JP2003191340A - Hollow molding product and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow molding product in which a local stress concentration at a connecting part can be eliminated and to provide a method for manufacturing the same. <P>SOLUTION: The hollow molding product is obtained by connecting at least two or more components and is made of a closed curve in which a boundary line of a section is a recess at all sites toward a center of the section. The connecting part of the molding product is installed at least at one position at a site having a smaller curvature of a circle having the same area as a sectional area of the product of the closed curve for drawing the boundary line of the section of the product. An adhesive material is charged in a groove- like welding part provided in the connecting part and connected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded article and a method for manufacturing the hollow molded article, which can reduce stress concentration generated in a joint portion when an internal pressure is applied.

[0002]

2. Description of the Related Art Injection molding method, blow molding method, extrusion molding method, compression molding method, etc. are used as a molding method for resin molded products, but generally one processing step due to restrictions such as mold structure. There are restrictions on the shape that can be molded with. For example, in the injection molding method, it is difficult to produce hollow molded products such as bent pipes and tanks due to the restriction of the mold structure. In such a case, a plurality of parts are molded in advance by an ordinary molding method, and these are combined and joined together, whereby a complicated shape such as a hollow molded product can be molded.

As a joining method, Japanese Patent Laid-Open No. 10-1604
DSI (Die Slide
Injection) molding method and DRI (Die Rotary Injecti) as proposed in Japanese Patent Laid-Open No. 10-15998.
on) There is a molding method.

1 and 2 are schematic views showing one embodiment of a hollow molded article molded by the DSI molding method.
FIG. 3 is a cross-sectional view of the hollow molded product shown in FIG. 1 or 2.

That is, in the DSI molding method, the shape of a molded product is divided into a plurality of parts in advance, each part is molded by a normal injection molding method in the same mold, and then the mold is moved to
This is a molding method for molding a complicated shape such as a hollow molded product by pouring a molten resin into the welded portion 23 of the joint portion 11 as a secondary molding after being combined with the shape of the molded product.

However, in the DSI molding method, it is difficult to completely weld the entire joint 11 and a crack-like unwelded portion 21 is generated on the inner surface of the joint.

The DRI molding method is a modification of the DSI molding method, in which the shape of the molded product is divided into a plurality of parts in advance, and each part is molded by a normal injection molding method in the same die,
After rotating the mold and combining it with the shape of the molded product,
As the secondary molding, a molding method of molding a complicated shape such as a hollow molded product by pouring a molten resin into the welded portion of the joint portion.

Like the DSI molding method, it is difficult for the DRI molding method to completely weld the entire joint portion, and crack-like unwelded portions occur on the inner surface of the joint portion.

[0009]

Problems to be Solved by the Invention DSI molding method and DRI
Since there is a crack-shaped unwelded part on the inner surface of the joint part of the resin hollow molded product molded by the molding method, the joint part is weaker in strength than the molded product body, and local to the joint part. When stress concentration occurs, it causes the destruction of the molded product. Therefore, it is an object of the present invention to provide a hollow molded article and a method for manufacturing the hollow molded article, which can eliminate local stress concentration at the joint.

[0010]

In order to achieve the above object, the present invention adopts the following configurations. That is, the present invention is (1) a hollow molded article obtained by joining at least two or more parts, which is a closed curve in which the boundary line of the cross section is concave toward all the parts toward the center of the cross section,
At least one portion where the joint portion 11 of the hollow molded product is smaller than the curvature of a circle having the same area as the cross-sectional area of the hollow molded product in the closed curve that draws the boundary line of the cross section of the hollow molded product. The hollow molded article, which is installed in the joining section 11, is obtained by injecting an adhesive material into the groove-shaped welded section 23 provided inside the joining section 11 and joining them.

Here, the boundary line of the cross section is the boundary line 24 formed by the inner surface of the hollow molded article in the cross section. Further, a closed curve that is concave at all parts toward the center of the cross section means that the boundary line 24 of the cross section is a closed curve, and the shape of the closed curve is convex toward the center 25 of the closed curve as shown in FIG. It means that the part 26 that is The cross-sectional area of the hollow molded product refers to the area closed by the closed curve 24, and the circle having the same area as the cross-sectional area of the hollow molded product is the same as the area closed by the closed curve 24. Circle with an area of 27
Refers to.

Further, a portion having a smaller area than the curvature of a circle having the same area as the cross-sectional area of the hollow molded article means that the closed curve 24 and the circle 27 in FIG.
The point where the closed curve 24 has a curvature closer to the tangent line 31 perpendicular to the perpendicular line 29 than the circle 27 when contacted at the upper contact point 30.

