Injection molding mold

Abstract

To suppress mold wear to the utmost even when injection molding a resin containing a fiber reinforcing material and by this, to enable continuous implementation of production of injection molded works at low cost.SOLUTION: This injection-molding mold 11 includes a mold cavity 13 becoming a molding space of an injection molded work W, a runner 15 connected to the mold cavity 13, and a gate 16 positioned at the tip of the runner 15 and open to the mold cavity 13. Cross sections of the runner 15 and the gate 16 both have flat shapes, and a longitudinal dimension L1 of the gate 16 is larger than a cross section longitudinal dimension W2 of the runner 15.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an injection mold.

Background Art

[0002] As is well known, injection-molded resin products are not limited to small parts, and are also applied to large and strength-required parts such as panel-shaped members that form part of an automobile body.

[0003] In addition, in this type of molded product, in order to improve strength or dimensional stability, resin blended with fibrous reinforcing materials such as carbon fiber and glass fiber is also injection-molded (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in this type of injection molding, there is a problem that the molding surface of the injection mold may be worn out by the fibrous reinforcing material contained in the injection material. That is, since the fibrous reinforcing material such as glass fiber contained in the injection material exhibits high rigidity, with injection, the fibrous reinforcing material in the injection material collides with the inner surface of the runner part, the inner surface of the gate part, or the inner surface of the mold (molding surface) near the gate part, so that the above-mentioned inner surface and molding surface tend to be worn out. Therefore, by continuing injection molding, the wear of the runner part and the gate part progresses, and the shape of the gate part changes, which may change the flow pattern of the injection material. Depending on the change in the flow pattern, there may be a problem of the occurrence of weld lines and ultimately molding defects. Or, the wear of the molding surface near the gate part may transfer the wear marks to the surface of the injection molded product, which may also lead to a deterioration in the appearance quality.

[0006] As mentioned above, when a mold becomes worn out, the worn part needs to be repaired, but naturally, this repair takes a considerable amount of time. In addition, to avoid production stopping during repairs, it is necessary to prepare a spare mold separately, which increases costs.

[0007] In view of the above circumstances, this specification aims to address the technical problem of minimizing mold wear as much as possible, even when injection molding resins containing fibrous reinforcing materials, thereby enabling the continuous production of injection-molded products at low cost. [Means for solving the problem]

[0008] The aforementioned problems are solved by the injection molding die according to the present invention. Specifically, this die is an injection molding die comprising a cavity that serves as the molding space for an injection molded product, a runner connected to the cavity, and a gate located at the tip of the runner and opening into the cavity, characterized in that both the cross-section of the runner and the gate have a flattened shape, and the longitudinal dimension of the gate is larger than the longitudinal dimension of the cross-section of the runner.

[0009] Conventionally, regarding the flow mechanism of injection material (resin) in injection molding, it has been thought that a skin layer of solidified resin is formed on the inner surface of the mold immediately after the start of injection, and that when injecting resin containing fibrous reinforcing material, the inner surface of the mold is protected from the fibrous reinforcing material by the skin layer. The inventors of this invention have conducted extensive studies on this point through flow analysis and actual machine verification, and have found that a skin layer is not formed on the entire inner surface of the mold immediately after the start of injection, and that depending on the flow velocity of the injection material, the skin layer is less likely to form in areas where the flow velocity is relatively high, and that wear on the inner surface of the mold due to the fibrous reinforcing material is more likely to occur in areas where the skin layer is less likely to form. In other words, the inventors have found that there is a certain correlation between the degree of wear due to the fibrous reinforcing material and the flow velocity of the injection material at the area of ​​wear.

