JP6437830B2 - Injection mold - Google Patents

Description

  The present invention relates to an injection mold and is suitable for molding with high accuracy.

  As an injection molding apparatus, there is an apparatus in which a cavity having a shape of a molded product is formed by clamping a set of molds in the left-right direction. In this case, one mold is fixed to a fixed platen fixed to the tie bar, and the other mold is fixed to a movable platen movable along the tie bar. When a set of molds is clamped, a clamping force for clamping the mold is applied to the movable platen while the molds are in contact with each other.

  At this time, it is known that the platen tends to bend. When the mold is fixed to the platen as described above, generally, the mold includes a mold plate on which irregularities are formed to form a molded product, and a mounting plate for attaching the mold plate to the platen. Consists of. Therefore, when the platen is bent, the template may be bent together with the mounting plate. In this case, there is a tendency that the molding accuracy is lowered such that a gap is generated between the contact surfaces of the mold plates and burrs are generated in the molded product, or the molded product has a shape different from the design value. In order to suppress such a decrease in molding accuracy, a clamping force from the platen is applied to a part of the region where the contact surface is projected on the surface of the mold plate opposite to the contact surface. Mold is known.

  Patent Document 1 below describes such an injection mold. In this injection mold, the size of the mounting plate is made smaller than that of the cavity die (corresponding to the mold plate) so that the mounting plate is joined to a part of the surface opposite to the contact surface of the cavity die. Has been.

JP 7-88913 A

  However, when the mounting plate is made small like the injection mold described in Patent Document 1, the mounting plate and the mold plate may fall down. When the template plate falls down, it becomes difficult to form a molded product as designed.

  Therefore, the present invention intends to provide an injection mold that can be molded with high accuracy.

  In order to solve the above-described problems, the present invention provides an injection mold fixed to a platen of an injection molding apparatus, which is a surface opposite to the platen side and abuts against another mold A mold plate having a back surface with respect to the contact surface, a first mounting plate fixed to the mold plate on the back side of the mold plate, and a surface of the first mounting plate opposite to the mold plate side A center press plate disposed in a projection region on the outer periphery of the abutting surface, and a connecting member for connecting the platen and the first mounting plate, the connecting member to the template So that the connecting member is fixed to the platen and is non-fixedly engaged with a region on the outer peripheral side of the center press plate in the first mounting plate. The first mounting plate is connected to the plastic By biasing the down side, it is characterized in that is sandwiched between the first mounting plate and the platen.

  In this mold for injection molding, although the center press plate smaller than the contact surface of the mold plate is interposed between the mold plate and the platen, the outer peripheral side of the first mounting plate from the center press plate is the platen. Since it is biased, it is possible to suppress the collapse of the mold plate as compared with the case where the center press plate is simply fixed to the mold plate.

  Further, as described above, it is known that the platen may be bent during mold clamping. However, in the injection mold according to the present invention, since the center press plate smaller than the contact surface of the mold plate is interposed between the platen and the first mounting plate, the platen is bent when the platen is bent. Transmission to the plate can be suppressed. Further, when the platen bends, the position of the fixing region of the platen connecting member with respect to the projection region of the center press plate of the platen may shift. However, in the injection mold of the present invention, the connecting member can move relative to the template. Specifically, when the first mounting plate is bent by the force of the connecting member urging the first mounting plate, the bending of the first mounting plate is relieved by the bending of the platen, and the connecting member is Move relatively. When the first mounting plate is hardly bent or when the platen is largely bent, the coupling member that is not fixed and engages the first mounting plate is disengaged from the first mounting plate. Therefore, even when the platen is bent as described above, it is possible to suppress the bending from being transmitted to the template via the connecting member.

  Thus, the injection mold of the present invention can be molded with high accuracy.

  Further, it is preferable that the first mounting plate has a protruding portion that protrudes from a back surface of the template, and the connecting member engages with the protruding portion.

  Since the engaging position of the connecting member is the projecting portion, the connecting member can be easily engaged with the first mounting plate.

  Further, it is preferable that a second mounting plate having a larger area than the center press plate is disposed between the center press plate and the platen.

  In general, the platen is not a replacement part of the injection molding apparatus and is not replaced with the mold. For this reason, it is preferable that the trace of the injection mold due to the clamping force does not remain on the platen. Therefore, by arranging the second mounting plate as described above, it is possible to suppress the trace of the injection mold from remaining on the platen.

  The second mounting plate may be fixed to the platen, and the connecting member may be fixed to the platen via the second mounting plate.

  With such a configuration, the template, the first mounting plate, the center press plate, the second mounting plate, and the connecting member become an integrated unit. Therefore, the injection mold can be easily attached to or removed from the platen by attaching or removing the second attachment plate to or from the platen. Moreover, it can prevent more appropriately that a metal mold | die falls by attaching a 2nd attachment plate firmly to a platen. The center press plate may be formed integrally with at least one of the first mounting plate and the second mounting plate.

  Further, it is preferable that the center press plate has a rotationally symmetric shape around the central axis of the platen.

  With such a configuration, even when a part of the force due to the bending of the platen is transmitted to the template, it is possible to suppress the transmission of the force due to the deflection unevenly distributed on the template.

  Moreover, it is preferable that the said center press plate is made into the shape which overlaps with the gate position of the shaping | molding die formed in the said contact surface side of the said template, and does not overlap with a part of said shaping | molding die.

