JPH0142970Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a hydraulic lift device installed in an agricultural vehicle such as a tractor by controlling the operation of a control valve that switches and controls the supply and discharge of hydraulic pressure to a lift cylinder. The present invention relates to a control device that controls the operation of the device.

2. Description of the Related Art Hydraulic lift devices installed on agricultural work vehicles and used to raise and lower work equipment are used for various control purposes, as is well known. In other words, for example, a hydraulic lift device that raises and lowers a rotary tiller towed by an agricultural tractor automatically moves the valve by the amount of control valve operation based on feedback from the hydraulic lift device when the rotary tiller is raised and lowered by displacement operation of a control valve. The purpose of so-called position control is to displace the hydraulic lift device in the opposite direction and return it to the neutral position, and to stop the operation of the hydraulic lift device when the work equipment is raised or lowered by an amount commensurate with the amount of valve operation. In addition, the control valve is displaced in conjunction with a sensor mechanism that detects the tilling load acting on the rotary tiller, and the hydraulic lift device automatically stabilizes the vertical position of the rotary tiller and the tilling load. The purpose of so-called draft control is to displace the control valve in conjunction with a sensor mechanism that detects the depth of tillage by the rotary tiller, and then adjust the vertical position of the rotary tiller using a hydraulic lift device. However, it is used for the purpose of so-called depth control, in which the tillage depth is automatically controlled to be constant, and for various control purposes. In order to control the operation of the control valve for such control purposes, the control link for slidingly displacing the spool of the control valve has one end connected to a position control lever, draft control lever, depth control lever, etc. At the same time, the other end is connected to a feedback mechanism that feeds back the amount of elevation of the lift arm or a sensor mechanism that detects the tilling load or tilling depth, etc., so that it can be displaced from one end side and the other end side. It will be done.

By the way, the lift cylinder of an agricultural hydraulic lift device is generally installed on the transmission case of an agricultural work vehicle, and its control valve is mounted on the transmission case as shown in, for example, Japanese Utility Model Application Publication No. 1506/1983. When it is placed on the side of the lift cylinder so that it is located above, and when it is placed on the side of the lift cylinder, for example,
As shown in Japanese Patent No. 21922, there is a case where the lift cylinder is placed on the lower surface side of the lift cylinder so as to face into the mission case. The former arrangement for the control valve offers advantages such as ease of incorporation of the control linkage associated with the control valve, whereas the latter arrangement provides the advantage that the control valve and its associated control linkage can This provides the advantage that the hydraulic lift device can be made more compact by being housed inside the case.

When adopting the former control valve arrangement, generally, as disclosed in the above-mentioned Japanese Utility Model Application Publication No. 1506/1983, a control link for spool displacement as described above lowers the spool of the control valve. The spool is brought into contact with the spool by the force of the return spring that slides in the direction of the operating position,
It is provided. In other words, the control link can be displaced from one end side and the other end side as described above, but for the control link for displacing the spool of the control valve located above the transmission case, both ends of the control link can be displaced from one end side and the other end side. It is easy to provide a displacement mechanism related to the control link so that the control link always maintains contact with the spool and performs a two-dimensional displacement, and it is possible to actively displace the control link and the spool. This is because there is no need to mechanically connect the

However, when the control valve is arranged so as to face inside the mission case as in the latter case, it is necessary to displace the control link from one end and the other end in a plane or two-dimensional manner. This becomes difficult due to constraints imposed by the case, and the control link has no choice but to perform three-dimensional displacement. The control link that performs three-dimensional displacement in this way can also be displaced to a position outside the spool end position of the control valve.
As disclosed in the publication, it was positively mechanically connected to the spool.

However, when positively connecting the spool of the control valve and the control link, it is necessary to connect the spool with the control link for position control and other control links such as draft control or depth control. It becomes difficult to associate two or more control links such that each control link independently displaces the spool. Conventionally, a control valve placed facing inside the transmission case was used exclusively for position control, and a relatively small control valve for draft control or depth control was placed separately outside the transmission case. Increasingly, methods have been adopted that are disadvantageous in terms of cost and space, such as the provision of

The purpose of this invention is to install a control valve that switches and controls the supply and discharge of hydraulic pressure to the lift cylinder on the lower side of the lift cylinder so that it faces inside the transmission case of the agricultural work vehicle. An object of the present invention is to provide a new control device for a hydraulic lift device that eliminates the above-mentioned problems.

