JP6081826B2 - Injection molding method and injection molding apparatus - Google Patents

Description

  The present invention relates to an injection molding method and an injection molding apparatus that are suitably used for molding a resin molded product having a plate-like portion.

  Conventionally, there is injection molding as a technique for forming a resin molded product or the like. Injection molding is a method to obtain a molded product by injecting a molten material such as molten resin from the gate into a mold cavity (molding space) that has been clamped, filling it, and cooling and solidifying it. It is. Injection molding is suitable for mass-production of products with relatively complicated shapes because it can form molded products with complicated shapes with a relatively small number of processes, and is used in a wide range of fields.

  In injection molding, for the purpose of reinforcing a molded product and improving rigidity, talc, which is a kind of filler, is mixed with a resin material. Examples of the resin molded article containing talc include relatively large and complicated parts such as bumpers and instrument panels (instrument panels) which are automobile parts.

  In such injection molding, a linear mark called a weld (also referred to as a weld line) may occur on the surface of a molded product. The weld is generated at a portion where two or more flow fronts (flow front ends) of the resin material flowing in the cavity of the mold meet. The joint part of the resin material is the resin in which the molten resin flows into the cavity from a plurality of gates or the cylindrical or columnar mold part existing in the cavity in order to form openings such as holes in the molded product. This is caused by the material wrapping around.

  Specifically, at the joint portion of the resin material, talc mixed with the resin material as described above is easily oriented in the vertical direction (longitudinal direction) with respect to the surface of the molded product. Here, the direction perpendicular to the surface of the molded product is, for example, the thickness direction in the plate-shaped portion of the molded product. This vertical orientation of talc causes welds. The weld generated in this way is a linear molding defect that looks like a flaw in a resin molded product, and causes the appearance quality of the molded product to be impaired. For this reason, it is desirable to suppress the occurrence of welds as much as possible.

  Therefore, as a technique for suppressing the occurrence of welds in a resin molded product by injection molding, there is a technique for suppressing the occurrence of welds by controlling the injection conditions. Here, the injection conditions include injection timing of molten resin from a plurality of gates, internal stress of the resin material in the cavity, and the like.

  For example, Patent Document 1 describes a technique for controlling the injection timing of molten resin from a plurality of gates as an injection condition. Specifically, in Patent Document 1, a main gate portion and an auxiliary gate portion, in which the injection directions of the resin material are different from each other in relation to the longitudinal direction of the molded product, are set, and the resin material injected from the main gate portion is A technique is disclosed in which a resin material is injected from an auxiliary gate portion after the length of the opening along the longitudinal direction of the molded product has been reached. According to this technique, it is considered that the occurrence of weld due to the influence of the presence of the opening can be suppressed by filling the resin material around the opening first.

  Further, there is a technique for controlling the injection pressure of the molten resin from a plurality of gates with respect to the internal stress of the resin material in the cavity as the injection condition. Specifically, for example, with respect to a pair of gates disposed at positions facing each other, the injection pressure from one gate is made stronger (or weaker) than the injection pressure from the other gate, so that both injections are performed. The difference is in the pressure. According to such a technique, imbalance occurs in the internal stress at the joining portion of the molten resin injected from the gates on both sides facing each other, and the talc is laid down, so that the occurrence of welds is suppressed.

JP 2013-1019 A

  As described above, the technique for suppressing the generation of welds by controlling the injection conditions has the following problems. First, according to the technique for controlling the injection timing of molten resin from a plurality of gates as in Patent Document 1, the injection timing varies depending on the gate. For this reason, compared with the case where it injects simultaneously from several gates, since the injection timing from each gate shifts | deviates, the cycle time of a formation process becomes long.

  Moreover, according to the technique for controlling the injection pressure of the resin material from the plurality of gates, the injection pressure varies depending on the gate. For this reason, it becomes difficult to maintain the overall pressure balance in the cavity, and molding defects such as burrs and steps in the mold parting line (PL) due to excessive pressure, or unintentional depressions due to insufficient pressure, called sinks, etc. Is likely to occur.

  The present invention has been made in view of the above-described problems, and suppresses welds without increasing cycle time and excessive or insufficient pressure in the cavity that causes molding defects. An object of the present invention is to provide an injection molding method and an injection molding apparatus.

In the injection molding method according to the present invention, at least two flow fronts of the resin material that flows in the process until the resin material injected into the cavity as the plate-shaped molding space of the mold is filled in the cavity are provided. In an injection molding method in which a joining resin portion to be joined is produced, the resin material is a mixture of rectangular plate-shaped talc, and in order to lay down the talc to be oriented in the thickness direction in the resin joining portion, By rotating a portion of the surface of the mold forming the cavity where the resin material of the resin merging portion is in contact at a rotation speed of 100 ° to 720 ° / sec, the speed of the resin merging at the resin merging portion is increased. A difference is caused , and the shrinkage amount of the resin joining portion due to cooling and solidification of the resin material is made larger than the shrinkage amount in a state where talc is oriented in the plate thickness direction. It is.

  In the injection molding method according to an aspect of the present invention, rotating a part of the surface forming the cavity is a mold for forming a surface on the non-design surface side of the molded product among the mold elements of the mold. A part of the mold element is rotated by using a direction perpendicular to the surface forming the cavity as a rotation axis direction.

The injection molding apparatus according to the present invention includes at least two flow fronts of a flowing resin material in a process until a resin material injected into a cavity as a plate-shaped molding space of a mold is filled in the cavity. An injection molding apparatus in which a merged resin joining portion is generated, wherein the resin material is a mixture of rectangular plate-shaped talc, and constitutes a part of at least one mold element that forms the cavity, A rotary mold that is provided so as to be rotatable with a direction perpendicular to the surface forming the cavity of the mold element as a rotation axis direction, and that constitutes a portion of the surface forming the cavity that contacts the resin material of the resin joining portion laying a section, and a driving unit for generating a rotation power for rotating the rotary part, the talc to be oriented in the thickness direction in the resin merging portion Ku, wherein the rotational power generated by the drive unit that rotates the rotary unit at a rotational speed of 100 ° to 720 ° / sec, causing the speed difference to a resin merging at the resin merging section, the resin merged The amount of shrinkage of the portion due to cooling and solidification of the resin material is made larger than the amount of shrinkage in a state where talc is oriented in the plate thickness direction .

  In the injection molding apparatus according to one aspect of the present invention, the mold includes a first mold element that forms a design surface side surface of the molded product as a mold element, and a non-design surface side surface of the molded product. The rotary mold part is provided as a part of the second mold element.

  According to the present invention, it is possible to suppress weld without prolonging cycle time and excessive or insufficient pressure in the cavity that causes molding defects.

Explanatory drawing about the generation mechanism of the weld which concerns on this invention. Explanatory drawing about the generation mechanism of the weld which concerns on this invention. The B partial enlarged view in FIG. Explanatory drawing about the generation mechanism of the weld which concerns on this invention. The figure which shows the outline | summary of the metal mold | die which concerns on one Embodiment of this invention. The figure which shows the structure of the injection molding apparatus which concerns on one Embodiment of this invention. The schematic diagram which shows the behavior of the resin material in the cavity when a weld generate | occur | produces. The schematic diagram which shows the behavior of the resin material in the cavity which concerns on one Embodiment of this invention. Explanatory drawing about the change of the flow rate of the resin material by the rotating core which concerns on one Embodiment of this invention. Explanatory drawing about the movement of the weld by rotation of the rotating core which concerns on one Embodiment of this invention. Explanatory drawing about the resin pressure difference by rotation of the rotating core which concerns on one Embodiment of this invention. The figure which shows the talc which concerns on the Example of this invention.

