Injection molding machine

Abstract

To provide an injection molding machine that can prevent vent-up of resin material without reducing productivity and has excellent heating efficiency of resin material.SOLUTION: An injection molding machine 1 comprises a screw 10 having a helical flight 12 on an outer periphery of a shaft portion 11 and rotating around a rotation axis L, and a barrel 20 having a feed opening 21, a cylinder 22 communicating with the feed opening 21 and accommodating the screw 10, and a vent opening 23, wherein the screw 10 has a compression melting section 10b that compresses and melts resin material 2, and a supply section 10a that supplies unmelted resin material 2 fed from the feed opening 21 of the barrel 20 into the cylinder 22 to the compression melting section 10b, the vent opening 23 of the barrel 20 opens at the supply section 10a of the screw 10, and the supply section 10a of the screw 10 is provided with a compression deformation section 18 that compresses and deforms the resin material 2 while keeping the resin material unmelted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an injection molding machine. [Background technology]

[0002] Patent Document 1 below discloses a vent-type injection molding machine. This vent-type injection molding machine includes a screw provided in a cylinder section and a vent section. The vent section has an upwardly opening vent port for volatilizing volatile components in the molten resin in the compression melting section, which is the second stage of the screw. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-100875 Summary of the Invention [Problem to be solved by the invention]

[0004] The injection molding machine suffers from the problem that if the amount of resin material supplied to the barrel section is too large, the molten resin overflows from the vent opening in the compression melt section of the screw, a phenomenon known as "vent-up." Therefore, if the amount of resin material supplied to the barrel section is reduced in order to address this problem, the molding cycle may be extended, which may result in a decrease in productivity. Furthermore, in the design of this type of injection molding machine, a technology is needed to improve the heating efficiency required for heating the resin material before injection.

[0005] The present invention has been made in consideration of such problems, and aims to provide an injection molding machine that can prevent venting of resin material without reducing productivity and has excellent heating efficiency for resin material. [Means for solving the problem]

[0006] One aspect of the present invention is a screw having a spiral flight on the outer periphery of a shaft portion and rotating around a rotation axis; a barrel having an inlet, a cylinder communicating with the inlet and accommodating the screw, and a vent port; Equipped with The screw has a compression melting section that compresses and melts a resin material, and a supply section that supplies the unmelted resin material that has been introduced into the cylinder from the inlet of the barrel to the compression melting section, the vent port of the barrel opens at the supply portion of the screw, The supply portion of the screw is provided with a compression deformation portion that compresses and deforms the resin material while it is still unmelted. injection molding machine, is located. [Effects of the Invention]

[0007] In the injection molding machine of the above aspect, the cylinder of the barrel accommodates a screw. The supply section of the screw is a part that supplies unmelted resin material, which is fed into the cylinder from an inlet of the barrel, to a compression-melting section, and the supply section is provided with a vent port of the barrel. In addition, the supply section is provided with a compression-deformation section that compresses and deforms the unmelted resin material.

[0008] In the injection molding machine having the above configuration, the vent port of the barrel opens in the supply section of the screw, so that vent-up, which occurs when the molten resin overflows from the vent port due to internal resin pressure when the vent port opens in the compressed melt section of the screw, can be prevented. Therefore, there is no need to take measures to reduce the amount of resin material supplied to the cylinder in anticipation of vent-up, and a decrease in productivity can be prevented.

[0009] Furthermore, with the injection molding machine having the above configuration, shear heat can be imparted to the unmelted resin material by compressing and deforming it in the compressive deformation portion of the screw, and moisture can be removed from the resin material by heating the resin material through shear heat. This eliminates the need for a prior drying process for the resin material, and reduces the energy required to heat the resin material. In addition, compressing and deforming the unmelted resin material in the compressive deformation portion of the screw increases the surface area of ​​the resin material. This allows heat to be efficiently transferred throughout the resin material.

[0010] According to the above-described aspect, it is possible to provide an injection molding machine that can prevent venting of the resin material without reducing productivity and that has excellent heating efficiency for the resin material. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of an injection molding machine according to a first embodiment. [Figure 2] An enlarged view of the injection molding machine in Figure 1. [Figure 3] 3 is a partially enlarged view schematically showing a state in which unmelted resin material is fed toward a compression melting portion in a feed portion of the screw in FIG. 2. FIG. [Figure 4] 5A and 5B are diagrams schematically illustrating the progress of compressive deformation of an unmelted resin material. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the above aspects are described below.

