Knee bolsters and rigid polyurethane foams for knee bolsters

Abstract

To provide a knee bolster which can stably alleviate impact.SOLUTION: A knee bolster 10 includes: a storage container 11 which receives a knee H of an occupant J in collision of a vehicle 90, alleviates impact to the knee H by compression fracture of a hard polyurethane foam 40 and stores the hard polyurethane foam 40; a first container constitution part 20 which constitutes a part of the storage container 11 and is fixed to the vehicle 90; a second container constitution part 30 which constitutes the other part of the storage container 11 and is opposite to the first container constitution part 20 across the hard polyurethane foam 40 in a compression direction of the hard polyurethane foam 40; and a movement regulation part which permits movement in the compression direction of the second container constitution part 30, and regulates movement in a direction crossing the compression direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a knee bolster that receives the knees of an occupant during a vehicle collision and absorbs the impact on the knees. [Background technology]

[0002] 2. Description of the Related Art Conventionally, knee bolsters that are made of rigid polyurethane foam and absorb shock by compressive destruction thereof have been known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-327066 A (paragraphs

[0017] ,

[0018] , Figure 1, etc.) Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned knee bolster, a situation may occur in which the compressive failure due to shear does not progress sufficiently, and shock absorption is not achieved sufficiently. Therefore, a knee bolster that can stably absorb shock is required. [Means for solving the problem]

[0005] In order to solve the above problems, First aspect of the inventionis a knee bolster that receives the knees of an occupant in the event of a vehicle collision and absorbs an impact on the knees by compressive failure of a rigid polyurethane foam, the knee bolster comprising: a container that contains the rigid polyurethane foam; a first container-forming portion that constitutes a part of the container and is fixed to the vehicle; a second container-forming portion that constitutes another part of the container and faces the first container-forming portion in the compression direction of the rigid polyurethane foam with the rigid polyurethane foam sandwiched therebetween; and a movement restricting portion that allows movement of the second container-forming portion in the compression direction and restricts movement of the second container-forming portion in a direction intersecting the compression direction.

[0006] Second aspect of the invention the first container-forming portion has a first fitting wall that fits into one end of the rigid polyurethane foam in the compression direction and a first end wall that abuts on one end surface of the rigid polyurethane foam in the compression direction, and the second container-forming portion has a second fitting wall that fits into the other end of the rigid polyurethane foam in the compression direction and a second end wall that abuts on the other end surface of the rigid polyurethane foam in the compression direction. First aspect 2 is a knee bolster according to the above.

[0007] Third aspect of the invention the movement restriction portion includes a plurality of arms extending from one of the first container component and the second container component to the other, and an arm guide provided on the other of the first container component and the second container component and having a through hole through which the arm penetrates in the compression direction. First or second aspect 2 is a knee bolster according to the above.

[0008] Fourth aspect of the invention a contact protrusion is provided on at least one of the pair of pressing opposing surfaces of the rigid polyurethane foam and the container, which face each other in the compression direction and press against each other, so that the contact area between the pair of pressing opposing surfaces increases stepwise during the process of compression and destruction of the rigid polyurethane foam. Any one of the first to third aspects 2 is a knee bolster according to the above.

[0009] Fifth aspect of the inventionA pair of pressing opposing surfaces of the first container-constituting portion and the rigid polyurethane foam, which face each other in the compression direction and press against each other, are curved surfaces that face each other in face-to-face contact. Any one of the first to third aspects 2 is a knee bolster according to the above.

[0010] Sixth aspect of the invention The knee support surface of the second container component that supports the knees is provided with a curved surface that is inclined toward the rear of the vehicle and bulges outward as it moves away from the center of the left and right of the occupant's body. Any one of the first to fifth aspects 2 is a knee bolster according to the above.

[0011] Seventh aspect of the invention The first container-constituting portion and the second container-constituting portion are provided with an engaging portion that engages with each other to prevent the first container-constituting portion and the second container-constituting portion from being separated from each other. Any one of the first to sixth aspects 2 is a knee bolster according to the above. Effect of the Invention

[0012] First aspect of the invention The knee bolster has a container that contains a rigid polyurethane foam, and the container is provided with first and second container components that face each other in the compression direction of the rigid polyurethane foam. The first container component is fixed to the vehicle, and the second container component is restricted by a movement restricting portion from moving in a direction intersecting the compression direction of the rigid polyurethane foam. Therefore, even if shear occurs in the rigid polyurethane foam during the compression process when the rigid polyurethane foam supports the knees of an occupant, it is possible to prevent the portion of the rigid polyurethane foam on the second container component side from shifting relative to the portion on the first container component side. This makes it possible to further compress the rigid polyurethane foam to absorb the impact, and makes it possible for the knee bolster to absorb the impact more stably than before.

[0013] Second aspect of the inventionIn the knee bolster, the rigid polyurethane foam can be compressed by the first end wall of the first container component and the second end wall of the second container component. In addition, since the rigid polyurethane foam is fitted between the first fitting wall and the second fitting wall, the rigid polyurethane foam is less likely to shift in a direction intersecting the compression direction, making it easier to support the knee and less likely to shift due to shear, making it possible to more stably cushion the shock. In addition, for example, if the container is configured so that one of the first container component and the second container component covers the other, the compression stroke of the rigid polyurethane foam can be lengthened.

