WO2009118919A1 - Injection molding machine and method of injection molding therewith - Google Patents

Injection molding machine and method of injection molding therewith Download PDF

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Publication number
WO2009118919A1
WO2009118919A1 PCT/JP2008/060600 JP2008060600W WO2009118919A1 WO 2009118919 A1 WO2009118919 A1 WO 2009118919A1 JP 2008060600 W JP2008060600 W JP 2008060600W WO 2009118919 A1 WO2009118919 A1 WO 2009118919A1
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WO
WIPO (PCT)
Prior art keywords
screw
molding material
heating cylinder
injection molding
axial direction
Prior art date
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PCT/JP2008/060600
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French (fr)
Japanese (ja)
Inventor
俊道 西澤
Original Assignee
Nishizawa Toshimichi
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Application filed by Nishizawa Toshimichi filed Critical Nishizawa Toshimichi
Priority to KR1020107015128A priority Critical patent/KR101205659B1/en
Priority to CN2008801245742A priority patent/CN101909849A/en
Publication of WO2009118919A1 publication Critical patent/WO2009118919A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
    • B29C45/47—Means for plasticising or homogenising the moulding material or forcing it into the mould using screws
    • B29C45/50—Axially movable screw
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
    • B29C45/58—Details
    • B29C45/60—Screws
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
    • B29C45/58—Details
    • B29C45/62—Barrels or cylinders

Definitions

  • the present invention relates to an injection molding machine, and more particularly to an in-line screw type injection molding machine suitable for injection molding of a thermoplastic resin and an injection molding method using the same.
  • a screw is rotated by a rotation driving means, and the molding material supplied into the heating cylinder from the base end side of the heating cylinder is plasticized by the rotation of the screw, thereby heating the cylinder. If the predetermined amount of plasticized and melted molding material is weighed at the tip of the heating cylinder by feeding it to the tip side and moving the screw axially rearward, the screw is moved forward by the axial movement means and plasticized. The molded molding material is injected from the tip of the heating cylinder and filled into a mold clamped by a mold clamping device.
  • the heating cylinder is connected to the cylindrical main body portion to which the molding material is supplied and the front end of the main body portion, and the taper is formed in a tapered shape toward the nozzle hole.
  • the taper angle of the taper portion of the heating cylinder is configured to exceed 20 °.
  • Japanese Patent Laid-Open No. 06-166070 JP 2002-001782 A Japanese Patent Laid-Open No. 2001-269973 JP 2005-329722 A JP 07-148785 A JP 09-057801 A Japanese Patent Laid-Open No. 06-055594 JP 07-294340 A
  • thermoplastic resin In the injection molding of thermoplastic resin, a plasticized molding material with a relatively high temperature (150 ° C to 400 ° C) is injected from the tip of the heating cylinder, and inside the mold cavity at a relatively low temperature (30 ° C to 120 ° C). And the filled molding material is cooled and solidified in the cavity of the mold.
  • the molding material is injected and filled into the mold, if the injection speed of the molding material from the heating cylinder (or the filling speed of the molding material into the mold) is slow, the mold is filled during the filling of the mold cavity.
  • thermoplastic resin is ideally filled with the molding material in the cavity of the mold instantly by ultra-high speed injection.
  • ultra-high-speed and ultra-high-pressure injection molding machine capable of performing ultra-high-speed injection, and capable of ultra-high-pressure injection to realize the ultra-high-speed injection was actively conducted.
  • the molded product molded with this ultra-high-speed / high-pressure injection molding machine has a problem that the strength of the molded product is greatly reduced due to local heat generated locally by the molding material (resin). was there.
  • the present invention has been made in view of the above circumstances, and an object thereof is to improve the quality of a molded product obtained by injection of a plasticized molding material at an ultrahigh speed and an ultrahigh pressure.
  • the present invention provides a heating cylinder for heating a molding material, a screw housed in the heating cylinder so as to be rotatable and movable in an axial direction, and a rotational driving means for rotationally driving the screw. And axial movement means for moving the screw in the axial direction, the screw is rotated by the rotation driving means, and the molding material supplied into the heating cylinder is plasticized by the rotation of the screw. Then, the screw is sent to the tip of the heating cylinder, the screw is moved rearward in the axial direction, and a predetermined amount of the plasticized and melted molding material is measured at the tip of the heating cylinder.
  • the heating cylinder is a molding material A cylindrical main body portion to be supplied, and a tapered portion which is provided in connection with the tip of the main body portion and is tapered toward the nozzle hole, and the taper angle of the tapered portion of the heating cylinder is 3 ° or more. It is configured to be 20 ° or less.
  • the surface temperature of the inner wall of the tapered portion of the heating cylinder may be maintained at a temperature of ⁇ 5 ° C. or higher as compared with the actual temperature of the molding material housed in the tapered portion and in a plasticized state.
  • the rotation control means includes a control means for controlling the axial movement means.
  • the control means moves the screw forward in the axial direction by the axial movement means after the screw is moved a predetermined distance rearward in the axial direction. It may be controlled so that the time until it is moved to within a predetermined time.
  • the present invention in the injection molding of a thermoplastic resin (molding material) by an in-line screw type injection molding machine, when the ultra-high speed / ultra-high pressure injection molding is executed, the local heating of the molding material locally becomes abnormally high. Because it can be prevented, ideal ultra-high-speed and ultra-high-pressure injection molding without mixing of molding material with reduced plasticity, which is caused by the slow filling speed of the cavity in the current low- and medium-speed injection molding An excellent effect is achieved that the process can be realized and the quality performance of the obtained molded product can be remarkably improved.
  • FIG. 1 is a side sectional view of an injection molding machine according to an embodiment of the present invention, showing a state in which a screw is retracted.
  • FIG. 2 is a side sectional view of the injection molding machine according to the embodiment of FIG. 1 and shows a state where the screw has advanced.
  • FIG. 3 is a graph showing the relationship between the tip angle of the heating cylinder (taper angle ⁇ of the tapered portion of the heating cylinder) and the tensile strength of the molded product.
  • FIG. 4 is a graph showing the relationship between the injection speed and the molded product tensile strength for each heating tube tip angle (taper angle ⁇ of the tapered portion of the heating tube).
  • FIG. 5 is a graph showing the relationship between the molded product weight and the molded product tensile strength.
  • FIG. 6 is a graph showing the relationship between the temperature difference in the heating cylinder and the incidence of low-strength molded products.
  • FIG. 7 is a graph showing the relationship between the metered resin storage time and the molded product tensile strength.
  • FIG. 8 is a side sectional view of an injection molding machine according to another embodiment, showing a state in which the screw is retracted.
  • FIG. 9 is a side sectional view of the injection molding machine according to the embodiment of FIG. 8 and shows a state where the screw has advanced.
  • FIG. 10 is a side sectional view of an injection molding machine according to another embodiment, showing a state in which the screw is retracted.
  • FIG. 11 is a side sectional view of the injection molding machine according to the embodiment of FIG. 10 and shows a state where the screw has advanced.
  • FIG. 1 is a side sectional view of an injection molding machine according to an embodiment of the present invention, showing a state in which a screw is retracted.
  • FIG. 2 is a side sectional view of the injection molding machine according to the embodiment of FIG. 1 and shows a state where the screw has advanced.
  • an injection molding machine 10 is an inline screw type injection molding machine.
  • the injection molding machine 10 includes a hopper 11 that stores a pellet-shaped molding material (resin material), a heating cylinder (heating cylinder) 12 that heats and melts the molding material supplied from the hopper 11, and a rotation inside the heating cylinder 12.
  • a screw 13 that is freely movable in the axial direction, a rotation driving means 14 that rotationally drives the screw 13, an axial movement means 15 that moves the screw 13 in the axial direction, the rotational driving means 14, and the axial direction
  • a control means (controller) 16 for controlling the moving means 15.
