JP2004098582A - Injection foam molding machine and method for injection foam molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection foam molding machine and a method for injection foam molding which suppress intrusion of foaming gas and air between a molded article and a mold, thereby prevent a swirl mark (trace of foaming gas) or a silver (silver streak) and make a movable die plate move parallel in momentary opening (core back) of the mold so as to make uniform the plate thickness of a foam molded article, on the occasion of foam molding by the injection foam molding machine. <P>SOLUTION: When a molten resin filled by injection in a mold cavity is to be foamed by opening the mold momentarily, the speed of the momentary opening is controlled so that an in-mold pressure detected by an in-mold pressure sensor may not become minus. A plurality of ball screw type jacks are used for the momentary opening of the mold on the occasion of foaming and servomotors for driving the jacks are subjected to a tuning control. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a configuration and a foam molding method of an injection foam molding machine in which a molten resin injected and filled into a mold cavity is foamed by slightly opening a mold to obtain a foam molded product.
[0002]
[Prior art]
Injection foam molding by injection molding machine, after hardening the surface, foaming the inside, aiming at obtaining a light and durable molded product with good appearance, heat-plasticized foaming property The resin is injected into the mold at a high speed, and after the injection is finished, the surface of the molded product in contact with the mold cools and cures. An injection foam molding method for lowering the internal pressure of the molded article to foam the inside of the molded article has been conventionally known.
However, such an injection-foam molded product has a problem in that a foaming gas generated by a sudden decrease in resin pressure during injection of a foaming resin is confined in a mold cavity, or a mold cavity is opened by increasing a space between molds. If the mold moving speed is too fast when expanding the mold to the volume of the molded product, the solidified layer on the surface will not be able to follow the movement of the inner surface of the mold, and will be separated from the inner surface of the mold and free solidification of the resin will not follow the inner surface of the mold. When a surface is formed, swirl marks (foaming gas traces) and silver (silver streaks) that impair the appearance are likely to occur. In order to prevent this, the unsolidified molded product immediately after injection is once pressurized and solidified in a state where foaming on the surface is suppressed, and then the volume is increased, or disclosed in, for example, Patent Document 1 (JP-A-2000-71277). As described above, a foam molding method has been devised in which a material having a low thermal conductivity is used for a mold, cooling is delayed, and solidification and foaming are made uniform.
[0003]
In addition, in the foam molding process using an injection foam molding machine having a plurality of cylinders dedicated to mold clamping, when the volume of the mold cavity is increased, the fixed mold and the movable mold are in a free state in which they are not clamped. Therefore, depending on the position of the foam molded product in the mold and the shape of the molded product, and when the distribution of the pressure in the mold during foam molding with respect to the mold is biased, the relative inclination of the mold is changed. This may cause unevenness in the thickness of the foam molded article.
A conventional example of an injection molding machine having a mechanism for preventing such a relative inclination of a mold and maintaining a parallel state of a die plate to which the mold is attached is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-351142. It has been disclosed. This conventional example includes a first driving means (such as a toggle mechanism or a hydraulic cylinder) for moving a movable mold relative to a fixed mold, and a plurality of pressing members disposed through the movable mold. After injection-filling a foamed resin with an injection foaming molding machine having a second drive means (such as a hydraulic cylinder or a compression spring force) for simultaneously moving the plurality of pressing members back and forth, the mold of the first drive means is The tightening force is loosened (in the case of a hydraulic cylinder, the hydraulic switching valve is set to a neutral state), and the second driving means is used to open the parting surface of the mold by a predetermined stroke at a high speed with a plurality of pressing members. The aim is to obtain homogenization of foaming.
