WO2020110371A1

WO2020110371A1 - Method for manufacturing bent resin pipe

Info

Publication number: WO2020110371A1
Application number: PCT/JP2019/029452
Authority: WO
Inventors: 栗林　延全
Original assignee: 横浜ゴム株式会社
Priority date: 2018-11-29
Filing date: 2019-07-26
Publication date: 2020-06-04
Also published as: JP2020082622A; JP7131339B2

Abstract

Provided is a method for manufacturing a bent resin pipe with which the pressure resistance of a desired inner bent portion of the bent resin pipe manufactured by resin injection molding using an assisting material is reliably improved. In the present invention: a half circumference holding part 15a, which protrudes from an inner bent portion 14a and extends by a predetermined length in an extension direction of a cavity 11, is formed in a mold 10 in a state of communicating with the cavity 11 in the previously selected bent inner portion 14a of bent parts 12A, 12B of the cavity 11 formed in the mold 10 and extending in a curve; the mold 10 is closed by fitting a half-circumference insert member 7a in a half-circumference part 15a, then the molten resin 17 is injected into the cavity 11, and then an assisting material 18 is injected into the cavity 11 and the molten resin 17 is cured, whereby the half-circumference insert member 7a is integrated to an inner bent portion 6a of bent parts 4A, 4B of a manufactured bent resin pipe 1.

Description

Method for manufacturing bent resin pipe

The present invention relates to a method for manufacturing a bent resin pipe, and more specifically, when manufacturing a bent resin pipe by resin injection molding using an assist material such as a gas assist molding method, a bent inner portion of the bent resin pipe is reinforced. The present invention relates to a method for manufacturing a bent resin pipe capable of reliably improving pressure resistance.

A gas-assisted molding method is known in which, when a resin pipe is molded by resin injection molding, a molten resin is injected into a mold and then a high pressure gas such as nitrogen gas is injected into the mold (for example, refer to Patent Document 1). .. Instead of high-pressure gas, water, metal balls, or resin balls may be injected into the mold at high pressure as an assist material.

When manufacturing a bent resin pipe by resin injection molding using an assist material in this way, the assist material injected into the mold cavity will pass through the cavity by the shortest route within the range where the bent portion of the bent resin pipe is molded. There is a characteristic. That is, in the bent portion of the cavity formed in the mold, the injected assist material passes so as to be unevenly distributed inside the bent portion of the cavity. Therefore, the injected resin is easily scraped by the assist material in the inside of the bend, and the thickness of the resin is smaller than that in the outside of the bend. Along with this, the manufactured bent resin tube has a room for improvement because it becomes difficult to secure pressure resistance to withstand a preset target internal pressure.

Japanese Patent Laid-Open No. 2003-181868

An object of the present invention is to reliably improve the pressure resistance by reinforcing the bent inner portion of the bent resin pipe when manufacturing the bent resin pipe by resin injection molding using an assist material such as a gas assist molding method. It is an object of the present invention to provide a method of manufacturing a bendable resin tube which is possible.

In order to achieve the above object, the method for producing a bent resin pipe of the present invention is such that after the molten resin is injected into a bending and extending cavity formed in a mold, an assist material is injected into this cavity and the injection is performed. In a method for manufacturing a bent resin tube for curing a resin to manufacture a bent resin tube, in a bent inner portion of a preselected bent portion of the cavity, a predetermined length is projected from the bent inner portion in the extending direction of the cavity. The extending holding portion is formed in the mold in a state of being communicated with the cavity, the insert member is fitted to the holding portion to close the mold, and then the molten resin is injected into the cavity. It is characterized in that the resin that has been injected and cured is integrated with the insert member.

According to the present invention, since the molten resin is injected into this cavity with the insert member fitted to the holding portion formed in the bending inner portion of the preselected bending portion of the cavity, the insert member is It is possible to manufacture an integrated bent resin tube. The reinforcing effect of the integrated insert member makes it possible to reliably improve the pressure resistance of the bent inner portion.

