JPS6144652B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding products, such as exterior parts such as resin bumpers for automobiles, by a rim molding method.

Conventionally, the first reinforcement measure for resin bumpers was
As shown in Figures A and B, a method has been adopted in which ribs 2 are erected inside the bumper 1 and integrally molded, but according to this method, the provision of the ribs 2 prevents the bumper from forming due to the difference in molding pressure. The quality of the bumper 1 may be affected by the occurrence of sink marks 3 on the surface 1a of the bumper 1, or by further promoting the unevenness of the surface 1a since the deflection (sagging) 4 due to heat is extremely different depending on the presence or absence of the ribs 2. This has resulted in the drawback that not only is the material significantly damaged, but also the demoldability is poor. Therefore, when molding the bumper 1, instead of the ribs 2, a magnet 6 is embedded in the upper mold 5 as shown in FIG. As shown in the figure, there is a method of fixing the iron plate 7 to the back surface of the skin layer 8 of the bumper 1, but this method easily reinforces the skin layer 8 of the bumper 1 and prevents sink marks and bending. However, due to the large difference in linear expansion coefficient between the elastomer forming the skin layer 8 and the iron plate 7, the problem arises that the bumper 1 warps due to heat, as shown in FIG. 4, resulting in thermal deformation. There were also problems in that it was difficult to prevent this and the weight was increased.
Alternatively, instead of the iron plate 7, several hard steel wires 9 are fixed in parallel to the back surface of the skin layer 8 of the bumper 1 as shown in FIG. 5 (the fixing method is the same as the method of fixing the iron plate 7). ), but even if the weight can be reduced, there is still a difference in linear expansion coefficient between the elastomer forming the skin layer 8 and the hard steel wire 9, so the problem of warping cannot be solved. Nakatsuta.

In order to solve the above-mentioned conventional problems, the applicant of the present application, in accordance with the previously filed Japanese Patent Application No. 56-213363, proposed that the reinforcing member be made of solid resin or foamed resin containing reinforcing material instead of the above-mentioned iron plate. We proposed a ``bumper structure and its rim forming method'' in which the reinforcing plate is temporarily fixed to the rim mold, and the reinforcing plate is fixed to the back side of the bumper during molding, thereby eliminating sink marks, bending, and warping. Although it is possible to provide a relatively lightweight bumper, the reinforcement method using the resin reinforcing plate has the problem that it is difficult to temporarily fix it to the rim mold, and the reinforcing plate is expensive. This was something that would occur.

Therefore, in order to solve the above problems, the present invention has the following features:
This is a further improved bumper that eliminates sink marks, bending, and warping, and without sacrificing the above-mentioned advantages of being able to provide a relatively lightweight bumper.
The purpose of the present invention is to propose a method for molding a rim molded product that is easy to mold and can be provided at low cost. A hard steel wire that is bent into a serpentine shape and serves as a reinforcing member is fitted into a groove cut in the upper die of the rim mold, and is fixed to the groove by attraction with a magnet embedded in the upper die. After closing the mold,
Shot cure is performed to embed the hard steel wire in the back surface of a bumper that will become a rim molded product, and after the mold is opened, the bumper is removed from the mold together with the hard steel wire embedded in the back surface of the bumper.

The present invention will be described below with reference to illustrative embodiments.

A is a resin bumper formed by rim molding, and is made up of a bumper body 11 and a skin layer 12 extending diagonally rearward from the upper front end over the entire length of the bumper body 11. ,
On the back surface of the skin layer 12, approximately half of the cross section of the hard steel wire 13, which serves as a reinforcing member and is continuously and repeatedly bent in a zigzag shape so as to absorb the coefficient of linear expansion, is provided with a plurality of hard steel wires 13 having a uniform cross section. The hard steel wire 13 is buried so that the longitudinal direction of the bumper a is parallel to the longitudinal direction of the bumper a. (See FIGS. 6 and 7) Next, a method of forming the bumper a will be described.

