JP3510675B2 - Manufacturing method of bumper beam - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a blow-molded bumper beam , and particularly, it can be used for automobile bumper beams and the like.

[0002]

2. Description of the Related Art Conventionally, in a bumper for an automobile, a metal bumper beam that is continuous in the longitudinal direction is provided on the back side of the bumper to reinforce the bumper beam to reduce deformation during a collision. In recent years, weight reduction, freedom of shape, restoration,
Due to requirements for corrosion resistance, plastic deformation resistance, and the like, a synthetic resin bumper beam integrally formed by blow molding has been used. In synthetic resin molding such as blow molding, the shape of the surface of the bumper beam is good, so the bumper beam itself may be used as a bumper.

Further, in such a bumper beam or bumper made of resin, a structure that meets the above-mentioned requirements and an improvement in strength is required, and without increasing the weight such as increasing the wall thickness, A bumper beam has been proposed which has a rib structure capable of improving the strength as a bumper beam in the longitudinal direction and which can be easily integrally molded by blow molding.

A thermoplastic resin is generally used as the material of the resin bumper beam. Examples of the thermoplastic resin include polypropylene, polycarbonate, polyamide, polyethylene terephthalate, polystyrene, polyoxymethylene, ABS resin, AS resin, polyphenylene oxide, and polyphenylene sulfide. Furthermore, ethylene-propylene rubber, ethylene-
Examples thereof include rubbers such as propylene-diene ternary rubber and / or glass fibers, carbon fibers, talc, mica, calcium carbonate and the like.

FIG. 10 and FIG. 11 are external views of a bumper beam 70, which is a conventional example of such a bumper beam, and a structure of a cross section that is substantially in the center in the longitudinal direction and is orthogonal to the longitudinal direction. And are shown. In FIG.
The bumper beam 70 includes a main body 71 that forms the main appearance shape of the molded product. The main body 71 has a longitudinal intermediate portion on the front surface side (when the bumper beam is arranged on the vehicle body,
It is curved so as to project to the surface opposite to the surface on which the vehicle body is mounted), and the back side (the surface side on the vehicle body mounting side when the bumper beam is placed on the vehicle body) is on both ends. It is provided with a flat mounting surface 72. Further, three bolts 73 are insert-molded on each mounting surface 72 so as to project perpendicularly from this surface.

In FIG. 11, the bumper beam 70 has a front surface portion 74 on the front surface side and a back surface portion 75 on the back surface side of the front surface portion 74. Both ends of the front surface portion 74 extend toward both ends of the back surface portion 75 and are connected to these both ends, respectively, and the cross section thereof has a substantially C-shape. The back surface portion 75 has a cross-sectional shape that is substantially flat on both sides and has an intermediate portion that protrudes toward the front surface side. The protruding portion is continuous in the longitudinal direction, and the front end of the front surface portion 74 and the joint portion 76 that are closely connected to the rear surface. Has become. Further, inside the main body 71, two hollow portions 78 partitioned by the joint portion 76 are formed.

FIG. 12 shows a cross section of a blow molding die 80 used for manufacturing the bumper beam 70. This cross section is a cross section orthogonal to the longitudinal direction at a position corresponding to substantially the center of the bumper beam 70 in the longitudinal direction. In FIG. 12, the mold 80 is mainly a surface portion 74 of the bumper beam 70.
And a back surface forming mold 80B mainly forming the back surface 75, and the front surface forming mold 80A and the back surface forming mold 80A It has a dividing surface 82 for dividing into 80B. The die 80 has a cavity 81 having a substantially C-shaped cross section, and the cavity 81 has a front surface forming surface 83 forming a front surface 74 of the bumper beam 70 and a back surface forming surface forming a back surface 75 on its inner surface. And a back surface forming surface 84
Has a rear surface protruding portion surface 84A whose substantially middle portion protrudes toward the vicinity of the front surface forming surface 83.

