JPH10146872A - Injection molding method using gas in combination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a fault of the external appearance of a molded article by a method wherein resin is filled in a mold wherein a closed section being adjacent to thick-wall ribs or containing them is formed by the thick-wall ribs provided on a side wall part and by a connecting rib provided on a base part and pressurized gas is injected between the resin and the mold. SOLUTION: A molded article 1 has a base part 6 and a side wall part 5 and also thick-wall ribs 2a and 2b provided on the side wall part 5 and connected by a connecting rib 4, and a closed section 7 is formed by the side wall part 5, the thick-wall ribs 2a and 2b and the connecting rib 4. In this case, the molded article is formed in a shape wherein the closed section 7 is made to abut on the thick-wall ribs 2a and 2b, with the thick-wall ribs 2a and 2b used as members constituting the closed section 7, or wherein the thick-wall ribs are surrounded by the closed section constituting members. In a mold therefor, a gas injection hole 8 is provided at an arbitrary position inside the closed section 7 and pressurized gas is injected between resin and the mold after the resin is filled. As the result, the other face of the molded article is pressed against a cavity face and thereby a sink mark and also nonuniformity in gloss are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method, and more particularly, to a combined gas injection molding method involving pressurized gas injection between a resin injected into a cavity and a cavity surface.

[0002]

2. Description of the Related Art In injection molding, when molding a relatively thick molded product or a molded product having a partially thick portion, the surface of the molded product is called sink mark due to shrinkage of the resin due to cooling. It is widely known to produce depressions.

Conventionally, the most common method for preventing sinking is to increase the injection pressure, extend the injection time, and cool the resin in the cavity to some extent while applying the supply pressure of the molten resin (resin pressurization method). Are known.

However, as described in Japanese Patent Application Laid-Open No. 50-75247, the prevention of sink by the above-mentioned resin pressurization method depends on the molding conditions depending on the thickness of the molded article and the like.
The molding operation becomes complicated, and sufficient shrinkage cannot be prevented unless a high resin pressure is applied. Therefore, burrs are generated on the parting surface, and the work load for removing the burrs increases. In addition, when an excessive resin pressure is applied, there is a problem in dimensional accuracy such that warpage occurs in a molded product. Furthermore, in the resin pressurization method, pressure is easily transmitted to a thick portion near the gate, but pressure is not sufficiently applied to a thick portion away from the gate portion, and depending on the position of the thick portion, the pressure is not completely increased. For example, the sink cannot be eliminated.

In Japanese Patent Laid-Open Publication No. 50-75247, after injecting a molten resin into a cavity, one side of the molded product is pushed up with a valve body, and one side of the molded product and one side of the molded product are molded. A gas injection molding method is proposed in which a cavity is formed between the core and a pressurized gas is press-fitted into the cavity, and the other surface of the molded product is pressed into contact with the corresponding cavity surface.

In this gas combined injection molding method, instead of applying no resin pressure in the resin pressurization method, pressurized gas is injected to prevent sink marks by pressurized gas injection. In this gas combined injection molding method, a cavity is formed on a predetermined one side of a molded product, pressurized gas is press-fitted, and the other surface of the molded product is pressed against a corresponding cavity surface by the pressure of the pressurized gas. Although it is intended to prevent sink marks, it is difficult to obtain a sufficient sink preventing effect only by pressing with the pressure of the pressurized gas.

As a method of preventing sink in a molded product having an uneven thickness (thick) portion, a pressurized gas is introduced into a molten resin constituting the uneven thickness portion to form a hollow portion. A method called assist molding is known. According to this method, sinking of the uneven thickness portion can be prevented, but due to a difference in the pressing force of the uneven thickness portion and the thin portion against the cavity surface, and secondary transfer after the pressurized gas is introduced into the resin, Gloss and gloss unevenness often occur on the flat surface side corresponding to the portion where the uneven thickness portion protrudes.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to completely prevent appearance defects from occurring by a combined gas injection molding method. .

