JPH0226082B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention provides a hydraulic circuit that has a switching valve between a variable displacement pump and an actuator and controls the speed of the actuator according to the discharge flow rate of the variable displacement pump. The present invention relates to a control device.

[Background of the invention]

In recent years, in order to achieve energy savings or higher functionality of hydraulic circuits, hydraulic circuits have been proposed in which the speed of an actuator is controlled in accordance with the discharge flow rate of a variable displacement pump.

FIG. 3 is a circuit diagram showing an example of a hydraulic circuit equipped with such a control device, and FIG. 4 is a block diagram showing an example of the control device shown in FIG. 3.

In this figure, 1 is a variable displacement pump, 1a is a discharge variable mechanism of the variable displacement pump 1, for example, a swash plate, 2 is a regulator that drives the swash plate 1a,
3 is a displacement meter that detects the position of the swash plate 1a; 4 is connected in a closed circuit to the variable displacement pump 1 through at least two main pipes, and is driven by pressure oil supplied from the variable displacement pump 1; An actuator, for example a hydraulic cylinder, 5 is a load driven by the hydraulic cylinder 4, 6 is interposed between the variable displacement pump 1 and the hydraulic cylinder 4, and 6 is the pressure supplied from the variable displacement pump 1 to the hydraulic cylinder 4. A switching valve that connects and disconnects oil; 7 is an operation lever that instructs the discharge amount of the variable displacement pump 1, that is, the speed of the hydraulic cylinder 4; 8 is a tilting amount of the swash plate 1a detected by the displacement meter 3; This is a control device that inputs the signal Y and the operating amount signal X _L of the operating lever 7, outputs a switching signal to the switching valve 6, and outputs a control signal to the regulator 2 for driving the swash plate 1a. .

This control device 8 is composed of, for example, a microcomputer, and as shown in _FIG . multiplexer 8a that outputs to the A/D converter of
and an A/D converter 8 that converts the analog signal input from the multiplexer 8a into a digital signal.
b, a central processing unit 8c that performs various types of control and arithmetic processing, a ROM 8d that stores the functional relationships of operating procedure programs, and an RA 8e that temporarily stores data during calculations. It has an output device 8f that outputs the control contents obtained by the control to the regulator 2 or the switching valve 6.

5 and 6 are flowcharts showing the operation procedure stored in the ROM 8d in the control device 8 described above, in which FIG. 5 shows the entire procedure, and FIG. 6 shows the step S in FIG. -8 is shown in detail.

As shown in FIG. 5, when the control device 8 is started, first in step S-1, the multiplexer 8a is switched, and the central processing unit 8c is operated by the control lever 7 via the A/D converter 8b. The amount X and the amount Y of tilting of the swash plate 1a, which is the output of _{the L} displacement meter 3, are read.

Next, in step S-2, the central processing unit 8c determines whether the operating amount X _L of the operating lever 7 is within the neutral range (A'≦ _XL ≦A) in which the hydraulic cylinder 4 is stopped. Ru.

Here, if it is determined that the operating amount X _L of the operating lever 7 is within the neutral range, the process moves to step S-3, and an OFF signal is output from the central processing unit 8c to the switching valve 6 via the output device 8f. , the switching valve 6 is held closed. Next, in step S-4, the central processing unit 8c sets the discharge amount command value X of the variable displacement pump 1 to zero. Next, the process moves to step S-8, where the discharge amount of the variable displacement pump 1 is controlled according to the discharge amount command value X (=0), and the process returns to the start.

In step S-2, the amount of operation of the operating lever 7
If it is determined that X _L is not within the neutral range, the process moves to step S-5, where an ON signal is output from the central processing unit 8c to the switching valve 6 via the output device 8f, and the switching valve 6 is switched to the open state. It will be done. Next, in step S-6, the discharge amount command value X of the variable displacement pump 1 is calculated from the function of the operation amount X _L of the operation lever 7 and the discharge amount command value X stored in the ROM 8d. A process of converting _L into a target tilting amount X ₀ corresponding to L is performed in the central processing unit 8c, and in step S-7,
This data of X=X ₀ is set in the RAM 8e.
Next, the process moves to step S-8, where the discharge amount of the variable displacement pump 1 is controlled according to the discharge amount command value X (=X ₀ ), and the process returns to the start.

