JP4963818B2 - Lower limb shock absorption pad for vehicle - Google Patents

Description

  The present invention relates to a vehicle shock absorbing pad for protecting a lower limb of an occupant at the time of a vehicle collision, and a vehicle capable of absorbing a shock more effectively even when the amount of shock absorption by a vehicle structure or the like is limited. The present invention relates to a lower limb shock absorbing pad.

  For example, Patent Documents 1 and 2 disclose inventions related to a vehicle shock absorbing pad for protecting a lower limb portion of an occupant during a vehicle collision. The shock absorbing pad (foot rest) disclosed in Patent Document 1 is formed from a solid foam made of polystyrene or the like, and this foot rest is arranged at the foot of a passenger in the vehicle compartment so that it can be used in the event of a vehicle collision. The foam is plastically deformed against the generated impact, and the occupant's legs are buried in the occupant's feet at the lowest possible speed, thereby protecting the lower limbs of the occupant.

  The foot rest of Patent Document 1 is made of a solid foam, but when such a solid foam is compressed, the impact absorption characteristics due to its plastic deformation are constant, so that the kinetic energy is effective. May not be absorbed. The lower limb shock absorbing pad disclosed in Patent Document 2 has been proposed to solve this problem, and is a vertically long recess extending in the vehicle front-rear direction on the surface that becomes the vehicle body side when the foam molded product is installed in the vehicle. The present invention relates to a foam molded product provided with a groove. A large amount of energy can be absorbed in a short time by plastic deformation of the concave groove at the time of a vehicle collision, and the impact load acting on the lower limbs of the occupant can be made less than the obstacle limit value.

Japanese Examined Patent Publication No. 6-17097 JP 2004-306791 A

  According to the vehicle impact absorbing pad of Patent Document 2, it is molded from a foam molded body, and the shape of the floor surface side is molded into a vertically long concave groove extending in the vehicle front-rear direction. , Extremely high shock absorbing performance can be obtained. Here, the shock absorbing performance is a performance of absorbing kinetic energy at the time of a vehicle collision by plastic deformation of the shock absorbing pad.

  By the way, when the vehicle impact absorbing pad is installed in a vehicle, it is subject to many restrictions due to the vehicle structure and the like. Taking the foot of the driver's seat as an example, the vehicle body is equipped with a device to which a brake pedal or accelerator pedal is connected on the right foot side, but there is no such device on the left foot side, so it is installed at the foot. Among the lower limb shock absorbing pads, the right foot side may be relatively thinner than the left foot side. In addition, the feet of the passenger seat are restricted by the piping mode of the duct mounted on the vehicle body.

  In the vehicle impact absorbing pad of Patent Documents 1 and 2, since the pad is made of a uniform hardness as a whole product, depending on the vehicle structure, there is a case where the impact absorbing performance is restricted and cannot be applied.

The vehicle lower limb shock absorbing pad of the present invention is made in view of the above-mentioned problems,
Since the shape (thickness) of the shock absorbing pad differs in plan due to constraints from the vehicle structure, we provide a vehicle lower limb shock absorbing pad that can absorb the shock more effectively even when the amount of shock absorption is limited. The purpose is to do.

  In order to achieve the above object, a vehicle lower limb shock absorbing pad according to the present invention is a vehicle lower limb shock absorbing pad on which an occupant's foot is placed, and the vehicle lower limb shock absorbing pad is planar. In a foam molded product in which regions of different hardness are formed using different raw materials.

  The thermoplastic resin for molding the lower limb impact absorbing pad is not particularly limited, and for example, a styrene-modified polyethylene resin, a polystyrene resin, a polyethylene resin, a polypropylene resin, or the like can be used. Above all, styrene-modified polyethylene resin bead foam molded products obtained by impregnating and polymerizing styrene monomers into polyethylene resin particles are foam molded products of polyethylene resin beads and polypropylene resin beads. In comparison, it is particularly preferred because of its superior dimensional stability and shape retention, and the fact that powder due to rubbing is less likely to occur as compared with foamed molded products of polystyrene-based 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, more preferably 55 to 75% by weight.

