JPH08336853A - Method for control of foam injection molding machine and mold used therefor - Google Patents

Abstract

PURPOSE: To facilitate foam molding of a thin wall thickness by a method wherein a distance between platens is set a constant value during the filling of resin, a pressure is kept after reaching a specific position of a screw, a specific change pattern wherein the distance between platens is a specific distance-reached point after a specific time has elapsed is followed and thereafter, the distance between platens is made a specific value. CONSTITUTION: After start of filling resin, a microprocessing unit 43 controls a pressure control valve 42 according to a distance between platens detected by a distance sensor 28 so that an initial distance between platens is kept at an aimed value. Then, after a screw has reached a specific position, filling is changed to a keeping process. After a specific time has elapsed, a value specified by a functional pattern from a distance between platens at start of control to a distance between platens at end of specific control is taken as an aimed value, and a pressure control valve 42 is controlled so that the distance between platens follows the functional pattern. Thereafter, the pressure control valve 42 is controlled so that the distance between platens at end of control is kept from a point of time of end of generation of the functional pattern to completion of cooling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam molding method by injection molding, which makes it possible to apply foam molding to a molded product having a wall thickness of 5 mm or less, which has been impossible in the past, thereby reducing the weight of the molded product. However, the present invention relates to a method for controlling a foam injection molding machine that can improve rigidity and improve the surface condition of exterior parts.

[0002]

2. Description of the Related Art A conventional foam molding method using an injection molding machine will be briefly described below. A polyethylene, polypropylene, ABS resin or the like is used as a base material and a foaming agent having a thermal decomposition temperature lower than the thermal decomposition temperature of the base material is kneaded and melted in a heating cylinder of an injection molding machine. At this time, in order to prevent the foaming agent from being gasified by thermal decomposition and becoming bubbles, the resin pressure in front of the screw in the heating cylinder is increased when the resin is plasticized. By filling the resin melted in the heating cylinder into the mold with a short shot, the resin, which had been suppressed by the pressure until then, is released all at once in the mold, and the foaming agent turns into bubbles, forming a bubble structure in the molded product. Is formed.

When the molded product obtained by such a foam molding method has a thickness of 5 mm or more, the resin pressure held in the heating cylinder is rapidly released when the resin is filled in the mold. Since the foaming agent in the resin is apt to gasify rapidly to form bubbles, it is possible to form a bubble structure in the molded product.

[0004]

However, in the case where the molded product by the foam molding method has a thin wall thickness of 5 mm or less, a high resin pressure must be maintained when the resin is filled in the mold, so that the filling is performed. Cannot be foamed inside. Moreover, in the case of a thin-walled molded product, the resin is instantly solidified by cooling after being filled in the mold, so that the resin cannot be foamed and solidifies.

As described above, the foam molding using an injection molding machine is a molding method which has been conventionally used only for thick-walled molded products having a wall thickness of 5 mm or more, and the wall thickness of the molded product is 5 mm.
It could not be used for the following thin-walled molded products.

Therefore, the object of the present invention is to reduce the wall thickness of the molded product to 5
An object of the present invention is to provide a method for controlling a foam injection molding machine, which can perform good foam molding even in the case of mm or less.

