JP5941946B2 - Injection mold and injection molding method - Google Patents

Description

  The present invention relates to an injection mold and an injection molding method in which a cavity is formed between one mold having an insert and the other mold.

  The injection mold consists of a fixed mold (hereinafter referred to as “fixed mold”) fixed to the fixed plate of the injection molding machine and a movable mold (hereinafter referred to as movable) fixed to the movable plate of the injection molding machine. Mold). When the injection molding machine is operated and the fixed mold and the movable mold are closed, a cavity having a shape matching the shape of the molded product is formed between the two molds. When a molding material such as molten resin is injected into the cavity from the injection molding machine and solidified, it becomes a molded product. Of the two molds, the convex mold may be referred to as a cavity and the concave mold may be referred to as a core. However, the cavity in this specification means a space.

  Patent Document 1 shows an injection molding method in which an opening forming body is provided in a cavity of an injection mold and a molded product having an opening is manufactured. When the molding material is injected into the cavity provided with the opening forming body, it is included in the molding material at the weld line where the molding material flowing clockwise around the opening forming body and the molding material flowing counterclockwise merge. There is a problem that the appearance line deteriorates due to the manifestation of the alignment lines in which the fillers are vertically aligned. In the method described in Patent Document 1, the mold is injected into the cavity after the fixed mold is heated to the softening point temperature of the molding material, and before the pressure holding process (before the molding material is completely filled with the cavity). Deterioration of the appearance is suppressed by injecting the molding material toward the orientation line or by orienting it in the horizontal direction.

  Incidentally, it is originally desirable to directly process the shape of the molded product into a fixed mold or a movable mold. However, for reasons such as mold workability, a fixed mold and a movable mold are often nested.

  Patent Document 2 shows an apparatus for improving the transferability of the uneven shape of the inner surface of the cavity to the molded product by increasing the temperature of the cavity, and shortening the molding cycle of the molded product and improving the productivity. ing. In the device described in Patent Document 2, a nest is attached to a fixed mold, a gap is formed between the outer peripheral surface of the nest and the inner peripheral surface of the fixed mold, and a heat insulating material is provided on the bottom surface side of the nest. It is provided, and the insert is made of a member having a higher linear expansion coefficient than other mold members, so that only the vicinity of the cavity can be efficiently controlled in temperature. Further, when the molding is performed, the insert is thermally expanded to close the gap formed around the insert, thereby preventing the occurrence of burrs due to the resin entering the gap.

JP 2013-82230 A JP 2000-238103 A

  In the method described in Patent Document 1, if only the fixed mold is heated when the mold is opened before the mold is closed, only the fixed mold is thermally expanded. Then, when the mold is closed, there is a possibility that a guide pin or the like that prevents the mating surfaces of the fixed mold and the movable mold from shifting will be galled. The method described in Patent Document 1 prevents the guide pin and the like from being galled by setting the heating start timing of the fixed mold immediately before or after the mold is closed. For this reason, the method described in Patent Document 1 has a problem that the molding cycle is extended because the stationary mold cannot be heated to the softening point temperature of the resin when the mold is opened.

  In the device described in Patent Document 2, when the shape of the cavity is complicated, the thickness of the nesting is greatly different for each part. Therefore, the coefficient of thermal expansion is grasped for each part, and the nesting is performed according to the coefficient of thermal expansion. It is necessary to perform heating control. It is extremely difficult to accurately perform such heating control. If the gap formed between the outer peripheral surface of the nesting and the inner peripheral surface of the fixed mold is too large compared to the thermal expansion amount of the nesting, the gap cannot be closed. Will occur. Conversely, if the amount of thermal expansion of the nesting is too large compared to the gap formed between the outer peripheral surface of the nesting and the inner peripheral surface of the stationary mold, stress is generated in the nesting and the stationary mold. In particular, stress tends to concentrate on the design surface of the insert, and cracks are likely to occur.

  The present invention has been made in view of such problems, and shortens the molding cycle, and the molding material flows into the gap formed between the outer peripheral surface of the insert and the inner peripheral surface of the mold. It is an object of the present invention to provide an injection mold and an injection molding method capable of preventing the occurrence of burrs and suppressing the occurrence of stress in the insert.

