JP2007144935A - Injection molding method and injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method capable of effectively preventing the occurrence of a strain state such as a sink or the like as the whole of the surface side of a resin molded product, and an injection molding machine. <P>SOLUTION: The injection molding machine 1 has a mold 2 provided with a gas introducing port 4 for introducing the gap between the back molding surface of a cavity 20 and the resin raw material in the cavity 20. A plurality of gas introducing ports 4 is provided along the passing direction L of the resin raw material in the cavity 20. In injection-molding the resin molded product 8, the resin raw material in a molten state is introduced into the cavity 20 from a resin introducing port 23 and, when the cavity 20 is filled with the resin raw material, the introduction of the gas is successively started previously from the gas introducing port 4 provided to the region where the resin raw material is previously charged in the cavity 20 and the resin raw material is successively pressed to the surface side molding surface of the cavity 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an injection molding method and an injection molding apparatus for obtaining a resin molded product by injection molding a resin raw material.

For example, in the method of manufacturing a resin molded product disclosed in Patent Document 1, in the molding of a molded product having a partial thick portion on the back surface side, a device for preventing sink marks on the surface side of the molded product is performed. ing.
That is, in Patent Document 1, an injection port for pressurized fluid is formed on the same side as the back surface side for molding the thick portion in the cavity of the mold for molding the molded product. Further, on the back side of the cavity, a portion corresponding to the base portion of the thick portion is formed of a heat insulating material.

  And by the heat insulating material, the cooling of the resin near the base of the thick-walled portion is delayed from the cooling of the surrounding resin, and the pressure injected between the back side of the molded product and the heat insulating material from the injection port The base of the thick part and the vicinity of the base are pressed from the back side of the cavity to the surface side of the cavity by the fluid so that sink marks do not occur on the surface side of the molded product.

  However, in the conventional injection molding technique, particularly when a large resin molded product or a resin molded product having a long length with respect to thickness or width is molded, a pressurized fluid inlet (gas inlet) is provided. In the case where a plurality of cavities are provided along the resin passage direction, no contrivance has been made to prevent the occurrence of sink marks or the like generated on the surface side of the resin molded product.

  That is, when performing injection molding of the above large or long resin molded product, it takes a certain amount of time (several seconds) for the molten resin to reach the end of the cavity from the resin inlet (resin introduction gate) in the cavity. ) Is required. At this time, as in the conventional case, after the molten resin has reached the end of the cavity, when the gas is introduced into the cavity from the inlet, the surface of the molten resin in contact with the mold near the resin inlet The skin layer (cured portion) formed on the surface is greatly grown, and the effect of preventing the above-described sink marks is reduced.

Japanese Patent No. 3611058

  The present invention has been made in view of such conventional problems, and effectively prevents the occurrence of a strain state such as sink marks (dents formed on the surface) on the entire front surface of the resin molded product. It is an object of the present invention to provide an injection molding method and an injection molding apparatus that can be used.

1st invention uses the shaping | molding die provided with the cavity for filling the resin raw material and obtaining a resin molded product, and the resin inlet which introduce | transduces the said resin raw material in this cavity,
The back side molding surface that molds the back side surface of the resin molded product in the cavity is provided with a plurality of gas introduction ports for introducing gas between the back side molding surface and the resin raw material in the cavity,
When the resin raw material is introduced into the cavity from the resin inlet, and the resin raw material is filled into the cavity, the gas inlet closer to the resin inlet is closer to the resin inlet. Injection characterized in that introduction of the gas is started before a gas inlet at a distant position, and the resin raw material is pressed into a front molding surface for molding the front side surface of the resin molded product in the cavity. It exists in the shaping | molding method (Claim 1).

In the injection molding method of the present invention, a molding die provided with the plurality of gas inlets is used. And it is possible to effectively prevent the occurrence of a strain state such as sink marks on the front side surface of the resin molded product by devising the timing of blowing gas from each gas inlet.
When injection molding a resin molded product, the resin raw material is introduced into the cavity from the resin introduction port.

  And when filling the resin raw material into the cavity, first from the gas inlet (the gas inlet provided in the part where the resin raw material is first filled) located near the resin inlet in the cavity. Then, introduction of gas between the back side molding surface in the cavity and the resin raw material in the cavity is started. Thereby, the resin raw material is pressed against the front side molding surface in the cavity first from the portion where the resin raw material is first filled in the cavity.