[0014] Third aspect of the invention The movement restricting portion may have a plurality of arms and through holes through which the arms pass, like the knee bolster of 2. In this case, it is possible to easily form the movement restricting portion.

[0015] Fourth aspect of the invention In the knee bolster of the present invention, when the compression of the rigid polyurethane foam starts, only a part of the pressure-opposing surfaces of the container and the rigid polyurethane foam come into contact, so the initial reaction force on the knee can be reduced compared to when the pressure-opposing surfaces come into full contact with each other. Furthermore, when the rigid polyurethane foam is further compressed, the contact area of ​​the pressure-opposing surfaces increases stepwise as the rigid polyurethane foam breaks down due to compression. This makes it possible to increase the load that the rigid polyurethane foam receives stepwise. This makes it possible to shorten the compression stroke of the rigid polyurethane foam to absorb the impact, compared to when the load is gradually increased, and makes it possible to make the knee bolster more compact.

[0016] Fifth aspect of the inventionIn the knee bolster, the opposing pressing surfaces of the first container-forming part and the rigid polyurethane foam, which face each other in the compression direction and press against each other, are curved surfaces that come into face-to-face contact with each other, so that the rigid polyurethane foam can be more easily received by the opposing pressing surfaces of the first container-forming part, even if the impact angle of the knee against the knee bolster changes, compared to when the opposing pressing surfaces are flat. These opposing pressing surfaces may be convex or concave on the outside of the container. In the former case, for example, the opposing pressing surfaces of the first container-forming part may be concave in the shape of a circular arc or a hemisphere.

[0017] Sixth aspect of the invention In the knee bolster of the second container component, the knee support surface that supports the occupant's knees is inclined toward the rear of the vehicle as it moves away from the left-right center of the occupant's body. That is, since the knee support surface is inclined toward the left-right center of the occupant, it is possible to support the occupant's knees toward the left-right center of the occupant. In addition, since the knee support surface is a bulging curved surface that bulges outward, it is possible to widen the range of impact angles of the knees that can be easily supported compared to when the knee support surface is a flat surface.

[0018] Seventh aspect of the invention According to the knee bolster, the second container component is restricted from moving away from the first container component, so that the degree of freedom in the positioning and orientation of the knee bolster can be increased. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a side view showing a state in which a knee bolster according to a first embodiment is attached to a vehicle; [Diagram 2] Plan view of knee bolster installed on vehicle [Diagram 3] A perspective view of the knee bolster from the front [Figure 4] A perspective view of the knee bolster from the rear side [Diagram 5] Knee bolster front view [Figure 6] Knee bolster plan view [Figure 7] FIG. 1 is a perspective view of a polyurethane foam received in a first container component; [Figure 8] Cross section of knee bolster taken along line AA in Figure 5 [Figure 9] Cross section of knee bolster from B to B in Fig. 5 [Figure 10] Cross section of knee bolster at CC in Figure 5 [Figure 11] Section AA of the compressed knee bolster [Figure 12] CC cross section of compressed knee bolster [Figure 13] 11 is a side view of the knee bolster according to the second embodiment. [Figure 14] A perspective view of the knee bolster from the front [Figure 15] A perspective view of the knee bolster from the rear side [Figure 16] FIG. 1 is a perspective view of a polyurethane foam received in a first container component; [Figure 17] Side cross-sectional view of knee bolster [Figure 18] Side cross-sectional view of compressed knee bolster [Figure 19] Side view of the impact body that will collide with the knee bolster in the analysis [Figure 20] Graph showing the analysis results [Figure 21] FIG. 2A is a side cross-sectional view of a knee bolster according to another embodiment; FIG. 2B is a side cross-sectional view of a knee bolster according to another embodiment; [Figure 22] FIG. 11 is a side cross-sectional view of a knee bolster according to another embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [First embodiment] 1 and 2, the knee bolster 10 of this embodiment is disposed on the rear side of an instrument panel 91 of a vehicle 90 (on the front side of the vehicle 90). The knee bolsters 10 are disposed in positions facing the left and right knees H of a seated occupant J from the front side. When the knees H of the occupant J move forward during a collision of the vehicle 90, for example, the knee bolsters 10 receive the knees H and reduce the impact on the knees H.

[0021] More specifically, a pipe-shaped reinforcement 92 extending in the vehicle width direction is provided on the rear side of an instrument panel 91 of a vehicle 90. Brackets 93 protruding forward are fixed to the reinforcement 92 at two locations facing the left and right knees H of an occupant J. Knee bolsters 10 are attached to the front faces of the brackets 93 and disposed adjacent to the instrument panel 91. When the knees H of the occupant J move forward and collide with the instrument panel 91 during a collision of the vehicle 90, the instrument panel 91 is pushed forward and deformed, and the knee bolster 10 receives the knees H together with the instrument panel 91.

