JP7155851B2 - Fiber-reinforced composite frame - Google Patents

Description

The present invention relates to a fiber reinforced composite frame.

Fiber-reinforced composite material frames are sometimes used as frames for automobiles, aircraft, and industrial machinery. For example, Patent Literature 1 discloses a configuration in which a frame made of a fiber-reinforced composite material is used for the center pillar of an automobile.

The fiber-reinforced composite material frame disclosed in Patent Document 1 is made of CFRP (carbon fiber reinforced resin) and has a substantially rectangular cross-sectional shape.

Fiber-reinforced composite frames are stronger and stiffer than steel frames of the same weight. Therefore, when a frame made of a fiber-reinforced composite material is used, it is possible to secure the same level of strength and rigidity while reducing the weight as compared to when a frame made of steel is used.

JP 2018-52390 A

However, in the fiber-reinforced composite material frame according to the prior art, when a bending load is applied, the edge stress on the side where the compressive stress is generated reaches the material strength before the edge stress on the side where the tensile stress is generated reaches the material strength. strength is reached and determines the bending strength of the frame. This is due to the occurrence of buckling in the compressive stress acting portion of the frame and the characteristics of the fiber-reinforced composite material in which the tensile strength of the material is higher than the compressive strength. That is, in the fiber-reinforced composite material frame according to the prior art, the strength of the material cannot be fully utilized on the side where the tensile stress is generated, resulting in deterioration of the mass efficiency of the bending strength.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fiber-reinforced composite material frame capable of obtaining high mass efficiency in terms of bending strength.

A fiber-reinforced composite frame according to one aspect of the present invention has a hollow cross-sectional shape, extends in a predetermined direction, and receives a bending load, and has at least a partial region in the longitudinal direction. In the above, the position of the longitudinal neutral axis of the fiber-reinforced composite material frame is set to be biased toward the compressed portion side where compressive stress is generated with respect to the longitudinal cross-sectional center axis, and the at least partial region is When viewed in a cross section in a direction that intersects with the predetermined direction, and the direction of deviation of the longitudinal neutral axis with respect to the longitudinal cross-sectional center axis is the height direction of the cross section, the cross-section of the compressed portion A tensile portion that generates a tensile stress when the bending load is applied is disposed on the opposite side in the height direction, and the compression is performed in the lateral direction that intersects both the predetermined direction and the height direction of the cross section. The maximum width of the portion is set wider than the maximum width of the tension portion, and the compression portion includes a groove recessed toward the tension portion in the middle portion in the lateral direction, and the ridges extending in the predetermined direction, and the difference between the width of the compression portion and the width of the tension portion is equal to the width of the groove in the width direction; They are almost the same.

In the above fiber-reinforced composite material frame, the longitudinal neutral axis is set biased toward the compressed portion side with respect to the longitudinal cross-sectional center axis, so the compressive side edge stress is made smaller than the tensile side edge stress. be able to. That is, in general, a frame made of a fiber-reinforced composite material has a compressive strength of only about 1/2 to 1/3 of a tensile strength when a bending load is applied. By biasing the vertical axis toward the compressed portion, the compressive side edge stress can be made smaller than the tensile side edge stress, and the occurrence of buckling and breakage in the compressed portion can be suppressed.

Therefore, in the fiber-reinforced composite material frame described above, high mass efficiency in bending strength is obtained by suppressing the occurrence of buckling and rupture of the compressed portion until the tensile side edge stress reaches the material strength or a strength close to it. be able to.

In addition, "having a hollow cross-sectional shape" in the above means that the frame formed of the fiber-reinforced composite material has a hollow cross-sectional shape. Therefore, the fiber-reinforced composite material frame according to the above aspect also includes a structure in which the hollow portion is filled with another member.

In addition, the "longitudinal cross-sectional center axis" in the above is the center of the dimension in the direction connecting the compression part and the tension part at the radius of curvature under bending load, and is the axis extending in the longitudinal direction of the fiber reinforced composite frame. is.

In the fiber-reinforced composite material frame according to the above aspect, the compressed portion in the at least partial region is provided with more ridge portions extending in the longitudinal direction than the tensile portion where a tensile stress is generated when the bending load is applied. may be

In the fiber-reinforced composite material frame described above, by providing more ridges in the compression section than in the tension section, buckling in the compression section is suppressed and the neutral axis is positioned on the side of the compression section with respect to the central axis of the longitudinal cross section. can be set biased to , and the bending strength can be improved when a bending load is applied to the compressed portion.

In the fiber-reinforced composite material frame according to the above aspect, when the height of the fiber-reinforced composite material frame in the cross-sectional view in the crossing direction is the cross-sectional height, the ridge line The portion may be provided in a range of 0.55 to 0.9 with respect to the cross-sectional height on the bending stress acting surface with respect to the end portion on the side of the tensile portion.

In the fiber-reinforced composite material frame described above, by providing the ridgeline at an appropriate position, it is possible to more efficiently suppress the occurrence of the buckling phenomenon in the compressed portion when a bending load is applied.

In the fiber-reinforced composite material frame according to the aspect described above, the cross section of the compression portion may be set larger than that of the tension portion in the at least partial region.

In the fiber-reinforced composite material frame described above, by making the cross section (size) of the compression section larger than that of the tension section, it is possible to improve the bending strength of the compression section. It is possible to suppress the occurrence of the buckling phenomenon.

In the fiber-reinforced composite material frame according to the aspect described above, the outer peripheral wall of the compression portion in the at least partial region may be thicker than the tension portion.

In the fiber-reinforced composite material frame described above, by making the thickness of the outer peripheral wall of the compression portion thicker than that of the tension portion, it is possible to improve the bending strength of the compression portion. It is possible to suppress the occurrence of the buckling phenomenon in the part.
In the fiber-reinforced composite material frame according to the above aspect, the fiber-reinforced composite material frame is a center pillar disposed between a front door opening and a rear door opening in an automobile body, and the height of the cross section is The longitudinal direction is the width direction of the vehicle body, and the compression portion is arranged so as to be located outside the tension portion in the vehicle width direction, and is arranged on both sides in the width direction. The wall portions may be formed such that, at least in part in the vehicle width direction, the distance between them gradually widens from the inner side to the outer side in the vehicle width direction.

