Foam molding injection molding machine and foam molding method

Abstract

To provide a foam molding injection molding machine capable of reducing costs during foam molding.SOLUTION: A foam molding injection molding machine comprises: a screw 60 rotatably disposed in a heating barrel 50 and movable in a longitudinal direction of the heating barrel 50; a compressor 110 that supplies compressed gas to the heating barrel 50; and a control unit 100 that controls an operation of the screw 60, wherein the heating barrel 50 has a nozzle 52 for injecting molten resin and a gas injection port 53 for injecting compressed gas supplied from the compressor 110 into the heating barrel 50, and after measuring the molten resin to be injected from the nozzle 52 by rotating the screw 60 while moving it toward a side opposite to the nozzle 52, the control unit 100 reverses a rotation direction of the screw 60 relative to the rotation direction during the measurement of the molten resin, thereby diffusing the compressed gas injected into the heating barrel 50 from the gas injection port 53 into the molten resin in the heating barrel 50.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an injection molding machine for foam molding and a foam molding method. [Background technology]

[0002] Conventionally, among the resin molding methods using an injection molding machine, there is foam molding in which the resin is mixed with a gas to form the resin. This type of foam molding is classified into chemical foaming, in which a foaming agent is mixed with the resin to form the resin, and physical foaming, in which a gas such as nitrogen or carbon dioxide is injected through a gas inlet provided in the heater barrel of the injection molding machine to form the resin.

[0003] In recent years, as there is a demand for reducing the environmental load, foam molding has been attracting attention as a means of reducing the amount of resin used, and among them, physical foaming, which is suitable for recycling, is expected to be more effective. As a method for foam molding by physical foaming, for example, as shown in Patent Documents 1 and 2, a method has been proposed in which a starvation zone is provided in a plasticizing cylinder and gas such as nitrogen or carbon dioxide is injected into the starvation zone in the plasticizing cylinder from a cylinder in which the gas is stored, via an introduction rate adjustment container. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6522701 [Patent Document 2] Patent No. 7128015 Publication Summary of the Invention [Problem to be solved by the invention]

[0005] However, when foam molding is performed by providing a starvation zone in the plasticizing cylinder of an injection molding machine and injecting high-pressure gas from a gas cylinder into the plasticizing cylinder, a high initial investment is required, and the gas cylinder needs to be replaced during operation, which increases the running costs. Therefore, there is room for improvement in terms of cost when performing foam molding using an injection molding machine.

[0006] The present invention has been made in view of the above, and has an object to provide an injection molding machine for foam molding and a foam molding method that can reduce costs when performing foam molding. [Means for solving the problem]

[0007] In order to solve the above problems and achieve the object, the injection molding machine for foam molding according to the present invention includes a heating barrel for melting a resin material therein to produce a molten resin, a screw rotatably disposed within the heating barrel and movable within the heating barrel in a longitudinal direction of the heating barrel, a compression device for supplying compressed gas to the heating barrel, and a control unit for controlling the operation of the screw, wherein the heating barrel includes a nozzle disposed at one end in the longitudinal direction of the heating barrel for injecting the molten resin, and a nozzle disposed on a wall surface within the range in the longitudinal direction of the heating barrel where the screw is disposed, and a control unit for controlling the operation of the screw. and a gas inlet for injecting the compressed gas into the heated barrel, and the control unit rotates the screw within the heated barrel and moves it opposite the side where the nozzle is located in the longitudinal direction of the heated barrel to send the molten resin to a portion of the heated barrel that is closer to the nozzle than the screw, thereby metering the molten resin to be injected from the nozzle, and then rotates the screw in the opposite direction to the rotation direction of the screw when metering the molten resin, thereby diffusing the compressed gas injected into the heated barrel from the gas inlet into the molten resin in the heated barrel.

[0008] In addition, in order to solve the above-mentioned problems and achieve the object, the foam molding method of the present invention is a foam molding method in which a foam molding injection molding machine including a heated barrel that melts a resin material inside to form a molten resin, and a screw that is rotatably arranged within the heated barrel and can move within the heated barrel in the longitudinal direction of the heated barrel, supplies compressed gas to the heated barrel, and molds a foam molded product from the molten resin to which the compressed gas has been supplied, the foam molding method including the steps of: moving the screw to the opposite side of the heated barrel in the longitudinal direction of the heated barrel while rotating the screw within the heated barrel, thereby sending the molten resin to a portion of the heated barrel that is closer to the nozzle than the screw, thereby metering the molten resin to be injected from the nozzle; and, after metering the molten resin, rotating the screw in the opposite direction to the rotational direction of the screw when metering the molten resin, thereby diffusing the compressed gas supplied to the heated barrel into the molten resin in the heated barrel. Effect of the Invention

[0009] The foam molding injection molding machine and foam molding method according to the present invention have the advantage that costs involved in foam molding can be reduced. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a foam injection molding machine according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of a main part showing the device configuration of the foam molding injection molding machine according to the embodiment. [Diagram 3] FIG. 3 is a plan view of the essential parts showing the device configuration of the foam molding injection molding machine according to the embodiment. [Figure 4] FIG. 4 is a detailed view of the heating barrel shown in FIG. [Diagram 5] FIG. 5 is a detailed view of the check ring shown in FIG. [Figure 6]FIG. 6 is an explanatory diagram of the steps performed in one cycle of injection and molding operations by a foam injection molding machine. [Figure 7] FIG. 7 is an explanatory diagram showing a change in pressure of the molten resin when the screw is rotated in the reverse direction with respect to the rotation direction of the screw in the metering process. [Figure 8] FIG. 8 is an explanatory diagram showing the state of the check ring when the molten resin is injected. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the foam molding injection molding machine and foam molding method according to the present disclosure will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. In addition, the components in the following embodiments include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[0012] [Embodiment] FIG. 1 is a perspective view of a foam injection molding machine 1 according to an embodiment. FIG. 2 is a cross-sectional view of a main part showing the device configuration of the foam injection molding machine 1 according to an embodiment. FIG. 3 is a plan view of a main part showing the device configuration of the foam injection molding machine 1 according to an embodiment. In the following description, the up-down direction of the foam injection molding machine 1 in a normal use state is described as the up-down direction Z of the foam injection molding machine 1, the upper side of the foam injection molding machine 1 in a normal use state is described as the upper side of the foam injection molding machine 1, and the lower side of the foam injection molding machine 1 in a normal use state is described as the lower side of the foam injection molding machine 1. In the following description, the longitudinal direction Y of the foam injection molding machine 1 is also described as the longitudinal direction Y in each part having the foam injection molding machine 1, and the direction perpendicular to both the up-down direction Z and the longitudinal direction Y of the foam injection molding machine 1 is described as the width direction X of the foam injection molding machine 1.

[0013] <Foam injection molding machine 1> The foam molding injection molding machine 1 according to this embodiment is configured to include a base 5, and an injection device 10 and a clamping device 15 that are arranged on the base 5. The foam molding injection molding machine 1 also includes, near the center in the longitudinal direction Y, a display unit 101 that displays various information about the foam molding injection molding machine 1, and an input unit 102 that an operator uses to perform input operations on the foam molding injection molding machine 1.

[0014] The base 5 is formed in a substantially rectangular parallelepiped shape whose longitudinal direction corresponds to the longitudinal direction Y of the foam molding injection molding machine 1, and a first rail 6 is disposed on the upper surface of the base 5. Two first rails 6 are disposed on the base 5, spaced apart from each other in the width direction X, and both of the two first rails 6 are formed extending along the longitudinal direction of the base 5. The injection device 10 is mounted on the first rail 6 so as to be movable along the extension direction of the first rail 6, and thus the injection device 10 is disposed so as to be movable in the longitudinal direction Y.

[0015] The clamping device 15 is disposed on one side of the injection device 10 in the longitudinal direction Y on the base 5. The clamping device 15 has a clamping mechanism and opens and closes a mold 16 (see FIG. 4) assembled to the clamping mechanism. The clamping device 15 is preferably driven by a servo motor, but may be driven by a hydraulic system. The foam molding injection machine 1 according to this embodiment has covers on the outside of the injection device 10 and the clamping device 15, and FIG. 1 shows the injection device 10 and the clamping device 15 covered with their respective covers.