The discharge amount control in step S-8 described above is performed in accordance with the procedure shown in FIG.

That is, first, in step S-81, a calculation is performed to subtract the swash plate tilting amount Y from the discharge amount command value X (=0 or =Xo), and the deviation ΔY is calculated.

Next, the process moves to step S-82, where the sign of the deviation ΔY is determined.

If the deviation ΔY is determined to be a negative value (-), the process moves to step S-83, where a control signal is sent from the central processing unit 8c to the regulator 2 via the output device 8f to move the swash plate 1a in the (-) direction. Output.

Also, in step S-82, the deviation ΔY=
If it is determined that the value is 0, proceed to step S-84.
Move to. Here, ΔY=0 means that the discharge amount command value X and the swash plate tilting amount Y match, so in step S-84,
A signal is output to the regulator 2 to stop the swash plate 1a.

If it is determined in step S-82 that the deviation ΔY is a positive value (+), the process moves to step S-85, where the regulator 2 is connected to the swash plate 1a.
A control signal is output that moves the motor in the (+) direction.

The control device 8 is designed to control the hydraulic circuit by constantly repeating the steps from step S-1 to step S-8 described above.

By the way, generally, as shown in FIG. 3, in the variable displacement pump 1, there is a flow rate qlt that leaks from a discharge port (not shown) to the oil tank, and a flow rate qli that leaks from the discharge port to the suction port.

These leaks occur on either the discharge port side or the suction port side of the variable displacement pump 1, on which the load is applied.

However, the conventional hydraulic circuit control device described above does not take any consideration into correcting this leakage flow rate, so when applied to a circuit that operates the boom of a hydraulic excavator, for example, the following problems occur. It was hot.

That is, when this hydraulic circuit is applied to a circuit that operates the boom of a hydraulic excavator, the hydraulic cylinder 4
Since the load 5 on the hydraulic circuit is high, the pressure in the hydraulic circuit is high, and there are relatively large leakage flows qlt and qli. When operating the operating lever 7 in such a situation, if the operating amount X _L of the operating lever 7 is larger than the neutral range A' to A, step S- of the flowchart in FIG.
2. As is clear from S-5, the switching valve 6 is switched from the closed state to the open state, and as a result, the variable displacement pump 1 and the hydraulic cylinder 4 communicate with each other. Therefore, even if the operating amount of the operating lever 7 is minute and the discharge amount of the variable displacement pump 1 is almost zero,
Pressure oil corresponding to the leakage flow rate qlt+qli is supplied to the head side circuit or rod side circuit of the hydraulic cylinder 4 via the switching valve 6, and the hydraulic cylinder 4 operates at a speed proportional to this. Therefore, the hydraulic cylinder 4
Even though I tried to lower the hydraulic cylinder 4 just a little, it ended up lowering by an amount equivalent to the leakage flow rate qlt + qli, or even though I operated the operating lever 7 to raise the hydraulic cylinder 4 slightly, it stopped. If it descends just before it descends, a problem will occur.

Further, when the operating lever 7 is returned to the neutral range A' to A, step S of the flowchart in FIG.
-2 and S-3, the switching valve 6 is switched from the open state to the closed state. However, as described above, in the open state before the switching valve 6 is switched, the hydraulic cylinder 4 operates at a speed equal to the leakage flow rate qlt + qli, so if the switching valve 6 is switched in such a situation, the shock will occur.

Such a problem is not only undesirable from the viewpoint of fine operability of various hydraulic machines to which this hydraulic circuit and control device is applied, but also from the viewpoint of safety protection of workers who operate these machines.

