JPS599888Y2 - Mold clamping pressure detection control device for injection molding machines - Google Patents

Description

[Detailed description of the invention] A conventional mold clamping pressure detection control device for an injection molding machine will be explained with reference to FIGS. 1 and 2. In FIG. 1, 1 is a mold clamping cylinder, 2 is an oil tank, and 3 4 is a prefill valve, 4 is a spring for closing the prefill valve, 5 is a booster cylinder, and 6 is a position detection device.

Further, 7 and 8 are large capacity pumps, the pump 7 being used for opening/closing the mold, increasing the pressure and injection, and the pump 8 being used for opening/closing the mold and increasing the pressure.

9 is a small capacity pump used for opening and closing the mold, increasing pressure, and maintaining mold clamping pressure.

10 is a relief valve for setting the mold clamping maximum pressure, and 11 is a relief valve for mold protection.

Reference numeral 12 is a pressure switch for switching from pressurization to mold clamping pressure maintenance, and reference numerals 13, 14, 15, 16, 17, and 18 are directional control valves, respectively.

FIG. 2 is a diagram showing the relationship between pressure and time during mold closing realized by the hydraulic circuit shown in FIG. 1.

The pressures I) A and p5 in FIG. 2 are respectively applied to the relief valve 10 in FIG. 11, and pressure p4 is the pressure set by pressure switch 12 of FIG.

Now, mold protection is carried out in the mold closing low speed section set by the position detection device 6, and at that time solenoids A and D are activated.
, K are excited, and the oil discharged from the pump 9 passes through the directional control valve 15 and flows from ■ to ■ to the booster cylinder 5.

Further, if there is a foreign object between the fixed mold and the movable mold, the oil pressure will increase, but when the pressure reaches the set pressure pA of the relief valve 11, it will be relieved and prevent the oil pressure from increasing any further.

However, even if the oil is relieved from the relief valve 11, it is difficult to detect it, so if the low mold closing speed does not end even after a certain period of time set by the timer has elapsed, an abnormal signal indicating that a foreign object has been detected is issued.

However, this method had the following drawbacks.

That is, the settings of IJ 17-F valve 11 for mold protection are as follows:
It takes time and effort to actually raise the hydraulic pressure to the set pressure, and even if a foreign object is bitten, the set pressure pA of the relief valve acts only for a certain period of time set by a timer, so there is no risk of crushing the foreign object or scratching the mold. There was a risk that the mold would close with the foreign object stuck or crushed, and the mold would move on to the next normal operation.

That is, there is a drawback that the abnormal signal indicating that a foreign object has been bitten is too slow to be output.

Next, the pressure is increased by pumps 7, 8, and 9 after the mold is closed.

At that time, solenoids B, D, F, and G are energized, and pumps 7, 8. The oil discharged from 9 joins and flows from ■ to ◎ and from ■ to ■, and is sent to the mold clamping cylinder 1 and the booster cylinder 5.

Next, when the oil pressure rapidly increases and reaches the set pressure p4 of the pressure switch 12, the solenoids F and G are demagnetized and only oil from the pump 9 is sent, and at the same time a signal to start injection is issued.

Thereafter, the oil pressure slowly rises, and when it reaches the set pressure p5 of the relief valve 10, it is relieved and maintained at that pressure.

However, this method had the following drawbacks.

That is, since injection starts after the completion of pressure increase, there is a large loss in pressure increase time.

Therefore, even if you try to shorten the pressure increase time by lowering the set pressure p4 of the pressure switch, the mold clamping maximum pressure p will change from the set pressure p4.
It took too long to reach 5, and there was a risk that injection would be completed before then and the mold would open.

Also, the set pressure p4 of the pressure switch 12 is set by the relief valve 10.
The pressure must be set to be lower than the set pressure p5, and not too low, but in reality, the point at which the pressure increase rate changes must be found using a pressure gauge, etc., and the adjustment must be made, which has the disadvantage of being time-consuming. .

