Resin molded article having through-hole, molding method therefor, molding mold, and needless

Abstract

A resin molded article is molded by injection molding, a through-hole is opened in a predetermined end surface of the resin molded article, and a protrusion protruding from the predetermined end surface in the axial direction of the through-hole is formed annularly along the edge of the opening of the through-hole.

Description

Technical Field

[0001] The present invention relates to a resin molded product having a through hole, a molding method thereof, a molding die, and a needle-free syringe using the resin molded product. Background Art

[0002] Conventionally, as a method for molding a resin molded product having a through-hole, a method using injection molding has been proposed in which a core pin having a through-hole shape is inserted into molten resin in a cavity for molding (for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-109471

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-166363 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] When a resin molded article having a through-hole is molded by injection molding, minute burrs are generated at the opening of the through-hole during the process of inserting a core pin into molten resin to form the hole. The minute burrs may peel off during use of the molded article.

[0009] The technology disclosed herein has been developed in view of the above-described actual situation, and an object thereof is to suppress the generation of minute burrs at the opening of a through-hole in a resin molded product having a through-hole.

[0010] Solutions for solving problems

[0011] To address the aforementioned issues, the disclosed technology employs the following configuration. Specifically, a resin molded article, one aspect of the disclosed technology, is an injection-molded resin molded article, wherein a through-hole is formed in a predetermined end face of the resin molded article, and a protrusion is formed along the opening edge of the through-hole, protruding from the predetermined end face toward the through-hole in the axial direction.

[0012] Furthermore, in the resin molded article, a thickness of the protrusion in a direction perpendicular to the axial direction may be greater than or equal to 1 μm and less than or equal to 1000 μm.

[0013] Furthermore, in the resin molded article, a thickness of the protrusion in a direction perpendicular to the axial direction may be greater than or equal to 3 μm and less than or equal to 100 μm.

[0014] Furthermore, in the resin molded article, a thickness of the protrusion in a direction perpendicular to the axial direction may be 5 μm or more and 15 μm or less.

[0015] In addition, in the above-mentioned resin molded product, the resin molded product may also be formed as a container for containing the injection target substance in a needle-free syringe that injects the injection target substance into the target area without passing through an injection needle, the through hole defines the flow path of the injection target substance, and the resin molded product uses the opening portion on the specified end face side of the through hole as an injection port to inject the injection target substance into the target area.

[0016] In addition, the technology disclosed in the present invention can also be a molding method of a resin molded product, which molds the resin molded product by injection molding, and the resin molded product is formed with a through hole opening at a specified end face. In the molding method of the resin molded product, it comprises: a mold closing step of closing the molding mold; and an injection step of injecting resin into the molding mold, the molding mold comprises: a cavity forming a space for injecting the resin; and a core inserted into the space by relative movement along a specified first direction relative to the cavity, defining an area in the space where the resin does not flow, the core having a core pin extending along the first direction of the molding mold and defining the shape of the through hole in the space, and the cavity having an end face facing the space and defining the shape of the specified end face of the resin molded product. A demarcating surface, wherein a core pin receiving hole is formed on the end face demarcating surface, and the core pin receiving hole includes: a recessed portion, which is open to the space and recessed in the first direction to form an inner wall portion; and a receiving portion, which is open to the recessed portion and extends along the first direction to receive the top end of the core pin of the core inserted into the space, and the opening width of the recessed portion is set to be larger than the opening width of the receiving portion. In the mold closing process, the core moves relative to the cavity along the first direction, thereby the core is inserted into the space of the cavity. In the injection process, the resin is received by the recessed portion in a manner that the resin injected into the space does not reach the receiving portion, thereby forming a protrusion protruding from the specified end face of the resin molded product along the opening edge of the through hole.

[0017] In addition, in the molding method of the above-mentioned resin molded product, it can also be constructed as follows: when the core pin is inserted into the core pin receiving hole, the distance between the core pin at the opening of the recess and the inner wall surface of the recess is greater than 10µm and less than 100µm.

[0018] In addition, in the molding method of the above-mentioned resin molded product, it can also be constructed as follows: when the core pin is inserted into the core pin receiving hole, the distance between the core pin at the opening of the recess and the inner wall surface of the recess is greater than 5µm and less than 15µm.

