Vehicle body structure and methods for improving impact energy absorption

Abstract

Vehicle body structure, comprehensive: a pair of front side frames (11) extending substantially in a longitudinal direction along a front part of a vehicle and comprising an outer side wall section (11c) and an inner side wall section (11d), wherein the outer side wall section (11c) is positioned on an outer or outward-facing side in a vehicle width direction of the vehicle and the inner side wall section (11d) is positioned on an inner or inward-facing side in the vehicle width direction of the vehicle, wherein the front side frame (11) has a substantially closed cross-section; a bead (11e) which is formed substantially at a central position in the longitudinal direction of the vehicle of the outer side wall section (11c) of the front side frame (11), wherein the bead (11e) is configured to cause the front side frame (11) to bend inwards at the central position of the outer side wall section (11c) where the bead (11e) is provided in a vehicle frontal collision; and a reinforcing member (51) which is provided inside the substantially closed cross-section of the front side frame (11) at a position in the longitudinal direction of the vehicle which essentially corresponds to a design position of the bead (11e), wherein the reinforcing member (51) extends between the outer side wall section (11c) and the inner side wall section (11d) of the front side frame (11), wherein the reinforcing member (51) is connected to the outer side wall section (11c) and the inner side wall section (11d) of the front side frame (11), wherein a connection length in the longitudinal direction of the vehicle of the reinforcing member (51) and the inner side wall section (11d) is set to be longer than that of the reinforcing member (51) and the outer side wall section (11c), wherein the reinforcing member (51) is made of a plate member which extends in a vertical direction and in the longitudinal direction of the vehicle, wherein an upper end section (51a) and a lower end section (51b) of the reinforcing member (51) are connected to the outer side wall section (11c) of the front side frame (11), wherein a central section in the vertical direction of the reinforcing member (51) is configured as a wave-like section (51d) which is configured to be bent in a rectangular-wave-like shape having several bend lines extending substantially in the longitudinal direction of the vehicle, and a raised tip surface of a portion of the wave-like section (51d) which is configured to project towards the inner side wall section (11d) of the front side frame (11) is connected to the inner side wall section (11d), wherein the upper end section (51a) of the reinforcing member (51) and an outwardly directed portion of an uppermost part of the wave-like section (51d) are configured to have a cutout at a central section in the vehicle width direction, wherein the lower end section (51b) of the reinforcing member (51) and an outwardly directed section of a lowest part of the wave-like section (51d) are configured to have a cutout at a central section in the vehicle width direction, and wherein the cutout at the upper end section (51a) and the cutout at the lower end section (51b) are arranged in the same position with respect to the longitudinal direction of the vehicle as the bead (11e).

Description

[0001] The present invention relates to a vehicle body structure comprising a pair of front side frames extending substantially in a vehicle longitudinal direction at a front portion of a vehicle and having a substantially closed cross-section. Furthermore, the invention relates to a method for improving impact energy absorption of a front vehicle body structure.

[0002] Conventionally, it is known that the front side frame is actively bent and impact energy is absorbed or absorbed by bending deformation of this front side frame in a vehicle frontal collision (see, for example, JP 2016 - 113 084 A).

[0003] The above-described patent document discloses a front side frame including a first region (where a bead is formed on an outer side wall portion in a vehicle width direction of the front side frame) that constitutes a compression-side wall portion and a tension-side wall portion by their outwardly bending deformation when a load is applied from a vehicle front side, and a second region (where a bead is formed on an inner side wall portion in the vehicle width direction of the front side frame) that constitutes a tension-side wall portion and a compression-side wall portion by their inwardly bending deformation when the load is applied from the vehicle front side.A reinforcing member forming a plurality of closed sub-sections adjacent to one another in a vertical direction in cooperation with a closed main cross-section of the above-described first region, a second reinforcing member forming a plurality of closed sub-sections adjacent to one another in the vertical direction in cooperation with a closed main cross-section of the above-described second region, and a motor mounting member provided to partition the above-described closed main cross-section. Each of the above-described first and second reinforcing members comprises a first dividing wall portion vertically dividing the above-described closed main cross-section, and a second dividing wall portion configured tois constructed such that its vertical distance from the first dividing wall portion on the tension side is smaller than its vertical distance from the first dividing wall portion on the compression side. The above-described first and second reinforcing members are arranged adjacent to each other with a mounting reinforcement interposed therebetween. Thereby, a truss structure is formed by contacting respective compression-side end portions of the first and second tensile-side dividing portions, which are supported on the tensile-side wall portions of the first and second dividing wall portions, so that cross-sectional collapse caused by bending deformation is suppressed, so that the absorbing efficiency of impact energy can be increased.