  The present invention relates to a mold element that forms a cavity in injection molding in which a resin merging portion where at least two flow fronts (flowing tip portions) merge is formed with respect to a molten resin injected into a cavity (molding space) of a mold. The part of the surface of the resin that is in contact with the resin merging part is partially rotated while maintaining the shape of the cavity, thereby causing a speed difference in the resin merging at the resin merging part and the weld generated on the surface of the molded product. It is intended to suppress the occurrence.

  In the description of the embodiment of the present invention, a mechanism for generating welds in a resin molded product will be described. In injection molding, for example, when relatively large and complicated parts such as bumpers and instrument panels, which are automotive parts, are used as molded products, the resin material is used for the purpose of reinforcing the molded products and improving rigidity. Mixing talc, which is a kind of filler, is performed. Talc is, for example, a powdered product made of hydrated magnesium silicate and has a rectangular plate-like structure with a size of several micrometers to 100 micrometers. In addition, as a resin material into which talc is mixed, a polypropylene resin that is a polyolefin resin is widely used.

  In the injection molding in which the resin material mixed with talc is used as described above, there is a problem that welds are generated in the resin joining portion where two or more flow fronts of the resin material flowing in the cavity of the mold join. . The resin joining part is a resin material that flows into the cavity from a plurality of gates, or the cylindrical or columnar mold part that exists in the cavity in order to form openings such as holes in the molded product. It is caused by wrapping around.

  Here, with reference to FIG. 1, a specific description will be given of a case where welds are generated in the merged resin portion due to the wraparound of the resin material in the cavity. 1A and 1B are diagrams schematically showing a state of a resin material in a plate-shaped molding space as a cavity in a plan sectional view.

  As shown in FIG. 1 (a), in the cavity 1 of the mold, there is an opening forming mold portion 2 which is a columnar mold portion for forming an opening in the molded product depending on the shape of the molded product. There is a case. In the configuration in which the opening forming mold portion 2 exists in the cavity 1 as described above, the resin material 3 is injected into the cavity 1 and flows in the cavity 1 as shown in FIG. In the process until it is filled, a resin merge portion 3C where the two flow fronts 3A and 3B merge is formed in the portion after passing through the opening forming mold portion 2. That is, in the flow of the resin material 3 with respect to the opening forming mold part 2, the resin material 3 branched by the opening forming mold part 2 merges from two directions at the downstream side portion of the opening forming mold part 2 (arrow A1). , A2), a resin junction 3C is generated. As shown in FIG. 1B, the resin material 3 filled in the cavity 1 is cooled and solidified in the resin joining portion 3 </ b> C generated in the cavity 1 in this manner, so that a molded product made of the resin material 3 is obtained. In this case, a weld 4 is formed as a linear trace.

  The occurrence of the weld 4 in the molded article made of the resin material 3 as described above is due to the orientation of talc mixed with the resin material 3 as described above. The weld generation mechanism will be described in detail with reference to FIG. 2, FIG. 3, and FIG. 2A and 2B are diagrams showing the flow state of the resin material 3 in the resin joining portion 3C in the cavity 1. FIG. FIG. 3 is an enlarged view of part B of FIG. FIG. 4 is a diagram showing the relationship between the orientation of talc and the shrinkage of the resin material 3.

  As shown in FIG. 2A, in the cavity 1 as a plate-shaped molding space, the surfaces of the mold elements forming the cavity 1 (hereinafter referred to as “mold surface”) face each other in the plate thickness direction. There is a mold surface 5 a of one mold element 5 and a mold surface 6 a of the other mold element 6. FIG. 2A shows a flow front of the molten resin flowing from two different directions (see arrows C1 and C2) with respect to the resin joining portion 3C.

  The resin material 3 flowing in the cavity 1 as described above flows in the cavity 1 while generating a fountain flow (jet flow) at the flow front. That is, in the resin material 3 flowing in the cavity 1, the fluidity of the surface layer portion 3D in contact with the mold surfaces 5a and 6a is gradually lowered due to the solidification due to the temperature decrease, whereas the inner layer portion 3E. Since the fluidity of the flow front portion is maintained by the high temperature state, a fountain-like flow is formed in the flow front portion from the inside to the outside (see arrow C3).

  In the resin material 3 that flows in such a manner, the talc in the material tends to exhibit an orientation corresponding to the direction of the shear stress generated by the flow of the resin material 3. Specifically, in the surface layer portion 3D of the resin material 3 in contact with the mold surfaces 5a and 6a, since the shear stress is relatively large, the talc is oriented in the lateral direction along the flow direction of the resin material 3. On the other hand, since the shear stress is relatively small in the inner layer portion 3E of the resin material 3, talc is oriented along the fountain-like flow (see arrow C3) as described above in the flow front. Here, the orientation with respect to talc corresponds to the rectangular plate-shaped talc extending along its longitudinal direction as described above.

  Then, as shown in FIG. 2B, the two flow fronts of the resin material 3 that have flowed in directions facing each other collide and join at the resin joining portion 3C. In the resin merging portion 3C, a slightly raised portion is formed at the end of the surface side (upper and lower mold surfaces 5a, 6a side) of the flow front portions that merge with each other, and the surface becomes a V-shaped V-notch in cross-sectional view. A groove 3F is formed.

  As shown in the enlarged view of FIG. 3, the V-shaped groove 3 </ b> F has a vertical direction (plate thickness direction, vertical direction in the figure) as it moves away from the boundary portion (center portion) of the resin merging portion 3 </ b> C with respect to the orientation of the talc 3x. It is formed due to the orientation that gradually tilts and becomes the lateral direction (perpendicular to the plate thickness direction, left and right in the figure). In other words, in the surface layer portion of the flowing resin material 3, the talc that is lying along the flow of the resin material 3 is the surface layer portion of the resin merging portion 3C where the two flow fronts where the fountain-like flow is formed collide with each other. The V-shaped groove 3F is formed by such talc orientation. As shown in FIG. 3, the portion where the V-shaped groove 3 </ b> F is formed on the surface portion of the resin material 3 is a portion raised by about several micrometers with respect to other flat portions.

  FIG. 4 schematically shows the orientation of talc in the resin junction 3C and the vicinity thereof. 4 shows the talc in the high temperature condition when the resin material 3 flows, that is, immediately after the two flow fronts merge, with respect to the portion of the resin joining portion 3C where the V-shaped groove 3F as shown in FIG. 3 is formed. The orientation and the shape of the resin are shown. 4 shows the talc orientation and resin under normal temperature conditions after cooling of the resin material 3 in a high temperature state, that is, in a state where the resin material 3 is solidified, in the same part as the diagram shown on the left side of FIG. The shape of is shown. That is, FIG. 4 shows a change in the shape of the resin due to the orientation of talc due to the solidified state by cooling from the high-temperature state immediately after merging in the vicinity of the resin merging portion 3C where the V-shaped groove 3F is generated. Indicates.

  As shown in FIG. 4, in the resin material 3, shrinkage occurs in the plate thickness direction (vertical direction in FIG. 4) by being cooled and solidified from the time of flow (molten state). The amount of shrinkage varies depending on the orientation of talc. Specifically, as shown in FIG. 4, talc is oriented in the vertical direction (plate thickness direction) (becomes standing), and other than the resin joining portion 3 </ b> C than the resin joining portion 3 </ b> C in which the V-shaped groove 3 </ b> F is formed. The flat portion, that is, the talc is oriented in the lateral direction (becomes lying), and the portions on both sides sandwiching the resin merging portion 3C have a larger contraction amount in the plate thickness direction.

