JP5237927B2 - Automotive roof reinforcement member and design method thereof - Google Patents

Description

  The present invention relates to an automobile roof reinforcing member and a design method thereof.

  For car bodies such as automobiles, in order to ensure rigidity and strength in the vehicle width direction (vehicle body width direction), such as a roof reinforcement member (roof reinforcement) that supports the roof panel from below, An extending frame part is provided.

  As is well known, such a roof reinforcing member is disposed close to the lower side of the roof panel and extends in the horizontal direction with respect to the vehicle body and in parallel with the vehicle width direction. And it joins with a roof panel or a roof side rail via the bracket provided in the edge part of the vehicle width direction, etc. directly.

  Further, the roof reinforcing member is often bonded and bonded to the roof panel via an adhesive such as mastic in order to ensure the rigidity of the roof panel. Further, if necessary, a joint hole, a seating surface, or the like for joining to the roof panel or the frame part is formed in the middle or end of the roof reinforcing member. The roof reinforcing member is selected from various cross-sectional shapes depending on the required strength and shape restrictions.

  Conventionally, as such a roof reinforcing member, a steel plate press-molded product having a cross-section formed into a hat shape (hat shape) has been used. However, in recent years, with the strengthening of side collision standards for automobile bodies, high deformation strength has been required for compressive loads in the vehicle width direction from the side of the automobile body, and countermeasures have been required. In addition, as is well known, there is a demand for further weight reduction and cost reduction along with these safety performance improvements, and the roof reinforcing member is also light weight, low cost and excellent in deformation strength against axial compression. It is desired.

  On the other hand, in the case of a steel roof reinforcing member, as a measure to improve the strength against the above-described axial compression, the press-formed products of the hat-type parts are combined and welded together to form a closed cross section. Is generally done. However, in such a method, an increase in cost due to an increase in the weight of parts, the number of parts, and the number of welding points is always a problem. In addition, as a countermeasure to the increase in component weight, material replacement from a conventional mild steel plate to a high-strength steel plate such as a high-strength 60 kg class has been performed, but due to a new problem of the occurrence of elastic buckling, Extremely thinning is difficult, and an increase in weight is inevitable. In addition, when an 80 kg or 100 kg class ultra high strength steel sheet is used, in addition to the problem of elastic buckling, there is a concern about problems such as strength reduction due to softening of the welded portion.

  When an aluminum alloy extruded profile is used for the roof reinforcing member, it is not necessary to join the molded products such as the steel plates together, and the closed cross-section must be integrated into a rectangular hollow material in advance by extrusion. Is possible. Moreover, an aluminum alloy has a lower density than a steel plate, and it is easy to change the thickness of each part (side) within the cross-sectional shape.

  On the other hand, in the roof reinforcing member, generally, the height in the vertical direction of the vehicle body is greatly limited in order to secure an indoor space or a vehicle height direction space. For this reason, as shown in Patent Document 1, the cross-sectional shape of the roof reinforcing member is the vertical direction of the vehicle body regardless of the material used such as an aluminum alloy material or a steel plate in order to improve the axial strength and rigidity. Instead, the closed cross section is often formed into a rectangular shape that is wide in the longitudinal direction of the vehicle body.

  In Patent Document 2, in the roof reinforcing member made of an aluminum alloy extruded section that has been closed into a wide rectangular shape as described above, a cross-sectional shape that minimizes an increase in weight and obtains a high axial compressive strength is disclosed. Propose to provide. That is, the thickness T of the flange constituting the rectangular closed cross section and the thickness t of the protruding flange formed at the end of the flange are in a fixed relationship, and the flange constituting the rectangular closed cross section The width-thickness ratio and the width-thickness ratio of the protruding flange are defined.

  In this Patent Document 2, a section having a large area in a portion located in the vertical direction of the vehicle body within a limited space in the vertical direction of the vehicle body by the projecting flange described above, the increase in weight is minimized, and bending is performed. A strong roof reinforcing member is obtained. That is, in order to increase the bending strength in the vertical direction of the vehicle body, the above-described projecting flange minimizes the area in the vicinity of the neutral axis and has a cross-sectional shape with a large area as far as possible from the neutral axis. In addition, by satisfying the width-thickness ratio of the flange constituting the rectangular closed cross section and the protruding flange, it is possible to suppress a decrease in the buckling limit stress of the flange constituting the closed cross section and minimize the increase in weight. Suppressing and obtaining high axial compression load.

