can be coaxially inserted into the other.

More specifically, as shown in FIG. 9, FIG. 11, and FIG. 12, 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.

<Modified example>
In the embodiment described above, the co-rotating shaft 221 of the first position control shaft 220 is coaxially fitted into the co-rotating shaft 421 of the first draft control shaft 420 . Instead, the co-rotating shaft 221 of the first position control shaft 220 has a hollow structure, and the co-rotating shaft 221 of the first draft control shaft 420 has a co-rotating shaft 221 of the first draft control shaft 420. , may be fitted coaxially.

In the above embodiment, 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 the embodiment described above, 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 herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1: Case 2: Lift arm 21: One end side 22: Other end side 3: Bracket 31: One end side 32: Other end side 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 100 : Hydraulic lifting device 20 : Position control transmission mechanism 210 : Position control cam 220 : First position control shaft 221 : Same direction rotating shaft 222 : Opposite direction rotating shaft 223 : Rotation transmission section 230: Second position control shaft 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: Rotation in the same direction Shaft 422: Reverse rotation shaft 423: Rotation transmission section 430: Second position control shaft

Claims (6)

Case and
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 a position of the spool;
a lift arm located outside the case, 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 about the other end as a fulcrum when the hydraulic cylinder is driven, thereby lifting and lowering the connected object;
a position control lever located outside the case and configured to be displaceable in response to an operation by an operator;
a position feedback rod located outside the case and configured to be displaceable in response to a relative rotation of the lift arm;
a position control transmission mechanism which, when the position control lever is operated, transmits a displacement of the position control lever toward the spool and displaces a position of the spool toward a side allowing supply and discharge of the hydraulic oil, and which, when the lift arm rotates relatively, transmits a displacement of the position feedback rod toward the spool and displaces a position of the spool toward a side restricting supply and discharge of the hydraulic oil;
In a hydraulic lifting device comprising:
The position control transmission mechanism includes:
a first position control shaft that rotates about an axis in response to the 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 a direction in which the object is lifted and lowered, and that rotates about an axis in response to a displacement of the position feedback rod when the lift arm rotates relatively to the first position control shaft;
a position control cam that, when the first position control shaft rotates, displaces a position of the spool toward a side allowing supply/discharge of the hydraulic oil in accordance with the rotation of the first position control shaft, and that, when the second position control shaft rotates, displaces a position of the spool toward a side restricting supply/discharge of the hydraulic oil in accordance with the rotation of the second position control shaft;
A hydraulic lifting device equipped with a The hydraulic lifting device according to claim 1,
The position 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 position control shaft is
a co-rotating shaft connected to the other end of the position control lever and configured to be rotatable in the same direction as the rotation direction of the position control lever;
a reverse rotation shaft connected to the position control cam and configured to be rotatable in a direction opposite to the rotation direction of the position control lever;
When the position 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 rotated 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 1 or 2,
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 be displaced 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 a The hydraulic lifting device according to claim 3,
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. The hydraulic lifting device according to claim 1 or 2,
a bracket located outside the case, having one end and the other end defined, the one end being configured to be connectable to an object, and the bracket rotating relative to the case with the other end as a fulcrum in response to a traction load from the connected object;
A draft control lever is located outside the case and configured to be displaceable in response to an operation by an operator;
A draft feedback rod is located outside the case and configured to be displaceable in response to relative rotation of the bracket;
a draft control transmission mechanism which, when the draft control lever is operated, transmits a displacement of the draft control lever toward the spool and displaces a position of the spool toward a side allowing supply and discharge of the hydraulic oil, and, when the bracket rotates relatively, transmits a displacement of the draft feedback rod toward the spool and displaces a position of the spool toward a side restricting supply and discharge of the hydraulic oil;
Further comprising:
The draft control transmission mechanism includes:
a first draft control shaft that rotates about an axis in response to a 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 a lifting direction of the object and that rotates about an axis in response to a displacement of the draft feedback rod when the bracket rotates relatively;
a draft control cam that displaces a position of the spool toward a side allowing supply/discharge of the hydraulic oil in accordance with the rotation of the first draft control shaft when the first draft control shaft rotates, and displaces a position of the spool toward a side restricting supply/discharge of the hydraulic oil in accordance with the rotation of the second draft control shaft when the second draft control shaft rotates;
A hydraulic lifting device equipped with a The hydraulic lifting device according to claim 5,
Either one of the first position control shaft and the first draft 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 position control shaft and the second draft control shaft has a hollow structure, and is configured such that the other can be coaxially fitted into the interior of the one;
The position control transmission mechanism and the draft control transmission mechanism are
The other is coaxially fitted into one of the first position control shaft and the first draft control shaft, and the other is fitted into one of the second position control shaft and the second draft control shaft. Fitted coaxially,
In response to displacement of either the position control lever or the draft control lever, the first position control shaft and the first draft control shaft rotate relative to each other around an axis,
A hydraulic lifting device configured such that the second position control shaft and the second draft control shaft rotate relative to each other around an axis in response to displacement of either one of the position feedback rod and the draft feedback rod.