[0013] In the injection molding machine of the above aspect, it is preferable that the compressive deformation portion is configured by partially expanding the outer diameter of the shank portion of the screw in the supply portion.

[0014] According to this injection molding machine, the outer diameter of the shank of the screw supply section is partially enlarged to partially reduce the groove depth of the screw, thereby physically compressing and deforming the unmelted resin material.

[0015] In the injection molding machine of the above aspect, it is preferable that the compressive deformation portion is configured by gradually expanding the outer diameter of the shank portion in the supply portion of the screw in at least one direction of the axial direction of the shank portion and the spiral direction of the flight.

[0016] This injection molding machine allows the unmelted resin material to be gradually compressed and deformed in the supply section of the screw while being supplied to the compression-melting section, thereby preventing large fluctuations in the screw torque when compressing and deforming the unmelted resin material.

[0017] In the injection molding machine of the above aspect, it is preferable that the vent port of the barrel opens in an exhaust portion of the supply portion of the screw that is offset in the axial direction of the shank from the compressive deformation portion.

[0018] According to this injection molding machine, it is possible to prevent vent-up by opening the vent port of the barrel in the exhaust section, which is away from the compressive deformation section, which is the section of the supply section of the screw where vent-up is most likely to occur.

[0019] In the injection molding machine of the above aspect, the exhaust portion of the screw is preferably located downstream of the compressive deformation portion in the material feed direction of the resin material.

[0020] According to this injection molding machine, by setting the exhaust section of the screw downstream of the compression deformation section in the material feed direction, the amount of moisture discharged from the resin material increases as the compression deformation of the unmelted resin material progresses, and the moisture discharged from the resin material can be efficiently discharged to the outside through the vent port of the barrel.

[0021] Hereinafter, specific examples of the injection molding machine according to the above-described embodiment will be described with reference to the drawings.

[0022] In the drawings used to explain this embodiment, unless otherwise specified, the axial direction of the shaft portion of the screw that constitutes the injection molding machine is indicated by arrow X, and the spiral direction of the flight of this screw is indicated by arrow Y.

[0023] (Embodiment 1) The injection molding machine 1 of the first embodiment shown in Figure 1 is an apparatus for plasticizing and injecting a granular or pelletized resin material 2. This injection molding machine 1 includes a screw 10, a barrel 20, and a heating device 30. This injection molding machine 1 is used with the screw 10 positioned so that it faces horizontally. The resin material 2 is a material that emits a high-boiling-point volatile gas when melted.

[0024] 1. Structure of screw 10 The screw 10 has a spiral flight 12 on the outer periphery of a shaft portion 11. The shaft portion 11 extends linearly in the axial direction X. The flight 12 extends spirally in a spiral direction Y (see Figure 2). As a result, a groove through which the resin material 2 moves is formed between the shaft portion 11 and the flight 12, extending in the spiral direction Y. One end (the right end in Figure 1) of the shaft portion 11 is a coupling 11a that is connected to a drive device (not shown). By connecting the coupling 11a of the shaft portion 11 to the drive device, the screw 10 becomes rotatable around the rotation axis L and capable of reciprocating along the rotation axis L.

[0025] 1, the screw 10 has a supply section 10a, a compression-melting section 10b, and a metering section 10c. The compression-melting section 10b is provided downstream of the supply section 10a in the material feed direction D, and the metering section 10c is provided downstream of the compression-melting section 10b in the material feed direction D (at the most downstream position of the screw 10).

[0026] The supply section 10a is a section located at the most upstream side in the material feed direction D. The supply section 10a has the function of quantitatively and continuously supplying the unmelted resin material 2, which has been fed into the cylinder 22 from the inlet 21 of the barrel 20, to the compression melt section 10b by the rotation of the screw 10 about the rotation axis L. In this supply section 10a, since the resin material 2 is unmelted and bulky, the outer diameter d (see FIG. 1) of the shaft 11 of the screw 10 is narrow (i.e., the groove depth of the screw 10 is deep).

