JP2019043046A - Injection molding die - Google Patents

Abstract

To provide an injection molding die capable of suppressing an occurrence of defects in resin molding caused by poor gas discharge at welds and resin flow terminals at a low cost.SOLUTION: An injection molding die 10 has a first mold 20, a second mold 30 which is freely openable and closable to the first mold 20 and forms a cavity 11 with the first mold 20 when closed to the first mold 20, and a lid member 35 securing a gas storage space 36 in a second mold recess 34 recessed from a second mold molding surface 31 of the second mold 30 in a mold clamping state by covering an opening of the second mold recess 34. The gas storage space 36 communicates with the cavity through a space between an opening inner peripheral surface of the second mold recess 34 and the lid member 35 or an air passage secured in a hole shape penetrating the lid member 35.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an injection mold.

Conventionally, in the injection molding of a resin molded product, the air in the cavity and the gas released from the resin injected into the cavity are compressed into the weld part and the resin flow terminal, and the weld part and the resin flow terminal stand out. Defects such as unfilled resin and gas burn may occur.
For such a problem, for example, there is a countermeasure (for example, Patent Document 1) in which an air-permeable insert is inserted at a position corresponding to a mold weld or a resin flow terminal and an exhaust port communicating to the outside of the mold is provided. Many have been adopted.

JP 2000-351136 A

  However, measures to insert an air-permeable insert at a position corresponding to the mold weld or resin flow terminal and to provide an exhaust port communicating to the outside of the mold are laborious and costly. There was a problem of sticking.

  The problem to be solved by the aspect of the present invention is to provide an injection mold that can suppress the occurrence of defects in resin molding due to poor gas discharge at the weld part and the resin flow terminal at low cost.

In order to solve the above problems, the present invention provides the following aspects.
The mold for injection molding according to the first aspect includes a first mold in which a recess for molding a resin molded product is formed, and the first mold can be freely opened and closed. A second mold that forms a cavity including the recess between the first mold and the second mold when the second mold is closed to the first mold when the two molds are closed. The second mold recess covering an opening opening to the second mold molding surface of the second mold recess formed to be recessed from the second mold molding surface, which is a part of the inner surface of the cavity. A recess cover member that secures a gas storage space in the chamber, the recess cover member protruding from the inner surface of the recess of the first mold and closing the second mold to the first mold. Provided in the opening of the second mold recess or the hole forming projection that is brought into contact with the second mold molding surface. It is a lid member, and the gas storage space is configured such that the second mold is closed to the first mold by a groove formed on one or both of the hole forming protrusion and the second mold molding surface. Sometimes the air passage secured between the hole forming projection and the second mold molding surface, or between the inner peripheral surface of the opening of the second mold recess and the lid member or It communicates with the cavity through a vent passage secured in a hole shape penetrating the lid member.
The lid member of the second mold may be provided at a position corresponding to a flow path end or a weld portion in the cavity of the molten resin flowing into the cavity.
The gas storage space is secured between the lid member and the bottom surface of the second mold recess, and the lid member has a front surface disposed flush with the second mold molding surface. May be.
When the second mold is closed to the first mold by a groove formed in one or both of the hole forming protrusion and the second mold forming surface, the hole forming protrusion and the first One or more of the air passages secured between the two mold forming surfaces may be opened at positions corresponding to flow path ends or welds in the cavity of the molten resin flowing into the cavity.

According to the injection mold according to the aspect of the present invention, the gas in the cavity that is compressed as the molten resin fills the cavity between the first mold and the second mold that are closed together. (Air, gas released from molten resin, etc.) can be stored in the gas storage space of the second mold. For this reason, it can reduce that the gas in a cavity remains in a cavity. Further, it is possible to prevent the gas in the cavity from being compressed to the weld part or the resin flow path terminal as the molten resin is filled into the cavity and becoming high pressure, thereby causing the resin gas to burn. As a result, according to the injection mold according to the aspect of the present invention, it is possible to prevent the occurrence of defects such as unfilled resin and gas burning, where the weld portion and the resin flow terminal are conspicuous.
The injection mold according to the embodiment of the present invention does not require an exhaust port communicating to the outside of the mold, and there is no gas in the cavity in the gas storage space in which there is no gas flow path to the inside or outside other than the ventilation path. Therefore, the processing cost of the mold can be kept low, and the occurrence of defects on the resin molding due to poor gas discharge at the weld part and the resin flow terminal can be suppressed at a low cost.