[0010] The present invention is based on the above findings and aims to reduce the flow velocity of the injection material near the gate, where a relatively high flow velocity distribution tends to occur. To achieve this, the longitudinal dimension of the flattened gate is made larger than the longitudinal dimension of the corresponding runner's cross-section. This configuration makes it possible to relatively reduce the flow velocity on the inner surface of the mold, especially immediately after injection from the gate. Therefore, it becomes possible to actively form a skin layer on the inner surface of the mold near the gate, effectively protecting the inner surface of the mold from the fibrous reinforcing material. Furthermore, even if a skin layer is not formed, the velocity of the fibrous reinforcing material is also reduced due to the reduced flow velocity, thus mitigating collisions with the inner surface of the mold. As a result of these effects, wear on the inner surface of the mold is suppressed, and the frequency of repairs can be reduced. In addition, if wear on the inner surface of the mold is suppressed, the time required for repairs is also shortened, so repairs can be completed within the operating period, and thus spare molds become unnecessary. Therefore, the injection molding mold according to the present invention makes it possible to suppress the total cost related to the continuous operation of injection molding. Furthermore, because the gate has a flattened shape, even if the cross-sectional area of ​​the gate increases by increasing its longitudinal dimension, it is relatively easy to cut the solidified portion in the runner and the injection-molded product at their boundary (gate). Therefore, it is possible to avoid situations where a portion of the solidified portion in the runner remains in the injection-molded product, thereby ensuring productivity.

[0011] Furthermore, in the injection molding die according to the present invention, the runner may have a shape in which its longitudinal cross-sectional dimension increases as it approaches the gate at the tip of the runner.

[0012] By shaping the tip of the runner as described above, the injection material can be diffused over a wider area. Therefore, it becomes possible to further reduce the flow velocity. In addition, because the fibrous reinforcing material is also diffused over a wider area by this shape, it becomes possible to more effectively suppress wear on the inner surface of the mold due to collision with the inner surface.

[0013] Furthermore, in the injection molding die according to the present invention, the cavity has a shape corresponding to a panel-shaped member, and the gate may open in a portion of the molding surface constituting the cavity that corresponds to the non-design side of the edge of the panel-shaped member. In this case, the portion corresponding to the corner created between the edge and the main body of the panel-shaped member by bending the edge towards the non-design side may be given an R shape.

[0014] In the case of injection-molded products that are panel-shaped members with a design surface, the area where a gate can be provided may be limited to the non-design surface area, as described above. In this case, the distance from the gate to the inner surface of the mold opposite the gate (the part of the molding surface that forms the design surface) becomes very short, equal to the thickness of the panel-shaped member, so there is a concern about wear on the molded surface due to the fibrous reinforcing material. In this regard, for example, if the edge is bent towards the non-design surface side as described above, and the distance from the gate to the molded surface opposite the gate is increased, wear on the molded surface due to the fibrous reinforcing material can be suppressed. On the other hand, by bending the edge, a corner inevitably occurs between the edge and the main body of the panel-shaped member. This corner is the corner of the molding surface of the injection molding die and is located in a position visible from the gate. Therefore, if, for example, the fibrous reinforcing material in the resin is injected linearly toward the corner, there is a high risk that the corner will be severely worn down due to collision with the fibrous reinforcing material. In this regard, by pre-shaping the corners of the molded surface corresponding to the corners of the injection-molded product as described above into an R shape, the frequency of collisions between the fibrous reinforcing material and the corners is reduced, or the collisions are mitigated. Therefore, with this configuration, it is possible to suppress wear on the molded surface during injection. [Effects of the Invention]

[0015] As described above, with the injection molding die according to the present invention, even when injection molding a resin containing fibrous reinforcing material, die wear can be suppressed as much as possible, making it possible to continue producing injection molded products at low cost. [Brief explanation of the drawing]

[0016] [Figure 1]It is a cross-sectional view of an injection molding apparatus according to an embodiment of the present invention. [Figure 2] It is a diagram conceptually showing the arrangement mode of a runner in an injection mold shown in FIG. 1 in relation to the positional relationship with an injection molded product. [Figure 3] It is an A-A cross-sectional view of the gate peripheral portion of the injection mold shown in FIG. 2. [Figure 4] It is an A-A cross-sectional view when the gate peripheral portion shown in FIG. 3 is viewed from the side of the injection molded product. [Figure 5] It is a perspective view conceptually showing the three-dimensional shape of the gate peripheral portion shown in FIG. 3. [Figure 6] It is a view of the gate shown in FIG. 3 as viewed from the direction of arrow B. [Figure 7] It is an A-A cross-sectional view of the gate peripheral portion of the injection mold shown in FIG. 2, and it is a cross-sectional view when the runner and the gate have conventional shapes. [Figure 8] It is a perspective view conceptually showing the three-dimensional shape of the gate peripheral portion shown in FIG. 7.