FIG. 1 is an explanatory view illustrating a bent resin pipe manufactured according to the present invention in a plan view. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a sectional view taken along the line AA of FIG. FIG. 4 is an explanatory view showing a modified example of the insert member in a plan view of a bent resin pipe. FIG. 5 is a sectional view taken along line BB of FIG. FIG. 6 is an explanatory view illustrating a molding device for manufacturing a bent resin pipe. FIG. 7 is an explanatory view illustrating the mold of FIG. 6 in plan view. FIG. 8 is an explanatory view illustrating the mold excluding the insert member of FIG. 7 by enlarging it in a plan view at a parting line. FIG. 9 is a sectional view taken along line CC before the mold of FIG. 7 is closed. FIG. 10 is a cross-sectional view illustrating a state where the mold of FIG. 9 is closed. FIG. 11 is a cross-sectional view taken along line CC before the mold of FIG. 7 is closed when an all-round insert member is used. FIG. 12 is a cross-sectional view illustrating a state where the mold of FIG. 11 is closed. FIG. 13 is an explanatory view schematically illustrating, in plan view at a parting line, the flow of the injected assist material inside the bent portion of the cavity of FIG. 7 after the injection of the molten resin.

Hereinafter, a method for manufacturing a bent resin pipe of the present invention will be described based on the embodiment shown in the drawings.

As illustrated in FIGS. 1 to 3, a bent resin pipe 1 manufactured according to the present invention is a tubular body having bent portions 4 (4A, 4B) and 5 and extending in this embodiment. The bent resin pipe 1 also has a straight portion 3. Openings 2 are formed at both longitudinal ends of the hollow conduit 1a of the bent resin pipe 1. An alternate long and short dash line CL in the drawing indicates a center line passing through the center of the cross section of the conduit 1a.

The wall thickness of the bent resin tube 1 is set to a predetermined reference value tm, but since the assist material 18 is used for molding as will be described later, in the bent portion 4, the wall thickness of the bent inner portion 6a is set. t1 is smaller than the reference value tm and the thickness t2 of the wall surface of the bent outer portion 6b (t1<tm<t2). In the bent portion 5, the thickness of the wall surface of the bent inner portion 6a is smaller than the thickness of the wall surface of the bent outer portion 6b, but the reference value tm or more. The wall thickness of the straight line portion 3 is within the allowable range of the reference value tm or more.

Therefore, in this embodiment, among the plurality of bent portions 4 and 5, the insert member 7 (half-circumference described later) that improves pressure resistance with respect to the bent portion 4 in which the wall thickness of the bent inner portion 6a is less than the reference value tm. The insert member 7a, the entire circumference insert member 7b, etc.) are integrated. Since the thickness of the wall surface of the bent portion 5 is equal to or greater than the reference value tm, the bent portion 5 is not subject to reinforcement by the insert member 7.

Since the shape of the bent resin pipe 1 is determined by the space restrictions such as the installation place, the bent resin pipe 1 may not have the straight line portion 3 and the number of the bent portions 4 and 5 is not limited. However, the bent resin pipe 1 has at least one bent portion 4 to be reinforced by the insert member 7. The bent resin pipe 1 illustrated in FIG. 1 has two

bent portions

4A and 4B to be reinforced by the insert member 7.

The insert member 7 is integrated with the bent inner portion 6a of the bent portion 4. More specifically, as illustrated in FIGS. 2 and 3, the bent inner portion 6a of the bent portion 4A is provided with a semi-circular insert member 7a protruding from the bent inner portion 6a to the outer side in the radial direction of the bent resin pipe 1. There is. The half-circumferential insert member 7 a has a shape that extends for a predetermined length in the extending direction of the bent resin tube 1 and extends for a half turn in the circumferential direction of the bent resin tube 1. That is, the semi-circular insert member 7a has a semi-cylindrical shape that covers the semi-circular range of the outer peripheral surface of the bent resin tube 1.

The half-circle insert member 7a is provided on the bent inner portion 6a so as to cover the range where the wall thickness is less than the reference value tm. In the bent inner portion 6a of the bent portion 4, there is a boundary point P at which the wall thickness is the reference value tm and less than the reference value tm. Therefore, as illustrated in FIG. 2, the half-surrounding insert member 7a extends between the boundary points P that are separated from each other in the extending direction of the bent resin tube 1. Alternatively, the semi-circular insert member 7a is extended between the positions where the wall thickness is slightly thicker than the reference value tm.

Various shapes can be adopted for the insert member 7, and as shown in FIG. 4 and FIG. 5, the entire circumference insert member 7b can also be adopted. The entire circumference insert member 7b extends a predetermined length in the extending direction of the bent resin pipe 1, and extends not only to the bent inner portion 6a of the bent portion 4 of the bent resin pipe 1 but also to the bent outer portion 6b. It is continuous all around the circumference. That is, the entire circumference insert member 7b has a cylindrical shape that covers the entire circumference of the outer peripheral surface of the bent resin tube 1.

