JP2007268821A - Injection molding machine and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine which introduces a gas of sufficient pressure in a sufficient flow rate in a short period of time to press the resin raw material in a cavity, and effectively prevents the occurrence of a strain state such as a sink or the like on the surface side of a resin molded product, and an injection molding method. <P>SOLUTION: The mold 2 of the injection molding machine 1 is constituted of: a cavity 20 in which the resin raw material 80 is charged; and the gas introducing port 21 opened to the back side molding surface 202 of the cavity 20. A valve member 3 for changing the opening area of the gas introducing port 21 is inserted and arranged in the gas introducing port 21. When the valve member 3 is advanced to a closing position, the resin raw material 80 charged in the cavity 20 is prevented from being penetrated in the gas introducing port 21. On the other hand, when the valve member 3 is retracted to an open position 302, the opening area of the gas introducing port 21 is expanded, and the gas G of sufficient pressure is introduced into the gap between the back side molding surface 202 of the cavity 20 and the resin raw material 80 in the cavity 20 in a sufficient flow rate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an injection molding apparatus and an injection molding method for obtaining a resin molded product having excellent surface accuracy by pressing a resin material filled in a cavity with a gas.

In the technology to obtain a resin molded product by injection molding a resin raw material into the mold cavity, a distortion state such as sink (dent formed on the surface) is formed on the design surface of the resin molded product. In order to prevent this, a gas is introduced between the back side molding surface in the cavity and the resin raw material in the cavity, and the resin raw material is pressed (pressurized) to the front side molding surface in the cavity. This stabilizes the appearance and shape of the design surface of the resin molded product.
As a technique for preventing the occurrence of sink marks or the like on the design surface of the resin molded product as described above, for example, there is one disclosed in Patent Document 1.

In the method for preventing sink of a synthetic resin injection molded product of Patent Document 1, a gap for introducing a pressure fluid into a molding die is formed in a core for molding the back side of the synthetic resin injection molded product.
This gap portion forms a cylindrical guide hole at the center of the core and forms a conical valve seat that opens into the mold at the upper end outlet of the guide hole, and a valve rod is inserted into the guide hole. In addition, a valve body is arranged in the valve seat. When the valve stem is retracted from the mold, the valve seat is closed by the valve body, and when the valve rod is advanced into the mold, the valve body is separated from the valve seat, and the valve body and the valve A gap for introducing a pressure fluid into the mold is formed between the seat and the seat. In this way, the molding surface of the synthetic resin molded product is pressed against the surface in the molding die to prevent the occurrence of sink marks.

However, in Patent Document 1, when the valve rod is advanced toward the mold and the valve body is separated from the valve seat, the pressure fluid is introduced into the mold from the gap between the valve body and the valve seat. In addition, the synthetic resin molded product in the mold is pressurized by the valve body.
Therefore, there is a limit to the size (opening area) of the gap formed between the valve body and the valve seat, and it is difficult to introduce a pressure fluid having a sufficient flow rate and pressure in a short time.

JP 50-75247 A

  The present invention has been made in view of such conventional problems, and can introduce a gas having a sufficient flow rate and pressure in a short time to press the resin raw material in the cavity. Furthermore, an object of the present invention is to provide an injection molding apparatus and an injection molding method that can effectively prevent the occurrence of a strain state such as sink marks.

According to a first aspect of the present invention, there is provided a cavity for filling a resin raw material to obtain a resin molded product, a resin inlet for introducing the resin raw material into the cavity, and a back side surface of the resin molded product in the cavity. In an injection molding apparatus provided with a molding die that is formed on a back side molding surface to be molded and formed with a gas inlet for introducing gas between the back side molding surface and the resin raw material in the cavity,
In the gas inlet, a valve member for changing the opening area of the gas inlet is inserted and arranged,
The valve member has a closed position for preventing the resin raw material filled in the cavity from entering the gas inlet, and retreats from the closed position to enlarge the opening area of the gas inlet, The injection molding apparatus is configured to move to an open position for introducing gas between the back-side molding surface and the resin raw material in the cavity (Claim 1).

