JP5073302B2 - Lower limb shock absorption pad - Google Patents

Description

  The present invention relates to an impact absorbing pad for a vehicle for protecting an occupant's lower limb from an impact generated at the time of a vehicle collision.

  As a vehicle shock absorbing pad for protecting the lower limbs of an occupant in the event of a vehicle collision, Patent Document 1 discloses that the top plate positioned indoors when installed in the vehicle and the entire back surface of the top plate are integrated. There is described a lower limb impact absorbing pad which is a foamed resin molded product including a plurality of vertically elongated ridges extending in a direction which is a longitudinal direction of the molded vehicle.

  The lower limb shock absorbing pad of the shape described in Patent Document 1 can absorb a lot of energy in a short time because the pad is mainly elastically deformed in the initial stage at the time of collision. From (the load value lower than the obstacle limit load value that gives damage to the lower limbs), the impact energy can be absorbed without greatly increasing the load by plastic deformation (breaking, etc.) of the elongated ridges. . Since such a load-strain curve can be obtained, it is possible to absorb the required energy generated during a collision within the range of the obstacle limit load value or less without increasing the overall thickness. It is possible to effectively relieve the impact force applied to the leg and greatly reduce the obstacles occurring in the lower limbs.

JP 2004-306791 A

  In recent years, various safety standards for vehicles such as automobiles have become more severe, and even in the field of vehicle lower limb shock absorbing pads, the maximum allowable load on the lower limb of an occupant during a collision is lower It tends to be lowered to the value. In addition, it is desired that the contents of the drop impact test for the lower limb shock absorbing pad be made more realistic, and as a result, a new technical problem is raised for the conventional lower limb shock absorbing pad. It can happen. In order to appropriately cope with such a demand, further technical improvement is required for the lower limb shock absorbing pad.

  The present invention has been made in view of the above circumstances, and even when the maximum allowable load applied to the lower limbs of an occupant at the time of a collision is set to a value lower than a conventional reference value, elastic deformation or destruction It is an object of the present invention to provide a more improved lower limb impact absorbing pad that can effectively absorb a required impact energy within a set reference value while proceeding plastic deformation accompanied with the above.

  In order to solve the above-mentioned problems, the present inventors, as a loader when performing a drop impact test on the lower limb shock absorbing pad, a loader having a shape conforming to the bottom surface of an actual shoe, that is, as shown in FIG. In addition, a loader 50 having a shape in which two loaders, a loader 51 corresponding to a toe part and a loader 52 corresponding to a heel part, are connected to each other by a connecting member 53 that connects the two loaders is used. A drop impact test was performed on the conventional lower limb impact absorbing pad 55 to obtain a load-strain curve. As a result, as shown by a curve Y3 in FIG. 10, in a conventional test method, that is, a drop impact test method in which the loader 51 and the loader 52 corresponding to the toe portion and the heel portion are dropped individually. In FIG. 10, the curve Y1 shows the result in the region where the loader 51 is dropped, and the curve Y2 shows the result in the region where the loader 52 is dropped. Experienced increasing load. If such a high load is applied to the lower limbs, there is a risk of causing damage to the lower limbs.

  As a cause of this, immediately after dropping, the loader 51 and the loader 52 are deformed into the lower limb shock absorbing pad within the allowable load in the process of entering (displaced) into the lower limb shock absorbing pad. The shock energy is absorbed while being raised. However, when the loader 50 is displaced by a predetermined amount, the connecting portion 53 comes into contact with the lower limb shock absorbing pad, and the impact load is further applied. It is presumed that the load received by 50 as a whole exceeded the allowable range and became a large value.

  It is possible to prevent such a high impact load from being generated in the loader 50 by making the entire lower limb shock absorbing pad soft. However, since it takes a long time to absorb the required impact energy and hinders safety, and it requires a thick lower limb shock absorbing pad, it is not a realistic solution.

  In the lower limb shock absorbing pad according to the present invention, in the region where the impact load is first applied at the time of collision in relation to the position of the lower limb portion of the occupant, the impact energy is mainly absorbed, and thereafter in the region where the impact load is applied. By adopting a shape that does not actively absorb impact energy, a realistic solution is given to the above problem.

