JP2018062061A - Method for producing tubular resin molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED To obtain a high-quality tubular resin molded body by suppressing the generation of burrs that may occur in a branched portion of a pipe when injection-molding a branched tubular resin molded body. A tubular resin molded body having a main pipe portion 11 and a branch pipe portion 12 is molded by an injection molding method. The main pipe portion 11 is formed by a method using both injection molding and press-fitting of pressurized fluid, for example, using a floating core, and the branch pipe portion 12 is formed using a core mold 41 and a sleeve 42. When the main pipe portion 11 is formed, a resin wall 45 that separates the main pipe portion and the branch pipe portion is formed adjacent to the core-type distal end surface 41a. After the main pipe portion 11 is formed, the core mold 41 is retracted in a state in which the pressurization of the pressurized fluid is maintained, and the resin wall 45 is separated from the tubular resin molded body. [Selection] Figure 6

Description

The present invention relates to a method for producing a tubular resin molded body integrally molded with a synthetic resin. In particular, the present invention relates to a method for manufacturing a branched tubular resin molded body using injection molding.

Tubular resin moldings integrally molded with synthetic resin are used in various applications such as various pipes, connector members, and pipe joints. In particular, if the tubular resin molded body is integrally formed by using synthetic resin injection molding, the tube end seal structure and the mounting member can be integrally formed, which is convenient.

A technique for manufacturing a tubular resin molded body using injection molding is known. If the hollow tubular portion is a short tubular resin molded body, the tubular resin molded body can be injection molded using a mold having a core mold that defines the inner peripheral surface shape of the tube.
Also, in recent years, a technology that forms a hollow tubular part by introducing a pressurized gas or liquid into the central part of the resin and eliminating the resin at the central part of the resin once injected into the cavity has been put into practical use. Has been. As such a technique, a gas-assisted injection technology (Gas-assisted Injection Technology: GIT method), a water-assisted injection technology (Water-assisted Injection Technology: WIT method), and the like are known. For example, Patent Document 1 discloses a tubular resin molded body formed by a water assist injection molding technique.

In addition, as a technique for forming a hollow tubular portion by introducing a pressurized gas or liquid during injection molding, a technique using a so-called floating core is also known. For example, in Patent Document 2, after injecting molten resin into a cavity, a floating core having a size that can pass through the cavity is pushed from the pressurized port of the cavity with a pressurized fluid and injected into the cavity. An injection molding technique is disclosed in which a hollow tubular portion is formed by advancing the molten resin along the mold cavity to the discharge port. According to the manufacturing method, it is disclosed that a hollow product having a complicated shape with a uniform hollow part size can be injection-molded.

In addition, a method of manufacturing a branched tubular resin molded body by applying the technology using the floating core is also known. For example, in Patent Document 3, a slide shaft that forms a branched tube portion is used as a main cavity. A technique is disclosed in which a branch pipe is formed by forming a communication hole. According to the manufacturing method, the communication hole can be formed easily and at a lower cost than when the communication hole portion is post-processed.

JP2015-139879A Japanese Patent Laid-Open No. 04-208425 Japanese Patent Laying-Open No. 2015-174441

However, even with the method disclosed in Patent Document 3, since the through-hole is provided by the slide shaft moving toward the inside of the main pipe portion, burrs that protrude to the inside of the main pipe portion at the branch portion are likely to occur. Such burrs may become a resistance that hinders the flow of the main pipe portion, or if such burrs remain, the burrs may be peeled off during use and mixed into the fluid.

In addition, when a branch pipe is manufactured as in Patent Document 3 by a molding method using a floating core, scraps generated when a through hole is made adhere to the inner peripheral surface of the main pipe portion, resulting in product defects. May be.

An object of the present invention is to provide a tubular resin molded body that suppresses the generation of burrs that may occur at the branch portion of a pipe when a branched tubular resin molded body is formed, and a high-quality tubular resin molded body is obtained. It is to provide a manufacturing method.

