JP4762523B2 - Bumper core material for vehicle body, molding apparatus and molding method thereof - Google Patents

Description

  The present invention relates to a bumper core material for a bumper attached to a vehicle body, an apparatus for molding the bumper core material, and a molding method thereof.

FIG. 12 is a side sectional view of a conventional bumper (2) attached to the rear part of a vehicle body of an automobile. The bumper (2) has a bumper core (1) made of synthetic resin foam attached to a reinforcement (20) attached to a vehicle body (not shown), and this is a skin made of a molded product such as polypropylene. (21) covered. In the following description, the vehicle body side, that is, the reinforcement (20) side with respect to the bumper core material (1) is referred to as the rear, and the opposite side to the reinforcement (20) is referred to as the front. The surface on which the reinforcement (20) is attached on the bumper core (1) is referred to as a reinforcement attachment surface (10). The bumper core material (1) is formed by filling foam resin beads in a mold and heating the foam resin beads to foam.
FIG. 13 is a perspective view of a conventional bumper core material (1). The bumper core member (1) is formed in an arc shape in accordance with the shape of the vehicle body to be attached, with the longitudinal direction aligned with the width direction of the vehicle body. Further, the bumper core material (1) is often formed with a rounded front surface according to the shape of the bumper (2). Here, the bumper core member (1) has a central portion in the longitudinal direction protruding in the front direction of the vehicle body, so that an impact such as a collision is easily applied to the central portion. Therefore, high strength is required for the central portion. On the other hand, both ends in the longitudinal direction of the bumper core material (1) are considered to receive less impact than the center, and may have low strength.

When the bumper core material (1) is formed from a foam molded body having a uniform density as a whole, if the bumper core material (1) is formed from a low-strength foam molded body, the strength is insufficient and the bumper core material (1) is easily damaged. Therefore, the entire bumper core material (1) is formed of a foam molded body having high strength. However, this increases an unnecessary weight and causes an increase in cost because the price of the bumper core material (1) is determined by the weight.
Therefore, it has been proposed that the central portion in the longitudinal direction of the bumper core material (1) is formed of a resin having high strength, that is, a high density, and both ends thereof are formed of a resin having a low density (for example, patents). Reference 1). The central portion in the longitudinal direction of the bumper core material (1) is a high-density high-strength portion (11) made of foamed resin beads having a small particle size, and both ends in the longitudinal direction are made of foamed resin beads having a large particle size. It is a low strength part (12) (12) with low density. This reduces the weight of the bumper core material (1) and prevents an increase in cost.

FIG. 14 is a partial sectional plan view of a conventional mold (3) for molding the bumper core material (1). As is well known, the mold (3) is composed of a fixed mold (4) and a movable mold (5), and a cavity (30) between the molds (4) and (5) is filled with foamed resin beads, A bumper core material (1) is formed. The cavity (30) is divided into a plurality of spaces S1 and S2 by the partition plate (31), and the space S1 becomes a high strength portion (11) and the space S2 becomes a low strength portion (12). The partition plate (31) passes through the slit (44) provided in the movable mold (5) and is provided so as to be able to appear and disappear in the cavity (30). On the movable die (5), a projecting portion (58) for forming a groove (18) of the bumper core material (1) is provided on the peripheral portion of the slit (44). The movable mold (5) includes a back plate (51), and a cylinder (32) connected to each partition plate (31) is provided on the back plate (51). The partition plate (31) moves in and out of the cavity (30) by the cylinder (32). Resin filling feeders (42) and (42) are connected to the fixed mold (4) in accordance with the spaces S1 and S2.
At the time of molding, with the partition plate (31) inserted into the cavity (30), the foamed resin beads preformed to a predetermined particle diameter from the feeders (42) and (42) are filled into the spaces S1 and S2. Is done. After the partition plate (31) is retracted from the cavity (30) by the cylinder (32), both molds (4) and (5) are heated to fuse the resin foam beads. After cooling, the mold is released to obtain a bumper core material (1) having a high-strength portion (11) and a low-strength portion (12) integrally. On the bumper core (1), the surface in contact with the front surface of the movable die (5) is the reinforcement mounting surface (10).

