JP6652532B2 - Injection mold - Google Patents

Description

  The present invention relates to a mold for injection molding.

A resin molded product used for the interior and exterior of an automobile or a housing of a home appliance, for example, is injection-molded using a resin material such as a polyolefin resin, a polystyrene resin, an ABS resin, a polycarbonate resin, or a polyamide resin. There are many.
Injection-molded resin molded products may cause sink marks due to volume shrinkage during molding. When sink marks occur on the design surface of the resin molded product (for example, a pattern such as a grain or satin finish or a surface having a mirror-like gloss), there is a possibility that the aesthetic appearance is impaired and the product properties are reduced.

In order to solve the above-described problem, for example, in Patent Document 1, a concave portion of a mold (corresponding to a “first mold” in claims) on a product visible surface side (design surface side) that causes sink marks. A method has been proposed in which a surface (corresponding to a “design surface forming portion” in the claims) is heated and held at a high temperature to guide a sink generation location to an invisible surface side (non-design surface side).
Similarly, in Patent Document 2, the mold cavity forming surface on the anti-design surface side (non-design surface side) (corresponding to “non-design surface forming portion” in the claims) has a mold cavity on the design surface side. Surface (corresponding to “design surface forming portion” in the claims) so that the resin is more easily released from the mold, and the temperature of the mold cavity surface on the design surface side is the temperature of the mold cavity surface on the anti-design surface side. By setting to be higher, the pressure of the resin injected and filled into the mold cavity is 0 Pa within a time range from 1 second to 7 seconds after completion of the injection, so that the design surface side Methods for suppressing the occurrence of sink marks have been proposed.

JP-A-6-315961 JP 2012-192715 A

In each of Patent Documents 1 and 2, the design surface side of the molded product is brought into close contact with the mold cavity surface by making the mold surface on the design surface side higher in temperature than the mold surface on the non-design surface side. In this technology, sink marks are concentrated on the non-design surface side opposite to the design surface to suppress sink marks on the design surface (hereinafter, also referred to as design surface side heat molding method).
However, in this design surface side heat molding method, if the gas in the cavity remains between the cavity surface and the molded product while being compressed at the flow terminals of the resin injected into the cavity or at the weld portion, the gas is maintained under pressure. The resin pressure after completion (including the shrinkage of the resin due to cooling) spreads between the design surface and the cavity surface of the molded product before the completion of solidification, causing sink marks on the design surface of the molded product and the close contact with the cavity surface. In some cases, a line was generated at the boundary with the separated part.

In a resin molding die, a groove for promoting exhaustion from a cavity to the outside of the die is conventionally formed on a parting surface. The opening of the groove on the inner surface of the cavity is generally several mm in width and about 0.005 to 0.02 mm in depth, which prevents resin outflow and allows the resin filled in the cavity to be kept under pressure.
As a measure for forming a groove for promoting exhaustion on the parting surface, it is possible to exhaust gas in the cavity as the resin is filled. For this reason, in this measure, it is possible to reduce the case where the gas in the cavity remains at the flow terminal of the resin injected into the cavity or at the weld portion.
However, even if the measures for forming the grooves for promoting exhaustion on the parting surface are applied to the design surface side heat molding method, if the gas in the compressed state remains near the resin flow terminal and the weld portion, this gas is maintained. The fact is that it is impossible to prevent the molded product before solidification from spreading between the design surface and the cavity surface due to a decrease in the resin pressure after the completion of the pressure.
In addition, since the design surface side and the non-design surface side of the mold are in contact with each other via the parting surface near the end surface of the molded product, heat transfer from the high-temperature design surface side to the non-design surface side causes In some cases, the adhesiveness of the resin to the design surface was reduced.

  The problem to be solved by the aspect of the present invention is to provide an injection molding die that can more reliably suppress the occurrence of sink marks and lines on the design surface of a molded product.