  Generally, the injection pressure of the fluid resin at the gate in the mold is higher than the pressure of the fluid resin at the cavity portion of the mold. Therefore, the mold clamping force and the injection pressure of the fluid resin can be balanced by clamping with a mold clamping force that is higher than the position of the cavity of the molding die.

  As described above, according to the injection molding die of the present invention, molding can be performed with high accuracy.

It is a figure which shows the molded article shape | molded by the injection die which concerns on embodiment of this invention. It is a figure which shows a mode that the metal mold | die for injection molding which concerns on embodiment of this invention was fixed to the platen. It is sectional drawing of a pair of template shown in FIG. It is a figure which shows the relationship between a shaping | molding die and a center press plate. It is a figure which shows typically the relationship between the mold plate by the side of movement, and the template plate by the side of fixed when the mold plate by the side of a movement is located in a mold open position, a primary mold clamping position, and a secondary mold clamping position. It is a flowchart which shows the manufacturing method of an injection molded product. It is a figure which shows the mode of an injection process. It is a figure which shows the mode of a secondary mold clamping process. It is a figure which shows the modification of a center press plate.

  Hereinafter, a preferred embodiment of an injection mold according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view showing a molded product molded by an injection mold according to an embodiment of the present invention. As shown in FIG. 1, in the injection mold according to the present embodiment, a molded product 100 including two light guide plates 101 is molded. Each light guide plate 101 is formed with a runner 102 connected thereto, and a sprue 103 is connected to each runner 102. 1A is a view seen from the side surface direction of the light guide plate 101, and FIG. 1B is a view seen from the direction in which the light guide plate 101 is viewed in plan view.

  The respective light guide plates 101 of the present embodiment have the same plate shape, and are generally rectangular when viewed in plan. The light guide plate 101 is used by being separated from the runner 102. Although not particularly illustrated, the light guide plate 101 of the present embodiment has an uneven surface on one side and a flat surface on the other side. Further, a specific side surface is used as a light incident surface, and the thickness of the incident surface is larger than the thickness of the light guide plate 101 other than the incident surface. The incident surface is, for example, a surface opposite to the runner 102 side. The thickness of the incident surface in the light guide plate 101 is, for example, about 0.5 mm, and the thickness other than the incident surface is generally constant at 0.3 mm or less.

  Examples of the type of resin used for the light guide plate 101 of the present embodiment include polycarbonate, methacrylic resin, and cycloolefin polymer.

  The resin used for the light guide plate 101 is mixed with at least one of a release agent, a plasticizer, an antioxidant, an antistatic agent, a flame retardant, a lubricant, a coloring agent, an impact resistance enhancer, a filler, and the like. Also good.

  When light is incident from such an incident surface of the light guide plate 101, the light propagates through the light guide plate 101 while repeating total reflection. Further, the light reflected by the uneven surface of the light guide plate 101 changes its path, and the light incident on the wide surface at an incident angle smaller than the total reflection angle of the light guide plate 101 is emitted from the light guide plate 101.

  Next, an injection mold for molding the molded product 100 will be described.

  FIG. 2 is a view showing a state where the injection mold according to the embodiment of the present invention is fixed to the platen. Specifically, FIG. 2 shows that a fixed-side injection mold 1 is fixed to a fixed-side platen 3 and a movable-side injection mold 2 is fixed to a movable-side platen 4. 1 shows a state where 1 and an injection mold 2 are in contact with each other. In FIG. 2, a part of the configuration such as a specific configuration of the template is simplified.

  First, the fixed-side injection mold 1 and the platen 3 will be described.

  The stationary side platen 3 is fixed to four tie bars 5. In FIG. 2, two tie bars 5 are visible. The platen 3 is formed with an injection machine insertion hole 3H into which an injection port (not shown) for injecting molten resin is inserted. The injection machine insertion hole 3H is formed at the center of the platen 3 when the platen 3 is viewed in plan, has a conical shape halfway, and is a through-hole having a constant diameter from the middle. A locate ring 31 is disposed in the injection machine insertion hole 3H.

  The fixed-side injection molding die 1 fixed to the platen 3 mainly includes a mold plate 11, a first mounting plate 12, a center press plate 13, a second mounting plate 14, and a connecting member 15. Prepare as.

  The mold plate 11 has a substantially rectangular parallelepiped shape, and the mold plate 11 includes a contact surface 11j and a contact surface that are in contact with an injection mold 2 that is another mold viewed from the injection mold 1. 11j and a back surface 11b which is the opposite surface. FIG. 3 is a cross-sectional view of the pair of templates shown in FIG. As shown in FIG. 3, the contact surface 11j of the template 11 is formed in a substantially flat shape. In the template 11, a sprue 53 serving as a resin flow path extends from the center of the contact surface 11j to the back surface 11b in a direction perpendicular to the contact surface 11j.

  Further, a heat insulating layer 61 is provided on the abutting surface 11j side of the template 11 at a position facing a molding die 51 of the template 21 described later. On the surface of the heat insulating layer 61, for example, a metal layer having a thickness of 0.05 mm to 0.5 mm is formed by plating, and if necessary, the metal layer has an uneven shape corresponding to the uneven surface of the light guide plate 101. Is done. The heat insulating layer 61 has a heat permeability lower than that of the portion other than the heat insulating layer 61 in the template 11 and can withstand the injection pressure of the resin and the pressing force of the mold. Examples of the material of the heat insulating layer 61 include ceramics such as alumina and zirconia, glass, thermosetting resin, super engineering plastics, and the like. In addition, as a method for forming the heat insulating layer 61, for example, a method of forming the heat insulating layer 61 by coating by a plasma spraying method or a thermal spraying method such as HVOF (High Velocity Oxygen Fuel), or the heat insulating layer 61 is installed as a nest. The method etc. are mentioned.