[0019] In addition, in the molding method of the above-mentioned resin molded product, it can also be constructed as follows: when the core pin is inserted into the core pin receiving hole, the distance between the core pin at the opening of the receiving part and the inner wall surface of the receiving part is less than 10µm.

[0020] In addition, in the molding method of the above-mentioned resin molded product, it can also be constructed as follows: when the core pin is inserted into the core pin receiving hole, the distance between the core pin at the opening of the receiving part and the inner wall surface of the receiving part is less than 5µm.

[0021] In addition, in the molding method of the above-mentioned resin molded product, it can also be constructed as follows: when the core pin is inserted into the core pin receiving hole, at the opening of the receiving part, the distance between the core pin and the inner wall surface of the receiving part is less than 2.5µm.

[0022] Furthermore, in the above-mentioned method for molding a resin molded article, a depth of the recessed portion from the end face defining surface in the axial direction may be 20 μm or more.

[0023] Furthermore, in the above-mentioned method for molding a resin molded article, a depth of the recessed portion from the end face defining surface in the axial direction may be 50 μm or more.

[0024] Furthermore, in the above-mentioned method for molding a resin molded article, the depth of the recessed portion from the end face defining surface in the axial direction may be 100 μm or more.

[0025] In addition, in the above-mentioned molding method of the resin molded product, the shape of the opening portion of the through hole and the shape of the cross-section of the recess perpendicular to the first direction may be similar to each other, and in the mold closing process, when the core pin is inserted into the core pin receiving hole, the inner wall portion of the recess faces the side surface of the core pin in a manner along the side surface of the core pin.

[0026] Furthermore, in the above-described method for molding a resin molded article, the opening of the recess may have an elliptical shape in a cross section perpendicular to the first direction.

[0027] Furthermore, in the above-described method for molding a resin molded product, the recess may be formed in a columnar shape extending in the first direction in a direction in which the core pin is inserted into the core pin receiving hole.

[0028] In addition, the technology disclosed in the present invention can also be a molding die for a resin molded product, which is used to mold a resin molded product by injection molding, wherein the resin molded product is formed with a through hole opening at a specified end face, and the molding die for the resin molded product comprises: a cavity forming a space for resin injection; and a core inserted into the space by relative movement along a specified first direction relative to the cavity, defining an area in the space where the resin does not flow, the core having a core pin extending along the first direction and having a shape defining the through hole in the space, and the cavity having a core pin facing the space and defining the resin molded product. The end face defining surface of the shape of the specified end face is formed with a core pin receiving hole on the end face defining surface, and the core pin receiving hole includes: a recessed portion, which is open to the space and recessed in the first direction; and a receiving portion, which is open to the recessed portion and extends along the first direction, and receives the top end of the core pin of the core inserted into the space, and the opening width of the recess is set to be larger than the opening width of the receiving portion, and the recess receives the resin in a manner that the resin injected into the space does not reach the receiving portion, thereby forming a protrusion protruding from the specified end face of the resin molded product along the opening edge of the through hole.

[0029] Furthermore, the technology disclosed herein may be a needle-less syringe including the above-mentioned resin molded article formed as a container containing an injection target substance, wherein the needle-less syringe injects the injection target substance into a target area without using an injection needle.

[0030] Effects of the Invention

[0031] According to the present disclosure, it is possible to provide a resin molded product in which minute burrs are less likely to be generated at the opening of a through-hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic cross-sectional view of a resin molded article according to an embodiment.

[0033] Figure 2 It is a schematic cross-sectional view of a molding die and a resin molded product according to an embodiment.

[0034] Figure 3 yes Figure 2 A partial enlarged view of .

[0035] Figure 4 yes Figure 2 A partial enlarged view of .

[0036] Figure 5 This is a flowchart of a method for molding a resin molded article according to an embodiment.

[0037] Figure 6This is a schematic cross-sectional view of a needle-less syringe using the resin molded article according to the embodiment. DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that each configuration and their combination in the present embodiment is an example, and additions, omissions, replacements, and other changes to the configuration may be appropriately made without departing from the spirit of the present invention. In addition, the present disclosure is not limited to the embodiments, but only to the claims. The embodiment described below is a scheme in which the resin molded product of the present disclosure is applied to a container for containing an injection target substance in a needle-free syringe, but the technology of the present disclosure is not limited to this. That is, the technology of the present disclosure is not limited to containers for needle-free syringes, but can also be applied to resin molded products with through holes.

