JP2004306791A - Leg part impact absorption pad for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leg part impact absorption pad for a vehicle capable of effectively absorbing impact by a collision without increasing thickness and not dispersing the impact absorption property depending on a placement space of the leg. <P>SOLUTION: The leg part impact absorption pad 10 for a vehicle placed with the leg 23 of an occupant is formed from a foam molded product of a thermoplastic resin bead. A plurality of lengthy recessed grooves 13 are formed on a surface becoming a vehicle body 21 side when it is installed on the vehicle at approximately equal space in parallel so as to be the same direction as the longitudinal direction of the vehicle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a shock absorbing pad for a vehicle for protecting an occupant's lower limbs during a vehicle collision, without effectively increasing the thickness of the shock absorbing pad for a vehicle, effectively absorbing the shock, The present invention relates to a lower limb impact absorbing pad for a vehicle in which the impact absorbing properties are not varied.
[0002]
[Prior art]
Regarding the structure for protecting the lower limbs of the occupant in the event of a vehicle collision, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-326870) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-103367) disclose a structure desired for the vehicle itself. The invention for imparting the shock absorbing property of the invention is disclosed. However, providing the vehicle with the function of cushioning impacts involves a change in the design of the vehicle body structure, and may require special materials and parts for the cushioning function, which increases costs. It is expected that it will run out.
[0003]
On the other hand, Patent Document 3 (Japanese Patent Publication No. Hei 6-17097) discloses that a solid foam that absorbs energy is arranged at the foot of a passenger compartment of a vehicle, and the foam is plastically deformed in response to an impact generated at the time of a collision. There is disclosed an invention in which the lower leg of an occupant is protected by burying the foot therein. According to the present invention, it is considered that the lower limbs of the occupant can be protected without a major design change of the vehicle body structure.
[0004]
[Patent Document 1]
JP 2000-326870 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-103367 [Patent Document 3]
Japanese Patent Publication No. Hei 6-17097
[Problems to be solved by the invention]
As described above, by using the foam, it is possible to absorb the kinetic energy generated at the time of the collision due to the strain (plastic deformation) of the foam, thereby reducing the impact on the lower leg of the occupant. By the way, when a solid foam is compressed, the kinetic energy may not be effectively absorbed because the shock absorption characteristic due to its plastic deformation is constant.
[0006]
That is, in general, the load-strain curve of an article accompanied by plastic deformation is a curve that rises to the right, and in the case of a solid foam, the absorption mode of kinetic energy (correlation between load and strain) is adjusted. Then, it depends exclusively on the expansion ratio. In the case of a hard material (low foaming ratio), the load-strain curve becomes a straight line rising to the right as indicated by A in FIG. 7A, and the energy absorption immediately after the collision is large and effective. However, the required energy absorption amount a (energy absorption amount for reducing the kinetic energy at the time of a collision to the kinetic energy sufficient not to impair the lower limbs of the occupant) (shown by oblique lines) was absorbed by the distortion of the foam. At this point, it is possible that the load exceeds the obstacle value limit line K (the limit value at which the lower limb of the occupant is injured).
[0007]
Conversely, when the strength is weakened by increasing the foaming ratio, it is effective in reducing the impact, but a considerable thickness is required to effectively reduce the impact. However, in the case of the lower limb impact absorbing pad for a vehicle, the thickness is naturally limited due to the space in the vehicle, and the load-strain curve at the normally allowable thickness is as shown by B in FIG. Before the required energy absorption amount a is absorbed by the distortion of the foam material, a so-called bottomed state (a state in which the heel is directly subjected to an impact from the vehicle body) occurs, and the load applied to the lower limb rapidly increases. Therefore, the load still exceeds the obstacle value limit line. Therefore, there is also a limitation on the expansion ratio of the foam.
[0008]
The present invention has been made in view of the above circumstances, and as shown by C in FIG. 7 (a), in the early stage of the collision, a short period of time similar to the load-strain curve of the foam having a low expansion ratio. In order to absorb a large amount of energy, and from the load value P lower than the obstacle value limit line K, the strain is advanced without greatly increasing the load, so that the required energy absorption amount a becomes the obstacle value limit line K. It is possible to absorb before it arrives, thereby effectively reducing the impact force applied to the lower limb of the occupant without reducing the thickness more than necessary, and reducing the obstacles occurring in the lower limb Accordingly, an object of the present invention is to provide a more improved vehicle lower limb impact absorbing pad. It is another object of the present invention to provide a vehicle lower limb impact absorbing pad in which a substantially equal impact mitigation effect is imparted to the lower limb of the occupant regardless of the position of the heel of the occupant at any position of the impact absorbing pad. It is in.
