Injection molding die

Abstract

The present invention provides an injection molding die capable of molding a member in which a weld seam is suppressed. This injection molding die (1) is provided with: an annular gate (5) that injects a molten resin (M) into a cavity (C) disposed in the center; and a plurality of branch runners (3) for supplying the molten resin (M) supplied by the main runner (2) to the pouring gate (5). The gate (5) has: a first ring section (51) having a plurality of gate inlets (53) respectively communicating with the plurality of sub-runners (3); a second ring section (52) which has a slit-shaped gate outlet (54) extending in the circumferential direction and communicating with the cavity (C), is disposed inside the first ring section (51), and is thinner than the first ring section (51); and a step part (55), which is disposed between the first ring part (51) and the second ring part (52), and which connects the first ring part (51) and the second ring part (52).

Description

Technical Field

[0001] The present invention relates to an injection molding die. Background Art

[0002] In the injection molding method, a fluid material such as molten resin injected from an injection machine is filled into a cavity formed by closing a mold, and the fluid material is cooled and solidified, thereby forming a molded product having a shape corresponding to the cavity.

[0003] In the past, when forming a cylindrical part with a hollow interior, a ring gate was used. The ring gate fills the resin from the outside to the central cavity, but when two sub-gates are used, for example, two branches are formed from the respective gate outlets to fill the annular cavity with resin, and the resins flowing in from two opposite directions merge to form a weld line in the cavity.

[0004] Therefore, a ring gate mold is proposed, which includes a ring gate and two sub-gates, and the two sub-gates are arranged in a state of being eccentric with respect to the center of the ring gate and rotated 180 degrees with the center of the ring gate as a base point (see Patent Document 1). According to this technology, the filler ejected from the sub-gates is ejected into the cavity while flowing in a spiral shape in the same direction in the ring gate, and the flow streams of the filler ejected from each sub-gate will not merge in opposite directions, so it is more difficult to form a weld.

[0005] [Prior Technical Literature]

[0006] (Patent Document)

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 7-290515 Summary of the invention

[0008] [Problems to be solved by the invention]

[0009] However, in the technology of Patent Document 1, since the timing of resin inflow into the cavity is different, a weld seam is easily formed due to the confluence of the filled resins. In addition, in order to make the flow streams merge in a spiral shape, it is necessary to control the flow path, and the mold must be made into a complex structure.

[0010] An object of the present invention is to provide an injection molding die capable of molding a component with a suppressed weld line.

[0011] [Technical means to solve the problem]

[0012] (1) The injection molding die of the present invention (e.g., the injection molding die 1 described later) comprises: an annular gate (e.g., the ring gate 5 described later) for injecting molten resin (e.g., molten resin M described later) into a cavity (e.g., the cavity C described later) disposed at the center; and

[0013] A plurality of branch runners (for example, a branch runner 3 described later) supply the molten resin supplied from a main runner (for example, a main runner 2 described later) to the gate;

[0014] The aforementioned gate has:

[0015] The first ring portion (for example, the first ring portion 51 described later) has a plurality of gate inlets (for example, the gate inlets 53 described later) respectively connected to the plurality of branch runners;

[0016] The second ring portion (e.g., the second ring portion 52 described later) has a slit-shaped gate outlet (e.g., the gate outlet 54 described later) extending in the circumferential direction and communicating with the aforementioned cavity, and is arranged on the inner side of the aforementioned first ring portion and is thinner than the aforementioned first ring portion; and,

[0017] The step portion (for example, the step portion 55 ) is disposed between the first ring portion and the second ring portion, and connects the first ring portion and the second ring portion.