[0022] 3 and 4, the knee bolster 10 has a substantially rectangular parallelepiped shape and is made by housing a hard polyurethane foam 40 (hereinafter simply referred to as polyurethane foam 40) in a housing 11. In this embodiment, the housing 11 is made of resin, but it may be made of metal.

[0023] The container 11 has first and second container-forming parts 20, 30 that sandwich the polyurethane foam 40. These container-forming parts 20, 30 are arranged to face each other in the opposing direction of the knee H of the occupant J and the knee bolster 10. When the knee bolster 10 receives the knee H of the occupant J, the polyurethane foam 40 is compressed and destroyed, thereby mitigating the impact on the knee H. In the knee bolster 10, the opposing direction of the first and second container-forming parts 20, 30 is also the compression direction of the polyurethane foam 40.

[0024] 5, knee bolster 10 has a rectangular shape when viewed from the opposing direction of first and second container components 20, 30, and is disposed so that its longitudinal direction is along the up-down direction. In this embodiment, knee bolsters 10 for the left and right knees of occupant J have a symmetrical structure, so the following will describe in detail only the right knee bolster 10.

[0025] 3 and 4, the first and second container components 20, 30 are box-shaped and open toward each other, with the first container component 20 fixed to the vehicle 90 (more specifically, the bracket 93 described above) and the second container component 30 disposed on the side of the occupant J. The second container component 30 has a larger opening than the first container component 20 so that it can be placed over the first container component 20.

[0026] The first container component 20 is composed of a substantially rectangular bottom wall 21 and an outer peripheral wall 22 erected from the outer edge of the bottom wall 21. The outer peripheral wall 22 is composed of a pair of long side walls 23 erected from the long side portions of the bottom wall 21 and facing each other in the vehicle width direction, and a pair of short side walls 24 erected from the short side portions of the bottom wall 21 and facing each other vertically. The pair of long side walls 23 and the pair of short side walls 24 are arranged so as to move away from each other as they move away from the bottom wall 21. In this embodiment, the bottom wall 21 and the outer peripheral wall 22 correspond to the "first end wall" and the "first fitting wall" respectively as described in the claims.

[0027] The bottom wall 21 of the first container-forming portion 20 is fixed to the bracket 93 described above. A fastener 29 for fastening the knee bolster 10 to the bracket 93 is attached to a base end surface of the bottom wall 21 that faces the bracket 93 (see FIG. 4). Note that the fastener 29 is disposed, for example, on one long side portion of the bottom wall 21 (on the central side in the left-right direction of the occupant J).

[0028] 4 and 10, the bottom wall 21 has an arc shape that bulges outward when viewed from the long side direction (i.e., the up-down direction). The bottom wall 21 is inclined with respect to the opposing direction of the first and second container-constituting portions 20, 30, and is disposed so as to move toward the second container-constituting portion 30 side (i.e., the occupant J side) from one long side portion where the fixing device 29 is disposed to the other long side portion. In this embodiment, the bottom wall 21 has an arc shape, so that the pressure-opposing surface 20M, which is an inner surface of the first container-constituting portion 20 and receives the polyurethane foam 40 in the compression direction, is an arc-shaped concave surface when viewed from the up-down direction.

[0029] A bottom rib 28 protrudes from the long side of the base end surface of the bottom wall 21 opposite the fixing device 29. The bottom rib 28 is formed by intersecting a plurality of vertical ribs 28T extending in the long side direction with a plurality of horizontal ribs 28Y extending in the short side direction. The protruding tip edge of the bottom rib 28 increases in amount as it goes away from the fixing device 29 so that it is substantially flush with the long side of the base end surface of the bottom wall 21 on the fixing device 29 side.

[0030] 6 and 7, a plurality of arms 27 protrude from the opening edge of the container opening of the first container-constituting portion 20. Specifically, the arms 27 are in the form of protruding pieces extending linearly from a plurality of positions in the circumferential direction of the outer peripheral wall 22 toward the second container-constituting portion 30. An engaging claw portion 27T protruding outward from the outer peripheral wall 22 is provided at the tip of each arm 27. In this embodiment, a total of six arms 27 are provided, one extending from two positions that equally divide each long side wall 23 and one extending from one position that equally divides each short side wall 24.

[0031] As shown in FIG. 3, the second container-forming portion 30 is composed of a bottom wall 31 having a substantially rectangular shape and an outer peripheral wall 32 erected from the outer edge of the bottom wall 31. The outer peripheral wall 32 has a pair of long side walls 33 erected from the long side of the bottom wall 31 and facing each other in the vehicle width direction, and a pair of short side walls 34 erected from the short side of the bottom wall 21 and facing each other vertically. The pair of long side walls 33 and the pair of short side walls 34 are arranged so as to move away from each other as they move away from the bottom wall 31. In addition, a flange portion 32F protrudes outward from the end of the outer peripheral wall 32 that is farther from the bottom wall 31 (i.e., the opening edge of the second container-forming portion 30). In this embodiment, the bottom wall 31 and the outer peripheral wall 32 correspond to the "second end wall" and the "second fitting wall" respectively described in the claims.