Another object of the present invention is to provide a mold suitable for the control method of the foam injection molding machine as described above.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a mold comprising a fixed mold attached to a fixed platen and a movable mold attached to a movable platen, and the fixed mold and the above-mentioned fixed mold by driving the movable platen. In a foam injection molding machine having a drive source for performing mold clamping as well as opening and closing with a movable mold, a distance sensor for detecting a platen distance L between the two platens and a clamping pressure by the drive source are set. A pressure sensor for detecting the mold clamping force; and a control unit for controlling the drive source using a distance detection signal from the distance sensor and a pressure detection signal representing the mold clamping force from the pressure sensor. When the resin filling is started, the control unit monitors the screw position and the first step of controlling the drive source so that the platen distance becomes a constant value LO during the filling process. Then, when the screw reaches a predetermined position, the second step of switching from the filling process to the pressure-holding process and the lapse of time after switching from the filling process to the pressure-holding process are monitored. The third step of controlling the drive source so that the distance between the platens follows a predetermined change pattern whose reaching point is the predetermined value Le from the time point elapsed, and the distance between the platens is the predetermined value Le.
When the drive source is reached, the distance between the platens is set to a constant value L.
The fourth step of controlling until the cooling is completed so as to be e is performed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic view of an injection device and a mold clamping device in a foam injection molding machine to which the present invention is applied. In the injection device, the resin charged from the hopper 11 is melted in the heating cylinder 12, while being measured and kneaded by the screw 13,
The molten resin is stored in front of the screw 13. The stored resin passes through the nozzle 16 by moving the screw 13 to the front, that is, the mold side by the hydraulic cylinder mechanism including the injection cylinder 14 and the piston 15, and the cavity formed by the fixed mold 17 and the movable mold 18. Filled inside. The needle valve 19 opens and closes the hole through which the resin flows out from the nozzle 16, and the injection cylinder 14 and the piston 15
This is for holding the resin pressure stored in front of the screw 13 until the filling is started by pushing the screw 13 forward by the hydraulic cylinder mechanism. Further, the drive oil whose flow rate or pressure is controlled flows in and out of the injection cylinder 14 through the inflow / outflow portion 14-1 according to the filling, holding pressure, and metering processes.

On the other hand, the mold clamping device is fixed to a frame (not shown) and has a rear platen 22 having four tie bars 23 (2 in the figure) with respect to a fixed platen 21 having a fixed mold 17.
Only the book is shown). A hydraulic piston 25 is arranged in a hydraulic cylinder 24 fixed to the rear platen 22, and a movable platen 26 to which a movable mold 18 is fixed is connected to the hydraulic piston 25.
The movable platen 26 is configured to be slidable on the tie bar 23 as the hydraulic piston 25 moves. That is, the movable platen 26 moves in the mold closing direction when injecting the driving oil from the inflow / outflow portion 24-1 of the hydraulic cylinder 24 through a pressure control valve (not shown), and moves in the mold opening direction when injecting the driving oil from the inflow / outflow portion 24-2. Moving.

The hydraulic cylinder 24 is provided with a pressure sensor 27 for detecting hydraulic pressure as a mold clamping force. With the mold closed, the hydraulic pressure in the hydraulic cylinder on the side of the inflow / outflow portion 24-1 is The mold clamping force can be controlled by adjusting based on the detected value of the pressure sensor 27. Further, the fixed platen 21 and the movable platen 26 are provided with a distance sensor 28 for detecting the distance L between the platens, and the fixed mold 17
It is possible to measure a delicate opening amount between each parting surface of the movable mold 18 and the movable mold 18. The term "distance between platens" as used herein means a distance between the parting surfaces, that is, a mold thickness including a so-called mold opening amount or a partial mold thickness, but the behavior is almost the same as the mold opening amount. Is.

Although not shown in the drawings, the injection device and the mold clamping device include a screw position sensor for detecting the screw position, the inside of the nozzle 16 or the die, in addition to the pressure sensor 27 and the distance sensor 28 described above. Various sensors such as a resin pressure sensor for detecting the resin pressure inside and an injection pressure sensor for detecting the hydraulic pressure of the injection cylinder 14 are provided.

FIGS. 2 and 3 show examples of a laser type and an eddy current type distance sensor, respectively. The laser type distance sensor shown in FIG. 2 includes a laser head 28-1 for transmitting / receiving laser light provided on the fixed platen 21 and a reflector 28-2 for laser reflection provided on the movable platen 26. A detection signal of the distance between platens is sent from 1 to a control unit described later. Such a laser system has a long measurement span and can measure up to the maximum mold opening amount, and the laser head 28-1 and the reflector 28-2 are not the fixed mold 17 and the movable mold 18, respectively, but the fixed platen. 21 and the movable platen 26, it is not necessary to adjust the distance sensor even when the mold is replaced.