Mode for Carrying Out the Invention

[0017] Hereinafter, the content of an injection mold according to an embodiment of the present invention and an injection molding apparatus provided with this mold will be described based on the drawings.

[0018] FIG. 1 shows a cross-sectional view of an injection molding apparatus 10 according to an embodiment of the present invention. This injection molding apparatus 10 mainly includes an injection mold 11 for obtaining an injection molded product of a predetermined shape, and an injection machine 12 for injecting and supplying a predetermined injection material to the injection mold 11.

[0019] As the material to be injected by the injection machine 12, a resin having an arbitrary and known composition can be used. For example, in the case of a relatively large panel-shaped member in the form of a thin plate as in this embodiment and when high strength is required, a resin obtained by blending a predetermined amount of fibrous reinforcing materials such as glass fibers and carbon fibers with a known base resin such as a thermoplastic resin can be suitably used as the injection material. Note that the dimensions (longitudinal dimension, aspect ratio) of the fibrous reinforcing material can be set within an arbitrary range as long as it functions as a reinforcing material for the resin to be injected.

[0020] The injection mold 11 for injection molding includes a main body of the injection mold 1 of the injection mold 11, a cavity 13 formed inside the main body and serving as a molding space for the injection molded product, a sprue 14 connected to the nozzle of the injection machine 12, a runner 15 connecting the sprue 14 and the cavity 13, and a gate 16 located at the tip of the runner 15 and opening into the cavity 13. In this embodiment, the injection mold 11 for injection molding is a mold for injection molding a panel-shaped member, and the cavity 13 has a shape corresponding to the panel-shaped member that becomes the injection molded product (see FIG. 2). In this illustrated example, an injection mold 11 for injection molding a back door inner as the panel-shaped member is illustrated.

[0021] Also, in this case, a plurality of runners 15 are disposed at predetermined positions of the cavity 13 via the gate 16. In this embodiment, as shown in FIG. 2, a plurality of runners 15 and gates 16 are provided in a portion of the cavity 13 corresponding to a region on the non-design surface W1 side of the edge Wa of the panel-shaped member W. In this illustrated example, one or more runners 15 and gates 16 are also provided in a portion corresponding to the central portion Wb on the non-design surface W1 side of the panel-shaped member W.

[0022] Figure 3 shows a cross-sectional view of the area around the gate 16 of the injection molding die 11 shown in Figure 2 (cross-sectional view AA in Figure 2). Figure 5 conceptually shows the three-dimensional shape of the area around the gate 16 shown in Figure 3, i.e., the runner 15 and cavity 13 near the gate 16. Figure 6 is a view of the gate shown in Figure 3 from its opening direction (viewed from the direction of arrow B in Figure 3). As shown in these figures (especially Figure 6), the gate 16 has a flattened shape. In this embodiment, the gate 16 opens to the portion of the cavity 13 corresponding to the edge Wa, such that the orientation along the edge Wa of the panel-shaped member W that will become the injection molded product coincides with the longitudinal direction of the gate 16 (see Figures 2 and 3).

[0023] At least the tip portion 15a of the runner 15 has a flattened shape, similar to the gate 16 (see Figure 5). Furthermore, the longitudinal direction of the flattened tip portion 15a coincides with the longitudinal direction of the gate 16.

[0024] In this case, the aspect ratio, that is, the ratio L1 / S1 of the longitudinal dimension L1 to the short-direction dimension S1 of the gate 16, is set to, for example, 10 or more, preferably 20 or more.

[0025] Here, the longitudinal cross-sectional dimension d1 of the tip portion 15a of the runner 15 is set to a value greater than the longitudinal cross-sectional dimension d2 of the runner 15 body (see Figure 5). In this embodiment, the tip portion 15a of the runner 15 has a shape such that its longitudinal cross-sectional dimension d1 increases as it approaches the gate 16. In this case, the longitudinal cross-sectional dimension d1 of the portion of the tip portion 15a of the runner 15 that connects to the gate 16 coincides with the longitudinal dimension L1 of the gate 16.

[0026] Regarding the shape of the cavity 13, in this embodiment, at least the portion of the edge Wa of the panel-shaped member W where the runner 15 (gate 16) is provided is bent toward the non-design surface W1 (see Figure 3). In this way, when the edge Wa of the panel-shaped member W formed by the cavity 13 is bent toward the non-design surface W1, a corner Wc is created between the edge Wa and the main body of the panel-shaped member W (see Figure 4). This corner Wc becomes a corner 17a on the molding surface 17 of the corresponding cavity 13. This corner 17a is positioned so that it can be seen from the gate 16 (see Figure 3 in both cases).

