JP2005239000A - Core for vehicular bumper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core for a vehicular bumper capable of satisfying the required performance that the energy absorption during the collision remains substantially constant over the entire period from the time when the energy absorption reaches the peak of the impact value to the time when the absorption period of the collision energy by the core for the vehicular bumper is ended, and satisfying the required performance without reducing the energy absorption even in the second and subsequent repeated collisions in a plurality of collisions. <P>SOLUTION: The core for the vehicular bumper is constituted by combining a shock-absorbing material for compressive deformation and a shock-absorbing material for bending deformation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is applied to a bumper for a vehicle and applies a suitable performance particularly to a bumper for a vehicle having a pedestrian protection function.

Various bumper core materials that have been devised to increase energy absorption have been devised as vehicle bumpers, and in recent years, various types of bumper cores designed to increase the protection performance against pedestrians have been proposed and put into practical use. ing.
For example, the shock absorber is cut at the longitudinal center between the bumper reinforcing material disposed at the front end of the vehicle and the bumper fascia covering the bumper reinforcing material, and the plate material with ribs is made of the shock absorbing material. A vehicle bumper (for example, Patent Document 1) in which the divided members of the shock absorbing material are bonded and fixed to each other through the dividing surface, or a shock energy absorbing member using a honeycomb material at the center and a foam on both sides thereof. In a vehicle bumper, there is a vehicle bumper having an energy absorption characteristic in which a honeycomb material and a foam material are formed by wrapping a predetermined range and both are combined in the wrapping portion (for example, Patent Document 2).
As a shock absorbing structure, a structure has been proposed in which ribs having different heights are arranged on the inner surface, and the shock is absorbed while the maximum load is kept low by dividing the impact load into a plurality (for example, Patent Document 3).
Japanese Patent Laid-Open No. 11-1149 Japanese Utility Model Publication No. 5-78654 JP-A-8-142785

  In the conventional vehicle bumper and shock absorbing structure described above, the energy absorption amount in the initial stage of compression is large at the time of the first collision, so that the required performance is satisfied. However, in the second and subsequent repeated collisions, the shock absorbing structure is satisfied. As a result of the deformation, the amount of energy absorption is remarkably lowered and the required performance cannot be satisfied.

  In view of the above problems, as a result of intensive studies, the present inventors can efficiently absorb the collision energy while suppressing the impact force by combining the cushioning characteristics of the cushioning material by compression deformation and the cushioning material by bending deformation. In addition, since any of the cushioning materials recovers to the shape before the collision after completion of the collision, it has been found that the amount of shock energy absorption is not significantly reduced even in the second repeated collision due to the same impact. It came to.

That is, a first aspect of the present invention relates to a vehicle bumper core material configured by a combination of a cushioning material by compression deformation and a cushioning material by bending deformation. As a preferred embodiment,
(1) The shape recovers almost completely after absorbing the impact.
(2) The impact value with respect to the core material for the vehicle bumper is substantially constant over the entire period from the time when the peak of the impact value is reached to the end point of the impact energy absorption period by the core material for the vehicle bumper.
(3) In two repeated collisions with the same impact force, the second impact peak value is 40% or more of the first impact peak value.
(4) The buffer material by the bending deformation is made of a rubber plate.
(5) The cushioning material by the compression deformation is composed of a foam molded body made of a synthetic resin.
(6) The cushioning material by the compression deformation is arranged so as to be compressed and deformed over the entire buffer period, and the cushioning material by the bending deformation is arranged to bend and deform at the initial stage of impact.
(7) The cushioning material by the bending deformation is provided over the entire width in the front-rear direction of the bumper.
The present invention relates to the core material for a vehicle bumper described above.

  According to the core material for a vehicle bumper of the present invention, the collision energy is absorbed by the combination of the shock absorbing material due to compression deformation and the shock absorbing material due to bending deformation. It is possible to configure the impact force to be substantially uniform, and it is possible to effectively absorb the collision energy while suppressing the impact value, thereby improving the protection performance of the pedestrian.

  Further, the amount of impact energy absorbed by the vehicle bumper core is substantially constant over the entire period from the point at which the impact energy absorption reaches a peak until the end of the shock energy buffer period by the vehicle bumper core. In addition, since a cushioning material by bending deformation is used, the shape before the collision is almost recovered after the first collision, and therefore it is possible to absorb the collision energy even in the second collision. is there. Therefore, if the cushioning material by compression deformation is arranged so as to compressively deform over the entire period of the buffering period and the bending cushioning material is arranged so as to bend and deform at the initial stage of the buffering period, the impact force acting on the pedestrian is kept low, It is possible to efficiently absorb the collision energy by effectively using the entire buffer period.

  If the cushioning material by bending deformation is provided over the entire width of the bumper in the front-rear direction, or if the cushioning material by bending deformation is provided along the length of the bumper and over the entire width in the front-rear direction of the bumper in a substantially horizontal plane, A collision load can be applied to the material from the initial stage of the collision, and the collision energy at the initial stage of the collision can be effectively absorbed by bending deformation.

