Foaming molding method, control method for injection molding machine for foaming molding, and injection molding machine for foaming molding

Abstract

To achieve a reduction in cost when performing foam molding, in a foam molding method in which a foamed molded product (M) is molded by injecting molten resin (R) containing uniformly dispersed bubbles (B) into a cavity (17) formed by a metal mold (16), the method includes: a step of, with a shut-off nozzle (53) that opens and closes a nozzle portion (52) that injects the molten resin R provided on a heating cylinder (50) open, causing a screw (60) to retreat, and taking atmospheric air (A) into the heating cylinder (50) from the nozzle portion (52); a step of closing the shut-off nozzle (53) and causing the screw (60) to advance, and diffusing the atmospheric air (A) taken into the heating cylinder (50) into the molten resin (R) in the heating cylinder (50); a step of, by causing the screw (60) to retreat while rotating with the shut-off nozzle (53) closed, transporting the molten resin (R) to the front side while causing the atmospheric air (A) to become bubbles (B) dispersed in the molten resin (R); and a step of opening the shut-off nozzle (53), and injecting the molten resin (R) containing the dispersed bubbles (B) into the cavity (17).

Description

TECHNICAL FIELD

[0001] The present application relates to a foaming molding method of molding a foamed molded product, a control method of a foaming molding injection molding machine, and a foaming molding injection molding machine. BACKGROUND

[0002] In the past, in molding of resin using an injection molding machine, there has been injection foaming molding called physical foaming using nitrogen or carbon dioxide as a foaming material. Such foaming molding can obtain effects such as weight reduction of a molded product and reduction of use of a material by performing molding while foaming a foaming material. As a method of injecting a foaming material into a molten resin when foaming molding is performed using an injection molding machine, for example, as shown in Patent Documents 1 to 3, a method of pressurizing a foaming material and supplying it to a heating cylinder of an injection molding machine is proposed. In addition, as another method, as shown in Patent Documents 4 and 5, a method of providing a starvation zone in a lead speed adjustment container or a screw, and injecting a foaming material such as nitrogen or carbon dioxide stored in a tank into the starvation zone in a plasticizing cylinder via the lead speed adjustment container is proposed.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent No. 2625576

[0006] Patent Document 2: Japanese Patent No. 3788750

[0007] Patent Document 3: Japanese Patent No. 4144916

[0008] Patent Document 4: Japanese Patent No. 6533009

[0009] Patent Document 5: Japanese Patent Application Laid-Open No. 2019-104125

[0010] Patent Document 6: Japanese Patent Application Laid-Open No. 2019-198993 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] However, when foaming molding is performed, in the case of using a foaming molding dedicated injection molding machine, a high-pressure gas generating device, or a lead speed adjustment container or the like, or using a screw having a starvation zone or the like for foaming molding, a high initial investment cost is incurred. Therefore, in the case of using an injection molding machine for foaming molding, there is room for improvement in terms of cost.

[0013] The present invention has been made in view of the above, and has as its object to provide a foam molding method, a control method for a foam molding injection molding machine, and a foam molding injection molding machine, which can reduce costs when performing foam molding.

[0014] Means for solving the problem

[0015] To solve the above problem and achieve the object, the foam molding method of the present invention is a foam molding method of injecting a molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold to mold a foam molded product, including: a step of retreating a screw provided inside a barrel that mixes the molten resin inside, opening a supply port provided on the barrel on a front side of the screw to supply atmosphere into the barrel, and taking the atmosphere into the barrel from the supply port; a step of advancing the screw and closing the supply port, diffusing the atmosphere taken into the barrel into the molten resin inside the barrel; a step of retreating the screw while rotating the screw to transport the molten resin to the front side while the atmosphere becomes the bubbles dispersed in the molten resin by closing the supply port; and a step of opening the supply port and injecting the molten resin containing the dispersed bubbles into the cavity.

[0016] Further, to solve the above problem and achieve the object, the foam molding method of the present invention is a foam molding method of injecting a molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold to mold a foam molded product, including: a step of retreating a screw provided inside a barrel that mixes the molten resin inside, opening a supply port provided on the barrel on a front side of the screw to supply atmosphere into the barrel, and taking the atmosphere into the barrel from the supply port; a step of advancing the screw and closing the supply port, diffusing the atmosphere taken into the barrel into the molten resin inside the barrel; a step of retreating the screw while rotating the screw to transport the molten resin to the front side while the atmosphere becomes the bubbles dispersed in the molten resin by closing the supply port; and a step of opening the supply port and injecting the molten resin containing the dispersed bubbles into the cavity.

[0017] Further, in order to solve the above problems and achieve the object, the present application provides a foaming molding method for molding a foaming molded product by injecting a molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold, the foaming molding method comprising: a step of retreating a screw provided inside a barrel in which the molten resin is mixed, opening a supply port provided on the barrel on a front side of the screw to enable supply of compressed gas into the barrel and taking the compressed gas into the barrel from the supply port; a step of advancing the screw to close the supply port and diffusing the compressed gas taken into the barrel into the molten resin in the barrel; a step of retreating the screw while rotating the screw to transport the molten resin to the front side while the compressed gas becomes the bubbles dispersed in the molten resin; and a step of injecting the molten resin containing the dispersed bubbles into the cavity.

[0018] Further, in order to solve the above problems and achieve the object, the present application provides a control method for a foaming molding injection molding machine for molding a foaming molded product by injecting a molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold, the control method comprising: a step of retreating a screw provided inside a barrel in which the molten resin is mixed in a state in which a cutoff nozzle provided on the barrel to open and close a nozzle portion for injecting the molten resin is opened, taking atmospheric air into the barrel from the nozzle portion; a step of closing the cutoff nozzle to advance the screw and diffuse the atmospheric air taken into the barrel into the molten resin in the barrel; a step of retreating the screw while rotating the screw to transport the molten resin to the front side while the atmospheric air becomes the bubbles dispersed in the molten resin; and a step of opening the cutoff nozzle to inject the molten resin containing the dispersed bubbles into the cavity.

[0019] Further, in order to solve the above problems and achieve the object, the injection molding machine for foam molding according to the present application is provided with: a metal mold that forms a cavity in which a foamed molded product is molded from a molten resin containing uniformly dispersed bubbles; a barrel that internally mixes the molten resin; a screw that is rotatably disposed inside the barrel and is capable of moving in the axial direction of rotation inside the barrel; a nozzle portion that is provided on the barrel and injects the molten resin inside the barrel toward the cavity; a cutoff nozzle that opens and closes the nozzle portion; and a control portion that controls the operation of the screw and the cutoff nozzle; the control portion, when injecting the molten resin inside the barrel toward the cavity, takes in atmospheric air into the barrel by causing the screw to retreat in a state in which the cutoff nozzle is open; causes the screw to advance by closing the cutoff nozzle, and diffuses the atmospheric air taken into the barrel into the molten resin inside the barrel; causes the atmospheric air to be dispersed inside the molten resin while transporting the molten resin to the front side by causing the screw to retreat while rotating in a state in which the cutoff nozzle is closed; and opens the cutoff nozzle, and injects the molten resin containing the dispersed bubbles toward the cavity.

[0020] Effects of the Invention

[0021] The foam molding method, the control method of the injection molding machine for foam molding, and the injection molding machine for foam molding according to the present application achieve the effect of being able to reduce the cost when performing foam molding. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a perspective view of the injection molding machine for foam molding according to Embodiment 1.

[0023] Figure 2 is a main part cross-sectional view showing the device structure of the injection molding machine for foam molding according to Embodiment 1.

[0024] Figure 3 is a main part plan view showing the device structure of the injection molding machine for foam molding according to Embodiment 1.

[0025] Figure 4 is a detailed view of the heating barrel shown in Figure 2

[0026] Figure 5 is a detailed view of the snap ring shown in Figure 4

[0027] Figure 6 is a flowchart showing the sequence when performing foam molding using the injection molding machine for foam molding according to Embodiment 1.

[0028] Figure 7 ​​is a schematic view showing a state in which the heating cylinder is retracted.

[0029] Figure 8 is a schematic view showing a state in which the screw is retracted.

[0030] Figure 9 is a schematic view showing a state in which the cutting nozzle is closed and the screw is advanced.

[0031] Figure 10 is an explanatory view showing a state in which the screw is retracted while rotating.

[0032] Figure 11 is an explanatory view for explaining the pressure distribution of the molten resin in the heating cylinder in the metering process.

[0033] Figure 12 is an explanatory view showing a state in which the molten resin subjected to metering is injected.

[0034] Figure 13 is an explanatory view showing a state of the snap ring at the time of injection of the molten resin.

[0035] Figure 14 is a schematic view of a main part of a heating cylinder possessed by an injection molding machine for foam molding according to Embodiment 2.

[0036] Figure 15 is a flowchart showing a sequence at the time of foam molding using the injection molding machine for foam molding according to Embodiment 2.

[0037] Figure 16 is a schematic view of a main part of a heating cylinder possessed by an injection molding machine for foam molding according to Embodiment 3.

[0038] Figure 17 is a flowchart showing a sequence at the time of foam molding using the injection molding machine for foam molding according to Embodiment 3.

[0039] Figure 18 is an explanatory view of a modification of the injection molding machine for foam molding according to Embodiment 2, which is a case where a tank is used in the supply of compressed gas.

[0040] Figure 19 is an appearance view of a foam molded sample obtained through an experiment of foam molding. DETAILED DESCRIPTION

[0041] Hereinafter, the embodiments of the control method of the injection molding machine for foam molding and the injection molding machine for foam molding according to the present disclosure will be described in detail based on the drawings. Note that the present disclosure is not limited by the embodiments. Furthermore, among the constituent elements of the following embodiments, those which can be substituted and which can be easily conceived by those skilled in the art, or those which are substantially the same, are included.