  For this reason, in the resin merging portion 3C and the vicinity thereof, the resin material is cooled and solidified, so that the talc is more flat than the resin merging portion 3C in which the talc is oriented in the vertical direction. The direction is greatly shrunk in the plate thickness direction, and the portion of the V-shaped groove 3F is relatively protruded (see reference sign D1 indicating the height difference). That is, a state in which the portion of the V-shaped groove 3F is relatively raised as a result of the thermal contraction of the flat portion with respect to the portion that forms the V-shaped groove 3F that becomes the raised portion as described above. Thus, a mountain-shaped portion is formed. Thereby, a protruding portion along the boundary line of the resin joining portion 3C appears on the surface of the resin molded product, and this protruding portion appears as a weld that is a linear trace.

  Thus, the weld in the resin molded product is caused by the vertical orientation of talc in the resin joining portion 3C. The phenomenon as a mechanism of occurrence of weld as described above is not limited to the case where the filler mixed with the resin material is talc, but other fillers such as calcium carbonate, glass fiber, wollastonite, mica, and various inorganic fillers. It is a phenomenon that can occur even with organic fillers.

  The present invention pays attention to the weld generation mechanism in the resin molded product as described above, and is based on the idea that eliminating the upright talc oriented in the vertical direction (plate thickness direction) leads to the elimination of the weld. It was made for the purpose of putting upright talc in the club.

  As an approach for laying upright talc at the resin junction, there is a method of controlling injection pressure of molten resin from a plurality of gates to the cavity by paying attention to the internal stress of the resin material in the cavity. That is, a difference is made in the injection pressure of the molten resin at a plurality of gates, an imbalance is generated in the internal stress at the resin joining portion, and the talc is laid down. However, according to such a method, since the injection pressure differs depending on the gate, it is difficult to maintain the pressure balance as a whole inside the cavity, and the intention is due to burrs and steps in the parting line (PL) due to excessive pressure, or insufficient pressure. Molding defects such as dents (sink marks) tend to occur.

  Therefore, the present invention focuses on dynamically applying an external force to the resin material in the cavity, and by applying an external force to the resin material, a speed difference is caused in the resin materials that merge with each other at the resin merging portion. Is going to lie down. The injection molding method according to the present invention rotates the part of the mold surface of the mold element that the resin material contacts in the resin merge part in the cavity on the spot when the upright talc in the resin merge part is laid down. Thus, a technique is adopted in which an external force is applied to the resin material to dynamically change the orientation of talc. Embodiments of the present invention will be described below.

  In the injection molding method according to the present embodiment, in the process until the resin material injected into the cavity of the mold is filled into the cavity, a resin joining portion where at least two flow fronts of the flowing resin material join is generated. This is an injection molding method. The injection molding method according to the present embodiment rotates the part of the mold element on the core side directly below the part where the weld occurs in the resin product in the mold for molding the resin product, so that the resin joining part is Thus, talc that is intended to be oriented in the vertical direction (plate thickness direction) is laid down to suppress welds and improve the appearance of the surface of the resin product.

  As shown in FIGS. 5 and 6, the injection molding die 11 according to this embodiment is for forming a rectangular plate-shaped resin product as an injection molded product. The resin product obtained by the mold 11 according to the present embodiment is, for example, a rectangular plate-like product having a plate thickness of 2.0 mm and a length and width of 200 mm × 300 mm. Therefore, in the mold 11, a cavity 12 corresponding to the shape and dimensions of the resin product is formed.

  A mold 11 according to this embodiment includes a movable mold 13 that is a core-side mold element, a fixed mold 14 that is a cavity-side mold element, and a mold that holds these molds and moves the movable mold 13. Machine (not shown). In the mold 11, the movable mold 13 and the fixed mold 14 constitute a mold that opens and closes by the operation of the movable mold 13. In the mold closed state of the mold, the cavity 12 is formed by the mold surfaces 23 and 24 of the movable mold 13 and the fixed mold 14, respectively.

  FIG. 5 is a plan view of the movable mold 13 constituting the mold 11 when viewed from the mold surface 23 side. In the following description, the longitudinal direction (left and right direction in FIG. 5) of the cavity 12 corresponding to the shape of the resin product in the mold 11 is the left and right direction, the movable mold 13 side with respect to the cavity 12 is the lower side, and the fixed mold 14 side is the upper side. The vertical direction is defined as Therefore, as shown in FIG. 6, among the mold surfaces forming the cavity 12, the upper surface is the mold surface 24 of the fixed mold 14, and the lower surface is the mold surface 23 of the movable mold 13.

  And in the metal mold | die 11 which concerns on this embodiment, the metal mold | die surface 24 of the fixed mold | type 14 turns into a design surface, and the metal mold | die surface 23 of the movable mold | type 13 turns into a non-design surface. That is, in the plate-shaped resin product formed by the mold 11, the surface formed by the mold surface 24 of the fixed mold 14 becomes the outer surface that appears on the appearance, and is formed by the mold surface 23 of the movable mold 13. The surface becomes the inner surface that does not appear in the appearance. As described above, the mold 11 according to this embodiment includes, as mold elements, a fixed mold 14 that is a first mold element that forms a design surface side surface of a molded product, and a non-design surface side of the molded product. And a movable mold 13 which is a second mold element that forms the surface of the second mold element.

  Further, as shown in FIG. 5, the mold 11 is provided with a gate 15 that is an injection port of the molten resin with respect to the cavity 12. In the present embodiment, as shown in FIG. 5, gates 15 are provided at two locations that are opposite to each other on the left and right sides of the cavity 12. In this way, the two gates 15 provided on the left and right sides of the cavity 12 are one in the vertical direction with respect to the left and right direction in the plan view as shown in FIG. 5 (the up and down direction in FIG. It is provided at a position offset to the side (lower side in FIG. 5). Hereinafter, the side (lower side in FIG. 5) on which the gate 15 is offset in the front-rear direction is referred to as the front side, and the opposite side (upper side in FIG. 5) is referred to as the rear side. The gate 15 is provided in the fixed mold 14 or the like and communicates with a resin passage called a hot runner or a sprue. Molten resin injected from an injection device configured as a cylinder device or the like is supplied to the resin passage.

  In the mold 11 having the above-described configuration, the cavity 12 is formed by the upper and lower mold surfaces 23 and 24 by the mold closing operation of the mold composed of the movable mold 13 and the fixed mold 14, and then from the injection device. The injected molten resin is guided to the gate 15 through the resin passage of the mold 11 and is simultaneously injected into the cavity 12 from the two gates 15 facing each other in the left-right direction (FIG. 5, arrows E1, E2). reference). The molten resin injected into the cavity 12 is cooled and solidified, and then taken out as a molded product from the mold that has been opened.

  As described above, in the configuration in which the molten resin is injected into the cavity 12 from the two gates 15 facing each other, the two flow fronts of the resin material injected from each gate 15 and flowing in the cavity 12 merge. Resin merging portion is generated. For this reason, if no countermeasure is taken, welds occur at the resin junction.

  Specifically, as described above, in each resin material that is injected and flows from a pair of opposing gates 15 provided at positions shifted to the front side on both the left and right sides of the cavity 12, as shown in FIG. As components in the flow direction, there are a component in the direction facing the other side in the left-right direction (see arrow F1) and a component in the direction from the front side toward the rear side (see arrow F2).

  For this reason, the resin material 16 simultaneously injected from the left and right gates 15 gradually merges from the front side to the rear side at a substantially central position in the left-right direction in the rectangular plate-shaped cavity 12. In other words, in the mold 11 of the present embodiment, the resin material 16 is injected from the gates 15 on both the left and right sides facing each other at a substantially central position in the left-right direction of the cavity 12 until the resin material 16 is filled in the cavity 12. A resin joining portion 16C where the two flow fronts 16A and 16B of the resin material 16 thus joined join each other is generated. 7 schematically shows the flow state of the resin material 16 in a form in which the space of the cavity 12 is cut out in a rectangular parallelepiped shape so as to include a part of the resin joining portion 16C of the resin material 16 flowing in the cavity 12. FIG. Therefore, in the rectangular parallelepiped shape shown in FIG. 7, the upper surface corresponds to a surface (design surface) that contacts the mold surface 24 of the fixed mold 14, and the lower surface corresponds to a surface (non-surface) that contacts the mold surface 23 of the movable mold 13. This corresponds to the design surface.