[0004] However, in a case where a reinforcing member such as the first and second reinforcing members of the above-described patent document is disposed inside the closed cross section of the front side frame, this reinforcing member is rectangularly wave-shaped so that it alternately protrudes toward the tension-side wall portion and the compression-side wall portion, and respective protrusion tip surfaces of its protrusion portions are connected to the tension-side wall portion and the compression-side wall portion by welding. Accordingly, since many welding points are required at both the tension-side wall portion and the compression-side wall portion, there is room for improvement in the productivity of the front side frame.

[0005] Furthermore, JP 2015 227124 A discloses a reinforcement body provided within a frame body. The frame body is formed in a closed cross-sectional shape to interconnect first and second vehicle body structural members. The reinforcement body includes first and second reinforcement members, which include base portions extending along the first and second vehicle body structural members and projections projecting from the base portions. The upper surface portions of the projections of the first and second reinforcement members are interconnected and connected to the frame body on a tensile side with respect to at least one neutral bending axis.

[0006] Further vehicle body structures are disclosed in the documents JP 2015-000691 A and DE 11 2017 000 111 T5.

[0007] The present invention has been developed in view of the above-described object, and it is an object of the present invention to improve the performance of impact energy absorption by the front side frame in the vehicle frontal collision, properly suppressing deterioration of the productivity of the front side frame in the case where the reinforcing member is arranged inside the closed cross section of the front side frame which is configured to be bent in the vehicle frontal collision.

[0008] This object is solved by the features of the independent claims.

[0009] The present invention is a vehicle body structure comprising: a pair of front side frames extending substantially in a vehicle longitudinal direction at a front part of a vehicle and including an outward-facing side wall portion and an inward-facing side wall portion, the outward-facing side wall portion being positioned on an outward-facing side in a vehicle width direction of the vehicle and the inward-facing side wall portion being positioned on an inward-facing side in the vehicle width direction of the vehicle, the front side frame having a substantially closed cross-section; a bead formed substantially at a central position in the vehicle longitudinal direction of the outward-facing side wall portion of the front side frame,wherein the bead is configured to cause the front side frame to bend inward at the central position of the outer side wall portion where the bead is provided in a vehicle frontal collision; and a reinforcing member provided inside the substantially closed cross section of the front side frame at a position in the vehicle longitudinal direction substantially corresponding to a formation position of the bead, wherein the reinforcing member extends between the outer side wall portion and the inner side wall portion of the front side frame. The reinforcing member is connected to the outer side wall portion and the inner side wall portion of the front side frame. A connection length in the vehicle longitudinal direction of the reinforcing member and the inner side wall portion is set.to be longer than those of the reinforcing member and the outer side wall portion. The reinforcing member is made of a plate member extending in a vertical direction and in the vehicle longitudinal direction. An upper end portion and a lower end portion of the reinforcing member are connected to the outer side wall portion of the front side frame. A central portion in the vertical direction of the reinforcing member is formed as a wave-like portion configured to be bent in a rectangular wave-like shape having a plurality of bending lines extending substantially in the vehicle longitudinal direction. A protrusion tip surface of a part of the wave-like portion configured to protrude toward the inner side wall portion of the front side frame,is connected to the inner sidewall portion. The upper end portion of the reinforcing member and an outward portion of an uppermost part of the wave-like portion are configured to have a cutout at a central portion in the vehicle width direction. The lower end portion of the reinforcing member and an outward portion of a lowermost part of the wave-like portion are configured to have a cutout at a central portion in the vehicle width direction. The cutout at the upper end portion and the cutout at the lower end portion are arranged at the same position with respect to the vehicle longitudinal direction as the bead.