In order to solve the above problems, the present invention provides the following aspects.
The injection mold according to the first aspect includes a first mold in which a concave portion for forming a design surface of a resin molded product is formed, and a first mold that is freely opened and closed with respect to the first mold. A second mold forming a cavity including the concave portion between the first mold and the second mold when the mold is closed with the mold, wherein the second mold is a part of an inner surface of the cavity. A back side molding surface for molding the back side opposite to the design surface of the resin molded product, a recess depressed from the back side molding surface, and an air passage secured in the recess and opening to the back side molding surface, A gas storage space secured in the recess and communicating with the cavity through the ventilation path is formed, and the ventilation path allows gas between the cavity and the gas storage space to flow therethrough, and from the cavity. It is restricted movable around a flow of molten resin, the recess of the second mold The formed at a position corresponding to the flow path terminal or weld in the cavity in the cavity of the inflow molten resin, the gas storage space, the gas transfer to the outside is possible only the air passage from the interior The gas is formed so as to be accommodated therein while maintaining a state of a pressure higher than the atmospheric pressure.
The injection mold has a first mold in which a concave portion for forming a design surface of a resin molded product is formed, and is freely openable and closable with respect to the first mold, and is closed to the first mold. And a second mold that forms a cavity including the recess between the first mold and the second mold, wherein the second mold is a part of an inner surface of the cavity and is a part of the resin molded product. A back side molding surface for molding the back side opposite to the design surface; a recess depressed from the back side molding surface; an air passage secured in the recess and opened to the back side molding surface; secured in the recess. A gas storage space communicating with the cavity through the ventilation path is formed, and the ventilation path allows gas between the cavity and the gas storage space to flow therethrough, and inflow of molten resin from the cavity. And the recess of the second mold is Is formed at a position corresponding to the flow path terminal or welds within the cavity of the molten resin flowing into tee, the second mold, the second mold clamping extending from said gas storage space An internal pressure adjusting exhaust path that is sometimes not covered by the first mold and that is open to the outside that is exposed; and a valve provided in the internal pressure adjusting exhaust path. Only when the gas pressure on the gas storage space side from the valve is equal to or higher than a set pressure set to a pressure higher than the atmospheric pressure, from the gas storage space side of the internal pressure adjusting exhaust passage to the outside of the second mold. It is also possible to adopt a configuration in which the gas storage space is formed so as to be able to accommodate the gas therein while maintaining the gas at a pressure higher than the atmospheric pressure .
Prior Symbol second die has a lid member disposed flush with the rear molding surface provided by spaced to the cavity side from the bottom surface of the recess in said recess, it said and said cover member recess The gas passage space may be secured between the inside surface of the plant or through the lid member, and the gas storage space may be secured between the bottom surface of the recess and the lid member.

According to the injection mold according to the aspect of the present invention, the gas in the cavity is compressed as the molten resin is injected into the cavity between the first mold and the second mold closed to each other. (Air, gas released from the molten resin, etc.) can be stored in the gas storage space of the second mold. For this reason, the gas in the cavity can be reduced from remaining in the cavity.
Further, when the resin pressure drops after the pressure holding of the molten resin in the cavity is completed, the gas stored in the gas storage space is transferred from the gas storage space to the resin molded product in the cavity and the second metal via the ventilation path. The resin is released between the mold and the back side of the mold, and forcibly separates the resin molded article from the back side of the second mold. The gas released from the gas storage space between the resin molded product and the rear molding surface of the second mold acts to press the resin molded product against the inner surface of the concave portion of the first mold by the pressure. As a result, the state of adhesion of the design surface of the resin molded product to the inner surface of the concave portion of the first mold can be maintained, and formation of a line on the design surface of the resin molded product can be prevented. In addition, sink marks due to solidification progress due to cooling of the resin molded product can be intensively generated not on the design surface of the resin molded product but on the back side opposite to the design surface, and thereby, the design surface of the resin molded product can be reduced. Sinking can be suppressed.

It is a figure showing the manufacturing method of the resin molding using the metallic mold for injection molding concerning one embodiment of the present invention, and the cavity ensured between the 1st metallic mold and the 2nd metallic mold in a clamped state. FIG. 3 is a partial front sectional view showing a state in which a molten resin is being filled into a mold. FIG. 2 is a partial front sectional view showing a state immediately before filling of a cavity with the molten resin of FIG. 1. FIG. 2 is a partial front sectional view showing a state in which filling of a cavity with the molten resin of FIG. 1 is completed and a resin molded product is present in the cavity. FIG. 2 is an enlarged view showing the vicinity of a storage space recess and a lid member of a second mold in FIG. 1, wherein (a) is a partial plan view and (b) is a partial front sectional view. It is a figure which shows the modification of a 2nd metal mold | die, and is a partial front sectional view which shows the 2nd metal mold of the structure which provided the exhaust path for internal pressure adjustment, and the leak valve in the 2nd metal mold of FIG.

