JPH03292806A - Hydraulic control device of working machine - Google Patents

Abstract

PURPOSE:To always maintain a suitable initial hydraulic operation by measuring an interval between the electric current-supplying time point of a control means and the driving starting time point of an article to be operated and subsequently adjusting an initial duty ratio just after the electric current supply starting time point with an initial duty ratio changing means in response to the measured values. CONSTITUTION:A hydraulic oil is supplied through an electromagnetic proportional control valve V into a hydraulic actuator 7 for driving an article to be operated. An electric current value supplied to the electromagnetic proportional control valve V is detected with a detection means, and the duty ratio of pulse currents to the electromagnetic proportional control valve V is changed by a control means on the basis of the detected value so that the supply of the hydraulic oil exhibits prescribed raising pressure characteristics. An interval between the electric current supply-starting time point from the control means and the driving-starting time point is measured with a measuring means and the initial duty ratio just after the electric current supply-starting time point by an initial duty ratio changing means in response to the measured value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hydraulic control device for a working machine such as an agricultural tractor, which is equipped with a hydraulic actuator such as a hydraulic cylinder for driving the working machine up and down. , configured to supply pressure oil to a hydraulic actuator that drives an operated object via an electromagnetic proportional control valve, and based on the detection result of a detection means that detects a supply current value to the electromagnetic proportional control valve, The present invention relates to a hydraulic control device for a working machine, including a control means for controlling the supply of pressure oil to the hydraulic actuator to have a predetermined pressure increasing characteristic by changing the duty ratio of the pulse current to the electromagnetic proportional control valve.

[Prior Art] In the above-mentioned hydraulic control device, there is a conventional hydraulic control device which was previously filed by the present applicant (Japanese Patent Application No. 1-28988). In other words, when the control means starts driving the hydraulic actuator, a predetermined pulse signal whose duty ratio is larger than the set duty ratio for obtaining the target opening degree is supplied at the time of the rise of the pulse current to the electromagnetic proportional control valve. It became.

[Problem to be solved by the invention]

In the conventional configuration described above, at the initial stage of driving the hydraulic actuator, it takes extra time to obtain the desired opening degree of the control valve due to the inertia of the spool in the control valve, the viscosity of the hydraulic oil, etc. This is to prevent wasted time.

However, in the above conventional structure, the initial duty ratio is set to give a uniformly constant duty ratio in consideration of the general characteristics of the control valve; Differences occur in the resistance value of the electromagnetic excitation coil due to fluctuations in the power supply or the temperature of the hydraulic fluid, and due to these factors, the wasted time at the start of driving as described above becomes unnecessarily long or shortened. If this happens too much, a driving shock may occur.

An object of the present invention is to eliminate the above-mentioned disadvantages.

[Means to solve the problem]

A characteristic configuration of the present invention is that, in the hydraulic control device for a work machine described at the beginning, a measuring means for measuring the time from the start of current supply from the control means to the time when the operated object starts to be driven; is longer than a predetermined time, the initial duty ratio immediately after the start of current supply is changed to an increasing side, and if the measured time is shorter than a predetermined time, the initial duty ratio is changed to a decreasing side. At a certain point, you have the means.

[Function] The measurement means measures the time from the start of current supply to the electromagnetic proportional control valve until the operated object starts to be driven;
That is, the initial operating time is measured, and based on the result of the measured time, the initial duty ratio for the next drive is corrected to bring the initial operating time to an appropriate value.

〔Effect of the invention〕

Therefore, according to the present invention, differences in the correspondence characteristics between the current value and the valve opening, that is, the control flow rate, caused by irregularities in the manufacturing characteristics of the electromagnetic proportional control valve and differences in oil temperature can be corrected as appropriate. This makes it possible to maintain proper initial hydraulic pressure at all times.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

As shown in Figure 5, an engine (4) is placed at the front of a car body (3) equipped with front and rear wheels (1) and (2), and a transmission case (5) is placed at the rear of the car body (3). A pair of left and right lift arms (6) are mounted on the top of this transmission case (5).
), and a lift cylinder (7) (an example of a hydraulic actuator) for driving the lift arm (6) up and down, is provided between the left and right rear fenders (8) at a position above the lift cylinder (7). A driver's seat (9) is provided to constitute an agricultural tractor.