Therefore, in the present invention, the skin layer (cured portion of the resin raw material) formed on the surface of the molten resin that contacts the molding surface of the cavity grows first from the portion where the resin raw material is first filled in the cavity. On the other hand, the above-mentioned pressing can be performed first from the resin raw material filled in the part where the skin layer grows first.
Therefore, according to the injection molding method of the present invention, it is possible to effectively prevent the occurrence of a strain state such as sink marks (dents formed on the surface) on the entire front surface of the resin molded product.

The second invention uses a molding die having a cavity for filling a resin raw material to obtain a resin molded product, and a resin inlet for introducing the resin raw material into the cavity.
The back side molding surface for molding the back side surface of the resin molded product in the cavity is provided with one or more gas inlets for introducing gas between the back side molding surface and the resin raw material in the cavity. ,
The resin raw material is introduced into the cavity from the resin inlet, and when the resin raw material flows in the cavity, introduction of the gas from at least one of the gas inlets is started, and the resin In the injection molding method, the raw material is pressed against the front molding surface for molding the front side surface of the resin molded product in the cavity.

In the injection molding method of the present invention, gas introduction is started from at least one gas introduction port when the resin raw material is flowing in the cavity.
Therefore, in the present invention, before the skin layer (cured portion of the resin material) formed on the surface of the molten resin that contacts the molding surface of the cavity grows too much, the resin material is transferred to the front side molding surface in the cavity. Can be pressed.
Therefore, also by the injection molding method of the present invention, it is possible to effectively prevent the occurrence of a strain state such as sink marks (dents formed on the surface) on the entire front surface of the resin molded product.

The third invention has a mold comprising a cavity for filling a resin material to obtain a resin molded product, and a resin inlet for introducing the resin material into the cavity.
The back side molding surface for molding the back side surface of the resin molded product in the cavity is provided with a gas inlet for introducing gas between the back side molding surface and the resin raw material in the cavity. A plurality of introduction ports are provided along the passage direction of the resin raw material in the cavity,
The introduction of the gas through the plurality of gas introduction ports is performed by introducing the resin raw material into the cavity from the resin introduction port, and introducing the gas provided in a portion of the cavity where the resin raw material is first filled. An injection molding apparatus is characterized in that it starts sequentially from the mouth first (Claim 7).

The injection molding apparatus of the present invention has a molding die provided with the plurality of gas introduction ports, and the introduction of the gas through the plurality of gas introduction ports is provided in a portion where the resin raw material is first filled in the cavity. It is configured to start sequentially from the gas inlet.
Thereby, also in this invention, a resin raw material can be pressed to the front side molding surface in a cavity in an order from the site | part with which a resin raw material is first filled in a cavity. And the said press can be performed sequentially from the resin raw material with which the site | part which the said skin layer grows first filled.
Therefore, according to the injection molding apparatus of the present invention, it is possible to effectively prevent the occurrence of a strain state such as sink marks on the entire front side surface of the resin molded product.

A preferred embodiment of the first to third inventions described above will be described.
In the first to third 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, gas introduction through the gas introduction port is sequentially started first from the gas introduction port formed at the site where the resin raw material is first filled in the cavity before the entire resin inside is filled with the resin raw material. can do. This is particularly effective when the size of the resin molded product is relatively large and the filling time of the resin material into the cavity is relatively long.
In addition, the introduction of the gas through the gas introduction port can be started immediately after the resin material is filled up to the formation position of the gas introduction port in the cavity.

In addition, the introduction of gas through the gas inlet can be started simultaneously from any of a plurality of gas inlets. Also in this case, the same effects as described above can be obtained by shifting the timing of starting the gas introduction between any of the plurality of gas inlets and the remaining gas inlets.
In addition, when introducing gas from the plurality of gas inlets, the gas inlet that started gas introduction earlier, when starting the gas introduction from other gas inlets later than this, It is preferable to maintain the gas introduction state. And it is preferable that the state of gas introduction from the plurality of gas inlets continues for a predetermined time after the resin raw material is filled in the entire cavity.

