JP2010099964A - Molding die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding die eliminating defects arising on the surface of a molded product by uniformly cooling a gate provided in the die. <P>SOLUTION: The molding die includes: a fixed die 30 to which an injection machine 40 for supplying molten resin for resin-molding is connected; a movable die 20 coming closer to the fixed die 30 to form a cavity C to be filled with the molten resin; the gate 51 provided in the fixed die 30 to supply the molten resin to the cavity; and a cooling part 23 provided in a position, facing the gate 51, in the movable die 20 to cool the molten resin filled in the gate 51. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a molding die used for manufacturing an interior part of a vehicle.

  Interior parts such as door panels are installed in the interior of the passenger compartment used by vehicle occupants. Many of these interior parts are manufactured by injection molding in which a molten resin is injected and filled into a cavity of a mold processed into a product shape to form a desired shape.

  The interior parts for a vehicle are intended to give a feeling of comfort to the person who uses the vehicle, and therefore the aesthetics of the outer shape are important. In general, in injection molding, the surface of a molded product may be uneven depending on the structure of the mold used and the nature of the plastic resin, which is a factor in producing a molded product having a poor appearance. .

  Patent Document 1 describes a means for cooling resin accumulated in a gate in a side gate mold having a gate for injecting molten resin on the side surface of a cavity. Patent Document 2 describes a cooling structure in an injection mold using a baffle pipe in which the inside of a cylindrical cooling pipe is separated by a baffle plate and a cooling medium introduction path and a discharge path are provided. Yes.

  In the prior art described in Patent Document 1, a cooling passage through which a cooling medium circulates is provided inside a cooling bush that constitutes a side surface of the side gate, and the molten resin filled in the gate can be directly cooled. Although it is possible, there is a difficulty that the structure of the mold becomes complicated.

  In the prior art described in Patent Document 2, it is easily provided without complicating the structure of the mold, and can be arranged in a narrow space. However, it was necessary to add a new cooling pipe.

Japanese Utility Model Publication No. 5-95722 JP 2003-71898 A

  Problems to be solved by the present invention will be described below with reference to the drawings.

  FIG. 7 schematically shows a cross-section of the molding die, and shows a state in which molten resin is filled in the cavity C of the die that has been clamped. The movable mold 20 that moves up and down by the hydraulic cylinder 21 and the fixed mold 30 to which the injection machine 40 is connected are guided and clamped by the guide pins 29. The movable mold 20 is provided with a cooling water passage 22 that circulates cooling water to cool the mold. On the other hand, the fixed-side mold 30 is provided with a runner 50 that is connected to the nozzle of the injection machine 40 and guides the molten resin into the mold, and a gate 51 that supplies the molten resin to the cavity C.

  A cavity C, which is a space corresponding to the shape of the product, is formed between the movable mold 20 and the fixed mold 30 that are clamped. The molten resin 12 supplied to the cavity C from the injector 40 through the runner 50 and the gate 51 is molded by filling the space of the cavity C, and becomes a molded product having a desired shape.

  Furthermore, in the foam molding according to the present invention, which will be described later, after the molten resin 12 supplied from the gate 51 is filled into the cavity C, the movable side mold 20 is raised and the interval between the cavities C is widened. A foaming agent is added to the molten resin 12, and the resin expands by foaming of the foaming agent by an amount corresponding to the expansion of the cavity C, and a molded product having a desired shape is obtained.

FIG. 8A schematically shows how molten resin is supplied from the gate 51 and spreads into the cavity C. FIG. In the injection molding, when the width W of the gate 51 is increased, the supply amount per unit time is increased, and high speed molding in which the cavity C is filled in a short time becomes possible. As a result, the cycle time of the molding process can be shortened, the cooling time after filling can be made uniform, and distortion remaining in the product can be reduced to prevent deformation of the product.

  However, when the width W of the gate 51 is increased, the volume of the gate itself increases, the degree of shrinkage during cooling increases, and there is a problem that a so-called shrinkage defect occurs on the product surface. In the foam molding, the molten resin foams and expands during the cooling process, so that the gate width W can be set wider than in the case of normal resin molding. However, since the volume of the gate 51 becomes large, it takes time for cooling, and there is a problem that the foaming of the resin continues and the surface 55 is raised as shown in FIG. 8B.