In order to eliminate this problem, the applicant first provided a means for detecting the discharge pressure of the variable displacement pump 1, and controlled the opening and closing of the switching valve based on the discharge pressure signal detected by the discharge pressure detection means. At the same time, we proposed a hydraulic circuit control device that controls the discharge flow rate of the variable displacement pump 1 based on the discharge flow rate calculation value of the variable displacement pump 1 calculated by taking into account the leakage flow rate (Japanese Patent Application No. 1983- No. 146218).

The control device for the hydraulic circuit will be explained below.

FIG. 7 is a circuit diagram showing the configuration of this conventional hydraulic circuit control device, in which the same members as shown in FIG. 5 are designated by the same reference numerals.

In this figure, 8' is a control device, 9 is a pressure detector that detects the pressure in the circuit on the head side of the hydraulic cylinder 4, 10 is a pressure detector that detects the pressure in the circuit on the rod side of the hydraulic cylinder 4, and 11 is a pressure detector that detects the pressure in the circuit on the rod side of the hydraulic cylinder 4. A shuttle moves in the horizontal direction in the diagram according to the level of pressure in the head side circuit and rod side circuit of the hydraulic cylinder 4. Reference numerals 12 and 13 indicate switches that output signals in response to the movement of the shuttle 11, such as proximity switches. It is.

As shown in FIG. 8, this control device 8' is different from the control device 8 shown in FIG. 6 by adding signal inputs of pressure detectors 9 and 10 to a multiplexer 8a.
Input device 8 for inputting proximity switches 12 and 13
It has a structure with the addition of g. The ROM 8d of this control device 8' stores a first calculation for determining the swash plate tilt angle corresponding to the leakage flow rate qlt+qli from the variable displacement pump 1, and a first calculation obtained by this first calculation. A function for performing a second calculation of adding the calculation value X ₁ to obtain the swash plate tilt angle corresponding to the new discharge flow rate (discharge amount command value) X of the variable displacement pump 1 is stored.

The functions stored in the ROM 8d of the control device 8' are:
It is obtained from FIGS. 9 and 10.

That is, FIG. 9 is a characteristic diagram qualitatively showing the characteristics of this hydraulic circuit, and the upper part shows the swash plate inclination showing the relationship between the tilt angle of the swash plate 1a of the variable displacement pump 1 and the pressure in the circuit. A rotation angle-pressure characteristic diagram is shown below, and a swash plate tilt angle-cylinder speed characteristic diagram showing the relationship between the swash plate tilt angle and cylinder speed is shown below. Here, the dashed line in the swash plate tilt angle-pressure characteristic diagram indicates the relief pressure, and the pressure value C indicates the pressure value preset for opening and closing the switching valve 6. In addition, in the swash plate tilt angle-cylinder speed characteristic diagram, (+) and (-) on the horizontal axis indicating the swash plate tilt angle indicate the swash plate tilt direction of the variable displacement pump 1, and the vertical axis indicates the cylinder speed. The (+) and (-) axes indicate the operating direction of the hydraulic cylinder 4. Note that such characteristics are common characteristics of this type of hydraulic circuit.

As can be seen from this figure, there is leakage from the variable displacement pump 1 in this circuit, so even if the variable displacement pump 1 is driven with the switching valve 6 closed, the swash plate tilt angle reaches a certain value. The circuit pressure does not rise until the swash plate tilt angle at which the cylinder speed becomes 0 when the switching valve 6 is opened and the hydraulic cylinder 4 is driven.
That is, when it reaches the value shown by the broken line, it increases rapidly from there. In other words, the discharge amount of the variable displacement pump 1 when the cylinder speed becomes 0 corresponds to the leakage amount qli+qlt from the variable displacement pump 1. Based on this relationship, by detecting the pressure value of the hydraulic circuit, the discharge flow rate of the variable displacement pump 1, that is, the leakage amount qli+qlt can be calculated.