[0039] [Device Configuration]

[0040] Figure 1 : is a schematic cross-sectional view of a resin molded product 1 according to an embodiment. Figure 2 : is a cross-sectional view of the molding die according to the embodiment along the central axis C. Figure 2 In the figure, a mold 10 used in injection molding is shown. Figure 1 An example of the resin molded article 1 shown. In the present embodiment, the direction in which the core 11 is inserted relative to the cavity 12 in the mold closing process described later corresponds to the "prescribed first direction". In the present embodiment, the "first direction" is a direction parallel to the center axis C of the molding die 10 and the center axis C' of the through hole of the resin molded article 1. The molding die 10 can mold the resin molded article 1 by performing an injection process of injecting molten resin into the internal space 121 after the mold closing process. In addition, for the convenience of explaining the embodiment, in the cavity 12, the direction in which the internal space 121 is opened is set as the base end side so as to receive the core 11, and in the cavity 12, the direction in which the core pin receiving hole 124 is arranged is set as the top end side. Such base end side and top end side merely represent the relative positional relationship between the resin molded article 1 and the elements in the molding die 10.

[0041] [Resin molded products]

[0042] Figure 1This is a schematic cross-sectional view of a resin molded article 1 according to an embodiment. The resin molded article 1 is a molded article obtained by molding molten resin using a molding die 10, which will be described later. In this embodiment, the resin molded article 1 is formed as a container for containing an injection target substance used in a needle-free syringe. For convenience, the central axis of the through-hole 4 of the resin molded article 1 is referred to as the central axis C'. Furthermore, the resin molded article 1 is formed into a generally cylindrical shape extending in a first direction. The resin molded article 1 includes: a storage space 2 for containing an arbitrary substance; a predetermined end surface 3, which is a portion defining the shape of the resin molded article 1; a through-hole 4, which opens at the predetermined end surface 3; and a side surface 5, which is a portion defining the shape of the resin molded article 1. The storage space 2 is formed as a hollow portion of the resin molded article 1. The predetermined end surface 3 constitutes the top surface of the resin molded article 1, and the side surface 5 constitutes the side surface of the resin molded article 1. The through-hole 4 is a through-hole that connects the storage space 2 with the external space of the resin molded article 1 and opens at the predetermined end surface 3. More specifically, the through hole 4 is formed to extend along the central axis C' of the through hole 4 toward the predetermined end surface 3, which is the distal end of the storage space 2, and an opening 4A is formed at the distal end of the through hole 4. Furthermore, in this embodiment, in a needle-free syringe 100 described later, the through hole 4 defines a flow path for an injection target substance, which will be described later. Furthermore, the opening 4A of the through hole 4 is formed in a circular shape and serves as an ejection port for the injection target substance.

[0043] A protrusion 3A is formed around the opening 4A, projecting from the predetermined end surface 3 toward the central axis C'. In this embodiment, the protrusion 3A is formed in an annular shape along the edge of the opening 4A. However, the opening 4A may be circular, but the protrusion 3A may be modified to have an elliptical or polygonal shape. Specifically, the cross-sectional shape of the opening 4A (the cross-sectional shape within the opening) and the cross-sectional shape of the protrusion 3A (the cross-sectional shape of the radially outer edge of the protrusion formed at the edge of the opening) may differ in a direction perpendicular to the central axis C'. Furthermore, the protrusion 3A may be formed not in an annular shape but in a shape such as a Landolt ring, formed by cutting out a portion of the annular shape, or in a discontinuous shape. However, the opening 4A may also have a polygonal shape, and even in this case, it is preferable that the protrusion 3A be formed along the edge of the opening 4A.

[0044] By setting distance t1 (described later), the thickness of protrusion 3A in a direction perpendicular to central axis C' is set to 1µm to 1000µm, preferably 3µm to 100µm, and more preferably 5µm to 15µm. By forming protrusion 3A with a stable shape of a certain size as described above, along opening 4A, the formation of fine burrs can be prevented.

[0045] [Molding die]

[0046] Figure 2 This is a cross-sectional view along the central axis C of a molding die 10 according to an embodiment. The molding die 10 is configured to extend along a first direction. The molding die 10 includes a cavity 12 having an interior space 121 for accommodating molten resin, and a core 11 defining a region within the interior space 121 where the molten resin does not flow. During the mold closing process, the core 11 is inserted by relative movement relative to the cavity 12 along the first direction, occupying a portion of the interior space 121. This region, which does not flow into the molten resin during the injection process, forms the accommodating space 2 for the resin molded article 1.

