JPH0484803A - Controller for hydraulic lifting and lowering of tractor - Google Patents

Abstract

PURPOSE:To enable sure lifting of a working machine to the target position even if the amount of a hydraulic fluid is small by increasing the duty ratio of a control pulse signal when lifting arms are not lifted to the set height within the set time in controlling a hydraulic lifting and lowering mechanism with an ON.0FF type solenoid valve. CONSTITUTION:When a lifting command is issued from the side of a controller so as to lift lifting arms of a tractor, a pulse signal is sent to a solenoid 50 to carry out control (duty control) for changing an ON time of pulses according to a deviation. Thereby, the flow rate control can be performed according to the duty ratio. If a current is passed through a solenoid 60 also on the lowering side, the amount of the hydraulic fluid discharged from a hydraulic cylinder 6 can be controlled by changing the value of the current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic lifting control device for a tractor.

[Prior Art and its Problems] Traditionally, there has been a tractor in which a hydraulic lifting mechanism provided at the rear of the body of the tractor is controlled by an ON/OFF type electromagnetic valve.

Typically, these tractors.

A potentiometer for detecting the height above the ground is attached to the rotating base of the lift arm that makes up the hydraulic lifting mechanism, and a potentiometer is installed on the hydraulic operating lever side to detect the rotating position of the lift arm.
A potentiometer for setting the height above the ground is provided, and the duty ratio of the pulse signal that excites the solenoid of the electromagnetic valve is changed based on the difference between the set value and the detected value, or in other words, the deviation.

However, with this kind of duty control, when the engine speed is relatively low, such as when idling, and when the weight of the work equipment is heavy, it is difficult to perform duty control simply based on the deviation. There was a problem with the machine not lifting. The graph in FIG. 6 shows this situation. The horizontal axis shows time, and the vertical axis shows the position of the lift arm, but if you issue a lift command to the electromagnetic valve to raise the work equipment, it will normally reach t. The target position should be reached after t1 time (t n <t'+
), the target position was not reached even after 30 seconds, and as a result, the electromagnetic valve continued to not unload, resulting in an abnormally high temperature of the hydraulic oil.

[Means for Solving the Problems] The present invention is proposed to eliminate the drawbacks mentioned above, and for this purpose, the following technical measures have been taken.

That is, the first invention turns on the hydraulic lifting mechanism of the tractor.
・For those controlled by OFF type electromagnetic valves, if the lift arm of the tractor does not reach the set height within the set time after lift output is output, the duty ratio of the control pulse signal is configured to increase. It is something.

Moreover, the second invention turns on the hydraulic lifting mechanism of the tractor.
-OF For those controlled by F-type electromagnetic valves,
If the lift arm of the tractor does not reach the set height within a set time after the lifting output is output, the lifting output is stopped after a certain period of time.

[This invention will be described in detail based on the following examples and drawings. First, to explain the configuration, reference numeral 1 is a tractor, which is equipped with front wheels 2.2 and rear wheels 3.3 at the front and rear of the machine body, respectively, and a hydraulic cylinder case 5 fixed to the rear upper part of a transmission case 4. There is. A single-acting hydraulic cylinder 6 is provided in the hydraulic cylinder case 5, and lift arms 7.7 are rotatably pivoted on both left and right sides of the hydraulic cylinder case 5. Here, the hydraulic cylinder 6, lift arms 7, 7, etc. are collectively referred to as a hydraulic lifting mechanism 8, and hydraulic oil is supplied and discharged into the hydraulic cylinder 6 by appropriately switching a control valve to be described later.

The lift arm 7.7 rotates in the near direction.

In addition, 3 links consisting of a top link 10 and a lower link 11
A rotary tiller 14 is connected to the rear end of the point linkage mechanism 12 as a ground work machine so as to be able to rise and fall freely, and a lift rod 15.15 is interposed between the lift arm 7.7 and the lower link 11°11. The equipment is connected.

