JP2019098601A - Method for molding tubular hollow body and tubular hollow body - Google Patents

Abstract

To suppress a molding cost.SOLUTION: A method comprises: a core setting step where a floating core 16 is detachably set at a pressurizing port 12 of a mold 10 for molding a tubular hollow body; an injection step, following the core set step, where a first resin R1 is injected into a main cavity 11; and a core moving step, following the injection step, where a pressurized fluid is pressure-fit from the pressurizing port 12 for the floating core 16 to be moved from the pressurizing port 12 toward a discharging part 14 in order to discharge the first resin R1 from the discharging part 14. The floating core 16 is formed from a second resin R2, which is a different kind from the first resin R1. In the injection step, the injection temperature of the first resin R1 to be injected into the main cavity 11 is higher than a melting point of the second resin R2. In the core moving step, the floating core 16, while being molten, is moved from the pressurizing port 12 toward the discharging part 14.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a tubular hollow body forming method and tubular hollow body for forming a tubular hollow body having a multilayer structure.

  The tubular hollow body made of resin is used for various parts such as a water pipe, an oil cooling pipe, an air duct and the like, and is formed into various bent shapes. As one method for producing such a tubular hollow body, there is fluid assist molding described in Patent Documents 1 and 2. In the fluid assist molding, a molding is provided that includes a main cavity having a pressurized port provided with a floating core at one end and a discharge part formed at the other end, and a sub cavity communicated with the discharge part of the main cavity. Prepare a mold. Then, after the resin is injected into the main cavity, the floating core is moved by pressing the pressurized fluid from the pressure port, and the resin in the main cavity and the floating core are discharged from the discharge part into the sub cavity. Thereby, the inner peripheral surface of the tubular hollow body is formed. Thereafter, the resin molded article is taken out from the main cavity and the sub cavity, and the portion discharged to the sub cavity is cut and removed from the molded article to obtain a tubular hollow body.

  Then, in the molding method described in Patent Document 1, the first resin for molding the outer layer portion and the second resin for forming the inner layer portion are injected into the main cavity, and then the floating core is moved, A two-layered tubular hollow body is formed.

  Further, in the molding method described in Patent Document 2, the outer layer portion is molded by injecting the first resin for molding the outer layer portion in the first molding die and moving the floating core, and the molded article is obtained. The two-layered tubular hollow body is formed by transferring the second resin for forming the inner layer portion to the second molding die and transferring the floating core to the second molding die.

Unexamined-Japanese-Patent No. 09-123212 gazette Patent No. 5038118 gazette Patent No. 5566382 gazette Patent No. 3411710 gazette

  However, the molding method described in Patent Document 1 requires a special injection device for injecting both the first resin for molding the outer layer portion and the second resin for forming the inner layer portion. There is a problem that the cost is high. Furthermore, in this molding method, since it is necessary to form the injected first resin and the second resin in layers, a very advanced injection technique is required. In addition, since the resin discharged into the sub cavity is a mixture of the first resin and the second resin, it is difficult to separate them, and there is also a problem that the discharged resin can not be reused.

  Further, even with the molding method described in Patent Document 2, it is necessary to prepare two molding dies of a molding die for molding the outer layer portion and a molding die for molding the inner layer portion, and a molded article of the first resin There is a problem that the molding cost becomes high because a process of transferring the first mold to the second mold is required.

  Then, this invention makes it a subject to provide the tubular hollow body shaping | molding method and tubular hollow body which can suppress shaping | molding cost.

  As a result of intensive studies on the above problems, the present inventor moves the floating core while melting it, and the inner layer portion is formed by the molten material of the floating core, thereby suppressing the forming cost and forming a tubular hollow body having a multilayer structure. We have found that it can be molded.

  Patent Documents 3 and 4 disclose using a material or the like having a melting point higher than that of a resin injected into a molding die as a floating core (projectile) so that the floating core does not melt. However, in the methods of Patent Documents 3 and 4, since the floating core is not melted, the inner layer portion can not be formed by the floating core.