[0004]
[Patent Document 1] JP-A-2000-71277 [Patent Document 2] JP-A-2000-351142
[Problems to be solved by the invention]
In order to prevent the generation of swirl marks (foaming gas traces) and silver (silver streaks) that impair the appearance of the foamed molded product, the unsolidified molded product immediately after injection is once pressurized and solidified while suppressing foaming on the surface Thereafter, the volume is increased or cooling is delayed by using a material having a low thermal conductivity for the mold disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-71277) to achieve solidification and uniform foaming. When the mold is opened and closed for foaming, the mold is moved to a fixed position at a constant speed regardless of whether the mechanism is hydraulic or the toggle mechanism is used. If it is difficult to cope with the change and the mold moving speed is too fast, the expansion due to foaming will not be in time, foaming gas or air will enter between the molded product and the mold, and if the mold moving speed is slow, foaming will occur. The resin hardens during expansion and foaming is insufficient. , It enters between the air of the molded product and the mold, swirl mark in either case takes (foaming gas mark) and silver (silver streaks) and easy at the same time cooling time, the production cycle is longer.
[0006]
Further, in the conventional example disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2000-351142), the opening of the parting surface of the mold is performed by the second driving means, so that the accuracy of the stop position is high. However, in order to adjust the stop position, it is necessary to replace the pressing member. When the second driving means uses a compression spring force, it is not easy to adjust the molding speed and the driving means is The operation has a problem that the stop position accuracy is not sufficient, a loss time is caused in starting and stopping, and a production cycle time is lengthened.
An object of the present invention is to provide an injection foam molding machine and an injection foam molding method that can control the foaming speed and expansion ratio during foam molding by an injection foam molding machine. In addition, during foam molding, injection foam molding machines and injection foaming that suppress the generation of swirl marks (foam gas traces) and silver (silver streaks) by suppressing foam gas and air from entering between the molded product and the mold A molding method is provided. It is still another object of the present invention to provide an injection foam molding machine and a foam molding method that can move a movable die plate in parallel when a mold is opened (core back) to make the thickness of a foam molded product uniform.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by the following configuration and method.
(1) A fixed-side mold attached to a fixed die plate, a movable-side mold attached to a movable die plate, a driving means capable of widening a distance between the two die plates, and a movable means by the driving means. A control device for controlling the moving speed of the side mold to control the expansion rate and expansion rate of the molten resin injected and filled in the mold cavity formed between the two molds. .
(2) The apparatus according to the above (1), further comprising an in-mold pressure sensor for detecting a pressure in the mold cavity, wherein the control device controls a moving speed of the movable mold based on a detection signal of the in-mold pressure sensor. Injection foam molding machine.
(3) The injection foam molding machine according to the above (1), wherein the driving means is a plurality of jacks mounted on the fixed die plate or the movable die plate so as to face the other die plate and driven synchronously.
(4) The injection foam molding machine according to the above item (1) or (3), wherein the driving means is a servo motor driven ball screw device.
(5) A fixed die plate having the fixed mold fixed to the mounting base, a movable die plate movable with the movable mold mounted on the mounting base facing the fixed die plate, and a movable die plate reciprocating. A movable die plate moving means for moving, a plurality of hydraulic clamping cylinders attached to the fixed die plate, a plurality of tie bars which can be integrated with the piston rod of the same clamping cylinder and penetrate through the through hole of the movable die plate; A tie bar fixing means capable of fixing a movable die plate, a four-way switching valve provided in a pipe from a hydraulic pressure source to each mold clamping cylinder, and a mold for each mold clamping cylinder at the same time as closing the discharge side of the four-way switching valve. A means for making a differential circuit between the tightening side and the releasing side, a relief valve capable of controlling the hydraulic pressure of the hydraulic power source to a set low pressure, and a device mounted on a movable die plate or a fixed die plate. A plurality of jacks using a ball screw mechanism that can increase the distance between the die plates by driving each servo motor, and after clamping and injection filling, the relief valve was operated to set the hydraulic pressure of each clamping cylinder. After the pressure is reduced, the servo motors of the plurality of jacks are synchronously driven to control the moving speed of the mold, thereby controlling the expansion speed and expansion rate of the resin foam molding. Molding machine.
[0008]
(6) A step of injecting and filling a molten resin into a mold cavity formed between the fixed mold and the movable mold, and a direction in which the movable mold is separated from the fixed mold after the injection and filling step. An injection foam molding method comprising controlling the moving speed of the movable mold so as to control the expansion speed and expansion rate of the molten resin injected and filled in the mold cavity.