The insert member 7 can be made of the same type (specification) of resin as the bent resin pipe 1 or a different type (specification) of resin. Alternatively, the metal insert member 7 may be used. When the insert member 7 is made of a resin or metal of a different type from the bent resin tube 1, a material having higher rigidity (breaking stress) than the resin 17 forming the bent resin tube 1 is used.

Each of the insert members 7 (7a, 7b) is set to have a substantially constant thickness, for example, and is set to have a size capable of obtaining a sufficient reinforcing effect. When the insert member 7 is made of the same resin 17 as the bent resin pipe 1, and if the minimum value of the wall thickness t1 at the bent inner portion 6a is t1n, the thickness ta of the half-circle insert member 7a is, for example, a reference value. Value tm-set to be equal to or greater than the minimum value t1n. That is, it is set to about (tm-t1n)≦ta≦(tm-t1n)×1.2. The thickness tb of the entire circumference insert member 7b is set similarly to the thickness ta of the half circumference insert member 7a.

The bent resin tube 1 is manufactured using the molding device 8 illustrated in FIG. The molding device 8 includes a cylinder 9 a that injects the molten resin 17 into the mold 10, and an assist material injection portion 9 b that injects the assist material 18 into the mold 10.

A suitable type of resin 17 is selected from various injectable resins 17 according to the performance required for the bent resin tube 1. For example, in the case of manufacturing the bent resin pipe 1 for an air conditioner mounted on an automobile, as the resin 17, for example, polyamide, polyphenylene sulfide or the like is used.

The assist material 18 may be a known material, and an appropriate material is selected from gases such as nitrogen gas, liquids such as water, and solids such as metal spheres and resin spheres. The assist material injection unit 9b employs a known appropriate mechanism according to the type of the assist material 18.

As illustrated in FIGS. 7 to 10, the mold 10 is composed of one mold 10a to be assembled and the other mold 10b. The

molds

10a and 10b are joined and separated with the parting line PL as a boundary.

The mold 10 has a cavity 11 formed therein. The cavity 11 is bent and extends in a shape similar to that of the bent resin tube 1 to be manufactured. The mold 10 is provided with a runner 16a connected to the cavity 11 via a gate 16b. The runner 16 a is connected to the nozzle of the molding device 8 via a sprue formed on the mold 10. The mold 10 is also provided with a discharge portion for the assist material 18 injected into the cavity 11.

In this embodiment, the mold 10 is further formed with an additional cavity 11a. More specifically, the runner 16a further extending from the cavity 11 is formed in a state where the additional cavity 11a, which is a cavity having the same shape as the half-circle insert member 7a, is in communication with the runner 16a.

A state in which a holding portion 15 (a half-circumference holding portion 15a, which will be described later, a full-circumference holding portion 15b, etc.) protruding from the bending inner side portion 14a communicates with the cavity 11 in the bending inner portion 14a of the preselected bending portion 12 of the cavity 11. And is formed in the mold 10. In the mold 10, portions corresponding to the bent portions 4 (4A, 4B) and 5 of the bent resin tube 1 are formed as bent portions 12 (12A and 12B) and 13 of the cavity 11, respectively. Further, a holding portion 15 into which the insert member 7 is fitted is formed at a position corresponding to the insert member 7 of the bent resin pipe 1.

The bent portion 12A of the cavity 11 is provided with a half circumference holding portion 15a having a recess in the shape of the half circumference insert member 7a. That is, the half-circumference holding portion 15a extends in the extending direction of the cavity 11 by a predetermined length, and also extends in the circumferential direction of the cavity 11 by a half circumference length. Similarly, the bent portion 12B of the cavity 11 is also provided with a half circumference holding portion 15a having a recess in the shape of the half circumference insert member 7a of the bent portion 4B of the bent resin tube 1.

Next, an example of the procedure of the method for manufacturing a bent resin pipe of the present invention will be described.

As illustrated in FIG. 9, before the

molds

10a and 10b are closed, the semi-circular holding member 15a is fitted with the semi-circular insert member 7a. After that, as illustrated in FIG. 10, the

molds

10a and 10b are assembled with each other to be in a mold closed state. The inner peripheral surface of the half-circumferential insert member 7a is smoothly (substantially without step) continuous with the adjacent inner peripheral surface of the cavity 11.