FIG . 13 shows an example of a method of manufacturing the bumper beam 70 by blow molding. First, the heat-melted molded resin is extruded in the vertical direction as a cylindrical parison 70A from the extruder 90 provided at a high position. At this time, the parison 70A is divided into blow molding dies 8
0 between the front surface forming die 80A and the back surface forming die 80B, and the insert-molded bolt 73 is previously placed inside the back surface forming die 80B ( FIG. 13 ) .
(See (A)).

Next, when the parison 70A becomes sufficiently long, a part of the parison 70A is sandwiched by the dividing surfaces 82 provided in the mold 80 along the longitudinal direction and, at the same time, both ends of the parison 70A in the longitudinal direction are sandwiched. Clip it. Further, air is blown into the parison 70A from the blow-out port 85 provided on the outer surface of the surface-portion forming mold 80A in the longitudinal direction to expand the parison 70A and expand the cavity 8
It is brought into close contact with the inner surface of 1 (see FIG. 13 (B)). After this, wait for cooling and open the mold 80 to open the bumper beam 70.
Is taken out (see FIG. 13 (C)).

Now, returning to FIG. 12, FIG.
13 shows the state of FIG. 13 (B) and the state of FIG. 13 (B), and the state immediately before the sandwiching of the parison 70A is completed (see FIG. 12 (A)) and the state immediately after (see FIG. 12 (B)). ) Is shown. In FIG. 12 (A), as the sandwiching of the mold 80 progresses, a part of the surface of the parison 70A facing the back surface forming mold 80B, which is continuous in the longitudinal direction, is a back surface projecting surface 84A. It is pushed in by the pinching direction.

Further, in FIG. 12B, at the same time when the sandwiching is completed, the portion pressed by the back surface projecting portion surface 84A comes into close contact with the inner surface of the surface facing the front surface forming die 80A to form the bonding portion 76. Form. When the sandwiching is completed, a part of the parison 70A is sandwiched along the longitudinal direction between the dividing surfaces 82 of the front surface forming die 80A and the back surface forming die 80B.

Next, the hollow portion 78 inside the parison 70A.
When air is blown into the parison 70A, the parison 70A expands in the direction of the arrow while reducing its wall thickness and comes into close contact with the inner surface of the cavity 81, thereby forming the bumper beam 70 shown in FIGS. At this time, the bumper beam 70
11 includes a front surface portion 74 and a back surface portion 75 from both ends of the front surface portion 74.
Traces 77 of the dividing surface are formed at the substantially center of each extending toward. Here, traces 77 of the division surface of the surface portion 74
The portion located on the front surface side is a front surface portion 74A, and the portion located on the back surface side is a surface rear portion 74B.

[0013]

However, as shown in FIG.
In the conventional example as shown in FIG. 13, the parison 70A is used.
Among the parts, the amount of expansion is different between the part that expands toward the front surface forming mold 80A and the part that expands toward the back surface forming mold 80B with the dividing surface 82 as a boundary, and thus the difference in wall thickness variation amount. Occurs. That is, in the portion of the back surface portion 75 excluding the connection portion 76 and the front surface rear portion 74B,
Thickness T0 of parison 70A before expansion (see Fig. 13)
The blow-up ratio (T0 / T1), which is the ratio of the wall thickness T1 of the bumper beam 70 after expansion (see FIG. 11) to the blow-up ratio (T0 / T1) at the wall thickness T2 of the front surface portion 74A (see FIG. 11) ( There is a problem that it is larger and thinner than T0 / T2).

Further, since the thin portion is formed, the rigidity becomes low, and there is a problem that it does not pass the 5MPH pendulum test which is an impact test. And, in order to improve the rigidity, it is necessary to increase the thickness of the thin portion,
There is a problem that it is difficult to increase the thickness of a part of the wall, and since the wall thickness is increased as a whole, the weight cannot be reduced. Further, there is a problem in that the material cost becomes high due to such thickening.

