JP4576311B2 - Shock absorber for vehicles - Google Patents

Description

  The present invention relates to a shock absorbing material for a vehicle used as a shock absorbing pad for protecting a passenger by attaching to a lower limb shock absorbing pad for protecting a lower limb of a vehicle occupant or a door trim or a rear side trim. In particular, the present invention relates to a shock absorber for a vehicle that is excellent in shock absorbing performance at the time of a vehicle collision and does not reach a predetermined limit load at which the shock load can cause an obstacle to an occupant.

  In order to protect the lower limbs of an occupant from an impact load at the time of a vehicle collision, a lower limb shock absorbing pad made of, for example, an arbitrary foamed resin is generally placed on the occupant foot of the vehicle. In addition, vehicle interior parts such as door trims, rear side trims, and luggage side trims have built-in shock absorbing pads to protect passengers from impact loads.

  Various disclosures of techniques related to the above-described shock absorbing pad (or lower limb shock absorbing pad) exist, and for example, Patent Documents 1 and 2 can be cited. In Patent Document 1, a pad housing / holding portion for housing and holding the shock absorbing pad mounting portion is formed on the back surface of the door trim, a through hole is formed in the upper wall portion constituting the pad housing / holding portion, and a through groove is formed in the side wall portion. The invention relating to the interior part that absorbs the impact force while suppressing the initial reaction force due to the impact by making the pad receiving and holding portion easy to buckle and deform by providing each of the pad housing and holding portion is disclosed.

On the other hand, the invention disclosed in Patent Document 2 also relates to an impact absorbing pad disposed on the back side of the door trim. This impact absorbing pad is configured so that, for example, the inward projection and the outward projection are displaced substantially vertically on both sides of the intermediate plate portion. It is configured to suppress the increase in impact load by making it easy to break the intermediate plate after the inward projection and outward projection are buckled and damaged when subjected to impact load. It is what.
JP 2004-345479 A JP 2004-338669 A

  According to the impact absorbing pads disclosed in Patent Documents 1 and 2 described above, it is possible to effectively suppress an increase in impact load at the time of a vehicle collision. However, since a solid impact absorbing pad is used in Patent Document 1, after the impact absorbing pad is plastically deformed, an increase in impact load cannot be denied, and as a result, the impact load may cause an obstacle to the occupant. There is a high possibility of exceeding the limit load. On the other hand, in the shock absorbing pad of Patent Document 2, after the inward projection and the outward projection are buckled and the intermediate plate portion is broken, the intermediate plate portion is formed into a solid plate shape. In particular, the impact load exceeds the predetermined limit load that can cause an obstacle to the occupant. That is, a problem common to these patent documents is that the impact load eventually exceeds the limit load due to the presence of the remaining pad collapse, and as a result, there remains a risk of causing some obstacle to the occupant. This is the point.

  The impact absorbing material for a vehicle of the present invention is made in view of the above-described problem, and in addition to effectively mitigating an impact at the time of a vehicle collision, a predetermined limit at which an impact load can cause an obstacle to an occupant. An object of the present invention is to provide a vehicle shock absorber capable of reliably preventing a load from being reached.

  In order to achieve the above object, the impact absorbing material for vehicles according to the present invention comprises a foamed molded product obtained by heating and foaming foamable resin particles in a mold, and a gap is formed between the particles constituting the foamed molded product. Is formed, and the foamed molded body is configured to have a plurality of pieces when compressed to a predetermined thickness.

  The shock absorbing material of the present invention can be used as a shock absorbing pad built in a vehicle interior part such as a lower limb shock absorbing pad, a door trim, a rear side trim, or a luggage side trim.

  The foamable resin particles for molding the shock absorbing material are not particularly limited. However, when thermoplastic resin particles are used as the foamable resin particles, styrene-modified polyethylene resin, polystyrene resin, polyethylene resin, polypropylene System resin etc. can be used. Among them, styrene-modified polyethylene resin resin particle foam molded products obtained by impregnating and polymerizing polyethylene resin particles with styrene monomers include polyethylene resin particle foam molded products and polypropylene resin particle foam molded products. Compared to the above, it is particularly preferable because it is excellent in dimensional stability and shape retention and is less likely to generate powder due to rubbing than a foamed molded product of polystyrene resin particles. The proportion of the styrene component in the styrene-modified polyethylene resin is 40 to 90% by weight, preferably 50 to 85% by weight, more preferably 55 to 75% by weight.

