JPH02256903A - Hydraulic circuit control device - Google Patents

Abstract

PURPOSE:To improve the operability, in case where a variable delivery hydraulic pump and an actuator are connected, by controlling a changeover valve and a regulator while considering the leakage from the variable delivery pump at the time when the direction of load is changed. CONSTITUTION:When an operating lever 7 is turned in the positive or negative direction, a control unit 8 carries out positive or negative connection of a variable delivery pump 1 and a hydraulic cylinder 4 by means of a changeover valve 6. In this case, the control of the changeover valve 6 and a regulator 2 is carried out while considering the leakage from the variable delivery pump 1 which is caused when the direction of a load 5 is changed by the hydraulic cylinder 4, in case where the connection is started, or where the connected state and connection is completed. Thus, unnecessary action of the actuator can be prevented for improving the minute operability of the actuator, and the operability and safety of a machinery can be improved.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to 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 saving or high functionality of hydraulic circuits, hydraulic circuits have been proposed in which the speed of an actuator is controlled according to the discharge flow rate of a variable displacement pump.

FIG. 4 is a circuit diagram showing an example of a hydraulic circuit equipped with such a control device, and FIG. 5 is a block diagram showing an example of the control device shown in FIG. 4.

In this figure, 1 is a variable displacement pump, 1a is a discharge variable mechanism of the variable displacement pump l, such as a swash plate, 2 is a regulator that drives the swash plate 1a, and 3 is a displacement meter that detects the position of the swash plate 1a. , 4 are connected to the variable displacement pump 1 in a closed circuit by at least two main lines, and the variable displacement pump 1
5 is a load driven by the hydraulic cylinder 4, and 6 is the variable displacement pump 1 and the hydraulic cylinder 4.
7 is an operation for instructing the discharge amount of the variable displacement pump 1, that is, the speed of the hydraulic cylinder 4. A lever 8 is a tilting amount signal Y of the swash plate 1a detected by the displacement meter 3 and an operation amount signal X of the operating lever 7.
This is a control device that inputs a signal L and outputs a switching signal to the switching valve 6, and also outputs a control signal to the regulator 2 for driving the swash plate 1a.

This control device 8 is constituted by, for example, a microcomputer, and as shown in FIG.
and a multiplexer 8a that inputs analog signals (Y, XL) from the operating lever 7, switches them and outputs them to the next A/D converter, and A that converts the analog signal input from the multiplexer 8a into a digital signal. /D
A converter 8b, a central processing unit 8C that performs various controls and arithmetic processing, a ROM 8d that stores programs of operating procedures and functional relationships, a RAM 8e that temporarily stores data during calculations, etc. an output device 8 that outputs the control contents obtained by the above to the regulator 2 or the switching valve 6;
f.

6 and 7 show R in the control device 8 described above.
6 is a flowchart showing the operation procedure stored in the OM8d, FIG. 6 shows the entire procedure, and FIG. 7 shows step S-8 in FIG. 6 in detail.

As shown in FIG. 6, when the control device 8 is started,
First, in step S-1, the multiplexer 8a is switched, and the operating amount XL of the operating lever 7 and the tilting amount of the swash plate 1a, which is the output of the displacement meter 3, are sent to the central processing unit 8C via the A/D converter 8b. Y is read.

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

Here, if it is determined that the operating amount XL of the operating lever 7 is within the neutral range, the process moves to step S-3, where an OFF signal is output from the central processing unit f8C to the switching valve 6 via the output device 8f. The switching valve 6 is held in the closed state.Next, in step S-4, the central processing unit 8C sets the discharge amount command fiX of the variable displacement pump 1 to O.
It will be held in

Next, the process moves to step S-8, where the discharge amount command value X
(-0), the discharge amount of the variable displacement pump 1 is controlled, and the process returns to the start.

If it is determined in step S-2 that the operating amount XL of the operating lever 7 is not within the neutral range, the process moves to step S-5, and an ON signal is output from the central processing unit 8C to the switching valve 6 via the output device 8f. Then, the switching valve 6 is switched to the open state. Next, in step S-6, the ROM8
From the function of the operation amount XL of the operation lever 7 and the discharge amount command value
. The central processing unit 8C performs a process of converting the X=Xo data into the RAM 8e in step S-7. 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 (''Xo), 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 5-81, the discharge amount command value
An operation is performed to subtract the swash plate tilting amount Y from (=O or =X0), and it is calculated from the deviation ΔY.