  In the first aspect of the invention, the resin molded product has a plate-like main body portion and a standing wall portion erected from the back side surface of the plate-like main body portion, and the cavity has the plate-like shape. A body part cavity for forming the body part and a wall part cavity for forming the standing wall part. The body part cavity has a closed space which is an area surrounded by the standing wall cavity. A plurality of the gas inlets are provided corresponding to the back-side molding surfaces in the plurality of closed spaces, and the resin raw material is introduced into the cavity from the resin inlet, and the resin raw material is provided. When the gas is provided in the closed space, the gas inlet provided in the closed space at a position closer to the resin inlet is closer to the gas provided in the closed space than the resin inlet. Prior to the introduction port It is preferred to start the introduction of (claim 2).

  In the third aspect of the invention, the resin molded product has a plate-like main body portion and a standing wall portion erected from the back side surface of the plate-like main body portion, and the cavity has the plate-like shape. A body part cavity for forming the body part and a wall part cavity for forming the standing wall part. The body part cavity has a closed space which is an area surrounded by the standing wall cavity. A plurality of gas inlets are provided corresponding to the back-side molding surfaces in the plurality of closed spaces, respectively, and the injection molding method or the injection molding apparatus is provided in the cavity from the resin inlet. When the resin raw material is introduced and the resin raw material is sequentially filled in the closed spaces, the gas is sequentially introduced first from the gas inlet provided in the closed space where the resin raw material is first filled. Can start Masui (claim 8).

  In these cases, a resin molded product in which the standing wall portion is erected from the back side surface of the plate-like main body portion is molded while effectively preventing the occurrence of a strain state such as sink marks on the entire front side surface. be able to. That is, by providing the gas introduction port for each closed space, the resin raw material filled in the cavity for each closed space can be pressed against the front side molding surface in the cavity. Therefore, in the closed space filled with the resin material first, the resin material can be pressed by the gas before the skin layer grows too much, and it is effective that a strain state such as sink occurs. Can be prevented.

  Further, when introducing the gas, the gas introduced between the back side molding surface in the closed space and the resin raw material filled in the closed space from the gas inlet is filled in the standing wall cavity. It is possible to prevent the resin raw material from reaching between the back-side molding surface in the adjacent closed space and the resin raw material filled in the closed space.

In the first aspect of the invention, the introduction of the gas through the gas introduction port may be performed after the resin material is filled in at least one of the closed spaces and before the resin material is filled in the entire cavity. (Claim 3).
In this case, before the skin layer grows too much in the cavity, it becomes easy to press the resin material against the front molding surface in the cavity.

In the second aspect of the invention, the resin molded product has a plate-like main body portion and a standing wall portion erected from the back side surface of the plate-like main body portion, and the cavity is the plate-like main body. A body portion cavity for forming the portion and a standing wall portion cavity for forming the standing wall portion, and the body portion cavity is formed in a part of the body portion cavity by the standing wall portion cavity. A closed space that is an enclosed region is formed, and the gas introduction port is provided corresponding to the back-side molding surface in the closed space, and a resin raw material that flows in the cavity is formed in the closed space. After the filling, it is preferable to start introducing the gas before filling the entire cavity.
Also in this case, before the skin layer grows too much in the cavity, it becomes easy to press the resin material against the front molding surface in the cavity.

In the second aspect of the invention, the resin molded product has a plate-like main body portion and a standing wall portion erected from the back side surface of the plate-like main body portion, and the cavity is the plate-like main body. A main body cavity for forming the portion and a vertical wall cavity for forming the standing wall portion, and the main body cavity includes a plurality of closed spaces that are surrounded by the standing wall cavity. The gas inlet is formed corresponding to the back-side molding surface in the plurality of closed spaces, and after the resin raw material flowing in the cavity fills any of the closed spaces The introduction of the gas can be started before the entire cavity is filled (Claim 6).
Also in this case, before the skin layer grows too much in the cavity, it becomes easy to press the resin material against the front molding surface in the cavity.