  When molding an impact absorbing material (foamed molded article), for example, a thermoplastic resin such as the above-mentioned styrene-modified polyethylene resin is impregnated with a foaming agent to form a foamable thermoplastic resin. Prefoamed particles are produced by prefoaming a plastic resin with heated steam or the like. Then, the pre-expanded particles are filled in a mold and foam-molded. Here, the expansion ratio of the shock absorbing material is preferably formed by pre-expanded particles adjusted within a range of 5 to 70 times, for example. Since the thing with a foaming ratio of less than 5 becomes very hard, sufficient plastic deformation performance by a foam cannot be expected. On the other hand, if the expansion ratio exceeds 70 times, the foam is too soft and it is difficult to obtain a reaction force as the foam.

  The impact absorbing material of the present invention is formed by artificially forming a gap between the foamable resin particles constituting the impact absorbing material, and when the impact absorbing material is compressed against an impact load at the time of a vehicle collision, the particle indirect The dressing is released and each particle is configured into a plurality of pieces. The compression state in which the shock absorber becomes multiple pieces varies depending on the material of the foamable resin particles used in the shock absorber and the porosity between the particles. Each parameter is set within a range in which the impact load does not exceed the limit load value according to the expandable resin particles and the porosity.

  According to the shock absorbing material of the present invention, the adhesion between particles is released within a range where the impact load does not exceed the impact limit load, and the foam molded body becomes a plurality of pieces, so that the impact load is reduced after plastic deformation of the foam molded body. The problem of increasing cannot occur. In the initial stage after the vehicle collision, the impact load increase is effectively mitigated by plastic deformation of the shock absorber, and the interparticle adhesion is released when the shock absorber is in a predetermined compression state. By drastically dropping the load (stress), the danger to the occupant due to the impact load can be significantly reduced as compared with the conventional shock absorbing pad.

  In another embodiment of the vehicle shock absorber according to the present invention, the predetermined thickness is 60 to 20% of a thickness before being compressed.

  According to the experiments by the inventors, in the shock absorbing material composed of the expandable resin particles exemplified above, the interparticle adhesion is released when compressed to 60 to 20% of the initial thickness. Has been demonstrated. Therefore, after the impact absorbing material is plastically deformed to such a compressed state, the interparticle adhesion is released, so that the impact load can be effectively abrupt before the impact load reaches the limit load that can impede the occupant. A reduction can be caused.

  In a preferred embodiment of the vehicle shock absorber according to the present invention, the ratio of the sum of voids between particles to the total volume of the foamed molded product is 10 to 40%.

  Similarly to the above, according to the experiments by the inventors, in the impact absorbing material composed of the expandable resin particles exemplified above, the ratio of the sum of voids between the particles to the total volume of the foamed molded product (void ratio) is 10 It has been demonstrated that by adjusting to ˜40%, the impact load can be effectively reduced drastically before reaching the limit load at which the impact load can damage the occupant. Changing the porosity leads to changing the adhesion area between the particles, and as a result, adjusting the adhesion between the particles.

  The porosity can be adjusted by appropriately adjusting the molding conditions when foaming the pre-expanded particles with a molding die. For example, when a plate-shaped shock absorber is manufactured in a mold, heating of a mold used as a mold is performed for 4 seconds, steam heating of one surface of the shock absorber is performed for 4 seconds, and steam heating of the other surface is performed. By applying a production method of 3 seconds, double-sided heating for 5 seconds, water cooling for 25 seconds, and cooling for 160 seconds, an impact absorbing material having a porosity of 20% can be obtained.

  The manufacturing method for arbitrarily adjusting the porosity within a range of 10 to 40% can easily finely adjust the porosity by adjusting the time required for each step described above, the steam heating temperature, and the like. .

  Furthermore, in a preferred embodiment of the shock absorber for a vehicle according to the present invention, a groove or a projection is provided on at least one surface of the foamed molded product.

  The impact-absorbing material of the present invention is an impact-absorbing material in which concave grooves and protrusions having arbitrary shapes are provided on one surface or both surfaces of a solid plate whose porosity is adjusted to 10 to 40%.

  For example, when a shock absorbing material is used as a lower limb shock absorbing pad, an embodiment in which a plurality of vertically long protrusions or concave grooves extending in the vehicle front-rear direction is provided on the bottom surface on the vehicle body side when the vehicle is installed. If the shock absorber is disposed inside the door trim, the plate-like member has a protrusion extending in the horizontal or vertical direction on one or both sides, or a circular or elliptical cross section. The polygonal projections can be scattered.

  According to the shock absorbing material of the present invention, the increase of the initial impact load at the time of impact can be effectively mitigated by buckling of the concave groove and the protrusion at the time of a vehicle collision, and further, plastic deformation of the solid plate-like portion and constant deformation Since it is possible to cause a sudden drop in the impact load due to the release of the interparticle adhesion in the compressed state, the safety of the occupant during a vehicle collision can be significantly improved.

  As can be understood from the above description, according to the shock absorber of the present invention, when the shock absorber is in a predetermined compressed state, the interparticle adhesion is released, and the shock absorber becomes a plurality of pieces. Since the load can be lowered before the impact load reaches the limit load that can cause an obstacle to the occupant, the safety at the time of a vehicle collision can be significantly improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an embodiment of the shock absorber of the present invention, and FIGS. 2 and 3 are perspective views of other embodiments of the shock absorber of the present invention. 4A is a view showing a state in which a load is applied to the shock absorber, FIG. 4B is a view showing a state in which the shock absorber is compressed under the load, and FIG. 4 is an enlarged view of a V portion of FIG. 4, FIG. 4 a is a diagram illustrating a state in which particles are bonded to each other, and FIG. 4 b is a diagram illustrating a state in which the adhesion between particles is released. . FIG. 6 is a graph showing experimental results comparing the shock absorbing performance of the shock absorbing material of the present invention and the conventional example.

  FIG. 1 shows an impact absorbing material 1 used as a lower limb impact absorbing pad. The shock absorbing material 1 has a plurality of vertically long concave grooves 12, 12,... Formed on the bottom surface on the vehicle body side when the flat plate material 1 is installed on the vehicle. The shock absorbing material 1 can use a styrene-modified polyethylene resin, a polystyrene resin, a polyethylene resin, a polypropylene resin, or the like as expandable resin particles that are raw materials. In addition, the ratio of the sum of voids between particles (void ratio) with respect to the total volume of the shock absorbing material 1 that is a foam-molded product is adjusted to a range of 10 to 40%.

  The shock absorber 1 is manufactured, for example, by pre-foaming the above-mentioned styrene-modified polyethylene resin with heated steam or the like to produce pre-foamed particles, and filling the pre-foamed particles into a mold that is a mold, The mold is heated for about 4 seconds, one side of the foamed product is steam heated for about 4 seconds, the other side is then steam heated for about 3 seconds, both sides are further heated for about 5 seconds, and finally water cooled for about 25 seconds. And is allowed to cool for about 160 seconds. In addition, the time etc. which each process requires are suitably adjusted so that it may become an impact-absorbing material which has a desired porosity.

  FIG. 2 shows a shock absorbing material 1A used as a lower limb shock absorbing pad, which is a shock absorbing material in which a plurality of vertically long protrusions 13, 13,. In addition to FIGS. 1 and 2, a shock absorbing material in a form in which a plurality of protrusions having circular, elliptical, or polygonal arbitrary cross sections are scattered on the bottom surface of the plate material 11 may be used.

  FIG. 3 shows the shock absorber 1B built in the door trim. The shock absorbing material 1B is configured such that a plurality of protrusions 14, 14,... Are provided on both surfaces of the plate material 11 so as to be in the same position with respect to the plate material. The protrusions 14, 14,... Provided on both surfaces of the plate material 11 may be provided in a staggered arrangement with respect to the plate material 11.

  Of course, the shock absorber of the present invention is not limited to the embodiment of the shock absorber shown in FIGS. Next, based on the shock absorber 1 shown in FIG. 1, an impact load acts on the shock absorber 1 at the time of a vehicle collision, and finally the adhesion between the foamable resin particles constituting the shock absorber 1 is released. The outline of the mode which becomes a plurality of pieces will be described.

  When the impact load F acts on the shock absorber 1 as shown in FIG. 4a, the shock absorber 1 is compressed as a whole due to the buckling of the groove 12 and the plastic deformation of the plate 11 as shown in FIG. 4b. (X direction).

  FIG. 5a is an enlarged view of a portion V in FIG. 4. While the plate material 11 is plastically deformed, the foamable resin particles 2, 2,... Constituting the plate material 11 have a predetermined gap between the particles. The bonding posture is maintained in the state of 3, 3,.

  When the compression of the shock absorber 1 further proceeds, the adhesion between the particles is released, and as shown in FIG. 5b, the shock absorber 1 has a plurality of foamable resin particles 2, 2,. The shape is broken. At the stage where the shock absorber 1 is broken into a plurality of pieces, the impact load is released at that stage, and the load value decreases rapidly.

  As described above, the shock absorbing material of the present invention does not cause an obstacle to the occupant by using a shock absorbing material having a predetermined range of porosity so that the adhesion between particles is released in a compressed state of a predetermined range. The impact load can be suppressed below an arbitrary limit load value.

