JP4185275B2 - Injection molding equipment - Google Patents

Description

【００５５】
【数２】

【００５６】
ここで、
Ｐは射出圧力
Ｓｎは底板の上から見た投影面積
Ｓｍは上型の下から見た投影面積
Ｓａはシール面積
Ｓｒは支持部材（支持部材本体）の断面積
Ｓｐは第２の下型の断面積
Ｆｎは射出圧力によって発生する底板の下向きの力（＝Ｐ・Ｓｎ）
Ｆｍは射出圧力によって金型を押し上げようとする力（＝Ｐ・Ｓｍ）
Ｆｒは支持部材に加わる力
Ｆｐは第２の下型に加わる力
Ｌｐは第２の下型のフランジ間の長さ
Ｌｒは支持部材の長さ
Δｌは支持部材の縮み量
Ｅは支持部材のヤング率（第２の下型のヤング率と同じと仮定）
ｎは支持部材の本数である。
第２の下型５６のフランジ部５６ｂ，５６ｃと連結ボルト７１は変形しないものと仮定する。
【００５７】
力の釣り合いを考えると
（Ｆｎ−Ｆｍ）＝ｎＦｒ＋Ｆｐ ・・・（２）
上記（Ａ）式を（２）式に代入数ると
【００５８】
【数３】

