JP3238564B2 - Hydraulic control device for tractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a tractor configured to raise and lower a working machine connected to a rear part of a tractor by extension and retraction of a lift cylinder driven by hydraulic control of a hydraulic control valve. It is.

[0002]

2. Description of the Related Art Conventionally, in a hydraulic control device in which a working machine connected to a rear part of a tractor is moved up and down by a telescopic operation of a lift cylinder driven by hydraulic control of a hydraulic control valve, at the start of work or at the end of a field. When resuming work after turning, when lowering the work machine to the plowing position, the lowering speed of the work machine is slowed down to prevent engine stalls and dashing phenomena caused by rapid contact of the work machine with the field scene. At the same time, there is known a configuration in which when the working machine is raised, the deceleration control is released and the work implement is rapidly raised.

[0003]

However, in the above-described hydraulic control device, the descent speed of the working machine is controlled by a descent speed adjusting valve interposed in a hydraulic oil return path from the lift cylinder to the oil pump. If the descent speed is set to a low value, the time required to reach the plowing depth position will be long, so that the descent speed cannot be reduced too much in terms of work efficiency, giving unnecessary work such as hunting to the work machine. In addition, there has been proposed a configuration in which the dashing phenomenon is prevented in conjunction with the above-described hydraulic control device. Is configured to decelerate the descent speed from the descent position, the time required to reach the normal plowing position is still long, and the work efficiency is reduced. There was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation and has been made in order to solve the conventional disadvantages. It is an object of the present invention to easily switch the lowering speed of a working machine by operating a hydraulic control valve. Irrespective of the lowering speed switching operation by the hydraulic control valve, the lowering speed is automatically reduced immediately before reaching the predetermined plowing depth in conjunction with the upward movement of the rear cover of the working machine, An object of the present invention is to provide a hydraulic control device for a tractor that can prevent stalling, hunting, and dashing phenomena while shortening the time required for lifting and lowering, and can smoothly perform field work with high work efficiency.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the technical means adopted by the present invention is to properly work a working machine connected to a rear part of a machine body by vertically moving a rear cover provided on the working machine. A tractor configured to connect a rear cover to a link mechanism for operating a hydraulic control valve in order to hold the hydraulic control valve at a deep position, and to lift and lower the work implement by a telescopic operation of a lift cylinder driven by hydraulic control of the hydraulic control valve. In the hydraulic control apparatus, a main oil passage from the lift cylinder to the oil pump is provided through a first auxiliary oil passage communicating with the main oil passage through an adjustment valve, and a down-throttle valve interlockingly connected to the hydraulic control valve. A second oil passage communicating with the main oil passage, and a hydraulic oil return path from the lift cylinder to the oil pump through the two oil passages; The hydraulic oil return path to the oil pump through only the sub oil passage 1 can be switched by the lowering operation of the hydraulic control valve. Irrespective of the descending operation of the pressure oil, a switch is made to the pressure oil return path that passes only through the first sub oil path.

[0006]

Therefore, according to the present invention, the descending work machine stops descending at the plowing depth position set by the hydraulic control of the hydraulic control valve. Since the rear cover moves upward, the lowering speed of the work machine is controlled to be reduced, so that the work machine can calmly reach the predetermined plowing position without inducing dushing, hunting, or the like.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the present invention will be described in detail with reference to an embodiment shown in the drawings. In FIG. 1, 1 is a tractor, 2 is a hydraulic control device, 3 is a lift arm for supporting a working machine (not shown) up and down via a link mechanism, and 4 and 5 are respectively disposed in a driver's seat 6 on the side. The position control lever and the automatic depth adjustment lever.

As shown in FIGS. 2 and 3, the hydraulic control device 2 comprises a lift cylinder 7 for driving the lift arm 3 up and down, a down-throttle valve 8 and a hydraulic control valve 9. Is connected to a down throttle valve 8 via a descending speed adjusting valve 10 and further connected to an oil pump 11 via a hydraulic control valve 9. The lower throttle valve 8 is provided with an adjusting valve 8a and a check valve 8b, a first auxiliary oil passage 12a communicating with the main oil passage 12 through the adjusting valve 8a, a check valve 8b and the lower throttle valve 8b.
And a second sub-oil passage 12b communicating with the main oil passage 12 through the switching of the throttle spool 8 ', and an inner ring 8c and an outer ring provided around the throttle spool 8'. The pressure oil passing through the lower throttle valve 8 is communicated and cut off by the contact and separation of 8d.

