JPH0340678B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION This invention relates to a mold contact detection device in a hydraulic press.

The slide of the hydraulic press is raised and lowered by a cylinder for raising and lowering the slide. The descending speed of the slide until the upper and lower molds come into contact with each other is mainly controlled by the amount of pressure oil discharged from the pressure oil chamber on the rod side of the hydraulic cylinder. In a hydraulic press, in order to bring the upper mold attached to the slide into gentle contact with the lower mold on the bolster without impact, the rod side of the hydraulic cylinder for raising and lowering the slide is pressed before the upper and lower molds come into contact with each other. The lowering speed of the slide is reduced by reducing the amount of pressure oil discharged from the pressure oil chamber. A state in which the amount of pressure oil discharged from a hydraulic cylinder is kept low is called a slow fall state. The stroke position of the slide (delay start position) at which deceleration of the descending speed of the slide should start is determined in advance, and is detected by a detector such as a limit switch. Further, the time for maintaining the delayed falling state is set in advance in a timer. When the time set by the timer has elapsed, sufficient pressure oil is supplied to the pressure oil chamber on the tail side of the hydraulic cylinder for lifting and lowering the slide in order to carry out the predetermined press working, and the slide is pushed down by a large pressing force.

However, with this method, if the delayed descent start position is set too high or the timer is set too short, the delayed descent state will be canceled before the upper and lower molds come into contact with each other. Sometimes I put it away. Then, before the upper and lower molds come into contact with each other, a large amount of pressure is applied to the slide, causing the slide to descend at high speed. Since the molds come into contact with each other in this high-speed descending state, there is a problem that the molds and the molded product are damaged. In addition, safety devices that are generally used to prevent danger from slides, such as devices that stop the slide when the worker's hands are removed from the slide activation pushbutton, are released when the slow descent state ends, so as mentioned above, However, it is extremely dangerous if the slow-down state is canceled before the upper and lower molds come into contact with each other.

Conversely, if the late descent start position is set too low,
If the timer is set too long, the slow falling state will continue for a while even after the upper and lower molds come into contact, resulting in a problem that the work speed will be slow and the work efficiency will be reduced.

In order to solve the above-mentioned problems, when the upper and lower molds come into contact with each other, the slow-down state can be canceled and a large pressing force can be applied to the slide. For this purpose, it is necessary to detect that the upper and lower molds are in contact with each other.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mold contact detection device for a hydraulic press that can detect that upper and lower molds have come into contact with each other.

The mold contact detection device for a hydraulic press according to the present invention includes a speed detection means for detecting the descending speed of a slide of a hydraulic press, and a mold contact determination standard in which the descending speed of the slide detected by the speed detection means is predetermined. a speed reduction determination means for determining whether the slide descending speed has become equal to or less than the reference speed for mold contact determination; The present invention is characterized in that it includes a mold contact determination means that determines that the upper and lower molds have contacted each other when it is determined multiple times in succession that the slide descending speed has become equal to or less than the reference speed for mold contact determination. The reference speed for mold contact determination is set to a value smaller than the descending speed of the slide in the slow descending state.

In the mold contact detection device for a hydraulic press according to the present invention, the speed reduction determining means determines whether the descending speed of the slide has become equal to or less than a predetermined reference speed for determining mold contact. Then, when the speed reduction determining means determines that the slide descending speed has become less than the reference speed for mold contact determination, or the speed reduction determining means determines that the slide descending speed has become less than the reference speed for mold contact determination. When it is determined that the upper and lower molds have contacted each other multiple times in succession, it is determined by the mold contact determining means that the upper and lower molds have contacted each other.