  In addition, the vehicle lower limb shock absorbing pad has a shape composed of a plurality of regions having different thicknesses, and has various forms depending on the vehicle type and the installation location (driver's seat side or passenger seat side). For example, in the pad installed at the foot of the driver's seat, the thickness is different in the left foot side and the right foot side, the thickness is different in the front-rear direction of the vehicle, and the thickness is different in the left and right and front and rear and so on. The form in which the thickness varies in the front-rear direction of the vehicle is to prevent the front of the pad from becoming a so-called bottom-down state when a concentrated load more than the weight of the occupant acts on the toes in a collision from the front or rear of the vehicle In addition, the density of the front portion of the pad is relatively higher than that of the rear portion.

  When molding the lower limb impact absorbing pad, a thermoplastic resin such as the above-mentioned styrene-modified polyethylene resin is impregnated with a foaming agent to form a foamable thermoplastic resin, and the foamable thermoplastic resin is heated. Prefoamed particles are produced by prefoaming with water vapor or the like. Then, the pre-expanded particles are filled in a mold and foam-molded. Here, the expansion ratio of the vehicle lower limb impact absorbing pad is preferably formed by pre-expanded particles adjusted within a range of, for example, 5 to 70 times. 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 becomes difficult to obtain a repulsive force as the foam.

  The lower limb impact absorbing pad of the present invention is a foamed molded product in which regions of different hardness are formed using different raw materials in the planar direction. By appropriately varying the hardness, an impact absorbing pad having a desired impact absorbing performance can be obtained at any part.

Here, the concept of the shock absorbing performance in this specification will be described with reference to FIG.
Generally, the load-strain curve of a product accompanied by plastic deformation is an upward curve. For example, in the case of a pad made of a hard raw material having a low foaming ratio, the load-strain curve is a straight line that rises to the right as schematically shown by line A in FIG. 8, and the pad absorbs impact energy. Therefore, the pad itself is not crushed, and therefore, the impact load is likely to exceed the obstacle value limit line K, that is, the limit value that impairs the lower limbs of the occupant. On the other hand, in the case of a pad made of a soft raw material with a high expansion ratio, the pad itself is crushed before absorbing the impact energy as shown by the line B in the figure, and therefore the impact load is crushed. There is a high possibility that it will rise rapidly later and exceed the limit value K that will cause damage to the lower limbs of the occupant.

  Therefore, in the initial stage of the vehicle collision, a large amount of impact energy can be absorbed in a short time like the load-strain curve of the foam having a low foaming ratio, and the load value P lower than the obstacle value limit value K By increasing the distortion of the foam itself instead of increasing the impact, it is possible to absorb the impact energy by the foam without damaging the lower limb (or reducing the impact on the lower limb within an allowable range). It is desirable that this is performed, and characteristics such as the C line in the figure are ideal. If the absorbed kinetic energy at the time of collision in the pad having the A-line characteristic is the E1 shaded portion in the figure, the pad having the C-line characteristic has the same area as the E1 shaded portion due to its plastic deformation performance. The E2 shaded portion can absorb the equivalent kinetic energy without exceeding the obstacle value limit value K. Such performance is the concept of shock absorbing performance referred to here.

  Another embodiment of the vehicle lower limb impact absorbing pad according to the present invention is characterized in that pre-expanded particles having different expansion ratios are used as different raw materials.

  As a method of forming a lower limb shock absorbing pad that is composed of a plurality of regions having different thicknesses and has equivalent shock absorbing performance as a whole product, a method of changing the foaming ratio of the raw material for each region having different thicknesses can be applied. For example, when the pad is composed of two regions having different thicknesses, the expansion ratio of the pre-expanded particles is manufactured in advance at different expansion ratios, and two types of pre-expanded particles are filled in the mold. It can be foam-molded. At this time, it is preferable to partition the inside of the mold cavity with a partition member, and simultaneously fill the left and right spaces of the partition member with the respective pre-expanded particles, and remove the partition member from the cavity after filling. A boundary region formed by both the foamed particles can be formed in a zigzag shape, and a pad that is difficult to be cut off in the boundary region can be formed.

  According to the lower limb impact absorbing pad of the present invention, the hardness of the pad can be varied in a variety of planes only by appropriately adjusting the expansion ratio of the pre-expanded particles of the same material. Even if it exists, it becomes possible to obtain the impact-absorbing pad provided with the desired impact-absorbing energy as the whole product.

  Another embodiment of the vehicle lower limb shock absorbing pad according to the present invention is characterized by using pre-expanded particles made of different materials as different materials.

