JPH0780882A - Forming of bumper fascia - Google Patents

Abstract

PURPOSE:To reduce mold closing pressure by improving the fluidity of a resin material at the time of forming. CONSTITUTION:Fan gates 6, 9 are established at the center of the edge parts at the upper and lower parts of a bumper fascia 1. Thick wall parts 4, 7 are formed at the upper surface part 1b and the lower end part. Gas is introduced from gas nozzles 16, 17 to form hollow parts 5, 8 at the thick wall parts 4, 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a bumper fascia of an automobile bumper by a resin injection molding method, and in particular, a bumper fascia having an opening such as an air intake in a central portion of a vertical wall portion. Regarding the method.

[0002]

2. Description of the Related Art When molding a bumper fascia having an air intake in the central portion by a resin injection molding method, as shown in FIGS. 4 and 5, a portion corresponding to the central edge portion of the upper surface portion 31a of the bumper fascia 31. The fan gate 32 is set to the mold, and the cavity (the product space of the mold) is filled with the resin material from the fan gate 32 to mold the bumper fascia 31 (similar technology is practically developed 63 No. -43711). In the case of the bumper fascia 31 shown in FIGS. 4 and 5, an air intake 34 is formed below the license plate mounting surface 33 at the center.

[0003]

In the conventional molding method as described above, in consideration of the fact that the bumper fascia 31 to be molded is a large molded product which is long in the lateral direction, while maintaining the fluidity of the resin material. A fan gate 32 having a wide width in the longitudinal direction is adopted in order to make the resin material evenly reach every corner of the cavity and to improve the so-called resin material around the cavity. Therefore, in order to ensure that the resin material reaches the end portion of the molded product, it is necessary to increase the injection pressure, which inevitably increases the mold clamping pressure.

This tendency is particularly apparent in the bumper fascia 31.
Bumper fascia 3 as if the skirt part or apron part was integrally formed at the lower end of
It becomes more noticeable as 1 itself becomes larger.

As a result, not only the entire molding equipment is increased in size, but also distortion due to residual stress may remain in the molded product depending on the size of the mold clamping pressure, which is still problematic in terms of molding stability and molding quality. Also left a problem.

On the other hand, in order to further improve the fluidity of the resin material, the present applicant has tried a bumper fascia molding method which also uses a gas injection method. In this method, as shown in FIG. 6, a thick wall portion 35 is formed along the longitudinal direction on the upper surface portion 31a of the bumper fascia 31, and is exposed to the cavity in advance immediately after the injection of the resin material into the cavity is completed. In addition, an inert gas typified by nitrogen gas is introduced into the resin material of the portion corresponding to the thick portion 35 from the gas nozzle. Then, the inert gas introduced into the cavity flows through a portion of the portion to be the molded article 31 having a small flow resistance, that is, a central portion of the thick portion 35 that is relatively delayed in solidification by cooling. It will spread in the longitudinal direction.

As a result, the flowing gas helps the resin material to flow by applying an internal pressure to the resin material, at the same time preventing the occurrence of sink marks and the like, and finally the gas passage through the thick portion 35. Remains as the hollow portion 36 as it is, the thick portion 35 functions as a reinforcing rib, and contributes to improving the rigidity of the molded product.

However, the effect of improving the resin fluidity brought about by forming the hollow portion 36 in the thick wall portion 35 by using the gas injection method together as described above clearly appears in the upper half portion of the bumper fascia 31. , The lower end of the bumper fascia 31 does not sufficiently spread. This is the thick wall portion 3 having the hollow portion 36.
Since 5 is formed only on the upper surface portion 31a of the bumper fascia 31, there is a limit to lowering the mold clamping pressure.

The present invention has been made by paying attention to the above problems, and an object thereof is to form a bumper fascia having a good molding quality while reducing the injection pressure and the mold clamping pressure. It is to provide the method.