An object of the present invention is to provide a method for manufacturing a bumper beam, which can suppress uneven thickness during blow molding to prevent a thin wall portion from being generated, and can satisfy both weight reduction and rigidity improvement.

[0016]

The method of the present invention has reached the finding that the uneven thickness is caused by the relative positional balance between the dividing surface of the mold and the shape of the molded product, and based on this finding, the dividing surface of the mold is reached. It is intended to achieve the above-mentioned object by changing the position of. Specifically, the cross-sectional shape includes a front surface portion arranged on the front surface side and a rear surface portion arranged rearward of the front surface portion, and both ends of the front surface portion extend toward both ends of the rear surface portion. have together are connected to these ends, a double wall structure in which a portion of the intermediate portion has a projecting portion that projects arranged so as to reach the vicinity of at least the surface portion of the back surface Te, and Longitudinal
In order to form a bumper beam in which the space portion is curved so as to project to the surface side, a cylindrical parison is sandwiched in a split mold having a cavity inside and the blower beam is blow-molded. In the manufacturing method, the dividing surface of the mold is provided so as to pass in the vicinity of a portion of the cavity corresponding to a connection position between the front surface portion and the back surface portion. When sandwiching both side portions along the direction with the split surface, at a position corresponding to the curved portion of the bumper beam on the split surface ,
Further , the mold is clamped so that the position closest to the portion corresponding to the tip portion of the protrusion is the position of the central axis of the parison, and air is blown into the parison.

[0017] In the method of manufacturing the bumper beam, and characterized in that preferably provided on the surface and the same surface forming the end portions of the rear surface portion of the cavity inner surface of the mold split surface of the mold To do.

[0018]

[0019]

[0020]

In the present invention as described above, since the dividing surface of the mold is provided at a position where the expansion amount of the parison is substantially uniform on the front surface side and the rear surface side with respect to the dividing position, the front and back sides depending on the expansion location. The difference in blow-up ratio on each side is reduced, and the uniformity of the wall thickness of the bumper beam is improved. Also,
Since the thin portion is not formed, the rigidity of the bumper beam is improved, and since it is not necessary to increase the thickness, the weight is reduced and the material cost is reduced. By the above, the said objective is achieved.

By providing the dividing surface of the mold on the same surface as the inner surface of the cavity which forms both end portions of the back surface of the bumper beam, the structure of the mold is simplified and the manufacture is facilitated. Furthermore, by introducing the parison between the molds so that the central axis of the parison is along the dividing surface, and clamping the mold so that both side portions facing the diametrical direction of the parison are sandwiched between the dividing surfaces, The difference in blow-up ratio on the side is further reduced, and the uniformity of wall thickness is further improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of the resin bumper beam 10 obtained by the manufacturing method according to the present invention in a cross section in the longitudinal direction substantially at the center in the longitudinal direction. At this time, the bumper beam 10 has a main body having substantially the same shape as the bumper beam 70 of the conventional example shown in FIG. 10, and the sectional shape of the present embodiment shown in FIG. 1 and the sectional shape of FIG. Is the same. Therefore, the illustration of the external appearance and the description of the main body are omitted here.

In FIG. 1, the bumper beam 10 has a front surface portion 11 on the front surface side and a back surface portion 12 on the back surface side with respect to the front surface portion 11 in a sectional shape. Also,
Both ends of the front surface portion 11 extend toward both ends of the back surface portion 12 and are connected to these both ends, respectively. A part of the back surface portion 12 is a projection portion 12A that is arranged so as to project toward the front surface side, and the tip portion of this projection portion 12A is the front surface portion 11.
And the connection portion 13 is formed. Further, a hollow portion 14 partitioned by the front surface portion 11 and the back surface portion 12 is formed.

