JP2743770B2 - Resin molded product having cavity inside and manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molded product having a cavity therein and a method for producing the same.

[0002]

2. Description of the Related Art For the purpose of reducing the weight of a resin molded product or reducing the amount of resin used, there has been proposed a resin molded product having a cavity therein mainly for a resin molded product for a vehicle (for example, Japanese Patent Application Laid-Open No. 3-248937). No. 2-63255). These resin molded products are injected with compressed gas during injection molding,
A cavity is formed throughout the inside. However, even in such molded products, it is difficult from experience to always obtain cavities of the same shape when performing a large number of moldings repeatedly, and the shape usually varies. There is a problem that a thick part causes sink marks to deteriorate the appearance, or unevenness of the internal stress causes deformation such as twisting, thereby impairing the mounting property.

On the other hand, there is a demand for a resin molded product having an internal space in which the back surface side of the resin molded product having such a cavity is opened. FIG. 8 is a perspective view of a resin molded product used as a spoiler for a vehicle, and FIG. 9 shows a structure of a resin molded product that can be generally considered as such a molded product.
It is XX sectional drawing of.

[0004] In the figure, reference numeral 1 denotes a resin molded product, the outer surface side of which is a design portion 2, a mounting portion 4 extends to the back side so as to surround the internal space 3, and the internal space 3 is open to the back side. In this molded product 1, the portions from the design portion 2 to the mounting portion 4 are integrally formed mainly with the thin portions 5 having thicknesses d ₁ and d ₂ in order to reduce the weight. However, if the strength of the mounting portion 4 is expected to be insufficient, the mounting portion 4 has a thickness D ₁ , D ₂ as shown in a broken line 4a in FIG.
A molded article in which the thick part 6 (> d ₁ , d ₂ ) is formed and the whole is integrally molded is also conceivable.

The above-mentioned resin molded product 1 is used by being attached to a mounting portion 8 such as a vehicle body panel with a fixing means 7 such as a double-sided adhesive tape interposed at a tip (back surface) of the mounting portion 4.

[0006]

However, such a resin molded product 1 has a structure in which the thin portion 5 and the thick portion 6 are integrally formed. The cooling and solidification of the thick portion 6 is delayed, and sinks occur on the outer surface side of the thick portion 6 to impair the appearance. In addition, the internal stress becomes non-uniform and deformation such as twisting of the entire molded product occurs. There are problems such as impairing the mountability in No. 4.

[0007] An object of the present invention is to form sinks and twists in a resin molded product in which a thin portion and a thick portion are integrally formed by forming an internal cavity in a thick portion without forming a cavity in a thin portion. An object of the present invention is to provide a resin molded product which prevents deformation, is lightweight, has excellent appearance and mounting properties, and a method for producing the same.

[0008]

The present invention relates to the following resin molded product and a method for producing the same. (1) Design part consisting of a plate-like thin part with almost the same thickness
And consists of a thick portion of the thickness greater than the thickness of the thin portion, meaning
On the part to be mounted so that an internal space is formed on the back side of the
It is formed in the inner space on the back side of the extending part and the design part.
Is and is integrally molded fittings support portion, before KiAtsu meat portion is formed with a substantially enclosed cavity therein, the cavity is formed substantially homothetic reduction outer shape of the thick portion and the thin portion substantially extends in Orazu, the fixture supporting portion preparative
A resin molded product which is connected to an attachment portion and has a cut portion between the thin portion and the thin portion . ( 2 ) The resin molded product according to the above (1), wherein the thick portion has an air passage connected to the cavity. ( 3 ) a thin portion forming portion having substantially the same gap in a planar shape, a thick portion forming portion having a gap larger than the gap ,
A molten resin was injected into the cavity by using an injection mold having a cavity formed with a fixture supporting portion forming portion connected to the thick portion forming portion and a compressed gas injection port in the thick portion forming portion. After the resin covers the gas inlet, the compressed gas is injected before the resin fills the cavity, and the resin in the cavity flows together with the compressed gas to form a thin portion in the thin portion forming portion, A thick part is formed by the thick part forming part, and a mounting part supporting part forming part is used.
Forming a fixture support and forming a cavity within the thickened portion having a substantially similar reduction in outer shape of the thickened portion, substantially sealed, and substantially not extending to the thinned portion. manufacturing method (1), wherein the resin molded article characterized by and this. ( 4 ) The method according to the above ( 3 ), wherein the gas injection port is formed at a position facing the gate of the injection mold. ( 5 ) The method according to ( 3 ) or ( 4 ), wherein the gas injection port is formed in a concave portion of the injection mold.