  The first mounting plate 12 is a plate-like member, and is fixed on the back surface 11b of the template 11 with a bolt (not shown). The first mounting plate 12 has a protruding portion 12p that protrudes from the back surface 11b of the template 11. The first mounting plate 12 of the present embodiment has a substantially rectangular shape larger than the back surface 11b of the template 11 when viewed in plan, and protrudes from the entire periphery of the back surface 11b. Therefore, in the present embodiment, the frame-like region on the outer peripheral side of the first mounting plate 12 is the protruding portion 12p that protrudes from the back surface 11b. A plurality of through holes 12h are formed in the protruding portion 12p. In the present embodiment, four through-holes 12h are formed, and the four through-holes 12h are respectively formed at positions that are equidistant from the center of the first mounting plate 12 toward each vertex of the rectangle. A connecting member 15 made of a screw is inserted into each through hole 12h. In FIG. 2, the two connecting members 15 are visible. The diameter of the through hole 12 h is sufficiently larger than the diameter of the screw portion of the connecting member 15 and smaller than the diameter of the head portion of the connecting member 15. Therefore, the connecting member 15 is not screwed into the through hole 12 h and is engaged with the first mounting plate 12 by the head portion being hooked on the first mounting plate 12. That is, the connecting member 15 is engaged with the first mounting plate 12 in an unfixed state. In addition, a through hole that communicates with the sprue portion 53 formed in the template 11 is formed at the center of the first mounting plate 12, and the diameter of the through hole is larger than that of the sprue portion 53 and is equal to the through hole of the locating ring 31. It is said that.

  The center press plate 13 is a plate-like member having a shape to be rotated around the central axis of the platen 3 when the platen 3 is viewed in plan, and is opposite to the template 11 side of the first mounting plate 12. On the surface, when the outer periphery of the contact surface 11j of the template 11 is projected, it is arranged so as to be located in this projection region. That is, the center press plate 13 has a size that falls within the projection area on the outer periphery of the contact surface 11j. As described above, in the present embodiment, since the first mounting plate 12 protrudes from the entire periphery of the back surface 11b, the center press plate 13 is located on the surface of the first mounting plate 12 opposite to the mold plate 11 side. Will be located. When the center press plate 13 is viewed in plan with the center press plate 13 arranged in this manner, the center press plate 13 is surrounded by a line connecting the four through holes 12 h of the first mounting plate 12. A through hole similar to the through hole leading to the sprue portion 53 formed in the first mounting plate 12 is formed in the center of the center press plate 13. The thickness of the center press plate should be in the range of 0.01 mm to 0.2 mm from the viewpoint of preventing the platen bending from being transmitted to the template and preventing the platen from being excessively bent. Is desirable.

  The second mounting plate 14 is a plate-like member and is disposed between the center press plate 13 and the platen 3. The second mounting plate 14 has a larger area than the center press plate 13 and the first mounting plate 12 when viewed in plan. The second mounting plate 14 is fixed to the platen 3 by screws with a fixing member 16 made of screws. In FIG. 2, the two fixing members 16 are visible. Further, the connecting member 15 inserted through each through hole 12 h of the first mounting plate 12 is screwed into the second mounting plate 14 and fixed. Thus, in the present embodiment, the connecting member 15 is fixed to the platen 3 via the second mounting plate 14. Moreover, the 1st attachment plate 12 is urged | biased by the 2nd attachment plate 14 side (platen 3 side) because the connection member 15 is screwed in the 2nd attachment plate 14. FIG. Therefore, the center press plate 13 disposed between the first mounting plate 12 and the second mounting plate 14 is sandwiched and fixed between the first mounting plate 12 and the second mounting plate 14. . From the viewpoint of preventing the template 11 from falling, it is preferable that at least the first mounting plate 12, the center press plate 13, and the second mounting plate 14 are fixed using screws as described above. Thus, at least the mold plate 11, the first mounting plate 12, the center press plate 13, the second mounting plate 14, and the connecting member 15 constitute a single unit and constitute an integral injection mold 1. In addition, a through hole similar to the through hole communicating with the sprue portion 53 formed in the first mounting plate 12 is formed at the center of the second mounting plate 14, and the through hole is disposed through the locating ring 31. In addition to the insertion hole 3H, it communicates with the sprue portion 53 of the mold plate through the through hole of the center press plate 13 and the through hole of the first mounting plate 12.

  Next, the movable side injection mold 2 and the platen 4 will be described.

  The movable platen 4 is a flat plate member configured to be movable along the four tie bars 5 and is different from the fixed platen 3 in that no injection machine insertion hole is formed.

  The movable-side injection mold 2 fixed to the platen 4 mainly includes a mold plate 21, a first mounting plate 22, a center press plate 23, a second mounting plate 24, and a connecting member 25. Prepare as.

