JP5221861B2 - Structural members for vehicles - Google Patents

Description

  The present invention relates to a structural member of a vehicle such as an automobile. More specifically, the present invention relates to a vehicle structural member for achieving both weight reduction of a vehicle body and improvement of vehicle crash safety.

  From the viewpoint of reducing the weight of a vehicle body against the background of global environmental protection and improving the collision safety of a vehicle, there is a demand for a structural member that is lightweight and has an excellent impact energy absorption capability. For example, it is possible to improve the performance by reducing the thickness of the structural member using a high-strength steel plate (hereinafter referred to as “HITEN”) or by increasing or optimizing the cross-sectional shape of the structural member. It has been actively studied from materials to shapes.

  Also, press forming a so-called tailor weld blank (hereinafter abbreviated as “TWB”), in which different materials such as thick and high strength materials and thin and low strength materials are welded and joined before press molding. By manufacturing a vehicle structural member, a thick material or a high-strength material is arranged in a region or region that dominates the performance of the vehicle structural member, and a thin material is not used in a region or region that does not greatly affect the performance. In addition, low-strength materials are also used, which promotes both weight reduction of structural members and maintenance / improvement of performance.

  One such vehicle structural member is a center pillar. FIG. 7 is an explanatory diagram showing an example of the center pillar 1. As shown in the figure, the center pillar 1 is fixedly disposed between the roof rail side 2 and the side sill 3 constituting the body side of the automobile body, thereby supporting the roof, holding the rear door, and various rigidity of the vehicle body. It plays an extremely important role in the maintenance of passengers and the protection of passengers in case of a side collision. In order to improve and improve the performance required for the center pillar 1, various inventions have been proposed so far.

  In Patent Document 1, for example, a high-strength steel plate having a tensile strength of 900 MPa or more is used for the outer panel of the center pillar, and an aluminum alloy plate is used for the inner panel, thereby maintaining and improving various performances of the center pillar. An invention for reducing the weight is disclosed.

  Patent Document 2 relates to a structural member that is provided with a swell on at least one of an extruded surface or a middle rib of a hollow aluminum extruded material or a hollow aluminum extruded material having a middle rib, although it relates to a bumper and the like instead of a center pillar. The invention is disclosed.

Furthermore, in Patent Document 3, for example, the number of manufacturing man-hours is increased while increasing strength by performing press forming after performing induction hardening in advance on a portion that becomes a ridge line in a steel plate before performing center pillar reinforcement press forming. An invention relating to a center pillar reinforce that suppresses an increase in the above is disclosed.
JP 2005-343329 A Japanese Patent Laid-Open No. 6-344023 JP 2002-68012 A

  As in the inventions disclosed in Patent Documents 1 and 2, if an attempt is made to reduce the weight by using an aluminum alloy plate as a structural member, the material cost increases, and the manufacturing cost increases. It is necessary to take measures against electric corrosion that becomes a problem when both are used together. For this reason, since the manufacturing cost also rises from this point, it is difficult to apply to all mass-produced vehicles. In particular, when high tension is used in the invention disclosed in Patent Document 1, ductility is inevitably lowered, and thus the formability of the structural member is lowered.

  FIG. 8 is an explanatory diagram showing a simplified structural example of the conventional vehicle structural member 4 disclosed in Patent Document 3. As shown in FIG. This structural member 4 is manufactured by welding a portion 4 a made of a thin material and a portion 4 b made of a thick material at the position of a welding line 5. For this reason, even with the invention disclosed in Patent Document 3, there are problems in terms of performance differences in the longitudinal direction of the structural members for vehicles and productivity. In addition, even with this invention, it is virtually impossible to further reduce the weight of the vehicle structural member.

  The object of the present invention is to achieve both weight reduction and high performance, can be applied to any metal material, and causes a performance difference (for example, bending performance difference) in the longitudinal direction as in a conventional TWB. It is to provide a vehicular structural member that does not occur, in other words, to provide a vehicular structural member with an increased amount of collision energy per unit mass absorbed by bending deformation.