  • the heating cylinder 12 includes a cylindrical main body portion 17 to which a hopper 11 is connected and a molding material is supplied from the hopper 11, and an injection nozzle portion 18 that is detachably attached to the tip of the main body portion 17. It is composed of The injection nozzle portion 18 has a nozzle hole 19 formed at the tip thereof, and a taper portion 20 that is connected to the tip of the main body portion 17 and is tapered toward the nozzle hole 19.
  • the taper part 20 of the heating cylinder 12 is configured such that the taper angle (heating cylinder tip angle) ⁇ is 3 ° or more and 20 ° or less, more preferably 3 ° or more and 15 ° or less (illustrated example). Then, 12 degrees).
  • a heater (cartridge heater, band heater, etc.) 21 is mounted on the outer periphery of the heating cylinder 12 (main body portion 17 and injection nozzle portion 18). The heating cylinder 12 is heated by the heater 21.
  • the screw 13 includes a screw main body 23 having a helical groove 22 and a screw head 24 that is detachably attached to the tip of the screw main body 23.
  • the spiral groove 22 formed in the screw body 23 is The depth is set to be deepest on the base end side and appropriately shallower toward the front end side.
  • the tip of the screw head 24 has a conical shape.
  • a backflow prevention ring (check ring) 25 is attached to the small diameter portion of the screw head 24.
  • the backflow prevention ring 25 allows the plasticized molding material to be sent out to the front end side of the heating cylinder 12 during the rotation of the screw 13, and is plasticized when the screw 13 moves forward to form the inside of the tapered portion 20 and the cylindrical main body.
  • the molding material accommodated inside the front end portion of the portion 17 is prevented from flowing backward to the rear end side of the heating cylinder 12.
  • the control means (controller) 16 controls the rotation drive means (motor, etc.) 14 and the axial movement means (motor, hydraulic cylinder, etc.) 15 etc. according to a predetermined program based on input signals from various sensors (not shown). It is supposed to be.
  • the molding material is supplied into the main body 17 of the heating cylinder 12 by the hopper 11.
  • the heating cylinder 12 (the main body portion 17 and the injection nozzle portion 18) is heated by a heater 21 to a temperature suitable for melting the molding material.
  • the surface temperature of the inner wall of the tapered portion 20 of the heating cylinder 12 and the inner wall of the distal end side portion of the cylindrical main body portion 17 is the inner temperature of the tapered portion 20 and the distal end of the cylindrical main body portion 17.
  • the controller 16 rotationally drives the screw 13 by the rotation driving means 14, the molding material supplied into the main body 17 of the heating cylinder 12 is plasticized and plasticized by the rotation of the screw 13.
  • the formed molding material is fed into the tapered portion 20 on the tip side of the heating cylinder 12.
  • the controller 16 is configured to rotate the screw 13 by the rotation driving means 14 while applying a predetermined back pressure to the screw 13 by the axial movement means 15, and within the tapered portion 20 and the cylindrical main body portion.
  • the screw 13 is retracted by the pressure of the molding material in a plasticized state.
  • the controller 16 If the controller 16 detects that the screw 13 has been retracted by a predetermined distance and a predetermined amount of molding material has been accommodated in the taper portion 20, the controller 16 holds the position of the screw 13 with the axial movement means 15 and rotates it. The rotation of the screw 13 by the driving means 14 is stopped. Thereafter, when the controller 16 advances the screw 13 at a predetermined speed by the axial direction moving means 15, the molding material plasticized and accommodated in the tapered portion 20 by the advance of the screw 13 is a nozzle at the tip of the heating cylinder 12. The molding material injected from the hole 19 and plasticized is filled into a mold clamped by a mold clamping device.
  • the controller 16 has a time (measurement resin storage time) from when the screw 13 is retracted by a predetermined distance (measurement completion) to when the screw 13 is advanced by the axial movement means 15 (injection start). Control is performed within a predetermined time (for example, within 5 minutes, more preferably within 10 minutes).
  • the present inventor studied the cause of the strength reduction of the molded product due to the ultra-high-speed and ultra-high-pressure injection, and found the essential cause.
  • the present inventor shows that in the molding machine in which the taper angle ⁇ of the taper portion 20 of the heating cylinder 12 is 20 ° or less, local heat generation of the molding material (resin) that is locally abnormally high is suppressed. As shown in FIGS. 3 and 4, even when the plasticized molding material is injected at an ultra-high speed, the strength of the molded product is not significantly reduced. ⁇ It was found that the strength of the molded product was improved by the effect of ultra-high pressure injection.
  • the pressure loss occurs more concentrated on the tip of the tapered portion 20 and the inner wall of the nozzle hole 19 as the plasticized molding material is injected at a higher speed.
  • the self-heating (shearing heat) of the molding material itself is concentrated, and local heating that is locally abnormally high occurs, and the injection molding material does not generate heat uniformly. If the temperature of the molding material that is injected and filled in the mold is not uniform, the molding material that has become extremely hot locally will decompose (lower molecular weight) and change its quality, or the shrinkage due to cooling of the molding material will be uneven. As a result, the strength of the molded product is reduced, and the dimensional accuracy of the molded product is significantly reduced.
  • the taper angle ⁇ of the taper portion 20 of the heating cylinder 12 is 3 ° or more and 20 ° or less, more preferably 3 ° or more and 15 ° or less.
  • the local heat generation which is locally abnormally high, is suppressed, and the temperature of the molding material injected and filled in the mold becomes uniform, so it can be obtained by injection of plasticized molding material at ultra high speed and ultra high pressure It becomes possible to improve the quality of the molded product.
  • the quality of the molded product is remarkably improved as compared with the molded product by the conventional molding machine in which the taper angle ⁇ exceeds 20 °.
  • a low-strength molded product having a light weight was occasionally generated. It has been found that the low-strength molded product having a light weight is inferior to the strength of the average-weight molded product.
  • This low-strength molded product that is light in weight is such that the surface temperature of the inner wall of the tapered portion 20 of the heating cylinder 12 and the inner wall of the distal end side portion of the cylindrical main body portion 17 It has been found that this occurs when the temperature is lower than a predetermined temperature compared to the actual temperature of the molding material contained in the portion and in a plasticized state.
  • Molding material in which the surface temperature of the inner wall of the taper portion 20 and the inner wall of the tip end portion of the cylindrical main body portion 17 is housed in the taper portion 20 and the tip end portion of the cylindrical main body portion 17 and is in a plasticized state. If the temperature is lower than the actual temperature of the (resin) by a predetermined temperature or more, the actual temperature of the molding material that comes into contact with the inner wall of the tapered portion 20 or the inner wall of the distal end portion of the cylindrical main body portion 17 is lowered. As a result, the flowability of the molding material whose actual temperature has decreased is deteriorated, and the molding material stays in the tapered portion 20 or the tip side portion of the cylindrical main body portion 17.
  • the molding material staying in the taper portion 20 or in the tip side portion of the cylindrical main body portion 17 changes in quality and loses its plasticity.
  • the molding material staying and changing in the tapered portion 20 or in the distal end portion of the cylindrical main body portion 17 is peeled off from the inner wall of the tapered portion 20 or the inner wall of the distal end portion of the cylindrical main body portion 17 and mixed.
  • the molding material flow path sprue, runner, gate
  • the mold cavity has insufficient filling amount.
  • the weight of the molded product is reduced and the strength of the molded product is reduced.
  • a deteriorated molding material is mixed into a molded product, for example, it becomes a starting point of fracture in a tensile strength test, and the strength of the molded product is remarkably lowered.
