Injection molding machine

Abstract

To provide an injection molding machine capable of reducing the size and shortening the duration of the plasticizing process.SOLUTION: An injection molding machine 1 of the present invention comprises: a barrel 2 provided with its one end having a nozzle 3 for injecting plasticized molding material; a heater 4 provided on the outer peripheral surface 2a of the barrel 2 to heat the molding material inside the barrel 2 through the barrel 2; a plunger 6 for pushing the molding material supplied into the barrel 2 to one end inside the barrel 2; and a rod 8 provided inside the barrel 2 and movable in an axial direction A of the barrel 2, having a torpedo 16 with a tapered portion formed at one end in the axial direction A that narrows from that one end to the other end, wherein the inner peripheral surface 2b of the barrel 2 has a tapered surface 20b whose inner diameter narrows from the other end to the one end in the axial direction A within the range opposite the portion where the heater 4 is provided in the outer peripheral surface 2a of the barrel 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an injection molding machine for injecting a plasticized molding material.

Background Art

[0002] Conventionally, parts such as those for automobiles are molded by using an injection molding machine and injecting a molding material such as a resin raw material. As such an injection molding machine, for example, Patent Document 1 below discloses an injection molding machine including a barrel and a screw provided in the barrel. This injection molding machine is called a so-called screw type injection molding machine, and since a single screw is used in the barrel to gradually plasticize the resin raw material while feeding it toward the nozzle side, the screw and the barrel have a long structure.

[0003] Also, for example, Patent Document 2 below discloses an injection molding machine aimed at miniaturization, which includes a barrel, a rod axially movable inside the barrel, and a torpedo provided in the middle of the rod. In this injection molding machine, the torpedo is axially movable via the movement of the rod. Thereby, the resin raw material is plasticized by moving the torpedo in one direction from the nozzle side of the barrel toward the opposite side, and the plasticized resin is injected by moving the torpedo in the other direction. Therefore, compared with the screw type injection molding machine disclosed in Patent Document 1 above, the length of the barrel in the axial direction can be shortened, so that miniaturization can be achieved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, it is known that resin raw materials with high melting points and high specific heat, such as fluororesins, are difficult to plasticize. When using the small injection molding machine disclosed in Patent Document 2 for injection molding such resin raw materials, the plasticization process takes longer compared to the screw-type injection molding machine disclosed in Patent Document 1, which has the disadvantage of being unsuitable for mass production. Therefore, there is room for improvement in small injection molding machines in terms of shortening the time required for the plasticization process.

[0006] Therefore, in view of the above circumstances, the present invention aims to provide an injection molding machine that can be miniaturized and that can shorten the time of the plasticization process. [Means for solving the problem]

[0007] An injection molding machine according to a first aspect of the present invention comprises a barrel with a nozzle for injecting plasticized molding material provided at one end, a heating unit provided on the outer circumferential surface of the barrel for heating the molding material inside the barrel via the barrel, an extrusion unit for pushing the molding material supplied to the inside of the barrel outwards at the one end, and a rod provided inside the barrel and movable in the axial direction of the barrel, having a torpedo with a tapered portion formed at one end that narrows from the one end to the other in the axial direction, wherein the inner circumferential surface of the barrel has a tapered surface in the range facing the portion on the outer circumferential surface of the barrel where the heating unit is provided, with an inner diameter that narrows from the other end to the one end in the axial direction.

[0008] Furthermore, in the injection molding machine according to the first aspect of the present invention, the inner circumferential surface of the barrel has, within the range, the tapered surface and another surface that is located on the one end side in the axial direction relative to the tapered surface and has substantially the same inner diameter along the axial direction.

[0009] Furthermore, the injection molding machine according to the first aspect of the present invention further comprises an internal heating unit provided inside the rod.

[0010] Furthermore, in the injection molding machine according to the first aspect of the present invention, the internal heating section extends into the interior of the torpedo.

