JP3808011B2 - Injection molding method and mold assembly of molded product having solid part and hollow part - Google Patents

Description

【００５１】
【発明の効果】
本発明においては、第１キャビティ部が溶融熱可塑性樹脂で充填された状態で、可動コアの前進端から後進端への移動に伴う第１キャビティ部の体積増加量に概ね等しい容積、中空部が第１キャビティ部に向かって拡大するが故に、キャビティ内の溶融熱可塑性樹脂の所望の部位にまで確実に加圧流体を到達せしめ、中空部及び中実部を有する成形品の成形において所望の部位にまで確実に中空部を形成することができる。しかも、中実部を形成すべき成形品の部分にまで中空部が延びることを確実に防止することができる。
【図面の簡単な説明】
【図１】図１は、実施例１の金型組立体の模式的な断面図である。
【図２】図２は、実施例１の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図３】図３は、図２に引き続き、実施例１の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図４】図４は、図３に引き続き、実施例１の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図５】図５は、図４に引き続き、実施例１の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図６】図６は、溶融熱可塑性樹脂の射出、加圧流体の導入、可動コアの移動のタイミングを表す図である。
【図７】図７の（Ａ）及び（Ｂ）のそれぞれは、射出成形品の模式的な側面図及び模式的な平面図であり、図７の（Ｃ）及び（Ｄ）のそれぞれは、図７の（Ｂ）の矢印Ｃ−Ｃ、及び、図７の（Ａ）の矢印Ｄ−Ｄに沿った射出成形品の模式的な断面図である。
【図８】図８は、実施例２の金型組立体の模式的な断面図である。
【図９】図９は、実施例２の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図１０】図１０は、図９に引き続き、実施例２の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図１１】図１１は、図１０に引き続き、実施例２の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図１２】図１２は、図１１に引き続き、実施例２の射出成形方法を説明するための金型組立体等の模式的な断面図である。
【図１３】図１３は、比較例１及び比較例２にて得られた成形品の長手方向に沿った模式的な断面図である。
【符号の説明】
１０・・・第１金型部（固定金型部）、１１・・・第２金型部（可動金型部）、１２・・・溶融熱可塑性樹脂流路、１３・・・ゲート部、１４・・・加圧流体導入部、２０・・・可動コア、２１・・・可動コア移動装置、３０・・・キャビティ、３１・・・第１キャビティ部、３２・・・第２キャビティ部、４０・・・溶融熱可塑性樹脂、５０・・・成形品、５１・・・中実部、５２・・・中空部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mold assembly for molding a beautiful molded product having no appearance of sink marks and warpage, and an injection molding method using the mold assembly. More specifically, the present invention provides a mold assembly. Mold assembly for molding a molded product having a hollow portion and a solid portion by introducing a pressurized fluid into the melted thermoplastic resin injected into the cavity, and the mold assembly The present invention relates to an injection molding method using the above.
[0002]
[Prior art]
When molding a molded product based on injection molding of a molten thermoplastic resin, for example, a technique for obtaining a beautiful molded product having no appearance of sink marks or warping is disclosed in, for example, JP-A-63-268611 and JP-B-03-47171. It is well known from the Gazette. In the techniques disclosed in these publications, a molten thermoplastic resin is injected into a cavity provided in a mold, and the cavity is filled with a molten thermoplastic resin, and then a pressurized fluid such as a pressurized gas is supplied. It introduce | transduces in the molten thermoplastic resin in a cavity, and the molded article which has a hollow part is obtained. Normally, a thick part is unevenly distributed in the molded product, and a hollow part is formed in the thick part. The pressurized fluid is introduced from a pressurized fluid introducing portion disposed in the mold. By effectively introducing a pressurized fluid into the molten thermoplastic resin in the cavity, the molten thermoplastic resin is effectively pressed against the cavity surface of the mold, resulting in effective prevention of sink marks and warpage in the molded product. Can do.
[0003]
[Problems to be solved by the invention]
However, in the techniques disclosed in these publications, since the pressurized fluid is introduced after the cavity is filled with the molten thermoplastic resin, the pressurized fluid is the melting heat corresponding to the thick part of the molded product. Only the volume resulting from the volume shrinkage accompanying the cooling of the plastic resin portion can be introduced. Therefore, the pressurized fluid may not reach the desired portion of the molten thermoplastic resin in the cavity, and it may not be possible to effectively prevent sinks and warpage from occurring in the molded product.
[0004]
If sink marks occur, increasing the pressure of the pressurized fluid is one of the countermeasures, but the effect of suppressing the sink marks is low, and conversely, the pressurized fluid protrudes into the thin part of the molded product. Or the surface appearance of the molded product may be deteriorated.
[0005]
Japanese Patent Application Laid-Open No. 5-96560 discloses a mold having a sub-cavity as a mold for molding an injection molded product having a hollow portion. By providing the sub-cavity, when the pressurized fluid is introduced into the molten thermoplastic resin injected into the cavity, the molten thermoplastic resin in the cavity is pushed out to the sub-cavity. As a result, the pressurized fluid can reach the desired portion of the molten thermoplastic resin in the cavity. However, after molding of the molded product, there is a problem that the processing of excising the part of the molded product molded by the subcavity is complicated, and there is a problem that the appearance of the part of the molded product that has been excised is impaired. Productivity is significantly impaired.