【００５９】
上記（Ｂ）式を用いてシール比Ｋを求める。シール圧Ｐａは次式によって表される。
【００６０】
【数４】

上記（４）式の両辺をＰで除してシール比Ｋを求める。
【数５】

【００６１】
【数６】

【００６２】
上記（６）式の前項は、通常のシール比、後項は支持部材による減少分で、シール比の低減率は次式で表される。
【００６３】
【数７】

【００６４】
このような射出成形装置２０によれば、金型３０を型締めする必要がないので、従来の型締め機構を備えた射出成形装置に比べて構造が簡単で部品点数を削減でき、また射出成形サイクルを短縮することができ、生産性を向上させることができる。
【００６５】
また、金型３０内にそれぞれ独立した第１〜第６の冷却回路６７Ａ〜６７Ｆからなる冷却機構６６を設け、これらの冷却回路６７Ａ〜６７Ｆに圧縮空気を所要の時間差をもって順次供給することにより、成形材料９の冷却硬化の時期を制御するようにしているので、ひけや脈理が発生ことがなく、品質の高い成形品を成形することができる。
また、成形品の大きさ、肉厚等に応じて第１〜第６の冷却回路６７Ａ〜６７Ｆに供給する圧縮空気のタイミング、供給時間等を制御するだけでよいので、制御も容易である。
【００６６】
なお、上記した実施の形態は、電磁流量計用測定管の内周面とフランジの配管接続端面にライニングを施す射出成形装置２０に適用した例を示したが、本発明はこれに何等特定されるものではなく、例えば容器やカップ状のもの、特に半導体製造工場のクリーンルームで使用されるものは、略１００％弗素樹脂製なので、本発明による射出成形装置を用いることにより、安価に製作することができる。
また、本実施の形態においては、冷却機構６６を６つの冷却回路６７Ａ〜６７Ｆによって構成したが、その数は任意であり、成形品の大きさによって適宜増減することができる。
さらに、上記実施の形態においては、射出成型用金型３０を型締め機構によって型締めしない射出成形装置２０について示したが、本発明はこれに限定されるものではなく従来の型締め機構を備えた射出成形装置にも適用することができることは勿論である。
さらにまた、上記した実施の形態においては、成形品が測定管のため、金型３０の下型４５を、第１、第２の下型５５，５６および中子５７とで構成し、第２の下型５６をライニングが施される前の測定管で構成した例を示したが、成形品によっては金型が１つの下型と上型と中子とで構成されるものであってもよい。
【００６７】
【発明の効果】
以上説明したように本発明に係る射出成形装置は、キャビティ内に注入された成形材料の冷却硬化の時期を任意に制御することができるため、ひけや脈理が発生せず高品質な成形品を成形することができる。
【００６８】
また、プッシャの成形材料を押圧する力を利用して下型と上型のシール面に面圧を発生させ、弗素樹脂からなる成形材料が外部へ漏れ出るのを防止するようにしたので、ボルトによる締結や油圧による型締め機構によって金型を型締めする必要がなく、射出成形装置の簡素化および金型製作費の低減を達成するとともに、金型の組立、分解作業が容易で生産性を向上させることができる。また、成形材料の漏出がないため、不良率を低減することができる。
また、Ｐａ／Ｐ＞０．３２の条件を満たす範囲内において金型設計を行うことができるので、設計の自由度を向上させることができる。
【図面の簡単な説明】
【図１】 本発明に係る射出成形装置の一実施の形態の一部を破断して示す概略構成図である。
【図２】 射出成形用金型の断面図である。
【図３】 底板の上から見た投影面積を示す図である。
【図４】 上型の下から見た投影面積を示す図である。
【図５】 シール面付近の拡大断面図である。
【図６】 第１の下型部材の平面図である。
【図７】 中子の底面図である。
【図８】 （ａ）〜（ｄ）は図７のＡ−Ａ線、Ｂ−Ｂ線、Ｃ−Ｃ線、Ｄ−Ｄ線断面図である。
【図９】 冷却のシーケンスを示す図である。
【符号の説明】
８…キャビティ、９…成形材料、２０…射出成形装置、２２…油圧シリンダ、３０…射出成形用金型、３１…トランスファポット、３２…プッシャ、４０…ノズル孔、４１ａ…シール面、４４…上型、４５…下型、４９…湯道、５０…スプルー、５１…ゲート、５３ａ…シール面、５５…第１の下型、５６…第２の下型、５６ｂ，５６ｃ…フランジ、５７…中子、６１ａ，６３ａ，６３ｂ，６５ａ…シール面、６６…冷却機構、６７Ａ〜６７Ｆ…冷却回路、７０…支持部材、Ａ，Ｂ，Ｃ…シール部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding apparatus, for example, an injection molding apparatus suitable for use in molding a lining in a measurement pipe of an electromagnetic flow meter, molding a resin pipe, or the like.
[0002]
[Prior art]
An electromagnetic flowmeter that measures the flow rate of a conductive fluid that flows in a measurement tube by using an electromagnetic induction phenomenon prevents a short circuit between an electromotive force generated in the fluid and a measurement tube made of a non-magnetic material such as stainless steel. In addition, the inner peripheral surface, which is usually the wetted surface of the measurement tube, and the surface to which the flange pipes integrally provided at both ends of the measurement tube are connected (hereinafter referred to as the pipe connection end surface) are covered with a lining material. . As the lining material, heat resistance, corrosion resistance, electrical insulation, etc. are required, so insulating materials such as fluorine resin are usually used, and it is formed by injection molding on the inner peripheral surface of the measurement tube and the pipe connection end surface of the flange Is formed by.
[0003]
When molding such a lining measuring tube with a transfer molding machine, load the measuring tube without lining into the mold and heat the mold to a temperature equal to or higher than the melting temperature of the lining material. The prepared lining material is injected under pressure into the mold, and the inner peripheral surface of the measurement tube and the pipe connection end surface of the flange are covered with the lining material.
[0004]
When lining the measuring tube, the fluororesin used as the lining material has poor adhesion to the metal and is easily peeled off from the measuring tube. Therefore, a reinforcing tube usually formed by a perforated plate called a punching plate is placed inside the measuring tube. By attaching this reinforcing tube in advance and covering it with a lining material, the mechanical coupling strength between the lining material and the measuring tube is increased to prevent the lining material from peeling, and the lining caused by temperature changes or pressure changes in the measuring tube. The deformation of the material is prevented (Japanese Patent Publication No. 5-48846, Japanese Patent Publication No. 5-48845, Japanese Utility Model Publication No. 2-28411).
[0005]
In order to form a measuring tube with such a lining using a transfer molding machine, the measuring tube with a reinforcing tube is loaded into the mold, and the mold is heated to a temperature higher than the melting temperature of the lining material. The lining material thus prepared is pressurized and injected into the mold to cover the inner peripheral surface of the measuring pipe and the pipe connection end face of the flange. After the molding material is filled in the cavity, a cooling medium such as compressed air is supplied to the mold to cure the molding material. After the whole is sufficiently cooled and solidified, the molded product is taken out from the mold.
[0006]
As a cooling method for molding materials, for example, a technical report published by DuPont
`` Preliminary Infomation from Plastic Technical Services Laboratryabout DU PONT TEFLON FLUOROCARBON RESIN, DU PONT TEFZEL FLUOROPOLYMERFLUOROCARBONS DIVISION, PLASTICS DEPARTMENT, ETDU PONT DE NEMOURS & CO. (INC.), WILM., DEL.19898 PBI # 36gust What is used for the transfer molding apparatus described in 1) is known. In this transfer molding apparatus, a pipe is passed through the core, and a large number of holes are formed in the peripheral surface of the pipe so as to become rougher as it is farther from the gate side, and a cooling medium is supplied into the core through the holes. By doing so, the core is forcibly cooled from the inside.
[0007]
[Problems to be solved by the invention]
The cooling method in the conventional transfer molding apparatus described above determines the cooling effect (cooling speed) depending on the number and density of holes formed in the pipe. There was a problem that the order and the like could not be freely changed, and the time required for molding became long. Moreover, since it is necessary to prepare pipes having different numbers of holes, density, etc. for each molded product, the types of pipes are increased, and there is a problem that storage, management, replacement work, and the like are troublesome.
[0008]
The present invention has been made to solve the above-described conventional problems. By adopting a multi-stage cooling method and cooling sequentially from a portion far from the gate of the mold toward the gate, the molding material in the cavity is effectively removed. It is an object of the present invention to provide an injection molding apparatus that can cool down and prevent the occurrence of sink marks and striae.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, a first invention includes a container having a nozzle hole at the bottom and containing a molten molding material, and a mold filled with the molding material injected from the nozzle hole of the container. An injection molding apparatus comprising: a pusher that pressurizes the molding material in the container; and a thrust imparting unit that imparts thrust in a direction in which the pusher substantially pressurizes the molding material in the container to the pusher or the mold. An apparatus, wherein the mold is composed of an upper mold arranged in a stack and a lower mold with a core;The core has a cylindrical core body and a cylindrical body fitted to the body, and a plurality of groove-shaped cores formed on the outer peripheral surface of the core body and spaced apart in the axial direction.Independent cooling circuits are provided, and the cooling hardening timing of the molding material injected into the cavity is stepped by supplying cooling media sequentially so that the closer to the gate to these cooling circuits, the slower the timing of cooling start. It is intended to be controlled.
