JP2012045903A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce material cost and to improve productive efficiency by reducing generation of defective products caused by mixing a minute amount of former color resin after completing color change.SOLUTION: A route of a runner is changed so as to prevent the former color resin P flowing along a side surface of the runner from being arranged on a design surface side of a product. For example, the runner 50 is made to diverge into a first branch runner 51 and a second branch runner 52, and the side surface where the former color resin P exists (an upper side surface of an upstream side runner 53) is made to be a unification surface of the first branch runner 51 and the second branch runner 52 to arrange the former color resin P at the center part of a downstream side runner 54 and to sandwich the former color resin P between latter color resins Q.

Description

  The present invention relates to an injection mold, and more particularly to a technique for reducing the occurrence of defective products after color change in injection molding using an injection mold having a hot runner.

  In resin injection molding, the color of the product may be changed by changing the color of the resin supplied to the mold. At this time, since the rear color resin is introduced into the screw after the front color resin, the front color resin and the rear color resin adjacent in the screw are mixed to produce a color mixture resin. A product molded with this color-mixed resin must be discarded as a defective product.

  For example, in the color changing method shown in Patent Document 1, the core layer made of a mixed color resin is completely covered inside the skin layer made of the previous color resin by adjusting the timing of the color change. The number of defective products is reduced by preventing the exposure of the mixed color resin.

JP 2003-300224 A

  However, in the case of an injection mold having a hot runner, defective products may occur even after the color change is completed, that is, after all the previous color resin and mixed color resin are injected into the cavity. The reason will be described in detail below.

  An injection mold 100 shown in FIG. 13 has a fixed mold 110 and a movable mold 120, and a hot runner nozzle 113 is provided on the inner periphery of a through hole 112 formed in the fixed mold 110. A heating unit 117 is provided on the outer periphery of the hot runner nozzle 113, and the resin flowing through the resin flow path (hot runner 141) inside the hot runner nozzle 113 is maintained in a molten state by being heated by the heating unit 117. .

  In the injection mold 100 as described above, the front end portion (near the outlet) of the hot runner nozzle 113 cannot secure a sufficient space for disposing the heating unit 117. In addition, since the tip of the hot runner nozzle 113 is in contact with the mold (cavity plate 111), heat is likely to escape. Furthermore, when the shoulder surface 141a is formed in the vicinity of the outlet of the hot runner 141 as shown in the drawing, the molten resin collides with the shoulder surface 141a, so that the fluidity of the molten resin is deteriorated. As described above, in the vicinity of the outlet of the hot runner 141, it is difficult to maintain a high temperature state, and the fluidity of the resin also decreases, so the front color resin P (or a mixed color resin, and so on) is solidified on the shoulder surface 141a. Easy to stick to. The front color resin P sticking to the inner wall of the hot runner 141 is gradually mixed into the rear color resin injected thereafter. At this time, the amount of the front color resin mixed in the product is small, but if this front color resin P is exposed to the design surface of the product even a little, the entire product must be discarded as a defective product.

  The problem to be solved by the present invention is that in an injection mold having a hot runner, it is possible to reduce the occurrence of defective products due to a small amount of front color resin after color change is completed, thereby reducing material costs and improving production efficiency. There is to plan.

  In order to investigate the state in which the front color resin is mixed in the rear color resin in the runner, the present inventors perform injection molding using the injection mold shown in FIG. 13 and immediately after the color change is completed. The cross section of the resin solidified in the runner was analyzed. As a result, it has been clarified that the front color resin is not scattered uniformly in the runner but is present near the side surface of the runner. Specifically, as shown in FIG. 14, the front color resin is present in the vicinity of one side surface (side surface on the fixed mold side) of the runner 150, and the central portion of the runner 150 or the other side surface (movable mold side). Almost no).