[0009]
[Means for Solving the Problems]
The vehicle lower limb impact absorbing pad according to the present invention is a vehicle lower limb impact absorbing pad on which an occupant's foot is placed, and is formed of a foamed molded article of thermoplastic resin beads, and has a vehicle body when installed in a vehicle. A plurality of vertically long grooves are formed on the side surface so as to be in the same direction as the front-rear direction of the vehicle, and are formed in parallel at substantially equal intervals.
[0010]
In the vehicle lower limb impact absorbing pad according to the present invention, a plurality of vertically long concave grooves are formed on the surface on the vehicle body side when installed on the vehicle so as to be in the same direction as the front-rear direction of the vehicle and are substantially parallel to each other at equal intervals. Have been. In the experiment of the present inventors, by forming such a plurality of vertically long concave grooves, as shown by C in FIG. A curve was obtained, and it was confirmed that, from a certain load value (a load value lower than the obstacle value limit line), it is possible to absorb energy while advancing the strain without greatly increasing the load. As a result, it is possible to absorb the necessary energy absorption within the range of the obstacle value limit line without increasing the thickness, and effectively reduce the impact force applied to the lower limb of the occupant, thereby preventing the lower limb from having a failure. Can be reduced.
[0011]
In addition, since the vertically long concave grooves are formed at substantially equal intervals in the same direction as the front-rear direction of the vehicle, the heel of the occupant in the driver's seat or the auxiliary seat can be positioned at any position of the vehicle lower limb impact absorbing pad. The shock absorbing properties do not vary. FIG. 8 shows the case where the groove is a vertically long groove (FIG. 8 (a)), the case where the groove is a horizontally long groove (FIGS. 8 (b1) and (b2)) and the case where the grooves are formed vertically and horizontally in a lattice shape. The difference in the stability of the shock absorption performance in the case of FIG. 8 (c) is explained. In the case of the vertically elongated groove as in the present invention, the position of the heel is in any position. In contrast, in the case of a horizontally long groove, as shown in FIG. 8 (b1), the position of the heel is on the groove (imaginary line position) or the position is not the groove. It can be seen that the impact absorption performance differs depending on whether there is (solid line position). Further, when the concave groove is transverse to the traveling direction of the vehicle, as shown in FIG. 8 (b2), the entirety of the groove is bent by the impact, and the impact absorbing performance is affected. It can be seen that the grooves formed vertically and horizontally in a lattice form also lack stability as in the case of the horizontally long grooves.
[0012]
The overall shape and size of the vehicle lower limb impact absorbing pad are arbitrary, and may be optimal according to the body shape of the vehicle to which the impact absorbing pad is attached. Preferably, it has a horizontal part and an inclined part, and a vertically long groove is formed on both of them. In this configuration, the occupant's heel can be placed more freely, and the heel and other parts of the sole can be protected by the shock absorbing performance of the vehicle's lower limb shock absorbing pad. Property can be ensured.
[0013]
The width of the vertically long grooves, the width between the vertically long grooves, or the depth of the grooves are appropriately set according to the required energy absorption required for the vehicle. According to the experiments of the present inventors, in the case of a normal passenger car, if the width of the vertical grooves is 5 to 15 mm and the width between the vertical grooves is 8 to 20 mm, the energy absorption amount that is sufficiently safe for practical use is sufficient. Obtained. When the width of the groove is larger than 15 mm and the width between the vertically long grooves is larger than 20 mm, the effect of absorbing the impact may differ depending on the position of the heel. If the width of the groove is smaller than 5 mm and the width between the vertically long grooves is smaller than 8 mm, the load point P as the inflection point shown in FIG. There was a tendency for the position to be close to K and the safety to decrease.
[0014]
Although many thermoplastic resins can be used as the thermoplastic resin forming the vehicle lower limb impact absorbing pad of the present invention, styrene-modified polyethylene resin, polyethylene resin, polypropylene resin and the like are preferable. Above all, foamed molded articles of styrene-modified polyethylene resin obtained by impregnating and polymerizing polyethylene resin particles with styrene monomer are foamed molded articles of polyethylene resin beads and foamed molded articles of polypropylene resin beads. It is particularly preferable because it is superior in dimensional stability and shape retention as compared with the above, and it is difficult to generate powder due to rubbing as compared with a foamed molded article of polystyrene resin beads. The proportion of the styrene component in the styrene-modified polyethylene resin is 40 to 90% by weight, preferably 50 to 85% by weight, and more preferably 55 to 75% by weight.
