[0001]The present disclosure relates to automobile hoods.
Background technology
[0002]Automobile hoods are known (see, for example, Patent Documents 1 and 2).
[0003]Patent Document 1 discloses a vehicle hood panel structure. This hood panel structure aims to reduce the injury value given to the pedestrian when the pedestrian collides with the hood panel.
[0004]
　Patent Document 2 discloses an automobile hood as an automobile exterior product. The main purpose of this automobile hood is to absorb the energy of contact when a pedestrian comes into contact with the automobile hood by deforming a small amount inward of the automobile.
Prior art literature
Patent documents
[0005]
Patent Document 1: Japanese Patent Application Laid-Open No. 2005-193863
Patent Document 2: Japanese Patent Application Laid-Open No. 2017-1553
Outline of the invention
Problems to be solved by the invention
[0006]
　Automobile hoods are required to be further reduced in weight, improved in tension rigidity, and improved in dent resistance. However, if the panel of the steel plate automobile hood is made thinner than 0.6 mm for weight reduction, both the tension rigidity and the dent resistance are not negligibly reduced.
[0007]
　In both Patent Documents 1 and 2, no problems and configurations are disclosed from the viewpoint of ensuring both sufficient tension rigidity and dent resistance while achieving weight reduction.
[0008]
　One of the purposes of the present disclosure is to ensure sufficient tension rigidity and dent resistance of the panel while achieving weight reduction in the automobile hood.
Means to solve problems
[0009]
　The gist of this disclosure is the following automobile hoods.
[0010]
　A panel,
　and the reinforcing member,
　and the panel and the reinforcing member and joining portions that are joined and
provided with,
　the reinforcing member includes a structure in which a plurality of units of hexagonal ring are arranged in close-packed,
　The unit has a floor, a vertical wall, and a top plate, the
　floor is adjacent to the panel, the
　top plate and the panel are separated from each other, and the
　vertical wall is the floor and the above. Between the top plate and the
　hexagonal annular ridge of the unit between the floor and the vertical wall, the
　floor has an annular end centered on the center of the annular unit. ,
　all of the end, a first circular inscribed in the ridge, located between the second circle, with 60% of the radius of the radius of the first circle in the first circle concentric
　the floor Is an automobile hood that includes a floor surface as a surface facing the panel, and
　the width of the floor surface is 2 mm or more over the entire area of ​​the annular end portion in the circumferential direction of the annular end portion
.
[0011]
　(2) The automobile hood according to (1), wherein the distance between the corner of the hexagonal ridge and the end of the ring is larger than the distance between the center of one side of the ridge and the end of the ring.
[0012]
　(3) The automobile hood according to (1) or (2), wherein the end is circular.
[0013]
　(4) The automobile hood according to (1) or (2) above, wherein the end is hexagonal.
[0014]
　(5) The automobile hood according to (1) or (2) above, wherein the end is a dodecagon.
[0015]
　(6)
　The automobile hood according to any one of (1) to (5) above , wherein the panel is a steel plate and the thickness of the panel is 0.35 mm to 0.60 mm.
[0016]
　(7)
　The automobile hood according to any one of (1) to (5 ) above, wherein the panel is an aluminum alloy plate and the plate thickness of the panel is 0.50 mm to 1.00 mm.
The invention's effect
[0017]
　According to the present disclosure, it is possible to secure sufficient tension rigidity and dent resistance of the panel while achieving weight reduction in the automobile hood.
A brief description of the drawing
[0018]
FIG. 1 is a schematic exploded perspective view of an automobile hood according to an embodiment of the present disclosure.
FIG. 2 is a plan view of a reinforcing member of an automobile hood.
FIG. 3 is a schematic cross-sectional view taken along line III-III of FIG.
FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 2, and the portion appearing behind the cross section is not shown.
FIG. 5 is an enlarged view of a part of FIG.
FIG. 6 is an enlarged plan view of the periphery of one unit of an automobile hood.
FIG. 7A is a simplified view of the periphery of one unit shown in FIG.
FIG. 7B is a diagram showing a part of FIG. 7A extracted.
FIG. 8A is a conceptual side view for explaining the case where the maximum support span of the panel by the annular end is too long.
FIG. 8B is a conceptual side view for explaining the case where the maximum support span of the panel by the annular end is appropriate.
FIG. 8C is a conceptual side view for explaining the case where the maximum supporting span of the panel by the annular end is too short.
FIG. 9A is a schematic plan view showing a main part of an example outside the first range.
FIG. 9B is a schematic plan view showing a main part of an example outside the second range.
FIG. 10A is a simplified diagram showing the periphery of one unit in the first modification.
FIG. 10B is a diagram showing a part of FIG. 10A extracted.
FIG. 11A is a simplified diagram showing the periphery of one unit in the second modification.
FIG. 11B is a diagram showing a part of FIG. 11A extracted.
FIG. 12 is a diagram for explaining an example of arrangement of joints in an automobile hood.
FIG. 13 is a conceptual plan view showing a main part of the third modification of the present disclosure, and shows a part where a joint part is provided.
FIG. 14 is a conceptual plan view showing a main part of the fourth modification of the present disclosure, and shows a part where a joint part is provided.
FIG. 15 is a conceptual plan view showing a main part of the fifth modification of the present disclosure, and shows a part where a joint part is provided.
FIG. 16 is a schematic plan view showing shapes A to D of the annular end portion.
FIG. 17 is a schematic plan view showing shapes E to H of the annular end portion.
FIG. 18 is a schematic plan view showing shapes I, J, and K of the annular end.
Mode for carrying out the invention
[0019]
　In the following, first, the background to the idea of ​​the present disclosure will be described, and then the embodiments will be described in detail.
[0020]
[Background to the Idea of ​​the Disclosure] In the
　present specification, the tension rigidity is a press-formed product having a relatively gentle curved surface and a very large surface area with respect to the plate thickness, for example, an outer panel of an automobile hood. In addition, it refers to the rigidity of the panel when a force is applied from the outside. Tension rigidity corresponds to the feeling of elastic resistance and deflection deformation when the panel is pushed by hand. This characteristic is usually expressed by the amount of deflection when a load is applied, and the smaller the amount of deflection when a constant load is applied, the higher the tension rigidity.
[0021]
　As used herein, dent resistance refers to the difficulty of residual dents after removing a local load on the panel for any reason. In an actual automobile body, it occurs when the outer panel such as a door is strongly pressed with a finger or palm, or when a stepping stone hits while driving. Dent is generated by plastic deformation of the part of the panel to which the load is applied. Therefore, when the strain of the panel reaches a certain magnitude when the load is applied to the panel, the strain remains even after unloading and dent occurs. The minimum value of the load that causes a constant residual strain on the panel is called the dent load, and the larger the dent load, the better the dent resistance.
[0022]
　In an automobile hood, the thinner the panel thickness, the lower both the tension rigidity and the dent resistance. In the past, it cannot be said that improvements have been made to automobile hoods from the viewpoint of ensuring sufficient tension rigidity and dent resistance while achieving weight reduction.