The injection molding apparatus of the present invention includes a molding die formed with the cavity, the resin inlet, and the gas inlet, and the valve member is inserted into the gas inlet.
When injection molding is performed using the injection molding apparatus of the present invention to obtain a resin molded product, first, the valve member is moved to the closed position. At this time, almost no gap can be formed between the valve member and the gas inlet (the gas inlet can be closed almost completely).

  Further, when the valve member is moved to the closed position, a gap can be formed in which the resin raw material filled in the cavity hardly enters the gas inlet (the opening area of the gas inlet is connected to the gas inlet). The resin material can be reduced to such an extent that the intrusion of the resin raw material can be prevented.)

Then, in a state where the valve member is in the closed position and the resin raw material is prevented from entering the gas inlet through the gap between the valve member and the gas inlet, the resin raw material is introduced into the cavity from the resin inlet. Fill.
Next, after the resin raw material introduced into the cavity reaches the position where the gas inlet is disposed, the valve member is moved backward from the cavity and moved to the open position. At this time, the distance by which the valve member is retracted is not limited, and the opening area of the gas inlet (or the gap amount between the valve member and the gas inlet) can be made sufficiently large.

  Therefore, when introducing the gas from the gas inlet between the back side molding surface in the cavity and the resin raw material in the cavity, a gas having a sufficient flow rate and pressure can be introduced in a short time. Thereby, the resin raw material can be sufficiently pressed against the front side molding surface in the cavity, and it is effective that a strain state such as sink (dent formed on the surface) is generated on the front side surface of the resin molded product. Can be prevented.

  Therefore, according to the injection molding apparatus of the present invention, a gas having a sufficient flow rate and pressure can be introduced in a short time to press the resin raw material in the cavity. It is possible to effectively prevent the occurrence of a strain state such as a dent formed on the surface.

According to a second aspect of the invention, there is provided a cavity for filling a resin raw material to obtain a resin molded product, a resin inlet for introducing the resin raw material into the cavity, and a back side surface of the resin molded product in the cavity. Opening in the back side molding surface to be molded, and having a gas introduction port for introducing gas between the back side molding surface and the resin raw material in the cavity, and in the gas introduction port, the gas introduction port In a method of performing injection molding using a molding die formed by inserting and arranging a valve member that changes the opening area of
A raw material filling step for filling the resin raw material into the cavity from the resin introduction port in a state where the valve member is moved to a closed position where the opening area of the gas introduction port is reduced,
Gas is introduced between the back-side molding surface and the resin raw material in the cavity in a state where the valve member is moved back to the open position where the opening area of the gas introduction port is enlarged by retreating from the cavity. And a pressing step of pressing the resin raw material into the front side molding surface for molding the front side surface of the resin molded product in the cavity (Claim 4).

In the injection molding method of the present invention, using the mold having the cavity, the resin inlet, the gas inlet and the valve member, the raw material filling step and the pressing step are performed to obtain a resin molded product.
When performing the raw material filling step, the valve member is moved to the closed position where the opening area of the gas inlet is reduced. At this time, the gas inlet can be closed not only completely, but also the opening area can be reduced to such an extent that the resin raw material can be prevented from entering the gas inlet.
Then, in a state where the valve member is in the closed position and the resin raw material is prevented from entering the gas inlet through the gap between the valve member and the gas inlet, the resin raw material is introduced into the cavity from the resin inlet. Fill.

  Next, in the pressing step, after the resin raw material introduced into the cavity reaches the position where the gas introduction port is disposed, the valve member is retracted from the cavity to an open position where the opening area of the gas introduction port is expanded. Move. At this time, the distance by which the valve member is retracted is not limited, and the opening area of the gas inlet (or the gap amount between the valve member and the gas inlet) can be made sufficiently large.

  Therefore, when introducing the gas from the gas inlet between the back side molding surface in the cavity and the resin raw material in the cavity, a gas having a sufficient flow rate and pressure can be introduced in a short time. Thereby, the resin raw material can be sufficiently pressed against the front side molding surface in the cavity, and it is effective that a strain state such as sink (dent formed on the surface) is generated on the front side surface of the resin molded product. Can be prevented.