[0042] [Embodiment 1]

[0043] Figure 1 is a perspective view of an injection molding machine 1 for foam molding relating to Embodiment 1. Figure 2 is a main part sectional view showing the device structure of the injection molding machine 1 for foam molding relating to Embodiment 1. Figure 3 is a main part plan view showing the device structure of the injection molding machine 1 for foam molding relating to Embodiment 1. In addition, in the following description, the up-down direction in the usual state of use of the injection molding machine 1 for foam molding is set as the up-down direction Z of the injection molding machine 1 for foam molding, and the upper side in the usual state of use of the injection molding machine 1 for foam molding is set as the upper side of the injection molding machine 1 for foam molding, and the lower side in the usual state of use of the injection molding machine 1 for foam molding is set as the lower side of the injection molding machine 1 for foam molding, and the description is made. Further, in the following description, the lengthwise direction Y of the injection molding machine 1 for foam molding is set as the lengthwise direction Y in each part having the injection molding machine 1 for foam molding, and the direction orthogonal to both the up-down direction Z and the lengthwise direction Y of the injection molding machine 1 for foam molding is set as the widthwise direction X of the injection molding machine 1 for foam molding, and the description is made.

[0044] <Injection molding machine 1 for foam molding>

[0045] The injection molding machine 1 for foam molding relating to this Embodiment 1 is configured with a base 5, and an injection device 10 and a mold clamping device 15, and the like arranged on the base 5. Further, in the injection molding machine 1 for foam molding, in the vicinity of the center in the lengthwise direction Y, a display part 101 that displays various information of the injection molding machine 1 for foam molding, and an input part 102 that is used by an operator when inputting an operation to the injection molding machine 1 for foam molding are arranged.

[0046] The base 5 is formed in the shape of a substantially rectangular parallelepiped with the lengthwise direction as the lengthwise direction Y of the injection molding machine 1 for foam molding, and a first rail 6 is arranged on the upper surface of the base 5. The first rail 6 is arranged with two rails that are apart in the widthwise direction X on the base 5, and both of the two first rails 6 are formed so as to extend along the lengthwise direction of the base 5. The injection device 10 is placed on the first rail 6 so as to be movable along the extending direction of the first rail 6, and thereby the injection device 10 is arranged so as to be movable in the lengthwise direction Y.

[0047] The mold clamping device 15 is arranged on one side of the injection device 10 in the lengthwise direction Y on the base 5. The mold clamping device 15 is provided with a mold clamping mechanism, and a metal mold 16 (refer to FIG. 1) that is assembled on the mold clamping mechanism. The mold clamping mechanism is configured with a mold clamping mechanism main body 17, a mold clamping mechanism movable body 18, and a mold clamping mechanism drive mechanism 19. Figure 4) opening and closing. The clamping device 15 is preferably a servo motor drive type, but can also be an oil pressure drive type. The injection molding machine 1 for foam molding according to the present embodiment 1 has a cover 20a, 20b covering the outside of the injection device 10 and the clamping device 15, Figure 1 The injection device 10 and the clamping device 15 are illustrated in a state where they are covered with the covers.

[0048] <Injection device 10>

[0049] In the following description, the side on which the clamping device 15 is located with respect to the injection device 10 in the length direction Y is referred to as the front or front side, and the side opposite to the side on which the clamping device 15 is located with respect to the injection device 10 in the length direction Y is referred to as the rear or rear side.

[0050] The injection device 10 includes a frame 20, a heating barrel 50, a screw 60, a rotation mechanism 70 that rotates the screw 60, an advance / retreat mechanism 80 that advances / retracts the screw 60, and a pushing mechanism 40 of the injection device 10. The frame 20 is formed of a base 21 and an upper frame 30 mounted on the base 21. The base 21 is a frame body that is flat in the vertical direction Z, and four feet 24 are provided on both sides in the length direction Y and both sides in the width direction X. The four feet 24 are placed so as to be freely movable along the extension direction of the two first rails 6 provided on the base 5. Thus, the base 21 is supported so as to be freely slidable with respect to the base 5 in the length direction Y.

[0051] The pushing mechanism 40 includes a drive motor 41 and a ball screw mechanism 43. The drive motor 41 is mounted on the rear wall 23 on the rear side in the length direction Y of the base 21. The drive motor 41 is arranged so that the drive shaft extends in the length direction Y, and the drive shaft of the drive motor 41 penetrates the rear wall 23 of the base 21 and is connected to the threaded portion 44 of the ball screw mechanism 43 via a connecting mechanism 42. Thus, when the drive motor 41 is driven, the drive force of the drive motor 41 is transmitted from the drive shaft to the ball screw mechanism 43 via the connecting mechanism 42, and the ball screw mechanism 43 can be rotated by the transmitted drive force.

[0052] The threaded portion 44 of the ball screw mechanism 43 extends in the longitudinal direction Y and passes approximately through the center of the base 21 in the width direction X. Its front end in the longitudinal direction Y is rotatably supported by the front wall 22 of the base 21 located on the front side in the longitudinal direction Y. Furthermore, the nut portion 45 of the ball screw mechanism 43 is fixed to the upper surface of the base 5 inside the base 21. Thus, when the propulsion mechanism 40 is driven by the drive motor 41, the threaded portion 44 of the ball screw mechanism 43 rotates under the driving force transmitted from the drive motor 41, and the threaded portion 44 can move relative to the nut portion 45 fixed to the base 5 in the extending direction of the threaded portion 44. Therefore, the propulsion mechanism 40 can move the base 21 supporting the threaded portion 44 relative to the base 5 on which the nut portion 45 is fixed in the longitudinal direction Y, and can move the frame 20 having the base 21 in the longitudinal direction Y on the first track 6 disposed on the base 5. Thus, the propulsion mechanism 40 enables the injection device 10 to move in the length direction Y.

[0053] The upper frame 30 is formed into a square frame shape and is rotatably mounted near the front end of the base 21 in the longitudinal direction Y by a support pin 33. Furthermore, the upper frame 30 is fixed to the base 21 in a non-rotatable state by a fixing threaded member 34 that secures the upper frame 30 to the base 21 at a location other than where the support pin 33 is located. Therefore, the upper frame 30 is configured such that if the fixing threaded member 34 is removed and the fixation by the fixing threaded member 34 is released, it can rotate relative to the base 21 about the support pin 33.

[0054] The upper frame 30 has a front wall 31 erected on its upper side in the vertical direction Z from the mounting part that is mounted to the base 21. The heating barrel 50 is mounted on the front wall 31 of the upper frame 30. The heating barrel 50 extends from the front wall 31 to its front side in the longitudinal direction Y, and a metal mold 16 (see reference) is disposed at its front end, i.e., the front end of the heating barrel 50. Figure 4 The nozzle portion 52 is closely spaced. Therefore, the heating barrel 50 is positioned on the upper side of the frame 20 in the vertical direction Z and on the front side of the frame 20 in the longitudinal direction Y.

[0055] In detail, the heating tank 50 is formed in a generally cylindrical shape and is arranged along the length direction Y in the axial direction, and is equipped with a heater 51 such as a belt heater (see reference). Figure 4 Thus, the heating tank 50 can melt the resin material inside. That is, the heating tank 50 can be heated to a higher temperature by the heater 51, and the resin material inside can be heated and melted to become molten resin as a plasticizing material.

[0056] The screw 60 is disposed inside the heating vat 50, has a spiral shape with an axial direction along the axial direction of the heating vat 50, that is, the screw 60 has a spiral groove on the outer peripheral surface. In this way, the screw 60 formed in a spiral shape can rotate in the heating vat 50 with the axis as the center. In addition, the screw 60 can move in the axial direction of the heating vat 50 while rotating. In other words, the screw 60 is disposed in the heating vat 50 with the central axis of the cylinder as the shape of the heating vat 50 substantially coinciding with the rotation axis of the screw 60, and can be disposed movably in the axial direction of the heating vat 50. The screw 60 rotatably disposed in the heating vat 50 can mix the molten resin by rotating inside the heating vat 50, and thus the heating vat 50 becomes a vat in which mixing of the molten resin can be performed inside.

[0057] In the vicinity of the portion of the heating vat 50 installed on one side of the upper frame 30, a hopper 55 is disposed. The hopper 55 communicates with the inside of the heating vat 50 and can supply a pellet (not shown) of a resin material as a raw material resin into the heating vat 50.

[0058] Further, on the upper frame 30, the second rails 35 are respectively disposed on the side walls 32 on both sides in the width direction X of the upper frame 30. The second rails 35 extend in the length direction Y, that is, extend substantially parallel to the heating vat 50.

[0059] The rotation mechanism 70 is disposed on the rear side of the heating vat 50 in the length direction Y and can rotate the screw 60 disposed inside the heating vat 50 around the central axis. The rotation mechanism 70 that rotates the screw 60 has a rotation mechanism main body 71, a drive motor 73, a transmission belt 74, and a pulley 75. Among them, the rotation mechanism main body 71 has a strut 72 extending in the width direction X, and the strut 72 is slidably placed on the two second rails 35 in the width direction X. Thus, the rotation mechanism main body 71 can be movably placed on the second rails 35 via the strut 72.

[0060] The drive motor 73 is disposed on the upper side of the rotation mechanism main body 71. The pulley 75 is disposed in front of the rotation mechanism main body 71 and is rotatably disposed with respect to the rotation mechanism main body 71 via a bearing 76. In addition, the pulley 75 is linked to the drive shaft of the drive motor 73 via the transmission belt 74, and thus the pulley 75 can be rotated by the driving force of the drive motor 73 transmitted via the transmission belt 74. In this way, the pulley 75 that can be rotated by the driving force transmitted from the drive motor 73 is integrally fixed coaxially with respect to the screw 60. In other words, the screw 60 is linked to the pulley 75 on the rear end side in the length direction Y. Thus, the screw 60 disposed in the heating vat 50 can be integrally rotated with the pulley 75 by the driving force transmitted from the drive motor 73 to the pulley 75.