[0023]
　Weight reduction, tension rigidity, and dent resistance will be described more specifically. First, the definition of tension rigidity is as described above. That is, the tension rigidity is the resistance to bending of the panel. For example, when the panel of an automobile hood is pushed by hand, the panel does not easily bend if the tension rigidity is high. The definition of dent resistance is as described above. That is, the dent resistance is the resistance to dents and flaws. For example, when a pebble hits a panel, the panel is easily dented and scratched if the dent resistance is low.
[0024]
　In recent years, in order to reduce the weight of automobiles, the strength of the members constituting the automobiles has been increasing. Generally, if the strength (tensile strength) of a member is increased, the thickness of the member can be reduced. As a result, it is considered that the weight of the member can be reduced. However, such weight reduction by increasing the strength does not simply hold true for exterior materials such as automobile panels. This is because the tension rigidity and dent resistance required for the exterior material of an automobile are not determined only by the strength of the exterior material.
[0025]
　The occurrence of deflection, which reflects the tension rigidity of the outer panel of the automobile hood as described above, mainly depends on the elastic modulus and plate thickness of the panel. In the steel sheet, there is no difference in Young's modulus between the low-strength material and the high-strength material. Therefore, simply replacing the low-strength material with a high-strength material does not improve the tension rigidity. On the other hand, when the low-strength material is replaced with the high-strength material, the dent resistance, which is a kind of resistance to plastic deformation, is improved. However, the effect of steel strength on dent resistance is much smaller than the effect of panel thickness on dent resistance. Therefore, even if the low-strength material is simply replaced with the high-strength material, the improvement in dent resistance cannot be expected so much.
[0026]
　Further, the relationship between the tension rigidity and the dent resistance of the panel and the plate thickness of the panel will be further described. As described above, when the panel is made thinner, both the tension rigidity and the dent resistance are lowered. Therefore, there is a limit to weight reduction while ensuring tension rigidity and dent resistance. The thickness of the panel, which is the limit, is about 0.65 mm in the case of a steel plate. However, it is desired that the automobile panel be thinner than 0.65 mm in order to reduce the weight.
[0027]
　However, the thickness of the panel has not been made thinner than 0.65 mm at present. This is because the thinner the panel thickness, the greater the amount of deflection of the panel when it is touched by hand for waxing or the like. In other words, the car does not feel luxurious. On the other hand, in order to suppress such deflection and reduce injuries to pedestrians in the event of a collision, a reinforcing member has been attached to the inner surface side of the vehicle in the panel.
[0028]
　In order to improve the tension rigidity of the panel by using the reinforcing member, it is preferable to increase the rigidity of the reinforcing member. However, if the plate thickness of the reinforcing member is increased in order to increase the rigidity of the reinforcing member, the reinforcing member becomes heavy, which is not preferable for reducing the weight of the automobile hood. Further, the dent resistance is not always improved even if the rigidity of the reinforcing member is increased. Due to such problems, it is difficult to secure both tension rigidity and dent resistance while reducing the weight of the automobile hood by simply using a reinforcing member.
[0029]
　As a result of diligent research, the inventor of the present application has focused on the above-mentioned problems and has conducted further diligent research. Then, I got the idea of ​​adopting a honeycomb structure as a reinforcing member of an automobile hood in consideration of the balance between strength and weight. However, simply adopting the honeycomb structure is not sufficient to ensure both high tension rigidity and high dent resistance. This is because the shorter the length of one side of the hexagonal annular unit constituting the honeycomb structure, the shorter the support span of the panel can be made, which is preferable for improving the tension rigidity. On the other hand, the shorter the length of one side is, the smaller the permissible value of elastic deflection of the panel is, so that the dent resistance is lowered. Further, the shorter the length of one side, the higher the mass density of the reinforcing member and the heavier the reinforcing member. The inventor of the present application has obtained the above-mentioned findings for the first time by continuing his diligent research even after he came up with the idea of ​​forming the reinforcing member with a honeycomb structure. Then, based on this knowledge, we came up with a configuration that satisfies all of the weight reduction, the securing of tension rigidity, and the securing of dent resistance. That is, we came up with the present disclosure, for which an example is shown below.
[0030]
[Explanation of Embodiment]
　Hereinafter, the embodiment of the present disclosure will be described with reference to the drawings.
[0031]
　FIG. 1 is a schematic exploded perspective view of an automobile hood 1 according to an embodiment of the present disclosure. FIG. 2 is a plan view of the reinforcing member 3 of the automobile hood 1. FIG. 3 is a schematic cross-sectional view taken along the line III-III of FIG. FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 2, and the portion appearing behind the cross section is not shown. In addition, in FIG. 3 and FIG. 4, the panel 2 which does not appear in FIG. 2 is shown by a two-dot chain line which is an imaginary line.
[0032]
　FIG. 5 is an enlarged view of a part of FIG. FIG. 6 is an enlarged plan view of the periphery of one unit 7 of the automobile hood 1. In FIG. 6, the other units 7 other than the one central unit 7 are shown by a line thinner than the central unit 7 so as to be easily distinguished from the central unit 7. FIG. 7A is a simplified view of one unit 7 shown in FIG. FIG. 7B is a diagram showing a part of FIG. 7A extracted. Hereinafter, unless otherwise specified, FIGS. 1 to 7B will be described as appropriate.
[0033]
　The automobile hood 1 is a front hood provided at the front of the automobile, and is also called a bonnet. The automobile provided with the automobile hood 1 is, for example, a passenger car. Examples of the above-mentioned passenger car include a sedan type passenger car, a coupe type passenger car, a hatchback type passenger car, a minivan type passenger car, an SUV (Sport Utility Vehicle) type passenger car and the like.
[0034]
　In the present specification, the terms front and rear, left and right, and up and down are referred to with reference to the time when the automobile hood 1 is attached to the automobile and the automobile hood 1 is closed. The front is the direction in which the car moves forward. The rear is the direction in which the car moves backward. The right is the turning direction of a moving vehicle when it makes a right turn. The left is the turning direction of a moving vehicle when it turns left. Further, in the present embodiment, the vehicle width direction of the vehicle to which the automobile hood 1 is mounted is referred to as the vehicle width direction X. Further, the vehicle length direction of the vehicle to which the vehicle hood 1 is mounted is referred to as the vehicle length direction Y. Further, the vehicle height direction of the vehicle to which the automobile hood 1 is mounted is referred to as the vehicle height direction Z.
[0035]
　The automobile hood 1 has a panel 2, a reinforcing member 3, and a joint portion 4 that joins the panel 2 and the reinforcing member 3.