[0006]
In order to ensure the formation of the hollow portion, a mold having a movable core in a cavity portion where the hollow portion is to be formed is known from, for example, Japanese Patent Laid-Open Nos. 4-212822 and 7-164486. It is. In these techniques, molten thermoplastic resin is injected into the cavity with the movable core positioned at the forward end. Then, after the injection is completed, a pressurized fluid is introduced into the molten thermoplastic resin in the cavity, and the movable core is moved to the reverse end in order to increase the volume of the cavity portion where the hollow portion is to be formed. However, in the techniques disclosed in these publications, a movable core is provided to form a hollow portion, and regarding a technique for forming a solid part of a molded product in a cavity portion provided with the movable core. Nothing is disclosed.
[0007]
Accordingly, it is an object of the present invention to ensure that the pressurized fluid reaches the desired portion of the molten thermoplastic resin in the cavity and that part of the molten thermoplastic resin that occupies the portion of the cavity that is to form the solid portion. A mold assembly that can surely suppress the intrusion of the pressurized fluid up to, and can form the hollow portion up to a desired site in the molding of the molded product having the hollow portion and the solid portion, and An object of the present invention is to provide an injection molding method using such a mold assembly.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a mold assembly of the present invention comprises:
A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
After injecting molten thermoplastic resin from the gate part into the cavity and filling the cavity with molten thermoplastic resin, the pressurized fluid is introduced from the pressurized fluid introduction part into the molten thermoplastic resin in the cavity. A mold assembly for molding a molded article having a portion and a hollow portion,
The cavity is composed of a first cavity part that should form a solid part of the molded product, and a second cavity part that extends from the first cavity part and should form a hollow part of the molded product,
The pressurized fluid introduction part is disposed in a part of the mold constituting the second cavity part,
The movable core is characterized in that it is arranged at a part of a mold constituting the first cavity part.
[0009]
In order to achieve the above object, the injection molding method of the present invention comprises:
A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
The cavity is composed of a first cavity part that should form a solid part of the molded product, and a second cavity part that extends from the first cavity part and should form a hollow part of the molded product,
The pressurized fluid introduction part is disposed in a part of the mold constituting the second cavity part,
The movable core is an injection molding method of a molded product having a solid part and a hollow part using a mold assembly disposed in a mold part constituting the first cavity part,
(A) The molten thermoplastic resin is injected into the cavity from the gate portion, and the cavity is filled with the molten thermoplastic resin, before the injection of the molten thermoplastic resin, or simultaneously with the start of the injection of the molten thermoplastic resin, or During the injection of the molten thermoplastic resin, the movable core is positioned at the forward end,
(B) After the cavity is filled with the molten thermoplastic resin, the pressurized fluid is introduced from the pressurized fluid introduction portion into the molten thermoplastic resin in the cavity, and before the pressurized fluid is introduced, or the pressurized fluid The movable core is moved toward the backward end simultaneously with the start of the introduction of the pressurized fluid or during the introduction of the pressurized fluid, and the movable core is positioned at the backward end during the introduction of the pressurized fluid. The solid part of the molded product is molded in step 2, and the hollow part of the molded product is formed in the second cavity portion.
[0010]
In the mold assembly or the injection molding method of the present invention (hereinafter collectively referred to simply as the present invention), depending on the shape or the like of the molded product to be molded, You may arrange | position in the part of the metal mold | die which comprises 1 cavity part, and may arrange | position in the part of the metal mold | die which comprises 2nd cavity part. The structure of the gate portion is essentially arbitrary, and examples thereof include a direct structure, a side gate structure, an overlap gate structure, a tunnel gate structure, and a pinpoint gate structure.
[0011]
In the present invention, the pressurized fluid introduction part is composed of a pressurized fluid introduction nozzle, and the tip part of the pressurized fluid introduction nozzle can be located in the second cavity part, but it is limited to such a structure. Instead, the pressurized fluid introduction part may be arranged in the molten thermoplastic resin flow path provided in the mold assembly, may be arranged in the tip part of the injection molding cylinder, or the gate. You may arrange in a part.
[0012]
In the present invention, for example, the first mold part can be a fixed mold part and the second mold part can be a movable mold part. In this case, for example, a gate part can be provided in the first mold part, and a pressurized fluid introduction nozzle can be arranged in the second mold part. Further, depending on the shape of the molded product to be molded, the movable core may be disposed on the first mold part side, the second mold part side, or the first mold. You may arrange | position to the part side and the 2nd metal mold | die part side. The movable core can be moved using, for example, a hydraulic cylinder, a pneumatic cylinder, or an electric motor.
[0013]
The number of movable cores used in the present invention is not particularly limited, and one movable core may be installed in order to form a molded product having one thick portion (for example, a boss or a rib). A movable core may be installed. In addition, for example, when a plurality of thick portions (for example, bosses or ribs) are provided in a molded product, the number of movable cores may be provided by that number. Furthermore, it is possible to form a plurality of thick portions by one movable core. The moving speed of the movable core from the forward end to the backward end may be constant, or may be changed according to the formation state of the hollow portion, for example.