[0016] <Injection device 10> In the following description, the side where the mold clamping device 15 is located relative to the injection device 10 in the longitudinal direction Y is referred to as the front or front side, and the side opposite the side where the mold clamping device 15 is located relative to the injection device 10 in the longitudinal direction Y is referred to as the rear or rear side.

[0017] The injection device 10 includes a frame 20, a heating barrel 50, a screw 60, a rotation mechanism 70 for rotating the screw 60, a forward / backward mechanism 80 for forward / backward movement of the screw 60, and a propulsion mechanism 40 of the injection device 10. The frame 20 is formed by having a base 21 and an upper frame 30 attached to the base 21. The base 21 is a frame body that is flat in the vertical direction Z, and legs 24 are arranged at four locations on both sides in the longitudinal direction Y and both sides in the width direction X. The four legs 24 are placed on two first rails 6 arranged on the base 5 so as to be freely movable along the extension direction of the first rails 6. As a result, the base 21 is supported so as to be freely slidable in the longitudinal direction Y relative to the base 5.

[0018] The propulsion mechanism 40 has a driving motor 41 and a ball screw mechanism 43. The driving motor 41 is attached to the rear wall 23 located on the rear side of the base 21 in the longitudinal direction Y. The driving motor 41 is disposed with its driving shaft extending in the longitudinal direction Y, and the driving shaft of the driving motor 41 penetrates the rear wall 23 of the base 21 and is connected to a screw portion 44 of the ball screw mechanism 43 by a connecting mechanism 42. As a result, when the driving motor 41 is driven, the driving force of the driving motor 41 is transmitted from the drive shaft via the connecting mechanism 42, and the ball screw mechanism 43 is rotatable by the transmitted driving force.

[0019] The screw portion 44 of the ball screw mechanism 43 is disposed extending in the longitudinal direction Y and penetrates through the approximate center of the base 21 in the width direction X, and the front end side in the longitudinal direction Y is rotatably supported by the front wall 22 located at the front side of the base 21 in the longitudinal direction Y. The nut portion 45 of the ball screw mechanism 43 is fixed to the upper surface of the base 5 inside the base 21. As a result, when the driving motor 41 is driven, the screw portion 44 of the ball screw mechanism 43 rotates due to the driving force transmitted from the driving motor 41, and the screw portion 44 can move relative to the nut portion 45 fixed to the base 5 in the extension direction of the screw portion 44. Therefore, the driving mechanism 40 can move the base 21 on which the screw portion 44 is supported 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 rail 6 arranged on the base 5. This allows the propulsion mechanism 40 to move the injection device 10 in the longitudinal direction Y.

[0020] The upper frame 30 is formed in a rectangular frame shape, and is rotatably attached to the base 21 at a position near the front end in the longitudinal direction Y by a support pin 33. The upper frame 30 is fixed in a non-rotatable state by a fixing screw 34 that fixes the upper frame 30 to the base 21 at a position other than where the support pin 33 is located. Therefore, when the fixing screw 34 is removed to release the fixation by the fixing screw 34, the upper frame 30 is configured to be rotatable relative to the base 21 around the support pin 33.

[0021] The upper frame 30 has a front wall 31 erected upward in the up-down direction Z from an attachment portion to the base 21, and the heating barrel 50 is attached to the front wall 31 of the upper frame 30. The heating barrel 50 extends from the front wall 31 to the front side in the longitudinal direction Y, and a nozzle 52 that is in close contact with the mold 16 (see FIG. 4) is disposed at the tip, i.e., the front end portion of the heating barrel 50. Therefore, the heating barrel 50 is disposed above the frame 20 in the up-down direction Z and in front of the frame 20 in the longitudinal direction Y.

[0022] Specifically, the heating barrel 50 is formed in a substantially cylindrical shape, and is disposed so that the axial direction is aligned with the longitudinal direction Y. That is, the heating barrel 50 is disposed so that the longitudinal direction of the heating barrel 50 coincides with the longitudinal direction Y of the foam molding injection molding machine 1. The heating barrel 50 is also provided with a heater 51 (see FIG. 4) such as a band heater, which allows the heating barrel 50 to melt the resin material therein. That is, the heating barrel 50 can increase the temperature of the heating barrel 50 by the heater 51, and the resin material therein can be heated and melted to become a molten resin, which is a plasticized material.

[0023] The screw 60 is disposed inside the heating barrel 50 and has a helical shape whose axial direction is along the axial direction of the heating barrel 50, that is, the screw 60 has a helical groove on the outer circumferential surface. In this way, the screw 60 formed with a helical shape is rotatable around the axial center in the heating barrel 50. In addition, the screw 60 is movable in the axial direction of the rotation in the heating barrel 50. In other words, the screw 60 is disposed in the heating barrel 50 so that the central axis of the cylinder, which is the shape of the heating barrel 50, and the rotation axis of the screw 60 are approximately aligned, and the screw 60 is disposed so as to be movable in the axial direction of the heating barrel 50 or in the longitudinal direction Y of the heating barrel 50. The screw 60 rotatably disposed in the heating barrel 50 is capable of kneading the molten resin by rotating inside the heating barrel 50, and therefore the heating barrel 50 is a barrel capable of kneading the molten resin inside.

[0024] A hopper 55 is disposed near the portion of the heating barrel 50 that is attached to the upper frame 30. The hopper 55 communicates with the inside of the heating barrel 50 and is capable of supplying pellets (not shown) that are a resin material that becomes the raw resin to the heating barrel 50.

[0025] Furthermore, second rails 35 are arranged on the side walls 32 of the upper frame 30, which are located on both sides in the width direction X of the upper frame 30. The second rails 35 extend in the longitudinal direction Y, that is, are formed to extend substantially parallel to the heating barrel 50.

[0026] The rotation mechanism 70 is disposed behind the heating barrel 50 in the longitudinal direction Y, and is capable of rotating the screw 60 disposed inside the heating barrel 50 around the central axis. The rotation mechanism 70 that rotates the screw 60 has a rotation mechanism main body 71, a driving motor 73, a transmission belt 75, and a pulley 76. Of these, the rotation mechanism main body 71 has a stay 72 extending in the width direction X, and the stay 72 is slidably mounted on the second rail 35 at two locations in the width direction X. As a result, the rotation mechanism main body 71 is movably mounted on the second rail 35 via the stay 72.

[0027] The driving motor 73 is disposed on the upper side of the rotating mechanism main body 71. The driving motor 73 has an encoder 74 that detects the rotational position of the driving motor 73. The pulley 76 is disposed in front of the rotating mechanism main body 71 and is rotatable relative to the rotating mechanism main body 71 via a bearing 77. The pulley 76 is connected to the driving shaft of the driving motor 73 via a transmission belt 75, so that the pulley 76 can rotate by the driving force of the driving motor 73 transmitted via the transmission belt 75. In this way, the pulley 76, which can rotate by the driving force transmitted from the driving motor 73, is fixed coaxially and integrally with the screw 60. In other words, the rear end side of the screw 60 in the longitudinal direction Y is connected to the pulley 76. As a result, the screw 60 disposed in the heating barrel 50 can rotate integrally with the pulley 76 by the driving force transmitted from the driving motor 73 to the pulley 76.

[0028] A forward / backward mechanism 80 is disposed behind the rotation mechanism main body 71 in the longitudinal direction Y. The forward / backward mechanism 80 is capable of moving the screw 60 disposed in the heating barrel 50 in the axial direction of the screw 60. That is, the forward / backward mechanism 80 is capable of moving the screw 60 in the longitudinal direction Y of the heating barrel 50 and the foaming injection molding machine 1, and is capable of moving the screw 60 forward and backward in the longitudinal direction Y. In detail, the forward / backward mechanism 80 has a driving motor 81, a transmission belt 83, a pulley 84, and a ball screw mechanism 86. Of these, the driving motor 81 is disposed on the side of the upper frame 30 in the width direction X. The driving motor 81 also has an encoder 82 that detects the rotational position of the driving motor 81, and the drive shaft of the driving motor 81 is connected to the pulley 84 via the transmission belt 83.