Hereinafter, an injection mold according to an embodiment of the present invention will be described with reference to the drawings.
1 to 3 are views showing an injection molding die 10 according to one embodiment of the present invention, and are front sectional views showing the injection molding die 10 in a mold-clamped state.
1 to 3 are diagrams illustrating a method of manufacturing the resin molded product 1 using the injection mold 10.
1 is in the course of filling the cavity 11 of the injection mold 10 with the molten resin 2, FIG. 2 is just before the filling of the cavity 11 with the molten resin 2 of FIG. 1, and FIG. 3 is the cavity 11 of the molten resin 2 in FIG. This shows a state where the resin molded product 1 molded from the molten resin 2 is present in the cavity 11 after the filling into the cavity 11 is completed.

The injection mold 10 shown in FIGS. 1 to 3 is a first mold in which a concave portion 21 (hereinafter, also referred to as a molding concave portion) for forming the design surface 1a of the resin molded product 1 (see FIG. 3) is formed. 20 (hereinafter, also referred to as a cavity mold) and a second mold 30 that opens and closes the cavity mold 20. As shown in FIG. 3, the second mold 30 has a molding surface 31 (hereinafter, also referred to as a back molding surface) for molding on the back surface 1 b side opposite to the design surface 1 a of the resin molded product 1.
Hereinafter, the second mold 30 is also referred to as a core mold.

The design surface 1 a of the resin molded product 1 is formed by the inner bottom surface 22 of the molding concave portion 21 of the cavity mold 20. Hereinafter, the inner bottom surface 22 of the molding concave portion 21 of the cavity mold 20 is also referred to as a design surface molding surface.
The back side molding surface 31 of the core mold 30 is formed through the cavity 11 which is a resin molding space secured between the core mold 30 and the cavity mold 20 when the core mold 30 is closed with the cavity mold 20. 20 is located on the side opposite to the design surface molding surface 22.

The cavity 11 of the injection mold 10 shown in FIGS. 1 to 3 is a core mold in which an opening (opening on the core mold 30 side) opposite to the design surface molding surface 22 of the cavity mold 20 is closed to the cavity mold 20. Secured by closing with 30.
As shown in FIGS. 1 to 3, the back molding surface 31 of the core mold 30 is a surface facing the cavity 11 of the core mold 30 closed to the cavity mold 20.

The core mold 30 of the injection mold 10 shown in FIGS. 1 to 3 has a core body 32 made of metal.
The back molding surface 31 of the core mold 30 is formed so as to be continuous with the back molding main surface 31a formed on the core mold main body 32 and the back molding main surface 31a on the lid member 35 fixed to the core mold main body 32. The front surface 35a (hereinafter, also referred to as a cover member front surface).

The core mold body 32 also has a parting surface 33 that is superimposed on the parting surface 23 of the cavity mold 20.
The parting surface 23 of the cavity mold 20 is formed so as to surround the opening of the molding recess 21 (the opening on the core mold 30 side).
The parting surface 33 of the core mold body 32 is formed so as to surround the back molding surface 31. The core mold 30 is closed to the cavity mold 20 by overlapping the parting surface 33 of the core mold body 32 with the parting surface 23 of the cavity mold 20.

The back side molding surface 31 of the core mold 30 shown in FIGS. 1 to 3 is a flat surface that is continuous from the parting surface 33 of the core mold 30.
However, the back molding surface 31 of the core mold 30 has a shape in which a part or the whole thereof projects toward the molding recess 21 of the cavity mold 20 so as to enter the molding recess 21 of the cavity mold 20 at the time of mold clamping. There may be.

  In the injection mold 10 shown in FIGS. 1 to 3, the molten resin 2 is injected and filled into the cavity 11 from an injection molding machine connected to a gate (not shown) located on the left side of the cavity 11 in the drawings. The left side in FIGS. 1 to 3 is hereinafter also referred to as a gate side. The molten resin 2 injected into the cavity 11 from the gate side flows and fills toward the right end of the flow path (hereinafter, also referred to as the end of the resin flow path) in FIGS.

The resin flow path is secured from the molten resin inflow port from the gate in the cavity 11 along the back molding surface 31 of the core mold 30. The molten resin 2 is supplied (injected) into the cavity 11 from the molten resin inflow port and flows through the resin flow path toward the terminal.
The end of the resin flow path is the farthest point from the molten resin inflow port in the resin flow path, and is located near the inner surface of the opening of the molding concave portion 21 of the cavity mold 20.

  In FIGS. 1 to 3, the illustration of the injection mold 10 on the gate side from the middle of the flow path of the molten resin 2 in the cavity 11 is omitted. Therefore, in FIGS. 1 to 3, a part of the parting surfaces 23 and 33 of the cavity mold 20 and the core mold body 32 that is located on the gate side from the cavity 11 is omitted.