[0011] Furthermore, in the injection molding machine according to the first aspect of the present invention, the extrusion unit is a linear type that moves along the axial direction, or a screw type that rotates with the axial direction as the center of rotation. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an injection molding machine that can be miniaturized and that can shorten the time of the plasticization process. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view showing the general configuration of an injection molding machine according to the first embodiment. [Figure 2] This is a conceptual diagram showing the first step of injection molding using the injection molding machine shown in Figure 1. [Figure 3] This is a conceptual diagram showing the second step of injection molding using the injection molding machine shown in Figure 1. [Figure 4] This is a conceptual diagram showing the third step of injection molding using the injection molding machine shown in Figure 1. [Figure 5] This is a conceptual diagram showing the fourth step of injection molding using the injection molding machine shown in Figure 1. [Figure 6] Figure 1 is a conceptual diagram showing the fifth step of injection molding using the injection molding machine. [Figure 7] This is a schematic cross-sectional view showing the general configuration of an injection molding machine according to the second embodiment. [Modes for carrying out the invention]

[0014] ---First Embodiment--- Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. For ease of understanding the description, in each drawing, elements having the same element or the same function are given the same reference numerals as much as possible, and duplicate descriptions are omitted.

[0015] <Overall Configuration> FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an injection molding machine 1 according to the first embodiment. For convenience of explanation, in FIG. 1, with respect to the rod 8 and the check ring 14 described later, only one side (right side of the paper surface) with respect to the axis X of the rod 8 and the check ring 14 is shown as a cross section, and the other side (left side of the paper surface) with respect to the axis X is shown as a side surface.

[0016] As shown in FIG. 1, the injection molding machine 1 internally plasticizes a resin raw material as a molding material and injects the plasticized resin raw material to the outside such as a mold. The injection molding machine 1 includes, for example, a barrel 2, a heater 4, a plunger 6, a rod 8, and a material supply unit 10.

[0017] The barrel 2 has a cylindrical shape. Hereinafter, the axial direction of the barrel 2 is referred to as the axial direction A. A nozzle 3 is provided at one end side in the axial direction A of the barrel 2. The nozzle 3 has a nozzle hole 3a and injects the plasticized resin raw material from the nozzle hole 3a toward the outside such as a mold. In FIG. 1, the nozzle 3 is shown as an open nozzle with the nozzle hole 3a opened, but the nozzle 3 may be a shut-off nozzle having a valve capable of opening and closing the nozzle hole 3a. Hereinafter, in the axial direction A, one end side (the injection side of the resin raw material) of the barrel 2 where the nozzle 3 is provided is referred to as the "lower side". Also, in the axial direction A, the other end side (the supply side of the resin raw material) of the barrel 2 opposite to the nozzle 3 is described as the "upper side".

[0018] The barrel 2 has, for example, a large-diameter portion 20 where the resin raw material is supplied, and a small-diameter portion 22 located below the large-diameter portion 20 and having an outer diameter smaller than that of the large-diameter portion 20.

[0019] The heater 4 is provided on the outer peripheral surface 2a of the barrel 2. The heater 4 is a heating unit that heats the barrel 2 from the outside and heats the resin raw material inside the barrel 2 through the barrel 2. The heater 4 includes a first heater portion 4a provided for the large-diameter portion 20 of the barrel 2, a second heater portion 4b provided for the small-diameter portion 22 of the barrel 2, and a nozzle heater portion 4c provided for the nozzle 3.

[0020] The inner peripheral surface 2b of the barrel 2 has a tapered surface 20b that is inclined with respect to the axial direction A and a parallel surface 22b (other surface) that is substantially parallel to the axial direction A in a range facing the portion of the outer peripheral surface 2a of the barrel 2 where the heater 4 is provided. The tapered surface 20b is formed such that the inner diameter narrows from the upper side to the lower side. The tapered surface 20b is formed in a range of the inner peripheral surface 2b of the barrel 2 that faces the portion of the outer peripheral surface 2a of the barrel 2 where the first heater portion 4a is provided, that is, at the position of the large-diameter portion 20. The formation range of the tapered surface 20b is set to a position below the movable range of the plunger 6 and above the movable range of the torpedo 16 (between the movable range of the plunger 6 and the movable range of the torpedo 16) in the inner peripheral surface 2b of the barrel 2.

[0021] The parallel surface 22b is located below the tapered surface 20b in the axial direction A and is formed such that the inner diameter is substantially the same along the axial direction A. The parallel surface 22b is formed in a range of the inner peripheral surface 2b of the barrel 2 that faces the portion of the outer peripheral surface 2a of the barrel 2 where the second heater portion 4b is provided, that is, at the position of the small-diameter portion 22. For example, the length of the parallel surface 22b in the axial direction A is longer than the length of the tapered surface 20b in the axial direction A.