[0032] Similar to the bottom wall 21 of the first container component 20, the bottom wall 31 of the second container component 30, when viewed from the long side direction (vertical direction), forms an arc that bulges outward and is inclined with respect to the opposing direction of the first and second container components 20, 30. The outer surface (tip surface) of the bottom wall 31 of the second container component 30 forms a knee support surface 30M that supports the knees H of the occupant J.

[0033] 3 and 5, grooves 35U extending from end to end in the short side direction are formed at two positions that equally divide the bottom wall 31 of the second container-forming portion 30 in the long side direction. The grooves 35U are formed by raising the bottom wall 31 inward (toward the first container-forming portion 20), and a protrusion 35T (see FIG. 8) extending in the short side direction is formed on the inner surface of the bottom wall 31 on the opposite side to the grooves 35U. A plurality of ribs 35R are bridged across the grooves 35U in the groove width direction.

[0034] As shown in Figs. 3 and 4, the outer peripheral wall 32 of the second container-forming portion 30 is formed with linear holes 36 extending in the opposing direction of the first and second container-forming portions 20, 30. The linear holes 36 are formed at a plurality of positions in the circumferential direction of the outer peripheral wall 32, and in this embodiment, the linear holes 36 are provided at two positions that equally divide each long side wall 33 and at one position that equally divides each short side wall 34. That is, each linear hole 36 is disposed at a position corresponding to the arm 27 of the first container-forming portion 20 in the circumferential direction of the outer peripheral wall 32. The end of the linear hole 36 on the side away from the bottom wall 31 is adjacent to the flange portion 32F. The linear hole 36 provided in the long side wall 33 is connected to the groove portion 35U of the bottom wall 31 described above. Linear ribs 36R protrude outward from both sides of the opening edge of each linear hole 36 that face each other in the circumferential direction of the outer circumferential wall 32.

[0035] Here, in the container 11, each arm 27 of the first container-constituting portion 20 is inserted into the inside of the second container-constituting portion 30 and passes through each straight hole portion 36 in the opposing direction of the first and second container-constituting portions 20, 30. This allows the second container-constituting portion 30 to move relative to the first container-constituting portion 20 in the opposing direction (i.e., the compression direction of the polyurethane foam 40), while restricting movement in a direction intersecting the opposing direction.

[0036] Furthermore, engaging claw portion 27T at the tip of arm 27 is exposed to the outside of second container-constituting portion 30 from straight hole portion 36, and when second container-constituting portion 30 moves away from first container-constituting portion 20 in the opposing direction, engaging claw portion 27T engages with a portion of the opening edge of straight hole portion 36 on the flange portion 32F side. This prevents second container-constituting portion 30 from moving away from first container-constituting portion 20.

[0037] In more detail, as shown in Figures 8 and 9, the first container component 20 and the second container component 30 are configured so that their outer peripheral walls 22, 32 extend toward each other, making it easy to insert the straight arm 27 into the straight hole portion 36.

[0038] 7 shows the polyurethane foam 40 contained in the container 11. The polyurethane foam 40 has a substantially rectangular parallelepiped shape. In detail, the polyurethane foam 40 has a shape in which the cross-sectional area decreases from a midpoint L in the opposing direction (i.e., the compression direction) of the first and second container-forming portions 20, 30 toward both ends.

[0039] A base end portion 41 of the polyurethane foam 40 from the midpoint L to the base end side is disposed on the first container-constituting portion 20 side, and has a generally quadrangular pyramid shape corresponding to the inner surface of the first container-constituting portion 20, and fits into the outer peripheral wall 22 and comes into face-to-face contact with the bottom wall 21 (see Figs. 8 and 9). That is, a pressing opposing surface 40M of the polyurethane foam 40 that faces and presses against the bottom wall 21 is a curved surface that bulges out in an arc when viewed from the top-bottom direction.

[0040] 7 and 8, the tip side portion 42 of the polyurethane foam 40, which is located closer to the second container-forming portion 30 than the midway position L, is composed of a base portion 42B and a contact protrusion 43 that protrudes in a stepped shape from the base portion 42B. The base portion 42B has a flattened truncated quadrangular pyramid shape and is connected to the base side portion 41 at the midway position L.

[0041] In this embodiment, when viewed from the opposing direction of the first and second container-forming parts 20, 30, the polyurethane foam 40 has a rectangular shape, and a plurality of abutment protrusions 43 are arranged in a row in the longitudinal direction. In this embodiment, three abutment protrusions 43 are provided, with the central abutment protrusion 43A having the largest protrusion amount, and the two abutment protrusions 43B on both sides having the same protrusion amount. The central abutment protrusion 43A is disposed so as to abut or be close to the bottom wall 31 of the second container-forming part 30 (see Figs. 8 and 9). The two abutment protrusions 43B on both sides are disposed at intervals from the bottom wall 31 of the second container-forming part 30 (see Figs. 8 and 10). As shown in Figs. 9 and 10, the protruding tip surface of each abutment protrusion 43 is a bulging curved surface that is an arc-shaped surface when viewed from above, corresponding to the inner surface of the bottom wall 31 of the second container-forming part 30. The valleys between the contact protrusions 43 have a shape that generally corresponds to the protrusions 35T of the second container-forming portion 30.