Further, FIG. 10 is a metering table showing the basic principle of control performed by the control device of the present invention, in which the horizontal axis shows the operation amount X _L of the operation lever 7,
The specific value of the discharge flow rate (target discharge amount) X ₀ that determines the cylinder speed is plotted on the vertical axis. In this hydraulic circuit control device, the operating amount of the operating lever 7 is X _L
In the range where is F, the discharge amount of the variable displacement pump 1 is 0, and when the operation amount X _L of the operating lever 7 becomes A, A', the variable displacement pump 1 starts discharging.
The pressure oil is set to be discharged from the variable displacement pump 1 in a discharge amount proportional to the operation amount X _L of the operation lever 7. Here, F is a dead zone forming a region where the speed of the hydraulic cylinder 4 is not controlled by the operating lever 7, and A and A' are preset calculation start values that specify the range of the dead zone F.

Therefore, by calculating the difference between the specific value (target discharge amount) X ₀ determined based on this metering table and the actual discharge amount of the hydraulic circuit,
Operation lever 7 required to obtain a discharge amount of a specific value X ₀
The manipulated variable X _L can be calculated.

The proximity switch 13 outputs a high level signal R (signal value 1) when the head side of the hydraulic cylinder 4 has high pressure, and outputs a low level signal R (signal value 0) when the rod side of the hydraulic cylinder 4 has high pressure. Output. On the other hand, the proximity switch 12 outputs a low level signal L when the head side of the hydraulic cylinder 4 has high pressure, and outputs a high level signal L when the rod side of the hydraulic cylinder 4 has high pressure. Incidentally, when the pressure on the head side and the rod side of the hydraulic cylinder 4 is the same, the proximity switches 12 and 13 both output low level signals L and R.

Control in the control device 8' is performed, for example, according to the procedure shown in the flowcharts of FIGS. 11 and 12. In this flowchart, P _L is the pressure value detected by the pressure detector 9, P _R is the pressure value detected by the pressure detector 10, and ΔX is the discharge flow rate of the variable displacement pump 1. It shows an increment corresponding to the amount of change.

First, in step S-100, the central processing unit 8c of the control device 8' receives the operating amount X L of the operating lever, the pressure of the pressure detectors 9 and 10, and the operating amount X _L of the operating lever. signal
P _L , P _R , pump swash plate tilting amount Y are read, and
Pressure signals L and R of the proximity switches 12 and 13 are read through the input device 8g. Next, step S
-101, the operating amount of the operating lever 7 is determined based on the metering table shown in FIG.
A process of converting X _L into a specific value (target discharge amount) X ₀ is performed by the central processing unit 8c. Next, the process moves to step S-200, where the direction of the load acting on the hydraulic cylinder 4 is detected.

Detection of the direction of the load in step S-200 is performed in accordance with the procedure shown in FIG.

That is, first, in step S-201, it is determined whether the pressure signal L of the proximity switch 12 is 1 or 0.

If it is determined that L=1, step S-202
Then, in order to indicate that the rod side of the hydraulic cylinder 4 is under high pressure, a process is performed in which the load direction flag f is set to (-), and the process moves to step S-102.

If it is determined in step S-201 that L≠1, the process moves to step S-203, where it is determined whether the pressure signal R of the proximity switch 13 is 1 or 0.

If it is determined in step S-203 that R=1, the process moves to step S-205, where a process is performed to set the load direction flag f to (+) to indicate that the head side of the hydraulic cylinder 4 is under high pressure. We now move on to step S-102.

Furthermore, if it is determined that R≠1 in step S-203, the head side and rod side of the hydraulic cylinder 4 are at the same pressure, so step S-2
The process moves to step S-04, where processing to set f=0 is performed, and the process moves to step S-102.

In step S-102, the central processing unit 8c determines whether the manipulated variable X _L is greater than or equal to the calculation start values A' to A.

If it is determined that the manipulated variable X _L is within the range of calculation start values A' to A, that is, if it is determined that it is within the dead zone F of the metering table shown in FIG. 10, step S-- Step 103, in the central processing unit 8c, a process is performed to set the first calculated value _X1 calculated according to the procedure described later to 0, and the process moves to the next step S-104. Step S
-104, an OFF signal is output from the central processing unit 8c to the switching valve 6 via the output device 8f, and the switching valve 6 is kept in the closed state shown in FIG.
Next, in step S-105, X=X ₀ +
An operation is performed to set X ₁ , and this X=X ₀ +X ₁ becomes
Stored in RAM8e. At this time, X ₀ is the operating amount X _L of the operating lever 7, which is between the dead zone F.
The neutral value is Xc. Next, step S-
8, a signal is output to the regulator 2 to set the swash plate 1a in a neutral state according to the discharge amount command value X,
The discharge amount of the variable displacement pump 1 is controlled and the process returns to the start.