The present invention includes at least a part in the axial direction, two wall portions that are spaced apart from each other, two ridge line portions that continue to the two wall portions, and a bottom portion that connects the two ridge line portions. a structural member for a vehicle comprising a first member having a cross-section of substantially hat shape to absorb collision energy by Rutotomoni bending deformation, part of the bottom, the remaining part of the bottom portion, two wall portions and and the second metal plate constituting the two ridge portions being constituted by a first metal plate different, and, if the intensity of the first metal plate is less than the strength of the second metal plate, or, the The thickness of the first metal plate is smaller than the thickness of the second metal plate, and the thickness of each of the first metal plate and the second metal plate is constant . There are structural members.

  In the vehicle structural member according to the present invention, the circumferential length (X) in the cross section of a partial region is 0.30 times or more and 0.90 times the circumferential length (L) in the bottom cross section. The following is desirable. More desirably, it is 0.50 times or more and 0.86 times or less.

In the vehicle structural member according to the present invention, it is desirable that the first metal plate and the second metal plate are joined by welding along the axial direction of the bottom portion.

From another point of view, at least a part in the axial direction is a first groove having a substantially groove-shaped cross section that includes two wall portions that are spaced apart from each other and a bottom portion that connects the two wall portions. of a member, part of the bottom, the remaining part of the bottom, and a second metal plate constituting the two walls is constituted by a first metal plate different, and the first or strength of the metal plate is less than the strength of the second metal plate, or the thickness of the first metal plate with less than the thickness of the second metal plate, the first metal plate, and a second The center pillar of an automobile body is characterized in that the thickness of each metal plate is constant .

  These vehicle structural members or center pillars may further include a second member joined to the first member to close the substantially hat-shaped opening of the first member.

  According to the present invention, it is possible to provide a vehicle structural member that is lightweight and has an excellent impact energy absorption capability. Therefore, both the weight reduction of the vehicle structural member and the improvement of the collision safety of the vehicle can be achieved.

  Hereinafter, the best mode for carrying out the structural member for a vehicle according to the present invention will be specifically described with reference to the accompanying drawings. In the following description, the center pillar is taken as an example of the vehicle structural member, but the present invention is not limited to the center pillar. For example, a bumper reinforcement, a side sill, a front pillar, etc. If the deformation mode at that time is a structural member for a vehicle that is bent at three points as in the case of the center pillar, it can be similarly applied.

First, the knowledge on which the present invention is based will be briefly described.
As shown in FIG. 7 described above, the deformation mode of the center pillar 1 in the side collision is a three-point bending that bends toward the cabin with the upper roof rail side 2 and the lower side sill 3 as fulcrums. Therefore, the center pillar 1 is desired to have a high durability against a three-point bending load and a small bending deflection.

  In order to elucidate the phenomenon in the three-point bending, the inventors of the present invention have two types of structures having a hat-shaped cross-sectional shape shown in FIGS. 9A and 9B simulating the center pillar 1. A three-point bending FEM numerical analysis was performed on the members 1-1 and 1-2 using general-purpose dynamic explicit software PAM-CRASH.

  FIG. 10 is an explanatory diagram showing a three-point bending analysis model in this FEM numerical analysis. In FIG. 10, the right side of the center line l is omitted. As shown in FIG. 10, an impactor 7 having a radius of 150 mm is applied to a structural member 1-1, 1-2 supported by a support portion 6, 6, which is a columnar body having a radius of 30 mm, with a bending span of 500 mm. The analysis was performed under the condition of pushing in at 8 m / s. In addition, the symmetry condition was applied in the analysis because the phenomenon can be regarded as symmetrical.