As shown in FIGS. 1 to 3, the core mold body 32 of the core mold 30 is formed with a recess 34 (hereinafter, also referred to as a recess for a storage space) that is recessed from the back molding main surface 31 a. .
The storage space recess 34 is formed in the core mold body 32 so as to be depressed from a position corresponding to the end of the resin flow path in the cavity 11 on the back molding main surface 31 a of the core mold body 32.

The core mold 30 has a lid member 35 inserted and fixed in the storage space recess 34.
The lid member 35 is provided so as to close the opening on the back-side molding main surface 31 a of the storage space recess 34. The front surface 35a (cover front surface) of the lid member 35 facing the cavity 11 is formed so as to be continuous with the back molding main surface 31a and is aligned with the back molding main surface 31a.

As shown in FIGS. 1 to 3, the lid member 35 is fixed to the core mold main body 32 so as to be separated from the inner bottom surface 34 a of the storage space recess 34 toward the cavity 11.
The core mold 30 is secured between the inner bottom surface 34a of the recess 34 for the storage space of the core mold body 32 and the cover member 35 (that is, on the back surface 35b side opposite to the front surface 35a of the cover member 35). The gas storage space 36 is provided.

The opening of the recess 34 for the storage space is formed by connecting the end of the recess 34 for the storage space in the depth direction (vertical direction in FIGS. 1 to 3) on the back side forming main surface 31 a to the end. The inner space 34a is formed by an expanded portion 34b whose cross-sectional dimension perpendicular to the depth direction of the recess 34 for the storage space is larger than that of the portion on the inner bottom surface 34a side (the recess main portion).
The lid member 35 is configured such that an outer peripheral portion of the back surface 35b is brought into contact with a step between an extended portion 34b (hereinafter, also referred to as a concave extended opening) of the storage space concave portion 34 and a concave main portion. It is housed in the recess opening 34b.
The lid member 35 shown in FIGS. 1 to 3 is specifically formed in a plate shape having a thickness in a direction perpendicular to the front surface 35a.

The direction of the cover member 35 along the front surface 35a is hereinafter also referred to as a surface direction.
The side peripheral surface 35c of the lid member 35 is formed in a similar shape that is slightly smaller than the inner peripheral surface of the recess expansion opening 34b. The side peripheral surface 35c of the lid member 35 is formed, for example, to a size smaller by about 0.1 mm (0.05 to 0.15 mm) in the center axis direction from the inner peripheral surface of the recess expansion opening 34b.

The cover member 35 is housed in the recess expansion opening 34 b and fixed to the core-type main body 32.
The lid member 35 in FIGS. 1 to 3 uses a non-permeable member such as a metal member.
As shown in FIGS. 4A and 4B, a gas storage space 36 and a cavity are provided between the lid member 35 (specifically, the side peripheral surface 35c thereof) and the inner peripheral surface of the recess opening 34b. A gas passage 37 is provided to allow gas flow between the gas passage 11 and the gas passage 11. One end of the air passage 37 is opened to the gas storage space 36, and the other end is opened to the back molding surface 31 of the core mold 30.

  The cover member 35 housed and fixed in the recess extension opening 34b is in a state where a clearance 38 is secured between the cover member 35 and the inner periphery of the recess extension opening 34b over the entire periphery of the side peripheral surface 35c, or Any state in which a part of the peripheral surface 35c is in contact with the inner peripheral surface of the recess expansion opening 34b can be adopted. FIGS. 4A and 4B show a state in which a part of the side peripheral surface 35c of the lid member 35 is in contact with the inner peripheral surface of the recess expansion opening 34b.

As shown in FIG. 4B, a clearance 38 between a side peripheral surface 35 c of the lid member 35 (hereinafter, also referred to as a lid member side peripheral surface) and an inner peripheral surface of the recess expansion opening 34 b is formed by a ventilation passage 37. Function as
Further, as shown in FIG. 4 (a), where the lid member side peripheral surface 35c is in contact with the inner peripheral surface of the recess extension opening 34b, the side peripheral surface 35c of the lid member 35 and the recess extension opening are provided. The ventilation path 37 is secured by minute irregularities on the inner peripheral surface of the groove 34b.

Since the air passage 37 is a very narrow space secured between the side peripheral surface 35c of the lid member 35 and the inner peripheral surface of the recess expansion opening 34b, the molten resin 2 supplied to the cavity 11 can enter. It does not occur, or very little, if any, of the molten resin 2.
The air passage 37 permits gas flow between the gas storage space 36 and the cavity 11, and regulates leakage of the molten resin 2 from the cavity 11 to the storage space recess 34.