It is a figure which shows the structure of the injection mold which concerns on one Embodiment of this invention, and the flow of the molding resin made to flow in into this injection mold from the injection port, It is the plane sectional view which looked at the 2nd metallic mold side from the cross section perpendicular to the projection direction from the crevice inner surface of the 1st metallic mold of the projection for hole formation which forms a hole. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, showing a vicinity of a weld portion of a molten resin filled in a cavity secured between a first mold and a second mold in a clamped state. . It is a BB sectional view taken on the line in FIG. It is a figure which expands and shows the recess for storage spaces of the 2nd metal mold | die of FIG. 1, and the vicinity of a cover member, Comprising: (a) is a partial top view, (b) is a partial front sectional view. It is a figure which shows the injection mold of a modification, and is a 2nd metal mold | die from the cross section perpendicular | vertical to the protrusion direction from the recessed part inner surface of the 1st metal mold | die of the 1st metal mold | die of the hole formation protrusion which forms the hole part of a resin molded product. It is the plane sectional view which looked at the side. It is CC sectional view taken on the line in 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 mold 10 according to an embodiment of the present invention. FIG. 1 shows a hole forming projection for forming a hole (through hole) of a resin molded product in the injection mold 10. FIG. 6 is a plan sectional view showing a structure of the second mold 30 as viewed from a cross section perpendicular to the protruding direction from the concave inner surface 22 of the first mold 20 of the portion 24. 2 is a cross-sectional view taken along the line AA in FIG. 1, and is a side sectional view showing the vicinity of the weld portion 3 of the molten resin 2 to be filled in the cavity 11 of the injection mold 10 in a mold-clamped state. 1 is a sectional view taken along line B-B in FIG.
1 and 2 show a state in the middle of filling the molten resin 2 into the cavity 11, FIG. 3 shows that the filling of the molten resin 2 into the cavity 11 is completed and the cavity 11 is molded from the molten resin 2. The state where the made resin molded product 1 exists is shown.

The injection mold 10 shown in FIGS. 1-3 is the 1st metal mold | die in which the recessed part 21 (henceforth a recessed part for shaping | molding) for the design surface 1a formation of the resin molded product 1 (refer FIG. 3) was formed. 20 (hereinafter also referred to as a cavity mold) and a second mold 30 that opens and closes relative to the cavity mold 20. As shown in FIG. 3, the 2nd metal mold | die 30 is the molding surface 31 (2nd metal mold | die molding surface. Hereafter, a back side molding surface for the shaping | molding of the back surface 1b side opposite to the design surface 1a of the resin molding 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 recess 21 of the cavity mold 20. Hereinafter, the inner bottom surface 22 of the molding recess 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 a cavity mold through a cavity 11 that 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. It is located on the opposite side of the 20 design surface molding surface 22.
The design surface molding surface 22 and the back side molding surface 31 are part of the inner surface of the cavity 11.

The cavity 11 of the injection mold 10 shown in FIGS. 1 to 3 is a core mold in which an opening (core mold 30 side opening) opposite to the design surface molding surface 22 of the cavity mold 20 is closed to the cavity mold 20. 30 is secured by blocking.
As shown in FIGS. 1 to 3, the back-side molding surface 31 of the core mold 30 is a surface facing the cavity 11 in 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 metal core mold body 32 (second mold body).
The back-side molding surface 31 of the core mold 30 is formed so as to be continuous with the back-side molding main surface 31a on the back-side molding main surface 31a formed on the core mold body 32 and the lid member 35 fixed to the core mold body 32. It is comprised by the front surface 35a (henceforth a lid member front surface).

The core mold body 32 is also formed with 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 (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-side molding surface 31. The core mold 30 is closed to the cavity mold 20 with the parting surface 33 of the core mold body 32 superimposed on 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 continues from the parting surface 33 of the core mold 30.
However, the back-side molding surface 31 of the core mold 30 has a shape such that a part or the whole projects toward the molding recess 21 of the cavity mold 20 so as to enter the molding recess 21 of the cavity mold 20 when clamping. There may be.

1 to 3, the molten resin 2 is injected and filled into the cavity 11 from an injection molding machine through a gate (not shown) located on the left side of the cavity 11 in FIGS. 1 and 3. . The left side in FIGS. 1 and 3 is hereinafter also referred to as a gate side.
On the gate side of the cavity 11, an injection port 12 that is an outlet of the molten resin 2 injected into the cavity 11 from the injection molding machine through the gate is opened.
The molten resin 2 injected into the cavity 11 from the injection port 12 flows toward the weld portion forming region 3A on the right side in FIGS. 1 and 3 and fills the cavity 11.
The weld portion forming region 3A is a region where the weld portion 3 of the molten resin 2 injected into the cavity 11 from the injection port 12 is formed.

