Injection molding machine

Abstract

Provided is an injection molding machine that can provide a relatively large clearance between an injection cylinder and a plunger while simultaneously suppressing leakage of molding material and suppressing contact between the plunger and the injection cylinder. [Solution] An injection molding machine is provided which comprises a plasticization section, an injection section, and a junction, the injection section including an injection cylinder (41), a plunger (42), and a seal cylinder (5), the seal cylinder (5) having a seal surface (51) facing the plunger (42), a front surface (52) forming a front flow path (521), and an outer surface (531) forming a side flow path, and between the injection cylinder (41) and the side of the plunger (42) there is provided a first clearance (C1) which is a gap through which the molding material can flow, and between the seal surface (51) and the side of the plunger (42) there is provided a second clearance (C2) which is a gap smaller than the first clearance (C1) and which can be reduced by the pressure of the molding material generated during holding pressure.

Description

[Technical Field]

[0001] The present invention relates to an injection molding machine, and more particularly to a screw pre-plasticizing injection molding machine. [Background technology]

[0002] Injection molding machines plasticize molding materials, measure out a predetermined amount, and inject it into a mold to produce the desired molded product. Injection molding machines currently in practical use can be broadly divided into in-line screw types and screw pre-plasticizing types.

[0003] A screw pre-plasticizing injection molding machine comprises a plasticizing cylinder, a rotatable screw mounted within the plasticizing cylinder, an injection cylinder, and a plunger mounted within the injection cylinder so that it can move forward and backward. The screw rotates within the plasticizing cylinder, plasticizing the molding material and sending it to the injection cylinder. The plunger within the injection cylinder then moves backward to measure the molding material, and after measuring, the plunger moves forward to inject the molding material. Even after the molding material has been filled into the mold cavity, a forward force is applied to the plunger for a while. This applies a predetermined pressure to the molding material for a predetermined period of time. This process is called pressure holding.

[0004] To prevent galling, a certain amount of clearance must be provided between the side of the plunger and the inner surface of the injection cylinder. The plasticized molding material passes through the gap between the plunger and the injection cylinder and can leak slightly from the rear of the injection cylinder. If the amount of molding material leaking is large or varies, molding stability will be compromised. Therefore, the clearance is usually made as small as possible to reduce and keep constant the amount of leakage, achieving stable molding.

[0005] On the other hand, with some molding materials, if the clearance between the plunger and the injection cylinder is too small, it can actually result in poor molding or severe wear of the components. For example, when using molding materials containing fillers, especially those containing metal fillers such as MIM materials, fillers that penetrate the clearance can be pressed against the plunger or injection cylinder and adhere to various parts. Furthermore, a small clearance can easily cause contact between the plunger and the injection cylinder. In particular, when using materials that generate corrosive gases during plasticization, corrosion can reduce the surface hardness of the plunger and injection cylinder. When a plunger with reduced surface hardness comes into contact with the injection cylinder, some of the steel that makes up the plunger or injection cylinder may leach into the molding material.

[0006] Patent Document 1 discloses an injection molding machine that provides a large clearance between the plunger and the injection cylinder and prevents leakage of the molding material by solidifying or thickening the molding material at the rear end of the injection cylinder. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 7121182 Summary of the Invention [Problem to be solved by the invention]

[0008] There is a demand for a simpler configuration that more effectively suppresses both leakage of molding material and contact between the plunger and the injection cylinder.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide an injection molding machine that can provide a relatively large clearance between the injection cylinder and the plunger while simultaneously suppressing leakage of molding material and suppressing contact between the plunger and the injection cylinder. [Means for solving the problem]