  In this invention, since the cooling timing of each cooling circuit can be individually controlled so that the molten molding material continues to be supplied with respect to the shrinkage of the molding material due to cooling and hardening, the quality is good without causing sink marks or striae. Can be molded.
[0010]
  According to a second invention, in the first invention described above,PusherThen, the molding material in the container is pressed to bring the sealing surfaces of the lower mold and the upper mold into close contact with each other over the entire circumference.
  In this invention, since the mold is substantially clamped by bringing the sealing surfaces into close contact with each other by the thrust substantially applied to the pusher in order to pressurize the molding material, it is not necessary to provide a conventional mold clamping means. .
[0011]
  According to a third invention, in the first or second invention,The molding material is fluorine resin,The injection pressure of the molding material when pressurized by the pusher is P, and the sealing pressure applied to each sealing surface is Pa.Then,
The following conditions
  Pa / P>0.32
Is to hold.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a schematic configuration diagram showing a part of an embodiment of an injection molding apparatus according to the present invention in a cutaway state, FIG. 2 is a sectional view of an injection molding die, and FIG. 3 is a projected area viewed from above a bottom plate. FIG. 4 is a diagram showing a projected area viewed from below the upper mold, FIG. 5 is an enlarged cross-sectional view near the seal surface, FIG. 6 is a plan view of the first lower mold member, and FIG. 8A to 8D are sectional views taken along lines AA, BB, CC, and DD in FIG. This embodiment shows an example applied to a pot type vertical injection molding apparatus 20 used for molding for lining a flange type measuring pipe for an electromagnetic flow meter. In FIG. 3, the hatched portion indicates the projected area, and the second circle from the inside indicates the outline of the conical recess formed on the top surface of the bottom plate. In FIG. 4, the hatched portion indicates the projected area, the second circle from the outside indicates the outline of the annular recess formed on the bottom surface of the upper mold, and the third circle from the outside indicates the outline of the conical recess. Yes.
[0013]
In FIG. 1, a frame 25 having sufficient mechanical strength is provided by a base plate 21 with legs installed on the floor, a cylinder mounting plate 23 to which a hydraulic cylinder 22 is fixed, and four struts 24 connecting them. Is configured. The frame 25 works as a thrust applying means for giving a thrust to a pusher 32 described later in cooperation with the hydraulic cylinder 22. Further, a mold mounting plate 26 installed on the base plate 21, an injection molding mold 30 installed on the mold mounting plate 26 via a heat insulating material 27 such as ceramic, and the mold 30 A bottomed cylindrical transfer pot 31 (container) placed on the pressure pot, the pusher 32 for pressurizing the heated and melted molding material 9 in the transfer pot 31, and the hydraulic cylinder 22 (thrust applying means) for lowering the pusher 32 ) And the like constitute a pot type vertical injection molding apparatus 20.
[0014]
The hydraulic cylinder 22 is installed downward on the cylinder mounting plate 23 installed above the support column 24, and has a plunger 33 that can be raised and lowered. When the plunger 33 is lowered by hydraulic pressure, the lower end surface of the plunger 33 comes into contact with the upper surface of the pusher 32 and is separated from the upper surface of the pusher 32 when the plunger 33 returns to its upper position.
[0015]
The pusher 32 is formed in a disc shape and is inserted into the transfer pot 31. An appropriate gap is provided between the inner peripheral surface of the transfer pot 31 and the pusher 32, and the work of fitting the pusher 32 into the transfer pot 31 is facilitated by letting air escape through the gap.
[0016]
The transfer pot 31 includes a cylindrical body 31A and a disk-shaped bottom plate 31B that covers the lower opening of the cylindrical body 31A. An annular groove 35 into which the bottom plate 31B is fitted is formed on the inner peripheral surface of the lower end portion of the cylindrical body 31A. It is made slidable in a state where there is almost no gap between the inner peripheral surface of the annular groove 35 and the outer peripheral surface of the bottom plate 31B (that is, a state in which the molten molding material 9 does not leak). A plurality of pins (stopping members) 37 project from the inner periphery of the lower end of the cylindrical body 31A so that the cylindrical body 31A and the bottom plate 31B are not separated, thereby supporting the bottom plate 31B and falling off from the cylindrical body 31A. Is preventing. The bottom plate 31B is restricted in the amount of displacement in the vertical direction by the step portion 38 formed on the inner peripheral surface of the cylindrical body 31A by the annular groove 35 and the pin 37. Further, the bottom plate 31B has a nozzle hole 40 made of a through hole in the center, and a conical protrusion 41 surrounding the nozzle hole 40 is integrally projected at the center of the lower surface. A lower end portion of the peripheral surface of the protrusion 41 forms a seal surface 41 a with the injection mold 30.
[0017]
The injection molding die 30 is constituted by an upper die 44 and a lower die 45 constituting a stacking member. The upper mold 44 has a conical recess 47 formed in the center of the lower surface and a sixth cooling circuit 67F of a cooling mechanism 66 described later formed in the wall thickness. The upper die 44 further comprises two members, the first and second upper die members 44A and 44B, in order to form the cooling circuit 67F. After the cooling circuit 67F is formed, the first and second members are formed. The upper mold members 44A and 44B are integrated by fastening with bolts.
[0018]
The concave portion 47 of the upper die 44 forms a runner 49 together with a core 57 to be described later. In particular, a portion that opens on the upper surface of the upper die 44 and communicates with the nozzle hole 40 forms a sprue 50, and the cavity 8. A lower end portion communicating with the gate 51 forms a gate 51. A conical recess 53 is formed around the sprue 50 in the center of the upper surface of the upper mold 44, and the protrusion 41 of the bottom plate 31 </ b> B is fitted in the recess 53. The inner wall surface of the recess 53 forms a seal surface 53a in close contact with the seal surface 41a of the protrusion 41, and a seal portion C is formed by these seal surfaces 41a and 53a.
[0019]
When the transfer pot 31 is placed on the upper die 44, when the protrusion 41 of the bottom plate 31B is fitted into the recess 53 of the upper die 44 and the sealing surfaces 41a and 53a are brought into close contact with each other, the nozzle hole 40 and the sprue 50 is automatically positioned and communicated to form the seal portion C. The area of the seal part C is set to be sufficiently smaller than the areas of the other two seal parts A and B described later. In the state where the transfer pot 31 is placed on the upper die 44, the lower end of the cylindrical body 31A is in contact with the upper surface of the upper die 44, so that the transfer pot 31 is satisfactorily seated. Since the transfer pot 31 is simply placed on the upper die 44 and is not fixed at all, if the pusher 32 is not receiving thrust from the hydraulic cylinder 22, it is placed on the upper die 44. It is also possible to rotate in the horizontal plane with the projection 41 and the recess 53 as the rotation axis (necessary for the sprue cutting operation described later).