The injection mold 10 shown in FIGS. 1 to 3 protrudes from the design molding surface 22 of the cavity mold 20, and its tip abuts against the back molding surface 31 when the core mold 30 is closed to the cavity mold 30. It has a hole forming projection 24. The hole forming protrusion 24 forms a hole (through hole) that penetrates the resin molded product 1 (see FIG. 3) and opens in the design surface 1 a and the back surface 1 b of the resin molded product 1.
1-3, the hole forming protrusion 24 of the injection mold 10 protrudes from the central portion of the design molding surface 22 of the cavity mold 20, and the tip thereof contacts the central portion of the back-side molding surface 31 of the core mold 30. Touched.

The weld portion forming region 3A is set by a flow path (resin flow path) in the cavity 11 of the molten resin 2 injected from the injection port 12 of the injection mold 10.
As shown in FIGS. 1 and 3, the weld portion forming region 3 </ b> A of the illustrated injection mold 10 is secured in the cavity 11 on the side opposite to the injection port 12 through the hole forming protrusion 24. The space 13 (hereinafter also referred to as a merge space) is set.

In the injection mold 10 shown in FIGS. 1 and 3, the molten resin 2 injected into the cavity 11 from the injection port 12 is diverted to both sides of the hole forming protrusion 24, and the hole forming protrusion is formed in the cavity 11. It flows into the merge space 13 on the side opposite to the injection port 12 from the opposite sides via the portion 24.
As shown in FIGS. 1 to 3, the weld portion forming region 3 </ b> A is secured and set at the center portion in the direction along the back-side molding surface 31 of the merge space 13. The molten resin 2 that has flowed into the merging space 13 from opposite sides contacts each other in the weld portion forming region 3A.
In the cavity 11, two resin flow paths are secured that flow from between the injection port 12 and the hole forming projection 24 and reach the weld portion forming region 3 </ b> A of the merge space 13.

As shown in FIGS. 1 to 3, the core body 32 of the core mold 30 has a recess 34 (second mold recess, hereinafter referred to as a storage space recess) recessed from the back side molding main surface 31 a. Say) is formed.
The recess 34 for the storage space is formed in the core mold main body 32 so as to be recessed from a position corresponding to the weld portion forming region 3A in the cavity 11 in the back side molding main surface 31a of the core mold main body 32.

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

As shown in FIGS. 1 to 3, the lid member 35 is fixed to the core-type 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 storage space recess 34 of the core mold main body 32 and the lid member 35 (that is, the back surface 35b side opposite to the front surface 35a of the lid member 35). The gas storage space 36 is provided.
The lid member 35 functions as a recess cover member that covers the opening that opens in the back molding surface 31 of the storage space recess 34 (recess) and secures the gas storage space 36 in the storage space recess 34. .

The opening of the storage space recess 34 has an end on the back side molding main surface 31a side in the depth direction (vertical direction in FIGS. 1 to 3) of the storage space recess 34 from the end to the inner bottom surface. As compared with the portion (recess main portion) on the 34a side, the recess 34 for the storage space is formed by an extended portion 34b whose sectional dimension perpendicular to the depth direction is expanded.
The lid member 35 has an outer peripheral portion of the back surface 35b abutted on a step between an extended portion 34b (hereinafter also referred to as a recessed extended opening) of the recessed portion 34 for the storage space and the recessed main portion. It is accommodated in the recess expansion opening 34b.
The lid member 35 shown in FIGS. 1 to 3 is specifically formed in a plate shape whose thickness is in a direction perpendicular to the front surface 35a.

Hereinafter, the direction along the front surface 35a of the lid member 35 is also referred to as a surface direction.
The lid member 35 is fixed to the core-type main body 32 by being press-fitted and fitted into the recess expansion opening 34b.
The lid member 35 in FIGS. 1 to 3 uses a non-breathable member such as a metal member.
The lid member 35 is fitted in the recess expansion opening 34b with the side peripheral surface 35c on the outer periphery in the surface direction coming into contact with the inner peripheral surface of the recess expansion opening 34b.

  As shown in FIGS. 4A and 4B, the side peripheral surface 35c of the cover member 35 and the recess expansion opening 34b are provided between the side periphery of the cover member 35 and the inner peripheral surface of the recess expansion opening 34b. A ventilation path 37 that allows gas flow between the gas storage space 36 and the cavity 11 is secured by the minute irregularities on the inner peripheral surface. One end of the air passage 37 is opened in the gas storage space 36, and the other end is opened in the back side molding surface 31 of the core mold 30.

Between the side periphery of the lid member 35 and the inner peripheral surface of the recess expansion opening 34b, the recess is expanded by the minute irregularities on the side peripheral surface 35c of the lid member 35 and the inner peripheral surface of the recess expansion opening 34b. An air passage 37 having a dimension in a direction perpendicular to the inner peripheral surface of the opening 34b of about 0.05 to 0.15 mm is secured.
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 recessed expansion opening 34b, the molten resin 2 supplied to the cavity 11 can enter. Even if it does not occur or the molten resin 2 enters, it is negligible.
The air passage 37 allows gas to flow between the gas storage space 36 and the cavity 11, and restricts intrusion of the molten resin 2 from the cavity 11 into the storage space recess 34.

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

The resin molded product 1 using the injection mold 10 shown in FIG. 1 to FIG. 3 is produced by using the injection molding machine (not shown) connected to the gate of the injection mold 10 in a clamped state to obtain the molten resin 2. 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 mold 10 to mold the resin molded product 1 (FIG. 1). 3). Then, the core mold 30 is separated from the cavity mold 20, the injection mold 10 is opened, and the resin molded product 1 is taken out from the cavity 11.
After the mold opening, the injection mold 10 can be used for manufacturing the resin molded product 1 again in the above procedure by clamping the mold.

The molten resin 2 that has been filled into the cavity 11 is rapidly cooled and solidified to form a resin molded product 1 molded by the inner surface of the cavity 11.
In the present specification, the molten resin 2 that is in the middle of cooling and solidifying after completion of filling into the cavity 11 will be described as a “resin molded product” in addition to the case where the entire molten resin 2 filled in the cavity 11 is solidified. .
The resin molded product 1 is completely solidified before the injection mold 10 is opened, and is taken out from the injection mold 10 by opening the injection mold 10 after completion of the entire solidification.

  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 released gas from the molten resin 2 is injected into the cavity 11 from the injection port 12. As the molten resin 2 fills the end of the resin flow path, the existence range in the cavity 11 is limited (compressed) to the weld portion forming region 3A of the molten resin 2, and the pressure also increases.

  However, in the injection mold 10 shown in FIGS. 1 to 3, the gas in the cavity 11 flows from the cavity 11 to the gas storage space 36 through the air passage 37 as the molten resin 2 is filled into the cavity 11. The gas is pushed out and accommodated in the gas storage space 36. The gas storage space 36 is formed in the cavity 11 in view of the volume of the cavity 11, the amount of gas released from the molten resin 2 in the cavity 11, the resin pressure of the molten resin 2 injected into the cavity 11 from the injection port 12, and the like. It is formed in a size that can accommodate the entire amount of gas.

As shown in FIG. 3, the filling of the molten resin 2 into the cavity 11 is performed by pushing out all the gas in the cavity 11 to the air passage 37 and the gas storage space 36, and the molten resin 11 is welded in the cavity 11. It is possible to fill the entire inside of the cavity 11 with no gap between the part forming region 3A.
For this reason, in the production of the resin molded product 1 using the injection mold 10, the weld portion 3 may not be conspicuous in the resin molded product 1, or the weld portion 3 may not be visually visible. Is possible. Further, in the manufacture of the resin molded product 1 using the injection mold 10, it is possible to prevent unfilling (insufficient filling) of the resin due to the presence of the compressed gas in the weld portion 3.

Further, in the production of the resin molded product 1 using the injection mold 10, the gas in the cavity 11 flows from the cavity 11 through the ventilation path 37 as the molten resin 2 is filled into the cavity 11. By being pushed out and accommodated in the gas storage space 36, it is possible to suppress an increase in gas pressure in the weld portion forming region 3A in the cavity 11. As a result, in the manufacture of the resin molded product 1 using the injection mold 10, the resin caused by the increase in the gas pressure in the weld portion forming region 3A in the cavity 11 as the molten resin 2 is filled into the cavity 11 progresses. It is possible to prevent gas burning.
The gas storage space 36 is formed in the cavity 11 in view of the volume of the cavity 11, the amount of gas released from the molten resin 2 in the cavity 11, the resin pressure of the molten resin 2 injected into the cavity 11 from the injection port 12, and the like. The resin is formed with a volume capable of preventing gas burning of the resin due to an increase in gas pressure in the weld portion forming region 3A in the cavity 11 as the molten resin 2 is filled.

