Resin molded article

Abstract

A resin molded article (10) is configured by integrally forming, from a resin, a main body section (11) provided with a rib (20) having only one end surface (24), and an extension section (17) extending from an end part (14b) of the main body section (11) and not provided with the rib (20). On a back surface (17a) of the extension section (17), a protrusion (30) is formed adjacent to the end surface (24) of the rib (20), the protrusion (30) being a trace in which a molten resin (R) that flowed from the rib (20) into the extension section (17) during molding has been guided.

Description

resin molded products

[0001] The present invention relates to a resin molded product having ribs.

[0002] Some resin molded products are provided with ribs to increase rigidity and strength. When resin molded products are obtained by injection molding, gas generated from the molten resin flowing inside the mold can cause molding defects called silver streaks, which are shiny stripes around the ribs. Patent Document 1 discloses a prior art for suppressing the occurrence of silver streaks.

[0003] Patent Document 1 discloses a mold for producing injection-molded vehicle lighting fixtures. This mold includes a mold body and a cavity insert for forming ribs. The occurrence of silver streaks can be suppressed by allowing gas to escape through the gap around the mold body and cavity insert.

[0004] Patent No. 6602296

[0005] However, nesting solutions require predicting defects in advance using flow analysis and other methods, and then configuring the nest, which makes it difficult to deal with defects discovered after the mold has been created. Furthermore, the nesting and its fixing components make it impossible to position the cooling water channels near the molten resin, reducing cooling efficiency. Nesting solutions require significant changes to the mold settings, making them more complex, which takes time and costs money.

[0006] An object of the present invention is to provide a resin molded product that can deal with molding defects at low cost.

[0007] The present disclosure provides a resin molded product in which a main body portion having a rib with only one end face on the back surface and an extension portion extending from the end of the main body portion and not provided with the rib are integrally formed, and a convex portion is formed on the back surface of the extension portion next to the end face of the rib as a trace of molten resin that flowed from the rib into the extension portion during molding and was guided therethrough.

[0008] The present invention can provide a resin molded product that can deal with molding defects at low cost.

[0009] 5 is a perspective view of a portion including a rib of a resin molded product according to Example 1. FIG. 5 is a view taken along the arrow 2 in FIG. 1. FIG. 3A is a view illustrating a mold around a rib of a resin molded product according to Example 1. FIG. 3B is a view illustrating a state in which molten resin has flowed into the mold shown in FIG. 3A. FIG. 5 is a cross-sectional view of a portion including a rib of a resin molded product according to Example 2. FIG. 5 is a perspective view of a portion including a rib of a resin molded product according to Example 3. FIG. 5 is a view taken along the arrow 6 in FIG.

[0010] <Example> An example will be described with reference to the accompanying drawings. The same reference numerals will be used to designate components and parts that perform the same functions, and duplicated descriptions will be omitted or simplified as appropriate.

[0011] 1 and 2, a portion of a resin molded product 10 according to Example 1 is shown. The resin molded product 10 has a main body 11 having a rib 20 on a back surface 11a (the side opposite to the design surface 10a), and an extension 17 extending from an end of the main body 11 and not having the rib 20.

[0012] (Main body 11) The main body 11 has, for example, a generally U-shaped cross section and includes a bottom 13, a first wall 14 extending from the end of the bottom 13 closer to the extension 17, and a second wall 15 extending from the end of the bottom 13 farther from the extension 17.

[0013] (Rib 20) The rib 20 is a plate-like member having a constant thickness. When viewed along the thickness direction of the rib 20 (see FIG. 2), the rib 20 is rectangular and has only one end surface 24.

[0014] In detail, the rib 20 has a first side 22 connected to the back surface 14a of the first wall 14, a second side 23 connected to the back surface 15a of the second wall 15, and a third side 21 connected to the back surface 13a of the bottom 13. The direction along the bottom 13 of the main body 11 is defined as the length direction L of the rib 20, and the direction intersecting the bottom 13 is defined as the height direction H of the rib 20.

[0015] Of the first side portion 22 to the third side portion 21, the first side portion 22 is located closest to the extension portion 17. The first side portion 22 extends from its lower end portion 22a to its upper end portion 22b and is connected as a whole to the back surface 14a of the first wall portion 14. Similarly, the second side portion 23 extends from its lower end portion 23a to its upper end portion 23b and is connected as a whole to the back surface 15a of the second wall portion 15. Note that the rib 20 may be a triangular rib having the first side portion 22 and the third side portion 21, without having the second side portion 23.