In addition, when it is determined in step S-102 that the operation amount X _L of the operating lever 7 is larger than the calculation start values A' to A, in step S-106, it is determined whether the switching valve 6 was previously ON or not. is judged.

Here, if it is determined that the switching valve 6 was previously OFF, the process moves to step S-107, and the central processing unit 8c determines whether the load direction flag f is (-).

If it is determined that f≠(-), the process moves to the next step S-108, and it is determined whether the load direction flag f is (+).

If it is determined that f≠(+), it means that f=0, so the process moves to step S-109, and the central processing unit 8c performs processing to set X ₁ =0. Next, step S-11
0, the output device 8 is output from the central processing unit 8c.
An ON signal is output to the switching valve 6 via f, and the switching valve 6 is switched to the open state. After that, in step S-111, the discharge amount command value X is set to specific values X ₀ and X ₁ (=0) corresponding to the operating _amount
The central processing unit 8c performs a calculation to obtain a second calculation value which is the sum of (X=X ₀ +X ₁ ). After that, the process moves to step S-8, where a signal for driving the swash plate 1a is outputted to the regulator 2 according to the discharge amount command value X (=X ₀ ), the discharge amount of the variable displacement pump 1 is controlled, and the start is started. return.

If it is determined in step S-107 that f=(-), the process moves to step S-112, where the central processing unit 8c calculates the pressure value of the pressure detector 10.
It is determined whether P _R is greater than or less than a preset value C (see FIG. 9).

If it is determined in step S-112 that P _R ≧C, the process moves to step S-110, where the switching valve 6 is switched to the open state, and in step S-111, the discharge amount command value X=X ₀₊
A second calculated value of X ₁ is obtained, and step S
-8, the discharge amount of the variable displacement pump 1 is controlled and the process returns to the start.

Furthermore, in step S-112, P _R <C
If it _is determined that An OFF signal is output from 8c to the switching valve 6 via the output device 8f, and the switching valve 6 is held in the closed state.
-Move to 115. In step S-115, the calculated value _{X 1} is set to the neutral value Xc (=0) when the operating amount X _L of the operating lever with the specific value
The central processing unit 8c performs a process of adding up the discharge amount command value X to obtain the discharge amount command value X. After that, step S-
At step 8, the discharge amount of the variable displacement pump 1 is controlled, and the process returns to the start.

Also, in step S-107, f≠(-)
It is determined that f=
If it is determined as (+), step S-11
6, the pressure value P _L of the pressure detector 9 is set to the set value C.
It will be judged whether it is more or less.

If it is determined in step S-116 that the pressure value P _L of the pressure detector 9 is equal to or higher than the set value C,
The process moves to step S-110, where an ON signal for switching the switching valve 6 to the open state is output, and then, in step S-111, a second calculated value for setting the discharge amount command value X=X ₀ +X ₁ is calculated. Then, in step S-8, the discharge amount of the variable displacement pump 1 is controlled, and the process returns to the start.

Also, in step S-116, the pressure value P _L
is determined to be less than the set value C, step S
-117, where the first operation of adding the increment ΔX to the operation value _X1 is performed, and then step S
-114, S-115, S-8 and return to the start.

In addition, when it is determined in step S-102 that the operation amount X _L of the operating lever 7 is larger than the range of calculation start values A' to A, and in step S-106 it is determined that the switching valve 6 was previously ON. means that the hydraulic cylinder 4 was driven last time, so the process immediately moves to step S-110, where an ON signal is output from the output device 8f to the switching valve 6 to keep the switching valve 6 open, and then , in step S-111, a second calculation is performed to set X=X ₀ +X ₁ . After that, the process moves to step S-8, and the discharge amount of the variable displacement pump 1 is controlled.
Return to start.

