JPH0446491Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a hydraulic control device for a tractor, and particularly relates to an improved draft control valve mechanism.

(Prior Art) A hydraulic control device for a tractor includes a hydraulic device for raising and lowering a working machine mounted on the tractor; a first control valve mechanism for switching the hydraulic device to raise, stop, and lower, respectively; a second control valve mechanism for controlling pressure on the piston of the hydraulic system in accordance with the traction resistance when traction resistance acts on the work equipment attached to the hydraulic system when the work equipment is lowered to the ground; This second control valve mechanism is provided in a side passage branched from the middle of the oil path from the first control valve mechanism to the hydraulic piston, as disclosed in Japanese Patent Publication No. 57-39601. .

The second control valve mechanism in this prior art is the tenth control valve mechanism.
It is configured as shown in the figure.

That is, 50 is a valve case, which has a pump port 51 and a tank port 52, into which a spool 53 for controlling the pressure of the pump port 51 is inserted, and the spool 53 can be pushed in against a spring 54.

Reference numeral 55 designates an operating lever, and a draft holding rod 57 is pivotally supported by a pin 56 eccentric to the lever axis, and the rod 57 is in contact with the head of the spool 53.

Reference numeral 58 denotes a link of a draft feedback link mechanism, which has a draft movable support pin 59, which is engaged with the holding rod 57.

(Problems to be solved by the invention) In the prior art, the engagement between the movable support pin 59 and the holding rod 57 is linear, and the pump port 51 cannot be closed by the spool 53 due to the amount of feedback operation, resulting in leakage. be.

That is, when the engine speed was low or the gravity of the work equipment was heavy, there were cases where leakage occurred and the pressure did not rise and the draft reaction did not occur.

For this reason, as shown in FIG.
The above-mentioned problem can be solved by providing an eccentricity of , but in this case, since the insertion holes of both shafts 55A and 58A are eccentric, it is difficult to obtain an accurate amount of eccentricity.

Therefore, the present invention solves the above-mentioned problems by only making slight improvements to the holding rod and the movable support pin.

(Means for Solving the Problems) The technical means taken by the present invention to achieve the above-mentioned object are characterized by: a hydraulic system for raising and lowering a working machine attached to a tractor; a first control valve mechanism for switching the device to raise, stop, and lower, respectively; a piston of the hydraulic device when traction resistance acts on the work device attached to the hydraulic device when it is lowered to the ground; a second control valve mechanism for controlling the pressure on the oil according to the traction resistance, and the second control valve mechanism is a side valve branched from the middle of the oil path from the first control valve mechanism to the hydraulic piston. In a hydraulic control device for a tractor installed on a road, the second control valve mechanism includes a spool 36 slidably inserted into a valve case 35 to control the pressure of the pump port 34A against a spring P; Lever shaft 3 of the operating lever 47 that operates the spool 36
8 is provided with a draft holding rod 40, and the holding rod 40 is equipped with a draft feed back link mechanism 42.
A movable support pin 41 for drafting is engaged with the diagonal portion 40 that slides the spool 36 in the direction of closing the pump port 34A.
It is at the point where A is formed.

(Embodiments and Operations) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 5, 1 is a tractor body, 2 is a front wheel, 3 is a rear wheel, and 4 is an engine. The engine 4 is mounted in front of the tractor body 1 and drives the rear wheels 3 via a transmission case 5.
Reference numeral 6 denotes a hydraulic cylinder body, which is mounted and fixed on the upper surface of the transmission case 5 in a closed manner, and is communicated with a hydraulic pump (not shown) through an oil passage. As shown in FIG. 1, a hydraulic piston 7 is slidably and oil-tightly fitted into the cylinder of the hydraulic cylinder main body 6, and the hydraulic piston 7 is rotatably connected to a hydraulic arm 9 via a rod 8. 10 is a hydraulic arm shaft which is pivotally supported by the hydraulic cylinder main body 6, and inside the hydraulic cylinder main body 6, the hydraulic arm 9 is fitted along with the hydraulic arm 9, and a lift arm 11 is pivoted on the outside. It is freely fixed. Reference numeral 12 denotes a control valve body, which is directly installed within the hydraulic cylinder body 6 and housed within the transmission case 5. Reference numeral 13 denotes a control valve, which is slidable within the valve body 12 and has a spring 14 interposed at one end, and the control valve body 12 and the control valve 13 constitute a first control valve mechanism for positioning. There is. 15
1 is a window stopper, which covers a window hole 16 formed in the hydraulic cylinder body 6. Reference numeral 17 denotes a control lever shaft, which penetrates the side wall of the hydraulic cylinder body 6 and is rotatably supported in parallel with the hydraulic arm shaft 10, and a control lever 18 shown in FIGS. 4 and 5 is fixed to the outer end. An eccentric pin 19 is provided at the inner end, that is, in parallel to the coaxial shaft 17 within the hydraulic cylinder body 6, and the lower part of the holding rod 20 is attached to the eccentric pin 19 to connect the control valve constituting the first control valve mechanism. It is brought into contact with one end of 13. Reference numeral 21 denotes an interlocking arm shaft, which is provided facing the control lever shaft 17 and concentrically protruding inward from the hydraulic cylinder main body 6.
2, and an interlocking rod 23 is pivotally connected to its lower end, and the other end of the rod 23 is pivotally connected to the hydraulic arm 9 via a stop 24, and the stop The rod 23 is screwed onto the interlocking arm 24, and when the rod 23 is rotated toward the axis, it can be screwed forward.
The relative position between the hydraulic arm 2 and the hydraulic arm 9 is variable. 2
A movable support pin 5 projects from the interlocking arm 22 and comes into contact with the holding rod 20.