  As a method of fixing the lid member 35 to the core-type main body 32, for example, mechanical fixing such as screwing using a set screw, welding, or adhesive fixing using a thermosetting resin having adhesiveness can be adopted. .

  In screwing, the cover member 35 is fixed to the core-type main body 32 by a set screw that has been passed through the core-type main body 32 and screwed into the cover member 35. In screwing, the fixing of the lid member 35 to the core-type main body 32 and the release of the fixing can be switched by rotating the set screw. Further, in the screwing, in a state where the set screw is detached from the cover member 35, the cover member 35 can be inserted into and removed from the recess expansion opening 34b.

In the case of welding, only a part of the side circumference of the lid member 35 is locally welded and fixed to the core-type main body 32 so that most of the side circumference of the lid member 35 is not welded to the core-type main body 32. A ventilation path 37 is secured between the periphery of the member 35 and the inner peripheral surface of the core type main body 32.
The adhesive fixation using the thermosetting resin having adhesive property is performed by locally fixing only a part of the outer surface of the lid member 35 to the core-type main body 32 using the thermosetting resin, and storing the outer surface of the lid member 35. Most of the portion located in the space recess 34 is not adhered to the core type main body 32. Thereby, the ventilation path 37 between the side circumference of the lid member 35 and the inner circumference of the core type main body 32 is secured.

  As shown in FIG. 3, the storage space recess 34 and the lid member 35 housed and fixed in the recess expansion opening 34 b are provided at a position corresponding to the end of the flow path of the molten resin 2 in the cavity 11. It is provided on the mold body 32. The storage space recess 34 and the cover member 35 are provided at positions separated from the molten resin inflow port (gate-side end) from the gate in the cavity 11.

The entire inner surface of the gas storage space 36 other than the lid member 35 side is formed of the metal forming the core type main body 32.
In the gas storage space 36, only the ventilation path 37 is a flow path that allows gas to flow in and out of the gas storage space 36.
The gas storage space 36 has no internal gas outlet other than the ventilation path 37. For example, if the cavity 11 side is air-tightly sealed, the gas can be stored while maintaining a pressure higher than the atmospheric pressure.

The production of the resin molded product 1 using the injection molding die 10 shown in FIGS. 1 to 3 is performed by melting the molten resin 2 from an injection molding machine (not shown) connected to the gate of the injection molding die 10 in a closed state. The cavity 11 is injected and filled (FIGS. 1 and 2), and the molten resin 2 in the cavity 11 is cooled and solidified while maintaining the mold-clamped state of the injection molding die 10 to form the resin molded product 1 (FIG. 1). 3). Then, the injection mold 10 is opened with the core mold 30 separated from the cavity mold 20, and the resin molded product 1 is taken out of the cavity 11.
After the mold is opened, the injection molding die 10 can be used again for manufacturing the resin molded article 1 by the above procedure by clamping the mold.

The molten resin 2 which has been completely filled into the cavity 11 is rapidly cooled and solidified to form a resin molded article 1 molded by the inner surface of the cavity 11.
In the present specification, the molten resin 2 that has been cooled and solidified after completion of the filling of the cavity 11 is also referred to as a “resin molded product” in addition to the solidified state of the entire molten resin 2 filled in the cavity 11. .
The resin molded article is completely solidified by the time the injection molding die 10 is opened, and is taken out of the injection molding die 10 by the opening of the injection molding die 10 after the entire solidification is completed.

  When the molten resin 2 is injected and filled into the cavity 11 from the injection molding machine, the gas in the cavity 11 such as the air in the cavity 11 and the gas released from the molten resin 2 is supplied to the gate side of the molten resin 2 in the cavity 11 ( As the filling progresses from the left end of the flow path (from the left side in FIGS. 1 to 3), the existing range in the cavity 11 is limited (compressed) to the end of the flow path of the molten resin 2, and the pressure increases.

  However, in the injection mold 10 shown in FIGS. 1 to 3, the gas in the cavity 11 is transferred from the cavity 11 to the gas storage space 36 through the ventilation path 37 as the filling of the molten resin 2 into the cavity 11 progresses. It is pushed out and stored in the gas storage space 36. The gas storage space 36 is formed in a size that can accommodate the entire amount of gas in the cavity 11. As shown in FIG. 3, when the molten resin 2 is filled into the cavity 11, all the gas in the cavity 11 is pushed out to the ventilation path 37 and the gas storage space 36 by the progress, and the molten resin 11 flows through the cavity 11. It is possible to fill the entire cavity 11 by spreading to the end without any gap.