[0047] Figure 3 and Figure 4 yes Figure 2 A partial enlarged view of the Figure 3 As shown, the core 11 includes a core body 111 and a core pin 112, and the core 11 extends in a first direction. During the mold closing process described later, the core body 111 occupies a portion of the interior space 121 of the cavity 12, thereby forming a receiving space 2 for the resin molded article 1. In this embodiment, the core pin 112 has a conical shape that converges toward the tip, extending toward the tip of the core body 111 and defining the shape of the through-hole 4 in the resin molded article 1. However, the shape of the core pin 112 is not limited; for example, a polygonal prism or an elliptical cylinder is also possible.

[0048] The cavity 12 includes an internal space 121 for accommodating molten resin; side defining surfaces 122 and end defining surfaces 123 that define the internal space 121; and a core pin receiving hole 124 for receiving the core pin 112. In the cavity 12, the side defining surfaces 122 define the shape of the side portions 5 of the resin molded article 1, and the end defining surfaces 123 define the shape of the end surface 3. Therefore, it is possible to form a portion on the top side from the end defining surfaces 123 using other components, making mold opening easier and thus facilitating removal of the resin molded article 1 molded by the mold 10. Furthermore, the core pin receiving hole 124 extends from the end defining surfaces 123 toward the top side in a first direction and opens into the internal space 121. The core pin receiving hole 124 includes a cylindrical recess 124A and a receiving portion 124B. However, the shapes of core pin receiving hole 124 and core pin 112 are not limited. For example, if core pin 112 is a polygonal prism, core pin receiving hole 124 may be a polygonal column having a similar cross-sectional shape in a cross section perpendicular to the first direction. Alternatively, if core pin 112 is an elliptical cylinder, core pin receiving hole 124 may be an elliptical cylinder having a similar cross-sectional shape in a cross section perpendicular to the first direction. The shape of recess 124A is not limited to a cylinder and may be another columnar shape. In any case, it is preferable that protrusion 3A of resin molded article 1 be formed so as to follow the shape of opening 4A.

[0049] like Figure 4As shown, core pin receiving hole 124 has a stepped structure, comprising: a recessed portion 124A, opening into interior space 121 and formed by inner wall surface 124AS ​​by being recessed in a first direction; and a receiving portion 124B, opening into recess 124A, extending in the first direction, and formed by inner wall surface 124BS. In this embodiment, side surface 112S of the core pin faces inner wall surface 124AS ​​along inner wall surface 124AS, forming a circular hole in the resin molded article 1. Furthermore, width W1, the opening diameter of recess 124A, is larger than width W2, the opening diameter of receiving portion 124B. This prevents molten resin from flowing into receiving portion 124B, located toward the tip of recess 124A, during the injection process described later. Furthermore, receiving portion 124B is shaped to receive the tip of core pin 112. When core 11 is inserted into cavity 12 in the mold closing step (described later), the tip of core pin 112 reaches a position closer to the tip of recess 124A. Specifically, the molten resin remaining in recess 124A forms protrusion 3A, and core pin 112 is positioned to penetrate this remaining molten resin. Consequently, the shape of through-hole 4 in resin molded article 1 is defined by core pin 112. At this time, the shape of the opening portion 4A of the through hole 4 of the resin molded product 1 formed by the core pin 112 and the shape of the cross-section perpendicular to the first direction in the recess 124A are similar to each other. When the core 11 is inserted into the cavity 12, the inner wall surface 124AS ​​of the recess 124A is configured to face the side surface 112S of the core pin 112 in a manner along the side surface 112S of the core pin 112, thereby suppressing the molten resin from flowing into the receiving portion 124B located closer to the top side than the recess 124A.

[0050] As described above, the opening width W1 of recess 124A is larger than the opening width W2 of receiving portion 124B. Consequently, even when core pin 112 is inserted into core pin receiving hole 124 in an eccentric position, receiving portion 124B functions as a guide for core pin 112, preventing wear between core pin 112 and recess 124A, with wear occurring preferentially between core pin 112 and receiving portion 124B. Specifically, in recess 124A, the gap between inner wall surface 124AS ​​of recess 124A and side surface 112S of core pin 112 is widened, trapping molten resin. This prevents the formation of minute burrs near opening 4A of the resulting resin molded article 1, even if core pin 112 or core pin receiving hole 124 wears due to continuous use.