  As shown in FIG. 3, the template 21 has a template main body 21m having a convex portion 21s, a frame portion 21c into which the convex portion 21s can be fitted, and an elasticity arranged between the template main body 21m and the frame portion 21c. It has the body 21e as a main structure. In FIG. 2, the detailed structure of the template 21 is omitted. The mold plate 21 has a surface 21 j opposite to the elastic body 21 e side of the frame portion 21 c as an abutting surface 21 j that abuts against an injection mold 2 that is another mold as viewed from the injection mold 2. The surface opposite to the contact surface 21j side in the template body 21m is the back surface 21b. In this embodiment, the elastic body 21e is formed of a spring, and when the distance between the frame portion 21c and the template main body 21m becomes smaller than a predetermined distance, the direction in which the distance between the frame portion 21c and the template main body 21m increases due to the elastic force. The frame portion 21c and the template body 21m are pushed.

  A pair of molding dies 51 for forming the light guide plate 101 which is a molded product is formed on the contact surface 11j side of the convex portion 21s in the template body 21m. In addition, a pair of runner portions 52 for allowing the resin to flow into the respective molds 51 are formed connected to the molds 51. The resin remaining in the runner portion 52 becomes the runner 102. The boundary between the runner portion 52 and the mold 51 is a gate 55, and the opposite side of the mold 51 to the gate 55 side is a resin flow end 56. In addition, a pair of runner portions 52 extend symmetrically perpendicularly to the sprue portion 53 with respect to the central axis of the sprue portion 53 of the template 11, and the pair of molds 51 are formed symmetrically with respect to the center. Yes. Further, at least a part of the surface of the template 21 forming the mold 51 is a heat insulating layer 62. The configuration of the heat insulating layer 62 is the same as that of the heat insulating layer 61 of the template 11, and an uneven shape corresponding to the uneven surface of the light guide plate 101 is provided on the surface metal layer as necessary.

  The first mounting plate 22 of the injection mold 2 is formed with a hole through which an unillustrated ejector rod is inserted, except that a through hole used for introducing a molding resin is not formed. The structure is the same as that of the first mounting plate 12 of the injection mold 1 and is fixed on the back surface 21b of the mold plate 21 by bolts (not shown). The first mounting plate 22 has a protruding portion 22p that protrudes from the back surface 21b of the template 21. In the present embodiment, similarly to the first mounting plate 12, a frame-like region on the outer peripheral side of the first mounting plate 22 is a protruding portion 22p that protrudes from the back surface 21b. In the protruding portion 22p, the same number of through holes 22h as the through holes 12h formed in the first mounting plate 12 are formed in the same number as the through holes 12h. Each through hole 22h is formed at a position that is equidistant from the center of the first mounting plate 22 toward each vertex of the rectangle. A connecting member 25 similar to the connecting member 15 of the injection mold 1 is inserted into each through hole 22h. Accordingly, the connecting member 25 is not screwed into the through-hole 22 h and is engaged with the first mounting plate 22 by the head portion being hooked on the first mounting plate 22. In FIG. 2, the two connecting members 25 are visible.

  The center press plate 23 has a hole through which an unillustrated ejector rod is inserted, but does not have a through hole used for introducing a molding resin. The configuration is the same as that of the center press plate 13. The center press plate 23 is disposed so as to be positioned in the projection region when projecting the outer periphery of the contact surface 21j of the mold plate 21 on the surface of the first mounting plate 22 opposite to the mold plate 21 side. Has been. As described above, in the present embodiment, since the first mounting plate 22 protrudes from the entire periphery of the back surface 21b, the center press plate 23 is the surface of the first mounting plate 22 opposite to the mold plate 21 side. It will be located inside. When the center press plate 23 is viewed in plan with the center press plate 23 arranged in this manner, the center press plate 23 is surrounded by a line connecting the four through holes 22 h of the first mounting plate 22.

  The second mounting plate 24 has an injection molding die 1 except that a hole through which an unillustrated ejector rod is inserted is formed but a through hole used for introducing a molding resin is not formed. The second mounting plate 14 is configured in the same manner, and is disposed between the center press plate 23 and the platen 4. The second mounting plate 24 has a larger area than the center press plate 23 and the first mounting plate 22 when viewed in plan. The second mounting plate 24 is fixed to the platen 4 with screws by a fixing member 26 similar to the fixing member 16. In FIG. 2, the two fixing members 26 are visible. Further, the connecting members 25 inserted through the respective through holes 22h of the first mounting plate 22 are screwed into the second mounting plate 24 and fixed. Thus, in the present embodiment, the connecting member 25 is fixed to the platen 4 via the second mounting plate 24. The first mounting plate 22 is biased toward the second mounting plate 24 (the platen 4 side) by screwing the connecting member 25. For this reason, the center press plate 23 disposed between the first mounting plate 22 and the second mounting plate 24 is sandwiched and fixed between the first mounting plate 22 and the second mounting plate 24. Thus, at least the mold plate 21, the first mounting plate 22, the center press plate 23, the second mounting plate 24, and the connecting member 25 form one unit and constitute an integral injection mold 2.

  FIG. 4 is a diagram showing the relationship between the mold formed on the mold plate 21 and the center press plate 23. Specifically, the center press plate 23, the mold 51 and the center press plate 23 when the center press plate 23 is viewed in plan view. It is a figure which mainly shows the positional relationship with the runner part. In this figure, the center press plate 23 is indicated by a broken line for convenience. In the present embodiment, the center press plate 23 has a substantially rectangular shape, and the center of the center press plate 23 substantially coincides with the center of the sprue portion 53 of the injection mold 1. Further, the gate 55 which is a boundary between the mold 51 and the runner portion 52 is located at a place where it overlaps with the center press plate 23, and a part of the mold 51 is located at a place where it does not overlap with the center press plate 23. In the present embodiment, at least the flow end portion 56 of the mold 51 is located in a place where a part of the mold 51 does not overlap the center press plate 23.