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for injection-molding a molded article having a substrate portion, a side wall portion, and a thick rib provided on the side wall portion. A resin is filled in a mold that forms a closed section adjacent to or including the thick rib with the provided auxiliary rib and / or the thick rib and the connecting rib provided on the substrate portion. And pressurized gas is injected between a resin filled in the mold and a mold.

According to the present invention, since the other surface of the molded product is uniformly pressed against the corresponding cavity surface by the pressurized gas which is press-fitted between one surface of the molded product and the corresponding cavity surface, it is possible to reliably prevent sinking. At the same time, it is possible to prevent the occurrence of uneven gloss and gloss as in the case of conventional gas assist molding.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The injection of molten resin in the present invention is preferably a full shot in which a closed section according to the present invention is sufficiently filled with the molten resin, and more preferably, leakage of pressurized gas from a mold is prevented. In order to facilitate prevention, it is preferable to inject a pressurized gas after injecting an excessive amount of molten resin in comparison with the volume of the cavity. Here, the excess amount of the molten resin compared to the cavity volume means that the volume of the molten resin at the temperature of the resin immediately after injection filling into the mold and the average mold pressure is smaller than the cavity volume. It means that it is large, and it is preferably an amount which becomes 103% by volume or more.

The press-fitting of the pressurized gas is not particularly limited as long as the press-fitting can be performed from a predetermined cavity surface side. The press-fitting mode may be performed by providing a dedicated passage or by using around an ejector pin.

The molded article obtained by the present invention is a box-shaped molded article having a substrate portion, a side wall portion, and a thick rib provided on the side wall portion, and preferably having a side wall portion along an end portion of the substrate portion. is there.

The resin that can be used in the present invention is not particularly limited as long as it is generally called a thermoplastic resin. For example, rubber-reinforced styrene resins such as polystyrene, high impact polystyrene, and medium impact polystyrene, styrene-acrylonitrile copolymer (SAN resin), acrylonitrile-butyl acrylate rubber-styrene copolymer (AAS resin), acrylonitrile-ethylene Propyl rubber-styrene copolymer (AES), acrylonitrile-chlorinated polyethylene-styrene copolymer (ACS), ABS resin (for example,
Styrene resins such as acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene-α-methylstyrene copolymer, acrylonitrile-methyl methacrylate-butadiene-styrene copolymer), and acrylics such as polymethyl methacrylate (PMMA) Resin, low density polyethylene (LDPE), high density polyethylene (HDPE), olefin resin such as polypropylene (PP), polyvinyl chloride resin such as polyvinyl chloride and polyvinylidene chloride, ethylene vinyl chloride vinyl acetate copolymer, Vinyl chloride copolymer resin such as ethylene vinyl chloride copolymer, polyethylene terephthalate (PE
TP, PET), polybutylene terephthalate (PBT)
P, PBT) and the like; polycarbonate resins such as polycarbonate (PC) and modified polycarbonate; polyamide resins such as polyamide 66, polyamide 6, and polyamide 46; polyacetals such as polyoxymethylene copolymers and polyoxymethylene homopolymers. (POM) resin, other engineering resins,
Super-engineering resins such as polyethersulfone (PES), polyetherimide (PEI),
Thermoplastic polyimide (TPI), polyetherketone (PEK), polyetheretherketone (PEE)
K), polyphenylene sulfide (PSU), etc.
Examples include cellulose derivatives such as cellulose acetate (CA), cellulose acetate butyrate (CAB) and ethyl cellulose (EC), liquid crystal polymers such as liquid crystal polymers and liquid crystal aromatic polyesters. Further, thermoplastic polyurethane elastomer (TPU), thermoplastic styrene butadiene elastomer (TSBC), thermoplastic polyolefin elastomer (TPO), thermoplastic polyester elastomer (TPEE), thermoplastic vinyl chloride elastomer (TPVC), thermoplastic polyamide elastomer (TPAE) ) Can also be used. In the present invention, the above-mentioned thermoplastic resin may be synthesized in the molding process of the present invention, or a blend of one or more of the above-mentioned thermoplastic resins may be used, and a filler and / or an additive may be used. May be used.

