JPH0745100B2 - Toggle type mold clamping device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a toggle type mold clamping device used in, for example, an injection molding machine or a die casting machine, and in particular, just before the completion of mold clamping for protecting a mold. The present invention relates to a toggle-type mold clamping device that can automatically set the condition of low-pressure mold clamping that lowers the mold clamping force to low pressure and low speed.

[Conventional technology]

Conventionally, as a mold clamping device such as an injection molding machine or a die casting machine, the stroke of the mold clamping cylinder and the movement stroke of the die plate are the same. There are known a so-called direct pressure type and a so-called toggle type in which the stroke of the die plate is different between near the completion of mold clamping and near opening of the mold with respect to the cylinder stroke.

Comparing the two, the toggle type mold clamping device moves little by little when the die plate stroke (mold clamping stroke) is close to the mold clamping completion point based on the stroke of the mold clamping cylinder, but when the mold opening progresses a little. Since it moves at a high speed, it is advantageous in satisfying both the requirements for protection of the mold and the molded product and the mold opening / closing speed.

The low-pressure mold clamping operation in this toggle type mold clamping device is an operation in which the mold clamping advance is temporarily slowed just before the completion of mold clamping, and the mold clamping force is reduced to a low pressure from that position to proceed.

If there is no foreign matter on the mold parting surface and it seems that mold clamping can be done safely, increase the mold clamping force again from the preset switching point and hit the resistance near the toggle point of the toggle mechanism. Win and complete the mold clamping.

However, if there is something wrong with the parting surface of the mold, for example, the molded product is caught without falling, when the mold clamping force is reduced to low pressure and low speed, the preset switching point from low pressure to high pressure is reached. Clamping stops because it cannot be reached. After a certain amount of time has passed in such a state,
Measures are taken such as determining that there is an abnormality and issuing an alarm and opening the mold immediately.

[Problems to be solved by the invention]

This low-pressure mold clamping operation is performed according to the above-described principle whether hydraulically driven or servomotor driven, and the range and degree of reducing the mold clamping drive force to make the mold clamping speed very small are substantially constant. It may be set, but the problem is how to set the position to switch from low pressure to high pressure again.

Conventionally, the mold clamping is manually performed in a state where the mold clamping driving force is small and the mold clamping speed is very small, and a position where the mold clamping is stopped by reaching the set point of the toggle mechanism is found. The distance from the mold clamping stop position to the mold clamping completion point 0 was measured, and a value obtained by adding a little empirical value was set as the switching point from low pressure to high pressure.

However, in the method of manually setting the switching point in this way, the series of operations are complicated, and the setting of the switching point tends to be performed loosely, and the function of die protection by low pressure mold clamping is lost or the opposite. In some cases, the mold clamping operation sometimes stopped halfway, and the cut and try setting took only a short time.

The object of the present invention is to eliminate such drawbacks of the prior art,
The point where the mold clamping force is switched from low pressure to high pressure automatically and
An object of the present invention is to provide a toggle-type mold clamping device that can be properly set in a short time.

[Means for solving problems]

In order to achieve this object, the present invention is directed to a toggle type mold clamping device that performs the above-mentioned low pressure mold clamping.

A mold clamping stroke sensor that detects the mold clamping stroke, a tact timer that outputs a takt signal sequence at a predetermined interval, and a position signal from the mold clamping stroke sensor that performs mold clamping with a pressure smaller than the normal mold clamping force. Stop point detection means for detecting a stop point at which the mold clamping stops halfway based on the takt signal from the takt timer, and switching to a position slightly before the stop point detected by the stop point detection means from the mold clamping start point It has a switching point setting means for calculating and setting points, and is configured to switch from low pressure to high pressure at the switching point set by the switching point setting means.

〔Example〕

Next, a toggle type mold clamping device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view in which a part of the toggle type mold clamping device is shown in section, FIG. 2 is a system diagram for setting a switching point, and FIG. 3 is a control flow chart for setting a switching point.
FIG. 4 is a characteristic diagram of the mold clamping force.