[0010]

SUMMARY OF THE INVENTION The present invention is a method for molding a bumper fascia of an automobile bumper having an opening at the center of a vertical wall by a resin injection molding method.
Gate parts are set at the upper and lower edges of the bumper fascia to fill the cavity with resin material from both gate parts, while the upper and lower ends of the bumper fascia are thickened along the longitudinal direction thereof. Along with the formation of the wall portion, gas is introduced into a portion of the resin material in the cavity corresponding to the thick portion by using the gas injection method together to form a hollow portion along the longitudinal direction of the thick portion. It is characterized by that.

[0011]

According to this method, the gas pressure is evenly propagated to the entire molded product by setting the thick portions above and below the bumper fascia and introducing the gas, thereby improving the resin fluidity by the gas pressure. The effect of spreads to the entire molded product.
As a result, the injection pressure and the mold clamping pressure can be reduced.

[0012]

1 to 3 are views showing an embodiment of the present invention. As shown in FIGS. 2 and 3, of the bumper fascia 1 formed by the method of the present invention, the central portion of the vertical wall portion 1a is formed. An air intake 3 as an opening is formed below the formed license plate attachment surface 2. In addition, in the upper surface portion 1b of the bumper fascia 1 excluding the bumper side portion 1c, or in the entire length including the bumper side portion 1c of the upper surface portion 1b, there is a thick portion 4 protruding upward and having a substantially rectangular cross section. A hollow portion 5 is formed integrally with the thick portion 4 along the longitudinal direction. Then, a fan gate 6 is set at the center of the thick portion 4 in the longitudinal direction.

On the other hand, a thick wall portion 7 is formed along the entire length of the lower edge portion of the bumper fascia 1, and the thick wall portion 7 is formed.
A hollow portion 8 is formed in the inside of the container along the longitudinal direction. The fan gate 9 is also set in the central portion in the longitudinal direction of the thick portion 7 on the lower side.

When molding the bumper fascia 1 having such a structure, injection molding is performed by a conventional method using the injection molding die 10 shown in FIG. That is, the core block (movable type) 11 and the cavity block (fixed type) 1
The injection nozzle 1 for the cavity 13 formed by 2 and
A bumper fascia 1 is formed by injecting and filling a resin material from both 4 and 15 through both fan gates 6 and 9.

At this time, the resin material filled in the cavity 13 first flows into portions corresponding to the upper and lower thick portions 4, 7 having a relatively large cross-sectional area and a small flow resistance, and then the thick portions 4, 4. After expanding along the longitudinal direction of 7, the final flow will be into the respective parts of the cavity 13 including the upper and lower thick parts 4, 7.

At the time of this injection molding, a gas injection method is also used, and as shown in FIG. 1, a pair of gas nozzles 16 and 17 provided in advance in the core block 11 to the thick portions 4, respectively.
An inert gas such as nitrogen gas is introduced into 7. And
If the introduction start timing of this inert gas is set immediately after the completion of the injection of the resin material, for example, the relatively thin general portion,
Also, while solidification is progressing in the surface layer portions of the thick portions 4 and 7, while solidification is relatively delayed in the central portions of the thick portions 4 and 7, The inert gas introduced into the thick portions 4, 7 passes through the central portions of the thick portions 4, 7 having low viscosity and low flow resistance as so-called gas channels and gradually spreads in the longitudinal direction of the thick portions 4, 7. It will be.

As a result, the inert gas assists the flow of the resin material so that the resin material reaches every corner of the cavity 13 uniformly, and at the same time, the passage of the inert gas remains as it is in each thick wall portion 4. By remaining inside the thick portions 4, 7, hollow portions 5, 8 are formed in the central portions of the thick portions 4, 7 along the longitudinal direction thereof.

Incidentally, various conditions such as the pressure of the inert gas, the introduction start timing and the gas introduction time are determined by the clamping pressure of the injection molding die 10, the size of the bumper fascia 1 which is a molded product, and the respective thicknesses. It is set as appropriate according to the cross-sectional area and length of the meat portions 4, 7.