When the conventional bumper core (1) is formed, if the protrusion (58) is not provided and the groove (18) is not formed, there are the following problems. Since the thickness of the partition plate (31) and the width of the slit (44) are larger than the particle size of the beads, as shown in an enlarged view in FIG. 15, after the partition plate (31) is removed from the cavity (30), The beads (6) (60) enter the transition path of the partition plate (31) by the foaming pressure. The entered beads (6) and (60) project on the surface of the movable mold (5) and become burrs (61) on the reinforcement mounting surface (10) indicated by dotted lines.
16 is a cross-sectional front view of FIG. 15 viewed from the B direction. The partition plate (31) has a rounded tip in accordance with the shape of the bumper core (1). In this case, after filling the foamed resin beads, when the partition plate (31) is removed from the cavity (30), a gap indicated by a dotted line in FIG. 16 is formed between the tip of the partition plate (31) and the cavity (30). (33) is possible. Therefore, the gap (33) is filled with foamed resin, and this also facilitates the formation of burrs (61) on the reinforcement mounting surface (10) on the bumper core (1).
If the burr (61) protrudes too much, the bumper core (1) will be lifted when the bumper core (1) is attached to the reinforcement (20). It becomes non-uniform over the longitudinal direction. Moreover, it becomes difficult to attach the bumper core material (1) to a desired position on the reinforcement (20), and the assembling workability of the bumper (2) is deteriorated. Therefore, the protrusion (58) is formed on the movable mold (5), the groove (18) is provided on the reinforcement mounting surface (10) of the bumper core (1), and the burr (61) is formed on the groove (18 ). As a result, the burr (61) is less likely to hit the reinforcement (20).

JP 2001-63496 A

In the conventional bumper core material (1), since the groove (18) is provided vertically, the thickness of the bumper core material (1) is reduced by the amount of the groove (18), and the strength is lowered.
An object of the present invention is to provide a bumper core material in which the reinforcement mounting surface has no burr or has a smaller burr than the conventional one while maintaining strength.

The molding apparatus for forming the bumper core material (1) is provided with a cavity (30) filled with foamed resin beads between the fixed mold (4) and the movable mold (5), and in the cavity (30), A plurality of partition plates (31) and (31) are provided so as to be able to appear and retract, and have a reinforcement mounting surface (10) that integrally includes a high-strength portion and a low-strength portion.
  The partition plate (31) enters the cavity from the mold side opposite to the reinforcement mounting surface side, and when the cavity entry is completed, the partition mounting plate (31) does not form a groove on the reinforcement mounting surface (10) and In order to prevent the occurrence, the tip part contacts the surface of the mold forming the reinforcement mounting surface (10).