Hereinafter, a further description will be given with reference to the drawings.

FIG. 1 shows a molded article according to an embodiment of the present invention. The closed section according to the present invention is composed of two thick ribs, a connecting rib connecting the thick ribs, and a side wall. It is an example formed with a part.

FIG. 1 is a perspective view of the molded article.
FIGS. 2A and 2B are projection views, in which FIG. 2A is a front view and FIG. 2B is a plan view. As shown in FIGS. 1 and 2, the molded article 1 includes a substrate portion 6, a side wall portion 5, and a thick rib 2 provided on the side wall portion 5.
a, 2b, and the thick ribs 2a and 2b are connected by a connecting rib 4. The side wall 5, the thick ribs 2a, 2b
b, a closed section 7 (a region shown by oblique lines in FIG. 2B) is formed by the connecting rib 4.

In the present invention, that the closed section is adjacent to or includes the thick rib means that the closed section is formed adjacent to the thick rib by using the thick rib as a constituent member of the closed section. Or means that the thick rib is enclosed in a closed section by surrounding the thick rib with a closed section constituting member without contacting the thick rib.

In the present invention, the thickness of the substrate portion 6 is T, the thickness of the side wall portion 5 is t, the height is H, the thickness of the thick ribs 2a and 2b is w, the thickness of the connecting rib 4 is d, If the height is h, h
Is preferably T or more, preferably 2T or more, more preferably 3T or more. Further, in the present invention, in a molded product in which the thickness w of the thick rib is 0.8 times or more of the thickness t of the side wall, further in a molded product in which the thickness is t or more, and further 1.5 times or more in t, a normal production method An appearance effect is obtained as compared with a molded article, and a design advantage is obtained better. Also, d is designed to be less than w, preferably 0.5 times or less of w. In the molded article, the thick ribs 2a and 2b are formed to have a uniform thickness, but the thickness usually has an inclination due to the design of the mold. In this case, w is defined by the maximum thickness at the portion in contact with the substrate.

In the present embodiment, a mold is formed so as to form the above-mentioned molded article 1, a gas injection port 8 is provided at an arbitrary position in the closed section 7, and sufficient resin, preferably, is provided in the closed section 7. After filling an excessive amount of resin, a molded article 1 is obtained by injecting pressurized gas between the resin and the mold filled in the closed section.

In the present molded article, the thick ribs 2a, 2b
Has a shape that is substantially L-shaped and has a tip portion protruding from the end of the side wall portion. The protruding portion is formed as a member for fitting the molded article 1 to another component. Yes, it is not necessary to have the shape in particular.

In order to prevent the pressurized gas injected into the closed section from leaking out of the closed section along the resin surface at the end of the side wall portion extending to the outside of the closed section, as shown in FIG. It is desirable that the thick ribs 2a and 2b forming the closed section are formed so as to be in contact with the end of the side wall portion. However, as shown in FIG. In the case where the thick rib 2 is formed so as to have a portion which is not formed, the design is made such that the distance L1 where the thick rib 2 does not contact the side wall 5 is within 10% of the height H of the side wall 5. It is desirable to do.

FIG. 4 shows an example of the fitting member.
As shown in (1), the outer wall 9 for fitting may be provided, but also in this case, the height L2 of the outer wall 9 is desirably designed to be within 10% of the height H of the side wall portion.

FIG. 5 is a perspective view of a molded article according to a second embodiment of the present invention, FIG. 6 is a projection view thereof, (a) is a front view, and (b) is a plan view. The present embodiment is an example in which a closed section according to the present invention is formed by two auxiliary ribs, a connecting rib connecting the auxiliary ribs, and a side wall.

