JPH0783643B2 - Working machine position control device for riding tractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Objectives of the Invention (1) Field of Industrial Application The present invention relates to work in response to hydraulic pressure supply in order to control the up-and-down position of a working machine that is connected to a riding tractor so as to be able to move up and down. A lift cylinder is connected to the work machine to enable the work machine to move upward and to lower the work machine by its own weight according to the hydraulic pressure release.
TECHNICAL FIELD The present invention relates to a work machine position control device for a riding tractor, to which a hydraulic control device is connected to a lift cylinder to switch and control a hydraulic pressure supply state, a hydraulic pressure supply stop state, and a hydraulic pressure release state.

(2) Conventional Technology Conventionally, in such a device, the working machine is moved up and down by the operation of the lift cylinder according to the operation of the operation lever, and the lifting operation of the working machine is fed back to control the operation of the lift cylinder. I have to.

(3) Problems to be Solved by the Invention However, in the above-mentioned conventional apparatus, the feedback control is performed both when the working machine is moving up and when it is moving down. Therefore, when the working machine is lowered to be grounded, the lift cylinder may be overloaded due to the grounding resistance of the working machine while the hydraulic pressure supply to the control shaft is stopped.

The present invention has been made in view of the above circumstances, and a working machine for a riding tractor capable of avoiding an overload on the lift cylinder due to a grounding resistance of the working machine during a descent operation with a simple configuration. An object is to provide a position control device.

B. Configuration of the Invention (1) Means for Solving the Problems According to the present invention, the hydraulic control device includes a hydraulic supply position within a limited range from the neutral position for stopping the hydraulic supply to both sides in the same direction. A feedback control link in which a lever provided with a control shaft rotatable between hydraulic pressure releasing positions, one end of which is fixed to the control shaft and the other end of which is provided with an abutting member, responds to the lifting operation of the working machine. The feedback control link mechanism and the operation lever are elastically urged in a direction in which the contact member slides on the intermediate portion in the longitudinal direction of the rotating bar that is rotatable about both ends where the mechanism and the operation lever are connected. , When the operation lever is operated to the up side, the control shaft is turned to the hydraulic pressure supply position, and the feedback control link mechanism is operated in response to the rising operation of the working machine to move the control shaft to the neutral position. The control shaft is rotated to the hydraulic pressure release position when it is operated and the operation lever is operated to the lower side, and the control shaft is rotated to the neutral position by the operation of the feedback control link mechanism according to the work machine's own weight lowering operation. However, the grounding resistance is connected to the rotary bar so as to separate the rotary bar from the abutting member in order to rotate the control shaft to the hydraulic pressure release position when the lowering of the weight of the working machine is suppressed.

(2) Operation According to the above configuration, by operating the operating lever to the upside, the rotating bar rotates about the connection point with the feedback control link mechanism as a fulcrum, and accordingly the lever rotates. The control shaft rotates to the hydraulic pressure supply position side, and the lift cylinder lifts the working machine. On the other hand, the feedback control link mechanism is activated in response to the work machine being lifted, and accordingly, the rotary bar is pivoted about the connection point with the operation lever as a fulcrum. By rotating the lever, the control shaft is rotated to the neutral position, the operation of the lift cylinder is stopped, and the raised position of the working machine is controlled to a desired position. Also, when the operating lever is operated to the lower side, the rotating bar rotates about the connection point with the feedback control link mechanism as a fulcrum, which causes the control shaft to rotate to the hydraulic pressure release position side as the lever rotates. It moves and the working machine descends due to its own weight. On the other hand, as the work implement descends, the feedback control link mechanism operates, and the rotating bar rotates about the connection point with the operating lever as a fulcrum. By the rotation, the control shaft is rotated to the neutral position, the operation of the lift cylinder is stopped, and the lowered position of the working machine is controlled to a desired position. Moreover, when the working machine touches the ground, the rotary shaft separates from the abutting member as far as the control shaft reaches the hydraulic pressure release position, so the lift cylinder is in the hydraulic pressure released state, and the lift cylinder is overloaded by the grounding resistance of the working machine. It does not work.