  The method for forming a tubular hollow body according to one aspect of the present invention is a method for forming a tubular hollow body having a multilayer structure comprising an outer layer portion and an inner layer portion laminated on the inner layer side of the outer layer portion. The hollow body has an outer shape, a main cavity into which the first resin is injected, a pressure port formed at one end of the main cavity, into which the pressurized fluid is pressed into the main cavity, and the other end of the main cavity After the core setting step of forming the floating core so as to be able to be detachably attached to the pressure port of the forming die having the discharge portion for discharging the first resin from the main cavity, and the core setting step, (1) After the injection step of injecting the resin and the injection step, the floating core is moved from the pressure port toward the discharge portion by pressing the pressurized fluid from the pressure port, and the first resin is discharged from the discharge portion Core transfer process The floating core is formed of a second resin different in type from the first resin, and in the injection step, the injection temperature of the first resin injected into the main cavity is higher than the melting point of the second resin In the core moving step, the floating core is moved from the pressure port toward the outlet while melting the floating core.

  In this tubular hollow body forming method, in the injection step, the first resin is injected into the main cavity, and then, in the core moving step, the pressurized fluid is pressed in from the pressure port to discharge the floating core from the pressure port. Move to the side and discharge the first resin from the discharge unit. Thereby, the first resin injected into the main cavity is formed hollow. Here, in the injection step, the first resin is injected into the main cavity at an injection temperature higher than the melting point of the second resin. For this reason, the floating core can be melted by heat input from the first resin injected into the main cavity and further by frictional heat with the first resin. Therefore, the first resin is formed in a hollow shape, and at the same time, the first resin is melted on the inner peripheral side of the first resin formed in a hollow shape by moving the floating core from the pressure port toward the discharge portion while melting the floating core. A second resin can be deposited. Thus, a tubular hollow body having a multilayer structure in which the outer layer portion of the first resin and the inner layer portion of the second resin are laminated can be obtained. When the tubular hollow body has a multilayer structure of three or more layers, for example, the tubular hollow body obtained by the above-mentioned tubular hollow body molding method further includes the above-mentioned tubular hollow body molding method, two-color molding, Further layers may be formed on the inner layer side and / or the outer layer side of the tubular hollow body by performing known fluid assisted molding or the like. As described above, since the tubular hollow body having a multilayer structure can be formed by a simple method of injecting the resin into the main cavity and moving the floating core, the forming cost can be suppressed.

  The injection temperature of the first resin may be 80 to 160 ° C. higher than the melting point of the second resin. In this tubular hollow body molding method, since the injection temperature of the first resin is 80 to 160 ° C. higher than the melting point of the second resin, the injection temperature of the first resin becomes too high while facilitating melting of the floating core. It can be suppressed.

  The melting point of the second resin may be lower than the melting point of the first resin. In this tubular hollow body molding method, since the melting point of the second resin forming the floating core is lower than the melting point of the first resin injected into the main cavity, the floating core is melted by the first resin injected into the main cavity It becomes easy to do.

  The melting point of the second resin may be 65 to 80 ° C. lower than the melting point of the first resin. In this tubular hollow body molding method, the melting point of the second resin is 65 to 80 ° C. lower than the melting point of the first resin, so the range of choice of the second resin can be expanded while facilitating melting of the floating core.

  The core moving step may be performed 4 to 6 seconds after the injection step is completed. In this method for forming a tubular hollow body, the heat transfer amount from the first resin injected into the main cavity to the floating core can be increased by performing the core moving step 4 to 6 seconds after the injection step is completed. Therefore, the floating core can be easily melted.

  The mold may further include a sub cavity in communication with the discharge portion and storing the first resin discharged from the discharge portion, and in the core moving step, the floating core may be stopped before the sub cavity. In this method for forming a tubular hollow body, the floating core and the melt of the floating core are not discharged to the sub cavity, so the resin discharged to the sub cavity can be easily reused. Thereby, the molding cost can be further suppressed.