[0018] The injection molding mold of the present invention has a main runner, a plurality of branch runners, and a ring gate for injecting molten resin into a cavity. The ring gate is composed of a first ring portion provided with a plurality of gate inlets, a second ring portion arranged inside the first ring portion and thinner than the first ring portion, and a step portion arranged between the two ring portions and connecting the two ring portions. Thus, the molten resin that passes through a plurality of branch runners and is ejected from a plurality of gate inlets to the ring gate starting from the main runner will flow from the first ring portion to the second ring portion via the step portion, so that the molten resin can be effectively merged in the ring gate. Furthermore, the ring gate has a slit-shaped gate outlet that is extended in the circumferential direction and connected to a cavity arranged in the center. Thus, the molten resin that effectively merges in the ring gate can flow into the cavity from the slit-shaped gate outlet at the same time, so that the component with suppressed welds can be formed.

[0019] (2) The injection molding die according to (1) above, wherein the gate outlet is a slit continuous in the circumferential direction.

[0020] In this structure, the gate outlet provided in the second ring portion is in the shape of a slit continuous in the circumferential direction, so that the molten resin can more easily flow into the cavity arranged in the center of the second ring portion at the same time, thereby improving the forming effect of the component with suppressed welds.

[0021] (3) The injection molding die according to (2), wherein the plurality of gate inlets are evenly arranged in a circumferential direction of the first ring portion.

[0022] In this structure, the plurality of gate inlets are evenly arranged in the circumferential direction of the first ring portion. Thus, the molten resin flows evenly from the plurality of gate inlets into the ring gate, and the molten resin can be more reliably merged in the ring gate.

[0023] (4) The injection molding die according to (3) above, wherein the plurality of gate inlets are provided in an even number.

[0024] A sub-gate is further provided, the sub-gate connecting the two adjacent gate inlets and communicating with the branch runner.

[0025] In this structure, the two gate inlets are connected by the sub-gate connected to the branch gate. Thus, the number of gate inlets provided in the circumferential direction of the first ring portion can be increased, and the molten resin can be reliably merged by evenly increasing the flow of the molten resin ejected to the ring gate.

[0026] (5) The injection molding die according to any one of (1) to (4), wherein the cavity is cylindrical in shape.

[0027] The gate is disposed approximately at the center of the cavity in the axial direction.

[0028] In this structure, the cavity formed by the mold is cylindrical, and the ring gate is set at the approximately central part of the axial direction of the cavity. Therefore, the molten resin branched up and down is evenly filled in the axial direction of the cavity from the gate outlet set at the approximately central part of the axial direction of the cavity, so that a cylindrical part with suppressed weld can be formed.

[0029] (Effects of the Invention)

[0030] According to the present invention, by filling the cavity with molten resins that merge in the gate at the same time, a component with a suppressed weld line can be molded. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a perspective view showing the external appearance structure of the injection molding die according to the present embodiment.

[0032] Figure 2 yes Figure 1 Floor plan.

[0033] Figure 3 yes Figure 2 Cross-sectional view along line III-III.

[0034] Figure 4 yes Figure 3 An enlarged view of the area surrounded by the dotted line.

[0035] Figure 5A This is a diagram showing a state where molten resin is ejected from a gate inlet to the first ring portion.

[0036] Figure 5B This is a diagram showing how molten resin flows into the second ring portion.

[0037] Figure 5C This is a diagram showing how molten resin flows from the second ring portion to the gate outlet.

[0038] Figure 5D This is a diagram showing how molten resin is filled into a cavity.

[0039] Figure 6 This is a diagram showing how the resin flows into the cavity according to the present embodiment.

[0040] Figure 7 The figure shows the state of resin flowing into the cavity in the prior art. DETAILED DESCRIPTION

[0041] Hereinafter, the structure of the injection molding die 1 according to one embodiment of the present invention will be described in detail with reference to the drawings. In addition, the so-called "same time" when the molten resin M flows into the cavity C at the same time does not strictly mean "simultaneous", but means "approximately at the same time", and the time when the molten resin M flows into the cavity C is flexible for explanation.

[0042] Figure 1 1 is a perspective view showing the appearance structure of the injection molding die 1 of this embodiment. Figure 1 In FIG. 1 , the outer shape of the injection molding die 1 is shown by two-dot chain lines, and the split structure is omitted. The outer shape of the mold is not limited to a cubic shape, but represents the internal structure of the injection molding die 1 when the mold is closed.