  Therefore, according to the injection molding method of the present invention, a gas having a sufficient flow rate and pressure can be introduced in a short time to press the resin raw material in the cavity. It is possible to effectively prevent the occurrence of a strain state such as a dent formed on the surface.

A preferred embodiment in the first and second inventions described above will be described.
In the first and second inventions, the resin molded product may be a radiator grille, a back garnish, a side molding, a wheel cover, an instrument panel, or the like. The gas injected into the mold can be high pressure gas such as air or nitrogen.

  In addition, the gas inlet has a reduced passage portion in which the cross-sectional area of the gas inlet port is reduced most at a portion on the distal end side that opens to the cavity, and the reduced portion at a portion communicating with the reduced passage portion. The gas passage has an enlarged passage portion in which the cross-sectional area of the gas introduction port is larger than the passage portion, and the valve member has an insertion portion to be inserted into the reduced passage portion and moves to the closed position. The insertion portion is inserted into the reduced passage portion to reduce the opening area of the gas introduction port, and when moved to the open position, the insertion portion is disposed in the enlarged passage portion, and It is preferable that the opening area of the gas inlet is enlarged (claims 2 and 5).

In this case, it is easy to change the opening area of the gas inlet by moving the valve member to the closed position and the open position.
That is, when the valve member is advanced to the cavity and moved to the closed position, the insertion portion can be inserted into the reduction passage portion to easily reduce the opening area of the gas introduction port. On the other hand, when the valve member is retracted from the cavity and moved to the open position, the insertion portion can be extracted from the reduction passage portion and disposed in the enlargement passage portion, so that the opening area of the gas inlet can be sufficiently enlarged. .

Further, the reduction passage portion in the gas introduction port has a taper shape that enlarges the cross-sectional area of the gas introduction port as the distance from the cavity increases, and the insertion portion in the valve member has the taper shape. It is preferable to have a taper shape facing the reduced passage portion.
In this case, when the valve member is moved from the closed position to the open position, the opening area of the gas inlet can be quickly expanded. Therefore, when the valve member is moved to the open position, the resin material in the cavity can be pressed with a gas having a sufficient flow rate and pressure in a shorter time.

Hereinafter, embodiments of an injection molding apparatus and an injection molding method according to the present invention will be described with reference to the drawings.
Example 1
As shown in FIGS. 1 and 2, the injection molding apparatus 1 of this example includes a molding die 2 in which a cavity 20 for filling a resin raw material 80 to obtain a resin molded product 8 is formed. The mold 2 is formed with a resin inlet 22 that opens into the cavity 20 and introduces the resin raw material 80 into the cavity 20. As shown in FIGS. 2 to 6, the molding die 2 has an opening in the back side molding surface 202 for molding the back side surface 802 of the resin molded product 8 in the cavity 20. A gas inlet 21 for introducing the gas G is formed between the resin raw material 80 and the resin raw material 80.

A valve member 3 for changing the opening area of the gas inlet 21 is inserted and disposed in the gas inlet 21. 2 to 4, the valve member 3 is advanced to the cavity 20 to close the gas inlet 21 and closes the gas inlet 21 as shown in FIGS. 5 and 6. 21 is configured to move to an open position 302 for opening 21.
As shown in FIGS. 3 and 4, the valve member 3 is configured to prevent the resin raw material 80 filled in the cavity 20 from entering the gas inlet 21 when moved to the closed position 301. is there. Further, as shown in FIGS. 5 and 6, when the valve member 3 moves to the open position 302, the opening area of the gas introduction port 21 is enlarged more than when the valve member 3 is located at the closed position 301, and the back side molding surface in the cavity 20. A gas G having a sufficient flow rate and pressure is introduced between 202 and the resin raw material 80 in the cavity 20.

Below, it demonstrates in full detail with FIGS. 1-6 about the injection molding apparatus 1 and the injection molding method of this example.
In the injection molding apparatus 1 of this example, in order to sufficiently press the resin raw material 80 in the cavity 20 by introducing the gas G having a sufficient flow rate and pressure into the cavity 20 in a short time, the valve member 3 is used. Is devised to sufficiently increase the opening area of the gas inlet 21 when the is moved to the open position 302.