An incidental object is such a control device,
The object of the present invention is to provide a device that operates with good responsiveness over a long period of time without requiring strict dimensional control.

Regarding the illustrated embodiment, the configuration of the control device for the agricultural hydraulic lift device according to the invention will be explained. This is a housing for a hydraulic lift device, and a lift cylinder 6 is constructed by forming a cylinder chamber 4 in the housing 1 and fitting a piston 5 into the cylinder chamber 4. The housing 1 rotatably supports a lift arm shaft 7 extending in the left-right direction.A pair of left and right lift arms 8 are attached to the lift arm shaft 7 outside the housing 1, and a pair of left and right lift arms 8 are attached to the lift arm shaft 7 inside the housing 1. A connecting rod 10 is provided between the rotary arm 9 and the piston 5, which are fixed to each other, and when the lift cylinder 6 is extended, the lift arm 8 is rotated upward, and when the lift arm 8 is rotated downward by the weight of the working machine. The lift cylinder 6 is designed to be moved in a retracting manner. The control valve 11, which supplies hydraulic pressure to the lift cylinder 6 to cause the cylinder 6 to extend, and drains oil from the lift cylinder 6 to cause the cylinder 6 to contract, is operated as shown in FIG. The lift cylinder 6 is placed on the lower surface side so as to face the inside of the valve case 2, and the valve case is attached to the housing 1 by a fixture 12 shown in FIG.
It is fixedly connected to the In the neutral position, the spool 13 of the control valve 11 blocks the inside of the cylinder chamber 4 behind the piston 5 to stop the lift arm 8, and the spool 13 of the control valve 11 acts in the direction of the position where oil is drained from the lift cylinder 6, that is, the downward action of lowering the lift arm 8. It is slidably biased in the position direction by a return spring 14.

The illustrated hydraulic lift device is configured to perform position control and draft control, and a position control lever 1 shown in FIGS.
5 and a draft control lever 16, and a feedback mechanism 17 for position control shown in FIG. 2 and a draft control sensor shown in FIGS. 1 and 2 are provided on the other outer side of the housing 1. A mechanism 18 is provided. On the other hand, as shown in FIG.
An operating shaft 19 that extends between the inside and outside of the housing 1 at one side position and is rotationally displaced by operating the position control lever 15, and a hollow operating shaft 20 that is rotationally displaced by operating the draft control lever 16, Other operating shafts are provided concentrically with each other, and are also disposed on the other side of the housing 1, straddling the inside and outside of the housing 1, and are rotatably displaced by the feedback mechanism 17, as shown in FIG. 21 and sensor mechanism 18
Another hollow operating shaft 22 which is rotationally displaced by
are placed concentrically with each other. and the fifth
As shown in the figure, the crank pin 2 is displaced by the rotational displacement of these operating shafts 19, hollow operating shafts 20, and other operating shafts 21 and hollow operating shafts 22.
3 and 24 and other crank pins 25 and 26 are arranged within the transmission case 2. That is, the crank pins 23 and 24 are connected to the arms 23 fixed to the operating shaft 19 and the hollow operating shaft 20, respectively.
The other crank pins 25 and 26 are attached to arms fixed to the other operating shaft 21 and the hollow operating shaft 22, respectively. 25
The shafts 21 and 22 are installed along the horizontal direction at eccentric positions with respect to the shafts a and 26a.

As shown in FIGS. 3-7, a horizontal support plate 27 is provided at the top of the mission case 2 and is fixed to the lower surface of the housing 1 with a fixture 28 shown in FIG. 4. And this support plate 27
As shown in FIGS. 6 and 7, a substantially semicircular support tube 29 is welded and fixed to the lower surface of the control valve 11. The operation bar 30 is slidably supported on this support tube 29. It is provided concentrically with the spool 13 of the spool 1, as described later.
3. The operation bar 30, whose sliding displacement in the opposite direction is restricted, is attached to the spool 13 by the force of the return spring 14, and the bolt 13a is screwed into the end of the spool 13.
It is assumed that the contact is made through the Operation bar 30
A rectangular regulating plate 31 is fixed or integrally formed at the base end of the operating bar 30. By abutting the regulating plate 31 against the lower surface of the support plate 27 as shown in FIG. are regulated.