  The different materials are, for example, that one pad is integrally formed from a plurality of types of raw materials among the styrene-modified polyethylene resin, polystyrene resin, polyethylene resin, and polypropylene resin described above.

  According to the lower limb impact absorption pad of the present invention, the expansion ratio of the pre-expanded particles of different materials can be adjusted to the same expansion ratio or different expansion ratios, so that the variation of different hardness regions can be further increased. In addition, it is possible to obtain an impact absorbing pad according to various restrictions depending on the vehicle structure.

  Furthermore, another embodiment of the vehicle lower limb impact absorbing pad according to the present invention is characterized in that a plurality of concave grooves are formed on a surface which is on the vehicle body side when installed in a vehicle.

  The shape of the groove formed on the vehicle body side surface of the lower limb impact absorbing pad is arbitrary, and the groove depth can be adjusted as appropriate. By forming a plurality of concave grooves in the surface of the pad on the vehicle body side, the surface of the vehicle body side is more easily crushed by impact load than the surface on the vehicle interior side due to the cross-sectional defect (plastic deformation). Easier to do). Therefore, it is preferable that the shape of the concave groove and the depth of the groove are adjusted so that the pad can move to the plastic deformation region before the obstacle value limit line K as described above. Of course, as disclosed in Patent Document 2, a plurality of vertically long concave grooves may be provided at substantially equal intervals.

  The other surface of the pad, that is, the surface on the vehicle interior side, is preferably formed into a flat surface or a smooth curved surface depending on the overall shape, and has a predetermined thickness. This thickness can be determined from the rigidity required of the pad, and is set so that after the pad exhibits the desired plastic deformation in the concave groove on the surface of the vehicle body, the entire pad can be expressed without compressing it. Is done.

  The lower limb shock absorbing pad of the present invention is provided with a concave groove of an arbitrary shape on the vehicle body side surface of the lower limb shock absorbing pad, in addition to varying the hardness in a plane according to the constraints of the vehicle structure. As a result, extremely high shock absorbing performance can be obtained.

  As can be understood from the above description, according to the lower limb impact absorbing pad for a vehicle of the present invention, by using pre-expanded particles having different expansion ratios or using pre-expanded particles having different materials, the hardness in the plane direction is increased. Thus, it is possible to obtain a pad in which different regions are formed. Therefore, even when there is a restriction due to the vehicle structure, it is possible to effectively absorb an impact at the time of a vehicle collision.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a vehicle illustrating a situation in which the pad of the present invention is installed in the vehicle interior, FIG. 2 is a perspective view of the vehicle interior of FIG. 1, and FIG. 3 is an embodiment of the pad of the present invention. It is the top view which showed the form, Comprising: The figure seen from the back surface (surface which becomes a vehicle body side at the time of installation) of a pad, FIG. 4 is the IV-IV arrow line view of FIG. 3, FIG. It is the top view which showed other embodiment of a pad, Comprising: The figure seen from the back surface (surface which becomes a vehicle body side at the time of installation) of a pad, FIG. 6 shows the VI-VI arrow line view of FIG. Yes. FIG. 7 is a graph illustrating the load-strain characteristics of the pad of the present invention, and is a graph compared with the load-strain characteristics of the comparative example. Needless to say, the pad (lower limb shock absorbing pad) of the present invention is not limited to the illustrated embodiment, and its overall shape and size are subject to restrictions from the vehicle type, vehicle body, and the like. The thickness and the like can be changed as appropriate.

  FIG. 1 shows a state in which the pad 1 of the present invention is installed at the foot portion (on the toe board) of the vehicle body in the compartment A1 of the vehicle A. The pads 1 are provided at the feet of the lower limbs of the driver seat and the passenger seat, respectively. The length of the pad 1 in the vehicle front-rear direction is a length that can accommodate at least the heel B1 to the toe B2, and the end of the pad 1 is connected to the end of the horizontal pad 2 installed on the lower surface of the vehicle interior. They are connected by bonding or fitting. In addition, although illustration is abbreviate | omitted, a floor carpet is laid on this pad 1 and the horizontal pad 2, and the pad 1 etc. cannot be visually recognized from a vehicle interior.