First, a hard steel wire 13 having a diameter of about 0.8φ to 2.0φ and serving as a reinforcing member is bent in advance in a zigzag shape so as to absorb the coefficient of linear expansion. Next, turn the surface into a bumper a
Rim forming machine b formed to match the back side of
After the upper mold 14 is raised and tilted by the cylinder 15, a release agent is applied to the upper mold 14. After applying the mold release agent, insert a screw 16 into the upper mold 14 at a position where the back surface of the skin layer 12 of the bumper a comes into contact.
The hard steel wire 13 is fitted into the groove 18a of an aluminum core 18, which has a magnet 17 embedded in the back surface and a plurality of grooves 18a cut into the front surface into which the hard steel wire 13 is inserted. It is suctioned and fixed to the groove 18a. (See Figure 8) Furthermore,
The amount of insertion of the hard steel wire 13 is desirably about 50 to 70% of the cross-sectional shape of the hard steel wire 13, as shown in FIG. 9, taking into account the liquid flow properties of the resin material used to form the bumper a. After that, the lower mold 19 is tilted by the cylinder 20 and a mold release agent is applied to the surface thereof (see Fig. 8).
After the mold is closed, a resin material is pumped from a mixing head (not shown) connected to the gate 26 to the gate 26, and the resin material is injected (shot) into the mold from the gate 26, and the back surface of the skin layer 12 of the bumper a is poured. After the hard steel wire 13 is embedded, the resin material is cured in the mold, that is, the resin material is cured by allowing a reaction time in the mold. (See Figure 10) Next, the process is performed in the order of mold opening, demolding, and deburring to complete the bumper a. The hard steel wire 13 is embedded in the back surface of the skin layer 12 of the bumper a formed as described above. 21 is the upper mold 1
4 is a temperature control pipe buried in the lower mold 19, and 22 is a temperature control pipe buried in the lower mold 19.

In addition, in the above embodiment, the hard steel wire 13 was bent in a zigzag shape to absorb the coefficient of linear expansion.
The shape is not limited to the above, but as long as it can absorb the coefficient of linear expansion of the hard steel wire 13 and has flexibility in elasticity as a whole like a spring material, the shape can be freely selected, such as a meandering shape. It is.

As described above, according to the present invention, the hard steel wire serving as the reinforcing member is repeatedly bent in the longitudinal direction so as to absorb the coefficient of linear expansion, and is buried in the back surface of the skin layer of the bumper. Therefore, unlike conventional products, there is no need to provide ribs, and since the hard steel wire is fitted into the groove cut into the mold during molding, there are fewer protrusions into the mold and good liquid flow during molding. Therefore, there were no sink marks or unevenness on the surface of the bumper, and the surface quality could be improved.

Further, according to the present invention, a hard steel wire is fitted into a groove cut in a mold, and the wire is attracted and fixed to the groove by a magnet embedded in the mold, and the molding pressure is lower than that in ordinary foam molding. Since the forming is done by low rim forming, the hard steel wire does not move.
Not only can it be embedded accurately in a predetermined position of a molded product, but it can also be easily removed from the mold after molding.

Further, according to the present invention, the hard steel wire is continuously and repeatedly bent in the longitudinal direction to absorb the coefficient of linear expansion of the hard steel wire, and the hard steel wire is made to have elasticity like a spring material. Since it has a degree of freedom, it can follow the expansion and contraction of the skin layer due to temperature changes, and therefore the skin layer will not warp. Furthermore, according to the present invention, sufficient strength can be maintained without increasing the thickness of the skin layer, so the curing time in the mold can be shortened, and the molding cycle can therefore be shortened. It has the following effects:

[Brief explanation of the drawing]

Figures 1A and 1B are a partial perspective view of a conventional resin bumper with ribs and a partial enlarged rear view showing its deformed state. Figure 2 is a side view of the upper mold showing the method of attaching a conventional steel plate as a reinforcing member. Figure 3 is a side view of a conventional bumper with a steel plate attached, Figure 4 is a sectional view taken along line A-A in Figure 3 showing the warped state of the skin layer, and Figure 5 is a straight hard bumper. FIG. 6 is a partial perspective view of the bumper with the steel wire attached as seen from the rear side; FIG.
The figure is a rear view of the same as above, Figure 8 is a side sectional view showing the mold opening state of the rim forming machine used in the present invention, Figure 9 is an enlarged sectional view of section B in Figure 8, and Figure 10 is bumper molding. FIG. 2 is an enlarged side cross-sectional view of the rim forming machine in a state shown in FIG. a is a bumper, 11 is a bumper body, 12 is a skin layer, 13 is a hard steel wire, b is a rim forming machine, 14 is an upper mold, 17 is a magnet, 18 is an aluminum core, 18
a is the groove, 19 is the lower mold.

Claims (1)

[Claims] 1. A hard steel wire with a uniform cross section that has been continuously and repeatedly bent is placed in the upper or lower mold in the longitudinal direction, and is fitted into a groove cut in the mold, and a magnet embedded in the mold is used to The hard steel wire is fixed in the groove by suction, and after the mold is closed, the hard steel wire is buried in the back surface of the molded product by shot curing, and after the mold is opened, the molded product is removed from the mold together with the hard steel wire buried in the back surface of the molded product. A method for forming a rim molded product, characterized in that: