JPH0140661Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a synthetic resin molded product, and more particularly to a plate-shaped resin molded product in which the thickness of the peripheral edge portion is reduced relative to the average thickness to prevent shrinkage in that portion. Nowadays, synthetic resin materials are used in almost every field, and their applications range from minute precision gears to large bathtubs. For example, synthetic resins are rapidly replacing conventional steel plates as materials for parts that are large and require strength, such as the outer panels of automobile bodies. By the way, many of these synthetic resin molded products are manufactured by injection molding. That is, a synthetic resin material is heated and melted in a cylinder, injected into a cavity in a molding die, and then solidified and molded.
However, when the molded product has a relatively large projected area, such as a fender for an automobile, the cavity is flat, so the flow of the molten resin during injection is poor, and the injection pressure is difficult to reach the periphery. As a result, the molten resin pressure at the periphery decreases,
Since resin shrinkage due to solidification is larger than in adjacent parts, shrinkage occurs in the peripheral part. The occurrence of shrinkage due to the decrease in resin flow is particularly noticeable when hard resin is used. For example, in the case of the above-mentioned automobile body panels, hard thermoplastic resins with relatively excellent impact resistance are used, such as polypropylene, polycarbonate resin, polycarbonate alloy resin, and polycarbonate ABC resin, due to strength requirements. . However, when this type of material is molded, shrinkage occurs significantly near the periphery of the molded member, and the shrinkage appears on the molded surface, making it difficult to secure a specified strength in that area, and it is also undesirable in terms of aesthetic appearance. do not have. One conventional solution to this problem is to divide the resin injection gate to increase the resin pressure near the peripheral edge. However, this measure has the following drawbacks. That is, since the gate is divided into a plurality of parts, weld marks are generated at the boundary surfaces where the resin flows injected from the respective gates collide, and the impact strength of that part is significantly reduced. Therefore, the inventor of the present invention continued to study intensively in order to obtain an injection molded product that can prevent the shrinkage that occurs near the peripheral edge of the plate. By making the thickness within a certain range relative to the average thickness of the part, it is possible to reduce the amount of resin shrinkage in the peripheral part without impeding the flow of molten resin during injection, thereby preventing the occurrence of shrinkage and improving the aesthetics. It has been found that a molded article with excellent properties and strength can be obtained, and the above-mentioned problems can be eliminated. Therefore, an object of the present invention is to prevent shrinkage occurring at the peripheral edge of a plate-shaped resin molded product, and to obtain a synthetic resin molded product that has excellent appearance and strength and can be manufactured at low cost. In order to achieve this object, the present invention provides a plate-shaped synthetic resin molded product including a curved or bent part along the peripheral edge, and the wall thickness t of the curved or bent part is the thickness of the remaining plate-shaped part. In a synthetic resin product having a width region W formed thinner than the thickness T, the width region W includes an inner width region W ₂ that gradually decreases from the plate portion having the wall thickness T toward the curved or bent portion, and It consists of an outer width region _W1 in which the thickness t is maintained substantially constant, and the width of the width region W is within a range of 6 to 10 times the wall thickness T, and the wall thickness t is It is characterized by being within the range of 6/10 to 8/10 of Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of an automobile 10 in which a resin molded product is used as a part of the outer panel constituting the vehicle body. For example, the fender 12 of this automobile 10 is molded by injection molding. Due to the requirement for strength, hard resins having excellent impact resistance such as polypropylene resin, polycarbonate resin, polycarbonate alloy resin, polycarbonate ABS resin, etc. are used as resin materials for these members.
Therefore, in the case of a member having a relatively large projected area, such as the fender 12, the end structure according to the present invention is used to prevent shrinkage that occurs at the peripheral edge. Therefore, with reference to FIGS. 2 to 4, the fender 12 which is a plate-shaped resin molded product according to the present invention.
I will explain about it. 2 is a side view of the fender 12, FIG. 3 is a sectional view taken along the line -- in FIG. 2, and FIG. 4 is an enlarged sectional view of the peripheral portion surrounded by the dashed line in FIG. As shown in FIG. 3, the fender 12 is made of synthetic resin and molded into a predetermined shape by injection molding. The fender 12 includes a plate portion 14 and a flange portion 16 formed around the periphery of the plate portion 14. The flange portion 16 extends around the entire circumference of the plate portion 14 and is formed substantially perpendicular to the plate portion 14 . That is, when the fender 12 is attached to the main body of the automobile 10, the flange portion 16 protrudes toward the inside of the vehicle body and has a predetermined thickness so that it can be secured with bolts or the like (not shown). Further, a bent portion 16a is further formed on the flange portion 16 provided at a position facing the peripheral edge of the bonnet 18 (see FIG. 1) of the automobile 10, and is configured to overlap with the peripheral edge portion of the bonnet 18. Therefore, in the present invention, from the end of the flange portion 16 toward the inside of the plate portion 14, the end portion of the plate portion 14 is made to have a thickness T at the center of the plate portion 14 within a predetermined width region W. On the other hand, it is formed so that it decreases by a predetermined value to become t (see FIGS. 2 to 4). As shown by the two-dot chain line in FIG.
extends around the entire circumference of the plate portion 14, and therefore, the plate thickness in this area W of the plate portion 14 is also large. Like this Fender 1
During injection molding in step 2, by molding the end portion of the plate portion 14 thinly, the molten resin easily enters this thin portion under constant pressure, and the shrinkage balance during solidification is also good. As a result, it is possible to prevent the occurrence of shrinkage in that part. As a result of experiments, in order to prevent the occurrence of shrinkage without causing waviness or deformation in the plate body, the above width region W should be within a range of 1 to 10 times the plate thickness T of the plate body portion 14. was confirmed. In particular, the width area W is
If the ratio is selected to be 6 to 10 times as large as 6 to 10 times, favorable effects can be obtained as shown in the table below. Further, among the width regions W of the plate portion 14, the thickness t of the outer width region W1 connected to the flange portion is 3/10 to 8/10 of the central thickness T of the plate portion 14. is essential. In particular, if this plate thickness t is selected from 6/10T to 8/10T,