A low tillage device (11) (an example of an object to be operated) is connected to the rear end of this agricultural tractor via a two-point link mechanism (10), and the two-point link mechanism (10) and the lift arm (6) This rotary tillage device (
11) is raised and lowered by the drive of the lift cylinder (7), and furthermore, a double-acting rolling cylinder (13) is interposed in one of the pair of lift ronds (12), so that this rotary tilling device (11) is configured to roll around the longitudinal axis (X) by driving a rolling cylinder (13).

The hydraulic system for performing this lifting and lowering operation and rolling operation is shown in FIG.
), a flow priority valve (15) for controlling the flow rate, and a controlled flow from the flow priority valve (15) to the rolling cylinder (
13), a solenoid proportional control valve (V ), and this control valve (V) includes a first valve (17) for controlling the rise, and a second valve (17) for controlling the pilot pressure that opens and closes the first valve (17).
18), a third valve (19) for descending control, and a fourth valve (20) for pilot pressure control that opens and closes this third valve (19).
) and a relief valve (21), and when controlling the rotary tiller (11) to the upward side, the second valve (18)
By supplying current to the solenoid (18a) and adjusting this current value, the pilot pressure changes in accordance with this current value, resulting in a valve opening proportional to this current value, and When controlling the rotary tiller (11) to the downward side, the current value of the current supplied to the solenoid (20a) of the fourth valve (20) is adjusted as described above, so that the valve is proportional to this current value. It is configured to provide an opening degree of .

Further, in this agricultural tractor, the rotary tilling device (1
1) to a predetermined level with respect to the ground (G), position control to raise and lower the plow to a predetermined level with the vehicle body (3) as a reference, and longitudinal axis (X).
) 3 types of automatic control including rolling control that sets the tilting posture around the surroundings, and forced lift control that takes priority over these 3 types of automatic control and raises the rotary tiller (11) to a predetermined level relative to the vehicle body. A control device is provided to perform the following.

Of this control device, a system that performs automatic plowing depth control, position control, and forced lift control is configured as shown in FIG. 1, and in this configuration, as shown in FIG.
), the first potentiometer (24) detects the setting position of the tilling depth setting dial (23) of the control box (22), and the swing-type rear cover (ll'a) of the rotary tiller (11). ) from the amount of rotation of the rotary tiller (
11) The second potentiometer (
25) constitutes a setting system and a feedback system for automatic plowing depth control, and a third potentiometer (25) that detects the setting position of the position lever (26) arranged on the side of the driver's seat (9) 27) and a fourth potentiometer (28) that detects the level of the rotary tiller (11) relative to the vehicle body from the amount of rocking of the lift arm (6), forming a position control setting system and a feed bank system. Further, a lift switch (29) is provided for causing the control box (22) to perform forced lift control.

In addition, in this forced rise control, the fourth potentiometer (
28).

Also, the signals from these four potentiometers are A/D
Via a converter (30), the signal is input to a control mechanism (31) comprising a microprocessor (not shown), and the signal from said lift switch (29) is input directly to the control mechanism (31), which control The mechanism (31) outputs an intermittent pulse signal to drive the power transistors (32), (32), so that the intermittent pulse current flows through the solenoid (18a).
), (20a), and a resistor (R) serving as a detection means for converting the current value of the current supplied to the solenoid (18a), (20a) into a voltage value is connected to the solenoid (18a), (20a). Route (33) from 20a)
), and the voltage value thus converted is configured to be feed-hacked to the control mechanism (31) via the feedback path (34) and the A/D converter (30), respectively. There is.

Further, this control device adjusts the current value of the current supplied to the solenoids (18a) and (20a) by adjusting the duty ratio of the intermittent signal, and controls the control valve (
V) is configured to adjust the opening degree.

Furthermore, among the three types of control, when controlling the automatic plowing depth control and the position control valve, the opening degree of the electromagnetic proportional control valve (V) is adjusted so that the larger the position deviation, the higher the vertical speed of the rotary tiller (11). is set, and when making this setting, the duty cycle is determined based on the current value/duty characteristic (1/D) set in advance.

