JP4359177B2 - Lower limb shock absorbing pad for vehicles with soundproofing - 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 in particular, can absorb a shock more effectively without increasing the thickness, and improve soundproof performance in an automobile interior. The present invention relates to a shock absorbing pad for a lower limb portion for a vehicle, which is provided with soundproofing that enables the above.

  Regarding the structure for protecting the lower limbs of an occupant in the event of a vehicle collision, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2003-127796), it is made of hard foamed plastic, the indoor side is formed into a flat surface, and the floor side Proposed a shock-absorbing automotive floor spacer (shock-absorbing pad) that has a honeycomb structure, slit structure, or protruding structure, and a structure in which the installation area on the floor surface when laid is 10% or more and 60% or less. ing. The shock absorbing pad having this configuration synergizes with the shock absorbing effect of the rigid foamed plastic itself and the structure of the honeycomb or the like, and exhibits high shock absorbing performance.

Further, in addition to the function as an impact relaxation material, Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-25361) is formed by heating and foaming as a material for an automobile floor raising material that is excellent in sound insulation and sound absorption. There has been proposed a perforated foamed plastic, characterized in that a through-hole having an area of about 5 mm ² is opened with an open area ratio of 3% or more.

Japanese Patent Laid-Open No. 2003-127796 JP 2003-25361 A

  As a vehicle lower limb shock absorbing pad, the shock absorbing pad having the structure described in Patent Document 1 can be expected to absorb the shock more effectively without increasing the thickness. However, now that the demand for quietness in the automobile interior is increasing, the lower limb impact absorption pad for vehicles is also required to have sound absorption and sound insulation in addition to shock absorption, In the automobile floor spacer described in Patent Document 1, no consideration is given to this point.

Perforated plastic foam described in Patent Document 2, although a certain degree also impact absorption effect because it is foamed plastic with improved sound absorbing property can be expected, the cross-sectional area of the hole as small as about ² 5 mm, essentially platy Because it is a foamed plastic, when it is used as a shock absorbing pad for the lower limbs of a vehicle, it cannot be expected to exceed the impact absorbing effect of the foamed plastic itself, ensuring sufficient safety for passengers It is difficult.

  The present invention has been made in view of the circumstances as described above, and can effectively absorb an impact without increasing the thickness, and is also effective in soundproof performance (both sound absorption and sound insulation properties or both) in an automobile interior. It is an object of the present invention to provide a vehicle lower limb shock absorbing pad that is improved in sound quality and is provided with soundproofing.

  The vehicle lower limb impact absorbing pad provided with soundproofing according to the present invention is a vehicle lower limb impact absorbing pad on which an occupant's foot is placed, and includes at least a foamed molded product of thermoplastic resin beads. The longitudinally long through-holes have a pad main body formed in parallel at substantially equal intervals (Claim 1).

  The above-mentioned vehicle lower limb shock absorbing pad has a vertically long through-hole formed in the pad body in parallel at substantially equal intervals, so that the impact is not increased as compared with a flat shock absorbing pad. It can be absorbed more effectively and the sound absorption is improved. Further, in the experiments by the present inventors, the shock absorption characteristics are greatly improved even when the through holes have the same aperture ratio as compared with a case where a large number of cylindrical through holes having a small diameter are simply formed. The reason for this is that when subjected to an impact, a plurality of vertically long legs (portions formed between the through holes) are easily broken or crushed so that the pad body is effective. It is thought that this is because it sinks downward and deforms.

  In the above-mentioned vehicle lower limb impact absorbing pad, the thermoplastic resin for molding the pad body includes polystyrene resin, polyolefin resin (for example, polypropylene resin, polyethylene resin), polyester resin (for example, polyethylene terephthalate). , Polybutylene terephthalate, polyethylene naphthalate), polycarbonate resin, and the like.