(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 tractor 1, and a transmission unit 2 is attached to a lower portion of the transmission unit 2. A pair of left and right rear wheels W, W are operably 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. A work sheet 3 is arranged above the transmission unit 2.

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. In this hydraulic control device 21, a casing 22 fixed to one side surface of a housing 14 is provided with a relief valve 23, a diversion valve 24, a one-way valve 25, a descending valve 26, an ascending control valve 27 and a descending control valve 28. Consists of

Hydraulic pump connected to oil tank 30 via filter 29
An oil passage 32 is connected to the outlet of 31 and the relief valve is connected to the oil passage 32.
23 is connected. Therefore, the pressure oil whose pressure is adjusted by the relief valve 23 is supplied to the oil passage 32.
32 is connected to the inlet port 33 of the diversion valve 24 and the inlet port 34 of the rising control valve 27.

The flow dividing valve 24 includes a valve body 36 that opens and closes between the inlet port 34 and the outlet port 35, and a back pressure chamber 37 that generates an oil pressure that urges the valve body 36 toward the closing side. 37 communicates with the inlet port 33 via an orifice 38 provided in the valve body 36. Also, the outlet port 34 is opened to the oil tank 30, and the back pressure chamber
The oil passage 39 communicating with 37 communicates with the first outlet port 41 of the rising control valve 27 and the inlet port 42 of the one-way valve 25.

The one-way valve 25 is opened only when the inlet port 42 becomes higher in pressure than the outlet port 43.The outlet port 43 communicates with the inlet port 44 of the down valve 26 and the lift cylinder via the oil passage 45. 4 hydraulic chamber 16 is connected. Further, the descending valve 26 includes a valve body 47 that opens and closes between the inlet port 44 and the outlet port 46, and a back pressure chamber 48 that generates an oil pressure that urges the valve body 47 toward the closing side. The chamber 48 communicates with the inlet port 44 via an orifice 49 provided in the valve body 47. The outlet port 46 is opened to the oil tank 30, and the oil passage 50 communicating with the back pressure chamber 48 communicates with the inlet port 51 of the lowering control valve 28.

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 limits the flow in the opposite direction. 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.

Referring also to FIG. 5, ascending control valve 27 is installed in oil tank 30.
To the second outlet port 57 and the first outlet port 41
The spool valve body 58
It is switched by the axial movement of the spool valve body.
The drive plate 61 is brought into contact with the contact pin 59 provided coaxially at one end of the 58, and the contact pin 59 is brought into contact with the drive plate 61 by the spring 62 provided between the spool valve body 58 and the casing 22. Directional spring biased. Moreover, the base end of the drive plate 61 is a spool valve body.
It is fixed to a control shaft 66 supported by the casing 22 so as to be rotatable around an axis line orthogonal to the axis line of 58, and the spool valve body 58 is rotated in response to the rotation of the control shaft 66 and the drive plate 61. Moves in the axial direction.

The first and second outlet ports 41,57 are the first outlet port 41
Are arranged on the drive plate 61 side and arranged on both sides of the inlet port 34. As shown in FIG. 5A, the control shaft 66 moves from the neutral position N as the hydraulic pressure supply stop position where the drive plate 61 is positioned substantially orthogonal to the axis of the spool valve body 58 as shown in FIG. It is possible to rotate to a sudden rising position as a hydraulic pressure supply position which is rotated in the direction indicated by arrow 92 by an angle α, and 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 hydraulic pressure 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 spool valve element 58 is in a position of blocking the inlet port 34 and the first outlet port 41 and communicating between the inlet port 34 and the second outlet port 57, as shown in FIG. Control shaft 66 and drive plate 61 as shown
Is in a sudden rising position, the spool valve element 58 is in a position of communicating between the inlet port 34 and the first outlet port 41 and blocking between the inlet port 34 and the second outlet port 57, as shown in FIG. 5 (b). Control shaft 66 and drive plate as shown
When 61 is in the gently rising position, the spool valve element 58 is in a position that shuts off both the inlet port 34 and the first and second outlet ports 41, 57, and as shown in FIG. When the 66 and the drive plate 61 are in the lowered position, the spool valve body 58 is in a position to shut off between the inlet port 34 and the first outlet port 41 and to communicate between the inlet port 34 and the second outlet port 57.