  An injection mold according to the present invention is an injection mold in which a cavity is formed between one mold having a nesting mechanism having a temperature raising mechanism and the other mold, and the outer periphery of the mold And a driven nest that closes the gap while operating according to thermal expansion of the nest, and a gap formed between the surface and the inner peripheral surface of the one mold.

  In the injection mold according to the present invention, the driven nest may be provided between the inflow path of the molding material communicating with the cavity and the gap.

  In the injection mold according to the present invention, the driven insert may move to a dividing surface of the one mold and the other mold in accordance with the thermal expansion of the insert.

  In the injection mold according to the present invention, the gap may be formed larger than the thermal expansion amount of the insert.

  In the injection mold according to the present invention, the one mold may be a concave mold.

  In the injection mold according to the present invention, the insert may be fixed to the one mold at a center of gravity position of a bottom surface attached to the one mold.

  In the injection mold according to the present invention, the driven insert may be formed of a member having a lower thermal conductivity than the insert or the one mold.

  An injection molding method according to the present invention is an injection molding method in which a molding material is injected into a cavity formed between one mold having a nest attached thereto and the other mold, and heat is applied to the nest. A gap is formed between a heating step and an outer periphery of the insert that thermally expands by the heating step and an inner periphery of the one mold, and the gap is closed while the driven insert is operated according to the thermal expansion of the insert. And a closing process.

  In the injection molding method according to the present invention, in the heating step, the nest may be heated to the melting temperature of the molding material when the mold is opened before the mold is closed.

  According to the injection mold and the injection molding method of the present invention, the driven nest that operates according to the thermal expansion of the nest is provided in the gap formed between the outer peripheral surface of the nest and the inner peripheral surface of one mold. ing. By operating the driven nest according to the thermal expansion of the nest, the occurrence of stress between the nest and one mold is suppressed, and the durability of the mold is improved. Since the driven insert closes the gap between the insert and one mold when the insert is thermally expanded, it is possible to reliably prevent the molding material from flowing into the gap and generating burrs.

  In addition, since a gap is formed between the insert and one mold, heat conduction from the insert to one mold can be suppressed when the temperature of the insert is raised. For this reason, the temperature raising efficiency of the insert is improved and the thermal expansion of one mold can be suppressed. Then, even when only one mold (nesting) is heated when the mold is opened, it is possible to suppress galling on the guide pins and the mold when the mold is closed. Therefore, the insert can be heated in a state where the mold is opened, and the molding cycle can be shortened.

  In addition, even if the nesting is composed of a member having a higher thermal conductivity than that of one mold and the heat transfer efficiency to the molding material is improved, a gap is formed between the nesting and the one mold. Therefore, the thermal expansion of the nesting is not restricted to one mold. For this reason, it can suppress that a stress arises between a nest | insert and one metal mold | die.

  In the injection mold according to the present invention, when the driven nest is provided between the inflow path of the molding material communicating with the cavity and the gap, the molding material flows into the gap when the molding material flows into the cavity. Thus, it is possible to efficiently suppress the formation of burrs.

  In the injection mold according to the present invention, when the driven nest moves to the dividing surface of one mold and the other mold in accordance with the thermal expansion of the nest, the molding material is formed when the molding material flows into the cavity. It is possible to efficiently suppress the material from flowing into the gap and becoming a burr.

  In the injection mold according to the present invention, when the gap is formed larger than the thermal expansion amount of the nest, it is possible to prevent stress from being generated due to contact between the nest and one mold during the thermal expansion of the nest. . For this reason, durability of a nest | insert and one metal mold | die can be improved more. Moreover, heat conduction from the insert to one mold can be suppressed. For this reason, the temperature raising efficiency of the nesting is improved.

  In the injection mold according to the present invention, when one mold is a concave mold, it is possible to leave a molded product in one mold without opening the molded product in one mold when the mold is opened. Then, the temperature rise of one mold can be started before the molded product is taken out from the other mold. For this reason, the molding cycle can be further shortened.

  In the injection mold according to the present invention, when the insert is fixed to one mold at the position of the center of gravity of the bottom surface attached to the one mold, the insert is uniformly expanded in the direction of the outer peripheral surface. Is possible. Therefore, it becomes easy to design the gap and the driven insert formed on the outer peripheral surface of the insert.