Also inside the mission case 2 are the 3rd, 4th, 5th,
A control link 32 for position control and a control link 33 for draft control shown in FIG. 30 or the regulating plate 31 at the proximal end thereof is supported as follows. That is, as clearly shown in FIG. 7, the regulation plate 31 is provided with a pin insertion hole 31a, and the control links 32, 33 are provided with pin insertion holes 32a, 33a in the center in the longitudinal direction. Pin insertion holes 34a are also provided in another rectangular regulation plate 34 that is to be interposed between the control link 32 located on the side and the control link 33 located on the lower side. 31a-34a and press the regulation plate 3 at the upper end.
1 is provided with a vertical pin 35 welded W (Fig. 5),
A nut 37 is screwed onto the threaded portion of the lower end of the vertical pin 35 via a washer 36 to support the control links 32, 33. Therefore, the control link 32 is held between the regulating plates 31 and 34, and the control link 33 is held between the regulating plates 31 and 34.
4 and the washer 36, the operation bar 30
They are respectively connected and supported so that they can only be horizontally rotated relative to each other around the vertical pins 35.

Control link 3 supported in this way
A vertical pin is fixed to one end of 2, 33 to form an engaging portion 38, 39, and a vertical pin is fixed to the other end of the pin. Engagement portions 40 and 41 are formed. The engaging portions 38 and 39 are respectively projected in the direction of the crank pins 23 and 24, and the other engaging portions 40 and 41 are respectively projected in the direction of the crank pins 25 and 26, Fourth
As shown in the figure, in the sliding direction of the operating bar 30 by the return spring 14, the crank pin 23,
24 and other crank pins 25 and 26. Therefore, the engaging parts 38, 39 are connected to the crank pins 23, 24, and the other engaging parts 40,
41 is maintained in engagement with the other crank pins 25 and 26 by the force of the return springs 14, respectively, and the sliding displacement of the operating bar 30 in the opposite direction of the spool 13 is controlled by the crank pins 32 and 33 via the control links 32 and 33. Pins 23, 24 and other crank pins 2
5, 26. As the operating shaft 19 and the hollow operating shaft 20 are rotated, the crank pins 23 and 24 are oscillated to change their vertical positions. are formed across a height range that can be constantly engaged with the crank pins 23, 24, and as the other operating shafts 21 and the hollow operating shaft 22 are rotated, the other crank pins 25, 26 are While the control links 32, 33 are pivoted to change their vertical positions, the other engaging parts 40, 41 at the other ends of the control links 32, 33 are in a height range where they can be constantly engaged with the other crank pins 25, 26. It is formed in a straddling manner.

As shown in FIG. 5, between the position control lever 15 and the operating shaft 19, an arm 44 is fixed to a cylindrical body 43 that fits over the operating shaft 19 outside the housing 1 and is secured with a key 42. and the position control lever 15 are fixedly connected by a rivet 45. Draft control lever 16 described above
Similarly, as shown in FIG. 5, between the housing 1 and the hollow operating shaft 20, an arm 48 is fixed to a cylindrical body 47 that fits over the hollow operating shaft 20 and is locked with a key 46, and this arm 48 and the draft control The levers 16 are connected by fixedly connecting them with rivets 49.

Further, as shown in FIGS. 2 and 5, the feedback mechanism 17 includes a rotating plate 50 provided to rotate integrally with the lift arm 8 on one side, and a pin fitted onto the other operating shaft 21 outside the housing 1. 51 Fixed cylinder body 5
An advancing/retracting rod 54 with a length adjustment part 54a and pivot pins 55, 5 at both ends are connected between the arm 53 on the top 2 and the arm 53 on the upper side.
6. As shown in FIGS. 1, 2, and 5, the sensor mechanism 18 includes a sensor arm 58 rotatably supported by the housing 1 around a fulcrum shaft 57, which is rotatably biased in one direction by a sensor spring 59. The upper end of the sensor arm 59 is connected to a top link in a three-point linkage device (not shown) by a wire 60, and the lower end of the sensor arm 58 is connected to another hollow operating shaft as shown in FIG. Cylindrical body 6 fitted onto 22 outside the housing 1 and secured with a key 61
An advancing/retracting rod 64 with a length adjusting part 64a and pivot pins 65, 6 at both ends are connected between the arm 63 on the top 2 and the arm 63 on the upper side.
6.