The present invention was proposed to eliminate the above-mentioned conventional drawbacks, and it is possible to safely and reliably protect the mold, reduce loss time when increasing mold clamping pressure, and provide easy-to-operate injection. The present invention aims to provide a mold clamping pressure detection and control device for a mold forming machine.

The embodiments shown in the drawings will be described below. FIG. 3 is a system diagram showing an embodiment of the present invention.

In FIG. 3, reference numeral 19 denotes a mold clamping cylinder in which a mold clamping ram 20 is slidably housed.

The mold clamping ram 20 is connected to a movable platen 22 via an ejector box 21.

23 is an oil tank, 24 is a prefill valve, and a spring 25 is for closing the valve 24.

26 is a booster cylinder in which a booster ram 27 is installed.

The booth ram 27 is connected to the movable platen 22.

28 is a mold opening/closing position detection device, 29 and 30 are large capacity pumps, respectively. Pump 29 is used for opening/closing the mold, increasing pressure and injection, and pump 30 is used for opening/closing the mold and increasing pressure.

31 is a small capacity pump used for opening and closing the mold, increasing pressure, and maintaining mold clamping pressure.

32, 33, 34, 35, 36 are solenoid A,
Directional switching valve with B, C, D, E, F, G, 37
, 38. 39 is a relief valve.

Further, the mold clamping maximum pressure is set by the IJ-F valve 39.

Further, 40 is a pressure sensor, 41 is a comparator, 42, 43, 4
4 is a digital setting device for setting the mold protection pressure, the first mold clamping pressure, and the second mold clamping pressure, respectively.

Further, the comparator 41 is for electrically comparing the pressure detected by the pressure sensor 40 and the pressure set by the digital setting devices 42, 43, and 44.

Next, to explain the operation, Fig. 4 is a diagram showing the relationship between pressure and time during mold closing realized by the hydraulic circuit shown in Fig. 3. Solenoids A, D, F, and G in Figure 3 are energized, and the pump 29,
All of the oil discharged from 30 and 31 passes through ◎ and is sent to the head side of the booster cylinder 26, where the mold closing operation is performed at high speed.

At that time, pressure oil is also sent to [phase] and {circle around (2)}, so the prefill valve 24 opens, and the amount of oil that changes in the mold clamping cylinder 19 due to the movement of the mold clamping ram 20 flows into the oil tank 23.

Next, when the limit switch in the position detection device 28 moves from the mold closing high speed to the mold closing low speed section, the solenoid F,
G is demagnetized and only solenoids A and D remain energized.

Therefore, the oil sent to the head side of the booster cylinder 26 is only from the small capacity pump 31, and the mold closing operation becomes slow.

The hydraulic pressure for the mold closing operation also changes from p1 to p2 in FIG. 4.

pA in FIG. 4 is the mold protection pressure set by the digital setting device 42. If the mold catches a foreign object and the working pressure detected by the pressure sensor 40 rises to pA, the solenoid D is immediately demagnetized. to stop the mold closing operation.

Note that the change time from p1 to p2 is determined by a timer,
Alternatively, the mold protection section is removed by a limit switch (Δt in FIG. 4).

The end of the mold protection zone is set by a limit switch in the position sensing device 28.

In this embodiment, this is also the end of the mold closing speed section.

Now, when the mold-closing low-speed section ends, we move on to the pressure increase operation.

At this time, the mold is completely closed and the mold clamping pressure increases.

First, when moving to the boost I section in Figure 4, solenoid A is deenergized, prefill valve 24 is closed by spring 25, solenoids B, F, and G are energized, and solenoid D remains energized. .

Therefore, the oil discharged from the pumps 29, 30, and 31 is sent to the head side of the empty mold clamping cylinder 19 and to the head side of the empty booster cylinder 26, but since the mold is closed, the mold clamping pressure is rapidly increased. rise to

When the mold clamping pressure detected by the pressure sensor 40 rises to the first mold clamping pressure p3 set by the digital setting device 43, an injection start signal is issued, and the next pressurization II operation is started.