[0022] The plunger 6 is an extrusion unit that pushes the resin material supplied into the barrel 2 downwards within the barrel 2. The plunger 6 is positioned to fit into an opening 2c formed at the upper end of the barrel 2. A through hole 6c is formed in the center of the plunger 6 through which the rod 8 passes. In other words, the plunger 6 is hollow. The plunger 6 is a linear extrusion unit that moves along the axial direction A. The plunger 6 is connected to an actuator (not shown) via a predetermined fixing member 7, for example, and moves in the axial direction A by the actuator. The plunger 6 may also move (be linked) with the movement of the rod 8 by being fixed to the rod 8.

[0023] The rod 8 is located inside the barrel 2 and is movable in the axial direction A. The rod 8 is positioned inside the barrel 2, for example, by passing through the through hole 6c of the plunger 6 (inserted into the plunger 6), and extends in the axial direction A of the barrel 2. The rod 8 is connected to an actuator (not shown) via a predetermined fixing member 9, for example, and is moved in the axial direction A by the actuator.

[0024] The rod 8 includes a stopper 12 and a torpedo 16. The stopper 12 is located at the lower end of the rod 8 and faces the nozzle 3 in the axial direction A. The torpedo 16 is located on the lower side of the rod 8 and is formed between the stopper 12 and the plunger 6. The torpedo 16 is integrally formed with the rod 8. The torpedo 16 moves integrally with the rod 8 along the axial direction A inside the barrel 2 via the movement of the rod 8.

[0025] Torpedo 16 narrows from bottom to top. reverse A tapered portion is formed. That is, the torpedo 16 is formed so that its outer diameter narrows from the bottom to the top. reverse It has a tapered outer surface, which is a tapered surface 16a. Furthermore, the torpedo 16 has a gear-shaped outer diameter at its lower end 16b, and numerous fins are formed on the end 16b.

[0026] Furthermore, a check ring 14 is provided between the torpedo 16 and the stopper 12, which can move freely between them. The check ring 14 prevents the resin material flowing from the torpedo 16 towards the nozzle 3 via the check ring 14 and the stopper 12 from flowing back in the opposite direction.

[0027] Furthermore, the rod 8 has an internal heater 18. The internal heater 18 is an internal heating unit that heats the rod 8 from the inside. The internal heater 18 extends along the axial direction A at the position of the axis X of the rod 8. The internal heater 18 extends downward from the upper end connected to a power supply (not shown) and extends at least inside the torpedo 16, thereby heating the torpedo 16 from the inside. In this way, the internal heater 18 heats the resin material supplied into the barrel 2 via the torpedo 16.

[0028] The material supply unit 10 is the part that supplies material into the barrel 2, and includes a hopper 30, a cylinder 32, a screw 34, and a preheater 36.

[0029] The hopper 30 stores pelletized (granular) resin raw material and charges the resin raw material into the cylinder 32. The cylinder 32 is a cylindrical member that is provided between the supply port 30a of the hopper 30 and the supply port 2d of the barrel 2 and extends between the supply port 30a and the supply port 2d.

[0030] The screw 34 is located inside the cylinder 32 and is rotatable by a material supply motor (not shown). The rotation of the screw 34 supplies the resin material charged into the cylinder 32 into the barrel 2 while it rotates. The preheater 36 is located on the outer circumferential surface 32a of the cylinder 32. The preheater 36 is a heating unit that heats the cylinder 32 from the outside and heats the resin material inside the cylinder 32 via the cylinder 32. In this way, the preheater 36 preheats the resin material before it is supplied into the barrel 2. The preheater 36 heats the resin material that is rotating inside the cylinder 32 by the screw 34 via the cylinder 32. As a result, the resin material is heated while being stirred, and is preheated with a high heat transfer effect.

[0031] <Injection molding process> Next, the injection molding process of resin raw materials using the injection molding machine 1 will be explained with reference to Figures 2 to 6. Figures 2 to 6 are schematic cross-sectional views of the injection molding machine 1 in Figure 1, and are conceptual diagrams showing each step of injection molding using the injection molding machine 1. For the sake of explanation, some components such as the screw 34, stopper 12, and check ring 14 in Figure 1 are omitted from the illustration in Figures 2 to 6. Although not shown, it is assumed that a mold for injecting the plasticized resin raw material is actually attached to the nozzle 3.

