Vehicle front structure

A vehicle front structure includes a crash box having a shape of a rectangular tube extending in the vehicle front-rear direction. The crash box extends farther outward in the vehicle width direction than a front side member, and is provided between the front side member and a bumper reinforcement. The crash box has an upper plate and a lower plate. Each of the upper plate and the lower plate has bead rows disposed in the vehicle width direction. Each of the bead rows is formed by beads extending in the vehicle width direction and arranged at predetermined intervals in the vehicle front-rear direction. The bead rows include a first bead row composed of first beads, and a second bead row composed of second beads longer than the first beads and disposed inward of the first bead row in the vehicle width direction.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2017-097243 filed on May 16, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a vehicle front structure. More particularly, the disclosure relates to a configuration of a crash box that is provided between a front side member and a bumper reinforcement and that undergoes compressive plastic deformation in the vehicle front-rear direction in a frontal collision.

2. Description of Related Art

A crash box that is provided between a front side member and a bumper reinforcement and that absorbs collision energy by undergoing compressive plastic deformation in the vehicle front-rear direction in the event of a frontal collision of the vehicle with a barrier is widely used. Since a front surface of an end of the bumper reinforcement on the outer side in the vehicle width direction is formed by a gently inclined surface, when a frontal collision occurs in which the collision load is input into a part of the vehicle farther on the outer side in the vehicle width direction than the front side member (hereinafter referred to as a small-overlap frontal collision), the collision load acting obliquely inward toward the rear side of the vehicle is input into an outer end of the bumper reinforcement. As a result, the crash box connected to the bumper reinforcement may tilt inward in the vehicle width direction and allow the barrier to pass by the front side member. Thus, in a small-overlap frontal collision, the crash box may fail to effectively absorb the collision energy.

In view of this situation, a structure has been proposed in which an end of a bumper reinforcement on the outer side in the vehicle width direction has a flat part that is parallel to the vehicle width direction (e.g., see Japanese Patent Application Publication No. 2017-24552 (JP 2017-24552 A)).

SUMMARY

When a small-overlap frontal collision occurs, the structure described in JP 2017-24552 A receives the collision load so as to be input into the end of the bumper reinforcement on the outer side in the vehicle width direction, toward the rear side of the vehicle. In the case of a small-overlap frontal collision, however, a larger collision load is input into a part of the crash box on the outer side in the vehicle width direction than a part thereof on the inner side in the vehicle width direction, so that the amount of compressive deformation of the outer-side part of the crash box becomes large earlier than the amount of compressive deformation of the inner-side part thereof. For this reason, the bumper reinforcement is likely to incline during a collision so as to reduce the angle relative to the vehicle front-rear direction, which causes an increase in the collision load input into the bumper reinforcement and acting inward in the vehicle width direction. As a result, the crash box connected to the bumper reinforcement is likely to tilt inward in the vehicle width direction and allow the barrier to pass by the front side member. Then, the crash box can no longer effectively absorb the collision energy. In this respect, there is room for improvement in the configuration described in JP 2017-24552 A.

Therefore, the present disclosure provides a vehicle front structure that allows a crash box to effectively absorb collision energy in the event of a small-overlap frontal collision in which the collision load is input into a part of the vehicle farther on the outer side in the vehicle width direction than the front side member.

An aspect of the disclosure provides a vehicle front structure, including: a front side member disposed outward of a center of a vehicle in a vehicle width direction and extending in a vehicle front-rear direction; a bumper reinforcement disposed at a front end of the vehicle and extending in the vehicle width direction; and a crash box having a shape of a rectangular tube extending in the vehicle front-rear direction, the crash box extending farther outward in the vehicle width direction than the front side member, being provided between an end of the front side member on a front side in the vehicle front-rear direction and the bumper reinforcement and being configured to undergo compressive plastic deformation in the vehicle front-rear direction in a frontal collision of the vehicle, the crash box having an upper plate and a lower plate, the upper plate being arranged upper side of the lower plate in a vehicle height direction, each of the upper plate and the lower plate having bead rows disposed in the vehicle width direction, each of the bead rows being formed by beads extending in the vehicle width direction and arranged at predetermined intervals in the vehicle front-rear direction, the bead rows including a first bead row composed of first beads, and a second bead row composed of second beads longer than the first beads and disposed inward of the first bead row in the vehicle width direction.

In the above aspect, the first bead row and the second bead row may be disposed such that the first beads and the second beads are staggered in the vehicle front-rear direction.

When the first and second beads are disposed as in this aspect, a part of the crash box on the inner side in the vehicle width direction undergoes compressive plastic deformation in the vehicle front-rear direction more easily than a part thereof on the outer side in the vehicle width direction. Thus, even in the case of a small-overlap frontal collision in which the collision load is input into a part of the vehicle farther on the outer side in the vehicle width direction than the front side member, the outer-side part and the inner-side part of the crash box move backward substantially equally during the collision, which makes the bumper reinforcement less likely to incline so as to reduce the angle relative to the vehicle front-rear direction, so that an increase in the collision load input into the bumper reinforcement and acting inward in the vehicle width direction is avoided. It is therefore possible to reduce the likelihood that the crash box tilts inward in the vehicle width direction and allows the barrier to pass by the front side member, and thereby to absorb the collision energy by the entire crash box. Thus, according to this aspect, the crash box can effectively absorb collision energy in the event of a small-overlap frontal collision in which the collision load is input into a part of the vehicle farther on the outer side in the vehicle width direction than the front side member.