As shown in FIG. 5 and FIG.
Has a substrate portion 16, a side wall portion 15, and a thick rib 12, auxiliary ribs 13a and 13b are formed on both sides of the thick rib 12, and the auxiliary ribs 13a and 13b are connected to connecting ribs 14a to 14b.
14c, the side wall portion 15, the auxiliary rib 13a,
13b and the connecting ribs 14a to 14c form a closed section 17 (a region indicated by oblique lines in FIG. 6B).

In the present invention, the auxiliary ribs 13a, 13b
Is less than the thickness w of the thick rib 12, and preferably 0.5 times or less the thickness t of the side wall portion 14.

Also in the present embodiment, a mold is formed so as to form the above-mentioned molded article 1, a gas injection port 18 is provided at an arbitrary position in the closed section 17, and sufficient resin, preferably, is provided in the closed section 17. After filling an excessive amount of resin, a molded article 10 is obtained by injecting a pressurized gas between the resin filled in the closed section and the mold.

In the present embodiment, only one thick rib is provided in the closed section 17, but a plurality of thick ribs may be surrounded by one closed section.

In the present invention, the auxiliary rib 13
By forming the tops of a and 13b up to the end of the side wall 15 as in the present embodiment, the pressurized gas injected into the closed section through the resin at the end of the side wall extending to the outside of the closed section. Leakage outside the closed section can be prevented.

In this embodiment, as in the modified example of the molded article 1 shown in FIGS. 3 and 4, a portion where the thick rib 2 and the side wall 5 are not in contact as shown in FIG. The thick rib 2 may be formed so as to have, and a fitting outer wall 19 can be provided as shown in FIG.

FIGS. 9A and 9B are projection views showing a molded article according to a third embodiment of the present invention, wherein FIG. 9A is a plan view, FIG. 9B is a sectional view of a measuring surface, and FIG. In this embodiment,
This is an example in which a closed section is formed by thick ribs, auxiliary ribs, connecting ribs connecting these ribs, and side walls.

This molded product has side walls 25a to 25c, a substrate 26, and thick ribs 22a to 22c.
And the thick rib 22a is connected to the thick rib 22a by connecting ribs 24a to 24c.
a to 24c and the auxiliary rib 23 form a closed section 27 (a region indicated by oblique lines in FIG. 9A).

In this molded product, the connecting ribs 24 of the same height are connected to the connecting ribs 24c for product design reasons.
d is formed, and the lower connecting rib 24b is connected to these connecting ribs 24c and 24d in a T-shape. In this molded product, a rising rib 29 is formed on the connecting rib 24b at the T-shaped joint. In the present invention, as described above, in a portion where a part of the closed section component extends outside the closed section and joins a substantially T-shape, the closed section area of the closed section component is defined as the outside area of the closed section. It is preferable that the height be equal to or higher than the height. As a result, the member (the connecting rib 2 in FIG.
Leakage of the pressurized gas along the resin surface of 4d) to the outside of the closed section is prevented, and the molded product can be sufficiently pressed against the mold to prevent sink marks. At this time, the starting rib 29
And the height of the connecting rib 24c together with the auxiliary rib 24d
Is preferably at least 90% or more of the height.

The above substantially T-shaped connecting portion includes a case where the other member is connected to the linear member at a non-perpendicular angle, and as shown in FIG. 10, connecting ribs 64c, 64c.
A member having the same height, such as a joint between d and 64b, is substantially L
The members having different heights are connected to the portions connected in the shape
This includes the case of forming a letter shape.

In the above substantially T-shaped coupling portion, as shown in FIGS. 9 and 10, in addition to forming the rising rib on the lower member, the higher member is fitted to the lower member. The height may be adjusted by notching. In addition, the upper end of each component in the connecting portion does not need to be particularly formed horizontally, and may be non-horizontal or curved.