[0036]
　The panel 2 is a part of the automobile hood 1 that forms a part of the outer surface of the automobile. The panel 2 is made of a metal material such as a mild steel plate or a high-strength steel plate. As the high-strength steel sheet, a steel sheet having a tensile strength of 340 MPa or more can be exemplified, and a steel sheet having a tensile strength of 440 MPa to 590 MPa can be exemplified. The panel 2 is formed by, for example, pressing a single steel plate. The plate thickness t1 (plate thickness of the steel plate) of the panel 2 is set to 0.60 mm or less, preferably 0.50 mm or less, and more preferably 0.40 mm or less. .. The lower limit of the plate thickness t1 of the panel 2 is preferably 0.35 mm. The plate thickness t1 of the panel 2 is, for example, 0.35 mm to 0.60 mm. In this way, the thinner the panel 2 is, the lighter the automobile hood 1 can be.
[0037]
　The panel 2 may be an aluminum alloy plate. In this case, the plate thickness of the panel 2 is set to a value equivalent to the plate thickness of the steel plate panel 2 from the viewpoint of tension rigidity and dent resistance. More specifically, the tension stiffness depends on the Young's modulus and plate thickness of the material. In addition, the dent resistance depends on the yield stress of the material and the plate thickness. Therefore, if the thickness of the panel 2 of the aluminum alloy plate is approximately 1.5 to 1.6 times the thickness of the panel 2 made of steel plate, the panel 2 made of aluminum alloy is considered from the viewpoint of tension rigidity and dent resistance. Can be said to be equivalent to the steel plate panel 2.
[0038]
　When the panel 2 is an aluminum alloy plate, an aluminum alloy plate having a tensile strength of 250 MPa or more can be exemplified, and preferably an aluminum alloy plate having a tensile strength of 300 MPa to 350 MPa can be exemplified. In this case, the plate thickness t1 (plate thickness of the aluminum alloy plate) of the panel 2 is set to 1.00 mm or less, preferably 0.80 mm or less, and more preferably 0.64 mm or less. Is set to. The lower limit of the plate thickness t1 of the panel 2 is preferably 0.50 mm. The plate thickness t1 of the panel 2 is, for example, 0.50 mm to 1.00 mm.
[0039]
　There are no particular restrictions on the shape of the panel 2. In the present embodiment, the panel 2 has a shape in which the central portion is convex upward in the vehicle height direction Z.
[0040]
　The reinforcing member 3 reinforces the panel 2 by being joined to the lower surface 2a of the panel 2. As a result, the reinforcing member 3 enhances both the tension rigidity and the dent resistance of the panel 2. That is, in the present embodiment, the tension rigidity and the dent resistance of the panel 2 are not ensured by increasing the plate thickness of the panel 2, but are ensured by the reinforcing member 3. The reinforcing member 3 is made of a metal material such as a steel plate. The reinforcing member 3 is formed by, for example, pressing a single steel plate. The reinforcing member 3 may be an integrally molded product, or may be formed by joining a plurality of members to each other. In the present embodiment, the reinforcing member 3 is an integrally molded product. The plate thickness t2 (plate thickness of the steel plate) of the reinforcing member 3 is preferably 0.3 mm to 0.8 mm. The upper limit of the plate thickness t2 of the reinforcing member 3 is preferably 0.6 mm. The plate thickness t2 of the reinforcing member 3 may be less than the plate thickness t1 of the panel 2, may be the same as the plate thickness t1 of the panel 2, or may be larger than the plate thickness t1 of the panel 2.
[0041]
　The reinforcing member 3 may be an aluminum alloy plate. In this case, the plate thickness of the reinforcing member 3 is set to a value equivalent to the plate thickness of the reinforcing member 3 of the steel plate from the viewpoint of tension rigidity and dent resistance. Therefore, as in the case of the panel 2, if the plate thickness of the reinforcing member 3 made of aluminum alloy is approximately 1.5 to 1.6 times the plate thickness of the reinforcing member 3 made of steel plate, the tension rigidity and resistance From the viewpoint of dentability, it can be said that the reinforcing member 3 made of aluminum alloy and the reinforcing member 3 made of steel plate are equivalent. When the reinforcing member 3 is made of an aluminum alloy, the plate thickness t1 (plate thickness of the aluminum alloy plate) of the reinforcing member 3 is 0.4 to 1.3 mm. The upper limit of the plate thickness t2 of the reinforcing member 3 is preferably 1.0 mm.
[0042]
　The reinforcing member 3 has an outer peripheral portion 5 and a honeycomb structure 6 arranged so as to be surrounded by the outer peripheral portion 5.
[0043]
　The outer peripheral portion 5 is a portion arranged along the outer peripheral portion of the panel 2. When the panel 2 closes the engine room, the outer peripheral edge portion 5a of the panel 5 is received by the vehicle body (not shown) together with the outer peripheral portion of the panel 2. As a result, the load acting on the upper surface 2b of the panel 2 is received by the vehicle body via the reinforcing member 3. The inner peripheral edge portion 5b of the outer peripheral portion 5 is a portion arranged so as to surround the honeycomb structure 6 and connected to the honeycomb structure 6.
[0044]
　The honeycomb structure 6 has a three-dimensional structure provided for receiving a load acting on the upper surface 2b of the panel 2. The honeycomb structure 6 is formed by combining members having a V-shaped cross section (hat shape in cross section).
[0045]
　The honeycomb structure 6 has a plurality of units 7 and a plurality of partial units 8 adjacent to the inner peripheral edge portion 5b of the outer peripheral portion 5 and continuous with the outer peripheral portion 5.
[0046]
　The unit 7 adjacent to the outer peripheral portion 5 of the reinforcing member 3 is connected to the outer peripheral portion 5 directly or via the partial unit 8.
[0047]
　The partial unit 8 has a configuration corresponding to a configuration in which a part of the unit 7 is cut out along the circumferential direction of the hexagonal unit 7. The partial unit 8 has a side portion similar to the side portion 10 described later of the unit 7. Then, this side portion is continuous with the inner peripheral edge portion 5b of the outer peripheral portion 5.
[0048]
　Each unit 7 is formed in a hexagonal ring shape in a plan view in the vehicle height direction Z. Hereinafter, when simply expressed as a plan view, it means a plan view in the vehicle height direction Z. In this embodiment, each unit 7 is formed in a substantially regular hexagon. A regular hexagon is a hexagon in which the lengths of each side are all equal and the internal angle is also constant at 120 degrees. Further, the “substantially regular hexagon” refers to a hexagon that can be treated as a regular hexagon in the present specification from the viewpoint of the tension rigidity of the panel 2 and the dent resistance. The shape of each unit 7 is substantially the same. In this case, "substantially the same" means that the configuration is the same except that the shape of each unit 7 is matched to the curved shape of the panel 2.
[0049]
　Each unit 7 may be formed in a hexagon other than a regular hexagon. Examples of hexagons other than regular hexagons include hexagons having uneven lengths on each side and hexagons having inconsistent internal angles of 120 degrees. As a hexagon with non-uniform length of each side, the length of the front end side and the length of the rear end side are set to a predetermined first length, and a predetermined second length different from the first length. An example of a hexagon having four sides set in is illustrated.