As a result of intensive studies, the inventor, in a method for forming a hollow tubular body that combines injection molding and pressurized fluid, after the main pipe portion is formed, the inner circumference of the branch pipe is maintained while maintaining the pressurized fluid pressure. The present invention has been completed by discovering that the above problem can be solved by retracting the core mold to be formed and separating the resin wall formed between the main pipe portion and the branch pipe portion from the tubular resin molded body.

The present invention is a method for producing a tubular resin molded body having a hollow tubular portion using injection molding of a thermoplastic resin, and the hollow tubular portion includes a main pipe portion and a branch pipe portion branched from the main pipe portion. The injection molding includes a mold having a cavity having a pressurized port capable of injecting pressurized fluid at one end and a discharge port at the other end, and the tubular resin molded body is formed by the cavity. The outer surface shape of the resin is defined, and after the molten thermoplastic resin is injected into the cavity and filled, a pressurized fluid is pressed into the cavity from the pressurized port, and a part of the resin in the cavity is discharged. To form the main pipe portion, and the mold has a core mold that defines the inner peripheral surface shape of the branch pipe portion, and the injection molding is formed by the main pipe portion The tip of the core mold when being A resin wall that separates the main pipe portion and the branch pipe portion adjacent to each other, and after the main pipe portion is formed, with the pressurization of the pressurized fluid maintained, the core mold is retracted, It is a manufacturing method of the tubular resin molding which has the process of cut | disconnecting the said resin wall from a tubular resin molding (1st invention).

In the first invention, preferably, prior to the injection of the thermoplastic resin, the floating core is provided in the pressurized port, the floating core is moved to the discharge port side by the pressurization of the pressurized fluid, and the main pipe portion is moved by the movement of the floating core. (Second invention). In the first invention or the second invention, it is preferable that when the resin is injected into the cavity, the front end surface of the core mold is substantially the same position as the outer peripheral surface of the main pipe portion and the radial direction of the main pipe portion. (Third invention). In any one of the first to third inventions, preferably, the core mold further includes a cylindrical sleeve disposed on an outer periphery of the core mold, and the resin is injected into the cavity. In this case, the distal end portion of the sleeve is arranged so as to protrude inward in the radial direction of the main pipe portion from the outer peripheral surface of the main pipe portion (fourth invention). In the fourth aspect of the invention, it is preferable that the distal end portion of the sleeve has a tapered surface so that the inner peripheral side of the sleeve protrudes more radially inward of the main pipe portion than the outer peripheral side of the sleeve (fifth). invention). In the fourth invention, it is preferable that the core mold is moved backward to maintain the resin wall while maintaining the state in which the distal end portion of the sleeve protrudes radially inward of the main pipe portion from the outer peripheral surface of the main pipe portion. Separated from the tubular resin molded body (sixth invention).

According to the method for producing a tubular resin molded body of the present invention (first invention), burrs are hardly generated at the location where the main pipe portion and the branch pipe portion merge, and the quality of the tubular resin molded body is improved. Furthermore, if it is made like 2nd invention, the thickness of the pipe wall of a main pipe part will become stable easily, and the quality of a tubular resin molding will be improved more. In addition, if the third to fifth inventions are employed, the generation of burrs is further suppressed, and the removal of scraps is more reliable, and the quality of the tubular resin molded body is further improved.

It is a partial cross section figure which shows the shape of the tubular resin molding manufactured by the manufacturing method of this invention. It is a schematic diagram which shows the example of a structure of the injection mold used for the manufacturing method of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of this invention. It is sectional drawing which shows the shape of the resin molding taken out from the metal mold | die in the process of the manufacturing method of this invention. It is a schematic diagram which shows the other structural example of the injection mold used for the manufacturing method of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking as an example a tubular resin molded body used for liquid transfer piping. The invention is not limited to the individual embodiments shown below, and can be carried out by changing the form.