  The injection mold 10 is configured to store the gas in the cavity 11 in the gas storage space 36 in which there is no gas flow path to the inside and outside other than the ventilation path 37, so that the exhaust gas communicated from the cavity to the outside of the mold. There is no need to provide a mouth, and the processing cost of the mold can be kept low. As a result, the injection mold 10 can suppress the occurrence of defects on the resin molding due to poor gas discharge at the weld part and the resin flow terminal at low cost.

In the gas storage space 36, the gas in the cavity 11 is stored in a compressed state.
The molten resin 2 is held at a predetermined pressure when the filling into the cavity 11 is completed. The resin pressure in the cavity 11 decreases due to volume shrinkage accompanying the cooling and solidification of the resin molded product 1 in the cavity 11.

  As the volume of the resin molded product 1 in the cavity 11 shrinks, the gas storage space 36 causes the gas in the gas storage space 36 to pass the resin molded product 1 in the cavity 11 through the air passage 37 due to its internal pressure. It may be formed by adjusting its volume so that it is pressed toward the design surface molding surface 22 and discharged between the resin molded product 1 and the back side molding surface 31. That is, the gas storage space 36 has a gas pressure that allows the gas in the gas storage space 36 to be discharged between the resin molded product 1 and the back side molding surface 31 by the subsequent volume contraction of the resin molded product 1 when the pressure holding is completed. Secure the volume so that it can be secured.

However, the gas pressure to be secured in the gas storage space 36 when the pressure holding is completed so that the gas in the gas storage space 36 can be discharged between the resin molded product 1 and the back side molding surface 31 due to the volume shrinkage of the resin molded product 1. Is lower than the upper limit of the gas pressure capable of preventing gas burning.
Due to the design of the injection mold, the gas in the gas storage space 36 is held in the gas storage space 36 so that the gas in the gas storage space 36 can be discharged between the resin molded product 1 and the back side molding surface 31 by the volume shrinkage of the resin molded product 1. When the gas pressure secured at the time of completion is higher than the gas pressure upper limit value capable of preventing gas burning, priority is given to securing a gas pressure equal to or lower than the upper limit value capable of preventing gas burning in the gas storage space 36.

When a resin molded product is molded with a normal mold, the gas in the mold is finally compressed to nearly zero as the mold resin (molten resin) fills the mold. Is done. For this reason, the gas pressure in the mold rises up to the resin pressure at the maximum.
The supply pressure (resin pressure) of the molten resin injected and supplied into the mold is generally 30 MPa in the case of molding polypropylene. For this reason, the pressure of the gas in the mold may also rise up to a maximum of 30 MPa. On the other hand, when using the metal mold | die of embodiment which concerns on this invention, the compressed gas is stored in gas storage space. For this reason, the effect of the gas storage space disappears only when the volume of the gas storage space is approximately 1/300 or less of the volume of the gas originally present in the weld portion. Expected to reduce pressure. Here, assuming that the area where the gas starts to be compressed in the weld part is 10 cm wide and 5 cm long, and the thickness of the molded product is 2.5 mm, the volume of the gas existing in this space is 12.5 cm ³ . Therefore, if the volume of the gas storage space is 2 cm ³ , the pressure of the gas compressed by the progress of filling the molten resin into the mold does not exceed 7 times the original pressure at the maximum, and the gas storage space The pressure can be greatly reduced.

  The gas discharged from the gas storage space 36 between the resin molded product 1 and the back side molding surface 31 peels the resin molded product 1 from the back side 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 side molding surface 31 of the core die 30 causes the resin molded product 1 in the cavity 11 to move toward the design surface molding surface 22 of the cavity die 20 by the pressure. 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 accurately formed by pressing the cavity mold 20 against the design surface molding surface 22 and further solidifying the formed resin of the resin molded product 1 while maintaining the close contact state. . In addition, by pressing the design surface 1a against the design surface molding surface 22 of the cavity mold 20 and maintaining the close contact state, a line is formed at the boundary between the contact portion and the separation portion on the inner surface of the cavity 11 on the design surface 1a. Occurrence can be prevented.