And the knowledge (a)-(d) listed below was obtained.
(A) It is not all parts in the cross section that dominate the shock absorption performance of the center pillar, but there are specific parts that greatly affect the shock absorption performance.
(B) Considering the specific part that controls the shock absorbing performance and the other parts that do not affect the performance, the center pillar's cross-sectional structure is determined to reduce the weight of the center pillar and ensure the performance. Can be achieved.
(C) The center pillar is not constituted by the TWB in which two or more different materials are arranged in the longitudinal direction as in the prior art, but the center pillar is constituted by using the TWB in which the different materials are arranged in the cross section, By reducing the thickness or reducing the strength of the portion that does not affect the performance in the cross section, it is possible to provide a center pillar that can achieve both weight reduction and performance securing.
(D) Further, in place of TWB, a tailor rolled blank material (hereinafter referred to as “TRB”) in which the thickness after rolling changes at a thickness boundary portion where the thickness changes by 10% or more at a width of 30 mm including the boundary. The center pillar can be reduced in weight and performance can be ensured by using an extruded material or the like and subjecting them to normal press molding.

Next, the center pillar of this embodiment will be described.
FIG. 1 is an explanatory view showing a structural member 10 of the present embodiment, in which FIG. 1 (a) is a perspective view and FIG. 1 (b) is a cross-sectional view. The structural member 10 is a simplified structure of an actual center pillar for facilitating the understanding of the present invention, and exhibits the same behavior as the actual center pillar during bending deformation. The structural member 10 will be described as a center pillar.

  As shown in FIG. 1 (a), the center pillar 10 of the present embodiment is joined to an upper portion 11a joined to the roof rail side and a side sill, like the conventional center pillar 1 described with reference to FIG. The lower portion 11b is provided on both end sides in the longitudinal direction. In the case of a side collision, the collision energy is absorbed by generating a three-point bending deformation that bends toward the cabin with the two points of the upper part 11a and the lower part 11b as fulcrums.

  As shown in FIGS. 1 (a) and 1 (b), the center pillar 10 includes two wall portions 12 and 12 which are arranged to face each other in a cross section, and these two wall portions 12 and 12. A first member 10a having a linear bottom portion 13 (a portion having a circumferential length L in the cross section), and a back plate 15 as a second member for closing the two wall portions 12, 12. Have That is, in the present embodiment, the “bottom part 13” means a part existing between the R-stop positions of the two wall parts 12 and 12, and “the length of the bottom part 13” means this in the cross section. It means the circumferential length of the bottom 13. For this reason, when the bottom 13 is formed in a straight line in the cross section as shown in FIG. 1 (b), the length of the bottom 13 is the distance L in FIG. 1 (b). On the other hand, when the bottom portion 13 is formed in a cross section that is convex toward the inside or outside of the hat shape, or when the bottom portion 13 is formed by combining such a curve and a straight line, the length of the bottom portion 13 is Means the circumferential length of the bottom 13 thus formed in the cross section.

  The walls 12 and 12 are spot-welded to the back plate 15 by overlapping portions 12b and 12b. Further, in this example, the end portions 12a and 12a of the wall portions 12 and 12 are linearly formed so as to form a part of the bottom portion 13, and the length of the end portions 12a and 12a and the bottom portion 13 is X. The parts are joined by appropriate welding described later. That is, in this example, the bottom portion 13 having a length L is constituted by end portions 12a and 12a and a portion having a length X.

  In the present embodiment, the center pillar 10 is configured using not only the first member 10a configured by the two wall portions 12 and 12 and the bottom portion 13 but also the back plate 15 which is the second member. You may make it comprise the center pillar 10 only with the 1st member 10a, without using the board 15. FIG.

  Moreover, in this Embodiment, the flat plate was used as the backplate 15 as shown to Fig.1 (a) or FIG.1 (b). However, the back plate 15 as the second member is joined to the two wall portions 12 and 12 constituting the first member 10a, and can close the substantially hat-shaped opening of the first member 10a. Therefore, the shape of the back plate 15 is not limited to a flat shape. For example, a substantially hat-shaped shape, a curved surface shape, a flat shape partially having irregularities or a curved surface, etc. It may be.