[0032] Figure 2 is a conceptual diagram showing the first step of injection molding using the injection molding machine 1 shown in Figure 1. As shown in Figure 2, in the first step (material supply step), a predetermined amount of pelletized resin raw material R is supplied into the barrel 2 by the material supply unit 10. At this time, the temperature inside the cylinder 32 is raised by heating the cylinder 32 with the preheater 36. As a result, the resin raw material R is preheated before being supplied into the barrel 2. The plunger 6 is located on the open port 2c side of the barrel 2 in the axial direction A, and the supply port 2d of the barrel 2 is open. The resin raw material R is supplied from the supply port 2d of the barrel 2 between the plunger 6 and the torpedo 16. At this time, the temperature inside the barrel 2 is raised by heating the barrel 2 with the first heater unit 4a and the second heater unit 4b, and by heating the rod 8 with the internal heater 18. Then, the process moves on to the second step.

[0033] Figure 3 is a conceptual diagram showing the second step of injection molding using the injection molding machine 1 shown in Figure 1. In the second step (plasticization step), the rod 8 and plunger 6 are moved from top to bottom, so that the supply port 2d of the barrel 2 is closed by the plunger 6. This prevents the plasticized resin raw material R from flowing back to the material supply unit 10. In addition, the pressing force of the plunger 6 presses the resin raw material R against the tapered surface 20b of the barrel 2. This tapered surface 20b is the part that faces the outer peripheral surface 2a heated by the first heater unit 4a, and is a part that tends to be particularly hot among the inner peripheral surface 2b of the barrel 2. The resin raw material R is plasticized when it comes into contact with this high-temperature tapered surface 20b. Furthermore, at this time, the tapered surface 16a of the torpedo 16 faces the parallel surface 22b of the barrel 2, and is indirectly heated by the heating of the small diameter portion 22 of the barrel 2 by the second heater section 4b, causing its temperature to rise. Then, the process moves to the third step.

[0034] Figure 4 is a conceptual diagram showing the third step of injection molding using the injection molding machine 1 shown in Figure 1. As shown in Figure 4, in the third step (plasticization step), the torpedo 16 is moved from the bottom to the top via the movement of the rod 8. At this time, the plunger 6 is not moved, and the state in which the supply port 2d of the barrel 2 is closed by the plunger 6 is maintained. The resin material R pushed in by the plunger 6 comes into contact not only with the tapered surface 20b of the barrel 2 but also with the tapered surface 16a of the torpedo 16. The temperature of this tapered surface 16a has risen in the second step due to the heating of the small diameter portion 22 of the barrel 2 by the second heater section 4b, and has also risen in temperature due to direct heating by the internal heater 18. The resin material R comes into contact with this tapered surface 16a, causing the resin material R to become plasticized. Then, the resin material R passes through the gap between the fins at the end 16b of the torpedo 16 and the inner circumferential surface 2b of the barrel 2 in the direction of the arrow, and then moves through the gap between the check ring 14 and the stopper 12 to the nozzle 3 side of the barrel 2. While passing through these gaps, the resin material R is plasticized by the heating and shear stress of the first heater section 4a, the second heater section 4b, and the internal heater 18. It then transforms into a fully plasticized resin J that can be molded and is stored at the tip of the barrel 2 on the nozzle 3 side. The internal pressure of this stored resin J pushes the torpedo 16 upward. Then, the process moves to the fourth step.

[0035] Figure 5 is a conceptual diagram showing the fourth step of injection molding using the injection molding machine 1 shown in Figure 1. In the fourth step (metering step), the position of the torpedo 16 is controlled so that the amount of resin J accumulated on the nozzle 3 side of the barrel 2 reaches the set amount. That is, the position of the torpedo 16 is stopped when the set amount of resin J required for injection molding has accumulated. At this time, the plunger 6 is not moved, and the state in which the supply port 2d of the barrel 2 is closed by the plunger 6 is maintained. Then, the process moves on to the fifth step.