FIG. 1 is a diagram showing the shape of a tubular resin molded body 1 manufactured by a manufacturing method to be described later. In the figure, the upper part and the right part of the tube center line are shown in cross section, and the other parts are shown. Shown in appearance. The tubular resin molded body 1 has a hollow tubular portion formed so as to be a hollow tube. The hollow tubular part is a branched tubular part having a main pipe part 11 and a branch pipe part 12 branched from the main pipe part 11. That is, the branch pipe part 12 is branched from the middle of the main pipe part 11, and both communicate with each other. The main pipe portion 11 may be a straight tube or a bent tube. The branch pipe portion 12 is preferably a straight tube, but may be a bent tube as long as the core type described later can be removed. According to the manufacturing method to be described later, even when the main pipe portion 11 is a bent tubular shape, in particular, a bent tube shape that makes it difficult to remove a normal core type, a branched tubular hollow tubular portion can be formed.

The tubular resin molded body 1 has a gate mark 15. The gate trace is a trace of an injection port (gate) through which resin is injected into the cavity of the mold when the tubular resin molded body 1 is injection-molded. In the present embodiment, the gate mark 15 is provided on the outer peripheral surface of the main pipe portion 11.

In addition to the main pipe part 11 and the branch pipe part 12, the tubular resin molded body 1 may include other parts. For example, the tubular resin molded body 1 can be provided with a flange 16 in the vicinity of the ends of the main pipe portion 11 and the branch pipe portion 12 to improve the attachment property and sealing property of the tube. Similarly, seal grooves, ridges, and the like may be provided near the ends of the main pipe portion 11 and the branch pipe portion 12. The tubular resin molded body 1 may be integrally formed with stays, fixing portions, bosses, and the like for attachment and connection.

As the resin material constituting the tubular resin molded body 1, various thermoplastic resins capable of injection molding can be used. As the thermoplastic resin, typically, general-purpose resins such as olefin resins, engineering plastics such as polyamide resins and polyacetal resins, and super engineering plastics such as polyphenyl sulfide resins and polyether ether ketone resins can be used. . Various kinds of reinforcing materials (such as talc) and reinforcing fibers may be blended in the thermoplastic resin. Examples of the reinforcing fiber include glass fiber, aramid fiber, and carbon fiber. You may mix | blend various fillers, additives, a coloring agent, etc. with a thermoplastic resin.

The tubular resin molded body 1 can be used, for example, as a constituent member such as a hydraulic pipe of an automatic transmission of an automobile or a water-cooled pipe of a cooling mechanism. In addition, the use of the tubular resin molded body 1 is not limited to this, and can be used as a tube used for transferring gas and fluid and transmitting pressure, and also as a tube used for transferring powder and granules. Can be used.

Hereinafter, the manufacturing method of the said tubular resin molding 1 is demonstrated. First, the resin molded body 5 (FIG. 7) is integrally molded using injection molding, and unnecessary portions are cut out from the resin molded body 5 to obtain the tubular resin molded body 1. FIG. 7 is a sectional view showing the shape of the resin molded body 5. In this example, the both ends of the main pipe portion are cut at the positions indicated by AA and BB in FIG. 7, and a gate and a runner (not shown) are cut off to obtain a tubular resin molded body as shown in FIG. 1 is obtained.

The process of injection molding the resin molded body 5 will be outlined. The mold used for injection molding of the resin molded body 5 has a gate and a cavity, and a molten thermoplastic resin is injected into the cavity through the gate, and then a pressurized fluid is pressed into the resin in the cavity. The main pipe portion 11 is formed by a method of discharging a part of the gas, for example, a so-called floating core method, and the branch pipe portion 12 is formed by a cavity mold and a core mold. Then, after the main pipe portion 11 is formed, the resin wall 45 separating the main pipe portion and the branch pipe portion is removed. Thereafter, the resin molded body 5 is taken out from the mold.

Hereinafter, an example of an injection molding process using the floating core will be described in detail with reference to FIGS. 2 to 6.

FIG. 2 is a schematic sectional view of a mold used in the injection molding process. The mold (cavity mold) 3 is configured to be openable and closable in a direction perpendicular to the paper surface so that the molded product can be taken out. The mold 3 is provided with cavities 311 and 312 and a gate 35. By injecting and filling molten thermoplastic resin into the cavity through the gate 35, the shape of the inner peripheral surface of the cavity is transferred and the outer surface shape of the resin molded body 5 is defined. The mold cavity has a main pipe part cavity 311 forming a main pipe part and a branch pipe part cavity 312 forming a branch pipe part.

A core die 41 that defines the shape of the inner peripheral surface of the branch pipe portion is provided at a portion where the branch pipe portion 12 is formed. The core mold 41 may have a cylindrical sleeve 42 disposed on the outer periphery of the core mold as in the present embodiment. When the core mold 41 includes the sleeve 42 as in the present embodiment, the branch pipe portion cavity 312 is substantially formed by the inner peripheral surface of the cavity mold and the outer peripheral surface of the sleeve 42. The core mold 41 and the sleeve 42 are configured to be slidable in the extending direction of the branch pipe portion 12 so that a molded product can be taken out.
It should be noted that it is not essential to provide the sleeve 42 in the core mold 41 as shown in the embodiments described later. When the sleeve 42 is not provided, the inner peripheral surface of the cavity mold and the outer peripheral surface of the core mold 41 define the branch pipe portion cavity 312.

With the mold closed during injection molding, the core mold 41 has a core mold tip surface 41 a that is the outer peripheral surface of the main pipe part (that is, the peripheral wall surface 311 a of the main pipe part cavity) and the radial direction of the main pipe part 11. Are preferably arranged at substantially the same position. More preferably, the tip surface 41a of the core mold 41 is substantially the same surface as an outer peripheral surface of the main pipe portion (ie, the main pipe portion cavity surface 311a).

With the mold closed during injection molding, the sleeve 42 has a sleeve tip 42a located radially inward of the main pipe portion relative to the outer peripheral surface of the main pipe portion (that is, the peripheral wall surface 311a of the main pipe portion cavity). It is preferable to arrange so as to protrude. The protrusion form of the sleeve tip 42a is preferably protruded radially inward of the main pipe part over the entire circumference of the cylindrical sleeve, but the protrusion may be partial.

Further, it is preferable that the distal end portion 42a of the sleeve 42 has a tapered surface so that the inner peripheral side of the sleeve protrudes more radially inward of the main pipe portion than the outer peripheral side of the sleeve. The portion 42a may be tapered in the opposite direction, that is, the outer peripheral side of the sleeve may be tapered such that it protrudes more radially inward of the main pipe portion than the inner peripheral side of the sleeve. It may be formed in a saw blade shape or a step shape.

The cavity of the mold is provided with a pressurized port 32 through which pressurized fluid can be injected into one end side of the main pipe portion cavity 311. Further, the cavity has a discharge port 33 on the other end side of the main pipe portion cavity 311. The gate 35 is provided on the peripheral wall surface of the main pipe portion cavity 311.

The pressurized port 32 is connected to a pressurized fluid system (not shown) for pressurizing and discharging pressurized fluid. Further, a portion for temporarily supporting the floating core is provided in a portion where the pressurization port communicates with the cavity, and the floating core 2 is disposed in this portion prior to the injection of the resin.

The floating core 2 may be made of metal or resin. In the case of resin, it may be the same type of resin as the thermoplastic resin used for injection molding or a different type of resin. The shape of the floating core 2 is a shape having a cross-sectional shape of the inner peripheral surface to be formed, such as a cylindrical shape, a conical shape, a bullet shape, and the like in addition to the illustrated spherical shape.

A waste cavity 34 is connected to the outlet 33 provided at the other end of the main pipe cavity 311. An opening / closing means 37 that can be opened and closed is provided between the discharge port 33 and the disposal cavity 34.

3 to 6 are diagrams showing each stage of the injection molding process.
First, the mold 3 is closed with the floating core 2 disposed on the pressure port 32 side. At this time, the opening / closing means 37 is closed. Preferably, the front end surface 41a of the core mold 41 is disposed at substantially the same position as the outer peripheral surface of the main pipe portion (that is, the peripheral wall surface 311a of the main pipe portion cavity) in the radial direction of the main pipe portion. Preferably, the distal end portion 42a of the sleeve is disposed so as to protrude radially inward of the main pipe portion from the outer peripheral surface of the main pipe portion (that is, the peripheral wall surface 311a of the main pipe portion cavity).