[0010] According to the present invention, since the joint length in the vehicle longitudinal direction of the reinforcing member and the outboard sidewall portion is set to be relatively short, the number of welding points of the reinforcing member welded to the outboard sidewall portion of the front side frame can be reduced, so that the deterioration of productivity can be correspondingly suppressed. Furthermore, by setting the joint length in the vehicle longitudinal direction of the reinforcing member and the outboard sidewall portion to be relatively short, the outboard sidewall portion of the front side frame is easily bent inward locally at the position where the bead is provided in the vehicle frontal collision (the outboard sidewall portion has a simple bent).slight buckling occurs locally at the position where the bead is provided). On the other hand, since the connecting length in the vehicle longitudinal direction of the reinforcing member and the inboard sidewall portion, where a tensile load is generated by this bending of the outboard sidewall portion, is set to be relatively long, this tensile load can be absorbed at a wide range in the vehicle longitudinal direction, so that the inboard sidewall portion is prevented from being bent locally unlike the outboard sidewall portion. Accordingly, the impact energy absorption performance of the front side frame in the vehicle frontal collision can be improved.

[0011] Furthermore, the reinforcing member does not block the smooth local bending of the outboard side wall portion, so that the outboard side wall portion of the front side frame can be properly bent at the position where the bead is provided by a relatively small load in the vehicle frontal collision (the buckling load can be made small accordingly).

[0012] According to another aspect, there is provided a method for improving impact energy absorption of a front vehicle body structure, comprising the steps of: Providing a pair of front side frames having a substantially closed cross-section; Forming a bead substantially at a central position in the vehicle longitudinal direction of an outer side wall portion of the front side frame, the bead being configured to cause the front side frame to bend inward at the central position of the outer side wall portion where the bead is provided in a vehicle frontal collision; Providing a reinforcing member inside the substantially closed cross-section of the front side frame at a position in the vehicle longitudinal direction which substantially corresponds to a formation position of the bead, wherein the reinforcing member extends between the outer side wall portion and an inner side wall portion of the front side frame,

[0013] Connecting the reinforcing member to the outer side wall portion and the inner side wall portion of the front side frame, and Setting or adjusting a connecting length in the vehicle longitudinal direction of the reinforcing member and the inner side wall portion to be longer than that of the reinforcing member and the outer side wall portion, wherein the reinforcing member is made of a plate member extending in a vertical direction and in the vehicle longitudinal direction, wherein an upper end portion and a lower end portion of the reinforcing member are connected to the outer side wall portion of the front side frame, and wherein a central portion in the vertical direction of the reinforcing member is formed as a wave-like portion which is formed to be bent in a rectangular wave-like shape having a plurality of bending lines extending substantially in the vehicle longitudinal direction, and a protrusion tip surface of a part of the wave-like portion which is formed to protrude toward the inner side wall portion of the front side frame is connected to the inner side wall portion, wherein the upper end portion of the reinforcing member and an outward portion of an uppermost part of the wave-like portion are formed to have a cutout at a central portion in the vehicle width direction, wherein the lower end portion of the reinforcing member and an outward portion of a lowermost part of the wave-like portion are formed to have a cutout at a central portion in the vehicle width direction, and wherein the cutout at the upper end portion and the cutout at the lower end portion are arranged at the same position with respect to the vehicle longitudinal direction as the bead.

[0014] Other features, aspects and advantages of the present invention will become apparent from the following description which refers to the accompanying drawings. Fig. 1 is a plan view showing a main portion of a front part of a vehicle to which a vehicle body structure according to an embodiment of the present invention is applied. Fig. 2 is a perspective view of a front side frame of the right side of the vehicle when viewed from a front and right (outward) side of the vehicle. Fig. 3 is a perspective view of the front side frame of the right side of the vehicle when viewed from a forward and left (inward) side of the vehicle. Fig. 4 is a sectional view taken along a line IV-IV of Fig. 3. Fig. 5 is a sectional view taken along a line VV of Fig. 3. Fig. 6 is a perspective view of a reinforcing member disposed inside a substantially closed cross section of the front side frame of the right side of the vehicle when viewed from the front and left (inward) side of the vehicle. Fig. 7 is a perspective view showing a state where an outer side wall portion of the front side frame is bent inward locally at a position where a bead is provided when an impact load is applied to the right side front side frame from a vehicle front. Fig. Fig. 8 is a perspective view showing a state where an inner side wall portion of the front side frame is bent inward in addition to the outer side wall portion which Fig. 7 corresponds. Fig. 9 is a graph showing a relationship between an amount (stroke) of retreat of a front end of the right side front side frame and a load applied to the front end of the front side frame in a vehicle frontal collision.