In the present invention, the "thick portion" refers to a portion having a thick outer shape, even if it has a hollow inside,
The “thin portion” refers to a portion having a smaller outer thickness than the “thick portion”.

[0010]

According to the resin molded product of the present invention, the resin is injected into the cavity of the injection mold, and after the resin covers the gas injection port, the compressed gas is injected into the cavity so that the thin portion is formed at the thin portion forming portion. The inside that opens and opens on the back side of the thin part to the part to be mounted while forming the thick part in the thick part forming part
Thick wall that exceeds the thickness of the thin part surrounding the space and internal space
Connecting the thick part to the mounting part consisting of
Forming a mounting support portion having a break between the meat portion,
It is manufactured by forming a cavity inside the thick portion that has a substantially similar reduced shape of the outer shape of the thick portion, is substantially sealed, and does not substantially extend to the thin portion.

In the resin molded article thus manufactured, since the thin portion and the thick portion are integrally formed and a cavity is formed inside the thick portion, the difference in cooling and solidification rate between the thin portion and the thick portion is obtained. Is reduced, so that non-uniform stress is not generated inside, and deformation such as twisting is reduced. Mounting bracket support
Even when sinking and deformation occur , sinking and deformation do not reach the outer surface side of the thick part separated by the cavity , thereby obtaining a resin molded product having a thick part maintaining a predetermined accurate shape. In addition, the mountability is improved and an excellent appearance is obtained. Sa
In addition, it is wide facing the part to be mounted due to the thick part in mounting
Since the area can be secured, the mounting stability increases, and the mounting fixture support
Since the holding part is connected to the thick part, the overall rigidity is increased
And a break is formed between the thin part and the fixture support
Design consisting of a thin part corresponding to the fixture support part
No sinking or deformation occurs on the surface of the part.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a bottom view of FIG. 8 showing a resin molded product of the embodiment, and FIGS. 2 (a), 2 (b), and (c) are AA cross section, BB cross section, and CC of FIG. 1, respectively. FIG. 10 is a sectional view, and the same reference numerals as those in FIGS. 8 and 9 indicate the same or corresponding parts.

In the figure, a resin molded product 1 is a long molded product used as a spoiler of a vehicle, and a design portion 2 is formed on an outer surface side in the same manner as a conventional product, and a mounting portion is formed so as to surround an internal space 3. 4 extends from the entire circumference to the back side, and the internal space 3 is open to the back side. The design portion 2 is mainly composed of a plate-shaped thin portion 5 having substantially the same thickness t ₁ and t ₂ , and the mounting portion 4 is formed from a thick portion 6 having a thickness T ₁ and T ₂ larger than the thickness of the thin portion 5. And are integrally molded. The thickness of the thin portion 5 is 3 to
3.5 mm or less is preferable. A cavity 11 is formed inside the thick part 6 along the longitudinal direction of the thick part 6. The cavity 11 has a reduced shape substantially similar to the outer shape of the thick portion 5, is substantially closed, and does not substantially extend to the thin portion 5.

The thickness of the thin portion 5 and the thick portion 6 is T ₁ ,
T ₂ > t ₁ , t ₂ , the thin portion 5 is made thinner to reduce the weight, and the thick portion 6 is made thicker to increase the mounting strength. Although the thickness of the thick portion 6 is thicker, the thickness T of the peripheral wall 12 of the thick portion 6 which is a wall around the cavity 11 is
The thickness is almost the same as the thickness of the surrounding wall.