[0029] The pulley 84 is rotatably supported on the upper frame 30 by a bearing 85. A screw portion 87 of a ball screw mechanism 86 is integrally connected to the pulley 84. The screw portion 87 of the ball screw mechanism 86 is disposed coaxially with the screw 60, and is also disposed coaxially with the pulley 76 of the rotation mechanism main body 71. The nut portion 88 of the ball screw mechanism 86 of the forward / reverse mechanism 80 is formed in a substantially cylindrical shape, and the screw portion 87 of the ball screw mechanism 86 is screwed into the nut portion 88.

[0030] A load cell 90 is disposed between the nut portion 88 of the ball screw mechanism 86 of the forward / rearward movement mechanism 80 and the rotation mechanism main body 71 of the rotation mechanism 70 in the longitudinal direction Y. The load cell 90 is disposed behind the rotation mechanism main body 71 of the rotation mechanism 70 and in front of the nut portion 88 of the ball screw mechanism 86 of the forward / rearward movement mechanism 80.

[0031] The load cell 90 is a load measuring device that measures a load applied in the axial direction, and is composed of a strain body and a strain sensor (both not shown) attached to the strain body. In this embodiment, the load cell 90 is arranged so that the axial direction is the longitudinal direction Y, and is formed in a substantially cylindrical shape that is flat in the longitudinal direction Y, and the inner diameter of the cylinder is larger than the outer diameter of the screw portion 87 of the ball screw mechanism 86 of the forward / reverse mechanism 80. The load cell 90 thus formed has a front surface in the longitudinal direction Y integrally fixed to the rotation mechanism main body 71 of the rotation mechanism 70, and a rear surface in the longitudinal direction Y integrally fixed to the nut portion 88 of the ball screw mechanism 86 of the forward / reverse mechanism 80. The load cell 90 arranged between the rotation mechanism main body 71 of the rotation mechanism 70 and the nut portion 88 of the ball screw mechanism 86 of the forward / reverse mechanism 80 is capable of detecting a load acting in the longitudinal direction Y between the rotation mechanism main body 71 and the nut portion 88.

[0032] 4 is a detailed view of the heating barrel 50 shown in FIG. 2. As shown in FIG. 4, 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 circumferential surface. A nozzle 52 is provided at one end in the longitudinal direction Y of the heating barrel 50, i.e., at the front end in the longitudinal direction Y of the heating barrel 50. The nozzle 52 is formed in a substantially cylindrical shape with an inner diameter smaller than the inner diameter of the heating barrel 50, and is disposed so as to open to the front side in the longitudinal direction Y of the heating barrel 50. In this manner, the nozzle 52 provided at the front end of the heating barrel 50 is capable of injecting the molten resin R in the heating barrel 50 into the cavity 17 formed by the mold 16 of the mold clamping device 15.

[0033] Here, the mold 16 will be described. The mold 16 has a fixed mold 16f and a movable mold 16m, and the fixed mold 16f and the movable mold 16m are combined to form one mold 16 for molding the molten resin R into a molded product. Of the fixed mold 16f and the movable mold 16m, the fixed mold 16f is disposed on the side where the heating barrel 50 is located in the longitudinal direction Y, and faces the nozzle 52. The movable mold 16m is disposed on the opposite side of the fixed mold 16f from the side where the heating barrel 50 is located in the longitudinal direction Y. The mold clamping device 15 moves the movable mold 16m in the longitudinal direction Y to separate the movable mold 16m from the fixed mold 16f or to bring the movable mold 16m into contact with the fixed mold 16f.

[0034] The mold 16 has a fixed mold 16f and a movable mold 16m, and when the fixed mold 16f and the movable mold 16m are brought into contact with each other and combined, there is a space between the fixed mold 16f and the movable mold 16m. When the fixed mold 16f and the movable mold 16m are combined, the space formed between them becomes a cavity 17 for molding a molded product from molten resin R in the mold 16. The fixed mold 16f has a through hole 18 that penetrates the surface facing the nozzle 52 and the cavity 17, and the heated barrel 50 can inject the molten resin R from the nozzle 52 into the through hole 18, thereby injecting the molten resin R in the heated barrel 50 into the cavity 17.

[0035] The screw 60 disposed within the heating barrel 50 has a flight 61 that protrudes outward in the radial direction of the screw 60 and is formed in a spiral shape centered on the axis of the screw 60. As a result, the screw 60 has a screw groove 62, which is a spiral groove-like portion, between adjacent rotational portions of the flight 61 that is formed in a spiral shape.

[0036] Further, the screw 60 is provided with a dam portion 67 that divides the screw 60 into a portion on the side where the nozzle 52 is located and a portion on the opposite side to the side where the nozzle 52 is located in the longitudinal direction Y of the heating barrel 50. The dam portion 67 is formed in an annular shape with an outer diameter equal to or larger than the outer diameter of the flight 61. For this reason, the distance between the inner peripheral surface of the heating barrel 50 and the outer peripheral surface of the dam portion 67 is smaller than the distance between the inner peripheral surface of the heating barrel 50 and the outer peripheral surface of the flight 61.

[0037] In this embodiment, the dam portion 67 is disposed near the center of the screw 60 in the longitudinal direction Y. In this embodiment, the portion of the screw 60 divided in the longitudinal direction Y by the dam portion 67 on the side where the nozzle 52 is located in the longitudinal direction Y is referred to as the second stage STG2, and the portion opposite the side where the nozzle 52 is located in the longitudinal direction Y is referred to as the first stage STG1. In this manner, the screw 60 divided by the dam portion 67 has a diameter including the flight 61 that is larger in the first stage STG1 from the side where the hopper 55 is located in the longitudinal direction Y to the side where the dam portion 67 is located, and the diameter is larger in the second stage STG2 from the side where the dam portion 67 is located in the longitudinal direction Y to the side where the nozzle 52 is located. For this reason, the diameter of the screw 60 in the second stage STG2 near the dam portion 67 is smaller than the diameter of the portion near the dam portion 67 in the first stage STG1.

[0038] A check ring 66 is disposed in the screw 60 formed in this manner near the front end in the longitudinal direction Y. The check ring 66 is disposed closer to the nozzle 52 than the second stage STG2, and is disposed in a groove 63 formed in the screw 60 near the front end in the longitudinal direction Y. The groove 63 has a groove width direction that is aligned with the axial direction of the screw 60, and is a groove formed around one revolution in the circumferential direction of the screw 60.

[0039] FIG. 5 is a detailed view of the check ring 66 shown in FIG. 4. The check ring 66 is formed in a substantially cylindrical shape, and is disposed in the groove portion 63 of the screw 60 with its axis substantially coinciding with the axis of the screw 60. The check ring 66 formed in a substantially cylindrical shape has an outer diameter that is approximately the same as the inner diameter of the heating barrel 50 and is slightly smaller than the inner diameter of the heating barrel 50. The inner diameter of the check ring 66 is also larger than the diameter of the groove bottom of the groove portion 63 of the screw 60, and a gap is formed between the inner peripheral surface of the check ring 66 and the groove bottom of the groove portion 63 of the screw 60. The width of the check ring 66 in the axial direction is also smaller than the groove width of the groove portion 63 of the screw 60. For this reason, the check ring 66 is capable of moving in the groove width direction within the groove portion 63.

[0040] Further, the screw 60 is formed with a communication portion 65 that communicates between a portion forward of the groove portion 63 in the longitudinal direction Y and the inside of the groove portion 63. The communication portion 65 opens into a groove wall 64 on the front side of the groove portion 63 in the groove width direction.

[0041] The foam injection molding machine 1 also has a compressor 110, which is a compression device that supplies compressed gas to the heated barrel 50. The heated barrel 50 is provided with a gas inlet 53 for injecting the compressed gas supplied from the compressor 110 into the heated barrel 50. In detail, the compressor 110 is capable of sucking in the surrounding air, compressing it, and discharging it as compressed gas. The gas inlet 53 is provided on the wall surface of the heated barrel 50 in the longitudinal direction Y of the heated barrel 50 in a range in which the screw 60 is disposed. The compressor 110 and the gas inlet 53 are connected by a supply pipe 105 that supplies the compressed gas compressed by the compressor 110 to the heated barrel 50. Therefore, the compressed gas compressed by the compressor 110 is supplied to the gas inlet 53 by the supply pipe 105, and is injected into the heated barrel 50 from the gas inlet 53.