  In the injection step, the first resin containing the reinforcing material may be injected into the main cavity. In this tubular hollow body molding method, since the first resin containing the reinforcing material is injected into the main cavity, the strength of the molded tubular hollow body can be increased.

  The tubular hollow body according to one aspect of the present invention is a tubular hollow body having a multilayer structure including an outer layer portion and an inner layer portion laminated on the inner layer side of the outer layer portion, wherein the outer layer portion is formed of a first resin The inner layer portion is formed of a second resin having a melting point lower than that of the first resin.

  In this tubular hollow body, the outer layer portion formed of the first resin and the inner layer portion formed of the second resin having a melting point lower than that of the first resin are laminated, and thus any of the methods described above It can be molded. For this reason, molding cost can be suppressed. That is, this tubular hollow body can be formed by any of the methods described above. Further, since the inner layer portion is formed of the second resin having a melting point lower than the first resin of the outer layer portion, for example, low permeability, corrosion resistance, chemical resistance, etc. are enhanced in the inner layer portion, and heat resistance in the outer layer portion Can be enhanced.

  The outer layer portion and the inner layer portion may be fused with each other. In this tubular hollow body, since the outer layer portion and the inner layer portion are fused to each other, it is possible to suppress peeling of the outer layer portion and the inner layer portion.

  The inner diameter at one end may be different from the inner diameter at the other end. In this tubular hollow body, since the inner diameter at one end is different from the inner diameter at the other end, the pressure of fluid flowing in the tubular hollow body can be changed.

  The inner diameter may be gradually reduced from one end to the other end. In this tubular hollow body, since the inner diameter gradually decreases from one end to the other end, the pressure of the fluid flowing in the tubular hollow body can be changed.

  The outer layer portion may contain a reinforcing material for reinforcing the first resin. In this tubular hollow body, since the outer layer portion contains a reinforcing material for reinforcing the first resin, the strength of the tubular hollow body can be enhanced.

  According to the tubular hollow body molding method and the tubular hollow body according to the present invention, the molding cost can be suppressed.

It is a schematic front view of the tubular hollow body which concerns on embodiment. It is sectional drawing in the direction orthogonal to the axial direction of the tubular hollow body shown in FIG. It is a schematic sectional drawing in the axial direction of the tubular hollow body shown in FIG. It is a schematic sectional drawing which shows a core installation process. It is a schematic sectional drawing which shows an injection | emission process. It is a schematic sectional drawing which shows a core movement process. It is a schematic sectional drawing which shows a core movement process. It is a schematic sectional drawing which shows a cutting process. It is a table | surface which shows the observation result of an Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The numerical range shown using "-" in this specification shows the range which includes the numerical value described before and after "-" as minimum value and the maximum value, respectively. The same or corresponding elements in the drawings will be denoted by the same reference symbols, without redundant description.

  As shown in FIG. 1, the tubular hollow body 1 according to the present embodiment is a hollow resin body that is formed in an elongated tubular shape from one end 1 a to the other end 1 b. The tubular shape of the tubular hollow body 1 is not particularly limited, and may be, for example, a circular tubular shape in which the cross sections of the outer peripheral surface 1c and the inner peripheral surface 1d are circular. In the present embodiment, the tubular hollow body 1 is described as being circular.

  The inner diameter of the tubular hollow body 1 at one end 1a is different from the inner diameter of the tubular hollow body 1 at the other end 1b. More specifically, the inner diameter of the tubular hollow body 1 gradually decreases from one end 1a to the other end 1b. Of the two ends of the tubular hollow body 1, either may be the one end 1a or the other end 1b.

  The tubular hollow body 1 includes one or more straight portions 2 and one or more bending portions 3 along the axis A of the tubular hollow body 1. The number, position, length, and the like of the straight portions 2 are not particularly limited. Further, the number, the position, the length, the shape (curvature) and the like of the bent portions 3 are not particularly limited.

  A fixing plate portion 4 for fixing the tubular hollow body 1 to another member such as an engine is provided on the outer peripheral surface 1 c of the tubular hollow body 1. The number, the position, the shape, and the like of the fixing plate portion 4 are not particularly limited. The fixed plate portion 4 may not necessarily be provided in the tubular hollow body 1.

