Injection molded body and method for producing same

Abstract

In a case (11) that is an injection molded body, groove parts (8) which increase the flow rates of two resin flows (A) having different directions are formed on both sides of a merging location (7) which is formed by the merging of the resin flows (A) at the time of injection molding.

Description

Injection molded article and manufacturing method thereof

[0001] The present invention relates to an injection-molded article obtained by injection molding a fluid material such as a molten resin, and a method for producing the same.

[0002] BACKGROUND ART Conventionally, when a product or part having a complex shape is manufactured using a resin material, injection molding has been widely used.

[0003] For example, the case of the door checker for an automobile door disclosed in Patent Document 1 is made of metal, but from the viewpoint of weight reduction, it is conceivable to make the case by injection molding using a resin material.

[0004] However, when manufacturing a part of a predetermined shape, such as a case, by injection molding, there is a concern that the resin flow may lack strength at the joining point.

[0005] That is, when manufacturing a case or the like by injection molding, molten resin material is injected under high pressure from the gate (injection port) of the mold into the cavity (injection space), but inside the cavity, at a location away from the gate where two resin flows flowing in different directions meet (the so-called weld), the resin flows may collide head-on and become opposing flows, preventing complete mixing and forming a linear seam called a weld line. Such a confluence where a weld line is formed has weak strength, and when stress is concentrated at the confluence, especially in a high-temperature environment, cracks and breakage are likely to occur along the weld line.

[0006] Therefore, conventionally, studies have been conducted to predict the locations of merging points and weld lines in advance and set the gate at the optimal position. However, there are cases where the locations where the gate can be set are limited due to constraints such as product function and mold structure, making it difficult to prevent defects due to insufficient strength at the merging points.

[0007] In particular, when molding a case for a door checker for an automobile door from resin, which is subject to large forces when the door is opened or closed, it is necessary to minimize or eliminate weld lines, which are prone to damage.

[0008] Japanese Patent Application Laid-Open No. 2017-197945

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an injection-molded article that can suppress the occurrence of weld lines at the confluence of two resin flows and improve the strength of the confluence.

[0010] In order to solve the above-mentioned problems, the injection-molded article of the present invention is an injection-molded article manufactured by injection molding using a resin material, and is characterized by having a confluence point formed by the confluence of two resin flows flowing in different directions during injection molding, and a flow rate changing structure that changes the flow rate of the resin flows on both sides of the confluence point during injection molding.

