JPH076528B2 - Work machine position control device for work vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention (1) Field of Industrial Application The present invention relates to a working machine connected to a work vehicle in a vertically movable manner.
In order to control the ascending / descending position, a lift cylinder is connected to enable the work machine to move up in response to pressure oil supply and to lower the work machine's own weight in response to pressure oil discharge, and a hydraulic control device is connected to the lift cylinder. The present invention relates to a work machine position control device for a connected work vehicle.

(2) Conventional Technology Conventionally, such a device is known, for example, from Japanese Patent Application Laid-Open No. 56-70180, and a hydraulic control device controls the supply of pressure oil to the lift cylinder to operate the lift cylinder. It controls the vertical position of the work machine.

(3) Problem to be Solved by the Invention By the way, when supplying pressure oil to the lift cylinder to raise the working machine, it is desirable to make the raising operation speed as fast as possible, but to stop the operation of the lift cylinder. , If the operating speed up to that point is high, shock will occur. Therefore, in order to avoid the shock, it is desirable to make the operation of the lift cylinder gentle just before the working machine reaches a desired position.

The present invention has been made in view of the above circumstances, and provides a work machine position control device for a work vehicle capable of switching between a state in which the lift cylinder is suddenly operated and a state in which the lift cylinder is gently operated with a simple configuration. The purpose is to

B. Configuration of the Invention (1) Means for Solving the Problems According to the present invention, a hydraulic control device includes a lift control valve capable of switching between supplying pressure oil to a lift cylinder and stopping supply of the pressure oil, and a pressure control valve from the lift cylinder. It is equipped with a lowering control valve that can switch between oil discharge and discharge stop, and a flow control valve that can control the communication state between the pressure oil supply source and the lift cylinder according to the operation of the rising control valve. A first body having a first inlet port connected to an oil supply source, a first outlet port connected to a lift cylinder, and a first release port connected to an oil tank, the first inlet port being a first outlet port A supply position for communication, a supply stop position for disconnecting the first inlet port from the first outlet port and the first release port, and a release position for communicating between the first inlet port and the first release port can be switched. And a first spool valve body slidably fitted thereto, and the flow control valve has a second inlet port communicating with the pressure oil supply source, a second outlet port communicating with the first outlet port, and a first tank communicating with the oil tank. A second spool valve element that can open and close between the second inlet port and the second release port is slidably fitted to the second main body having two release ports while being biased toward the closing side. , The second spool valve body is provided with an orifice communicating between the second inlet port and the second outlet port, and the orifice generated by the flow of oil from the second inlet port through the orifice toward the second outlet port When the pressure difference between the front and rear exceeds the biasing force, the second spool valve body is moved to the opening side.

(2) Operation According to the above configuration, when the lowering control valve is in the discharge stop state and the first spool valve body of the ascending control valve is in the supply position, the second spool valve body of the flow control valve has the second inlet port and the second inlet port. At the closed position that shuts off between the two release ports, almost all of the pressure oil from the pressure oil supply source is supplied to the lift cylinder via the lift control valve, and the lift cylinder suddenly operates.

Further, when the first spool valve element of the rising control valve is set to the supply stop position, a large amount of pressure oil from the pressure oil supply source tries to flow to the lift cylinder side through the flow control valve. When a pressure difference occurs between the front and rear, and the pressure difference exceeds the biasing force on the closing side (that is, the side that shuts off between the second inlet port and the second release port) acting on the second spool valve body. , The second spool valve element moves to the open side (that is, the side communicating between the second inlet port and the second release port) against the biasing force, and a part of the pressure oil from the pressure oil supply source Is discharged to the oil tank, and the remaining pressure oil is supplied to the lift cylinder while being throttled by the orifice. Therefore, the amount of pressure oil supplied to the lift cylinder is reduced, and the operation of the lift cylinder is slowed down.

Further, when the first spool valve body of the raising control valve is set to the release position, almost the entire amount of the pressure oil from the pressure oil supply source is guided to the oil tank, and in this state, the lowering control valve is discharged so that the lift cylinder of the lift cylinder moves. The hydraulic pressure is released and the working machine descends due to its own weight.

(3) Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings. First, in FIG. 1, a transmission unit 2 is attached to a rear portion of a vehicle body 1a of a riding type tractor 1 as a work vehicle. A pair of left and right rear wheels W, W at the bottom of 2
Is steerably suspended. The transmission unit 2 includes a clutch, a transmission, a rear differential device and a front wheel drive shaft so that the rear wheel W, W and the front wheel (not shown) can be driven by the power of an engine (not shown). It is a thing. In addition, above the transmission unit 2, the work sheet 3
Is provided.

Below the work seat 3, a lift cylinder 4 is installed on the transmission unit 2, and a working machine 5 such as a rotary cultivator that is lifted and lowered by the lift cylinder 4 is provided behind the transmission unit 2 via a link mechanism 6. Connected to the end.