(2) A hollow molded article obtained by joining at least two or more parts, which is a hollow curve having a closed curve in which the boundary line of the cross section is concave toward all the parts toward the center of the cross section. The joint portion 11 of the molded product is installed in at least one portion of the closed curve that draws the boundary line of the cross section of the hollow molded product and has the smallest curvature.
The adhesive is injected into the groove-shaped welded portion 23 provided inside,
Hollow molded product characterized by being joined.

Here, in the closed curve which draws the boundary line of the cross section of the hollow molded product, the portion having the smallest curvature is the circle having the same area as the cross sectional area of the hollow frame molded product in FIG. Of the tangents 3 that are smaller than the curvature of
Refers to a part having a curvature close to 1.

(3) The hollow molded product according to any one of (1) and (2), wherein the hollow molded product has a pipe shape or a tank shape.

(4) The hollow molded article according to any one of (1) to (3), wherein the hollow molded article is made of resin.

(5) Any of the above (1) to (4), wherein the adhesive material injected into the groove-shaped welded portion 23 provided inside the joining portion 1) by an injection molding machine is a resin. Hollow molded product described above.

(6) A hollow molded article obtained by joining at least two or more parts, which is a hollow molded product having a closed curve in which the boundary line of the cross section is concave toward all the parts toward the center of the cross section. The joint portion 11 of the molded product is installed at least at one location in a region smaller than the curvature of a circle having the same area as the cross-sectional area of the hollow molded product in the closed curve that draws the boundary line of the cross section of the hollow molded product. A method for manufacturing a hollow molded article, characterized in that an adhesive is injected into a groove-shaped welded portion 23 provided inside the joint portion 11 and the joint is performed.

(7) A hollow molded article obtained by joining at least two or more parts, which is a hollow curve having a closed curve in which the boundary line of the cross section is concave toward all the parts toward the center of the cross section. The joint portion 11 of the molded product is installed in at least one portion of the closed curve that draws the boundary line of the cross section of the hollow molded product and has the smallest curvature.
The adhesive is injected into the groove-shaped welded portion 23 provided inside,
A method for producing a hollow molded article, which is characterized by being joined.

(8) The method for producing a hollow molded product according to any one of (6) and (7), wherein the hollow molded product has a pipe shape or a tank shape.

(9) The design method for determining the joint position of the hollow molded article according to any one of (6) to (8), wherein the hollow part is made of resin.

(10) Any of the above (6) to (9), wherein the adhesive material injected by the injection molding machine into the groove-shaped welded portion 23 provided inside the joint portion 11 is a resin. The method for producing a hollow molded article as described above.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The hollow molded article to which the present invention is applied is a hollow article obtained by joining at least two parts.

The material of the hollow molded article is not particularly limited, but a thermoplastic resin is preferably used, and among them, in particular,
Nylon resin, polypropylene, styrene resin, polyester resin, polycarbonate, polyacetal and the like are preferably used. These can be used as a polymer alloy, or can be used by adding additives such as glass fiber, flame retardant, colorant, and weather resistance agent.

The present invention is a hollow molded article obtained by joining at least two or more parts, which is a closed curve having a boundary line of the cross section which is concave at all portions toward the center of the cross section. At least one joint portion 11 of the hollow molded product is located at a portion smaller than the curvature of a circle having the same area as the cross-sectional area of the hollow molded product in the closed curve that draws the boundary line of the cross section of the hollow molded product. A hollow molded article and a designing method therefor, characterized in that the adhesive material is injected into a groove-shaped welded portion 23 provided inside the joint portion 11 and the joint portion is joined. Of the closed curve of the cross section,
It is preferable to install it in a portion having the smallest curvature.

In the present invention, the hollow molded article preferably has a pipe shape illustrated in FIG. 1 or a tank shape illustrated in FIG. Here, the pipe shape is a hollow article shape in which the overall shape is a straight line or a curved line, and the tank shape is a hollow article shape in which the overall shape is a sphere or a three-dimensional shape conforming to a sphere. is there.

In the present invention, the hollow molded article is preferably a resin part.

In the present invention, the adhesive material for joining the hollow molded article is preferably a resin which is injected into the groove provided in the joint portion by an injection molding machine.

The use of the hollow molded article of the present invention is not particularly limited, but it is preferably a member for use in the flow of gas, liquid or fluid, and is particularly preferably used as a part related to an internal combustion engine.