  In such an aluminum alloy extruded hollow profile, the width-thickness ratio of the flange constituting the rectangular closed cross-section portion is in addition to the buckling strength as a structural member such as a bumper reinforcement, a side member, and a side shell. It is also well known that it is defined to increase the collision energy absorption performance (see Patent Document 3).

JP 2003-112656 A JP 2006-240543 A Japanese Patent No. 2672753

  However, in these prior arts, depending on the design of the vehicle body, the unique impact load when the roof reinforcing member is curved not in a straight line but in an arch shape over the vehicle width direction (axial direction) No attention is paid to the deformation behavior. That is, when the roof reinforcing member is curved in an arch shape in the vehicle width direction (axial direction), there is a unique collision that is not in the case of a straight shape in the vehicle width direction (axial direction). The load deformation behavior is shown.

  When the roof (roof panel) is curved in an arch shape in the vehicle width direction, the roof reinforcing member that supports the curved roof shape is also provided in the vehicle width direction (axis). (Curved) curved in an arch shape over the direction). Therefore, even when the roof reinforcing member is made of an aluminum alloy extruded hollow shape having the rectangular closed cross section, depending on the design of the vehicle body, this shape is bent and the axial direction is the vehicle width direction. In many cases, the arch is curved and extended.

  Here, if the arch height (the arch-shaped height, the bending height or the bending degree) changes with respect to the axial compression strength of the design target, the cross-sectional strength of the necessary roof reinforcing material also changes. For example, in the case of the above-described linear roof reinforcing material in which the arch height is substantially zero, the axial compression strength (axial compression maximum load) is equal to the cross-sectional strength. However, when this arch height is increased, the center portion of the roof reinforcement is easily deformed upward in the vehicle body due to the action of axial compression. Therefore, in order to obtain a predetermined axial compression strength, the cross-sectional strength of the roof reinforcement is reduced. Need to be bigger.

  Further, when the cross-sectional strength of the roof reinforcing material is increased, as described above, a wide cross-section of the reinforcing material is often taken due to the restriction in the height direction of the roof (the restriction on the height in the vertical direction of the vehicle body). In addition, it is possible to reduce the thickness and weight by applying a high-strength material. However, when the arch height increases, when the cross section is widened or thinned by a high strength material, elastic buckling of the cross section of the roof reinforcement material is likely to occur, and a predetermined cross sectional strength cannot be obtained. There are many.

  In this respect, too, it is pointed out that the above-mentioned Patent Document 2 also causes a phenomenon that the axial compressive strength is lowered if the flange width is designed too wide, and this is because the plate constituting the cross section buckles. . In addition to setting the flange width wide to improve bending strength, and to prevent the buckling of the plates that make up the cross section, by setting a reinforcing rib in the vertical direction of the vehicle body called the middle rib, It is pointed out in the above-mentioned Patent Document 2.

  And also in the said patent document 1, as a cross-sectional shape example of a roof reinforcement member, the cross-sectional shape of the eye shape which divided | segmented and reinforced the flange width in the said rectangular closed cross-section with two medium ribs extended in a vehicle body up-down direction. Extruded hollow profiles with the are listed as examples.

  However, in Patent Document 2, the width-thickness ratio of the projecting flange portion is made smaller than the width-thickness ratio of the flange of the main body, and the elastic flange of the projecting flange portion is prevented to improve the strength of the entire member. . However, this method is not always efficient for the roof reinforcing member having an arch-like curved shape extending in the axial direction, and in order to achieve a predetermined axial compressive strength, as described later, the roof reinforcing member is closed. In addition to rigidity and strength, it is very efficient to prevent elastic buckling of the cross-sectional portion (particularly the flange portion) in terms of rigidity and strength.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an automotive roof reinforcing member made of an aluminum alloy extruded profile having an arch-like curved shape extending in the axial direction, and can suppress elastic buckling and can provide a lightweight and high axial compressive strength. And providing a design method thereof.