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 can come into contact with the other end of the spool valve body 58 of the raising control valve 27 coaxially, and the other end of the spool valve body 58 in the neutral state with the poppet valve body 64 in the closed position. Contacts the poppet valve body 64. Thus, when the spool valve element 58 moves from the neutral position shown in FIG. 4 to the lowered position as shown in FIG. 5 (c), the spool valve element 58 is pressed and the poppet valve element 64 opens. To do. Also spool valve body 58
When is in the sudden rising position and the slowly rising position, the poppet valve body 64 is not in contact with the spool valve body 58 and the spring 65 maintains the closed state of the lowering control valve 28. Moreover, the fifth
As shown in FIG. 6C, the drive plate 61 is at an angle β from the neutral position N.
When it reaches the lowered position by rotating only
The spool valve element 58 is restricted from further movement by the lowering control valve 28, and therefore the control shaft 66 and the drive plate are
The 61 does not rotate downward from the neutral position at an angle β or more.

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 of communicating between the inlet port 34 and the second outlet port 57, 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 shuts off the inlet port 34 and the second outlet port 57, and the inlet port 34 and the second outlet port 57 are closed. The 1 exit ports 41 communicate with each other. As a result, the pressure oil from the hydraulic pump 31 passes through the ascending control valve 27, the one-way valve 25, and the slowly descending valve 52 to the hydraulic chamber 16 of the lift cylinder 4.
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, the flow dividing valve 24 remains closed.

Further, when the control shaft 66 and the drive plate 61 are rotated to the gently raised position as shown in FIG. 5 (b), the spool valve body 58 of the ascending control valve 27 is placed between the inlet port 34 and the outlet ports 41, 57. Shut off. As a result, the flow dividing valve 24 is opened by lowering the pressure of the back pressure chamber 37, the inlet port 33 communicates with the outlet port 35, and the oil passage 39 through the orifice 38 and the back pressure chamber 37.
Communicate with. Therefore, a part of the pressure oil from the hydraulic pump 31 is made to flow to the oil tank 30, the remaining pressure oil is supplied to the hydraulic chamber 16 via the one-way valve 24 and the gentle descending valve 52, and the lift cylinder 4 is gently extended. Operate. As a result, the rising speed of the working machine 5 also becomes gentle.

Further, when the control shaft 66 and the drive plate 61 are rotated to the lowered position as shown in FIG. 5 (c), the inlet port 34 of the ascending control valve 27 communicates with the second outlet port 57 and the descending control valve 28 opens. Speak. For this reason, the pressure in the back pressure chamber 48 decreases in the down valve 26. On the other hand, the weight of the working machine 5 is the hydraulic chamber of the lift cylinder 4.
Acting on 16, so inlet port 44 on down valve 26
The hydraulic pressure in the hydraulic chamber 16 is high
Oil pressure is 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. The operation lever 67 is rotatably attached to the support bracket 70 and its operation position is rubbed. 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 ascending side operating position P _u shown by a chain line in FIG. 9 (solid line in FIG. 10) and a maximum descending side operating position P _d shown by a solid line in FIG. 9 (chain line in FIG. 10). It is rotatable between and.

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 has the other end of the connecting pin 90 in the fixed position and the operating lever 67 and the swing plate 71 from the maximum descending side operating position P _d to the maximum raising side operating position P _{u as} shown by the arrow 91. The lever 88, which is rotated in the same direction as the swing plate 71 when it is rotated to the side, is driven by the lever 88 that follows the rotation bar 86 as the roller 87 slides on the rotation bar 86. The control shaft 66 is arranged to rotate in the direction shown by the arrow 92 in response to the rotation of the moving bar 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 69 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 operating position P _u 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.
The fulcrum, the lever 88 and the control shaft 66 rotate in the direction indicated by the arrow 92 in accordance with the rotation of the rotation bar 86, and the control shaft 66 and the drive plate 61 are shown in FIG. 5 (a). As shown in the figure, it will be in the ascending position. As a result, the inlet port 34 of the rising control valve 27
Also, the first outlet port 41 is electrically connected, and the pressure oil from the hydraulic pump 31 is supplied to the hydraulic chamber 16 of the lift cylinder 4. Therefore, the lift cylinder 4 extends and the link mechanism 6
The working machine 5 is lifted up via the.