In the fiber-reinforced composite material frame according to the above aspect, high mass efficiency in terms of bending strength can be obtained.

It is a model side view which shows the partial structure of the vehicle body which concerns on 1st Embodiment. It is an enlarged view which shows the A section of FIG. FIG. 3 is a view showing the III-III cross section of FIG. 2, and is a schematic cross-sectional view showing the cross-sectional structure of the central portion of the center pillar. FIG. 3 is a diagram showing the IV-IV cross section of FIG. 2, and is a schematic cross-sectional view showing the cross-sectional structure of the lower portion of the center pillar. (a) is a model diagram showing compressive stress and tensile stress when a bending load acts on a center pillar according to a comparative example; 1 is a model diagram showing compressive stress and tensile stress when is applied. FIG. FIG. 4 is a model diagram showing compressive stress and tensile stress when a bending load acts on a center pillar made of steel as a reference example. (a) is a schematic cross-sectional view showing the cross-sectional structure of the central portion of a center pillar according to a second embodiment, and (b) is a schematic cross-sectional view showing the cross-sectional structure of the central portion of a center pillar according to a third embodiment. be. (a) is a schematic cross-sectional view showing the cross-sectional structure of the middle part of a center pillar according to a fourth embodiment, and (b) is a schematic cross-sectional view showing the cross-sectional structure of the middle part of a center pillar according to a fifth embodiment. be. 4 is a graph showing the relationship between mass and bending strength in samples 1 to 12. FIG. Fig. 4 is a graph showing the relationship between ridge position and maximum bending moment without buckling; FIG. 11 is a schematic plan view showing a partial configuration of a vehicle body according to a sixth embodiment; 11. It is a schematic plan view which shows the structure of the front side frame shown to C part of FIG.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described, considering drawing into consideration. In addition, the form described below is an example of the present invention, and the present invention is not limited to the following forms except for its essential configuration.

In the figures used in the following explanation, "FR" is the front of the vehicle, "RE" is the rear of the vehicle, "UP" is the upper of the vehicle, "LO" is the lower of the vehicle, "RI" is the right of the vehicle, and "LE" is the front of the vehicle. The left side of the vehicle body, "OUT" indicates the outer side of the vehicle body, and "IN" indicates the inner side of the vehicle body.

[First embodiment]
1. Configuration of Vehicle Body 1 The configuration of the vehicle body 1 according to the present embodiment will be described with reference to FIG.

As shown in FIG. 1, the vehicle body 1 includes side sills 2 extending in the longitudinal direction on the lower side and roof side rails 4 extending in the longitudinal direction on the upper side. The vehicle body 1 also includes a center pillar 4 that connects the side sill 2 and the roof side rail 3 and is arranged between the front door opening 6 and the rear door opening 7 . Furthermore, the vehicle body 1 also has a rear pillar 5 on the rear side of the rear door opening 7 .

Here, the center pillar 4 according to this embodiment corresponds to a fiber-reinforced composite material frame. More specifically, the center pillar 4 is made of carbon fiber reinforced resin.

Although FIG. 1 shows only a portion of the right side surface of the vehicle body 1, the center pillar on the left side surface is also formed with the same structure as the center pillar 4. As shown in FIG.

2. center pillar 4
A configuration of the center pillar 4 will be described with reference to FIG. FIG. 2 is an enlarged view showing part A of FIG.

As shown in FIG. 2, the center pillar 4 is a vertically extending frame. The center pillar 4 is configured such that its width gradually decreases from the bottom to the top.

In this embodiment, the lower portion of the center pillar 4 is referred to as a lower portion 4a, the middle portion as a middle portion 4b, and the upper portion as an upper portion 4c.

3. Cross-Sectional Structure of Middle Part 4b of Center Pillar 4 A cross-sectional structure of the middle part 4b of the center pillar 4 will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view showing the III-III cross section of FIG.

As shown in FIG. 3, the center pillar 4 according to the present embodiment is a frame having a hollow structure including a central portion 4b made of a fiber-reinforced composite material (for example, a carbon fiber-reinforced composite material). That is, the center pillar 4 according to this embodiment is a fiber-reinforced composite material frame that has a hollow cross-sectional shape and extends in the vertical direction.

As shown in FIG. 3, the central portion 4b of the center pillar 4 has a substantially rectangular cross-sectional shape with rounded corners, and an internal space 4d is formed inside. In the inside-outside direction of the vehicle body 1, the middle portion 4b of the center pillar 4 has a dimension of H1. Therefore, in the inside-outside direction of the vehicle body 1, the longitudinal cross-sectional center axis Ax4b of the middle portion 4b of the center pillar 4 is on the center line drawn from both outer surfaces of the outer portion 4b1 and the inner portion 4b2 to a point H2 (=H1/2). Located in

In the central portion 4b of the center pillar 4 according to the present embodiment, the thickness TB1 of the outer peripheral wall of the outer portion _4b1 is formed thicker than the thickness _TB2 of the outer peripheral wall of the inner portion 4b2. For example, the thickness T _B1 is thicker than the thickness T _B1 by a ratio of 1.20 to 1.40.

The central portion 4b of the center pillar 4 has a thickness T _B1 of the outer portion 4b1 and a thickness T _B2 of the inner portion 4b2 different from each other, so that the longitudinal neutral axis _AxNB is G1 with respect to the longitudinal cross-sectional central axis Ax4b. is set so as to be biased toward the outer portion 4b1.

Here, in the central portion 4b of the center pillar 4, the outer portion 4b1 is the side on which compressive stress is generated when a bending load acts toward the inside of the central portion 4b due to a side collision or the like. That is, in the central portion 4b of the center pillar 4 according to the present embodiment, the longitudinal neutral axis AxN _B is the compressed portion (outer portion 4b1) where compressive stress is generated when a bending load is applied with respect to the longitudinal cross-sectional central axis Ax4b. set to the side.