  Further, as shown in FIGS. 1A and 1B, the center pillar 10 of the present embodiment has a length X in at least a part of the bottom portion 13 (FIG. 1B). Part) and the end portions 12a and 12a of the wall portions 12 and 12 are joined by weld lines 14 and 14 along the axial direction of the bottom portion 13.

  This joining means may be continuous welding such as mash seam, plasma, laser, and arc that are generally used. However, in the case of intermittent welding such as spot welding, for example, it is desirable to take measures such as increasing the number of welding points and strengthening the joint strength.

Since the principle of the present invention does not depend on the material, the material constituting the portion where the length of the wall 12 and the bottom 13 is X may be a metal material and is not limited to a specific metal material.
Although the center pillar 10 of the present embodiment is manufactured by performing press molding on TWB, the present invention is not limited to TWB, and press molding may be performed on TRB. However, the degree of freedom with respect to the plate thickness difference and the range of the thin portion is higher in the TWB including the joining position. Furthermore, in the TWB, it is possible to use different materials having different material strengths. Therefore, it is preferable to use the TWB.

  Further, the center pillar 10 of the present embodiment does not perform press molding to TWB or TRB, but has a thin wall portion and a thick wall portion, for example, by hot extrusion or cold extrusion, without undergoing press molding. You may make it manufacture directly.

Thus, the center pillar 10 of the present embodiment has a substantially hat-shaped cross-sectional shape as a whole.
As shown in FIG. 1B, the center pillar 10 has at least a partial region of the bottom 13 having a substantially hat shape in at least a part of the cross section in the axial direction (all in the illustrated example), ie, FIG. The region of length X in (b) is made of a material having a thinner plate thickness or a lower strength than other regions excluding this region. The reason for this will be explained.

  Consider a situation of side collision of a center pillar having a substantially hat-shaped cross section as a whole and made of a single material. FIG. 2 is an explanatory view showing an example of deformation behavior of the central cross section in the axial direction of the center pillar 16 having a substantially hat-shaped cross section in a side collision, and FIG. 3 is a load-displacement chart (load) in this central cross section. It is a graph which shows an example of a characteristic.

  As shown in FIGS. 2 and 3, at the collision portion of the center pillar 16, the cross section is crushed by the load, and the ridgelines 19 and 19 positioned between the planar bottom portion 18 and the wall portions 17 and 17, and the wall portion 17. , 17 and the bending deformation occurs. At this time, the strain mainly concentrates on the ridge lines 19 and 19, and the load becomes maximum when the ridge lines 19 and 19 are buckled. After that, the deformation becomes local and the load gradually decreases.

  As described above, the portions responsible for the stress in the cross section are mainly the ridgelines 19 and 19 and the wall portions 17 and 17, and the role of the planar bottom portion 18 is considered to be small. The present invention is based on the technical idea that the planar bottom portion 18 is made of a thin-walled material or a low-strength material, so that weight reduction or cost reduction can be achieved while maintaining performance.

  Based on this technical idea, the center pillar 10 according to the present embodiment has at least a part of the bottom portion 13 (the region of length X in FIG. 1B) more than other regions excluding this region. It is made of a material with a thin plate thickness or a material with low strength.

Next, the length X for arranging the thin-walled material or the low-strength material will be described.
As shown in FIG.1 (b), it is set as the structure which has a different material in some of the bottom parts 13, or some of the wall parts 12a and 12 in addition to the bottom parts 13, and the circumferential direction length between the boundary surfaces in a cross section The change in performance when the length X is changed with the length X being examined. Here, when X = 0, it represents a conventional shape of a uniform material.

  In the present embodiment, for the case of a hat-shaped member having a vertical wall angle of 92 ° and 120 °, three types of cases in which the plate thickness or material strength of the length X portion and the other portion of the hat are different, The maximum load in bending deformation and the maximum load per unit mass were obtained by analysis. Table 1 shows the arrangement of materials in each case.

