JPH0160683B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a hydraulic circuit, which has a switching valve between a variable displacement pump and an actuator, and includes control means for controlling the speed of the actuator according to the discharge flow rate of the pump. In particular, the present invention relates to a hydraulic circuit control device that can improve operability.

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. Reference numeral 4 indicates an operating device, that is, an operating lever, which commands the discharge flow rate of the variable displacement pump 1 and also switches the on/off switching valve 3. Reference numeral 5 indicates an operation for turning the on/off switching valve 3 ON in accordance with the operating amount X _L of the operating lever 4. It is a control means that outputs a signal or an OFF signal and also outputs a command signal having a discharge amount command value X to the discharge amount control device 1a. 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 control means 5 described above is composed of, for example, a digital arithmetic unit, including an A/D converter 5a that converts an analog signal into a digital signal, and a central processor that performs various controls and arithmetic processing. It has a device (CPU) 5b, a memory 5c in which a control procedure program is set with a predetermined functional relationship, and a driver circuit 5d that outputs control contents to the discharge amount control device 1a. 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,
Lines 9 and 10 are respectively connected to the operating lever 4, the switching valve 3, and the discharge amount control device 1a.

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 zero. 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 to the switching valve 3.
is maintained in the closed state shown in FIG. Then step 3
As shown at 3, 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. 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. 1 and becomes open. Next, as shown in step 35, the central processing unit 5b calculates the operating amount X _L of the operating lever 4 and the discharge amount command value X stored in the memory 5c.
A process is performed to select a specific value X _O corresponding to the manipulated variable X _L from the functional relationship with the operation amount X L, and this X=X _O is set in the memory 5c. And step 33 and step 3
After step 5, 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 q1t that leaks from the discharge port (not shown) into the tank, and a flow rate q1i 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 in the circuit will increase due to the boom load being applied to cylinder 2, and the leakage flow rate will increase.
Both q1t and q1i become larger. In such a situation, when attempting to slightly operate the operating lever 4 to slightly move the cylinder 2, conventionally the switching valve 3 would close, as is clear from steps 31 and 34 in the flowchart of FIG. state to open state. As a result, cylinder 2 and variable displacement pump 1 communicate with each other, and cylinder 2 switches to a control mode based on the discharge amount of pump 1. Even if the discharge amount of pump 1 is almost 0, cylinder 2 is activated by the leakage flow rate q1t + q1i. Resulting in.

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 increased to q1t + q1i. This causes a situation in which the cylinder 2 falls by a corresponding amount, and in other words, the speed of the cylinder 2 cannot be controlled below the speed corresponding to the leakage flow rate, resulting in a problem of 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.

To achieve this objective, the present invention provides an actuator that is driven and loaded by a variable displacement pump, and an actuator that is interposed between these variable displacement pumps and the actuator to provide pressure that is supplied from the variable displacement pump to the actuator. In a hydraulic circuit having a switching valve that connects and disconnects the flow of oil, a control device for a hydraulic circuit that commands the discharge flow rate of a variable displacement pump and an operating device that commands switching of the switching valve. Calculation to determine the value that determines the discharge flow rate of the variable displacement pump by adding a compensation value that compensates for the leakage flow rate of the variable displacement pump to the discharge amount command value corresponding to the command amount output from the operating device when the valve is opened. The variable displacement pump is configured to have a means for controlling the discharge flow rate of the variable displacement pump according to the value determined by the calculating means.

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

Note that the first of the embodiments of the present invention described below
The basic schematic configuration of this embodiment is almost the same as that of the hydraulic circuit control device shown in FIGS. 1 and 2 described above. We will use Figure 2 and Figure 2.

In the first embodiment of the present invention, the control means 5
The operating lever 4 constitutes an operating device when the switching valve 3 is opened by the central processing unit 5b and the memory 5c.
A compensation value ΔX that provides a flow rate to compensate for the leakage flow rate qlt + qli of the variable displacement pump ₁ is added to the command value output from the variable displacement pump 1, that is, a specific value X _O of the discharge amount command value X corresponding to the manipulated variable X L. Calculating means for determining a value for determining the discharge flow rate of is configured. That is, in the memory 5c, a functional relationship between the operating amount X _L of the operating lever 4 and the discharge amount command value X is set, and a compensation value ΔX for compensating for the leakage flow rate qlt+qli is set. Note that the compensation value ΔX is a constant and has a value equal to the leakage flow rate qlt+qli that is assumed to occur on average during normal work performed in the hydraulic machine equipped with this embodiment. Further, as will be described later, the central processing unit 5b performs processing to select a specific value X _O of the discharge amount command value X corresponding to the operating amount X _L of the operating lever 4, and also performs a calculation of X _O +ΔX be.