FIG. 2 shows a bumper beam 1 according to the present invention.
0 shows a cross section of a blow-molding die 20 used for manufacturing 0. This cross section is a cross section orthogonal to the longitudinal direction of a portion corresponding to substantially the center of the bumper beam 10 in the longitudinal direction. Figure 2
At the mold 20,
Is provided with a front surface forming die 20A for forming a back surface portion and a back surface forming die 20B for forming a back surface portion 12, and a cavity 21 having a substantially C-shaped cross section is formed inside each of them when they are clamped. I have it.

Of the inner surface of the cavity 21, the back surface portion 1
A split surface 22 is provided on the same surface as the surfaces forming both end portions of 2 to divide the die 20 into a front surface forming die 20A and a back surface forming die 20B. An inner surface of the cavity 21 is provided with a front surface forming surface 23 that forms the front surface 11 of the bumper beam 10 and a back surface forming surface 24 that forms the back surface 12. The back surface forming surface 24 has A rear surface protruding portion surface 24A is formed such that a substantially central portion thereof protrudes toward the vicinity of the front surface forming surface 23.

In this embodiment, the bumper beam 10 is manufactured according to the following manufacturing method. At this time, the difference between the manufacturing method of the conventional example and the manufacturing method of the present embodiment is the difference in the introduction position of the parison 10A and the mold used during blow molding. For simplification, the differences from the conventional example are as follows. Explained.

The difference in the introduction position of the parison 10A is shown in FIG.
As shown in (A) and (B), the central axis P of the parison 10A is
0 is the front surface forming die 20A and the back surface forming die 20B.
Is to position the parison 10A along the positions P1 and P2 of the respective dividing planes, and the mold clamping is performed at the positions P1 and P2 of the dividing planes on both side portions A1 and A2 which are diametrically opposed to the parison 10A (FIG. 2 and FIG. 3 (A)). Figure 13 shows the difference between the molds.
The conventional die 80 shown in FIGS. 3A to 3C is replaced with the die 20 according to the present invention shown in FIGS.

Returning to FIG. 2, the parison 1 in the mold 20.
The molding state of 0A is as follows. The mold 2 is shown in FIG.
The state immediately before the completion of mold clamping 0 is shown, and the state immediately after that is shown in FIG. 2 (B). In FIG. 2 (A), as the sandwiching of the die 20 progresses, a part of the surface of the parison 10A facing the back surface forming die 20B is sandwiched by the back surface projecting surface 24A so as to be continuous in the sandwiching direction. Is pushed into.

In FIG. 2B, at the time when the sandwiching is completed, the portion pressed by the back surface protruding portion surface 24A comes into close contact with the inner surface of the surface facing the front surface forming die 20A and the connection portion 13 is formed. Form. When this sandwiching is completed, the parts on both sides of the parison 10A are sandwiched along the longitudinal direction between the dividing surfaces 22 of the front surface forming die 20A and the back surface forming die 20B.

Further, a blowing port provided above the front surface molding die 20A in the longitudinal direction (see reference numeral 85 in FIG. 3).
From this, air is blown into each hollow portion 14 of the parison 10A. Then, the parison 10 </ b> A expands in the direction of the arrow while reducing the thickness thereof and adheres closely to the inner surface of the cavity 21, whereby the bumper beam 10 is formed.

According to this embodiment, the following effects are obtained. That is, in the parison 10A, the portion that expands toward the front surface forming surface 23 and the portion that expands toward the rear surface forming surface 24 of the cavity 21 with the dividing surface 22 as a boundary have a small difference in expansion amount from each other, and are thick. The blow-up ratios of the inflated portions can be made substantially the same, and the wall thickness T3 of the front surface portion 11 (see FIG. 1) and the wall thickness T4 of the back surface portion 12 (see FIG. 1) can be made equal to each other. The difference can be reduced.

Further, since the thin portion is not formed, the rigidity is improved and the 5MPH pendulum test can be passed without increasing the thickness. Further, since the thin wall portion is not generated, it is not necessary to increase the wall thickness as in the conventional case, so that the weight can be reduced and the material cost can be reduced.

