JPH03222725A - Method and apparatus for detecting blowing pressure in foam molding machine - Google Patents

Abstract

PURPOSE:To finish heating process and remove a molded item from a mold at proper timing by detecting the blowing pressure in the molding space of the mold by a method wherein minute gap is produced between mold halves after the closing of foaming mold so as to detect blowing pressure by conversing the load applied to the pressure sensing part of a pressure detecting means to electric signal. CONSTITUTION:By moving a moving retainer 4, minute gap is produced between a stationary mold half 3 and a moving mold half 5 so as to fill the stock beads of expandable synthetic resin in the molding space of a foaming mold 2 in order to perform heat expanding and cooling process of the beads. At this time, the position of the moving mold half 5 is detected with a position detecting means 16 and fed back to a servo controlling section 17. The servo controlling section 17 controls a servo motor 9 so as to converse the load applied to the strain gage of a load cell into electric signal, resulting in allowing to easy detect the blowing pressure. When the blowing pressure reaches a certain value in heating process, satisfactory fusion is realized. Further, the removal of a molded item is performed by opening the mold, when the blowing pressure goes down below the set value.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a method and device for detecting the foaming pressure of a raw material in a mold in a foam molding machine that produces molded products using a foamed synthetic resin material. It is related to.

[Conventional technology]

When creating molded products using foamed synthetic resin materials such as foamed polystyrene, a pair of foam molding molds is closed, raw material beads are filled into the molding space, and the following steps are performed: heating and foaming, cooling, mold opening, and molding. The process of taking out items is performed sequentially.

At this time, the raw material beads that have been pre-foamed and filled in the mold are heated by steam, thereby generating an expansion force called foaming pressure, which, together with the rise in temperature, fuses together.

When this fusion is completed, cooling is performed, the mold is opened, and the molded product is taken out.

The foaming pressure of the foamed synthetic resin material in the mold increases as heating progresses and decreases as it cools.If the molded product is taken out when the foaming pressure is above a certain value, it will deform due to its own residual foaming pressure. , it is necessary to allow sufficient cooling time.

In addition, in the heating step, it is necessary to take a heating time so that the foaming pressure is at least a certain value so that sufficient fusion is achieved.

Usually, each step in foam molding is controlled by a timer, and heating and cooling steps are also performed based on the time set in this timer.

Another method is to attach a pressure sensor to a foam mold to directly measure the foaming pressure inside the mold, and control the heating, cooling, and mold opening processes based on this.

For example, in the technique disclosed in Japanese Utility Model Application Publication No. 57-90820, a pressure sensor is incorporated into a filler in which raw materials are filled to detect the foaming pressure in the mold.

Furthermore, Japanese Patent Laid-Open No. 59-230730 discloses a device in which a pressure sensor is provided on an eject pin for ejecting a molded product to detect the foaming pressure within the mold.

[Problem to be solved by the invention]

If a timer is used to remove the molded product from a foam molding machine, the cooling time set may not be sufficient (
If the molded product is removed while the foaming pressure is still high, the molded product will be deformed due to the remaining foaming pressure, as described above.

For this reason, it is necessary to set a sufficient cooling time for the timer, which may result in unnecessary cooling, lengthening the cycle time and reducing work efficiency.

In addition, in the heating process, sufficient fusion will occur if the foaming pressure increases to a certain value, and there is no need to heat any further.

Even if heating is performed further than that, the quality will improve to some extent, but the quality will be higher than necessary, and additional cooling time will be required, resulting in a longer cycle time.

In other words, even in the heating process, time control using a timer is wasteful and reduces work efficiency.

Additionally, mounting a pressure sensor on the mold requires additional work, and even if a pressure sensor is incorporated into the filler or eject pin as described above, the filler or eject pin will become larger. This includes problems such as making installation difficult and impairing the original function.

Furthermore, the foaming pressure that can be detected by a sensor provided in the mold is limited to the position of the sensor, and it is impossible to detect the entire foaming pressure.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a method and apparatus for detecting the foaming pressure of a foamed synthetic resin material filled into a mold of a foam molding machine.