[0027] As will be described in detail later, this supply unit 10a is provided with a compressive deformation unit 18 that compresses and deforms the unmelted resin material 2. That is, in this embodiment, the supply unit 10a not only functions as a supply mechanism for the unmelted resin material 2, but also serves the function of compressing and deforming this resin material 2. The supply unit 10a is set to a temperature condition below the melting temperature of the resin material 2 in order to maintain the unmelted state of the resin material 2. Therefore, in this supply unit 10a, only moisture, which has a lower boiling point than volatile gases, is discharged from the unmelted resin material 2.

[0028] The compression-melting section 10b has a compression-melting function of compressing and melting (plasticizing) the resin material 2 supplied from the supply section 10a. This compression-melting section 10b is a zone where the outer diameter of the shaft section 11 of the screw 10 continuing from the supply section 10a gradually increases (i.e., the groove depth of the screw 10 gradually becomes shallower). The compression-melting section 10b is set to a temperature condition that exceeds the melting temperature of the resin material 2 in order to melt the resin material 2. Therefore, in this compression-melting section 10b, high-boiling-point volatile gases are emitted from the resin material 2 as the resin material 2 melts. This compression-melting section 10b is also called the "compression section."

[0029] The metering section 10c has a metering function of measuring the resin material 2 plasticized in the compression melting section 10b. This compression melting section 10b is a zone continuing from the compression melting section 10b, in which the outer diameter of the shaft section 11 of the screw 10 is constant (i.e., the groove depth of the screw 10 is constant).

[0030] The structures of the compression and melting section 10b and the metering section 10c are known, and detailed explanation of these structures will be omitted in this specification.

[0031] 2. Barrel 20 Structure The barrel 20 has an inlet 21, a cylinder 22, and a vent port 23. The inlet 21 is provided for charging the granular resin material 2 into the cylinder 22. A hopper (not shown) to which the resin material 2 is supplied is connected to the top of the inlet 21. The resin material 2 supplied to the hopper is charged into the cylinder 22 through the inlet 21 by falling under its own weight. The cylinder 22 is a cylindrical internal space that communicates with the inlet 21 and accommodates the screw 10 so that it can rotate about the rotation axis L and move back and forth along the rotation axis L.

[0032] The vent port 23 opens upward to connect the cylinder 22 to the outside of the barrel 20. In this embodiment, the vent port 23 opens in an exhaust section 19 of the supply section 10a of the screw 10 that is offset in the axial direction X from the compressive deformation section 18. In this embodiment, the exhaust section 19 is a portion located downstream of the compressive deformation section 18 in the material feed direction D of the resin material 2. The vent port 23 allows moisture discharged from the unmelted resin material 2 in the supply section 10a of the screw 10 to be exhausted to the outside.

[0033] Although not specifically shown, a nozzle is provided at the tip end (left end in FIG. 1) of the barrel 20 for injecting the resin material 2 plasticized by compression and melting into a mold outside the cylinder 22.

[0034] 3. Structure of the heating device 30 The heating device 30 is a heater provided on the outer periphery of the barrel 20. A plurality of heating devices 30 are provided in regions radially outside the cylinder 22 corresponding to the supply section 10a, the compression melting section 10b, and the metering section 10c of the screw 10, respectively. Therefore, each of the supply section 10a, the compression melting section 10b, and the metering section 10c of the screw 10 can be heated by the heat generated by the heater of the heating device 30. Note that the location where the heating device 30 is provided is not limited to this and can be appropriately changed as needed. The heating device 30 corresponding to the supply section 10a of the screw 10 is controlled so that the resin material 2 remains in an unmelted state in the supply section 10a. This heating device 30 may be omitted as needed.

[0035] As shown in FIG. 2, in the supply section 10a of the screw 10, the shaft portion 11 includes a plurality of shaft regions 13, 14, 15, 16, 17. Both of the two shaft regions 13, 17 are regions where the outer diameter d of the shaft portion 11 is d1 (the region where the groove depth of the screw 10 is a). The shaft region 14 is a region where the outer diameter d of the shaft portion 11 gradually increases from d1 to d2 in at least one of the axial direction X and the helical direction Y. That is, in this shaft region 14, the outer diameter d of the shaft portion 11 may increase only in the axial direction X, or may increase only in the helical direction Y, or may increase in both the axial direction X and the helical direction Y. The shaft region 15 is a region where the outer diameter d of the shaft portion 11 is d2 (>d1) (the region where the groove depth of the screw 10 is b (<a)). The shaft region 16 is a region where the outer diameter d of the shaft portion 11 gradually decreases from d2 to d1 in at least one of the axial direction X and the helical direction Y. That is, in this shaft region 16, the outer diameter d of the shaft portion 11 may decrease only in the axial direction X, or may decrease only in the helical direction Y, or may decrease in both the axial direction X and the helical direction Y.