Examples of components related to the internal combustion engine include tanks, pipes and intake manifolds.

FIG. 1 is a schematic view showing a pipe shape which is one embodiment of the present invention.

FIG. 2 is a schematic view showing the shape of a tank which is another embodiment of the present invention.

FIG. 3 is a schematic view showing a cross section of the hollow molded article shown in FIG. 1 or 2.

The molding method of the hollow molded article to which the present invention is applied is not particularly limited, but the DSI molding method or the DRI molding method is preferable.

As a preferred embodiment of the present invention, an example applied to a pipe-shaped hollow molded product having an elliptical cross section will be described below.

The above-mentioned hollow molded article is formed by molding the upper and lower parts by a usual injection molding method, then combining them with the shape of the hollow molded article, and secondarily injecting a resin into the joint portion 11. There is.

Due to the limitation of the molding method, the hollow molded article is
A crack-shaped unwelded portion 2 on the inner surface and the outer surface of the joint portion 11.
There will be 1, 22.

Further, the body of the hollow molded product and the welded portion 23.
The material strength of the boundary portion with the adhesive material injected into is extremely lower than that of other portions.

As a result, when the internal pressure is applied, the crack-like unwelded portion 21 on the inner surface is deformed in the direction of tearing from both sides of the crack, and is welded to the main body of the hollow molded article at the root of the unwelded portion 21. If stress concentration exceeding the material strength occurs at the boundary with the adhesive material injected into the portion 23, the hollow molded article may be broken.

The unwelded portion 22 on the outer surface has almost no influence on the strength of the hollow molded article against an internal pressure load due to its position and size.

In the present invention, in order to improve the strength of the hollow molded product against an internal pressure load, a joint portion is formed in a portion of the cross section of the hollow portion having a smaller area than the curvature of a circle having the same area as the sectional area of the hollow molded product. The feature is that they are arranged.

In the hollow molded article, the joint portions 11 are arranged at two locations, which are the areas having the smallest curvature of the elliptical cross section.

Here, in general, when an internal pressure is applied to a hollow product, the hollow product is deformed so that the hollow product tends to approach a circle with respect to the hollow cross section.

Therefore, in a region where the curvature is larger than a circle having the same area as the cross-sectional area of the hollow article, a deformation that tends to reduce the curvature occurs, and when a crack exists on the inner surface of the region, the crack is generated. Deformation occurs in the direction of tearing from both sides.

Further, in a region where the curvature is smaller than a circle having the same area as the cross-sectional area of the hollow article, deformation which tends to increase the curvature occurs, and when a crack exists on the inner surface of the region, the crack is generated. Is deformed in the direction pushed from both sides.

Therefore, when an internal pressure is applied to the hollow molded product according to the present invention, the joint portion 11 has a large curvature due to the joint portion being arranged at a portion having the smallest curvature of the elliptical cross section of the hollow molded product. Deformation occurs in the direction.
As a result, the unwelded portion 21 on the inner surface of the hollow molded product, which is problematic in terms of strength of the hollow molded product, is deformed in a direction in which it is pushed from both sides.

As a result, local stress concentration does not occur at the boundary between the body of the hollow molded product and the adhesive material injected into the welded portion 23, and the strength of the hollow molded product against the internal pressure load can be obtained. .

[0048]

[Examples] The following is a CAE analysis software "ABAQ" assuming that a pipe-shaped hollow molded article is loaded with internal pressure.
It is a simulation result by "US". In addition, "C
"AE analysis" refers to simulations such as flow analysis, thermal analysis, and structural analysis using a computer.

[Embodiment 1] FIG. 6 shows a major axis of the outer peripheral portion of 40 m.
m, 5 mm thick with an elliptical cross section with a minor axis of 30 mm at the outer periphery
FIG. 3 is a cross-sectional view of the pipe-shaped hollow molded article of FIG. The pipe-shaped hollow molded product is a straight pipe having no bend in the direction perpendicular to the hollow cross section, and is assumed to have an arbitrary length.

In the hollow molded product, it is assumed that two parts are joined together at a portion having the smallest curvature in the elliptical cross section.

In the hollow molded product, glass fiber reinforced nylon resin is used as the material for both the hollow molded product body and the adhesive, and the material strength at the boundary between the hollow molded product body and the welded portion 23 is assumed to be 60 MPa. .