  If the cushioning material by compression deformation is made of a foamed molded product made of a synthetic resin material, the foaming ratio can be set according to the required cushioning characteristics while ensuring sufficient cushioning performance, and the bumper core material is lightweight. Can be configured.

  The core material for a vehicle bumper according to the present invention is formed by combining a cushioning material by compression deformation and a cushioning material by bending deformation. The impact energy acting on the core material by using two types of shock absorbers as the core material is absorbed when the shock absorbing material due to compression deformation is compressed and deformed over the entire buffer period, and the shock absorbing material due to bending deformation is buffered. It is absorbed by bending deformation around the initial period in the period.

  The core member for a vehicle bumper according to the present invention preferably has a characteristic that substantially completely recovers after a collision load is applied, that is, after shock absorption. In the present invention, the total recovery means that the width of the core material in the front-rear direction of the bumper after the collision load is applied to any width of the core material in the front-rear direction of the bumper before the collision load is applied. Is preferably 90% or more, more preferably 95% or more.

  By combining the cushioning material by compression deformation and the cushioning material by bending deformation, the core material of the present invention begins to act on the impact load, and the impact energy absorption reaches a peak at 10 to 20% of the buffering period, and then the buffering period. It is preferable that it is substantially constant over the entire period up to the end point. Furthermore, it is preferable that the impact energy absorption amount changes at ± 40% with respect to the peak value.

  Furthermore, the core material for a vehicle bumper according to the present invention has the impact energy absorption amount in the second collision with respect to the peak value of the first collision energy absorption amount in two repeated collisions with the same impact force. The peak value is preferably 40% or more, more preferably 80% or more, and particularly preferably 90% or more.

  The buffer material by compression deformation is not particularly limited as long as it can buffer the impact load by compression deformation. For example, a synthetic resin or a synthetic rubber material can be adopted. Examples include resins, polyolefin-based synthetic resins such as polyethylene-based resins and polypropylene-based resins, copolymers thereof, and foam-molded products thereof. Among them, the use of foam-molded products made of synthetic resins can reduce the weight of the core material. preferable.

  There is no particular limitation on the method for producing the foamed molded body made of a synthetic resin, and a known method such as an extrusion molding method or a bead method can be used. When molding such a foamed molded article by the bead method, since the material itself has flexibility, for example, ethylene propylene random polypropylene resin, ethylene propylene block polypropylene resin, homopolypropylene ethylene propylene butene end terpolymer, Polyolefin resins such as linear low density polyethylene (LLDPE) and crosslinked low density polyethylene (crosslinked LDPE) can be suitably used. Further, the expansion ratio of the foamed molded product is preferably in the range of 3 to 150 times, although it depends on the material of the raw material beads. Specifically, in the pre-expanded beads made of a polyolefin-based synthetic resin material, if the expansion ratio is too low, the impact force may be increased, and if it is too small, the collision energy may not be sufficiently absorbed. Double to 90 times, more preferably 2 to 60 times are adopted.

  The material of the buffer material by bending deformation is not particularly limited as long as the material can be buffered by a collision load by bending deformation, and the material can be recovered by 80% even at 60% compression during the impact period, more preferably 90%. Those that recover are preferred. Synthetic rubber materials or metal materials can be used as the material. Adopting a rubber plate is preferable because it satisfies the condition of resilience.

  The cushioning material by compression deformation is formed in a shape that fits the space between the bumper reinforcement and the bumper fascia, and is installed in the space without any gap, and is placed on the front side of the bumper reinforcement so as to compressively deform over the entire cushioning period. One opening that is disposed and extends in the vehicle width direction is formed in the middle of the cushioning material in the height direction due to compression deformation up to both ends of the cushioning material due to compression deformation.

  Examples of the shape of the buffer material by bending deformation include a cross-sectional shape. It consists of an elongated, substantially flat plate-like fixed part and a pair of bent parts fixed at right angles to each other in the middle of the fixed part. The fixed part is an elongated flat plate with the same length as the fixed part. Is formed in a larger outer shape than the opening of the cushioning material, and is attached to the rear surface of the cushioning material by compression deformation so as to block the rear surface of the opening. And the outer peripheral part of a fixing | fixed part is clamped between the buffer material by compression, and a bumper reinforcement material in the state assembled | attached to the front surface of the bumper reinforcement material with the bumper fascia and the buffer material by compression deformation.

  Both ends of the bent portion are mounted in the fixing groove of the cushioning material by compression deformation and fixed to the cushioning material by compression deformation, and the distal end portion of the bending portion is compressed and deformed so that the bending portion is bent and deformed at the initial stage of the buffering period Is placed near the bumper fascia through the opening of the cushioning material. When the bending allowance space is formed between the inner wall of the opening of the cushioning material due to compressive deformation and the bent part, and between the upper and lower bent parts, the inner wall and the bent part of the cushioning material due to compressive deformation are mutually connected. It is configured so that the bending deformation of the bent portion can be made smoothly and reliably. The permissible bending space may be provided with a through-hole in the entire width of the bumper in the front-rear direction, but may be provided in the shape of a bottomed hole that opens toward the front. It is preferable to set the depth. Furthermore, it is preferable to set the distance between the bent parts and the distance between the bent parts and the cushioning material due to the compressive deformation to 1/3 or more of the entire width in the front-rear direction of the bumper so that the bending deformation of the bent parts can be performed smoothly and reliably.