The conventional control device configured in this way increases the pressure in the discharge side circuit of the variable displacement pump 1 to almost the same pressure as the head side circuit or rod side circuit of the hydraulic cylinder 4 forming the high pressure side, and in that state. Open the switching valve 6 and calculate the second calculated value (=X ₀
+ _X1 ) Since the control is performed using a command signal having a discharge amount command value X equal to
It is possible to realize speed control of the hydraulic cylinder 4 according to X _L.

However, in the conventional hydraulic circuit control device shown in FIGS. 7 to 12, when it is determined that the operating amount _X As shown in steps S-103 to S-105 in the figure, the calculated value X ₁ =
0 to switch the switching valve 6 to the closed state, so if you slightly operate the operating lever 7 to slightly operate the hydraulic cylinder 4 and then return the operating lever 7 to the neutral position to stop the hydraulic cylinder 4, the operation When the lever 7 is returned to the neutral position, the switching valve 6 is switched to the closed state even though the hydraulic cylinder 4 is operating at a speed corresponding to the leakage flow rates qli and qlt, and the shock is shut off when stopped. A problem has been discovered in which smooth fine operations may not be possible under certain conditions.

For example, as shown in FIG. 13, when the arm 22 (load 5) of the working machine 21 connected to the hydraulic cylinder 4 is driven from the A position to the B position and then stopped at the B position, the load When the load 5 is in the A position, pressure oil leaks in the rod side circuit of the hydraulic cylinder 4, that is, on the suction side of the variable displacement pump 1, and when the load 5 reaches the B position, the pressure oil leaks in the rod side circuit of the hydraulic cylinder 4, that is, in the variable displacement pump 1. Pressure oil leaks on the discharge side of the displacement pump 1.

However, in the hydraulic circuit control device previously proposed by the applicant, during operation, the correction state is maintained when the drive is started, that is, when the switching valve 6 is opened, but when the control device is stopped, pressure oil leaks. Since no correction has been made for the influence of
If you operate the pump above the dead zone and then immediately return it to within the dead zone, pressure oil will leak from the suction side of the variable displacement pump 1 even after the load 5 moves from position A to position B. In some cases, the discharge amount of the variable displacement pump 1 is corrected in the event that such a problem occurs.

Therefore, when the operating lever 7 is returned to the dead zone, the switching valve 6 is switched to the closed state while pressure oil corresponding to the leakage amount qlt + qli is being supplied from the variable displacement pump 1 to the hydraulic cylinder 4. Shock occurs in the hydraulic system.

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic circuit control device that eliminates the drawbacks of the conventional hydraulic circuit control devices described above and allows smooth operation without any shock when stopping. .

[Summary of the invention]

In order to achieve this object, the present invention calculates the discharge flow rate of a variable displacement pump according to a preset procedure when the operation amount of a control lever exceeds a dead zone in which the speed of the actuator is not controlled by the control lever. Then, when the operating lever is returned to the dead zone, the direction of the load acting on the actuator is detected, and the load is applied in the discharge direction of the variable displacement pump. When the load is applied to the variable displacement pump in the suction direction, the first calculated value is added to the target value of the discharge flow rate of the variable displacement pump corresponding to the operation amount of the control lever, and when the variable displacement pump is loaded in the suction direction. , subtract the first calculated value from the target value of the discharge flow rate of the variable displacement pump corresponding to the operation amount of the operating lever to obtain a second calculated value corresponding to the discharge command value of the variable displacement pump. , the switching valve is closed when the difference between the discharge flow rate of the variable displacement pump and the second calculated value falls within a preset range.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The hydraulic circuit and control device of this embodiment are completely similar to those shown in FIGS. 7 and 8.

FIG. 1 is a flowchart of the entire operating procedure, and FIG. 2 is a flowchart showing details of the operating procedure of step S-300.