As shown in FIG. 3, in the central portion 4b of the center pillar 4 according to the present embodiment, when making the thickness _TB1 thicker than the thickness _TB2 , the thick portion is added to the inner space 4d side. are distributing. As a result, in the central portion 4b of the center pillar 4, the thickened portion is not conspicuous in appearance, and excellent appearance quality can be achieved.

4. Cross-Sectional Structure of Lower Part 4a of Center Pillar 4 A cross-sectional structure of the lower part 4a of the center pillar 4 will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view showing the IV-IV cross section of FIG.

As shown in FIG. 4, the lower portion 4a of the center pillar 4 also has a substantially rectangular cross-sectional shape with rounded corners, similarly to the central portion 4b, and an internal space 4d is formed inside. In the inside-outside direction of the vehicle body 1, the lower portion 4a of the center pillar 4 has a dimension of H3. In the in-and-out direction of the vehicle body 1, the longitudinal cross-sectional center axis Ax4a of the lower portion 4a of the center pillar 4 is on the center line drawn at H4 (=H3/2) from both outer surfaces of the outer portion 4a1 and the inner portion 4a2. To position.

In the lower portion 4a of the center pillar 4, unlike the middle portion 4b, the entire outer peripheral walls of the outer portion 4a1 and the inner portion 4a2 are formed with a substantially constant thickness _TA . Therefore, at the lower portion 4a of the center pillar 4, the longitudinal neutral axis _AxNA is set to substantially coincide with the longitudinal cross-sectional central axis Ax4a.

Here, the lower portion 4a of the center pillar 4 is set as a region where it is assumed that even if a side collision or the like occurs, no direct bending load or no large bending load will act. , As described above, the longitudinal neutral axis _AxNA is set to substantially coincide with the longitudinal cross-sectional central axis Ax4a.

5. Compressive stress and tensile stress when bending load is applied Compressive stress and tensile stress generated when bending load is applied to the central portion 4b of the center pillar 4 will be described with reference to FIGS. 5 and 6. FIG. FIG. 5A is a model diagram showing compressive stress and tensile stress when a bending load acts on a center pillar according to a comparative example, and FIG. FIG. 4 is a model diagram showing compressive stress and tensile stress when a bending load acts on the middle portion 4b from the outside of the vehicle body 1; FIG. 6 is a model diagram showing compressive stress and tensile stress when a bending load acts on a center pillar made of steel as a reference example.

First, the comparative example shown in FIG. 5(a) shows the stress generated when a bending load is applied to a fiber-reinforced composite material frame in which the longitudinal neutral axis AxN and the longitudinal cross-sectional central axis substantially coincide. there is As shown in FIG. 5(a), in the comparative example, since the compressive side edge stress and the tensile side edge stress are substantially the same stress, the compressive side edge stress reaches the material strength before the tensile side edge stress reaches the material strength. reaches That is, as described above, in a fiber-reinforced composite material frame, the compressive strength when a bending load is applied is only about 1/2 to 1/3 of the tensile strength. A buckling phenomenon occurs on the side where the compressive stress is generated (the side of the bending center AxB) before the tensile side edge stress reaches the material strength on the side).

Next, in the embodiment shown in FIG. 5(b), similarly to the above, the longitudinal neutral axis AxN _B is set with respect to the longitudinal cross-sectional center axis Ax4b on the side where compressive stress acts when a bending load is applied (the bending center AxB side). In this embodiment, as an example, _yc : _yy =1:3. In other words, in this embodiment, _{y c} is 1/4 of the cross-sectional height (y _c +y _y ), and y y is 3/4 (=0.75) of the cross-sectional height (y _c +y _y ). .

As shown in FIG. 5(b), in the embodiment, the longitudinal neutral axis AxN _B is biased toward the side where compressive stress acts when a bending load is applied with respect to the longitudinal cross-sectional center axis Ax4b. The compressive side edge stress _σc when a bending load is applied can be suppressed to about 1/3 of the tensile side edge stress _σy . Therefore, in the embodiment, before the tensile side edge stress reaches the material strength on the side where the tensile load occurs (the side opposite to the bending center AxB), the buckling phenomenon occurs on the side where the compressive stress occurs (the side of the bending center AxB). occurrence can be suppressed.

Next, the reference example shown in FIG. 6 is steel which is an elastoplastic material. When a bending load is applied to steel, a uniform compressive stress is generated in the area from the longitudinal neutral axis AxN (which coincides with the longitudinal cross-sectional center axis) toward the outer wall surface on the bending center side, and the bending center A uniform tensile stress is generated in the area toward the outer wall surface on the opposite side. That is, in steel, it can be said that it is in a fully plastic state assuming that there is no loss due to buckling.

6. Effect In the center pillar 4 as the fiber-reinforced composite material frame according to the present embodiment, the longitudinal neutral axis _AxNB is biased toward the outer portion (compression portion) 4b1 with respect to the longitudinal cross-sectional central axis Ax4b in the middle portion 4b. Therefore, the compressive side edge stress σ _c can be made smaller than the tensile side edge stress σ _y . That is, in the fiber-reinforced composite material frame, the compressive strength when a bending load is applied is only about 1/2 to 1/3 of the tensile strength. By biasing AxN _B toward the outer portion (compressed portion) 4b1 with respect to the longitudinal cross-sectional center axis Ax4b, the compressive side edge stress _σc is made smaller than the tensile side edge stress _σy . It is possible to suppress the occurrence of the buckling phenomenon at (compression portion) 4b1.

Therefore, in the central portion 4b of the center pillar 4 according to the present embodiment, the bending strength is reduced by suppressing the occurrence of the buckling phenomenon and breakage of the compressed portion 4b1 until the tensile side edge stress _σy reaches the material strength or a strength close thereto. A high mass efficiency in can be obtained.