[0036] Figure 6 is a conceptual diagram showing the fifth step of injection molding using the injection molding machine 1 shown in Figure 1. In the fifth step (injection step), the rod 8 is moved downward, and the resin J accumulated in the nozzle 3 side of the barrel 2 is injected from the nozzle hole 3a of the nozzle 3 towards the mold. Subsequently, holding pressure is applied to prevent the resin J filled in the mold from flowing back into the injection molding machine 1, and the fifth step is completed.

[0037] After the fifth step, the process moves to a cooling step for the resin J filled in the mold. After cooling is complete, the mold is opened and the molded product is removed, completing one molded product. Alternatively, the process can be repeated from the first step in parallel with this cooling step, allowing for continuous production of molded products. When repeating the process, the material supply into the barrel 2, as described in the first step, may be performed between the fourth and fifth steps, and after the fifth step, the first step may be omitted, and the process may proceed directly to the second step. In other words, after the plasticization and metering step of the resin raw material R, the plunger 6 may be moved upward to open the supply port 2d of the barrel 2, and material for the next injection molding may be supplied from the supply port 2d before proceeding to the injection step. After the injection step, the process may proceed directly to the next plasticization step.

[0038] <Effects and Effects> As described above, according to the injection molding machine 1 of this embodiment, the resin raw material R can be plasticized by moving the torpedo 16 from the bottom to the top via the movement of the rod 8, and the plasticized resin J can be injected by moving the torpedo 16 from the top to the bottom. In this way, since the plasticization process and the injection process can be performed by moving the torpedo 16, it is possible to make the machine smaller compared to conventional screw-type injection molding machines that gradually plasticize the resin raw material by feeding it to the nozzle side with a single screw inside the barrel. Furthermore, in this embodiment, since the inner circumferential surface 2b of the barrel 2 has a tapered surface 20b, the cross-sectional area is reduced in the portion of the tapered surface 20b, so that in the plasticization process, the resin raw material R comes into contact with the tapered surface 20b due to the pressing force of the plunger 6. This tapered surface 20b is the portion that faces the outer circumferential surface 2a heated by the first heater portion 4a, and is a portion of the inner circumferential surface 2b of the barrel 2 that tends to have a particularly high temperature. When the resin raw material R comes into contact with the high-temperature tapered surface 20b, the resin raw material R can be plasticized with a high heat transfer effect. In addition, since the cross-sectional area of ​​the tapered surface 16a of the torpedo 16, which is located below the tapered surface 20b of the barrel 2, is also reduced, the resin raw material R also comes into contact with this tapered surface 16a and is plasticized there as well. In this way, by performing plasticization in two stages on the tapered surface 20b of the barrel 2 and the tapered surface 16a of the torpedo 16, the heat transfer effect to the resin raw material R can be further enhanced, and the time required for the plasticization process can be shortened. As a result, miniaturization can be achieved and the time required for the plasticization process can be shortened.

[0039] Furthermore, according to this embodiment, the inner circumferential surface 2b of the barrel 2 has a tapered surface 20b and a parallel surface 22b in the area facing the portion of the outer circumferential surface 2a of the barrel 2 where the heater 4 is provided. The tapered surface 20b of the barrel 2 is the part that comes into contact with the resin raw material R due to the reduction in cross-sectional area and loses heat, while the parallel surface 22b of the barrel 2 is the part that loses less heat and has a higher temperature compared to the tapered surface 20b. Therefore, in the plasticization process, when the temperature of the tapered surface 16a rises due to heating by the second heater section 4b, the tapered surface 16a comes into contact with the parallel surface 22b, which has a higher temperature, allowing the temperature of the tapered surface 16a to rise more efficiently. As a result, the tapered surface 16a, which has a higher temperature, comes into contact with the resin raw material R, and the time of the plasticization process can be shortened more effectively.

[0040] Furthermore, according to this embodiment, the internal heater 18 provided inside the rod 8 allows the inside of the barrel 2 to be heated not only from the outside but also from the inside. In addition, the internal heater 18 can also directly heat the torpedo 16 itself. Therefore, the internal heater 18 can further increase the temperature of the tapered surface 20b and the tapered surface 16a, thereby improving the heat transfer effect of the tapered surface 20b and the tapered surface 16a to the resin raw material R. As a result, the time of the plasticization process can be shortened more effectively. Moreover, in conventional screw-type injection molding machines, it was difficult to provide a heater inside the barrel because the screw provided inside the barrel rotates. However, according to this embodiment, since the internal heater 18 is provided for the rod 8 (a non-rotating member) that moves in the axial direction A inside the barrel 2, the internal heater 18 can be easily provided.