After the mold is closed, as shown in FIG. 3, molten resin is injected into the cavities 311 and 312 through the gate 35 and filled. The resin filling at this stage does not need to completely fill the entire cavity of the mold. If the resin filling into the entire cavity is completed by press-fitting a pressurized fluid, which will be described later, the resin filling at this stage is an incomplete filling so that the resin does not reach a part of the cavity. May be.

After the injection of the resin from the gate 35 is completed, the opening / closing means 37 provided at the discharge port 33 is opened, and pressurized fluid is press-fitted into the main pipe cavity 311 from the pressurized port 32. The pressurized fluid may be a gas such as nitrogen gas, carbon dioxide gas, or air, or may be a liquid such as glycerin, liquid paraffin, or water. The pressurized fluid is preferably a fluid that does not react with or be compatible with the injected resin, and an inert gas such as nitrogen gas is particularly preferable. The pressurization of the pressurized fluid may be performed by a known pressurized fluid system.

When the pressurized fluid is injected, as shown in FIG. 4, the floating core 2 is pushed by the pressurized fluid and moves in the resin in the cavity. At this time, the floating core 2 leaves the resin near the outer periphery of the main pipe cavity 311 that has started to be cooled and solidified, and the molten resin at the center that is delayed in cooling is thrown out from the discharge port 33 to the cavity 34, while moving toward the discharge port 33. And move forward. And after the floating core 2 passes, the main pipe part 11 which has an internal diameter substantially equal to the diameter of the floating core 2 will be formed. Further, the resin of the portion that becomes the tube wall of the main pipe portion 11 is pressed against the inner peripheral surface of the main pipe portion cavity by the pressure of the pressurized fluid, and is cooled in a state where the shape of the pipe is maintained, The main pipe part is formed. Further, the resin filled in the branch pipe part cavity 312 is cooled from the inner peripheral surface of the cavity mold and the part in contact with the outer peripheral face of the sleeve (or core mold) and solidified to form the branch pipe part 12. .

When the pressurization of the pressurized fluid is further advanced, as shown in FIG. 5, the floating core 2 reaches the position of the discharge port 33 and the entire main pipe portion 11 is formed. By holding the pressurized fluid pressure applied to the inside of the main pipe portion 11 formed in this state, the resin and the peripheral wall surface of the main pipe portion cavity 311 can be sufficiently brought into pressure contact, and the main pipe portion 11 of the molded body. The outer surface shape is accurately formed, which is preferable.
In the state where the main pipe portion 11 is formed, a resin wall 45 that separates the main pipe portion 11 and the branch pipe portion 12 is formed adjacent to the tip 41a of the core die 41 of the branch pipe portion. Due to the resin wall 45, the internal space of the main pipe portion and the internal space of the branch pipe portion are not yet in communication.

In this embodiment, the floating core 2 is configured to stop on the front side of the discharge port 33, but the diameter of the discharge port is increased so that the floating core 2 reaches the disposal cavity 34 beyond the discharge port 33. You may make it do.

After the main pipe portion 11 and the resin wall 45 are formed, the core mold 41 is moved backward as shown in FIG. Disconnect from 5). Due to the combination of pressurization of the pressurized fluid and retraction of the core mold 41, the peripheral portion of the resin wall 45 is sheared and broken, and the resin wall 45 is separated from the resin molded body (5) so as to be pulled by the core mold 41. It is. When the resin wall 45 is separated, the pressurization of the pressurized fluid may be released as appropriate.

Preferably, in the step of retracting the core mold 41 and separating the resin wall 45, the core 42 is maintained in a state in which the distal end portion 42a of the sleeve 42 protrudes radially inward of the main pipe portion from the outer peripheral surface of the main pipe portion. The mold 41 is retracted. When the sleeve is provided, it is preferable to configure the mold so that the sleeve 42 and the core mold 41 can perform separate forward and backward movements.