The link mechanism 6 includes a top link 7 pivotally supported by the transmission unit 2 so as to be vertically swingable, and a pair of left and right lower members pivotally supported by the transmission unit 2 below the top link 7. It is provided with links 8 and 8 and a pair of left and right lift arms 9 and 9 that are connected to the lift cylinder 4 and are individually connected to the intermediate portions of both lower links 8 and 8, and one lift arm 9 is telescopic. It is connected to the middle part of one lower link 8 via a cylinder 10 and the other lift arm 9
Is connected to the intermediate portion of the other lower link 8 via a lift rod 11.

According to the link mechanism 6, the working machine 5 can be lifted by swinging the lift arms 9 and 9 upward by supplying pressure oil to the lift cylinder 4, and the working machine 5 can be released by releasing the hydraulic pressure of the lift cylinder 4. 5 can be lowered by its own weight. Further, the work machine 5 can be tilted left and right with respect to the riding tractor 1 by the expansion and contraction operation of the expansion and contraction cylinder 10 to maintain a horizontal state.

2 and 3, on the transmission unit 2,
A housing 14 formed by integrally connecting a cylinder body 12 of the lift cylinder 4 and a bracket 13 is fixed. The lift cylinder 4 is formed by slidably fitting a piston 15 in a cylinder body 12, and a front end wall 12a of the cylinder body 12 is formed.
A hydraulic chamber 16 is defined between the piston and the piston 15. In addition, the piston 15 has a piston rod extending on the side opposite to the hydraulic chamber 16.
17 are connected. On the other hand, a lifting / lowering drive shaft 18 having an axis perpendicular to the axis of the piston 15 is rotatably supported by the bracket 13, and a swing arm 19 having a proximal end fixed to an intermediate portion of the lifting / lowering drive shaft 18. The piston rod 17 is connected. Moreover, the lifting drive shaft 18 projects from the bracket 13 to both sides, and the base ends of both lift arms 9, 9 of the link mechanism 6 are fixed to both projecting ends of the lifting drive shaft 18.

In FIG. 4, the hydraulic chamber in the lift cylinder 4
The hydraulic control device 21 for controlling the supply of pressure oil to the 16
It is disposed on one side surface of the housing 14. The hydraulic control device 21 includes a relief valve 23 and a flow dividing valve 2 as a flow control valve in a casing 22 fixed to one side surface of a housing 14.
4, a one-way valve 25, a descending valve 26, an ascending control valve 27 and a descending control valve 28 are provided.

An oil passage 32 is connected to an outlet of a hydraulic pump 31 as a pressure oil supply source connected to an oil tank 30 via a filter 29, and a relief valve 23 is connected to the oil passage 32. Therefore oil passage 32
The pressure oil whose pressure has been adjusted by the relief valve 23 is supplied to the oil passage 32, and the oil passage 32 is connected to the flow dividing valve 24 and the rising control valve 27.

Referring also to FIG. 5, the rising control valve 27 has a first outlet port 41 that communicates with the oil passage 39, a first release port 57 that communicates with the oil tank 30, and a first inlet port 34 that communicates with the oil passage 32. The casing 22 as the first main body is provided with the first spool valve body 58.
Is slidably fitted, and a drive plate 61 made of a leaf spring is brought into contact with an abutment pin 59 provided coaxially at one end of the first spool valve body 58, so that the first spool valve body 58 has a casing. The contact pin 59 is spring-biased in the direction of contacting the drive plate 61 by the spring 62 interposed between the contact pin 59 and the drive plate 61. Moreover, the base end of the drive plate 61 is fixed to a control shaft 66 supported by the casing 22 so as to be rotatable about an axis orthogonal to the axis of the first spool valve body 58. As the 61 is rotated, the first spool valve body 58 moves in the axial direction.

The first outlet port 41 and the first release port 57 are arranged on both sides of the first inlet port 34 with the first outlet port 41 arranged on the drive plate 61 side. As shown in FIG. 5A, the control shaft 66 has a neutral position N as a supply stop position in which the drive plate 61 is positioned substantially orthogonal to the axis of the first spool valve body 58 as shown in FIG. In addition to being able to rotate to a suddenly rising position as a supply position which is rotated by an angle α in the direction indicated by arrow 92, as shown in FIG. 5 (c), it is slightly moved from the neutral position N to the opposite side to the arrow 92. It is possible to rotate to a lowered position as a release position that is rotated by a certain angle β. Moreover, between the neutral position N and the suddenly rising position, as shown in FIG. 5 (b), there is a gently rising position that is rotated in the direction of arrow 92 from the neutral position N by an angle α'smaller than the angle α.