In the third aspect of the invention, the introduction of the gas through the gas introduction port may be performed after the resin raw material is filled in the closed space provided with the gas introduction port, and then the resin raw material is placed in the next closed space. It is preferable to start before charging.
In this case, the introduction of gas from the gas inlet can be started each time the resin raw material is filled in each closed space. Thereby, the resin raw material filled in the cavity is pressed into the front side molding surface in the cavity for each closed space, and the resin raw material is pressed with the gas before the skin layer grows too much. It is possible to effectively prevent a distortion state such as sink marks from occurring on the entire side surface.

In the third aspect of the present invention, the introduction of the gas through the gas introduction port is started sequentially from the gas introduction port at a portion where the passage length of the resin raw material from the resin introduction port is short. (Claim 10).
In this case, the gas can be introduced in the order in which the resin raw material passes through each part in the cavity.
Moreover, the site | part or closed space where the said resin raw material is first filled can be made into the site | part or closed space where the passage route length of the said resin raw material from the said resin inlet is short.

  In the first to third aspects of the invention, the introduction of the gas through the gas introduction port can be started immediately after the resin material is filled in the closed space provided with the gas introduction port. In this case, after the resin material is filled in the closed space, the introduction of the gas can be started quickly before the skin layer grows too much in the closed space.

Further, the flow state of the resin raw material in the cavity can be monitored using a sensor provided in the mold. Then, the sensor detects that the resin material is filled in the closed space, and when this is detected, the introduction of gas can be started from the gas inlet provided in the closed space.
In addition, when the time required for the resin raw material to fill each closed space is known under predetermined injection molding conditions, the introduction of the gas from each of the gas inlets is performed as a resin raw material from the resin inlet to the cavity. Can be started after a predetermined time has elapsed.

Embodiments of an injection molding method and an injection molding apparatus according to the present invention will be described below with reference to the drawings.
As shown in FIGS. 1 to 3, the injection molding method and the injection molding apparatus 1 of this example are a molding die provided with a plurality of gas introduction ports 4 for introducing a gas G that presses the resin raw material 80 in the cavity 20. 2 is used. Then, by devising the timing at which the gas G is blown out from each gas inlet 4, it is possible to effectively prevent the occurrence of a strain state such as sink marks on the front side surface 801 of the resin molded product 8.

As shown in FIGS. 2 and 3, the injection molding apparatus 1 of this example includes a cavity 20 for filling a resin raw material 80 to obtain a resin molded product 8, and a resin introduction for introducing the resin raw material 80 into the cavity 20. A mold 2 having a mouth 23 is provided.
The back side molding surface 202 that molds the back side surface 802 of the resin molded product 8 in the cavity 20 is provided with a gas introduction port 4 for introducing the gas G between the back side molding surface 202 and the resin raw material 80 in the cavity 20. is there. A plurality of the gas inlets 4 are provided along the passage direction L of the resin raw material 80 in the cavity 20.

  In molding the resin molded product 8 using the injection molding apparatus 1, a molten resin material 80 is introduced into the cavity 20 from the resin inlet 23 as shown in FIGS. 4 to 9. When the resin raw material 80 is filled into the cavity 20, the gas introduction port 4 located near the resin introduction port 23 has a gas ahead of the gas introduction port 4 located far from the resin introduction port 23. Start introducing G. In this example, the introduction of the gas G is sequentially started first from the gas inlet 4 provided in the cavity 20 where the resin raw material 80 is first filled. Thereby, the resin raw material 80 is sequentially pressed to the front side molding surface 201 for molding the front side surface 801 of the resin molded product 8 in the cavity 20 from the portion where the resin raw material 80 is first filled in the cavity 20.

Hereinafter, the injection molding method and the injection molding apparatus 1 of this example will be described in detail with reference to FIGS.
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. Further, a boss portion 812 for attaching the resin molded product 8 to another component or the like is formed on the back side surface 802 of the plate-like main body portion 81 so as to protrude. The boss 812 has an annular cross section. And the screw hole for screwing the bis | screw arrange | positioned to said other components can be formed in the internal peripheral surface of the boss | hub part 812 in the resin molded product 8 by which injection molding was carried out.

  The standing wall portion 82 of this example includes an outer peripheral standing wall portion 821 erected from the edge of the back side surface 802 of the plate-like main body portion 81 and a partition standing wall portion 822 erected from the back side surface 802 of the plate-like main body portion 81. . The resin molded product 8 of this example is a radiator grill. The partition wall portion 822 of this example is a reinforcing rib that reinforces the resin molded product 8 and is formed orthogonal to the longitudinal direction (left-right direction) W of the radiator grill.