  Among these, it is preferable to use foamed beads of a styrene-modified polyolefin resin obtained by impregnating and polymerizing a polyolefin-based resin particle with a styrene monomer, particularly a styrene-modified polyethylene resin. The reason for this is that the molded product of the styrene-modified polyolefin resin is superior in dimensional stability and shape retention compared to the polypropylene resin and polyethylene resin, and is less likely to generate dust due to rubbing than the polystyrene resin. In addition, the expansion molding of polyethylene resin beads and polypropylene resin beads has a large dimensional shrinkage ratio, and it is difficult to obtain dimensional accuracy compared to the foam molding of styrene modified polyolefin resin beads. This is because the power is small.

  When the styrene-modified polyolefin resin is used, the proportion of the styrene component is 40 to 90% by weight, preferably 50 to 85% by weight, and more preferably 55 to 75% by weight. If the proportion of the styrene component is less than 40% by weight, the molded pad body has a disadvantage that the material strength is considerably reduced and sufficient impact absorption cannot be obtained. Similarly, there are inconveniences such as generation of powder due to rubbing and generation of rubbing noise with the body (body panel) of an automobile.

  The styrene-modified polyolefin resin is impregnated with a foaming agent by a dry method or a wet method to form a foamable styrene-modified polyolefin resin, which is then pre-foamed with heated steam, etc. to form thermoplastic resin beads By filling the mold and supplying heated steam, the vehicle lower limb impact absorbing pad (pad body) according to the present invention is obtained. The expansion ratio is 10 to 50 times, preferably 20 to 40 times. If it is less than 10 times, the pad body to be molded has a disadvantage that it is too strong as an impact absorbing material, and those exceeding 40 times have low strength. There is a disadvantage that sufficient shock absorbing performance cannot be obtained. Butane, propane or the like can be used as the blowing agent.

  In order to obtain a desired shock absorbing performance, in the experiments conducted by the present inventors, the vertically long through hole formed in the pad body has a width of about 5 to 15 mm and is formed between adjacent through holes. It turned out that it is desirable for the width | variety of a leg shape to be about 8-20 mm.

  In another form of the vehicle lower limb impact absorbing pad provided with soundproofing according to the present invention, a sound insulating sheet is laminated on one surface of the pad main body. In the vehicle lower limb shock absorbing pad of this form, the pad main body having a through hole is positioned between the sound insulating sheet and the vehicle body panel by attaching the sound insulating sheet side to the vehicle body panel (iron plate of the vehicle body) with the sound insulating sheet side being the indoor side. A hollow double wall structure will be formed, and the sound insulation effect with respect to the sound from the outside of a vehicle will improve. As shown in a later embodiment, an effective sound insulation effect can be obtained particularly in a high frequency region. Further, by arranging the sound insulation sheet on the pad main body, there is an effect that the impact load from the heel of the passenger in the driver's seat or the auxiliary seat can be distributed over the entire surface of the pad main body.

  Sound insulation sheets include natural rubber, synthetic rubber (eg, butyl rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, chloroprene rubber, acrylic rubber, acrylonitrile butadiene rubber, etc.), synthetic resin (eg, polyester resin, Sheet made of polyethylene resin, polypropylene resin, ethylene vinyl acetate resin, SIS, SBS, EPDM, etc.), bitumen, etc., talc, clay, mica, mica, sulfuric acid Examples thereof include a sheet in which barium, calcium carbonate, waste paper defibrated material, slug wool, silica balloon or the like is added as one or more fillers. In addition, recycled rubber and recycled resin can be used alone or mixed with other materials as appropriate. Among these, a polypropylene resin sheet mixed with barium sulfate or calcium carbonate as a filler is particularly effective.

  A carpet having no air permeability may be further laminated on the upper surface of the sound insulating sheet. By laminating carpets that do not have air permeability, the sound insulation can be further improved, and the softness of the carpet provides improved cushioning and better treading comfort. The carpet having no air permeability is not particularly limited, and examples thereof include polyester resins, thermoplastic elastomers, vinyl chloride resins, polystyrene resins, polyethylene resins, polypropylene resins and the like. A non-breathable synthetic resin layer may be laminated on one side or both sides of a carpet having air permeability described later.