The process then moves to step 5-82, 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 5-83, and the output device 8 is output from the central processing unit 8C.
A control signal for moving the swash plate 1a in the (-) direction is output to the regulator 2 through .

If it is determined in step 5-82 that the deviation ΔY=0, the process moves to step 5-84. Here, ΔY=0 means that the discharge amount command value X and the swash plate tilting amount Y are the same.
-84, a signal is output to the regulator 2 to stop the swash plate 1a.

If it is determined in step 5-82 that the deviation ΔY is a positive value (+), the process moves to step 5-85, and a control signal is output to the regulator 2 to move the swash plate 1a in the (+) direction. be done.

The control device 8 performs the steps S-1 to S-1 described above.
-8 steps are always repeated to control the hydraulic circuit.

By the way, at -M, the variable displacement pump 1 has a flow rate qlt leaking from the discharge boat (not shown) to the oil tank and a flow rate 1 leaking from the discharge boat to the suction boat, as shown in FIG.
iqli exists. These leaks occur on either the discharge boat side or the suction boat side of the variable displacement pump 1, on which the load is applied.

However, in the conventional hydraulic circuit control device described above, no consideration is given to correcting this leakage flow rate.
For example, when applied to a circuit that operates the boom of a hydraulic excavator, the following problems occur.

That is, when this hydraulic circuit is applied to a circuit that operates the boom of a hydraulic excavator, the load 5 applied to the hydraulic cylinder 4 is
is large, the pressure in the hydraulic circuit is high, and there are relatively large leakage flows fiqlt, qli. When the control lever 7 is operated in such a situation, if the operation txt of the control lever 7 is larger than the neutral range A' to A, as is clear from steps S-2 and 3-5 of the flowchart in FIG. 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, the amount of operation of the operating lever 7 is minute and the variable displacement pump 1
Even if the discharge amount is almost O, the leakage flow of 1qlt + qli of pressure oil is supplied to the head side circuit or rod side circuit of the hydraulic cylinder 4 via the switching valve 6, and the hydraulic pressure is increased at a speed proportional to this. Cylinder 4 will operate. Therefore, even though the hydraulic cylinder 4 is intended to be lowered only slightly, it is lowered by an amount corresponding to the leakage flow tqlt+alt, or the hydraulic cylinder 4
A problem occurs in that even though the operating lever 7 is operated in an attempt to raise the motor slightly, the motor falls just before it stops.

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

Such defects are not only undesirable from the viewpoint of fine operability of various hydraulic machines to which this hydraulic circuit and control device are applied, but also from the viewpoint of safety protection of workers who are required to operate these machines. do not have.

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. proposed a control device for a hydraulic circuit that controls the discharge flow rate of a variable displacement pump 1 based on a calculated value of the discharge flow rate of the variable displacement pump 1, which is calculated in consideration of the leakage flow rate (Japanese Patent Application No. 57-146218). ).

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

FIG. 8 is a circuit diagram showing the configuration of a control device for this conventional hydraulic circuit, in which members similar to those shown in FIG. 4 are designated by the same reference numerals.

In this figure, 8' is a control device, 9 is a hydraulic cylinder 4
10 is a pressure detector that detects the pressure in the rod side circuit of the hydraulic cylinder 4; 11 is a pressure detector for detecting the pressure in the head side circuit and the rod side circuit of the hydraulic cylinder 4. 12.13 is a switch that outputs a signal in response to the movement of the shuttle 11, such as a proximity switch.

As shown in FIG. 9, this control device 8' is different from the control device 8 shown in FIG.
It has a structure in which an input device 8g is added for inputting No. 3. 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 l, and a first calculation value obtained by this first calculation. A function for performing a second calculation of calculating the swash plate tilt angle corresponding to the new discharge flow rate (discharge amount command value) X of the variable displacement pump 1 by adding X is stored.

The functions stored in the ROM 8d of the control device 1B' are the first
It is obtained from Fig. 0 and Fig. 11.