[0010] According to the present invention, there is provided a molding machine comprising: a plasticizing section to which a molding material containing at least a resin is supplied and which plasticizes the molding material; an injection section to which the molding material sent from the plasticizing section is measured and injected and which performs pressure dwell by applying a predetermined pressure to the molding material for a predetermined period of time; and a junction which connects the plasticizing section and the injection section; the plasticizing section includes a plasticizing cylinder to which the molding material is supplied and a screw rotatably provided within the plasticizing cylinder; and the injection section includes an injection cylinder to which the molding material is supplied from the plasticizing cylinder, a plunger provided in the injection cylinder so as to be able to advance and retreat; and a seal cylinder provided at the rear end of the injection cylinder and through which the plunger is inserted; The cylinder has a seal part that seals the gap between the injection cylinder and the plunger, and the seal part has a seal surface facing the plunger, a front surface that forms a front flow path that is a gap between the injection cylinder and the seal part and the injection cylinder through which the molding material can flow, and an outer surface that forms a side flow path that is a gap between the injection cylinder and the seal part and the injection cylinder through which the molding material can flow, and a first clearance that is a gap through which the molding material can flow is provided between the injection cylinder and the side of the plunger, and a second clearance that is a gap smaller than the first clearance and can be reduced by the pressure of the molding material generated during holding pressure is provided between the seal surface and the side of the plunger. [Effects of the Invention]

[0011] In the injection molding machine according to the present disclosure, a seal cylinder having a seal portion is provided at the rear end of the injection cylinder. The second clearance between the plunger and the seal portion is set relatively small compared to the first clearance between the plunger and the injection cylinder, but the second clearance is configured to be further reduced by the pressure of the molding material during dwelling. As a result, even if the first clearance is set relatively large, the seal cylinder seals the gap between the injection cylinder and the plunger, thereby effectively suppressing leakage of the molding material. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a schematic configuration diagram of an injection unit of an injection molding machine according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. 2 is a front perspective view of the seal cylinder. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 2 is a cross-sectional view of a seal cylinder. [Figure 7] FIG. [Figure 8] FIG. 10 is a rear perspective view of the auxiliary guide cylinder. [Figure 9] FIG. 10 is a rear view of the auxiliary guide cylinder. [Figure 10] FIG. 4 is a cross-sectional view of an auxiliary guide cylinder. DETAILED DESCRIPTION OF THE INVENTION

[0013] First, we will explain the molding material used in the injection molding machine of this embodiment. A wide variety of molding materials containing at least a resin can be used as the molding material. However, the present invention is suitable for use with molding materials containing a resin and a filler. This is particularly suitable when the filler is made of a material that has a high affinity with the steel of the injection cylinder 41 and plunger 42. Examples of materials that have a high affinity with the steel of the injection cylinder 41 and plunger 42 include metals, such as stainless steel, nickel-chromium alloys, and titanium. Furthermore, the present invention is suitable for use with molding materials that generate corrosive gases during plasticization.

[0014] Examples of materials containing resin and metal filler include MIM (Metal Injection Molding) materials and plastic magnet materials. MIM materials are a type of material used in powder injection molding, and are molding materials made by mixing metal powder as a filler and resin as a binder. Plastic magnet materials are molding materials made by mixing magnetic metal powder as a filler and resin as a binder. The filler may be in powder form or fiber form.

[0015] Examples of molding materials that are prone to generating corrosive gases during plasticization include materials that generate corrosive gases from the resin itself and materials that contain flame retardants. Examples of materials that generate corrosive gases from the resin itself include fluororesin and polyvinyl chloride. Examples of materials that often contain flame retardants include acrylonitrile butadiene styrene, polystyrene, polypropylene, polyethylene, polycarbonate, polycarbonate-acrylonitrile butadiene styrene alloy, modified polyphenylene ether, olefin thermoplastic elastomer, polyamide (including aliphatic polyamide, semi-aromatic polyamide, and aromatic polyamide), polybutylene terephthalate, and saturated polyester (including polyethylene terephthalate).

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The various modified examples described below can be implemented in any combination. In the drawings, connecting members such as bolts that connect various parts and positioning members such as positioning pins are omitted as appropriate. Furthermore, the values ​​of the size of each clearance described below are values ​​at room temperature (i.e., between approximately 5°C and approximately 35°C) unless otherwise specified.

[0017] The injection molding machine of this embodiment is a screw pre-plasticizing injection molding machine. The injection molding machine includes an injection unit 1, a clamping unit (not shown), and a control device (not shown) that controls the injection unit 1 and the clamping unit. The injection unit 1 plasticizes the molding material, measures out a predetermined amount, and then injects it into a mold (not shown) held by the clamping unit. It also applies a predetermined pressure to the molding material for a predetermined period of time. Because the molding material filled in the mold undergoes thermal contraction, the dwelling pressure additionally supplies the insufficient molding material to the mold. The clamping unit is configured to open, close, and clamp the mold. During injection and dwelling, the clamping unit closes the mold and applies a predetermined clamping force to the mold. After the molding material injected into the mold cavity cools and forms a molded product, the clamping unit opens the mold, ejects the molded product, and then closes the mold again. Well-known configurations, such as a direct pressure type or toggle type, can be used as the clamping unit.