The gist of the roof reinforcing member of the present invention for achieving the above object is a roof reinforcing member that supports a roof panel of an automobile and extends curvedly in an arch shape in the vehicle width direction, and has a rectangular closed cross section. The aluminum alloy extruded hollow member has a 0.2% proof stress σy of 200 MPa or more, a maximum thickness of the rectangular closed cross section of 3 mm or less, and a full width of the rectangular closed cross section. B has a wide and thin shape having a dimensionless width-thickness ratio parameter Rf defined by the following formula of 1.00 or more, and the rectangular closed cross-section is divided by a middle rib. The width of the individual rectangular closed cross section is less than 1.00 in the dimensionless width-thickness ratio parameter Rf, and has a maximum axial load of 15 kN or more.
However, the dimensionless width-thickness ratio parameter Rf = {(σy / E) × [12 (1−ν ² ) / π ² k]} ^1/2 × (B / tf). Where E is the Young's modulus (MPa) of the aluminum alloy, B is the full width (mm) of the rectangular closed cross section, tf is the flange side thickness (mm) of the rectangular closed cross section, ν is Poisson's ratio, k Is a buckling coefficient (k = 4).

Further, the gist of the design method of the roof reinforcing member of the present invention for achieving the above object is a method of designing a roof reinforcing member that supports an automobile roof panel and curves and extends in an arch shape in the vehicle width direction. The roof reinforcing member is an aluminum alloy extruded hollow member having a rectangular closed cross section, and the 0.2% proof stress σy of the aluminum alloy extruded hollow member is 200 MPa or more. The rectangular closed cross-section portion has a maximum thickness of 3 mm or less, and a full-width B of the rectangular closed cross-section portion having a dimensionless width-thickness ratio parameter Rf defined by the following formula: By dividing the width of each divided rectangular closed cross section by the dimensionless width-thickness ratio parameter Rf to less than 1.00, the axial direction of the roof reinforcing member is divided by the middle rib. The maximum load is that it was equal to or greater than 15kN.
However, the dimensionless width-thickness ratio parameter Rf = {(σy / E) × [12 (1−ν ² ) / π ² k]} ^1/2 × (B / tf). In this equation, σy is the 0.2% proof stress (MPa) of the extruded aluminum alloy profile, E is the Young's modulus (MPa) of the aluminum alloy, B is the full width (mm) of the rectangular closed cross section, and tf is The flange side thickness (mm) of the rectangular closed cross section, ν is Poisson's ratio, and k is a buckling coefficient (k = 4).

  In the present invention, in order to increase the deformation strength against axial compression loaded by the side collision, the maximum load (maximum bending strength or maximum deformation at which bending deformation in the vertical direction of the vehicle body occurs with respect to axial compression) is presupposed. Strength) is increased. For this reason, in the present invention, the entire width B (the flange width), which is the entire length of the width (the longitudinal direction of the vehicle body, the direction perpendicular to the axis direction and the horizontal direction) of the rectangular closed cross section, is set widely. . The process up to this point is the same as that of Patent Document 2.

  However, in the present invention, at this time, the 0.2% proof stress σy of the aluminum alloy extruded hollow section constituting the rectangular closed cross section is set to 200 MPa or more, and the maximum thickness of the rectangular closed cross section is set to 3 mm or less. , Minimize the weight increase of roof reinforcement members.

  Characteristically, in the present invention, the rectangular closed cross section is further divided by an intermediate rib, and the width of each divided rectangular closed cross section is less than 1.00 in the dimensionless width-thickness ratio parameter Rf. And As a result, in the present invention, the roof reinforcing member made of an aluminum alloy extruded hollow member can actually suppress elastic buckling. And even if it is the roof reinforcement member which has the arch-shaped curved shape over this axial direction, the axial maximum load with respect to the said side collision can be raised to 15 kN or more, for example.

It is a schematic diagram which shows the beam model of an arch-shaped roof reinforcement member. It is explanatory drawing which shows the analysis result of FEM and theoretical formula of the beam model of FIG. It is explanatory drawing which shows the result which arranged the analysis result of FIG. 2 by load efficiency and the dimensionless width-thickness ratio parameter Rf. FIG. 4A is a cross-sectional view of a roof reinforcing member, FIG. 4A is a conventional rectangular closed cross-section as a prototype, and FIGS. 4B and 4C are rectangular closed cross-sections of the present invention. Sectional drawing of a roof reinforcement member is shown, Fig.5 (a) is the conventional rectangular closed cross section used as a prototype, (b) and (c) show the rectangular closed cross section of this invention. It is a perspective view of Fig.5 (a).

  Hereinafter, embodiments of the roof reinforcing member of the present invention will be described with reference to the drawings.

(Deformation behavior of roof reinforcement members)
In order to improve the maximum load of the arch-shaped roof reinforcing member, it is necessary to know this arch-shaped collision load deformation behavior. For this elucidation, first, a roof reinforcing member having a rectangular closed cross-section portion in which the shape condition and the strength condition were variously changed by the beam model as shown in FIG. 1 was analyzed by both the FEM and the theoretical formula.

