JPH02565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a hydraulic circuit that has a switching valve between a variable displacement pump and an actuator and controls the speed of the actuator in accordance with the discharge flow rate of the pump.

FIG. 1 is a circuit diagram showing the basic configuration of a control device for a hydraulic circuit of this type, and FIG. 2 is a block diagram showing an example of control means included in the control device shown in FIG. In Fig. 1, 1 is a variable displacement pump;
a is a discharge amount control device that controls the discharge flow rate of the variable displacement pump 1; 2 is an actuator, such as a cylinder, driven by pressure oil supplied from the variable displacement pump 1; and 3 is the variable displacement pump 1 and the cylinder 2.
This is an on/off switching valve that is interposed between the variable displacement pump 1 and the cylinder 2 to connect and disconnect the flow of pressure oil supplied from the variable displacement pump 1 to the cylinder 2. 4 commands the pump discharge flow rate of the variable displacement pump 1, and also controls the on/off switching valve 3.
An operating device, that is, an operating lever 5, outputs an ON signal or an OFF signal to the on/off switching valve 3 in accordance with the operating amount X _L of the operating lever 4, and outputs a discharge amount command value to the discharge amount control device 1a. It is a control means that outputs a command signal having X. Note that 6 indicates a load driven by the cylinder 2, and 7 indicates a relief valve interposed between the variable displacement pump 1 and the on/off switching valve 3.

As shown in FIG. 2, the above-mentioned control means 5 is composed of, for example, a digital arithmetic unit, and includes an A/D converter 5 that converts an analog signal into a digital signal.
a, a central processing unit (CPU) 5b that performs various controls and arithmetic processing, a memory 5c in which control procedure programs and predetermined functional relationships are set, and a driver circuit that outputs control contents to the discharge amount control device 1a. 5d. In the conventional hydraulic circuit control device, the functional relationship between the operation amount X _L of the operation lever 4 and the discharge amount command value X is set in the memory 5c constituting the control means 5. Also 8, 9,
Reference numeral 10 indicates lines connected to the operating lever 4, the switching valve 3, and the discharge amount control device 1a, respectively.

In the case of conventional hydraulic circuit control devices,
Control is performed according to the procedure shown in the flowchart of FIG. That is, first, as shown in step 30, the operation amount X _L of the operation lever 4 is read into the central processing unit 5b via the A/D converter 5a of the control means 5. Next, as shown in step 31, the central processing unit 5b determines whether the operating lever 4 is being operated, that is, whether the operating amount _XL is 0. At this time, if it is determined that the operating lever 4 is not operated, the process moves to step 32, and the switching valve 3 is transferred from the central processing unit 5b to the driver circuit 5d.
An OFF signal is output, thereby keeping the switching valve 3 in the closed state shown in FIG. Next, as shown in step 33, the memory 5c performs a process of setting the discharge amount command value X to 0 according to a command from the central processing unit 5b. Furthermore, if it is determined in step 31 that the operating lever 4 is being operated, the process moves to step 34, where an ON signal is output from the central processing unit 5b to the switching valve 3 via the driver circuit 5d. The switching valve 3 is switched to the right from the state shown in FIG.
It becomes open. Next, as shown in step 35, the central processing unit 5b determines a specific value corresponding to the operation amount X L from the functional relationship between the operation amount X _L of the operating lever 4 and the discharge amount command value _X stored in the memory 5c. Performs processing to select X _O , and this X = X _O is memory 5
It is set to c. After steps 33 and 35, the process moves to step 36, where a command signal having a discharge amount command value X is outputted from the central processing unit 5b to the discharge amount control device 1a via the driver circuit 5d. The discharge amount control device 1a controls the discharge flow rate of the variable displacement pump 1 according to this discharge amount command value X.

Conventionally, the hydraulic circuit control device configured as described above has had the following problems. That is, the variable displacement pump 1 generally has a
There is a flow rate qlt that leaks from the discharge port (not shown) into the tank, and a flow rate qli that leaks from the discharge port to the suction port as shown by arrow 12 in the figure.
Therefore, if this hydraulic circuit is applied, for example, to a circuit that operates the boom of a hydraulic excavator (corresponding to load 6), the pressure of the circuit will increase because the boom load is applied to cylinder 2, and the leakage flow rate will increase.
Both qlt and qli become larger. In such a situation, if you slightly manipulate the operating lever 4 to slightly move the cylinder 2, as is clear from steps 31 and 34 of the flowchart in Fig. 3, in the past, the switching valve 3 would close. state to open state. As a result, the cylinder 2 and variable displacement pump 1 communicate with each other,
The control mode of cylinder 2 is switched depending on the discharge amount of pump 1, even if the discharge amount of pump 1 is almost 0.
However, cylinder 2 will operate due to the leakage flow rate qlt + qli.