On the other hand, even if the measurement span is short as in the eddy current method, if the sensor unit 31 is attached to the mount 30 with a variable stroke, the mold is closed when the mold is replaced. It is only necessary to adjust the sensor unit 31 so that it is within the measurement span.

In any of the methods, compared with the method of directly mounting the sensor on the mold, the mold does not need to have a special structure for installing the sensor, and the existing mold does not have the structure for mounting the sensor. However, since it can be used as it is, the workability of die replacement is improved and the die cost can be reduced.

FIG. 4 shows the configuration of a control system necessary for executing the control system according to the present invention. This control system includes a setting signal from a setter 41 for inputting a platen distance, a mold clamping force, etc., a pressure detection signal from a pressure sensor 27, a platen distance detection signal from a distance sensor 28, and the above-mentioned various types. Based on the detection signal from the sensor, etc., the sequence processing of the injection molding machine, the function pattern generation, the hydraulic cylinder 24
It has a microprocessing unit 43 for outputting a command value to the pressure control valve 42 for use, a memory 44 for storing data such as a distance between platens, and a mold clamping force. The microprocessing unit 43 also has a time monitoring function using a timer.

FIG. 5 shows the mold structure required to carry out the molding method according to the invention. Mold is fixed platen 21
And a movable mold 18 attached to the movable platen 26. When the movable platen 26 of the mold clamping device is opened and closed, the movable mold 1
8 also operates, and the space between the parting surfaces of each mold is opened and closed. When the resin is filled, as shown in FIG. 5 (a), the parting surfaces of the mold are closed, and the resin flowing from the nozzle 16 (FIG. 1) is sprued on the stationary mold 17. It flows into the cavity 37 through 36. The resin filled in the mold is foamed by opening the movable mold 18 to open the space between the parting surfaces and increasing the volume of the cavity 37. Ejector plate 3
By ejecting the ejector pin 34 supported by 3, the molded product can be separated from the movable mold 18 and taken out.

This mold has a return pin 35 for returning the molded product to its original position after it is ejected. This is because when the movable mold 18 is closed and the parting surfaces of the mold are closed, the tip of the return pin 35 is fixed.
Then, the ejector plate 33 supporting the return pin 35 returns to its original position, so that the ejector pin 34 also returns to its original position. In addition, in order to generate a force for opening the parting surfaces, the movable mold 18
A spring 38 is disposed between the fixed mold 17 and the fixed mold 17. Figure 5
(B) shows a state where the parting surfaces between the fixed mold 17 and the movable mold 18 are separated by a distance A.

In FIG. 6, in order to generate a force for opening between the parting surfaces, the return pin 35 disposed on the movable mold 18 is lengthened and compressed when the parting surfaces are closed. It is a mold with a structure.

FIG. 7 shows a structure in which a hydraulic mechanism 40 including a hydraulic cylinder and a piston is incorporated in the movable mold 18 in order to generate a force for opening the parting surfaces so that the parting surfaces can be opened. It is a mold taken.

FIG. 8 is a flow chart showing the flow of the control operation from the mold closing to the mold opening executed by the control system shown in FIG. 4, in which the platen distance L, the mold clamping force P, and the injection speed. Also, the control operation will be described with reference to FIG. 9 showing changes in pressure. In step S1, the mold closing operation before starting the molding is performed. In step S2, the mold closing operation is performed as is conventionally done, and the position of the movable platen 26 is measured,
Alternatively, it is determined from the detection signal of the pressure sensor 27 that the mold has been closed. In step 3, the inter-platen distance L when the mold is closed is stored in the memory 44 by the microprocessing unit 43 as the initial inter-platen distance LO.