As shown in FIGS. 4 and 6, the gas introduction port 21 of the present example has a reduced passage portion 211 in which the cross-sectional area of the gas introduction port 21 is reduced most at the tip side opening to the cavity 20, A portion communicating with the reduced passage portion 211 has an enlarged passage portion 212 in which the cross-sectional area of the gas inlet 21 is larger than that of the reduced passage portion 211. Further, the valve member 3 of this example is formed by forming an insertion portion 32 to be inserted into the reduction passage portion 211 at the distal end portion of the rod 31.
Further, the gas inlet 21 and the valve member 3 of this example have a circular cross section.

The enlarged passage portion 212 in this example is formed by expanding the diameter of the reduced passage portion 211.
Further, the reduced passage portion 211 of the present example has a tapered shape that is enlarged in diameter as it moves away from the cavity 20. Moreover, the insertion part 32 in the valve member 3 has a taper shape facing the taper-shaped reduction passage part 211.

  As shown in FIG. 4, the valve member 3 is configured to insert the insertion portion 32 into the reduction passage portion 211 and close the gas introduction port 21 when advanced to the closed position 301. Further, as shown in FIG. 6, when the valve member 3 is retracted to the open position 302, the insertion portion 32 is disposed in the enlarged passage portion 212, and the entire reduced passage portion 211 is opened to the cavity 20. The gas inlet 21 is configured to open.

  As shown in FIG. 4, the front end surface of the valve member 3 in the closed position 301 can be slightly protruded into the cavity 20 from the back side molding surface 202. In addition, the front end surface of the valve member 3 in the closed position 301 can form substantially the same surface as the back side molding surface 202 in the cavity 20. In addition, as shown in FIG. 7, the reduction | decrease channel | path part 211 can also be formed in a straight shape.

As shown in FIG. 4, the gap S between the valve member 3 and the gas inlet 21 at the closed position 301 can be set to 0 to 50 μm. Further, the opening area A1 of the gas inlet 21 when the valve member 3 is in the closed position 301 can be set to 0 to 0.1 mm ² .
On the other hand, as shown in FIG. 6, the opening area A2 of the gas inlet 21 when the valve member 3 is at the open position 302 can be set to 3 to 120 mm ² . In this example, the opening area A2 of the gas introduction port 21 when the valve member 3 is in the open position 302 is the cross-sectional area of the reduced passage portion 211 in the gas introduction port 21.
Further, when the valve member 3 is set to the open position 302, the cross-sectional area of the gap formed between the enlarged passage portion 212 and the gas inlet 21 can be made larger than the cross-sectional area of the reduced passage portion 211. .

The gas inlet 21 is connected to a pressure accumulation tank (not shown) for accumulating nitrogen gas. This pressure accumulation tank has a sufficient capacity so that almost no pressure drop occurs at the gas inlet 21 when the gas G is introduced into the cavity 20. The pressure in the pressure accumulating tank can be, for example, 3 to 30 MPa, and the capacity of the pressure accumulating tank can be, for example, 0.5 to 10 L. Moreover, the piping connecting the gas inlet 21 and the pressure accumulating tank has a sufficient cross-sectional area so that almost no pressure drop occurs.
A pressure regulator can be provided in the piping between the pressure accumulation tank and the gas inlet 21. In this case, the pressure of the gas G introduced into the cavity 20 can be maintained at the pressure set by the pressure regulator.

As shown in FIG. 1, the resin molded product 8 to be molded in this example includes a plate-like main body portion 81 and a standing wall portion 82 erected from the back side surface 802 of the plate-like main body portion 81. The standing wall portion 82 in this example is formed on the outer edge portion and the intermediate portion of the back side surface 802 of the plate-like main body portion 81.
As shown in FIG. 2, the cavity 20 includes a body cavity 23 for molding the plate-like body 81 and a standing wall cavity 24 for molding the standing wall 82. The periphery of the back-side molding surface 202 in the main body cavity 23 for introducing the gas G from the gas inlet 21 is surrounded by the standing wall cavity 24.