The gas in the cavity 11 is stored in the gas storage space 36 in a compressed state.
The molten resin 2 is maintained at a predetermined pressure when the filling of the cavity 11 is completed. The resin pressure in the cavity 11 decreases due to volume shrinkage accompanying cooling and solidification of the resin molded product 1 in the cavity 11. At this time, the gas in the gas storage space 36 is compressed by the internal pressure of the resin molded product 1 (which may contain the molten resin 2 being solidified) in the cavity 11 through the ventilation path 37 through the ventilation path 37. It is pressed toward the molding surface 22 and discharged between the resin molded product 1 and the back molding surface 31. The gas discharged from the gas storage space 36 between the resin molded product 1 and the back molding surface 31 peels the resin molded product 1 from the back molding surface 31 of the core mold 30. As a result, the gas that has entered the back surface 1b of the resin molded product 1 and the back molding surface 31 of the core mold 30 moves the resin molded product 1 in the cavity 11 toward the design surface molding surface 22 of the cavity mold 20 by the pressure. By pressing, the design surface 1 a of the resin molded product 1 is pressed against the design surface molding surface 22 of the cavity mold 20.

  As a result, the design surface 1a of the resin molded product 1 is precisely formed by pressing the cavity mold 20 against the design surface molding surface 22 and further solidifying the resin forming the resin molded product 1 while maintaining the close contact state. . Further, by pressing the design surface 1a against the design surface forming surface 22 of the cavity mold 20 and maintaining the close contact state, there is an inconvenience that a line is formed at the boundary between the contact portion of the design surface 1a with the inner surface of the cavity 11 and the separated portion. Occurrence can be prevented.

Further, sinks due to cooling and volume shrinkage of the resin molded product 1 separated from the back molding surface 31 of the core mold 30 result in depressions on the back surface 1b of the resin molded product 1, and the design surface 1a (O The influence of sink marks can be controlled so that depressions due to sink marks on the front surface) do not occur.
Therefore, in molding (manufacturing) the resin molded product 1 using the injection molding die 10, the design surface 1a of the resin molded product 1 can be formed with high accuracy and stably. For this reason, in molding (manufacturing) the resin molded product 1 using the injection mold 10, the gas in the cavity is more excellent in aesthetics than a technology in which only gas for promoting gas exhaust formed on the parting surface is used. It is possible to more reliably obtain the designed surface 1a.

  For example, in the design side heat molding method described in Patent Literatures 1 and 2, as described above, the design of a molded product is performed by setting the mold surface on the design side to a higher temperature than the mold surface on the non-design side. The surface side is brought into close contact with the mold cavity surface, and the generation of sink marks is concentrated on the non-design surface side opposite to the design surface, thereby suppressing the generation of sink marks on the design surface. However, in this design surface side heat molding method, the non-design surface having a lower temperature than the design surface side mold from the high temperature design surface side mold through the parting surface which is in contact with the mold in the mold-clamped state. Due to the heat transfer to the side mold, the temperature difference between the design side mold and the non-design side mold decreases. As a result, in the design surface side heat molding method, the close contact between the concave surface of the design surface side mold and the molded product is hindered, and sink marks are generated on the design surface side of the molded product, and the concave surface of the design surface side mold is reduced. A line may be formed at a boundary position between a close contact portion and a separated portion of the mold on the design surface side with respect to the concave surface due to a gas flow between the design surface of the molded product and the mold surface.

On the other hand, in molding (manufacturing) the resin molded product 1 using the injection molding die 10 shown in FIGS. 1 to 3, the resin molded product 1 and the core mold 30 are connected to the gas storage space 36 via the ventilation passage 37. The resin molded product 1 in the cavity 11 is separated from the back molding surface 31 of the core mold 30 by the pressure of the gas discharged between the back mold surface 31 and the molding surface design surface 22 of the cavity mold 20. Press the surface 1a. As a result, in the molding of the resin molded product 1 using the injection molding die 10, the state of close contact of the molded product design surface 1 a with the design surface molding surface 22 of the cavity mold 20 can be stably maintained, and the molded product design surface 1 a The formation of depressions and lines due to sink marks can be prevented.
In molding of the resin molded product 1 using the injection molding die 10 shown in FIGS. 1 to 3, regardless of whether or not heat is transferred from the cavity mold 20 to the core mold 30 in the mold-clamped state, the molded product design surface 1 a is formed. Dents and lines due to sink marks can be prevented.