[0015]
In molding, the styrene-modified polyethylene resin is impregnated with a foaming agent in a dry or wet manner to form an expandable styrene-modified polyethylene resin, and the expandable styrene-modified polyethylene resin is prefoamed with heated steam or the like. Next, pre-expanded particles of the expandable styrene-modified polyethylene resin are filled in a molding die, and foam molding may be performed by a conventional method. The foaming ratio of the lower limb impact absorbing pad for a vehicle according to the present invention is 10 to 50 times, preferably 20 to 40 times. If the expansion ratio is less than 10 times, the load P in FIG. 7 (a) approaches or exceeds the obstacle value limit line K because it is very hard, and the impact due to collision cannot be effectively absorbed. Can occur. Those exceeding 50 times become very soft, so that the load P in FIG. 7 (a) becomes significantly lower than the obstacle value limit line K, so that the kinetic energy can be reduced to a level that does not impair the lower limbs. Before absorbing the required amount of energy, there is a danger that the bottom will be reached. For this reason, the load applied to the lower limb rapidly rises, and the load exceeds the obstacle value limit line K, which is not preferable because the impact due to the collision cannot be effectively absorbed.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a view of one embodiment of a vehicle lower limb impact absorbing pad according to the present invention as viewed from the back side, and FIG. 2 is a diagram of FIG. 1 in a case where the vehicle lower limb impact absorbing pad is attached to a vehicle. It is sectional drawing in the II-II line.
[0017]
In this example, the vehicle lower limb impact absorbing pad 10 is a foam molded product having a foaming ratio of 30 times obtained by filling a molding die with pre-expanded particles (beads) of styrene-modified polyethylene resin and heating by steam. It has a horizontal portion 11 and an inclined portion 12, and the thickness of both is approximately equal to 35 mm. On both back surfaces, that is, almost the entire surface that is the vehicle body side when installed on the vehicle, a plurality of vertically long grooves 13 are arranged in parallel at substantially equal intervals in the same direction as the front-rear direction of the vehicle. In this example, the width of the vertical grooves 13 is 9 mm, the width between the vertical grooves 13 is 9 mm, and the depth is 23 mm.
[0018]
As shown in FIG. 2, the vehicle lower limb impact absorbing pad 10 is attached to a passenger seat side of a vehicle body 21 of the vehicle with appropriate fasteners, and an appropriate floor carpet 22 is laminated thereon. Then, the vehicle (automobile) is driven with the heel of the foot 23 of the occupant sitting on the passenger seat side riding on the horizontal portion 11 and the toe side riding on the inclined portion 12. Although not shown, a similar vehicle lower limb impact absorbing pad is also attached to the floor on the driver's seat side. In this case, since an operating tool such as an accelerator pedal exists on the driver's seat side, the inclined portion 12 has a more limited area, or in some cases, only the horizontal portion 11.
[0019]
Assume that a collision occurs during driving. The kinetic energy generated by the collision is effectively absorbed by the vehicular lower limb impact absorbing pad 10, and it is possible to avoid the occupant's lower limb from being disturbed with a considerable probability. That is, the energy absorbing behavior of the vehicle lower limb impact absorbing pad 10 according to the present invention is schematically shown in FIG. 7A, and as shown in FIG. Like the foam pad, it absorbs a large amount of energy in a short time, and absorbs energy from a required load P lower than the obstacle value limit line K while advancing the strain without greatly increasing the load. Therefore, the required energy absorption amount a required to reduce the kinetic energy amount at the time of collision to a kinetic energy amount that does not impair the lower limbs of the occupant without increasing the thickness is changed to the obstacle value limit line K. , The impact force applied to the lower limb of the occupant can be effectively alleviated, and obstacles generated in the lower limb can be reduced. FIG. 7B schematically shows the variation of the “required load value P lower than the failure value limit line” when the ratio of the groove 13 to the entire back surface is different. When the ratio decreases, the load value P1 increases, and when the ratio increases, the load value P2 decreases. The optimum value may be selected according to the actual vehicle.
[0020]
【Example】
Next, the effectiveness of the vehicle lower limb impact absorbing pad 10 according to the present invention will be described with reference to examples. As a test piece 1, pre-expanded particles (beads) of a styrene-modified polystyrene resin were subjected to in-mold foam molding to produce an impact-absorbing pad having the shape shown in FIG. The expansion ratio is 30 times, and the dimensions are 100 mm wide × 100 mm long × 35 mm thick. The groove width of the groove 13 was 9 mm and the depth was 23 mm, and the ratio of the area of the groove 13 to the total area of the bottom surface was 50%.