[0051] Furthermore, as described above, receiving portion 124B functions as a guide for core pin 112. This eliminates the need for a stepped structure, as compared to a structure where recess 124A and receiving portion 124B have the same opening width (W1) and width (W2). This reduces damage to core pin 112 caused by collision with end defining surface 123, deformation of mold 10 due to the heat of the molten resin, and other factors. Furthermore, since recess 124A has a larger opening width than receiving portion 124B, there is room for adjustment when inserting core pin 112 into core pin receiving hole 124, which is also useful as an aid to insertion. This makes it easier to reliably insert core pin 112 into core pin receiving hole 124, enabling more reliable molding of through-hole 4.

[0052] like Figure 4 As shown, in this embodiment, in the state where the core pin 112 is inserted into the core pin receiving hole 124, the distance t1 between the side surface 112S of the core pin 112 and the inner wall surface 124AS ​​of the recess 124A is configured to be 10µm to 100µm, more preferably 5µm to 15µm, at the opening of the recess 124A on the same plane as the end surface defining surface 123. This facilitates forming the thickness of the protrusion 3A of the resin molded article 1 perpendicular to the central axis C' to 1µm to 1000µm, preferably 3µm to 100µm, more preferably 5µm to 15µm, thereby giving the protrusion 3A of the resin molded article 1 a stable shape of a certain size, thereby preventing the generation of fine burrs.

[0053] Furthermore, in this embodiment, when core pin 112 is inserted into core pin receiving hole 124, distance t2 between side surface 112S of core pin 112 and inner wall surface 124BS of receiving portion 124B is configured to be 10 µm or less, preferably 5 µm or less, and more preferably 2.5 µm or less. This reliably suppresses the flow of molten resin into receiving portion 124B, preventing the formation of minute burrs near opening 4A of resin molded article 1.

[0054] Furthermore, in this embodiment, the depth t3 from the end surface defining surface 123 toward the tip of the recessed portion 124A of the core pin receiving hole 124 is set to be 20µm or greater, preferably 50µm or greater, and more preferably 100µm or greater. This intentionally retains the molten resin in the recessed portion 124A, preventing it from reaching the receiving portion 124B, thereby preventing the formation of minute burrs.

[0055] The opening of recess 124A of core pin receiving hole 124 can have an elliptical shape, for example, in a cross-section perpendicular to the first direction. Furthermore, inner wall surface 124AS ​​of recess 124A can also be formed into a conical shape, converging toward the closed end, i.e., the tip, of core pin receiving hole 124, or a dome-shaped funnel shape, bulging toward side demarcating surface 122. Any such configuration, as long as it provides a stable shape with a certain height and size for protrusion 3A of resin molded article 1, can be modified to suit the intended use. In this embodiment, recess 124A is formed into a columnar shape, resulting in a rectangular cross-section along the first direction. This design facilitates mold fabrication. Furthermore, a conical shape, converging toward the tip, of recess 124A facilitates guidance when inserting core pin 112 into receiving portion 124B.

[0056] [Molding Methods for Resin Molded Products]

[0057] Next, a molding method of the resin molded article 1 according to the embodiment will be described. However, the molding method of the resin molded article 1 of the present disclosure is not limited to the following method. Figure 5 Flowchart of the molding method of the resin molded article 1 according to the embodiment. Figure 5 To explain.

[0058] First, in the preparation process of step S11, a molten resin is prepared to be the material of the resin molded article 1. For example, raw materials such as resin pellets are melted in advance to prepare for the subsequent process.

[0059] Next, in the mold closing process of step S12, core 11 is moved relative to cavity 12 so as to be inserted into it. When mold 10 is closed, core 11 is positioned so that a portion of internal space 121 of cavity 12 is occupied by core 11. This defines an area where molten resin does not flow in subsequent processes. This area thus forms accommodation space 2 and through-hole 4.

[0060] Next, in the injection process of step S13 , a nozzle (not shown) is pressed against any molten resin inlet (not shown) of the mold to flow the molten resin, whereby the molten resin is formed into the shape of the resin molded article 1 .

[0061] Next, in step S14, in the cooling step of cooling the molten resin, the resin is brought into a state defined in the shape of the resin molded article 1. By going through the cooling step, the fluid molten resin is fixed as the resin molded article 1 in the shape including the through-hole 4, the protrusion 3A, and the like.