That is, as shown in FIG. 4, the control shaft 66 and the drive plate 61 are
Is in the neutral position, the first spool valve element 58 is
The control shaft is in a release position where the inlet port 34 and the first outlet port 41 are shut off and the first inlet port 34 and the first release port 57 communicate with each other, and as shown in FIG. 5 (a).
When the 66 and the drive plate 61 are in the ascending position, the first spool valve element 58 is arranged so that the first inlet port 34 and the first outlet port
It is in a supply position where it communicates between 41 and shuts off between the first inlet port 34 and the first release port 57, and FIG.
When the control shaft 66 and the drive plate 61 are in the gently rising position as shown by, the first spool valve body 58 shuts off the first inlet port 34 and the first outlet port 41 and the first release port 57 together. When in the stop position and the control shaft 66 and the drive plate 61 are in the lowered position as shown in FIG. 5 (c), the first spool valve element 58 shuts off between the first inlet port 34 and the first outlet port 41. In addition, the first inlet port 34 and the first release port 57 remain in the open position in which they are in communication with each other.

The lowering control valve 28 includes a poppet valve body 64 that can be opened and closed between the outlet port 63 and the inlet port 51 that communicate with the oil tank 30, and a spring 65 that urges the valve body 64 in the valve closing direction. It is arranged coaxially with the rising control valve 27. That is, the poppet valve body 64 is the first spool valve body 58 of the rising control valve 27.
The other end of the first spool valve element 58, which is in the neutral state with the poppet valve element 64 in the closed position, contacts the poppet valve element 64. Thus, when the first spool valve element 58 moves from the neutral position shown in FIG. 4 to the lowered position as shown in FIG. 5 (c), the first spool valve element 58 is pressed by the poppet valve element 64. Opens the valve. When the first spool valve element 58 is in the sudden rising position and the slowly rising position, the poppet valve element 64 is not in contact with the first spool valve element 58, and the spring 65 maintains the closed state of the lowering control valve 28. It Moreover, as shown in FIG.
Is in the lowered position rotated by the angle β from the neutral position N, the first spool valve body 58 of the raising control valve 27 is restricted from further movement by the lowering control valve 28, and therefore the control shaft 66 is controlled. And the drive plate 61 does not rotate downward from the neutral position at an angle β or more.

The shunt valve 24 is a second valve that communicates with the hydraulic pump 31 via the oil passage 32.
The second spool valve body 36 is slidably fitted to the casing 22 as the second main body having the inlet port 33, the second outlet port 40 communicating with the oil passage 39, and the second release port 35 communicating with the oil tank 30. The second spool valve element 36 has the second
An orifice 38 communicating between the inlet port 33 and the second outlet port 40 is provided, and the second spool valve element 36 has a spring 37.
As a result, a biasing force in the direction of blocking the second inlet port 33 and the second release port 35 is always received. Further, the second outlet port 40 communicates with the oil passage 39.

In the flow dividing valve 24, when a large amount of pressure oil from the hydraulic pump 31 tries to flow from the second inlet port 33 of the valve 24 to the lift cylinder 4 side via the orifice 38 and the second outlet port 40, The pressure difference generated before and after
When the biasing force of the spring 37 acting on the second spool valve element 36 on the closing side (that is, the side blocking the second inlet port 33 and the second release port 35) is exceeded, the second spool valve element 36 moves to the opening side (that is, the side that communicates between the second inlet port 33 and the second release port 35) against the biasing force, whereby a part of the pressure oil from the hydraulic pump 31 is stored in the oil tank. The remaining pressure oil is squeezed by the orifice 30, and is throttled by the orifice 38 to flow to the second outlet port 40.

The one-way valve 25 is opened only when the inlet port 42 leading to the oil passage 39 has a higher pressure than the outlet port 43, and the outlet port 43 communicates with the inlet port 44 of the descending valve 26 and the oil passage 45. It is connected to the hydraulic chamber 16 of the lift cylinder 4 via. The lowering valve 26 also has an inlet port 44 and an outlet port 46.
A valve body 47 for opening and closing the space, and a back pressure chamber 48 for generating an oil pressure for urging the valve body 47 toward the closing side are provided, and the back pressure chamber 48 has an orifice 49 provided in the valve body 47. Through the entrance port 44. Further, the outlet port 46 is opened to the oil tank 30,
The oil passage 50 leading to the back pressure chamber 48 is an inlet port 51 of the lowering control valve 28.
Communicate with.