  Further detailed analysis revealed that the front color resin P in the runner 150 behaved as shown in FIG. That is, the front color resin P stuck to the vicinity of the outlet of the hot runner 141 is supplied to the runner 150 by being pulled by the rear color resin Q and flows along the side surface of the runner. At this time, of the front color resin P stuck to the entire circumference of the shoulder surface 141a of the hot runner 141, the front color resin closer to the cavity flows along the side surface 151 on the fixed mold 110 side of the runner 150 (FIG. 15 P1). On the other hand, of the front color resin P sticking to the shoulder surface 141a, the front color resin far from the cavity stays at the end of the runner 150 opposite to the cavity (see P2 in FIG. 15).

  The present inventors consider that the use of the behavior of the front color resin as described above can suppress the exposure of the front color resin to the product surface and reduce the occurrence of defective products, leading to the following inventions. It was. That is, the injection mold according to the present invention includes a cavity, a hot runner that circulates the molten resin while heating, and a runner that communicates the cavity and the hot runner, and the front color that flows along the side surface of the runner The runner path is changed so that the resin is not arranged on the design surface side of the product.

  Specifically, for example, the runner is branched into a first branch runner and a second branch runner, these are merged again before the cavity, and the front color resin flows along the side surface of the runner before the branch. By making the side surface to be a joining surface of the first branch runner and the second branch runner, the front color resin can be prevented from being arranged on the design surface side of the product.

  As described above, since the front color resin flows along the side surface of the runner, if the runner is branched, the molten resin consisting only of the rear color resin and the molten resin mixed with the front color resin can be separated. it can. If the side surface on which the front color resin exists is the joining surface of the first branch runner and the second branch runner, the front color resin can be disposed at the center of the runner and sandwiched between the rear color resins. By injecting the resin in this state into the cavity from the runner, it is possible to reduce the risk that the front color resin is exposed on the surface (design surface) of the product. Further, since the front color resin can be used as a part of the product, the yield can be increased as compared with the case where the front color resin is discarded. The “molten resin consisting only of the rear color resin” refers to a molten resin that does not substantially contain the front color resin, and includes a case where a very small amount of the front color resin is mixed (the same applies hereinafter).

  At this time, if the flow path areas and flow path lengths of the respective branch runners are different, the resin concentrates on the branch runner having a relatively low flow resistance, and the front color resin may not be separated well. Therefore, it is preferable that the flow path areas and flow path lengths of the first branch runner and the second branch runner are made equal so that the flow resistance of the molten resin flowing through each branch runner becomes equal.

  Alternatively, the runner is branched into a main runner that communicates with the cavity and a retreat runner that does not communicate with the cavity, and the front color resin that flows along the side surface of the runner before the branch flows into the retreat runner. It is possible to prevent the color resin from being arranged on the design surface side of the product.

  As described above, since the front color resin flows along the side surface of the runner, if the runner is branched, the molten resin consisting only of the rear color resin and the molten resin mixed with the front color resin can be separated. it can. Then, by causing the front color resin to flow into the retreat runner that does not communicate with the cavity, it is possible to prevent the front color resin from being supplied to the cavity and to prevent the front color resin from being mixed into the product.

  In this case, if the entire circumference of the side surface of the runner before branching is made continuous with the side surface of the retreat runner, the pre-colored resin that flows along the side surface of the runner can be surely flowed into the retreat runner. Further, if the retreat runner communicates with the outside of the mold, the resin mixed with the front color resin can be discharged to the outside of the mold. Alternatively, the retreat runner may be a dead end inside the mold and discarded after the resin is solidified.

  Alternatively, by twisting the runner and changing the direction of the side surface, the front color resin that flows along the side surface can be disposed on the back side of the product.

  As described above, since the front color resin is present near the side surface of the runner, if this side surface is disposed on the back surface (the surface opposite to the design surface) of the product, the front color resin present near the side surface is the product. The risk of exposure to the design surface can be reduced. For example, if the side surface of the runner in which the front color resin exists is disposed on the back side of the product, the runner may be extended to the cavity as it is. However, if the side surface of the runner where the front color resin exists is arranged on the design surface side of the product, the front color resin is supplied to the design surface side of the product when the runner is extended straight. The risk of exposing the colored resin is increased. Therefore, as described above, the runner is twisted to change the direction of the side surface, and the front color resin flowing along the side surface is disposed on the back side of the product, so that the front color resin is exposed on the design surface of the product. The risk of doing so can be reduced.