[0016] (Extension 17) The extension 17 extends from the upper end 14b of the first wall 14 (the end of the main body 11) along the length of the rib 20 in a direction away from the rib 20. In other words, the extension 17 is formed in a stepped shape with respect to the bottom 13.

[0017] (Protrusion 30) A protrusion 30 is formed on the back surface 17a of the extension 17 adjacent to the end surface 24 of the rib 20 (at the end of the end surface 24 of the rib 20 extended in the longitudinal direction of the rib 20). The protrusion 30 is a trace of the molten resin R that flowed from the first side 22 into the extension 17 during molding, guided therethrough. The end of the end surface 24 closest to the extension 17 is the extension side end 24a. The starting point 30a of the protrusion 30 is not connected to the extension side end 24a. The starting point 30a of the protrusion 30 is located immediately adjacent to the extension side end 24a, with a gap between them. The cross section of the protrusion 30 is a roughly semicircular shape that bulges upward, but this can be modified as appropriate. The width W1 of the protrusion 30 is slightly larger than the thickness W2 of the rib 20 (W1 > W2). The protrusions 30 may be spaced apart from the ribs 20 or may be connected to the ribs 20 .

[0018] When viewed from a direction facing the back surface 17a of the extension 17, the protrusion 30 has a branched shape. The branched shape can be changed as appropriate, but the protrusion 30 has, for example, a base 31 extending linearly from near the end surface 24 of the rib 20, a plurality of first branched portions 32 branching off midway through or from the tip of the base 31, and a second branched portion 33 branching off from the tip of each of the first branched portions 32. Only some of the plurality of first branched portions 32 may have the second branched portion 33.

[0019] 3A and 3B , the resin molded article 10 (see FIG. 1 ) is obtained by injection molding. The method for manufacturing the resin molded article 10 includes a filling step of filling the cavity 41 of the mold 40 with molten resin R.

[0020] 2 and 3A, the cavity 41 has a main body molding portion 42 capable of molding the main body 11 of the resin molded product 10, a rib molding portion 43 capable of molding the rib 20, and an extension molding portion 44 capable of molding the extension 17. The extension molding portion 44 has a back surface molding portion 45 capable of molding the back surface 17a of the extension 17. The back surface molding portion 45 has a recess 46 formed therein that can mold the protrusion 30.

[0021] Generally, molding defects such as silver streaks occur in downstream areas based on the flow direction of the molten resin R. When silver streaks occur in the extension 17, the extension 17 is a part that is molded after the main body 11 having the ribs 20 (the arrow (1) in FIG. 2 indicates the flow direction of the molten resin R during molding). In the filling process, the molten resin R flows into the rib molding section 43, and then into the extension molding section 44 and the recess 46.

[0022] 1 to 3, the direction from the rib 20 toward the extension portion 17 is the direction in which the molten resin R flows during molding.

[0023] When the flow direction of the molten resin R (arrow (1) in Figure 2) is used as a reference, the first side 22 can be said to be the downstream end of the rib 20, and the second side 23 can be said to be the upstream end of the rib 20. The extension 17 can be said to be a portion located downstream of the main body 11.

[0024] <Example 2> See Figure 4. An extension 51 of an injection-molded product 50 of Example 2 extends from an upper end 14b of the first wall 14 (an end of the main body 11) along the height direction H of the rib 20. A convex portion 30 is formed on a back surface 51a of the extension 51. Note that the direction in which the extension 51 extends from the upper end 14b of the first wall 14 as a starting point is not limited to Examples 1 and 2; for example, the extension 51 may extend obliquely upward.

[0025] 5 and 6, an injection-molded product 60 of Example 3 has a main body 61 having a rib 70 on a back surface 61a (opposite the design surface 60a), and an extension 67 extending from an end of the main body 61 and not having the rib 70.

[0026] (Main body 61) The main body 61 has an approximately L-shaped cross section and has a first wall 63 adjacent to the extension 67 and a second wall 64 extending from one end of the first wall 63 in a direction intersecting the first wall 63.

[0027] (Rib 70 ) When viewed in the thickness direction of the rib 70 (see FIG. 6 ), the rib 70 has a triangular shape and only one end face 73 .

[0028] The rib 70 has a first side 71 that is continuous with the back surface 63 a of the first wall portion 63 and a second side 72 that is continuous with the back surface 64 a of the second wall portion 64. The height H of the rib 70 decreases as it approaches the extension portion 27.