[0050]
　The honeycomb structure 6 has a structure in which a plurality of hexagonal annular units 7 are closely arranged. In this case, "closest pack" means that when each side portion 10 of the unit 7 has another adjacent unit 7, the unit 7 is arranged without a gap with one side portion 10 of the other unit 7. Say that. Specifically, the unit 7 is partitioned from other units in the top plate 13. As shown in FIG. 6, the tip 13b of the top plate 13 forms the boundary of the top plate 13 including the tip 13b. This boundary is formed in a hexagonal shape in a plan view. Due to such a close-packed hexagonal arrangement, the honeycomb structure 6 can withstand a load in all directions including the vehicle height direction Z in the entire region in a plan view in substantially the same manner.
[0051]
　In the present embodiment, the plurality of units 7 are formed symmetrically in the vehicle width direction X as a whole. Specifically, in the present embodiment, three units 7 are lined up in the front-rear direction at the center of the vehicle width direction X. Then, in a plan view, the plurality of units 7 are arranged symmetrically in the vehicle width direction X with reference to the virtual line A1 extending in the front-rear direction through the center of the vehicle width direction X in the three units 7. Not limited to this, since the tension rigidity, the dent resistance and the mass do not depend on the direction of the unit 7, there is no restriction on the direction of the unit 7.
[0052]
　In the present embodiment, the four units 7 arranged in the vehicle length direction Y are arranged in order from the three units 7 arranged at the center position in the vehicle width direction X to the right side, and further, in the vehicle length direction Y. Three units 7 arranged side by side are arranged, two units 7 arranged in the vehicle length direction Y are arranged, and two units 7 arranged in the vehicle length direction Y are further arranged. Further, in the same manner as described above, the four units 7 arranged in the vehicle length direction Y are arranged in order from the three units 7 arranged at the center position in the vehicle width direction X toward the left side, and further, the vehicle length. Three units 7 arranged in the direction Y are arranged, two units 7 arranged in the vehicle length direction Y are arranged, and two units 7 arranged in the vehicle length direction Y are further arranged.
[0053]
　Each unit 7 has six side portions 10 (10a to 10f). In the present embodiment, in each unit 7, the front side portion 10a and the rear side portion 10d extend along the vehicle width direction X, respectively. Then, in each unit 7, the remaining four side portions 10 extend in a direction inclined with respect to the vehicle length direction Y in a plan view.
[0054]
　Each side portion 10 (10a to 10f) has a floor 11, a vertical wall 12, and a top plate 13.
[0055]
　The floor 11 is adjacent to the panel 2 and is the portion of the side portion 10 that is closest to the panel 2. The floor 11 is a strip-shaped portion. The floor 11 is a flange portion of the side portion 10, and the floor 11 of the six side portions 10 forms a hexagonal flange. The inner ends of the six floors 11 form an annular end 20 centered on the center of the annular unit 7 as a whole. The annular end 20 of the unit 7 on the center side of the unit 7 is an end arranged on the center side of the unit 7. The annular end 20 is centered on the center of the unit 7.
[0056]
　In a cross section orthogonal to the longitudinal direction of the side portion 10 (cross section shown in FIG. 5), the outer end portion 11c of the floor 11 has a virtual line V1 including an upper surface 11b (straight line portion) of the floor 11 and an upper side surface of the vertical wall 12. It is an intersection of virtual lines V2 including an intermediate portion (straight line portion) of 12a. The intersection of the virtual lines V1 and V2 is not only the outer end portion 11c but also the first ridge line 31. When the floor 11 and the vertical wall 12 are connected in a curved shape as in the present embodiment, the outer end portion 11c becomes a virtual end portion. That is, in the present embodiment, the first ridge line 31 is a virtual line. On the other hand, when the floor 11 and the vertical wall 12 are connected in a linearly pointed shape, the outer end portion 11c serves as a connection point between them. In this case, the first ridge line 31 is a solid line.
[0057]
　In the present embodiment, the first ridge line 31 is a hexagonal annular ridge line in a plan view. The first ridge line 31 is between the floor 11 and the vertical wall 12. The first ridge line 31 is also a part of the floor 11 and a part of the vertical wall 12. The first ridge line 31 is adjacent to the panel 2.
[0058]
　Both ends of the floor 11 in the longitudinal direction are formed in a curved shape in a plan view, and are smoothly continuous with the floor 11 of the adjacent side portion 10. In each unit 7, the floor 11 of at least a part of the side portions 10 is adhered to the joint portion 4 on the upper surface 11b as the floor surface, and is adhered to the panel 2 via the joint portion 4. The upper surface 11b is a surface of the floor 11 facing the lower surface 2a of the panel 2.
[0059]
　In this embodiment, the length L1 of one side of the first ridge line 31 is set to 40 mm or more and 75 mm or less. When the length L1 of one side of the first ridge line 31 is less than the above lower limit, the span in which one unit 7 supports the panel 2 is short, and the tension rigidity can be increased. However, the allowable value of the deflection of the panel 2 becomes small, and the dent resistance decreases. Further, as a result of the number of the hexagonal annular units 7 arranged closest to each other becoming too large, the reinforcing member 3 becomes heavy. On the other hand, if the length L1 of one side of the first ridge line 31 exceeds the above upper limit, the span in which one unit 7 supports the panel 2 becomes too long, and as a result, it is difficult to secure sufficient tension rigidity. By setting the length L1 of one side of the first ridge line 31 to the above range, it is possible to secure sufficient tension rigidity and sufficient dent resistance while making the reinforcing member 3 lighter. Therefore, in the automobile hood 1, it is possible to secure sufficient tension rigidity and dent resistance for the panel 2 while achieving weight reduction of the panel 2.
[0060]
　The width W1 (width in a cross section orthogonal to the longitudinal direction of the side portion 10) of the upper surface 11b of the floor 11 is the distance between the inner end portion 20 and the outer end portion 11c of the floor 11. The width W1 is 2 mm or more over the entire area of ​​the annular end 20 in the circumferential direction of the annular end 20. In order to achieve both the weight reduction of the automobile hood 1 and the improvement of the dent resistance of the panel 2, the width W1 of the upper surface 11b of the floor 11 may be 2 mm or more over the entire circumference as described above. is necessary. If the width W1 is less than 2 mm at the central portion of the side portion 10 in the longitudinal direction, the panel 2 is subjected to a relatively low load as a load P1 at the position C1 on the center position of the unit 7. Deflection is likely to occur. Therefore, the tension rigidity of the panel 2 is reduced.
[0061]
　In this way, the width W1 of the upper surface 11b of the floor 11 is set to at least 2 mm or more, and the center of the annular end portion 20 is aligned with the center of the first ridge line 31. As shown in FIG. 7, at each corner portion (vertex) of the hexagonal first ridge line 31, the distance between the corner portion and the annular end portion 20 is the corner portion width W11 of the width W1. Further, on each of the six sides of the first ridge line 31, the distance between the center of one side of the first ridge line 31 and the annular end portion 20 is the central width W12 of the width W1. In the present embodiment, the corner width W11> the center width W12. By setting the corner width W11> the center width W12, it is possible to achieve both the improvement of the tension rigidity of the panel 2 and the improvement of the dent resistance while achieving the weight reduction of the reinforcing member 3.