[Means to solve the problem]

In order to achieve the above object, the present invention comprises a fixed formwork fixed to a foam molding machine main body and to which one of the molds for foam molding is attached, and a fixed formwork movable in opposition to the fixed formwork. ,
consisting of a movable formwork to which the other mold of the foam molding mold is attached, and a ball screw and a ball nut engaged;
A foam molding machine having a moving means for moving the movable formwork opposite to the fixed formwork, and a servo motor for rotationally driving a ball nut or a ball screw of the moving means, the moving form being attached to the movable formwork. a position detecting means for the mold; a servo control section to which a position signal detected by the position detecting means is fed back and controlling the servo motor based on the feedback; A pressure detecting means associated with the movable mold is provided, and after the foam molding mold is closed, a minute gap is created between the two molds, and the distance between the two molds is determined during foam molding. The foaming pressure acting in the direction of expanding the gap is detected by the position detection means and fed to the servo control unit, and the foam molding process is performed while the servo motor is controlled to maintain the minute gap constant. This constitutes a foaming pressure detection device in a foam molding machine that converts the load applied to the pressure sensitive part of the pressure detection means into an electrical signal to detect foaming pressure.

Here, a load cell can be used as the pressure detection means.

Further, in the present invention, there is provided a fixed formwork which is fixed to the main body of the foam molding machine and to which one of the molds for foam molding is attached, and which is movable opposite to the fixed form frame, and the mold for foam molding is a movable formwork to which the other mold of the mold is attached; a moving means formed by engagement of a ball screw and a ball nut to move the movable formwork against the fixed formwork; and a ball nut or ball of the moving means. a servo motor that rotationally drives a screw; a pressure detection means in which a pressure sensitive part is connected between the tip of the ball screw of the moving means and the movable formwork; and position detection of a movable mold attached to the movable formwork. and a servo control section configured to feed back a position signal detected by the position detection means and control the servo motor based on the feedback, which closes the foam mold. After that, a minute gap is created between the two molds, and the foaming pressure that acts in the direction of increasing the distance between the two molds during foam molding is detected by the position detection means and fed to the servo control section, Foam molding in which the foam molding process is performed while the servo motor is controlled to maintain a constant gap, and at the same time, the load applied to the pressure sensitive part of the pressure detection means is converted into an electric signal to detect the foaming pressure. This invention discloses a method for detecting foaming pressure in a foaming machine.

[For production]

The method and device for detecting foaming pressure in a foam molding machine according to the present invention are as described above, and the pressure detecting means maintains a minute gap between both molds after closing the molds, and detects changes in the foaming pressure inside the molds. The foaming pressure is detected by detecting a change in the load applied to the pressure sensitive part and converting this into an electric signal.

〔Example〕

The details of the present invention will be explained based on illustrated embodiments.

FIG. 1 is an explanatory view of the main parts of a foam molding machine body used in the present invention.

1 in the figure is a fixed formwork attached to the foam molding machine main body,
One of the fixed molds 3 of the foam molding molds 2 is attached thereto.

A filler for filling raw material beads and an eject bin (none of which are shown) for taking out a molded product are attached to the back side of the fixed mold 3.

4 is a movable mold that is movable in opposition to the fixed mold 1, and is the other movable mold 5 of the foam molding molds 2.
is installed.

This movable formwork 4 is usually guided by tie bars (not shown) that are erected from the fixed formwork 1 to move.

The movable formwork 4 is moved by a moving means 6 that converts rotational motion into linear motion, and this moving means 6 includes, for example, a ball screw 7 whose tip is attached to the back side of the movable formwork 4 and this ball screw. 7 and a ball nut 8 which is screwed together.

Reference numeral 9 denotes a servo motor attached to the main body of the foam molding machine, and the rotational force of this servomotor 9 is transmitted to the ball nut 8 via the belt 10, but the method of transmitting the rotational force is not limited to this.

Reference numeral 11 denotes a pressure detection means connected between the tip of the ball screw 7 and the movable formwork 4, and in the illustrated one, the main body is attached to the tip of the ball screw 7, and the pressure sensitive part 13 comes into contact with the back side of the movable formwork 4. A load cell 12 arranged as shown in FIG.

The load cell 12 has a strain gauge inside and generates an electrical signal according to the load applied to the pressure sensitive part 13.

A joint 14 having a substantially U-shaped cross section and having a through hole 15 through which a ball screw 7 can be inserted is attached to the back side of the movable formwork 4.
It is inserted into the through hole 15 of No. 4.

The tip of the ball screw 7 is connected to the through hole 15 of the joint 4.
The diameter of the ball screw 7 is larger than that of the mold, and the tip of the ball screw 7 is engaged with the joint 4 when the mold is opened, thereby making it possible to reliably move the movable mold 4.