In the above aspect, the second beads composing the second bead row may be equal in number to the first beads composing the first bead row, or larger in number than the first beads composing the first bead row.

When the first and second beads are disposed as in this configuration, the inner-side part of the crash box undergoes compressive plastic deformation in the vehicle front-rear direction more easily than the outer-side part thereof. Moreover, load can be smoothly transmitted, so that the crash box undergoes compressive plastic deformation more stably. Thus, the crash box can effectively absorb collision energy in the event of a small-overlap frontal collision.

In the above aspect, the first bead row may be disposed outward of the front side member in the vehicle width direction.

When the first bead row that constitutes a starting point of compressive plastic deformation is disposed as in this configuration near a point at which a collision load is input in a small-overlap frontal collision, a region where the first bead row is disposed is allowed to stably undergo compressive plastic deformation during a collision.

In the above aspect, the second bead row may be disposed such that a position of the second bead row in the vehicle width direction overlaps a position of the front side member in the vehicle width direction in a front view of the vehicle.

This configuration allows a region where the second bead row is disposed to undergo compressive plastic deformation during a small-overlap frontal collision earlier than a region where the first bead row is disposed.

In the above aspect, the bead rows may include a third bead row composed of third beads longer than the first beads, disposed farther on an inner side in the vehicle width direction than the second bead row, and disposed in a region where a position of the third bead row in the vehicle width direction overlaps a position of the front side member in the vehicle width direction in a front view of the vehicle; and the third beads may be disposed such that the second beads and the third beads are staggered.

When the third bead row is disposed as in this configuration, the crash box can effectively absorb collision energy also in the event of a head-on collision, since the third bead row constitutes a starting point of compressive plastic deformation of the crash box in the event of a head-on collision.

In the above aspect, the crash box may have an inner plate and an outer plate, the inner plate being inward of the outer plate in the vehicle width direction, the inner plate may have a vertical bead row formed by vertical beads of a predetermined length extending in the vehicle height direction, the vertical beads being arranged at predetermined intervals in the vehicle front-rear direction, and the outer plate may have no beads.

This configuration allows the inner-side part of the crash box to undergo compressive plastic deformation in the vehicle front-rear direction more easily than the outer-side part thereof. Thus, it is possible to further reduce the likelihood that the crash box tilts inward in the vehicle width direction and allows the barrier to pass by the front side member, and thereby to more effectively absorb the collision energy by the entire crash box.

In the above aspect, the vehicle front structure may further include: a gusset projecting outward in the vehicle width direction from a side surface of a front end portion of the front side member on an outer side of the front end portion of the front side member in the vehicle width direction; and a clearance filling member mounted on a portion of the crash box, the portion projecting farther outward in the vehicle width direction than the front side member, such that a leading end of the clearance filling member faces a front surface of the gusset across a clearance. The clearance filling member is configured to transmit a collision load from the crash box to the gusset when the clearance is lost during the frontal collision.

This configuration allows the portion of the crash box projecting farther outward in the vehicle width direction than the front side member to undergo compressive plastic deformation in the vehicle front-rear direction after the inner-side part of the crash box undergoes compressive plastic deformation. Thus, the outer-side part and the inner-side part of the crash box move backward substantially equally during a collision, which makes the bumper reinforcement less likely to incline so as to reduce the angle relative to the vehicle front-rear direction. Moreover, the portion of the crash box projecting farther outward in the vehicle width direction than the front side member can be crushed flat, and thereby the collision energy can be absorbed more effectively.

In the above aspect, the vehicle front structure may further include: a lower bumper reinforcement disposed below the bumper reinforcement in the vehicle height direction and extending in the vehicle width direction; a first member held and fixed at a fixed portion between a front end of the front side member and a rear end of the crash box and extending downward from the fixed portion; a second member disposed below the front side member in the vehicle height direction, the second member being connected at a front end of the second member to the first member, and extending from the first member toward a rear side of the vehicle; and a lower crash box disposed between the second member and the lower bumper reinforcement, the lower crash box being assembled to the second member via the first member, being connected to the first member, and being configured to undergo compressive plastic deformation in the vehicle front-rear direction in the frontal collision.

With this configuration in which the upper crash box and the lower crash box are connected to each other through the first member, the lower bumper reinforcement moves backward along with the bumper reinforcement, substantially parallel to the vehicle front-rear direction, in the event of a small-overlap frontal collision. Thus, the lower crash box as well as the upper crash box does not tilt inward in the vehicle width direction, and the lower crash box can also effectively absorb the collision energy. It is therefore possible to effectively absorb collision energy by the entire vehicle front structure in the event of a small-overlap frontal collision.