When the foamed resin beads are filled into the cavity (30), the tip of the partition plate (31) contacts the surface of the mold that forms the reinforcement mounting surface (10). After filling the cavity (30) with the foamed resin beads, the partition plate (31) is moved to the mold on the side opposite to the reinforcement mounting surface (10) side, and is removed from the cavity (30). Accordingly, the gap (33) as shown by the dotted line in FIG. 16 does not occur on the reinforcement mounting surface (10) side. As a result, the burr (61) protruding from the reinforcement mounting surface (10) is eliminated or made smaller than the conventional one.
Further, after the partition plate (31) is removed from the cavity (30) through the slit (44), the foamed resin beads are heated. Since the width of the slit (44) is formed thinner than the particle diameter of the foamed resin beads constituting the high-strength part (11), the foamed resin beads enter the transition path of the partition plate (31). However, the foamed resin beads do not protrude outward from the reinforcement mounting surface (10), or the protruding amount is small.
As a result, the burr (61) protruding from the reinforcement mounting surface (10) can be eliminated or made smaller than before without the groove (18) being provided on the reinforcement mounting surface (10) as in the prior art. I was able to. Therefore, the bumper core material (1) is stably attached to the reinforcement (20). Further, unlike the prior art, the formation of the groove (18) does not reduce the strength of the bumper core material (1).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of the bumper core material (1). The bumper core material (1) is formed in an arc shape as in the prior art, and the longitudinal direction substantially coincides with the width direction of the vehicle body. The front surface of the bumper core material (1) is formed in a rounded shape. However, unlike the prior art, the groove (18) is not provided on the reinforcement mounting surface (10). The central portion in the longitudinal direction of the bumper core material (1) is a high-density high-strength portion (11) made of foamed resin beads having a small particle size, and both ends in the longitudinal direction are made of foamed resin beads having a large particle size. It is a low strength part (12) (12) with low density. The applicant has proposed to use beads having a diameter of about 1-5 mm obtained by pre-foaming the raw material particles 5-30 times as expanded resin beads, and the resin constituting the expanded resin beads will be described later. To do. Further, the particle size of the beads of the low strength portion (12) is about twice the particle size of the beads of the high strength portion (11), but is not limited to this value.
2 is a cross-sectional view of FIG. 1 taken along the plane including the line AA. The upper surface and the lower surface of the bumper core member (1) are tapered surfaces (13) inclined downward and upward from the reinforcement mounting surface (10) side toward the front, respectively. Accordingly, when the bumper core material (1) is formed using a mold that opens and closes to the left and right, the tapered surface (13) has a draft.

  FIG. 3 is a perspective view of a mold (3) for molding the bumper core material (1). As is well known, the mold (3) is composed of a fixed mold (4) and a movable mold (5). The fixed mold (4) is configured by covering the front surface of the fixed frame (40) with a first back plate (41). The movable mold (5) is constructed by covering the rear surface of the movable frame (50) with a second back plate (51), and the movable mold (5) is fixed to the fixed mold (4) by a slide mechanism (not shown). To approach and separate. The first back plate (41) is provided with feeders (42), (42), (42) for injecting beads of foamed resin into the stationary frame (40).

FIG. 4 is a cross-sectional plan view in which the mold (3) of FIG. 3 is broken at the plane including the line DD. The stationary side frame (40) includes a concave mold (43), and the tip of the feeder (42) is fitted into the concave mold (43). The moving side frame (50) has a convex type (52) also called a core, and is formed between the concave type (43) and the convex type (52) when the fixed type (4) and the moving type (5) are combined. The cavity 30 is filled with foamed resin beads, and the bumper core 1 is formed by steam heating and cooling (see FIG. 1). The front end surface of the convex mold (52) is formed in an arc shape, and the surface facing the front end surface of the convex mold (52) on the bumper core member (1) is the reinforcement mounting surface (10). That is, the reinforcement mounting surface (10) is formed by the convex mold (52).
Steam chambers (45) and (53) into which heated steam is introduced are formed between the concave mold (43) and the first back plate (41) and between the convex mold (52) and the second back plate (51), respectively. The foamed resin beads in the cavity (30) are foamed and fused by the heated steam.
The cavity (30) is divided into a plurality of spaces S1 and S2 by the partition plates (31) and (31), and the space S1 becomes a high strength portion (11) and the space S2 becomes a low strength portion (12). The feeders (42), (42) and (42) are arranged according to the spaces S1 and S2. The partition plate (31) passes through the slit (44) (see FIG. 5) provided in the concave mold (43) and can be projected and retracted in the cavity (30) without rattling. The partition plate (31) The cylinder (32) attached to the first back plate (41) moves in and out of the cavity (30). That is, the partition plate (31) is inserted into the cavity (30) from the fixed mold (4) side, unlike the conventional configuration shown in FIG.
The thickness of the partition plate (31) and the width of the slit (44) are smaller than the particle diameter of the foamed resin beads having the smaller particle diameter, specifically 1.5 mm or less. 5 is an enlarged view of FIG. 4 viewed from the G direction, and FIGS. 6A and 6B are cross-sectional front views of FIG. 3 taken along the plane including the line EE. Since the partition plate (31) is thinner than the conventional one, the strength is insufficient, and there is a possibility that the partition plate (31) may be deformed when an impact or the like is applied carelessly. Therefore, the partition plate (31) is fitted into the slit (44) in a state where rattling is restricted, and the slit (44) guides the forward and backward movement of the partition plate (31), and the partition plate (31) is slit ( It is received on both side walls of 44) to compensate for the lack of strength.
As a general material for the mold (3), aluminum, stainless steel, iron, copper, steel, etc. can be used. The mold (3) is made of aluminum (AC7A), and the partition plate (31) is formed. It is preferable to form with stainless steel (SUS304). By forming the mold (3) and the partition plate (31) with different materials, the partition plate (31) can slide smoothly. In the examples, the thickness of the partition plate (31) is 1 mm, and the particle diameter of the foamed resin beads is 1.2 to 1.5 mm when the particle diameter is small, and 1.9 to 2.5 when the particle diameter is large. 3 mm.