  In the injection mold according to the present invention, when the driven insert is formed of a member having a lower thermal conductivity than the insert or one of the molds, the heat of the insert is transferred to the one mold via the driven insert. Heat transfer to can be suppressed.

  In the injection molding method according to the present invention, in the heating process, if the nest is heated to the melting temperature of the molding material when the mold is opened before the mold is closed, the molding material can be injected into the cavity immediately after the mold is closed. The molding cycle can be shortened.

FIG. 1 is a cross-sectional view of an injection mold according to the first embodiment. FIG. 2 is an enlarged cross-sectional view of the driven insert and its peripheral portion. FIG. 3 is a flowchart showing the procedure of the injection molding method according to the first embodiment. FIG. 4 is a time chart showing the temperature transition of the nesting during the injection molding. FIG. 5 is a cross-sectional view of the fixed mold side according to the second embodiment. FIG. 6 is a bottom view of the fixed mold according to the second embodiment. FIG. 7 is a sectional view on the fixed mold side according to the third embodiment.

  Hereinafter, an injection mold and an injection molding method according to the present invention will be described with reference to the drawings.

[First Embodiment]
<Configuration of entire injection mold>
FIG. 1 is a cross-sectional view of an injection mold 2 according to the first embodiment. The injection mold 2 includes, as main components, a fixed mold 4, a nesting 6, and a movable mold 8 that constitute a mold body, a fixed mold 4, and a stationary platen of an injection molding machine (not shown, the same applies hereinafter). Between the movable mold 8 and the movable side mounting plate 12, between the movable mold 8 and the movable side mounting plate 12. A spacer block 16 that forms a space 14 interposed therebetween, an upper plate 18 and a lower plate 20 provided inside the space 14, an ejector pin 22 that is attached to the upper plate 18 and inserted into the movable mold 8, Have A cavity 24 is formed between the insert 6 and the movable mold 8, and a gap 26 is formed between the outer peripheral surface 6 c of the insert 6 and the inner peripheral surface 30 b of the fixed mold 4. The injection mold 2 has a driven insert 28 that closes the gap 26 while operating according to the operation of the insert 6 between the insert 6 and the fixed mold 4. A split surface (referred to as a partition line or a parting line) PL is formed at the joint between the fixed mold 4 and the movable mold 8.

  The fixed mold 4 is a concave mold, and is fixed to a fixed plate of the injection molding machine by a fixed side mounting plate 10. The fixed die 4 has a pocket portion 30 that is pocketed on the partition line PL side, a guide pin bush 32 that opens on the partition line PL side, and a gate 34 and a sprue 36 that communicate with the nozzle of the injection molding machine. . The pocket portion 30 is a portion to which the insert 6 is attached, and supports the insert 6 at the bottom portion 30a. The guide pin bush 32 prevents the displacement of the fixed mold 4 and the movable mold 8 by inserting the guide pin 46 on the movable mold 8 side when the fixed mold 4 and the movable mold 8 are closed. .

  The insert 6 is a component having a recess 6 a that forms a cavity 24. The shape of the concave portion 6a matches the shape of the convex portion of the molded product. Since the insert 6 is formed of a material having high thermal conductivity such as a copper alloy, the entire insert 6 can be heated or lowered in a short time. The bottom 6 b side of the insert 6 is detachably attached to the bottom 30 a of the pocket portion 30 of the fixed mold 4. Inside the nest 6 are formed a plurality of cooling channels 38 for circulating a cooling fluid, and a plurality of heating channels 40 for circulating a heating fluid.

  The cooling flow path 38 is connected to a cooling device (not shown) that circulates a cooling fluid (here, cooling oil), and forms a part of the temperature lowering mechanism. When the nest 6 is cooled, the cooling oil circulates between the cooling device and the cooling flow path 38. Similarly, the heating channel 40 is connected to a heating device (not shown) that circulates a heating fluid (heating oil in this case), and forms a part of the temperature raising mechanism. During the heating of the insert 6, the heating oil circulates between the heating device and the heating flow path 40. In addition, although the cooling flow path 38 and the heating flow path 40 are each arrange | positioned in the separate position inside the nesting 6, it is also possible to use the same flow path in common.