DETAILED DESCRIPTION OF EMBODIMENTS

Structure of Body of Vehicle100

A vehicle front structure80of an embodiment will be described below with reference to the drawings. First, the structure of a body of a vehicle100in which the vehicle front structure80of the embodiment is incorporated will be described with reference toFIG. 1. As shown inFIG. 1, the vehicle100includes a framework structure made of metal, such as aluminum. The vehicle100includes a front frame101located on a front side of front pillars104, a rear frame103, and a cabin frame102forming a cabin110between the front pillars104and the rear frame103. The front frame101includes front side members10, a bumper reinforcement40, crash boxes50, a dashboard panel105dividing between the cabin frame102and an engine room108, the front pillars104, and upper members106respectively connected to the front pillars104and extending toward a front side of the vehicle. An engine, a driving motor, etc. are installed on the front side members10. Between the front side members10and the upper members106, suspension towers107housing a suspension device of front wheels are provided. A rear end portion17of each front side member10extends downward along a surface of the dashboard panel105, and is connected to an under reinforcement109disposed on a lower surface of the cabin frame102.

Configuration of Vehicle Front Structure80

FIG. 2is a plan view showing a part of a left-side part of the vehicle front structure80shown inFIG. 1, andFIG. 3is a perspective view of the same part. The vehicle front structure80of this embodiment is a combination of the structure shown inFIG. 2andFIG. 3and the same but symmetrical structure provided respectively on left and right sides. As shown inFIG. 2andFIG. 3, the vehicle front structure80of this embodiment includes the front side member10, the bumper reinforcement40, and the crash box50. The vehicle front structure80of this embodiment further includes a gusset20and a clearance filling member59.

Front Side Member10

As shown inFIG. 2andFIG. 3, the front side member10is a rigid member that is disposed on an outer side in the vehicle width direction and extends in a vehicle front-rear direction. The front side member10is a hollow rectangular structure with a closed cross-section formed by a front side member inner11that has a substantially U-shaped cross-section when cut along a plane orthogonal to a longitudinal direction thereof, and a front side member outer12that has a substantially flat-plate shape and closes an open side of the front side member inner11. An L-shaped flange15is spot-welded to a front end14of the front side member10.

As shown inFIG. 2andFIG. 3, the gusset20projecting outward in the vehicle width direction is mounted on a side surface of a front end portion13of the front side member10on the outer side in the vehicle width direction. The gusset20is a hollow triangular columnar member having a substantially triangular shape in a plan view, and is formed by a ceiling part21having a triangular shape in a plan view, a bottom part (not shown), and a side part22connecting, in a vehicle height direction, ends of the ceiling part21and the bottom part on the outer side in the vehicle width direction. The ceiling part21is spot-welded to an upper flange16of the front side member inner11. The bottom part (not shown) is spot-welded to the front side member inner11. The side part22has mount portions23that are bent so as to extend along a surface of the front side member outer12and spot-welded to the front side member outer12. The gusset20is mounted on the side surface of the front side member10such that the vertex of the side part22projects outward in the vehicle width direction, and a front end surface25of the gusset20that is a front-side inclined surface faces a rear end of the clearance filling member59to be described later. A part of the flange15mounted on the front end14of the front side member10is placed over and spot-welded to a front corner24of the gusset20.

As shown inFIG. 2andFIG. 3, the crash box50is fixed with bolts58to the flange15on the front side of the front end14of the front side member10. The crash box50absorbs collision energy by undergoing compressive plastic deformation in the vehicle front-rear direction in a frontal collision. As shown inFIG. 2andFIG. 3, the crash box50is formed by a main body50A that is a cornered cocoon-shaped rectangular tubular member extending in the vehicle front-rear direction, a rear end plate56covering a rear end of the main body50A, and a front end plate57covering a front end of the main body50A. As shown inFIG. 4, beads62,64,66that are recesses are provided in an upper plate51and a lower plate54of the main body50A. Moreover, vertical beads68that are recesses are provided in a vehicle inner-side plate52that is a plate of the main body50A on the inner side in the vehicle width direction. No beads are provided in a vehicle outer-side plate53that is a plate of the main body50A on the outer side in the vehicle width direction. The arrangement of the beads62,64,66and the vertical beads68and details of the main body50A will be described later.

As shown inFIG. 2, the main body50A is formed by a vehicle inner-side part50C that is located at a position overlapping the flange15of the front side member10in a front view of the vehicle and can transmit load to the flange15, and a vehicle outer-side part50B that projects farther outward in the vehicle width direction than the flange15. The vehicle inner-side part50C includes a second upper plate51b, a second lower plate54b, a third upper plate51c, and a third lower plate54cshown inFIG. 4, and the vehicle outer-side part50B includes a first upper plate51aand a first lower plate54ashown inFIG. 4. As shown inFIG. 2, the length of the main body50A in the vehicle width direction is larger than the length of the front side member10in the vehicle width direction, and the vehicle outer-side part50B projects farther outward in the vehicle width direction than the front side member10. The length of the main body50A in the vehicle height direction is smaller than the length of the front side member10in the vehicle height direction, and thus the main body50A does not project from the front side member10in the height direction.