Referring again to FIG. 2, the outlet port 43 of the one-way valve 25 is provided on the front end wall 12a of the cylinder body 12 of the lift cylinder 4.
And an oil passage 45 communicating with the inlet port 44 of the descending valve 44 is provided. Moreover, the slow-down valve 52 is arranged on the front end wall 12a so as to be interposed between the oil passage 45 and the hydraulic chamber 16. The slow-down valve 52 adjusts the minimum opening degree of the check valve 54, which allows the flow of oil from the passage 53 communicating with the oil passage 45 to the hydraulic chamber 16 but controls the flow in the opposite direction, and the check valve 54. And an adjusting bolt 55. An overload relief valve 56 is arranged on the front end wall 12a so as to be interposed between the hydraulic chamber 16 and the oil tank 30. The overload relief valve 56 opens when the hydraulic pressure in the hydraulic chamber 16 rises excessively, and releases the excess pressure to the oil tank 30.

In such a hydraulic control device 21, when the control shaft 66 and the drive plate 61 are in the neutral position as shown in FIG.
27 is in a state where the first inlet port 34 and the first release port 57 are in communication with each other, and the lowering control valve 28 is still closed. Returning to the oil tank 30 via 27, the lift cylinder 4 is thus inactive.

Next, when the control shaft 66 and the drive plate 61 are turned to the sudden rising position as shown in FIG. 5 (a), the rising control valve 27 blocks the first inlet port 34 and the first opening port 57, and also the first inlet port. The port 34 and the first outlet port 41 communicate with each other. As a result, the pressure oil from the hydraulic pump 31 is raised by the control valve 2
7, lift valve 4 via one-way valve 25 and slow-down valve 52
Is supplied to the hydraulic chamber 16 and the lift cylinder 4 is extended. The extension operation of the lift cylinder 4 is transmitted to the link mechanism 16 via the elevating drive shaft 18, whereby the working machine 5 is driven upward. At this time, since the flow rate of the pressure oil passing through the flow dividing valve 24 is small, a large pressure difference does not occur before and after the orifice 38, so that the second spool valve body 36 is closed based on the biasing force of the spring 37. The position (that is, the position where the second inlet port 33 and the second release port 34 are closed) is maintained.

Further, when the control shaft 66 and the drive plate 61 are turned to the gently rising position as shown in FIG. 5 (b), the first spool valve element 58 of the rising control valve 27 causes the first inlet port 34 and the first outlet port 41 to move. Further, the supply stop position is established to shut off the connection with the first release port 57. As a result, a large amount of pressure oil from the hydraulic pump 31 tries to flow to the lift cylinder 4 side through the flow dividing valve 24, so that a pressure difference occurs before and after the orifice 38 in the flow dividing valve 24, and this pressure difference is When the biasing force of the spring 37 acting on the second spool valve element 36 on the closing side (that is, the side blocking the second inlet port 33 and the second release port 35) is exceeded, the second spool valve element Since 36 moves to the opening side (that is, the side that communicates between the second inlet port 33 and the second release port 35) against the biasing force, a part of the pressure oil from the hydraulic pump 31 enters the oil tank 30. The one-way valve 24 and the slow-down valve 52 are flown while the remaining pressure oil is throttled by the orifice 38.
Is supplied to the hydraulic chamber 16 via the, and the lift cylinder 4 slowly extends. As a result, the rising speed of the working machine 5 also becomes gentle.

When the control shaft 66 and the drive plate 61 are further rotated to the lowered position as shown in FIG. 5 (c), the first inlet port 34 of the ascending control valve 27 communicates with the first release port 57 and the descending control valve 28 Opens the valve. For this reason, the pressure in the back pressure chamber 48 decreases in the down valve 26. On the other hand, since the weight of the working machine 5 acts on the hydraulic chamber 16 of the lift cylinder 4, the inlet port of the lowering valve 26
The hydraulic pressure of 44 is high, so the lowering valve 26 opens and the hydraulic chamber
16 hydraulic pressures are released. Moreover, at this time, the discharge of the pressure oil from the hydraulic chamber 16 is restricted by the action of the slow-down valve 52, the contraction operation of the lift cylinder 4 is slow, and the working machine 5 is also slowly lowered.

Referring to FIG. 6, FIG. 7, FIG. 8, FIG. 9 and FIG. 10 together, a control shaft 66 for actuating the ascending control valve 27 and the descending control valve 28 has an operating lever 67 for position control. The feedback control link mechanism 69 is connected via the position control link mechanism 68, and the feedback control link mechanism 69 is connected via the position control link mechanism 68.

A support bracket 70 formed in a substantially U-shape is fixed to the outer surface of the casing 22 of the hydraulic control device 21, and the operation lever 67 is rotatably attached to the support bracket 70 at its operation position. It is supported to be held by force. That is, the base end of the operation lever 67 is fixed to the swing plate 71, and the swing shaft 71 is provided with the pivot 72. On the other hand, the support bracket 70 has a through hole 73 penetrating the pivot 72, and a support cylinder 74 connected to the through hole 73 is fixed to the outer surface of the support bracket 70. The oscillating plate 71 supports a friction plate 75 made of a material having a large friction coefficient, and a supporting bracket 70.
The pivot 72 is inserted into the through hole 73 and the support cylinder 74. Moreover, the pivot 72 and the support cylinder
A cylindrical liner 76 is interposed between 74.