  When the insert 6 is attached to the bottom 30 a of the pocket portion 30 of the fixed mold 4, a gap 26 is formed between the outer peripheral surface 6 c of the insert 6 and the inner peripheral surface 30 b of the pocket portion 30 of the fixed mold 4. . The volume of the gap 26 when the nesting 6 is not thermally expanded is larger than the thermal expansion amount of the nesting 6 (the volume of the increase of the nesting 6 due to thermal expansion). In other words, the volume of the pocket portion 30 formed in the fixed mold 4 is formed larger than the volume of the insert 6 thermally expanded at the melting temperature of the molding material. For this reason, the gap 26 is maintained even if the insert 6 is thermally expanded. The gap 26 functions as a heat insulating layer.

  The movable mold 8 is a convex mold and is fixed to the movable platen of the injection molding machine by a movable side mounting plate 12. The movable mold 8 has a convex portion 8 a that forms a cavity 24. The shape of the convex portion 8a matches the shape of the concave portion of the molded product. Moreover, the movable mold 8 has a guide pin 46 on the partition line PL side. The guide pin 46 is inserted into the guide pin bush 32 on the fixed mold 4 side when the mold is closed, thereby preventing the positional deviation between the fixed mold 4 and the movable mold 8. Further, the movable mold 8 has a groove-like runner 42 on the surface of the partition line PL of the movable mold 8 and facing the portion from the sprue 36 of the fixed mold 4 to the recess 6 a of the insert 6. .

  The lower plate 20 is attached to the movable side attachment plate 12. The upper plate 18 is movably supported by the lower plate 20, and moves to the movable mold 8 side according to the operation of a drive mechanism (not shown). The ejector pin 22 is inserted into the movable mold 8 and has an end attached to the upper plate 18. As the upper plate 18 moves to the movable mold 8 side, the ejector pin 22 protrudes from the convex portion 8a of the movable mold 8 and pushes out the molded product.

  When the fixed mold 4 and the movable mold 8 are closed, a cavity 24 is formed between the concave portion 6 a of the insert 6 and the convex portion 8 a of the movable mold 8. In addition, an inflow path of a molding material including a gate 34, a sprue 36, and a runner 42 is formed between a nozzle of an injection molding machine (not shown) and the cavity 24.

<Configuration and operation of driven nesting>
One of the features of the first embodiment is that the injection mold 2 is formed between the outer peripheral surface 6 c of the insert 6 and the inner peripheral surface 30 b of one mold, that is, the pocket portion 30 of the fixed mold 4. And a driven nest 28 that closes the gap 26 while operating according to the thermal expansion of the nest 6. A description related to the driven nest 28 will be given with reference to FIG. FIG. 2 is an enlarged cross-sectional view of the driven nest 28 and its peripheral portion.

  Of the outer peripheral surface 6c of the insert 6, an inclined surface 6d is formed on the partition line PL side. In addition, an inclined surface 30c is formed on the partition line PL side of the inner peripheral surface 30b of the pocket portion 30 of the fixed mold 4. Further, a step portion 30 d is formed on the inner peripheral surface 30 b of the pocket portion 30 of the fixed mold 4.

  The driven nest 28 is a tapered part and is made of a material having low thermal conductivity such as stainless steel. Furthermore, the thermal conductivity of the driven insert 28 is lower than that of the insert 6 or the fixed mold 4. One tapered surface 28 a of the driven nest 28 is slidably in contact with the inclined surface 6 d of the nest 6. The other tapered surface 28 b of the driven insert 28 is slidably in contact with the inclined surface 30 c of the fixed mold 4. Further, the tapered end portion 28 c of the driven insert 28 is connected to the step portion 30 d of the fixed mold 4 via a spring 44. The end 28d of the follower insert 28 on the thick side faces the runner 42 of the movable mold 8. With such a configuration, the driven nest 28 is interposed between the gap 26 and the runner 42 and closes the gap 26 with respect to the runner 42.

