JP7809873B2 - resin molded products - Google Patents

Description

The present invention relates to a resin molded product equipped with ribs.

Some resin molded products have ribs to increase their rigidity and strength. When resin molded products are obtained by injection molding, gas generated from the molten resin flowing inside the mold can cause a molding defect known as silver streaks, which are shiny, streaky patterns around the ribs. Patent Document 1 discloses prior art for suppressing the occurrence of silver streaks.

Patent Document 1 discloses a mold for producing injection-molded vehicle lighting fixtures. This mold includes a mold body and a nest for forming ribs. By allowing gas to escape through the gap around the mold body and the nest, the occurrence of silver streaks can be suppressed.

Patent No. 6602296

However, nesting solutions require predicting defects in advance using flow analysis and setting up the nest, which makes it difficult to respond when defects are discovered after the mold has been created. Furthermore, the nesting and its fixing parts make it impossible to position the flow channels for cooling water to cool the heated molten resin 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.

The objective of this invention is to provide a resin molded product that can address molding defects at low cost.

In the present disclosure, there is provided a main body portion having a rib having only one end surface on a back surface thereof;
an extension portion that extends from an end of the main body portion and is not provided with the rib; and
A resin molded product is provided in which 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.

The present invention can provide resin molded products that can address molding defects at low cost.

FIG. 2 is a perspective view of a portion including a rib of the resin molded product according to the first embodiment. FIG. 2 is a view taken along line 2 in FIG. 1 . Fig. 3A is a diagram illustrating a mold around a rib of a resin molded product according to Example 1. Fig. 3B is a diagram illustrating a state in which molten resin has flowed into the mold shown in Fig. 3A. FIG. 10 is a cross-sectional view of a portion including a rib of a resin molded product according to a second embodiment. FIG. 11 is a perspective view of a portion including a rib of a resin molded product according to a third embodiment. FIG. 6 is a view taken along line 6 in FIG. 5 .

<Example>
The embodiments will be described with reference to the accompanying drawings. Components and parts that perform the same functions are given the same reference numerals, and duplicated descriptions will be omitted or simplified as appropriate.

Example 1
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.

(Main body 11)
The main body 11 has, for example, an approximately 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.

(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 .

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

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.

(Extension part 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.

(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 and was guided thereto. The end of the end surface 24 closest to the extension 17 is designated as 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 generally 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 .

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

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

See Figures 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 ribs 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.

Generally, molding defects such as silver streaks occur in downstream areas relative to 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 (arrow (1) in Figure 2 indicates the flow direction of the molten resin R during molding). During the filling process, the molten resin R flows into the rib molding section 43, and then into the extension molding section 44 and recess 46.

See Figures 1 to 3. The direction from the rib 20 toward the extension 17 is the flow direction of the molten resin R during molding.

When the flow direction of the molten resin R (arrow (1) in Figure 2) is used as the 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 the portion located downstream of the main body 11.

Example 2
4 , the extension 51 of the injection-molded product 50 of Example 2 extends from the upper end 14b of the first wall 14 (the end of the main body 11) along the height direction H of the rib 20. A convex portion 30 is formed on the 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.

Example 3
5 and 6, the 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 the end of the main body 61 and not having the rib 70.

(Main body portion 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.

(Rib 70)
When viewed along the thickness direction of the rib 70 (see FIG. 6), the rib 70 has a triangular shape and only one end surface 73 .

The rib 70 has a first side 71 that connects to the back surface 63a of the first wall portion 63, and a second side 72 that connects to the back surface 64a of the second wall portion 64. The height H of the rib 70 decreases as it approaches the extension portion 27.

(Extension part 67)
The extension 67 extends from an end 63b of the first wall 63 (an end of the main body 61, opposite 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 located downstream of the main body 61.

(Protrusion 80)
A convex 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 the molten resin that flowed from the main body 61 into the extension 67 during molding, where it was guided. 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.

The protrusion 80 has a base 81 extending from a starting point 80a and multiple first branch portions 82 branching off from the base 81 midway.

(Effects of the Example)
1 to 3, the first resin molded product 10 is integrally formed of resin from a main body 11 having a rib 20 having only one end surface 24 on a back surface 11a thereof, and an extension 17 extending from an end 14b of the main body 11 and not provided with the rib 20,
On the back surface 17a of the extension portion 17, next to the end face 24 of the rib 20, a convex protrusion 30 is formed, which is a trace where the molten resin R that flowed from the rib 20 into the extension portion 17 was guided during molding.

The mold 40 has recesses 46 for forming the protrusions 30, which allows gas to be dispersed as the molten resin R flows from the rib 20 (main body 11) into the extension 17, making it less likely for silver streaks to occur and preventing deterioration of the appearance of the design surface.

If silver streaks occur on the back surface 17a of the extension 17, simply adding a recess 46 for forming the protrusion 30 to an existing mold is sufficient. Compared to nesting solutions, this provides a resin molded product 10 that can address molding defects at low cost. 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.

Secondly, in the first resin molded product 10, the width W1 of the convex portion 30 is set wider than the thickness W2 of the rib 20 (W1 > W2). In other words, because the width of the concave portion 46 is set 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.

See Figure 5. Third, in the first or second resin molded product 10, the convex portion 80 is formed in a serpentine shape. This allows a larger amount of molten resin R to flow, resulting in better gas dispersion.

See Figures 1 and 5. Fourth, in any of the first to third resin molded products 10, the convex portions 30, 80 have a branched shape. This allows more molten resin R to flow, allowing for better gas dispersion.

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.

10... resin molded product 11... main body portion, 11a... back surface 14a... upper end portion of first wall portion (end portion of main body portion)
17...extension portion, 17a...back surface of extension portion 20...rib, 24...end surface of rib 30...protrusion 50...injection molded product 51...extension portion 60...injection molded product 61...main body portion, 61a...back surface of main body portion 63...end portion of bottom portion (end portion of main body portion)
67...extension portion, 67a...back surface of extension portion 70...rib, 73...end surface of rib 80...projection portion L...length direction of rib W1...width of projection portion W2...thickness of rib

Claims (2)

A resin molded product formed by hardening a molten resin,
a main body portion having a rib on the back surface;
an extension portion that is located downstream of the main body portion with respect to the flow direction of the molten resin during molding and that does not have the rib formed thereon,
If the end of the rib closest to the extension portion is defined as the extension portion side end,
a linear protrusion is formed on the rear surface of the extension portion at a distance from the extension portion side end portion ,
The linear protrusions are formed to meander or branch so as to extend in the width direction of the rib as a whole,
A resin molded product that allows gas generated during molding to escape so that it spreads in a plane around the convex portion and the convex portion . A resin molded product formed by hardening a molten resin,
a main body portion having a rib on the back surface;
an extension portion that is located downstream of the main body portion with respect to the flow direction of the molten resin during molding and that does not have the rib formed thereon,
If the end of the rib closest to the extension portion is defined as the extension portion side end,
On the back surface of the extension portion, only a linear convex portion is formed continuously with the extension portion side end portion ,
The linear protrusions are formed to meander or branch so as to extend in the width direction of the rib as a whole,
A resin molded product that allows gas generated during molding to escape so that it spreads in a plane around the convex portion and the convex portion .