  In the resin junction 16C generated in the cavity 12, the resin material 16 filled in the cavity 12 is cooled and solidified, thereby causing the resin material 16 to be oriented due to the orientation of talc mixed in the resin material 16. The weld which becomes a linear trace generate | occur | produces in the molded article by 16. FIG. That is, as shown in FIG. 7, in the resin material 16, the boundary portion of the resin joining portion 16 </ b> C in which talc is oriented in the vertical direction (plate thickness direction) and the other portion in which talc is oriented in the lateral direction A difference occurs in the amount of shrinkage in the thickness direction, and due to the difference in the amount of shrinkage in the plate thickness direction, a protruding portion along the boundary line of the resin joining portion 16C appears as a weld on the surface of the resin molded product. In the case of the mold 11 of the present embodiment, the weld appears as a linear line mark extending in the front-rear direction at a substantially central position in the left-right direction of the resin product.

  Therefore, in the injection molding method of the present embodiment, in order to suppress the occurrence of the weld as described above, the resin material of the resin joining portion 16C contacts the surface (mold surface) of the mold 11 on which the cavity 12 is formed. By rotating the portion, a speed difference is generated in the resin material that joins at the resin joining portion 16C.

  Specifically, in the mold element constituting the mold 11, a part forming the mold surface is a mold member independent of other parts, and the mold member is perpendicular to the mold surface as a rotation axis direction. By providing it rotatably, a part of the mold surface is partially rotated while maintaining the shape of the mold surface, that is, the shape of the cavity 12 (without changing the shape). In other words, the mold element constituting the mold 11 is composed of a non-rotating part that does not rotate with the direction perpendicular to the mold surface as the rotation axis direction and a rotating part that rotates with the direction perpendicular to the mold surface as the rotation axis direction. To do.

  Then, the partial rotation of the mold element is performed on a portion where the resin material of the resin merging portion 16C where the weld is generated comes into contact. In the mold 11 according to this embodiment, the direction perpendicular to the mold surface corresponds to the approaching and separating direction of the movable mold 13 and the fixed mold 14 with respect to the other mold element.

  Thus, in the structure in which the portion corresponding to the resin joining portion 16C of the mold element is partially rotated, the mold surface portion of the main body portion that does not rotate with the direction perpendicular to the mold surface as the rotation axis direction as the mold surface. (Non-rotating region) and a portion corresponding to the resin merging portion 16C and a mold surface portion (rotating region) that rotates with the direction perpendicular to the mold surface as the rotation axis direction exist. That is, the non-rotating region of the mold surface of the mold element constituting the mold 11 is a fixed part throughout the process from the injection of the resin material into the cavity 12 until it is filled. While there is no influence of active movement on the stress received from the resin material flowing inside, the rotation area of the mold surface has a predetermined timing in the process from injection to filling of the resin material. It is a part that rotates at a point, and acts on the stress received from the flowing resin material by a rotating operation.

  In order to perform such partial rotation of the mold surface, the mold 11 according to the present embodiment is rotated as a mold member constituting the movable mold 13 as shown in FIGS. 5, 6, and 8. It has a core 30. FIG. 8 is a diagram schematically showing the flow state of the resin material 16 in a manner in which the space of the cavity 12 is cut out in a rectangular parallelepiped shape as in FIG.

  The rotary core 30 is a mold member that is independent of other parts of the movable mold 13 that form the mold surface 23. As shown in FIG. 5 and FIG. 6, the rotary core 30 has a cylindrical outer shape, and the movable mold 13 is arranged so that one end face 30 a having a circular shape faces the mold surface 23 of the movable mold 13. Provided in a buried state. Therefore, the movable mold 13 is provided with a hole 13a that forms a cylindrical space corresponding to the outer shape of the rotary core 30, and the rotary core 30 is rotatably inserted into the hole 13a. Provided in the state. In the present embodiment, in the horizontal mold surface 23, the upper end surface 30 a of the rotary core 30 is flush with other portions of the mold surface 23, that is, forms a common plane. Provided. The diameter of the rotary core 30 is, for example, about 20 mm for the product size of 2.0 mm in thickness and 200 mm × 300 mm in length and width as described above.

  The rotary core 30 is provided so as to be rotatable with a direction perpendicular to the mold surface 23 of the movable mold 13 (a direction perpendicular to the paper surface in FIG. 5 and a vertical direction in FIG. 6) as the rotation axis direction. That is, as shown in FIG. 6, the rotary core 30 is provided so as to be rotatable around the rotation axis G1 along the central axis direction in the cylindrical outer shape (see arrow G2). The rotary core 30 is provided so as to rotate at a rotation speed of 100 ° to 720 ° / second, for example. In the present embodiment, the rotating core 30 rotates using a motor as a power source, as will be described later.

  The rotary core 30 is provided at a position where the weld is formed, that is, at a position corresponding to the resin joining portion 16 </ b> C in the cavity 12. That is, the rotary core 30 is provided at a position where the resin material that joins at the resin joining portion 16 </ b> C contacts the upper end surface 30 a that forms a part of the mold surface 23 of the movable die 13. In the present embodiment, as described above, a weld is generated in a linear shape in the front-rear direction at a substantially central position in the left-right direction of the resin product, so that the rotary core 30 corresponds to the weld in the left-right direction and the front-rear direction. Is provided at the center (see FIG. 5).

  As described above, in the configuration in which the rotary core 30 is provided in the movable mold 13, the movable mold 13 as the mold element constituting the mold 11 serves as a rotating unit that rotates with the direction perpendicular to the mold surface as the rotation axis direction. The rotating core 30 and the main body portion 13A as a non-rotating portion that does not rotate with the direction perpendicular to the mold surface as the rotation axis direction. In the configuration in which the movable mold 13 has the rotary core 30, in the present embodiment, a part of the horizontal mold surface 23 is formed as a portion rotated by the upper end face 30 a of the rotary core 30. That is, the mold surface 23 of the movable mold 13 is a non-rotating region 23A formed by the main body portion 13A and a rotating region formed by the upper end surface 30a of the rotating core 30 corresponding to the resin joining portion 16C. 23B.

  Of the mold surface 23 of the movable mold 13, the non-rotating region 23 </ b> A formed by the main body portion 13 </ b> A is a fixed part from the beginning until the resin material is injected into the cavity 12 until it is filled. This is a portion that is not affected by the active movement with respect to the stress received from the resin material flowing in the inside. On the other hand, in the mold surface 23 of the movable mold 13, the rotation region 23 </ b> B formed by the rotating core 30 is a portion that rotates at a predetermined timing and flows in the process from injection to filling of the resin material. It acts on the stress received from the resin material by a rotating operation.

  As described above, in the configuration including the rotating core 30 that forms a part of the mold surface, the rotating core 30 rotates during the injection molding, whereby an external force is applied to the resin material that flows in the resin joining portion 16C. When an external force acts on the resin material that flows in this manner, a difference in speed occurs in the resin that joins at the resin joining portion 16C. Thereby, the part which forms the linear trace as a weld moves on the rotation core 30 (on the end surface 30a) with rotation of the rotation core 30, and the line as a weld deform | transforms. By moving the weld, the height of the peak of the peak-shaped portion formed due to the orientation of talc as described above is reduced, and as a result, the weld is suppressed.