[0015] Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings.

[0016] Fig. 1 shows a main portion of a front part of a vehicle 1 to which a vehicle body structure according to the embodiment of the present invention is applied. An engine compartment 2, where an unillustrated powertrain driving right and left front wheels (not illustrated) of the vehicle 1 is arranged, is provided at the front part of the vehicle 1. The powertrain includes an engine and a transmission to which torque (power) generated by the engine is input. The engine and the transmission are aligned in a vehicle width direction between a pair of right and left front side frames 11, which will be described later. Hereinafter, the directional terms of "front," "rear," "left," "right," "up," and "down" will be used.“downward” relative to the vehicle 1 is simply referred to as “forward”, “backward”, “left”, “right”, “upward” and “downward”.

[0017] The right and left front side frames 11, which have an approximately rectangular, substantially closed cross-section extending substantially in a longitudinal direction, are arranged at both end portions in the vehicle width direction of the engine compartment 2. An instrument panel, which separates the engine compartment 2 from a cabin 12, is provided at a rear end portion of the engine compartment 2. A cowl member 14 is connected to an upper end portion of the instrument panel. Respective rear end portions of right and left apron reinforcement members 19, which extend substantially in the longitudinal direction, are connected to both ends in the vehicle width direction of the cowl member 14. The instrument panel is positioned below the cowl member 14, which Fig. 1 does not appear.

[0018] A wheel housing panel 17 and a suspension tower 18 are provided on the outward side in the vehicle width direction of each of the right and left front side frames 11. The wheel housing panel 17 is configured in an arc shape to cover the front wheel, and a front wheel housing is formed in this arc shape. Respective lower end portions of the right and left suspension towers 18 are fixed to the right and left front side frames 11, and respective upper end portions of the right and left suspension towers 18 are fixed to the right and left skirt reinforcement members 19.

[0019] An impact bushing 31 is provided on a front end surface (represented by a flange portion 11g) of each of the right and left front side frames 11, and respective front end surfaces of the right and left impact bushings 31 are fixed to both right and left end portions of a bumper beam 32 extending in the vehicle width direction. The impact bushing 31 is fixed to the flange portion 11g of the front side frame 11 via a flange portion 31a provided at a rear end of the impact bushing 31. The right and left front side frames 11 extend obliquely rearward and downward from substantially the same longitudinal position as the instrument panel 13.

[0020] Since the vehicle body structure according to the present embodiment is configured to be laterally symmetrical (symmetrical to a plane passing through a center in the vehicle width direction of the vehicle 1), the right-side part of the vehicle 1 (the right-side front side frame 11) will be described mainly with reference to the drawings. Hereinafter, the right-side front side frame 11 will be simply referred to as the front side frame 11. Furthermore, the descriptions of "forward" and "inward" in Fig. 2 - 8 an outside or outward-facing side or an inside or inward-facing side in the vehicle width direction.

[0021] As this is Fig. 2-5, the front side frame 11 includes an upper wall portion 11a, a lower wall portion 11b facing the upper wall portion 11a, an outward side wall portion 11c as one side wall portion positioned on the outward side in the vehicle width direction of the vehicle 1, and an inward side wall portion 11d as another side wall portion positioned on the inward side in the vehicle width direction of the vehicle 1 and facing the outward side wall portion 11c. The outward side wall portion 11c is formed by an outer member 21, and the lower wall portion 11b and the inward side wall portion 11d are formed by an outer member 21.are formed by an inner member 22 which is configured to have a hat-shaped cross-section.

[0022] The outer member 21 includes flange portions 21a, 21b at an upper side and a lower side of the outer side wall portion 11c (an upper end portion and a lower end portion of the outer member 21), and the inner member 22 includes flange portions 22a, 22b at an outer end portion in the vehicle width direction of the upper wall portion 11a and an outer end portion in the vehicle width direction of the lower wall portion 11b. These upper side flange portions 21a, 22a and these lower side flange portions 21b, 22b are respectively joined to each other by welding. The substantially closed cross section is formed by the outer member 21 and the inner member 22, which are joined to each other as described above.Herein, the flange portions 21a, 21b of the outer member 21 are arranged at substantially the same position in the vehicle width direction as the outer side wall portion 11c.