  As shown in FIG. 1, the plate-like main body portion 81 of this example is formed by forming a plurality of main body portion constituting portions 811 that are long in the left-right direction W, and each main-body portion structure at the left and right ends of the plate-like main body portion 81 The part 811 is connected. The outer peripheral standing wall portion 821 of this example is formed on both sides in the vertical direction H of the main body component portion 811, and the partition standing wall portion 822 of the present example Each is formed at a plurality of locations.

As shown in FIGS. 2 and 3, the cavity 20 of this example forms a body portion cavity 21 for forming the plate-like body portion 81, a standing wall portion cavity 22 for forming the standing wall portion 82, and a boss portion 812. And a boss cavity 212. The main body cavity 21 is formed by forming a plurality of closed spaces 3 that are regions surrounded by the standing wall cavity 22.
The main body cavity 21 in this example includes a plurality of cavity constituent parts 211 for molding the main body constituent part 811. Further, the standing wall portion cavity 22 of this example includes an outer peripheral standing wall portion cavity 221 for molding the outer peripheral standing wall portion 821 and a partition standing wall portion cavity 222 for molding the partition standing wall portion 822.

  As shown in FIGS. 2 and 3, the closed space 3 of this example is formed in the body portion cavity 21 as a region surrounded by the outer peripheral standing wall cavity 221 and the partition standing wall cavity 222. A plurality of the closed spaces 3 are formed in the left-right direction W of the cavity 20. The closed space 3 of the present example includes a central closed space 31 positioned at the central portion of the main body cavity 21, end closed spaces 33 positioned at both ends in the left-right direction W of the main body cavity 21, and the central portion It consists of the intermediate part closed space 32 formed between the closed space 31 and the end part closed space 33.

Further, a plurality of central part closed spaces 31 and intermediate part closed spaces 32 are formed on the left and right sides of the main body cavity 21 corresponding to the plurality of cavity constituting parts 211.
Further, a plurality of the boss cavities 212 of this example are formed in each end closed space 33.
Further, the length of the passage route of the resin raw material 80 from the resin introduction port 23 becomes longer in the order of the central portion closed space 31, the intermediate portion closed space 32, and the end portion closed space 33.

  As shown in FIGS. 2 and 3, the resin introduction port 23 of this example is provided in the central portion of the cavity 20, and the resin raw material 80 introduced from the resin introduction port 23 is left and right in the cavity 20 of this example. Branch and fill in direction W. In addition, the resin introduction port 23 of this example is provided in each of the plurality of cavity constituting portions 211, and the flow of the resin raw material 80 introduced into each cavity constituting portion 211 from each resin introduction port 23 is caused by the cavity 20. At the end in the left-right direction W.

The gas inlet 4 is provided on the back side molding surface 202 in each closed space 3. In this example, one gas inlet 4 is formed in each of the central closed space 31 and the intermediate closed space 32, and a plurality of gas inlets 4 are formed in the end closed space 33. .
Each gas inlet 4 forms a gap 43 through which the gas G passes between the gas passage hole 41 formed in the back side molding surface 202 of the cavity 20 and the cylindrical body 42 arranged in the gas passage hole 41. Do it.

  The injection molding apparatus 1 of this example performs injection molding of the resin molded product 8, and the injection pressure of the resin raw material 80 injected into the mold 2 is, for example, 30 to 50 MPa, and is injected into the mold 2. The heating temperature of the resin raw material 80 to be set is, for example, 200 to 250 ° C. The gas G introduced into the cavity 20 from each gas inlet 4 is a high pressure gas of 5 to 15 MPa.

Although not shown in the drawings, each gas inlet 4 is configured to blow out and block the gas G by a valve that opens and closes the flow path of the gas G, respectively. Further, the timing of blowing the gas G from each gas inlet 4 can be controlled by a control means such as a sequencer (programmable controller).
And the control means in the injection molding apparatus 1 is a closed space where the resin raw material 80 is first filled when the resin raw material 80 introduced into the cavity 20 from the resin inlet 23 is sequentially filled in each closed space 3. The introduction of the gas G is started sequentially from the gas inlet 4 formed in FIG. More specifically, the control means of the present example is a resin raw material in order from the closed space 3 close to the resin inlet 23, that is, in the order of the central closed space 31, the intermediate closed space 32, and the end closed space 33, respectively. The gas G is introduced from the gas inlet 4 every time 80 is filled.