  The speed change of the resin material accompanying the rotation of the rotary core 30 will be described with reference to FIG. 9 (a) and 9 (b) are diagrams showing the central portion where the rotary core 30 is present on the mold surface 23 of the movable mold 13 in an enlarged plan view similar to FIG. It is a figure which shows the state of the flow of the resin material in front and back (upstream side and downstream side) of the rotary core. FIG. 9A is a diagram showing a weld formation state on the upstream side of the flow of the resin material 16 with respect to the rotating core 30, and FIG. 9B is a diagram showing a weld formation state on the downstream side of the flow. It is. The rotating core 30 is assumed to rotate clockwise in the plan view shown in FIGS. 9A and 9B (see arrows H1 and H2).

  First, the upstream side of the rotary core 30 will be described with reference to FIG. FIG. 9A shows the speed distribution when the resin reaches the rotating core 30. As shown in FIG. 9A, at a substantially central position in the left-right direction in the cavity 12, two flow fronts 16A of the resin material 16 injected simultaneously from the left and right gates 15 (see FIG. 5) facing each other. , 16B are joined to form a resin joining portion 16C. Here, as shown in FIG. 9A, for each flow front 16A, 16B of the resin material 16 flowing in the cavity 12, there are reaching points Ja, Jb with respect to the rotary core 30 in the flow process. That is, each flow front 16A, 16B of the resin material 16 having a curved shape convex in the traveling direction in a plan view is in a point contact state with the rotary core 30 when reaching the circular rotary core 30. These contact points become reaching points Ja and Jb with respect to the rotary core 30. The rotation of the rotary core 30 acts on the resin material 16 from the time when each flow front 16A, 16B of the resin material 16 reaches the rotary core 30.

  As described above, each resin material 16 that is injected and flows from the pair of gates 15 provided at positions shifted to the front side on both the left and right sides of the cavity 12 is a direction facing the other side in the left-right direction as a component in the flow direction. And a component in a direction from the front side to the rear side, the diagonally backward direction is defined as the traveling direction. Specifically, the resin material 16 on the left side in FIG. 9A is a resin material injected from the gate 15 on the left side, and the traveling direction of the flow front 16A is an obliquely rearward direction to the right (upward obliquely in the figure). Direction). In this way, the traveling speed component at the arrival point Ja of the resin material 16 coming from the left gate 15 with respect to the rotary core 30 is defined as Va (see the solid arrow extending from the arrival point Ja). Similarly, the traveling direction of the flow front 16B of the resin material 16 injected from the right gate 15 is an obliquely rearward leftward direction (upwardly diagonally left in FIG. 9A), and the rotating core 30 of the resin material 16 The traveling speed component at the arrival point Jb with respect to is Va ′. The directions of the traveling velocity components Va and Va ′ at the arrival points Ja and Jb are substantially along the same direction as the circular radial direction of the rotary core 30 in plan view. Further, it is assumed that the traveling velocity components Va and Va 'at the left and right arrival points Ja and Jb are symmetrical in the left-right direction.

  In addition, at the arrival points Ja and Jb of the resin material 16 with respect to the rotary core 30, a rotational speed component due to the rotation of the rotary core 30 exists. The direction of the rotational speed component is a tangential direction with respect to the circular shape of the rotary core 30 in plan view. Specifically, as shown in FIG. 9A, in the rotating core 30 that rotates clockwise as described above (see arrow H1), the front left side (lower left side in the figure) with respect to the circular shape of the rotating core 30. The direction of the rotational speed component Vb at the left arrival point Ja located at) is an obliquely backward left direction (upwardly diagonally to the left in the figure) (see broken line arrows extending from the arrival point Ja). Similarly, the direction of the rotational speed component Vb ′ at the right arrival point Jb located on the right front side (lower right side in the figure) with respect to the circular shape of the rotary core 30 is the left diagonal forward direction (FIG. 9A). (See the broken arrow extending from the reaching point Jb).

  As described above, the direction of the traveling speed component and the rotational speed at the arrival points Ja and Jb of the resin material 16 with the traveling speed components (Va, Va ′) and the rotational speed components (Vb, Vb ′) with respect to the rotating core 30. It is almost perpendicular to the direction of the component. That is, the angle between the direction of the traveling speed component Va and the rotational speed component Vb at the left arrival point Ja is θ, and the angle between the direction of the traveling speed component Va ′ and the rotational speed component Vb ′ at the right arrival point Jb. When θ ′, θ = θ′≈90 deg.

  Therefore, when the traveling speed component of the resin material 16 after being accelerated / decelerated by the rotation of the rotary core 30 at the left arrival point Ja is V, V≈Va. Similarly, when the traveling speed component of the resin material 16 after being accelerated and decelerated by the rotation of the rotary core 30 at the right arrival point Jb is V ′, V′≈Va ′. Therefore, V = V ′. From the above, on the upstream side of the rotating core 30, it can be said that the traveling speed of the resin material 16 from the left and right joining each other at the resin joining portion 16 </ b> C is the same.

  Next, the downstream side of the rotary core 30 will be described with reference to FIG. FIG. 9B shows a velocity distribution during resin passage with respect to the rotating core 30. As shown in FIG. 9B, in the middle of the resin material 16 passing over the rotary core 30, the passing point Ka with respect to the circular shape of the rotary core 30 of each flow front 16A, 16B of the resin material 16 in plan view. , Kb exists. That is, with respect to the left and right flow fronts 16A and 16B that progress from the outer side to the inner side and from the front side to the rear side while forming a curved shape that is convex in the traveling direction, the intersection point of the rotary core 30 with the circular shape in plan view There are passing points Ka and Kb.

  The direction of the traveling speed component Va of the resin material 16 at the left passing point Ka is the right rearward direction (upwardly diagonally right in the figure), and the traveling speed component Va ′ of the resin material 16 at the right passing point Kb is The direction is a diagonally left rear direction (a diagonally upward left direction in the figure). The directions of the traveling velocity components Va and Va ′ at the passing points Ka and Kb are both along the direction substantially the same as the tangential direction with respect to the circular shape of the rotary core 30 in plan view. Further, it is assumed that the traveling speed components Va and Va 'at the left and right passing points Ka and Kb are symmetrical in the left-right direction.

  Further, as shown in FIG. 9B, in the rotating core 30 that rotates clockwise (see arrow H <b> 2), the left side that is located on the left rear side (upper left side in the drawing) with respect to the circular shape of the rotating core 30. The direction of the rotational speed component Vb at the passing point Ka is an obliquely rearward rightward direction (upwardly obliquely upward in the figure), which is the same direction as the traveling speed component Va. Further, the direction of the rotational speed component Vb ′ at the right passing point Kb located on the right rear side (upper right side in the figure) with respect to the circular shape of the rotary core 30 is the right diagonally forward direction (right in FIG. 9B). Diagonally downward) and in the opposite direction to the traveling speed component Va ′.

  As described above, at the passing points Ka and Kb with respect to the rotating core 30 of the resin material 16 in which the traveling speed components (Va, Va ′) and the rotating speed components (Vb, Vb ′) exist, The angle θ formed between the direction of the traveling speed component Va and the rotational speed component Vb is θ≈0 deg, and the angle θ ′ formed between the direction of the traveling speed component Va ′ and the rotational speed component Vb ′ for the right passing point Kb. Is θ′≈180 deg.

  Therefore, the traveling speed component V of the resin material 16 after acceleration / deceleration at the left passing point Ka is V≈Va + Vb. Further, the traveling speed component V ′ of the resin material 16 after acceleration / deceleration at the right passing point Kb is V′≈Va′−Vb ′. Therefore, V> V ′. From the above, on the downstream side of the rotary core 30, it can be said that there is a difference in the traveling speed of the resin material 16 from the left and right that join each other at the resin joining portion 16C.