  Moreover, the injection molding apparatus 1 of this example performs injection molding of a thermoplastic resin, and the injection pressure of the resin raw material 80 introduced into the cavity 20 is, for example, 30 to 50 MPa and is introduced into the cavity 20. The heating temperature of the resin raw material 80 is, for example, 200 to 250 ° C. Moreover, the pressure of the gas G introduced into the cavity 20 from the gas introduction port 21 shall be 3-30 Mpa, for example. The gas G in this example was nitrogen gas.

  In addition, although illustration is abbreviate | omitted, the valve member 3 can move to the closed position 301 which closes the gas introduction port 21, and the open position 302 which opens the gas introduction port 21 with actuators, such as a cylinder, a solenoid, and a motor. The movement operation of the valve member 3 can be controlled by a control means such as a sequencer (programmable controller).

Next, a method for molding the resin molded product 8 using the injection molding apparatus 1 will be described, and the effects of the injection molding apparatus 1 and the injection molding method will be described.
In the injection molding method of this example, the following raw material filling step and pressing step are performed to obtain a resin molded product 8.

When performing the raw material filling step, as shown in FIG. 2, the valve member 3 is moved to the closed position 301 that has been advanced to the cavity 20. At this time, the insertion portion 32 in the valve member 3 is inserted into the reduction passage portion 211 in the gas introduction port 21. At this time, the gas inlet 21 does not need to be completely closed, and the opening area can be reduced to such an extent that the resin raw material 80 can be prevented from entering the gas inlet 21.
As shown in FIGS. 3 and 4, the valve member 3 is in the closed position 301, and the resin raw material 80 enters the gas introduction port 21 from the gap between the valve member 3 and the gas introduction port 21. The resin raw material 80 heated and melted is filled into the cavity 20 from the resin introduction port 22 in a state where the above is prevented.

  Next, in the pressing step, as shown in FIGS. 5 and 6, after the resin raw material 80 introduced into the cavity 20 reaches the position where the gas introduction port 21 is disposed, the valve member 3 is retracted from the cavity 20. Then, the gas inlet 21 is moved to the open position 302 where the opening area of the gas inlet 21 is enlarged. At this time, the insertion portion 32 in the valve member 3 is extracted from the reduced passage portion 211 and disposed in the enlarged passage portion 212, whereby the entire reduced passage portion 211 is opened.

Then, the gas G is introduced from the gas inlet 21 into the cavity 20. At this time, the portion of the resin raw material 80 that faces the back-side molding surface 202 has started to cure and forms a skin layer. For this reason, the gas G introduced from the gas introduction port 21 does not enter the inside of the resin raw material 80 in the cavity 20 and stays between the back-side molding surface 202 and the skin layer of the resin raw material 80 facing it.
Thus, the resin raw material 80 filled in the cavity 20 can be cooled and solidified to mold the resin molded product 8.

  When the valve member 3 is moved to the open position 302, the distance by which the valve member 3 is retracted is not limited, and the opening area of the gas inlet 21 (the amount of gap between the valve member 3 and the gas inlet 21) is set. Can be large enough. In this example, the opening area of the gas inlet 21 can be opened with the same size as the cross-sectional area of the reduced passage portion 211, and can be made sufficiently large.

  Therefore, when the gas G is introduced from the gas inlet 21 between the back-side molding surface 202 in the cavity 20 and the resin raw material 80 in the cavity 20, the gas G having a sufficient flow rate and pressure is introduced in a short time. can do. Thereby, the resin raw material 80 can fully be pressed to the front side molding surface 201 in the cavity 20, and the front side surface (design surface) 801 of the resin molded product 8 is distorted such as sink marks (dents formed on the surface). It is possible to effectively prevent the state from occurring.

  Moreover, in the said press process, it is preferable to perform quickly the timing which introduce | transduces the gas G from the gas inlet 21 into the cavity 20 after the completion of a raw material filling process. On the other hand, if the portion of the resin raw material 80 facing the back-side molding surface 202 is uncured, the gas G introduced into the cavity 20 enters the inside of the resin raw material 80, and the pressing effect by the pressing step is increased. There is a possibility that it cannot be obtained.