A radiator support30that is formed by bending a flat plate into a crank shape is held between a part of the rear end plate56that is located on the inner side of the vehicle and covers a rear end of the vehicle inner-side part50C of the main body50A, and the flange15mounted on the front end14of the front side member10. The rear end plate56and the radiator support30are fastened together with the bolts58to the flange15.

The clearance filling member59is mounted on a rear end-side surface of a part of the rear end plate56that is located on the outer side of the vehicle and covers the rear end of the vehicle outer-side part50B of the main body50A. The clearance filling member59is a member that is fixed to the rear end plate56and defines a clearance S between the front end surface25of the gusset20and the clearance filling member59.

As shown inFIG. 1toFIG. 3, the bumper reinforcement40is mounted on a front-side surface of the front end plate57of the crash box50. The bumper reinforcement40is a rigid member that is disposed at the front end of the vehicle and extends in the vehicle width direction, and that is suspended across front ends of the crash boxes50that are disposed respectively on both sides of the vehicle as shown inFIG. 1.

Detailed Structure of Crash Box50

As shown inFIG. 4, the main body50A of the crash box50is a cornered cocoon-shaped rectangular tubular member that extends in the vehicle front-rear direction and is formed by welding, along joint lines55, an inversed U-shaped upper half50U with a center portion recessed inward and a U-shaped lower half SOL with a center portion recessed inward.

The main body50A includes the upper plate51, the lower plate54, the vehicle inner-side plate52, and the vehicle outer-side plate53. The upper plate51includes the first upper plate51alocated on the outer side in the vehicle width direction, the third upper plate51clocated at the same level as the first upper plate51aand on the inner side in the vehicle width direction, and the second upper plate51blocated between the first upper plate51aand the third upper plate51cand at a lower level than the first upper plate51aand the third upper plate51c. The second upper plate51bis connected to each of the first upper plate51aand the third upper plate51cby an inclined plate. Thus, the upper plate51has a bent plate structure, with the first upper plate51aand the third upper plate51cforming ridges and the second upper plate51bforming a valley. Similarly to the upper plate51, the lower plate54includes the first lower plate54alocated on the outer side in the vehicle width direction, the third lower plate54clocated at the same level as the first lower plate54aand on the inner side in the vehicle width direction, and the second lower plate54blocated between the first lower plate54aand the third lower plate54cand at a higher level than the first lower plate54aand the third lower plate54c. The second lower plate54bis connected to each of the first lower plate54aand the third lower plate54cby an inclined plate. Similarly to the upper plate51, the lower plate54has a bent plate structure, with the first lower plate54aand the third lower plate54cforming ridges and the second lower plate54bforming a valley.

The vehicle inner-side plate52is connected to each of the third upper plate51cand the third lower plate54cby an inclined plate. Similarly, the vehicle outer-side plate53is connected to each of the first upper plate51aand the first lower plate54aby an inclined plate.

As shown inFIG. 2, the second upper plate51b, the second lower plate54b, the third upper plate51c, and the third lower plate54care located at positions overlapping the flange15of the front side member10in a front view of the vehicle, and the vehicle inner-side plate52is located at a position overlapping the front side member10in a front view of the vehicle. Thus, the second upper plate51b, the second lower plate54b, the third upper plate51c, the third lower plate54c, and the vehicle inner-side plate52are included in the vehicle inner-side part50C that is a part that transmits a load acting in the vehicle front-rear direction directly to the front side member10. On the other hand, the first upper plate51a, the first lower plate54a, and the vehicle outer-side plate53are located farther on the outer side in the vehicle width direction than the front side member10, and are included in the vehicle outer-side part50B that is a part that transmits a load acting in the vehicle front-rear direction to the front side member10through the gusset20.

As shown inFIG. 2andFIG. 4, the first beads62of a length L1extending in the vehicle width direction are disposed in a region of each of the first upper plate51aand the first lower plate54aon the inner side of the vehicle, in two stages at a predetermined interval in the vehicle front-rear direction. The first beads62disposed in two stages form one first bead row61. As described above, the first upper plate51aand the first lower plate54aare located farther on the outer side in the vehicle width direction than the front side member10, and therefore the first bead rows61are disposed farther on the outer side in the vehicle width direction than the front side member10. Thus, the first bead rows61are disposed at such positions that the first bead rows61transmit a load acting in the vehicle front-rear direction to the front side member10through the gusset20.

The second beads64of a length L2extending in the vehicle width direction are disposed in each of the second upper plate51band the second lower plate54b, in two stages at a predetermined interval in the vehicle front-rear direction. The second beads64disposed in two stages form one second bead row63. Similarly, the third beads66of a length L3extending in the vehicle width direction are disposed in each of the third upper plate51cand the third lower plate54c, in three stages at predetermined intervals in the vehicle front-rear direction. The third beads66disposed in three stages form one third bead row65. As described above, the second upper plate51b, the second lower plate54b, the third upper plate51c, and the third lower plate54care located at positions overlapping the flange15of the front side member10in a front view of the vehicle, and therefore the second bead rows63and the third bead rows65are disposed at such positions that these bead rows can transmit a load acting in the vehicle front-rear direction directly to the front side member10through the flange15.