[0062]
　In the present disclosure, in plan view, all of the annular end portions 20 are between the first circle CR1 and the second circle CR2. The first circle CR1 is a circle inscribed in the first ridge line 31. The second circle CR2 is concentric with the first circle CR1. Further, the second radius r2 as the radius of the second circle CR2 is set to 60% (r2 = 0.6r1) of the first radius r1 as the radius of the first circle CR1.
[0063]
　In a plan view, the center point P1 of the first circle CR1, the center point P2 of the second circle CR2, the center point P3 (center of the figure) of the hexagonal annular first ridge line 31, and the center point P20 of the annular end portion 20. Are in agreement. In the present embodiment, the annular end portion 20 is formed in a perfect circle or a substantially perfect circle centered on the center point P3 of the first ridge line 31 in a plan view. In this case, the "substantially perfect circle" means the blank or intermediate to form the unit 7 after the blank or intermediate molded product to be the reinforcing member 3 is drilled to form the annular end portion 20. This means that the molded product does not become a strict perfect circle due to further press working or the like.
[0064]
　Since the annular end portion 20 is arranged between the first circular CR1 and the second circular CR2 in a plan view, the inner portion of the annular end portion 20 of the unit 7 becomes hollow, and the reinforcing member 3 can be reduced in weight. Further, as shown in the conceptual side view of FIG. 8B, the maximum support span SP of the panel 2 by the annular end portion 20, that is, the diameter of the annular end portion 20, can be set to a value that is neither too large nor too small. As a result, the tension rigidity of the panel 2 can be sufficiently ensured, and the dent resistance can be sufficiently ensured. That is, it is possible to achieve both the weight reduction of the automobile hood 1, the sufficient tension rigidity of the panel 2, and the sufficient dent resistance of the panel 2. Therefore, even when the indenter ID is pushed into the upper surface 2b of the panel 2, dent is unlikely to occur.
[0065]
　As described above, the annular end portion 20 is between the first circle CR1 and the second circle CR2, and the width W1 is 2 mm or more on all the upper surfaces 11 of the floor 11. With this configuration, it is possible to secure sufficient tension rigidity and dent resistance of the panel 2 while achieving weight reduction in the automobile hood 1.
[0066]
　Further, by making the annular end portion 20 circular, it is possible to receive the load from the panel 2 in a stable posture at the annular end portion 20 while reducing the weight of the reinforcing member 3.
[0067]
　If any part of the annular end portion 20 is larger than the first circle CR1, as shown in the conceptual side view of FIG. 8A, the maximum support span SP (annular) of the panel 2 by the annular end portion 20' The diameter of the end 20') becomes too large. As a result, the range of the upper surface 11b of the floor 11 that can be adhered to the panel 2 is narrowed. Therefore, the efficiency of the work of applying the joint portion 4 to the floor 11 is deteriorated. Moreover, the tension rigidity of the panel 2 is reduced. Furthermore, the dent resistance is also reduced. More specifically, the dent resistance is greatly affected by the restraint of the surroundings (annular end portion 20') with respect to the load acting on the panel 2 by pushing the indenter ID into the upper surface 2b of the panel 2. Therefore, when the distance between the point of action of the load by the indenter ID and the surrounding restraint position (annular end 20') is long as shown in FIG. 8A, the panel is used when the load by the indenter ID is low (low load), for example. The deflection of 2 becomes large. As a result, it becomes difficult to maintain the curvature shape of the panel 2 at the time of design, so that the dent resistance tends to decrease and the dent DT tends to occur.
[0068]
　On the other hand, when even a part of the annular end portion 20 ″ enters the inside of the second circle CR2, as shown in the conceptual side view of FIG. 8C, the inner portion of the annular end portion 20 ″ of the unit 7 The cavity is small. Therefore, the reinforcing member 3 becomes heavy, and the weight efficiency (the ratio of the effect of reinforcing the reinforcing member 3 to the weight of the reinforcing member 3) deteriorates. Further, the effect of improving the dent resistance of the panel 2 by the reinforcing member 3 is also reduced. More specifically, as described above, the dent resistance is greatly affected by the restraint of the surroundings (annular end 20 ″) with respect to the load from the indenter ID acting on the panel 2. Therefore, if the distance between the point of action of the load from the indenter ID and the annular end 20'' (restraint position) becomes too short as shown in FIG. 8C, the load from the indenter ID is, for example, low (low load). At the time), almost no deflection of the panel 2 occurs. As a result, a local stress is generated at the point of action of the load from the indenter ID, so that a stress state exceeding the yield load of the panel 2 is likely to occur, and a dent DT is likely to occur.
[0069]
　As is well shown in FIGS. 7A and 7B, in this embodiment, the annular end 20 is annular in plan view. Then, in the present embodiment, the radius r20 of the annular end portion 20 is 90% of the first radius r1. The radius of the annular end portion 20 may be 80% of the first radius r1, 70% of the first radius r1, or 60% of the first radius r1. ..
[0070]
　On the other hand, FIGS. 9A and 9B show two examples outside the scope of the present disclosure. As examples outside the first range, an example in which the radius r20'''' of the annular end 20'''' is 50% of the first radius r1 (FIG. 9A) and a radius r20'' of the annular end 20'''' An example (FIG. 9B) in which'' is 20% of the first radius r1 can be mentioned. As described above, in the out-of-range example shown in FIGS. 9A and 9B, the annular ends 20''', 20'''' are located inside the second circle CR2.
[0071]
　In the above description, a form in which the annular end portion 20 has a circular shape has been described as an example. However, the configuration of the annular end portion 20 is not limited to the above configuration. In a plan view, a polygon can be shown as an example in which the annular end portion 20 has a shape other than a circular shape. Even when the annular end 20 is polygonal, the lower limit of the width W1 is 2 mm, and the entire area of ​​the annular end 20 is arranged between the first circle CR1 and the second circle CR2.
[0072]
　Preferable examples of the above-mentioned polygons in the present disclosure include hexagons and dodecagons.
[0073]
　10A and 10B show a first modification as an example in which a hexagonal annular end 20A is provided instead of the circular annular end 20. The annular end 20A is a regular hexagon or a substantially regular hexagon. In this case, the "substantially regular hexagon" is a blank or an intermediate molded product to be a reinforcing member 3 for forming the annular end portion 20A, and then the blank or an intermediate molded product for forming the unit 7. This means that the intermediate molded product does not have a strict regular hexagon due to further press working or the like. In this first modification, each vertex of the annular end 20A is on a line segment L10A connecting the center point P20 of the annular end 20A and the midpoint of the corresponding side of the hexagonal first ridge 31. Have been placed. Each vertex of the annular end portion 20A may be arranged on a line segment connecting the center point P20 of the annular end portion 20A and the corresponding vertex of the hexagonal first ridge line 31.