[0021]
As shown in FIG. 4, a synthetic resin processed product 2 similar to a heel is attached to a compression tester, and the test piece 1 is attached to a fixing jig 3 at an angle (37 °) that is actually assumed in a vehicle. A compression test was performed to obtain a load-strain curve. The load was applied at a rate of 10 mm / min. In addition, the test piece 1 was configured so that the direction of the groove was a slope direction (a direction parallel to the paper surface in FIG. 4). The result is shown as a curve S1 in FIG. As a comparative example, a test piece having the same shape as that of the test piece 1 except for having no concave groove was formed under the same molding conditions. For that, a compression test was performed in the same manner as in Test Piece 1, and a load-strain curve was obtained. The result is shown as a curve S2 in FIG.
[0022]
As shown in FIG. 5, the comparative example product (having no groove) has an almost constant upward curve with an increase in the load and the magnitude of the strain, whereas the test piece 1 has a slope in the middle. Has an inflection point where the load becomes gentler, and thereafter, the amount of strain with respect to an increase in load is larger than before. This indicates that the test piece 1 can change the position of the inflection point and the amount of strain change with respect to the subsequent increase in the load by appropriately adjusting the size of the concave groove 13 and the ratio of the groove 13 to the bottom area. ing. That is, since the vehicle lower limb impact absorbing pad 10 according to the present invention has the concave grooves 13, the kinetic energy at the time of collision does not impair the lower limbs of the occupant without increasing the thickness. It is possible to absorb the amount of energy (energy amount a shown by oblique lines in FIG. 7A) required to reduce the energy to the amount of energy without exceeding a predetermined load value (failure value limit line K). This indicates that the impact force applied to the lower leg of the occupant can be effectively reduced.
[0023]
Next, as shown in FIG. 6A, a similar compression test was performed by changing the contact position of the synthetic resin processed product (heel) 2 with respect to the test piece 1 as shown in (1) to (3). A load-strain curve was obtained. The result is shown in FIG. As shown in FIG. 6B, the change in the load-strain curve is extremely small. This is presumed to be due to the fact that the direction of the groove 13 is formed in parallel at substantially equal intervals so that the direction of the groove 13 is the same as the front-rear direction of the vehicle, supporting the effectiveness of the present invention.
[0024]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the lower limb part impact absorption pad for vehicles which can absorb an impact more effectively without increasing thickness, and whose impact absorbing property does not vary with the place of a foot can be obtained. Thereby, the lower leg of the occupant at the time of the vehicle collision can be more effectively protected.
[Brief description of the drawings]
FIG. 1 is a back view of one embodiment of a vehicle lower limb impact absorbing pad according to the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 when the vehicle lower limb impact absorbing pad shown in FIG. 1 is attached to the vehicle.
FIG. 3 is a diagram illustrating a test piece used in the embodiment.
FIG. 4 is a diagram illustrating a state of a compression test in an example.
FIG. 5 is a diagram showing load-strain curves in an example and a comparative example.
6A and 6B are diagrams illustrating an example in which a compression test is performed in the same manner as in FIG. 4 with different heel positions, and FIG. 6A illustrates a different heel position, and FIG. ) Shows the load-strain curve for each case.
FIG. 7 is a schematic diagram for explaining a load-strain curve by the vehicle lower limb impact absorbing pad of the present invention in comparison with a load-strain curve of a conventional solid elastic body.
FIG. 8 is a conceptual diagram for explaining a difference in shock absorbing performance due to a difference in directionality of a groove.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Lower limb part shock absorbing pad for vehicles, 11 ... Horizontal part, 12 ... Inclined part, 13 ... Longitudinal groove, 21 ... Body, 23 ... Occupant's foot, 1 ... Test piece, 2 ... Synthetic resin similar to heel Processed product, 3 ... Fixing jig

Claims (4)

A vehicle lower limb impact absorbing pad on which an occupant's foot is placed, wherein the vehicle lower limb impact absorbing pad is made of a foamed molded product of thermoplastic resin beads, and is provided with a vehicle body side when installed in a vehicle. A lower limb impact absorbing pad for a vehicle, wherein a plurality of vertically long concave grooves are formed in the same surface in parallel with the front-rear direction of the vehicle at substantially equal intervals in parallel. The vehicle lower limb according to claim 1, wherein the vehicle lower limb impact absorbing pad has a horizontal portion and an inclined portion, and each of the horizontal portion and the inclined portion is formed with a vertically elongated groove. Part shock absorbing pad. The lower limb impact absorbing pad for a vehicle according to claim 1 or 2, wherein the width of the vertically long groove is 5 to 15 mm, and the width between the vertically long grooves is 8 to 20 mm. 4. The lower limb impact absorbing pad for a vehicle according to claim 1, wherein the thermoplastic resin is a styrene-modified polyethylene resin.

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