[0061] Behind the rotation mechanism body portion 71 in the length direction Y, an advance / retract mechanism 80 is arranged. The advance / retract mechanism 80 is capable of moving the screw 60 arranged in the heating barrel 50 in the axial direction of the screw 60. That is, the screw 60 is capable of advancing or retracting in the length direction Y. In detail, the advance / retract mechanism 80 has a drive motor 81, a transmission belt 83, a pulley 84, and a ball screw mechanism 86. Among these, the drive motor 81 is arranged on the side in the width direction X of the upper frame 30. Further, the drive motor 81 has an encoder 82 that detects the rotational position of the drive motor 81, and the drive shaft of the drive motor 81 is linked to the pulley 84 via the transmission belt 83.

[0062] The pulley 84 is rotatably supported by a bearing 85 on the upper frame 30. On the pulley 84, a threaded portion 87 of the ball screw mechanism 86 is integrally linked. The threaded portion 87 of the ball screw mechanism 86 is arranged coaxially with the screw 60, and is also arranged coaxially with respect to the pulley 75 possessed by the rotation mechanism body portion 71. The nut portion 88 of the ball screw mechanism 86 possessed by the advance / retract mechanism 80 is formed in a substantially cylindrical shape, and the threaded portion 87 of the ball screw mechanism 86 is screwed with this nut portion 88.

[0063] Between the nut portion 88 of the ball screw mechanism 86 possessed by the advance / retract mechanism 80 in the length direction Y and the rotation mechanism body portion 71 possessed by the rotation mechanism 70, a load cell 90 is arranged. The load cell 90 is arranged on the rear side of the rotation mechanism body portion 71 possessed by the rotation mechanism 70 and on the front side of the nut portion 88 of the ball screw mechanism 86 possessed by the advance / retract mechanism 80.

[0064] The load cell 90 is a load measuring device that measures a load applied in the axial direction, and is composed of a strain generator, a strain sensor mounted on the strain generator, and the like (all not shown). In the present embodiment 1, the load cell 90 is arranged in the orientation in which the axial direction is the length direction Y, and is formed in a substantially cylindrical shape that is flat in the length direction Y, and the inner diameter of the cylinder is larger than the outer diameter of the threaded portion 87 of the ball screw mechanism 86 possessed by the advance / retract mechanism 80. The front side in the length direction Y of the load cell 90 thus formed is integrally fixed to the rotation mechanism body portion 71 possessed by the rotation mechanism 70, and the rear side in the length direction Y is integrally fixed to the nut portion 88 of the ball screw mechanism 86 possessed by the advance / retract mechanism 80. The load cell 90 arranged between the rotation mechanism body portion 71 of the rotation mechanism 70 and the nut portion 88 of the ball screw mechanism 86 possessed by the advance / retract mechanism 80 is capable of detecting a load acting in the length direction Y between the rotation mechanism body portion 71 and the nut portion 88.

[0065] Figure 4 isFigure 2 A detailed view of the heating barrel 50 is shown. The heating barrel 50 is formed in a substantially cylindrical shape, and a heater 51 such as a band heater is disposed on the outer peripheral surface. A nozzle portion 52 is provided on the front end in the length direction Y of the heating barrel 50. The nozzle portion 52 is formed in a substantially cylindrical shape with an inner diameter smaller than that of the heating barrel 50, and is disposed with an opening on the front side in the length direction Y of the heating barrel 50. In this way, the nozzle portion 52 provided on the front end of the heating barrel 50 is able to inject the molten resin inside the heating barrel 50 into the cavity 17 formed by the metal mold 16 possessed by the mold clamping device 15. Figure 4

[0066] Here, if the metal mold 16 is described, the metal mold 16 has a stationary metal mold 16f and a movable metal mold 16m, and by combining the stationary metal mold 16f and the movable metal mold 16m, one metal mold 16 that shapes the molten resin into a molded product is formed. Of the stationary metal mold 16f and the movable metal mold 16m, the stationary metal mold 16f is disposed on the side on which the heating barrel 50 is located in the length direction Y, opposite the nozzle portion 52. The movable metal mold 16m is disposed on the side opposite the side on which the heating barrel 50 is located in the length direction Y with respect to the stationary metal mold 16f. The mold clamping device 15 is able to cause the movable metal mold 16m to move away from the stationary metal mold 16f or to cause the movable metal mold 16m to come into contact with the stationary metal mold 16f by causing the movable metal mold 16m to move in the length direction Y.

[0067] The metal mold 16 having the stationary metal mold 16f and the movable metal mold 16m causes the movable metal mold 16m to come into contact with the stationary metal mold 16f, and in the state of combining the stationary metal mold 16f and the movable metal mold 16m, a space is present between the stationary metal mold 16f and the movable metal mold 16m. The metal mold 16, in the state of combining the stationary metal mold 16f and the movable metal mold 16m, forms the space between the two as the cavity 17 in which the molded product is shaped from the molten resin in the metal mold 16. On the stationary metal mold 16f, a through hole 18 that is a hole that penetrates the side opposite the nozzle portion 52 and the cavity 17 is formed, and by injecting the molten resin from the nozzle portion 52 into the through hole 18, the heating barrel 50 is able to inject the molten resin inside the heating barrel 50 into the cavity 17.

[0068] On the heating barrel 50, a cutoff nozzle 53 that opens and closes the nozzle portion 52 is also provided. The cutoff nozzle 53 has an opening and closing portion 53a, an opening and closing lever 53b, and an actuator 53c. Of these, the opening and closing portion 53a is disposed in the vicinity of the nozzle portion 52 on the inside of the heating barrel 50, and by moving in the length direction Y, is able to open and close the nozzle portion 52. That is, the opening and closing portion 53a is able to open and close the hole of the nozzle portion 52 that communicates the inside and the outside of the heating barrel 50 from the inside of the heating barrel 50.

[0069] ​The opening and closing lever 53b connects the opening and closing portion 53a with the actuator 53c, and by transmitting the force output from the actuator 53c to the opening and closing portion 53a, the opening and closing portion 53a can be moved in the length direction Y.

[0070] The actuator 53c is a source of generating a force that moves the opening and closing portion 53a of the cutting nozzle 53, and is disposed outside the heating tub 50. The actuator 53c can open and close the nozzle portion 52 by the opening and closing portion 53a by transmitting the force generated by the actuator 53c to the opening and closing portion 53a via the opening and closing lever 53b. The actuator 53c can use, for example, a solenoid, a pneumatic cylinder, an oil hydraulic cylinder, or the like, and is not limited in structure as long as it is a mechanism that can generate a force that moves the opening and closing portion 53a.

[0071] The screw 60 disposed inside the heating tub 50 has a spiral piece 61 that protrudes to the outside in the radial direction of the screw 60 and is formed in a spiral shape with the axis of the screw 60 as the center. Thus, the screw 60 has a spiral-shaped groove-shaped portion between adjacent circumferential portions of the spiral-shaped spiral piece 61.

[0072] On the thus formed screw 60, a snap ring 65 is disposed near the end portion on the front side in the length direction Y. The snap ring 65 is disposed in the groove portion 62 of the screw 60 formed near the end portion on the front side in the length direction Y. The groove portion 62 has a groove width direction that is the axis direction of the screw 60, and is a groove formed for one turn in the circumferential direction of the screw 60.

[0073] Figure 5 is Figure 4 A detailed view of the snap ring 65 is shown in FIG. 6. The snap ring 65 is formed in a substantially cylindrical shape, and is disposed in the groove portion 62 of the screw 60 in a state in which the axis thereof substantially coincides with the axis of the screw 60. The outer diameter of the substantially cylindrical snap ring 65 is a diameter that is the same as or slightly smaller than the inner diameter of the heating tub 50. In addition, the inner diameter of the snap ring 65 is a diameter that is larger than the diameter of the groove bottom of the groove portion 62 of the screw 60, and a gap is formed between the inner peripheral surface of the snap ring 65 and the groove bottom of the groove portion 62 of the screw 60. In addition, the width in the axis direction of the snap ring 65 is smaller than the groove width of the groove portion 62 of the screw 60. Thus, the snap ring 65 can move in the groove width direction within the groove portion 62.

[0074] In addition, on the screw 60, a communication portion 64 that communicates the portion on the front side in the length direction Y with respect to the groove portion 62 with the inside of the groove portion 62 is formed. The communication portion 64 is opened on the groove wall 63 on the front side in the groove width direction of the groove portion 62.

[0075] Further, the injection molding machine for foam molding 1 has a control section 100 that performs various controls of the injection molding machine for foam molding 1. The control section 100 has a CPU (Central Processing Unit) that performs arithmetic processing, and a RAM (Random Access Memory) and a ROM (Read Only Memory) that function as a memory that stores various information. All or a part of each function of the control section 100 is realized by loading an application program held in the ROM into the RAM and executing it by the CPU, by performing readout and writing of data in the RAM and the ROM.

[0076] The display section 101 and the input section 102 are connected to the control section 100, and the display section 101 displays information transmitted from the control section 100. Further, the input section 102 transmits information of an input operation to the control section 100. Further, the encoder 82 provided in the drive motor 81 of the forward / backward mechanism 80 and the load cell 90 provided between the forward / backward mechanism 80 and the rotation mechanism 70 are connected to the control section 100, and can transmit detection results to the control section 100. Furthermore, the heater 51, the actuator 53c of the cutoff nozzle 53, the drive motor 73 of the rotation mechanism 70, the drive motor 81 of the forward / backward mechanism 80, and the drive motor 41 of the advancing mechanism 40 are connected to the control section 100, and act by a control signal from the control section 100. That is, the control section 100 can control the actions of the heating barrel 50, the screw 60, and the cutoff nozzle 53.

[0077] <Effects of the injection molding machine for foam molding 1>

[0078] The injection molding machine for foam molding 1 according to the present embodiment 1 includes the above structure, and the effects thereof will be described below. The injection molding machine for foam molding 1 repeats a cycle of the injection-molding action as one cycle. Each cycle includes a plurality of processes for injection of a resin material for molding and molding of a product. Each cycle includes, for example, an injection process, a cooling process, a mold opening process, a take-out process, an intermediate process, a mold closing process, and a metering process.

[0079] The injection process is a process of injecting a resin material, i.e., a molten resin, after being melted by the heating barrel 50, into the cavity 17 formed by the movable metal mold 16m and the fixed metal mold 16f, by pushing the nozzle section 52 provided on the heating barrel 50 against the through hole 18 of the fixed metal mold 16f of the mold clamping device 15.