In FIG. 11, the outer periphery of the support cylinder 74 is formed in a substantially oval shape having a pair of flat surfaces 74a, 74a parallel to each other,
A first receiving plate 77 is fitted to the outer periphery of the support cylinder 74 to allow the movement of the support cylinder 74 along the axial direction but prevent the rotation around the axis. Further, a disc spring 78 is interposed between the first receiving plate 77 and the support bracket 70, and the spring force of the disc spring 78 causes the first receiving plate 77 to move outward in the axial direction of the support cylinder 74. Be energized.

Further, the pivot 72 has a screw shaft portion 72 protruding outward from the support cylinder 74.
a is coaxially provided so as to project, and a second receiving plate 79 having a hole 79a for projecting the screw shaft portion 72a outward and covering the opening end of the support cylinder 74 is brought into contact with the first receiving plate 76. . Moreover, the first
A pin 81 parallel to the axis of the support cylinder 74 is inserted through the second receiving plates 76 and 79, and the two receiving plates 76 and 79 are substantially integrated.

A nut 83 is screwed onto the screw shaft portion 72a protruding from the second receiving plate 79 with a washer 82 made of a material having a small friction coefficient such as an oil-containing resin interposed between the washer 82 and the outer surface of the second receiving plate 79.
A lock nut 84 is attached to the screw shaft portion 72a protruding from the nut 83.
Are screwed together.

In this way, the oscillating plate 71, that is, the operating lever 67 is supported by the supporting bracket 70, but the oscillating plate 71 is pressed against the supporting bracket 70 via the friction plate 75 by the spring force of the disc spring 78. The operation rotation position of the operation lever 67 is held by the frictional force between the rocking plate 71 and the friction plate 75 unless an external force is applied.

By the way, the rotation range of the operation lever 67 and the swing plate 71 is
The swing plate 71 is restricted to a range in which the stopper 93 provided on the support bracket 70 and the support bracket 70 itself contact. That is, the operating lever 67 has a maximum rising side operating position Pu shown by a chain line in FIG. 9 (solid line in FIG. 10) and a maximum descending side operating position Pd shown by a solid line in FIG. 9 (chain line in FIG. 10). It can be rotated between.

The position control link mechanism 68 has a rotating bar 86 whose one end is connected to the swing plate 71 via a connecting pin 85 parallel to the pivot 72.
A lever 88, one end of which is fixed to the control shaft 66 protruding from the casing 22, and the other end of which is provided with a roller 87 as a contact member slidable in contact with the side surface of the rotating bar 86. Is composed of a coil spring 89 compressed between the support bracket 70 and the lever 88 so as to exert a spring force in the direction of slidingly contacting the side surface of the rotating bar 86. The other end of the rotating bar 86 is for feedback control. The link mechanism 69 is connected via the connecting pin 90.

The rotating bar 86 moves from the maximum descending side operating position Pd to the maximum ascending side operating position Pu side with the operating lever 67 and the oscillating plate 71 as shown by an arrow 91 with the connecting pin 90 at the other end in the fixed position. The lever 88, which is rotated in the same direction as the swing plate 71 when it is rotated, is driven by the rotation bar 86 as the roller 87 slides on the rotation bar 86. The control shaft 66 is disposed so as to rotate in the direction shown by the arrow 92 in response to the rotation of 86.

Referring again to FIGS. 2 and 3, in order to detect the vertical position of the working machine 5, that is, the rotational position of the lift drive shaft 18, the lift drive shaft 18 is mounted on the bracket 13 integral with the cylinder body 12 of the lift cylinder 4. Axis with axis parallel to
94 is rotatably supported. One end of a link plate 95 is fixed to the inner end of the rotating shaft 94, and one end of a link plate 97 is connected to the other end of the link plate 95 via a pin 96 parallel to the rotating shaft 94. The other end of the plate 97 is connected to the swing arm 19.
As a result, the rotating shaft 94 is rotated by the amount of rotation of the lifting drive shaft 18, that is, the amount of angular displacement corresponding to the vertical position of the working machine 5.

The rotating shaft 94 is projected from the bracket 13, and the outer end of the rotating shaft 94 and the other end of the rotating bar 86 in the position controlling link mechanism 68 are connected to the feedback controlling link mechanism 69.
Are connected via.

The feedback control link mechanism 68 has a link 100, one end of which is connected to the outer end of the rotating shaft 94 via a bolt 98, and one end of which is connected to the other end of the rotating bar 86 via the connecting pin 90. A link 101 and a connecting means 102 for connecting the other ends of the links 100, 101 by adjusting their connecting positions are provided.