Therefore, the introduction of the gas G is after the part of the resin raw material 80 facing the back side molding surface 202 begins to harden and the skin layer is formed, and as soon as possible after the raw material filling process is completed (within 0.5 seconds). Preferably it is done. On the other hand, when the introduction of the gas G is started after 0.5 seconds have elapsed after completion of the filling step, the skin layer is solidified, and the pressing effect by the pressing step may not be obtained.
Therefore, in order to introduce the gas G having a sufficient flow rate and pressure within a short time of 0.5 seconds or less, the injection molding apparatus 1 and the injection molding method using the gas inlet 21 and the valve member 3 of this example are employed. It is most effective to do.

Moreover, in this example, the influence which the difference in the introduction timing of the said gas G has on the sink (the dent formed in the surface) which arises on the surface of the rib (the said standing wall part 82) of the resin molded product 8 was investigated.
The size of sink marks (the amount of dents) when the timing of introducing the gas G of 5 MPa into the cavity 20 is changed between 0.1 and 2 seconds after the filling of the resin raw material 80 into the cavity 20 is completed. The result of measuring is shown in FIG.

In the figure, the horizontal axis indicates the time (rise time) (seconds) until the introduction of the gas G after the filling of the resin raw material 80 into the cavity 20 is started and the pressure of the gas G in the cavity 20 becomes 5 MPa. The vertical axis indicates the size (μm) of rib sink marks. And it turned out that the relationship between the rise time and the size of rib sink marks is almost proportional.
Then, it was found that when the target value of sink marks (allowable sink size) is 2 μm or less, the rise time needs to be at least 0.5 seconds or less. Further, it was found that the rise time is more preferably 0.2 seconds or less in order to set the sink value to 2 μm or less.

With respect to the measurement result, according to the configuration of this example (configuration using the gas inlet 21 and the valve member 3), the rise time can be easily reduced to about 0.2 seconds, and the sink target can be set. It was found that it can be easily achieved (the target value of sink marks can be 2 μm or less).
On the other hand, in the conventional configuration (the configuration in which the gas G is introduced into the cavity 20 through a narrow gap that does not use the valve member 3 and can prevent the resin raw material 80 from entering), the rise time is less than 0.6 seconds. It was difficult to do and found to be difficult to achieve sink marks.

  Therefore, according to the injection molding apparatus 1 and the injection molding method of this example, the gas G having a sufficient flow rate and pressure can be introduced in a short time, and the resin raw material 80 in the cavity 20 can be pressed. It is possible to effectively prevent the occurrence of a strain state such as sink marks (dents formed on the surface) on the front side surface 801 of the product 8.

(Example 2)
In this example, as shown in FIGS. 9 to 14, a plurality of gas inlets 21 </ b> A to 21 </ b> C are formed on the back side molding surface 202 in the cavity 20 </ b> Z of the mold 2 </ b> Z, and the gas is introduced into the cavity 20 </ b> Z from each gas inlet 21 </ b> A to C. This is an example in which the order of introducing G is devised.
The resin molded product 8Z of this example is a radiator grille as shown in FIGS. The main body cavity 23 in this example is formed by forming a plurality of closed spaces 4 that are regions surrounded by the standing wall cavity 24. Further, the plurality of closed spaces 4 are formed as a first closed space 4A, a second closed space 4B, and a third closed space 4C in the order closer to the resin inlet 22.

Further, as shown in FIG. 10, the resin introduction port 22 of this example is provided in the central portion of the cavity 20Z, and in the cavity 20Z of this example, the resin raw material 80 introduced from the resin introduction port 22 is arranged in the left-right direction W. Branch and fill.
As shown in FIG. 11, the gas inlet 21 of this example is provided on the back side molding surface 202 in each closed space 4, and the first gas inlet 21A and the second closed space 4B provided in the first closed space 4A. The second gas inlet 21B provided in the third closed space 4C and the third gas inlet 21C provided in the third closed space 4C are formed.
The first valve member 3A is inserted into the first gas introduction port 21A, the second valve member 3B is inserted into the second gas introduction port 21B, and the third gas introduction port 21C. The third valve member 3C is inserted and arranged.