Lift arm 8 of position control lever 15 or draft control lever 16
In the illustrated case, the amount of operation in the upward direction is restricted as follows. That is, a rotation regulating plate 67 shown in FIGS. 3 and 4 is fixed to the lower surface of the support plate 27 using the fixing device 28, and the lever 15 or 16 is operated in the upward direction of the lift arm 8. the crank pin 23 or 2 via the operating shaft 19 or the hollow operating shaft 20.
44 to swing and displace the crank pins 23, 2.
4 to push the engaging portion 38 or 39 and move the control link 32 or 33 to the vertical pin 35.
When performing horizontal rotational displacement around the engaging portion 38,
39 comes into contact with the rotation regulating plate 67 on the opposite side of the crank pins 23, 24, as shown in FIG. It is designed to be done.

In FIGS. 3, 4, and 7, 68 is the spool 13.
This is a retaining ring attached to the operating bar 30 to prevent the operating bar 30 from being pulled out in the opposite direction.

The illustrated hydraulic lift device is constructed as described above, and when performing position control, the draft control lever 16 is moved to a position corresponding to the lowest position of the lift arm 8.
The crank pin 24 is moved via the hollow operating shaft 20 and the arm 24a from the one-dot chain line position shown in FIG.
3. Keep it largely removed from the engaging portion 39 of No. 3. At this time, the position of the operation bar 30 is restricted only by the control link 32, regardless of the control link 33. This is because, as will be described later, when the control link 32 is rotationally displaced, the vertical pin 35 position is changed, and the operation bar 30 is slidably displaced, the control link 33 can freely rotate around the vertical pin 35. vertical pin 35 position, therefore operation bar 30
This is because it does not affect the position.

To explain the action during position control with reference to Fig. 8, Fig. 8a shows the solid line, and Fig. 8b shows the solid line.
From the lift arm's highest state where the engaging portion 38 at one end of the control link 32 is in contact with the rotation regulating plate 67, as shown by the chain line in the figure, the position control lever 15 is operated in the downward direction of the lift arm 8, and the operating shaft 19 and Crank pin 2 via arm 23a
3 to the position shown in FIG. 8b, the force of the return spring 14 causes the spool 13 and the operating bar 30 to slide in the direction of arrow A, while the control link 32 rotates around the engaging portion 40. The vertical pin 35 is dynamically displaced to the position shown by the solid line in FIG. 8b, and the position of the vertical pin 35 is moved from the position shown by the chain line in FIG. 8b to the position shown by the solid line. As described above, when the spool 13 is slid in the direction of arrow A and the control valve 11 is moved to the lowering position, the lift cylinder 6 is retracted and the lift arm 8 is rotated downward. The crank pin 25 is moved in the direction opposite to the arrow A from the position shown in FIG. It is then displaced to the position shown in FIG. 8c. At this time, the other engaging portion 4 at the other end of the control link 32
0 is pushed by the crank pin 25, the control link 32 moves around the engaging portion 38 at one end from the position shown by the solid line in FIG. 8b and the chain line in FIG. 8c to the position shown by the solid line in FIG. 8c. As a result, the vertical pin 35 is moved from the position shown by the chain line in FIG. The control valve 11 is returned to the neutral position and the lift arm 8 is stopped.

From the state shown by the solid line in FIG. 8c, operate the position control lever 15 by an appropriate amount in the upward direction of the lift arm 8 to move the crank pin 23 from the position shown in FIG. 8c to the position shown in FIG. 8d. When the engaging part 38 at one end is pushed by the crank pin 23, the control link 32 moves around the other engaging part 40, as shown by the solid line in FIG.
It is rotated from the position shown by the chain line in FIG. d to the position shown by the solid line in FIG. 8d. At this time, the vertical pin 35 is moved from the position shown by the chain line in FIG. Then, the control valve 11 is moved to the raising position. As a result, when the lift arm 8 is rotated upward, the other crank pin 25 is moved from the position shown in FIG. 8 d to the position shown in FIG. 8 e via the feedback mechanism 17.
Since the control link 32 is moved to the position shown in the figure, the force of the return spring 14 causes the spool 13 and the operating bar 30 to slide in the direction of arrow A, and the control link 32 to rotate around the engaging portion 38. 8d, the vertical pin 35 is moved from the position shown by the chain line in FIG. 8d to the position shown by the solid line, the control valve 11 is returned to the neutral position, and the lift arm 8 is raised. Rotation stops.