Also in this embodiment, a mold is formed so as to form the above-mentioned molded article, a gas injection port 28 is provided at an arbitrary position in the closed section 27, and sufficient resin, preferably excess After the resin is filled, a molded article is obtained by injecting a pressurized gas between the resin filled in the closed section 27 and the mold.

FIG. 11 is a sectional view showing an example of a mold used in the present invention.

As shown in FIG. 11, the mold 34 includes a fixed mold 35 and a movable mold 36, and a cavity 37 is formed between the fixed mold 35 and the movable mold 36. The cavity 37 is filled with a molten resin during molding. I have.

On the other hand, on the side of the cavity surface 39 corresponding to the back surface (non-design surface) of the molded product, the periphery of the ejector pin 40 that is connected to the atmosphere is sealed by an O-ring 41. A gas injection pin 42 is provided on the cavity surface 39 side. The tip of the gas injection pin 42 has a cavity surface 3
9, which is embedded in the movable mold 36 facing the inside of the cavity 37, and is sent from a gas introduction path 47 connected to a pressurized gas source (not shown) via a valve 43. The incoming pressurized gas is supplied to the cavity 37 through a gap left between the moving side mold 36 and the pressurized gas. In the figure, reference numeral 44 denotes an O-ring for preventing the pressurized gas from escaping from the joint of the mold components.

The mold 34 shown in FIG. 11 is for molding a substantially box-shaped molded product having a rib 45 connected to a side wall portion on the inside, and a parting surface 46 is formed on the side wall of this box-formed product. Located along the edge of the part.

Further, the molding method of the present invention will be described with reference to FIG.

First, a molten resin is injected into the cavity 37 with the mold 34 closed. As for the injection amount, it is desirable that the closed section surrounded by the thick rib, the auxiliary rib, and the side wall is filled with a sufficient amount of resin, more preferably an excessive amount of resin.
Before, at or after the completion of the injection of the molten resin, the valve 43 is opened to supply a pressurized gas from a pressurized gas source (not shown) to a gas introduction path 47 provided in the mold 34. Start of pressurized gas injection before completion of injection as described above,
Either at the completion or after the completion, it is preferably at the completion of the injection or immediately after the completion.

As the pressurized gas, for example, air, carbon dioxide, nitrogen or the like is used. Regarding the type of gas used,
It is preferable to select according to the pressure of the pressurized gas, molding material, molding conditions, and the like. The pressure of the pressurized gas varies depending on the type of resin used, the shape of the molded article, the size of the molded article, and the like, but is usually 10 to 250 kgf / cm ² , preferably ² kg / cm ² .
It is 0 to 200 kgf / cm ² .

The pressurized gas supplied to the gas introduction path 47 is
Through the gap between the gas injection pin 42 and the moving mold 36,
Cavity surface 3 which is a closed area surface surrounded by ribs
It is pressed into the cavity 37 from the 9th side. This pressurized gas is pressed between the inner surface of the box-shaped part in the cavity 37 and the cavity surface 39, thereby pressing the outer surface of the box-shaped part against the corresponding cavity surface 38. The pressurization by the pressurized gas suppresses the occurrence of sink marks on the surface of the molded product on the cavity surface 38 side, improves the transferability on the cavity surface 38 side, and also causes the problem of poor appearance due to sink marks, uneven gloss, and the like. Reduce.
Furthermore, since sink marks are induced (squeezed) at the roots of the ribs on the rear surface of the molded product, the releasability when the molded product is removed from the mold 34 is also improved.

After the pressurized gas is injected as described above, the pressurized gas is discharged out of the mold 34 as necessary, and the molded product is taken out of the mold 34.