[0018] As shown in FIG. 1, injection unit 1 includes a plasticizing section 2, a junction 3, and an injection section 4. FIG. 1 shows a cross-sectional view of part of the configuration. Unless otherwise specified, the side from which the molding material is injected (left side in FIG. 1) will be referred to as the "front," the side from which the molding material is introduced (right side in FIG. 1) will be referred to as the "rear," the side on which plasticizing section 2 is provided (upper side in FIG. 1) will be referred to as the "top," and the side on which injection section 4 is provided (lower side in FIG. 1) will be referred to as the "bottom." Furthermore, although the following description will be given using a horizontal injection molding machine as an example, the injection molding machine may be of other types, such as a vertical injection molding machine.

[0019] The plasticizing section 2 plasticizes the supplied molding material and sends it forward. The plasticizing section 2 includes a plasticizing cylinder 21, a screw 23, a check device 25, a screw driver 27, and a heater 29.

[0020] The plasticizing cylinder 21 is a cylindrical body into which the molding material is supplied. A material inlet 211 is formed at the rear side of the plasticizing cylinder 21, and the molding material is introduced into the material inlet 211 via a hopper or the like (not shown). The plasticizing cylinder 21 is heated to a predetermined temperature by a heater 29.

[0021] The screw 23 is rotatably provided within the plasticizing cylinder 21. The screw 23 sends the molding material supplied to the plasticizing cylinder 21 forward while plasticizing the molding material by heat from the heater 29 and shear heat.

[0022] The check device 25 is, for example, a single-acting cylinder, which advances the screw 23 when metering is complete to block the flow path and prevent backflow of the molding material during injection. Note that the check device 25 may be replaced by another check mechanism such as a ball valve.

[0023] The screw drive 27 may be any actuator that rotates the screw 23, such as a hydraulic motor or an electric motor.

[0024] The junction 3 connects the plasticizing section 2 and the injection section 4. The molding material sent from the plasticizing cylinder 21 passes through a communication passage 31 in the junction 3 and is sent to the injection cylinder 41. Note that a heater may be provided in the junction 3 to make the junction heatable.

[0025] The injection unit 4 measures the molding material sent from the plasticization unit 2 and injects it into the mold. Following injection, the injection unit 4 performs a pressure hold to keep the molding material remaining in the injection unit 4 pressed at a predetermined pressure. As shown in FIGS. 1 and 2 , the injection unit 4 includes an injection cylinder 41, a plunger 42, a seal cylinder 5, an auxiliary guide cylinder 6, a connecting cylinder 43, a nozzle 44, a connecting member 45, a plunger driver 46, a coupling 47, and heaters 48 and 49.

[0026] The injection cylinder 41 is a cylindrical body that measures the molding material sent from the plasticizing cylinder 21. The measuring chamber 411 of the injection cylinder 41 is an inner hole through which the plunger 42 is inserted, and a desired amount of molding material is measured into the measuring chamber 411. In this embodiment, a supply flow path 412 is formed on the rear side of the injection cylinder 41, and the supply flow path 412 is connected to the communication path 31 of the junction 3. The injection cylinder 41 is heated to a predetermined temperature by a heater 48.

[0027] A first clearance C1, which is a gap through which the molding material can flow, is formed between the inner surface of the injection cylinder 41 and the side surface of the plunger 42. The molding material supplied from the supply channel 412 is sent to the side surface of the plunger 42 via the seal cylinder 5 and then to the front surface of the plunger 42 through the first clearance C1. The first clearance C1 also serves as a flow path for metering the molding material, so it is preferable that the first clearance C1 be sufficiently large. Furthermore, the first clearance C1 is preferably sufficiently large to prevent filler adhesion and contact between the plunger 42 and the injection cylinder 41. On the other hand, the larger the first clearance C1, the greater the amount of molding material retained in the injection cylinder 41 and the pressure loss during injection. The size of the first clearance is, for example, approximately 0.5 mm to approximately 1.5 mm, more preferably approximately 0.9 mm to approximately 1.1 mm. In this embodiment, the size of the first clearance is approximately 1 mm.