[0014]
The forward / backward movement of the movable core can be controlled based on a control signal sent from an injection molding machine or a pressurized fluid supply device. The control of the reverse end position and the moving speed of the movable core may be determined based on the desired effect such as the prevention of sink due to the pressurized fluid. Further, the position of the backward end position of the movable core can be determined using extremely simple mechanical position control, for example, a reverse stopper sleeve, a reverse stopper pin, a reverse stopper block, or the like.
[0015]
In the injection molding method of the present invention, when the volume of the hollow portion of the molded product is V _h , and the volume increase amount of the first cavity portion accompanying the movement of the movable core from the forward end to the reverse end is V ₁ , Satisfying 0.7 V _h <V ₁ <V _h , preferably 0.7 V _h <V ₁ <0.9 V _h is hollow to a desired part in molding of a molded product having a hollow part and a solid part This is desirable from the viewpoint of reliably forming the portion.
[0016]
In the injection molding method of the present invention, the movable core may be moved again in the forward end direction after the movable core is positioned at the backward end during the introduction of the pressurized fluid. The volume shrinkage of the thermoplastic resin can be compensated.
[0017]
In the present invention, after the cavity is filled with the molten thermoplastic resin, the pressurized fluid is introduced from the pressurized fluid introduction part into the molten thermoplastic resin in the cavity. The inside may be simultaneously filled with the molten thermoplastic resin, or after a certain time has passed after filling. In the present invention, the cavity is 100% filled with a molten thermoplastic resin. The volume of the pressurized fluid introduced compensates the volume shrinkage accompanying the cooling of the thermoplastic resin mainly in the second cavity portion of the cavity and the volume increase in the first cavity portion due to the movement of the movable core. The total volume. In some cases, the volume further includes a volume that compensates for volume shrinkage accompanying the cooling of the thermoplastic resin in the first cavity.
[0018]
Examples of resins suitable for use in the present invention include crystalline thermoplastic resins and amorphous thermoplastic resins. Specifically, polyolefin resins such as polyethylene resins and polypropylene resins; polyamide 6 and polyamide 66 Polyamide resins such as polyamide MXD6; Polyoxymethylene (polyacetal, POM) resin; Polyester resins such as polyethylene terephthalate (PET) resin and polybutylene terephthalate (PBT) resin; Polyphenylene sulfide resin; Polystyrene resin, ABS resin, AES Styrenic resin such as resin and AS resin; Methacrylic resin; Polycarbonate resin; Modified PPE resin; Polysulfone resin; Polyethersulfone resin; Polyarylate resin; Imide resins; polyether ketone resins; polyether ether ketone resin; can be illustrated a liquid crystal polymer; polyester carbonate resin.
[0019]
Furthermore, a thermoplastic resin made of a polymer alloy material can be used. Here, the polymer alloy material is composed of a blend of at least two types of thermoplastic resins, or a block copolymer or graft copolymer in which at least two types of thermoplastic resins are chemically bonded. A polymer alloy material is widely used as a high-functional material that can have the unique performance of each of the individual thermoplastic resins. As a thermoplastic resin constituting a polymer alloy material in which at least two kinds of thermoplastic resins are blended, styrene resins such as polystyrene resin, ABS resin, AES resin, and AS resin; polyolefin resins such as polyethylene resin and polypropylene resin; methacrylic resin Polycarbonate resin; polyamide resin such as polyamide 6, polyamide 66, polyamide MXD6; modified PPE resin; polyester resin such as polybutylene terephthalate resin and polyethylene terephthalate resin; polyoxymethylene resin; polysulfone resin; polyimide resin; Polyarylate resin; Polyether sulfone resin; Polyether ketone resin; Polyether ether ketone resin; Polyester carbonate resin Can. As a polymer alloy material obtained by blending two types of thermoplastic resins, a polymer alloy material of a polycarbonate resin and an ABS resin can be exemplified. Such a combination of resins is expressed as polycarbonate resin / ABS resin. The same applies to the following. Furthermore, as a polymer alloy material blended with at least two kinds of thermoplastic resins, polycarbonate resin / PET resin, polycarbonate resin / PBT resin, polycarbonate resin / polyamide resin, polycarbonate resin / PBT resin / PET resin, modified PPE resin / HIPS Examples thereof include resin, modified PPE resin / polyamide resin, modified PPE resin / PBT resin / PET resin, modified PPE resin / polyamide MXD6 resin, polyoxymethylene resin / polyurethane resin, and PBT resin / PET resin.
[0020]
In addition, stabilizers, ultraviolet absorbers, release agents, dyes and pigments can be added to the various thermoplastic resins described above, and inorganic fillers such as glass beads, mica, kaolin, calcium carbonate, Or an organic filler can also be added.
[0021]
In the present invention, as the pressurized fluid to be introduced, gaseous substances such as nitrogen gas, carbon dioxide gas, air and helium gas can be used at room temperature, and liquids such as water and gases liquefied under high pressure can also be used. It is.