[0062] Next, in the mold opening process of step S15 , the mold is opened by relatively moving the core 11 so as to be pulled out from the cavity 12 .

[0063] [Needle-free syringe]

[0064] Figure 6 1 is a schematic cross-sectional view of a needle-free syringe 100 using a resin molded article 1 according to an embodiment. In this embodiment, the resin molded article 1 is formed as a container for accommodating an injection target substance used in the needle-free syringe 100. Figure 6 2 is a cross-sectional view showing a state where the resin molded product 1 is attached to the needle-less syringe 100 .

[0065] Examples of the specified substances included in the injection target substance include biologically derived substances that can be injected into the target area of ​​a living organism, and substances that exhibit desired physiological activities. Examples of biologically derived substances include DNA, RNA, nucleic acids, antibodies, and cells. Examples of substances that exhibit physiological activities include drugs composed of low molecular weight substances, proteins, peptides, and the like, vaccines, inorganic substances such as metal particles used for thermotherapy or radiotherapy, and substances with various pharmacological / therapeutic effects including carriers. Furthermore, the liquid serving as the medium for the injection fluid can be any liquid suitable for injecting the specified substances into the target area, regardless of whether it is aqueous or oily. Furthermore, the viscosity of the liquid serving as the medium is not particularly limited, as long as the specified substances can be injected through the needle-free injector 100.

[0066] In the needle-less syringe 100, the syringe assembly 101 is detachably mounted on and off the housing 102. Before the needle-less syringe 100 is operated, or in the preparation stage, the storage space 2 between the container ("resin molded article 1" in this embodiment) and the plunger 103 included in the syringe assembly 101 is filled with injection liquid. The syringe assembly 101 is a unit that is replaced each time the injection liquid is injected.

[0067] When the needle-free injector 100 is operated, the target injection substance passes through the through-hole 4, with the opening 4A serving as the injection port, and is ejected into the target area of ​​the injection object. In other words, in the resin molded article 1, the through-hole 4 defines a flow path for the target injection substance, with the opening 4A functioning as the injection port. In this embodiment, the ignition current is supplied to the igniter 105 based on the operation of the first switch 104A and the second switch 104B, allowing the target injection substance to be ejected into the target area without passing through the injection needle. By using the disclosed technology, it is possible to prevent tiny burrs from peeling off the resin molded article 1 during the injection of the target injection substance.

[0068] While the embodiments of the present disclosure have been described above, the various aspects disclosed in this specification may be combined with any other features disclosed in this specification.

[0069] Description of Reference Numerals

[0070] 1: Resin molded products;

[0071] 2: Accommodation space;

[0072] 3: Specify the end face;

[0073] 4: Through hole;

[0074] 10: Molding mold;

[0075] 11: core;

[0076] 112: core pin;

[0077] 12: cavity;

[0078] 124: core pin receiving hole;

[0079] 100: needle-free syringe;

[0080] C, C': central axis.

Claims

1. A resin molded article formed by injection molding, wherein: A through hole is opened at a predetermined end surface of the resin molded article, A protrusion is formed along an opening edge of the through hole and protrudes from the predetermined end surface in an axial direction of the through hole.

2. The resin molded article according to claim 1, wherein The thickness of the protrusion in a direction perpendicular to the axial direction is greater than or equal to 1 μm and less than or equal to 1000 μm.

3. The resin molded article according to claim 1, wherein The thickness of the protrusion in a direction perpendicular to the axial direction is greater than or equal to 3 μm and less than or equal to 100 μm.

4. The resin molded article according to claim 1, wherein The thickness of the protrusion in a direction perpendicular to the axial direction is 5 μm or more and 15 μm or less.

5. The resin molded article according to claim 1, wherein The resin molded article is formed as a container for containing an injection target substance in a needle-less syringe for injecting the injection target substance into a target area without using an injection needle. The through hole defines the flow path of the injection target substance, The resin molded article uses the opening portion on the predetermined end surface side of the through hole as an injection port to inject the injection target substance into the target area.