  In the present embodiment, as described above, the center press plate 13 of the fixed-side injection molding die 1 has the same configuration as the center press plate 23 of the movable-side injection molding die 2, and Arrange them in overlapping positions. Therefore, as shown in parentheses in FIG. 4, the gate 55, which is the boundary between the mold 51 and the runner part 52, is located at a location overlapping the center press plate 13, and a part of the mold 51 including the flow end 56. Is located where it does not overlap the center press plate 13.

  Further, as described above, the injection mold 2 can be moved together with the platen 4 by moving the platen 4. Due to the movement of the injection mold 2, the mold plate 21 has a mold open position where the mold plate 11 and the mold plate 21 do not contact each other, and the contact surface 11 j of the mold plate 11 and the contact surface 21 j of the mold plate 21. Can be positioned at a primary mold clamping position where they are in contact with each other, and at a secondary mold clamping position where the convex portion 21s of the template body 21m is further pushed into the frame portion 21c than the primary mold clamping position. FIG. 5 is a diagram schematically showing the relationship between the mold plate 11 and the mold plate 21 when the mold plate 21 is located at such a mold opening position, a primary mold clamping position, and a secondary mold clamping position. Specifically, FIG. 5A shows a state where the template 21 is positioned at the mold open position, and FIG. 5B shows a state where the template 21 is positioned at the primary mold clamping position. (C) shows a state in which the template 21 is positioned at the secondary mold clamping position.

  As shown in FIG. 5, the mold plate 21 is movable between the mold opening position, the primary mold clamping position, and the secondary mold clamping position in a state where the frame portion 21c is fitted and held in the convex portion 21s. . That is, as shown in FIG. 5A, when the template 21 is located at the mold open position, the contact surface 21j of the frame portion 21c and the contact surface 11j of the template 11 are not in contact with each other. The part 21c is held. Further, as shown in FIG. 5B, when the template 21 is located at the primary clamping position, the frame portion 21c with the heat insulating layer 61 of the template 11 and the heat insulating layer 62 of the template 21 facing each other. Is retained. At this time, a cavity SPC surrounded by the inner peripheral surface of the frame portion 21c, the heat insulating layer 61 of the mold plate 11 of the injection mold 1 and the heat insulating layer 62 of the mold plate 21 of the injection mold 2 is formed. . Further, as shown in FIG. 5C, when the template 21 is located at the secondary mold clamping position, the heat insulating layer 62 of the template 21 is more than the primary mold clamping position (FIG. 5B). The frame portion 21c is held in a state approaching the side. Therefore, when the mold plate 21 is located at the secondary mold clamping position, the cavity SPC is smaller in the direction between the mold plate 11 and the mold plate 21 than when the mold plate 21 is located at the primary mold clamping position. FIG. 3 shows a state where the template 21 is located at the secondary mold clamping position.

  Next, a method for manufacturing an injection molded product using the injection mold 1 and the injection mold 2 will be described.

  FIG. 6 is a flowchart showing a method for manufacturing an injection molded product. As shown in FIG. 6, the method for manufacturing an injection molded product according to this embodiment includes a primary mold clamping process P1, an injection process P2, a secondary mold clamping process P3, a pressure holding process P4, a cooling process P5, and a mold opening. The process P6 is provided as a main process.

<Primary mold clamping process P1>
In the primary mold clamping process P1, the platen 4 is moved and the mold plate 21 of the injection mold 2 is moved from the mold open position shown in FIG. 5A to the primary mold clamp position shown in FIG. 5B. The As a result, the region surrounded by the frame wall of the frame portion 21 c is sandwiched between the heat insulating layer 61 of the template 11 of the injection mold 1 and the heat insulating layer 62 of the template 21 of the injection mold 2. Thus, the cavity SPC is formed.

  Since the frame portion 21c is held in a state where the convex portion 21s of the template 21 is fitted, even if the position of the template 21 is shifted relative to the template 11, the frame portion The cavity SPC surrounded by the inner peripheral surface 21c, the heat insulating layer 61 of the mold plate 11 of the injection mold 1 and the heat insulating layer 62 of the mold plate 21 of the injection mold 2 is stably maintained.

<Injection process P2>
Next, the injection process P2 is performed. FIG. 7 is a diagram showing the state of this process. In this step, molten resin is injected into the opening of the locating ring 31 from an injection molding machine inserted into an injection machine insertion hole 3H formed in the stationary platen 3. The injected molten resin flows into the sprue portion 53 of the template 11. As shown in FIG. 7, the molten resin MS that has flowed into the sprue portion 53 flows into the cavity SPC, and flows from the gate 55 into the space formed by the mold 51 through the runner portion 52. At this time, the specified injection amount of the molten resin MS is injected at a predetermined injection speed. As a kind of resin used for this molten resin MS, the resin used for the light-guide plate 101 can be mentioned, for example. Note that the resin MS is preferably an amorphous resin.

<Secondary mold clamping process P3>
Next, the secondary mold clamping process P3 is performed. In this process, the platen 4 is further moved in a state where there is a gap between the cavity SPC formed in the primary mold clamping process P1 and the molten resin MS injected into the cavity SPC, and the mold of the injection mold 2 is formed. The plate 21 is moved from the primary mold clamping position (FIG. 5B) to the secondary mold clamping position (FIG. 5C). That is, before the cavity SPC formed in the primary mold clamping process P1 is filled with the molten resin MS without a gap, the movement of the mold plate 21 is started from the primary mold clamping position, and the heat insulating layer 62 of the mold plate 21 is moved to the primary mold. It is brought closer to the template 11 side on the fixed side than the tightening position.