In this state, the molten resin 17 is injected into the mold 10 from the cylinder 9a. The injected resin 17 passes through the sprue formed on the mold 10, the runner 16a, and the gate 16b and is injected into the cavity 11 and the rib molding portion 15. The rib molding portion 15 is filled with the molten resin 17, and the wall surface of the cavity 11 is covered with the molten resin 17. In this embodiment, the resin 17 injected into the mold 10 is filled in the additional cavity 11a through the runner 16a that extends further.

Then, the assist material 18 is injected into the mold 10 from the assist material injection portion 9b at a predetermined high pressure. The injected assist material 18 passes through the inside of the cavity 11 in which the molten resin 17 is injected at a high pressure along the extending direction thereof.

When integrating the entire circumference insert member 7b with the bent resin pipe 1, as shown in FIGS. 11 and 12, an entire circumference holding portion 15b having a recess in the shape of the entire circumference insert member 7b is formed in the cavity 11. To be done. That is, the entire circumference holding portion 15b extends in the extending direction of the cavity 11 by a predetermined length, and continuously extends over the entire circumference of the cavity 11 in the circumferential direction to communicate with the cavity 11. It is formed in the mold 10.

Then, as illustrated in FIG. 11, before the

molds

10a and 10b are closed, the entire circumference holding portion 15b is fitted with the entire circumference insert member 7b. After that, as illustrated in FIG. 12, the

molds

10a and 10b are assembled to each other to be in a mold closed state. The inner peripheral surface of the entire circumference insert member 7b is smoothly (substantially without step) continuous with the adjacent inner peripheral surface of the cavity 11.

As illustrated in FIG. 13, in the bent portion 12A of the cavity 11, the assist material 18 injected at high pressure tends to pass biasedly toward the inner side of the bend, which is the shortest route of the cavity 11. Therefore, the resin 17 of the bent inner portion 14a of the bent portion 12A is more scraped by the assist material 18 that passes under high pressure. As a result, the thickness t1 of the resin 17 on the wall surface of the bent inner portion 14a is smaller than the thickness t2 of the resin 17 on the wall surface of the bent outer portion 14b, and is smaller than the reference value tm.

The assist material 18 also passes through the other

bent portions

12B and 13 as described above. Therefore, in the bent portion 12B as well, the thickness t1 of the resin 17 on the wall surface of the bent inner portion 14a becomes smaller than the reference value tm. On the other hand, since the bent portion 13 has a relatively large radius of curvature, it is difficult for the resin 17 on the wall surface of the bent inner portion 14a to be scraped by the assist material 18 that passes under high pressure. As a result, the thickness of the resin 17 on the wall surface of the bent inner portion 14a of the bent portion 13 can be ensured to be equal to or greater than the reference value tm, so that the holding portion 15 in which the insert member 7 is fitted and arranged has the

bent portions

12A and 12B. It is only provided.

In order to select the bent portion in which the holding portion 15 is provided, for example, molding is performed using the molding device 8 in the state where the holding portion 15 is not provided in the cavity 11 of FIG. To manufacture. The thickness of the resin 17 on the wall surface of the bent inner portion of the bent portion of the bent resin tube 1 is measured to confirm whether or not the reference value tm or more. The bent portion where the measured thickness of the resin 17 is less than the reference value tm is specified as the bent portion 4 into which the insert member 7 is integrated. Then, the holding portion 15 is provided on the bent portion 12 of the cavity 11 corresponding to the specified bent portion 4. The thicknesses ta, tb, etc. of the insert member 7 can be set based on the thickness of the resin 17 on the wall surface of the bent inner portion measured at this time.

If such measurement data is accumulated to some extent, it is possible to calculate the thickness of the resin 17 on the wall surface of the inner side portion of each bent portion by a molding simulation analysis using the accumulated data. Then, based on the calculated thickness of the resin 17, the bent portion 12 in which the holding portion 15 is provided can be determined.

In the mold 10, the injected resin 17 is cured to form a resin pipe along the cavity 11, and the insert member 7 is joined to the resin pipe. That is, the bent resin pipe 1 in which the insert member 7 is integrated is manufactured. In the bent portion 4 (4A, 4B) of the bent resin tube 1, the thickness t1 of the resin 17 on the wall surface of the bent inner portion 6a is smaller than the reference value tm, but is reinforced by the integrated insert member 7. ing. Therefore, even if a preset target internal pressure acts on the bent resin tube 1, it becomes possible to withstand. According to this manufacturing method, by providing the insert member 7 having appropriate specifications, it is possible to reliably improve the pressure resistance of the desired bent inner portion 6a of the bent resin pipe 1 by the reinforcing effect of the insert member 7. Become.