[0022]
In the present invention, the pressurized fluid introduction part is arranged in the mold part constituting the second cavity part, and the movable core is arranged in the mold part constituting the first cavity part. Therefore, after filling the cavity with the molten thermoplastic resin, the pressurized fluid is introduced into the molten thermoplastic resin in the cavity from the pressurized fluid introduction part, and before the pressurized fluid is introduced or When the movable core is moved toward the reverse end simultaneously with the start of introduction or during the introduction of the pressurized fluid, the first cavity portion is filled with the molten thermoplastic resin from the advance end of the movable core. A volume approximately equal to the volume increase amount V ₁ of the first cavity portion accompanying the movement to the reverse end is expanded toward the first cavity portion. As a result, the pressurized fluid reliably reaches the desired portion of the molten thermoplastic resin in the cavity, and the hollow portion is reliably formed to the desired portion in the molding of the molded product having the hollow portion and the solid portion. be able to. And it can prevent reliably that a hollow part extends to the part of the molded article which should form a solid part.
[0023]
【Example】
Hereinafter, the present invention will be described based on examples with reference to the drawings.
[0024]
Example 1
FIG. 1 is a schematic cross-sectional view of a mold assembly according to the first embodiment. Further, a schematic side view and a plan view of the injection-molded product are shown in FIGS. 7A and 7B, respectively, and arrows CC in FIG. 7B and FIG. 7A. (C) and (D) of FIG. 7 show schematic cross-sectional views of the injection-molded product along the arrow DD.
[0025]
The mold assembly includes a first mold part (fixed mold part 10), a second mold part (movable mold part 11), a gate part 13, a pressurized fluid introduction part 14, and a movable core 20. I have. As shown in FIG. 1, the first mold part (fixed mold part 10) and the second mold part (movable mold part 11) are clamped in the first mold part (fixed mold part 11). A cavity 30 is formed by the mold part 10), the second mold part (movable mold part 11) and the movable core 20. Here, the cavity 30 includes a first cavity part 31 in which the solid part 51 of the molded product 50 is to be formed, and a second cavity that extends from the first cavity part 31 and in which the hollow part 52 of the molded product 50 is to be formed. Part 32. The gate part 13 is disposed in a mold part that constitutes the first cavity part 31. Specifically, the gate portion 13 is provided in the fixed mold portion 10 and has a side gate structure. The gate portion 13 communicates with an injection cylinder (not shown) through a molten thermoplastic resin flow path 12 provided in the first mold portion (fixed mold portion 10).
[0026]
The pressurized fluid introduction part 14 is disposed in a mold part constituting the second cavity part 32, and specifically comprises a pressurized fluid introduction nozzle. The tip of the pressurized fluid introduction nozzle is located in the second cavity portion 32. Specifically, the pressurized fluid introduction nozzle is arranged on the first mold part (fixed mold part 10) side, and is moved back and forth by a pressurized fluid introduction nozzle moving device (not shown) composed of a hydraulic cylinder. It is movable. The pressurized fluid introduction unit 14 is connected to a pressurized fluid supply device (not shown) via a pipe (not shown).
[0027]
The movable core 20 is disposed in a mold part constituting the first cavity part 31. Specifically, the movable core 20 is disposed on the movable mold part side. The movable core 20 can be moved back and forth by a movable core moving device 21 composed of a hydraulic cylinder. FIG. 1 shows a state where the movable core 20 is located at the forward end. The forward / backward movement of the movable core 20 is controlled based on a control signal sent from the pressurized fluid supply device.
[0028]
In Example 1, the volume of the molded product 50 is 6.5 cm ³ , the volume V _h of the hollow portion 52 of the molded product 50 is 0.3 cm ³ , and the first cavity portion accompanying the movement of the movable core 20 from the forward end to the reverse end. The volume increase V ₁ of 31 was 0.25 cm ³ and the moving distance was 5 mm. The molded product was molded from a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., trade name: Iupilon S3000 natural color).
[0029]
Hereinafter, referring to FIGS. 1 to 5 which are schematic sectional views of the mold assembly and the like, and FIG. 6 showing the timing of the injection of the molten thermoplastic resin, the introduction of the pressurized fluid, and the movement of the movable core 20. The injection molding method of Example 1 will be described.
[0030]
First, a thermoplastic resin is plasticized and melted in an injection cylinder (not shown). On the other hand, the movable core moving device 21 is operated to position the movable core 20 at the forward end (see FIG. 1). Further, by operating the pressurized fluid introduction nozzle moving device, the distal end portion of the pressurized fluid introduction portion (pressurized fluid introduction nozzle) 14 is positioned in the second cavity portion 32. Then, as schematically shown in FIG. 2, the molten thermoplastic resin 40 is injected into the cavity 30 through the molten thermoplastic resin flow path 12 and the gate portion 13, and the cavity 30 is filled with the molten thermoplastic resin 40. Fully filled. The injection conditions are illustrated in Table 1 below.