[0029] (Extension 67) The extension 67 extends from the end 63b of the first wall 63 (the end of the main body 61, the opposite side to the second wall 64) along the longitudinal direction L of the rib 70. Note that the arrow (2) in Fig. 6 indicates the flow direction of the molten resin R during molding. Based on this flow direction, the extension 67 can be said to be a portion located downstream of the main body 61.

[0030] (Protrusion 80) A protruding protrusion 80 is formed on the back surface 67a of the extension 67, next to the end surface 73 of the rib 70. The protrusion 80 is a trace of molten resin that flowed from the main body 61 into the extension 67 during molding, and was guided therethrough. The end of the end surface 73 that is closer to the extension 67 is the extension side end 73a. The starting point 80a of the protrusion 80 is not connected to the extension side end 73a. The starting point 80a of the protrusion 80 is located immediately adjacent to the extension side end 73a, with a gap between them. When viewed from a direction facing the back surface 67a of the extension 67, the protrusion 80 is serpentine.

[0031] The protrusion 80 has a base 81 extending from a starting point 80 a and a plurality of first branched portions 82 branching off from the base 81 midway.

[0032] 1 to 3. A first resin molded product 10 is integrally formed from resin of a main body 11 having a rib 20 with only one end face 24 on its back surface 11a, and an extension 17 extending from an end 14b of the main body 11 and not provided with the rib 20. A convex protrusion 30 is formed on the back surface 17a of the extension 17 adjacent to the end face 24 of the rib 20 as a trace of molten resin R that flowed from the rib 20 into the extension 17 during molding and was guided therethrough.

[0033] The mold 40 has a recess 46 for forming the protrusion 30, so that gas can be dispersed when the molten resin R flows from the rib 20 (main body 11) to the extension 17, making it less likely for silver streaks to occur and preventing deterioration of the appearance of the design surface.

[0034] If silver streaks occur on the back surface 17a of the extension 17, it is sufficient to add a recess 46 for forming the protrusion 30 to an existing mold. Compared to measures using nesting, this method can provide a resin molded product 10 that can address molding defects at low cost. Note that the same effect can be achieved with the resin molded product 50 shown in Figure 4 and the resin molded product 60 shown in Figures 5 and 6.

[0035] Second, in the first resin molded product 10, the width W1 of the protrusion 30 is set to be wider than the thickness W2 of the rib 20 (W1>W2). In other words, since the width of the recess 46 is set to be wider than the width of the rib molding portion 43, the molten resin R flowing from the rib molding portion 43 to the extension molding portion 44 can be more reliably guided.

[0036] 5. Thirdly, in the first or second resin molded product 10, the convex portion 80 is formed in a serpentine shape, which allows a larger amount of molten resin R to flow and allows for better gas dispersion.

[0037] 1 and 5. Fourth, in any of the first to third resin molded products 10, the protrusions 30, 80 have a branched shape, allowing a larger amount of molten resin R to flow and disperse the gas more effectively.

[0038] The present invention is not limited to the examples, as long as the functions and effects of the present invention are achieved. Furthermore, the elements constituting each example can be combined as appropriate. The resin molded product of the present invention is suitable for use as an interior or exterior resin molded product for a vehicle.

[0039] DESCRIPTION OF SYMBOLS 10...Resin molded product 11...Main body, 11a...Back surface 14a...Upper end of first wall (end of main body) 17...Extension, 17a...Back surface of extension 20...Rib, 24...End surface of rib 30...Convex portion 50...Injection molded product 51...Extension 60...Injection molded product 61...Main body, 61a...Back surface of main body 63...End of bottom (end of main body) 67...Extension, 67a...Back surface of extension 70...Rib, 73...End surface of rib 80...Convex portion L...Longitudinal direction of rib W1...Width of convex portion W2...Thickness of rib

Claims

1. A resin molded product in which a main body portion is provided with a rib having only one end face on the back surface, and an extension portion that extends from the end of the main body portion and does not have the rib are integrally formed, and a convex portion is formed on the back surface of the extension portion next to the end face of the rib as a trace of molten resin that flowed from the rib into the extension portion during molding.

2. The resin molded product according to claim 1, wherein the width of the protrusion is set to be wider than the thickness of the rib.

3. The resin molded product according to claim 1, wherein the protrusion is formed in a serpentine shape.

4. A resin molded product according to any one of claims 1 to 3, wherein the convex portion has a branched shape.

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