In this embodiment, the insert member 7 is molded by hardening the resin 17 filled in the additional cavity 11a. That is, it is very efficient since the insert member 7 can be additionally molded together with the manufacture of the bent resin tube 1 in which the insert member 7 is integrated. After that, the additionally molded insert member 7 can be used by fitting it to the holding portion 15 when molding the bent resin pipe 1 in which the insert member 7 is integrated.

Also, according to this manufacturing method, it is possible to mass-produce even the bent resin pipe 1 having a complicated shape. According to the manufactured bent resin tube 1, it is possible to secure necessary pressure resistance while reducing the weight as compared with the metal tube. For example, it is possible to manufacture a bent resin tube 1 having an inner pressure of 5 MPa or more and an inner diameter of 10 mm or more and 20 mm or less. Since it can also be used as a low-pressure pipe, it is possible to significantly reduce the weight by replacing a general-purpose bent metal pipe with this bent resin pipe 1.

It is also possible to use an insert member 7 having an arc-shaped cross section in which the length extending in the circumferential direction of the cavity 11 is shorter than that of the half-circle insert member 7a, or an arc shape in which the cross section is elongated. In this case, the holding portion 15 is a recess having an arc-shaped cross section of the insert member 7. In order to fit the insert member 7 into the holding portion 15 so as not to come off easily, it is desirable to use the insert member 7 that extends in the circumferential direction at least as much as the half-round insert member 7a.

In order to ensure the required pressure resistance more reliably, it is desirable to manufacture the bent resin pipe 1 in which the entire circumference insert member 7b is integrated. If the thickness ta and tb of the insert member 7 cannot be set to a large value due to the restriction of the installation space of the bent resin pipe 1, the insert made of a material having higher rigidity (breaking stress) than the resin 17 forming the bent resin pipe 1. It is preferable to use the member 7. By forming the insert member 7 with such a material, the thickness ta and tb of the insert member 7 can be made thinner. On the other hand, when the insert member 7 is made of the same type of resin as the resin 17 forming the resin bending tube 1, both can be more firmly integrated.

DESCRIPTION OF SYMBOLS 1 Bending resin pipe 1a Pipe line 2 Opening part 3 Straight part 4 (4A, 4B) Bending part 5 Bending part 6a Bending inner part 6b Bending outer part 7 (7a, 7b) Insert member 8 Molding device 9a Cylinder 9b Assist material injection part 10 (10a, 10b) Mold 11 Cavity 11a Additional cavity 12 (12A, 12B) Bending portion 13 Bending portion 14a Bending inner portion 14b Bending outer portion 15 (15a, 15b) Holding portion 16a Runner 16b Gate 17 Resin 18 Assist material

Claims

A method for manufacturing a bent resin tube, in which a molten resin is injected into a bent and extending cavity formed in a mold, an assist material is injected into the cavity, and the injected resin is cured to manufacture a bent resin tube. At
A holding portion, which projects from the bending inner portion and extends a predetermined length in the extending direction of the cavity, is formed in the mold at the bending inner portion of the preselected bending portion of the cavity in communication with the cavity. In advance, after inserting the insert member into the holding portion and closing the mold, the molten resin is injected into the cavity to integrate the cured resin and the insert member. A method for manufacturing a bent resin pipe, characterized by:
The method for manufacturing a bent resin pipe according to claim 1, wherein the insert member has a shape that covers a half circumferential range of an outer peripheral surface of the cavity in a cross-sectional view.
The method for manufacturing a bent resin pipe according to claim 1, wherein the insert member has a shape that covers the entire circumferential range of the outer peripheral surface of the cavity in a cross-sectional view.
The method for manufacturing a bent resin pipe according to any one of claims 1 to 3, wherein the insert member is made of the same resin as the resin.
An additional cavity for molding the insert member is formed in the mold, and the insert member is molded by filling the additional cavity with the resin injected when molding the bent resin pipe, The method for producing a bent resin pipe according to claim 4, wherein the molded insert member is subsequently fitted into the holding portion and used when the bent resin pipe is molded.
The method for manufacturing a bent resin pipe according to any one of claims 1 to 3, wherein the insert member is made of a resin different from the resin.
The method for manufacturing a bent resin pipe according to any one of claims 1 to 3, wherein the insert member is made of metal.