[0042] In the knee bolster 10, in the event of a collision of the vehicle 90, the knee support surface 30M of the second container-constituting portion 30, which is disposed opposite the knee H of the occupant J, receives the knee H. When the knee support surface 30M receives the knee H, the second container-constituting portion 30 moves closer to the first container-constituting portion 20, as shown in the change from FIG. 8 (FIG. 9) to FIG. 11 (FIG. 12), and the polyurethane foam 40 is compressed. Here, the portion of the polyurethane foam 40 that first receives the second container-constituting portion 30 is the central contact protrusion 43A, which is the closest to the bottom wall 31, of the three contact protrusions 43. When the second container-constituting portion 30 is further pressed in by the knee H, the central contact protrusion 43A is compressed and crushed (see FIG. 11 and FIG. 12), and the second container-constituting portion 30 also comes into contact with the portion of the tip surface of the polyurethane foam 40 other than the central contact protrusion 43A. In this embodiment, next, the contact protrusions 43B on both sides also come into contact with the second container-constituting part 30, and thereafter, the polyurethane foam 40 is crushed while receiving the second container-constituting part 30 with the three contact protrusions 43. At this time, the protruding stripes 35T of the second container-constituting part 30 are received in the valleys between the contact protrusions 43 and come into contact with the valley bottoms. Also, in this embodiment, the surfaces of the polyurethane foam 40 and the first container-constituting part 30 that face each other in the compression direction (the above-mentioned pressing facing surfaces 40M, 20M) come into full face contact during the compression process of the polyurethane foam 40.

[0043] In this manner, in the knee bolster 10 of the present embodiment, during the process of compression and destruction of the polyurethane foam 40 due to the collision of the knees H of the occupant J, the contact area between the surfaces of the polyurethane foam 40 and the container 11 that press against each other in the compression direction increases stepwise.

[0044] In the knee bolster 10 of this embodiment, when the polyurethane foam 40 starts to be compressed, only a portion of the pressure-opposing surfaces of the container 11 and the polyurethane foam 40 that face each other in the compression direction contact each other, so that the initial reaction force on the knee H can be made smaller than when the pressure-opposing surfaces contact each other over their entire surfaces. Furthermore, when the polyurethane foam 40 is further compressed, the contact area of ​​these pressure-opposing surfaces increases stepwise during the compression destruction of the polyurethane foam 40. Therefore, the load received by the polyurethane foam 40 can be increased stepwise. As a result, the compression stroke of the polyurethane foam 40 for absorbing the impact can be shortened compared to when the load is gradually increased, and the knee bolster 10 can be made more compact.

[0045] Furthermore, even if the tip surface of the polyurethane foam 40 that faces the knee H of the occupant J is an uneven surface having stepped abutment protrusions 43A, 43B, etc., as described above, by covering it from the occupant J side with the second container component 30, it is possible to give the knee supporting surface 30M that supports the knee H a shape that makes it easy to support the knee H.

[0046] The knee bolster 10 for the right knee has been described above, but the knee bolster 10 for the left knee is similar to the knee bolster 10 for the right knee, except that the structure is symmetrical with that for the right knee. In this embodiment, as shown in FIG. 2, knee bolsters 10 for the left and right knees of the occupant J are arranged symmetrically in the vehicle 90. Here, the knee support surface 30M of each knee bolster 10 is arranged to be inclined toward the rear of the vehicle 90 as it moves away from the center of the left and right sides of the body of the occupant J. That is, since the knee support surface 30M is inclined toward the center of the left and right sides of the occupant J, it is possible to support the knee H of the occupant J on the center of the left and right sides of the occupant J. In addition, since the knee support surface 30M is a bulging curved surface that bulges outward, it is possible to widen the range of impact angles of the knee H that can be easily supported compared to when it is a flat surface.

[0047] Here, in the process of compressing the polyurethane foam 40, shear may occur, for example, obliquely to the compression direction in the polyurethane foam 40. In this case, if the portion of the polyurethane foam 40 on the distal end side and the portion on the proximal end side of the shear point are misaligned from each other, it may become difficult to sufficiently compress the polyurethane foam 40, which may cause a problem that the polyurethane foam 40 cannot sufficiently cushion the impact.

[0048] In contrast, the knee bolster 10 of this embodiment has a container 11 that contains the polyurethane foam 40, and the container 11 is provided with first and second container components 20, 30 that face each other in the compression direction of the polyurethane foam 40. The first container component 20 is fixed to the vehicle 90, and the second container component 30 is restricted from moving in a direction intersecting the compression direction of the polyurethane foam 40. Therefore, even if shear occurs in the polyurethane foam 40 during the compression process when the knees H of the occupant J are supported, it is possible to prevent the portion of the polyurethane foam 40 on the second container component 30 side from shifting relative to the portion on the first container component 20 side. This makes it possible to further compress the polyurethane foam 40 to absorb the impact, and the knee bolster 10 can absorb the impact more stably than before.