In this example, the pressing step is started when the raw material filling step is performed. In this pressing step, the introduction of the gas G is started first from the gas inlet 21 provided in the closed space 4 where the resin raw material 80 is first filled in the cavity 20Z.
Specifically, first, before starting the injection molding, the valve members 3A to 3C are moved to the closed position 301 as shown in FIG. Then, as a raw material filling step, as shown in FIG. 12, filling of the resin raw material 80 from the resin inlet 22 into the cavity 20Z is started, and the resin raw material 80 flowing in the cavity 20Z fills the first closed space 4A. Sometimes, the first valve member 3A is retracted from the closed position and moved to the open position.

  At this time, the gas G is introduced from the first gas introduction port 21A between the back-side molding surface 202 in the first closed space 4A and the resin raw material 80 in the first closed space 4A. Thereby, the resin raw material 80 in the 1st closed space 4A can be pressed to the front side molding surface 201 in the 1st closed space 4A.

Next, as shown in FIG. 13, when the resin raw material 80 flowing in the cavity 20Z fills the second closed space 4B, the second valve member 3B is retracted from the closed position and moved to the open position.
At this time, the gas G is introduced from the second gas introduction port 21B between the back-side molding surface 202 in the second closed space 4B and the resin raw material 80 in the second closed space 4B. Thereby, the resin raw material 80 in the 2nd closed space 4B can be pressed to the front side molding surface 201 in the 2nd closed space 4B.

Next, as shown in FIG. 14, when the resin raw material 80 flowing in the cavity 20Z fills the third closed space 4C, the third valve member 3C is retracted from the closed position and moved to the open position.
At this time, the gas G is introduced from the third gas introduction port 21C between the back-side molding surface 202 in the third closed space 4C and the resin raw material 80 in the third closed space 4C. Thereby, the resin raw material 80 in the 3rd closed space 4C can be pressed to the front side molding surface 201 in the 3rd closed space 4C.

Thus, the resin raw material 80 filled in the cavity 20Z can be cooled and solidified to mold the resin molded product 8Z.
The pressing of the resin material 80 by the gas G introduced into the first closed space 4A and the gas introduced into the third closed space 4C until the pressing of the resin material 80 by the gas G introduced into the third closed space 4C is completed. The pressing of the resin raw material 80 by G can be continued.

In this example, in the cavity 20Z, the resin material 80 is filled first (first closed space 4A) in order, that is, the skin layer (cured portion of the resin raw material 80) is formed first. The resin raw material 80 can be sequentially pressed. Therefore, it is possible to effectively prevent the occurrence of a strain state such as sink marks on the entire front side surface 801 of the resin molded product 8Z.
Also in this example, other configurations are the same as those of the first embodiment, and the same effects as those of the first embodiment can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective explanatory view showing a resin molded product and a cavity of a molding die corresponding to the resin molded product in Example 1. Sectional explanatory drawing which shows the injection molding apparatus in Example 1. FIG. Sectional explanatory drawing which shows the injection molding apparatus of the state which filled the resin raw material in the cavity in Example 1. FIG. Sectional explanatory drawing which expands and shows the periphery of the valve member in a closed position in Example 1. FIG. Sectional explanatory drawing which shows the injection molding apparatus in the state which introduce | transduced the gas in the cavity in Example 1. FIG. Sectional explanatory drawing which expands and shows the periphery of the valve member in an open position in Example 1. FIG. Sectional explanatory drawing which expands and shows the periphery of the other gas introduction port and valve member in Example 1. FIG. In Example 1, the horizontal axis represents the rise time (seconds) of the gas pressure (5 MPa) in the cavity, and the vertical axis represents the size of rib sink marks (μm), showing the relationship between the two. The perspective explanatory drawing which shows the resin molding in Example 2, and the cavity of the shaping | molding die corresponding to this. FIG. 6 is an explanatory plan view showing a cavity of a molding die in Example 2. Sectional explanatory drawing which shows the injection molding apparatus in Example 2. FIG. Sectional explanatory drawing which shows the injection molding apparatus in the state which introduce | transduces gas in a cavity from the 1st valve member in Example 2. FIG. Sectional explanatory drawing which shows the injection molding apparatus in the state which introduce | transduces gas in the cavity from the 2nd valve member in Example 2. FIG. Sectional explanatory drawing which shows the injection molding apparatus in the state which introduces gas in the cavity from the 3rd valve member in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 2 Mold 20 Cavity 201 Front side molding surface 202 Back side molding surface 21 Gas introduction port 211 Reduction passage part 212 Expansion passage part 22 Resin introduction port 3 Valve member 301 Closed position 302 Open position 32 Insertion part 8 Resin molded product 80 Resin raw material 801 Front side 802 Back side G Gas