6. A method for molding a resin molded product, wherein the resin molded product is molded by injection molding, wherein the resin molded product has a through hole opened at a predetermined end surface, wherein: The method comprises: a mold closing step of closing the molding mold; and an injection step of injecting resin into the molding mold. The molding die has: a cavity forming a space for the resin to be injected; and The core is inserted into the space by being relatively moved along a predetermined first direction relative to the cavity, and defines a region in the space where the resin does not flow. The core has a core pin extending in the first direction and defining the through hole in the space. The cavity has an end face defining a shape of the predetermined end face of the resin molded product and faces the space. A core pin receiving hole is formed on the end face defining surface, and the core pin receiving hole includes: a recessed portion, which opens into the space and is recessed in the first direction to form an inner wall portion; and a receiving portion, which opens to the recess and extends along the first direction and receives the top end of the core pin of the core inserted into the space, The opening width of the recess is set to be larger than the opening width of the receiving portion, In the mold closing step, the core is moved relative to the cavity along the first direction, thereby inserting the core into the space of the cavity. In the injection step, the resin injected into the space is received by the recess so as not to reach the receiving portion, thereby forming a protrusion projecting from the predetermined end surface of the resin molded product along the opening edge of the through hole.

7. The method for forming a resin molded article according to claim 6, wherein: The core pin is inserted into the core pin receiving hole, and the distance between the core pin at the opening of the recess and the inner wall surface of the recess is 10 μm or more and 100 μm or less.

8. The method for forming a resin molded article according to claim 6, wherein The core pin is inserted into the core pin receiving hole, and the distance between the core pin at the opening of the recess and the inner wall surface of the recess is 5 μm or more and 15 μm or less.

9. The method for forming a resin molded article according to claim 6, wherein: The core pin is inserted into the core pin receiving hole, and the distance between the core pin and the inner wall surface of the receiving portion at the opening of the receiving portion is 10 μm or less.

10. The method for forming a resin molded article according to claim 6, wherein The structure is such that when the core pin is inserted into the core pin receiving hole, the distance between the core pin at the opening of the receiving portion and the inner wall surface of the receiving portion is 5 μm or less.

11. The method for forming a resin molded article according to claim 6, wherein: The core pin is inserted into the core pin receiving hole, and the distance between the core pin at the opening of the receiving portion and the inner wall surface of the receiving portion is 2.5 μm or less.

12. The method for forming a resin molded article according to claim 6, wherein: The depth of the recessed portion from the end face defining surface in the axial direction is 20 μm or more.

13. The method for forming a resin molded article according to claim 6, wherein: The depth of the recess from the end face defining surface in the axial direction is 50 μm or more.

14. The method for molding a resin molded article according to claim 6, wherein The depth of the recessed portion from the end face defining surface in the axial direction is 100 μm or more.

15. The method for forming a resin molded article according to claim 6, wherein: The shape of the opening of the through hole and the shape of the cross section of the recess perpendicular to the first direction are similar to each other. In the mold closing step, with the core pin inserted into the core pin receiving hole, the inner wall of the recess faces the side surface of the core pin so as to follow the side surface of the core pin.

16. The method for molding a resin molded article according to claim 6, wherein: The opening of the recessed portion has an elliptical shape in a cross section perpendicular to the first direction.

17. The method for forming a resin molded article according to claim 6, wherein: The recessed portion is formed in a columnar shape extending in the first direction toward a direction in which the core pin is inserted into the core pin receiving hole.

18. A molding die for a resin molded product, for molding a resin molded product by injection molding, wherein the resin molded product has a through hole opened at a predetermined end surface, the molding die comprising: A cavity forming a space for resin injection; and A core is inserted into the space by being relatively moved along a predetermined first direction relative to the cavity, defining a region in the space where the resin does not flow, the core having a core pin extending along the first direction and defining the through hole in the space. The cavity has an end face defining a shape of the predetermined end face of the resin molded product and faces the space. A core pin receiving hole is formed on the end face defining surface, and the core pin receiving hole includes: a recessed portion, opening into the space and recessed toward the first direction; and a receiving portion, which opens to the recess and extends along the first direction and receives the top end of the core pin of the core inserted into the space, The opening width of the recess is set to be larger than the opening width of the receiving portion, The recessed portion receives the resin injected into the space so as not to reach the receiving portion, thereby forming a protrusion protruding from the predetermined end surface of the resin molded product along the opening edge of the through hole.

19. A needle-free syringe, wherein: The resin molded article according to claim 1 is provided with a container formed to accommodate an injection target substance, The needle-free injector injects the injection target substance into a target area without using an injection needle.

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