[0041] Furthermore, according to this embodiment, since the internal heater 18 extends into the interior of the torpedo 16, the heat transfer effect of the tapered surface 16a of the torpedo 16 to the resin raw material R is further enhanced, thereby suitably achieving the above effect.

[0042] Furthermore, according to this embodiment, since the extrusion section that pushes the resin raw material R into the barrel 2 is a linear plunger 6, it is effective in plasticizing the resin raw material R, which has high viscosity and poor fluidity when heated.

[0043] ---Second Embodiment--- Next, with reference to Figure 7, the injection molding machine 1A according to the second embodiment will be described. In the second embodiment, the same reference numerals are used for components or functions as in the first embodiment, and their descriptions are omitted as appropriate. Differences from the first embodiment will be described. Figure 7 is a schematic cross-sectional view showing the general configuration of the injection molding machine 1A according to the second embodiment. For convenience of explanation, in Figure 7, the rod 8, check ring 14, and screw 40 (described later) are shown as cross-sections only on one side (right side of the paper) with respect to the axis X, while the other side (left side of the paper) with respect to the axis X is shown as a side view.

[0044] As shown in Figure 7, the injection molding machine 1A according to the second embodiment also includes a barrel 2, a heater 4, a rod 8, and a material supply unit 10, similar to the injection molding machine 1 according to the first embodiment. The injection molding machine 1A according to the second embodiment differs from the injection molding machine 1 according to the first embodiment in that it includes a screw 40 instead of a plunger 6, and further includes a needle throttling valve 50 provided at the tip (lower end) of the rod 8.

[0045] The screw 40 is an extrusion unit that pushes the resin raw material R supplied to the inside of the barrel 2 downwards within the barrel 2. The screw 40 is provided to fit into the opening 2c of the barrel 2. A through hole 40c is formed in the center of the screw 40 through which the rod 8 passes. In other words, the screw 40 is hollow. In the second embodiment, the rod 8 is positioned inside the barrel 2 with the rod 8 passing through the through hole 40c of the screw 40 (inserted into the screw 40).

[0046] The screw 40 is a screw-type extrusion unit that rotates with the axial direction A as its center of rotation. The screw 40 is connected to a motor (not shown) via a predetermined power transmission mechanism 42, for example, and is rotated by the motor. The screw 40, driven by rotation, continuously extrudes the resin raw material R supplied into the barrel 2, bringing it into contact with the tapered surface 20b of the barrel 2 and the tapered surface 16a of the torpedo 16. The screw 40 stops rotating, for example, at least during the injection process, and continues to rotate otherwise.

[0047] The needle throttling valve 50 is located on the stopper 12 side of the rod 8. The needle throttling valve 50 is movable in the axial direction A as the rod 8 moves in the axial direction A. The needle throttling valve 50 adjusts the opening degree of the nozzle hole 3a of the nozzle 3 by moving in the axial direction A. By adjusting the opening degree of the nozzle hole 3a, the needle throttling valve 50 adjusts the amount of resin J injected from the nozzle hole 3a toward the outside of the mold or the like.

[0048] <Effects and Effects> As described above, in the injection molding machine 1A according to the second embodiment, the plasticization process and the injection process can be performed by moving the torpedo 16, thus enabling miniaturization. Furthermore, in addition to the high-temperature tapered surface 20b of the barrel 2 providing a high heat transfer effect to the resin raw material R, the heat transfer effect to the resin raw material R can be further enhanced by performing plasticization in two stages using the tapered surface 20b of the barrel 2 and the tapered surface 16a of the torpedo 16. As a result, the time required for the plasticization process can be shortened. Thus, miniaturization can be achieved and the time required for the plasticization process can be shortened.