Next, the method for molding the resin molded product 8 using the injection molding apparatus 1 will be described in more detail.
In the injection molding of the resin molded product 8, as shown in FIGS. 4 and 5, a molten resin raw material 80 is introduced into each cavity component 211 in the cavity 20 from the plurality of resin introduction ports 23. At this time, the resin raw material 80 flows from the resin inlets 23 toward the left and right of the cavity constituting portions 211.

  As shown in the figure, when the resin raw material 80 is filled in the central part closed space 31 and the standing wall part cavity 22 positioned around the central part closed space 31 in each cavity component 211, that is, the resin raw material When the 80 flow front ends 80A are filled up to the first partition wall cavity 222A, the control means starts introducing the gas G from the gas inlet 4A provided in the central closed space 31.

At this time, while the resin raw material 80 is flowing in the cavity 20, the gas G is injected between the back-side molding surface 202 in the central closed space 31 and the resin raw material 80 in the central closed space 31. This resin raw material 80 is pressed against the front side molding surface 201 in the central space 31.
In addition, the gas G introduced from the gas inlet 4A provided in the central closed space 31 is intermediately adjacent to the central closed space 31 by the resin raw material 80 filled in the first partition wall cavity 222A. Reaching into the partially closed space 32 is prevented.

  Next, as shown in FIG. 6 and FIG. 7, when the resin raw material 80 is filled in the intermediate wall closed space 32 in each cavity component 211 and the standing wall cavity 22 located around the intermediate closed space 32, That is, when the flow front end portion of the resin raw material 80 is filled up to the inside of the second partition wall cavity 222B, the control means starts introducing the gas G from the gas introduction port 4B provided in the intermediate portion closed space 32. .

At this time, while the resin raw material 80 is flowing in the cavity 20, the gas G is injected between the back side molding surface 202 in the intermediate portion closed space 32 and the resin raw material 80 in the intermediate portion closed space 32, This resin raw material 80 is pressed against the front side molding surface 201 in the intermediate portion closed space 32.
The gas G introduced from the gas inlet 4B provided in the intermediate portion closed space 32 is adjacent to the intermediate portion closed space 32 by the resin raw material 80 filled in the second partition wall cavity 222B. Reaching into the partially closed space 33 is prevented.

Next, as shown in FIGS. 8 and 9, when the resin raw material 80 is filled in the end portion closed space 33, the standing wall portion cavity 22 positioned around the end portion closed space 33, and the boss portion cavity 212. That is, when the resin raw material 80 is filled in the entire cavity 20, the control means starts introducing the gas G from the gas inlet 4 </ b> C provided in the end closed space 33.
At this time, the gas G is injected between the back side molding surface 202 in the end portion closed space 33 and the resin raw material 80 in the end portion closed space 33, and the resin raw material 80 becomes the front side molding surface 201 in the end portion closed space 33. Is pressed.

  When the gas G is introduced into the intermediate closed space 32, the state of introducing the gas G into the central closed space 31 is maintained, and when the gas G is introduced into the end closed space 33. The gas G is introduced into the central closed space 31 and the intermediate closed space 32. After the resin material 80 is filled in the entire cavity 20, the resin material 80 in all the closed spaces 3 is pressed against the front side molding surface 201 by the gas G injected from all the gas inlets 4 </ b> A, B, C. The resin raw material 80 is cooled and cured by maintaining the state for a predetermined time, and the resin molded product 8 is molded.

  Thus, in this example, when the resin raw material 80 is filled into the cavity 20, the gas introduction ports 4 </ b> A and B provided in the closed space 3 where the resin raw material 80 is first filled in the cavity 20. First, introduction of the gas G between the back side molding surface 202 in the cavity 20 and the resin raw material 80 in the cavity 20 is started. Thereby, the resin raw material 80 is pressed to the front side molding surface 201 in the cavity 20 in order from the closed space 3 where the resin raw material 80 is first filled in the cavity 20.

