JP2985251B2 - Hydraulic lifting control of tractor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic lift control device for a tractor.

[Prior art and its problems] Conventionally, there is a type in which a hydraulic elevating mechanism provided at a rear portion of a tractor body is controlled by an ON / OFF type electromagnetic valve. Normally, such a tractor is equipped with a potentiometer for detecting the height of the ground at the turning base of the lift arm that constitutes the hydraulic lifting mechanism, and a grounding lever on the hydraulic operating lever side. A potentiometer for setting the height is provided to change the duty ratio of the pulse signal for exciting the solenoid of the electromagnetic valve based on the difference between the set value and the detected value, in other words, on the basis of the deviation.

However, in such a duty control, when the rotation speed of the engine is relatively low, such as at the time of idling, and when the weight of the work machine is heavy, the duty control based on the deviation may not be performed simply by performing the duty control. There was a problem that the machine did not lift. The graph in FIG.
This shows the situation. The horizontal axis is the time, and the vertical axis is the position of the lift arm, but when raising the work machine by issuing a lift command to the electromagnetic valve,
When it should reach the target position to the original if t ₀ hours later, for the weight of the working machine is heavy, even after a lapse of t ₃ hours (t ₀ <t ₃₎ does not reach the target position, and for this reason the electromagnetic valve does not unload Problems such as abnormally high temperature of the hydraulic oil due to the connection of the state occurred, and durability was difficult.

[Means for Solving the Problems] The present invention proposes to solve the above-mentioned drawbacks, and therefore has taken the following technical means.

That is, in the case where the hydraulic lift mechanism of the tractor is controlled by the energized output to the electromagnetic valve, when the electromagnetic valve outputs an ascending output and the lift arm of the tractor does not reach the set height within the set time, the It is configured to stop the rising output.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the structure will be described. Reference numeral 1 denotes a tractor, which is provided with front wheels 2, 2 and rear wheels 3, 3 at the front and rear portions of the fuselage, and a hydraulic cylinder case 5 is fixedly provided at the rear upper portion of the transmission case 4. I have. A single-acting hydraulic cylinder 6 is provided in the hydraulic cylinder case 5, and lift arms 7, 7 are pivotally mounted on both left and right sides of the hydraulic cylinder case 5. Here, the hydraulic cylinder 6, and the lift arms 7, 7 and the like are collectively referred to as a hydraulic elevating mechanism 8, but hydraulic oil is supplied and discharged into the hydraulic cylinder 6 by appropriately switching a control valve described later. The lift arms 7, 7 rotate vertically.

A rotary tilling device 14 as a ground working machine is connected to the rear end of a three-point link mechanism 12 including a top link 10 and a lower link 11 so as to be movable up and down.
Between the lower link 11, 11 and the lift rod 15, 15
Are interposed and connected.

20 is a hydraulic control lever for position control,
A ground height setting device 21 composed of a potentiometer for setting the ground height of the rotary tillage device 14 connected to the rear portion of the tractor 1 is attached to the turning base of the hydraulic operation lever 20. On the other hand, one-sided lift arm 7
A ground height detector 23 for detecting the rotation angle of the ground work machine, that is, the height of the ground work machine, is also attached to the base of the lift arm 7, and the lift arms 7, 7 rotate to the position set by the hydraulic operation lever 20. And stop at the set position.

The rotary tilling device 14 connected to the rear part of the tractor 1 includes a tilling portion 34 and a main cover 35 that covers the upper portion of the tilling portion 34.
And a rear cover 36 and the like pivotally attached to the rear of the main cover 35.The lower end of the rear cover 36 is slidably contacted with the ground to elastically press the cultivated soil surface so as to be level. At the upper rear end of the cover 35, a tillage depth detector 37 for detecting the rotation angle of the rear cover 36 is provided. The tillage depth setting device 40 for setting the tillage depth is provided near the cockpit of the tractor 1.

FIG. 2 is a block diagram showing a control system. Referring to this block diagram, a ground height setting device 21 for setting the height of the rotary tillage device 14, a tillage depth setting device 40 for setting the tillage depth, and Ground height detector 23 and tillage depth detector 37 are A / D converter 25
Is connected to the control device 27 composed of a CPU via the.

Then, on the output side of the control device 27, the lift arm 7,
An ascending electromagnetic valve 46 and a descending electromagnetic valve 47 for moving the actuator 7 up and down are connected. The solenoid valve for raising and lowering is a poppet type control valve, and is incorporated in a hydraulic circuit shown in FIG. 3 to operate the hydraulic lifting mechanism 8 described above.

More specifically, the ascending electromagnetic valve 46 is a solenoid.
First open / close valve 51 that is opened / closed by exciting 50
The poppet 52 is configured such that an end face thereof is pressed against a seat surface 54 by a spring 53 provided in the back room. When the first on-off valve 51 is at this position, the operating pressure oil sent from the hydraulic pump 55 is
First, it enters the back chamber of the poppet 52, but since the back chamber and the tank 56 are in communication, it overcomes the pressing force of the spring 53 and pushes up the valve seat, so that all the working pressure oil flows into the tank T1 and is released. Loaded.