Referring also to FIG. 12, the connecting means 102 includes a long hole 103 formed at the other end of the link 101 along the longitudinal direction of the link 101 and the other end of the link 101 at the link. An adjusting bolt 104 fixed with an axis along the longitudinal direction of 101,
The adjusting bolt 104 has an annular engaging groove 105a on the outer periphery of the intermediate portion.
Adjusting nut 105 that is screwed in and out of the engagement groove 105a
A connecting plate 106 having at one end a locking portion 106a to be engaged with,
A connecting shaft 107 fixed to the other end of the connecting plate 106 so as to be inserted into the long hole 103 while penetrating the other end of the link 100 and slidingly contacting one surface of the link 101, and inside the long hole 103 of the connecting shaft 107. A lock bolt 109 is screwed to the connecting shaft 107 through a washer 108 between the lock bolt 109 and the link 101 to fix the position.

A circular hole 110 is formed at the other end of the link 100. In addition, the connecting shaft 107 includes a columnar portion 107a which is inserted into the circular hole 110 through the cylindrical liner 110 and a rectangular prismatic portion 107b which is movable in the long hole 103 so that the link 101 is interposed therebetween. The columnar portion 107a is continuously provided via a step portion 107b that is in sliding contact with one surface, and the column portion 107a has a length between the connecting plate 106 and the link 101 such that the link 100 can swing around the axis of the connecting shaft 107. The length of the prismatic portion 107b is set so that the tip of the prismatic portion 107b does not protrude from the elongated hole 103 when the step portion 107c is in sliding contact with one surface of the link 101. Further, the connecting shaft 107 is provided with a screw hole 115 extending over its entire length, and a lock bolt 109 is screwed into the screw hole 115.

According to the connecting means 102, the position of the connecting shaft 107 in the elongated hole 103, that is, the connecting position of the two links 100 and 101 can be adjusted by loosening the lock bolt 109 and rotating the adjusting nut 105. The position can be fixed by tightening the bolt 109.

According to such a feedback control link mechanism 69, when the working machine 5 is lifted, it is possible to perform the operation as shown in FIGS.
The link 101 moves in the direction indicated by the arrow 112 in the figure, and when the link 101 moves downward, the link 101 moves in the direction opposite to the direction indicated by the arrow 112.

Moreover, the operation lever 67 and the position control link mechanism 68 are
When the operation lever 67 is operated to the upward side (the state shown by the solid line in FIG. 10), the control shaft 66 is rotated in the direction of the arrow 92, and the feedback control link mechanism 69 corresponding to the upward movement of the working machine 5 is operated. When the control shaft 66 is rotated to the neutral position N by the operation and the operating lever 67 is operated to the descending side (the state shown by the solid line in FIG. 9), the control shaft 66 is moved from the neutral position N to the arrow 92.
While rotating in the opposite direction, the control shaft 66 is rotated to the neutral position N by the operation of the feedback control link mechanism 69 according to the operation of lowering the working machine 5 by its own weight, but the grounding resistance causes the working machine 5 to lower its own weight. When restrained, the control shaft 66 is connected to the rotating bar 86 so as to separate the rotating bar 86 from the roller 87 as shown in FIG. 9 so as to rotate the control shaft 66 to the hydraulic pressure released position.

Next, the operation of this embodiment will be described. When the working machine 5 in the lowered state is operated to rise, the operation lever
Rotate 67 in the direction indicated by arrow 91, and release the hand from operation lever 67 at any position. Thus, the swing plate integrated with the operating lever 67
71 is pressed against the support bracket 70 side via the friction plate 75 by the spring force of the disc spring 78, so that the friction force between the friction plate 75 and the rocking plate 71 causes the rocking plate 71, that is, the operating lever.
The 67 position is retained. Moreover, since the spring force of the disc spring 78 can be adjusted by the nut 83 and the lock nut 84, the frictional force can be easily adjusted.

Assuming that the operation lever 67 is rotated to the maximum lift operation position Pu as shown by the solid line in FIG. 10, the rotation bar 86 in the position control link mechanism 68 has a connecting pin 90.
Is rotated as a fulcrum, and the lever 88 and the control shaft 66 are rotated in a direction indicated by an arrow 92 in accordance with the rotation of the rotation lever 86.
The control shaft 66 and the drive plate 61 are in the sudden rising position as shown in FIG. 5 (a). As a result, conduction is established between the first inlet port 34 and the first outlet port 41 of the rising control valve 27, and the hydraulic pump
The pressure oil from 31 is supplied to the hydraulic chamber 16 of the lift cylinder 4. Therefore, the lift cylinder 4 is extended and the working machine 5 is raised via the link mechanism 6.