For this reason, even though the operating lever 4 is moved to raise the cylinder 2 slightly, the cylinder 2 may drop down, or even if the cylinder 2 is lowered only slightly, the leakage flow rate is qlt + qli. This causes a situation in which the cylinder 2 falls by a corresponding amount, in other words, it is not possible to control the speed of the cylinder 2 below a speed corresponding to the leakage flow rate, resulting in poor fine controllability. Such defects in fine operability are also a problem from the standpoint of protecting the safety of workers working on various hydraulic machines to which the above-mentioned hydraulic circuit control device is applied.

The present invention has been made in view of the actual situation in the prior art, and its purpose is to provide a hydraulic circuit control device that can control the speed of the actuator below the speed of the actuator corresponding to the leakage flow rate of a variable displacement pump. It's about doing.

The present invention achieves this objective. A variable displacement pump, an actuator that is driven by the variable displacement pump and subjected to a load, and an actuator that is interposed between the variable displacement pump and the actuator to cut off the flow of pressure oil supplied from the variable displacement pump to the actuator. In a hydraulic circuit having a switching valve that is in contact with the switching valve, in a control device for a hydraulic circuit that is equipped with an operating device that commands the discharge flow rate of a variable displacement pump and also commands switching of the switching valve, a command from the operating device to exceed the dead zone. A first calculation value that is a discharge amount command value to set the discharge flow rate of the variable displacement pump to exceed the leakage flow rate and reach a preset pressure setting value when the amount is output. a first calculation means, a valve opening control means for outputting a control signal to open the switching valve when the pressure reaches the set pressure value, a first calculation value obtained by the first calculation means and the above operation; a second calculation means for calculating a second calculation value that determines the discharge flow rate of the variable displacement pump by adding a discharge amount command value of the variable displacement pump corresponding to the signal output from the device; The discharge flow rate of the variable displacement pump is controlled according to the calculated value of No. 2.

The hydraulic circuit control device of the present invention will be described below.

Figure 4 is a characteristic diagram commonly seen in this type of hydraulic circuit, with the upper part showing the relationship between the pump tilting angle and the pressure in the circuit, and the lower part showing the relationship between the pump tilting angle and the pressure in the circuit. A tilt angle-cylinder speed characteristic diagram showing the relationship with cylinder speed is drawn. Note that 13 in the tilt angle-pressure characteristic diagram indicates relief pressure. In addition, in the tilting angle-cylinder speed characteristic diagram, + and - on the horizontal axis indicating the pump tendency angle indicate the tilting direction of variable displacement pump 1, and + and - on the vertical axis indicating the cylinder speed indicate the operating direction of cylinder 2. It shows. As can be seen from the dashed line 14 in FIG. 4, the pump tilt angle at which the cylinder speed is zero is the angle at which the pressure in the circuit increases. The present invention focuses on the relationship between the pump tilt angle, that is, the discharge amount of the variable displacement pump and the circuit pressure. In FIG. This is a preset pressure setting value that will be passed when the pressure is exceeded.

FIG. 5 is a circuit diagram showing the configuration of a control device for a hydraulic circuit of the present invention, FIG. 6 is an explanatory diagram showing the basic principle of control performed by the control device of the present invention, and FIG. 3 is a flowchart illustrating a control procedure in the embodiment shown in FIG.

In FIG. 5, 15 is a pressure detector for detecting the pressure in the circuit on the head side of the cylinder 2, and 16 is a pressure detector for detecting the pressure in the circuit on the rod side of the cylinder 2. Reference numeral 17 is a shuttle that moves in the horizontal direction in the drawing according to the height of the circuit on the head side and rod side of the cylinder 2. Reference numerals 18 and 19 are switches that output signals in accordance with the movement of the shuttle 17, such as proximity switches. . Note that pressure detectors 15 and 16
and the proximity switches 18, 19 are connected to the control means 5. In addition, the proximity switch 19 outputs a signal R at a high level (signal value 1) when the head side is at high voltage.
On the other hand, the proximity switch 18 outputs a low level signal L (signal value 0) at this time, and when the rod side of the cylinder 2 is under high pressure, the proximity switch 1
8 outputs a high level signal L, and the proximity switch 19 outputs a low level signal R. Note that when both the head side and rod side of the cylinder 2 are at the same pressure, the proximity switches 18 and 19 both output low level signals L and R.
Other basic configurations are the same as those shown in FIGS. 1 and 2 described above. That is, the control means 5 includes, for example, an A/D converter 5a, a central processing unit (CPU) 5b,
It is composed of a digital arithmetic unit having a memory 5c and a driver circuit 5d. The central processing unit 5b and memory 5c of the control means 5 are configured to control the leakage flow rate qlt+qli when the command amount, that is, the operation amount X _L that exceeds the dead zone is output from the operating lever 4 constituting the command means described later. , a first calculation value _X1 , which is a discharge amount command value for setting the discharge flow rate of the variable displacement pump 1 to reach the preset pressure setting value C mentioned above, is obtained.
a calculation means, a valve opening control means that outputs a control signal to open the switching valve 3 when the pressure reaches the set pressure C, and a first calculation value obtained by the first calculation means.
A _{second calculated value} ( It constitutes a second calculating means for calculating the discharge amount command value)X.