When moving to the boost II section, the solenoid F is demagnetized and the oil discharged from the large capacity pump 29 is sent to an injection operation (circuit not shown).

Therefore, the pressure is increased by the oil discharged from the pumps 30 and 31 at a slower speed than in the pressure increase section (3).

When the mold clamping pressure detected by the pressure sensor 40 rises to the second mold clamping pressure p4 set by the digital setting device 44, the next mold clamping pressure holding operation is started.

When the mold clamping pressure is maintained in this manner, the solenoid G is also demagnetized and only the oil discharged from the small capacity pump 31 is sent to the head side of the mold clamping cylinder 19 and the booster cylinder 26.

At the beginning of this section, the mold clamping pressure varies from the second mold clamping pressure p4 to the highest mold clamping pressure p set by the relief valve 39.
After that, the pressure is relieved from the relief valve 39, so that the pressure is maintained at a constant pressure of p5.

Further, the injection operation started after the completion of the pressure increase I is also completed in the middle of the mold clamping holding section.

Since the present invention is constructed as described in detail above, it does not have the drawbacks of the conventional method in terms of mold protection.

In other words, conventionally, when a mold bites a foreign object, pressure is applied to the mold to protect the mold for a certain period of time set by a timer, etc., so in reality, the foreign object may be crushed or the mold may be damaged during that certain period of time. However, in this invention, the mold closing operation is stopped as soon as the working pressure detected by the pressure sensor reaches the full mold protection pressure set by the digital setting device, so it is not possible to use the conventional method as described above. It prevents foreign objects from spilling out and damage to the mold, and is extremely effective in protecting the mold.

In addition, in terms of mold clamping pressure increase, in the conventional method, the injection operation was started after the completion of pressure increase, so the entire pressure increase time became loss time, but in the present invention, the first
The mold clamping pressure p3 and the second mold clamping pressure p4 are set, and when the mold clamping pressure detected by the pressure sensor reaches p3, the injection operation is started, and when it reaches p4, the mold clamping pressure is maintained. , the only loss in pressure increase time is the time required to reach the first mold clamping pressure p3.

Therefore, compared to the conventional method shown by the two-dot chain line in Figure 4,
The loss time is reduced by the time Δt in the figure.

In addition, compared to the conventional method using two pressure switches as a method of using the first mold clamping pressure and the second mold clamping pressure,
It is much easier to set the pressure by using a pressure sensor and a digital setting device as in the present invention.

Furthermore, it is economical to use the same pressure sensor for mold protection and mold clamping pressure increase operation, and since a digital setting device is used to set the mold pressure, operation is easy and accurate. It is.

The present invention can be applied to mold protection for die casting machines, FRP presses, and forging presses.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional injection molding machine, and Figure 2 is a system diagram of a conventional injection molding machine.
Figure 3 is a diagram showing the relationship between pressure and time during mold closing; Figure 3 is a system diagram of an injection molding machine showing an embodiment of the present invention;
FIG. 4 is a diagram showing the relationship between pressure and time during mold closing in FIG. 2. Explanation of the main parts of the figure, 19...Mold clamping cylinder,
20...Mold clamping ram, 28...Mold opening/closing position detection device, 29, 30...Large capacity pump, 31...Small capacity pump, 37 , 38, 3
9... Relief valve, 40... Pressure sensor, 41... Comparator, 42, 43, 4
4...Digital setting device, pA...
Mold protection pressure, p3...First mold clamping pressure, n...
...Second mold clamping pressure.

Claims (1)

[Scope of utility model registration request] In an injection molding machine that detects oil pressure in the main circuit and controls each step of mold clamping and injection operation, there is a pressure sensor connected to the main circuit, and a pressure sensor connected to the sensor via a comparator. It consists of a digital setting device for mold protection pressure, a digital setting device for first mold clamping pressure, and a digital setting device for second mold clamping pressure. When the detected value of the sensor reaches each setting value of each digital setting device, the predetermined 1. A mold clamping pressure detection control device for an injection molding machine.