[0011] 1 is a perspective view showing the overall configuration of a case for an automobile door checker according to an embodiment of the injection-molded article of the present invention, in which grooves are formed on the outer surface of the case on both sides of a joining point of resin flows during injection molding. FIG. 1 is an explanatory perspective view showing a state in which resin flows that join at the joining point in the case of FIG. 1 are turbulent flows that are not counterflowing. FIG. 2 is an explanatory cross-sectional view of the joining point of the joining side end wall of FIG. 1 in the vicinity of the joining point, showing a structure in which grooves are formed on both sides of the joining point on the outer surface of the joining side end wall. FIG. 2 is an explanatory view showing the resin flow at the joining point and its surroundings as viewed from above the case. FIG. 4 is an explanatory view for explaining the weld meeting angle, which is the angle at which two resin flows collide in FIG. 4. FIG. 5 is an explanatory view (simulation result) showing that weld lines that occur at locations where the weld meeting angle is small during injection molding when viewed from the outside of the case of FIG. 1. FIG. 6 is an explanatory view (simulation result) showing that weld lines that occur at locations where the weld meeting angle is small during injection molding when viewed from the inside of the case of FIG. 1. 10 is an explanatory diagram (simulation result) showing that a case having no grooves on the joining end wall as a comparative example, viewed from the outside, shows that a linear weld line has occurred over a wide area at a location where the weld meeting angle is small during injection molding. FIG. 11 is an explanatory diagram (simulation result) showing that a case having no grooves on the joining end wall as a comparative example, viewed from the inside, shows that a linear weld line has occurred over a wide area at a location where the weld meeting angle is small during injection molding. FIG. 12 is an explanatory diagram (simulation result) showing that a case having no grooves on the joining end wall as a comparative example, viewed from the inside, shows that a linear weld line has occurred over a wide area at a location where the weld meeting angle is small during injection molding. FIG. 13 is a schematic explanatory diagram showing a molding die used in a method for manufacturing a case of the present invention, and a case and surplus molded body molded with the molding die. FIG. 14 is an explanatory perspective view showing a state in which a portion of the resin flows that have joined at the joining point during injection molding in FIG. 10 flows toward a sub-space portion where the surplus molded body is molded, thereby preventing the generation of counterflows. FIG. 15 is an enlarged perspective view of a case having grooves on both sides of the joining point on each of the outer and inner surfaces of the case according to another modified example of the present invention. FIG. 16 is an explanatory perspective view of an automobile door checker including the case of FIG. 1. FIG. 17 is an exploded perspective view of the automobile door checker of FIG. 13.10A and 10B are diagrams showing a structure for changing the flow rate of resin flows on both sides of a joining point in an injection-molded article of the present invention, in which (a) is a diagram showing a structure having grooves that increase the flow rate corresponding to the cases of Figures 1 to 4, (b) is a diagram showing a structure having holes that increase the flow rate inside the case instead of grooves, and (c) is a diagram showing a structure having surplus molded body that decreases the flow rate corresponding to Figure 11. Figure 10A is a perspective view of a resin side cover for a vehicle seat according to another embodiment of the injection-molded article of the present invention.

[0012] Hereinafter, an injection molded article according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0013] In the following embodiments, a housing case 11 (hereinafter referred to as case 11) that houses multiple movable parts of an automobile door checker 1 (see FIGS. 13 and 14) that has the function of holding an automobile door in an open position will be described as an example of an injection-molded article according to an embodiment of the present invention. The configuration of automobile door checker 1 will be described later.

[0014] 1 and 2, the case 11 is a long, narrow, hollow resin case, and specifically includes a main wall 2 having a through hole 2a, a pair of side walls 3 rising from both longitudinally extending edges of the main wall 2, and a gate-side end wall 4 and a junction-side end wall 5 rising from both lateral edges of the main wall 2 extending in the short direction. The case 11 is open on the side facing the main wall 2 (the upper side in FIG. 1). The gate-side end wall 4 and the junction-side end wall 5 face each other and are spaced apart in the longitudinal direction of the main wall 2.

[0015] A gate portion 6 is formed on the outer surface of the gate-side end wall 4 , which corresponds to the injection port of the cavity of the mold through which the resin material is injected when the case 11 is injection molded.

[0016] On the other hand, the confluence side end wall 5 has a confluence 7 formed by two resin flows A flowing in different directions converging when the case 11 is injection molded.

[0017] The case 11 is injection molded using a resin material, such as glass fiber reinforced polyamide or glass fiber reinforced polypropylene, for example, which can be injection molded.

[0018] In this embodiment, the confluence point 7 is a confluence side end wall 5 located opposite the gate side end wall 4 on which a gate portion 6 corresponding to the location where the resin material is injected into the cavity of the mold during injection molding of the case 11 is provided, and is positioned on a line BL that passes through the gate portion 6 and runs along the longitudinal direction of the case 11.

[0019] As shown in Figures 1 to 4 and 6 and 7 , grooves 8 that narrow the flow path of the resin flow A are formed on both sides of the confluence point 7 (on both sides of line BL). Specifically, as shown in Figure 6 , the grooves 8 extend on both sides of the confluence point 7 on the outer surface 5a of the confluence-side end wall 5 over the entire height of the confluence-side end wall 5. That is, the confluence point 7 is separated from other parts of the confluence-side end wall 5 by the grooves 8 on both sides. These grooves 8 narrow the flow path of the resin flow A, thereby changing the direction and flow speed of the resin flow A. As a result, it is possible to generate turbulence R in the resin flows A that are confluent at an angle to each other while avoiding opposing flows that would result in a head-on collision when the resin flows A converge at the confluence point 7.