In addition, in the middle portion 4b of the center pillar 4 according to the present embodiment, as an example of means for biasing the longitudinal neutral axis AxN _B toward the compression portion 4b1 side with respect to the longitudinal cross-sectional center axis Ax4b, the outer portion The thickness T _B1 of the outer peripheral wall of the (compressed portion when a bending load is applied) 4b1 is made thicker than the thickness T _B2 of the outer peripheral wall of the inner portion (the tension side when the bending load is applied) 4b2.

[Second embodiment]
The configuration of the center pillar 14 according to the second embodiment will be described with reference to FIG. 7(a). FIG. 7A is a schematic cross-sectional view showing the cross-sectional structure of the central portion of the center pillar 14 according to this embodiment. Note that the lower portion and the upper portion of the center pillar 14 are formed with the same structure as the center pillar 4 according to the first embodiment, so repeated explanations are omitted.

As shown in FIG. 7A, the center pillar 14 according to the present embodiment is also a frame with a hollow structure including a central portion made of a fiber-reinforced composite material (for example, a carbon fiber-reinforced composite material). That is, the center pillar 14 according to this embodiment is also a fiber-reinforced composite material frame having a cross-sectional configuration in which the inner space 14d is surrounded by the outer peripheral wall.

In the central portion of the center pillar 14 according to the present embodiment, the thickness _TC of the outer peripheral wall is substantially the same over the entire circumference. In addition, in the central portion of the center pillar 14, the width W1 of the outer portion 14a is set wider than the width W2 of the inner portion 14b.

Furthermore, in the central portion of the center pillar 14, a ridgeline portion 14c is provided on the outer portion 14a. The ridgeline portions 14c are provided at both side portions of the groove recessed toward the inner space 14d side from the widthwise both side portions. The difference between the width W1 and the width W2 in the central portion of the center pillar 14 corresponds to the width of the groove between the ridge line portions 14c.

In the central portion of the center pillar 14, by providing the ridgeline portion 14c on the outer portion 14a, the longitudinal neutral axis _AxNC is set to be biased toward the outer portion 14a side by G2 with respect to the longitudinal cross-sectional central axis Ax14.

Here, even in the central portion of the center pillar 14 according to the present embodiment, the outer portion 14a is the side on which compressive stress is generated when a bending load acts inward due to a side collision or the like. That is, even in the central portion of the center pillar 14 according to the present embodiment, the longitudinal neutral axis _AxNC is on the compressed portion (outer portion 14a) side where compressive stress is generated when a bending load is applied with respect to the longitudinal cross-sectional central axis Ax14. is set biased toward

In the central portion of the center pillar 14 according to the present embodiment, a ridgeline portion 14c is provided on the outer portion (portion on the compression side when a bending load is applied) so that the longitudinal neutral axis _AxNC is aligned with the longitudinal cross-sectional central axis Ax14. buckling phenomenon occurs in the outer portion (compression portion) 14a by making the compression side edge stress _σc smaller than the tensile side edge stress _σy can be suppressed.

[Third embodiment]
The configuration of the center pillar 24 according to the third embodiment will be described with reference to FIG. 7(b). FIG. 7B is a schematic cross-sectional view showing the cross-sectional structure of the central portion of the center pillar 24 according to this embodiment. Since the lower portion and upper portion of the center pillar 24 are also formed with the same structure as the center pillar 4 according to the first embodiment, redundant description will be omitted.

As shown in FIG. 7B, the center pillar 24 according to the present embodiment is also a frame with a hollow structure including a central portion made of a fiber reinforced composite material (for example, a carbon fiber reinforced composite material). That is, the center pillar 24 according to this embodiment is also a fiber-reinforced composite material frame having a cross-sectional configuration in which the inner space 24d is surrounded by the outer peripheral wall.

In the middle portion of the center pillar 24 according to the present embodiment, similarly to the middle portion 4b of the center pillar 4 according to the first embodiment, the thickness _TD1 of the outer peripheral wall of the outer portion 24a is equal to the thickness of the outer peripheral wall of the inner portion 24b. It is formed thicker than the thickness _TD2 . Also in this embodiment, when the thickness _TD1 is made thicker than the thickness _TD2 , the thick portion is distributed to the inner space 24d side. As a result, even in the central portion of the center pillar 24 according to the present embodiment, the thick portion is inconspicuous in appearance, and excellent appearance quality can be achieved.

Further, in the central portion of the center pillar 24, the width W3 of the outer portion 24a is set wider than the width W4 of the inner portion 24b, similarly to the central portion of the center pillar 14 according to the second embodiment.

Furthermore, in the central portion of the center pillar 24 according to the present embodiment, a ridgeline portion 24c is provided on the outer portion 24a, similarly to the central portion of the center pillar 14 according to the second embodiment. The formation form of the ridgeline portion 24c is the same as that of the ridgeline portion 14c according to the second embodiment.

In the central portion of the center pillar 24 according to the present embodiment, the thickness _TD1 of the outer portion 24a is made thicker than the thickness _TD2 of the inner portion 24b, and the outer portion 24a is provided with the ridge line portion 24c. The directional neutral axis AxN _D is set to be biased toward the outer portion 24a by G3 with respect to the longitudinal cross-sectional center axis Ax24.

Also in the central portion of the center pillar 24 according to the present embodiment, the outer portion 24a is the side on which compressive stress is generated when a bending load acts _toward the inside due to a side collision or the like. is biased toward the compressed portion (outer portion) 24a where compressive stress is generated when a bending load is applied with respect to the central axis Ax24 of the longitudinal cross section.

In the central portion of the center pillar 24 according to the present embodiment, the thickness _TD1 of the outer portion 24a is made thicker than the thickness _TD2 of the inner portion 24b, and the outer portion (portion on the compression side when a bending load is applied) By providing the ridgeline portion 24c at the ridgeline portion 24c, the longitudinal neutral axis AxN _D is biased toward the outer portion (compressed portion) 24a side with respect to the longitudinal cross-sectional center axis Ax24, so that the compressive side edge stress _σc is reduced to the tension side. By making the edge stress σ _y smaller than the edge stress σ y , it is possible to suppress the occurrence of the buckling phenomenon in the outer portion (compressed portion) 24 a.

