JP6652533B2 - Injection mold - Google Patents

Description

  The present invention relates to a mold for injection molding.

Conventionally, in the injection molding of a resin molded product, the air in the cavity or the gas released from the resin injected into the cavity is compressed into the weld portion and the resin flow terminal, and the weld portion and the resin flow terminal stand out. In some cases, defects such as unfilled resin and gas burning occurred.
In order to solve such a problem, for example, there is a countermeasure (for example, Patent Document 1) that inserts a gas-permeable nest at a position corresponding to a weld portion of a mold or a resin flowing terminal to provide an exhaust port communicating outside the mold. Many are adopted.

JP 2000-351136 A

  However, measures to insert a breathable nest at the position corresponding to the weld part of the mold or the resin flow terminal and to provide an exhaust port communicating outside the mold require labor and cost for machining the mold. There was a problem of sticking.

  An object of the present invention is to provide an injection molding die capable of suppressing inexpensive resin molding defects caused by poor gas discharge at a weld portion or a resin flow terminal at low cost.

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 molding a resin molded product is formed, and a first mold that is openable and closable with respect to the first mold. A second mold for forming a cavity including the recess between the first mold and the first mold when the second mold is closed to the first mold; The second mold recess covering the opening of the second mold recess formed in the second mold forming surface, which is a part of the inner surface of the cavity, opening to the second mold molding surface. A recess cover member for securing a gas storage space in the place, wherein the recess cover member protrudes from the inner surface of the recess of the first mold and closes the second mold to the first mold. a pore-forming collision portion is brought into contact with the second mold surface when the said gas storage space, the hole forming projections and the front When the second mold is closed to the first mold by a groove formed on one or both of the second mold molding surfaces, the gap between the hole forming projection and the second mold molding surface is formed. through the vent path to be reserved reserved so as to communicate with the cavity, one or more of the air passage, the position corresponding to the flow path terminal or welds in the cavity of the molten resin flowing into the cavity It is open to.

According to the injection mold according to the aspect of the present invention, the gas in the cavity is compressed as the molten resin fills the cavity between the first mold and the second mold closed together. (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, it is possible to prevent the gas in the cavity from being compressed to the weld portion or the terminal of the resin flow path as the filling of the molten resin into the cavity progresses to a high pressure, thereby causing gas burning of the resin. As a result, according to the mold for injection molding according to the aspect of the present invention, it is possible to prevent defects such as unfilled resin and gas burns in which the weld portion and the resin flow terminal are conspicuous.
The injection mold according to the aspect of the present invention does not require the provision of an exhaust port communicating with the outside of the mold, and the gas in the cavity is provided in the gas storage space where there is no gas flow path to the inside and outside except for the ventilation path. , The processing cost of the mold can be reduced, and the occurrence of defects in resin molding due to poor gas discharge at the weld portion and the resin flow terminal can be suppressed at 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 which flowed into this injection mold from the injection opening, FIG. 3 is a plan sectional view of a second mold side as viewed from a cross section perpendicular to a direction in which a hole forming projection that forms a hole) protrudes from an inner surface of a recess of a first mold. FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and is a diagram illustrating 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 mold-clamped state. . FIG. 2 is a sectional view taken along line BB of FIG. 1. 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 metal mold | die for injection molding of a modified example, Comprising: The 2nd metal mold | die from the cross section perpendicular | vertical to the protrusion direction of the hole forming protrusion which forms the hole of a resin molded product from the recessed part inner surface of the 1st mold It is the plane sectional view which looked at the side. FIG. 7 is a sectional view taken along line CC of FIG. 6.

Hereinafter, an injection mold according to an embodiment of the present invention will be described with reference to the drawings.
FIGS. 1 to 3 are views showing an injection molding die 10 according to one 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 molding die 10. FIG. 5 is a plan sectional view showing a structure of a second mold 30 viewed from a cross section perpendicular to a direction in which a portion 24 protrudes from a recess inner surface 22 of a first mold 20. FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and is a side cross-sectional view showing the vicinity of a weld portion 3 of a molten resin 2 to be filled into a cavity 11 of an injection molding die 10 in a mold-clamped state. 1 is a cross-sectional view taken along line BB of FIG.
1 and 2 show a state in which the cavity 11 is being filled with the molten resin 2. FIG. 3 shows that the cavity 11 has been completely filled with the molten resin 2 and the cavity 11 is formed from the molten resin 2. 1 shows a state in which a molded resin article 1 is present.