That is, FIG. 10 is a characteristic diagram qualitatively showing the characteristics of this hydraulic circuit, and the swash plate 1a of the variable displacement pump 1 is shown above.
The swash plate tilting angle that shows the relationship between the tilting angle and the circuit pressure -
A 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 chain chain in the swash plate tilting angle-pressure characteristic diagram indicates the relief pressure, and the pressure value 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 diagram, this circuit includes a variable displacement pump 1
Because of the leakage, even if the variable displacement pump 1 is operated with the switching valve 6 closed, the pressure in the circuit will not rise until the swash plate tilt angle reaches a certain value, and when the switching valve 6 is opened, the pressure in the circuit will not increase. When the swash plate tilt angle at which the cylinder speed becomes 0 when the hydraulic cylinder 4 is driven, that is, the value shown by the broken line, increases rapidly from there. In other words, the discharge amount of the variable displacement pump 1 when the cylinder speed becomes O corresponds to the leakage amount qli+qlL 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. 11 is a metering table showing the basic principle of control performed by the control device of the present invention,
The horizontal axis represents the operating amount XL of the operating lever 7, and the vertical axis represents a specific value of the discharge flow rate (target discharge amount) Xo that determines the cylinder speed. In this hydraulic circuit control device, when the operating amount xL of the operating lever 7 is in the range F, the discharge amount of the variable displacement pump 1 is 0, and the operating amount txt of the operating lever 7 is A, A'.
When this happens, the variable displacement pump 1 starts discharging, and from then on,
A device including the variable displacement pump 1 is set to discharge pressurized oil at an amount proportional to the operating amount XL of the operating 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, the specific value X is determined by calculating the difference between the specific value (target discharge amount) Xo determined based on this metering table and the actual discharge amount of the hydraulic circuit. It is possible to calculate the operation N x L of the operating lever 7 necessary to obtain the discharge amount.

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 when the head side of the hydraulic cylinder 4 has high pressure, and outputs a high level signal when the rod side of the hydraulic cylinder 4 has high pressure. In addition, when the pressure on the head side and rod side of the hydraulic cylinder 4 is the same, the proximity switches 12 and 13 both output low level signals, and R
It is designed to output .

Control in the control device 8' is performed, for example, according to the procedures shown in the flowcharts of FIGS. 12 and 13. In addition, in this flowchart, P is the pressure detector 9.
P and I are pressure values detected by the pressure detector 10, and ΔX is an increment corresponding to the amount of change in the discharge flow rate of the variable displacement pump 1.

First, in step S-100, the control lever 7 is operated 11
L, the pressure signals PL2 and PR of the pressure detectors 9 and 10, and the tilting amount Y of the pump swash plate are read, and the pressure signals R of the proximity switches 12 and 13 are read via the input device 8g. Next, in Stella 7'S-101, the 12th
Based on the metering table shown in the figure, the central processing unit 8c performs processing to convert the operation ffi XL of the operating lever 7 into a specific value (target discharge XO). 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 according to the procedure shown in FIG. 13.

That is, first, in step S-201, it is determined whether the pressure signal of the proximity switch 12 is 1 or 0.
＼ If it is determined that L=1, the process moves to step S-202.
In order to indicate that the rod side of the hydraulic cylinder 4 is under high pressure, processing is performed to set the load direction flag f to (-), and the process moves to step S-102.

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

If it is determined in step S-203 that the R key is 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 then move on to step S-102.

Further, if it is determined in step S-203 that it is 1 during R, the pressure is the same on the head side and rod side of the hydraulic cylinder 4, so the process moves to step S-204 and f-0
After that, the process moves to step S-102.

In step S-102, the central processing unit 8c
It is determined whether the operation it XL is greater than or equal to the calculation start values A' to A.

If it is determined that the manipulated variable XL is within the range of the calculation start value A' to A, that is, if it is determined that it is within the unfavorable zone F of the metering table shown in FIG. 11, step S- 103, the central processing unit 8c performs a process of setting the first calculation value X1 calculated according to the procedure described later to 0, and the process moves to the next step S-104. In step S-104, 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 kept in the closed state shown in FIG.

Next, in step S-105, X=XO×X,
An operation is performed, and this X ” X o + X +
is stored in RAM8e. At this time, since the operation NxL of the operating lever 7 is within the dead zone F, Xo has a neutral value Xc. Next, the process moves to step S-8, where a signal is outputted 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.