[0031]
[Table 1]
Resin temperature: 280 ° C
Mold temperature: 80 ° C
Injection pressure: 1 × 10 ⁸ Pa (1 × 10 ³ kg / cm ² f)
Injection time: 1.5 seconds [0032]
The cavity 30 is completely filled with the molten thermoplastic resin 40, and at the same time, the pressurized fluid (specifically, the pressurized fluid introduction nozzle (pressurized fluid introduction nozzle) 14) enters the molten thermoplastic resin 40 within the cavity 30. , Pressure 7 × 10 ⁶ Pa = 7 × 10 kg / cm ² f of nitrogen gas) was introduced (see FIG. 3). As a result, the hollow portion 52 started to be formed in the molten thermoplastic resin 40 in the cavity 30.
[0033]
After 2.0 seconds from the start of injection of the molten thermoplastic resin, the movable core moving device 21 was operated to move the movable core 20 from the forward end to the reverse end. The moving speed of the movable core 20 was 5 mm / second. During the movement of the movable core 20, the pressurized fluid continued to be introduced. This state is schematically shown in FIG. 4, and the tip of the hollow portion 52 formed in the molten thermoplastic resin 40 in the cavity 30 extends toward the first cavity portion 31.
[0034]
Then, the movable core 20 was positioned at the backward movement end while the pressurized fluid was continuously introduced (see FIG. 5). In this way, the solid part 51 of the molded product 50 was molded in the first cavity part 31, and the hollow part 52 of the molded product 50 was formed in the second cavity part 32.
[0035]
Thereafter, the thermoplastic resin in the cavity 30 is cooled and solidified, and the pressurized fluid introduction part (pressurized fluid introduction nozzle) 14 is retracted for 30 seconds from the start of injection of the molten thermoplastic resin, and the inside of the hollow part 52 is added. The pressurized fluid was released into the atmosphere. Then, the mold was opened for 45 seconds from the start of injection of the molten thermoplastic resin, and the molded product was taken out from the mold assembly.
[0036]
In the obtained molded product 50, the hollow portion 52 was formed up to a desired site, and no sink marks were observed in the solid portion 51.
[0037]
(Comparative Example 1)
With the movable core 20 positioned at the reverse end (see FIG. 5 for the position of the movable core 20), the same injection molding as described in Example 1 was performed. FIG. 13 shows a schematic cross-sectional view along the longitudinal direction of the molded product obtained as a result. The molded product does not have the hollow portion 52 formed up to a desired portion, and the solid portion. 51 was sinking.
[0038]
(Example 2)
The mold assembly of the second embodiment is a modification of the mold assembly of the first embodiment. As shown in a schematic cross-sectional view in FIG. 8, in the second embodiment, the gate portion 13 </ b> A is disposed in a mold portion that constitutes the second cavity portion 32. Specifically, the gate portion 13A is provided in the fixed mold portion 10 and has a direct structure. The gate portion 13A communicates with an injection cylinder (not shown) through a molten thermoplastic resin flow path 12A provided in the first mold portion (fixed mold portion 10). Except for this point, the mold assembly of the second embodiment has the same structure and configuration as the mold assembly of the first embodiment, and a detailed description thereof will be omitted.
[0039]
Specifications such as the volume of the molded product 50 and the volume V _h of the hollow portion 52 in Example 2 were the same as those of the molded product of Example 1. The same thermoplastic resin as in Example 1 was used. Furthermore, the volume increase amount V ₁ and the movement distance of the first cavity portion 31 accompanying the movement of the movable core 20 from the forward end to the reverse end are also the same as those in the first embodiment.
[0040]
Hereinafter, the injection molding method of Example 2 will be described with reference to FIGS. 8 to 12 and FIG. 6 which are schematic sectional views of a mold assembly and the like.
[0041]
First, a thermoplastic resin is plasticized and melted in an injection cylinder (not shown). On the other hand, the movable core moving device 21 is operated to position the movable core 20 at the forward end (see FIG. 8). Further, by operating the pressurized fluid introduction nozzle moving device, the distal end portion of the pressurized fluid introduction portion (pressurized fluid introduction nozzle) 14 is positioned in the second cavity portion 32. Then, as schematically shown in FIG. 9, the molten thermoplastic resin 40 was injected into the cavity 30 from the gate portion 13, and the cavity 30 was completely filled with the molten thermoplastic resin 40. The injection conditions were the same as those exemplified in Table 1.
[0042]
The cavity 30 is completely filled with the molten thermoplastic resin 40, and at the same time, the pressurized fluid introduction part (pressurized fluid introduction nozzle) 14 is added to the molten thermoplastic resin 40 in the cavity 30 in the same manner as in the first embodiment. A pressurized fluid was introduced (see FIG. 10). As a result, the hollow portion 52 started to be formed in the molten thermoplastic resin 40 in the cavity 30.
[0043]
After 2.0 seconds from the start of injection of the molten thermoplastic resin, the movable core moving device 21 was operated to move the movable core 20 from the forward end to the reverse end. The moving speed of the movable core 20 was 5 mm / second. During the movement of the movable core 20, the pressurized fluid continued to be introduced. This state is schematically shown in FIG. 11, and the distal end of the hollow portion 52 formed in the molten thermoplastic resin 40 in the cavity 30 extends toward the first cavity portion 31.