[Fourth embodiment]
The configuration of the center pillar 34 according to the fourth embodiment will be described with reference to FIG. 8(a). FIG. 8A is a schematic cross-sectional view showing the cross-sectional structure of the central portion of the center pillar 34 according to this embodiment. Since the lower portion and the upper portion of the center pillar 34 are also formed with the same structure as the center pillar 4 according to the first embodiment, redundant description will be omitted.

As shown in FIG. 8A, the center pillar 34 according to the present embodiment is also a frame with a hollow structure including a central portion made of a fiber-reinforced composite material (for example, a carbon fiber-reinforced composite material). That is, the center pillar 34 according to this embodiment is also a fiber-reinforced composite material frame that has a hollow cross-sectional shape and extends in the vertical direction, as in the first to third embodiments.

As shown in FIG. 8A, the central portion of the center pillar 34 has a substantially rectangular cross-sectional shape with rounded corners on the outer peripheral portion, and an internal space 34i is formed inside.

The central portion of the center pillar 34 according to the present embodiment has substantially the same thickness _TE of the outer peripheral wall over the entire circumference, like the central portion of the center pillar 14 according to the second embodiment.

In the central portion of the center pillar 34 according to this embodiment, ribs 34c, 34d, and 34e are provided on the side of the outer portion 34a in the internal space 34i. The ribs 34c, 34d, and 34e are formed in the central portion of the center pillar 34 so as to be continuous in the longitudinal direction (the direction perpendicular to the plane of the drawing).

The internal space 34i in the central portion of the center pillar 34 is partitioned into three small rooms (chambers) 34f, 34g, and 34h on the side of the outer portion 34a by the ribs 34c, 34d, and 34e. The ribs 34c, 34d, and 34e are connected to each other and the ribs 34c, 34d, and 34e are connected to the outer peripheral wall at their abutting points.

In the central portion of the center pillar 34 according to this embodiment, a plurality of ribs 34c, 34d, and 34e are provided in the interior space 34i. , 34g and 34h, the longitudinal neutral axis _AxNE is set to be biased toward the outer portion 34a by G4 with respect to the longitudinal cross-sectional central axis Ax34.

Note that, even in the central portion of the center pillar 34 according to the present embodiment, the outer portion 34a is the side on which compressive stress is generated when a bending load acts _toward the inside due to a side collision or the like. is biased toward the compressed portion (outer portion) 34a where compressive stress is generated when a bending load is applied with respect to the central axis Ax34 in the longitudinal direction.

Therefore, in the central portion of the center pillar 34 according to the present embodiment as well, the longitudinal neutral axis AxN _E is biased toward the outer portion (compression portion) 34a with respect to the longitudinal cross-sectional center axis Ax34. By making the stress _σc smaller than the tensile side edge stress _σy , it is possible to suppress the occurrence of the buckling phenomenon in the outer portion (compressed portion) 34a.

[Fifth embodiment]
The configuration of the center pillar 44 according to the fifth embodiment will be described with reference to FIG. 8(b). FIG. 8B is a schematic cross-sectional view showing the cross-sectional structure of the central portion of the center pillar 44 according to this embodiment. Note that the lower portion and upper portion of the center pillar 44 are also formed with the same structure as the center pillar 4 according to the first embodiment, so redundant description will be omitted.

As shown in FIG. 8B, the center pillar 44 according to the present embodiment is also a frame with a hollow structure including a central portion made of a fiber reinforced composite material (for example, a carbon fiber reinforced composite material). That is, the center pillar 44 according to this embodiment is also a fiber-reinforced composite material frame that has a hollow cross-sectional shape and extends in the vertical direction, as in the first to fourth embodiments.

As shown in FIG. 8B, the central portion of the center pillar 44 has a substantially rectangular cross-sectional shape with rounded corners on the outer peripheral portion, and an internal space 34i is formed inside.

In the central portion of the center pillar 44 according to the present embodiment, the thickness T _F1 of the outer peripheral wall of the outer portion 44a is equal to the thickness T of the outer peripheral wall of the inner portion 44b, as in the first and third embodiments. It is formed thicker than _F2 . Also in this embodiment, when the thickness _TF1 is made thicker than the thickness TF2, the thicker portion is distributed to the inner space _44i side. As a result, even in the central portion of the center pillar 44 according to the present embodiment, the thick portion is inconspicuous in appearance, and excellent appearance quality can be achieved.

In the central portion of the center pillar 44 according to this embodiment, ribs 44c, 44d, and 44e are provided on the side of the outer portion 44a in the internal space 44i, as in the fourth embodiment. Each rib 44c, 44d, 44e is formed in the central portion of the center pillar 44 so as to be continuous in the longitudinal direction (the direction perpendicular to the plane of the drawing).

Regarding the internal space 44i in the central part of the center pillar 44, the ribs 44c, 44d and 44e also partition the outer part 44a side into three small rooms (chambers) 44f, 44g and 44h. The ribs 44c, 44d, and 44e are connected to each other, and the ribs 44c, 44d, and 44e to the outer peripheral wall are connected to each other at their abutting points.

In the central portion of the center pillar 44 according to this embodiment, a plurality of ribs 44c, 44d, and 44e are provided in the interior space 44i. , 44g and 44h, the longitudinal neutral axis AxN _F is set to be biased toward the outer portion 44a by G5 with respect to the longitudinal cross-sectional center axis Ax44.

Also in the central portion of the center pillar 44 according to the present embodiment, the outer portion 44a is the side on which compressive stress is generated when a bending load acts toward the inside due to a side collision or the like, and the neutral longitudinal axis AxN _F is biased toward the compressed portion (outer portion) 44a where compressive stress is generated when a bending load is applied with respect to the central axis Ax44 of the longitudinal cross section.