(When filling with resin)
The procedure of the molding operation will be shown below, and the filling operation of the foamed resin beads will be shown first. As shown in FIGS. 4 and 6 (a), when filling the foamed resin beads, the partition plate (31) is advanced and fitted into the cavity (30) by the cylinder (32). The tip of the partition plate (31) is in contact with the tip surface of the convex mold (52).
From the feeder (42), beads having a small particle diameter are filled into the space S1, and beads having a large particle diameter are filled into the space S2. After the completion of filling, the cylinder (32) is driven and the partition plate (31) is pulled out from the cavity (30) toward the fixed mold (4) as shown in FIG. 6 (b).
FIG. 7 is an enlarged view of the portion F in FIG. 4 at this time, and it seems that the beads (6) and (60) flow out toward the slit (44). However, as described above, the thickness of the partition plate (31) and the width of the slit (44) are thinner than the particle diameter of the foamed resin bead (60) having the smaller particle diameter, so the beads ( 6) The amount that (60) protrudes is zero or very small.
Further, since the partition plate (31) is pulled out toward the fixed mold (4), the gap (33) as shown by the dotted line in FIG. 16 does not occur on the reinforcement mounting surface (10) side. As a result, the burr (61) protruding from the reinforcement mounting surface (10) is eliminated or reduced.

(When melting and releasing)
When the partition plate (31) is pulled out of the cavity (30) by the cylinder (32), heated steam is introduced into the steam chambers (45) and (53). The concave mold (43) and the convex mold (52) are heated to fuse the foamed resin beads in the spaces S1 and S2. A bumper core material (1) in which the high strength portion (11) and the low strength portions (12) (12) are integrated is formed.
After cooling both molds (43) and (52), as shown in FIG. 8, the movable mold (5) moves backward and is released. In this way, the bumper core material (1) is obtained.

(Effect of this example)
In this example, when the resin foam beads are filled in the cavity (30), the tip of the partition plate (31) is in contact with the surface of the movable mold (5) that forms the reinforcement mounting surface (10). . After filling the cavity (30) with the foamed resin beads, the partition plate (31) is moved toward the stationary mold (4) and is removed from the cavity (30). Accordingly, the gap (33) as shown by the dotted line in FIG. 16 does not occur on the reinforcement mounting surface (10) side. As a result, the burr (61) protruding from the reinforcement mounting surface (10) is eliminated or reduced.
In addition, the foamed resin beads are heated after removing the partition plate (31) from the cavity (30), but the thickness of the partition plate (31) and the width of the slit (44) constitute the high-strength portion (11). Since it is formed smaller than the particle diameter of the foam resin beads, even if the foam resin beads enter the transition path of the partition plate (31), the foam resin beads are outside the reinforcement mounting surface (10). Does not protrude or the protruding amount is small.
Thus, the burr (61) protruding from the reinforcement mounting surface (10) can be eliminated or reduced without providing the groove (18) as in the prior art. Therefore, the bumper core material (1) is stably attached to the reinforcement (20).