  In view of the above problems, an object of the present invention is to realize a molding die capable of uniformly cooling a gate and eliminating defects generated on the surface of a molded product.

  In order to solve the above-described problems, a molding die according to the present invention is melted by being clamped to a fixed side die connected to an injection machine that supplies molten resin for resin molding, and the fixed side die. A movable mold that forms a cavity filled with resin, a fixed mold, a gate that supplies molten resin to the cavity, and a gate facing the gate in the movable mold. And a cooling unit that cools the molten resin filled therein.

  According to the present invention, in a state where the movable side mold and the fixed side mold are clamped, the cooling unit through which the cooling medium flows cools the molten resin filled in the gate. Since the cooling unit is provided at a position facing the gate, the entire opening of the gate can be uniformly cooled. Thereby, solidification of the resin can proceed without unevenness from the surface of the molten resin in contact with the movable mold to the inside of the gate, and unevenness on the surface can be prevented.

  Further, in the molding die according to the present invention, the cooling part is a cooling hole having a partition that separates a cooling medium introduction path and a discharge path for cooling the molten resin filled in the gate. And Thereby, since a cooling medium circulates to the front-end | tip of the hole of a cooling part, high cooling efficiency can be obtained.

  Furthermore, in the molding die according to the present invention, the cooling section is inserted into a cooling water passage provided in the movable die, and constitutes a part of the passage of the cooling medium. Thereby, it is not necessary to provide a new passage for the cooling medium for the cooling section, and the structure of the mold is not complicated.

  According to the molding die according to the present invention, the gate can be uniformly cooled, and defects generated on the surface of the molded product can be eliminated.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the drawings. First, the configuration of the cooling part of the molding die according to the present invention will be described. Next, foam molding using the molding die according to the present invention will be described.

  FIG. 1 is a diagram schematically showing a cross section of a molding die according to the present invention. The movable mold 20 is installed so that it can be moved up and down by a hydraulic cylinder 21. A cooling medium passage 22 is provided inside the movable mold. A cooling unit 23 is provided in the middle of the passage 22. A partition wall 24 is provided inside the cooling unit 23, and the inside is divided into two to form a cooling medium introduction path and a discharge path, and constitutes a part of the cooling medium path 22. As shown by the arrows in the figure, in this embodiment, the cooling medium is cooling water supplied from the outside.

  On the other hand, a runner 50 and a gate 51 connected to the runner 50 are provided inside the fixed mold 30. The nozzle of the injection machine 40 is connected to the runner 50, and the resin melted inside the injection machine 40 is supplied from the gate 51 to the cavity C through the runner 50.

  By inserting a guide pin 29 provided on the movable side mold 20 into the guide hole 28 of the fixed side mold 30, the movable side mold 20 and the fixed side mold 30 are positioned relative to each other. The movable mold 20 is lowered by the cylinder 21 and the mold is clamped. In a state where the movable side mold 20 and the fixed side mold 30 are clamped, the tip of the cooling unit 23 provided in the movable side mold 20 faces the gate 51 provided in the fixed side mold 30. And is located in the vicinity of the gate 51.

  FIG. 2 is a cross-sectional view schematically showing an enlarged portion of the cooling unit 23 provided in the movable-side mold 20. The cooling unit 23 is formed by drilling a hole communicating with the cooling medium passage 22 from the mounting surface side of the movable mold 20. Further, the hole formed by the drill is sealed by a cap 24a in which a partition wall 24 is coupled. The inside of the cooling unit 23 is separated by a partition wall 24 to form a cooling medium introduction path 23a and a discharge path 23b.

  In this embodiment, the cooling part 23 is formed by a method in which a cooling hole is directly drilled in the movable mold 20. However, as a structure in which the part indicated by the broken line H in FIG. Also good. Next, foam molding using the molding die according to the present invention will be described.