The length L2of the second beads64is larger than the length L1of the first beads62. In this embodiment, the length L3of the third beads66is substantially equal to the length L2of the second beads64. The relation among the lengths L1, L2, L3is L3≈L2>L1. The first bead row61and the second bead row63are disposed such that the first beads62and the second beads64are staggered. As shown inFIG. 2andFIG. 4, the first beads62and the second beads64are disposed so as to be separated from each other and alternate with each other in both the vehicle front-rear direction and the vehicle width direction. Similarly, the second bead row63and the third bead row65are disposed such that the second beads64and the third beads66are staggered, and such that the second beads64and the third beads66are separated from each other and alternate with each other in both the vehicle front-rear direction and the vehicle width direction. The first beads62and the third beads66may be disposed at the same positions in the vehicle front-rear direction, or may be disposed at positions shifted from each other in the vehicle front-rear direction.

As shown inFIG. 4, the beads62,64,66are recesses extending in the vehicle width direction. Ends of the third bead66in the vehicle width direction each form a cutout appearing in the adjacent inclined plate. Both ends of the second bead64are recessed from the second upper plate51b. An end of the first bead62on the inner side in the vehicle width direction forms a cutout appearing in the adjacent inclined plate as with the third bead66, while an end of the first bead62on the outer side in the vehicle width direction is recessed from the first upper plate51a.

As shown inFIG. 4, the vertical beads68each extending in the vehicle height direction are disposed in three stages at predetermined intervals, in each of a vehicle inner-side plate52U of the upper half50U and a vehicle inner-side plate52L of the lower half SOL forming the vehicle inner-side plate52of the main body50A. The vertical beads68disposed in three stages form one vertical bead row67. Thus, one vertical bead row67is disposed in each of the vehicle inner-side plate52U and the vehicle inner-side plate52L, and therefore the vertical bead rows67are disposed in two stages in the height direction in the vehicle inner-side plate52of the main body50A. As with the first bead62, an end of the vertical bead68on the side of the joint line55is recessed from the vehicle inner-side plate52U or52L, while an end thereof on the other side forms a cutout appearing in the adjacent inclined plate.

As described above, the vehicle inner-side plate52is located at a position overlapping the flange15of the front side member10in a front view of the vehicle, and therefore the vertical bead rows67are disposed at such positions that the vertical bead rows67can transmit a load acting in the vehicle front-rear direction directly to the front side member10.

When a compressive force is applied to the beads62,64,66,68in a direction orthogonal to the direction in which the groove having a cross-section extends, the stress concentrates at a bottom portion of the groove, causing these beads to deform so as to close the opening of the groove. As a result, the surfaces provided with the beads62,64,66,68are crushed by undergoing accordion-like compressive plastic deformation. Thus, the beads62,64,66,68form starting points of accordion-like compressive plastic deformation of the surfaces provided with the beads62,64,66,68. Moreover, the beads62,64,66,68form low-rigidity portions of the plate members.

As described above, no beads are provided in a vehicle outer-side plate53U of the upper half50U and a vehicle outer-side plate53L of the lower half SOL forming the vehicle outer-side plate53of the main body50A.

Workings and Effects of Vehicle Front Structure80of Embodiment in the Event of Small-Overlap Frontal Collision

The workings and effects of the vehicle front structure80of this embodiment, configured as has been described above, in the event of a small-overlap frontal collision will be described with reference toFIG. 5toFIG. 8. A small-overlap frontal collision here refers to a type of frontal collisions of the vehicle100, in which a part of the vehicle farther on the outer side in the vehicle width direction than the front side member10collides with a barrier B.

As shown inFIG. 5, in the case of a small-overlap frontal collision, a part of the bumper reinforcement40farther on the outer side in the vehicle width direction than the front side member10collides with the barrier B. Since the clearance S remains between the clearance filling member59and the front end surface25of the gusset20immediately after the collision, the collision load input into the bumper reinforcement40is not transmitted to the gusset20, but propagates in a direction toward an obliquely rear side of the vehicle, from a load input point located farther on the outer side in the vehicle width direction than the front side member10, through the upper plate51and the lower plate54of the crash box50, to the front side member10. As indicated by the arrows inFIG. 5, the load propagates in the direction toward the obliquely rear side of the vehicle, from the input point through clearances between the staggered beads62,64,66.

Then, the collision load is input from the flange15into the front side member10as a load acting toward the rear side of the vehicle. This load is received by the front side member10, and compresses the vehicle inner-side part50C of the crash box50in the vehicle front-rear direction. This compressive force acts on the second beads64, the third beads66, and the vertical beads68in a direction of closing the V-shaped openings as indicated by the opposite arrows inFIG. 5, and thus the beads64,66,68undergo compressive deformation so as to close the openings thereof. With these beads serving as starting points, the second upper plate51b, the third upper plate51c, the second lower plate54b, the third lower plate54c, and the vehicle inner-side plate52included in the vehicle inner-side part50C of the crash box50undergo accordion-like compressive deformation.