  That is, the lower limb shock absorbing pad according to the present invention extends in a direction that becomes the front-rear direction of the vehicle, which is integrally formed on the back side of the top plate that is positioned indoors when installed in the vehicle. A lower limb impact absorbing pad, which is a foamed resin molded product comprising a plurality of substantially parallel elongated ridges, wherein the vertically elongated portion of the lower limb impact absorbing pad has a portion on the back side of the top plate. There is a region in which no ridge is formed.

  In the lower limb impact absorbing pad, the region having a plurality of vertically elongated ridges includes at least a region to which an impact load is first applied at the time of collision. And the area | region exhibits the main load support function, Absorption of impact energy advances effectively by mainly deforming and longitudinally deforming a plurality of vertically long ridges. Since a part of the area where the vertically long ridges are not formed on the back side of the top plate has essentially no load support function, a large load is applied to the lower limbs due to the area after the collision. It will not rise. By appropriately setting the area ratio of the plurality of vertically elongated ridges on the floor, the maximum load received by the lower limbs at the time of collision can be reduced to a predetermined value or less, and greatly exceeds that value even after the collision. An increase in the load on the lower limb can be avoided. Further, by appropriately setting the expansion ratio of the foamed resin molded product, it is possible to absorb a predetermined amount of impact energy within a predetermined time and within a predetermined displacement.

  In a specific aspect of the lower limb shock absorbing pad according to the present invention, the region where the vertically long ridges are not formed is a region where the toe side of the occupant's foot is located when installed in the vehicle. In this case, the region including the plurality of vertically long ridges includes at least a region where the occupant's heel is located. The impact force at the time of impact is initially applied to the foot or the heel part of the shoe, so that the vertically elongated protrusions cause plastic deformation of the elongated protrusions at a load value lower than the obstacle limit load value at which the lower limbs are damaged. Design the strip. After a certain period of time, the area that is dented between the shoe heel and the toes hits the top plate of the lower limb shock absorbing pad, but there is a vertically elongated ridge formed on the back side of the area. No large impact load exceeding the obstacle limit load value is applied to the lower limbs.

  In still another specific aspect of the lower limb shock absorbing pad according to the present invention, a second ridge in a direction intersecting with the vertically elongated ridge is partially formed in a region where the vertically elongated ridge is not formed. It is formed, or a third ridge in the same direction as the vertically elongated ridge is partially formed. In the lower limb shock absorbing pad according to the present invention, there are a region where a vertically long ridge is formed on the back surface and a region where the long ridge is not formed, and in the non-formed region, there is a cavity between the top plate and the vehicle frame. Arise. Depending on the physical properties of the resin material that forms the lower limb impact absorbing pad, a dent may occur when the occupant steps into the area during normal driving. Such dents do not interfere with the driving of the vehicle, but may deteriorate indoor comfortability. Said 2nd protrusion and 3rd protrusion function as a support | pillar with respect to a dent, and avoid this inconvenience.

  In still another specific aspect of the lower limb shock absorbing pad according to the present invention, the region where the second ridge or the third ridge is formed is the root of the occupant's toe when installed in the vehicle. The region is a region where the portion is to be located and its vicinity. In a normal case, the shoe sole is in contact with the heel portion and the portion where the base portion of the toe is located, and the other portion is in a floating state. Accordingly, in the natural state, the shoe sole of the occupant is in a state in which the above-described heel portion and the base portion of the toe are in contact with the lower limb shock absorbing pad, and at the time of collision, the heel portion is first impacted. However, depending on how the foot is placed and how force is applied, it is conceivable that the first impact load is also applied in the vicinity of the region where the base of the toe is located. In such a case, the second ridge or the third ridge can function as a shock absorber by forming the second ridge or the third ridge at the above-described position. Can do. In this case, when the contact area of the second protrusion or the third protrusion is increased, the load resistance as the whole lower limb shock absorbing pad is increased, the shock absorbing power is reduced, and the obstacle limit load value is exceeded. It can happen that the load is applied to the lower limbs and damages the lower limbs. In order to avoid this, when providing the 2nd ridge or the 3rd, it is recommended to reduce the ground contact area of the vertically long ridge in the region where the buttock is located depending on the area. Is done.