[0074]
　By making the annular end portion 20A circular in this way, it is possible to receive the load from the panel 2 in a stable posture at the annular end portion 20A while reducing the weight of the reinforcing member 3.
[0075]
　11A and 11B show a second modification as an example in which a dodecagonal annular end 20B is provided instead of the circular annular end 20. The annular end 20B is a regular dodecagon or a substantially regular dodecagon. In this case, the "substantially regular dodecagon" is a blank or an intermediate molded product to be a reinforcing member 3 for forming the annular end portion 20B, and then the blank or an intermediate molded product for forming the unit 7. This means that the intermediate molded product does not have a strict regular dodecagon due to further press working or the like. In this second modification, two types of vertices AP1 and AP2 are set as the vertices of the annular end portion 20B. Each vertex AP1 is arranged on a line segment L10B connecting the center point P20 of the annular end portion 20B and the corresponding one vertex of the hexagonal first ridge line 31. Further, the apex AP2 is arranged on the line segment L20B connecting the center point P20 of the annular end portion 20B and the midpoint of the corresponding side of the hexagonal first ridge line 31. Then, the vertices AP1 and the vertices AP2 are arranged alternately. In the second modification, the distance DS1B from the center point P20 of the annular end portion 20B to the apex AP1 and the distance DS2B from the center point P20 of the annular end portion 20B to the apex AP2 are the same. The distance DS1B and the distance DS2B may be different as long as the annular end portion 20B is arranged between the first circle CR1 and the second circle CR2.
[0076]
　By forming the annular end portion 20B into a dodecagonal shape in this way, it is possible to receive the load from the panel 2 in a stable posture at the annular end portion 20B while reducing the weight of the reinforcing member 3. The above is the schematic configuration of the floor 11.
[0077]
　As shown in FIG. 5, a vertical wall 12 extends downward from the floor 11.
[0078]
　The vertical wall 12 is arranged between the floor 11 and the top plate 13, and connects the floor 11 and the top plate 13. The vertical wall 12 is provided over the entire area in the longitudinal direction of the side portion 10 where the vertical wall 12 is provided. The angle θ1 formed by the vertical wall 12 with respect to the floor 11, for example, the angle θ1 formed by the upper side surface 12a of the vertical wall 12 and the upper surface 11b of the floor 11 is preferably set in the range of 40 degrees to 90 degrees. .. When the angle θ1 is equal to or greater than the above lower limit, the vertical wall 12 can sufficiently function as a pillar, so that the vertical wall 12 can receive the load transmitted from the panel 2 to the floor 11 with a small amount of deformation. can. Further, when the angle θ1 is equal to or less than the above upper limit, the unit 7 has a shape that expands toward the end as the unit 7 moves downward (a shape in which the distance between the vertical walls 12 and 12 facing each other becomes wider toward the lower side in the vehicle height direction Z). Therefore, it is easy to mold.
[0079]
　The length of the vertical wall 12 in the vehicle height direction Z is a component of the vehicle height direction Z among the distances between the first ridge line 31 and the second ridge line 32, and is about 16 mm in the present embodiment. In the cross section orthogonal to the longitudinal direction of the side portion 10, the second ridge line 32 is an intersection of the virtual line V3, which is a tangent line to the top of the lower side surface 13c of the top plate 13, and the virtual line V2. The intersection of the virtual lines V2 and V3 is not only the second ridge line 32 but also the inner end portion 13d of the top plate 13. When the vertical wall 12 and the top plate 13 are connected in a curved shape as in the present embodiment, the second ridge line 32 becomes a virtual ridge line. On the other hand, when the vertical wall 12 and the top plate 13 are connected in a linearly pointed shape, the second ridge line 32 is a solid line. The second ridge line 32 can be said to be a part of the vertical wall 12 and a part of the top plate 13.
[0080]
　In the present embodiment, the second ridge line 32 is a hexagonal annular ridge line like the first ridge line 31. The second ridge line 32 is located on the outer periphery of the lower end of the vertical wall 12 and is separated from the panel 2. The first ridge line 31 is an example of a “hexagonal annular ridge line between the vertical wall and the floor”, and is a ridge line at the end of the vertical wall 12 on the floor 11 side. The first ridge line 31 and the second ridge line 32 are similar to each other in a plan view in the present embodiment. In a plan view, the total length of the second ridge line 32 is longer than the total length of the first ridge line 31. In the vehicle height direction Z, the distance from the panel 2 to the second ridge line 32 is longer than the distance from the panel 2 to the first ridge line 31. The smaller the inclination angle θ1 of the vertical wall 12, the larger the ratio of the length of one side of the second ridge line 32 to the length L1 of one side of the first ridge line 31. Therefore, the length of one side of the second ridge line 32 is preferably set to 40 mm or more and 95 mm or less.
[0081]
　In the present embodiment, the thickness of the unit 7 (the length in the vehicle height direction Z) can be set by setting the length and the angle θ1 of the vertical wall 12. The floor 11 is continuous with the upper end of the vertical wall 12. The top plate 13 is continuous with the lower end of the vertical wall 12. In a cross section orthogonal to the longitudinal direction of the side portion 10, the floor 11 and the vertical wall 12 are continuous with each other in a smoothly curved shape, and are connected in a manner in which stress concentration is unlikely to occur. Similarly, the top plate 13 and the vertical wall 12 are continuous with each other in a smoothly curved shape, and are connected in a manner in which stress concentration is unlikely to occur. The floor 11 and the vertical wall 12, and the vertical wall 12 and the top plate 13 may be connected in a sharp shape, respectively.
[0082]
　The top plate 13 is the portion of the unit 7 that is most distant from the panel 2. The top plate 13 is formed in a curved shape that is convex downward or a shape that extends substantially horizontally. The top plate 13 is provided over the entire area in the longitudinal direction of the side portion 10 where the vertical wall 12 is provided. In a cross section orthogonal to the longitudinal direction of the side portion 10, the floor 11, the vertical wall 12, and the top plate 13 are arranged in this order from the inside to the outside of the unit 7. The tip 13b of the top plate 13 in one unit 7 is integrated with the tip 13b of the top plate 13 in the adjacent unit 7.
[0083]
　FIG. 12 is a diagram for explaining an example of arrangement of the joint portion 4 in the automobile hood 1. Next, the joint portion 4 will be described more specifically with reference to FIGS. 5 and 12. In FIG. 5, the joint portion 4 is shown by hatching, which is a cut surface. The joint portion 4 is an adhesive in this embodiment. As this adhesive, a mastic sealer (mastic adhesive) can be exemplified. As this mastic sealer, a resin-based adhesive can be exemplified. The adhesive may have a property of being cured at room temperature (for example, 20 degrees Celsius), or may have a property of being cured by undergoing a heating step or a drying step.