[0020] The grooves 8 are preferably formed on both sides of the confluence 7 on the front and back surfaces of the case 11, i.e., on the same surface of at least one of the outer surface 5 a or inner surface 5 b of the confluence-side end wall 5, so that the resin flows A collide with each other at an oblique angle. In this embodiment, the grooves 8 are formed on both sides of the confluence 7 on the outer surface 5 a of the confluence-side end wall 5.

[0021] 2 and 3, the groove 8 is a portion that narrows the flow path of the resin flow A during injection molding. The depth δ1 of the groove 8, the thickness δ2 of the bottom wall 8a of the groove 8 (i.e., the width of the flow path narrowed by the groove 8), and the thickness t of the confluence 7 are each set to a size that generates a turbulence R in the resin flow A at the confluence 7.

[0022] (Explanation of weld meeting angle) As shown in Figures 2 and 4, the flow path of resin flow A narrows at groove portion 8 and then suddenly expands at confluence 7. At confluence 7, two different resin flows A merge at an angle to each other while avoiding counterflows, causing turbulence R in resin flow A.

[0023] 5, two different resin flows A (referred to as A1 and A2) meet at an angle to each other to avoid opposing flows, provided that the weld meeting angle θ, which is the collision angle between the two resin flows A1 and A2, is sufficiently large. Specifically, the weld meeting angle θ is defined as the angle between the leading edges (flow fronts) a1 and a2 of the two resin flows A1 and A2.

[0024] Next, the distribution of the weld meeting angle θ in the case 11 shown in FIG. 1 when it is injection molded was investigated by computer simulation, and the locations where the weld meeting angle θ is small, i.e., the locations where weld lines occur, are shown in FIGS. 6 and 7.

[0025] 6 and 7 show that, when viewed from the outside and inside of the case 11 of this embodiment, the weld line WL1 that occurs at the confluence 7 where the weld meeting angle θ is small during injection molding is smaller than when there is no groove 8. This shows that the grooves 8 on both sides of the confluence 7 reduce the number of locations where the weld meeting angle θ is small, i.e., the locations where the two resin flows A flow in opposite directions.

[0026] 8 and 9 show comparative examples in which the distribution of the weld meeting angle θ was investigated by computer simulation for a case 21 that does not have a groove in the confluence-side end wall 25, and the locations where weld lines occur are shown. The comparative example case 21 has the same other configuration (main wall portion 22, pair of side walls 23, and gate-side end wall (not shown)) as the case of the above embodiment.

[0027] As shown in Figures 8 and 9, the comparative example case 21 does not have grooves on either side of the middle part of the confluence side end wall 25 (outer surface 25a and inner surface 25b) where the confluence occurs, and therefore it can be seen that the weld line WL2 that occurs at the point where the weld meeting angle is small occurs linearly over a wide area.

[0028] (Description of Automobile Door Checker) Next, the configuration of the door checker 1 including the case 11 of the above embodiment will be described with reference to FIGS.

[0029] 13, the door checker 1 includes a housing 10 and a check plate 13. The housing 10 is disposed so as to extend in a direction intersecting the direction of movement of the check plate 13 (the direction indicated by arrow B). The housing 10 includes a housing base 12 and the case 11 of the above embodiment, which is a housing case.

[0030] 14, the door checker 1 includes, as a plurality of movable parts, a pair of sliding guides 16, 17 and a pair of elastic bodies 18, 19. The pair of sliding guides 16, 17 and the pair of elastic bodies 18, 19 are housed in the housing space 11a of the case 11.