In step S4, resin filling is started.
Before starting the filling of the resin, it is necessary to measure the resin in the heating cylinder 12. When a foaming agent is kneaded as a base material such as polyethylene, polypropylene or ABS resin, or a mixture of the base material and the respective pellets of the foaming agent is introduced from the hopper 11 of the foam injection molding machine, the resin is stored in the heating cylinder 12. The screw 13 is melted as it rotates, and is stored in front of the screw 13. The resin is melted by the heater wound around the outer circumference of the heating cylinder 12, the screw 13 and the resin generated by the rotation of the screw 13 in the heating cylinder 12, the resin and the inner wall of the heating cylinder 12, and the shear heat generated between the resins. Be seen.

Since the melting temperature and the decomposition temperature of the foaming agent are usually lower than that of the resin as the base material, the foaming agent in the heating cylinder 12 starts to decompose first. Resin is heating cylinder 1
When the foaming agent decomposes when it is plasticized inside, it gasifies and becomes bubbles, but when the screw 13 is rotated to melt the resin, by injecting driving oil from the inflow / outflow portion 14-1 of the injection cylinder 14. , The resin stored in front of the screw 13 is pressed to suppress the gasification of the foaming agent. At that time, the needle valve 19 for opening and closing the resin outflow hole of the nozzle portion 16 is closed. And, needle valve 1 until the start of filling
9 is closed and holds the resin pressure stored in front of the screw 13. Then, the needle valve 19 opens at the start of filling.

When the filling is started, in step S5, the microprocessing unit 43 maintains the initial inter-platen distance LO as a target value and maintains the initial value, according to the inter-platen distance L detected by the distance sensor 28. 42, and the mold clamping force P changes according to this. As described above, when the mold clamping force P is changed and the platen-to-platen distance is filled while maintaining the initial platen-to-platen distance LO, the initial platen-to-platen distance LO is set as the target value, and therefore even when the resin filling pressure is received. There is no opening between the parting surfaces of the fixed mold 17 and the movable mold 18, and no burr is generated. Thus, by appropriately changing the mold clamping force P according to the filling pressure, it is possible to obtain the effect that the occurrence of burrs can be prevented.

Instead of controlling the pressure control valve 42 so as to maintain the initial platen distance LO as the target value in step S5, when the resin filling is started, the microprocessing unit 43 causes the mold clamping force P to be maintained. Is the target value P1
When the pressure control valve 42 is controlled so as to maintain the pressure at a constant value, and the resin filling proceeds, the resin pressure in the mold increases and the initial platen distance LO cannot be maintained with the mold clamping force P1, and the platen distance L increases. . Then, the microprocessing unit 43 performs a determination operation as to whether the inter-platen distance L matches a preset value La, and if they match, the microprocessing unit 43 sets the inter-platen distance La as a target value and ends this filling process. The method of controlling the pressure control valve 42 may be performed so as to maintain

As described above, by controlling the mold clamping force during the filling process and opening the platen distance to a predetermined value, discharge of gas and air generated from the resin is promoted.
Moreover, even if the resin filling progresses and the space between the platens is opened by the resin pressure in the mold, when the preset platen distance La is reached, the platen distance La is controlled as the target value. If is appropriate, there is no burr. At this time, the fixed mold 17 and the movable mold 18
A small amount is opened between the parting surfaces, but the platen distance L
If the value of a is appropriate, the resin will not enter the gap between the parting surfaces, and the occurrence of burrs can be prevented.

In the mold clamping operation during the filling process, the screw position is monitored by the microprocessing unit 43, and the mold clamping force P reaches the target value P1 from the start of the filling until the screw reaches a predetermined position. The pressure control valve 42 is controlled to maintain. After the screw 13 reaches a predetermined position, the microprocessing unit 43 monitors the platen distance L and determines whether or not the platen distance L matches the preset value La. The pressure control valve 42 may be controlled so that the distance La is set as a target value and is maintained until the end of the filling process.

In step S6, the microprocessing unit 43 monitors the detection signal from the screw position sensor and determines whether or not the screw has moved to a predetermined position. When the screw reaches the predetermined position, the process proceeds to step S7 and the VP
Switching, that is, switching from the filling process to the pressure holding process is performed.