Further, the core mold 41 is provided with a hole, an undercut shape, an unevenness, a groove, or the like so that the resin wall 45 is separated from the core mold 41 integrally. It is preferable that the resin wall 45 is easily held at the tip 41a.

Further, the core mold 41 is preferably retracted at the final stage of the pressurization holding time after the pressurization of the pressurized fluid in the floating core method in order to improve the molding efficiency and certainty.

After the core mold 41 is retracted and the resin wall 45 is cut off, the metal mold 3 is relieved when the resin in the cavity of the mold 3 is sufficiently solidified, and the sleeve 42 and the core mold 41 are retracted as necessary. The mold 3 is opened and the molded resin molded body 5 is taken out. The resin molded body 5 taken out is shown in FIG.

As shown in AA and BB in FIG. 7, unnecessary portions for forming the tubular resin molded body 1 in FIG. Further, the gate and runner portions are separated from the resin molded body 5. Thereby, the tubular resin molding 1 is obtained. In addition, when obtaining the tubular resin molding 1 from the resin molding 5, you may perform drilling by drilling, the assembly | attachment of another member, etc. as needed.

Hereafter, the effect | action and effect of the said tubular resin molding 1 and the said manufacturing method are demonstrated.
When the tubular resin molded body 1 is manufactured by the above manufacturing method, the resin wall 45 formed so as to separate the main pipe portion 11 and the branch pipe portion 12 is efficiently separated by the pressure by the pressurized fluid and the retraction of the core mold 41. be able to. When the resin wall 45 is separated in this way, the main pipe portion and the resin wall 45 around the resin wall are maintained in a shape formed by a method (particularly the floating core method) that combines injection molding and press-fitting of pressurized fluid. It can be cut off as it is, and the shape of the molded body becomes accurate and the quality is improved. And since the resin wall 45 is cut | disconnected by the branch pipe part side, it is hard to produce a burr | flash in the part which cut | disconnected the resin wall 45. FIG.

Moreover, even if burrs may be generated at the part where the resin wall 45 is cut off, the resin wall 45 is cut off to the branch pipe part side, so that the burr is not formed by protruding into the main pipe part 11 and is tubular. The quality of the resin molding is improved.

Furthermore, when the resin is injected into the cavity, the tip surface 41a of the core mold 41 is arranged at substantially the same position in the radial direction of the main pipe portion as the outer peripheral surface of the main pipe portion. The formation of the main pipe portion by a method combining injection molding and press-fitting of pressurized fluid (particularly the floating core method) becomes more accurate and reliable, and the quality of the tubular resin molded body is improved. That is, by arranging both at substantially the same position in the radial direction of the main pipe part, the cooling and solidifying speed of the resin injected and filled in the main pipe part cavity 311 is more improved between the branch part and other parts. It becomes uniform, and the thickness of the main pipe portion formed by a method combining injection molding and press-fitting of pressurized fluid (particularly the floating core method) is easily stabilized, and the quality of the tubular resin molded body is improved.

Further, the core mold 41 further includes a cylindrical sleeve 42 disposed on the outer periphery of the core mold, and when the resin is injected into the cavity, the distal end portion 42a of the sleeve 42 is connected to the main pipe portion. When arranged so as to protrude radially inward of the main pipe portion from the outer peripheral surface, the tip end portion 42a of the sleeve 42 bites in the thickness direction with respect to the formed main pipe portion 11 and the resin wall 45. In this state, the main pipe portion 11 is formed. Therefore, in the step of retracting the core mold 41 and separating the resin wall 45, the portion to be separated can be thinned by shear deformation. Therefore, the resin wall 45 is more reliably separated and the occurrence of burrs is suppressed. Further, since the sleeve 42 is arranged on the outer periphery of the core mold 41, the separated resin wall 45 is collected inside the sleeve 42 without contacting the inner periphery of the resin molded body 5 (branch pipe portion 12). Is done. Thereby, it is prevented that the resin wall 45 remains in the resin molded body 5 or the tubular resin molded body 1, and the quality of the tubular resin molded body is further improved.