[0020]
The lower mold 45 includes first and second lower molds 55 and 56 (both are stacked members) and the core 57. The first lower mold 55 includes first and second lower mold members 55A and 55B arranged in a stacked manner, and is positioned on the mold attachment plate 26 via the heat insulating material 27. It is fixed. On the first lower mold 55, the second lower mold 56 and the core 57 are similarly positioned and installed, and the upper mold 44 is also positioned and installed on these. . The joint portion of the upper die 44 and the second lower die 56 that are in close contact with each other forms the seal portion A, and the joint portion of the first and second lower dies 55 and 56 that are in close contact with each other forms the seal portion B. ing. The areas of the seal part A and the seal part B are substantially equal.
[0021]
The first lower mold member 55A has a hole 60 through which the core 57 passes in the center, and an annular recess 61 surrounding the periphery of the hole 60 is formed on the upper surface. The outer peripheral portion of the bottom surface of the recess 61 forms a seal surface 61a with which the lower surface of the second lower mold 56 is in close contact.
[0022]
As the second lower mold 56, a measuring tube for an electromagnetic flow meter that has not been subjected to a lining process is used. The second lower die 56 has a cylindrical tube body 56a whose inner diameter is larger than the outer diameter of the core 57, and the same shape that is integrally provided at both ends of the tube body 56a or fixed by welding. And two flanges 56b and 56c. A reinforcing tube 16 formed of a perforated plate is disposed inside the tube main body 56 a via a spacer 17.
[0023]
On the pipe connection end faces of the flanges 56b and 56c, annular grooves 63A and 63B filled with the molding material 9 are formed, respectively. The surface outside the annular groove 63A of the upper flange 56b forms a seal surface 63a in close contact with the seal surface 65a of the upper mold 44, and the seal portion A is formed by these seal surfaces 63a and 65a. . The seal surface 65 a is an outer peripheral portion of the bottom surface of the annular recess 65 formed on the lower surface of the upper mold 44.
[0024]
A surface outside the annular groove 63B of the lower flange 56c forms a seal surface 63b in close contact with the seal surface 61a of the first lower mold 55, and the seal portion is formed by these seal surfaces 61a and 63b. B is formed.
[0025]
The core 57 includes a columnar core main body 57A, a cylindrical body 57B fitted to the core main body 57A, and a conical body 57C fixed to the upper surface of the core main body 57A and the cylindrical body 57B by welding. Thus, a cooling circuit 66 is formed inside. A space provided between the core 57 and the first and second lower molds 55 and 56 forms the cavity 8 filled with the molding material 9. The conical body 57 </ b> C is coaxially inserted into the recess 47 of the upper mold 44 with an appropriate gap, the gap forms the runner 49 through which the molding material 9 passes, and a lower end portion communicating with the cavity 8 is formed. The gate 51 is formed.
[0026]
A plurality of support members 70 are provided between the first upper mold member 44 </ b> A of the upper mold 44 and the first lower mold 55. The support member 70 is erected on the first lower mold 55, the connection bolt 71 is screwed to the upper end, and the head abuts against the lower surface of the second upper mold member 44 B, and is molded. You can choose whether to attach or remove depending on conditions. Here, since it demonstrates supposing the removed state first, please refer FIG. 2 as what the support member 70 and the connection volt | bolt 71 are not drawn. The state in which the support member 70 and the connecting bolt 71 are mounted as shown in FIG. 2 will be described later.
[0027]
Such an injection mold 30 is simply assembled by stacking and arranging the upper mold 44, the lower mold 45 and the transfer pot 31 by its own weight, and has no conventional mold clamping mechanism. 32 is basically different from the conventional mold in that molding is performed by sealing the three seal portions A, B, and C using a force for pressing the molding material 9 at 32.
[0028]
2 and 6 to 9, the cooling mechanism 66 of the mold 30 includes first to sixth cooling circuits 67A to 67F. The first cooling circuit 67A is composed of an annular groove 81 formed on the lower surface side of the first lower mold member 55A, and a through hole provided in the second lower mold member 55B, and communicates with the annular groove 81, respectively. It comprises a port 82, an air discharge port 83 and the like. The air supply port 82 is connected to an air supply source (not shown), and the air discharge port 83 is open to the atmosphere.
[0029]
The second to fifth cooling circuits 67B to 67E are formed inside the core 57, and have annular grooves 85 to 88 formed on the outer peripheral surface of the core body 57A so as to be spaced apart in the axial direction. The annular grooves 85 to 88 are communicated with the air supply passages 89a to 89d and the air discharge passage 90 formed in the core body 57A through the communication passages 91a to 91d and 92a to 92d, respectively. . The air supply passages 89a to 89d are non-through holes that open to the lower surface of the core body 57A, and are formed around the air discharge passage 90 at a required angle in the circumferential direction. That is, as shown in FIG. 70, the air supply passages 89a to 89d are formed to be spaced apart by 135 ° in the clockwise direction. Therefore, the air supply passage 89b is spaced 135 ° clockwise from the air supply passage 89a, the air supply passage 89c is spaced 135 ° clockwise from the air supply passage 89b, and the air supply passage 89d is It is spaced 135 ° clockwise from the supply passage 89c. The air discharge passage 90 is a non-through hole that opens to the center of the lower surface of the core body 57A, and has a larger hole diameter than the air supply passages 89a to 89d.
[0030]
In FIG. 6, the second lower mold member 55 </ b> B includes passages 95 a to 95 d, 96 communicating with the air supply passages 89 a to 89 d and the air discharge passage 90 in addition to the air supply port 82 and the air discharge port 83. Is formed. These passages 95a to 95d, 96 are formed by through holes penetrating the upper and lower surfaces of the second lower mold member 55B. Each of the passages 95a to 95d is connected to an air supply source, and the passage 96 is open to the atmosphere.
[0031]
In FIG. 2, the sixth cooling circuit 67 </ b> F has an annular groove 98 formed in the upper mold 44, and an air supply port 99 and an air discharge port 100 communicating with the annular groove 98. The air supply port 99 is connected to an air supply source (not shown), and the air discharge port 100 is open to the atmosphere.
[0032]
The first to sixth cooling circuits 67 </ b> A to 67 </ b> F are configured such that the compressed air is sequentially supplied from the air supply source by the switching operation of the solenoid valve, so By cooling sequentially toward 51, the cooling and hardening timing of the molding material 9 injected into the cavity 8 is controlled.
[0033]