Therefore, in the central portion of the center pillar 44 according to the present embodiment as well, the longitudinal neutral axis AxN _F is biased toward the outer portion (compression portion) 44a with respect to the longitudinal cross-sectional center axis Ax44. By making the stress _σc smaller than the tensile side edge stress _σy , it is possible to suppress the occurrence of the buckling phenomenon in the outer portion (compressed portion) 44a.

[Confirmation of effects exhibited by the center pillar according to each embodiment]
Effects of the center pillars 4, 14, 24, 34, 44 according to the first to fifth embodiments were confirmed. The results will be described with reference to FIG. FIG. 9 shows samples 1 to 3 as comparative examples, sample 4 having the same form as the first embodiment, samples 5 to 7 having the same form as the second embodiment, and the same form as the third embodiment. 10 is a graph showing the relationship between the mass and bending strength of Sample 8, Samples 9 to 11 having the same form as the fourth embodiment, and Sample 12 having the same form as the fifth embodiment.

(1) Samples 1 to 3
Samples 1 to 3 are samples in which the thickness of the outer peripheral wall is constant over the entire circumference with respect to the cross-sectional structure of the central portion 4b of the center pillar 4 according to the first embodiment. Three types of samples 1 to 3 having different masses were produced, and the bending strength of each was measured.

In samples 1 to 3, the longitudinal neutral axis and the longitudinal cross-sectional center axis coincide.

(2) Sample 4
A sample 4 adopts the same cross-sectional structure as the central portion 4b of the center pillar 4 according to the first embodiment, and has a mass of M1. The flexural strength of sample 4 was also measured. In Sample 4, the longitudinal neutral axis is set to be biased toward the compressed portion side with respect to the longitudinal cross-sectional central axis.

(3) Samples 5-7
Samples 5 to 7 employ the same cross-sectional structure as the central portion of the center pillar 14 according to the second embodiment. Samples 5 to 7 having different masses were produced and their bending strengths were measured. For Samples 5 to 7, the longitudinal neutral axis is also set biased toward the compressed portion side with respect to the longitudinal cross-sectional central axis.

(4) Sample 8
A sample 8 adopts the same cross-sectional structure as the central portion of the center pillar 24 according to the third embodiment, and has a mass of M2. The flexural strength of sample 8 was also measured. Note that the longitudinal neutral axis of sample 8 is also set to be biased toward the compressed portion side with respect to the central axis of the longitudinal cross-section.

(5) Samples 9-11
Samples 9 to 11 are samples that employ the same cross-sectional structure as the central portion of the center pillar 34 according to the fourth embodiment. Samples 9 to 11 having different masses were produced and their bending strengths were measured. For Samples 9 to 11, the longitudinal neutral axis is also set biased toward the compressed portion side with respect to the longitudinal cross-sectional central axis.

(6) Sample 12
A sample 12 adopts the same cross-sectional structure as the central portion of the center pillar 44 according to the fifth embodiment, and has a mass of M3. The flexural strength of sample 12 was also measured. Also for the sample 12, the longitudinal neutral axis is set biased toward the compressed portion side with respect to the longitudinal cross-sectional central axis.

(7) Confirmation Results As shown in FIG. 9, the bending strength of samples 1 to 3 increases as the mass increases. That is, since the outer peripheral wall of sample 2 is thicker than that of sample 1, and the outer peripheral wall of sample 3 is thicker than that of sample 2, the bending strength increases in proportion to the increase in mass. ing.

The bending strength of sample 4 is SB4, which is higher than the bending strength SB1 at point P1 with the same mass M1 estimated from samples 1-3. This is because even if the mass M1 is the same, by making the wall thickness of the compression portion side thicker than that of the tension portion side, the longitudinal neutral axis is shifted to the compression portion side with respect to the longitudinal cross-sectional center axis. This is the effect of setting biased to . That is, it can be seen that sample 4 can obtain a higher mass efficiency in bending strength than samples 1-3.

The flexural strength of samples 5 to 7 also increased as the mass increased. As for samples 5 to 7, the bending strength is higher as the thickness of the outer peripheral wall is thicker and the mass is larger. The bending strength at the mass M1 estimated from Samples 5 to 7 is higher than the bending strength SB4 of Sample 4. By adopting the cross-sectional structure of the middle part of the center pillar 14 according to the second embodiment, this is higher than the case of adopting the cross-sectional structure of the middle part 4b of the center pillar 4 according to the first embodiment with the same mass. It shows that bending strength can be obtained.

The bending strength of sample 8 is SB8, which is higher than the bending strength SB2 at point P2 with the same mass M2 estimated from samples 5-7. Similar to the relationship between Samples 1 to 3 and Sample 4, even if the mass M2 is the same, by making the thickness of the compression part side thicker than the tension part side, This is the effect of setting the vertical axis biased toward the compressed portion side with respect to the central axis of the cross section in the longitudinal direction. That is, it can be seen that sample 8 can obtain a higher mass efficiency in bending strength than samples 5-7.

The flexural strength of samples 9 to 11 also increased with increasing mass. As for samples 9 to 11, the bending strength is higher as the thickness of the outer peripheral wall is thicker and the mass is larger. The bending strength at the mass M2 estimated from Samples 9 to 11 is higher than the bending strength SB8 of Sample 8. This is because the use of the cross-sectional structure of the central portion of the center pillar 34 according to Embodiment 4 provides a higher bending force with the same mass than the case of adopting the cross-sectional structure of the central portion of the center pillar 24 according to Embodiment 3. It shows that strength can be obtained.

The bending strength of sample 12 is SB12, which is higher than the bending strength SB3 at point P3 with the same mass M3 estimated from samples 9-11. Similar to the relationship between Samples 1 to 3 and Sample 4 and the relationship between Samples 5 to 7 and Sample 8, even if the mass M3 is the same, the thickness on the side of the compression portion is the same as the thickness on the side of the tension portion. This is the effect of setting the longitudinal neutral axis biased toward the compressed portion side with respect to the central axis of the longitudinal cross-section by making it thicker than the thickness. That is, it can be seen that sample 12 can obtain a higher mass efficiency in bending strength than samples 9-11.