  FIG. 2 shows a situation where the pad 1 is installed at the foot on the passenger seat side. In the foot portion on the passenger seat side, the vehicle body side shape of the vehicle body is different between the left and right sides (X1 direction and X2 direction in the figure) due to the piping mode of the duct mounted on the vehicle body. Due to the difference in the body shape and the space in the vehicle interior, the thickness of the pad 1 is different between the left and right sides (X1 side and X2 side).

  3 is a view of the pad 1 shown in FIGS. 1 and 2 as seen from the back side (vehicle body side), and FIG. 4 is a view taken along arrows IV-IV in FIG. The pad 1 is provided with vertically long concave grooves 11 (longitudinal convex portions 12) extending in the same direction as the vehicle front-rear direction so as to be provided at equal intervals. By providing the concave grooves 11, 11,... (Convex portions 12, 12,...), The convex portions 12, 12,. It can be set as the pad which has a load-strain characteristic which does not give (refer later).

  As shown in FIGS. 3 and 4, the pad 1 is composed of two regions (1A region and 1B region) in which the thickness of the pad 1 is different on the left and right sides (X1 side and X2 side). In this case, the thickness is changed in accordance with the restrictions on the shape of the vehicle body and the space in the passenger compartment. Although the thickness of the pad 1 is different between t1 and t2, the pad 1 is required to have the same shock absorbing performance as the whole pad, and therefore the hardness is adjusted on the left and right sides of the pad. Here, the hardness is adjusted by changing the expansion ratio of the left and right pre-expanded particles constituting the pad 1, using pre-expanded particles of different materials, and further expanding ratio of the pre-expanded particles of different materials. Is changed for each part of the pad, and the 1B region having a relatively small thickness is adjusted to be harder than the 1A region.

  When both the left and right regions are molded with pre-expanded particles of styrene-modified polyethylene resin, the expansion ratio of the pre-expanded particles is set to 15 times in the region on the left foot side where the thickness is relatively thin (1B in FIG. 4). In the region on the right foot side (1A in FIG. 4), the preformed particles can be molded from a raw material with an expansion ratio of 30 times. In this case, the thicknesses t1 and t2 can be formed to about 50 mm and 30 mm, respectively.

  First, the pad 1 is formed by pre-expanded particles having different expansion ratios in advance. In the above embodiment, for example, the pre-expanded particles in the 1A region are produced at an expansion ratio of 30 times, the pre-expanded particles in the 1B region are produced at an expansion ratio of 15 times, and these two types of pre-expanded particles are molded. The pad 1 can be formed integrally. At this time, the inside of the cavity of the mold is partitioned by a partition member, and each pre-expanded particle is simultaneously filled in the left and right spaces of the partition member, and after filling, the partition member is removed from the cavity and then foamed by steam pressurization. The pad 1 can be formed by a method in which the particles are fused.

  FIG. 5 shows a pad 10 having different hardness in two regions (regions X1 and X2 in FIG. 5) divided in the longitudinal direction of the vehicle. The pad 10 is also provided with concave grooves 11, 11,... Extending in the front-rear direction of the vehicle on the back surface. FIG. 6 is a view taken in the direction of the arrow in FIG. 5, and the cross-sectional view has a substantially triangular shape corresponding to the shape of the vehicle body. The X1 side (10A region) in FIG. 6 is the toe side, and the X2 side (10B region) is the heel side. Here, it is desirable to adjust the hardness of the 10A region to be relatively hard with respect to the 10B region. In the case of a frontal or rearward collision of the vehicle, a load exceeding the weight of the occupant acts on the toes at the time of the collision, while the load hardly acts on the heel. Therefore, by changing the hardness of each part according to the load acting on the pad at the time of collision, the pad can exhibit a predetermined shock absorbing performance for each part.

[Example 1]
FIG. 7 is a graph showing the load-strain characteristics of one embodiment of the pad of the present invention together with a comparative example. This load-strain characteristic is obtained by an impact relaxation effect confirmation experiment based on “Dynamic compression test method for packaging buffer material” of JISZ0235. In this test, a test piece resembling the pad shown in FIGS. 3 and 4 is prepared, and the scissors jig is dropped from a predetermined height from the surface of the test piece. An accelerometer is attached to the jig, and a displacement meter is attached to the test piece to measure the amount of displacement when the jig is dropped, and the load applied to the test piece over time after the jig is dropped ( kN) and the displacement (mm) of the test piece.