Furthermore, when it is determined in step S-102 that the operating amount XL of the operating lever 7 is larger than the calculation start value A~A, it is determined in step S-106 whether or not the switching valve 6 was turned ON last time. be done.

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
It is determined whether the load direction flag f is (-).

If it is determined to be f key (-), proceed to the next step S-10.
8, it is determined whether the load direction flag f is (+).

If it is determined that rki(+), it means that f=o, so the process moves to step S-109, and the central processing unit 8C performs processing to set XL=O. Next, in step S-110, 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. Thereafter, in step S-111, the discharge amount command value
Specific values X0 and x+ (=0) corresponding to the manipulated variable Xt of -7
The central processing unit 8C performs a calculation to obtain a second calculation value, which is the sum of (X = Xo + X+). after that,
Proceeding to step S-8, a signal for driving the diagonal 1rIila is outputted to the regulator 2 according to the discharge amount command value X (=Xo), the discharge amount of the variable displacement pump 1 is controlled, and the process returns to the start.

If it is determined in step S-107 that f=(-), the process moves to step S-112, and the central processing unit 8C sets the pressure value PR of the pressure detector 10 to a preset value C( (See FIG. 10) It is determined whether it is greater than or less than.

In step S-112, if it is determined that PR≧C, the process moves to step S-110 described above, and the switching valve 6
is switched to the open state, and in step S-111, a second calculated value is determined to be the discharge amount command value X-X0 +X, and in step S-8, the variable displacement pump 1 is
The discharge amount is controlled and the process returns to the start.

If it is determined in step S-112 that RR<C, the process moves to step S-113, where the central processing unit 8C performs a first calculation to subtract the increment ΔX from the calculation value XI, and then, Proceeding to step S-114, the OFF signal is sent from the central processing unit 8C to the switching valve 6 via the output device 8f.
The signal is output, the switching valve 6 is kept closed, and the process moves to step S-115. In step S-115,
Specific value X00 Calculated value X is the neutral value XC (=O) when the operation IXL of the operation lever 7 is within the dead zone F.

The central processing unit t8c performs a process of adding up the discharge amount command value X to obtain the discharge amount command value X. Thereafter, the discharge amount of the variable displacement pump 1 is controlled in step S-8, and the process returns to the start.

Furthermore, if it is determined in step S-107 that r is key (-), and if it is determined that j=(+) in step S-108, the process moves to step S-116, and the pressure detector 9
It is determined whether the pressure value PL is greater than or equal to the set value C.

In step S-116, the pressure value P of the pressure detector 9
If it is determined that L is equal to or greater than the set value C, the process moves to step S-110 described above and the switching valve 6 is switched to the open state.
The N signal is output, and then, in step S-111, a second calculated value is determined to set the discharge amount command value X=xo+xl, and in step S-8, the variable displacement pump 1
The discharge amount is controlled and the process returns to the start.

Further, the pressure value P is determined in step S-116.

is determined to be less than the set value C, step S-11
7, where the first step is to add the increment ΔX to the calculated value X1.
is performed, and then steps S-114 and S-1
15. Return to the start via S-8.

Further, in step S-102, it is determined that the operation IXL of the operating lever 7 is larger than the range to the calculation start value A'~, and in step S-106, the switching valve 6 was previously turned ON.
If it is determined that it was, it means that the hydraulic cylinder 4 was driven last time, so immediately proceed to step S-
In step S-110, an ON signal is output from the output device 8f to the switching valve 6, and the switching valve 6 is held in the open state. Then, in step S-111, a second calculation of X − Xo + X l is performed. be exposed. After that, the process moves to step S-8, the discharge amount of the variable displacement pump 1 is controlled, and the process returns to the start.

The conventional control device configured in this manner 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 obtain the second calculated value (""X.

Since the control is performed using a command signal having a discharge amount command ZX equal to .

By the way, as shown in FIG. 14, for example, the arm 22 (load 5) of the working machine 21 connected to the hydraulic cylinder 4 is
When performing an operation of driving from position to position B and then stopping at position B, when the load 5 is at position A, the rod side circuit of the hydraulic cylinder 4, that is, the variable displacement pump 1
When the load 5 reaches position B, pressure oil leaks from the head side circuit of the hydraulic cylinder 4, that is, from the discharge side of the variable displacement pump 1.