[0049] In the knee bolster 10 of this embodiment, the polyurethane foam 40 is fitted to the outer peripheral wall 22 of the first container component 20 and the outer peripheral wall 32 of the second container component 30. Therefore, the polyurethane foam 40 is less likely to shift in a direction intersecting the compression direction, making it easier to receive the knee H and less likely to shift due to shear, making it possible to more stably cushion the impact on the knee H. In addition, depending on the seated posture of the occupant J and the physique of the occupant J, it is considered that the direction of impact of the knee H against the knee bolster 10 is inclined with respect to the opposing direction of the first and second container components 20, 30. However, even in this case, in the knee bolster 10, the movement of the second container component 30 in a direction intersecting the opposing direction is restricted, making it possible to suppress shear from occurring in the polyurethane foam 40.

[0050] In addition, the knee bolster is required to be able to stably bear a load even with a long compression stroke. In contrast, in the knee bolster 10 of the present embodiment, as described above, the polyurethane foam 40 is accommodated in the container 11 and crushed without cracking when subjected to an impact, so that the knee bolster 10 can stably bear a load even with a long compression stroke, and long-stroke crushing is possible with a constant load. Furthermore, by providing the container 11 that accommodates the polyurethane foam 40, it is possible to prevent partial falling off of the polyurethane foam 40 even if cracks occur during the compression process. These also enable the knee bolster 10 to absorb shock more stably than ever before.

[0051] Furthermore, in this embodiment, the movement regulating portion that regulates the movement of the second container component 30 is configured to have a plurality of arms 27 and a straight hole portion 36 through which the arms 27 pass, making it possible to form the movement regulating portion in the container.

[0052] In this embodiment, the first and second container components 20, 30 are provided with an engagement portion (the engagement claw portion 27T and the opening edge of the linear hole portion 36) that engages with each other to restrict separation, so that the second container component 30 is restricted from moving away from the first container component 20. This increases the degree of freedom in the arrangement posture of the knee bolster 10. For example, as shown in FIG. 1, in the event of a collision of the vehicle 90, it is considered that the knee H of the occupant J is likely to move obliquely upward toward the front so as to rotate around the heel of the occupant J as a fulcrum, so the knee bolster 10 is arranged to face the knee H of the occupant J from the obliquely upward toward the front. In this case, the second container component 30 is arranged below the first container component 20 fixed to the vehicle 90, but the above-mentioned engagement portion restricts the second container component 30 from moving away from the first container component 20, so that it is possible to prevent the second container component 30 from falling off.

[0053] In this embodiment, the opposing pressing surfaces 20M, 40M of the first container-constituting portion 20 and the polyurethane foam 40, which face each other in the compression direction and press against each other, are curved surfaces that come into face-to-face contact with each other. Therefore, compared to a case in which the opposing pressing surfaces 20M, 40M are flat surfaces, the polyurethane foam 40 can be more easily received by the opposing pressing surface 20M of the first container-constituting portion 20 even if the impact angle of the knee H against the knee bolster 10 changes.

[0054] In addition, since the second container-constituting part 30 can cover the first container-constituting part 20, it is possible to lengthen the compression stroke of the polyurethane foam 40. This makes it possible to reduce the load on the knees H while absorbing impact.

[0055] In this embodiment, the straight hole 36 of the second container component 30 corresponds to the "through hole" in the claims, the outer peripheral wall 32 corresponds to the "arm guide" in the claims, and the arm 27 and the outer peripheral wall 32 correspond to the "movement restricting portion" in the claims. Also, the engaging claw 27T of the arm 27 and the opening edge of the straight hole 36 correspond to the "engaging portion" in the claims.

[0056] [Second embodiment] A knee bolster 10V of the second embodiment shown in Figures 13 and 14 is a modification of the knee bolster 10 of the first embodiment. The knee bolster 10V of the second embodiment has a substantially cylindrical shape and is attached to the vehicle 90 so as to face knees H (see Figure 18) of an occupant J in the axial direction.

[0057] In this embodiment, the container 11V that contains the polyurethane foam 40V is composed of first and second container-forming portions 20V, 30V that sandwich the polyurethane foam 40V in the axial direction of the knee bolster 10V. The first container-forming portion 20V and the second container-forming portion 30V are substantially bowl-shaped, and their container openings are butted against each other. The second container-forming portion 30V has a larger opening than the first container-forming portion 20V, and is placed over the first container-forming portion 20V.

[0058] The first container-forming portion 20V is fixed to a bracket 93 of the vehicle 90 and has a bottom wall 21V (see FIG. 17) that bulges out in a hemispherical shape and a cylindrical outer peripheral wall 22V that stands upright from the outer edge of the bottom wall 21V. As shown in FIG. 15, a fastener 29 for fastening the first container-forming portion 20V (i.e., the knee bolster 10V) to the bracket 93 is attached to the base end surface of the bottom wall 21V that faces the bracket 93. In this embodiment, the fastener 29 is attached to the center of the bottom wall 21V. A rib 28 is provided protruding from the base end surface of the bottom wall 21. The rib 28 is formed by intersecting an annular rib 28H that extends in the circumferential direction of the first container-forming portion 20V and radial ribs 28K that extend radially from the vicinity of the center of the bottom wall 21. The amount of protrusion of the rib 28 increases with increasing distance from the center of the bottom wall 21V so that the protruding tip edge of the rib 28 is substantially flush with the center of the bottom wall 21V.