During position control, the lift arm 8 always assumes a vertically moving posture corresponding to the operating position of the position control lever 15 due to the above-described action.

When performing draft control, move the position control lever 15 to the lowest position of the lift arm 8 and move the crank pin 23 through the operating shaft 19 and arm 23a in a state similar to that shown in FIG. 8a. the control link 32 to remove it from the engaging portion 38 of the control link 32. The action during draft control performed in this state is as follows:
It is almost the same as the action during position control explained with reference to the figure, and the crank pin 24 and other crank pins 26 and the engaging part 39 and the other engaging part 41
The interaction between the control link 33 and the position of the vertical pin 35 is changed, whereby sliding displacement of the spool 13 and the operation bar 30 is obtained. During this draft control, the draft control lever 16 is operated to move the crank pin 24 to an appropriate position, and the lift arm 8 is rotated downward to the corresponding position.
When a desired tilling load is set on the sensor spring 59 and the tilling operation is carried out in this state,
The sensor arm 58 of the sensor mechanism 18 rotates as the tillage load changes, and the load change is detected. 41a to the other crank pin 4
1 position is changed, and the attitude of the control link 33 is changed and controlled so as to keep the tilling load constant at the set value.

As described above, the functions of the position control and draft control themselves are the same as in the conventional case.
26 is operated by levers 15 and 16 or by feedback mechanism 17 or sensor mechanism 18.
The engaging parts 38, 39 at one end of the control links 32, 33, which are supported so that they can only rotate horizontally, despite being subjected to rocking displacement dimensionally, that is, not only in the horizontal direction but also in the vertical direction. The engaging portions 40 and 41 at the ends are connected to the crank pins 23 and 2.
4 and other crank pins 25, 26, each control link 32, 33 is always displaced only two-dimensionally on the same horizontal plane, and the vertical pin 35
And displacement of the spool 13 via the operation bar 30 can always be reliably achieved.

As is clear from the above description, the control device for the agricultural hydraulic lift device of this invention connects the control valve 11, which switches and controls the supply and discharge of hydraulic pressure to the lift cylinder 6, to the transmission case 2 of the agricultural vehicle.
In an agricultural hydraulic lift device that is arranged on the lower surface side of the lift cylinder 6 so as to face inside, the operation bar 30 is brought into contact with the spool 13 of the control valve 11 by the force of the return spring 14 of this spool 13. It is arranged concentrically with the spool 13 and is slidably supported while restricting rotational displacement, and is provided with a vertical pin 35 on the operation bar 30 at the center in the longitudinal direction so that it can only rotate horizontally relative to the spool 13. Connected control links 32 and 33 are provided, and crank pins 23 and 24 and a feedback mechanism 17 or a sensor are provided at one end and the other end of the control links 32 and 33, respectively, and are rockingly displaced by operating the levers 15 and 16. The other crank pin 25 is rocked by the mechanism 18,
26 and the other engaging portions 40, 41, which are respectively engaged by the force of the return spring 14, are constantly engaged with the crank pins 23, 24 and other crank pins 25, 26. This structure is characterized by being formed over a possible height range, and has the following advantages.