First, the schematic configuration of the toggle type mold clamping device will be described with reference to FIG. The movable die plate 2 is movably supported by the fixed die plate 1 via a tie bar 10, and the movable die plate 2 is connected to the tailstock 3 via a plurality of links. The link includes a first link 5 having one end connected to the tailstock 3, and a second link 4 having one end connected to the other end of the first link 5 and the other end connected to the moving plate 2. The third link 6 has one end connected to the intermediate portion of the first link 5 and the other end connected to the crosshead 9. The links 4, 5 and 6 are connected to each other by connecting toggle pins 7 and 8. A piston rod 12 of a mold clamping cylinder 11 is connected to the cross head 9. Further, a fixed die 13 is attached to the fixed die plate 1, and a movable die 14 is attached to the movable die plate 2.

By driving the mold clamping cylinder 11, the cross head 9 and the links 4, 5 and 6 are actuated to increase the force, whereby the movable die plate 2 moves toward the fixed die plate 1 side and abuts. Further, by applying a force by the mold clamping cylinder 11, the four divers 10 are extended this time with the movable mold 14 in contact with the fixed mold 13, and the reaction force causes the mold 1 to move.
The parting surfaces of 3 and 14 are tightened to complete the mold clamping.

Next, the automatic setting of the switching point for switching the mold clamping force from low pressure to high pressure will be described with reference to FIGS. 2 and 3.

As shown in FIG. 2, the piston rod 12 of the mold clamping cylinder 11
A rack 16 is attached to the rack via a bracket 15. A pinion 17 meshes with the rack 16 to rotate at a fixed position, and a potentiometer 18 is mounted coaxially with the pinion 17. Therefore, the mold clamping stroke of the mold clamping cylinder 11 is converted into the DC voltage output of the potentiometer 18, and the detected value is input to the control unit 19. Because of this, the rack
The mold clamping stroke sensor for detecting the mold clamping trooke is constituted by the 16, pinion 17 and the potentiometer 18.

The mold clamping cylinder 11 is connected to a hydraulic circuit having a hydraulic pump 20, a proportional electromagnetic relief valve 21, a proportional electromagnetic flow rate adjusting valve 22, a direction switching valve 23, etc. so that the mold clamping force and the mold clamping speed are controlled. It has become.

The control unit 19 includes an input interface (IN) 24, an output interface (OUT) 25, a central processing unit (C).
PU) 26, random access memory (RAM) 27, read only memory (ROM) 28, and keyboard (KB) 29, which are connected to each other by a bus such as a control bus and a data bus. . A stroke signal (position signal) from the potentiometer 18 is taken into the control unit 19 via the input interface 24. Further, the control section 19 controls the proportional electromagnetic relief valve 21 and the proportional electromagnetic flow rate adjusting valve 22 via the output interface 25.

Next, the control operation of automatic switching point setting will be described mainly with reference to FIG.

In the case of this embodiment, after the die thickness is adjusted when the die is replaced with a new die, the switching point is continuously set automatically. In the figure, steps (hereinafter abbreviated as S) 1 to S11 are steps for adjusting the die thickness and tightening the die when a new die is replaced. At this time, for example, the mold opening / closing pressure is an intermediate pressure of about 40 kg / cm ² , and the mold opening / closing speed is low at about 20% of the mold opening / closing speed during normal molding. The mold pressure and the mold opening / closing speed are input and set in advance via the keyboard 29 (see FIG. 2) and stored in a predetermined address of the RAM 27. Therefore, when adjusting the mold thickness, the mold opening / closing pressure and the mold opening / closing speed are automatically called from the RAM 27 and executed. The mold opening is performed in S1, and it is determined in S2 whether the mold opening is completed. If completed, in S3, the entire toggle type mold clamping device is retracted by about 10 mm to perform the mold thickness adjustment retreat.

Then, the mold is clamped in S4, and it is determined in S5 whether the mold clamping is completed. If it stops during mold clamping, the mold is clamped after returning to the previous stage of S1 and opening the mold, then retracting the whole mold clamping device further by about 10 mm in S3. The above steps are repeated until it is determined in S5 that the mold clamping is completed. Next, the entire toggle-type mold clamping device is advanced to advance the mold thickness adjustment (S6). Then, in S7, it is judged whether the forward movement has stopped, and if it stops,
The mold opening is executed in S8.

