JPH0229421B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold clamping force detection method for a toggle type mold clamping device, and more specifically, it is configured to be able to detect whether the mold clamping force is excessive or normal. The present invention relates to a mold clamping force detection method for a toggle type mold clamping device.

FIG. 1 shows a schematic structure of a toggle type mold clamping device to which the present invention is applied.

In FIG. 1, a link housing 3 and a fixed platen 4 are erected at both ends facing each other on a machine base 2 of a toggle mold clamping device 1, and these are connected by four tie bars 5 on the top, bottom, left and right. and is firmly fixed with tie bar nuts 6. Reference numeral 7 denotes a movable platen whose four corners are slidably fitted and supported by tie bars 5, and the movable platen 7 and the link housing 3 are telescopically connected by two sets of toggle links 8, either vertically or horizontally. ing. A hydraulic cylinder 9 for mold clamping is horizontally fixed to the link housing 3, and its piston rod 1
The active end of the crosshead 11 is fixed to the center of a crosshead 11 that connects the upper and lower toggle links 8.
Reference numeral 12 denotes a guide shoe that guides the movable platen 7 by slidingly contacting the lower surface thereof. A fixed mold 13 and a movable mold 14 are mounted on the fixed platen 4 and the movable platen 7 so as to face each other.

In the toggle mold clamping device 1 configured as described above, when pressure oil is fed into the head chamber 15 of the hydraulic cylinder 9, the piston rod 10 moves forward, and the movable platen 7 connected with the crosshead 11 and the link 8 moves forward. Mold clamping is performed by moving toward the fixed platen 4 side. Also, when pressure oil is fed into the rod chamber 16 of the hydraulic cylinder 9, the piston rod 10
moves backward, the movable platen 7 is separated from the fixed platen 4, and the mold is opened.

Figure 2 is a relationship diagram between the stroke of the clamping cylinder and the pressure inside the hydraulic cylinder during one molding cycle from the start of mold clamping to the completion of mold opening in a mold clamping device having a toggle mechanism. The stroke S of the clamping cylinder is shown, and the hydraulic cylinder internal pressure P is plotted on the vertical axis, and the solid line shows the mold clamping curve and the chain line shows the mold opening curve. Moreover, FIG. 2 shows a stroke-pressure diagram in a normal state with no abnormalities anywhere. As is clear in the figure, both molds 13 and 14 are moved from the mold clamping starting point _O1 .
During the stroke x leading to the so-called mold matching point O ₂ where the two contacts, the pressure b is maintained at approximately the pressure b while fluctuating between the pressure a and the pressure b. Also, the mold matching point
After passing O ₂ , the pressure P increases to pressure c during the stroke x ₄ , and then decreases and then increases again to end mold clamping at point O ₃ . At the time of mold opening, the pressure P drops rapidly from the starting point _O3 , and then the pressure rises slightly, and the mold opening is performed while maintaining almost the pressure d, and the mold opening is completed at the point _O4 where the pressure has increased.

By the way, the pressure C at the peak of the pressure diagram in Figure 2 is determined by the mold clamping force F by a coefficient K depending on the thickness of the mold.
will give you. That is, if the area of the cylinder is A, it is expressed by the following equation.

F=A・K・C Therefore, if this pressure is controlled by a pressure control valve, the mold clamping force can be controlled.

However, if the set value of this pressure control valve (relief valve) is Pc corresponding to the pressure C, due to the override characteristic, as shown in Fig. 3,
In reality, from a pressure of about 0.85Pc, the amount of oil escaping from the valve increases, the amount of oil supplied to the mold clamping cylinder decreases, the mold clamping time becomes longer, and the mold does not work in the scheduled cycle. Put it away.

Therefore, in order to correct the above-mentioned override with respect to the pressure C required to generate the clamping force according to the thickness of the mold, the pressure control valve setting Pc is set to 1.1.
~1.2C, turn the link housing nut,
By shifting the timing when the molds are brought together, even if the circuit has the ability to build up pressure up to Pc, the actual pressure inside the cylinder can be adjusted so that it only builds up to C. This state is when the cycle is going as planned and the desired mold clamping force is being generated.