FIG. 6 is an explanatory diagram showing the basic principle of control performed by the control device of the present invention, in which the horizontal axis represents the operation amount X _L of the operating lever 4, and the vertical axis represents the discharge flow rate that determines the cylinder speed. A specific value of X ₀ is taken.
In FIG. 6, F is a dead zone forming a region where the speed of the cylinder 2 is not controlled by the operating lever 4, A and A' are predetermined values,
That is, it is a value that specifies the range of the dead zone F, and is a calculation start value corresponding to the point in time when the calculation for obtaining the above-mentioned first calculation value _X1 is started. The dead zone F is a range in which the discharge amount of the variable displacement pump 1 is always 0 and the switching valve 3 is always closed. In the control device of the present invention, the amount of operation of the operation lever 4
When X _L reaches the calculation start value A, A', the switching valve 3
The _first calculated value A specific value of the discharge amount command value X of the variable displacement pump 1 corresponding to the operation amount X _{L of}
A second calculation is performed by adding the first calculation value X ₁ to Then, cylinder 2 is operated.

Note that when the pressure on the actuator side is low, the switching valve is opened when the calculation start values A and A' are reached. Also, calculation start values A, A', pressure setting value C,
The correlation between the operating amount X _L of the operating lever 4 and the discharge amount command value X for giving the specific value X ₀ is set in advance in the memory 5c of the control means 5.

The control in the embodiment shown in FIG. 5 described above is as follows:
For example, this is carried out according to the procedure shown in the flowchart of FIG. In this flowchart,
P _L is the pressure value detected by the pressure detector 15;
P _R is the pressure value detected by the pressure detector 16;
ΔX indicates an increment corresponding to the amount of change in the discharge flow rate of the variable displacement pump 1.

First, as shown in step 60, the A/D of the control means 5
The operating amount X _L of the operating lever 4, the pressure values P _L and P _R of the pressure detectors 15 and 16, and the pressure signals L and R of the proximity switches 18 and 19 are read into the central processing unit 5b via the converter 5a. . Next, as shown in step 61, in this central processing unit 5b, the manipulated variable X _L is changed to the dead zone F.
It is determined whether the calculation start value A'-A is greater than or equal to the range of A'-A. At this time, the manipulated variable X _L is the calculation start value
If it is smaller than the range of A'-A, that is, if it is determined that it is in the dead zone F in FIG. Then, in step 63, the central processing unit 5b passes through the driver circuit 5d to the switching valve 3.
An OFF signal is output, thereby keeping the switching valve 3 in the closed state shown in FIG. Next, as shown in step 64, the central processing unit 5b sets _the current discharge amount command value X (=0) to the calculated value A command signal of the discharge amount command value X (=0) is output to the discharge amount control device 1a via the circuit 5d.

In addition, when it is determined in step 61 that the manipulated variable X _L is larger than the range of the calculation start value A'-A, the central processing unit 5b checks whether the switching valve 3 was previously turned ON as shown in step 66. is determined.
At this time, if the previous switching valve 3 was OFF, the process moves to step 67, where the central processing unit 5b determines whether the pressure signal L of the proximity switch 18 is 1 or 0. When the pressure signal L is 0, the process moves to step 68, where the central processing unit 5b determines whether the pressure signal R of the proximity switch 19 is 1 or 0. When this pressure signal R is 0, the values of both pressure signals L and R are 0, and the cylinder 2
The pressure on the head side and rod side of the actuator is almost the same, and almost no force is applied to the actuator. Therefore, the process moves to step 69, where X ₁ =0 is subsequently set in the central processing unit 5b. Next, as shown in step 70, the central processing unit 5b converts the discharge amount command value X into a second calculated value as the sum of specific values X ₀ and _{X 1 (} =0) corresponding to the operating amount An operation is performed to find the . Next, as shown in step 71, the driver circuit 5 is transferred from the central processing unit 5b.
An ON signal is output to the switching valve 3 through step d, and step 65
Then, the current discharge amount command value X (=X ₀ ) is commanded to the discharge amount control device 1a.