  Many things can be used for the resin material which forms the leg absorption pad of the present invention. A thermoplastic resin is preferable, and a styrene-modified polyethylene resin, a polyethylene resin, and a polypropylene resin are more preferable. Among them, foamed resin molded products made of styrene-modified polyethylene resin obtained by impregnating and polymerizing polyethylene resin particles with styrene monomer are foamed resin molded products of polyethylene resin beads and foamed polypropylene resin beads. It is particularly preferable because it is excellent in dimensional stability and shape retention compared to a resin molded product, and is less likely to generate powder due to rubbing than a foamed resin molded product 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.

  In molding, a styrene-modified polyethylene resin is impregnated with a foaming agent in a dry or wet manner to form a foamable styrene-modified polyethylene resin, and the foamable styrene-modified polyethylene resin is pre-foamed with heated steam or the like. Next, pre-expanded particles of the expandable styrene-modified polyethylene resin are filled in a mold, and foam molding (in-bead mold foam molding) may be performed by a conventional method.

  The expansion ratio of the lower limb impact absorbing pad according to the present invention is 10 to 50 times, preferably 15 to 30 times. When the expansion ratio is less than 10 times, it may be too hard to effectively absorb the impact caused by the collision. Those exceeding 50 times are too soft and are not preferable because they may become bottomed out before the necessary amount of energy is absorbed.

  According to the present invention, even when the maximum allowable load applied to the occupant's lower limb at the time of a collision is set to a value lower than the conventional reference value, the setting is performed while advancing plastic deformation accompanied by elastic deformation or fracture. Thus, a more improved lower limb impact absorbing pad can be obtained that can effectively absorb the required impact energy within the reference value.

  Hereinafter, the present invention will be described with reference to embodiments. FIG. 1 is a view of a first embodiment of a lower limb shock absorbing pad according to the present invention as viewed from the back side, and FIG. 2 is a view of a second embodiment of a lower limb shock absorption pad according to the present invention as viewed from the back side. FIG. 3 is a view of a third embodiment of the lower limb shock absorbing pad according to the present invention as seen from the back side. FIG. 4 schematically shows a state in which an occupant's foot is on the lower limb impact absorbing pad of the third embodiment.

  The lower extremity impact absorbing pad 10A of the first embodiment shown in FIG. 1 has an expansion ratio of 30 times obtained by filling pre-expanded particles (beads) of styrene-modified polyethylene resin into a mold and performing in-mold foam molding. It is a foamed resin molded product and has a rectangular shape as a whole. The lower limb shock absorbing pad 10A includes a top plate 11 located on the indoor side when installed in a vehicle, and a plurality of substantially parallel (in the illustrated case) integrally formed on the back side of the top plate 11. 5) vertically elongated ridges 12 and side walls 13. The vertically elongated ridges 12 are arranged in a direction that is the front-rear direction of the vehicle when the lower-limb impact absorbing pad 10A is installed in the vehicle. Are formed in parallel at substantially equal intervals. The side wall 13 is provided so that the lower limb shock absorbing pad 10A can be installed in a stable posture in the vehicle, and may be omitted entirely or partially depending on the shape of the vehicle body. When formed, the side wall 13 also functions to absorb impact energy in the same manner as the vertically elongated protrusion 12.

  In the lower limb impact absorbing pad 10A, the vertically long ridge 12 is formed to extend from one end of the top plate 11 to a distance of about ¼ to ½ of the total length, and then Is not formed. That is, in the illustrated example, a hollow region 14 is formed between the tip end of the vertically elongated ridge 12 and the other end of the top plate 11 where the vertically elongated ridge 12 is not formed. When the lower limb shock absorbing pad 10A is installed in the vehicle, the region where the vertically elongated ridges 12 are formed becomes the region where the occupant's heel rides, and the hollow region 14 where the vertically elongated ridges 12 are not formed is the toes. This is the area where the side rides.