[0042] In this way, the compressor 110 that supplies the compressed gas to the heating barrel 50 compresses the compressed gas to a pressure at which the compressed gas becomes a supercritical fluid and supplies the compressed gas to the heating barrel 50. The compressor 110 preferably supplies the compressed gas to the heating barrel 50 at a pressure of 5 MPa or less while keeping the compressed gas in a supercritical fluid state. In other words, since the critical pressure of air is 3.7 MPa, the compressor 110 preferably converts the air into compressed gas with a pressure in the range of 3.7 MPa or more and 5 MPa or less and supplies the compressed gas to the heating barrel 50.

[0043] Furthermore, the screw 60 is movable in the longitudinal direction Y within the heating barrel 50, but the gas inlet 53 is disposed on the side where the nozzle 52 is disposed relative to any position of the dam portion 67 within the movement range of the dam portion 67 when the screw 60 moves in the longitudinal direction Y of the heating barrel 50. In other words, the gas inlet 53 is disposed within the range of the second stage STG2 in the longitudinal direction Y, regardless of the movement position of the screw 60 in the longitudinal direction Y.

[0044] Furthermore, the foam molding injection molding machine 1 according to this embodiment has an air separation unit 120 that separates the compressed gas compressed by the compressor 110. The air separation unit 120 is disposed on the compressed gas supply path between the compressor 110 and the gas inlet 53, and is connected to the compressor 110 and the gas inlet 53 by a supply pipe 105. The air separation unit 120 disposed between the compressor 110 and the gas inlet 53 in this manner is capable of separating the components of the compressed gas compressed by the compressor 110 and supplying a portion of the compressed gas to the gas inlet 53. That is, the air separation unit 120 is capable of separating the components of the compressed gas compressed by the compressor 110 while the compressed gas remains in a supercritical fluid state, and supplying a portion of the compressed gas in a supercritical fluid state to the gas inlet 53.

[0045] In this embodiment, the air separation unit 120 is capable of separating nitrogen from the compressed gas compressed by the compressor 110 and supplying the separated compressed nitrogen gas to the gas inlet 53. Therefore, the gas inlet 53 is capable of supplying the nitrogen compressed by the compressor 110 and separated by the air separation unit 120 into the heated barrel 50. Since the critical pressure of nitrogen is 3.4 MPa, it is preferable that the compressor 110 and the air separation unit 120 convert the nitrogen into compressed gas with a pressure in the range of 3.4 MPa or more and 5 MPa or less and supply the compressed gas into the heated barrel 50.

[0046] The foam injection molding machine 1 also has a control unit 100 that performs various controls of the foam injection molding machine 1. The control unit 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 memories for storing various information. All or part of the functions of the control unit 100 are realized by loading an application program held in the ROM into the RAM and executing it on the CPU, thereby reading and writing data from and to the RAM and ROM.

[0047] The display unit 101 and the input unit 102 are both connected to the control unit 100, and the display unit 101 displays information transmitted from the control unit 100. The input unit 102 transmits information inputted to the control unit 100. The encoder 74 disposed on the driving motor 73 of the rotation mechanism 70, the encoder 82 disposed on the driving motor 81 of the forward / reverse mechanism 80, and the load cell 90 disposed between the forward / reverse mechanism 80 and the rotation mechanism 70 are all connected to the control unit 100, and are capable of transmitting detection results to the control unit 100.

[0048] Furthermore, the heater 51 of the injection device 10, the driving motor 73 of the rotation mechanism 70, the driving motor 81 of the forward and backward movement mechanism 80, and the driving motor 41 of the propulsion mechanism 40 are connected to the control unit 100 and are operated by control signals from the control unit 100. That is, the control unit 100 is capable of controlling the operation of the heating barrel 50 and the screw 60. Therefore, the control unit 100 is capable of controlling the temperature of the heating barrel 50 heated by the heater 51, controlling the rotation of the screw 60 by the rotation mechanism 70, controlling the movement of the screw 60 in the longitudinal direction Y by the forward and backward movement mechanism 80, and the like.

[0049] <Action of foam injection molding machine 1> The foam injection molding machine 1 according to this embodiment includes the above-mentioned configuration, and its operation will be described below. The foam injection molding machine 1 repeats a cycle of injection and molding operations, with one injection and molding operation being one cycle. FIG. 6 is an explanatory diagram of the steps performed in one cycle of injection and molding operations by the foam injection molding machine 1. Each cycle of injection and molding operations by the foam injection molding machine 1 includes a plurality of steps for injecting a resin material used for molding and molding a product. Each cycle includes, for example, a filling step P1, a pressure holding step P2, a cooling step P3, a mold opening step P4, a product removal step P5, and a mold closing step P6.

[0050] The filling process P1 is a process in which a nozzle 52 provided on the heated barrel 50 of the injection device 10 is pressed against the through hole 18 of the fixed mold 16f of the mold clamping device 15, and molten resin R, which is a resin material melted by the heated barrel 50, is injected into and filled in the cavity 17 formed by the movable mold 16m and the fixed mold 16f.

[0051] The pressure holding process P2 is a process in which the screw 60 of the injection device 10, which has filled the cavity 17 formed by the movable mold 16m and the fixed mold 16f attached to the mold clamping device 15 with resin material, is waited in a state of maintaining the pressure of the resin material injected into the cavity 17 without rotating within the heated barrel 50.

[0052] The cooling process P3 is a process in which the temperature of the molding resin, which is the resin material injected into the cavity 17 formed by the fixed mold 16f and movable mold 16m of the mold clamping device 15, drops and solidifies, and the molding resin waits for a certain period of time until it becomes a molded product.

[0053] The mold opening process P4 is a process of separating the movable mold 16m from the fixed mold 16f in order to remove a molded product molded by the fixed mold 16f and the movable mold 16m of the mold clamping device 15.

[0054] The product removal process P5 is a process in which a push-out member (not shown) provided in the mold clamping device 15 pushes out the molded product from the movable die 16m, and the molded product, which is the product, is removed from the movable die 16m.

[0055] The mold closing process P6 is a process of combining the movable mold 16m and the fixed mold 16f of the mold clamping device 15 to form a cavity 17, which is a space corresponding to the product shape, between the movable mold 16m and the fixed mold 16f.

[0056] The cooling step P3 performed by the foam injection molding machine 1 includes a measurement step P3a, a screw reverse rotation step P3b, and a screw rotation stopping step P3c.

[0057] The metering process P3a is a process of sending the molten resin R to be injected in the next cycle to the end side where the nozzle 52 is located in the heated barrel 50 of the injection device 10, and preparing the resin material to be used in the next cycle. That is, the metering process P3a is a process of moving the screw 60 to the side opposite the side where the nozzle 52 is located in the longitudinal direction Y while rotating the screw 60 in the heated barrel 50 in a direction in which the molten resin R in the screw groove 62 formed in the screw 60 in a spiral shape is sent to the side where the nozzle 52 is located.

[0058] The screw reverse rotation step P3b is a step of rotating the screw 60 in the direction opposite to the rotation direction of the screw 60 rotated in the metering step P3a.

[0059] The screw rotation stopping step P3c is a step of stopping the rotation of the screw 60 that has been reversely rotated in the screw reverse rotation step P3b.

[0060] When a molded product is formed by the foam injection molding machine 1, the cycle of injection and molding operations is repeatedly executed, and in the repeatedly executed cycle, in order to smoothly inject the resin material in the heating barrel 50, the control unit 100 continuously heats the inside of the heating barrel 50 by the heater 51. As a result, the heating barrel 50 holds in a molten state the resin material that is put into the hopper 55 in the form of pellets and supplied from the hopper 55 to the heating barrel 50.

[0061] In addition, the compressor 110 continuously compresses air and supplies the compressed gas to the heating barrel 50, and the compressed nitrogen gas compressed by the compressor 110 and separated by the air separation unit 120 is continuously injected into the heating barrel 50 through the gas inlet 53.