When the upper and lower molds come into contact, the descending speed of the slide decreases, so that the slide descending speed becomes less than the reference speed for determining mold contact. Therefore, the contact between the upper and lower molds is accurately detected by the mold contact determination means. Since it is possible to cancel the slow descent state based on this mold contact detection, it is possible to bring the molds into contact with each other while the slide descends at a low speed, thereby preventing damage to the mold or molded product. This can be prevented and a large pressing force can be applied to the slide when the upper and lower molds come into contact with each other, making it possible to improve work efficiency. Also, safety can be maintained.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows a hydraulic circuit for raising and lowering a slide of a hydraulic press. The slide 1 is raised and lowered by a hydraulic cylinder 2. Switching of the pressure oil supply to the upper chamber 2U and lower chamber 2D of the hydraulic cylinder 2 is performed by a switching valve 3 with a pilot electromagnetic valve. As shown in FIG. 2, this switching valve 3 has a characteristic that the flow rate Q changes depending on the magnitude of the current I supplied to the ascending and descending solenoids 3U and 3D of the pilot solenoid valve. . When the slide is descending at high speed, current IH is supplied to solenoid 3D, and when descending at low speed, current IL is supplied to solenoid 3D, and at this time, the flow rates of pressure oil are QH and QL, respectively. The first port of the switching valve 3 is connected to the cylinder lower chamber 2D, the second port is connected to the cylinder upper chamber 2U, and the third port is connected to the main pump 4.
The fourth ports are respectively connected to the tank 5 via conduits. The input port of the pilot solenoid valve of the switching valve 3 is connected to the auxiliary pump 6, and the output port is connected to the tank 5 via conduits.

The upper chamber 2U of the cylinder 2 is further connected to the tank 5 via a conduit provided with a check valve 7 with a pilot. Check valve with pilot 7
The pilot port is connected to the auxiliary pump 6 via a conduit provided with a normally closed solenoid operated switching valve 8. The check valve 7 is a switching valve 8
is closed and pressure oil is not supplied to the pilot port from the auxiliary pump 6, the flow of pressure oil from the cylinder upper chamber 2U to the tank 5 is prevented. When the switching valve 8 is opened and pressure oil is supplied to the pilot port, the cylinder upper chamber 2U is opened to the tank 5. Switching valve 3 and cylinder upper chamber 2
A conduit connecting U, a conduit connecting the switching valve 3 and the main pump 4, and an auxiliary pump 6 and the switching valve 3,
A safety valve 9 is provided in each conduit connecting the two.

A pressure switch is installed in the conduit connecting the switching valve 3 and the cylinder upper chamber 2U to detect when the slide has been lowered to the lower limit position (the slide stroke position at which pressurization for press working should be finished). 10 are provided. A rack 11 is fixed to the slide 1 and moves up and down as the slide 1 moves up and down. This rack 11 has a pinion 13 fixed to the rotating shaft of an absolute encoder 12 for detecting the stroke position of the slide 1.
are interlocking. The absolute encoder 12 is attached and fixed to a press frame (not shown) or the like. In this embodiment, the absolute encoder 12 outputs a signal indicating the current position of the slide with respect to the upper surface of the bolster (not shown), and this position detection signal represents the distance from the upper surface of the bolster to the lower surface of the slide 1. ing.

FIG. 3 shows the electrical configuration of the slide elevation control device. The slide elevation control device is controlled by a central processing unit CPU20. CPU20
, an upper limit position setting signal from the slide upper limit position setter 24 for setting the upper limit position of the slide stroke (this is determined according to the height of the mold, etc.), and an upper limit position setting signal from the delayed fall start position setter 25. delay start position setting signal, absolute encoder 12
The position detection signal from the clock pulse generator 23 is input through the input interface 26, and the clock pulse from the clock pulse generator 23 is input. In this embodiment, the distance from the upper surface of the bolster to the determined upper limit position of the slide stroke and the distance from the upper surface of the bolster to the determined slow descent start position are set in each of the setting devices 24 and 25, respectively. The CPU 20 determines whether the current position of the slide detected by the absolute encoder 12 has reached the upper limit position set in the setting device 24, and sets the current slide position when the slide 1 is being lowered. A judgment is made as to whether the position has reached the late fall start position set in the container 25, and a mold contact detection process, which will be described later, is performed.
The CPU 20 is a ROM that stores the execution program.
21 and setters 24 and 25, respectively, and a RAM 22 that stores the upper limit position and slow-down start position set in the setters 24 and 25, and a reference value for determining speed reduction used in the mold contact detection process.