That is, the control device of this invention can be one in which the draft control mechanism in the illustrated embodiment is removed and only position control is performed, or it can be one in which a depth control mechanism is further added to the one in the illustrated embodiment. As explained above, in the conventional hydraulic lift device where the control valve is placed on the bottom side of the lift cylinder so as to face the inside of the work vehicle's transmission case, the spool of the control valve and the three-dimensional Since the control links that can perform a large amount of oscillating displacement are actively mechanically connected, only one control link could be associated with one spool, whereas the control link that can only freely perform sliding displacement was used. An operating bar 30 for spool displacement is provided, and control links 32 and 33 are connected to the operating bar 30 by vertical pins 35 so as to allow only horizontal rotation, thereby allowing only two-dimensional displacement. control link 3
Crank pins 23, 24 and other crank pins 2 that perform three-dimensional rocking displacement are provided at both ends of the crank pins 2, 33.
Engagement parts 38, 39 that can always engage with 5, 26
and other engaging portions 40, 41 to obtain the displacement of the spool 13 of the control valve 11 by two-dimensional displacement of the control links 32, 33.
Even if multiple control links are connected, when trying to obtain spool displacement using one control link, the crank pin that is designed to engage the engaging portion at one end of the other control link must be operated by lever operation. The spool can be disengaged from the engagement position with the engagement portion, and the spool can be independently displaced by the first control link while avoiding interference from other control links, and the spool can be moved vertically by two-dimensional displacement of the control link. The spool 13 can always be reliably displaced via the pin 35 and the operating bar 30, and thus the device of the present invention allows a single control valve to be used for various control purposes. This solves the above-mentioned problems of conventional hydraulic lift devices in which the control valve is disposed on the lower surface of the lift cylinder.

As described above, this invention is based on the valve spool 13.
The control links 32 and 33 are supported by a slidable operation bar 30 that allows the control links 32 and 33 to be freely rotated horizontally.
33 is connected to the crank pin 2 at its both end engaging portions.
The aforementioned problem was solved by simply engaging the control links 3, 24 and 25, 26, respectively.
As a structure for simply engaging the corresponding control link with the valve spool without mechanically connecting it, the structure shown in FIGS. 9 and 10 can also be considered.

That is, 132, 133 in Figures 9 and 10
are control links corresponding to the control links 32 and 33, and these control links 132 and 133 are not mechanically connected to the pin 13b attached to the end of the spool 13 of the control valve 11, as shown in the figure. It is only allowed to engage. For this purpose, the control links 132, 133 are connected to the ball portions 132a, 133 at both ends.
a, 132b, 133b are also swingably connected to crank arms 123, 124 and 125, 126 in place of the crank pins 23, 24, 25, 26, whereas the housing 1 similar to the above Regulation plate 2 attached to the bottom of
00 are provided with guide portions 201 and 202 that horizontally guide the control links 132 and 133. Crank arms 123, 124 are connected to arms 23a, 24a similar to those described above by crank pins 123a, 124a, and crank arms 125, 126 are connected to arms 25a, 26a similar to those described above by crank pins 125a, 124a.
126a. In FIG. 10, 203 and 204 are the spherical parts 132a and 204, respectively.
Clan arms 123, 124 installed in 133a
control links 132, 13
This is a split pin that prevents No. 3 from falling out. 9th and 10th
The structure of other parts shown in the figures is substantially the same as in the embodiment described above, and corresponding parts are designated by the same reference numerals.

According to the structure shown in FIGS. 9 and 10, the crank arms 123, 125, 124, 126 swing up and down while the ball parts 132a, 132b, 133
a, 133b are changed in the front and rear positions, thereby changing the postures of the control links 132, 133, but since the control links 132, 133 are guided by the guide parts 201, 202, they can be moved in the front and rear direction while maintaining the horizontal state. Change only the tilted posture seen in . Therefore, pin 13 at the end of spool 13
The engagement state of the control links 132 and 133 with respect to b is maintained, and the control link 13
2, 133 are not mechanically connected to the spool 13, the required valve actuation control can be obtained; therefore, it is possible to provide a plurality of control links for controlling the control valve 11 or its spool 13. become. Control links 132, 13 shown in chain lines in FIG.
In position 3, the first control link is valve 11.
This is a standby position in which other control links are moved by lever operation when used for control.

As described above, the structure shown in FIGS. 9 and 10 also solves the above-mentioned problems of the prior art, but this structure causes the following dimensional control problem.

That is, the guide portion 201 shown in FIG.
202 and the control links 132, 133 becomes a problem, and if the gaps are made relatively large, the horizontal movement of the control links 132, 133 due to the rotation of the crank arms 123, 125 and 124, 126 will become a problem. This is converted into vertical movement, resulting in problems such as a delay in the operation of the valve 11, a delay in the lift arm following the operation of the position control lever, etc., and a delay in the tiller during draft control or depth control. This results in vertical hunting and a decrease in tillage finishing accuracy. On the other hand, the guide part 201,
If the gap between the control link 202 and the control links 132 and 133 is closed too much, the control link 13
2, 133 becomes excessive, and the movement of the control valve 11 is delayed, which also causes problems such as a delay in follow-up of the lift arm. In addition, the guide parts 201, 202 and the control link 13
Even if the gap between 2 and 133 is initially appropriate, the gap becomes larger due to wear due to repeated use, causing the above-mentioned problems.