Further, the pressure sensitive part 13 of the load cell 12 is arranged so as to be in contact with the back surface of the movable formwork 4 when the mold is closed.

FIG. 2 is a simplified diagram for explaining the main parts of the present invention.

That is, the rotation of the servo motor 9 is converted into a position signal by a position detection means 16 such as a rotary encoder, and thereby the position of the movable formwork 4 can be detected.

The position detection means 16 can also directly detect the position of the movable formwork 4 using an optical encoder, a magnetic scale, etc., and one that determines the home position pulse and detects the subsequent change in the increase pulse is used. It is something.

The position of the movable formwork 4 detected by the position detection means 16 is converted into a position pulse signal and fed back to the servo control section 17.

The servo control unit 17 has a set reference position and a position detection means 16.
The servo motor 9 is controlled by a transfer function determined to correct the deviation by determining a deviation from the device signal consisting of the following.

The rotational force of the servo motor 9 is converted into linear motion via the moving means 6, and further moves the movable formwork 4 via the pressure detecting means 11.

As shown in FIG. 1, the pressure detection means 11 can be composed of a load cell inserted between the back surface of the movable formwork 4 and the tip of the ball screw 7, and detects the load from the ball screw 7 applied to the strain gauge as foaming pressure. It then converts it into an electrical signal and outputs it.

FIG. 3 is an explanatory cross-sectional view of the foam molding mold 2. FIG.

That is, the foam molding mold 2 has a fixed mold 3 and a movable mold 5, which form a molding space 18 when the molds are closed together.

At this time, the bonding surface of the fixed mold 3 or the movable mold 5 has 0
A packing 19 made of an elastic body such as a ring is attached, and when the fixed mold 3 and the movable mold 5 are brought into complete contact, the packing 19 is compressed and elastically deformed.

Normally, this packing 19 has a diameter of about 6 to 1 m, and protrudes by about 1 to 2 cylinders from the 5 to 5 joint surface provided on one side of the mold 2.

For this reason, from a state where the mold 2 is completely in contact, it is necessary to
Even when the 0 μm mold is open, the molding space 18 forms a closed space necessary for foam molding, and the packing 19 is elastically deformed and tightened by the torque of the servo motor 9 due to the force P. An elastic force E is generated in the opposing direction.

In addition, the foamed synthetic resin raw material beads filled in the molding space 18 are heated, thereby generating a foaming pressure F in a direction that resists the tightening force P.

Therefore, if a minute gap is created in the foam mold 2 and the servo motor 9 is controlled to keep this gap constant, the tightening force P due to the torque of the servo motor 9 will be Foaming pressure F of foamed synthetic resin and packing 19
is always balanced with the sum of the elastic force E.

FIG. 4 is a flowchart of the present invention.

First, drive the servo motor 9 to move the movable formwork 4,
The foam molding mold 2 is brought into complete contact.

The position of the movable mold 5 at this time is assumed to be Xo=O.

Next, the movable mold 4 is moved to create a minute gap between the fixed mold 3 and the movable mold 5.

This minute gap is, for example, a gap of about 10 μm,
This is enough to maintain the elastically deformed state of the gasket 19 shown in FIG. 3.

If 100 pulses of the position pulse signal Xref are required to set this minute gap to 10 μm, then
It is sufficient to set ef = 100 (pulse).

Alternatively, if a clamping force of 101 is required to completely close the mold in a sealed state, the same result can be obtained by setting the position pulse of the clamping state with a force of about 10% IL as X ref.

In this state, raw material beads of a foamed synthetic resin such as foamed polystyrene are filled into the molding space 18 of the foaming mold 2, and heating, foaming, and cooling steps are performed.

At this time, the position of the movable mold 5 is detected by the position detection means 16, converted into a position pulse X, and fed back to the servo control section 17.

The servo control unit 17 generates a reference position pulse X ref (・
100 (pulse)) and the detected position pulse X to find the deviation α, and then determine the speed control command based on this position loop gain Go and other transfer functions so that the deviation α becomes 0. Controls the servo motor 9.

At this time, the load applied to the strain gauge of the load cell 12 when tightened by the servo motor 9 is a force P, which is converted into an electric signal and detected.

That is, if the servo motor 9 is controlled so that the minute gap in the foam mold 2 is maintained at 10 μm, the sum of the elastic force E by the packing 19 and the foaming pressure F of the foamed synthetic resin in the molding space 18 is Tightening by the torque of the servo motor 9 is a force P
is always in balance.