  The overall shape and dimensions of the lower limb shock absorbing pad 10A are appropriately set according to the conditions on the vehicle side where the pad is used and the required shock absorbing capacity. As an example, the overall height a is 50 mm, the thickness b of the top plate 11 is 8 mm, the length c of the vertically elongated ridge 12 is 70 mm, the thickness d of the vertically elongated ridge 12 is 7 mm, and the vertically elongated ridge 12. The pitch e is about 25 mm.

  A lower limb shock absorbing pad 10B of the second form shown in FIG. 2 is provided in the hollow region 14 where the vertically long ridges 12 are not formed in the lower limb shock absorbing pad 10A of the first form. The configuration is different from that of the lower limb shock absorbing pad 10A in that the second ridge 15 in the direction orthogonal to the ridge 12 is formed. Other configurations are the same as those of the lower limb shock absorbing pad 10A, and the same reference numerals are given and description thereof is omitted. The width (thickness) of the second protrusion 15 is not limited, but is about 7 mm in this example. This 2nd protrusion 15 is formed in the area | region where the toe side of a passenger | crew's foot | leg will be located, when the lower limb part impact absorption pad 10B is installed in a vehicle.

  A lower limb impact absorbing pad 10C of the third form shown in FIG. 3 has the longitudinally elongated area 14 in the hollow area 14 where the vertically elongated protrusions 12 are not formed in the lower limb impact absorbing pad 10A of the first form. The configuration is different from that of the lower limb impact absorbing pad 10A in that a third ridge 16 in the same direction as the ridge 12 is formed. Other configurations are the same as those of the lower limb shock absorbing pad 10A, and the same reference numerals are given here and the description thereof is omitted. Although the formation position of the third protrusion 16 is not limited, it is preferably formed so as to include a region where the toe side of the occupant's foot is located when the lower limb shock absorbing pad 10C is installed in the vehicle. . There are no particular restrictions on the number or size of the third protrusions 16, but in the illustrated example, five third protrusions having a width (thickness) of 7 mm and a length of 60 mm on the extension line of each vertically elongated protrusion 12. A protrusion 16 is formed.

  The lower limb shock absorbing pad 10 described above is installed in the vehicle at a place where a foot of an occupant sitting in a driver seat or a passenger seat is placed. FIG. 4 shows a state in which the lower limb shock absorbing pad 10C shown in FIG. 3 is installed in the vehicle as an example, and the lower limb shock absorbing pad 10C is placed at an appropriate position of the vehicle body 20 with the top plate 11 as an indoor side. A suitable floor spacer 21 for raising is disposed behind the lower limb impact absorbing pad 10C. Although not shown, an appropriate floor carpet is laminated thereon. The floor spacer 21 is not necessarily required depending on the shape of the vehicle body. However, if the floor spacer 21 is required, it can be integrally formed with the lower limb impact absorbing pad 10C.

  As shown in FIG. 4, in the state where the lower limb shock absorbing pad 10 </ b> C is installed in the vehicle, the shoe 25 worn by the occupant is in the region where the elongated protrusion 12 of the lower limb shock absorbing pad 10 </ b> C is formed. In the region where the heel portion 26 is placed and the third protrusion 16 is formed, the vicinity of the base portion of the toe of the shoe sole, which is the toe portion 27, mainly rides.

  Suppose a collision occurs while driving. The kinetic energy generated by the collision is effectively absorbed by the lower limb shock absorbing pad 10C, and it is possible to avoid the obstacle of the occupant's lower limb with a considerable probability. In other words, the impact force at the time of collision is mainly that elastic deformation or plastic deformation occurs mainly in a region where the vertically long ridges 12 are formed and in a region where a part of the third ridges 16 is formed. To avoid being damaged and damaging the lower limbs of the occupant. Thereafter, when the lower limb shock absorbing pad 10C is deformed, a region 28 that is dented between the heel portion 26 and the toe portion 27 of the shoe 25 comes into contact with the top plate 11 of the lower limb shock absorbing pad 10C. Since neither the vertically elongated ridge 12 nor the third ridge 16 is formed on the back surface side of the region, the obstacle limit load value is obtained when the recessed region 28 comes into contact with the top plate 11. It is possible to avoid a large impact load exceeding the upper limb of the occupant.