Therefore, in this example, the skin layer (cured portion of the resin raw material 80) formed on the surface of the molten resin that contacts the molding surfaces of the cavity 20 (the front-side molding surface 201 and the back-side molding surface 202) is within the cavity 20 While the resin material 80 grows first from the closed space 3 where the resin material 80 is filled first, the pressing can be sequentially performed first from the resin material 80 filled in the closed space 3 where the skin layer grows first.
Then, in the closed space 3 filled with the resin raw material 80, the resin raw material 80 can be pressed by the gas G before the skin layer grows too much, and a strain state such as sink marks is generated. Can be effectively prevented.

  In addition, when the partition wall portion (reinforcing rib) 822 is formed on the back side surface 802 of the resin molded product 8, a strain state such as sink marks is likely to occur on the front side surface 801 corresponding to the formation position of the partition wall portion 822. On the other hand, as described above, before the skin layer in the resin material 80 filled in the cavity 20 grows too much, the resin material 80 in each closed space 3 is sequentially pressed against the front-side molding surface 201. It is possible to effectively prevent the occurrence of a distortion state such as sink marks on the front side surface 801 corresponding to the position where the partition wall portion 822 is formed.

  Therefore, according to this example, it is possible to effectively prevent the occurrence of a strain state such as sink marks (dents formed on the surface) on the entire front side surface 801 of the resin molded product 8. Moreover, the injection molding method and the injection molding apparatus 1 described above are particularly suitable when performing injection molding of a large or long resin molded product 8.

  In addition, the injection molding method and the injection molding apparatus 1 described above can be applied not only to the radiator grill but also to various resin molded products that perform resin injection molding. When performing injection molding of various resin molded products, the same operation as described above is performed by providing a plurality of the gas introduction ports 4 along the passage direction L of the resin raw material 80 in the cavity 20. Thus, the same effect as described above can be obtained.

The perspective view which shows the resin molded product in an Example. The top view which shows the formation state of the cavity in the shaping | molding die of the injection molding apparatus in an Example. The figure which shows the injection molding apparatus in an Example, and is A direction arrow sectional drawing in FIG. The top view which shows the cavity of the state which filled the resin raw material in the center part closed space in an Example, and introduced the gas from the gas inlet provided in the center part closed space. It is a figure which shows the injection molding apparatus in an Example, and is A direction arrow sectional drawing in FIG. The top view which shows the cavity of the state which filled the resin raw material in the intermediate part closed space in the Example, and introduced the gas from the gas inlet provided in the intermediate part closed space. The figure which shows the injection molding apparatus in an Example, and is A direction arrow sectional drawing in FIG. The top view which shows the cavity of the state which filled the resin raw material in the edge part closed space, and introduced the gas from the gas inlet provided in the edge part closed space in an Example. It is a figure which shows the injection molding apparatus in an Example, and is A direction arrow sectional drawing in 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 Body part cavity 22 Standing wall part cavity 23 Resin inlet 3 Closed space 31 Central part closed space 32 Middle part closed space 33 End part closed space 4 Gas inlet 8 Resin molded product 80 Resin raw material 801 Front side 802 Back side 81 Plate-shaped main body 82 Standing wall G Gas

Claims (10)