[0080] The cooling step is a step in which the resin material, i.e., the molding resin, injected into the cavity 17 formed by the stationary metal mold 16f and the movable metal mold 16m of the clamping device 15 is cooled to solidify and is left for a certain time until the molding resin becomes a molded product.

[0081] The mold opening step is a step in which the movable metal mold 16m is separated from the stationary metal mold 16f in order to take out the molded product molded by the stationary metal mold 16f and the movable metal mold 16m of the clamping device 15.

[0082] The taking-out step is a step in which the molded product is ejected from the movable metal mold 16m by an ejection member (not shown) provided in the clamping device 15 in order to unload the molded product from the movable metal mold 16m.

[0083] The intermediate step is a step in which the molded product ejected from the movable metal mold 16m is moved to a prescribed position.

[0084] The mold closing step is a step in which the movable metal mold 16m of the clamping device 15 is combined with the stationary metal mold 16f, and a space corresponding to the shape of the product, i.e., the cavity 17, is formed between the movable metal mold 16m and the stationary metal mold 16f.

[0085] The metering step is a step in which the molten resin to be injected in the next cycle is delivered to the end portion side where the nozzle portion 52 of the heating barrel 50 provided in the injection device 10 is located, and the resin material to be used in the next cycle is prepared. The metering step is performed during the cooling step in the clamping device 15.

[0086] When the molded product is molded with the injection molding machine 1 for foam molding, the cycle of the injection-molding operation is repeatedly performed, but in the repeatedly performed cycle, the control section 100 continuously heats the inside of the heating barrel 50 by the heater 51 so that the resin material in the inside of the heating barrel 50 can be smoothly injected. Thus, the resin material which is thrown into the hopper 55 in a state of a pellet and is supplied from the hopper 55 into the heating barrel 50 is maintained in a molten state.

[0087] The control section 100 performs control while judging the start or end of each step in the cycle of the injection-molding operation. In order to judge the start or end of each step, for example, in the program for causing the injection molding machine 1 for foam molding to operate by the control section 100, a flag is previously provided for the first step or the final step of each step. Thus, the control section 100 can judge the start or end of each step in the process of executing the program for causing the injection molding machine 1 for foam molding to operate. That is, the control section 100 judges that the processing is shifted to the next step when the flag is executed before or after the processing of the step of each step by providing the flag.

[0088] Further, the control section 100 causes the display section 101 to display the shift of the process when the process is shifted. That is, the display section 101 displays the current process of the injection molding machine 1 for foam molding. Thereby, the operator can recognize the current operation state of the injection molding machine 1 for foam molding by visually observing the display section 101.

[0089] The injection molding machine 1 for foam molding is basically operated by the above processes, and a molded product is formed from the molten resin by repeatedly performing these processes, but the injection molding machine 1 for foam molding according to the present embodiment 1 is capable of forming a foam molded product from the molten resin containing bubbles. Next, the foam molding method of forming the foam molded product will be described.

[0090] <Method of foam molding>

[0091] In the foam molding method according to the present embodiment 1, when the foam molded product is formed, the atmosphere is taken into the heating cylinder 50, the taken-in atmosphere is dispersed into the molten resin in the heating cylinder 50 to become bubbles, and further, the bubbles are made into a supercritical fluid state by imparting pressure to the molten resin. Then, the molten resin containing the bubbles in the supercritical fluid state is injected into the cavity 17 of the metal mold 16, the bubbles grow by the pressure of the molten resin decreasing, and the foam molding is performed to form the foam molded product. When the foam molding based on such a foam molding method is performed using the injection molding machine 1 for foam molding, the movement of the heating cylinder 50 in the length direction Y by the advancing mechanism 40 and the movement of the screw 60 in the length direction Y by the forward / backward mechanism 80 are performed while switching the opening and closing of the nozzle section 52 by the cutoff nozzle 53.

[0092] Figure 6 is a flowchart showing the order when the foam molding is performed using the injection molding machine 1 for foam molding according to the present embodiment 1. Figure 7is a schematic view showing a state in which the heating barrel 50 is retracted. When foaming molding is performed using the injection molding machine 1 according to the embodiment 1, first, the heating barrel 50 is retracted, and the cutoff nozzle 53 is opened (step ST11). In detail, the heating barrel 50 is moved in the length direction Y by the action of the advancing mechanism 40, and the heating barrel 50 possessed by the injection device 10 is retracted by the retraction of the injection device 10. When the injection device 10 is moved by the advancing mechanism 40, the drive motor 41 possessed by the advancing mechanism 40 is driven, and the driving force generated by the drive motor 41 is transmitted to the threaded portion 44 of the ball screw mechanism 43 via the coupling mechanism 42, and the threaded portion 44 is rotated. Thereby, the threaded portion 44 is relatively moved in the length direction Y with respect to the nut portion 45 of the ball screw mechanism 43 fixed to the base 5, and the injection device 10 is moved in the length direction Y while being supported by the first rail 6. In this way, the nozzle portion 52 of the heating barrel 50 possessed by the injection device 10 is slightly separated from the metal mold 16 by moving the injection device 10 in the length direction Y by the advancing mechanism 40.

[0093] Further, the cutoff nozzle 53 is opened by the action of the actuator 53c of the cutoff nozzle 53, and the nozzle portion 52 is brought to an open state. That is, the actuator 53c of the cutoff nozzle 53 is actuated, and the opening and closing portion 53a inside the heating barrel 50 is opened by transmitting the force generated by the actuator 53c to the opening and closing portion 53a via the opening and closing lever 53b, and the hole of the nozzle portion 52 is opened by separating the opening and closing portion 53a from the hole of the nozzle portion 52. Thereby, the inside of the heating barrel 50 is communicated with the gas environment outside the heating barrel 50 via the hole of the nozzle portion 52.

[0094] Figure 8 is a schematic view showing a state in which the screw 60 is retracted. Next, the screw 60 is retracted, and the atmosphere is taken into the heating barrel 50 (step ST12). That is, in the state in which the cutoff nozzle 53 is opened, the screw 60 is moved in the length direction Y by the action of the advancing / retracting mechanism 80, and the screw 60 is retracted. When the screw 60 is retracted by the advancing / retracting mechanism 80, the drive motor 81 possessed by the advancing / retracting mechanism 80 is driven, the driving force generated by the drive motor 81 is transmitted to the pulley 84 via the transmission belt 83, is transmitted from the pulley 84 to the threaded portion 87 of the ball screw mechanism 86, and the threaded portion 87 is rotated. Thereby, the nut portion 88 of the ball screw mechanism 86 is moved in the length direction Y, and the load cell 90 and the rotating mechanism 70 as a whole are moved in the length direction Y while being supported by the second rail 35. Thereby, the screw 60 linked to the pulley 75 of the rotating mechanism 70 is moved in the length direction Y together with the pulley 75 of the rotating mechanism 70, and the screw 60 is retracted.

[0095] When the atmosphere A is taken into the heating cylinder 50, the atmosphere A, that is, the air present around the heating cylinder 50, is taken into the heating cylinder 50 from the nozzle portion 52 by thus retreating the screw 60. In detail, since the snap ring 65 is provided on the screw 60 with an outer diameter that is the same degree as the inner diameter of the heating cylinder 50, in the case of retreating the screw 60, the portion of the heating cylinder 50 on the front side of the screw 60 becomes under pressure. Therefore, in the case of retreating the screw 60, by the under pressure generated at the portion on the front side of the snap ring 65, the atmosphere A enters from the nozzle portion 52, and the atmosphere A is taken into the portion of the heating cylinder 50 on the front side of the snap ring 65.

[0096] Further, the retreat amount of the screw 60 at the time of retreating the screw 60 in order to take the atmosphere A into the heating cylinder 50 is preferably adjusted according to the amount of bubbles required for the foamed molded product that is molded.

[0097] Figure 9 is a schematic view showing a state in which the cutoff nozzle 53 is closed and the screw 60 is advanced. Next, the cutoff nozzle 53 is closed and the screw 60 is advanced, and further the heating cylinder 50 is advanced (step ST13). That is, in the state in which the nozzle portion 52 is closed by closing the cutoff nozzle 53 by operating the actuator 53c of the cutoff nozzle 53, the screw 60 is advanced by moving the screw 60 in the length direction Y by operating the advance / retreat mechanism 80. By this, the atmosphere A taken into the heating cylinder 50 is diffused into the molten resin R in the heating cylinder 50. In detail, when molding of the molded product is performed with the injection molding machine 1 for foaming molding, the resin material is held in a molten state in the heating cylinder 50, and therefore, the molten resin R remains in the portion of the heating cylinder 50 on the rear side of the snap ring 65.

[0098] On the other hand, since the atmosphere A is taken into the portion of the heating cylinder 50 on the front side of the snap ring 65, in the case of advancing the screw 60 in the state in which the nozzle portion 52 is closed, the atmosphere A taken into the portion on the front side of the snap ring 65 is compressed by the advancing screw 60. By this, the atmosphere A taken into the portion on the front side of the snap ring 65 flows into the portion on the rear side of the snap ring 65 through the portion in which the snap ring 65 is provided. That is, the atmosphere A on the front side of the snap ring 65 in the heating cylinder 50 flows into the portion on the rear side of the snap ring 65 through the communication portion 64 formed on the screw 60, through the gap between the inner peripheral surface of the snap ring 65 and the groove bottom of the groove portion 62 of the screw 60, and through between the rear side groove wall 63 of the groove portion 62 of the screw 60 and the screw 60. By this, the atmosphere A taken into the heating cylinder 50 is diffused into the molten resin R in the portion on the rear side of the snap ring 65.

[0099] Further, the heating pot 50 advances the injection device 10 by moving the injection device 10 in the length direction Y by actuating the advancing mechanism 40, and advances the heating pot 50 possessed by the injection device 10 by advancing the injection device 10. Thereby, the nozzle portion 52 of the heating pot 50 is brought into contact with the metal mold 16, and the nozzle portion 52 of the heating pot 50 is brought into communication with the through hole 18 formed on the fixed metal mold 16f. In addition, either the advancing operation of the screw 60 or the advancing operation of the heating pot 50 can be performed first, or both operations can be performed simultaneously.