Therefore, the foaming pressure F is expressed as F=P-E-α, and it is possible to easily know this foaming pressure by detecting the load applied to the strain gauge of the load cell 12.

However, α is a disturbance such as the vacuum pressure during evacuation in the molding space and the vapor pressure during heating.

In the heating process, sufficient fusion is achieved when the foaming pressure reaches a certain value, for example, 1.2 to 2.0 kg.
If the heating step is completed at a foaming pressure of approximately /cJ, appropriate heating can be performed in the minimum necessary time.

In addition, the molded product is removed by opening the mold when the foaming pressure drops to a set value.
If the foaming pressure F drops to about 0.4 to 0.05 kg/ccil, it can be taken out without deformation.

The foaming pressure detection method and device for a foaming molding machine according to the present invention have the above-described configuration, and can detect the foaming pressure in the molding space 18 of the foaming mold 2 using the load cell 12. By performing the heating step and the cooling step at appropriate foaming pressures, the molded product can be taken out at an appropriate time.

Furthermore, the foaming pressure obtained here is the entire foaming pressure within the molding space 18 of the foam molding mold 2, and is highly reliable and can prevent deformation of the molded product. It is.

Further, since it is not necessary to attach it to the foam molding mold 2, the foaming pressure can be controlled no matter what kind of mold is used.

FIG. 5 is an explanatory side view of a second embodiment of the foaming pressure detection device in the foaming molding machine according to the present invention.

1 is a fixed formwork attached to the main body of the foam molding machine;
One of the fixed molds 3 of the foam molding molds 2 is attached thereto.

Reference numeral 4 denotes a movable mold that is movable in opposition to the fixed mold 1, to which the movable mold 5, which is the other of the molds 2 for foam molding, is attached.

This movable formwork 4 moves while being guided by tie bars 20 that pass through the fixed formwork 1, and a dummy frame 21 is attached to the other side of the tie bars 20.

A pole nut 22 is fixed to the dummy frame 21,
The mold is supported by the main body of the foam molding machine and has a fixed tip.
A ball screw 23, which is loosely attached to the back surface, is screwed into this pole nut 22.

The rotational force of a servo motor 25 is transmitted to the ball screw 23 via, for example, a belt 24, and the rotational force of the servo motor 25 is transmitted to the ball screw 23, converted into linear motion by the pole nut 22, and moved into the dummy frame. 21 is moved, and from this the movable formwork 4 is moved.

A joint 27 having a substantially U-shaped cross section and having a through hole 26 through which a ball screw 23 can be inserted is attached to the back side of the fixed formwork 1 . It has a large diameter and is attached to the joint 27 in a loose state.

In addition, a load cell 28 is provided at the tip of the ball screw 23.
A pressure detecting means 11 is provided, and a pressure sensitive part 29 of the load cell 28 is in contact with the back surface of the fixed formwork 1 to detect the pressure with the tip of the ball screw 23.

In this second embodiment, similarly to the first embodiment, the servo motor 25 is driven to move the movable formwork 4, and - once the molding die 2 is
completely adhere.

Next, move the movable formwork 4, and move the fixed mold 3 and the movable mold 5.
A small gap is created between the two.

A servo motor 25 is operated to keep this minute gap constant.
The process of foam molding is carried out while controlling the process.

The foaming pressure generated within the molding space 18 of the foam molding mold 2 is
It acts in the direction of separating both molds, and acts in the direction of opening the movable formwork 4.

This foaming pressure acts on the dummy frame 21 via the tie bar 20, is further transmitted to the ball screw 23 via the pole nut 22, and is detected by the strain gauge of the load cell 28.

Therefore, by converting the load applied to the load cell 28 into an electrical signal, the foaming pressure within the molding space of the mold can be obtained.

In this embodiment, an excessive load is not applied to the load cell 28 when the mold is closed, and it is possible to reduce failures of the load cell 28.

FIG. 6 is an explanatory side view of a third embodiment of the present invention.

That is, the fixed mold 3 is attached to the fixed formwork 1,
A movable mold 5 is attached to the movable formwork 4.

Further, a pole nut 30 is attached to the movable formwork 4, and a ball screw 31 is screwed into the pole nut 30.

The ball screw 31 is supported by a bearing on the fixed formwork 1 and is rotationally driven by a servo motor 32.

A washer-shaped load cell 33 is inserted between the pole nut 30 and the movable formwork 4, and a load is applied in advance for initial tightening.

As the load cell 33 inserted between the pole nand 30 and the movable formwork 4, it is also possible to use a plurality of load cells.