  By such an operation, as shown in FIG. 8, it is surrounded by the part of the mold 51 in the heat insulating layer 62 of the movable-side mold 21, the inner peripheral surface of the frame portion 21 c, and the heat-insulating layer 61 of the fixed-side mold 11. The thickness T of the cavity SPC is smaller than that in the primary mold clamping step, and the space by the mold 51 in the cavity SPC is a space corresponding to the injection molded product. In addition, a large pressure is applied to the molten resin MS flowing in the cavity SPC as compared with the primary mold clamping process P1 by transmitting an external force applied to the moving platen 4 to the mold plate 21. The molten resin MS is quickly filled inside.

  At this time, since a large clamping force is applied to the platens 3 and 4 from the outside, the platens 3 and 4 may bend. When the platens 3 and 4 are bent, it is assumed that the bending is transmitted to the templates 11 and 21. In this case, the mold plates 11 and 21 are also bent, and the distance between the mold plate 11 and the mold plate 21 is increased in the vicinity of the sprue portion 53, and there is a tendency that a molded product as designed cannot be obtained. However, in the injection mold 1 of the present embodiment, the center press plate 13 is disposed in the projection region on the outer periphery of the contact surface 11j of the mold plate 11. Therefore, even if the second mounting plate 14 is bent due to the bending of the platen 3, the center press plate is compared with the bending amount of the template 11 when the template 11 is fixed directly to the second mounting plate 14. The amount of bending of 13 is small. For this reason, it is suppressed that the center press plate 13 absorbs the bending of the platen 3 and the template 11 is bent. Similarly, in the injection mold 2, the center press plate 23 is disposed in the projection area on the outer periphery of the contact surface 21 j of the mold plate 21. Therefore, even if the second mounting plate 24 is bent due to the bending of the platen 4, the center press plate is compared with the bending amount of the template 21 when the template 21 is directly fixed to the second mounting plate 24. The amount of bending of 23 is small. For this reason, it is suppressed that the center press plate 23 absorbs the bending of the platen 4 and the template 21 is bent. Moreover, as shown in FIG. 4, the center press plates 13 and 23 are arranged so as to overlap the gate 55 having a large resin injection pressure and not to overlap the flow end portion 56 of the mold 51 having a small resin injection pressure. Yes. Thus, the center press plates 13 and 23 apply a high mold clamping force to the portions of the mold plates 11 and 21 where the resin injection pressure is high, and apply them to the portions of the mold plates 11 and 21 where the resin injection pressure is low. A low mold clamping force is applied to further suppress the bending of the mold plates 11 and 21.

  Further, when the platens 3 and 4 are bent, the fixing region (the fixing members 15 and 25 via the second mounting plates 14 and 24 of the platens 3 and 4 with respect to the projection region of the center press plates 13 and 23 of the platens 3 and 4 ( There is a tendency that the positions of the projection members 15 and 25 of the platens 3 and 4 are shifted. However, in the injection molds 1 and 2 of the present embodiment, the connecting members 15 and 25 are inserted through the through holes formed in the first mounting plates 12 and 22, and the connecting members 15 and 25 are the first mounting plate 12. , 22 can be moved relative to the templates 11, 21. For this reason, even if it is a case where the platens 3 and 4 bend, it can suppress that the said bending is transmitted to the template 11 and 21 via the connection members 15 and 25. FIG. Furthermore, the connecting members 15 and 25 of the injection molds 1 and 2 are not screwed into the first mounting plates 12 and 22, but are merely inserted through the through holes 12h and 25h. is there. Therefore, even if the platens 3 and 4 are bent, the urging force of the connecting members 15 and 25 to the first mounting plates 12 and 22 is weakened, or the connecting members 15 and 25 are engaged with the first mounting plate 12. This prevents the force due to the bending of the platens 3 and 4 from being transmitted to the first mounting plates 12 and 22.

  The space thickness T by the mold 51 in the cavity SPC formed in the secondary mold clamping step P3 is smaller than 0.5 mm. That is, the maximum distance between the surface of the heat insulating layer 61 of the mold plate 11 and the surface of the heat insulating layer 62 of the mold plate 21 that forms a space by the mold 51 in the secondary mold clamping step P3 is set to be smaller than 0.5 mm. The The timing at which the movable mold plate 21 starts to move from the primary mold clamping position may be after the injection of the molten resin MS is stopped, or while the molten resin MS is being injected. Also good.