(7) The injection foam molding method according to the above (6), wherein the pressure in the mold cavity is detected, and the moving speed of the movable mold is controlled so that the mold internal pressure in the mold cavity does not become negative.
(8) Using the injection foaming molding machine described in (5) above, melt-plasticize and mold-fill the cavity of the mold by injection, and then reduce the resin pressure and increase the mold cavity volume. In the foam molding method for molding a foam molded article, after injection filling of a foamable resin, the abutment plates of the plurality of jacks are brought into contact with a movable die plate or a fixed die plate, and the relief valve is operated to operate each mold clamping cylinder. After the hydraulic pressure is reduced to the set low pressure, the plurality of jacks are synchronously driven by a servo motor to move the movable die plate in parallel while controlling the expansion speed of the resin foam molding (core back) and stop at the set position. An injection foam molding method in which foaming pressure is maintained, cooling, pressure reduction, and release are performed after foaming is completed.
(9) In the injection foam molding method described in the above (8), an in-mold pressure sensor for detecting a foaming pressure is installed in the movable mold, and the mold internal pressure during the foam molding process of the resin in the mold cavity becomes negative. An injection foam molding method that controls the expansion rate to an unusual level.
(10) In the injection foam molding method according to the above item (8) or (9), when a ball screw device driven by a servo motor is used for the movable die plate moving means, and the resin foam molding process in the mold cavity is performed, An injection foam molding method for controlling the moving speed of the jack and the movable die plate moving means so as to be synchronized.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
An injection foam molding machine and a foam molding method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view showing a mold clamping device of the injection foam molding machine and a hydraulic system diagram of the mold clamping device. FIG. 2 shows a movable die plate and a ball screw type jack of the mold clamping device of the injection foam molding machine of FIG. Front view, FIG. 3 is a side sectional view showing a fixed mold and a movable mold of the mold clamping device of FIG. 1 in a clamped state, and FIG. 4 is a slightly opened state of the fixed mold and the movable mold of the mold clamping device of FIG. FIG. 5 is a graph showing the timing of the foam molding step of the mold clamping device of FIG. 1.
[0010]
In the figure, reference numeral 1 denotes a base, and a fixed die plate 2 to which a fixed mold 4 is attached is fixedly provided at one end of the base 1. A movable die plate 3 on which a movable mold 5 is mounted is movably mounted on the base 1 so as to face the fixed die plate 2. Reference numeral 22 denotes a guide rail fixed to the base 1, and a linear bearing 21 fixed to the movable die plate 3 is guided by the guide rail 22 and supports the movable die plate 3. The fixed die plate 2 is provided with a plurality (four in this example) of mold clamping cylinders 9A to 9D having a short stroke and a large cross-sectional area. The mold clamping cylinders 9C and 9D are provided symmetrically to the mold clamping cylinders 9A and 9B with respect to the vertical center cross section of the fixed die plate 2. Tie bars 7A to 7D are directly connected to one side surface of rams 6A to 6D that slide in the mold clamping cylinders 9A to 9D, respectively, and the tie bars 7A to 7D approach because the opposed movable die plate 3 is closed. Then, it passes through the four insertion holes opened in the movable die plate 3.
[0011]
The tip portions of the tie bars 7A to 7D form a plurality of ring grooves at the same pitch, respectively, while the opposite die side surface of the movable die plate 3 is engaged with the ring grooves of the tie bars 7A to 7D. Further, four pairs of split nuts 11 facing each other are provided so as to be moved by a hydraulic cylinder or the like in a direction perpendicular to the axes of the tie bars 7A to 7D and fixed with the tie bars 7A to 7D therebetween. Reference numeral 8 denotes an injection cylinder.