  FIG. 3 is a press chart showing the press stroke of the movable mold 20 that moves up and down by the hydraulic cylinder 21 with respect to the time axis. The state in which the movable mold 20 shown in FIG. 2 is in the upper position is an initial state in which the mold A in the figure is opened. First, the movable mold 20 is lowered from the upper position in the initial state A to the bottom dead center B by the hydraulic cylinder 21. At this time, the clearance between the movable mold 20 and the fixed mold 30, that is, the distance between the cavities C is the narrowest state of 0 to 5 mm.

  When the movable mold 20 is positioned at the bottom dead center B, injection of molten resin is started from the injection machine 40 and supplied from the gate 51 to the cavity C. The supplied resin is obtained by adding a general-purpose foaming agent such as azodicarbonamide to polypropylene (PP) resin. The molten resin is supplied to the cavity C at a time between point B and point D.

  Next, the hydraulic cylinder 21 raises the movable mold 20 to the point E in the figure, and increases the volume of the cavity C. At this time, the foaming agent added to the molten resin foams and bubbles generated in the resin expand the volume of the molten resin filled by the increase in the volume of the cavity C, and a molded product having a desired shape is obtained. Formed. Further, during the time from point E to point F, the molten resin filled in the cavity C is cooled, and the shape of the molded product is fixed.

  Next, the hydraulic cylinder 21 raises the movable mold 20 to the upper position G, opens the mold, takes out the molded product to the outside, and completes one molding cycle. In order to efficiently produce a molded product by injection molding, it is important to shorten this cycle, and it is required to shorten the injection times B to D and the foaming and cooling times E to F of the molten resin. It is done.

  FIG. 4 is a schematic diagram illustrating a state in which the molten resin 12 is supplied from the gate 51 into the cavity C in the state of B to D in which the movable side mold 20 and the fixed side mold 30 are clamped. In order to shorten the filling time B to D of the cavity C with the molten resin 12, as described above, the width W of the gate 51 (see FIG. 8A) is set wide, and the melting per unit time is performed. What is necessary is just to increase the injection quantity of resin. Further, by filling the cavity C in a short time by increasing the injection amount of the molten resin, it is possible to eliminate filling unevenness and eliminate defects due to insufficient filling.

  The molten resin 12 supplied into the cavity C from the gate 51 is deprived of heat by being brought into contact with the surfaces of the movable mold 20 and the fixed mold 30 and is cured. As a result, a cured skin layer is formed on the surface of the filled molten resin 12, and when a foaming reaction occurs later, the resin can be uniformly foamed to eliminate uneven foaming. For this reason, it is necessary to keep the temperature of the movable mold 20 and the fixed mold 30 below a predetermined temperature, and cooling water is constantly circulated in the cooling medium passage 22 of the movable mold 20. . The stationary mold 30 also has a cooling medium passage (not shown) through which cooling water circulates.

  When the width W of the gate 51 is increased to increase the injection amount of the molten resin, the volume of the gate 51 itself increases, and as described above, it takes time to cool the molten resin filled in the gate 51. There is a problem. Thereby, in the case of normal solid molding without adding a foaming agent, a defect called shrinkage occurs. In the case of foam molding according to the present invention, the resin expands due to the foaming reaction in the molding process, so the upper limit of the gate width that does not cause the shrinkage is widened, and the filling times B to D of the molten resin 12 are shortened. Is advantageous. However, since the cooling time of the molten resin filled in the gate 51 becomes longer, a foaming problem occurs after the reaction of the foaming agent continues, and the surface portion of the product corresponding to the gate may swell. (See FIG. 8 (b))

  FIG. 5 is a schematic diagram showing a state where the molten resin 12 filled in the cavity C is expanded by the foaming reaction of the foaming agent in the state of E to F where the movable mold 20 is raised to the point E. It is. It is preferable to take out the molded product after the molten resin 12 is sufficiently cooled and the foaming reaction is stopped within the period of E to F shown in FIG. 3. In order to improve the production efficiency, the period of E to F is used. To shorten the cycle time.