  The tubular hollow body 1 has a multilayer structure in which a plurality of resin layers are stacked. In the present embodiment, the tubular hollow body 1 is described as having a two-layer structure including the outer layer portion 5 and the inner layer portion 6 stacked on the inner layer side of the outer layer portion 5.

  The outer layer portion 5 is formed of a first resin. As the first resin for forming the outer layer portion 5, for example, it is preferable to use a resin having properties excellent in heat resistance, impact resistance, corrosion resistance and the like. Examples of the first resin include polyamide (PA) such as polyamide 6 (PA 6) and polyamide 66 (PA 66), aromatic polyamide, polyphenylene sulfide (PPS) and the like.

  The inner layer portion 6 is formed of a second resin different in type from the first resin. The melting point of the second resin is lower than the melting point of the first resin. The melting point of the second resin is not particularly limited as long as it is lower than the melting point of the first resin, but is preferably 65 to 80 ° C. lower than the melting point of the first resin, more preferably 65 to 70 ° C. lower, and 65 ° C. lower Is particularly preferred. As the second resin for forming the inner layer portion 6, for example, it is preferable to use a resin having a property of being excellent in chemical resistance, heat resistance and the like. Examples of the second resin include polyamide (PA) such as polyamide 6 (PA 6) and polyamide 66 (PA 66), polypropylene (PP), polyethylene (PE), ethylene-vinyl alcohol copolymer (EVOH), etc. .

  The first resin of the outer layer portion 5 and the second resin of the inner layer portion 6 may contain a reinforcing material (not shown). Examples of the reinforcing material include fibrous reinforcing materials such as glass fibers, carbon fibers and natural fibers, and granular reinforcing materials such as glass beads. The reinforcing material may be contained in both the first resin of the outer layer portion 5 and the second resin of the inner layer portion 6, but is contained only in the first resin of the outer layer portion 5 from the viewpoint of ease of manufacture and the like. It may be

  The outer layer 5 and the inner layer 6 are fused with each other. That is, no interface is formed between the outer layer portion 5 and the inner layer portion 6 when the outer layer portion and the inner layer portion are laminated by two-color molding or two times of fluid assist molding. However, if the outer layer portion 5 and the inner layer portion 6 are fused to each other, an interface may be formed between the outer layer portion 5 and the inner layer portion 6.

  Next, the method for forming a tubular hollow body according to the present embodiment will be described.

  First, as shown in FIG. 4, a molding die 10 is prepared. The mold 10 is a mold for molding the tubular hollow body 1 by fluid-assisted molding. The mold 10 includes a main cavity 11, a pressure port 12, an injector 13, a discharge portion 14, a sub cavity 15, and a floating core 16.

  The main cavity 11 forms the outer shape (the shape of the outer peripheral surface 1c) of the tubular hollow body 1 and is a cavity into which the first resin (the first resin heated and melted) is injected. The pressure port 12 is a port which is formed at one end of the main cavity 11 and into which the pressurized fluid is pressed. The injector 13 is an injection device that is in communication with the pressure port 12 and injects a pressurized fluid. The discharge part 14 is a flow path which is formed at the other end of the main cavity 11 and discharges the first resin from the main cavity 11. Note that the discharge part 14 may be a simple opening that communicates the main cavity 11 and the sub cavity 15. The sub cavity 15 is a cavity in communication with the discharge unit 14 and is a cavity for storing the first resin discharged from the discharge unit 14.

  The floating core 16 is also called a projectile. The floating core 16 is detachably provided to the pressure port 12. The floating core 16 is provided in the main cavity 11 with the pressure port 12 in the back so that the floating core 16 is pressed by the pressurized fluid that is press-fit from the pressure port 12. The maximum diameter of the floating core 16 is smaller than the inner diameter of the main cavity 11 and sufficiently larger than the inner diameter of the discharge part 14. For this reason, when the pressurized fluid is press-fit from the pressure port 12, the floating core 16 moves the main cavity 11 from the pressure port 12 toward the discharge portion 14 side, and the discharge portion 14 side of the main cavity 11 It collides with the wall and stops. The shape of the floating core 16 is not particularly limited, and can be shell-shaped, conical, hemispherical, spherical or the like. In the present embodiment, the floating core 16 is described as having a shell shape.