In step S-102 of FIG. 1, it is determined that the operating amount X _L of the operating lever 7 is within the dead zone A' to A, and in step S-118, the switching valve 6 was previously turned ON. , if it is determined that the hydraulic cylinder 4 and variable displacement pump 1 are still connected, step S-30
Move to 0.

When the process reaches step S-300, as shown in FIG. 2, first, in step S-301, the central processing unit 8c determines whether the load direction flag f is set to (-).

If it is determined in step S-301 that f=(-), the loaded state of the hydraulic cylinder 4 is such that the pressure on the rod side is high. Therefore, variable displacement pump 1
The leakage amount qli+qlt occurs from the port connected to the rod side of the hydraulic cylinder 4. Therefore, the process moves to step S-302, where the central processing unit 8c performs processing to set the first calculated value X ₁ =-|X ₁ |, which is the leakage correction value of the variable displacement pump 1, and then The process moves to step S-306. In step S-306, the discharge amount command value X=
The calculation of X ₀ +X ₁ , that is, the calculation of X=X ₀ −|X ₁ | is performed to obtain the second calculation value X. However, the specific value X ₀ =Xc (=0) at this time. Then,
In step S-307, it is determined whether the deviation between the discharge amount command value It is determined whether the swash plate tilting amounts Y of the displacement pump 1 substantially match. As will be described later, this range α is used to determine the timing to switch the switching valve 6, and the smaller this value is, the better the fine operability of the hydraulic cylinder 4 is, and the smaller the shock when stopping. can do. Therefore, the size of this range α is arbitrarily set in consideration of the practically required fine operability and degree of shock.

In step S-307, |Y-X|>α
If it is determined that
The switching valve 6 is kept open and the process returns to the start via step S-8. Then, the operation procedure of the control device 8' is as described above: S-100→S-101→S→
200→S-102→S-118→S-300→
When it is determined in step S-307 that the discharge amount command value X and the swash plate tilting amount Y of the variable displacement pump 1 are within the range of α while circulating with S-8, the process proceeds to step S-8. -309, an OFF signal for switching the switching valve 6 to the closed state is output from the output device 8g, the switching valve 6 is switched to the closed state, and then, in step S-8, the discharge amount of the variable displacement pump 1 is set to the discharge amount command value. Control is performed to make X (X ₀ +X ₁ ). Then, when the process returns to the start from step S-8 and reaches step S-118 again,
Since it is determined that the switching valve 6 was OFF last time, processing is performed to set X ₁ = 0 in step S-103, and a signal to keep the switching valve 6 in the closed state is output in step S-104. In step S-8, an operation is performed to neutralize the tilting angle of the swash plate of the variable displacement pump 1.

Similarly, in step S-301, f≠(-)
If it is determined that f=(+) in step S-303, the hydraulic cylinder 4
Since the _pressure is high on the head side _of the
Control is performed according to the above procedure as |.

Also, in step S-301, f≠(-)
If it is determined that f≠(+) in step S-303, the hydraulic cylinder 4
Since the pressure is the same on the head side and rod side, a process is performed to set X ₁ =0 in step S-305, and then control is performed according to the above procedure.

In the operating procedure of this embodiment, if it is determined in step S-102 of FIG. 1 that the operation amount X _L of the operating lever 7 is larger than the calculation start values A' to A The procedure when it is determined that the operating amount X _L of the operating lever 7 is larger than the calculation start values A' to A, and it is determined in step S-118 that the switching valve 6 was previously OFF is the same as the conventional procedure described above. Since it is exactly the same as in the example, the explanation will be omitted.

The hydraulic circuit control device of this embodiment includes step S
- In 102, it is determined that the operating amount X _L of the operating lever 7 is smaller than the calculation start values A' to A, and
If it is determined in step S-118 that the switching valve 6 was in the open state last time, the load at the time of stop is corrected, and the deviation between the discharge amount command value X and the swash plate tilt amount Y, which is the output signal of the displacement meter 3, is Since the switching valve 6 is switched to the closed state when the discharge amount command value X and the actual swash plate tilting amount Y of the variable displacement pump 1 are approximately equal to each other within a certain range α,
The leakage amount qli + qlt of the variable displacement pump ₁ can be offset by the first calculated value This eliminates the shock when stopping.