  Although not particularly illustrated, the above (that is, when the recessed area 28 hits the top plate 11, a large impact load exceeding the obstacle limit load value is not applied to the occupant's lower limb). The lower limb shock absorbing pad 10A shown in FIG. 1 and the lower limb shock absorbing pad 10B shown in FIG.

  Next, effectiveness of the lower limb shock absorbing pad according to the present invention will be described with reference to Examples and Comparative Examples.

[Example]
For the test, a lower limb impact absorbing pad 10C having a shape shown in FIG. 3 obtained by in-mold foam molding of pre-expanded particles (beads) of a styrene-modified polystyrene resin was used. The expansion ratio of the lower limb shock absorbing pad 10C is 30 times, and the dimensions are as shown in FIG. 6, the overall height a: 50 mm, the top plate 11 thickness b: 8 mm, and the length of the vertically elongated ridges 12. c: 70 mm, width (thickness) of the vertically elongated ridges 12 and the third elongated ridges d: 7 mm, pitch e between the elongated ridges 12 and the third elongated ridges 16: 25 mm, and the elongated elongated ridges 12 The distance f from the third protrusion 16 is 100 mm, the length g of the third protrusion 16 is 60 mm, the overall length h is 250 mm, and the width (thickness) i of the side wall 13 is 7 mm. .

As shown in FIG. 5, the lower limb impact absorbing pad 10C is fixed on the fixing jig 54, and the load element 50 described above based on FIG. 9 is dropped from a 700 cm height drop tester, thereby JISZ0235. Was subjected to a drop impact test in accordance with “Dynamic compression test method for packaging cushioning material” to obtain a load-strain curve. The total weight of the loader 50 is 15 kg, of which the weight of the loader 51 corresponding to the toe part is 6 kg, the weight of the loader 52 corresponding to the buttocks is 6 kg, and the weight of the connecting member 53 is 3 kg. . The bottom area of the loader 51 was 100 cm ² , the bottom area of the loader 52 was 100 cm ² , and the length of the connecting member 53 was 10 cm.

  An accelerometer is attached to the loader 50, and a displacement meter for measuring the amount of displacement due to the drop of the loader 50 is attached to the lower limb shock absorbing pad 10C. The shock absorbing pad 10C load (kN) and the displacement (mm) of the lower limb shock absorbing pad 10C were obtained, and the strain (displacement) was calculated. The obtained load-strain curve is shown as curve A in the graph of FIG. In the graph of FIG. 8, the load-strain curve R is a load-strain curve currently required for the lower limb shock absorbing pad, and the energy absorption amount at the initial stage of the collision is large, that is, the curve rises sharply. From then on, it is required to be able to absorb a lot of impact energy at a load that does not exceed 2 kN, which is a lower value than before.

  The slope of the initial rise in the load-strain curve A of the lower limb shock absorbing pad 10C according to the present invention is a steep slope that approximates the required load-strain curve R, and before the bottoming occurs. It can be seen that a lot of impact energy can be absorbed in a state where the maximum load is less than 2 kN.

[Comparative Example 1]
As a test piece, a lower limb impact absorbing pad 10D having the shape shown in FIG. 7 was used. This lower limb shock absorbing pad 10D is different from the lower limb shock absorbing pad 10C used in the embodiment only in that the vertically long ridges 12 are formed on the entire back surface of the top plate 11 in the longitudinal direction. Yes. That is, except for the point that the length of the vertically elongated protrusion 12 is 250 mm, the other dimensions are the same as those of the lower limb impact absorbing pad 10C shown in FIG. A drop impact test was performed on the lower limb impact absorbing pad 10D under the same conditions as the lower limb impact absorbing pad 10C to obtain a load-strain curve. The obtained load-strain curve is shown as curve B in the graph of FIG.

  The inclination of the initial rise in the load-strain curve B of the lower limb shock absorption pad 10D which is the comparative example 1 is a steep inclination approximated to the required load-strain curve R, and the initial impact energy absorption amount Can be satisfied, but the maximum load increases to nearly 4 kN, and does not satisfy the condition of the load-strain curve R required for the lower limb shock absorbing pad. The reason for this is understood to be that the vertically elongated ridges 12 are formed on the back side of the top plate 11 over the entire longitudinal direction.