Reference numeral 20 denotes a hydraulic control lever for position control 1-roll, and a rotary base of this hydraulic control lever 20 has a potentiometer for setting the height above the ground of the rotary tilling device 14 connected to the rear of the tractor 1. A ground height setting device 21 is attached. On the other hand, a ground height detector 23 is attached to the base of the one-sided lift arm 7 to detect its rotation angle, that is, the height of the ground work equipment.
The lift arm 7.7 is configured to rotate to a position set by the hydraulic operating lever 20 and stop at the set position.

Further, the rotary tilling device 14 connected to the rear part of the tractor 1 includes a tilling section 34, a main cover 35 that covers the upper part of the tilling section 34, a palm bar 36 etc. which is pivotally attached to the rear part of the main cover 35, and a rear cover. The lower end of the main cover 36 is configured to slide against the ground and apply elastic pressure to level the tilled soil surface, and the upper rear end of the main cover 35 has a plowing depth for detecting the rotation angle of the plow cover 36. A detector 37 is provided. A plowing depth setting device 40 for setting the plowing depth is provided near the driver's seat of the tractor 1.

FIG. 2 is a block diagram showing the control system. To explain this block diagram, there is a ground height setting device 21 that sets the height of the rotary tillage device 14, and a tilling depth setting device 4 that sets the tilling depth.
0, the ground height detector 23, and the plowing depth detector 37 are A/
It is connected via a D converter 25 to a control device 27 consisting of a CPU.

On the output side of the control device 27, a lift arm 7.
A rising electromagnetic valve 46 and a descending electromagnetic valve 47 are connected to each other. The electromagnetic valves for both raising and lowering are poppet-type control valves, which are incorporated into the hydraulic circuit shown in FIG. 3 to operate the hydraulic lifting mechanism 8 described above.

More specifically, the ascending electromagnetic valve 46 includes a first on-off valve 51 and a poppet 52, which are controlled to open and close by energizing a solenoid 50.
Due to the spring 53 provided in the back chamber, its end surface is connected to the seat surface 5.
It is configured so that it can be pressed against 4. First on-off valve 5
1 is in this position, the hydraulic oil sent from the hydraulic pump 55 first enters the back chamber of the poppet 52, but since the back chamber and the tank 56 are in communication, the spring 53
The valve seat is pushed up by overcoming the pressing force of , and all of the hydraulic oil flows into the tank T1 and is unloaded.

When a lifting command is issued from the control device 27 to raise the working machine, a pulse signal is sent to the solenoid 50.
A so-called duty control, which is a control that changes the ON time of the pulse according to the deviation, is performed. As a result, it becomes possible to control the flow rate according to the duty ratio.

The descending side has substantially the same configuration, and the descending electromagnetic valve 47 consists of a second on-off valve 58 and a poppet 59, and by changing the current value energized to the solenoid 60 of the second on-off valve 58, The amount of hydraulic fluid discharged can be controlled.

In the figure, 62 is an operating pressure oil supply oil passage, 63 is a check valve installed in this oil passage, 64 and 65 are relief valves, and 66 is a slow return valve that adjusts the descending speed.

Next, the contents of the control program will be explained based on the flowchart shown in FIG.

First, the height above the ground set by the hydraulic operating lever 20 and the detected value from the height above the ground detector 23 attached to the lift arm 7 are read (step S1), and the deviation between these values is calculated ( Step S2). Then, the ON time per cycle of the pulse signal is determined based on the deviation (step S3), and if the deviation is zero, the output is turned OFF (step 513), and immediately after there is a rising output request, the request is generated. A timer is started (steps S5 and S6). The set time of this timer is the maximum time that one working machine is considered to reach the target height when the engine is idling (time t in Fig. 6), and after reaching the specified time, α This duty control is repeated until the deviation is zero, that is, 221 toral (step S9).

Note that duty control is also performed for the F descending side output command based on the deviation, but in this case there is no need to correct the ON time, the above-mentioned timer is reset, and the correction value is also reset at the same time. Yes (step S12.81
4.515).

The curve of graph C in FIG. 6 shows the characteristics when this control is used.