The rotating shaft 94 also rotates in response to the lifting operation of the work machine 5, the link 101 in the feedback control link mechanism 69 moves in the direction indicated by the arrow 112, and the rotating bar 86 also uses the connecting pin 85 as a fulcrum. It can be rotated. As a result, the lever 88 and the control shaft 66, which are provided with the roller 87 that makes sliding contact with the rotation bar 86, rotate in the direction opposite to the arrow 92. Therefore, the drive plate 61 rotates to the descending side, and immediately before the work implement 5 is raised to the desired position, the drive plate 61 is in the gently raised position as shown in FIG. 5 (b).

In the gently rising position, the rising control valve 27 blocks the first inlet port 34 from the first outlet port 41 and the first release port 57, and flows from the diversion valve 24 into the hydraulic chamber 16 of the lift cylinder 4. Only a small amount of pressure oil will be supplied, and the lifting operation of the work implement 5 will be moderated. Then control axis 66
Is in the neutral position as shown in FIG. 4, the rising control valve 27 has the first inlet port 34 and the first release port 57.
The spaces communicate with each other, and the pressure oil supply to the hydraulic chamber 16 of the lift cylinder 4 is stopped. Therefore, when the working machine 5 rises in response to the operation of the operation lever 67, it initially rises rapidly,
Immediately before reaching the desired position, the rising speed slows down,
The desired position is reached at the slow rising speed.

Further, when lowering the work implement 5 in the raised position, the operation lever 67 may be rotated in the direction opposite to the arrow 91.
Then, following the rotation of the rotation bar 85, the lever 88 also rotates in the direction opposite to the arrow 92, and the drive plate 61 becomes the lowered position as shown in FIG. 5 (c). When the control shaft 66 is rotated by the angle β to the descending position, the descending control valve 28 is opened, pressure oil is discharged from the hydraulic chamber 16 of the lift cylinder 4 while being restricted by the slow descending valve 52, and the lift cylinder 4 moves. The work device 5 is gently contracted and the work implement 5 is gently lowered. At this time, in the feedback control link mechanism 69, the link 101 moves to the opposite side of the arrow 112, and the rotation control bar mechanism 68 of the position control link mechanism 68 moves.
Rotates about the connecting pin 85 as a fulcrum. Therefore, the lever 88 and the control shaft including the roller 87 that is in sliding contact with the rotating bar 86
66 rotates in the direction of arrow 92, and when the control shaft 66 is in the neutral position as shown in FIG. 4, the lowering control valve 28 shuts off between the inlet port 51 and the outlet port 63, and the hydraulic pressure of the lift cylinder 4 increases. The discharge of pressure oil from the chamber 16 is stopped, and the working machine 5
Reaches a desired position according to the operation of the operation lever 67.

Next, it is assumed that the operating lever 67 is operated to the lower side to the maximum as shown by the solid line in FIG. 9 in order to ground the working machine 5. In this case, the lever 88 also rotates in the direction opposite to the arrow 92 following the rotation of the rotating bar 85, and the drive plate 61 is in the lowered position as shown in FIG. 5 (c). Moreover, the neutral position N of the drive plate 61
The maximum rotation angle from the to the descending side is β, and the drive plate 61 and the control shaft 66 are prevented from rotating to the descending side by the angle β or more. Therefore, even if the amount of rotation of the rotation bar 86 to the lower side in response to the operation of the operation lever 67 is large, the control shaft 66 rotates only by the angle β, and as shown in FIG.
Is separated from the side surface of the rotating bar 86.

On the other hand, when the working machine 5 descends until it comes into contact with the ground, the rotary bar 86 comes to the position shown by the chain line in FIG.
The control shaft 66 and the drive plate 61 remain in the lowered position, and the hydraulic chamber 16 of the lift cylinder 4 remains open. Therefore, even if the grounding resistance of the working machine 5 acts on the lift cylinder 4 via the link mechanism 6, the lifting drive shaft 18, and the swing arm 19, the hydraulic chamber 16 of the lift cylinder 4 is in a hydraulic pressure released state, so that the lift is lifted. The cylinder 4 is not overloaded.

By the way, the feedback control link mechanism 69 feeds back the operation amount of the working machine 5 to the position control link mechanism 68, and in order to accurately transmit the operation amount,
It is necessary to adjust the connection points of the links 100 and 101. Then, in the adjustment, in the connecting means 102 connecting the links 100 and 101, the lock bolt 109 is loosened and the adjusting nut is adjusted.
When the rotating operation of 105 is performed, the connecting shaft 107 moves along the long hole 103. Therefore, when the position of the communication shaft 107 in the elongated hole 103, that is, the connecting position of the links 100 and 101 reaches a desired position, the connecting position can be fixed by tightening the lock bolt 109. Therefore, the connection points can be adjusted extremely easily, and the adjustment operation is easy, so that the adjustment accuracy is also high.