However, in reality, adjusting the time when the molds fit together by turning the nut on the link housing by hand is
This cannot be done accurately and there is a risk that the mold clamping force will be exceeded.

If the mold clamping force is exceeded, there is a risk that a major accident may occur in which the platen, tie bars, tie bar nuts, etc. are damaged.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a mold clamping force detection method for a toggle type mold clamping device that can reliably detect over, insufficient, and normal mold clamping force. The purpose is

FIG. 4 is a block circuit diagram illustrating one embodiment of the present invention, in which the same parts as in FIG. 1 are designated by the same reference numerals.

In this embodiment, a fixed bar 17 is provided horizontally on the link housing 3 side, and limit switches L ₁ and L ₂ are provided on this with a predetermined distance apart, and
A striker 18 is provided on the crosshead 11 side.

Limit switch _L1 detects the mold clamping start position,
Limit switch _L2 detects the mold clamping limit. The gate circuit 1 is then connected to the gate circuit 1 via the inverter I.
Connected to 9. The output of the gate circuit 19 is input to another gate circuit 21. The output of the gate circuit 21 is input to a flow rate integration counter 36.

On the other hand, the mold clamping cylinder 9 is equipped with a pressure detector 23, the output of which is passed through an amplifier 24 to a pressure comparator 2.
5 is input. A pressure setting device 26 sets the set pressure Pc and inputs it to the pressure comparator 25.

Here, the inputs of both the pressure setter 26 and the amplifier 24 are compared, and the output from the pressure comparator 25 is input to the flow rate integration counter 36.

A flow rate detector 33 is provided in the middle of the pipe 32 connecting the mold clamping cylinder 9 and the hydraulic pressure source 31, and a relief valve 34 is provided between the flow rate detector 33 and the hydraulic pressure source 31, to which a set pressure Pc is set. ing. An exchange amplifier 35 is provided between the flow rate detector 33 and the gate circuit 21 to convert the flow rate into a digital signal.

The output of the gate circuit 21 is the flow rate integration counter 36
The output from this counter is input to the flow rate comparison calculator 37 and compared with the reference flow rate from the flow rate setting device 38. Based on this difference in flow rate, it is determined whether the mold clamping force is excessive or insufficient or normal. In this case, if the flow rate exceeds the alarm 29
Alternatively, the signal is input to the machine operation stop circuit 30. It is also possible to notify the operator that the mold clamping force is excessive or to completely stop the device.

Next, the operation of this embodiment configured as above will be explained.

First, the mold clamping cylinder 9 is activated, and when the movable mold moves and is aligned with the fixed mold, the mold clamping operation is started. At this time, the striker 18 separates from the limit switch _{L1 .}
is turned off. As a result, a signal is input to the gate circuit 19 via the inverter I. At the same time, the timer 20 starts operating, starts measuring time, and sequentially inputs the measurement results to the gate circuit 21. In this state, neither gate circuits 19 nor 21 are open.

Eventually, when the mold clamping limit is reached, the striker 18
Since it moves away from the limit switch L ₂ , L ₂ is turned off, and the signal inverted by the inverter I is input to the gate circuit 19 .

As a result, the gate circuit 19 is opened and a signal is output, so that the gate circuit 21 is also opened. When the signal is input to the gate circuit 19, the flow rate detector 33 starts operating from this time, and the flow rate signal is input to the gate circuit 21 via the exchange amplifier 35.

On the other hand, when the mold clamping limit is reached, limit switch _L2
is turned off, the gate circuit 19 opens, the output signal thereof causes the gate circuit 21 to open, the flow rate integration counter 36 counts the flow rate up to now, and inputs the flow rate signal to the flow rate comparison calculator 37. and,
It is compared with a reference flow rate signal up to the mold clamping limit, and if the flow rate exceeds the reference flow rate, the alarm 29 and drive stop circuit 30 are activated to issue an alarm or stop the device. Of course, if it is determined from the comparison of the flow rates whether the mold clamping force is normal or insufficient, it can be displayed separately.