[0084]
　The joint portion 4 is provided so as to sufficiently secure both tension rigidity and dent resistance while achieving weight reduction of the automobile hood 1. Specifically, the joint portion 4 is provided on at least two side portions 10 parallel to each other on the six side portions 10. Then, in the present embodiment, in each unit 7, the joint portion 4 is provided on all of the six side portions 10. In the present embodiment, on the upper surface 11b of the floor 11 of each side portion 10, the joint portions 4 are provided over the entire area in the longitudinal direction of the side portions 10, and the joint portions 4 provided on the adjacent side portions 10 are provided with each other. Are integrated. As a result, in the present embodiment, in each unit 7, the joint portion 4 has a hexagonal shape.
[0085]
　The thickness t3 of the joint portion 4 is, for example, about several mm, which is an extremely large value with respect to both the plate thickness t1 of the panel 2 and the plate thickness t2 of the reinforcing member 3. Therefore, the ratio of the joint portion 4 in terms of material cost and weight in the automobile hood 1 cannot be ignored. Therefore, the amount of the joint portion 4 used is preferably as small as possible from the viewpoint of material cost and weight reduction of the automobile hood 1. On the other hand, the joint portion 4 is also a load transmission portion provided for transmitting the load from the panel 2 to the unit 7. Therefore, from the viewpoint of achieving all of the weight reduction, the tension rigidity improvement, and the dent resistance improvement, it is possible to specify a more preferable usage mode of the joint portion 4 in each unit 7.
[0086]
　FIG. 13 is a conceptual plan view showing a main portion of the third modification of the present disclosure, and shows a portion where the joint portion 4 is provided. As a third modification of the present embodiment, the following configuration shown in FIG. 13 can be mentioned. That is, the joint portion 4 is provided on a part of the side portions 10 (10a to 10f) of the six side portions 10 (10a to 10f) of each annular unit 7. Then, in the modification of the present disclosure, the joint portion 4 is provided on at least two side portions 10 of the six side portions 10 facing each other in parallel and separated from each other. ing. In the side portion 10 provided with the joint portion 4, the joint portion 4 extends in a straight line shape along the longitudinal direction of the side portion 10.
[0087]
　The length W2 of the joint portion 4 in the plan view is set in the range of 20% to 100% of the total length W3 of the floor 11 in the longitudinal direction of the floor 11, and is preferably set in the range of 50% to 100%. ing. In FIG. 13, an example of length W2 = total length W3 is shown. By setting the length W2 of the joint portion 4 to be equal to or greater than the above lower limit, it is possible to sufficiently secure the joint strength between the floor 11 on which the joint portion 4 is provided and the panel 2. Further, when the step of adhering the joint portion 4 to the panel 2 and the floor 11 by heating is adopted, thermal strain occurs in the panel 2 and the reinforcing member 3 due to the heating in the heating step of the joint portion 4. However, the above thermal strain can be reduced by providing the joint portion 4 only on a part of the six side portions 10 of the unit 7.
[0088]
　As described above, in the third modification, in each unit 7, the joint portion 4 is provided on a part of the side portions 10 of the six side portions 10, and the remaining side portions 10 are the joint portions 4. Is not provided. The entire remaining side portion 10 faces the panel 2 directly up and down.
[0089]
　As shown in FIG. 13, four side portions 10 of the six side portions 10 are joined to the joint portion 4, and are connected to the panel 2 by the joint portion 4. That is, two sets of a pair of side portions 10 facing each other in parallel in a plan view are provided with a joint portion 4. The remaining two distant sides 10 (two non-adjacent sides 10) are not provided with a joint 4 and are directly adjacent to the panel 2 (via air only). ..
[0090]
　More specifically, among the six side portions 10, the joint portion 4 includes a front side portion 10a and a rear side portion 10d extending parallel to each other, a right rear side portion 10c extending parallel to each other, and a left front side portion 10f. It is provided in. That is, the joint portion 4 is provided on the four side portions 10 of the unit 7 except for the right front side portion 10b and the left rear side portion 10e. As a result, as shown by the arrow B1 in the honeycomb structure 6, the joint portion unset region 14 is provided from the left rear to the right front (toward diagonally forward to the right).
[0091]
　With such a configuration, in the honeycomb structure 6, a plurality of aggregates 15 of zigzag streaky joints 4 extending from the left rear to the right front are provided. With such a structure of the honeycomb structure 6, it is possible to satisfy the three requirements of weight reduction, ensuring tension rigidity, and ensuring dent resistance at a high level.
[0092]
　As long as the relative positional relationship of the joints 4 shown in FIG. 13 is satisfied, the same effect can be obtained even if the arrangement of the joints 4 is changed. For example, the overall arrangement of the plurality of joints 4 in the third modification shown in FIG. 13 may be replaced symmetrically with respect to the vehicle width direction X.
[0093]
　Further, instead of the third modification shown in FIG. 13, the joint portion 4 may be arranged in the manner shown in the fourth modification of FIG. In FIG. 14, the joint portion 4 is, for example, of the six side portions 10 in the unit 7, the right front side portion 10b and the left rear side portion 10e as two sides extending in parallel with each other, and any of these two side portions 10. It is provided on two side portions 10 that are in contact with both ends of the. That is, the joints 4 are provided on the four side portions 10 of the unit 7. In this second modification, the first unit 21 as an aggregate of units 7 having no joint portion 4 provided on the rear side portion 10d and the left front side portion 10f is joined to the front side portion 10a and the right rear side portion 10c. A second unit 22 and a second unit 22 as an aggregate of the units 7 to which the unit 4 is not provided are provided. In the first unit 21, the units 7 are connected from the left rear to the right front. Similarly, in the second unit 22, the units 7 are connected from the left rear to the right front. The first unit 21 and the second unit 22 are arranged alternately.
[0094]
　As long as the relative positional relationship of the joints 4 shown in FIG. 14 is satisfied, the same effect can be obtained even if the arrangement of the joints 4 is changed. For example, the overall arrangement of the plurality of joints 4 in the fourth modification shown in FIG. 14 may be replaced symmetrically with respect to the vehicle width direction X.
[0095]
　In the third modification and the fourth modification described above, a mode in which the joint portion 4 is provided on the four side portions 10 and the joint portion 4 is not provided on the two side portions 10 of each unit 7 has been described as an example. However, this does not have to be the case. For example, as shown in the fifth modification of FIG. 15, in each unit 7, the joint portion 4 may be provided on two side portions 10 out of the six side portions 10. That is, a set of two side portions 10 and 10 facing each other in parallel in a plan view is provided with a joint portion 4. The remaining four side portions 10 are directly adjacent to the panel 2 because the joint portion 4 is not provided.
[0096]
　In the fifth modification shown in FIG. 15, for example, the joint portion 4 is provided only on the right rear side portion 10c and the left front side portion 10f extending in parallel with each other among the six side portions 10 in the unit 7. As a result, in each unit 7, the four side portions 10 are not provided with the joint portions 4. As described above, in each unit 7, if the joint portion 4 is provided on the two side portions 10 (10c, 10f) which are a part of the six side portions 10 and are parallel to each other, the weight can be reduced. In addition, the three requirements of ensuring tension rigidity and ensuring dent resistance can be satisfied at a high level.