  In another form of the vehicle lower limb impact absorbing pad according to the present invention, the sound absorbing material is laminated on one surface of the pad main body. By disposing the vehicle lower limb shock absorbing pad in this form in the vehicle with the sound absorbing material on the indoor side and the pad main body on the vehicle body panel side, the sound absorbing property in the vehicle is greatly improved. The reason why the sound absorbing property is improved is that the back air layer region is formed behind the sound absorbing material by the vertically long through holes formed in the pad main body, thereby improving the sound absorbing property in the middle and low frequency region. The reason why the sound absorption is improved by forming the rear air layer region is that the energy of the sound wave reflected on the vehicle body panel is the highest because the distance from the vehicle body panel corresponds to a quarter of the wavelength of the sound. It is effective to place the sound-absorbing material at a position where the sonic energy is high. With this type of shock absorbing pad, the position of the sound-absorbing material is reflected by the thickness of the pad body from the vehicle body panel that is the reflective surface. That is, the sound absorbing material is moved closer to a position where the energy of the sound wave to be absorbed is high. Furthermore, the presence of the rear air layer region lowers the acoustic spring constant, which improves the sound insulation performance. Although depending on the material of the sound-absorbing material, the sound-absorbing layer laminated on the pad body also has the effect of dispersing the impact load from the heel over the entire surface of the pad body.

  In addition, although there is no restriction | limiting in particular in a sound absorption material, What is generally used in the field | area of a motor vehicle can be used suitably. Specifically, recycled materials (for example, crushed products of urethane, cotton, chemical fibers, etc.) such as felt (for example, cotton, chemical fibers, etc., which are solidified with PET), polyurethane foam, nonwoven fabric, etc. Can be enumerated with PET resin, defibrated fibers, fiber materials made of animals and plants, glass wool, asphalt foam, and the like.

  In the vehicle lower limb impact absorbing pad, a carpet having air permeability may be further laminated on the upper surface (inside the room) of the sound absorbing material. In the experiments by the present inventors, the sound absorbing property in the room was further improved by further laminating the air permeable carpet. In addition, as a carpet which has air permeability, a tufted carpet, a needle punch carpet, a Wilton carpet, an akismin star carpet, a step, a hook drag, a nonwoven fabric, etc. are mentioned. Examples of the carpet material include natural fibers such as wool, hemp and cotton, and synthetic resin fibers such as polyamide resin fibers, polyester resin fibers, polyacrylic resin fibers, and polypropylene resin fibers. Among these, tufted carpets and needle punch carpets using polyester resin fibers and polyamide resin fibers are preferable.

  In another form of the vehicle lower limb shock absorbing pad provided with soundproofing according to the present invention, a sound absorbing material is laminated on one surface of the pad main body, and further, foam molding of a thermoplastic resin bead having air permeability is formed thereon. The products are stacked (claim 6). The foamed molded product of thermoplastic resin beads to be laminated eliminates the instability of the scaffold due to the softness of the sound absorbing material, gives a good feeling of stepping, and is hollow by using a material with lower air permeability than the sound absorbing material. A double wall structure can be formed to improve sound insulation performance in addition to sound absorption. An air permeable carpet may be further laminated on the upper surface of the air permeable foam molded article (Claim 7), and a more stable feeling of stepping can be obtained.

  In the vehicle lower limb shock absorbing pad provided with soundproofing according to the present invention, it is recommended that the through hole of the pad main body be formed so that the longitudinal direction is the same as the longitudinal direction of the vehicle. As a result, it has been shown through experiments that, even if the occupant's heel in the driver's seat or auxiliary seat is in any position on the vehicle's lower limb shock absorption pad, the shock absorption characteristics do not vary, and equal shock absorption can be obtained. It was confirmed.