  Thus, the rotation of the rotary core 30 causes a speed difference in the resin joining at the resin joining portion 16C, so that the weld moves and the line as the weld is deformed. The movement of the weld accompanying the rotation of the rotary core 30 will be described with reference to FIG. FIG. 10A is a diagram illustrating a weld state when the rotating core 30 does not rotate, and FIG. 10B is a diagram illustrating a weld state when the rotating core 30 rotates.

  As shown in FIG. 10A, when the rotary core 30 does not rotate, the speed difference as described above does not occur for the resin material 16 that merges at the resin merge portion 16C. For this reason, a linear weld 35 is formed along the front-rear direction at the center position in the left-right direction of the rotary core 30.

  On the other hand, as shown in FIG. 10B, when the rotating core 30 rotates clockwise (see the arrow L1), the speed difference as described above occurs in the resin material 16 that merges at the resin merge portion 16C. The linear weld 35 as shown in FIG. 10A moves, and the shape of the line as the weld 35 is deformed. Specifically, as shown in FIG. 10B, on the end surface 30a (rotation region 23B) of the rotary core 30, the front and rear direction (see FIG. In the vertical direction in FIG. 4, the portion of the rear side of the center position of the rotary core 30 moves to the right and the portion of the front side moves to the left, so that the weld 35 is curved in an S shape.

  More specifically, as shown in FIG. 10A, with respect to the position of the weld 35 on the rotary core 30, the point Pa on the rear side (downstream side) of the center position M1 of the rotary core 30 in the front-rear direction and the rotation. When focusing on the point Pb on the front side (upstream side) of the center position M1 of the core 30, the point Pa on the rear side moves to the right side and the point Pb on the front side moves to the left side due to the clockwise rotation of the rotary core 30. To do. That is, the S-shaped curve of the weld 35 on the rotating core 30 as described above is curved so that the rear side portion where the point Pa exists is convex to the right side, and the front portion where the point Pb exists. Is curved so as to be convex on the left side.

  As for the amount of movement of the weld in the left-right direction, the point Pa on the rear side of the center position M1 of the rotary core 30 is larger than the point Pb on the front side of the center position M1. That is, as shown in FIG. 10B, the movement amount Xa of the rear point Pa to the right side with respect to the straight line portion upstream of the rotating core 30 of the weld 35 is shifted to the left side of the front point Pb. Is greater than the amount of movement Xb (Xa> Xb).

  As described above, a speed difference is generated in the resin material 16 that joins at the resin joining portion 16C by the rotation of the rotating core 30, and the weld position moves. Further, on the downstream side where the rotation direction of the rotary core 30 and the traveling direction of the resin material 16 overlap, the speed difference becomes larger than the upstream side, and the amount of movement of the weld also increases. In this respect, as described above, the height of the peak due to the orientation of the talc is reduced by the movement of the weld, and the weld is suppressed. Therefore, the greater the amount of weld movement, the lower the height of the peak. Weld is suppressed. Therefore, the weld level varies depending on the position within the range of the rotary core 30.

  Moreover, the reduction of the weld seen from the surface of the pressure difference of the resin material produced when the rotating core 30 rotates is demonstrated using FIG. FIG. 11A is a diagram showing a state of talc in the resin joining portion 16C when the rotating core 30 does not rotate, and FIG. 11B is a diagram showing talc in the resin joining portion 16C when the rotating core 30 rotates. It is a figure which shows the state of. In addition, illustration of the rotation core 30 is abbreviate | omitted in FIG. 11 (a), (b).

  When the rotary core 30 does not rotate, as shown in FIG. 11A, there is no difference in resin pressure between the resin materials 16 that merge together at the resin merge portion 16C. That is, the resin pressure from both the left and right sides with respect to the resin joining portion 16C is equal. For this reason, the resin material 16 in the resin confluence portion 16C in the cavity 12 is not solidified and the resin confluence in the surface layer portion 16D having a relatively low fluidity due to the effect of solidification on the inner layer portion 16E having a relatively high fluidity. In the central portion (boundary portion) of the portion 16C, vertical talc oriented in the vertical direction is generated (see the portion indicated by reference numeral N1). Upright talc causes welds.

  On the other hand, when the rotating core 30 rotates, as shown in FIG. 11B, the resin pressure difference after the resin joining at the resin joining portion 16C is received by receiving an external force from the rotating core 30 where the resin material 16 rotates. Arise. As a result, as shown in FIG. 11B, a phenomenon occurs in which the inner layer portion 16E having high fluidity without being solidified moves from the higher resin pressure to the lower one with respect to the surface layer portion 16D. In the example shown in FIG. 11 (b), the resin pressure from the right side is stronger than the resin pressure from the left side with respect to the central resin junction 16C in the left-right direction. In this case, the inner layer portion 16E is shown. Moves from the right side to the left side.

  In this way, the inner layer portion 16E, which is the central portion in the plate thickness direction, moves in the direction perpendicular to the plate thickness direction (the direction along the plate surface) relative to the surface layer portion 16D in the resin joining portion 16C. Thus, the surface layer portion 16D receives stress and the talc lies down (see the portion indicated by reference numeral N2 in FIG. 11B). That is, when the inner layer portion 16E moves in the lateral direction with respect to the surface layer portion 16D in the resin merging portion 16C, the talc can be laid down in the surface layer portion 16D, and the occurrence of upright talc can be suppressed. Thus, when the rotary core 30 rotates, a pressure difference is generated in the resin material 16 that merges from the two directions, and the vertical orientation of talc in the resin merge portion 16C is relaxed, and welds are suppressed. .

  According to the injection molding method of the present embodiment as described above, welds can be suppressed without increasing the cycle time and excessive or insufficient pressure in the cavity 12 causing molding defects. That is, according to the injection molding method of this embodiment, it is not necessary to set the injection timing of the resin material 16 from the plurality of gates 15 to be different from each other. The cycle time does not become long. Further, as described above, although the pressure difference occurs between the resin materials 16 that merge at the resin merge portion 16C due to the rotation of the rotating core 30, the injection pressures of the resin materials 16 from the plurality of gates 15 need to be different depending on the gates. Absent. For this reason, it becomes easy to maintain the pressure balance as a whole in the cavity 12, and molding defects such as burrs and steps in the mold parting line (PL) due to excessive pressure, or unintentional depressions (sinks) due to insufficient pressure, etc. Is less likely to occur. And by rotation of the rotation core 30, since an upright talc can be laid in the resin confluence | merging part 16C, a weld can be suppressed and the appearance of a resin product can be improved.

  Moreover, in the metal mold | die 11 of this embodiment, the rotation core 30 is provided as a part of movable mold | type 13 which is a metal mold | die element | mold which forms the surface by the side of the non-design surface in a molded article. That is, in the injection molding method of the present embodiment, rotating a part of the mold surface forming the cavity 12 forms a non-design surface side surface of the molded product among the mold elements of the mold 11. This is performed by rotating a part of the movable mold 13 which is a mold element to be rotated with the direction perpendicular to the mold surface 23 as the rotation axis direction.

  According to such an injection molding method, in the resin molded product, the concave portion along the circular shape at the boundary portion between the rotary core 30 and the main body portion 13A of the movable mold 13 is transferred, and a circular mark is generated. However, since the circular traces are present on the non-design surface of the resin product and do not appear in the appearance, the appearance of the resin product can be improved more effectively by suppressing welds.

  Subsequently, the configuration of the injection molding apparatus according to the present embodiment will be described with reference to FIGS. 5, 6, and 8. The configuration of the injection molding apparatus described here is an example of a configuration for rotating the rotary core 30 as described above.