[0012]
As shown in FIG. 2, four sets of ball screw jacks 50 are mounted symmetrically in parallel with the die 5 on the die mounting surface of the movable die plate 3. Good). As shown in FIG. 1, the jack main body 52 is fixed to the movable die plate 3, and a bearing 56 provided inside the jack main body 52 rotatably supports a ball screw nut 53 in a thrust direction while supporting the ball screw nut 53. The shaft end of the ball screw 51 screwed via a ball is fixed to a backing plate 58. A pin 57 parallel to the ball screw 51 is slidably fitted in a hole provided in the backing plate 58 and serves to prevent the backing plate 58 from rotating. A toothed belt pulley 53 a is provided at an end of the ball screw nut 53, and the rotation and torque of the servomotor 54 are transmitted to the ball screw nut 53 via a toothed belt 55. Since the servomotor 54 is tuned and rotated by the control device 37, the movement speed and the stop position of each ball screw 51 are also tuned and the stop position of the abutment plate 58 attached to the ball screw 51 is movable in all four sets. The distance from the die mounting surface of the die plate 3 is the same.
[0013]
The mold opening / closing means for moving the movable die plate 3 for a large distance in the mold opening direction is installed in parallel with the moving direction of the movable die plate 3, and is rotatable by a bearing box 17 and a bearing box 18 attached to the base 1. The ball screw shaft 13 is supported by being restrained in the axial direction and driven by a servo motor 15 via a power transmission belt 16, and is supported by a bracket 3 a fixed below the movable die plate 3. And a ball screw nut 14 that moves linearly with the rotation of the ball screw shaft 13. The rotation speed and rotation speed of the ball screw shaft 13 are controlled by the control device 37 via the servomotor 15.
[0014]
This mold clamping device starts from a state where the mold of FIG. 1 is opened, that is, a state where the movable die plate 3 is sufficiently separated from the fixed die plate 2 as shown by a two-dot chain line, as shown by a solid line. Until the mold 4 and the mold 5 are closed, the movable die plate 3 moves by the rotation of the ball screw shaft 13 driven by the servomotor 15. The mold moving speed control circuit built in the control device 37 slowly accelerates the movable die plate 3, moves at a constant speed, then decelerates and stops just before the mold 5 contacts the mold 4.
[0015]
At the stop position of the movable die plate 3, the split nut 11 operates, and the inner ring groove of the split nut 11 engages with the ring groove at the tip of the tie bars 7A to 7D to be connected to the tie bars 7A to 7D. Next, after the mold clamping side chambers (port 2a side) of the mold clamping cylinders 9A to 9D are pressurized and mold-clamped, the four sets of ball screw jacks 50 move forward simultaneously to attach the abutment plate 58 to the mold of the fixed die plate 2. Contact the mounting surface. After the mold clamping, a fixed amount of high-pressure molten foaming resin is injected and filled into the cavity of the mold from the injection cylinder 8, and the mold clamping side chambers (port 2a side) of the mold clamping cylinders 9A to 9D are depressurized with almost no interval. Then, the four sets of ball screw jacks 50, 50, 50, 50 are synchronously driven to rotate, and the distance between the fixed die plate 2 and the movable die plate 3 against the (low pressure) clamping hydraulic pressure of the clamping cylinders 9A to 9D. To expand the foaming resin in the cavity surrounded by the mold 4 and the mold 5. When the resin in the mold reaches a predetermined expansion coefficient, the four sets of ball screw jacks 50, 50, 50, 50 are stopped in synchronization. During foaming expansion of the resin, the mold pressure sensor 28 detects the mold pressure and limits the speed of the jack 50 so that the mold pressure does not become negative. (Swirl marks (foaming gas traces) and silver (silver streaks) easily enter between molds.)
[0016]
While maintaining this state, the molten foamed resin in the mold cavity is cooled and solidified from the mold contact surface to form a foamed product. After cooling and solidifying, the hydraulic pressure of the hydraulic circuit of the mold clamping cylinders 9A to 9D is reduced to zero. The split nut 11 is operated in reverse to release the connection with the tie bars 7A to 7D, the ball screw shaft 13 is rotated in reverse to move the movable mold 5 and the movable die plate 3 to the open side, and return to the original fully open position. Stop. After the molded product is removed, the next mold closing process starts.