The injection mold 10 maintains the mold clamping state from the start of filling the molten resin 2 until a preset mold clamping holding time elapses, and opens the mold after the mold clamping holding time has elapsed.
During the mold clamping holding time, gas is discharged from the gas storage space 36 between the resin molded product 1 and the back molding surface 31 of the core mold 30, and after gas is discharged from the gas storage space 36, resin molding is performed. The injection mold 10 is set to open when the product 1 is further cooled.

(Modification)
5 and 6 show a modification of the injection mold.
As shown in FIG. 6, the injection mold is recessed from the second mold molding surface 31 into the second mold 30 </ b> A that opens and closes with respect to the first mold 20, and the first mold of the second mold 30. Along with opening / closing with respect to 20, a second mold recess 41 (storage space recess) is formed which is opened and closed by a hole forming projection 24 protruding from the inner surface of the recess 21 of the first mold 20. It is. Hereinafter, the second mold recess 41 of the injection mold 10A of FIGS. 5 and 6 is also referred to as an opening / closing recess.

  An injection mold 10A shown in FIGS. 5 and 6 is a second mold 30A (hereinafter referred to as “opening / closing recess 41”) formed in the second mold 30 of the injection mold 10 shown in FIGS. A core type). The open / close recess 41 is formed at the center of the second mold molding surface 31 (back side molding surface) of the second mold 30A.

When the second mold 30 is closed to the first mold 20 (in a mold-clamped state), the hole forming projection 24 has a tip surface thereof that is the second mold forming surface 31 (back side molding) of the second mold 30A. The gas storage space 42 is secured in the second mold recess 41 so as to cover the opening that opens to the second mold molding surface 31 of the open / close recess 41.
The front end surface of the hole forming projection 24 is overlapped with the second mold molding surface 31 around the opening / closing recess 41. The portion where the tip end surface of the hole forming protrusion 24 of the second mold molding surface 31 around the opening / closing recess 41 overlaps is also referred to as a protrusion contact portion 31b.

When the injection mold 10A shown in FIGS. 5 and 6 starts filling the cavity 11 with the molten resin 2 in the clamped state shown in FIG. 6, the protrusion abutting portion 31b of the second mold molding surface 31 and The gas in the cavity 11 can be stored by being introduced into the gas storage space 42 in the open / close recess 41 through the air passage 43 secured by the groove formed in one or both of the front end surfaces of the hole forming projection 24. The air passage 43 of FIG. 6 is specifically secured by a groove formed on the tip end surface of the hole forming projection 24.
The groove forming the air passage extends, for example, with a cross-sectional size of about 0.02 to 0.07 mm in depth and about 1 to 3 mm in width. However, in the vent passage 43 formed in the shape of a hole by combining the grooves formed in the protrusion contact portion 31b and the tip end surface of the hole forming protrusion 24, the total depth of the grooves to be combined is It is preferable that it is 0.02-0.07 mm.

The air passage 43 allows gas to flow between the gas storage space 42 and the cavity 11, and restricts the molten resin 2 from entering the gas storage space 42 from the cavity 11.
Further, the cross-sectional size of the groove constituting the air passage 43 allows the gas to flow between the gas storage space 42 and the cavity 11 and restricts the molten resin 2 from entering the gas storage space 42 from the cavity 11. If there is no particular limitation, it can be set as appropriate.

When the second mold 30 is closed to the first mold 20, the gas storage space 42, which is the inner space of the opening / closing recess 41, is communicated with the cavity 11 via the air passage 43 so that gas can flow.
As shown in FIGS. 5 and 6, the air passage 43 of the injection mold 10 </ b> A is provided between the injection port 12 side and the gas storage space 42 from the hole forming protrusion 24 of the cavity 11, and the weld portion of the cavity 11. Each is formed to extend between the formation region 3 </ b> A and the gas storage space 42. The gas storage space 42 communicates with the region on the injection port 12 side from the hole forming projection 24 of the cavity 11 and the weld portion forming region 3 </ b> A of the cavity 11 through the communication path 43.

As shown in FIG. 5, one end of the communication passage 43 extending from the gas storage space 42 to the cavity 11 is a region on the injection port 12 side from the hole forming projection 24 of the cavity 11 and a weld portion forming region 3A of the cavity 11. It is not limited to the one that opens, and one that has one end opened in the middle of each of the resin flow paths on both sides via the hole-forming projection 24 is also formed.
Each communication passage 43 is formed so that the end opposite to the gas storage space 42 is opened and communicated with the cavity 11. A gas storage space 42 in the open / close recess 41 (hereinafter also referred to as an open / close gas storage space) allows gas to flow in from the upstream side (injection port 12 side) of the resin flow path with respect to the weld portion forming region 3A of the cavity 11. It is.