[0043] Figure 2 Yes Figure 1 FIG. 1 is a top view of the injection molding die 1 shown in FIG. Figure 2 In FIG. 1 , the outer shape of the injection molding die 1 is omitted.

[0044] Figure 3 yes Figure 2 FIG. 1 is a cross-sectional view taken along line III-III in the plan view of the injection molding mold 1 shown in FIG. Since the flow path of the auxiliary gate 4 is also to be shown, Figure 2 The section line shown in FIG. 4 is not a straight line but is curved along the sub gate 4. The arrows in the figure indicate the direction of the flow of the molten resin M injected into the main runner 2 and filling the cavity C.

[0045] like Figure 3 As shown, the injection molding mold 1 includes a fixed mold 110, a movable mold 120, and a core 130. The fixed mold 110 is fixed at the top and is molded together with the movable mold 120 that can move forward and backward when the molten resin M is filled. The core 130 is arranged between the fixed mold 110 and the movable mold 120, and the internal shape of the injection molding mold 1 after the mold is closed corresponds to the shape of the cavity C, so that a cylindrical component with a through hole can be molded.

[0046] The fixed mold 110 has a main runner 2 and a branch runner 3. A sub-gate 4 communicating with the branch runner 3 and a ring gate 5 are formed between the fixed mold 110 and the movable mold 120 that are molded together.

[0047] The main runner 2 is a mold flow path where the molten resin M injected from the injection machine first flows, and is provided outside the fixed mold 110. Figure 1 As shown, the uppermost end of the main runner 2 is a funnel-shaped liquid inlet for flowing in the molten resin M. The flow path of the main runner 2 is tapered in a manner that increases in diameter from the upper end to the lower end.

[0048] The branch runner 3 is a cylindrical mold flow path whose front end is connected to the main runner 2. Figure 3 The upper part of the runner 3 is arranged outside the fixed mold 110. Return Figure 2 The sub-runner 3 is radially branched into four branches with the lower end axis of the main runner 2 as the center when viewed from above. Figure 1 The side view of one branch runner 3 is substantially U-shaped, and the four branches have the same shape and are evenly arranged in the circumferential direction of the main runner 2. The ends of the branch runners 3 are connected to respective auxiliary gates 4.

[0049] like Figure 1 and Figure 2 As shown, the auxiliary gate 4 branches into two branches in the horizontal direction from the end of the branch runner 3, and the ends of the two tubular flow paths are connected to the ring gate 5, so the shape is roughly U-shaped when viewed from above. The ends of the two branched flow paths are connected to the gate inlet 53 set in the ring gate 5.

[0050] The ring gate 5 has a first ring portion 51, a second ring portion 52 and a step portion 55. Figure 2 The ring gate 5 is in the shape of a disk. The first ring portion 51 has the above-mentioned gate inlet 53 in the circumferential direction, which is connected to the ends of the two flow paths branched from the four auxiliary gates 4. That is, the ring gate 5 has 8 gate inlets 53 evenly arranged in the circumferential direction on the outer peripheral side. Return Figure 3 The thickness of the first ring portion 51 is equal to the height of the tubular flow path of the sub-gate 4 .

[0051] The second ring portion 52 is disposed on the inner circumference side of the first ring portion 51. The second ring portion 52 has a gate outlet 54 communicating with the cavity C, and the gate thickness is thinner than the first ring portion 51. A slope that slopes downward from the first ring portion 51 to the second ring portion 52 forms a step portion 55.

[0052] The gate outlet 54 connects the second ring portion 52 and the cavity C and is in the shape of a slit that is continuous in the circumferential direction of the cavity C. The gate outlet 54 has the same thickness as the second ring portion 52 and is thinner than the first ring portion 51 as described above. The ring gate 5 is provided at the substantially central portion of the cavity C in the axial direction.