In addition, in the control operation explained above, when performing either automatic plowing depth control or position control,
Rotary tillage bag! This control system is configured as an oven loop type in which the current value supplied to the solenoids (18a) and (20a) is not fed back during the lifting/lowering operation of (11).

Furthermore, the outline of the control operations for both automatic plowing depth control and position control can be expressed as shown in the flowchart in Figure 3. ), its operation is explained below.

In other words, during control, the control target (xo
) is set to the signal of the setting device, that is, the signal from either the first or third potentiometer (24) or (27), and the current level of the rotary tiller (11) (
XR) and the sensor signals, that is, the second and fourth sensors (25
), (28) is set, and the position deviation (Ex) is determined by subtraction (#
L#2 step).

Next, the overall value of the positional deviation (Ex) is compared with the value (ε) set as the dead zone, and the positional deviation (E,
) is greater than the deadband value (ε), and only if
The control direction is determined by determining the control direction (steps #3 to #6).

Next, a target flow rate (Qo) is determined based on the positional deviation (Ex), a target current value (■°) is determined based on the target flow rate (Qo) and the characteristics of the control valve (V), Target current value (
3) and the current value/duty characteristic (D) set as described above, the duty ratio (D″') is determined (Steps #7, #8, and #9).

In addition, #7. #8. In the process in step #9, a decision is made based on the characteristics represented in the illustrated graph, and this decision is made by map data or calculation.

Next, set the value determined in step #9 for the maximum value (D□X), and set the initial value (D Value (Dp+
), and from this initial value (D, ) to the maximum value (Dff
i, X) while outputting a pulse signal (#
10. #11 step).

Also, the current start point (to) for the electromagnetic proportional control valve (V)
) to the time when the tilling device (work 1) starts to be driven, that is, the time (tl) when the signal of any one of the second and fourth sensors (25) and (28) starts to change. ), please refer to Figure 2), and this measurement time (T)
is larger than the predetermined set time (To), the stored data of the set initial duty ratio (Dp) is set to the standard value (DP
Change the first correction setting (I! (DPE)) to a larger value than I) (Steps #13 and #14).

If the measurement time (T) is shorter than the set time (To), change the stored data to a second correction set value (DP3) smaller than the standard 4iCDx (step #15).
. The initial duty ratio data corrected in this way is used as #10 in the next control. Used as the initial value of #11 stamp.

In addition, in step #12 of the above flowchart, the measuring means (
Configure A) and #13. #14. The #15 step constitutes the initial duty ratio changing means (B).

Note that the object to be operated is not limited to the tilling device (11), and various other objects such as a power transmission flanch can be used.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of the hydraulic control device for a working machine according to the present invention, in which Fig. 1 is a control block diagram, Fig. 2 is a timing chart, Fig. 3 is a control flowchart, Fig. 4 is a hydraulic circuit diagram, and Fig. 5 is a hydraulic control device for a working machine. The figure is an overall side view of an agricultural tractor. (7)...Hydraulic actuator, (11)...
...Operated object, (31) ...Control means,
(8)...Measuring means, (B)...Initial duty ratio changing means, (R)...Detecting means, (V)...Control valve , (T) , (To)
······time.

Claims (1)

[Claims] Hydraulic actuator (7) that drives the operated object (11)
) is configured to supply pressure oil through an electromagnetic proportional control valve (V), and based on the detection result of a detection means (R) that detects a supply current value to the electromagnetic proportional control valve (V). , a control means (31) for controlling the supply of pressure oil to the hydraulic actuator (7) to have a predetermined pressure increasing characteristic by changing the duty ratio of the pulse current to the electromagnetic proportional control valve (V). A hydraulic control device for a machine, the time (T
), and if the measurement time (T) is longer than the predetermined time (To), the initial duty ratio immediately after the start of current supply is changed to the increasing side, and the measurement time (T) is changed to the increasing side. A hydraulic control device for a working machine, comprising: initial duty ratio changing means (B) for changing the initial duty ratio to a decreasing side if the initial duty ratio is shorter than a predetermined time (To).