In this way, the structure shown in FIGS. 9 and 10 forcibly guides the control links 132 and 133, which can be displaced not only horizontally but also vertically at both ends, in the horizontal direction at a midway point in the length direction. However, this invention supports the control links 32, 33 so that they can only rotate horizontally, and the control links 32, 33
Upper and lower long engaging parts 38, 40 and 39, 4 at both ends
Crank pins 23 and 2 that swing the crank pins 1 and 2
5, 24, and 26, and does not forcibly correct the posture of the control links 32, 33, it can respond for a long time without requiring precise dimensional adjustment. A control device is provided that operates smoothly.

As shown in FIGS. 9 and 10, the control links 132 and 133 are connected to both end spherical portions 132a,
According to the structure in which the crank arms 123, 125 and 124, 126 are connected to the crank arms 123, 125 and 124, 126 in a swingable manner, it is difficult to assemble it outside and must be assembled inside the narrow housing. Links 32, 33
According to the present invention, the crank pins are simply engaged with the crank pins 23, 25 and 24, 26.
As can be clearly understood from Fig. 7, the operating bar 36
The control links 32 and 33 supported by the vertical pins 35 can be assembled externally as a subassembly and then incorporated into the housing, which provides the advantage of easy assembly.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a hydraulic lift device equipped with an embodiment of this invention, Fig. 2 is a side view of the same hydraulic lift device, Fig. 3 is a longitudinal sectional side view taken along the - line in Fig. The figure is a partially omitted bottom view taken along the arrow - in Fig. 3, Fig. 5 is a vertical cross-sectional rear view of only the main parts, Fig. 6 is a sectional view taken along the - line in Fig. 4, and Fig. 7 is the same. 8a, b, c, d, and e are respectively plan views showing the functions, and FIG. 9 is an example of a device having a problem solved by this invention. FIG. 10 is a partially sectional bottom view taken along the arrow - in FIG. 9. FIG. 1... Housing, 2... Mission case,
6...Lift cylinder, 8...Lift arm, 1
1...Control valve, 13...Spool,
13a... Bolt, 14... Return spring, 15...
Position control lever, 16...Draft control lever, 17...Feedback mechanism, 18...Sensor mechanism, 19...Operation shaft,
20... Hollow operating shaft, 21... Other operating shaft, 22
...Other hollow operating shafts, 23, 24...Crank pins, 23a, 24a...Arms, 25, 26...
Other crank pins, 25a, 26a...arm,
27...Support plate, 29...Support cylinder, 30...
...Operation bar, 31...Regulation plate, 32, 33...Control link, 34...Other regulation plate, 35...
... Vertical pin, 36 ... Washer, 37 ... Nut, 38, 39 ... Engagement part, 40, 41 ... Other engagement part, 50 ... Rotating plate, 53 ... Arm, 54
...Advance/retreat rod, 58...Sensor arm, 59...
Sensor spring, 63... Arm, 64...
Advance/retreat rod, 67... Rotation regulating plate.

Claims (1)

[Scope of utility model registration request] In agricultural hydraulic lift equipment, the control valve that switches and controls the supply and discharge of hydraulic pressure to the lift cylinder is placed on the bottom side of the lift cylinder so as to face the inside of the transmission case of the agricultural work vehicle. An operation bar that comes into contact with the spool by the force of the return spring is arranged concentrically with the spool and supported so as to be slidable, while restricting rotational displacement. A control link that is connected to the bar by a vertical pin so that it can rotate only relatively horizontally is provided, and one end and the other end of the control link are each equipped with a crank pin and a feedback mechanism or sensor that can be oscillated by operating a lever. The engaging portion and the other engaging portion, which are respectively engaged by the force of the return spring with the other crank pin that is oscillatedly displaced by the mechanism, are set in a height range that allows them to constantly engage with the above-mentioned crank pin and the other crank pin. A control device characterized by being formed in a straddling manner.