[0100] Figure 10 is an explanatory view showing a state in which the screw 60 is rotated while being retreated. Next, the screw 60 is rotated while being retreated, and the taken-in air A is made to be dispersed as bubbles B in the molten resin R (step ST14). That is, in a state in which the cutoff nozzle 53 is closed, the screw 60 is retreated by moving the screw 60 in the length direction Y by actuating the advancing / retreating mechanism 80 while rotating the screw 60 by actuating the rotating mechanism 70. When the screw 60 is rotated by the rotating mechanism 70, the driving motor 73 possessed by the rotating mechanism 70 is driven, a driving force generated by the driving motor 73 is transmitted to the pulley 75 via the transmission belt 74, and is transmitted from the pulley 75 to the screw 60, whereby the screw 60 is rotated.

[0101] In this way, in a case in which the screw 60 is rotated by the rotating mechanism 70, the molten resin R in the heating pot 50 is mixed by the rotation of the screw 60, and therefore the air A that has flowed into the heating pot 50 by the molten resin R being mixed and has been diffused into the molten resin R is divided into fine bubbles B. Thereby, the air A that has been diffused into the molten resin R in the heating pot 50 is dispersed as bubbles B in the molten resin R.

[0102] Further, the direction of rotation of the screw 60 in a case in which the screw 60 is rotated while being retreated is a direction of rotation in which the molten resin R present between adjacent circumferential portions of the helical blade 61 possessed by the screw 60 can be transported to the front side in the length direction Y by the rotation of the screw 60.

[0103] The molten resin R conveyed to the front side by the rotation of the screw 60 passes through a portion provided with the snap ring 65, and is conveyed to a portion on the front side of the snap ring 65. That is, the molten resin R located on the rear side of the snap ring 65 passes between the rear-side groove wall 63 of the groove portion 62 of the screw 60 and the screw 60, and passes through a gap between the inner peripheral surface of the snap ring 65 and the groove bottom of the groove portion 62 of the screw 60, and passes through the communication portion 64 formed on the screw 60, and flows to the portion on the front side of the snap ring 65. Thus, the molten resin R in which the bubbles B are dispersed is extruded to the front end side of the heating cylinder 50 on the front side of the snap ring 65, that is, the side on which the nozzle portion 52 of the heating cylinder 50 is located. In this way, the screw 60 retreats while rotating, and at the same time, the atmosphere A taken into the heating cylinder 50 is caused to be dispersed as bubbles B in the molten resin R, and the molten resin R is conveyed to the front side.

[0104] The step of conveying the molten resin R in the heating cylinder 50 to the front end side of the heating cylinder 50 is a metering step of the injection molding machine 1 for foaming molding. In the metering step, the molten resin R is metered for the amount of the molten resin R to be injected into the cavity 17 formed in the metal mold 16 in one injection step, and the molten resin R is ensured in the portion on the front end side in the heating cylinder 50. Specifically, in the metering step, the molten resin R is metered on the basis of the amount of movement of the screw 60 when the screw 60 retreats, or the position in the length direction Y in the heating cylinder 50, and the pressure of the molten resin R conveyed to the portion on the front end side in the heating cylinder 50.

[0105] In the control of the metering step, the amount of movement of the screw 60 is obtained on the basis of the detection result in the encoder 82 possessed by the drive motor 81 of the advance / retreat mechanism 80. That is, the advance / retreat mechanism 80 moves the screw 60 in the length direction Y by transmitting the driving force generated by the drive motor 81 to the screw 60, but the encoder 82 can detect the rotational position of the rotating body (not shown) possessed by the drive motor 81. Therefore, the control section 100 obtains the position of the screw 60 in the length direction Y by obtaining the rotational position of the rotating body of the drive motor 81 detected by the encoder 82.

[0106] The encoder 82 possessed by the drive motor 81 of the advance / retreat mechanism 80 is a screw position detection section that detects the position of the screw 60 in the length direction Y in the heating cylinder 50. The control section 100 obtains the position of the screw 60 in the length direction Y on the basis of the detection result in the encoder 82 possessed by the drive motor 81 of the advance / retreat mechanism 80 in the metering step, and thereby obtains the amount of retreat of the screw 60.

[0107] Further, the detection of the pressure of the molten resin R that is fed to the front end side of the heating cylinder 50 is performed using the detection result of the load cell 90. The load cell 90 is used as a back pressure detection section that detects the pressure of the molten resin R that is pressed by the screw 60 to the front end side in the heating cylinder 50, that is, the back pressure.

[0108] If the detection of the back pressure of the molten resin R using the load cell 90 is described, in the case where the molten resin R in the heating cylinder 50 is pressed by the screw 60 to the front end side in the heating cylinder 50, a force acting to the rear side in the length direction Y is applied to the screw 60 by the reaction when the molten resin R is pressed to the front side. The force applied to the screw 60 in the length direction Y is transmitted to the load cell 90 fixed to the rotation mechanism main body section 71 through the pulley 75 of the rotation mechanism 70 and the rotation mechanism main body section 71 from the screw 60.

[0109] Since the surface on the opposite side of the surface of the load cell 90 that is fixed to the rotation mechanism main body section 71 is fixed to the nut section 88 of the ball screw mechanism 86 of the advance / retreat mechanism 80, the force to the rear side in the length direction Y of the load cell 90 from the rotation mechanism main body section 71 of the rotation mechanism 70 acts as a force that compresses the load cell 90 in the length direction Y. The load cell 90 detects the magnitude of the force thus applied to the load cell 90 and transmits it to the control section 100. The control section 100 acquires the magnitude of the force transmitted from the load cell 90 as the force acting on the screw 60 in the length direction Y.

[0110] The control section 100 acquires the back pressure of the molten resin R pressed to the front side by the screw 60 by acquiring the magnitude of the force acting on the screw 60 in the length direction Y based on the detection result in the load cell 90 in the metering process. That is, in the metering process, the control section 100 acquires the position of the screw 60 in the length direction Y based on the detection result in the encoder 82 and acquires the back pressure of the molten resin R based on the detection result in the load cell 90, and acquires the amount of the molten resin R pressed to the front end side, that is, the side where the nozzle section 52 of the heating cylinder 50 is located, and performs the metering of the molten resin R. Thus, in the metering process, the metering of the amount of the molten resin R to be injected from the heating cylinder 50 to the cavity 17 of the metal mold 16 possessed by the mold clamping device 15 in one injection process is performed.

[0111] In the metering process, the molten resin R in the heating cylinder 50 is pressed to the front end side in the heating cylinder 50 by the rotation of the screw 60, and the back pressure is generated in the molten resin R, but the gas bubbles B are contained in the molten resin R. Therefore, the pressure acting on the molten resin R by the rotation of the screw 60 also acts on the gas bubbles B.

[0112] At this time, the air contained in the bubble B becomes a supercritical state by the pressure acting on the bubble B from the molten resin R. Therefore, the back pressure of the molten resin R in the metering process is set to a pressure at which the air contained in the bubble B becomes a supercritical state, for example, the back pressure is set to 3.7 MPa or more. That is, the control section 100 controls the rotation mechanism 70 and the advance / retract mechanism 80 in the metering process so that the back pressure of the molten resin R obtained based on the detection result in the load cell 90 becomes 3.7 MPa or more.

[0113] Figure 11 is an explanatory view regarding the pressure distribution of the molten resin R in the heating barrel 50 in the metering process. Here, the heating barrel 50 is capable of continuously supplying the shot as the resin material from the hopper 55 into the heating barrel 50, and the heating barrel 50 is opened to the ambient atmosphere via the hopper 55. On the other hand, in the metering process, the molten resin R in the heating barrel 50 is pressed to the front side in the length direction Y as a whole by the screw 60. Therefore, the pressure of the molten resin R becomes the largest near the center of the screw 60 in the length direction Y, although the pressure on the rear side in the length direction Y, that is, the side on which the hopper 55 is located, becomes low, the front side in the length direction Y is ensured to be in a state where the pressure is high, and the set back pressure is ensured on the front side than the check ring 65.

[0114] Thus, since the molten resin R in the heating barrel 50 is pressed to the front side as a whole by the screw 60, even if the heating barrel 50 is in a state where it is opened to the ambient atmosphere via the hopper 55, a high pressure is ensured at the portion on the front end side in the heating barrel 50.

[0115] Figure 12 is an explanatory view showing the state of the molten resin R in which injection is performed. Next, the shut-off nozzle 53 is opened, and the molten resin R containing the dispersed bubble B is injected into the cavity 17 (step ST15). That is, the molten resin R in which the metering is performed in the heating barrel 50 in the metering process is injected into the cavity 17 formed in the metal mold 16 in the injection process. At the time of injecting the molten resin R into the cavity 17, first, the actuator 53c of the shut-off nozzle 53 is caused to operate to open the shut-off nozzle 53, and the nozzle portion 52 is opened, whereby a state in which the hole of the nozzle portion 52 communicates with the through hole 18 formed on the fixed metal mold 16f is achieved.

[0116] After the shut-off nozzle 53 is opened, the screw 60 is caused to advance by causing the advance / retract mechanism 80 to operate. By this, the molten resin R located on the front side of the screw 60 in the heating barrel 50, that is, the molten resin R in which the metering is performed in the metering process, is pressed out from the nozzle portion 52 by the screw 60, and is injected into the cavity 17 formed in the metal mold 16.

[0117] Here, on the screw 60, a snap ring 65 is provided whose outer diameter is the same size as the inner diameter of the heating cylinder 50, but there is a gap between the inner peripheral surface of the snap ring 65 and the screw 60. Therefore, in the metering process, when the screw 60 is rotated, the molten resin R located on the rear side of the snap ring 65 is pressed out to the front side of the snap ring 65 through the gap.