In FIG. 1, 32 is a pump side oil passage;
Reference numeral 33 denotes a cylinder side oil passage, which is opened in each valve body 12 constituting the first control valve mechanism, and hydraulic oil pumped from the pump enters from the pump side oil passage 32 and flows into the valve body 12. The cylinder side oil passage 33 is controlled by the sliding of the valve 13.
It is possible to freely flow into the country. 34 is an oil passage for draft control, and a side passage is opened from the middle of the cylinder side oil passage 33, and the draft valve case 3
5 and can be freely communicated with. The case 35 has a pump port 34A and a tank port 37A. Reference numeral 36 denotes a draft spool, which is slidably supported in the axial direction within the draft valve case 35 by a spring P to allow hydraulic oil to flow freely into the discharge path 37, and in particular, the flow rate can be changed from zero to a set value. Draft valve case 3 that can be controlled within a range
5 and the draft spool 36 constitute a second control valve mechanism.

Note that the hydraulic oil discharged from the discharge path 37 is returned to the tank 48. Next, the second control valve mechanism including the draft valve case 35 and the draft spool 36 will be explained with reference to FIGS. An eccentric pin 39 for drafting is provided in a protruding manner so as to rotate together with the draft. Reference numeral 40 denotes a draft holding rod, which is rotatably fixed to the draft eccentric pin 39 and hangs down, so that it can come into contact with a draft movable support pin 41 that projects from the other side.

The support pin 41 and the holding rod 40 are engaged with each other, and the engaging portion has a diagonal portion 40 on the rod 40 side in this example.
A is formed.

A feedback crank 42 has one end connected to a load spring 43 and the other end connected to a feedback lever 44. Reference numeral 45 denotes a feedback lever shaft, which is rotatable by the feedback lever 44, and the movable support pin 41 also rotates together with the same shaft 45.

Next, the effects of the embodiments of the present invention will be explained.
First, in the state shown in FIG. 1, the hydraulic piston 7 is at the top dead center, that is, the lift arm 11 is at the lowest position, and from this state, the control lever shaft 17 is rotated in the direction of the arrow A through the control lever 18. When the control valve 1 is moved, the holding rod 20 moves the first control valve mechanism against the elastic force of the spring 14 while contacting the movable support pin 25.
3 in the direction of the arrow B, and press the hydraulic piston 7.
Forms an oil path that pushes down. The state at that time is shown in FIG. When the hydraulic piston 7 is pushed down, the hydraulic arm 9, the coaxial shaft 10, and the lift arm 11 are simultaneously rotated in the direction of the arrow C through the rod 8. The interlocking arm 22 is rotated in the direction of the arrow D, and the movable support pin 25 is separated from the holding rod 20, but the elastic force of the spring 14 causes the control valve 13 to rotate.
It is biased in the direction of symbol B', rotates the holding rod 20 in the circumferential direction, and finally automatically returns the control valve 13 to its original state, stopping the movement of the hydraulic piston 7. It is shown in FIG. Next, when attempting to raise the hydraulic piston 7, the operation is reversed to that described above, and by rotating the control lever shaft 17 in the counterclockwise direction shown by the arrow as shown in FIG. is biased by the spring 14 and the sign
It is pulled out in the direction of B′, and as a result,
The hydraulic pressure on the upper surface of the hydraulic piston 7 is released into the opened hydraulic circuit, and the hydraulic piston 7 rises due to the force of gravity hanging down from the lift arm 11 and stops at an appropriate position. The relative operating position of the control lever shaft 17 and the control valve 13 can be adjusted by the interlocking rod 23. Insert a screwdriver through the window hole 16 and press the interlocking rod 23.
All you have to do is screw it into engagement with the upper end.