However, in the hydraulic circuit control device previously proposed by the applicant, no correction is made for the effect when the direction of the load is reversed during operation and the direction of pressure oil leakage changes accordingly. Therefore, if the operating lever 7 is operated beyond the dead zone, or if the operating lever 7 is operated beyond the dead zone and immediately returned to within the dead zone, the position of the load 5 will change from position A to position B. Even after the movement, the discharge amount of the variable displacement pump 1 may be corrected because pressure oil leakage is occurring on the suction side of the variable displacement pump 1.

For this reason, an inconvenience was discovered in which the switching valve 6 was switched to the closed state while pressure oil corresponding to the leakage 1 iqlt + qli was being supplied from the variable displacement pump 1 to the hydraulic cylinder 4, causing a shock to the hydraulic system. .

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is 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 shock when stopped. It is.

[Summary of the invention]

In order to achieve this object, the present invention adjusts the discharge flow rate of a variable displacement pump in a preset procedure when the amount of operation of a control lever exceeds a dead zone in which the speed of the actuator is not controlled by the control lever. The first calculated value corresponding to the leakage flow rate from the variable flow pump is calculated, and when the operating lever is returned to the dead zone, the direction of the load acting on the actuator is detected, and the direction of the load acting on the actuator is determined. When a load is applied, the variable displacement pump corresponding to the operation amount of the control lever adds the first calculated value to the target value of the discharge flow rate, and a load is applied to the variable displacement pump in the suction direction. Sometimes, 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 control lever to obtain the second calculated value corresponding to the discharge command value of the variable displacement pump. When the difference between the discharge flow rate of the variable displacement pump and the second calculated value falls within a preset range, the switching valve is controlled to be closed. When the lever is operated beyond the dead zone, the direction of the load acting on the actuator is detected to obtain the second calculated value, and the discharge amount of the variable displacement pump is controlled according to this second calculated value. It is characterized by:

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. The hydraulic circuit and control device of this example are as follows:
This is exactly the same as that shown in FIGS. 8 and 9.

FIG. 1 is a flowchart of the entire operating procedure, FIG. 2 is a flowchart showing details of the operating procedure of step S-300, and FIG. 3 is a flowchart showing details of the operating procedure of step S-400.

In step S-102 of FIG. 1, it is determined that the operating amount X 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, the process moves to step S-300.

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 (->).

In step S-301, if it is determined that f=(-), the load state of the hydraulic cylinder 4 is such that the pressure on the rod side is high. Therefore, the leakage amount of variable displacement pump 1 qlL + q
lt is generated from the boat connected to the rod side of the hydraulic cylinder 4. Therefore, next step S-3
02, the central processing bag ff8c calculates the first calculated value X+= which is the leakage correction value of the variable displacement pump I.
The process of setting l Xr l is performed, and the next step S-3
Move to 06. In step S-306, the discharge amount command value X-X0+XI is calculated, that is, x = xo I
The calculation of Xl 1 is performed and the second calculation value X is determined.

However, the specific value X at this time. =Xc (=0).

Next, in step S-307, the discharge amount command amount X
Check whether the deviation of the swash plate tilting amount Y, which is the output signal of the displacement meter 3, is within a certain range α, that is, whether the discharge amount command value X and the actual swash plate tilting amount Y of the variable displacement pump l are A judgment is made as to whether or not they almost match. This range α is
As will be described later, this value is for determining the timing of switching 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 at the time of stopping. Therefore, the size of this range α is arbitrarily set in consideration of the practically required fine operability and degree of shock.

If it is determined in step S-307 that l Y-X l >α, the process moves to step S-308, where the output device 8f outputs an ON signal to the switching valve 6, keeping the switching valve 6 open, The process returns to the start via step S-8. Then, the operating procedure of the control device 8' is as described above for S-100.
-3-101→S-200→S-102-3-118-
3-300-3-8, when it is determined in step S-307 that the discharge amount command value X and the swash plate tilt IY of the variable displacement pump 1 are within the range of α. ,
In step S-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 changed to the discharge amount. Command value X (Xa
+Xl). Next, return to the start from step S-8, and step S-118 again.
When reaching , it is determined that the switching valve 6 was OFF last time, so in step S-103, ・Xt=
0, a signal is output to keep the switching valve 6 closed in step S-104, and step S-104 is performed.
At -8, an operation is performed to neutralize the swash plate tilting angle of the variable displacement pump 1.