In order to mold the measuring pipe of the electromagnetic flow meter by lining the inner peripheral surface of the second lower mold 56 and the annular grooves 63A and 63B of the flanges 56b and 56c using the injection molding apparatus 20 as described above, The mold 30 is placed in a heating furnace together with the transfer pot 31 and the molding material 9 and heated to a predetermined temperature (350 to 370 ° C.).
[0034]
While the molding material 9 is heated and melted, the pusher 32 is removed from the transfer pot 31 and kept at room temperature, and is attached to the transfer pot 31 immediately before the operation of injecting the molten molding material 9 into the cavity 8. . The heated mold 30 and transfer pot 31 are placed on the mold mounting plate 26, the hydraulic cylinder 22 is driven, and the pusher 32 is pressed by the plunger 33, thereby giving a predetermined thrust Fl to the pusher 32. When the pusher 32 is applied with the thrust Fl and pressurizes the molding material 9, the molding material 9 is pressurized and injected into the cavity 8 from the nozzle hole 40 of the bottom plate 31 </ b> B through the sprue 50, the runner 49 and the gate 51. The pressure injection time of the molding material 9 by the pusher 32 is about 2 minutes, and the air in the cavity 8 is discharged from the seal portions A and B to the outside by the injection pressure P by the pusher 32. That is, the seal portions A and B are processed to have a surface roughness that allows air to be discharged but not molten resin. Since the viscosities of air and molten resin differ greatly, this can be achieved by adjusting the surface roughness of the seal portions A and B.
[0035]
When the molten molding material 9 is pressurized by pushing down the pusher 32, the molding material 9 is injected from the nozzle hole 40 while pressing the bottom plate 31 </ b> B downward, and the radial gap between the transfer pot 31 and the pusher 32. It tries to leak upward (usually about 0.3 to 1.0 mm on one side). If the temperature of the pusher 32 is set lower than the temperature of the molding material 9, the molding material 9 in contact with the pusher 32 is rapidly cooled and solidified to close the gap and act as a packing. There is no leakage. Further, the molten molding material 9 pushes the molding material 9 solidified in the gap by the pressure upward. The molding material 9 solidified in the gap acts to lift the transfer pot 31 upward by the frictional force with the transfer pot 31. Then, the lower end of the cylindrical body 31 </ b> A of the transfer pot 31 is separated from the upper surface of the upper mold 44. When the pin 37 eventually hits the lower surface of the bottom plate 31B, the transfer pot 31 is prevented from being lifted further. In this state, the transfer pot 31 and the upper mold 44 are in contact with each other only at the seal portion C, and most of the thrust Pl applied to the pusher 32 is added to the seal portion C. As described above, since the area of the seal portion C is smaller than the area of any of the seal portions A and B, a sufficiently large seal pressure is generated in the seal portion C, and the molten molding material 9 leaks from the seal portion C. Can be prevented.
[0036]
The force Fl that the hydraulic cylinder 22 pushes down the pusher 32 acts on the area S1 of the lower surface of the pusher 32 and generates an injection pressure P in the molding material 9 melted inside the transfer pot 31. The force Fn generated on the bottom plate 31B in response to the injection pressure P is downward, and works to press the upper mold 44 against the second lower mold 56 via the seal portion C. Strictly speaking, the weights of the pusher 32, the transfer pot 31, the molding material 9, and the upper die 44 also work so as to press the upper die 44 downward, but as will be described later, they are negligibly small with respect to Fn. When the second lower mold 56 is pressed against the first lower mold 55, a clamping force of the same magnitude is generated between them. The pressing force Fn of the bottom plate 31B against the mold 30 is obtained from the projected area Sn (hatched portion in FIG. 3) when the pressure receiving surface of the bottom plate 31B is viewed in the direction of the force Fl and the injection pressure P.
Fn = P · Sn = Fl · Sn / Sl
[0037]
On the contrary, an upward thrust (force for pulling the upper mold 44 away from the second lower mold 56) Fm is generated in the mold 30 by the injection pressure P. This thrust Fm is obtained from the projected area Sm (shaded portion in FIG. 4) viewed from below the upper mold 44 and the injection pressure P.
Fm = P · Sm = Fl · Sm / Sl
[0038]
Therefore, the force F by which the upper mold 44 presses the seal portion A (same as the seal portion B) of the second lower mold 56 by the pressing force Fn against the upper mold 44 of the bottom plate 31B is:
F = Fn−Fm
It becomes.
When Fn becomes smaller than Fm, the pressing force F becomes negative, so that the upper mold 44 is lifted and the seal is damaged.
When the area of the seal part A is Sa and the pressure (seal pressure) generated in the seal part A is Pa, the seal pressure Pa is
Pa = (Fn−Fm) / Sa = (Sn−Sm) P / Sa
= Fl. (Sn-Sm) /Sl.Sa
It becomes.
[0039]
Here, how much the weight of the molding material 9, the upper mold 44, the second lower mold 56, the transfer pot 31 and the like actually affects the seal ratio (a value obtained by dividing the seal pressure Pa by the injection pressure P) K. As a result, the total weight of the molding material 9, the upper mold 44, the second lower mold 56, the transfer pot 31 and the like when the diameter of the measurement tube is 100 mm and 40 mm is about 21.5 kg and 4.3 kg, respectively. Then, since the total weight is extremely small compared to the pressing force Fn by the bottom plate 31B (when the diameter is 100 mm: 5148 Kgf, when the diameter is 40 mm: 1825 Kgf) and the thrust Fm (when the diameter is 100 mm: 3382 Kgf, when the diameter is 40 mm: 1378 Kgf). It has been found that the influence on the seal ratio K is extremely small and can be ignored as the error range. As will be described later, the seal ratio K was 2.04 when the aperture was 100 mm, and 1.41 when the aperture was 40 mm.
[0040]
In order to prevent leakage of the molding material 9 from the seal portion A, the minimum condition (that is, a necessary condition) is that the sealing pressure Pa is a positive value. We sought to see if it could leak.
As is clear from the above formula, if the thrust of the pusher 32 is increased, the injection pressure P and the seal pressure Pa are increased. However, it has been found that if the thrust of the pusher 32 is excessively increased, internal stress remains in the molded product, causing deformation and cracking due to cracks.
[0041]
Here, the concept of seal ratio K is introduced. That is, K = Pa / P = (Fn−Fm) / Sa · P = (Sn−Sm) / Sa