[0031] 13 and 14, an end of the check plate 13 is attached to one of the body or door of the vehicle via a pin 14 and a bracket 15. Meanwhile, the housing 10 is attached to the other of the body or door using two bolts 120 of the housing base 12.

[0032] (Features of this embodiment) (1) In the case 11, which is the injection molded body of this embodiment, groove portions 8, which are speed-increasing structures that increase the flow rate, are formed on both sides of the confluence 7, which is formed when two resin flows A flowing in different directions meet during injection molding, as a flow rate changing structure that suddenly changes the flow rate of the two resin flows A.

[0033] With this configuration, when the case 11 is injection molded, two resin streams A flowing in different directions inside the mold pass through grooves 8 on either side of the predetermined confluence point 7 and then merge at the confluence point 7 while becoming turbulent. Therefore, the flow path of the resin streams A narrows at the grooves 8 and then suddenly expands at the confluence point 7, so that the two resin streams A flow faster and merge at an angle to each other, avoiding a head-on collision between opposing flows when they meet at the confluence point 7. Specifically, the two resin streams A collide at a collision angle (weld meeting angle θ shown in FIG. 5 ) that is sufficiently greater than 0 degrees. At this time, the two resin streams A merge while generating turbulence R, as shown in FIGS. 2 and 4 .

[0034] This suppresses the occurrence of linear weld lines caused by collisions between resin flows A. In other words, the weld lines shown in Figures 6 and 7 become smaller or disappear, improving the strength of the junction 7 of the case 11.

[0035] (2) In the case 11, which is the injection-molded article of this embodiment, grooves 8 are formed on both sides of the confluence 7 on the same surface of at least one of the front and back surfaces on both sides of the confluence 7, that is, on the outer surface 5a, which is the front surface in Figures 1 to 4.

[0036] With this configuration, the two resin flows A flow along the outer surface 5a on both sides of the joining point 7 of the molded body, then suddenly narrow in the groove 8, and then collide and join at an angle inclined from their opposing directions at the joining point 7, thereby reliably generating turbulence in the resin flow. This further suppresses the occurrence of weld lines. Therefore, weld lines are further reduced or eliminated more reliably. This further improves the strength of the joining point 7.

[0037] (3) In the above-described case 11, as shown in a simplified diagram in Fig. 15(a), grooves 8 are formed on both sides of the confluence 7, causing the flow rate of the resin flow A to suddenly increase. A structure that suddenly increases the rate of the resin flow A on both sides of the confluence 7 can also be achieved with structures other than the structure having the above-described grooves 8. For example, as another embodiment of the present invention, a structure in which holes 38 are provided on both sides of the confluence 7 along the confluence 7, as shown in Fig. 15(b), can also function as a speed-increasing structure that increases the flow rate of the resin flow A. The holes 38 are formed by inserting a cylindrical core for forming the holes 38 into the mold during injection molding of the case 11.

[0038] 15(b), the flow path of resin flow A narrows at hole 38 and then suddenly expands at confluence 7. This increases the flow velocity of the two resin flows A, and when they meet at confluence 7, they merge at an angle to each other, avoiding opposing flows that would result in a head-on collision. This prevents the occurrence of linear weld lines caused by the collision of the resin flows A. This improves the strength at confluence 7.

[0039] (4) The case 11, which is the injection-molded article of this embodiment, is the case 11 of an automobile door checker 1 that has the function of holding an automobile door in an open position. In the automobile door checker 1, a large load acts on the case 11 when the door is opened or closed. However, by providing the grooves 8 on both sides of the junction 7 as described above, the occurrence of weld lines is suppressed. This improves the strength of the junction 7 in the case 11 of the automobile door checker, which is subjected to a large load, and improves the durability of the case 11 and the door checker.