  According to the present invention, the impact can be effectively absorbed without increasing the thickness, and the soundproofing performance (both or both of the sound absorbing property and the sound insulating property) in the automobile room is also effectively improved. It is possible to obtain a vehicle lower limb shock absorbing pad with soundproofing. Accordingly, it is possible to more effectively protect the lower limbs of the occupant at the time of a vehicle collision, and it is possible to maintain high indoor noise reduction during normal driving.

  Hereinafter, the present invention will be described with reference to embodiments. FIG. 1A is a view of one form of a vehicle lower limb shock absorbing pad provided with soundproofing according to the present invention as seen from the back side, and FIG. 1B is a line bb in FIG. 1A. FIG. 1C is a schematic view taken along the line cc in FIG. 1A showing a part thereof enlarged. FIG. 2 schematically shows a state in which the vehicle lower limb shock absorbing pad is attached to the vehicle.

  In this example, the vehicle lower limb impact absorbing pad A shown in FIG. 1 is obtained by filling pre-expanded beads (particles) of styrene-modified polyethylene resin in a molding die and heating with steam to obtain an expansion ratio of 20 to 40. The pad main body 10 is a double foam molded product, the sound insulating sheet 15 is laminated on the indoor side, and the non-breathable carpet 30 is further laminated thereon. In addition, the non-breathable carpet 30 can be omitted, and when the purpose is mainly shock absorption, the pad main body 10 alone can be used as the vehicle lower limb shock absorbing pad A.

  The pad main body 10 has a thickness of about 20 to 40 mm, has a horizontal portion 11 and an inclined portion 12, and the entire surface of the horizontal portion 11 and the inclined portion 12 is in the same direction as the longitudinal direction of the vehicle. A plurality of vertically long through holes 13 are formed in parallel at substantially equal intervals. The vertically long through-hole 13 functions not only as a shock absorbing function but also as a back air layer. The width is about 5 to 15 mm, and the width between adjacent vertically long through-holes is about 8 to 20 mm. It is desirable to be. The sound insulation sheet 15 is preferably a non-foamed sheet of polyolefin resin mixed with, for example, barium sulfate as a filler, and has a thickness of about 1 to 2 mm. The non-breathable carpet 30 has a thickness of about 2 to 8 mm.

  As shown in FIG. 2, the vehicle lower limb impact absorbing pad A is attached to the vehicle panel 21 with an appropriate fastener so that the pad main body 10 faces the panel 21. In the illustrated example, a dash silencer 22 is attached to the interior side of the vehicle panel 21 and the pad body 10 is placed thereon. However, the dash silencer 22 may be omitted.

  In this example, the vehicle (automobile) is driven with the heel of the occupant's foot 23 resting on the horizontal portion 11 and the toe side riding on the inclined portion 12. Note that the overall shape of the vehicle lower limb shock absorbing pad A shown in the figure is an example, and various shapes are used depending on the shape of the vehicle, the position of the operation tool, and the like. Although not shown, the inclined portion 12 has a narrower area, or in some cases, only the horizontal portion 11 is formed.

  The vehicle lower limb shock absorbing pad A in this form has effective shock absorbing characteristics exhibited by the pad main body 10, and engine sound or the like is generated indoors by the action of the sound insulating sheet 15 and the non-breathable carpet 30. It is effectively prevented from entering. Thereby, high quietness is maintained in the vehicle interior.

  FIG. 3 shows another embodiment of the vehicle lower limb impact absorbing pad provided with soundproofing according to the present invention. FIG. 3 (a) is a cross-sectional view corresponding to FIG. 1 (b). FIG. 2B is a schematic diagram showing a part corresponding to FIG. In this lower limb shock absorbing pad A1 for a vehicle, the pad main body 10 is the same as that shown in FIG. 1, and a sound absorbing material 16 such as a felt having a thickness of about 10 mm is provided on the interior side surface instead of a sound insulating sheet. 1 is different from that of FIG. 1 in that air-permeable carpet 31 is further laminated thereon. The thickness of the air-permeable carpet 31 is preferably about 2 to 8 mm. However, the air-permeable carpet 31 can be omitted.