  Since the opening angle of the wall portion in the actual product is in the range of about 92 ° to 120 °, the model shape of 92 ° shown in FIG. 9A in cases 1 and 3 and the case 2 shown in FIG. 9B. A 120 ° model shape was used. Cases 1 and 2 were examined for light weight and high performance by thinning the X-length portion. Case 3 examined the case where materials having different strengths were arranged in the portion of X length.

The relationship between the range of the inter-interface distance X in cases 1 to 3 and the change in performance (maximum load, maximum load / mass) is shown in graphs in FIGS. 4 (a) to 4 (c), respectively.
As shown in the graphs of FIGS. 4A to 4C, the maximum load value is substantially constant when X is in a range of L> X ≧ 0 in relation to the circumferential length L of the straight portion at the bottom. Thus, according to the present embodiment, it is understood that the maximum load per unit mass, that is, the efficiency can be increased by reducing the weight of the bottom. However, when the boundary surface extends beyond this not only to the bottom but also to the ridgeline (X ≧ L), the maximum load value decreases. Thus, if the circumferential length X in the cross section of a partial region is equal to or less than the circumferential length L in the bottom cross section, a decrease in the maximum load value can be prevented. In order to sufficiently obtain such an effect, it is desirable that 0.30L ≦ X ≦ 0.90L. More desirably, 0.50L ≦ X ≦ 0.86L.

FIG. 5 is an explanatory diagram showing an outline of a shape example of the center pillar 10 of the present embodiment. In this figure, the center pillar comprised without using the back board which is a 2nd member is shown.
As shown in the figure, the center pillar 10 has a substantially hat-shaped cross section that absorbs collision energy by bending deformation, and includes at least one of the substantially hat-shaped bottom portions 13 in a partial cross section in the axial direction. At least a part of the region (a region surrounded by a broken line in FIG. 5) is made of a material having a thinner plate thickness or a lower strength than other regions in the same cross section. These regions are joined by welding at the positions of the welding lines 14 and 14 extending in the axial direction of the bottom portion 13.

  According to the center pillar 10 of the present embodiment, since it is lightweight and has an excellent impact energy absorption capability, it is possible to achieve both reduction in weight and improvement in vehicle crash safety.

The present invention will be described more specifically with reference to examples.
In this example, a member having a cross-sectional shape shown in FIG. 9 imitating a center pillar as a structural member for a vehicle according to the present invention is manufactured, and a three-point bending test is performed under the same conditions as the analysis model shown in FIG. It was. That is, as shown in FIG. 6, the above-mentioned member imitating the center pillar is formed by press-molding a blank using a hat channel mold 20 composed of three molds of a punch 24, a die 21 and a holder 22. Produced. FIG. 6 shows only half of the mold 20.

  Here, as shown in FIG. 6, the press molding is performed from the die face surface pressed by the die (upper die) 21 and the holder (lower die) 22 to the vertical wall portion of the die 21 as the molding proceeds. Is so-called deep drawing.

  As the blank 23, TWB in which two types of steel plates having different thicknesses or materials were welded at a welding speed of 4 m / min and a length of 600 mm in the longitudinal direction by a 4.5 kW YAG laser apparatus was used. As the steel sheet, residual austenitic steel (ferrite, bainite, and residual austenitic steel) generally used as a structural member for automobiles was used.

  In addition, when TWB made of steel plates with different plate thicknesses is press-formed, a 1.0 mm plate is punched to eliminate stress concentration on the difference thickness portion due to the plate thickness difference when the blank 23 comes into contact with the punch 24. A spacer was set on the bottom of 24 according to the width of the thin portion.