[0044]
Then, the movable core 20 was positioned at the backward movement end while the pressurized fluid was continuously introduced (see FIG. 12). In this way, the solid part 51 of the molded product 50 was molded in the first cavity part 31, and the hollow part 52 of the molded product 50 was formed in the second cavity part 32.
[0045]
Thereafter, in the same manner as in Example 1, the thermoplastic resin in the cavity 30 is cooled and solidified, the pressurized fluid in the hollow portion 52 is released to the atmosphere, the mold is opened, and the molded product is molded from the mold assembly. Was taken out.
[0046]
In the obtained molded product 50, the hollow portion 52 was formed up to a desired site, and no sink marks were observed in the solid portion 51.
[0047]
(Comparative Example 2)
With the movable core 20 positioned at the reverse end (see FIG. 12 for the position of the movable core 20), injection molding similar to that described in Example 2 was performed. As a result, as shown in FIG. 13, the hollow part 52 was not formed up to the desired site in the molded product, and sink marks were generated in the solid part 51.
[0048]
As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these. The structure and configuration of the mold assembly described in the examples, the thermoplastic resin used, and the injection molding conditions are examples, and can be appropriately changed. For example, in the mold assembly described in the second embodiment, the pressurized fluid introducing portion may be disposed in the molten thermoplastic resin flow path 12A provided in the mold assembly, or the injection molding cylinder. It may be arranged in the front end portion or in the gate portion 13A.
[0049]
In Example 1 and Example 2, the movable core is positioned at the forward end before the injection of the molten thermoplastic resin into the cavity is started, and the pressurized fluid is introduced simultaneously with the completion of the injection of the molten thermoplastic resin into the cavity. After starting the introduction of the pressurized fluid, the movable core was started to move to the reverse end, but the injection molding method of the present invention is not limited to such a form. Table 2 below summarizes the timing at which the movable core is positioned at the forward end, the timing for starting the introduction of the pressurized fluid, and the timing for starting the movement of the movable core to the backward end. Example 1 and Example 2 correspond to Case 2 in Table 2. In the case 3, the case 8, and the case 13, the movement start of the movable core to the backward end must be performed simultaneously with or after the completion of the injection of the molten thermoplastic resin into the cavity. It is necessary to start the introduction of the pressurized fluid during the movement of the core. Further, in the case 11 to case 15, the time when the movable core is positioned at the forward end needs to be before the molten thermoplastic resin injected into the cavity reaches the first cavity portion. Further, in any of the cases 1 to 15, after the movable core is positioned at the backward movement end, the movable core is advanced in order to compensate for the volume shrinkage accompanying the cooling of the thermoplastic resin in the first cavity portion. It may be moved again in the end direction.
[0050]
[Table 2]

[0051]
【The invention's effect】
In the present invention, in a state where the first cavity portion is filled with the molten thermoplastic resin, the volume of the hollow portion is substantially equal to the volume increase amount of the first cavity portion accompanying the movement of the movable core from the forward end to the reverse end. Since it expands toward the first cavity portion, the pressurized fluid is surely reached to the desired portion of the molten thermoplastic resin in the cavity, and the desired portion in the molding of the molded product having the hollow portion and the solid portion. It is possible to reliably form the hollow portion. And it can prevent reliably that a hollow part extends to the part of the molded article which should form a solid part.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a mold assembly of Example 1. FIG.
FIG. 2 is a schematic cross-sectional view of a mold assembly and the like for explaining an injection molding method according to the first embodiment.
FIG. 3 is a schematic cross-sectional view of a mold assembly and the like for explaining the injection molding method of Example 1 following FIG. 2;
4 is a schematic cross-sectional view of a mold assembly and the like for explaining the injection molding method of Example 1 following FIG. 3. FIG.
5 is a schematic cross-sectional view of a mold assembly and the like for explaining the injection molding method of Example 1 following FIG. 4. FIG.
FIG. 6 is a diagram showing the timing of injection of molten thermoplastic resin, introduction of pressurized fluid, and movement of the movable core.
7 (A) and 7 (B) are a schematic side view and a schematic plan view of an injection molded product, respectively. FIG. 7 (C) and FIG. It is typical sectional drawing of the injection molded product along arrow CC of FIG. 7, (B), and arrow DD of (A) of FIG.
FIG. 8 is a schematic cross-sectional view of a mold assembly according to a second embodiment.
FIG. 9 is a schematic cross-sectional view of a mold assembly and the like for explaining an injection molding method according to a second embodiment.
FIG. 10 is a schematic cross-sectional view of a mold assembly and the like for explaining the injection molding method of Example 2 following FIG. 9;
FIG. 11 is a schematic cross-sectional view of a mold assembly and the like for explaining the injection molding method of Example 2 following FIG.
FIG. 12 is a schematic cross-sectional view of a mold assembly and the like for explaining the injection molding method of Example 2 following FIG.