  The vehicle lower limb shock absorbing pad A1 in this form has an effect of the sound absorbing material 16 and the air-permeable carpet 31 in addition to exhibiting effective shock absorbing characteristics by the pad body 10, and as described above, Since the material 16 is located away from the vehicle body panel 21 and the vertically long through holes 13 formed in the pad main body 10 function as a rear air layer region, the sound absorption of the room sound is improved and the vehicle interior is high. Silence is maintained.

  FIG. 4 shows still another embodiment of the vehicle lower limb impact absorbing pad provided with soundproofing according to the present invention, and FIG. 4 (a) is a sectional view corresponding to FIG. 1 (b). FIG. 2B is a schematic diagram illustrating a part corresponding to FIG. In this vehicle lower limb shock absorbing pad A2, the pad main body 10 is basically the same as that shown in FIG. 1, but is thicker from the indoor side over the entire region where the vertically long through-hole 13 is formed. An engraving of about 2/3 of the height is formed, and a sound absorbing material 16 such as a felt having a thickness of about 10 mm similar to that used in the shock absorbing pad A1 shown in FIG. A foam molded product 17 of thermoplastic resin beads having air permeability having a thickness of about 10 mm is laminated. Further, a breathable carpet 31 is further laminated over the entire surface of the pad main body 10. Also in this case, the air-permeable carpet 31 may be omitted.

  The foamed molded product 17 of thermoplastic resin beads having air permeability may be a porous molded product, or may be post-processed with a needle or the like to provide air permeability. The foam molded product 17 has a lower air permeability than the sound absorbing material 16 located on the vehicle body panel 21 side, and thus, the hollow double wall structure as described above is formed between the vehicle body panel 21. Not only the sound absorption performance but also the sound insulation performance can be improved. Furthermore, by laminating the foam molded product 17 on the sound absorbing material 16, the fluffy surface can be eliminated and the treading feeling becomes good. Further, even if the dash silencer 22 on the vehicle body panel side is omitted, effective shock absorption characteristics and high soundproofing properties can be obtained.

  It is assumed that a collision occurs during driving when the vehicle lower limb impact absorbing pad provided with soundproofing according to the present invention is used. The kinetic energy generated by the collision is effectively absorbed by the pad main body 10 that constitutes the vehicle lower limb impact absorbing pad, and it is possible to avoid the obstacle of the occupant's lower limb with a considerable probability. That is, the energy absorption behavior of the vehicle lower limb shock absorbing pad A according to the present invention is as follows. Immediately after the collision, it absorbs a lot of energy in a short time like a solid foam pad. From the required load, energy is absorbed while advancing strain without greatly increasing the load. Therefore, without increasing the thickness, it is possible to effectively relieve the amount of kinetic energy at the time of collision, that is, the impact force applied to the lower limbs of the occupant, thereby reducing the obstacles occurring in the lower limbs. On the other hand, the presence of the vertically long through hole 13 significantly improves the soundproofing effect. Further, the pad body 10 can be further effectively laminated by appropriately stacking the sound insulating sheet 15, the sound absorbing material 16, the non-breathable carpet 30, the breathable carpet 31 and the like as shown in the drawings. Soundproof performance (sound insulation effect or sound absorption effect) can be achieved.