  In the method for forming a tubular hollow body according to the present embodiment, the core setting step, the injection step, the core moving step, the removing step, and the cutting step are performed in this order.

  As shown in FIG. 4, in the core installation step, the floating core 16 formed of the second resin R2 is detachably provided in the pressure port 12 of the molding die 10. The second resin R2 that forms the floating core 16 is the same as the second resin that forms the inner layer portion 6 of the tubular hollow body 1. The floating core 16 may be formed of the second resin R2 containing a reinforcing material. This reinforcing material is the same as the reinforcing material contained in the inner layer portion 6 of the tubular hollow body 1 described above.

  As shown in FIG. 5, in the next injection process, the sub cavity 15 is closed by a hydraulic cylinder or the like, and the first resin R1 is injected into the main cavity 11. The first resin R1 injected into the main cavity 11 is the same as the first resin forming the outer layer portion 5 of the tubular hollow body 1 described above. One or more gates (not shown) communicated with the main cavity 11 are formed in the molding die 10, and the first resin R1 heated and melted is injected from the gate into the main cavity 11. Then, the first resin R1 is filled in the main cavity 11 and the discharge part 14.

  In the injection step, the first resin R1 is heated and melted to make the injection temperature of the first resin R1 injected into the main cavity 11 higher than the melting point of the second resin R2 forming the floating core 16. The injection temperature of the first resin R1 is not particularly limited as long as it is higher than the melting point of the second resin R2, but is preferably 80 to 160 ° C. or more higher than the melting point of the second resin R2, and is higher than 90 to 160 ° C. More preferably, it is particularly preferable that the temperature is 95 to 160 ° C. or higher. For example, the injection temperature of the first resin R1 can be 95 ° C. higher than the melting point of the second resin R2.

  Further, in the injection step, the first resin R1 containing a reinforcing material may be injected into the main cavity 11. This reinforcing material is the same as the reinforcing material contained in the outer layer portion 5 of the tubular hollow body 1 described above.

  In the next core moving step, the sub cavity 15 is opened by a hydraulic cylinder or the like. Then, as shown in FIG. 6 and FIG. 7, the pressurized fluid is press-fit from the pressure port 12 to move the floating core 16 from the pressure port 12 toward the discharge part 14 side. That is, when the pressurized fluid is pressed into the main cavity 11 from the pressurizing port 12, the floating core 16 provided in the pressurizing port 12 is pressed by the pressurized fluid, and thus along the axis B of the main cavity 11. The pressure port 12 moves toward the discharge unit 14 side. Then, the floating core 16 is stopped before the sub cavity 15. Specifically, the floating core 16 moving from the pressure port 12 toward the discharge unit 14 collides with the wall surface of the main cavity 11 on the discharge unit 14 side to stop the movement. As the pressurized fluid, it is preferable to use a gas or liquid which does not react or become compatible with the first resin R1 under the injection temperature and pressure of the first resin R1. Examples of the pressurized fluid include nitrogen gas, carbon dioxide gas, air, water, glycerin, liquid paraffin and the like. Then, by moving the floating core 16 in this manner, the first resin R1 is discharged from the discharge unit 14 to the sub cavity 15. Thus, the first resin R1 injected into the main cavity 11 is formed in a hollow shape.

  Here, since the first resin R1 is injected into the main cavity 11 at an injection temperature at which the melting point of the second resin R2 is lower than that of the first resin R1 and higher than the melting point of the second resin R2, the main cavity 11 is The floating core 16 can be melted by the heat input from the first resin R1 injected into the first resin R1 and further by the frictional heat with the first resin R1. At this time, the core moving step may be performed immediately after the end of the injection step, but from the viewpoint of facilitating melting of the floating core 16, the core moving step may be performed 4 to 6 seconds after the end of the injection step. Preferably, the core moving step is more preferably performed 5 to 6 seconds after the end of the injection step, and it is particularly preferable to perform the core moving step 6 seconds after the end of the injection step.