  Alternatively, the runner is branched into a first branch runner that distributes the rear color molten resin made of only the rear color resin and a second branch runner that distributes the front color mixed molten resin mixed with the front color resin, and the first branch After injecting the back-colored molten resin from the runner into the cavity, the front-colored resin is injected into the cavity from the second branch runner and the front-colored resin is wrapped with the back-colored resin, so that the front-colored resin becomes the design surface of the product It can be prevented from being placed on the side.

  As described above, since the front color resin flows along the side surface of the runner, if the runner is branched, a molten resin consisting only of the rear color resin (rear color molten resin) and a molten resin mixed with the front color resin (Pre-color mixed molten resin) can be separated. At this time, the runner was branched into a first branch runner for circulating the rear color molten resin and a second branch runner for circulating the front color mixed molten resin, and the rear color molten resin was injected into the cavity from the first branch runner. Later, when the front color resin is injected into the cavity from the second branch runner and the front color resin is wrapped with the rear color resin, exposure of the front color resin to the product surface can be prevented. For example, the front color mixed molten resin can be wrapped with the rear color molten resin by adjusting the path length of each branch runner, the position of the gate, the injection pressure, and the like. Thereby, since the front color resin is covered with the rear color resin, it is possible to prevent the front color resin from being exposed on the surface (design surface) of the product.

  In this case, if a plate-like runner extending in a direction perpendicular to the flow direction of the resin at the outlet of the hot runner is provided, the fore-color resin that flows along the side surface of the runner can surely flow into the plate-like runner. By extending the second branch runner from the plate-like runner, the front color resin can be reliably introduced into the second branch runner.

  As described above, the present inventors have found that the front color resin after color change flows in the vicinity of the side surface of the runner, and based on this finding, prevents exposure of the front color resin to the design surface of the product. Thus, the occurrence of defective products can be suppressed, the material cost can be reduced, and the production efficiency can be improved.

It is sectional drawing of the injection mold which concerns on 1st Embodiment of this invention. It is an expanded sectional view of the said injection mold. It is a perspective view which shows typically the runner of the said injection mold. 3A is a cross-sectional view taken along the line AA in FIG. 3, FIG. 3B is a cross-sectional view taken along the line BB, FIG. 3C is a cross-sectional view taken along the line CC, and FIG. FIG. It is a perspective view which shows typically the runner which concerns on the other example of 1st Embodiment. (A) is sectional drawing of the runner of the injection mold which concerns on 2nd Embodiment of this invention, (b) is sectional drawing in the XX line of (a) figure. It is sectional drawing of the runner which concerns on the other example of 2nd Embodiment. It is a perspective view which shows typically the runner of the injection mold which concerns on 3rd Embodiment of this invention. It is sectional drawing of the injection mold of FIG. It is a perspective view which shows typically the runner of the injection mold which concerns on 4th Embodiment of this invention. 10A is a plan view of the runner of FIG. 10 (a view of FIG. 10B viewed from the M direction), and FIG. 10B is a side view thereof (a view of FIG. 10A viewed from the N direction). (A)-(c) is a figure which shows a mode that injection molding is performed with the injection mold which has the runner of FIG. It is an expanded sectional view of an injection mold which has a hot runner. It is sectional drawing in the ZZ line of resin solidified within the runner of the injection mold of FIG. It is sectional drawing which shows the behavior of the molten resin in the injection mold of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an injection mold 1 according to the first embodiment of the present invention. The injection mold 1 is for molding an instrument panel of an automobile, for example, and has a fixed mold 10 and a movable mold 20. As shown in FIG. 1, a cavity 30 is formed by the fixed mold 10 and the movable mold 20 in a clamped state. Molten resin is supplied to the cavity 30 via the hot runner 40 and the runner 50. In the illustrated example, a pair of hot runners 40 and runners 50 communicate with the cavity 30.