  • the surface temperature of the inner wall of the tapered portion 20 of the heating cylinder 12 and the inner wall of the distal end portion of the cylindrical main body portion 17 (heating cylinder inner wall temperature) is set to the inside of the tapered section 20 and the cylindrical Compared to the actual temperature of the molding material housed in the distal end portion of the main body portion 17 and in a plasticized state (actual temperature of the metering resin), it should be ⁇ 5 ° C. or more, preferably in the range of ⁇ 5 ° C. to + 20 °
  • the mixed molding material can be prevented from being mixed. Therefore, as shown in FIG. Occurrence can be prevented.
  • the upper limit of the temperature difference between the heating cylinder inner wall temperature and the measured resin actual temperature is preferably + 20 ° C. If the temperature difference in the heating cylinder is + 30 ° C or higher, the upper end of the heating cylinder 12 is accommodated. This is because the molding material in a plasticized state is rapidly reduced in molecular weight by thermal decomposition, and the allowable time from the completion of measurement to the start of injection becomes too short, which is not practical.
  • the quality of the molded product is remarkably improved as compared with the molded product by the conventional molding machine in which the taper angle ⁇ exceeds 20 °.
  • a low-strength molded product with a heavy weight was occasionally generated. It has been found that the low-strength molded product having a heavy weight is inferior to the strength of the average-weight molded product.
  • the low-strength molded product having a heavy weight occurs when the time from when the screw 13 is retracted by a predetermined distance until the screw 13 is advanced by the axial movement means 15 is longer than usual.
  • the molding material (resin) accommodated in the tapered portion 20 is heated or heated by the heater 21.
  • the molding material maintained at a high temperature or at a high temperature has a low molecular weight and fluidity is improved, and the filling amount of the molding material into the mold cavity becomes excessive.
  • the weight of the molded product increases, and the strength of the molded product decreases due to the resin having a low molecular weight.
  • the time from when the screw 13 is retracted by a predetermined distance until the screw 13 is advanced by the axial movement means 15 is a predetermined time.
  • the time from when the screw 13 is retracted by a predetermined distance until the screw 13 is advanced by the axial movement means 15 is a predetermined time.
  • a tip passage 26 having a substantially constant cross-sectional area toward the nozzle hole 19 may be formed between the tip of the tapered portion 20 and the nozzle hole 19.
  • a tip passage 27 that is tapered toward the nozzle hole 19 may be formed between the tip of the tapered portion 20 and the nozzle hole 19.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

The quality of molding product obtained by injecting a plasticized molding material at an ultrahigh speed in an extra-high pressure is enhanced. There is disclosed an inline screw injection molding machine comprising a heating tube (12) for heating a molding material; a screw (13) rotatably and axially movably housed in the heating tube (12); rotation driving means (14) for driving the rotation of the screw (13); and axial moving means (15) for axial movement of the screw (13). The heating tube (12) has a cylindrical main body part (17) into which the molding material is fed and a taper part (20) provided in relationship linked to the distal end of the main body part (17) so as to have a configuration gradually diminishing toward a nozzle hole (19). The taper angle (θ) of the taper part (20) of the heating tube (12) is in the range of 3° to 20°.

Description

射出成形機及びそれを用いた射出成形方法Injection molding machine and injection molding method using the same
　本発明は、射出成形機、殊に熱可塑性樹脂の射出成形に適したインラインスクリュー式の射出成形機及びそれを用いた射出成形方法に関する。 The present invention relates to an injection molding machine, and more particularly to an in-line screw type injection molding machine suitable for injection molding of a thermoplastic resin and an injection molding method using the same.
　例えば、熱可塑性樹脂の射出成形に用いられる射出成形機として、成形材料（樹脂材料）を加熱する加熱筒と、その加熱筒内に回転自在且つ軸方向に移動自在に設けられたスクリューと、そのスクリューを回転駆動させる回転駆動手段と、スクリューを軸方向に移動させる軸方向移動手段とを備えたインラインスクリュー式の射出成形機が知られている（特許文献１～８等参照）。 For example, as an injection molding machine used for injection molding of thermoplastic resin, a heating cylinder that heats a molding material (resin material), a screw that is rotatably and axially movable in the heating cylinder, There is known an in-line screw type injection molding machine provided with a rotation driving means for rotationally driving a screw and an axial direction moving means for moving the screw in the axial direction (see Patent Documents 1 to 8).
　このインラインスクリュー式の射出成形機においては、スクリューを回転駆動手段で回転駆動させて、そのスクリューの回転により加熱筒の基端側から加熱筒内に供給される成形材料を可塑化させて加熱筒先端側に送り出し、上記スクリューを軸方向後方に移動させて、上記加熱筒の先端に所定量の可塑化溶融状態の成形材料を計量したならば、スクリューを軸方向移動手段で前進させて、可塑化された成形材料を上記加熱筒先端から射出して型締装置により型締めされた金型内に充填するようになっている。 In this in-line screw type injection molding machine, a screw is rotated by a rotation driving means, and the molding material supplied into the heating cylinder from the base end side of the heating cylinder is plasticized by the rotation of the screw, thereby heating the cylinder. If the predetermined amount of plasticized and melted molding material is weighed at the tip of the heating cylinder by feeding it to the tip side and moving the screw axially rearward, the screw is moved forward by the axial movement means and plasticized. The molded molding material is injected from the tip of the heating cylinder and filled into a mold clamped by a mold clamping device.
　従来のインラインスクリュー式の射出成形機においては、加熱筒は、成形材料が供給される円筒状の本体部と、その本体部先端に繋げて設けられ、ノズル孔に向かい先細り形状に形成されたテーパー部とを有し、加熱筒のテーパー部のテーパー角度が２０°を超えるように構成されている。 In a conventional in-line screw type injection molding machine, the heating cylinder is connected to the cylindrical main body portion to which the molding material is supplied and the front end of the main body portion, and the taper is formed in a tapered shape toward the nozzle hole. And the taper angle of the taper portion of the heating cylinder is configured to exceed 20 °.
特開平０６－１６６０７０号公報Japanese Patent Laid-Open No. 06-166070 特開２００２－００１７８２号公報JP 2002-001782 A 特開２００１－２６９９７３号公報Japanese Patent Laid-Open No. 2001-269973 特開２００５－３２９７２２号公報JP 2005-329722 A 特開平０７－１４８７８５号公報JP 07-148785 A 特開平０９－０５７８０１号公報JP 09-057801 A 特開平０６－０５５５９４号公報Japanese Patent Laid-Open No. 06-055594 特開平０７－２９４３４０号公報JP 07-294340 A
　熱可塑性樹脂の射出成形においては、可塑化された比較的高温（１５０℃～４００℃）の成形材料が加熱筒先端から射出されて比較的低温（３０℃～１２０℃）の金型のキャビティ内に充填され、充填された成形材料が金型のキャビティ内で冷却されて固化される。成形材料を射出して金型内に充填する際に加熱筒からの成形材料の射出速度（或いは金型への成形材料の充填速度）が遅いと、金型のキャビティへの充填途中に、金型のキャビティへと繋がる成形材料の流路（スプルー、ランナー、ゲート）の表面やキャビティの表面に接触した成形材料の固化が始まり、その成形材料の可塑度が低下する。このようにして可塑度が低下した成形材料を無理に圧力をかけて金型のキャビティ内へ充填すると、可塑度が低下した成形材料の混入により成形品の品質が低下するという問題があった。 In the injection molding of thermoplastic resin, a plasticized molding material with a relatively high temperature (150 ° C to 400 ° C) is injected from the tip of the heating cylinder, and inside the mold cavity at a relatively low temperature (30 ° C to 120 ° C). And the filled molding material is cooled and solidified in the cavity of the mold. When the molding material is injected and filled into the mold, if the injection speed of the molding material from the heating cylinder (or the filling speed of the molding material into the mold) is slow, the mold is filled during the filling of the mold cavity. Solidification of the molding material in contact with the surface of the molding material flow path (sprue, runner, gate) leading to the cavity of the mold or the surface of the cavity starts, and the plasticity of the molding material decreases. Thus, when the molding material having a lowered plasticity is forcibly pressurized and filled into the cavity of the mold, there is a problem that the quality of the molded product is deteriorated due to the mixing of the molding material having the lowered plasticity.
　そのため、熱可塑性樹脂の射出成形プロセスは、超高速射出により成形材料を瞬時に金型のキャビティ内に充填するのが理想的であるとされている。１９８０年代には、超高速射出可能で、更にその超高速射出を実現するために超高圧射出可能な、超高速・超高圧射出成形機の研究が盛んに行われた。 Therefore, the injection molding process of thermoplastic resin is ideally filled with the molding material in the cavity of the mold instantly by ultra-high speed injection. In the 1980s, research on an ultra-high-speed and ultra-high-pressure injection molding machine capable of performing ultra-high-speed injection, and capable of ultra-high-pressure injection to realize the ultra-high-speed injection was actively conducted.
　しかしながら、熱可塑性樹脂においては、この超高速・超高圧射出成形機で成形した成形品は、成形材料（樹脂）の局部的に異常高温となる局部発熱により成形品強度が大幅に低下するという問題があった。 However, in the case of thermoplastic resin, the molded product molded with this ultra-high-speed / high-pressure injection molding machine has a problem that the strength of the molded product is greatly reduced due to local heat generated locally by the molding material (resin). was there.
　本発明は、上記事情に鑑みてなされたものであり、その目的は、可塑化された成形材料を超高速・超高圧射出して得られる成形品の品質を向上させることにある。 The present invention has been made in view of the above circumstances, and an object thereof is to improve the quality of a molded product obtained by injection of a plasticized molding material at an ultrahigh speed and an ultrahigh pressure.
　上記目的を達成するために、本発明は、成形材料を加熱する加熱筒と、該加熱筒内に回転自在且つ軸方向に移動自在に収容されたスクリューと、該スクリューを回転駆動させる回転駆動手段と、上記スクリューを軸方向に移動させる軸方向移動手段とを備え、上記スクリューを上記回転駆動手段で回転駆動させて、そのスクリューの回転により上記加熱筒内に供給される成形材料を可塑化させて上記加熱筒先端側に送り出し、上記スクリューを軸方向後方に移動させて、上記加熱筒の先端に所定量の可塑化溶融状態の成形材料を計量したならば、上記スクリューを上記軸方向移動手段で軸方向前方に移動させて、可塑化された成形材料を上記加熱筒先端から射出するインラインスクリュー式の射出成形機において、上記加熱筒は、成形材料が供給される円筒状の本体部と、その本体部先端に繋げて設けられ、ノズル孔に向かい先細り形状に形成されたテーパー部とを有し、上記加熱筒のテーパー部のテーパー角度が３°以上２０°以下となるように構成したものである。 In order to achieve the above object, the present invention provides a heating cylinder for heating a molding material, a screw housed in the heating cylinder so as to be rotatable and movable in an axial direction, and a rotational driving means for rotationally driving the screw. And axial movement means for moving the screw in the axial direction, the screw is rotated by the rotation driving means, and the molding material supplied into the heating cylinder is plasticized by the rotation of the screw. Then, the screw is sent to the tip of the heating cylinder, the screw is moved rearward in the axial direction, and a predetermined amount of the plasticized and melted molding material is measured at the tip of the heating cylinder. In the in-line screw type injection molding machine that injects the plasticized molding material from the tip of the heating cylinder by moving it forward in the axial direction, the heating cylinder is a molding material A cylindrical main body portion to be supplied, and a tapered portion which is provided in connection with the tip of the main body portion and is tapered toward the nozzle hole, and the taper angle of the tapered portion of the heating cylinder is 3 ° or more. It is configured to be 20 ° or less.
　ここで、上記加熱筒のテーパー部内壁の表面温度が、そのテーパー部内に収容されて可塑化状態にある成形材料の実温度に比べて－５℃以上の温度に維持されても良い。 Here, the surface temperature of the inner wall of the tapered portion of the heating cylinder may be maintained at a temperature of −5 ° C. or higher as compared with the actual temperature of the molding material housed in the tapered portion and in a plasticized state.
　又、上記回転駆動手段及び上記軸方向移動手段を制御する制御手段を備え、該制御手段は、上記スクリューが軸方向後方に所定距離移動されてからそのスクリューを上記軸方向移動手段で軸方向前方に移動させるまでの時間が所定時間以内となるように制御するものであっても良い。 The rotation control means includes a control means for controlling the axial movement means. The control means moves the screw forward in the axial direction by the axial movement means after the screw is moved a predetermined distance rearward in the axial direction. It may be controlled so that the time until it is moved to within a predetermined time.
　本発明によれば、インラインスクリュー式射出成形機による熱可塑性樹脂（成形材料）の射出成形において、超高速・超高圧射出成形を実行した際に成形材料が局部的に異常高温となる局部発熱を防止することが出来るので、現状の低・中速射出成形でのキャビティへの充填速度が遅いことにより発生する、可塑度が低下した成形材料の混入のない理想的な超高速・超高圧射出成形プロセスを実現させ、得られる成形品の品質性能を著しく向上させることが出来るという優れた効果を奏する。 According to the present invention, in the injection molding of a thermoplastic resin (molding material) by an in-line screw type injection molding machine, when the ultra-high speed / ultra-high pressure injection molding is executed, the local heating of the molding material locally becomes abnormally high. Because it can be prevented, ideal ultra-high-speed and ultra-high-pressure injection molding without mixing of molding material with reduced plasticity, which is caused by the slow filling speed of the cavity in the current low- and medium-speed injection molding An excellent effect is achieved that the process can be realized and the quality performance of the obtained molded product can be remarkably improved.
図１は、本発明の一実施形態に係る射出成形機の側断面図であって、スクリューが後退した状態を示す。FIG. 1 is a side sectional view of an injection molding machine according to an embodiment of the present invention, showing a state in which a screw is retracted. 図２は、図１の実施形態に係る射出成形機の側断面図であって、スクリューが前進した状態を示す。FIG. 2 is a side sectional view of the injection molding machine according to the embodiment of FIG. 1 and shows a state where the screw has advanced. 図３は、加熱筒先端角度（加熱筒のテーパー部のテーパー角度θ）と成形品引張強度との関係を示すグラフである。FIG. 3 is a graph showing the relationship between the tip angle of the heating cylinder (taper angle θ of the tapered portion of the heating cylinder) and the tensile strength of the molded product. 図４は、射出速度と成形品引張強度との関係を加熱筒先端角度（加熱筒のテーパー部のテーパー角度θ）毎に示すグラフである。FIG. 4 is a graph showing the relationship between the injection speed and the molded product tensile strength for each heating tube tip angle (taper angle θ of the tapered portion of the heating tube). 図５は、成形品重量と成形品引張強度との関係を示すグラフである。FIG. 5 is a graph showing the relationship between the molded product weight and the molded product tensile strength. 図６は、加熱筒内温度差と低強度成形品の発生率との関係を示すグラフである。FIG. 6 is a graph showing the relationship between the temperature difference in the heating cylinder and the incidence of low-strength molded products. 図７は、計量樹脂貯留時間と成形品引張強度との関係を示すグラフである。FIG. 7 is a graph showing the relationship between the metered resin storage time and the molded product tensile strength. 図８は、他の実施形態に係る射出成形機の側断面図であって、スクリューが後退した状態を示す。FIG. 8 is a side sectional view of an injection molding machine according to another embodiment, showing a state in which the screw is retracted. 図９は、図８の実施形態に係る射出成形機の側断面図であって、スクリューが前進した状態を示す。FIG. 9 is a side sectional view of the injection molding machine according to the embodiment of FIG. 8 and shows a state where the screw has advanced. 図１０は、他の実施形態に係る射出成形機の側断面図であって、スクリューが後退した状態を示す。FIG. 10 is a side sectional view of an injection molding machine according to another embodiment, showing a state in which the screw is retracted. 図１１は、図１０の実施形態に係る射出成形機の側断面図であって、スクリューが前進した状態を示す。FIG. 11 is a side sectional view of the injection molding machine according to the embodiment of FIG. 10 and shows a state where the screw has advanced.