The CPU 20 outputs an H level when the current slide position detected by the absolute encoder 12 is lower than the upper limit position set in the setting device 24, and an L level when the current slide position becomes equal to the upper limit position. When the first detection signal a and the slide 1 are lowered,
When the current slide position detected by the absolute encoder 12 becomes equal to the slow descent start position set in the setting device 25, it is determined that the upper and lower molds have contacted each other in the mold contact detection process. The second detection signal b, which remains at H level until detected, is output to the valve drive control circuit 28 via the output interface 27.

The valve drive control circuit 28 receives the detection signals a and b.
In addition, there is an operation start signal c from an operation start switch 29 which is provided on the operation panel (not shown) and is turned on by the operator when starting the operation of the press, and a lower limit position detection signal from the pressure switch 10. d has been input. The valve drive control circuit 28 is
Based on these input signals a to d, the switching valves 3,
This controls the current supplied to solenoids 3D, 3U, and 8S of No.8.

The operation of the slide lifting device will be described below with reference to FIGS. 1 to 4. When the operation start switch 29 is turned on by the operator and the operation start signal c is inputted to the valve drive control circuit 28 while the slide 1 is at the upper limit position set in the setting device 24, the operation start signal c is inputted from the valve drive control circuit 28. A current IH (see FIG. 2) is sent to the lowering solenoid 3D of the switching valve 3. Then, the switching valve 3 is switched to the position PD, and pressure oil is supplied from the pump 4 to the upper chamber 2 of the cylinder 2.
At the same time, the lower chamber 2D of the cylinder 2 is opened to the tank 5. In this case, the gravitational force due to the slide 1's own weight is greater than the pressing force of the piston of the cylinder 2 due to the pressure oil sent to the upper chamber 2U of the cylinder 2, so the slide 1 is lowered at high speed by its own weight. Therefore, the descending speed of the slide 1 is mainly controlled by the discharge flow rate of pressure oil from the lower chamber 2D of the cylinder 2. Upper chamber 2U
Even though the amount of oil supplied to the lower chamber 2D and the amount of oil discharged from the lower chamber 2D are almost equal, the volume on the lower chamber 2D side is smaller by the volume of the rod, so the upper chamber 2U is running out of oil. is subject to negative pressure. As a result, the insufficient amount of oil is sent to the upper chamber 2U through the check valve 7.

When the slide 1 starts descending, the current slide position becomes lower than the set upper limit position, so the first detection signal a becomes H level.

When the slide 1 descends at high speed and the current slide position detected by the absolute encoder 12 becomes equal to the set slow descent start position,
At the same time that the mold contact detection process by the CPU 20 is started, the second detection signal b becomes H level.
When the second detection signal b reaches H level, the valve drive control circuit 28 reduces the current IH supplied to the solenoid 3D to IL. By this,
The flow rate of the switching valve 3 decreases from QH to QL, and the flow rate of pressure oil discharged from the lower chamber 2D of the cylinder 2 decreases, so that the descending speed of the slide 1 becomes very slow (slow descending state).

The mold contact detection process is a process that detects contact between the upper mold and the lower mold by detecting that the descending speed of the slide 1 has further decreased from a slow speed in the slow descending state, and the processing procedure is as follows: is shown in FIG. Absolute encoder 1
When the current slide position detected by step 2 becomes equal to the set slow descent start position A (step 3
1), reading of clock pulses from the clock pulse generator 23 is started (step 3).
2). When the first clock pulse is input, the position detection signal from the absolute encoder 12 is read, and the current slide position B1 is set to B1.
The data is stored in the buffer (step 33). next
An operation A-B1 is performed to subtract the current slide position B1 stored in step 33 from the late descent start position A already stored in the RAM 22.
This calculation result C1 is stored in the C buffer (steps 34, 37). Then, the process returns to step 32 and the second clock pulse is input.