Furthermore, since the dividing surface 22 of the mold 20 is provided on the same surface as the inner surface of the cavity 21 that forms both ends of the back surface portion 12, the mold becomes simple and the mold is The production cost can be reduced. Further, the setup time such as mold matching and mounting is shortened, and since the burr is located at the corner portion, the work of removing the burr is facilitated, the work efficiency is improved, and the appearance is also improved.

Positions P1 and P2 of the respective divided surfaces of the front surface molding die 20A and the back surface molding die 20B.
Since the mold 20 is clamped so as to be positioned on the central axis P0 of the parison 10A, the front surface portion 11 and the back surface portion 12 are formed in each half circumference of the parison 10A. The front surface portion 11 and the back surface portion 12 have the same length. As a result, it is possible to further reduce the difference in blow-up ratio in the substantially middle portion of the bumper beam in the longitudinal direction, and to further improve the uniformity of wall thickness.

In order to confirm the effect of the present invention, a comparative experiment by the following 5MPH pendulum test was conducted. As the bumper beam of the present invention, the bumper beam 10 was manufactured by the mold and manufacturing method of the above-described embodiment. As a comparative example to this, the conventional example (see FIG.
Bumper beam 70 according to

Further, the material of the bumper beam of each of the examples and the comparative examples has a melt index of 0.5 g / 1.
0 minutes, ethylene content 1.5% by weight, isotactic pentad fraction 96 mol% block polypropylene (block PP) 70% by weight, melt index 0.
2 g of high density polyethylene (HDPE) 03g / 10 min
0% by weight, average particle size 1.5 μm, average aspect ratio 1
Using a resin composition containing 10% by weight of talc of No. 5, a bumper beam having a product length of 1.6 m was further molded under the following molding conditions.

Molding conditions Molding machine screw: 90mmφ Die: 100mmφ Accumulator: 25 liters Mold clamping pressure: 60 ton Screw rotation speed: 40 rpm Motor load: 115A

Temperature conditions Cylinder No. 1: 230 ℃ No. 2: 210 ℃ No. 3: 190 ℃ No. 4: 190 ℃ Crosshead No. 1: 190 ℃ No. 2: 190 ℃ No. 3: 190 ℃ Dice No. 1: 190 ℃ No. 2: 190 ℃ Molding cycle: 230sec Mold temperature: 28 ℃ Resin temperature: 225 ° C

Further, the 5MPH pendulum test is shown in FIG.
And the impact test apparatus shown in FIG. 5 was used. That is, the impact test apparatus 30 is composed of a general impact test apparatus capable of applying a predetermined pressure at a predetermined speed (8 km / Hr = 5 miles / Hr) as shown in FIG.
A pressing pole 33 is attached to the center of the lower pressing surface 31 via a pole fitting 32. The pressing pole 33 is composed of a cylinder having an outer diameter of 7 inches and a predetermined length, and the pole attachment 32 includes a plate-shaped body 32A and two shafts 32B as shown in detail in FIG. It is composed of and. Then, the bumper beam 10 to be tested is attached to the mounting base 34 made of H-shaped steel, and the pressing pole 33 is brought into contact with the center of the bumper beam 10 to be tested in the longitudinal direction,
The impact tester 30 performs the reduction.

In this comparative experiment, the bumper beam 10 of the example and the bumper beam 70 of the comparative example were each compressed to an allowable deformation amount of 40 mm and then visually inspected. Table 1 shows the experimental results.

[0041]

[Table 1]

According to the experimental results, no abnormality was found in the examples, whereas in the comparative example, cracks were found at the positions corresponding to the thin portion and the divided surface of the mold.
From this, it was found that the example was superior to the comparative example, and the effect of the present invention was remarkably shown.