[0040] (5) The case 11 of the injection-molded article of this embodiment is a long, narrow, hollow case. The confluence 7 is located on the opposite side of the gate-side end wall 4 (e.g., on the confluence-side end wall 5, on a line BL that passes through the gate 6 and runs along the longitudinal direction of the case 11) from the gate-side end wall 4, which is the end where the gate 6 is provided, corresponding to the location where the resin material is injected into the cavity of the mold during injection molding of the case 11. As a result, during injection molding of the long, narrow case 11, the two resin streams A can be reliably merged at the confluence 7, causing turbulence in the resin streams A and suppressing the occurrence of weld lines. This stabilizes the quality of the injection-molded long, narrow case 11.

[0041] (6) In addition, in the case 11 of the injection molded body of this embodiment, as shown in Figures 11 and 15(c) described below, an excess molded body 9 may be formed from a portion of the resin material that meets at the meeting point 7.

[0042] With this configuration, the surplus resin flow 9 is formed from a portion of the resin material resulting from the joining of the two resin flows A at the joining point 7, and a portion of the two resin flows A at the joining point 7 flows to the surplus resin flow 9. Furthermore, as shown in FIG. 15( c), the flow path is enlarged by the formation of the surplus resin flow 9 at the joining point 7, slowing the flow rate of the resin flow A at the joining point. This reliably prevents the occurrence of opposing flows that collide head-on, further suppressing the occurrence of weld lines. This further improves the strength at the joining point 7.

[0043] 11 and 15(c) above, the surplus molded body 9 is preferably configured to be separable from the joining point 7, for example, to have a constriction or a slit so that the surplus molded body 9 can be easily separated by cutting, bending, etc. By using such a configuration, in the manufacturing process of the case 11, the surplus molded body 9 can be easily separated from the joining point 7 after the case 11 is resin-molded.

[0044] (Method for Manufacturing Case 11) The following manufacturing method is considered as an example of a preferred method for manufacturing the injection-molded article of the present invention. This manufacturing method includes a preparation step of preparing a mold having a main space corresponding to the injection-molded article of a predetermined shape and an injection port for injecting a resin material into the main space; a molding step of injecting the resin material into the main space of the mold through the injection port to form an injection-molded article; a removal step of removing the injection-molded article from the mold; and a post-processing step of performing post-processing on the removed injection-molded article. The mold further includes protrusions that protrude inward from the main space on both sides of a portion of the main space corresponding to a joining point of the resin material, so as to form grooves in the injection-molded article, and sub-spaces that communicate with the portions corresponding to the joining point. In the molding step, the resin material is injected into the main space and a portion of the resin material that joins at the joining point is allowed to flow into the sub-space, thereby forming an injection-molded article with grooves formed on both sides of the joining point and forming an excess molded article corresponding to the sub-space. In the post-processing step, the excess molding is separated from the injection molding.

[0045] 10, a molding die 30 is prepared, which has a main space 31 corresponding to the case 11 of a predetermined shape and an injection port 32 for injecting a resin material (see resin flow A) into the main space 31. The molding die 30 further has, on both sides of a portion 35 in the main space 31 corresponding to the joining point 7 of the resin material, protrusions 34 that protrude inward of the main space 31 to form grooves 8 in the case 11, and sub-spaces 33 (so-called waste cavities) that communicate with the portions 35 corresponding to the joining point 7.

[0046] In the molding process, resin material is injected into the main space 31 through the injection port 32, and a portion of the resin material that meets at the meeting point 7 is allowed to flow into the sub-space 33, thereby molding a case 11 with grooves 8 formed on both sides of the meeting point 7 and molding an excess molded body 9 (see Figures 10 and 11) that corresponds to the sub-space 33.

[0047] Thereafter, in the removal step, the case 11 and the surplus molded body 9 are removed from the molding die 30 while still connected. Then, as a post-processing step, the surplus molded body 9 is separated from the case 11. The surplus molded body 9 may have any configuration as long as it can be separated from the joining point 7 of the case 11. The surplus molded body 9 is preferably configured so that the portion connected to the joining point 7 is constricted so that it can be separated from the joining point 7 by cutting using, for example, an existing cutting tool (e.g., a cutter or nippers).