The injection mold 10A shown in FIGS. 5 and 6 is located at a position corresponding to the weld portion forming region 3A of the second mold molding surface 31 (back side molding surface) of the second mold 30A. The storage space recess 34, the lid member 35, and the gas storage space 36 (hereinafter also referred to as a lid back gas storage space) having the same structure as that described in FIG.
However, the recess 34 for the storage space and the lid member 35 of the injection mold 10A shown in FIGS. 5 and 6 are located at a position separated outward from the projecting portion abutting portion 31b of the second mold molding surface 31. Is provided.

By the way, the molten resin 2 injected and introduced into the cavity 11 from the injection port 12 does not necessarily proceed to flow into the weld portion 3 while filling the resin flow path in the cavity 11 without any gap. In some cases, the molten resin 2 flowing in the resin flow path has a part of the flow that is extremely advanced, and the shape of the flow leading portion of the molten resin 2 becomes a very elongated shape along the extending direction of the resin flow path. is there.
In addition, an air passage 43 that connects the open / close gas storage space 42 and the cavity 11 and an air passage 37 that connects the lid back gas storage space 36 and the cavity 11 are injected into the cavity 11. If the molten resin 2 blocks the gas, the molten resin 2 hinders gas inflow from the cavity 11 to the gas storage space.

  For example, the opening on the cavity 11 side of the air passage 37 that connects the lid back gas storage space 36 and the cavity 11 is blocked by the extreme advance of a part of the molten resin 2 that flows in the resin flow path. If this happens, gas storage from the cavity 11 to the lid back gas storage space 36 is not performed. For this reason, the storage of the gas in the cavity 11 from the weld portion formation region 3A into the lid back gas storage space 36 by the subsequent filling of the molten resin 2 in the resin flow path is also performed on the opening of the air passage 37 on the cavity 11 side. It is regulated by the molten resin 2 that closes the surface.

  However, as described above, the injection mold 10A shown in FIGS. 5 and 6 passes through the ventilation path 43 from a plurality of locations on the resin flow path upstream side (injection port 12 side) of the cavity 11 from the weld portion formation region 3A. An open / close gas storage space 42 through which gas can flow is provided. Therefore, the injection mold 10A shown in FIGS. 5 and 6 allows the lid back gas storage space 36 and the cavity 11 to communicate with each other by the extreme advance of the flow of a part of the molten resin 2 flowing in the resin flow path. Even if the opening on the cavity 11 side of the air passage 37 is blocked, the resin flows as the resin flows along the resin flow path 43 through the air passage 43 and the resin unfilled area communicating with the open / close gas storage space 42 is filled with the resin. It is possible to store the gas in the unfilled region by flowing into the open / close gas storage space 42. As a result, in the injection mold 10A shown in FIGS. 5 and 6, the gas stored in the open / close gas storage space 42 can reduce the compression of the gas in the cavity 11 to the weld formation region 3A. Further, the injection mold 10A shown in FIGS. 5 and 6 allows the gas in the resin unfilled region existing in the resin flow path to flow into the open / close gas storage space 42 for storage, thereby not filling the resin in the resin flow path. It is possible to smoothly and reliably fill the region with the resin.

In resin molding using a mold that does not have the storage space recess 34 and the open / close gas storage space 42, the molten resin that has flowed into the cavity and has flowed into both sides of the hole-forming protrusions flows. It flows from the collision part of the front to the outside (cavity outside direction) and inside (hole forming projection). The gas existing between the molten resin and the inner surface of the cavity from the collision point between the flow fronts to the outside can be discharged through the parting surface. On the other hand, the gas existing between the molten resin and the hole-forming projections inward from the collision point between the flow fronts is confined between the molten resin and the hole-forming projections, and the volume is substantially reduced. Is compressed until 0 becomes zero. The pressure of this gas reaches the supply pressure of the molten resin injected and supplied into the cavity.
On the other hand, the injection mold 10 </ b> A according to the embodiment of the present invention has an open / close gas storage space 42 that communicates with the resin flow path in the cavity 11 via the ventilation path 43. Therefore, in the injection mold 10A, the gas in the cavity 11 pressed by the molten resin 2 directed inward from the collision point between the flow fronts of the weld portion forming region 3A is opened and closed in the open / close gas storage space 42 via the vent passage 43. Can be stored inside. In the injection mold 10A, even if the opening on the side of the weld portion forming region 3A of the air passage 37 that connects the lid back gas storage space 36 and the cavity 11 is blocked by the molten resin 2, the weld portion forming region 3A It is possible to store the gas in the cavity 11 pressed by the molten resin 2 inward from the collision point between the flow fronts in the open / close gas storage space 42 via the vent passage 43. As a result, the injection mold 10 </ b> A can suppress the increase in gas pressure as compared with the case where the open / close gas storage space 42 is not provided.