In step 67, when L=1, the process moves to step 72, where the central processing unit 5b determines whether the pressure value P _R of the pressure detector 16 is greater than or equal to a preset value C, and in this case, In step 70 described above, the discharge amount command value X=X ₀ +X ₁ is calculated to obtain a second calculated value. Next, the process moves to step 71, the switching valve 3 is opened, and the process moves to step 65. If the pressure value P _R is less than or equal to the set value C in step 72, the process moves to step 73, where the central processing unit 5b performs the first calculation of subtracting the increment ΔX from the calculated value _X1 , and then steps 63 and 64 , move on to 65.

If it is determined that L=0 in step 67 and R=1 in step 68, the process moves to step 74, where the central processing unit 5b determines whether the pressure value P _L of the pressure detector 15 is greater than or equal to the set value C. . If the pressure value P _L is equal to or higher than the set value C, the discharge amount command value X = X ₀ + X ₁ is determined as the second calculated value in step 70, the switching valve 3 is opened in step 71, and the This discharge amount command value X is then commanded to the discharge amount control device 1a. Also, in step 74, the pressure value
If it is determined that P _L is less than or equal to the set value C, a first calculation is performed in which an increment ΔX is added to the calculated value X ₁ in step 75, and then steps 63, 64, and 65 are performed.

In addition, if X _L is larger than the range of calculation start value A'-A in step 61 and the previous switching valve 3 was ON in step 66, it means that cylinder 2 was driven last time, and immediately proceed to step 70. Shift, the second of X = X ₀ + X ₁
calculations are performed. Then steps 63, 64, 65
Move to.

In the embodiment configured in this way, the pressure in the discharge side circuit of the variable displacement pump 1 is increased to approximately the same pressure as the head side circuit or rod side circuit of the cylinder 2 forming the high pressure side, and the pressure is maintained at that level. Open the switching valve 3 at , and calculate the second calculated value (=X ₀ +
Since the control is performed using a command signal having a discharge amount command value X equal to X ₁ ), the speed of the cylinder 2 can be controlled in accordance with the operation amount _XL of the operation lever 4.

Since the hydraulic circuit control device of the present invention is configured as described above, it is possible to perform speed control below the speed of the actuator corresponding to the leakage flow rate of the variable displacement pump, and has the effect of improving fine operability. be. Therefore, it is possible to prevent the actuator from operating unintentionally by the worker who operates the actuator, contributing to the safety of the worker.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram illustrating a conventional hydraulic circuit control device, and FIG. 2 is a block diagram showing an example of a control means constituting the hydraulic circuit control device shown in FIG.
FIG. 3 is a flowchart illustrating a control procedure in a conventional hydraulic circuit control means, and FIG. 4 is a pump tilting angle-pressure characteristic and pump tilting angle-cylinder generally seen in a hydraulic circuit to which the present invention is applied. A characteristic diagram showing speed characteristics, FIG. 5 is a circuit diagram showing a schematic configuration of an embodiment of the control device for a hydraulic circuit of the present invention, and FIG. 6 is a basic principle of control performed by the control device of the present invention. FIG. 7 is a flowchart illustrating the control procedure in the embodiment shown in FIG. 1... Variable displacement pump, 1a... Discharge rate control device, 2... Cylinder (actuator), 3...
On/off switching valve, 4... Operating lever, 5... Control means, 5a... A/D converter, 5b... Central processing unit (CPU), 5c... Memory, 5d... Driver circuit, 7... Relief Valve, 15, 16...pressure detector, 17...shuttle, 18, 19...proximity switch.

Claims (1)

[Claims] 1 A variable displacement pump, an actuator that is driven by the variable displacement pump and subjected to a load, and an actuator that is interposed between the variable displacement pump and the actuator to control the flow of pressure oil supplied from the variable displacement pump to the actuator. In a hydraulic circuit having a switching valve that connects and disconnects, the control device for the hydraulic circuit is equipped with an operating device that commands the discharge flow rate of the variable displacement pump and commands switching of the switching valve, wherein: When the command amount exceeding the dead zone is output, the leakage flow rate is exceeded, and
a first calculation means for calculating a first calculation value which is a discharge amount command value for setting the discharge flow rate of the variable displacement pump to reach a preset pressure setting value; Valve opening control means outputs a control signal for opening the switching valve, and a discharge amount of the variable displacement pump corresponding to a first calculation value obtained by the first calculation means and a signal output from the operation device. and a second calculation means for calculating a second calculation value that determines the discharge flow rate of the variable displacement pump by adding the command value, and the discharge flow rate of the variable displacement pump is determined according to the second calculation value. A control device for a hydraulic circuit.