[0023] As this is Fig. 2, a bead 11e configured to extend substantially in a vertical direction and to be concave inward in the vehicle width direction is formed substantially at a central position in the longitudinal direction of the outer side wall portion 11c of the front side frame 11. In the present embodiment, since a recess portion 11f concave inward in the vehicle width direction is formed at a portion of the outer side wall portion 11c positioned below the bead 11e, the bead 11e is formed only above this recess portion 11f. This bead 11e causes the front side frame 11 to bend inward in the vehicle width direction at a longitudinal position where the bead 11e is provided in a frontal collision of the vehicle 1.Herein, in a case where the above-described recessed portion 11f is not provided at the portion of the outer side wall portion 11c positioned below the bead 11e, the bead 11e may be provided to extend substantially over an entire part substantially in the vertical direction of the outer side wall portion 11c.

[0024] It is preferable that the bead 11e be disposed at a position in the longitudinal direction of the front side frame 11 where the wheel housing panel 17 and the suspension tower 18 are not connected (particularly, where the suspension tower 18 is not connected). In the present embodiment, the bead 11e is disposed at substantially the same longitudinal position as a front end of the wheel housing panel 17.

[0025] As this is Fig. 3-6, a reinforcing member 51 is provided inside the substantially closed cross section of the front side frame 11 at a position in the longitudinal direction corresponding to a forming position of the bead 11e, so that the reinforcing member 51 extends between the outer side wall portion 11c and the inner side wall portion 11d.

[0026] The reinforcing member 51 is made of a plate member extending vertically in the longitudinal direction. The upper end portion 51a and the lower end portion 51b of the reinforcing member 51 are connected to the outer side wall portion 11c by welding. In the present embodiment, as shown in Fig. 4 and Fig. 5, the upper end portion 51a of the reinforcing member 51 is interposed between the flange portions 21a, 22a of the upper side of the outer member 21 and the inner member 22 and connected to the two flange portions 21a, 22a. Furthermore, the lower end portion 51b of the reinforcing member 51 is interposed between the flange portions 21b, 22b of the lower side of the outer member 21 and the inner member 22 and connected to the two flange portions 21b, 22b. Since the flange portions 21a, 21b of the outer member 21 (and the flange portions 22a, 22b of the inner member 22) are arranged at substantially the same position in the vehicle width direction of the outer side wall portion 11c as described above, it can be considered that the upper end portion 51a and the lower end portion 51b of the reinforcing member 51 are connected to the outer side wall portion 11c.

[0027] A central portion in the vertical direction of the reinforcing member 51 is formed as a wave-like portion 51d configured to be bent into a rectangular wave-like shape having a plurality of bending lines (six bending lines in the present embodiment) extending substantially in the vehicle longitudinal direction. Bent portions are referred to as bent portions 51c. An uppermost portion and a lowermost portion of the wave-like portion 51d each extend substantially outward in the vehicle width direction and are continuous with the upper end portion 51a and the lower end portion 51b, which are connected to the outer side wall portion 11c.

[0028] Landing tip surfaces (upper and lower landing tip surfaces) of parts of the wave-like portion 51d that protrude toward the inner side wall portion 11d are joined to the inner side wall portion 11d by welding. Hereinafter, the upper-side landing tip surface will be referred to as an upper-side joining surface 51e, and the lower-side landing tip surface will be referred to as a lower-side joining surface 51f. The upper-side joining surface 51e and the lower-side joining surface 51f each include portions that face the bead 11e of the inner side wall portion 22d in the longitudinal direction and extend over a certain range substantially in the longitudinal direction. It is preferable that this certain range be wider in the longitudinal direction than a range where a torsional load is applied.-stress is generated at the inner side wall portion 11d when the outer side wall portion 11c of the front side frame 11 is bent inward locally at the position where the bead 11e is provided, as will be described later.