The seal ratio K is a dimensionless numerical value determined when the injection mold 30 is designed, and the condition for preventing the molding material 9 from leaking from the seal portion A (that is, a sufficient condition) is K = Pa / P> C. However, C is a constant value determined by the type, viscosity, temperature and the like of the molding material 9 in actual molding, and is a value obtained inductively by experiments. If the seal ratio K is smaller than the constant value C, the molding material 9 leaks out from the seal portion A, and if it is larger, it does not leak out. Molding is actually performed by changing the seal ratio K, the type of the molding material 9, the viscosity and the temperature, and the value of the sealing ratio K when the molding material 9 stops leaking is defined as a constant C. For example, assuming that the leakage from the sealing portion A of the molding material 9 is stopped when molding is performed with the seal ratio K being 0.3, the constant value C is 0.3. Therefore, in order to prevent the molding material 9 from leaking from the seal portion A, the seal ratio K needs to be larger than 0.3. In the experiment, a mold having a large seal area S was manufactured and molded, and the seal portion A was gradually cut to gradually reduce the seal area S to increase the seal ratio K, and the molding was repeated. The seal ratio K when the leakage of the material 9 from the seal portion A stops is regarded as a constant value C. Although the seal part A has been described as an example so far, the seal part B can be considered in the same manner. Further, as described above, since the seal portion C has a small area, a considerably large seal ratio can be obtained, and there is no practical problem.
[0042]
After the injection of the molding material 9 is completed, it is left for several minutes while maintaining the thrust Fl from the hydraulic cylinder 22, and the residual stress distribution of the molded body is made uniform. Next, compressed air as a cooling medium is supplied to the first to sixth cooling circuits 67 </ b> A to 67 </ b> F to cool the mold 30 from the inside for a certain time, and the molding material 9 in the cavity 8 is solidified.
[0043]
FIG. 9 shows a cooling procedure for the mold 30. In all the cooling steps, the thrust Fl is continuously applied from the hydraulic cylinder to the pusher 32, and the pressure P of the molten molding material 9 remaining in the transfer pot 31 is maintained. After the injection of the molding material 9 is completed, it is allowed to stand for several minutes to uniform the residual stress distribution of the molded article). Next, compressed air is sequentially supplied to the first to sixth cooling circuits 67A to 67F while taking a predetermined time to cool the mold 30, and the molding material 9 in the cavity 8 is gradually moved from the bottom upward. To solidify.
[0044]
In actual cooling, the first cooling circuit 67A has a pressure of 3 to 5 kgf / cm.² The compressed air 210 is supplied for a predetermined time (about 4 minutes) to cool the molding material 9 filled in the annular recess 61 of the first lower die 55A and the annular groove 81 of the lower flange 56c.
[0045]
Next, compressed air is supplied to the second cooling circuit 67B for a certain period of time when the upper portion of the annular recess 61 and the annular groove 81 of the molding material 9 filled in the annular groove 81 starts to solidify. The lower end of 57 is cooled. The time difference from the start of cooling by the first cooling circuit 67A to the start of cooling by the second cooling circuit 67B is about one and a half minutes. Similarly, compressed air is sequentially supplied to the third to fifth cooling circuits 67C to 67E with a predetermined time difference (about 1 minute), and cooling of the core 57 is advanced upward. The cooling time by the second to fifth cooling circuits 67B to 67E is about 3 minutes, respectively. Then, before the cooling by the fifth cooling circuit 67E is finished, compressed air is supplied to the sixth cooling circuit 67F for a predetermined time (about four and a half minutes) to cool the upper mold 44, and the molding material 9 in the cavity 8 is cooled. To solidify completely. In this way, the molten molding material 9 is replenished from the transfer pot 31 in accordance with the volume shrinkage generated by the solidification of the molding material 9 in the cavity 8, and a clean molded body free from sink marks can be obtained.
[0046]
When the molding material 9 in the mold 30 is completely solidified and molding is completed, the molding material 9 can be easily cut at the connection portion between the nozzle hole 40 and the sprue 50 by rotating the transfer pot 31. Next, the upper mold 44 is lifted together with the transfer pot 31, the second lower mold 56 is taken out from the first lower mold 55, and the molding material 9 solidified at the flash, runner 49 and gate 51 portions is cut. Finish molding. The second lower mold 56 is used as a measurement pipe which is a molded product in which the inner peripheral surface and the pipe connection end faces of the flanges 56b and 56c are covered with a lining material. When the measurement tube is subsequently formed, a new second lower die 56 is placed on the first lower die 55, and the upper die 44 and the transfer pot 31 are further placed thereon, and the above procedure is followed. Therefore, molding is performed.
[0047]
【Example】
When PFA resin 450HP-J manufactured by Mitsui DuPont Fluorochemical Co. is used as the molding material 9, when the mold temperature is 360 ° C, the resin temperature is 360 ° C, and the seal ratio K is 0.32, It was confirmed that no leakage occurred.
[0048]
In the above description, the case where the support member 70 and the connecting bolt 71 are removed and molding is performed in FIG. 2 has been described. However, when the pressing force F = Fn−Fm is large and the mold 30, particularly the second lower mold 56 that is a molded product is thin and the strength is low, the second lower mold 56 is plastically deformed by buckling. Or may be destroyed.
[0049]
Therefore, in order to solve such a problem, an embodiment in the case where the support member 70 and the connecting bolt 71 are mounted and molded in FIG. 2 will be described.
In the present embodiment, the support member 70 is interposed between the upper die 44 and the first lower die 55, and the upper end of the connecting bolt 71 is brought into contact with the upper die 44, so that the second die is moved from the upper die 44 to the second die. A part of the pressing force Fn transmitted to the lower die 56 is received by the support member 70 so that the pressing force F applied to the second lower die 56 is reduced.
[0050]
The support member 70 is formed in a cylindrical shape that can be elastically deformed by compression, and is vertically erected at equal intervals in the circumferential direction near the outer periphery of the first lower mold 55 so that the upper end thereof is the first. A screw hole 73 extends above the lower mold 55 and is screwed into the connecting bolt 71 at the center of the upper surface. As the material of the support member 70, hardened steel or the like is used.
[0051]
The connecting bolt 71 is made of hardened steel and is screwed into the screw hole 73 of each support member 70 so that the head is in contact with the lower surface of the upper mold 44. Other structures are substantially the same as those in the above-described embodiment.
[0052]
In the injection mold 30 having such a structure, when a thrust Fl is applied to the pusher 32 and the molten molding material 9 in the transfer pot 31 is pressurized and injected into the cavity 8 of the mold 30, the pressing force Fn is the mold. The mold 30 is added to the support member 70 through the mold 30. For this reason, although the support member 70 mainly bends, the elastic force (reaction force) R of the support member 70 acts on the upper mold | type 44 at this time, and functions as a tension rod. Therefore, the pressing force F applied to the mold 30 is reduced, and even if the second lower mold 56 has a low strength, it is not plastically deformed or broken due to buckling, and the resin that requires high pressure is used. The present invention can also be applied to lining and molding of a measuring tube with low strength.
[0053]
Next, the seal ratio K in the injection mold 30 using the support member 70 will be described.
The support member 70 and the second lower mold 56 are contracted by Δl by the injection pressure P.
[0054]
[Expression 1]