  The fixed mold 10 includes a cavity plate 11, a hot runner block 12, a hot runner nozzle 13, a sprue bushing 14, and a fixed side mounting plate 15. The cavity plate 11 is fixed to the hot runner block 12 via a heat insulating material 16, and the hot runner block 12 is fixed to the fixed side mounting plate 15. The cavity plate 11 is formed with a molding surface 11a for forming the cavity 30 and a through hole 11b in which the hot runner nozzle 13 is accommodated.

  2, the hot runner nozzle 13 includes a small-diameter portion 13a provided on the distal end side (left side in the drawing) and a large-diameter portion 13b provided on the proximal end side (right side in the drawing). Have. The small diameter portion 13a of the hot runner nozzle 13 is fitted and fixed to the small diameter inner peripheral surface 11b1 of the through hole 11b of the cavity plate 11, and the large diameter portion 13b of the hot runner nozzle 13 is connected to the large diameter inner peripheral surface 11b2 of the through hole 11b. It is opposed through a gap. A heating unit 17 is provided on the outer periphery of the hot runner nozzle 13. A pin 18 is provided on the inner periphery of the hot runner nozzle 13. The pin 18 can be advanced and retracted in the mold clamping direction (left-right direction in FIG. 1) by the drive unit 19. As shown by the solid line in FIG. 2, the pin 18 is retracted so that the molten resin in the hot runner nozzle 13 can be supplied to the runner 50. As shown by a dotted line in FIG. 2, the pin 18 is advanced to close the outlet of the hot runner nozzle 13, so that the molten resin in the hot runner nozzle 13 cannot be supplied to the runner 50.

  As shown in FIG. 1, the movable mold 20 includes a core plate 21, a nesting 22, a movable side mounting plate 23, and an ejector pin 24. The core plate 21 is fixed to the movable side mounting plate 23 via the spacer block 25. The ejector pin 24 is arranged flush with the molding surface 22a of the insert 22 during molding. After molding, the molded product can be removed from the movable die 20 by causing the ejector pin 24 to protrude from the molding surface 22a by the drive unit 26.

  The hot runner 40 and the runner 50 communicate the nozzle 30 (not shown) that contacts the sprue bush 14 with the cavity 30. In the present embodiment, as shown in FIG. 1, the hot runner 40 is branched into two and opens to the end of the cavity 30 through the runner 50. The hot runner 40 is formed on the sprue bush 14, the hot runner block 12, and the hot runner nozzle 13. The resin in the hot runner 40 includes a heating unit (not shown) provided on the sprue bushing 14, a heating unit (not shown) provided on the hot runner block 12, and a heating unit 17 (provided on the hot runner nozzle 13). (See FIG. 2). Thereby, the resin in the hot runner 40 is maintained in a molten state.

  FIG. 3 schematically shows a space corresponding to the runner 50 (that is, a resin solidified inside the runner 50). The runner 50 is formed by clamping the fixed mold 10 and the movable mold 20 (the mold clamping line is indicated by a chain line L in the figure). The upstream end of the runner 50 is formed in a disc shape and communicates with a hot runner 40 (shown by a chain line) inside the hot runner nozzle 13. The runner 50 branches into two branch runners (a first branch runner 51 and a second branch runner 52) on the way, and these merge again on the downstream side to become one. Of the runner 50, a portion before branching (ie, upstream of the branch runners 51 and 52) is the upstream runner 53, and a portion after joining (ie, downstream of the branch runners 51 and 52) is downstream. Say Lanna 54.

  The two branch runners 51 and 52 are divided into two directions by dividing the upstream runner 53 by the clamping line L, and the two places are switched on the downstream side and merge. Specifically, of the branch runners 51 and 52, the first branch runner 51 is on the upper side in the figure and the second branch runner 52 is on the lower side in the figure on the upstream side, but the second branch runner is on the downstream side. 52 is the upper side in the figure, and the first branch runner 51 is the lower side in the figure. Therefore, the first branch runner 51 straddles the mold clamping line L from the upper side to the lower side in the figure, and the second branch runner 52 straddles the mold clamping line L from the lower side to the upper side in the figure. The first branch runner 51 and the second branch runner 52 are designed so that the flow resistance of the resin flowing inside is equal. Specifically, the flow path areas (cross-sectional areas in the direction orthogonal to the resin flow direction) and flow path lengths of the first branch runner 51 and the second branch runner 52 are equal.