  As a result, it was found that the analysis results of the FEM and the theoretical formula are different in a roof reinforcing member having an arch-like curved shape extending in the axial direction and having a rectangular closed cross section. That is, it has been found that there is a specific region where the actual maximum load (FEM analysis) of the roof reinforcing member and the maximum load of the roof reinforcing member predicted (designed) in advance by a theoretical formula are greatly different. This point will be described below in order.

(Beam model in Fig. 1)
First, FIG. 1 will be described. In the beam model of the arch-shaped roof reinforcing member in FIG. 1, P is the axial compressive load, δ ₀ is the arch height in the vehicle body vertical direction as an initial deflection, and L is the length of the roof reinforcing member. The maximum load Pmax of the roof reinforcing member is the maximum axial compressive load (maximum axial compressive load).

(Theoretical formula)
The theoretical formula for obtaining the maximum load Pmax of the roof reinforcing member in FIG. 1 is expressed by the following well-known formula 1. This formula 1 is described in, for example, the Structural Mechanics Official Collection, Japan Society of Civil Engineers, 1986, P.I. 314 and the like.

1 / Pmax = 1 / P _E + δ ₀ / M _P (1)
Here, P _{E is the} bending buckling load, δ _{0 is the} arch height (the maximum height of the arch arc), and M _{P is the} total plastic bending moment.

That is, in Equation 1 above, the reciprocal of the maximum load Pmax of the beam having the arch is the reciprocal δ ₀ / M _P obtained by dividing the reciprocal of the bending buckling strength P _E and the total plastic bending moment M _P by the arch height δ _0. And the sum.

(Figure 2)
Results obtained by analyzing the maximum load Pmax of the roof reinforcing member having the rectangular closed cross-section portion in which the shape condition and the strength condition are variously changed by the analysis of both the theoretical formula 1 and the FEM analysis using the beam model of FIG. Are shown in FIG.

FIG. 2 also shows the shape condition and strength condition of the rectangular closed cross section of the roof reinforcing member. Here, in both analyses, a roof reinforcing member having a rectangular closed cross section having a flange projecting sideways on both sides as shown in FIG. The arch height δ ₀ of the roof reinforcing member was 30 mm, and the length L of the straight portion was 990 mm, all under the same conditions. Note that ABAQUS, which is a general-purpose code, is used for FEM analysis.

  4 and 5 including FIG. 5A, in common, S is a flange width (mm) extending from the rectangular closed cross section in the lateral direction (vehicle body longitudinal direction), and H is a rectangular closed cross section. The height (mm) in the vertical direction of the vehicle body, tf or tf1 is the thickness (mm) of the rectangular closed cross section, and tf2 is the thickness (mm) of the overhanging flange. B is the full width (mm) of the rectangular closed cross section in the longitudinal direction of the vehicle body, and B1, B2, and B3 are widths (mm) in the longitudinal direction of the vehicle body of the respective rectangular closed cross sections partitioned by the intermediate ribs. In addition, the thickness tf or tf1 of the rectangular closed cross section and the thickness tf2 of the protruding flange are the same in all the portions of the rectangular closed cross section in these analyses.

(Figure 3)
FIG. 3 shows a result of arranging the analysis results of FIG. 2 with the load efficiency on the vertical axis and the dimensionless width-thickness ratio parameter Rf on the horizontal axis.

  Here, the load efficiency on the vertical axis in FIG. 3 means the maximum axial compression load Pmax (theoretical solution: Pmax, theory) according to the theoretical formula 1 and the maximum axial compression load Pmax (FEM solution: Pmax, FEM) according to FEM analysis. Ratio, Pmax, theory / Pmax.

Also, the dimensionless width-thickness ratio parameter Rf on the horizontal axis in FIG. 3 is Rf = {(σy / E) × [12 (1-ν ² ) / π ² k]} ^1/2 × (B / tf) ·・ ・ (Expression 2) In this equation, σy is the 0.2% proof stress (MPa) of the extruded aluminum alloy profile, E is the Young's modulus (MPa) of the aluminum alloy, B is the full width (mm) of the rectangular closed cross section, and tf is The flange-side thickness of the rectangular closed cross section (flange thickness: mm), ν is the Poisson's ratio, and k is the buckling coefficient (k = 4). By the way, this equation 2 is expressed as follows using the √ symbol.