FIG. 13 is a schematic cross-sectional view along the longitudinal direction of the molded articles obtained in Comparative Examples 1 and 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... 1st mold part (fixed mold part), 11 ... 2nd mold part (movable mold part), 12 ... Molten thermoplastic resin flow path, 13 ... Gate part, 14 ... pressurized fluid introduction part, 20 ... movable core, 21 ... movable core moving device, 30 ... cavity, 31 ... first cavity part, 32 ... second cavity part, 40 ... Melt thermoplastic resin, 50 ... Molded product, 51 ... Solid part, 52 ... Hollow part

Claims (15)

A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
After injecting a molten thermoplastic resin from the gate portion into the cavity and completely filling the cavity with the molten thermoplastic resin, a pressurized fluid is introduced from the pressurized fluid introduction portion into the molten thermoplastic resin in the cavity, A mold assembly for molding a molded product having a solid part and a hollow part,
Cavity, a first cavity portion for forming the thin portion of the molded article consisting of a solid portion extending from the first cavity portion, the second cavity portion for forming the thick part of the molded article having a hollow portion And consists of
The pressurized fluid introduction part is disposed in a part of the mold constituting the second cavity part,
The movable core is disposed in a portion of a mold that constitutes the first cavity portion. 2. The mold assembly according to claim 1, wherein the gate portion is disposed in a portion of the mold constituting the first cavity portion. 2. The mold assembly according to claim 1, wherein the gate part is disposed in a part of a mold constituting the second cavity part. The pressurized fluid introduction part consists of a pressurized fluid introduction nozzle,
The mold assembly according to claim 1, wherein a distal end portion of the pressurized fluid introduction nozzle is located in the second cavity portion. A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
After injecting a molten thermoplastic resin from the gate portion into the cavity and completely filling the cavity with the molten thermoplastic resin, a pressurized fluid is introduced from the pressurized fluid introduction portion into the molten thermoplastic resin in the cavity, A mold assembly for molding a molded product having a solid part and a hollow part,
The cavity is composed of a first cavity part that should form a solid part of the molded product, and a second cavity part that extends from the first cavity part and should form a hollow part of the molded product,
The gate part is disposed in a part of the mold constituting the first cavity part,
The movable core is a part of a mold that constitutes the first cavity part, and is disposed closer to the second cavity part than the gate part,
The pressurized fluid introduction part consists of a pressurized fluid introduction nozzle,
A die assembly characterized in that a tip portion of the pressurized fluid introduction part is a part of a mold constituting the second cavity part and is located in the vicinity of a part farthest from the first cavity part. A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
After injecting a molten thermoplastic resin from the gate portion into the cavity and completely filling the cavity with the molten thermoplastic resin, a pressurized fluid is introduced from the pressurized fluid introduction portion into the molten thermoplastic resin in the cavity, A mold assembly for molding a molded product having a solid part and a hollow part,
The cavity is composed of a first cavity part that should form a solid part of the molded product, and a second cavity part that extends from the first cavity part and should form a hollow part of the molded product,
The gate portion is disposed in a mold portion corresponding to the substantially central portion of the second cavity portion,
The movable core is disposed in a portion of the mold that constitutes the first cavity portion,
The pressurized fluid introduction part consists of a pressurized fluid introduction nozzle,
A die assembly characterized in that a tip portion of the pressurized fluid introduction part is a part of a mold constituting the second cavity part and is located in the vicinity of a part farthest from the first cavity part. A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
Cavity, a first cavity portion for forming the thin portion of the molded article consisting of a solid portion extending from the first cavity portion, the second cavity portion for forming the thick part of the molded article having a hollow portion And consists of
The pressurized fluid introduction part is disposed in a part of the mold constituting the second cavity part,
The movable core is an injection molding method of a molded product having a solid part and a hollow part using a mold assembly disposed in a mold part constituting the first cavity part,
(A) The molten thermoplastic resin is injected into the cavity from the gate portion, and the cavity is filled with the molten thermoplastic resin, before the injection of the molten thermoplastic resin, or simultaneously with the start of the injection of the molten thermoplastic resin, or During the injection of the molten thermoplastic resin, the movable core is positioned at the forward end,
(B) After the cavity is completely filled with the molten thermoplastic resin, a pressurized fluid is introduced into the molten thermoplastic resin in the cavity from the pressurized fluid introduction part, and before the pressurized fluid is introduced or added. Simultaneously with the start of the introduction of the pressurized fluid or during the introduction of the pressurized fluid, the movable core is moved toward the reverse end, and the movable core is positioned at the reverse end during the introduction of the pressurized fluid, whereby the first An injection molding method characterized in that a thin part of a molded product comprising a solid part is formed in a cavity part, and a hollow part is formed in a thick part of the molded product in a second cavity part. A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
The cavity includes a first cavity portion that should form a thin portion of a molded product that is a solid portion, and a second cavity portion that extends from the first cavity portion and should form a thick portion of the molded product having a hollow portion. And consists of
The pressurized fluid introduction part is disposed in a part of the mold constituting the second cavity part,
The movable core is an injection molding method of a molded product having a solid part and a hollow part using a mold assembly disposed in a mold part constituting the first cavity part,
