JPH03184700A - Detecting device for abnormal pressure of hydraulic circuit - Google Patents

Abstract

PURPOSE:To remove an apparent abnormal pressure by outputting an alarm only when an abnormal pressure is detected in a rough cycle and an abnormal pressure is found in a supplementary test of fine interval which is made continuously in an abnormal pressure detecting device of a hydraulic circuit of the digital sampling system. CONSTITUTION:In an abnormal pressure detecting device of hydraulic circuit driving a mobile body by a cylinder device with a hydraulic circuit containing a servo valve, an operating pressure of the servo valve is detected by a pressure sensor and compared with a reference pressure to detect the abnormal pressure. In this case, only when an abnormal pressure by an ordinary sampling time is found and an abnormal pressure is found in a continuously performed short sampling time, an alarm is outputted. Thus, apparent abnormal pressure by a noise can be removed and an alarm can be outputted quickly to actual abnormal pressure.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an abnormal pressure detection device for a hydraulic circuit.

(Prior Art) In a hydraulic circuit, the operating pressure of the circuit must be appropriate. For example, in a bending machine, a servo valve is included in the hydraulic circuit, and by controlling a cylinder device via this servo valve, a ram is driven, and a movable mold attached to this ram is moved. On the other hand, since the bending of the plate material is performed by precisely controlled operations between the movable mold and the fixed mold, the operating pressure must be kept constant in order to precisely operate the movable mold.

Conventionally, an abnormal pressure detection device for a hydraulic circuit that detects that the pressure is above a certain value or within a certain range, for example, when detecting that the pressure is above a certain value,
Detection pressure is P1 Reference pressure is P.

As such, when P≧po, it was determined that the pressure was abnormal. Furthermore, in the digital sampling method, Pmilo is detected at every preset sampling time.

(Problem to be Solved by the Invention) However, in the abnormal pressure detection device for a hydraulic circuit using a digital sampling system as described above, since the sampling interval is set to a constant value (for example, 60 m5),
There is a problem in that if an alarm is output for a single abnormality, an apparent abnormality due to noise will be detected. Furthermore, if an alarm is output when an abnormality occurs multiple times in order to avoid the influence of noise, there is a problem in that it takes too much time to output the alarm.

In general, the above-mentioned sampling interval is set in relation to other control members, so it cannot be shortened beyond a certain point.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an abnormal pressure detection device for a hydraulic circuit using a digital sampling system, which can eliminate apparent abnormal pressure caused by noise, and can promptly output an alarm in case of actual abnormal pressure. purpose.

[Structure of the Invention] (Means for Solving the Problems) The present invention for solving the above problems has a hydraulic circuit including a servo valve, and drives a moving body such as a ram by a cylinder device connected to the servo valve. The abnormal pressure detection device for a digital sampling type hydraulic circuit as described above includes a pressure sensor for detecting the operating pressure of the servo valve, and a comparison means for comparing the pressure value detected by the sensor with a reference pressure to detect abnormal pressure. , the first one that sets the sampling time of this comparison means.
timing setting means; and when the comparing means detects abnormal pressure at the normal timing set by the means, the first
a second timing setting means for outputting a second comparison command to the comparison means after a time considerably shorter than the time set by the timing setting means; The present invention is characterized by comprising an abnormal pressure notifying means that notifies that the actual pressure is abnormal pressure when detected.

(Function) In the abnormal pressure detection device for a hydraulic circuit using a digital sampling system of the present invention, the sampling interval (for example, 60 m5) is usually determined by the first timing setting means, and the detected pressure is compared with the reference pressure by the comparison means. .

When abnormal pressure is detected by the comparison means, the second timing setting means immediately performs the next sampling at a fairly short interval (for example, 1 m5), and the detected pressure is compared with the reference value. For example, an alarm is output when an abnormality is detected.