[0055]
[Expression 2]

[0056]
here,
P is injection pressure
Sn is the projected area viewed from above the bottom plate
Sm is the projected area viewed from below the upper mold
Sa is the seal area
Sr is the cross-sectional area of the support member (support member body)
Sp is the cross-sectional area of the second lower mold
Fn is the downward force generated by the injection pressure (= P · Sn)
Fm is the force to push up the mold by the injection pressure (= P · Sm)
Fr is the force applied to the support member
Fp is the force applied to the second lower mold
Lp is the length between the flanges of the second lower mold
Lr is the length of the support member
Δl is the amount of shrinkage of the support member
E is the Young's modulus of the support member (assuming the same as the Young's modulus of the second lower mold)
n is the number of support members.
It is assumed that the flange portions 56b and 56c of the second lower mold 56 and the connecting bolt 71 are not deformed.
[0057]
Considering the balance of power
(Fn−Fm) = nFr + Fp (2)
When the above equation (A) is substituted into equation (2)
[0058]
[Equation 3]

[0059]
The seal ratio K is obtained using the above equation (B). The seal pressure Pa is expressed by the following formula.
[0060]
[Expression 4]

The seal ratio K is obtained by dividing both sides of the above equation (4) by P.
[Equation 5]

[0061]
[Formula 6]

[0062]
The previous term of the above equation (6) is a normal seal ratio, the latter term is a decrease by the support member, and the reduction ratio of the seal ratio is expressed by the following equation.
[0063]
[Expression 7]