  When the insert 6 is heated and thermally expanded, the driven insert 28 operates as follows. With the thermal expansion of the insert 6, the inclined surface 6 d of the insert 6 operates in the direction toward the inclined surface 30 c of the fixed mold 4. Then, the tapered surface 28 a of the driven insert 28 is pressed by the inclined surface 6 d of the insert 6. This pressing force can be decomposed into a force A acting on the runner 42 side and a force B acting on the inclined surface 30 c side of the fixed mold 4. The driven nest 28 moves to the runner 42 side while extending the spring 44 by the force A acting on the runner 42 side. At this time, the driven nest 28 slides the tapered surface 28 a with respect to the inclined surface 6 d of the insert 6 and also slides the tapered surface 28 b with respect to the inclined surface 30 c of the fixed mold 4, To work. Thus, even if the insert 6 is thermally expanded, the driven insert 28 is always interposed between the gap 26 and the runner 42 and closes the gap 26 with respect to the runner 42.

  On the other hand, when the insert 6 is cooled and contracts, the driven insert 28 operates as follows. As the nesting 6 contracts, the inclined surface 6 d of the nesting 6 operates in the direction opposite to the inclined surface 30 c side of the fixed mold 4. Then, the driven nest 28 moves to the spring 44 side by the restoring force of the spring 44. At this time, the driven insert 28 slides the tapered surface 28a with respect to the inclined surface 6d of the insert 6 and also slides the tapered surface 28b with respect to the inclined surface 30c of the fixed mold 4 while moving on the spring 44 side. To work. As described above, the driven nest 28 is always interposed between the gap 26 and the runner 42 even when the nest 6 is contracted, and closes the gap 26 with respect to the runner 42.

  The taper angles of the tapered surfaces 28a and 28b of the driven insert 28 and the inclination angles of the inclined surface 6d of the insert 6 and the inclined surface 30c of the fixed mold 4 can be arbitrarily set. However, if each angle and the position of the driven nest 28 are designed so that the end 28d of the driven nest 28 coincides with the partition line PL when the nest 6 is thermally expanded, there is an advantage that the molding material is not wasted. Since it is obtained, it is preferable. Specifically, the amount of thermal expansion of the insert 6 at the melting temperature of the molding material may be calculated, and the amount by which the inclined surface 6d of the insert 6 operates toward the inclined surface 30c of the fixed mold 4 may be calculated. If the movement amount of the inclined surface 6d of the nesting 6 is known, the movement amount of the driven nesting 28 for each taper angle can be calculated. Therefore, by adjusting the position and taper angle of the driven nest 28 to the optimum values, the end 28d of the driven nest 28 can coincide with the partition line PL when the nest 6 is thermally expanded.

<Injection molding method>
Next, the procedure of the injection molding method using the injection mold 2 will be described using the flowchart of FIG. 3 and with reference to FIGS. FIG. 3 is a flowchart showing the procedure of the injection molding method according to the first embodiment. FIG. 4 is a time chart showing the temperature transition of the insert 6 during injection molding.

  First, heating oil at a predetermined temperature T2 (≧ melting temperature of molding material) is supplied to the heating flow path 40 of the insert 6 to heat the insert 6 (step S1). For example, when the molding material is polypropylene, the temperature of the heating oil is about 220 ° C. In FIG. 4, the time point when the insert 6 starts to be heated is indicated as t0. The temperature T of the nesting 6 at the time point t0 is T1. When the heat of the heating oil is conducted to the insert 6, the temperature of the insert 6 starts to rise.

  When the supply of the heating oil to the heating flow path 40 is continued, the temperature T of the nest 6 is increased and the nest 6 is thermally expanded as after time t0 in FIG. When the insert 6 is thermally expanded, the inclined surface 6d of the insert 6 presses the tapered surface 28a of the driven insert 28 as shown in FIG. Then, the driven nest 28 slides one taper surface 28a to the inclined surface 6d of the nest 6 and slides the other taper surface 28b to the inclined surface 30c of the fixed mold 4 while moving it toward the runner 42 side. Operates (step S2).

  Assuming that the nest 6 continues to thermally expand until the temperature T of the nest 6 reaches the predetermined temperature T2 of the heated oil, the driven nest 28 is runner 42 until the temperature T of the nest 6 reaches the predetermined temperature T2 of the heated oil. (Step S3: NO). The driven insert 28 always contacts the inclined surface 6d of the insert 6 and the inclined surface 30c of the fixed mold 4 during the operation toward the runner 42 to close the gap 26.