Therefore, an apparent abnormality due to noise is not determined by one abnormal pressure detection, and an actual abnormal pressure, not an apparent abnormal pressure due to noise, can be detected by the second abnormal pressure detection. Here, since the second abnormal pressure detection is performed in a time considerably shorter than the normal sampling interval compared to the first time, a large detection delay does not occur.

(Example) The present invention will be explained in detail below.

Figure 2 shows the hydraulic circuit of the bending machine.

In the figure, in the bending machine of this example, a pair of cylinder devices CYLI and CYL2 are arranged at both ends of a ram 1 extending left and right when viewed from the front side of the bending machine main body, and both cylinder devices CY
The ram 1 is driven up and down by simultaneously hydraulically driving the pistons PSTI and 2 of LI and CYL2. Linear scales LSCI, 2 are installed at both ends of ram 1.
is fixed, and by detecting this linear scale LSCI, 2 with a position detector (not shown), the vertical position of the ram 3 can be managed.

In the illustrated bending machine, a punch is fixed to the lower part of the ram 1, a die holder (not shown) is placed directly below the ram 1, and a die (not shown) placed above the die holder is placed above the die holder (not shown). The workpiece is bent by moving the ram 1 toward and away from the workpiece.

The hydraulic circuit includes an oil pump P that sucks oil in an oil tank OT shown at the bottom of the figure via a suction filter SFN and discharges it to a pipe OLI via a line filter ILF. Line filter ■LF is provided with a pressure switch PS1 for detecting a pressure difference between its input and output sides and for detecting clogging thereof. The pipe OLI is provided with a proportional solenoid valve 5OLE for pressure adjustment, and a pressure switch PS2 for detecting a pressure increase.

An oil purifier 2 is arranged on the side of the oil tank OT.

The piping OLI includes the cylinder devices CYL1, CY.
Two directional and flow adjustable servo valves SVI for driving L2 respectively.

SV2 is provided.

First, let's look at the circuit including the servo valve SVI on the left side of the diagram.The servo valve SVI can connect two boats on the - side to two boats on the other side in parallel or in a crossed manner by inputting an electrical signal. The two boats on one side are connected to the pipe OLI and drain pipe OL2.

One of the other two boats of the servo valve SVI is connected to the cylinder device CYL1 via piping OL3.
It is connected to the upper chamber of. Also, the other boat is a plumbing office worker.
4, and this piping OL4 is connected to piping OL5 via a pilot logic valve Lv1, and this piping OL4 is connected to piping OL5 via a pilot logic valve Lv1.
5 is connected to piping OL6 via a counterbalance valve CBVI. A bypass pipe OL7 equipped with a logic valve LV2 with a pilot is provided between the pipes OL5 and OL6.
is provided. Piping OL6 is connected to the cylinder device CY.
It is connected to the lower chamber side of L1. The logic valve Lv
The pilot section 1 is connected to the pipe OL7 or the drain pipe via the solenoid valve 5OL3. Further, the pilot portion of the logic valve Lv2 is connected to the piping OL6 or the drain pipe via the solenoid valve 5OL4. A pressure switch PS3 is provided in the pipe OL6.

A pipe OL8 is connected to the upper chamber of the cylinder device CYL1, and a drain pipe is connected to the pipe OL8 via a logic valve LV3 with a pilot. The pilot part of this logic valve LV3 is a solenoid valve 5OL5.
The pilot pressure of the pipe OL1 can be inputted via the pipe OL1.

The same applies to the other cylinder device CYL2. Corresponding parts are shown with the same reference numerals. A pressure sensor 3 is provided between both pipes OL3.

In the hydraulic circuit having the above configuration, for example, for the left circuit, the servo valve SVI is in the state shown, and the piping O
It is assumed that pressure oil flows into the upper chamber of the cylinder device CYL1 via LI. Then, the solenoid valve 5O is turned on based on the turning-on operation of the descending foot pedal (not shown).
L3 opens the logic valve Lv1, and the oil in the lower chamber flows into the pipe OL4 via the pipe OL6, the counterbalance valve CBv1, and the logic valve LVI.