[0049] Furthermore, in the first embodiment, when the resin raw material R is extruded by the plunger 6, plasticization can only occur during the stroke in which the plunger 6 moves downward, resulting in intermittent plasticization. In contrast, according to the second embodiment, the thrust force from the rotation of the screw 40 allows the resin raw material R to be continuously extruded and brought into contact with the tapered surface 20b and the tapered surface 16a, thus enabling continuous plasticization. In addition, according to the second embodiment, the screw 40 can increase the contact surface area of ​​the resin raw material R with the inner circumferential surface 2b of the barrel 2 compared to the first embodiment, thereby further enhancing the heat transfer effect. As a result, the time of the plasticization process can be more effectively shortened.

[0050] Furthermore, according to the second embodiment, the extrusion section that pushes the resin raw material R into the barrel 2 is of the screw type, which is effective in plasticizing the resin raw material R, which has low viscosity and good fluidity when heated.

[0051] Furthermore, according to the second embodiment, by providing the needle throttle valve 50, the injection amount can be adjusted to be appropriate even when the amount of resin J increases due to continuous plasticization.

[0052] <Variation> The present invention is not limited to the embodiments described above. That is, any design modifications made to the above embodiments by those skilled in the art are also included within the scope of the present invention, as long as they retain the features of the present invention. Furthermore, the elements of the above embodiments and the modifications described later can be combined to the extent that it is technically possible, and any combination thereof is also included within the scope of the present invention, as long as it retains the features of the present invention.

[0053] For example, the extrusion unit that pushes the resin raw material R into the barrel 2 may be interchangeable between a linear type and a screw type. For example, if the viscosity of the resin raw material R is high when heated, a linear type plunger 6 may be used, and if the viscosity is low, a screw type screw 40 may be used, and the extrusion unit may be interchangeable depending on the viscosity of the resin raw material R.

[0054] Furthermore, although the above embodiment describes an example in which the torpedo 16 is integrally formed with the rod 8, the torpedo 16 may be constructed separately from the rod 8 and fixed to the rod 8. Also, the internal heater 18 of the rod 8 does not necessarily have to extend into the torpedo 16, and the rod 8 does not necessarily have to have an internal heater 18.

[0055] In the above embodiment, an example was described in which the plunger 6 or screw 40, which serves as the extrusion unit, enters the barrel 2 and the rod 8 passes through the plunger 6 or screw 40, but the invention is not limited to this. For example, the injection molding machine 1 does not necessarily have to be equipped with a plunger 6 and a screw 40, and a pushing device, which serves as the extrusion unit for pushing the resin raw material R into the barrel 2, may be provided outside the barrel 2, and the resin raw material R may be pushed into the barrel 2 by the external pushing device. [Explanation of symbols]

[0056] 1,1A: Injection molding machine, 2: Barrel, 2a: Outer surface of barrel, 2b: Inner surface of barrel, 3: Nozzle, 4: Heater (heating part), 6: Plunger (extrusion part), 8: Rod, 16: Torpedo, 18: Internal heater (internal heating part), 20b: Tapered surface, 22b: Parallel surface (other surface), 40: Screw (extrusion part), R: Resin raw material (molding material)

Claims

1. A vertical injection molding machine having the lower side in the direction of gravity as one end and the upper side in the direction of gravity as the other end, A nozzle for injecting the plasticized molding material is provided on one end, and a barrel extending in the direction of gravity, A first heating unit is provided on the outer circumferential surface of the barrel and heats the molding material inside the barrel via the barrel, An extrusion section that pushes the molding material supplied to the inside of the barrel toward the one end within the barrel, A rod having a torpedo provided inside the barrel and movable in the axial direction of the barrel, with an inverse tapered portion formed on one end of the barrel in the axial direction, which narrows from that end toward the other end; A second heating unit is provided inside the rod and heats the molding material inside the barrel via the rod, Equipped with, The inner circumferential surface of the barrel has a tapered surface in the region of the outer circumferential surface of the barrel facing the portion where the first heating portion is provided, where the inner diameter narrows in the axial direction from the other end to the one end. The injection molding machine is characterized in that the second heating section extends in the axial direction to a position including the inverse tapered portion.

2. The injection molding machine according to claim 1, characterized in that the inner circumferential surface of the barrel has, within the range, the tapered surface and another surface located toward the one end in the axial direction relative to the tapered surface and having substantially the same inner diameter along the axial direction.

3. The injection molding machine according to claim 1 or 2, characterized in that the extrusion unit is a linear type that moves along the axial direction, or a screw type that rotates with the axial direction as the center of rotation.

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