  In the molding die according to the present invention, a cooling part 23 is provided in the middle of the passage 22 of the cooling medium. The cooling unit 23 constitutes a part of the circulation path of the cooling medium, and the tip portion thereof is disposed in the vicinity of the gate 51 at a position facing the gate 51 in a clamped state. Accordingly, in the molten resin injection process (B to D) shown in FIG. 4 and the foaming and cooling processes (E to F) shown in FIG. It receives a strong cooling locally compared to other parts.

  In particular, in the foaming and cooling processes (E to F) after the supply of new molten resin is stopped, the molten resin of the portion corresponding to the gate 51 is from the surface on the side in contact with the surface of the movable mold 20. As the curing progresses, the skin layer becomes thicker toward the inside. Due to the local cooling effect of the cooling part 23, the curing speed is faster than the other parts in the cavity C, and the cured skin layer becomes thicker. Further, since the cooling unit 23 is disposed at a position facing the gate 51, the opening surface of the gate 51 can be uniformly cooled and covered with a skin layer.

  As a result, even when the molten resin filled in the gate 51 is not sufficiently cooled and the foaming reaction of the foaming agent remains, the surface portion corresponding to the gate 51 is less likely to bulge. be able to. That is, the foaming and cooling processes (E to F) can be shortened, and the production efficiency can be improved.

  FIG. 6 is a schematic view showing another embodiment of the present invention. The partial cross section of the cooling part 23, the gate 51, and the runner 52 in the state by which the movable mold 20 and the fixed mold 30 were clamped is shown. The runner 52 that communicates with the gate 51 provided in the fixed mold 30 is a hot runner around which the tape heater 53 is wound. By heating with the tape heater 53, the resin supplied from the injection machine 40 is kept in a molten state and supplied from the gate 51 into the cavity C. Resin is supplied to and shut off from the gate 51 by the vertical movement of the valve pin 54.

  In the molding die of the present embodiment, a nest 54 having a gate 51 made of a material having low heat conduction is used so that the heat of the hot runner 52 is not transmitted to the cavity C. As a material of the nesting 54, for example, chrome stainless steel is used.

  However, even if the insert 52 made of a material with low heat conduction is used, the heat from the hot runner 52 cannot be completely cut off. By inserting the cooling unit 23 according to the present invention into the passage of the cooling medium and disposing the cooling unit 23 at a position facing the gate 51, local cooling is possible. As a result, the gate cooling problem caused by the hot runner 52 can be solved without providing a new cooling medium passage, and the above-described defects such as shrinkage and bulging that occur on the surface of the molded product can be prevented. Thus, the width of the gate can be increased, and the manufacturing efficiency can be improved.

  Although the preferred embodiments of the present invention have been described in detail above, the molding die according to the present invention is not limited to the above-described embodiments, and is within the scope of the gist of the present invention described in the claims. Various modifications and changes are possible.

It is the schematic diagram which showed the cross section of the shaping die based on this invention. It is the schematic diagram which showed the cross section of the cooling part of the shaping die concerning this invention. It is a press chart figure of the shaping die concerning the present invention. It is the schematic diagram which showed the embodiment of the foam molding which concerns on this invention. It is the schematic diagram which showed the embodiment of the foam molding which concerns on this invention. It is the schematic diagram which showed the cross section of the cooling part of the shaping die concerning this invention. It is the schematic diagram which showed the cross section of the normal molding die. It is explanatory drawing which showed the gate of the normal molding die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Molding die 20 Movable side die 22 Coolant passage 23 Cooling part 24 Partition 30 Fixed side die 51 Gate C Cavity

Claims (3)

A fixed mold to which an injection machine for supplying molten resin for resin molding is connected;
A movable mold that is clamped to the fixed mold and forms a cavity filled with the molten resin;
A gate provided in the fixed mold, and supplying the molten resin to the cavity;
A cooling unit that is provided at a position facing the gate in the movable side mold and cools the molten resin filled in the gate;
A molding die comprising: The cooling part is
2. The molding die according to claim 1, wherein the molding die is a cooling hole having a partition for separating a cooling medium introduction path and a discharge path for cooling the molten resin filled in the gate. The cooling part is
3. The molding die according to claim 2, wherein the molding die is inserted into a cooling medium passage provided in the movable mold and constitutes a part of the cooling medium passage.

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