[0118] In contrast, when the molten resin R that was metered in the metering process is injected, the snap ring 65 becomes a state in which movement of the molten resin R between the both sides in the length direction Y cannot be performed. Figure 13 is an explanatory view that shows the state of the snap ring 65 at the time of injection of the molten resin R. In the injection process, when the molten resin R in the heating cylinder 50 is injected from the nozzle portion 52, the screw 60 is advanced by the advancement / retraction mechanism 80 being caused to act by the control portion 100. Thereby, a pressing force that pushes to the front side in the length direction Y is applied to the molten resin R located on the front side of the snap ring 65 in the heating cylinder 50 from the screw 60. The snap ring 65 that is provided in the groove portion 62 of the screw 60 can move in the groove width direction within the groove portion 62 because the width in the length direction Y is smaller than the groove width of the groove portion 62 of the screw 60.

[0119] Further, when a pressing force that pushes to the front side is applied to the molten resin R located on the front side of the snap ring 65 by the screw 60 being advanced, a pressing force that pushes to the rear side as a reaction force is applied to the snap ring 65 from the molten resin R. Thereby, the snap ring 65 moves relatively to the rear side within the range in which the groove portion 62 is formed on the screw 60 with respect to the groove portion 62, and the snap ring 65 abuts against the groove wall 63 on the rear side in the groove width direction of the groove portion 62.

[0120] Therefore, there is no longer a gap between the groove wall 63 on the rear side in the groove width direction of the groove portion 62 and the snap ring 65, and the molten resin R can no longer pass through. That is, in the case where the molten resin R located on the front side of the snap ring 65 flows into the gap between the inner peripheral surface of the snap ring 65 and the groove bottom of the groove portion 62 through the communication portion 64 formed on the screw 60, it can no longer flow to the rear side from that position. Thus, when the molten resin R that was metered in the metering process is injected in the injection process by the screw 60 being advanced, the molten resin R located on the front side of the snap ring 65 does not flow to the rear side of the snap ring 65 and is pressed out from the nozzle portion 52.

[0121] At this time, since the dispersed bubbles B are contained in the molten resin R, in the injection process, the molten resin R containing the uniformly dispersed bubbles B is injected from the nozzle portion 52 to the cavity 17 formed in the metal mold 16 via the through port 18 of the fixed metal mold 16f. Thereby, the cavity 17 is filled with the molten resin R containing the uniformly dispersed bubbles B.

[0122] Here, in the metering process, by performing metering while increasing the back pressure of the molten resin R, the air contained in the bubbles B in the molten resin R becomes a supercritical state. On the other hand, the pressure of the molten resin R in the cavity 17 when the molten resin R is injected into the cavity 17 becomes lower than the back pressure of the molten resin R in the metering process located on the front side of the check ring 65. Therefore, the bubbles B contained in the molten resin R grow in the cavity 17. Thus, the foaming molding is performed in the cavity 17 into which the molten resin R is injected, and the molten resin R containing the uniformly dispersed bubbles B is molded into the foamed molded product M.

[0123] <Effects of Embodiment 1>

[0124] The foaming molding method, the control method of the injection molding machine 1 for foaming molding, and the injection molding machine 1 for foaming molding described above with regard to Embodiment 1 make the atmosphere A taken into the heating cylinder 50 into a state in which the bubbles B are dispersed in the molten resin R, and inject the molten resin R containing the dispersed bubbles B into the cavity 17. Thereby, it is possible to perform foaming molding without using a dedicated injection molding machine for foaming molding, and to use an existing injection molding machine as the injection molding machine 1 for foaming molding, and to perform foaming molding without using a device such as a high-pressure gas generating device. As a result, it is possible to achieve a reduction in cost when performing foaming molding.

[0125] Furthermore, since the air contained in the bubbles B dispersed in the molten resin R is made into a supercritical fluid state by applying pressure to the bubbles B in the metering process, a gas having a high pressure or a device for increasing the pressure of a gas is not used in the gas used for foaming molding, and by applying a large pressure to the bubbles B in the metering process of the molten resin R, it is possible to make the air contained in the bubbles B into a supercritical fluid. As a result, it is possible to perform foaming molding more reliably while suppressing an increase in cost.

[0126] [Embodiment 2]

[0127] The injection molding machine 1 for foaming molding with regard to Embodiment 2 is roughly the same structure as the injection molding machine 1 for foaming molding with regard to Embodiment 1, but is characterized in that the heating cylinder 50 is provided with the supply port 56. The other structures are the same as Embodiment 1, so the description thereof is omitted and the same reference numerals are assigned.

[0128] Figure 14Fig. 2 is a schematic view of a main portion of a heating cylinder 50 of an injection molding machine 1 for foam molding according to Embodiment 2. The injection molding machine 1 for foam molding according to Embodiment 2 is similar to Embodiment 1 in that the heating cylinder 50 is provided with a cutoff nozzle 53. Further, in Embodiment 2, on a front side of the heating cylinder 50 in the length direction Y relative to the screw 60, a supply port 56 is provided which is capable of supplying the atmosphere A into the heating cylinder 50. The supply port 56 is disposed between a position in the length direction Y of the heating cylinder 50 at which the screw 60 is disposed and the opening and closing portion 53a of the cutoff nozzle 53 of the heating cylinder 50.

[0129] Further, at the supply port 56, a check valve 57 is disposed which switches between a state in which the inside and outside of the heating cylinder 50 are communicated via the supply port 56 and a state in which the communication between the inside and outside of the heating cylinder 50 is cut off. The check valve 57 is disposed in the heating cylinder 50 with the inside and outside of the heating cylinder 50 communicated in the communication direction of the check valve 57, the supply port 56 is disposed on the end portion side of the check valve 57 on the inside of the heating cylinder 50 in the communication direction, and opens into the heating cylinder 50. On the other hand, on the end portion side of the check valve 57 on the outside of the heating cylinder 50 in the communication direction, a supply pipe 58 is connected which is capable of causing the atmosphere outside the heating cylinder 50 to flow toward the check valve 57. The end portion on the side opposite the check valve 57 of the supply pipe 58 is open to the atmosphere, and the supply pipe 58 is capable of supplying the atmosphere to the check valve 57.

[0130] The check valve 57 is capable of opening and closing based on the difference between the pressure of the gas environment inside the heating cylinder 50 and the atmospheric pressure, and opens when the pressure of the gas environment inside the heating cylinder 50 is lower than the atmospheric pressure by a prescribed pressure difference or more, and is in a closed state when it is not. That is, the check valve 57 is configured to open when the pressure of the gas environment inside the heating cylinder 50 in which the supply port 56 opens is lower than the atmospheric pressure outside the heating cylinder 50 supplied by the supply pipe 58 by a prescribed pressure difference or more, and is closed when it is not. By these, the supply port 56 is capable of switching between a state in which the atmosphere A can be supplied into the heating cylinder 50 and a state in which the atmosphere A cannot be supplied into the heating cylinder 50 in correspondence with the difference between the pressure of the gas environment inside the heating cylinder 50 and the atmospheric pressure.

[0131] <Method of foam molding>

[0132] Figure 15is a flowchart showing the order when foaming molding is performed using the injection molding machine 1 for foaming molding according to Embodiment 2. When foaming molding is performed using the injection molding machine 1 for foaming molding according to Embodiment 2, first, the screw 60 is retracted in a state where the shut-off nozzle 53 is closed, the supply port 56 is opened, and the atmosphere A is taken into the heating cylinder 50 from the supply port 56 (Step ST21). That is, in a case where the screw 60 is retracted by operating the advance / retract mechanism 80 in a state where the shut-off nozzle 53 is closed, the pressure of the gas environment of the portion between the screw 60 and the shut-off nozzle 53 in the heating cylinder 50 is lowered. Thus, the check valve 57 which communicates with the supply port 56 opened in the heating cylinder 50 at the portion between the screw 60 and the shut-off nozzle 53 in the length direction Y becomes an opened state by the difference between the pressure of the gas environment in the heating cylinder 50 and the atmospheric pressure, that is, the supply port 56 becomes an opened state.

[0133] Thus, if the screw 60 is further retracted in a state where the supply port 56 is opened, the atmosphere A around the heating cylinder 50 enters the heating cylinder 50 by the difference between the pressure of the portion between the screw 60 and the shut-off nozzle 53 in the heating cylinder 50 and the atmospheric pressure communicated via the check valve 57 and the supply pipe 58. In other words, by retracting the screw 60 in a state where the shut-off nozzle 53 is closed, the portion between the screw 60 and the shut-off nozzle 53 in the heating cylinder 50 becomes a negative pressure, so the check valve 57 is opened, and the atmosphere A around the heating cylinder 50 flows into the heating cylinder 50 from the supply port 56 via the supply pipe 58. In this case, the screw 60 is retracted at a relatively fast speed in a state where the rotation of the screw 60 is stopped, so that the negative pressure of the portion between the screw 60 and the shut-off nozzle 53 in the heating cylinder 50 can be increased to open the check valve 57. Thus, the atmosphere A is taken into the heating cylinder 50 from the supply port 56.

[0134] Next, the screw 60 is advanced, and the supply port 56 is closed (Step ST22). That is, by advancing the screw 60 by operating the advance / retract mechanism 80, the pressure of the portion between the screw 60 and the shut-off nozzle 53 in the heating cylinder 50 is increased, and the check valve 57 is closed. Thus, the supply port 56 opened in the heating cylinder 50 is closed. In this state, by further advancing the screw 60, the atmosphere A taken into the heating cylinder 50 is diffused into the molten resin R in the heating cylinder 50.

[0135] Specifically, in the case where the screw 60 is advanced in the state where the cutoff nozzle 53 and the supply port 56 are closed, the atmosphere A taken into the portion between the screw 60 and the cutoff nozzle 53, that is, the atmosphere A taken into the portion on the front side of the snap ring 65 is compressed by the advanced screw 60. Thus, the atmosphere A taken into the portion on the front side of the snap ring 65 flows into the portion on the rear side of the snap ring 65 through the portion where the snap ring 65 is disposed. Thus, the atmosphere A taken into the heating cylinder 50 from the supply port 56 is diffused into the molten resin R in the portion on the rear side of the snap ring 65.