On the other hand, when the servo valve Sv1 is operated in the opposite direction, the piping OL
Pressure oil of I is connected to pipe OL4. It flows into the lower chamber of the cylinder device cYL, 1 through OL5, logic valve LV2, and piping OL6, and moves up the ram 1. Cylinder device eCYL2
The same applies to During this time, the pressure sensor 3 is connected to the pipe OL.
3 pressure is detected.

FIG. 1 is a block diagram of a control device that controls the hydraulic circuit configured as described above.

In the figure, an NC device (NC) 4 that controls the above-mentioned bending machine
A programmable controller (PC) 5 is connected to the , and a manual data input device (MDi) 6 is connected to the .
and CRT7 are connected.

A digital input (Di) 8 and a digital output (Do) 9 are connected to the PC 5, and Di8
Do9 has a sensor group 10, and Do9 has an actuator group 11.
is connected.

The sensor group 10 includes a foot pedal device switch for giving a lifting command to the ram 1 and a pressure switch of the hydraulic circuit, as well as various sensors such as various limit switches of the bending machine.

Further, the actuator group includes not only the solenoid valve of the hydraulic circuit but also various actuators of the bending machine. However, the servo valve Sv1. SV2 is connected to the NC device 4 via a hydraulic position module (not shown). It is assumed that the analog signal detected by the pressure sensor 3 is appropriately converted into a digital value and given to a plurality of bits of Di8. Here, noise may be superimposed on the analog signal, resulting in an abnormal value.

The PC5 receives signals from the sensor group 10 and the NC4.
It inputs signals from the PC 5 and NC 4, and outputs predetermined control signals to the actuator group 11.

The PC 5 has a sequencer 12 for warm-up operation. Further, the NC device 4 has a pressure check section 13.

Examples of screen displays of the CRT 7 are shown in FIGS. 3 and 4. The screen 7A shown in FIG. 3 is the user parameter setting screen 7.
An explanatory diagram of A, FIG. 4 is an explanatory diagram of a screen 7B showing operating conditions during warm-up operation, for example.

In FIG. 3, setting items for various parameters are arranged on the screen 7A, so the user can
By operating i6, a predetermined value can be input into a predetermined item.

For example, it is possible to select warm-up operation in items 3 and 4.5, set the time, and set the oil pressure during warm-up operation.

Therefore, by inputting data for appropriate items in MD16 as described above, for example, during warm-up operation, the screen 7 shown in Figure 4
B is displayed and warm-up operation is executed. In FIG. 4, comments such as the remaining time of the warm-up operation are displayed on the screen 7B showing the operating conditions.

Figure 5 shows the image flow of warm-up mode.

When the NC power is turned on in step 501, step 50
In steps 2 to 507, the main motor is turned on with reference to an appropriate message display, and in step 508, the remaining time of warm-up operation is displayed and the main motor is turned on. -/B 509 = 513, warm-up operation is executed. Step 512 returns the process to step 508 unless the main motor is turned off.

Step 513 allows the timer time-up to be set explicitly.

At step 514, the warm-up operation is ended by turning on the time-up flag, and at step 515, it is determined whether the return to the origin is completed and an appropriate message is output.

FIG. 6 is a timing chart of the warm-up operation performed by the warm-up operation sequencer 12. By controlling the timing of each member shown in the figure, a smooth warm-up operation is executed while appropriately outputting messages in the process shown in FIG.

Therefore, by appropriately performing the warm-up operation as described above at the start of operation, the user can stabilize the hydraulic circuit by keeping the oil temperature at a constant value and perform predetermined bending with high precision.

Incidentally, if the warm-up operation method as described above is not adopted, the warm-up operation becomes arbitrary, and the hydraulic circuit cannot be stabilized. Further, even if the oil pressure is stabilized as described below, highly accurate bending cannot be performed.