  The molten resin supplied from the hot runner 40 branches to the branch runners 51 and 52 through the upstream runner 53 and joins again at the downstream runner 54. In the upstream runner 53, as shown in FIG. 4A, a small amount of the forecolor resin P mixed in the molten resin exists in the vicinity of the side surface (upper surface in the drawing) on the fixed mold 10 side. As shown in FIG. 4B, the upstream runner 53 is divided into two at the upper and lower sides at the clamping line L and branches to the branch runners 51 and 52. As shown in FIG. The second branch runner 52 does not contain the front color resin P. The second branch runner 52 may also contain a very small amount of the forecolor resin P, but in this embodiment, a case where it is completely separated will be described.

  Thereafter, the locations of the first branch runner 51 and the second branch runner 52 are switched as shown in FIG. 4C, and the branch runners 51 and 52 are merged as shown in FIG. 4D. At this time, by setting the side surface on which the front color resin P is present as the joining surface of both branch runners 51 and 52, the front color resin P can be disposed inside the downstream runner 54 and sandwiched by the rear color resin Q. . In the illustrated example, the upper and lower surfaces of the upstream runner 53, that is, the upper surface 51 a of the first branch runner 51 and the lower surface 52 a of the second branch runner 52 are merged surfaces, and these surfaces are arranged in the central portion of the downstream runner 54. Is done. On the other hand, the surface formed by branching the upstream runner 53, that is, the lower surface 51b of the first branch runner 51 and the upper surface 52b of the second branch runner 52 become the lower surface 54a and the upper surface 54b of the downstream runner 54. In this manner, by injecting the molten resin from the runner into the cavity with the front color resin P sandwiched between the rear color resins Q, it is possible to prevent the front color resin P from being exposed to the product surface.

  The form of the branch runners 51 and 52 is not limited to the above. For example, in the above example, each of the first branch runner 51 and the second branch runner 52 has four bent portions, and the downstream runner 54 is also provided with one bent portion. If the runner 50 is configured as shown in FIG. 4, the number of bent portions can be reduced. Specifically, the first branch runner 51 has one bent portion, the second branch runner 52 has three bent portions, and the bent portion of the downstream runner 54 is omitted. The first branch runner 51 and the second branch runner 52 have the same flow path length. According to this configuration, the overall length of the runner 50 can be shortened, the flow of the resin in the runner 50 can be smoothed, and the risk that the front color resin can diffuse throughout the runner 50 can be reduced. In particular, in FIG. 5, the flow of the resin is made smoother by making the curvature of the bent portions of the branch runners 51 and 52 gentle (increasing the curvature radius).

  Next, an injection mold according to the second embodiment of the present invention will be described. Since this injection mold is the same as the injection mold 1 shown in FIG. 1 except for the shape of the runner, the duplicate description will be omitted, and the configuration of the runner will be mainly described.

  The runner 60 shown in FIG. 6 includes an upstream runner 61 communicating with a hot runner (not shown), and a main runner 62 and a retreat runner 63 branched from the upstream runner 61. The main runner 62 extends on an extension line of the upstream runner 61 and communicates with the cavity. The retreat runner 63 extends in a different direction from the upstream runner 61 and does not communicate with the cavity. In the illustrated example, the retreat runner 63 is formed in a disk shape extending in a direction substantially orthogonal to the upstream runner 61, and the outer diameter end of the retreat runner 63 is a dead end inside the mold. The entire circumference of the side surface of the upstream runner 61 is continuous with the side surface of the retreat runner 63. Specifically, as shown in FIG. 6B, the retreat runner 63 extends from the entire circumference of the side surface of the upstream runner 61. It is formed in a shape.