  As shown in FIG. 4, when the temperature T of the nesting 6 reaches the vicinity of the predetermined temperature T2 of the heating oil at time t1, the temperature increase of the nesting 6 is stopped. At this time, the end 28d of the driven insert 28 and the partition line PL are located on the same plane. Even after the thermal expansion of the insert 6, the gap 26 is maintained between the outer peripheral surface 6 c of the insert 6 and the inner peripheral surface 30 b of the pocket portion 30 of the fixed mold 4.

  When the temperature T of the insert 6 reaches the predetermined temperature T2 (step S3: YES), the stationary mold 4 and the movable mold 8 are closed (step S4). The mold closing timing may be, for example, when the temperature T of the nesting 6 is detected by a temperature sensor or the like and the detected value becomes close to the predetermined temperature T2 of the heating oil, or the nesting 6 as shown in FIG. If the temperature transition is known, it may be when a predetermined time has elapsed since the supply of the heating oil was started.

  After mold closing in step S4, the molten molding material is injected from the nozzle of the injection molding machine into the cavity 24 through the gate 34, the sprue 36, and the runner 42 (step S5).

  After the molding material is injected and filled in the cavity 24 in step S5, the molding material in the cavity 24 is pressurized and compressed to control the orientation of the molding material (step S6).

  Almost simultaneously with step S6, the supply of the heating oil to the heating flow path 40 of the insert 6 is stopped, and then the cooling oil of a predetermined temperature T1 or less is supplied to the cooling flow path 38 of the insert 6 to cool the insert 6. (Step S7). In FIG. 4, the time when the supply of the cooling oil is started is shown as t2. The temperature T of the nesting 6 at the time point t2 is T2. When the temperature of the cooling oil conducts heat to the insert 6, the temperature T of the insert 6 starts to drop.

  When the supply of the cooling oil to the cooling flow path 38 is continued, the temperature T of the nesting 6 is lowered and the nesting 6 is contracted, as shown after time t2 in FIG. When the insert 6 is contracted, the inclined surface 6d of the insert 6 moves in a direction away from the inclined surface 30c of the fixed mold 4. Then, the driven nest 28 slides one of the tapered surfaces 28 a on the inclined surface 6 d of the nested 6, and the other tapered surface 28 b slides on the inclined surface 30 c of the fixed mold 4 while restoring the spring 44. It moves to the spring 44 side by the force (step S8).

  Assuming that the nesting 6 continues to contract until the temperature T of the nesting 6 reaches the predetermined temperature T1, the driven nesting 28 continues to operate toward the spring 44 until the temperature T of the nesting 6 reaches the predetermined temperature T1 (step S40). S9: NO). The driven insert 28 always contacts the inclined surface 6d of the insert 6 and the inclined surface 30c of the fixed mold 4 to close the gap 26 during the operation toward the spring 44 side.

  As shown in FIG. 4, when the temperature T of the insert 6 reaches the vicinity of the predetermined temperature T1 at time t3, the supply of the cooling oil to the cooling flow path 38 of the insert 6 is stopped. At this time, the molding material is solidified.

  When the temperature T of the insert 6 reaches the predetermined temperature T1 (step S9: YES), the stationary mold 4 and the movable mold 8 are opened (step S10). Similar to the mold closing timing, the mold opening timing may be, for example, when the temperature T of the nesting 6 is detected by a temperature sensor or the like and the detected value becomes close to the predetermined temperature T1, as shown in FIG. If such a temperature transition of the insert 6 is known, a predetermined time may have elapsed since the supply of the cooling oil was started.

  When the upper plate 18 shown in FIG. 1 is moved to the movable mold 8 side after the mold opening in step S10, the ejector pins 22 protrude from the convex portions 8a of the movable mold 8 and push out the solidified molded product. In this way, the molded product is taken out from the convex portion 8a of the movable mold 8 (step S11).

  When the molding process is to be continued (step S12: NO), in order to manufacture the next molded product, the process returns to step S1 almost simultaneously with step S11, and the predetermined temperature T2 (≧ the molding material of the molding material) is placed in the heating flow path 40 of the insert 6. Start supplying heated oil at the melting temperature. And the process after step S1 is repeated.