In the first embodiment configured as described above, control is performed, for example, according to the procedure shown in the flowchart of FIG. 4. That is, first step 40
As shown in FIGS. 1 and 2, A/
The operating amount X _L of the operating lever 4 is read into the central processing unit 5b via the D converter 5a. Then step 4
As shown by 1, the central processing unit 5b determines whether the operating lever 4 can be operated, that is, whether the operating amount X _L is 0. At this time, if it is determined that the operating lever 4 is not operated, the process moves to step 42, and an OFF signal is output from the central processing unit 5b to the switching valve 3 via the driver circuit 5d.
This keeps the switching valve 3 in the closed state shown in FIG. Next, as shown in step 43, 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.

Further, if it is determined in step 41 that the operating lever 4 is being operated, the process moves to step 44.
An ON signal is output from the central processing unit 5b to the switching valve 3 via the driver circuit 5d, thereby switching the switching valve 3 from the state shown in FIG. 1 to the right and into the open state. Next, as shown in step 45, 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. In addition to performing the process of selecting X _O , the compensation value ΔX for compensating for the leakage flow rate qlt + qli stored in the memory 5c is read out and X _O +ΔX is calculated. And X=X _O +
ΔX is set in the memory 5c. Step 4 mentioned above
After Step 3 and Step 45, the process moves to Step 46, 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.

In the first embodiment configured in this way, whenever the switching valve 3 is opened, the discharge amount (specific value X _O ) corresponding to the operating amount X _L of the operating lever 4 and the variable displacement pump 1 are adjusted. A command signal having a discharge amount command value X obtained by adding the compensation amount (compensation value ΔX) for compensating for the leakage flow rate qlt+qli is output from the control means 5 to the discharge amount control device 1a, so that the cylinder pressure due to the influence of the leakage flow rate qlt+qli is output from the control means 5 to the discharge amount control device 1a. Therefore, the speed of the cylinder 2 can be controlled in accordance with the operating amount X _L of the operating lever 4.

FIG. 5 is a circuit diagram showing the embodiment of FIG. 2 of the present invention. In the same figure, 13 is the load pressure of the circuit
A pressure detector 14 detects P _L and a temperature detector 14 detects the temperature T _F of the pressure oil flowing through the circuit, which are respectively connected to the control means 5 . Note that the other members including the control means 5 are constructed in the same manner as those shown in FIGS. 1 and 2, for example.

In the embodiment shown in FIG. 2, the central processing unit 5b and memory 5c (each illustrated in FIG. 2) of the control means 5 control the operation amount X _L of the operating lever 40 when the switching valve 3 is opened. A calculation means is configured to obtain a value that determines the discharge flow rate of the variable displacement pump 1 by adding a compensation value ΔX that provides a flow rate to compensate for the leakage flow rate qlt + qli of the specified value X _O of the discharge amount command value X corresponding to , generally the leakage flow rate of variable displacement pump 1 is qlt+
qli depends on the circuit load pressure P _L as shown in Figure 7, and also depends on the pressure oil temperature in the circuit as shown in Figure 9.
Depends on T _F. Therefore, in the memory 5c, the functional relationship between the operating amount X _L of the operating lever 4 and the discharge amount command value X is set, and the load pressure P _L as shown in FIG. Leakage flow rate qlt + qli
and the functional relationship with the pressure specific value fP _L equal to the 10th
As shown in the figure, the functional relationship between the pressure oil temperature T _F and the specific oil temperature value fT _F , which is equal to the leakage flow rate qlt + qli shown in Fig. 9, is set in advance, and furthermore, the reference temperature considered in normal work, Reference pressure, e.g. 50
The cut-off setting value ΔX _O is set equal to the leakage flow rate qlt + qli occurring at 100 kg/cm ² at ℃. In addition, the central processing unit 5b calculates ΔX=ΔX _O・f as described later.
After calculating ( _PL )・f(T _F ), X=X _O +ΔX
It is designed to perform the following calculations.