Using a mold provided with a cavity for filling a resin raw material to obtain a resin molded product, and a resin inlet for introducing the resin raw material into the cavity,
The back side molding surface that molds the back side surface of the resin molded product in the cavity is provided with a plurality of gas introduction ports for introducing gas between the back side molding surface and the resin raw material in the cavity,
When the resin raw material is introduced into the cavity from the resin inlet, and the resin raw material is filled into the cavity, the gas inlet closer to the resin inlet is closer to the resin inlet. Injection characterized in that introduction of the gas is started before a gas inlet at a distant position, and the resin raw material is pressed into a front molding surface for molding the front side surface of the resin molded product in the cavity. Molding method. In Claim 1, the said resin molded product has a plate-shaped main-body part and the standing wall part erected from the back side surface of this plate-shaped main-body part,
The cavity has a main body cavity for molding the plate-shaped main body part, and a vertical wall cavity for molding the vertical wall part,
The body portion cavity is formed by forming a plurality of closed spaces that are regions surrounded by the standing wall portion cavity.
The gas inlets are respectively provided corresponding to the back-side molding surfaces in the plurality of closed spaces,
When the resin raw material is introduced into the cavity from the resin inlet and the resin raw material is filled in the closed spaces, a gas inlet provided in the closed space at a position close to the resin inlet. The injection molding method is characterized in that the introduction of the gas is started before the gas inlet provided in the closed space at a position far from the resin inlet.   3. The gas introduction according to claim 2, wherein the introduction of the gas through the gas introduction port is started after the resin raw material is filled in at least one of the closed spaces and before the resin raw material is filled in the entire cavity. An injection molding method characterized by the above. Using a mold provided with a cavity for filling a resin raw material to obtain a resin molded product, and a resin inlet for introducing the resin raw material into the cavity,
The back side molding surface for molding the back side surface of the resin molded product in the cavity is provided with one or more gas inlets for introducing gas between the back side molding surface and the resin raw material in the cavity. ,
The resin raw material is introduced into the cavity from the resin inlet, and when the resin raw material flows in the cavity, introduction of the gas from at least one of the gas inlets is started, and the resin An injection molding method comprising pressing a raw material onto a front molding surface for molding the front side surface of the resin molded product in the cavity. In claim 4, the resin molded product has a plate-like main body portion and a standing wall portion erected from the back side surface of the plate-like main body portion,
The cavity has a main body cavity for molding the plate-shaped main body part, and a vertical wall cavity for molding the vertical wall part,
The body part cavity is formed in a part of the body part cavity forming a closed space that is an area surrounded by the standing wall cavity,
The gas inlet is provided corresponding to the back-side molding surface in the closed space,
An injection molding method characterized in that the introduction of the gas is started after the resin raw material flowing in the cavity fills the closed space and before the entire cavity is filled. In claim 4, the resin molded product has a plate-like main body portion and a standing wall portion erected from the back side surface of the plate-like main body portion,
The cavity has a main body cavity for molding the plate-shaped main body part, and a vertical wall cavity for molding the vertical wall part,
The body portion cavity is formed by forming a plurality of closed spaces that are regions surrounded by the standing wall portion cavity.
The gas inlets are respectively provided corresponding to the back-side molding surfaces in the plurality of closed spaces,
An injection molding method characterized in that after the resin raw material flowing in the cavity fills any of the closed spaces, the introduction of the gas is started before the entire cavity is filled. A mold having a cavity for filling a resin raw material to obtain a resin molded product, and a resin inlet for introducing the resin raw material into the cavity;
The back side molding surface for molding the back side surface of the resin molded product in the cavity is provided with a gas inlet for introducing gas between the back side molding surface and the resin raw material in the cavity. A plurality of introduction ports are provided along the passage direction of the resin raw material in the cavity,
The introduction of the gas through the plurality of gas introduction ports is performed by introducing the resin raw material into the cavity from the resin introduction port, and introducing the gas provided in a portion of the cavity where the resin raw material is first filled. An injection molding apparatus configured to start sequentially from the mouth. In Claim 7, the said resin molded product has a plate-shaped main-body part and the standing wall part erected from the back side surface of this plate-shaped main-body part,
The cavity has a main body cavity for molding the plate-shaped main body part, and a vertical wall cavity for molding the vertical wall part,
The body portion cavity is formed by forming a plurality of closed spaces that are regions surrounded by the standing wall portion cavity.
The gas inlets are respectively provided corresponding to the back-side molding surfaces in the plurality of closed spaces,
When the resin raw material is introduced into the cavity from the resin inlet, and the resin raw material is sequentially filled in the closed spaces, the gas introduction provided in the closed space where the resin raw material is filled first. An injection molding apparatus characterized in that introduction of the gas is started sequentially from the mouth.   9. The gas introduction through the gas introduction port according to claim 8, wherein the resin raw material is filled in the closed space provided with the gas introduction port, and then the resin raw material is filled in the next closed space. An injection molding apparatus, characterized in that it is configured to start between the two.   In any one of Claims 7-9, introduction | transduction of the said gas by the said gas inlet is carried out sequentially from the said gas inlet in the site | part with a short passage path | route length of the said resin raw material from the said resin inlet. An injection molding device configured to start.

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