[0053] The cavity C is a cylindrical hollow having a fixed height formed when the fixed mold 110 and the movable mold 120 are molded together. The core 130, which is longer in the axial direction than the cavity C, is arranged at the center of the cavity C, so that the cavity C becomes a hollow shape for molding a cylindrical component having a through hole.

[0054] Next, a method of filling the injection molding die 1 with molten resin M injected from an injection machine to form a component with suppressed weld lines will be described in detail with reference to the drawings.

[0055] like Figure 3 As shown by the arrows, the molten resin M is filled into the funnel-shaped liquid inlet provided at the upper end of the main runner 2. The molten resin M passes through the branch runners 3 branched in four directions and reaches the four sub-gates 4 respectively. At the sub-gates 4, the molten resin M further branches into two flow paths and flows into the ring gate 5 evenly from the eight gate inlets 53.

[0056] Figure 4 The figure shows a situation where the molten resin M flows in from the gate inlet 53 of the ring gate 5, flows from the first ring portion 51 to the second ring portion 52, and then continuously fills the cavity C from the gate outlet 54. Figure 3 The arrows in the figure indicate the direction in which the molten resin M flows.

[0057] Figure 5A to Figure 5D Schematically shows a plan view of the molten resin M converging in the ring gate 5. Figure 5A The molten resin M ejected into the ring gate 5 finally flows into Figure 5D The arrows in the figure indicate the direction in which the molten resin M flows. Figure 5A to Figure 5D In FIG. 1 , the outer shape of the injection molding die 1 is omitted.

[0058] like Figure 4 and Figure 5AAs shown in FIG. 1 , the molten resin M having passed through the auxiliary gate 4 is ejected toward the ring gate 5 from eight gate inlets 53 evenly arranged in the outer peripheral direction of the ring gate 5. The molten resin M evenly flows into the first ring portion 51 connected to the gate inlets 53 and continuously expands toward the direction of the cavity C arranged in the center. Figure 5A As shown, in the ring gate 5, the molten resins M have not yet merged.

[0059] Then, if Figure 4 and Figure 5B As shown, the molten resin M flows from the first ring portion 51 to the second ring portion 52 via the stepped portion 55 having an inclined surface. Since the thickness of the second ring portion 52 is thinner than that of the first ring portion 51, the momentum and amount of the molten resin M flowing in from the gate inlet 53 are suppressed in front of the second ring portion 52. Therefore, by retaining a fixed amount of molten resin M at the stepped portion 55 connecting the first ring portion 51 and the second ring portion 52, the molten resins M are reliably merged with each other via the stepped portion 55. Here, the completely merged molten resin M flows from the stepped portion 55 to the second ring portion 52, and continuously flows in a manner concentrated in the direction of the cavity C arranged in the center.

[0060] Then, if Figure 4 and Figure 5C As shown, the molten resin M reaching the second ring portion 52 maintains a uniform flow relative to the circumferential direction of the ring gate 5, and continuously flows toward the gate outlet 54 connected to the cavity C. As described above, at the step portion 55, the molten resin M continuously ejected from the gate inlet 53 gradually stagnates, and the pressure of the accumulated resin continuously squeezes the molten resin M from the step portion 55 toward the second ring portion 52. Therefore, the molten resin M flowing in the second ring portion 52 maintains a state of being completely merged via the step portion 55, and without generating a gap, it continues to expand to the cavity C arranged in the center with momentum.

[0061] Then, if Figure 4 and Figure 5D As shown, the molten resin M that advances in a completely merged state and reaches the gate outlet 54 without time difference flows into the cavity C that is a hollow arranged in the center of the ring gate 5 through the gate outlet 54. The gate outlet 54 is arranged at the approximately central part of the axial direction of the cavity C, and is in the shape of a slit that is continuous in the circumferential direction of the cavity C. The height of the gate is the same as the thickness of the second ring portion 52. Therefore, the flow of the molten resin M that completely merges at the ring gate 5 will not be broken by passing through the gate outlet 54 from the second ring portion 52, and the momentum will not be offset. With this structure, the molten resin M is uniformly filled into the cavity C from the circumferential direction of the ring gate 5 at the same time.