  Incidentally, this dimensionless width-thickness ratio parameter Rf is disclosed in Patent Document 3 as a flange width-thickness ratio Rf as a structural member having a flange that is applied to the body, chassis, etc. of an automobile and receives a load. . That is, in Patent Document 3, a flange is formed by a vertical panel and receives a load in a direction perpendicular to the vertical panel, and a horizontal panel fixed to a predetermined position of the flange to support the flange. The structure of the structural member consisting of the web is assumed.

And in this structure, the width-to-thickness ratio Rf of the flange is represented by Rf = {12 (1-ν ² ) / 4π ² } ^1/2 × (σy / E) ^1/2 × (bf / tf). It is described that. Here, bf represents the height of the flange, tf represents the thickness of the flange, ν represents the Poisson's ratio, E represents the elastic modulus, and σy represents the yield stress. The width-thickness ratio Rf of the present invention is changed to the above formula 2 so as to match the width-thickness ratio as a roof reinforcing member having a rectangular closed cross section based on the width-thickness ratio Rf of this panel structure. .

  The above-described roof reinforcing member having an arch shape and a rectangular closed cross section will be described with reference to FIG. 3 because there is a specific region where the maximum load is greatly different between the FEM analysis and the theoretical formula analysis.

  As can be seen from FIG. 3, the load efficiency on the vertical axis is approximately 100% up to a small range of Rf on the horizontal axis up to 1.0, and the theoretical solution Pmax and theory agree well with the FEM solutions Pmax and FEM. ing. That is, when the full width B of the rectangular closed cross section is designed to increase the maximum load of the roof reinforcing member using the theoretical formula 1 according to the beam model of FIG. 1, the Rf of the horizontal axis is 1.0 or less. If so, it means that the predicted value (design value) and the actual value at the maximum load of the roof reinforcing member agree well.

  In contrast, when Rf on the horizontal axis increases beyond 1.0, the load efficiency on the vertical axis falls below 100%, and the FEM solutions Pmax and FEM become smaller than the theoretical solutions Pmax and theory. In other words, when the full width B of the rectangular closed cross section increases, the maximum load of the actual roof reinforcing member by the FEM solutions Pmax and FEM becomes smaller than the theoretical solutions Pmax and theory. In order to increase the maximum load of the roof reinforcing member, the beam model shown in FIG. 1 is used to increase the total width B of the rectangular closed cross section by exceeding Rf of the horizontal axis to 1.0. In this case, it means that the actual maximum load value of the roof reinforcing member is smaller than the design value (predicted value).

  For example, in FIG. 3, four examples of case 2-2, case 4-2, case 6-2, and case 8-2 in which only the full width B of the rectangular closed cross section is different (the other conditions are the same) are compared. The load efficiency of case 2-2 with Rf of 1.0 is 100%, and the theoretical solution Pmax and theory and the FEM solutions Pmax and FEM are in good agreement. However, the load efficiency of case4-2 with Rf 1.61 is 82%, the load efficiency of case6-2 with Rf 2.01 is 73%, and the load efficiency of case8-2 with Rf 2.61 is 62%. , Each has fallen significantly.

  Thus, when Rf on the horizontal axis is larger than 1.0, it means that it becomes difficult to design an optimal rectangular closed cross-sectional shape for increasing the maximum load value of the roof reinforcing member. This is because the rectangular closed cross-section of the roof reinforcing member has a wide and thin shape, and therefore, when the Rf of the horizontal axis is larger than 1.0, it is easily elastically buckled. .

(Elastic buckling measures)
Thus, in order to increase the maximum load value of the roof reinforcing member that is easily elastically buckled, the thickness of the rectangular closed cross section (thickness of the flange) is normally increased as described above. However, an increase in the wall thickness that is effective for the elastic buckling sacrifices the weight reduction of the roof reinforcing member, and makes it meaningless to use an aluminum alloy extruded profile.

  For this reason, in the present invention, as a premise, in order to increase the maximum load value without hindering weight reduction, the roof reinforcing member is composed of a high-strength aluminum alloy extruded hollow shape having a rectangular closed cross section. The rectangular closed cross section is formed into a wide and thin shape. That is, the 0.2% proof stress σy of the extruded aluminum alloy hollow member is 200 MPa or more, the maximum thickness tf of the rectangular closed cross section is 3 mm or less, and the total width B of the rectangular closed cross section is dimensionless. The width-thickness ratio parameter Rf is increased (widened) to 1.00 or more.