What has been described above is the action of so-called position control. In this case, the draft lever 47 is placed in the "up" position in the U direction, and the draft spool 3 is moved by the draft holding rod 40.
6 is pressed, communication between the draft control oil passage 34 and the discharge passage 37 is cut off.
Next, the effect of the draft control will be explained. First, when the traction resistance exceeds a set value, the load spring 43 senses and deflects, and this displacement is controlled by the feedback link 42 and the feedback lever 44. The clever shaft 45 will be rotated, and at the same time the draft movable support pin 4 will be rotated.
1 position change. When applying draft control, the control lever 18 for position control should be raised.
In this state, hydraulic oil is sent to the cylinder side oil passage 33 to apply pressure to the piston 7. On the other hand, this cylinder side oil passage 33 is provided with a draft valve 36 whose side is taken out midway and constitutes a second control valve mechanism between the draft control oil passage 34 and the discharge passage 37 leading to the tank. . Therefore, the draft lever 47 is moved as indicated by the arrow D in FIG.
The draft spool 36 is positioned as shown in FIG. 1 in the direction shown in FIG. In this position, while lifting and towing a work machine such as a plow with the lift arm 11, etc.,
When the traction resistance exceeds a set value, the load spring 43 is deflected, and this deflection is fed back via the feedback link 42 in the direction opposite to the arrow S in FIG. Due to this feedback, the draft movable support pin 41 rotates clockwise in FIG. The hydraulic pressure acting on the piston 7 becomes large.
In this case, as a result, the lift arm 11 acts in the lifting direction, but during this lifting process, the weight acting on the rear wheel 3 of the tractor 1 due to the lifting reaction force of the work equipment is added to the lift arm 11. , the traction force of the rear wheels 3 increases. Therefore, when the amount of restriction of the spool 36 becomes large and the pressure acting on the piston 7 becomes large, the lift arm 1
1 rises, and when the work equipment is lifted and the traction resistance becomes small and returns to the set value, the feedback link 42 returns in the S direction in FIG. 2 by the load spring 43.
On the other hand, the draft spool 36 is returned to the direction of reducing the amount of throttling by the action of the spring P, the pressure acting on the hydraulic piston 7 is reduced, and the lift arm 11 is lowered again by the weight of the working machine. In addition, in this drafting work state, the hydraulic arm 9 swings,
Due to this rocking, the interlocking rod 23, which is a position feedback rod, follows and operates, and as shown in FIG. 6, the position valve 13
7 from the state of switching to the upward direction
As shown in the figure, since feedback is provided only before the valve 13 is stopped or placed in the neutral position, the interlocking rod 23 controls the valve 13 constituting the first control valve mechanism during the drafting operation.
It is clear that this is not intended to provide any feedback. Therefore, in the case of draft control, the pressure acting on the hydraulic piston 7 is controlled by the amount of restriction of the draft spool 36. Furthermore, when the draft lever 47 is in the "lower" position, that is, fully tilted in the direction of symbol D in FIG. Since the lift arm 11 moves and does not produce any throttling effect, even if the load spring 43 of the sensing mechanism is operated to its maximum displacement, the lift arm 11 does not rise and remains in a floating state. As mentioned above, move the draft lever 47 to the "up" position, that is, to the second position.
If the lift arm 11 is tilted in the direction of symbol U in the figure and the communication between the draft control oil passage 34 and the discharge passage 37 is completely cut off, the lift arm 11 can be raised freely regardless of the displacement of the load spring 43, and the position control can be performed. It is what is done.

(Effect of the invention) The present invention has a configuration in which a side passage is formed in the middle of the oil path from the first control valve mechanism for position to the hydraulic piston, and the second control valve mechanism for draft is provided in this side passage. The draft control is based on the degree of throttling of the valve constituting the second control valve mechanism, that is, the engagement part between the draft movable support pin and the draft restraining rod in the case where the draft action is performed by controlling the pressure on the hydraulic piston. Since the diagonal section is provided in the shaft, even when the engine speed is low or the weight of the work equipment is heavy, there is no oil pressure leakage and draft action can be performed.

In other words, the pump port can be closed just before the operating lever is raised (within the draft range), which allows the pump port to be closed regardless of the engine speed range (flow rate) while still taking advantage of the advantages of the pressure-sensitive type. Draft can react regardless.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main parts according to an embodiment of the present invention, Fig. 2 is a detailed sectional view of the draft (second control valve mechanism), Fig. 3 is a vertical sectional plan view thereof, and Fig. 4 is Fig. 1.
- 4-line sectional view, Figure 5 is a side view of the tractor, Figure 6 is a side view of the tractor.
8 is a sectional view of the operating state, FIG. 9 is a vertical sectional plan view of a comparative example, and FIG. 10 is a sectional view of a conventional example. 35... Valve case, 36... Spool, 4
0... Holding rod, 41... Movable support pin, 40A...
...oblique part.

Claims (1)

[Claims for Utility Model Registration] A hydraulic system for raising and lowering a working machine mounted on a tractor; a first control valve mechanism for switching the hydraulic system to raise, stop, and lower, respectively;
a second control valve mechanism for controlling pressure on a piston of the hydraulic system in accordance with traction resistance when traction resistance acts on the work machine attached to the hydraulic system when the work machine is lowered to the ground;
In the hydraulic control device for a tractor, the second control valve mechanism is installed in a side road branching from the middle of the oil path from the first control valve mechanism to the hydraulic piston. A spool 36 that controls the pressure of the pump port 34A against a spring P is slidably inserted into the valve case 35, and a lever shaft 3 of an operating lever 47 that operates the spool 36 is inserted into the valve case 35.
8 is provided with a draft holding rod 40, and the holding rod 40 is equipped with a draft feed back link mechanism 42.
A movable support pin 41 for drafting is engaged with the diagonal portion 40 that slides the spool 36 in the direction of closing the pump port 34A.
A hydraulic control device for a tractor, characterized in that A is formed.