[0017]
As shown in FIG. 1, the hydraulic control circuit of the mold clamping cylinders 9A to 9D includes a control device 37, a hydraulic pump driving motor 32, a hydraulic pump 31, and a hydraulic pressure of hydraulic oil delivered from the hydraulic pump 31. An electromagnetic proportional control relief valve 36 that can be switched in stages, a hydraulic four-way switching valve 34, a supply pipe 44 for supplying hydraulic oil sent from the hydraulic pump 31 to the hydraulic four-way switching valve 34, and a hydraulic pressure from the hydraulic four-way switching valve 34 The mold-clamping side pipes 45A to 45D provided to the ports 2a and 2c of the cylinders 9A to 9D, the on-off valve 33 installed in the supply pipe 44, and the ports 2b and 2d of the hydraulic cylinders 9A to 9D from the hydraulic four-way switching valve 34 Release pipes 46A to 46D disposed up to the opening and closing valve 35A installed in a differential circuit pipe connecting the mold clamping side pipes 45A to 45D and the release pipes 46A to 46D. 35D, is constituted by a hydraulic meter 39 installed in the supply pipe 44.
[0018]
The injection foam molding process will be described with reference to FIG. 5, which is a graph showing the timing of the foam molding process of the mold clamping device of this embodiment.
(1) Mold closing: The ball screw shaft 13 is rotationally driven by the servo motor 15 to move the movable die plate 3 toward the closing side at a high speed, and then the rotational speed of the servo motor 15 is controlled to decelerate the movable die plate 3, Stop.
(2) Connection of tie bars: Four sets of split nuts 11 are operated to connect with tie bars 7A to 7D.
(3) Clamping: The hydraulic pump 31 is driven, the electromagnetic proportional control relief valve 36 is instructed to control the hydraulic pressure to a specified high pressure, the four-way switching valve 34 is switched to the mold clamping side, and the mold clamping cylinders 9A to 9D are closed. The hydraulic oil is sent to the mold-side ports 2a and 2c to clamp the mold 4 and the mold 5. The four sets of ball screw jacks 50 are moved synchronously to bring the abutment plate 58 into contact with the mold mounting surface 2 e of the fixed die plate 2.
[0019]
(4) Injection filling: Injecting and filling a fixed amount of molten foamed resin into the mold cavity.
(5) Foaming expansion: After injection filling of the molten foaming resin, the resin gate on the mold side is closed and held for a short time (0.4 seconds or less). The pressure is lowered to the set low pressure (the mold clamping force is FM shown in FIG. 5). The four sets of ball screw jacks 50 are tuned to push out the abutment plate 58, and the distance between the fixed mold 4 and the movable mold 5 is increased. The resin is foamed and expanded (the interval s is increased from the state of FIG. 3 to the state of FIG. 4. At this time, the pressing force of the jack 50 is FJ shown in FIG. 5, and FJ ≧ FM−FB). At this time, the expansion speed of the molded product (the ball screw moving speed of the jack 50) is controlled so that the expansion pressure FB of the expandable resin detected by the in-mold pressure sensor 28 does not become negative. When the molded product expands to the set thickness s, the tuning of the ball screw jack 50 is stopped.
[0020]
(6) Holding and cooling: The molded product is cooled for a set time while the distance between the fixed die plate 2 and the movable die plate 3 is maintained by the ball screw jack 50 described above.
(7) Release: After cooling the molded product, the hydraulic four-way switching valve 34 is switched to the release side, the open / close valves 35A to 35D are opened, and the mold-side piping 45 and the release-side piping 46 are passed through. A differential circuit is formed, and the mold clamping cylinders 9A to 9D are caused to perform a releasing operation. The on-off valve 33 is closed, the hydraulic four-way switching valve 34 is switched to the mold clamping side to lower the hydraulic oil of the mold clamping cylinders 9A to 9D to the pressure of the drainage tank, and the split nut 11 is operated in reverse to tie bars 7A to 7D. The ball screw jack 50 is returned to the position before the mold clamping, and the ball screw shaft 13 is rotated in the reverse direction to when the mold is closed to move the movable die plate 3 to the open side, and stops at the original fully open position. I do. The molded product is taken out, and one cycle of the injection foam molding process is completed.