[0062] like Figure 4As shown, the flow of the molten resin M flowing into the cavity C from the substantially central portion in the axial direction of the cavity C branches at a constant speed in the vertical direction while filling the circumference, and completely fills the cavity C which is a hollow. Since the flow of the molten resin M branched in the vertical direction and filled inside the cavity C does not face each other, the possibility of the occurrence of a weld caused by the confluence of the resin in the cavity C is suppressed.

[0063] After the molten resin M is filled, the molten resin M is cooled and solidified, and then the movable mold 120 is moved to open the mold with the fixed mold 110. The core 130 appears outside due to the mold opening, so it can be easily extracted, so that a cylindrical component with a through hole and suppressed weld can be formed.

[0064] According to this embodiment, the following effects are achieved.

[0065] The injection molding mold 1 of this embodiment has: a ring gate 5, which injects molten resin M into the cavity C arranged in the center; and four branch runners 3, which supply the molten resin M supplied by the main runner 2 to the ring gate 5; the ring gate 5 has: a first ring portion 51, which has 8 gate inlets 53 respectively connected to the four branch runners 3; a second ring portion 52, which has a slit-shaped gate outlet 53 extending along the circumferential direction and connected to the cavity C, and is arranged on the inner side of the first ring portion 51 and is thinner than the first ring portion 51; and a step difference portion 55, which is arranged between the first ring portion 51 and the second ring portion 52, and connects the first ring portion 51 and the second ring portion 52.

[0066] Thus, the molten resin M that passes through the four branch runners 3 and is ejected from the eight gate inlets 53 to the ring gate 5 starting from the main runner 2 flows from the first ring portion 51 to the second ring portion 52 via the step portion 55, so that the molten resin M can be reliably merged in the ring gate 5. Furthermore, the ring gate 5 has a slit-shaped gate outlet 54 that extends in the circumferential direction and communicates with the cavity C arranged in the center. Thus, the molten resin M that has reliably merged in the ring gate 5 can flow uniformly from the slit-shaped gate outlet 54 into the cavity C at the same time, so that a component with suppressed welds can be formed.

[0067] Figure 6 1 is a schematic plan view showing a situation in which a molten resin M is filled into a cylindrical cavity C in the present invention. Figure 6 In the figure, the outline of the ring gate 5 is omitted. The arrows in the figure indicate the direction in which the molten resin M flows.

[0068] Figure 7 The schematic plan view shows a state in which a cylindrical cavity C1 is filled with molten resin M in the prior art. The arrows in the figure show the direction in which the molten resin M flows.

[0069] Conventionally, when molten resin M is ejected from gate outlet 54B provided in sub-gate 4B into cavity C1, molten resin M flows into cavity C1 in two branches, and a weld seam is formed at point WP where two flows of molten resin M meet in opposite directions.

[0070] In contrast, in the present invention, as described above, the molten resin M is uniformly filled into the cavity C from the circumference of the ring gate 5 at the same time through the circumferentially continuous slit-shaped gate outlet 54. Therefore, in the cavity C, there is no possibility that the flow flows of the molten resin M will merge in opposite directions, and the possibility of generating a welding seam is suppressed.

[0071] In addition, the gate outlet 54 of the present embodiment is a slit that is continuous in the circumferential direction.

[0072] As a result, the molten resin M can more easily flow into the cavity C arranged in the center of the ring gate 5 at the same time, thereby improving the molding effect of the component with suppressed welds. In addition, since the molten resin M can more easily flow into the cavity C at the same time, the composition of the resin flowing into the cavity can be made uniform, and a molded product can be formed that is excellent in not only the effect of suppressing welds in the appearance shape but also excellent in mechanical properties such as tensile strength, tensile elongation, bending strength, impact resistance, etc.