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 inlet port 34 from the outlet ports 41 and 57, and supplies only a small amount of pressure oil flowing from the diversion valve 24 to the hydraulic chamber 16 of the lift cylinder 4. As a result, the lifting operation of the work implement 5 is alleviated. Next, when the control shaft 66 reaches the neutral position as shown in FIG.
And the second output port 57 communicate with each other, and the lift cylinder 4
The supply of pressure oil to the hydraulic chamber 16 is stopped. Therefore, when the work implement 5 rises in response to the operation of the operation lever 67, the work implement 5 rises rapidly at first, but the rising speed becomes gentle immediately before reaching the desired position, and at the gently rising speed, the desired position is reached. Will be reached.

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 ground 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 frame 19,
Since the hydraulic chamber 16 of the lift cylinder 4 is in the hydraulic pressure released state, the lift 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 connecting shaft 107 in the elongated hole 103, that is, the connecting position of both links 100, 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.

C. Effects of the Invention As described above, according to the present invention, when the operation lever is operated to the up side, the control shaft is rotated to the neutral position by the operation of the feedback control link mechanism according to the up operation of the work implement. It is possible to control the rising position of the work machine, and when the operation lever is operated to the down side, the feedback control link mechanism operates according to the work machine's own weight lowering operation to rotate the control shaft to the neutral position for work. It is possible to control the lowering position of the machine, and when the working machine touches the ground when the working machine lowers its own weight, the rotating cylinder is moved away from the abutting member so as to rotate the control shaft to the hydraulic pressure release position. Since the hydraulic pressure is maintained in the hydraulically released state, it is possible to prevent the lift cylinder from being overloaded by the ground resistance of the working machine.

[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 ... Riding tractor, 5 ... Working machine, 21 ... Hydraulic control device, 66 ... Control shaft, 67 ... Operating lever, 69 ... Feedback control link mechanism, 86 ... Rotating bar, 87 ... ... Roller as contact member, 88 ... Lever

Claims (1)

[Claims] Claims: 1. To control the ascending / descending position of a working machine connected to a riding tractor so as to be able to move up and down, it is possible to raise the working machine in response to hydraulic pressure supply and to lower the working machine by its own weight in response to hydraulic pressure release. A lift cylinder is connected to the work machine, and a hydraulic control device is connected to the lift cylinder to switch between a hydraulic pressure supply state, a hydraulic pressure supply stop state, and a hydraulic pressure release state. The device is provided with a control shaft rotatable between a hydraulic supply position and a hydraulic release position in a limited range from a neutral position for stopping the hydraulic supply to both sides in the circumferential direction, and one end thereof is fixed to the control shaft. A lever with a contact member at the other end is used as a fulcrum at both ends where the feedback control link mechanism that responds to the lifting operation of the work machine and the operation lever are connected. Is resiliently biased in a direction to sliding contact with the contact member in the longitudinal direction intermediate portion of the rotatable pivot bar,
The feedback control link mechanism and operating lever are
When the operation lever is operated to the up side, the control shaft is rotated to the hydraulic pressure supply position, and the feedback control link mechanism is operated in response to the rising operation of the working machine to rotate the control shaft to the neutral position. The control shaft is rotated to the hydraulic pressure release position during the downward operation of the and the control shaft is rotated to the neutral position by the operation of the feedback control link mechanism according to the downward movement of the work machine by its own weight. A riding tractor characterized by being connected to a rotating bar so as to separate the rotating bar from the abutting member so as to rotate the control shaft to the hydraulic pressure release position when the descent of the working machine is suppressed. Work machine position control device.