[0062] The control unit 100 performs control while determining the start or end of each process in the cycle of the injection molding operation. In order to determine the start or end of each process, for example, a flag is defined in advance at the first or last step of each process in a program for operating the foam injection molding machine 1 by the control unit 100. This allows the control unit 100 to determine the start or end of each process while executing the program for operating the foam injection molding machine 1. In other words, by defining the flag, the control unit 100 can determine that the process has moved to the next process when the flag is executed before or after the processing of each step.

[0063] Furthermore, when the process has shifted, the control unit 100 causes the display unit 101 to display the shift of the process. That is, the display unit 101 displays the current process of the foam molding injection machine 1. This allows the operator to recognize the current operating state of the foam molding injection machine 1 by visually checking the display unit 101.

[0064] The foam molding injection machine 1 has the above-mentioned steps as its basic steps, and by repeating these steps, it is possible to mold a molded product from molten resin R, but the foam molding injection machine 1 according to this embodiment is capable of molding a foam molded product from molten resin R that contains bubbles. Next, a foam molding method for molding a foam molded product will be described.

[0065] <Foam molding method> In the foam molding method according to this embodiment, compressed gas supplied from the compressor 110 into the heated barrel 50 is diffused into the molten resin R in the heated barrel 50, thereby dispersing the compressed gas in a supercritical fluid state into the molten resin R. Thereafter, the molten resin R containing the compressed gas in a supercritical fluid state is injected into the cavity 17 of the mold 16, and the pressure of the molten resin R is reduced, causing the compressed gas to grow as bubbles, thereby performing foam molding and forming a foam-molded product.

[0066] When foam molding by such a foam molding method is performed using the foam molding injection molding machine 1, the operation of the screw 60 is controlled by the control unit 100 while the compressed gas in a supercritical fluid state compressed by the compressor 110 is supplied into the heated barrel 50. Specifically, foam molding by the foam molding injection molding machine 1 according to the embodiment is performed by metering the molten resin R in the metering step P3a, and then diffusing the compressed gas into the molten resin R in the heated barrel 50 by rotating the screw 60 in the opposite direction to the rotation direction in the metering step P3a.

[0067] To give a detailed explanation of the metering step P3a in the foam molding injection molding machine 1 that performs foam molding in this manner, the resin material to be metered in the metering step P3a is charged in the form of pellets into a hopper 55, and is supplied from the hopper 55 into the heating barrel 50. The heating barrel 50 is heated by a heater 51, so that the inside of the heating barrel 50 becomes hot, and the resin material supplied into the heating barrel 50 in the form of pellets melts in the heating barrel 50 and becomes a molten resin R.

[0068] In the metering process P3a, while rotating the screw 60 inside the heating barrel 50 in which the resin material is melted, the screw 60 is moved rearward in the longitudinal direction Y. The rotation of the screw 60 is performed by controlling the rotation mechanism 70 with the control unit 100. That is, by controlling the rotation mechanism 70 with the control unit 100, the driving motor 73 of the rotation mechanism 70 is driven. As a result, the driving force generated by the driving motor 73 is transmitted to the pulley 76 by the transmission belt 75, and is transmitted from the pulley 76 to the screw 60, causing the screw 60 to rotate.

[0069] The rotation direction of the screw 60 here is a direction in which the molten resin R located in the screw groove 62 formed in the screw 60 in a spiral shape can be sent to the front end side in the longitudinal direction Y, that is, to the side where the nozzle 52 is located, by the rotation of the screw 60. In the following explanation, of the rotation directions of the screw 60, the direction in which the molten resin R can be sent to the side where the nozzle 52 is located in the longitudinal direction Y will be explained as forward rotation, and the opposite direction to the forward rotation will be explained as reverse rotation.

[0070] The movement of the screw 60 backward in the longitudinal direction Y, that is, the retreat of the screw 60, is performed by controlling the forward / reverse mechanism 80 with the control unit 100. When the forward / reverse mechanism 80 retreats the screw 60, the control unit 100 controls the forward / reverse mechanism 80 to drive the driving motor 81 of the forward / reverse mechanism 80. The driving force generated by the driving motor 81 is transmitted to the pulley 84 by the transmission belt 83, and is transmitted from the pulley 84 to the screw portion 87 of the ball screw mechanism 86, causing the screw portion 87 to rotate. As a result, the nut portion 88 of the ball screw mechanism 86 moves in the longitudinal direction Y, and together with the nut portion 88, the load cell 90 and the entire rotation mechanism 70 move in the longitudinal direction Y while being supported by the second rail 35. Therefore, the screw 60 connected to the pulley 76 of the rotation mechanism 70 also moves in the longitudinal direction Y together with the pulley 76 of the rotation mechanism 70, and the screw 60 retreats.

[0071] In the metering process P3a, the screw 60 is rotated forward as described above, and is then retracted, so that the molten resin R in the heating barrel 50 is sent by the screw 60 to a portion of the heating barrel 50 that is closer to the nozzle 52 than the screw 60. At this time, the screw 60 is provided with a dam portion 67, and the screw 60 is divided into a first stage STG1 and a second stage STG2 by the dam portion 67. When the screw 60 rotates forward, the resin material located in the first stage STG1 passes through the portion between the inner circumferential surface of the heating barrel 50 and the dam portion 67 and moves to the second stage STG2.

[0072] At that time, the diameter of the screw 60 in the vicinity of the dam portion 67 in the second stage STG2 is smaller than the diameter of the screw 60 in the vicinity of the dam portion 67 in the first stage STG1, so the volume of the space formed by the inner circumferential surface of the heating barrel 50 and the screw 60 is large in the portion near the dam portion 67 in the second stage STG2. Therefore, the pressure of the resin material is relatively small in the portion where the resin material that has passed over the dam portion 67 and been sent from the first stage STG1 to the second stage STG2 is located by the forward rotation of the screw 60, that is, in the portion near the dam portion 67 in the second stage STG2.

[0073] In addition, the diameter of the second stage STG2 of the screw 60 increases from the side where the dam portion 67 is located toward the side where the nozzle 52 is located in the longitudinal direction Y, and therefore the volume of the space formed by the inner circumferential surface of the heating barrel 50 and the screw 60 decreases from the side where the dam portion 67 is located toward the front side. Therefore, the pressure of the molten resin R sent to the side where the nozzle 52 is located in the longitudinal direction Y in the metering process P3a increases from the side where the dam portion 67 is located toward the front side.

[0074] In the metering step P3a, the control unit 100 controls the rotation and movement of the screw 60 as described above, thereby extruding the molten resin R in the heating barrel 50 toward the front end side of the heating barrel 50. At that time, the control unit 100 measures the molten resin R using the amount of movement of the screw 60 when extruding the molten resin R toward the front end side portion of the heating barrel 50 while retracting the screw 60, and the pressure of the molten resin R sent to the front end side portion of the heating barrel 50.

[0075] In this case, the metering of the molten resin R means storing the amount of molten resin R to be injected into the mold 16 held by the clamping device 15 in one filling step P1 in a portion of the heated barrel 50 that is located forward of the check ring 66 in the longitudinal direction Y, thereby ensuring the amount of molten resin R to be used in one filling step P1.

[0076] Here, when the molten resin R is sent to the front end side in the metering step P3a, the check ring 66 arranged on the screw 60 is pushed forward by the molten resin R sent to the front side, and is pressed against the front groove wall 64 of the groove portion 63 formed in the screw 60 (see FIG. 5). Therefore, a gap is formed between the rear groove wall 64 of the groove portion 63 formed in the screw 60 and the check ring 66, so that the molten resin R located behind the check ring 66 passes through the gap and further passes between the inner circumferential surface of the check ring 66 and the groove bottom of the groove portion 63, and is extruded into the communication portion 65. As a result, when the molten resin R is extruded to the front side of the check ring 66 by the screw 60 in the metering step, the molten resin R located behind the check ring 66 is extruded to the front side of the check ring 66.