Similarly, if it is determined in step S-301 that it is f key (-), and if it is determined that it is r- (+) in step S-303, it means that the head side of the hydraulic cylinder 4 is under high pressure. Therefore, step S-304
Control is performed according to the above procedure with xl=+lXI+.

Further, if it is determined in step S-301 that it is f key (-), and if it is determined that f key (+) in step S-303, then the head side and rod side of the hydraulic cylinder 4 are at the same pressure. Therefore, in step S-305, processing is performed to set X1=0, and then control is performed according to the above procedure.

In addition, in the operation procedure of this embodiment, step S in FIG.
- If it is determined in step S-102 that the operation it is determined to be larger than A, and step S
-118, the procedure when it is determined that the switching valve 6 was OFF last time is exactly the same as in the conventional example described above, so the explanation will be omitted.

Therefore, in the hydraulic circuit control device of this embodiment, step S
-102, it is determined that the operation amount X of the operation lever 7 is smaller than the calculation start values A' to A, and in step S
- If it is determined that the switching valve 6 was in the closed state last time at 118, the load correction at the time of stop is performed, and there is a 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. 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 l almost match, the variable displacement The leakage fq l i +qlt of the pump l can be offset by the first calculated value X1, and when the speed of the actuator (hydraulic cylinder 4) reaches approximately O, the switching valve 6 can be switched to the closed state. It can eliminate the shock when stopping.

The operations from step S-400 onwards will be explained below with reference to FIG. The operations following step S-400 relate to a procedure for correcting the direction of the load acting on the actuator during driving.

In step S-102 of FIG. 1, the operation amount X1 of the operation lever 7. is determined to be larger than the dead zone A'~A,
And, in step S-106, the previous switching valve 6 was
If it is determined that the hydraulic cylinder 4 and the variable displacement pump 1 are still connected to each other, the process moves to step S-400.

When step S-400 is reached, as shown in FIG. 3, first, in step S-401, the central processing unit 8c determines whether the load direction flag f is (=). Ru.

In steps S to 401, if it is determined that f-(-), the load state of the hydraulic cylinder 4 is such that the pressure on the rod side is high. Therefore, the leakage amount qli + q of variable displacement pump 1
lt is generated from a boat connected to the rod side of the hydraulic cylinder 4. Therefore, next step S-40
2, the central processing unit 8c calculates the first calculated value x + = which is the leakage correction value of the variable displacement pump 1.
The process of performing l x t is performed, and the process moves to step S-110 in FIG. Then, in step S-110, an ON signal is output to the switching valve 6, and then in step S-110, an ON signal is output to the switching valve 6.
111, the calculation of the discharge amount command value X=XO+X, that is, the calculation of x=xo l XI l is performed, and the second calculation value X is obtained. Thereby, the amount of leakage qli+q I t generated from the port of the variable displacement pump 1 connected to the rod side of the hydraulic cylinder 4 can be offset by the calculated value X1.

In step S-401, if it is determined that f is medium (-), the process moves to step S-403, where F= (+
) is determined.

If it is determined in step S-403 that f-(+), this means that the head side of the hydraulic cylinder 4 is under high pressure, so in step S-404
Processing is performed to set I=+lx+l. Then,
In step S-111, the calculation x=xo+XI is performed, and the amount of leakage qli+qlt generated on the head side of the hydraulic cylinder 4 of the variable displacement pump 1 can be offset.

Further, if it is determined in step S-401 that it is f-key (-), and if it is determined that it is f-key (+) in step S-303, the head side and rod side of the hydraulic cylinder 4 are at the same pressure. Therefore, in step S-405, processing is performed to set XI = OXIXl 1, that is, X, -0, and then control is performed in the same procedure as above.