The hydraulic control valve 9 comprises a switching valve 9a, a poppet 9b and a check valve 9c connected in series to the switching valve 9a, and a valve spool 9 'of the hydraulic control valve 9 is connected. The poppet 9b and the throttle spool 8 'are connected via links 13a and 13b.

On the other hand, FIG.
As shown in the figure, a link mounting plate 16 which supports the automatic plowing depth adjustment link 14 and the position control link 15 in a vertically parallel manner is mounted, and a position control arm 17 interlocked with the tilting operation of the position control lever 4, and a plow The pivoting operation of the tillage depth automatic adjustment arm 18 interlocked with the tilting operation of the deep automatic adjustment lever 5 causes the pivot shaft 1
The sensor arm 22, which is configured to individually rotate one end of each of the links 14, 15 with the fulcrum 9 as a fulcrum, and connected to a rear cover 20 of a working machine (not shown) via a pull wire 21, It is in contact with the other end of the deep automatic adjustment link 14.

At the other end of the position control link 15, a feedback arm 24 is connected via a feedback link 24 to a lift power arm 23 which is coaxially supported by a pivot shaft of the lift arm 3. 25 are in contact with each other, and the link mounting plate 1
The valve spool 9 ′ is urged through the link mounting plate 16 in the downward direction of the working machine indicated by the arrow DOWN by the tension of the coil ammunition 26 interposed between the valve arm 6 and the base end of the lift power arm 23. It is configured as follows. In addition,
27 is an oil tank and 28 is an import communicating with the oil pump 11.

In the configuration described above, when the position control lever 4 is tilted in the UP direction, the position control arm 17 rotates in the direction of arrow A shown in FIG. The position control link 15 presses the link mounting plate 16 toward the valve spool 9 ′ through the pivot 19 with the other end of the valve fulcrum as a fulcrum, so that the valve spool 9 ′ holds the neutral position shown in FIG. The main oil passage 12 moves from the stopped state
At the same time, the throttle spool 8 'also moves in the retracting direction via the connection link 13b.
The space between the inner ring 8c and the outer ring 8d is opened.

When the down throttle valve 8 and the hydraulic control valve 9 are retracted, the pressure oil fed from the oil pump 11 passes through the hydraulic control valve 9 and the main oil passage 12 and then to the first auxiliary oil. A second sub oil passage 12b is reached via a passage 12a and an opened down throttle valve 8, and
The adjusting valve 8a and the check valve 8b are respectively opened by the pressure of the pressure oil that has reached the first sub oil passage 12a, and the pressure oil is supplied to the lift cylinder 7 from both the sub oil passages 12a and 12b. 3 is rotated in the ascending direction.

At this time, the lift power arm 23 is rotated in the direction of arrow B shown in FIG. 4 in connection with the rotation of the lift arm 3, and the coil bullet 2 interposed between the lift power arm 23 and the base end thereof.
6, the valve spool 9 'protrudes in the direction of arrow DOWN, and the lift power arm 23
At the contact position regulated by the feedback arm 25 retracted with the rotation of the valve spool 9 ', the valve spool 9' returns to the stopped state holding the neutral position shown in FIG.