Reference numeral 13 denotes a ventilation hole, which is formed at the tip of the thick portion 6, that is, on the back surface, which is the outer surface of the mounting portion 4, so as to communicate with the cavity 11, and is connected to the ventilation passage 14. Reference numeral 15 denotes an attachment support portion having an L-shaped cross section. The attachment support 9 such as a clip is attached to the attachment hole 16 and attached to the attached portion 8. Between the fixture support portion 15 and the design portion 2
A gap 17 is formed as a disconnection . Reference numeral 18 denotes a protrusion for preventing the molded product from moving when the molded product 1 is removed from the injection mold.

FIG. 3 is a sectional view of an injection mold, FIG. 4 is a plan view of a core mold, FIG. 5 is a perspective view of a part of a molded product, FIG. 6 is a partial sectional view showing a used state, and FIG. It is a timing chart of injection molding.

Reference numeral 21 denotes an injection mold, in which a cavity 24 is formed between a cavity mold 22 and a core mold 23. The cavity 24 is formed of a gap corresponding to the thin portion 5 and a thin portion forming portion 25 having a shape, and a gap corresponding to the thick portion 6 larger than the gap and a thick portion forming portion 26 having a shape. In addition, the cavity 24 has a thick wall
An attachment support portion forming portion connected to the component portion 26 is formed.
However, illustration is omitted. 27 is a gate,
The core mold 23 is provided so as to open at the center of the thick portion forming portion 26 on one side, and is connected to the sprue 28 and the runner 29. 30 is a cold slug.

A concave portion 31 is formed in a portion of the core die 23 opposite to the gate 27 of the thick portion forming portion 26 on both sides, and a gas injection port 32 is opened in the center thereof. Also recess 3
A ventilation path forming portion 33 is formed in the core mold 23 near 1. The gas injection port 32 is connected to a gas injection pipe 34 through a check valve 35.
To the gas injector 36 via Reference numeral 37 denotes a gas cylinder, 38 denotes a gas vent, and 39 denotes an open valve, which are provided on both sides so that the gas pressure, the gas flow rate, the gas injection timing, and the like can be controlled independently of each other. I have. The injection molding die 21 is provided with a slide core die for forming the fixture support portion 15, but is not shown.

The method of manufacturing the resin molded product 1 is performed according to the timing chart of FIG. First, the injection molding die 21 is clamped, a molten liquid resin 41 is supplied from an injection nozzle (not shown) of the injection molding machine, and the resin is injected into the cavity 24 from the gate 27 through the runner 29 and the sprue 28 directly. During this time, the gas injector 36 is in the OFF state, and the gas vent 38
Is open.

The resin 41 injected into the cavity 24 is
The cavity 24 is filled as shown in FIGS. Then, the resin 41 covers the gas injection port 32 and is preferably filled to about 70 to 80% of the cavity 24, that is, almost to the position of b in FIG. When the resin 41 is not filled and an unfilled space remains in the cavity 24, the opening valve 39 is closed to shield the gas vent 38 from the atmosphere, the gas injector 36 is driven, and the gas is injected through the gas injection pipe 34. A gas 42 such as a compressed nitrogen gas is injected into the cavity 24 from the inlet 32. At this time, the resin 41 is used for the gate 2
It is preferable to continue injection from step 7.

The injected gas 42 enters the cavity 24 through the center of the recess 31 with the resin 41 adhered to the peripheral wall of the recess 31. The gas 42 that has entered the cavity 24 first forms a small cavity in the resin 41 in the thick portion forming portion 26, and subsequently the flow of the resin supplied from the gate 27,
By the gas 42 supplied continuously and the expansion force of the gas, the cavity 11 is formed in the thick portion forming portion 26 having the least flow resistance, and the cavity 11 is formed on the side not yet filled with the resin as shown in FIG. Proceed towards. Thereby, the resin 41 is expanded in the cavity 24 and the thick portion forming portion 2
6 and the entire thin wall portion forming portion 25 is filled.
Thus, the thin portion 5 and the thick portion 6 are formed, and the cavity 11 is formed in the thick portion 6. The inner wall of the cavity 11 is formed so as to be continuous in the longitudinal direction of the thick portion 6, and the cavity remains near the boundary with the thin portion 5 and substantially does not extend to the thin portion 5.