[0027] In this embodiment, the corner portion 17a of the molded surface 17 positioned as described above has an R shape (see Figure 3).

[0028] Next, the effects of the injection molding die 11 with the above configuration will be explained in comparison with a conventional injection molding die 21 (see Figures 7 and 8).

[0029] For example, as shown in Figures 7 and 8, when an injection molding die 21 equipped with a runner 22 having a conventional shape with a constant longitudinal cross-sectional dimension is used, and a resin containing fibrous reinforcing material is injected by an injection machine 12 at an injection pressure and injection volume (flow rate) at a level considered necessary for injection molding, the resin passes through the gate 23 and is injected into the cavity 24 at the same speed as when it flows through the runner 22. In this case, immediately after the start of injection, a skin layer R formed by solidified resin is formed on the inner surface of the injection molding die 21 (molding surface 25, runner 22, and inner surface of gate 23). However, the skin layer R is less likely to form in areas where the flow velocity of the injected material is relatively high. In Figure 7, for example, the skin layer R is less likely to form in the area of ​​the molding surface 25 near the gate 23, or in the area facing the gate 23. Since areas where the skin layer R is less likely to form are more susceptible to attack by the fibrous reinforcing material, the areas where the skin layer R is less likely to form tend to experience more wear on the inner surface of the die due to the fibrous reinforcing material.

[0030] In contrast, in the injection molding die 11 according to this embodiment, the longitudinal dimension L1 of the flattened gate 16 is made larger than the longitudinal cross-sectional dimension d2 of the corresponding runner 15 (runner 15 body) in order to reduce the flow velocity of the injection material near the gate 16, which tends to show a relatively high flow velocity distribution. By configuring it in this way, the flow velocity, especially near the gate 16 on the inner surface of the die 11, can be relatively reduced. Therefore, it becomes possible to actively form a skin layer R in this region and effectively protect the inner surface of the die 11 from the fibrous reinforcing material. Furthermore, even if a skin layer R is not formed, the velocity of the fibrous reinforcing material is also reduced due to the reduction in flow velocity, so collision with the inner surface of the die 11 is also mitigated. As a result of the above effects, wear on the inner surface of the die 11 is suppressed, so the frequency of repairs can be reduced. Also, if wear on the inner surface of the die 11 is suppressed, the time required for repairs will be shorter, so repairs can be completed within the operating period, and thus spare dies become unnecessary. Based on the above, the injection molding die 11 according to this embodiment makes it possible to suppress the total cost associated with the continuous execution of injection molding. Furthermore, since the gate 16 has a flattened shape, even if the cross-sectional area of ​​the gate 16 increases by increasing its longitudinal dimension L1, the portion solidified by the runner 15 and the injection molded product (in this case, the panel-shaped member W) can be cut relatively easily at their boundary (the portion of the gate 16). Therefore, it is possible to avoid situations in which a portion of the solidified portion by the runner 15 remains in the injection molded product and to ensure productivity.

[0031] Furthermore, in this embodiment, the tip portion 15a of the runner 15 is shaped such that its longitudinal cross-sectional dimension d1 increases as it approaches the gate 16 at the tip of the runner 15, allowing the injection material to be diffused over a wider area. Therefore, it is possible to further reduce the flow velocity. In addition, by adopting the above shape, the fibrous reinforcing material is also diffused over a wider area, making it possible to more effectively suppress wear on the inner surface of the mold 11 due to collision with the inner surface.

[0032] Furthermore, in this embodiment, the cavity 13 is shaped to correspond to the panel-like member W, and the gate 16 is opened in the portion of the molding surface 17 constituting the cavity 13 that corresponds to the area on the non-design surface W1 side of the edge Wa of the panel-like member W (see Figures 2 to 4). In this case, by bending the edge Wa toward the non-design surface W1 side, the corner portion 17a, which corresponds to the corner Wc created between the edge Wa and the main body of the panel-like member W, is given an R shape (see Figure 3).