When the position control lever 4 is tilted in the DOWN direction, the position control arm 17 rotates in the direction of arrow C shown in FIG. Since the position control link 15 pulls the link mounting plate 16 to the lift power arm 23 via the pivot 19 by pulling the coil spring 26, the valve spool 9 '
Moves from the stopped state where the neutral position shown in FIG. 3 is held and moves in the protruding direction to communicate with the main oil passage 12, and at the same time, the throttle spool 8 'and the poppet 9 are connected via the connecting links 13a and 13b.
b also moves in the projecting direction, and the inner ring 8c of the throttle spool 8 'passes through the outer ring 8d, so that the throttle spool 8' is opened and communicated, and the lowering speed adjusting valve 10 The pressure oil returned to the oil pump 11 via the control valve 8a
A first sub-oil passage 12a communicating with the main oil passage 12 through
The second sub oil passage 12 communicating with the main oil passage through the space between the inner ring 8c and the outer ring 8d of the down throttle valve 8 opened.
b, reaches the main oil passage 12 communicating with the hydraulic control valve 9, after which the hydraulic control valve 9
The pressure oil is returned to the oil tank 27 via the poppet 9b which has been opened.

Then, as the work machine at the ascending position starts to descend at the speed adjusted by the descending speed adjusting valve 10 by the downward movement of the lift arm 3 accompanying the retracting operation of the lift cylinder 7, the lift The lift power arm 23 is rotated in the direction of the arrow B ′ shown in FIG. 4 in conjunction with the rotation of the arm 3, and the base of the lift power arm 23 is The tension force of the coil ammunition 26 interposed between the end portion and the end portion is loosened, and the position control link 15 rotates in the direction of the arrow UP with the contact position with the position control arm 17 as a fulcrum. With rotation, the valve spool 9 'is retracted to the neutral position, and the work implement descends.

At this time, as shown in FIG. 7, the inner ring 8 of the throttle spool 8 'interlocked with the retracted valve spool 9'.
c coincides with the outer ring 8 d immediately before reaching the target plowing depth position set by the automatic plowing depth adjustment lever 5 and
b is closed and the pressure oil returned from the lift cylinder 7 is connected to the first oil passage 12 through the adjustment valve 8a.
Only the auxiliary oil passage 12a, the return amount of the pressurized oil decreases, the retracting operation of the lift cylinder 7 slows down, and the lowering speed of the working machine supported by the lift arm 3 decreases to the target plowing. It becomes slow from just before the depth until reaching the target tillage depth.

On the other hand, in order to keep the lowered working machine at a predetermined plowing depth position, the automatic plowing depth adjustment lever 5 is set to "D".
When the position control lever 4 is tilted in the DOWN direction after being operated to the "EEP" side or the "SHALLLOW" side, the automatic plowing depth adjusting arm 18 moves the lift power arm 2 in conjunction with the operation of the automatic plowing depth adjusting lever.
3, the link 14 is rotated by the pulling force of the coil ammunition 26 until the link 14 automatically contacts the automatic adjusting arm with the sensor arm 22 as a fulcrum. By the rotation, the valve spool 9 ′ moves in the protruding direction from the stopped state holding the neutral position shown in FIG. 3 and communicates with the main oil passage 12, similar to the above-described lowering operation,
When the work machine is lowered to the contact position of the feedback arm 24 set by the position control lever 4, the lowering of the work implement is stopped at that position.

At this time, immediately before the target plowing depth set by the automatic plowing depth adjustment lever 5, the rear cover 20 of the working machine comes into contact with the upper surface of the field and rotates upward, and the pulling wire 21 shown in FIG.
The sensor arm 22 rotates toward the valve spool 9 ′ with the pulling in the direction D, and the automatic cultivation depth adjustment link 14 makes the valve spool 9 ′ with the automatic cultivation depth arm 18 as a fulcrum.
Of the valve spool 9 ′.
, The throttle spool 8 'moves in the retracting direction, the second sub oil passage 12b is closed by the inner ring 8c and the outer ring 8d, and the pressure oil returned from the lift cylinder 7 passes through the adjustment valve 8a. Only the first sub-oil passage 12a communicating with the main oil passage 12 through the passage, the return amount of the pressurized oil is reduced, the retracting operation of the lift cylinder 7 becomes slow, and the lift cylinder 7 is supported by the lift arm 3. The descending speed of the operated working machine is reduced from immediately before the target plowing depth to when reaching the target plowing depth.