[0077] In the control of the metering process P3a, the movement amount of the screw 60 is obtained based on the detection result of the encoder 82 of the drive motor 81 of the forward / reverse mechanism 80. In other words, the forward / reverse mechanism 80 moves the screw 60 in the longitudinal direction Y by transmitting the driving force generated by the drive motor 81 to the screw 60, and the encoder 82 is capable of detecting the rotational position of a rotor (not shown) of the drive motor 81. Therefore, the control unit 100 obtains the position of the screw 60 in the longitudinal direction Y by obtaining the rotational position of the rotor of the drive motor 81 detected by the encoder 82.

[0078] The encoder 82 of the driving motor 81 of the forward / reverse mechanism 80 serves as a screw position detection unit that detects the position of the screw 60 in the longitudinal direction Y within the heating barrel 50. In the measurement process P3a, the control unit 100 obtains the position of the screw 60 in the longitudinal direction Y based on the detection result of the encoder 82 of the driving motor 81 of the forward / reverse mechanism 80, thereby obtaining the retreat amount of the screw 60.

[0079] The pressure of the molten resin R sent to the front end portion of the heating barrel 50 is detected using the detection result of the load cell 90. The load cell 90 is used as a back pressure detection unit that detects the back pressure, which is the pressure of the molten resin R extruded by the screw 60 to the front end side in the heating barrel 50.

[0080] To explain detection of the back pressure of the molten resin R by the load cell 90, when the screw 60 extrudes the molten resin R in the heating barrel 50 toward the front end inside the heating barrel 50, a force acts on the screw 60 toward the rear in the longitudinal direction Y due to a reaction caused when the molten resin R is extruded toward the front. The force in the longitudinal direction Y acting on the screw 60 is transmitted from the screw 60 to the pulley 76 of the rotation mechanism 70, and then from the pulley 76 to the rotation mechanism main body 71, whereby it is transmitted to the load cell 90 fixed to the rotation mechanism main body 71.

[0081] Since the surface of the load cell 90 opposite to the surface fixed to the rotation mechanism main body 71 is fixed to the nut portion 88 of the ball screw mechanism 86 of the forward / reverse mechanism 80, a rearward force in the longitudinal direction Y from the rotation mechanism main body 71 of the rotation mechanism 70 acts on the load cell 90 as a force compressing the load cell 90 in the longitudinal direction Y. The load cell 90 detects the magnitude of the force acting on the load cell 90 in this manner and transmits it to the control unit 100. The control unit 100 obtains the magnitude of the force transmitted from the load cell 90 as a force acting on the screw 60 in the longitudinal direction Y.

[0082] In the measurement process P3a, the control unit 100 obtains the magnitude of the force acting on the screw 60 in the longitudinal direction Y based on the detection result of the load cell 90, thereby obtaining the back pressure of the molten resin R extruded forward by the screw 60. That is, in the measurement process P3a, the control unit 100 obtains the position of the screw 60 in the longitudinal direction Y based on the detection result of the encoder 82, and obtains the back pressure of the molten resin R based on the detection result of the load cell 90, thereby obtaining the amount of molten resin R extruded to the tip side, which is the side where the nozzle 52 of the heating barrel 50 is located, and measures the molten resin R.

[0083] As described above, in the metering step P3a, the control unit 100 moves the screw 60 in the heating barrel 50 in the longitudinal direction Y of the heating barrel 50 to the side opposite to the side where the nozzle 52 is located.

[0084] As a result, in the metering process P3a, the molten resin R is extruded toward the tip side in the heated barrel 50, and the molten resin R extruded by the screw 60 is metered based on the position of the screw 60 detected by the encoder 82 and the back pressure detected by the load cell 90. In the metering process P3a, the molten resin R is metered in this manner, so that the amount of molten resin R to be injected from the heated barrel 50 into the mold 16 of the mold clamping device 15 is metered in one filling process P1. That is, in the metering process P3a, the amount of molten resin R to be injected from the nozzle 52 into the mold 16 in the filling process P1 of the next cycle is metered.

[0085] The control unit 100 thus moves the screw 60 backward in the longitudinal direction Y while rotating it in the metering step P3a to meter the molten resin R, and then stops the movement of the screw 60 in the longitudinal direction Y and reverses the rotation of the screw 60 in the screw reverse rotation step P3b. In the screw reverse rotation step P3b, the foam molding injection molding machine 1 rotates the screw 60 in the reverse direction relative to the rotation direction of the screw 60 when metering the molten resin R, thereby diffusing the compressed gas injected into the heating barrel 50 from the gas inlet 53 into the molten resin R in the heating barrel 50.

[0086] That is, compressed gas supplied from the compressor 110 is continuously injected into the heating barrel 50 from the gas inlet 53, but in the metering process P3a, the molten resin R is sent to the side where the nozzle 52 is disposed by the forward rotating screw 60, so the pressure of the molten resin R is high. For this reason, the compressed gas supplied into the heating barrel 50 is difficult to diffuse into the molten resin R whose pressure is high.

[0087] Therefore, in this embodiment, when the metering step P3a is completed in the foam molding injection molding machine 1, the control unit 100 controls the rotation of the drive motor 73 of the rotation mechanism 70 to rotate the screw 60 in reverse, thereby reducing the pressure of the molten resin R in the heated barrel 50 and diffusing the compressed gas supplied into the heated barrel 50 into the molten resin R. After the molten resin R is metered in the metering step P3a, when the control unit 100 controls the rotation mechanism 70 to rotate the screw 60 in reverse in the screw reverse rotation step P3b, it is preferable to rotate the screw 60 in reverse within a range of 45° or more and 720° or less.

[0088] Fig. 7 is an explanatory diagram showing a change in pressure of the molten resin R when the screw 60 is rotated in the reverse direction with respect to the rotation direction of the screw 60 in the metering process P3a. Note that Fig. 7 is a diagram showing the pressure of the molten resin R for each position in the longitudinal direction Y of the heating barrel 50, and the pressure of the molten resin R shown by the graph on the upper side of Fig. 7 shows the change in pressure caused by the reverse rotation of the screw 60 for each position in the longitudinal direction Y of the heating barrel 50 shown on the lower side.

[0089] At the completion of the metering step P3a, the pressure of the molten resin R in the screw groove 62 is high, and in particular, the pressure of the molten resin R in the screw groove 62 located in the second stage STG2, which is located closer to the nozzle 52 than the first stage STG1, is higher than the pressure of the molten resin R in the screw groove 62 located in the first stage STG1. For this reason, at the completion of the metering step P3a, the pressure of the molten resin R in the screw groove 62 located in the second stage STG2 is higher than the pressure of the compressed gas injected into the heating barrel 50 from the gas injection port 53.

[0090] In the screw reverse rotation process P3b performed after the completion of the metering process P3a, the movement of the screw 60 in the longitudinal direction Y is stopped and the screw 60 is rotated in the reverse direction, so that the pressure of the molten resin R in the screw groove 62 located in the second stage STG2 is reduced, and the pressure of the molten resin R in the screw groove 62 located in the second stage STG2 is lower than the pressure of the compressed gas injected into the heating barrel 50. In other words, when the movement of the screw 60 in the longitudinal direction Y is stopped and the screw 60 is rotated in the reverse direction, the molten resin R located in the screw groove 62 moves to the rear side in the longitudinal direction Y. Therefore, a part of the molten resin R located in the second stage STG2 moves to the side located in the first stage STG1 through the part between the inner circumferential surface of the heating barrel 50 and the weir portion 67. As a result, the pressure of the molten resin R in the screw groove 62 in the second stage STG2 gradually decreases with the reverse rotation of the screw 60.

[0091] In the screw reverse rotation process P3b, the pressure of the molten resin R in the screw groove 62 in the second stage STG2 gradually decreases with the reverse rotation of the screw 60 in this way, and by rotating the screw in reverse at a predetermined rotation angle, the pressure of the molten resin R in the screw groove 62 in every part of the second stage STG2 becomes lower than the pressure of the compressed gas injected into the heating barrel 50. That is, the pressure of the compressed gas in the heating barrel 50 becomes higher than the pressure of the molten resin R in the screw groove 62 in the second stage STG2.