[0073] In addition, the eight gate inlets 53 of the present embodiment are evenly arranged in the circumferential direction of the first ring portion 51 .

[0074] Thus, the molten resin M flows evenly into the ring gate 5 from the eight gate inlets 53 , and the molten resin M can be more reliably joined in the ring gate 5 .

[0075] In addition, the present embodiment has an even number of eight gate inlets 53 provided, and further includes four sub-gates 4 that connect two adjacent gate inlets 53 and communicate with four branch runners 3 .

[0076] Thus, the number of gate inlets 53 arranged in the outer peripheral direction of the first ring portion 51 can be increased, and the flow flow of the molten resin ejected into the annular gate 5 can be evenly increased to make the flow flow of the molten resin M ejected into the annular gate 5 more uniform and effectively merged.

[0077] In addition, the cavity C of the present embodiment has a cylindrical shape, and the ring gate 5 is provided at a substantially central portion of the cavity C in the axial direction.

[0078] Thus, the molten resin M branched up and down is uniformly filled in the axial direction of the cavity C from the gate outlet 54 of the ring gate 5 provided at the substantially axial center of the cavity C, thereby forming a cylindrical component with suppressed welds.

[0079] In addition, in the present embodiment, the gate outlet 54 is a slit shape continuous in the circumferential direction, but the present invention is not limited thereto, and a plurality of slit-shaped gate outlets may be provided in the circumferential direction. In the case where a plurality of slit-shaped gate outlets are provided in the circumferential direction, the molten resin M flowing from the gate outlet into the cavity C can be reliably merged in the cavity before reaching the core 130 by setting the shape or number of the gate outlets, and the same effect can be achieved.

[0080] In addition, in this embodiment, the four auxiliary gates 4 are connected to the four branch runners 3, but the present invention is not limited to this structure. The number of branch runners is not limited, and the configuration and shape are not limited. In addition, it is also possible to set a structure in which the branch runner without auxiliary gates is connected to the ring gate, which can be freely designed in accordance with the mold.

[0081] In the present embodiment, the ring gate 5 is provided at the substantially central portion of the cavity C in the axial direction, but the present invention is not limited thereto. The ring gate 5 may be provided at a free position relative to the cavity C in the axial direction.

[0082] As mentioned above, the preferred embodiment of the present invention has been described. However, the present description is not limited to the above-mentioned embodiment, and can be appropriately changed within the scope of the gist of the present invention.

[0083] Reference numerals

[0084] C-type cavity

[0085] 1Injection molding die

[0086] 2 Main runner

[0087] 3 points pouring channel

[0088] 5. Ring gate (ring-shaped gate)

[0089] 51 First Ring

[0090] 52 Second ring

[0091] 53 Gate entrance

[0092] 54 Gate outlet

[0093] 55 Step difference

Claims

1. An injection molding die, comprising: The annular gate injects molten resin into the cavity disposed in the center; and A plurality of branch runners supply the molten resin supplied from the main runner to the gate; The aforementioned gate has: The first ring portion has a plurality of gate inlets respectively connected to the plurality of sub-runners; The second ring portion has a slit-shaped gate outlet extending in the circumferential direction and communicating with the aforementioned cavity, and is arranged inside the aforementioned first ring portion and is thinner than the aforementioned first ring portion; and, The step portion is disposed between the first ring portion and the second ring portion, and connects the first ring portion and the second ring portion.

2. The injection molding die according to claim 1, wherein: The gate outlet is a slit that is continuous in the circumferential direction.

3. The injection molding die according to claim 2, wherein: The plurality of gate inlets are evenly arranged in a circumferential direction of the first ring portion.

4. The injection molding die according to claim 3, wherein: The aforementioned multiple gate inlets are provided in an even number, A sub-gate is further provided, the sub-gate connecting the two adjacent gate inlets and communicating with the branch runner.

5. The injection molding die according to any one of claims 1 to 4, wherein: The aforementioned cavity is cylindrical in shape. The gate is disposed approximately at the center of the cavity in the axial direction.

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