符号の説明Explanation of symbols
　１０　射出成形機
　１２　加熱筒
　１３　スクリュー
　１４　回転駆動手段
　１５　軸方向移動手段
　１６　コントローラ（制御手段）
　１７　本体部
　１９　ノズル孔
　２０　テーパー部 DESCRIPTION OF SYMBOLS 10 Injection molding machine 12 Heating cylinder 13 Screw 14 Rotation drive means 15 Axial direction movement means 16 Controller (control means)
17 Main body 19 Nozzle hole 20 Taper
　以下、本発明の好適な実施形態を添付図面に基づいて詳述する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
　図１は、本発明の一実施形態に係る射出成形機の側断面図であって、スクリューが後退した状態を示す。図２は、図１の実施形態に係る射出成形機の側断面図であって、スクリューが前進した状態を示す。 FIG. 1 is a side sectional view of an injection molding machine according to an embodiment of the present invention, showing a state in which a screw is retracted. FIG. 2 is a side sectional view of the injection molding machine according to the embodiment of FIG. 1 and shows a state where the screw has advanced.
　図１及び図２に示すように、本実施形態に係る射出成形機１０は、インラインスクリュー式の射出成形機である。射出成形機１０は、ペレット状の成形材料（樹脂材料）を貯留するホッパー１１と、ホッパー１１から供給された成形材料を加熱・溶融する加熱筒（加熱シリンダ）１２と、加熱筒１２内に回転自在且つ軸方向に移動自在に設けられたスクリュー１３と、スクリュー１３を回転駆動させる回転駆動手段１４と、スクリュー１３を軸方向に移動させる軸方向移動手段１５と、これら回転駆動手段１４及び軸方向移動手段１５を制御する制御手段（コントローラ）１６とを備えている。 As shown in FIGS. 1 and 2, an injection molding machine 10 according to this embodiment is an inline screw type injection molding machine. The injection molding machine 10 includes a hopper 11 that stores a pellet-shaped molding material (resin material), a heating cylinder (heating cylinder) 12 that heats and melts the molding material supplied from the hopper 11, and a rotation inside the heating cylinder 12. A screw 13 that is freely movable in the axial direction, a rotation driving means 14 that rotationally drives the screw 13, an axial movement means 15 that moves the screw 13 in the axial direction, the rotational driving means 14, and the axial direction And a control means (controller) 16 for controlling the moving means 15.
　本実施形態に係る加熱筒１２は、ホッパー１１が接続され、ホッパー１１から成形材料が供給される円筒状の本体部１７と、本体部１７の先端に着脱自在に装着された射出ノズル部１８とから構成されている。射出ノズル部１８は、その先端に形成されたノズル孔１９と、本体部１７先端に繋げて設けられ、ノズル孔１９に向かい先細り形状に形成されたテーパー部２０とを有している。本実施形態では、加熱筒１２のテーパー部２０のテーパー角度（加熱筒先端角度）θが、３°以上２０°以下、より好ましくは３°以上１５°以下となるように構成される（図示例では、１２°）。加熱筒１２（本体部１７及び射出ノズル部１８）の外周には、ヒーター（カートリッジヒーターやバンドヒーター等）２１が装着されている。加熱筒１２がヒーター２１によって加熱される。 The heating cylinder 12 according to this embodiment includes a cylindrical main body portion 17 to which a hopper 11 is connected and a molding material is supplied from the hopper 11, and an injection nozzle portion 18 that is detachably attached to the tip of the main body portion 17. It is composed of The injection nozzle portion 18 has a nozzle hole 19 formed at the tip thereof, and a taper portion 20 that is connected to the tip of the main body portion 17 and is tapered toward the nozzle hole 19. In the present embodiment, the taper part 20 of the heating cylinder 12 is configured such that the taper angle (heating cylinder tip angle) θ is 3 ° or more and 20 ° or less, more preferably 3 ° or more and 15 ° or less (illustrated example). Then, 12 degrees). A heater (cartridge heater, band heater, etc.) 21 is mounted on the outer periphery of the heating cylinder 12 (main body portion 17 and injection nozzle portion 18). The heating cylinder 12 is heated by the heater 21.
　本実施形態に係るスクリュー１３は、螺旋状の螺旋溝２２を有するスクリュー本体２３と、スクリュー本体２３の先端に着脱自在に装着されるスクリューヘッド２４とから構成されている。スクリュー１３の回転により、加熱筒１２内に供給される成形材料を可塑化させて、可塑化された成形材料を加熱筒１２先端側に送り出すため、スクリュー本体２３に形成される螺旋溝２２は、その深さが基端側で最も深く、先端側に向かうにつれて適宜浅くなるように設定されている。スクリューヘッド２４は、その先端が円錐形状に形成されている。スクリューヘッド２４の小径部には逆流防止リング（チェックリング）２５が装着されている。逆流防止リング２５は、スクリュー１３の回転中は可塑化された成形材料が加熱筒１２先端側へ送り出されることを許容し、スクリュー１３の前進時には可塑化されてテーパー部２０内及び円筒状の本体部１７の先端側部分の内部に収容された成形材料が加熱筒１２後端側へ逆流することを抑制するものである。 The screw 13 according to the present embodiment includes a screw main body 23 having a helical groove 22 and a screw head 24 that is detachably attached to the tip of the screw main body 23. In order to plasticize the molding material supplied into the heating cylinder 12 by the rotation of the screw 13 and send the plasticized molding material to the tip side of the heating cylinder 12, the spiral groove 22 formed in the screw body 23 is The depth is set to be deepest on the base end side and appropriately shallower toward the front end side. The tip of the screw head 24 has a conical shape. A backflow prevention ring (check ring) 25 is attached to the small diameter portion of the screw head 24. The backflow prevention ring 25 allows the plasticized molding material to be sent out to the front end side of the heating cylinder 12 during the rotation of the screw 13, and is plasticized when the screw 13 moves forward to form the inside of the tapered portion 20 and the cylindrical main body. The molding material accommodated inside the front end portion of the portion 17 is prevented from flowing backward to the rear end side of the heating cylinder 12.
　制御手段（コントローラ）１６は、各種センサ（図示せず）からの入力信号に基づき、所定のプログラムに従って回転駆動手段（モータ等）１４及び軸方向移動手段（モータや油圧シリンダ等）１５等を制御するようになっている。 The control means (controller) 16 controls the rotation drive means (motor, etc.) 14 and the axial movement means (motor, hydraulic cylinder, etc.) 15 etc. according to a predetermined program based on input signals from various sensors (not shown). It is supposed to be.
　本実施形態に係る射出成形機１０の作動を説明する。 The operation of the injection molding machine 10 according to this embodiment will be described.