Then, when a lift command is issued from the control device 27 side to raise the working machine, a pulse signal is given to the solenoid 50, and control for changing the ON time of the pulse according to the deviation, so-called duty control, is performed. As a result, the flow rate can be controlled in accordance with the duty ratio.

The descending side has almost the same configuration.
Consists of a second on-off valve 58 and a poppet 59, and the second on-off valve
The amount of hydraulic oil discharged from the hydraulic cylinder 6 can be controlled by changing the value of the current supplied to the solenoid 60 of 58.

In the drawing, reference numeral 62 denotes a hydraulic oil supply oil passage, 63 denotes a check valve interposed in the oil passage, 64 and 65 denote relief valves, and 66 denotes a slow return valve for adjusting a descending speed.

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

First, the ground height set value by the hydraulic operation lever 20 and the detection value of the ground height detector 23 attached to the lift arm 7 are read (step S1), and the deviation between these values is calculated (step S1). Step S2). Then, the ON time per cycle of the pulse signal is determined based on the deviation (step S3). If the deviation is zero, the output is turned off (step S13), and there is a rising output request, and immediately after the request is generated. , A timer is started (steps S5 and S6).
The set time of this timer is the maximum time during which the working machine is expected to reach the target height when the engine is idling (time t _{0 in} FIG. 6), and after reaching the specified time, α Only the ON time of the pulse is added (step S9), and this duty control is repeated until the deviation becomes zero, that is, a neutral state.

Note that duty control is also performed on the descending side output command based on the deviation, but in this case, correction of the ON time is not necessary, the timer is reset, and the correction value is reset at the same time. (Steps S12, S14,
S15).

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

In the above example, when the lift arm 7 does not reach the predetermined position within the set time after the rising command is issued, the pulse signal is turned on.
Although the time is increased, the flowchart of FIG. 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 elapsed in this state, the rising output is cut off. I was trying.

In this case, the position where the lift arm 7 is stopped is stored as a target height, and the ascending command is reset.

As described above, when the lift command is stopped at a position where the lift arm 7 is stopped, instead of lifting the lift arm 7 to a predetermined height by correcting the ON time of the pulse, a solenoid is used. No power is supplied to 50, so the durability of the electromagnetic valve is improved and the temperature of the hydraulic oil itself does not rise, so that hydraulic equipment does not move abnormally and accuracy can be improved. .

In the control described above, the control shown in FIG. 4 and the control shown in FIG. 5 are independently performed. However, a combination of these controls may be performed simultaneously, for example, after a rising command is issued. If the lift arm 7 does not reach the predetermined target position within the set time, first, the ON time of the pulse signal is increased at a predetermined rate, and if the lift arm 7 still does not reach the predetermined position, the rising command is cut off for the first time. Good.

In the case of the control shown in FIG. 5,
Although the lift arm's set position and the actual position of the lift arm are offset, if the CPU issues a lift command to the lift solenoid valve again within this range, useless output will be repeated. Therefore, there is a possibility that the durability of the electromagnetic valve may cause a problem. In order to avoid such inconvenience, when the lift arm is stopped just before the set position, and there is a deviation between the actual position of the lift arm and the set position, a It is desirable to configure a control program so as to stop the “up” and “down” outputs.

[Effects of the Invention] Since the present invention is configured as described above, the following technical effects can be obtained.

That is, in the case of controlling the hydraulic raising / lowering mechanism of the tractor by the energized output to the electromagnetic valve, when an elevating output is output to the electromagnetic valve and the wrist arm of the tractor does not reach the set height within the set time, the By configuring the ascending output to stop, the lift arm will be stopped before the target position, and at this point the ascending output will be cut, so there is also a problem that current continues to flow through the solenoid of the solenoid valve In addition, it has a feature that the durability of the electromagnetic valve is improved as compared with the conventional device.

[Brief description of the drawings]

1 is an overall side view, FIG. 2 is a block diagram, FIG. 3 is a hydraulic circuit diagram, FIGS. 4 and 5 are flowcharts, and FIG. 6 is a graph showing hydraulic flow characteristics. DESCRIPTION OF SYMBOLS 1... Tractor, 7... Lift arm, 8... Hydraulic lifting mechanism, 14... Ground work machine (rotary tillage device), 21.
… Ground height setting device, 23… ground height detector, 37… cultivation depth detector, 40… cultivation depth setting device, 46…
47… Lowering electromagnetic valve, 50, 60… Solenoid, 52, 59
... Poppet, 51 ... First open / close valve, 58 ... Second open / close valve

Claims (1)

(57) [Claims] An apparatus for controlling a hydraulic pressure raising / lowering mechanism of a tractor by a power output to an electromagnetic valve, wherein when a lifting output is output to the electromagnetic valve and the lift arm of the tractor does not reach a set height within a set time. Is a hydraulic lift control device for a tractor, wherein the lift output is stopped.