  And the welding line was set to the flat part inside the R part of the punch 24, and it shape | molded with the cushion pressure of 50 tons. Under this molding condition, the welding position does not move from the set position during molding, so that the welded portion does not break due to excessive tension, and the cross-sectional shape shown in FIG. 9A or 9B is obtained. A panel having In addition, the length of the depth direction of this panel was 600 mm, and the cross-sectional direction length X of the thin part was 60 mm.

  Table 2 shows the three-point bending test results.

  Comparative Example 1 in Table 2 is formed by a blank made of a single plate having a constant plate thickness and material as in the prior art. Inventive Examples 1 and 2 are inventive examples formed by TWB composed of a thin plate and a thick plate. Furthermore, Invention Example 1 and Comparative Example 1 in Table 2 are cases of a panel having the cross-sectional shape shown in FIG. 9 (a), and Invention Example 2 and Comparative Example 2 have the cross-sectional shape shown in FIG. 9 (b). This is the case of a panel having the same.

  By comparing Invention Example 1 and Comparative Example 1 in Table 2 with Invention Example 2 and Comparative Example 2, the invention example has a performance per unit mass (F / M) as compared with the Comparative Example. You can see that it has improved.

It is explanatory drawing which shows the structural member of embodiment, FIG. 1 (a) is a perspective view, FIG.1 (b) is a cross-sectional view. It is explanatory drawing which shows an example of the deformation | transformation behavior of the center cross section of the axial direction of the center pillar which has a substantially hat-shaped cross-sectional shape. It is a graph which shows an example of the load-displacement chart in the center cross section of the axial direction of the center pillar which has a substantially hat-shaped cross-sectional shape. 4A to 4C are graphs showing the relationship between the range of the inter-interface distance X in cases 1 to 3 and the change in performance (maximum load, maximum load / mass). It is explanatory drawing which shows the outline of the example of a shape of the center pillar of embodiment. It is explanatory drawing which shows the metal mold | die used in the Example. It is explanatory drawing which shows an example of a center pillar. It is explanatory drawing which simplifies and shows the structural example of the conventional structural member for vehicles disclosed by patent document 3. FIG. FIG. 9A and FIG. 9B are explanatory views showing hat-shaped cross-sectional shapes of two types of structural members subjected to FEM numerical analysis. It is explanatory drawing which shows the 3 point | piece bending analysis model in FEM numerical analysis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Center pillar 2 Roof rail side 3 Side sill 4 Vehicle structural member 4a Thin part 4b Thick part 5 Weld line 10 Structural member (Center pillar)
11a Upper part 11b Lower part 12 Wall part 12a End part 12b Overlapping part 13 Bottom part 14 Welding line 15 Back plate 16 Center pillar 17 Wall part 18 Bottom part 19 Edge line 20 Die 21 Die 22 Holder 23 Blank 24 Punch

Claims (4)

  At least partly in the axial direction, the two wall portions that are spaced apart from each other, the two ridge line portions that continue to each of the two wall portions, and the bottom portion that connects the two ridge line portions and bent A vehicle structural member including a first member having a substantially hat-shaped cross section that absorbs collision energy by deformation, wherein a part of the bottom part is a remaining part of the bottom part, the two wall parts, and The first metal plate is different from the second metal plate constituting the two ridge lines, and the strength of the first metal plate is smaller than the strength of the second metal plate, Alternatively, the thickness of the first metal plate is smaller than the thickness of the second metal plate, and the thickness of each of the first metal plate and the second metal plate is constant. The structural member for vehicles characterized by the above-mentioned.   The circumferential length (X) in the cross section of the partial region is 0.30 times or more and 0.90 times or less of the circumferential length (L) in the cross section of the bottom portion. Vehicle structural member.   The structural member for a vehicle according to claim 1 or 2, wherein the first metal plate and the second metal plate are joined by welding along an axial direction of the bottom portion. Furthermore, the first being joined to the member by the vehicle structural member as claimed in 1 wherein any one of claims 1 to 3 comprising a second member for closing the opening of the substantially hat-shaped.

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