[0033] As previously described, when the edge Wa of the panel-shaped member W is bent toward the non-design surface W1, a corner Wc is created between the edge Wa and the main body of the panel-shaped member W. In this case, a corner 25a corresponding to this corner Wc is provided on the molding surface 25 of the mold 21 (see Figure 7). Due to its structure, this corner 25a is located in a position visible from the gate 23. Therefore, if, for example, the fibrous reinforcing material in the resin is injected linearly from the gate 23 toward the corner 25a, there is a high risk that the corner 25a will be severely damaged due to collision with the fibrous reinforcing material. In contrast, in this embodiment, the corner 17a of the molding surface 17 is made R-shaped (see Figure 3), so the frequency of collisions between the fibrous reinforcing material and the corner 17a is reduced, or the collisions are mitigated. Therefore, with this configuration, it is possible to suppress wear on the molding surface 17 during injection.

[0034] Although one embodiment of the present invention has been described above, the injection molding die according to the present invention may also have configurations other than those described above, without departing from the spirit of the invention.

[0035] For example, in the above embodiment, the shape of the runner 15 tip side (tip portion 15a) is exemplified as having a shape in which the longitudinal cross-sectional dimension d1 increases as it approaches the gate 16, but of course, it is not limited to this. As long as the longitudinal dimension L1 of the gate 16 is larger than the longitudinal cross-sectional dimension d2 of the runner 15 body, and the inside of the cavity 13 can be filled with injection material (resin compounded with fibrous reinforcing material) by injection, the tip side of the runner 15 can take any shape.

[0036] Furthermore, there are no particular restrictions on the short-side dimension S1 of the gate 16. For example, the short-side dimension S1 can be set to any size as long as it is possible for the worker to separate the solidified portion of the runner 15 from the injection-molded product at the gate 16 portion by hand after molding.

[0037] Furthermore, the positional relationship between the gate 16 and the corner 17a is also arbitrary. For example, from the viewpoint of minimizing the impact of the fibrous reinforcing material on the corner 17a, an excess material Wd may be provided between the gate 16 and the corner 17a, or more precisely, on the corner 17a side of the edge Wa that is bent toward the non-design surface W1 side relative to the gate 16 (see Figure 4). By providing the excess material Wd adjacent to the gate 16 of the injection molded product (panel-shaped member W) in this way, a space 18 corresponding to this excess material Wd is formed between the gate 16 and the corner 17a. As a result, the corner 17a can be moved away from the gate 16 by the amount of space 18, so this configuration also makes it possible to mitigate the impact of the fibrous reinforcing material on the corner 17a.

[0038] Furthermore, while the above explanation has illustrated the case of injection molding a panel-shaped member W as an injection-molded product, it goes without saying that the injection molding die according to the present invention can be applied to injection-molded products that have a shape other than a panel-shaped member W. [Explanation of symbols]

[0039] 10 Injection molding equipment 11 Injection mold 12 Injection machine 13 Cavity 14 Spruce 15 Runner 15a Tip Gate 16 17 Molding surface 17a Corner 18 Space 21 Injection mold 22 Runner Gate 23 24 Cavity 25 Molding surface 25a Corner L1 Longitudinal dimension R Skin Layer S1 Short side dimension d1, d2 Longitudinal dimensions of the cross-section (runner) W Panel-shaped member W1 Non-design surface W2 Design surface Wa edge Wb central part Wc corner Wd Extra flesh part

Claims

[Claim 1] In an injection molding die comprising a cavity that serves as the molding space for an injection-molded product, a runner connected to the cavity, and a gate located at the tip of the runner and opening into the cavity, A resin containing a fibrous reinforcing material is injected into the cavity via the runner and the gate. The cavity has a shape corresponding to the panel-like member as an injection-molded product, in which one side is a design surface and the other side is a non-design surface, and the portion corresponding to the edge of the panel-like member is bent towards the non-design surface of the panel-like member. The gate has an opening in the portion corresponding to the end face of the edge, An excess material portion is provided on the non-design surface side of the edge of the panel-like member to increase the thickness dimension of the end face, and a space corresponding to the excess material portion is provided in the cavity. The cross-section of the runner and the gate both have a flattened shape. An injection molding die characterized in that the longitudinal dimension of the gate is larger than the longitudinal cross-sectional dimension of the runner.

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