Therefore, when the work is lowered to the cultivation depth position at the start of the work or after the turn at the field edge, when the work machine is lowered to the cultivation depth, the speed adjusted by the descent speed adjusting valve 10 is maintained until the target cultivation depth is reached. The working machine can be lowered quickly, and the working machine can be controlled to slow down from just before the target plowing depth to the target plowing depth. However, it is possible to prevent stalling and dashing phenomena caused by the quick grounding of the working machine, and to smoothly perform field work using the tractor.

[0021]

In summary, the present invention provides a link mechanism for operating a hydraulic control valve so that a working machine connected to a rear part of a machine body is held at a proper plowing position by vertically moving a rear cover provided on the working machine. A hydraulic control device for a tractor configured to connect a rear cover to a lifter and to raise and lower a work implement by a telescopic operation of a lift cylinder driven by hydraulic control of the hydraulic control valve, wherein a main oil from the lift cylinder to an oil pump is provided. A first sub-oil passage communicating with the main oil passage through an adjustment valve and a second sub-oil passage communicating with the main oil passage through a down-throttle valve operatively connected to a hydraulic control valve are respectively provided in the passage. Provided,
The hydraulic oil return path from the lift cylinder to the oil pump through both sub oil passages and the oil pump, and the hydraulic oil return path from the lift cylinder to the oil pump through only the first auxiliary oil passage are lowered by operating the hydraulic control valve. It is configured to be switchable, and to switch to a pressure oil return path that passes only through the first sub oil path, regardless of the operation of lowering the hydraulic control valve, when the upward movement of the rear cover is detected when the work machine is lowered. Therefore, while controlling the descent speed of the work equipment with the descent speed adjustment valve interposed in the hydraulic oil return path from the lift cylinder to the oil pump, unnecessary behavior such as hunting and dashing phenomenon Time required to reach the cultivation depth position can be shortened, and work efficiency can be improved. Easily descending speed can be switched,
Moreover, regardless of the lowering speed switching operation by the hydraulic control valve, the lowering speed can be automatically reduced immediately before reaching the predetermined plowing position in conjunction with the upward movement of the rear cover of the work implement, so that the plowing depth is automatically set. Even when the work machine is raised and lowered with the vertical movement of the rear cover, the work machine can be finely moved up and down more smoothly, and the field work can be performed smoothly. To play.

[Brief description of the drawings]

FIG. 1 is an overall side view of a tractor.

FIG. 2 is a partially omitted circuit diagram of a hydraulic control device.

FIG. 3 is a partial sectional plan view showing a structure of a hydraulic control device.

FIG. 4 is a perspective view of a main part of the hydraulic control device.

FIG. 5 is an operation explanatory view showing a switching state of the hydraulic control device when the work machine is raised.

FIG. 6 is an operation explanatory view showing a switching state of the hydraulic control device when the work machine is lowered.

FIG. 7 is an operation explanatory view showing a switching state of the hydraulic control device that closes the second sub-oil passage when the work machine is lowered.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tractor 2 Hydraulic control device 7 Lift cylinder 8 Down throttle valve 8a Adjustment valve 9 Hydraulic control valve 11 Oil pump 12 Main oil passage 12a First auxiliary oil passage 12b Second auxiliary oil passage 20 Rear cover

Claims (1)

(57) [Claims] 1. A rear cover is connected to a link mechanism for operating a hydraulic control valve so as to hold a working machine connected to a rear part of the machine body at an appropriate plowing position by vertically moving a rear cover provided on the working machine; and In a hydraulic control device for a tractor configured to raise and lower a working machine by extension and retraction of a lift cylinder driven by hydraulic control of the hydraulic control valve, an adjustment valve is provided in a main oil passage from the lift cylinder to an oil pump. A first sub-oil passage communicating with the main oil passage via a hydraulic control valve, and a second sub-oil passage communicating with the main oil passage via a down-throttle valve interlocked with the hydraulic control valve. A hydraulic oil return path through the oil passage to the oil pump;
The hydraulic oil return path to the oil pump through only the sub oil passage can be switched by the lowering operation of the hydraulic control valve. A hydraulic control device for a tractor, characterized in that it is configured to switch to a pressure oil return path that passes only through the first sub oil path regardless of a descending operation.