The applicant uses the above molding method to pre-expanded particles obtained by expanding styrene-modified polyethylene resin (trade name: PIOCELAN (registered trademark) POOP, manufactured by Sekisui Plastics Co., Ltd.) to 5 times and 20 times. A bumper core material (1) was prepared using, and burr was measured with an inspection jig (7).
FIG. 10 is a rear view of the measuring jig (7), and FIG. 11 is a cross-sectional view of FIG. 10 taken along the plane including the line XX. The measuring jig (7) is provided with a plurality of holding parts (71) and measuring parts (72) on the fixed part (70) along the longitudinal direction of the bumper core (1). The holding part (71) is provided with a bumper core material (1), and the measuring part (72) is formed of an aluminum plate having a thickness of 3 mm and is fitted into a groove (73) formed in the fixing part (70). In other words, it is provided so as to be able to approach and separate from the bumper core material (1). The part of the measuring section (72) facing the bumper core material (1) is formed in a shape in which a predetermined gap (about 2 mm) is provided along the shape of the measurement location of the bumper core material (1).
At the time of burr measurement, after the bumper core material (1) is installed on the holding part (71), the measurement part (72) is fitted into the groove (73). The measurement part (72) is brought close to the bumper core material (1) along the groove (73), and a gap X1 at a predetermined position on the bumper core material (1) and the measurement part (72) is measured with a taper gauge.
The bumper core material (1) has a length in the longitudinal direction of about 110 cm along the arc surface, and a height of the central portion in the longitudinal direction is about 13 cm. A burr | flash generate | occur | produces in K part of FIG. 1 which is a boundary of a high intensity | strength part (11) and a low intensity | strength part (12). At the boundary K1 on the reinforcement mounting surface (10), the burr was 0 mm. Moreover, the burr | flash was 1 mm or less in boundary K2 on surfaces other than a reinforcement attachment surface (10) on a bumper core material (1).

In the above description, the reinforcement mounting surface (10) is opposed to the convex type (52) of the movable type (5). However, as shown in FIG. 9, the convex mold (52) is provided in the fixed mold (4), the reinforcement mounting surface (10) is formed by the convex mold (52), and the partition plate (31) is moved. The mold (5) may enter the cavity (30).
In order to fill the foamed resin beads into the cavity (30), a so-called compression filling method in which a pressure difference is provided between the cavity (30) and the feeder (42) may be used.
The foamed resin beads include those obtained by impregnating a synthetic resin with a physical foaming agent, foamed by heating, and pre-foamed. Synthetic resins include polystyrene resins such as styrene modified polyethylene resins, polystyrene, high impact polystyrene, styrene-ethylene copolymers, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, and polymethyl methacrylate resins. And polymethacrylic resins such as polyethylene, polypropylene, and polyolefin resins such as ethylene-vinyl acetate copolymer, and polyester resins such as polyethylene terephthalate. Mixtures of these synthetic resins and copolymer of monomers can also be used.
Examples of the physical foaming agent include aliphatic hydrocarbons such as propane, butane, pentane and hexane, aliphatic cyclized hydrogens such as cyclopentane and cyclobutane, and inorganic gases such as carbon dioxide, nitrogen and air. Can be mentioned. These physical foaming agents may be used alone or in combination of two or more.

  The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof. In addition, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims.