  In the molding of the resin molded product 1 using the injection molding die 10 shown in FIGS. 1 to 3, the resin molded product 1 was discharged from the gas storage space 36 between the resin molded product 1 and the back molding surface 31 of the core mold 30. Since the gas presses the molded product 1 toward the design surface molding surface 22 of the cavity mold 20 due to the pressure, even if gas remains at the end of the resin flow path in the cavity 11, the residual gas is It is possible to prevent the molded product 1 from expanding between the molded product design surface 1a and the design surface molding surface 22 of the cavity mold 20 due to the volume shrinkage of the molded product 1, and it is possible to prevent depressions and lines due to sink marks on the molded product design surface 1a. Formation can be minimized.

The injection molding die 10 maintains the clamped state from the start of filling of the molten resin 2 until a preset clamp holding time has elapsed, and opens after the mold clamp holding time has elapsed.
During the mold holding time, gas is discharged from the gas storage space 36 to the space between the resin molded product 1 and the back molding surface 31 of the core mold 30 during the process. The injection molding die 10 is set to be opened at a timing when the cooling of the article 1 further proceeds.

As described above, the present invention has been described based on the best mode, but the present invention is not limited to the above-described best mode, and various modifications can be made without departing from the gist of the present invention.
The core mold 30 of the injection mold 10 shown in FIGS. 1 to 3 has a lid member 35 and a gas storage space 36 at a position corresponding to the end of the resin flow path in the cavity 11. However, the lid member and the gas storage space may be provided, for example, at a position corresponding to a weld in the cavity in the second mold.
The injection molding die can adopt a configuration having one or both of the terminal of the resin flow path in the cavity and the weld part. The lid member and the gas storage space can be provided at one or more of the end of the resin flow path of the cavity and the weld portion.

The lid member is made of a porous material having air permeability (hereinafter, also referred to as an air-permeable porous material) formed of a material having excellent heat resistance, such as ceramics, or an inner diameter of several microns to several tens of A metal member having a through-hole of about a micron (hereinafter, also referred to as a through-hole-formed metal member) can be employed.
The air-permeable porous material has pores that function as air passages. When a cover member having a gas-permeable porous material and having a ventilation path secured by holes of the gas-permeable porous material is used, or when a metal member with a through hole is used for the cover member, the inside of the opening of the recess for the storage space is used. Either a configuration in which a ventilation path is secured between the peripheral surface and the lid member, or a configuration in which a ventilation path is not secured between the inner peripheral surface of the opening of the storage space recess and the lid member can be adopted.
In the case of using a porous material, for example, by using a porous material having a size that embeds the entire recess for the storage space, a space for gas storage is not separately provided in the cavity mold, and the porous material is formed in the porous member. High pressure gas can be stored.

  Further, when the amount of gas discharged from the gas storage space 36 is too large and a problem such as gas entering into the molded article occurs, the pellet-shaped solid is sealed in the gas storage space to reduce the amount of gas discharged. It is also possible to control.

The injection molding die 10 illustrated in FIGS. 1 to 3 has a configuration in which neither the cavity die 20 nor the parting surfaces 23 and 33 of the core die 30 have grooves for promoting exhaustion.
In the injection mold 10, a gap formed between the resin molded product and the back molding surface of the second mold by the exhaust gas from the gas storage space is one or both of the first mold and the second mold. The exhaust gas from the gas storage space can be prevented from being exhausted from the exhaust groove by communicating with the exhaust groove on the parting surface. For this reason, in the injection molding die 10, the gas discharged from the gas storage space to between the resin molded product and the back molding surface of the second mold directs the resin molded product to the design surface molding surface of the first mold. Pressing force can be reliably ensured.

As shown in FIG. 5, the second mold of the injection molding mold extends from the gas storage space 36 and is not covered by the first mold 20 at the time of mold clamping, and is open to the exposed outer surface 39 for internal pressure adjustment. A configuration including an exhaust path 41 and a leak valve 42 provided in the internal pressure adjusting exhaust path 41 can also be adopted.
The second mold 30A shown in FIG. 5 has a configuration in which an exhaust passage 41 for adjusting the internal pressure and a leak valve 42 are provided in the core mold 30 shown in FIGS.
The leak valve 42 of the second mold 30A in FIG. 5 is used when the gas pressure on the gas storage space 36 side from the leak valve 42 of the internal pressure adjusting exhaust passage 41 becomes equal to or higher than a set pressure set higher than the atmospheric pressure. The gas exhaust from the gas storage space 36 side of the internal pressure adjusting exhaust path 41 to the outside of the second mold 30A is allowed.
The set pressure at which the leak valve 42 allows gas to be exhausted from the gas storage space 36 side of the internal pressure adjusting exhaust passage 41 to the outside of the second mold 30A is, for example, a gas pressure inside the cavity 11 and the gas storage space 36 that is resin. Gas is discharged from the gas storage space 36 to the space between the resin molded product 1 and the rear molding surface 31 of the second mold 30A when the resin molded product 1 in the cavity 11 is shrunk in volume during the molding process without burning. (Including peeling of the resin molded product 1 from the back molding surface 31 by gas pressure) is set to a possible range.
When the gas pressure on the gas storage space 36 side from the leak valve 42 of the internal pressure adjustment exhaust passage 41 is lower than the set pressure, the leak valve 42 is connected to the second mold from the gas storage space 36 side of the internal pressure adjustment exhaust passage 41. Restrict gas exhaust to the outside of 30A.