[0064]
According to such an injection molding apparatus 20, since it is not necessary to clamp the mold 30, the structure is simple and the number of parts can be reduced as compared with an injection molding apparatus having a conventional mold clamping mechanism. The cycle can be shortened and productivity can be improved.
[0065]
In addition, by providing a cooling mechanism 66 including first to sixth cooling circuits 67A to 67F that are independent from each other in the mold 30, and sequentially supplying compressed air to these cooling circuits 67A to 67F with a required time difference, Since the timing of cooling and hardening of the molding material 9 is controlled, there is no sink or striae, and a molded product with high quality can be molded.
Further, since it is only necessary to control the timing and supply time of the compressed air supplied to the first to sixth cooling circuits 67A to 67F according to the size, thickness, etc. of the molded product, control is also easy.
[0066]
In the above-described embodiment, an example is shown in which the present invention is applied to the injection molding apparatus 20 for lining the inner peripheral surface of the measurement pipe for electromagnetic flowmeter and the pipe connection end face of the flange. However, the present invention is not limited to this. For example, containers and cups, especially those used in the clean room of a semiconductor manufacturing plant, are made of approximately 100% fluororesin, so they can be manufactured at low cost by using the injection molding apparatus according to the present invention. Can do.
Moreover, in this Embodiment, although the cooling mechanism 66 was comprised by six cooling circuit 67A-67F, the number is arbitrary and can be increased / decreased suitably according to the magnitude | size of a molded article.
Further, in the above embodiment, the injection molding apparatus 20 in which the injection mold 30 is not clamped by the mold clamping mechanism is shown. However, the present invention is not limited to this, and a conventional mold clamping mechanism is provided. Of course, the present invention can also be applied to other injection molding apparatuses.
Furthermore, in the above-described embodiment, since the molded product is a measurement tube, the lower mold 45 of the mold 30 is constituted by the first and second lower molds 55 and 56 and the core 57, and the second Although an example in which the lower die 56 is configured with a measuring tube before being lined is shown, depending on the molded product, the mold may be composed of one lower die, an upper die, and a core. Good.
[0067]
【The invention's effect】
As described above, since the injection molding apparatus according to the present invention can arbitrarily control the timing of cooling and hardening of the molding material injected into the cavity, it does not cause sink marks or striae and is a high-quality molded product. Can be molded.
[0068]
  Also,PusherThe surface pressure is generated on the sealing surfaces of the lower mold and the upper mold by using the force that presses the molding material, preventing the molding material made of fluororesin from leaking outside. There is no need to clamp the mold with a hydraulic mold clamping mechanism, simplifying the injection molding device and reducing the mold production cost, as well as facilitating assembly and disassembly of the mold and improving productivity. Can do. Further, since there is no leakage of the molding material, the defect rate can be reduced.
  In addition, since the mold design can be performed within a range satisfying the condition of Pa / P> 0.32, the degree of freedom in design can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a part of an embodiment of an injection molding apparatus according to the present invention in a cutaway manner.
FIG. 2 is a cross-sectional view of an injection mold.
FIG. 3 is a diagram showing a projected area viewed from above the bottom plate.
FIG. 4 is a diagram showing a projected area viewed from below the upper mold.
FIG. 5 is an enlarged cross-sectional view of the vicinity of a seal surface.
FIG. 6 is a plan view of a first lower mold member.
FIG. 7 is a bottom view of the core.
8A to 8D are cross-sectional views taken along lines AA, BB, CC, and DD in FIG.
FIG. 9 is a diagram showing a cooling sequence.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 8 ... Cavity, 9 ... Molding material, 20 ... Injection molding apparatus, 22 ... Hydraulic cylinder, 30 ... Mold for injection molding, 31 ... Transfer pot, 32 ... Pusher, 40 ... Nozzle hole, 41a ... Sealing surface, 44 ... Top 45, lower mold, 49 ... runner, 50 ... sprue, 51 ... gate, 53a ... sealing surface, 55 ... first lower mold, 56 ... second lower mold, 56b, 56c ... flange, 57 ... medium Child, 61a, 63a, 63b, 65a ... sealing surface, 66 ... cooling mechanism, 67A to 67F ... cooling circuit, 70 ... support member, A, B, C ... seal part.

Claims (3)

A container having a nozzle hole at the bottom and containing a molten molding material; a mold filled with the molding material injected from the nozzle hole of the container; and a pusher for pressurizing the molding material in the container; An injection molding apparatus comprising: a thrust applying unit that applies a thrust in a direction in which the pusher substantially pressurizes the molding material in the container to the pusher or the mold,
The mold is composed of an upper mold arranged in a stacked manner and a lower mold having a core, and the core has a cylindrical core body and a cylindrical body fitted to the body, and the core A plurality of groove-shaped independent cooling circuits are formed on the outer peripheral surface of the child main body so as to be spaced apart from each other in the axial direction, and the cooling start time is sequentially delayed as the cooling circuit is closer to the gate. An injection molding apparatus characterized in that a cooling medium is supplied step by step to control the timing of cooling and hardening of the molding material injected into the cavity. The injection molding apparatus according to claim 1, wherein
An injection molding apparatus, wherein the molding material in the container is pressed by the pusher to bring the sealing surfaces of the lower mold and the upper mold into close contact with each other over the entire circumference. The injection molding apparatus according to claim 1 or 2,
When the molding material is a fluorine resin, the injection pressure of the molding material when pressed by the pusher is P, and the sealing pressure applied to each sealing surface is Pa .
The following conditions Pa / P> 0.32
An injection molding device characterized in that

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