The injection of the gas 42 is performed later than the injection of the resin 41, and after a short time after the injection of the gas 42, the injection of the resin is stopped and cooling is started. Maintain the holding pressure. When the pressure-holding and cooling are completed, the gas injector 36 is stopped, the gas vent 38 is opened, the gas 42 is discharged, the pressure in the cavity 11 is returned to the atmospheric pressure, the mold is opened, and the molded product 43 is taken out. The movement preventing projection 18 prevents the molded product 43 from moving when the slide core moves when the mold is opened.

The removed molded product 43 has a shape corresponding to the resin molded product 1, but has a convex portion 44 and an annular concave portion 45 corresponding to the concave portion 31 as shown in FIG. Vent holes 13 are formed as traces. The ventilation path 14 is formed by the ventilation path forming part 33.
Then, when the convex portion 44 is folded to form a circular concave portion 46, the vent hole 13 is opened in the circular concave portion 46. A colored layer of a desired color can also be formed on the surface of the molded article thus obtained by painting or the like.

As shown in FIG. 6, the resin molded article 1 thus manufactured is fixed to the mounting portion 4 with a fixing means 7 such as a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers 7a and 7b. It is fixed to the part 8. At the same time, as shown in FIG.
And is mounted in the mounting hole 8a of the mounted portion 8 and fixed by two types of fixing means.

In the fixed state, the cavity 11 is
Since it communicates with the atmosphere through the air passage 3 and the air passage 14, even if the internal air expands or contracts due to a temperature difference, the resin molded product 1 does not deform.

In the resin molded article 1 described above, the thin portion 5 and the thick portion 6 are integrally formed, and the cavity 11 is formed inside the thick portion 6, so that the thin portion 5 and the thin portion 5 during injection molding are formed. The difference between the cooling and solidifying speeds of the thick portion 6 is reduced, so that non-uniform stress is not generated inside, and deformation such as twisting is reduced. Also, no sink marks occur on the outer surface side of the thick portion 6, whereby a resin molded product 1 having a thick portion (attachment portion) maintaining a predetermined accurate shape is obtained, and the attachability is improved. Excellent appearance is obtained.

When the gas injection port 32 is opened at a position opposite to the gate 27 of the injection mold 21 as in the above embodiment, the injection of the gas 42 is stopped because the injected resin 41 is a part separated on both sides. It is easy and uniform, but may be at other locations as the case may be. In addition, the gas inlet 3 is
When the opening 2 is opened, the resin pressure is not directly applied, and the resin stops at the concave portion and the peripheral portion of the injection port 32 solidifies relatively faster than the other portions, so that the injection of the gas 42 becomes easy. In some cases, it may be another location.

In the above embodiment, the fixing means 7 for fixing the thick portion 6 having the cavity 11 is an example of a double-sided adhesive tape. However, a fixing bolt or other fixing means may be used. Although the above embodiment relates to a resin molded product used for a spoiler for a vehicle, it can also be applied to a resin molded product for other uses such as a body side molding, a wheel opening trim, a finisher, and the like. , Structure and the like can be changed.

[0029]

According to the resin molded product of the present invention, since a thin portion and a thick portion are integrally formed and a cavity is formed in the thick portion, deformation such as sink and torsion is reduced, and the mounting property and Excellent appearance , and a thick part for mounting
High mounting stability because a large area can be secured facing
As the mounting support is connected to the thick part,
Between the thin part and the mounting fixture support part.
A thin portion corresponding to the mounting fixture support
The surface of the design part consisting of the part will not sink or deform.
No.