[Example 1: Test of sound insulation performance]
Sound insulation for the vehicle lower limb shock absorbing pad A (described based on FIGS. 1 and 2), A1 (described based on FIG. 3), and A2 (described based on FIG. 4) according to the present invention. The performance was tested according to the sound transmission loss measurement method in the laboratory of JISA1416. In addition, sound insulation performance is the sound measured only by the steel plate (thickness 0.8mm) from the value of the sound transmission loss of the laminated body which laminated | stacked the vehicle lower limb part impact absorption pad which is a measuring object on the steel plate (thickness 0.8mm). Evaluation was made by subtracting the value of transmission loss, which is shown in FIG.

  As a test pad body 10, pre-expanded beads (particles) of a styrene-modified polyethylene resin are filled in a molding die, and foam molding with an expansion ratio of 30 times obtained by in-mold foam molding using heated steam is performed. Commonly used is a plate-like body having a vertical width of 500 mm, a horizontal width of 600 mm, and a thickness of 30 mm, in which through holes 13 having a vertical length of 460 mm and a horizontal width of 8 mm are formed at an 18 mm pitch (the interval between the through holes is 10 mm). . The opening ratio of the through holes is about 38%.

Example 1-1 As shown in FIG. 1C, a test pad A was obtained by laminating a polypropylene sheet added with barium sulfate having a thickness of 1 mm as the sound insulation sheet 15 on the pad body 10. The result is shown as curve A in FIG.

[Comparative Example 1-1] A test pad B was prepared in the same manner as in Example 1-1, except that a pad body in which the vertically long through-hole 13 was not formed was used, and the same sound insulation performance test was performed. It was. The result is shown as curve B in FIG.

[Evaluation] From FIG. 5A, even in the case of a vehicle lower limb shock absorbing pad having the same layer configuration, a significant difference appears in the sound insulation performance depending on whether or not a vertically long through hole is formed in the pad main body 10. You can see that Thereby, it is shown that the vehicle lower limb shock absorbing pad according to the present invention has an advantage.

[Example 1-2] As shown in FIG. 3 (b), the pad main body 10 is laminated with a 10 mm-thick felt (laminated product of a high-density layer 3 mm and a low-density layer 7 mm) as a sound-absorbing material 16. A1. The result is shown as a curve A1 in FIG.

[Comparative Example 1-2] A test pad B1 was prepared in the same manner as in Example 1-2, except that a pad body having no vertically long through holes 13 was used, and the same sound insulation performance test was performed. It was. The result is shown as a curve B1 in FIG.

[Evaluation] From FIG. 5 (b), the test pad A 1 has a noise performance in the vicinity of a frequency of 250 Hz compared to the test pad A in Example 1-1 by replacing the sound insulation sheet with a felt sound absorbing material. It can be seen that it has improved. Further, in comparison with the test pad A in Example 1-1, the sound insulation performance is reduced at a frequency higher than the vicinity of the frequency of 400 Hz, but the sound insulation performance is higher than that of the test pad B1 of the comparative example product. Recognize. This can also be understood as being caused by the pad main body 10 having a vertically long through hole.

[Example 1-3] As shown in FIG. 4B, a 10 mm-thick felt (laminated product of a high-density layer 3 mm and a low-density layer 7 mm) is laminated on the pad main body 10 as a sound absorbing material 16. Further, a foam molded article 17 having a thickness of 10 mm and having air permeability was laminated to obtain a test pad A2. The foamed molded article 17 having air permeability is a foamed molding with a foaming ratio of 30 times obtained by filling pre-expanded beads of styrene-modified polyethylene resin into a molding die and molding in mold using heated steam. In the product, a gap having air permeability is formed between the pre-expanded beads. The result is shown as curve A2 in FIG.

[Evaluation] From FIGS. 5C and 5B, it can be seen that the test pad A2 exhibits the same sound insulation performance as the test pad A1. That is, it can be seen that the sound insulation performance is improved at a frequency of 250 Hz as compared with the test pad A in Example 1-1. Moreover, in comparison with the test pad A in Example 1-1, although the sound insulation performance is reduced at a frequency higher than around 400 Hz, the sound insulation performance is higher than that of the test pad B1 of the comparative example product. I understand that.