Further, when the shape of the distal end portion 42a of the sleeve 42 is tapered so that the inner peripheral side of the sleeve protrudes inward in the radial direction of the main pipe portion as compared with the outer peripheral side of the sleeve, The recovery of the resin wall 45 into the sleeve 42 is more preferable, which is preferable. With such a tip shape, the resin wall 45 cut off at the tip of the sleeve 42 is drawn into the sleeve together with the core mold 41 without deforming the peripheral edge. is there. Further, when the shape of the sleeve front end portion 42a is like this, the resin wall 45 is cut along a surface along the inner peripheral surface of the sleeve 42, so that burrs are less likely to occur.

Further, if the sleeve 42 is provided, when the core mold 41 is retracted and the resin wall 45 is separated from the resin molded body, the distal end portion 42a of the sleeve 42 is radially inward of the main pipe portion relative to the outer peripheral surface of the main pipe portion. If the protruding state is maintained, the deformation of the cut-off portion is suppressed, the generation of burrs is further suppressed, and the recovery of the resin wall 45 into the sleeve 42 becomes more reliable, and the tubular resin molded body The quality of the is further improved.

The invention is not limited to the embodiment described above, and can be implemented with various modifications. Other embodiments and modifications of the invention will be described below, but in the following description, different parts from the above embodiment will be mainly described, and detailed description of the same parts will be omitted. Moreover, these embodiments can be implemented by combining some of them or replacing some of them.

The mutual timing of the advancement and retraction of the sleeve 42 and the core mold 41 can be changed. In the embodiment described above, the sleeve 42 is not moved when the resin wall 45 is separated, and only the core mold 41 is retracted. However, when the resin wall 45 is separated, the sleeve 42 and the core mold 41 may be retracted simultaneously. The core mold 41 may be retracted while moving forward toward the radially inner side of the main pipe portion.

In the description of the above embodiment, the embodiment in which the core mold includes the sleeve 42 has been described, but the sleeve is not essential. For example, a tubular resin molded body having a branch tubular hollow tubular portion can also be manufactured using a mold as shown in FIG.

In the mold shown in FIG. 8, the inner peripheral surface of the branch pipe portion is defined by the outer peripheral surface of the core mold 61 having no sleeve. Even when such a mold is used, as in the first embodiment, after forming the main pipe portion by the floating core method, the core mold 61 is moved backward while maintaining the pressurization of the pressurized fluid. The resin wall (45) separating the part (1) and the branch pipe part (12) can be separated to produce a resin molded body in which the main pipe part and the branch pipe part communicate with each other. The body quality can be increased.

In this mold, the outer peripheral portion 61b of the tip surface 61a of the core die 61 is formed in a ring shape toward the radially inner side of the main pipe portion. As with the tip end portion 42a of the mold sleeve 42 of the mold according to the first embodiment, this protruding portion reduces the thickness of the portion where the resin wall (45) is cut off, thereby further suppressing the generation of burrs. Since it works, it is preferable to provide such a protruding portion. Further, in the case where such a protruding portion is provided, the protruding portion 61b protrudes most at the outermost peripheral portion of the tip surface of the core die 61 as in the present embodiment, and the inner portion of the core die tip surface. It is preferable to form in a taper shape or a step shape in which the protrusion amount decreases as it goes in the circumferential direction. With such a protruding shape, the main pipe portion and the branch pipe portion can be connected to each other's inner peripheral surface without a step.

In the description of the above embodiment, the manufacturing method using the floating core method in which the floating core 2 is used to move the floating core 2 by press-fitting a pressurized fluid to form the main pipe portion 11 has been described. However, the invention is not limited to the floating core method. That is, the formation of the main pipe portion using injection molding is provided with a mold having a cavity having a pressurized port capable of injecting pressurized fluid at one end and a discharge port at the other end, and tubular resin molding by the cavity. After defining the outer shape of the body and injecting and filling a molten thermoplastic resin into the cavity, a pressurized fluid is press-fitted into the cavity from the pressurized port, and a part of the resin in the cavity is discharged. If it discharges | emits from an exit and forms a main pipe part, it can implement similarly. That is, as an embodiment of the present invention, the main pipe portion 11 is formed by a so-called GIT method or WIT method, and then the resin wall separating the main pipe portion and the branch pipe portion is pressurized with a pressurized fluid and a core type It may be removed by retreating, and the same effect can be obtained.

Note that it is more preferable to use a floating core because the thickness of the main pipe portion 11 becomes more accurate and the resin wall 45 can be separated with higher quality.

In the description of the above embodiment, an example of a mold in which the discharge port 33, the opening / closing mechanism 37, and the discard cavity 34 are sequentially arranged is shown, but the specific shape of the discharge port and the discard cavity is not particularly limited, For example, both may have the same cross-sectional shape in a cross section perpendicular to the resin flow direction. Further, the opening / closing mechanism 37 may be omitted if a series of injection processes and a pressurizing process of pressurized fluid can be performed.

According to the said manufacturing method, the tubular resin molding excellent in quality can be manufactured efficiently, and industrial utility value is high.

DESCRIPTION OF SYMBOLS 1 Tubular resin molding 11 Main pipe part 12 Branch pipe part 15 Gate trace 16 Flange 2 Floating core 3 Injection mold 311 Main pipe part cavity 312 Branch pipe part cavity 32 Pressurization port 33 Discharge port 34 Waste cavity 35 Gate 37 Opening / closing means 41 Core mold 42 Sleeve 45 Resin wall 5 Resin molded body 61 Core mold

Claims (6)

A method for producing a tubular resin molded body having a hollow tubular portion using injection molding of a thermoplastic resin,
The hollow tubular portion is a branched tube having a main tube portion and a branch tube portion branched from the main tube portion,
The injection molding is
A mold having a cavity having a pressurized port capable of injecting pressurized fluid at one end and a discharge port at the other end is prepared, and the outer surface shape of the tubular resin molded body is defined by the cavity,
After injecting and filling a molten thermoplastic resin into the cavity,
A pressurized fluid is pressed into the cavity from the pressurized port, and a part of the resin in the cavity is discharged from the discharge port to form the main pipe part.
Furthermore, the mold has a core mold that defines the inner peripheral surface shape of the branch pipe part,
Furthermore, the injection molding is
When the main pipe portion is formed, a resin wall that separates the main pipe portion and the branch pipe portion is formed adjacent to the tip surface of the core mold,
After the main pipe portion is formed, with the pressurization of the pressurized fluid maintained, the core mold is retracted, and the resin wall is separated from the tubular resin molded body.
Manufacturing method of tubular resin molding. Prior to injection of thermoplastic resin, a floating core is provided in the pressure port,
The method for producing a tubular resin molded body according to claim 1, wherein the floating core is moved to the discharge port side by press-fitting a pressurized fluid, and the main pipe portion is formed by the movement of the floating core. The top end surface of the core mold is disposed at substantially the same position as the outer peripheral surface of the main pipe portion in the radial direction of the main pipe portion when the resin is injected into the cavity. Manufacturing method of tubular resin molding. The core mold further includes a cylindrical sleeve disposed on the outer periphery of the core mold,
4. The device according to claim 1, wherein when the resin is injected into the cavity, the distal end portion of the sleeve is disposed so as to protrude radially inward of the main tube portion from the outer peripheral surface of the main tube portion. A method for producing a tubular resin molded product according to claim 1. The method for producing a tubular resin molded body according to claim 4, wherein the distal end portion of the sleeve has a tapered surface such that the inner peripheral side of the sleeve protrudes more radially inward of the main pipe portion than the outer peripheral side of the sleeve. . 5. The resin wall is separated from the tubular resin molded body by retracting the core mold while maintaining a state in which a distal end portion of the sleeve protrudes radially inward of the main pipe portion from an outer peripheral surface of the main pipe portion. The manufacturing method of the tubular resin molding of description.

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