[0036] In this embodiment, the outer diameter d of the shank portion 11 of the screw 10 gradually increases from d1 to d2 in the shank region 14, then remains at d2 in the shank region 15, and gradually decreases from d2 to d1 in the shank region 16. In this case, both of the two shank regions 14 and 15 are regions in which the outer diameter d of the shank portion 11 in the supply section 10a of the screw 10 is increased relative to the shank region 13. The region combining the two shank regions 14 and 15 is a region in which the outer diameter d of the shank portion 11 is partially increased relative to the two shank regions 13 and 17, and is also a region in which the outer diameter d of the shank portion 11 is gradually increased from the shank region 13. As the shank portion 11 becomes thicker, the groove depth becomes shallower, and the unmelted resin material 2 around the shank portion 11 is compressed and deformed. Therefore, the portions of the screw 10 corresponding to the two shank regions 14 and 15 of the shank portion 11 constitute a compressive deformation portion 18 capable of compressively deforming the unmelted resin material 2.

[0037] 4. Compression deformation of resin material 2 Next, the compressive deformation of the resin material 2 will be described with reference to FIGS.

[0038] As shown in Figure 3, the unmelted resin material 2 undergoes compressive deformation as it passes through the supply section 10a of the screw 10. The unmelted resin material 2 deforms, for example, from an initial state C0 through a first deformed state C1 to a second deformed state C2. At this time, shear heat is imparted to the resin material 2, and the surface area increases due to the compressive deformation of the resin material 2. This promotes the discharge of moisture from the resin material 2. The moisture discharged from the resin material 2 is exhausted to the outside through the vent port 23 of the barrel 20.

[0039] 4, the moisture contained in the center of the unmelted resin material 2 is more easily discharged as the deformation state of the unmelted resin material 2 progresses. That is, the moisture contained in the center of the resin material 2 is more easily discharged in the first deformed state C1 than in the initial state C0, and is more easily discharged in the second deformed state C2 than in the first deformed state C1.

[0040] 5. Effects According to the above-described first embodiment, the following effects can be obtained.

[0041] In the injection molding machine 1 of the first embodiment, the screw 10 is housed in the cylinder 22 of the barrel 20. The supply section 10a of the screw 10 is a portion that supplies the unmelted resin material 2 that has been introduced into the cylinder 22 from the inlet 21 of the barrel 20 to the compression-melting section 10b, and the vent port 23 of the barrel 20 is open in this supply section 10a. In addition, the supply section 10a is provided with a compression-deformation section 18 that compresses and deforms the resin material 2 while it is still unmelted.

[0042] According to the injection molding machine 1, the vent port 23 of the barrel 20 opens in the supply portion 10a of the screw 10, and therefore it is possible to prevent vent-up, in which the molten resin overflows from the vent port 23 due to internal resin pressure when the vent port 23 opens in the compressed melt portion 10b of the screw 10. Therefore, it is not necessary to take measures to reduce the amount of resin material 2 supplied to the cylinder 22 in anticipation of vent-up, and it is possible to prevent a decrease in productivity.

[0043] Furthermore, according to the injection molding machine 1, shear heat can be imparted to the resin material 2 by compressing and deforming the unmelted resin material 2 in the compressive deformation portion 18 of the screw 10, and the heating of the resin material 2 by the shear heat can cause moisture to be expelled from the resin material 2. This eliminates the need for a prior drying process of the resin material 2, and reduces the energy required to heat the resin material 2. In addition, the surface area of ​​the resin material 2 can be increased by compressing and deforming the unmelted resin material 2 in the compressive deformation portion 18 of the screw 10. This allows heat to be efficiently transferred to and heated throughout the resin material 2.

[0044] Therefore, it is possible to provide an injection molding machine 1 that can prevent the resin material 2 from venting up without reducing productivity and that has excellent heating efficiency for the resin material 2.