[0059] As shown in Fig. 14, the second container-forming portion 30V has a bottom wall 31V that bulges out in a semispherical shape and a cylindrical outer peripheral wall 32V that stands upright from the outer edge of the bottom wall 31V. An annular groove 31U is formed in the knee-support surface 30M of the bottom wall 31V of the second container-forming portion 30V around the central axis C (see Fig. 17) of the knee bolster 10V. An annular protrusion 31T (see Fig. 17) is formed in the part of the inner surface of the bottom wall 31V opposite the annular groove 31U. A plurality of ribs 35R are provided across the annular groove 31U in the groove width direction (radial direction).

[0060] As in the first embodiment, an arm 27 extends from the outer peripheral wall 22V and protrudes toward the second container-constituting portion 30V from the opening edge of the container opening of the first container-constituting portion 20V. The arm 27 is inserted into a straight hole 36 provided in the second container-constituting portion 30V. An engagement claw portion 27T at the tip of the arm 27 engages with the opening edge of the straight hole 36, thereby preventing the second container-constituting portion 30V from moving away from the first container-constituting portion 20V. The arm 27 and the straight hole 36 are disposed at equal intervals (for example, at four locations) in the circumferential direction of the first container-constituting portion 20V and the second container-constituting portion 30V, respectively.

[0061] As shown in Fig. 16, the polyurethane foam 40V has a symmetrical shape about a central axis C (see Fig. 17). An annular groove 42U is formed around the central axis C on the tip surface of the polyurethane foam 40V facing the second container-forming portion 30V, and the inner portion of the groove forms a contact protrusion 43V that protrudes most from the tip surface of the polyurethane foam 40V. The polyurethane foam 40V is fitted into the first and second container-forming portions 20V, 30V.

[0062] As shown in the change from FIG. 17 to FIG. 18, when the knee support surface 30M is pressed in by the impact of the knee H of the occupant J during a collision of the vehicle 90, the second container-constituting portion 30V is pushed in the axial direction, and the contact protrusion 43V is first compressed and crushed, as in the first embodiment. After that, the substantially entire tip end surface of the polyurethane foam 40V comes into face-to-face contact with the second container-constituting portion 30V. During this compression process, the first container-constituting portion 20V and the base end surface of the polyurethane foam 40V come into face-to-face contact with each other entirely in the compression direction. Thus, in this embodiment as well, the contact area between the container 11V and the polyurethane foam 40V in the compression direction increases stepwise during the compression process.

[0063] The knee bolster 10V of this embodiment can achieve the same effects as the knee bolster 10 of the first embodiment. Since the knee bolster 10V of this embodiment has a hemispherical knee-receiving surface 30M, the knees H of the occupant J can be easily received even if the collision direction of the knees H is tilted up, down, left, or right with respect to the central axis C. The knee bolster 10V of this embodiment has the same structure for both the left and right knees.

[0064] [Verification by simulation] The effect of the knee bolster 10V according to the second embodiment was confirmed by computer analysis. Specifically, a simulation was performed to determine the relationship between the compression amount of the knee bolster 10V and the load when the collision body 100 collided with the knee bolster 10V.

[0065] <Analysis contents> Three conditions with different impact angles of the impact body 100 against the knee bolster 10V were analyzed. In this analysis, the impact body 100 was a flat plate, and the flat plate surface of the impact body 100 was set at a right angle to the impact direction of the impact body 100 against the knee bolster 10V (so that the impact direction was the thickness direction of the impact body 100) (see FIG. 19). In analysis 1, the impact body 100 (shown by a two-dot chain line in FIG. 19) was collided with the knee bolster 10V on the central axis C of the knee bolster 10V. In analysis 2, the impact body 100 (shown by a one-dot chain line in FIG. 19) was collided with the knee bolster 10V in a direction where the inclination angle θ from the central axis C (see FIG. 19) was 15 degrees. In analysis 3, the impact body 100 was collided with the knee bolster 10V in a direction where the inclination angle θ from the central axis C was 30 degrees. In either case, the collision direction of the collision body 100 was set to be perpendicular to the surface of the hemispherical knee-support surface 30M of the second container-constituting part 30V at the collision point. Therefore, in analyses 1 and 2, the collision point was located in a part of the bottom wall 31V of the second container-constituting part 30V that was more inward than the annular groove 31U (the part that abutted against the contact protrusion 43V). On the other hand, in analysis 3, the collision point was located near the annular groove 31U of the bottom wall 31V. The collision body 100 was set to be larger than the groove width of the annular groove 31U.