[0048] 10-11, in the molding process of the manufacturing method for case 11, after two resin flows A join at the joining point 7, a portion of the joined resin flows A flow in parallel toward the subspace 33 where the surplus molded body 9 is molded. This reliably prevents the two resin flows A from colliding head-on at the joining point 7 and further suppresses the occurrence of weld lines. This further improves the strength at the joining point 7.

[0049] Furthermore, the manufacturing method of the above-mentioned case 11 includes a post-processing step of separating the excess molded body 9 from the case 11, so that it becomes possible to separate the excess molded body 9 from the confluence point 7 after the case 11 has been resin-molded in the molding step.

[0050] The above-described manufacturing method is merely an example, and is not intended to be limiting, of manufacturing the case 11. In other words, when manufacturing the case 11, the surplus molded body 9 does not necessarily need to be molded together with the case 11.

[0051] (Modifications) In the above embodiment, the grooves 8 are formed on both sides of the joining point 7 on the outer surface 5a of the joining-side end wall 5, but the present invention is not limited to this. As another modification of the present invention, as shown in Fig. 12, a pair of grooves 8 may be formed on the outer surface 5a of the joining-side end wall 5 and a pair of grooves 28 may be formed on the inner surface 5b on both sides of the joining point 7 of the case 11 so that the resin flows A collide with each other at an oblique angle. Alternatively, a pair of grooves 28 may be formed only on the inner surface 5b of the joining-side end wall 5 on both sides of the joining point 7 of the case 11.

[0052] Furthermore, while the above embodiment includes a structure for abruptly changing the flow rate, the present invention is not limited to this. As another modification of the present invention, a structure for gradually changing the flow rate rather than abruptly may be provided. For example, the flow rate may be gradually increased by gradually forming the arcs of the grooves 8 and holes 38, or the flow rate may be gradually decreased by gradually expanding the flow path toward the surplus molded body 9. In this way, even if the flow rate is gradually changed, it is possible to prevent the occurrence of opposing flows that collide head-on and suppress the occurrence of weld lines.

[0053] (Scope of Application of the Present Invention) In the above embodiment, the case 11 of an automobile door checker is described as an example of an injection-molded article of the present invention, but the present invention is not limited thereto. The present invention is widely applicable to any injection-molded article manufactured by injection molding using a resin material. For example, the present invention can be applied to vehicle seat side covers, pole guides that are installed on vehicle seats and support headrests, frames (bezels) of seat forward-leaning levers that are installed on the shoulders of vehicle seats, frames (covers) of anchors on the back side of vehicle seats that can be connected to child seats, frames (covers) of anchors on the seat bottom side of vehicle seats that can be connected to child seats, frames (bezels) that are installed on vehicle seats and serve as seatbelt outlets, cup holders, armrests, and other resin interior parts of automobiles.

[0054] For example, as shown in FIG. 16, when applied to a resin side cover 40 of a vehicle seat, it is possible to suppress the occurrence of weld lines 44 at a position where an opening 42 and an upper edge 43 are close to each other, away from the location 41 of the resin injection port when the side cover 40 is molded.

[0055] <Summary of the embodiment> The above embodiment can be summarized as follows.

[0056] The injection-molded body of this embodiment is an injection-molded body manufactured by injection molding using a resin material, and is characterized by having a confluence point formed by the confluence of two resin flows flowing in different directions during injection molding, and a flow rate changing structure that changes the flow rate of the resin flows on both sides of the confluence point during injection molding.

[0057] With this configuration, when an injection-molded body is formed by injection molding, two resin flows flowing in different directions inside the mold have different flow velocities on both sides of a predetermined confluence point, causing the two resin flows to merge while being turbulent. This suppresses the occurrence of linear weld lines caused by the collision of the resin flows. This improves the strength of the injection-molded body at the confluence point.