Although the present invention has been described based on the best mode, 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 of FIGS. 1 to 3 includes a lid member 35 and a lid back gas storage space 36 at a position corresponding to the weld portion forming region 3 </ b> A in the cavity 11. However, the lid member and the lid back gas storage space may be provided at a position corresponding to the resin flow path terminal in the cavity in the second mold, for example.
The injection mold can employ a configuration having one or both of the weld portion forming region 3A and the resin flow path terminal in the cavity. The lid member and the gas storage space can be provided in one or more of the weld part forming region 3A and the resin flow path terminal of the cavity.

  The injection mold can adopt a configuration in which one or both of a lid member and a lid back gas storage space and an opening / closing recess are provided in the second mold.

The lid member is made of, for example, 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, and an inner diameter of several microns to several tens that functions as an air passage. A metal member in which a through hole of about a micron is formed (hereinafter also referred to as a through hole forming metal member) can be employed.
The breathable porous material has pores that function as a ventilation path. When using a lid member that has a breathable porous material and has a ventilation path secured by air holes in the breathable porous material, or when a through-hole-forming metal member is used as the lid member, the inside of the opening of the recess for the storage space Either a configuration in which an air passage is secured between the peripheral surface and the lid member, or a configuration in which no air passage is secured between the inner peripheral surface of the opening of the storage space recess and the lid member can be employed.

  DESCRIPTION OF SYMBOLS 1 ... Resin molded product, 1a ... Design surface (of resin molded product), 1b ... Back surface (resin molded product), 2 ... Molten resin, 3 ... Weld part, 3A ... Weld formation area, 10 ... Injection mold , 11 ... cavity, 20 ... first mold (cavity mold), 21 ... recess (recess for molding), 22 ... inner bottom surface (of the recess for molding), 23 ... parting surface, 24 ... recess cover member, hole Projection protrusions 30, 30A ... second mold (core mold), 31 ... second mold molding surface (back side molding surface), 31a ... second mold molding main surface, back side molding main surface, 32 ... first 2 mold main body, core mold main body, 33 ... parting surface, 34 ... second mold recess, storage space recess, 35 ... recess cover member, lid member, 36 ... gas storage space, 37 ... air passage 41 ... second mold recess, storage space recess (open / close recess), 42 ... gas storage space (open / close gas storage space), 3 ... the air passage.

Claims (4)

A first mold in which a concave portion for molding a resin molded product is formed, and the first mold is openable and closable with respect to the first mold, and when the first mold is closed with the first mold A second mold that forms a cavity including the recess therebetween, and a second mold that is part of the inner surface of the cavity of the second mold when the second mold is closed to the first mold A recess cover member that covers an opening of the second mold recess formed to be recessed from the mold molding surface and that opens to the second mold molding surface to secure a gas storage space in the second mold recess. And
The recess cover member protrudes from the inner surface of the recess of the first mold, and forms a hole that comes into contact with the second mold forming surface when the second mold is closed to the first mold. A projection member, or a lid member provided in the opening of the second mold recess,
The gas storage space is formed when the second mold is closed to the first mold by a groove formed on one or both of the hole forming protrusion and the second mold forming surface. A ventilation path secured between the projection for projection and the second mold molding surface, or between the inner peripheral surface of the opening of the second mold recess and the lid member, or through the lid member An injection mold that communicates with the cavity through a vent passage secured in a hole shape. In the injection mold according to claim 1,
The lid member of the second mold is an injection mold provided at a position corresponding to a flow path end or a weld portion in the cavity of the molten resin flowing into the cavity. The injection mold according to claim 1 or 2,
The gas storage space is secured between the lid member and the bottom surface of the second mold recess, and the lid member has a front surface disposed flush with the second mold molding surface. Mold for molding. In the injection mold according to claim 1,
When the second mold is closed to the first mold by a groove formed in one or both of the hole forming protrusion and the second mold forming surface, the hole forming protrusion and the first One or more air passages secured between two mold forming surfaces are for injection molding opened at a position corresponding to a flow path end or weld in the cavity of the molten resin flowing into the cavity. Mold.

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