The method for manufacturing a resin molded product according to the present invention comprises the steps of forming a thin portion , a thick portion, and connecting the thick portion .
Injection gas is used after the resin covers the gas injection port, using an injection molding die having a cavity formed of the fixture support part molding part and a gas injection port in the thick part formation part. Forming a thick part at the thick part forming part and a mounting part supporting part by the mounting part supporting part forming part.
And a cavity can be formed in the thick part, and the above-mentioned resin molded product can be manufactured efficiently.

[Brief description of the drawings]

FIG. 1 is a bottom view of FIG. 8 showing a resin molded product of an example.

2A is a cross-sectional view taken along the line AA in FIG. 1, and FIG.
Sectional drawing, (c) is CC sectional drawing.

FIG. 3 is a sectional view of an injection mold.

FIG. 4 is a plan view of a core type.

FIG. 5 is a perspective view of a part of a molded product.

FIG. 6 is a partial cross-sectional view showing a use state of a molded product.

FIG. 7 is a timing chart of injection molding.

FIG. 8 is a perspective view of a resin molded product.

FIG. 9 is a sectional view taken along line XX of FIG. 8 showing a resin molded product.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 resin molded product 2 design portion 3 internal space 4 mounting portion 5 thin portion 6 thick portion 7 fixing means 8 mounted portion 9 mounting tool 11 cavity 12 peripheral wall 13 vent hole 14 air passage 15 mounting tool support portion 21 injection molding die 22 Cavity mold 23 Core mold 24 Cavity 25 Thin part forming part 26 Thick part forming part 27 Gate 28 Sprue 29 Runner 31 Concave part 32 Gas injection port 33 Ventilation path forming part 36 Gas injector 37 Gas cylinder 41 Resin 42 Gas

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-312447 (JP, A) JP-A-5-245879 (JP, A) JP-A-5-118170 (JP, A) JP-A-4- 310712 (JP, A) JP-A-4-103317 (JP, A) JP-A-3-218811 (JP, A) JP-A-4-78510 (JP, A)

Claims (5)

(57) [Claims] Consisting 1. A substantially the same thickness of the plate-shaped thin portion
The design part consists of a design part and a thick part thicker than the thin part.
Extends to the part to be attached to form an internal space on the back side of
That a mounting portion, formed integrally with the fixture support portion formed in the internal space of the rear surface side of the design portion, before KiAtsu meat portion is formed with a substantially enclosed cavity therein, the The cavity is formed in a reduced shape that is substantially similar to the outer shape of the thick portion, and does not substantially extend to the thin portion. The mounting support portion is connected to the mounting portion and cuts between the thin portion.
A resin molded product characterized by having an extraordinary part . Wherein the thick portions and having a ventilation path connecting a cavity according to claim 1 Symbol placement of the resin molded article. 3. A thin-walled portion forming portion having substantially the same gap in a planar shape, a thick-walled portion forming portion having a gap larger than the gap, and a fixture supporting portion forming portion connected to the thick-walled portion forming portion. and a molten resin is injected into the cavity by using an injection mold having a compressed gas injection port in the thick part forming portion, and the injected resin covers the gas injection port. By injecting compressed gas before filling the cavity, the resin in the cavity is caused to flow together with the compressed gas, thereby forming a thin portion in the thin portion forming portion and forming a thick portion in the thick portion forming portion. At the same time, a fixture support portion is formed by the fixture support portion forming portion, and the inside of the thick portion has a substantially similar reduced shape of the outer shape of the thick portion, is substantially sealed, and is substantially thin. characterized that you form a cavity that does not extend to the part Motomeko 1 tree <br/> method for producing a fat molded article according. 4. A person <br/> method according to claim 3, wherein the gas inlet, characterized in that formed at a position opposed to the gate of the injection mold. 5. A method towards the claims 3 or 4, wherein the gas inlet is to be formed on the concave portion of the injection mold.