In the second embodiment configured in this manner, control is performed, for example, according to the procedure shown in the flowchart of FIG. That is, first, as shown in step 50, the A/D of the control means 5 shown in FIGS.
The operating amount X _L of the operating lever 4, the load pressure P _L detected by the pressure detector 13, and the temperature T _F detected by the temperature detector 14 are sent to the central processing unit 5b via the converter 5a. is loaded. Next, as shown in step 51, the central processing unit 5b determines whether the operating lever 4 is being operated, that is, whether the operating amount X _L is 0. If it is determined that the operating lever 4 is not operated at this time, the switching valve 3 is turned off in step 52, and X=0 is set in the memory 5c in step 54, as in the first embodiment. Ru. Further, if it is determined that the operation is being performed in step 51 described above, the process moves to step 54 where the switching valve 3 is turned on, and then the process moves to step 55.

In this step 55, the central processing unit 5b
Load pressure P _L and pressure specific value f stored in c
The pressure specific value f(P _L ) corresponding to the load pressure P _L is selected from the functional relationship with (P _L ), and the pressure specific value f(P L ) corresponding to the pressure oil temperature T _F and the oil temperature specific value f(T _F ) is selected. Select a specific oil pressure value f (T _F ) corresponding to the temperature T _F of the pressure oil, read out the initial setting value ΔX _O , and calculate ΔX=
Calculate ΔX _O・f(P _L )・f(T _F ). Next, the process moves to step 56, and the central processing unit 5b determines a specific value X O 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. This process is performed to select the
From X _O and ΔX obtained in step 55, calculate X=X _O +ΔX. The discharge amount command value X obtained in this manner is set in the memory 5c. After steps 53 and 56 described above, the process moves to step 57, and the discharge amount of the variable displacement pump 1 is controlled in the same manner as in the first embodiment described above. Even in this way, the leakage flow rate qlt
The speed of cylinder 2 can be controlled without being affected by +qli.

Note that in the first and second embodiments described above, the control means 5
Although a digital arithmetic unit is used as the control means 5, it is also possible to construct the control means 5 by an analog arithmetic circuit. In addition, in the second embodiment, the compensation value ΔX is calculated based on the circuit load pressure P _L and temperature T _F.
are calculated, but these load pressures
The compensation value ΔX may be calculated based on only one of P _L and temperature T _F. In addition, the compensation value ΔX may be calculated based on an element related to the leakage flow rate other than the load pressure P _L and temperature T _F , and the compensation value ΔX may be calculated based on an element related to the leakage flow rate other than the load pressure P _L and temperature T _F. The compensation value ΔX may be calculated based on .

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 explaining a conventional hydraulic circuit control device and a first embodiment of the present invention, and FIG.
FIG. 3 is a flowchart illustrating a control procedure in a conventional hydraulic circuit control device, and FIG. A flowchart illustrating the control procedure in the embodiment, FIG. 5 is a circuit diagram illustrating the second embodiment of the present invention, and FIG. 6 is a flowchart illustrating the control procedure in the second embodiment of the present invention, FIG. 7 is a diagram showing the relationship between load pressure and leakage flow rate that is commonly seen, FIG. 8 is a diagram showing the relationship between load pressure and pressure specific value set in the second embodiment of the present invention, and FIG. FIG. 10 is a diagram showing the relationship between the temperature of pressure oil and the leakage flow rate which is commonly seen, and FIG. 10 is a diagram showing the relationship between the temperature of the pressure oil and the leakage flow rate set in the second embodiment of the present invention. 1... Variable displacement pump, 1a... Discharge amount 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, 13... Pressure Detector, 14...Temperature detector.

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 includes an operating device that commands the discharge flow rate of the variable displacement pump and commands switching of the switching valve. A value that determines the discharge flow rate of the variable displacement pump by adding a compensation value that provides a flow rate to catch the leakage flow rate of the variable displacement pump to the discharge amount command value corresponding to the command amount output from the operating device when the valve is opened. 1. A control device for a hydraulic circuit, comprising a calculation means for determining the value, and controlling a discharge flow rate of the variable displacement pump according to the value determined by the calculation means.