In this third embodiment, the same control as in the first and second embodiments is carried out to detect the foaming pressure in each step of foam molding.

That is, the foaming pressure after the mold is closed is applied to the pole nand 30 via the movable mold 4, and the load on the load cell 33 changes from the initial tightening load.

By measuring this amount of change, the foaming pressure can be easily determined.

[Effects of the Invention] The method and device for detecting foaming pressure in a foam molding machine according to the present invention are as described above, and by detecting the load applied to the load cell, the foaming pressure in the molding space of the mold for foam molding is determined. can be detected, and the heating process can be completed and the molded product taken out at an appropriate time.

Furthermore, the foaming pressure obtained here is the entire foaming pressure within the molding space of the foam molding die, and is highly reliable, making it possible to prevent deformation of the molded product.

Furthermore, since there is no need to attach it to a mold for foam molding, the foaming pressure can be controlled no matter what kind of mold is used.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the main parts of the foam molding machine body used in the foaming pressure detection method and device for the foam molding machine according to the present invention, and FIG. 2 is a simplified block diagram for explaining the main parts of the foam molding machine. 3 is an explanatory sectional view of a foam molding mold used in the present invention, FIG. 4 is a flowchart of the present invention, FIG. 5 is an explanatory side view of a second embodiment of the present invention, and FIG. FIG. 7 is an explanatory side view of a third embodiment of the invention. 1: Fixed formwork, 2: Foaming mold, 3: Fixed mold, 4: Movable formwork, 5: Movable mold,
6: Movement means, 7: Ball screw, 8: Pole nut, 9: Servo motor, 10: Belt, 11:
Pressure detection means, 12: Roth cell, 13: Pressure sensitive part,
14: joint, 15: through hole,
16: Position detection means, 17: Servo control section, 18
: Molding space, 19: Panokin, 20: Taiher 21: Dummy frame, 22: Ball nut, 23
: Ball screw, 24: Heald, 25: Servo motor, 26: Through hole, 27: Joint, 28
: Load cell, 29: Pressure sensitive part, 30: Pole nut, 31: Ball screw, 32: Servo motor, 33: Load cell. Diagram

Claims (1)

[Scope of Claims] 1) A fixed formwork fixed to the main body of the foam molding machine and to which one of the molds for foam molding is attached; a movable formwork to which the other mold of the use mold is attached; a moving means formed by engagement of a ball screw and a ball nut for moving the movable formwork against the fixed formwork; and balls of the moving means. A foam molding machine comprising: a servo motor that rotationally drives a nut or a ball screw; and a position detection means for a movable mold attached to the movable mold, and a position signal detected by the position detection means is fed back; a servo control unit that controls the servo motor based on the above, and a pressure detection unit in which a pressure sensing unit is associated between the tip of the ball screw of the moving unit and the moving formwork, and After the mold is closed, a micro gap is created between the two molds, and the foaming pressure acting in the direction of increasing the distance between the two molds during foam molding is detected by the position detection means and fed back to the servo control section, Foam molding in which the foam molding process is performed while the servo motor is controlled to keep the micro gap constant, and at the same time, the load applied to the pressure sensitive part of the pressure detection means is converted into an electrical signal to detect the foaming pressure. Foaming pressure detection device in the machine. 2) A foaming pressure detection device in a foam molding machine according to claim 1, which utilizes a load cell as the pressure detection means. 3) A fixed formwork that is fixed to the foam molding machine main body and to which one of the foam molding molds is attached; a movable formwork to which a mold is attached; a moving means that is formed by engaging a ball screw and a ball nut and moves the movable formwork opposite to the fixed formwork; and a rotating ball nut or ball screw of the moving means. a driving servo motor; a pressure detecting means in which a pressure sensitive part is associated between a ball screw tip of the moving means and the movable mold; a position detecting means of a movable mold attached to the movable mold; a servo control unit configured to feed back a position signal detected by the position detection means and control the servo motor based on the feedback, and after closing the foam mold, A microgap is created between the two molds, and the foaming pressure acting in the direction of increasing the distance between the two molds during foam molding is detected by the position detection means and fed back to the servo control section to keep the microgap constant. A foaming pressure detection method in a foaming molding machine, wherein the foaming process is performed while the servo motor is controlled so as to hold the foaming pressure, and at the same time, the load applied to the pressure sensitive part of the pressure detection means is converted into an electric signal to detect the foaming pressure. .