  The molten resin supplied from the hot runner to the runner 60 passes through the upstream runner 61 and flows into the main runner 62 and the retreat runner 63. At this time, as indicated by a dotted arrow in FIG. 6A, most of the rear color resin Q existing near the center of the upstream runner 61 flows into the main runner 62. On the other hand, the front color resin P existing in the vicinity of the side surface of the upstream runner 61 flows into the interior of the retreat runner 63 along the wall surface of the retreat runner 63 as shown by the solid line arrow in FIG. P is captured inside the retreat runner 63. In particular, in the present embodiment, as shown in FIG. 6B, since the entire side surface of the upstream runner 61 is continuous with the retreat runner 63, the front color resin P existing on the entire side surface of the upstream runner 61. Can reliably flow into the retreat runner 63. Accordingly, the front color resin P can be prevented from being mixed into the main runner 62 and only the rear color resin Q can be supplied to the cavity, so that the front color resin can be prevented from being mixed into the product.

  In the above example, the retreat runner 63 is provided on the entire circumference of the runner 60, but is not limited thereto. For example, when the front color resin P is present not in the entire circumference of the upstream runner 61 but only in a part thereof, the retreat runner 63 may be provided only in a portion where the front color resin P exists. In the example shown in FIG. 7, a semicircular retreat runner 63 is formed on the side surface of the upstream runner 61 on the cavity plate 11 side.

  By the way, in the above example, the retreat runner 63 has a dead end inside the mold. Therefore, if the retreat runner 63 is filled with resin, the front color resin P overflows from the retreat runner 63 and enters the main runner 62. There is a fear. Therefore, for example, if retreat runners are formed at a plurality of locations separated in the flow direction, the front color resin P overflowing from the retreat runner on the upstream side can be captured by the retreat runner on the downstream side (not shown). Alternatively, if the retreat runner 63 is communicated with the outside of the mold, the front color resin P that has flowed into the retreat runner 63 can be discharged to the outside, so that the front color resin P is supplied to the cavity via the main runner 62. Can be avoided (not shown). In the above example, the main runner 62 and the retreat runner 63 branch to the main runner 62 and the retreat runner 63 via the upstream runner 61. However, the present invention is not limited to this, and for example, the upstream runner 61 is omitted and the main runner 40 immediately after the hot runner 40 exits. The runner 62 and the retreat runner 63 may be branched (not shown).

  Next, an injection mold according to the third embodiment of the present invention will be described. Since this injection mold is the same as the injection mold 1 shown in FIG. 1 except for the shape of the runner, the duplicate description will be omitted, and the configuration of the runner will be mainly described.

  The runner 70 shown in FIG. 8 includes an upstream runner 71 communicating with the hot runner 40, a downstream runner 72 communicating with the cavity, and an inversion runner 73 provided between the upstream runner 71 and the downstream runner 72. Prepare. The reverse runner 73 twists the runner 70 in the middle, and changes the direction of the side surface between the upstream runner 71 and the downstream runner 72. Specifically, as shown in FIG. 9, an upstream runner 71 and a downstream runner 72 are arranged along a clamping line L, and these are connected by a substantially U-shaped inverted runner 73. In order to make it possible to take out the resin solidified in the reversing runner 73 from the mold, a slide mold 74 is provided which can slide in a direction perpendicular to the mold clamping direction (direction perpendicular to the paper surface of FIG. 9).

  By providing the runner 70 with the reverse runner 73, the directions of the side surfaces of the upstream runner 71 and the downstream runner 72 are reversed. That is, the upper side (fixed mold 10 side) side surface 71 a of the upstream runner 71 is connected to the lower side (movable mold 20 side) side surface 72 b of the downstream runner 72 via the outer peripheral side surface 73 a. Is done. On the other hand, the lower side surface 71 b of the upstream runner 71 is connected to the upper side surface 72 a of the downstream runner 72 via the inner peripheral side surface 73 b of the reverse runner 73.

  When molten resin is supplied to the runner 70, as shown in FIG. 9, a small amount of the front color resin P is mixed in the rear color resin Q (refer to the dotted line) mainly flowing through the runner 70. In the upstream runner 71, the front color resin P flows along the upper surface 71a. In the reverse runner 73, the front color resin P flows along the outer peripheral side surface 73a. In the downstream runner 72, the front color resin P flows along the lower side surface 72b. Thus, the direction of the side surface on which the front color resin P exists is changed between the upstream runner 71 and the downstream runner 72.