Here, in the first embodiment, _yc is 1/4 (=0.25) of the cross-sectional height ( _yc + _yy ), in other words, _yy is the cross-sectional height ( _yc + _yy ) By setting it to 0.75″, it is possible to suppress the occurrence of the buckling phenomenon of the compressed portion 4b1 until the tensile side edge stress σ _y reaches the material strength or strength close to it, and obtain high mass efficiency in bending strength. can be done. However, the ratio of y _c to the cross-sectional height (y _c +y _y ) can be set to a preferable value depending on the material used. For example, y _c is in the range of 0.18 to 0.5 with respect to the section height (y _c +y _y ), in other words, y _y is in the range of 0.5 to 0.5 with respect to the section height (y _c +y _y ). It can be set within the range of 0.82.

[Relationship between ridgeline and rib position and maximum bending moment without buckling]
In the second embodiment, the ridgeline portion 14c is provided on the central outer portion 14a of the center pillar 14, and in the third embodiment, the ridgeline portion 24c is provided on the central outer portion 24a of the center pillar 24. In the fourth embodiment, the ribs 34c, 34d, and 34e are provided on the side of the outer portion 34a in the inner space 34i in the middle of the center pillar 34. In the fifth embodiment, the inner space 44i in the middle of the center pillar 44 is provided. ribs 44c, 44d, and 44e are provided on the side of the outer portion 44a.

The relationship between the positions where these ridges 14c, 24c and ribs 34c, 34d, 34e, 44c, 44d, 44e are provided and the maximum bending moment without buckling will be described with reference to FIG. FIG. 10 is a graph showing the relationship between the positions of the ridgelines 14c and 24c and the maximum bending moment without buckling.

In FIG. 10, the value obtained by dividing the position H5 of the ridgeline based on the inner edge of the center pillar (the edge on the side where tensile stress is generated when a bending load is applied) by the height H1 of the center pillar The vertical axis is the bending moment without buckling (ratio to the maximum bending moment) M/Mmax.

As shown in FIG. 10, it can be seen that the maximum bending moment Mmax (M/Mmax=1) without buckling is obtained when the value of H5/H1 is 0.75. Also, it can be seen that an efficient bending moment M can be obtained when the value of H5/H1 is within the range of 0.55 to 0.9 (within the range indicated by "B" in FIG. 10).

Therefore, by setting H5/H1 within the range of 0.55 to 0.9, it is possible to efficiently suppress the occurrence of the buckling phenomenon in the compressed portion when a bending load is applied.

In FIG. 10, the configuration in which the ridge line portion is provided on the outer side of the central portion of the center pillar is taken as an example, but the same applies to the configuration in which the rib is provided on the outer side of the inner space of the central portion of the center pillar.

[Sixth embodiment]
The configurations of the vehicle body 10 and the front side frame 12 according to the sixth embodiment will be described with reference to FIGS. 11 and 12. FIG. FIG. 11 is a schematic plan view showing a partial configuration of the vehicle body 10 according to this embodiment, and FIG. 12 is a schematic plan view showing the structure of the front side frame 12 shown in section C of FIG.

As shown in FIG. 11, a vehicle body 10 according to this embodiment includes a floor panel 11, a front side frame 12, and a bumper reinforcement 13 at a vehicle front portion 10a. A pair of left and right front side frames 12 are provided and spanned between the floor panel 11 and the bumper reinforcement 13 .

As shown in FIG. 12, the front side frame 12 according to this embodiment extends in the longitudinal direction of the vehicle body 10 and has a hollow cross-sectional shape. The front side frame 12 is a frame made of a fiber-reinforced composite material (for example, a carbon fiber-reinforced composite material).

The front side frame 12 is provided with a plurality of beads 12c to 12e spaced apart from each other in the longitudinal direction. Of these, the beads 12c and 12e are provided on the right side portion 12a, and the bead 12d is provided on the left side portion 12b. In addition, in the front side frame 12 provided on the right side of the vehicle body 10, the formation direction of the plurality of beads is left-right opposite to the form shown in FIG.

As shown in FIG. 12 , when an object collides with the vehicle body 10 from the front, a force indicated by an arrow acts on the front side frame 12 via the bumper reinforcement 13 . When such a force acts, the front side frame 12 is deformed so as to bend with the beads 12c to 12e inside, thereby absorbing the impact of the collision.

In the front side frame 12, the longitudinal neutral axis _AxNG is set biased with respect to the longitudinal cross-sectional center axis Ax12 at and near the locations where the beads 12c to 12e are provided. Specifically, at and near the location where the bead 12c is provided, the longitudinal neutral axis AxN _G is set biased toward the compressed portion 12f where compressive stress is generated when a bending load due to frontal collision acts. there is Conversely, in the location where the bead 12c is provided and its vicinity, the longitudinal neutral axis AxN _G is set on the side away from the side of the tensile portion 12g where tensile stress is generated when the bending load due to the frontal collision acts. It is

Similarly, the location where the bead 12d is provided and its vicinity are on the side of the compression portion 12h where compression stress is generated when a bending load due to frontal collision acts, and are opposite to the tension portion 12i where tensile stress is generated. The longitudinal direction neutral axis _AxNG is set biased to the side. In addition, the location where the bead 12e is provided and its vicinity are on the side of the compression portion 12j where compression stress is generated when the bending load due to the frontal collision acts, and on the side opposite to the tension portion 12k where tensile stress is generated. , the longitudinal neutral axis _AxNG is set biased.

As described above, in the front side frame 12 according to the present embodiment, at the locations where the beads 12c to 12e are provided and in the vicinity thereof, when a bending load due to a frontal collision acts, a compressive stress is generated on the side of the compression portion 12f. , the longitudinal neutral axis _AxNG is set biased. For this reason, in the front side frame 12 according to the present embodiment, the longitudinal neutral axis _AxNG is set so as to deviate from the longitudinal central axis Ax12 in the longitudinal direction while being alternately left and right.