  A bumper reinforcement extending in the vehicle width direction is provided at the front end of the vehicle body, and the core material of the present invention is mounted between the bumper reinforcement and the bumper fascia.

  The front bumper is composed of a bumper fascia and a core material, and the collision load at the time of the previous collision is transmitted to the core material 3 via the bumper fascia and is received by deformation of both, and when a larger collision load acts The bumper reinforcing material is received by a collision load acting on the bumper reinforcing material and the bumper reinforcing material being deformed. The same can be applied to the core material of the rear bumper.

(Test pieces)
150 x 100 x 55 mm size molded pre-expanded beads made of polypropylene resin as the cushioning material by compression so that the magnification of the molded product becomes 45 times (raw material Eperan-PP specification manufactured by Kaneka Chemical Industry) A buffer material by bending of 100 × 5 × 55 mm made of a plate member of acrylotributadiene rubber, which is a synthetic rubber material, was manufactured as a buffer material by bending. Then, a test piece was prepared by assembling the cushioning material by bending two cushioning materials by compression with an interval.

Moreover, the test piece which combined the non-foamed plate-shaped member which consists of polypropylene resin which buckles by one compression instead of the buffer material by bending was created as a comparative example.
(Test method)
Each test piece is sequentially set on a cradle, and is compressed at a speed of 10 mm / min with a jig made of a round bar of φ70 mm along the width direction at the center in the length direction of the test piece to obtain the thickness of the test piece. The sample was compressed 60%, and after removing the load, it was compressed again under the same conditions. The peak load value of the test piece at the time of the first compression, the displacement amount at that time, the peak load value at the time of the second compression were measured, the reduction rate of the load was calculated, and the measurement results shown in Table 1 were obtained.

表１から、１回目の圧縮前後においてその寸法の減少率は、比較例のポリプロピレン系樹脂からなる非発泡の板状部材の箇所において１６．６％であったのに対し、圧縮による緩衝材と曲げによる緩衝材を用いた本発明例は、２．０％、０．９％と略全回復をした。また、荷重減少率は４５．８％であり、比較例の９２．４％と比較して、荷重減少率を減少させる事ができ、繰り返しの衝撃においても性能低下が抑えられている事が分かった。

From Table 1, the reduction rate of the dimension before and after the first compression was 16.6% in the portion of the non-foamed plate-like member made of the polypropylene resin of the comparative example, whereas the cushioning material by compression and In the present invention example using the buffer material by bending, 2.0% and 0.9% were almost fully recovered. Moreover, the load reduction rate is 45.8%, and compared with 92.4% of the comparative example, the load reduction rate can be reduced, and it is understood that the performance degradation is suppressed even in repeated impacts. It was.

Front bumper longitudinal section Front bumper front view Perspective view of test piece used in evaluation test Longitudinal section of the specimen Energy absorption curve of core material for vehicle bumper of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bumper reinforcement material 2 Bumper fascia 3 Core material 4 Front bumper 10 Buffer material by compression deformation 11 Opening part 12 Fixing groove 13 Bending tolerance part 20 Buffer material by bending deformation 21 Fixing part 22 Bending part 30 Buffer material 31 by compression deformation 31 Bending deformation By cushioning material

Claims (8)

  A vehicle bumper core material composed of a combination of a cushioning material by compression deformation and a cushioning material by bending deformation.   The core member for a vehicle bumper according to claim 1, wherein the shape recovers substantially completely after absorbing the shock.   The impact value with respect to the core material for a vehicle bumper is substantially constant over the entire period from the time when the peak of the impact value is reached to the end point of the impact energy absorption period by the core material for the vehicle bumper. Core material for vehicle bumpers.   The core material for a vehicle bumper according to any one of claims 1 to 3, wherein the second impact peak value is 40% or more of the first impact peak value in two repeated collisions with the same impact force.   The core material for a vehicle bumper according to any one of claims 1 to 4, wherein the buffer material by bending deformation is made of a rubber plate.   The core material for a vehicle bumper according to any one of claims 1 to 5, wherein the cushioning material by compression deformation is formed of a foamed molded body made of a synthetic resin.   The buffer material by the said compression deformation is arrange | positioned so that it may compress-deform over the whole period of a buffer period, and the buffer material by a bending deformation will be arrange | positioned so that it may bend and deform in the initial stage of an impact. Core material for vehicle bumpers.   The core member for a vehicle bumper according to any one of claims 1 to 7, wherein the buffer material by the bending deformation is provided over the entire width of the bumper in the front-rear direction.

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