JPH07114568B2 - Hydraulic lifting control device for ground work machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a controller for a proportional flow rate control valve, which is mainly used in a hydraulic lifting control device for lifting and lowering a ground work machine connected to a tractor or the like. is there.

[Prior art and its problem] Conventionally, when a ground work machine connected to a tractor is vertically moved, a pulse signal is sent to the drive unit of each proportional flow control valve for raising and lowering to change the ON time of the pulse signal ( Although the PWM control) was used to control the flow rate, the temperature of the solenoid coil of the flow control valve also rises due to the rise of the oil temperature in the tractor's mission case, and this temperature rise causes the inside of the solenoid coil to rise. There is a problem in that the resistance increases, and as a result, the output current with respect to the ON time decreases and the required flow rate cannot be secured.

[Means for Solving the Problem] The present invention is proposed in view of the above-mentioned problems, and provides a hydraulic lifting control device for a ground work machine capable of always securing a target flow rate and improving the work system. The following technical measures were taken for this purpose.

That is, in the hydraulic lifting control device for a ground work machine equipped with the proportional flow rate control valve 31 for rising and the proportional flow rate control valve 32 for lowering, the pulse current value flowing in the solenoid of each proportional flow rate control valve 31, 32 is detected and set. A / D to convert digital signal to digital signal
A conversion unit 40 and a control unit that performs digital processing based on the signal from the A / D conversion unit 40 and adjusts the pulse width of the pulse current so as to maintain the current value supplied to the solenoid at a predetermined value. The hydraulic lift control device for a ground work machine is provided with 30.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

First, the configuration will be described. 1 is a tractor equipped with an engine 2 at the front of the machine body, the rotational power of the engine 2 is appropriately reduced by a transmission in a mission case 3 behind the engine 2, and the power is transmitted to the front wheels 4, 4 and It is transmitted to the rear wheels 5, 5. A hydraulic cylinder case 6 is mounted on the upper rear part of the transmission case 3 in the rear part of the machine body, and lift arms 8, 8 are rotatably pivoted on both left and right sides of the case 6. Reference numeral 10 is a rotary tiller, which is movably connected to the tractor 1 via a three-point link mechanism including a top link 11, lower links 12, 12.

The rotary tiller 10 comprises a tiller 14, a main cover 15 that covers the tiller 14, a rear cover 16 that is pivotally attached to the rear end of the main cover 15, and the lower edge of the rear cover 16 is on the ground. Perform plowing work while making sliding contact.

FIG. 2 is a block diagram of a control device for hydraulically controlling the rotary tiller 10, and the details will be described based on this block diagram.

Ground height setting device 19 mounted on the rotation base of the hydraulic operation lever 18 of the tractor 1, plowing depth setting device 20 for setting the working depth of the rotary tiller 10, and mounting on the rotation base of the one-side lift arm 8. Height detector 25, rotary tiller 10
The cultivation depth detectors 26, which are attached to the rear end of the main cover 15 and detect the depth of cultivation of the rotary tiller 10 by detecting the rotation angle of the rear cover 16, are respectively connected via the A / D converter 27. Is connected to a control unit 30 composed of a CPU, and an ascending proportional flow rate control valve 31 and a descending proportional flow rate control valve 32 that constitute a hydraulic lift control device are connected to the output side of the control unit 30. The proportional flow rate control valves 31 and 32 change the flow opening area of the pressure oil provided on the spool in proportion to the value of the current supplied to the solenoids of the respective control valves 31 and 32. Is output from the control unit 30, and a pulse current having a pulse width proportional to the current value is supplied to each solenoid.

Reference numerals 35 and 36 denote current detectors interposed between the CPU and the flow rate control valves 31 and 32, and detect current values flowing in the solenoids of the proportional flow rate control valves 31 and 32. Reference numeral 40 is an A / D converter that converts the current value detected by the current detectors 35 and 36 into a digital signal. A determination unit that estimates the oil temperature from the detected current value is provided in the control unit 30.

Further, reference numeral 37 is a switch for forcibly raising and lowering which is directly connected to the control unit 30. By turning this switch 37 on and off, the rotary tiller 10 connected to the tractor 1 is forcibly moved up and down. Can be made.

Next, the operation of this embodiment will be described based on the flow chart shown in FIG. The procedure shown in this control flow is such that the control program is stored in the memory of the control unit 30.

Taking depth control (cultivation depth control) as an example, during working, the working depth setting device 20 sets the working depth, and the working depth detector 26 detects the working depth and always sets it. Control is performed such that the tilling part 14 of the rotary tiller 10 is located at the depth thus set. When the proportional flow control valves 31 and 32 are operating, the current flowing through the solenoid of the control valve 31 (or 32) is detected by the current detector 35 (or 36), and the control unit
The temperature of the hydraulic oil is estimated by the oil temperature determination unit in the CPU from the ON time of the pulse signal for driving the control valve sent from 30 and the detected current (step).

When there is a difference between the set value and the detected value of the working depth, the output request command is issued (step), and when the working depth is too deep, and the rising command is issued to make it shallow, the target is calculated from the deviation. The flow rate is calculated, and at the same time, the temperature characteristics of the proportional flow control valve for rising 31 are corrected from the estimated temperature, and the proportional flow control valve
The target current value to be supplied to 31 is determined (step).

Then, the ON time of the pulse signal for obtaining the target flow rate is set by adding the resistance change amount of the flow control valve 31 and the change of the temperature characteristic (step), and the current is applied to the solenoid of the proportional flow control valve 31 for rising. (Step).

For the output on the falling side, the same comparison operation as the above-mentioned operation is performed (step), and after the target current value is determined, the ON time is set and the current is supplied to the proportional flow control valve for descending 32. It is what is done.

FIG. 4 (a) shows the waveform of the pulse signal, and FIG. 4 (b) and FIG. 4 (c) respectively show the current flowing through the proportional flow control valve and the detected current value. The dotted line in the figure shows how the current decreases due to the influence of the increase in oil temperature.

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

That is, the temperature of the solenoid of the proportional flow control valves 31, 32 rises due to the rise of the temperature of the hydraulic oil in the mission case, and as a result, the internal resistance of the solenoid increases and the current value flowing in the solenoid increases. However, in the present invention, the current detection means is not provided.
Since the signals from 35 and 36 are fed back to the control unit 30 via the A / D converter 40, it is possible to easily perform an operation based on the fed back signal and obtain a current value of a desired value. In addition, it is possible to perform up-and-down control of the ground work machine with high accuracy because it is less affected by the temperature rise of the hydraulic oil.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is an overall side view, FIG. 2 is a block diagram, FIG. 3 is a flow chart, FIG. 4A is a pulse signal waveform, and B is a control valve. The flowing current and C are detected currents. Explanation of code 1 …… Tractor 2 …… Engine 3 …… Mission case 19 …… Ground height setting device 20 …… Grounding depth setting device 25 …… Ground height detector 26 …… Grounding depth detector 30 …… Control Part 31 …… Proportional flow control valve for raising 32 …… Proportional flow control valve for lowering

Claims (1)

[Claims] 1. A hydraulic current elevating / lowering control device for a ground work machine equipped with a proportional flow rate control valve for rising 31 and a proportional flow rate control valve for lowering 32 detects a pulse current value flowing in a solenoid of each proportional flow rate control valve 31, 32. Then convert this to a digital signal
A / D conversion means 40, and performs digital processing based on the signal from this A / D conversion means 40, and adjusts the pulse width of the pulse current so as to maintain the current value supplied to the solenoid at a predetermined value. A hydraulic lifting control device for a ground work machine, which is provided with a control unit 30 that operates.