  The injection molding apparatus 50 according to this embodiment includes at least two flow fronts 16A of the resin material 16 that flows in the process until the resin material 16 injected into the cavity 12 of the mold 11 is filled in the cavity 12. This is an injection molding apparatus in which a resin joining portion 16C where 16B joins is generated. In the present embodiment, gates 15 are provided at two positions facing each other on both the left and right sides of the cavity 12 (see FIG. 5), and the resin materials 16 injected simultaneously from the gates 15 merge to form a resin merge. Part 16C is produced.

  As shown in FIG. 6, the injection molding apparatus 50 according to the present embodiment includes a rotary core 30 as a rotary mold part and a motor 51 as a drive part.

  The rotary core 30 constitutes a part of the movable mold 13 that is one of the mold elements forming the cavity 12. The rotary core 30 is rotatably provided with the direction perpendicular to the mold surface 23 forming the cavity 12 of the movable mold 13 as the rotation axis direction (see the rotation axis G1) (see arrow G2). The rotating core 30 constitutes a portion of the mold surface 23 that forms the cavity 12 that contacts the resin material 16 of the resin joining portion 16C. That is, the upper end face 30 a of the rotary core 30 forms a rotation region 23 </ b> B where the resin material 16 of the resin joining portion 16 </ b> C contacts with the mold surface 23. The details of the rotary core 30 are as described above.

  The motor 51 generates rotational power for rotating the rotary core 30 and is, for example, a stepping motor. The rotational power of the motor 51 is output from the output shaft 53 via a reduction gear 52 provided integrally with the motor 51. The motor 51 and the speed reducer 52 are provided so that the output shaft 53 side faces upward and the axial direction of the output shaft 53 is parallel to the rotational axis direction of the rotary core 30. That is, the rotary core 30, the motor 51, and the speed reducer 52 are all provided such that the rotation axis direction is the vertical direction (up and down direction) with respect to the mold surface 23.

  The rotation of the output shaft 53 is transmitted to the rotary core 30 by the gear mechanism 54. The gear mechanism 54 includes a drive side gear 54a provided on the output shaft 53 and a driven side gear 54b provided on the rotary core 30 and meshed with the drive side gear 54a. The drive side gear 54 a is fixed to the upper end portion of the output shaft 53. The driven gear 54 b is provided in a bowl shape so as to rotate integrally with the rotary core 30 at the lower end of the cylindrical outer shape of the rotary core 30. The drive side gear 54 a and the driven side gear 54 b mesh with each other while being adjacent to each other in the horizontal direction, and transmit the rotation of the output shaft 53 to the rotary core 30.

  The rotary core 30 is provided in a state of being inserted into the hole 13a formed in the movable mold 13 as described above. The rotary core 30 is provided so as to be rotatable with respect to the hole 13 a via an oil-free bush 55. The oil-free bush 55 is provided in a state of being fitted in a circumferential groove 13b provided on an inner peripheral surface forming the hole 13a.

  The lower end portion of the rotary core 30 penetrates the hole portion 13 a and protrudes into a concave portion 13 c provided on the lower side of the movable mold 13. The recess 13c is continuous with the hole 13a into which the rotary core 30 is inserted, and forms an accommodation space for accommodating the gear mechanism 54 and the like in the movable mold 13. This accommodation space is formed by providing a receiving plate 56 that closes the recess 13 c from the lower side with respect to the movable mold 13. Thus, the lower end portion of the rotary core 30 protrudes from the upper side with respect to the storage space formed by the recess 13c, and a driven gear 54b is provided at the protruding portion of the rotary core 30, and is lower than the storage space. A drive side gear 54a that meshes with the driven side gear 54b is provided on the output shaft 53 protruding from the side.

  The rotary core 30 is rotatably supported via a thrust ball bearing 57 with respect to a receiving plate 56 that forms an accommodation space together with the recess 13c by closing the recess 13c from below. The thrust ball bearing 57 is provided in a state of being fitted into a recess 56a formed on the upper surface of the receiving plate 56, and supports the rotary core 30 from below. The receiving plate 56 is a part that supports the rotary core 30, the motor 51, the speed reducer 52, and the like, and also serves to reinforce the movable mold 13.

  Further, the rotary core 30 is provided with a support shaft 31 extending downward from the lower end surface of the cylindrical outer shape. The support shaft 31 has a smaller diameter than the outer diameter of the rotary core 30, is provided at a position coaxial with the rotary core 30, and rotates integrally with the rotary core 30. The support shaft 31 penetrates the thrust ball bearing 57 and the receiving plate 56 in the vertical direction, and projects the lower end portion to the lower side of the receiving plate 56. A nut member 58 that restricts the movement of the support shaft 31 in the axial direction is provided on the lower protruding portion of the support shaft 31 from the receiving plate 56. The nut member 58 is provided at a position having a predetermined backlash with respect to the lower surface of the receiving plate 56.

  In such a configuration, the receiving plate 56 that closes the concave portion 13c of the movable mold 13 from the lower side is fitted to the stepped portion formed in the concave portion 13c by the fixture 59 with respect to the main body portion 13A of the movable mold 13. By being fixed, rotating parts such as the rotating core 30 and the driven gear 54 b are sandwiched between the main body part 13 </ b> A of the movable mold 13 and the receiving plate 56. The structure including the motor 51 and the speed reducer 52 with respect to the receiving plate 56 fixed to the movable mold 13 is the outside from the outside in the state where the output shaft 53 protrudes upward from the receiving plate 56 (in FIG. Attached from the side).

  The movable mold 13 provided with the configuration for rotating the rotary core 30 such as the motor 51 and the gear mechanism 54 is attached to the movable mounting plate 61 via the spacer block 60. The movable mold mounting plate 61 is fixed to the movable portion of the molding machine that holds the movable mold 13 and the like as described above, and connects the molding machine and the movable mold 13. The spacer block 60 is a member for maintaining a space between the lower side of the movable mold 13 and the movable mounting plate 61.

  In the space between the movable mold 13 and the movable mold mounting plate 61 formed by the spacer block 60, a lower protruding portion from the receiving plate 56 of the support shaft 31 extending from the lower side of the rotary core 30, A motor 51, a speed reducer 52, and the like are located. Here, the motor 51 and the speed reducer 52 having an integrated configuration are fitted into a fitting hole 56 b formed in the receiving plate 56 of the upper speed reducer 52 and the lower end of the lower motor 51. The portion is provided in a positioned state by fitting it into a fitting recess 61 a formed on the upper surface of the movable mounting plate 61.

  In the configuration as described above, the rotation of the motor 51 is transmitted to the rotary core 30 by the reduction gear 52, the drive side gear 54a provided on the output shaft 53, and the driven side gear 54b. As a result, the rotary core 30 rotates with the direction perpendicular to the mold surface 23 as the rotation axis direction (see the rotation axis G1).

  The rotary core 30 is rotated at a predetermined timing in the injection molding process by the injection molding device 50. For example, the rotation of the rotary core 30 is started at a timing several seconds after the start of injection of the resin material from the gate 15. Further, the stopping of the rotation of the rotary core 30 is controlled by the rotation amount of the rotary core 30 (for example, 5 rotations (1800 °)), the elapsed time from the start of rotation (for example, 5 seconds), or the like. Further, the rotary core 30 rotates at a rotation speed of, for example, about 100 ° to 720 ° / second. The rotation operation (start / stop of rotation), the timing, the rotation speed, and the like of the rotary core 30 are controlled by a controller (not shown) included in the injection molding apparatus 50.