The present invention relates to a molded product in which thick ribs partially protrude from the rear surface (non-design surface) of the molded product, that is, the cavity surface 3.
In the molding of a molded product having a thick rib protruding from the surface of the molded product, sink, luster and gloss unevenness, which are likely to occur in response to the ribs and bosses, can be prevented on the surface of the molded product (design surface) on the cavity surface 38 side. And the problem of appearance due to the presence of the boss can be solved.

[0047]

【Example】

EXAMPLE A box-shaped OA / office equipment housing 50 shown in FIG. 12 was manufactured. FIG. 13 is a plan view thereof.

The thickness of the substrate portion 56 and the side wall portions 55a to 55h of the housing 50 of the present embodiment is 2 mm, and the thickness of the thick ribs 52a to 52h.
Reference numeral 55i denotes a taper-shaped portion having a thickness of 3.2 mm at a portion in contact with the substrate portion 56, a thickness of 2 mm at a tip portion, and a connecting rib 54a.
The thickness of 54 g was 1 mm and the height was 10 mm. However,
Since the height q of the step-shaped portion is 20 mm, the thick rib 52
The height r, r 'of the highest part of 54d, 54h combined with e, 52h was 30 mm. Also, the connecting rib 54f
Is a rib required for the structure, and has a height of 15 mm and a wall thickness of 1 mm together with the connecting rib 54h following the rib. In addition, connecting rib g
In order to connect the connecting ribs 54h and 54f in a T-shape, a rising rib 59 is provided at the connecting portion to eliminate the difference in elevation. 70a and 70b are openings.

The thick ribs 52a and 52c are connected to the connecting rib 54.
b so as not to contact the thick rib 52b.
a and 54b, thereby forming a closed section 57a as shown in FIG. 58a is a gas inlet for injecting pressurized gas into the closed section 57a. Here, the resin injected into the closed section 57a and the thick rib 5
Gas injection port 58a between the mold on the side where 2a-52c is located
The resin is pressed against the surface of the molded article by the pressurized gas injected from the inside, and sinks are induced on the root sides of the thick ribs a to c.

Similarly, the thick ribs 52d and 52e are connected by connecting ribs 54c and 54d to connect the closed section 57b, and the thick ribs 52f and 52g are connected by the connecting rib 54e and closed section 57b.
c, and the thick ribs 52h and 52i
g to form closed sections 57d, and pressurized gas is injected from gas injection ports 58b to 58d provided in each closed section to induce sink marks toward the root of the thick rib.

The molding conditions of this example are shown below.

(A) Material used: HIPS Cylinder temperature: 200 ° C. Injection pressure: 100 kg / cm ² (gauge pressure) Pressure of pressurized gas: 30 kg / cm ² (gauge pressure) (B) Material used: ABS cylinder temperature: 220 ° C Injection pressure: 140 kg / cm ² (gauge pressure) Pressure of pressurized gas: 80 kg / cm ² (gauge pressure)

The obtained HIPS and ABS molded articles were both molded articles having no appearance defects such as sink marks and uneven gloss on the surface (design surface) opposite to the thick rib. Further, the molded product was easily released from the mold, and was excellent in moldability. Furthermore, the molded article of this example had a thick fitting rib, and was able to produce a molded article having considerably superior mechanical strength as compared with a conventionally designed OA / office equipment housing.

[Comparative Example 1] Normal injection molding was performed using the same mold and the same resin as in Example 1. The respective molding conditions are shown below.

(A) Material used: HIPS Cylinder temperature: 200 ° C. Injection pressure: 100 kg / cm ² (gauge pressure) Resin holding pressure: 40 kg / cm ² (gauge pressure) (B) Material used: ABS Cylinder temperature: 220 ° C. Injection pressure: 100 kg / cm ² (gauge pressure) Resin pressure: 40 kg / cm ² (gauge pressure)

Both of the obtained molded products were sinked to the surface (design surface) on the opposite side of the thick rib, and the appearance was poor.