Meanwhile, the load input into the vehicle outer-side part50B of the crash box50deforms the rear end plate56toward the rear side of the vehicle, and causes the vehicle outer-side part50B to move backward toward the gusset20. As long as the clearance S remains between the clearance filling member59and the front end surface25of the gusset20, the collision load input into the bumper reinforcement40is not transmitted to the gusset20, and therefore the vehicle outer-side part50B is not subjected to a large compressive force. In addition, no large beads are provided in the vehicle outer-side part50B. For these reasons, the vehicle outer-side part50B does not undergo as much compressive deformation as the vehicle inner-side part50C.

As a result, as shown inFIG. 6, at the point in time when the clearance filling member59hits the front end surface25of the gusset20, the second upper plate51b, the third upper plate51c, the second lower plate54b, the third lower plate54c, and the vehicle inner-side plate52forming the vehicle inner-side part50C of the crash box50have undergone accordion-like compressive deformation, while the first upper plate51a, the first lower plate54a, and the vehicle outer-side plate53forming the vehicle outer-side part50B have merely moved backward toward the rear side of the vehicle and have not undergone significant deformation. Since the amount of backward movement of a part of the bumper reinforcement40connected to the vehicle inner-side part50C due to the compressive deformation of the vehicle inner-side part50C, and the amount of backward movement of a part of the bumper reinforcement40connected to the vehicle outer-side part50B due to the backward movement of the vehicle outer-side part50B, are substantially equal to each other, the bumper reinforcement40moves backward substantially parallel to the vehicle front-rear direction, without inclining relative to the vehicle front-rear direction. Thus, an inclination angle θ1of the bumper reinforcement40relative to the vehicle front-rear direction shown inFIG. 5and an inclination angle θ2of the bumper reinforcement40relative to the vehicle front-rear direction shown inFIG. 6are substantially equal to each other.

When time has passed from the state shown inFIG. 6, as shown inFIG. 7, the collision load input into the vehicle outer-side part50B of the crash box50is transmitted to the gusset20through the clearance filling member59. As the load acting in the vehicle front-rear direction that is transmitted to the gusset20is received by the front side member10, this collision load compresses the vehicle outer-side part50B of the crash box50in the vehicle front-rear direction. Under this compressive force, the first beads62provided in the first upper plate51aand the first lower plate54aundergo compressive deformation so as to close the openings. Starting from this compressive deformation of the first beads62, the first upper plate51a, the first lower plate54a, and the vehicle outer-side plate53forming the vehicle outer-side part50B are crushed like an accordion as shown inFIG. 7. In this process, the collision load is transmitted also to the vehicle inner-side part50C of the crash box50, so that the second upper plate51b, the third upper plate51c, the second lower plate54b, the third lower plate54c, and the vehicle inner-side plate52forming the vehicle inner-side part50C are further crushed from the state shown inFIG. 6. The vehicle inner-side part50C is unlikely to incline the bumper reinforcement40by exerting a reaction force in the vehicle front-rear direction, since the rigidity of the vehicle inner-side part50C in the vehicle front-rear direction has become extremely low as a result of the compressive plastic deformation during the period from the state shown inFIG. 5to the state shown inFIG. 6. Accordingly, the bumper reinforcement40moves backward substantially parallel to the vehicle front-rear direction, without inclining relative to the vehicle front-rear direction. Thus, an inclination angle θ3of the bumper reinforcement40relative to the vehicle front-rear direction shown inFIG. 7is substantially equal to the inclination angles θ1, θ2of the bumper reinforcement40relative to the vehicle front-rear direction shown inFIG. 5andFIG. 6.

When time has further passed from the state shown inFIG. 7, as shown inFIG. 8, the second upper plate51b, the third upper plate51c, the second lower plate54b, the third lower plate54c, the vehicle inner-side plate52forming the vehicle inner-side part50C, and the first upper plate51a, the first lower plate54a, and the vehicle outer-side plate53forming the vehicle outer-side part50B reach a state of being substantially completely crushed flat. When these plates are crushed flat, a reaction force in the vehicle front-rear direction exerted by the vehicle inner-side part50C and that exerted by the vehicle outer-side part50B become substantially equal to each other, so that the vehicle outer-side part50B which is located closer to the input point of the collision load and into which a larger load is input is compressed a little more than the vehicle inner-side part50C. Accordingly, the bumper reinforcement40slightly inclines relative to the vehicle front-rear direction. Thus, an inclination angle θ4of the bumper reinforcement40relative to the vehicle front-rear direction shown inFIG. 8is slightly smaller than the inclination angles θ1to θ3of the bumper reinforcement40relative to the vehicle front-rear direction shown inFIG. 5toFIG. 7.