In this way, by comparing the flow rate up to the mold clamping limit with the reference flow rate, excess mold clamping force can be detected and countermeasures can be taken.

In reality, when this over-clamping force condition occurs several times in a row, a warning is issued to the operator and the operation is stopped.

Of course, when the mold clamping force is normal or insufficient, it can be expressed by a lamp or numerical value.

The method described above measures the flow rate based on the position signal of the mold clamping cylinder 9, but this method measures the flow rate between the pressure signal at the start of mold clamping and the pressure signal at the mold clamping limit. gives similar results.

That is, the pressure at the start of mold clamping is detected by the pressure detector 23, and the detected signal is amplified by the amplifier 24 and input to the pressure comparator 25. Simultaneously with the generation of the pressure signal at the start of mold clamping, the flow rate integration counter 36 is started for flow rate measurement. When a pressure signal at the mold clamping limit is generated, this signal is compared with the pressure set by the pressure setting device 26, and when the two match, the flow rate integration counter 36 also stops operating.

The count result by the flow rate integration counter 36 is input to a flow rate comparison calculator 37 and compared with a reference flow rate. As a result, in the event that the flow rate exceeds the flow rate, an alarm may be issued or the operation of the device may be stopped in the same manner as described above.

In this way, excess or deficiency of mold clamping force or normality is detected, making it easy to maintain normal operating conditions at all times.In the event that excessive mold clamping force is detected,
In order to deal with this, an alarm can be issued or the equipment can be stopped, so there is no possibility of damage to tie bars or other accidents due to excessive mold clamping force.

In the above embodiment, excess mold clamping force is detected based on the flow rate up to the mold clamping limit, and an alarm or a command to stop the device is issued.
The flow rate is compared with the set value, and depending on the difference and which one is larger, it is detected whether the mold clamping force is excessive, insufficient, or within a predetermined normal range, and then the mold It is also possible to send feedback to an automatic clamping force adjustment device so that the mold clamping force can always be kept in a normal state.

As is clear from the above explanation, by comparing the flow rate from the start of mold clamping to the mold clamping limit with the reference flow rate, it is possible to detect whether the mold clamping force is excessive or insufficient, or is normal.
There is no time delay in measurement, and mold clamping force can always be detected accurately, making it easier to maintain normal operation.
If overflow is detected, the system is configured to issue an alarm or stop the device, so tie bars, tie bar nuts,
Alternatively, damage to the platen or the like can be prevented.

[Brief explanation of drawings]

Fig. 1 is a front view (partial sectional view) of a toggle type mold clamping device to which the present invention is applied, Fig. 2 is a diagram showing the relationship between the stroke and pressure of the mold clamping cylinder, and Fig. 3 is a diagram of the relief valve. A diagram explaining the override characteristic, and FIG. 4 is a block circuit diagram showing one embodiment of the present invention. 1... Toggle type mold clamping device, 3... Link housing, 4... Fixed platen, 5... Tie bar,
6... Tie bar nut, 7... Movable platen, 9
... Clamping cylinder, 10 ... Piston rod, 1
9, 21...gate circuit, 23...pressure detector,
25...Pressure comparator, 26...Pressure setting device, 29
...Alarm, 30...Operation stop circuit, 33...Flow rate detector, 35...Conversion amplifier, 36...Flow rate integration counter, 38...Flow rate setting device.

Claims (1)

[Claims] 1. A pressure control valve is provided to control the output of the mold clamping cylinder of the toggle type mold clamping device, and this set pressure is set slightly higher than the pressure required to generate the target mold clamping force, and the position at a predetermined position before the mold clamping limit is set. The flow rate supplied to the mold clamping cylinder from the signal or pressure signal to the mold clamping limit position signal or pressure signal is measured, this flow rate is compared with a preset flow rate, and the result of this comparison is used to determine whether the mold clamping force is excessive. A mold clamping force detection method for a toggle type mold clamping device, characterized in that it is configured to determine whether it is insufficient or normal.