(A) The molten thermoplastic resin is injected into the cavity from the gate portion, and the cavity is filled with the molten thermoplastic resin, before the injection of the molten thermoplastic resin, or simultaneously with the start of the injection of the molten thermoplastic resin, or During the injection of the molten thermoplastic resin, the movable core is positioned at the forward end,
(B) The inside of the cavity is completely filled with the molten thermoplastic resin, the thin part of the molded product is formed in the first cavity part, and the thick part of the molded product is formed in the second cavity part. A pressurized fluid is introduced into the molten thermoplastic resin from the pressurized fluid introducing portion, and a hollow portion is formed in the thick portion of the molded product to compensate for volume shrinkage accompanying the cooling of the thermoplastic resin in the second cavity portion. Before introducing the pressurized fluid, simultaneously with the start of the introduction of the pressurized fluid, or during the introduction of the pressurized fluid, the movable core is moved toward the reverse end, and the movable core is moved backward during the introduction of the pressurized fluid. By locating it at the end, the thin part of the molded part consisting of the solid part is enlarged in the first cavity part, and accordingly, the hollow part is enlarged in the thick part of the molded part in the second cavity part. On the surface of the molded product Injection molding process, characterized in that to prevent the occurrence of Ruhike and warpage. The injection molding method according to claim 7 or 8 , wherein the gate part is disposed in a part of a mold constituting the first cavity part. The injection molding method according to claim 7 or 8 , wherein the gate portion is arranged at a portion of a mold constituting the second cavity portion. The pressurized fluid introduction part consists of a pressurized fluid introduction nozzle,
The injection molding method according to claim 7 , wherein a tip end portion of the pressurized fluid introduction nozzle is located in the second cavity portion. When the volume of the hollow part of the molded product is V _h and the volume increase amount of the first cavity part accompanying the movement of the movable core from the forward end to the reverse end is V ₁ ,
0.7V _h <V ₁ <V _h
The injection molding method according to claim 7 or 8 , wherein: The injection molding method according to claim 7 or 8, wherein the movable core is moved again in the forward end direction after the movable core is positioned at the backward end during the introduction of the pressurized fluid. A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
The cavity is composed of a first cavity part that should form a solid part of the molded product, and a second cavity part that extends from the first cavity part and should form a hollow part of the molded product,
The gate part is disposed in a part of the mold constituting the first cavity part,
The movable core is a part of a mold that constitutes the first cavity part, and is disposed closer to the second cavity part than the gate part,
The pressurized fluid introduction part consists of a pressurized fluid introduction nozzle,
The tip of the pressurized fluid introduction part is a solid part using a mold assembly which is a part of a mold constituting the second cavity part and is located in the vicinity of the part farthest from the first cavity part And an injection molding method of a molded product having a hollow part,
(A) The molten thermoplastic resin is injected into the cavity from the gate portion, and the cavity is filled with the molten thermoplastic resin, before the injection of the molten thermoplastic resin, or simultaneously with the start of the injection of the molten thermoplastic resin, or During the injection of the molten thermoplastic resin, the movable core is positioned at the forward end,
(B) After the cavity is completely filled with the molten thermoplastic resin, a pressurized fluid is introduced into the molten thermoplastic resin in the cavity from the pressurized fluid introduction part, and before the pressurized fluid is introduced or added. Simultaneously with the start of the introduction of the pressurized fluid or during the introduction of the pressurized fluid, the movable core is moved toward the reverse end, and the movable core is positioned at the reverse end during the introduction of the pressurized fluid, whereby the first An injection molding method characterized by forming a solid part of a molded product in a cavity part and forming a hollow part of the molded product in a second cavity part. A first mold part, a second mold part, a gate part, a pressurized fluid introduction part, and a movable core are provided, and the first mold part and the second mold part are clamped in the first mold. A cavity is formed by the mold part, the second mold part and the movable core,
The cavity is composed of a first cavity part that should form a solid part of the molded product, and a second cavity part that extends from the first cavity part and should form a hollow part of the molded product,
The gate portion is disposed in a mold portion corresponding to the substantially central portion of the second cavity portion,
The movable core is disposed in a portion of the mold that constitutes the first cavity portion,
The pressurized fluid introduction part consists of a pressurized fluid introduction nozzle,
The tip of the pressurized fluid introduction part is a solid part using a mold assembly which is a part of a mold constituting the second cavity part and is located in the vicinity of the part farthest from the first cavity part And an injection molding method of a molded product having a hollow part,
(A) The molten thermoplastic resin is injected into the cavity from the gate portion, and the cavity is filled with the molten thermoplastic resin, before the injection of the molten thermoplastic resin, or simultaneously with the start of the injection of the molten thermoplastic resin, or During the injection of the molten thermoplastic resin, the movable core is positioned at the forward end,
(B) After the cavity is completely filled with the molten thermoplastic resin, a pressurized fluid is introduced into the molten thermoplastic resin in the cavity from the pressurized fluid introduction part, and before the pressurized fluid is introduced or added. Simultaneously with the start of the introduction of the pressurized fluid or during the introduction of the pressurized fluid, the movable core is moved toward the reverse end, and the movable core is positioned at the reverse end during the introduction of the pressurized fluid, whereby the first An injection molding method characterized by forming a solid part of a molded product in a cavity part and forming a hollow part of the molded product in a second cavity part.

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