Fig. 7 shows a method for comparing detected pressures. In the figure, the horizontal axis represents time, and the vertical axis represents pressure. A solid line P is a detection value detected by the pressure sensor 3. A number of lines shown intersecting the solid line P indicate noise N.

As shown in the figure, the noise N is superimposed on the signal line and appears instantaneously. The normal sampling period T1 is assumed to be 60 ms.

FIG. 8 is a flowchart of the pressure check process performed by the pressure check section 13.

In step 801, PkPo (Pa is a reference value) is determined.

If p<p□, it is normal, so the process moves to step 802 and waits for the next sampling. This waiting time is 60m
It is 5.

pap (, in the case of P≧po, the process moves to step 803, waits for a time T2 (1 ms) which is considerably shorter than the waiting time of step 802, determines papO in step 804 as in step 801, and when P≧po, an alarm is generated in step 805. Output.

In other words, even if the pressure is abnormal at time t1 shown in FIG. 7, the apparent abnormality due to the noise N is not mistaken, and the actual abnormal pressure is determined only when the abnormal value is still displayed even after time T2. Detect and output alarm.

Although one reference value Po is shown in FIGS. 7 and 8, the same applies to area designation.

Therefore, in this example, apparent abnormal pressure due to noise is not determined to be abnormal pressure, and an alarm is not outputted blindly. In addition, since an alarm can be output for actual abnormal pressure after time T2 (T2 <TI) has elapsed after time T1, an alarm can be outputted quickly for actual abnormal pressure.

As described above, in this example, the pressure can be kept constant in the hydraulic circuit that has been warmed up and stabilized, and in the event of an actual abnormality, an alarm can be immediately output to ensure the safety of the equipment.

In the above embodiment, one additional test was performed after time t1, but this may be repeated two or three times. in this case,
Abnormal pressure detection due to noise can be more reliably avoided, and only the time corresponding to the detection (n-T2 in the case of n times) is delayed.

The present invention is not limited to the above-mentioned embodiments, but can be implemented in any appropriate manner by making appropriate design changes.

[Effects of the invention] As described above, in the present invention, when abnormal pressure is detected at a rough sampling period, additional tests are performed at small intervals, and only when abnormal pressure is detected in this additional test, for example, an alarm is output. Instantaneous abnormal pressure caused by noise is not detected, and actual abnormal pressure can be quickly processed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control device for a bending machine equipped with an abnormal pressure detection device for a hydraulic circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a hydraulic circuit, and FIGS. The figure is a CRT
Figure 5 is a flowchart showing the warm-up operation method, Figure 6 is its timing chart, Figure 7 is an illustration showing the oil pressure sampling method, and Figure 8 is a flowchart of abnormal pressure detection processing. be. 3...Pressure sensor 7...CRT 12...Sequencer for warm-up operation 13...Pressure check section P...Detected pressure Po...Reference value

Claims (1)

[Claims] In an abnormal pressure detection device for a hydraulic circuit of a digital sampling system, which has a hydraulic circuit including a servo valve and drives a moving object such as a ram by a cylinder device connected to the servo valve, the operating pressure of the servo valve is detected. A pressure sensor for detecting, a comparison means for comparing the pressure value detected by the sensor with a reference pressure to detect abnormal pressure, a first timing setting means for setting the sampling time of the comparison means, and a first timing setting means for setting the sampling time of the comparison means; second timing setting means for outputting a second comparison command to the comparing means after a time considerably shorter than the time set by the first timing setting means when the comparing means detects abnormal pressure at the timing; An abnormal pressure detecting device for a hydraulic circuit, characterized in that the abnormal pressure detecting device for a hydraulic circuit is equipped with an abnormal pressure notifying means for notifying that the actual pressure is an abnormal pressure when the comparing means detects an abnormality at a second timing set by the means. .