The VP switching operation can also be performed by monitoring the detection signal of the resin pressure sensor or the injection pressure sensor described above in the microprocessing unit 43. That is, the microprocessing unit 43 determines whether or not the resin pressure in the nozzle 16 or the mold has reached a predetermined value after starting the filling,
VP switching may be performed when a predetermined value is reached, or whether the hydraulic pressure in the injection cylinder 14 has risen to a predetermined hydraulic pressure may be monitored, and VP switching may be performed when the predetermined hydraulic pressure is reached. Furthermore, the VP switching may be performed when a predetermined time has elapsed from the start of filling, by the time monitoring function of the timer of the microprocessing unit 43.

The VP switching operation can also be performed by monitoring the detection signal of the pressure sensor 27 which detects the mold clamping force in the microprocessing unit 43. That is, the microprocessing unit 43 monitors the mold clamping force P detected by the pressure sensor 27, and determines whether the mold clamping force P exceeds the predetermined value P2. This is because the mold tries to open due to the progress of filling and the resin starting to fill the mold, while the microprocessing unit 43 causes the initial platen distance L
This is because the command value to the pressure control valve 42 is increased to hold O, and the mold clamping force P is increased. Further, the differential value ΔP of the mold clamping force P may be monitored and a determination operation may be performed as to whether the differential value ΔP exceeds a predetermined value ΔP2.

FIG. 10 shows the behavior of the mold clamping force P and its differential value ΔP. Here, when the differential value ΔP exceeds a predetermined value ΔP2, the process proceeds to step S7 and the VP is switched, that is, the pressure is maintained from the filling step. Switch to the process. According to such a determination operation, it is possible to accurately grasp the filling of the mold with the resin. The determination of the VP switching timing based on the differential value ΔP of the mold clamping force is as shown in FIG.
It may be possible to perform that the increase of P stops and reaches a certain value.

In step S8, the microprocessing unit 43 starts counting with a timer from the time when the filling process is switched to the pressure holding process. Then, continuously from step S5 until the predetermined time t1 elapses, the microprocessing unit 43 sets the initial inter-platen distance LO as the target value and maintains it so as to correspond to the inter-platen distance L detected by the distance sensor 28. To control the pressure control valve 42. In step S9, it is determined whether or not the predetermined time t1 has elapsed, and when the predetermined time t1 has elapsed, the process proceeds to step S10. Then, the microprocessing unit 43 generates the function pattern LP1 having a smooth shape from the control start platen distance LO to the predetermined control end platen distance Le. Then, with the value defined by the function pattern LP1 as the target value, the platen distance L is determined by the function pattern L.
The mold control force P is adjusted by controlling the pressure control valve 42 so as to follow P1. At this time, since the volume of the cavity in the mold increases, the resin pressure in the mold sharply decreases, and the foaming agent contained in the resin becomes gas bubbles due to gasification. This creates a cell structure in the molded product.

The function pattern LP1 is, for example, a first-order lag function as shown by the solid line in FIG. As described above, in step S10, the distance between the platens can be precisely controlled by the expansion ratio of the molded product desired to be obtained.

Further, as shown in FIGS. 10A and 10B, the function pattern LP1 depends on the setting of the control start platen distance LO, the control end platen distance Le, and the time constant T1 defining the function pattern LP1. Since the shape of can be changed arbitrarily, the wall thickness of the molded product, the expansion ratio of the molded product,
The operator can set optimum conditions according to the type of resin (viscosity, temperature characteristics, solidification rate, etc.). For example, when the molded product has a large wall thickness, the foaming speed is slow, and therefore, a method can be used in which the time constant T1 is set to a long time and the mold is slowly opened. On the contrary, when the wall thickness is thin, the foamed structure cannot be formed unless the foaming is rapidly performed. Therefore, it is possible to adopt a method in which the time constant T1 is set to a short time and the mold is quickly opened.