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 (a second mold molding surface; hereinafter, 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. , Also referred to as).
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 via 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 design surface forming surface 22 and the back side forming surface 31 are each a 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 (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 metal core body 32 (second mold body).
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 via a gate (not shown) located on the left side of the cavity 11 in FIGS. . 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 which 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 forming area 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 molding die 10 shown in FIGS. 1 to 3 protrudes from the design molding surface 22 of the cavity mold 20, and its tip comes into contact with the back molding surface 31 when the core mold 30 is closed to the cavity mold 30. It has a projection 24 for forming a hole. The hole forming projections 24 form holes (through holes) that penetrate the resin molded product 1 (see FIG. 3) and open on the design surface 1 a and the back surface 1 b of the resin molded product 1.
1 to 3 protrudes from the central part of the design molding surface 22 of the cavity mold 20, and the tip of the projection 24 contacts the central part of the back 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 molding die 10 is secured on the side opposite to the injection port 12 through the hole forming protrusion 24 in the cavity 11. Is set in the space 13 (hereinafter, also referred to as a merge space).

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 Through the part 24, it flows into the confluence space 13 on the side opposite to the injection port 12 from both sides facing the same.
As shown in FIGS. 1 to 3, the weld portion forming region 3 </ b> A is secured and set at a central portion of the merging space 13 in a direction along the rear molding surface 31. The molten resin 2 that has flowed into the joining space 13 from both sides facing each other comes into contact with each other in the weld portion forming region 3A.
In the cavity 11, two resin flow paths which diverge from between the injection port 12 and the hole forming protrusion 24 and reach the weld portion forming region 3 </ b> A of the joining space 13 are secured.

As shown in FIGS. 1 to 3, the core mold body 32 of the core mold 30 has a recess 34 (a second mold recess, hereinafter referred to as a recess for a storage space) recessed from the main back 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 depressed from a position corresponding to the weld portion forming region 3A in the cavity 11 on the back molding main surface 31a of the core mold main 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. The cover member front surface 35a constitutes a part of the back side forming main surface 31.

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 cover member 35 functions as a recess cover member that covers an opening opening on the back side molding surface 31 of the storage space recess 34 (concave) and secures the gas storage space 36 in the storage space recess 34. .

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 side of the back side forming main surface 31 a to the inner bottom surface. The storage space recess 34 is formed by an expanded portion 34b whose cross-sectional dimension perpendicular to the depth direction is larger than that of the portion on the 34a side (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 lid member 35 is press-fitted and fitted into the recess expansion opening 34b 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.
The cover member 35 is fitted into the recess expansion opening 34b by bringing the side peripheral surface 35c of the outer periphery in the surface direction into contact with the inner circumferential surface of the recess expansion opening 34b.

  As shown in FIGS. 4A and 4B, a side peripheral surface 35c of the lid member 35 and a concave extension opening 34b are provided between the periphery of the lid member 35 and the inner peripheral surface of the depression extension opening 34b. The air passage 37 that allows the gas to 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 to the gas storage space 36, and the other end is opened to the back molding surface 31 of the core mold 30.

Between the side circumference of the lid member 35 and the inner peripheral surface of the concave extension opening 34b, the concave expansion is performed by the minute unevenness of the side peripheral surface 35c of the lid member 35 and the internal peripheral surface of the concave expansion opening 34b. The ventilation path 37 whose dimension in the direction perpendicular to the inner peripheral surface of the opening 34b is 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 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 ventilation path 37 permits gas flow between the gas storage space 36 and the cavity 11, and regulates the 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 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 product 1 is completely solidified before 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, gases in the cavity 11 such as air in the cavity 11 and gas released from the molten resin 2 are injected into the cavity 11 from the injection port 12. As the filling of the molten resin 2 at the end of the resin flow path progresses, the existing range in the cavity 11 is limited (compressed) to the weld portion forming region 3A 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. In consideration 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, etc., the gas storage space 36 Is formed in a size that can accommodate the entire amount of the gas.