  However, this alone makes it easier for elastic buckling to occur, and the maximum load value cannot be increased substantially. Therefore, in the present invention, in order to prevent elastic buckling and to increase the maximum load value of the roof reinforcing member, the rectangular closed cross section is further divided by the middle rib and divided. Further, the width of each rectangular closed cross section is reduced (narrow) to less than 1.00 by the dimensionless width-thickness ratio parameter Rf.

(Division of rectangular closed cross-section by middle rib)
Specifically, in the rectangular closed cross-section of FIGS. 4 and 5, compared to the conventional rectangular closed cross-section of the mouth type that does not have the middle ribs of FIGS. 4 (a) and 5 (a). 4 (b), 5 (b), 4 (c), and 5 (c), one or more middle ribs are provided in the rectangular closed cross section, and the rectangular closed cross section is divided.

  Here, the rectangular closed cross-sectional structure (shape) of FIGS. 4 and 5 will be described in detail below. First, FIG. 4A and FIG. 5A are conventional rectangular closed cross-sections of a mouth type that does not have a middle rib in the vertical direction of the vehicle body, as described above. 4 (b) and 5 (b) show a rectangular closed section of a Japanese shape that has one middle rib in the vertical direction of the vehicle body at the center of the rectangular closed section and divides the rectangular closed section into two. is there. 4 (c) and 5 (c), the rectangular closed cross-section portion is divided into three parts with two middle ribs in the vertical direction of the vehicle body and spaced apart in the front-rear direction of the vehicle body. It is a rectangular closed cross section of an eye shape.

  In the rectangular closed cross section of FIGS. 4 and 5, two flanges (1 and 2) extend in the longitudinal direction of the vehicle (the vertical direction in the drawing) and extend in the longitudinal direction of the vehicle (the horizontal direction in the drawing). Horizontal wall). 3 and 4 connect these two flanges 1 and 2 to each other, with two webs extending in the vehicle body vertical direction (the vertical direction in the figure) and spaced in the vehicle longitudinal direction (the horizontal direction in the figure). Vertical wall). Reference numerals 5, 6, 7, and 8 denote a total of four overhanging flanges that extend from both ends of the flanges 1 and 2 to both sides (vehicle body longitudinal direction).

  In the rectangular closed cross section of FIG. 5, all of (a), (b), and (c) have four overhanging flanges 5, 6, 7, and 8. On the other hand, the rectangular closed cross-section portion of FIG. 4 has a rectangular cross-sectional shape in which any of (a), (b), and (c) does not have these overhanging flanges.

  In addition, rectangular closed cross sections such as a mouth shape and an eye shape having such a middle rib are known per se, and are also known as a roof reinforcing member using the above-described conventional aluminum alloy extruded hollow shape. In other words, the present invention is indistinguishable from the conventional roof reinforcing member only in terms of the cross-sectional shape of a rectangular closed cross-section such as a mouth mold or an eye mold.

  The present invention is distinguished from the conventional roof reinforcing member in that the elastic buckling is likely to occur, the entire width B is widened to a dimensionless width-thickness ratio parameter Rf of 1.00 or more, and The high strength and thin rectangular closed cross section and an arch-shaped axis. In such a technical field, as described above, it has never been known that the occurrence of the elastic buckling itself and the maximum load value itself are prevented while preventing the elastic buckling. Therefore, in such a technical field, a roof reinforcing member having a rectangular closed cross-section portion that is divided by providing an intermediate rib after the total width B is increased to a dimensionless width-thickness ratio parameter Rf of 1.00 or more. Did not exist.

(Full width of rectangular cross section)
Thus, the total width (the total length in the width direction) B of the rectangular closed cross section of the roof reinforcing member of the present invention is 1.00 or more, preferably 1 in the dimensionless width-thickness ratio parameter Rf in order to increase the maximum load value. .38 or more, more preferably 1.61 or more, and even more preferably 1.72 or more, as large as possible (wide).

(Width of rectangular closed section divided by middle rib)
Further, the rectangular closed cross section by the middle rib is divided into rectangles divided (partitioned) by the middle rib in FIGS. 4B, 5B, 4C, and 5C. The widths B1, B2, and B3 of the divided rectangular closed cross-section portions of the closed cross-section portions (flanges 1 and 2) are set as small as possible with a dimensionless width-thickness ratio parameter Rf of less than 1.00. . If these widths B1, B2, and B3 are increased to 1.00 or more in the dimensionless width-thickness ratio parameter Rf, elastic buckling that is likely to occur when the total width B of the rectangular closed cross section is increased as described above. Cannot be prevented, and the maximum load value of the arched roof reinforcing member cannot be increased.