[Example]
FIG. 6 is a graph showing the load-compressibility characteristics of an embodiment of the shock absorber of the present invention together with a comparative example. This load-compressibility characteristic was obtained by an impact relaxation effect confirmation experiment based on “Dynamic compression test method for packaging buffer material” of JISZ0235. In this test, test pieces resembling the shock absorbing material and the shock absorbing material made only of the plate material shown in FIG. An accelerometer is attached to the scissors jig, a displacement meter that measures the amount of compression due to the drop of the scissors jig is attached to the test piece, and the load ( kN) and the compression rate (%) of the test piece.

  FIG. 6 shows experimental results of four examples. All examples are molded from pre-expanded particles of styrene-modified polyethylene resin. In the graph, X1 is a shock absorber with a porosity of 20%, X2 is a shock absorber with a porosity of 30%, and X3 has a porosity of 20% and is provided with a groove. 1, X4 is the experimental result regarding the shock absorber shown in FIG. 1 having a porosity of 30% and also provided with a concave groove. Here, the size of the shock absorbing material is (400 × 200 × 50 mm), and when the concave grooves are provided, six concave grooves with a depth of 30 mm are provided at almost equal intervals. Yes.

  The method for producing a shock absorbing material with a porosity of 20% is 4 seconds for heating the mold used as a mold, 4 seconds for steam heating on one side of the shock absorbing material, 3 seconds for steam heating on the other side, and double-sided heating. For 5 seconds, water cooling for 25 seconds, and cooling for 160 seconds. On the other hand, the method for producing a shock absorber with a porosity of 30% is: 3 seconds for mold heating, 2 seconds for steam heating on one side of the shock absorber, 2 seconds for steam heating on the other side, 3 seconds for double-sided heating, In this manufacturing method, water cooling is performed for 20 seconds and cooling is performed for 150 seconds.

  From the graph, for example, in an impact absorbing material having a void ratio of 30% and a concave groove formed, the intergranular adhesion is released at a compression ratio of 80%, and the load suddenly increases before reaching a predetermined limit load K. In the case of an impact absorbing material having a void ratio of 20% without concave grooves, the intergranular adhesion is released at a compression ratio of 40%, and the load rapidly decreases before reaching the limit load K. In other examples, the interparticle adhesion was released at a compression rate of about 50 to 60%.

[Comparative example]
On the other hand, the experimental result of a conventional shock absorber in which no voids are artificially formed between particles is X5 in the graph. This shock absorbing material has a heating time of a mold used as a mold for 4 seconds, a steam heating of one surface of the shock absorbing material for 8 seconds, a steam heating of the other surface for 6 seconds, a double-sided heating for 15 seconds, and a water cooling of 25 seconds. The product is manufactured by performing cooling for 2 seconds and cooling for 160 seconds. As apparent from the graph, the increase in impact load is remarkable, and the adhesion between particles is not released, so that the load value exceeds the limit load K. Therefore, even if the increase in impact load can be mitigated by plastic deformation due to the shock absorber or the impact absorption performance due to the buckling of the concave grooves and protrusions, eventually exceeding the limit load will cause some obstacles to the passenger. The possibility of gaining remains.

  As is clear from the experimental results, according to the shock absorber of the present invention, in addition to effectively mitigating the impact load at the time of vehicle collision, the impact load does not exceed an arbitrary limit load, The possibility of damaging passengers can be greatly reduced.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

The perspective view of one Embodiment of the shock absorber of this invention. The perspective view of other embodiment of the impact-absorbing material of this invention. The perspective view of other embodiment of the shock absorber of this invention. (A) is the figure which showed the state which the load is acting on the shock-absorbing material, (b) is the figure which showed the state by which the shock-absorbing material is compressed under the load action. It is the enlarged view of the V section of FIG. 4, (a) is the figure which showed the condition where particle | grains have adhere | attached, (b) is the figure which showed the condition where the adhesion | attachment between particles was released. The graph which showed the experimental result which compared the impact-absorbing performance of the impact-absorbing material of this invention, and a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,1A, 1B ... Shock-absorbing material, 11 ... Plate material, 12 ... Groove, 13, 14 ... Protrusion, 2 ... Expandable resin particle, 3 ... Air gap

Claims (3)

It consists of a foamed molding obtained by heating and foaming expandable resin particles in a mold,
A gap is formed between the particles constituting the foamed molded article,
The ratio of the sum of the voids between the particles to the total volume of the foam molded article is 10 to 40%,
A shock absorber for a vehicle, wherein the foam molded body is configured to have a plurality of pieces when compressed to a predetermined thickness.   The vehicle shock absorber according to claim 1, wherein the predetermined thickness is 60 to 20% of a thickness before being compressed. At least one surface of the foamed molded, automotive shock absorber according to claim 1 or 2, characterized in that grooves or projections are provided.

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