[0021]
In the case of a thin molded product, the moving amount s of the core back is small, but the moving speed of the mold is strictly controlled to a predetermined value, and high accuracy of the stop position is required. Like the mold clamping device, the mold opening means is a plurality of ball screw jacks 50, the plurality of servomotors 54 are tuned, and the core back speed and the mold stop position are controlled by the rotation of the servomotors 54. If it is strictly performed by the number, it is possible to make the thickness of the molded product uniform and at the same time to keep the thickness of the molded product within the range of ± 0.05 mm. That is, in foam molding, it is necessary to perform a core-back at a speed of 1 to 20 mm / sec with a moving amount of 0.5 to 5.0 mm without a pause (within 0.4 sec) at the time of completion of injection filling. A servo motor driven ball screw device is optimal for quick control. When high-precision control is not required, a jack using a hydraulic cylinder can be used instead of the ball screw jack driven by the servo motor.
The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and it is needless to say that various design changes can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the ball screw jack 50 is used as the die opening (core back) means, but the mold clamping cylinders 9A to 9D and the rams 6A to 6D or the servo used for opening and closing the mold is used. The motor 15 and the ball screw shaft 13 can be used.
[0022]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the injection foam molding machine and the injection foam molding method of the present invention, when the molten resin injected and filled into the mold cavity is foamed by slightly opening (core backing) the mold, the opening speed is controlled. Thus, the foaming rate and the foaming ratio of the molten resin can be controlled, so that a high-quality foam molded article can be obtained.
In particular, in the case of a thin-walled foam molded product, the moving amount of the core back is small, but the moving speed of the mold is strictly controlled to a predetermined value, and high accuracy of the stop position is required. Using a plurality of ball screw type jacks for opening the mold (core back) during foaming, the servo motor that drives the jack is tuned and the core back speed and the mold stop position are controlled. If it is performed more strictly, it is possible to make the thickness of the molded product uniform and at the same time to keep the thickness of the molded product within the range of ± 0.05 mm. Further, the production cycle can be shortened.
[0023]
In addition, by controlling the opening speed so that the mold pressure detected by the mold pressure sensor does not become negative, the filled resin can be opened while maintaining the internal pressure, so that the surface of the molded product Always keeps pressed against the mold by the foaming pressure, suppressing foaming gas and air from entering between the molded product and the mold, and swirl mark foaming gas traces on the surface of the molded product and silver (silver strip) Scars) can be prevented. By using a ball screw device driven by a servo motor for the movable die plate moving means, and controlling the moving speed of the jack and the movable die plate moving means to be synchronized during the resin foaming step, the movable die plate is moved. It is possible to prevent a biasing force from being applied to the ball screw device of the moving means.
[Brief description of the drawings]
FIG. 1 is a schematic side view showing a mold clamping device of an injection foam molding machine according to an embodiment of the present invention, and a hydraulic system diagram of the mold clamping device.
FIG. 2 is a front view showing a movable die plate and a ball screw type jack of the mold clamping device of the injection foam molding machine of FIG.
FIG. 3 is a side sectional view showing a state in which a fixed mold and a movable mold of the mold clamping device of FIG. 1 are clamped.
FIG. 4 is a side sectional view showing a state where a fixed mold and a movable mold of the mold clamping device of FIG. 1 are slightly opened.