[Example 2: Test of sound absorption performance]
The sound absorbing performance of the vehicle lower limb shock absorbing pads A1 (explained based on FIG. 3) and A2 (explained based on FIG. 4) according to the present invention described above is used as a method for measuring the reverberation chamber method sound absorption coefficient of JISA1409. Tested accordingly. As a test pad body 10, pre-expanded beads (particles) of a styrene-modified polyethylene resin are filled in a molding die, and foam molding with an expansion ratio of 30 times obtained by in-mold foam molding using heated steam is performed. A plate-like body having a length of 1000 mm, a width of 1200 mm, and a thickness of 30 mm, and through holes 13 having a length of 960 mm and a width of 8 mm formed at an 18 mm pitch (interval between the through holes is 10 mm) was used in common. The opening ratio of the through holes is about 41%.

[Example 2-1] As shown in FIG. 3 (b), a test pad in which felt of 10 mm thickness (laminated product of high density layer 3 mm and low density layer 7 mm) is laminated on the pad main body 10 as the sound absorbing material 16. A1. The result is shown as curve A1 in FIG.

[Comparative Example 1-2] A test pad was used in the same manner as in Example 2-1, except that the pad main body was not a vertically long through hole 13 but a vertically long groove having a depth of 20 mm. B1 was produced and the same sound absorption performance test was performed. The result is shown as curve B1 in FIG.

[Evaluation] From FIG. 6A, even in the case of a vehicle lower limb shock absorbing pad having the same layer configuration, a significant difference appears in the sound absorbing performance depending on whether or not a vertically long through hole is formed in the pad main body 10. You can see that Thereby, it is shown that the vehicle lower limb shock absorbing pad according to the present invention has an advantage.

Example 2-2 As shown in FIG. 4B, a 10 mm thick felt (laminated product of a high density layer 3 mm and a low density layer 7 mm) is laminated on the pad body 10 as the sound absorbing material 16, Further, a foam molded article 17 having a thickness of 10 mm and having air permeability was laminated to obtain a test pad A2. The foamed molded article 17 having air permeability is a foamed molding with a foaming ratio of 30 times obtained by filling pre-expanded beads of styrene-modified polyethylene resin into a molding die and molding in mold using heated steam. In the product, a gap having air permeability is formed between the pre-expanded beads. The result is shown as curve A2 in FIG.

[Evaluation] From FIGS. 6B and 6A, the test pad A2 shows an excellent sound absorbing performance equivalent to the test pad A1.

[Example 3: Test of cage shape dynamic impact characteristics]
The heel-shaped dynamic impact characteristics of the above-described vehicle lower limb impact absorbing pad A according to the present invention (explained based on FIGS. 1 and 2) were tested. As a test pad body 10, pre-expanded beads (particles) of a styrene-modified polyethylene resin are filled in a molding die, and foam molding with an expansion ratio of 30 times obtained by in-mold foam molding using heated steam is performed. A plate-shaped body having a vertical width of 200 mm, a horizontal width of 200 mm, and a thickness of 30 mm, and through holes 13 having a vertical length of 160 mm and a horizontal width of 8 mm formed at an 18 mm pitch (interval between the through holes is 10 mm) was used. As shown in FIG. 1C, a test pad A was obtained by laminating a polypropylene sheet added with 1 mm thick barium sulfate as the sound insulation sheet 15 on the pad body 10. However, in the test, the non-breathable carpet 30 was not laminated.

  In the test, as shown in FIG. 7B, an aluminum processed product 51 (25 kg) similar to a heel is attached as a load to a drop impact tester, and the test pad A is placed on the horizontal table 52 with the sound insulation sheet 15 on the upper surface. It was attached in this way. The aluminum processed product 51 was dropped at a dropping speed of 3.3 m / s (H = 57 cm) (total energy amount 140 J) to obtain a load-strain curve of the test pad A. The result is shown as curve A in FIG. As a comparative example, the test pad B was prepared in the same manner as the test pad A, except that the pad body was not a vertically long through-hole 13 but a vertically long groove having a depth of 20 mm. The same test was performed. The result is shown as curve B in FIG.