In addition, in the operation procedure of this embodiment, step S in FIG.
-102, the operation IXL of the operation lever 7 is the calculation start value A'
~ If it is determined that it is smaller than A, and step S
-102, the operation amount X of the operating lever 7 is the calculation start value A'
~A is determined to be larger than A, and step S-102
The procedure when it is determined that the switching valve 6 was OFF last time is the same as that of the conventional example and the first embodiment, so the explanation will be omitted. By doing so, it is possible to eliminate the influence of leakage 1lqli+qlt of the variable displacement pump 1 not only when the actuator (hydraulic cylinder 4) is stopped but also during driving.

〔Effect of the invention〕

The hydraulic circuit control device of the present invention performs the following operations when starting the connection between the variable displacement hydraulic pump and the actuator, when the variable displacement hydraulic pump and the actuator are connected, and when ending the connection between the variable displacement 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, eliminating the need for an actuator when starting the connection between the variable displacement hydraulic pump and the actuator. This not only prevents unnecessary movement of the 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, and when the variable displacement pump and actuator are disconnected. is prevented, and the fine operability of the actuator can be further improved. Therefore, the operability of machines to which this hydraulic circuit control device is applied and the safety of workers tasked with operating these machines can be significantly improved.

[Brief explanation of drawings]

1, 2, and 3 are flowcharts showing an example of the operation procedure performed by the hydraulic circuit control device according to the present invention, FIG. 4 is a circuit diagram showing an example of a conventional hydraulic circuit, and FIG. 5 6 is a block diagram showing an example of a control device applied to control a conventional hydraulic circuit, FIGS. 6 and 7 are flow charts showing an example of operating procedures performed by the conventional control device, and FIG. 8 is a block diagram showing an example of a control device applied to control a conventional hydraulic circuit. A circuit diagram showing another example of the circuit,
FIG. 9 is a block diagram showing another example of a control device applied to the control of a conventional hydraulic circuit, and FIG. 10 is a graph showing the relationship between the tilting angle, discharge pressure, and cylinder speed of a variable displacement pump.
11 is a metering table showing the basic principle of control performed by the control device shown in FIG. 9; FIGS. 12 and 13 are flow charts showing an example of the operation procedure performed by the control device shown in FIG. FIG. 14 is an explanatory diagram for explaining the disadvantages of the prior art. l......Variable displacement pump, 1a...
...Swash plate, 2...Regulator, 3
......Displacement meter, 4...Hydraulic cylinder, 5...Load, 6...
...Switching valve, 7......Operating lever 8.
8'......Control device, 8a...
...Multiplexer, 8b...A/D converter, 8C...Central processing unit, 8d
・・・・・・・・・ROM, 8e・・・・・・・・・R
AM, 8f... Output device, 8g...
...Input device, 9.10...Pressure detector, 11...Shuttle, 12.13...
·······Proximity switch. Shima 8 Ward No. 11 Figure 10 Figure 10

Claims (1)

[Scope of Claims] A variable displacement pump, an actuator connected to the variable displacement pump in a closed circuit through at least two main pipes, and a variable displacement pump interposed between the variable displacement pump and the actuator, A hydraulic circuit having a switching valve that connects and disconnects the flow of pressure oil supplied from the pump to the actuator, a control means that controls opening and closing of the switching valve and a discharge flow rate of the variable displacement pump; and an operating lever connected to a control means, the variable displacement pump discharges in accordance with a preset procedure when the operating amount of the operating lever exceeds a dead zone in which the speed of the actuator is not controlled by the operating lever. Calculating the flow rate to obtain a first calculated value corresponding to the leakage flow rate from the variable displacement pump, and outputting a signal to open the switching valve when the discharge pressure of the variable displacement pump reaches a preset pressure. At the same time, the discharge flow rate of the variable displacement pump is determined based on the specific value of the discharge flow rate of the variable displacement pump corresponding to the operating amount of the operation lever and the first calculated value when the switching valve is opened. In a control device for a hydraulic circuit to be controlled, 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 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 operation lever, and when a load is applied in the suction direction of the variable displacement pump, the operation lever A second calculated value corresponding to the discharge command value of the variable displacement pump is obtained by subtracting 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 variable displacement pump. When the difference between the discharge flow rate of the displacement pump and the second calculated value falls within a preset range, the switching valve is controlled to close; When the operating lever is operated beyond the dead zone, the direction of the load acting on the actuator is detected to obtain the second calculated value, and the variable displacement pump discharges according to the second calculated value. A control device for a hydraulic circuit characterized by controlling the amount.