It is assumed that the hollow molded article is molded by the DSI method. Therefore, a crack having a depth of 4 mm is provided on the inner surface of the joined portion of the hollow molded article and a crack having a depth of 1 mm is provided on the outer surface of the hollow molded article assuming an unwelded portion.

An internal pressure 41 of 1.0 MPa was applied to the above hollow molded article.

FIG. 7 is a diagram in which the deformation of the hollow molded product shown in FIG. 6 when an internal pressure is applied is emphasized five times.

FIG. 8 is an enlarged view of the vicinity of the joint portion of the modified view shown in FIG.

Table 1 shows the stress generated in the stress evaluation section 44.

The hollow molded product is deformed by an internal pressure load so as to approach a true circle with respect to the hollow cross section.

Therefore, at a joint portion arranged in a portion having a curvature in the hollow cross section that is smaller than the curvature of a circle having the same area as the cross-sectional area of the hollow molded product, deformation occurs in the direction in which the curvature becomes larger.

As a result, the unwelded portion 21 of the crack-shaped inner surface is deformed in the direction of being pushed inward from both sides of the crack.

Therefore, the stress evaluation unit 4 which is the root of the crack
No stress is concentrated on 4.

Stress generated in the stress evaluation section 44, 9.1M
Pa is a material strength of 60 at the boundary between the hollow-molded product body of the assumed glass fiber reinforced nylon resin and the welded portion 23.
Since it is much lower than MPa, it can be said that the hollow molded article has sufficient strength under the assumed internal pressure load condition.

[Comparative Example 1] FIG. 9 shows a major axis of the outer peripheral portion of 40 m.
m, 5 mm thick with an elliptical cross section with a minor axis of 30 mm at the outer periphery
FIG. 3 is a cross-sectional view of the pipe-shaped hollow molded article of FIG. The pipe-shaped hollow molded product is a straight pipe having no bend in the direction perpendicular to the hollow cross section, and is assumed to have an arbitrary length.

In the hollow molded product, it is assumed that two parts are joined together at a portion having the largest curvature in the elliptical cross section.

In the above hollow molded product, the same glass fiber reinforced nylon resin as in Example 1 was used as the material for both the hollow molded product body and the adhesive, and the material strength at the boundary between the hollow molded product body and the welded portion 23 was increased. It is assumed to be 60 MPa.

The hollow molded article is assumed to be molded by the DSI method. Therefore, a crack having a depth of 4 mm is provided on the inner surface of the joined portion of the hollow molded article and a crack having a depth of 1 mm is provided on the outer surface of the hollow molded article assuming an unwelded portion.

To the hollow molded article, as in Example 1, 1.
An internal pressure 41 of 0 MPa was applied.

FIG. 10 is a diagram in which the deformation of the hollow molded product shown in FIG. 9 under an internal pressure load is emphasized five times.

FIG. 11 is an enlarged view of the vicinity of the joint of the modified view shown in FIG.

Table 1 shows the stress generated in the stress evaluation section 44.

[0070]

[Table 1]

Like the first embodiment, the hollow molded article is deformed by an internal pressure load so that the hollow cross section tends to be close to a perfect circle.

Therefore, at the joint portion arranged at a portion having a curvature larger than that of a circle having the same area as the cross-sectional area of the hollow molded product, deformation occurs in a direction in which the curvature becomes smaller.

As a result, the unwelded portion 21 of the crack-shaped inner surface is deformed in the direction of tearing outward from both sides of the crack.

Therefore, the stress evaluation unit 4 which is the root of the crack
Stress concentrates on 4.

Stress generated in the stress evaluation unit 44, 88.4
Mpa is the material strength of 6 at the boundary between the welded part 23 and the hollow molded product body of the assumed glass fiber reinforced nylon resin.
Since it exceeds 0 MPa, the hollow molded article does not have sufficient strength under the assumed internal pressure load condition.
It can be said that there is a high possibility of destruction from the joint.

[0076]

According to the present invention, in the design of a hollow molded article in which at least two or more parts are joined by an adhesive poured into a groove provided inside the joint, the cross section of the hollow molded article is Occurrence at the joint when the internal pressure of the hollow molded product is applied by setting the joint at a part smaller than the curvature of the circle having the same area as the cross-sectional area of the hollow molded product in the closed curve drawing the boundary line. The stress concentration that occurs can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing a preferred embodiment of the hollow molded article of the present invention.

FIG. 2 is a schematic view showing another preferred embodiment of the hollow molded article of the present invention.

FIG. 3 is a cross-sectional view of the hollow molded article shown in FIGS. 1 and 2.