[0136] Next, the screw 60 is retracted while being rotated, and the taken-in atmosphere A is dispersed as bubbles B in the molten resin R (step ST23). That is, by rotating the screw 60 by operating the rotation mechanism 70 in the state where the supply port 56 is closed, and retracting the screw 60 by operating the advance / retraction mechanism 80, the taken-in atmosphere A into the heating cylinder 50 is dispersed as bubbles B in the molten resin R while the molten resin R is transported to the front side, and the molten resin R is metered. In other words, in the metering process of the molten resin R, the taken-in atmosphere A into the heating cylinder 50 is dispersed as bubbles B in the molten resin R by the operation of the screw 60 in the metering process in which the molten resin R is transported to the front side while being mixed.

[0137] In this case, the retraction speed of the screw 60 is slower than that in the case where the atmosphere A is taken into the heating cylinder 50 from the supply port 56 in step ST21, and in addition, since the molten resin R is transported to the front side by rotating the screw 60, the portion between the screw 60 and the cutoff nozzle 53 in the heating cylinder 50 does not become a negative pressure, and the check valve 57 does not open. Thus, the back pressure of the molten resin R in the heating cylinder 50 which is sent to the front side of the snap ring 65 provided on the screw 60 can be increased, and the pressure acting on the bubbles B contained in the molten resin R can also be increased. Thus, the air contained in the bubbles B in the molten resin R can be brought to a supercritical state.

[0138] Next, the cutoff nozzle 53 is opened, and the molten resin R containing the dispersed bubbles B is injected into the cavity 17 (step ST24). That is, by opening the cutoff nozzle 53, and advancing the screw 60 by operating the advance / retraction mechanism 80, the molten resin R which has been metered in the metering process in the heating cylinder 50 is injected into the cavity 17 formed in the metal mold 16 in the injection process.

[0139] In this case, since the portion between the screw 60 in the heating cylinder 50 and the cutoff nozzle 53 is made to have a high pressure by advancing the screw 60, the check valve 57 does not open. Therefore, the molten resin R in the heating cylinder 50 located on the front side of the check ring 65 is pressed out from the nozzle portion 52 by advancing the screw 60 to increase the pressure. Thus, the molten resin R containing the bubbles B uniformly dispersed is injected from the nozzle portion 52 into the cavity 17 formed in the metal mold 16 via the through hole 18 of the fixed metal mold 16f, and the molten resin R containing the bubbles B uniformly dispersed is filled in the cavity 17.

[0140] At this time, the air contained in the bubbles B in the molten resin R becomes a supercritical state in the heating cylinder 50, but the pressure of the molten resin R in the cavity 17 is lower than the back pressure of the molten resin R located on the front side of the check ring 65 in the metering process. Therefore, the bubbles B contained in the molten resin R grow in the cavity 17. Thus, the foaming molding is performed in the cavity 17 into which the molten resin R is injected, and the molten resin R containing the bubbles B uniformly dispersed is molded into the foamed molded product M.

[0141] <Effects of Embodiment 2>

[0142] The foaming molding method, the control method of the foaming molding injection molding machine 1, and the foaming molding injection molding machine 1 according to Embodiment 2 described above can take in the atmosphere A into the heating cylinder 50 from the supply port 56 because the supply port 56 can switch between the state in which the atmosphere A can be supplied into the heating cylinder 50 and the state in which the atmosphere A cannot be supplied into the heating cylinder 50. Thus, the atmosphere A can be taken into the heating cylinder 50 without performing the operation of moving the injection device 10 in the length direction Y by the advancing mechanism 40 to separate or approach the nozzle portion 52 of the heating cylinder 50 with respect to the metal mold 16. Therefore, the frequency of the operation of the advancing mechanism 40 can be reduced, the durability of the advancing mechanism 40 can be ensured, and thus the frequency of the parts exchange can be reduced. As a result, the reduction of the cost when the foaming molding is performed can be achieved.

[0143] [Embodiment 3]

[0144] The foaming molding injection molding machine 1 according to Embodiment 3 is roughly the same structure as the foaming molding injection molding machine 1 according to Embodiment 2, but has a feature in that the compressed gas is supplied into the heating cylinder 50. The other structures are the same as those of Embodiment 2, and thus the description thereof is omitted and the same reference numerals are given.

[0145] Figure 16is a main part view of the heating cylinder 50 of the injection molding machine 1 for foam molding according to Embodiment 3. The injection molding machine 1 for foam molding according to this Embodiment 3 is the same as Embodiment 2 in that the supply port 56 is provided between the position where the screw 60 is arranged in the length direction Y of the heating cylinder 50 and the opening / closing portion 53a of the cutoff nozzle 53 of the heating cylinder 50. In this way, the check valve 57 is arranged at the supply port 56 provided on the heating cylinder 50, and the supply pipe 58 is connected to the end portion on the outside of the heating cylinder 50 in the communication direction of the check valve 57.

[0146] The compressor 110 is connected to the end portion on the opposite side of the side where the check valve 57 is connected to the supply pipe 58 in this Embodiment 3. The compressor 110 is capable of sucking the atmosphere and compressing the sucked atmosphere as the compressed gas C to supply to the supply pipe 58. Therefore, the supply pipe 58 is capable of supplying the compressed gas C supplied from the compressor 110 to the check valve 57. In addition, the compressed gas C supplied from the compressor 110 has a pressure of less than 1 MPa.

[0147] The check valve 57 is configured to open when the pressure of the gas environment inside the heating cylinder 50 where the supply port 56 is open is lower than the pressure of the compressed gas C supplied from the supply pipe 58 by a prescribed pressure difference or more, and to close when it is not. Thus, the supply port 56 is capable of switching between a state where the compressed gas C can be supplied to the inside of the heating cylinder 50 and a state where the compressed gas C cannot be supplied to the inside of the heating cylinder 50 in accordance with the difference between the pressure of the gas environment inside the heating cylinder 50 and the pressure of the compressed gas C.

[0148] <Method of foam molding>

[0149] Figure 17 is a flowchart showing the sequence when foam molding is performed using the injection molding machine 1 for foam molding according to Embodiment 3. When foam molding is performed using the injection molding machine 1 for foam molding according to Embodiment 3, the screw 60 is retracted in the state where the cutoff nozzle 53 is closed, and the supply port 56 is opened to take the compressed gas C from the supply port 56 into the heating cylinder 50 (Step ST31). That is, by operating the advance / retract mechanism 80 to retract the screw 60 in the state where the cutoff nozzle 53 is closed, the check valve 57 becomes in the open state by the difference between the pressure of the gas environment inside the heating cylinder 50 and the pressure of the compressed gas C supplied from the compressor 110, that is, the supply port 56 becomes in the open state.

[0150] Accordingly, the compressed gas C supplied from the compressor 110 to the heating cylinder 50 via the supply pipe 58 enters the heating cylinder 50 from the supply port 56. That is, in the state where the cutoff nozzle 53 is closed, the compressed gas C is taken into the heating cylinder 50 from the supply port 56 by retracting the screw 60 in the state where the rotation of the screw 60 is stopped.

[0151] Next, the screw 60 is advanced to close the supply port 56 (step ST32). That is, the screw 60 is advanced by operating the advance / retreat mechanism 80, the pressure of the portion between the screw 60 and the cutoff nozzle 53 in the heating cylinder 50 is increased, and the check valve 57 is closed. Thus, the supply port 56 opened in the heating cylinder 50 is closed. In this state, the compressed gas C taken into the portion on the front side of the snap ring 65 is compressed by further advancing the screw 60, and flows into the portion on the rear side of the snap ring 65 through the portion where the snap ring 65 is disposed. Thus, the compressed gas C taken into the heating cylinder 50 is diffused into the molten resin R in the heating cylinder 50.

[0152] Next, the screw 60 is advanced to close the supply port 56 (step ST32). That is, the screw 60 is advanced by operating the advance / retreat mechanism 80, the pressure of the portion between the screw 60 and the cutoff nozzle 53 in the heating cylinder 50 is increased, and the check valve 57 is closed. Thus, the supply port 56 opened in the heating cylinder 50 is closed. In this state, the compressed gas C taken into the portion on the front side of the snap ring 65 is compressed by further advancing the screw 60, and flows into the portion on the rear side of the snap ring 65 through the portion where the snap ring 65 is disposed. Thus, the compressed gas C taken into the heating cylinder 50 is diffused into the molten resin R in the heating cylinder 50.

[0153] Next, the screw 60 is advanced to close the supply port 56 (step ST32). That is, the screw 60 is advanced by operating the advance / retreat mechanism 80, the pressure of the portion between the screw 60 and the cutoff nozzle 53 in the heating cylinder 50 is increased, and the check valve 57 is closed. Thus, the supply port 56 opened in the heating cylinder 50 is closed. In this state, the compressed gas C taken into the portion on the front side of the snap ring 65 is compressed by further advancing the screw 60, and flows into the portion on the rear side of the snap ring 65 through the portion where the snap ring 65 is disposed. Thus, the compressed gas C taken into the heating cylinder 50 is diffused into the molten resin R in the heating cylinder 50.

[0154] <Effects of Embodiment 3>

[0155] The above-described foaming molding method, the control method of the injection molding machine 1 for foaming molding, and the injection molding machine 1 for foaming molding according to Embodiment 3 can increase the amount of the gas taken into the heating cylinder 50 for foaming molding because the compressed gas C having the pressure increased is taken into the heating cylinder 50 from the supply port 56. Therefore, more gas bubbles B can be dispersed in the molten resin R when the compressed gas C taken into the heating cylinder 50 is dispersed in the molten resin R as the gas bubbles B. Thus, foaming molding can be performed more easily while reducing the frequency of the operation of the advancing mechanism 40 and ensuring the durability of the advancing mechanism 40. As a result, the cost at the time of foaming molding can be reduced more reliably while foaming molding is performed more easily.