[0028] The plunger 42 is a generally cylindrical member that is movably mounted within the injection cylinder 41. However, the tip of the plunger 42 may have a generally conical shape. A first clearance C1 is provided between the side surface of the plunger 42 and the inner surface of the injection cylinder 41, providing a sufficient gap for the molding material to flow through. During metering, the plunger 42 is retracted by the pressure of the molding material that is supplied to the injection cylinder 41, passes through the first clearance C1, and is delivered to the front surface of the plunger 42. The position of the plunger 42 can be detected by an encoder (not shown), allowing the desired amount of molding material to be metered within the injection cylinder 41. However, during metering, the plunger 42 may also be actively retracted by the plunger drive device 46. After metering the desired amount of molding material, the plunger 42 is advanced at a predetermined speed or pressure to extrude the molding material from the injection cylinder 41 into the nozzle 44.

[0029] A nozzle 44 is attached to the front surface of the injection cylinder 41, and the nozzle 44 abuts against the sprue bushing of the mold at least during injection. The molding material pushed out by the plunger 42 is injected into the mold from the tip of the nozzle 44. The molding material enters the mold through the opening in the sprue bushing and passes through the sprue and runner to be delivered to the cavity. The nozzle 44 is heated to a predetermined temperature by a heater 49.

[0030] The seal cylinder 5 is a cylindrical body provided at the rear end of the injection cylinder 41 and through which the plunger 42 is inserted. The seal cylinder 5 seals the gap between the injection cylinder 41 and the plunger 42 to prevent leakage of the molding material. That is, the seal cylinder 5 closes the flow path to an extent that the molding material is almost unable to flow through, thereby preventing the molding material from leaking behind the seal cylinder 5. Furthermore, the seal cylinder 5 of this embodiment slidably holds the inserted plunger. The seal cylinder 5 may be housed in the injection cylinder 41 and the connecting cylinder 43. The detailed configuration of the seal cylinder 5 will be described later.

[0031] The auxiliary guide cylinder 6 is provided behind the seal cylinder 5 and is a cylindrical body through which the plunger 42 is inserted. The auxiliary guide cylinder 6 slidably holds the inserted plunger. The auxiliary guide cylinder 6 may be housed in a connecting member 45. The detailed configuration of the auxiliary guide cylinder 6 will be described later.

[0032] The connecting cylinder 43 is a cylindrical body that houses the sealing cylinder 5 and is attached to the injection cylinder 41. The plunger 42 is inserted into the connecting cylinder 43, but since the connecting cylinder 43 of this embodiment is not intended to seal the molding material or support the plunger 42, the gap between the inner surface of the connecting cylinder 43 and the side surface of the plunger 42 only needs to be set sufficiently large. The connecting cylinder 43 is connected to a plunger drive device 46 via a connecting member 45. The plunger drive device 46 may be any actuator that moves the plunger 42 forward and backward, such as a hydraulic cylinder or an electric cylinder. The piston of the plunger drive device 46 and the plunger 42 are connected by a coupling 47.

[0033] The seal cylinder 5 of this embodiment shown in FIGS. 3 to 7 includes a seal portion 5A and a guide portion 5B, and serves to seal the molding material and to guide and support the plunger .

[0034] The seal portion 5A seals the gap between the injection cylinder 41 and the plunger 42 at the rear end of the injection cylinder 41. In particular, the seal portion 5A of this embodiment is configured to bend inward due to the pressure of the molding material generated during dwelling, thereby reducing the second clearance C2. The seal portion 5A is inserted into the injection cylinder 41 so as to form a gap with the inner surface of the injection cylinder 41. The seal portion 5A has a seal surface 51, a front surface 52, and an outer surface 53.