FIG. 4 is a schematic diagram showing an aspect of a closed curve in which a portion that is convex toward the center of the cross section exists.

FIG. 5 is a schematic diagram showing an aspect of a portion of a closed curve that is smaller than the curvature of a circle having the same area as the closed curve.

6 is a cross-sectional view of the hollow molded article shown in Example 1. FIG.

FIG. 7 is a deformation diagram of the hollow molded article shown in FIG. 6 when an internal pressure is applied.

FIG. 8 is an enlarged view of the vicinity of the joint of the modification shown in FIG.

9 is a cross-sectional view of the hollow molded article shown in Comparative Example 1. FIG.

10 is a deformation diagram of the hollow molded product shown in FIG. 9 when an internal pressure is applied.

FIG. 11 is an enlarged view of the vicinity of the joint of the modified view shown in FIG.

[Explanation of symbols]

11: Joining part 21: Inner unwelded part 22: Outer unwelded part 23: Welded part 24: Closed curve 25: Center of closed curve 26: Portion convex toward the center of closed curve 27: Same area as closed curve Circle 28: Center of a circle having the same area as the closed curve 29: Perpendicular line shared by the closed curve and a circle having the same area as the closed curve 30: Closed curve and contact point 31 of the circle having the same area as the closed curve: Closed curve Tangent line 41 at the contact point of a circle having the same area as the closed curve: internal pressure 42: shape before deformation 43: shape after deformation 44: stress evaluation part

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02M 37/00 321 F16L 9/12 F16L 9/12 B65D 8/22 Z // B65D 8/22 B29L 22: 00 B29L 22:00 F02M 35/10 102N F term (reference) 3E061 AA30 AB09 AD05 DA06 DB01 3H111 AA01 BA15 CA08 CA33 CB02 CB15 EA02 4F211 AD05 AG07 AG24 AH17 AH55 TA08 TC08 TC14 TD01 TN82

Claims (10)

[Claims] 1. A hollow molded article obtained by joining at least two or more parts, which is a closed curve having a boundary line of the cross section which is concave at all portions toward the center of the cross section. The joint portion of the article is installed in at least one place in a portion smaller than the curvature of a circle having the same area as the cross-sectional area of the hollow molded article in the closed curve that draws the boundary line of the cross section of the hollow molded article. A hollow molded article, characterized in that an adhesive is injected into a groove-shaped welded portion provided inside the joint and then joined. 2. A hollow molded article obtained by joining at least two or more parts, which is a closed curve having a boundary line of a cross section which is concave at all portions toward the center of the cross section. The joint portion of the product is installed in at least one place in the portion having the smallest curvature in the closed curve that draws the boundary line of the cross section of the hollow molded product, and the groove-shaped welded portion provided inside the joint portion. A hollow molded article, which is obtained by injecting an adhesive and joining them. 3. The hollow molded article according to claim 1, wherein the hollow molded article has a pipe shape or a tank shape. 4. The hollow molded article according to claim 1, wherein the hollow molded article is made of resin. 5. The hollow molded article according to claim 1, wherein the adhesive material injected by the injection molding machine into the groove-shaped welded portion provided inside the joint is resin. 6. A hollow-molded article obtained by joining at least two or more parts, which is a closed curve having a boundary line of the cross section which is concave at all portions toward the center of the cross section. The joint portion of the article is installed in at least one place in a portion smaller than the curvature of a circle having the same area as the cross-sectional area of the hollow molded article in the closed curve that draws the boundary line of the cross section of the hollow molded article. A method for manufacturing a hollow molded article, characterized in that an adhesive is injected into a groove-shaped welded portion provided inside the joint and then joined. 7. A hollow molded article obtained by joining at least two or more parts, which is a closed curve having a boundary line of the cross section which is concave toward all the parts toward the center of the cross section. The joint portion of the product is installed in at least one place in the portion having the smallest curvature in the closed curve that draws the boundary line of the cross section of the hollow molded product, and the groove-shaped welded portion provided inside the joint portion. A method for producing a hollow molded article, which comprises injecting an adhesive and joining the same. 8. The method for producing a hollow molded product according to claim 6, wherein the hollow molded product has a pipe shape or a tank shape. 9. The method for producing a hollow molded article according to claim 6, wherein the hollow component is made of resin. 10. The hollow molded article according to claim 6, wherein the adhesive material injected by the injection molding machine into the groove-shaped welded portion provided inside the joint portion is a resin. Production method.