[0092] As a result, the compressed gas in the heating barrel 50 spreads over a wide range of the molten resin R, which has a relatively low pressure in the second stage STG2, and is diffused into the molten resin R located in the second stage STG2. That is, in the second stage STG2, the molten resin R comes into contact with the compressed gas over the entire area of ​​the screw groove 62 located in the second stage STG2, and the compressed gas in the heating barrel 50 is diffused into the molten resin R in the second stage STG2. The compressed gas in the heating barrel 50 is thus diffused into the molten resin R in the second stage STG2 and comes into contact with the molten resin R over a wide contact area, so that it permeates the molten resin R even at a relatively low pressure. Furthermore, the compressed gas diffused into the molten resin R is in a supercritical fluid state, so that it easily permeates the molten resin R with which it comes into contact.

[0093] In this way, once the screw 60 has been rotated in reverse at a predetermined rotation angle in the screw reverse rotation step P3b, the reverse rotation of the screw 60 is stopped in the screw rotation stopping step P3c. For example, once the screw 60 has been rotated in reverse within a range of 45° or more and 720° or less in the screw reverse rotation step P3b, the reverse rotation of the screw 60 is stopped in the screw rotation stopping step P3c.

[0094] The screw 60, whose rotation has been stopped in the screw rotation stopping step P3c, continues to stop rotating through the mold opening step P4, the product removal step P5, the mold closing step P6, the filling step P1, and the pressure holding step P2 until the start of the next measurement step P3a. That is, the screw 60, whose rotation has been stopped in the screw rotation stopping step P3c, continues to stop rotating during the period between the screw rotation stopping step P3c, the mold opening step P4, the product removal step P5, the mold closing step P6, the filling step P1, and the pressure holding step P2, which is set as a stop period RS (see FIG. 6).

[0095] As a result, the pressure of the molten resin R located in the second stage STG2 does not change, so the molten resin R located in the second stage STG2 continues to be in contact with the compressed gas at a low pressure. Therefore, the compressed gas in the heating barrel 50 is diffused into the molten resin R over the stop period RS during which the rotation of the screw 60 stops, and comes into contact with the molten resin R over a wide contact area. Therefore, the compressed gas in the heating barrel 50 permeates the molten resin R even at a relatively low pressure.

[0096] After the reverse rotation of the screw 60 is stopped in the screw rotation stopping process P3c, the foam molding injection molding machine 1 goes through the mold opening process P4, the product removal process P5, and the mold closing process P6, and then in the filling process P1, the molten resin R in the heated barrel 50 is injected from the nozzle 52 into the cavity 17 formed in the mold 16.

[0097] When the molten resin R in the heated barrel 50 is injected in the filling step P1, the forward and backward movement mechanism 80 is operated while the rotation of the screw 60 is stopped to move the screw 60 forward. As a result, the molten resin R located in front of the screw 60 in the heated barrel 50, which has been metered in the metering step P3a, is pushed out from the nozzle 52 by the screw 60 and injected into the cavity 17 formed in the mold 16.

[0098] Here, a check ring 66 having an outer diameter approximately the same as the inner diameter of the heating barrel 50 is disposed on the screw 60, but there is a gap between the inner peripheral surface of the check ring 66 and the screw 60. Therefore, when the screw 60 is rotated in the metering process P3a, the molten resin R located behind the check ring 66 is pushed out to the front side of the check ring 66 through this gap.

[0099] In contrast, when the molten resin R metered in the metering step P3a is injected, the check ring 66 is in a state in which the molten resin R cannot move between both sides in the longitudinal direction Y. FIG. 8 is an explanatory diagram showing the state of the check ring 66 when the molten resin R is injected. When the molten resin R in the heating barrel 50 is injected from the nozzle 52 in the filling step P1, the control unit 100 operates the forward / backward mechanism 80 to move the screw 60 forward. As a result, a pressing force toward the front in the longitudinal direction Y is applied from the screw 60 to the molten resin R located in front of the check ring 66 in the heating barrel 50. The check ring 66 arranged in the groove portion 63 of the screw 60 has a width in the longitudinal direction Y that is smaller than the groove width of the groove portion 63 of the screw 60, so that the check ring 66 can move in the groove width direction in the groove portion 63.

[0100] Furthermore, when a forward pressing force is applied to the molten resin R located in front of the check ring 66 as the screw 60 advances, a rearward pressing force acts as a reaction force from the molten resin R on the check ring 66. As a result, the check ring 66 moves rearward relative to the groove portion 63 within the range in which the groove portion 63 is formed in the screw 60, and the check ring 66 comes into contact with the groove wall 64 located on the rear side of the groove portion 63 in the groove width direction.

[0101] Therefore, there is no gap between the groove wall 64 located on the rear side in the groove width direction of the groove portion 63 and the check ring 66, and the molten resin R cannot pass through. That is, even if the molten resin R located in front of the check ring 66 flows into the gap between the inner peripheral surface of the check ring 66 and the groove bottom of the groove portion 63 through the communication portion 65 formed in the screw 60, it cannot flow rearward from that position. Therefore, when the molten resin R metered in the metering process P3a is injected in the filling process P1 by moving the screw 60 forward, the molten resin R located in front of the check ring 66 is extruded from the nozzle 52 without flowing rearward of the check ring 66.

[0102] At this time, since the compressed gas in a supercritical fluid state has permeated into the molten resin R, in the filling step P1, the molten resin R permeated with the compressed gas in a supercritical fluid state is injected from the nozzle 52 through the through hole 18 of the fixed mold 16f into the cavity 17 formed in the mold 16. As a result, the cavity 17 of the mold 16 is filled with the molten resin R permeated with the compressed gas in a supercritical fluid state.

[0103] When the cavity 17 of the mold 16 is filled with the molten resin R, the pressure of the molten resin R becomes lower than the back pressure of the molten resin R measured at a position forward of the check ring 66 in the measuring step P3a. Therefore, the compressed gas permeating the molten resin R turns into bubbles and grows in the cavity 17 as the pressure of the molten resin R decreases. Therefore, foam molding is performed in the cavity 17 into which the molten resin R is injected, and the molten resin R into which the compressed gas diffuses and permeates is molded as a foam molded product.

[0104] <Effects of the embodiment> In the injection molding machine 1 for foam molding and the foam molding method according to the above embodiment, the screw 60 is rotated in the metering step P3a while supplying compressed gas to the heated barrel 50 to measure the molten resin R, and then the screw 60 is rotated in the opposite direction to the rotation direction of the screw 60 when measuring the molten resin R, thereby diffusing the compressed gas into the molten resin R in the heated barrel 50. This makes it possible to efficiently diffuse the compressed gas in the heated barrel 50 into the molten resin R by using a compressed gas with a relatively low pressure as the gas to be supplied to the heated barrel 50 without using a cylinder to supply high-pressure gas to the heated barrel 50. Therefore, since foam molding can be performed without using a cylinder containing high-pressure gas, the initial investment cost when performing foam molding can be reduced. In addition, since no cylinder is used, it is not necessary to replace the cylinder during operation, and the running cost when performing foam molding can also be reduced. As a result, the cost when performing foam molding can be reduced.

[0105] The control unit 100 measures the molten resin R in the measurement step P3a, and then rotates the screw 60 in the reverse rotation step P3b within a range of 45° to 720°. This allows the compressed gas to diffuse into the molten resin R while suppressing problems such as clogging of the resin material in the heating barrel 50. In other words, when the reverse rotation of the screw 60 is less than 45°, the reverse rotation of the screw 60 is too little, so there is a risk that the pressure of the molten resin R in the screw groove 62 located in the second stage STG2 is not effectively reduced even if the screw 60 is reversed. In this case, there is a risk that the compressed gas in the heating barrel 50 is not effectively diffused into the molten resin R. In addition, when the reverse rotation of the screw 60 exceeds 720°, the reverse rotation of the screw 60 is too much, so there is a risk that the amount of movement of the resin material in the heating barrel 50 when it moves backward in the longitudinal direction Y due to the reverse rotation becomes too large. In this case, there is a possibility that the resin material located at the first stage STG1 will move farther behind the position of the hopper 55 in the longitudinal direction Y, which may cause problems such as clogging of the resin material.