Here, the two regions in the test piece simulating the pad 1 shown in FIGS. 3 and 4 are both formed from pre-expanded particles of a styrene-modified polyethylene resin. The 1A region is formed by 30 times pre-expanded particles, and the 1B region is formed by 15 times pre-expanded particles, respectively. The total weight of the pad is 230 g. In this example, both the load-strain characteristics of the 1A region and the 1B region are shown by the graph X. Note that the range between the graphs K1 and K2 is an allowable region that does not damage the lower limbs. For example, (F ₁ , S ₁ ) is changed to (1.5 kN, 5%), (F ₂ , S ₂ ). Can be set to (2.5 kN, 7%).

[Example 2]
5 and 6, for example, the front region 10 </ b> A and the rear region 10 </ b> B of the pad 10 are pre-expanded particles of polystyrene-modified polyethylene resin and polystyrene-based resin, which are different materials, respectively. Molded from expanded particles. Here, the pad 10 can be molded by setting the expansion ratio of the pre-expanded particles of the styrene-modified polyethylene resin to 15 times and the expansion ratio of the pre-expanded particles of the polystyrene resin to 30 times, and the total weight of the pad is 220 g.

[Comparative Example 1]
On the other hand, as Comparative Example 1, a pad is formed from pre-expanded particles in which the 1A region and 1B region both have an expansion ratio of 15 times. In this comparative example, the entire product is molded with a constant expansion ratio regardless of the difference in thickness. In this case, the shock absorbing performance is satisfied, but the weight of the entire pad is increased to 340 g.

[Comparative Example 2]
Further, as Comparative Example 2, the 1A region and the 1B region are both formed from pre-expanded particles having an expansion ratio of 30 times. In this case, the thin 1B region has the characteristics of the graph X, but the thick 1A region has the characteristics of the graph Y and cannot satisfy the shock absorbing performance. Note that the weight of the pad is 170 g.

  As is clear from the results of this analysis, the pad is desired for the entire product by adjusting the expansion ratio of the pre-expanded particles of the same or different resin for each part of the shock absorbing pad according to the vehicle structure. Thus, the possibility of causing damage to the left and right lower limbs at the time of a vehicle collision can be extremely reduced. Moreover, it becomes possible to reduce the weight of the entire product by excluding from the product an area that is excessively heavy due to the hardness being too thick.

  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 illustrated embodiment is composed of two different density regions before and after the pad, or right and left, but depending on the shape of the pad (change in thickness), the pad is composed of three or more different density regions. It may be.

The longitudinal cross-sectional view of the vehicle explaining the condition by which the pad of this invention was installed in the vehicle interior. The perspective view of the vehicle interior of FIG. It is the top view which showed one Embodiment of the pad of this invention, Comprising: The figure seen from the back surface (surface which becomes a vehicle body side at the time of installation) of a pad. IV-IV arrow line view of FIG. It is the top view which showed other embodiment of the pad of this invention, Comprising: The figure seen from the back surface (surface which becomes a vehicle body side at the time of installation) of a pad. VI-VI arrow line view of FIG. It is the graph explaining the load-strain characteristic which the pad of this invention has, Comprising: The graph compared with the load-strain characteristic of a comparative example. The graph explaining the load-strain characteristic of the pad which has the conventional pad and an ideal characteristic.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,10 ... Pad (lower limb part impact absorption pad), 1A, 1B ... Area | region where hardness differs 10A, 10B ... Area | region where hardness differs, 11 ... Concave groove, 2 ... Horizontal pad, A ... Vehicle, A1 ... Car Room, B1 ... 踵, B2 ... toe

Claims (4)

A vehicle lower limb shock absorbing pad on which an occupant's foot is placed,
The vehicle lower limb shock absorbing pad has a region having a different thickness in the plane direction, and a relatively thin region uses a heterogeneous raw material that is harder than a relatively thick region. A vehicular lower limb shock absorbing pad, which is formed of a foamed molded article having the same shock absorbing performance as a whole .   The vehicular lower limb impact absorption pad according to claim 1, wherein pre-expanded particles having different expansion ratios are used as different raw materials.   3. The vehicle leg impact absorbing pad according to claim 1, wherein pre-expanded particles made of different materials are used as different raw materials.   The lower limb impact absorbing pad for a vehicle according to any one of claims 1 to 3, wherein a plurality of concave grooves are formed on a surface on the vehicle body side when installed in a vehicle.

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