As shown in FIG. 3, the filling of the molten resin 2 into the cavity 11 is performed by pushing all the gas in the cavity 11 into the ventilation path 37 and the gas storage space 36 by the progress, and the molten resin 11 is welded in the cavity 11. It is possible to fill the entire cavity 11 by spreading to the portion forming region 3A without any gap.
For this reason, in manufacturing the resin molded product 1 using the injection mold 10, it is necessary to make the weld portion 3 inconspicuous in the resin molded product 1 or to make the weld portion 3 invisible in appearance. It is possible. In the production of the resin molded product 1 using the injection molding die 10, it is also possible to prevent the resin from being unfilled (insufficiently filled) due to the presence of the compressed gas in the weld portion 3.

In the manufacture of the resin molded product 1 using the injection mold 10, the gas in the cavity 11 is transferred from the cavity 11 to the gas storage space 36 through the ventilation passage 37 as the filling of the molten resin 2 into the cavity 11 progresses. By being pushed out into the gas storage space 36, the gas pressure in the weld portion formation region 3 </ b> A in the cavity 11 can be suppressed from rising. As a result, in the production of the resin molded product 1 using the injection molding die 10, the resin caused by the increase in the gas pressure in the weld portion forming region 3 </ b> A in the cavity 11 with the progress of filling the molten resin 2 into the cavity 11. It is possible to prevent gas burning.
In consideration 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 gas storage space 36 It is formed while securing a volume capable of preventing gas burning of the resin due to an increase in the gas pressure in the weld portion forming region 3A in the cavity 11 as the filling of the molten resin 2 into the cavity 11 progresses.

  The injection molding die 10 has a configuration in which the gas in the cavity 11 is stored in the gas storage space 36 in which there is no gas flow path to the inside and outside except for the ventilation path 37, so that the exhaust gas communicates from the cavity to the outside of the die. There is no need to provide a port, and the processing cost of the mold can be kept low. As a result, the injection molding die 10 can suppress the occurrence of defects in resin molding due to poor gas discharge at the weld portion and the resin flow terminal at low cost.

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.

  When the volume of the resin molded product 1 in the cavity 11 shrinks, the gas in the gas storage space 36 is compressed by the internal pressure of the resin molded product 1 in the cavity 11 into the cavity mold 20 through the air passage 37. The volume may be adjusted so as to be pressed toward the design surface molding surface 22 and discharged between the resin molded product 1 and the back molding surface 31. That is, when the pressure holding is completed, the gas storage space 36 increases the gas pressure at which the gas in the gas storage space 36 can be discharged between the resin molded product 1 and the back molding surface 31 due to the subsequent volume contraction of the resin molded product 1. Secure enough space to secure it.

However, in order to allow the gas in the gas storage space 36 to be discharged between the resin molded product 1 and the rear molding surface 31 due to the volume shrinkage of the resin molded product 1, the gas pressure secured in the gas storage space 36 at the completion of the pressure holding. Is lower than the upper limit of the gas pressure that can prevent gas burning.
Due to the design of the injection molding die, the gas in the gas storage space 36 can be discharged between the resin molded product 1 and the back molding surface 31 by the volume shrinkage of the resin molded product 1 so that the gas is held in the gas storage space 36. If the gas pressure to be secured at the time of completion is higher than the gas pressure upper limit that can prevent gas burning, priority is given to securing the gas pressure in the gas storage space 36 to be equal to or lower than the upper limit that can prevent gas burning.

When a resin molded product is molded using a normal mold, the gas in the mold is compressed to an infinitely near zero volume as the molding 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 increase to a maximum of 30 MPa. On the other hand, when using the mold of the embodiment according to the present invention, the compressed gas is stored in the gas storage space. For this reason, the effect of the gas storage space is lost only when the volume of the gas storage space is about 1/300 or less of the volume of the gas originally existing in the weld portion. The effect of pressure reduction can be expected. Assuming that the area where the gas starts to be compressed in the weld portion is 10 cm in width, 5 cm in length, and the thickness of the molded product is 2.5 mm, the volume of gas existing in this space is 12.5 cm ³ . For this reason, if the volume of the gas storage space is assumed to be 2 cm ³ , the pressure of the gas compressed by the progress of filling the molten resin into the mold does not exceed at most seven times the original pressure. The pressure can be greatly reduced.