[0029] A protrusion tip surface (positioned between the upper-side connecting surface 51e and the lower-side connecting surface 51f in the vertical direction) of a part of the wave-like portion 51d protruding toward the outer side wall portion 11c is positioned between the outer side wall portion 11c and the inner side wall portion 11d in the vehicle width direction, and is not connected to either of the outer side wall portion 11c and the inner side wall portion 11d.

[0030] The upper end portion 51a and the lower end portion 51b of the reinforcing member 51, which is connected to the outer side wall portion 11c, respectively branch in the vehicle longitudinal direction with the bead 11e interposed therebetween, and are connected to the outer side wall portion 11c. That is, the upper end portion 51a of the reinforcing member 51 and an outward portion of the uppermost part of the wave-like portion 51d are configured to have a cutout at a central portion in the vehicle width direction thereof, and the lower end portion 51b of the reinforcing member 51 and an outward portion of the lowermost part of the wave-like portion 51d are configured to have a cutout at a central portion in the vehicle width direction thereof. Thereby,A joint length in the vehicle longitudinal direction of the reinforcing member 51 and the inner side wall portion 11d is set to be longer than that of the reinforcing member 51 and the outer side wall portion 11c. Furthermore, in the present embodiment, a joint area of ​​the reinforcing member 51 and the inner side wall portion 11d is set to be larger than that of the reinforcing member 51 and the outer side wall portion 11c.

[0031] Before joining the outer member 21 and the inner member 22, the upper-side joining surface 51e and the lower-side joining surface 51f of the wave-like portion 51d of the reinforcing member 51 are joined to the inner member 22 (the inner side wall portion 11d) at the longitudinal position corresponding to the bead 11e. Herein, it is preferable that the reinforcing member 51 be joined to the inner member 22 by positioning it.Then, when the outer member 21 and the inner member 22 are joined together, the upper end portion 51a of the reinforcing member 51 is joined to the two flange portions 21a, 22a in a state where this upper end portion 51a is interposed between the upper side flange portions 21a, 22a, and the lower end portion 51b of the reinforcing member 51 is joined to the two flange portions 21b, 22b in a state where this lower end portion 51b is interposed between the lower side flange portions 21b, 22b.

[0032] In a case where a collision load is applied to the front side frame 11 by means of the bumper beam and the impact bushing 31 from the vehicle front side in the frontal collision of the vehicle 1, as shown in Fig. 7, the outer side wall portion 11c of the front side frame 11 is bent inward locally at the position where the bead 11e is provided (buckling occurs locally at the position where the bead 11e is provided). Herein, since the connecting length in the longitudinal direction of the outer side wall portion 11c and the reinforcing member 51 is short, and also the upper end portion 51a and the lower end portion 51b of the reinforcing member 51 are each branched in the vehicle longitudinal direction with the bead 11e interposed therebetween and connected to the outer side wall portion 11c, the reinforcing member 51 does not block the local bending of the outer side wall portion 11c.

[0033] Bending of the outer sidewall portion 11c causes a tensile load to be generated at a portion of the inner sidewall portion 11d facing the bead 11e and its longitudinally surrounding portion. Here, the upper-side connecting surface 51e and the lower-side connecting surface 51f of the wave-like portion 51d of the reinforcing member 51 are connected to a region of the inner sidewall portion 11d that is wider than the above-described longitudinal region where the tensile load is generated, and the reinforcing member 51 is configured not to be easily bent inward by the above-described bent portions 51c of the wave-like portion 51d of the reinforcing member 51.Accordingly, the above-described tensile load can be absorbed at the wide area in the longitudinal direction of the inner side wall portion 11d, so that local bending occurring at the outer side wall 11c can be suppressed at the inner side wall portion 11d. That is, while the inner side wall portion 11d can be easily bent inward after the outer wide wall 11c is locally bent inward when the reinforcing member 51 is not provided, the inner side wall 11d can be prevented from being bent by providing the reinforcing member 51, so that the impact energy absorption performance of the front side frame 11 in the frontal collision of the vehicle 1 can be improved.

[0034] Finally, the inner side wall portion 11d is also bent inwardly together with the wave-like portion 51d of the reinforcing member 51, as shown in Fig. 8 is shown.