  Then, in the core moving step, the floating core 16 is moved from the pressure port 12 toward the discharge unit 14 while being melted. As a result, the first resin R1 is formed into a hollow shape, and at the same time, the melted second resin R2 adheres to the inner peripheral side of the first resin R1, and the second resin R2 is formed on the inner peripheral side of the first resin R1. It will be in the state of being stacked. Here, since the floating core 16 moves from the pressure port 12 toward the discharge unit 14 while melting, the floating core 16 gradually decreases in size from the pressure port 12 toward the discharge unit 14. Therefore, the inner diameter of the laminate of the first resin R1 and the second resin R2 gradually decreases from the tip of the main cavity 11 on the pressure port 12 side to the tip of the discharge portion 14 side. That is, the inner diameter of the laminate of the first resin R1 and the second resin R2 is smaller at the end on the discharge portion 14 side than at the end on the pressure port 12 side of the main cavity 11.

  Then, since the floating core 16 collides with the wall surface of the main cavity 11 on the discharge portion 14 side and stops, the melt of the floating core 16 and the floating core 16 is not discharged to the sub cavity 15. Even if the melt of the floating core 16 is discharged to the sub cavity 15, the amount of discharge is very small. Then, it waits until the first resin R1 and the second resin R2 cool and harden.

  As shown in FIG. 8, in the next take-out step, the molded article M of the first resin R1 and the second resin R2 is taken out of the molding die 10 by a hydraulic arm or the like. Then, by cutting and removing both ends of the molded article M, the tubular hollow body 1 shown in FIG. 1 is obtained.

  When the tubular hollow body 1 has a multilayer structure of three or more layers, for example, the tubular hollow body 1 obtained by the above-mentioned tubular hollow body forming method further includes the above-mentioned tubular hollow body forming method, two colors Further layers may be formed on the inner layer side and / or the outer layer side of the tubular hollow body 1 by performing molding, known fluid assisted molding, or the like.

  As described above, in the method for forming a tubular hollow body according to the present embodiment, the first resin R1 is injected into the main cavity 11 in the injection step, and then the pressurized fluid is pressed from the pressure port 12 in the core movement step. The floating core 16 is moved from the pressure port 12 toward the discharge unit 14, and the first resin R 1 is discharged from the discharge unit 14. Thus, the first resin R1 injected into the main cavity 11 is formed in a hollow shape. Here, in the injection step, the first resin R1 is injected into the main cavity 11 at an injection temperature higher than the melting point of the second resin R2. Therefore, the floating core 16 can be melted by the heat input from the first resin R1 injected into the main cavity 11, and further by the frictional heat with the first resin R1. Therefore, the first resin R1 is formed in a hollow shape by moving the floating core 16 from the pressure port 12 toward the discharge portion 14 while melting the floating core 16, and at the same time, the first resin R1 is melted on the inner peripheral side of the first resin R1. Two resin R2 can be attached. Thereby, it is possible to obtain the tubular hollow body 1 having a multilayer structure in which the outer layer portion 5 of the first resin R1 and the inner layer portion 6 of the second resin R2 are stacked. As described above, since the tubular hollow body 1 having a multilayer structure can be formed by a simple method of injecting the resin into the main cavity 11 and moving the floating core 16, the forming cost can be suppressed.

  Moreover, in this tubular hollow body molding method, the floating core 16 is easily melted by making the injection temperature of the first resin R1 80 to 160 ° C. higher than the melting point of the second resin R2; It is possible to prevent the injection temperature from becoming too high.

  Moreover, in this tubular hollow body molding method, the melting point of the second resin R2 forming the floating core 16 is made lower than the melting point of the first resin R1 injected into the main cavity 11, whereby the resin is injected into the main cavity 11. The first resin R1 facilitates the melting of the floating core 16.