　成形材料はホッパー１１により加熱筒１２の本体部１７内に供給される。加熱筒１２（本体部１７及び射出ノズル部１８）はヒーター２１により成形材料を溶融させるのに適した温度に加熱される。本実施形態では、加熱筒１２のテーパー部２０内壁及び円筒状の本体部１７の先端側部分の内壁の表面温度（加熱筒内壁温度）が、テーパー部２０内及び円筒状の本体部１７の先端側部分の内部に収容されて可塑化状態にある成形材料の実温度（計量樹脂実温度）に比べて－５℃以上の温度、好ましくは－５℃から＋２０℃の範囲内の温度に維持される。 The molding material is supplied into the main body 17 of the heating cylinder 12 by the hopper 11. The heating cylinder 12 (the main body portion 17 and the injection nozzle portion 18) is heated by a heater 21 to a temperature suitable for melting the molding material. In the present embodiment, the surface temperature of the inner wall of the tapered portion 20 of the heating cylinder 12 and the inner wall of the distal end side portion of the cylindrical main body portion 17 (heating tube inner wall temperature) is the inner temperature of the tapered portion 20 and the distal end of the cylindrical main body portion 17. It is maintained at a temperature of -5 ° C or higher, preferably in the range of -5 ° C to + 20 ° C, compared to the actual temperature (measured resin actual temperature) of the molding material contained in the side portion and in a plasticized state. The
　コントローラ１６が回転駆動手段１４でスクリュー１３を回転駆動させると、そのスクリュー１３の回転により、加熱筒１２の本体部１７内に供給された成形材料が本体部１７内で可塑化され、可塑化された成形材料が加熱筒１２先端側のテーパー部２０内に送り出される。又、コントローラ１６は、軸方向移動手段１５でスクリュー１３に所定の背圧をかけつつ、回転駆動手段１４でスクリュー１３を回転駆動させるようになっており、テーパー部２０内及び円筒状の本体部１７の先端側部分の内部側に送り出されて、例えば油圧駆動のインラインスクリュー式射出成形機の場合、可塑化状態にある成形材料の圧力でスクリュー１３が後退される。 When the controller 16 rotationally drives the screw 13 by the rotation driving means 14, the molding material supplied into the main body 17 of the heating cylinder 12 is plasticized and plasticized by the rotation of the screw 13. The formed molding material is fed into the tapered portion 20 on the tip side of the heating cylinder 12. The controller 16 is configured to rotate the screw 13 by the rotation driving means 14 while applying a predetermined back pressure to the screw 13 by the axial movement means 15, and within the tapered portion 20 and the cylindrical main body portion. In the case of, for example, a hydraulically driven in-line screw injection molding machine, the screw 13 is retracted by the pressure of the molding material in a plasticized state.
　コントローラ１６は、スクリュー１３が所定距離だけ後退されて所定量の成形材料がテーパー部２０内に収容されたことを検知したならば、軸方向移動手段１５でスクリュー１３の位置を保持すると共に、回転駆動手段１４によるスクリュー１３の回転を停止する。しかる後、コントローラ１６が軸方向移動手段１５によってスクリュー１３を所定速度で前進させると、そのスクリュー１３の前進により、可塑化されてテーパー部２０内に収容された成形材料が加熱筒１２先端のノズル孔１９から射出され、可塑化された成形材料が型締装置により型締めされた金型内に充填されることとなる。 If the controller 16 detects that the screw 13 has been retracted by a predetermined distance and a predetermined amount of molding material has been accommodated in the taper portion 20, the controller 16 holds the position of the screw 13 with the axial movement means 15 and rotates it. The rotation of the screw 13 by the driving means 14 is stopped. Thereafter, when the controller 16 advances the screw 13 at a predetermined speed by the axial direction moving means 15, the molding material plasticized and accommodated in the tapered portion 20 by the advance of the screw 13 is a nozzle at the tip of the heating cylinder 12. The molding material injected from the hole 19 and plasticized is filled into a mold clamped by a mold clamping device.
　又、本実施形態では、コントローラ１６は、スクリュー１３が所定距離だけ後退されて（計量完了）からスクリュー１３を軸方向移動手段１５で前進させる（射出開始）までの時間（計量樹脂貯留時間）が所定時間以内（例えば、５分以内、より好ましくは１０分以内）となるように制御する。 In the present embodiment, the controller 16 has a time (measurement resin storage time) from when the screw 13 is retracted by a predetermined distance (measurement completion) to when the screw 13 is advanced by the axial movement means 15 (injection start). Control is performed within a predetermined time (for example, within 5 minutes, more preferably within 10 minutes).
　ここで、本発明者は、超高速・超高圧射出による成形品の強度低下の原因を研究し、本質的な原因をつきとめた。 Here, the present inventor studied the cause of the strength reduction of the molded product due to the ultra-high-speed and ultra-high-pressure injection, and found the essential cause.
　詳しくは、本発明者は、加熱筒１２のテーパー部２０のテーパー角度θを２０°以下とした成形機においては、成形材料（樹脂）の局部的に異常高温となる局部発熱が抑制され、図３及び図４に示すように、可塑化された成形材料を超高速で射出しても成形品の大幅な強度低下はみられず、むしろ可塑化された成形材料を高速で射出するほど超高速・超高圧射出の効果が発揮されて、成形品の強度が向上することをつきとめた。 Specifically, the present inventor shows that in the molding machine in which the taper angle θ of the taper portion 20 of the heating cylinder 12 is 20 ° or less, local heat generation of the molding material (resin) that is locally abnormally high is suppressed. As shown in FIGS. 3 and 4, even when the plasticized molding material is injected at an ultra-high speed, the strength of the molded product is not significantly reduced.・ It was found that the strength of the molded product was improved by the effect of ultra-high pressure injection.
　可塑化されてテーパー部２０内に収容された成形材料（樹脂）は、スクリュー１３による押圧により加圧されて金型内へ送られる際に、テーパー部２０やノズル孔１９の内壁との摩擦抵抗によって圧力損失を生じ、その圧力損失によって成形材料自体が自己発熱（せん断発熱）する。テーパー角度θが２０°以下である成形機においては、テーパー部２０全長とノズル孔１９の内面全体で均等に圧力損失を生じ、その結果射出方向に無理なく徐々に成形材料が自己発熱する。これに対して、テーパー角度θが２５°以上である成形機では、可塑化された成形材料を高速で射出するほど、テーパー部２０の先端とノズル孔１９の内壁に集中して圧力損失を生じ、その結果成形材料自体の自己発熱（せん断発熱）も集中し、局部的に異常高温となる局部発熱を生じ、射出された成形材料の発熱が均一でなくなる。射出されて金型内に充填された成形材料の温度が均一でないと、局部的に異常高温になった成形材料が分解（低分子量化）し変質したり、成形材料の冷却による収縮が不均一になるので、成形品の強度が低下したり、成形品の寸法精度が著しく低下するのである。 When the molding material (resin) plasticized and accommodated in the taper portion 20 is pressed by the screw 13 and sent into the mold, the friction resistance between the taper portion 20 and the inner wall of the nozzle hole 19 is obtained. Causes a pressure loss, and the pressure loss causes the molding material itself to self-heat (shear heat). In a molding machine having a taper angle θ of 20 ° or less, pressure loss is evenly generated across the entire length of the tapered portion 20 and the entire inner surface of the nozzle hole 19, and as a result, the molding material gradually self-heats gradually without difficulty in the injection direction. On the other hand, in a molding machine having a taper angle θ of 25 ° or more, the pressure loss occurs more concentrated on the tip of the tapered portion 20 and the inner wall of the nozzle hole 19 as the plasticized molding material is injected at a higher speed. As a result, the self-heating (shearing heat) of the molding material itself is concentrated, and local heating that is locally abnormally high occurs, and the injection molding material does not generate heat uniformly. If the temperature of the molding material that is injected and filled in the mold is not uniform, the molding material that has become extremely hot locally will decompose (lower molecular weight) and change its quality, or the shrinkage due to cooling of the molding material will be uneven. As a result, the strength of the molded product is reduced, and the dimensional accuracy of the molded product is significantly reduced.