As specific means for setting the longitudinal neutral axis AxN _G to be biased with respect to the longitudinal central axis Ax12, any one of the means of the first embodiment to the fifth embodiment can be adopted. .

[Modification]
In the middle portion 4b of the center pillar 4 according to the first embodiment, the outer portion 4b1 and the inner portion 4b2 have different thicknesses in two stages, but the present invention is not limited to this. For example, the thickness may be changed in three stages or more.

In the second embodiment and the third embodiment, the ridgeline portions 14c and 24c are provided only on the outer portions 14a and 24a of the center pillars 14 and 24, but the number of ridgeline portions provided on the outer portions (compression portions) , the present invention is not limited to this. In the present invention, the same effect as described above can be obtained by providing more ridge line portions in the outer portion (compression portion) than in the inner portion (tension portion).

In the fourth embodiment and the fifth embodiment, the ribs 34f to 34h and 44f to 44h are provided only on the side of the outer portions 34a and 44a in the internal spaces 34i and 44i of the center pillars 34 and 44, respectively. The invention is not limited to this. In the present invention, the same effect as described above can be obtained by providing more ribs on the side of the outer portion (compression portion) than on the inner portion (tension portion) of the internal space.

In the first to fifth embodiments, the center pillars 4, 14, 24, 34, and 44 are used as an example of the fiber-reinforced composite frame. In the sixth embodiment, the fiber-reinforced composite frame Although the front side frame 12 is used as an example, the present invention is not limited to this. For example, application to side sills and roof side rails is also possible.

In addition, the present invention can be applied not only to vehicle bodies such as automobiles, but also to various structures (for example, industrial equipment, etc.).

In addition, in the first embodiment and the second embodiment, the external shape in cross section is a square with rounded corners, but the present invention is not limited to this. For example, the external shape of the cross section may be circular, elliptical, oval, or a polygonal cross section that is more polygonal than triangular or pentagonal.

Further, in the first embodiment to the sixth embodiment, the carbon fiber reinforced composite material is used as an example of the fiber reinforced composite material, but the present invention is not limited to this. For example, fiber reinforced composite materials such as glass fiber reinforced resin (GFRP), aramid fiber reinforced resin (ArFRP), silicon carbide fiber reinforced resin (SiCFRP), and fiber reinforced resin using metal fibers such as non-ferrous metals are adopted. It is also possible to

4, 14, 24, 34, 44 center pillar (fiber reinforced composite frame)
4b1, 14a, 24a, 34a, 44a outer portion (compression portion)
4b2, 14b, 24b, 34b, 44b inner part (tension part)
4d, 14d, 24d, 34i, 44i Internal space 12 Front side frame (frame made of fiber reinforced composite material)
12f, 12h, 12j compression part 12g, 12i, 12k tension part 14c, 24c ridgeline part 34c, 34d, 34e, 44c, 44d, 44e rib 34f, 34g, 34h, 44f, 44g, 44h small room (room)
Ax4b, Ax14, Ax24, Ax34, Ax44 longitudinal cross-sectional center axis AxN _B , _AxNC , AxN _D , AxN _E , AxN _F longitudinal neutral axis

Claims (6)

A fiber-reinforced composite frame having a hollow cross-sectional shape, extending in a predetermined direction, and receiving a bending load,
In at least a partial region in the longitudinal direction, the position of the longitudinal neutral axis of the fiber-reinforced composite material frame is set biased toward the compressed portion side where compressive stress is generated with respect to the longitudinal cross-sectional center axis. ,
When the at least partial region is viewed in a cross section in a direction intersecting the predetermined direction, and the direction of bias of the longitudinal neutral axis with respect to the longitudinal cross-sectional center axis is the height direction of the cross section, the compressed portion A tensile portion that generates a tensile stress when the bending load is applied is disposed on the opposite side in the height direction of the cross section to the
The maximum width of the compression portion is set wider than the maximum width of the tension portion in a lateral direction that intersects both the predetermined direction and the height direction of the cross section,
The compressing portion includes a groove recessed toward the tensile portion in the middle portion in the transverse direction, and ridge lines extending in the predetermined direction, which are disposed on both side portions of the groove in the transverse direction. and
The difference between the width of the compression portion and the width of the tension portion is substantially the same as the width of the groove in the lateral direction.
Fiber-reinforced composite frame. The fiber-reinforced composite frame according to claim 1,
The compressed portion in the at least partial region is provided with more ridges extending in the longitudinal direction than the tensile portion where tensile stress is generated when the bending load is applied.
Fiber-reinforced composite frame. The fiber-reinforced composite frame according to claim 2,
When the height of the fiber-reinforced composite material frame in the height direction of the cross section in the cross-sectional view in the crossing direction is the cross-sectional height,
The ridgeline portion is provided in a range of 0.55 to 0.9 with respect to the cross-sectional height with respect to the end portion on the side of the tensile portion on the bending stress acting surface,
Fiber-reinforced composite frame. The fiber-reinforced composite frame according to any one of claims 1 to 3,
In the at least partial region, the cross section of the compression portion is set larger than the tension portion,
Fiber-reinforced composite frame. The fiber-reinforced composite frame according to any one of claims 1 to 4 ,
The outer peripheral wall of the compression portion in the at least partial region is provided thicker than the tension portion,
Fiber-reinforced composite frame. The fiber-reinforced composite frame according to any one of claims 1 to 5,
The fiber-reinforced composite frame is a center pillar disposed between a front door opening and a rear door opening of an automobile body,
The height direction of the cross section is the vehicle width direction of the vehicle body,
The compression portion is arranged to be positioned outside the tension portion in the vehicle width direction,
The two walls arranged on both sides in the lateral direction are formed so that the distance between them gradually widens from the inside to the outside in the vehicle width direction at least in part in the vehicle width direction. ing,
Fiber-reinforced composite frame.

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