  As shown in FIG. 1, since the injection mold 1 is provided with the ejector pin 24, a mark of the ejector pin 24 is formed on the product molded in the cavity 30 (not shown). For this reason, the injection mold 1 is designed so that the side where the ejector pin 24 is formed (the movable mold 20 side) is the back surface of the product and the opposite side (the fixed mold 10 side) is the design surface. The On the other hand, in the upstream runner 71 communicating with the hot runner 40, the front color resin P flows along the side surface on the fixed mold 10 side (see FIG. 9). For this reason, if the upstream runner 71 is communicated with the cavity as it is, the front color resin P is disposed on the surface on the fixed mold 10 side, which is the design surface of the product, and the front color resin P may be exposed on the design surface. Get higher.

  Therefore, as shown in FIGS. 8 and 9, a reversing runner 73 is provided, and the upstream runner 71 and the downstream runner 72 reverse the direction of the side surface so that the downstream runner 72 has a side surface on the movable mold 20 side. A front color resin P is disposed. When the molten resin is injected from the downstream runner 72 into the cavity 30, the front color resin P is disposed on the back side of the product, so that the risk of the front color resin P being exposed on the design surface of the product can be reduced.

  The form of the runner 70 is not limited to the above. For example, in FIG. 8, the reversing runner 73 is bent at a substantially right angle, but the reversing runner 73 may be smoothly curved (not shown), for example.

  Next, an injection mold according to the fourth embodiment of the present invention will be described. Since this injection mold is the same as the injection mold 1 shown in FIG. 1 except for the shape of the runner, the duplicate description will be omitted, and the configuration of the runner will be mainly described.

  The runner 80 shown in FIG. 10 branches into a first branch runner 81 and a second branch runner 82, and each of the branch runners 81 and 82 communicates with the cavity. In the present embodiment, the path length of the first branch runner 81 is shorter than the path length of the second branch runner 82. As shown in FIG. 11 (b), the first branch runner 81 has an introduction portion 81a extending in the same direction as the resin flow direction (left-right direction in FIG. 11 (b)) at the outlet 41 of the hot runner 40, It communicates with the cavity while bending. The second branch runner 82 is provided with two second branch runners 82 extending in a direction orthogonal to the introduction portion 81a of the first branch runner 81 and extending in opposite directions in the illustrated example. A plate-like runner 83 is provided at a branch portion between the first branch runner 81 and the second branch runner 82. The plate-like runner 83 extends in all directions perpendicular to the resin flow direction at the outlet 41 of the hot runner 40 (a direction parallel to the paper surface of FIG. 11A). In the present embodiment, the plate-like runner 83 has an elliptical shape, the introduction portion 81a of the first branch runner 81 extends from the center thereof, and the second branch runners 82 extend from both ends in the long side direction.

  When the molten resin is supplied from the hot runner 40, the front color resin exists on the entire circumference of the side surface (inner wall surface) of the outlet 41 of the hot runner 40, and only the rear color resin exists in the central portion of the outlet 41. The front color resin flowing along the side surface of the outlet 41 flows into the plate-like runner 83 and further flows into the second branch runner 82. At this time, since the entire periphery of the side surface of the outlet 41 of the hot runner 40 is continuous with the side surface of the plate-like runner 83, the pre-color resin existing on the entire periphery of the side surface of the outlet 41 should be reliably captured by the plate-like runner 83 Can do. On the other hand, the rear color resin present at the center of the outlet 41 of the hot runner 40 flows into the introduction part 81a of the first branch runner 81 extending on the extension of the resin flow direction at the outlet 41. In this way, the molten resin supplied from the hot runner 40 to the runner 80 is separated into the front color mixed molten resin P ′ mixed with the front color resin and the rear color molten resin Q ′ made only of the rear color resin.