  As shown in FIG. 7 (a), even in the case of a vehicle lower limb impact absorbing pad having the same layer configuration, a vertically long through hole is formed in the pad body 10, or a concave groove with a ceiling is formed instead of the through hole. It can be seen that there is a difference in the load-strain curve. That is, the test pad A is a vehicle lower limb shock absorbing pad having the same layer configuration, and the strain amount with respect to the load increase at a dynamic load of 1.5 to 2.0 KN is larger than that of the test pad B. However, it can be seen that the kinetic energy at the time of the collision can be more effectively absorbed by forming a vertically long through hole in the pad main body 10 instead of a concave groove with a ceiling. This also demonstrates the effectiveness of the present invention.

FIG. 1 (a) is a view of one embodiment of a vehicle lower limb shock absorbing pad provided with soundproofing according to the present invention as seen from the back side, and FIG. 1 (b) is a cross-sectional view taken along line bb of FIG. 1 (a). FIG. 1 and FIG. 1C are schematic views taken along line cc in FIG. The figure which shows typically the state which attached the lower limb part impact absorption pad for vehicles to the vehicle. FIG. 3 shows another embodiment of a vehicle lower limb shock absorbing pad provided with soundproofing according to the present invention. FIG. 3 (a) is a cross-sectional view corresponding to FIG. 1 (b), and FIG. The schematic diagram which expands and shows a part corresponding to 1 (c). FIG. 4 shows still another embodiment of the vehicle lower limb shock absorbing pad provided with soundproofing according to the present invention. FIG. 4 (a) is a cross-sectional view corresponding to FIG. 1 (b), and FIG. The schematic diagram which expands and shows a part corresponding to FIG.1 (c). Example 1: The graph which shows the result of the test of sound insulation performance. Example 2: The graph which shows the result of the test of sound absorption performance. Example 3: A graph showing the result of a test of the saddle shape dynamic impact characteristics.

Explanation of symbols

  A, A1, A2 ... Lower limb impact absorbing pad for vehicle, 10 ... Pad body, 13 ... Vertically long through hole, 15 ... Sound insulation sheet, 16 ... Sound absorbing material, 17 ... Breathable foam molded product, 30 ... Ventilation Carpet with no nature, 31 ... Breathable carpet

Claims (7)

A vehicle lower limb shock absorbing pad on which an occupant's foot is placed, wherein the vehicle lower limb shock absorbing pad is made of at least a foamed product of thermoplastic resin beads, and has a plurality of vertically long through holes. A vehicle lower limb shock absorbing pad having soundproofing characteristics, comprising a pad main body formed in parallel at substantially equal intervals so that a longitudinal direction is the same as a longitudinal direction of a vehicle .   The sound absorbing sheet according to claim 1, wherein a sound insulation sheet is laminated on one surface of the pad main body.   The lower limb impact-absorbing pad for vehicles according to claim 2, wherein a carpet having no air permeability is laminated on the upper surface of the sound-insulating sheet.   The sound absorbing material according to claim 1, wherein a sound absorbing material is laminated on one surface of the pad main body.   5. The vehicle lower limb impact absorbing pad according to claim 4, wherein an air permeable carpet is laminated on an upper surface of the sound absorbing material.   5. The lower limb impact absorbing pad for vehicles according to claim 4, wherein a foamed product of thermoplastic resin beads having air permeability is further laminated on the upper surface of the sound absorbing material.   7. The vehicle lower limb shock absorbing pad for soundproofing according to claim 6, wherein a carpet having air permeability is laminated on an upper surface of a foamed molded product of thermoplastic resin beads.

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