[0035] The seal surface 51 is a part of the inner surface of the seal cylinder 5 and is a surface formed around the entire circumference facing the plunger 42. A second clearance C2 is formed between the seal surface 51 and the side surface of the plunger 42. The second clearance C2 is smaller than the first clearance C1 and is set to a size that does not interfere with the sliding of the plunger 42 but does not substantially prevent the molding material from flowing through. As will be described later, the second clearance C2 is reduced by the pressure of the molding material generated during dwelling. The size of the second clearance C2 when no molding material pressure is applied is, for example, between about 2 μm and about 15 μm, more preferably between about 6 μm and about 8.5 μm. The size of the second clearance C2 reduced by dwelling may be substantially 0 μm. The seal cylinder 5 may be slightly deformed by the external pressure applied when it is attached to the injection cylinder 41, but the range of the size of the second clearance C2 described above is the value after attachment.

[0036] The front surface 52 is the front end surface of the seal cylinder 5. The front surface 52 forms a front flow passage 521, which is a gap through which the molding material can flow, between the front surface 52 and the inner surface of the injection cylinder 41. In this embodiment, the front surface 52 is inclined so that the diameter of the front surface is smaller than that of the rear surface, at least in a portion thereof. Pressure generated in the molding material in the front flow passage 521 by pressure retention acts in a direction substantially perpendicular to the front surface 52. By inclining the front surface 52, pressure can be applied to the front surface 52 more suitably to reduce the second clearance C2. The inclination angle θ of the front surface 52, when a straight line horizontal to the axial direction of the plunger 42 is taken as a reference line, is, for example, approximately 77° to approximately 83°, more preferably approximately 79° to approximately 81°. The inner surface of the injection cylinder 41 facing the front surface 52 may be inclined at approximately the same angle as the front surface 52.

[0037] The outer surface 53 is the outer peripheral surface of the front part of the sealing cylinder 5. The outer surface 53 forms a side flow passage 531, which is a gap through which the molding material can flow, between the outer surface 53 and the inner surface of the injection cylinder 41. Preferably, a groove 532 is formed around the entire periphery of the outer surface 53 along the circumferential direction, and the side flow passage 531 is configured to include the groove 532. At the lower end of the groove 532, the sealing unit 5A may further have a groove outlet 533 that communicates with the front surface 52 and the lower end of the groove 532. The supply flow passage 412 of the injection cylinder 41 is located above the outer surface 53, i.e., above the groove 532. The molding material sent from the plasticizing unit 2 is supplied from above the groove 532 via the supply flow passage 412.

[0038] In this embodiment, the flow path resistance of the front flow path 521 is configured to be greater than the flow path resistance of the side flow path 531. That is, the molding material is configured to flow more easily through the side flow path 531 than through the front flow path 521. To make it easier for the molding material to flow through the side flow path 531 than through the front flow path 521, for example, the cross-sectional area of ​​the side flow path 531 is configured to be greater than the cross-sectional area of ​​the front flow path 521. Furthermore, in this embodiment, the amount of molding material sent from the plasticizing unit 2 to the injection unit 4 via the supply flow path 412 is configured to be greater than the amount of molding material discharged from the groove outlet 533. To make the amount of molding material discharged from the groove outlet 533 smaller than the amount of molding material supplied, for example, the cross-sectional area of ​​the supply flow path 412 is configured to be greater than the cross-sectional area of ​​the groove outlet 533.

[0039] When metering begins, the molding material sent from the plasticizing section 2 passes through the communication passage 31 of the junction 3 and the supply passage 412 of the injection cylinder 41 and is supplied above the groove 532. Because the sealing section 5A is configured to allow the molding material to flow more easily toward the side passages 531 than toward the front passage 521, most of the molding material is first sent downward along the groove 532 and discharged forward from the groove outlet 533. The molding material discharged from the groove outlet 533 passes through the front passage 521 near the groove outlet 533 and is sent to the first clearance C1. Since the amount of molding material being supplied exceeds the amount discharged from the groove outlet 533, the molding material is gradually discharged forward from the front passage 521 other than near the groove outlet 533 and sent to the first clearance C1. In this way, the molding material passes through the first clearance C1 and is sent forward of the plunger 42. The molding material sent to the front of the plunger 42 is stored in the injection chamber 411 while pushing the plunger 42 down.