[0058] In the above-described injection molded article, it is preferable that the flow rate changing structure includes speed increasing structures provided on both sides of the joining point to increase the speed of the resin flow during injection molding.

[0059] With this configuration, the flow speed of the two resin streams increases on both sides of the predetermined confluence during injection molding, causing the two resin streams to merge while being turbulent. This suppresses the occurrence of linear weld lines caused by the collision of the resin streams and improves the strength of the injection-molded body at the confluence.

[0060] In the above-described injection molded article, it is preferable that the speed increasing structure be formed by providing linear grooves along the joining point on both sides of the joining point.

[0061] With this configuration, when an injection-molded body is injection-molded, two resin flows flowing in different directions inside the mold pass through grooves on both sides of a predetermined confluence point before joining at the confluence point. Therefore, the flow path of the resin flows narrows at the grooves and then suddenly expands at the confluence point, so the two resin flows flow faster and merge at an angle to each other, avoiding opposing flows that would result in a head-on collision. This suppresses the occurrence of linear weld lines caused by the collision of resin flows. This improves the strength of the injection-molded body at the confluence point.

[0062] In the injection molded article, it is preferable that the grooves are formed on both sides of the joining point on the same surface of at least one of the front and back surfaces of the injection molded article on both sides of the joining point.

[0063] With this configuration, the two resin flows flow along the same surface on either the front or back side of the molded body at the joining point, then suddenly narrow in the groove, and then collide and join at an angle inclined from the opposing directions at the joining point, thereby reliably generating turbulence in the resin flow. This further suppresses the occurrence of weld lines, and further improves the strength of the joining point.

[0064] In the above-described injection molded article, it is preferable that the speed increasing structure be formed by providing linear holes along the joining point on both sides of the joining point.

[0065] With this configuration, when an injection-molded body is injection-molded, two resin flows flowing in different directions inside the mold pass through holes on either side of a predetermined confluence point before joining at the confluence point. Therefore, the flow path of the resin flows narrows at the holes and then suddenly expands at the confluence point, so the two resin flows flow faster and merge at an angle to each other, avoiding opposing flows that would result in a head-on collision. This suppresses the occurrence of linear weld lines caused by the collision of resin flows. This improves the strength of the injection-molded body at the confluence point.

[0066] In the above-described injection-molded article, the injection-molded article may be a case for an automobile door checker having a function of holding an automobile door in an open position.

[0067] Automobile door checkers are subject to large loads on their cases when the doors are opened and closed. However, by providing grooves on both sides of the joining point as described above, the occurrence of weld lines is suppressed. This improves the strength of the joining point on the case of an automobile door checker, which is subject to large loads, and improves the durability of the case and the door checker.

[0068] In the above-mentioned injection-molded body, it is preferable that the injection-molded body is a long, thin, hollow case, and that the confluence point is located opposite the end where the gate portion, which is the location where the resin material is injected into the cavity of the mold during injection molding of the case, is provided.

[0069] With this configuration, when injection molding a long, thin, hollow case, the confluence is located directly opposite the gate, so even when injection molding a long, thin case, the two resin streams can reliably merge at the confluence, causing turbulence in the resin flow and suppressing the occurrence of weld lines, thereby stabilizing the quality of the injection-molded case.

[0070] In the above-mentioned injection molded article, it is preferable that a surplus molded article is formed from a portion of the resin material that has joined at the joining point.

[0071] With this configuration, the surplus molded body is formed from a portion of the resin material that is formed when the two resin flows meet at the confluence, which reliably prevents the occurrence of opposing flows that collide head-on with each other at the confluence and further suppresses the occurrence of weld lines, thereby further improving the strength at the confluence.

[0072] In the above-mentioned injection molded article, the surplus molded article is preferably configured to be separable from the joining point.