　そこで、本実施形態にあっては、加熱筒１２のテーパー部２０のテーパー角度θを、３°以上２０°以下、より好ましくは３°以上１５°以下となるように構成することにより、成形材料の局部的に異常高温となる局部発熱が抑制され、射出され金型内に充填された成形材料の温度が均一になるので、可塑化された成形材料を超高速・超高圧射出して得られる成形品の品質を向上させることが可能となる。 Therefore, in the present embodiment, by forming the taper angle θ of the taper portion 20 of the heating cylinder 12 to be 3 ° or more and 20 ° or less, more preferably 3 ° or more and 15 ° or less, a molding material is obtained. The local heat generation, which is locally abnormally high, is suppressed, and the temperature of the molding material injected and filled in the mold becomes uniform, so it can be obtained by injection of plasticized molding material at ultra high speed and ultra high pressure It becomes possible to improve the quality of the molded product.
　但し、ＧＦ（グラスファイバー）を含有する樹脂や融点の高いエンジニアリングプラスチック等、熱可塑性樹脂の中でも流動性の低い樹脂の場合、テーパー角度θを５°以下とすると、テーパー部２０での流動抵抗が高くなり、連続射出成形初期段階の１ショット目の射出成形までに時間がかかり、実用的でない。よって、成形する樹脂の流動性により３°から２０°の範囲から最適なテーパー角度θを選択することも有効である。 However, in the case of a resin having low fluidity among thermoplastic resins such as a resin containing GF (glass fiber) and an engineering plastic having a high melting point, if the taper angle θ is 5 ° or less, the flow resistance at the tapered portion 20 is reduced. It takes a long time until the first shot injection molding in the initial stage of continuous injection molding, which is not practical. Therefore, it is also effective to select the optimum taper angle θ from the range of 3 ° to 20 ° depending on the fluidity of the resin to be molded.
　又、加熱筒１２のテーパー部２０のテーパー角度θを２０°以下とした成形機においては、テーパー角度θが２０°を超える従来の成形機による成形品に比べて、著しい成形品品質の向上が認められたが、図５に示すように、重量が軽い低強度成形品が時々発生した。この重量が軽い低強度成形品は、強度が平均重量の成形品の強度に比べて劣ることが判明した。 Further, in the molding machine in which the taper angle θ of the tapered portion 20 of the heating cylinder 12 is 20 ° or less, the quality of the molded product is remarkably improved as compared with the molded product by the conventional molding machine in which the taper angle θ exceeds 20 °. Although it was recognized, as shown in FIG. 5, a low-strength molded product having a light weight was occasionally generated. It has been found that the low-strength molded product having a light weight is inferior to the strength of the average-weight molded product.
　この重量が軽い低強度成形品は、加熱筒１２のテーパー部２０内壁及び円筒状の本体部１７の先端側部分の内壁の表面温度が、テーパー部２０内及び円筒状の本体部１７の先端側部分の内部に収容されて可塑化状態にある成形材料の実温度に比べて所定温度以上低い場合に発生することがわかった。 This low-strength molded product that is light in weight is such that the surface temperature of the inner wall of the tapered portion 20 of the heating cylinder 12 and the inner wall of the distal end side portion of the cylindrical main body portion 17 It has been found that this occurs when the temperature is lower than a predetermined temperature compared to the actual temperature of the molding material contained in the portion and in a plasticized state.
　テーパー部２０内壁及び円筒状の本体部１７の先端側部分の内壁の表面温度が、テーパー部２０内及び円筒状の本体部１７の先端側部分の内部に収容されて可塑化状態にある成形材料（樹脂）の実温度に比べて所定温度以上低いと、そのテーパー部２０の内壁或いは円筒状の本体部１７の先端側部分の内壁に接触する成形材料の実温度が低下する。その結果、実温度が低下した成形材料の流動性が悪くなり、その成形材料はテーパー部２０内或いは円筒状の本体部１７の先端側部分の内部に滞留する。テーパー部２０内或いは円筒状の本体部１７の先端側部分の内部に滞留した成形材料は変質して可塑性が失われる。このテーパー部２０内或いは円筒状の本体部１７の先端側部分の内部に滞留して変質した成形材料がテーパー部２０の内壁或いは円筒状の本体部１７の先端側部分の内壁から剥がれて混入すると、変質した成形材料が金型のキャビティへの充填途中に金型のキャビティへと繋がる成形材料の流路（スプルー、ランナー、ゲート）に詰まり、金型のキャビティへの成形材料の充填量が不足する。その結果、成形品重量が軽くなり、成形品強度が低下するのである。又、変質した成形材料が成形品に混入した場合には、例えば引張強度試験における破壊の起点となり、成形品強度が著しく低下するのである。 Molding material in which the surface temperature of the inner wall of the taper portion 20 and the inner wall of the tip end portion of the cylindrical main body portion 17 is housed in the taper portion 20 and the tip end portion of the cylindrical main body portion 17 and is in a plasticized state. If the temperature is lower than the actual temperature of the (resin) by a predetermined temperature or more, the actual temperature of the molding material that comes into contact with the inner wall of the tapered portion 20 or the inner wall of the distal end portion of the cylindrical main body portion 17 is lowered. As a result, the flowability of the molding material whose actual temperature has decreased is deteriorated, and the molding material stays in the tapered portion 20 or the tip side portion of the cylindrical main body portion 17. The molding material staying in the taper portion 20 or in the tip side portion of the cylindrical main body portion 17 changes in quality and loses its plasticity. When the molding material staying and changing in the tapered portion 20 or in the distal end portion of the cylindrical main body portion 17 is peeled off from the inner wall of the tapered portion 20 or the inner wall of the distal end portion of the cylindrical main body portion 17 and mixed. In the middle of filling the mold cavity into the mold cavity, the molding material flow path (sprue, runner, gate) that leads to the mold cavity is clogged, and the mold cavity has insufficient filling amount. To do. As a result, the weight of the molded product is reduced and the strength of the molded product is reduced. Further, when a deteriorated molding material is mixed into a molded product, for example, it becomes a starting point of fracture in a tensile strength test, and the strength of the molded product is remarkably lowered.
　そこで、本実施形態にあっては、加熱筒１２のテーパー部２０内壁及び円筒状の本体部１７の先端側部分の内壁の表面温度（加熱筒内壁温度）を、テーパー部２０内及び円筒状の本体部１７の先端側部分の内部に収容されて可塑化状態にある成形材料の実温度（計量樹脂実温度）に比べて－５℃以上とし、好ましくは－５℃から＋２０℃の範囲内の温度に維持することにより、テーパー部２０内での成形材料の滞留を抑制することができ、さらに変質した成形材料の混入もなくなるので、図６に示すように、重量が軽い低強度成形品の発生を防止することが可能となる。加熱筒内壁温度と計量樹脂実温度との温度差（加熱筒内温度差）の上限を好ましくは＋２０℃とするのは、加熱筒内温度差を＋３０℃以上にすると、加熱筒１２先端に収容されて可塑化状態にある成形材料の熱分解による低分子量化が早まり、計量完了から射出開始までの許容時間が短くなり過ぎて、実用的でないためである。 Therefore, in the present embodiment, the surface temperature of the inner wall of the tapered portion 20 of the heating cylinder 12 and the inner wall of the distal end portion of the cylindrical main body portion 17 (heating cylinder inner wall temperature) is set to the inside of the tapered section 20 and the cylindrical Compared to the actual temperature of the molding material housed in the distal end portion of the main body portion 17 and in a plasticized state (actual temperature of the metering resin), it should be −5 ° C. or more, preferably in the range of −5 ° C. to + 20 ° By maintaining the temperature, stagnation of the molding material in the tapered portion 20 can be suppressed, and further, the mixed molding material can be prevented from being mixed. Therefore, as shown in FIG. Occurrence can be prevented. The upper limit of the temperature difference between the heating cylinder inner wall temperature and the measured resin actual temperature (heating cylinder temperature difference) is preferably + 20 ° C. If the temperature difference in the heating cylinder is + 30 ° C or higher, the upper end of the heating cylinder 12 is accommodated. This is because the molding material in a plasticized state is rapidly reduced in molecular weight by thermal decomposition, and the allowable time from the completion of measurement to the start of injection becomes too short, which is not practical.