After confirming that the mold opening is completed in S9, this time S1
At 0, the entire mold clamping device is further advanced based on the tightening command value from the control unit 19, and at S11, the completion of the advance is confirmed and the tightening is completed.

Subsequently, the step (S12 to S21) of the automatic setting of the low pressure mold clamping switching point of the present invention is started.

The setting of the mold clamping pressure in this low pressure mold clamping switching point automatic setting process is further reduced to a low pressure of about 20 kg / cm ² , and the mold opening / closing speed is about 20% of the normal mold opening / closing speed as in the above-mentioned mold pressure adjustment. It is said that The mold clamping pressure and the mold opening / closing speed are also input and set at a predetermined address of the RAM 27 by the keyboard 29. When S11 ends, in S12 the proportional solenoid relief valve
The mold clamping pressure and the mold opening / closing speed are changed with respect to 21 and the proportional electromagnetic flow rate adjusting valve 22. In this embodiment, since the mold opening / closing speed is the same as that in the mold thickness adjusting step as described above, the mold opening / closing speed is not substantially changed.

Then, in S13, mold clamping is performed at low pressure and low speed, and in S14, it is determined whether or not the process is stopped halfway. Since the mold clamping pressure is as low as 20 kg / cm ² as described above, there is not enough mold clamping force to fully extend the toggle mechanism, so it stops at the midpoint S of the mold clamping stroke (see Fig. 4). Will be done.

The midway stop can be determined as follows. That is, although not shown, the CPU 26 is provided with a tact timer (oscillator) that outputs a tact signal train (reference pulse signal train) at a predetermined interval, so that the potentiometer during low pressure, low speed mold clamping is provided. The mold clamping forward speed is calculated based on the position signal from the meter 18 and the takt signal from the takt timer, and when the forward speed reaches zero, it is judged to be stopped, so that the mold clamping stroke is stopped midway. The point can be detected. Therefore, in the case of this embodiment, the CPU2
The tact timer 6, the potentiometer 18, and the arithmetic unit of the CPU 26 constitute stop point detection means.

If it is determined that the vehicle has stopped midway in S14, the stop point is detected. As shown in FIG. 4, since the mold clamping completion point is set to 0 point, the distance l from the 0 point to the stop point on the way is calculated based on the position signal from the potentiometer 18, The stop point can be detected and its position
It is stored in a predetermined address of RAM 27.

Next, in S16, L = 1 + C is calculated. Here, C is a value input and set in advance by the keyboard (KB) 29, which is 0.
5mm is suitable. L calculated in this way
Indicates a position slightly before the midway stop point (point S) based on the mold clamping completion point (0 point), and this point is automatically set as a switching point for switching from low pressure to high pressure.
Stored at a predetermined address in RAM 27. Therefore, in the case of this embodiment, the keyboard (KB) 29, the arithmetic unit of the CPU 26 and the R
AM27 constitutes a switching point setting means.

Next, in S17, try to perform low-pressure mold clamping under the same conditions as during normal molding. At this time, since the low pressure is switched to the high pressure at the point P, the mold should be completely clamped. However, if the resistance condition of the mold, for example, the resistance is large due to the spring for the return pin etc., and it stops during mold clamping, that is, if YES is determined in S18, the process proceeds to S19 and once, Open the mold and set the low-pressure mold clamping pressure to 2 in S20.
Increase the kg / cm ² to correct the mold pressure, return to the previous stage of S17 and perform mold clamping. After confirming that the mold can be completely clamped in this way, the process of automatically setting the switching point is completed.

In this embodiment, when YES is determined in S18, the mold clamping pressure is slightly increased and corrected in S20, but instead of correcting the mold clamping pressure, the value of the constant C used in the calculation of S16 is slightly increased. You may.

FIG. 4 is a mold clamping force characteristic diagram showing the potentiometer 18 described above.
The output from is converted into the mold clamping stroke (mm) and is plotted on the horizontal axis.
The mold clamping force t is plotted on the vertical axis.