  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 due to 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.

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.

(Modification)
5 and 6 show a modification of the injection mold.
As shown in FIG. 6, the injection mold is depressed from a second mold forming surface 31 in a 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. A second mold recess 41 (storage space recess) 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 with opening and closing of the first mold 20. It is. The second mold recess 41 of the injection mold 10A in FIGS. 5 and 6 is hereinafter also referred to as an opening / closing recess.

  The injection mold 10A shown in FIGS. 5 and 6 has a second mold 30A (hereinafter, referred to as a second mold) having a configuration in which an opening / closing recess 41 is formed in the second mold 30 of the injection mold 10 shown in FIGS. Core type). The opening / closing recess 41 is formed at the center of the second mold forming surface 31 (backside molding surface) of the second mold 30A.

When the second mold 30 is closed to the first mold 20 (mold closed state), the hole forming projection 24 has a tip end surface having a 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 is in contact with the first mold surface 31 and opens in the second mold forming surface 31 of the opening / closing recess 41.
The tip end surface of the hole forming projection 24 is overlapped with the second mold forming surface 31 around the opening / closing recess 41. The portion where the tip surface of the hole forming projection 24 of the second mold forming surface 31 around the opening / closing recess 41 overlaps is hereinafter also referred to as a projection contact portion 31b.

When the injection molding die 10A shown in FIG. 5 and FIG. 6 starts filling the cavity 11 with the molten resin 2 in the mold clamping state shown in FIG. 6, the protrusion contact portion 31b of the second die molding surface 31 and The gas in the cavity 11 can be caused to flow into the gas storage space 42 in the opening / closing recess 41 through the ventilation path 43 secured by a groove formed in one or both of the end faces of the hole forming projection 24 and stored therein. The air passage 43 in 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, the air passage 43 formed by combining the grooves formed in the protrusion contact portion 31b and the tip end surface of the hole forming protrusion 24 with each other has a hole-shaped shape. It is preferably 0.02 to 0.07 mm.

The air passage 43 permits gas flow between the gas storage space 42 and the cavity 11, and regulates the intrusion of the molten resin 2 from the cavity 11 into the gas storage space 42.
Further, the cross-sectional size of the groove constituting the ventilation passage 43 permits gas flow between the gas storage space 42 and the cavity 11 and regulates the intrusion of the molten resin 2 from the cavity 11 into the gas storage space 42. There is no particular limitation so long as 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 space inside the opening / closing recess 41, communicates with the cavity 11 via the ventilation passage 43 so as to allow gas flow.
As shown in FIGS. 5 and 6, the air passage 43 of the injection mold 10 </ b> A is provided between the hole forming projection 24 of the cavity 11 and the injection port 12 side and the gas storage space 42, and the weld portion of the cavity 11. It is formed so as to extend between the formation region 3A and the gas storage space 42, respectively. The gas storage space 42 is communicated 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 3A of the cavity 11 via the communication passage 43.

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

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

By the way, the molten resin 2 injected and flown into the cavity 11 from the injection port 12 does not always proceed to flow to the weld portion 3 while burying the resin flow path in the cavity 11 without gaps. In some cases, the molten resin 2 flowing in the resin flow path has a part of the flow extremely advanced and the shape of the flow leading portion of the molten resin 2 becomes extremely elongated along the extending direction of the resin flow path. is there.
In addition, the ventilation path 43 for communicating the open / close gas storage space 42 and the cavity 11 and the ventilation path 37 for communicating the lid back gas storage space 36 and the cavity 11 have an opening on the cavity 11 side injected into the cavity 11. When the molten resin 2 is closed, the molten resin 2 impedes gas flow from the cavity 11 into the gas storage space.