[0073] According to this configuration, in the process of manufacturing injection molded articles, after the injection molded articles have been resin molded, the surplus molded articles can be easily separated from the joining point.

[0074] The method for manufacturing an injection-molded body of this embodiment includes a preparation step of preparing a molding die having a main space portion corresponding to an injection-molded body of a predetermined shape and an injection port for injecting a resin material into the main space portion, and a molding step of molding the injection-molded body by injecting the resin material from the injection port into the main space portion of the molding die, wherein the molding die further has a sub-space portion that communicates with the portion corresponding to the confluence point, and in the molding step, the resin material is injected into the main space portion and a portion of the resin material that has merged at the confluence point is caused to flow into the sub-space portion, thereby molding the injection-molded body and molding an excess molded body that corresponds to the sub-space portion.

[0075] In the above-described manufacturing method for an injection-molded article, after two resin flows meet at a confluence point during the molding process, a portion of the combined resin flow flows into the sub-space, thereby reliably preventing the two resin flows from colliding head-on at the confluence point and further suppressing the occurrence of weld lines, thereby further improving the strength at the confluence point.

[0076] The above-mentioned method for producing an injection-molded article preferably includes a post-processing step of separating the surplus molded article from the injection-molded article.

[0077] In this manufacturing method, in the post-processing step, after the injection molded body is resin molded in the molding step, the excess molded body can be separated from the joining point.

[0078] As described above, according to the injection molded article and the manufacturing method thereof of this embodiment, it is possible to suppress the occurrence of weld lines at the joining point of two resin flows and improve the strength of the joining point.

Claims

1. An injection-molded product manufactured by injection molding a resin material, characterized in that it has a confluence point formed when two resin flows flowing in different directions meet during injection molding, and a flow rate changing structure that changes the flow rate of the resin flows on both sides of the confluence point during injection molding.

2. An injection molded article according to claim 1, characterized in that the flow rate changing structure is provided with a speed increasing structure on both sides of the joining point to increase the speed of the resin flow during injection molding.

3. An injection molded article according to claim 2, characterized in that the speed increasing structure is a linear groove provided on both sides of the joining point along the joining point.

4. An injection molded article according to claim 3, characterized in that the grooves are formed on both sides of the joining point on the same surface of at least one of the front and back surfaces of the injection molded article on both sides of the joining point.

5. An injection molded article according to claim 2, characterized in that the speed increasing structure is formed by linear holes provided along the joining point on both sides of the joining point.

6. The injection-molded article according to any one of claims 1 to 5, characterized in that the injection-molded article is a case for an automobile door checker that has the function of holding an automobile door in an open position.

7. An injection-molded article according to any one of claims 1 to 5, wherein the injection-molded article is a long, thin, hollow case, and the confluence is located on the opposite side of an end of the case provided with a gate portion, which is the location where the resin material is injected into the cavity of the mold during injection molding of the case.

8. An injection molded article according to any one of claims 1 to 5, characterized in that a surplus molded body is formed from a portion of the resin material that has joined at the joining point.

9. An injection molded article according to claim 8, characterized in that the surplus molded article has a structure that allows it to be separated from the joining point.

10. A method for producing an injection-molded article according to any one of claims 1 to 5, comprising: a preparation step of preparing a molding die having a main space corresponding to an injection-molded article of a predetermined shape and an injection port for injecting a resin material into the main space; a molding step of injecting the resin material from the injection port into the main space of the molding die to form the injection-molded article; and a removal step of removing the injection-molded article from the molding die, wherein the molding die further has a sub-space communicating with a part corresponding to the joining point, and wherein in the molding step, the resin material is injected into the main space and a part of the resin material that has joined at the joining point is caused to flow into the sub-space, thereby forming the injection-molded article and molding an excess molded article corresponding to the sub-space.

11. A method for producing an injection molded article according to claim 10, characterized in that it comprises a post-processing step of separating the excess molded article from the injection molded article.

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