The bumper fascia 1 molded as described above has the thick portions 4 having the hollow portions 5 and 8.
Since 7 exerts a reinforcing effect, the rigidity of the upper surface portion 1b of the bumper fascia 1 is improved, and also the lower end portion of the bumper fascia 1 is improved without an excessive increase in wall thickness. It will be.

The effect of improving the fluidity of the resin by the above-mentioned gas injection method greatly changes depending on the length and cross-sectional area of each thick portion 4, 7, and by extension, the length and cross-sectional area of the hollow portions 5, 8. On the other hand, when the fan gates 6 and 9 are set at the upper and lower two places of the bumper fascia 1 and the resin material is filled as described above, a weld line (weld mark) is easily generated at a portion where the resin material joins.

Therefore, the position of the weld line can be controlled by appropriately selecting the dimensional conditions of the thick portions 4 and 7 and actively controlling the flow of the resin material in the cavity 13. For example, it is possible to control so that the weld line is located on the lower end side, which does not cause any particular problem in terms of appearance quality of the bumper fascia 1.

[0022]

As described above, according to the present invention, the gate portions are set at the upper edge portion and the lower edge portion of the bumper fascia, and the cavity is filled with the resin material from both gate portions, while the bumper fascia A thick portion is formed along the longitudinal direction at the upper end and the lower end, and gas is introduced into the portion of the resin material in the cavity corresponding to the thick portion by the combined use of the gas injection method. Since the hollow part is formed along the longitudinal direction of the part, the fluidity of the resin material is assisted by the gas pressure introduced into the thick part, so that the overall fluidity of the resin material is better than that of the conventional one. Greatly improved.

As a result, the injection pressure and the mold clamping pressure of the resin material can be reduced, and the molding equipment can be downsized, and the molding stability and the molding quality are greatly improved. .

Further, the thick wall portion having the hollow portion is formed at the upper end portion and the lower end portion of the bumper fascia, so that the bumper fascia itself can be formed at the upper and lower ends without increasing the excessive thickness of the entire bumper fascia. In addition to improving the rigidity, the position of weld lines can be positively controlled by appropriately selecting the dimensional conditions for the thick parts at the upper and lower ends of the bumper fascia. There is an advantage that a weld line can be generated at an arbitrary position where there is no gap.

[Brief description of drawings]

FIG. 1 is a sectional view of an injection molding die showing an embodiment of the present invention.

FIG. 2 is a perspective view of a bumper fascia molded by the method of the present invention.

FIG. 3 is a vertical sectional view of FIG.

FIG. 4 is a perspective view of a bumper fascia molded by a conventional molding method.

5 is a vertical sectional view of FIG.

6 is a vertical cross-sectional view of the bumper fascia of FIG. 4 combined with a gas injection method.

[Explanation of reference numerals] 1 ... Bumper fascia 1a ... Vertical wall portion 1b ... Upper surface portion 3 ... Air inlet (opening portion) 4 ... Thick portion 5 ... Hollow portion 6 ... Fan gate 7 ... Thick portion 8 ... Hollow portion 9 … Fan gate 11… Core block 12… Cavity block 13… Cavity 16, 17… Gas nozzle

Claims (1)

[Claims] 1. A method of molding a bumper fascia of an automobile bumper having an opening in a central portion of a vertical wall portion by a resin injection molding method, wherein a gate portion is provided at an upper edge portion and a lower edge portion of the bumper fascia, respectively. While filling the cavity from both gates with the resin material while forming a thick portion along the longitudinal direction at the upper end and the lower end of the bumper fascia, the cavity can be formed by using the gas injection method together. A method for forming a bumper fascia, characterized in that a gas is introduced into a portion of the resin material inside corresponding to the thick portion to form a hollow portion along the longitudinal direction of the thick portion.