[0035] Herein, a relationship between a magnitude (stroke) of retreat of the front end of the front side frame 11 and the load applied to the front end of the front side frame 11 in the frontal collision of the vehicle 1 is shown in Fig. 9 shown.

[0036] A peak of two graphs showing a case where the reinforcing member 51 is provided and another case where the reinforcing member 51 is not provided shows a buckling load of the outer sidewall portion 11c exhibiting local buckling. In each case, the load decreases as the stroke increases after the buckling load is generated, but the decreasing rate of the load in the case where the reinforcing member 51 is provided is smaller (smoother) than that in the case where the reinforcing member 51 is not provided. Since an area of ​​a lower part of each graph represents the amount of impact energy absorption, the impact energy is more absorbed in the case where the reinforcing member 51 is provided compared to the case where the reinforcing member 51 is not provided.

[0037] According to the present invention, since the joint length in the vehicle longitudinal direction of the reinforcing member 51 and the outer side wall portion 11c is set to be relatively short, the number of welding points of the reinforcing member 51 welded to the outer side wall portion 11c of the front side frame 11 can be reduced, so that the deterioration of productivity can be suppressed. Furthermore, by setting the joint length in the vehicle longitudinal direction of the reinforcing member 51 and the outer side wall portion 11c to be relatively short, the outer side wall portion 11c of the front side frame 11 is slightly bent inward locally at the position where the bead 11e is provided in the vehicle frontal collision (the outer side wall portion 11c has a slight buckling locally at the position where the bead 11e is provided).On the other hand, since the connecting length in the vehicle longitudinal direction of the reinforcing member 51 and the inner side wall portion 11d, where the tensile load is generated by this bending of the outer side wall portion 11c, is set to be relatively long, this tensile load can be absorbed over a wide range in the vehicle longitudinal direction, so that the inner side wall portion 11d is suppressed from being bent locally unlike the outer side wall portion 11c. Accordingly, the impact energy absorption performance of the front side frame 11 in the frontal collision of the vehicle 1 can be improved.

[0038] The present invention should not be restricted to the above-described embodiment, and any other modifications or improvements may be applied within the scope of the present invention.

[0039] For example, while the upper end portion 51a and the lower end portion 51b of the reinforcing member 51 each branch in the longitudinal direction with the bead 11e interposed therebetween in the above-described embodiment, these portions 51a, 51b may be configured not to branch and to be joined to the outer side wall portion 11c at substantially the same longitudinal position as the bead 11e. That is, in the case where the joining length in the vehicle longitudinal direction of the upper end portion 51a and the lower end portion 51b of the reinforcing member 51 and the outer side wall portion 11c is relatively short, the outer side wall portion 11c is easily bent at the position where the bead 11e is provided.Herein, in order to configure the outer side wall portion 11c to be bent more easily (to reduce the buckling load), it is preferable that the upper end portion 51a and the lower end portion 51b of the reinforcing member 51 are configured like the above-described embodiment.

[0040] Furthermore, while the central portion in the vertical direction of the reinforcing member 51 is configured like the wave-like portion 51 in the above-described embodiment, any configuration is applicable as long as the connecting length in the longitudinal direction of the reinforcing member 51 and the inner side wall portion 11d is set to be longer than that of the reinforcing member 51 and the outer side wall portion 11c, so that the inner side wall portion 11d can be prevented from being easily bent locally. For example, a portion of the reinforcing member 51 of the above-described embodiment positioned between the upper-side connecting surface 51e and the lower-side connecting surface 51f may be a bead configured to extend substantially in the longitudinal direction and be concaved outward in the vehicle width direction.Alternatively, this type of bead may be formed on the upper side joining surface 51e and / or the lower side joining surface 51f.