A plurality of types of set values of the time constant T1 are set as fixed values and stored in the memory 44, and the operator sets the control end platen distance Le, and at the same time, selects the optimum value from these values. The value may be selected so that the optimum pattern can be selected.

In step S9, the time elapsed after the switching from the filling process to the pressure-holding process is monitored, and when the predetermined time elapses, the microprocessing unit 43 starts the control start from the control start platen distance LO to end the predetermined control. A function pattern LP1 having a smooth shape up to the platen distance Le is generated, and the pressure control valve 42 is controlled so that the platen distance L follows the function pattern LP1 with a value defined by the function pattern LP1 as a target value. To adjust the mold clamping force P. Instead of this method, the position of the screw, the hydraulic pressure of the injection cylinder, the nozzle or mold internal pressure, and the time elapsed from the start of filling are monitored, and when the respective predetermined values are reached, the microprocessing unit 43
Generates a function pattern LP1 having a smooth shape from the control start platen distance LO to a predetermined control end platen distance Le.
A method of adjusting the mold clamping force P by controlling the pressure control valve 42 so that the platen distance L follows the function pattern LP1 with the value defined by 1 as the target value may be executed.

At the timing of switching from filling to holding pressure, the microprocessing unit 43 generates a function pattern LP1 having a smooth shape from the control start platen distance LO to the predetermined control end platen distance Le, The platen distance L is the function pattern L with the value defined by the function pattern LP1 as the target value.
A method of controlling the pressure control valve 42 so as to follow P1 and adjusting the mold clamping force P may be executed. These also can improve the foaming rate of the molded product or adjust the foaming rate by a method that can determine the timing for foaming the resin filled in the mold. For example, when the molded product has a large wall thickness, the foaming speed is slow, and therefore a method of delaying the control start time can be used. Conversely, if the wall thickness is thin,
Since the foamed structure cannot be formed unless the foaming is performed rapidly immediately after the filling, it is possible to take a method of delaying the control start time.

In step S11, the microprocessing unit 43 determines whether or not the value defined by the function pattern LP1 matches the control end platen distance Le. If they match, the generation of the function pattern LP1 is ended and the step ends. The process moves to S12. In step S12, the microprocessing unit 43 controls the pressure control valve 42 so that the control end platen distance Le is maintained as a target value from the end point of generation of the function pattern LP1 to the completion of cooling.

Incidentally, from step S10 to step S12
When opening the platens, the target value is the value defined by the function pattern LP1 from the control start platen distance LO to the control end platen distance Le, and then the control end platen distance Le is the target value until cooling is completed. The pressure control valve 42 is controlled so as to maintain this. In order to increase the expansion ratio of the molded product, it is necessary to open the space between the parting surfaces of the mold as shown in FIG. 5 (b). The lower the resin pressure in the mold, the higher the expansion ratio, and in such molding, the resin pressure in the mold reduces the force to open between the platens, so that the pressure control valve 42 controls the flow-in / out portion 24-1 side. The distance between the platens is controlled by adjusting the hydraulic pressure in the hydraulic cylinder and the hydraulic pressure in the hydraulic cylinder on the side of the inflow / outflow portion 24-2. Thereby, the opening amount between the parting surfaces can be adjusted.

As shown in FIG. 5 (b), a spring 38 is inserted into the mold so that a force is applied between the parting surfaces of the fixed mold 17 and the movable mold 18 to form a mold. Between the parting surfaces of the
Moreover, the opening amount can be precisely controlled. By adopting this method, the inflow / outflow portion 24 controlled by the pressure control valve 42
It is not necessary to adjust the hydraulic pressure in the hydraulic cylinders on both the -1 side and the inflow / outflow portion 24-2 side, and it is sufficient to control only the inflow / outflow portion 24-1 side by the pressure control valve 42, and the hydraulic circuit is simplified. it can.