When the second clock pulse is input,
The slide position detection signal is read again, and the current slide position B2 is stored in the B buffer (step 33). As a result, the contents of the B buffer are updated from B1 to B2. Since this is the second clock pulse, the process proceeds from step 34 to step 35, where the calculation (A-B2)-C1 is performed. C1=A
-B1, the calculation result D1 is the difference (B( 1)-B(2)), that is, it represents the slide downward distance between both times. Next, it is determined whether or not this calculation result D1 is less than a reference value for speed reduction determination stored in advance in the RAM 22 (step 36). The reference value is set to a value smaller than the distance that the slide 1 descends in a time corresponding to the period of the clock pulse when the slide 1 is descending at a slow speed.

In step 36, if the calculation result D1 is less than the reference value, it is determined that the upper and lower molds have contacted each other, and the process proceeds to step 38, where the second detection signal b is inverted to L level. Then, the mold contact detection process ends.

If D1 exceeds the reference value in step 36, the process proceeds to step 37, where A-B2 is calculated, and the calculation result C2 is stored in the C buffer (step 37). As a result, the contents of the C buffer are
Updated from C1 to C2. Then, the process returns to step 32 and waits for the next clock pulse to be input.

Then, when the next clock pulse is input, the current slide position Bn is stored, (A-B(n))- in the same way as when the second clock pulse is input.
C(n-1)=(B(n-1)-B(n)=D(n-1
),
That is, the distance that slide 1 has descended from the time of inputting the previous clock pulse to the time of inputting the current clock pulse is calculated, and it is determined that D(n-1) is less than the reference value (steps 32 to 36).
If D(n-1) is less than the reference value, step 38
On the other hand, if (n-1) is larger than the reference value, the process proceeds to step 37.

D(n-1) determined in a process based on clock pulses input before the mold contacts
is larger than the reference value, so step 36
Then proceed to step 37. D(n-1) determined in a process based on the clock pulse input for the first time after the mold contacts, or
D(n-1) obtained in processing based on the input of the next clock pulse becomes less than the reference value. Therefore, after the moment of mold contact, the first clock pulse is input, or
At a time approximately equal to the time when the next clock pulse is input, the second detection signal b is inverted to the L level. By setting the period of the clock pulse to a minute time, the second detection signal b can be inverted to the L level at approximately the same time as the time when the mold comes into contact.

When the second detection signal b is inverted to L level by the mold contact detection process, the valve drive control circuit 2
8, the supply current to the descending solenoid 3D is
Increased from IL to IH. As a result, the flow rate of the pressure oil sent from the main pump 4 to the upper chamber 2U of the cylinder 2 increases from QL to QH, so a large pressing force acts on the piston of the cylinder 2, causing the slide 1 to descend. , a predetermined pressing process is performed.

Thereafter, the pressure switch 10 detects that the slide 1 has reached the lower limit position, and the lower limit position detection signal d is sent to the valve drive control circuit 28.
, the valve drive control circuit 28 stops supplying current to the descending solenoid 3D and supplies current to the ascending solenoid 3U and the solenoid 8S. As a result, the switching valve 8 is opened and pressure oil is sent from the pump 6 to the pilot port of the check valve 7, so that the upper chamber 2U of the cylinder 2 is opened to the tank 5 via the check valve 7. Further, the switching valve 3 is switched to the position PU, pressure oil is sent from the pump 4 to the lower chamber 2D of the cylinder 2, and the upper chamber 2U is opened to the tank 5 via the switching valve 3. As a result, the piston of the cylinder 2 is pushed up by the pressure oil from the pump 4, and the slide 1 is raised.