　又、加熱筒１２のテーパー部２０のテーパー角度θを２０°以下とした成形機においては、テーパー角度θが２０°を超える従来の成形機による成形品に比べて、著しい成形品品質の向上が認められたが、図５に示すように、重量が重い低強度成形品が時々発生した。この重量が重い低強度成形品は、強度が平均重量の成形品の強度に比べて劣ることが判明した。 Further, in the molding machine in which the taper angle θ of the tapered portion 20 of the heating cylinder 12 is 20 ° or less, the quality of the molded product is remarkably improved as compared with the molded product by the conventional molding machine in which the taper angle θ exceeds 20 °. Although recognized, as shown in FIG. 5, a low-strength molded product with a heavy weight was occasionally generated. It has been found that the low-strength molded product having a heavy weight is inferior to the strength of the average-weight molded product.
　この重量が重い低強度成形品は、スクリュー１３が所定距離だけ後退されてからスクリュー１３を軸方向移動手段１５で前進させるまでの時間が通常より長い場合に発生することがわかった。 It was found that the low-strength molded product having a heavy weight occurs when the time from when the screw 13 is retracted by a predetermined distance until the screw 13 is advanced by the axial movement means 15 is longer than usual.
　スクリュー１３が所定距離だけ後退されてからスクリュー１３を軸方向移動手段１５で前進させるまでの時間が通常より長いと、テーパー部２０内に収容された成形材料（樹脂）がヒーター２１によって加熱又は高温を持続されて、加熱又は高温を持続された成形材料が低分子量化して流動性は向上し、金型のキャビティへの成形材料の充填量が過剰になる。その結果、成形品重量が重くなり、低分子量化した樹脂により成形品強度が低下するのである。 If the time from when the screw 13 is retracted by a predetermined distance until the screw 13 is advanced by the axial movement means 15 is longer than usual, the molding material (resin) accommodated in the tapered portion 20 is heated or heated by the heater 21. Thus, the molding material maintained at a high temperature or at a high temperature has a low molecular weight and fluidity is improved, and the filling amount of the molding material into the mold cavity becomes excessive. As a result, the weight of the molded product increases, and the strength of the molded product decreases due to the resin having a low molecular weight.
　そこで、本実施形態にあっては、射出成形を行う際に、スクリュー１３が所定距離だけ後退されてからスクリュー１３を軸方向移動手段１５で前進させるまでの時間（計量樹脂貯留時間）が所定時間以内（例えば、５分以内、より好ましくは１０分以内）となるように制御することにより、樹脂の低分子量化を抑制することができ、図７に示すように、重量が重い低強度成形品の発生を防止することが可能となる。 Therefore, in the present embodiment, when injection molding is performed, the time from when the screw 13 is retracted by a predetermined distance until the screw 13 is advanced by the axial movement means 15 (measured resin storage time) is a predetermined time. By controlling to be within (for example, within 5 minutes, more preferably within 10 minutes), the low molecular weight of the resin can be suppressed. As shown in FIG. Can be prevented.
　以上、本発明の好適な実施形態について説明したが、本発明は上記実施形態には限定されず他の様々な実施形態を採ることが可能である。 The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.
　例えば、図８及び図９に示すように、テーパー部２０先端とノズル孔１９との間に、ノズル孔１９に向かい断面積がほぼ一定に形成された先端通路２６を形成しても良く、図１０及び図１１に示すように、テーパー部２０先端とノズル孔１９との間に、ノズル孔１９に向かい先細り形状に形成された先端通路２７を形成しても良い。 For example, as shown in FIGS. 8 and 9, a tip passage 26 having a substantially constant cross-sectional area toward the nozzle hole 19 may be formed between the tip of the tapered portion 20 and the nozzle hole 19. As shown in FIG. 10 and FIG. 11, a tip passage 27 that is tapered toward the nozzle hole 19 may be formed between the tip of the tapered portion 20 and the nozzle hole 19.

Claims (4)

  1. 　成形材料を加熱する加熱筒と、該加熱筒内に回転自在且つ軸方向に移動自在に収容されたスクリューと、該スクリューを回転駆動させる回転駆動手段と、上記スクリューを軸方向に移動させる軸方向移動手段とを備え、
    　上記スクリューを上記回転駆動手段で回転駆動させて、そのスクリューの回転により上記加熱筒内に供給される成形材料を可塑化させて上記加熱筒先端側に送り出し、上記スクリューを軸方向後方に移動させて、上記加熱筒の先端に所定量の可塑化溶融状態の成形材料を計量したならば、上記スクリューを上記軸方向移動手段で軸方向前方に移動させて、可塑化された成形材料を上記加熱筒先端から射出するインラインスクリュー式の射出成形機において、
    　上記加熱筒は、成形材料が供給される円筒状の本体部と、その本体部先端に繋げて設けられ、ノズル孔に向かい先細り形状に形成されたテーパー部とを有し、
    　上記加熱筒のテーパー部のテーパー角度が３°以上２０°以下となるように構成したことを特徴とする射出成形機。     A heating cylinder for heating the molding material, a screw accommodated in the heating cylinder so as to be rotatable and movable in the axial direction, a rotational drive means for rotationally driving the screw, and an axial direction for moving the screw in the axial direction Moving means,
    The screw is rotated by the rotation driving means, the molding material supplied into the heating cylinder is plasticized by the rotation of the screw, and is sent to the leading end side of the heating cylinder, and the screw is moved rearward in the axial direction. When a predetermined amount of the plasticized and molten molding material is weighed at the tip of the heating cylinder, the screw is moved forward in the axial direction by the axial movement means, and the plasticized molding material is heated. In the inline screw type injection molding machine that injects from the tip of the cylinder,
    The heating cylinder has a cylindrical main body portion to which a molding material is supplied, and a tapered portion that is connected to the front end of the main body portion and is tapered toward the nozzle hole.
    An injection molding machine characterized in that a taper angle of the taper portion of the heating cylinder is 3 ° or more and 20 ° or less.
  2. 　上記加熱筒のテーパー部内壁の表面温度が、そのテーパー部内に収容されて可塑化状態にある成形材料の実温度に比べて－５℃以上の温度に維持される請求項１に記載の射出成形機。 The injection molding according to claim 1, wherein the surface temperature of the inner wall of the tapered portion of the heating cylinder is maintained at a temperature of -5 ° C or higher as compared with the actual temperature of the molding material contained in the tapered portion and in a plasticized state. Machine.
  3. 　上記回転駆動手段及び上記軸方向移動手段を制御する制御手段を備え、
    　該制御手段は、上記スクリューが軸方向後方に所定距離移動されてからそのスクリューを上記軸方向移動手段で軸方向前方に移動させるまでの時間が所定時間以内となるように制御するものである請求項１又は２に記載の射出成形機。     Control means for controlling the rotation driving means and the axial movement means;
    The control means controls the time from when the screw is moved a predetermined distance rearward in the axial direction to when the screw is moved forward in the axial direction by the axial movement means within a predetermined time. Item 3. The injection molding machine according to Item 1 or 2.
  4. 　請求項１又は２に記載の射出成形機により射出成形を行う際に、上記スクリューが軸方向後方に所定距離移動されてからそのスクリューを上記軸方向移動手段で軸方向前方に移動させるまでの時間が所定時間以内となるように制御することを特徴とする射出成形方法。 When injection molding is performed by the injection molding machine according to claim 1 or 2, a time from when the screw is moved a predetermined distance rearward in the axial direction until the screw is moved forward in the axial direction by the axial movement means. Is controlled to be within a predetermined time.
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