[0040] If the molding material stagnates and is heated for a long period of time, carbonization and deterioration may occur. In this embodiment, the injection unit 4 is configured with a so-called first-in, first-out flow path, which makes it difficult for the molding material to stagnate. Specifically, the molding material is supplied from the rear side of the injection cylinder 41 and circulated to the front side, thereby preventing stagnation in the first clearance C1, the front flow path 521, and the side flow path 531. Furthermore, the provision of the groove outlet 533 effectively prevents stagnation in a downward area away from the supply flow path 412. In particular, the flow path is configured so that the molding material is discharged not only around the groove outlet 533 but also from the entire front flow path 521, thereby effectively preventing stagnation in areas other than the downward area.

[0041] When the plunger 42 reaches the desired position, metering is determined to be complete. After metering is complete, the check device 25 blocks the flow path between the plasticizing section 2 and the injection section 4. The plunger 42 then moves forward to perform injection and hold. During hold, a pressure much greater than that during metering or injection is applied to the molding material. The pressure of the molding material present in the front flow path 521 and the side flow path 531 is transmitted to the front surface 52 and the outer surface 53, deflecting the seal portion 5A inward. As a result, the second clearance C2 between the seal surface 51 and the plunger 42 is reduced, preventing the molding material from flowing into the second clearance C2 and leaking to the rear. At this time, the second clearance C2 may be reduced to substantially 0 μm, bringing the seal surface 51 and the plunger 42 into contact. The pressure of the molding material (i.e., the dwell pressure) and the amount of deflection of the seal portion 5A are approximately proportional. In this embodiment, when the pressure of the molding material reaches approximately 35 MPa to approximately 55 MPa, the second clearance C2 becomes substantially 0 μm. Because the plunger 42 hardly moves during dwell pressure, even if the second clearance C2 is reduced, galling is unlikely to occur. When dwell pressure is completed, the deflection of the seal portion 5A returns to its original size, and the size of the second clearance C2 also returns to its original size. According to the configuration of this embodiment, the second clearance C2 automatically reduces due to the pressure of the molding material during dwell pressure, so no special control is required for sealing, making sealing easier to achieve. Furthermore, since the second clearance C2 returns to its original size when dwell pressure is completed, there is no interference with the sliding of the plunger 42 during the next metering and injection.

[0042] In order to allow the seal portion 5A to bend, it is preferable that the seal cylinder 5 be made of a material with high strength and toughness. For example, cold work tool steel QCM8 (manufactured by Sanyo Special Steel Co., Ltd.) can be used as the material for the seal cylinder 5.

[0043] The guide portion 5B slidably holds the inserted plunger 42 behind the seal portion 5A. The guide portion 5B is inserted into the injection cylinder 41 and the connecting cylinder 43 so that its outer periphery contacts the inner surfaces of the injection cylinder 41 and the connecting cylinder 43. This closes the rear end of the injection cylinder 41. The guide portion 5B of this embodiment has six guide surfaces 54 evenly spaced circumferentially, and the plunger 42 is supported by the guide surfaces 54. However, the position and number of the guide surfaces 54 are not limited thereto. The clearance between the guide surfaces 54 and the plunger 42 is desirably small enough to allow the plunger 42 to slide smoothly. The clearance is, for example, between approximately 2.5 μm and approximately 4 μm. The guide surfaces 54 prevent the plunger 42 from tilting and prevent contact between the plunger 42 and the injection cylinder 41.

[0044] The gap between the inner surface of the seal cylinder 5, excluding the seal surface 51 and the guide surface 54, and the side surface of the plunger 42 may be set to be sufficiently large.

[0045] The auxiliary guide cylinder 6 of this embodiment shown in FIGS. 8 to 10 guides and supports the plunger 42. The auxiliary guide cylinder 6 slidably holds the inserted plunger 42 behind the seal cylinder 5. To more stably support the plunger 42, the auxiliary guide cylinder 6 is preferably positioned at a certain distance from the seal cylinder 5. The auxiliary guide cylinder 6 of this embodiment has three guide surfaces 61 evenly spaced circumferentially, and the plunger 42 is supported by the guide surfaces 61. However, the position and number of the guide surfaces 61 are not limited thereto. The clearance between the guide surfaces 61 and the plunger 42 is preferably small enough to allow the plunger 42 to slide smoothly. The clearance is, for example, approximately 5 μm to approximately 7 μm. The guide surfaces 61 prevent the plunger 42 from tilting and prevent contact between the plunger 42 and the injection cylinder 41. The gap between the inner surface of the auxiliary guide cylinder 6 excluding the guide surface 61 and the side surface of the plunger 42 may be set to be sufficiently large.