【table】

[Table] As shown in Table 1, the peripheral plate thickness T is 2/10T.
Below, undulations can be seen on the surface of the molded product. In addition, when the thickness T of the peripheral edge is in the range of 3/10 to 5/10T,
The filling properties were rather poor, but only slight shrinkage and waviness were observed. In this range, the surface condition after painting is good and the product can be used satisfactorily. Furthermore, this plate thickness T is 6/10T ~ 8/10T
The surface condition is the best in the range, and no shrinkage or waviness occurs. The surface condition after painting is also good, making it suitable as a product. However, it was confirmed that when the plate thickness T is 9/10T or more, the shrinkage and waviness become noticeable, and this becomes even more noticeable after painting. On the other hand, the relationship between the width area W and the surface condition is shown in Table 2. When the width area W is less than 1T, the change in plate thickness in the width area W becomes rapid, leaving line marks on the surface of the molded product. These line marks become even more visible after painting. Also, the width range W is 1T~
With 6T, some lines are observed on the surface of the molded product, but after painting, these lines disappear and the appearance is good. There is no problem in using it as a product that requires aesthetic appearance. Further, when the width range W is 6T to 10T, the surface condition is even better, and the product after painting has the best aesthetic appearance. On the other hand, if the width W is 11T or more, deformation occurs after molding and lines become noticeable. As described above, in the present invention, the thickness of a predetermined width area around the periphery of the plate body of a plate-shaped resin molded product is reduced by a predetermined value compared to the thickness of other parts, so that the flow of melted resin is reduced. It can be injected into the cavity at the same pressure without interfering with the process, and therefore, the balance of shrinkage is improved, which has the effect of preventing the occurrence of shrinkage, etc., and producing a molded product with excellent aesthetic appearance. Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and it goes without saying that various improvements and design changes can be made without departing from the gist of the present invention. It is.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an automobile in which the resin molded product according to the present invention is partially used as an outer panel for the vehicle body, and Fig. 2 is a resin molded product according to the present invention used as a fender of the automobile shown in Fig. 1. FIG. 3 is a sectional view taken along the line -- in FIG. 2, and FIG. 4 is an enlarged sectional view of the portion surrounded by the line in FIG. 10...Car, 12...Fender, 14...
...Plate member, 16...Flange portion, 18...Bonnet.

Claims (1)

[Claims for Utility Model Registration] A plate-shaped synthetic resin molded product including a curved or bent portion along the periphery, where the wall thickness t of the curved or bent portion is equal to the wall thickness T of the remaining plate-shaped portion. In a synthetic resin product having a thinner width region W, the width region W is an inner width region that gradually decreases from the plate portion having the wall thickness T toward the curved or bent portion.
W ₂ and an outer width region W ₁ in which the wall thickness t is maintained substantially constant, and the width of the width region W is 6 to 10 times the wall thickness T.
A synthetic resin molded product characterized in that the wall thickness t is within the range of 6/10 to 8/10 of the wall thickness T.