JPS6140361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control system for a tractor that exhibits excellent adaptability to changes in traction resistance.

As is well known, some tractors have conventionally been equipped with control mechanisms for position control and draft control. Position control is for keeping the lifting position of the work equipment constant in order to maintain a constant plowing depth despite various soil properties, while draft control is for keeping the traction force constant and flattening when the soil quality is the same. The plowing depth is kept constant even on uncultivated land, and the traction resistance is kept constant even when there is an uneven pre-tilling ridge or uneven ground, so the traction force of the tractor is always sufficient and the work equipment can quickly remove obstacles such as blocks of stone. It has the characteristic that it can jump over time and not cause troubles such as engine stop. However, this advantage of draft control can actually become a drawback when highly precise agricultural work is required. In some areas, uncultivated land is left uncultivated by tractors, and in extreme cases, this results in a washboard-like wavy pattern that impedes crop growth. The cause of this is due to the structure of the control valve for lifting the work equipment. To explain this with reference to FIG. 9, 12 is the valve body, 13 is the control valve, and this valve 13 has a spool 3
1 is engraved. Further, Q is an unload valve, and J is a check valve. 32 is a passage on the inlet side of the hydraulic oil, and 33 is a passage on the hydraulic oil outlet side, and when the hydraulic oil is pumped from a hydraulic pump (not shown) to raise the lift arm, it is designated by a symbol.
The valve 13 is positioned so that pressurized oil enters the area indicated by _Q1 , closes the unload valve Q, and opens the check valve J to allow the oil to flow in the direction of the solid arrow. Also, when the engine is stopped or in neutral, the operating circuit of the unload valve Q is opened, and the oil in the _Q1 part escapes from the part indicated by symbol e, and the hydraulic oil flows as indicated by the dotted arrow. Also, when the lift arm descends, the valve 13 changes to the dotted line state and the unload valve Q opens, and the oil in part _Q1 escapes from e and the pressure oil from the pump flows as shown by the dotted arrow and reaches the tank.
On the other hand, the pressure oil in the cylinder flows in the direction indicated by symbol E and reaches the tank. That is, in the same figure,
In the edge part of the spool 31 surrounded by a circle,
When the lift arm is raised, oil is prevented from flowing through this part, while when the lift arm is stopped, the symbol e is circled and shown in the enlarged diagram.
Hydraulic oil escapes through the gap marked with 0.5mm. This gap of 0.5 mm corresponds to a swing angle of about 5 degrees when converted to the movement of the lift arm, and cannot be set unnecessarily large. Therefore, as long as such a valve is used in a tractor equipped with a draft control function, the response of the lift arm to the displacement of the load spring that senses the traction force is accompanied by a time delay, as shown by the dotted line in Fig. 10. The change was gradual, and it was difficult to achieve an ideal linear change. The nature of this gradual change means that when the tractor encounters particularly heavy soil, for example, the rear wheel load increases;
The traction drive torque of the rear wheels increases, making it easier for the tractor to escape. At the same time, the load on the work equipment is removed with a time delay due to the action of the draft control, which causes the tractor body to jump, resulting in a rough finish similar to that of a washboard.

The present invention has been made to solve such problems, and in a draft control device for a tractor, the operation is such that the response of the lift arm to the displacement of the load spring is linear as shown by the solid line in FIG. In addition, a draft control valve is installed in the side passage taken out from the oil passage for position control, making it easy to add draft control to position control. To provide a hydraulic control device in which a position function and a position and draft function can be selectively and easily used by separately providing a control valve and a draft control valve, and by separately providing an operating body for each control valve. It is something.

The illustrated embodiment will be described in detail below: 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. 7 is a hydraulic piston which allows a hydraulic arm 9 to rotate freely via a rod 8; 10 is a hydraulic arm shaft which is pivotally supported in the hydraulic cylinder main body 6, and within the main body 6, the hydraulic arm 9 A lift arm 11 is fixed to the outside so as to be able to swing freely. 12
is a control valve body, which is directly installed in the hydraulic cylinder body 6 and housed in 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. 1
Reference numeral 5 denotes a window plug, 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.A control lever 18 is fixed to the outer end, and the case is fixed to the inner end. 5, an eccentric pin 19 is provided in parallel with the coaxial shaft 17, and a holding rod 20 is pivotally supported and suspended from the eccentric pin 19, and the lower side of the holding rod 20 is brought into contact with one end of the control valve 13. ing. 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, on which the interlocking arm 22 is pivotally supported, and at the lower end thereof. The interlocking rod 23 is pivotally connected, and the other end of the rod 23 is pivotally connected to the hydraulic arm 9 via a stop 24.
On the other hand, the rod 23 is screwed on, and when the rod 23 is rotated toward the axis, it can be screwed forward, thus connecting the interlocking arm 22 and the hydraulic arm 9.
The relative position with respect to is variable. Reference numeral 25 denotes a movable support pin that protrudes from the interlocking arm 22 and is connected to the holding rod 20.
It corresponds to