  In this respect, these widths B1, B2, and B3 are made as small as possible (narrow) by setting the dimensionless width-thickness ratio parameter Rf to preferably 0.7 or less, more preferably 0.5 or less, and further preferably 0.3 or less. To do. However, the widths B1, B2, and B3 of the rectangular closed cross sections divided by these middle ribs do not have to be the same Rf and width, and may be changed as necessary.

(Design of rectangular closed section)
A method for designing a rectangular closed cross section of a roof reinforcing member for increasing the dimensionless width-thickness ratio parameter Rf of the full width B of the rectangular closed cross section of the roof reinforcing member of the present invention is shown in FIGS. 4 and 5 as an example. This will be specifically described below.

Strength:
In order to increase the maximum load value and prevent elastic buckling, the aluminum alloy extruded hollow member used in the present invention has a maximum thickness tf of the rectangular closed cross section of 3 mm or less. A material having as high a strength as possible with a% proof stress σy of 200 MPa or more is required. In order to satisfy such a required strength, a high-strength A6000-based or A7000-based tempered (heat treated) aluminum alloy extruded hollow shape member is preferable. Such an aluminum alloy extruded hollow shape can be produced by a conventional method combining hot extrusion, tempering (heat treatment) such as solution hardening and artificial aging.

Rectangular closed cross section thickness:
The thickness tf or tf1 of the flanges 1 and 2 and the webs 3 and 4 of the rectangular closed cross section is set to 3 mm or less at the maximum in order not to hinder weight reduction. However, the preferable minimum thickness is 1.5 mm, and the thickness tf or tf1 of the rectangular closed cross section is preferably in the range of 1.5 to 3 mm. The thickness tf2 of the overhanging flanges 5, 6, 7, and 8 also follows this.

  In the actual roof reinforcing member design, the thickness tf or tf1 of the rectangular closed cross section and the thickness tf2 of the overhanging flange may be the same at all locations of the rectangular closed cross section. However, depending on the flange or web, or depending on the part on the same flange or the same web, such as thickening the part that requires more strength and more thickness, and thinning the other part, the part or part The thickness may be changed. Therefore, tf in the expression 2 of the dimensionless width-thickness ratio parameter Rf is the average thickness (mm) on the flange side (flange) of the rectangular closed cross section.

Body height H:
Larger (higher) height H in the vehicle body vertical direction of the rectangular closed cross-section increases the maximum load value and can prevent elastic buckling. However, as described above, the roof reinforcing member is greatly limited in order to secure a vehicle interior space or a vehicle height direction space. In addition, it is greatly limited in terms of weight reduction. For this reason, it is preferable to set it as the range of 30 mm at the maximum, usually 10-25 mm.

Full width B:
The total width (the total length in the width direction) B of the rectangular closed cross section is increased (widened) as much as possible in order to increase the dimensionless width-thickness ratio parameter Rf as described above and increase the maximum load value. For this purpose, the absolute value of the total width (total length in the width direction) B of the rectangular closed cross-section is at least 50 mm in relation to the above-described other factors constituting the expression of the dimensionless width-thickness ratio parameter Rf. It is preferably as large as possible, preferably 80 mm or more, and more preferably 150 mm.

Width B1, B2, B3 partitioned by the middle rib:
In order to prevent elastic buckling, the widths B1, B2, and B3 of the divided rectangular closed cross-sections (flanges 1 and 2) divided (partitioned) by the intermediate ribs are as follows. Rf is less than 1.00. For this purpose, if the other factors constituting the expression of the dimensionless width-thickness ratio parameter Rf are within the above-mentioned range, the widths B1, B2, B3 of the divided rectangular closed cross-sections are determined in the vehicle longitudinal direction. Each width is set to 50 mm or less at the maximum. However, the widths B1, B2, and B3 of the rectangular closed cross sections divided by the middle ribs do not have to be the same width, and may be changed as necessary.

Overhang flange:
The overhanging flanges 5, 6, 7, and 8 are necessary for joining the rectangular closed cross section with the roof panel and the roof side rail as a roof reinforcing member, and prevent the elastic buckling. It is not necessary to increase the load value.

  With respect to the roof reinforcing member having the rectangular closed cross section shown in FIG. 5A and shown in a perspective view in FIG. 6, the influence of the division by the middle ribs 9 and 10 on the maximum load and load efficiency was analyzed. The results are shown in Table 1.