[0045] According to the injection molding machine 1, by preventing vent-up, it is possible to maintain a high back pressure in the cylinder 22 of the barrel 20. This improves the kneadability of the resin material 2 in the compressed melt portion 10b and reduces variations in the density of the resin material 2. Furthermore, by reducing variations in the density of the resin material 2, it is possible to ensure the dimensional accuracy and appearance quality of the product after injection.

[0046] According to the injection molding machine 1, the outer diameter d of the shank 11 is partially expanded in the supply section 10a of the screw 10 to partially reduce the groove depth of the screw 10, thereby physically compressing and deforming the unmelted resin material 2. In particular, in this embodiment, the unmelted resin material 2 can be supplied to the compression-melting section 10b in the supply section 10a of the screw 10 while being gradually compressed and deformed. This makes it possible to prevent the torque of the screw 10 from fluctuating greatly when compressing and deforming the unmelted resin material 2.

[0047] According to the injection molding machine 1, it is possible to prevent vent-up by opening the vent port 23 of the barrel 20 in the exhaust section 19 that is separated from the compressive deformation section 18, which is the section of the supply section 10a of the screw 10 where vent-up is most likely to occur. In particular, in this embodiment, by setting the exhaust section 19 of the screw 10 downstream of the compressive deformation section 18 in the material feed direction D, it becomes possible to efficiently exhaust the moisture discharged from the resin material 2 to the outside through the vent port 23 of the barrel 20 in response to the increase in the amount of moisture discharged from the resin material 2 as the compressive deformation of the unmelted resin material 2 progresses.

[0048] 6. Other forms The present invention is not limited to the exemplary embodiments described above, and various applications and modifications are possible without departing from the scope of the present invention. For example, the following embodiments can be implemented by applying the above embodiments.

[0049] In the above embodiment, an example is given of a case where a compressive deformation portion 18 is provided at one location on the screw 10 and a vent port 23 is provided at one location on the barrel 20, but the number of compressive deformation portions 18 and vent ports 23 is not limited to this, and at least one of the compressive deformation portions 18 and the vent ports 23 may be provided in multiple numbers.

[0050] In the above-described embodiment, an example is given of the case where the exhaust section 19 of the screw 10 is set downstream of the compressive deformation section 18 in the material feed direction D, but alternatively, the exhaust section 19 of the screw 10 may be set upstream of the compressive deformation section 18 in the material feed direction D.

[0051] In the above embodiment, an example is given of gradually increasing the outer diameter d of the shaft portion 11 in the supply portion 10a of the screw 10, but instead, the outer diameter d of the shaft portion 11 may be increased in stages. [Explanation of symbols]

[0052] 1...injection molding machine, 2...resin material, 10...screw, 10a...supply section, 10b...compression melt section, 11...shank section, 12...flight, 18...compression deformation section, 19...exhaust section, 20...barrel, 21...feed port, 22...cylinder, 23...vent port, d...outside diameter of shaft section, D...material feed direction, L...rotation axis, X...axial direction, Y...spiral direction

Claims

1. a screw having a spiral flight on the outer periphery of a shaft portion and rotating around a rotation axis; a barrel having an inlet, a cylinder communicating with the inlet and accommodating the screw, and a vent port; Equipped with The screw has a compression melting section that compresses and melts a resin material, and a supply section that supplies the unmelted resin material that has been introduced into the cylinder from the inlet of the barrel to the compression melting section, the vent port of the barrel opens at the supply portion of the screw, The supply portion of the screw is provided with a compression deformation portion that compresses and deforms the resin material while it is still unmelted. Injection molding machine.

2. 2. The injection molding machine according to claim 1, wherein the compressive deformation portion is formed by partially expanding an outer diameter of the shank portion of the screw at the supply portion.

3. 3. The injection molding machine according to claim 2, wherein the compressive deformation portion is configured by gradually expanding an outer diameter of the shank portion of the screw at the supply portion in at least one direction of an axial direction of the shank portion and a spiral direction of the flight.

4. 4. The injection molding machine according to claim 1, wherein the vent port of the barrel opens in an exhaust portion of the supply portion of the screw that is deviated from the compressive deformation portion in the axial direction of the shank.

5. 5. The injection molding machine according to claim 4, wherein the exhaust portion of the screw is located downstream of the compressive deformation portion in the material feeding direction of the resin material.

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