As has been described above, in the vehicle front structure80of this embodiment, the second bead rows63and the third bead rows65of longer beads are disposed in the second upper plate51b, the third upper plate51c, the second lower plate54b, and the third lower plate54cforming the vehicle inner-side part50C of the crash box50; the vertical bead rows67are disposed in the vehicle inner-side plate52; the first bead rows61of shorter beads are disposed in the first upper plate51aand the first lower plate54aforming the vehicle outer-side part50B; and no beads are disposed in the vehicle outer-side plate53. Thus, the vehicle inner-side part50C of the crash box50undergoes compressive deformation in the vehicle front-rear direction more easily than the vehicle outer-side part50B. Moreover, the crash box50is configured such that the vehicle inner-side part50C can transmit a load acting in the vehicle front-rear direction directly to the front side member10immediately after a collision, while the vehicle outer-side part50B transmits a load acting in the vehicle front-rear direction to the front side member10after the clearance S becomes zero. From immediately after a collision to an initial stage of the collision, this configuration allows the vehicle inner-side part50C to undergo compressive plastic deformation and the vehicle outer-side part50B to move backward until the clearance S becomes zero, and after the initial stage of the collision, this configuration allows the vehicle outer-side part50B and the vehicle inner-side part50C, of which the rigidity has decreased as a result of the compressive plastic deformation in the initial stage, to undergo compressive plastic deformation together. Thus, the vehicle outer-side part50B and the vehicle inner-side part50C of the crash box50move backward substantially equally during a collision, which makes the bumper reinforcement40less likely to incline so as to reduce the angle relative to the vehicle front-rear direction.

Thus, the vehicle front structure80can avoid causing an increase in the collision load input into the bumper reinforcement40and acting inward in the vehicle width direction, and can reduce the likelihood that the crash box50tilts inward in the vehicle width direction and allows the barrier B to pass by the front side member10. Moreover, the collision energy can be absorbed by the entire crash box50, as both the vehicle inner-side part50C and the vehicle outer-side part50B of the crash box50can be crushed flat. Thus, the present disclosure allows the crash box50to more effectively absorb the collision energy in the event of a small-overlap frontal collision in which the collision load is input into a part of the vehicle farther on the outer side in the vehicle width direction than the front side member10.

Vehicle Front Structure900of Comparative Example and Deformation Thereof in the Event of Small-Overlap Frontal Collision

Next, deformation of parts of a vehicle including a vehicle front structure900of a comparative example in the event of a small-overlap frontal collision will be described with reference toFIG. 9toFIG. 11.

As shown inFIG. 9, a crash box90of the comparative example has a laterally long, substantially octagonal shape, with beads96of a uniform length provided in three stages in each of an upper plate91and a lower plate94, and with similar vertical beads95provided in each of a vehicle inner-side plate92and a vehicle outer-side plate93. A clearance filling member99at its initial position is in contact with the front end surface25of the gusset20.

As shown inFIG. 9, when a small-overlap frontal collision occurs, a part of the bumper reinforcement40farther on the outer side in the vehicle width direction than the front side member10collides with the barrier B. Thus, the collision load is input into a part of the vehicle farther on the outer side in the vehicle width direction than the front side member10. This collision load is received by the front side member10and the gusset20. Under this collision load, the crash box90is compressed in the vehicle front-rear direction. Since the input point of the collision load is located closer to the outer side of the crash box90in the vehicle front-rear direction, a vehicle outer-side part of the crash box90is subjected to a larger load than a vehicle inner-side part thereof. The vertical beads95are provided in the vehicle outer-side plate93of the crash box90as in the vehicle inner-side plate92. Thus, as shown inFIG. 10, in an initial stage of the collision, the vehicle outer-side plate93undergoes significant compressive deformation. As a result, the bumper reinforcement40inclines in a direction of reducing the inclination angle θ1relative to the vehicle front-rear direction shown inFIG. 9, so that the angle relative to the vehicle front-rear direction is reduced to an inclination angle θ5smaller than the inclination angle θ1.

Then, components of the collision load input from the barrier B into the bumper reinforcement40that act toward the inner side of the vehicle increase, causing the bumper reinforcement40to move toward the inner side of the vehicle. Meanwhile, the crash box90deforms such that the entire crash box90tilts toward a right side that is the inner side in the vehicle width direction.

When time has passed from the state shown inFIG. 10, components of the collision load input from the barrier B into the bumper reinforcement40that act toward the inner side of the vehicle further increase, so that the crash box90further tilts toward the right side as shown inFIG. 11. Then, the bumper reinforcement40further moves toward the right side as shown inFIG. 11, since the vehicle inner-side plate92is not significantly crushed despite the vehicle outer-side plate93being substantially completely crushed. After the state shown inFIG. 11is reached, the barrier B passes by the front side member10on the outer side thereof in the vehicle width direction.

Thus, in the vehicle front structure900of the comparative example, when a small-overlap frontal collision occurs, the bumper reinforcement40inclines so as to reduce the angle relative to the vehicle front-rear direction during the collision, so that the collision load input into the bumper reinforcement40and acting inward in the vehicle width direction increases. As a result, the crash box90tilts inward in the vehicle width direction and allows the barrier B to pass by the front side member10. Therefore, the crash box90cannot effectively absorb the collision energy.