The present invention is not limited to the above embodiments, but includes other configurations within the scope of achieving the object of the present invention, and the following modifications and the like are also included in the present invention. That is, in the above-described embodiment, the dividing surface 22 of the mold 20 is provided on the same surface as the surface forming the both ends of the back surface portion 12 of the surface of the cavity 21, but, for example, as shown in FIG.
As shown in FIG. 6A, the dividing surface 22 may be parallel to the surfaces forming both ends of the back surface portion 12 and may be arranged on the back surface side of this surface. As shown in FIG. It may be arranged to project.

Further, as shown in FIG. 6 (C), even if it is provided on the same surface as the surface forming both ends of the surface portion 11, the mold 2
Since the relative position balance between the divided surface 22 of 0 and the shape of the molded product is maintained, the wall thickness of the molded product becomes uniform. In short, it suffices that the cavity 21 is provided so as to pass through the vicinity of the portion corresponding to the connection position between the front surface portion 11 and the back surface portion 12 of the cavity 21. However, it is preferable to provide the dividing surface 22 on the same surface of the surface of the cavity 21 as the surface forming both end portions of the back surface portion 11 because the mold becomes easier.

[0045]

The material of the mold 20 may be any metal as long as it is aluminum, zinc alloy, cast iron, steel,
Beryllium copper alloy is suitable. Also, parison 1
Since the mold wears severely at the part where 0A is sandwiched, a part made of hardened hardened steel may be fitted separately.

In the above embodiment, the bumper beam 1
The back surface portion 0 of 0 is arranged so as to project so that a part thereof comes into close contact with the front surface portion 11. For example, as shown in FIG. 7, a part of the back surface portion 12 is arranged so as to project near the front surface portion 11. It does not have to be in close contact with each other. But,
The close contact improves the mechanical strength of the bumper beam 10, which is preferable.

In the above embodiment, the cross-sectional shape of the surface portion 11 is substantially C-shaped, but as shown in FIGS. 8 (A) to 8 (C), it is U-shaped, V-shaped, U-shaped or the like. May be. Further, both end portions of the back surface portion 12 are not limited to flat surfaces, and may have a curved surface shape as shown in FIGS. 8D to 8F or may be formed from two or more surfaces. . Further, the shape of the protrusion 12A may be such that the tip has an acute angle as shown in FIGS. 8G and 8H, or the tip has a wider width than the opening.

In short, the shapes of the front surface portion 11, the rear surface portion 12 and the connecting portion 12A are arbitrarily determined as long as the relative position balance with the dividing surface of the mold is maintained so that the thickness after molding is uniform. You may be taken. Furthermore, bumper beam 1
The rib structure formed in the longitudinal direction of 0 is shown in FIGS.
May be arranged in multiple rows, or discontinuous rib structures may be arranged in a staggered manner.

The material of the bumper beam 10 can be arbitrarily selected from the thermoplastic resins generally used conventionally. In particular, in terms of molding processability in blow molding and mechanical strength such as rigidity, impact resistance, and pinch-off strength, which are physical properties of the bumper beam 10, a melt index of 1.0 g / 10 minutes or less, an isotactic pentad. Propylene homopolymer having a fraction of 93 mol% or more or melt index of 1.0 g / 10 min or less, ethylene unit content of 15 wt% or less, and isotactic pentad fraction of a propylene homopolymer part of 93 mol% or more- Resin composition comprising 50 to 99% by weight of ethylene copolymer, 1 to 30% by weight of ethylene resin or ethylene rubber, and 1 to 30% by weight of talc having an average particle size of 10 μm or less and an average aspect ratio of 3 to 20. Is preferred.

Also, if desired, the composition may further comprise
Thermoplastic resins such as maleic anhydride-modified polyolefin and acrylic acid-modified polyolefin, inorganic fillers such as calcium carbonate, mica, glass fiber and carbon fiber, antioxidants, UV inhibitors, lubricants, flame retardants, coloring Various additives such as agents may be contained.