  Moreover, in this tubular hollow body molding method, the floating core 16 is easily melted by setting the melting point of the second resin R2 to be 65 to 80 ° C. lower than the melting point of the first resin R1, while selecting the second resin R2. You can broaden the range of

  Moreover, in this tubular hollow body molding method, the heat input from the first resin R1 injected into the main cavity 11 to the floating core 16 is performed by performing the core moving step 4 to 6 seconds after the injection step is completed. Since the size can be increased, the floating core 16 can be easily melted.

  Moreover, in this tubular hollow body molding method, the second resin R2 forming the floating core 16 is not discharged to the sub cavity 15, so the resin discharged to the sub cavity 15 can be easily reused. Thereby, the molding cost can be further suppressed.

  Moreover, in this tubular hollow body molding method, the strength of the molded tubular hollow body 1 can be enhanced by injecting the first resin R1 containing the reinforcing material into the main cavity 11.

  In the tubular hollow body 1 according to the present embodiment, the outer layer portion 5 formed of the first resin and the inner layer portion 6 formed of the second resin having a melting point lower than that of the first resin are laminated, It can be molded by the above method. For this reason, molding cost can be suppressed. Further, since the inner layer portion 6 is formed of the second resin having a melting point lower than that of the first resin of the outer layer portion 5, for example, low permeability, corrosion resistance, chemical resistance, etc. are enhanced in the inner layer portion 6, and the outer layer portion The heat resistance can be enhanced at 5.

  Further, in the tubular hollow body 1, since the outer layer portion 5 and the inner layer portion 6 are fused to each other, peeling of the outer layer portion 5 and the inner layer portion 6 can be suppressed.

  Further, in the tubular hollow body 1, the inner diameter at one end 1a is different from the inner diameter at the other end 1b, so the pressure of the fluid flowing in the tubular hollow body 1 can be changed.

  Further, in the tubular hollow body 1, the inner diameter gradually decreases from the one end 1a to the other end 1b, so that the pressure of the fluid flowing in the tubular hollow body 1 can be changed.

  Further, in the tubular hollow body 1, the strength of the tubular hollow body can be enhanced by the outer layer portion 5 containing a reinforcing material for reinforcing the first resin.

  As mentioned above, although the suitable embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment.

  For example, in the above-described tubular hollow body molding method, the melting point of the second resin R2 is described as being lower than that of the first resin R1, but the first resin R1 is used as the main cavity at an injection temperature higher than the melting point of the second resin R2. If it injects to 11, the melting point of 2nd resin R2 does not necessarily need to be lower than 1st resin R1.

  Also, in the above embodiment, the cross-sectional shapes of the tubular hollow body, the main cavity, and the floating core are described as being circular, but the cross-sectional shapes of these are not limited to circular. It may be a polygon or the like.

  Moreover, although the said embodiment demonstrated as what is a multilayer structure in the whole area of a tubular hollow body, it is good also as a part of tubular hollow body of a multilayer structure into a single layer structure.

  Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

Example 1
The tubular hollow body of Example 1 was molded using the mold shown in FIG. In the core setting step, a floating core formed of polyamide 6 (PA 6) having a melting point of 225 ° C. was provided in the pressure port. In the injection process, polyphenylene sulfide (PPS-GF) containing glass fibers was injected into the main cavity at an injection temperature of 320 ° C. Then, after holding for 6 seconds as it was, the core moving step was performed, and the floating core was moved from the pressure port toward the discharge unit side by pressing the pressurized fluid from the pressure port. Thereafter, the molded body was taken out of the molding die to obtain a tubular hollow body.

(Example 2)
In Example 2, the conditions were the same as in Example 1 except that the injection temperature was 330.degree.

(Example 3)
In Example 3, the same conditions as in Example 1 were followed except that the core moving step was performed after holding for 5 seconds after the injection step.

(Example 4)
In Example 4, the same conditions as in Example 1 were followed except that the core moving step was performed after holding for 4 seconds after the injection step.

(Evaluation)
The tubular hollow bodies of Examples 1 to 4 were cut, and the laminated state of the outer layer portion and the inner layer portion was observed. The results are shown in FIG. In FIG. 9, the case where the inner layer portion is sufficiently stacked on the inner layer side of the outer layer portion is A, the case where the inner layer portion is partially stacked on the inner layer side of the outer layer portion is B, and the inner layer on the inner layer side of the outer layer portion. The case where the part was not laminated was C.

  As shown in FIG. 9, in all the examples, it was confirmed that the inner layer portion was laminated on the inner layer side of the outer layer portion. In particular, in Examples 1 and 2 in which the holding time from the end of the injection step to the core moving step was 5 seconds or more, it was confirmed that the inner layer portion was sufficiently laminated on the inner layer side of the outer layer portion.

DESCRIPTION OF SYMBOLS 1 ... Tubular hollow body, 1a ... one end, 1b ... other end, 1c ... outer peripheral surface, 1d ... inner peripheral surface, 2 ... linear part, 3 ... bending part, 4 ... fixed plate part, 5 ... outer layer part, 6 ... Inner layer portion 10: mold for molding 11: main cavity 12: pressure port 13: injector 14: discharge portion 15: sub-cavity 16: floating core A: axial axis of tubular hollow body B: main Axial axis of cavity, M: molded article, R1: first resin, R2: second resin.

Claims (12)

A tubular hollow body forming method for forming a tubular hollow body having a multilayer structure comprising an outer layer portion and an inner layer portion laminated on the inner layer side of the outer layer portion,
A main cavity into which the first resin is injected, and a pressure port which is formed at one end of the main cavity and into which the pressurized fluid is pressed and which is formed into the outer shape of the tubular hollow body, and the main A core setting step of detachably attaching a floating core to the pressing port of the molding die having a discharge part formed at the other end of the cavity and discharging the first resin from the main cavity;
An injection process of injecting a first resin into the main cavity after the core installation process;
After the injection step, the floating core is moved from the pressure port toward the discharge portion by pressing the pressurized fluid from the pressure port, and the core is discharged from the discharge portion. A transfer process,
The floating core is formed of a second resin different in type from the first resin,
In the injection step, the injection temperature of the first resin injected into the main cavity is made higher than the melting point of the second resin,
In the core moving step, the floating core is moved from the pressure port toward the discharge portion while melting the floating core.
Tubular hollow body molding method. The injection temperature of the first resin is 80 to 160 ° C. higher than the melting point of the second resin,
The method for forming a tubular hollow body according to claim 1. The melting point of the second resin is lower than the melting point of the first resin,
The method for forming a tubular hollow body according to claim 1. The melting point of the second resin is 65 to 80 ° C. lower than the melting point of the first resin,
The method for forming a tubular hollow body according to claim 1. The core moving step is performed 4 to 6 seconds after the injection step is completed,
The method for forming a tubular hollow body according to any one of claims 1 to 4. The molding die further includes a sub cavity communicating with the discharge unit and storing the first resin discharged from the discharge unit,
In the core moving step, the floating core is stopped before the sub cavity.
The method for forming a tubular hollow body according to any one of claims 1 to 5. In the injection step, the first resin containing a reinforcing material is injected into the main cavity,
The method for forming a tubular hollow body according to any one of claims 1 to 6. A tubular hollow body having a multilayer structure comprising an outer layer portion and an inner layer portion laminated on the inner layer side of the outer layer portion,
The outer layer portion is formed of a first resin,
The inner layer portion is formed of a second resin having a melting point lower than that of the first resin,
Tubular hollow body. The outer layer portion and the inner layer portion are fused to each other,
A tubular hollow body according to claim 8. The inner diameter at one end is different from the inner diameter at the other end,
The tubular hollow body according to claim 8 or 9. The inner diameter gradually decreases from one end to the other end,
The tubular hollow body according to claim 8 or 9. The outer layer portion contains a reinforcing material for reinforcing the first resin,
The tubular hollow body according to any one of claims 8 to 11.

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