The curve TH shown in the figure is a characteristic curve of the mold clamping force when the mold clamping is performed under normal high pressure, and the mold clamping force is as high as hundreds of tons near the completion of the mold clamping.

Dotted line AB in the figure indicates that the four tie bars are extended by further increasing the mold clamping force from the point A where the mold clamping progresses and the parting surfaces of the fixed mold and the moving mold match. The actual mold clamping force by which the parting surface of the mold is clamped by the reaction force is shown. In this case, the mold clamping force of 180 tons is obtained when the mold clamping is completed. What is important here is that the mold clamping force TH by the toggle mechanism must always exceed the mold clamping force AB required to actually extend the tie bar, and the mold clamping is not completed.

Since the mold clamping force during low-pressure mold clamping as described above is about a fraction of the normal mold clamping, the mold clamping force TL is also a fraction of the mold clamping force TH even if the toggle mechanism increases the force. Fall in strength. Therefore, when the mold clamping is completed in the low-pressure mold clamping, the toggle mechanism cannot be fully extended, and the mold clamping operation stops at the point S where the straight line AB intersects.

The position of this stop point, that is, the distance 1 from the mold clamping completion point (0 point) is detected and calculated based on the position signal from the potentiometer 18 and the tact signal from the tact timer as described above, and the information thereof is calculated. Is stored in a predetermined address of the RAM 27. Then, in the CPU 26, one stationary number (0.5 mm in this embodiment) is added to this value, and the value is stored at a predetermined address of the RAM 27 as a switching point P from low pressure to high voltage.

In the case of the example in Fig. 4, 1.4 mm before the mold clamping completion point (0 point) is detected as the midway stop point (S point), so 0.5 mm of the constant is added to it, and the switching point P (1.9 mm ) Is set automatically. Therefore, as shown by the thick arrow in the figure,
High mold clamping force (curve TH) at mold clamping stroke 3.0 mm
To low pressure (TL) to perform low-pressure mold clamping at low speed,
From the position of the mold clamping stroke of 1.9 mm, the mold clamping pressure is automatically switched from low pressure to high pressure again to perform the mold clamping, and the mold clamping is completed at the point B.

〔The invention's effect〕

Since the present invention is configured as described above, the switching point from low pressure to high pressure, which is complicated to operate, can be set completely automatically, so that operability can be improved. Further, since the setting of the switching point is proper, the mold clamping operation does not stop in the middle of the molding cycle and the mold is not damaged, unlike the conventional case, and the reliability of the operation is improved. be able to.

[Brief description of drawings]

The drawings are all for explaining a toggle type mold clamping device according to an embodiment of the present invention. FIG. 1 is a side view of a part of the toggle type mold clamping device in section, and FIG. 2 is a switching point setting. FIG. 3 is a control flow chart for setting a switching point, and FIG. 4 is a characteristic diagram of mold clamping force. 11 …… Mold clamping cylinder, 16 …… Rack, 17 …… Pinion,
18 ... Potentiometer, 19 ... Control part, 21 ... Proportional electromagnetic relief valve, 22 ... Proportional electromagnetic flow control valve, 24 ... Input interface, 25 ... Output interface, 26 ...
… Central processing unit, 27 …… random access memory, 28 …… read only memory, 29 …… keyboard.

Claims (1)

[Claims] 1. In a toggle type mold clamping device for reducing mold clamping force to a low pressure for a predetermined time before completion of mold clamping and then switching to normal high pressure again to complete mold clamping, a mold clamping stroke sensor for detecting a mold clamping stroke. And a tact timer that outputs a tact signal sequence at predetermined intervals, and mold clamping is performed with a pressure smaller than the normal mold clamping force, and the mold clamping is performed based on the position signal from the mold clamping stroke sensor and the tact signal from the tact timer. It has a stop point detecting means for detecting an intermediate stop point, and a switching point setting means for calculating and setting a switching point before the stop point detected by the stop point detecting means when viewed from the mold clamping start point. A toggle type mold clamping device characterized in that it is configured to switch from low pressure to high pressure at a switching point set by a switching point setting means.