[Comparative Example 2] Connecting rib 5 shown in FIG.
A molded product having the same structure as that of the example except that 4a to 54h was not formed was molded under the same molding conditions.

In the obtained molded product, the sink of the surface (design surface) on the opposite side of the thick rib was slightly smaller than that of the normal molding of Comparative Example 1, but the introduced pressurized gas was It easily leaked out of the mold, and no satisfactory appearance was obtained. Further, even if the pressure of the pressurized gas is increased or the press-fitting period of the pressurized gas is increased, sink marks on the surface (design surface) on the opposite side of the thick rib cannot be completely eliminated.

[0059]

As described above, according to the present invention,
By forming the necessary thick ribs, it is possible to mold resin molded products with sufficient strength without generating sink marks, unevenness in gloss and luster, and are more mechanical than conventional OA and office equipment housings. Molding of molded products with excellent strength is realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a molded product according to an embodiment of the present invention.

FIG. 2 is a projection view of a molded article according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a modification of the molded product shown in FIG. 1;

FIG. 4 is a perspective view showing a modification of the molded product shown in FIG.

FIG. 5 is a perspective view of a molded product according to a second embodiment of the present invention.

FIG. 6 is a projection view of a molded article according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a modification of the molded product shown in FIG.

FIG. 8 is a perspective view showing a modification of the molded product shown in FIG.

FIG. 9 is a projection view of a molded article according to a third embodiment of the present invention.

FIG. 10 is a perspective view showing a modification of the molded article shown in FIG.

FIG. 11 is a sectional view of an example of a mold used in the present invention.

FIG. 12 is a perspective view of a molded article molded in an example of the present invention.

FIG. 13 is a plan view of a molded article molded in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2, 2a, 2b Thick rib 4 Connecting rib 5 Side wall 6 Substrate 7 Closed section 8 Gas inlet 9 Outer wall 11 Molded product 12 Thick rib 13a, 13b Auxiliary rib 14a-14c Connecting rib 15 Side wall Reference Signs List 16 substrate section 17 closed section 18 gas inlet 19 outer wall section 22a to 22c thick rib 23 auxiliary rib 24a to 24d connecting rib 25a to 25c side wall section 26 substrate section 27 closed section 28 gas inlet 29 rising rib 34 mold 35 Fixed-side mold 36 Moving-side mold 37 Mold cavity 38 Cavity surface on molded product surface (design surface) side 39 Cavity surface on molded product back surface (non-design surface) 40 Ejector pin 41 O-ring 42 Gas injection pin 43 Valve 44 O-ring 45 Rib 46 Parting surface 47 Gas introduction path 50 Molded product 52a to 52i Thick rib 54a To 54h Connecting rib 55a to 55h Side wall 56 Substrate 57a to 57d Closed section 58a to 58d Gas inlet 59 Startup rib 62a to 62c Thick rib 64a to 64d Auxiliary rib 65 Sidewall 66 Substrate 69 Startup rib 70a 70b opening

Claims (5)

[Claims] 1. A gas injection molding method for a molded article having a substrate portion, a side wall portion, and a thick rib provided on the side wall portion, comprising: a side wall portion; an auxiliary rib provided on the side wall portion; The resin is filled in a mold that forms a closed section adjacent to or including the thick rib with the thick rib and the connection rib provided on the substrate portion, and the resin and the mold filled in the closed section are filled. And pressurized gas is injected between them. 2. The injection molding method according to claim 1, wherein the closed section is formed by two thick ribs, a connecting rib connecting the thick ribs, and a side wall. 3. The closed section is formed by a thick rib, an auxiliary rib, a connecting rib connecting these ribs, and a side wall.
The combined gas injection molding method as described above. 4. The gas injection molding method according to claim 1, wherein the closed section is formed by two auxiliary ribs, a connecting rib connecting the auxiliary ribs, and a side wall. 5. The method for injection molding with gas according to claim 1, wherein the resin is filled in the closed section sufficiently.