Further, in the above-mentioned embodiment, the blowing port 85 for blowing air into the hollow portion 14 has the surface portion molding die 20.
Although it is provided on the front surface of the outer surface of A and above in the longitudinal direction, the position of the blowing port 85 may be arbitrarily determined depending on the shape of the bumper beam to be molded, and may be an appropriate number.

Furthermore, the number of vehicle body mounting bolts 73 (see FIG. 10) arranged at both ends of the bumper beam 10 is not limited to three, but may be appropriately determined according to the required mounting strength and the like. Good. And this bolt does not have to be integrally molded with the bumper beam,
It need not be located on the bumper beam side. For example, a method may be used in which a bolt hole is provided on the bumper beam side and a bolt is passed through this hole to attach the bolt to the vehicle body, or a bolt hole may be placed on the vehicle body side to attach the bolt hole. In short, the bumper beam should be attached to the vehicle body.

[0054]

As described above, according to the present invention, the relative position balance between the dividing surface of the mold and the product shape is maintained,
Since the thickness of the bumper beam is uniform in the cross section, it is possible to pass the 5MPH pendulum test without increasing the thickness and to obtain a bumper beam that satisfies both weight reduction and rigidity at the same time. effective.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a bumper beam obtained according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a cross section of an intermediate portion of the embodiment.

FIG. 3 is an explanatory view explaining a blow molding process of the bumper beam of the embodiment.

FIG. 4 is a side view showing a bumper beam impact test state according to the embodiment.

5 is a perspective view showing a schematic configuration of a pressure pole portion used in the impact test device of FIG.

FIG. 6 is a sectional view showing a main part of a modified example of the present invention.

FIG. 7 is a cross-sectional view showing a cross section of an intermediate portion of another modification of the present invention.

FIG. 8 is a cross-sectional view showing a cross section of an intermediate portion of still another modification of the present invention.

FIG. 9 is a sectional perspective view showing a middle section of another bumper beam molded by the present invention.

FIG. 10 is an overall perspective view showing a bumper beam of a conventional example.

FIG. 11 is a cross-sectional view showing a cross section of an intermediate portion of the bumper beam of the conventional example.

FIG. 12 is a cross-sectional view showing a blow molding die used for manufacturing the bumper beam of the conventional example.

FIG. 13 is an explanatory view for explaining a blow molding process of the bumper beam of the conventional example.

[Explanation of symbols]

10 Bumper beam 10A parison 11 Back side 12 surface 12A protrusion 20 mold 21 cavity 22 division plane P0 central axis P1, P2 Position of division plane

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-92744 (JP, A) JP-A-5-92473 (JP, A) JP-A-60-42137 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B29C 49/00-49/80

Claims (2)

(57) [Claims] 1. A cross-sectional shape includes a front surface portion disposed on the front surface side and a rear surface portion disposed rearward of the front surface portion, and both ends of the front surface portion extend toward both ends of the rear surface portion. And are connected to both ends of these ,
It has a double wall structure in which a part of the intermediate portion of the back surface portion is a protruding portion that is arranged so as to reach at least the vicinity of the surface portion , and the longitudinal intermediate portion is on the front surface side.
A method for manufacturing a bumper beam, wherein a cylindrical parison is sandwiched and blow-molded in a split mold having a cavity therein to form a bumper beam curved so as to project. A surface is provided so as to pass in the vicinity of a portion of the cavity corresponding to a connection position between the front surface portion and the back surface portion, and both ends in the longitudinal direction of the parison and both side portions along the longitudinal direction are defined by the dividing surface. When sandwiched, it corresponds to the curved part of the bumper beam of the divided surface
The mold is clamped so that the position closest to the part corresponding to the tip of the protrusion is the position of the central axis of the parison, and air is blown into the parison. Production method. 2. The method of manufacturing a bumper beam according to claim 1, wherein the dividing surface of the mold is provided on the same surface as a surface forming both end portions of the back surface part in the cavity inner surface of the mold. A method for manufacturing a bumper beam, which comprises placing the bumper beam.