In addition to the method of inserting a spring into the mold, the return pin 35 of the mold is lengthened as shown in FIG. 6 to close the space between the parting surfaces of the mold.
Even by the method of compressing the mold and opening the space between the parting surfaces of the mold, that is, the space between the platens by utilizing the repulsive force, a hydraulic mechanism 40 including a hydraulic cylinder and a piston is provided in the mold as shown in FIG. You may use it.

Thus, one molding cycle is completed. Although this example shows a hydraulic molding machine, the present invention can also be applied to an electric molding machine. It goes without saying that control can be performed by adjusting the torque and torque.

[0043]

As described above, good foam molding can be performed even when the thickness of the molded product is 5 mm or less.

Further, by controlling the position between the platens, the thickness of the molded product, that is, without changing the mold, that is,
The expansion ratio can be freely changed.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an inner injection device and a mold clamping device of a foam injection molding machine to which the present invention is applied.

FIG. 2 is a diagram for explaining an example of a distance sensor used in the present invention.

FIG. 3 is a diagram for explaining another example of the distance sensor used in the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a control system according to the present invention.

FIG. 5 is a view showing a mold structure in which a spring is inserted in the mold according to the present invention.

FIG. 6 is a view showing a mold structure in which a return pin in the mold according to the present invention is elongated.

FIG. 7 is a view showing a mold structure incorporating a hydraulic cylinder and a piston in the mold according to the present invention.

FIG. 8 is a flow chart diagram for explaining a control operation according to the present invention.

FIG. 9 is a diagram showing changes in the distance between platens, the mold clamping force, the injection speed, and the pressure in the course of the control operation according to the present invention.

FIG. 10 is a diagram showing changes in the mold clamping force and its differential value for explaining the timing of VP switching according to the present invention.

FIG. 11 is a diagram showing an example of a function pattern for defining the distance between platens generated by the present invention.

[Explanation of symbols]

 11 Hopper 12 Heating Cylinder 13 Screw 14 Injection Cylinder 15 Piston 16 Nozzle 17 Fixed Die 18 Movable Die 21 Fixed Platen 22 Rear Platen 23 Tie Bar 24 Hydraulic Cylinder 25 Hydraulic Piston 26 Movable Platen 33 Ejector Plate 34 Ejector Pin 35 Return Pin 36 Sprue 37 Cavity 38 Spring 39 Parting surface 40 Hydraulic mechanism

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B29C 45/77 7365-4F B29C 45/77 // B29K 105: 04

Claims (15)

[Claims] 1. A mold including a fixed mold attached to a fixed platen and a movable mold attached to a movable platen, and the movable platen is driven to open and close the fixed mold and the movable mold. In addition, in a foam injection molding machine having a drive source for performing mold clamping, a distance sensor for detecting a platen distance L between the two platens, and a clamping pressure by the drive source for detecting mold clamping force. A pressure sensor; and a control unit that controls the drive source using a distance detection signal from the distance sensor and a pressure detection signal representing the mold clamping force from the pressure sensor, and the control unit is a resin. When the filling is started, the first step of controlling the driving source so that the distance between the platens becomes a constant value LO during the filling step, and the screw position is monitored to check the screw position. The second step of switching from the filling process to the pressure-holding process when reaching the predetermined position and the time elapsed after switching from the filling process to the pressure-holding process are monitored, and when the predetermined time has elapsed, A third step of controlling the drive source so that the inter-platen distance follows a predetermined change pattern having a predetermined value Le as a reaching point; and when the inter-platen distance reaches a predetermined value Le, the drive source is And a fourth step of controlling until the cooling is completed so that the distance between the platens becomes a constant value Le, and a control method of the foam injection molding machine. 2. In place of the first step, when the resin filling is started, the drive source is controlled so as to maintain the predetermined mold clamping force during the filling step, and the resin filling is performed. When the distance between the platens increases as a result of progressing to the platen and reaches a predetermined platen distance La, a step of controlling the platen distance to a constant value La is executed. 1. The method for controlling the foam injection molding machine according to 1. 3. When the resin filling is started instead of the first step, the driving source is controlled so as to maintain the predetermined mold clamping force during the filling process, and the screw is controlled. When the position is monitored and the screw reaches a predetermined position, the distance between the platens is monitored, and as a result of the progress of resin filling, the distance between the platens increases and reaches the predetermined distance between platens La. Then, the method of controlling the foam injection molding machine according to claim 1, wherein the step of controlling the distance between the platens to be a constant value La is executed. 4. In place of the second step, a step of monitoring the resin pressure in the nozzle portion or the mold and switching from the filling step to the pressure holding step when the resin pressure reaches a predetermined value is executed. The method for controlling a foam injection molding machine according to any one of claims 1 to 3, wherein: 5. Instead of the second step, a step of monitoring the oil pressure of the injection cylinder and switching from the filling step to the pressure holding step when the oil pressure reaches a predetermined oil pressure is executed. The method for controlling a foam injection molding machine according to any one of claims 1 to 3. 6. Instead of the second step, a step of monitoring the lapse of time from the start of filling and executing a step of switching from the filling step to the pressure holding step when a predetermined time has elapsed from the start of filling The method for controlling a foam injection molding machine according to any one of claims 1 to 3, wherein: 7. The mold clamping force represented by the pressure detection signal is monitored instead of the second step, and the mold clamping force reaches a predetermined level, or the slope of increase of the mold clamping force is constant. 4. The method for controlling a foam injection molding machine according to claim 1, wherein the step of switching from the filling step to the pressure holding step is executed when the inclination reaches a predetermined level. . 8. The driving so that the platen distance follows a predetermined change pattern whose reaching point is a predetermined value Le when the filling step is switched to the pressure holding step instead of the third step. The method for controlling a foam injection molding machine according to any one of claims 1 to 7, wherein the step of controlling the power source is executed. 9. Instead of the third step, the position of the screw is monitored, and when the screw reaches a predetermined position, the platen distance follows a predetermined change pattern having a predetermined value Le as a reaching point. 8. The method for controlling a foam injection molding machine according to claim 1, wherein the step of controlling the drive source is executed as described above. 10. The hydraulic pressure of the injection cylinder is monitored instead of the third step, and when the hydraulic pressure reaches a predetermined hydraulic pressure, the platen distance is changed to a predetermined change pattern having a predetermined value Le as a reaching point. The control method of the foam injection molding machine according to claim 1, wherein the step of controlling the drive source is executed so as to follow. 11. Instead of the third step, the resin pressure in the nozzle portion or the mold is monitored, and when the resin pressure reaches a predetermined value, the distance between the platens is set to a predetermined value Le as a reaching point. 2. The step of controlling the drive source so as to follow the change pattern of 1.
7. The method for controlling the foam injection molding machine according to any one of 7 to 7. 12. In place of the third step, the passage of time from the start of filling is monitored, and when a predetermined time has elapsed from the start of filling, the distance between the platens is a predetermined value Le.
The method for controlling a foam injection molding machine according to any one of claims 1 to 7, wherein the step of controlling the drive source is executed so as to follow a predetermined change pattern having a reaching point. 13. Molding by inserting a spring that exerts a force that opens between the fixed mold and the movable mold when the parting surfaces of the fixed mold and the movable mold are closed. The mold used for the control method of the foam injection molding machine according to claim 1, wherein the space between the parting surfaces can be opened instantaneously. 14. The return pin is lengthened and compressed so that a force that opens between the fixed mold and the movable mold acts when the parting surfaces of the fixed mold and the movable mold are closed. The mold used in the method for controlling the foam injection molding machine according to claim 1, wherein a force is applied so that the parting surfaces can be opened instantaneously during molding. 15. A hydraulic piston in the mold so that when the parting surfaces of the fixed mold and the movable mold are closed, a force is exerted to open between the fixed mold and the movable mold. 2. A foam injection molding machine according to claim 1, wherein a cylinder and a cylinder are provided, and a hydraulic piston is driven by a hydraulic source during molding so that the space between the parting surfaces can be opened instantaneously. Mold used for control method.