JPH0717452Y2 - Preventing sink marks on the sharp corners of synthetic resin products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention mainly relates to a sink preventive shape of an acute angle portion of a synthetic resin molded product to be injection molded.

(Prior Art) By the way, as shown in FIG. 1, it is conceivable that the front portion of the vehicle body is made of a synthetic resin molded product (1) and a steel plate (2) constituting the vehicle body is joined thereto.

In this case, as shown in FIG. 4, the corner portion of the corner portion D formed by the outer surface B and the end surface C of the plate-shaped wall portion A of the synthetic resin molded product may be 65 ° or less. A sink mark E is apt to occur on the outer surface C portion of the plate-shaped wall portion A in the vicinity of the corner portion D, which impairs the appearance.

Therefore, conventionally, the injection pressure is set high, or a gate is added.

(Problems to be solved by the invention) As described above, when the injection pressure is set to be high, the burrs of the synthetic resin molded product increase, the removal work takes time, and the productivity is lowered. The injection molding apparatus becomes expensive and the cost becomes high.

The present invention has been made in view of such problems,
An object of the object is to provide a shape capable of preventing the occurrence of a sink mark at an acute angle portion without increasing the injection pressure or adding a gate.

(Means for Solving the Problem) In order to achieve the above object, the present invention is a synthetic resin molded product having an angle of 65 ° or less between an outer surface and an end surface of a plate-shaped wall, An intersection point P of the line L ₁ parallel to the outer surface that passes through the intermediate point Q in the thickness direction of the end face of the wall portion and the bisector L ₂ of the angle of the plate-shaped wall portion, and the intersection point P The distance T from the outer surface to the outer surface is obtained, and the angle with the end face is larger than 65 ° including the point S whose distance is 1.9 times or less of the distance T from the intersection P on the bisector L ₂ as a starting point. The corners are chamfered along a surface of 115 ° or less.

(Operation) By chamfering the corners of the plate-shaped wall portion as described above, the cooling delay at the corners of the plate-shaped wall portion is alleviated, and the occurrence of sink marks can be prevented.

In this case, by setting the point S to a distance dimension 1.9 times the distance L ₂ , it is possible to minimize the chamfering amount of the corner portion of the plate-shaped wall portion and prevent the occurrence of sink marks.

(Example) The drawing shows an example in which the present invention is applied to the synthetic resin molded product (1) shown in FIG.

With reference to FIGS. 2 and 3, (3) shows a plate-shaped wall portion of the synthetic resin molded product (1), and an end surface (5) of the outer surface (4) of the plate-shaped wall portion (3). The angle of the corner (6) formed by
May have an acute angle of 65 ° or less.

When the applicant of the present application repeated the experiment, the following was found.

That is, using thermoplastic polyester manufactured by DuPont, mold temperature 40 ℃, synthetic resin temperature 240 ℃, instantaneous injection pressure 1000 kg /
It was filled at a medium speed with a cm ² into a mold to form a plate-like body having a wall thickness of 6 mm.

As a result, when the angle of the corner portion (6) becomes 65 ° or less, the fourth
As shown in the figure, sink marks E of about 15 to 20 μ were formed on the outer surface near the corner D.

Therefore, as shown in FIG. 3, a line passing through the midpoint Q of the length in the thickness direction of the end surface (5) of the wall portion (3) and parallel to the outer surface (4).
The intersection point P between L ₁ and the bisector L ₂ of the angle of the corner portion (6) is obtained, and the outer surface (4) of the plate-like wall portion (3) is obtained from the intersection point P.
The distance T to the end surface (5) is greater than 65 ° and includes a point S that is 1.9 times or less the distance T from the intersection P on the bisector L ₂ as a starting point. As a result of chamfering the corner portion (6) along the surface (7) of not more than °, it was found that sink marks did not occur.

In this case, when the distance from the intersection P to the point S is more than 1.9 to 2.1 times the distance T, a slight sink mark is generated to the extent that the outer surface (4) can be concealed if it is painted, and if it is 2.15 times or more, it cannot be concealed even if it is painted. It caused a relatively large sink mark.

The angle between the chamfered surface (7) and the end surface (5) (hereinafter θ
Is less than 65 °, the chamfered surface (7) is sinked, and the angle between the chamfered surface (7) and the outer surface (4) is
When the angle is 65 ° or less, the outer surface (4) is sinked, and when the angle formed by the outer surface (4) and the end surface (5) is less than 65 °, the chamfered surface (7) and the outer surface (4) form A sufficient condition for making the angle greater than 65 ° is that θ be 115 ° or less, where θ is 65 ° <θ ≦ 115 °.

(Effect of the device) As described above, according to the present invention, it is possible to reliably prevent sink marks on the outer surface of a synthetic resin molded product in the vicinity of an acute angle without setting a high injection pressure or adding a gate. In addition to improving the moldability, the chamfering amount of the acute angle portion can be minimized and the occurrence of sink marks can be prevented, so that the degree of freedom in designing the molded product can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part of a vehicle body having a synthetic resin molded product according to the present invention, FIG. 2 is an enlarged cross-sectional view of an II-II line thereof, and FIG. FIG. 4 is a cross-sectional view of a main part of a conventional synthetic resin molded product. (1) …… Synthetic resin molded product (3) …… Plate wall, (4) …… Outer surface (5) …… End surface, (6) …… Corner (7) …… Chamfered surface

Claims (1)

[Scope of utility model registration request] 1. A synthetic resin molded product having an angle between the outer surface and the end surface of the plate-shaped wall portion of 65 ° or less, which is a midpoint Q of the length of the end surface of the plate-shaped wall portion in the thickness direction. Line L parallel to the outer surface through
The intersection point P between ₁ and the bisector line L ₂ of the angle of the plate-shaped wall portion and the distance T from the intersection point P to the outer surface are obtained, and the bisector line is obtained.
The corner portion is chamfered along a surface that includes a point S having a distance of 1.9 times or less of the distance T starting from the intersection point P on L ₂ and an angle with the end surface that is greater than 65 ° and 115 ° or less. A shape that prevents the sinking of sharp corners of synthetic resin molded products.