By the way, of the molten resin MS injected into the cavity SPC after the start of the secondary mold clamping process P3, at least in the space by the mold 51, the site along the flow direction in contact with the mold 11 and the mold 21 is The glass transition temperature (Tg) or higher. Specifically, for example, the molding resin is polycarbonate, the heat permeability of the heat insulating layer 61 of the template 11 and the heat insulating layer 62 of the template 21 is 2900 J / s ^0.5 m ² k. When the thickness of the metal layer on the surface of these heat insulating layers 61 and 62 is 0.1 mm, the temperature of the molten resin MS at the start of injection is 340 ° C., and the temperature of the mold plates 11 and 21 is If each is set to 100 ° C., the period of transition from the injection start time to the secondary mold clamping process P3 is set to 0.01 to 0.1 seconds, so that the mold plate 11 and the mold plate 21 are included in the molten resin MS. The part along the flow direction in contact is equal to or higher than the glass transition temperature.
<Pressure holding process P4>
Next, the pressure holding process P4 is performed. In this process, after the specified injection amount of the molten resin MS is injected, the injection pressure of the molten resin is lowered from the injection pressure in the injection process, and is increased for a certain period of time by the reduced injection pressure. The

<Cooling process P5>
Next, the cooling process P5 is performed. In this step, the molten resin MS filled in the cavity SPC formed in the secondary mold clamping step is cooled, for example, by cooling the template 11 and the template 21.

<Mold opening process P6>
Next, the mold opening process P6 is performed. In this step, the mold 2 for injection molding is moved by moving the movable platen 4, and the mold plate 21 is moved from the secondary mold clamping position (FIG. 5C) to the mold open position (FIG. 5A). ). At this time, the molded body solidified in the cavity SPC formed in the secondary mold clamping process P3 moves away from the fixed mold plate 11 and moves together with the movable mold plate 21. Thus, a molded product 100 including the light guide plate 101 shown in FIG. 1 is obtained.

  As described above, in the injection molds 1 and 2 according to the present invention, the center press plates 13 and 23 are disposed between the first mounting plates 12 and 22 and the platens 3 and 4, and the connecting members 15 and 25. By urging the first mounting plates 12 and 22 toward the platens 3 and 4, the center press plates 13 and 23 are held between the first mounting plates 12 and 22 and the platens 3 and 4. Moreover, although the center press plates 13 and 23 smaller than the contact surfaces 11j and 21j of the template plates 11 and 21 are interposed between the template plates 11 and 21 and the platens 3 and 4, the first mounting plate 12 is used. , 22, the outer peripheral side of the center press plates 13, 23 is urged by the platens 3, 4, so that the mold plates 11, 21 are more than the case where the center press plates 13, 23 are directly fixed to the mold plates 11, 21. The fall can be suppressed.

  Further, as described above, even when the platens 3 and 4 are bent at the time of mold clamping, it is possible to suppress the bending of the platens 3 and 4 from being transmitted to the mold plates 11 and 21. Moreover, when the platens 3 and 4 are bent, that is, the relative positions of the fixing regions of the connecting members 15 and 25 of the platens 3 and 4 with respect to the projection regions of the center press plates 13 and 23 of the platens 3 and 4 are in the mold clamping direction. When displaced, the connecting members 15 and 25 fixed to the platens 3 and 4 can move in the mold clamping direction with respect to the mold plates 11 and 21. Specifically, when the first mounting plates 12 and 22 are bent by the force of the connecting members 15 and 25 urging the first mounting plates 12 and 22, the first mounting plate 12 is bent by the bending of the platens 3 and 4. , 22 is relaxed, the connecting members 15, 25 move relative to the mold plates 11, 21, and the first mounting plates 12, 22 are hardly bent or the platens 3, 4 are bent. When it is larger, the engaging members 15 and 25 that engage with the first mounting plates 12 and 22 without being fixed are disengaged from the first mounting plates 12 and 22. Therefore, even when the platens 3 and 4 are bent as described above, it is possible to suppress the bending from being transmitted to the template via the connecting members 15 and 25. For this reason, it is possible to suppress the bending of the platens 3 and 4 from being transmitted to the mold plates 11 and 21 via the first mounting plates 12 and 22.

  When the molded product is thin like the light guide plate 101, the injection pressure for injecting the resin must be increased, and the mold clamping force must be increased, and the platens 3 and 4 are inevitably increased. Tend to bend more. However, according to the injection molds 1 and 2 of this embodiment, since the bending of the platens 3 and 4 can be suppressed from being transmitted to the mold plates 11 and 21 as described above, the injection pressure of the resin It is possible to effectively suppress the occurrence of burrs when molding a molded product that is difficult to mold unless the strength is increased.

  In addition, the cavity SPC formed by the template 11 and the template 21 has a symmetrical shape with respect to the central axis of the sprue portion 53, and the center press plates 13 and 23 have a symmetrical shape with respect to the central axis of the sprue portion 53. It is said. Therefore, it is possible to balance the injection pressure of the fluid resin in the cavity and the clamping force applied to the mold plates 11 and 21.

  Thus, the injection molds 1 and 2 of the present invention can be molded with high accuracy.

  Further, second mounting plates 14 and 24 having a larger area than the center press plates 13 and 23 are arranged between the center press plates 13 and 23 and the platens 3 and 4. Therefore, it is possible to suppress the traces of the injection molds 1 and 2 from remaining on the platens 3 and 4.

  As mentioned above, although the said embodiment was demonstrated to the example about this invention, this invention is not limited to these.

  For example, in the above embodiment, the center press plate 13 is arranged in the injection mold 1 and the center press plate 23 is arranged in the injection mold 2, but one of the center press plates 13, 23 is missing. Also good. Even in this case, it is possible to suppress the bending of the mold of the injection mold in which the center press plate is arranged.