[0156] Further, the compressed gas C has a pressure of less than 1 MPa, so in the injection molding machine 1 for foaming molding, the strength of the portion where the compressed gas C does not flow can be greatly increased and more gas bubbles B can be dispersed in the molten resin R using the compressed gas C. As a result, foaming molding can be performed more easily while the cost at the time of foaming molding can be reduced more reliably.

[0157] Further, by setting the pressure of the compressed gas C to be less than 1 MPa, the compressed gas C can be used without going through the procedures such as the application of equipment required when a high-pressure gas is used. Thus, the cost at the time of using the compressed gas C can be more reliably suppressed, so the cost at the time of foaming molding can be more reliably reduced.

[0158] [Modified Example]

[0159] In addition, in Embodiment 2 described above, the compressor 110 is used as the supply source of the compressed gas C into the heating cylinder 50, but a device other than the compressor 110 can be used as the supply source of the compressed gas C. Figure 18 is a modified example of the injection molding machine 1 for foaming molding according to Embodiment 2 and is a diagram illustrating the case where the storage tank 120 is used in the supply of the compressed gas C. In the supply source of the compressed gas C into the heating cylinder 50, for example, the storage tank 120 in which the compressed gas C is stored can be used as illustrated in Figure 18 In this case, it is preferable that an inert gas such as nitrogen be used in the compressed gas C and the storage tank 120 in which the inert gas such as nitrogen is stored be used as the storage tank 120.

[0160] Thus, by using the tank 12 in which the compressed gas C is stored as the supply source of the compressed gas C to the heating tank 50, it is not necessary to use the power source such as the electric power source for operating the compressor 110 as the supply source of the compressed gas C. Therefore, it is possible to easily supply the compressed gas C to the heating tank 50 regardless of the equipment of the installation site of the injection molding machine 1 for foam molding. As a result, it is possible to easily perform the foam molding while reducing the cost for performing the foam molding.

[0161] <Experiment of the foam molding method>

[0162] The inventors performed an experiment on the foam molding using the foam molding method according to Embodiment 1. Next, the experiment of the foam molding is described. The experiment of the foam molding was performed by molding samples by the foam molding using the foam molding method according to Embodiment 1 and the standard molding without performing the foam molding, respectively. Figure 19 is an appearance view of the foam molded sample obtained by the experiment of the foam molding. Figure 19 is a photograph of the foam molded sample obtained by the experiment of the foam molding. Figure 19 In the two samples shown, the left side is a foam molded sample 200 as a sample obtained by the foam molding using the foam molding method according to Embodiment 1, and the right side is a standard molded sample 210 as a sample obtained by the standard molding without performing the foam molding.

[0163] The foam molded sample 200 and the standard molded sample 210 are both in a plate shape of 100 mm in length, 75 mm in width, and 4 mm in thickness, and the metal mold used in the molding is formed using a thick wall metal mold having a large thickness dimension. A gate (the through hole 18 of the fixed metal mold 16f of the injection molding machine 1 for foam molding according to Embodiment 1) in which the molten resin is filled is disposed at the center of the sample. In the molding machine used in the molding, the injection molding machine 1 for foam molding in which the foam molded sample 200 is molded and the injection molding machine in which the standard molded sample 210 is molded are both standard injection molding machines except that the screw diameter is 36 mm, the clamping force of the clamping device is 980 kN, and a cutoff nozzle is attached.

[0164] In the resin used as the material of the molded product, polypropylene was used, the screw stroke at the time of metering in the metering step was set to 36 mm, the back pressure was set to 10 MPa, and the filling speed was 25 mm / s. Further, in order to confirm the effect of foaming in the foaming step, the pressure holding after filling of the molten resin into the metal mold was set to 0 MPa, and the pressure holding was not used. In the foaming step using the foaming molding method according to the related embodiment 1, the screw was retracted by 144 mm in the state where the cutting nozzle was opened, and after the air was sucked from the nozzle portion into the heating cylinder, the air taken into the heating cylinder was diffused into the molten resin by moving or rotating the screw in the length direction Y.

[0165] The foaming molded sample 200 and the standard molded sample 210 were both 4 mm in thickness, and were thick-walled, so as shown in FIG. 6, in the standard molded sample 210, shrinkage 211 as a molding defect occurred on the entire surface, while in the foaming molded sample 200, no shrinkage occurred. From this, it was found that in the case where foaming molding was performed using the foaming molding method according to the related embodiment, the inhibitory effect of shrinkage could be confirmed in thick-walled molding as well, and effective foaming molding could be performed. Figure 19

[0166] BRIEF DESCRIPTION OF THE DRAWINGS

[0167] ​1… injection molding machine for foam molding; 5… base; 6… 1st rail; 10… injection device; 15… mold clamping device; 16… metal mold; 16f… fixed metal mold; 16m… movable metal mold; 17… cavity; 18… through hole; 20… frame; 21… base; 22… front wall; 23… rear wall; 24… foot; 30… upper frame; 31… front wall; 32… side wall; 33… support pin; 34… fixing screw; 35… 2nd rail; 40… advancing mechanism; 41… drive motor; 42… link mechanism; 43… ball screw mechanism; 44… threaded portion; 45… nut portion; 50… heating barrel; 51… heater; 52… nozzle portion; 53… cutoff nozzle; 53a… opening / closing portion; 53b… opening / closing lever; 53c… actuator; 55… hopper; 56… supply port; 57… check valve; 58… supply pipe; 60… screw; 61… helical blade; 62… groove portion; 63… groove wall; 64… communication portion; 65… snap ring; 70… rotating mechanism; 71… rotating mechanism main body portion; 72… brace; 73… drive motor; 74… transmission belt; 75… pulley; 76… bearing; 80… forward / backward mechanism; 81… drive motor; 82… encoder; 83… transmission belt; 84… pulley; 85… bearing; 86… ball screw mechanism; 87… threaded portion; 88… nut portion; 90… force gauge; 100… control section; 101… display section; 102… input section; 110… compressor; 120… storage tank; 200… foam molded sample; 210… standard molded sample; 211… shrinkage cavity; R… molten resin; A… atmosphere; B… bubble; C… compressed gas; M… foam molded product.

Claims

1. A foaming molding method of molding a foamed molded product by injecting a molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold, characterized by comprising: a process of retreating a screw provided inside a barrel that kneads the molten resin inside, opening a supply port provided at a front side of the barrel than the screw, and taking atmospheric air into the barrel from the supply port; a process of advancing the screw and closing the supply port, and diffusing the atmospheric air taken into the barrel into the molten resin inside the barrel; a process of retreating the screw while rotating the screw in a state where the supply port is closed, and transporting the molten resin to the front side while the atmospheric air becomes the bubbles dispersed in the molten resin; and a process of opening the supply port, and injecting the molten resin containing the dispersed bubbles into the cavity.

2. A foaming molding method of molding a foamed molded product by injecting a molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold, characterized by comprising: a process of retreating a screw provided inside a barrel that kneads the molten resin inside, opening a supply port provided at a front side of the barrel than the screw, and taking atmospheric air into the barrel from the supply port; a process of advancing the screw and closing the supply port, and diffusing the atmospheric air taken into the barrel into the molten resin inside the barrel; a process of retreating the screw while rotating the screw in a state where the supply port is closed, and transporting the molten resin to the front side while the atmospheric air becomes the bubbles dispersed in the molten resin; and a process of opening the supply port, and injecting the molten resin containing the dispersed bubbles into the cavity.

3. A foaming molding method of molding a foamed molded product by injecting a molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold, characterized by comprising: a process of retreating a screw provided inside a barrel that kneads the molten resin inside, opening a supply port provided at a front side of the barrel than the screw, and taking compressed gas into the barrel from the supply port; a process of advancing the screw and closing the supply port, and diffusing the compressed gas taken into the barrel into the molten resin inside the barrel; a process of retreating the screw while rotating the screw in a state where the supply port is closed, and transporting the molten resin to the front side while the compressed gas becomes the bubbles dispersed in the molten resin; and a process of opening the supply port, and injecting the molten resin containing the dispersed bubbles into the cavity.

4. The foaming molding method according to claim 3, characterized in that: the compressed gas has a pressure of less than 1 MPa. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 5. A control method of an injection molding machine for foam molding, which is a control method of an injection molding machine for foam molding that injects molten resin containing uniformly dispersed bubbles into a cavity formed by a metal mold to mold a foam molded product, characterized by comprising: a process of, in a state where a cutoff nozzle that opens and closes a nozzle portion that injects the molten resin is opened, retreating a screw provided inside a barrel that uniformly mixes the molten resin to take atmospheric air into the barrel from the nozzle portion; a process of closing the cutoff nozzle to advance the screw to diffuse the atmospheric air taken into the barrel into the molten resin in the barrel; a process of, by retreating the screw while rotating the screw in a state where the cutoff nozzle is closed, transporting the molten resin to the front side while the atmospheric air becomes the bubbles dispersed in the molten resin; and a process of opening the cutoff nozzle to inject the molten resin containing the dispersed bubbles into the cavity.

6. An injection molding machine for foam molding, characterized by comprising: a metal mold that forms a cavity in which a foam molded product is molded from molten resin containing uniformly dispersed bubbles; a barrel that uniformly mixes the molten resin inside; a screw that is rotatably provided inside the barrel and is movable in the axial direction of rotation in the barrel; a nozzle portion that is provided on the barrel to inject the molten resin in the barrel into the cavity; a cutoff nozzle that opens and closes the nozzle portion; and a control portion that controls the operation of the screw and the cutoff nozzle; the control portion of the injection molding machine for foam molding, when injecting the molten resin in the barrel into the cavity, takes atmospheric air into the barrel from the nozzle portion by retreating the screw in a state where the cutoff nozzle is opened; diffuses the atmospheric air taken into the barrel into the molten resin in the barrel by advancing the screw with the cutoff nozzle closed; transports the molten resin to the front side while the atmospheric air becomes the bubbles dispersed in the molten resin by retreating the screw while rotating the screw in a state where the cutoff nozzle is closed; and opens the cutoff nozzle to inject the molten resin containing the dispersed bubbles into the cavity. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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