[0106] In contrast, when the reverse rotation of the screw 60 in the screw reverse rotation process P3b is within a range of 45° or more and 720° or less, the pressure of the molten resin R in the screw groove 62 located in the second stage STG2 can be reduced while suppressing clogging of the resin material at a position behind the hopper 55 in the first stage STG1. Therefore, it is possible to diffuse the compressed gas into the molten resin R while suppressing problems such as clogging of the resin material in the heating barrel 50. As a result, it is possible to perform foam molding more reliably while suppressing an increase in cost.

[0107] In addition, since the compressor 110 supplies compressed air at a pressure of 5 MPa or less, a relatively general-purpose compressor 110 can be used, and the cost of the device that supplies compressed gas to the heating barrel 50 can be reduced. This makes it possible to more reliably reduce the cost of foam molding, and as a result, it is possible to more reliably reduce the cost of foam molding.

[0108] Furthermore, since the air separation unit 120 is disposed between the compressor 110 and the gas inlet 53, a gas that easily becomes a supercritical fluid can be separated by the air separation unit 120 and supplied to the heating barrel 50 as the compressed gas to be supplied into the heating barrel 50. This allows the compressed gas at a relatively low pressure to be more reliably diffused into the molten resin R in the heating barrel 50, and the compressed gas can be permeated into the molten resin R. As a result, foam molding can be performed more reliably while suppressing increases in costs.

[0109] In addition, the screw 60 is provided with a dam portion 67, and the gas inlet 53 is disposed on the side where the nozzle 52 is disposed, relative to any position of the dam portion 67 in the range of movement of the dam portion 67 when the screw 60 moves in the longitudinal direction Y of the heated barrel 50. This allows compressed gas to be supplied to the portion of the heated barrel 50 that is closer to the nozzle 52 than the dam portion 67. This allows compressed gas to be supplied more reliably to the molten resin R located in the portion of the heated barrel 50 closer to the nozzle 52, regardless of the position of the screw 60 in the longitudinal direction Y. Therefore, the resin material is sufficiently melted, and the compressed gas can be diffused to the molten resin R that is close to the timing of injection from the nozzle 52. As a result, foam molding can be performed more reliably while suppressing an increase in cost.

[0110] [Variations] In the above embodiment, compressed gas is supplied from the compressor 110 to the heating barrel 50 via the air separation unit 120, but compressed air may be supplied directly from the compressor 110 to the heating barrel 50 without using the air separation unit 120. If compressed air in a supercritical fluid state can be supplied from the compressor 110 to the heating barrel 50 without separating the compressed air in the air separation unit 120, the air separation unit 120 does not need to be used. Regardless of the presence or absence of the air separation unit 120, by supplying compressed air in a supercritical fluid state to the heating barrel 50, the compressed air can be diffused into the molten resin R, and foam molding can be performed more reliably. In addition, if the air separation unit 120 is not used, the cost of foam molding can be further reduced.

[0111] Moreover, by supplying compressed air by the compressor 110 of 5 MPa or less without using the air separation unit 120, foam molding can be performed without going through the procedures such as facility application required when using high pressure gas. This makes it possible to more reliably reduce the cost of foam molding, and as a result, it is possible to more reliably reduce the cost of foam molding.

[0112] In the above-described embodiment, in the screw reverse rotation step P3b, the movement of the screw 60 in the longitudinal direction Y is stopped and the screw 60 is rotated in the reverse direction. However, when the screw 60 is rotated in the reverse direction, the screw 60 may be moved in the longitudinal direction Y. For example, after the metering step P3a, the screw 60 may be rotated in the reverse direction while performing a so-called suck-back, which is an operation of the screw 60 for relieving the back pressure of the molten resin R. If the pressure of the molten resin R in the heating barrel 50, particularly the pressure of the molten resin R located in the second stage STG2, can be reduced by rotating the screw 60 in the reverse direction, the screw 60 may be moved slightly in the longitudinal direction Y in the screw reverse rotation step P3b. [Explanation of symbols]

[0113] 1...foam injection molding machine, 5...base, 6...first rail, 10...injection device, 15...mold clamping device, 16...mold, 16f...fixed mold, 16m...movable mold, 17...cavity, 18...through hole, 20...frame, 21...base, 22...front wall, 23...rear wall, 24...leg, 30...upper frame, 31...front wall, 32...side wall, 33...support pin, 34...fixing screw, 35...second rail, 40...propulsion mechanism, 41...driving motor, 42...connection mechanism, 43...ball screw mechanism, 44...screw portion, 45...nut portion, 50...heating barrel, 51...heater, 52...nozzle, 53...gas inlet, 55...hopper, 60...screw, 61 ...flight, 62...screw groove, 63...groove portion, 64...groove wall, 65...connection portion, 66...check ring, 67...dam portion, 70...rotation mechanism, 71...rotation mechanism main body, 72...stay, 73...driving motor, 74...encoder, 75...transmission belt, 76...pulley, 77...bearing, 80...forward / reverse mechanism, 81...driving motor, 82...encoder, 83...transmission belt, 84...pulley, 85...bearing, 86...ball screw mechanism, 87...screw portion, 88...nut portion, 90...load cell, 100...control portion, 101...display portion, 102...input portion, 110...compressor, 105...supply pipe, 120...air separation device, R...molten resin

Claims

1. a heating barrel for melting the resin material therein to form molten resin; a screw rotatably disposed within the heating barrel and movable within the heating barrel in a longitudinal direction of the heating barrel; a compressor for supplying compressed gas to the heated barrel; A control unit for controlling the operation of the screw; Equipped with The heating barrel comprises: a nozzle disposed at one end in a longitudinal direction of the heating barrel and configured to inject the molten resin; a gas inlet that is disposed on a wall surface of the heating barrel in a range in which the screw is disposed in the longitudinal direction of the heating barrel and that injects the compressed gas supplied from the compression device into the heating barrel; having The control unit rotates the screw within the heated barrel while moving it to the opposite side of the nozzle in the longitudinal direction of the heated barrel, thereby sending the molten resin to the portion of the heated barrel that is closer to the nozzle than the screw, thereby metering the molten resin to be injected from the nozzle, and then rotates the screw in the opposite direction to the rotation direction of the screw when metering the molten resin, thereby diffusing the compressed gas injected into the heated barrel from the gas injection port into the molten resin in the heated barrel.

2. 2. The foam injection molding machine according to claim 1, wherein the control unit rotates the screw in the reverse direction within a range of 45 degrees or more and 720 degrees or less after metering the molten resin.

3. 3. The foam injection molding machine according to claim 1, wherein the compression device supplies the compressed gas to the heating barrel at a pressure of 5 MPa or less.

4. 3. The foam injection molding machine according to claim 1, further comprising an air separation unit disposed between the compressor and the gas inlet, the air separation unit separating components of the compressed gas compressed by the compressor and supplying a portion of the compressed gas to the gas inlet.

5. A dam portion is disposed on the screw to divide the screw into a portion on a side where the nozzle is located in the longitudinal direction of the heating barrel and a portion on the opposite side where the nozzle is located; 3. The foam molding injection molding machine according to claim 1, wherein the gas inlet is positioned on the side where the nozzle is located relative to any position of the dam part within the range of movement of the dam part when the screw moves in the longitudinal direction of the heating barrel.

6. a heating barrel for melting the resin material therein to form molten resin; a screw rotatably disposed within the heating barrel and movable within the heating barrel in a longitudinal direction of the heating barrel; A foam molding method for molding a foam-molded product from the molten resin to which the compressed gas has been supplied by supplying compressed gas to the heated barrel in a foam molding injection molding machine comprising: a step of rotating the screw in the heating barrel, while moving the screw in the longitudinal direction of the heating barrel to a side opposite to a side where a nozzle of the heating barrel is located, thereby feeding the molten resin to a portion of the heating barrel on the nozzle side relative to the screw, and measuring the amount of the molten resin to be injected from the nozzle; a step of diffusing the compressed gas supplied to the heating barrel into the molten resin in the heating barrel by rotating the screw in a reverse direction to a rotation direction of the screw when the molten resin is metered after the molten resin is metered; A foam molding method comprising the steps of:

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