32 is a pump-side oil passage, and 33 is a cylinder-side oil passage, each of which is opened in the hydraulic cylinder body 12, in which hydraulic oil enters from the pump-side oil passage 32 and is controlled within the valve body 12. The oil can freely flow into the cylinder side oil passage 33. Reference numeral 34 denotes a draft control oil passage, and a side passage is opened in the middle of the cylinder side oil passage 33 so that it can freely communicate with the draft valve body 35. Reference numeral 36 denotes a draft valve, which is slidably supported in the axial direction within the draft valve body 36 to allow hydraulic oil to flow freely into the discharge path 37, and in particular can control the amount of flow within a range from zero to a set value. It is. Same discharge path 3
The hydraulic oil discharged from 7 is recycled to tank 48. Next, the peripheral members of the draft valve body 35 will be explained with reference to FIGS. 7 and 8.
7 is a draft lever, and the draft lever shaft 3
8, and an eccentric pin 39 for drafting is protruded from the other end so as to rotate with the draft. Reference numeral 40 denotes a draft holding rod, which is rotatably supported by 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. A feedback link 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.

According to the configuration according to the embodiment of the present invention, first, the second
In the state shown in the figure, the hydraulic piston 7 is at the top dead center, that is, the lift arm 11 is at the lowest position. From this state, when the control lever shaft 17 is rotated in the direction of the arrow A through the control lever 18, , the movable support pin 25 is accompanied by the holding rod 20.
The control valve 13 is pushed in the direction of the arrow B against the elastic force of the spring 14 while in contact with the hydraulic piston 7, thereby forming an oil passage so as to push down the hydraulic piston 7. 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 rotates in the direction of the arrow D, and the movable support pin 25 separates from the holding rod 20, but the elastic force of the spring 14 causes the control valve 13 to move in the direction B'. assisted,
The holding rod 20 is also rotated in the same direction, and the control valve 13 is finally automatically returned to its original state, thereby stopping the movement of the hydraulic piston 7.
This state is shown in FIG. Next, when trying to raise the hydraulic piston 7, the operation is opposite to that described above, so by rotating the control lever shaft 17 in the direction of symbol A' as shown in FIG. 14 and is pulled out in the direction of symbol B',
As a result, the hydraulic pressure on the upper surface of the hydraulic piston 7 is released into the opened hydraulic circuit, and the lift arm 1
The hydraulic piston 7 rises due to the gravity applied to the piston 1 and stops at an appropriate position. Furthermore, the control lever shaft 17 and the control valve 1
3 can be freely adjusted by the interlocking rod 23, and a screwdriver can be inserted through the window hole 16 and screwed into engagement with the upper end of the interlocking rod 23.

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 direction of symbol U shown in FIG. is pressed to block communication between the draft control oil passage 34 and the discharge passage 37. Next, the action of the draft control will be explained. First, when the traction resistance exceeds the set value, the load spring 43 senses and deflects, and this displacement is used to control the feed by the feedback link 42 and the feedback lever 44. The back lever shaft 45 is rotated, and at the same time, the position of the draft movable support pin 41 is changed. When the draft control is to be applied, the control lever 18 for position control is placed in the "up" state, and hydraulic oil is sent to the cylinder side oil passage 33 to apply pressure to the piston 7. On the other hand, a side passage is taken out in the middle of this cylinder side oil passage 33, and a draft valve 36 is provided between the draft control oil passage 34 and a discharge passage 37 communicating with the tank. Therefore, the draft lever 47 is moved in the direction of arrow D in FIG.
The draft valve 36 is positioned as shown in the figure, and the pressure acting on the hydraulic piston 7 is maintained at a predetermined pressure by the throttling effect of this valve 36. In the process of towing a work machine such as a plow while suspending it with the lift arm 11 or the like in this position, if the traction resistance exceeds a set value, the load spring 43 is deflected, and this deflection is compensated for by the feedback link 42. The signal is fed back in the direction opposite to the arrow S in FIG. Due to this feedback, the draft movable support pin 41 rotates clockwise in FIG.
6 moves against the spring P, the amount of restriction of the draft valve 36 increases, and the hydraulic pressure acting on the piston 7 increases. At this time, 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. When the throttle amount of the valve 36 becomes large and the pressure acting on the piston 7 becomes large, the lift arm 11 rises and lifts the work equipment, where the traction resistance becomes small and returns to the set value. The feedback link 42 returns in the S direction in FIG. As the weight of the work machine decreases, the lift arm 11 is lowered again by the weight of the working machine. Note that in this drafting work state, the hydraulic arm 9 swings, and this swing causes the interlocking rod 23, which is a position feedback rod, to swing.
is operated accordingly, but only between the state in which the position valve 13 is being switched to the upward direction as shown in FIG. 3 and before the valve 13 is stopped or placed in the neutral position as shown in FIG. It is clear that the interlocking rod 23 does not provide any feedback to the valve 13 during the drafting operation. Therefore, in the case of draft control, since the pressure acting on the hydraulic piston 7 is controlled by the amount of restriction of the draft valve 36, the stepwise operation as shown in FIG. 10 is eliminated.
Ideal (solid line) control is possible. If the draft lever 47 is moved to the "lower" position, that is, fully tilted in the direction of symbol D in FIG. The load spring 4 of the sensing mechanism moves and does not cause any throttling effect.
3 reaches the maximum operating displacement, the lift arm 11 does not rise and remains in a floating state. As mentioned before, if the draft lever 47 is moved to the "up" position, immediately in the direction of symbol U in FIG. 7, and the communication between the draft control oil passage 34 and the discharge passage 37 is completely cut off, Regardless of the displacement of the load spring 43, the lift arm 11 can be raised freely and its position can be controlled.