  Specifically, in FIG. 3, only the full width B of the rectangular closed cross section is different (other conditions are the same), and the dimensionless width-thickness ratio parameter Rf is more than 1.0. -2, case6-2, and case6-2 (corresponding to FIG. 4 (a)), the cross section is divided into a day shape and an eye shape by the intermediate ribs 9 and 10, respectively, and the divided individual rectangles are closed. The Rf of the cross-sectional widths B1, B2, and B3 was variously changed. As in FIG. 2, the maximum load (theoretical solution Pmax, theory and the FEM solution Pmax, FEM) and the load efficiency were obtained. In Table 1, the date in parentheses indicates the cross section of the day shape in FIG. 4B, and the eye indicates the cross section of the eye shape in FIG. 4B.

  As can be seen from Table 1, in the example in which the Rf of the divided widths B1, B2, and B3 is less than 1.00, the load efficiency of case4-2 with Rf of 1.61 is 98%, from the original 82% The load efficiency of case6-2 with Rf 2.01 is significantly improved from the original 73%, which is 98%, and the load efficiency of case8-2 with Rf 2.61 is 100%, the original 62% % Has improved significantly.

  On the other hand, even if divided by the middle ribs 9 and 10, the other comparative examples in which the Rf of the widths B1, B2, and B3 is 1.00 or more do not improve the load efficiency so much, and are still the maximum. The difference between the theoretical load solutions Pmax and theory and the FEM solutions Pmax and FEM is large, and the actual maximum load does not increase.

  According to the present invention, in an automotive roof reinforcing member made of an aluminum alloy extruded profile having an arch-like curved shape extending in the axial direction, a high shaft is provided that suppresses elastic buckling while minimizing an increase in weight. Maximum direction load (axial compressive strength) is obtained. Therefore, it is suitable for an automobile roof reinforcing member having an arch-like curved shape extending in the axial direction, which requires both weight reduction and maximum load.

  1, 2 ,: Flange, 3, 4: Web, 5, 6, 7, 8: Overhang flange

Claims (2)

A roof reinforcing member that supports a roof panel of an automobile and extends in an arch shape in the vehicle width direction, and is formed of an aluminum alloy extruded hollow member having a rectangular closed cross section, and the aluminum alloy extruded hollow member 0.2% proof stress σy is 200 MPa or more, the maximum thickness of the rectangular closed cross section is 3 mm or less, and the total width B of the rectangular closed cross section is 1 as a dimensionless width-thickness ratio parameter Rf defined by the following formula: The rectangular closed cross-section portion is divided by a middle rib, and the width of each divided rectangular closed cross-section portion is the dimensionless width-thickness ratio. A roof reinforcing member having a parameter Rf of less than 1.00 and a maximum axial load of 15 kN or more.
However, the dimensionless width-thickness ratio parameter Rf = {(σy / E) × [12 (1−ν ² ) / π ² k]} ^1/2 × (B / tf). Where E is the Young's modulus (MPa) of the aluminum alloy, B is the full width (mm) of the rectangular closed cross section, tf is the flange side thickness (mm) of the rectangular closed cross section, ν is Poisson's ratio, k Is a buckling coefficient (k = 4). A method for designing a roof reinforcing member that supports a roof panel of an automobile and extends in an arch shape in the vehicle width direction. The roof reinforcing member is an aluminum alloy extruded hollow member having a rectangular closed cross section. The 0.2% proof stress σy of the extruded aluminum alloy hollow profile is 200 MPa or more, the maximum thickness of the rectangular closed cross section is 3 mm or less, and the total width B of the rectangular closed cross section is defined by the following equation: The dimensionless width-thickness ratio parameter Rf is set to a wide and thin shape having a width of 1.00 or more, and the rectangular closed cross section is divided by a middle rib. A method for designing a roof reinforcing member, wherein the maximum load in the axial direction of the roof reinforcing member is set to 15 kN or more by setting the dimension width thickness ratio parameter Rf to less than 1.00.
However, the dimensionless width-thickness ratio parameter Rf = {(σy / E) × [12 (1−ν ² ) / π ² k]} ^1/2 × (B / tf). Where E is the Young's modulus (MPa) of the aluminum alloy, B is the full width (mm) of the rectangular closed cross section, tf is the flange side thickness (mm) of the rectangular closed cross section, ν is Poisson's ratio, k Is a buckling coefficient (k = 4).

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