When the current slide position detected by the absolute encoder 12 reaches the set upper limit position, the first detection signal a is inverted to L level. Then, the valve drive control circuit 28 stops supplying current to the lifting solenoid 3U and the solenoid 8S. As a result, the switching valve 3 is switched to the neutral position, the switching valve 8 is closed, and the check valve 7 controls the cylinder 2.
The outflow from the upper chamber 3U to the tank 5 is prevented. As a result, the slide 1 stops at the set upper limit position and maintains that state.

In the above embodiment, the pressure switch detects that the slide has reached the lower limit position, but a lower limit position setting device is provided to set the lower limit position, and the pressure switch detects that the slide has reached the lower limit position. It may be arranged to detect that the slide has reached the lower limit position when the calculated current slide position becomes equal to the lower limit position set in the lower limit position setter.

In addition, in the mold contact detection process described above, step 3
If the calculation result in step 5 is below the standard value, the second
Detection signal b has been inverted to L level, but if the calculation result in step 35 becomes less than the reference value for the first time, memorize this and proceed to step 37 to input the next clock pulse. The second detection signal b may be inverted to the L level when the calculation result in step 35 is less than the reference value. In other words, the calculation result in step 35 is 2.
If the value is below the standard value twice in a row, signal b is set to L.
The level may be reversed. The signal b may be inverted to the L level when the calculation result in step 35 is below the reference value consecutively for an arbitrary number of times of three or more. By doing this, for example, even if large vibrations occur when the descending speed of the slide is slowed down to a very low speed at the slow descent start position, it is possible to prevent false detection of mold contact due to the vibrations. Ru.

Furthermore, in the mold contact detection process, AB(n) is calculated in step 37, the calculation result is stored in the C buffer, and (A-B(n) is calculated in step 35).
B(n))-C(n-1) is calculated and this calculation result D(n-1) is compared with the reference value in step 37.
Slide current position B stored in B buffer
(n) is stored in the C buffer, and in step 35, the previous slide current position B(n-1) stored in the C buffer is changed to the current slide current position B(n) stored in the B buffer.
Alternatively, it may be determined in step 36 whether the result of the calculation in step 35 (B(n-1)-B(n)) is less than or equal to a reference value.

Although the slide position is detected using an absolute encoder, other methods may be used.

[Brief explanation of the drawing]

Figure 1 shows the hydraulic circuit for raising and lowering the slide, Figure 2 is a graph showing the relationship between the current supplied to the solenoid of the switching valve with a pilot solenoid valve and the flow rate, and Figure 3 shows the electrical configuration of the slide raising and lowering control device. The block diagram, FIG. 4 is a time chart showing the relationship between the operation of each part of the slide elevation control device and the stroke position of the slide, and FIG. 5 is a flow chart showing the mold contact detection processing procedure by the CPU. 1...Slide, 14...Absolute encoder, 20...CPU, 21...ROM, 22...RAM,
23...Clock pulse generator.

Claims (1)

[Scope of Claims] 1. Speed detection means for detecting the descending speed of the slide of a hydraulic press, and whether the descending speed of the slide detected by the speed detection means has fallen below a predetermined reference speed for mold contact determination. and when the speed reduction determination means determines that the slide descending speed has become below the reference speed for mold contact determination, or the speed decrease determination means determines that the slide descending speed has become A mold contact detection device for a hydraulic press, comprising: mold contact determination means for determining that the upper and lower molds are in contact when it is determined multiple times in succession that the speed has fallen below a reference speed for mold contact determination. 2. The speed detecting means comprises position detecting means for detecting the position of the slide, and calculating means for calculating the amount of descent of the slide at regular intervals based on the detection of the position of the slide by the position detecting means. Mold contact detection device in hydraulic press. 3. The mold contact detection device in a hydraulic press according to claim 2, wherein the slide position detection means is an encoder.