FIG. 5 is a graph showing the timing of a foam molding step of the mold clamping device of FIG. 1;
[Explanation of symbols]
2 ... fixed die plate 3 ... movable die plate 4 ... fixed mold 5 ... movable mold 6A, 6B, 6C, 6D ... ram 7A, 7B, 7C, 7D ... tie bar 8 ... injection unit 9A, 9B, 9C, 9D ... Clamping cylinder 11 Split nut 13 Ball screw shaft 14 Ball screw nut 33, 35A, 35B, 35C, 35D Open / close valve 28 Mold pressure sensor 31 Hydraulic pump 32 Motor 34 4-way switching valve 37 Control Device 50: Ball screw jack 51: Ball screw 53: Ball screw nut 52: Jack body 54: Servo motor 58: Backing plate

Claims (10)

A fixed-side mold attached to the fixed die plate, a movable-side mold attached to the movable die plate, a driving unit capable of increasing an interval between the two die plates, and a movable-side mold by the driving unit. And a control device for controlling the moving speed of the molten resin and controlling the expansion rate and expansion rate of the molten resin injected and filled into the mold cavity formed between the two molds. Foam molding machine. 2. The apparatus according to claim 1, further comprising an in-mold pressure sensor for detecting a pressure in the mold cavity, wherein the control device controls a moving speed of the movable mold based on a detection signal of the in-mold pressure sensor. The injection foam molding machine as described in the above. The injection foam molding machine according to claim 1, wherein the driving means is a plurality of jacks attached to the fixed die plate or the movable die plate so as to face the other die plate and driven synchronously. . The injection foam molding machine according to claim 1, wherein the driving unit is a ball screw device driven by a servo motor. A fixed die plate having a fixed mold fixed to a mounting base; a movable die plate capable of moving the movable mold on the mounting base in opposition to the fixed die plate; and a movable die plate for reciprocating the movable die plate. Die plate moving means, a plurality of hydraulic mold clamping cylinders attached to the fixed die plate, a plurality of tie bars integral with the piston rod of the mold clamping cylinder, and a plurality of tie bars penetrating through the through hole of the movable die plate, A tie-bar fixing means capable of fixing the same, a four-way switching valve provided in a pipe extending from a hydraulic pressure source to each mold clamping cylinder, a discharge side of the four-way switching valve being closed, Means for making the release side a differential circuit, a relief valve capable of controlling the hydraulic pressure of the hydraulic power source to a set low pressure, and mounted on a movable die plate or a fixed die plate. A plurality of jacks using a ball screw mechanism that can increase the distance between the die plates by driving the servo motors, and after clamping and injection filling, the relief valve was operated to set the hydraulic pressure of each clamping cylinder. A control device for controlling the expansion speed and expansion rate of the resin foam molding by controlling the moving speed of the mold by synchronously driving the servo motors of the plurality of jacks after the low pressure. Injection foam molding machine. Injecting and filling a molten resin into a mold cavity formed between the fixed mold and the movable mold, and moving the movable mold in a direction away from the fixed mold after the injection filling step. An injection foam molding method, comprising the steps of: controlling a moving speed of the movable mold so as to control an expansion speed and an expansion rate of a molten resin injected and filled in a mold cavity. 7. The injection foam molding method according to claim 6, wherein the pressure in the mold cavity is detected, and the moving speed of the movable mold is controlled so that the mold internal pressure in the mold cavity does not become a negative pressure. . A foam molded product obtained by melt-plasticizing a mold cavity using the injection foam molding machine according to claim 5 and injecting and filling a compressed foamable resin, then reducing the resin pressure and increasing the volume of the mold cavity. In the foam molding method, the foaming resin is injected and filled, then the abutment plates of the plurality of jacks are brought into contact with a movable die plate or a fixed die plate, and the relief valve is operated to set the hydraulic pressure of each mold clamping cylinder. After the pressure is lowered, the plurality of jacks are synchronously driven by a servo motor to move the movable die plate in parallel while controlling the expansion speed of the resin foam molding (core back), and stop at the set position to stop foaming. After the completion, the foaming pressure is maintained, the cooling, the pressure is reduced, and the mold is released. In the injection foam molding method according to claim 8, an in-mold pressure sensor for detecting a foaming pressure is installed in the movable mold so that the mold internal pressure during the resin foam molding process in the mold cavity does not become a negative pressure. An injection foam molding method characterized in that the expansion rate is controlled at a high level. 10. The foam molding method according to claim 8 or 9, wherein a ball screw device driven by a servo motor is used as the movable die plate moving means, and the jack and the movable die plate move during the resin foam molding process in the mold cavity. An injection foam molding method, wherein the moving speed of the injection foam molding is controlled so as to be synchronized with the means.

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