[Comparative Example 2]
The test piece has the same shape as the lower limb impact absorbing pad 10D shown in FIG. 7, but the pitch e of the vertically elongated ridges 12 is 50 mm and the total ground contact area of the vertically elongated ridges 12 is reduced. Then, a drop impact test was performed under the same conditions as the lower limb impact absorbing pad 10C to obtain a load-strain curve. The obtained load-strain curve is shown as curve C in the graph of FIG.

  As shown by the load-strain curve C of the lower limb shock absorbing pad as Comparative Example 2, the maximum load in the shock energy absorbing process can be reduced to 2 kN or less by reducing the number of the vertically long ridges 12. However, the slope of the initial rise is smaller than the slope of the required load-strain curve R, and does not satisfy the condition of the load-strain curve R required for the lower limb shock absorbing pad.

[Discussion]
From the results of the drop impact test of Example and Comparative Examples 1 and 2, the impact absorption performance (a steep rise at the beginning of impact energy absorption and a low maximum load) currently required for the lower limb impact absorption pad is satisfied. For this purpose, in the form in which the vertically elongated ridges are formed over the entire length of the back surface side of the top plate 11, only by reducing the number of the vertically elongated ridges (that is, by reducing the ground contact area of the vertically elongated ridges). It turns out that it is not sufficient and it is necessary to form the area | region in which the vertical elongate protrusion 12 is not formed in a part of the back surface side of the top plate in a leg extremity absorption pad.

The figure which looked at the 1st form of the leg shock absorption pad by the present invention from the back side. The figure which looked at the 2nd form of the leg shock absorption pad by the present invention from the back side. The figure which looked at the 3rd form of the leg shock absorption pad by the present invention from the back side. The figure which shows typically the state in which a passenger | crew's leg has got on the lower limb part impact absorption pad of a 3rd form. The figure explaining the outline | summary of the drop impact test in an Example. The figure for demonstrating the shape and dimension of the leg extremity impact-absorbing pad used in the Example. The figure for demonstrating the leg absorption pad used in the drop impact test in the comparative example 1. FIG. The graph which shows the load-strain curve in an Example and a comparative example. The figure for demonstrating the one aspect | mode of a drop impact test. The graph for demonstrating that a different load-strain curve is obtained by the test content of a drop impact test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10A-10C ... Lower limb part impact-absorbing pad by this invention, 11 ... Top plate, 12 ... Longitudinal ridge, 14 ... Area | region where the vertically long ridge is not formed, 25 ... Shoes, 26 ... Buttocks, 27 ... Toe , 28 ... Area recessed between the heel part and the toe part of the shoe, 50 ... Load element, 51 ... Load element corresponding to the toe part, 52 ... Load element corresponding to the heel part, 53 ... 2 Connecting member connecting two load elements

Claims (4)

A top plate positioned indoors when installed in a vehicle, and a plurality of substantially parallel elongated protrusions extending in the front-rear direction of the vehicle integrally formed on the back side of the top plate. A lower limb shock absorbing pad which is a foamed resin molded product comprising:
The vertically long ridge is integrally formed on the back surface side of the top plate in a state of being connected only to the back surface of the top plate, and the vertically long shape is formed on a part of the back surface side of the top plate in the lower limb shock absorbing pad. A region where no ridge is formed, and the region where the vertically long ridge is not formed is a region where a toe side of an occupant's foot is located when installed in a vehicle. Shock absorption pad. Wherein the vertically elongated protrusion is not formed region, leg portion of claim 1 in which the second protrusion in a direction intersecting the vertically elongated ridge is characterized in that it is formed in a part Shock absorbing pad. Wherein the vertically elongated protrusion is not formed region, leg portion shocks according to claim 1, the third protrusion of the vertically elongated protrusion in the same direction, characterized in that it is formed in a part Absorption pad. The area where the second protrusion or the third protrusion is formed is an area where a base portion of a toe of an occupant is located when it is installed in a vehicle and its vicinity. The lower limb part impact-absorbing pad according to claim 2 or 3 .

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