  DESCRIPTION OF SYMBOLS 1 ... Resin molding, 1a ... Design surface (of resin molding), 1b ... Back surface (of resin molding), 2 ... Molten resin, 10 ... Injection molding die, 11 ... Cavity, 20 ... First die (Cavity mold), 21: concave portion for molding, 22: inner bottom surface (of concave portion for molding), 23: parting surface, 30, 30A: second mold (core mold), 31: rear molding surface, 31a: rear surface Molding main surface, 32 core body, 33 parting surface, 34 recess for storage space, 35 lid member, 36 gas storage space, 37 air passage, 38 air passage (clearance), 39 ... Outer surface (of the second mold), 41 ... Exhaust passage for adjusting internal pressure, 42 ... Valve (leak valve).

Claims (3)

A first mold in which a concave portion for forming a design surface of a resin molded product is formed; and a first mold that is freely openable and closable with respect to the first mold, and is closed when the first mold is closed. And a second mold that forms a cavity including the concave portion, and
In the second mold, a back-side molding surface that is a part of the inner surface of the cavity and that forms a back surface opposite to the design surface of the resin molded product, a recess that is depressed from the back-side molding surface, a ventilation passage which is open to the rear molding surface is secured in said recess, and a gas storage space communicating with the cavity is ensured through said air passage in said recess is formed,
The ventilation path is formed so that a gas can flow between the cavity and the gas storage space, and the flow of the molten resin from the cavity can be regulated,
The concave portion of the second mold is formed at a position corresponding to a flow path terminal or a weld portion of the molten resin flowing into the cavity in the cavity,
An injection molding die in which the gas storage space is formed such that the gas can be moved from the inside to the outside only through the air passage, and the gas can be accommodated therein while maintaining a state of a pressure higher than the atmospheric pressure. A first mold in which a concave portion for forming a design surface of a resin molded product is formed; and a first mold that is freely openable and closable with respect to the first mold, and is closed when the first mold is closed. And a second mold that forms a cavity including the concave portion, and
In the second mold, a back-side molding surface that is a part of the inner surface of the cavity and that forms a back surface opposite to the design surface of the resin molded product, a recess that is depressed from the back-side molding surface, a ventilation passage which is open to the rear molding surface is secured in said recess, and a gas storage space communicating with the cavity is ensured through said air passage in said recess is formed,
The ventilation path is formed so that a gas can flow between the cavity and the gas storage space, and the flow of the molten resin from the cavity can be regulated,
The concave portion of the second mold is formed at a position corresponding to a flow path terminal or a weld portion of the molten resin flowing into the cavity in the cavity,
The second mold extends from the gas storage space, and is provided with an exhaust path for internal pressure adjustment that opens to an outer surface that is not covered with the first mold and is exposed when the second mold is clamped. A valve provided in a gas exhaust passage for the internal pressure adjusting exhaust gas, the gas pressure on the gas storage space side from the valve of the internal pressure adjusting exhaust passage becomes equal to or higher than a set pressure set higher than atmospheric pressure. Only when, permitting gas exhaust from the gas storage space side of the internal pressure adjusting exhaust path to the outside of the second mold,
An injection molding die in which the gas storage space is formed so as to be able to store a gas therein while maintaining a state of a pressure higher than the atmospheric pressure. The injection mold according to claim 1 or 2 ,
Prior Symbol second die has a lid member disposed flush with the rear molding surface provided by spaced to the cavity side from the bottom surface of the recess in said recess, it said and said cover member recess An injection molding die in which the ventilation path is secured between the inside surface of the plant or through the lid member, and the gas storage space is secured between the bottom surface of the recess and the lid member.

Images