  If the molding process is to be terminated (step S12: YES), the process is terminated after the molded product is taken out in step S11.

<Effects on Configuration of First Embodiment>
In the first embodiment, the volume of the gap 26 when the nesting 6 is not thermally expanded is larger than the thermal expansion amount of the nesting 6 (the volume of the increase of the nesting 6 due to thermal expansion). For this reason, even if the insert 6 is thermally expanded, the gap 26 is maintained. That is, even if the insert 6 is thermally expanded, the outer peripheral surface 6 c of the insert 6 and the inner peripheral surface 30 b of the pocket portion 30 of the fixed mold 4 are not in contact with each other, and no stress is generated on the insert 6. Therefore, the insert 6 is not cracked due to stress.

  In the first embodiment, since the gap 26 functions as a heat insulating layer, heat conduction from the insert 6 to the fixed mold 4 is suppressed. That is, the heat of the insert 6 is not taken away by the fixed mold 4. For this reason, the temperature of the insert 6 can be quickly raised, and the molding cycle can be shortened.

  In the first embodiment, since the gap 26 functions as a heat insulating layer, heat conduction from the insert 6 to the fixed mold 4 is suppressed. That is, the fixed mold 4 does not take heat of the insert 6 and does not thermally expand. For this reason, even if the mold is closed after raising the temperature of the insert 6 while the mold is open, no galling occurs between the guide pin bush 32 of the fixed mold 4 and the guide pin 46 of the movable mold 8. Therefore, it is possible to raise the temperature of the insert 6 while the mold is open. If the mold is closed and the temperature of the insert 6 is raised as in the prior art, the temperature of the insert 6 is taken away by the movable mold 8. On the other hand, as in the first embodiment, when the mold 6 is opened to raise the temperature of the insert 6, the temperature of the insert 6 is not lost to the movable mold 8. Also in this respect, the temperature of the insert 6 can be quickly raised, and the molding cycle can be shortened.

  In the first embodiment, the driven nest 28 is disposed between the runner 42 and the gap 26 and always closes the gap 26. For this reason, when filling the cavity 24 with the molding material, the molding material does not flow into the gap 26 from the runner 42. Accordingly, it is possible to prevent the molding material from flowing into the gap 26 and becoming a burr.

  In the first embodiment, the end portion 28d of the driven nest 28 moves to a position that coincides with the partition line PL when the nest 6 is thermally expanded. For this reason, generation | occurrence | production of an excess burr | flash can be prevented.

  In the first embodiment, the driven nest 28 is made of a material having a lower thermal conductivity than the nest 6 or the fixed mold 4. For this reason, it is suppressed that the heat of the insert 6 is conducted to the fixed mold 4 through the driven insert 28.

  In the first embodiment, the insert 6 is made of a material having high thermal conductivity. For this reason, the temperature of the insert 6 can be raised rapidly, and the cycle of injection molding can be shortened.

[Second Embodiment]
FIG. 5 is a cross-sectional view of the fixed mold 52 according to the second embodiment. FIG. 6 is a bottom view of the fixed mold 52 according to the second embodiment. As shown in FIGS. 5 and 6, the insert 54 has a knock pin 64 and a plurality of positioning blocks 66 on the bottom surface 54 b. The knock pin 64 is formed at the center of gravity position on the bottom surface 54 b of the insert 54. Each positioning block 66 is arranged such that the radial direction about the knock pin 64 is the longitudinal direction. The fixed mold 52 has a pin hole 60 and a plurality of guide holes 62 penetrating from the bottom portion 56 a of the pocket portion 56 to the bottom surface 58 at positions facing the knock pins 64 and the plurality of positioning blocks 66 of the insert 54.

  As shown in FIG. 6, the width W <b> 1 of the guide hole 62 of the fixed mold 52 is substantially the same as the width W <b> 2 of the positioning block 66 of the insert 54. On the other hand, the length L1 of the guide hole 62 of the fixed mold 52 is longer than the length L2 of the positioning block 66 of the insert 54, and a gap is formed at both longitudinal ends of the guide hole 62 and the positioning block 66. .