Claims (6)

A cavity for filling a resin raw material to obtain a resin molded product, a resin inlet for introducing the resin raw material into the cavity, and a back side molding surface for molding the back side surface of the resin molded product in the cavity In an injection molding apparatus provided with a molding die that is opened and forms a gas inlet for introducing gas between the back-side molding surface and the resin raw material in the cavity,
In the gas inlet, a valve member for changing the opening area of the gas inlet is inserted and arranged,
The valve member has a closed position for preventing the resin raw material filled in the cavity from entering the gas inlet, and retreats from the closed position to enlarge the opening area of the gas inlet, An injection molding apparatus configured to move to an open position for introducing gas between the back side molding surface and the resin raw material in the cavity. The gas introduction port according to claim 1, wherein the gas introduction port has a reduced passage portion in which a cross-sectional area of the gas introduction port is reduced most at a portion on a distal end side that opens to the cavity, and a portion that communicates with the reduced passage portion. , And has an enlarged passage portion in which the cross-sectional area of the gas inlet is enlarged more than the reduced passage portion,
The valve member has an insertion portion that is inserted into the reduction passage portion, and when the valve member moves to the closed position, the insertion portion is inserted into the reduction passage portion so that an opening area of the gas introduction port is increased. An injection molding apparatus, wherein the insertion portion is arranged in the enlarged passage portion to enlarge the opening area of the gas introduction port when being reduced and moved to the open position. In Claim 1 or 2, the reduced passage portion in the gas inlet has a tapered shape that increases the cross-sectional area of the gas inlet as the distance from the cavity increases.
The injection molding device according to claim 1, wherein the insertion portion of the valve member has a tapered shape facing the tapered reduced passage portion. A cavity for filling a resin raw material to obtain a resin molded product, a resin inlet for introducing the resin raw material into the cavity, and a back side molding surface for molding the back side surface of the resin molded product in the cavity A gas inlet for introducing gas between the back-side molding surface and the resin raw material in the cavity, and changing the opening area of the gas inlet in the gas inlet In a method of performing injection molding using a mold formed by inserting and arranging a valve member,
A raw material filling step for filling the resin raw material into the cavity from the resin introduction port in a state where the valve member is moved to a closed position where the opening area of the gas introduction port is reduced,
Gas is introduced between the back-side molding surface and the resin raw material in the cavity in a state where the valve member is moved back to the open position where the opening area of the gas introduction port is enlarged by retreating from the cavity. And a pressing step of pressing the resin raw material on the front molding surface for molding the front side surface of the resin molded product in the cavity. 5. The gas introduction port according to claim 4, wherein the gas introduction port has a reduced passage portion in which a cross-sectional area of the gas introduction port is reduced most at a portion on a distal end side that opens to the cavity, and a portion that communicates with the reduced passage portion. , And has an enlarged passage portion in which the cross-sectional area of the gas inlet is enlarged more than the reduced passage portion,
The valve member has an insertion portion that is inserted into the reduction passage portion, and when the valve member moves to the closed position, the insertion portion is inserted into the reduction passage portion so that an opening area of the gas introduction port is increased. An injection molding method, wherein the insertion portion is arranged in the enlarged passage portion to enlarge the opening area of the gas introduction port when it is reduced and moved to the open position. In claim 4 or 5, the reduced passage portion in the gas inlet has a tapered shape that increases the cross-sectional area of the gas inlet as the distance from the cavity increases.
The injection molding method, wherein the insertion portion of the valve member has a tapered shape facing the tapered reduced passage portion.

Images