[0066] <Analysis results> The graph in Fig. 20 shows the relationship between the compression amount and the load of the knee bolster 10V under each analysis condition. As can be seen from the graph, it was confirmed that the knee bolster 10V can obtain similar shock absorbing characteristics (the change characteristics of the compression amount and the load) even if the impact angle of the impact body changes within a range of 30 degrees from the central axis C. Therefore, the knee bolster 10V can exhibit good shock absorbing properties even if the impact angle of the impact body 100 varies. This is considered to be due to the fact that the pressing opposing surfaces of the polyurethane foam 40V and the container 11V, which press against each other in the compression direction, are curved surfaces (particularly the curved surfaces that are convex toward the outside of the container 11V). For example, the radius of curvature of the bottom wall 31V of the second container portion 30V and the bottom wall 21V of the first container portion 20V may be the same. In this case, when an impact object 100 is received perpendicularly by the knee-receiving surface 30M, it becomes possible for the polyurethane foam 40V to be more easily received by the bottom wall 21V of the first container portion 20V.

[0067] The two-dot chain line in the graph of Fig. 20 represents the target value when the load is changed stepwise as the shock absorbing characteristic of the knee bolster. From the graph, it was confirmed that the above-mentioned stepwise change in the shock absorbing characteristic can be realized under all of the analysis conditions 1 to 3. Therefore, even when a load change is required in which the load increases stepwise as the polyurethane foam 40V is compressed, it is possible to gradually increase the area of ​​contact between the polyurethane foam 40V and the container 11V in the compression direction by providing the contact protrusion 43V, and it was confirmed that such a stepwise load change can be realized.

[0068] [Other embodiments] (1) In the above embodiment, both the first container-constituting portion 20 and the second container-constituting portion 30 are container-shaped. However, as in the knee bolster 10W shown in FIG. 21(A), only one of the container-constituting portions (the second container-constituting portion 30W in the example of the figure) may be container-shaped. In this case, the other container-constituting portion (the first container-constituting portion 20W in the example of the figure) may be, for example, prismatic or cylindrical. In addition, the movement of the second container-constituting portion 30 in the direction intersecting the compression direction of the polyurethane foam 40 relative to the first container-constituting portion 20 may be restricted by one of the first container-constituting portion 20 and the second container-constituting portion 30 covering the other. In this case, the arm 27 and the straight hole portion 36 may not be provided. In addition, a plurality of arms 27 may be provided extending from the outer peripheral wall 32 of the second container-constituting portion 30 toward the first container-constituting portion 20, and a plurality of straight hole portions 36 may be provided in the outer peripheral wall 22 of the first container-constituting portion 20.

[0069] (2) In the above embodiment, the contact protrusion 43 of the polyurethane foam 40 is provided on the surface facing the second container-constituting portion 30. However, it may be provided on the surface facing the first container-constituting portion 20 as in the knee bolster 10X shown in FIG. 21(B), or on the surfaces facing both container-constituting portions 20, 30. Also, as in the knee bolster 10Z shown in FIG. 22, the contact protrusion 11T may be provided on the surface of the first container-constituting portion 20 or the second container-constituting portion 30 that faces and presses against the polyurethane foam 40 in the compression direction. With these configurations, it is possible to gradually increase the contact area between the polyurethane foam 40 and the container 11 in the compression direction during the compression process of the polyurethane foam 40. The polyurethane foam 40 does not necessarily need to be provided with the contact protrusion 43.

[0070] (3) In the above embodiment, the pressing surfaces 20M, 40M of the polyurethane foam 40 and the first container-constituting part 20, which press against each other, are convex toward the outside of the container 11, but they may be concave. That is, the pressing surface 20M of the first container-constituting part 20 may be a convex curved surface having an arc or hemispherical shape, and the pressing surface 40M of the polyurethane foam 40 may be a concave curved surface having an arc or hemispherical shape.

[0071] (4) In the above embodiment, the knee bolster 10 is provided for each of the left and right knees H of the occupant J. However, for example, the knee bolster may be wide enough to support both knees of the occupant J. [Explanation of symbols]

[0072] 10 Knee Bolster 11 Container 20 First container component 30 Second container component J Crew H knee

Claims

1. A knee bolster that receives the knees of an occupant during a vehicle collision and absorbs impact to the knees by compressive failure of a hard polyurethane foam, The rigid polyurethane foam; A container for containing the rigid polyurethane foam, A knee bolster in which the contact area between the surfaces of the rigid polyurethane foam and the container which press against each other in the compression direction of the rigid polyurethane foam increases stepwise during the process of compression and destruction of the rigid polyurethane foam.

2. The rigid polyurethane foam has a plurality of contact protrusions protruding in a stepped manner in a compression direction of the rigid polyurethane foam, the protrusions having different protrusion amounts, 2. The knee bolster according to claim 1, wherein the contact area between the plurality of contact protrusions and the container increases stepwise during the process of compressive destruction of the rigid polyurethane foam.

3. 3. The knee bolster according to claim 2, wherein the plurality of contact protrusions are arranged such that a protruding amount of the central contact protrusion is greatest.

4. A rigid polyurethane foam used for a knee bolster that receives the knees of an occupant during a vehicle collision and absorbs impact to the knees by compressive failure of the rigid polyurethane foam, The rigid polyurethane foam has a plurality of protrusions protruding in a stepped manner with different protrusion amounts in a compression direction of the rigid polyurethane foam, The rigid polyurethane foam for knee bolsters, wherein the plurality of protrusions are arranged so that the protrusion amount of the central protrusion is greatest.

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