It is a perspective view of a bumper core material. 2 is a cross-sectional view of FIG. 1 taken along the plane including the line AA. It is a perspective view of the metal mold | die which shape | molds a bumper core material. It is the cross-sectional top view which fractured | ruptured the metal mold | die of FIG. 3 in the surface containing DD line. It is the enlarged view which looked at FIG. 4 from the G direction. (a), (b) is the cross-sectional front view which fractured | ruptured FIG. 3 in the surface containing the EE line | wire. It is an enlarged view of the F section of FIG. 4, and shows the state with which the foamed resin bead was filled. It is a cross-sectional top view which shows the state which the movable mold | type moved. It is a cross-sectional top view which shows another metal mold | die. It is a rear view of a measurement jig. It is sectional drawing which fractured | ruptured FIG. 10 in the surface containing a XX line. It is side surface sectional drawing of the conventional bumper. It is a perspective view of the conventional bumper core material. It is a partial cross section top view of the conventional metal mold | die which shape | molds a bumper core material. It is an enlarged view of the C section of FIG. 14, and shows the state without a protrusion part. It is the cross-sectional front view which looked at FIG. 15 from the B direction.

Explanation of symbols

(1) Bumper core material
(4) Fixed type
(5) Mobile type
(10) Reinforcement mounting surface
(11) High strength part
(12) Low strength part
(30) Cavity
(31) Partition plate
(44) Slit

Claims (4)

A cavity (30) filled with foamed resin beads is provided between the fixed mold (4) and the movable mold (5), and a plurality of partition plates (31) (31) can appear and disappear in the cavity (30). And forming a bumper core material (1) having a reinforcement mounting surface (10) integrally comprising a high strength portion and a low strength portion,
The partition plate (31) enters the cavity from the mold side opposite to the reinforcement mounting surface side, and when the cavity entry is completed, the partition mounting plate (31) does not form a groove on the reinforcement mounting surface (10) and An apparatus for molding a bumper core material for a vehicle body, characterized in that, in order to prevent the occurrence , a tip end portion is in contact with a surface of a mold forming a reinforcement mounting surface (10). The partition plate (31) is fitted in a slit formed in the mold on the opposite side of the mold located on the reinforcement mounting surface (10) side in a state in which the backlash is restricted, and guided into the cavity. The molding apparatus of the bumper core material (1) for a vehicle body according to claim 1 . A bumper core material (1) having a reinforcement mounting surface (10) is integrally formed with a high-strength portion made of expanded resin beads having a small particle size and a low-strength portion made of expanded resin beads having a large particle size. A molding method,
The partition plate (31) is inserted into the cavity (30) formed between the fixed mold (4) and the movable mold (5) from the mold side opposite to the reinforcement mounting surface (10) side. Partitioning the cavity (30) into spaces S1 and S2,
In order to prevent the generation of burrs without forming a groove on the reinforcement mounting surface (10) side, the tip of the partition plate (31) contacts the surface of the mold that forms the reinforcement mounting surface (10). A process of
Filling the spaces S1 and S2 partitioned by the partition plate (31) with foamed resin beads forming a high strength portion and foamed resin beads forming a low strength portion, respectively;
Removing the partition plate (31) from the cavity (30) toward the mold opposite to the reinforcement mounting surface (10) side;
A method for forming a bumper core material. A reinforcement mounting surface (10) having a high-strength portion made of expanded resin beads having a small particle size and a low-strength portion made of expanded resin beads having a large particle size,
The partition plate (31) is inserted into the cavity (30) formed between the fixed mold (4) and the movable mold (5) from the mold side opposite to the reinforcement mounting surface (10) side. Partitioning the cavity (30) into spaces S1 and S2,
In order to prevent the generation of burrs without forming a groove on the reinforcement mounting surface (10) side, the tip of the partition plate (31) contacts the surface of the mold that forms the reinforcement mounting surface (10). A process of
Filling the spaces S1 and S2 partitioned by the partition plate (31) with foamed resin beads forming a high strength portion and foamed resin beads forming a low strength portion, respectively;
A bumper core formed by a step of pulling the partition plate (31) from the cavity (30) toward the mold opposite to the reinforcement mounting surface (10) side.

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