[Effects of the Invention] The hydraulic circuit control device of the present invention, when starting the connection between the variable displacement hydraulic pump and the actuator,
The switching valve and regulator are controlled by taking into account leakage from the variable displacement pump that exists when the load direction of the actuator changes when the variable displacement hydraulic pump and actuator are connected. This not only prevents unnecessary movement of the actuator when starting the connection between the pump and actuator, but also prevents unnecessary movement of the actuator when the load direction of the actuator changes while the variable displacement hydraulic pump and actuator are connected. This can further improve the fine operability of the actuator.
Therefore, the operability of machines to which this hydraulic circuit control device is applied and the safety of workers involved in operating these machines can be significantly improved.

[Brief explanation of drawings]

1 and 2 are flowcharts showing the operating procedure of a control device for a hydraulic circuit according to a first embodiment of the present invention, FIG. 3 is a circuit diagram showing an example of a conventional hydraulic circuit, and FIG. A block diagram showing an example of a control device applied to the control of a conventional hydraulic circuit, FIGS. 5 and 6 are flowcharts showing an example of operating procedures performed by the conventional control device, and FIG. Fig. 8 is a block diagram showing another example of a control device applied to control the conventional hydraulic circuit, Fig. 9 shows the tilting angle and discharge of a variable displacement pump. A graph showing the relationship between pressure and cylinder speed, Fig. 10 is a metering table showing the basic principle of control performed by the control device of Fig. 8, and Figs. 11 and 12 are the control of Fig. 8. FIG. 13 is a flowchart showing an example of the operation procedure performed by the apparatus, and is an explanatory diagram for explaining the disadvantages of the conventional technology. 1: Variable displacement pump, 1a: Swash plate, 2: Regulator, 3: Displacement meter, 4: Hydraulic cylinder, 5: Load, 6: Switching valve, 7: Operation lever, 8, 8': Control device, 8a: Multiplexer , 8b: A/D converter, 8c: central processing unit, 8d: ROM,
8e: RAM, 8f: Output device, 8g: Input device,
9, 10: Pressure detector, 11: Shuttle, 12,
13: Proximity switch.

Claims (1)

[Claims] 1. A variable displacement pump, an actuator that is connected to the variable displacement pump in a closed circuit by at least two main pipes, and a device that is interposed between the variable displacement pump and the actuator and that supplies the actuator from the variable displacement pump. The hydraulic circuit includes a switching valve that connects and disconnects the flow of pressure oil, a control means that controls opening and closing of the switching valve and a discharge flow rate of the variable displacement pump, and a control means that is connected to the control means. and a control lever, which calculates the discharge flow rate of the variable displacement pump according to a preset procedure when the operation amount of the control lever exceeds a dead zone in which the speed of the actuator is not controlled by the control lever. A first calculated value corresponding to the leakage flow rate from the variable displacement pump is calculated, and when the discharge pressure of the variable displacement pump reaches a preset pressure, a signal is output to open the switching valve, and the operation is performed as described above. A hydraulic circuit that controls the discharge flow rate of the variable displacement pump based on a specific value of the discharge flow rate of the variable displacement pump corresponding to the operating amount of the lever and the first calculated value when the switching valve is opened. In the control device, when the operating lever is returned to the dead zone, the direction of the load acting on the actuator is detected, and when the load is applied in the discharge direction of the variable displacement pump, the operating amount of the operating lever is detected. Add the above first calculated value to the target value of the discharge flow rate of the variable displacement pump corresponding to
Further, when a load is applied to the suction direction of the variable displacement pump, the first calculated value is subtracted from the target value of the discharge flow rate of the variable displacement pump corresponding to the operation amount of the operation lever, and the variable displacement A second calculated value corresponding to the pump discharge command value is calculated, and the discharge flow rate of the variable displacement pump and the second calculated value are calculated.
A control device for a hydraulic circuit, characterized in that the switching valve is controlled to be closed when the difference between the calculated value and the calculated value falls within a preset range.