In the present invention, a hydraulic cylinder main body containing a hydraulic piston of a hydraulic lifting device is provided by covering an opening of a tractor body, and a liquid supply oil path for the hydraulic piston is formed in the hydraulic cylinder main body, and pressure oil from a hydraulic pump is provided. a hydraulic lifting device for a work machine is configured to operate, and a position control valve is provided in the liquid sending oil path and within the hydraulic cylinder body;
A side passage leading to the tank is formed in the hydraulic cylinder body in the middle of the liquid sending oil passage that communicates this valve and the hydraulic piston, and a draft valve is provided in this side passage and on the outer wall of the hydraulic cylinder body, and a draft valve is provided separately and independently. Operating bodies for each of the valves provided in the construction are provided independently, and a traction force sensing member of the working machine and the draft valve are interlocked by a feedback means, and the draft valve is configured to respond to the displacement of the traction force sensing member. Since the present invention relates to a hydraulic control device for a tractor that is characterized in that it controls the pressure acting on a hydraulic piston in response, it has the following advantages.

Since the draft control valve is installed in a side passage in the middle of the liquid supply oil path that communicates the position control and the hydraulic piston, the draft control function can be performed by pressure control in the same way as the position control function. Since the draft control valve is installed on the outer wall of the hydraulic cylinder body, there is no need for any complicated linkage mechanism as in the past, and the draft control function can be performed sensitively and reliably.

Furthermore, since the position valve and the draft valve are provided separately and independently, and the operating bodies for operating each valve are provided independently, the position control function and the draft control function can be selectively performed. In addition, the draft valve is installed in the side road leading to the tank that communicates with the position valve and the hydraulic piston's liquid supply oil path, making it easy to lift and move the work equipment such as when driving on the road. This can be done by shutting off the liquid supply circuit with a draft valve, which has the advantage of reducing the risk of increasing the temperature of the hydraulic oil, thus reducing the risk of uncertain operation and early deterioration of the hydraulic oil. There is.

In addition, a side passage communicating with the tank is formed in the oil passage leading to the position valve and the hydraulic piston, and a draft valve is installed in this side passage, so draft control can be easily applied to the hydraulic lifting device with position control. You can add additional equipment, and in this case,
Since the draft control valve is provided on the outer wall of the hydraulic cylinder body, there is an advantage that not only can additional equipment be easily installed, but also maintenance of the draft valve can be carried out without disassembling the hydraulic cylinder body.

[Brief explanation of the drawing]

Fig. 1 is an overall outline drawing according to an embodiment of the present invention;
The figure is a sectional view of the main part of Figure 1, and Figures 3, 4, and 5.
This figure is an explanatory diagram of the operation of the position control shown in FIG. 2, and FIG. 6 is an elevational sectional view of FIG. 3. FIG. 7 is an explanatory diagram of the operation of the draft control shown in FIG. 2, and FIG. 8 is an elevational sectional view of FIG. 7. FIG. 9 is an explanatory diagram of the structure of the control valve,
FIG. 10 is a graph showing the correlation between the load spring and the lift arm. 6... Hydraulic cylinder body, 13... Position control valve, 33... Cylinder side oil path,
34...Draft control oil path, 36...
Draft valve, 43...load spring.

Claims (1)

[Claims] 1. A hydraulic cylinder main body 6 containing a hydraulic piston 7 of a hydraulic lifting device is provided by covering an opening of the tractor body 5, and liquid supply oil passages 32 and 33 for the hydraulic piston 7 are formed in the hydraulic cylinder main body 6. The hydraulic lifting device for the working machine is operated by pressure oil from the hydraulic pump, and the liquid sending oil passages 32, 3
A position valve 12 is provided in the hydraulic cylinder body 6 in the hydraulic cylinder body 6, and side passages 34 and 37 connected to the tank 48 are provided in the middle of the liquid sending oil passage 33 that communicates the valve 12 with the hydraulic piston 7. 6, a draft valve 35 is provided in the side passages 34, 37 and on the outer wall of the hydraulic cylinder main body 6, and operating bodies 18, 47 of the separately provided valves 12, 35 are provided independently, respectively. Further, the traction force sensing member 43 of the working machine and the draft valve 35 are provided in conjunction with each other by feedback means 42 and 44, and the draft valve 35 detects the pressure acting on the hydraulic piston 7 in response to the displacement of the traction force sensing member 43. A hydraulic control device for a tractor characterized by controlling.