In the above embodiments, the case where the riding type tractor is used as the working vehicle has been described, but the present invention is also applicable to a working vehicle such as a walking type tractor.

C. Effects of the Invention As described above, according to the present invention, when the first spool valve element of the rising control valve is switched from the supply position to the supply stop position, the pressure oil from the pressure oil supply source passes through the flow control valve and lift cylinder. Of the flow control valve, a pressure difference is generated before and after the orifice of the flow control valve, and the pressure difference acts on the second spool valve body on the closed side (that is, the second inlet port and the second release port). When the biasing force of the port (the side that shuts off between the ports) is exceeded, the second spool valve element moves to the open side (that is, the side that communicates between the second inlet port and the second release port) against the biasing force. Moving. As a result, even when the lift control valve shuts off the pressure oil supply source and the lift cylinder, the flow control valve causes a part of the pressure oil from the pressure oil supply source to escape to the oil tank, leaving the remaining pressure oil. Is being supplied to the lift cylinder while being throttled by the orifice, the amount of pressure oil supplied to the lift cylinder can be reduced and the operation of the lift cylinder can be moderated. Moreover, such a gradual operation immediately before the end of the operation of the lift cylinder can be realized with a simple configuration in which the flow control valve is connected in parallel to the lift control valve, which contributes to cost reduction.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a rear perspective view of a riding tractor to which the present invention is applied, FIG. 2 is an enlarged vertical sectional view of a lift cylinder, and FIG. III-III
A line sectional view, FIG. 4 is a hydraulic control circuit diagram, FIG. 5 is a diagram sequentially showing operation modes of the ascending control valve and the descending control valve, and FIG. 6 is a plan view showing an operating portion for operating the working machine, 7th
6 is a sectional view taken along line VII-VII in FIG. 6, and FIG. 8 is VIII in FIG.
-VIII line sectional view, Figure 9 is a sectional view taken along the line IX-IX in Figure 6 showing the operating lever in the lowered position, and Figure 10 is a sectional view showing the operating lever in the raised position. 11 is a sectional view taken along line XI-XI in FIG. 6, and FIG. 12 is an enlarged sectional view taken along line XII-XII in FIG. 1 ... Passenger tractor as a working vehicle, 4 ... Lift cylinder, 5 ... Working machine, 21 ... Hydraulic control device, 22 ... Casing as first and second main bodies, 24 ... Flow control valve Flow control valve, 27 ... rise control valve, 28 ... down control valve, 30 ... oil tank, 31 ... hydraulic pump as a pressure oil supply source, 33 ... second inlet port, 34 ... first Inlet port, 35 …… Second release port, 36 …… Second spool valve body,
40 …… Second exit port, 41 …… First exit port, 57 ……
1st release port, 58 ... 1st spool valve body

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F15B 11/00

Claims (1)

[Claims] 1. A working machine (5) connected to a working vehicle (1) so as to be able to move up and down, in order to control the ascending / descending position of the working machine (5). Work machine position control for a work vehicle in which a lift cylinder (4) is connected to enable the work machine (5) to descend by its own weight according to discharge and a hydraulic control device (21) is connected to the lift cylinder (4) In the device, the hydraulic control device (21) includes a rising control valve (27) capable of switching between pressure oil supply to the lift cylinder (4) and supply stop.
Between the pressure oil supply source (31) and the lift cylinder (4) depending on the operation of the lowering control valve (28) capable of switching the pressure oil discharge from the lift cylinder (4) and the discharge stop, and the ascending control valve (27). And a flow control valve (24) capable of controlling the communication state of the lift control valve (27) with the first inlet port (34) connected to the pressure oil supply source (31) and the lift cylinder (4). A first body (22) having a first outlet port (41) connected thereto and a first release port (57) connected to the oil tank (30),
A supply position for communicating the first inlet port (34) with the first outlet port (41), and disconnecting the first inlet port (34) from the first outlet port (41) and the first release port (57). Supply stop position and first inlet port (34) and first
The first spool valve body (58) is slidably fitted so that the release position communicating with the release ports (57) can be switched, and the flow control valve (24) includes a pressure oil supply source (31). A second inlet port (33), a second outlet port (40) leading to the first outlet port (41) and a second leading to an oil tank (30)
A second main body (22) having a release port (35) has a second spool valve body (36) capable of opening and closing between the second inlet port (33) and the second release port (35) and a biasing force toward the closing side. The second spool valve body (36) is fitted slidably in the received state and has an orifice (38) communicating between the second inlet port (33) and the second outlet port (40). It is provided, and its second inlet port (33) to the orifice (38)
The second spool valve body (36) is moved to the open side when the pressure difference before and after the orifice (38) caused by the flow of oil toward the second outlet port (40) exceeds the biasing force. A working machine position control device for a working vehicle, characterized in that