  The connecting members 15 and 25 are constituted by screws inserted into through holes 12h and 22h formed in the first mounting plates 12 and 22, and the head portions of the screws are hooked on the first mounting plates 12 and 22, The members 15 and 25 are configured to be engaged with the first mounting plates 12 and 22 in a non-fixed manner. However, the configuration of the connecting members 15 and 25 is not limited to screws. For example, it is a member in which one end is fixed to the second mounting plates 14 and 24 in the same manner as the connecting members 15 and 25 and a hook is formed on the other end. The first mounting plates 12, 22 may be urged toward the platens 3, 4 by engaging with the plate 22 in a non-fixed manner. Further, the number of connecting members does not have to coincide with the above embodiment.

  The second mounting plates 14 and 24 are not essential components. When the injection molds 1 and 2 do not have the second mounting plates 14 and 24, the connecting members 15 and 25 may be directly fixed to the platens 3 and 4. In this case, the center press plates 13 and 23 are sandwiched and fixed between the first mounting plates 12 and 22 and the platens 3 and 4. However, from the viewpoint of avoiding applying excessive pressure to the platens 3 and 4, the injection molds 1 and 2 preferably have the second mounting plates 14 and 24 as in the above embodiment.

  Moreover, in the said embodiment, the 1st attachment plates 12 and 22 shall protrude from the whole periphery of the back surfaces 11b and 21b of the template plates 11 and 21. FIG. However, in the present invention, the center press plates 13 and 23 are disposed on the surface of the first mounting plates 12 and 22 opposite to the mold plates 11 and 21, and the connecting members 15 and 25 are the first mounting plates 12 and 22. What is necessary is just to engage the area | region of the outer peripheral side rather than the center press plates 13 and 23. Therefore, at least a part of the first mounting plates 12 and 22 may be located inside the back surfaces of the template plates 11 and 21.

  The first mounting plates 12 and 22 may not be directly fixed on the rear surfaces 11b and 21b of the template plates 11 and 21, but may be fixed to the template plates 11 and 21 via other members.

  Moreover, in the said embodiment, although the elastic body 21e consisted of the spring, if a force is provided in the direction which separates the template main body 21m and the frame part 21c, it will not be restricted to a spring. Moreover, it does not need to be an elastic body, and may be constituted by a hydraulic cylinder or the like that applies a force in a direction separating the template body 21m and the frame portion 21c.

  In the above embodiment, the movable side template 21 is configured to include the template body 21m and the frame portion 21c. However, the template 21 is composed of a single template like the template 11, and the molding die 51 and the like. A concave mold may be formed.

  Moreover, in the said embodiment, the center press plates 13 and 23 were made into the rectangle when planarly viewed. However, the present invention is not limited to this. FIG. 9 is a view showing a modification of the center press plates 13 and 23 in the same manner as in FIG. As shown in FIG. 9, the center press plate may be circular when viewed in plan. Even in this case, it is preferable that the center press plate overlaps with the gate 55 and does not overlap with a part of the mold 51 including the flow end portion 56 of the resin. However, the center press plates 13 and 23 may be configured to overlap the entire mold 51.

  In the above embodiment, the molded product is a light guide plate. However, the present invention is not limited to this. The injection pressure of the gate part is considerably higher than the cavity part, such as a molded part that has a thin wall shape and the pressure loss of the cavity part of the template is large, and a molded part that has a high melt resin viscosity and a high injection pressure. Effective for molded products.

  As described above, according to the present invention, an injection mold that can be molded with high accuracy is provided and can be used in the field of manufacturing an injection molded product.

1, 2 ... Molds for injection molding 3, 4 ... Platen 5 ... Tie bars 11, 21 ... Templates 11b, 21b ... Back side of template 11j, 21j ... Templates Contact surfaces 12, 22 ... first mounting plates 12p, 22p ... projecting portions 13, 23 ... center press plates 14, 24 ... second mounting plates 15, 25 ... connecting member 16, 26 ... Fixing member 51 ... Mold 52 ... Runner part 53 ... Sprue part 55 ... Gate 56 ... Flow end part 61, 62 ... Heat insulation layer 100 ... Molded product 101 ... Light guide plate 102 ... Runner 103 ... Sprue MS ... Molten resin SPC ... Cavity

Claims (6)

An injection mold fixed to a platen of an injection molding apparatus,
A mold plate having a contact surface that is a surface opposite to the platen side and is in contact with another mold, and a back surface with respect to the contact surface;
A first mounting plate fixed to the template on the back side of the template;
A center press plate disposed in a projection region of the outer periphery of the contact surface in a surface opposite to the template side of the first mounting plate;
A connecting member for connecting the platen and the first mounting plate;
With
The connecting member is fixed to the platen so as to be able to move relative to the template, and is non-fixedly engaged with a region on the outer peripheral side of the center press plate in the first mounting plate,
The center press plate is sandwiched between the platen and the first mounting plate by the connecting member urging the first mounting plate toward the platen side. Mold. The first mounting plate has a protruding portion that protrudes from the back surface of the template,
The injection mold according to claim 1, wherein the connecting member is engaged with the protruding portion. The injection mold according to claim 1 or 2, wherein a second mounting plate having a larger area than the center press plate is disposed between the center press plate and the platen. The second mounting plate is fixed to the platen;
The injection mold according to claim 3, wherein the connecting member is fixed to the platen via the second mounting plate. The injection molding according to any one of claims 1 to 4, wherein the center press plate has a rotationally symmetric shape around a central axis of a resin flow path that leads from the platen to the mold plate. Mold. The said center press plate overlaps with the gate position of the shaping | molding die formed in the said contact surface side of the said template, and is made into the shape which does not overlap with a part of said shaping | molding die. The injection mold according to any one of the above.

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