  The knock pin 64 of the insert 54 is inserted into the pin hole 60 of the fixed mold 52, and the plurality of positioning blocks 66 of the insert 54 are inserted into the plurality of guide holes 62 of the fixed mold 52, respectively. It is fixed to the fixed mold 52.

  With such a structure, when the insert 54 is heated, the insert 54 thermally expands around the knock pin 64 as a base point. At this time, the positioning block 66 is guided by the guide hole 62 so as to operate in the radial direction around the knock pin 64. Accordingly, the direction of thermal expansion of the insert 54 is restricted to the longitudinal direction of each guide hole 62.

  In the second embodiment, the insert 54 is fixed to one mold, that is, the fixed mold 52 at the position of the center of gravity of the bottom surface 54 b attached to one mold, that is, the fixed mold 52. For this reason, it becomes possible to inflate the nest 54 evenly around. Therefore, it becomes easy to design the fixed mold 52, the insert 54, and the driven insert 28.

  The guide hole 62 regulates the expansion direction of the insert 54. For this reason, it becomes easier to design the fixed mold 52, the insert 54, and the driven insert 28.

[Third Embodiment]
FIG. 7 is a cross-sectional view of the fixed mold 4 according to the third embodiment. The third embodiment is different from the first embodiment in that a heat insulating plate 72 is provided between the fixed mold 4 and the insert 6 of the injection mold 2.

  By providing the heat insulating plate 72 between the fixed mold 4 and the insert 6, heat conduction from the bottom surface 6 b of the insert 6 to the fixed mold 4 is suppressed. For this reason, it is possible to further shorten the molding cycle as compared with the first embodiment.

  Further, the height of the insert 6 can be adjusted by adjusting the thickness of the heat insulating plate 72.

[Modification of each embodiment]
In the first embodiment, the driven nest 28 has the tapered surfaces 28a and 28b. However, the driven nest 28 may have only one of the tapered surfaces (referred to as an inclined surface in this case).

  Further, in the first embodiment, the nesting 6 and the driven nesting 28 are provided in the fixed mold 4 which is a concave shape, but the application of the present invention is not limited to unevenness and fixed / movable. The present invention can be applied to a mold having a nested structure.

  Moreover, it is also possible to combine each embodiment.

2 ... Injection mold 4, 52 ... Fixed mold 6, 54 ... Nest 6c ... Outer peripheral surface 6d ... Inclined surface 8 ... Movable mold 24 ... Cavity 26 ... Gap 28 ... Driven insert 28a, 28b ... Tapered surfaces 28c, 28d ... End 30 ... Pocket 30b ... Inner peripheral surface 30c ... Inclined surface 40 ... Heating channel 42 ... Runner 44 ... Spring

Claims (8)

An injection mold in which a cavity is formed between one mold attached with a nest having a temperature raising mechanism and the other mold,
A gap formed between the outer peripheral surface of the insert and the inner peripheral surface of the one mold,
An injection mold comprising: a driven nest that closes the gap while operating according to thermal expansion of the nest. The injection mold according to claim 1,
The injection mold according to claim 1, wherein the driven nest is provided between an inflow passage of a molding material communicating with the cavity and the gap. In the injection mold according to claim 1 or 2,
An injection mold according to claim 1, wherein the driven insert moves to a dividing surface of the one mold and the other mold in accordance with thermal expansion of the insert. In the injection mold according to any one of claims 1 to 3,
The injection mold, wherein the gap is formed larger than the thermal expansion amount of the insert. In the injection mold according to any one of claims 1 to 4,
The one mold is a concave mold, wherein the mold is an injection mold. In the injection mold according to any one of claims 1 to 5 ,
The injection mold, wherein the driven nest is formed of a member having a lower thermal conductivity than the nest or the one mold. An injection molding method for injecting a molding material into a cavity formed between one mold having a nest and the other mold,
A heating step of applying heat to the nest;
A closing step of closing the gap while operating a driven insert according to the thermal expansion of the insert while forming a gap between the outer periphery of the insert and the inner periphery of the one mold that thermally expands by the heating step; An injection molding method comprising the steps of: The injection molding method according to claim 7 ,
An injection molding method characterized in that, in the heating step, the insert is heated to a melting temperature of the molding material when the mold is opened before the mold is closed.

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