In the previous example, if the lift arm 7 does not reach the predetermined position within the set time after the lift command is issued, the pulse signal is turned ON.
However, the flowchart in Figure 5 shows that when the lift arm 7 does not reach the predetermined position within the set time and a certain period of time has passed in this state, the lifting output is cut off. This is what I tried to do.

In this case, the position where the lift arm 7 is stopped is
Store it as the target height and reset the climb command.

In this way, instead of correcting the ON time of the pulse and lifting the lift arm 7 to a predetermined height, the lift command is stopped at a position where the lift arm 7 is stopped. When this is adopted, the solenoid 50 is not energized, which improves the durability of the solenoid valve, and the temperature of the hydraulic fluid itself does not rise, so the hydraulic equipment does not move abnormally. , accuracy can also be improved.

Although the control explained above is the one in which the first invention and the second invention are carried out independently, the control in which the first invention and the second invention are combined may be carried out at the same time1, for example, when the ascending command is If the lift arm 7 does not reach the predetermined target position within the set time after being released, first turn on the pulse signal.
The time may be increased at a predetermined rate, and the ascending command may be cut only when the predetermined position is still not reached.

In addition, in the case of the second invention described above, there is a deviation between the lift arm setting position and the actual lift arm position, but within this range, the CPU again issues a lift command to the lift solenoid valve. If this occurs, the output will be repeated without any force, which may cause problems with the durability of the electromagnetic valve. In order to avoid such inconvenience, when the lift arm is stopped before the set position for raising, and there is a deviation between the actual position of the lift arm and the set position, , between [upper J
``It is desirable to set up a control program to stop the output of the lower J.

[Effects of the Invention] Since the present invention is configured as described above, it has the following technical effects.

That is, as in the first invention, the hydraulic lifting mechanism of the tractor is set to 0.
In those controlled by N-OF''F type electromagnetic valves,
The structure is configured to increase the duty ratio of the control pulse signal if the lift arm of the 1-rafter does not reach the set height within the set time after the lift output is issued.
Even when the amount of hydraulic oil sent from the hydraulic pump is small, such as when idling, the work equipment can be reliably raised to the target position. This eliminates the problem of the oil temperature rising above 200 lbs.

Further, as in the second invention, the hydraulic lifting mechanism of the tractor can be adjusted to zero.
For those controlled by N-OFF type electromagnetic valves, if the lift arm of the tractor does not reach the set height within the set time after lift output is output, it is configured to stop the lift output after a certain period of time. As a result, the lift arm will be stopped before the target position, and the lift output will be cut off at this point, so there will be no problem such as continuous current flowing through the solenoid of the electromagnetic valve.
The electromagnetic valve has a feature of improved durability compared to conventional devices.

[Brief explanation of the drawing]

1 is an overall side view, FIG. 2 is a block diagram, FIG. 3 is a hydraulic circuit diagram, FIGS. 4 and 5 are flow charts, and FIG. 6 is a graph showing hydraulic flow characteristics. Explanation of symbols 1 Tractor 50, 60 52, 59 Lift 1-arm hydraulic lifting mechanism ground work equipment (rotary tillage system: t) Ground texture setting device Ground texture detector Tilling depth detector Tilling depth setting device Solenoid valve for raising Solenoid valve for lowering Solenoid poppet 1st on-off valve 2nd on-off valve

Claims (1)

[Scope of Claims] 1) In a tractor whose hydraulic lifting mechanism is controlled by an ON/OFF type electromagnetic valve, a lifting output is output,
A hydraulic lift control device for a tractor, characterized in that the tractor lift arm is configured to increase the duty ratio of a control pulse signal when the lift arm of the tractor does not reach a set height within a set time. 2) In a tractor whose hydraulic lifting mechanism is controlled by an ON/OFF type electromagnetic valve, the lifting output is output,
A hydraulic lift control device for a tractor, characterized in that, if the lift arm of the tractor does not reach a set height within a set time, the lifting output is stopped after a certain period of time.