  Then, as shown in FIG. 12A, the rear color molten resin Q ′ reaches the cavity 30 through the first branch runner 81. In the present embodiment, since the path length of the first branch runner 81 is shorter than the path length of the second branch runner 82, the rear color melt resin Q ′ of the first branch runner 81 is melted by the front color mixture of the second branch runner 82. The cavity is reached before the resin P ′. Thereafter, as shown in FIG. 12B, the previous color mixed molten resin P ′ reaches the cavity 30 through the second branch runner 82. At this time, the gate positions and injection pressures of the first branch runner 81 and the second branch runner 82 are adjusted, and the front color mixed molten resin P ′ is injected into the skin layer formed of the rear color molten resin Q ′. Thus, the front color resin can be wrapped with the rear color resin.

  At this time, if the injection pressure of the first branch runner 81 is higher than the injection pressure of the second branch runner 82, the color molten resin Q ′ is injected from the first branch runner 81 and reaches the cavity 30 first. Then, there is a possibility that the rear color molten resin Q ′ may enter the second branch runner 82 and flow backward in the second branch runner 82. Accordingly, the injection pressure of the first branch runner 81 is preferably lower than the injection pressure of the second branch runner 82. In this case, the injection pressure of the first branch runner 81 is insufficient, and there is a possibility that the rear color molten resin Q ′ is not filled up to the end of the cavity 30. Therefore, as described above, the front color mixed resin P ′ is wrapped with the rear color molten resin Q ′, and the rear color molten resin Q ′ is extruded with the front color mixed molten resin P ′ having a relatively high injection pressure. The rear color molten resin Q ′ can be filled up to 30 ends (see FIG. 12C). As described above, since the front color mixed molten resin P ′ is covered with the rear color molten resin Q ′ except for the vicinity of the gate, it is possible to prevent the front color resin from being exposed to the product surface.

  Although the case where a product is an instrument panel is shown in the above embodiment, the injection mold of this invention can be applied if it is a resin molded product in which color change is performed. For example, the present invention can be applied to an injection mold that molds an inner panel of a door, a bumper, or the like.

  Moreover, you may combine the above embodiment suitably. For example, the first branch runner 81 of the runner 80 (see FIG. 10) of the injection mold according to the fourth embodiment may contain a very small amount of front color resin. If the shape of the runner 70 (see FIG. 8) according to the third embodiment is applied and the first color runner 81 is twisted so that the front color resin is disposed on the back surface of the product, the front color resin is applied to the product surface. The exposure situation can be prevented more reliably.

1 Injection mold 10 Fixed mold 11 Cavity plate 12 Hot runner block 13 Hot runner nozzle 14 Sprue bush 20 Movable mold 21 Core plate 22 Nest 24 Ejector pin 30 Cavity 40 Hot runner 50 Runner 51 First branch runner 52 Second branch runner 53 upstream runner 54 downstream runner 60 runner 61 upstream runner 62 main runner 63 retreat runner 70 runner 71 upstream runner 72 downstream runner 73 reverse runner 80 runner 81 first branch runner 82 second branch runner 83 plate-like runner L Clamping line P Front color resin Q Rear color resin

Claims (5)

An injection mold comprising a cavity, a hot runner that circulates molten resin while heating, and a runner that communicates the cavity and the hot runner,
An injection mold characterized by changing the runner path so that the precolored resin that flows along the side surface of the runner is not disposed on the design side of the product.   The runner is branched into a first branch runner and a second branch runner, these are merged again before the cavity, and the side where the front color resin flows along the side of the runner before the branch is the first branch. The injection mold according to claim 1, wherein the runner and the second branch runner are merged surfaces.   The runner is branched into a main runner that communicates with the cavity and a retreat runner that does not communicate with the cavity, and the front color resin that flows along the side surface of the runner before the branch is caused to flow into the retreat runner. Injection mold.   The injection mold according to claim 1, wherein the runner is twisted to change the direction of the side surface so that the front color resin flowing along the side surface is arranged on the back side of the product.   From the first branch runner, the runner is branched into a first branch runner that distributes the rear color molten resin consisting only of the rear color resin and a second branch runner that distributes the front color mixed molten resin mixed with the front color resin. The injection mold according to claim 1, wherein after injection of the rear color molten resin into the cavity, the front color mixed molten resin is injected into the cavity from the second branch runner so that the front color resin is wrapped with the rear color resin.

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