  For example, due to the extremely advanced flow of a part of the molten resin 2 flowing in the resin flow path, the opening on the cavity 11 side of the ventilation path 37 that connects the back cover gas storage space 36 and the cavity 11 is closed. If this happens, gas storage from the cavity 11 to the gas storage space 36 behind the lid is not performed. Therefore, the gas in the cavity 11 is stored from the weld portion formation region 3A into the gas storage space 36 on the back side of the lid due to the progress of filling of the molten resin 2 in the resin flow path thereafter, and the opening of the ventilation passage 37 on the cavity 11 side. Is regulated by the molten resin 2 that closes off.

  However, as described above, the injection mold 10A of FIGS. 5 and 6 passes through the air passage 43 from a plurality of locations on the resin flow path upstream side (injection port 12 side) of the cavity formation region 3A of the cavity 11. Open / close gas storage space 42 through which gas can flow. For this reason, the injection mold 10A shown in FIGS. 5 and 6 allows the back gas storage space 36 and the cavity 11 to communicate with each other due to the extremely advanced 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 ventilation path 37 is closed, the resin flows along with the progress of filling the molten resin 2 into the resin unfilled area that communicates with the open / close gas storage space 42 via the ventilation path 43 in the resin flow path. The gas in the unfilled area can flow into and be stored in the open / close gas storage space 42. As a result, in the injection mold 10A shown in FIGS. 5 and 6, compression of the gas in the cavity 11 into the weld portion formation region 3A can be reduced by storing the gas in the openable gas storage space 42. In addition, the injection mold 10A shown in FIGS. 5 and 6 allows the gas in the resin unfilled area existing in the resin flow path to flow into the open / close gas storage space 42 to be stored therein, so that the resin not filled in the resin flow path. The resin can be smoothly and reliably filled in the region.

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 wrapped around both sides of the hole forming protrusion in the cavity is subjected to the flow of the resin. The fluid flows outward (from the outside of the cavity) and inward (the projection for forming holes) from the collision point between the fronts. 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 directed inward from the collision point between the flow fronts is confined between the molten resin and the hole-forming projections, and has a substantial volume. Are compressed until 0 is reached. 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 of the embodiment according to the present invention has the openable / closable gas storage space 42 that communicates with the resin flow path in the cavity 11 via the ventilation path 43. For this reason, the injection mold 10 </ b> A transmits the gas in the cavity 11, which is pressed by the molten resin 2 toward the inside from the collision point between the flow fronts in the weld portion forming region 3 </ b> A, via the ventilation passage 43, the open / close gas storage space 42. Can be stored in In the injection molding die 10A, even if the opening on the weld portion forming region 3A side of the ventilation passage 37 that connects the back gas storage space 36 and the cavity 11 is closed by the molten resin 2, the weld portion forming region 3A The gas in the cavity 11 pressed by the molten resin 2 inward from the collision point between the flow fronts can be stored in the openable / closable gas storage space 42 via the ventilation passage 43. As a result, the injection molding die 10A can suppress a rise in gas pressure lower than in the case where there is no opening / closing gas storage space 42.

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 cover member 35 and a back gas storage space 36 at a position corresponding to the weld portion forming region 3A in the cavity 11. However, the cover member and the gas storage space behind the cover may be provided, for example, in a position corresponding to the resin flow path terminal in the cavity in the second mold.
The injection molding die can adopt 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 portion forming region 3A of the cavity and the terminal of the resin flow path.

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

The lid member is made of, for example, a porous material having air permeability (hereinafter, also referred to as a gas-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.

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

Claims (1)

A first mold in which a concave portion for molding a resin molded article is formed, and a first mold which is openable and closable with respect to the first mold and which closes with the first mold. A second mold that forms a cavity including the recess between the second mold and a second mold that is a 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 secures a gas storage space in the second mold recess by covering an opening of the second mold recess formed in the second mold recess surface formed from the mold molding surface. And
The recess cover member is formed with a hole protruding from the inner surface of the recess of the first mold and abutting on the second mold forming surface when the second mold is closed with the first mold. is the use butt section,
The gas storage space forms the hole 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 molding surface. A projecting part and the second mold molding surface are secured so as to communicate with the cavity through a ventilation path secured between the projecting portion and the second mold molding surface ,
One or more of the air passages is an injection molding die in which the molten resin flowing into the cavity is opened at a position corresponding to a flow path end or a weld portion in the cavity .

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