[0046] As several examples have already been specifically shown, the present invention is not limited to the configuration of the embodiments shown in the drawings, and various modifications or applications are possible within the scope that does not deviate from the technical concept of the present invention. [Explanation of symbols]

[0047] 2. Plasticization Section 21 Plasticizing cylinder 23 screw 3 Junction 4 Injection part 41 Injection cylinder 42 Plunger 5 Seal Cylinder 5A Seal part 51 sealing surface 52 Front 521 Front flow channel 53 External surface 531 Side channel 532 Groove 533 Groove outlet 5B Guide part 6 Auxiliary guide cylinder C1 First Clearance C2 Second Clearance θ Tilt angle

Claims

1. a plasticizing section to which a molding material containing at least a resin is supplied and which plasticizes the molding material; an injection unit that measures and injects the molding material sent from the plasticization unit and performs pressure dwell by applying a predetermined pressure to the molding material for a predetermined period of time; a junction connecting the plasticizing section and the injecting section, The plasticizing section includes: a plasticizing cylinder to which the molding material is supplied; a screw rotatably provided within the plasticizing cylinder; The injection unit includes: an injection cylinder into which the molding material is fed from the plasticizing cylinder; a plunger provided in the injection cylinder so as to be able to move forward and backward; a seal cylinder provided at a rear end of the injection cylinder and through which the plunger is inserted, the seal cylinder has a seal portion that seals between the injection cylinder and the plunger, The sealing portion is a seal surface facing the plunger; a front surface that forms a front surface flow path, which is a gap between the injection cylinder and the front surface and through which the molding material can flow; an outer surface that forms a side flow path, which is a gap through which the molding material can flow, between the injection cylinder and the outer surface; a first clearance, which is a gap through which the molding material can flow, is provided between the injection cylinder and a side surface of the plunger; an injection molding machine, wherein a second clearance is provided between the sealing surface and the side surface of the plunger, the second clearance being a gap smaller than the first clearance and capable of shrinking due to the pressure of the molding material generated during dwelling.

2. The injection molding machine according to claim 1 , wherein the side flow passage includes a groove formed along a circumferential direction of the outer surface.

3. 3. The injection molding machine according to claim 2, wherein the molding material sent from the plasticizing section is supplied from above the groove.

4. The injection molding machine according to claim 2 , wherein the seal portion further has a groove outlet communicating with the front surface and a lower end of the groove.

5. a flow resistance of the front flow passage is greater than a flow resistance of the side flow passage, 5. The injection molding machine according to claim 4, wherein the amount of the molding material sent from the plasticizing section to the injection section is greater than the amount of the molding material discharged from the groove outlet.

6. 2. The injection molding machine according to claim 1, wherein the front surface is inclined at least in part so that the diameter of the front side is smaller than that of the rear side.

7. 7. The injection molding machine according to claim 6, wherein an inclination angle of the front surface when a straight line horizontal to the axial direction of the plunger is taken as a reference line is between 77° and 83°.

8. 2. The injection molding machine according to claim 1, wherein the seal cylinder further includes a guide portion, located rearward of the seal portion, for slidably holding the inserted plunger.

9. 2. The injection molding machine according to claim 1, further comprising an auxiliary guide cylinder provided rearward of the seal cylinder and configured to slidably hold the inserted plunger.

10. 2. The injection molding machine according to claim 1, wherein the first clearance has a size of 0.5 mm or more and 1.5 mm or less.

11. 2. The injection molding machine according to claim 1, wherein the second clearance when no pressure of the molding material is applied is equal to or greater than 2 μm and equal to or less than 15 μm.

12. 2. The injection molding machine according to claim 1, wherein the molding material comprises the resin and a filler.

13. The injection molding machine according to claim 12, wherein the filler is made of metal.

14. 2. The injection molding machine according to claim 1, wherein the molding material is a material that generates a corrosive gas when plasticized.

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