By contrast, as described above, the vehicle front structure80of the embodiment having been described with reference toFIG. 1toFIG. 8can avoid causing an increase in the collision load input into the bumper reinforcement40and acting inward in the vehicle width direction, and can reduce the likelihood that the crash box50tilts inward in the vehicle width direction and allows the barrier B to pass by the front side member10. Moreover, the collision energy can be absorbed by the entire crash box50, as both the vehicle inner-side part50C and the vehicle outer-side part50B of the crash box50can be crushed flat.

Workings and Effects of Vehicle Front Structure80of Embodiment in the Event of Head-on Collision

Next, the workings and effects of the vehicle front structure80of the embodiment in the event of a head-on collision will be briefly described with reference toFIG. 12toFIG. 15. A head-on collision refers to a type of frontal collision in which the vehicle100collides with the barrier B head-on from the front side.

Since the bumper reinforcement40is a bow-shaped member that protrudes toward the front side at a center in the vehicle width direction as shown inFIG. 1, when a head-on collision occurs, a part of the bumper reinforcement40at the center in the vehicle width direction collides with the barrier B as shown inFIG. 12.

As the collision progresses, the barrier B inclines the bumper reinforcement40such that the angle of the bumper reinforcement40relative to the vehicle front-rear direction becomes 90° as shown inFIG. 13. Then, the crash box50starts to be compressed under the collision load.

As shown inFIG. 14, from an initial stage to an intermediate stage of the collision, the vehicle inner-side part50C of the crash box50undergoes compressive deformation, starting from the vertical bead rows67and the third bead rows65. Thereafter, the vehicle outer-side part50B undergoes compressive plastic deformation as shown inFIG. 15. Then, the vehicle inner-side part50C and the vehicle outer-side part50B of the crash box50are substantially completely crushed as shown inFIG. 15.

Thus, the vehicle front structure80of this embodiment can effectively absorb collision energy in the event of a head-on collision, as the crash box50can be entirely crushed by compressive deformation starting from the vertical bead rows67and the third bead rows65.

In the above embodiment, the first bead row61and the second bead row63have been described as being formed by the beads that are disposed in two stages, and the third bead row65has been described as being formed by the beads that are disposed in three stages. However, the arrangement of the bead rows is not limited to this example; alternatively, the first bead row61may be composed of two stages of beads, while the second bead row63and the third bead row65may be composed of three stages of beads. Moreover, instead of dividing the upper plate51and the lower plate54respectively into three regions of the first upper plate51ato the third upper plate51cand three regions of the first lower plate54ato the third lower plate54c, these plates may be each divided into two regions on the outer side and the inner side in the vehicle width direction, and the first bead row61may be disposed in the vehicle outer-side region and the second bead row63may be disposed in the vehicle inner-side region.

Configuration of Vehicle Front Structure85of Another Embodiment

Next, a vehicle front structure85of another embodiment will be described with reference toFIG. 16andFIG. 17. Those parts that are the same as in the vehicle front structure80of the embodiment described above with reference toFIG. 1toFIG. 8will be denoted by the same reference signs and description thereof will be omitted.

As shown inFIG. 16andFIG. 17, the vehicle front structure85of this embodiment includes a radiator support35that is long in the height direction in place of the radiator support30of the vehicle front structure80of the embodiment described above with reference toFIG. 1toFIG. 8, and further includes a lower bumper reinforcement45, a second member75, and a lower crash box70.

The radiator support35being a first member is a plate-shaped member bent into a crank shape. The radiator support35is held between the front end14of the front side member10and the rear end plate56of the crash box50, and is fixed by being fastened to the flange15along with the rear end plate56of the crash box50so as to extend downward from a fixed portion.

The lower bumper reinforcement45is a rigid member that is disposed below the bumper reinforcement40and extends in the vehicle width direction.

The second member75is a rigid member that is disposed below the front side member10, connected at a leading end to a lower end of the radiator support35with a bolt79, and extends from the radiator support35toward the rear side of the vehicle. The second member75is connected at a rear end to a suspension member76with a bolt78. The suspension member76is a plate-shaped member that is connected at a rear end to the under reinforcement109disposed on the lower surface of the cabin frame102and that covers a lower front side of the vehicle. The suspension member76is connected at a front end to the front side member10by a vertical member77.

The lower crash box70is disposed between the second member75and the lower bumper reinforcement45, and assembled to the second member75via the radiator support35. The lower crash box70absorbs collision energy by undergoing compressive plastic deformation in the vehicle front-rear direction between the lower bumper reinforcement45and the second member75in a frontal collision. The lower crash box70is a columnar member provided with a plurality of circular holes71, and is mounted on the radiator support35through a square base plate72. The rear end plate56of the crash box50is also fixed to the radiator support35, and therefore the crash box50and the lower crash box70are connected to each other through the radiator support35.

Since the crash box50and the lower crash box70are thus connected to each other through the radiator support35, in the event of a small-overlap frontal collision, the lower bumper reinforcement45moves backward substantially parallel to the vehicle front-rear direction along with the bumper reinforcement40. Thus, the lower crash box70as well as the upper crash box50does not tilt inward in the vehicle width direction, and the lower crash box70can also effectively absorb the collision energy. Therefore, the vehicle front structure85can effectively absorb a larger amount of collision energy than the vehicle front structure80of the above-described embodiment.