  As described above, the injection molding apparatus 50 according to the present embodiment causes the resin core that is joined at the resin joining portion 16 </ b> C in the cavity 12 to generate a speed difference by rotating the rotary core 30 with the rotational power generated by the motor 51. . Thereby, as described above, talc can be laid down in the resin junction 16C, and the occurrence of welds is suppressed. Note that the configuration for rotating the rotary core 30 is not limited to the injection molding apparatus 50 of the present embodiment, and a known technique may be appropriately adopted as the configuration for rotating the rotary core 30. it can. For example, a configuration that uses a linearly acting actuator such as a cylinder mechanism instead of the motor 51 as a drive unit that generates rotational power, converts the linear motion of the actuator into rotational motion, and transmits rotational power to the rotary core 30. It may be.

  According to the injection molding apparatus 50 of the present embodiment as described above, as described above, welds are suppressed without increasing cycle time and excessive or insufficient pressure in the cavity that causes molding defects. be able to.

  Moreover, in the injection molding apparatus 50 of this embodiment, the metal mold | die 11 forms the fixed mold | type 14 which forms the surface by the side of the design surface in a molded product, and the surface by the side of the non-design surface in a molded product as a metal mold | die element. The rotary core 30 is provided as a part of the movable mold 13.

  According to such a configuration, in the resin molded product, even when the concave portion along the circular shape of the boundary portion between the rotary core 30 and the main body portion 13A of the movable mold 13 is transferred and a circular mark is generated, Since the circular traces are present on the non-design surface of the resin product and do not appear on the appearance, the appearance of the resin product can be improved more effectively by suppressing welds.

  In the injection molding method and the injection molding apparatus 50 according to the present embodiment described above, the rotary core 30 is provided only on the movable mold 13 among the mold elements constituting the mold 11. The mold part only needs to constitute a part of at least one mold element forming the cavity 12. For example, in this embodiment, the rotary core 30 is provided in the fixed mold 14, or the movable mold 13. And may be provided on both of the fixed mold 14. Further, in this embodiment, the resin merging portion in the cavity 12 is targeted to the resin merging portion 16C generated by injecting the resin material from the two gates 15; There is no limitation on the configuration (for example, the number of gates, etc.) that causes the occurrence. Therefore, as the resin merging portion, for example, a resin merging portion in which resin materials injected into the cavity from three or more gates may be merged, or a resin material injected into the cavity from one gate. However, it may be a resin merging portion generated by, for example, wrapping around a cylindrical or columnar mold portion existing in the cavity in order to form an opening such as a hole in the molded product.

  Examples of the present invention will be described below. In the present embodiment, the plate thickness is 2.0 mm using a resin material in which talc having a length of 7 μm and a thickness of 2 μm as shown in FIG. A rectangular plate-like product having a size of 200 mm × 300 mm in length and width was formed. Moreover, as the rotating core 30, the one having a diameter of 20 mm was adopted. As conditions for injection molding, the injection speed is [8 mm / second], the rotation start timing of the rotary core 30 is 6.5 seconds after the injection of the resin material from the gate 15, and the rotation speed of the rotary core 30 is 720. The condition of ° / second was used.

  In the present example, molding was performed in two patterns when the rotation amount of the rotary core 30 was 360 ° and 1080 °. The molded product obtained under the conditions in the former case is referred to as Example Product 1, and the molded product obtained under the conditions in the latter case is referred to as Example Product 2. Moreover, the molded product obtained on the conditions when the rotation core 30 is not rotated was employ | adopted as a comparative example product.

  In the present example, the height of the mountain of both the example product 1 and the example product 2 is 0. 0 relative to the comparative product. It was about a few micrometers low. In addition, regarding the movement distance of the weld, the example product 2 having a larger amount of rotation of the rotary core 30 was several millimeters longer than the example product 1.

  Here, “the height of the mountain” means the height of the mountain-shaped portion that forms the V-shaped groove formed on the surface of the resin joining portion by the upright talc, that is, the height between the flat portion and the top of the mountain-shaped portion. This is the difference, and corresponds to the dimension of the symbol D1 in the example shown in FIG. The height of the hill affects the visibility of the weld. The lower the height of the hill, the less noticeable the weld and the better the appearance of the resin product. The “weld moving distance” is a moving amount at a point where the moving amount of the weld in the left-right direction on the rotary core 30 is the largest on the basis of the comparative example product. In the example shown in FIG. The movement amount Xa corresponds to the movement distance of the weld.

  According to the present example, it was found that the height of the mountain was lower in both the example product 1 and the example product 2 as compared with the comparative product. From this result, it can be said that rotating the rotating core 30 reduces the height of the peaks and makes the weld relatively inconspicuous as compared with the case where the rotating core 30 is not rotated. As described above, from this example, it was proved that by using the injection molding technique according to the present invention, the height of a mountain can be reduced and the occurrence of welds can be suppressed.

  As described above, the injection molding method and the injection molding apparatus according to the present invention is an upright which causes a weld by causing a difference in speed of the resin joining at the resin joining portion, not by the injection conditions but by the structure of the mold. The object is to lay talc and suppress the occurrence of welds on the surface of the molded product. The injection molding technique according to the present invention can be widely applied in, for example, injection molding having a thin plate-shaped product region.

11 Mold 12 Cavity 16 Resin Material 16A Flow Front 16B Flow Front 16C Resin Merge Part 13 Movable Mold (Second Mold Element)
14 Fixed mold (first mold element)
23 Mold surface 30 Rotating core (Rotating mold part)
50 Injection molding device 51 Motor (drive unit)

Claims (4)

Injection molding in which a resin joining portion where at least two flow fronts of the flowing resin material join is formed in the process until the resin material injected into the cavity as a plate-like molding space of the mold is filled in the cavity. A method,
The resin material is a mixture of rectangular plate-shaped talc,
In order to lay down the talc to be oriented in the plate thickness direction in the resin merging portion, the portion of the surface of the mold where the cavity is formed, the portion where the resin material of the resin merging portion is in contact is 100 ° to 720 ° / second. By rotating at a rotational speed, a speed difference is generated in the resin that joins at the resin joining portion, and the shrinkage amount due to cooling and solidification of the resin material of the resin joining portion is in a state where talc is oriented in the plate thickness direction. An injection molding method , wherein the shrinkage amount is larger than the shrinkage amount . Rotating part of the surface forming the cavity forms part of the mold element forming the surface on the non-design surface side of the molded product among the mold elements of the mold. The injection molding method according to claim 1, wherein the injection molding method is performed by rotating with a direction perpendicular to the surface as a rotation axis direction. Injection molding in which a resin joining portion where at least two flow fronts of the flowing resin material join is formed in the process until the resin material injected into the cavity as a plate-like molding space of the mold is filled in the cavity. A device,
The resin material is a mixture of rectangular plate-shaped talc,
Forming a part of at least one mold element forming the cavity, wherein the mold element is rotatably provided with a direction perpendicular to a surface forming the cavity as a rotation axis direction; Among them, a rotating mold part that constitutes a part where the resin material of the resin merging part comes into contact,
A drive unit that generates rotational power for rotating the rotary mold unit,
In order to lay down the talc to be oriented in the plate thickness direction in the resin merging portion, the rotational mold portion is rotated at a rotational speed of 100 ° to 720 ° / second by the rotational power generated by the driving portion, thereby the resin A difference in speed is generated in the resin joining at the joining portion, and the shrinkage amount of the resin joining portion due to cooling and solidification of the resin material is made larger than the shrinkage amount in a state where talc is oriented in the plate thickness direction <br> An injection molding apparatus characterized by the above. The mold has, as mold elements, a first mold element that forms a surface on the design surface side of the molded product and a second mold element that forms a surface on the non-design surface side of the molded product. And
The injection molding apparatus according to claim 3, wherein the rotary mold part is provided as a part of the second mold element.

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