[0097]
　In addition, instead of the fifth modification shown in FIG. 15, a modification (not shown) in which the joint portion 4 is provided only on the front side portion 10a and the rear side portion 10d parallel to each other among the six side portions 10 An example of a modification (not shown) in which the joint portion 4 is provided only on the right front side portion 10b and the left rear side portion 10e parallel to each other can be exemplified.
[0098]
　By adopting any of the above-described embodiment and each modification of the joint portion 4, the performance of the panel 2 can be improved (at least the tension rigidity is improved, and the dent resistance is improved) and the weight is reduced. realizable.
[0099]
　In the above-described embodiment and each modification, in the side portion 10 provided with the joint portion 4, the joint portion 4 is not limited to the case where it is formed in a continuous linear shape, and is intermittently dotted. It may be arranged.
[0100]
　According to the automobile hood 1 of the present embodiment, of the six side portions 10 of the unit 7, the side portion 10 provided with the joint portion 4 is 20% or more of the side portion 10 in the extending direction of the side portion 10. It is in contact with the joint 4 over the range of. According to this configuration, both the tension rigidity and the dent resistance of the panel 2 can be increased. In particular, if the joint portion 4 has a linear shape that extends continuously at the side portion 10, the joint portion 4 may be provided in a dot shape at the hexagonal corner portion, or the joint portion 4 may be provided in a dot shape in the center of the side portion 10. It is possible to increase both the tension rigidity and the dent resistance of the panel 2 as compared with the case where the panel 2 is provided.
[0101]
　Further, according to the automobile hood 1 of the present embodiment, the plate thickness t1 of the steel plate panel 2 is 0.6 mm or less. As described above, when the plate thickness t1 of the panel 2 is 0.6 mm or less, the tension rigidity and the dent resistance obtained from the rigidity of the panel 2 itself are compared with the case where the plate thickness t1 of the panel 2 is 0.65 mm or more. And, it drops extremely. More specifically, the tension rigidity of the panel 2 depends on the Young's modulus and the plate thickness of the panel 2, and in particular, changes depending on the square of the plate thickness. When the design plate thickness of the panel 2 made of the steel plate is changed from 0.65 mm to 0.6 mm, the tension rigidity that the panel 2 can secure by itself is extremely lowered. This decrease in rigidity is particularly remarkable in terms of the feel when the panel 2 is pushed by a human hand, and causes a decrease in the commercial value of the automobile. As described above, regarding the tension rigidity of the steel panel 2, there is a critical significance between the plate thickness t1 of 0.6 mm and 0.65 mm. Then, even when a thin panel 2 having a plate thickness t1 of 0.6 mm or less is used as in the present embodiment, the reinforcing member 3 for reinforcement and rigidity and the panel 2 can be combined to form the automobile hood 1. It is possible to secure tension rigidity and dent resistance substantially equivalent to those when the plate thickness t1 of the panel 2 is 0.65 mm. Moreover, since the plate thickness t1 of the panel 2 is reduced, the weight reduction of the automobile hood 1 can be achieved through the weight reduction of the panel 2.
[0102]
　Further, the steel panel 2 and the reinforcing member 3 are superior to the aluminum alloy panel and the reinforcing member in terms of material cost. Further, in an automobile hood made of an aluminum alloy, the idea of ​​ensuring tension rigidity with a reinforcing member below the panel has not existed in the first place. Moreover, since the aluminum alloy has a lower Young ratio than steel, the rigidity of the aluminum alloy is lower than that of steel. Therefore, in order to secure the same rigidity as the steel automobile hood 1 in the aluminum alloy automobile hood, it is necessary to increase the plate thickness of the member. Therefore, in order to satisfy both the tension rigidity and the dent resistance of the aluminum alloy panel, the plate thickness is increased. Therefore, as in the present embodiment, the viewpoint of improving both the tension rigidity and the dent resistance while reducing the plate thickness of the panel 2 and the reinforcing member 3 does not exist in the aluminum alloy automobile hood. However, as described above, from the viewpoint of tension rigidity and dent resistance, the thickness of the steel plate panel and the reinforcing member and the aluminum alloy plate panel and the reinforcing member can be set to have equivalent performance. Therefore, in the present embodiment, the panel 2 and the reinforcing member 3 may be a steel plate or an aluminum alloy plate.
[0103]
　The embodiments and modifications of the present disclosure have been described above. However, the present disclosure is not limited to the embodiments and modifications described above. The present disclosure may be modified in various ways within the scope of the claims.
Example
[0104]
　A shape model of the automobile hood 1 shown in the embodiment and the modified example was created on a computer using CAD (Computer Aided Design) software. That is, an automobile hood 1 having a panel 2, a reinforcing member 3, and a joint portion 4 was created on a computer. Then, the tension rigidity and the dent resistance were evaluated by CAE (Computer Aided Engineering) analysis of the shape model of the automobile hood 1, that is, by performing computer simulation. The characteristics of each part are as follows.
[0105]
　Panel 2: Made of 590 MPa class high-strength steel plate. Yield stress = 375 MPa, tensile strength = 622 MPa, plate thickness t1 = 0.4 mm.
　Reinforcing member 3: Made of mild steel plate. Yield stress = 163 MPa, tensile strength = 325 MPa, plate thickness t2 = 0.3 mm.
　The elastic modulus of the steel sheet was Young's modulus = 206 GPa and Poisson's ratio = 0.3.
[0106]
　In this example, Disclosure Examples 1 to 7 and Comparative Examples 1 to 4 were prepared. Regarding the disclosure examples 1 to 7 and the comparative examples 1 to 4, the length L1 of one side of the hexagonal first ridge line 31, the corner width W11 on the upper surface 11b of the floor 11, and the central width W12 on the upper surface 11b are shown in Table. As shown in 1.
[0107]
　As shown in FIG. 16, the shapes A and B (Examples 1 and 2 of the present disclosure) have a dodecagonal annular end 20B. Shape C (Comparative Example 1) has a hexagonal annular end 20A'. Each vertex of the annular end 20A'is located on the corresponding midpoint of the six sides of the first ridge 31. With this configuration, the central width W12 is zero mm. The annular end portion 20A of the shape D (the third disclosure example 3) is arranged similar to the first ridge line 31 in a plan view.
[0108]
　As shown in FIG. 17, the shapes E and F (Examples 4 and 5 of the present disclosure) have a dodecagonal annular end 20B. The shapes G and H (Comparative Examples 2 and 3) have a dodecagonal annular end 20B'. At the annular end 20B', there are apex AP1'adjacent to the apex of the first ridge line 31 and apex AP2'adjacent to the midpoint of the first ridge line 31. The distance DS2B'from the center point P3 of the hexagonal first ridge line 31 to the apex AP2'is smaller than the distance DS1B' from the center point P3 to the apex AP1'. Further, in the shapes G and H, a part of the annular end portion 20B'is located outside the first circle CR1. Further, in the shapes G and H, the corner width W11