Claims

[1] Vehicle body structure, comprising: a pair of front side frames (11) extending substantially in a vehicle longitudinal direction at a front part of a vehicle and comprising an outer side wall portion (11c) and an inner side wall portion (11d), the outer side wall portion (11c) being positioned on an outer or outward side in a vehicle width direction of the vehicle and the inner side wall portion (11d) being positioned on an inner or inward side in the vehicle width direction of the vehicle, the front side frame (11) having a substantially closed cross-section; a bead (11e) formed substantially at a central position in the vehicle longitudinal direction of the outer side wall portion (11c) of the front side frame (11), the bead (11e) being configured to cause the front side frame (11) to bend inward at the central position of the outer side wall portion (11c) where the bead (11e) is provided in a vehicle frontal collision; and a reinforcing member (51) provided inside the substantially closed cross-section of the front side frame (11) at a position in the vehicle longitudinal direction substantially corresponding to a formation position of the bead (11e), the reinforcing member (51) extending between the outer side wall portion (11c) and the inner side wall portion (11d) of the front side frame (11), wherein the reinforcing member (51) is connected to the outer side wall portion (11c) and the inner side wall portion (11d) of the front side frame (11), wherein a connecting length in the vehicle longitudinal direction of the reinforcing member (51) and the inner side wall portion (11d) is set to be longer than that of the reinforcing member (51) and the outer side wall portion (11c), wherein the reinforcing member (51) is made of a plate member extending in a vertical direction and in the vehicle longitudinal direction, wherein an upper end portion (51a) and a lower end portion (51b) of the reinforcing member (51) are connected to the outer side wall portion (11c) of the front side frame (11), wherein a central portion in the vertical direction of the reinforcing member (51) is formed as a wave-like portion (51d) configured to be bent in a rectangular wave-like shape having a plurality of bending lines extending substantially in the vehicle longitudinal direction, and a ridge tip surface of a part of the wave-like portion (51d) configured to protrude toward the inner side wall portion (11d) of the front side frame (11) is connected to the inner side wall portion (11d), wherein the upper end portion (51a) of the reinforcing member (51) and an outward portion of an uppermost part of the wave-like portion (51d) are configured to have a cutout at a central portion in the vehicle width direction, wherein the lower end portion (51b) of the reinforcing member (51) and an outward portion of a lowermost part of the wave-like portion (51d) are configured to have a cutout at a central portion in the vehicle width direction, and wherein the cutout at the upper end portion (51a) and the cutout at the lower end portion (51b) are arranged at the same position with respect to the vehicle longitudinal direction as the bead (11e). [2] A method for improving impact energy absorption of a front vehicle body structure, comprising the steps of: Providing a pair of front side frames (11) having a substantially closed cross-section; Forming a bead (11e) substantially at a central position in the vehicle longitudinal direction of an outer side wall portion (11c) of the front side frame (11), the bead (11e) being configured to cause the front side frame (11) to bend inward at the central position of the outer side wall portion (11c) where the bead (11e) is provided in a vehicle frontal collision; Providing a reinforcing member (51) inside the substantially closed cross-section of the front side frame (11) at a position in the vehicle longitudinal direction which substantially corresponds to a formation position of the bead (11e), wherein the reinforcing member (51) extends between the outer side wall portion (11c) and an inner side wall portion (11d) of the front side frame (11), Connecting the reinforcing member (51) to the outer side wall portion (11c) and the inner side wall portion (11d) of the front side frame (11), and Setting a connecting length in the vehicle longitudinal direction of the reinforcing member (51) and the inner side wall portion (11d) to be longer than that of the reinforcing member (51) and the outer side wall portion (11c), wherein the reinforcing member (51) is made of a plate member extending in a vertical direction and in the vehicle longitudinal direction, wherein an upper end portion (51a) and a lower end portion (51b) of the reinforcing member (51) are connected to the outer side wall portion (11c) of the front side frame (11), wherein a central portion in the vertical direction of the reinforcing member (51) is formed as a wave-like portion (51d) which is formed to be bent in a rectangular wave-like shape having a plurality of bending lines extending substantially in the vehicle longitudinal direction, and a protrusion tip surface of a part of the wave-like portion which is formed to protrude toward the inner side wall portion (11d) of the front side frame (11) is connected to the inner side wall portion (11d), wherein the upper end portion (51a) of the reinforcing member (51) and an outward portion of an uppermost part of the wave-like portion (51d) are formed to have a cutout at a central portion in the vehicle width direction, wherein the lower end portion (51b) of the reinforcing member (51) and an outward portion of a lowermost part of the wave-like portion (51d) are formed to have a cutout at a central portion in the vehicle width direction, and wherein the cutout at the upper end portion (51a) and the cutout at the lower end portion (51b) are arranged at the same position with respect to the vehicle longitudinal direction as the bead (11e).

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